Polyurethane and polyisocyanurate rigid foams prepared using ternary blowing agent mixtures

A rigid foam, prepared by the process of reacting

• a) an organic isocyanate;
• b) an isocyanate reactive component comprising one or more polyols selected from the group consisting of polyoxyalkylene polyether polyols, polyester polyols, and mixtures thereof;
• c) an effective amount of one or more catalysts which promote the formation of urethane and/or isocyanurate linkages;
• and
• d) a ternary blowing agent mixture comprising
• i) water,
• ii) monochlorodifluoromethane, and
• iii) a third blowing agent component selected from the group consisting of methylene chloride, 1,1,1,-trichloroethane, and mixtures thereof,
• at an isocyanate index of from 70 to about 900.

In a process for the preparation of a rigid foam containing urethane and/or isocyanurate linkages by the reaction of a polyol component with an isocyanate component, the improvement comprising selecting as a blowing agent for said foam a ternary blowing agent comprising

• i) water in an amount of from 0.1 to about 10 weight percent;
• ii) monochlorodifluoromethane in an amount of from about 1 to about 20 weight percent;
• and
• iii) a third blowing agent component selected from the group consisting of methylene chloride, 1,1,1-trichloroethane, and mixtures thereof in an amount of from 1 to about 20 weight percent,
• wherein all said weight percents are based on the weight of the polyol component.