CAOUTCHOUCS DE SILICONE VULCANISABLES A LA TEMPERATURE AMBIANTEET ADHERANT SANS UTILISATION D'APPRET

摘要

1284204 Silicone rubber compositions DOW CORNING CORP 19 April 1971 [6 April 1970] 23201/71 Headings C3S and C3T A composition which cures to a silicone rubber when exposed to moisture at roomtemperature comprises: (A) 100 parts wt. of a polydiorganosiloxane having a unit formula R 2 SiO and a viscosity of 1000 to 200,000 cs. at 25‹ C. and being terminated by OH radicals or R(YO) 2 SiO 0À5 , where R is C 1-18 hydrocarbon (h.c.) or halogenated h.c., Y is acetoxy or alkoxy, and (B) a mixture comprising at least 10% weight of an alkoxyacetoxysilane wherein a : b is 0À85 : 1 to 1À75 : 1, (a+b+c)= 2À4-3, c=0-1, R111=R, R11 is C 1-6 alkyl, alkoxyalkyl or phenyl, the number of silicon atoms generally being 2-5, and the remaining portion of the mixture comprising silanes of the formula R111 d Si(OOCCH 3 ) e (OR11) f in which d = 0 or 1, e and f=1, 2 or 3, (d+e+f)=4, in the total remaining portion of the mixture, the silane mixture being such that in the average formula the ratio of e to f is 0À85 : 1 to 1À75 : 1, d=0-1, or (b) a mixture of (a) with a silane R g Si(OY) 4-g in which g=0 or 1, and/or partial hydrolysates thereof, wherein (a) provides at least 0À5 parts wt. in the total mixture of (A) and (B). The compositions may include a curing catalyst such as metal salts of carboxylic acids such as dibutyl tin-diacetate, -di-2-ethylhexoate, -dilaurate, Pb-, CO-, or Zn-naphthenate, iron-2-ethyl hexoate and chromium octoate, or oxalic acid, morpholine, triethanolamine, toluene sulphamide and titanium esters and amines; and fillers such as fume SiO 2 , SiO 2 aerogels and precipitated SiO 2 , diatomaceous earth, quartz, TiO 2 and ZnO. Mixture (a) may be prepared by heating a mixture of alkoxysilanes and acetoxysilanes under anhydrous conditions to 100-200‹ C for 1-100 hours or for shorter heating periods by using a catalyst such as FeCl 3 , commercial acid clays or exchange resins. Alternatively mixture (a) may be prepared by heating a mixture of an alkoxysilane, acetic anhydride and acid clay at 100-125‹ C. for 1-10 hours. Numerous examples of the preparation of mixture (a) are given. Uses.-As sealants, coatings, electrical insulation, encapsulants and caulking materials. The silicone rubber also has improved adhesion to unprimed surfaces, particularly metals such as Al, Ti and stainless steel.