Stabilization of polypropylene against discoloration, embritlement and reduction in melt viscosity

Claim 1

A STABILIZER COMBINATION FOR USE IN IMPROVING RESISTANCE OF POLYPROPYLENE TO DETERIORATION IN PHYSICAL PROPERTIES ON EXPOSURE OF LIGHT AND HEAT, CONSISTING ESSENTIALLY OF (1) A TRANSESTERIFIED REACTION PRODUCT OF AN ORGANIC POLYHYDRIC PHENOL HAVING FROM SIX TO ABOUT FIFTY CARBON ATOMS IS AN AMOUNT OF FROM ABOUT 1 TO ABOUT 20 PARTS BY WEIGHT, AND AN ORGANIC PHOSPHITE TRIESTER FREE FROM PHENOLIC HYDROXYL GROUPS HAVING UP TO ABOUT 60 CARBON ATOMS IN AN AMOUNT OF FROM ABOUT 0.1 TO ABOUT 50 PARTS BY WEIGHT, OBTAINED BY A TRANSESTERIFICATION OF THE PHENOL AND PHOSPHITE AT AN ELEVATED TEMPERATURE SUFFICIENT TO FORM A HOMOGENEOUS MIXTURE AND (2) A SALT OF AN ORGANIC ACID HAVING FROM ABOUT SIX TO ABOUT TWENTY-FOUR CARBON ATOMS AND A METAL OF GROUP II OF THE PERIODIC TABLE IN AN AMOUNT OF FROM ABOUT 0.05 TO ABOUT 30 PARTS BY WEIGHT, SAID STABILIZER BEING COMPATIBLE WITH POLYPROPYLENE AND HAVING A LOW VAPOR PRESSURE AT POLYPROPYLENE WORKING TEMPERATURES.