Purification of chloroprene by plural stage distillation and the addition of polymerization inhibitors

Claim 1

IN THE PROCESS FOR ISOLATING AND PURIFYING CRUDE CHLOROPRENE OBTAINED BY REACTING MONOVINYLACETYLENE WITH HYDROGEN CHLORIDE, DEACIDIFIED BY A WATER WASH AND CONTAINING MONOVINYLACETYLENE AND HIGHER IMPURITIES SUCH AS DICHLOROBUTENE, DIMERIC CHLOROPRENE AND METHYLVINYL KETONE, WHICH COMPRISES SEPARATING IN DISTILLATION STAGES CHLOROPRENE FROM SAID IMPURITIES AND SAID MONOVINYLACETYLENE, ALL SEPARATING STAGES BEING CARRIED OUT IN THE PRESENCE OF SUBSTANCES PROHIBITING POLYMERIZATION, THE IMPROVEMENT WHICH CONSISTS ESSENTIALLY OF WITHDRAWING ALL MONOVINYLACETYLENE AT A TEMPERATURE OF 5*C. AND 765 MM. HG AT THE HEAD OF A FIRST DISTILLING STAGE, CONDUCTING THE FIRST STAGE''S SUMP PRODUCT CONSISTING OF CHLOROPRENE AND HIGHER BOILING POINT IMPURITIES TO A SECOND DISTILLATION STAGE, DISTILLING OFF PURE CHLOROPRENE AT A TEMPERATURE OF 60*C. AND 765 MM. HG AT THE HEAD OF SAID SECOND STAGE, THE TEMPERATURES AND CHLOROPRENE PARTIAL PRESSURES IN THE STILLS OF THE FIRST AND SECOND DISTILLATION STAGES BEING BETWEEN ABOUT 60-70*C. AND BETWEEN ABOUT 760 AND 850 MM. HG, RESPECTIVELY, CONDUCTING THE SECOND STAGE''S SUMP PRODUCT CONSISTING OF THE HIGHER BOILING POINT IMPURITIES AND RESIDUAL CHLOROPRENE TO A THIRD DISTILLATION STAGE WHEREIN THE RESIDUAL CHLOROPRENE IS DISTILLED OFF UNDER REDUCED PRESSURE BELOW ABOUT 650 MM. HG AND RECONDUCTED INTO SAID SECOND STAGE, ALL STAGES BEING CARRIED OUT IN THE PRESENCE OF A SUBSTANCE INHIBITING THE A-POLYMERIZATION AND BEING SELECTED FROM THE GROUP CONSISTING OF HYDROQUINONE, PYROCATECHOL AND PHENOTHIAZINE, AND IN THE PRESENCE OF NNITROSODIPHENYLAMINE INHIBITING THE W-POLYMERIZATION.