Polyester polyols containing secondary alcohol groups and their use in making polyurethanes such as flexible polyurethane foams

A copolyester which is a liquid at 50° C., having (a) an initiator segment which is the residue after removal of hydroxyl and amino hydrogen atoms from an initiator compound other than glycerine that has at least two hydroxyl, primary amino or secondary amino groups, and (b) an average of at least three ester units per copolyester molecule derived from a hydroxyl-containing fatty acid having 7 or more carbon atoms or mixture of two or more of said fatty acids, wherein at least a portion of the hydroxyl-containing fatty acids are secondary hydroxyl-containing fatty acids which contain a secondary hydroxyl group which is at least 5 carbon atoms removed from the carbonyl carbon of the acid group of the fatty acid, wherein the copolyester contains from 3.5 to 10 ester units per copolyester molecule derived from the hydroxyl-containing fatty acid, from about 5 to about 95% of the ester units in the copolyester are derived from the secondary hydroxyl-containing fatty acid and a portion of the ester units are derived from a primary hydroxyl-containing fatty acid.