Process for preparing polyvinylidene fluoride copolymer

• US 7,208,555 B2
• Filed: 09/17/2003
• Issued: 04/24/2007
• Est. Priority Date: 09/25/2002
• Status: Expired due to Fees

• Current Assignee: Kureha Corporation
• Original Assignee: Kureha Corporation
• Inventors: Suzuki, Kazuyuki, Tada, Masahito, Ikeda, Tsukasa, Katsurao, Takumi
• Primary Examiner(s): Smith; Duane
• Assistant Examiner(s): WU, IVES J
• Application Number:
  US10/528,654
• Publication Number:
  US 20050245708A1
• Time in Patent Office: 1,315 Days
• Field of Search: 526/250, 526/242, 201/704, 201/705, 201/710, 201/198.1, 528/490, 528/502, 428/422, 428/500, 210/705, 210/708, 156/182
• US Class Current: 526/250
• CPC Class Codes: C08F 14/18 Monomers containing fluorine
• CPC Class Codes: C08F 214/22 Vinylidene fluoride
• CPC Class Codes: C08F 6/14 Treatment of polymer emulsions C08F6/001, C08F6/006, C08F6/008, C08F6/02, C08F6/04 take precedence
• CPC Class Codes: C08F 6/24 Treatment of polymer suspensions C08F6/001, C08F6/006, C08F6/008, C08F6/02, C08F6/04 take precedence
• CPC Class Codes: C08F 8/00 Chemical modification by after-treatment graft polymers, block polymers, crosslinking with unsaturated monomers or with polymers C08F251/00 - C08F299/00; of conjugated diene rubbers C08C
• CPC Class Codes: C08L 27/16 Homopolymers or copolymers or vinylidene fluoride
• CPC Class Codes: Y10S 526/923 Ethylenic monomers containing at least one salt group
• CPC Class Codes: Y10T 428/31544 Addition polymer is perhalogenated
• CPC Class Codes: Y10T 428/31855 Of addition polymer from unsaturated monomers

Abstract

The present invention provides a polyvinylidene fluoride copolymer capable of forming a uniform film, a solution of the copolymer and a thin film comprising the polyvinylidene fluoride copolymer. The polyvinylidene fluoride copolymer of the present invention is characterized in that the ratio of the scattered-light intensity (I) for a 15% solution of the polyvinylidene fluoride copolymer in dimethylformamide solvent to the scattered-light intensity (I₀) for dimethylformamide, (I/I₀), is 10 or lower. The polyvinylidene fluoride copolymer solution comprises the polyvinylidene fluoride copolymer and an organic solvent capable of dissolving the copolymer.

Claims

1. A process for preparing a polyvinylidene fluoride copolymer, wherein the ratio of the scattered-light intensity (I) for a 15% solution of the polyvinylidene fluoride copolymer in dimethylformamide solvent to the scattered-light intensity (I₀) for dimethylformamide, (I/I₀), is 10 or lower, wherein

slurry or wet cake of a polyvinylidene fluoride copolymer obtained by suspension polymerization is dispersed in water or an organic solvent in which the copolymer is insoluble;

the resulting mixture is stirred;

after stirring, the mixture is settled;

after settling, the copolymer particles floating in the upper part of the mixture are separated from the copolymer particles precipitated in the lower part of the mixture;

the operations of stirring, settling and separation are repeated; and

then, the copolymer particles floating in the upper part of the mixture is recovered.

2. A process for preparing a polyvinylidene fluoride copolymer as recited in claim 1, wherein the polyvinylidene fluoride copolymer is at least one selected from a copolymer of vinylidene fluoride and monofluoroethylene;

a copolymer of vinylidene fluoride and trifluoroethylene;

a copolymer of vinylidene fluoride and tetrafluoroethylene;

a copolymer of vinylidene fluoride and hexafluoropropylene;

a copolymer of vinylidene fluoride, trifluoroethylene and tetrafluoroethylene;

a copolymer of vinylidene fluoride, trifluoroethylene and chlorotrifluoroethylehe;

a copolymer of vinylidene fluoride, trifluoroethylene and hexafluoropropylene; and

a copolymer of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene.

3. A process for preparing a polyvinylidene fluoride copolymer as recited in claim 2, wherein the copolymer contains not less than 40 mol % and not more than 90 mol % of vinylidene fluoride.

4. A process for preparing a polyvinylidene fluoride copolymer as recited in claim 1, wherein the operations of stirring, settling and separation are repeated not less than three times.