CS240980B2 - Apparatus for production of foil made from plastic substance having colour strip with various colour intensity - Google Patents

Abstract

1. Process for the extrusion of a foil (20) possessing a coloured strip with variable colour intensity, in which a first flow (1) of a molten thermoplastic synthetic resin is extruded through a wide slit nozzle (4a) after widening out in the transverse direction to the extrusion direction (P) ans is shaped to a foil (20), with an additional flow of molten thermoplastic synthetic resin being injected into this first melt flow (1) before the latter leaves the nozzle (4a), characterised in that - the injection takes place at a position at which the melt flow (1) has already widened out completely in the direction transverse to the extrusion direction, - with the injected melt flow (2c) possessing a wedge-shaped cross-section and the injection taking place at right angles to the extrusion direction and with corresponding constriction of the first melt flow (1).

Description

BACKGROUND OF THE INVENTION The present invention relates to a film production apparatus having a color strip of varying color intensity in which a melt stream of a thermoplastic synthetic material plasticized in an extruder is fed to a flat extruder and allowed to flow through a manifold channel for extruding the film in the transverse direction. and then allowed to flow parallel to the extrusion direction up to the nozzle outlet with a height-adjustable feed region, and another melt jet of a dyed thermoplastic synthetic material is injected into the melt stream prior to the nozzle exit.

The film forming apparatus having a color strip is based on an extruder for melting a stream of thermoplastic synthetic material and a flat extrusion head with a distribution channel with upstream throttle field, damper, inlet region formed by the upper jaw and lower jaw, with the nozzle exit slot for shaping the flat extrusion head still has an injection port for another partial flow of thermoplastic melt.

It is known from DT-OS 20 35 578 to produce a film having a color band of different color intensity, according to which a stream of colored synthetic material is injected when the main stream is still spilled in the transverse direction.

The colored melt stream is injected in the region of the distribution channel, whereby the colored melt stream is simultaneously poured in a direction transverse to the extrusion direction and is distributed.

A similar method and apparatus are known from EP-OS 0 052 491, in which a colored melt is injected to form a color strip into a colorless melt stream by arranging the color strip perfectly in the colorless melt.

For this purpose, a torpedo-shaped probe has been formed, which is arranged inside the extrusion channel and flows around the colorless melt from all sides.

К

In the manufacture of transparent films colored in partial areas, such as used as an intermediate film for automotive safety glass, a precisely defined and dimensioned transition area of the colorless portion in the colored portion with a continuous color intensity transition is required, such films being produced reproducibly with the same quality.

The disadvantage of the method according to DT-OS 20 35 578 is that it is very difficult to precisely control the desired color strip in terms of its cross-section, spillage, dimensions and color intensity, since the colored substance is injected into the distribution channel and is subject to further spillage transversely to the extrusion direction.

Also in the method and apparatus according to EP-OS 0 052 491, it is difficult to maintain the exact dimensions and course of the color gradients, since the colored melt is injected inside the flow of colorless mass when completely displaced and yet slight fluctuations in pressure ratios lead to different color strips. it concerns the color intensity and dimensions.

The pressure fluctuations induced by the extruder cannot be completely neglected, but this cannot be fully compensated by the method and the method of EP-OS 0 052 491 with respect to the position of the color strips.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and apparatus by which it is possible to produce in a simple manner reproducibly and with the same quality a film having a color band of different color intensity, such as known as colored polyvinyl butyral safety glass films.

The invention has taken a new path by proposing that one colorless melt stream and one colored melt stream now be formed into a sheet of desired width Ba or Bb and fused together along the side edge along the side edge of the sheet to a width of Ba + Bb and width Bc, calculated from the transition line of the colored film to the area of the colorless film, was saved

240,986, with a corresponding displacement of colorless flow melt a wedge ^{^} extending color strip consisting of a partial stream of the colored flow melt through a slot die having a wedge-shaped inlet slot, located - seen in the extrusion direction - in front of the barrier and of the distribution channel.

Thus, according to the process of the invention, a wide film is produced which has an uncolored film region and a region perfectly by means of a transition region consisting of a colored and uncoloured melt in the form of a wedge-shaped strip of a colored film. '

In this case, the transition region in which the colored melt stream of different cross-section and correspondingly different color intensity is deposited as a result of the displacement of the colorless melt stream from one side is also produced by means of a slot die.

The extrusion slot nozzle makes it possible to produce an accurately colored area with a corresponding cross-sectional area according to the length or width of the nozzle exit slot, while allowing the same output velocity of the colored melt over the width of the desired color strip, even at different thicknesses. This allows the desired exact control of the color band.

The basic construction of an extrusion slot nozzle is described, for example, in Kunststoff-Maschinenfiihrer, Carl Hanser, Verlag Munich, Wien, pages 95-98. The film production apparatus comprising a color band of different color intensity according to the invention takes into account In the apparatus, the injection port for another thermoplastic melt was formed as a small extrusion slot nozzle - observed in the extrusion direction - on the front side of the damper of a large flat extrusion head and a nozzle plate with a nozzle outlet slot mounted transversely to the extrusion direction along the front edge.

The feed of the additional melt stream according to the invention is thus provided downstream of the distribution channel, i.e. after the main melt stream has been completely spread in the transverse direction over the entire desired film width and flows in the extruder direction parallel along the entire width.

According to the invention, the front edge of the damper is used simultaneously as the edge of the nozzle exit slot for the additional melt flow and is converted into a small extrusion slot nozzle within the entire flat extrusion head in this region in accordance with the size of the nozzle plate.

The device according to the invention has the essential advantage over known injection nozzles, torpedoes or other substantially round or oval tubular injection devices that, even at the melt to be injected, the mass is distributed over the required cross-section corresponding to the flow, so that The output velocity of the additional melt stream due to the use of a suitably designed device was the same at each point of the exit slot so that melting with the already present melt stream without friction was achieved.

A further advantageous development of the invention is that the damper of the large flat extrusion head has a feed hole with a connecting hole leading to an extrusion slot nozzle for the partial melt flow. Depending on the design of the die, it can be fed asymmetrically or symmetrically, which also depends on the design of the die exit slot and the desired cross-section.

A preferred embodiment of the extrusion slot nozzle provides that it is flush on one side into the nozzle plate with a distribution channel, a septum, and a nozzle outlet slot.

The distributor plate is then mounted on the leading edge of the damper and together with it forms a flow channel for the partial melt flow in the region formed.

To achieve the color band of the wedge outlet slot, the small extruded slit-shaped cross section decreasing from the predetermined slit-nozzle is designed so that the partial-slit-nozzles of the nozzle have the same exit velocity.

According to the invention, the nozzles have a wedge-shaped shape and a gap width of up to 0 along their length, but the melt extrusion flow has an outlet

According to the invention, the nozzle outlet slot is adjustable, for example by means of a suitable adjustment of the nozzle plate, for example by means of screws, shims and the like.

The advantageous construction of the device according to the invention, for producing color strips of different color intensity in one melt stream, by means of which a film with a colorless region and a colored region and transition region is produced, provides for two flat extrusion heads of the same geometric shape or different width The nozzles that are fed from the extruder were arranged side by side and connected so as to provide a through nozzle exit slot with a width given by the sum of the individual nozzle widths. The injection orifice designed as an extrusion slot nozzle extended from the transition line next to the arranged flat extrusion head. in the desired width into a partial area of one of the flat extrusion heads and has been connected via a supply channel to the melt flow of the other flat extrusion head.

AND

The invention is preferably used for the production of polyvinyl butyral-based films which are used as interfaces for safety glass in the automotive and construction industries.

The invention is explained in more detail below with reference to the drawings of one exemplary embodiment.

They show:

Fig. 1 is a cross-sectional view of a known flat die head; Fig. 2 is a cross-sectional view A of the inlet of the flat die head of Fig. 1 in a schematic representation; Fig. 4 is a cross-sectional view of a film having a colorless, colored and transition region; Fig. 5 is a schematic view of the film manufacturing apparatus of Fig. 4; Fig. 6 is a cutaway view of the open flat extrusion head of Fig. 5; Fig. 7 is a cross-sectional view of BB of Fig. 6, Fig. 8 is a cross-sectional view of an extrusion slot nozzle consisting of a damper and plate of Fig. 7; Fig. 9 a top view of the extrusion slot nozzle of Fig. 8; according to section CC of FIG. 9 and FIG. 11, view E of the slot die of FIG. 8.

In FIG.

P ^s c ^hook gaping ^is a schematic diagram slot die '4a, in which the current _1 melt from the extruder enters the inlet channel' · '3 aa, then flows through the manifold channel 5a divides into desired width.

A throttle field is connected to the distribution channel 5a, a channel with a constant slot height, the length of which is reduced in accordance with the mass pressure in which the flow of material is regulated and at its end passes into the upstream region 11a in the damper 6a and finally into the outlet region 7a nozzle.

By adjusting the damper by means of the tension and set screws 12, corresponding flow corrections can be made in this region, which is analogous to the nozzle outlet region which is adjustable by the upper jaw 8a which is adjustable by the screw 13. At the nozzle outlet slot 9a the molded melt then exits flat extrusion head.

FIG. 2 is a schematic view of the cross-sectional structure of the flow channel, from the melt inlet through the distribution channel 5a, the throttle field 10a, and the upstream region 11a in the damper region.

According to the invention, it is possible to construct and connect two flat extrusion heads in such a way that an extremely wide foil can be produced from the same or different types of synthetic material in the same or different colors.

It is essential that the flat die heads 4a, 4b have the same geometry with respect to the flow cross section design, but they may have different widths Ba, Bb. It is preferred that the melts 6, 2 are formed on the basis of the same thermoplastic synthetic materials but of different coloration, optionally colorless and colored.

Accordingly, regions of the foils 20a and 20b are then formed and bonded in the actual foil 20. To form the color strip region 20c in the foil 20, a separate embossing slot nozzle 21 is inserted into one of the flat embossing heads 4a, 4b, in the example of FIG. 3 into the flat extrusion head 4a.

Advantageously, the die slot 21 is disposed in a transition region extending from one flat die head 4 to the other flat die head 4b, but this is governed by: the desired arrangement and formation of the color strip region 20c.

FIG. 4 shows a cross-sectional view of a preferred film arrangement, in particular based on polyvinylbutyral, with a color band produced by extrusion. In this case, films having a width of Ba + Bb are produced which have a colorless region 20a and a colored region 20b.

Observed from the transition area colored areas 20a of the film to a colorless area 20b of the film · decreases color intensity of a colored band toward colorless film, an area 20c ^{of the film to Ter} with výtodou ^P ro ^{is running} hook ^key newly ^Ita under Lime al ^f and ^{in Angle} range ³ ° to ²⁰ °.

According to this region of the film having a color band '20' which has a width of Bc, corresponding flat embossing heads are constructed, for example as shown in the schematic representation in FIG. 5.

In this case, the colorless melt stream is plasticized by means of an extruder 14 and passed through the melt pumps, the feed channel 3a to the first flat extruder head 4a. In the second extruder 15, the colored synthetic plastic melt is melted into the melt and is fed via the melt pumps 16b through the feed channel 3b to the second flat extrusion head 4b.

The melt stream 2c is separated from the melt stream to form a ribbon of color and is discharged through a conduit 3c and further, for example by means of a melt pump 17, to be fed to the flat extrusion head to form the ribbon of color 20c in the film 20. 4a embedded extrusion slot nozzles 21.

FIGS. 6 and 7 show the extrusion slot nozzle 21 and its installation in the flat extrusion head 4a. Referring to FIG. 6, it follows that the flat embossing head 4a for the colorless film 20a and the flat embossing head 4b for the color film 20b are arranged directly adjacent to each other, and the interfacing surface of the flat embossing heads 4a, 4b simultaneously form a transition line 27 between the two film regions 20a, 20b.

arrow P indicates a film extrusion mixture 20, seen in the extrusion direction, an additional extrusion slit nozzle 21 is provided in front of the dam 6a to inject a partial stream of colored melt into the area of the colorless film;

In this case, the damper 6 and can be formed, for example, with a recess 28 in which the nozzle plate 22 is inserted to form a flow cross section for the extrusion slot nozzle 21. FIG. 7 shows the construction of the extrusion slot nozzle 21 in a flat region of the extrusion head 4a, in vertical cross-section.

The colorless melt 7 comes from the distribution channel 5a and is uniformly distributed by the throttle field, so that upon entering the upstream region 11a in the region of the damper 6a, the colorless melt 1 is poured parallel to the extrusion direction over the desired film width.

At the leading edge 29 of the damper 6a, a nozzle outlet slot, at the desired width, for the partial melt flow 2c, extends from the die slot nozzle 21. The partial melt stream 2c is fed, for example, by recessing in the damper 6a to the cross-sectional flow of the die slot 21, the cross-sectional flow of the die gap 21 is formed by a nozzle plate 22 which is mounted on the front side of the damper 6a. corresponding flow retention, for example by means of screws (not shown).

FIGS. 8 to 11 show a preferred construction of the extrusion slot nozzle 21 for supplying a partial melt flow to the main melt flow already distributed in the extrusion slot nozzle.

Giant. 8 shows once again to a larger scale the cross section of the damper 6a of FIG. 7, with a separate melt flow inlet 30 and a flow orifice 23 into the flow cross section of the dispensing die 21.

The cross-sectional flow of the extrusion slit nozzle 21 is formed between the end face of the damper 6a and the nozzle plate 22 arranged in front thereof, the nozzle exit slot 24 extending along the edge 29 of the damper 6a. 8. It also follows that it is advantageous to insert the nozzle plate 22 into the recesses 28 of the damper 6a. The section Dd of FIG. 9 corresponds to that of FIG. 8.

FIG. 10 shows the construction of the flow cross section in the nozzle plate 22 according to section CC of FIG. 9. The flow cross section of the extrusion slot 21 has a substantially distribution channel 211, a baffle 210 with throttle field function and a nozzle exit slot 24. The length L of the nozzle exit slot 24 is selected according to the desired width of the fed ink ribbon in the film.

As is apparent from FIG. 11, it is preferable to provide the wedge nozzle exit slot 24. In such a construction of the nozzle outlet slot 24, it is preferable, as shown in FIG. 9, to provide a one-sided power supply.

The incorporation of an additional die die 21 according to the invention into a flat die head for introducing a color different melt to produce a color band of defined color intensity and size is, as exemplified, possible with two flat die heads interconnected, but 1 using only one large flat extrusion heads.

> 24О.ШГ ·

Claims (6)

1. Apparatus for producing a plastic film having a color band of different color intensity, with an extruder for melting a stream of thermoplastic synthetic material with a flat extrusion head with a flow channel with a throttle field, damper, front area formed between the upper jaw and lower jaw with an exit slot of the film-forming nozzle, the flat extrusion head still having an injection port for a further thermoplastic partial melt stream, characterized in that the injection port is formed as an extrusion slot nozzle (1) seen in the extrusion direction at the leading edge of the slide (ба) flat extrusion heads (4а) and nozzle plates (22) attached thereto with a nozzle outlet slot (24) extending transversely in the extrusion direction along the leading edge of the damper (ба). Apparatus according to claim 1, characterized in that the damper (ба) has a feed opening (28) with a connecting bore (23) in the direction of the partial melt die (21). Device according to claim 1 or 2, characterized in that the extrusion slot nozzle (21) is flush on one side into the nozzle plate (22) with a distribution channel (211), a partition (210) and an outlet slot (24). nozzles. Device according to one of Claims 1 to 3, characterized in that the nozzle outlet slot (24) is wedge-shaped and the width of the outlet slot decreases along its length L from a predetermined slot width k0, but the extrusion slot nozzle (21). has a structure ensuring a constant outflow rate of the partial melt flow over the entire length of the exit slot (24). Device according to one of Claims 1 to 4, characterized in that the nozzle plate (2) is adjustable and the outlet slot (24) is adjustable. Device according to one of Claims 1 to 5, characterized in that it is provided with two flat extrusion heads (4a, 4b) of the same geometrical shape, possibly with different nozzle widths, which are arranged for feeding one extruder with one jet each. За, З, (melt) stacked side by side and connected, the through nozzle exit slot having a width given by the sum of the widths of the individual nozzles and an injection port constructed as an extrusion slot nozzle (21) extending from the transition line (27) side by side (4a, 4b) over the width of Bc into a partial region of one of the flat extrusion heads (4a) and is connected by a feed channel (Зс) to the melt flow (2) of the other flat extrusion head (4Ь).