Room-temperature-curable organopolysiloxane compositions with flame-retarding properties imparted to them by adding a platinum compound and an inorganic filler are known in the art. For example, Japanese Patent Application Publication No. (hereinafter referred to as “Kokai”) H4-18451 discloses a room-temperature-curable organopolysiloxane composition consisting of a dimethylpolysiloxane having both molecular terminals capped with trimethoxysilyl groups, silica powder, quartz powder, zinc carbonate, a platinum compound (a platinum-ethylene complex obtained by reacting chloroplatinic acid with ethylene and dehydrochlorinating the reaction product), a triethylamine salt, and dibutyltin dioctoate.
Furthermore, Kokai H5-230376 discloses a composition comprising a dimethylpolysiloxane having both molecular terminals capped with hydroxyl groups, an alumina hydrate, carbon black, a platinum compound {a complex of platinum with a vinylsiloxane (1,3-divinyl-1,1,3,3-tetramethyidisiloxane)}, and methyltris-(methylethylketoxime)-silane.
Another publication, Kokai H5-125285 discloses a room-temperature-curable organopolysiloxane composition consisting of a dimethylpolysiloxane having both-molecular terminals capped with hydroxyl groups, aluminum hydroxide powder, calcium carbonate, a platinum compound (an isopropanol solution of chloroplatinic acid), and vinyltris-(methylethylketoxime) silane.
However, the aforementioned room-temperature-curable organopolysiloxanes admixed with platinum compounds normally have low storage stability, and after long-term storage, are subject to gradual decrease in flame-retarding properties. In particular, flame-retarding properties drop most significantly in a cured body made from the aforementioned composition after long-term storage at high temperatures. This limits the field of application of the aforementioned compositions.
It is an object of the present invention to provide a room-temperature-curable organopolysiloxane characterized by excellent flame-retarding properties which are preserved in a cured silicone article, made from the aforementioned composition, even after long-term storage at high temperatures.