Polyester Polyol and Polyol Blends and Rigid Polyurethane Foam Manufacturing

A polyol blend comprising

• a) at least 40% by weight, based on the combined weights of all polyols in the resin blend, of a polyether polyol having a hydroxyl functionality of greater than four and a hydroxyl equivalent weight of up to 250;
• b) at least 10% by weight, based on the combined weights of all polyols in the polyol blend, of at least one polyether polyol having a hydroxyl functionality of 2 to 4 and a hydroxyl equivalent weight of up to 700;
• and
• c) 8 to 30% by weight, based on the combined weights of all polyols in the polyol blend, of a polyester polyol formed by polycondensation of
• (i) at least aromatic dicarboxylic acid, aromatic dicarboxylic anhydride or aromatic dicarboxylic acid diester;
• (ii) a polyol having at least two hydroxyl groups per molecule, or a mixture of two or more such polyols;
• and
• (iii) an epoxy compound having at least one aliphatic oxirane group and at least one straight chain alkyl or alkenyl group having at least six carbon atoms;
• until the carboxylic acid, anhydride or ester groups and the aliphatic oxirane groups are essentially consumed, to produce a polyester polyol having an average hydroxyl functionality of at least 2 hydroxyl groups per molecule, a hydroxyl equivalent weight of 100 to 2000 and at least one straight chain alkyl or alkenyl group having at least six carbon atoms corresponding to the straight chain alkyl or alkenyl group of the epoxy compound.