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, an infrared absorption spectrum of the titanium catalyst comprises a first characteristic peak and a second characteristic peak, the first characteristic peak is the characteristic peak of ester carbonyl of hydroxyl carboxylic ester, the second characteristic peak is the characteristic peak of complexing Ti and carbonyl oxygen of ester, and the first characteristic peak and the second characteristic peak are different. The ratio of the absorbance value of the first characteristic peak to the absorbance value of the second characteristic peak is 1: (0.18-0.42), and a polyester material prepared from the titanium catalyst has good brightness and chromaticity and excellent thermal stability.

Description

Technical Field

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

[0002] Generally, polyesters are prepared by esterification or transesterification reactions of dibasic acids and / or their derivatives with diols and melt polycondensation reactions. For example, semi-crystalline biodegradable polyesters such as poly(butylene adipate terephthalate) (PBAT) and poly(butylene succinate) (PBS), and amorphous special polyesters such as poly(ethylene terephthalate-co-1,4-cyclohexanedimethanol) (PETG).

[0003] Compounds of antimony, germanium, titanium, etc. are usually used as catalysts in polyester synthesis reactions. Among them, resins prepared with antimony-based catalysts have a relatively dull color and are not environmentally friendly, while germanium-based catalysts are relatively expensive and have a high cost. Therefore, titanium-based catalysts that are environmentally friendly and relatively inexpensive have become a research hotspot. Commonly used titanium-based catalysts are inorganic salts of titanium (such as fluoro-titanate esters, potassium oxalate titanate, etc.) or organic esters (such as tetrabutyl titanate, etc.). These catalysts have good dispersibility in the reaction system and a fast catalytic reaction rate. However, since the activity of titanium is not regulated, a large number of side reactions occur during the polycondensation process, resulting in poor quality of polyester products, such as severe yellowing of the hue and increase of the terminal carboxyl group, etc. Moreover, this type of titanium-based catalyst has poor hydrolysis resistance and is easily deactivated during the reaction process, leading to low catalyst utilization rate. Therefore, it is necessary to regulate its activity and improve its hydrolysis resistance.

[0004] Patent CN107216452A discloses a preparation method of a nano titanium-based rare earth composite catalyst and its application in the synthesis of polyesters, copolyesters, especially biodegradable polyesters. Using a titanate ester and a nano-silica, alumina or zirconia support, by adding an organic acid for hydrolysis reaction to obtain titanium dioxide nanoparticles supported, and then mixing with a chloride or acetate of a rare earth metal to obtain the final catalyst, which improves the hydrolysis resistance of the catalyst. However, it is a heterogeneous catalyst with poor dispersibility and is prone to phenomena such as agglomeration.

[0005] Patent CN112266471A discloses a method for preparing PBAT by complexing an amino acid (ester), a titanate ester, a silicate ester, 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 esters, metal acetates, etc. as stabilizers and auxiliaries, with a high cost, and the temperature rising program 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 obtain a polyester material with good brightness and chromaticity. Summary of the Invention

[0007] In view of the above-mentioned drawbacks in the prior art, the present invention provides a titanium-based catalyst for polyester synthesis, a preparation method thereof, and an application thereof. The polyester material prepared using this catalyst has good brightness and chromaticity, and excellent thermal stability performance.

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

[0009] A titanium-based catalyst for polyester synthesis, wherein the infrared absorption spectrum of the titanium-based catalyst has a first characteristic peak and a second characteristic peak. Among them, the first characteristic peak is the characteristic peak of the ester carbonyl of hydroxycarboxylic acid ester, and the second characteristic peak is the characteristic peak of the complexation of Ti with the carbonyl oxygen of the ester group, and the ratio of the absorbance value of the first characteristic peak to the absorbance value of the second characteristic peak is 1:(0.18 - 0.42).

[0010] It should be noted that those skilled in the art can identify chemical bonds or functional groups in the catalyst according to the chemical shifts of each characteristic peak. In the present invention, the first characteristic peak generally appears near 1737 cm -1 . Affected by experimental conditions and test conditions, there may be a slight error, and it may appear in the range of 1730 cm -1 to 1743 cm -1 , preferably near 1737 ± 1 cm -1 . Similarly, the second characteristic peak generally appears near 1685 cm -1 . Affected by experimental conditions and test conditions, there may be a slight error, and it may appear in the range of 1675 cm -1 to 1688 cm -1 , preferably near 1685 ± 1 cm -1 . The inventors of the present invention surprisingly found that by controlling the ratio of the absorbance value of the first characteristic peak to the absorbance value of the second characteristic peak, a catalyst more favorable for polyester synthesis can be obtained. This catalyst has excellent activity and hydrolysis resistance, and the polyester prepared using this catalyst has good brightness and chromaticity.

[0011] Preferably, the titanium-based catalyst is a complex of titanate, preferably a complex of titanate and 2-hydroxycarboxylic acid or its ester.

[0012] The present invention also provides a preparation method of the titanium-based catalyst for polyester synthesis, and the preparation method includes the following steps:

[0013] S1: Add a titanium compound to a reaction vessel,

[0014] S2: Add 2-hydroxycarboxylic acid or its ester compound and carry out a reaction;

[0015] In one embodiment of the present invention, the titanium compound is a titanate compound, selected from at least one or more of tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate, or tetrabutyl titanate;

[0016] In one embodiment of the present invention, in S1, the reaction vessel is heated to 20 - 150 °C, preferably 70 - 110 °C.

[0017] In one embodiment of the present invention, the 2-hydroxycarboxylic acid or its ester compound described in S2 is selected from one or several of lactic acid and its ester compounds, citric acid and its ester compounds, malic acid and its ester compounds, tartaric acid and its ester compounds, preferably at least one or more of lactic acid, citric acid, malic acid, tartaric acid, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, trimethyl citrate, triethyl citrate, tripropyl citrate, tri-n-butyl citrate, triisobutyl citrate, tri-sec-butyl citrate, tri-tert-butyl citrate, dimethyl malate, diethyl malate, dipropyl malate, dibutyl malate, dimethyl tartrate, diethyl tartrate, dipropyl tartrate, dibutyl tartrate, more preferably one or several of citric acid, trimethyl citrate, triethyl citrate, tripropyl citrate, tri-n-butyl citrate, triisobutyl citrate, tri-sec-butyl citrate, tri-tert-butyl citrate, and even more preferably citric acid and / or tri-n-butyl citrate;

[0018] In one embodiment of the present invention, the molar ratio of the 2-hydroxycarboxylic acid or its ester compound to the titanium compound described in S2 is 1:(0.8 - 1.5), preferably 1:(1.2 - 1.4);

[0019] In some preferred embodiments of the present invention, the 2-hydroxycarboxylic acid or its ester compound is continuously added to the titanium compound within a period of time or added intermittently in several portions to the titanium compound.

[0020] 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 amounts and multiple times to enable the 2-hydroxycarboxylic acid or its ester added each time to 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 dropwise addition, or the 2-hydroxycarboxylic acid or its ester compound is evenly divided into 10 - 1000 portions and one portion is added at regular intervals within the reaction time.

[0021] In one embodiment of the present invention, the addition time of the 2-hydroxycarboxylic acid or its ester compound described in S2 is 3 - 50 h, preferably 4 - 20 h, and more preferably 6 - 12 h;

[0022] In one embodiment of the present invention, the reaction temperature in S2 is 20 - 150 °C, preferably 70 - 110 °C; after the addition of the 2-hydroxycarboxylic acid or its ester compound is complete, the reaction can continue for 0 - 12 h, preferably 0.5 - 3 h.

[0023] In one embodiment of the present invention, the preparation method further includes: S3: adding a phosphorus compound for reaction.

[0024] In one embodiment of the present invention, the phosphorus compound 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;

[0025] In one embodiment of the present invention, the molar ratio of the phosphorus compound to the titanium compound is (0 - 0.5):1, preferably (0.15 - 0.5):1, more preferably (0.2 - 0.35):1;

[0026] In the present invention, the phosphorus compound can be added during the synthesis of the polyester, or can be added during the preparation of part of the catalyst and part during the synthesis of the polyester, and the present invention does not make additional limitations.

[0027] 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.

[0028] The present invention also provides the application of the titanium-based catalyst, which is used as a catalyst in the preparation of polyester.

[0029] A method for preparing a polyester, wherein a dicarboxylic acid or its ester and a diol are subjected to esterification or transesterification and polycondensation reactions in the presence of the titanium-based catalyst of the present invention to obtain a polyester.

[0030] Preferably, based on the titanium content, the addition amount of the titanium-based catalyst is 1 - 5000 ppm, preferably 1 - 500 ppm of the total mass of the dicarboxylic acid.

[0031] Preferably, the dicarboxylic acid or its ester includes one or more 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;

[0032] 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;

[0033] Preferably, the molar ratio of the dibasic acid or its ester to the diol is 1:1.1 to 1:3.0;

[0034] Preferably, the polyester includes polybutylene adipate terephthalate, polyethylene terephthalate-1,4-cyclohexanedimethanol ester.

[0035] In one embodiment of the present invention, the present invention provides a method for preparing polybutylene adipate terephthalate. Add the titanium-based catalyst, terephthalic acid, adipic acid, and 1,4-butanediol of the present invention into a reaction kettle, carry out an esterification reaction at 150-200°C for 1-3 hours, then evacuate the reaction kettle to between 1000 and 30000 Pa and maintain for 10-60 minutes, and then evacuate to below 100 Pa and keep the temperature constant at 240-265°C for 60-200 minutes to obtain polybutylene adipate terephthalate (PBAT).

[0036] Further, based on the titanium content, the addition amount of the titanium-based catalyst accounts for 20-500 ppm, preferably 50-150 ppm, of the total mass of terephthalic acid and adipic acid.

[0037] In the present invention, 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;

[0038] Further, the molar ratio of terephthalic acid to adipic acid is 0.1:0.9 to 0.9:0.1.

[0039] In one embodiment of the present invention, the present invention also provides a method for preparing polyethylene terephthalate-1,4-cyclohexanedimethanol ester. Add the titanium-based catalyst, terephthalic acid, ethylene glycol, and 1,4-cyclohexanedimethanol of the present invention into a reaction kettle, carry out an esterification reaction at 0-550 kPa and 150-230°C for 2-6 hours, then evacuate the reaction kettle to between 1000 and 30000 Pa and maintain for 10-60 minutes, and then evacuate to below 100 Pa and keep the temperature constant at 240-265°C for 60-300 minutes to obtain polyethylene terephthalate-1,4-cyclohexanedimethanol ester (PETG).

[0040] Further, based on the titanium content, the addition amount of the titanium-based catalyst accounts for 1 to 50 ppm, preferably 2 to 20 ppm, of the mass of terephthalic acid.

[0041] In the present invention, 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;

[0042] Further, the molar ratio of ethylene glycol to 1,4-cyclohexanedimethanol is between 0.1:0.9 and 0.9:0.1.

[0043] Compared with the prior art, the technical solution of the present invention has the following positive effects: 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, and can be used for actual engineering applications. The polyester prepared by using the titanium-based catalyst of the present invention has good brightness and chromaticity, and excellent thermal stability. Description of the Drawings

[0044] Figure 1 It is the infrared spectrum of the catalyst of Example 1 of the present invention. Detailed Embodiments

[0045] To facilitate the understanding of 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.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field 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 top, bottom and other orientation terms 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 according to their different positions and different usage states.

[0047] Sources of Main Raw Materials

[0048] Tetrabutyl titanate, reagent grade, Aladdin Reagent Co., Ltd.;

[0049] Tetra-isopropyl titanate, reagent grade, Aladdin Reagent Co., Ltd.;

[0050] Citric acid, reagent grade, Aladdin Reagent Co., Ltd.;

[0051] Tributyl citrate, reagent grade, Aladdin Reagent Co., Ltd.;

[0052] Tartaric acid, reagent grade, Aladdin Reagent Co., Ltd.;

[0053] Dibutyl malate, reagent grade, Aladdin Reagent Co., Ltd.;

[0054] Ethyl acetate, reagent grade, Aladdin Reagent Co., Ltd.;

[0055] Trimethyl phosphate, reagent grade, Aladdin Reagent Co., Ltd.;

[0056] Triethyl phosphate, reagent grade, Aladdin Reagent Co., Ltd.;

[0057] Adipic acid (AA), industrial grade, Henan Shenma Nylon Chemical Co., Ltd.;

[0058] Terephthalic acid (PTA), industrial grade, Hengli Petrochemical Co., Ltd.;

[0059] 1,4-Butanediol (BDO), industrial grade, Xinjiang Meike Chemical Co., Ltd.;

[0060] 1,4-Cyclohexanedimethanol, industrial grade, Kailing Chemical Co., Ltd.;

[0061] Ethylene glycol, industrial grade, China Petroleum & Chemical Corporation.

[0062] Main test methods

[0063] Infrared: Measured using a Nicolet-iS5 Fourier transform mid-infrared spectrometer from Thermo Fisher Scientific, USA. The infrared spectral information is collected and analyzed using a diamond single-loop ATR accessory (incident angle of 45°) and a deuterated triglycine sulfate (DTGS) detector. The number of scans is set to 32 times, and the resolution is 4 cm -1 , and the spectral range is 4000 - 400 cm -1 .

[0064] The color value of the product is evaluated based on the L,a,b color system. In this system, L is the lightness factor, and a and b are color measurement numbers. b represents the yellow-blue balance and is very important for the color of polyester. The lower the b value, the better the color. The color values (L value, a value, and b value) are automatically measured using a Color35 automatic color difference meter from BYK Gardner.

[0065] Thermal stability: Measured using an MI-40 melt indexer from Göttfert, Germany. According to the standard of GB / T3682.1 - 2018, at a temperature of 190 °C and a load of 2.16 kg, a melt index MFR0 is obtained after a melting time of 5 min, and a melt index MFR1 is obtained after a melting time of 20 min. R = MFR0 / MFR1. The lower the R value, the worse the thermal stability.

[0066] Catalyst Preparation:

[0067] Example 1

[0068] Transfer 340 g of tetrabutyl titanate to a reaction kettle, with a stirring rate of 100 rpm. Heat up to 80 °C, and use a peristaltic pump to uniformly pump 259 g of tributyl citrate at a flow rate of 0.39 ml / min. After the addition, continue the reaction for 2 h. Control the addition of 43.8 g of trimethyl phosphate and continue the reaction for 24 h to obtain titanium-based catalyst A. Detected by an infrared spectrometer, the absorbance of the characteristic peak at 1737 cm -1 is 0.158, and the absorbance of the characteristic peak at 1685 cm -1 is 0.060, and the absorbance ratio is 1:0.38.

[0069] Example 2

[0070] 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 pump 269 g of tributyl citrate at a flow rate of 0.64 ml / min. After the addition, continue the reaction for 1.5 h. Add 37.8 g of trimethyl phosphate and continue the reaction for 48 h to obtain titanium-based catalyst B. Detected by an infrared spectrometer, the absorbance of the characteristic peak at 1738 cm -1 is 0.168, and the absorbance of the characteristic peak at 1686 cm -1 is 0.057, and the absorbance ratio is 1:0.34.

[0071] Example 3

[0072] Transfer 284 g of tetraisopropyl titanate to a reaction kettle, with a stirring rate of 50 rpm. Heat up to 50 °C, add 13.9 g of tartaric acid, and after reacting for 1 h, add another 13.9 g of tartaric acid. Repeat this process until a total of 125.1 g of tartaric acid is added. After the addition, heat up to 100 °C and continue the reaction for 3 h. Add 40.4 g of triethyl phosphate and continue the reaction for 100 h to obtain titanium-based catalyst C. Detected by an infrared spectrometer, the absorbance of the characteristic peak at 1735 cm -1 is 0.169, and the absorbance of the characteristic peak at 1684 cm -1 is 0.049, and the absorbance ratio is 1:0.29.

[0073] Example 4

[0074] 340 g of tetrabutyl titanate was transferred to the reactor, stirred at 300 rpm, heated to 140 ° C, added with 22.6 g of citric acid, reacted for 1 hour, and then added with 22.6 g of citric acid, and repeated until a total of 226 g of citric acid was added. After the addition was completed, the reaction was continued for 10 hours, and 19.6 g of phosphoric acid was added, and the reaction was continued for 200 hours to obtain titanium catalyst D. After detection by infrared spectrometer, 1737 cm -1 The absorbance of the characteristic peak is 0.173, 1685 cm -1 The absorbance of the characteristic peak is 0.052, and the absorbance ratio is 1:0.30.

[0075] Example 5

[0076] 340 g of tetrabutyl titanate was transferred to the reactor, the stirring rate was 400 rpm, the temperature was raised to 100 °C, and 170 g of dibutyl malate was uniformly pumped in at a flow rate of 0.09 ml / min using a peristaltic pump. After the addition was completed, the reaction was continued for 0.5 h to obtain titanium catalyst E. After detection by infrared spectrometer, 1740 cm -1 The absorbance of the characteristic peak is 0.179, 1689 cm -1 The absorbance of the characteristic peak is 0.041, and the absorbance ratio is 1:0.23.

[0077] Comparative Example 1

[0078] Compared with Example 2, tri-n-butyl citrate is added at one time.

[0079] 340 g of tetrabutyl titanate was transferred to the reactor, the stirring rate was 200 rpm, the temperature was raised to 100 °C, 269 g of tri-n-butyl citrate was directly added at one time, the reaction was continued for 1.5 h after the addition was completed, 37.8 g of trimethyl phosphate was added, and the reaction was continued for 48 h to obtain titanium catalyst F. After detection by infrared spectrometer, the -1 The absorbance of the characteristic peak is 0.182, 1686 cm -1 The absorbance of the characteristic peak at is 0.026, and the absorbance ratio is 1:0.14.

[0080] Comparative Example 2

[0081] Compared with Example 2, ethyl acetate is used.

[0082] 340 g of tetrabutyl titanate was transferred to the reactor, the stirring rate was 200 rpm, the temperature was raised to 100 ° C, and 65.7 g of ethyl acetate was uniformly pumped in at a flow rate of 0.16 ml / min using a peristaltic pump. After the addition was completed, the reaction was continued for 1.5 h, and 37.8 g of trimethyl phosphate was added. The reaction was continued for 48 h to obtain titanium catalyst G. After detection by infrared spectrometer, 1738 cm -1The absorbance of the characteristic peak at this position is 0.154, 1686 cm -1 The absorbance of the characteristic peak at this position is 0.068, and the absorbance ratio is 1:0.44.

[0083] Synthesize PBAT using a titanium-based catalyst

[0084] Example 6:

[0085] Add 5 mol of terephthalic acid, 5 mol of adipic acid, 11 mol of butanediol, and 1.54 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 = 87.3, a = -1.1, b = 3.0, and R = 86.

[0086] Example 7:

[0087] Add 5 mol of terephthalic acid, 5 mol of adipic acid, 12 mol of butanediol, and 2.68 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 = 87.7, a = -1.2, b = 2.4, and R = 89.

[0088] Example 8:

[0089] Add 5 mol of terephthalic acid, 5 mol of adipic acid, 13 mol of butanediol, and 2.15 g of catalyst C to a 5 L polyester kettle, heat up to 180 °C, and react for 1.5 hours to complete the esterification process. Gradually evacuate the reaction kettle to 5000 Pa and maintain for 30 min, then gradually evacuate to below 100 Pa, heat up to 260 °C and maintain, and carry out the polycondensation reaction for 120 min to obtain a polymer melt. After water cooling and pelletizing, the product is obtained, with L = 83.1, a = -0.4, b = 4.2, and R = 80.

[0090] Example 9:

[0091] In a 5L polyester kettle, 4 mol of terephthalic acid, 6 mol of adipic acid, 13 mol of butanediol, and 5.65 g of catalyst D were added. The temperature was raised to 180 °C and the reaction was carried out 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, and the polycondensation reaction was carried out for 140 min to obtain a polymer melt, which was cooled and pelletized by water to obtain the product, L = 85.3, a = -0.8, b = 3.8, R = 83.

[0092] Example 10

[0093] In a 5L polyester kettle, 5 mol of terephthalic acid, 5 mol of adipic acid, 11 mol of butanediol, 0.97 g of catalyst E, and 0.077 g of trimethyl phosphate were added. The temperature was raised to 170 °C and the reaction was carried out 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, and the polycondensation reaction was carried out for 150 min to obtain a polymer melt, which was cooled and pelletized by water to obtain the product, L = 81.9, a = -0.1, b = 4.5, R = 78.

[0094] Comparative Example 3

[0095] Compared with Example 7, catalyst F was used.

[0096] In a 5L polyester kettle, 5 mol of terephthalic acid, 5 mol of adipic acid, 12 mol of butanediol, and 2.68 g of catalyst F were added. The temperature was raised to 190 °C and the reaction was carried out 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, and the polycondensation reaction was carried out for 140 min to obtain a polymer melt, which was cooled and pelletized by water to obtain the product, L = 76.9, a = 3.4, b = 10.3, R = 62.

[0097] Comparative Example 4

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

[0099] In a 5L polyester kettle, 5 mol of terephthalic acid, 5 mol of adipic acid, 12 mol of butanediol, and 1.84 g of catalyst G were added. The temperature was raised to 190 °C and the reaction was carried out 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, and the polycondensation reaction was carried out for 140 min to obtain a polymer melt, which was cooled and pelletized by water to obtain the product, L = 79.3, a = 2.8, b = 8.1, R = 68.

[0100] Synthesis of PETG Using Titanium-based Catalysts

[0101] Example 11

[0102] In a 5L polyester reactor, 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. Then, it was pressurized with nitrogen to 200 kPa and kept at a constant pressure. The temperature in the reactor was raised to 180 °C and reacted for 3 hours to complete the esterification process. The pressure in the reactor returned to normal pressure. The reactor 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 180 min, a polymer melt was obtained. After water cooling and pelletizing, the product was obtained, with L = 70.4, a = -0.9, b = -1.4, and R = 87.

[0103] Example 12

[0104] In a 5L polyester reactor, 10 mol of terephthalic acid, 10 mol of ethylene glycol, 4 mol of 1,4-cyclohexanedimethanol, and 0.29 g of catalyst B were added. Then, it was pressurized with nitrogen to 300 kPa and kept at a constant pressure. The temperature in the reactor was raised to 190 °C and reacted for 4 hours to complete the esterification process. The pressure in the reactor returned to normal pressure. The reactor 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 200 min, a polymer melt was obtained. After water cooling and pelletizing, the product was obtained, with L = 71.6, a = -0.8, b = -1.5, and R = 91.

[0105] Example 13

[0106] In a 5L polyester reactor, 10 mol of terephthalic acid, 14 mol of ethylene glycol, 4 mol of 1,4-cyclohexanedimethanol, and 0.14 g of catalyst C were added. Then, it was pressurized with nitrogen to 400 kPa and kept at a constant pressure. The temperature in the reactor was raised to 160 °C and reacted for 6 hours to complete the esterification process. The pressure in the reactor returned to normal pressure. The reactor 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 120 min, a polymer melt was obtained. After water cooling and pelletizing, the product was obtained, with L = 68.1, a = -0.4, b = -0.8, and R = 82.

[0107] Example 14

[0108] In a 5L polyester kettle, 10 mol of terephthalic acid, 9 mol of ethylene glycol, 4 mol of 1,4-cyclohexanedimethanol, and 0.53 g of catalyst D were added. Then, it was pressurized with nitrogen to 150 kPa and kept at a constant pressure. The temperature in the reaction kettle was raised to 230 °C and reacted for 5 hours to complete the esterification process, and the pressure in 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, and 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 cooled by water and pelletized to obtain the product, L = 69.2, a = -0.5, b = -1.1, R = 84.

[0109] Example 15

[0110] In a 5L polyester kettle, 10 mol of terephthalic acid, 9 mol of ethylene glycol, 4 mol of 1,4-cyclohexanedimethanol, 0.11 g of catalyst E, and 0.009 g of trimethyl phosphate were added. Then, it was pressurized with nitrogen to 300 kPa and kept at a constant pressure. The temperature in the reaction kettle was raised to 220 °C and reacted for 2 hours to complete the esterification process, and the pressure in 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, and 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 cooled by water and pelletized to obtain the product, L = 67.2, a = -1.0, b = 0.4, R = 80.

[0111] Comparative Example 5

[0112] Compared with Example 12, catalyst F was used.

[0113] In a 5L polyester kettle, 10 mol of terephthalic acid, 10 mol of ethylene glycol, 4 mol of 1,4-cyclohexanedimethanol, and 0.29 g of catalyst F were added. Then, it was pressurized with nitrogen to 300 kPa 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, and the pressure in the kettle returned to normal pressure. The reaction kettle was gradually evacuated to 10000 Pa and maintained for 60 min, and then gradually evacuated to below 100 Pa, and the temperature was raised to 250 °C and maintained for the polycondensation reaction. After reacting for 200 min, a polymer melt was obtained, which was cooled by water and pelletized to obtain the product, L = 62.3, a = -1.4, b = 5.1, R = 65.

[0114] Comparative Example 6

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

[0116] 10 mol of terephthalic acid, 10 mol of ethylene glycol, 4 mol of 1,4-cyclohexanedimethanol and 0.20 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, and 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, and the temperature was raised to 250 °C and maintained for polycondensation reaction for 200 min to obtain a polymer melt, which was granulated by water cooling to obtain the product, L = 64.1, a = -1.2, b = 2.5, R = 70.

[0117] It is easy to understand that the above embodiments are merely examples given 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 on the basis of the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A titanium-based catalyst for polyester synthesis, characterized in that, The infrared absorption spectrum of the titanium-based catalyst includes a first characteristic peak and a second characteristic peak. Among them, the first characteristic peak is the characteristic peak of the ester carbonyl of the hydroxycarboxylic acid ester, and the second characteristic peak is the characteristic peak of the complexation of Ti with the carbonyl oxygen of the ester group. Moreover, the ratio of the absorbance value of the first characteristic peak to the absorbance value of the second characteristic peak is 1:(0.18 - 0.42).

2. The titanium-based catalyst according to claim 1, wherein The first characteristic peak appears in the range of 1730 cm -1 to 1743 cm -1 and is preferably around 1737 ± 1 cm -1 ; The second characteristic peak appears in the range of 1675 cm -1 to 1688 cm -1 and is preferably around 1685 ± 1 cm -1 ; Preferably, the titanium-based catalyst is a complex of titanate.

3. The preparation method of the titanium-based catalyst according to claim 1 or 2, characterized in that, The preparation method includes the following steps: S1: Add a titanium compound into a reaction vessel. S2: Add a 2-hydroxycarboxylic acid or its ester compound and carry out a reaction.

4. The preparation method according to claim 3, characterized in that, The titanium compound is a titanate compound, selected from one or more of tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate or tetrabutyl titanate; Preferably, in S1, the reaction vessel is heated to 20 - 150 °C, preferably 70 - 110 °C.

5. The preparation method according to claim 3 or 4, characterized in that, The 2-hydroxycarboxylic acid or its ester compound described in S2 is selected from one or more of lactic acid and its ester compounds, citric acid and its ester compounds, malic acid and its ester compounds, tartaric acid and its ester compounds; preferably at least one or more of lactic acid, citric acid, malic acid, tartaric acid, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, trimethyl citrate, triethyl citrate, tripropyl citrate, tri-n-butyl citrate, triisobutyl citrate, tri-sec-butyl citrate, tri-tert-butyl citrate, dimethyl malate, diethyl malate, dipropyl malate, dibutyl malate, dimethyl tartrate, diethyl tartrate, dipropyl tartrate, dibutyl tartrate; more preferably one or more of citric acid, trimethyl citrate, triethyl citrate, tripropyl citrate, tri-n-butyl citrate, triisobutyl citrate, tri-sec-butyl citrate, tri-tert-butyl citrate; And / or, the molar ratio of the 2-hydroxycarboxylic acid or its ester compound to the titanium compound described in S2 is 1:(0.8 - 1.5), preferably 1:(1.2 - 1.4); Preferably, the 2-hydroxycarboxylic acid or its ester compound is continuously added to the titanium compound within a period of time or intermittently added to the titanium compound in multiple batches; Preferably, the addition time of the 2-hydroxycarboxylic acid or its ester compound described in S2 is 3 - 50 h, preferably 4 - 20 h, more preferably 6 - 12 h; Preferably, the reaction temperature in S2 is 20 - 150 °C, preferably 70 - 110 °C; Preferably, after the addition of the 2-hydroxycarboxylic acid or its ester compound is complete, the reaction is carried out for 0 - 12 h, preferably 0.5 - 3 h.

6. The preparation method according to any one of claims 3-5, characterized in that, The preparation method further includes: S3: Add a phosphorus compound and carry out a reaction; Preferably, the phosphorus compound is selected from one or several of phosphoric acid, phosphorous acid, phosphate ester or phosphite ester, preferably phosphate ester, more preferably trimethyl phosphate and / or triethyl phosphate; Preferably, the molar ratio of the phosphorus compound to the titanium compound is (0 - 0.5):1, preferably (0.15 - 0.5):1, more preferably (0.2 - 0.35):1; Preferably, the reaction temperature in S3 is 20 - 150 °C, preferably 70 - 110 °C; the reaction time is 10 - 240 h, preferably 24 - 120 h.

7. Use of the titanium-based catalyst according to claim 1 or 2 or the titanium-based catalyst prepared by the preparation method according to any one of claims 3-6, which is used as a catalyst in the process of preparing polyester.

8. A method for preparing polyester, in which a dibasic acid or its ester and a diol are subjected to esterification or transesterification and polycondensation reactions in the presence of the titanium-based catalyst according to claim 1 or 2 or the titanium-based catalyst prepared by the preparation method according to any one of claims 3-6 to obtain polyester; Preferably, a phosphorus compound is further added in the method for preparing the polyester; Preferably, based on the titanium content, the addition amount of the titanium-based catalyst is 1-5000 ppm, preferably 1-500 ppm of the total mass of the dibasic acid; Preferably, the dibasic acid or its ester includes one or more 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; 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; Preferably, the molar ratio of the dibasic acid or its ester to the diol is 1:1.1-1:3.0; Preferably, the polyester includes polybutylene adipate terephthalate, polyethylene terephthalate-1,4-cyclohexanedimethanol ester.

9. A method for preparing polybutylene adipate terephthalate, adding the titanium-based catalyst according to claim 1 or 2 or the titanium-based catalyst prepared by the preparation method according to any one of claims 3-6, terephthalic acid, adipic acid, and 1,4-butanediol into a reaction kettle, carrying out an esterification reaction at 150-200 °C for 1-3 h, then evacuating the reaction kettle to between 1000-30000 Pa and maintaining for 10-60 min, and then evacuating to below 100 Pa, and maintaining a constant temperature reaction at 240-265 °C for 60-200 min to obtain polybutylene adipate terephthalate; Preferably, based on the titanium content, the addition amount of the titanium-based catalyst accounts for 20-500 ppm, preferably 50-150 ppm of the total mass of terephthalic acid and adipic acid; Preferably, 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; Preferably, the molar ratio of terephthalic acid to adipic acid is 0.1:0.9-0.9:0.

1.

10. A preparation method of polyethylene terephthalate-1,4-cyclohexanedimethanol ester. Add the titanium-based catalyst described in claim 1 or 2 or the titanium-based catalyst prepared by the preparation method described in any one of claims 3-6, terephthalic acid, ethylene glycol, and 1,4-cyclohexanedimethanol into a reaction kettle, and carry out an esterification reaction at 0-550 kPa and 150-230 °C for 2-6 h. Then, evacuate the reaction kettle to a pressure between 1000-30000 Pa and keep it for 10-60 min, and then evacuate it to below 100 Pa and keep a constant temperature reaction at 240-265 °C for 60-300 min to obtain polyethylene terephthalate-1,4-cyclohexanedimethanol ester; Preferably, calculated based on the titanium content, the addition amount of the titanium-based catalyst accounts for 1-50 ppm, preferably 2-20 ppm, of the mass of terephthalic acid; Preferably, 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; Preferably, the molar ratio of ethylene glycol to 1,4-cyclohexanedimethanol is 0.1:0.9-0.9:0.1.

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