Antifouling coating compositions

A coating composition resistant to fouling by aquatic organisms, comprising an organopolysiloxane composition which cures to an elastomer in the presence of moisture and which comprises a polydiorganosiloxane (A) having a viscosity of 500 to 1,000,000 mPa.s at 25.degree. C. and formed of recurring diorganosiloxy units of the formula --(R.sub.2)SiO--, where the radicals R, which can be the same or different within each unit and from unit to unit, represent hydrocarbon radicals having 1 to 10 carbon atoms, the polydiorganosiloxane (A) being terminated with silicon-bonded hydrolysable groups and/or being terminated with silicon-bonded hydroxyl groups and mixed with a stoichiometric excess of a crosslinking agent (B) for alpha, omega-dihydroxypolydiorganosiloxanes, said crosslinking agent (B) containing at least two silicon-bonded hydrolysable groups per molecule, characterised in that the coating composition is packed in two separate packages to be mixed before application of the coating composition to an underwater surface, the first of the said packages comprising the polydiorganosiloxane (A) and any crosslinking agent (B), and the second of the said packages comprising an alpha, omega-dihydroxypolydiorganosiloxane (C) having a viscosity of 500 to 10,000 mPa.s at 25.degree. C. and formed of recurring diorganosiloxy units of the formula --(R.sub.2)SiO--, where R is defined as above, the second package being free of cross-linking agent for the alpha,omega-dihydroxy-polydiorganosiloxane and free of any catalyst for crosslinking between silicon-bonded hydrolysable groups and silicon-bonded hydroxyl groups, at least 50% of the total radicals R in the polydiorganosiloxanes (A) and (C) being methyl radicals and at least 0.1% of the total radicals R in the polydiorganosiloxanes (A) and (C) being phenyl radicals.

A process for coating a surface, which is intended to be under water or in contact with water in use, with a polydiorganosiloxane composition to inhibit fouling of the surface by aquatic organisms, said polydiorganosiloxane composition comprising an alpha, omega-dihydroxypolydiorganosiloxane (A) having a viscosity of 500 to 1,000,000 mPa.s at 25.degree. C. and formed of recurring diorganosiloxy units of the formula --(R.sub.2)SiO--, where the radicals R, which can be the same or different within each unit and from unit to unit, represent hydrocarbon radicals having 1 to 10 carbon atoms, and a separately packaged crosslinking agent (B) for alpha, omega-dihydroxypolydiorganosiloxanes, said crosslinking agent (B) containing at least two silicon-bonded ketiminoxy groups per molecule, said process comprising mixing the crosslinking agent (B) and the alpha, omega-dihydroxypolydiorganosiloxane (A) at a ratio of moles of crosslinking agent (B) to moles of silicon-bonded hydroxyl groups in the polydiorganosiloxane (A) in the range 0.7:1 to 1.5:1 and applying the resulting mixture to said underwater surface within 8 hours of said mixing and allowing said mixture to cure on the surface in the presence of moisture to form an elastomer, wherein the composition contains a non-reactive methyl phenyl silicone oil of viscosity 20 to 5000 mPa.S, said non-reactive methyl phenyl silicone oil being present in either the first package or the second package or both and being present at 1 to 50 wt % based on the combined weight of the polydiorganosiloxane (A) and crosslinking agent (B).

A process for coating a surface, which is intended to be under water in contact with water in use, with a polydiorganosiloxane composition to inhibit fouling of the surface by aquatic organisms, said organopolysiloxane composition comprising a polydiorganosiloxane (A) having a viscosity of 500 to 1,000,000 mPa.s at 25.degree. C. and formed of recurring diorganosiloxy units of the formula --(R.sub.2)SiO--, where the radicals R, which can be the same or different within each unit and from unit to unit, represent hydrocarbon radicals having 1 to 10 carbon atoms, the polydiorganosiloxane (A) being terminated with silicon-bonded hydrolysable groups and/or being terminated with silicon-bonded hydroxyl groups and mixed with a stoichiometric excess of a crosslinking agent (B) for alpha, omega-dihydroxypolydiorganosiloxanes, said crosslinking agent (B) containing at least two silicon-bonded hydrolysable groups per molecule, said process comprising mixing the polydiorganosiloxane (A) and any crosslinking agent (B) with a separately packaged alpha, omega-dihydroxypolydiorganosiloxane (C) having a viscosity of 500 to 10,000 mPa.s at 25.degree. C. and formed of recurring diorganosiloxy units of the formula --(R.sub.2)SiO--, where R is defined as above, the package comprising polydiorganosiloxane (C) being free of crosslinking agent for the alpha, omega-dihydroxypolydiorganosiloxane (C) and free of any catalyst for crosslinking between silicon-bonded hydrolysable groups and silicon-bonded hydroxyl groups, to form a mixed composition in which at least 50% of the total radicals R in the polydiorganosiloxanes (A) and (C) are methyl radicals and at least 0.1% of the total radicals R in the polydiorganosiloxanes (A) and (C) are phenyl radicals, and applying the mixed composition to the surface within 8 hours of mixing and allowing said mixed composition to cure to an elastomer film on the surface in the presence of moisture.