Process for making polybutylene terephthalate (PBT) from polyethylene terephthalate (PET)

A composition comprising a modified polybutylene terephthalate random copolymer that (1) is derived from a polyethylene terephthalate component selected from the group consisting of polyethylene terephthalate and polyethylene terephthalate copolymers and (2) at least one residue derived from the polyethylene terephthalate component,

• wherein the modified polybutylene terephthalate random copolymer (i) has an intrinsic viscosity that is more than 0.55 dL/g and a melting temperature that is more than 200° C., and (ii) the at least one residue derived from the polyethylene terephthalate component includes from 0.1 to 10 moles % 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 to 23 equivalents, relative to the total of 100 equivalents of diol 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, alkaline earth metal salts, phosphorous-containing compounds, phosphorous-containing anions, sulfur-containing compounds, sulfur-containing anions, and combinations thereof,
• wherein the modified polybutylene terephthalate is made from a process comprising
• (a) depolymerizing a polyethylene terephthalate component with a 1,4-butane diol component at a temperature ranging from 180° C. to 230° C., under agitation, at a pressure that is at least atmospheric pressure in the presence of a catalyst component, under an inert atmosphere, to produce a molten mixture containing a component selected from the group consisting of ethylene terephthalate oligomers, oligomers containing butylene terephthalate moieties, ethylene isophthalate oligomers, oligomers containing butylene isophthalate moieties, oligomers containing diethylene terephthalate moieties, oligomers containing diethylene glycol isophthalate moieties, oligomers containing butylene, ethylene and diethylene terephthalate moieties, oligomers containing butylene, ethylene and diethylene isophthalate moieties, oligomers containing all butylene, ethylene and diethylene isophthalates and terephthalates, 1,4-butane diol, ethylene glycol, and combinations thereof;
• and
• (b) agitating the molten mixture at subatmospheric pressure and increasing the temperature of the molten mixture to an elevated temperature under conditions sufficient to form the modified polybutylene terephthalate random copolymer,
• wherein a basic compound selected from the group consisting of an alkali metal compound, an alkaline earth metal compound, an aluminum compound and a combination thereof is added to the reactor in step (a) in an amount sufficient to reduce the amount of tetrahydrofuran produced in the process.