Patent ID: 7902263

Claim:
A process comprising: (a) forming a molten mixture comprising a polyethylene terephthalate component selected from the group consisting of polyethylene terephthalate and polyethylene terephthalate copolymers with a 1,4-butane diol component at a temperature ranging from 180° C. to 230° C.; (b) adding a catalyst component to the molten mixture and depolymerizing the polyethylene terephthalate component, under agitation, at a pressure that is at least atmospheric pressure, under an inert atmosphere, to produce a second molten mixture containing a component selected from the group consisting of oligomers containing ethylene terephthalate moieties, oligomers containing ethylene isophthalate moieties, oligomers containing diethylene terephthalate moieties, oligomers containing diethylene isophthalate moieties, oligomers containing butylene terephthalate moieties, oligomers containing butylene isophthalate moieties, covalently bonded oligomeric moieties containing at least two of the foregoing moieties, 1,4-butane diol, ethylene glycol, tetrahydrofuran, and combinations thereof; (c) agitating the second molten mixture at subatmospheric pressure and increasing the temperature of the second molten mixture to an elevated temperature under conditions sufficient to form a third molten mixture comprising a modified polybutylene terephthalate random copolymer containing at least one residue derived from the polyethylene terephthalate component; wherein the third molten mixture has a melting point from 200° C. to 223° C.; wherein the modified polybutylene terephthalate random copolymer contains from 0.1 to 10 mole % ethylene glycol groups and from 0.1 to 10 mole % diethylene glycol groups, based on the total moles of diol groups in the copolymer, as part of a mixture of ethylene glycol groups, diethylene glycol groups and isophthalic acid groups at an amount ranging from more than 0 equivalents to 23 equivalents, relative to the total of 100 equivalents of diol groups and 100 equivalents of diacid groups in the modified polybutylene terephthalate random copolymer, and from more than 0 ppm to less than 1000 ppm of an inorganic residue selected from the group consisting of antimony-containing compounds, germanium-containing compounds, titanium-containing compounds, cobalt-containing compounds, tin-containing compounds, aluminum, aluminum salts, alkali salts, phosphorous-containing compounds, phosphorous-containing anions, sulfur-containing compounds, sulfur-containing anions, and combinations thereof.