Method for producing modified polytetrafluoroethylene, method for producing modified polytetrafluoroethylene powder, and method for producing stretched porous material

Patent metadata

Field	Value
Publication number	US-11780943-B2
Application number	US-202017021129-A
Country	US
Kind code	B2
Filing date	Sep 15, 2020
Priority date	Apr 27, 2018
Publication date	Oct 10, 2023
Grant date	Oct 10, 2023

Abstract

To provide a method for producing modified polytetrafluoroethylene, in which formation of a fluorinated oligomer as a by-product is little. A method for producing modified polytetrafluoroethylene which contains substantially no C 6-34 fluorinated oligomer containing hydrophilic functional groups and which contains substantially no fluorinated surfactant, the method comprising conducting copolymerization of tetrafluoroethylene and a monomer having a polar group, in a liquid dispersion 1 comprising a polymer containing units derived from a non-fluorinated monomer and an aqueous medium, or in a solution 2 obtainable by mixing at least one member selected from the group consisting of a polyalkylene oxide compound and a hydrocarbon-containing surfactant, with an oxidizing agent, in an aqueous medium, under such a condition that the amount of the monomer having a polar group to be used, is at most 0.150 mass % to the whole amount of tetrafluoroethylene, to obtain modified polytetrafluoroethylene.

First claim

What is claimed is:

1. A method for producing modified polytetrafluoroethylene, which comprises conducting copolymerization of tetrafluoroethylene and a monomer having a polar group,
in a dispersion 1 comprising a polymer containing units based on a non-fluorinated monomer, and an aqueous medium,
under such a condition that the amount of the monomer having a polar group to be used, is at most 0.150 mass % to the whole amount of tetrafluoroethylene to be supplied to the polymerization system.

2. The method for producing modified polytetrafluoroethylene according to claim 1 , wherein the polar group is a group represented by the formula (A) or a group represented by the formula (B),
—SO 3 M  Formula (A)

—COOM  Formula (B)

in the formula (A) and the formula (B), M represents a hydrogen atom, NH 4 or an alkali metal atom.

3. The method for producing modified polytetrafluoroethylene according to claim 2 , wherein the monomer having a polar group is a monomer represented by the formula (3),
CR 31 R 32 ═CR 33 -L 3 -R 34   Formula (3)

in the formula (3), R 31 and R 32 are each independently a hydrogen atom or a fluorine atom, R 33 represents a hydrogen atom, a fluorine atom or an alkyl group which may be substituted by a fluorine atom, L 3 represents a single bond or a divalent linking group, and R 34 represents a group represented by the above formula (A) or the above formula (B).

4. The method for producing modified polytetrafluoroethylene according to claim 1 , wherein in the aqueous medium, polymerization of the non-fluorinated monomer is conducted, and then in the dispersion 1 comprising the polymer containing units based on the non-fluorinated monomer and the aqueous medium, copolymerization of the tetrafluoroethylene and the monomer having a polar group is conducted.

5. The method for producing modified polytetrafluoroethylene according to claim 1 , wherein in the non-fluorinated monomer is a monomer represented by the formula (1),
CH 2 ═CR 11 -L 1 -R 12   Formula (1)

in the formula (1), R 11 represents a hydrogen atom or an alkyl group, L 1 represents a single bond, —CO—O—*, —O—CO—* or —O—, * represents the bonding position to R 12 , and R 12 represents a hydrogen atom, an alkyl group, an alkenyl group or a nitrile group, provided that when L 1 is a single bond, R 12 is a nitrile group.

6. The method for producing modified polytetrafluoroethylene according to claim 1 , wherein at the time of the copolymerization of the tetrafluoroethylene and the monomer having a polar group, a polymerization initiator is used, and the amount of the polymerization initiator to be used, is at least 0.10 mass % to the whole amount of tetrafluoroethylene to be supplied to the polymerization system.

7. The method for producing modified polytetrafluoroethylene according to claim 1 , wherein the amount of the monomer having a polar group to be used, is at most 0.150 mol % to the whole amount of tetrafluoroethylene to be supplied to the polymerization system.

8. A method for producing modified polytetrafluoroethylene, which comprises conducting copolymerization of tetrafluoroethylene and a monomer having a polar group,
in a dispersion 2 obtainable by mixing at least one member selected from the group consisting of a polyalkylene oxide compound and a hydrocarbon-containing surfactant, with an oxidizing agent, in an aqueous medium,
under such a condition that the amount of the monomer having a polar group to be used, is at most 0.150 mass % to the whole amount of tetrafluoroethylene to be supplied to the polymerization system, to obtain modified polytetrafluoroethylene.

9. The method for producing modified polytetrafluoroethylene according to claim 8 , wherein copolymerization of the tetrafluoroethylene and the monomer having a polar group is conducted in the dispersion 2, and
the polyalkylene oxide compound is a compound represented by the formula (2)
R 21 —(O-L 2 ) n -O—R 22   Formula (2)

in the formula (2), R 21 and R 22 are each independently a hydrogen atom, an alkyl group, an acryloyl group or a methacryloyl group, L 2 represents a C 1-4 alkylene group, and n represents from 1 to 50.

10. The method for producing modified polytetrafluoroethylene according to claim 8 , wherein a polymerization initiator is used at the time of the copolymerization of the tetrafluoroethylene and the monomer having a polar group, and
the amount of the polymerization initiator to be used is at least 0.10 mass % to the whole amount of tetrafluoroethylene to be supplied to the polymerization system.

11. The method for producing modified polytetrafluoroethylene according to claim 8 , wherein the amount of the monomer having a polar group to be used, is at most 0.150 mol % to the whole amount of tetrafluoroethylene to be supplied to the polymerization system.

12. A method for producing a modified polytetrafluoroethylene powder, which comprises producing an aqueous dispersion in which the modified polytetrafluoroethylene obtained by the method as defined in claim 1 is dispersed in the form of particles, and coagulating the particulate modified polytetrafluoroethylene to obtain a modified polytetrafluoroethylene powder.

13. A modified polytetrafluoroethylene powder, in which units based on a monomer having a polar group, are from 0.005 to 0.150 mol %, to units based on tetrafluoroethylene,
of which the standard specific gravity is at most 2.230, and
which contains substantially no C 6-34 fluorinated oligomer containing hydrophilic functional groups and no fluorinated surfactant.

14. A method for producing a stretched porous material, which comprises producing a modified polytetrafluoroethylene powder by the method as defined in claim 12 , paste-extruding the modified polytetrafluoroethylene powder to obtain an extruded bead, and stretching the extruded bead to obtain a stretched porous material.

Assignees

• Agc Inc

Inventors

• Higuchi Shinya
• Ebata Shiro
• Kose Takehiro

Classifications

• C08F214/265 Primary

  with non-fluorinated comonomers · CPC title

• C08F2/10

  Aqueous solvent · CPC title

• C08J3/16

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

• C08J2327/22

  modified by chemical after-treatment · CPC title

• C08F2/44

  Polymerisation in the presence of compounding ingredients, e.g. plasticisers, dyestuffs, fillers · CPC title