DE2051529A1 - Polymer tubular foil extruder - Google Patents

Abstract

Extruder has a rotary extrusion nozzle provided with an annular channel and interconnected with the extruder by a holder having a rotary flow path for ejection of the extrudant along sectors of the annular channel within the nozzle.

Description

Device and method for extruding tubular plastic film The invention relates to a method and an apparatus for extruding a Tubing made of plastic film, in which the flow of the molten polymer Materials in the extruder in a new way and with a new flow path from Inlet guided to the outlet of the device is moved to the desired flow properties to achieve.

There have been numerous attempts to regulate the flow of the polymer melt carried out in an extruder for the production of tubular film.

For example, it is known to use a film tube to create an inner age and an appearance, which take turns Helical and spiral paths limit flow in an extruder as shown in U.S. Patent 3,376,705.

Another example is U.S. Patent 3. # 18,687, which describes an extruder with a double forked guide inlet with a holder for improvement which shows flow properties.

Although these patents and other flow control devices for a polymer They show melt but do not show flow control to achieve better ones Flow properties in which the melt is guided through a novel flow path is which flow path is directed so that the outlet in the form of a rotating Current takes place in the circumferential direction around the annular channel of the extrusion nozzle.

The advantages of using a rotating pUee when extruding of polymeric material in tubular form are known per se. Although it appears has that in this type of rotating nozzle the polymer flows within the annulus The nozzle also revolves around slight errors or imperfections in the Polymer stream, which flows with a laminar flow, is to be randomly distributed this is not the case. Rather, the tubular stream of the polymer moves within the annulus essentially directly to the nozzle lips, instead of with the rotating part of the nozzle unit during the forward movement of the material to the To run around nozzle lips. This has many disadvantages. On these disadvantages belongs the fact that whenever the tube-shaped matter is wound up on a roller the many thousands of layers have the tendency. to emphasize the. so that an unsatisfactory variable thickness roll is obtained. Furthermore if an imperfection occurs in the polymer flow, which inevitably occurs even with a large Care is the case when the electricity comes back together, recalls "the polymer, that it has been separated and there is a "weld line", which is a weak one Place in the tube wall of the film after the extrusion causes or cause can. When the current is discharged or when a device is used for the Exit of the polymeric material in the circumferential direction around the annular space in the hose extrusion nozzle around, therefore, the aforementioned problems are substantially reduced.

The invention provides a device for regulating the polymer flow before extrusion in the production of tubing made of plastic film with improved I) lIY-sical or strength properties as well as a decay created which can be carried out by the device at the appropriate star, In the Manufacture of plastic film for a variety of uses, it is known improve their properties by increasing the flow of the polymeric material is regulated in the extruder before the tubular film is formed. This usually happens in that the heated material, i.e. the polymeric melt, is controlled by a control device is conveyed or guided with a helical or spiral flow path.

Nevertheless, in the manufacture of such films by known methods the tubular film, if it is formed in the usual manner, one or more Zones or

Areas of greater or lesser thickness than the hose (hence Thickness fluctuations) caused by imperfections or changes the polymer flow are caused, which in turn has the consequence that an uneven The course of the polymeric material in the extruder is produced.

When extruding polymeric materials in web or

Tubular shape it is known that the thickness or strength of the film, you Volume weight and roll formation characteristics of the hose all immediately due to the smoothness of the flow of the polymer Material through the extrusion die and other parts of the extruder, for example the lialtevorrichtung, which is between the usual screw conveyor and the extrusion head is arranged, regulated or determined. For example, when the hose # wraps every continuous and standing change in hose thickness comes on the to lie with others, so that the cumulative effect creates a hard streak Od. The like. Builds up, which deforms the coil, whereby the usability is impaired and waste is created. Furthermore, there are congestion zones in the flow path in the flow device and undesirable in the extruder scoring head because the polymeric material undergoes degradation and a poor quality film is obtained, especially when particulate be extruded from a degraded polymer. This causes the foil to break and an undesirable appearance of the fo # ie.

The device according to the invention is a device for extrusion polymeric material in the form of a tube made of plastic film with a loading device for the polymer material, a rotating extrusion nozzle with an annular channel and associated die lips for extruding the polymeric material in the form of a Hose, a lialtevorrichtung, which the loading device with the rotating extrusion nozzle connects and one rotating stream outlet flow path share for the exit long circumference of the annulus within the rotating Has extrusion nozzle.

The holder of the device preferably has inner and outer elements with surfaces that delimit a polymer material flow channel between them, wherein the inner and the outer element are rotatable with respect to each other, the Strömwig Canal comprises a first flow path which is essentially tubular, and a second rotating flow path which communicates with the first flow path and in which at least the downstream part of the flow path has the shape of a stream. It is even more preferred that parts of the surfaces of the inner and the outer member have substantial contact with each other to create the tubular To convert flow path into a current flow path. It is even more in a smooth way it is preferable that the surfaces of the inner and appearance elements be helical Limiting courage with a single inlet that connects the first path with the second flow path connects, Further, it is preferable that the helical groove be a single one Has outlet which is connected to the annular space of the extrusion nozzle.

With the device described above, in the most expedient Way a process can be carried out in which the polymeric material in the form a tube made of plastic film is extruded through a rotating nozzle, which has an annular space in which the po nier material to a rotating Stream shaped and into the annulus of the rotating extrusion nozzle in the circumferential direction directed or caused to emerge. In an even more preferred embodiment of the aforementioned The material becomes special along the way radially spaced parts of the annular space to emerge.

When a current flows, the flow is like within a pipe to understand, while under hose flow a flow course is to be understood, which is similar to the walls of a hose, such as when there is material between flows through the indene of concentrically arranged tubes.

When applying the method according to the invention and when using it The novel flow guidance and control device for this can be made of polypropylene and Polyethylene films with excellent properties and very high uniformity in thickness achieve, for the widest possible range of uses.

In the accompanying drawings: FIG. 1 shows a side view in elevation of an extruder according to the invention showing a polymer material feeder and shows an extrusion nozzle connected to one another by a holder according to the invention are connected; Fig. 2 is a sectional view showing in more detail the Holder part of the extruder with its novel polymer material flow control device shows; 3 shows a development of the flow paths of the polymer material flow control device according to Fig. 2, in which the hatched area is that part of an inner element of the holder, which is in contact with a wall of a separate element of the holder is located; Fig. 4 is a partial sectional view of a modified one Holder of an extruder according to the invention; 5 shows a development of the flow control device the age of Fig. 4; 6 shows a partial view in section of a further embodiment the holder of an extruder according to the invention; 7 shows a development of the flow control device des lialters of Figures 6 and Figures 8 and 9 are graphs showing performance results show when using the extruder according to the invention; Description of the preferred Embodiments In the drawing is a fiction, according to device 10 for Conveying flowable polymeric material and extruding this material in the form of a sculpture made of plastic film, for example made of polypropylene film, with which a film of improved physical properties can be obtained can be.

From Figs. 1 and 2 it is particularly evident that polymeric material the device 10 according to the invention is supplied from a supply source (not shown) and through a polymer material feeder 20 in a holder 30 is moved or conveyed through which the polymer in one novel route to an extrusion nozzle 40 from which the polymer flows in shape a tube T is extruded.

From Fig. 2 it can be seen in particular that the polymer material feed device 20 of any suitable and conventional type and, for example, a screw conveyor may be, which has a cylindrical outer part 21 and a screw conveyor element 22 has, which latter is rotatable within the appearance part 22 to the polymer Material in flowable form with the aid of the webs 23 from a filling - ': inlet opening (not shown) to a feed exit port 24 to move forward.

The polymeric material that is in molten form from the feeder 20, flows into and through the holder 30, which controls the direction of flow of the material changed by 900. The molten polymer enters the holder 30 by means of a line 31 and through a line 32, which the course of the material gradually changed as shown in FIG. The polymer material flows through lines 31 and # w into holder 30 and through inlet 33 into a general with 34 designated polymer flow control device in the holder, which is so formed and is arranged so that it approximates the change in direction of the polymer flow axial alignment with the loading device 20 to that in approximate alignment completed with the extrusion nozzle 40.

The flow control device 34 of the holder 30 is, as shown in Fig. 2, in direct communication with conduit 32 so that there is a flow of the polymeric material through the inlet 33 and directly into the flow control device 34 can take place. If desired, the holder 30 or

associated parts with multiple inlets (not shown ) be provided, which are in direct or indirect connection with the flow control device 34 stand to the primary material essentially completely around this and within this, as shown, for example, in U.S. Patent 3,418,678.

As best seen in Figure 3, the flow control device has 34 a rotatable inner member 35 and a stationary outer member 36 with surfaces 36 'and 37' which delimit a polymer material flow channel 37 between them that the polymeric material is forced in new ways and in new ways to flow as it moves through the old 30 to the spray head 40, as follows is explained.

The holder 30 is provided with a number of exit channels #, for example eight channels 38, provided near its end. These outlet channels 38 are distributed at equal radial distances around the central axis of the holder 30 and are in communication with inlet channels 41 which are inside the extrusion nozzle 40 are provided so that they allow the flow of the polymeric material.

The nozzle 40 is attached to the exit end of the holder 30. It can also a helical distribution flow of polymeric material within the Extrusion nozzle 40 as it is conveyed through the polymer material flow channel 42 in FIG of the nozzle 40 from which it is extruded in the form of a tube T, as shown in Fig. 1 shown.

The extrusion nozzle 40 is detachable from the holder 30 in a suitable manner attached. For example, the DUoe 40 can be rotated in that illustrated in FIG. 1 Way are stored in that their inner part 43 on the inner element 35 of the holder 30, which extends axially completely through the old 30 and on his other end by suitable means, for example provided with a sprocket S for connection to a chain drive, not shown is.

The outer surface 35 'of the inner element 35 interacts with the opposite Inner surface 36 'of look member 36 together to form a novel polymer flow channel 37 to limit the flow control device 34 between them.

The polymer flow channel delimited by these outer and inner surfaces 35 'and 36' 37 comprises: a first flow path P-1 substantially in the form of an annular one or tubular flow path passing through portions of surfaces 352 and 36 'of the inner and the appearance of the element 35 and 36, respectively, is limited, which are substantially different from one another spaced the length of the path, which path P-1 to flow channel 42 in nozzle 40 is substantially parallel; a second flow path P-2, which with the first flow path P-1 is connected and generally has the shape of a narrowed Has flow path through portions of surfaces 352 and 36 'of the inner and outer Elements 35 and 36 is limited in which considerable contact, as at 50 shown in Fig. 2, there is between the surface parts to a groove or a to form single circumferential flow channel 39 between them, which the polymer flow changed from a hose flow in the first path P-1 to a current flow in the second path P-2, which is substantially parallel to the first flow path P-1; and a third flow path P-3, which communicates with the second flow path P-2, and usually the shape one has tubular flow path through parts of the inner surfaces 35 'and 36 of the Elements 35 and 36 is limited, which differ from each other essentially via the full path at intervals, with this third flow path P-3 by first and is substantially parallel to the second flow path P-1 and P-2.

The helical flow path constrains all of the polymeric material to flow into the only circumferential helical groove 39, since the helical line a small amount of play between the helical thread rib 35 ", until it is substantially in contact with the wall 36 'of the look element 36 is located for at least one revolution. This has the consequence that an increasing Play between the thread 36 "and the wall 36 'of the outer element 36 and thus there is an increasing flow of polymeric material in the axial direction.

The depth of the helical groove 39 therefore takes on a maximum depth at the point at which practically contact with the helical There is thread ribs, and then decreases again accordingly when the polymer is moved axially in the direction of the nozzle 40. In a similar way, the bridge tip takes the Helical line closes, remains at a maximum at the point of contact and decreases then off.

from this it follows that the inner and outer elements 35 and 36 of the holder 30 in a complementary relationship an uninterrupted hose path or -channel 37 for 8 stepping motion molten thermoplastic Form polymer by the holder 30.

In the preferred embodiment, the inner member 35 rotates of the holder 30, while the outer member 36 of the holder is stationary. The circumferential helical ut 39, which extends at a point between the lateral j # Linlaß 33 and the nozzle 40 is located between better threads 35 "of the surface 35 'of the inner element 35, which is the flat 36' of the look element 36 are facing. The outer parts of the outer threads 37 ″ are located substantially in contact with the outer member 36 as shown at 50. the Appearance of threads that are essentially in contact with the wall or surface 36 'of the outer element 36, usually exceed a little more than a full turn. Hence, as best seen in Figures 2 and 3, where is the thread ribs 35 "are essentially in contact with the wall 36 'of the appearance Elements 36 are located, the tubular path P-1 interrupted and the entire polymer flow must pass through the groove or through the current path P-2 through the helical Ribs 35 "is formed. After the polymer flow through an effective circulation has passed through, the flow starts when the helical part runs out, a progressively increasing axial flow in the tubular To have way P-3.

From this it can be seen without further ado that the entire polymer, the has flowed in the tubular web P-1 through the single circumferential flow path P-2 is conveyed before it is again axially in the tubular path P-3 and thus can tile to the final tube formation. The important criterion for degradation the rough weight Change and to achieve other desired ones Film properties of the extruded film made of polymeric material with improved Flow properties consists in the fact that the polymer sent through a relatively ## ssig narrow channel or path P-2 flowing at a given programmed rate rotates as explained below.

The preferred flow path 34 according to the invention is best shown in FIG. 2 and 3 shown. As can be seen, the interruption in the tubular Channel 37 caused by a single flow channel P-2 'which then divides into two flow channels P-2 "and P-2" 'is split, which in turn is divided into the third tubular Flow path P-3 open.

Therefore, in the path P-2, the appearance of areas 35 'of the interior promote Element 35, which is essentially in contact with the inner wall 36 'of the outer Elements 36 are all polymeric through a single rotating axial inlet and then split the polymer flow for helical movement before the axial tubular flow is resumed.

A variant flow control device 60 in the form of a single helix is shown in Figs. 4 and 5 and serves to interrupt the tubular polymer flow.: in a holder. The inner element 35 has outer threaded parts 35 "which are located in the are substantially in contact with a wall of the outer member 36.

The extruder pressure which the melted thermoplastic polymer moved through the device, the polymer conveys inwardly through inlet 33 and around the inner element 35 in a tubular flow course. The pressure then conveys the polymer out of the tubular channel. the groove 39, which is formed by the outer ribs 35 ″ on the inner element 35.

The outer thread part extends over a little more than a full one Rotation around the inner element before the external thread in its height and Long begins to lose weight. The polymer therefore inevitably flows through the only one rotating guide inlet 39 of the second flow path P-2 before the advancing increasing axial flow to nozzle 40 begins. The polymer flow course is thereby Easier to see that the corresponding development of the helix on the inner member 35 in Fig. 5 is considered.

Another modification of the invention is shown in Figs. 6 and 7, in which the interruption of the polymer flow by a modified flow control device 70 is caused. In this case the outer part has 35 "of the inner element 35, which is in contact with the wall 36 'of the void element 36 substantially located, the tendency to punch the polymer through a single axial inlet 39 to convey before moving in a helical path. Here too will the tubular passage of the polymer is interrupted and the polymer becomes conveyed through the single rotating guide inlet of the second flow path P-2, before it resumes the hose flow, as can best be seen from the corresponding Development and the course of the polymer flow shown in FIG. 7 results.

This rotation or constriction of the whole polymer at a given one Site has a substantial reduction in standing thickness change (i.e. the non-repetitive weight or thickness change in the extruded film) in the finished slide result. Therefore, any potential standing change in thickness, which has been introduced before this point, reduced to a minimum and converted into a rotating thickness that be made randomly can.

from this it follows that by regulating the flow of the polymer through the Ilalter and in that it moves in the novel channel 39 in this holder is interrupted, the hose flow of the material or in a current flow to a Intermediate point of the mentioned channel changed and then again to a hose flow is converted back. This interruption of the hose flow and change too a flow of current gives surprising and unexpected results in the finished product Foil or in the extruded foil by improving the flow properties of the primary material through the holder prior to the extrusion of the film. In summary It can be said that the improved polymer flow properties achieved by the inventive process measures with interrupted flow and the novel guide path as well as through the novel flow control device of the invention Device, results in a more even and improved flow, which in turn results in an improved extruded film that gives the desired results has improved properties.

Lin comparison of the effectiveness of the inventive device was carried out in the manner indicated in the following examples.

Example 1 Polyethylene was made at a rate of 613,257 kg / h (1352 lbs / hr.) at a melting temperature of 197 ° C through an annular nozzle with 81.3 cm (32 ") in diameter with a nominal gap of 0.635 mm (0.025 ") extruded and at a speed of 77.7 m in peeled off the minute (85 yds./minute) to a 0.038 mm (0.0015 ") sheet underneath Use of essentially the apparatus of Figure 2 of U.S. Patent 2,987,765 in a similar way as in this patent in column 4, line 45 to column 5, line 10 described in this patent.

Initially a conventional jjalter section with rotating Inlet used essentially as shown in Figure 1 of U.S. Patent 3,376,605. The tubular film obtained was slit into two coils, those with east and west are designated. These wraps were subsequently 8-8 "wide Coils slotted with an outer diameter of 260.35 mm (10 1/4 "), weighed and the percentage deviation from the lightest wrap is noted (see upper graph Representation in Fig. 3).

The inventive device was using the only one rotating guide inlet of the type shown in Figs. 4 and 5 then into the System installed and a similar test carried out (see graphic below Representations of FIG. 8). From the graphical representations it is easy to see that the only rotating guide inlet is the standing thickness weight change significantly improved in the extruded film.

Example 2 In a similar manner to Example 1, polyethylene was made at a speed of 476,270 kglh (1050 lbs.lhr.) by a 32 "diameter ring nozzle with a nominal gap 0.762 mm (0.030) extruded and at a speed of 77.7 m (85 yds) peeled off per minute to produce a 0.05 mm (0.002 #) film.

When using a conventional holder section with rotating Inlet wraps were obtained again, and the percentage deviation from the lightest Wrap was noted (see upper graphs of Figure 9).

When using a rotating inlet with a single guide 6 and 7, a similar evaluation was made and graphed in FIGS lower diagrams of FIG. 9 shown.

The essential improvement in the standing thickness weight change is again obvious.

In addition to the free design of the thickness deviations by Rotation, which is made possible by the novel flow control device according to the invention it is also possible to prevent this rotating thickness irregularity before the random Design to reduce to a minimum that the aforementioned flow control device combined with a nozzle lip adjustment device 80 in the extrusion nozzle 40 will.

As best seen in FIG. 1, the extrusion nozzle has 40 spaced apart circular nozzle lips 81 and 82, which with with respect to one another by suitable means, for example by adjusting screws 83, are adjustable to the thickness for example in the in that U.S. Patent 3,267,519 to regulate the manner shown. It can also be seen that the inner part of the extrusion nozzle 40 and the holder 30 are firmly connected to one another, so that it is possible by simply adjusting selected adjusting screws 83, to regulate the stationary rotating thickness in this area of the nozzle lips 81 and 82. With this arrangement with flexible lips, the small adjustments that are necessary to ensure uniformity in thickness at the individual sections of the annular Make sure lip part of nozzle 40 can be made easily.

Claims (1)

Patent claims ) Device for extruding polymeric material in the form of a tube made of synthetic foil, with a polymer material feeder, a rotatable one Extrusion nozzle, which has an annular channel and associated nozzle lips for extrusion of the polymeric material in the form of a tube, a holder that holds the The feeding device connects to the rotating extrusion nozzle, characterized in that that the holder (30) has a rotating current outlet flow path for the outlet along peripheral parts of the annular space within the rotating extrusion nozzle (40) having. Device according to claim 1, characterized in that the holder () 0) has an inner (35) and an outer (36) element which have surfaces which delimit a polymer material flow channel between them and the inner and the outer element are rotatable with respect to each other, the flow channel a first Flow path (P-1), which is essentially tubular, and a second rotatable Comprises flow path (P-2) which is in communication with the first flow path, wherein at least the downstream part of the flow path is in the form of a stream. Device according to claim 2, characterized in that parts of the Surfaces of the inner () 5) and the outer t) 6) element are essentially in contact stand together in order to convert the hose-shaped flow path into a current flow path. Device according to claim 2, characterized in that parts of the Surfaces of the inner and outer elements with a helical groove (39) limit a single inlet connecting the first path with the second path. Device according to claim 4, characterized in that the helical Groove () 9) has a single outlet, which the annular space of the extrusion nozzle (40) assigned. Device according to claim 1, characterized in that the rotatable Extrusion nozzle has nozzle lip parts (81, 82) which, with respect to one another are adjustable. Device according to claim 6, characterized in that parts of the Extrusion nozzle (40) and the holder (30) are firmly connected to one another. Process for extruding polymeric material in the form of a tube made of plastic film through a rotating nozzle with an annular space, characterized in, that the polymeric material is shaped into a rotating stream and in the circumferential direction is brought to exit into the annular space of the rotating extrusion nozzle. Method according to claim 8, characterized in that the material along special, radially spaced apart parts of the annular space is made to exit. L e r s e i t e