WO2007110529A1

WO2007110529A1 - Blend of a functionalized pvdf and a tfe-based polymer or a pvf

Info

Publication number: WO2007110529A1
Application number: PCT/FR2007/050961
Authority: WO
Inventors: Anthony Bonnet; François Beaume; Aude Lapprand
Original assignee: Arkema France
Priority date: 2006-03-27
Filing date: 2007-03-20
Publication date: 2007-10-04
Also published as: FR2898901A1; FR2898901B1

Abstract

The invention relates to a blend of at least one modified PVDF obtained by the irradiation grafting of at least one unsaturated polar monomer and • at least one tetrafluoroethylene (TFE)-based polymer selected from the following polymers: - TFE/ethylene copolymers (ETFE); - TFE/HFP copolymers (FEP); - TFE/HFP/ethylene terpolymers (EFEP); - TFE/HFP/VDF terpolymers, or a polyvinyl fluoride (PVF). The invention also relates to a structure combining at least one layer of the blend and at least one layer of another material. The other material may be a thermoplastic polymer selected from: • polyamides (for example PA 6, 11, 12, 6,6, etc.); • polyolefins (PE, PP, EPDM) • polyvinyl chloride (PVC) • chlorinated PVC (C-PVC) • polyethylene terephthalate (PET) • EVOH (ethylene-vinyl alcohol copolymer) • polyetherketone (PEEK) • polyoxymethylene (acetal) • polyethersulphone • a polyurethane. The other material may also be a vulcanized or unvulcanized elastomer. The said structure may take various forms: film, tube, hollow body, sheet, etc. The other material may also be an inorganic material selected from glass, metal, quartz and concrete.

Description

MIXING FUNCTIONALIZED PVDF AND POLYMER BASED ON TFE OR PVF

FIELD OF THE INVENTION The present invention relates to a mixture of at least one PVDF on which is grafted by irradiation an unsaturated polar monomer and at least one polymer based on TFE (tetrafluoroethylene) or a PVF. (polyvinyl fluoride). The invention also relates to structures comprising at least one layer of the mixture and at least one layer of another material such as a thermoplastic polymer or an inorganic material, and the use of these structures.

[The technical problem]

TFE based polymers such as for example PTFE, ETFE or EFEP as well as PVF do not exhibit sufficient adhesion with many polymers such as polyamide. There is therefore a need to improve the adhesion of these polymers. However, these polymers have, compared with PVDF, mechanical and / or chemical properties complementary to those of PVDF (better flexibility, better resistance to cold impact, etc.).

The chemical graft modification of an unsaturated polar monomer makes it possible to improve the adhesion, but this modification is not easy because the TFE molecule has a high chemical inertness (the CF bond is more resistant than the CH bond). In the case of ETFE, the presence of ethylene units is also problematic because the grafting can lead in this case to a more or less important crosslinking. The direct copolymerization of the unsaturated polar monomer with the fluorinated monomer (s) is also not easy because the introduction of a new monomer into the polymerization process often leads to a modification of the polymerization kinetics and requires modifications. of the process. The Applicant has developed a mixture of at least one PVDF on which is grafted by irradiation an unsaturated polar monomer and at least one polymer based on TFE (tetrafluoroethylene) or a PVF (polyvinyl fluoride). This mixture makes it possible to improve the adhesion of the TFE or PVF-based polymer while retaining the good mechanical and / or chemical properties. The mixture also has a complementarity of the properties of the PVDF and the other polymer.

[The prior art] Application EP 1484346 published December 08, 2004 describes multilayer structures comprising a fluoropolymer grafted by irradiation. The structures can be in the form of bottles, tanks, containers or pipes.

The application EP 1541343 published June 08, 2005 describes a multilayer structure based on a fluoropolymer modified by radiation grafting for storing or transporting chemicals. In this chemical application, we mean products that are corrosive or dangerous, or products that we want to maintain purity.

Application EP 1101994 published May 23, 2001 discloses a tube for gasoline based on a fluoropolymer and a thermoplastic resin which may be a polyamide or a polyolefin. The fluorinated polymer is preferably an ethylene / TFE copolymer or a terpolymer TFE / HFP / VDF, optionally modified by grafting.

International Application WO 2006/042764 published April 27, 2006 describes on pages 12-13 that it is possible to mix a radiation-modified PVDF and a homo- or copolymer of TFE. [Brief description of the invention]

The invention relates to a mixture of at least one modified PVDF obtained by irradiation grafting of at least one unsaturated polar monomer and

At least one tetrafluoroethylene-based polymer (TFE) chosen from:

- TFE / ethylene copolymers (ETFE);

TFE / HFP (FEP) copolymers;

TFE / HFP / ethylene terpolymers (EFEP);

terpolymers TFE / HFP / VDF. • or polyvinyl fluoride (PVF).

The invention also relates to a structure associating at least one layer of the mixture and at least one layer of another material. The other material may be a thermoplastic polymer chosen from: polyamides (for example PA 6, 11, 12, 6, 6, etc.);

• polyolefins (PE, PP, EPDM)

• polyvinyl chloride (PVC)

• chlorinated PVC (C-PVC)

• polyethylene terephthalate (PET) • EVOH (ethylene-ethylene-vinyl alcohol copolymer)

• polyetherketone (PEEK)

• polyoxymethylene (acetal)

• polyethersulfone

• A polyurethane The other material may also be a vulcanized elastomer or not.

This structure can be in various forms: film, tube, hollow body, plate, ....

The other material may also be an inorganic material chosen from:

• glass ;

• metal ; • quartz;

• concrete.

[Detailed Description of the Invention] As regards the modified PVDF, this is obtained by grafting by irradiation of an unsaturated polar monomer on a PVDF.

PVDF is a homopolymer of VDF (vinylidene fluoride, CH ₂ = CF ₂ ) or a copolymer of VDF and at least one other monomer copolymerizable with VDF preferably containing at least 50% by weight, preferably at least 75% by weight. %, even more preferably at least 85% of VDF. The copolymerizable monomer is, for example, chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), trifluoroethylene (VF ₃ ) and tetrafluoroethylene (TFE). Preferably, the PVDF is a homopolymer.

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 rate of 100 s ¹ using a capillary rheometer. Indeed, these PVDF are well suited to 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 rate of 100 s ^-1 using a capillary rheometer.

Thus, PVDF marketed under the trademark KYNAR ^® 710 or 720 are perfectly suited for this formulation.

The process for obtaining the modified PVDF is as follows.

In a 1 ^st stage, the PVDF is previously mixed with the polar unsaturated monomer by any melt-blending technique known in the prior art, such as an extruder or a kneader used in the i ndustry thermoplastics. 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 5576106.

In the mixture to be irradiated, the proportion of PVDF is, by weight, between 80 to 99.9% for 0.1 to 20% of unsaturated monomer, respectively. Preferably, the proportion of PVDF is from 90 to 99% for 1 to 10% of unsaturated monomer, respectively.

In a step 2 ^ ^6, the mixture of the 1 ^st step is irradiated (irradiation beta β or γ gamma) in solid state using an electron or photon source with an irradiation dose 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 unsaturated monomer content which is grafted is 0.1 to 5% by weight (i.e., the unsaturated grafted monomer corresponds to 0.1 to 5 parts for 99.9 to 95 parts by weight). fluoropolymer), preferably from 0.5 to 5%, preferably from 0.9 to 5%. The grafted unsaturated monomer content is dependent on the initial content of the unsaturated monomer in the fluoropolymer / unsaturated monomer mixture to be irradiated. It also depends on the effectiveness of the grafting, and therefore the duration and energy of the irradiation.

In a 3 ^rd step, the unsaturated monomer that has not been grafted and the residues released by the grafting, especially HF, may then be optionally removed. This last step may be necessary if the ungrafted unsaturated monomer is likely to hinder adhesion or for toxicology problems. This operation can be performed 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 It is also possible to dissolve the modified fluoropolymer in a suitable solvent such as, for example, N-methylpyrrolidone, and then to precipitate the polymer in a non-solvent, for example in water or in an alcohol, or to wash the fluorinated polymer modified with a solvent inert with respect to the fluoropolymer and graft functions. For example, when grafting maleic anhydride, it can be washed with chlorobenzene.

One of the advantages of this irradiation grafting method is that it is possible to obtain higher levels of grafted unsaturated monomer than with conventional grafting methods using a radical initiator and in which the fluoropolymer is in the molten state. 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 the fluoropolymer), or even greater than 1, 5%, which is not possible with a conventional grafting process in an extruder.

The process is also simpler to implement than an extruder grafting process because for the latter method, it is necessary to adapt the radical initiator to the fluoropolymer. Since certain fluorinated polymers have high melting temperatures above 200 ° C., it is sometimes not possible to find a radical initiator which has an adequate decomposition rate (that is to say which has an adequate decomposition temperature). ).

Irradiation grafting takes place at "cold", typically at temperatures below 100 ° C or even 50 ° C, so that the mixture of the fluorinated polymer and the unsaturated monomer is not in the molten state as for a conventional grafting process in extruder. An essential difference is therefore that, in the case of a semi-crystalline fluorinated polymer (as is the case with PVDF for example), the grafting takes place in the amorphous phase and not in the crystalline phase, whereas Homogeneous grafting occurs in the case of grafting in a melt extruder. The unsaturated monomer is distributed therefore not identically on the chains of the fluoropolymer in the case of radiation grafting and in the case of extruder grafting. The modified fluorinated product therefore has a different distribution of the unsaturated monomer on the fluoropolymer chains compared to a product that would be obtained by grafting into an extruder.

During this grafting step, it is preferable to avoid the presence of oxygen. A nitrogen or argon sweep of the fluoropolymer / unsaturated monomer mixture is therefore possible to remove oxygen.

The modified PVDF exhibits the very good chemical and oxidation resistance, as well as the good thermomechanical behavior, of the starting PVDF.

As regards the unsaturated polar monomer, it has a C = C double bond as well as at least one polar function 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, 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, itaconic anhydride, crotonic anhydride , acrylate or glycidyl 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.

Unsaturated monomers are those which have two C = C double bonds which could lead to a crosslinking of PVDF, for example di- or triacrylates. 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 melt blending, it makes it possible to obtain good adhesion properties,

it is particularly reactive with respect to the functions of a functionalized polyolefin, especially when these functions are epoxide functions,

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

As regards the TFE-based polymer, it may be chosen from the following polymers: • TFE / ethylene copolymers (ETFE);

• TFE / HFP copolymers (FEP);

• TFE / HFP / ethylene terpolymers (EFEP);

• terpolymers TFE / HFP / VDF.

ETFE

It is a fluorinated polymer having good barrier properties (impermeability), very good resistance to cold impact and great flexibility (flexibility). It has a better chemical resistance to the bases compared to PVDF. ETFE preferably comprises TFE and ethylene in a molar ratio between 70/30 and 30/70.

EFF FEP has an excellent chemical resistance better than that of PVDF. The modified FEP / PVDF mixtures thus have adhesion and a very good chemical resistance.

EFEP

EFEP has a very high flexibility and good resistance to cold impact. Compared with ETFE, it is also easier to extrude at lower temperatures, which are especially compatible for coextrusion with a polyolefin and / or a functionalized polyolefin.

terpolymers TFE / HFP / VDF

They have a very high flexibility, good resistance to cold impact, good transparency and good barrier properties including alcoholic essences. PVDF homopolymer has equivalent barrier properties but less flexibility; a PVDF copolymer (eg VDF / HFP) has an equivalent flexibility but the barrier properties are poorer than for the PVDF homopolymer.

The TFE / HFP / VDF terpolymers preferably comprise TFE, HFP and VDF with the following mol%: TFE: 40-85%, HFP: 5-20% and VDF: 5-55%, preferably TFE: 60-85%, HFP: 5-20%, VDF: 5-35% (total: TFE ₊ HFP ₊ VDF = 100%).

ETFE and EFEP are fluorinated polymers which have a good impermeability especially to gasoline and good flexibility. They are therefore well suited for the manufacture of tubes and pipes for gasoline.

With respect to EVOH, this term refers to a saponified ethylene-vinyl acetate copolymer. It is a copolymer having an ethylene content of 10 to 70 mol%. Preferably, good barrier properties are obtained when the ethylene content is between 25 and 60 mol%. Preferably, the degree of saponification of its vinyl acetate component is at least 85 mol%, preferably at least 90%, even more preferably at least 95%. The contents of ethylene and the degree of saponification can be determined, for example, by NMR. EVOH is a good barrier to oxygen. Advantageously, the EVOH has a melt index between 0.5 and 100 g / 10 min (230 ° C., 2.26 kg), preferably between 5 and 30. It is understood that the EVOH may contain small amounts of other comonomer ingredients, including alpha-olefins such as propylene, isobutene, alpha-octene, unsaturated carboxylic acids or their salts, partial alkyl esters, complete alkyl esters ,. .. It is also possible to combine two types of EVOH to improve barrier and / or mechanical properties.

As regards PGA, this term refers to poly (glycolic acid), that is to say a polymer containing by weight at least 60%, advantageously 70%, preferably 80% of the following units (1):

(-O-CH ₂ -C (= O) -) (1)

This polymer can be manufactured by heating at a temperature between 120 and 250 ° C 1,4-dioxane-2,5-dione in the presence of a catalyst such as a tin salt, such as SnCl ₄ . The polymerization is carried out in bulk or in a solvent. The AMP may contain the following other reasons (2) to (6):

(-O- (CH ₂ ) _n -OC (= O) - (CH ₂ ) _m -C (= O)) (2) with n integer from 1 to 10 and m integer from 0 to 10;

(CH ₂ ) _j H

with j integer included between 1 and 10;

wherein k is an integer of 2 to 10 and R 1 and R 2 are each independently of one another H or C 1 -C 10 alkyl;

(-OCH ₂ CH ₂ CH ₂ -OC (= O) -) (5) or

(-O-CH ₂ -O-CH ₂ CH ₂ -) (6)

PGA is described in European Patent EP 925915 B1.

As regards the mixture, it comprises at least one modified PVDF and at least one TFE-based polymer. It can also be a mixture of a modified PVDF and a PVF.

The mixture comprises for 100 parts of the mixture of 1 to 99 parts of modified PVDF for 99 to 1 parts of polymer-based TFE or PVF, respectively. Preferably, these proportions are 10 to 50 parts of PVDF modified to 50 to 10 parts of TFE-based polymer or PVF.

The mixture is preferably obtained in the melt, for example by compounding with the aid of an extruder. It can also be a mixture of powders of the polymers.

The invention also relates to a structure associating at least one layer of the mixture and at least one layer of another material. The other material may be a thermoplastic polymer chosen from:

Polyamides (for example PA 6, 1 1, 12, 6, 6, ...);

• polyolefins (PE, PP, EPDM)

• polyvinyl chloride (PVC) • Chlorinated PVC (C-PVC)

• polyethylene terephthalate (PET)

• EVOH (ethylene-ethylene-vinyl alcohol copolymer)

• polyetherketone (PEEK) • polyoxymethylene (acetal)

• polyethersulfone

• a polyurethane

The other material may also be a vulcanized elastomer or not.

This structure can be in various forms: film, tube, hollow body, plate, ....

The other material may also be an inorganic material chosen from:

• glass ; • metal ;

• quartz;

• concrete.

The metal may be for example iron, copper, aluminum, titanium, lead, tin, cobalt, silver, tungsten, nickel, zinc. The term metal also covers mixtures of these metals as well as their alloys. Possible alloys are steels such as carbon steels, nickel, chromium, nickel-chromium, chromium-molybdenum, silicon, stainless steel, cast iron, Permalloy. Aluminum alloys are, for example, aluminum-magnesium, aluminum-silicon, aluminum-copper-nickel-magnesium, aluminum-silicon-copper-nickel-magnesium alloys. Copper alloys are for example brass, bronze, silicon bronze, silicon brass, nickel bronze. Nickel alloys are, for example, nickel-manganese (nickel-D), nickel-aluminum (nickel-Z), nickel-silicon, Monel and Hastelloy alloys. Aluminum alloys also include aluminum oxides as well as, for example, aluminum-copper, aluminum-aluminum alloys, and aluminum alloys. silicon, aluminum-manganese, aluminum-copper-nickel-manganese. Preferably, it will be aluminum, steel and stainless steel.

Examples of structures associating the mixture according to the invention and a thermoplastic polymer

There may be mentioned the following structures which may be in the form of film, plate, tube or hollow body (bottle, reservoir, ...).

The structure 1 comprises in order: • a layer of the mixture according to the invention

• a layer of a thermoplastic material

For example, the structure 1 in the form of a tube or reservoir comprises an inner layer in contact with the fluid to be transported or stored consisting of the mixture according to the invention and an outer layer of a polyolefin. This structure is useful for fuel tanks for automobiles.

The structure 1 in the form of a tube or reservoir comprises an inner layer in contact with the fluid to be transported or stored consisting of the mixture according to the invention and an outer layer of a polyamide. This structure is useful for gasoline pipes for automobiles.

A more complex form of structure 1 is that of a multilayer tube comprising (in order from the inside to the outside of the tube): a layer of the mixture according to the invention;

A layer of a barrier material selected from EVOH or a mixture based on EVOH or PGA;

A layer of an adhesion binder;

A layer of a polyolefin; • a barrier layer CB;

Optionally a layer of a polyolefin. This tube can be used for transporting water or gas, a gasoline, a cryogenic liquid or a coolant. The gasoline can be for example MI5 (% weight: 15% methanol, 42.5% toluene, 42.5% isooctane), the Fuel C (% weight: 50% toluene, 50% isooctane), the CE10 (% weight: 10% ethanol, 45% toluene and 45% isooctane, methyltertiobutyl ether).

The barrier layer CB may be a layer of EVOH or PGA or it may advantageously be a metal sheath. In addition to its barrier function, the metal sheath also has the function of reinforcing the mechanical strength of the tube. The metal may be steel, copper or aluminum or an alloy of aluminum. It is preferably aluminum or an alloy of aluminum for reasons of corrosion resistance and flexibility. The metal sheath is manufactured according to one of the methods known to those skilled in the art. Reference may be made in particular to the following documents which describe processes for producing plastic / metal composite tubes: US Pat. No. 6,822,205, EP 0581208 A1, EP 0639411 B1, EP 0823867 B1 and EP 0920972 A1. Preferably, the method of:

• conforming around a plastic tube a metal strip having longitudinal edges bent towards a common side and placed in abutment on each other extending substantially parallel to the longitudinal axis of the plastic tube,

• then the longitudinal edges are welded together. They therefore form a longitudinal weld joint.

After having welded the longitudinal edges of the metal strip, a tubular metal sheath is thus obtained.

Structure 2 comprises in order:

A layer of the mixture according to the invention

A layer of a thermoplastic material a layer of the mixture according to the invention

Structure 3 comprises in order: • a layer of a thermoplastic material

A layer of the mixture according to the invention

• a layer of a thermoplastic material

For example, the structure 3 in the form of a tube or reservoir comprises a layer of the mixture according to the invention disposed between two polyolefin layers. This structure is useful for fuel tanks for automobiles.

In all these structures, according to one variant, a layer of adhesion binder may be disposed between the layer of the mixture according to the invention and the layer of the thermoplastic material or of the elastomer in order to improve the adhesion between said layers. For example, the structure 1 with a binder layer comprises in order: • a layer of the mixture according to the invention

• a layer of adhesion binder

• a layer of a thermoplastic material

The binder is advantageously a functionalized polyolefin having functions capable of reacting with the grafted functions on the PVDF. For example, if maleic anhydride has been grafted onto the PVDF, the functionalized polyolefin layer consists of a copolymer of ethylene, of glycidyl methacrylate and optionally of an alkyl acrylate optionally in admixture with polyethylene. Similarly, if glycidyl methacrylate has been grafted onto the PVDF, the functionalized polyolefin layer consists of a copolymer of ethylene, of maleic anhydride and optionally of an alkyl acrylate optionally mixed with polyethylene. .

According to another variant for structures 1 or 2, it is also possible to have a layer of a fluoropolymer against the layer of the mixture and on the opposite side to the layer of the thermoplastic material or the elastomer. Structure 1 thus comprises in order:

• a layer of a fluoropolymer

A layer of the mixture according to the invention a layer of a thermoplastic material or elastomer or the structure 2 comprises in order:

A layer of the mixture according to the invention

A layer of a thermoplastic material or elastomer

A layer of the mixture according to the invention, a layer of a fluoropolymer which can be placed against at least one of the layers of the mixture according to the invention and on the opposite side to the layer of the thermoplastic material. The fluorinated polymer may for example be a PVDF or a TFE-based polymer.

In the preceding structures, the inner layer in contact with the fluid to be transported or stored may contain carbon black, carbon nanotubes or any other additive capable of rendering it conductive in order to prevent the accumulation of static electricity. Preferably, the conductive layer has a maximum resistivity of 10 ⁶ Ω / m ² .

These structures can be manufactured by the usual techniques such as extrusion, coextrusion, coextrusion blow molding, coating, extrusion coating.

Examples of Structure Associating the Mixture According to the Invention with an Inorganic Material

In the case of a metal, the structure may be in the form of a metal tube covered on its inside and / or outside by the mixture according to the invention. An adhesion primer can enhance the adhesion between the metal and the mixture according to the invention. The mixture is useful for protecting the inorganic material, for example against corrosion.

The mixture may be advantageously in the form of a powder which can be deposited on the inorganic material by electrostatic powdering.

Claims

1. Mixture of at least one modified PVDF obtained by the irradiation grafting of at least one unsaturated polar monomer and at least one tetrafluoroethylene (TFE) based polymer chosen from the following polymers:

- TFE / ethylene copolymers (ETFE);

TFE / HFP (FEP) copolymers;

TFE / HFP / ethylene terpolymers (EFEP); terpolymers TFE / HFP / VDF.

• or polyvinyl fluoride (PVF).

2. Mixture according to any one of claims 1 characterized in that proportion of modified PVDF is from 1 to 99 parts, preferably from 10 to 50 parts, of modified PVDF for 99 to 1 parts, preferably 50 to 10 parts, TFE-based polymer or PVF.

3. Mixture according to any one of the preceding claims, characterized in that the modified PVDF is obtained by the process comprising the following steps:

• in a ^1st stage, the PVDF is blended in molten medium to the polar unsaturated monomer;

• in a ^2nd stage, the mixture of 1 ^st step is irradiated (in β or γ irradiation) in the solid state using an electron or photon source with an irradiation dose between 10 and 200 kGray preferably between 10 and 150 kGray;

• in a ^3rd optional step, the unsaturated monomer that has not been grafted and the residues released by the grafting are eliminated.

4. Mixture according to any one of the preceding claims, characterized in that the unsaturated polar monomer has a C = C double bond and at least one polar function which may be a function: carboxylic acid,

- carboxylic acid salt,

- carboxylic acid anhydride,

epoxide, carboxylic acid ester,

- silyl,

alkoxysilane,

- carboxylic acid amide,

hydroxy, isocyanate.

Mixture according to any one of the preceding claims, characterized in that the unsaturated polar monomer is chosen from methacrylic acid, acrylic acid, maleic acid, fumaric acid, itaconic acid and citraconic acid, indecylenic acid, allylsuccinic acid, cyclohex-4-ene-1,2-dicarboxylic acid, 4-methyl-cyclohex-4-ene-1,2-dicarboxylic acid, bicyclo acid (2,2,1) hept-5-ene-2,3-dicarboxylic acid, x-methylbicyclo (2,2,1-hept-5-ene-2,3-dicarboxylic acid, zinc undecylenate, calcium or sodium, maleic anhydride, itaconic anhydride, citraconic anhydride, dichloromaleic anhydride, difluoromaleic anhydride, itaconic anhydride, crotonic anhydride, acrylate or glycidyl methacrylate, allyl glycidyl ether, vinyl silanes such as vinyl trimethoxysilane, vinyl triethoxysilane, vinyl triacetoxysilane, γ-methacryloxypropyltrimethoxysilane.

6. Mixture according to any one of the preceding claims, characterized in that the mixture is produced in a molten state.

7. Structure associating at least one layer of the mixture according to any one of claims 1 to 6 and at least one layer of another material.

8. Structure according to claim 7 characterized in that the other material is a thermoplastic polymer selected from:

Polyamides (for example PA 6, 1 1, 12, 6, 6, ...);

• polyolefins (PE, PP, EPDM) • polyvinyl chloride (PVC)

• chlorinated PVC (C-PVC)

• polyethylene terephthalate (PET)

• EVOH (ethylene-ethylene-vinyl alcohol copolymer)

• polyetherketone (PEEK) • polyoxymethylene (acetal)

• polyethersulfone

• a polyurethane

Or an elastomer, vulcanized or not.

9. Structure according to claim 8 characterized in that it is in the form of film, tube, hollow body or plate.

10. Structure according to one of claims 7 to 9 characterized in that it comprises in order: • a layer of the mixture;

A layer of the thermoplastic material or elastomer.

11. Structure according to one of claims 7 to 9 characterized in that it comprises in order: • a layer of the mixture;

A layer of the thermoplastic material or elastomer;

• a layer of the mixture.

12. Structure according to one of claims 7 to 9 characterized in that it comprises in order:

A layer of the thermoplastic material or elastomer;

• a layer of the mixture; A layer of the thermoplastic material or elastomer.

13. Structure according to one of claims 7 to 12 characterized in that a layer of an adhesion binder is disposed between the layer of the mixture and the layer of the thermoplastic material or the layer of the elastomer.

14. Structure according to claim 7 characterized in that the other material is an inorganic material chosen from:

• glass ; " metal ;

• quartz;

• concrete.