Europaisches Patentamt European Patent Office © Publication number: 0 526 572 B1 Office europeen des brevets © EUROPEAN PATENT SPECIFICATION © Date of publication of patent specification: 05.07.95 © Int. CI.6: C07C 31/20, C07C 69/82, C07C 27/02, C07C 67/03 © Application number: 91909232.0 @ Date of filing: 16.04.91 © International application number: PCT/US91/02586 © International publication number: WO 91/16289 (31.10.91 91/25) RECOVERY OF ETHYLENE GLYCOL AND DIMETHYL TEREPHTHALATE FROM POLYETHYLENE TEREPHTHALATE. ® Priority: 24.04.90 US 521070 © Proprietor: EASTMAN KODAK COMPANY (a New Jersey corporation) @ Date of publication of application: 343 State Street 10.02.93 Bulletin 93/06 Rochester, New York 14650 (US) © Publication of the grant of the patent: 05.07.95 Bulletin 95/27 @ Inventor: NAUJOKAS, Andrius, Algimantas 972 Garden Lane © Designated Contracting States: Webster, NY 14580 (US) AT BE CH DE DK ES FR GB GR IT LI LU NL SE Inventor: RYAN, Kevin, Michael 202 Darla Drive © References cited: Brockport, NY 14420 (US) DE-B- 1 247 291 US-A- 3 037 050 US-A- 3 321 510 US-A- 3 488 298 US-A- 3 776 945 US-A- 4 163 860 © Representative: von Hellfeld, Axel, Dr. US-A- 4 578 502 Dipl.-Phys. et al Wuesthoff & Wuesthoff Patent- und Rechtsanwalte Schweigerstrasse 2 00 D-81541 Munchen (DE) CM m CO CM m Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid (Art. 99(1) European patent convention). Rank Xerox (UK) Business Services (3. 10/3.09/3.3.3) 1 EP 0 526 572 B1 2 Description terephthalate by interchange in a substantially an- hydrous methanol medium in the presence of a This invention relates to the recovery of eth- magnesium methylate catalyst. ylene glycol and dimethylterephthalate from scrap U.S. Patent 3,701,741 relates to a method of polyethylene terephthalate polyesters. More par- 5 recovering substantially pure poly- ticularly, it relates to a simplified method of obtain- ethyleneterephthalate) from scrape poly- ing the constituent monomers of polyethylene ethyleneterephthalate) contaminated with impuri- terephthalate from scrap wherein the process is ties by dissolving the contaminated material at ele- practiced under atmospheric conditions without de- vated temperatures and super-atmospheric pres- terioration of the yields. io sure in a volatile solvent. This patent does not relate to the recovery of the monomeric ingredients Description of Related Art that comprise the polymer. U.S. Patent 3,488,298 relates to a process for Various methods have been disclosed here- recovering dimethylterephthalate and ethylene gly- tofore for the recovery of ethylene glycol and 75 col from poly(ethyleneterephthalate) scrap by for- terephthalic acid or derivatives thereof. ming a mixture comprising the poly- U.S. Patent 3,776,945 teaches a process of ethyleneterephthalate) scrape, catalyst and metha- depolymerizing polyethylene terephthalate waste to nol, heating the mixture to approach equilibrium, obtain dimethylterephthalate and ethylene glycol treating the partially hydrolyzed mixture with an by subdividing the waste into dimensions between 20 excess of phosphorus-containing compound, heat- 4 and 35 mesh and treating at a temperature of ing the treated mixture to fractionate the constitu- 100°C to 300 °C and a pressure from 1 to 150 ents and recovering methanol, ethylene glycol and atmospheres with methanol in a quantity that the dimethylterephthalate. proportion of methanol to waste is between 1:1 and It can be seen from the above-recited art that 10:1 by weight in the presence of acid catalysts. 25 many different techniques have been employed in U.S. Patent 3,321,510 relates to a process of the recovery of the monomeric constituents from decomposing polyethyleneterephthalate by first poly(ethyleneterephthalate) resins. treating with steam at a temperature of from about These resins have found wide spread use in 200 °C to 450 °C and then reducing the steam- many and varied applications. For example, poly- treated polyethyleneterephthalate in the form of a 30 (ethyleneterephthalate) polyester resins find appli- brittle solid product to a powder having a mean cations in the preparation of many types of films, particles size of from about 0.0005 to 0.002 mil- including photographic film base, in fibers and in limeters and subsequently atomizing the fine pow- the preparation of food containers such as bottles. der with a gaseous substance including inert gas Thus, there is a widespread need for a simple and and methanol vapor to form an aerosol which is 35 economical method of treating such polyesters to conducted through a reaction zone at a tempera- recover the initial ingredients utilized in the prep- ture of 250 ° C to 300 ° C in the presence of excess aration of the polyester polymers. methanol vapors. U.S. Patent 3,037,050 relates to the recovery of Summary of the Invention terephthalate acid dimethyl ester by treating 40 polyethyleneterephthalate in the form of bulky or The invention provides an improved method (in lumpy solid masses with super-heated methanol particular at atmospheric pressure) of recovering vapor in the presence of any suitable esterification ethylene glycol and dimethylterephthalate from catalyst substantially at atmospheric pressure. polyethyleneterephthalate scrap resins by dissolv- U.S. Patent 4,578,502 relates to a procedure 45 ing the scrap polyester resin in oligomers of the for recovering monomeric polycarboxylic acids and same monomers as present in the scrap, passing polyols from solid scrap polyesters by granulating super-heated methanol through the solution and the scrap resin, slurring the resin with sufficient recovering the ethylene glycol and dimethyltereph- solvents such as water or methanol, depolymeriz- thalate. In the process according to the invention ing the slurried resin by the application of heat and 50 the scrap is heated to a temperature of 20° to pressure for a time sufficient to convert substan- 270 °C during the contact with methanol. The pro- tially all of the resin into its monomeric compo- cess is also advantageous in that the recovered nents, crystallizing the monomeric polycarboxylic dimethylterephthalate add ethylene glycol is freed acid present by flash crystallization and recovering of impurities by this method. Thus, the make up of the polycarboxylic acid and then the polyol by 55 the scrap polyester from which the constituents are distillation. recovered need not be considered prior to the U.S. Patent 4,163,860 relates to a process for recovery procedure and the inventive method is converting a bis-(diol) terephthalate to dimethyl- very satisfactory. For example, the following scrap 2 3 EP 0 526 572 B1 4 sources are available even if they contain large control means may be employed, Fig. 1 depicts a amounts of impurities: container 25 having contents 27 which cane be (1) ground bottle scrap including all the compo- maintained at a suitable constant temperature by nents present, such as, bottle contents, bottle an external heating means (not shown). The con- caps, labels and polyethylene bottom cups; 5 tents 27 may be a salt bath for example. Container (2) subbed film scrap; 25 is provided with a means (not shown) for raising (3) photographic film; and lowering in order that reactor 1 1 can be posi- (4) washed film scrap; tioned relative with respect to the contents 27 of (5) still dregs from polyester recovery plant; and container 25. A reservoir 29 is connected by (6) scrap polyester containing polymers includ- io means of conduit 31 with sparging means 15. Con- ing acetate resins, polyvinyl chloride and the duit 31 has disposed therein pump 33 for de- like. By oligomers of the same monomers is livering the contents of reservoir 29 to sparging meant, that the monomers which form constitu- means 15 via conduit 31. Conduit 31 has asso- ent parts of the oligomer are the same as that of ciated therewith a heating means which in the case the polymer, i.e., ethylene glycol and tereph- is as shown is a length of conduit 31 doubled upon thalic acid or dimethylterephthalate. In accor- itself and disposed within heating medium 27 in dance with Grant and Hacks Chemical Dictio- container 25. Reactor 11 is further provided with nary, Fifth Edition, published by MaGraw-Hill outlet means 35 connected to first distillation de- Book Company, an oligomer is "a polymer vice 37 by conduit 39. Conduit 41 is provided to whose properties change with the addition or 20 return the overheads from distillation device 37 to removal of one or a few repeating units. The reservoir 29. Conduit 43 conveys the higher boilers properties of a true polymer do not change to second distillation device 45. markedly with such modification". In accordance In operation, oligomers of dimethylterephthalate with this invention an oligomer is any low molec- and ethylene glycol are introduced into reactor 11 ular weight polyester polymer of the same con- 25 to at least approximately 50% of the volume of the stituency as that of the scrap material being reactor 11 and agitator 13 and heating means de- employed as the starting component wherein picted as container 25 and contents thereof 27 the scrap polymer will dissolve in the low molec- actuated to bring the temperature of the oligomers ular weight oligomer. The constituent units of to from 220 °C to 270 °C. Scrap feeding means 17 the oligomer used in accordance with this inven- 30 loaded with polyethylene-terephthalate scrap resin tion will repeat "n" times wherein the "n" will is actuated to deliver scrap resin to the contents of vary between 2 and 100 and a molecular range reactor 11.