Methods of depolymerizing terephthalate polyesters

A method, comprising:

• forming a reaction mixture comprising a terephthalate polyester, an amidine organocatalyst, and a glycol in an amount of about 8 to about 16 molar equivalents relative to total moles of terephthalate repeat unit present in the terephthalate polyester, the glycol comprising 2 to 5 carbons, wherein the glycol is a co-catalyst;
• and
• heating the reaction mixture at a temperature in the range of about 120° C. to about 210° C. to depolymerize the terephthalate polyester, thereby forming a terephthalate reaction product comprising a monomeric dihydroxy terephthalate diester in an amount of 90 wt. % or more based on a total weight of the terephthalate reaction product.

A method of preparing bis(2-hydroxyethyl)terephthalate (BHET), comprising:

• forming a reaction mixture comprising poly(ethylene terephthalate) (PET), ethylene glycol in an amount of 4 to about 20 molar equivalents relative to a PET repeat unit, and an amidine organocatalyst;
• and
• heating the reaction mixture at a temperature in the range of about 120° C. to about 210° C. to depolymerize the poly(ethylene terephthalate), thereby producing a terephthalate reaction product comprising bis(2-hydroxyethyl)terephthalate (BHET), wherein the BHET is present in an amount of 94 wt. % to 100 wt. % based on a total weight of the terephthalate reaction product.

A method of preparing bis(4-hydroxybutyl)terephthalate (BHBT), comprising:

• forming a reaction mixture comprising poly(butylene terephthalate) (PBT), an amidine organocatalyst, and 4 to 20 molar equivalents of 1,4-butanediol relative to moles of poly(butylene terephthalate) repeat unit present in the PBT;
• and
• heating the reaction mixture at a temperature in the range of about 120° C. to about 210° C. to depolymerize the poly(butylene terephthalate), thereby forming a terephthalate reaction product comprising bis(4-hydroxybutyl)terephthalate (BHBT).