CN115572377B - Method for synthesizing polyester elastomer by recycling aromatic polyester plastic and polyester elastomer - Google Patents

Abstract

The invention discloses a method for synthesizing a polyester elastomer using recycled aromatic polyester plastic and the polyester elastomer. The preparation method comprises the following steps: (1) washing, drying and crushing the recycled aromatic polyester plastic; (2) mixing the crushed aromatic polyester, diol A and catalyst A in a protective gas atmosphere to obtain alcoholysis solution A; or mixing the crushed aromatic polyester, diol B, dibasic acid B, catalyst B and thermal stabilizer B to obtain alcoholysis solution B; (3) mixing alcoholysis solution A, diol A', dibasic acid A, catalyst A' and thermal stabilizer A in a protective gas atmosphere to obtain the polyester elastomer through polycondensation reaction A; or mixing alcoholysis solution B in a protective gas atmosphere to obtain the polyester elastomer through polycondensation reaction B. The invention does not require the recycled aromatic polyester plastic to be purified, thus realizing the "upgraded recycling" of the aromatic polyester plastic and having better economic benefits.

Description

A method for synthesizing polyester elastomer using recycled aromatic polyester plastic and polyester elastomer

Technical Field

The present invention relates to the field of polymer materials, and more particularly to a method for synthesizing a polyester elastomer using recycled aromatic polyester plastics and the polyester elastomer.

Background technique

Aromatic polyester plastics are difficult to degrade under natural conditions due to their high crystallinity and chemical inertness, so they easily pollute the environment. However, aromatic polyester plastics are in great demand around the world, such as polyethylene terephthalate (PET), a thermoplastic polyester widely used in synthetic fibers, beverages, food and other liquid containers.

There are two main methods for recycling aromatic polyesters: physical recycling and chemical recycling. Among them, there are three main ways of physical recycling: after the waste PET bottles are collected, sorted, cleaned and crushed, they are first added to other plastic products as products to reduce production costs; second, they are crushed and granulated and then made into new low-end packaging containers through inflation and stretching molding processes; third, modified granulation is used to produce fibers. However, the added value of products recycled by physical methods is low, so chemical recycling is more recommended. The most representative chemical recycling method is alcoholysis recycling. At present, the most commonly used method is to alcoholyze aromatic polyester plastics to obtain alcoholysis solution. The alcoholysis solution must be filtered first to remove the filter residue and additives, and then the filtrate obtained by filtration is concentrated and evaporated, and then cooled and crystallized at low temperature. The crystallized monomer is filtered and collected and then heated and dried, and finally a high-purity ester product is obtained, and then the obtained ester product can be put into subsequent production. Chinese invention patent CN113801621A discloses a method of first alcoholyzing PET to obtain diethylene glycol terephthalate, adding diisocyanate, polyester polyol, etc. to heat the reaction, and then adding diethylene glycol terephthalate, chain extender, crosslinking agent, phosphorus-containing compound, etc. to finally obtain a water-based polyurethane adhesive. Chinese invention patent CN112708251A discloses a method for preparing a high-temperature resistant aromatic-aliphatic bio-based polyester elastomer. The bio-based polyester elastomer obtained by adding diols and dibasic acids has excellent mechanical properties and heat resistance, and can be used in the tire industry.

The existing technology mainly has the following problems:

(1) Aromatic polyester plastics cannot be degraded in the natural environment. The current method for treating these aromatic polyester plastics is mainly physical recycling, which has low added value;

(2) Currently, aromatic polyester plastics are recycled through chemical recycling, which has high requirements for the recycled plastics and complex recycling processes, resulting in high recycling costs.

(3) Although polyester elastomers can be directly polymerized from aromatic monomers, the cost of the raw materials is high and the molecular weight of the synthesized polyester elastomer is low;

Therefore, the present invention aims to develop a simple "upcycling" method for aromatic polyesters, using a two-step process or directly in one step to achieve the transformation from recycled waste plastics to elastomers.

Summary of the invention

In order to solve the technical problems existing in the prior art, the present invention provides a method for synthesizing a polyester elastomer using recycled aromatic polyester plastics and the polyester elastomer.

The present invention uses recycled aromatic polyester plastics to synthesize polyester elastomers through the route of alcoholysis and repolymerization, thereby realizing the "upgraded recycling" of aromatic polyester plastics. The "upgraded recycling" is mainly reflected in the preparation of a material that can generate high added value.

The present invention can be carried out through a one-step or two-step synthesis route. The synthesis route is simple, has low requirements on the reaction device, is more suitable for production on the current traditional polyester production line, and is more convenient for subsequent pilot testing and industrialization.

One of the objects of the present invention is to provide a method for synthesizing a polyester elastomer from recycled aromatic polyester plastics, comprising the following steps:

(1) washing, drying and crushing the recovered aromatic polyester plastic to obtain aromatic polyester powder or aromatic polyester flakes;

(2) in a protective gas atmosphere, the aromatic polyester powder or aromatic polyester flakes obtained in step (1), diol A, and catalyst A are uniformly mixed to obtain alcoholysis solution A; or the aromatic polyester powder or aromatic polyester flakes obtained in step (1), diol B, dibasic acid B, catalyst B, and thermal stabilizer B are uniformly mixed to obtain alcoholysis solution B;

(3) in a protective gas atmosphere, the alcoholysis solution A obtained in step (2), diol A', dibasic acid A, catalyst A', and thermal stabilizer A are uniformly mixed to obtain the polyester elastomer through polycondensation reaction A; or the alcoholysis solution B obtained in step (2) is mixed in a protective gas atmosphere to obtain the polyester elastomer through polycondensation reaction B.

In a preferred embodiment of the present invention,

step 1),

Cleaning is to use clean water to wash away impurities on the surface;

Drying temperature: 30℃～100℃; drying time: 0.5h～4h;

The pulverization can be performed by a pulverizer; preferably, the PET plastic is subjected to a low temperature treatment before pulverization, preferably with liquid nitrogen.

In a preferred embodiment of the present invention,

The aromatic polyester is one of polyethylene terephthalate (PET), polypropylene terephthalate (PTT), and polybutylene terephthalate (PBT); preferably polyethylene terephthalate;

The protective gas is nitrogen.

In a preferred embodiment of the present invention,

The diol A is two of 1,2-ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 2,3-butylene glycol, 1,5-pentanediol, and 1,6-hexanediol; and/or,

The diol A' is a mixture of two of 1,2-ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 2,3-butylene glycol, 1,5-pentanediol, 1,6-hexanediol and 1,4-butylene glycol, or 1,4-butylene glycol; and/or,

The diol B is a mixture of two of 1,2-ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 2,3-butylene glycol, 1,5-pentanediol, 1,6-hexanediol and 1,4-butylene glycol; and/or,

The catalyst A, catalyst A' and catalyst B are independently selected from at least one of alkyl aluminum having 1 to 12 carbon atoms, organic tin, organic zinc and titanate; preferably tetrabutyl titanate; and/or,

The dibasic acid A and dibasic acid B are independently selected from one of 1,4-succinic acid, 1,5-pentanedioic acid, 1,6-hexanedioic acid, 1,10-decanedioic acid and itaconic acid; and/or,

The heat stabilizer A and the heat stabilizer B are independently selected from at least one of phosphoric acid, triphenyl phosphate, trimethyl phosphate, triethyl phosphate, phosphorous acid, triphenyl phosphite, trimethyl phosphite, triethyl phosphite, hydroquinone, and o-methylhydroquinone.

In a preferred embodiment of the present invention,

Step (2),

The mass ratio of the aromatic polyester powder or aromatic polyester flake to diol A is 1:(2-12); preferably 1:(2-5);

The mass of the catalyst A is 0.05% to 0.6% of the total mass of the alcoholysis solution A; preferably 0.1% to 0.3%.

In a preferred embodiment of the present invention,

Step (2),

The mass ratio of the aromatic polyester powder or aromatic polyester flake to diol B is 1:((0.5-10); preferably 1:(1-7); and/or,

The mass ratio of the aromatic polyester powder or aromatic polyester flake to the dibasic acid B is 1:(1-8); preferably 1:(1-6); and/or,

The mass of the 1,4-butenediol accounts for 5 to 20% of the total mass of the diol B, preferably 10 to 16%; and/or,

The mass of the heat stabilizer B is 0.05-0.4% of the total mass of the alcoholysis solution B; preferably 0.05-0.2%; and/or,

The mass of the catalyst B is 0.05-0.6% of the total mass of the alcoholysis solution B, preferably 0.2-0.4%.

In a preferred embodiment of the present invention,

Step (2),

The mixing temperature for preparing alcoholysis solution A is 160-220° C., preferably 170-210° C.; the mixing time is 3-15 hours, preferably 8-12 hours; in a reaction device with mechanical stirring, the system is stirred at a fixed speed until the system is clear and the polyester plastic is evenly alcoholyzed in the system;

The mixing temperature for preparing alcoholysis solution B is 160-220° C., preferably 170-210° C.; the mixing time is 3-15 hours, preferably 8-12 hours; in a reaction device with mechanical stirring, the system is stirred at a fixed speed until the system is clarified and the polyester plastic is evenly alcoholyzed in the system.

In a preferred embodiment of the present invention,

Step (3),

The mass ratio of alcoholysis liquid A to diol A' is 1:(0.05-1); preferably 1:(0.1-0.6);

The mass ratio of alcoholysis liquid A to dibasic acid A is 1:(0.4-3); preferably 1:(0.4-1);

The mass of the 1,4-butenediol accounts for 5 to 20% of the sum of the mass of the diol A and the diol A', preferably 10 to 16%;

The mass of the heat stabilizer A is 0.05-0.4% of the total mass of the materials added to the reaction; preferably 0.05-0.2%; and/or,

The mass of the catalyst A' is 0.05-0.6% of the total mass of the materials added to the reaction, preferably 0.2-0.4%.

In a preferred embodiment of the present invention,

Step (3),

Alcoholysis solution A, diol A', dibasic acid A, catalyst A', and thermal stabilizer A are mixed at 170-210°C for 5-8h, and stirred at a fixed speed in a reaction device with mechanical stirring until the system becomes clear;

The pre-condensation temperature of the polycondensation reaction A is 190-250° C., preferably 210-230° C.; the pre-condensation pressure is 5 kPa-30 kPa, preferably 10 kPa-20 kPa; the pre-condensation time is 0.5-2 h, preferably 0.5-1 h; the purpose is to remove the diol monomer added in excess during the feeding stage;

The polycondensation temperature of polycondensation reaction A is 190-250° C., preferably 210-230° C.; the polycondensation pressure is 100-500 Pa; the polycondensation time is 6-10 hours; until obvious climbing occurs in the system, the reaction is terminated, and the product is obtained;

The pre-condensation temperature of the polycondensation reaction B is 190-250° C., preferably 210-230° C.; the pre-condensation pressure is 5 kPa-30 kPa, preferably 10 kPa-20 kPa; the pre-condensation time is 0.5-2 h, preferably 1-2 h; the purpose is to remove the diol monomer added in excess during the feeding stage;

The polycondensation temperature of polycondensation reaction B is 190-250° C., preferably 210-230° C.; the polycondensation pressure is 100-500 Pa; the polycondensation time is 6-10 h; until obvious rod climbing appears in the system, the reaction is terminated, and the product is obtained.

A second object of the present invention is to provide a polyester elastomer obtained by the above-mentioned method for recycling aromatic polyester plastics.

For example, the polyester elastomer structure made from PET plastic, ethylene glycol, butanediol, 1,4-butene glycol, and succinic acid is as follows:

Wherein, n=2, 3, 4, 5 or 6; m=2, 3, 4 or 8

a, b, d are 0 to 0.55 mole fractions respectively; a, b, d are not 0 at the same time;

x and y are 0 to 0.55 mole fractions respectively; x and y are not 0 at the same time;

c and z are 0 to 0.10 mole fractions.

Compared with the prior art, the present invention has the following beneficial effects:

The invention does not need to purify the recycled aromatic polyester plastic, and only needs to be simply washed with water. The obtained product may contain some additives contained in the raw materials, but has little effect on the performance of the product. The material source is more extensive and has better economic benefits.

Compared with the existing technology of preparing polyester elastomers by direct polycondensation of dibasic acid and diol monomers, the present invention can prepare polyester elastomers with higher molecular weight under similar preparation conditions.

The invention directly utilizes waste polyester plastics for chemical recycling to prepare polyester elastomers with application value, thus having good economic and social benefits.

The present invention adopts a one-step or two-step process, has low requirements on recycled plastic components, a simple synthesis route and low cost.

The process route of the present invention is suitable for production on a conventional polyester production line and is convenient for subsequent pilot testing and industrialization.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a hydrogen nuclear magnetic spectrum of polyester elastomers prepared in Example 2, Example 5 and Comparative Example 1;

FIG2 is a Fourier infrared spectra of polyester elastomers prepared in Example 2, Example 5, and Comparative Example 1;

FIG3 is a DSC graph of the polyester elastomers prepared in Example 2, Example 5, and Comparative Example 1.

Detailed ways

The present invention is described in detail below in conjunction with specific drawings and embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the content of the present invention still fall within the scope of protection of the present invention.

The PET plastic used in the examples is recycled PET bottles, and other raw materials are conventional commercially available raw materials.

Test Methods:

Gel permeation chromatography (GPC): The solvent was tetrahydrofuran;

Fourier transform infrared spectroscopy (FTIR): ATR was used, the wave number range was from 4000 cm-1 to 700 cm-1, and each sample was scanned 16 times;

Nuclear magnetic resonance spectroscopy (NMR): The NMR spectrometer was 600M, and the solvent was deuterated chloroform;

Differential Scanning Calorimetry (DSC): The test temperature range is -100 to 100°C, first dropping from room temperature to -100°C, and then raising the temperature to 100°C, with a temperature change rate of 10°C/min.

Example 1

The discarded PET plastic bottles were simply washed with clean water to remove impurities on the surface, and then placed in a 30°C drying oven for 4 hours, and then the obtained PET flakes were crushed with a pulverizer to obtain PET fragments. The treated PET fragments (6.8g), 1,2-ethylene glycol (34g), and tetrabutyl titanate (0.1% of the total mass) were added to a 100ml four-necked flask with mechanical stirring, and the system temperature was first raised to 170°C, and the reaction was carried out under a nitrogen atmosphere until the solution was clear and uniform, which was a uniform alcoholysis, and the alcoholysis solution was obtained after about 8 hours.

The alcoholysis solution (40.8g), 1,3-propylene glycol (13.8g), 1,4-butenediol (7.5g), 1,4-butanediol (37.7g), tetrabutyl titanate (0.4% of the total mass), phosphorous acid (0.04% of the total mass), and hydroquinone (0.16% of the total mass) after alcoholysis are added to a four-necked flask with mechanical stirring. The system temperature is first raised to 170°C, and the reaction is uniform under a nitrogen atmosphere until it is clear and uniform, which takes about 5 hours. After alcoholysis, the temperature is raised to 230°C, and the pressure is reduced to 20kPa to extract the excess alcohol from the reaction. This process lasts for about 0.5h. Then, the temperature is maintained and the vacuum is pumped to 100pa. The reaction is about 6h. There is an obvious pole climbing phenomenon. Take it out while hot to obtain a polyester elastomer.

Example 2

The discarded PET plastic bottles were simply washed with clean water to remove the impurities on the surface, and then placed in a 70°C drying oven for drying for 2 hours, and the obtained PET flakes were crushed with a pulverizer to obtain PET fragments. The treated PET fragments (23g), 1,4-butanediol (32g), 1,2-ethylene glycol (15g), and tetrabutyl titanate (0.3% of the total mass) were added to a four-necked flask with a mechanical stirrer, and the system temperature was first raised to 190°C, and the reaction was carried out under a nitrogen atmosphere until the solution was clear and uniform, which was a uniform alcoholysis, and the alcoholysis solution was obtained after about 5 hours.

Add the alcoholysis solution (70g), 1,4-butenediol (7g), 1,4-butanediol (33g), tetrabutyl titanate (0.2% of the total mass), phosphorous acid (0.01% of the total mass), and hydroquinone (0.04% of the total mass) after alcoholysis to a four-necked flask with mechanical stirring. First, raise the system temperature to 200°C, and react in a nitrogen atmosphere until it is clear and uniform, which means the alcoholysis is uniform. It takes about 8 hours. After alcoholysis, raise the temperature to 220°C, reduce the pressure to 10kPa to extract the excess alcohol, and this process lasts for about 1 hour. Then maintain the temperature and draw the vacuum to 300pa. React for about 10 hours. There is an obvious pole climbing phenomenon. Take it out while hot to obtain a polyester elastomer.

Example 3

The discarded PET plastic bottles were simply washed with clean water to remove impurities on the surface, and then placed in a 100°C drying oven for drying for 0.5 h. The obtained PET sheets were then crushed to obtain PET fragments. The treated PET fragments (15.5 g), 1,4-butanediol (22 g), 1,2-ethylene glycol (10 g), and tetrabutyl titanate (0.2% of the total mass) were added to a four-necked flask with mechanical stirring. The system temperature was first raised to 210°C, and the reaction was carried out under a nitrogen atmosphere until the solution was clear and uniform, which means the alcoholysis was uniform. The reaction time was about 3 h, and an alcoholysis solution was obtained.

The alcoholysis solution (47g), 1,4-butanediol (2.5g), 1,4-butenediol (5g), 1,2-ethylene glycol (2g), 1,4-butanedioic acid (38g), tetrabutyl titanate (0.2% of the total mass), phosphorous acid (0.01% of the total mass), and hydroquinone (0.04% of the total mass) after alcoholysis are added to a 100ml four-necked flask with mechanical stirring. The system temperature is first raised to 200°C, and the reaction is carried out in a nitrogen atmosphere until it is clear and uniform, which means that the alcoholysis is uniform, which takes about 8h. After alcoholysis, the temperature is raised to 230°C, and the pressure is reduced to 20kPa to extract the excess alcohol in the reaction. This process lasts for about 1h. Then the temperature is maintained and the vacuum is pumped to 500pa. The reaction is about 10h. There is an obvious pole climbing phenomenon. Take it out while hot to obtain a polyester elastomer.

Example 4

PET crushing: Wash the discarded PET plastic bottles with clean water to remove impurities on the surface, then put them into a 70°C drying oven for 2 hours. Then cool the obtained PET sheets with liquid nitrogen and crush them with a crusher to obtain PET powder.

The treated PET powder (30.5g), 1,4-butanediol (24.5g), 1,4-butenediol (5.5g), 1,2-ethylene glycol (6.5g), 1,4-butanedioic acid (28.5g), tetrabutyl titanate accounting for 0.2% of the total mass of the reaction materials, phosphorous acid (0.01% of the total mass), and hydroquinone (0.04% of the total mass) were added to a four-necked flask with mechanical stirring. The system temperature was first raised to 200°C, and the reaction was carried out in a nitrogen atmosphere until it was clear and uniform, which was uniform alcoholysis, and it took about 8h. After alcoholysis, the temperature was raised to 220°C, and the pressure was reduced to 10kPa to extract the excess alcohol in the reaction. This process lasted for about 1h. Then the temperature was maintained and the vacuum was pumped to 300pa. The reaction was about 8h. There was an obvious pole climbing phenomenon. It was taken out while hot to obtain a polyester elastomer.

Example 5

The PET crushing method is the same as in Example 4.

The treated PET powder (23g), 1,4-butanediol (32g), 1,4-butenediol (7g), 1,2-ethylene glycol (15g), 1,4-butanedioic acid (33g), tetrabutyl titanate (0.4% of the total mass), phosphorous acid (0.04% of the total mass), and hydroquinone (0.16% of the total mass) were added to a four-necked flask with mechanical stirring. The system temperature was first raised to 200°C, and the reaction was carried out in a nitrogen atmosphere until the clarification was uniform, which was uniform alcoholysis, and it took about 10 hours. After alcoholysis, the temperature was raised to 230°C, and the pressure was reduced to 20kPa to extract the excess alcohol in the reaction. This process lasted for about 2 hours. Then the temperature was maintained and the vacuum was pumped to 500pa. The reaction was about 10 hours. There was an obvious pole climbing phenomenon. It was taken out while hot to obtain a polyester elastomer.

Example 6

The PET crushing method is the same as in Example 4.

The treated PET powder (15.5g), 1,4-butanediol (24.5g), 1,4-butenediol (5g), 1,2-ethylene glycol (12g), 1,4-butanedioic acid (38g), tetrabutyl titanate (0.2% of the total mass), phosphorous acid (0.01% of the total mass), and hydroquinone (0.04% of the total mass) were added to a four-necked flask with mechanical stirring. The system temperature was first raised to 170°C, and the reaction was carried out in a nitrogen atmosphere until the clarification was uniform, which was uniform alcoholysis, and it took about 12 hours. After alcoholysis, the temperature was raised to 230°C, and the pressure was reduced to 20kPa to extract the excess alcohol in the reaction. This process lasted for about 0.5h. Then the temperature was maintained and the vacuum was pumped to 100pa. The reaction was about 6h. There was an obvious pole climbing phenomenon. It was taken out while hot to obtain a polyester elastomer.

Example 7

PET crushing: Wash the discarded PET plastic bottles with clean water to remove impurities on the surface, then put them into a 70°C drying oven for 2 hours. Then cool the obtained PET sheets with liquid nitrogen and crush them with a crusher to obtain PET powder.

The treated PET powder (9.3g), 1,2-propylene glycol (25g), 1,4-butene glycol (6.5g), 1,2-ethylene glycol (17.4g), 1,4-butanedioic acid (51.8g), tetrabutyl titanate accounting for 0.2% of the total mass of the reaction materials, phosphorous acid (0.01% of the total mass), and hydroquinone (0.04% of the total mass) were added to a four-necked flask with mechanical stirring. The system temperature was first raised to 200°C, and the reaction was carried out in a nitrogen atmosphere until the clarification was uniform, which was uniform alcoholysis, and it took about 8h. After alcoholysis, the temperature was raised to 220°C, and the pressure was reduced to 10kPa to extract the excess alcohol of the reaction. This process lasted for about 1h. Then the temperature was maintained and the vacuum was pumped to 300pa. The reaction was about 8h. There was an obvious climbing phenomenon. It was taken out while hot to obtain a polyester elastomer.

Example 8

PET crushing: Wash the discarded PET plastic bottles with clean water to remove impurities on the surface, then put them into a 70°C drying oven for 2 hours. Then cool the obtained PET sheets with liquid nitrogen and crush them with a crusher to obtain PET powder.

The treated PET powder (7.5g), 2,3-butanediol (23g), 1,4-butenediol (5g), 1,2-ethylene glycol (14g), 1,4-butanedioic acid (40.5g), tetrabutyl titanate accounting for 0.2% of the total mass of the reaction materials, phosphorous acid (0.01% of the total mass), and hydroquinone (0.04% of the total mass) were added to a four-necked flask with mechanical stirring. The system temperature was first raised to 200°C, and the reaction was carried out in a nitrogen atmosphere until the clarification was uniform, which was uniform alcoholysis, and it took about 8h. After alcoholysis, the temperature was raised to 220°C, and the pressure was reduced to 10kPa to extract the excess alcohol of the reaction. This process lasted for about 1h. Then the temperature was maintained and the vacuum was pumped to 300pa. The reaction was about 8h. There was an obvious pole climbing phenomenon. It was taken out while hot to obtain a polyester elastomer.

Example 9

PET crushing: Wash the discarded PET plastic bottles with clean water to remove impurities on the surface, then put them into a 70°C drying oven for 2 hours. Then cool the obtained PET sheets with liquid nitrogen and crush them with a crusher to obtain PET powder.

The treated PET powder (7.5g), 1,5-pentanediol (26.6g), 1,4-butenediol (5g), 1,2-ethylene glycol (14g), 1,4-butanedioic acid (40.5g), tetrabutyl titanate accounting for 0.2% of the total mass of the reaction materials, phosphorous acid (0.01% of the total mass), and hydroquinone (0.04% of the total mass) were added to a four-necked flask with mechanical stirring. The system temperature was first raised to 200°C, and the reaction was carried out in a nitrogen atmosphere until it was clear and uniform, which was uniform alcoholysis, and it took about 8h. After alcoholysis, the temperature was raised to 220°C, and the pressure was reduced to 10kPa to extract the excess alcohol in the reaction. This process lasted for about 1h. Then the temperature was maintained and the vacuum was pumped to 300pa. The reaction was about 8h. There was an obvious pole climbing phenomenon. It was taken out while hot to obtain a polyester elastomer.

Comparative Example 1

Comparative Example 1 is compared with Example 2 and Example 5. The mass percentage of terephthalic acid in the polyester is the same;

1,4-Butanediol (32g), 1,4-butenediol (7g), 1,2-ethylene glycol (15g), 1,4-butanediol (33g), terephthalic acid (19.2g), tetrabutyl titanate (0.2% of the total mass), phosphorous acid (0.01% of the total mass), and hydroquinone (0.04% of the total mass) were added to a 100ml four-necked flask with mechanical stirring. The system temperature was first raised to 200°C, and the reaction was carried out in a nitrogen atmosphere until the clarification was uniform, which was uniform alcoholysis, and it took about 8h. After alcoholysis, the temperature was raised to 220°C, and the pressure was reduced to 10kPa to extract the excess alcohol in the reaction. This process lasted for about 1h. Then the temperature was maintained and the vacuum was pumped to 300pa. The reaction was about 8h. There was an obvious pole climbing phenomenon. It was taken out while hot to obtain a polyester elastomer.

Table 1

Example 1 Example 2 Example 3 Example 4 Example 5 Tg/℃ -16.98 -18.4 -21.6 -11.3 -17.1 Tm/℃ — 45.1 43.6 58.6 57.5 ΔHm(J/g) — 2.2 5.5 4.2 1.3 Example 6 Example 7 Example 8 Example 9 Comparative Example 1 Tg/℃ -20.9 -10.01 -17.13 -31.14 -17.4 Tm/℃ 50.9 — — — 47.3 ΔHm(J/g) 5.1 — — — 1.9

Table 1 shows the Tg, Tm and ΔHm test data of the polyester elastomers prepared in Examples 1 to 9 and Comparative Example 1. It can be seen from Table 1 that the polyester elastomers prepared in Examples 1 to 9 using PET as raw material have comparable performance to the polyester elastomer synthesized using monomers in Comparative Example 1.

FIG1 is the H NMR spectra of the polyester elastomers prepared in Example 2, Example 5 and Comparative Example 1. It can be seen that there are no unknown impurity peaks, which proves that the polyester elastomers synthesized from PET in Example 2 and Example 5 are basically consistent with Comparative Example 1.

Figure 2 is the Fourier infrared spectra of the polyester elastomers prepared in Example 2, Example 5 and Comparative Example 1. It can be seen from the figure that 1725 cm ^-1 is the stretching vibration peak of the (C=O) carbon group, the absorption peak at 810 cm ^-1 is the out-of-plane vibration absorption peak of the (-CH-) on the benzene ring, and 2961 cm ^-1 is the stretching vibration peak of ( _-CH2- ). The groups of the polyesters synthesized by PET in Example 2 and Example 5 are consistent with those of the polyester synthesized by monomer in Comparative Example 1, and no unknown groups appear.

FIG3 is a DSC graph of the polyester elastomers prepared in Example 2, Example 5, and Comparative Example 1. It can be seen that the polyester synthesized in Comparative Example 1 and the polyester synthesized in Example 2 and Example 5 have similar Tg ratios when the proportions of the components are similar. This proves that the application ranges of the polyesters obtained in Example 2, Example 5 and Comparative Example 1 are comparable, and the polyester synthesized by PET may also be applicable to scenarios where the polyester synthesized by monomers can be used.

Table 2

Example 1 Example 2 Example 3 Example 4 Example 5 Mn(kg/mol) 48.1 56.1 50.3 44.7 48.5 Mw(kg/mol) 95.3 86.7 87.1 115.2 86.8 D 1.98 1.54 1.73 2.57 1.78 Example 6 Example 7 Example 8 Example 9 Comparative Example 1 Mn(kg/mol) 49.7 50.2 49.6 52.1 35.6 Mw(kg/mol) 90.1 95.7 92.3 98.4 83.4 D 1.81 1.89 1.71 2.18 2.34

Table 2 shows the number average molecular weight, weight average molecular weight and molecular weight distribution index of the polyester elastomers prepared in Examples 1 to 9 and Comparative Example 1. It can be seen from Table 2 that the polyester elastomers synthesized through PET in Examples 1 to 9 have higher molecular weight than the polyester synthesized through monomer in Comparative Example 1, and may have better performance.

Examples 1 to 3 are prepared by a two-step synthesis route, and Examples 4 to 9 are prepared by a one-step synthesis route. The synthesis routes are relatively simple, and the requirements for the reaction device are not high, which is conducive to industrialization. Compared with the direct synthesis of polyester elastomers using monomers, Examples 1 to 9 can prepare polyesters with higher molecular weight and better mechanical properties using recycled aromatic polyester plastics under the same preparation conditions, thus realizing the "upgrading and recycling" of aromatic polyester plastics.

Claims (16)

1. A method for synthesizing a polyester elastomer using recycled aromatic polyester plastics, the method comprising the following steps: (1) washing, drying and crushing the recovered aromatic polyester plastic to obtain aromatic polyester powder or aromatic polyester flakes; (2) In a protective gas atmosphere, the aromatic polyester powder or aromatic polyester flakes obtained in step (1), diol A, and catalyst A are uniformly mixed to obtain alcoholysis solution A; or the aromatic polyester powder or aromatic polyester flakes obtained in step (1), diol B, dibasic acid B, catalyst B, and thermal stabilizer B are uniformly mixed to obtain alcoholysis solution B; (3) in a protective gas atmosphere, the alcoholysis solution A obtained in step (2), diol A', dibasic acid A, catalyst A', and thermal stabilizer A are uniformly mixed to obtain the polyester elastomer through polycondensation reaction A; or the alcoholysis solution B obtained in step (2) is mixed in a protective gas atmosphere to obtain the polyester elastomer through polycondensation reaction B; The diol A is two of 1,2-ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 2,3-butylene glycol, 1,5-pentanediol, and 1,6-hexanediol; The diol A' is a mixture of two of 1,2-ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 2,3-butylene glycol, 1,5-pentanediol, 1,6-hexanediol and 1,4-butylene glycol, or 1,4-butylene glycol; The diol B is a mixture of two of 1,2-ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 2,3-butylene glycol, 1,5-pentanediol, 1,6-hexanediol and 1,4-butylene glycol; The dibasic acid A and dibasic acid B are independently selected from one of 1,4-succinic acid, 1,5-glutaric acid, 1,6-hexanediol, 1,10-decanedioic acid and itaconic acid; In step (2), the mass ratio of the aromatic polyester powder or aromatic polyester flakes to diol A is 1:(2-12); the mass ratio of the aromatic polyester powder or aromatic polyester flakes to diol B is 1:(0.5-10); the mass of the 1,4-butene diol accounts for 5-20% of the total mass of diol B; the mass ratio of the aromatic polyester powder or aromatic polyester flakes to dibasic acid B is 1:(1-8); In step (3), the mass ratio of the alcoholysis solution A to the diol A' is 1:(0.05-1); the mass ratio of the alcoholysis solution A to the dibasic acid A is 1:(0.4-3); the mass of the 1,4-butenediol accounts for 5-20% of the sum of the masses of the diol A and the diol A'. 2. The method for synthesizing polyester elastomer using recycled aromatic polyester plastic as claimed in claim 1, characterized in that: step 1), Cleaning is done with clean water; and/or, Drying temperature 30℃~100℃; drying time 0.5h~4h; and/or, The crushing is carried out by using a crusher. 3. The method for synthesizing polyester elastomer using recycled aromatic polyester plastic as claimed in claim 1, characterized in that: The aromatic polyester is one of polyethylene terephthalate, polypropylene terephthalate and polybutylene terephthalate; and/or, The protective gas is nitrogen. 4. The method for synthesizing polyester elastomer using recycled aromatic polyester plastic as claimed in claim 1, characterized in that: The catalyst A, catalyst A' and catalyst B are independently selected from at least one of alkyl aluminum having 1 to 12 carbon atoms, organic tin, organic zinc and titanate; and/or, The heat stabilizer A and the heat stabilizer B are independently selected from at least one of phosphoric acid, triphenyl phosphate, trimethyl phosphate, triethyl phosphate, phosphorous acid, triphenyl phosphite, trimethyl phosphite, triethyl phosphite, hydroquinone, and o-methylhydroquinone. 5. The method for synthesizing polyester elastomer using recycled aromatic polyester plastic as claimed in claim 4, characterized in that: The catalyst A, catalyst A' and catalyst B are tetrabutyl titanate. 6. The method for synthesizing polyester elastomer using recycled aromatic polyester plastic as claimed in claim 1, characterized in that: Step (2), The mass ratio of the aromatic polyester powder or aromatic polyester flake to diol A is 1:(2-5); and/or, The mass of the catalyst A is 0.05% to 0.6% of the total mass of the alcoholysis solution A. 7. The method for synthesizing polyester elastomer using recycled aromatic polyester plastic as claimed in claim 6, characterized in that: The mass of the catalyst A is 0.1% to 0.3% of the total mass of the alcoholysis solution A. 8. The method for synthesizing polyester elastomer using recycled aromatic polyester plastic as claimed in claim 1, characterized in that: Step (2), The mass ratio of the aromatic polyester powder or aromatic polyester flake to diol B is 1:(1-7); and/or, The mass ratio of the aromatic polyester powder or aromatic polyester flake to the dibasic acid B is 1:(1-6); and/or, The mass of the 1,4-butenediol accounts for 10-16% of the total mass of the diol B; and/or, The mass of the heat stabilizer B is 0.05-0.4% of the total mass of the alcoholysis solution B; and/or, The mass of the catalyst B is 0.05-0.6% of the total mass of the alcoholysis solution B. 9. The method for synthesizing polyester elastomer using recycled aromatic polyester plastic as claimed in claim 8, characterized in that: The mass of the heat stabilizer B is 0.05-0.2% of the total mass of the alcoholysis solution B; and/or, The mass of the catalyst B is 0.2-0.4% of the total mass of the alcoholysis solution B. 10. The method for synthesizing polyester elastomer using recycled aromatic polyester plastic as claimed in claim 1, characterized in that: Step (2), The mixing temperature for preparing alcoholysis solution A is 160-220°C; the mixing time is 3-15h; The mixing temperature for preparing alcoholysis solution B is 150-220°C; the mixing time is 3-15h. 11. The method for synthesizing polyester elastomer using recycled aromatic polyester plastic as claimed in claim 10, characterized in that: The mixing temperature for preparing alcoholysis solution A is 170-210°C; the mixing time is 8-12h; The mixing temperature for preparing alcoholysis solution B is 170~210°C; the mixing time is 8~12h. 12. The method for synthesizing polyester elastomer using recycled aromatic polyester plastic as claimed in claim 1, characterized in that: Step (3), The mass ratio of alcoholysis liquid A to diol A' is 1:(0.1-0.6); and/or, The mass ratio of alcoholysis solution A to dibasic acid A is 1:(0.4-1); and/or, The mass of the 1,4-butenediol accounts for 10-16% of the sum of the masses of the diol A and the diol A'; and/or, The mass of heat stabilizer A is 0.05-0.4% of the total mass of materials added to the reaction; and/or, The mass of catalyst A' is 0.05-0.6% of the total mass of the materials added to the reaction. 13. The method for synthesizing polyester elastomer using recycled aromatic polyester plastic as claimed in claim 12, characterized in that: The mass of heat stabilizer A is 0.05-0.2% of the total mass of materials added to the reaction; and/or, The mass of catalyst A' is 0.2-0.4% of the total mass of the materials added to the reaction. 14. The method for synthesizing polyester elastomer using recycled aromatic polyester plastic as claimed in claim 1, characterized in that: Step (3), Alcoholysis solution A, diol A', dibasic acid A, catalyst A', and thermal stabilizer A are mixed at 170-210°C for 5-8h; and/or, The pre-condensation temperature of the polycondensation reaction A is 190-250°C; the pre-condensation pressure is 5kPa-30kPa; the pre-condensation time is 0.5-2h; the polycondensation temperature is 190-250°C; the polycondensation pressure is 100-500Pa; the polycondensation time is 6-10h; and/or, The pre-condensation temperature of polycondensation reaction B is 190~250℃; the pre-condensation pressure is 5kPa~30kPa; the pre-condensation time is 0.5~2h; the polycondensation temperature is 190~250℃; the polycondensation pressure is 100~500Pa; and the polycondensation time is 6~10h. 15. The method for synthesizing polyester elastomer using recycled aromatic polyester plastic as claimed in claim 14, characterized in that: The pre-condensation temperature of the polycondensation reaction A is 210-230°C; the pre-condensation pressure is 10kPa-20kPa; the pre-condensation time is 0.5-1h; the polycondensation temperature is 210-230°C; and/or, The pre-condensation temperature of polycondensation reaction B is 210~230℃; the pre-condensation pressure is 10kPa~20kPa; the pre-condensation time is 1~2h; the polycondensation temperature is 210~230℃. 16. A polyester elastomer obtained by the method for synthesizing a polyester elastomer by recycling aromatic polyester plastic as claimed in any one of claims 1 to 15.