Patent GB-1536155-A (GB)
Title: Urethanes with siloxanes
IPC: C09K23/54
Filed: 1975-12-09
Abstract: 1536155 Urethane dispersions modified with siloxanes DOW CORNING CORP 9 Dec 1975 [8 Aug 1975] 50400/75 Headings C3R C3T and C3M A homogeneous polymeric dispersion comprises (a) 55-99 pbw of a curable or solvent dispersed, air-driable urethane resin composition; (b) 1-45 pbw of a fluid which is incompatible with the urethane resin and which has a viscosity not exceeding 20,000,000 cs at 25 C., wherein (a) + (b) totals 100 pbw; and (c) 1-20% 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) siloxane-organic copolymers consisting essentially of SiO 2  units, (CH 3 ) 3 SiO 1/2  units and D(CH 3 ) 3 SiO 1/2  units in which D is a polyoxyethylene unit having a M.Wt. of at least 500, or a polyoxyethylenepolyoxypropylene unit having a M.Wt. of at least 2500, the polyoxypropylene portion constituting up to 50 mole per cent of the organic portion of the siloxane-polyoxyalkylene copolymer, D being attached to the Si atom via a Si-C bond, the ratio of SiO 2  units to the total (CH 3 ) 3 SiO 1/2  and D(CH 3 ) 3 SiO 1/2  units being from 1 : 0À4 to 1 : 1À2; and (2) copolymers which are reaction products derived from heating a mixture of a siloxane consisting essentially of SiO 2  and (CH 3 ) 3 SiO 1/2  units in a ratio of 1 : 0À4 to 1 : 1À2, and a hydroxylated polyoxyethylene polymer having a M.Wt. of at least 500 or a hydroxylated polyoxyethylene-polyoxypropylene copolymer having a M.Wt. of at least 2500, the polyoxypropylene portion constituting 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 copolymer composed of SiO 2  units and R 3 SiO 1/2  units; liquid polyolefins, e.g. polybutadiene, polybutene and styrene-butadiene 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. In the examples dispersions are prepared from (1) (a) a 2-part urethane potting compound, (b) naphthol mineral spirits, and (c) a copolymer of a siloxane of SiO 2  and (CH 3 ) 3 SiO 1/2  units and a 50/50 ethylene oxide/propylene oxide copolymer as dispersing agent; and xylene, the dispersion forming a microporous foam after gelling and removal of solvent at elevated temperatures; or (2) the same formulation as (1) except that (b) is mineral oil; or (3) (a) a 2 component RTV urethane resin, (b) a trimethylsilyl endblocked trifluoropropylmethylsiloxane (1000 cs) as a lubricant, and (c) the dispersing agent of Example 1, the dispersion being gelled at room temperature and then cured to a rubber by heating. Other similar examples are described.