FR2842529A1 - Composition useful for producing coextruded polyvinylidene fluoride (PVDF) films comprises PVDF, polymethyl methacrylate, acrylic elastomer and ultraviolet absorber - Google Patents

Abstract

Composition (I) coextrudable with polyvinylidene fluoride (PVDF) comprises 20-40% PVDF, 40-60% polymethyl methacrylate, 5-18% acrylic elastomer and 1-4% UV absorber. Independent claims are also included for: (1) coextruded films comprising a layer of (I) and a base layer comprising 50-100% polyvinylidene fluoride (PVDF) and 0-50% polymethyl methacrylate (PMMA); (2) coextruded films comprising a layer of (I), a middle layer comprising 50-75% PVDF and 25-50% PMMA, and an outer layer comprising 75-100% PVDF and 0-25% PMMA; (3) substrates covered with a film as above with (I) facing the substrate.

Description

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COMPOSITION COEXTRUDABLE WITH PVDF [Field of the Invention]
PVDF (polyvinylidene fluoride) due to its very good resistance to weathering, radiation and chemicals is used to protect objects or materials. In addition, it is appreciated for its shiny appearance and its resistance to graffiti. We therefore have to coat all kinds of substrates with a PVDF film. However, PVDF adheres very poorly to most substrates, it is therefore necessary to have an adhesive composition between the PVDF and the substrate. The present invention relates to this composition.

 Advantageously, this composition is coextruded with the PVDF to form a bilayer film, then this film is then fixed on the substrate, for example by hot pressing. The bilayer film can also be placed in a mold, the PVDF layer being placed against the wall of the mold, then inject the substrate in the molten state into the mold. It is also possible, depending on the nature of the substrate, to coextrude the PVDF, the adhesive composition and the substrate to directly obtain the substrate coated with PVDF and the adhesive composition being between the PVDF and the substrate.

[The prior art and the technical problem]
Patent GB 1578517 describes ABS coated with a PVDF film, a polyurethane layer can be placed between PVDF and ABS.

 US patent 4226904 describes PMMA covered with a PVDF film.

To improve the adhesion, a solution of PMMA in dimethylformamide is deposited on the PVDF film and after evaporation of the solvent, the PVDF film is pressed on the PMMA.

 US Patent 4,415,519 describes an ABS or PVC substrate covered with a PVDF film, an adhesive is placed between the PVDF and the substrate. This adhesive can be either PMMA or a mixture by weight of 40% of PMMA,

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 30% PVDF and 30% ABS is another mixture by weight of 30% PMMA, 40% of a polyacrylic derivative and 30% ABS.

 US Pat. No. 4,364,886 describes an ABS or unsaturated polyester substrate covered with a PVDF film, an adhesive is placed between the PVDF and the substrate. This adhesive is a mixture by weight of 30% of PMMA, 40% of an acrylic elastomer and 30% of ABS.

 US Pat. No. 5,242,976 describes a composition coextrudable with PVDF to make it adhere to substrates. The composition is a mixture by weight of 27 to 50% of PMMA, of 17.5 to 36.5% of PVDF and of 25 to 47.45% of an acrylic elastomer.

 In all of these prior arts above there is no mention of anti UV additives in the adhesive composition.

 Patent EP 733 475 B1 describes substrates coated with PVDF, the structure successively comprises the substrate, an adhesive layer, a layer of PVDF made opaque to UV and visible radiation and a layer of PVDF. The opaque PVDF layer is obtained by adding to the PVDF a product chosen from metal oxides, pigments and benzophenones. The examples only illustrate PVDF loaded with 15% by weight of zinc oxide.

 US Pat. No. 5,256,472 describes bilayer films comprising a first layer consisting essentially of PVDF and of a minor amount of PMMA and a second layer intended to ensure adhesion to a substrate. This adhesive layer consists by weight of 50 to 95 (preferably 70 to 90) parts of PMMA, 5 to 50 (preferably 10 to 30) parts of PVDF and 0.1 to 15 parts of a UV absorber. It is explained that the presence of the UV absorber is necessary because this adhesive layer is sensitive to radiation and that if no UV absorber is applied then the adhesive is destroyed and the layer consisting essentially of PVDF comes off from the substrate. . PMMA designates homopolymers of methyl methacrylate or copolymers of methyl methacrylate with a copolymerizable monomer and also mixtures with an acrylate rubber, but without specifying the proportions of PMMA and rubber. It is

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 also clarified that if the proportion of PMMA is less than 50 parts there is exudation of the anti UV. This document does not specify it but it was discovered that this exudation harms the transparency of the films and above all causes detachment. In addition, these films have no mechanical strength, which makes their handling difficult. It is necessary that the adhesive layer contains an elastomer, in fact without elastomer the adhesion is not good and the film has no mechanical strength. According to the teaching of US 5,242,976 already cited, this proportion must be between 25 and 47.45%, but these proportions cause a defect in resistance to radiation.

 We have now found a composition coextrudable with PVDF such that the UV inhibitors no longer exude, such that the bilayer PVDF film / coextrudable composition has good mechanical strength, which causes excellent adhesion of the PVDF layer to the substrate and which resists radiation.

[Brief description of the invention]
The present invention relates to a composition coextrudable with PVDF and comprising: # 20 to 40 parts of PVDF, # 40 to 60 parts of PMMA, # 5 to 18 parts of an acrylic elastomer, # 1 to 4 parts of a UV absorber , # the total making 100 parts.

The invention also relates to coextruded films consisting of: # a layer of the previous coextrudable composition (also called an adhesive layer) and directly attached thereto, # a layer based on PVDF comprising as main constituents 50 to 100 parts of PVDF for respectively 50 to 0 parts of PMMA (this layer is also called for simplification "layer of
PVDF ").

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According to a second form of the invention, the PVDF layer is in the form of 2 layers: # one disposed against the coextrudable layer and comprising as main constituents 50 to 75 parts of PVDF for 50 to 25 parts of PMMA respectively, # the other (also called outer layer) comprising as main constituents 75 to 100 parts of PVDF for respectively
25 to 0 parts of PMMA.

 These films have sufficient mechanical properties to allow their handling, their implementation and their use as a coating transparent to visible light but opaque to UV radiation.

 The invention also relates to the substrates coated with this film, the coextrudable (adhesive) composition being placed against the substrate.

[Detailed description of the invention]
PVDF is thus designated PVDF, homopolymers of vinylidene fluoride (VF2) and copolymers of vinylidene fluoride (VF2) preferably containing at least 50% by weight of VF2 and at least one other monomer copolymerizable with VF2 . Advantageously, the comonomer is fluorinated, it can be chosen for example from vinyl fluoride; trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro (alkyl vinyl) ethers such as perfluoro (methyl vinyl) ether (PMVE), perfluoro (ethyl vinyl) ether (PEVE) and perfluoro (propyl vinyl) ether (PPVE); perfluoro (1,3-dioxole); perfluoro (2,2-dimethyl-1,3 -dioxole) (PDD). Preferably the optional comonomer is selected from chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), trifluoroethylene (VF3) and tetrafluoroethylene (TFE).

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 Advantageously, the PVDF has a viscosity ranging from 100 Pa. S to 2000 Pa. S, the viscosity being measured at 230 C, at a shear gradient of 100 s-1 using a capillary rheometer. Indeed, these PVDFs are well suited for extrusion and injection. Preferably, the PVDF has a viscosity ranging from 300 Pa. S to 1200 Pa.s, the viscosity being measured at 230 C, at a shear gradient of 100s-1 using a capillary rheometer.

 With regard to PMMA, homopolymers of methyl methacrylate and copolymers containing at least 50% by weight of methyl methacrylate are thus designated. By way of example of a comonomer, mention may, for example, be made of alkyl (meth) acrylates, acrylonitrile, butadiene, styrene and isoprene. Examples of alkyl (meth) acrylates are described in KIRKOTHMER, Encyclopedia of chemical technology, 4th edition in Vol 1 pages 292-293 and in Vol 16 pages 475-478. Advantageously, the PMMA can contain 0 to 20% by weight and preferably 5 to 15% of methyl acrylate and / or ethyl acrylate. PMMA can be functionalized, that is to say that it contains for example acid, acid chloride, alcohol and anhydride functions.

These functions can be introduced by grafting or by copolymerization.

Advantageously, it is an acid function provided by the acrylic acid comonomer. Two neighboring acrylic acid functions can dehydrate to form an anhydride. The proportion of functions can be from 0 to 15% by weight of the PMMA including the optional functions.

 The MVI (melt volume index) of the PMMA can be between 2 and 15 cm3 / 10 min measured at 230 C under a load of 3.8 kg.

 As regards the acrylic elastomer, the elastomers based on at least one monomer chosen from acrylonitrile, alkyl (meth) acrylates and core shell (core shell) are thus designated. Regarding the core-shell copolymer, it is in the form of fine particles having an elastomer core and at least one thermoplastic shell, the particle size is generally less than m and advantageously between 50 and 300 nm.

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 As an example of a core, mention may be made of isoprene or butadiene homopolymers, isoprene copolymers with at most 30 mol% of a vinyl monomer and butadiene copolymers with at most 30% in moles of a vinyl monomer. The vinyl monomer can be styrene, an alkylstyrene, acrylonitrile or an alkyl (meth) acrylate. Another core family is made up of homopolymers of an alkyl (meth) acrylate and copolymers of an alkyl (meth) acrylate with at most 30 mol% of a monomer chosen from another (meth) alkyl acrylate and a vinyl monomer. The alkyl (meth) acrylate is advantageously butyl acrylate. The vinyl monomer can be styrene, an alkylstyrene, acrylonitrile, butadiene or isoprene. The core of the core shell copolymer can be crosslinked in whole or in part. It suffices to add at least difunctional monomers during the preparation of the core, these monomers can be chosen from poly (meth) acrylic esters of polyols such as butylene di (meth) acrylate and trimethylol propane trimethacrylate . Other difunctional monomers are for example divinylbenzene, trivinylbenzene, vinyl acrylate and vinyl methacrylate. The core can also be crosslinked by introducing therein, by grafting or as a comonomer during the polymerization, unsaturated functional monomers such as anhydrides of unsaturated carboxylic acids, unsaturated carboxylic acids and unsaturated epoxides. By way of example, mention may be made of maleic anhydride, (meth) acrylic acid and glycidyl methacrylate.

 The bark or barks are homopolymers of styrene, of an alkylstyrene or of methyl methacrylate or of copolymers comprising at least 70 mol% of one of these preceding monomers and at least one comonomer chosen from the other preceding monomers , another alkyl (meth) acrylate, vinyl acetate and acrylonitrile. The bark can be functionalized by introducing therein, by grafting or as a comonomer during the polymerization, unsaturated functional monomers such as anhydrides of unsaturated carboxylic acids, unsaturated carboxylic acids and unsaturated epoxides. By way of example, mention may be made of maleic anhydride, (meth) acrylic acid and glycidyl methacrylate. As

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 examples that may be mentioned are core # shell copolymers having a polystyrene shell and core # shell copolymers having a PMMA shell. There are also core-bark copolymers with two barks, one made of polystyrene and the other outside of PMMA. Examples of copolymer and their preparation process are described in the following patents: US 4 180 494, US 3 808 180, US 4096 202, US 4 260 693, US 3 287 443, US 3 657 391, US 4 299 928 , US 3,985,704, US5773520.

 Advantageously, the core represents, by weight, 70 to 90% of the core shell copolymer and the shell 30 to 10%.

 As an example of a copolymer, mention may be made of that consisting of (i) from 75 to 80 parts of a core comprising at least 93% of butadiene, 5% of styrene and 0.5 to 1% of divinylbenzene in moles and (ii) 25 to 20 parts of two barks of essentially the same weight, one inside made of polystyrene and the other outside made of PMMA.

 As another example, mention may be made of those having a poly (butyl acrylate) core or a copolymer of butyl acrylate and butadiene and a PMMA shell.

 All these core shell copolymers are sometimes called soft / hard because of the elastomer core.

 There are also other types of core shell copolymers such as hard / soft / hard, that is to say that they have in this order a hard core, a soft shell and a hard shell. The hard parts can be made of the polymers of the bark of the previous soft / hard and the soft parts can be made of the polymers of the core of the previous soft / hard.

 Mention may be made, for example, of those constituted in this order: of a core made of a copolymer of methyl methacrylate and of ethyl acrylate, of a shell made of a copolymer of butyl acrylate and of styrene, of a bark made of a copolymer of methyl methacrylate and of ethyl acrylate.

 There are still other types of core shell copolymers such as hard (core) / soft / semi hard. Compared to the previous ones, the difference comes from the "semi-hard" outer bark which is made up of two barks: one

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 intermediate and the other external. The intermediate shell is a copolymer of methyl methacrylate, styrene and at least one momer chosen from alkyl acrylates, butadiene and isoprene. The outer shell is a homopolymer or copolymer PMMA.

 Mention may be made, for example, of those constituted in this order: of a core made of a copolymer of methyl methacrylate and of ethyl acrylate, of a shell made of a copolymer of butyl acrylate and of styrene, of a bark made of a copolymer of methyl methacrylate, butyl acrylate and styrene, a bark made of a copolymer of methyl methacrylate and ethyl acrylate.

 When choosing the proportions of acrylic elastomer, account must be taken of that which may already be contained in the PMMA. Indeed, there are commercial qualities of PMMA known as "impact quality" which contain acrylic impact modifiers, most often of the core bark type. These acrylic impact modifiers can also be present in PMMA because they were introduced during its polymerization or prepared simultaneously during its polymerization.

 As regards the UV absorber, these products are known in themselves. Such products are cited in US Pat. No. 5,256,472. Benzotriazoles and benzophenores are advantageously used. By way of example, Tinuvin 213 or Tinuvin 109 and preferably Tinuvin 234 from the company Ciba Seciality Chemicals can be used.

 The composition coextrudable with PVDF advantageously comprises: # 25 to 35 parts of PVDF, # 45 to 55 parts of PMMA, # 8 to 18 parts of an acrylic elastomer, # 2 to 3 parts of a UV absorber, # the total making 100 games.

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The composition coextrudable with PVDF preferably comprises: # 30 to 35 parts of PVDF, # 50 to 55 parts of PMMA, # 8 to 12 parts of an acrylic elastomer, # 2 to 3 parts of a UV absorber, # le total making 100 parts.

 The coextrudable composition can be prepared by mixing PVDF, PMMA and acrylic elastomer in the molten state in which the UV absorber is added. Advantageously, the devices for mixing thermoplastics are used.

 As regards the coextruded film consisting of the coextrudable composition and the PVDF layer, the thickness of the PVDF layer is advantageously between 2 and 50 m and that of the coextrudable composition between 10 and 100 m.

 Advantageously, the PVDF-based layer comprises as main constituents 70 to 100 parts of PVDF for 30 to 0 parts of PMMA respectively and preferably 75 to 85 parts of PVDF for 25 to 15 parts of PMMA respectively.

According to a second form of the invention, the PVDF layer is in the form of 2 layers: # one disposed against the coextrudable layer and comprising as main constituents 50 to 75 parts of PVDF for 50 to 25 parts of PMMA respectively, # the other (also called outer layer) comprising as main constituents 75 to 100 parts of PVDF for respectively
25 to 0 parts of PMMA That is to say that the films of the invention comprise in order: # a coextrudable layer of the composition of the invention (the adhesive layer),

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# a layer placed against the coextrudable layer and comprising as main constituents 50 to 75 parts of PVDF for respectively 50 to 25 parts of PMMA, # a layer (also called outer layer) comprising as principal constituents 75 to 100 parts of PVDF for respectively
25 to 0 parts of PMMA.

 Advantageously, the layer placed against the coextrudable layer comprises as main constituents 50 to 65 parts of PVDF for respectively 50 to 35 parts of PMMA.

 Advantageously, the layer (also called outer layer) comprises as main constituents 85 to 100 parts of PVDF for 15 to 0 parts of PMMA respectively and preferably 90 to 100 parts of PVDF for 10 to 0 parts of PMMA respectively.

 The thickness of the layer of coextrudable composition is advantageously between 10 and 100 m and that of each of the other layers is advantageously between 2 and 50 m.

 The invention also relates to the substrates coated with this film, the coextrudable composition being placed against the substrate.

As regards the substrate, one can cite by way of example: # chlorinated polymers: PVC, plasticized PVC, chlorinated PE # polymers and copolymers containing styrene such as ABS, SAN, PS, # saturated polyesters (PET, PBT , ...) and copolyesters or mixtures, unsaturated polyester resins (SMC), # epoxy and phenolic resins, # copolymers of ethylene and alkylacrylate or acetate (EMA, EVA) functionalized or not, # PA (polyamides) and CoPA (copolyamides), PEBA, polyesteramides and
TPU (thermoplastic polyurethane, abbreviation of Thermoplastic polyurethane),

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 # EVOH (copolymer of ethylene and vinyl alcohol), # aluminum, steel or mixtures of metals, # lignin-based composites, # acrylic compounds (PMMA, ...), # glass, # PVC, PU foam.

[Examples] The following products were used: Kynar 720: PVDF homopolymer from the company ATOFINA and from MVI (Melt Volume Index or melt flow index) 10 cm 3/10 min (230 ° C., 5 kg).

 Kynar 740: Homopolymer PVDF from ATOFINA and MVI (Melt Volume Index or melt volume index) 1.1 cm3 / 10 min (230 C, 5 kg).

 OROGLAS BS8: PMMA from the company ATOGLAS from MVI 4.5 cm3 / 10 min (230 C, 3.8 kg) in the form of a pearl containing a methyl acrylate comonomer at 12%.

 OROGLAS V 825 T: PMMA from the company ATOGLAS de MVI 2.5 cm3 / 10 min (230 C, 3.8 kg).

 Tinuvin 109: UV absorber of the benzotriazole type sold by Ciba Specialty Chemicals.

 Tinuvin 213: UV absorber of the hydroxyphenyl benzotriazole type sold by Ciba Specialty Chemicals.

 Tinuvin 234: UV absorber of hydroxyphenyl benzotriazole type sold by Ciba Specialty Chemicals.

D320: abbreviation of Durastrengh D320, denotes an elastomer having a soft / hard shell core, the core of which is a copolymer of butyl acrylate and butadiene, and the shell is made of PMMA of dimension 80 nm sold by the company CECA .

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 ParaloidKM 355: designates a soft / hard shell core elastomer, the core of which is a homopolymer of butyl acrylate and the shell is made of PMMA of dimension 150 nm sold by the company Rhom and Haas.

The compositions in the examples are in% by weight.

Example 1 (according to the invention) A two-layer film containing a layer composed of 80% PVDF Kynar 720 and 20% altuglas BS8 15 m thick and a binder 35 m thick according to the following formulation: Kynar 720 31.8%, 51.7% altuglas BS8, 2.5% Tinuvin 234 and 15% D320, this film has an elongation at break of 197%, a haze of 14 and after 7 days in the oven no exudation is observable . This film has sufficient UV absorbance for its use in outdoor applications.

Example 2: (according to the invention) A two-layer film containing a layer composed of 80% PVDF Kynar 720 and 20% altuglas BS8 15 m thick and a binder 35 m thick according to the following formulation: Kynar 740 33.6%, 53.9% altuglas BS8, 2.5% Tinuvin 234 and 10% D320, this film has an elongation at break of 210%, a haze of 11 and after 7 days spent in the oven no exudation is observable . This film has sufficient UV absorbance for use in outdoor applications.

Example 3: (according to the invention) A two-layer film containing a layer composed of 80% PVDF Kynar 740 and 20% altuglas BS8 15 m thick and a binder 35 m thick according to the following formulation: Kynar 740 33.6%, 53.9%

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 altuglas BS8, 2.5% of Tinuvin 109 and 10% of D320, this film has an elongation at break of 150%, a haze of 8 and after 7 days spent in an oven no exudation is observable. This film has sufficient UV absorbance for its use in outdoor applications.

Example 4: (according to the invention) A two-layer film containing a layer composed of 80% PVDF Kynar 740 and 20% altuglas BS8 15 m thick and a binder 35 m thick according to the following formulation: Kynar 740 33.6%, 53.9% altuglas BS8, 2.5% Tinuvin 213 and 10% D320, this film has an elongation at break of 150%, a haze of 6.5 and after 7 days in the oven no exudation n is observable. This film has sufficient UV absorbance for use in outdoor applications.

Example 5: (According to the invention) A bilayer film containing a layer composed of 80% PVDF Kynar 740 and 20% altuglas BS8 1 of 5 m thick and a binder of 35 m thick according to the following formulation: Kynar 740 33.6%, 53.9% altuglas BS8, 2.5% Tinuvin 234 and 10% D320, this film has an elongation at break of 150%, a haze of 6.5 and after 7 days in the oven no exudation is not observable. This film has sufficient UV absorbance for its use in outdoor applications.

Example 6: (comparative) A two-layer film containing a layer composed of 80% PVDF Kynar 720 and 20% V825T oroglas 15 m thick and a binder 35 m thick according to the following formulation: Kynar 720 32. 5%, 32.5% V825T oroglas, 2.5% Tinuvin 234 and 32. 5% Paraloid KM355, ce

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 film presents an elongation breaking of 150%, a haze of 15 and after 1 day spent in an oven an exudation is observable. This film has an UV absorbance not sufficient for its use in outdoor applications.

Example 7: (Comparative) A two-layer film containing a layer composed of 80% PVDF Kynar 720 and 20% V825T oroglas 15 m thick and a binder 35 m thick according to the following formulation: Kynar 720 32. 5%, 32.5% of oroglas V825T, 2.5% of Tinuvin 234 and 32. 5% of Durastrength D320, this film has an elongation at break of 150%, a haze of 15 and after 1 day spent in an oven an exudation is observable . This film has an UV absorbance not sufficient for its use in outdoor applications.

Claims (14)

1 Composition coextrudable with PVDF and comprising: # 20 to 40 parts of PVDF, # 40 to 60 parts of PMMA, # 5 to 18 parts of an acrylic elastomer, # 1 to 4 parts of a UV absorber, # the total making 100 games.  2 Composition according to claim 1 in which the proportions are advantageously: # 25 to 35 parts of PVDF, # 45 to 55 parts of PMMA, # 8 to 18 parts of an acrylic elastomer, # 2 to 3 parts of a UV absorber , # the total making 100 parts.  3 Composition according to claim 2 in which the proportions are advantageously: # 30 to 35 parts of PVDF, # 50 to 55 parts of PMMA, # 8 to 12 parts of an acrylic elastomer, # 2 to 3 parts of a UV absorber , # the total making 100 parts.  4 Composition according to any one of the preceding claims in which the acrylic elastomer is a core shell copolymer.  5 Composition according to claim 4 in which the core shell copolymer is chosen from soft / hard, hard / soft / hard and hard / soft / semi hard. <Desc / Clms Page number 16>  5 Composition according to claim 4 wherein the core # orce copolymer is chosen from soft / hard, hard / soft / hard and hard / soft / semi hard.  6 Coextruded films consisting of: # a layer of the coextrudable composition according to any one of the preceding claims and directly attached to it, # a layer based on PVDF comprising as main constituents 50 to 100 parts of PVDF for respectively 50 to 0 parts of PMMA 7 Films according to claim 6 in which the layer based on PVDF as main constituents 70 to 100 parts of PVDF for respectively 30 to 0 parts of PMMA.  8 Films according to claim 7 in which the PVDF-based layer as main constituents 75 to 85 parts of PVDF for 25 to 15 parts of PMMA respectively.  9 Films according to any one of claims 6 to 8 in which the thickness of the PVDF layer is advantageously between 2 and 50 m and that of the coextrudable composition between 10 and 100 m.  10 coextruded films comprising in order: # a coextrudable layer of the composition according to any one of claims 1 to 5 (the adhesive layer), # a layer placed against the coextrudable layer and comprising as main constituents 50 to 75 parts of PVDF for respectively 50 to 25 parts of PMMA, # a layer (also called outer layer) comprising as main constituents 75 to 100 parts of PVDF for respectively 25 to 0 parts of PMMA. <Desc / Clms Page number 17>  11 films according to claim 10 in which the layer disposed against the coextrudable layer comprises as main constituents 50 to 65 parts of PVDF for respectively 50 to 35 parts of PMMA.  12 Films according to claim 10 or 11 in which the outer layer comprises as main constituents 85 to 100 parts of PVDF for respectively 15 to 0 parts of PMMA.  13 films according to any one of claims 10 to 12 in which the thickness of the layer of coextrudable composition is advantageously between 10 and 100 m and that of each of the other layers is advantageously between 2 and 50 m.  14 Substrates coated with a film according to any one of claims 6 to 13, the coextrudable composition being disposed against the substrate.