Sponge-forming liquid silicone rubber composition and silicone rubber sponge

Patent metadata

Field	Value
Publication number	US-11034815-B2
Application number	US-201716464455-A
Country	US
Kind code	B2
Filing date	Nov 21, 2017
Priority date	Nov 28, 2016
Publication date	Jun 15, 2021
Grant date	Jun 15, 2021

Abstract

A sponge-forming liquid silicone rubber composition is provided. The composition generally maintains a stable emulsified state, can form a low-density silicone rubber sponge having a uniform and fine open-cell foam structure even when a coating or molding method involving shearing force and thin layer formation is used, is less likely to contract during curing, and that forms a silicone rubber sponge having a density close to the density designed on the basis of water content. A low-density silicone rubber sponge material using the sponge-forming liquid silicone rubber composition is also provided. The sponge-forming liquid silicone rubber composition comprises (A) an alkenyl group-containing organopolysiloxane, (B) an organopolysiloxane having a silicon atom-bonded hydrogen atom, (C) a mixture of water and an inorganic thickener, (D) an emulsifier, and (E) a hydrosilylation reaction catalyst. The contained amount of the component (C) in the entire composition is 70 mass % or more.

First claim

The invention claimed is:

1. A hydrosilylation reaction-curable sponge-forming liquid silicone rubber composition comprising:
(A) 100 parts by mass of an alkenyl group-containing organopolysiloxane;
(B) an organopolysiloxane having at least two silicon atom-bonded hydrogen atoms per molecule in an amount such that the number of moles of hydrogen atoms bonded to silicon atoms in component (B) is 0.4 to 20 per mole of alkenyl groups in component (A);
(C) 250 to 850 parts by mass mixture of water and an inorganic thickener;
(D) 0.1 to 15 parts by mass of an emulsifier;
(E) a hydrosilylation catalyst in an amount sufficient to crosslink the composition; and
(F) 0.001 to 5 parts by mass of a curing retarder;
wherein component (A) is an organopolysiloxane mixture of components (A-L) and (A-R) at a mass ratio of 93:7 to 75:25:
(A-L) a linear or branched organopolysiloxane having at least two alkenyl groups per molecule; and
(A-R) a resin-like organopolysiloxane containing a SiO 4/2 unit and/or a RSiO 3/2 unit where R is a monovalent hydrocarbon group, alkoxy group, or hydroxyl group, and having at least two alkenyl groups per molecule; and
wherein the content of component (C) is 70% by mass or more relative to the entire composition.

2. The hydrosilylation reaction-curable sponge-forming liquid silicone rubber composition according to claim 1 , wherein the density of a silicone rubber sponge obtained by crosslinking the sponge-forming liquid silicone rubber composition and then removing water from the silicone rubber is 0.45 g/cm 3 or less.

3. The hydrosilylation reaction-curable sponge-forming liquid silicone rubber composition according to claim 1 , wherein at least a portion of component (D) is a silicone surfactant having an HLB value of less than 6.

4. The hydrosilylation reaction-curable sponge-forming liquid silicone rubber composition according to claim 3 , wherein component (D) is a silicone surfactant having an HLB value of less than 6 represented by the general formula:
R A a R B Q c L d SiO (4-a-b-c-d)/2
where R A is a monovalent organic group excluding R B , L and Q, a hydrogen atom, or a hydroxyl group, R B is a substituted or unsubstituted linear or branched monovalent hydrocarbon group having from 9 to 60 carbon atoms or a linear or branched organosiloxane group bonded to a silicon atom via a divalent organic group, L is a silylalkyl group having a carbosiloxane dendrimer structure bonded to a silicon atom via a divalent organic group, and Q is a monovalent hydrophilic group, and where each of a, b, c and d is a number in the ranges 1.0≤a≤2.5, 0≤b≤1.5, 0.001≤c≤1.5, and 0≤d≤1.5, and where c is a number such that the HLB value of the entire molecule is less than 6.

5. The hydrosilylation reaction-curable sponge-forming liquid silicone rubber composition according to claim 3 , wherein at least a portion of component (D) is a silicone surfactant having an HLB value of less than 6 represented by the following structural formula:

where R 1 is a monovalent hydrocarbon group, hydroxyl group or alkoxy group, R 2 is a group selected from a polyoxyalkylene group represented by —R 3 —O—(C 2 H 4 O) d (C 3 H 6 O) e R 4 where R 3 is an alkylene group having from 2 to 30 carbon atoms and R 4 is a hydrogen atom or an alkyl group having from 1 to 30 carbon atoms or an inorganic group represented by R 5 —(CO)— where R 5 is an alkyl group having from 1 to 30 carbon atoms, and each of d and e is an integer in the ranges of 0≤c≤50 and 0≤d≤50, respectively, provided 1≤d+e, and each A is independently a group selected from R 1 and R 2 , m is a number in a range from 1 to 500, and n is a number in a range from 0 to 100, provided at least one A is R 2 when n is 0.

6. The hydrosilylation reaction-curable sponge-forming liquid silicone rubber composition according to claim 5 , wherein component (D) is a silicone surfactant having an HLB value in a range from 3 to 5 represented by Formula 1, where R 1 is a group selected from an alkyl group or halogenated alkyl group having from 1 to 6 carbon atoms, a phenyl group and a hydroxyl group, A is R 1 , m is a number in the range from 5 to 100, and n is a number in the range from 1 to 5.

7. The hydrosilylation reaction-curable sponge-forming liquid silicone rubber composition according to claim 3 , wherein component (D) comprises:
(D-1) a non-silicone nonionic surfactant having an HLB value of 3 or more;
(D-2) a non-silicone nonionic surfactant having an HLB value of less than 3 provided the mass ratio of component (D-1) to component (D-2) is at least 1; and
(D-3) a silicone surfactant having an HLB value of less than 6.

8. The hydrosilylation reaction-curable sponge-forming liquid silicone rubber composition according to claim 1 , wherein component (E) is obtained by dispersing or encapsulating and then micronizing a hydrosilylation reaction catalyst in a thermoplastic resin.

9. The hydrosilylation reaction-curable sponge-forming liquid silicone rubber composition according to claim 1 , wherein component (A-L) is an organopolysiloxane comprising from 10 to 90 mass % of (A-1) a diorganopolysiloxane having an average of two alkenyl groups at the molecular chain end and no alkenyl groups in a molecular side chain and from 10 to 90 mass % of (A-2) a diorganopolysiloxane having at least two alkenyl groups in a molecular side chain.

10. The hydrosilylation reaction-curable sponge-forming liquid silicone rubber composition according to claim 1 , wherein the inorganic thickener in component (C) is smectite.

11. The hydrosilylation reaction-curable sponge-forming liquid silicone rubber composition according to claim 1 , further comprising (G) at most 20 parts by mass silica fine powder per 100 parts by mass component (A).

12. A silicone rubber sponge obtained by crosslinking the sponge-forming liquid silicone rubber composition according to claim 1 and then removing water from the silicone rubber.

13. The silicone rubber sponge according to claim 12 , wherein the average cell diameter is 1 μm or more and less than 50 μm, and the open cell ratio is 90% or more.

14. A method for producing the sponge-forming liquid silicone rubber composition according to claim 1 , the method comprising:
1) mixing a portion of component (A) with component (B), component (D) and component (F);
2) mixing the remaining portion of component (A) with component (E); and
3) mixing together the mixture obtained in step 1), the mixture obtained in step 2), and component (C), and then subjecting the resulting mixture to mechanical emulsification.

15. A method for producing the sponge-forming liquid silicone rubber composition according to claim 1 , the method comprising:
1) mixing a portion of component (A) and component (B) with a non-silicone emulsifier in component (D) and component (F);
2) mixing the remaining portion of component (A) with component (E);
3) mixing component (C) and a silicone emulsifier in component (D); and
4) mixing together the mixtures obtained in step 1), step 2), and step 3), and then subjecting the resulting mixture to mechanical emulsification.

16. A method for producing the sponge-forming liquid silicone rubber composition according to claim 1 , the method comprising:
1) mixing a portion of component (A) with component (B) and component (F);
2) mixing the remaining portion of component (A) with component (E);
3) mixing component (C) with component (D); and
4) mixing together the mixtures obtained in step 1), step 2), and

Assignees

• Dow Toray Co Ltd

Inventors

• Endo Shuji
• Toyama Takatoshi
• Nozoe Tsugio

Classifications

• C08L2312/00

  Crosslinking · CPC title

• C08J2205/05

  Open cells, i.e. more than 50% of the pores are open · CPC title

• C08J2483/05

  containing silicon bound to hydrogen · CPC title

• C08J2383/04

  Polysiloxanes · CPC title

• C08L83/04

  Polysiloxanes · CPC title