RTV silicone rubber, crosslinked by condensation - prepd. by mixing hydroxy-terminated polysiloxane with silane and organo-metallic catalyst in form of aged or heat-treated soln. in polysiloxane

摘要

Silicone rubbers which can be crosslinked by condensation reactions at room temp. (I) are mfd. by mixing, in the absence of moisture, OH-terminated polydiorgano-siloxane(s) of formula HO-(SiR20)n-H (II) with silane(s) of formula (R')4-aSiXa (III) or their partly hydrolysed prods. to give a mixt. with viscosity 500-1 million mPa.s at 25 deg.C and with a condensation catalyst of formula (R"O)bML4-b (IV) or a partial hydrolysate thereof, and opt. other additives such as cocatalystis, accelerators, stabilisers, active and inactive fillers and plasticiser oils. Catalyst (IV) is added as a mixt. wtih polydiorganosiloxane(s) of formula (R"')3Si-(OSi(R"')3 (V) with viscosity 15-50,000 mPa.s and OHs1 content 0.005-8 wt. % and this mixt. is stored at room temp. before use and/or heated at up to 200 deg.C. R, R', R"' = opt. substd. 1-8C hydrocarbyl; n, m = whole no; X = aximato, acetoxy, alkoxy, amido, aminoxy, or amino gp. M = Ti or Zr; R2 = opt. substd. 1-18C alkyl; L = dibentate chelating ligand; a = 2.1-4; b = 2-4. USE/ADVANTAGE - Used pref. as moisture-cured, 1-component (RTV-1) siloxane rubbers. The process enables the prodn. of (I) in a single mixing step, using a catalyst prepn. which is stable for long periods at room temp. coneniently handled and metered, and does not cause a sharp increase in viscosity when added to (II)