Process for manufacturing fluoropolymer hybrid composites

Abstract

The invention pertains to a process for manufacturing a fluoropolymer hybrid organic/inorganic composite comprising: (i) partially hydrolyzing and/or polycondensing, in the presence of an aqueous medium, a metal compound of formula (I): X4-mAYim, wherein X is a hydrocarbon group, Y is a hydrolysable group selected from the group consisting of an alkoxy group, an acyloxy group and a hydroxyl group, A is a metal selected from the group consisting of Si, Ti and Zr, and m is an integer from 1 to 4, so as to obtain an aqueous medium comprising a pre-gelled metal compound comprising one or more inorganic domains consisting of A-O-A bonds and one or more residual hydrolysable groups Y [compound (M)], and then (ii) reacting in the molten state at least a fraction of hydroxyl groups of a functional fluoropolymer [polymer (F)] with at least a fraction of hydrolysable groups Y of said pre-gelled metal compound [compound (M)], so as to obtain a fluoropolymer hybrid organic/inorganic composite. The invention also pertains to uses of said fluoropolymer hybrid organic/inorganic composite in several applications.

Claims

1. A process for manufacturing a fluoropolymer hybrid organic/inorganic composite, the process comprising: (i) partially hydrolysing and/or polycondensing, in the presence of an aqueous medium, a metal compound of formula (I):
X.sub.4-mAY.sub.m wherein X is a hydrocarbon group, Y is a hydrolysable group selected from the group consisting of an alkoxy group, an acyloxy group and a hydroxyl group, A is a metal selected from the group consisting of Si, Ti and Zr, and m is an integer from 1 to 4, so as to obtain an aqueous medium comprising a pre-gelled metal compound comprising one or more inorganic domains consisting of A-O-A bonds and one or more residual hydrolysable groups Y [compound (M)], and (ii) reacting in the molten state at least a fraction of hydroxyl groups of a functional fluoropolymer [polymer (F)] with at least a fraction of hydrolysable groups Y of said compound (M), so as to obtain a fluoropolymer hybrid organic/inorganic composite.

2. The process according to claim 1, wherein the metal compound of formula (I) complies with formula (I-A):
R.sub.4-mE(OR).sub.m(I-A) wherein m is an integer from 1 to 4, E is a metal selected from the group consisting of Si, Ti and Zr, R and R, equal to or different from each other and at each occurrence, are independently selected from C.sub.1-C.sub.18 hydrocarbon groups, optionally comprising one or more functional groups.

3. The process according to claim 1, wherein polymer (F) comprises recurring units derived from at least one fluorinated monomer and at least one comonomer comprising at least one hydroxyl group [comonomer (MA)].

4. The process according to claim 3, wherein the polymer (F) comprises at least 0.01% by moles of recurring units derived from at least one comonomer (MA).

5. The process according to claim 4, wherein polymer (F) comprises at least 0.1% by moles of recurring units derived from at least one comonomer (MA).

6. The process according to claim 3, wherein polymer (F) comprises at most 20% by moles of recurring units derived from at least one comonomer (MA).

7. The process according to claim 5, wherein polymer (F) comprises at most 3% by moles of recurring units derived from at least one comonomer (MA).

8. The process according to claim 3, wherein comonomer (MA) is selected from the group consisting of (meth)acrylic monomers of formula (II) or vinylether monomers of formula (III): ##STR00012## wherein each of R.sub.1, R.sub.2 and R.sub.3, equal to or different from each other, is independently a hydrogen atom or a C.sub.1-C.sub.3 hydrocarbon group, and R.sub.OH is a hydrogen atom or a C.sub.1-C.sub.5 hydrocarbon moiety comprising at least one hydroxyl group.

9. The process according to claim 1, wherein polymer (F) is selected from the group consisting of: polymers (F-1) comprising recurring units derived from at least one comonomer (MA), from at least one per(halo)fluoromonomer selected from tetrafluoroethylene (TFE) and chlorotrifluoroethylene (CTFE), and from at least one hydrogenated monomer selected from ethylene, propylene and isobutylene, optionally containing one or more additional comonomers, in amounts of from 0.01% to 30% by moles, based on the total amount of TFE and/or CTFE and said hydrogenated monomer(s); and polymers (F-2) comprising recurring units derived from at least one comonomer (MA), from vinylidene fluoride (VDF), and, optionally, from one or more fluorinated monomers different from VDF.

10. The process according to claim 9, wherein the polymers (F-2) comprise: (a) at least 60% by moles of vinylidene fluoride (VDF); (b) optionally, from 0.1% to 15% by moles of a fluorinated monomer selected from vinylfluoride (VF.sub.1), chlorotrifluoroethylene (CTFE), hexafluoropropene (HFP), tetrafluoroethylene (TFE), trifluoroethylene (TrFE), perfluoromethylvinylether (PMVE) and mixtures thereof; and (c) from 0.01% to 20% by moles of at least one (meth)acrylic monomer of formula (II).

11. The process according to claim 10, wherein polymers (F-2) comprise: (a) at least 75% by moles of vinylidene fluoride (VDF); (b) optionally, from 0.1% to 12% by moles of a fluorinated monomer selected from vinylfluoride (VF.sub.1), chlorotrifluoroethylene (CTFE), hexafluoropropene (HFP), tetrafluoroethylene (TFE), trifluoroethylene (TrFE), perfluoromethylvinylether (PMVE) and mixtures thereof; and (c) from 0.05% to 18% by moles of at least one (meth)acrylic monomer of formula (II).

12. The process according to claim 10, wherein polymers (F-2) comprise: (a) at least 85% by moles of vinylidene fluoride (VDF); (b) optionally, from 0.1% to 10% by moles of a fluorinated monomer selected from vinylfluoride (VF.sub.1), chlorotrifluoroethylene (CTFE), hexafluoropropene (HFP), tetrafluoroethylene (TFE), trifluoroethylene (TrFE), perfluoromethylvinylether (PMVE) and mixtures thereof; and (c) from 0.1% to 10% by moles of at least one (meth)acrylic monomer of formula (II).

13. The process according to claim 1, wherein the aqueous medium of step (i) comprises at least one acid catalyst.

14. The process according claim 1, wherein the aqueous medium of step (i) further comprises one or more organic solvents (S).

15. The process according to claim 1, wherein the aqueous medium of step (i) consists of water, at least one acid catalyst and one or more alcohols.

16. The process according to claim 1, wherein in step (i) the hydrolysis and/or polycondensation of the metal compound of formula (I) is carried out at room temperature or upon heating at temperatures lower than 100 C.

17. The process according to claim 1, wherein in step (ii), polymer (F) and the aqueous medium comprising compound (M) are reacted in the molten state at temperatures between 100 C. and 300 C. as a function of the melting point of the polymer (F).

18. The process according to claim 17, wherein in step (ii), polymer (F) and the aqueous medium comprising compound (M) are reacted in the molten state at temperatures between 150 C. and 250 C. as a function of the melting point of the polymer (F).

19. The process according to claim 1, wherein in step (ii), polymer (F) is blended with a non-functional fluoropolymer prior to reaction with compound (M).

20. The process according to claim 1, wherein an inorganic filler (I) is further used in step (i) and/or step (ii).

Description

EXAMPLE 1

Manufacture of VDF-HEA/Silica Hybrid Composite

(1) (i) Manufacture of the Pre-Gelled Metal Compound

(2) In a 500 ml beaker equipped with a magnetic stirrer running at a moderated speed were introduced in sequence 200 g of tetraethoxysilane (TEOS), 69.45 g of water (TEOS:H.sub.2O molar ratio=4:1), 50 g of ethanol (TEOS:EtOH weight ratio=4:1) and 2.69 g of citric acid (1% by weight based on the total weight of TEOS and water), and left under stirring for three hours at room temperature.

(3) (ii) Reactive Extrusion

(4) The extrusion conditions according to the general procedure as detailed hereinabove were followed.

(5) The pre-gelled metal compound aqueous solution obtained under step (i) of Example 1 was fed using a peristaltic pump in the main feeder of the twin-screw extruder.

(6) The VDF-HEA (0.2% by moles) copolymer [polymer (F-B)] was added thereto at a feed rate of 528 g/h while the pre-gelled metal compound aqueous solution was fed at a feed rate of 472 g/h.

(7) The pre-gelled metal compound aqueous solution was maintained under vigorous stirring during all the process.

(8) The amount of SiO.sub.2 in the fluoropolymer hybrid organic/inorganic composite pellets so obtained was 14.5% by weight.

(9) The theoretical amount of SiO.sub.2, calculated assuming complete TEOS hydrolysis and/or polycondensation, would be 20% by weight of the fluoropolymer hybrid organic/inorganic composite pellets.

EXAMPLE 2

Manufacture of VDF-HEA/Silica Hybrid Composite

(10) The same procedure as detailed under Example 1 was followed but using a blend of SOLEF 6008 PVDF homopolymer and the VDF/HEA (1.1% by moles) copolymer [polymer (F-A)] in a weight ratio of 80:20.

(11) The amount of SiO.sub.2 in the fluoropolymer hybrid organic/inorganic composite pellets so obtained was 8.8% by weight.

(12) The theoretical amount of SiO.sub.2, calculated assuming complete TEOS hydrolysis and/or polycondensation, would be 20% by weight of the fluoropolymer hybrid organic/inorganic composite pellets.

COMPARATIVE EXAMPLE 1

Manufacture of VDF-HEA/Silica Hybrid Composite

(13) The VDF-HEA (0.2% by moles) copolymer [polymer (F-B)] and citric acid in an amount of 0.5% by weight of said polymer (F-B) were fed in the main feeder of the twin-screw extruder at a feed rate of 528 g/h.

(14) An aqueous medium containing 200 g of TEOS, 69.45 g of water and 50 g of ethanol was then fed using a peristaltic pump to the main feeder of the twin-screw extruder at a speed rate of 472 g/h.

(15) The same extrusion conditions as those reported under Example 1 were used.

(16) The amount of SiO.sub.2 in the fluoropolymer hybrid organic/inorganic composite pellets so obtained was 2.3% by weight.

(17) The theoretical amount of SiO.sub.2, calculated assuming complete TEOS hydrolysis and/or polycondensation, would be 20% by weight of the fluoropolymer hybrid organic/inorganic composite pellets.

(18) It has been thus shown that by the process of the invention fluoropolymer hybrid organic/inorganic composites are obtained that advantageously comprise enhanced amounts of inorganic domains as compared with composites obtained by the processes known in the art.

EXAMPLE 3

Manufacture of a Film

(19) The pellets obtained from the process as detailed under Example 1 were processed by compression moulding at 230 C. in a press obtaining a 300 m film with an elastic modulus of 1982 MPa.

EXAMPLE 4

Manufacture of a Film

(20) The pellets obtained from the process as detailed under Example 2 were extruded in a Brabender single screw extruder having a diameter of 19 mm and a length to diameter ratio of 25. This extruder was equipped with a flat die having an opening of 1000.5 mm.

(21) Different temperature profiles giving a range of melt temperatures between 190 C. and 270 C. were set: the higher the temperature, the smoother the final film.

(22) By setting the calendar temperature at 70 C. with a line speed of 0.4 m/min and a screw rotation speed of 20 rpm, a 500 m film of good quality was obtained.