EP2052002A2

EP2052002A2 - Vinylidene fluoride copolymer functionalized by radiation grafting of an unsaturated polar monomer

Info

Publication number: EP2052002A2
Application number: EP07823697A
Authority: EP
Inventors: Anthony Bonnet; Aude Lapprand; Pascal Sebire
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2006-08-08
Filing date: 2007-08-07
Publication date: 2009-04-29
Also published as: JP2010500440A; WO2008017789A2; US20100255378A1; NO20090985L; JP5457180B2; FR2904828A1; WO2008017789A3; CN101522735A; CA2660341A1; FR2904828B1

Abstract

The invention relates to a VDF copolymer and at least one monomer copolymerisable with the VDF having at least 50% of its weight in VDF, preferably at least 75%, onto which at least one unsaturated polar monomer is radiation-grafted, characterized in that, prior to grafting, the VDF copolymer has the following characteristics: a crystallization temperature Tc (measured by DSC as per the ISO Standard 11357-3) ranging between 50°C and 120°C, preferably from 85°C to 110°C; a constraint to the σy threshold ranging from 10 to 40 MPa, preferably from 10 to 30 MPa; a viscosity v in the molten state (measured with a capillary rheometer at 230°C at 100 s-1) ranging from 100 to 1500 Pa s, preferably from 400 to 1200 Pa s. The invention further relates to a mixture comprising said modified copolymer and a PVDF. Said modified copolymer or the mixture may also be associated with a thermoplastic polymer, an elastomer or an inorganic material.

Description

VINYLIDENE FLUORIDE COPOLYMER FUNCTIONALIZED BY IRRADIATION GRAFTING UNSATURATED POLAR MONOMER

FIELD OF THE INVENTION The invention relates to a functionalized PVDF which is obtained by irradiation grafting of at least one unsaturated polar monomer on a PVDF, as well as to a mixture comprising this functionalized PVDF and a non-PVDF. amended. The functionalized PVDF or the mixture has the particularity of adhering to many materials such as thermoplastic polymers or inorganic materials, which makes it possible to obtain multilayer structures. The invention also relates to these multilayer structures and to a coextrusion process in which a layer of the functionalized PVDF or mixture is coextruded.

[The technical problem]

PVDF is known to offer excellent mechanical stability properties, a very high chemical inertness, as well as a good resistance to aging. These qualities are exploited for various fields of application. For example, the manufacture of extruded or injected parts for the chemical engineering industry or microelectronics, the use in the form of a sealing sheath for the transport of gases or hydrocarbons, the production of films or coatings. allowing protection in the architectural field and the production of protective elements for electrotechnical purposes. However, it is also known that it is difficult to adhere the PVDF to other materials.

The European applications EP 1484346, EP 1537989, EP 1541343 or the international applications WO 2006/045630 or WO 2006/042764 describe a process for modifying a fluoropolymer, in particular PVDF, making it possible to adhere the fluoropolymer to thermoplastic polymers. or inorganic materials. The method comprises irradiation grafting an unsaturated polar monomer. The Applicant has found that membership can be greatly increased if the fluoropolymer that is modified by this process is a particular PVDF copolymer with certain thermal and mechanical characteristics. The Applicant has also found that it is possible to obtain a higher coextrusion line speed in the presence of this functionalized PVDF.

[The prior art]

European application EP 1101994 discloses a gasoline tube comprising a layer of a functionalised fluoropolymer. The latter may be a fluoropolymer functionalized by radiation grafting.

European applications EP 1484346, EP 1537989, EP 1541343 and EP 1637319 describe a process for modifying a fluorinated polymer, especially PVDF, comprising grafting under irradiation an unsaturated polar monomer. PVDF can be a homo- or copolymer.

The international application WO 2006/045630 describes a mixture of a functionalized PVDF and a flexible fluorinated polymer having a viscosity ν between 100 and 1500 Pa s, a crystallization temperature Tc between 50 and 120 ^° C. The functionalized PVDF is preferably obtained by radiation grafting and preferably comprises more than 80 mol% of VDF, or even better it is a homopolymer.

Application EP 1508927 describes examples of functionalized PVDF used alone or as a mixture. In the examples, KYNARFLEX ^® grades are used

2801 or KYNAR ^® 761. The modified KYNARFLEX ^® 2801 is a VDF-HFP copolymer and has the following characteristics: 11% HFP, a σy between 20 and 34 MPa, a Tc of 116.8 ° C and a viscosity v of the order of

2500 Pa s (230 ⁰ C, 100 s ^"1). The KYNAR ^® 761 is a PVDF homopolymer. The 2801 grade is more viscous than the PVDF which is modified according to the invention.

After the irradiation step, the PVDF has a certain degree of crosslinking due to the fact that cross-linking nodes are created between the PVDF chains: this has the effect of further increasing the melt viscosity, which makes the functionalized PVDF more difficult to transform and implement, whether in the molten state or in solution in a solvent.

In none of these documents is reference made to the PVDF having the thermal and mechanical characteristics of the invention.

[Brief description of the invention]

The invention relates to a copolymer of VDF and at least one monomer copolymerizable with VDF having a VDF content by weight of at least 50%, preferably at least 75%, onto which is grafted by irradiation with less an unsaturated polar monomer characterized in that the copolymer of VDF present before grafting the following characteristics:

A crystallization temperature Tc (measured by DSC according to the ISO 11357-3 standard) ranging from 50 and 120 ^° C., preferably from 85 to

1 10 ⁰ C;

A threshold stress σy ranging from 10 to 40 MPa, preferably from 10 to 30 MPa;

A viscosity v in the molten state (measured with a capillary rheometer at 230 ° C. at 100 sec ^-1 ) ranging from 100 to 1500 Pa s, preferably from 400 to

1200 Pa s.

Preferably, the VDF copolymer exhibits, before grafting, a tensile Young's modulus ranging from 200 to 1000 MPa, preferably from 200 to 600 MPa.

The invention also relates to a mixture comprising this modified copolymer and a PVDF. This modified copolymer or mixture may be associated with a thermoplastic polymer, an elastomer or an inorganic material. [Detailed description of the invention]

As regards the PVDF on which the grafting is carried out, it is a copolymer of VDF (vinylidene fluoride, CH ₂ = CF ₂ ) whose content in weight is at least 50%, preferably at least 75% and at least one monomer copolymerizable with VDF. The comonomer can be, for example, vinyl fluoride (VF), trifluoroethylene, chlorotrifluoroethylene (CTFE),

1, 2-difluoroethylene, tetrafluoroethylene (TFE), hexafluoropropene (HFP),

3,3,3-trifluoropropene and 2-thfluoromethyl-3,3,3-trifluoro-1-propene. Preferably, for reasons of ease of extrusion, it is a thermoplastic PVDF.

VDF-HFP copolymers whose HFP weight content varies from 4 to 22%, preferably from 10 to 20% (content calculated before grafting the unsaturated polar monomer), are preferred.

PVDF also has the following characteristics (before grafting):

A crystallization temperature Tc (measured by DSC according to the ISO 11357-3 standard) ranging from 50 and 120 ^° C., preferably from 85 to 110 ^° C.;

A threshold stress σy (measured at 20 ° C.) ranging from 10 to 40 MPa, preferably from 10 to 30 MPa;

A melt viscosity ν (measured by capillary rheometer at 230 ^° C. at 100 sec ^-1 ) ranging from 100 to 1500 Pa s, preferably from 400 to 1200 Pa s.

It also has before grafting a tensile Young's modulus (ASTM D-638) which preferably ranges from 200 to 1000 MPa, preferably from 200 to 600 MPa.

Compared to Grade KYNARFLEX ^® 2801 which is described in EP 1508927, PVDF that is modified initially present lower a viscosity v, which means that after modification, the viscosity of the functionalized PVDF is also less than the modified KYNARFLEX 2801. This facilitates the implementation of functionalized PVDF whether in the molten state or in solution in a solvent.

The functionalized PVDF or the mixture have, compared to the functionalized PVDFs of the prior art, the following advantages:

• stronger adhesion to polymers and inorganic materials;

• greater ease of implementation whether in the molten state or in solution in a solvent;

• they allow a higher speed of coextrusion.

Grades KYNARFLEX ^® 2500 and 2750 sold by Arkema are examples of PVDF suitable for the invention: characteristics KYNARFLEX ^® 2500 VDF-HFP copolymer having 19% HFP Tc: 87.4 ° C σy: 15 MPa v: 1000 Pa.s tens Young modulus: 220 MPa.

characteristics of KYNARFLEX ^® 2750 VDF-HFP copolymer with 16% HFP Tc: 103 ⁰ C σy: 18 MPa v: 900 Pa.s Young's modulus traction: 360 MPa

As regards the functionalized PVDF, this is obtained by the grafting under irradiation of at least one unsaturated polar monomer on the PVDF defined above. We will talk about functionalized PVDF later. The process comprises the following steps: a), the PVDF is premixed with at least one unsaturated polar monomer by all the melt mixing techniques known from the prior art. The mixing step is carried out in any mixing device such as extruders or kneaders used in the thermoplastics industry. Preferably, an extruder will be used to form the mixture into granules. The grafting takes place on a mixture (in the mass) and not on the surface of a powder as described, for example, in US Pat. No. 5,576,106. The proportion of PVDF is, by weight, between 80 to 99.9% by weight. %, preferably from 90 to 99% for 0.1 to 20%, preferably 1 to 10% unsaturated polar monomer, respectively.

b). then, the mixture is irradiated (irradiation β or γ) in the solid state using an electronic or photonic source under an irradiation dose of between 10 and 200 kGray, preferably between 10 and 150 kGray. The mixture may for example be packaged in polythene bags, the air is removed and the bags are closed. Advantageously the dose is between 2 and 6 Mrad and preferably between 3 and 5 Mrad. Irradiation with a cobalt-60 bomb is particularly preferred.

The content of unsaturated polar monomer which is grafted is, by weight, between 0.1 and 5% (that is to say that the unsaturated polar monomer grafted corresponds to 0.1 to 5 parts for 99.9 to 95%). parts of PVDF), advantageously from 0.5 to 5%, preferably from 0.9 to 5%. This content depends on the initial content of the unsaturated polar monomer in the mixture to be irradiated. It also depends on the effectiveness of the grafting, and therefore the duration and energy of the irradiation.

vs). the unsaturated polar monomer which has not been grafted, and the residues released by the grafting, in particular the HF, can then optionally be removed. This last step may be necessary if the ungrafted unsaturated polar monomer is likely to hinder adhesion or for toxicology problems. This operation can be carried out according to techniques known to those skilled in the art. Vacuum degassing may be applied, possibly by applying heating at the same time. It is also possible to dissolve the functionalized PVDF in a suitable solvent such as, for example, N-methylpyrrolidone, then to precipitate it in a non-solvent, for example in water or in an alcohol, or to wash the PVDF functionalized with a solvent inert with respect to the fluoropolymer and grafted functions. For example, when grafting maleic anhydride, it can be washed with chlorobenzene.

This is one of the advantages of this irradiation grafting process that higher grafted unsaturated polar monomer contents can be obtained than with conventional grafting methods using a radical initiator. Thus, typically, with the irradiation grafting method, it is possible to obtain contents greater than 1% (1 part of unsaturated monomer per 99 parts of PVDF), or even greater than 1, 5%, which does not is not possible with a conventional grafting process in extruder

On the other hand, the grafting by irradiation takes place at "cold", typically at temperatures below 100 ^° C., or even 50 ^° C., so that the mixture to be irradiated is not in the molten state, as for one conventional grafting process in extruder. An essential difference is that the grafting takes place in the amorphous phase and not in the crystalline phase while homogeneous grafting occurs in the case of grafting in the melt extruder. The unsaturated polar monomer is therefore not distributed identically on the PVDF chains in the case of radiation grafting and in the case of grafting in an extruder. The functionalized PVDF therefore has a different distribution of the unsaturated polar monomer on the PVDF chains compared to a product that would be obtained by grafting in an extruder.

During this grafting step, it is preferable to avoid the presence of oxygen. A nitrogen or argon sweep of the mixture to be irradiated is therefore possible to eliminate the oxygen. Functionalized PVDF has very good resistance oxidation and the good thermomechanical behavior of PVDF before its modification.

As regards the unsaturated polar monomer, it has a C = C double bond as well as at least one polar group which may be a function:

carboxylic acid,

- carboxylic acid salt,

- carboxylic acid anhydride,

epoxide, carboxylic acid ester,

- silyl,

alkoxysilane,

- Carboxylic acid amide, hydroxy, - isocyanate.

Mixtures of several unsaturated monomers are also possible.

Unsaturated carboxylic acids having 4 to 10 carbon atoms and their functional derivatives, particularly their anhydrides, are particularly preferred unsaturated monomers. Examples of unsaturated monomers are methacrylic acid, acrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, undecylenic acid, allylsuccinic acid, and the like. cyclohex-4-ene-1,2-dicarboxylic acid, 4-methyl-cyclohex-4-ene-1,2-dicarboxylic acid, bicyclo (2,2,1) hept-5-ene 2,3-dicarboxylic acid, x-methylbicyclo (2,2,1-hept-5-ene-2,3-dicarboxylic acid, zinc, calcium or sodium undecylenate, maleic anhydride, itaconic anhydride, citraconic anhydride, dichloromaleic anhydride, difluoromaleic anhydride, crotonic anhydride, glycidyl acrylate or methacrylate, allyl glycidyl ether, vinyl silanes such as vinyl trimethoxysilane, vinyl triethoxysilane vinyl triacetoxysilane, γ-methacryloxypropyltrimethoxysilane. Other examples of unsaturated monomers include C ₁ -C ₈ alkyl esters or glycidyl ester derivatives of unsaturated carboxylic acids such as methyl acrylate, methyl methacrylate, ethyl acrylate, methacrylate and the like. ethyl acrylate, butyl acrylate, butyl methacrylate, glycidyl acrylate, glycidyl methacrylate, monoethyl maleate, diethyl maleate, monomethyl fumarate, dimethyl fumarate, monomethyl, and diethyl itaconate; amide derivatives of unsaturated carboxylic acids such as acrylamide, methacrylamide, maleic monoamide, maleic diamide, N - monoethylamide maleic, N, N - diethylamide maleic, N - maleic monobutylamide, N, N - dibutylamide maleic, furamic monoamide, furamic diamide, fumaric N-monoethylamide, N, N-diethylamide fumaric, fumaric N-monobutylamide and N, N-dibutylamide furamic; imide derivatives of unsaturated carboxylic acids such as maleimide, N-butylmaleimide and N-phenylmaleimide; and metal salts of unsaturated carboxylic acids such as sodium acrylate, sodium methacrylate, potassium acrylate, potassium methacrylate and zinc, calcium or sodium undecylenates.

Preferably, the unsaturated monomer does not have more than one C = C double bond, as this leads to crosslinking of the copolymer. Di- or triacrylates are examples of unsaturated monomers having more than one C = C bond. From this point of view, maleic anhydride as well as zinc, calcium and sodium undecylenates are good graftable compounds because they have little tendency to homopolymerize or even to give rise to crosslinking.

Advantageously, maleic anhydride is used. This monomer indeed offers the following advantages: it is solid and can be easily introduced with the fluoropolymer granules before mixing in the molten state, - being solid, it is also more easily handled (it is particularly volatile),

it makes it possible to obtain good adhesion properties,

it is particularly reactive with respect to many chemical functions,

unlike other unsaturated monomers such as (meth) acrylic acid or acrylic esters, it does not homopolymerise and does not have to be stabilized.

The functionalized PVDF may be used alone or in admixture with another PVDF, which may be a homo- or copolymer PVDF. Preferably, this other PVDF is chosen so that the two PVDF are compatible and that the mixture has only one melting peak by DSC. Preferably, the other PVDF is a copolymer of VDF and at least one monomer copolymerizable with VDF having a VDF content by weight of at least 50%, preferably at least 75% and which has the same thermal and mechanical characteristics specified above. The mixture comprises, by weight, from 1 to 99%, preferably from 50 to 99%, of the functionalized PVDF for 99 to 1%, and preferably 1 to 50%, of another PVDF, respectively. The mixture can be prepared in a melt using a mixing tool suitable for thermoplastics, for example using an extruder.

Uses of functionalized PVDF or mixture

The functionalized PVDF or the mixture may be associated with a thermoplastic polymer, an elastomer or an inorganic material. The invention also relates to a multilayer structure comprising at least one layer comprising at least one functionalized PVDF or the mixture and:

At least one layer comprising at least one thermoplastic polymer and / or at least one elastomer, at least one layer of an inorganic material. For each multilayer structure of the present application, each layer is defined as broadly as possible by the expression "layer comprising a polymer X". The multilayer structure is also defined in parallel by "layer of the polymer X".

Multilayer structure with a thermoplastic polymer layer This structure can be prepared for example by the coextrusion, rotational molding or extrusion blow molding technique. It can take the form of a film, a tube, a container or a hollow body.

As examples of thermoplastic polymers, mention may be made of:

Polyamides (for example PA 6, 11, 12, 6, 6, ...);

Polymers comprising predominantly (> 50% by weight) ethylene or propylene. For example, polyolefins (PE, PP) as well as copolymers of ethylene and of at least one ethylene comonomer chosen from alpha-olefins, preferably butene or octene, vinyl saturated carboxylic acids, preferably vinyl acetate or vinyl propionate, alkyl (meth) acrylates, preferably methyl acrylate, butyl acrylate or ethyl acrylate;

• vinyl chloride-based polymers such as PVC (soft, rigid), chlorinated PVC (CPVC) or vinylidene chloride (eg PVDC);

• ABS (acrylonitrile-butadiene-styrene copolymer) or SAN (styrene-acrylonitrile copolymer);

Acrylic polymers, especially homo- or copolymer PMMA;

Saturated polyesters (PET, PBT, PBN);

• polycarbonates; • phenylene polysulfide (PPS);

• polyphenylene oxide (PPO);

• EVOH (ethylene-ethylene-vinyl alcohol copolymer); • polyetherketone (PEEK);

• polyoxymethylene (acetal);

• polyethersulfone;

• polyurethanes; Styrene-based polymers and copolymers, especially impact polystyrene or crystal as well as styrene-diene block copolymers of the SBS type;

Fluoropolymers such as, for example, PVDF, PTFE, copolymers of TFE and HFP, copolymers of ethylene and TFE, copolymers of ethylene and chlorotrifluoroethylene, polyvinyl fluoride.

The polyolefin may be a polyethylene of the MDPE (medium density), HDPE (high density), LDPE (low density), LLDPE (linear low density), polyethylene prepared by metallocene type or more generally monosite type or else cross-linked polyethylene (PEX). It may be a homo- or copolymer. The copolymer may in particular be a copolymer having a comonomer content greater than 5% by weight, for example an ethylene-octene copolymer of the ENGAGE ^® type. Others include olefin elastomers blocks (CBO) recently developed by DOW under the brand INFUSE ^® which include hard and soft blocks, which are prepared according to the teaching of WO 2005090425, WO 2005090426 and WO 2005090427.

Thermoplastic elastomers which according to the definition proposed in NUPAC in 2002 are melt-processable copolymers and which have a continuous elastomeric phase reinforced by a dispersion of vitreous or crystalline domains which act as junction points in a limited temperature range. Among the elastomers-thermoplastics, mention will be made especially TPO. As examples of elastomers, mention may be made of:

• polychloroprene;

• nitrile rubber (eg acrylonitrile-butadiene copolymer);

• acrylic elastomers; • fluorinated elastomers;

• EPMs and EPDMs;

• polyurethane elastomers;

Copolyether amides and copolyester amides (eg PEBAX grades marketed by ARKEMA).

For more details on elastomers, reference may be made to Ullmann's Encyclopaedia of Industrial Chemistry Vol. A23, ed. 1993, isbn 3-527-20123-8, pp.239-334.

When the adhesion between the functionalized PVDF layer or the mixture and the thermoplastic or elastomeric polymer layer is not sufficient, at least one layer of an adhesion binder may be placed between these two layers. The adhesion binder advantageously has chemical functions which react with those present on the functionalized PVDF. For example, if acid anhydride functions have been grafted onto PVDF, the adhesion binder advantageously comprises epoxide or hydroxy functions. The adhesion binder layer may be optionally split. That is to say between the thermoplastic polymer layer and the layer of functionalized PVDF or mixture can be providing a 1 ^st layer of binder and a 2 ^nd layer of another binder, the two layers of binder being arranged against each other.

As an example of a multilayer structure, mention may be made of the one comprising arranged in the order one against the other: a layer comprising at least one thermoplastic polymer and / or at least one elastomer;

Optionally at least one layer of an adhesion binder; A layer comprising the functionalized PVDF or the mixture;

Optionally a layer comprising a fluoropolymer, preferably a PVDF homo- or copolymer.

In the case of a tube, container or hollow body, the thermoplastic polymer layer is the outer layer or the inner layer. An example of such a structure is that for which the thermoplastic polymer is a polyethylene, which is in the form of a tube or a container and which is used for the transport or storage of a chemical that may damage the polyolefin the polyethylene layer being the outer layer. The chemical may be, for example, a hydrocarbon (gasoline, fuel, etc.) or a corrosive product (acid, base, hydrogen peroxide, etc.). The functionalized PVDF layer or mixture and / or the fluoropolymer layer protects the polyolefin layer. In the case of a hydrocarbon, it avoids the swelling of the polyolefin.

Another example of a multilayer structure comprises arranged in order one against the other:

Optionally a layer comprising a fluoropolymer, preferably a homo- or copolymer PVDF;

A layer comprising the functionalized PVDF or the mixture;

Optionally at least one layer of an adhesion binder;

A layer comprising at least one thermoplastic polymer and / or at least one elastomer; Optionally at least one layer of an adhesion binder;

A layer comprising the functionalized PVDF or the mixture;

An example of such a structure is that for which the thermoplastic polymer is a polyethylene, which is in the form of a tube or a container and which is used for the transport or storage of a chemical product. likely to damage the polyolefin. The chemical may be, for example, a hydrocarbon (gasoline, fuel, etc.) or a corrosive product (acid, base, hydrogen peroxide, etc.). The functionalised PVDF or mixture layers and / or the optional layers of the fluoropolymer serve to protect the polyethylene inner layer. In the case of a hydrocarbon, they also prevent the swelling of polyethylene.

Multilayer structure with a layer of inorganic material By inorganic material is meant: "a metal;

• glass ;

• concrete;

• silicon;

• quartz.

The layer comprising the functionalized PVDF or the mixture therefore constitutes a protective coating for the inorganic material. In other words, the inorganic material is coated with a composition comprising at least one functionalized PVDF or the mixture according to the invention. This composition protects for example against corrosion in all its forms. It may also optionally comprise at least one acrylic polymer, for example a PMMA. It may also optionally comprise one or more additives chosen from anti-UV agents, mineral fillers, pigments and / or dyes, conductive fillers such as carbon black or carbon nanotubes, etc.

The metal can be for example iron, copper, aluminum, titanium, lead, tin, cobalt, silver, tungsten, nickel, zinc or an alloy (for example steel , carbon steels, nickel, chromium, nickel-chromium, chromium-molybdenum, silicon, stainless steel, cast iron, Permalloy, aluminum-magnesium, aluminum-silicon, aluminum-copper-nickel alloys - magnesium, aluminum-silicon-copper-nickel-magnesium, brass, bronze, silicon bronze, silicon brass, nickel bronze).

The metal may first undergo a physical and / or chemical pretreatment the purpose of which is to clean the metal surface and promote the adhesion of the functionalized PVDF layer or mixture. Possible pretreatments are: alkaline degreasing, solvent degreasing such as trichlorethylene, brushing, grinding, phosphating, chromating, anodizing (eg for aluminum and its alloys), anodizing chromic, silanization, abrasion, etching and in particular sulfochromic etching. A possible pretreatment may be to apply an adhesion promoter. The adhesion promoters have been described by Cassidy P. E. in the journal Ind. Eng. Chem. Prod. Res. Development, 1972, Volume 11, No. 2, p.170-177 or by Kinlock AJ. in J Mat. ScL, 1980, 15, p. 2141-66. Some examples of possible chemical pretreatments are Alodine NR1453, Alodine NR2010, Accomet C or Safeguard 6000. Pretreatment may also consist of a combination of these various pretreatments, including the combination of a physical pretreatment. and chemical.

The metal can be in various forms and geometry such as for example in the form:

An elongated surface such as, for example, a sheet, a plate or a sheet, a hollow body such as, for example, a container, a container, a bottle, a bottle, a chemical reactor,

• a tube, an elbow, a valve, a needle, a pump,

• a wire, strand, cable or guy,

• an electrode.

The coating can be applied in the molten state, in solution in a solvent or in powder form. In the case of a powder, it is possible to use the bed technique fluidized by soaking a heated metal piece in a fluidized bed of the powder is usable or the electrostatic powder coating technique. The powder is introduced into a gun where it is conveyed by compressed air and passes through a nozzle raised to a high electrical potential generally between ten and a hundred kV. The applied voltage may be of positive or negative polarity. The flow rate of the powder in the gun is generally between 10 and 200 g / min, preferably between 50 and 120 g / min. During its passage in the nozzle, the powder is charged with a certain amount of electricity, the particles of powders conveyed by the compressed air are applied to the metal part connected to the earth, that is to say say to a zero electrostatic potential. The particles of the powder are retained on this surface by their electrostatic charge and the electrostatic attraction forces are sufficient for the powder-coated object to be displaced and heated in an oven.

use in the field of electrodes

The functionalized PVDF or the mixture can be used in the manufacture of positive or negative electrodes, in particular for lithium-ion batteries. The electroactive layer containing either mixed oxide fillers or carbon and / or graphite feeds and other ingredients for adjusting the electrical performance is generally carried out by dispersing the charges in a solvent in the presence of a polymeric binder fluorinated. The dispersion is then deposited on a metal collector by a "cast" method, the solvent is then evaporated to obtain a negative or positive electrode depending on the nature of the charge used. The performance of a battery greatly depends on the characteristics of the binder. A good binder makes it possible to produce sufficiently charged layers of electroactive ingredients which makes it possible to have a high specific capacity. The binder must also be stable against oxidation-reduction reactions during charge / discharge cycles and must also be insensitive to the electrolyte present in the battery. The electrolyte typically contains carbonate type solvents (ethyl carbonate, propylene) and a lithium salt (LiPF6, LiBF ₄ ). We will be able to see EP 1508927, US 2003/0072999, US 2003/0232244, US 5460904 for more details on fluorinated polymeric binders. In Examples 2 and 3 of EP 1508927 A2, the functionalized PVDF may be replaced by functionalized PVDF or the mixture of the invention.

The invention also relates to the use of the functionalized PVDF or the mixture according to the invention for the manufacture of a positive or negative electrode of a battery, preferably a lithium-ion battery.

It also relates to a positive or negative electrode for lithium-ion battery comprising the structure composed of a

A layer of a Li metal;

And a layer 1-2 comprising the functionalized PVDF or the mixture of the invention. The metal is preferably aluminum for a positive electrode and copper for a negative electrode.

Coextrusion process

The Applicant has found that it is possible with the coextrusion technique in which at least one layer comprising the coextrusion is coextruded.

Functionalized PVDF or the mixture and at least one layer of a thermoplastic polymer to increase the coextrusion line speed (i.e. a multilayer structure speed coextruded in m / min) without impairing the quality of the adhesion between the functionalized PVDF layer (or mixture) and the layer (s) in contact.

The invention also relates to the coextrusion method using the functionalized PVDF or the mixture of coextruding at least one layer of the functionalized PVDF or mixture and at least one layer of a thermoplastic polymer or an elastomer. [Examples] Products used:

KYNAR ^® 720: PVDF homopolymer from Arkema with a melt index 20 g / 10 min (230 ⁰ C, 5 kg) and melting temperature of 170 ⁰ C with the following characteristics:

Tc: 135 ° C. σy: 55 MPa v: 900 Pa s (230 ^° C., 100 s- ¹ ) Young's modulus: 2200 MPa

OREVAC ^® 18302: LLDPE-type polyethylene grafted with maleic anhydride with a melt index of 1 g / 10 min and a melting point of 124 ° C

LOTADER ^® AX 8840: copolymer of ethylene (92% by weight) and glycidyl methacrylate (8% by weight) from the company ARKEMA having a melt index of 5 according to ASTM D-1238.

PEX: obtained from a mixture of 95% by weight BORPEX ^® ME-2510 and 5% MB-51, two products marketed by BOREALIS. The crosslinking is carried out by heating and is due to the presence of silane functions on the polyethylene.

PVDF-1: VDF-HFP copolymer having 16% by weight of HFP with: Tc: 103 ° C. σy: 18 MPa v: 900 Pa.s Young's modulus traction: 360 MPa

Example 1 Preparation of a Functionalized PVDF

In a Werner 40 extruder, the PVDF-1 is mixed at 190 ^° C. with 2% by weight of maleic anhydride. This mixture is done with all the wells of the extruder closed, with a screw speed of 200 rpm and a flow rate of 60 kg / h.

The product which is pelletized is introduced into a bag having a sealed layer of aluminum. This bag is irradiated under 20 kgray. The product after irradiation was again passed into the extruder at 245 ° C under a maximum vacuum and at 200 rpm. The flow rate is 25 kg / h. The infrared analysis of the product after this devolatilization step shows a degree of grafting of

0.31% and a free maleic anhydride level of 300 ppm. This product is called Functionalized PVDF 1.

Example 2 Preparation of a Functionalized PVDF

We use the conditions of Example 1 but with the Kynar 720 ^® PVDF instead of -1. The infrared analysis of the product after devolatilization shows a degree of grafting of 0.50% and a free maleic anhydride level of 300 ppm. This product is called Functionalized PVDF 2.

Example 3 (comparative)

Using a Mc Neil extruder, a multilayer pipe (outer diameter: 14 mm) is produced having the following structure:

KYNAR ^® 720 (130 μm) / functionalized PVDF 2 (50 μm) / LOTADER ^® AX 8840 (50 μm) / PEX (780 μm).

The PEX layer is the outer layer. All layers adhere to each other. Extrusion is carried out at 40 m / minute under the following conditions:

• PE layer: 230 ⁰ C

• LOTADER ^® AX 8840: 250 ⁰ C

• Functional PVDF: 250 ° C

• KYNAR ^® 720: 250 ⁰ C The adhesion between the layers of the functionalized PVDF and Lotader ^® 8840, 5 days after the extrusion is measured at 10 N / cm by circumferential coat. The adhesion is adhesive type.

Example 4 (comparative)

Under the same conditions as in Example 3, a tube having the following structure is manufactured:

KYNAR ^® 720 (130 microns) / functionalized PVDF 2 diluted to 50% in a VDF-HFP copolymer containing 16% HFP and having a viscosity at 230 ⁰ C of 900 Pa.s at 100 s ^"1 (50 .mu.m) / LOTADER ^® AX 8840 (50 μm) / PEX (780 μm).

Extrusion is carried out at 40 m / minute. The PEX layer is the outer layer. All layers adhere to each other. The adhesion between the layers of PVDF mixture and Lotader ^® 8840 is measured at 20 N / cm by circumferential peel after 5 days. The adhesion is adhesive type.

Example 5 (according to the invention)

Is manufactured in the same conditions as in Example 3, a tube having the following structure: KYNAR ^® 720 (130 microns) / functionalized PVDF 1 (50 .mu.m) / Lotader ^® AX 8840 (50 .mu.m) / PEX (780 .mu.m).

Extrusion is carried out at 40 m / minute. The adhesion is measured at 60 N / cm by circumferential peel after 5 days. The adhesion is of cohesive type in the layer of LOTADER ^® 8840. Table I

In the structures of Examples 3 to 5, the LOTADER AX 8840 serves as an adhesion binder between the functionalized PVDF and the PEX.

Example 6 (according to the invention)

Manufacturing a film on a sheath CoIMn extruder having the following structure: KYNAR ^® 2500-20 (50 .mu.m) / functionalized PVDF 1 (25 microns) / EVOH (25 .mu.m) / Orevac ^® 18302 (10 .mu.m) / PE (140 .mu.m ).

The extrusion is carried out at 230 ^° C. on a film of 250 μm in total thickness. The adhesion is measured at 18 N / cm between functionalized PVDF 1 and EVOH.

Example 7 (Comparative) A film is produced on CoIMn sheath extruder having the following structure:

KYNAR ^® 2500-20 (50 μm) / functionalized PVDF 2 (25 μm) / EVOH (25 μm) /

OREVAC ® ⁵ '18302 (10 μm) / PE (140 μm).

The extrusion is carried out at 230 ° C on a film of 250 microns in total thickness. The adhesion is measured at 0.5 N / cm between functionalized PVDF 1 and EVOH.

Table 2

A threshold stress σy ranging from 10 to 40 MPa, preferably from 10 to 30 MPa;

10. Mixture according to claim 9, characterized in that the PVDF mixed with the copolymer on which the unsaturated polar monomer has been grafted has a Young's modulus ranging from 200 to 1000 MPa, preferably from 200 to 600 MPa.

11. A multilayer structure comprising at least one layer comprising the copolymer as defined in any one of claims 1 to 5 or the mixture as defined in any one of claims 6 to 10 and: at least one layer comprising at least at least one thermoplastic polymer and / or at least one elastomer,

At least one layer of an inorganic material.

12. Multilayer structure comprising arranged in the order one against the other:

A layer comprising at least one thermoplastic polymer and / or at least one elastomer;

Optionally at least one layer of an adhesion binder;

A layer comprising the copolymer as defined in any one of claims 1 to 5 or the mixture as defined in any one of claims 6 to 10;

13. Multilayer structure comprising arranged in the order against each other: Optionally a layer comprising a fluoropolymer, preferably a homo- or copolymer PVDF;

Optionally at least one layer of an adhesion binder;

Optionally at least one layer of an adhesion binder; A layer comprising the copolymer as defined in any one of claims 1 to 5 or the mixture as defined in any one of claims 6 to 10;

14. multilayer structure according to any one of claims 12 to 13 characterized in that the thermoplastic polymer is chosen from:

Polyamides, preferably PA 6, PA 11, PA 12 and PA 6.6;

Polymers comprising more than 50% by weight of ethylene and / or propylene;

Polymers comprising more than 50% by weight of vinyl chloride;

• acrylic polymers; Saturated polyesters (PET, PBT, PBN);

• polycarbonates;

• phenylene polysulfide (PPS);

• polyphenylene oxide (PPO);

• polyoxymethylene (acetal); • polyethersulfone;

• polyurethanes;

Polymers and copolymers comprising more than 50% by weight of styrene; Fluoropolymers such as PVDF, PTFE, copolymers of

TFE and HFP, copolymers of ethylene and TFE, copolymers of ethylene and chlorotrifluoroethylene, polyvinyl fluoride.

15. multilayer structure according to claim 13 characterized in that the thermoplastic polymer is a polyolefin or a copolymer of ethylene and at least one comonomer of ethylene selected from alpha-olefins, preferably butene or octenes, vinyl esters of saturated carboxylic acids, preferably vinyl acetate or vinyl propionate, alkyl (meth) acrylates, preferably methyl acrylate, butyl acrylate or ethyl acrylate.

16. multilayer structure according to claim 15 characterized in that the polyolefin is a polyethylene homo- or copolymer of the type medium density (DME), a HDPE (high density), a LDPE (low density), a LLDPE (linear low density) polyethylene prepared by a metallocene or more generally monosite type of catalysis or a crosslinked polyethylene (PEX).

17. Multilayer structure according to any one of claims 11 to 16 in the form of a film, a tube, a container or a hollow body.

18. Protective coating of an inorganic material comprising

The copolymer of VDF as defined in any one of claims 1 to 5 or the mixture as defined in any one of claims 6 to 10;

Optionally, at least one acrylic polymer. 19. The coating of claim 18 characterized in that the inorganic material is:

• a metal; " glass ;

• concrete;

• silicon;

• quartz.

20. Use of a modified copolymer according to any one of claims 1 to 5 or the mixture as defined in any one of claims 6 to 10 for the manufacture of a positive or negative electrode of a battery, of preferably a lithium-ion battery.

21. Positive or negative electrode for lithium-ion battery comprising the structure consisting of a

A layer of a Li metal;

And a layer 1-2 comprising the modified copolymer according to any one of claims 1 to 5 or the mixture as defined in any one of claims 6 to 10.

22. Electrode according to claim 21 characterized in that the metal is aluminum or copper.

Claims

1. Copolymer of VDF and at least one monomer copolymerizable with VDF having a VDF content by weight of at least 50%, preferably of at least 75%, onto which is grafted by irradiation at least one unsaturated polar monomer , characterized in that the copolymer of VDF present before grafting has the following characteristics:

A threshold stress σy ranging from 10 to 40 MPa, preferably from 10 to 30 MPa;

A melt viscosity (measured with a capillary rheometer at 230 ° C. at 100 sec ^-1 ) ranging from 100 to 1500 Pa s, preferably from 400 to 1200 Pa s.

2. Copolymer according to claim 1 characterized in that the copolymer of VDF present before grafting a tensile Young's modulus ranging from 200 to 1000 MPa, preferably from 200 to 600 MPa.

3. Copolymer according to claim 1 or 2 characterized in that the VDF comonomer is chosen from vinyl fluoride (VF), trifluoroethylene, chlorotrifluoroethylene (CTFE), 1,2-difluoroethylene, tetrafluoroethylene (TFE), hexafluoropropene (HFP), 3,3,3-trifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene.

4. Copolymer according to one of claims 1 to 3 characterized in that the copolymer of VDF is a VDF-HFP copolymer which has before grafting a content by weight of HFP ranging from 4 to 20%, preferably from 10 to 20% .

5. Copolymer according to any one of claims 1 to 4 characterized in that the method of irradiation grafting of the unsaturated polar monomer comprises the following steps: a), the copolymer of VDF is mixed with at least one unsaturated polar monomer in medium melted; b). the mixture is irradiated in the solid state by means of an electron or photon irradiation under an irradiation dose of between 10 and 200 kGray, preferably between 10 and 150 kGray; vs). optionally the non-grafted unsaturated polar monomer and the residues released by the grafting are removed.

6. Mixture of at least one copolymer on which has been grafted the unsaturated polar monomer as defined in any one of claims 1 to 5 and at least one PVDF homo- or copolymer.

7. Mixture according to claim 6 characterized by a proportion by weight of 1 to 99%, preferably from 50 to 99% of the copolymer on which the unsaturated polar monomer has been grafted for 99 to 1%, preferably from 1 to 99%. 50% of a PVDF homo- or copolymer.

8. Mixture according to claim 6 characterized in that the PVDF is compatible with the copolymer on which was grafted the unsaturated polar monomer and having only one melting peak by DSC.

9. Mixture according to one of claims 6 to 8 characterized in that the PVDF which is mixed with the copolymer on which has been grafted unsaturated polar monomer is a copolymer of VDF and at least one monomer copolymerizable with VDF having a VDF content by weight of at least 50%, preferably at least 75%, having the following characteristics: a crystallization temperature Tc (measured by DSC according to ISO 11357-3) ranging from 50 to 120 ^° C. preferably from 85 to 110 ^° C .;