Silicone rubber compositions for liquid injection molding machines
AssigneeGeneral Electric Company
InventorLuisito A. Tolentino
Life of this patent
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Abstract
A SiH-olefin platinum catalyzed composition having a Durometer Hardness of at least 60 where the novel ingredients are a combination of 10 to 50 parts by weight of fumed silica and 5 to 50 parts by weight of calcined diatomaceous earth per 100 parts of the base vinyl-containing compound. Such a composition is useful for forming molded parts in liquid injection molding machines, both of the plunger type and of the reciprocating screw type.
Claims49
A silicone rubber composition which in the uncured state does not have a viscosity that exceeds 1.5.times.10.sup.6 centipoise at 25.degree. C. and has a Durometer in the cure state that exceeds 60 comprising:
- (A) 100 parts by weight of a linear vinyl terminated diorganopolysiloxane polymer having a viscosity that is in the range of 100 to 100,000 centipoise at 25.degree. C. where the organo group is a monovalent hydrocarbon radical and the vinyl content varies from 0.05 to 0.20 weight percent;
- (B) from 10 to 50 parts by weight of fumed silica;
- (C) from 5 to 50 parts by weight of calcined diatomaceous earth;
- (D) from 1 to 200 parts per million of platinum as a platinum catalyst;
- and
- (E) from 1 to 50 parts by weight of a hydride-containing organopolysiloxane cross-linking agent wherein the hydrogen content varies from 0.2 to 1.0 percent by weight where the organo group is a monovalent hydrocarbon radical.
A process for forming a silicione rubber composition which in the uncured state does not have a viscosity that exceeds 1.5.times.10.sup.6 centipoise at 25.degree. C. and has a Durometer in the cured state that exceeds 60 comprising:
- (1) mixing
- (A) 100 parts by weight of a linear vinyl terminated diorganopolysiloxane polymer having a viscosity that is in the range of 100 to 100,000 centipoise at 25.degree. C. where the organo group is a monovalent hydrocarbon radical and the vinyl content varies from 0.05 to 0.20 weight percent;
- (B) from 10 to 50 parts by weight of fumed silica;
- (C) from 5 to 50 parts by weight of calcined diatomaceous earth;
- (D) from 1 to 200 parts per million of platinum as a platinum catalyst;
- and
- (E) from 1 to 50 parts by weight of a hydride organopolysiloxane cross-linking agent wherein the hydrogen content varies from 0.2 to 1.0 percent by weight where the organo group is a monovalent hydrocarbon radical;
- and (2) heating the composition so as to allow the composition to cure to a silicone elastomer.
A process for forming a silicone elastomeric part which has a Durometer in the cure state that exceeds 60 and an Elongation that exceeds 200% and which in the silicone composition in the uncured state has a viscosity that does not exceed 1.5.times.10.sup.6 centipoise at 25.degree. C., comprising (1) passing into a liquid injection molding machine a silicone composition having:
- (A) 100 parts by weight of a linear vinyl terminated diorganopolysiloxane polymer having a viscosity that is in the range of 100 to 100,000 centipoise at 25.degree. C. where the organo group is a monovalent hydrocarbon radical and the vinyl content varies from 0.05 to 0.20 weight percent:
- (B) from 10 to 50 parts by weight of fumed silica;
- (C) from 5 to 50 parts by weight of calcined diatomaceous earth;
- (D) from 1 to 200 parts per million of platinum as a platinum catalyst;
- and
- (E) from 1 to 50 parts by weight of a hydride organopolysiloxane cross-linking agent wherein the hydrogen content varies from 0.2 to 1.0 percent by weight where the organo group is a monovalent hydrocarbon radical;
- (2) heating the above composition in the liquid injection molding machine so as to form an elastomeric part;
- and (3) ejecting the formed part from the liquid injection molding machine.
Dependencies are inferred from the claim text.