Process for manufacturing a fluoropolymer

Abstract

The present invention pertains to a process for manufacturing a semi-crystalline fluoropolymer, to the fluoropolymer obtainable by said process and to uses of said fluoropolymer in various applications.

Claims

1. A process for manufacturing a polymer (F), wherein polymer (F) is a semi-crystalline fluoropolymer comprising: from 51% to 70% by moles of recurring units derived from tetrafluoroethylene (TFE), and from 49% to 30% by moles of recurring units derived from vinylidene fluoride (VDF), wherein the molar amounts of said recurring units are relative to the total moles of recurring units in said polymer (F), said process being carried out by emulsion polymerization in an aqueous polymerization medium without addition of one or more surfactants.

2. The process according to claim 1, said process being carried out at a pressure comprised between 10 bar and 35 bar.

3. The process according to claim 2, said process being carried out at a pressure comprised between 11 bar and 25 bar.

4. The process according to claim 1 or 2, wherein the semi-crystalline polymer (F) further comprises recurring units derived from at least one fluorinated monomer different from tetrafluoroethylene (TFE) and vinylidene fluoride (VDF).

5. The process according to claim 1, wherein the semi-crystalline polymer (F) further comprises recurring units derived from at least one perfluoroalkylvinylether (PAVE) of formula (I):
CF.sub.2═CF—O—R.sub.f  (I) wherein R.sub.f is a C.sub.1-C.sub.6 alkyl group or a C.sub.1-C.sub.6 (per)fluoroalkyl group.

6. The process according to claim 5, wherein the perfluoroalkylvinylether (PAVE) of formula (I) is selected from the group consisting of perfluoromethylvinylether (PMVE) of formula CF.sub.2═CF—O—CF.sub.3, perfluoroethylvinylether (PEVE) of formula CF.sub.2═CF—0—CF.sub.2—CF.sub.3 and perfluoropropylvinylether (PPVE) of formula CF.sub.2═CF—0—CF.sub.2—CF.sub.2—CF.sub.3.

7. The process according to claim 5, wherein the semi-crystalline polymer (F) further comprises from 0.1% to 5% by moles of recurring units derived from at least one perfluoroalkylvinylether (PAVE) of formula (I), wherein the molar amounts of said recurring units are relative to the total moles of recurring units in said polymer (F).

8. The process according to claim 1, wherein the semi-crystalline polymer (F) comprises: from 51% to 70% by moles of recurring units derived from tetrafluoroethylene (TFE), from 49% to 30% by moles of recurring units derived from vinylidene fluoride (VDF), and from 0.1% to 5% by moles of recurring units derived from at least one perfluoroalkylvinylether (PAVE) of formula (I):
CF.sub.2═CF—O—R.sub.f  (I) wherein R.sub.f is a C.sub.1-C.sub.6 alkyl group or a C.sub.1-C.sub.6 (per)fluoroalkyl group, wherein the molar amounts of said recurring units are relative to the total moles of recurring units in said polymer (F).

9. The process according to claim 8, wherein semi-crystalline polymer (F) consists of: from 55% to 65% by moles of recurring units derived from tetrafluoroethylene (TFE), from 40% 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 the at least one perfluoroalkylvinylether (PAVE) of formula (I), wherein the molar amounts of said recurring units are relative to the total moles of recurring units in said polymer (F).

10. The process according to claim 1, wherein the semi-crystalline polymer (F) has a melt flow index of less than 5 g/10 min as measured according to ASTM D1238 at 300° C. under a load of 5 Kg.

11. The process according to claim 10, wherein the semi-crystalline polymer (F) has a melt flow index of less than 1 g/10 min, as measured according to ASTM D1238 at 300° C. under a load of 5 Kg.

12. The process according to claim 1, wherein polymer (F) is a semi-crystalline fluoropolymer comprising: from 60% to 65% by moles of recurring units derived from tetrafluoroethylene (TFE), and from 40% to 35% by moles of recurring units derived from vinylidene fluoride (VDF), wherein the molar amounts of said recurring units are relative to the total moles of recurring units in said polymer (F).

13. A process for manufacturing a polymer (F), wherein polymer (F) is a semi-crystalline fluoropolymer comprising: more than 50% by moles of recurring units derived from tetrafluoroethylene (TFE), and less than 50% by moles of recurring units derived from vinylidene fluoride (VDF), wherein the molar amounts of said recurring units are relative to the total moles of recurring units in said polymer (F), said process being carried out by emulsion polymerization in an aqueous polymerization medium without addition of one or more surfactants, wherein the semi-crystalline polymer (F) further comprises recurring units derived from at least one perfluoroalkylvinylether (PAVE) of formula (I):
CF.sub.2═CF—O—R.sub.f  (I) wherein R.sub.f is a C.sub.1-C.sub.6 alkyl group or a C.sub.1-C.sub.6 (per)fluoroalkyl group, wherein the semi-crystalline polymer (F) further comprises from 1.5% to 3.5% by moles of recurring units derived from at least one perfluoroalkylvinylether (PAVE) of formula (I), 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) The aqueous latex obtained by the process for manufacturing the polymer (F-1) as detailed above has been treated by addition of TERGITOL® TMN-100X branched secondary alcohol ethoxylate surfactant and then concentrated via clouding in the presence of KNO.sub.3 thereby providing an aqueous dispersion comprising 46.9% by weight of the polymer (F-1) and 2.8% by weight of TERGITOL® TMN-100X branched secondary alcohol ethoxylate surfactant, with respect to the total weight of said aqueous dispersion. The aqueous dispersion is free from one or more fluorinated surfactants.

(2) A film has been obtained by casting the aqueous dispersion so obtained onto a substrate and drying at room temperature followed by thermal treatment at 260° C. for 10 minutes.

COMPARATIVE EXAMPLE 1

(3) A film has been obtained by casting an aqueous dispersion comprising HYFLON® D5510 TFE/PMVE copolymer onto a substrate and drying at room temperature followed by thermal treatment at 320° C. for 10 minutes.

(4) Measurement of the Hardness

(5) The pendulum damping test has been used following ASTM D4366 standard procedure (test method A—König Pendulum Hardness) to detect differences in coating hardness of the film, where hardness is defined as resistance to its deformation. The amplitude of oscillation of a pendulum touching a surface decreases more rapidly the softer the surface of the film.

(6) Measurement of the Film Forming Temperature

(7) The aqueous latex was casted on a substrate, dried at room temperature and then baked at high temperature for 10 minutes. Different trials were performed, carrying out the baking step at increasing temperature, starting from 200° C., until a good film formation was detected, i.e. no cracks and particles coalescence.

(8) Measurement of the Chemical Resistance to HCl

(9) Apply 10 drops of a 10% (by volume) solution of 37% hydrochloric acid in tap water and cover it with a watch glass. After 15 minutes exposure, washed off with running tap water and check the presence of no blistering or any other visual change.

(10) Measurement of the Chemical Resistance to HNO.sub.3

(11) Place the test panel completely over the mouth of one-half full bottle of 70% nitric acid for 30 minutes. Rinse the sample with tap water and check any visual change after one-hour recovery period.

(12) The results are set forth in Table 1 here below:

(13) TABLE-US-00001 TABLE 1 Film forming ability Chemical resistance Run Hardness [T, ° C.] [HCl, HNO.sub.3] Ex. 1 53 260 positive C. Ex. 1 42 320 positive

(14) In view of the above, it has been found that the aqueous latex of the invention, which is advantageously free from one or more surfactants, as compared to aqueous latexes comprising fully fluorinated fluoropolymers such as HYFLON® D5510 TFE/PMVE copolymer, advantageously provides for coatings having a higher hardness at a relatively lower film forming temperature in combination with a high chemical resistance to acids.