Process for converting scrap polyester into active prepolymer particles followed by powder build-up to high molecular weights

Claim 1

A PROCESS FOR PREPARING A BUILT-UP LINEAR CONDENSATION POLYESTER OF A GLYCOL HAVING FROM 2 TO 8 CARBON ATOMS AND AN AROMATIC DICARBOXYLIC ACID, SAID BUILT-UP POLYESTER HAVING A MOLECULAR WEIGHT OF AT LEAST 14,000 COMPRISING (I) MIXING THE FOLLOWING CONSTITUENTS UNDER AN INERT ATMOSPHERE AT AN ELEVATED TEMPERATURE (A) ONE MOLE PROPORTION OF SCRAP LINEAR CONDENSATION POLYESTER OF SAID GLYCOL AND SAID AROMATIC DICARBOXYLIC ACID HAVING A MOLECULAR WEIGHT IN THE RANGE OF FROM ABOUT 2,500 TO ABOUT 150,000 SAID MOLES BEING CALCULATED ON THE BASIS OF THE MOLECULAR WEIGHT OF EACH REPEATING UNIT IN SAID SCRAP POLYESTER, SAID SCRAP POLYESTER BEING SUBSTANTIALLY FREE OF SURFACE COATINGS AND WHEN A SOLID, BEING IN THE FORM OF SMALL PIECES HAVING AT LEAST ONE DIMENSION LESS THAN ABOUT 0.2 INCH, (B) FROM ZERO TO ABOUT 10 MOLE PROPORTIONS OF A DIALKYL ESTER OF SAID AROMATIC DICARBOXYLIC ACID, SAID ALKYL RADICALS CONTAINING FROM ABOUT 1 TO 6 CARBON ATOMS, (C) AN AMOUNT BETWEEN ABOUT 0.05 AND ABOUT 25 MOLE PROPORTIONS OF SAID GLYCOL, SAID AMOUNT BEING AT LEAST AS GREAT AS THE AMOUNT OF SAID DIALKYL ESTER, SAID ELEVATED TEMPERATURE BEING IN THE RANGE OF FROM 25*C. LESS THAN, UP TO 50*C. MORE THAN THE BOILING POINT OF SAID GLYCOL, WHEREBY ALL OF SAID SCRAP POLYESTER IS DISSOLVED AND SUBSTANTIALLY ALL OF THE ALKANOL FROM SAID DIALKYL ESTER IS REMOVED, THEREBY RESULTING IN A COMPOSITION COMPOSED OF BIS(GLYCOL) ESTERS OF SAID AROMATIC DICARBOXYLIC ACID AND LOW POLYMERS THEREOF HAVING A DEGREE OF POLYMERIZATION OF LESS THAN ABOUT 10 ON THE AVERAGE, (II) HEATING SAID RESULTING COMPOSITION AND SUBSTANTIALLY COMPLETELY REMOVING THAT PORTION OF SAID GLYCOL VAPORIZED BY SAID HEATING, THEREBY FORMING A PREPOLYMER HAVING A MOLECULAR WEIGHT OF FROM ABOUT 2,500 TO ABOUT 12,000, SAID HEATING BEING PERFORMED UNDER AN INERT ATMOSPHERE WITH AT LEAST THE LATTER PART OF SAID HEATING BEING PERFORMED UNDER A SUBSTANTIAL VACUUM, (III) FORMING SAID PREPOLYMER INTO SOLID PARTICLES OF A SIZE SUBSTANTIALLY PASSING THROUGH A 20-MESH SCREEN, AND (IV) HEATING SAID PARTICLES OF PREPOLYMER WITH AGITATION IN AN INERT ATMOSPHERE, WHEREBY SAID PARTICLES REMAIN SUBSTANTIALLY FREE-FLOWING, AT A TEMPERATURE OF FROM ABOUT 10*C. BELOW, TO ABOUT 90*C. BELOW, THE CRYSTALLINE MELTING POINT OF SAID PREPOLYMER, UNTIL SAID BUILT-UP POLYESTER IS OBTAINED.