Process for manufacturing a dispersion of a vinylidene fluoride polymer

1. A process for manufacturing a dispersion of a vinylidene fluoride (VDF) thermoplastic polymer [polymer (F)], said process comprising polymerizing VDF in an aqueous phase comprising:

at least one fluorinated surfactant (FS) complying with formula (IB) here below:

wherein:

X 1 , X 2 and X 3 , equal to or different from each other, are independently selected from the group consisting of H, F and C 1 -C 6 (per)fluoroalkyl groups, optionally comprising one or more catenary or non-catenary oxygen atoms,

R F represents a divalent perfluorinated C 1 -C 3 bridging group,

L represents a bond or a divalent group and

Y represents an anionic functionality, selected from the group consisting of:

wherein X a is a hydrogen atom, a monovalent metal, or an ammonium group of formula —N(R′ n ) 4 , wherein R′ n , equal or different at each occurrence, is a hydrogen atom or a C 1 -C 6 hydrocarbon group;

wherein the at least one fluorinated surfactant has a molecular weight of less than 400; and

at least one functional (per)fluoropolyether (functional PFPE) comprising at least one (per)fluoropolyoxyalkylene chain [chain (R′ F )] and at least one functional group, said functional PFPE having a number average molecular weight of at least 1000 and a solubility in water of less than 1% by weight at 25° C.,

wherein said functional PFPE is present in the aqueous phase in an amount of 0.001 to 0.3 g/L.

2. The process of claim 1 , wherein the fluorinated surfactant (FS) complies with formula (IIIB) here below:

wherein:

X 1 , X 2 and X 3 , equal to or different from each other, are independently selected from the group consisting of H, F and C 1 -C 6 (per)fluoroalkyl groups, optionally comprising one or more catenary or non-catenary oxygen atoms,

R F represents a divalent perfluorinated C 1 -C 3 bridging group, and

X a is a hydrogen atom, a monovalent metal, or an ammonium group of formula —N(R′ n ) 4 , wherein R′ n , equal or different at each occurrence, is a hydrogen atom or a C 1 -C 6 hydrocarbon group.

3. The process of claim 1 , wherein the fluorinated surfactant (FS) complies with formula (VIIIB) here below:

wherein:

R F represents a divalent perfluorinated C 1 -C 3 bridging group;

X a is a hydrogen atom, a monovalent metal, or an ammonium group of formula —N(R′ n ) 4 , wherein R′ n , equal or different at each occurrence, is a hydrogen atom or a C 1 -C 6 hydrocarbon group;

X* 1 and X* 2 , equal to or different from each other, are independently a fluorine atom, a —R′ f group or a —OR′ f group, wherein R′ f is a C 1 -C 3 perfluoroalkyl group;

R* f is a divalent fluorinated group; and

k is an integer from 1 to 3.

4. The process of claim 3 , wherein the fluorinated surfactant (FS) complies with formula (IXB) here below:

wherein

R F represents a divalent perfluorinated C 1 -C 3 bridging group; and

X a is a hydrogen atom, a monovalent metal, or an ammonium group of formula —N(R′ n ) 4 , wherein R′ n , equal or different at each occurrence, is a hydrogen atom or a C 1 -C 6 hydrocarbon group;

X* 1 and X* 2 , equal to or different from each other, are independently a fluorine atom, a —R′ f group or a —OR′ f group, wherein R′ f is a C 1 -C 3 perfluoroalkyl group, R F 1 is a fluorine atom or a —CF 3 group and k is an integer from 1 to 3.

5. The process of claim 4 , wherein the fluorinated surfactant (FS) is selected from the group consisting of surfactants (FS) having formulae (X) and (XI) here below:

wherein X a is a hydrogen atom, a monovalent metal, or an ammonium group of formula —N(R′ n ) 4 , wherein R′ n , equal or different at each occurrence, is a hydrogen atom or a C 1 -C 6 hydrocarbon group.

6. The process of claim 1 , wherein the functional PFPE complies with formula (XII) here below:

T 1 -(CFW 1 ) p1 O—R F —(CFW 2 ) p2 -T 2   (XII)

wherein:

R F is a (per)fluoropolyoxyalkylene chain [chain (R′ F )] such that the number average molecular weight of the functional PFPE is at least 1000;

T 1 and T 2 , equal to or different from each other, are selected from:

i) functional end-groups selected from the group consisting of carboxylic acid, phosphonic acid and sulphonic acid groups, in their acid or salt form, and

ii) non-functional end-groups selected from a group consisting of a fluorine atom, a chlorine atom and a C 1 -C 3 (per)fluoroalkyl group comprising, optionally, one or more chlorine atoms, with the proviso that at least one of T 1 and T 2 is a functional end-group as defined above;

W 1 and W 2 , equal to or different from each other, independently represent a fluorine atom or a —CF 3 group;

p 1 and p 2 , equal to or different from each other, are independently integers comprised between 1 and 3.

7. The process of claim 6 , wherein the functional PFPE complies with formula (XIV) here below:

X p OOC—CF 2 —O—(CF 2 ) n′ (CF 2 CF 2 O) m′ —CF 2 —COOX p   (XIV)

wherein n′ and m′ are independently integers >0 such that the number average molecular weight of the functional PFPE is at least 1000, wherein the recurring units of (CF 2 ) and (CF 2 CF 2 O) are generally statistically distributed along the perfluoropolyoxyalkylene chain, and wherein X p , equal to or different from each other, is a hydrogen atom, a monovalent metal, or an ammonium group of formula —N(R′ n ) 4 , wherein R′ n , equal or different at each occurrence, is a hydrogen atom or a C 1 -C 6 hydrocarbon group.

8. A process for manufacturing a dispersion of a vinylidene fluoride (VDF) thermoplastic polymer [polymer (F)], said process comprising polymerizing VDF in an aqueous phase comprising:

at least one surfactant selected from the group consisting of non-fluorinated surfactants [surfactant (HS)] and fluorinated surfactants having a molecular weight of less than 400 [surfactant (FS)]; and

at least one functional (per)fluoropolyether (functional PFPE) that complies with formula (XIV) here below:

X p OOC—CF 2 —O—(CF 2 ) n′ (CF 2 CF 2 O) m′ —CF 2 —COOX p   (XIV)

wherein n′ and m′ are independently integers >0 such that the number average molecular weight of the functional PFPE is at least 1000, wherein the recurring units of (CF 2 ) and (CF 2 CF 2 O) are generally statistically distributed along the perfluoropolyoxyalkylene chain, and wherein X p , equal to or different from each other, is a hydrogen atom, a monovalent metal, or an ammonium group of formula —N(R′ n ) 4 , wherein R′ n , equal or different at each occurrence, is a hydrogen atom or a C 1 -C 6 hydrocarbon group, said functional PFPE having a solubility in water of less than 1% by weight at 25° C.,

wherein said functional PFPE is present in the aqueous phase in an amount of 0.001 to 0.3 g/L.

9. The process of claim 8 , wherein the surfactant is a surfactant (FS) complying with formula (IA) here below:

R f —(OCF 2 CF 2 ) k-1 —O—CF 2 —COOX a   (IA)

wherein R f is a C 1 -C 3 perfluoroalkyl group comprising, optionally, one or more ether oxygen atoms, k is 2 or 3 and X a is selected from the group consisting of a monovalent metal and an ammonium group of formula NR N 4 , wherein R N , equal or different at each occurrence, is a hydrogen atom or a C 1 -C 3 alkyl group.

10. The process of claim 9 , wherein the surfactant (FS) complies with formula (IIIA) here below:

CF 3 CF 2 O—CF 2 CF 2 —O—CF 2 —COOX a ′  (IIIA)

wherein X a ′ is selected from the group consisting of Li, Na, K, NH 4 and NR N′ 4 , wherein R N′ is a C 1 -C 3 alkyl group.

11. The process of claim 8 , wherein the surfactant (FS) complies with formula (IIIB) here below:

wherein:

X 1 , X 2 and X 3 , equal to or different from each other, are independently selected from the group consisting of H, F and C 1 -C 6 (per)fluoroalkyl groups, optionally comprising one or more catenary or non-catenary oxygen atoms,

R F represents a divalent perfluorinated C 1 -C 3 bridging group, and

X a is a hydrogen atom, a monovalent metal, or an ammonium group of formula —N(R′ n ) 4 , wherein R′ n , equal or different at each occurrence, is a hydrogen atom or a C 1 -C 6 hydrocarbon group.

12. The process of claim 8 , wherein the surfactant (FS) complies with formula (VIIIB) here below:

wherein:

R F represents a divalent perfluorinated C 1 -C 3 bridging group;

X a is a hydrogen atom, a monovalent metal, or an ammonium group of formula —N(R′ n ) 4 , wherein R′ n , equal or different at each occurrence, is a hydrogen atom or a C 1 -C 6 hydrocarbon group;

X* 1 and X* 2 , equal to or different from each other, are independently a fluorine atom, a —R′ f group or a —OR′ f group, wherein R′ f is a C 1 -C 3 perfluoroalkyl group;

R* f is a divalent fluorinated group; and

k is an integer from 1 to 3.

13. The process of claim 12 , wherein the surfactant (FS) complies with formula (IXB) here below:

wherein

R F represents a divalent perfluorinated C 1 -C 3 bridging group; and

X a is a hydrogen atom, a monovalent metal, or an ammonium group of formula —N(R′ n ) 4 , wherein R′ n , equal or different at each occurrence, is a hydrogen atom or a C 1 -C 6 hydrocarbon group;

X* 1 and X* 2 , equal to or different from each other, are independently a fluorine atom, a —R′ f group or a —OR′ f group, wherein R′ f is a C 1 -C 3 perfluoroalkyl group, R F 1 is a fluorine atom or a —CF 3 group and k is an integer from 1 to 3.

14. The process of claim 13 , wherein the surfactant (FS) is selected from the group consisting of surfactants (FS) having formulae (X) and (XI) here below:

wherein X a is a hydrogen atom, a monovalent metal, or an ammonium group of formula —N(R′ n ) 4 , wherein R′ n , equal or different at each occurrence, is a hydrogen atom or a C 1 -C 6 hydrocarbon group.

15. The process of claim 8 , wherein the surfactant is a surfactant (FS) complying with formula:

R FS -E-Y r

wherein:

Y r is an anionic functionality, selected from the group consisting of:

wherein X a is a hydrogen atom, a monovalent metal, or an ammonium group of formula —N(R′ n ) 4 , wherein R′ n , equal or different at each occurrence, is a hydrogen atom or a C 1 -C 6 hydrocarbon group;

E is a C 4 -C 24 hydrocarbon non fluorinated divalent group, possibly comprising one or more catenary oxygen atom(s); and

R FS is a —OR FS f group, a —N(R FS f ) 2 , or a —OAr(R FS f ) r group, wherein R FS r , equal to or different from each other at each occurrence, is a C 1 -C 6 perfluoroalkyl group, Ar is an aromatic moiety, and r is an integer of 1 to 3.

16. The process of claim 15 , wherein the surfactant (FS) complies with formula:

R FS (CH 2 ) n SO 3 X r

wherein:

X r is a hydrogen atom, a monovalent metal, or an ammonium group of formula —N(R′ n ) 4 , wherein R′ n , equal or different at each occurrence, is a hydrogen atom or a C 1 -C 6 hydrocarbon group;

n is an integer of 4 to 20; and

R FS is a —OR FS f group, a —N(R FS f ) 2 , or a —OAr(R FS f ) r group, wherein R FS r , equal to or different from each other at each occurrence, is a C 1 -C 6 perfluoroalkyl group, Ar is an aromatic moiety, and r is an integer of 1 to 3.

17. The process according to claim 8 , wherein said at least one surfactant is selected from the group consisting of non-fluorinated surfactants [surfactants (HS)].

18. The process of claim 17 , wherein said surfactants (HS) are selected from the group consisting of:

alkanesulfonates, selected from the group consisting of linear C 7 -C 10 1-alkanesulfonates, linear C 7 -C 20 2-alkanesulfonates, and linear C 7 -C 20 1,2-alkanedisulfonates; and

alkylsulfates selected from the group consisting of linear C 7 -C 20 1-alkylsulfates, linear C 7 -C 20 2-alkylsulfates, and linear C 7 -C 20 1,2-alkyldisulfates.