| 摘要 |
Room - temperature "vulcanizable" compositions comprise (1) at least one hydroxy-endblocked essentially linear diorganosiloxane polymer wherein the organo groups are monovalent hydrocarbon or halo- or cyano-hydrocarbon radicals, (2) at least one acyloxy silane or siloxane curing agent RmSi(OOCR1)4- m o (R1COO)3- m Rm SiO (R2SiOp) SiRm (OOCR1)3- m where R is a monovalent hydrocarbon or halo-or cyano-hydrocarbon radical, R1 is H or a C1- 18 monovalent hydrocarbon radical free from aliphatic unsaturation, m is 0 or 1 and p is from 0 to 20,000, and (3) 0.1 to 5% by weight of (1) of an anhydride of one or more saturated aliphatic carboxylic acids having 3 to 6 carbon atoms in the anhydride molecule. The composition may also contain a condensation catalyst, inert organic solvents and the conventional optional ingredients for silicone rubbers. Specified anhydrides are formic/acetic, propionic/acetic and butyric/formic mixed acid anhydrides and acetic and propionic acid anhydrides. Extensive lists of possible organo groups in ingredient (1) and R and R1 groups in ingredient (2) are given. A long list of possible condensation catalysts includes oxalic acid, p-aminobenzoic acid, morpholine, various alkanolamines toluene sulphamide, urea derivatives, and numerous carboxylic acid salts of lead, tin, nickel, cobalt, iron, cadmium, chromium, zinc, manganese, zirconium, antimony, barium, calcium, titanium and bismuth including simple metal salts such as cobalt naphthenate and organometal salts such as trinaphthyl lead cyclohexenylacetate. Specified inert solvents include various hydrocarbons, halohydrocarbons, ethers, ketones and fluid organosiloxane polymers free from Si-bonded OH and acyloxy groups. The anhydride may be added to (i) not more than 48 hours before, with, or after (ii). Fillers may be included, numerous examples being given. |
