Composition for polyurethane foam containing polyrotaxane, polyurethane foam derived from composition, and method for producing polyurethane foam

A method for producing a polyurethane foam comprising the steps of:

• 1) preparing (A) a polyol having three or more OH groups;
• 2) preparing (B) a compound having two or more isocyanate groups;
• 3) preparing (C) a polyrotaxane comprising a pseudopolyrotaxane, which has a linear molecule and a cyclic molecule(s) in which the linear molecule is included in a cavity (cavities) of the cyclic molecule(s) in a skewered manner, and capping groups, each of which locates at each end of the pseudopolyrotaxane in order to prevent the dissociation of the cyclic molecule(s);
• and
• 4) mixing the (A) polyol having three or more OH groups, the (B) compound having two or more isocyanate groups, the (C) polyrotaxane, a foaming agent, and a foam stabilizer, to foam and react the mixture;
• to obtain the polyurethane foam,
• wherein the (A) polyol having three or more OH groups is comprised in a mixed polyols,
• an amount of the (A) polyol having three or more OH groups ranges from 20 to 90 parts by weight in 100 parts by weight of the mixed polyols, an apparent density of the polyurethane foam ranges from 80 to 180 kg/m3;
• and a
• compression set of the polyurethane foam, measured in accordance with JISK6400-4 at 70° C. at a compression rate of 50% for 22 hours, is 40% or less.