Oil compositions containing stabilized copolymer ester-type pour point depressants

Claim 1

A MINERAL LUBRICATING OIL CONTAINING (A) A MINOR AMOUNT, SUFFICIENT TO IMPROVE THE DETERGENT CHARACTER OF SAID OIL, OF A BASIC METAL SULFONATE AND (B) A MINOR AMOUNT, SUFFICIENT TO DEPRESS THE POUR POINT OF SAID OIL OF AN ESTERIFIED COPOLYMER WHICH HAS BEEN STABILIZED AGAINST THE DELETERIOUS EFFECT NORMALLY EXERTED ON SAID ESTERIFIED COPOLYMER BY THE BASIC METAL SULFONATE IN THE OIL, WHICH EFFECT REDUCES THE ABILITY OF SAID ESTERIFIED COPOLYMER TO LOWER THE POUR POINT OF SAID OIL; SAID ESTERIFIED COPOLYMER HAVING BEEN FORMED BY REACTING A VINYL COMPOUND, SELECTED FROM THE GROUP CONSISTING OF STYRENE, 1-OLEFINS, VINYL ESTERS AND VINYL ETHERS, WITH MALEIC ANHYDRIDE IN ABOUT EQUIMOLAR QUANTITIES AND THEN ESTERIFYING THE COPOLYMER THUS FORMED WITH AN ALCOHOL MATERIAL SELECTED FROM THE GROUP CONSISTING OF PRIMARY, NORMAL, SATURATED, ALIPHATIC ALCOHOLS HAVING FROM 12 TO 14 CARBON ATOMS AND A MIXTURE OF PRIMARY, NORMAL, SATURATED ALIPHATIC ALCOHOLS HAVING FROM 10 TO 18 CARBON ATOMS AND AN AVERAGE OF FROM 12 TO 14 CARBON ATOMS PER MOLECULE; SAID ESTERIFIED COPOLYMER HAVING BEEN STABILIZED BY REACTION OF SAID ESTERIFIED COPOLYMER WITH FROM ABOUT 1 TO ABOUT 10 PER CENT BY WEIGHT OF A PRIMARY AMINE AT A TEMPERATURE OF FROM ABOUT 125* C. TO ABOUT 200* C., FOR A PERIOD OF FROM ABOUT 1 TO ABOUT 5 HOURS.