# US 5,344,904 A · Vinylidene fluoride polymer and method of making same

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- Number: US 5,344,904 A
- Document ID: US5344904A
- Status: Granted
- Kind: A
- Application number: 08/111,541
- Filed: 1993-08-25
- Granted: 1994-09-06
- Earliest claimed: 1991-08-01
- Assignees: Kureha Chemical Industry Co., Ltd.
- Inventors: Hideki Wakamori; Fujio Suzuki; Katsuo Horie
- Web page: https://patentgrep.com/patent/US5344904A

## CPC

- C08F 214/22: Vinylidene fluoride
- C08F: MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS

## 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.

## Claims

### Claim 1

A vinylidene fluoride polymer comprising the monomer unit content of 99.5-96 wt. % of vinylidene fluoride and the monomer unit content of 0.5-4 wt. % of monomers selected from hexafluoropropylene and/or tetrafluoroethylene, and having a logarithmic viscosity of 0.9-1.3 dl/g, a molecular-weight distribution, as expressed by the ratio (Mw/Mn) of weight-average molecular weight and number-average molecular weight, 2.2-2.8, a crystalline melting point of 163.degree.-176.degree. C. and a spherulite size of 1-30 .mu.m.

### Claim 2 (depends on 1)

A vinylidene fluoride polymer as set forth in claim 1 comprising the monomer unit content of 99.0-97 wt. % of vinylidene fluoride and the monomer unit content of 1.0-3 wt. % of monomers selected from hexafluoropropylene and/or tetrafluoroethylene, and having a molecular-weight distribution, as expressed by the ratio (Mw/Mn) of weight-average molecular weight and number-average molecular weight, of 2.3-2.6, a crystalline melting point of 168.degree.-173.degree. C. and a spherulite size of 5-25 .mu.m.