US 12,077,637 B2
Addition-curable liquid silicone rubber composition for LED headlamps, and LED headlamp
Shigeki Shudo, Annaka (JP); and Mikio Iino, Annaka (JP)
Assigned to SHIN-ETSU CHEMICAL CO., LTD., Tokyo (JP)
Appl. No. 17/283,898
Filed by SHIN-ETSU CHEMICAL CO., LTD., Tokyo (JP)
PCT Filed Sep. 19, 2019, PCT No. PCT/JP2019/036664
§ 371(c)(1), (2) Date Apr. 8, 2021,
PCT Pub. No. WO2020/080028, PCT Pub. Date Apr. 23, 2020.
Claims priority of application No. 2018-194807 (JP), filed on Oct. 16, 2018.
Prior Publication US 2021/0355285 A1, Nov. 18, 2021
Int. Cl. C08L 83/04 (2006.01); C08G 77/00 (2006.01); C08G 77/08 (2006.01); C08G 77/12 (2006.01); C08G 77/20 (2006.01); C08K 5/3492 (2006.01); F21S 41/141 (2018.01); F21S 45/10 (2018.01)
CPC C08G 77/20 (2013.01) [C08G 77/08 (2013.01); C08G 77/12 (2013.01); C08G 77/70 (2013.01); C08K 5/34924 (2013.01); F21S 41/141 (2018.01); F21S 45/10 (2018.01)] 10 Claims
 
1. An addition-curable liquid silicone rubber composition for LED headlamps, comprising:
(A) (A-1) 100 parts by weight of an organopolysiloxane containing at least two silicon-bonded alkenyl groups per molecule, having an average degree of polymerization of less than 2,000, and being liquid at 25° C., and (A-2) 10 to 100 parts by weight of an organopolysiloxane containing at least two silicon-bonded alkenyl groups per molecule, having an average degree of polymerization of at least 2,000, and being gum at 25° C.,
(B) 10 to 150 parts by weight of a silicone resin comprising units selected from among R23SiO1/2 units (M units), SiO4/2 units (Q units), R22SiO2/2 units (D units), and R2SiO3/2 units (T units), wherein R2 is a C1-C6 substituted or unsubstituted monovalent hydrocarbon group, the total of M and Q units is at least 80 mol % of the overall constitution units, and a molar ratio of M units to Q units is from 0.5 to 1.5, the silicone resin containing at least two alkenyl groups per molecule (overall constitution units),
(C) an organohydrogenpolysiloxane containing at least two silicon-bonded hydrogen atoms (Si—H groups) per molecule, the content of Si—H groups being up to 0.0085 mol/g, in such an amount that the number of Si—H groups in component (C) is 1 to 3 per one of total silicon-bonded alkenyl groups in components (A) and (B),
(D) a catalytic amount of a platinum group metal base catalyst, and
(E) triallyl isocyanurate in an amount of 0.01 to less than 0.05 part by weight per 100 parts by weight of components (A), (B) and (C) combined.