Fluoropolymer hybrid composite

Abstract

The present invention pertains to a fluoropolymer hybrid organic/inorganic composite, to a film comprising said fluoropolymer hybrid organic/inorganic composite and to uses of said film in various applications, in particular in electrochemical and in photo-electrochemical applications.

Claims

1. A composition (C) comprising: an aqueous medium comprising at least one pre-gelled metal compound (GM) obtainable by at least partial hydrolysis and/or partial polycondensation of at least one metal compound (M) of formula (I):
X.sub.4-mM(OY).sub.m  (I) wherein M is a metal selected from the group consisting of Si, Ti and Zr, X and Y, equal to or different from each other and at each occurrence, are hydrocarbon groups, optionally comprising one or more functional groups, and m is an integer comprised between 1 and 4, at least one polymer (FF), wherein polymer (FF) is a functional fluoropolymer comprising at least one hydroxyl group, and at least one poly(alkylene oxide) (PAO) of formula (II):
HO—(CH.sub.2CHR.sub.AO).sub.n—R.sub.B  (II) wherein R.sub.A is a hydrogen atom or a C.sub.1-C.sub.5 alkyl group, R.sub.B is a hydrogen atom or a —CH.sub.3 alkyl group and n is an integer comprised between 2000 and 40000.

2. The composition (C) according to claim 1, wherein polymer (FF) comprises recurring units derived from at least one fluorinated monomer and from at least one monomer (OH), wherein monomer (OH) is a functional monomer comprising at least one hydroxyl group.

3. The composition (C) according to claim 1, wherein monomer (OH) is selected from the group consisting of (meth)acrylic monomers of formula (III) and vinylether monomers of formula (IV): ##STR00013## 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 C.sub.1-C.sub.5 hydrocarbon group comprising at least one hydroxyl group.

4. The composition (C) according to claim 1, wherein polymer (FF) comprises recurring units derived from: (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 the group consisting of vinyl fluoride, chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), tetrafluoroethylene (TFE), trifluoroethylene (TrFE), perfluoromethylvinylether (PMVE) and mixtures therefrom, and (c′) from 0.01% to 20% by moles of at least one (meth)acrylic monomer of formula (III).

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

6. The composition (C) according to claim 1, wherein compound (GM) comprises one or more domains of formula —[O-MX.sub.4-m*(OY).sub.m*-2]O—, wherein M is a metal selected from the group consisting of Si, Ti and Zr, X and Y, equal to or different from each other and at each occurrence, are hydrocarbon groups, optionally comprising one or more functional groups, and m* is an integer comprised between 2 and 4.

7. A process for manufacturing a fluoropolymer hybrid organic/inorganic composite (H), said process comprising processing in molten phase the composition (C) according to claim 1.

8. The process according to claim 7, wherein composition (C) is processed in molten phase, using an extruder.

9. A fluoropolymer hybrid organic/inorganic composite (H) obtainable by the process according to claim 7, said composite (H) comprising recurring units derived from at least one fluorinated monomer and from at least one functional monomer (OM) comprising one or more domains of formula —[O-M(OZ.sub.1)(OZ.sub.2)]O—, wherein M is a metal selected from the group consisting of Si, Ti and Zr, and Z.sub.1 and Z.sub.2, equal to or different from each other, are hydrocarbon groups, optionally comprising one or more functional groups.

10. A compounded fluoropolymer hybrid organic/inorganic composite (H′) comprising: at least one composite (H) according to claim 9, at least one metal salt (M), and optionally, at least one polymer (F), wherein polymer (F) is a fluoropolymer.

11. A fluoropolymer film comprising at least one composite (H) according to claim 9.

12. A process for manufacturing the fluoropolymer film according to claim 11, said process comprising processing in molten phase the at least one composite (H).

13. The process according to claim 12, said process comprising processing in molten phase, using an extruder, the at least one composite (H).

14. An electrochemical device or a photo-electrochemical device comprising at least one fluoropolymer film according to claim 11.

15. A method for making an electrochemical device, wherein the method comprises using at least one fluoropolymer film according to claim 11 as a separator for such electrochemical devices.

16. The composition (C) according to claim 1 wherein n is an integer comprised between 4000 and 35000.

17. The composition (C) according to claim 1 wherein n is an integer comprised between 11500 and 30000.

18. The composition (C) according to claim 4, wherein polymer (FF) comprises recurring units derived from: (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 the group consisting of vinyl fluoride, chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), tetrafluoroethylene (TFE), trifluoroethylene (TrFE), perfluoromethylvinylether (PMVE) and mixtures therefrom, and (c′) from 0.05% to 15% by moles of at least one (meth)acrylic monomer of formula (III).

19. The composition (C) according to claim 4, wherein polymer (FF) comprises recurring units derived from: (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 the group consisting of vinyl fluoride, chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), tetrafluoroethylene (TFE), trifluoroethylene (TrFE), perfluoromethylvinylether (PMVE) and mixtures therefrom, and (c′) from 0.1% to 10% by moles of at least one (meth)acrylic monomer of formula (III).

Description

EXAMPLE 1

(1) A powder blend of polymer (FF-1) and PAO-1 in a weight ratio of 31:69 was prepared.

(2) A pre-gel metal compound was prepared under step (i). The pre-gel metal compound so obtained and the powder blend were fed continuously to the main hopper and extruded according to the temperature profile B. The rate for the polymer blend was 0.795 kg/h, the rate for the pre-gel metal compound was 0.520 kg/h.

(3) The extrudate was pelletized and dried in a vacuum oven for 4 hours at 45° C. The composite so obtained contained 7.85% by weight of SiO.sub.2 according to EDS measurements.

(4) The pellets prepared under step (ii) and the LiTFSI solution were fed to the extruder at rates of 1.2 kg/h and 0.6 kg/h, respectively. The material was collected and cut by the pelletizer.

(5) The composition of the final composite was the following: 73.7% by weight of a blend of polymer (FF-1) and PAO-1 (weight ratio polymer (FF-1):PAO-1=31:69), 6.3% by weight of SiO.sub.2 and 20% by weight of LiTFSI. The ionic conductivity values of a film made of the composite so obtained are set forth in Table 3.

COMPARATIVE EXAMPLE 1

(6) The same procedure under Example 1 was followed except that step (i) was omitted (no pre-gel metal compound was fed to the reactor).

(7) Steps (ii) and (iii) were carried out simultaneously due to the absence of the pre-gel metal compound.

(8) The composition of the final composite was the following: 80% by weight of a blend of polymer (FF-1) and PAO-1 (weight ratio polymer (FF-1):PAO-1=38:62) and 20% by weight of LiTFSI.

(9) The ionic conductivity values of a film made of the composite so obtained are set forth in Table 3.

EXAMPLE 2

(10) The same procedure under Example 1 was followed but replacing polymer (FF-1) with polymer (FF-2) and stopping the process after step (ii). The step (iii) was thus omitted.

(11) The composition of the final composite was the following: 90.6% by weight of a blend of polymer (FF-2) and PAO-1 (weight ratio polymer (FF-2):PAO-1=31:69) and 9.4% by weight of SiO.sub.2.

(12) The composite so obtained was in the form of regular pellets which can be easily handled and processed in molten phase.

COMPARATIVE EXAMPLE 2

(13) The same procedure under Example 2 was followed but steps (i) and (iii) were omitted. No pre-gel metal compound and no electrolytic salt were thus added to the composite. The extrudate of step (ii) had a remarkable die swell. The melt strength was very poor and, during the process, melt pulsation and breaking was observed. For these reasons, it was not possible to pull the material with the automatic system and to cut it with the cutter thereby obtaining regular pellets.

(14) The final composite so obtained contained a blend of polymer (FF-2) and PAO-1 in a weight ratio of 31:69.

EXAMPLE 3

(15) The same procedure under Example 1 was followed but using polymer (FF-2) instead of polymer (FF-1).

(16) The ionic conductivity values of a film made of the composite so obtained are set forth in Table 3.

EXAMPLE 4

(17) The same procedure under Example 1 was followed but using polymer (FF-3) instead of polymer (FF-1).

(18) The ionic conductivity values of a film made of the composite so obtained are set forth in Table 3.

(19) TABLE-US-00003 TABLE 3 Ionic conductivity (μS/mm) Example 23° C. 40° C. 55° C. 70° C. 80° C. 1 3.09 6.45 21.8 29.8 78.7 Comp. 1 1.22 2.24 13.4 20.5 38.5 3 3.77 6.49 17.5 35.3 51.5 4 3.71 8.86 22.6 36.7 65.9

(20) In view of the above, it has been surprisingly found that either the composite (H) or the composite (H′) obtainable by the process according to the invention is advantageously in the form of regular pellets which are free flowing and can thus be easily handled and processed in molten phase.

(21) Also, it has been surprisingly found that either the composite (H) or the composite (H′) obtainable by the process according to the invention successfully enables manufacturing separators for both electrochemical devices and photo-electrochemical devices exhibiting outstanding ionic conductivity values.