WO1997049777A2

WO1997049777A2 - Metal-adhesive polyvinylidene fluoride compositions

Info

Publication number: WO1997049777A2
Application number: PCT/EP1997/003381
Authority: WO
Inventors: Yoshiyuki Miyaki; Jérome MAILLET; Kazuyoshi Ohashi; Philippe Bussi
Original assignee: Elf Atochem S.A.
Priority date: 1996-06-26
Filing date: 1997-06-25
Publication date: 1997-12-31
Also published as: WO1997049777A3; AU3438797A

Abstract

The present invention offers a method for improving the adhesion of polyvinylidene fluoride resins to metal materials. It consists of either adding to the said polyvinylidene fluoride resin and acrylic and/or methacrylic polymer having functional groups with bonding properties or affinity in respect of metal and an acrylic and/or methacrylic elastomer (not necessary when the resin is a vinylidene fluoride copolymer) or inserting between the said polyvinylidene fluoride resin and the metal a composition comprising a polyvinylidene fluoride, and acrylic and/or methacrylic polymer having functional groups with bonding properties or affinity in respect of metal and an acrylic and/or methacrylic elastomer (which must be present only when the polyvinylidene fluoride of the composition is not a copolymer).

Description

SPECIFICATION Metal-adhesive polyvinylidene fluoride compositions TECHNICAL FIELD

The present invention relates to a method for the adhesion/lamination of polyvinylidene fluoride resins and metals which are not inherently adhesive thereto, and the invention can be applied to steel pipe linings, chemical plant components, and binders for the electrodes of batteries, etc, where corrosion resistance, weathering resistance or chemical resistance is demanded. PRIOR ART Being a fluoropolymer of outstanding weathering and chemical resistance, etc, which can be melted and moulded, vinylidene fluoride homopolymer and vinylidene fluoride copolymer resins (hereinafter both abbreviated to PVDF) are used as coating materials and also for electrical/electronic components, steel pipe linings, chemical plant components and weather-resistant antifouling film, etc. However, since they have practically no adhesive properties in terms of other materials, it suffers from the problem that it is difficult to modify or composite with multi-materials. Hence, the mixing of other polymers with the PVDF has been attempted to resolve this disadvantage, but there are few polymers having adhesion properties or compatibility in respect of PVDF, and because of adverse effects on the physical properties of the PVDF, etc, the application range is extremely restricted.

For example, methyl methacrylate resin (hereinafter abbreviated to PMMA) is known to be a material with good compatibility for PVDF (JP-A-43-12012 and JP-A- 51-18197), but the glass transition temperature of PMMA is very high when compared to that of PVDF, so mixtures of these lack flexibility and have poor adhesion to metals. On the other hand, composites with polycarbonate (JP-A-57- 8244), composites with modified polyolefins having functional groups (JP-A-62- 57448), and composites with polyimides (JP-A-2-308856) have also been proposed, but these combinations are poor in terms of compatibility and they are inferior in terms of their adhesion to metals. In addition, composites with acrylic or methacrylic elastomers have been proposed (JP-A-4-218552), but adhesion to metals with this system has never been studied.

DISCLOSURE OF THE INVENTION

The present invention has the objective of improving the adhesion of PVDF resin to metal materials, and of offering a method for obtaining a composite of metal material and PVDF resin.

The present inventors have found that a composition composed of at least a PVDF resin, at least an acrylic and/or methacrylic polymer having functional groups with bonding properties or affinity in respect of metal, and at least an acrylic and/or methacrylic elastomer so as a composition composed of at least a PVDF copolymer resin, at least an acrylic and/or methacrylic polymer having functional groups with bonding properties or affinity in respect of metal, both exhibit adhesion properties in respect of metal materials, and they have discovered that such characteristics are effective in the production of composite materials comprising PVDF resin and metal. Specifically, the present invention relates to a method for the adhesion of PVDF resin to metal which is characterized in that, when adhering PVDF resin to metal, from 0.5 to 100 parts by weight of at least an acrylic and/or methacrylic polymer (b1) having functional groups with bonding properties or affinity in respect of metal and from 1 to 200 parts by weight of at least an acrylic and/or methacrylic elastomer (d) are added and mixed per 100 parts by weight of PVDF resin (a1). When the PVDF resin is a vinylidene fluoride (VF2) copolymer resin (a2), per 100 parts by weight of the-said VF2 copolymer resin it can be added and mixed 0.5 to 200 parts by weight of at least an acrylic and/or methacrylic polymer (b2) having functional groups with bonding properties or affinity in respect of metal.

Further, in the present invention, the above PVDF resin compositions i-e a1+b1+c1 and a2+b2 with metal-adhesion improved by the aforesaid method can be employed as the adhesive agent when adhering PVDF resin to a metal. In particular, in the case where this adhesion process is a melt process, it is preferred that there be used as the said adhesive agent

- either a composition composed of per 100 parts by weight of PVDF resin (a1), from 5 to 100 parts by weight of an acrylic and/or methacrylic polymer (b1) having functional groups with bonding properties or affinity in respect of metal and from 10 to 200 parts by weight of an acrylic and/or methacrylic elastomer (d) - or a composition composed of per 100 parts by weight of PVDF copolymer resin (a2) and from 5 to 200 parts by weight of an acrylic and/or methacrylic polymer (b2) having functional groups with bonding properties or affinity in respect of metal. In such circumstances, if the content of the (b1) and (d) components or if the content of the (b2) component(s) is too low, then it is difficult to obtain excellent adhesion to the metal material.

The PVDF resins (a1) referred to here can be selected from polyvinylidene fluoride homopolymer and the copolymers of vinylidene fluoride with at least another monomer which can copolymerize with vinylidene fluoride, and these resins can be used on their own or as mixtures of two or more types. In the copolymers, the vinylidene fluoride component should be at least 50 wt%, preferably at least 70 wt% and more preferably at least 80 wt%. As examples of the other copolymerizable monomers, there can be cited fluorine-based monomers such as tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, trifluorochloroethylene and vinyl fluoride, etc, and one or more than one of these can be used.

In the present invention, the VF2 copolymer resin (a2) from which the metal- adhesive composition is a copolymer of vinylidene fluoride (VF2) and at least one monomer selected from tetrafluoroethylene, hexafluoropropylene, trifluoroethylene and trifluorochloroethylene, and the vinylidene fluoride component should be at least 50 wt% but no more than 99 wt%, preferably from 70 to 99 wt%, and more preferably from 80 to 99 wt%.

In the case where the metal-adhesive composition is used as an adhesive for the adhesion of a metal material and a vinylidene fluoride resin which lacks metal- adhesion properties, then the vinylidene fluoride resin (a1 or a2) from which the metal-adhesive composition is composed and the vinylidene fluoride resin of the surface layer may be identical or they may be different. The PVDF resin (a1 or a2) employed in the adhesive layer can be selected to have suitable properties such as melt flow rate (MFR), copolymer composition and melting point in accordance with the adhesion/fabrication process.

Component (b1 and b2) employed in the present invention is a polymer in which the chief component is an alkyl acrylate and/or alkyl methacrylate, and in the main chain, side chains or at the terminals it possesses functional groups with bonding properties or affinity in respect of metal. As examples of such polymers, there are the random copolymers, block copolymers and graft polymers produced by methods such as radical polymerization, ionic polymerization or co-ordination polymerization from at least one type of monomer selected from alkyl acrylates and alkyl methacrylates, plus monomer with a functional group having bonding properties or affinity in respect of metal.

As examples of functional groups with bonding properties or affinity in respect of metal, there can be cited carboxylic acid groups or carboxylic acid anhydride groups, epoxy groups (glycidyl groups), mercapto groups, sulphide groups, oxazoline groups, phenolic groups and ester groups, etc. Examples of the (b1 and b2) component polymer are the copolymers of monomer with a carboxylic acid group or carboxylic acid anhydride group, and an alkyl acrylate and/or alkyl methacrylate. In such circumstances, specific examples of the alkyl acrylate and alkyl methacrylate are methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate and butyl methacrylate. Further, as specific examples of the monomer with a carboxylic acid group or carboxylic acid anhydride group, there are acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, alkenylsuccinic acid, acrylamido-glycolic acid, allyl 1 ,2- cyclohexanedicarboxylate and other such unsaturated carboxylic acids, and maleic anhydride, alkenylsuccinic anhydride and other such unsaturated carboxylic acid anhydrides, etc.

Further, it is preferred that at least 50 wt%, and more preferably at least 70 wt%, of the aforesaid component acrylic or methacrylic polymer (b1 and b2) be composed of at least one type of monomer selected from acrylate and/or methacrylate esters. The amount of the functional groups with bonding properties or affinity in respect of metal, contained therein, will preferably be from 0.01 to 2 mole per 1kg of the acrylic and/or methacrylic polymer. In the case where the (b1 and b2) component is a copolymer of at least one monomer selected from acrylate and/or methacrylate esters and monomer having a carboxylic acid group or carboxylic acid anhydride group, the proportion of the monomer with a carboxylic acid group or carboxylic acid anhydride group will preferably be from 0.2 to 30 wt% of the said copolymer, more preferably from 1 to 20 wt%. Further, as the (b1 and b2) compositional component, there may also be included in the molecular chain, besides the above, a vinyl monomer such as styrene or modified units such as imides, but the amount of these will not be more than 50 wt%, and preferably not more than 30 wt% of the acrylic polymer.

The acrylic and/or methacrylic elastomer which is the (d) component of the present invention is either a grafted acrylic and/or methacrylic elastomer, or a conjugated diene type elastomer on which is grafted homopolymer or copolymer of monomer selected from alkyl acrylates and/or alkyl methacrylates. Now, these may be 100% graft polymers or they may be mixtures of homopolymers or copolymers containing some grafted material. In the majority of cases such elastomer will have a core/shell structure. In order that these acrylic and/or methacrylic elastomers confer suitable elastic characteristics, it is necessary that they have a glass transition temperature of no more than -10°C.

In regard to conjugated diene type elastomers which have been grafted with homopolymer or copolymer of monomer selected from alkyl acrylates and/or alkyl methacrylates, in the majority of cases the skeletal portion (core portion) is a diene polymer or a copolymer of diene monomer and monomer selected from aromatic vinyl compounds, alkyl acrylates and alkyl methacrylates (eg polybutadiene, butadiene/styrene copolymer, butadiene/butyl acrylate copolymer, etc), to which the homopolymer or copolymer of monomer selected from alkyl acrylates and alkyl methacrylates is grafted, forming a shell. As examples of preferred elastomers, there can be cited alkyl (Ci to C5) methacrylate/butadiene/styrene copolymer (MBS), alkyl (C1 to C12) acrylate/butadiene/styrene copolymer, and alkyl (C1 to C5) methacrylate/alkyl (C1 to C12) acrylate/ butadiene copolymer. As typical examples of the aforesaid grafted acrylic and/or methacrylic elastomer (d), there are the core-shell polymers in which the core is a homopolymer or copolymer comprising monomer selected from alkyl (Ci to Cs) acrylates and alkyl (Ci to Cs) methacrylates, or a block copolymer of silicone and homopolymer or copolymer comprising monomer selected from alkyl (Ci to Cs) acrylates and (Ci to Cβ) methacrylates, having a glass transition temperature of no more than -10°C, to which there is grafted the homopolymer or copolymer of monomer selected from alkyl (Ci to C5) acrylates and (Ci to C5) methacrylates different from that of the core, to form the shell. As further examples of the acrylic and/or methacrylic elastomer employed as the (d ) component, there are the core-shell polymers known from JP-A-8-30102 where a vinyl polymer is grafted to a composite (core) having a structure of mutually intertwined polyorganosiloxane component and acrylic and/or methacrylic elastomer component. These kinds of elastomer (d) can be produced by known methods such as bulk polymerization, suspension polymerization, bulk-suspension polymerization, emulsion polymerization or solution polymerization. For example, there is the three- stage polymerization method where, in the first stage butadiene is polymerized and a rubbery core obtained, in the second stage styrene is polymerized, and in the third stage methyl methacrylate is polymerized and the shell formed.

The (d) component employed in the present invention can be a thermoplastic elastomer with a rubbery character, preferably having a flexural modulus of no more than 800 MPa at room temperature and showing a breaking elongation of at least 20%. The metal-adhesive compositions of the present invention can be produced by conventional means, namely using a screw mixing machine, and heating and mixing the two or three components (a1 , b1 and d or a2 and b2) in the prescribed proportions. Here, conventionally-known methods can be adopted as the method of melting and mixing; for example, there is used a Banbury mixer, rubber mill, or single or twin-screw extruder, etc, and normally the resin composition is obtained by melt blending at 100 to 300°C, and preferably in the range 150 to 260°C, depending on the composition.

As examples of the metal materials used in the present invention, there can be cited iron, stainless steel, aluminium, copper, nickel, titanium, lead, silver, chromium and alloys of various kinds. There are no particular restrictions on the form thereof. WAYS FOR CARRYING OUT THE INVENTION

As explained above, by means of the present invention it becomes possible to perform the adhesion of PVDF resins and metal materials easily. The metal- adhesive polyvinylidene fluoride composite material referred to in the present invention comprises PVDF resin such as an extrusion moulded article (film, sheet, plate, pipe, rod, profile extruded article, strand, monofilament, fibre, etc), injection moulded article or press moulded article, etc, part or the entire face of which comprises a layer of the aforesaid metal-adhesive composition, and it is not especially restricted. Means for the production thereof include calendering, coextrusion, extrusion lamination, multilayer injection, fluid immersion coating, dipping, spraying and coating the surface of a moulded body, etc. Here, the PVDF resin used as substrate and the PVDF resin used in the metal-adhesive composition may be the same or different.

The method of the present invention for adhering polyvinylidene fluoride resin compositions to metals is valuable in many fields, such as the structural components of equipment where chemical inertness is demanded, exterior building materials and industrial materials where weatherability over a prolonged period is required, and also for the binders for electrodes in lithium batteries.

Further, the method of the present invention can also be employed for fluorocoating materials or for binders for the electrodes of lithium batteries, etc, where the PVDF resin is employed as a solution or dispersion in a solvent, and it is useful in improving the adhesion between the PVDF resin and the metal substrate (in the case of a battery, the current collector).

Below, the present invention is explained by examples but the invention is not to be restricted in any way by the said examples. EXAMPLES

The evaluation of the adhesion properties was conducted as follows. Using film of thickness about 0.2 mm produced from the metal-adhesive composition, film of thickness about 0.3 mm produced from separate PVDF resin, and degreased metal sheet, these were superimposed in the order PVDF film/adhesive composition film/metal sheet, and then pressing carried out for 10 minutes at 180°C, at a maximum pressure of about 10 kg/cm². After cooling to room temperature, using a tensile tester a 1 cm width of the PVDF/adhesive composition layer was peeled off at a rate of 200 mm/minute from the metal sheet at 23°C, and the strength measured. Example 1

100 parts by weight of PVDF homopolymer resin (a1) pellets (made by Elf Atochem, Kynar® 710, melting point 170°C, melt flow rate (MFR) = 12 g/10 min at 230°C under a 2.16 kg load), 30 parts by weight of copolymer of maleic anhydride and methyl methacrylate (b1)(made by Sumitomo Chemical Co., Sumipex TR) and 70 parts by weight of an acrylic elastomer to which polymethyl methacrylate was grafted (c1)(made by the Kureha Chemical Industry Co., Paraloid® EXL2315) were introduced into a blender and, after mixing together, pellets of composition comprising these 3 components were produced using a twin-screw extruder set at a cylinder temperature of 170-240X. The Vicat softening point of this composition was 113°C.

When the adhesive strength in terms of steel sheet was measured by the above method, using film of thickness about 0.2 mm produced by means of a single screw extruder from the pellets obtained and separately-produced Kynar® 710 film (thickness 0.3 mm), the value was 6.0 kg/cm. Example 2

A metal-adhesive composition was produced in the same way as in

Example 1 except that instead of the Kynar®710 in Example 1 there was employed Kynar® 2820 which is a copolymer of VF2 and hexafluoropropylene (made by Elf

Atochem, melting point 142°C, MFR = 1 g/10 min at 230°C under a 2.16 kg load).

The Vicat softening point of this composition was 70°C.

When the adhesive strength in terms of steel sheet was measured by the above method, using film of thickness 0.2 mm produced from this composition and separately-produced Kynar® 710 film of thickness 0.3 mm, the value was 5.8 kg/cm. Example 3

A metal-adhesive composition was produced in the same way as in Example 1 except that to the 100 parts by weight of Kynar® 710 (a1) as in Example 1 were added 60 parts by weight of Sumipex TR (b1 ) and 40 parts by weight of Paraloid® EXL2315 (d ).

When the adhesive strength in terms of aluminium sheet was measured by the above method, using film of thickness 0.2 mm produced from this composition and separately-produced Kynar® 710 film of thickness 0.3 mm, the value was 6.5 kg/cm. Example 4

A metal-adhesive composition was produced in the same way as in Example 1 except that as the acrylic polymer (b1 ) with carboxylic acid anhydride groups in Example 1 there was used a copolymer comprising 11 wt% maleic anhydride, 74 wt% methyl methacrylate and 15 wt% styrene (made by Rohm, Plexiglas ® HW55), and as the polymethyl methacrylate grafted acrylic elastomer (d) there was used MBS resin (made by the Rohm and Haas Co., Paraloid® EXL3647). When the adhesive strength in terms of steel sheet was measured by the above method, using film of thickness 0.2 mm produced from this composition and separately-produced Kynar® 710 film of thickness 0.3 mm, the value was 7.5 kg/cm. Example 5 A metal-adhesive composition was produced in the same way as in

Example 1 using, as the PVDF resin in that example, 100 parts by weight of a copolymer of hexafluoropropylene and VF2 (a1)(made by Elf Atochem, Kynar® 2850, MFR = 5 g/10 min at 230°C under a 12.5 kg load , melting point 157X, hexafluoropropylene content 5 wt%); as the acrylic polymer with carboxylic acid anhydride groups, 30 parts by weight of a copolymer comprising maleic anhydride, N-methyldimethylglutarimide, monomer containing carboxylic acid, and methyl methacrylate (b1)(made by Rohm and Haas, Paraloid® EXL4151), and as the polymethyl methacrylate grafted acrylic elastomer, 70 parts by weight of MBS resin (d)(made by Rohm and Haas, Paraloid® EXL3647). When the adhesive strength in terms of steel sheet was measured by the above method, using film of thickness 0.2 mm produced from this composition and separately-produced Kynar® 710 film of thickness 0.3 mm, the value was 8.0 kg/cm. Example 6

For the purposes of obtaining a two-layer thermoplastic structure, there was used a co-extruder comprising a coextrusion head and two extruders for supplying molten resin thereto (extruder A having a screw of L/D = 15 and compression ratio 3.5, and extruder B having a screw of UD = 20 and compression ratio 4). From extruder A there was extruded PVDF resin (made by Elf Atochem, Kynar® 740) and from extruder B there was extruded the adhesive composition obtained in Example 1 , to produce a composite film comprising a 0.3 mm PVDF resin layer and a 0.1mm adhesive layer. The cylinder temperatures of extruders A and B at this time were made 170-240°C and 150-220X respectively.

When the adhesive strength between the film obtained and copper plate was measured by the same method as above, it was 5.6 kg/cm. Example 7

100 g of PVDF resin powder (a1)(made by Elf Atochem, Kynar® 461 , melting point 170°C, MFR = 12 g/10 min at 230°C under a 2.16 kg load), 2 g of copolymer of maleic anhydride and methyl methacrylate (b1)(Sumipex TR) and 2 g of polymethyl methacrylate grafted acrylic elastomer (c1)(made by Kureha Chemical Industry Co., Paraloid® EXL2315) were dissolved in 1000 ml of N-methylpyrrolidone to produce a solution.

This solution was applied onto an aluminium sheet of thickness 1 mm, dried for 1 hour at 120°C, and there was obtained an aluminium sheet coated with about 0.1 mm of PVDF resin. When the PVDF resin layer was cut at 1 mm intervals and a cross-cut adhesion test performed (based on JIS K5400 6.15) and also a tape peeling test performed, absolutely no separation of the PVDF resin layer was noted in either case. Comparative Example 1

100 parts by weight of PVDF resin pellets (a1)(Kynar® 710) and 30 parts by weight of copolymer of maleic anhydride and methyl methacrylate (b1)(Sumipex TR) were introduced into a blender and, after mixing together, there was produced a film of thickness about 0.2 mm using a twin-screw extruder set at a cylinder temperature of 170-240°C.

When the adhesive strength in terms of steel sheet was measured by the above method, using this film and separately-produced Kynar® 710 film (of thickness 0.3 mm), the value was no more than 1 kg/cm. Comparative Example 2 100 parts by weight of PVDF resin powder (a1)(Kynar® 461) and 2 parts by weight of copolymer of maleic anhydride and methyl methacrylate (b1)(Sumipex TR) were dissolved in 1000 ml of N-methylpyrrolidone and a solution produced. This solution was applied onto a aluminium sheet of thickness 1 mm, dried for 1 hour at 120°C, and an aluminium sheet coated with about 0.1 mm of PVDF resin obtained. When the PVDF resin layer was cut at 1 mm intervals and a cross-cut adhesion test and a tape peeling test carried out, the PVDF resin layer completely separated away in the tape peeling test. Example 8

100 parts by weight of VF2 copolymer resin pellets (a2) comprising VF2 and hexafluoropropylene (made by Elf Atochem, Kynar® 2800, MFR = 6 g/10 min at 230°C under a 12.5 kg load, melting point 142X, hexafluoropropylene content 10 wt%) and 100 parts by weight of a copolymer of maleic anhydride and methyl methacrylate (b2)(Sumipex TR) were introduced into a blender and, after mixing together, pellets of composition comprising these two components were produced using a twin-screw extruder set at a cylinder temperature of 170-240°C.

When the adhesive strength in terms of steel sheet, aluminium sheet, copper sheet and stainless steel (SUS316) sheet was measured by the above method, using film of thickness about 0.2 mm produced by means of a single screw extruder from the pellets obtained, and using separately-produced Kynar® 710 film (thickness 0.3 mm), the values were 6.5 kg/cm, 7.0 kg/cm, 5.3 kg/cm and 7.2 kg/cm respectively. Example 9

100 parts by weight of VF2 copolymer resin pellets (a2)(Kynar® 2850) and 60 parts by weight of a copolymer of 11 wt% maleic anhydride, 74 wt% methyl methacrylate and 15 wt% styrene (b2)(made by the Rohm Co., Plexiglas® HW55) were introduced into a blender and, after mixing together, pellets of composition comprising these two components were produced using a twin-screw extruder set at a cylinder temperature of 170-240°C.

When the adhesive strength in terms of steel sheet was measured by the above method, using film of thickness 0.3 mm produced from this composition, the value was 6.2 kg/cm.

Example 1Q

For the purposes of obtaining a two-layer thermoplastic structure, there was used a co-extruder comprising a coextrusion head and two extruders for supplying molten resin thereto (extruder A having a screw of L/D = 15 and compression ratio 3.5, and extruder B having a screw of LVD = 20 and compression ratio 4). From extruder A there was extruded PVDF resin (made by Elf Atochem, Kynar® 740) and from extruder B there was extruded the adhesive composition obtained in Example 8, to produce a composite film comprising a 0.3 mm PVDF resin layer and a 0.1 mm adhesive layer. The cylinder temperatures of extruders A and B at this time were made 170-240°C and 140-210°C respectively.

When the adhesive strength in terms of copper sheet and steel sheet was measured by the same method as above using the film obtained, the results were 5.3 kg/cm and 6.0 kg/cm respectively. Example 11 100 g of copolymer resin powder comprising VF2 and hexafluoropropylene

(made by Elf Atochem, Kynar® 2801 , MFR = 6 g/10 min at 230°C under a 12.5 kg load, melting point 142 °C, hexafluoropropylene content 10 wt%) and 2 g of copolymer of maleic anhydride and methyl methacrylate (Sumipex TR) were dissolved in 1000 ml of N-methylpyrrolidone to produce a solution. This solution was applied onto an aluminium sheet of thickness 1 mm, dried for 1 hour at 120°C, and there was obtained an aluminium sheet coated with about 0.1 mm of the dried composition. When the composition layer was cut at 1 mm intervals and a cross-cut adhesion test performed (based on JIS K5400 6.15) and also a tape peeling test performed, absolutely no separation of the composition layer was noted in either case.

Comparative Example 3

100 parts by weight of PVDF resin pellets (a1)(Kynar® 710) and 100 parts by weight of copolymer of maleic anhydride and methyl methacrylate (b1)(Sumipex TR) were introduced into a blender and, after mixing together, there was produced a film of thickness about 0.2 mm using a twin-screw extruder set at a cylinder temperature of 170-240°C.

When the adhesive strength in terms of steel sheet was measured by the above method, using this film and using separately-produced Kynar®710 film (of thickness 0.3 mm), the value was no more than 1 kg/cm. Comparative Example 4

A solution was prepared in the same way as in Example 11 but instead of the copolymer comprising vinylidene fluoride and hexafluoropropylene in Example 11 there was used vinylidene fluoride homopolymer Kynar® 710. When the adhesion was tested in terms of aluminium sheet, 90 % of composition resin layer peeled away in the tape peeling test.

Claims

1. Metal-adhesive polyvinylidene fluoride-based composition characterized in that it comprises per 100 parts by weight of at least a polyvinylidene fluoride resin (a1), from 0.5 to 100 parts by weight of at least an acrylic and/or methacrylic polymer having functional groups with bonding properties or affinity in respect of metal (b1) and from 1 to 200 parts by weight of at least an acrylic and/or methacrylic elastomer (d).

2. Metal-adhesive vinylidene fluoride copolymer-based composition characterized in that it comprises, per 100 parts by weight of at least a vinylidene fluoride copolymer resin (a2) and from 0.5 to 200 parts by weight of at least an acrylic and/or methacrylic polymer having functional groups with bonding properties or affinity in respect of metal (b2) and that the vinylidene fluoride proportion of the copolymer resin (a2) is 50-99 wt%.

3. Metal-adhesive composition according to claim 1 or 2, where the functional groups with bonding properties or affinity in respect of metal are carboxylic acid groups and/or carboxylic anhydride groups and/or epoxy groups.

4. Metal-adhesive composition according to claim 1 to 3, where the acrylic and/or methacrylic polymer having functional groups with bonding properties or affinity in respect of metal (b1 or b2) is a copolymer comprising from 0.2 to 30 parts by weight of monomer with a carboxylic acid group and/or carboxylic acid anhydride group and 100 parts by weight of at least one monomer selected from alkyl acrylates and/or alkyl methacrylates.

5. Metal-adhesive composition according to claim 1 to 4, where the acrylic and/or methacrylic elastomer (d) is a grafted elastomer with a glass transition temperature of no more than -10°C.

6. Metal-adhesive composition according to claim 1 to 5, where the acrylic and/or methacrylic elastomer (d) is a grafted acrylic and/or methacrylic elastomer, or a conjugated diene elastomer grafted with homopolymer and/or copolymer of monomer selected from alkyl acrylates and/or alkyl methacrylates.

7. Metal-adhesive composition according to claim 6, where the conjugated diene elastomer is polybutadiene or a copolymer of styrene and butadiene.

8. Metal-adhesive composition according to claim 6, where the acrylic and/or methacrylic elastomer (d) is an elastomer having a butadiene-styrene copolymer skeletal structure on which skeletal structure is grafted polymer of monomer selected from Ci to C4 alkyl methacrylates and Ci to C4 alkyl acrylates, or an elastomer having a skeletal structure selected from the copolymers of conjugated dienes and C2 to C12 alkyl acrylates, on which skeletal structure is grafted polymer of monomer selected from Ci to C4 alkyl acrylates and Ci to C4 alkyl methacrylates.

9. Metal-adhesive composition according to claim 6, where the acrylic and/or methacrylic elastomer (d) is a graft copolymer having a skeletal structure of homopolymer or copolymer of monomer selected from alkyl acrylates and alkyl methacrylates, on which skeletal structure is grafted homopolymer or copolymer of monomer selected from alkyl methacrylates and alkyl acrylates other than that in the said skeletal structure.

10. Metal-adhesive composition according to claim 6 to 9, where the acrylic and/or methacrylic elastomer (d) has a flexural modulus at room temperature of no more than 800 MPa.

11. Method for the adhesion of polyvinylidene fluoride resin to metal, characterized in that the-said polyvinylidene fluoride resin is replaced by a composition as defined in any one of claims 1 to 10 when adhering to metal.

12. Method for the adhesion of polyvinylidene fluoride resin to metal characterized in that, when adhering polyvinylidene fluoride resin to metal, there is used as the adhesive intermediate agent a composition as defined in any one of claims 1 to 10.

13. Method for the adhesion to metal according to claim 11 or 12 by means of calendering, coextrusion, extrusion lamination, multilayer injection, fluid immersion coating, dipping, spraying and/or coating the surface of a moulded body.

14. Metal-adhesive polyvinylidene fluoride-based composite material comprising a layer based on the metal-adhesive composition as defined in any one of claims 1 to 10 and a layer of polyvinylidene fluoride resin.

15. Use of a composition as defined in any one of claims 1 to 10 as a binder of batteries electrodes, and preferably for lithium batteries.

16. Use of a metal-adhesive polyvinylidene fluoride-based composite material as defined in claim 14 as a binder of batteries electrodes, and preferably for lithium batteries.