DE7038729U - Device for Estruding plastic tubular film - Google Patents

Description

Patent attorney
Dr. Ing.Walter Abitz
Dr. Dieter F. Morf
Dr Hans-Λ. Brown _{kQ October 1970}

8 Munich 86, nenenauinlr. » P-1926

E. I. DU PONT DE NEMORS AND COMPANY 10th and Market Streets, Wilmington, Del. I9898, V.St.A.

Device for extruding tubular plastic film

The invention relates to a device for extruding a tube made of plastic film, in which the flow of the molten polymeric material in the extruder in a new way and with a new flow path from the inlet to the outlet of the Device is moved in a guided manner in order to achieve the desired flow properties.

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

It is known, for example, to produce a film tube using an inner and an outer holder.

703872 $ 21.1.71

deliver, the alternating helical and spiral Limit ways to improve flow in an extruder as shown in U.S. Patent 3,376,705.

Another example is U.S. Patent 3,418,687 which describes an extruder with a double bifurcated guide inlet with a holder to improve fluid properties shows.

Although these patents and others show polymer melt flow control devices, they do not a flow control to achieve better flow properties in which the melt through a new flow guide device is passed, which flow path is directed so that the outlet in the form of a rotating stream in the circumferential direction around the annular channel of the extrusion nozzle he follows.

The advantages of using a rotating die when extruding polymeric material into tubing are known per se. Although this type of rotating nozzle appears to cause the polymer streams within the The annular space of the nozzle also by ^ ifen to slight Randomly distributing defects or imperfections in the polymer stream flowing with a laminar flow, this is not the case. Rather, the moves like a hose otrom the polymer within the annulus essentially directly to the nozzle lips, instead of with the rotating part of the nozzle unit when moving forward of the material to circulate to the nozzle lips. This has many disadvantages. One of these disadvantages the fact that ate whenever the tubular material is wound up on a roller, the many thousands of layers have a tendency to produce the imperfections

so that an unsatisfactory roller with ver f F-1926 Thickness is obtained. Further if one U.N- to highlight changeable

Perfection occurs in the polymer stream, which is inevitably the case even with great care when the stream comes back together, the polymer "remembers" that it has been separated and creates a "weld line", which causes or can cause a weak point in the tube wall of the film after extrusion. At the Exit of the stream or, when using a device for the exit of the polymeric material in the Circumferential direction around the annular space in the hose extrusion nozzle around the aforementioned problems are therefore substantially reduced.

The invention provides a device v.ird for controlling the polymer flow prior to extrusion in the production of tubes made of plastic film having improved phy sical and strength properties ^ together.

In the manufacture of plastic film for a variety of uses, it is known to improve their properties by increasing the flow of the polymeric material regulated in the extruder before the tubular film is formed will. This is done, usually by regulating the heated material, i.e., the polymeric melt, through a control device with helical or spiral flow path is promoted or managed.

Nevertheless, in the production of such films by known processes, the film tube, if it is in the conventional manner is formed, one or more zones or areas of greater or lesser thickness than the Hose (i.e. fluctuations in thickness) caused by imperfections

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or changes in the polymer flow will. which in turn has the consequence "that an unequal Course of the polymeric material in the extruder caused by Mr. will.

When extruding polymeric materials in web or tube form, it is known that the thickness oda? Strength of Film, its density and the roll formation characteristics of the tube all immediately through the evenness of the flow of the polymeric material through the extrusion nozzle and other parts of the extruder, for example the holding device, the one between the usual screw conveyor and the spray head is arranged »regulated or determined * If, for example, the hose is wound, everyone comes continuing and standing tube thickness changes to lie on top of the other, so that by the cumulative Effect builds up a hard strip or the like, which deforms the roll, which impairs its usability and waste is created. Furthermore, there are congestion zones in the flow path in the holding device and in the extruder head undesirable because the polymeric material undergoes degradation and a film of poor quality is obtained especially when particles are extruded from a degraded polymer. This causes the foil to break and an undesirable appearance of the film.

The device according to the invention is a device for extruding polymeric material in the form of a tube made of plastic film with a feed device for the polymeric material, a rotating extrusion nozzle with an annular channel and associated nozzle slipper for Extruding the polymeric material in the form of a tube, a holding device that holds the feeder connects to the rotating extrusion nozzle and one

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rotating current outlet flow? - away for the outlet along circumferential parts of the annular ring within the rotating Has extrusion nozzle.

The holder of the device preferably has internal and outer elements with surfaces that form a polymer material flow channel limit between them, the inner and the outer element referring to each other are rotatable, the flow channel a first flow path which is substantially tubular and a second rotating flow path which coincides with the first Flow path is in communication and in which at least the downstream part of the flow path has the shape of a Stromes has. It is even more preferred that portions of the surfaces of the inner and outer members be substantial Have contact with each other to convert the tubular footpath into a current flow path. It's in the same Way even more preferable that the surfaces of the inner and outer elements be helical Limit the groove with a single inlet connecting the first path to the second flow path. Further it is preferable that the helical groove has a single outlet connected to the annulus of the extrusion nozzle is.

By using the inventive and control device can be polyprocyxon and poly-ethylene foils of excellent properties and very achieve high uniformity in thickness, for which there are extensive possible uses.

In the accompanying drawings show:

Fig. 1 is a side view in elevation of an inventive Extruder showing a polymer material feeder and extrusion nozzle, which with 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 Figure 11 shows polymer material flow control device;

3 shows a development of the flow paths of the polymer material flow control device according to Fig. 2, in which-the hatched area that part of an inner Represents element of the holder, which is in contact with a wall of an outer element of the holder

is located;

FIG. K shows a partial view in section of a modified holder of an extruder according to the invention;

Fig. 5 is a development of the flow control device of the holder according to Fig. 4;

Fig. 6 is a partial view in section of a further embodiment of the holder according to the invention Extruders;

Fig. 7 is a development of the flow control device of the holder according to Fig. 6 and

8 and 9 are graphs showing performance results using the inventive Show extruder;

Description of the preferred embodiments

In the drawing is a device according to the invention for conveying flowable polymers! Material and for extruding this material in the form of a tube T made of plastic film, for example made of polypropylene film, with which a film of improved physical properties can be obtained.

From Fig. 1 and 2 shows in particular that polymeric material of the inventive device 10 of a feed source, not shown, and fed through a polymer or polymer material feeder 20

moved into a holder 30 b?, w. is conveyed through which the polymer flows in a novel path to an extrusion die 40, from which the polymer in the form of a
Hose T exti ided »

From FIG. 2 it can be seen in particular that the polymer material charging device 20 can be of any suitable and conventional type and, for example, a screw conveyor which has a cylindrical outer part 21 and a screw conveyor element 22, the latter being rotatable within the outer part 22, around the polymer
To move material in flowable form with the aid of the webs 23 from a loading inlet opening (not shown) to a loading outlet opening 24 forward.

The polymeric M. tarial, which is supplied in molten form from the loading device 20, flows into and c-rch the holder 30, which changes the flow direction of the material by 90 °. The molten polymer enters the holder 30 by means of a conduit 31 and through a conduit 32 which gradually changes the course of the material as shown in FIG. The polymeric material flows through lines 31 and 32 into holder 30 and through
an inlet 33 to a polymer flow control device, generally designated 34, in the holder so formed
and is arranged that he the change in direction of the
Polymer flow from the in approximate axial alignment with the loading device 20 to that in approximate alignment with the extrusion nozzle UO completed.
The flow control device 34 of the holder 30 is, as shown in Fig. 2, in direct communication with the conduit 32 so that a flow of the polymeric material through the
Inlet 3 3 and directly into the flow control device 34 can take place. If desired, the holder 30 or parts assigned to it can have several inlets (not

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shows), which are in direct or indirect connection with the flow control device, 34 stand in order to distribute the primary material essentially completely around and within it, as shown, for example, in U.S. Patent 3,418,678.

As best seen in FIG. 3, the flow regulator 34 has a rotatable inner member 35 and 35 a stationary outer element 36 with surfaces 36 · and 37 ', which delimit a polymer material flow channel 37 between them, through which the polymer material is forced, to flow in a novel way and in new ways as it moves through the holder 30 to the spray head 40, as explained below.

The holder 30 is provided with a number of outlet channels 38, for example eight channels 38, provided near his land. These outlet channels 38 are radial with the same Distances distributed around the central axis of the holder 30 and are in communication with inlet channels 41, which are provided within the extrusion nozzle 40 to allow the polymeric material to flow therethrough. The nozzle 40 is attached to the exit end of the holder 30. There can also be a helical distribution flow of polymeric material within the extrusion die 40 take place during its conveyance through the polymer material flow channel 42 in the nozzle 40, from which it is in Tube shape T is extruded as shown in FIG.

The extrusion nozzle 40 is detachable on the holder 30 in a suitable manner Way attached. For example, the nozzle can be rotated in the manner shown in Fig. 1 thereby be stored that its inner part 4 3 is attached to the inner element 35 of the holder 30, which is axially extends completely through the holder 30 and at his

other end by suitable means, for example with a sprocket S for connection to a not shown Chain drive is provided.

The outer surface 35 'of the inner element 35 cooperates the opposite inner surface 36 'of the outer element 36 together to define a novel polymer flow channel of the flow control device 34 between them. The bounded by these outer and inner surfaces 35 'and 36' Polymer flow channel 37 comprises:

a first flow path P-I substantially in shape an annular or tubular flow path, that by parts of surfaces 35 'and 36' of the inner and the outer element 35 and 36, respectively, which extend from one another substantially over the length of the path are at a distance, which path P-I is substantially parallel to the flow channel 42 in the nozzle UO is;

a second flow path P-2, which communicates with the first flow path P-I, and generally the Has the shape of a narrowed flow path through parts of the surfaces 35 'and 36' of the inner and outer Element 35 and 36 is limited in which substantial contact, as shown at 50 in Fig. 2, exists between the surface parts to a rage or a single circumferential river channel 39 between them to form which the polymer flow from a hose flow in the first path P-I to a current flow in the second Changed path P-2, which is substantially parallel to the first flow path P-I; and

a third flow path P-3 that coincides with the second flow path P-2 is related and usually the form

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has a tubular flow path that runs through Parts of the inner surfaces 35 * and 36 'of the elements 35 and 36 are delimited, which are from each other in the are substantially spaced over the full path, this third flow path P-3 to the first and second flow paths P-I and P-2 are substantially parallel.

The helical flow path forces the whole polymer Material to flow into the single circumferential helical groove 39, since the helical lines decrease of the play between the helical thread rib 35 "until it is essentially in contact with the wall 36 'of the outer element 36 for at least one revolution. As a result, a increasing play between the thread 36 "and the wall 36 'of the outer element 36 and thus an increasing flow polymeric material in the axial direction.

The depth of the helical groove 39 therefore increases to a maximum depth at the point where practically There is contact with the helical thread ribs, and then decreases again accordingly when the polymer moves axially towards the nozzle 40. Similarly, the web tip of the helix increases, remains at a maximum at the point of contact and then decreases.

It follows from this that the inner and outer elements 35 and 36 of the holder 30 are in a complementary relationship an uninterrupted hose path or channel 37 for

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moving motion molten thermoplastic Form polymer by the holder 30.

In the preferred embodiment, the inner member 35 of the holder 30 rotates while the outer member of the holder is stationary. The circumferential helical groove 39, which is located at a point between the lateral inlet 33 and the nozzle UO, is formed between outer threads 35 "of the surface 35 'of the inner element 35, which face the Eöche 36' of the outer element 36. The outer parts of the outward threads 37 ″ are essentially in contact with the outer element 36, as shown at 50. The outer threads, which are substantially in contact with the wall or surface 3b ^{5 of} the outer member 36, normally exceed a little more than a full revolution. Therefore, as can best be seen from Fig. 2 and 3, where the thread ribs 35 "are essentially in contact with the wall 36 'of the outer element 36, the tubular path PI is interrupted and the entire polymer flow must be through the groove or pass through the current path P-2 formed by the helical ribs 35 ". After the polymer flow has passed through one effective cycle, as the helical portion drains, the flow begins to have a progressively increasing axial flow in the tubular path P-3.

From this it can be readily seen that all of the polymer that flowed in the tubular web P-I is, is conveyed through the single circumferential flow path P-2, before it is again axially in the tubular Path P-3 and thus flow to the final hose formation can. The important criterion for reducing the space

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weight change and to achieve other desired ones Film properties of the extruded polymer film Material with improved flow properties is made in that the entire polymer by a relative narrow channel or path P-2 flowing rotating at a given programmed speed, as explained below.

The preferred flow path 34 according to the invention is best shown in FIGS. As can be seen, the interruption in the tubular channel 37 is brought ^{about by a single flow channel P-2 1} , which is then divided into two flow channels P-2 "and P-2 ¹¹¹ , which in turn form the third tubular flow path P-3 Thus, in path P-2, the outer surface portions 35 'of inner member 35 which are substantially in contact with inner wall 36' of outer member 36 convey all of the polymer through a single rotating axial inlet and then divide the polymer flow for helical movement before the axial tubular flow is resumed.

A modified single helix flow control device 60 is shown in Figs serves to interrupt the tubular polymer flow in a holder. The inner member 35 has outer threaded parts 35 ″ which are essentially in contact with a wall of the outer element 36. The extruder pressure that moves the molten thermoplastic polymer through the device promotes the polymer inwardly through inlet 33 and around inner member 35 in a tubular flow path. The pressure then promotes the polymer from the tubular channel through the groove 39, which through the outer ribs 35 ″ on the inner element 35 is formed.

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The outer thread part extends a little more than one full turn around the inner element before the external thread decreases in height and length begins. The polymer therefore inevitably flows through the single rotating guide inlet 39 of the second Flow path P-2 before the progressively increasing axial Flow to nozzle 40 begins. The course of the polymer flow is easier to see because the corresponding © Development of the helix on the inner element 35 in FIG. 5 is considered.

Another variation of the invention is illustrated in Figures 6 and 7, in which the disruption of polymer flow is caused by a modified flow regulator 70. In this case the outer part has 35 "of the inner member 35, which connects to the wall 36 ' of the outer element 36 is essentially in contact, tending to transport the entire polymer through a single axial inlet 39 before moving in a helical Way to promote. Here, too, the tubular passage of the polymer is interrupted and the polymer is 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, ' which is shown in Fig. 7 results.

This rotation or constriction of the whole polymer at a given point has a substantial reduction the standing change in thickness (i.e. the non-random change in weight or thickness in the extruded Foil) in the finished foil. Hence any potential standing thickness change that preceded this one Body has been introduced, reduced to a minimum and converted into a «rotating thickness, the

can be made randomly.

It follows that by regulating the flow of the polymer through the holder and by moving it in the novel channel 39 in this holder, the hose flow of the material is interrupted or changed into a current flow at an intermediate point of the mentioned channel and then again is converted back to a ski foot. This interruption of the hose flow and change to a current flow gives surprising and unexpected results in the finished film or in the extruded film by improving the flow properties of the primary material through the holder prior to extrusion of the film. In summary, it can be said that the improved polymer flow properties, which are caused by the interrupted flow and by the novel guide path and by the novel flow control device, result in a more uniform and improved flow, which in turn leads to an improved extruded film which has the desired improved properties .

A comparison of the effectiveness of the device according to the invention was carried out in the manner indicated in the following examples.

example 1

Polyethylene was fed at a rate of 613.257 kg / h (1352 lbs / hr.) With a melt temperature of 197 C through an annular die with a diameter of 81.3 cm (32 ") having a nominal gap of 0.635 mm (0.025")

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extruded and peeled off at a rate of 85 yards per minute (77.7 meters per minute) a 0.038 mm (0.0015 ") film using essentially the apparatus of FIG USA patent 2.98 7.76 5 in a similar manner as in this patent in column 4, line 45 to column 5, line 10, of this patent.

Initially, a conventional rotating inlet retainer section was constructed substantially as shown in FIG U.S. Patent 3,376,605 shown used. The tubular film obtained was slit into two wraps, which are marked with east and west «ii / io * These wraps were follow ^ ^ u 8-8 "wide wraps from an outer diameter of 260.35 now (10 1/4 ") £ "slices, weighed and the percentage deviation of noted the lightest wrap (see upper graph in Fig. 8). -

The device according to the invention was used of the only rotating guide inlet from the in 4 and 5 then built into the system and a similar experiment carried out (see below graphs of Fig. 8). From the graphs it can be seen without further ado that the only rotating guide inlet the standing thicknesses Weight changes in the extruded film are borrowed improved.

Dei & play 2

In a manner similar to Example 1, polyethylene was fed at a rate of 476.270 kg / h (1050 lbs./hr.)

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extruded through an 81.3 in (32 ") diameter annular die with a nominal gap of 0.762 mm (0.0 30") and at a rate of 77.7 m (85 yards) per minute for manufacture peeled off a 0.05 mm (0.002 ⁿ ) film.

Using a conventional holder section with a rotating inlet, wraps were obtained again, and the percentage deviation from the lightest wrap was noted (see upper graphs of FIG Fig. 9).

Using a rotating inlet with a single guide shown in Figures 6 and 7, a similar evaluation was made and shown graphically in the lower diagrams of FIG. 9.

The major improvement in standing thickness weight change is again evident.

In addition to the random 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 have this rotating thickness irregularity before the random design to look down a minimum that the mentioned flow control device is combined with a nozzle lip adjusting device 80 in the extrusion nozzle 40.

As can best be seen from FIG. 1, the extrusion die uo has spaced apart circular ones Nozzle lips 81 and 82, which with respect to one another by suitable means, for example by adjusting screws Θ3, are adjustable to

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spiclsweioc in cicx · Xu the USA-Fdtent o.2G7.biä shown way to regulate. 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 to regulate the stationary rotating thickness in this area of the nozzle lips 81 and 82 by simply adjusting selected adjusting screws. With this arrangement with flexible lips, the small adjustments which are necessary in order to ensure uniformity in thickness at the individual sections of the annular lip part of the nozzle 40 can easily be carried out.

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Claims (6)

F - 926 October 20, 1970 S c h u t ζ a η s ρ r ü c h e 1. Apparatus for extruding polymeric material into shape a hose made of plastic film, with a polymer material charging device, a rotatable extrusion nozzle, which has an annular channel and associated lip lips for extruding the polymeric material in the form of a tube, a holder which holds the loading device connects to the rotatable extrusion nozzle, thereby characterized in 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). 2. Device according to claim 1, characterized in that. the holder (30) has an inner (35) and an outer (36) element possesses, which have surfaces which delimit a polymer material flow channel between them and the interior and the outer element are rotatable with respect to one another, the flow channel has a first flow path (P-I) which essentially is tubular, and comprises a second rotatable flow path (P-2), which with the first flow path in Is connected, at least the downstream part of the flow path is in the form of a stream. 3. Apparatus according to claim 2, characterized in that Portions of the surfaces of the inner (35) and outer (36) elements are essentially in contact with one another to convert the tubular flow path into a current flow path. 70387 ^ 21.1.71 F-1926 4. A device according to claim 2, characterized in that parts of the surfaces of the inner and outer elements delimit a helical groove (j> 9) with a single inlet: ,, which connects the first path with the second path. 5. Apparatus according to claim 4, characterized in that the helical groove (39) has a single outlet, which isc assigned to the annulus of the extrusion nozzle (40). 6. The device according to claim 1, characterized in that the rotatable extrusion plate has DUstnlippenteile (81,82) which are adjustable with respect to one another. 7 * Device according to claim 6, characterized in that parts of the extrusion nozzle (40) and the holder (^ O) are firmly connected to one another. j - 20 -