Depigmenting alkenyl aromatic polymer compositions by the combined pigmentsettling action of an aliphatic carboxylic acid and a diatomaceous filter aid

Claim 1

PROCESS FOR DEPIGMENTING AN ALKENYL AROMATIC POLYMER COMPOSITION CONTAINING AN INORGANIC PIGMENT THAT IS INSOLUBLE IN ANY ORGANIC, SOLVENT IN WHICH SAID POLYMER COMPOSITION IS DISSOLVED, WHICH PROCESS COMPRISES DISSOLVING A PIGMENTED POLYMERIC COMPOSITION IN AN ORGANIC SOLVENT FOR SAID POLYMER CMPOSITION THAT IS NON-REACTIVE WITH SAID POLYMER AND SAID PIGMENT AND IN WHICH SOLVENT SAID PIGMENT IS INSOLUBLE; INCORPORATING IN THE SOLUTION MINOR PROPORTIONS OF BETWEEN ABOUT 5 AND ABOUT 1/10 PERCENT EACH, BASED ON THE WEIGHT OF THE SOLUTION, OF (1) AN ALIPHATIC MONOCARBOXYLIC ACID THAT CONTAINS NOT MORE THAN 5 CARBONS ATOMS IN ITS MOLECULE AND (2) A DIATOMACEOUS FILTER AID; INTIMATELY MIXING THE ACID AND THE FILTER AID WITH THE SOLUTION TO CAUSE THE PIGMENT TO SETTLE THEREFORM WITH THE FILTER AID IN THE FORM OF LARGE CURDS; SEPARATING THE PIGMENT-CONTAINING FILTER AID FROM THE POLYMER SOLUTION; AND SUBSEQUENTLY RECOVERING THE RECLAIMED AND PURIRIED POLYMER FROM SAID SOLUTION.