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Abstract

Sprayable aliphatic polyurea-polyurethane coating compositions and methods are disclosed. A quasi-prepolymer composition is prepared by mixing an aliphatic polyisocyanate with a stoichiometrically deficient quantity of polyol such that substantially all of the available hydroxyl groups of the polyol react with the isocyanate groups of the aliphatic polyisocyanate. Suitable catalysts may be used to accelerate the urethane bonding in the quasi-prepolymer compositon. The polymeric coating is preferably formed by reacting the quasi-prepolymer composition with a low molecular weight or a mixture of low and high molecular weight amine terminated polyether compounds. The amine terminated polyether compounds have amine groups capable of reacting with the unreacted isocyanate groups of the quasi-prepolymer Mixing of the quasi-prepolymer composition and the amine terminated polyether is preferably done at a sufficiently fast rate of result in a substantially homogeneous product. The currently preferred method of mixing is impingement mixing. The resulting mixture preferably has a sufficiently slow cure time such that the mixture is capable of being sprayed, but has a sufficiently fast cure time such that the mixture may be sprayed uniformly on non-horizontal surfaces.

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