CS264335B2 - Process for manufacturing foil like interlayer for safety glass - Google Patents

Abstract

1. Process for the production of foils (4) with low surface adhesivity from a plasticised melt (A) having a plasticiser-containing polyvinylbutyral basis or a basis or polymers with similar properties, by extrusion with a broad slit tool (1), wherein the plasticised melt (A) is shaped with the wide slit tool (1) with input channel (10), distribution channel (11) and outlet gap (13) to form a foil, characterized in that the wide slit tool (1) is subjected in a region which - seen in the extrusion direction - is after the distribution channel (11), to a temperature which is so much lower than the remaining wide slit tool (1) that a temperature difference between the surface and the interior of the flow of melt (A) shaped to the foil is produced so that a roughening of the foil surface and accordingly a low surface adhesivity is produced as a result of the shearing of the solidifying melt flow taking place as a result, and that the foil emerging from the wide slit tool (1) is guided into a water bath (5) with a water temperature in the region of 2 to 40 degrees C.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for the manufacture of a safety glass intermediate layer having low surface adhesion and which is produced by extrusion using a flat film extrusion die, which films are made of polyvinyl butyral or polymers having similar properties.

Films made of polyvinyl butyral (PVB), which contain a plasticizer, are used, for example, for the production of laminated safety glass. These films of this material are already exceptionally smooth and adhesive (or sticky) at room temperature. This high degree of adhesion is unnecessary on one side to achieve the effect of glass-foil-glass bonding in safety laminated glasses, but further handling of the foil in the manufacture of said glasses must temporarily eliminate this adhesion. In the production of such films by prior art extrusion, whereby PVB films with a smooth and adhesive surface are produced, direct application of these films to the production of laminated glasses is avoided.

Several different methods are known in the art to temporarily eliminate the surface adhesion of the polyvinyl butyral films by roughening the surface of the films or by performing direct creasing over the entire surface of the film.

In order to achieve this roughening of the surface of a polyvinyl butyral film containing a plasticizer, a process has been proposed according to U.S. Pat. No. 4,035,549, wherein a roughened roll of calender and simultaneous heat treatment is provided

Rough surface structures of these films. In this process, however, due to the high adhesion, it is very difficult to separate the film from the calender rolls without problems. In this uneven film separation, wrinkled and weak areas occur on the film thus produced. As can be seen from the above, roughening or texturing is not achieved on both sides of the film simultaneously, but rather subsequently, in this process. However, when the film is heated to effect a texture on the second surface, due to the elastic inertia of the thermoplastic material, the partially roughened surface formed on the first surface of the film is removed.

This disadvantage of strong sticking of the film to the calender rolls is eliminated by another prior art process disclosed in UK Patent No. 1,271,188. In this process, the grinding matting rolls used to achieve a roughening of the film surface are maintained in a water bath heated to about 80 ° C. In doing so, the water film covering the surface of the rubber-coated matting rollers prevents the film from sticking to the matting roll surfaces so that both sides of the film can be roughened simultaneously. However, using this process due to the too high compression effect of the rubber matting rollers, seizure of these matting rollers into the surface of the film can occur, whereby undesirable cut edges on the roughened surfaces are formed on the surface of the film. Upon further processing of the film, these cut edges on the roughened surfaces may cause bubbles to form in the laminated safety glass. For this reason, these PVB films with undesirable edges on roughened surfaces cannot be used for the stated purposes.

It is an object of the present invention to provide a simple and safe process for the production of films, such as polyvinyl butyral, which have low surface adhesion, without the need for subsequent matting of the produced films, eliminating the drawbacks and advantages of prior art processes. techniques. The object is therefore to produce a film which can advantageously be used for the production of safety laminated glasses, without the formation of bubbles during further compression of the film in the manufacture of laminated glasses.

In the description of the present invention, the term polyvinyl butyral (PVB) is also meant to include other polymers having similar properties to a polyvinyl butyral containing plasticizer, taking into account their applications. This group of substances includes, among other materials, for example, ethylene vinyl acetate copolymers or other other ethylene copolymers. These aforementioned similar properties are particularly understood to surface adhesion or stickiness, as well as softness and elasticity similar to that of Uma ^r at ambient temperature.

SUMMARY OF THE INVENTION A process for producing a film as an interlayer for safety glass having low surface adhesion, from a plasticized melt based on a polyvinyl butyral containing plasticizer or a polymer with similar properties, extruded by a flat film extrusion die, wherein the plasticized melt contains no liquid additives such as water; the plasticized melt is formed on the film in a flat sheet extrusion die having an inlet channel, a distribution channel and an exit slot, according to the present invention, in that the flat sheet extrusion die is in the region of , which is located downstream of the distribution channel, heats to a temperature that is 20 to 80 ° C lower than the core temperature of the melt flow formed on the film and this raw film discharged from the flat film extrusion die ducted into a water bath at a water temperature ranging from 2 to 40 ° C.

In the process according to the invention, on the one hand, the viscosity is dependent on the temperature of the melt and on the other hand the limited thermal conductivity of the melt. Due to the sudden cooling of the melt flow, which is achieved by adequately tempering the walls of the flat film extrusion die, particularly in the exit slot zone, the melt flow surface is rapidly cooled while the melt core, i.e. the middle inner region of the film, still retains its original higher temperature. . Due to this temperature difference, the melt flow viscosity is also lower in the central region than on the surface. This achieves a higher flow rate in the central region of the melt than on the surface of the solidifying melt flow. This shear effect in the melt flow results in roughening of the film surface. It has been found that polyvinyl butyral films which contain a plasticizer can also achieve low surface adhesion without the need for further processing of the film. The films produced by the process of the present invention have DC roughening on both surfaces without any cut edges so that the films can be advantageously used for other manufacturing processes, such as the production of safety laminated glass.

The roughening and matting formed on both surfaces of the film by the process of the present invention will then disappear again when the film is compressed in the manufacture of the safety laminated glass and the surface will become smooth and transparent. In this treatment of the film, the uniformly dimming of the air removal between the film and the glass during compression in the manufacture of the safety laminated glass helps favorably, so that using the film produced by the process of the present invention for the production of safety laminated glass it is possible to produce the laminated safety glass. The roughening thus obtained has only a relatively small roughening depth with a small temperature difference between the portion forming the outlet orifice of the slot and the remaining portion of the extrusion die, and greater roughening can be achieved with a higher temperature difference between the said portions.

In the manufacture of safety laminated glass, the glass sheets together with the film as between the layer are directly pressed to the so-called pre-assembly. Quite unexpectedly, it has been found that the temperature required to form the preform is lower than the film of the same material, but prepared according to prior art techniques.

When using a film prepared by the process of the present invention, a temperature of about 60 ° C is used, while using a film of the same material but prepared by the process of UK Patent No. 1,271,188, a temperature of about 60 ° C is used. 80 ° C.

All plasticized polyvinyl butyrals which are suitable for the production of films for safety laminated glass can be used for the production of films according to the invention. These polyvinyl butyrals are in particular polymers which contain vinyl alcohol units in an amount of from 10 to 30% by weight, preferably in an amount of from 15 to 25% by weight, and further optionally with up to 10% by weight, but usually less than about 5% by weight of the acetate units based on polyvinyl acetate.

In principle, any plasticizer or plasticizer mixture which is compatible with the polyvinyl butyral used can be used according to the invention. Commercially available and commercially available plasticizers and their compatibility with polyvinyl butyral are disclosed, for example, in Modern Plastics Encyclopedia, 1981-1982, st. Examples of particularly suitable plasticizers are esters of aliphatic diols with aliphatic carboxylic acids, in particular esters of diethylene glycol, triethylene glycol and tetraethylene glycol with aliphatic carboxylic acids having 6 to 10 carbon atoms, such as 2-butyl butyric acid and n heptanoic as well as esters of dicarboxylic acids such as adipic acid, sebacic acid or phthalic acid with aliphatic alcohols containing 4 to 8 carbon atoms such as dihexyl adipate, dibutyl phthalate or dihexyl phthalate, and phosphoric esters such as for example, tricresyl phosphate or trioctyl phosphate, and mixtures of various plasticizers from this group, such as phthalic acid esters and adipic esters.

These plasticizers are used in conventional amounts, i.e. the polyvinyl butyral / plasticizer mixtures may contain the plasticizer in an amount of from 15 to 50% by weight, preferably in an amount of from 25 to 40% by weight.

Commonly used additive agents such as stabilizers, ultraviolet radiation, pigments and / or colorants, antioxidants, flame retardants, and other auxiliary agents such as small amounts of alkaline agents, for example 0.001 to 0.001 to 0.15, may be added to the polyvinyl butyral / plasticizer mixture. 0.1% alkali hydroxide or alkali reacting alkali salts, and in addition, commonly used antiblocks, such as carboxylic acids, in particular potassium salts and magnesium salts of formic acid and / or acetic acid, or dicarboxylic acid salts, may be added to said mixture, and it is also possible to add lecithin or betaines to the above mixture. For example, the concentration of said antiblocks is from 0.001 to 0.2% by weight. Exemplary ultraviolet stabilizers include benzotriazole derivatives, as well as other tackifiers, such as montanoic acid esters at concentrations ranging, for example, from 0.1 to 2% by weight. The percentages by weight of the adjuvants are in each case based on the total amount of polyvinyl butyral and the plasticizer.

In the process according to the invention, the thermoplastic melt is preferably softened at a temperature in the range of from 200 to 250 ° C, in particular at about 220 ° C, and is then fed to a flat film extrusion die at this temperature. As the mixture enters the flat film extrusion die, this temperature in the mass changes to the temperature of the flat film extrusion die, and the mixture continues to flow through the die at a constant temperature until it is further cooled in the next zone by a steep impact mode. is a feature of the process of the present invention in the region of the exit orifice of the slot, thereby providing the desired surface roughening of the film extending from the flat film extrusion die.

In accordance with the invention, films having low adhesion and / or low adhesion are prepared. surface tack, of polyvinyl butyral or of polymers having similar properties, by extruding a thermoplastic melt onto the film in a flat film extrusion die with an inlet channel, a distribution channel and an exit zone, wherein the process is a portion of the film extrusion die downstream of the distribution channel in the melt-extruding direction, tempered to a temperature lower than that of the other portions of the die, to the extent that a temperature difference occurs between the melt flow surface and the melt core to achieve a shear effect in the solidifying melt flow; hence uniform roughening of the film surface and low surface adhesion of the film.

According to a preferred embodiment of the process of the present invention, the temperature in the region of the exit orifice of the flat film die is controlled to a temperature in the range of about 100 ° C to 180 ° C. Without limiting the scope of the present invention, this process can be used to extrude polyvinyl butyral films having a thickness of 0.36 millimeter and 0.76 millimeter and a width of 2 to 3.5 meters. The exit slot has a width and height adjusted to the nozzle size. The length of the outlet slot, i.e. the length of the slot in the direction of flow, ranges from 1 cm to 3 centimeters. This represents a lower temperature region in the process of the present invention.

In the case of large dimensions of the flat film extrusion die, another preferred embodiment of the process of the present invention is that the temperature in the region of the exit orifice of the flat film extrusion die can be controlled in two steps, the inlet zone of the exit orifice wherein the melt enters first is regulated to a temperature in the range of from 160 ° C to 180 ° C, and the outlet zone of the exit orifice of the slit is regulated to a temperature in the range of from 100 ° C to 160 ° C. If the temperature difference 4t between the temperature of the first melt-contacting parts in the flat foil extrusion die, for example 200 ° C, and the outlet exit temperature of the slot, such as 180 ° C, is only 20 ° C, thereafter, only a small roughening of the film surface is achieved in the range of several _of µm. Conversely, if the temperature difference Δt between the temperature of the other portions of the flat film extrusion die and the exit orifice of the slit is up to 40 ° C, then greater roughening is achieved, with a roughening depth in the range of up to about 25 µm.

According to another preferred embodiment of the process of the invention, the surface texture formed by the film emerging from the flat film extrusion die is fixed by introducing the film thus produced directly into the water bath at a temperature of from 2 ° C to 40 ° C .

In a preferred embodiment of the invention the surfaces of the film through the roughening depth in the range _from 10 to 40 microns, even more preferred is a roughness height in the range of 20 to 30 / Um.

The process of the present invention is particularly suitable for the production of films of polyvinyl butyral and plasticizer, wherein the amount of plasticizer based on the weight of the total mixture of polyvinyl butyral and plasticizer ranges from 15 to 50% by weight, 0.38 millimeter or 0.76 millimeter thick. which are roughened to a depth in the range of 20 to 27 µm on the surface of the film, the width of the film being in the range of 2 to 3.5 meters. Preferably, the extrusion rate of the film is in the range of 5 to 20 meters / minute.

The process of the present invention will be described in more detail below with reference to the accompanying drawings, in which:

Fig. 1 is a schematic cross-sectional view of the apparatus for carrying out the process of the invention; Fig. 2 is a schematic longitudinal cross-sectional view of a flat sheet extrusion die forming part of the apparatus for carrying out the process of the invention shown in Fig. 1; Fig. 4 is a schematic view along the line DD of the lower portion of the flat sheet extrusion die shown in Fig. 2; and Fig. 4 shows a schematically temperature curve showing temperatures in the flat die; Fig. 5 shows a schematic view of the extruder; temperature control units.

FIG. 1 schematically illustrates the passage of a polyvinyl butyral-based thermoplastic melt A in the process according to the invention, the melt being fed from an extruder not shown in the drawing and introduced into a flat film extrusion die 1 in the inlet This material exits from the flat sheet extrusion die 1 in the form of a sheet 4 from the outlet of the die or from the outlet orifice of the slot 16. Since the sheet 4 is then fed to the water bath for cooling immediately after leaving a flat film extrusion nozzle according to the invention, as shown in FIG. 1, is preferably provided with its outlet vertically directly above the water surface of the water bath 5. The water in the water bath preferably has a process according to the invention a temperature in the range of 2 ° C to 4 ° C Low: 14 ° C. The film thus produced is first guided vertically through the water bath, which is then fed out of the water bath through a guide roller 6 and is discharged by means of a pair of guide rollers 7. This pair of guide rollers 7 is preferably made as rubber rollers. by means of which only a slight compression of the produced film 4, which withdraws from the water bath 5 already in solidified form, can be used, the film being removed in the direction of arrow C. In order to obtain the effect of the surface treatment according to the invention flat film extrusion nozzles 1 are provided in the region of the film outlet in the flat film extrusion nozzle 1, which are shown in detail in FIG. 2, and a hot heating medium such as e.g. oil. By means of this medium it is possible to control the temperature of the film extrusion die in this region. In addition, the entire flat film extrusion nozzle 1 can also be heated uniformly, for example by means of electrical resistance heating, which is not shown in detail in this figure.

FIG. 2 shows in principle in cross-section in greater detail the design and construction of a flat film extrusion die 2 ^for carrying out the process according to the invention. This flat film extrusion die 1 consists of an upper part 1a and a lower part 1b, which are fixed to each other by means of a screw connection, not shown in this figure. The upper part 1a and the lower part 1b are made of metal and comprise heating means, not shown in detail, by means of which the entire nozzle is heated to a temperature in the range of 160 to 200 ° C. A flow channel for guiding the thermoplastic melt A is introduced into the contact zone zone of the upper part 1a and the lower part 1b. Since the flat film extrusion die, as shown in FIG. 1, has a vertical extrusion film outlet, the inlet of thermoplastic melt A is arranged at an angle of 90 °, the inlet to the flat film extrusion die forming an inlet zone 15. ^{and an} inlet channel 10 which is introduced into the distribution channel 11 of the flat nozzle. 2a, the tapered zone 12 and the exit orifice of the slot 13 are disposed through this distribution channel 11, whereby the thermoplastic melt is already guided in a direction parallel to the extrusion direction of the desired film to the thickness. the outlet mouth of the slot 13 is formed on both sides by the walls of the upper part 1a and the lower part 1b of the flat film extrusion die. In this arrangement, the upper part is usually made adjustable, at least in the region of the front zone, referred to herein as the nozzle mouth 14, which adjustable position serves to control the thickness of the film being produced.

In the region of the outlet orifice of the slot 13, channels 2a, Ja are arranged in a parallel direction to the width of the nozzle outlet 16. ¹ - 2b and 3b in a paired configuration in the upper part ba and in the lower part 1b of the flat film extrusion die. A heat exchange medium, such as oil, is introduced into these channels 2a, 2b, 8a and 3b. Each of these pairs of channels 2a, 2b and 3a, 3b is connected to a separate oil circuit, and the temperature of the oil and thus of the circuit can be independently adjusted to the desired value. A melt which is extruded through a flat die 2 P ^ro film extrusion by passing through the aforementioned channels, leaves the slot nozzle as a film in the direction of arrow В in the outlet 16 from the nozzle.

FIG. 3 again schematically illustrates the passage of melt flowing to the lower portion 1b of the flat film extrusion die, which is shown along the line DD shown in FIG. 2. The melt is fed through the inlet channel 11 and is distributed through the distribution channel. 11 extends across the width of the flat film extrusion die and deviates from the original direction, and is further guided through the tapered zone 12, being gradually transformed into the final mold in several stages, into the outlet orifice of the slot 13 .16 nozzle.

The following examples illustrate the process of the present invention in more detail. Example 1

In the process of this example, polyvinylbutyral suitable for extrusion films was used, which contained 21.0% by weight of vinyl alcohol units and whose viscosity was 75 mPa.s, as a 5% solution in ethanol at 23 ° C, DIN 53 015.

This polymer was mixed with 29% by weight (based on the weight of polymer and plasticizer) of triethylene glycol ester and bis-2-ethylbutyric acid. The mixture was extruded into a film of 0.76 mm thickness and 2.20 m width in an extruder at an extrusion rate of 10 meters / minute. In the process, the extruder was heated to a temperature in the inlet zone of 175 ° C, in the middle zone to 190 ° C, and in the last zone, which also includes a flat film extrusion die, to 200 ° C. The temperature in the melt of the polymer and the plasticizer reaches a maximum value of 220 ° C.

The flat film extrusion die 6 is heated in the region of the exit orifice of the slot 13 to a temperature of up to 80 ° C, and preferably up to 40 ° C below the temperature of the other parts of the flat film extrusion die. by means of a heat exchange control medium, such as heated oil, which flows through channels 2a, 2b and 3a, 3b. The oil flowing through channels 2a, 2b has a temperature of 170 ° C, while the oil flowing through channels 3a and 3b has a temperature of 150 ° C. The thermoplastic melt, i.e. the polymer / plasticizer mixture, passes through the flat film extrusion die, gradually shares the temperature of the flat film extrusion die, and gradually cools to 150 ° C in the region of the exit orifice. As a result of this temperature gradient between the film extrusion die temperature of 190 ° C and the outlet temperature of the slot of 150 ° C, the melt velocity of the polymer and the plasticizer suddenly decelerates suddenly along the contact surfaces of the flow channel of the film extrusion die. creates a further difference in melt flow rates in the central region of this flow channel. The surface of the melt flowing along the surface of the flat film extrusion die in the region of the exit orifice of the slit no longer remains smooth, but rather has a roughened character. The roughening depth in this context depends on the temperature of the heat transfer medium used to control the temperature in the channels 2a. 2b and 3a, 3b, ⁱⁿ comparison with ^the temperature of other portions of the flat die film extrusion, and these relationships are independent of the thickness of the extruded film.

.If, for example in this embodiment, maintaining a temperature of oil which flows through the passages and JL За, at a value of 150 ° C, then achieving a uniform roughening of the two surfaces of the extruded film in the depth of the roughening _of 25 microns. Conversely, if the temperature of the oil flowing through channels За and 3b is maintained at 140 ° C, then roughening is achieved at a depth of 35 µm, and if the temperature of the oil flowing through channels За and 3b is maintained at 165 ° C then a uniform roughening of the surfaces of said film is achieved at a roughening depth of 15 µm. That is, the higher the temperature gradient between the medium flowing in channels 2a, 2b and 3a, 3b and the temperature control used and between the flat film extrusion die, the greater the roughening depth can be achieved. After the film leaves the flat extrusion die, the film is directly fed into a water bath having a temperature of, for example, 5 ° C. After the film has solidified, the film is removed from the water bath using guide rollers and a pair of rollers.

FIG. 4 is a temperature curve illustrating the temperature profile of the flat film extrusion die along the entire melt channel in the process of Example 1. The thermoplastic melt passes through the flat film extrusion die while in intense contact with the film. the metal surfaces of the flat film extrusion die and the temperature of the melt is directly shared with the flat film extrusion die. That is, the thermoplastic melt that enters the flat sheet extrusion die having a temperature in the mass higher than that of the flat sheet extrusion die receives the temperature of the flat sheet extrusion die already in the inflow channel.

As can be seen from FIG. 4, the flat film extrusion die is maintained at a constant temperature, e.g. 190 ° C, over most of the flow passage, specifically said constant temperature is maintained in the inlet channel 10, the distribution channel 11 and the tapered region. In the region of the outlet orifice of the slot 13, cooling is carried out at two points, namely in the region of the channels 2 and in the region of the channels 2 ^{in the} form of a two-stage cooling from 190 ° C to 170 ° C and 150 ° C. In this way, the thermoplastic melt is quenched suddenly during this short process in the region of the exit orifice of the slot 13, the temperature difference being Δ t = 40 ° C. This cooling is sufficient to disrupt the smooth surface of the film and to produce the desired uniform roughening on both sides of the extruded film.

Fig. 5 shows a temperature control unit in the flat nozzle 2 by means of which the temperature regime can be adjusted in the process shown in Fig. 4 in this example according to the invention. The nozzle 2 is heated, for example, in the region of the outlet opening of the slot 13 by means of channels 3 and 2 through which the heat transfer medium, i.e. oil, flows. The temperature of this heated oil is controlled and controlled by the control unit 20a, 20b and 30a, 30b, i.e. each channel is controlled and regulated separately. The other parts of the nozzle are also heated by heated oil flowing through the channels 111, the temperature of which is controlled and controlled by the control unit 100.

Claims (5)

CLAIMS 1. A method of making a film as an interlayer for safety glasses having low surface adhesion, from a plasticized melt based on a polyvinyl butyral containing plasticizer or a polymer with similar properties, extruded by a flat film extrusion die, wherein the plasticized melt contains no liquid additives such as water. and the plasticized melt is formed into a film in a flat sheet extrusion die having an inflow channel, a distribution channel and an outlet slot, wherein the flat sheet extrusion die is in a region which is placed downstream of the distribution channel, tempering to a temperature that is 20 to 80 ° C lower than the core temperature of the melt flow formed on the film, and this raw film removed from the flat film extrusion die is discharged into a water bath with a temperature in the range of 2 to 40 ° C. 2. Process according to claim 1, characterized in that the thermoplastic melt is softened to a temperature in the mass of from 200 to 250 [deg.] C. Method according to Claims 1 to 2, characterized in that the temperature in the outlet region. the orifice of the film extrusion die gap ranges from 100 to 180 ° C. 4. A method according to any one of claims 1 to 3, wherein the temperature in the region of the exit orifice of the film extrusion die is controlled in two stages, wherein the inlet region of the exit orifice of the slit is regulated to a first temperature in the range of 160 ° C to 180 ° C. and the outlet region of the exit orifice of the slot is regulated to a second temperature that is lower than said first temperature and is in the range of from 100 ° C to 160 ° C. 5. A method according to claims 1 to 4, characterized in that the film is extruded at an extrusion rate in the range of 5 to 20 meters / minute.