Titanium catalyst for polyester synthesis as well as preparation method and application of titanium catalyst

Abstract

The invention discloses a titanium catalyst for polyester synthesis as well as a preparation method and application thereof, a nuclear magnetic resonance hydrogen spectrogram of the titanium catalyst has the following characteristics: the ratio of integral values of all characteristic peaks between 2.4 ppm and 3.5 ppm to integral values of all characteristic peaks between 2.7 ppm and 3.0 ppm is 1: (0.5-0.8). Polyester prepared by adopting the titanium catalyst has the advantages of excellent activity, hydrolysis resistance, low cost and simple preparation process, and the prepared polyester material has good brightness and chromaticity and small molecular weight distribution coefficient.

Description

Technical Field

[0001] The present invention belongs to the field of catalysts for polyester synthesis, and particularly relates to a titanium-based catalyst for polyester synthesis, a preparation method thereof, and an application thereof. Background Art

[0002] Polyester is a kind of polymer material widely used in daily life, which is mainly prepared by esterification or transesterification reactions followed by polycondensation reactions. Catalysts are crucial in this production process, directly affecting the reaction rate, the molecular weight distribution of the product, and the material properties.

[0003] In traditional polyester synthesis, antimony-based catalysts are widely used. They have stable activity and low cost, but there are problems such as low catalytic activity and high toxicity of residual antimony. In recent years, titanium-based catalysts that are green, environmentally friendly, non-toxic, and harmless have been widely studied and applied. Among them, the more studied titanium-based catalysts can be divided into inorganic titanium-based catalysts such as nano-titanium dioxide and supported titanium catalysts, and organic titanium-based catalysts such as titanium composite catalysts and complex titanium catalysts.

[0004] Patent CN111704713A discloses a preparation method of a titanium-based catalyst for polyester synthesis. In a polyol system, a catalyst carrier such as silica, a titanate compound, and a small amount of other solvents are added and reacted to obtain a catalyst suspension. The catalyst preparation does not require separation, but this catalyst is a heterogeneous catalyst with poor dispersibility and is prone to phenomena such as agglomeration, and the polyester prepared has a large molecular weight distribution coefficient.

[0005] Patent CN112266471A discloses a method for preparing PBAT by complexing an amino acid (ester), a titanate, a silicate, a metal acetate, and a phosphoric acid compound to obtain a catalyst, which solves the problem of easy hydrolysis of ordinary titanium-based catalysts. However, this method still requires the use of silicate, metal acetate, etc. as stabilizers and auxiliaries, with a high cost, and the temperature rising procedure in the esterification stage needs to be strictly controlled, and the operation is complex.

[0006] In summary, it is of great significance to develop a titanium-based catalyst with excellent activity, hydrolysis resistance, low cost, and simple preparation process, and to prepare a polyester material with good brightness and chromaticity and a small molecular weight distribution coefficient. Summary of the Invention

[0007] Aiming at the problems existing in the prior art, the present invention provides a titanium-based catalyst, a preparation method thereof, and an application thereof in polyester preparation. The polyester material prepared using this catalyst has good brightness and chromaticity and a small molecular weight distribution coefficient.

[0008] To achieve the above invention purpose, the technical solution of the present invention is as follows:

[0009] A titanium-based catalyst for polyester synthesis, the nuclear magnetic resonance hydrogen spectrum of the titanium-based catalyst has the following characteristics, the integral value ratio of all characteristic peaks between (2.4 - 3.5 ppm) to the integral value of all characteristic peaks between (2.7 - 3.0 ppm) is 1:(0.5 - 0.8).

[0010] Preferably, the titanium-based catalyst is a complex of titanate, preferably a complex of titanate and citric acid and / or citrate ester.

[0011] It should be noted that those skilled in the art can identify the chemical environment of the hydrogen atoms of each component in the catalyst according to the chemical shift of each characteristic peak. The complexes formed by titanate and citric acid and / or citrate ester ligands mainly include one or more of the following structures:

[0012]

[0013] R1 and R2 are each independently selected from one of hydrogen, methyl, ethyl, isopropyl, and butyl.

[0014] The complexation form of the catalyst will affect the chemical environment of the hydrogen atoms in the ligand, resulting in changes in the nuclear magnetic resonance hydrogen spectrum. Taking tributyl citrate as an example, as Figure 1 shown in the nuclear magnetic resonance hydrogen spectrum of tributyl citrate, the characteristic peaks of the hydrogen atoms on the two methylene groups indicated by a and b are between 2.7 - 3.0 ppm,

[0015] The integral value ratio of all characteristic peaks between (2.5 - 3.2 ppm) to the integral value of all characteristic peaks between (2.7 - 3.0 ppm) is about 1. When tributyl citrate is complexed with a titanium compound, referring to the nuclear magnetic resonance hydrogen spectrum of the titanium-based catalyst prepared in Example 1 of the present invention as shown in Figure 2 shown, the characteristic peak shapes of the hydrogen atoms on the two methylene groups indicated by a and b change significantly, and obvious bulges appear at the positions of some characteristic peaks. This is caused by the change in the chemical environment of the hydrogen atoms due to the complexation of citrate ester and titanium. To a certain extent, the size of the bulge is related to the complexation degree of citrate ester and titanium.

[0016] The inventor surprisingly found that the size of the bulge of the characteristic peaks between 2.4 - 3.5 ppm can have a greater impact on the performance of the titanium catalyst. By controlling the integral value ratio of all characteristic peaks between (2.4 - 3.5 ppm) to the integral value of all characteristic peaks between (2.7 - 3.0 ppm) in the nuclear magnetic resonance hydrogen spectrum of the catalyst, a titanium catalyst with more excellent performance can be obtained. The polyester material prepared with this catalyst has good brightness and chromaticity and a small molecular weight distribution coefficient.

[0017] A preparation method of a titanium-based catalyst for polyester synthesis, the preparation method comprises the following steps:

[0018] S1: Add a titanium compound into a reaction vessel.

[0019] S2: Add citric acid and / or a citric acid ester compound and carry out a reaction.

[0020] Preferably, the preparation method further includes: optionally, S3: Add a phosphorus compound and carry out a reaction.

[0021] In one embodiment of the present invention, the titanium compound described in S1 is selected from titanates, preferably at least one or more of tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate or tetrabutyl titanate;

[0022] In one embodiment of the present invention, in S1, optionally, it further includes heating to 20 - 150°C, preferably 70 - 110°C.

[0023] In one embodiment of the present invention, the citric acid and / or citric acid ester compound described in S2 is selected from one or more of citric acid, trimethyl citrate, triethyl citrate, tripropyl citrate, tributyl citrate, triisobutyl citrate, trisec-butyl citrate, tritert-butyl citrate, more preferably citric acid and / or tributyl citrate;

[0024] In one embodiment of the present invention, the molar ratio of the citric acid and / or citric acid ester compound to the titanium compound in S2 is 1:(0.8 - 1.5), preferably 1:(1.2 - 1.4);

[0025] In some preferred embodiments of the present invention, the citric acid and / or citric acid ester compound is continuously added to the titanium compound within a period of time or added intermittently in multiple portions to the titanium compound.

[0026] In the present invention, continuous addition can be carried out at a certain flow rate until the substance is completely added; during intermittent addition, it is added in small portions multiple times so that the 2-hydroxycarboxylic acid or its ester added each time can fully react. Preferably, the amount added each time does not exceed 1 / 3 of the molar amount of the titanium compound. For example, in a laboratory scale, it can be added in the form of dropping, or the citric acid and / or citric acid ester compound is evenly divided into 8 - 1000 portions and one portion is added at intervals within the reaction time.

[0027] In one embodiment of the present invention, the addition time of the citric acid and / or citric acid ester compound in S2 is 3 - 50 h, preferably 4 - 20 h, more preferably 6 - 12 h; in one embodiment of the present invention, the reaction temperature of S2 is 20 - 150°C, preferably 70 - 110°C; the continuation reaction time after the addition of the citric acid and / or citric acid ester compound is 0 - 12 h, preferably 0.5 - 3 h.

[0028] In one embodiment of the present invention, the phosphorus compound in S3 is selected from one or more of phosphoric acid, phosphorous acid, phosphate esters or phosphite esters, preferably phosphate esters, more preferably trimethyl phosphate and / or triethyl phosphate;

[0029] In one embodiment of the present invention, the molar ratio of the addition amount of the phosphorus compound in S3 to the titanium compound is (0 - 0.5):1, preferably (0.15 - 0.5):1, more preferably (0.2 - 0.35):1;

[0030] In one embodiment of the present invention, the reaction temperature in S3 is 20 - 150 °C, preferably 70 - 110 °C; the reaction time is 10 - 240 h, preferably 24 - 120 h.

[0031] The present invention also provides a method for preparing a polyester, in which a dicarboxylic acid or its ester and a diol are subjected to an esterification polycondensation reaction in the presence of the titanium-based catalyst and an optional phosphorus compound described in the present invention to obtain a polyester.

[0032] The addition amount of the titanium-based catalyst is 1 - 5000 ppm, preferably 1 - 500 ppm, based on the titanium content and the mass of the dicarboxylic acid and its ester derivatives.

[0033] Preferably, the dicarboxylic acid or its ester includes one or several of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,11-undecanedicarboxylic acid, hexadecanedicarboxylic acid, dimethyl oxalate, dimethyl malonate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, dimethyl pimelate, dimethyl suberate, dimethyl azelate, dimethyl sebacate, dimethyl 1,11-undecanedicarboxylate, dimethyl hexadecanedicarboxylate, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, dimethyl terephthalate, dimethyl isophthalate, dimethyl naphthalenedicarboxylate;

[0034] Preferably, the diol includes one or more of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,4-cyclohexanedimethanol;

[0035] Preferably, the molar ratio of the dicarboxylic acid to the diol is 1:1.1 to 1:3.0;

[0036] In some preferred embodiments of the present invention, the phosphorus compound can be added during the synthesis of the polyester, or can be added during the preparation of the catalyst, or can be partially added during the preparation of the catalyst and partially added during the synthesis of the polyester, and the present invention does not make additional limitations.

[0037] Preferably, the molar ratio of the total amount of phosphorus compound added to the titanium compound is (0.15 - 0.5):1, more preferably (0.25 - 0.35):1.

[0038] Preferably, the polyester polyol includes polybutylene adipate terephthalate and polyethylene terephthalate - 1,4 - cyclohexanedimethanol ester.

[0039] In one embodiment of the present invention, a method for preparing polybutylene adipate terephthalate is provided. The titanium - based catalyst, terephthalic acid, adipic acid, 1,4 - butanediol, and an optional phosphorus compound of the present invention are added to a reaction kettle, and an esterification reaction is carried out at normal pressure and 150 - 200 °C for 1 - 3 h. Then, the reaction kettle is evacuated to a pressure between 1000 - 30000 Pa and maintained for 10 - 60 min, and then evacuated to below 100 Pa, and kept at a constant temperature of 240 - 265 °C for 60 - 200 min to obtain polybutylene adipate terephthalate (PBAT).

[0040] Furthermore, the addition amount of the titanium - based catalyst, calculated based on the titanium content, accounts for 20 - 500 ppm of the total mass of terephthalic acid and adipic acid, preferably 50 - 150 ppm.

[0041] In the present invention, the molar ratio of the sum of terephthalic acid and adipic acid to 1,4 - butanediol is 1:1.1 - 1:1.5, preferably 1:1.1 - 1:1.3, and among them, the molar ratio of terephthalic acid to adipic acid is between 0.1:0.9 and 0.9:0.1.

[0042] In one embodiment of the present invention, a method for preparing polyethylene terephthalate - 1,4 - cyclohexanedimethanol ester is provided. The titanium - based catalyst, terephthalic acid, ethylene glycol, 1,4 - cyclohexanedimethanol, and an optional phosphorus compound of the present invention are added to a reaction kettle, and an esterification reaction is carried out at 0 - 550 kPa and 150 - 230 °C for 2 - 6 h. Then, the reaction kettle is evacuated to a pressure between 1000 - 30000 Pa and maintained for 10 - 60 min, and then evacuated to below 100 Pa, and kept at a constant temperature of 240 - 265 °C for 60 - 300 min to obtain polyethylene terephthalate - 1,4 - cyclohexanedimethanol ester (PETG).

[0043] Furthermore, the addition amount of the titanium - based catalyst, calculated based on the titanium content, accounts for 1 - 50 ppm of the mass of terephthalic acid, preferably 2 - 20 ppm.

[0044] In the present invention, the molar ratio of terephthalic acid to the sum of ethylene glycol and 1,4 - cyclohexanedimethanol is 1:1.1 - 1:2.0, preferably 1:1.1 - 1:1.5;

[0045] Preferably, the molar ratio of ethylene glycol to 1,4 - cyclohexanedimethanol is 0.1:0.9 to 0.9:0.1.

[0046] Compared with the prior art, the positive effects of the technical solution of the present invention are as follows: The homogeneous titanium - based catalyst prepared by the present invention has good reaction activity, hydrolysis resistance, and light stability, can be stored for a long time, and has a simple preparation process, low cost, and is easy to implement. It can be used for actual engineering applications, is suitable for preparing polyesters with good brightness and chromaticity, and has a small molecular weight distribution coefficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is the nuclear magnetic resonance hydrogen spectrum of tributyl citrate.

[0048] Figure 2 It is the nuclear magnetic resonance hydrogen spectrum of the catalyst prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0049] For the convenience of understanding the present invention, the present invention will be further described below in conjunction with embodiments. It should be understood that the following embodiments are only for better understanding of the present invention, and do not mean that the present invention is limited only to the following embodiments.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. The term "and / or" as used herein may include any and all combinations of one or more of the related listed items. The orientation terms such as top and bottom mentioned or likely to be mentioned in this specification are defined relative to the structure shown in each drawing, and they are relative concepts, so they may change accordingly depending on their different positions and different usage states.

[0051] Sources of Main Raw Materials

[0052] Tetrabutyl titanate, reagent grade, Aladdin Reagent Co., Ltd.;

[0053] Tetra - isopropyl titanate, reagent grade, Aladdin Reagent Co., Ltd.;

[0054] Citric acid, reagent grade, Aladdin Reagent Co., Ltd.;

[0055] Tributyl citrate, reagent grade, Aladdin Reagent Co., Ltd.;

[0056] Malic acid, reagent grade, Aladdin Reagent Co., Ltd.;

[0057] Dibutyl malate, reagent grade, Aladdin Reagent Co., Ltd.;

[0058] Trimethyl phosphate, reagent grade, Aladdin Reagent Co., Ltd.;

[0059] Triethyl phosphate, reagent grade, Aladdin Reagent Co., Ltd.;

[0060] Adipic acid (AA), industrial grade, Henan Shenma Nylon Chemical Co., Ltd.;

[0061] Terephthalic acid (PTA), industrial grade, Hengli Petrochemical Co., Ltd.;

[0062] 1,4-Butanediol (BDO), industrial grade, Xinjiang Meike Chemical Co., Ltd.;

[0063] 1,4-Cyclohexanedimethanol, industrial grade, Kailing Chemical Co., Ltd.;

[0064] Ethylene glycol, industrial grade, China Petroleum & Chemical Corporation.

[0065] Main test methods

[0066] Nuclear magnetic resonance was measured using a Bruker AV 600 nuclear magnetic resonance spectrometer. 1 For 1H NMR, 10 mg of the catalyst sample was dissolved in 0.7 ml of deuterated chloroform, and the chloroform solvent peak was calibrated at 7.28 ppm.

[0067] The color value of the product was evaluated based on the L, a, b color system. In this system, L is the luminance factor, and a and b are color measurement numbers. b represents the yellow-blue balance and is very important for the color of the polyester. The lower the b value, the better the color. The color values (L value, a value, and b value) were automatically measured using a BYK Gardner Color35 automatic color difference meter.

[0068] GPC test (determination of molecular weight distribution PDI): Dichloromethane was used as the mobile phase, and polystyrene was used as the standard reference.

[0069] Catalyst preparation:

[0070] Example 1

[0071] 340 g of tetrabutyl titanate was transferred to a reaction kettle, the stirring rate was 100 rpm, the temperature was raised to 80 °C, 257 g of tributyl citrate was uniformly pumped in at a flow rate of 0.35 ml / min using a peristaltic pump. After the addition was completed, the reaction continued for 2 h, 46.7 g of trimethyl phosphate was added, and the reaction continued for 24 h to obtain titanium-based catalyst A. The ratio of the integral value of all characteristic peaks between (2.4 - 3.5 ppm) to the integral value of all characteristic peaks between (2.7 - 3.0 ppm) was 1:0.72.

[0072] Example 2

[0073] Transfer 340 g of tetrabutyl titanate to a reaction kettle, with a stirring rate of 200 rpm. Heat up to 100 °C, and use a peristaltic pump to uniformly inject 267 g of tributyl citrate at a flow rate of 0.63 ml / min. After the addition, continue the reaction for 1 h. Then add 40 g of trimethyl phosphate and continue the reaction for 48 h to obtain titanium-based catalyst B. The ratio of the integral values of all characteristic peaks between (2.4 - 3.5 ppm) to the integral values of all characteristic peaks between (2.7 - 3.0 ppm) is 1:0.58.

[0074] Example 3

[0075] Transfer 284 g of tetraisopropyl titanate to a reaction kettle, with a stirring rate of 50 rpm. Heat up to 50 °C, and use a peristaltic pump to uniformly inject 251 g of triethyl citrate at a flow rate of 0.46 ml / min. After the addition, heat up to 90 °C and continue the reaction for 3 h. Then add 40.4 g of triethyl phosphate and continue the reaction for 100 h to obtain titanium-based catalyst C. The ratio of the integral values of all characteristic peaks between (2.4 - 3.5 ppm) to the integral values of all characteristic peaks between (2.7 - 3.0 ppm) is 1:0.79.

[0076] Example 4

[0077] Transfer 340 g of tetrabutyl titanate to a reaction kettle, with a stirring rate of 300 rpm. Heat up to 140 °C, add 21.3 g of citric acid, and after reacting for 1 h, add another 21.3 g of citric acid, and repeat this process until a total of 213 g of citric acid is added. After the addition, continue the reaction for 10 h. Then add 19.6 g of phosphoric acid and continue the reaction for 200 h to obtain titanium-based catalyst D. The ratio of the integral values of all characteristic peaks between (2.4 - 3.5 ppm) to the integral values of all characteristic peaks between (2.7 - 3.0 ppm) is 1:0.64.

[0078] Example 5

[0079] Transfer 340 g of tetrabutyl titanate to a reaction kettle, with a stirring rate of 400 rpm. Heat up to 100 °C, and use a peristaltic pump to uniformly inject 248 g of tributyl citrate at a flow rate of 1.03 ml / min. After the addition, continue the reaction for 0.5 h to obtain titanium-based catalyst E. The ratio of the integral values of all characteristic peaks between (2.4 - 3.5 ppm) to the integral values of all characteristic peaks between (2.7 - 3.0 ppm) is 1:0.75.

[0080] Comparative Example 1

[0081] Compared with Example 2, malic acid is used.

[0082] Transfer 340 g of tetrabutyl titanate to a reaction kettle, with a stirring rate of 200 rpm. Heat up to 100 °C, add 16.5 g of malic acid. After reacting for 1 hour, add another 16.5 g of malic acid, and repeat this process successively until a total of 99 g of malic acid is added. After the addition is completed, continue the reaction for 1 h, then add 40 g of trimethyl phosphate, and continue the reaction for 48 h to obtain titanium-based catalyst F. The ratio of the integral value of all characteristic peaks between (2.4 - 3.5 ppm) to the integral value of all characteristic peaks between (2.7 - 3.0 ppm) is 1:0.9.

[0083] Comparative Example 2

[0084] Compared with Example 2, dibutyl malate was used.

[0085] Transfer 340 g of tetrabutyl titanate to a reaction kettle, with a stirring rate of 200 rpm. Heat up to 100 °C, and use a peristaltic pump to uniformly inject 182 g of dibutyl malate at a flow rate of 0.43 ml / min. After the addition is completed, continue the reaction for 1 h, then add 40 g of trimethyl phosphate, and continue the reaction for 48 h to obtain titanium-based catalyst G. The ratio of the integral value of all characteristic peaks between (2.4 - 3.5 ppm) to the integral value of all characteristic peaks between (2.7 - 3.0 ppm) is 1:0.85.

[0086] Synthesize PBAT using a titanium-based catalyst

[0087] Example 6:

[0088] Add 5 mol of terephthalic acid, 5 mol of adipic acid, 11 mol of butanediol, and 1.44 g of catalyst A to a 5 L polyester kettle. Heat up to 150 °C and react for 3 hours to complete the esterification process. Gradually evacuate the reaction kettle to 1000 Pa and maintain for 20 min, then gradually evacuate to below 100 Pa, heat up to 240 °C and maintain, and carry out the polycondensation reaction for 150 min to obtain a polymer melt. After water cooling and pelletizing, the product is obtained, with L = 87.1, a = -1.1, b = 3.2, and PDI = 2.21.

[0089] Example 7:

[0090] Add 5 mol of terephthalic acid, 5 mol of adipic acid, 12 mol of butanediol, and 2.47 g of catalyst B to a 5 L polyester kettle. Heat up to 190 °C and react for 2 hours to complete the esterification process. Gradually evacuate the reaction kettle to 10000 Pa and maintain for 60 min, then gradually evacuate to below 100 Pa, heat up to 250 °C and maintain, and carry out the polycondensation reaction for 140 min to obtain a polymer melt. After water cooling and pelletizing, the product is obtained, with L = 87.5, a = -1.3, b = 2.5, and PDI = 2.19.

[0091] Example 8:

[0092] 5 mol of terephthalic acid, 5 mol of adipic acid, 13 mol of butanediol, and 2.57 g of catalyst C were added to a 5 L polyester kettle. The temperature was raised to 180 °C and reacted for 1.5 hours to complete the esterification process. The reaction kettle was gradually evacuated to 5000 Pa and maintained for 30 min, then gradually evacuated to below 100 Pa, the temperature was raised to 260 °C and maintained for the polycondensation reaction. After reacting for 140 min, a polymer melt was obtained, which was cooled by water and pelletized to obtain the product, L = 82.1, a = -0.2, b = 4.3, PDI = 2.39.

[0093] Example 9:

[0094] 4 mol of terephthalic acid, 6 mol of adipic acid, 13 mol of butanediol, and 5.53 g of catalyst D were added to a 5 L polyester kettle. The temperature was raised to 180 °C and reacted for 2 hours to complete the esterification process. The reaction kettle was gradually evacuated to 5000 Pa and maintained for 30 min, then gradually evacuated to below 100 Pa, the temperature was raised to 250 °C and maintained for the polycondensation reaction. After reacting for 140 min, a polymer melt was obtained, which was cooled by water and pelletized to obtain the product, L = 83.4, a = -0.3, b = 4.1, PDI = 2.35.

[0095] Example 10

[0096] 5 mol of terephthalic acid, 5 mol of adipic acid, 11 mol of butanediol, 1.13 g of catalyst E, and 0.076 g of trimethyl phosphate were added to a 5 L polyester kettle. The temperature was raised to 170 °C and reacted for 2 hours to complete the esterification process. The reaction kettle was gradually evacuated to 1000 Pa and maintained for 20 min, then gradually evacuated to below 100 Pa, the temperature was raised to 240 °C and maintained for the polycondensation reaction. After reacting for 150 min, a polymer melt was obtained, which was cooled by water and pelletized to obtain the product, L = 85.1, a = -0.9, b = 3.9, PDI = 2.28.

[0097] Comparative Example 3

[0098] Compared with Example 7, catalyst F was used.

[0099] 5 mol of terephthalic acid, 5 mol of adipic acid, 12 mol of butanediol, and 1.83 g of catalyst F were added to a 5 L polyester kettle. The temperature was raised to 190 °C and reacted for 2 hours to complete the esterification process. The reaction kettle was gradually evacuated to 10000 Pa and maintained for 60 min, then gradually evacuated to below 100 Pa, the temperature was raised to 250 °C and maintained for the polycondensation reaction. After reacting for 140 min, a polymer melt was obtained, which was cooled by water and pelletized to obtain the product, L = 80.5, a = 0.1, b = 5.0, PDI = 3.29.

[0100] Comparative Example 4

[0101] Compared with Example 7, catalyst G was used.

[0102] 5 mol of terephthalic acid, 5 mol of adipic acid, 12 mol of butanediol, and 2.15 g of catalyst G were added to a 5 L polyester kettle, and the temperature was raised to 190 °C and reacted for 2 hours to complete the esterification process. The reaction kettle was gradually evacuated to 10,000 Pa and maintained for 60 min, and then gradually evacuated to below 100 Pa, the temperature was raised to 250 °C and maintained for the polycondensation reaction for 140 min to obtain a polymer melt, which was cooled and pelletized by water to obtain a product, L = 81.6, a = -0.1, b = 4.7, PDI = 2.87.

[0103] Synthesis of PETG using a titanium-based catalyst

[0104] Example 11

[0105] 10 mol of terephthalic acid, 11 mol of ethylene glycol, 4 mol of 1,4-cyclohexanedimethanol, and 0.39 g of catalyst A were added to a 5 L polyester kettle, and then pressurized with nitrogen to 200 kPa and maintained at a constant pressure. The temperature in the reaction kettle was raised to 180 °C and reacted for 3 hours to complete the esterification process, and the pressure in the kettle returned to normal pressure. The reaction kettle was gradually evacuated to 1,000 Pa and maintained for 20 min, and then gradually evacuated to below 100 Pa, the temperature was raised to 240 °C and maintained for the polycondensation reaction for 180 min to obtain a polymer melt, which was cooled and pelletized by water to obtain a product, L = 70.3, a = -0.9, b = -1.3, PDI = 2.24.

[0106] Example 12

[0107] 10 mol of terephthalic acid, 10 mol of ethylene glycol, 4 mol of 1,4-cyclohexanedimethanol, and 0.30 g of catalyst B were added to a 5 L polyester kettle, and then pressurized with nitrogen to 300 kPa and maintained at a constant pressure. The temperature in the reaction kettle was raised to 190 °C and reacted for 4 hours to complete the esterification process, and the pressure in the kettle returned to normal pressure. The reaction kettle was gradually evacuated to 10,000 Pa and maintained for 60 min, and then gradually evacuated to below 100 Pa, the temperature was raised to 250 °C and maintained for the polycondensation reaction for 200 min to obtain a polymer melt, which was cooled and pelletized by water to obtain a product, L = 71.9, a = -0.8, b = -1.5, PDI = 2.21.

[0108] Example 13

[0109] In a 5L polyester kettle, 10 mol of terephthalic acid, 14 mol of ethylene glycol, 4 mol of 1,4-cyclohexanedimethanol, and 0.18 g of catalyst C were added. Then, it was pressurized to 400 kPa with nitrogen and kept at a constant pressure. The temperature inside the reaction kettle was raised to 160 °C and reacted for 6 hours to complete the esterification process. The pressure inside the kettle returned to normal pressure. The reaction kettle was gradually evacuated to 5000 Pa and maintained for 30 min, and then gradually evacuated to below 100 Pa. The temperature was raised to 260 °C and maintained for the polycondensation reaction. After reacting for 120 min, a polymer melt was obtained, which was pelletized by water cooling to obtain the product, with L = 67.7, a = -0.7, b = 0.2, and PDI = 2.51.

[0110] Example 14

[0111] In a 5L polyester kettle, 10 mol of terephthalic acid, 9 mol of ethylene glycol, 4 mol of 1,4-cyclohexanedimethanol, and 0.52 g of catalyst D were added. Then, it was pressurized to 150 kPa with nitrogen and kept at a constant pressure. The temperature inside the reaction kettle was raised to 230 °C and reacted for 5 hours to complete the esterification process. The pressure inside the kettle returned to normal pressure. The reaction kettle was gradually evacuated to 5000 Pa and maintained for 30 min, and then gradually evacuated to below 100 Pa. The temperature was raised to 250 °C and maintained for the polycondensation reaction. After reacting for 280 min, a polymer melt was obtained, which was pelletized by water cooling to obtain the product, with L = 68.7, a = -0.5, b = -0.9, and PDI = 2.47.

[0112] Example 15

[0113] In a 5L polyester kettle, 10 mol of terephthalic acid, 9 mol of ethylene glycol, 4 mol of 1,4-cyclohexanedimethanol, 0.13 g of catalyst E, and 0.009 g of trimethyl phosphate were added. Then, it was pressurized to 300 kPa with nitrogen and kept at a constant pressure. The temperature inside the reaction kettle was raised to 220 °C and reacted for 2 hours to complete the esterification process. The pressure inside the kettle returned to normal pressure. The reaction kettle was gradually evacuated to 5000 Pa and maintained for 30 min, and then gradually evacuated to below 100 Pa. The temperature was raised to 250 °C and maintained for the polycondensation reaction. After reacting for 100 min, a polymer melt was obtained, which was pelletized by water cooling to obtain the product, with L = 69.5, a = -0.6, b = -1.2, and PDI = 2.32.

[0114] Comparative Example 5

[0115] Compared with Example 12, catalyst F was used.

[0116] 10 mol of terephthalic acid, 10 mol of ethylene glycol, 4 mol of 1,4-cyclohexanedimethanol and 0.22 g of catalyst F were added into a 5 L polyester kettle. Then, it was pressurized to 300 kPa with nitrogen and kept at a constant pressure. The temperature in the reaction kettle was raised to 190 °C and reacted for 4 hours to complete the esterification process. The pressure in the kettle was restored to atmospheric pressure. The reaction kettle was gradually evacuated to 10,000 Pa and maintained for 60 min, and then gradually evacuated to below 100 Pa. The temperature was raised to 250 °C and maintained for the polycondensation reaction for 200 min to obtain a polymer melt, which was cooled by water and pelletized to obtain the product, with L = 66.3, a = -1.2, b = 0.7, and PDI = 3.32.

[0117] Comparative Example 6

[0118] Compared with Example 12, catalyst G was used.

[0119] 10 mol of terephthalic acid, 10 mol of ethylene glycol, 4 mol of 1,4-cyclohexanedimethanol and 0.26 g of catalyst G were added into a 5 L polyester kettle. Then, it was pressurized to 300 kPa with nitrogen and kept at a constant pressure. The temperature in the reaction kettle was raised to 190 °C and reacted for 4 hours to complete the esterification process. The pressure in the kettle was restored to atmospheric pressure. The reaction kettle was gradually evacuated to 10,000 Pa and maintained for 60 min, and then gradually evacuated to below 100 Pa. The temperature was raised to 250 °C and maintained for the polycondensation reaction for 200 min to obtain a polymer melt, which was cooled by water and pelletized to obtain the product, with L = 66.9, a = -1.0, b = 0.5, and PDI = 2.79.

[0120] It is easy to understand that the above examples are only for clear illustration and do not mean that the present invention is limited thereto. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A titanium catalyst for polyester synthesis, characterized in that: The hydrogen nuclear magnetic resonance spectrum of the titanium-based catalyst has the following characteristics: the ratio of the integral value of all characteristic peaks between (2.4-3.5ppm) to the integral value of all characteristic peaks between (2.7-3.0ppm) is 1: (0.5-0.8).

2. A titanium catalyst for polyester synthesis, characterized in that: The titanium-based catalyst is a complex of titanate, preferably a complex of titanate and citric acid and / or citric acid ester.

3. A method for preparing a titanium-based catalyst according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: S1: Add titanium compounds into the reaction vessel, S2: adding citric acid and / or a citrate ester compound to react; Preferably, the preparation method further comprises: optional S3: adding a phosphorus compound to react.

4. The method for preparing a titanium-based catalyst according to claim 3, characterized in that: Optionally, S1 further comprises heating to 20-150° C., preferably 70-110° C.; Preferably, the titanium compound in S1 is selected from titanate esters, preferably at least one or more of tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate or tetrabutyl titanate; Preferably, the citric acid and / or citric acid ester compound described in S2 is selected from one or more of citric acid, trimethyl citrate, triethyl citrate, tripropyl citrate, tri-n-butyl citrate, tri-isobutyl citrate, tri-sec-butyl citrate, and tri-tert-butyl citrate, more preferably citric acid and / or tri-n-butyl citrate; Preferably, the molar ratio of the citric acid and / or citric acid ester compound to the titanium compound in S2 is 1:(0.8-1.5), preferably 1:(1.2-1.4).

5. The method for preparing a titanium-based catalyst according to claim 3 or 4, characterized in that: Citric acid and / or a citrate ester compound is added to the titanium compound continuously over a period of time or intermittently in multiple times; Preferably, the continuous addition is continued at a certain flow rate until the substance is completely added; Preferably, the intermittent addition process is carried out in small amounts and multiple times so that the 2-hydroxycarboxylic acid or its ester added each time can react fully. Preferably, the amount added each time does not exceed 1 / 3 of the molar amount of the titanium compound.

6. The method for preparing a titanium-based catalyst according to any one of claims 3 to 5, characterized in that: S2 The citric acid and / or citric acid ester compound is added for 3-50 hours, preferably 4-20 hours, more preferably 6-12 hours; and / or, The reaction temperature of S2 is 20-150°C, preferably 70-110°C; and / or, After the addition of citric acid and / or citric acid ester compounds is completed, the reaction time is continued for 0-12 hours, preferably 0.5-3 hours.

7. The method for preparing a titanium-based catalyst according to any one of claims 3 to 6, characterized in that: S3 The phosphorus compound is selected from one or more of phosphoric acid, phosphorous acid, phosphate ester or phosphite ester, preferably phosphate ester, more preferably trimethyl phosphate and / or triethyl phosphate; and / or, S3: the molar ratio of the phosphorus compound added to the titanium compound is (0-0.5):1, preferably (0.15-0.5):1, more preferably (0.2-0.35):1; and / or, The reaction temperature in S3 is 20-150°C, preferably 70-110°C; the reaction time is 10-240h, preferably 24-120h.

8. A method for preparing polyester, characterized in that: The polyester is obtained by esterifying or transesterifying a dibasic acid or its ester and a diol in the presence of a titanium catalyst as claimed in claim 1 or 2 and an optional phosphorus compound, and performing a polycondensation reaction; Preferably, the titanium catalyst is added in an amount of 1-5000 ppm, preferably 1-500 ppm, based on the mass of the dibasic acid and its ester derivatives in terms of titanium content; Preferably, the dibasic acid or its ester comprises oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,11-undecanedicarboxylic acid, hexadecanedicarboxylic acid, dimethyl oxalate, dimethyl malonate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, dimethyl pimelate, dimethyl suberate, dimethyl azelaic acid, dimethyl sebacate, dimethyl 1,11-undecanedicarboxylic acid, dimethyl hexadecanedicarboxylic acid, terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, dimethyl terephthalate, dimethyl isophthalic acid, dimethyl naphthalene dicarboxylic acid, one or more; Preferably, the diol includes one or more of ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, and 1,4-cyclohexanedimethanol; Preferably, the molar ratio of the dibasic acid to the diol is 1:1.1 to 1:3.0; Preferably, the phosphorus compound is added during polyester synthesis or during catalyst preparation, or partly during catalyst preparation and partly during polyester synthesis; Preferably, in the reaction system, the molar ratio of the total amount of phosphorus compound added to the titanium compound is (0.15-0.5):1, more preferably (0.25-0.35):1; Preferably, the polyester polyol includes polybutylene terephthalate adipate and polyethylene terephthalate-1,4-cyclohexanedimethanol.

9. A method for preparing polybutylene terephthalate adipate, comprising adding the titanium catalyst according to claim 1 or 2, terephthalic acid, adipic acid, 1,4-butanediol, and an optional phosphorus compound into a reactor, carrying out an esterification reaction at normal pressure and 150-200° C. for 1-3 hours, then evacuating the reactor to a pressure between 1000 and 30000 Pa for 10-60 minutes, and then evacuating the reactor to a pressure below 100 Pa, and maintaining a constant temperature reaction at 240-265° C. for 60-200 minutes to obtain polybutylene terephthalate adipate; Preferably, the titanium catalyst is added in an amount of 20 to 500 ppm, preferably 50 to 150 ppm, based on the total mass of terephthalic acid and adipic acid in terms of titanium content; Preferably, the molar ratio of the sum of terephthalic acid and adipic acid to 1,4-butanediol is 1:1.1 to 1:1.5, preferably 1:1.1 to 1:1.3; Preferably, the molar ratio of terephthalic acid to adipic acid is 0.1:0.9 to 0.9:0.

1.

10. A method for preparing polyethylene terephthalate-1,4-cyclohexanedimethanol ester, comprising adding the titanium catalyst according to claim 1 or 2, terephthalic acid, ethylene glycol, 1,4-cyclohexanedimethanol, and an optional phosphorus compound into a reactor, carrying out an esterification reaction at 0-550 kPa and 150-230° C. for 2-6 hours, then evacuating the reactor to between 1000 and 30000 Pa for 10-60 minutes, and then evacuating the reactor to below 100 Pa, and maintaining a constant temperature reaction at 240-265° C. for 60-300 minutes to obtain polyethylene terephthalate-1,4-cyclohexanedimethanol ester; Preferably, the titanium catalyst is added in an amount of 1 to 50 ppm, preferably 2 to 20 ppm, based on the mass of terephthalic acid in terms of titanium content; Preferably, the total molar ratio of terephthalic acid to ethylene glycol and 1,4-cyclohexanedimethanol is 1:1.1 to 1:2.0, preferably 1:1.1 to 1:1.5; Preferably, the molar ratio of ethylene glycol to 1,4-cyclohexanedimethanol is 0.1:0.9 to 0.9:0.1.

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