# US 12,006,407 B2 · Method for producing low molecular weight polytetrafluoroethylene, low molecular weight polytetrafluoroethylene, and powder

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- Number: US 12,006,407 B2
- Document ID: US12006407B2
- Status: Granted
- Kind: B2
- Application number: 18/103,443
- Filed: 2023-01-30
- Published: 2023-06-15
- Granted: 2024-06-11
- Earliest claimed: 2016-08-04
- Assignees: Daikin Industries, Ltd.
- Applicants: Daikin Industries, Ltd.
- Inventors: Ken Yoshida; Hirotoshi Yoshida; Keisuke Hagi; Masayuki Tsuji; Taketo Kato; Yuuji Tanaka; Taku Yamanaka; Kazuya Kawahara; Masamichi Sukegawa; Kazutaka Hosokawa
- Web page: https://patentgrep.com/patent/US12006407B2

## CPC

- C08J 3/12: Powdering or granulating
- C08F 8/06: Oxidation
- C08F 8/50: Partial depolymerisation
- C08F 14/26: Tetrafluoroethene
- C08J 3/28: Treatment by wave energy or particle radiation
- C08F 2500/07: High density, i.e. > 0.95 g/cm3
- C08F 2500/17: Viscosity
- C08F 2800/20: as weight or mass percentages
- C08F 2810/40: taking place solely at one end or both ends of the polymer backbone, i.e. not in the side or lateral chains
- C08J 2327/18: Homopolymers or copolymers of tetrafluoroethylene
- C08J 2327/22: modified by chemical after-treatment
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- C08F: MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS

## Abstract

Powder including low molecular weight polytetrafluoroethylene having a melt viscosity of 1×102 to 7×105 Pa·s at 380° C., having a melt viscosity of 1×102 to 7×105 Pa·s at 380° C., having an average particle size of 1.0 to 50 μm, and containing 30 or more carboxyl groups at ends of the molecule chain per 106 carbon atoms in the main chain, wherein the powder is substantially free from C8-C14 perfluorocarboxylic acids and salts thereof.

## Claims

### Claim 1

Powder comprising low molecular weight polytetrafluoroethylene,
the low molecular weight polytetrafluoroethylene having a melt viscosity of 1×102 to 7×105 Pa·s at 380° C., having an average particle size of 1.0 to 50 μm, and containing 30 or more carboxyl groups at ends of the molecule chain per 106 carbon atoms in the main chain,
the powder being substantially free from C8-C14 perfluorocarboxylic acids and salts thereof,
wherein the powder has a specific surface area of not smaller than 0.5 m2/g but smaller than 7.0 m2/g, or not smaller than 9.0 m2/g and not larger than 20 m2/g,
wherein the perfluorocarboxylic acids and salts thereof amount to less than 25 ppb.

### Claim 2

A method for producing low molecular weight polytetrafluoroethylene, comprising:
(1) irradiating polytetrafluoroethylene to provide low molecular weight polytetrafluoroethylene having a melt viscosity of 1×102 to 7×105 Pa·s at 380° C.;
(2) pulverizing the low molecular weight polytetrafluoroethylene; and
(3) heating the low molecular weight polytetrafluoroethylene pulverized in the step (2), wherein the heating is performed at a temperature of 100° C. or higher.

### Claim 3 (depends on 2)

The production method according to claim 2,
wherein the heating is performed at a temperature of 100° C. to 300° C.

### Claim 4 (depends on 2)

The production method according to claim 2,
wherein the heating is performed at a temperature of 100° C. to 200° C.

### Claim 5 (depends on 2)

The production method according to claim 2,
wherein the polytetrafluoroethylene has a standard specific gravity of 2.130 to 2.230.

### Claim 6 (depends on 2)

The production method according to claim 2,
wherein both the polytetrafluoroethylene and the low molecular weight polytetrafluoroethylene are in the form of powder.

### Claim 7 (depends on 2)

The production method according to claim 2, further comprising:
(4) heating the polytetrafluoroethylene up to a temperature that is not lower than the primary melting point thereof to provide a molded article before the step (1),
the molded article having a specific gravity of 1.0 g/cm3 or higher.

### Claim 8 (depends on 2)

Low molecular weight polytetrafluoroethylene obtainable by the production method according to claim 2.