Vinylidene fluoride polymer and method of making same

Details Vinylidene fluoride polymer and method of making same Vinylidene fluoride polymer and method of making same

1993-08-25

1994-09-06

Schofer, Joseph L.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

526255, 526216, 525276, C08F 1422

Patent

active

053449045

ABSTRACT:
This invention provides PVDF having such crystallization properties as to produce small spherulite sizes without sacrifices to properties, processability, purity, etc., and a suspension polymerization method to obtain the same.
The PVDF obtained by this invention comprises the monomer unit content of 99.5-96 wt. % of vinylidene fluoride, and the monomer unit content of 0.5-4 wt. % of comonomers selected from hexafluoropropylene and/or tetrafluoroethylene, and has a logarithmic viscosity of 0.9-1.3 dl/g, and a molecular-weight distribution, as expressed in the ratio (Mw/Mn) of weight-average molecular weight and number-average molecular weight, of 2.2-2.8.
In order to manufacture the PVDF of this invention, a mixture of vinylidene fluoride monomers containing 1-5 wt. % of monomers selected from hexafluoropropylene and/or tetrafluoroethylene is suspension-polymerized in an aqueous medium, using an oil-soluble initiator so that the logarithmic viscosity [.eta..sub.1 ] is kept at 1.3-1.9 dl/g until the polymerization conversion rate of vinylidene fluoride monomers becomes 10-50%, and the polymerization is continued by adding a chain transfer agent at that polymerization conversion rate so that the logarithmic viscosity [.eta..sub.2 ] of the eventually obtained polymers becomes 0.3-0.7 dl/g lower than [.eta..sub.1 ], and yet remains in the range of 0.9-1.3 dl/g.

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