Production method of modified polytetrafluoroethylene and composition
A method for producing modified polytetrafluoroethylene including: polymerizing tetrafluoroethylene and a modifying monomer in an aqueous medium in the presence of a polymer (I) containing a polymerization unit (I) based on a monomer represented by the following general formula (I) to obtain a modified polytetrafluoroethylene: CX 1 X 3 =CX 2 R(—CZ 1 Z 2 -A 0 ) m (I) wherein X 1 and X 3 are each independently F, Cl, H, or CF 3 ; X 2 is H, F, an alkyl group, or a fluorine-containing alkyl group; A 0 is an anionic group; R is a linking group; Z 1 and Z 2 are each independently H, F, an alkyl group, or a fluorine-containing alkyl group; and m is an integer of 1 or more. Also disclosed is a composition containing the modified polytetrafluoroethylene and the polymer (I).
1. A method for producing modified polytetrafluoroethylene comprising:
polymerizing tetrafluoroethylene and a modifying monomer in an aqueous medium in the presence of a polymer (I) containing a polymerization unit (I) based on a monomer represented by the following general formula (I), a content of the polymerization unit (I) in the polymer (I) being 80 mol % or more based on all polymerization units, and substantially in the absence of a fluorine-containing surfactant to obtain a modified polytetrafluoroethylene:
CX 1 X 3 =CX 2 R(—CZ 1 Z 2 -A 0 ) m (I)
wherein X 1 and X 3 are each independently F, Cl, H, or CF 3 ;
X 2 is H, F or CF 3 ;
A 0 is an anionic group;
R is a linking group;
Z 1 and Z 2 are each independently H, F, an alkyl group, or a fluorine-containing alkyl group; and
m is 1.
2. The production method according to claim 1 , further comprising:
adding the modifying monomer before the initiation of polymerization or when the concentration of particles of the modified polytetrafluoroethylene formed in the aqueous medium is 5.0% by mass or less.
3. The production method according to claim 1 , wherein the total amount of the modifying monomer is 0.000010% by mass or more based on the obtained modified polytetrafluoroethylene.
4. The production method according to claim 1 , wherein the total amount of the modifying monomer is 1.0% by mass or less based on the obtained modified polytetrafluoroethylene.
5. The production method according to claim 1 , wherein the modifying monomer includes at least one selected from the group consisting of hexafluoropropylene, a perfluoro(alkyl vinyl ether) and a (perfluoroalkyl)ethylene.
6. The production method according to claim 1 , wherein the modifying monomer is a compound represented by the following general formula (4):
CX i X k =CX j R a —(CZ 1 Z 2 ) k —Y 3 (4)
wherein X i , X j , and X k are each independently F, Cl, H, or CF 3 ; Y 3 is a hydrophilic group; R a is a linking group; Z 1 and Z 2 are each independently H, F, or CF 3 ; and k is 0 or 1.
7. The production method according to claim 1 , wherein in the polymerization, tetrafluoroethylene and the modifying monomer are polymerized further in the presence of a nucleating agent.
8. The production method according to claim 7 , wherein the nucleating agent is a nonionic surfactant.
9. The production method according to claim 1 , wherein the modified polytetrafluoroethylene has an average primary particle size of 500 nm or less.
10. The production method according to claim 1 , wherein the modified polytetrafluoroethylene has an aspect ratio of primary particles of less than 2.00.
11. The production method according to claim 1 , wherein the anionic group is an anionic group that is a sulfate group, a carboxylate group, a phosphate group, a phosphonate group, a sulfonate group, or —C(CF 3 ) 2 OM wherein M is —H, a metal atom, —NR 7 4 , imidazolium optionally having a substituent, pyridinium optionally having a substituent, or phosphonium optionally having a substituent, and R 7 is H or an organic group.
12. A composition comprising:
a modified polytetrafluoroethylene; and
a polymer (I) containing a polymerization unit (I) based on a monomer represented by the following general formula (I):
CX 1 X 3 =CX 2 R(—CZ 1 Z 2 -A 0 ) m (I)
wherein X 1 and X 3 are each independently F, Cl, H, or CF 3 ; X 2 is H, F or CF 3 ; A 0 is an anionic group; R is a linking group; Z 1 and Z 2 are each independently H, F, an alkyl group, or a fluorine-containing alkyl group; and m is 1,
wherein a content of the polymerization unit (I) in the polymer (I) is 80 mol % or more based on all polymerization units,
which is substantially free from a fluorine-containing surfactant.
13. The composition according to claim 12 , having a breaking strength of 10.0 N or more.
14. The composition according to claim 12 , having a stress relaxation time of 50 seconds or more.
15. The composition according to claim 12 , having an extrusion pressure of 10.0 MPa or more and 30.0 MPa or less.
16. The composition according to claim 12 , having an endothermic peak temperature in the range of 333 to 347° C.
17. The composition according to claim 12 , having a standard specific gravity of 2.250 or less.
18. The composition according to claim 12 , wherein the modified polytetrafluoroethylene has an aspect ratio of primary particles of less than 2.00.
19. The composition according to claim 12 , wherein the anionic group is an anionic group that is a sulfate group, a carboxylate group, a phosphate group, a phosphonate group, a sulfonate group, or —C(CF 3 ) 2 OM wherein M is —H, a metal atom, —NR 7 4 , imidazolium optionally having a substituent, pyridinium optionally having a substituent, or phosphonium optionally having a substituent, and R 7 is H or an organic group.
20. The composition according to claim 12 , which is a powder.