Abstract: A urethane prepolymer composition useful as sealant is disclosed. The composition comprises a reaction product of an organic polyisocyanate and a polyether polyol mixture at an NCO/OH equivalent ratio from 1.6 to 2.5. The polyether polyol mixture contains (a) from 75 to 95 % by weight of the mixture of a polyoxyalkylenediol having an average MW from 400 to 1,000 and an oxyethlene unit content greater than 50 % by weight, and (b) the balance of the mixture of a polyoxyalkylenetriol having an average MW from 5,000 to 10,000 and an oxyethylene unit content greater than 50 % by weight. An equivalent composition is produced by reacting the polyoxyalkylenediol and polyoxyalkylenetriol with the organic polyisocyanate separately and mixing together after the reaction.

Abstract: An anti-corrosive polyurethane coating composition which has excellent metal corrosion inhibiting property, water resistance, adhesion property to metals, impact resistance and other properties required for anti-corrosive paints, and can be coated thick with one coating operation, containing as an essential component a polyurethane resin having a density of crosslinking of 1.10 to 2.00 per 1,000 atomic weight of the resin and produced by reaction of (A) a polyol component having a hydroxyl value of 160 to 350 mgKOH/g and being composed of a castor oil polyol alone or a mixture of a castor oil polyol and a low molecular polyol having a functionality of at least 2, preferably at least 3, and (B) a polyisocyanate component in an NCO/active hydrogen ratio of 0.85-1.151 by equivalent.