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CN-122011347-A - Regeneration preparation method of PETG or PCTG copolyester

CN122011347ACN 122011347 ACN122011347 ACN 122011347ACN-122011347-A

Abstract

The invention relates to the technical field of PETG or PCTG copolyester, and discloses a regeneration preparation method of PETG or PCTG copolyester, which comprises the following steps of (1) carrying out esterification reaction on a mixture containing terephthalic acid bis (2-hydroxyethyl) ester, terephthalic acid bis (2-hydroxyethyl) ester dimer and terephthalic acid cyclohexanedimethanol ester and terephthalic acid and cyclohexanedimethanol in the presence of an antioxidant, and (2) carrying out first polycondensation and second polycondensation on esterification reaction products in sequence in the presence of a stabilizer. The invention can directly polymerize and prepare the regenerated PETG (or PCTG) copolyester product by utilizing the catalyst remained in the high-purity monomer obtained by chemical recovery under the condition of no catalyst addition, thereby being environment-friendly, saving the production cost and having good economic benefit.

Inventors

  • HAN LING
  • ZHANG LONGGUI
  • YIN JIE
  • ZHANG XINRU
  • ZHANG WEI
  • REN MINQIAO
  • ZHU GUIXIANG
  • SONG JIANHUI

Assignees

  • 中国石油化工股份有限公司
  • 中石化(北京)化工研究院有限公司

Dates

Publication Date
20260512
Application Date
20241112

Claims (12)

  1. 1. A method for preparing PETG or PCTG copolyester by regeneration, which is characterized by comprising the following steps: (1) Esterifying a mixture comprising bis (2-hydroxyethyl) terephthalate, bis (2-hydroxyethyl) terephthalate dimer, and cyclohexanedimethanol terephthalate with terephthalic acid and cyclohexanedimethanol in the presence of an antioxidant; (2) The esterification reaction product is subjected to first polycondensation and second polycondensation in this order in the presence of a stabilizer.
  2. 2. The process of claim 1 wherein the amount of terephthalic acid is 0.03 to 9 moles and the amount of cyclohexanedimethanol is 0.04 to 9 moles based on the total amount of the materials of the bis (2-hydroxyethyl) terephthalate, the bis (2-hydroxyethyl) terephthalate dimer and the cyclohexanedimethanol terephthalate in the mixture.
  3. 3. The process according to claim 1, wherein the esterification reaction conditions include a temperature of 200 to 260℃and a pressure of normal pressure; And/or the time of the esterification reaction is such that the actual liquid output of the micromolecular product generated by the reaction reaches more than 90wt% of the theoretical liquid output; and/or the esterification reaction is carried out under an inert atmosphere, preferably comprising nitrogen and/or an inert gas.
  4. 4. The method of claim 1, wherein the antioxidant comprises at least one of 4,4' -butylidenebis (6-tert-butyl-3-methylphenol), pentaerythritol tetrakis (3, 5-di-tert-butyl-4-hydroxyhydrocinnamate), n-stearyl 3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate, 3, 5-bis (1, 1-dimethylethyl) -4-hydroxy-phenylpropionate-1, 6-adipyl ester, and triethylene glycol ether-bis (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate; and/or the addition amount of the antioxidant is 10-200ppm of the total weight of the esterification monomer feed.
  5. 5. The method of claim 1, wherein the stabilizer is a phosphorous-containing compound, preferably the stabilizer comprises at least one of triphenyl phosphate, triphenyl phosphite, trimethyl phosphate, trimethyl phosphite, triethyl phosphate, triethyl phosphite, and triethyl phosphate triacetate; And/or the addition amount of the stabilizer is 20-200ppm of the total weight of the esterification reaction monomer feed.
  6. 6. The process according to claim 1, wherein the conditions of the first polycondensation reaction comprise a temperature of 235 to 280℃for a period of 1 to 2 hours and a system pressure of 1000 to 20000Pa; And/or the conditions of the second polycondensation reaction include a temperature of 255 to 285 ℃ for 0.4 to 3 hours, a system pressure of 300Pa or less, preferably 200Pa or less, more preferably 60Pa or less.
  7. 7. The process of claim 1, wherein the mixture comprising bis (2-hydroxyethyl) terephthalate, bis (2-hydroxyethyl) terephthalate dimer, and cyclohexanedimethanol terephthalate is obtained by: (I) Depolymerizing copolyester with the average grain diameter of 0.1-5cm in the presence of a catalyst and a depolymerizing agent to obtain depolymerized liquid containing terephthalic acid bis (2-hydroxyethyl) ester, terephthalic acid bis (2-hydroxyethyl) ester dimer and terephthalic acid cyclohexanedimethanol ester, wherein the copolyester is polyethylene terephthalate-1, 4-cyclohexanedimethanol ester, the water content in the copolyester is less than or equal to 2 wt%, and the catalyst is a titanium-containing catalyst; (II) purifying the product obtained by the depolymerization reaction.
  8. 8. The process of claim 7 wherein the average particle size of the copolyester is 0.1-3cm; And/or the water content of the copolyester is less than or equal to 1 weight percent.
  9. 9. The method of claim 7, wherein the catalyst is at least one of an organo-titanium catalyst, a titanium-silicon complex catalyst, and a titanium-rare earth complex catalyst; and/or the catalyst is used in an amount of 0.1 to 0.5g, preferably 0.1 to 0.3g, per 100g of copolyester; and/or, the depolymerizing agent is ethylene glycol; And/or the weight ratio of depolymerizing agent to copolyester is 2-6:1, preferably 2.5-5:1; and/or the conditions of the depolymerization reaction include a temperature of 190-240 ℃, preferably 200-230 ℃, a pressure of 0.2-0.6MPa, preferably 0.35-0.5MPa, and a time of 1-10 hours, preferably 2.5-5 hours.
  10. 10. The method of claim 7, wherein the purification process comprises the steps of: (a) Carrying out first solid-liquid separation on the depolymerization liquid to obtain first filtrate; (b) Mixing the first filtrate with a diluent, and then performing second solid-liquid separation to obtain a second filtrate; (c) Mixing the second filtrate with activated carbon, and then performing third solid-liquid separation to obtain a third filtrate; (d) The third filtrate is crystallized and dried to obtain a mixture containing bis (2-hydroxyethyl) terephthalate, bis (2-hydroxyethyl) terephthalate dimer and cyclohexanedimethanol terephthalate.
  11. 11. The method of claim 10, wherein the first solid-liquid separation is performed at 80-105 ℃; and/or the diluent is water, preferably deionized water, the weight ratio of the depolymerization liquid to the diluent is 1:1-10, more preferably 1:2-5, and the condition of mixing the first filtrate with the diluent comprises the temperature of 70-90 ℃ and the time of 1-3h.
  12. 12. The process according to claim 10 or 11, wherein the amount of activated carbon is 1-10g per 100g of copolyester, and the condition of mixing the second filtrate with activated carbon comprises a temperature of 70-90 ℃ for 0.1-2h; and/or the crystallization conditions comprise a temperature of 2-10 ℃ and a time of 4-12h; And/or the drying conditions comprise a temperature of 50-90 ℃ and a time of 1-3h.

Description

Regeneration preparation method of PETG or PCTG copolyester Technical Field The invention relates to the technical field of PETG or PCTG copolyester, in particular to a regeneration preparation method of PETG or PCTG copolyester. Background The PETG or PCTG copolyester is a copolyester formed by copolymerizing terephthalic acid (PTA), ethylene Glycol (EG) and 1, 4-Cyclohexanedimethanol (CHDM) serving as monomers, is totally called ethylene terephthalate-1, 4-cyclohexanedimethanol ester, and compared with ethylene terephthalate (PET), the PETG or PCTG copolyester is characterized in that 1, 4-Cyclohexanedimethanol (CHDM) is randomly inserted into a high molecular chain, so that the regular arrangement of the molecular chain is hindered, the crystallinity is obviously reduced, and the amorphous form is finally presented. The copolyester with CHDM content less than 50% is called PETG copolyester, and the copolyester with CHDM content greater than 50% is called PCTG copolyester. By regulating the ratio of CHDM to EG, PETG or PCTG copolyester can have different properties. The PETG copolyester has high transparency, excellent impact resistance and toughness, excellent processing and forming properties, no whitening after cold bending, no crack, easy printing and modification, and is widely applied to plates, sheets, shrink films, bottles, profiles and the like with high transparency requirements. PETG's secondary processability is excellent, can adopt multiple shaping methods such as injection molding, extrusion, mould pressing, blowing, plastic uptake to process, and the usage is extensive. Because PETG copolyester cannot be biodegraded, the physical method recycling means can only degrade and recycle, the operation is simple, but the regenerated polyester product with stable performance cannot be obtained, and the performance requirement cannot be met after multiple times of circulation. Disclosure of Invention The invention aims to overcome the defects that a regenerated PETG or PCTG copolyester product with stable performance cannot be obtained by a physical recovery means in the prior art, and the regenerated product has poor performance, and provides a regeneration preparation method of the PETG or PCTG copolyester. In order to achieve the above object, the present invention provides a method for the regenerative preparation of PETG or PCTG copolyester, comprising the steps of: (1) Esterifying a mixture comprising bis (2-hydroxyethyl) terephthalate, bis (2-hydroxyethyl) terephthalate dimer, and cyclohexanedimethanol terephthalate with terephthalic acid and cyclohexanedimethanol in the presence of an antioxidant; (2) The esterification reaction product is subjected to first polycondensation and second polycondensation in this order in the presence of a stabilizer. Through the technical scheme, the invention has at least the following beneficial effects: The invention can directly polymerize and prepare the regenerated PETG (or PCTG) copolyester product by utilizing the catalyst remained in the high-purity monomer obtained by chemical recovery under the condition of no catalyst addition, thereby being environment-friendly, saving the production cost and having good economic benefit. Detailed Description The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein. The invention provides a regeneration preparation method of PETG or PCTG copolyester, which comprises the following steps: (1) Esterifying a mixture comprising bis (2-hydroxyethyl) terephthalate, bis (2-hydroxyethyl) terephthalate dimer, and cyclohexanedimethanol terephthalate with terephthalic acid and cyclohexanedimethanol in the presence of an antioxidant; (2) The esterification reaction product is subjected to first polycondensation and second polycondensation in this order in the presence of a stabilizer. According to the present invention, preferably, the amount of terephthalic acid is 0.03 to 9mol and the amount of cyclohexanedimethanol is 0.04 to 9mol based on the total amount of the materials of the bis (2-hydroxyethyl) terephthalate, the bis (2-hydroxyethyl) terephthalate dimer and the cyclohexanedimethanol terephthalate in the mixture. According to the present invention, it is preferable that the esterification reaction conditions include a temperature of 200 to 260℃and a pressure of normal pressure. According to the present invention, it is preferable that the esterification reaction is carried out for such a time that the actual liquid output of the small molecule product produced by the reaction reaches 90wt% or more (e