Alcoholysis regeneration method for waste functionalized PET (polyethylene terephthalate) based on middle polymer

Abstract

The invention relates to a mid-polymer-based waste functionalized PET alcoholysis regeneration method, which comprises the following steps: conveying a melt obtained by melting waste functionalized PET to a closed reactor, and introducing overheated dihydric alcohol steam into the closed reactor to depolymerize the waste functionalized PET to obtain a mid-polymer; then adding a functional monomer and dihydric alcohol into the closed reactor to carry out co-esterification with the middle polymer, sending a co-esterified product to a polymerization stage of the primary polyester to carry out a reaction, and preparing functional regenerated polyester after the reaction is finished; the polymerization degree of the middle polymer is 3-30, and the molecular weight distribution PDI is less than 3. According to the invention, depolymerization in a homogeneous state can be realized, the process that solid-phase PET is gradually depolymerized from the surface layer to the inner layer is avoided, the polymerization degree of a depolymerization product can be controlled to prepare a middle polymer, and the uniformity is increased after repolymerization.

Description

[0001] This application is a divisional application of the patent application "A method for alcoholysis and regeneration of waste PET based on intermediate polymers". The application date of the original application is November 6, 2024, and the application number is 2024115698471. Technical Field

[0002] The invention belongs to the technical field of polymerization and relates to a method for alcoholysis regeneration of waste functionalized PET based on a mesomer. Background Art

[0003] Ethylene terephthalate (PET) is the most commonly used engineering plastic and fiber raw material. It has good chemical stability in the natural environment, but it cannot be naturally degraded. The continuous accumulation of PET in the environment after disposal will cause microplastic and toxin pollution problems. Therefore, the recycling and reuse of PET has gradually become a research hotspot in recent years. Chemical recycling can depolymerize PET into terephthalic acid, ethylene glycol and other derivative chemicals at the molecular level, which can be "recycled" or "upgraded" after separation and purification. Ethylene glycol is one of the raw materials for polyester polymerization reaction, and it can also be used as a nucleophilic reagent to depolymerize polyester. After alcoholysis, no other chemical components will be introduced, making it an ideal PET chemical depolymerizer.

[0004] For example, patent CN113214458A discloses a method for preparing recycled polyester by efficient alcoholysis of waste polyester, reporting the use of oligomers and ethylene glycol to depolymerize PET to BHET and then repolymerize it to form recycled polyester. Patent CN115141363A discloses a method for preparing recycled cationic polyester using waste polyester, depolymerizing PET to BHET copolymerized cationic recycled polyester by diol. Patent CN117999305A discloses a method for manufacturing recycled polyester resin, reporting that polycarboxylic acids and polyols are added in one step to depolymerize, then directly esterified, and then polycondensed to prepare recycled PET, and direct regeneration after depolymerization is achieved by adding polyvalent raw materials.

[0005] At present, in the prior art, PET alcoholysis recovery is mainly through the depolymerization of PET in a diol solution, and the depolymerization temperature is usually below the melting point of PET. Due to the different depolymerization efficiencies from the outside to the inside, in order to make the alcoholysis solution depolymerize evenly, the final target of alcoholysis is mainly BHET and DMT, and the depolymerization is carried out with excess diol as a medium. If you want to obtain functionalized regenerated polyester, use BHET or DMT as a raw material and polymerize it with a functionalized monomer. Since the chemical method of functionalized PET is limited by complex components, it is difficult to recycle functionalized PET, because the BHET or DMT obtained after depolymerization will contain small molecules produced by the depolymerization of the functional components, affecting the purity of BHET or DMT. Even if the purity of BHET or DMT is improved by purification, it will increase the process difficulty and still waste the original functional components in the raw materials.

[0006] Therefore, it is of great significance to study a method for alcoholysis regeneration of waste functionalized PET based on mesomer to solve the problems of difficult control of polymer structure, wide molecular weight distribution, and limited large-scale promotion and application in the existing technology. Summary of the invention

[0007] The purpose of the invention is to solve the problems existing in the prior art and provide a method for alcoholysis regeneration of waste functionalized PET based on a mesomer.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A method for regenerating waste PET by alcoholysis based on intermediate polymers, wherein the melt obtained by melting the waste PET is transported to a closed reactor, superheated diol steam is introduced into the closed reactor to depolymerize the waste PET to obtain intermediate polymers, and then the intermediate polymers are sent to the polymerization stage of virgin polyester for reaction, and the regenerated polyester is prepared after the reaction is completed;

[0010] The degree of polymerization of the mesopolymer is 3 to 30, and the molecular weight distribution PDI is <3.

[0011] In the prior art, PET alcoholysis recovery is mainly through the depolymerization of PET in a diol solution. The depolymerization temperature is usually below the melting point of PET. Due to the different depolymerization efficiencies from the outside to the inside, in order to make the alcoholysis solution depolymerize evenly, the final target of alcoholysis is mainly BHET and DMT. The depolymerization is carried out with excess diol as the medium. If the chemical method of PET to PET is used for recovery, then alcoholysis to monomers such as BHET or DMT is not the best recovery solution. The method of repolymerizing PET from PET to intermediate polymers has a short process, low energy consumption and high efficiency. The existing method of using excessive diol for depolymerization cannot achieve the degree of polymerization control of the intermediate polymer; the PET alcoholysis adopted by the present invention is to pass the superheated diol vapor into the polyester melt to achieve alcoholysis, pass the superheated diol vapor into the closed reactor, inject the polyester melt into the closed reactor, and depolymerize at a certain temperature. The saturated vapor pressure can make the diol content in the melt consistent and evenly distributed, so as to depolymerize to obtain the intermediate polymer with uniform molecular weight distribution, realize homogenization, and avoid the uneven depolymerization from the surface layer to the inner layer in the solid state.

[0012] As the preferred technical solution:

[0013] A method for alcoholysis regeneration of waste PET based on intermediate polymer as described above, wherein the waste PET is waste PET bottle flakes, polyester waste yarn, polyester waste cloth or waste textiles containing polyester; the melting temperature of the waste PET is 250-270°C; single-component waste PET such as waste PET bottle flakes, polyester waste yarn, polyester waste cloth can be directly depolymerized and regenerated; waste textiles containing polyester include colored polyester textiles and polyester-cotton blended textiles, and the colored polyester textiles need to be decolorized before being recycled to prepare recycled PET or blended with masterbatch before spinning to complement the color to prepare dark recycled PET, and the polyester-cotton blended textiles need to filter out the cotton component before the intermediate polymer melt is conveyed (the cotton filtration is a three-stage filtration with filtration precisions of 500 mesh, 200 mesh and 100 mesh respectively) for recycling and reuse;

[0014] In the above-mentioned method for alcoholysis regeneration of waste PET based on intermediate polymer, the diol is ethylene glycol, 1,3-propylene glycol, 1,4-butanediol or 1,5-pentanediol.

[0015] In the above-mentioned method for alcoholysis regeneration of waste PET based on intermediate polymer, the temperature of superheated diol vapor is 250-270°C, the mass ratio of superheated diol vapor to melt is 2-10:1, and the depolymerization time is 10-30 min.

[0016] As described above, a method for alcoholysis regeneration of waste PET based on a mid-polymer, the general structural formula of the mid-polymer is:

[0017]

[0018] Wherein, x=3-30, R is (CH2) z , z = 2 to 5; by controlling the mass ratio of superheated diol vapor to melt and the depolymerization time, the value range of x can be controlled, thereby regulating the polymerization degree of the intermediate polymer.

[0019] The above-mentioned method for alcoholysis regeneration of waste PET based on intermediate polymer has the following specific process: the waste PET is melted and transported to a closed reactor, and then superheated diol vapor is introduced into the closed container to depolymerize the waste PET to obtain intermediate polymer, and then the intermediate polymer is sent to different polymerization stages of virgin PET according to the degree of polymerization of the intermediate polymer, so as to polymerize and obtain recycled polyester; wherein the addition amount of the intermediate polymer is 10 to 100 wt% of the recycled polyester (when the addition amount is 100 wt%, there is no virgin PET);

[0020] By controlling the flow rate and residence time of superheated diol vapor, PET can be controllably depolymerized into intermediate polymers with a certain degree of polymerization; according to different degrees of polymerization, the intermediate polymers transport the original PET to different polymerization stages to achieve polyester regeneration.

[0021] The above-mentioned method for regenerating waste PET by alcoholysis based on intermediate polymer, the polymerization of virgin PET includes 5 polymerization stages, which is a five-reactor polymerization, and the devices used include a first esterification reactor, a second esterification reactor, a first precondensation reactor, a second precondensation reactor and a final polycondensation reactor;

[0022] When x is 3 to 5, the intermediate polymer is sent to the first esterification reactor of the virgin PET;

[0023] When x is 6 to 12, the intermediate polymer is sent to the second esterification reactor of the virgin PET;

[0024] When x is 13 to 25, the intermediate polymer is sent to the first precondensation reactor of the virgin PET;

[0025] When x is 26-30, the intermediate polymer is sent to the second precondensation reactor of the original PET.

[0026] In the above-mentioned method for alcoholysis regeneration of waste PET based on intermediate polymer, the temperature of the first esterification kettle and the second esterification kettle is 240-260°C, and the pressure is 0-0.5MPa; the temperature of the first precondensation kettle, the second precondensation kettle and the final condensation kettle is 260-280°C, and the pressure is <200Pa.

[0027] According to the above-mentioned method for regenerating waste PET by alcoholysis based on medium polymer, the degree of polymerization of the obtained recycled PET is 100-150, the intrinsic viscosity is 0.65-0.90 dl / g, and the melting point is 250-260°C.

[0028] At present, in the prior art, PET alcoholysis recovery is mainly through the depolymerization of PET in a diol solution. The depolymerization temperature is usually below the melting point of PET. Due to the different depolymerization efficiencies from the outside to the inside, in order to make the alcoholysis solution depolymerize evenly, the final target of alcoholysis is mainly BHET and DMT, and the depolymerization is carried out with excess diol as the medium. If you want to obtain functionalized recycled polyester, use BHET or DMT as the raw material and polymerize it with the functionalized monomer. Since the chemical method of functionalized PET is limited by complex components, it is difficult to recycle functionalized PET, because the BHET or DMT obtained after depolymerization will contain small molecules produced by the depolymerization of the functional components, which affects the purity of BHET or DMT. Even if the purity of BHET or DMT is improved by purification, it will increase the difficulty of the process and still waste the original functional components in the raw materials;

[0029] The alcoholysis of PET used in the present invention is to pass the superheated diol steam into the waste functionalized PET to realize alcoholysis; the hot diol steam is directly passed into the closed reactor to carry out alcoholysis on the waste functionalized PET melt to realize homogenization, avoiding the uneven depolymerization from the surface layer to the inner layer in the solid state; at this time, the intermediate polymer obtained by alcoholysis is an intermediate polymer with functional components, and then the functional monomer can be added according to the demand to adjust the proportion of the functional components (functional monomers different from the functional components in the raw materials can also be added), so as to obtain the functionalized recycled polyester desired by the technicians. Therefore, the method of the present invention not only effectively recovers the waste functionalized PET, shortens the process, but also makes full use of the functional components therein.

[0030] A method for alcoholysis regeneration of waste functionalized PET based on intermediate polymer, wherein the melt obtained by melting the waste functionalized PET is transported to a closed reactor, superheated diol steam is introduced into the closed reactor to depolymerize the waste functionalized PET to obtain intermediate polymer, and then functional monomers and diols are added to the closed reactor to co-esterify the intermediate polymer, and the co-esterified product is sent to the polymerization stage of the original polyester for reaction, and the functionalized regenerated polyester is prepared after the reaction is completed;

[0031] The degree of polymerization of the mesopolymer is 3 to 30, and the molecular weight distribution PDI is <3.

[0032] As the preferred technical solution:

[0033] A method for alcoholysis regeneration of waste functionalized PET based on a mesomer as described above, wherein the waste functionalized PET is flame retardant PET or cationic dye-dyeable PET; the melting temperature of the waste functionalized PET is 220-240°C;

[0034] In the above-mentioned method for alcoholysis regeneration of waste functionalized PET based on intermediate polymer, the diol is one or more of ethylene glycol, 1,3-propylene glycol, 1,4-butanediol and 1,5-pentanediol.

[0035] In the above-mentioned method for alcoholysis regeneration of waste functionalized PET based on intermediate polymer, the functional monomer is sodium 5-sulfonate of isophthalic acid, 3-hydroxyphenylphosphatidyl propionic acid, [(6-oxy-6H-dibenzo-(C,E)(1,2)-oxaphosphorin-6-one)-methyl]-succinic acid or isophthalic acid.

[0036] As described above, in the alcoholysis regeneration method of waste functionalized PET based on the intermediate polymer, the temperature of the superheated diol steam is 250-270°C, the mass ratio of the superheated diol steam to the melt is 2-10:1, and the depolymerization time is 10-30 min; the co-esterification temperature is 220-240°C, the co-esterification time is 2-4 h, the co-esterification pressure is 0.2-0.5 MPa, the amount of functional monomer added is 5-10 wt% of the intermediate polymer, and the alcohol-acid ratio of the diol added after depolymerization to obtain the intermediate polymer to the functional monomer is 1.1-1.3:1.

[0037] As described above, the alcoholysis regeneration method of waste functionalized PET based on the intermediate polymer has the general structural formula of:

[0038]

[0039] Among them, x = 3 to 30. By controlling the mass ratio of superheated diol vapor to melt and the depolymerization time, the value range of x can be controlled, thereby regulating the degree of polymerization of the intermediate polymer. R is (CH2) z , z=2~5, R0 is the functional component, the raw material corresponding to the functional component is the functional monomer, and the functional monomer corresponding to the functional component in the mesopolymer may or may not be the same substance as the functional monomer added after depolymerization to obtain the mesopolymer.

[0040] The above-mentioned method for alcoholysis regeneration of waste functionalized PET based on intermediate polymer has the following specific process: the waste functionalized PET is melted and transported to a closed reactor, and then superheated diol steam is introduced into the closed container to depolymerize the waste PET to obtain intermediate polymer, and then functional monomers and diols are added to the closed reactor to co-esterify with the intermediate polymer, and then the co-esterified product is sent to different polymerization stages of virgin PET according to the degree of polymerization of the intermediate polymer, so as to polymerize and obtain regenerated functional polyester; wherein the addition amount of the intermediate polymer is 10 to 100 wt% of the functionalized regenerated polyester, and when the addition amount is 100 wt%, there is no virgin PET;

[0041] By controlling the inflow rate and residence time of superheated diol vapor, PET can be controllably depolymerized into intermediate polymers with a certain degree of polymerization; according to different degrees of polymerization, the intermediate polymers are transported to the same polymerization stage of the original PET to achieve polyester regeneration.

[0042] The above-mentioned method for alcoholysis regeneration of waste functionalized PET based on intermediate polymer, the polymerization of virgin PET includes 5 polymerization stages, which is a five-reactor polymerization, and the devices used include a first esterification reactor, a second esterification reactor, a first precondensation reactor, a second precondensation reactor and a final polycondensation reactor;

[0043] When x is 3 to 5, the intermediate polymer is sent to the first esterification reactor of the virgin PET;

[0044] When x is 6 to 12, the intermediate polymer is sent to the second esterification reactor of the virgin PET;

[0045] When x is 13 to 25, the intermediate polymer is sent to the first precondensation reactor of the virgin PET;

[0046] When x is 26-30, the intermediate polymer is sent to the second precondensation reactor of the original PET.

[0047] In the above-mentioned method for alcoholysis regeneration of waste functionalized PET based on intermediate polymer, the temperature of the first esterification kettle and the second esterification kettle is 240-260°C, and the pressure is 0-0.5MPa; the temperature of the first precondensation kettle, the second precondensation kettle and the final condensation kettle is 260-280°C, and the pressure is <200Pa.

[0048] According to the above-mentioned method for alcoholysis regeneration of waste functionalized PET based on intermediate polymer, the degree of polymerization of the obtained recycled PET is 100-150, the intrinsic viscosity is 0.65-0.85 dl / g, and the melting point is 230-250°C.

[0049] Beneficial effects:

[0050] (1) The present invention is a method for regenerating waste PET by alcoholysis based on intermediate polymers. First, the waste PET is melted and then transported to a reactor. Then, superheated diol is introduced into the melt. Depolymerization can be achieved in a homogeneous state, avoiding the process of gradual depolymerization of solid-phase PET from the surface layer to the inner layer. The degree of polymerization of the depolymerization product can be controlled to prepare the intermediate polymer, and the uniformity is increased after repolymerization.

[0051] (2) The present invention is a method for regenerating waste PET by alcoholysis based on intermediate polymers. Diol is used as one of the raw materials for polyester synthesis. The introduction of diol as a depolymerizing agent into the molecular chain does not affect its repolymerization. The chemical structure of the alcoholysis product is mainly a hydroxyl alcohol structure, and ester exchange can be directly carried out to achieve polycondensation reaction.

[0052] (3) In the alcoholysis regeneration method of waste PET based on intermediate polymer of the present invention, diol is not directly used as a medium, but is directly passed into the melt in the form of superheated steam. The degree of polymerization of the intermediate polymer is controlled by flow rate and time. Under superheated conditions, excess diol steam overflows from the melt and directly accumulates at the upper end of the reactor, where it can be directly recovered and reused, thereby greatly reducing costs.

[0053] (4) In the alcoholysis regeneration method of waste PET based on intermediate polymers of the present invention, intermediate polymers with different polymerization degrees can be added to the first esterification kettle, the second esterification kettle, the first pre-polycondensation kettle, the second pre-polycondensation kettle and the final polycondensation kettle, which are connected with the original polyester preparation process, and can realize partial addition or full regeneration process, and the addition ratio of recycled polyester can be adjusted according to actual needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 The schematic diagram is a method for alcoholysis regeneration of waste PET based on intermediate polymer;

[0055] Figure 2 The schematic diagram is a method for alcoholysis regeneration of waste functionalized PET based on intermediate polymer; wherein y is the original degree of polymerization of the functional PET before depolymerization. DETAILED DESCRIPTION

[0056] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0057] The test methods involved in the performance indicators of the present invention are as follows:

[0058] Degree of polymerization: Calculated by viscosity average molecular weight; calculation formula: [η] = KM α , x = M / 228; where K and α are solvent constants; the test solvent is phenol / tetrachloroethane with a mass ratio of 1:1; at 25°C, K = 2.1×10 -4 , α=0.82), [η] is the test relative viscosity, M is the average molecular weight of the polymer, and x is the degree of polymerization. Intrinsic viscosity: Use an Ubbelohde viscometer with a capillary diameter of 0.7-0.8mm for testing. Use an electronic balance to take 0.25g of the sample to be tested and dissolve it in a phenol-tetrachloroethane solvent with a mass ratio of 1:1. Use a 50ml volumetric flask to prepare a solution with a concentration of 0.005g / ml. Dissolve it completely in a 60-70℃ water bath, and then put the prepared solution into a 25℃ constant temperature water bath for ten minutes; the temperature of the constant temperature water bath is 25±0.1℃. Observe and record the solution flowing through the upper and lower scale lines of the Ubbelohde viscometer, take the average of three tests for each sample as the final result, and the calculation process is according to the following formula.

[0059]

[0060] Where: η r —relative viscosity; t1—solution flow time (s); t0—solvent flow time (s); η sp —Specific viscosity; [η]—intrinsic viscosity.

[0061] Molecular weight distribution PDI: The number average molecular weight and molecular weight distribution (PDI) of the samples were tested using a GPC-50 gel permeation chromatograph produced by PL Company of the United Kingdom. The equipment was equipped with a differential refractometer and a PL gel column (5μm mixed-C), with 1,1,1,3,3,3-hexafluoro-2-propanol as the eluent and a flow rate of 1mL / min. During the test, the sample was dried and dissolved in hexafluoroisopropanol to prepare a 1.0mg / mL solution, and the test was carried out when the column temperature reached 40±1℃.

[0062] The raw materials in the embodiments of the present invention are derived from bulk chemical raw materials.

[0063] Example 1

[0064] A method for regenerating waste PET by alcoholysis based on intermediate polymer, such as Figure 1 As shown, the specific steps are as follows:

[0065] (1) Preparation of raw materials:

[0066] Waste PET: Waste PET bottle flakes;

[0067] Diol: ethylene glycol;

[0068] (2) melting the waste PET at 250° C. to obtain a melt which is transported to a closed reactor, and then passing 250° C. superheated diol vapor into the closed container to depolymerize the waste PET for 30 min to obtain a polymer having a degree of polymerization of 3 and a molecular weight distribution (PDI) of 1.3;

[0069] Among them, the mass ratio of superheated diol vapor to melt is 10:1; the structural formula of the intermediate polymer is:

[0070]

[0071] (3) according to the degree of polymerization of the intermediate polymer, sending the intermediate polymer to the first esterification kettle of the original PET for polymerization reaction, the polymerization of the original PET includes 5 polymerization stages, the equipment used includes the first esterification kettle, the second esterification kettle, the first pre-polycondensation kettle, the second pre-polycondensation kettle and the final polycondensation kettle, and the reaction is completed to prepare the recycled polyester;

[0072] Among them, the addition amount of the intermediate polymer is 100wt% of the recycled polyester; the temperature of the first esterification kettle and the second esterification kettle is 240℃, and the pressure is 0.5MPa; the temperature of the first precondensation kettle, the second precondensation kettle and the final condensation kettle is 260℃, and the pressure is 100Pa.

[0073] The degree of polymerization of the recycled PET finally obtained is 150, the intrinsic viscosity is 0.9 dl / g, and the melting point is 260°C.

[0074] Example 2

[0075] A method for regenerating waste PET by alcoholysis based on intermediate polymer, the specific steps are as follows:

[0076] (1) Preparation of raw materials:

[0077] Waste PET: waste polyester yarn;

[0078] Diol: 1,3-propylene glycol;

[0079] (2) the waste PET is melted at a temperature of 255° C. to obtain a melt which is transported to a closed reactor, and then superheated diol vapor at 255° C. is introduced into the closed container to depolymerize the waste PET for 25 min to obtain a polymer having a degree of polymerization of 8 and a molecular weight distribution (PDI) of 1.7;

[0080] Among them, the mass ratio of superheated diol vapor to melt is 6:1; the structural formula of the intermediate polymer is:

[0081]

[0082] (3) according to the degree of polymerization of the intermediate polymer, sending the intermediate polymer to the second esterification kettle of the original PET for polymerization reaction, the polymerization of the original PET includes 5 polymerization stages, the equipment used includes the first esterification kettle, the second esterification kettle, the first pre-polycondensation kettle, the second pre-polycondensation kettle and the final polycondensation kettle, and the reaction is completed to prepare the recycled polyester;

[0083] Among them, the addition amount of the intermediate polymer is 75wt% of the recycled polyester; the temperature of the first esterification kettle and the second esterification kettle is 245℃, and the pressure is 0.4MPa; the temperature of the first precondensation kettle, the second precondensation kettle and the final condensation kettle is 265℃, and the pressure is 100Pa.

[0084] The degree of polymerization of the recycled PET finally obtained is 130, the intrinsic viscosity is 0.82 dl / g, and the melting point is 257°C.

[0085] Example 3

[0086] A method for regenerating waste PET by alcoholysis based on intermediate polymer, the specific steps are as follows:

[0087] (1) Preparation of raw materials:

[0088] Waste PET: Waste polyester fabric;

[0089] Diol: 1,4-butanediol;

[0090] (2) the waste PET is melted at 260° C. to obtain a melt which is transported to a closed reactor, and then superheated diol vapor at 260° C. is introduced into the closed container to depolymerize the waste PET for 20 min to obtain a polymer having a degree of polymerization of 21 and a molecular weight distribution (PDI) of 2.3;

[0091] Among them, the mass ratio of superheated diol vapor to melt is 4:1; the structural formula of the intermediate polymer is:

[0092]

[0093] (3) according to the degree of polymerization of the intermediate polymer, sending the intermediate polymer to the first pre-polycondensation kettle of the virgin PET for polymerization reaction, the polymerization of the virgin PET includes 5 polymerization stages, the equipment used includes the first esterification kettle, the second esterification kettle, the first pre-polycondensation kettle, the second pre-polycondensation kettle and the final polycondensation kettle, and the reaction is completed to prepare the recycled polyester;

[0094] Among them, the addition amount of the intermediate polymer is 50wt% of the recycled polyester; the temperature of the first esterification kettle and the second esterification kettle is 250℃, and the pressure is 0.2MPa; the temperature of the first precondensation kettle, the second precondensation kettle and the final condensation kettle is 270℃, and the pressure is 100Pa.

[0095] The degree of polymerization of the recycled PET finally obtained is 125, the intrinsic viscosity is 0.78 dl / g, and the melting point is 255°C.

[0096] Example 4

[0097] A method for regenerating waste PET by alcoholysis based on intermediate polymer, the specific steps are as follows:

[0098] (1) Preparation of raw materials:

[0099] Waste PET: Colored polyester waste textiles;

[0100] Diol: 1,5-pentanediol;

[0101] (2) the waste PET is melted at 265° C. to obtain a melt which is transported to a closed reactor, and then superheated diol vapor at 270° C. is introduced into the closed container to depolymerize the waste PET for 15 min to obtain a polymer having a degree of polymerization of 28 and a molecular weight distribution (PDI) of 2.7;

[0102] Among them, the mass ratio of superheated diol vapor to melt is 2:1; the structural formula of the intermediate polymer is:

[0103]

[0104] (3) according to the polymerization degree of the intermediate polymer, sending the intermediate polymer to the second pre-polycondensation kettle of the virgin PET for polymerization reaction, the polymerization of the virgin PET includes 5 polymerization stages, the equipment used includes the first esterification kettle, the second esterification kettle, the first pre-polycondensation kettle, the second pre-polycondensation kettle and the final polycondensation kettle, and the reaction is completed to prepare the recycled polyester;

[0105] Among them, the addition amount of the intermediate polymer is 25wt% of the recycled polyester; the temperature of the first esterification kettle and the second esterification kettle is 255℃, and the pressure is 0.1MPa; the temperature of the first precondensation kettle, the second precondensation kettle and the final condensation kettle is 275℃, and the pressure is 150Pa.

[0106] The degree of polymerization of the recycled PET finally obtained is 110, the intrinsic viscosity is 0.71 dl / g, and the melting point is 253°C.

[0107] Example 5

[0108] A method for regenerating waste PET by alcoholysis based on intermediate polymer, the specific steps are as follows:

[0109] (1) Preparation of raw materials:

[0110] Waste PET: polyester-cotton blended waste textiles (polyester / cotton ratio is 80 / 20);

[0111] Diol: ethylene glycol;

[0112] (2) the waste PET is melted at 270° C. to obtain a melt which is transported to a closed reactor, and then superheated diol vapor at 250° C. is introduced into the closed container to depolymerize the waste PET for 10 min to obtain a polymer having a degree of polymerization of 15 and a molecular weight distribution (PDI) of 2.0;

[0113] Among them, the mass ratio of superheated diol vapor to melt is 8:1; the structural formula of the intermediate polymer is:

[0114]

[0115] (3) according to the degree of polymerization of the intermediate polymer, sending the intermediate polymer to the first pre-polycondensation kettle of the virgin PET for polymerization reaction, the polymerization of the virgin PET includes 5 polymerization stages, the equipment used includes the first esterification kettle, the second esterification kettle, the first pre-polycondensation kettle, the second pre-polycondensation kettle and the final polycondensation kettle, and the reaction is completed to prepare the recycled polyester;

[0116] Among them, the addition amount of the intermediate polymer is 10wt% of the recycled polyester; the temperature of the first esterification kettle and the second esterification kettle is 260℃, and the pressure is 0MPa; the temperature of the first precondensation kettle, the second precondensation kettle and the final condensation kettle is 280℃, and the pressure is 150Pa.

[0117] The degree of polymerization of the finally obtained recycled PET is 100, the intrinsic viscosity is 0.65 dl / g, and the melting point is 250°C.

[0118] Example 6

[0119] A method for regenerating waste functionalized PET by alcoholysis based on intermediate polymer, such as Figure 2 As shown, the specific steps are as follows:

[0120] (1) Preparation of raw materials:

[0121] Waste functionalized PET: flame retardant PET;

[0122] Diol: ethylene glycol;

[0123] Functional monomer: 3-hydroxyphenylphosphinopropionic acid;

[0124] (2) The waste functionalized PET was melted at 230°C and transported to a closed reactor, and then superheated diol vapor at 250°C was introduced into the closed container to depolymerize the waste PET for 30 minutes to obtain a polymer with a degree of polymerization of 3 and a molecular weight distribution (PDI) of 1.6, and then functional monomers and diols were added to the closed reactor to co-esterify with the polymer at 220°C and 0.2 MPa for 4 hours;

[0125] The mass ratio of superheated diol vapor to melt is 10:1; the amount of functional monomer added is 8wt% of the intermediate polymer; the ratio of diol added after depolymerization to the functional monomer is 1.15:1; the structural formula of the intermediate polymer is:

[0126] R0 is a functional component, and the raw material corresponding to the functional component is a functional monomer;

[0127] (3) according to the degree of polymerization of the intermediate polymer, the co-esterified product is sent to the first esterification kettle of the original PET for polymerization reaction. The polymerization of the original PET includes 5 polymerization stages. The equipment used includes the first esterification kettle, the second esterification kettle, the first pre-polycondensation kettle, the second pre-polycondensation kettle and the final polycondensation kettle. After the reaction is completed, the functionalized recycled polyester is prepared.

[0128] Among them, the addition amount of the intermediate polymer is 50wt% of the functionalized recycled polyester; the temperature of the first esterification kettle and the second esterification kettle is 240°C, and the pressure is 0.5MPa; the temperature of the first precondensation kettle, the second precondensation kettle and the final condensation kettle is 260°C, and the pressure is 100Pa.

[0129] The degree of polymerization of the finally obtained recycled PET is 100, the intrinsic viscosity is 0.65 dl / g, and the melting point is 240°C.

[0130] Example 7

[0131] A method for alcoholysis regeneration of waste functionalized PET based on mid-polymer, the specific steps are as follows:

[0132] (1) Preparation of raw materials:

[0133] Waste functionalized PET: Cationic dyes can dye PET;

[0134] Diol: 1,3-propylene glycol;

[0135] Functional monomer: sodium 5-sulfonisophthalate;

[0136] (2) The waste functionalized PET was melted at 240°C and transported to a closed reactor, and then superheated diol vapor at 255°C was introduced into the closed container to depolymerize the waste PET for 25 minutes to obtain a polymer with a degree of polymerization of 6 and a molecular weight distribution (PDI) of 1.9, and then functional monomers and diols were added to the closed reactor to co-esterify the polymer at 225°C and 0.3 MPa for 3.5 hours;

[0137] The mass ratio of superheated diol vapor to melt is 7:1; the amount of functional monomer added is 10wt% of the intermediate polymer; the ratio of diol added after depolymerization to the functional monomer is 1.1:1; the structural formula of the intermediate polymer is:

[0138] R0 is a functional component, and the raw material corresponding to the functional component is a functional monomer;

[0139] (3) according to the degree of polymerization of the intermediate polymer, the co-esterified product is sent to the second esterification kettle of the original PET for polymerization reaction. The polymerization of the original PET includes 5 polymerization stages. The device used includes a first esterification kettle, a second esterification kettle, a first pre-polycondensation kettle, a second pre-polycondensation kettle and a final polycondensation kettle. After the reaction is completed, the functionalized recycled polyester is prepared;

[0140] Among them, the addition amount of the intermediate polymer is 70wt% of the functionalized recycled polyester; the temperature of the first esterification kettle and the second esterification kettle is 245°C, and the pressure is 0.1MPa; the temperature of the first precondensation kettle, the second precondensation kettle and the final condensation kettle is 265°C, and the pressure is 100Pa.

[0141] The degree of polymerization of the recycled PET finally obtained is 120, the intrinsic viscosity is 0.7 dl / g, and the melting point is 245°C.

[0142] Example 8

[0143] A method for alcoholysis regeneration of waste functionalized PET based on mid-polymer, the specific steps are as follows:

[0144] (1) Preparation of raw materials:

[0145] Waste functionalized PET: flame retardant PET;

[0146] Diol: 1,4-butanediol;

[0147] Functional monomer: [(6-oxo-6H-dibenzo-(C,E)(1,2)-oxaphosphorin-6-one)-methyl]-succinic acid;

[0148] (2) The waste functionalized PET was melted at 220°C and transported to a closed reactor, and then superheated diol vapor at 260°C was introduced into the closed container to depolymerize the waste PET for 20 minutes to obtain a polymer with a degree of polymerization of 26 and a molecular weight distribution (PDI) of 2.9, and then functional monomers and diols were added to the closed reactor to co-esterify with the polymer at 230°C and 0.35 MPa for 3 hours;

[0149] The mass ratio of superheated diol vapor to melt is 2:1; the amount of functional monomer added is 5wt% of the intermediate polymer; the ratio of diol added after depolymerization to the functional monomer is 1.3:1; the structural formula of the intermediate polymer is:

[0150] R0 is a functional component, and the raw material corresponding to the functional component is a functional monomer;

[0151] (3) according to the degree of polymerization of the intermediate polymer, the co-esterified product is sent to the second pre-polycondensation kettle of the original PET for polymerization reaction. The polymerization of the original PET includes 5 polymerization stages. The device used includes a first esterification kettle, a second esterification kettle, a first pre-polycondensation kettle, a second pre-polycondensation kettle and a final polycondensation kettle. After the reaction is completed, the functionalized recycled polyester is prepared;

[0152] Among them, the addition amount of the intermediate polymer is 25wt% of the functionalized recycled polyester; the temperature of the first esterification kettle and the second esterification kettle is 250°C, and the pressure is 0.4MPa; the temperature of the first precondensation kettle, the second precondensation kettle and the final condensation kettle is 270°C, and the pressure is 100Pa.

[0153] The degree of polymerization of the recycled PET finally obtained is 135, the intrinsic viscosity is 0.78 dl / g, and the melting point is 235°C.

[0154] Example 9

[0155] A method for alcoholysis regeneration of waste functionalized PET based on mid-polymer, the specific steps are as follows:

[0156] (1) Preparation of raw materials:

[0157] Waste functionalized PET: Cationic dyes can dye PET;

[0158] Diol: 1,5-pentanediol;

[0159] Functional monomer: isophthalic acid;

[0160] (2) The waste functionalized PET was melted at 230° C. and transported to a closed reactor. The waste PET was depolymerized by passing superheated diol vapor at 270° C. into the closed container for 15 min to obtain a polymer having a degree of polymerization of 19 and a molecular weight distribution (PDI) of 2.4. Subsequently, the functional monomer and diol were added to the closed reactor to co-esterify the polymer at 235° C. and 0.4 MPa for 2.5 h.

[0161] The mass ratio of superheated diol vapor to melt is 6:1; the amount of functional monomer added is 6wt% of the intermediate polymer; the ratio of diol added after depolymerization to the alcohol-acid ratio of the functional monomer is 1.25:1; the structural formula of the intermediate polymer is:

[0162] R0 is a functional component, and the raw material corresponding to the functional component is a functional monomer;

[0163] (3) according to the degree of polymerization of the intermediate polymer, the co-esterified product is sent to the first pre-polycondensation kettle of the virgin PET for polymerization reaction. The polymerization of the virgin PET includes 5 polymerization stages. The device used includes a first esterification kettle, a second esterification kettle, a first pre-polycondensation kettle, a second pre-polycondensation kettle and a final polycondensation kettle. After the reaction is completed, the functionalized recycled polyester is prepared;

[0164] Among them, the addition amount of the intermediate polymer is 10wt% of the functionalized recycled polyester; the temperature of the first esterification kettle and the second esterification kettle is 255°C, and the pressure is 0.2MPa; the temperature of the first precondensation kettle, the second precondensation kettle and the final condensation kettle is 275°C, and the pressure is 150Pa.

[0165] The degree of polymerization of the recycled PET finally obtained is 145, the intrinsic viscosity is 0.83 dl / g, and the melting point is 250°C.

[0166] Example 10

[0167] A method for alcoholysis regeneration of waste functionalized PET based on mid-polymer, the specific steps are as follows:

[0168] (1) Preparation of raw materials:

[0169] Waste functionalized PET: flame retardant PET;

[0170] Diol: a mixed solution of 1,4-butanediol and 1,5-pentanediol in a volume ratio of 1:1;

[0171] Functional monomer: 3-hydroxyphenylphosphinopropionic acid;

[0172] (2) The waste functionalized PET was melted at 225°C and transported to a closed reactor, and then superheated diol vapor at 260°C was introduced into the closed container to depolymerize the waste PET for 25 minutes to obtain a polymer with a degree of polymerization of 15 and a molecular weight distribution (PDI) of 2.1, and then functional monomers and diols were added to the closed reactor to co-esterify with the polymer at 240°C and 0.5 MPa for 2 hours;

[0173] The mass ratio of superheated diol vapor to melt is 4:1; the amount of functional monomer added is 8wt% of the intermediate polymer; the ratio of diol added after depolymerization to the functional monomer is 1.2:1; the structural formula of the intermediate polymer is:

[0174] R0 is a functional component, and the raw material corresponding to the functional component is a functional monomer;

[0175] (3) according to the degree of polymerization of the intermediate polymer, the co-esterified product is sent to the first pre-polycondensation kettle of the virgin PET for polymerization reaction. The polymerization of the virgin PET includes 5 polymerization stages. The device used includes a first esterification kettle, a second esterification kettle, a first pre-polycondensation kettle, a second pre-polycondensation kettle and a final polycondensation kettle. After the reaction is completed, the functionalized recycled polyester is prepared;

[0176] Among them, the addition amount of the intermediate polymer is 100wt% of the functionalized recycled polyester; the temperature of the first esterification kettle and the second esterification kettle is 260°C, and the pressure is 0MPa; the temperature of the first precondensation kettle, the second precondensation kettle and the final condensation kettle is 280°C, and the pressure is 150Pa.

[0177] The degree of polymerization of the recycled PET finally obtained is 150, the intrinsic viscosity is 0.90 dl / g, and the melting point is 230°C.

Claims

1. A method for alcoholysis regeneration of waste functionalized PET based on mid-polymer, characterized in that: The melt obtained by melting the waste functionalized PET is transported to a closed reactor, superheated diol steam is introduced into the closed reactor to depolymerize the waste functionalized PET to obtain a mid-polymer, and then functional monomers and diols are added to the closed reactor to co-esterify the mid-polymer, and the co-esterified product is sent to the polymerization stage of the original polyester for reaction, and the functionalized recycled polyester is prepared after the reaction is completed; The degree of polymerization of the mesopolymer is 3 to 30, and the molecular weight distribution PDI is <3.

2. The method for alcoholysis regeneration of waste functionalized PET based on mid-polymer according to claim 1, characterized in that: The waste functionalized PET is flame-retardant PET or PET dyeable with cationic dyes; the melting temperature of the waste functionalized PET is 220-240°C.

3. The method for alcoholysis regeneration of waste functionalized PET based on mid-polymer according to claim 1, characterized in that: The diol is one or more of ethylene glycol, 1,3-propylene glycol, 1,4-butanediol and 1,5-pentanediol.

4. The method for alcoholysis regeneration of waste functionalized PET based on mid-polymer according to claim 1, characterized in that: The functional monomer is sodium 5-sulfonate of isophthalic acid, 3-hydroxyphenylphosphoryl propionic acid, [(6-oxy-6H-dibenzo-(C,E)(1,2)-oxaphosphorin-6-one)-methyl]-succinic acid or isophthalic acid.

5. The method for alcoholysis regeneration of waste functionalized PET based on mid-polymer according to claim 1, characterized in that: The temperature of the superheated diol steam is 250-270°C, the mass ratio of the superheated diol steam to the melt is 2-10:1, and the depolymerization time is 10-30 minutes; the co-esterification temperature is 220-240°C, the co-esterification time is 2-4 hours, the co-esterification pressure is 0.2-0.5 MPa, the amount of functional monomer added is 5-10wt% of the intermediate polymer, and the alcohol-acid ratio of the diol added after depolymerization to obtain the intermediate polymer to the functional monomer is 1.1-1.3:

1.

6. The method for alcoholysis regeneration of waste functionalized PET based on mid-polymer according to claim 1, characterized in that: The general structural formula of the mesopolymer is: Wherein, x=3-30, R is (CH2) z , z=2~5, R0 is the functional component, and the raw material corresponding to the functional component is the functional monomer.

7. The method for alcoholysis regeneration of waste functionalized PET based on mid-polymer according to claim 1, characterized in that: The specific process of the alcoholysis regeneration method of waste functionalized PET based on intermediate polymer is as follows: the waste functionalized PET is transported to a closed reactor after being melted, and then superheated diol vapor is introduced into the closed container to depolymerize the waste PET to obtain intermediate polymer, and then functional monomers and diols are added to the closed reactor to co-esterify with the intermediate polymer, and then the co-esterified product is sent to different polymerization stages of the original PET according to the polymerization degree of the intermediate polymer, thereby polymerizing to obtain regenerated functional polyester; wherein the addition amount of the intermediate polymer is 10 to 100 wt% of the functionalized recycled polyester.

8. The method for alcoholysis regeneration of waste functionalized PET based on mid-polymer according to claim 7, characterized in that: The polymerization of virgin PET includes five polymerization stages, which is a five-pot polymerization. The devices used include the first esterification pot, the second esterification pot, the first pre-polycondensation pot, the second pre-polycondensation pot and the final polycondensation pot; When x is 3 to 5, the intermediate polymer is sent to the first esterification reactor of the virgin PET; When x is 6 to 12, the intermediate polymer is sent to the second esterification reactor of the virgin PET; When x is 13 to 25, the intermediate polymer is sent to the first precondensation reactor of the virgin PET; When x is 26-30, the intermediate polymer is sent to the second precondensation reactor of the original PET.

9. The method for alcoholysis regeneration of waste functionalized PET based on mid-polymer according to claim 8, characterized in that: The temperature of the first esterification kettle and the second esterification kettle is 240-260°C, and the pressure is 0-0.5MPa; the temperature of the first pre-polycondensation kettle, the second pre-polycondensation kettle and the final polycondensation kettle is 260-280°C, and the pressure is <200Pa.

10. A method for alcoholysis regeneration of waste functionalized PET based on intermediate polymer according to any one of claims 1 to 9, characterized in that: The polymerization degree of the obtained recycled PET is 100-150, the intrinsic viscosity is 0.65-0.85 dl / g, and the melting point is 230-250°C.

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