Production method of polytetrafluoroethylene particle

Patent metadata

Field	Value
Publication number	US-2024150533-A1
Application number	US-202318400039-A
Country	US
Kind code	A1
Filing date	Dec 29, 2023
Priority date	Jun 30, 2021
Publication date	May 9, 2024
Grant date	—

Abstract

A method for producing a polytetrafluoroethylene particle, which includes subjecting tetrafluoroethylene to suspension polymerization in an aqueous medium to prepare a suspension-polymerized particle of polytetrafluoroethylene, washing and then crushing the suspension-polymerized particle or crushing the suspension-polymerized particle with washing to prepare a crushed particle, dehydrating the crushed particle to prepare a crushed particle having a water content of 40% by mass or less, and subjecting the dehydrated crushed particle to heat treatment to produce a polytetrafluoroethylene particle.

First claim

What is claimed is:

1 . A method for producing a polytetrafluoroethylene particle, comprising:
subjecting tetrafluoroethylene to suspension polymerization in an aqueous medium to prepare a suspension-polymerized particle of a polytetrafluoroethylene; washing and then crushing the suspension-polymerized particle or crushing the suspension-polymerized particle with washing to prepare a crushed particle; dehydrating the crushed particle to prepare a crushed particle having a water content of 40% by mass or less; and subjecting the dehydrated crushed particle to heat treatment to produce a polytetrafluoroethylene particle.

2 . The production method according to claim 1 , the method comprising, after dehydrating the crushed particle, further drying the crushed particle.

3 . The production method according to claim 2 , wherein the crushed particle is dried by airflow drying.

4 . The production method according to claim 1 , wherein a temperature of the heat treatment is 200° C. or higher.

5 . The production method according to claim 1 , wherein the heat treatment is performed using a conductive heat-receiving type dryer.

6 . The production method according to claim 1 , wherein the heat treatment is performed using a material-stirring type dryer or a material-conveying type dryer.

7 . The production method according to claim 1 , the method comprising, in the heat treatment or during transferring of the polytetrafluoroethylene particle after the heat treatment, forming a solid-gas mixture containing the polytetrafluoroethylene particle generated by the heat treatment and gas, separating the solid-gas mixture into the polytetrafluoroethylene particle and the gas, and recovering the polytetrafluoroethylene particle to produce the polytetrafluoroethylene particle.

8 . The production method according to claim 1 , wherein an average particle size of the crushed particle is 100 to 800 μm.

9 . The production method according to claim 1 , the method comprising, after subjecting the crushed particle to the heat treatment to produce the polytetrafluoroethylene particle, further crushing the polytetrafluoroethylene particle to produce a polytetrafluoroethylene particle having an average particle size of 200 μm or less.

10 . The production method according to claim 1 , wherein tetrafluoroethylene and a modifying monomer are subjected to suspension polymerization.

11 . The production method according to claim 1 , wherein a standard specific gravity of the polytetrafluoroethylene particle is 2.200 or less.

12 . The production method according to claim 1 , wherein a specific surface area of the polytetrafluoroethylene particle is 5.0 m 2 /g or less.

13 . The production method according to claim 1 , wherein the polytetrafluoroethylene particle is substantially free from a compound represented by the following general formula (2):
[C n-1 F 2n-1 COO − ]M +   General formula (2):
wherein n represents an integer of 9 to 12 and M + represents a cation.

14 . The production method according to claim 1 , wherein suspension polymerization is carried out in the presence or absence of a surfactant, and an amount of the surfactant is 2000 mass ppm or less based on the aqueous medium.

15 . A method for producing a polytetrafluoroethylene formed article, the method comprising producing the polytetrafluoroethylene particle by the production method according to claim 1 , and then forming the polytetrafluoroethylene particle to give a formed article.

16 . A method for producing a polytetrafluoroethylene compression-molded article, the method comprising producing the polytetrafluoroethylene particle by the production method according to claim 1 , and then compression molding the polytetrafluoroethylene particle to give a compression-molded article.

17 . A polytetrafluoroethylene particle obtained by the production method according to claim 1 .

Assignees

• Daikin Ind Ltd

Inventors

• Tanaka Takayuki
• Miyamoto Masayoshi
• Minamiyama Tomoki
• Kusunoki Takeki
• Taira Tokahiro
• YAMABE Takuya
• Yoshida Hirotoshi
• Kato Taketo
• Yamanaka Taku
• Tsukamoto Mitsuo

Classifications

• C08J3/16

  by coagulating dispersions {(C08J3/122 takes precedence)} · CPC title

• C08J7/08 Primary

  Heat treatment · CPC title

• C08J3/12

  Powdering or granulating · CPC title

• C08F114/26

  Tetrafluoroethene · CPC title

• C08J2327/18

  Homopolymers or copolymers of tetrafluoroethylene · CPC title