White, biaxially oriented, flameproof polyester film with cyclo-olefinic copolymer, method for its manufacture and its use

The present invention relates to a white, biaxially oriented, flame retardant polyester film comprising at least one layer containing a polyester raw material and a cycloolefin copolymer (COC). The invention further relates to a process for producing the polyester film and to its use.

White, biaxially oriented polyester films are known in the art. These known from the prior art films are characterized either by good manufacturability, a good appearance or by an acceptable processing behavior.

DE-A 2 353 347 describes a process for producing a mono- or multilayer, milky polyester film which is characterized in that a mixture of particles of a linear polyester with 3 to 27 wt .-% of a homopolymer or copolymers of Ethylene or propylene, extruding the mixture as a film, quenching the film and biaxially orienting it by stretching in mutually perpendicular directions and heat-setting the film. A disadvantage of the process is that the regenerate produced in the production of the film (essentially a mixture of polyester raw material and ethylene or propylene copolymer) can no longer be used, since otherwise the film turns yellow. The process is therefore uneconomical and produced with regenerated film could not prevail on the market. In addition, the film has clearly too high roughness and thus has a very matt appearance (very low gloss), which is undesirable for many applications.

EP-A 0 300 060 describes a monolayer polyester film which contains, in addition to polyethylene terephthalate, 3 to 40% by weight of a crystalline propylene polymer and 0.001 to 3% by weight of a surface-active substance. The surfactant causes the number of vacuoles in the film to increase while decreasing their size to the desired extent. As a result, a higher opacity and a lower density of the film is achieved. A further disadvantage of the film is that the regenerate produced in the production of the film (essentially a mixture of polyester raw material and propylene homopolymer) can no longer be used, since otherwise the film turns yellow. The process is therefore uneconomical and produced with regenerated film could not prevail on the market. In addition, the film has clearly too high roughness and thus has a very dull appearance (very low gloss), which is undesirable for numerous applications.

EP-A 0 360 201 describes an at least two-layered polyester film which contains a base layer with fine vacuoles whose density is between 0.4 and 1.3 kg / dm³ and which has at least one cover layer whose density is greater than 1.3 kg / dm³ is. The vacuoles are obtained by adding 4 to 30% by weight of a crystalline propylene polymer and then biaxially stretching the film. The additional cover layer improves the manufacturability of the film (no streaking on the surface of the film), increases the surface tension and reduces the roughness of the laminated surface. A further disadvantage is that the resulting in the production of the film regenerate (essentially a mixture of polyester raw material and propylene homopolymer) can no longer be used, otherwise the film is yellow. The process is therefore uneconomical and produced with regenerated film could not prevail on the market. In addition, the films listed in the examples still have too high roughness and thus has a dull appearance (low gloss), which is undesirable for many applications.

EP-A 0 795 399 describes an at least two-layered polyester film which contains a base layer with fine vacuoles whose density is between 0.4 and 1.3 kg / dm³ and has at least one outer layer whose density is greater than 1.3 kg / dm³ is. The vacuoles are obtained by adding 5 to 45% by weight of a thermoplastic polymer to the polyester raw material in the base and then biaxially stretching the film. As thermoplastic polymers, inter alia Polypropylene, polyethylene, polymethylpentene, polystyrene or polycarbonate, polypropylene being the preferred thermoplastic polymer. The additional cover layer improves the manufacturability of the film (no streaking on the surface of the film), the surface tension is increased and the roughness of the laminated surface can be adapted to the respective requirements. Further modification of the film in the base layer and / or in the outer layers with white pigments (usually TiO₂) and / or with optical brighteners allows the adaptation of the film properties to the respective application requirements. Another disadvantage remains that the resulting in the production of the film Regenerat (essentially a mixture of polyester raw material and the additive raw material) can no longer be used, otherwise the film is changed undefined in the color, which is highly undesirable. The process is thus uneconomical and produced with regenerated film could not prevail on the market. In addition, the films listed in the examples still have too high roughness and thus has a dull appearance (low gloss), which is undesirable for many applications.

DE-A 195 40 277 describes a mono- or multilayer polyester film which contains a base layer with fine vacuoles whose density is between 0.6 and 1.3 kg / dm³ and has a birefringence in the plane ranging from -0.02 to 0.04. The vacuoles are achieved by adding 3 to 40% by weight of a thermoplastic resin to the polyester raw material in the base and then biaxially stretching the film. As thermoplastic resins, inter alia Polypropylene, polyethylene, polymethylpentene, cyclic olefin polymers, polyacrylic resins, polystyrene or polycarbonate, polypropylene and polystyrene being preferred raw materials. By maintaining the specified limits for the birefringence of the film, the claimed film is characterized in particular by a superior tensile strength and superior isotropic properties. The disadvantage, however, remains that the resulting in the production of the film Regenerat can no longer be used, otherwise the film is undefined in the color is changed, which in turn is very undesirable. The process is thus uneconomical and produced with regenerated film could not prevail on the market. In addition, the films listed in the examples still have too high roughness and thus have a dull appearance (low gloss), which is undesirable for many applications.

In DE-A 23 46 787 a flame-retardant plastic is described. In addition to the plastic as such, its use for the production of films and fibers is described. In the production of films with this, in DE-A claimed, phospholane-modified raw material but showed the following deficiencies:<ul id="ul0001" list-style="dash" compact="compact"><li>The plastic is very susceptible to hydrolysis and must be very well pre-dried.</li><li>When drying with dryers, which correspond to the prior art, the plastic adheres, so that the production of a film, if at all, succeeds only under the most difficult conditions.</li><li>The films produced under extreme and uneconomic conditions embrittle at temperature loads, ie the mechanical properties are due to the rapid embrittlement strong back, so that the film is technically unusable. Already after 48 hours of temperature stress, this embrittlement occurs.</li></ul>

The object of the present invention was to provide a white, biaxially oriented polyester film characterized by high gloss and improved manufacturability, ie low production costs, characterized and which also has good thermal stability and a high flammability. In particular, it should be ensured that the inherent in the manufacturing process for the film waste material (regenerate) in a concentration of 10 to 70 wt .-%, based on the total weight of the film, can be used again for the production process without causing the physical and optical properties of the regenerated film are adversely affected. In particular, no appreciable yellowing of the film should occur due to the addition of regenerant.

A heavy flammability means that the white film in a so-called fire protection test the conditions according to DIN 4102, Part 2, and in particular the conditions according to DIN 4102, Part 1, met and classified in the building material class B 2, especially B1, the flame retardant materials can.

Furthermore, the film is to pass the UL test 94, the so-called "Vertical Burning Test for Flammability of Plastic Material", so that it can be classified in Class 94 VTM-0. This means that the film no longer burns 10 seconds after removal of the bunsen burner, that after 30 seconds no more annealing is observed and that no dripping is detected during the whole time.

For the economic production counts that the plastics or the Kunststoffkom components that are needed to produce the flame retardant ble film, can be dried with industrial dryers that meet the standard of technology. It is essential that the raw materials do not stick together and are not thermally degraded. These prior art industrial dryers include vacuum dryers, fluidized bed dryers, fluidized bed dryers, and fixed bed dryers (shaft dryers). These dryers work on average at temperatures between 100 and 170 ° C, where usually flame retardant finished plastics must be bonded and mining mined, so that no film production is possible.

In the most gently drying vacuum dryer, the plastic undergoes a temperature range of approx. 30 ° C to 130 ° C at a vacuum of 50 mbar. Thereafter, a so-called post-drying in a hopper at temperatures of 100 to 130 ° C and a residence time of 3 to 6 hours is required. Even with this procedure, the known plastic sticks extremely.

Good thermostability means that the film after 100 hours annealing at 100 ° C in a convection oven has no embrittlement and no poor mechanical properties.

The object is achieved by a white, biaxially oriented, flame retardant polyester film with at least one base layer of polyester raw material dissolved, whose characteristic features are to be seen therein in that at least the base layer additionally contains cycloolefin copolymer (COC) in an amount of from 2 to 60% by weight, contains based on the weight of the base layer, wherein the glass transition temperature of the cycloolefin copolymer (COC) is in the range of 70 to 270 ° C, and that the film contains at least one flame retardant, which is preferably added directly as a masterbatch to the polyester raw material during film production.

A white, biaxially oriented polyester film in the context of the present invention refers to a film which has a brightness of more than 70%, preferably more than 75% and particularly preferably more than 80%. Furthermore, the opacity of the film according to the invention is more than 55%, preferably more than 60% and particularly preferably more than 65%.

To achieve the desired whiteness of the film of the invention, the amount of COC in the base layer should be greater than 2 wt .-%, otherwise the whiteness is less than 70%. If the amount of COC, on the other hand, is greater than 60% by weight, then the film can no longer be produced economically, since it can no longer be stretched in a process-safe manner.

Furthermore, it is necessary that the glass transition temperature of the COC used is greater than 70 ° C. Otherwise, if the glass transition temperature of the COC used is less than 70 ° C, the raw material mixture is difficult to process because it can only be extruded poorly. The desired whiteness is no longer achieved and the used regrind leads to a film that tends to increased yellowing. On the other hand, if the glass transition temperature of the selected COC is greater than 270 ° C, then the raw material mixture in the extruder will not be sufficiently homogenize. This then results in a film with undesirable inhomogeneous properties.

In the preferred embodiment of the film according to the invention, the glass transition temperature of the COCs used is in a range from 90 to 250 ° C and in the most preferred embodiment in a range from 110 to 220 ° C.

Surprisingly, it has been found that a white, opaque, glossy film can be produced by the addition of a COC in the manner described above.

Depending on the amount and the type of COC added, the whiteness and opacity of the film can be precisely adjusted and adapted to the respective requirements. By this measure, it is possible to dispense with other common white and opakmachende additives largely. Furthermore, it was very surprising that the surface roughness of the film is much lower and thus the gloss of the film is substantially higher than in comparable films according to the prior art. Almost sensational was the additional effect that, despite the presence of flame retardant, the regenerate shows no tendency to yellow, as observed with the use of polymeric additives and conventional flame retardants of the prior art.

All these features described were unpredictable. This is all the more so since COC is obviously largely incompatible with polyethylene terephthalate, but is known to be oriented with similar draw ratios and stretching temperatures to polyethylene terephthalate. Under these conditions, those skilled in the art would have expected that no white opaque sheeting of high gloss could be produced at these manufacturing conditions.

In the preferred and the particularly preferred embodiments, the film according to the invention is characterized by a high / or. by a particularly high degree of whiteness and a high / resp. by a particularly high opacity, the color change of the film by the Regeneratzugabe remains extremely low.

The film according to the invention contains at least one flame retardant, which is metered in via the so-called masterbatch technology directly in the film production, wherein the concentration of the flame retardant in the range of 0.5 to 30.0 wt .-%, preferably from 1.0 to 20.0 wt .-%, based on the weight of the layer containing the flame retardant is. In the preparation of the masterbatch, a ratio of flame retardant to thermoplastic in the range of 60 to 40 wt .-% to 10 to 90 wt .-% is generally complied with.

The typical flame retardants include bromine compounds, chloroparaffins and other chlorine compounds, antimony trioxide, Aluminiumtrihydrate, wherein the halogen compounds are disadvantageous due to the resulting halogen-containing by-products. Furthermore, the low light resistance of a film so equipped with the development of hydrogen halides in case of fire is extremely disadvantageous.

Suitable flame retardants which are used according to the invention are, for example, organic phosphorus compounds such as carboxyphosphinic acids, their anhydrides and dimethyl methylphosphonate.

Since the flame retardants generally have a certain sensitivity to hydrolysis, the additional use of a hydrolysis stabilizer may be useful.

The hydrolysis stabilizer used are generally phenolic stabilizers, alkali metal / alkaline earth metal stearates and / or alkali metal / alkaline earth metal carbonates in amounts ranging from 0.01 to 1.0% by weight. Phenolic stabilizers are preferred in an amount of 0.05 to 0.6 wt .-%, in particular 0.15 to 0.3 wt .-% and with a molecular weight of more than 500 g / mol. Pentaerythrityl tetrakis-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate or 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) Benzene are particularly advantageous.

Therefore, it was more than surprising that by means of masterbatch technology, a suitable predrying and / or precrystallization and optionally use of small amounts of a hydrolysis stabilizer a flame retardant and thermoformable film with the required property profile economically and above all without bonding in the dryer can be produced and that the film does not embrittle after temperature stress and does not break when kinking.

It was very surprising that with this excellent result and the required flame protection<ul id="ul0002" list-style="dash" compact="compact"><li>The yellowness of the film compared to a non-finished film within the measurement accuracy is not adversely affected;</li><li>no outgassing, no nozzle deposits, no frame evaporations occur, whereby the film has an excellent appearance, has an excellent profile and excellent flatness;</li><li>the flame-retardant, UV-stable film is characterized by an excellent stretchability, so that it can be manufactured reliably and stably on "high-speed film-lines" at speeds of up to 420 m / min production-safe.</li></ul>

Thus, such a film is also economically viable.

The film according to the invention is single-layered or multi-layered. Single-layered embodiments are constructed like the COC-containing layer described below. Multilayer embodiments are at least two-ply and always comprise the COC-containing layer and at least one further layer, wherein the COC-containing layer is the base layer, but can additionally also form the intermediate or covering layer of the multilayer film. In a preferred embodiment, the COC-containing layer forms the base layer of the film with at least one, preferably double-sided cover layer (s), wherein optionally one or both sides intermediate layer (s) can be present on one side. In a further preferred embodiment, the COC-containing layer also forms an intermediate layer of the multilayer film. Further embodiments with COC-containing interlayers have a five-layer structure and, in addition to the COC-containing base layer, have COC-containing interlayers on both sides. In another embodiment, in addition to the base layer, the COC-containing layer may form one or both sides of the cover layer (s) on the base or intermediate layer. For the purposes of the present invention, the base layer is the layer which accounts for more than 50 to 100%, preferably 70 to 90%, of the total film thickness. The cover layer is in any case the layer which forms the outer layer of the film, wherein it is preferred according to the invention that one or two cover layers are arranged on the COC-containing base layer and that the flame retardant is contained in the cover layer (s) are.

The particular embodiment of the invention is a non-transparent, white film. In the context of the present invention, non-transparent films are understood as meaning those films whose light transmittance according to ASTM-D 1003-77 is less than 95%, preferably less than 75%.

The COC-containing layer (the base layer) of the film according to the invention contains a polyester raw material, preferably a polyester homopolymer, a COC, the flame retardant and optionally further additives in respective effective amounts. In general, this layer contains at least 20% by weight, preferably 40 to 98% by weight, in particular 70 to 96% by weight, of polyester raw material, based on the weight of the layer.

The base layer of the film contains as its main component a thermoplastic polyester. Suitable for this are polyesters of ethylene glycol and terephthalic acid (= polyethylene terephthalate, PET), of ethylene glycol and naphthalene-2,6-dicarboxylic acid (= polyethylene-2,6-naphthalate, PEN), of 1,4-bis-hydroxymethyl-cyclohexane and terephthalic acid (= Poly-1,4-cyclohexanedimethylene terephthalate, PCDT) and from ethylene glycol, naphthalene-2,6-dicarboxylic acid and biphenyl-4,4'-dicarboxylic acid (= polyethylene-2,6-naphthalatbibenzoat, PENBB). Particular preference is given to polyesters which consist of at least 90 mol%, preferably at least 95 mol%, of ethylene glycol and terephthalic acid units or of ethylene glycol and naphthalene-2,6-dicarboxylic acid units. The remaining monomer units are derived from other aliphatic, cycloaliphatic or aromatic diols or Dicarboxylic acids, as they may also occur in the layer A (A = cover layer 1) or the layer C (C = cover layer 2) of a multilayer film ABC (B = base layer).

Suitable other aliphatic diols are, for example, diethylene glycol, triethylene glycol, aliphatic glycols of the general formula HO- (CH₂)_n-OH, where n is an integer from 3 to 6 (in particular propane-1,3-diol, butane-1,4-diol, pentane-1,5-diol and hexane-1,6-diol) or branched aliphatic Glycols with up to 6 carbon atoms. Of the cycloaliphatic diols, mention may be made of cyclohexanediols (in particular cyclohexane-1,4-diol). Suitable other aromatic diols correspond for example to the formula HO-C₆H₄XC₆H₄-OH, where X is -CH₂-, -C (CH₃)₂-, -C (CF₃)₂-, -O-, -S- or -SO₂- stands. In addition, bisphenols of the formula HO-C₆H₄-C₆H₄-OH well suited.

Other aromatic dicarboxylic acids are preferably benzene dicarboxylic acids, naphthalene dicarboxylic acids (for example naphthalene-1,4- or 1,6-dicarboxylic acid), biphenyl-x, x'-dicarboxylic acids (in particular biphenyl-4,4'-dicarboxylic acid), diphenylacetylene-x, x ' dicarboxylic acids (especially diphenylacetylene-4,4'-dicarboxylic acid) or stilbene-x, x'-dicarboxylic acids. Of the cycloaliphatic dicarboxylic acids, mention may be made of cyclohexanedicarboxylic acids (in particular cyclohexane-1,4-dicarboxylic acid). Of the aliphatic dicarboxylic acids, the (C₃-C₁₉) -Alkandisäuren particularly suitable, wherein the alkane moiety may be straight or branched.

The preparation of the polyester can, for example done after the transesterification process. It is based on Dicarbonsäureestem and diols, which are reacted with the usual transesterification catalysts, such as zinc, calcium, lithium, magnesium and manganese salts. The intermediates are then polycondensed in the presence of commonly used polycondensation catalysts, such as antimony trioxide or titanium salts. The preparation can also be carried out by the direct esterification process in the presence of polycondensation catalysts. It starts directly from the dicarboxylic acids and diols.

According to the invention, the COC-containing layer (base layer) or the film in one-layer embodiments, a cycloolefin copolymer (COC) in an amount of at least 4.0 wt .-%, preferably 5 to 50 wt .-% and particularly preferably 6 to 40 wt .-%, based on the weight of the base layer or based on the weight of the film in a single-layered embodiment. It is essential to the present invention that the COC is incompatible with the polyethylene terephthalate and does not form a homogeneous melt mixture with it.

Cycloolefin polymers are homopolymers or copolymers which contain polymerized cycloolefin units and optionally acyclic olefins as comonomer. Cycloolefin polymers which contain from 0.1 to 100% by weight, preferably from 10 to 99% by weight, particularly preferably from 50 to 95% by weight, based in each case on the total mass of the cycloolefin polymer, of polymerized cycloolefin units are suitable for the present invention. Particularly preferred are polymers which are composed of the monomers of the cyclic olefins of the formulas I, II, III, IV, V or VI:<chemistry id="chem0001" num="0001"><img file="EP1132425B1_D0001.tif" /></chemistry><chemistry id="chem0002" num="0002"><img file="EP1132425B1_D0002.tif" /></chemistry><chemistry id="chem0003" num="0003"><img file="EP1132425B1_D0003.tif" /></chemistry><chemistry id="chem0004" num="0004"><img file="EP1132425B1_D0004.tif" /></chemistry><chemistry id="chem0005" num="0005"><img file="EP1132425B1_D0005.tif" /></chemistry>

In these formulas, R¹, R², R³, R⁴, R⁵, R⁶, R⁷ and R^8th the same or different and denote a hydrogen atom or a C₁-C₃₀hydrocarbon radical; ortwo or more of the radicals R¹ to R^8th are cyclically linked, wherein the same radicals in the different formulas have the same or different meaning. C₁-C₃₀Hydrocarbon radicals are, for example, linear or branched C₁-C_8th-Alkyl radicals, C₆-C₁₈-Aryl radicals, C₇-C₂₀-Alkylenarylreste or cyclic C₃-C₂₀Alkyl radicals or acyclic C₂-C₂₀-Alkenyl.

Optionally, the COCs may contain from 0 to 45% by weight, based on the total weight of the cycloolefin polymer, of polymerized units of at least one monocyclic olefin of the formula VII:<chemistry id="chem0006" num="0006"><img file="EP1132425B1_D0006.tif" /></chemistry>

Here n is a number from 2 to 10.

Optionally, the COCs may contain from 0 to 99% by weight, based on the total weight of COC, of ​​polymerized units of an acyclic olefin of formula VIII:<chemistry id="chem0007" num="0007"><img file="EP1132425B1_D0007.tif" /></chemistry>

Here are R⁹, R¹⁰, R¹¹, and R¹² the same or different and denote a hydrogen atom or C.₁-C₁₀Hydrocarbon residues, eg a C₁-C_8thAlkyl radical or C₆-C₁₄Aryl.

Likewise suitable in principle are cycloolefin polymers which are obtained by ring-opening polymerization of at least one of the monomers of the formulas I to VI and subsequent hydrogenation.

Cycloolefin homopolymers are built up from a monomer of the formulas I-VI. These cycloolefin polymers are less suitable for the purposes of the present invention. For the purposes of the present invention, cycloolefin copolymers (COC) are suitable which contain at least one cycloolefin of the formulas I to VI and acyclic olefins of the formula VIII as comonomer. Preferred acyclic olefins are those which have 2 to 20 C atoms, in particular unbranched acyclic olefins having 2 to 10 C atoms, such as, for example, ethylene, propylene and / or butylene. The proportion of polymerized units of acyclic olefins of the formula VIII is up to 99 wt .-%, preferably 5 to 80 wt .-%, particularly preferably 10 to 60 wt .-%, based on the total weight of the respective COCs.

Of the COCs described above, particularly preferred are those containing polymerized units of norbornene-based polycyclic olefins, particularly preferably norbornene or tetracyclododecene. Also particularly preferred are COCs which contain polymerized units of acyclic olefins, in particular ethylene. Again, particularly preferred are norbornene / ethylene and tetracyclododecene / ethylene copolymers which contain from 5 to 80% by weight, preferably from 10 to 60% by weight, of ethylene (based on the weight of the copolymer).

The cycloolefin polymers generically described above generally have glass transition temperatures T_G in the range between -20 ° C and 400 ° C. For the invention, however, essentially those COCs are usable which have a glass transition temperature T._G of greater than 70 ° C, preferably greater than 90 ° C and in particular greater than 110 ° C. The viscosity number (decalin, 135 ° C, DIN 53 728) is suitably between 0.1 and 200 ml / g, preferably between 50 and 150 ml / g.

The preparation of the COCs is done by a heterogeneous or homogeneous catalysis with organometallic compounds and is described in a variety of documents. Suitable catalyst systems based on mixed catalysts of titanium or Vanadium compounds in conjunction with organoaluminum compounds are described in DD 109 224, DD 237 070 and EP-A-0 156 464. EP-A-0 283 164, EP-A-0 407 870, EP-A-0 485 893 and EP-A-0 503 422 describe the preparation of COCs with catalysts based on soluble metallocene complexes. The production process of COC described in the above publications is hereby incorporated by reference.

The COCs are incorporated into the film either as pure granules or as a granulated concentrate (masterbatch) by premixing the polyester granules or powder with the COC or the COC masterbatch and then feeding them to the extruder. In the extruder, the components are further mixed and heated to processing temperature. It is expedient for the inventive method that the extrusion temperature above the glass transition temperature T_G of the COC, generally at least 5 K, preferably 10 to 180 K, in particular 15 to 150 K, above the glass transition temperature of the COCs.

In principle, the same polymers can be used for the intermediate layers and for the outer layers as for the base layer. In addition, other materials can also be present in the outer layers, in which case the outer layers preferably consist of a mixture of polymers, a copolymer or a homopolymer which contain ethylene-2,6-naphthalate units and ethylene terephthalate units. Up to 30 mol% of the polymers can be prepared from other comonomers (eg Ethylene isophthalate units.) Exist. The base layer and the other layers may additionally contain conventional additives such as stabilizers, antiblocking agents and other fillers. They are expedient the Polymerbzw. the polymer mixture already added before melting. Stabilizers used are, for example, phosphorus compounds, such as phosphoric acid or phosphoric acid esters.

Typical antiblocking agents (also referred to as pigments in this context) are inorganic and / or organic particles, for example calcium carbonate, amorphous silica, talc, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum oxide, lithium fluoride, calcium, barium , Zinc or manganese salts of the dicarboxylic acids used, carbon black, titanium dioxide, kaolin or crosslinked polymer particles, eg Polystyrene or acrylate particles.

As additives it is also possible to choose mixtures of two or more different antiblocking agents or mixtures of antiblocking agents of the same composition but of different particle size. The particles can the polymers of the individual layers of the film in the respective advantageous amounts, eg be added as a glycolic dispersion during the polycondensation or via masterbatches in the extrusion. Pigment concentrations of from 0 to 25% by weight have proved to be particularly suitable (based on the weight of the respective layer). A detailed description of the antiblocking agents can be found, for example, in EP-A-0 602 964.

To improve the whiteness of the film, the base layer or other additional layers may contain further pigmentation. It has proved to be particularly favorable, as additional additives barium sulfate having a particle size of 0.3 to 0.8 microns, preferably from 0.4 to 0.7 microns or titanium dioxide with a particle size of 0.05 to 0.3 microns to select. This gives the film a brilliant, white appearance. The amount of barium sulfate or titanium dioxide is in the range of 1 to 25 wt .-%, preferably from 1 to 20 wt .-%, and most preferably from 1 to 15 wt .-%.

The total thickness of the film can vary within wide limits and depends on the intended use. The preferred embodiments of the film according to the invention have total thicknesses of 4 to 400 .mu.m, wherein 8 to 300 .mu.m, in particular 10 to 300 .mu.m, are preferred. The thickness of any intermediate layer (s) present is generally in each case independently of one another 0.5 to 15 μm, intermediate layer thicknesses of 1 to 10 μm, in particular 1 to 8 μm, being preferred. The indicated values ​​refer to an intermediate layer. The thickness of the cover layer / s is chosen independently of the other layers and is preferably in the range of 0.1 to 10 .mu.m, in particular from 0.2 to 5 .mu.m, preferably from 0.3 to 2 .mu.m, with cover layers applied on both sides with respect to thickness and composition may be the same or different. The thickness of the base layer results accordingly from the difference between the total thickness of the film and the thickness of the applied cover and Zwischenschicht / s and therefore can vary within wide limits analogous to the total thickness.

In a particular embodiment, the cover layers may also consist of a polyethylene naphthalate homopolymer or of an ethylene terephthalate-ethylene naphthalate copolymer or a compound.

In this embodiment, the thermoplastics of the overcoats also have a similar standard viscosity as the polyethylene terephthalate of the base layer.

In the multi-layered embodiment, the flame retardant is preferably contained in the base layer. However, if necessary, the outer layers can be equipped with flame retardant.

In another embodiment, the flame retardant may be contained in the cover layers. If required and in the case of particularly high fire protection requirements, the base layer may additionally contain a so-called "basic equipment" of flame retardant.

Here, unlike in the single-layered embodiment, the amount by weight of flame retardant refers to the weight of each layer provided with the agent.

Fire tests according to DIN 4102 Part 1 and Part 2 and the UL test 94 have also surprisingly shown that films of the invention meet the requirements.

As a result, the flame retardant, multilayer films produced by the known coextrusion technology become economically extremely interesting in comparison with the completely flame-resistant monofilms, since significantly fewer additives are required to achieve comparable flame retardancy.

In the production of the film has been found that the flame retardant film can be excellent in the longitudinal and transverse directions without breaks. Furthermore, no outgassing was found in the production process, which could be attributed to the presence of flame retardants, which is essential to the invention, since most conventional flame retardants at extrusion temperatures of about 260 ° C show very disturbing, unpleasant gas emissions, which on the decomposition of these compounds among the Processing conditions are due, and are therefore unfit.

Surprisingly, already inventive films in the thickness range of 5 to 300 microns meet the building material class B1 according to DIN 4102 Part 1 and the UL test 94th

In the production of the white, flame retardant film was further found that the flame retardant can be incorporated by means of masterbatch technology, a suitable predrying or precrystallization of Flammschutzmasterbatches without sticking in the dryer, so that an economical film production is possible.

It was more than surprising that the incorporation is further facilitated by the small addition of a hydrolysis stabilizer in the flame retardant masterbatch, so that the throughputs and thus the production rates can be increased without problems. In a very specific embodiment, the film contains even in the layers which are equipped with flame retardant, small amounts of a hydrolysis stabilizer.

Measurements showed that the film of the invention does not embrittle at temperatures of 100 ° C over a longer period of time, which is more than surprising. This result is due to the synergistic effect of suitable precrystallization, pre-drying, masterbatch technology and flame retardant finishing.

Furthermore, the film according to the invention without environmental pollution and without loss of mechanical properties is easily recyclable, making them suitable, for example, for use as a short-lived advertising signs for trade fair construction and other promotional items where fire protection is desired.

The invention further relates to a process for the preparation of the polyester film according to the invention by the extrusion or coextrusion process known per se.

According to the invention, the flame retardant, if appropriate with the hydrolysis stabilizer, is added via the masterbatch technology. The flame retardant is fully dispersed in a carrier material. Suitable carrier materials are the polyester raw material itself, for example polyethylene terephthalate or else other polymers which are compatible with the polyester raw material.

Important in the case of masterbatch technology is that the particle size and the bulk density of the masterbatch is similar to the particle size and the bulk density of the polyester raw material, so that a homogeneous distribution and thus a homogeneous stabilization can take place.

The polyester films can be prepared by known methods from polyester raw material with optionally other raw materials, the flame retardant, if necessary the hydrolysis stabilizer and / or other conventional additives in the usual amount of 1.0 to max. 30 Wt .-% both as a monofilm and as a multilayer, possibly coextruded films are made with the same or differently shaped surfaces, wherein one surface is for example pigmented and the other surface contains no pigment. Likewise, one or both surfaces of the film can be provided with a conventional functional coating by known methods.

It is essential to the invention that the masterbatch, which contains the flame retardant and optionally the hydrolysis stabilizer, is precrystallized or is pre-dried. This predrying involves a gradual heating of the masterbatch under reduced pressure (20 to 80 mbar, preferably 30 to 60 mbar, in particular 40 to 50 mbar) and with stirring and, if appropriate, subsequent drying at a constant, elevated temperature also under reduced pressure. The masterbatch is preferably at room temperature from a dosing in the desired blend together with the polymers of the base and / or outer layers and optionally other raw material components batchwise in a vacuum dryer, which in the course of drying or Residence a temperature range of 10 to 160 ° C, preferably 20 ° C to 150 ° C, in particular 30 ° C to 130 ° C, passes, filled. During the approx. The raw material mixture is stirred at 10 to 70 rpm, preferably 15 to 65 rpm, in particular 20 to 60 rpm, for 6 hours, preferably 5 hours, in particular 4 hours, residence time. The thus pre-crystallized or Pre-dried raw material mixture is in a downstream likewise evacuated container at temperatures of 90 to 180 ° C, preferably from 100 to 170 ° C, in particular from 110 to 160 ° C over a period of 2 to 8 hours, preferably from 3 to 7 hours, in particular from 4 to 6 hours, after-dried.

As part of the coextrusion process, this is done that the melts corresponding to the single-layer film / the melts corresponding to the individual layers of the film are / are extruded / coextruded through a flat die, the film thus obtained is removed for solidification on one or more rolls, the film is then biaxially stretched (oriented), the biaxially stretched film is then heat-set and optionally corona or flame-treated on the surface layer provided for further treatment.

The biaxial stretching is generally carried out sequentially. It is preferably first in the longitudinal direction (ie in the machine direction, = MD direction) and then in the transverse direction (ie perpendicular to the machine direction, = TD direction) stretched. This leads to an orientation of the molecular chains. The stretching in the longitudinal direction preferably takes place with the aid of two rollers rotating at different speeds according to the desired stretch ratio. For cross-stretching is generally used a correspondingly suitable clip frame.

Simultaneous, ie simultaneous stretching of the film according to the invention in both directions (MD direction and TD direction) with the aid of a suitable clip frame has proven to be impractical. That is, this stretching results in a film that has too low a whiteness and too little opacity.

The temperature at which the stretching is carried out may vary within a relatively wide range and depends on the desired properties of the film. In general, the longitudinal stretching at 80 to 130 ° C and the transverse extension at 90 to 150 ° C is performed. The longitudinal stretch ratio is generally in the range of 2.5: 1 to 6: 1, preferably 3: 1 to 5.5: 1. The transverse stretch ratio is generally in the range of 3.0: 1 to 5.0: 1, preferably 3.5: 1 to 4.5: 1.

In the subsequent thermosetting, the film is held at a temperature of 150 to 250 ° C for about 0.1 to 10 seconds. Subsequently, the film is cooled and then wound up in the usual manner.

To set other desired properties, the film may be chemically treated or corona or flame treated. The treatment intensity is chosen so that the surface tension of the film is generally above 45 mN / m.

Likewise, the film can be coated to set other properties. Typical coatings are adhesion-promoting, antistatic, slip-resistant or dehesive layers. It is advisable to apply these additional layers via on-line coating by means of aqueous dispersions prior to transverse stretching on the film.

The particular advantage of the film according to the invention is its high degree of whiteness and its high opacity combined with good flame resistance. Surprisingly, the gloss of the film was also very high. The whiteness of the film is more than 70%, preferably more than 75% and particularly preferably more than 80%. The opacity of the film according to the invention is more than 55%, preferably more than 60% and particularly preferably more than 65%. The gloss of the film according to the invention is more than 80, preferably more than 90 and more preferably more than 100.

Another particular advantage of the invention is that in the production of the film inherent accumulating regenerate in a concentration of 10 to 70 wt .-%, based on the total weight of the film, can be used again, without affecting the physical properties of the film significantly negatively affected. In particular, the regenerate (consisting essentially of polyester raw material and COC) does not change the film indefinitely in color, which is the case with the films of the prior art.

In addition, an advantage of the invention is that the manufacturing costs of the film of the invention are comparable to conventional opaque films of the prior art. The other processing and use relevant properties of the film according to the invention remain substantially unchanged or even improved.

The film is ideal for packaging light and / or air sensitive food and beverages. In addition, it is also excellently suited for use in the industrial sector, for example in the production of embossing foils or as a label film. Besides, the film is of course particularly suitable for image recording papers, signatures, magnetic recording cards, to name but a few possible applications.

The processing and the winding behavior of the film, especially on high-speed machines (winder, metallizer, printing and laminating) is very good. A measure of the processing behavior is the coefficient of friction of the film, which is less than 0.6. The winding behavior is influenced decisively by the roughness of the film in addition to a good thickness profile, an excellent flatness and low friction coefficients. It has been found that the winding of the film according to the invention is particularly good if, while retaining the other properties, the mean roughness is in a range of 50 to 250 nm. The roughness can be, inter alia vary within the specified range by varying the COC concentration and the process parameters during the manufacturing process.

The following table (Table 1) summarizes the most important film properties according to the invention once again at a glance and thus particularly illustratively.<tables id="tabl0001" num="0001"><img file="EP1132425B1_D0008.tif" /></tables>

To characterize the raw materials and the films, the following measured values ​​were used:

SV (DCE), IV (DCE)

The standard viscosity SV (DCE) is measured on the basis of DIN 53726 in dichloroacetic acid. The intrinsic viscosity (IV) is calculated as follows from the standard viscosity (SV)<maths id="math0001" num=""><math display="block"><mrow><msup><mrow><mtext>IV (DCE) = 6.67 x 10</mtext></mrow><mrow><mtext>-4</mtext></mrow></msup><mtext> SV (DCE) + .118</mtext></mrow></math><img file="EP1132425B1_D0009.tif" /></maths>

yellowness

The yellow value YID is the deviation from the colorlessness in the direction "yellow" and is measured according to DIN 6167.

fire behavior

The fire behavior is determined according to DIN4102, part 2, building material class B2, and according to DIN 4102, part 1, building material class B1, as well as according to UL test 94.

friction

The friction was determined according to DIN 53 375. The coefficient of sliding friction was measured 14 days after production.

surface tension

The surface tension was determined by means of the so-called ink method (DIN 53 364).

roughness

The roughness Ra of the film was determined according to DIN 4768 at a cut-off of 0.25 mm.

Whiteness and opacity

The determination of the whiteness and the opacity is carried out with the aid of the electrical remission photometer "ELREPHO" from Zeiss, Oberkochem (DE), standard illuminant C, 2 ° normal observer. The opacity is determined according to DIN 53 146. The whiteness is defined as WG = RY + 3RZ - 3RX. WG = Whiteness, RY, RZ, RX = corresponding reflection factors when using the Y, Z and X colorimetric filter. As a white standard, we use a barium sulphate compact (DIN 5033, part 9). A detailed description is eg in Hansl Loos "Farbmessung", "Verlag Beruf und Schule, Itzehoe (1989).

Light transmission

The light transmission is measured according to ASTM-D 1033-77.

shine

The gloss was determined according to DIN 67 530. The reflector value was measured as an optical parameter for the surface of a film. Based on the standards ASTM-D 523-78 and ISO 2813, the angle of incidence was set at 60 °. A light beam strikes the flat test surface under the set angle of incidence and is reflected by it or scattered. The light rays incident on the photoelectronic receiver are displayed as a proportional electrical quantity. The measured value is dimensionless and must be specified with the angle of incidence.

Glass transition temperature

The glass transition temperature T_G was determined on the basis of film samples with the aid of DSC (Differential Scanning Calorimetry) (DIN 73 765). A DSC 1090 from DuPont was used. The heating rate was 20 K / min and the weight approximately 12 mg. In the first heating process, the glass transition T_G determined. The samples often showed enthalpy relaxation (a peak) at the beginning of the stepped glass transition. As T_G the temperature was taken at which the step-like change in the heat capacity - regardless of the peak-shaped Enthalpierelaxation - reached its half height in the first heating process. In all cases, only a single glass transition stage was observed in the thermogram on initial heating.

example 1

(Invention)

Chips of polyethylene terephthalate (prepared via the transesterification process with Mn as transesterification catalyst, Mn concentration: 100 ppm) were dried at 150 ° C. to a residual moisture content of below 100 ppm and fed to the extruder for the base layer B. In addition, chips were from COC the Fa. Ticona ® Topas 6015 (COC consisting of 2-norbornene and ethylene, see also W. Hatke: films from COC, Kunststoffe 87 (1997) 1, pp. 58-62) with a glass transition temperature T._G of about 160 ° C also supplied to the extruder for the base layer B. The quantitative proportion of the COC on the whole film was 10% by weight. In addition, 4% by weight of phosphorus-containing flame retardant was added.

The flame retardant is the organic phosphorus compound dimethylmethylphosphonate ® Amgard P 1045 from Albright &amp; Wilson, which is soluble in PET.

The flame retardant is added according to the invention in the form of a masterbatch. The masterbatch is composed of 20% by weight of flame retardant and 80% by weight of PET with a standard viscosity SV (DCE) of 810.

The masterbatch had a bulk density of 750 kg / m³, By extrusion and subsequent stepwise orientation in the longitudinal and transverse directions, a white, opaque monolayer film with a total thickness of 23 microns was prepared

Base layer B, mixture of: <tables id="tabl0002" num="0002"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">86.0% by weight</entry><entry namest="col2" nameend="col2" align="left">Polyethylene terephthalate homopolymer having an SV of 800</entry></row><row><entry namest="col1" nameend="col1" align="left">10.0% by weight</entry><entry namest="col2" nameend="col2" align="left">Cycloolefin copolymers (COC) from Ticona, Topas 6015</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">4.0% by weight</entry><entry namest="col2" nameend="col2" align="left">Amgard P 1045</entry></row></tbody></tgroup></table></tables>

The production conditions in the individual process steps were: <tables id="tabl0003" num="0003"><table frame="all"><tgroup cols="3" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="52.50mm" /><colspec colnum="2" colname="col2" colwidth="52.50mm" /><colspec colnum="3" colname="col3" colwidth="52.50mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" morerows="1" align="left">extrusion</entry><entry namest="col2" nameend="col2" align="left">Temperatures base layer</entry><entry namest="col3" nameend="col3" align="left">280 ° C</entry></row><row><entry namest="col2" nameend="col2" align="left">Temperature of the take-off roll</entry><entry namest="col3" nameend="col3" align="left">30 ° C</entry></row><row><entry namest="col1" nameend="col1" morerows="1" align="left">longitudinal stretching</entry><entry namest="col2" nameend="col2" align="left">temperature</entry><entry namest="col3" nameend="col3" align="left">80 - 125 ° C</entry></row><row><entry namest="col2" nameend="col2" align="left">Longitudinal stretching ratio</entry><entry namest="col3" nameend="col3" align="left">4.2</entry></row><row><entry namest="col1" nameend="col1" morerows="1" align="left">transverse stretching</entry><entry namest="col2" nameend="col2" align="left">temperature</entry><entry namest="col3" nameend="col3" align="left">80 - 135 ° C</entry></row><row><entry namest="col2" nameend="col2" align="left">Transverse stretching ratio</entry><entry namest="col3" nameend="col3" align="left">4.0</entry></row><row><entry namest="col1" nameend="col1" morerows="1" rowsep="1" align="left">fixation</entry><entry namest="col2" nameend="col2" align="left">temperature</entry><entry namest="col3" nameend="col3" align="left">230 ° C</entry></row><row rowsep="1"><entry namest="col2" nameend="col2" align="left">duration</entry><entry namest="col3" nameend="col3" align="left">3 s</entry></row></tbody></tgroup></table></tables>

The film had the required good properties and shows the desired handling and the desired processing behavior. The properties of films produced in this way are shown in Table 2.

Example 2

(Invention)

Compared to Example 1, 50% by weight of regenerate has now been added to the base layer. The amount of COC in the film thus produced was again 10 wt .-%, the flame retardant 4 wt .-%. The process parameters were not changed compared to Example 1. The yellow discoloration of the film was visually observed. From Table 2 it can be seen that hardly a yellow discoloration of the film has become visible.

Base layer B, mixture of: <tables id="tabl0004" num="0004"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">43.0% by weight</entry><entry namest="col2" nameend="col2" align="left">Polyethylene terephthalate homopolymer having an SV of 800</entry></row><row><entry namest="col1" nameend="col1" align="left">50.0% by weight</entry><entry namest="col2" nameend="col2" align="left">Regenerate (86% by weight of polyester + 10% by weight of Topas 6015 + 4% by weight of Amgard P 1045)</entry></row><row><entry namest="col1" nameend="col1" align="left">5.0% by weight</entry><entry namest="col2" nameend="col2" align="left">Cycloolefin copolymers (COC) from Ticona, Topas 6015</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">2,0Gew .-%</entry><entry namest="col2" nameend="col2" align="left">Amgard P 1045</entry></row></tbody></tgroup></table></tables>

Example 3

(Invention)

Compared to Example 1, a film having a thickness of 96 μm was now produced. The amount of COC in the film was 8 wt .-%, the flame retardant 4 wt .-%. The process parameters were not changed compared to Example 1. The yellow discoloration of the film was visually observed. From Table 2 it can be seen that no yellow discoloration of the film has become visible.

Base layer B, mixture of: <tables id="tabl0005" num="0005"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">88.0% by weight</entry><entry namest="col2" nameend="col2" align="left">Polyethylene terephthalate homopolymer having an SV of 800</entry></row><row><entry namest="col1" nameend="col1" align="left">8.0% by weight</entry><entry namest="col2" nameend="col2" align="left">Cycloolefin copolymers (COC) from Ticona, Topas 6015</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">4,0Gew .-%</entry><entry namest="col2" nameend="col2" align="left">Amgard P 1045</entry></row></tbody></tgroup></table></tables>

Example 4

(Invention)

Compared to Example 3, 50% by weight of regenerate has now been added to the base. The amount of COC in the film was again 8% by weight and that of flame retardant was 4.0% by weight. The process parameters were not changed compared to Example 1. The yellow discoloration of the film was visually observed. From Table 2 it can be seen that hardly a yellow discoloration of the film has become visible.

Base layer B, mixture of: <tables id="tabl0006" num="0006"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">44.0% by weight</entry><entry namest="col2" nameend="col2" align="left">Polyethylene terephthalate homopolymer having an SV of 800</entry></row><row><entry namest="col1" nameend="col1" align="left">50.0% by weight</entry><entry namest="col2" nameend="col2" align="left">Self-regenerant (86% by weight of polyester + 10% by weight of Topas 6015 + 4% by weight of Amgard P 1045)</entry></row><row><entry namest="col1" nameend="col1" align="left">4.0% by weight</entry><entry namest="col2" nameend="col2" align="left">Cycloolefin copolymers (COC) from Ticona, Topas 6015</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">2.0% by weight</entry><entry namest="col2" nameend="col2" align="left">Amgard P 1045</entry></row></tbody></tgroup></table></tables>

Comparative Example 1

Example 1 from DE-A 2 353 347 was worked up. In a modification of the example, an additional 50% by weight of regenerate was co-processed. From Table 2 it can be seen that a clear yellow discoloration of the film has become visible.

In addition, the roughness of the film is clearly too high for many applications and the gloss is too low for many applications. This is most likely due to the use of other polymeric additives.

Base layer B, mixture of: <tables id="tabl0007" num="0007"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">47.5% by weight</entry><entry namest="col2" nameend="col2" align="left">Polyethylene terephthalate homopolymer having an SV of 800</entry></row><row><entry namest="col1" nameend="col1" align="left">50.0% by weight</entry><entry namest="col2" nameend="col2" align="left">Self-regenerant (95% by weight of polyester + 5% by weight of polypropylene)</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">2.5% by weight</entry><entry namest="col2" nameend="col2" align="left">polypropylene</entry></row></tbody></tgroup></table></tables>

Comparative Example 2

Example 1 from EP-A 0 300 060 was worked up. In a modification of the example, an additional 50% by weight of regenerate was co-processed. From Table 2 it can be seen that a clear yellow discoloration of the film has become visible. In addition, the roughness of the film is clearly too high for many applications and the gloss is too low for many applications. This is most likely due to the use of other polymeric additives.

Base layer B, mixture of: <tables id="tabl0008" num="0008"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">45.0% by weight</entry><entry namest="col2" nameend="col2" align="left">Polyethylene terephthalate homopolymer having an SV of 800</entry></row><row><entry namest="col1" nameend="col1" align="left">50.0% by weight</entry><entry namest="col2" nameend="col2" align="left">Self-regenerant (95% by weight of polyester + 5% by weight of polypropylene)</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">5.0% by weight</entry><entry namest="col2" nameend="col2" align="left">polypropylene</entry></row></tbody></tgroup></table></tables>

Comparative Example 3

Example 1 from EP-A 0 360 201 was worked up. In a modification of the example, an additional 50% by weight of regenerate was co-processed. From Table 2 it can be seen that a clear yellow discoloration of the film has become visible. In addition, the roughness of the film is clearly too high for many applications and the gloss is too low for many applications. This is most likely due to the use of other polymeric additives.

Base layer B, mixture of: <tables id="tabl0009" num="0009"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">40.0% by weight</entry><entry namest="col2" nameend="col2" align="left">Polyethylene terephthalate homopolymer having an SV of 800</entry></row><row><entry namest="col1" nameend="col1" align="left">50.0% by weight</entry><entry namest="col2" nameend="col2" align="left">Self-regenerant (95% by weight of polyester + 5% by weight of polypropylene)</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">10.0% by weight</entry><entry namest="col2" nameend="col2" align="left">polypropylene</entry></row></tbody></tgroup></table></tables>

Comparative Example 4

Example 1 from DE-A 195 40 277 was worked up. In a modification of the example, an additional 50% by weight of regenerate was co-processed. From Table 2 it can be seen that a clear yellow discoloration of the film has become visible. In addition, the roughness of the film is clearly too high for many applications and the gloss is too low for many applications. This is most likely due to the use of other polymeric additives.

Base layer B, mixture of: <tables id="tabl0010" num="0010"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">43.5% by weight</entry><entry namest="col2" nameend="col2" align="left">Polyethylene terephthalate homopolymer having an SV of 800</entry></row><row><entry namest="col1" nameend="col1" align="left">50.0% by weight</entry><entry namest="col2" nameend="col2" align="left">Self-regenerate (95% by weight of polyester + 5% by weight of polystyrene)</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">6.5% by weight</entry><entry namest="col2" nameend="col2" align="left">polystyrene</entry></row></tbody></tgroup></table></tables><tables id="tabl0011" num="0011"><img file="EP1132425B1_D0010.tif" /></tables>

All films prepared according to Examples 1 to 4 and Comparative Examples 1 to 4 were treated over a period of 200 hours at a temperature of 100 ° C in a circulating air dryer cabinet. In the films of Examples 1 to 4, the mechanical properties are unchanged. The films do not exhibit the slightest embrittlement phenomena, while the films of the comparative examples have cracks which are recognizable to the naked eye and break into pieces in an attempt to bend them.

According to DIN 4102 Part 2 / Part 1, the films according to Examples 1 to 4 fulfill the building material classes B 2 and B 1 and they pass the UL test 94, whereas the films of Comparative Examples 1 to 4 do not.