CN112646134B - Method for continuously preparing spinnable colorless regenerated polyester from colored waste polyester textiles - Google Patents
Method for continuously preparing spinnable colorless regenerated polyester from colored waste polyester textiles Download PDFInfo
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- 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
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/03—Preparation of carboxylic acid esters by reacting an ester group with a hydroxy group
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- 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
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids
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- 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
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Abstract
The invention provides a method for continuously preparing spinnable colorless regenerated polyester from colored waste polyester textiles. The method comprises the following steps: crushing and melting the colored waste polyester textile to obtain a waste polyester melt; continuous supercritical methanol alcoholysis: carrying out continuous supercritical methanol alcoholysis on the waste polyester melt to obtain an alcoholysis product; carrying out continuous flash evaporation treatment on the alcoholysis product to obtain a primary purified monomer; carrying out continuous recrystallization treatment on the primarily purified monomer to obtain a secondary purified monomer; and (3) sequentially carrying out ester exchange reaction, pre-polycondensation reaction and final polycondensation reaction on the secondary purified monomer to obtain the spinnable colorless regenerated polyester. The invention effectively solves the problems that in the prior art, the colored waste polyester textiles contain dyes, inorganic pigments, other dyeing auxiliaries and the like, so that colorless waste polyester and regenerated polyester fiber with the performance comparable to that of the original polyester fiber are difficult to prepare, and the quality is reduced in the regeneration process, so that the colored waste polyester textiles can not be recycled for multiple times.
Description
Technical Field
The invention relates to the technical field of recycling of waste textiles, in particular to a method for continuously preparing spinnable colorless recycled polyester from colored waste polyester textiles.
Background
China is a large country for producing and consuming textile garments, and therefore is also a large country for producing waste textiles, and the production amount of the waste textiles is about 2600 million tons per year according to statistics. If the resource is not utilized reasonably, not only the environment pollution is caused, but also the resource is greatly wasted. Because most of the waste textiles are waste Polyester (PET) textiles, and most of the waste textiles are colored waste polyester textiles, the best high-valued recovery method at present is to prepare regenerated polyester after tackifying by a chemical method.
However, because the textile contains dyes, inorganic pigments, other dyeing auxiliaries and the like, the existence of the dyes, the inorganic pigments and the other dyeing auxiliaries can cause difficulty in a chemical re-tackifying process, and the quality of regenerated polyester is degraded, so that the regenerated polyester cannot be recycled for multiple times; meanwhile, the chemical recycling of the textiles also has the following problems: if the colored polyester textiles are not sorted according to colors and directly chemically recycled before treatment, only black recycled polyester can be obtained, and the application field and the grade of a final product are greatly restricted; if the raw materials are sorted according to colors before being treated and then reused, the problem of great color difference between the product color and the raw materials caused by factors such as chemical reaction and the like can occur in the regeneration process, secondary dyeing or color complementing and color matching and other treatments are needed during later use, environmental pollution is easy to cause, and the problem of poor processing performance caused by the fact that impurities such as inorganic pigments, dyes, gel aggregation particles and the like are not removed also exists.
Chinese patent CN1304924A discloses a method for depolymerizing ethylene terephthalate waste, but the waste polyester raw material is mainly beverage bottle, but the operation method is intermittent operation, and is not suitable for recycling waste polyester textile containing dye, inorganic pigment and other dyeing auxiliary agent.
Disclosure of Invention
The invention mainly aims to provide a method for continuously preparing spinnable colorless regenerated polyester from colored waste polyester textiles so as to solve the problem that the colored waste polyester textiles in the prior art cannot be effectively regenerated due to the fact that the colored waste polyester textiles contain dyes, inorganic pigments, other dyeing auxiliaries and the like.
In order to achieve the above objects, according to one aspect of the present invention, there is provided a method for continuously preparing spinnable-grade colorless recycled polyester from colored waste polyester textiles, which comprises the following steps: a melting step: crushing and melting the colored waste polyester textile to obtain a waste polyester melt; a continuous supercritical methanol alcoholysis step: continuously conveying the waste polyester melt and an alcoholysis agent to a supercritical methanol alcoholysis device for continuous supercritical methanol alcoholysis to obtain an alcoholysis product; a continuous flash evaporation step: continuously introducing the alcoholysis product into a multi-stage flash evaporation device arranged in series for continuous flash evaporation treatment to obtain a primary purified monomer; wherein along the material flow sequence, the flash pressure in each stage of flash evaporation device is gradually reduced; a continuous recrystallization step: continuously passing the primarily purified monomer through a multi-stage recrystallization device arranged in series for continuous recrystallization treatment to obtain a secondary purified monomer; a polymerization step: and (3) sequentially carrying out ester exchange reaction, pre-polycondensation reaction and final polycondensation reaction on the secondary purified monomer to obtain the spinnable colorless regenerated polyester.
Further, the continuous supercritical alcoholysis step comprises: continuously introducing the waste polyester melt and an alcoholysis agent into a supercritical methanol alcoholysis device to carry out continuous supercritical methanol alcoholysis, wherein the temperature in the supercritical methanol alcoholysis device is 255-285 ℃, the pressure in the supercritical methanol alcoholysis device is 8.5-12 MPa, and the retention time of materials is 30-120 min.
Further, the alcoholysis agent is methanol, and the mass ratio of the alcoholysis agent to the waste polyester melt is 8-20.
Furthermore, in the continuous flash evaporation step, the material temperature in the last stage flash evaporation device is 160-210 ℃, and the pressure is 0.1-1 MPa.
Further, the detergent adopted in the continuous recrystallization step is methanol and/or ethylene glycol, the temperature in each stage of recrystallization device is 20-50 ℃ respectively and independently, and the retention time of the materials in each stage of recrystallization device is 60-300 min respectively and independently.
Further, after the continuous recrystallization treatment, the method further comprises the step of distilling the monomer obtained by recrystallization under reduced pressure to obtain a secondary purified monomer; preferably, in the reduced pressure distillation step, the operation temperature is 220-240 ℃, the absolute pressure is 6.65-10 KPa, and the material retention time is 40-120 min.
Further, the melting step comprises: crushing the colored waste polyester textiles to obtain a crushed material; conveying the crushed materials to a melting screw through a conveying screw for primary melting to obtain primary molten materials; continuously feeding the primary molten material into a melting kettle for further melting to obtain a waste polyester melt; preferably, the operation temperature in the melting kettle is 255-275 ℃, the pressure is 0.5-1 MPa, and the time is 15-30 min; preferably, the colored waste polyester textile is a PET textile.
Further, the step of polymerizing comprises: continuously introducing the secondary purified monomer and ethylene glycol into a three-stage ester exchange kettle arranged in series according to the mol ratio of 2.1-2.5 for ester exchange reaction, and then filtering to obtain an ester exchange product; continuously introducing the ester exchange product into two-stage pre-polycondensation reactors arranged in series for pre-polycondensation reaction, and then filtering to obtain a pre-polycondensation product; and continuously passing the pre-polycondensation product through a final polycondensation reactor to carry out final polycondensation reaction to obtain spinnable colorless regenerated polyester.
Furthermore, in the ester exchange reaction process, an acetate catalyst is added at the same time, and the addition amount of the acetate catalyst is 0.04-0.06% of the weight of the secondary purified monomer; preferably, the operation temperature in the first-stage ester exchange kettle is 180-190 ℃, and the material retention time is 60-180 min; the operation temperature in the second-stage ester exchange kettle is 200-210 ℃, and the material retention time is 60-180 min; the operation temperature in the third stage ester exchange kettle is 220-235 ℃, and the material retention time is 60-180 min.
Furthermore, the operation temperature in the first-stage pre-polycondensation reactor is 245-255 ℃, the absolute pressure is 35-50 KPa, and the material retention time is 40-90 min; the operation temperature in the second-stage pre-polycondensation reactor is 275-280 ℃, the absolute pressure is 1.5-3.0 KPa, and the material retention time is 90-120 min; preferably, in the final polycondensation reaction process, the operation temperature is 283-288 ℃, the absolute pressure is 133-200 pa, and the material retention time is 90-240 min.
The invention provides a method for continuously preparing spinnable colorless regenerated polyester from colored waste polyester textiles, which comprises the following steps of crushing and melting, realizing the compaction and homogenization treatment of the waste polyester textiles, and preparing for subsequent alcoholysis; secondly, carrying out continuous supercritical alcoholysis on the waste polyester melt and an alcoholysis agent, wherein in the process, the alcoholysis agent exists in a supercritical form, thereby accelerating alcoholysis of the polyester and forming a corresponding alcoholysis monomer. Because the colored waste polyester textiles contain a large amount of dyes, inorganic pigments and other dyeing auxiliaries, the invention effectively removes volatile small-molecule dyes carried in alcoholysis products and unreacted alcoholysis agent and the like through a continuous flash evaporation step, and then decolors and purifies alcoholysis monomers through a continuous recrystallization step to obtain the alcoholysis monomers with high purity. Finally, the spinning-grade colorless regenerated polyester is prepared through the ester exchange, the pre-polycondensation and the final polycondensation which are sequentially carried out, the slicing index of the regenerated polyester completely meets the requirement of the filament-grade polyester slice, and the quality of the regenerated polyester can be comparable to that of the original polyester. In addition, because dyes, pigments and other impurities which are not beneficial to the chemical re-tackifying process are removed in the treatment process, the recycling can be realized for multiple times or even infinite times.
Besides, the invention provides a continuous regeneration process, which can meet the industrial requirements and has a very wide application prospect.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.
As described in the background section, the colored waste polyester textiles in the prior art cannot be effectively recycled due to the fact that the colored waste polyester textiles contain dyes, inorganic pigments and other dyeing auxiliaries.
In order to solve the problems, the invention provides a method for continuously preparing spinnable colorless regenerated polyester by using colored waste polyester textiles, which comprises the following steps: a melting step: crushing and melting the colored waste polyester textile to obtain a waste polyester melt; a continuous supercritical methanol alcoholysis step: continuously introducing the waste polyester melt and an alcoholysis agent into a supercritical methanol alcoholysis device to carry out continuous supercritical methanol alcoholysis to obtain an alcoholysis product; a continuous flashing step: continuously introducing the alcoholysis product into a multi-stage flash evaporation device arranged in series for continuous flash evaporation treatment to obtain a primary purified monomer; wherein along the material flow sequence, the flash pressure in each stage of flash evaporation device is gradually reduced; a continuous recrystallization step: continuously passing the primarily purified monomer through a multi-stage recrystallization device arranged in series for continuous recrystallization treatment to obtain a secondary purified monomer; a polymerization step: and (3) sequentially carrying out ester exchange reaction, pre-polycondensation reaction and final polycondensation reaction on the secondary purified monomer to obtain the spinnable colorless regenerated polyester.
The invention provides a method for continuously preparing spinnable colorless regenerated polyester from colored waste polyester textiles, which comprises the following steps of firstly, crushing and melting to realize the compaction and homogenization treatment of the waste polyester textiles and prepare for subsequent alcoholysis; secondly, carrying out continuous supercritical methanol alcoholysis on the waste polyester melt and an alcoholysis agent, wherein in the process, the alcoholysis agent exists in a supercritical form, thereby accelerating the alcoholysis of the polyester and forming a corresponding alcoholysis monomer. Because the colored waste polyester textiles contain a large amount of dyes, inorganic pigments and other dyeing auxiliaries, the invention effectively removes volatile small-molecule dyes carried in alcoholysis products and unreacted alcoholysis agent and the like through a continuous flash evaporation step, and then decolors and purifies alcoholysis monomers through a continuous recrystallization step to obtain the alcoholysis monomers with high purity. Finally, the spinnable colorless regenerated polyester is prepared through the ester exchange, the pre-polycondensation and the final polycondensation which are sequentially carried out, the slicing indexes of the polyester completely meet the requirements of filament-grade polyester slices (the main quality indexes of the slices are 80-95L value, 0.65-0.69 dl/g of intrinsic viscosity, less than or equal to 41mol/t of end carboxyl group content and less than or equal to 2.3 DEG content), and the quality of the regenerated polyester can be comparable with that of the original polyester. In addition, because the dye, the pigment and other impurities which are not beneficial to the chemical re-tackifying process are removed in the treatment process, the recycling can be realized for multiple times or even infinite times.
In the main quality index of the above-mentioned section, when the color difference test is performed in the Lab color mode, the L value represents the brightness of the sample, and when the a and b values are fixed, the higher the L value is, the brighter the sample is, the whiter the sample is. The intrinsic viscosity is a value of the slice measured by a Ubbelohde viscometer method, can represent the viscosity average molecular weight of the slice, the fiber grade needs to be not less than 0.645, and the requirement of filament fiber is higher. In addition, the national standard of fiber grade polyester chip also defines the limit values of the terminal carboxyl and the diglycol content between each grade from a superior product to a qualified product.
Besides, the invention provides a continuous regeneration process, which can meet the industrial requirements and has a very wide application prospect.
Specifically, the treatment method provided by the invention has the following beneficial effects:
(1) The whole process of preparing the yarn spinnable colorless regenerated polyester by taking the colored waste polyester textiles as raw materials is continuous operation. General equipment can be adopted in the process, and the universality and the integration of large-scale industrial popularization are good; meanwhile, the inherent unsolvable defects of intermittent operation, such as batch quality difference, high running cost and the like caused by intermittent operation, are overcome;
(2) Through separation processes such as continuous flash evaporation, continuous recrystallization and optional reduced pressure distillation, impurities such as dyes, pigments, dyes and gel agglutinated particles generated in the polymerization and production processing processes can be removed to the maximum extent, raw materials with high purity are obtained, and recycling of waste polyester textiles can be realized for many times or even unlimited times; and the quality of the obtained colorless regenerated polyester can be comparable to that of the original polyester. Meanwhile, the method can save petroleum resources which are in shortage day by day, and reduce environmental pollution and environmental protection pressure.
Preferably, the colored waste polyester textile is a PET textile. Most polyester textiles are PET textiles and the above recycling method provided by the present invention is more effective for the treatment of PET textiles.
The continuous supercritical methanolysis is actually to depolymerize polyester macromolecules in the colored waste polyester textiles, for example, to alcoholyze PET polyester macromolecules to form dimethyl terephthalate (DMT). In order to more fully alcoholyze the waste polyester melt in a continuous feed and discharge process, in a preferred embodiment, the continuous supercritical methanolysis step comprises: continuously introducing the waste polyester melt and the alcoholysis agent into a supercritical methanol alcoholysis device to carry out continuous supercritical methanol alcoholysis, wherein the temperature in the supercritical methanol alcoholysis device is 255-285 ℃, the pressure in the supercritical methanol alcoholysis device is 8.5-12 MPa, and the retention time of materials is 30-120 min. More preferably, the alcoholysis agent is methanol, and the mass ratio of the methanol to the waste polyester melt is 8-20. Controlling the ratio of the two components within the above range is beneficial to promote more complete alcoholysis of the polyester melt into monomers.
In the actual operation process, because the supercritical alcoholysis process is a high-pressure process, in order to improve the safety of process equipment and more fully separate redundant alcoholysis agent methanol and small molecular by-products (ethylene glycol), the invention carries out continuous flash evaporation treatment on alcoholysis products by a multi-stage flash evaporation device, so that the pressure can be released step by step, and the continuity and the safety of the operation are kept while the redundant alcoholysis agent and the small molecular by-products are fully separated. In a preferred embodiment, in the continuous flashing step, the material temperature in the last stage of the flashing device is 160-210 ℃ and the pressure is 0.1-1 MPa. Preferably, the continuous flash process adopts three-stage flash evaporation devices connected in series, the temperature of the material in the first-stage flash evaporation device is 224-260 ℃, the pressure is 5.5-8.0 MPa, the temperature of the material in the second-stage flash evaporation device is 192-235 ℃, the pressure is 3.0-5.0 MPa, and the third stage is the last-stage flash evaporation device. After the continuous flash evaporation treatment, the excessive methanol after the alcoholysis reaction, the ethylene glycol generated by the reaction, the low boiling point auxiliary agent in the waste polyester textile and the like are changed into gaseous state, the alcoholysis product such as dimethyl terephthalate (DMT) is changed into liquid state, gas-liquid separation is generated, and the primary purified monomer is obtained. In practical operation, for the purposes of saving raw materials and improving environmental protection, the gaseous substances generated in the continuous flashing step are preferably fed into a process tower to separate methanol and ethylene glycol, and are collected and recycled.
The continuous recrystallization process is a further decoloring and purifying step after continuous flash evaporation of the alcoholysis monomer, the process is to perform multistage continuous recrystallization separation on the primarily purified monomer, and organic dyes, inorganic pigments and the like in the process can be removed more fully to obtain the alcoholysis monomer with higher purity and whiteness. In a preferred embodiment, the washing agent used in the continuous recrystallization step is methanol and/or ethylene glycol, the temperature in each recrystallization stage is 20 to 50 ℃ independently, and the residence time of the material in each recrystallization stage is 60 to 300min independently. In the actual recrystallization process, filtration is carried out after recrystallization at each stage, solid is discharged, and liquid enters the next stage of recrystallization. In order to further improve the recrystallization effect and adapt to continuous production, it is more preferable that the temperature in the above-mentioned multiple-stage recrystallization device arranged in series is gradually decreased, for example, the temperature in the first stage is 50 ℃ and the temperature in the last stage is 20 ℃, and the temperature is three or four stages. Further preferably, three stages of series-connected recrystallization devices are adopted in the continuous recrystallization process, detergents are filled in each stage of recrystallization device in advance, the temperature in the first stage of recrystallization device is 50-40 ℃, the retention time of materials is 60-90 min, and after the first continuous recrystallization, a first recrystallization product is obtained by filtering; continuously introducing the first recrystallization product into a second-stage recrystallization device, keeping the temperature in the second-stage recrystallization device at 40-30 ℃, keeping the material for 90-180 min, and filtering to obtain a second recrystallization product after second continuous recrystallization; and continuously introducing the second recrystallization product into a third-stage recrystallization device, keeping the temperature in the third-stage recrystallization device at 30-20 ℃, keeping the material retention time at 180-300 min, and filtering after the third continuous recrystallization to obtain the secondary purified monomer.
In a preferred embodiment, after the continuous recrystallization treatment, the process further comprises the step of subjecting the monomer obtained by recrystallization to distillation under reduced pressure to obtain a second purified monomer. And further combining with reduced pressure distillation operation after recrystallization, decoloring and purifying to obtain a monomer with higher purity. Preferably, in the reduced pressure distillation step, the operating temperature is 220-240 ℃, the absolute pressure is 6.65-10 KPa, and the material retention time is 40-120 min.
As mentioned above, the colored waste polyester textiles are crushed and melted in advance before alcoholysis, so that the colored waste polyester textiles are subjected to compaction and homogenization treatment, the stability of a subsequent alcoholysis process is improved, and the treatment efficiency is improved. In a preferred embodiment, the melting step includes: crushing the colored waste polyester textiles to obtain a crushed material; conveying the crushed materials to a melting screw through a conveying screw for preliminary melting to obtain preliminary melted materials; and continuously feeding the primary molten material into a melting kettle for further melting to obtain the waste polyester melt. The screw is used for preliminary melting and is combined with the deep melting of the melting kettle, so that the melting efficiency can be further improved, and the waste textiles can be more fully treated. Preferably, the operation temperature in the melting kettle is 255-275 ℃, the pressure is 0.5-1 MPa, and the time is 15-30 min. In the actual operation process, the waste polyester textiles can also be subjected to manual color sorting or visible light identification automatic sorting before being crushed. In order to improve the safety of melting, it is preferable to protect the melting kettle with an inert gas, such as nitrogen. After the melting, the textile does not need to be washed and dried, and the carried trace non-terylene chemical fiber fabric part does not need to be removed, which can be finished in the subsequent purification process. The melting screw can be a single screw or a double screw, and generally has 6 heating zones, the temperature of the heating zones can be gradually increased, for example, the temperature of the first zone is 220 ℃, the temperature of the second zone is 240 ℃, the temperature of the third zone is 255 ℃, and the temperature of the latter zones can be 255 ℃ or sequentially increased to 275 ℃ according to the material state.
The polymerization step is carried out by adopting a common process in the preparation process of the polyester. In a preferred embodiment, the step of polymerizing comprises: continuously introducing a secondary purified monomer and ethylene glycol into a three-stage ester exchange kettle which is arranged in series according to a molar ratio of 2.0-2.5 to perform ester exchange reaction, and then filtering (filtering some inorganic dyes and other impurities brought by waste polyester textiles so as to avoid influencing hue and subsequent reaction processes) to obtain an ester exchange product; continuously introducing the ester exchange product into two-stage pre-polycondensation reactors arranged in series for pre-polycondensation reaction, and then filtering (further filtering impurities from upstream and some impurities such as agglutinated particles and the like generated in the pre-polycondensation process) to obtain a pre-polycondensation product; and continuously passing the pre-polycondensation product through a final polycondensation reactor to carry out final polycondensation reaction to obtain spinnable colorless regenerated polyester.
In order to obtain spinnable colorless regenerated polyester with better performance and improve the stability in the continuous production process, in a preferred embodiment, acetate catalyst is added in the ester exchange reaction process, and the addition amount of the acetate catalyst is 0.04-0.06% of the weight of the secondary purification monomer; preferably, the operation temperature in the first-stage ester exchange kettle is 180-190 ℃, and the material retention time is 60-180 min; the operation temperature in the second-stage ester exchange kettle is 200-210 ℃, and the material retention time is 60-180 min; the operation temperature in the third stage ester exchange kettle is 220-235 ℃, and the material retention time is 60-180 min. Specific acetate catalysts include, but are not limited to, one or more of zinc acetate, cobalt acetate, magnesium acetate, and calcium acetate. Conducting the transesterification reaction under the above conditions allows the alcoholysis monomer to more fully transesterify, such as dimethyl terephthalate (DMT) to form bis-hydroxy ethylene terephthalate (BHET).
In a preferred embodiment, the first stage prepolycondensation reactor is operated at a temperature of 245 to 255 ℃, an absolute pressure of 35 to 50KPa, and a material residence time of 40 to 90min; the operation temperature in the second-stage pre-polycondensation reactor is 275-280 ℃, the absolute pressure is 1.5-3.0 KPa, and the material retention time is 90-120 min; preferably, in the final polycondensation reaction process, the operation temperature is 283-288 ℃, the absolute pressure is 133-200 pa, and the material retention time is 90-240 min. The pre-polycondensation and the final polycondensation are carried out under the process conditions, the pre-polycondensation degree of each stage is more suitable for the requirement of continuous operation, the production stability is higher, the liquid phase tackifying effect in the final polycondensation is better, and the obtained colorless regenerated polyester melt can be directly spun by a melt or cooled by a cooling water tank and cast into a belt and cut into particles to obtain colorless regenerated PET chips.
In conclusion, the method for continuously preparing the spinnable colorless regenerated Polyester (PET) by using the colored waste polyester textiles provided by the invention comprises the following steps of: (1) Continuously feeding the melt prepared from the colored waste textiles and an alcoholysis agent into a supercritical alcoholysis device capable of continuously running, wherein PET in the textiles is completely alcoholyzed into dimethyl terephthalate (DMT); (2) DMT and other materials such as dye, inorganic pigment and other auxiliary agents and impurity agents carried in the DMT continuously enter a multistage flash evaporation device to complete pressure reduction and gas-liquid separation; (3) Liquid DMT enters a multi-stage continuous recrystallization separation device, the DMT is separated out through multi-stage cooling recrystallization, dyes, pigments and the like are retained in a detergent, and a solid-liquid mixture is filtered and separated through a continuous filtering device to obtain high-purity DMT; preferably, if higher purity DMT is to be obtained, continuous distillation under reduced pressure is carried out; (4) Heating and melting the decolorized high-purity solid DMT, and continuously conveying the molten DMT and ethylene glycol to three-stage ester exchange kettles which are sequentially connected in series to obtain ethylene terephthalate (BHET); (5) BHET continuously enters a preshrinking reactor and a final shrinking reactor to prepare colorless regenerated Polyester (PET), and the quality index of the colorless regenerated polyester meets the spinning requirement of filaments.
Preferably, the solid-liquid mixture of DMT obtained in the above recrystallization process continuously enters a filtration apparatus, the apparatus adopts a design of a lattice type filtration chamber which circularly rotates without stopping, when the filter cake pressure reaches a certain value, the lattice rotates out, the lattice with a new filter screen enters until the filter cake pressure of the lattice reaches, the lattice rotates out, and the circulation is performed in sequence. And (3) scraping filter cakes on the filter screen out of the rotated lattices by a scraper, conveying the filter cakes to an intermediate storage tank, continuously conveying the high-purity DMT from the storage tank, heating and conveying the DMT to the ester exchange reactor.
The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the present application as claimed.
Example 1
The colored waste polyester textile is crushed into cloth strips or pieces, is preliminarily melted by a special screw and a melting screw and then is continuously fed into a feeding device 2 Staying in the protected melting kettle at 255 ℃ and 0.5MPa for 30min; then pumping the melt after being melted and homogenized into a supercritical alcoholysis reactor through a melt pump, and simultaneously pumping methanol which is a stoichiometric alcoholysis agent into the reactor through a high-pressure plunger pump, wherein the mass ratio of the methanol to the polyester melt is 15; then sequentially entering three-stage flash evaporation devices which are connected in series, wherein the system temperature of the 1 st-stage flash evaporation device is 224 ℃, the pressure is 5.5MPa, the material retention time is 20min, the system temperature of the 2 nd-stage flash evaporation device is 192 ℃, the pressure is 3.0MPa, the retention time is 20min, the system temperature of the 3 rd-stage flash evaporation device is 160 ℃, the pressure is 0.1MPa, and the retention time is 20min; carrying out flash evaporation treatment, then carrying out alcoholysis reaction, then changing residual alcoholysis agent methanol, generated glycol, low-boiling-point auxiliary agents and the like brought by waste polyester textiles into gas state, entering a process tower for separation and refining and recycling, entering a middle tank for liquid alcoholysis products, adding detergent methanol for washing and cooling, and then entering three-stage continuous recrystallization filtering devices connected in series; the system temperature of the 1 st-stage recrystallization device is 50 ℃, the retention time is 90min, the system temperature of the 2 nd-stage recrystallization device is 40 ℃, the retention time is 180min, the system temperature of the 3 rd-stage recrystallization device is 30 ℃, the retention time is 300min, the materials after recrystallization enter a continuous filtration device for solid-liquid separation after recrystallization of each stage, and the method comprises the steps ofDyes or pigments in the colored waste polyester textiles are completely removed in the continuous recrystallization and filtration processes and enter washing liquid, and a purified alcoholysis product DMT enters an intermediate storage tank and enters a three-stage ester exchange reactor after being heated and melted; the method comprises the following steps of (1) pumping ester exchanger ethylene glycol from a level 1 ester exchange kettle according to the molar ratio of 2.1 to DMT, adding catalysts of cobalt acetate and antimony trioxide into the ethylene glycol, wherein the addition amounts are respectively 0.04% of the amount of DMT and 0.03% of the amount of theoretically obtained BHET, the temperature of the level 1 ester exchange kettle is 180 ℃, the retention time is 180min, the temperature of the level 2 ester exchange kettle is 200 ℃, the retention time is 180min, the temperature of the level 3 ester exchange kettle is 220 ℃, the retention time is 180min, by-products of methanol and the like enter a process tower to be separated and recycled, an ester exchange product is dihydroxy ethyl terephthalate (BHET), the temperature of the level 1 preshrinking reactor is 245 ℃, the system pressure is 50KPa, the retention time is 90min, the temperature of the level 2 preshrinking reactor is 275 ℃, the system pressure is 3.0KPa, the retention time is 120min, and then pumping the materials into a final reactor by a melt pump, the temperature of the final polymerization reactor is 283 ℃, the system pressure is 200Pa, the PET is 240min, and the melt is pumped out after colorless casting, and the melt is cast into a water cooling belt to obtain granules. The quality indexes and spinning conditions of the tested regenerated PET chips are shown in the following table 1:
table 1: quality index and filament spinnability of recycled PET (polyethylene terephthalate) slices
| Name (R) | [η]/dl.g -1 | L | Carboxyl end groups/mol.t -1 | DEG content/%) | Spinnability of filament |
| Recycled PET (polyethylene terephthalate) slice | 0.650 | 85 | 39.0 | 1.05 | 3000m/min spinnable |
Example 2
The colored waste polyester textiles are crushed into cloth strips or pieces, are preliminarily melted by a special screw and a melting screw and are continuously fed into a feeding screw N 2 Staying in the protected melting kettle at 265 ℃ and 0.5MPa for 20min; then pumping the melt which is melted and homogenized into a supercritical alcoholysis reactor through a melt pump, and simultaneously pumping methanol which is a stoichiometric alcoholysis agent into the reactor through a high-pressure plunger pump, wherein the mass ratio of the methanol to the waste polyester melt is 12, the temperature of the supercritical reactor is 265 ℃, the pressure of the supercritical reactor is 10.0MPa, and the material retention time is 90min; then sequentially entering three-stage flash evaporation devices which are connected in series, wherein the system temperature of the 1 st-stage flash evaporation device is 235 ℃, the pressure is 6.8MPa, the material retention time is 20min, the system temperature of the 2 nd-stage flash evaporation device is 205 ℃, the pressure is 4.3MPa, the retention time is 20min, the system temperature of the 3 rd-stage flash evaporation device is 170 ℃, the pressure is 0.4MPa, the retention time is 20min, the residual alcoholysis agent methanol after alcoholysis treatment and generated ethylene glycol and low-boiling-point auxiliary agents brought by waste polyester textiles are changed into gaseous state after flash evaporation treatment, entering a process tower for separation and refining and recycling, entering a liquid alcoholysis substance into an intermediate tank, feeding detergent methanol for washing and cooling, and then entering three-stage continuous recrystallization filtering devices which are connected in series; the system temperature of a 1 st-stage recrystallization device is 45 ℃, the retention time is 80min, the system temperature of a 2 nd-stage device is 35 ℃, the retention time is 120min, the system temperature of a 3 rd-stage device is 25 ℃, the retention time is 240min, the materials after recrystallization enter a continuous filtering device for solid-liquid separation after recrystallization of each stage, and the colored waste polyester is spunDye or pigment in the fabric is completely removed in the continuous recrystallization and filtration processes and enters washing liquid, and the purified alcoholysis product DMT enters an intermediate storage tank and enters a three-stage ester exchange reactor after being heated and melted; the method comprises the following steps of (1) pumping ester exchanger ethylene glycol according to a metering amount of 2.2 mol ratio to DMT from a 1-level ester exchange kettle, adding catalysts of cobalt acetate, zinc acetate and antimony trioxide into the ethylene glycol, wherein the addition amount of acetate is 0.05% of the amount of DMT, and the addition amount of antimony trioxide is 0.03% of the amount of BHET obtained theoretically, the temperature of the 1-level ester exchange kettle is 185 ℃, the residence time is 150min, the temperature of the 2-level ester exchange kettle is 205 ℃, the residence time is 150min, the temperature of the 3-level ester exchange kettle is 225 ℃, the residence time is 150min, a byproduct of methanol and the like enters a process tower to be separated and recycled, an ester exchange product of dihydroxyethyl terephthalate (BHET) enters a two-level preshrinking reactor, the temperature of the 1-level preshrinking reactor is 255 ℃, the system pressure is 40KPa, the residence time is 60min, the temperature of the 2-level preshrinking reactor is 280 ℃, the system pressure is 2.0KPa, the residence time is 100min, and then the materials are pumped into a final polymerization reactor, the temperature of the system pressure is 285 Pa, the PET is 150min, and a melt is pumped into a colorless melt, and then is pumped into a water cooling and is carried out for granulation. The quality indexes and spinning conditions of the tested recycled PET chips are shown in the following table 2:
table 2: quality index of regenerated PET (polyethylene terephthalate) slice and spinnability of filament
Example 3
The colored waste polyester textiles are crushed into cloth strips or pieces, are preliminarily melted by a special screw and a melting screw and are continuously fed into a feeding screw N 2 Staying in the protected melting kettle at 275 ℃ and 1MPa for 15min; then the melt which is melted and homogenized is pumped into a supercritical alcoholysis reactor through a melt pump, and simultaneously, methanol which is subjected to stoichiometric alcoholysis is pumped into the reactor through a high-pressure plunger pump, wherein the mass ratio of the supercritical methanol to the waste polyester melt is 10:1, the temperature of a supercritical reactor is 275 ℃, the pressure is 11.0MPa, and the retention time of materials is 60min; then sequentially enter three stages which are connected in seriesA flash evaporation device, wherein the temperature of a 1 st-stage flash evaporation device system is 245 ℃, the pressure is 7.5MPa, the material retention time is 20min, the temperature of a 2 nd-stage flash evaporation device system is 215 ℃, the pressure is 5.1MPa, the retention time is 20min, the temperature of a 3 rd-stage flash evaporation device system is 188 ℃, the pressure is 0.7MPa, the retention time is 20min, the residual alcoholysis agent methanol after the alcoholysis reaction after the flash evaporation treatment, the generated ethylene glycol, low-boiling-point auxiliaries brought in the waste polyester textiles and the like become gaseous, the gaseous state is fed into a process tower to be separated, refined and recycled, the liquid alcoholysis product is fed into a middle tank, a washing agent methanol is added to be washed and cooled, and then the gaseous state enters a three-stage continuous recrystallization filtering device which is connected in series with one another; the system temperature of a 1 st-stage recrystallization device is 40 ℃, the retention time is 60min, the system temperature of a 2 nd-stage recrystallization device is 30 ℃, the retention time is 90min, the system temperature of a 3 rd-stage recrystallization device is 20 ℃, the retention time is 180min, after recrystallization of each stage of materials, solid-liquid separation is carried out in a continuous filtering device, dyes or pigments in colored waste polyester textiles are completely removed in the continuous recrystallization and filtering process and enter washing liquid, and a purified alcoholysis product DMT enters an intermediate storage tank and enters a three-stage ester exchange reactor after being heated and melted; the method comprises the following steps of (1) pumping ester exchanger ethylene glycol according to the metering quantity of 2.4 mol ratio of DMT into a 1-level ester exchange kettle, adding catalysts of cobalt acetate, zinc acetate, calcium acetate and ethylene glycol antimony into the ethylene glycol, adding acetate according to 0.06% of the DMT, adding ethylene glycol antimony according to 0.03% of the theoretically obtained BHET, feeding a 1-level ester exchange kettle at 190 ℃, staying for 60min, feeding a 2-level ester exchange kettle at 210 ℃, staying for 60min, feeding a 3-level ester exchange kettle at 230 ℃, staying for 90min, feeding a byproduct of methanol and the like into a process tower for separation and recycling, feeding a product of ester exchange, namely dihydroxyethyl terephthalate (BHET), into a two-level pre-shrinking reactor, feeding the material into a final polymerization reactor at 255 ℃, under 35KPa of system pressure, staying for 40min, feeding the 2-level pre-shrinking reactor at 280 ℃, under 1.5KPa of system pressure and 90min, feeding the material into the final polymerization reactor through a melt pump, feeding the material into the final polymerization reactor at 133Pa of system pressure, under 90min, feeding a PET melt into a water-cooling and granulating the melt after regeneration. The quality indexes and spinning conditions of the tested recycled PET chips are shown in the following table 3:
table 3: quality index of regenerated PET (polyethylene terephthalate) slice and spinnability of filament
Example 4
The colored waste polyester textiles are crushed into cloth strips or pieces, are preliminarily melted by a special screw and a melting screw and are continuously fed into a feeding screw N 2 Staying in the protected melting kettle at 255 ℃ and 0.5MPa for 30min; then pumping the melt which is melted and homogenized into a supercritical alcoholysis reactor through a melt pump, and simultaneously pumping methanol which is a stoichiometric alcoholysis agent into the reactor through a high-pressure plunger pump, wherein the mass ratio of the methanol to the waste polyester melt is 8, the temperature of the supercritical reactor is 285 ℃, the pressure is 12.0MPa, and the material retention time is 30min; then sequentially entering three-stage flash evaporation devices which are connected in series, wherein the system temperature of the 1 st-stage flash evaporation device is 260 ℃, the pressure is 8.0MPa, the material retention time is 20min, the system temperature of the 2 nd-stage flash evaporation device is 235 ℃, the pressure is 5.0MPa, the retention time is 20min, the system temperature of the 3 rd-stage flash evaporation device is 160 ℃, the pressure is 0.1MPa, the retention time is 20min, the residual alcoholysis agent methanol after alcoholysis treatment and generated ethylene glycol and low-boiling-point auxiliary agents brought by waste polyester textiles are changed into gaseous state after flash evaporation treatment, entering a process tower for separation and refining and recycling, entering a liquid alcoholysis substance into an intermediate tank, feeding detergent methanol for washing and cooling, and then entering three-stage continuous recrystallization filtering devices which are connected in series; the system temperature of a 1 st-stage recrystallization device is 40 ℃, the retention time is 60min, the system temperature of a 2 nd-stage recrystallization device is 30 ℃, the retention time is 90min, the system temperature of a 3 rd-stage recrystallization device is 20 ℃, the retention time is 180min, after recrystallization of each stage of materials, solid-liquid separation is carried out in a continuous filtering device, dyes or pigments in colored waste polyester textiles are completely removed in the continuous recrystallization and filtering process and enter washing liquid, and a purified alcoholysis product DMT enters an intermediate storage tank and enters a three-stage ester exchange reactor after being heated and melted; the ester exchanger ethylene glycol is added into a 1-stage ester exchange kettle according to the molar ratio of 2.5 to DMTCobalt acetate, zinc acetate, calcium acetate, magnesium acetate and the like are added into the ethylene glycol, the addition amount of acetate is 0.06 percent of the amount of DMT, the addition amount of ethylene glycol antimony is 0.03 percent of the amount of BHET obtained theoretically, the temperature of a 1 st-stage ester exchange kettle is 190 ℃, the retention time is 60min, the temperature of a 2 nd-stage ester exchange kettle is 210 ℃, the retention time is 60min, the temperature of a 3 rd-stage ester exchange kettle is 235 ℃, the retention time is 60min, by-products such as methanol and the like enter a process tower for separation and reuse, an ester exchange product is bis-hydroxyethyl terephthalate (BHET) and enters a second-stage pre-shrinking reactor, the temperature of the 1 st-stage pre-shrinking reactor is 255 ℃, the system pressure is 35KPa, the retention time is 40min, the temperature of the 2 nd-stage pre-shrinking reactor is 280 ℃, the system pressure is 1.5KPa, the retention time is 90min, then materials are pumped into a final polymerization reactor by a melt pump, the temperature of the final polymerization reactor is 288 ℃, the system pressure is 133Pa, the retention time is 90min, and a water-cooling casting belt is pelletized after a colorless PET melt is pumped out by a pump. The quality indexes and spinning conditions of the tested recycled PET chips are shown in the following table 4:
table 4: quality index of regenerated PET (polyethylene terephthalate) slice and spinnability of filament
Example 5
The colored waste polyester textiles are crushed into cloth strips or pieces, are preliminarily melted by a special screw and a melting screw and are continuously fed into a feeding screw N 2 Staying in the protected melting kettle at 255 ℃ and 0.5MPa for 30min; then pumping the melt after being melted and homogenized into a supercritical alcoholysis reactor through a melt pump, and simultaneously pumping methanol which is a stoichiometric alcoholysis agent into the reactor through a high-pressure plunger pump, wherein the mass ratio of the methanol to the waste polyester melt is 15, the temperature of the supercritical reactor is 255 ℃, the pressure of the supercritical reactor is 8.5MPa, and the material retention time is 120min; sequentially feeding the materials into three-stage flash evaporation devices which are connected in series, wherein the system temperature of the 1 st-stage flash evaporation device is 224 ℃, the pressure is 5.5MPa, the retention time of the materials is 20min, the system temperature of the 2 nd-stage flash evaporation device is 192 ℃, the pressure is 3.0MPa, the retention time is 20min, the system temperature of the 3 rd-stage flash evaporation device is 160 ℃, the pressure is 0.1MPa, the retention time is 20min, and alcohol after flash evaporation treatment is subjected to alcohol evaporation treatmentThe residual alcoholysis agent methanol after the decomposition reaction, the generated glycol, the low-boiling-point auxiliary agent brought by the waste polyester textile and the like are changed into gas, the gas enters a process tower for separation and refining and then is recycled, the liquid alcoholysis product enters a middle tank, the detergent methanol is injected into the middle tank for washing and cooling, and then the liquid alcoholysis product enters three-stage continuous recrystallization filtering devices which are connected in series; the system temperature of a 1 st-stage recrystallization device is 50 ℃, the retention time is 90min, the system temperature of a 2 nd-stage recrystallization device is 40 ℃, the retention time is 180min, the system temperature of a 3 rd-stage recrystallization device is 30 ℃, the retention time is 300min, after each stage of recrystallization, the recrystallized materials enter a continuous filtering device for solid-liquid separation, the liquid part enters a process tower for rectification, separation and recovery, the solid part enters a reduced pressure distillation device for further purification, the device operation temperature is 220 ℃, the system pressure is 6.65KPa, and the retention time is 120min, dyes or pigments in colored waste polyester textiles are completely removed in the continuous recrystallization, filtration and reduced pressure distillation processes, and the purified alcoholysis product DMT enters an intermediate storage tank and enters a three-stage ester exchange reactor after being heated and melted; the method comprises the following steps of (1) pumping ester exchanger ethylene glycol according to a molar ratio of 2.1 to DMT from a 1-stage ester exchange kettle, adding catalysts of cobalt acetate and antimony trioxide into the ethylene glycol, wherein the addition amounts of the cobalt acetate and the antimony trioxide are respectively 0.04% of the DMT and 0.03% of the theoretical BHET, the temperature of the 1-stage ester exchange kettle is 180 ℃, the residence time is 180min, the temperature of the 2-stage ester exchange kettle is 200 ℃, the residence time is 180min, the temperature of the 3-stage ester exchange kettle is 220 ℃, the residence time is 180min, byproducts of methanol and the like enter a process tower to be separated and recycled, an ester exchange product is dihydroxy ethyl terephthalate (BHET), the BHET enters a two-stage pre-shrinking reactor, the temperature of the 1-stage pre-shrinking reactor is 245 ℃, the system pressure is 50KPa, the residence time is 90min, the temperature of the 2-stage pre-shrinking reactor is 275 ℃, the system pressure is 3.0KPa, the residence time is 120min, and then pumping the materials into a final polymerization reactor, the temperature of the final polymerization reactor is 283 ℃, the system pressure is 200Pa, the PET melt is 240min, and the colorless melt is pumped out and then cast into a water cooling belt. The quality indexes and spinning conditions of the tested recycled PET chips are shown in the following table 5:
TABLE 5 quality index and filament spinnability of recycled PET chips
Example 6
The colored waste polyester textile is crushed into cloth strips or pieces, is preliminarily melted by a special screw and a melting screw and then is continuously fed into a feeding device 2 Staying in the protected melting kettle at 265 ℃ and 0.5MPa for 20min; then pumping the melt after being melted and homogenized into a supercritical alcoholysis reactor through a melt pump, and simultaneously pumping methanol which is subjected to stoichiometric alcoholysis agent into the reactor through a high-pressure plunger pump, wherein the mass ratio of the methanol to the waste polyester melt is 12, the temperature of the supercritical reactor is 265 ℃, the pressure of the supercritical reactor is 10.0MPa, and the material retention time is 90min; then sequentially entering three-stage flash evaporation devices which are connected in series, wherein the system temperature of the 1 st-stage flash evaporation device is 235 ℃, the pressure is 6.8MPa, the material retention time is 20min, the system temperature of the 2 nd-stage flash evaporation device is 205 ℃, the pressure is 4.3MPa, the retention time is 20min, the system temperature of the 3 rd-stage flash evaporation device is 170 ℃, the pressure is 0.4MPa, the retention time is 20min, the residual alcoholysis agent methanol after the alcoholysis reaction after the flash evaporation treatment, the generated ethylene glycol, the low-boiling-point auxiliary agents and the like brought by the waste polyester textiles are changed into gaseous state, the gaseous state is separated and refined and recycled in a process tower, the liquid alcoholysis substance enters an intermediate tank, the washing agent methanol is injected for washing and cooling, and then the gaseous state enters three-stage continuous recrystallization filtering devices which are connected in series; the system temperature of a 1 st-stage recrystallization device is 45 ℃, the retention time is 80min, the system temperature of a 2 nd-stage recrystallization device is 35 ℃, the retention time is 120min, the system temperature of a 3 rd-stage recrystallization device is 25 ℃, the retention time is 240min, the recrystallized material enters a continuous filtering device for solid-liquid separation after each-stage recrystallization, the liquid part enters a process tower for rectification separation and recovery, the solid part enters a reduced pressure distillation device for further purification, the operation temperature of the device is 240 ℃, the system pressure is 10.0KPa, and the retention time is 40min, the dye or pigment in the colored waste polyester textiles is completely removed in the continuous recrystallization, filtration and reduced pressure distillation processes, and the purified alcoholysis product DMT enters an intermediate storage tank and enters a three-stage ester exchange reactor after being heated and melted; the molar ratio of the ester exchanger ethylene glycol to DMT was 2.2Adding catalysts of cobalt acetate, zinc acetate and antimony trioxide into the ethylene glycol, wherein the addition amount of acetate is 0.05 percent of that of DMT, the addition amount of antimony trioxide is 0.03 percent of that of BHET obtained theoretically, the temperature of a 1 st-stage ester exchange kettle is 185 ℃, the residence time is 150min, the temperature of a 2 nd-stage ester exchange kettle is 205 ℃, the residence time is 150min, the temperature of a 3 rd-stage ester exchange kettle is 225 ℃, the residence time is 150min, byproducts of methanol and the like enter a process tower for separation and reuse, an ester exchange product is dihydroxy ethyl terephthalate (BHET) and enters a secondary pre-shrinking reactor, the temperature of the 1 st-stage pre-shrinking reactor is 255 ℃, the system pressure is 40KPa, the residence time is 60min, the temperature of the 2 nd-stage pre-shrinking reactor is 280 ℃, the system pressure is 2.0KPa, and the residence time is 100min, then adding materials into a final polymerization reactor by a melt pump, the temperature of the final polymerization reactor is 285 ℃, the system pressure is 133Pa, the residence time is 150min, and a colorless regenerated PET melt is extruded by a water-cooling belt for granulation. The quality indexes and spinning conditions of the tested recycled PET chips are shown in the following table 6:
table 6: quality index and filament spinnability of recycled PET (polyethylene terephthalate) slices
Comparative example 1
The colored waste polyester textile is crushed into cloth strips or pieces, is preliminarily melted by a special screw and a melting screw and then is continuously fed into a feeding device 2 Staying in the protected melting kettle at 275 ℃ and 1MPa for 15min; then pumping the melt which is melted and homogenized into a supercritical alcoholysis reactor through a melt pump, and simultaneously pumping methanol which is a stoichiometric alcoholysis agent into the reactor through a high-pressure plunger pump, wherein the mass ratio of the methanol to the waste polyester melt is 10, the temperature of the supercritical reactor is 275 ℃, the pressure is 11.0MPa, and the material retention time is 60min; then sequentially entering three-stage flash evaporation devices which are connected in series, wherein the system temperature of the 1 st-stage flash evaporation device is 245 ℃, the pressure is 7.5MPa, the material retention time is 20min, the system temperature of the 2 nd-stage flash evaporation device is 215 ℃, the pressure is 5.1MPa, the retention time is 20min, the system temperature of the 3 rd-stage flash evaporation device is 188 ℃, the pressure is 0.7MPa, the retention time is 20min, and alcoholysis is performed after flash evaporation treatmentThe residual alcoholysis agent methanol after the reaction, the generated glycol, the low boiling point auxiliary agent brought by the waste polyester textile and the like become gaseous, the gaseous alcoholysis agent methanol and the low boiling point auxiliary agent are separated and refined in a process tower and then recycled, and the liquid alcoholysis product DMT enters an intermediate storage tank and enters a three-stage ester exchange reactor after being heated and melted; the method comprises the following steps of (1) pumping ester exchanger ethylene glycol according to the metering quantity of 2.4 mol ratio of DMT into a 1-level ester exchange kettle, adding catalysts of cobalt acetate, zinc acetate, calcium acetate and ethylene glycol antimony into the ethylene glycol, adding acetate according to 0.06% of the DMT, adding ethylene glycol antimony according to 0.03% of the theoretically obtained BHET, feeding a 1-level ester exchange kettle at 190 ℃, staying for 60min, feeding a 2-level ester exchange kettle at 210 ℃, staying for 60min, feeding a 3-level ester exchange kettle at 230 ℃, staying for 90min, feeding a byproduct of methanol and the like into a process tower for separation and recycling, feeding a product of ester exchange, namely dihydroxyethyl terephthalate (BHET), into a two-level pre-shrinking reactor, feeding the product of bis (hydroxyethyl terephthalate) into the 1-level pre-shrinking reactor at 255 ℃, under 35KPa of system pressure, standing for 40min, feeding the 2-level pre-shrinking reactor at 280 ℃, under 1.5KPa of system pressure, staying for 90min, feeding the material into a final polymerization reactor by a melt pump, under the system pressure of 133Pa, feeding a PET melt into the final polymerization reactor for 90min, and pumping the melt into a water-cooling and pelletizing the melt after regeneration. The quality indexes and spinning conditions of the tested recycled PET chips are shown in the following table 7:
table 7: quality index and filament spinnability of recycled PET (polyethylene terephthalate) slices
Comparative example 2
The colored waste polyester textiles are crushed into cloth strips or pieces, are preliminarily melted by a special screw and a melting screw and are continuously fed into a feeding screw N 2 Staying in the protected melting kettle at 265 ℃ and 0.5MPa for 20min; then pumping the melt after being melted and homogenized into a supercritical alcoholysis reactor through a melt pump, and simultaneously pumping methanol which is subjected to stoichiometric alcoholysis agent into the reactor through a high-pressure plunger pump, wherein the mass ratio of the methanol to the waste polyester melt is 12, the temperature of the supercritical reactor is 265 ℃, the pressure of the supercritical reactor is 10.0MPa, and the material retention time is 90min;then sequentially entering three-stage flash evaporation devices which are connected in series, wherein the system temperature of the 1 st-stage flash evaporation device is 235 ℃, the pressure is 6.8MPa, the material retention time is 20min, the system temperature of the 2 nd-stage flash evaporation device is 205 ℃, the pressure is 4.3MPa, the retention time is 20min, the system temperature of the 3 rd-stage flash evaporation device is 170 ℃, the pressure is 0.4MPa, the retention time is 20min, the residual alcoholysis agent methanol after the alcoholysis reaction after the flash evaporation treatment, the generated ethylene glycol and the low-boiling auxiliary agent brought in the waste polyester textile are changed into gas, the gas enters a process tower for separation, refining and recycling, the liquid alcoholysis product enters an intermediate tank, a washing agent methanol is injected for washing and cooling, then the liquid enters a continuous filtering device for solid-liquid separation, the liquid part enters the process tower for rectification, separation and recovery, the solid part enters a reduced pressure distillation device, the operation temperature is 240 ℃, the system pressure is 10.0KPa, the retention time is 40min, the purified alcoholysis product DMT enters an intermediate storage tank, and enters a three-stage ester exchange reactor after being heated and melted; the method comprises the following steps of (1) pumping ester exchanger ethylene glycol according to a metering quantity that the molar ratio of the ester exchanger ethylene glycol to DMT is 2.2. The quality indexes and spinning conditions of the tested recycled PET chips are shown in the following table 8:
table 8: quality index and filament spinnability of recycled PET (polyethylene terephthalate) slices
From the above data, the higher L value of the slice obtained in the examples indicates higher whiteness. And the L value is higher, the spinning speed (filament spinnability) is obviously and greatly improved, which shows that the comprehensive indexes such as the slice purity, the quality and the like are greatly improved, and the melt uniformity and the strength in the spinning process can sufficiently meet the requirement of the filament spinnability.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. A method for continuously preparing spinnable colorless regenerated polyester from colored waste polyester textiles is characterized by comprising the following steps:
a melting step: crushing and melting the colored waste polyester textile to obtain a waste polyester melt;
continuous supercritical methanol alcoholysis: continuously conveying the waste polyester melt and the alcoholysis agent to a supercritical methanol alcoholysis device for continuous supercritical methanol alcoholysis to obtain an alcoholysis product; the continuous supercritical alcoholysis step comprises the following steps: continuously introducing the waste polyester melt and the alcoholysis agent into the supercritical methanol alcoholysis device for continuous supercritical methanol alcoholysis, wherein the temperature in the supercritical methanol alcoholysis device is 255 to 285 ℃, the pressure in the supercritical methanol alcoholysis device is 8.5 to 12MPa, and the retention time of materials is 30 to 120min; the alcoholysis agent is methanol, and the mass ratio of the alcoholysis agent to the waste polyester melt is 8 to 20;
a continuous flashing step: continuously introducing the alcoholysis product into a multi-stage flash evaporation device arranged in series for continuous flash evaporation treatment to obtain a primary purified monomer; wherein along the material flow sequence, the flash pressure in each stage of the flash evaporation device is gradually reduced; in the continuous flash evaporation step, the temperature of the material in the flash evaporation device at the final stage is 160-210 ℃, and the pressure is 0.1-1Mpa;
a continuous recrystallization step: continuously passing the primarily purified monomer through a multi-stage recrystallization device arranged in series for continuous recrystallization treatment to obtain a secondary purified monomer; the detergent adopted in the continuous recrystallization step is methanol and/or ethylene glycol, the temperature in each recrystallization device is 20-50 ℃ respectively and independently, and the retention time of the materials in each recrystallization device is 60-300min respectively and independently;
a polymerization step: carrying out ester exchange reaction, pre-polycondensation reaction and final polycondensation reaction on the secondary purified monomer in sequence to obtain the spinnable colorless regenerated polyester; the polymerization step comprises:
continuously introducing the secondary purified monomer and ethylene glycol into a three-stage ester exchange kettle arranged in series according to the mol ratio of 2.1-2.5;
continuously introducing the ester exchange product into two stages of pre-polycondensation reactors which are arranged in series for carrying out the pre-polycondensation reaction, and then filtering to obtain a pre-polycondensation product;
continuously passing the pre-polycondensation product through a final polycondensation reactor to carry out the final polycondensation reaction to obtain the spinnable colorless regenerated polyester;
in the ester exchange reaction process, simultaneously adding an acetate catalyst, wherein the addition amount of the acetate catalyst is 0.04 to 0.06 percent of the weight of the secondary purification monomer; the operating temperature in the ester exchange kettle of the first stage is 180 to 190 ℃, and the material retention time is 60 to 180min; the operating temperature in the ester exchange kettle of the second stage is 200 to 210 ℃, and the material retention time is 60 to 180min; the third stage is that the operation temperature in the ester exchange kettle is 220 to 235 ℃, and the material retention time is 60 to 180min; the operation temperature in the first-stage pre-polycondensation reactor is 245-255 ℃, the absolute pressure is 35-50KPa, and the material retention time is 40-90min; the operation temperature in the second-stage pre-polycondensation reactor is 275-280 ℃, the absolute pressure is 1.5-3.0 KPa, and the material retention time is 90-120min; in the final polycondensation reaction process, the operation temperature is 283 to 288 ℃, the absolute pressure is 133 to 200pa, and the material residence time is 90 to 240min.
2. The method for continuously preparing spinnable-grade colorless regenerated polyester by using the colored waste polyester textile as claimed in claim 1, characterized in that after the continuous recrystallization treatment, the method further comprises the step of distilling the monomer obtained by recrystallization under reduced pressure to obtain the secondary purified monomer.
3. The method for continuously preparing the spinnable colorless regenerated polyester from the colored waste polyester textiles as claimed in claim 2, wherein in the step of reduced pressure distillation, the operating temperature is 220 to 240 ℃, the absolute pressure is 6.65 to 10KPa, and the material residence time is 40 to 120min.
4. The method for continuously preparing spinnable-grade colorless regenerated polyester by using the colored waste polyester textile as claimed in claim 1, wherein the melting step comprises the following steps:
crushing the colored waste polyester textiles to obtain a crushed material;
conveying the crushed materials to a melting screw through a conveying screw to perform primary melting to obtain primary molten materials;
and continuously feeding the primary molten material into a melting kettle for further melting to obtain the waste polyester melt.
5. The method for continuously preparing the spinnable colorless regenerated polyester from the colored waste polyester textiles as claimed in claim 4, wherein the operating temperature in the melting kettle is 255-275 ℃, the pressure is 0.5-1MPa, and the time is 15-30min.
6. The method for continuously preparing the spinnable-grade colorless regenerated polyester from the colored waste polyester textiles according to claim 4, wherein the colored waste polyester textiles are PET textiles.
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| CN113185811B (en) * | 2021-04-28 | 2022-07-26 | 湖北山特莱新材料有限公司 | Traceable cyclic regeneration type water-soluble polyester chip |
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