Platinum complexes of unsaturated siloxanes, substantially free of inorganic halogen and inhibitory compounds, provide superior hydrosilation catalysts when the unsaturated siloxane comprises, per gram-atom of platinum, (i) a combination of one mole of (CH.sub.2 .dbd.CH)((R).sub.2 Si).sub.2 O, and one mole of (CH.sub.2 .dbd.CH) (R).sub.2 SiOSi(R.sub.2)OH; (ii) two moles of (CH.sub.2 .dbd.CH)((R).sub.2 Si).sub.2 O; or (iii) a mixture of (i) and (ii), wherein R is free of aliphatic unsaturation and is selected from alkyl, cycloalkyl, and aryl groups.
A platinum catalyst composition having improved thermal stability, and all of the utilities of platinum catalyst compositions of trhe art, is provided by mixing certain organosiloxanes which contain aryl and alkenyl groups, such as 1,3-divinyl-1,3-diphenyldimethyldisiloxane, in a quantity of at least 2 moles, with a platinum complex having as a ligand an organosiloxane which contains alkyl and alkenyl groups, such as 1,3-divinyltetramethyldisiloxane (or a mixture of said platinum complex and said organosiloxane), in a quantity of 1 mole of platinum atoms. In a preferred embodiment the mixture is distilled in vacuo to remove part or all of the organosiloxane which contains alkyl and alkenyl groups, and most preferably to remove at least a portion of the complexed organosiloxane which contains alkyl and alkenyl groups.
A platinum catalyst composition having improved thermal stability, and all of the utilities of platinum catalyst compositions of the art, is provided by mixing certain organosiloxanes which contain aryl and alkenyl groups, such as 1,3-divinyl-1,3-diphenyldimethyldisiloxane, in a quantity of at least 2 moles, with a platinum complex having as a ligand an organosiloxane which contains alkyl and alkenyl groups, such as 1,3-divinyltetramethyldisiloxane (or a mixture of said platinum complex and said organosiloxane), in a quantity of 1 mole of platinum atoms. In a preferred embodiment the mixture is distilled in vacuo to remove part or all of the organosiloxane which contains alkyl and alkenyl groups, and most preferably to remove at least a portion of the complexed organosiloxane which contains alkyl and alkenyl groups.
Platinum complexes of unsaturated siloxanes, substantially free of inhibitory compounds, provide superior hydrosilation catalysts when produced by heating a platinum compound with an unsaturated siloxane of the formula wherein R is free of aliphatic unsaturation and is selected from alkyl, cycloalkyl, and aryl groups, the amount of siloxane being selected to provide not less than about 0.01 gram atom of platinum per mole of vinyl content, and a platinum content of not less than about 2 percent by weight in the catalyst. Curable silicone compositions containing such catalysts are also provided.
A specific amount of a low molecular weight vinyl siloxane is blended with a platinum-vinyl siloxane complex to provide a platinum complex catalyst, which is prevented from deterioration with time at elevated temperatures and from blackening and precipitation, and maintains its catalytic activity unaffected.
To provide a high-purity platinum complex catalyst composition that has an excellent storage stability, is easy to handle, and has a high catalytic activity. Also, to provide a process for the preparation of this platinum complex catalyst composition and provide a microparticulate thermoplastic resin catalyst composition.
