# US 8,541,477 B2 · Methods of depolymerizing terephthalate polyesters > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,541,477 B2 - Document ID: US8541477B2 - Status: Granted - Kind: B2 - Application number: 13/040,550 - Filed: 2011-03-04 - Published: 2012-09-06 - Granted: 2013-09-24 - Earliest claimed: 2011-03-04 - Assignees: International Business Machines Corporation; King Abdulaziz City for Science and Technology - Applicants: Abdullah M Alabdulrahman; Hamid A Almegren; Fares D Alsewailem; Phillip Joe Brock; Daniel Joseph Coady; Kazuki Fukushima; James Lupton Hedrick; Hans Werner Horn; Julia Elizabeth Rice - Inventors: Abdullah M Alabdulrahman; Hamid A Almegren; Fares D Alsewailem; Phillip Joe Brock; Daniel Joseph Coady; Kazuki Fukushima; James Lupton Hedrick; Hans Werner Horn; Julia Elizabeth Rice - Web page: https://patentgrep.com/patent/US8541477B2 ## CPC - C07C 67/03: by reacting an ester group with a hydroxy group - C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS ## Abstract A method comprises forming a reaction mixture comprising a terephthalate polyester, a glycol comprising 2 to 5 carbons, and an amidine organocatalyst; and heating the reaction mixture at a temperature of about 120° C. or more to depolymerize the terephthalate polyester, thereby forming a terephthalate reaction product comprising a monomeric dihydroxy terephthalate diester; wherein the terephthalate reaction product contains terephthalate oligomers in an amount less than the amount of terephthalate oligomers that would result from i) substituting the amidine organocatalyst with an equimolar amount of a guanidine catalyst and ii) depolymerizing the terephthalate polyester under otherwise identical reaction conditions. ## Claims ### Claim 1 A method, comprising: forming a reaction mixture comprising a terephthalate polyester, a glycol comprising 2 to 5 carbons, and an amidine organocatalyst; and heating the reaction mixture at a temperature of about 120° C. or more to depolymerize the terephthalate polyester, thereby forming a terephthalate reaction product comprising a monomeric dihydroxy terephthalate diester; wherein the terephthalate reaction product contains terephthalate oligomers in an amount less than the amount of terephthalate oligomers that would result from i) substituting the amidine organocatalyst with an equimolar amount of a guanidine catalyst and ii) depolymerizing the terephthalate polyester under otherwise identical reaction conditions. ### Claim 2 (depends on 1) The method of claim 1, wherein the glycol is present in an amount of about 4 to about 20 molar equivalents relative to total moles of terephthalate repeat unit present in the terephthalate polyester. ### Claim 3 (depends on 1) The method of claim 1, wherein the glycol is present in an amount of about 8 to about 16 molar equivalents relative to total moles of terephthalate repeat unit present in the terephthalate polyester. ### Claim 4 (depends on 1) The method of claim 1, wherein the terephthalate reaction product comprises 90 wt. % or more of monomeric dihydroxy terephthalate diester, based on total weight of the terephthalate reaction product. ### Claim 5 (depends on 1) The method of claim 1, wherein the glycol is a co-catalyst. ### Claim 6 (depends on 1) The method of claim 1, wherein the terephthalate polyester is post-consumer poly(ethylene terephthalate) (PET). ### Claim 7 (depends on 1) The method of claim 1, wherein the terephthalate polyester is post-consumer poly(butylene terephthalate) (PBT). ### Claim 8 (depends on 1) The method of claim 1, wherein the reaction mixture is heated at a temperature in the range of about 120° C. to about 190° C. ### Claim 9 (depends on 1) The method of claim 1, wherein the reaction mixture is heated at a temperature in the range of about 130° C. to about 180° C. ### Claim 10 (depends on 1) The method of claim 1, wherein the amidine catalyst is present in an amount of 0.001 to 0.1 molar equivalents relative to total moles of terephthalate repeat unit present in the terephthalate polyester. ### Claim 11 (depends on 1) The method of claim 1, wherein the glycol is selected from the group consisting of ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol. ### Claim 12 (depends on 1) The method of claim 1, wherein the terephthalate polyester is poly(ethylene terephthalate) (PET), the glycol is ethylene glycol, and the dihydroxy terephthalate diester is bis(2-hydroxyethyl)terephthalate (BHET). ### Claim 13 (depends on 1) The method of claim 1, wherein the terephthalate polyester is poly(butylene terephthalate) (PBT), the glycol is 1,4-butanediol, and the dihydroxy terephthalate diester is bis(4-hydroxybutyl)terephthalate (BHBT). ### Claim 14 (depends on 1) The method of claim 1, wherein the amidine catalyst is selected from the group consisting of 1,8-diazabicycloundec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), polymer supported DBU, polymer supported DBN, and combinations thereof. ### Claim 15 (depends on 1) The method of claim 1, wherein a chemical formula of the amidine organocatalyst does not contain any metal selected from the group consisting of beryllium, magnesium, calcium, strontium, barium, radium, aluminum, gallium, indium, thallium, germanium, tin, lead, arsenic, antimony, bismuth, tellurium, polonium, and metals of Groups 3 to 12 of the Periodic Table. ### Claim 16 (depends on 1) The method of claim 1, wherein an organic acid is included in the reaction mixture before depolymerizing the terephthalate polyester. ### Claim 17 (depends on 16) The method of claim 16, wherein the organic acid is present in an amount of 0.1 to 10 molar equivalents relative to moles of the amidine base. ### Claim 18 (depends on 16) The method of claim 16, wherein the organic acid is terephthalic acid. ### Claim 19 (depends on 1) The method of claim 1, further comprising i) cooling the reaction mixture after the depolymerization and ii) isolating the dihydroxy terephthalate diester by direct filtration. ### Claim 20 (depends on 1) The method of claim 1, wherein the amidine organocatalyst is a pre-formed amidine salt organocatalyst comprising an amidine base and an organic acid. ### Claim 21 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. ### Claim 22 (depends on 21) The method of claim 21, wherein an organic acid is included in the reaction mixture before depolymerizing the terephthalate polyester. ### Claim 23 (depends on 21) The method of claim 21, wherein the amidine organocatalyst is a pre-formed amidine salt organocatalyst comprising an amidine base and an organic acid. ### Claim 24 (depends on 21) The method of claim 21, wherein the glycol is present in an amount of about 8 to about 16 molar equivalents relative to the terephthalate repeat unit and the terephthalate reaction product contains less than about 10 wt. % of terephthalate oligomers based on a total weight of the terephthalate reaction product. ### Claim 25 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. ### Claim 26 (depends on 25) The method of claim 25, wherein an organic acid is included in the reaction mixture before depolymerizing the poly(ethylene terephthalate), and the terephthalate reaction product comprises the BHET in an amount of 96 wt. % to 100 wt. % based on a total weight of the terephthalate reaction product. ### Claim 27 (depends on 25) The method of claim 25, wherein the amidine organocatalyst is a pre-formed amidine salt organocatalyst comprising an amidine base and an organic acid, and the terephthalate reaction product comprises the BHET in an amount of 96 wt. % to 100 wt. % based on a total weight of the terephthalate reaction product. ### Claim 28 (depends on 25) The method of claim 25, wherein the ethylene glycol is present in an amount of about 8 to about 16 molar equivalents relative to moles of the poly(ethylene terephthalate) (PET) repeat unit. ### Claim 29 (depends on 25) The method of claim 25, wherein the poly(ethylene terephthalate) is post-consumer poly(ethylene terephthalate). ### Claim 30 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). ### Claim 31 (depends on 30) The method of claim 30, wherein an organic acid is included in the reaction mixture before depolymerizing the poly(butylene terephthalate). ### Claim 32 (depends on 30) The method of claim 30, wherein the amidine organocatalyst is a pre-formed amidine salt organocatalyst comprising an amidine base and an organic acid. ### Claim 33 (depends on 30) The method of claim 30, wherein the 1,4-butanediol is present in an amount of about 8 to about 16 molar equivalents relative to moles of the poly(butylene terephthalate) repeat unit and the terephthalate reaction product comprises 90 wt. % or more of bis(4-hydroxybutyl)terephthalate (BHBT) based on a total weight of the terephthalate reaction product. ### Claim 34 (depends on 30) The method of claim 30, wherein the poly(butylene terephthalate) is post-consumer poly(butylene terephthalate). ### Claim 35 (depends on 1) The method of claim 1, wherein the amidine organocatalyst is 1,8-diazabicycloundec-7-ene (DBU). ### Claim 36 (depends on 21) The method of claim 21, wherein the amidine organocatalyst is 1,8-diazabicycloundec-7-ene (DBU). ### Claim 37 (depends on 25) The method of claim 25, wherein the amidine organocatalyst is 1,8-diazabicycloundec-7-ene (DBU). ### Claim 38 (depends on 30) The method of claim 30, wherein the amidine organocatalyst is 1,8-diazabicycloundec-7-ene (DBU).