CN117794892A - Diethylene glycol terephthalate and preparation method thereof - Google Patents
Diethylene glycol terephthalate and preparation method thereof Download PDFInfo
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- CN117794892A CN117794892A CN202380012957.5A CN202380012957A CN117794892A CN 117794892 A CN117794892 A CN 117794892A CN 202380012957 A CN202380012957 A CN 202380012957A CN 117794892 A CN117794892 A CN 117794892A
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- diethylene glycol
- glycol terephthalate
- activated carbon
- polyester
- aqueous solution
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- SLGGJMDAZSEJNG-UHFFFAOYSA-N 2-(2-hydroxyethoxy)ethanol;terephthalic acid Chemical compound OCCOCCO.OC(=O)C1=CC=C(C(O)=O)C=C1 SLGGJMDAZSEJNG-UHFFFAOYSA-N 0.000 title claims abstract description 106
- 238000002360 preparation method Methods 0.000 title claims abstract description 23
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 78
- 229920000728 polyester Polymers 0.000 claims abstract description 52
- 238000001816 cooling Methods 0.000 claims abstract description 39
- 239000007864 aqueous solution Substances 0.000 claims abstract description 26
- 239000000706 filtrate Substances 0.000 claims abstract description 23
- 238000001179 sorption measurement Methods 0.000 claims abstract description 18
- 238000006136 alcoholysis reaction Methods 0.000 claims abstract description 17
- 238000001914 filtration Methods 0.000 claims abstract description 16
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 claims description 61
- 238000000034 method Methods 0.000 claims description 15
- MIDXCONKKJTLDX-UHFFFAOYSA-N 3,5-dimethylcyclopentane-1,2-dione Chemical compound CC1CC(C)C(=O)C1=O MIDXCONKKJTLDX-UHFFFAOYSA-N 0.000 claims description 12
- 235000013736 caramel Nutrition 0.000 claims description 12
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 10
- 239000002253 acid Substances 0.000 claims description 9
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 8
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 4
- 229910017604 nitric acid Inorganic materials 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 abstract description 20
- 238000001035 drying Methods 0.000 abstract description 6
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 30
- -1 ion modified activated carbon Chemical class 0.000 description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 11
- 239000012535 impurity Substances 0.000 description 10
- 230000000694 effects Effects 0.000 description 9
- 239000000047 product Substances 0.000 description 9
- 239000000243 solution Substances 0.000 description 9
- 238000012360 testing method Methods 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 8
- 229910052799 carbon Inorganic materials 0.000 description 7
- QPKOBORKPHRBPS-UHFFFAOYSA-N bis(2-hydroxyethyl) terephthalate Chemical compound OCCOC(=O)C1=CC=C(C(=O)OCCO)C=C1 QPKOBORKPHRBPS-UHFFFAOYSA-N 0.000 description 5
- 239000000975 dye Substances 0.000 description 5
- 239000000049 pigment Substances 0.000 description 5
- 239000011148 porous material Substances 0.000 description 5
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 4
- ADCOVFLJGNWWNZ-UHFFFAOYSA-N antimony trioxide Chemical compound O=[Sb]O[Sb]=O ADCOVFLJGNWWNZ-UHFFFAOYSA-N 0.000 description 4
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 4
- 238000004042 decolorization Methods 0.000 description 4
- 239000000835 fiber Substances 0.000 description 4
- 239000011259 mixed solution Substances 0.000 description 4
- 229920000642 polymer Polymers 0.000 description 4
- 229920002635 polyurethane Polymers 0.000 description 4
- 239000004814 polyurethane Substances 0.000 description 4
- 238000004064 recycling Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 239000000654 additive Substances 0.000 description 3
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 3
- 239000012043 crude product Substances 0.000 description 3
- 238000004090 dissolution Methods 0.000 description 3
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 3
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 3
- 238000000746 purification Methods 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- HZAXFHJVJLSVMW-UHFFFAOYSA-N 2-Aminoethan-1-ol Chemical compound NCCO HZAXFHJVJLSVMW-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 239000000940 FEMA 2235 Substances 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- WNLRTRBMVRJNCN-UHFFFAOYSA-N adipic acid Chemical compound OC(=O)CCCCC(O)=O WNLRTRBMVRJNCN-UHFFFAOYSA-N 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 230000032050 esterification Effects 0.000 description 2
- 238000005886 esterification reaction Methods 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 239000012760 heat stabilizer Substances 0.000 description 2
- NAQMVNRVTILPCV-UHFFFAOYSA-N hexane-1,6-diamine Chemical compound NCCCCCCN NAQMVNRVTILPCV-UHFFFAOYSA-N 0.000 description 2
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000000178 monomer Substances 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- 238000006068 polycondensation reaction Methods 0.000 description 2
- 238000006116 polymerization reaction Methods 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- 239000004408 titanium dioxide Substances 0.000 description 2
- WVLBCYQITXONBZ-UHFFFAOYSA-N trimethyl phosphate Chemical compound COP(=O)(OC)OC WVLBCYQITXONBZ-UHFFFAOYSA-N 0.000 description 2
- FEWJPZIEWOKRBE-JCYAYHJZSA-N Dextrotartaric acid Chemical compound OC(=O)[C@H](O)[C@@H](O)C(O)=O FEWJPZIEWOKRBE-JCYAYHJZSA-N 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- FEWJPZIEWOKRBE-UHFFFAOYSA-N Tartaric acid Natural products [H+].[H+].[O-]C(=O)C(O)C(O)C([O-])=O FEWJPZIEWOKRBE-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000001361 adipic acid Substances 0.000 description 1
- 235000011037 adipic acid Nutrition 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 150000001412 amines Chemical class 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004040 coloring Methods 0.000 description 1
- 238000004440 column chromatography Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000002845 discoloration Methods 0.000 description 1
- 238000004821 distillation Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000010812 external standard method Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000010813 internal standard method Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 239000004310 lactic acid Substances 0.000 description 1
- 235000014655 lactic acid Nutrition 0.000 description 1
- 229920002521 macromolecule Polymers 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000009958 sewing Methods 0.000 description 1
- 239000000741 silica gel Substances 0.000 description 1
- 229910002027 silica gel Inorganic materials 0.000 description 1
- 239000011975 tartaric acid Substances 0.000 description 1
- 235000002906 tartaric acid Nutrition 0.000 description 1
- 239000004753 textile Substances 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/48—Separation; Purification; Stabilisation; Use of additives
- C07C67/52—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
- C08G63/12—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from polycarboxylic acids and polyhydroxy compounds
- C08G63/16—Dicarboxylic acids and dihydroxy compounds
- C08G63/18—Dicarboxylic acids and dihydroxy compounds the acids or hydroxy compounds containing carbocyclic rings
- C08G63/181—Acids containing aromatic rings
- C08G63/183—Terephthalic acids
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J11/00—Recovery or working-up of waste materials
- C08J11/04—Recovery or working-up of waste materials of polymers
- C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
- C08J11/18—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with organic material
- C08J11/22—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with organic material by treatment with organic oxygen-containing compounds
- C08J11/24—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with organic material by treatment with organic oxygen-containing compounds containing hydroxyl groups
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C69/00—Esters of carboxylic acids; Esters of carbonic or haloformic acids
- C07C69/76—Esters of carboxylic acids having a carboxyl group bound to a carbon atom of a six-membered aromatic ring
- C07C69/80—Phthalic acid esters
- C07C69/82—Terephthalic acid esters
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/62—Plastics recycling; Rubber recycling
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Crystallography & Structural Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Sustainable Development (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention discloses a diethylene glycol terephthalate and a preparation method thereof, which mainly comprises the steps of conducting alcoholysis on recycled polyester to obtain a diethylene glycol terephthalate aqueous solution, heating the aqueous solution, adding activated carbon for adsorption, filtering to remove the activated carbon to obtain filtrate, cooling the filtrate to 2-10 ℃ for 1.0-5.0 h, crystallizing, filtering and drying to obtain purified diethylene glycol terephthalate with the N element content below 500 ppm. The polyester further prepared from the diethylene glycol terephthalate has good color tone and heat resistance.
Description
The invention relates to diethylene glycol terephthalate and a preparation method thereof, in particular to diethylene glycol terephthalate with low foreign matter content and a preparation method thereof, wherein the diethylene glycol terephthalate is obtained by alcoholysis of recycled polyester.
Polyester (PET) is one of the most commonly used polymers at present, however, its recycling is a great concern for environmental protection due to the non-biodegradability of PET. Ethylene glycol alcoholysis is a widely used chemical recovery method for polyesters in industry and academia, i.e., the recovered PET is degraded into monomer molecules or oligomers by using excess ethylene glycol under certain conditions, and then the monomer molecules or oligomers are prepared into various polymers with application value. However, researches show that the color and purity of the polyester alcoholysis product are affected by the dyes, pigments and the like contained in the recycled polyester product, so that the recycling of the polyester alcoholysis product is limited.
Chinese patent CN109574835a discloses a method for decolorizing polyester alcoholysis product BHET with ion modified activated carbon. Although this method can improve the color of BHET, the preparation cost increases due to the need to prepare ion-modified activated carbon in the early stage. Meanwhile, ions are easy to separate from the activated carbon into the BHET in the use process, new foreign matters are generated, the cyclic utilization of polyester alcoholysis products is limited, the adsorption capacity of the ion modified activated carbon is weakened, and the purification effect is reduced.
The invention aims to provide diethylene glycol terephthalate obtained by alcoholysis of recycled polyester and a preparation method thereof. The content of N element in the diethylene glycol terephthalate is low, and polyester prepared from the diethylene glycol terephthalate has good color tone and heat resistance.
The technical scheme of the invention is as follows: and (3) diethylene glycol terephthalate which is obtained by alcoholysis of recycled polyester, wherein the content of N element in the diethylene glycol terephthalate is below 500 ppm.
The diethylene glycol content in the diethylene glycol terephthalate is preferably 0.5wt% or less, more preferably 0.2wt% or less.
The invention also discloses a preparation method of the diethylene glycol terephthalate, which comprises the steps of preparing an aqueous solution from recycled polyester through alcoholysis to obtain the diethylene glycol terephthalate, heating, adding activated carbon for adsorption, filtering to remove the activated carbon to obtain filtrate, and finally cooling, crystallizing, filtering and drying the filtrate to obtain the purified diethylene glycol terephthalate. The final cooling temperature of the filtrate is 2-10 ℃, and the cooling time is 1.0-5.0 h.
Before the activated carbon adsorption treatment, an acid is preferably added to the aqueous solution of diethylene glycol terephthalate so that the pH of the aqueous solution of diethylene glycol terephthalate is preferably 7.O or less.
The acid is preferably one or more of hydrochloric acid, sulfuric acid and nitric acid.
The caramel discoloration rate of the activated carbon is preferably 20% or more, more preferably 30 to 80%.
According to the invention, the diethylene glycol terephthalate obtained by alcoholysis of the recycled polyester is subjected to filtration treatment by using the activated carbon, so that the content of N element in the diethylene glycol terephthalate is low, and the polyester further prepared from the diethylene glycol terephthalate has good color tone and heat resistance.
The polyester articles available for recycling in the prior art are of a wide variety including waste textiles, waste rags from sewing plants, bottle flakes, waste silk, and the like.
One of the methods for chemically recycling polyesters is to depolymerize recycled polyesters into single molecules or oligomers, and various additives can be added to the depolymerized products by the method, so that the prepared polyesters are diversified, and the method has the advantages of simple production process and small equipment investment. However, since the recycled polyester often contains impurities such as dyes, pigments, polyurethane, etc., and alkylene glycol dimers that are brought about during the depolymerization process, these limit reuse of the recycled polyester alcoholysis product, and make the polyester produced therefrom poor in color tone and heat resistance.
The content of N element and diethylene glycol (DEG) in the diethylene glycol terephthalate (BHET) obtained by alcoholysis of the recycled polyester is low, and particularly the content of N element is below 500 ppm. When the N element is more than 500ppm, the impurities derived from the N element become large, which results in deterioration of the color tone and heat resistance of the polyester produced from the BHET, and deterioration of the color tone and strength of the polyester product such as fiber and the like. Meanwhile, diethylene glycol also affects the heat resistance of the polyester, and if the diethylene glycol content is high, the regularity of the polyester is poor, the creep irreversible part of the polyester product such as fiber is increased in the later period, the shrinkage rate of the fiber is increased, and the application of the fiber to clothing is affected. Therefore, in the present invention, the diethylene glycol content in the diethylene glycol terephthalate is preferably 0.5% or less wtr%, more preferably 0.2% or less by weight.
The preparation method of the diethylene glycol terephthalate comprises the steps of alcoholysis of recycled polyester, heating of the obtained mixed solution of the diethylene glycol terephthalate and water, adsorption by activated carbon, filtration and removal of the activated carbon to obtain filtrate, cooling and crystallization of the filtrate, filtration and drying to obtain the purified diethylene glycol terephthalate.
During alcoholysis, the recycled polyester and the excessive glycol are mixed and depolymerized at 150-250 ℃, the mixed solution of the diethylene glycol terephthalate and the glycol is obtained after the depolymerization, and the glycol is removed by reduced pressure distillation at 80-150 ℃ to obtain the primary diethylene glycol terephthalate. After adding water into the solution, heating to 60-100 ℃, heating, dissolving, filtering and recrystallizing to obtain crude product of the diethylene glycol terephthalate.
The concentration of the aqueous solution of diethylene glycol terephthalate is not particularly limited, and may preferably be 10 to 50wt% from the viewpoint of convenience of handling. When the aqueous solution is heated, the heating temperature is not particularly limited, and those skilled in the art can appropriately adjust the heating temperature according to the treatment effect. In view of the fact that the temperature of the aqueous solution should be favorable for dissolution of diethylene glycol terephthalate and prevention of dissolution of foreign matters, thereby contributing to improvement of purification effect, the heating temperature is preferably 60 to 100 ℃, and more preferably 80 to 90 ℃ because the temperature is increased to facilitate adsorption of activated carbon.
After the temperature of the diethylene glycol terephthalate aqueous solution is raised, adding active carbon into the diethylene glycol terephthalate aqueous solution, wherein the weight ratio of the addition amount of the active carbon to the diethylene glycol terephthalate is preferably 0.1-2.0: 1, which is more advantageous for the absorption of foreign matters. The adsorption treatment time of the activated carbon is not particularly limited, and a person skilled in the art can reasonably adjust the adsorption treatment time according to the treatment effect, and the general treatment time is 0.5-5.0 h.
After the adsorption treatment is finished, filtering an aqueous solution of the diethylene glycol terephthalate and the activated carbon to remove the activated carbon to obtain a filtrate, and then cooling, crystallizing, filtering and drying the filtrate to obtain the purified diethylene glycol terephthalate. The effect of separating the diethylene glycol terephthalate from impurities in the diethylene glycol terephthalate can be effectively achieved by controlling the final cooling temperature of the filtrate and the cooling time, and the purity and the production efficiency of the diethylene glycol terephthalate are improved. The final cooling temperature of the filtrate is 2-10 ℃, and when the final cooling temperature is higher than 10 ℃, the precipitation of the diethylene glycol terephthalate is not facilitated, and the yield is reduced; when the final cooling temperature is lower than 2 ℃, the foreign matters in the filtrate are also partially separated out, and the purity of the diethylene glycol terephthalate is reduced. The time required for cooling refers to the time required for the filtrate to reach the final temperature after cooling from the initial temperature before cooling, and the time is defined as 1.0-5.0 h. If the cooling time is less than 1.0h, the cooling speed must be increased in order to reach the required final temperature, and the foreign matters are easily separated out, so that the purity of the diethylene glycol terephthalate is low; if the cooling time exceeds 5.0 hours, foreign matters may be precipitated to lower the purity while affecting the purification efficiency.
Since a small amount of nitrogen-containing compounds such as dyes, pigments, polyurethane and the like remain in the depolymerized diethylene glycol terephthalate, this part of impurities is difficult to remove by simple decolorization, recrystallization and the like. However, this part of the residual substances has a very significant adverse effect on the color tone and heat resistance of the polyester after repolymerization. The diethylene glycol terephthalate aqueous solution before the activated carbon treatment is alkaline, the pH value is above 7.0, the solubility of the nitrogen-containing compound in the aqueous solution is small, the foreign particles are large, and the diethylene glycol terephthalate aqueous solution is not easy to be adsorbed by the activated carbon. Therefore, in order to improve the purity of the final diethylene glycol terephthalate, it is preferable to add an acid to the diethylene glycol terephthalate aqueous solution before the activated carbon adsorption treatment, and adjust the pH of the diethylene glycol terephthalate aqueous solution to 7.0 or less to improve the solubility of the nitrogen-containing compound in the diethylene glycol terephthalate aqueous solution, so that the nitrogen-containing compound is more easily dissolved into water, thereby facilitating adsorption of the nitrogen-containing compound by the activated carbon. In order to improve the removal efficiency of the nitrogen-containing compound, the pH of the aqueous solution of diethylene glycol terephthalate to which the acid is added after the adjustment is more preferably 6.0 or less. However, since the diethylene glycol content of the final diethylene glycol terephthalate increases due to the diethylene glycol formation promoted when the pH of the aqueous solution of diethylene glycol terephthalate is too small, the pH of the aqueous solution of diethylene glycol terephthalate after the acid adjustment is most preferably 3.0 to 6.0.
The acid is not particularly limited in the present invention, and the acid may be selected from a group consisting of hydrochloric acid, citric acid, sulfuric acid, lactic acid, nitric acid, tartaric acid, and the like, preferably one or more of hydrochloric acid, sulfuric acid, and nitric acid, without affecting the purity of the final diethylene glycol terephthalate.
In addition to improving the solubility of the nitrogen-containing compound in water by adjusting the pH of the aqueous solution of diethylene glycol terephthalate, the nitrogen-containing compound removal rate can be reduced by selecting an appropriate activated carbon. The surface of the activated carbon has pore structures with different sizes, wherein larger pores provide a conveying channel for dye, macromolecular coloring substances and other foreign matters. The adsorption effect of the active carbon on foreign matters in the diethylene glycol terephthalate can be effectively improved through the combination effect of pores with different sizes. The caramel decoloration rate of the activated carbon is characterized by the degree of development of the middle and large holes of the activated carbon, and the higher the caramel decoloration rate is, the higher the ratio of the middle and large holes in the activated carbon is, and the higher the absorptivity of the activated carbon to macromolecular substances is. In the diethylene glycol terephthalate, the total molecular weight span of the nitrogen-containing compounds such as dye, pigment and polyurethane and other organic component foreign matters is large, and the caramel decolorization rate of the used activated carbon is preferably more than 20 percent by combining the proportion relation of the nitrogen-containing compounds, the pigment and the polyurethane and other organic component foreign matters. Although the higher the caramel decolorization rate is, the better the adsorption effect of the activated carbon is, if the caramel decolorization rate of the activated carbon is too high, the large proportion of medium and large pores in the activated carbon is indicated, and the small proportion of small pores is indicated, so that the removal of small molecular foreign matters (such as amine derivatives such as hexamethylenediamine) is not facilitated. Therefore, the caramel color-changing rate of the activated carbon is more preferably 30 to 80 percent.
In a preferred embodiment, the aqueous solution prepared from the final diethylene glycol terephthalate is acidic, i.e. the pH value is less than 7.0, by the addition of acidic substances as pH regulator.
The invention is characterized by low N element and diethylene glycol content and high purity. The polyester prepared by using the polyester as a raw material has the advantages of excellent color tone, low diethylene glycol content, good heat resistance and good spinnability.
The invention will now be described in more detail by way of examples. The physical properties of the examples were measured by the following methods.
(1) Caramel color reduction the caramel color reduction was measured according to the B method in GB/T7702.18-1997 standard. The final results were averaged over 10 tests.
(2) Weighing 15-20 mg of sample with N element content, burning the sample in oxygen flow, oxidizing the organic component with oxidant to convert N element into volatile oxide quantitatively, silica gel packing column chromatography to measure the concentration with heat conducting pool detector, and final external standard method to determine N element content. The final results were averaged over 10 tests.
(3) The heat resistance evaluation method weighed 8g of the slices and put into a test tube, and the slices were heat-treated by heat-preserving at 300℃for 3 hours under nitrogen, and the carboxyl content of the slices before and after the heat treatment was measured, respectively. The larger the carboxyl group content DeltaCOOH (COOH before heat treatment-COOH after heat treatment) value before and after heat treatment, the worse the heat resistance of the polyester. The final results were averaged over 10 tests.
(4) Test of diethylene glycol 0.5g of the sample was weighed, dissolved by adding 2ml of ethanolamine and 10mg of adipic acid under heating, 10ml of methanol was added after dissolution, and after cooling until the amine salt precipitated, the mixture was crushed by shaking in an ultrasonic cleaner. 15g of TPA was added for neutralization, and the mixture was filtered to obtain a sample. A2 μm sample was taken by syringe, injected into LC for testing, and the diethylene glycol content was determined by internal standard method. The final results were averaged over 10 tests.
(5) The hue test was performed by using a color difference meter (SM-T45) manufactured by SUGA tester, and correcting with a standard white board under a C2 light source, and after correcting, the cut pieces were put into a dedicated glass, and the cut piece Lab values (L value (lightness index), a value (red/green index), and b value (yellow/blue index)) were measured. Wherein a lower b value indicates a better hue. The final results were averaged over 10 tests.
(6) pH value the pH was measured with a glass electrode according to the method prescribed in JIS Z8802:2011.
Example 1
Preparation of diethylene glycol terephthalate: and (3) mixing the recycled polyester with excessive ethylene glycol, depolymerizing at 180 ℃, obtaining a mixed solution of diethylene glycol terephthalate and ethylene glycol after depolymerization, and distilling the solution at 130 ℃ under reduced pressure to remove the ethylene glycol to obtain the primary diethylene glycol terephthalate. After adding water into the solution, heating to 100 ℃, dissolving and filtering by heating, and recrystallizing to obtain the crude product of the diethylene glycol terephthalate. Dissolving crude diethylene glycol terephthalate in water, heating the water solution, adding hydrochloric acid to adjust the pH value of the water solution of the diethylene glycol terephthalate to 3, adding active carbon with caramel decoloration rate of 80% for adsorption, filtering to remove the active carbon to obtain filtrate, and finally cooling, crystallizing, filtering and drying the filtrate to obtain purified diethylene glycol terephthalate. The final temperature of the filtrate was 5℃and the time required for cooling was 3.0h. The content of N element in the purified diethylene glycol terephthalate was 30ppm, and the content of diethylene glycol was 0.45wt%.
And (3) polyester: putting purified diethylene glycol terephthalate into an esterification kettle, heating and melting at 200 ℃, adding heat stabilizer trimethyl phosphate, catalyst antimony trioxide and additive titanium dioxide, and then transferring to a polymerization kettle to perform polycondensation reaction at 290 ℃. And (5) discharging and granulating after the polymer reaches the required viscosity to obtain the polyester chip. Specific physical properties are shown in Table 1.
Examples 2 to 19 the pH of the aqueous diethylene glycol terephthalate solution, the caramel adsorption rate of activated carbon, the recrystallization temperature and time were changed, and the conditions were the same as in example 1, except that the examples were shown in tables 1 to 2.
Comparative example 1 preparation of diethylene glycol terephthalate: and (3) mixing the recycled polyester with excessive ethylene glycol, depolymerizing at 180 ℃, obtaining a mixed solution of diethylene glycol terephthalate and ethylene glycol after depolymerization, and distilling the solution at 130 ℃ under reduced pressure to remove the ethylene glycol to obtain the primary diethylene glycol terephthalate. After adding water into the solution, heating to 100 ℃, dissolving and filtering by heating, and recrystallizing to obtain the crude product of the diethylene glycol terephthalate. Dissolving the crude diethylene glycol terephthalate in water, heating the water solution, adding active carbon with caramel decoloration rate of 80% for adsorption, filtering to remove the active carbon to obtain filtrate, and drying to obtain purified diethylene glycol terephthalate. The final temperature of the filtrate was 1℃and the time required for cooling was 3.0h. The content of N element in the purified diethylene glycol terephthalate was 800ppm, and the content of diethylene glycol was 0.6wt%.
And (3) polyester: putting purified diethylene glycol terephthalate into an esterification kettle, heating and melting at 200 ℃, adding heat stabilizer trimethyl phosphate, catalyst antimony trioxide and additive titanium dioxide, and then transferring to a polymerization kettle to perform polycondensation reaction at 290 ℃. And (5) discharging and granulating after the polymer reaches the required viscosity to obtain the polyester chip. The relevant parameters are shown in table 3.
The final temperature of the filtrate is too low, so that crystal inclusion impurities are precipitated together, the content of N element and DEG in the obtained diethylene glycol terephthalate is increased, and the finally prepared polyester has poor color tone and low heat resistance.
Comparative example 2 preparation of diethylene glycol terephthalate: the final cooling temperature was 5℃and the time required for cooling was 0.2h, and other preparation conditions were the same as in comparative example 1, and the relevant parameters are shown in Table 3.
The cooling speed is too high, so that impurities are precipitated, the content of N element and DEG in the obtained diethylene glycol terephthalate is increased, and finally the prepared polyester is poor in color tone and low in heat resistance.
Comparative example 3 preparation of diethylene glycol terephthalate: the final cooling temperature was 1℃and the time required for cooling was 3.0 hours, and other preparation conditions were the same as in example 3, and the relevant parameters are shown in Table 3.
The final temperature of the filtrate is too low, so that crystal inclusion impurities are precipitated together, the content of N element and DEG in the obtained diethylene glycol terephthalate is increased, and the finally prepared polyester has poor color tone and low heat resistance.
Comparative example 4 preparation of diethylene glycol terephthalate: the final cooling temperature was 5℃and the time required for cooling was 0.2h, and other preparation conditions were the same as in example 3, and the relevant parameters are shown in Table 3.
When the diethylene glycol terephthalate is prepared, the cooling is too fast, impurities are precipitated, the content of N element in the diethylene glycol terephthalate is high, the DEG content is increased, and finally the prepared polyester is poor in color tone and low in heat resistance.
Comparative example 5 preparation of diethylene glycol terephthalate: the final cooling temperature was 5℃and the time required for cooling was 6.0 hours, and other preparation conditions were the same as in comparative example 1, and the relevant parameters are shown in Table 3.
The cooling time is too long, namely the cooling speed is too slow, so that impurities are precipitated, the content of N element and DEG in the obtained diethylene glycol terephthalate is increased, and finally the prepared polyester has poor color tone and low heat resistance.
Comparative example 4 preparation of diethylene glycol terephthalate: the final cooling temperature was 5℃and the time required for cooling was 6.0 hours, and other preparation conditions were the same as in example 3, and the relevant parameters are shown in Table 3.
The cooling time is too long, namely the cooling speed is too slow, so that impurities are precipitated, the content of N element and DEG in the obtained diethylene glycol terephthalate is increased, and finally the prepared polyester has poor color tone and low heat resistance.
Claims (8)
- Diethylene glycol terephthalate, obtained by alcoholysis of recycled polyester, characterized in that: the content of N element in the diethylene glycol terephthalate is below 500 ppm.
- The diethylene glycol terephthalate of claim 1, wherein: the diethylene glycol content in the diethylene glycol terephthalate is below 0.5 wt%.
- The diethylene glycol terephthalate of claim 2, wherein: the diethylene glycol content in the diethylene glycol terephthalate is below 0.2 wt%.
- The preparation method of the diethylene glycol terephthalate according to claim 1, wherein the recovered polyester is subjected to alcoholysis to obtain the diethylene glycol terephthalate, the diethylene glycol terephthalate is prepared into an aqueous solution, then the aqueous solution is heated, then activated carbon is added for adsorption, then the activated carbon is removed by filtration to obtain a filtrate, and finally the filtrate is cooled, crystallized, filtered and dried to obtain the purified diethylene glycol terephthalate, and the preparation method is characterized in that: the final cooling temperature of the filtrate is 2-10 ℃, and the cooling time is 1.0-5.0 h.
- The process for producing diethylene glycol terephthalate according to claim 4, wherein: acid is added to the diethylene glycol terephthalate aqueous solution before the activated carbon adsorption treatment, so that the pH of the diethylene glycol terephthalate aqueous solution is 7.O or less.
- The process for producing diethylene glycol terephthalate according to claim 5, wherein: the acid is one or more of hydrochloric acid, sulfuric acid and nitric acid.
- The process for producing diethylene glycol terephthalate according to claim 4, wherein: the caramel decoloration rate of the activated carbon is more than 20%.
- The process for producing diethylene glycol terephthalate according to claim 7, wherein: the caramel decoloration rate of the activated carbon is 30-80%.
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| WO2022003990A1 (en) * | 2020-06-29 | 2022-01-06 | 株式会社シンテック | Method for producing high-purity bis(2-hydroxyethyl) terephthalate, regenerated poly(ethylene terephthalate), decoloring solvent, and method for purifying bis(2-hydroxyethyl) terephthalate |
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