PBET copolyester, preparation method therefor and use thereof

Abstract

Disclosed are a PBET copolyester, a preparation method therefor, and a use thereof, belonging to the technical field of polymer materials. The PBET copolyester of the present application has a specific diol unit composition, carboxyl end-group content, and half-peak width and peak value of a cold crystallization peak in a second cooling curve, and thus has better mechanical properties and aging resistance, and is suitable for preparing electronic and electrical components.

Description

PBET copolyester and preparation method and application thereof TECHNICAL FIELD

[0001] The application belongs to the technical field of polymer materials, and particularly relates to a PBET copolyester and a preparation method and application thereof. BACKGROUND

[0002] Polyethylene terephthalate (PET) is one of the most commonly used plastics, but PET is difficult to degrade in the natural environment, and therefore waste PET needs to be recycled to alleviate its pollution to the environment. At present, PET is mainly recycled by a physical method, but the method can cause the quality of PET to decrease. Patent CN200780015944.4 discloses a chemical method for recycling PET, which comprises the following steps: reacting a diol component selected from ethylene glycol, propylene glycol and combinations thereof with a PET component under conditions sufficient to depolymerize the PET component into a first molten mixture; and wherein the first molten mixture is combined with 1,4-butanediol under conditions to produce a second molten mixture, and then placed under conditions of less than 1 atmosphere to produce a modified polybutylene terephthalate random copolymer. However, the modified polybutylene terephthalate random copolymer prepared by the method has poor aging resistance and mechanical properties. SUMMARY

[0003] Based on the defects of the prior art, the purpose of the present application is to provide a PBET copolyester and a preparation method and application thereof, which has better aging resistance and mechanical properties.

[0004] The present application provides a PBET copolyester, which comprises a repeating unit A and a repeating unit B.

[0005] The repeating unit A is derived from an aromatic dicarboxylic acid, wherein the aromatic dicarboxylic acid is terephthalic acid.

[0006] The repeating unit B is derived from a diol, and the diol comprises the following components in terms of mole percentage: 96% to 99.9% of 1,4-butanediol and 0.1% to 4% of ethylene glycol.

[0007] The end carboxyl group content of the PBET copolyester is 12 to 35 mmol / t.

[0008] When the PBET copolyester is subjected to thermal performance testing, the half-peak width of the cold crystallization peak in the second cooling curve is 5.7 to 7.5 DEG C, and the peak value is 184 to 190 DEG C, wherein the method of the thermal performance testing is as follows:

[0009] The sample weight is 10 mg, the determination atmosphere is nitrogen atmosphere, the temperature is raised to 300℃ at a temperature raising rate of 10℃ / min, then kept constant for 20 min, the temperature is lowered to 50℃ at a temperature lowering rate of 10℃ / min, then kept constant for 20 min, the temperature is raised to 300℃ at a temperature raising rate of 10℃ / min, then kept constant for 2 min, and the temperature is lowered to 50℃ at a temperature lowering rate of 10℃ / min.

[0010] In some embodiments, the hydrolysis rate constant k of the PBET copolyester satisfies: k≤0.002 day- 1 , ln(η sp,x / η sp,0 )=-kx, wherein η sp,0 represents the initial intrinsic viscosity of the PBET copolyester, η sp,x represents the intrinsic viscosity of the PBET copolyester after being placed in an environment with a temperature of 85℃ and a relative humidity of 85% for x days, and x=40.

[0011] In some embodiments, the k=0.0005~0.002 day- 1 .

[0012] In some embodiments, the η sp,0 is 0.7~1.2 dl / g.

[0013] In some embodiments, the molar ratio of the repeating unit A and the repeating unit B is 1:(1~1.02).

[0014] In some embodiments, the aromatic dicarboxylic acid comprises the following components in terms of molar percentage: 98%~100% of terephthalic acid, and 0~2% of isophthalic acid.

[0015] The present application provides the use of the PBET copolyester in electronic and electrical parts.

[0016] In some embodiments, the electronic and electrical parts include a fan or a connector in a notebook computer.

[0017] The present application provides a preparation method of the PBET copolyester, characterized in that it comprises the following steps:

[0018] PET, 1,4-butanediol and a catalyst are mixed and dispersed, and a first alcoholysis is performed under the conditions of inert atmosphere, pressure of 70~101.325 kPa, stirring speed of 40~50 r / min and temperature of 190~210℃ for 90~150 min to obtain a first alcoholysis product;

[0019] The first alcoholysis product is subjected to a first dealcoholization treatment to remove free 1,4-butanediol and ethylene glycol to obtain a product after the first dealcoholization treatment;

[0020] adding 1,4-butanediol and a catalyst to the product after the first dealcoholization treatment, and heating the mixture under an inert atmosphere at a pressure of 70 to 101.325 kPa, a stirring speed of 40 to 50 r / min, and a temperature of 180 to 205°C for 60 to 120 min to perform a second alcoholysis to obtain a second alcoholysis product;

[0021] performing a second dealcoholization treatment on the second alcoholysis product to remove free 1,4-butanediol and ethylene glycol to obtain a product after the second dealcoholization treatment;

[0022] adding 1,4-butanediol to the product after the second dealcoholization treatment, and heating the mixture under an inert atmosphere at a pressure of 70 to 101.325 kPa, a stirring speed of 40 to 50 r / min, and a temperature of 180 to 200°C for 30 to 60 min to perform a third alcoholysis to obtain a third alcoholysis product;

[0023] performing a third dealcoholization treatment on the third alcoholysis product to remove free 1,4-butanediol and ethylene glycol, and performing a polycondensation reaction at a pressure of 200 Pa or less, a stirring speed of 20 to 50 r / min, and a temperature of 225 to 235°C to obtain a PBET copolyester having an intrinsic viscosity of 0.7 to 1.2 dl / g;

[0024] In the above process, the total weight of the 1,4-butanediol used in the first alcoholysis and the second alcoholysis is 1.2 to 1.5 times the weight of the initially charged PET, the weight of the 1,4-butanediol used in the first alcoholysis is 30% to 53% of the total weight of the 1,4-butanediol used in the first alcoholysis and the second alcoholysis, and the weight of the 1,4-butanediol used in the third alcoholysis is 0.2 to 0.3 times the weight of the initially charged PET.

[0025] The catalysts used in the first alcoholysis and the second alcoholysis are Ti-containing catalysts, and the total weight of Ti in the catalysts is 40 to 80 ppm of the weight of the initially charged PET, and the weight of the catalyst used in the first alcoholysis is 50% to 100% of the total weight of the catalysts used in the first alcoholysis and the second alcoholysis.

[0026] In some embodiments, the preparation method satisfies at least one of conditions (1) to (6):

[0027] (1) the catalysts each include at least one of tetra-n-butyl titanate (TNBT) and tetraisopropyl titanate;

[0028] (2) the pressure of the polycondensation reaction is 10 to 200 Pa;

[0029] (3) the aromatic dicarboxylic acid units in the PET comprise the following molar percentages of components: 98-100% terephthalic acid, 0-2% isophthalic acid;

[0030] (4) the first alcohol removal treatment step comprises: vacuuming for 30-70 min to a pressure of 1-5 kPa at a temperature of 190-210°C and a stirring speed of 40-50 r / min;

[0031] (5) the second alcohol removal treatment step comprises: vacuuming for 30-70 min to a pressure of 1-5 kPa at a temperature of 180-205°C and a stirring speed of 40-50 r / min;

[0032] (6) the third alcohol removal treatment step comprises: vacuuming for 30-70 min to a pressure of 1-5 kPa at a temperature of 180-200°C and a stirring speed of 40-50 r / min.

[0033] Compared with the prior art, the application has the beneficial effects that the PBET copolyester has a specific diol unit composition, a carboxyl end group content, and a half-peak width and peak value of the second cooling curve, and has better mechanical properties and aging resistance, and is suitable for preparing electronic and electrical component parts. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a second cooling curve diagram obtained by testing the thermal properties of the PBET copolyester of Example 2. DETAILED DESCRIPTION

[0035] The term "carboxyl end group content" refers to the content of carboxyl groups (-COOH) at the end of the polymer molecular chain. Non-limiting examples of commonly used units include: meq / kg, mmol / kg, or mmol / t (where t represents ton).

[0036] The term "hydrolysis rate constant" refers to the decrease in the concentration (or amount of substance) of the target substance hydrolyzed per unit time. The k of the application is the k value under the condition of a temperature of 85°C and a relative humidity of 85%.

[0037] The term "intrinsic viscosity" refers to the specific viscosity of a high polymer solution when the concentration of the solution tends to zero; that is, it represents the contribution of a single molecule to the viscosity of the solution, and reflects the characteristics of the high polymer itself. Intrinsic viscosity is independent of temperature and humidity. In the application, η sp,0 represents the initial intrinsic viscosity of the PBET copolyester, and "initial" refers to the time when the copolyester is placed in an environment with a temperature of 85°C and a relative humidity of 85%.

[0038] In a first aspect, the present application provides a PBET copolyester, which comprises a repeating unit A and a repeating unit B;

[0039] The repeating unit A is derived from an aromatic dicarboxylic acid, wherein the aromatic dicarboxylic acid is phthalic acid;

[0040] The repeating unit B is derived from a diol, which comprises the following molar percentage of components: 96% to 99.9% 1,4-butanediol (BDO), 0.1% to 4% ethylene glycol (EG);

[0041] The end carboxyl content of the PBET copolyester is 12 to 35 mmol / t;

[0042] When the PBET copolyester is subjected to thermal performance test, the half-peak width of the cold crystallization peak in the second cooling curve is 5.7 to 7.5℃, and the peak value is 184 to 190℃, wherein the method of the thermal performance test is as follows:

[0043] The sample weight is 10 mg, the determination atmosphere is nitrogen atmosphere, after heating to 300℃ at a heating rate of 10℃ / min, constant temperature for 20 min, cooling to 50℃ at a cooling rate of 10℃ / min, constant temperature for 20 min, heating to 300℃ at a heating rate of 10℃ / min, constant temperature for 2 min, and cooling to 50℃ at a cooling rate of 10℃ / min.

[0044] The molecular formula of phthalic acid is C8H6O4, and two carboxyl groups are connected to two carbon atoms in the benzene ring to form a binary aromatic carboxyl.

[0045] The molar percentage of the 1,4-butanediol in the diol can be selected as 96% to 99.9%, such as 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.9% or a range formed by any two of the above values.

[0046] The molar percentage of the ethylene glycol in the diol can be selected as 0.1% to 4%, such as 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% or a range formed by any two of the above values.

[0047] The end carboxyl content in the PBET copolyester can be selected as 12 mmol / t, 14 mmol / t, 16 mmol / t, 18 mmol / t, 20 mmol / t, 22 mmol / t, 24 mmol / t, 26 mmol / t, 28 mmol / t, 30 mmol / t, 32 mmol / t, 35 mmol / t or a range formed by any two of the above values.

[0048] The half-peak width of the second cooling curve cold crystallization peak of the PBET copolyester can be selected to be 5.7°C, 5.8°C, 5.9°C, 6.0°C, 6.1°C, 6.2°C, 6.3°C, 6.4°C, 6.5°C, 6.6°C, 6.7°C, 6.8°C, 6.9°C, 7.0°C, 7.1°C, 7.2°C, 7.3°C, 7.4°C, 7.5°C, or a range formed by any two of the above values.

[0049] The peak value of the second cooling curve cold crystallization peak of the PBET copolyester can be selected to be 184°C, 185°C, 186°C, 187°C, 188°C, 189°C, 190°C, or a range formed by any two of the above values.

[0050] In some embodiments, the thermal performance test can be selected to be performed in a thermal analysis instrument, such as a NETZSCH 204 F1 thermal analysis instrument from Germany.

[0051] The inventors have found that, by controlling the half-peak width and the peak value of the second cooling curve cold crystallization peak of the PBET copolyester within the above specific ranges, and by coordinating the end carboxyl content with the above specific values, the hydrolysis rate constant k of the material can be maintained within a suitable range, and the material can have good aging resistance; by coordinating the specific ratio of 1,4-butanediol to ethylene glycol, the material can have good mechanical properties, such as high tensile strength. The PBET copolyester has good aging resistance and mechanical properties, and is suitable for use in the preparation of electronic and electrical component parts, such as fans or connectors in notebook computers.

[0052] The half-peak width and the peak value of the second cooling curve cold crystallization peak of the PBET copolyester provide information on the crystallization behavior of the material, reflecting the crystallization rate, crystallinity, and thermal stability of the material, and are dependent on the monomer composition, monomer composition ratio, and molecular weight of the PBET, as well as the reaction temperature and reaction time during the synthesis of the PBET. For example, excessively high temperature and long reaction time can result in the production of thermal degradation impurities, and the more impurities, the weaker the crystallization ability, the wider the half-peak width, and the smaller the peak value of the second cooling curve cold crystallization peak.

[0053] In some embodiments, the hydrolysis rate constant k of the PBET copolyester satisfies: k≤0.002 day-1. 1 , ln(η sp,x / η sp,0 )=-kx, where η sp,0 represents the initial intrinsic viscosity of the PBET copolyester, η sp,x represents the intrinsic viscosity of the PBET copolyester after being placed in an environment with a temperature of 85°C and a relative humidity of 85% for x days, and x=40. Exemplarily, the k is 0.0005 day-1.-1 0.0007 days -1 0.0009 days -1 0.0010 days -1 0.0012 days 1 0.0014 days 1 0.0016 days -1 0.0018 days -1 0.002 days -1 or a range formed by any two of the above values.

[0054] In some embodiments, the k = 0.0005-0.002 days -1 .

[0055] In some embodiments, the η sp,0 is 0.7-1.2 dl / g. For example, the η sp,0 is 0.7 dl / g, 0.8 dl / g, 0.9 dl / g, 1.0 dl / g, 1.1 dl / g, 1.2 dl / g, or a range formed by any two of the above values.

[0056] In some embodiments, the molar ratio of the repeating unit A and the repeating unit B in the PBET copolyester is 1:(1-1.02), such as 1:1, 1:1.01, 1:1.02, or a range formed by any two of the above values.

[0057] In some embodiments, the aromatic dicarboxylic acid comprises the following molar percentage of components: terephthalic acid 98-100%, isophthalic acid 0-2%. The molar percentage of the terephthalic acid in the aromatic dicarboxylic acid can be selected as 98%, 98.2%, 98.4%, 98.6%, 98.8%, 99%, 99.2%, 99.4%, 99.6%, 99.8%, 100%, or a range formed by any two of the above values. The molar percentage of the isophthalic acid in the aromatic dicarboxylic acid can be selected as 0, 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, or a range formed by any two of the above values.

[0058] The content of the BDO and the EG in the diol, the content of the terephthalic acid and the isophthalic acid in the aromatic dicarboxylic acid, and the molar ratio of the repeating units A and B in the PBET copolyester can be measured by conventional means in the art, for example, by nuclear magnetic resonance spectroscopy (H-NMR). 1

[0059] In some embodiments, the nuclear magnetic resonance spectroscopy method comprises the following steps: ​

[0060] The test was performed using a Bruker AVANCE AV600 spectrometer, the test frequency was 600 MHz, the test solvent was deuterated chloroform (CDCI3), and the internal standard was tetramethylsilane (TMS);

[0061] S PTA represents the peak area of terephthalic acid, the peak area of terephthalic acid is 1 the integral area of the peak at 8.25 ppm in the H NMR spectrum;

[0062] S IPA represents the peak area of isophthalic acid, the peak area of isophthalic acid is 1 the sum of the integral areas of the peaks at 7.75 ppm and 8.85 ppm in the H NMR spectrum;

[0063] S BDO is the peak area of BDO, the peak area of BDO is 1 the integral area of the peak at 4.65 ppm in the H NMR spectrum;

[0064] S EG is the peak area of EG, the peak area of EG is 1 the integral area of the peak at 4.95 ppm in the H NMR spectrum;

[0065] the mole percentage of the BDO in the diol = S BDO / (S BDO +S EG );

[0066] the mole percentage of the EG in the diol = S EG / (S BDO +S EG );

[0067] the mole percentage of the terephthalic acid in the aromatic dicarboxylic acid = S PTA / (S PTA +S IPA );

[0068] the mole percentage of the isophthalic acid in the aromatic dicarboxylic acid = S IPA / (S PTA +S IPA );

[0069] the mole ratio of the repeating units A and B = (S PTA +S IPA ):(S BDO +S EG ).

[0070] The carboxyl end group content of the PBET copolyester can be measured by conventional means in the art, for example, according to GB / T 14190-2017 Test methods for polyester (PET) chips for fiber use, Method 5.4.2 Method B (photometric titration).

[0071] η sp,x and η sp,0 may be measured by conventional means in the art, for example, by the following method: the intrinsic viscosity can be measured using a Ubbelohde capillary viscometer with a capillary inner diameter of 0.83 mm, model 1835.

[0072] In some embodiments, η sp,x and η sp,0 The specific test method includes the following steps:

[0073] 0.1250 ± 0.0001 g of the sample was weighed into a 250 mL conical flask, 25 mL of a mixed solvent of phenol and o-dichlorobenzene (volume ratio of phenol to o-dichlorobenzene was 3:2) was added, after heating and dissolving, the sample solution was obtained after cooling to room temperature; then the sample solution was placed in a water bath at 25 ± 0.01 °C for 10 min, and the efflux time of the sample solution and the above-mentioned mixed solvent of phenol and o-dichlorobenzene was measured in a Ubbelohde capillary viscometer at 25 °C, and the intrinsic viscosity was calculated;

[0074] The formula for the intrinsic viscosity of the PBET copolyester is: η sp = (η - η0) / η0, where η is the viscosity of the sample solution, in units of Pa·s; η0is the viscosity of the mixed solvent of phenol and o-dichlorobenzene, in units of Pa·s; η sp is the intrinsic viscosity of the PBET copolyester, in units of dl / g.

[0075] In a second aspect, the present application provides the use of the PBET copolyester in electronic and electrical parts. As an example, the electronic and electrical parts are fans and connectors in a notebook computer.

[0076] In some embodiments, the present application provides an electronic appliance part derived from (or made from, or formed from) a composition comprising the PBET copolyester. The term "derived" (or "made", or "formed") means that it can be obtained by a variety of processes, including but not limited to molding, such as injection molding, compression molding, blow molding, rotational molding; extrusion, such as sheet extrusion, film extrusion, such as blown-film extrusion; thermoforming; vacuum forming; and melt-blown process.

[0077] In some embodiments, the electronic appliance part is derived from (or made from, or formed from) a composition comprising the PBET copolyester.

[0078] In some embodiments, the electronic appliance part is derived from (or made from, or formed from) a composition comprising the PBET copolyester without chemical change (i.e., the electronic appliance part comprises the PBET copolyester, for example, the electronic appliance part is a housing comprising the PBET copolyester); or with chemical change.

[0079] In some embodiments, the electronic appliance part is derived from (or made from, or formed from) a composition comprising the PBET copolyester without chemical change (i.e., the electronic appliance part comprises the PBET copolyester, for example, the electronic appliance part is a housing comprising the PBET copolyester); or with chemical change.

[0080] In some embodiments, the electronic appliance part is derived from (or made from, or formed from) a composition comprising the PBET copolyester without chemical change (i.e., the electronic appliance part comprises the PBET copolyester, for example, the electronic appliance part is a housing comprising the PBET copolyester); or with chemical change.

[0081] mixing and dispersing PET, 1,4-butanediol and catalyst, heating under inert atmosphere, pressure 70-101.325 kPa, stirring speed 40-50 r / min and temperature 190-210 °C for 90-150 min to obtain a first alcoholysis product;

[0082] removing free 1,4-butanediol and ethylene glycol from the first alcoholysis product to obtain a first alcohol-removed product;

[0083] adding 1,4-butanediol and a catalyst to the product after the first dealcoholization treatment, and heating the product under an inert atmosphere at a pressure of 70-101.325 kPa, a stirring speed of 40-50 r / min, and a temperature of 180-205 °C for 60-120 min to obtain a second alcoholysis product;

[0084] dealcoholizing the second alcoholysis product to remove free 1,4-butanediol and ethylene glycol, thereby obtaining a product after the second dealcoholization treatment;

[0085] adding 1,4-butanediol to the product after the second dealcoholization treatment, and heating the product under an inert atmosphere at a pressure of 70-101.325 kPa, a stirring speed of 40-50 r / min, and a temperature of 180-200 °C for 30-60 min to obtain a third alcoholysis product;

[0086] dealcoholizing the third alcoholysis product to remove free 1,4-butanediol and ethylene glycol, and then performing a polycondensation reaction under a pressure of 200 Pa or less, a stirring speed of 20-50 r / min, and a temperature of 225-235 °C to obtain a PBET copolyester having an intrinsic viscosity of 0.7-1.2 dl / g;

[0087] In the first alcoholysis and the second alcoholysis, the total weight of the 1,4-butanediol is 1.2-1.5 times the weight of the PET, and the weight of the 1,4-butanediol used in the first alcoholysis is 30%-53% of the total weight of the 1,4-butanediol used in the first alcoholysis and the second alcoholysis. In the third alcoholysis, the weight of the 1,4-butanediol is 0.2-0.3 times the weight of the PET.

[0088] In the first alcoholysis and the second alcoholysis, the total weight of Ti in the catalyst is 40-80 ppm of the weight of the PET, and the weight of the catalyst used in the first alcoholysis is 50%-100% of the total weight of the catalyst used in the first alcoholysis and the second alcoholysis.

[0089] In some embodiments, the weight of the 1,4-butanediol used in the first alcoholysis is 30%-50% of the total weight of the 1,4-butanediol used in the first alcoholysis and the second alcoholysis.

[0090] In some embodiments, the catalysts each include at least one of tetra-n-butyl titanate (TNBT) and tetraisopropyl titanate.

[0091] In some embodiments, the pressure of the polycondensation reaction is 10-200 Pa.

[0092] In some embodiments, the aromatic dicarboxylic acid units in the PET comprise the following molar percentage of components: 98-100% terephthalic acid, 0-2% isophthalic acid.

[0093] In some embodiments, the first step of the first dealcoholization treatment comprises or the following: vacuum extraction at a temperature of 190-210°C and a stirring speed of 40-50 r / min for 30-70 min until the pressure reaches 1-5 kPa. In some embodiments, free 1,4-butanediol and ethylene glycol are removed by vacuum extraction at a temperature of 190-210°C and a stirring speed of 40-50 r / min for 30-70 min until the pressure reaches 1-5 kPa.

[0094] In some embodiments, the second step of the second dealcoholization treatment comprises or the following: vacuum extraction at a temperature of 180-205°C and a stirring speed of 40-50 r / min for 30-70 min until the pressure reaches 1-5 kPa. In some embodiments, free 1,4-butanediol and ethylene glycol are removed by vacuum extraction at a temperature of 180-205°C and a stirring speed of 40-50 r / min for 30-70 min until the pressure reaches 1-5 kPa.

[0095] In some embodiments, the third step of the third dealcoholization treatment comprises or the following: vacuum extraction at a temperature of 180-200°C and a stirring speed of 40-50 r / min for 30-70 min until the pressure reaches 1-5 kPa. In some embodiments, free 1,4-butanediol and ethylene glycol are removed by vacuum extraction at a temperature of 180-200°C and a stirring speed of 40-50 r / min for 30-70 min until the pressure reaches 1-5 kPa.

[0096] In some embodiments, the polycondensation reaction is performed until the intrinsic viscosity of the PBET copolyester reaches the target value.

[0097] The PET can be virgin material or recycled material.

[0098] The PBET copolyester can be prepared by the above method or other methods, for example, the alcoholysis and dealcoholization parameters in the three-step alcoholysis process are different from the above method, but the corresponding PBET copolyester can be obtained by increasing the number of alcoholysis and dealcoholization.

[0099] In order to better illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described below in conjunction with specific examples and comparative examples, which are intended to help understand the content of the present application in detail, rather than limit the present application. All other examples obtained by those of ordinary skill in the art without creative labor shall fall within the protection scope of the present application. The experimental reagents and instruments involved in the implementation of the present application are all common reagents and instruments unless otherwise specified. In the present application, the open technical features described include both the closed technical scheme consisting of the listed features and the open technical scheme containing the listed features.

[0100] Example 1

[0101] The present embodiment provides a preparation method of a PBET copolyester, comprising the following steps:

[0102] Into a polymerization reactor, 3500g of recycled PET (the aromatic dicarboxylic acid units in the PET include the following molar percentage of components: 99.07% of terephthalic acid, 0.93% of isophthalic acid), 2350g of BDO and 0.8g of TNBT are put, the stirring speed is 50r / min under the nitrogen atmosphere and 91kPa, the temperature is raised to 190℃ and kept for 140min to obtain the first alcoholysis product, and the low boiling point moisture and THF generated in the heating process are discharged through the fractionating column;

[0103] The stirring speed is kept unchanged, the vacuum system is opened, vacuum is extracted to 5.0kPa at 190℃ for 70min to remove the free 1,4 butanediol and ethylene glycol, then the vacuum extraction is stopped, and N2 is used to raise the pressure to normal pressure (101.325kPa, same below) to obtain the alcohol-removed product;

[0104] The stirring speed is kept unchanged, 2900g of BDO and 0.7g of TNBT are added, vacuum is extracted to 91kPa, the temperature is raised to 196℃ and kept for 120min to obtain the second alcoholysis product, and the low boiling point moisture and THF generated in the heating process are discharged through the fractionating column;

[0105] The stirring speed is kept unchanged, the vacuum system is opened, vacuum is extracted to 5.0kPa at 196℃ for 70min to remove the free 1,4 butanediol and ethylene glycol, then the vacuum extraction is stopped, and N2 is used to raise the pressure to normal pressure (101.325kPa, same below) to obtain the alcohol-removed product;

[0106] The stirring speed is kept unchanged, 2900g of BDO and 0.7g of TNBT are added, vacuum is extracted to 91kPa, the temperature is raised to 196℃ and kept for 120min to obtain the second alcoholysis product, and the low boiling point moisture and THF generated in the heating process are discharged through the fractionating column;

[0107] Keeping the rotation speed unchanged, the vacuum system was opened, and the temperature was raised to 180°C for 60 min to remove free 1,4-butanediol and ethylene glycol by vacuumizing to 1 kPa, and then the temperature was raised to 234°C and the rotation speed was adjusted to 50 r / min, and the temperature and pressure were kept stable until the intrinsic viscosity reached the target value, and then the stirring was stopped to obtain the target PBET copolyester.

[0108] Example 2

[0109] The present embodiment provides a method for preparing a PBET copolyester, comprising the following steps:

[0110] In a polymerization reactor, 3500 g of recycled PET (the aromatic dicarboxylic acid units in the PET include the following components in mole percentage: 100% terephthalic acid, 0% isophthalic acid), 2200 g of BDO, and 0.9 g of TNBT were put in, and stirring was started under a nitrogen atmosphere and at normal pressure, the rotation speed was 40 r / min, the temperature was raised to 200°C and kept for 150 min to obtain the first alcoholysis product, and in the heating process, the low-boiling water and THF generated were discharged through a fractionating column;

[0111] Keeping the rotation speed unchanged, the vacuum system was opened, and the temperature was raised to 200°C for 30 min to remove free 1,4-butanediol and ethylene glycol by vacuumizing to 1.0 kPa, and then the vacuum was stopped, and N2 was used to raise the pressure to normal pressure to obtain the alcohol-removed product;

[0112] Keeping the rotation speed unchanged, 2000 g of BDO and 0.6 g of TNBT were added, the normal pressure was maintained, and the temperature was raised to 189°C and kept for 75 min to obtain the second alcoholysis product, and in the heating process, the low-boiling water and THF generated were discharged through a fractionating column;

[0113] Keeping the rotation speed unchanged, the vacuum system was opened, and the temperature was raised to 189°C for 30 min to remove free 1,4-butanediol and ethylene glycol by vacuumizing to 1.0 kPa, and then the vacuum was stopped, and N2 was used to raise the pressure to normal pressure (101.325 kPa, the same below) to obtain the alcohol-removed product;

[0114] Keeping the rotation speed unchanged, 700 g of BDO was added, vacuumizing to 73 kPa, and the temperature was raised to 195°C and kept for 30 min to obtain the third alcoholysis product, and in the heating process, the low-boiling water and THF generated were discharged through a fractionating column;

[0115] Keeping the rotation speed unchanged, the vacuum system was opened, and the system was vacuumized to 2.4 kPa at 195 ℃ for 30 min to remove free 1,4-butanediol and ethylene glycol, and then the temperature was increased to 225 ℃, the vacuum was continued to 50 Pa, and the stirring speed was adjusted to 50 r / min. The temperature and pressure were kept stable until the intrinsic viscosity reached the target value. The stirring was stopped, and the target PBET copolyester was obtained.

[0116] Example 3

[0117] The present example provides a method for preparing a PBET copolyester, comprising the following steps:

[0118] In a polymerization reactor, 3500 g of recycled PET (the aromatic dicarboxylic acid units in the PET include the following components in mole percentage: 98% terephthalic acid, 2% isophthalic acid), 1900 g of BDO, and 1 g of TNBT were added. The stirring was started under a nitrogen atmosphere and at 83 kPa, the stirring speed was 44 r / min, the temperature was increased to 198 ℃ and kept for 122 min to obtain the first alcoholysis product. During the heating process, the low-boiling water and THF generated were discharged through a fractionating column;

[0119] The rotation speed was kept unchanged, the vacuum system was opened, and the system was vacuumized to 2.3 kPa at 198 ℃ for 55 min to remove free 1,4-butanediol and ethylene glycol. Then the vacuum was stopped, and N2 was used to increase the pressure to normal pressure to obtain the alcohol-removed product;

[0120] The rotation speed was kept unchanged, 2650 g of BDO and 1 g of TNBT were added, the system was vacuumized to 83 kPa, and the temperature was increased to 200 ℃ and kept for 89 min to obtain the second alcoholysis product. During the heating process, the low-boiling water and THF generated were discharged through a fractionating column;

[0121] The rotation speed was kept unchanged, the vacuum system was opened, and the system was vacuumized to 2.3 kPa at 200 ℃ for 55 min to remove free 1,4-butanediol and ethylene glycol. Then the vacuum was stopped, and N2 was used to increase the pressure to normal pressure (101.325 kPa, the same below) to obtain the alcohol-removed product;

[0122] The rotation speed was kept unchanged, 820 g of BDO was added, the system was vacuumized to 70 kPa, and the temperature was increased to 184 ℃ and kept for 39 min to obtain the third alcoholysis product. During the heating process, the low-boiling water and THF generated were discharged through a fractionating column;

[0123] Keeping the rotation speed unchanged, the vacuum system was opened, and the temperature was raised to 228°C and vacuumed to 80 Pa for 70 min at 182°C to remove free 1,4-butanediol and ethylene glycol, and the rotation speed was adjusted to 30 r / min, and the temperature and pressure were kept stable until the intrinsic viscosity reached the target value, and the stirring was stopped to obtain the target PBET copolyester.

[0124] Example 4

[0125] The present embodiment provides a method for preparing a PBET copolyester, comprising the following steps:

[0126] In a polymerization reactor, 3500 g of recycled PET (the aromatic dicarboxylic acid units in the PET include the following components in mole percentage: 99.07% terephthalic acid, 0.93% isophthalic acid), 1575 g of BDO and 0.5 g of TNBT were put in, the stirring was started under a nitrogen atmosphere and 99 kPa, the rotation speed was 47 r / min, the temperature was raised to 204°C and kept for 90 min to obtain the first alcoholysis product, and the low-boiling water and THF generated in the heating process were discharged through a fractionating column;

[0127] Keeping the rotation speed unchanged, the vacuum system was opened, and the temperature was raised to 228°C and vacuumed to 80 Pa for 70 min at 182°C to remove free 1,4-butanediol and ethylene glycol, and the rotation speed was adjusted to 30 r / min, and the temperature and pressure were kept stable until the intrinsic viscosity reached the target value, and the stirring was stopped to obtain the target PBET copolyester.

[0128] Keeping the rotation speed unchanged, 3675 g of BDO and 0.5 g of TNBT were added, vacuumed to 99 kPa, and the temperature was raised to 180°C and kept for 102 min to obtain the second alcoholysis product, and the low-boiling water and THF generated in the heating process were discharged through a fractionating column;

[0129] Keeping the rotation speed unchanged, the vacuum system was opened, and the temperature was raised to 228°C and vacuumed to 80 Pa for 70 min at 182°C to remove free 1,4-butanediol and ethylene glycol, and the rotation speed was adjusted to 30 r / min, and the temperature and pressure were kept stable until the intrinsic viscosity reached the target value, and the stirring was stopped to obtain the target PBET copolyester.

[0130] Keeping the rotation speed unchanged, 3675 g of BDO and 0.5 g of TNBT were added, vacuumed to 99 kPa, and the temperature was raised to 180°C and kept for 102 min to obtain the second alcoholysis product, and the low-boiling water and THF generated in the heating process were discharged through a fractionating column;

[0131] Keeping the rotation speed unchanged, the vacuum system was opened, and vacuum was drawn to 4.2 kPa at 190 ℃ for 43 min to remove free 1,4-butanediol and ethylene glycol, then the temperature was increased to 235 ℃ and vacuum was continued to 160 Pa, and the stirring speed was adjusted to 25 r / min, the temperature and pressure were kept stable until the intrinsic viscosity reached the target value, the stirring was stopped, and the target PBET copolyester was obtained.

[0132] Example 5

[0133] The present embodiment provides a method for preparing a PBET copolyester, comprising the following steps:

[0134] In a polymerization reactor, 3500 g of recycled PET (the aromatic dicarboxylic acid units in the PET include the following components in mole percentage: terephthalic acid 99.07%, isophthalic acid 0.93%), 2000 g of BDO, and 0.5 g of TNBT were put in, the stirring was started under a nitrogen atmosphere and 70 kPa, the stirring speed was 40 r / min, the temperature was increased to 201 ℃ and kept for 95 min to obtain a first alcoholysis product, and the low-boiling water and THF generated during the heating process were discharged through a fractionating column;

[0135] Keeping the rotation speed unchanged, the vacuum system was opened, and vacuum was drawn to 4.6 kPa at 201 ℃ for 40 min to remove free 1,4-butanediol and ethylene glycol, then vacuum was stopped, and N2 was used to increase the pressure to normal pressure to obtain the alcohol-removed product;

[0136] Keeping the rotation speed unchanged, 2200 g of BDO and 0.5 g of TNBT were added, vacuum was drawn to 70 kPa, and the temperature was increased to 186 ℃ and kept for 112 min to obtain a second alcoholysis product, and the low-boiling water and THF generated during the heating process were discharged through a fractionating column;

[0137] Keeping the rotation speed unchanged, the vacuum system was opened, and vacuum was drawn to 4.6 kPa at 186 ℃ for 40 min to remove free 1,4-butanediol and ethylene glycol, then vacuum was stopped, and N2 was used to increase the pressure to normal pressure (101.325 kPa, the same below) to obtain the alcohol-removed product;

[0138] Keeping the rotation speed unchanged, 910 g of BDO was added, vacuum was drawn to 97 kPa, and the temperature was increased to 200 ℃ and kept for 55 min to obtain a third alcoholysis product, and the low-boiling water and THF generated during the heating process were discharged through a fractionating column;

[0139] Keeping the rotation speed unchanged, the vacuum system was opened, and vacuum was drawn to 5 kPa at 200 °C for 56 min to remove free 1,4-butanediol and ethylene glycol, then the temperature was increased to 230 °C and vacuum was continued to 20 Pa, and the stirring speed was adjusted to 36 r / min, the temperature and pressure were kept stable until the intrinsic viscosity reached the target value, the stirring was stopped, and the target PBET copolyester was obtained.

[0140] Example 6

[0141] The present embodiment provides a method for preparing a PBET copolyester, comprising the following steps:

[0142] In a polymerization reactor, 3500 g of recycled PET (the aromatic dicarboxylic acid units in the PET include the following components in mole percentage: terephthalic acid 99.07%, isophthalic acid 0.93%), 1600 g of BDO, and 2 g of TNBT were added, stirring was started under a nitrogen atmosphere at 70 kPa, the stirring speed was 50 r / min, the temperature was increased to 210 °C and kept constant for 100 min to obtain a first alcoholysis product, and low-boiling water and THF generated during the heating process were discharged through a fractionating column;

[0143] Keeping the rotation speed unchanged, the vacuum system was opened, and vacuum was drawn to 1.5 kPa at 210 °C for 45 min to remove free 1,4-butanediol and ethylene glycol, then vacuum was stopped, and N2 was used to increase the pressure to normal pressure to obtain the alcohol-removed product;

[0144] Keeping the rotation speed unchanged, 3300 g of BDO was added, vacuum was drawn to 70 kPa, and the temperature was increased to 205 °C and kept constant for 60 min to obtain a second alcoholysis product, and low-boiling water and THF generated during the heating process were discharged through a fractionating column;

[0145] Keeping the rotation speed unchanged, the vacuum system was opened, and vacuum was drawn to 1.5 kPa at 205 °C for 45 min to remove free 1,4-butanediol and ethylene glycol, then vacuum was stopped, and N2 was used to increase the pressure to normal pressure (101.325 kPa, the same below) to obtain the alcohol-removed product;

[0146] Keeping the rotation speed unchanged, 770 g of BDO was added, the temperature was increased to 191 °C and kept constant for 60 min under normal pressure to obtain a third alcoholysis product, and low-boiling water and THF generated during the heating process were discharged through a fractionating column;

[0147] Keeping the rotation speed unchanged, the vacuum system was opened, and the temperature was increased to 232°C and the pressure was reduced to 105 Pa under vacuum for 49 min to remove the free 1,4-butanediol and ethylene glycol, and the stirring speed was adjusted to 42 r / min, the temperature and pressure were kept stable until the intrinsic viscosity reached the target value, the stirring was stopped, and the target PBET copolyester was obtained.

[0148] Comparative Example 1

[0149] The present comparative example provides a preparation method of a PBET copolyester, which is different from Example 1 in that the BDO is completely replaced by ethylene glycol in an equal molar amount during the first alcoholysis, i.e., 1619 g of ethylene glycol is used to replace 2350 g of BDO.

[0150] Comparative Example 2

[0151] The present comparative example provides a preparation method of a PBET copolyester, which is different from Example 1 in that the amount of BDO used during the first alcoholysis is changed from 2350 g to 1100 g.

[0152] Comparative Example 3

[0153] The present comparative example provides a preparation method of a PBET copolyester, which is different from Example 1 in that the amount of BDO used during the second alcoholysis is changed from 2900 g to 1500 g.

[0154] Comparative Example 4

[0155] The present comparative example provides a preparation method of a PBET copolyester, which includes the following steps:

[0156] In the polymerization reactor, 3500 g of recycled PET (the aromatic dicarboxylic acid units in the PET include the following molar percentage of components: 98% terephthalic acid, 2% isophthalic acid), 1900 g of BDO and 1 g of TNBT were added, the stirring was started under a nitrogen atmosphere and at a pressure of 83 kPa, the stirring speed was 44 r / min, the temperature was increased to 198°C and kept at 198°C for 122 min to obtain the first alcoholysis product, and the low-boiling water and THF generated during the heating process were removed through a fractionating column;

[0157] Keeping the rotation speed unchanged, the vacuum system was opened, and the temperature was increased to 232°C and the pressure was reduced to 105 Pa under vacuum for 49 min to remove the free 1,4-butanediol and ethylene glycol, and the stirring speed was adjusted to 42 r / min, the temperature and pressure were kept stable until the intrinsic viscosity reached the target value, the stirring was stopped, and the target PBET copolyester was obtained.

[0158] Keeping the rotation speed unchanged, 2650 g of BDO and 1 g of TNBT were added, vacuum was applied to 83 kPa, and the temperature was raised to 200 °C and kept constant for 57 min to obtain the second alcoholysis product. During the heating process, the low-boiling water and THF generated were discharged through the fractionating column;

[0159] Keeping the rotation speed unchanged, the vacuum system was started, and vacuum was applied to 2.3 kPa at 200 °C for 55 min to remove free 1,4-butanediol and ethylene glycol, then vacuum was stopped, and N2 was used to raise the pressure to normal pressure (101.325 kPa, the same below) to obtain the de-alcoholized product;

[0160] Keeping the rotation speed unchanged, 920 g of BDO was added, vacuum was applied to 80 kPa, and the temperature was raised to 189 °C and kept constant for 52 min to obtain the third alcoholysis product. During the heating process, the low-boiling water and THF generated were discharged through the fractionating column;

[0161] Keeping the rotation speed unchanged, the vacuum system was started, and vacuum was applied to 2.2 kPa at 186 °C for 68 min to remove free 1,4-butanediol and ethylene glycol, then the temperature was raised to 242 °C and vacuum was continued to 350 Pa, and the stirring speed was adjusted to 30 r / min. The temperature and pressure were kept stable until the intrinsic viscosity reached the target value, and then the stirring was stopped to obtain the target PBET copolyester.

[0162] Comparative Example 5

[0163] This comparative example provides a preparation method of a PBET copolyester, which is different from Example 6 in that the amount of TNBT used in the second alcoholysis is changed from 0 to 3 g.

[0164] Example 7

[0165] This example provides a preparation method of a PBET copolyester, which comprises the following steps: treating the PBET copolyester obtained in Comparative Example 2 as follows:

[0166] In the polymerization reactor, 3500 g of the PBET obtained in Comparative Example 2, 2000 g of BDO and 1.4 g of TNBT were added, and the stirring was started under a nitrogen atmosphere and at 75 kPa, the stirring speed was 44 r / min, the temperature was raised to 200 °C and kept constant for 102 min to obtain the alcoholysis product. During the heating process, the low-boiling water and THF generated were discharged through the fractionating column;

[0167] The rotation speed was kept constant, the vacuum system was opened, and the temperature was raised to 198°C and the vacuum was removed to 1.3 kPa for 55 min to remove free 1,4-butanediol and ethylene glycol, and then the temperature was raised to 228°C and the vacuum was continued to 50 Pa and the stirring speed was adjusted to 30 r / min, the temperature and pressure were kept stable until the intrinsic viscosity reached the target value, the stirring was stopped, and the target PBET copolyester was obtained.

[0168] The half-peak width of the cold crystallization peak in the second cooling curve and the peak hydrolysis rate constant k (x = 40) of the PBET copolyesters obtained in the examples and comparative examples, the carboxyl terminal group content, the initial intrinsic viscosity, the proportion of BDO units and ethylene glycol units in the diol units, and the proportion of terephthalic acid units and isophthalic acid units in the aromatic dicarboxylic acid units are shown in Table 1. In addition, the molar ratio of the repeating unit A and the repeating unit B in the PBET copolyesters obtained in the examples and comparative examples is 1:1.

[0169] The PBET copolyesters obtained in the above examples and comparative examples were tested as follows:

[0170] Tensile strength test: the tensile strength of the samples without aging treatment and the samples placed in an environment with a temperature of 85°C and a relative humidity of 85% for 40 days were both tested according to the standard ISO 527-2:2012, and the tensile strengths were recorded as N0 and N 40 , respectively, and the tensile strength retention rate I after hydrothermal aging was calculated, and the calculation formula is as follows: I = (N 40 / N0) * 100%.

[0171] The test results are shown in Table 1.

[0172] Table 1

[0173] Note: In Table 1, “BDO” represents the molar proportion of the repeating unit derived from BDO in the repeating unit derived from diol, “ethylene glycol” represents the molar proportion of the repeating unit derived from ethylene glycol in the repeating unit derived from diol, “terephthalic acid” represents the molar proportion of the repeating unit derived from terephthalic acid in the repeating unit derived from aromatic dicarboxylic acid, and “isophthalic acid” represents the molar proportion of the repeating unit derived from isophthalic acid in the repeating unit derived from aromatic dicarboxylic acid.

[0174] From the above data, the initial tensile strength of the PBET copolyesters obtained by the embodiments of the present application is above 55 MPa, and the tensile strength retention rate after aging for 40 days in an environment with a temperature of 85℃ and a relative humidity of 85% is above 95.5%. The initial tensile strength and / or aging resistance of the PBET copolyesters of Comparative Examples 1-5 deviate due to the high half-peak width of the second cooling curve crystallization peak, or the high half-peak width and low peak value, and / or the low proportion of the repeating units derived from 1,4-butanediol in the glycol units.

[0175] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A PBET copolyester, characterized in that, Includes repeating unit A and repeating unit B; The repeating unit A is derived from an aromatic dicarboxylic acid, wherein the aromatic dicarboxylic acid is phthalic acid; The repeating unit B is derived from a diol comprising the following molar percentage components: 96%–99.9% 1,4-butanediol and 0.1%–4% ethylene glycol; The PBET copolyester has a terminal carboxyl group content of 12–35 mmol / t; When the thermal properties of the PBET copolyester were tested, the half-maximum width of the cold crystallization peak in the second cooling curve was 5.7–7.5 °C, and the peak value was 184–190 °C. The method for testing the thermal properties is as follows: The sample weight was 10 mg. The test atmosphere was nitrogen. The temperature was increased to 300℃ at a rate of 10℃ / min and held for 20 min. The temperature was then decreased to 50℃ at a rate of 10℃ / min and held for 20 min. The temperature was then increased to 300℃ at a rate of 10℃ / min and held for 2 min. Finally, the temperature was decreased to 50℃ at a rate of 10℃ / min.

2. The PBET copolyester as described in claim 1, characterized in that, The hydrolysis rate constant k of the PBET copolyester satisfies: k ≤ 0.002 days -1 ,ln(η sp,x / η sp,0 )=-kx, Where, η sp,0 This indicates the initial intrinsic viscosity of the PBET copolyester. η sp,x The intrinsic viscosity of the PBET copolyester is expressed as x days after being placed in an environment with a temperature of 85°C and a relative humidity of 85%, where x = 40.

3. The PBET copolyester as described in claim 2, characterized in that, The k = 0.0005 to 0.002 days -1 .

4. The PBET copolyester as described in claim 1, characterized in that, The η sp,0 The concentration is 0.7–1.2 dl / g.

5. The PBET copolyester as described in claim 1, characterized in that, The molar ratio of repeating unit A to repeating unit B is 1:(1~1.02).

6. The PBET copolyester as described in claim 1, characterized in that, The aromatic dicarboxylic acid comprises the following components in molar percentage: 98%–100% terephthalic acid and 0–2% isophthalic acid.

7. The application of PBET copolyester as described in any one of claims 1 to 6 in electronic and electrical components.

8. The PBET copolyester as described in claim 7, characterized in that, The electronic components include fans or connectors in laptops.

9. A method for preparing a PBET copolyester as described in any one of claims 1 to 6, characterized in that, Includes the following steps: PET, 1,4-butanediol and catalyst were mixed and dispersed, and the first alcoholysis was carried out for 90-150 min under an inert atmosphere, pressure of 70-101.325 kPa, stirring speed of 40-50 r / min and temperature of 190-210℃ to obtain the first alcoholysis product. The first alcoholysis product is subjected to a first de-alcoholization treatment to remove free 1,4-butanediol and ethylene glycol, to obtain the product after the first de-alcoholization treatment; 1,4-Butanediol and a catalyst were added to the product after the first alcoholysis treatment, and the product was heated for a second alcoholysis for 60-120 min under an inert atmosphere, a pressure of 70-101.325 kPa, a stirring speed of 40-50 r / min, and a temperature of 180-205 °C to obtain the second alcoholysis product. The second alcoholysis product is subjected to a second alcohol removal treatment to remove free 1,4-butanediol and ethylene glycol, to obtain the product after the second alcohol removal treatment. 1,4-Butanediol was added to the product after the second alcoholysis treatment, and the product was heated for a third alcoholysis for 30-60 minutes under an inert atmosphere, a pressure of 70-101.325 kPa, a stirring speed of 40-50 r / min, and a temperature of 180-200 °C to obtain the third alcoholysis product. The third alcoholysis product is subjected to a third de-alcoholization treatment to remove free 1,4-butanediol and ethylene glycol, and then polycondensation reaction is carried out under the conditions of pressure below 200 Pa, stirring speed of 20-50 r / min and temperature of 225-235 °C to obtain PBET copolyester with intrinsic viscosity of 0.7-1.2 dl / g. The total weight of 1,4-butanediol used in the first and second alcoholyses is 1.2 to 1.5 times the initial weight of PET. The weight of 1,4-butanediol used in the first alcoholyses is 30% to 53% of the total weight of 1,4-butanediol used in the first and second alcoholyses. The weight of 1,4-butanediol used in the third alcoholyses is 0.2 to 0.3 times the initial weight of PET. The catalysts used for the first and second alcoholyses are Ti-containing catalysts, and the total weight of Ti in the catalyst is 40 to 80 ppm of the initial PET feed weight. The weight of the catalyst used for the first alcoholyse is 50% to 100% of the total weight of the catalysts used for the first and second alcoholyses.

10. The preparation method according to claim 9, characterized in that, At least one of conditions (1) to (6) must be satisfied: (1) All catalysts include at least one of tetrabutyl titanate (TNBT) and tetraisopropyl titanate; (2) The pressure of the polycondensation reaction is 10-200 Pa; (3) The aromatic dicarboxylic acid unit in the PET comprises the following components in molar percentage: 98% to 100% terephthalic acid and 0% to 2% isophthalic acid; (4) The first alcohol removal process includes: evacuating to a pressure of 1-5 kPa for 30-70 minutes at a temperature of 190-210℃ and a stirring speed of 40-50 r / min; (5) The second alcohol removal process includes: evacuating to a pressure of 1-5 kPa for 30-70 minutes at a temperature of 180-205℃ and a stirring speed of 40-50 r / min; (6) The third alcohol removal process includes: evacuating to a pressure of 1-5 kPa for 30-70 minutes at a temperature of 180-200℃ and a stirring speed of 40-50 r / min.

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