Method for the preparation of semi-rigid polyurethane modified polyurea foam compositions

A method for the preparation of a semi-rigid polyurethane modified polyurea foam composition which comprises reacting at a temperature of from about 0.degree. C. to 50.degree. C., an organic di- or polyisocyanate, a polyether polyol mixture consisting essentially of from about 25 to 75 percent by weight polyether polyol having a hydroxyl number of about 25 to 75 and a functionality of 2 to 3 and correspondingly from about 75 to 25 percent by weight polyether polyol having a hydroxyl number of about 200 to 800 and a functionality of 4 to 8, and from about 2 to 40 parts by weight based on the polyether polyol mixture of an alkylene or dialkyl carbonate, the reaction being carried out in the presence of from about 0.5 to 5.0 parts by weight based on the polyether polyol of a tertiary amine catalyst, from about 1 to 3 parts by weight per 100 parts polyether polyol of a polyalkylene oxide siloxane block copolymer surfactant which may contain hydrolyzable SiOC groups and a blowing agent selected from the group consisting of water which reacts with the di-or polyisocyanate to generate carbon dioxide, fluorocarbons having a boiling point below 60.degree. C. and mixed with water and methylene chloride mixed with water.