Novel Fluoropolymer Synthesis and Characterization

EXAMPLE 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_a=NH₄, 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.

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.

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_m=218° C. and MFI=5 g/10′.

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

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_m=249° C. and MFI=5 g/10′.

EXAMPLE 2

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

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_m=219° C. and MFI=1.5 g/10′.

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 X₁=NH₄, 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 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.

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_m=232° C. and MFI=8 g/10′.

EXAMPLE 3

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.

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

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_m=226° C. and MFI=8 g/10′.

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

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.

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.

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.

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.