Process for making polyester polyols having a low acid number

Claim 1

IN A PROCESS FOR THE PREPARATION OF POLYESTER POLYOLS BY THE MELT-CONDENSATION ESTERIFICATION OF A POLYHYDRIC ALCHOL SELECTED FROM THE GROUP CONSISTING OF POLYETHER DIOLS AND POLYESTER DIOLS AND A POLYCARBOXYLIC ACID AT A TEMPERATURE FROM ABOUT 150* TO ABOUT 300*C WHEREIN RESIDUAL AMOUNTS OF ACTIVE CATALYST IS UNDESIRABLE, THE IMPROVEMENT FOR PRODUCING SUCH POLYOLS HAVING AN ACID NUMBER LESS THAN ONE WHICH COMPRISES, CONTINUING THE ESTERIFICATION UNTIL THE PRODUCT HAS AN ACID NUMBER OF 480 OR LESS AND THEN ADDING TO THE ESTERIFICATION MIXTURE OF REACTANTS AND PRODUCT A DISTILLABLE ALCOHOL IN AN AMOUNT OF 0.1 TO 1.4 MOLES PER MOLE OF CARBOXYLIC ACID CHARGED AND CONTAINING THE ESTERIFICATION WHILE SIMULTANEOUSLY DISTILLING OFF THE EXCESS DISTILLABLE ALCHOL UNTIL THE ESTERIFICATION IS COMPLETED, SAID DISTILLABLE ALCOHOL HOL BEING SELECTED FROM THE GROUP CONSISTING OF (A) MONOHYDROXY NORMAL, BRANCHED OR CYCLO ALKYL, ALKENE OR ALKINE ALCOHOLS CONTAINING FROM 1 TO 6 CARBON ATOMS, (B) AROMATIC MONOHYDROXY ALCOHOLS, (C) DIHYDROXY NORMAL, BRANCHED OR CYCLO ALKYL, ALKENE OR ALKINE ALCOHOLS CONTAINING FROM 2 TO 8 CARBON ATOMS DIALKYL ETHER GYCOLS CONTAINING FROM 2 TO 8 CARBON ATOMS IN EACH ALKYL GROUP AND MIXTURES THEREOF, SAID POLYETHER AND POLYESTER DIOLS HAVING A MOLECULAR WEIGHT FROM 200 TO 4500, SAID DISTILLABLE ALCOHOL BEING SAID MONOHYDROXY ALCOHOLS WHEN SAID ACID NUMBER IS LESS THAN 60 PRIOR TO SAID DISTILLABLE ALCOHOL ADDITION AND DIALCOHOLS OR MIXTURES OF DI-AND MONOALCOHOLS WHEN SAID ACID NUMBER IS GREATER THAN 60.