DE10026165A1 - Glossy, white, opaque, flame-retardant polyester laminate film, useful e.g. in protective coverings, comprising base layer(s) containing cycloolefin copolymer and covering layer(s) - Google Patents

Abstract

A polyester film (I) consisting of at least one base layer and at least one covering layer, the base layer contains (in addition to a thermoplastic polyester) a cycloolefin copolymer (COC) and the film contains at least one flame retardant. An Independent claim is included for the preparation of (I), by coextruding the starting materials necessary for the base, covering and optionally intermediate layers using an extruder having a flat die and biaxially orienting, thermo-fixing and optionally further processing the obtained film.

Description

The present invention relates to a white, high gloss, biaxially oriented, heavy Flammable, coextruded polyester film, which consists of at least one base layer and at least one cover layer, the base layer being a polyester and a Contains cycloolefin copolymer (COC). The invention further relates to a method for Production of the polyester film and its use.

White, biaxially oriented polyester films are known in the prior art.

DE-A 23 53 347 describes a process for producing one or more layered, milky polyester film described, which is characterized in that a mixture of particles of a linear polyester and 3 to 27 wt .-% a homopolymer or copolymer of ethylene or propylene which Extruded mixture as a film, quenching the film and stretching it vertically mutually biaxially oriented directions and heat-set the film. A disadvantage of the method is that it is incurred during the production of the film Regenerate (essentially a mixture of polyester raw material and ethylene or Propylene copolymer) can no longer be used, otherwise the film discolored or turns yellow. The process is therefore uneconomical. Also points the film has high roughness and therefore has a very matt appearance (very low Gloss), which is undesirable for many applications.

EP-A 0 300 060 describes a single-layer polyester film which, apart from Polyethylene terephthalate still 3 to 40 wt .-% of a crystalline propylene polymer and contains 0.001 to 3% by weight of a surfactant. The surfaces active substance causes the number of vacuoles in the film to increase and  at the same time their size decreases to the desired extent. This will make a higher one Opacity and a lower density of the film achieved. It is also disadvantageous here that Regenerate accumulating in the production of the film (essentially a mixture of Polyester raw material and propylene homopolymer) can no longer be used because otherwise the film turns yellow. The process is therefore uneconomical. In addition, the film has high roughness and is therefore very matt Appearance (very low gloss), which is undesirable for many applications.

EP-A 0 360 201 describes an at least two-layer polyester film which has a base layer with fine vacuoles, the density of which is between 0.4 and 1.3 kg / dm ³ and at least one cover layer, the density of which is greater than 1. 3 kg / dm ³ . The vacuoles are created 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), the surface tension is increased and the roughness of the laminated surface can be reduced. It is also disadvantageous here that the regrind obtained 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 is discolored yellow. The process is therefore uneconomical. In addition, the films listed in the examples have high roughness and thus have a matt appearance (low gloss), which is undesirable for many applications.

EP-A 0 795 399 describes an at least two-layer polyester film which has a base layer with fine vacuoles, the density of which is between 0.4 and 1.3 kg / dm ³ , and at least one cover layer, the density of which is greater than 1 , 3 kg / dm ³ . The vacuoles are created by adding 5 to 45% by weight of a thermoplastic polymer to the polyester raw material of the base layer and then biaxially stretching the film. Polypropylene, polyethylene, polymethylpentene, polystyrene or polycarbonate are mentioned as thermoplastic polymers, polypropylene being the preferred thermoplastic polymer. The additional cover layer improves the manufacturability of the film (no streaking on the surface of the film), increases the surface tension and the roughness of the laminated surface can be adapted to the respective requirements. A further modification of the film in the base layer and / or in the outer layers with white pigments (usually TiO ₂ ) and / or with optical brighteners enables the film properties to be adapted to the respective application requirements. However, it is also disadvantageous here that the regrind obtained in the production of the film (essentially a mixture of polyester raw material and the additive raw material) can no longer be used, since otherwise the color of the film is changed indefinitely, which is undesirable for many applications . The process is therefore uneconomical. In addition, the films listed in the examples have high roughness and thus have a matt appearance (low gloss), which is undesirable for many applications.

DE-A 195 40 277 describes a single or multilayer polyester film which has a base layer with fine vacuoles, the density of which is between 0.6 and 1.3 kg / dm ³ , and has a birefringence in the plane which ranges from -0.02 to 0.04. The vacuoles are created by adding 3 to 40% by weight of a thermoplastic resin to the polyester raw material of the base layer and then biaxially stretching the film. Thermoplastic resins include polypropylene, polyethylene, polymethylpentene, cyclic olefin polymers, polyacrylic resins, polystyrene or polycarbonate, polypropylene and polystyrene being preferred raw materials. By adhering to the specified limits for the birefringence of the film, the claimed film is distinguished in particular by good tear strength and good isotropy properties. The disadvantage remains that the regrind obtained in the production of the film can no longer be used, since otherwise the color of the film is changed indefinitely, which is undesirable for many applications. The process is therefore uneconomical. In addition, the films listed in the examples have high roughness and thus have a matt appearance (low gloss), which is undesirable for many applications.

DE-A 23 46 787 describes a flame-retardant plastic. In addition to plastic as such, its use for the production of films and fibers is also described. The following deficits are evident in the production of films with this phospholane-modified raw material:

• - The plastic / raw material is very sensitive to hydrolysis and must be very good be pre-dried.
• - When drying with state-of-the-art dryers, glued the plastic, so the making of a film, if any, only under difficult conditions succeed.
• - The films produced under uneconomical conditions become brittle Temperature loads, d. H. the mechanical properties are due of the rapidly occurring embrittlement, making the film technically becomes unusable. This occurs after 48 hours of thermal stress Embrittlement on.

The object of the present invention was therefore a white polyester film To provide, which is characterized in particular by a very high gloss and by a improved manufacturability, d. H. low manufacturing costs, excellent and above also has good thermal stability and flame resistance without to have the above-mentioned disadvantageous properties. In particular, should be guaranteed that the regenerate that is inherent in the manufacturing process in a concentration of preferably 10 to 70 wt .-%, based on the total Ge importance of the film, can be reused without losing the physical Properties of the film are significantly negatively affected. In particular, should no significant discoloration or yellowing of the Slide occur.  

Flammability means that the film is 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, fulfilled and thus in building material class B2, especially B1, which can be classified as flame retardant.

Furthermore, the film is said to be UL test 94, the so-called "horizontal buming test for Flammability of Plastic Material ", so that they are in class 94 VTM-0 can be classified.

The economic production includes that the plastics or the plastic components that are required to manufacture the flame retardant film with Industrial dryers that meet the standard of technology are dried can. It is essential that the raw materials do not stick together and not thermally be dismantled. These state of the art industrial dryers include Vacuum dryer, fluid bed dryer, fluid bed dryer and fixed bed dryer (Shaft dryer). These dryers generally operate at temperatures between 100 and 170 ° C, at which usually flame retardant plastics glue so that film production is not possible.

In the most gently drying vacuum dryer, the plastic runs through one Temperature range from approx. 30 ° C to 130 ° C at a vacuum of 50 mbar. After that is a so-called post-drying in a hopper at temperatures from approx. 100 to 130 ° C and a residence time of 3 to 6 hours required. Even with this Procedure glues the plastic described in the prior art.

A good thermal stability means that the film after 100 hours of annealing at 100 ° C in a forced air oven, no embrittlement and no bad mecha African properties.  

A high surface gloss means that the gloss at <100 (DIN 67 530 at a Measuring angle of 20 °), preferably <120 and in particular <130.

The task is solved by a white, high-gloss, biaxially oriented, heavy Flammable, coextruded polyester film in the thickness range of preferably 4 to 500 microns consisting of at least one base layer and at least one cover layer, wherein at least the base layer additionally contains a cycloolefin copolymer (COC). The concentration of the COC is preferably 2 to 60% by weight, based on the Weight of the base layer. The glass transition temperature of the cycloolefin copolymer (COC) is preferably in the range from 70 to 270 ° C. and at least one film surface surface (covering layer) has a gloss value (measuring angle 20 °) of greater than 100. The Foil contains at least one flame retardant.

Under a white polyester film in the sense of the present invention is a film understood that a whiteness of more than 70%, preferably of more than 75% and particularly preferably of more than 80%. Furthermore, the opacity is the film of the invention more than 55%, preferably more than 60% and especially preferably more than 65%.

To achieve the desired degree of whiteness of the film according to the invention, the The proportion of the cycloolefin copolymer (COC) in the base layer may be greater than 2%. On the other hand, if the cycloolefin copolymer (COC) content is greater than 60%, there is Risk that the film can no longer be produced economically, since it is under Circumstances that can no longer be reliably drawn under certain circumstances.

It is further preferred that the glass transition temperature of the used Cycloolefin copolymers (COC) is greater than 70 ° C. Otherwise (with a glass transition temperature of less than 70 ° C) the raw material mixture is worse processable (more difficult to extrude), the desired degree of whiteness may become no longer reached and the regrind used leads to a film that increases  May have yellowing. On the other hand, the glass transition temperature of the selected cycloolefin copolymers (COC) greater than 270 ° C, so the Raw material mixture may no longer be sufficiently homogeneous in the extruder disperse. This would then have a film with inhomogeneous properties Episode.

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

Surprisingly, it was found that the addition of a cycloolefinco polymeric (COC) in the manner described above a white, opaque, glossy film can be made.

According to the amount and type of cycloolefin copolymer (COC) added the degree of whiteness and the opacity of the film can be set precisely and the respective Requirements are adjusted. With this measure it is possible to share with others To largely do without common white and opaque additives. Furthermore was it is very surprising that the surface roughness of the film is much less and so that the gloss of the film is much higher than with comparable films after State of the art. The additional effect of that was completely unexpected the regenerate, despite the presence of flame retardant, has no tendency to Yellowing shows how this is otherwise when using polymeric additives and conventional Liche flame retardant is observed according to the prior art.

All of these features described would not be predictable. This is all the more because z. B. COCs largely to the preferred polyester polyethylene terephthalate are incompatible, but it is known that they have similar stretch ratios and stretch temperatures are oriented, such as polyethylene terephthalate. Under this prerequisite  the specialist would have expected that in the manufacture according to the invention conditions no white, opaque film with high gloss can be produced.

In particular in the preferred and the particularly preferred embodiments is characterized by a high / or. through a particularly high whiteness and a high or. due to a particularly high opacity in combination with a high surface gloss on at least one film surface che, whereby the color change of the film is extremely small due to the addition of regenerate remains.

The film according to the invention contains at least one flame retardant, which over the so-called masterbatch technology is metered in directly during film production, the concentration of the flame retardant in the range from 0.5 to 30.0% by weight, preferably from 1.0 to 20.0% by weight, based on the weight of the layer of crystallizable thermoplastics. During the production of the masterbatch, generally a ratio of flame retardant to thermoplastic in the range of 60 40% to 10% to 90% by weight.

Typical flame retardants include bromine compounds, chlorinated paraffins and other chlorine compounds, antimony trioxide, aluminum trihydrates, the halogen compounds disadvantageous due to the resulting halogen-containing by-products are. Furthermore, the low light resistance of a film equipped with it in addition to the development of hydrogen halide in the event of fire extremely disadvantageous.

Suitable flame retardants that are used according to the invention are for example organic phosphorus compounds such as carboxyphosphinic acids, the Anhydrides and dimethyl methylphosphonate. It is essential to the invention that the organic phosphorus compound is soluble in the thermoplastic, otherwise the required optical properties are not met.  

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

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

So it was more than surprising that using masterbatch technology, one suitable predrying and / or pre-crystallization and, if appropriate, use of small amounts of a hydrolysis stabilizer are flame retardant and thermoformable film with the required property profile economically and without Bonding can be made in the dryer and that the film after exposure to temperature not embrittled and does not break when bent.

It was very surprising that with this excellent result and the required flame protection:

• - The yellowness index of the film in comparison to a film that has not been finished The measuring accuracy is not negatively influenced,
• - no outgassing, no nozzle deposits, no frame evaporation occur, which gives the film an excellent appearance, an excellent Profile and excellent flatness,
• - The flame retardant film has excellent stretchability distinguished so that they are reliable and stable on "high-speed film lines" Reliable production at speeds of up to 420 m / min can be.

Such a film is also economically viable.

The film according to the invention is multi-layered. Are multi-layer embodiments at least two layers and always include the COC-containing base layer and at least one more top layer. In a preferred embodiment, the COC-containing layer, the base layer of the film with at least one, preferably with cover layers on both sides, with intermediate if necessary on one side or on both sides layers may be present. The layer structure would then be z. B. A-B-C, where B the base layer and A and C are the cover layers, which are the same or different can. In a further preferred embodiment, the COC-containing layer forms also an intermediate layer of the multilayer film. Further embodiments with COC containing intermediate layers are built up of five layers and, in addition to the COC base layer containing COC-containing intermediate layers on both sides. In another Embodiment can the COC-containing layer in addition to the base layer, one-sided form a cover layer on the base or intermediate layer. The base layer is in According to the present invention, that layer which preferably 50% to 99.5%, preferably 60 to 95% of the total film thickness. The top layers are the layers that form the outer layers of the film. The base layer and / or possibly the cover layers and / or possibly the intermediate layers contain this Flame retardant and possibly the hydrolysis stabilizer.

The COC-containing base layer of the film according to the invention contains a thermoplastic rule polyester, preferably a polyester homopolymer, a COC, a flame protective agents and, where appropriate, other additives added in each effective Amounts. In general, this layer preferably contains 20% by weight to 98% by weight, preferably 40 to 98% by weight, in particular 70 to 98% by weight, of thermoplastic cal polyester, based on the weight of the layer, and 0.5 to 30 wt .-%, preferably 1.0 to 20 wt .-% flame retardant, based on the weight of the Base layer.  

Suitable thermoplastic polyesters for the base layer are preferably made of polyester Ethylene glycol and terephthalic acid (= polyethylene terephthalate, PET), from ethylene glycol and naphthalene-2,6-dicarboxylic acid (= polyethylene-2,6-naphthalate, PEN), from 1,4-bis- hydroximethyl-cyclohexane and terephthalic acid (= poly-1,4-cyclohexanedimethylene ephthalate, PCDT) and from ethylene glycol, naphthalene-2,6-dicarboxylic acid and biphenyl 4,4'-dicarboxylic acid (= polyethylene-2,6-naphthalate bibenzoate, PENBB). Especially preferred are polyesters which contain at least 90 mol%, preferably at least 95 mol%, from ethylene glycol and terephthalic acid units or from ethylene glycol and Naphthalene-2,6-dicarboxylic acid units exist. The remaining monomer units are derived from other aliphatic, cycloaliphatic or aromatic diols or Dicarboxylic acids, such as z. B. in layer A (A = top layer 1) and / or Layer C (C = top layer 2) of a multilayer film ABC (B = base layer) can occur.

Suitable other aliphatic diols are, for example, diethylene glycol, triethylene glycol, aliphatic glycols of the general formula HO- (CH ₂ ) _n -OH, where n represents 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, cyclohexanediols (in particular cyclohexane-1,4-diol) may be mentioned. Suitable other aromatic diols correspond, for example, to the formula HO-C ₆ H ₄ -XC ₆ H ₄ -OH, where X is -CH ₂ , -C (CH ₃ ) ₂ , -C (CF ₃ ) ₂ , -O-, - S- or -SO ₂ stands. In addition, bisphenols of the formula HO-C ₆ H ₄ -C ₆ H ₄ -OH are also very suitable.

Other aromatic dicarboxylic acids are preferably benzenedicarboxylic 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, cyclohexanedicarboxylic acids (in particular cyclohexane-1,4-dicarboxylic acid) should be mentioned. Of the aliphatic dicarboxylic acids, the (C ₃ -C ₁₉ ) alkanedioic acids are particularly suitable, it being possible for the alkane portion to be straight-chain or branched.

The preparation of the polyesters to be used according to the invention can, for. B. after Transesterification procedures are carried out. One starts from dicarboxylic acid esters and diols from that with the usual transesterification catalysts, such as zinc, calcium, lithium, Magnesium and manganese salts are implemented. The intermediate products are then in the presence of common polycondensation catalysts such as antimony trioxide or titanium salts, polycondensed. The production can be just as good after Direct esterification process in the presence of polycondensation catalysts respectively. Here one starts directly from the dicarboxylic acids and the diols.

According to the invention, the COC-containing layers contain a cycloolefinco polymer (COC) in an amount of preferably at least 2.0% by weight, in particular 4 to 50 wt .-% and particularly preferably 6 to 40 wt .-%, based on the weight Equipped COC. It is very advantageous for the present invention if the cycloolefin copolymer (COC) used with the thermo plastic polyester, e.g. B. polyethylene terephthalate is incompatible and with this does not form a homogeneous mixture.

Cycloolefin polymers are generally homopolymers or copolymers which contain polymerized cycloolefin units and optionally acyclic olefins as comonomers. Cycloolefin polymers which polymerize 0.1 to 100% by weight, preferably 10 to 99% by weight, particularly preferably 50-95% by weight, based in each case on the total mass of the cycloolefin polymer, are particularly suitable for the present invention Contain cycloolefin units. Particularly preferred are polymers which are composed of the monomers of the cyclic olefins of the formulas I, II, III, IV, V or VI:

In these formulas, R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ^{8 are,} independently of one another, the same or different and represent a hydrogen atom or a C ₁ -C ₃₀ hydrocarbon radical; or two or more of the radicals R ¹ to R ⁸ are cyclically linked, the same radicals in the different formulas having the same or different meaning. C ₁ -C ₃₀ hydrocarbon radicals are preferably linear or branched C ₁ -C ₈ alkyl radicals, C ₆ -C ₁₈ aryl radicals, C ₇ -C ₂₀ alkylene aryl radicals or cyclic C ₃ -C ₂₀ alkyl radicals or acyclic C ₂ -C ₂₀ alkenyl groups.

Optionally, the cycloolefin polymers according to the invention can contain 0 to 45% by weight, based on the total mass of the cycloolefin polymer, of polymerized units of at least one monocyclic olefin of the formula VII:

Here n is a number from 2 to 10.

The cycloolefin polymers can optionally contain 0 to 99% by weight, based on the total mass of the cycloolefin polymer, of polymerized units of an acyclic olefin of the formula VIII:

Herein R ⁹ , R ¹⁰ , R ¹¹ and R ^{12 are} independently the same or different and represent a hydrogen atom or a C ₁ -C ₁₀ hydrocarbon radical, e.g. B. a C ₁ -C ₈ alkyl radical or C ₆ -C ₁₄ aryl radical.

Also suitable in principle are cycloolefin polymers which are ring-opening Polymerization of at least one of the monomers of the formulas I to VI and closing hydrogenation can be obtained.

Cycloolefin homopolymers are composed of a monomer of the formulas I-VI. These cycloolefin polymers are less for the purposes of the present invention suitable. For the purposes of the present invention, cycloolefinco in particular polymers (COC) suitable which contain at least one cycloolefin of the formulas I to VI and contain at least one comonomer. Preferred comonomers are those acyclic olefins of formula VIII. In the foregoing and below, the Cycloolefin copolymers which can be used according to the invention are called COC. Are preferred as acyclic olefins VIII are those which have 2 to 20 C atoms, especially unbranched acyclic olefins with 2 to 10 carbon atoms such as as ethylene, propylene and / or butylene. The proportion of polymerized units acyclic olefins of the formula VIII is up to 99% by weight, preferably 5 to 80% by weight, particularly preferably 10 to 60 wt .-%, based on the total weight of the respective cycloolefin copolymer.

Among the cycloolefin copolymers, those are particularly preferred polymerized units of polycyclic olefins with norbornene basic structure, especially preferably contain norbornene, 5-methyl-norbornene or tetracyclododecene. Suitable monomers are also dimethyl octahydronaphthalene and cyclopentene. Cycloolefin copolymers (COC) which polymerized are also particularly preferred Contain units of acyclic olefins, especially ethylene. Again special preferred are norbornene / ethylene and tetracyclododecene / ethylene copolymers, which Contain 5 to 80 wt .-%, preferably 10 to 60 wt .-% of acyclic olefin VIII (based on the weight of the copolymer).

The cycloolefin polymers described generally have a glass transition temperatures between -20 ° C and 400 ° C. Are preferred for the invention  Cycloolefin copolymers (COC) can be used which have a glass transition temperature of greater than 70 ° C, preferably greater than 90 ° C and in particular greater than 110 ° C exhibit. The viscosity number (decalin, 135 ° C, DIN 53 728) is expedient between 0.1 and 200 ml / g, preferably between 50 and 150 ml / g.

The cycloolefin copolymers (COC) are produced by a heterogeneous process or homogeneous catalysis with organometallic compounds and is in a variety described by documents. Suitable catalyst systems based on Mixed catalysts made of titanium or vanadium compounds in connection with Aluminum organyls are described in DD 109 224, DD 237 070 and EP-A-0 156 464 described. EP-A-0 283 164, EP-A-0 407 870, EP-A-0 485 893 and EP-A-0 503 422 describe the production of cycloolefin copolymers (COC) with catalysts, based on soluble metallocene complexes. To the writings mentioned above Manufacturing process of cycloolefin polymers described is hereby expressly referred.

The cycloolefin copolymers are incorporated into the film either as pure granules or as granulated concentrates (masterbatch) by premixing the polyester granules or powder with the cycloolefin copolymer (COC) or the cycloolefin copolymer (COC) masterbatch and then feeding it to the extruder. The components are mixed further in the extruder and heated to processing temperature. It is expedient for the process according to the invention that the extrusion temperature is above the glass transition temperature T _{g of} the cycloolefin copolymer (COC), generally at least 5 ° C., preferably 10 to 180 ° C., in particular 15 to 150 ° C., above the glass transition temperature of the cycloolefin copolymer (COC).

In principle, the same polymers can be used for the intermediate layers and cover layers used as for the base layer. The cover layers and if necessary, the intermediate layers of a mixture of polymers, a copolymer  or a homopolymer consisting of ethylene-2,6-naphthalate units and / or contain ethylene terephthalate units. Up to 30 mol% of the polymers can consist of further comonomers (e.g. ethylene isophthalate units).

It is essential to the invention that at least one top layer is not coated with cycloolefinco polymer (COC) is equipped. This top layer essentially contains the mentioned thermoplastic polyester and is optionally with antiblocking and / or lubricants equipped.

The base layer and the other layers can be in addition to the COC, the flame Protective agents and, if necessary, the hydrolysis stabilizer, additional conventional additives, such as. B. Stabilizers and antiblocking agents included. You will be useful to the polymer or added to the polymer mixture before melting. As stabilizers are, for example, phosphorus compounds, such as phosphoric acid or phosphoric acid reester, used.

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, Ba rium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum oxide, Lithium fluoride, calcium, barium, zinc or manganese salts of the used Dicarboxylic acids, carbon black, titanium dioxide, kaolin or cross-linked polymer particles, e.g. B. Polystyrene or acrylate particles.

Mixtures of two or more different ones can also be used as additives Antiblocking agents or mixtures of antiblocking agents of the same composition, but different particle size can be selected. The particles can Polymers of the individual layers of the film in the respective advantageous concentrations trations, e.g. B. as a glycolic dispersion during polycondensation or over Masterbatches during extrusion. Have been particularly suitable  pigment concentrations of 0 to 25% by weight (based on the weight the respective layer). A detailed description of suitable antiblocking agents can be found for example in EP-A-0 602 964.

Suitable lubricants are e.g. B. polydimethylsiloxane, carboxylic acids, metal salts of Carboxylic acids, carboxylic acid amides, carboxylic acid esters. A detailed description can be found, for example, in Plastic Additives, 2nd Edition, Carl Hanser Verlag Munich Vienna, pp. 309 to 347.

To improve the whiteness of the film, the base layer and / or, if necessary, a other additional layer contain another pigmentation. Here it has proven to be particularly favorable as additional barium sulfate additives in one Grain size of preferably 0.3-0.8 microns, in particular 0.4-0.7 microns or titanium dioxide in a grain size of preferably 0.05-0.3 microns to choose. This gives the film a brilliant, white look. The particle concentration of barium sulfate is preferably 1 to 25% by weight, preferably 1 to 20% by weight, and very preferably at 1 to 15 wt .-%, based on the weight of the layer equipped with it.

The total thickness of the film can vary within wide limits and depends according to the intended use. The preferred embodiments of the films according to the invention have total thicknesses of 4 to 500 μm, 8 to 300 μm, in particular 10 to 300 μm, are particularly preferred. The thickness of the, if applicable existing intermediate layer (s) is generally independent in each case 0.5 to 15 µm from each other, with intermediate layer thicknesses of 1 to 10 µm, ins particularly 1 to 8 µm are preferred. The stated values relate to each on an intermediate layer. The thickness of the top layer / s becomes independent of the selected other layers and is preferably in the range from 0.1 to 10 μm, in particular 0.2 to 5 microns, preferably 0.3 to 2 microns, with applied on both sides Cover layers with respect to thickness and composition may be the same or different can. The thickness of the base layer results from the difference of  Total thickness of the film and the thickness of the top and intermediate layers applied and can therefore vary within wide limits analogously to the total thickness.

In a special embodiment, the cover layers can also consist of one Polyethylene naphthalate homopolymers or from an ethylene terephthalate ethylene naphthalate copolymers or a compound.

In this embodiment, the thermoplastics of the cover layers also have one Standard viscosity similar to that of the polyethylene terephthalate of the base layer.

In the multi-layer embodiment, the flame retardant is preferably in the Base layer included. However, the top layers and If necessary, existing intermediate layers are equipped with flame retardants be.

In another embodiment, the flame retardant can only be in the deck layers may be included. If necessary and with particularly high fire protection requirements The base layer can additively a so-called "basic equipment" on flame contain protective agents.

During the production of the film it was found that the flame retardant The film can be oriented in the longitudinal and transverse directions without tears. Of Furthermore, no outgassing was found in the production process that relates to the presence of flame retardants, which is very beneficial since most conventional flame retardants at extrusion temperatures above 260 ° C very annoying, unpleasant outgassing show on the decomposition of these compounds are due to the processing conditions.  

Surprisingly, films according to the invention already meet in the thickness range of 4 to 500 µm the requirements of building material class B1 according to DIN 4102 part 1 and the UL test 94.

During the production of the white, flame-retardant film, it was further determined that the flame retardant is particularly advantageous using masterbatch technology gie, a suitable predrying or pre-crystallization of the flame retardant masterbate ches in the dryer without sticking, so that an economical Foil production is possible.

With a small addition of a hydrolysis stabilizer in the flame retardant masterbatch familiarization is made even easier, so that the throughputs and so that production speeds can be increased. In a very special one Embodiment therefore contains the film in the layers with flame retardant are equipped, additional small amounts of a hydrolysis stabilizer.

Measurements showed that the film according to the invention with temperature loads of 100 ° C does not become brittle over a longer period of time.

Furthermore, the film according to the invention is without environmental pollution and without loss the mechanical properties can be easily recycled, which makes them exemplary wise for use as short-lived advertising signs for exhibition stand construction and others Promotional items where fire protection is desired is suitable.

The invention further relates to a method for producing the invention Polyester film according to the known coextrusion process.

The flame retardant, if appropriate with the hydrolysis stabilizer, is preferred the masterbatch technology added. The flame retardant is in one Carrier material fully dispersed. The polyester used comes as the carrier material  raw material itself, such as B. polyethylene terephthalate, or other polymers with are compatible with the polyester raw material.

The advantage of masterbatch technology is that the grain size and that Bulk weight of the masterbatch similar to the grain size and bulk density of the Is polyester raw material, so that a homogeneous distribution and thus a homogeneous Stabilization can take place.

The polyester films can be made from known polyester raw materials with other raw materials, the flame retardant, possibly the hydrolysis stabilizer and / or other conventional additives in the usual amount of 1.0 to max. 30% by weight as multilayer, coextruded films with the same or differently designed Surfaces are produced, one surface being pigmented, for example and the other surface contains no pigment. Likewise, one or both Surfaces of the film by known methods with a conventional functional Coating.

It is preferred that the masterbatch containing the flame retardant and given if the hydrolysis stabilizer contains, is pre-crystallized or pre-dried. These Predrying involves 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 necessary, drying at constant, elevated Temperature also under reduced pressure. The masterbatch is preferably at Room temperature from a dosing container in the desired mix together with the polymers of the base and / or cover layers and optionally Intermediate layers and possibly other raw material components in batches into one Vacuum dryer, which has a temperature spectrum in the course of the drying or dwell time from approx. 10 to 160 ° C, preferably 20 ° C to 150 ° C, in particular 30 ° C to 130 ° C, passes through, filled. During the approx. 6-hour, preferably 5-hour, ins the raw material mixture is at a special 4-hour residence time at 10 to 70 rpm,  preferably 15 to 65 rpm, in particular 20 to 60 rpm, stirred. That way crystallized or pre-dried raw material mixture is in a downstream likewise evacuated containers at temperatures of about 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, post-dried.

Within the framework of this process, the individual layers are processed the melt corresponding to the film are co-extruded through a flat die, the film thus obtained is pulled off on one or more rollers for consolidation, the film is then biaxially stretched (oriented), the biaxially stretched film heat-set and optionally on the surfaces intended for treatment layer is corona or flame treated.

Biaxial stretching is generally carried out sequentially. Doing so preferably only in the longitudinal direction (i.e. in the machine direction, = MD direction) and then in the transverse direction (i.e. perpendicular to the machine direction, = TD direction) stretched. This leads to an orientation of the molecular chains. Stretching in The longitudinal direction is preferably carried out with the help of two in accordance with the desired Stretch ratio of rolls running at different speeds. Used for cross stretching generally a corresponding tenter frame.

The temperature at which the drawing is carried out can be in a relative vary widely and depends on the desired properties of the Foil. In general, the longitudinal stretching at 80 to 130 ° C and the transverse stretching carried out at 90 to 150 ° C. The aspect ratio is generally in the range from 2.5: 1 to 6: 1, preferably from 3: 1 to 5.5: 1. The transverse stretching ratio is generally in the range from 3.0: 1 to 5.0: 1, preferably from 3.5: 1 to 4.5: 1.  

In the subsequent heat setting, the film is held at about 0.1 to 10 s Temperature kept from about 150 to 250 ° C. Then the film is in the usual Way wrapped up.

The film can be chemically treated to set other desired properties will be corona and flame treated as well. The intensity of treatment should be should be chosen so that the surface tension of the film is generally over 45 mN / m lies.

The film can also be coated to set further properties. Typical coatings are adhesion-promoting, antistatic, slip-improving or layers with an adhesive effect. It makes sense to add these additional layers over in-line coating by means of aqueous dispersions before transverse stretching on the film to apply.

The particular advantage of the film according to the invention is expressed by a high level Whiteness, due to a high opacity in combination with at least one high shiny surface and at the same time good flame resistance. The whiteness the film is more than 70%, preferably more than 75% and particularly preferred 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 shine of The film according to the invention is at least one side more than 100, preferably more than 120 and particularly preferably more than 130 at a measuring angle of 20 ° (DIN 67 530). According to DIN 4102, the film meets the requirements of building material classes B1 and B2 and UL test 94.

Another advantage of the invention is that this is in the manufacture of the film Regenerate accumulating in a concentration of 10 to 70 wt .-%, based on the total weight of the film, can be used again without the physical properties of the film are significantly affected.  

In particular, the regenerate (essentially made of polyester raw material, The film does not contain flame retardants and cycloolefin copolymers (COC) undefined changed in color, which is the case with the films according to the prior art Case is. It is preferred that the high-gloss top layer remains regenerate-free.

In addition, another advantage of the invention is that the manufacturing costs of the film according to the invention are comparable to conventional trans Parent films according to the state of the art. The other processing and Properties relevant to the use of the film according to the invention remain in the essentially unchanged or even improved.

The film is ideal for interior cladding, trade fair construction and Trade fair articles, for protective cladding of machines and vehicles. Next to it is also excellent for use in industrial areas, e.g. B. in the manufacture of Embossing foils or as a label foil, suitable. In addition, the film is of course special suitable for imaging papers, printing sheets, magnetic recording maps to name just a few possible uses.

The processing and winding behavior of the film, especially on fast running machines (winders, metallizers, printing and laminating machines) very good. The coefficient of friction is a measure of the processing behavior the film that is less than 0.6. The winding behavior is next to a good one Thickness profile, excellent flatness and low coefficient of friction decisively influenced by the roughness of the film. It has been found that the winding of the film according to the invention is particularly good when under Retaining the other properties mean roughness in a range from 50 to 250 nm. The roughness can a. by varying the COC concentration of the Cover layer thickness, possibly the cover layer formulation and the process parameters for Manufacturing process vary in the specified range.  

The table below (Table 1) summarizes the most important film properties according to the invention.

The following measured values were used to characterize the raw materials and the foils:
DIN = German Institute for Standardization
ISO = International Organization for Standardization
ASTM = American Society for Testing and Materials

SV value (standard viscosity)

The standard viscosity SV (DCE) is based on DIN 53 726 in dichloroacetic acid measured.

The intrinsic viscosity (IV) is calculated from the standard viscosity as follows

IV (DCE) = 6.67.10 ^-4 SV (DCE) + 0.118

friction

The friction was determined in accordance with DIN 53 375. The sliding friction number was 14 days measured after production.

Surface tension

The surface tension was measured using the so-called ink method (DIN 53 364) certainly.

Roughness

The roughness R _{a of} the film was determined according to DIN 4768 with a cut-off of 0.25 mm.

Whiteness and opacity

The degree of whiteness and the opacity are determined with the aid of the electric reflectance 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 color measurement filter. A barium sulfate compact (DIN 5033, part 9) is used as the white standard. A detailed description is e.g. B. in Hansl Loos "color measurement", Verlag Beruf und Schule, Itzehoe (1989).

Translucency

The light transmittance is measured in accordance with ASTM-D 1033-77.

shine

The gloss was determined in accordance with DIN 67 530 at a measuring angle of 20 °. Measured was the reflector value as an optical parameter for the surface of a film. A The light beam strikes the flat test surface and at the set angle of incidence is reflected or scattered by it. The on the photoelectronic receiver striking light rays are displayed as a proportional electrical quantity. The 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 using DSC (differential scanning calorimetry) (DIN 73 765). The device DSC 1090 from DuPont was used. The heating rate was 20 K / min and the initial weight was about 12 mg. The glass transition T _{g was} determined in the first heating process. The samples often showed enthalpy relaxation (a peak) at the beginning of the step-shaped glass transition. The T _g was the temperature at which the step-like change in heat capacity - regardless of the peak-shaped enthalpy relaxation - reached half its height in the first heating process. In all cases, only a single glass transition step was observed in the thermogram when it was first heated.

Fire behavior

The fire behavior is according to DIN 4102 part 2 fire class B2 and according to DIN 4102 Part 1 flammability class B1 and determined according to UL Test 94.

The following examples serve to explain the invention in more detail: are co-extruded, multilayer films.

example 1

According to the coextrusion technology, a 23 µm thick multilayer film with the layer sequence ABA is produced, where B is the base layer and A the cover layers. The base layer B is 21 µm thick and the two cover layers which cover the base layer are each 1 µm thick. Polyethylene terephthalate chips (produced by the transesterification process with Mn as the 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 made of cycloolefin copolymers (COC) from Ticona, Germany ®Topas 6015 (COC consisting of 2-norbornene and ethylene, see also W. Hatke: Films made of COC, Kunststoffe 87 (1997) 1, pp. 58-62) with a glass transition temperature T _g of 170 ° C also fed to the extruder for the base layer B. The proportion of the cycloolefin copolymer (COC) in the base layer was 10% by weight. In addition, the base layer contains 4% by weight of dimethyl methylphosphonate (®Amgard P 1045 from Albright & Wilson) as a flame retardant, which is metered in using masterbatch technology (Masterbatch 2).

The 1 µm thick cover layers contain 73% polyester (RT49, Kosa, German land), 7% of a masterbatch 1 that contains 10,000 ppm silicon dioxide in addition to polyester (®Sylobloc, Grace., Germany) contains and 20 wt .-% of a masterbatch 2, that in addition to RT49 contains 20% by weight of dimethyl methylphosphonate.  

A white, opaque three-layer film with a total thickness of 23 μm was produced by coextrusion and subsequent stepwise orientation in the longitudinal and transverse directions.
Base layer B, mixture of:
70.0% by weight of polyethylene terephthalate homopolymer (RT49, Kosa, Germany)
10.0% by weight of cycloolefin copolymers (COC) from Ticona, ®Topas 6015
20.0% by weight of masterbatch 2 with 20% by weight of dimethyl methylphosphonate (®Amgard P 1045 from Albright & Wilson)

The manufacturing conditions in the individual process steps were:

Extrusion

Base and top layer temperatures 280 ° C Pull roller temperature 30 ° C

Longitudinal extension

temperature 80-125 ° C Longitudinal stretch ratio 4.2

Transverse stretching

temperature 80-135 ° C Cross stretch ratio 4.0

Fixation

temperature 230 ° C Duration 3 s

The film had the required good properties and shows the desired one Handling and the desired processing behavior. The properties achieved Films produced in this way are summarized in Table 2.

Example 2

In comparison to Example 1, 50% by weight of regenerate was now added to the base layer. The concentration of the cycloolefin copolymer (COC) in the film thus produced was again 10% by weight. The concentration of the flame retardant in the base layer and the top layer was identical to Example 1. The process parameters were not changed in comparison to Example 1. The yellowing of the film was observed visually. Table 2 shows that hardly any yellow discoloration of the film has become visible.
Base layer B, mixture of:
25.0% by weight of polyethylene terephthalate homopolymer (RT49, Kosa, Germany)
50.0% by weight of regrind (90% by weight of polyester + 10% by weight of Topas 6015)
5.0% by weight of cycloolefin copolymers (COC) from Ticona, ®Topas 6015
20.0% by weight of masterbatch 2 with 20% by weight of dimethyl methylphosphonate (®Amgard P 1045 from Albright & Wilson)
Cover layers: As in example 1.

Example 3

In comparison to Example 1, an ABA film with a thickness of 96 μm was now produced, the 92 μm thick base layer being covered by the 2 μm thick cover layers. The concentration of the cycloolefin copolymer (COC) in the base layer was 8% by weight. The concentration of the flame retardant was analogous to Example 1. The process parameters were not changed compared to Example 1. The yellowing of the film was observed visually. Table 2 shows that no yellowing of the film has become visible.
Base layer B (92 µm), mixture of:
72.0% by weight of polyethylene terephthalate homopolymer (RT49, Kosa, Germany)
8.0% by weight of cycloolefin copolymers (COC) from Ticona, ®Topas 6015
20.0% by weight of masterbatch 2 with 20% by weight of dimethyl methylphosphonate (®Amgard P 1045 from Albright & Wilson)
Cover layers: As in Example 1. However, the thickness of the cover layers is 2 µm.

Example 4

In comparison to Example 3, 50% by weight of regenerate was now added to the base. The concentration of the cycloolefin copolymer (COC) in the base layer was 8% by weight. The concentration of the flame retardant was analogous to Example 1. The process parameters were not changed compared to Example 1. The yellowing of the film was observed visually. Table 2 shows that the film hardly showed any yellow discoloration.
Base layer B, mixture of:
37.0% by weight of polyethylene terephthalate homopolymer (RT49, Kosa, Germany)
50.0% by weight of self-regenerated material (90% by weight of polyester + 10% by weight of Topas 6015)
3.0% by weight of cycloolefin copolymers (COC) from Ticona, ®Topas 6015
20.0% by weight of masterbatch 2 with 20% by weight of dimethyl methylphosphonate (®Amgard P 1045 from Albright & Wilson)
Cover layers: As in example 3.

Comparative Example 1

Example 1 from DE-A 23 53 347 was reworked. In a modification of the example, an additional 50% by weight of regrind was processed. Table 2 shows that a clear yellowing of the film has become visible. In addition, the roughness of the film is too high for many applications and the gloss is too low for many applications.
Base layer B, mixture of:
47.5% by weight of polyethylene terephthalate homopolymer (RT49, Kosa, Germany)
50.0% by weight of regenerated material (95% by weight of polyester + 5% by weight of polypropylene)
2.5% by weight polypropylene

Comparative Example 2

Example 1 from EP-A 0 300 060 was reworked. In a modification of the example, an additional 50% by weight of regrind was processed. Table 2 shows that a clear yellowing 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:
45.0% by weight of polyethylene terephthalate homopolymer (RT49, Kosa, Germany)
50.0% by weight of regenerated material (95% by weight of polyester + 5% by weight of polypropylene)
5.0 wt% polypropylene

Comparative Example 3

Example 1 from EP-A 0 360 201 was reworked. In a modification of the example, an additional 50% by weight of regrind was processed. Table 2 shows that a clear yellowing of the film has become visible. In addition, the roughness of the film is too high for many applications and the gloss is too low for many applications.
Base layer B, mixture of:
40.0% by weight of polyethylene terephthalate homopolymer (RT49, Kosa, Germany)
50.0% by weight of regenerated material (95% by weight of polyester + 5% by weight of polypropylene)
10.0% by weight of polypropylene

Comparative Example 4

Example 1 from DE-A 195 40 277 was reworked. In a modification of the example, an additional 50% by weight of regrind was processed. Table 2 shows that a clear yellowing of the film has become visible. In addition, the roughness of the film is too high for many applications and the gloss is too low for many applications.
Base layer B, mixture of:
43.5% by weight of polyethylene terephthalate homopolymer (RT49, Kosa, Germany)
50.0% by weight of regenerated material (95% by weight of polyester + 5% by weight of polypropylene)
6.5% by weight of polystyrene

The films according to Examples 1 to 4 meet building material classes B2 and B1 according to DIN 4102 Part 2 / Part 1 and they pass UL test 94, but the films of Comparative Examples 1 to 4 do not.

Claims (21)

1. polyester film which has at least one base layer (B) and at least one cover layer, characterized in that at least the base layer contains a thermoplastic polyester, a cycloolefin copolymer (COC) and the film contains at least one flame retardant. 2. Polyester film according to claim 1, characterized in that it has a Layer structure A-B-C has, with the outer layers A and C the same or ver are different and at least one of the outer layers does not contain COC. 3. Polyester film according to claim 1 or 2, characterized in that it is white tere top and / or intermediate layers. 4. Polyester film according to one or more of claims 1 to 3, characterized characterized in that the thermoplastic polyester ethylene glycol and Terephthalic acid units or ethylene glycol and naphthalene-2,6-dicarbon contains acid units. 5. Polyester film according to one or more of claims 1 to 4, characterized characterized in that the thermoplastic polyester is poly ethylene terephthalate. 6. Polyester film according to one or more of claims 1 to 5, characterized characterized that the layers equipped with the COC the COC of 2 to 60% by weight, preferably 4 to 50% by weight, in particular 6 to 40% by weight, each based on the weight of the layers equipped with it, contain.   7. polyester film according to one or more of claims 1 to 6, characterized characterized in that the COC polynorbornene, polytetracyclododecene, poly dimethyloctahydronaphthalene, polycyclopentene or poly (5-methyl) norbornene contains. 8. Polyester film according to one or more of claims 1 to 7, characterized characterized in that the COC as a copolymer ethylene, propylene and / or Contains butylene, preferably ethylene. 9. Polyester film according to one or more of claims 1 to 8, characterized characterized in that the COC is a norbornene / ethylene or a tetracyclo dodecene / ethylene copolymer. 10. Polyester film according to one or more of claims 1 to 9, characterized characterized that the COC has a glass transition temperature of 70 to 270 ° C, preferably 90 to 250 ° C, in particular from 110 to 220 ° C. 11. Polyester film according to one or more of claims 1 to 10, characterized characterized in that the film preferably has a degree of whiteness of greater than 70% greater than 75%, in particular greater than 80%. 12. Polyester film according to one or more of claims 1 to 11, characterized characterized in that the film has an opacity of greater than 55%, preferably greater 60%, in particular greater than 65%. 13. Polyester film according to one or more of claims 1 to 12, characterized characterized in that the film has a surface gloss of at least one side greater than 100, preferably greater than 120, in particular greater than 130.   14. Polyester film according to one or more of claims 1 to 13, characterized characterized that as a flame retardant organic phosphorus compounds such as carboxyphosphinic acids, their anhydrides, or preferably dimethylmethyl phosphonate or mixtures of organic phosphorus compounds be used. 15. Polyester film according to one or more of claims 1 to 14, characterized characterized in that the flame retardant in a concentration of 0.5 to 30 wt .-%, based on the weight of the layers equipped with it is available. 16. Polyester film according to one or more of claims 1 to 15, characterized characterized in that the film additionally a hydrolysis stabilizer or Mixtures of various hydrolysis stabilizers, preferably from 0.01 to 1% by weight, based on the weight of the layers equipped with it. 17. Polyester film according to one or more of claims 1 to 16, characterized characterized in that the film also contains conventional additives such as antiblocking agents, Contains pigments, stabilizers or lubricants. 18. A method for producing a polyester film according to one or more of the Claims 1 to 17, characterized in that one for the manufacture the base and top layers and, if necessary, intermediate layers raw materials coextruded through extruders through a flat die and the The film obtained is biaxially stretched and heat-set and optionally further acts. 19. The method according to claim 18, characterized in that the flame protectant and, if appropriate, the hydrolysis stabilizer by means of Masterbatch technology is added.   20. Use of a polyester film according to one or more of the claims 1 to 17 for the production of moldings. 21. Shaped body produced using a polyester film according to a or more of claims 1 to 17.