Process for producing PTFE and articles thereof

Patent metadata

Field	Value
Publication number	US-11072671-B2
Application number	US-201113642583-A
Country	US
Kind code	B2
Filing date	Apr 28, 2011
Priority date	Apr 28, 2010
Publication date	Jul 27, 2021
Grant date	Jul 27, 2021

Abstract

Described herein is a process for making PTFE having a standard specific gravity of less than 2.160 g/cm 3 comprising: polymerizing a tetrafluoroethylene monomer in an aqueous medium comprising an emulsifier and an initiator in a reaction vessel and contacting the aqueous medium with a fluorinated polyether. Also described herein are the polymerizable compositions and articles thereof.

First claim

The invention claimed is:

1. A polymerizable composition for preparing a PTFE latex, the polymerizable composition comprising:
an amount of water;
a tetrafluoroethylene monomer;
an emulsifier according to formula VI
[R f —O-L-COO − ] i X i +   (VI)

wherein L represents a linear partially or fully fluorinated alkylene group or an aliphatic hydrocarbon group, R f represents a linear partially or fully fluorinated aliphatic group or a linear partially or fully fluorinated group interrupted with one or more oxygen atoms, X i + represents a cation having the valence i and i is 1, 2 and 3;

an initiator; and
0.1 to 0.75 wt % of a fluorinated polyether based on the amount of water, wherein the fluorinated polyether is at least one of the following:
R f —(OCF 2 ) x —(OCF 2 CF 2 ) y —(OCF(CF 3 )—CF 2 ) z —(OCF(CF 3 )) a -Q  (II)

wherein R f is selected from perfluoroalkyl groups having from 1 to 10 carbon atoms; Q is selected from R f or R′ f —(OCF 2 ) x —(OCF 2 CF 2 ) y —(OCF(CF 3 )—CF 2 ) z —(OCF(CF 3 )) a wherein R′ f may be selected from a perfluorinated alkyl group having 1 to 10 carbon atoms, R′ f may be the same or different than R f ; and wherein each x, y, z, and a is independently selected from 0 to 10, with the proviso that the sum of x+y+z+a is at least 1;
R f —(OC 3 F 6 ) n —O—CHFCF 2 —  (III)

wherein R f is selected from a perfluorinated alkyl group having from 1 to 4 carbon atoms, and n is from 1 to 10; and
(iii) a fluorinated polyether which is a derivative of hexafluoropropylene oxide having at least 1 repeating unit of —[(CF 3 )CFCF 2 O]—;

wherein, upon polymerization of the polymerizable composition, the PTFE latex is formed such that the PTFE latex has an average particle size of at least 150 nm, and upon coagulation of the PTFE latex to form a coagulated PTFE, the coagulated PTFE has a standard specific gravity of less than 2.160 g/cm 3 , wherein the polymerizable composition comprises more moles of the fluorinated polyether than moles of the emulsifier, and wherein the PTFE latex contains a homopolymer of tetrafluoroethylene.

2. The polymerizable composition according to claim 1 , wherein the partially fluorinated polyether has a boiling point of between 50 to 300° C.

3. The polymerizable composition according to claim 1 , wherein the fluorinated polyether has a molecular weight of less than 2000 grams/mole.

4. The polymerizable composition according to claim 1 , wherein the emulsifier is selected from a perfluorinated alkanoic acid, a perfluorinated or partially fluorinated acid comprising one or more ether linkages, or their salts.

5. The polymerizable composition according to claim 1 , further comprising a seed particle.

6. The polymerizable composition according to claim 1 , wherein the coagulated PTFE is essentially free of alkane hydrocarbons having between 15 to 60 carbon atoms.

7. The polymerizable composition according to claim 1 , comprising at least 0.5% by weight of the fluorinated polyether versus the amount of water.

8. The polymerizable composition according to claim 1 , comprising less than 5000 ppm of the emulsifier based on the amount of water.

9. The polymerizable composition according to claim 1 , wherein the emulsifier is not added simultaneously with the fluorinated polyether.

10. The polymerizable composition according to claim 1 , wherein the PTFE latex has an average particle size of at most 350 nm.

11. The polymerizable composition according to claim 1 , wherein the fluorinated polyether comprises at least one of: CF 3 CF 2 CF 2 O[CF(CF 3 )CF 2 O] n CFHCF 3 wherein n is within the range of 1 to 3.

12. The polymerizable composition according to claim 1 , wherein the fluorinated polyether has a boiling point of between 100 to 300° C.

13. The polymerizable composition according to claim 1 , wherein the fluorinated polyether is selected from at least one of:
CHF 2 CF 2 CF 2 OCF(CF 3 )CF 2 OCFHCF 3 , CHF 2 CF 2 CF 2 OCF(CF 3 )CF(CF 3 )OCF 2 CF 2 CHF 2 , CF 3 CF 2 CF 2 OCF(CF 3 )CF(CF 3 )OCF 2 CF 2 CF 3 , CF 3 (OCF(CF 3 )CF 2 ) n (OCF 2 ) m OCF 3 wherein n and m are independently, within the range of 1 to 5, CF 3 CF 2 CF 2 O[CF(CF 3 )CF 2 O] n CFXCF 3 wherein X is selected from H, F, or CF 3 and n is within the range of 2 to 8,
[C 3 F 7 O[CF(CF 3 )CF 2 O] n CF(CF 3 )—] 2 wherein n is within the range of 1 to 3,
[C 3 F 7 OCF(CF 3 )CF 2 OCF(CF 3 )CF 2 OCF(CF 3 )] 2 , [C 3 F 7 OCF(CF 3 )CF 2 OCFHCF 2 —] 2 , and including all isomers and combinations thereof.

14. An article made from the PTFE coagulate according to claim 1 , wherein the article is a garment, fiber, or sheet.

15. A process for making PTFE comprising: polymerizing a tetrafluoroethylene monomer in an aqueous medium comprising water, an emulsifier, and an initiator in a reaction vessel, contacting the aqueous medium with 0.1 to 0.75 wt % of a fluorinated polyether based on the amount of water, wherein the polymerizing forms a PTFE latex, and coagulating and drying the PTFE latex to form a PTFE coagulate, wherein the PTFE latex has an average particle size of at least 150 nm and the PTFE coagulate has a standard specific gravity of less than 2.160 g/cm 3 wherein the aqueous medium comprises more moles of the fluorinated polyether than moles of the emulsifier and wherein the PTFE latex contains a homopolymer of tetrafluoroethylene, wherein the emulsifier is according to formula VI
[R f —O-L-COO − ] i X i +   (VI)

wherein L represents a linear partially or fully fluorinated alkylene group or an aliphatic hydrocarbon group, R f represents a linear partially or fully fluorinated aliphatic group or a linear partially or fully fluorinated group interrupted with one or more oxygen atoms, X i + represents a cation having the valence i and i is 1, 2 and 3; and the fluorinated polyether is at least one of the following:
R f —(OCF 2 ) x —(OCF 2 CF 2 ) y —(OCF(CF 3 )—CF 2 ) z —(OCF(CF 3 )) a -Q  (II)

wherein R f is selected from perfluoroalkyl groups having from 1 to 10 carbon atoms; Q is selected from R f or R′ f —(OCF 2 ) x —(OCF 2 CF 2 ) y —(OCF(CF 3 )—CF 2 ) z —(OCF(CF 3 )) a wherein R′ f may be selected from a perfluorinated alkyl group having 1 to 10 carbon atoms, R′ f may be the same or different than R f ; and wherein each x, y, z, and a is independently selected from 0 to 10, with the proviso that the sum of x+y+z+a is at least 1;
R f —(OC 3 F 6 ) n —O—CHFCF 2 —  (III)

wherein R f is selected from a perfluorinated alkyl group having from 1 to 4 carbon atoms, and n is from 1 to 10; and
(iii) a fluorinated polyether which is a derivative of hexafluoropropylene oxide having at least 1 repeating unit of —[(CF 3 )CFCF 2 O]—.

16. The process according to claim 15 , wherein a weight ratio of the partially fluorinated polyether to emulsifier is greater than 1:1.

17. The process according to claim 15 , wherein the fluorinated polyether is added separately from the emulsifier.

18. The process according to claim 15 , wherein the polymerizing is conducted at a temperature of at most 80° C.

19. The process according to claim 15 , wherein the PTFE latex has a P n of at least 500,000.

20. A PTFE coagulate made by the process according to claim 15 .

Assignees

• Frey Oliver
• Hintzer Klaus
• Neumann Wolfgang
• Streiter Andre
• 3M Innovative Properties Co

Inventors

• Frey Oliver
• Hintzer Klaus
• Neumann Wolfgang
• STREITER André

Classifications

• C08F214/262 Primary

  with fluorinated vinyl ethers · CPC title

• D01F6/12

  from polymers of fluorinated hydrocarbons · CPC title

• C08F2/24

  with the aid of emulsifying agents · CPC title

• Y10T428/2982

  Particulate matter [e.g., sphere, flake, etc.] · CPC title