Manufacture of lubricating oils

Claim 1

IN A DEWAXING PROCESS IN WHICH A LUBRICATING OIL STOCK IS PARTIALLY DEWAXED IN A FIRST DEWAXING STEP AND THEN THE PARTIALLY DEWAXED OILS IS DEWAXED IN A SECOND DEWAXING GROUP COMPRISING ADMIXING THE PARTIALLY DEWAXED OIL WITH UREA AT A TEMPERATURE IN THE RANGE OF 0 TO 100*F. TO FORM A PRECIPITATED UREA-HYDROCARBON COMPLEX, SEPARATING SAID COMPLEX FROM THE LAST SAID ADMIXTURE AND RECOVERING AN OIL HAVING A LOW POUR-POINT , THE IMPROVEMENT WHICH COMPRISES CONDUCTING SAID FIRST DEWAXING STEP BY FORMING AN ADMIXTURE OF SAID LUBRICATING OIL STOCK WITH METHYL ISOBUTYL KETONE AND WITH LIQUID PROPANE, SAID ADMIXTURE HAVING A VOLUME RATIO OF SAID OIL STOCK TO SAID KETONE WITHIN THE LIMITS OF 0.20:1 TO 1:1 AND A VOLUME RATIO OF SAID PROPANE TO SAID KETONE WITHIN THE LIMITS OF 1:1 TO 5:1, CHILLING THE RESULTING ADMIXTURE TO A SUBATMOSPHERIC TEMPERATURE WITHIN THE RANGE OF 0 TO -60* F. BY VAPORIZING PROPANE THEREFROM SO AS TO THEREBY PRECIPITATE WAX FROM THE OIL COMPONENT TO PARTIALLY DEWAX SAID OIL, AND SEPARATING THE PRECIPITATED WAX FROM SAID ADMIXTURE.