US 3887417 A
A process for making a melded fabric comprising forming a web of randomly arranged continuous filaments wherein the continuous filaments can increase in length by at least 3%, subjecting the web to a treatment to effect said increase in length of the said filaments whilst restraining the web from change in length or width so as to produce a filament configuration within the web wherein at least 10% of the filaments lie at an angle of between 45 DEG and 90 DEG to the plane of the web at the mid-plane of the web, and subsequently bonding the web so that the ratio of the number of bonds to the number of filaments in the plane of greatest bonding parallel to the surface of the fabric is between 0.05 and 0.2.
Description (OCR text may contain errors)
United States Patent 1191 Davies 1 June 3,1975
[ NON-WOVEN FABRICS  Inventor: Barrie Linton Davies, Pontypoal,
England  Assignee; Imperial Chemical Industries Limited, London, England  Filed: Nov. 3, 1971  Appl. No.: 195,203
Related US. Application Data  Division of Ser No. 817,796, April 21, 1969.
 US. Cl. 156/181; 156/62; 156/183;
156/306; 161/150; 161/157 [51 Int. Cl D04h 3/08  Field of Search 161/57, 58, 59, 72, 75,
FOREIGN PATENTS OR APPLICATIONS 932.483 7/1963 United Kingdom 161 Primary ExaminerGeorge F. Lesmes Assistant Examiner-Paul .I. Thibodeau Arrorney, Agent, or FirmCushman, Darby & Cushman [5 7] ABSTRACT A process for making a melded fabric comprising forming a web of randomly arranged continuous filaments wherein the continuous filaments can increase in length by at least 3%, subjecting the web to a treatment to effect said increase in length of the said filaments whilst restraining the web from change in length or width so as to produce a filament configuration within the web wherein at least 10% of the filaments lie at an angle of between 45 and 90 to the plane of the web at the mid-plane of the web, and subsequently bonding the web so that the ratio of the number of bonds to the number of filaments in the plane of greatest bonding parallel to the surface of the fabric is between 0.05 and 0.2.
8 Claims, 5 Drawing Figures NON-WOVEN FABRICS This is a division of application Ser. No. 817,796, filed Apr. 21, I969.
The invention relates to improvements in melded fabrics and to methods for making them, and relates particularly to improvements in melded fabrics comprising continuous filaments and a process for making them.
By melded fabrics we mean fabrics having fioriform structure consisting of an assembly of filaments which is consolidated by the inter-engagement of the filaments at cross over points or junctions between contiguous filaments, whether or not such inter-engagement involves coalescence of the filaments.
Melded fabrics comprising continuous filaments are already known, such fabrics being made by depositing continuous filaments on a moving surface by filament advancing means such as rotating rolls or air ejection devices to form a uniform filamentary sheet, which is subsequently stabilised and strengthened by bonding adhesively the filaments of the sheet. Physical properties such as drape, tear strength, breaking strength, extension to break, wear resistance and aesthetic properties such as handle or prior art melded fabrics can be varied widely depending upon the particular process by which they are made, important structural factors affecting these properties being the distribution of filaments and the nature of bonding. Melded fabrics having adequate physical properties have in general been those possessing a structure such that the individual filaments are well separated from each other and such that the adhesive which binds the filaments together is present only at filament cross-over points and is not spread between and around filaments elsewhere. We have found however, that, even when such conditions are complied with, the prior art fabrics although possessing the desired physical properties, do not possess the highly desirable handle and wear properties of woven or knitted fabrics and it is an object of the present invention to provide melded fabrics comprising continuous filaments which have superior handle and wear properties compared with prior art melded fabrics.
Our invention is based on our discovery that when the dynamic friction between two samples of the same melded fabric is low, the fabric has a good and attrac tive handle. This concept is entirely new and important, since it had not been realised before our discovery that this property, among others relating to handle, was particularly lacking in prior art melded fabrics.
Accordingly, the present invention comprises, in one of its aspects a melded fabric comprising a sheet of continuous filaments interconnected throughout the sheet by a multiplicity of bonds between contiguous filaments and having a fabric surface fabric surface dynamic coefficient of friction (hereinafter referred to, for convenience, as the coefficient of friction) not greater than 0.4 and an abrasion resistance as hereinafter defined of at least 300 cycles.
Coefficient of friction of a melded fabric is measured by the following test. A sample of the unlubricated fabric is clamped to a flat horizontal surface by means of a horseshoe-shaped weight. A portion of the same unlubricated fabric is firmly wrapped without crinkles or folds round a block of Perspex (Registered Trade Mark) having a rectangular cross-section of dimensions 5 cm. length by 3 cm. width, and 6.5 mm. thickness to form a sledge with the ends of the fabric clamped together on the top surface of the sledge. An inextensible cord incorporating a calibrated strain gauge is attached to one of the ends of the sledge and the sledge is placed in contact with the fixed fabric. The sledge is loaded to give a pressure P between the fabric surfaces of between lg/cm and Sg/cm and the horizontal force F in grams required to tow the sledge (by means of the attached cord) across the fixed fabric at a speed of 2.5 mm/sec. is measured by means of the strain gauge. The coefficient of friction as used herein is defined as being the value of F/lSP and is not greater than 0.4 for fabrics of the present invention.
Abrasion resistance as used in this specification is measured on a Martindale tester which abrades a horizontally clamped test sample, the abrasion area being circular and having an area of about cm.". The abrader is a disc of 10 cm area, covered with a worsted abradant cloth and the rate of abrasion is 1 cycle per second. The abradant cloth has a weight of 187 gm. and is composed of 2 X 32s worsted yarn, having [2.5 t.p.i. Z twist in the singles and 12.5 t.p.i. S twist in the doubled yarn, as warp; and 2 X 24s worsted yarn, having 10.5 t.p.i. Z twist in the singles and 10 t.p.i. S twist in the doubled yarn, as weft. The fabrics are inspected after different numbers of abrandant cycles for surface loops by folding the fabric to form a sharp edge and the abrasion resistance is measured as the number of abradant cycles before more than two filament loops of at least 2 mm. length appear per cm. of edge. The fabrics of the present invention run for at least 300 cycles before such loops appear.
One way in which melded fabrics can be provided with the preferred frictional and abrasion resistance properties of the invention is by arranging for filaments to be in a particular configuration in the fabric and bonded by particular bonding characteristics, the configuration of filaments being such that at least 10%, preferably 25% or more of the filaments crossing the mid-plane of the fabric do so at an angle of between 45 and to the plane of the fabric and the bonding characteristics being such as to provide between 0.05 and 0.2 bonds per filament as defined hereinafter at the plane of greatest bonding. Such a filament configura tion in addition can provide the fabrics with an attractive crinkled appearance due to the undulations of the constituent filaments which are present in the configuration.
The configuration of filaments within the fabrics and the bonding characteristics of fabrics may be determined by examining sections in the plane of the fabrics, the sections being prepared as follows.
Small blocks of an optically clear methacrylate resin (HT cement supplied by Hopkin & Williams Ltd.) are prepared by curing in small cylindrical gelatine capsules (size 0 supplied by Parke Davis and Co.) for 3 hours at 80C. The block of methacrylate resin is then removed from the capsule by softening the gelatine in water and stripping off. The block is placed in a jig and sawn into two along its mid plane. Rough edges are removed by carefully trimming with a sharp blade.
10 mm. X 5 mm. samples are cut from the melded web and immersed firstly in destabilised butyl methacrylate monomer, secondly, surface coated with the aforementioned HT cement and finally inserted between the halves of the previously prepared methacrylate cement block, taking care not to distort or compress the web sample.
The assembly is then inserted into a gelatine capsule similar to that used in preparation of the block and cured for 2 hours at 60C to 65C and then for 2 3 hours at 80 85C. We have found that this procedure greatly reduces the possibility of bubble formation within the fabric sample. After curing and cooling, the gelatine capsule is removed in the same way as before and the sample block is mounted on a microtome specimen holder in such a way that sections parallel to the plane of the melded fabric sample can be cut. Microtome sections of thickness about lOum are cut from the assembly in the plane of the melded fabric sample and are mounted on glass slides for microscope examination. using medicinal paraffin as immersion fluid to avoid any interaction with the embedding matrix. Photomicrograph records are then made of web sections using standard white light illumination with a bluegreen filter in, for example, a Zeiss Photomicroskop- POL apparatus. Positive prints of X 150 magnification about X cms. size are prepared for determining the filament configuration and bonding characteristics as follows.
To determine the configuration of the filaments within the sample, mid-plane sections of the fabric are examined.
Filaments perpendicular to the plane of the section will appear as circles in the photographs and filaments for example at 45 to the section plane will appear as ellipses of 1.4 major/minor axis ratio. Filaments lying at smaller angles to the plane of the section will appear as much more elongated ellipses which may be distorted by the curvature of the filament path within or relative to the plane of the section. The configuration of the filaments is obtained by counting the total number of filament cross-sections (NJ appearing in the mid plane section and counting, conveniently by means of a graticule, the number of filaments (N whose indi vidual cross-section shape lies between a circle and an ellipse of axial ratio 1.4. The percentage of filaments lying at angles between 45 and 90 to the plane of the section is given by N /N X lO0%.
The bonding characteristics of the sample are determined by examining the plane parallel to the plane of the fabric containing the greatest number of bonded filaments. ln uniformly bonded structures the plane of greatest bonding is the mid-plane section. Bonds which occur within the thickness of the crosssection are readily recognised in the photographs since the boundaries of each individual filament appear as a continuous dark line under the conditions of illumination and dif fering refractive index between filaments and surrounding matrix resin. Where two filaments are bonded by fusion this optical contrast disappears over the length of the bonded peripheries and the dark line boundary then continuously encloses the areas of the two bonded filaments.
The extent of bonding of filaments in the web is measured by counting the total number of filaments (N appearing in the section and by counting the number of bonds between filaments (N The number of bonds per filament is defined as N /N The mid-plane section is readily obtained by microtoming the entire thickness of the fabric sample into sections and selecting the centre section. We have found. however. that for many melded fabrics there is little or no variation in filament configuration and number of bonds per filament within 1 10% of the thickness around the midplane section and consequently it is often sufficient to cut a section in the vicinity of the mid-plane of the fabric sample.
We have found that melded fabrics having configuration of filaments and bonding characteristics required to give the preferred frictional and abrasion resistance properties can be prepared from continuous composite filaments having a potentially adhesive component, the filaments being such that they increase in length by at least 3%, preferably at least l0% after the web is formed and before the filaments of the web are bonded together to form a fabric. Accordingly the invention comprises in another of its embodiments a process for making a melded fabric having superior handle and abrasion resistance properties to prior-art melded fabrics in which a melded web comprising continuous composite filaments is formed, the composite filaments comprising two or more fibre-forming synthetic polymeric components, at least one of which components comprises at least a proportion of the periphery of each filament and is capable of being rendered adhesive without substantially affecting the remainder of each filament, the filaments being such that they can increase in length by at least 3% preferably 10% or more. subjecting the web to a treatment to effect the said in crease in length in the filaments of the web whilst restraining the web, so as to produce a filament configuration in which at least 10%, preferably 25% or more of the filaments, crossing the mid-plane of the web, lie at an angle of between 45 and to the plane of the web, and subsequently subjecting the web to a treatment to render adhesive the aforesaid component so as to provide between 0.05 and 0.2 bonds per filament in the web at the plane of greatest bonding.
The continuous filament webs may be made by any method. but particularly useful methods involve the use of air ejectors which forward and deposit the filaments onto, say, a foraminous moving surface to form the webs. Provided that the fabric obtained by the process of this invention possesses the required filament configuration and bonding characteristics, the continuous filaments may be composed of more than one species. some of which may not, for example. increase in length on treatment. The filaments may be laid in a random manner or may be laid in a plurality of merging and overlapping substantially parallel bands with the filaments in each band being randomly arranged and the web may contain only composite filaments containing a binder component or may contain such filaments in admixture with other filaments. When laying the continuous filaments to form the web by means of an air ejector. we have found that the proportion of the filaments crossing the mid plane of the fabric product at angles between 45 and 90 is increased as the air pressure applied to the air ejector is increased.
The continuous filaments of this aspect of the invention must be chosen so that they can be made to increase in length by at least 3%, preferably at least 10% or more whilst in the web, and before the web is bonded. Such filament grown may take place merely by exposure to the atmosphere or by the application of some suitable treatment, for instance, a heat or solvent or swelling agent treatment. This capability of length increase of the filaments is to be distinguished from increase in length of filaments by application of pressure to certain parts of the web, for instance, during embossing.
It is necessary that the web be restrained from increase in length and width whilst the filaments are treated to increase in length. This may be done by rolling the web up with interleaving paper to form a swiss roll" structure under controlled tension conditions or by restraining the web between belts or plates at least one of which is preferably perforated or porous to allow the filaments of the web to be more effectively exposed to the treatment causing their length increase. By restraining the web whilst length increase takes place, configuration is imparted to the structure and additionally an attractive crinkled surface is imparted to the web, the actual restraining force depending upon the particular configuration desired, but preferably being between 0.05 p.s.i. and 5.0 psi. perpendicular to the plane of the web. If the pressure is too low when the undulations of the crinkled effect are too widely spaced to be useful and if the pressure is too high then the undulations are too narrowly spaced, or may not be produced at all. The surface appearance and filament configuration can also be further controlled by allowing the filaments to utilize part of their capability for length increase without the application of any restraining pressure and carrying out further length increase with the application of restraining pressure.
The crinkled appearance of the surface so obtained is not a regular effect, the undulations occurring for short lengths and in all directions and the surface is to be contrasted with that formed by forming a sheet of filaments with a Concertina fold wherein the undulations extend parallel to each other across the width of the fabric.
The filaments capable of length increase used in this embodiment of the present invention may comprise a freshly-spun low birefringence polyamide component or components, the filaments being capable of increasing their length on exposure to heat or moisture. The length increase may take place on exposure of the polyamide to the atmosphere or to heat and is found to take place rapidly on exposure to steam. For example, we have found that filaments of polyhexamethylene adipa mide, optionally sheathed with a copolymer of hexamethylene adipamide and epsilon caprolactam, having a birefringence of between 0.002 and 0.04, preferably between 0.006 and 0.035 increase in length on exposure to heat or moisture to the extent required by this aspect of the present invention. Alternatively the filaments may be capable of increasing their length by virtue of previous processing treatments applied to the filaments.
The use of continuous composite filaments compris ing two or more fibre forming synthetic polymeric components, at least one of which components occupies at least a proportion of the periphery of each filament and is capable of being rendered adhesive without substantially affecting the remainder of each filament provides a particularly useful and convenient method of bonding the fabrics to produce the desired bonding characteristics. When bonding methods including, for instance, the use of non-fibrous binders or homogeneous binder fibres are used, then the binder flows into at least some of the interstices of the structure thus bonding together filaments which are not in contiguous relationship and generally imparting a harsh and stiff handle and decreased flexibility to the structures. When composite filaments, as defined above, are used the adhesive component does not fiow excessively, but remains associated with the non-adhesive components of the filaments producing bonds only where some of the filaments touch.
The components used for the composite filaments should be such that one component occupying at least a proportion of the periphery of the filaments can be rendered adhesive without affecting the remainder and the component may, for instance, become adhesive at a lower temperature than the remainder under the particular bonding conditions chosen or may be rendered adhesive by a solvent of such a type and/or in such a concentration that it does not render the remainder adhesive. Thus, when, for instance, the unaffected component is poly(hexamethylene adipamide) or poly- (ethylene terephthalate), the component to be rendered adhesive may comprise, for instance poly(epsi lon caprolactam) or a copolymer of hexamethylene adipamide and epsilon caprolactam, or poly(omega aminoundecanoic acid), a copolymer of hexamethylene adipamide and hexametbylene sebacamide.
The arrangement and proportions of the components of the composite filaments will depend on the treatment utilised to effect the required length increase and the bonding characteristics required. We have found that, especially when a polyamide is incorporated in the filaments, the component to be rendered adhesive may usefully form a sheath around the remainder of the filaments or may be present in the form of a narrow strip extending along the surface of the filaments.
The use of composite filaments in the webs of the present invention is preferred as a suitable means of obtaining the correct bonding conditions. Their known use as potentially crimpable filaments (depending on structure configuration) is in no way related to the requirement for increase in length in the filaments and the filament configuration in the web obtained thereby, although composite filaments which increase in length and in addition are potentially crimpable are not excluded from the invention.
The length increase of the filaments must take place in a separate stage before the binder component is rendered adhesive and may be effected by exposure to the atmosphere or by the exposure to heat, for instance, by treating with steam.
British Pat. Ser. No. 932,483, relates to a melded web containing at least by weight of synthetic organic spontaneously elongateable fibres, the term "spontaneously elongateable" indicating that the fibres are capable of elongating spontaneously at least 3% upon heating at a temperature 30C above the second order transition temperature of the fibres for 5 minutes. The process involves forming a web which is treated in such a way that the fibres elongate and the structure is bonded. The specification teaches that it is essential that some bonding occurs before all of the desired amount of elongation is completed, and likewise it is essential that some elongation occurs before all of the desired amount of bonding is completed. Preferably, both bonding and elongation takes place simultaneously. The process of the present invention is distinguished from the process described in British Pat. Ser. No. 932,483 by the essentiality of causing the continuous filaments to increase in length before the bonding treatment, there being no increase in filament length during or after the bonding treatment.
We have found that the products described in British Pat. No. 932,483 do not have the combination of abrasion resistance and frictional properties of the fabrics of the present invention and we therefore believe that it is an essential requirement that, in order to obtain the desired combination of properties increase in filament length and bonding of the web should be accomplished in separated steps.
The bonding step may involve the use of heat or solvents, but ifheat is used it is preferable to have at least some steam present to prevent degradation of the poly mers of the filaments. When using heat the actual temperature employed depends upon the temperature at which the binder component is rendered adhesive by the particular heat treatment used and, depending on the amount of binder component used. care may have to be exercised to prevent the binder component from attaining too high a temperature, C to 10C above that at which it becomes adhesive usually being sufficient. When dry heat bonding this temperature will generally be around the melting point of the component, but if bonding is carried out in an atmosphere which solvates or placticises the adhesive, for instance saturated steam is used for rendering a polyamide adhesive then the temperature at which the polyamide is rendered adhesive is much lower than the dry heat melting point, and such use provides easier tempera ture control, savings in cost and also generally protects and preserves the quality of the filaments as a whole. When solvent bonding is used the type and concentration of the solvent is selected depending on the various components used in order to attain the required bonding characteristics. Pressure may be applied during bonding, i.e., whilst the binder component is adhesive, and may be more or less than the restraining pressure applied during the filament length increase treatment.
It may be possible, depending on the nature of the filaments in the web, to effect length increase in the filaments and to cause the web to bond in the same apparatus, whilst still satisfying the requirement that increase in filament length is completed before bonding is started. For example, suppose that a particular type of filament increases in length as it is heated up to a temperature of 120C, but further increase in temperature does not produce further increase in length. Sup pose further that the potentially adhesive component of the filament becomes adhesive at 180C. It would be FIG. 1 is a representation of a photograph of a perpendicular section through the fabrics of the present invention after an abrasion resistance test;
FIG. 2 is a representation ofa section in the plane of the bonded fabric at its midplane,
FIG. 3 is a representation of the bonded fabric as seen through a scanning electron microscope.
FIG. 4 is a representation of a plan view of the sur face of the fabric; and
FIG. 5 is a representation of the optical diffraction pattern obtained from a photographic negative of the surface represented in FIG. 4.
EXAMPLE 1 Continuous bicomponent core-and-sheath composite filaments, the proportions of sheath to core being 35:65, the sheath comprising a :30 copolymer of hexamethylene adipamide and epsilon caprolactam and the core comprising poly(hexamethylene adipamide), were extruded from a 28 hole composite filament spinneret at an extrusion temperature of 280C. The filaments were split into 4 groups of 7 filaments and the groups were fed into 4 air ejectors supplied with air at psi. and traversing linearly across a foraminous conveyor belt, advancing perpendicularly to the direction of traverse of the air ejectors. The air ejectors drew down and forwarded the filaments and deposited them on the conveyor in a random manner to produce a web weighing 1.9 ozs/sq.yd. and the web was wound up in 25 yard lengths, interleaved with tissue paper in a swiss roll fashion.
The 25 yd. roll of web was then treated with saturated steam in an Autosetter (Andrew Engineering Company Ltd. Bulwell. England) at 35 p.s.i., the steaming cycle involving the application of vacuum for 2 minutes to produce a vacuum of 22 inches of mercury, followed by 2 minutes introduction of saturated pressure steam followed by 2 minutes exhaust and the cycle being repeated twice more. Increase in length of filaments was achieved partly during exposure to the surrounding atmosphere (without restraint) and partly whilst restrained during the steaming treatment. The web was unwound from the roll and found to be adhesively bonded and possess excellent handle and drape. Properties of the bonded web were measured in the machine direction (L) and in the cross-direction (X) then feasible to pass the web through an oven having 50 and found to be as follows:
Mean Wt/area Density Bending Flexural Breaking "/1 Extension Breaking Tear Tear Thickness gm/m gm/cm length Rigidity Load at Break strength Load Factor cm cm mg. cm. kg Kg/gm/cm kg Kg g/cm Machine Direction Ullifi 64.4 0.115 3.35 242.35 2.38 121.8 146.0 1.66 O (126 L Cross- Direction 3.27 225.69 2.111 140.5 1230 I58 0.025 X a temperature of C and to produce a bonded structure according to the present invention, since the filaments are heated at a finite rate (albeit rapidly) and their increase in length occurs at temperatures distinct from and lower than, the bonding temperature.
The invention will now be described in more detail with reference to the following examples and figures of which.
The bending length was measured as described in British Standard method 3356 by measuring the length of a 1 cm. wide strip of the web which, extending over an edge from a horizontal platform, bends to such an ex tent that the leading edge of the strip touches a plane passing through the platform edge and inclined downwards from the horizontal at an angle of 41.5". The bending length is equal to half the measured length.
The flexural rigidity was calculated from the bending length and the web weight using the formula Flexural Rigidity 0.1 W C mg. cm. where W is the weight of the fabric in gm. and C is the bending leng th in cm.
The breaking load and extension at break were mea sured on an lnstron Tensile Tester using rectangular sample strips, measuring 2.54 cm. width and 10 cm. be tween clamps, the strips being extended at 10 cm./min. rate of extension and the Breaking Load being the max imum load reached. The Breaking strength was calculated by dividing the Breaking Load by the weight of the strip expressed as gms/cm length of strip.
The Tear Load was also measured on an lnstron Tensile Tester using rectangular sample strips measuring 5.] cm. in width and 10.2 cm. in length, each strip having a cut 7.6 cm. long in the middle of the strip and extending from one end along the longest axis of the strips. The tails on opposite sides of the cut were gripped in the clamps of the tester and pulled apart at 10 cm/min, the Tear Load being the average peak load recorded during the tear of 2.5 cm. along the uncut length of the strip.
The coefficient of friction of the bonded web was measured by the technique described hereinbefore and found to be 0.27 and the abrasion resistance was also measured by the technique described hereinbefore and found to be at least 300 cycles, FIG. 1 showing a representation of the web surface after 300 abradant cycles. Sections in the plane of the fabric at the mid-plane were taken by the technique described hereinbefore, a typical representation of such a section being shown in FIG. 2. From the sections taken, the percentage of filaments lying between 45 and 90 to the plane of the fabric was calculated at 45% and the number of bonds per filament at 0.18 bonds per filament.
A scanning electron-microscope view of the bonded web is shown in FIG. 3 and illustrates the fact that there is no spread of adhesive into the interstices of the web, the adhesive being confined to areas at which the filaments are in contact.
A view of the surface of the web enlarged by a factor of 1.33 is shown in FIG. 4, the surface of the web hav ing being lightly contacted with an inked roller, so that the crests of the undulations are inked but the troughs are not, the figure showing the crinkled surface affect obtained and the random nature of the undulations.
A quantitative measure of the randomness and the spacing of the undulations of the web surface can be obtained by photographing a 30 cm. X 30 cm. square sample of the inked web with transmitted and reflected light with a size reduction factor of 24 and then placing the photograph negative in a parallel beam of monochromatic light from a filtered mercury arc source. The Fraunhofer diffraction pattern produced is then recorded on film using a 500 mm focal length lens, a view of the diffraction pattern obtained, enlarged by a factor of 10, being shown in FIG. 5. A measure of the average spacing of the undulations is obtained from the diame ter of the pattern and a measure of the randomness from the angular intensity distribution of the pattern.
EXAMPLES 2 7 The following series of Examples illustrates the importance of using filaments which increase in length to form fabrics of the present invention. In this series continuous bicomponent core and sheath composite filaments were used, the sheath being 35% of the area of the filament and comprising a :30 copolymer of hexamethylene adipamide and epsilon caprolactam and the core being poly(hexamethylene adipamide). 40 such filaments were extruded from a composite filament spinneret at an extrusion temperature of 272C. Ten of the filaments were used, the remainder being collected as waste. The threadline was taken in a 180 wrap around each of three feed rolls, then in a total wrap of 580 around 4 draw rolls before being fed to a single traversing air ejector as used in Example 1. The threadline was drawn in a controlled manner between feed rolls and draw rolls: the speed of the latter was maintained at 685 m./min. The 10 filaments were deposited to form a web as in FIG. 1. 6 webs were made with different draw ratios. The webs were wound up in terleaved with paper and were treated in a similar manner to that described in Example I.
The resulting bonded webs were examined and tested, and the results appear in Table 2.
Samples of the filaments used in each Example were collected below the air ejector and were rapidly pinned to a vertical board and a 0.1 g tensioning weight was attached. The length of the sample was measured. The filament samples with the tensioning load removed were then exposed to saturated steam at a pressure of 1 atmosphere for 1 minute, and then were allowed to condition under ambient conditions (i.e., the conditions under which the first length measurements were made) for 120 minutes. The filaments were reloaded and the growth expressed as a percentage of the original length was calculated. These results also appear in Table 2.
TABLE 2 Ratio: Bending Flexural Breaking Breaking Example Draw Roll Speed Wt/Area Density Length Rigidity Load Extension Strength Feed Roll Speed (gm' l (g/crn) [cm.) (mg.cm.) (kg) at BreakUX (Kg/g/cm) L 1.875 4I (ll 19 3.6 l'9l.5 I72 35 I 2 X 3.9 244.] L62 I70 3 L L62 4" ().I l4 3.l [I I55 44 X 3.3 141.8 1.76 167 L l.4l 39 Ill i3 3.0 1052 I45 50 I57 4 X 3,] H62 L31 I33 I. l 25 35 (N31 2.2 37.3 l.4l 67 I62 5 X 2. 426 L55 163 L I I5 3i 0.094 2 l 32.5 L44 8. I80 6 X 2.1 32.5 1.68 1% L l.ll5 34 H.097 2.3 4L4 |.5fi 78 I119 7 X v .3 414 L35 I64 TABLE 2 Continued 4 Abrasion Filaments Filament Example Tear Tear l-actor Coefficicnt Resistance inclined Bonds per Mean Period growth in Load (Kglglcm) of Friction at 300 at 40 Filament of Crinkle saturated (k Cycles 9017!) (mm) steam Filamentation L 1.04 0.0252 0.265 greater than 0.014 -41 2 Specified X 0.96 0.0233 v l. 1.27 0.0317 0.259 0 0.006 3.1 3
X l 14 0.0285 L 1.70 0.0436 0.322 0 0.010 -0.9 4
X l. 0.0295 L 1.05 0.0298 0.291 Filamentation 16 0.052 1.65 +3.i 5 as specified X 1.22 0.0348 L 0.90 0.0291 0.329 No Filamen- 17 0.062 1.55 +70 6 tation L Machine Direction X Cross Direction An examination of the results tabulated in Table 2 shows that the filaments of Examples 2, 3 and 4 shrink on exposure to saturated steam and that they do not and were treated in an atmosphere of saturated stearr at 50 p.s.i.g. for 5 minutes. The sample had the follow ing properties.
TABLE 3 Bending Flexural Breaking Breaking Tear Example Wt/area Density Length Rigidity Load Extension to Strength Load Tear Factor (g.m) (g.cm*) (cm) tmgcm.) (Kg) Break (7%) (Kg) (kg) (Kg/g/cm 2) Filaments Coefficient Abrasion Resistance inclined Bonds per Mean Period of Filament Growth Mean Spun Example of Friction at 300 Cycles at Filament Crinkle (mm) in Saturated Bire 90 (71] Steam (70) fringence L 0.4 No filamentation 27.5 0.05 2.3 7.5 0.0147
therefore fall within the requirements of our invention. It will be noted further that these Examples do not satisfy the abrasion test requirements, neither the number of bonds per filament nor the filament configuration. On the other hand, filaments of Examples 5. 6 and 7 increase in length appreciably on exposure to pressurised saturated steam and that physical properties. filament configuration and number of bonds per filament fall within the scope of the invention.
It should also be noted that the fabrics of Examples 5. 6 and 7 show markedly lower flexural rigidity than samples 2. 3 and 4 and therefore have improved drape.
EXAMPLE 8 Ten bi-component filaments consisting of 79% poly(hexamethylene adipamide) and 21% copolymer of hexamethylene adipamide (70%) and epsilon eapro lactam (30%), the latter component forming a potentially adhesive strip along the filament, were sprayed by a traversing air ejector situated below the spinning assembly on to a foraminous conveyor advancing pe rpendicularly to the direction of traverse of the air ejector. The webs were wound up interleaved with tissue paper The use of such filaments produces a fabric which falls within the scope of the invention. The fabric had a soft. pleasant handle, good drape and was hard wearing and was suitable for use as an apparel fabric.
EXAMPLE 9 The fabrics of the present invention are characterised by low friction and good abrasion resistance. Samples of commercially available bonded melded fabrics comprising continuous filaments were tested to compare their friction and abrasion resistance with the fabrics of the present invention.
Sample 9A comprised a web containing continuous filaments of poly(ethylene terephthalate) with a small proportion of continuous filaments of a copolyester having a lower melting point than the poly(ethylene terephthalate) filaments. The structure had been bonded by a treatment which caused the copolyester filaments to melt, flow and envelope portions of the poly(ethylene terephthalate) filaments.
Sample 913 comprised a web containing continuous filaments of poly(epsilon caprolactam) bonded with a polyacrylate latex material.
The properties of samples 9A and 9B are compared with those of the fabric of Example 6 below.
What I claim is:
1. in a process for making a non-woven fibrous web of continuous filaments bonded at their cross-over points, said process being of the kind including the steps of forming a web of continuous filaments of a type which are capable of elongating at least 3% and effecting elongation and bonding of the filaments at their cross-over points while restraining the web from change in length or width, the improvements comprising effecting and completing the elongation of said filaments under said restraint before said bonding step, and subsequently effecting said bonding step without effecting any increase in filament length so as to produce a filament configuration within the web wherein at least 10% of the filaments lie at an angle of between 45 and 90 to the plane of the web at the mid-plane of the web, thereby producing a web having improved handle and wear properties.
2. A process as in claim 1 wherein the improvement further comprises using as said continuous filaments composite filaments having at least two fibre-forming synthetic polymeric components, at least one of which forms at least a portion of the periphery of each filament and is capable of being rendered adhesive without substantially affecting the remainder of each filament.
3. A process as in claim 1 wherein the filaments include polyamide filaments.
4. A process as in claim 1 wherein the filaments include polyamide bi-component filaments having a birefringence of between 0.0025 and 0.04.
5. A process as in claim 4 wherein one component of the bi-component filaments comprises poly(hexamethylene adipamide) and the second component comprises a copolymer of hexamethylene adipamide and epsilon caprolactam and is situated to form at least a portion of the peripheral surface of the filament.
6. A process as in claim 4 wherein the step of elongating the filaments is carried out by exposing the web to moisture.
7. A process as in claim 4 wherein the step of elongating the filaments is carried out by exposing the web to an atmosphere of steam at atmospheric pressure.
8. A process as in claim 4 wherein the step of elongating the filaments is carried out by exposing the web to saturated pressurized steam.