1536156 Polyurethane dispersions modified with siloxanes DOW CORNING CORP 9 Dec 1975 [8 Aug 1975] 32774/78 Divided out of 1536155 Headings C3R C3T and C3M A homogeneous polymeric dispersion comprises (a) 55 to 99 pbw of a curable urethane resin composition or an air-driable, essentially pre-cured urethane resin composition which is solvent-dispersed; (b) 1 to 45 pbw of a fluid which is incompatible with the urethane resin composition and which has a viscosity not exceeding 20,000,000 cs. at 25‹ C., wherein (a)+(b) is equal to 100 pbw; (c) 1 to 20% wt. based on the weight of (b) of a dispersing agent capable of maintaining (b) dispersed in (a) which is a siloxane-organic copolymer selected from (1) polydimethylsiloxane - organic copolymers in which the polydimethylsiloxane portion has a molecular weight of at least 1400 and the organic portion consists essentially of a polyoxyethylene polymer having a molecular weight of at least 500, or a polyoxyethylenepolyoxypropylene copolymer having a molecular weight of at least 1000 and the polyoxypropylene portion constitutes up to 50 mole per cent of the organic portion of the siloxanepolyoxyalkylene copolymer, said organic portion being attached to silicon atoms via siliconcarbon bonds, and (ii) polydimethylsiloxaneorganic copolymers which are reaction products produced by heating a mixture of an hydroxylated polydimethylsiloxane, having a molecular weight of at least 1400, and a hydroxylated polyoxyethylene polymer, having a molecular weight of at least 500, or a hydroxylated polyoxyethylenepolyoxypropylene copolymer having a molecular weight of at least 1000 and the polyoxypropylene portion constitutes up to 50 mole per cent of the organic portion of the siloxane-polyoxyalkylene copolymer. Suitable additives (b) include fluid siloxanes such as trimethylsilyl endblocked polydimethylsiloxane, trimethylsilyl endblocked trifluoropropylmethylsiloxane and mixtures of either siloxane with a siloxane oopolymer composed of SiO 2 units and R 3 SiO 1/2 units; liquid polyolefins, e.g. polybutadiene, polybutene and styrenebutadiene copolymers; mineral oils and other petroleum oils and solvents such as naphthol mineral spirits. Additive (b) may function as a lubricant or it may be a solvent used in the manufacture of microporous coatings where the solvent forms the pores in the reacting medium, and after curing, the solvent is evaporated. Optional additives include fillers pigments, heat and light stabilizers, and antioxidants.
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