Siloxane elastomers containing manganous oxide

Claim 2

A composition comprising 100 parts by weight of polydiorganosiloxane, wherein each organic radical is selected from the group consisting of methyl, vinyl, 3,3,3-trifluoropropyl, and phenyl, there being up to 2 percent vinyl radicals, up to 50 percent 3,3,3-trifluoropropyl radicals, and up to 10 percent phenyl radicals based on the total number of organic radicals in the polydiorganosiloxane and from 1.98 to 2.002 organic radicals per silicon atom in the polydiorganosiloxane, from 10 to 100 parts by weight of reinforcing silica filler treated to prevent crepe hardening, and from 0.1 to 5 parts by weight of manganous oxide, the particles of which have a maximum dimension of less than 15 micrometers.

Claim 3

The composition of claim 1 in which there is also present from 0.1 to 5 parts by weight of organic peroxide vulcanizing agent suitable for vulcanizing the composition.

Claim 4

The composition of claim 2 in which there is also present from 10 to 100 parts of extending filler.

Claim 5

The composition of claim 3 in which there is also present an effective amount of flame-retardant additive.

Claim 6

The composition of claim 2 wherein the polydiorganosiloxane is endblocked with dimethylvinylsiloxy units, the reinforcing filler is present in an amount of from 10 to 50 parts by weight, and the manganous oxide is present in an amount of from 0.1 to 2 parts by weight.

Claim 7

The composition of claim 5 in which there is also present from 10 to 50 parts by weight of a siliceous extending filler; from 0.1 to 5 parts by weight of organic peroxide vulcanizing agent suitable for vulcanizing the composition; from 10 to 150 parts by weight per one million parts by weight of the polydiorganosiloxane of platinum as an unsupported platinum-containing material as a flame-retardant additive; and an effective amount of at least one additional flame-retardant additive selected from the group consisting of fume titanium dioxide, carbon black, Group II metal oxides, rare earth metal oxides and rare earth metal hydroxides, triazoles, and aromatic acid selected from the group consisting of mononuclear aromatic acids and halogenated mononuclear aromatic acids.

Claim 8

A process of preparing a siloxane composition having improved heat stability in the cured form comprising mixing 100 parts by weight of dimethylvinylsiloxy endblocked polydiorganosiloxane wherein each organic radical is selected from the group consisting of methyl, vinyl, 3,3,3-trifluoropropyl, and phenyl, there being up to 2 percent vinyl radicals, up to 50 percent 3,3,3-trifluoropropyl radicals, and up to 10 percent phenyl radicals based on the total number of organic radicals in the polydiorganosiloxane and from 1.98 to 2.002 organic radicals per silicon atom in the polydiorganosiloxane; from 10 to 100 parts by weight of reinforcing silica filler treated to prevent crepe hardening; from 0.1 to 5 parts by weight of manganous oxide, the particles of which have a maximum dimension of less than 15 micrometers; and from 0.1 to 5 parts by weight of organic peroxide vulcanizing agent suitable for vulcanizing the composition to produce a curable homogeneous mixture.

Claim 9

A process of preparing a siloxane composition having improved heat stability in the cured form comprising mixing 100 parts by weight of dimethylvinylsiloxy endblocked polydiorganosiloxane wherein each organic radical is selected from the group consisting of methyl, vinyl, 3,3,3-trifluoropropyl, and phenyl, there being up to 2 percent vinyl radicals, up to 50 percent 3,3,3-trifluoropropyl radicals, and up to 10 percent phenyl radicals based on the total number of organic radicals in the polydiorganosiloxane and from 1.98 to 2.002 organic radicals per silicon atom in the polydiorganosiloxane; from 10 to 100 parts by weight of reinforcing silica filler treated to prevent crepe hardening; from 0.1 to 5 parts by weight of manganous oxide, the particles of which have a maximum dimension of less than 15 micrometers; and from 0.1 to 5 parts by weight of organic peroxide vulcanizing agent suitable for vulcanizing the composition to produce a curable homogeneous mixture.

Claim 10

The process in accordance with claim 7 further characterized by forming the curable homogeneous mixture into a desired shape and thereafter heating the curable homogeneous mixture to prepare a cured siloxane composition having improved heat stability.