Polyurethane foam-forming reaction mixtures, polyurethane foams formed therefrom, and methods for their production and use

A process for making a molded rigid foam comprising:

• (a) depositing the foam-forming reaction mixture into a mold, and
• (b) allowing the foam-forming reaction mixture to react in the mold to form the mold rigid foam, wherein the foam-forming reaction mixture comprises:
• (1) a polyol blend comprising:
• (i) a saccharide-initiated polyether polyol having a hydroxyl number of 400 to 600 mg KOH/g and a functionality of 4.0 to 6.0, which is present in an amount of at least 40% by weight, based on total weight of polyol, and
• (ii) an aromatic amine-initiated polyether polyol having a hydroxyl number of 100 to 550 mg KOH/g and a functionality of 1.5 to 5.0, which is present in an amount of at least 30% by weight, based on total weight of polyol,
• with the proviso that the polyol blend contains less than 3% by weight, based on total weight of polyol, of a polyol having a hydroxyl number of 15 to 300 mg/KOH g and a functionality of 1.5 to 4.0;
• (2) a blowing agent composition comprising (i) a physical blowing agent, and (ii) a chemical blowing agent;
• (3) a catalyst;
• (4) a surfactant;
• and
• (5) a polyisocyanate comprising at least 85% by weight, based on total weight of polyisocyanate, of a polymeric MDI having an NCO content of 29.0% to 32.0% by weight and a viscosity at 25° C. of 300 to 750 mPa·s, measured according to EN ISO 3219, October 1994, wherein the polymeric MDI comprises, based on total weight of the polymeric MDI, 25% to 40% by weight of monomeric MDI.