CA2128915A1 - Process and device for the manufacture of mouldings and mouldings manufactured in accordance with that process - Google Patents

Abstract

A process and device for the manufacture of mouldings and mouldings manufacturedin accordance with that process Abstract In a process for the manufacture of mouldings, especially optical lenses, specifically contact lenses (CL), a starting material that is crosslinkable by the impingement of suitable energy is introduced into a mould (1) having a cavity (15), which mould is at least partially permeable to the energy concerned. The starting material is introduced into the cavity in a still at least partially uncrosslinked state, the mould cavity determining the shape of the moulding (CL) to produced. By means of impingement of the energy concerned, the starting material is crosslinked to an extent sufficient for it to be possible for the moulding (CL) to be released from the mould. The filling of the mould cavity is carried out in the starting material that is still at least partially in the uncrosslinked state.
(Figs. 1A-C)

Description

2~289~5 A ~rocess and device gor the manufacture oï mouldin~s and mouldin~ manufactored in accordalace with thatproces3 The invention relates to a process for the manufactu~e of mouldings, especially optical lenses and specifically con~act lenses, in accordance with the preamble of ~he respective independent patent claim. The invention furthermore relates to mouldings, especially optical lenses and specifically contact lenses, manufactured in accordance with that process or by means of that device.

Contact lenses that are to be manufactured economically in large numbers are preferably produced by so-called mould processes and specii~lcally by the full-mould pr~cess.
those processes, the lenses are manu~actured in their final form usually between two mould halves (moulds), so that nei~er subsequent machining ~f ~e surfaces of the lenses nor machining of the rim is necessary. Mould processes are known, for example, from WO-A-87J04390 and from PP-A-0 367 513.

In those known mould processes, the georne~y of the contact lens ~a~ is tO be produced is deterrnined by the mould cavity. The rim of ~e contact lens is also fo~ned by ~he mould, which usually con~ists of ~wo mould halves. The geometry of the rim is dete~mined by the contour of the two mould halves ~ the region in which they are in contact with one another.

In order to produce a contact lens, first of aU a de~ermined amount ~f a flowable staning material is in~oduced into the female mould half. The mould is then closed by applying the male mould half. Normally, the st~r~ng material is supplied in slight excess, so that the excess amolmt is forced into an overflow chamber externally adjacent to the mould caYity when the mould is closed. The subsequent polym~isation or crosslinldng of ~he star~ing material is effec~ed by irradiation with W light s)r by thermal action ~r by another, non-~ermal, method, during ~e course of which both the starti1lg nmaterial in the mould cavity and the excess material in ~e overflow cham~er a~ fully cu~ed. The full cure of the excess matenlal m~y be del~yed slightly, since it may initially be inhibited by atmospheric oxygen. In order to achieve fault-ftee separation of the contac~ lens from ~e ~ ` 2~ 2891 S

excess material, the excess material must be well sealed off or expelled from the zone in which the two mould halves are in contact with one another. Only in that manner is it possible to obtain fault--free contact lens rims.

The mateTials cu~rently used for the moulds are pre~erably plastics, such as, for example, polypropylene. The moulds are produced by injection moulding and used only once (disposable moulds). The reasons for this are, inter alia, that tne moulds are in some cases contaminated by the excess material, are damaged when the contact lens is separated, or are irreversibly deformed in some areas.

In th~ case of injection-moulded moulds, variadons in the dimensions must also be expected as a result of variations in the manu~actu~ing process ~tempe~atures, pressures, material properties). Shrinkage of the moulds may also occur after injection moulding.
The dimensional variations in the mould may lead to variatiolls in the parameters of ~e contact lens being produced (vertex refractive pawer, diameter, base curve, middle thickness etc.), which may have an adverse effeet on the quality of the lenses and thus result in a reduced yield. If the seal between the mould halves is inadequate, the excess material is not cleanly separated, which results in the formation of so-called flash at the contact lens rim. Where that is rela~ively pronounced, such a cosmetic fault at the rim of the lens may also cause i~itation to the wearer, and such lenses therefore have to be identified by inspection and removed.

Particularly in view of the quality requirements of the contact lens rim, tne moulds are also used only once, because it is not possible to mle out absolutely a certain deformation of the moulds in the region in which tney are in contact with one another.

A further mould pr~cess for the manu~acture of, inter alia, contact lenses is described in IJS-A-4 113 224. That process uses a mould in which the cavity is not compleLely sealed but is connected by a thin annular gap to a resenroir channel (overllow cha~nel~ surround-ing ~e cavity. During ~e crosslinking process, material can flow back out ~f the reservoir through the annular gap and into the mould cavity to compensate for the relatively large sh~inkage in v~lume which occurs with the lens matenals customarily used.

The matenal in the reservoir channel can be prevented from crosslinking by an inhibiting gas atmosphere or by being shielded from the energy radiation causing the crosslinking To ensure that material flows back into the mould cavity, the material loca~ed in the mould ~ , 2l289~5 cavity is~ at least to beg~n with~ subjected to radia~on only in a central region, which is smaller than the diameter of the mould ca~ity, or is exposed to a stronger in~ensity of radiation in that central region than in the edge region of the mould cavity surrounding that central region. After crosslinking has commenced in the central region and has progressed to a certain degree, however, the material disposed in the edge region and the adjacent annular gap, and that located in the reservoir channel, is also exposed to the full radi~on and crosslinked. The burrs and flash mentioned further above are inevitably formed, so that the mouldings or contact lenses manufactured by that known process require subsequent machining.

A further problem arising during manu~acture according to processes described hitherto is that air inclusions may occur when ~e mould is closed. Air inclusions in the lenses result, however, in the lenses being identified as rejects in the subsequent inspection (quality con~ol). The mould has hitherto 'oeen closed correspondingly slowly, so as to enable the air to escape as ~ully as possible from the mould cavity. The comparatively slow closure of the mould, however, takes up a relatively large amount of timeO

The aim of ~e invention is therefore to provide a process and a device of the kind mentioned in which, inter alia, the degree of efficiency is high, that is to say the mould can be used effilciently, and in which expenditure is comparatively low, but always with the proviso that the moulding (e.g. cont~ct lens) produced is free from air inclusions.

In respect of the process, that aim is achieved by carrying out the filling of the mould cavity in the starting material that is still at least paltially in the uncrosslinked state. As a result, nght from the beginning, when the mould is being filled, there can be no air in the mollld, and so ail inclusions are completely avoided. I~e rnould can consequently be closed more quickly~ and thus used more efficienrly, while at the same time expenditu~e is comparadvely very low. Fur~ermore~ in tha~ manner an exact measurement of the required amount of s~arting matenal is provided automatically, since the filling talces ylace in the sta~ng material.

In one variant of the process, ~or the purpose of ~IIling the mould cavity, the cavity can be connectesl to a reservoir which su~ounds i~, in which the starting material is stored and fr~m which ~e mould cavity is flooded. This is a procéss vaTian~ that is especially uncomplicated technologically.

~ 21289~

In a further process variant, the mould is also closecl in the s~ing material so as to exclude the risk of air in any way getting into the mould cavity dunng the closing operation.

In a further variant, a mould is used that comprises a container and a mould member displaceable in the manner of a piston in that container. The mould member can be moved away from and towards the container wall lying opposite it for the purpose of opening and closing the mould. Starting material is fed in between the container wall and the mould member as the mould is opened and conveyed away again as the mould is closed. As a result of the movement of the displaceable mould member away from the opposite-lying container wall the space between the displaceable mould member and the container wall is filled with starting material without air being able to penetrate in~o that space. Sub-sequently, as a result of the movemen~ of the displaceable mould member towards the con-tainer wall, the star~ing material disposed between the mould member and the container wall is conveyed away agairl, the material located in the mould cavi~ naturally remaining there. It is also impossible for any ~ir to enter the mould cavity as the mould member moves towards the container wall, as a result of which mouldings that are free from air inclusions can be produced in a simple and ef~lcient manner.

For example, a mould baving ~wo mould halves may be used in which one mould half is provided on the containe~ wall and the other mould half is provided on the displaceable mould member. In that ar~angement a mould having a male mould half and a female mould half may ~e used, ~e male mould half being provided on dle con~ainer wall and ~e female mould half on the displaceable m3uld member. Pumps may advantageously be used to feed in and convey away the star~ng mateIial. In a further advantageolls process va~iant, the piston may be dIiven in order to feed in and convey away the s~ng matelial.

The c~osslinked rnoulding can be removed from the mould in an especially simple manner by flushing out the mould with star~ng material. This can be e~fected, for example, by the moulding being ~separated from the mould by the flow ~ star~ng mate~ial as the mould is opened and being flushed out of the mGuld by the flow of star~ing material as the mould is closed.

ln one variant of the process, in a firsit cycle the mould is opened and closed a~ain.
Subsequendy, at least th~e crosslinking necessa~y for it to be possible for the moulding to be released fr~3m the mould is effes~ted by the action of energy. In a second cycle the :`
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mould is opened again, the moulding being separated from the mould. The piston-like mould member is then moved towards the opposite-lying container wall again and the mould is thus closed again, the crosslinked mouldin,g being flushed out of the mould. This "two-cycle" variant of the proeess is distinguished by the face that the moulding is produced in the ~Irst cycle and then flushed out of the mould in a second cycle. The mould can simultaneously be cleaned in the "flushing cycle ".

The process variant just described can be carried ou~ ei~her by providing first a "production cycle" (first cycle) and then a separate "flushing cycle" (second cycle, for example using a flushing liquid), or al~ernatively the flushing can be a~ranged to coincide with dle production cycle of a new moulding1 that is to say as new starting material is introduced into the mould cavity the moulding prodùced in the preceding cycle is llushed out of the mould. The "two-cycle" vaTiant of the process then becomes a "single-cycle"
variant.

The crosslinked moulding can9 however, also be removed ~om the mould by means of a gripping device. This can be effected by deposi~ng the moulding removed from the mould by the ~ripping device on the displaceable mould member outside ~e space between the displaeeable mould member and the opposite-lying container wall. The moulding deposited on the displaceable mould member can be held fast thereto by negative pressure and then released from it again by positive pressure.

In a ~urther process var~ant, the mould is not completely closed after the starting material has been introduced into the mould cavity, so that an annular gap containing uncrosslinked star~ng material, which gap su~rounds the mould cavity and is in communication with tha~
mould cavity, remains open. By ~is means on the one hand a s~inkage in volume occul~ing during crosslinking can be comE~ensated by starting ma~rial flowing back through the annular gap into the mould cavity, and on the o~her hand the mould halves ~re prevented from being pressed hard against one another duling manufacture of the ~oulding. Especially in view of the risk of the mould halves being irreversibly deformed by mechanical stress, mould halves have hitherto been used only oncet as explained in the introduction. In accordance with this process vanant, ~e mould halves can be used repeatedly.

It is also conceivable for the mould to be closesl further following crosslinking shrinkage as crosslinking of the material progresses.

... .. . ..... ~ . .. .. . .. . ., ~ .. . . . . .

` 212~1$

~ - 6-It is, however, in any event important to use a starting material that is of at least viscous ,flowability prior to the crosslinking, so tha~ star~ng material can flow back through the annular gap into the mould cavity to compensatc for shrlnkage.

According to a fur~er process variant, the impingement upon the ma~erial of the energy causing crosslinking is restricted spatially to the region of the mould cavity, so that substantially only ~he starting material located in the mould cavity, that is to say the region of the moulding, specifically of the contact lens, is crosslinked. Any excess starting material present is not polymelised or crosslinked. l[n that arrangement, partial areas of the moulding rim are foImed not by a mechanical limitation of the material by mould walls but by a spatial res~icdon of the impinging energy (usually UV or some other radia~on) that tIiggers the polymerisadon or crosslinking. As a result of those two measures, con~act between the two mould halves can in a preferred arrangPmen~ be avoided, so that they are not deformed and can accordingly be used again. In addilion, the known problem of volum~ shrinkage which occurs dur~ng crosslinking can also be dealt with veIy simply thereby wilhout it being necessary, as in the case, for example, of US-A-4 113 224, for the moulding to be m~chanically processed subsequendy.
, one process variant, the spatial res~riction of the energy impingemen~ is e~fected by masldng for ~he mould that is at least partially impermeable to the particular form of ener~y used. The energy used for the closslinking 2S radiation energy, especially UV
radiation, gamma radiation, electron radiation or thermal radiation, the radiation energy preferably being in the form of a substantially parallel beam in order on the one hand to achieve good restriction and on the other hand eff1cient use of the energy.

In a fur~er variant, ~e mould used is one that is highly pe~neable, a~ leas~ at one side, to the energy form eausing the crosslinking. The spatial restriction of ~e energy impingement is effected by paIts ~f the mould that are impermeable or of poor permeability to dle energy ~orm.

In a f~her variant of the proeess the mould used is one tha~ is highly pelmeable, at least from one direc~on, to the energy form causlng the crosslinking. llle spatial res~iction of the energy impingement is effected by a mask that is imperrneable or of poor permeability to the energy and that is provided outside the mould cavity on or in the mould.

~12~91 5 In that arrangement the mask is preferably arranged in the region of the separating planes or separadng faces of different parts of Ihe mould, especially in regions of those parts that are in contact with the crosslinkable starting mate~ial.

In a further process variant, the energy causing the crosslirlking is kept away from the starting material disposed in the annular gap, so that the crosslinking can occur in the mould cavity only and so that it is possible especially for starting material to flow back in ordOE to compensate for the volume shrinkage. The mould can also be closed filrther following crosslinking shrinkage as crosslinking of ~e material progresses.

In that arrangement a material that is of at least viscous flowability prior to crosslinking is used, so that starting mate~ial can flow back through the annular gap into the mould cavity to compensate for shrinkage. If, after the moulding has been released from the mould, there is any uncrosslinked material still adheIing to it, that material can be removed by washing with a suitable solvent. In any event, however, subsequent mechanical processing of the moulding is dispensed with.

In respect of ~e device, the aim of the inven~don is achieved by a~ranging the mould cavity, during filling, in star~ng material that is still at least panially in the uncrosslinked state. As a result, right from the beginning, when ~he mould is being filled, there can be no air in the mould, and so air inclusions are completely avoided. l'he mould can conse-quendy be closed more quickly and thus used more e~lciendy, while at the same dme expenditure is comlparatively very low.

In one example embodiment the device comprises a reservoir for supplying the star~ing material ~at surrounds ~he mould cavity. The reservoir can be connected to the mould cavi~. When the mould cavity is being filled, ~he ~eservoir is connected to the mould cavity and floods that cavity. This allows several s~ucturally especially simple further developments, which will be explained in more presise detail.

In a further example embodiment, ~e devioe eomprises means for losing the mould which is arranged in the starting material, the mould, in this case too, always being closed in the s~ar~ing material so that no aLr can enter the mould cavity.

In an advantageous example embodiment, the mould comprises a con~iner and a mould member displaceable in ~e manner of a piston in that container, which mould member can . .: , . . . , , ~ . : - . : . .

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212~9~5 i be moved away from and towards the container wall lyin~ opposite it for the purpose of opening and closing the mould. Pr~vided in the container is an inlet through which s~ting material flows in between the container wall and the mould member as the mould is opened. Also provided in the container is an outlet through which s~arting material flows out again as the mould is closed. This example embodiment is structurally comparatively simple, that is to say not very complicated, and is therefore well suited to practical use.

The mould in that arrangement p~eferably has two mould halves, one mould half being provided on the container wall and the other on the displaceable mould member. The mould has (especially in the manufacture of contact lenses) a male mould half and a female mould half. Preferably, the male mould half is provided on the container wall and the female mould hal~ on the displat eable mould member. In that arrangement themoulding (contact lens) can later be released from dle mould especially simply.

Pumps are preferably provided for feeding in andlor conveying away st~ting material which, as the mould is opened, ~eed in stt~rting material through the inle~ and between the container wall and the mould member and, as the mould is closed, convey it back through ~e outlet. Such purnps operate reliably and therefore do not represent any special expenditure.

In a further exarnple embodiment, means are provided for driving the mould member that is displaceable in the manner of a piston. Those means may be provided, bo~ in a device that works without and in a device tha~ works with pumps, for the purpose of moving the mould member displaceable in the manner of a piston in the direction towards ~e opposite-lying container wall and thus forcing starting material disposed between the mould balves out again.

In a furiher example embodiment of the device, means are provided for producing a flow.
That flow separates the moulding from ~he mould when the mould is opened and flushes ~e moulding ou~ of the mould when the mould is closed. l'hose means may be in ~he form of jets or similarly acting means. It is important that they produce a flow or a turbulence in the starting material disposed be~ween the mould halves so that the moulding (cont~ct lens) is lifted off the mould half by means of the flow or turbulence.

In a ~urther example embodiment of the deYice, in a first cycle ("production cycle") star~ng ma~erial first of all flows in through the inlet and between the container wall and ---` 2~l2~91~

g the displaceable mould member and then flows back out through the outlet. The energy source then acts upon the mould with an amount of energy necessary for it to be possible for the moulding to be released from the mould, so that crosslinking occurs. Then7 in a second cycle, for example starting material again flows in through the inlet and between the container wall and the displaceable mould member, separates the moulding from the mould and flushes it out through the outlet.
t That "two-cycle" device is distinguished by the fact that in the first cycle the moulcling is produced, and then in the second cycle (flushing cycle, cleaning cycle) the moulding is flushed out of the mould and the mould is also simultaneously cleaned.

That device may either be so constructed that, as described, there is first of all a "prodwction cycle" (first cycle) and then a separate "flushing cycle" (second cycle), or alternatively it may be so constructed that the flushing out coincides with the production cycle of a new moulding, that is to say, as new starting material is introduced into the mould cavity, the mowlding produced in the preceding cycle is flushed out of the mould.
The "two-cycle" device then bet~omes a "single-cycle" device. In the "single-cycle"
device, however, starting material must be used for flushing, whereas in ~he "two-cycle"
device the use of a special cleaning liquid in the flushing cycle is also possible.

To remove the moulding, a gIipping device may be provided tha~ remuves ~e crosslinked rnoulding from the mould. For that purpose the container preferably has on a container wall other than ~e shape-giving ~ace a hollow or recess that extends substantially in the direction of rnovement of the displaceable rnould rnember. The gripping device is arranged in that hollow or recess. The displaceable mould member comprises, on an outer wall that does not lie opposite the shape-giving container wall, an indentation in which the gripping device deposits the remo ved moulding. This is a structurally e~pecially advantageous and simple aTrangement of the device.

In a possible further develapment of that device the displaceable mould member com-prises a channel that leads to the indentation and can be connected to a negati~e pressure or positive pressure source. The channel is connected to ~he negative pressure source when the g;ripping device deyosits the removed moulding in the indentation of the mould member. In order to release the lens it is then connected to the positive pressure source.
By this means the lens can be produced duIing one cycle and removed, deposited on the mould member and then taken off the mould member during the next cycle. This is 212891~

possible both in a device cons~ucted as a "two-cycle" device and in a device cons~ucted as a "single- cycle" device.

In a fur~er example embodiment of the device, the m ould is provided with spacers that hold ehe two mould halves a small distance apart from one another when the mould is in the closed position, so that an annular gap that surrounds the mould cavity and is in communication therewith is formed.

By that means, on the one hand volume shrinkage occurring during crosslinking can be compensated, since starting material can flow back into the mould cavity through the annular gap. On the other hand the spacers prevent the mould halves from being pressed hard against one another during production of ~e moulding. Particularly in view of the risk of the mould halves being irreversibly deformed as a result of mechanical stress, mould halves have hitherto been used only once, as explained in ~he introducti~n. Using this example embodiment of the device it is possible ~or the mould halves ~ be used repeatedly. It is fur~heImore possible in a filrther development of the device for the mould to be provided with resilient means or displacement means ~at a~low the two mould halves to move closer together following crosslinking sl~inkage.

In a fur~her example embodiment, means are provided that restnct the impingement of energy upon the rnould to the region of dle mould cavi~, so ~at substantially only the star~ng material located in the mould cavi~, that is to say the region of the moulding, speci~lcally of the cont ct lens, is crosslinked. Any excess starting material present i3 not polymerised or crosslinked. In that arrangement, partial areas of the moulding rim are formed not by a mechanical limitation of the material by mould walls bue by a spa~ial res~ricdon of the impinging energy (usually UV radiation or another form of radiation) that triggers the polymerisation or crosslinking. As a result of those two meas~es, in a preferred alTangemene contact between the two mould halves can be avoided, so that they are not defolmed and can accordingly be used again. In addieion, the known p~oblem of volume shrinkage which occurs during crl>sslinl~ng can be dealt with very simply lhereby without it bieing necessary, as in the case, for example, of US-A-4 11 3 224, for the moulding to be mechanically processed subsequently.

In a further development of the example embodiment just mentioned, the muuld is provided with a mask that is impeImeable or of poor permeability tv the energy, which mask screens from the energy all cavities, with the exception of the mould cavity, ~hat ` -" 2~2~91~

may contain uncrosslinked material and all mould faces that may come into contact with the material. In that a~rangement the mould may cornp~ise twu mould halves that are separated along a separating face, and the mask is a}Tanged outside dle mould cavity on one of the two mould halves and/or on both mould halves in the region of the separating face.
. .
In a furtiler example embodiment of the device, ~he energy so~rce produces UV-radiation, and at least one of the halves of the mould consists of W-permeable material, especially quartz. The mask in that arrangement may consist of a L~yer of material that is imperm-eable to W radiation, especially a chTome layer. In dle example embodiment of the device having an annular gap, the mask may be alTanged in the region of the annular gap.

In the example embodiments of the device in which the crosslinking is restricted spatially to ~e re~on OI the mould cavi~, the mould may naturally also be provided with lesilient means oq displacement means that allow dle two mould halves to move closer together follo~g crosslinl~ng shrinkage.

In par~cular, mouldings, especially op~eal lenses and specifically con~act lenses, can be manufactured in acc~rdance with the process and using ~he device desc~ibed.

The invention is explained in detail in the following wi~ reference to the drawings~ which are a~ least pa~dy in diagramma~c form or in secdon.
j: . . .
Figs. lA-C show an example embodiment of the device acco~ing ~o the invention, ,~
Figs. 2A-C show a fur~her example embodiment of the device according to the invention, Yigs. 3A-C show a va~iant o~ ~e example embodiment of Fig. 2, Figs. 4A-C show a f~her example embodiment of ~he device according tS) ~e invention, and l~ig. S is an enlarged illustration of dle nm atea of m examyle embooiment 212891~

of a mould in the closed position.

The example embodiment of the device according to the invention shown in Figs. lA-C is designed for ~e manufacture of contact lenses from a liquid starting material that can be polymerised or crosslinked, for example, by UV racliation. ~ig. lA shows the mould 1 in ~e closed position. The mould 1 is ~ranged in a container 10 that is full s)f uncrosslinked liquid star~ng materi,al M. The device furthermore comprises an energy source in the form of a W light source 2a, and also means 2b tha~ direct the energy supplied by the W light source 2a onto the mould 1 in the form of a parallel beam 3. l~ose means 2b may especi-ally also comp~ise a shutter that is arranged between the UV light source 2a and the container 10. The UV light sou~ce 2a and the means 2b can obviously ~lso be cornbined into a single unit.

Details on the general construction and on questions conce~ing dimensions, material and st:abilit~ e~c., as well as, for exam~le, on sui~able materials i~or ~e mouldings and on aspects conce~g proce~sing technology, are dealt wi~ very comprehensively in EP-A-O 3~7 513 and especially in US-A-4 113 224, a:nd those documents are therefore expressly declared to be an integral part of the presen~ descrip~on (incorporation by reference).

~e mould 1 compIises two mould halves 11 and 12, each of which has a curved mould face 13 and 14, respectively, which toged~er define a mould cavity 15 which in tum ~termines the shape of the contact lens CL to be produce~i The face 13 ~ the uppe~
mould h~lf 11 is concave and determines the fron~ face wi~ dle rim ~$ea adjacent dle~to.
That mould half 11 is usually re~e~ o as ~he ~emale mould half. The faee 14 of the lower mould ha~ 12 is convex and determines the rear or base face of the contact lens, and the rim area ~hereof adjacent thereto. That mould half 12 is usually referred to ass the male mould half.

Unlike lhe moulds known, for example, from ~he documents WO-A-87/04390 or EP-A-0 367 513 mentioned in the intr~duc~Lion, ~he mould cavity is no~ comple~ly and tightly sealed but, in th~ example embs)diment shown, is ~pen all the way round in ~e region of its circumferenLtial rim, which defines the Tim of the cont~ct lens ~ to be pr~duced. Ihe mould cavity 15 is also in co~nunica~on ~here with a lelatively na~row annular gap 16, as is also the case in the moulds shown in IJS-A-4 113 224. The cmnular gap 16 is limited by a fLIt mould wall 17 on the female mould half 11 and a flat mould 2~2~9:15 wall 18 on the male mould half 12. To prevent complete closure of the mould, spacers in the form of spacer bolts 19 are p~ovided on the male mould half 12 which keep the ~emale mould half 11 at a distance, that is to say prevent complete closure of the mould and thus de~me the annular gap 16. The spacer bolts may be adjustable (for example by means of a thread not shown, prov~ded in the male mould half) or may alternatively be of resilient construc~ion. In that manner the two mould halves 11 and 12 can be moved towards one another during the crosslinking operation by adjusting the spacers or against a resilient force in order to compensate for shIinkage. The mould can obviously be opened and closed in the usual manner, for example by means a~ a closing unit indicated here by the a~row la only. Adjus~nent of the distance between the two rnould halves t~ compensate for sl~inkage can a~so be carIied out, ~o~ example, by means of that extemal closing unit.

In another arrangement, not shown here, a number of segment-shaped gaps may be provided instead of the continuous annular gap 16 and the space~s 19, the inte~mediate spaces between the individual segment gaps taldng over the func~ion of ~e spacers.
Ob viously, other configurations are also possible.

The two mould halves l l and 12 consist o~ a matenal that is as permeable as possible to ~e selected energy, which in ~is case, as already mentioned, is, for example, W light, for example they consist of polypropylene usually used for such puIposes or of anothe~
polyolefin. Since the irradiation wi~ W light is in this ~ase ~om one side only, that is *om above, it is actually necessary only for the upper, that is to say in ~is case ~he female, mould half 11 to be UV-permeable. Obviously, the same applies also for iIradiation from below ~rough dle male mould half 12. Acco~ding to an especiallyexpedient and advantageous arrangement of ~e inven~n, at least ~e mould half that is i~diated with W light consists of quartz. Not only does that material have especially good UV permeabili~,r but it~is also veIy hard and resistant, so that moulds made fr~m i~
can very readily be reused. A prerequisite for that, however, which i~ disclosed in fi~her detail in the ~ollowing, is ~at ~e mould is closed eilher wi~hout fo~ce or not fully, so that dle mould halves are nol daraaged by con~act. W~p~rmeable special glasses or sapphi~e are possible alternatives to gua~z. On account of the ~act that the mould or mould halves can be re-used, expenditure on their manufacture may be rela~vely high in order ~o obtain moulds of extremely high precision and repr~ducibility. Siince ~e mould halves do not ~ouch in the ~egion of the lens being produced, ~at is to say in the region of ~he mould cavity 15 or of the actual mould faces, damage by contact is excluded. A high deg~ee of durability of the moulds is thereby assured. This also has ~avourable consequences in - , ~ - : ' '-,d' --~ 21289~

general for the reproducibility of the contact lenses or mouldings being p3:oduced.
.,~
The space between the two mould halves 11 and 12 and thus also the mould cavity 15 is arranged in ~e uncrosslinked star~ing ma~enal M for the entire production process. In accordance with dle general concept of the invention, in any event at least the mould cavity is ar~anged completely in the starting materi~l in its uncrosslinked state during ~Illing. Fig. lB shows that ~he UppeF mould half 11, even in the opened position, is not completely clear of the star~g mate~ial M, the space between the mould halves 11 and 12 always remaining below the liquid surface o~ the starting material M disposed in ~e container 10. Consequently, the space between the two mould halves, and especially also the mould cavity, are always in communication with the star~ing ma~e~ial M disposed in the container 10. As a Iesult air can at no time enter ~e space between ~e two mould halves 11 and 12.
.~
When the mould cavity is full and ~e mould is closed (Fig. lA), the mould is ~mpinged upon by W rays 3 and the moulding is thus crosslinked.

After crosslinking, the mould is opened and the moulding in dle ~o~m of ~e contact lens CL is released :~om the mould, that is to say taken o~ and removed fr~m the mould. There is shown symbolic~lly m Fig. IC for that purpose a glipping device 4 which, when the 3 upper mould half has been raised, takes the contact lens CL off ~e m~le mould half 12 ~Fig. lB) and removes it from the mould ~Fig lC). The release andremoval of ~he con~act lens or moulding fiom the mould may, however, also be ca~ied out by other means, as will be explained by way of the other example embodiments. A~er removal of the contact lens or moulding, the mould can be closed again and a new con~act lens ~L pr~duced.

Since ~e en~re pr~duction process according to Pigs. lA-C takes place below the liquid sulface of the stalting mateIial M in the container 10~ no air can enter the space between the two mould halves 11 and 12 or, in pa~cular, the mould cavi~ lS. Since the mould is opened ~nd closed below ~he liquid suri~ace, ~he mould can also be closed comparatively quickly, which was n~ possible with the processes and cleviees according to the state of the art. It is thus possible ~or con~act lenses ihat a~ free ~om any air inclusions to be produced efficiently and with low expendit~re.

In the example em~odiment shown in Figs. lA-C, in addition impirlgement of UV rays upon the mould is restricted to the material in the mould cavity 1~, that is to say only the 2~89~

material disposed in the mould cavity 15 is crosslinked. In particular, the starting material in the annular gap 16, which surrounds the mould cavity 15, and the remainder of the starting material M disposed in the container 10 are not impinged upon by energy and a~e not crosslinked. "Mould cavity" therefore here denotes that cavity of the closed mould which is defined by the complete contour of ~he moulding to be produced, specifically therefore the contact lens CL. The annular gap 16 opening into the mould cavity does not, therefore, ~orm part of the mould cavity 15 here.

For realisation in practice, according to Figs. lA-C there is provided on the mould wall 17, in the region of the annular gap 16, a mask 21 that is in,~permeable (or at least of poor permeability compared with the permeability of the mould) to the energy used, in tbis case therefore W light, which mask extends right up to the mould cavity and, with theexception ~ the mould cavity, screens from the radiated energy all remaining parts, cavities or surfaces of the mould that ale in contact with or may come into contact with the here liquid uncrosslinked, possibly excess, materia~. ParLial areas of the lens n~n are i~ormed not by a limitation of the mateIial by mould walls but by a spatial restriction of the radia~on or other energy tnggering polymerisation or crosslinking. The side walls of the upper mould half are also provided with ~e mask 21 so as to prevent the staIting rnatelial M that su~Tounds the mould in the container 10 from being cr~sslinked.

In the case of UV light, the mask may preferably be a thin c}~ome layer, which can be produced according to processes as known, for example, in photo and W lithography.
Other metals or metal oxides m~y also be suitable mask materials. The mask can also be coated with a protec~ive layer, for example of silicon dioxide if the material used for ~he mould or mould half is quartz. The mask does not necessarily have to be fixed but could, for ex~mple, be constructed or a ranged to be removable or exchangeable. It could, in principle, be provided anywhere at or on the mould as long as it was able ~o fulfil dle function for which it was intended, namely the sc~eening of all areas OI the mould ca~ying wncrosslinked material with the exception of the mould cavity. Pre~erably, the mask is atranged on, or just below, a wall surface tha~ is in contact with ~e uncrosslink~id star~ing material, since in that manner undesired diffraction and scattenng effects can be substan-tially excluded. That is not, however, absolutetly essential. In principle it is even possible ~o dispense with a mask or masking in or on the mould if ~e energy impingement can be res~ricted locally to the nnould cavity by some other means9 where necessary taking into c~nsideraeion the optical effect of the mould. In the case of UV radiation dlis could be achieved, for example, by a spatially restricted light source9 a soitable lens arrangement . , ~ . " - -, ~ . - -2~2~91 ~

optionally in combination with external masks, screens or the like and taking into consideration the optical effect of the mould.
:1 A further example emb~diment of the device according to the invention is shown in ~igs.
2A-C. In that example embodiment one mould half, in this case the male mould half7 is formed by one wall of a container lOa, in this case the container base lOOa. The male mould half is thus formed directly on the container base lOOa. Also provided in the container lOa is a mould member l l a displaceable ;n the manner of a piston, which can be moved away from the container wall Iying opposite it, in this case the container base lOOa, and back towards the container base, while maintaining a seal along the side walls of the container. The mould can thereiore be opened and closed in that manner. The mould melmber 1 la is correspondingly formed as the female mould half on its face 17a that faces the container base. Container base lOOa and mould face 17a define the mould cavi~,r 15a when the mould is in the closed position (Fig. 2A). Naturally, ~e mould member does not necessarily have to be constructed in the form of a piston and it would equally be possible for a diaphragm to be provided to which ~e mould half was attached. O~er methods of altering the volume are also possible.

Provided in the container lOa, in this case the con~ainer base lOOa, is an inlet lOla through which star~ng matelial can flow into the space bet~een the mould member 1 la and the container base lOOa. 'rhe space between the mould member lla and the conta~ner base lOOa is for ~at purpose continuously in communication with a reservoir R. By means of pumps Pl and P2 at the inlet 101a and oudet 102a respectively7 s~ng material can be conveyed to and from the space between mould member 1 la and container base lOOa, it being important for ~e space between mould member l l a and container base lOOa always to be ~llled with starting material M so that no air can penetrate into that space. The pumps Pl and P2 are represented wi~ an inte~ated non-retum valve, but it is also possible to use pumps wi~hout an integrated non-return valve and to cvnnect the valve separately between pump and container or, depending on the type of pump, ~ dispense wi~h such a non-return valve completely.

YVhen the mould is in the closed position (Fig. 2A), it is impinged upon by energy, in this case again UV radiation 3. In this case, too, the impingement of energy upon the mould is, for example, from above. Crosslinking is caused thereby. The crosslinked moulding C~ is then lifted from the mould and removed from the mould. For that pu~pose, first of all liquid starting material 1!~ is fçd by means of the pump Pl ~hrough the inlet lOla into the --` 2~L2~915 space between the container base lOOa and the mould member 1 la, and the piston-like mould member 1 la is moved upwards (Fig. 2B). The moulding, in this case in the form of the contact lens CL, can then be separated from the mould and removed. That can be effected, for example, by means of a special ~ipping device, as already described with reference to Fig. 1. The contact lens CL can, howev~er, equally be flushed out of the mould, as will be explained in more detail in the following.

The mould member 1 la displaceable in the manner of a piston is then moved downwards again and the material disposed between the mould member 1 la and the container base lOOa is conveyed away through the outlet 102a (Fig. 2C). The material can be conveyed away by means of the pump P2 provided at the ou~et.

It is, in principle, possible here for the mould member 1 la displaceable in the manner of a piston to be driven solely by the liquid star~ng material fed in and conveyed away from between mould member 1 la and container base lOOa, so that the pumps Pl and P2 supply the driving energy necessary sherefor. It is also possible for ~ere to be no pumps at all and for the mould member 1 la displaceable in the manner oi a piston ~o be driven mechanic~
ally, that is to say for star~ng mateIial to be sucked in during the upwa~l movement and fo~ced back out again during the downward movement. Obviously combinations wi~
pumps aMd a mechanical drive are also possible.

A mask 21a is provided on the mould member 1 la. ln a similar manner to that described for the upper mould half 11 in Figs. lA-C, it extends over ~e annular gap 16a up to ~e mould caYity 15a, and also optionally along the side walls of the mould member 1 la displaceable i n the manner of a piston. If the mould is then impinged upon by UV
radiation 3, crosslinking occurs in the region of the mould cavity 15a only, with consequent formation of the -moulding. The material in the remaining areas, especially i n the annular gap 16a, and also other s~ing material in the container lOa, is no~ cross-linked. ~ pIinciple, the same considera~ions in respect of the materials and the production and moundng of soch masks as those already made in the explanations of Figs. lA-C
apply here too.

Figs. 3A-C show an example embodiment ~f the device that in plinciple is ve~y similar to the example embodiment of Figs. 2A-C. One difference, nowever, is ~hat no pump P2 is provided at the outlet 102a in the example embodiment according to Figs. 3A-C, but the outlet 102a is constructeld as a defoIrnable flap or plate or as a trap door. In the explanation 212~915 of Figs. 3A-C, especially the release from the mould of the moulding, in this case there-fore of the contact lens CL, will be described in detail in the following. The filling of the mould cavity lSa is canied out analogously to the example embodimen~ according to Figs. 2A-C by means of the pump Pl. When the mould is in the closed position (Fig. 3A), the contact lens CL is produced by crosslinking by ixnpingement of UV radiation 3 upon the mould.

As the piston-like mould member 1 la (Fig. 3B) moves upwards, liquid starting material flows into the container lOa between the container base lOOa and the mould member 1 la displaceable in the manner of a piston. The inlet lOla may be constructed as a jet or similarly acting flow-producing means. As the liquid starling mateIial is fed through the inlet, the crosslinked contact lcns CI~ is lifted from the mould by the flow produced and, with appropriate arran~ement of the jet, is flushed towards the outlet 102a, which in this case is constructed as a deformable flap or plate. During the downward moYement of the piston-lilce rnould member 1 la (Fig. 3C), the flap is deformed downwards by the pressure generated and opens the outlet 102a, so that the liquid sta~ng material together with the contact lens CL can be flushed out through the outlet 102a The contact lens can be collected in a sieve S that is permeable to the liquid starting material. The star~ng material may, ~or example, be recycled and reused, wheIe necessary after it has been cleaned.
While the contact lens is being flushed out, the mould cavity 15a is filled with new starting material, so that a new contact lens CL can immediately be crosslinked by the impingement of W radiation 3.

It has been described above that, for the purpnse of lifting off and flushing ou~, liquid starting material is fed into the container lOa, in the same cycle the mould cavity 15a is filled again and, with the mould in ~he closed position, the mould is again imphlged upon by W radiation 3 for ~he puIpose of crosslinking and producing he next contact lens CL.
The device ~us operates, as it were, as a "single-cycle" device, since in each cycle (upward and downw~d movement of ~he piston-like mould member 1 l a) a contact lens is produced and flushed out of the mould.

It is, however, also possible ~or the production of the contact lens to be cal~ied out in a first cycle ("production cycle"), that is to say for the piston-like mould member 1 la to be moved upwards, for liquid starting material to flow between the mould member 112 and the container base lOOa and then for the mould member 1 la to be moved downw~ds again. In the closed position the mould is then impinged upon by UV radia~ion 3, as a 2~2891~

result of which crosslinking occurs and the contact lens CL is thus produced. Then, in a separate second cycle ("flushing cycle"), the contact lens can be flllshed out of the mould without a new contact lens being produced in that second cycle, whereas in the "single-cycle" device a new contact lens CL is again produced. For the flushing ope~ation in the "two-cycle" device, it is there~ore possible to use liquid starting material, but it is also possible, in particular, to use a separate cleaning liquid. This is of advantage in as much as the mould can be especially well cleaned on the inside during the ~ushing cycle before starting mateIial flows in again in the next cycle and the next contact lens Cl, is produced.
In the example embodiment according to Figs. 3A-C, therefore, both a "single-cycle"
operation (a contact lens is produced in every cycle) and a "two-cycle" operation (a contact lens is produced in the first cycle and in the second cycle it is flushed out and the mould cleaned without a new contact lens being produced) are possible.

A fi~her example embodiment of the device according to the invention is shown in Figs.
4A-C. That exarnple embodiment is in principle also similar to the example embodiments described with reference to Figs. 2A-C and ~igs. 3A-C, but differs significantly from those in that it comprises a somewhat differendy constructed mould member 1 lb displaceable in the manner of a piston. In addition, the contaîner lOb is also significan~ly di~ferently cons~ucted in the respect that there is provided in one of its side walls 103b a hollow or recess 104b which extends ~n tlie direction of movement of dle piston-like mould member 1 lb. ArTanged in ~at recess 104b is a gripping device 4b. The mould member 1 lb has an indentation 114b on its outer wall 113b e~actly in the regi~n in which the recess 104b is provided in ~e side wall 103b of the container 1 lb. The mould member 1 lb furthermore comprises a channel 115b which can be connected to a negative pressure source and positive pressure source P3. l`he gripping device 4b can also be connected to ~at negative pressure alld positive pressuIe source P3.

The manufacture of the con~act lens CL by crosslinlcing by means of impingement of UV
radiation 3 upon the mould is canied out in the same manner as already described wi~h reference to Figs. 2A-C and Figs. 3A-C. The explanation of Figs. 4A-C is therefore directed mainly to ~e manner in which the contact lens CL is removed from the mould.
When the mould is in the closed position, ~e m~uld is again impinged upon by UV
radiation 3 and the contact lens CL is produced by crosslinldng (Fig. 4A). Star~ng material is then pumped by means of the pump Pl between the mould member 1 lb and the container base lOOb, and the mould member 1 lb is rnoved upwards (Fig. 4B~. The grippin~ device 4b is then pivoted out of the recess 104b and over the con~ac~ lens CL.
i - 2~2~9~;

The gripping device 4b has a borehole in its gripper plate 40b through which negative pressure is then applied by means of the negative pressure source P3, so ~Ihat the contact lens CL is lifted and sucked towards the gripper plate 40b. When the contact lens CL has been sucked against the gripper plate 40b, the ~ipping device 4b is pivoted back into the recess 104b and the mould member 1 lb is moved downwards again. As ~lat happens, the liquid starting material disposed between mould member 1 lb and container base lOOb is sucked away by means of the pump P2 (Fig 4C).

The gripping device 4b disposed in the recess lO~b at the same time either glides along ~e outer wall 113b of the mould member 1 lb or is held in the recess 104b until the gripper plate 40b is located opposite the indentation 114b on the outer wall o~ the mould member 1 lb. At that point positive pressure is applied through the borehole in the gripper plate 40b, so that the contact lens CL is released from ~e gripper plate 40b and deposited in ~e indentation 114b. Negative pressure is applied through the channel 1 lSb leading to the indentation 114b at the same time as the contact lens CL is released from the gripper plate 40b, so that the contact lens C~ is simply deposited by the gripper plate 40b in ~e indentation 114b (Fig. 4A).

When the mould member 1 lb has been moved upwards, the indentation 114b of the mould member 1 lb is located outside the container lOb (Fig. 4B). ~f positive pressure is then applied through the channel 115b, ~e contac~ lens CL is released from the indentation 114b and can be conveyed away for further processing. In this connection it should in particular be noted t~at the side wall 103b can also be extended even further upwalds and can have a furdler recess in which the contact lens CL can be deposited or into which it can be flushed. By that rneans even better guidance o~ the mould member 1 lb andprese~ation of its corresponding sealing faces, which glide along the container wall, is achieved.

In Figs. 4A-C the pump P3 is proYided for the application of positive pressure or negative pressure, the positive pressu~e connection HP and negative pressure cs)nnection NP of which pump are connected to the channel 1 lSb or the borehole in the gripper plate 40b depending on the position of the mould member displaceable in the manner of a piston.
The pump P3 can suck star~ng material out of the reservoir R in which the starting material is stored, by means of which the necessary pressure is generated. Figs. 4A-C
show at the inlet lOlb and at the outlet 102b two separate reservoirs into which the pumps Pl or P2 and P3 respectively project, but obviously it is also possible for there to be one "::
- :.

~!,~, , - ~ .

2128~91~

reservoir only.

It should be noted at this point that also the example embodirnent according to Figs. 4A-C
can operate ~oth as a "single-cycle" device and as a "two-cycle" device. It must, however, be ensu~ed in the case of dle "single-cycle" device that it is always only star~g material that flows into the container lOb. In the "two-cycle" device, on the other hand, in the second cyçle in which the contact lens CL is also removed, a cleaning liquid can be fed in.

As already discussed in the explanation of the individual Figures, as the mould halves are closed 0xcess starting material is forced into the annular gap 16 between the two mould halves. The width or height (~y) of the annular gap 16, which is shown more clearly in Fig. 5, is made sufficiently great for contact between the two mould halves 11 and 12 (or contact between the mould member 11, 1 la and 1 lb and the container base 100, lOOa and lOOb respectively) in the region of the mask 21 to be avoided with absolute reliability. The positioning (spacing) of the ~vo mould halves is effected by the spacer bolts 19 (Figs.
lA-C).

In Fig. 5, the mould cavity 15 has, by way of example, a shape tha~ corresponds to the typical rim geometry of a so-called scft contact lens. The cavity rim, and thus the contact lens rim, is formed here by a wall ~ace 22 on dle male mould half 12 and a wall face 23 on the female mould half 11, dle two wall faces being a~ranged at right angles to one another.
The width and height of those two wall faces, that is to say dle rim areas of the contact lens defined by them, are indicated by X and Y respectively. It is obviously also possible in practice for ~e lens Iim ~o be somewhat rounded.

As can be seen clearly, the wall face 23 of the mould half 11 does not quite extend up to the wall face 22 but is lower by the amount ~y of the annular gap 16. Typical gap heights ~y are in ~he range below about 100 ~lm ~or the manu~acture of contact lenses. Tests have shown that, at lease when parallel energy radiation is used, a clean s~uctllring of the rim of the moulding being p~oduced is still possible even with gap heights of approximately 1 mm. Conversely~ however, the wideh or height of the annular gap can also readily be reduced to practically zero, provided that the mould is closed without force, that is to say that thc two mould halves lie one on ~op of the other w~out external pressure. In that case only a ~llm of uncrosslinlced material a few microme~s thick remains between the two mould halves in the region of the annular gap, which, however, because of the screening from the UY radiation, likewise cannot result in the formation of flash. On crosslinlcing, therefore, a clean and burr-free con~act lens rim is forrned that does not require any subse-3 quent mechanical processing. On account of the force-free closure of the mould, the mould is also not damaged, at least if a suitable material has been chosen, and can thus be used repeatedly.
i However, even if the mould is closed with the use of force, and where necessaIy used only once, the device according to the invention is still distinguished from the known devices by the fact that the mould is closed in the starting material and can thus be closed more quickly without there being arly risk of air inclusions.

When energy is applied ~om one side, the mould half remote from the energy source can, in principle, be made from any ma~erial that is compatible with the crosslinkable or cross-linked material or components thereof. If metals are used, however, depending on the nature of the energy radiation the possibility of reflections must be expected, which may possibly result in undes~red ef~ects such as over-exposure, the formation of defects at the edges, or the like. Absorbent materials do not have those disadvantages.

In principle it is also possible to exploit in a controlled manner the diffrac~iorl and/or scatt~ring ef~ects of the radia~ion impinging upon the mould in order to produce a moulding wi~ a contour thae is intentionally not sharp or has somewhat rounded edges.
The same effect can also be achieved using masks with locally variable permeability. It is ~hus possible for sharp-edged rims of the moulding to be rounded in a controlled manner by con~olled i;ncomplete crosslinking and by partial dissolution of the incompletely rosslinked regions with a suitable solvent, which may also be the uncrosslinked starting matelial itself. Isopropanol, for example, is a suitable solvent wnen using HEMA(hyd~oxyethyl methacrylaee) as the stalting material.

Fur~ermore, it is clear ~at the device explained with reference to the Figures may also comprise several cavities instead of only one, so that several contac~ lenses can be produced simultaneously in ~ne cycle. That variarl~ is especially efficient.

In addition, in the v~iants with the piston-like mould member a throughflow con~rol can be effected in a controlled manner to the effect that ~Irst of all t}~e pistorl-like mould member is acted upon by force mechanically, and rclease of the starting ma~erial into the container as it is fed in is slightly delayed and release from the container as it is conveyed away is sligh~y delayed. This applies also to the variant in which both pumps are used and 2l289~ ~

the piston is driven mechanically. With this measure it is possible for a reduced pressure when feeding in, and a raised pressure when conveying away, to be generated in the container in a controlled manner, or for the pressure in the container to be influenced generally in that manner.

Also possible is a variant in which the number of cycles by which a new contact lens is produced is vatiable. For example, a sensor can detect whether a contact lens has actually been ~ushed out of the mould, and only when the sensor has detected such a flushed-out contact lens is t~e mould fully closed and a new contact lens produced. If the sensor has not detected a flushed-out contact lens, flushing of the mould is cont nued un~l the contact lens has been flushed out of the mould.

~or contact lenses CL tnere may be used as starting material that can be crosslinked by irradiation with UV light, for example, the HEMA~ (hydroxyethyl methacrylate) or poly-H~MA used widely for such pmposes, especially in admix~ure with a suitable crosslinker, such as, for example, ethylene glycol dimethacrylate. ~or other mo7,11dings, depending on the intended use other material may possibly be used and7 in principle, it iS also possible for other folms of energy, for example electron radiat;on, gamma radia~on, tnermal energy etc., ~ be used to ~igger crosslinldng depending on the nature of ~e crosslinkable ma~erial. In ~he manufac~e of contac~ lenses, materials that are crosslinkable by W light are generally cus~omary but not absolutely essential.

Suutable star~ng materials are in par~cular special prepolymers, e~ally those based on polyvinyl alcohol, that comprise cyclic acetal groups and crosslinkable groups.

Contact lenses based on pol~yl alcohol are a~ready kn~wn. For e7cample, contast lenses comprisillg p~lyvinyl alcohol that has (meth)acryloyll groups bonded by way of ure~ane ~sroups are disclosed, for example, in EP 216 074. Contact lenses made of polyvinyl alcohol crosslinked wi~ polyepoxides a~e described in EP 18~ 375.

Also already known arc some special acetals tha~ comprise crosslinkable g~oups.
Reference is made in ~at connec~on7 for example, to EP 201 693, EP 215 245 and FP 211 432. EP 201 693 describes, inter alia, acetals of unbranched aldehydes having from 2 to 11 carbon a~oms ~at caIry a terminal amino grollp which has been subs~tuted by a C3-C24-olefinically unsaturated organic radical. Iha~ organic radical has a fune~ion-ali~y which removes electrons rom the ni~rogen atom, and also the olefinically unsatur-~;
``~ 2~2891S

ated functionality is polymerisable. Also claimed in EP 201 693 are reaction products of the above-characterised acetals with a 1,2-diol, a 1 ,3-diol, a polyvinyl alcohol or a cellulose. Products of that kind are not, however, expressly described.
,i Inasmuch as one of the acetals according to EP 201 693 is mentioned at all in connection -, with, for example, polyvinyl alcohol, as is ~he case, inter alia, in Example 17 of that Patent Application, then the acetal polymerisable by way of i~s olefinic group is ISrst copolymer-'~,, ised, for example, with vinyl acetate. The copolymer so obtained is then reacted with polyvinyl alcohol, and an emulsion with a pH of 5.43 and a viscosity of 11640 cps which contains 37 % solids is oôtained.
.~.
In con~ast, according to one aspect of the p~esent invention, the prepolymers comprise a 1,3-diol basic structure in which a certain percentage of the 1,3-diol units have been modified to a 1,3-dioxane having in the 2-position a radical ~hat is polymerisable but not polymerised. The polymerisable radical is especially an aminoalkyl radical having a polymerisable group bonded to the nitrogen atom.

The prepolymer according to the invention is prefe~ably a deri~ative of a polyvinyl alcohol having a molecular weight of at least about 2000 tha~, based on ~e number of hydro~cy ~oups of the polyvinyl alcohol, comprises froin approximately O.S to approx-3 imately 80 % of units of formula I

\CH /CH2\CH /CH2 ,1 1 1 ~' \ CH / (I) ~,, I R1 , wherein R is lower alkylene hav;ng up to 8 carbon atoms, ~, Rl is hydrogen or lower aL~yl and R2 is an olefinically unsaeurated, elec~ron-a~erac~ing, copolymerisable ~dical preferably havint~ t p to 25 catbon atoms.

~ 2~289~

~5 R2 is, for exarnple, an olefinically unsaturated acyl radical of formula R3-co-, in which R3 is an ole~mically unsaturated copolymerisable radical having from 2 to 24 carbon atoms, preferably from 2 to 8 carbon atoms, especially preferably from 2 to 4 carbon atoms. ~ ano~er embodiment, the radical R2 iS a radical of formula II

~CO~NH~(R4~NH~CO~O)q-R5- 0~C0-R3 (II) wherein q is zero or one and R4 and Rs are each independently lower alkylene having fr~m 2 to 8 carbon atoms,arylene having from 6 to 12 carbon atoms, a saturated divalent cycloaliphatic grollp having from 6 to 10 ca:rbon atoms, arylenealkylene or alkylenearylene having from 7 to 14 carbon atorns or aryleneaLt~ylene~ylene having from 13 to 16 carbon atoms, and R3 is as de~med above.

The prepolymer according to the invention is therefore especially a de}ivative of a poly-vinyl alcohol having a molecular weight of at least about 2000 tha~, based on ~he number of hydroxy groups of the polyvinyl alcohol, comprises from approxirnately 0.5 to approx-imately 80 % of uni~s of f~mula III

~CH2~ /CH

\ C:H /
~R1 R N
\ [CO-NH-(R4-NH-CO-O)q-R5-C)~p-CO-R3 wherein R is lower aL~cylene, Rl is hydrogen or lower alkyl, p is zero or one, q IS zero or one, R3 is an olefimically unsaturated ~opolymerisable ~dical having from 2 to 8 carbon atoms and 212~91S

R4 and Rs are each independently lower aLlcylene having from 2 to 8 carbon atoms,arylene having from 6 to 12 carbon atoms, a saturated divalent cycloaliphatic group having from 6 to 10 carbon atoms, aryleneaLlcylene or aL1cylenearylene having from 7 to 14 carbon atoms or aryleneaLkylenearylene having from 13 to 16 carbon atoms.

Lower aLkylene R pre~erably has up to 8 carbon atoms and may be straight-chained or branched. Suitable examples include octylene, hexylene, pentylene, butylene, propylene, ethylene, methylene, 2-propylene, 2-butylene or 3-pentylene. Preferably lower aL~cylene R
has up to 6 and especially preferably up to 4 carbon atoms. The meanings methylene and butylene are especially prefe~red.

Rl is p~eferably hydrogen or lower alkyl having up to seven, especially up to four, carbon atoms, especially hydrogen.

Lower aLkylene R4 or Rs preferably has from 2 to 6 carbon atoms and is especially straight-chained. Suitable examples include propylene, butylene, hexylene, dimethyl-ethylene and, especially preferably, ethylene.

Arylene R4 or Rs is preferably phenylene that is unsubstituted or is sllbstituted by lower alkyl or lower aLkoxy, especially 1,3-phenylene or 1,4-phenylene or methyl-1,4-phenylene.

A saturated divalen~ cycloalipbatic group ~4 or R5 is preferably cyclohexylene or cyclo-hexylene-lower aLIcylene, for example cy~lohexylenemethy3~ne, that is unsubstituted or is substituted by one or more methyl groups9 such as, for example, trimethylcyclohexylene-methylene, for example the divalent isophorone radical.

T'he arylene unit of aL~ylenearylene or aryleneaLkylene R4 or R5 is preferably phenylene, unsubstituted or substituted by lower aLI~yl vr lower aL~coxy, and the aLkylene unit l:hereof is preferably lower aL~ylene, such as methylene or ethylene, especially methylene. Sueh radicals R4 or R~ are therefore preferably phenyleneme~ylene or me~ylenephenylene.

A~yleneaL~ylenearylene R4 or Rs is preferably phenylene-lower alkylene-phenylenehaYing up to 4 carbon atoms in the aL~ylene unit, for example phenyleneethylene-phenylene.

~12891~

The radicals R4 and R5 are each independently prefe,rably lower aLIcylene having from 2 to 6 carbon atoms, phenylene, unsubs~ituted or substituted by lower aL~yl, cyclohexylene or cyclohexylene-lower aLlcylene, unsubstituted or subs~dtuted by lower aL1cyl, phenylene-lower alkylene, lower allylene-phenylene or phenylene-lower aLIcylene-phenylene.
Wi~in the scope of this invention, the term "lower" used in connection with radicals and compounds denotes radicals or compounds having up to 7 carbon atoms, preferably up to 4 carbon atoms, unless defined othenvise.

l~wer aLkyl has especially up to 7 carbon atoms, preferably up to 4 carbon atoms, and is, for example, rtlethyl, ethyl, propyl, butyl or ~ert-butyl.

Lower aLIcoxy has especially up to 7 carbon atoms, preferably up to 4 carbon a~oms, and is, for example, methoxy, ethoxy, propoxy, butoxy or teit-butoxy.

The olefinically unsaturated copolymerisable radical R3 having from 2 to 24 carbon atoms is preferably aL~enyl having ~rom 2 to 24 carbon a~orns, especially aLI~enyl h~ving from 2 to 8 carbon atoms and especially preferably aLIcenyl having from 2 to 4 carbon atoms, for example ethenyl, 2-propenyl, 3-propenyl, 2-butenyl, hexenyl, octenyl or dodecenyl. The meanings ethenyl and 2-prop~onyl are pre~eIIed, so ~at ~he group -Co-R3 is the acyl radical of acrylic or medlacrylic acid.

The divalen~ group ^R4-NH-Co-o- is pIesent when q is one and absent when q is zero.
Prepolymers in which q is zero are pre~e~d.

The divalent group -Co-NH-(~4-NH-Co-o)q-E~s-O- is present when p is one and absent when p is zer~. Prepolymers in which p is zero are pref~

In prepolymers in which p is one ~he index q is preferably zero. Prepolymers in which p is one, the index ~q is zero and Rs is lower allylene are especially preferred.

A preferred prepolymer according to ~e invention is theIefore especially a derivative of a polyvinyl alcohol having a molecular weight of at least about 2000 that, based on ~e number of hydroxy groups of ~e polyvinyl alcohol, comprises ~om approximately 0.5 to a~proximately 80 % of units of fonnula Il~ in which R is lower alkylene having up to 6 carboll atoms, p is zero and R3 is aLlcenyl having from 2 to 8 carbon atoms.

``\
2 1 2 8 ~

A further preferred prepolymer according to the invention is therefore especially a derivative of a polyvinyl alcohol having a molecular weight of at least about 20ûû that, based on the number of hydroxy groups of the poly vinyl alcohol, comprises fIom approx-imately 0.5 to approximately 80 % of units of formula I:~ in which R is lower aLI~ylene having up to 6 carbon atoms, p is one, q is ~ero, R5 iS lower alkylene having from 2 to 6 carbon atoms and R3 is aL~enyl having from 2 to 8 carbon atoms.

A further preferred prepolymer according to the invention is therefore especially a derivative of a polyvinyl alcohol having a molecular weight of at least about 2ûOû that, based on the number of hydroxy groups of the polyvinyl alcohol, comprises from approx-imately 0.5 to approximately 80 % of units of formula m in which R is lower aLkylene having up to 6 carbon atoms, p is one, q is one, R4 is lower alkylene having from 2 to 6 carbon atoms, phenylene, unsubstituted or substiltuted by lower aL1~yl, cyclohexylene or cyclohexylene-lower alkylene, unsubstituted or substituted by lower alkyl, phenylene-lower aLtcylene, lower alkylene-phenylene or phenylene-lower aL~cylene-phenylene, Rs is lower aLlcylene having firom 2 to 6 carbon atoms and R3 is alkenyl having from 2 tO 8 carbon atoms.

The prepolymers according to the invention are derivatives of polyvinyl alcohol having a molecular weight of at least about 2000 that, based on the number of hydroxy groups of the polyvinyl alcohol, comprises from approximately 0.5 to approximately 80 %, especially approximately from 1 to 50 %, preferably approximately from 1 to 25 %, preferably approximately from 2 to 15 % and especially preferably approximately *om 3 to 10 %, of units of formula III. Pr~polymers according to the inven~on which are provided for the manufacture of ~on~act lenses comprise, based on the number of hyd~oxy groups of the polyvinyl alcohol, especially from approximately 0.5 to app~oximately 25 %, especially approximately from 1 tO 15 % and especially preferably approximately ~om 2 to 12 %, of units of formula III.

Poly~rinyl alcohols ~at can be derivatised in accordance with the invention pTefer~ly have a molecular weight of a~ least 10 00(). As an upper limit the polyvinyl alcohols may have a molecular weight of up to 1 Qûû 000. Preferably, the polyvinyl alcohols have a molecular weight of up to 300 ûOI), especially up to approximately 100 000 and especially preferably up to approximately 5û 000.

2~2891~

Polyvinyl alcohols suitable in accordance with the invention usually have a poly(2-hydroxy)ethylene s~ructure. The polyvinyl alcohols Iderivatised in accordance with the invention may, however, also comprise hydroxy groups in the form of 1,2-glycols, such as copolymer units of l,~-dihydroxyethylene, as may be obtained, for exarnple, by the aLkaline hydrolysis of vinyl acetate/vinylene carbonate copolymers.

In addition, ~e polyvinyl alcohols deriva~dsed in accordance with the invention may also comprise small p~opor~ons, for exarnple up to 20 %, preferably up to 5 %, of copolym~r units of ethylene, propylene, acrylamide, methacrylamide, dimethacrylamide, hydroxy-ethyl methacrylate, methyl methacrylate, methyl acrylate, ethyl acrylate, vinylpynolidone, hydroxyethyl acrylate, allyl alcohol, styrene or simil~r customarily used comonomers.

Commercially available polyvinyl alcohols may be used, such as, for example, Vinol~
107 produced by Air P~ducts (MW = 22 000 to 31 000, 98 - 98.8 % hydrolysed3, Polysciences 4397 (MW = 25 000, 98.5 % hydrolysed), BP 14 p~oduced by Chan Chun,13lvanol~ 90 - 50 produced by DuPont, 11~-120 produced by Unitika, Moviol~8) 4-88, 10-98 and 20-98 produced by Hoechst. Other manufacturers are, for e~ample, Nippon C~ohsei ~Gohsenol g~)9 Monsanto (Gelvatol g~), Wacker (Polyviol~) and ~he Japanese manufacturers Kuraray, l:)enki and Shin-Etsu.

As already mentioned, it is also possible to use copolymers of hydrolysed vinyl ace~a~e, which are obtainable, for example, in the ~n of hydrolysed ethylene/vinyl acetate (EVA), or vinyl chloride/vinyl acetate, N-vinylpyrrolidonetvinyl acetate and maleic acid anhydride/vinyl acetate.

Pol~yl alcohol is usually prepared by hydrolysis of the corresponding homopolymeric polyvinyl acetate. In a prefeiTed em~diment, the polyvinyl alcohol deriva!dsed in accordance wi~ the invention comprises less dl~ 50 % of polyvinyl acetate units,especially less tlhan 20 % of polyvinyl acetate units.

The compounds comprising units of formula m may be prepared in a manner known ~rse. ~or example, a polyvinyl aiLcohol having a molecular weight of at least about 2000 that comprises ~ts of formula I~

-CH(OH)-C~2- (I~l) "~

... ~ ... . . .

. 2~2891~

may be reacted with approxima~ly from 0.5 to 80 %, based on the number of hydroxy groups of the compound of formula IV, of a compound of formula (V) R' R"

\ CH / (V) , I R1 R N /
\ lC~ NH~(R4~NH~CC)~O~q~R5~0]p~CO~R3 in which i, R' and R" are each independently hydrogen, lower alkyl or lower aLlcanoyl, such as ace~l or propionyl, and the o~er variables are as defined for formula m, especially in an acidic medium.

Alternatively9 a polyvinyl alcohol having a molecular weight of at least about 2000 that compIi~es units of formula IV may be reacted wi~ a compound of formula VI

R~ R~' \ CH / (VI) j I ~R1 R--N
¦- \H
in which ~e variables are as defined for the compound of formula V, especially under acidic condi~ons, and the cyclic acetal obtainable in that manner may then be reacted w~th a compound of formula VII

3 OCN~(R4~NH~CO~O)q~R5~~CO~R3 (VII) in which the vaIiables alre as defined ~or the compound of formula V.

Alternatively, dle leaction product of a compound of fonnula IV and a compound of .

~ 2-~289~

formula VI may be reacted, similarly to the product ob~ainable as descTibed above, with a compolmd of forrnula (VIII) X-Co-R3 (VIII) in which R3 is, for example, aL~cenyl having from 2 ItO 8 carbon atoms and X is a reactive group, for example etherified or esterified hydroxy, for example halogen, especially chlorine.

Compounds of formula V in which p is zero are known, for example, from EP 201 693.
Compounds of ~ormula VI are also described therein. Compounds of formula VII areknown Per se, or can be prepared in a manner known ~ se. ~n exarnple of a compound of formula VII in which q is zero is isocyanatoethyl methacrylate. An example of a compound of formula V~ in which q is one is the reaction product of isophorone diiso-cyanate with 0.5 equivalent of hydroxyethyl methacrylate. Compounds of formula vm are hlown ~ se; a typicakepresentative is methacryloyl chloIide. Compounds of foqmula V
in which p and/or q a~ 1 can be prepared in a manner known Per se from the above-mentioned compounds, ~or example by $eaction of a compound of fo~nula VI with is~
cyanatoethyl methacrylate or by reaction of a compound of formula VI with isopho~ne diisocyanate which has pTeviously been teTminated with 0.5 equivalent of hydroxyethyl metha~late.

Surprisingly the p~epolymers of formulae I and IlI are extraordinarily stable. This is unexpected for the person skilled in the art because~ ~or example, higher functional acrylates usually have to be stabilised. ~ such compounds are not stabilised then rapid polymerisation usually occurs. Spontaneous c~osslinking by homopolymerisa~on does not oceur, howev~r, with the prepolymers of the invention. The prepolymers of formulae I and I~ can furthermore be purified in a manner known ~ se, for example by precipitation with acetone, dialysis or ultrafiltration, ul~rafiltration being especially preferred. By means of that purification process the prepolymers o~ formulae I and m can be obtainesl in ext~emely pme fo~ or example in the folm of concen~ated aqueous solutions that arc free, or at least substantially free, f~om reaC~iDn products, such as salts, and starting materials, such as, for example, compounds of formula V or other non-polymeric consti~uents.

The prefelTed purification process for the prepolyme~s of the inveTItion, ultrafiltration, can `"\
2l28~9~

be carried out in a manner known ~ se. It is possible for the ultrafiltration to be carried out repeatedly, for example f~om two to ten times. Alternatively, the ultrafiltration can be carried out continuously until the selected degree of purity is attained. The selected degree of p~ity can in pnnciple be as high as desired. A suitable measure for the degree of p~ity is, for example, the sodium chloride content of the solution, which can be dete~mined simply in known manner.

The prepolymers of formulae I and m according to the invention are on the other hMd crosslirJkable in an extremely effective and controlled manner, especially by photocross-linking.
.
In the case of photocrosslinking, appropriately a photoinitiator is added which can initiate radical crosslinking. Examples thereof are farniliar to the person skilled in the art and suitable photoiniators that may be mentioned specifically are benzoin methyl ether, l-hydroxycyclohexylphenyl ketone, Daracure 1173 or Irgacure types. The crosslinlcing can then be tAggered by actinic radiation, such as, for example, UV light, or ionising radiation, such as, for example, gamma radiation or X-radiation.

The photopolymerisation is suitably carried out in a solvent. A suitable solvent is in principle any solvent that dissolves polyvinyl alcohol and the vinylic cornonomers optionally used in addition, for example water, alcohols, such as lower aL~anols, for example ethanol or methanol, also carboxylic acid amides, such as dimethylformamide, or dimethyl sulfoxide, and also a mixtuFe of suitable solvents, such as, for exa~ple, a mix~ure of water wi~ an alcohol, such as, for example, a wa~r/e~hanol ~r a w~ter/-methanol n~ixture.

The photocrossl~ng is ca~ried out preferably di~ec~ly from an aqueous solution of the prepolymers according to tbe invention, which can be obtained by the preferred pulifica-~on s~ep, ultrafiltration, where appropriate after the addition of an additional vinylic j ~ comonomer. For example, an approximately 15 to 40 % aqueous solution can be photo-crosslinked.

The process for the preparation of ~e polymers of the invention may complise, for example, photocro~sslinking a prepolymer comprising units of folmula I or ~I, especially in substantially pure form, that is to say, for example, a~ter single or repeated ukra-~lltration, pre~erably in solution, especially in aqueous solution, in the absence or presence ~i' '` ' ' ''' ' " " ' ' 21~9~.5 of an addi~ional vinylic comonomer.

The vinylic comonomer which, in accordance with the invention, may be used in addition in the photocrosslinking, may be hydrophilic or hydrophobic, or a mixture of a hydro-phobic and a hydrophilic vinylic monomer. Suitable vinylic monomers include especially those customarily used in the manufacture of contac~ lenses. A hydrophilic vinylic monomeX denotes a monomer that typically yields as homopolymer a polymer that iswater-solu~le or can absorb at least 10 % by weight of water. Analogously, a hydrophobic vinylic monomer denotes a monomer that typically yields as homopolymer a polymer that is water-insoluble and can absorb less than 10 % by weight of water.

Generally, approximately from O.ûl to 80 units of a typical vinylic comonomer react per unit of formula I or m.

If a vinylic comonomer is used, the crosslinked polymers according to the invention preferably comprise approximately from 1 to 15 %, especially preferably approximately from 3 to 8 %, of units of formula I os III, based on the number of hydroxy groups of the polyvinyl alcohol, which are reacted with approximately from 0.1 to 80 units of the vinylic monomer.

Il Irhe proportion of the vinylic comonomers, if used, is pre~erably f~m 0.5 to 80 units per unit of ~ormula I, especially from 1 to 30 units per unit of fonnula I, and especially preferably from S to 20 units per unit of formula I.

It is also lpreferable to use a hydrophobic vinylic comonomer or a ~xture of a hydrophobic vinylic comonomer with a hydrophilic vinylic comonomer, the mixture comprising at least 50 % by weight of a hydrophobic ~inylic comonomer. In that manner the mechanical properties of the polymer can be improved without the water cvntent falling substantially. In principle, however, both conventiollal hydrophobic vinylic comonomers and convelltional hydrophilic vinylic comonomers are suitable for thecopolymeIisadon with polyvinyl alcohol comprising groups of formula I.

Suitable hydrophobic vinylic comonomers include, wi~hout the list being exhaustive, Cl-Clgalkyl aclylates and methacrylates, C3-CI8aLcyl acrylamides and me~hacrylamides, I
ac~lonitrile, methacrylonitrile, vinyl-Cl-ClgaLkanoates, C2-Ct8aL~cenes, C2-C12hal~
enes, s~rene, Cl-C6allylstyrene, vinyl aLIcyl ethers, in which the alkyl moiety contains 212~9~

from 1 to 6 carbon atoms, C2-CIOperfluoroalkyl acrylates and methacrylates or corres-pondingly partially fluorinated acrylates and methacrylates, C3-CI2perfluoroalkyl-ethyl-thiocarbonylaminoethyl acrylates and methacrylatçs, acryloxy- and methacryloxy-aLI~ylsil-oxanes, N-vinylcarbazole, Cl-CI2alkyl esters of maleic acid, fumaric acid, itaconic acid, mesaconic acid and the like. Cl-C~,aL~cyl esters of vinylically unsaturated carboxylic acids having from 3 to 5 carbon atoms or vinyl esters of carboxylic acids having up to S carbon atoms, for example, are preferred.

Examples of suitable hydrophobic vinylic comonomers include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, rnethyl methacrylate, ethyl metha~ylate, propyl methacrylate, vinyl acetate, vinyl prop-ionate, vinyl butyrate, vinyl valerate, styrene, chloroprene, vinyl chloride, vinylidene chloride, acrylonitrile, l-butens, butadiene, methacrylonitrile, vinyltoluene, vinyl ethyl ether, perfluorohexyle~ylthiocarbonylaminoethyl methacrylate, isobornyl methacrylate, trifluoroethyl methacrylate, hexatluoroisopr~pyl methacrylate, hexafluorobutyl meth-acrylate, ~is-trime~ylsilyloxy-silyl-propyl me~acrylate7 3-methacryloxypropylpe methyldisiloxane and bis(methacryloxypropyl)tetramethyldisiloxane.

Sui~ble hydrophilic vinylic comonomers include, without the list being exhaustive, hydroxy-substituted lower aL~cyl acryla~es and methacrylates, acrylamide, methacrylamide, lower alkyl acrylamides and methacrylamides, ethoxylated acrylates and methacrylates, hydroxy-substituted lower alkyl acrylamides and methacrylamides7 hydroxy-substituted lower alkyl vinyl e~ers, sodium ethylenesulfonate, sodium styrenesul~onate, 2-acryl-amid~2-methylpropaneslJlfonic acid, N-vinylpylrole, N-vinylsuccinimide, N-vinyl-pyrrolidone, 2- or ~vinylpyridine, acrylic acid, medlacrylic acid7 amino- (the term "amino" also including quaternary ammonium~, mono-lower aL~ylamino- or di-lower allylamin~lower allyl acrylates and methacA~la~es, allyl alcohol and the like Hydroxy-substituted CrC4aLkyl(medl)acrylates, five- t~ seven-membered N-vinyl lactams, N,N-di-Cl-C4aLkyl(meth)acrylamides and vinylically unsaturated carboxylic acids having a total of ~om 3 to 5 carbon atoms, for example, a~e preferred.

Examples of suitable hydrophilic vinylic comonomers include hydroxyethyl methacrylate, hydroxyethyl acrylate, acrylamide, methacrylamide, dimethylacrylamide, allyl alcohol, vinylpyridine, vinylpyrr~lidone, glycerol methacrylate, N-(l,l-dimethyl-3-oxobutyl)-acrylamide, and the like.

21289~

Preferred hydrophobic vinylic comonomers are methyl methacrylate and vinyl acetate.

Preferred hydrophilic vinylic comonomers are 2-hydroxyethyl methacrylate, N-vinyl-pyrrolidone and acrylamide.

In the following Examples, unless e~pressly stated otherwise amounts are amounts by weight, and temperatures are in degrees Celsius. The Examples are not intended to limit the invention in any way, for instance to the scope of the Examples.

Example la): Over a period of 4 hours, 104.5 parts of methacryloyl chloride dissolved in 105 parts of dichloromethane are added dropwise at a maximum of 15C, while cooling with ice, to 10S.14 parts of aminoacetaldehyde dimethylacetal and 101.2 parts of trie~hyl-amine in 200 parts of dichloromethane. When the reaction is complete, the dichloro-methane phase is washed with 200 parts of water then with 200 pa~s of lN HCI solution, and then twice with 200 parts of water. After drying with arLhydrous magnesium sulfate9 the dichlororne~hane phase is concen~rated by evaporation and stabilised wi9~h 0.1 % of 2,6-di-tert-butyl-p-cresol, based on ~he reacdon product. After distillation at 90C/1~3 mbar, 112 g of methacrylarnidoacetaldehyd~ dimedlylacetal are obtained in the form of a colourless liquid, boiling point 92C/1~3 mb~r (65 % yield).

Example lb): ~2.6 g of aminoacetaldehyde dimethy1acetal are dissolved in 1~0 ml of deionised water and cooled to 5C with ice. SubseqLuently, 50 ml of methacrylic acid chloride and 50 ml of 30 % sodium hydroxide solution are simultaneously so added over a period of 40 minutes that the pH value remains at 10 and the temperat~e does not exceed 20C. When the addition is complete, ~he r~maining content of aminoacetaldehyde dimethylacetal is determined as 0.18 % by gas chromatography. The amine is reacted fully by ~e fur~er addition of 2.2 ml of methacrylic acid chloride and 2.0 ml of 30 % sodium hydroxide solution. The solution is then neutralised with lN hydr~chloric acid (pH = 7).
The aqueous phase is ex~¢acted with 50 ml of pe~oleum ether and washed with water. The pe~oleum ether phase contains 3.4 g of secondary product. The aqu~ous phases aIecombined and yield 402.8 g of a 20.6 % solution of methacryla~doacetaldehyde dimethylaceeal. According to a gas chromatogram, the product is 98.2 %.

Example 2: 10 parts of polyvinyl alcohol ha~ing a molecular weight of 22 0~) and a degree of hydrolysis of 97.5 - 99.5 % are dissolved in 90 parts of water, 2.5 parts of meth-acrylamidvacetaldehyde dimethylacetal a~e added and the mixture is acidified with 10 2 1 2 ~

parts of concentrated hydrochloric acid. The solution is stabilised with 0.02 parts of 2,6-di-tert-butyl-p-cresol. After stirring for 20 hours at room temperature, the solution is adjusted to pH 7 with 10 % sodium hydroxide solut;on and then ultrafiltered seven times using a 3kD membrane (ratio 1:3). After concentration, an 18.8 % aqueous solution of methacrylamidoacetaldehydo-1,3-acetal of polyvinyl alcohol having a viscosity of2240 cP at 25C is obtained.

Example 3: 10 parts of the solution of methacrylamidoacetaldehydo-1,3-acetal of polyvinyl alcohol obtained in accordance with Example 2 are photochemically crosslinked by adding 0.034 parts of Darocure 1173 ((:IBA-GEMY) thereto. The rnixture is irradiated in the forrn of a 100 micron thick layer between two glass plates with 200 pulses of a 5000 watt irradiation device produced by Staub. A solld transparen~ film with a solids content of 31 % is obtained.

Example 4: 110 g of polyvinyl alcohol (Moviol 4-88, Hoechst) are dissolved at 90C in 440 g of deionised water and cooled to 22C. 10().15 g of a 20.6 ~o aqueous solution of methacrylamidoacetaldehyde dimethylacetal, 38.5 g of concentrated hydrochloric acid (37 % p.a., Merck) and 44.7 g of deionised water are added thereto. The mL~cture is sti~red at room temperature for 22 hours and then adjusted to pH 7.0 wi~ a 5 % NaOH solution.
The solu~ion is diluted to 3 litres with deionised water, filtered and ultrafilte~d using a Omega membrane produced by Fil~on. After the thIee-~old specimen volume has permeated, the solution is concentrated. 660 g of a 17.9 % solution of the methacrylamido-acetaldehydo-1,3-acetal of pDlyvinyl alcohol having a viscosity of 210 cp are obtained.
The inherent viscosity of the polymer is 0.319. The nitrogen content is 0.96 %. According to NMR investigadon, 11 mol % of the OH groups have been acetalised and S mol % of the OH groups acetylated. Concentration of the aqueous polymer solution under reduced pressure and with air draft yields a 3û.8 % solution ha~ing a viscosity of 3699 cp.

Example S: 66.6 g of deionised wa~er, 3.3 g of monomenc 4-methacrylamidobutyr-aldehyde diethylacetal and 20.0 g of concen~ated hyd~ochloric acid (37 % p.a., Merck) are added ta 133.3 g of a lS % polyvinyl alcohol solution (Moviol 4-88, Hoechst) and the mixture is stirred at room temperature for 8 hours. The solution is then adjusted to pH 7 with ~ % sodium hydroxide solution. After ultrafiltration of the solution wsing a 3-KD-Omega membrane produced by Filtron, ths sodium chloIide content ~ the polymer solution being reduced from 2.07 % to 0.04 %, a 20 % polymer soluLion of the methacryl-amidobutyraldehydo-1,3-acetal of polyvinyl alcohol having a viscosiey of 4~ cp is obtained. The inherent viscosity of the polymer is 0.332. The nitrogen content is 0.41 %.
According to NMR inv~stigation, 7.5 mol % of the OH groups are charged with acetal groups and 7.3 mol % of the OH groups are charged wi~h acetate groups.

Example 6: 2.4 g (14.8 mmol) of aminobutyraldehyde diethylacetal (Fluka) and 20 g of concentrated hydrochloric acid (37 ~b p.a., Merck) are added to 200 g of a 10 % polyvinyl alcohol solu~ion (Moviol ~88, Hoechst). The solution is stirred at room temperature for 48 hours and then neutralised wi~h 10 % sodium hydroxide solution. The solution is diluted to 400 ml. 200 ml of the solution are further processed in accordance with Example 7. 0.8~ g (8.1 mmol) of me~acrylic acid chloride (I ~luka) is added to the remaining 200 ml of the solution and ~e pH value is maintained at 10 with 2N sodium hydroxide solution. After 30 minutes at room ~emperature, the pH is adjusted to 7.0 and the solution is purified analogously to axample 5 using a 3-KD-Omega membrane produced by Piltr~n. Concenbration yields a 27.6 % polymer solution of dle methac~yl-arnidobutyraldchydo- 1,3 acetal of polyvinyl alcohol having a viscosity of 2920 cp. The inherent viscosity of the polymer is 0.435. The nitrogen content is 0.59 %.

E~ample 7: 1.3 g (8.5 mmol) of 2-isocyanatoethyl me~acrylate are added to 200 ml of the polym~r solution of 13xample 6 and the pH maintained at 10 with 2N sodium hydroxide solution. After 15 minutes at roorn temperature the solution is neu~alised with 2N hydro-chloric acid and ultrafiltered analogously to Example 6. Concentra~ion yields a 27.1 %
polymer solution of the 4-(2-methacryloylethyl-ureido~butyraldehydo-193-acetal of poly-vinyl alcohol having a viscosity of 2320 cp. The inhe~ent viscosi~ of ~e polymer is 0.390. The nitrogen content is 1.9 %.

Example 8: 0.7 % Darocur 1173 lbased on the content of polymer) is added to the 30.8 %
polymer solu~on according to Example 4 ha~ing a viscosi~ o~ approximately 3600 cp.
The solution is introduced into a ~ansparen~ contact lens mould of polypropylene and the mould is closed. The solution is i~adiated for 6 seconds from a distance of 18 cm using a 200 wa~t Oriel UV lamp. T'sle mould is opened and the finished contact lens can be removed. The contact lens is transparent and has a water content of 61 %. The modulus is 0.9 mPa, the flexural elongation (DIN S3 371) 50 %. The contact lens is autoclaved for 40 minutes at 121C. No changes in shape can be detected in a contact lens ~eated in that manner.

Example 9: 0.0268 g of Da~ocur 1173 (0.7 % based on the polymer content~ and 0.922 g 21 2891 ~

.
of methyl methacrylate are added to 10.00 g of a 27.1 % polymer solution according to Example 7. After the addition of 2.3 g of methanol a clear solution is obtained. That solution is irradiated for a period of 14 seconds analogously to Example 8, using a 200 watt Oriel lamp. A transparent contact lens having a water content of 70.4 % is obtained.

Example 10: 1.04 g of acrylarnide and 0.03 g of Darocur 1173 are added to 12.82 g of a 24.1 6 % solution of the prepolymer of Example 4. The clear solution is then irradiated for 14 seconds analogously to Exarnple 8, using a 200 watt Oriel lamp. A contact lens having a water content of 64.4 % is obtained.

The polymers according to the invention can be processed in a manner known 1~ se into mouldings, especially contact lenses, for example by carrying out the photocrosslinking of the prepolymers according to the invention in contact lens moulds in the manner described in detail fiJrther above. Further examples of mouldings according to the invention, besides contact lenses, are biomedicinal or especially oph~almic mouldings, for example intraocular lenses, eye bandages, mouldings that can be used in surgery, such as heart valves, artificial arteries or the like, and also films or membranes, for example membranes for diffusion control, photos~ructurizable films for information storage, or photoresist materials, for example membralles or mouldings ~or etch resist or screen printing resist.

Contact lenses tha~ comprise a polymer according to the invention as described above or consist substantially or wholly of such a polymer have a wide range of unusual and extremely advantageous properties, which include, for example, their excellent compat-ibility with the human cornea, which is based on a balanced relationship of water content, oxygen permeability and mechanical properties. The contact lenses according to the invention furthermore exhibit a high degree of dimensional stability. No changes in shape are de~ected even after autoclaving at, ~or example, about 120C.

Attention may also be drawn to the fact that such contact lenses can, as described, be produced in a very simple and efficient manner compared with ~he state of the art. This is as a result of several factors. E~irst, the starting materials can be obtained or produced a~ a favourable cost. Secondly, there is the advantage that the prepolymers are suIprisingly stable, so that they can be subjected to a high degree of purification. It is there~ore possible to use for the cr~sslinking a material that requires practically no subsequent purifica~on, such as especially a complicated extraction of unpolymerised constituents.

2~2~9~5 - 39 ~

Also, the polymerisation can be calried out in aqueous solution, so that a subsequent hydration step is not necessaIy. Finally, the photopolyme~isation occurs within a short period, so that the process for manufac~ing ~e contact lenses according to ~e invention can be organised to be ex~emely economical from that point of view also.

All of the advantages mentioned above naturally ~p]ply not only to contact lenses but also to other mouldings according to the invention. Taking into account all the various advant-ageous aspects in dle manufacture ~f the mouldings according to the invention it can be seen dlat ~e mouldings according to the invention ~ue especially suitable as mass-produced ~icles, such as, for example~ con~t lenses that are worn for a short time and then replaced by new _ses.

Claims (42)

1. A process for the manufacture of mouldings (CL), especially optical lenses, specifically contact lenses, from a starting material (M) that is crosslinkable by the impingement of suitable energy (3), in a mould (1) that is at least partially permeable to the energy con-cerned and that has a mould cavity (15) determining the shape of the moulding (CL) to be produced, the starting material (M) being introduced into the mould (1) in a still at least partially uncrosslinked state, and mould crosslinked in that mould, to a degree sufficient for it to be possible for the moulding to be released from the mould, by impingement of the energy (3) concerned, wherein the filling of the mould cavity (15) is carried out in the starting material (M) that is still at least partially in the uncrosslinked state.

2. A process according to claim 1, wherein for filling the mould cavity (15) the cavity is connected to a reservoir (R) which surrounds it, in which the starting material is stored and from which the mould cavity (15) is flooded.

3. A process according to either claim 1 or claim 2, wherein the mould (1) is closed in the starting material.

4. A process according to any one of the preceding claims, wherein a mould is used that comprises a container (10a, 10b) and a mould member (11a, 11b) that is displaceable in that container and can be moved away from and towards the container wall (100a, 100b) lying opposite it for the purpose of opening and closing the mould, starting material being fed in between the container wall (100a, 100b) and the mould member (11a, 11b) as the mould is opened and conveyed away again as the mould is closed.

5. A process according to claim 4, wherein a mould (1) having two mould halves is used in which one mould half is provided on the container wall (100a, 100b) and the other mould half is provided on the displaceable mould member (11a, 11b).

6. A process according to claim 5, wherein a mould having a male mould half and a female mould half is used, the male mould half being provided on the container wall (100a, 100b) and the female mould half being provided on the displaceable mould member (11a, 11b).

7. A process according to any one of claims 4 to 6, wherein pumps (P1, P2) are used to feed in and convey away the starting material.

8. A process according to any one of claims 4 to 6, wherein the displaceable mould member (11a, 11b) is driven in order to feed in and convey away the starting material.

9. A process according to any one of claims 1 to 8, wherein the crosslinked moulding (CL) can be released from the mould by flushing out the mould with starting material.

10. A process according to any one of claims 4 to 8, and according to claim 9, wherein the moulding (CL) is separated from the mould by the flow of starting material as the mould is opened and is flushed out of the mould by the flow of starting material as the mould is closed.

11. A. process according to claim 9, wherein in a first cycle the mould is opened and closed again, then at least the crosslinking necessary for it to be possible for the moulding (CL) to be released from the mould is effected by the impingement of energy (3) and, in a second cycle, the mould is opened again, the moulding being separated from the mould and the mould member (11a) then being moved back towards the opposite-lying container wall (100a) again in order to close the mould, in the course of which the crosslinked moulding is flushed out of the mould.

12. A process according to any one of claims 1 to 8, wherein the crosslinked moulding is removed from the mould by means of a gripping device (4).

13. A process according to any one of claims 4 to 8 and according to claim 12, wherein the moulding (CL) removed from the mould by the gripping device (4, 4b) is deposited on the displaceable mould member (11b) outside the space between the displaceable mouldmember (11b) and the opposite-lying container wall (100b).

14. A process according to claim 13, wherein the moulding deposited on the displaceable mould member is held fast thereto by negative pressure (NP) and then released from it by positive pressure (HP).

15. A process according to any one of claims 1 to 14, wherein the mould is not fully closed after the introduction of the starting material into the mould cavity, so that an annular gap (16) containing uncrosslinked starting material remains open, which gap surrounds the mould cavity and is in communication with that mould cavity.

16. A process according to claim 15, wherein the mould is closed further following cross-linking shrinkage as crosslinking of the material progresses.

17. A process according to claim 16, wherein a starting material that is of at least viscous flowability prior to the crosslinking is used, and wherein starting material can flow back through the annular gap (16) into the mould cavity (15) to compensate for shrinkage.

18. A process according to any one of claims 1 to 17, wherein the starting material is a prepolymer that is a derivative of a polyvinyl alcohol having a molecular weight of at least about 2000 that, based on the number of hydroxy groups of the polyvinyl alcohol,comprises from approximately 0.5 to approximately 80 % of units of formula I
(I) wherein R is lower alkylene having up to 8 carbon atoms, R1 is hydrogen or lower alkyl and R2 is an olefinically unsaturated, electron-attracting, copolymerisable radical preferably having up to 25 carbon atoms.

19. A process according to claim 18, wherein the starting material is a prepolymer wherein R2 is an olefinically unsaturated acyl radical of formula R3-CO-, in which R3 is an olefin-ically unsaturated copolymerisable radical having from 2 to 24 carbon atoms, preferably from 2 to 8 carbon atoms, especially preferably from 2 to 4 carbon atoms.

20. A process according to claim 19, wherein the starting material is a prepolymer wherein R3 is alkenyl having from 2 to 8 carbon atoms.

21. A process according to claim 18, wherein the starting material is a prepolymer wherein the radical R2 is a radical of formula II

-CO-NH-(R4-NH-CO-O)q-R15-O-CO-R3 (II) wherein q is zero or one and R4 and R5 are each independently lower alkylene having from 2 to 8 carbon atoms,arylene having from 6 to 12 carbon atoms, a saturated divalent cycloaliphatic group having from 6 to 10 carbon atoms, arylenealkylene or alkylenearylene having from 7 to 14 carbon atoms or arylenealkylenearylene having from 13 to 16 carbon atoms, and R3 is an olefinically unsaturated copolymerisable radical having from 2 to 24 carbon atoms, preferably from 2 to 8 carbon atoms, especially preferably from 2 to 4 carbon atoms.

22. A process according to claim 18 wherein the starting material is a derivative of a polyvinyl alcohol having a molecular weight of at least about 2000 that, based on the number of hydroxy groups of the polyvinyl alcohol, comprises from approximately 0.5 to approximately 80 % of units of formula III

(III) wherein R is lower alkylene, R1 is hydrogen or lower alkyl, p is zero or one, q is zero or one, R3 is an olefinically unsaturated copolymerisable radical having from 2 to 8 carbon atoms and R4 and R5 are each independently lower alkylene having from 2 to 8 carbon atoms,arylene having from 6 to 12 carbon atoms, a saturated divalent cycloaliphatic group having from 6 to 10 carbon atoms, arylenealkylene or alkylenearylene having from 7 to 14 carbon atoms or arylenealkylenearylene having from 13 to 16 carbon atoms.

23. A process according to claim 22, wherein the starting material is a prepolymer wherein R is lower alkylene having up to 6 carbon atoms, p is zero and R3 is alkenyl having from 2 to 8 carbon atoms.

24. A process according to claim 22, wherein the starting material is a prepolymer wherein R is lower alkylene having up to 6 carbon atoms, p is one, q is zero, R5 is lower alkylene having from 2 to 6 carbon atoms and R3 is alkenyl having from 2 to 8 carbon atoms.

25. A process according to claim 22, wherein the starting material is a prepolymer wherein R is lower alkylene having up to 6 carbon atoms, p is one, q is one, R4 is lower alkylene having from 2 to 6 carbon atoms, phenylene, unsubstituted or substituted by lower alkyl, cyclohexylene or cyclohexylene-lower alkylene, unsubstituted or substituted by lower alkyl, phenylene-lower alkylene, lower alkylene-phenylene or phenylene-lower alkylene-phenylene, R5 is lower alkylene having from 2 to 6 carbon atoms and R3 is alkenyl having from 2 to 8 carbon atoms.

26. A process according to claim 18, wherein the starting material is a derivative of a polyvinyl alcohol having a molecular weight of at least about 2000 that, based on the number of hydroxy groups of the polyvinyl alcohol, comprises from approximately 1 to approximately 15 % of units of formula I.

27. A device for the manufacture of mouldings (CL), especially optical lenses, specifically contact lenses, having a closable and openable mould (1) that has a mould cavity (15) determining the shape of the moulding to be produced, which mould is intended to receive a crosslinkable starting material and is at least partially permeable to energy (3) that causes the crosslinking of the starting material and is supplied from the outside, and having an energy source (2a) and also means (2b) for the impingement of the energy upon the mould, wherein during filling of the mould cavity (15) the mould cavity is arranged in starting material (M) that is still at least partially in the uncrosslinked state.

28. A device according to claim 27, which comprises a reservoir (R) for supplying the starting material, which reservoir surrounds the mould cavity (15) and can be connected to the mould cavity (15), and wherein during filling of the mould cavity the reservoir (R) is connected to the mould cavity (15) and floods that cavity.

29. A device according to either claim 27 or claim 28, which comprises means (1a), for closing the mould (1) arranged in the starting material.

30. A device according to any one of claims 27 to 29, wherein the mould comprises a container (10a, 10b) and a mould member (11a, 11b) displaceable in that container, which mould member can be moved away from and towards the container wall (100a, 100b) lying opposite it for the purpose of opening and closing the mould, and wherein there is provided in the container an inlet (101a, 101b) through which starting material flows in between the container wall (100a, 100b) and the mould member (11a, 11b) as the mould is opened, and wherein there is provided in the container an outlet (102a, 102b) through which starting material flows out again as the mould is closed.

31. A device according to claim 30, wherein the mould comprises two mould halves, one mould half being provided on the container wall (100a, 100b) and the other on the displaceable mould member (11a, 11b).

32. A device according to claim 31, wherein the mould comprises a male mould half and a female mould half, and wherein the male mould half is provided on the container wall (100a, 100b) and the female mould half is provided on the displaceable mould member (11a, 11b).

33. A device according to any one of claims 30 to 32, wherein pumps (P1, P2) areprovided which, as the mould is opened, feed in starting material through the inlet (101a, 101b) and between the container wall (100a, 100b) and the mould member (11a, 11b) and, as the mould is closed, convey starting material away again through the outlet (102a,

34. A device according to any one of claims 30 to 32, wherein means are provided for driving the displaceable mould member (11a, 11b).

35. A device according to any one of claims 27 to 34, wherein means are provided for producing a flow that separates the moulding from the mould when the mould is opened and flushes the moulding out s)f the mould when the mould is closed.

36. A device according to any one of claims 30 to 32 and according to claim 35, wherein, in a first cycle, starting mateIial first of all flows in through the inlet (101a) and between the container wall (100a) and the displaceable mould member (11a) and then flows back out through the outlet (102a), the energy source (2a) then acts upon the mould with an amount of energy (3) necessary for it to be possible for the moulding to be released from the mould, and then, in a second cycle, starting material flows in through the inlet (101a) and between the container wall (100a) and the displaceable mould member (11a), separates the moulding (CL) from the mould and then flushes it out through the outlet (102a).

37. A device according to any one of claims 27 to 34, wherein a gripping device (4) is provided which removes the crosslinked moulding (CL) from the mould.

38. A device according to any nne of claims 30 to 34 and according to claim 37, wherein the container (10b) comprises, on a container wall (103b) other dlan the shape-giving face (102b), a hollow or recess (104b) that extends substantially in the direction of movement of the displaceable mould member (11b), the gripping device (4b) being arranged in that hollow or recess (104b), and wherein the displaceable mould member (11b) comprises, on an outer wall (113b) 1hat does not lie opposite the shape-giving container wall (100b), an indentation (114b) in which the gripping device (4b) deposits the removed moulding (CL).

39. A devise according to claim 38, wherein the displaceable mould member comprises a channel (115b) that leads to the indentation (114b) and can be connected to a negative pressure or positive pressure source (P3), whicb channel (115b) is connected to the negative pressuIe souuce when the glipping device (4b) deposits the removed moulding (CL) in the indentation (114b) of the mould member (11b) and then is connected to the positive pressure source in order to release the lens.

40. A device according to any one of claims 31 to 39, wherein the mould is provided with spacers (19) that hold the two mould halves a small distance apart from one another when the mould is in the closed position, so that an annular gap (16) is formed that surrounds the mould cavity (15) and is in communication with that cavity.

41. A device according to claim 40, wherein the mould is provided with resilient means or displacement means that allow the two mould halves to move closer together following crosslinking shrinkage.

42. A moulding (CL), especially an optical lens, specifically a contact lens, produced in accordance with the process according to any one of claims 1 to 17.