Melt-processible fluoropolymer

Abstract

The present invention pertains to a melt-processible fluoropolymer, to a composition comprising the melt-processible fluoropolymer, to a process for manufacturing the melt-processible fluoropolymer and to uses of the melt-processible fluoropolymer in various applications.

Claims

1. A fluoropolymer [polymer (F)] comprising: from 60% to 80% by moles of recurring units derived from tetrafluoroethylene (TFE), from 15% to 35% by moles of recurring units derived from vinylidene fluoride (VDF), and from 1% to 5% by moles of recurring units derived from perfluoropropylvinylether of formula CF.sub.2CFOC.sub.3F.sub.7, wherein the molar amounts of said recurring units are relative to the total moles of recurring units in said polymer (F).

2. The polymer (F) of claim 1, said polymer (F) having a melting point (T.sub.m) comprised between 170 C. and 300 C.

3. The polymer (F) of claim 2, said polymer (F) having a melting point (T.sub.m) comprised between 200 and 225 C.

4. The polymer (F) according to claim 1, said polymer having a melt flow index, measured at 300 C. under a 5 kg load according to ASTM D 1238, of at least 0.2 g/10 min and/or of at most 20 g/10 min.

5. The polymer (F) according to claim 4, said polymer having a melt flow index, measured at 300 C. under a 5 kg load according to ASTM D 1238, of at least 0.5 g/10 min and at most 10 g/10 min.

6. The polymer (F) according to claim 1, said polymer (F) having an elongation at break higher than 350%, as measured at 200 C. according to ASTM D 3307 standard method, and/or having a strain hardening index (SHI), measured according to the following equation:
SHI=[ (200% strain) (100% strain)]/[ (200% strain) (100% strain)] wherein represents the applied stress on the material and represents the strain, wherein the stress and the strain were measured according to ASTM D 3307 standard method, of at least 2.5 MPa at a temperature of 23 C.

7. The polymer (F) according to claim 6, said polymer (F) having a strain hardening index (SHI) of at least 3 MPa at a temperature of 23 C.

8. An aqueous latex comprising at least one polymer (F) according to claim 1.

9. The aqueous latex according to claim 8, said aqueous latex further comprising at least one surfactant (S).

10. The aqueous latex according to claim 9, wherein the surfactant (S) is selected from the group consisting of: hydrogenated surfactants (H), fluorinated surfactants (F), and mixtures thereof.

11. A composition (C) comprising at least one polymer (F) according to claim 1.

12. An article comprising at least one polymer (F) according to claim 1.

13. A pipe comprising at least one polymer (F) according to claim 1.

14. The pipe according to claim 13, said pipe being a flexible riser.

15. The flexible riser according to claim 14, said flexible riser being an unbonded flexible riser.

16. The flexible riser according to claim 14, said flexible riser being a bonded flexible riser.

17. The polymer (F) of claim 1, which comprises: from 65% to 78% by moles of recurring units derived from tetrafluoroethylene (TFE), from 20% to 30% by moles of recurring units derived from vinylidene fluoride (VDF), and from 1.5% to 3.5% by moles of recurring units derived from perfluoropropylvinyl-ether of formula CF.sub.2CFOC.sub.3F.sub.7, wherein the molar amounts of said recurring units are relative to the total moles of recurring units in said polymer (F).

Description

EXAMPLE 1

(1) In an AISI 316 steel vertical autoclave, equipped with baffles and a stirrer working at 570 rpm, 3.5 liter of demineralized water were introduced. The temperature was then brought to reaction temperature of 80 C. and the selected amount of 34% w/w aqueous solution of cyclic surfactant of formula (VI) as defined above, with X.sub.a=NH.sub.4, was added. VDF and ethane were introduced to the selected pressure variation reported in Table 1. A gaseous mixture of TFE-VDF in the molar nominal ratio reported in Table 1 was subsequently added via a compressor until reaching a pressure of 20 bar. Then, the selected amount of a 3% by weight water solution of sodium persulfate (NaPS) as initiator was fed. The polymerization pressure was maintained constant by feeding the above mentioned TFE-VDF while adding the PPVE monomer at regular intervals until reaching the total amount indicated in the table 1.

(2) When 1000 g of the mixture were fed, the reactor was cooled at room temperature, the latex was discharged, frozen for 48 hours and, once unfrozen, the coagulated polymer was washed with demineralized water and dried at 160 C. for 24 hours.

(3) The composition of the obtained polymer F-1, as measured by NMR, was Polymer (F-1)(693/99): TFE (69.6% mol)VDF (27.3% mol)PPVE (2.1% mol), having melting point T.sub.m=218 C. and MFI=5 g/10.

EXAMPLE 2

(4) The procedure of example 1 was repeated, by introducing the amount of ingredients indicated in the second column of Table 1.

(5) The composition of the obtained polymer F-2, as measured by NMR, was Polymer (F-1)(693/100): TFE (68% mol)VDF (29.8% mol)PPVE (2.2% mol), having melting point T.sub.m=219 C. and MFI=1.5 g/10.

COMPARATIVE EXAMPLE 1

(6) The procedure of example 1 was repeated, by introducing the amount of ingredients indicated in the third column of Table 1.

(7) The composition of the obtained polymer P-1, as measured by NMR, was Polymer (C-1)(693/67): TFE (71% mol)VDF (28.5% mol)PPVE (0.5% mol), having melting point T.sub.m=249 C. and MFI=5 g/10.

COMPARATIVE EXAMPLE 2

(8) In an AISI 316 steel horizontal reactor, equipped with a stirrer working at 42 rpm, 56 liter of demineralized water were introduced. The temperature was then brought to reaction temperature of 65 C. and the selected amount of 40% w/w aqueous solution of cyclic surfactant of formula (VI) as defined above, with X.sub.1=NH.sub.4, was added. VDF and ethane were introduced to the selected pressure variation reported in Table 1.

(9) A gaseous mixture of TFE-VDF in the molar nominal ratio reported in Table 1 was subsequently added via a compressor until reaching a pressure of 20 bar.

(10) Then, the selected amount of a 0.25% by weight water solution of sodium persulfate (NaPS) as initiator was fed. The polymerization pressure was maintained constant by feeding the above mentioned TFE-VDF while adding the PPVE monomer at regular intervals until reaching the total amount indicated in the table 1.

(11) When 16000 g of the mixture were fed, the reactor was cooled at room temperature, the latex was discharged, frozen for 48 hours and, once unfrozen, the coagulated polymer was washed with demineralized water and dried at 160 C. for 24 hours. The composition of the obtained polymer C-2, as measured by NMR, was Polymer (C-2)(SA1100): TFE (70.4% mol)VDF (29.2% mol)PPVE (0.4% mol), having melting point T.sub.m=232 C. and MFI=8 g/10.

COMPARATIVE EXAMPLE 3

(12) The procedure of Comparative Example 2 was repeated, by introducing the following changes: demineralized water introduced into the reactor: 66 litres; polymerization temperature of 80 C. polymerization pressure: 12 abs bar Initiator solution concentration of 6% by weight MVE introduced in the amount indicated in table 1 Overall amount of monomers mixture fed in the reactor: 10 000 g, with molar ratio TFE/VDF as indicated in Table 1.

(13) All the amount of ingredients are indicated in the fifth column of Table 1.

(14) The composition of the obtained polymer (C-3), as measured by NMR, was Polymer (C-3)(693/22): TFE (72.1% mol)VDF (26% mol)PMVE (1.9% mol), having melting point T.sub.m=226 C. and MFI=8 g/10.

(15) TABLE-US-00001 TABLE 1 (F-1) (F-2) (C-1) (C-2) (C-3) Surfactant solution [g] 50 50 50 740 800 Surfactant [g/l] 4.85 4.85 4.85 5.28 4.12 Initiator solution [ml] 100 100 100 2500 600 Initiator [g/kg] 3.0 3.0 3.0 0.39 6.0 VDF [bar] 1.8 1.8 0 1.8 1.8 TFE/VDF mixture 70/30 70/30 70/30 70/30 69/30.sup.1 [molar ratio] FPVE [g] 122 122 31 660 0.sup.2 Ethane [bar] 0.6 0.3 0.25 2 0.1 .sup.1gaseous mixture containing 1% moles of perfluoromethylvinylether (FMVE); .sup.2initial partial pressure of FMVE 0.35 bar.

(16) The results regarding polymers (F-1), (F-2) of the invention, and comparative (C-1), (C-2) and (C-3) are set forth in Table 2 here below

(17) TABLE-US-00002 TABLE 2 693/99 693/100 693/67 SA1100 693/14 (F-1) (F-2) (C-1) (C-2) (C-3) Elongation at 577 739 290 40 35 break [%, 200 C.] Tensile modulus 425 374 484 594 500 [MPa, 23 C.] Tensile yield stress 11.6 11.4 14.0 15.5 12.5 [MPa, 23 C.] Tensile modulus 29 38 56 76 [MPa, 170 C.] Tensile modulus 12 10 48 47 23 [MPa, 200 C.] SHI [MPa, 23 C.] 3.6 5.1 1.9 1.6 1.7 ESR as yielding No No Yielding Yielding Yielding [time, 23 C.] Yielding Yielding after 1 after 1 after 1 min min min

(18) In particular, the polymer (F) of the present invention as notably represented by the polymers (F-1), (F-2), surprisingly exhibits a higher elongation at break at 200 C. as compared to the polymers (C-1) and (C-2) of the prior art.

(19) Also, the polymer (F) of the present invention as notably represented by the polymers (F-1), (F-2), despite its lower tensile modulus, which remains nevertheless in a range perfectly acceptable for various fields of use, surprisingly exhibits a higher strain hardening rate by plastic deformation as compared to the polymers (C-1) and (C-2) of the prior art.

(20) Finally, the polymer (F) of the present invention as notably represented by the polymers (F-1) and (F-2) surprisingly exhibits higher environmental stress resistance when immersed in fuels as compared to the polymers (C-1) and (C-2) of the prior art.

(21) Yet, comparison of polymer (F) according to the present invention with performances of polymer (C-3) comprising perfluoromethylvinylether (FMVE) as modifying monomer shows the criticality of selecting perfluoropropylvinylether: indeed, FMVE is shown producing at similar monomer amounts, copolymer possessing too high stiffness, and hence low elongation at break, unsuitable for being used e.g. in O&G applications.