CN114773668B - Degradable PBAT polymer regenerated from waste PBT, and preparation and application thereof - Google Patents

Degradable PBAT polymer regenerated from waste PBT, and preparation and application thereof Download PDF

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CN114773668B
CN114773668B CN202210271615.2A CN202210271615A CN114773668B CN 114773668 B CN114773668 B CN 114773668B CN 202210271615 A CN202210271615 A CN 202210271615A CN 114773668 B CN114773668 B CN 114773668B
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pbt
waste
degradable
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CN114773668A (en
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朱科宇
江振林
张运
侯芳
陈敏萱
朱敏
范欣
任皖挺
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Shanghai University of Engineering Science
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    • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
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    • C09J167/00—Adhesives based on polyesters obtained by reactions forming a carboxylic ester link in the main chain; Adhesives based on derivatives of such polymers
    • C09J167/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
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    • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
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Abstract

The invention relates to a degradable PBAT polymer regenerated from waste PBT, and preparation and application thereof, wherein a waste PBT material is used as a raw material to carry out alcoholysis and filtration to obtain regenerated BHBT, and then the regenerated BHBT and BHAT are subjected to ester exchange polycondensation reaction to obtain the degradable PBAT polymer; adding phytic acid, sodium phytate or potassium phytate as a complexing agent in the alcoholysis; the weight average molecular weight of the prepared degradable PBAT polymer is 10000-80000, the melting point is 40-125 ℃, the melt index measured under the conditions that the temperature is 190 ℃ and the load is 2.16kg is 8-50 g/10min, the carboxyl end group content is 15-80 mmol/t, the b value of chromaticity is 5-20, the intrinsic viscosity is 0.5-1.6 dL/g, and the biodegradation rate in 90 days is 50-90%. The PBAT material which can be completely biodegraded is prepared by chemical alcoholysis and repolymerization, and can be used in the fields of packaging, tableware, agricultural films, biomedical polymer materials and the like.

Description

Degradable PBAT polymer regenerated from waste PBT, and preparation and application thereof
Technical Field
The invention belongs to the technical field of recycling of waste materials, and relates to a degradable PBAT polymer regenerated from waste PBT, and preparation and application thereof.
Background
The PBAT has good biodegradability, can be completely degraded by microorganisms in nature after being used, and becomes a mainstream degradable plastic product in the future. Compared with the traditional non-degradable plastic PE, the unit cost of PBAT is higher than 26 percent, which is very not favorable for large-area application and popularization in domestic markets. The reason for this is that the cost of PBAT production is higher than other degradable materials widely accepted by the market due to the high price of the raw materials (PTA, AA, and BDO) of terephthalic acid.
The patent application CN202011580761.0 discloses a production device for recycling polyester to regenerate degradable material PBAT, comprising the steps of conducting alcoholysis on dried recycled PET through an alcoholysis reaction system to obtain crude BHET, then obtaining a BHET monomer through a dealcoholization system, reacting with BDO in a first esterification reaction system to obtain a BHBT monomer, reacting with an AA esterified substance in a second esterification reaction system to obtain a copolymerized esterified substance, and then conducting polycondensation through a pre-polycondensation reaction system and a final polycondensation reaction system to improve the weight average molecular weight to obtain the PBAT product. The invention has reasonable process, high automation degree, high production efficiency and stable product quality. However, in the method, rectification and impurity removal can not be performed on the polyester in the alcoholysis process, only the recycled polyester with single component and less impurity-containing materials can be regenerated, and in the general polyester chemical alcoholysis recycling process, the alcoholysis reaction of the polyester is accelerated by introducing the alcoholysis catalysts such as metal ions of zinc, magnesium, cobalt, tin and the like, but because the introduced alcoholysis catalysts are difficult to remove, the residual metal ions cause the influence on the quality of the product in the process of preparing the new polyester, such as difficult polymerization, yellow product color and even serious degradation; in order to reduce the influence of the existing metal ions and pigments on the quality, a small molecular monomer such as dimethyl terephthalate is generated by complete degradation in the polyester alcoholysis process, and polymerization is carried out after flash distillation and rectification of the small molecular monomer, so that the product purity is improved, but the problems of high cost and difficulty in large-scale popularization and application are inevitably caused; however, the prior art does not have a process technology for preparing the high-quality degradable polymer PBAT after the alcoholysis of the polyester.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a preparation method for regenerating waste PBT into a degradable PBAT polymer. Firstly, pretreating the waste PBT, then carrying out alcoholysis on the waste PBT serving as a raw material under the condition that butanediol is used as a solvent to obtain a polymeric esterified monomer BHBT, then carrying out esterification on adipic acid and butanediol to obtain BHAT, and finally carrying out ester exchange polycondensation reaction on the BHBT and the BHAT to prepare a biodegradable PBAT polymer; the scheme for preparing the raw material and producing the PBAT by alcoholysis of the waste PBT not only solves the problem of recycling the PBT, but also converts the non-degradable PBT into the environment-friendly biodegradable PBAT material, thereby realizing high-value utilization of the waste PBT material.
In order to achieve the purpose, the invention adopts the following scheme:
a preparation method for regenerating waste PBT into a degradable PBAT polymer comprises the steps of carrying out alcoholysis and filtration by taking a waste PBT material as a raw material to obtain regenerated BHBT, and then carrying out ester exchange and polycondensation on the regenerated BHBT (dibutyl terephthalate) and BHAT (dibutyl adipate) to obtain the degradable PBAT polymer;
and adding phytic acid, sodium phytate or potassium phytate as a complexing agent in the alcoholysis. The selected complexing agent has strong integration capability on metal ions in a wide pH range, and meanwhile, phytic acid and salts thereof have certain aging resistance, so that the complexing reaction can be ensured to be carried out at high temperature, the aim of removing the metal ions is fulfilled, sodium ions or potassium ions of valence-state metal ions introduced into the complexing agent can promote intramolecular association, and a small amount of the sodium ions or the potassium ions has certain promotion effect on the subsequent polymerization reaction; conventional metal ion complexing agents such as EDTA have poor heat stability and have-NH in the molecular structure 2 Resulting in decomposition of the alcoholysis product (the amino group in EDTA is itself a basic structure, which leads to alkaline hydrolysis of the polyester, and in addition the amino structure itself reacts with the carboxylic acid structure, which forms an amide compound and ultimately affects the polymerization of the polyester).
As a preferred technical scheme:
in the above preparation method for regenerating the waste PBT into the degradable PBAT polymer, the metal ions remaining in the regenerated BHBT include one of zinc, aluminum, calcium, titanium (contained in the waste PBT material) and antimony (contained in the waste PBT material), and the residual amount of the metal ions in the regenerated BHBT: 6-15 ppm of calcium ions, 1.5-6.25 ppm of aluminum ions, 3-7.5 ppm of zinc ions, 2-5 ppm of titanium ions and 2.25-3.75 ppm of antimony ions.
According to the preparation method for regenerating the waste PBT into the degradable PBAT polymer, the mass fraction of polyurethane in the waste PBT material is less than 5%.
According to the preparation method for regenerating the waste PBT into the degradable PBAT polymer, the mass fraction of the polyethylene terephthalate in the waste PBT material is less than 10%.
The sources of the waste PBT material comprise vehicle injection molding part leftover material-plastic PBT and textile leftover material-fiber PBT. The content of PBT in the automotive injection molding leftover material-PBT for plastics is more than 60 percent, and the content of PBT in the textile leftover material-PBT for fibers is generally more than 90 percent. In the waste PBT material, the waste PBT material is usually blended and modified with other plastic matrixes, such as polyethylene terephthalate, polyurethane, nylon and polycarbonate. Wherein nylon and polycarbonate are not alcoholyzed during alcoholysis and can be removed by filtration, and polyethylene terephthalate and polyurethane are alcoholyzed during the alcoholysis stage, and the dissolved products interfere with further polymerization of the PBT alcoholysis product. Thus, it is preferred in the present invention that the mass fraction of polyurethane in the waste PBT material is less than 5% and the mass fraction of polyethylene terephthalate is less than 10%.
Because the waste PBT material contains a certain amount of polyurethane and polyethylene glycol terephthalate, in the alcoholysis process of the polyurethane material, ester groups start to decompose at 160 ℃, carbamate is decomposed into isocyanate and small molecular alcohol at 180-190 ℃, more groups participate in the decomposition process, side reactions are easy to occur, and urea groups are mainly broken to generate amine and polyol. Amines, isocyanates and other substances can all have adverse effects on the mechanical and thermal properties of the PBAT material prepared by repolymerization of the waste PBT alcoholysis product. This is achieved byIn addition, the polyurethane generates CO upon decomposition 2 And toxic gases. Part of ethylene glycol can be generated in the alcoholysis process of the polyethylene terephthalate material, so that BHET is generated in the subsequent polymerization process, and an ET chain segment is a hard chain segment which is not easy to degrade, so that the biodegradation performance of the final PBAT product is seriously influenced.
The complexing agent adopted in the invention has a phytic acid structure as a cyclic compound containing twelve phosphonic acid functional groups, and can react with amines and alcohol to form a phosphonic acid amide or phosphonate structure;
based on the characteristics, the small molecular amines and the polyol compounds generated in the alcoholysis process of the polyurethane contained in the waste PBT material can be mostly removed by suction after the vacuum reaction, and the residual amine compounds which are difficult to remove can react with the complexing agent (phytic acid and phytate thereof) to form gel particles, so that the gel particles are filtered to remove impurities;
meanwhile, in the polyethylene terephthalate contained in the waste PBT material, a large amount of glycol is generated in the alcoholysis process and is sucked and separated, and a part of chain segments containing glycol structures which are not completely subjected to alcoholysis and a small amount of glycol which is not sucked and separated are remained, wherein the chain segments containing glycol structures can react with complexing agents (phytic acid and phytate thereof) to form large gel particles so as to be filtered and decontaminated, and the small amount of glycol which is not sucked and separated can react with adjacent phosphonic acid functional groups on the phytic acid so as to form a stable eight-membered cyclic phosphonate structure in space so as to be filtered and decontaminated;
therefore, the method avoids the influence of alcoholysis products of polyurethane and polyethylene glycol terephthalate contained in the waste PBT material on the performance of the final PBAT product, so that the repolymerized PBAT has higher color value and degradable performance.
The preparation method for regenerating the waste PBT into the degradable PBAT polymer is characterized in that the alcoholysis process comprises the following specific steps: adding a waste PBT material, 1, 4-Butanediol (BDO), a catalyst, an anti-aging agent and an anti-ether agent into a reaction kettle, introducing nitrogen for protection (the function is to protect dihydric alcohol from being oxidized, keep the system in a normal pressure state, also can lead out water in the system and ensure that the reaction is carried out in a positive direction), dissolving at 180-200 ℃, gradually heating to 210-230 ℃ after the system is clarified, and keeping the temperature for reacting for 1.5-2 hours; recording the water yield, vacuumizing when the water yield reaches 90% of a theoretical value, controlling the vacuum degree of a system to be 100-1000 Pa, and controlling the time to be 20-45 min (the vacuum polycondensation process is a process for improving the esterification rate, and the higher esterification rate can ensure that the weight average molecular weight of the subsequently prepared PBAT is kept at a higher degree; the vacuumizing time is not too long, and the main purpose is to remove the residual 1, 4-butanediol and water after the reaction, not to carry out the high-degree polycondensation reaction, but to keep the alcoholysis solution to be the BHBT solution with higher purity and low weight average molecular weight); adding a complexing agent (the complexing agent is added at this stage because in the alcoholysis process, firstly, the waste PBT particles are solid, the 1, 4-butanediol is liquid, and metal ion impurities are mainly in the waste PBT particles, so that the waste PBT particles need to be subjected to alcoholysis to form a homogeneous system, and then, the complexing agent is used for complexation to form precipitates, and the precipitates are filtered and removed; firstly, because metal ions exist in waste products, particularly high-valence metal ions which influence alcoholysis and polycondensation, heavy metal ions need to be removed, in addition, the temperature in the alcoholysis process is high, the conventional complexing agent is difficult to resist high temperature, and meanwhile, the structure of the conventional complexing agent is not suitable for the complexing reaction of an alcoholysis system, so that the qualities of alcoholysis and condensation are seriously influenced; in addition, the phytic acid complex metal ions are carried out in a melt or liquid environment, and the corresponding phytic acid and the corresponding salt thereof have high-temperature resistance, and particularly, the phytic acid and the corresponding salt thereof are in a stable phosphate structure and do not influence the alcoholysis reaction of the polyester under the high-temperature condition.
According to the preparation method for regenerating the waste PBT into the degradable PBAT polymer, in the alcoholysis reaction, the mass ratio of the waste PBT material to the 1, 4-butanediol is 1: 0.35-1: 0.50;
the catalyst is zinc acetate, aluminum acetate, cobalt acetate or calcium acetate;
the mass of the catalyst is 0.025-0.12 wt% of that of the PBT powder particles;
the anti-aging agent is triphenyl phosphate, triphenyl phosphite, trimethyl phosphite or triethyl phosphite;
the mass of the anti-aging agent is 0.075-0.2 wt% of that of the waste PBT material;
the ether inhibitor is sodium acetate or magnesium acetate;
the mass of the ether inhibitor is 0.1-0.2 wt% of the mass of the waste PBT material;
the mass of the complexing agent is 0.01-0.05 wt% of that of the waste PBT material.
According to the preparation method for regenerating the waste PBT into the degradable PBAT polymer, the waste PBT material is also pretreated before alcoholysis; the pretreatment process comprises the following steps: the waste PBT material is processed by the existing grinder to obtain PBT powder particles with the particle size of less than 2mm, then sieving is carried out, and finally the PBT powder particles are dried in a vacuum oven at 100-120 ℃ for 6-12 h.
The preparation method for regenerating the waste PBT into the degradable PBAT polymer comprises the following steps: adding adipic acid and 1, 4-butanediol with a molar ratio of 1: 1.05-1: 1.35 into a reaction kettle, introducing nitrogen for protection, controlling the esterification reaction temperature to be 180-195 ℃, and keeping the temperature for reaction for 2-3 hours; and recording the water yield, and stopping the reaction when the acid value reaches 20-40 KOH mg/g when the water yield reaches 90% of a theoretical value to obtain the BHAT.
The preparation method for regenerating the waste PBT into the degradable PBAT polymer comprises the following specific steps of carrying out ester exchange and polycondensation reaction on the monomer BHBT and the BHAT to obtain the degradable PBAT polymer: adding BHBT, BHAT and a condensation catalyst in a molar ratio of 35: 65-45: 55 into a reaction kettle, introducing nitrogen for protection, dissolving for 15min at 200-210 ℃, gradually heating to 225-235 ℃, and keeping the temperature for reacting for 1-1.5 h; recording the water yield, when the water yield reaches 90% of a theoretical value, heating to 255-265 ℃ to perform polycondensation reaction, controlling the vacuum degree of a system to be 50-1000 Pa, and controlling the time to be 3.5-4.5 h to prepare the degradable PBAT polymer; the PBAT is prepared by multi-step condensation reaction, the PBAT with high weight-average molecular weight can be obtained without involving a solid phase polycondensation stage, the phenomenon that the PBAT with higher weight-average molecular weight can be obtained only by the commonly adopted solid phase polycondensation in the prior art is avoided, the production cost is saved, the problem that the product quality is yellow and red due to the fact that the molecular weight is improved by introducing a chain extender in the prior art is also avoided, and the economic benefit is higher.
According to the preparation method for regenerating the waste PBT into the degradable PBAT polymer, the condensation catalyst is a composite catalyst of ethylene glycol antimony and tetrabutyl titanate with the mass ratio of 1: 1; tetrabutyl titanate and ethylene glycol antimony are used as composite catalysts, the problems of slow molecular weight increase and large repolymerization difficulty caused by the polycondensation effect of a single catalytic system or large esterification effect difference are solved, the titanium catalyst has good catalytic effect on the esterification reaction, the ethylene glycol antimony is a high-efficiency catalyst in the polycondensation stage, and the titanium catalyst and the ethylene glycol antimony are used as the composite catalysts to obtain the PBAT copolyester with high weight-average molecular weight. The addition amount of the condensation catalyst is 0.01-0.05 wt% of BHAT.
The invention also provides a degradable PBAT polymer prepared by the preparation method for regenerating the waste PBT into the degradable PBAT polymer, wherein the degradable PBAT polymer has the weight-average molecular weight of 10000-80000, the melting point of 40-125 ℃, the melt index of 8-50 g/10min, the carboxyl end group content of 15-80 mmol/t, the b value of chromaticity of 5-20, the intrinsic viscosity of 0.5-1.6 dL/g and the biodegradation rate of 50-90 days, which are measured under the conditions that the temperature is 190 ℃ and the load is 2.16 kg.
The invention also provides the use of a degradable PBAT polymer as described above for application to fibers, packaging film bags, adhesives or adhesive tapes. The preparation processes of the fiber, the packaging film bag and the adhesive tape are consistent with those of the existing fiber, film bag and adhesive tape, and the preparation processes of the adhesive is consistent with those of the existing polyester adhesive.
The principle of the invention is as follows:
one of the technical problems to be solved by the invention is as follows: how to remove metal ions, such as titanium and antimony, contained in the waste PBT material and metal ions, such as zinc, aluminum and calcium (mainly divalent metal ions having a large influence on polymerization), introduced in the alcoholysis process of the waste PBT material, has an influence on a final polycondensation product is specifically: the metal ion residue often causes difficulty in molecular weight growth when polymerizing PBAT, and the weight average molecular weight of the polycondensation product is low, making it difficult to prepare a PBAT polymer having a high weight average molecular weight.
The invention adopts the principle that the complexing agent chelates metal ions, introduces the complexing agent in the alcoholysis reaction process to remove heavy metal ions, and particularly comprises the following steps: phytic acid, sodium phytate or potassium phytate has strong chelating effect with metal ions, and reacts with metal ions in polymer melt and metal ions in catalyst remained in alcoholysis to generate insoluble compound, and then the insoluble compound is filtered and removed to remove metal ion impurities, and meanwhile, the phytic acid and the salt thereof have strong oxidation resistance and color protection performance, so that the color formation of the alcoholysis solution can be protected. It should be noted that: if a conventional complexing agent such as EDTA and its salt compounds is used, the polycondensation reaction for synthesizing PBAT is affected because the complexing agent has a large amount of ammonium groups in the structure, the decomposition temperature is low, the degradation is easy, and the reaction with alcoholysis products is also generated. The complexing agent adopted in the invention has a phytic acid structure as a cyclic compound containing twelve phosphonic acid functional groups, and can react with amines and alcohol to form a phosphonic acid amide or phosphonate structure; based on the characteristics, the micromolecule amines and the polyalcohol compounds generated in the alcoholysis process of the polyurethane contained in the waste PBT material can be mostly removed by suction after the vacuum reaction, and the residual amine compounds which are difficult to remove can react with the complexing agent (phytic acid and phytate thereof) to form gel particles, so that the gel particles are filtered to remove impurities; meanwhile, in the polyethylene terephthalate contained in the waste PBT material, a large amount of ethylene glycol is generated in the alcoholysis process and is sucked and separated, and a part of chain segments containing ethylene glycol structures which are not completely subjected to alcoholysis and a small amount of ethylene glycol which is not sucked and separated remain, wherein the chain segments containing the ethylene glycol structures can react with complexing agents (phytic acid and phytate thereof) to form large gel particles so as to be filtered and decontaminated, and the small amount of ethylene glycol which is not sucked and separated can react with adjacent phosphonic acid functional groups on the phytic acid so as to form a stable eight-membered cyclic phosphonate structure in space so as to be filtered and decontaminated. Therefore, the method not only solves the problem of high energy consumption caused by refining alcoholysis monomers, but also provides a new optimization idea for the technical difficulty that the residual of substances such as metal ions in alcoholysis liquid in the prior art influences the subsequent polycondensation reaction.
In addition, in the existing chemical recovery process of polyester such as PET and PBT, PET or PBT is obtained mainly through alcoholysis repolymerization, and the existing alcoholysis recovery process of waste PBT has the advantages of mild reaction conditions, good reaction safety and low process implementation difficulty.
Aiming at the problem, the invention firstly introduces a small amount of BDO as raw material in the process of alcoholysis of PBT to prepare BHBT, and introduces complexing agent to remove the influence of metal ion impurities, and then prepares a degradable polymer PBAT with molecular weight meeting the application requirements; the method realizes the preparation of the degradable PBAT polymer by the alcoholysis of the PBT, and does not prepare the non-biodegradable PBT polymer by the alcoholysis of the PBT and then polymerizing in the prior art, thereby reducing the use cost of the raw materials BDO and PTA in the polymerization process of the PBAT (the corresponding waste PBT component contains BDO, so the consumption of the BDO raw materials is reduced, and the cost is reduced).
The flexible aliphatic hydrocarbon group of PBT in the invention is- (CH) 2 ) 4 Compared with PET, the density and distance between the benzene ring and the adjacent ester group are reduced, the molecular chain is more flexible, and the alcoholysis process is more favorably realized. The PBAT prepared by the waste PBT belongs to biodegradable plastic, is copolyester polymerized by aliphatic polyester and aromatic polyester, has excellent comprehensive application performance, good flexibility, excellent mechanical property and thermal stability, and can be used for packaging, tableware, food, beverage, food packaging, and packaging, and packaging,Agricultural film, biomedical polymer material and other fields.
Advantageous effects
(1) According to the preparation method for regenerating the waste PBT into the degradable PBAT polymer, disclosed by the invention, the waste PBT material is recycled, so that the problem that the impurity-containing plastic is difficult to recycle is solved, and especially, the degradable high polymer material is prepared from the traditional high polymer material which cannot be degraded by a chemical alcoholysis repolymerization method;
(2) according to the preparation method for regenerating the waste PBT into the degradable PBAT polymer, the waste PBT is subjected to alcoholysis to obtain the regenerated BHBT, so that the use amount of raw materials PTA and BDO can be greatly reduced, the production cost of PBAT is effectively reduced, and the economic benefit of PBAT is remarkably improved;
(3) according to the preparation method for regenerating the waste PBT into the degradable PBAT polymer, the PBAT material which can be completely biodegraded is prepared by chemical alcoholysis repolymerization in the recycling of the waste PBT, so that the recycling of the traditional material and the low-carbon green use of the environment are realized, and the problems that the existing waste PBT is single in recycling and regenerating mode and the regenerated product is not degradable are solved.
Drawings
FIG. 1 is an infrared spectrum of an alcoholysis repolymerization PBAT of example 4 of the present invention;
FIG. 2 is a nuclear magnetic spectrum of an alcoholysis repolymerization of PBAT of example 4 of the present invention.
Detailed Description
The invention will be further illustrated with reference to specific embodiments. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.
The test method of each parameter in the invention is as follows:
(1) weight average molecular weight: measuring by using a 410 type gel permeation chromatograph of Waters company in America, wherein a mobile phase is tetrahydrofuran, the flow rate is 1mL/min, and polystyrene is used as a standard sample;
(2) melting point: measuring by adopting a Q20 differential scanning calorimeter, taking nitrogen as protective gas, wherein the gas flow is 50mL/min, the temperature is increased at the speed of 10 ℃/min, and the maximum melting peak value in the temperature increasing process is the melting point;
(3) melt index: an LSD-450 melt flow rate instrument is adopted to carry out determination according to determination of thermoplastic melt mass flow rate and melt volume flow rate (GB/T3682-2000);
(4) content of terminal carboxyl group: the determination is carried out according to a photometric method in a titration analysis method for determining the content of terminal carboxyl groups in polyester (FZ/T54012-2006), and an o-cresol-trichloromethane mixed solution (mass ratio is 7:3) is used as a solvent;
(5) chroma: measuring according to fiber grade polyester chip (GB/T14189-93), taking a proper amount of sample, placing the sample into a measuring cup on an object stage, and automatically measuring by using a Color 35 type automatic Color difference meter of BYK Gardner company;
(6) intrinsic viscosity: according to the polyester chip of fiber grade (GB/T14189-93), a mixed solution (mass ratio is 1:1) of phenol and tetrachloroethane is used as a solvent by adopting an Ubbelohde viscosity method to prepare a solution with the mass concentration of about 0.002g/ml, and an IV2400 automatic Ubbelohde viscometer is used for measuring in a constant-temperature water bath at the temperature of (25 +/-0.05);
(7) biodegradation rate for 90 days: method for determining the carbon dioxide released according to the determination of the ultimate aerobic biological decomposition capacity of a material under controlled composting conditions part 1: the determination was carried out by the general method (GB/T19277.1-2011);
(8) analyzing the content of metal elements: the content of metal ions in the BHBT material was measured by ICP (inductively coupled plasma Spectroscopy).
The waste PBT material used by the invention is derived from the automotive injection molding part leftover material-PBT for plastics or the textile leftover material-PBT for fibers; the mass fraction of polyurethane in the waste PBT materials of examples 1 to 4 was 2%, and the mass fraction of polyethylene terephthalate was 3%. The textile leftover material is provided by the science and technology limited company of the Xinsheng new material in the stannless market, wherein the PBT textile waste material has the main indexes of 1.25dL/g of intrinsic viscosity and 15mmol/kg of carboxyl end groups; the leftover material of the automotive injection molding part is provided by Jiangsu Jinfa new science and technology material company Limited, is the leftover material of a vehicle window motor shell and an automobile bumper, has the intrinsic viscosity of 1.30dL/g, the terminal carboxyl group of 20mmol/kg and the melt index of 18 g/min.
Example 1
A preparation method for regenerating waste PBT into a degradable PBAT polymer comprises the following specific steps:
(1) treatment of waste PBT: processing waste PBT material from vehicle injection molding leftover materials to obtain PBT powder particles with the particle size of less than 2mm, sieving, and finally drying the PBT powder particles in a vacuum oven at 100 ℃ for 12 hours;
(2) preparation of regenerated monomer BHBT: adding the PBT powder particles dried in the step (1), 1, 4-butanediol, a catalyst, an anti-aging agent and an anti-ether agent into a reaction kettle, introducing nitrogen for protection, dissolving at 180 ℃, gradually heating to 220 ℃ after the system is clarified, and keeping the temperature for reaction for 1.8 hours; recording the water yield, vacuumizing when the water yield reaches 90% of a theoretical value, controlling the vacuum degree of a system to be 1000Pa, and controlling the time to be 30 min; then adding a complexing agent, reacting for 10min, and filtering unreacted substances while the solution is hot to obtain regenerated BHBT;
wherein the mass ratio of the PBT powder particles to the 1, 4-butanediol is 1: 0.35;
the catalyst is zinc acetate;
the mass of the catalyst is 0.035 wt% of the mass of the PBT powder particles;
the anti-aging agent is triphenyl phosphate;
the mass of the age resister is 0.075 wt% of that of the PBT powder particles;
the ether inhibitor is sodium acetate;
the mass of the ether inhibitor is 0.15 wt% of that of the PBT powder particles;
the complexing agent is phytic acid;
the mass of the complexing agent is 0.01 wt% of that of the PBT powder particles;
the residual quantity of metal ions in the prepared regenerated BHBT is as follows: 10ppm of calcium ions, 5ppm of aluminum ions, 7ppm of zinc ions, 4ppm of titanium ions and 3ppm of antimony ions;
(3) preparation of BHAT: adding adipic acid and 1, 4-butanediol into a reaction kettle, introducing nitrogen for protection, controlling the esterification reaction temperature to be 180 ℃, and keeping the temperature for reaction for 2 hours; recording the water yield, and stopping the reaction when the acid value reaches 20KOH mg/g when the water yield reaches 90 percent of a theoretical value to obtain BHAT;
wherein the molar ratio of the adipic acid to the 1, 4-butanediol is 1: 1.05;
(4) preparation of degradable PBAT polymer: adding the regenerated BHBT prepared in the step (2), BHAT prepared in the step (3) and a condensation catalyst into a reaction kettle according to a certain proportion, introducing nitrogen for protection, dissolving for 15min at 200 ℃, then gradually heating to 225 ℃, and keeping the temperature for reacting for 1 h; recording the water yield, heating to 255 ℃ to perform high-temperature polycondensation reaction when the water yield reaches 90% of a theoretical value, controlling the vacuum degree of a system to be 500Pa, and controlling the time to be 3.5h to prepare the degradable PBAT polymer;
wherein the molar ratio of BHBT to BHAT is 35: 65;
the condensation catalyst is a composite catalyst of ethylene glycol antimony and tetrabutyl titanate with the mass ratio of 1: 1;
the addition amount of the condensation catalyst is 0.01 wt% of the BHAT;
the prepared degradable PBAT polymer has the weight-average molecular weight of 32000, the melting point of 101 ℃, the melt index of 25g/10min, the carboxyl end group content of 23mmol/t, the b value of chromaticity of 11, the intrinsic viscosity of 0.7dL/g and the biodegradation rate of 50 percent in 90 days under the conditions that the temperature is 190 ℃ and the load is 2.16 kg;
the prepared degradable PBAT polymer is applied to fibers, packaging film bags, adhesives and adhesive tapes.
Example 2
A preparation method for regenerating waste PBT into a degradable PBAT polymer comprises the following specific steps:
(1) treatment of waste PBT: processing waste PBT material from vehicle injection molding leftover materials to obtain PBT powder particles with the particle size of less than 2mm, sieving, and finally drying the PBT powder particles in a vacuum oven at 120 ℃ for 8 hours;
(2) preparation of regenerated monomer BHBT: adding the dried PBT powder particles in the step (1), 1, 4-butanediol, a catalyst, an anti-aging agent and an anti-ether agent into a reaction kettle, introducing nitrogen for protection, dissolving at 195 ℃, gradually heating to 230 ℃ after the system is clarified, and keeping the temperature for reaction for 2 hours; recording the water yield, vacuumizing when the water yield reaches 90% of a theoretical value, controlling the vacuum degree of a system to be 500Pa, and controlling the time to be 20 min; then adding a complexing agent, reacting for 15min, and filtering unreacted substances while the solution is hot to obtain regenerated BHBT;
wherein the mass ratio of the PBT powder particles to the 1, 4-butanediol is 1: 0.45;
the catalyst is aluminum acetate;
the mass of the catalyst is 0.025 wt% of that of the PBT powder particles;
the anti-aging agent is triphenyl phosphite;
the mass of the age resister is 0.09 wt% of that of the PBT powder particles;
the ether inhibitor is magnesium acetate;
the mass of the ether inhibitor is 0.10 wt% of that of the PBT powder particles;
the complexing agent is sodium phytate;
the mass of the complexing agent is 0.04 wt% of that of the PBT powder particles;
the residual quantity of metal ions in the prepared regenerated BHBT is as follows: 15ppm of calcium ions, 6.25ppm of aluminum ions, 7.5ppm of zinc ions, 5ppm of titanium ions and 3.75ppm of antimony ions;
(3) preparation of BHAT: adding adipic acid and 1, 4-butanediol into a reaction kettle, introducing nitrogen for protection, controlling the esterification reaction temperature to be 190 ℃, and keeping the temperature for reaction for 2.5 hours; recording the water yield, and stopping the reaction when the acid value reaches 40KOH mg/g when the water yield reaches 90 percent of a theoretical value to obtain BHAT;
wherein the molar ratio of adipic acid to 1, 4-butanediol is 1: 1.35;
(4) preparation of degradable PBAT polymer: adding the regenerated BHBT prepared in the step (2), BHAT prepared in the step (3) and a condensation catalyst into a reaction kettle according to a certain proportion, introducing nitrogen for protection, dissolving for 15min at 205 ℃, then gradually heating to 227 ℃, and keeping the temperature for reacting for 1.5 h; recording the water yield, when the water yield reaches 90% of a theoretical value, heating to 265 ℃ to perform high-temperature polycondensation reaction, controlling the vacuum degree of a system to be 50Pa, and controlling the time to be 3.8h to prepare the degradable PBAT polymer;
wherein the molar ratio of BHBT to BHAT is 45: 55;
the condensation catalyst is a composite catalyst of ethylene glycol antimony and tetrabutyl titanate with the mass ratio of 1: 1;
the addition amount of the condensation catalyst is 0.02 wt% of the BHAT;
the prepared degradable PBAT polymer has the weight-average molecular weight of 10000, the melting point of 40 ℃, the melt index of 50g/10min, the carboxyl end group content of 80mmol/t, the b value of chromaticity of 5, the intrinsic viscosity of 0.5dL/g and the 90-day biodegradation rate of 90 percent, which are measured under the conditions that the temperature is 190 ℃ and the load is 2.16 kg;
the prepared degradable PBAT polymer is applied to fibers, packaging film bags, adhesives and adhesive tapes.
Example 3
A preparation method for regenerating waste PBT into a degradable PBAT polymer comprises the following specific steps:
(1) treatment of waste PBT: processing waste PBT material from textile leftover materials to obtain PBT powder particles with the particle size of less than 2mm, then sieving, and finally drying the PBT powder particles in a vacuum oven at 110 ℃ for 6 hours;
(2) preparation of regenerated monomer BHBT: adding the PBT powder particles dried in the step (1), 1, 4-butanediol, a catalyst, an anti-aging agent and an anti-ether agent into a reaction kettle, introducing nitrogen for protection, dissolving at 200 ℃, gradually heating to 210 ℃ after a system is clarified, and keeping the temperature for reaction for 1.5 hours; recording the water yield, vacuumizing when the water yield reaches 90% of a theoretical value, controlling the vacuum degree of a system to be 100Pa, and controlling the time to be 45 min; then adding a complexing agent, reacting for 18min, and filtering unreacted substances while the solution is hot to obtain regenerated BHBT;
wherein the mass ratio of the PBT powder particles to the 1, 4-butanediol is 1: 0.50;
the catalyst is cobalt acetate;
the mass of the catalyst is 0.12wt% of that of the PBT powder particles;
the anti-aging agent is trimethyl phosphite;
the mass of the age resister is 0.20 wt% of that of the PBT powder;
the ether inhibitor is sodium acetate;
the mass of the ether inhibitor is 0.20 wt% of that of the PBT powder particles;
the complexing agent is potassium phytate;
the mass of the complexing agent is 0.05wt% of that of the PBT powder particles;
the residual quantity of metal ions in the prepared regenerated BHBT is as follows: 6ppm of calcium ions, 1.5ppm of aluminum ions, 3ppm of zinc ions, 2ppm of titanium ions and 2.25ppm of antimony ions;
(3) preparation of BHAT: adding adipic acid and 1, 4-butanediol into a reaction kettle, introducing nitrogen for protection, controlling the esterification reaction temperature to be 195 ℃, and keeping the temperature for reaction for 3 hours; recording the water yield, and stopping the reaction when the acid value reaches 30KOH mg/g when the water yield reaches 90 percent of a theoretical value to obtain BHAT;
wherein the molar ratio of adipic acid to 1, 4-butanediol is 1: 1.25;
(4) preparation of degradable PBAT polymer: adding the regenerated BHBT prepared in the step (2), BHAT prepared in the step (3) and a condensation catalyst into a reaction kettle according to a certain proportion, introducing nitrogen for protection, dissolving for 15min at 210 ℃, gradually heating to 235 ℃, and keeping the temperature for reacting for 1.2 h; recording the water yield, heating to 262 ℃ to perform high-temperature polycondensation when the water yield reaches 90% of a theoretical value, controlling the vacuum degree of a system to be 1000Pa, and controlling the time to be 4.1h to prepare the degradable PBAT polymer;
wherein the molar ratio of BHBT to BHAT is 42: 58;
the condensation catalyst is a composite catalyst of ethylene glycol antimony and tetrabutyl titanate with the mass ratio of 1: 1;
the addition amount of the condensation catalyst is 0.05wt% of BHAT;
the prepared degradable PBAT polymer has the weight-average molecular weight of 80000, the melting point of 125 ℃, the melt index of 8g/10min, the carboxyl end group content of 15mmol/t, the b value of chromaticity of 20, the intrinsic viscosity of 1.6dL/g and the biodegradation rate of 69% in 90 days, which are measured under the conditions that the temperature is 190 ℃ and the load is 2.16 kg;
the prepared degradable PBAT polymer is applied to fibers, packaging film bags, adhesives and adhesive tapes.
Example 4
A preparation method for regenerating waste PBT into a degradable PBAT polymer comprises the following specific steps:
(1) and (3) treatment of waste PBT: processing waste PBT material from textile leftover materials to obtain PBT powder particles with the particle size of less than 2mm, then sieving, and finally drying the PBT powder particles in a vacuum oven at 105 ℃ for 10 hours;
(2) preparation of regenerated monomer BHBT: adding the PBT powder particles dried in the step (1), 1, 4-butanediol, a catalyst, an anti-aging agent and an anti-ether agent into a reaction kettle, introducing nitrogen for protection, dissolving at 180 ℃, gradually heating to 225 ℃ after a system is clarified, and keeping the temperature for reaction for 1.6 hours; recording the water yield, vacuumizing when the water yield reaches 90% of a theoretical value, controlling the vacuum degree of a system to be 800Pa, and controlling the time to be 35 min; then adding a complexing agent, reacting for 16min, and filtering unreacted substances while the solution is hot to obtain regenerated BHBT;
wherein the mass ratio of the PBT powder particles to the 1, 4-butanediol is 1: 0.40;
the catalyst is calcium acetate;
the mass of the catalyst is 0.10 wt% of that of the PBT powder particles;
the anti-aging agent is triethyl phosphite;
the mass of the age resister is 0.15 wt% of that of the PBT powder particles;
the ether inhibitor is magnesium acetate;
the mass of the ether inhibitor is 0.18 wt% of that of the PBT powder particles;
the complexing agent is phytic acid;
the mass of the complexing agent is 0.03 wt% of that of the PBT powder particles;
the residual quantity of metal ions in the prepared regenerated BHBT is as follows: 6ppm of calcium ions, 1.5ppm of aluminum ions, 3ppm of zinc ions, 2ppm of titanium ions and 2.25ppm of antimony ions;
(3) preparation of BHAT: adding adipic acid and 1, 4-butanediol into a reaction kettle, introducing nitrogen for protection, controlling the esterification reaction temperature to be 192 ℃, and keeping the temperature for reaction for 2.8 hours; recording the water yield, and stopping the reaction when the acid value reaches 35KOH mg/g when the water yield reaches 90 percent of a theoretical value to obtain BHAT;
wherein the molar ratio of the adipic acid to the 1, 4-butanediol is 1: 1.15;
(4) preparation of degradable PBAT polymer: adding the regenerated BHBT prepared in the step (2), BHAT prepared in the step (3) and a condensation catalyst into a reaction kettle according to a certain proportion, introducing nitrogen for protection, dissolving for 15min at 208 ℃, then gradually heating to 232 ℃, and keeping the temperature for reacting for 1.3 h; recording the water yield, heating to 257 ℃ to perform high-temperature polycondensation when the water yield reaches 90% of a theoretical value, controlling the vacuum degree of a system to be 800Pa, and controlling the time to be 4.5h to prepare the degradable PBAT polymer;
wherein the molar ratio of BHBT to BHAT is 38: 62;
the condensation catalyst is a composite catalyst of ethylene glycol antimony and tetrabutyl titanate with the mass ratio of 1: 1;
the addition amount of the condensation catalyst is 0.04 wt% of the BHAT;
the infrared spectrum of the alcoholysis-repolymerization PBAT is shown in figure 1 and ranges from 2961 cm to 3000cm -1 Nearby absorption peaks are C-H symmetrical and asymmetrical stretching vibration peaks of methylene; 1720cm -1 The peak at (a) belongs to the C ═ O carbonyl oscillation peak in the fatty chain; PBAT contains a benzene ring structure, and stretching vibration of a C-O-C group of the PBAT generally shows more than two peaks which are positioned at 1269cm -1 And 1105cm -1 Nearby; 737cm -1 A strong peak nearby is caused by out-of-plane bending vibration of C-H on the disubstituted benzene ring, and is 700-900 cm -1 The absorption peak between can indicate the existence of benzene ring; 1450-1500 cm -1 The absorption peak at moderate intensity is due to-CH 3 The above peaks indicate the presence of a para-disubstituted benzene ring. Comparison of the infrared spectra of FIG. 2 with native PBAT indicates that PBAT is ultimately synthesized by the present invention.
The NMR spectrum of the alcoholysis repolymerization PBAT is shown in figure 2, and a resonance peak at the delta-7.266 ppm corresponds to CDCl 3 A peak of (a); the peak at the position of delta-8.099 ppm corresponds to the peak (g) of a hydrogen atom on the benzene ring of PTA, and the structure of the benzene ring is proved; the peak at delta-4.092-4.437 ppm is a hydrogen atom proton peak corresponding to two methylene groups (a) connected with an oxygen atom on BDO; the doublet peak at delta 2.329-2.337 pmm corresponds to the proton (c) peak near the carboxyl end in AA; delta is 1.696-1.977The ppm position corresponds to the proton peak of hydrogen atoms on two methylene groups (b) in the middle of BDO, and the PBAT copolyester contains a specific chain segment structure, thereby proving that the PBAT is synthesized.
The prepared degradable PBAT polymer has the weight-average molecular weight of 70000, the melting point of 113 ℃, the melt index of 12g/10min, the carboxyl end group content of 26mmol/t, the b value of chromaticity of 19, the intrinsic viscosity of 1.5dL/g and the biodegradation rate of 80% in 90 days under the conditions that the temperature is 190 ℃ and the load is 2.16 kg;
the prepared degradable PBAT polymer is applied to fibers, packaging film bags, adhesives and adhesive tapes.
Comparative example 1
A preparation method of a degradable PBAT polymer regenerated from waste PBT, which is basically the same as that in example 4, and is characterized in that the waste PBT material in the step (1) is selected, wherein the mass fraction of polyurethane is 12%, and the mass fraction of polyethylene glycol terephthalate is 3%;
the residual amount of metal ions in BHBT and various indexes of the prepared degradable PBAT polymer are shown in Table 1.
Comparative example 2
A preparation method for regenerating waste PBT into a degradable PBAT polymer is basically the same as that in example 4, except that the waste PBT material in the step (1) is selected, and the mass fraction of polyurethane is 16%;
the metal ion residual amount of BHBT and various indexes of the prepared degradable PBAT polymer are shown in Table 1.
Comparative example 3
A preparation method for regenerating waste PBT into degradable PBAT polymer is basically the same as example 4, and only differs in the selection of waste PBT material in the step (1), wherein the mass fraction of polyurethane is 2%, and the mass fraction of polyethylene terephthalate is 24%.
The residual amount of metal ions in BHBT and various indexes of the prepared degradable PBAT polymer are shown in Table 1.
Comparative example 4
A preparation method for regenerating waste PBT into degradable PBAT polymer is basically the same as example 4, and only differs from the method in the step (1) in the selection of waste PBT material, wherein the mass fraction of polyethylene terephthalate is 28%.
The residual amount of metal ions in BHBT and various indexes of the prepared degradable PBAT polymer are shown in Table 1.
Comparative example 5
A preparation method for regenerating waste PBT into degradable PBAT polymer, which is basically the same as the example 4, and only differs from the method in the step (2) in that no complexing agent is added.
The residual amount of metal ions in BHBT and various indexes of the prepared degradable PBAT polymer are shown in Table 1.
Comparative example 6
The preparation method of the degradable PBAT polymer regenerated from the waste PBT is basically the same as the example 4, and the difference is only that the complexing agent added in the step (2) is complexon.
The metal ion residual amount of BHBT and various indexes of the prepared degradable PBAT polymer are shown in Table 1.
Comparative example 7
The preparation method of the degradable PBAT polymer regenerated from the waste PBT is basically the same as the example 4, and is only different from the example 4 in that the mass of phytic acid added as a complexing agent in the step (2) is 0.005 wt% of that of PBT powder particles.
The residual amount of metal ions in BHBT and various indexes of the prepared degradable PBAT polymer are shown in Table 1.
TABLE 1
Figure BDA0003553561920000131
Figure BDA0003553561920000141
Comparing example 4 with comparative examples 1 and 2, the PBAT polyesters prepared in comparative examples 1 and 2 have low weight average molecular weight, high chroma, high carboxyl end group content, and reduced biodegradation rate, because the polyurethane content in the waste PBT material is too high, the urethane group is decomposed into isocyanate and small molecular alcohol in the alcoholysis process, and more groups participate in the decomposition process, so that side reactions are easily generated, mainly, the urea group is broken to generate amine and polyol. The length of a molecular chain segment is not easy to rise due to more side reactions, and the molecular weight is low, so that the content of a short molecular chain segment is high, and the content of terminal carboxyl groups at two ends of the chain segment is high; amine substances can increase the yellowness of PBAT products, substances such as small molecular alcohol and other polyols participate in the reaction to reduce the content of BA and BT chain segments in the PBAT materials, isocyanate causes chain segment fracture in the process of preparing the PBAT materials by polymerization again to reduce the weight average molecular weight of the products, and the degradation performance of the synthesized multicomponent hybrid polymer is reduced to cause the integral performance of the materials to be obviously deteriorated; meanwhile, the product in the degradation process is basically an unpolymerized small molecular structure, so that a polymer is difficult to form, and the material performance is obviously deteriorated. As can be seen from comparative examples 1 and 2, the polyurethane has a large influence on the polymerization process, especially on the condensation process, and meanwhile, the compound generated by the decomposition of the polyurethane catalyzes and degrades the polyester, so that the acid value is high, the compound is seriously yellowish and brownish, and the compound has certain biodegradation toxicity and influences the biodegradation performance; in addition, polyethylene terephthalate has a similar structure to PBT, and although the alcoholysis polycondensation of the polyethylene terephthalate has a small influence on the performance, the alcoholysis environment is seriously deteriorated due to the presence of polyurethane, so that the quality and the performance of the product obtained after the whole alcoholysis condensation are deteriorated, and the performance is influenced.
Comparing example 4 with comparative examples 3 and 4, the weight average molecular weight and the biodegradation rate of the PBAT polyesters prepared by the comparative examples 3 and 4 are reduced because the content of polyethylene terephthalate in the waste PBT material is too high, the terephthalic acid and the ethylene glycol generated in the alcoholysis process participate in the repolymerization process to generate ethylene glycol chain segments, and the ester exchange reaction in the polycondensation stage is influenced because the amount of the terephthalic acid is increased and the ethylene glycol chain segments are hard to degrade due to the increase of the amount of the terephthalic acid in the polycondensation stage, so that the biodegradation performance and the weight average molecular weight are reduced.
Comparing example 4 with comparative example 5, the combination of properties of the PBAT polyester obtained in comparative example 5 is poor, since no addition of additivesComplexing agents causing residual metal ions in the material to affect subsequent reactions, e.g. Zn 2+ The reduction and thermal degradation of the polymer in the reaction stage can be accelerated, so that the weight average molecular weight of the product is reduced, and the content of terminal carboxyl is increased; such as Al 3+ The polymerization reaction is blocked to be slow, and the weight average molecular weight is not easy to increase. In addition, heavy metals can also generate toxic action on microorganisms in the degradation process, so that the PBAT polyester is not easy to degrade, and metal impurities can influence the color formation of the material, so that the comprehensive performance of the material is reduced.
Comparing example 4 with comparative example 6, the PBAT polyester prepared in comparative example 6 has a deepened chroma and a reduced biodegradation rate, because after adding the metal complexing agent, ethylenediamine tetraacetic acid, forms a water-soluble stable chelate with metal ions, insoluble products can be removed, and water-soluble ones remain in the system, thereby affecting polymerization and having a small promotion effect on the increase of the weight average molecular weight in the polycondensation stage. Example 4 Using a phytic acid based complexing agent, the metal ions and complexing agent can be made to form an insoluble material which can be filtered. In addition, the color of the chelate formed by the complexone and the metal ions is further deepened along with the deepening of the self color of the metal ions, so that the chroma of the finished product is increased.
Comparing example 4 with comparative example 7, the comprehensive performance of the PBAT polyester prepared in comparative example 7 is reduced because the addition amount of the complexing agent is reduced, so that the subsequent reaction is not completely influenced by the removal of the metal ions, the physiological activity of microorganisms in the degradation stage is influenced by the metal ions, the degradation rate of the finished product is reduced, and meanwhile, the color formation of the material is also influenced by the residual metal impurities.

Claims (10)

1. A preparation method for regenerating waste PBT into degradable PBAT polymer is characterized by comprising the following steps: carrying out alcoholysis and filtration by taking a waste PBT material as a raw material to obtain regenerated BHBT, and then carrying out ester exchange and polycondensation reaction on the regenerated BHBT and BHAT to obtain a degradable PBAT polymer;
BHBT is dibutyl terephthalate, BHAT is dibutyl adipate;
adding phytic acid, sodium phytate or potassium phytate as a complexing agent in the alcoholysis;
the mass fraction of polyurethane in the waste PBT material is less than 5 percent;
the mass fraction of the polyethylene terephthalate in the waste PBT material is less than 10 percent.
2. The method for preparing the degradable PBAT polymer from the waste PBT, according to claim 1, wherein the residual amount of metal ions in the regenerated BHBT is as follows: 6-15 ppm of calcium ions, 1.5-6.25 ppm of aluminum ions, 3-7.5 ppm of zinc ions, 2-5 ppm of titanium ions and 2.25-3.75 ppm of antimony ions.
3. The method for preparing the degradable PBAT polymer regenerated from the waste PBT as claimed in claim 1, wherein the alcoholysis comprises the following steps: adding the waste PBT material, 1, 4-butanediol, a catalyst, an anti-aging agent and an anti-ether agent into a reaction kettle, introducing nitrogen for protection, dissolving at 180-200 ℃, gradually heating to 210-230 ℃ after the system is clarified, and keeping the temperature for reacting for 1.5-2 hours; recording the water yield, vacuumizing when the water yield reaches 90% of a theoretical value, controlling the vacuum degree of a system to be 100-1000 Pa, and controlling the time to be 20-45 min; and then adding a complexing agent, reacting for 15-20 min, and filtering to obtain the regenerated BHBT.
4. The preparation method of the degradable PBAT polymer regenerated from the waste PBT, according to claim 3, is characterized in that the mass ratio of the waste PBT material to the 1, 4-butanediol is 1: 0.35-1: 0.50;
the catalyst is zinc acetate, aluminum acetate, cobalt acetate or calcium acetate;
the mass of the catalyst is 0.025-0.12 wt% of that of the waste PBT material;
the anti-aging agent is triphenyl phosphate, triphenyl phosphite, trimethyl phosphite or triethyl phosphite;
the mass of the anti-aging agent is 0.075-0.2 wt% of that of the waste PBT material;
the ether inhibitor is sodium acetate or magnesium acetate;
the mass of the ether inhibitor is 0.1-0.2 wt% of the mass of the waste PBT material;
the mass of the complexing agent is 0.01-0.05 wt% of the mass of the waste PBT material.
5. The method for preparing the waste PBT regenerated into the degradable PBAT polymer according to the claim 1, characterized in that the waste PBT material is also pretreated before alcoholysis; the pretreatment process comprises the following steps: processing the waste PBT material to obtain PBT powder particles with the particle size of less than 2mm, sieving, and finally drying the PBT powder particles in a vacuum oven at 100-120 ℃ for 6-12 h.
6. The method for preparing the degradable PBAT polymer regenerated from the waste PBT, according to claim 1, wherein the BHAT is prepared by the following steps: adding adipic acid and 1, 4-butanediol with a molar ratio of 1: 1.05-1: 1.35 into a reaction kettle, introducing nitrogen for protection, controlling the esterification reaction temperature to be 180-195 ℃, and keeping the temperature for reaction for 2-3 hours; and recording the water yield, and stopping the reaction when the acid value reaches 20-40 KOH mg/g when the water yield reaches 90% of a theoretical value to obtain the BHAT.
7. The method for preparing the degradable PBAT polymer from the waste PBT in a regeneration manner according to claim 1, wherein the specific process of performing transesterification and polycondensation on the BHBT and the BHAT to obtain the degradable PBAT polymer is as follows: adding BHBT, BHAT and a condensation catalyst in a molar ratio of 35: 65-45: 55 into a reaction kettle, introducing nitrogen for protection, dissolving for 15min at 200-210 ℃, gradually heating to 225-235 ℃, and keeping the temperature for reacting for 1-1.5 h; recording the water yield, heating to 255-265 ℃ to perform polycondensation when the water yield reaches 90% of a theoretical value, controlling the vacuum degree of a system to be 50-1000 Pa, and controlling the time to be 3.5-4.5 h, thereby preparing the degradable PBAT polymer.
8. The method for preparing the degradable PBAT polymer regenerated from the waste PBT, according to claim 7, is characterized in that the condensation catalyst is a composite catalyst of ethylene glycol antimony and tetrabutyl titanate with a mass ratio of 1: 1; the addition amount of the condensation catalyst is 0.01-0.05 wt% of BHAT.
9. The degradable PBAT polymer prepared by the preparation method for regenerating the waste PBT into the degradable PBAT polymer, which is disclosed by any one of claims 1-8, is characterized in that: the weight average molecular weight of the degradable PBAT polymer is 10000-80000, the melting point is 40-125 ℃, the melt index measured under the conditions that the temperature is 190 ℃ and the load is 2.16kg is 8-50 g/10min, the carboxyl end group content is 15-80 mmol/t, the b value of chromaticity is 5-20, the intrinsic viscosity is 0.5-1.6 dL/g, and the biodegradation rate in 90 days is 50-90%.
10. The use of the degradable PBAT polymer of claim 9 characterized by: applied to fibers, packaging film bags or adhesive tapes.
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