Stabilization of polypropylene against discoloration

Claim 1

A POLYPROPYLENE COMPOSITION HAVING IMPROVED RESISTANCE TO DISCOLORATION AND EMBRITTLEMENT ON AGING AND HEATING, COMPRISING A PROPYLENE POLYMER AND A SUFFICIENT AMOUNT TO IMPROVE ITS RESISTANCE TO DISCOLORATION AND EMBRITTLEMENT OF A STABILIZER COMBINATION CONSISTING ESSENTIALLY OF FROM ABOUT 0.05 TO ABOUT 1% BASED ON THE WEIGHT OF POLYPROPYLENE OF AN ORGANIC POLYSULFIDE HAVING THE FORMULA R(S)NR, WHEREIN N IS A NUMBER WITHIN THE RANGE FROM ABOUT 2 TO ABOUT 6, AND EACH R IS AN ORGANIC RADICAL HAVING FROM ONE TO ABOUT THIRTY CARBON ATOMS AND IS SELECTED FROM THE GROUP CONSISTING OF ALKYL, ARYL, ALKARYL, ARALKYL, CYCLOALKYL, HETEROCYCLIC, THIURAM, AND CARBOXY RADICALS; FROM ABOUT 0.1 TO ABOUT 2% BASED ON THE WEIGHT OF POLYPROPYLENE OF AN ORGANIC TRIVALENT PHOSPHORUS COMPOUND SELECTED FROM THE GROUP CONSISTING OF PHOSPHITES, (RA)3P, AND PHOSPHINES, R3P, WHEREIN A IS SELECTED FROM THE GROUP CONSISTING OF OXYGEN AND SULFUR, AND THE R RADICALS ARE SELECTED FROM THE GROUP CONSISTING OF ARYL, ALKYL, CYCLOALKYL, ARALKYL AND ALKARYL GROUPS HAVING COLLECTIVELY A TOTAL OF ABOUT FIFTY CARBON ATOMS; AND FROM ABOUT 0.005 TO ABOUT 1% BASED ON THE WEIGHT OF POLYPROPYLENE OF AN ORGANIC PHENOL HAVING UP TO ABOUT FIFTY CARBON ATOMS THE STABILIZER COMBINATION BEING COMPATIBLE WITH THE PROPYLENE POLYMER, AND HAVING A LOW VAPOR PRESSURE AT PROPYLENE POLYMER WORKING TEMPERATURES.