FR2593112A1 - EXTRUDER LINE FOR THE MANUFACTURE OF A MULTILAYER BREATHABLE SHEET - Google Patents

Abstract

Extruder die for the manufacture, by coextrusion, of a multilayer blown sheet from several laminated thermoplastic materials comprising a lower die part 1 equipped with a device for supplying several flows of plastic material via several supply ducts 2, an upper die part 3 with annular outlet slit 4 for the exit of a flow of multilayer plastic material in the form of a sheath, a die core 5 and a laminating device 6. Channels transfer 7, 8 in the form of an annular slot are arranged in the upper 3 and lower 1 parts of the die. The supply ducts 2 open into the single transfer channel 7, in the form of an annular slot, which is arranged in the lower part of the die and which surrounds the die core, said transfer channel being shaped as a laminating device 6 The annular exit slot 4 is connected to the laminator 6 via a single transfer channel 8, without core strips, in the upper part of the die. (CF DRAWING IN BOPI)

Description

The invention relates to an extruder die for the manufacture, by means of

  extruding, from a multi-layer puffed sheet from a plurality of laminated thermoplastics, comprising a die bottom portion provided with a device for feeding a plurality of plastic streams through a plurality of conduits

  a die upper part with annular slot

  outlet for the output of a flow of plastic material.

  multilayer tick in the form of a sheath, a die core and a laminating device, annular slot-shaped transfer channels being arranged in the parts

  lower and upper die. We understand by

  This is the sum of the mechanical measures that ensure unmixed stratification. This includes taking into account the mass fluxes that add up during lamination and preventing the occurrence of shear forces between the different layers by velocity differences or similar measurements. It goes without saying that in the extruder die of the above kind,

  the lower and upper parts of the die are

  placed symmetrically around the axis of the die, with the exception of the supply ducts. In a similar way, the transfer channels and the annular exit slot are also symmetrical of revolution. Moreover, it goes without saying that the kernel can include an arrival system

  blowing air and possibly also an evaluation system

  blowing air when it comes to the manufacture of

blown sheets.

  In the extruder die of the kind described, which is well known in the art, the feed ducts of the lower part of the die open into a

  particular transfer channel. The laminating device

  is in the upper part of the die. he

  consists of a plurality of corresponding helical distributors

  spanning a plurality of plastic streams, which are nested within each other and connected to the plurality of transfer channels which follow a conically tapering channel towards the exit annular slot in which lamination takes place proper. The impeller dispensers are mounted upstream because the transfer channels for the plurality of plastic streams are divided in the upper part of the die by core bars which immobilize or support the core. Harmful influences on the flow of plastic material must be eliminated in the propeller distributors before the stratification can be carried out in such a way that, on this point, the

  propeller distributors are part of the struc-

  and make it complicated and expensive. The service time without fail is often insufficient because

  plastic may be stuck in the

  propeller scorers. In this case, it is necessary to carry out an expensive disassembly of the nested propeller distributors

  in each other, cleaning and reassembling them.

  The object of the present invention is to improve an extruder die of the aforementioned type so that it is no longer necessary to provide a die upper part with a plurality of helical distributors.

nested.

  According to the invention, this object is achieved by the fact that the supply ducts open into a single annular slot-shaped transfer channel devoid of core strips and surrounding the core of the die, said transfer channel being shaped into laminating device, and that the annular exit slot is connected to the laminator by means of a single transfer channel, without core bars, the upper part of the die. The invention exploits the discovery that it is not necessary for an extruder die of the type described above to place the lamination device in the upper part of the die, shortly before the slot.

  annular exit. By housing the stratification device

  in the lower part of the die and by adopting, moreover, the arrangement described, it is surprising to note that no mixing occurs on the subsequent course of the flow of multilayer plastic material, between the

  layering device and the annular exit slot.

  In addition, the invention takes advantage of the fact that

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  no longer necessary for holding or securing the die core when the supply lines open into the single ring-shaped transfer channel

  which surrounds the core of the die.

  For the extruder die according to the invention,

  may be advantageous to adjust the thickness of the annular slot

  output area under special service conditions and plastics used. For this, it is planned

  according to the invention that the annular exit slot is

  formed as a mouthpiece of a conical section of the transfer channel in the upper portion of the die, which is disposed between an upper nozzle member and a member

  lower nozzle. The width of the annular slot of

  tie can then be variable by adjustment or by replacing at least one of the nozzle elements. This operation can also be carried out during production and influenced by measures relating to the adjustment technique. To ensure homogeneous circumference conditions everywhere

  of the blown sheet, which also includes a resistance

  flow rate for the flow of plastic material

  In the case of the laminate, the invention recommends placing corrugations in the transfer channel in the direction of flow of the multilayer plastic stream and upstream of the conical section of the transfer channel.

  essentially in the circumferential direction.

  The advantages obtained lie in the fact that, while renouncing the use of

  in each other, the extruder die according to the

  vention makes it easy to make sheets

  multilayer puffs made from thermal materials

  a variety of moplastics. Moreover, the extrusion industry

  deuse according to the invention can be carried out easily and

maintained without great expense.

  The description that follows, next to the desîn

  annexed by way of non-limiting example, will allow

  understand how the invention can be put into practice.

  The single figure represents an axial section of a

  half of an extruder die according to the invention comprising

both the supply ducts.

  The extruder die shown in the figure is intended for the manufacture, by coextrusion, of a multilayer puffed sheet from a plurality of laminated thermoplastics. It basically comprises a lower part of die i with device for

  the supply of several flows of plastic material through the

  a plurality of supply ducts 2, a die upper portion 3 with annular exit slot 4 for the output of a multilayer plastic material stream in the form of a sheath, a die core 5 and a device

of stratification 6.

  In addition, transfer channels 7, 8 are provided, one of which 7 is arranged in the lower part of

  1, while the other 8 is located in the upper part of

  3. The transfer channel 8 of the die upper part 3 opens into the annular slot of

exit 4.

  The supply ducts 2 open into the single transfer channel 7, in the form of an annular slot, in the lower part of the die 1, which surrounds the die core 5 and which is devoid of core bars. It is clear from the drawing that this transfer channel 7 is shaped as a layering device 6, namely

  in such a way that the mass flows can add up.

  In terms of design, care was taken

  shearing efforts between the different

  plastic streams are avoided by different

  speed warnings or similar measures. The lunge slot

  output 4 is connected to this strati-

  6 via a single transfer channel 8 without core bars in the upper part of the die. In the exemplary embodiment and according to a preferred embodiment of the invention, the arrangement has been chosen so that the annular outlet slot 4 is shaped at the mouth of a conical section 9 of the transfer channel 8 in the upper part of die 3,

  which section is disposed between an upper nozzle element

  10, and a lower nozzle member 11. The width of the exit annular slot 4 can therefore be varied by adjusting or replacing at least one of the nozzle members 10, 11. Viewed in the direction of the flow of the multilayer plastic stream, undulations 12, which extend substantially in the circumferential direction and are visible in the portion of the drawing shown on a larger scale, are arranged in the transfer channel 8,

  upstream of the conical section 9 of the transfer channel 8.

Claims (3)

  An extruder die for the manufacture, by coextrusion, of a multilayer puffed sheet from a plurality of laminated thermoplastic materials comprising a die bottom portion provided with a device for feeding a plurality of plastic streams by via a plurality of supply ducts, a die upper part with annular outlet slot for the output of a flow of multilayer plastic material in the form of   sheath, a die core and a laminating device   cation, annular slot-shaped transfer channels being arranged in the lower and upper portions of the   the sector, characterized by the fact that   2 (2) open into a single annular slot-shaped transfer channel (7) in the lower die part (1), said transfer channel (7) surrounding the die core (5) and being lamination (6), and that the annular exit slot (4) is connected to the lamination device (6) via a single transfer channel (8) without core bars provided   in the upper part of die (3).   Extruder die according to Claim 1, characterized in that the annular outlet slot (4) is formed as a mouthpiece of a conical section (9) of the transfer channel (8) in the upper part of the die ( 3) and disposed between an upper nozzle member (10) and a lower nozzle member (11), and that the width of the annular exit slot (4) can be varied by adjusting or replacing at least one elements of nozzle (10, 11).   Extruder die according to Claim 2,   characterized by the fact that viewed in the direction of the   flow of multilayer plastic material, corrugated   tions (12), which extend essentially in the direction   conferential, are arranged in the transfer channel (8), upstream of the conical section (9) of said transfer channel (8).