Crosslinkable blends of VDF copolymers

1. A crosslinkable composition (C) comprising:

A) at least one fluoropolymer [polymer (FA)] comprising:

(i) recurring units derived from vinylidene fluoride (VDF) monomer;

(ii) recurring units derived from at least one hydroxyl group-containing vinyl monomer (HA),

wherein the total amount of recurring units (ii) in said polymer (FA) is of at most 10.0% by moles, with respect to the total moles of recurring units of polymer (FA); said polymer (FA) being characterized by a fraction of randomly distributed units (HA) of at least 40%; and

B) at least one a fluoropolymer [polymer (FB)], different from polymer (FA), comprising:

(i) recurring units derived from vinylidene fluoride (VDF) monomer;

(iii) recurring units derived from at least one carboxyl group-containing vinyl monomer (CA);

wherein the total amount of recurring units (iii) in said polymer (FB) is of at most 10.0% by moles, with respect to the total moles of recurring units of polymer (FB); said polymer (FB) being characterized by a fraction of randomly distributed units (CA) of at least 40%; and

further comprising at least one acidic crosslinking catalyst.

2. The composition (C) of claim 1 wherein the hydroxyl group-containing vinyl monomer (HA) is a compound of formula (I):

wherein:

R 1 , R 2 and R 3 , equal to or different from each other, are independently selected from a hydrogen atom, a halogen atom, and a C 1 -C 3 hydrocarbon group and R OH is a C 2 -C 10 hydrocarbon chain moiety comprising at least one hydroxyl group and possibly containing in the chain one or more oxygen atoms, carbonyl groups or carboxy groups.

3. The composition (C) of claim 2 wherein monomer (HA) is a compound of formula (Ia):

wherein:

R 1 , R 2 and R 3 , equal to or different from each other, are independently selected from a hydrogen atom and a C 1 -C 3 hydrocarbon group and R′ OH is a C 1 -C 5 hydrocarbon moiety comprising at least one hydroxyl group.

4. The composition (C) of claim 3 wherein monomer (HA) of formula (Ia) is selected from the group consisting of hydroxyethyl (meth) acrylate (HEA), 2-hydroxypropyl acrylate (HPA), and mixtures thereof.

5. The composition (C) of claim 1 wherein the carboxyl group-containing vinyl monomer (CA) is a compound of formula (II):

wherein:

R 1 , R 2 and R 3 , equal to or different from each other, are independently selected from a hydrogen atom and a C 1 -C 3 hydrocarbon group and R H is a C 2 -C 10 hydrocarbon moiety comprising at least one carboxyl group.

6. The composition (C) of claim 1 wherein (CA) is a compound of formula (Ila):

wherein

R 1 , R 2 and R 3 , equal to or different from each other, are independently selected from a hydrogen atom and a C 1 -C 3 hydrocarbon group and R′ H is a hydrogen or a C 1 -C 5 hydrocarbon moiety comprising at least one carboxyl group.

7. The composition (C) of claim 6 wherein monomer (CA) is selected from the group consisting of acrylic acid (AA), (meth) acrylic acid and mixtures thereof.

8. The composition (C) according to claim 1 wherein polymer (FA) further comprises recurring units derived from one or more fluorinated comonomers (CF) different from VDF.

9. The composition (C) according to claim 1 wherein polymer (FB) further comprises recurring units derived from one or more fluorinated comonomers (CF) different from VDF.

10. The composition (C) according to claim 1 wherein:

polymer (FA) comprises:

at least 70% by moles of vinylidene fluoride (VDF),

from 0.1% to 3.0% by moles of at least one hydroxyl group-containing vinyl monomer (HA);

optionally from 0.5 to 3.0% by moles of recurring units derived from at least one fluorinated comonomer (CF), and

polymer (FB) comprises:

at least 70% by moles of vinylidene fluoride (VDF),

from 0.1% to 3.0% by moles of at least one carboxyl group-containing vinyl monomer (CA);

optionally from 0.5 to 3.0% by moles of recurring units derived from at least one fluorinated comonomer (CF).

11. The composition (C) of claim 1 wherein the acidic crosslinking catalyst is a Lewis acid selected from the group consisting of boron trifluoride, aluminum chloride, zinc chloride, stannous chloride, antimony trichloride, ferric chloride, boron trifluoridedimethyl ether complex, boron trifluoride-diethyl ether complex, boron trifluoride-dipropyl ether complex and antimony trioxide.

12. A process for preparing a crosslinked fluoropolymer (XLF) comprising the step of submitting a composition (C) according to claim 1 to a heat treatment at a temperature comprised between 130° C. and 250° C.

13. A shaped article comprising the crosslinked fluoropolymer (XLF) obtained according to the process of claim 12 .

14. A method for making a shaped article comprising the crosslinked fluoropolymer (XLF), the method comprising:

A) processing a composition (C) according to claim 1 into a shaped article;

B) thermally treating the shaped article provided in step (a) at a temperature comprised between 130° C. and 250° C.

15. The composition (C) of claim 1 wherein monomer (HA) is selected from the group consisting of hydroxyethyl (meth) acrylate (HEA), 2-hydroxypropyl acrylate (HPA), hydroxyethylhexyl(meth)acrylate, and mixtures thereof.