IE55733B1

IE55733B1 - A flat die for the extrusion of multi-layered and multi-coloured plastics films,sheets or panels

Info

Publication number: IE55733B1
Application number: IE2465/84A
Authority: IE
Original assignee: Siamp Cedap Reunies
Priority date: 1983-10-03
Filing date: 1984-09-27
Publication date: 1991-01-02
Also published as: FR2552707A1; ES290734Y; BR8404965A; EP0136959A3; DE3465269D1; ES290734U; EP0136959A2; EP0136959B1; FR2552707B1; ATE28820T1; AU564920B2; JPH0527530B2; AU3378084A; IE842465L; JPS6096430A; NZ209750A

Abstract

1. A flat die for the extrusion of multi-layered and multi-coloured films, sheets or plates of plastics material, in which die channels (12, 13, 14), for supplying plastics materials of different colours to an intermediate layer (A, B, C), open into a cavity positioned transversely with respect to the direction of extrusion, which leads into a smooth passage (15) in which the intermediate layer of the film, sheet or plate is formed, and which, before emerging from the outlet (6) of the die, joins with two other ducts (16, 19) which are linked to channels (18, 22) for distributing the plastics materials intended for forming a support layer (D) and a covering layer (E) respectively, the above-mentioned cavity containing a means for spreading out, in the intermediate layer (A, B, C), the streams of plastics material admitted by the supply channels (12, 13, 14), the flat die being characterised in that said means comprises a thin fixed plate (7) the upper face of which is provided with raised teeth (9) having a height and a width which decrease from their upstream end to their downstream end where they end in a point, the teeth (9) delimiting trapezoidal spaces (10), the profile of which, considered in a plane which is parallel to the base plane of the plate (7), increases from upstream to downstream in such a way that the spaces (10) are in contact at their downstream ends, each of these spaces (10) being supplied with coloured plastics material (A, B, C) by the channels (12, 13, 14) which introduce the plastics material into the trapezoidal spaces at their upstream ends and moving in the direction of extrusion.

Description

ι The subject’of the invention is a flat die making it possible to produce by extrusion multi-layered and multi-coloured plastics films, sheets or panels which take the form of contiguous Longitudinal· strips of dif5 ferent coLour from one another and which appear on one and the same supporting Layer of a single colour and under one and the same Layer of transparent material.

Such films, sheets or panels have many uses, especially in the packaging industry, since they are suit10 able, among other things, for the manufacture of boxes or pots by means of forming, and. these, boxes can each have several shades or have different colours from one box to another in the same set of boxes.

To obtain the same effects in these particular 15 uses, it is known to use either plastics sheets on which strips of different colours are printed side by side, or p last i cs sheets on which strips of different colours are Laminated. In both cases, the sheets are very expensive, and their quality is not sufficient to enable them to withstand thermoforming operations.

The invention overcomes these disadvantages and provides in accordance with the invention a flat die for the extrusion of multi-layered and multi-coloured plastics films, sheets or panels of plastics material, which comprises feed channels fox supplying plastics materials of different colours to an intermediate layer, which channels open into a chamber positioned transversely with respect to the axis of direction of extrusion, which leads into a flattened passage in which the intermediate layer of the film, sheet or panel is formed, and which, before emerging from the gap of the die, joins with two other passages which are linked to channels for distributing the plastics materials intended for forming a supporting layer and a covering layer respectively, said chamber containing a means for spreading out, in the intermediate layer, the streams of plastics material admitted by the feed channels, said means comprising a thin fixed plate the upper face of which is provided with raised teeth having a height and a width which decrease from their up10 stream end to their downstream end where they end in a point, the teeth delimiting trapezoidal spaces, the profile of which, considered in a plane which is parallel to the base plane of the plate, increases from upstream to downstream in such a way that the spaces are in contact at their downstream .' ends, each of said spaces being supplied with coloured plastics material by the channels which introduce the plastics material into the trapezoidal spaces at their upstream ends and moving in the direction of extrusion.

This plate arranged in the form of a comb const?20 tutes an essential element of the diez since it acts as a distributor of the coloured plastics material, to produce a sheet or a film formed by strictly contiguous strips differing from one another in their colour.

If the sheet or film has only two colours for its various strips, the comb alone is sufficient to distribute the coloured plastics material. If, on -the other hand, the number of colours Is greater than two, according to another characteristic of the invention the comb is then associated with at least one other plate which is located above it and in the same chamber as the tatter in the die and which, in combination with it, carries out the distribution of a plastics material cf a certain colour.

The number of these* superimposed plates depends on the number of colours to be provided in the film or the sheet. The comb and one plate correspond to three colours, the comb and two plates to four colours, and so on and so forth.

Moreover, the invention will be properly understood and its advantages as well as other characteristics will emerge clearly from the following description made with reference to the attached diagrammatic drawing which illustrates an embodiment of this die and 1n which: Figure 1 is a perspective view of a portion of a sheet according to the invention; Figures 2 arid 3 are highly diagrammatic views, in perspective and in plan respectively, illustrating the arrangement uhich makes it possible to manufacture this sheet; Figures 4 and 5 are views of a die for manufacturing this sheet, in Longitudinal section along 4-4 of Figure 5 and in cross-section aLong 5-5 of Figure 4 respectively.

As ,shown in Figure 1, a sheet according to the invention comprises six plasticsstrips (A, B, C, A, B, C) included between an opaque base layer (0) and a transparent covering layer (E). The strips (A, B, C> are of different colours and show through the transparent Layer (E). The various materials used can be of any type, for example polystyrene.

A flat die is used for the manufacture of this multi-layered and multi-coloured sheet, and as is known this die comprises an upper body (1)/ a middle body <2), a lower body (3) and two lips <4, 5) which delimit the gap (6) of adjustable height determining the thickness of the sheet.

The plastics feed channels are arranged in the various bodies of the die, and there are five of these channels, that Is to say three channels for the three coloured plastics/ one channel for the opaque base layer plastic and one channel for the transparent covering plast1c · It is the arrangement of these various channels and of the system for distributing the various streams of plastics material vdiich constitutes the special feature of the die.

The upper body (1) and the middle body (2) de15 limit a chamber which opens out on the rear face of the die and in which two plates (7 and 8) are superimposed.

One (7) has on its front edge a profile similar to that of a comb, since it is provided with teeth (9) ending in a point and delimiting trapezoidaL spaces (10), into each of which opens a coloured-plastics feed channel. With regard to the three coloured plastics (A, B, C), these are distri-buted via three longitudinal channels (12, 13, 14) which are each subdivided into two channels within the die, since the sheet must possess six coloured strips. To make it easier to understand this arrangement, the channels distributing the plastics naterial of colour (A) are represented by broken lines in Figure 3, those distributing the plastics material of colour (B) are represented by solid lines, and those distributing the plastics material of colour (C) are represented by dot-and-dash lines Of these channels, the one (12) intended for the plastics material of colour (A) is arranged in the upper face of the middle body (2) of the die and in the Lower face of. * the comb plate (7); the one (13) intended for the plasties material of oolour (fi) is arranged in the lower face of the upper body (1) and in the upper face of the intermediate plate (8); and the one (14) intended for the plastics material of colour (C) is arranged in the upper face of the comb plate (7) and in the lower face of the intermediate plate (8).

Each channeL (12, 13, 14) is profiled in the downstream direction, in order to open by each of its two branches into a space (10) delimited between two teeth (9) of the comb plate (7). As shown 1n Figure 3, it is possible, from that moment, Jor the plastics material coming from each channel to be transformed in this space (10) Into a strip which is joined, at the end of each tooth of the comb, to the adjacent strip, thus forming a web.

Downstream of the comb (7), this web formed as a result of the juxtaposition of these strips moves into a passage (15) which is delimited by the upper body (1) and the middle body (2) of the die and which opens into another passage (16) delimited by the middle body (2) and the upper lip (4)· This passage (16) communicates at its front end with a transverse channel (17), into which opens a longitudinal channel (18), via which the plastics material intended for constituting the covering layer (E) of the final sheet is introduced; at its downstream end, this channel (16) ' β opens into the gap (6) between the two Lips <4, 5) of the die; furthermore, there opens into this gap a passage (19) which extends from a transverse channel (21) fed via a longitudinal channel (22) v?ith plastics material intended for constituting the supporting Layer (D) of the final multicoloured sheet.

It goes without saying that the invention is not limited to the sole embodiment of this die described above by way of example; on the contrary, it embraces aLl its alternative embodiments, in particular whatever the means provided for adjusting the speed of movement of the various streams and strips of plastics material, and these means can consist especially of individual valves associated with various channels·

Claims

CLAIMS:

1. A flat die for the extrusion of multi-layered and multi-coloured films, sheets or panels of plastics material, which comprises feed channels for supplying plastics materials of different colours to an intermediate layer, which channels open into a chamber positioned transversely with respect to the axis of direction of extrusion, which leads into a flattened passage in which the intermediate layer of the film, sheet or panel ie formed, and which, before emerging from the gap of the die, joins with two other passages which are linked to channels for distributing the plastics materials intended for forming a supporting layer and a covering layer respectively, said chamber containing a means for spreading out, in the Intermediate layer, the streams of plastics material admitted by the feed channels, said means comprising a thin fixed plate the upper face of which is provided with raised teeth having a height and a width which decrease from their upstream end to their downstream end where they end in a point, the teeth delimiting trapezoidal spaces, the profile of which, considered in a plane which is parallel to the base plane of the plate increases from upstream to downstream in such a way that the spaces are in contact at their downstream ends, each of said spaces being supplied with coloured plastics material by the channels which introduce the plastics material into the trapezoidal spaces at their upstream ends and moving in the direction of extrusion.

2. λ die according to Claim 1, for the production of a film, sheet or panel having more than two colours, wherein the cosh is associated with at least one other plate which is located above it and in the sane chamber as ths latter in the die and which, in combination with 5 it, carries out the distribution of a plastics material of a certain colour.

3. « A die according to Clain 1 or 2, which consists of three bodies, namely an upper body, a middle body and a lower body, of which the upper body and middle body 10 delimit a parallelepiped chamber which receives, from the bottom upwards, the comb plate and the plate or plates, the channels for introducing the streams of coloured plastics material into the spaces of the comb are arranged respectively under the comb plate, between 15 this plate and the plate and above the plate, the spaces of the comb which are fed by the channels open into a passage delimited by the upper body and the middle body of the die, and two channels arranged in the upper body and the lower body for introducing the 20 streams of supporting-layer plastics and covering plastics open respectively into a passage communicating with said passage and into a passage, these passages ending in the gap delimited by the two lips of the die. 25

4. A die according to any one of Claims l to 3, wherein a valve for adjusting the flow of plastics material is placed on each of the channels. 5 · A flat die as claimed in Claim 1, substantially as hereinbefore described with reference to and as illustrated ln the accompanying drawings.