A titanium-magnesium bimetallic catalyst for synthesizing polyethylene naphthalate resin, a preparation method and application thereof

Abstract

The application discloses a titanium-magnesium bimetallic catalyst for synthesizing polyethylene naphthalate resin and a preparation method and application thereof, and the preparation method comprises the following steps: carrying out static reaction on a titanium salt, a magnesium salt, a hydrolysis promoter and water at 100-300 DEG C for 12-48 h to obtain a bimetallic gel; adding ethylene glycol into the bimetallic gel and reacting at 80-180 DEG C for 3-6 h, filtering and drying to obtain a titanium-magnesium bimetallic catalyst for polymerization. The titanium-magnesium bimetallic catalyst in the application forms a multiradical ring intermediate through an ester bond and a hydroxyl group, changes an electron cloud arrangement mode, effectively inhibits the occurrence of an etherification side reaction, reduces the generation of a diethylene glycol segment, and avoids the yellowing problem of a PEN resin. The catalyst has the advantages of simple synthesis, remarkable catalytic effect, low colority of a PEN product and the like, and has a wide industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical technology, specifically relating to a titanium-magnesium bimetallic catalyst for the synthesis of polyethylene naphthalate resin, its preparation method, and its application. Background Technology

[0002] Polyethylene naphthalate (PEN) is a high-performance polyester material with excellent physicochemical properties. Industrially, it is often synthesized through a polycondensation reaction between dimethyl naphthalate and ethylene glycol. The chemical structure of PEN is similar to that of polyethylene terephthalate (PET), but the difference lies in the fact that PEN uses a more rigid naphthalene ring instead of the benzene ring in the PET molecular chain. This naphthalene ring structure gives PEN superior performance compared to PET. Compared to PET resin, PEN resin exhibits excellent thermal stability, small molecule barrier properties, UV blocking properties, and chemical resistance. It is widely used in electronics, high-end electronic device packaging, optical devices, specialty fibers and fabrics, and food packaging, and is hailed as one of the most influential emerging polymer materials of the 21st century.

[0003] Catalysts play a crucial role in the polycondensation of PEN. An ideal catalyst not only needs to efficiently promote the polycondensation reaction of PEN, increasing the polymerization rate and the molecular weight of the product, but also must possess excellent resistance to side reactions under high-temperature conditions, especially the ability to inhibit etherification. Currently, commonly used catalysts in the industrial synthesis of polyesters include antimony-based, titanium-based, bismuth-based, and zinc-based catalysts. For example, CN103772673A discloses a method for synthesizing PET polyester chips using titanium glycolate as a catalyst, obtaining PET polyester products with low color values. CN118063746A discloses a polymerization catalyst containing antimony triacetate, achieving good catalytic performance. CN110577631A discloses an industrial synthesis method for PEN using a titanium-based catalyst, obtaining high-viscosity PEN resin after solid-phase thickening.

[0004] Among various catalysts, titanium-based catalysts have become one of the most widely used catalyst systems due to their high catalytic efficiency and low toxicity. However, under the high-temperature conditions of polycondensation, titanium-based catalysts are prone to inducing etherification side reactions between hydroxyl groups in the polymerization reaction. This generates excessive diethylene glycol fragments, which in turn exacerbates the yellowing of polyester products due to oxidation, ultimately affecting the mechanical properties and optical transparency of the finished product. Currently, industrial methods often aim to avoid etherification side reactions by controlling the polymerization process, such as lowering the reaction temperature and adding antioxidants. While these methods have achieved some success, they do not address the root cause of the problem.

[0005] Therefore, selecting a suitable catalyst, especially one that can maintain stability at high temperatures and suppress etherification side reactions, is a key issue in the industrial production of PEN. Current research focuses on developing catalytic systems that can effectively control the reaction pathway and avoid etherification side reactions at high temperatures to ensure high-quality PEN products. Summary of the Invention

[0006] To address the uncontrollable etherification side reaction in the polycondensation of poly(ethylene naphthalate) (PEN) under titanium-based catalytic systems in existing technologies, this invention aims to provide a titanium-magnesium bimetallic catalyst for the synthesis of polyethylene naphthalate (PEG) resin, its preparation method, and its applications. This catalyst interacts with the ester bonds and hydroxyl groups in PEG resin to form a multi-ring intermediate and adjusts the internal electron cloud arrangement of the molecule, successfully suppressing the etherification side reaction. This mechanism effectively reduces the formation of diethylene glycol fragments, thereby avoiding the yellowing problem of PEN resin during polymerization, significantly improving the color and quality of the product, and possessing significant industrial application value.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a titanium-magnesium bimetallic catalyst for the synthesis of polyethylene naphthalate resin includes the following steps:

[0009] Titanium salt, magnesium salt, hydrolysis accelerator and water were subjected to a static reaction at 100-300℃ for 12-48 h to obtain a bimetallic gel.

[0010] Ethylene glycol was added to the bimetallic gel and reacted at 80-180℃ for 3-6 h. The mixture was then filtered and dried to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0011] A further improvement of the present invention is that the molar ratio of titanium salt, magnesium salt and hydrolysis accelerator is 0.5-1.5:1.0-3.0:0.005-0.02.

[0012] A further improvement of this invention is that the mass of water is 2-4 times the total mass of titanium salt, magnesium salt, and hydrolysis accelerator.

[0013] A further improvement of the present invention is that the titanium salt is tetrabutyl titanate or titanium chloride.

[0014] A further improvement of the present invention is that the magnesium salt is magnesium acetate, magnesium nitrate or magnesium chloride.

[0015] A further improvement of the present invention is that the hydrolysis promoter is one or a mixture of two of ammonia, sodium bicarbonate, sodium acetate, methylamine, and pyridine.

[0016] A further improvement of the present invention is that when the hydrolysis promoter is a mixture of two substances selected from ammonia, sodium bicarbonate, sodium acetate, methylamine, and pyridine, the mass ratio of the two substances is 1:1.

[0017] A further improvement of this invention is that the mass of ethylene glycol is 1-3 times the mass of the bimetallic gel.

[0018] A titanium-magnesium bimetallic catalyst for the synthesis of polyethylene naphthalate resin, wherein the catalyst has an intrinsic viscosity of 0.65-1.10 dL / g, a diethylene glycol content of 0.05%-1%, a yellowness value YI of 0.05-0.5, and a transmittance of >89%.

[0019] Application of a titanium-magnesium bimetallic catalyst for the synthesis of polyethylene naphthalate resin in the synthesis of PEN resin.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) The catalyst production process is simple. The bimetallic catalyst provided by this invention uses conventional chemical reagents, the reaction conditions are relatively mild, the amount of solvent used is small, the calcination temperature is low, the energy consumption is low, the total preparation time is short, and the industrial production is highly feasible. It overcomes the problem that the existing industrial synthesis process is complicated by multiple steps such as high temperature and high pressure hydrolysis, multi-stage impregnation, ultrasonic washing and dispersion, high temperature calcination, physical grinding and crushing, and sieving.

[0022] (2) High catalytic efficiency. The bimetallic catalyst of this invention significantly reduces the amount required, requiring only 0.3% of the total mass to achieve the same polymerization effect and synthesize PEN products with the same intrinsic viscosity. This overcomes the problem of excessive amounts of catalyst, typically around 0.5% of the total mass, used in the industrial synthesis of polyester resins with intrinsic viscosity >0.6 Dl / g. The high efficiency of this catalyst not only reduces the amount of catalyst used and saves production costs, but also reduces the incidence of side reactions during production, further improving product quality and consistency. In addition, reducing the amount of catalyst used can also reduce the potential impact of metal residues on product performance, meeting the requirements of green and environmentally friendly production, and has great industrial application value.

[0023] (3) Fewer etherification side reactions. The titanium-magnesium bimetallic catalyst in this invention effectively inhibits the occurrence of etherification side reactions by forming a multi-ring intermediate with ester bonds and hydroxyl groups and changing the electron cloud arrangement, thereby reducing the generation of diethylene glycol fragments and effectively avoiding the occurrence of etherification side reactions. This avoids the yellowing problem of PEN resin, and the content of ether in the product is as low as 0.5%. The polymer molecular chain has good regularity and is easy to crystallize. It is easier to crystallize during processing to form PEN products with higher strength. This catalyst has the advantages of simple synthesis, significant catalytic effect, and low color of PEN products, and is suitable for industrial application scenarios that require excellent physical properties. Attached Figure Description

[0024] Figure 1 The infrared spectrum of the titanium-magnesium bimetallic catalyst of Example 1 of the present invention is shown. Detailed Implementation

[0025] The present invention will now be described more fully with reference to embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0026] Traditional titanium-based catalysts are commonly used in the preparation of PEN resin due to their high catalytic efficiency and low toxicity. However, under high-temperature conditions, titanium-based catalysts are prone to initiating hydroxyl etherification side reactions during polymerization, generating excessive diethylene glycol fragments, which in turn leads to oxidative yellowing of the product and affects product quality. The titanium-magnesium bimetallic catalyst in this invention effectively suppresses the etherification side reaction by forming a multi-ring intermediate with ester bonds and hydroxyl groups and altering the electron cloud arrangement, thereby reducing the formation of diethylene glycol fragments and avoiding the yellowing problem of PEN resin. This catalyst has advantages such as simple synthesis, significant catalytic effect, and low color of PEN products, and has broad prospects for industrial application.

[0027] This invention provides a method for preparing a titanium-magnesium bimetallic catalyst for the synthesis of polyethylene naphthalate (PEN) resin, comprising the following steps:

[0028] Titanium salt (tetrabutyl titanate or titanium chloride), magnesium salt (magnesium acetate, magnesium nitrate or magnesium chloride), and hydrolysis accelerator are weighed into a high-pressure reactor at a molar ratio of 0.5-1.5:1.0-3.0:0.005-0.02. Water, with a mass of 2-4 times the total mass of the mixture, is then added. After stirring evenly, the mixture is heated to 100-300℃ and allowed to react statically for 12-48 h to obtain a bimetallic gel. Ethylene glycol solvent, with a mass of 1-3 times the mass of the bimetallic gel, is added to the system. The mixture is heated to 80-180℃ and stirred for 3-6 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension is placed in an oven at 100-220℃ and dried for 2-3 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0029] The hydrolysis accelerator is one or a mixture of two of the following: ammonia, sodium bicarbonate, sodium acetate, methylamine, and pyridine, with a mass ratio of 1:1 between the two substances.

[0030] The performance evaluation of titanium-magnesium bimetallic catalysts was conducted using the following methods:

[0031] 153.0 g of dimethyl naphthalene, 97.0 g of ethylene glycol, and 0.75 g of titanium-magnesium bimetallic catalyst were weighed into a stainless steel reactor and heated to 220℃ for 2 h to carry out transesterification reaction, releasing methanol as a byproduct from the system. The temperature was then increased to 300℃ and the pressure of the reaction system was reduced to 100 Pa. After reacting for 2 h under these conditions, the product was discharged while hot, granulated, and PEN resin was obtained.

[0032] The performance testing methods for PEN resin are as follows:

[0033] Intrinsic viscosity test: According to GB / T 14190-2008, dissolve an appropriate amount of PEN resin in a mixed solvent of phenol and tetrachloroethane (mass ratio = 1:1). Fill the Ubbelohde viscometer with the PEN solution using a syringe, ensuring that there are no air bubbles in the solution. Record the time it takes for the solution to flow from the upper mark to the lower mark, and simultaneously record the solvent outflow time. Finally, calculate the intrinsic viscosity of the PEN product using the viscosity formula.

[0034] Diethylene glycol content test: Take an appropriate amount of PEN resin and methanol and place them in a hydrothermal reactor. After alcoholysis at 200℃ for 2 h, the degradation products are obtained. At the same time, use methanol as solvent and ethylene glycol and diethylene glycol as solutes to prepare standard solutions of different concentrations to establish a standard curve. Set appropriate parameters on a gas chromatograph (Picken, GC-6860 SA, HP-INNOWAX), record the retention time and elution peak area, and calculate the diethylene glycol content.

[0035] The yellowness value YI was measured using a digital colorimeter (SHTI-101), three times in parallel, and the average value was recorded.

[0036] Transmittance test: Cut the PEN film into 100*100cm shapes and test the transmittance on a UV spectrophotometer.

[0037] The ammonia concentration in this invention is 25%.

[0038] The technical solution of the present invention will be described in detail below through specific embodiments:

[0039] Example 1

[0040] 30.6 g of tetrabutyl titanate, 19.4 g of magnesium acetate, 0.01 g of ammonia and 150 g of water were added to a high-pressure reactor. After stirring evenly, the mixture was heated to 200°C and reacted statically for 24 h to obtain a bimetallic gel. 200 g of ethylene glycol was added to the system, and the mixture was heated to 120°C and stirred for 4 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in an oven at 200°C and dried for 2 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0041] See Figure 1 It can be seen that 1125 cm -1 The absorption peak at 1438 cm⁻¹ represents the Ti-O bond. -1 The absorption peak for the Mg-O bond is at 3450 cm⁻¹. -1 The peak at 2950 cm⁻¹ represents the stretching vibration peak of the hydroxyl group in the catalyst. -1 The peak at 1718 represents the stretching vibration of the methyl group in the catalyst, and the peak at 1718 represents the stretching vibration of the ester bond in the catalyst. The above infrared spectra prove the successful preparation of the bimetallic catalyst.

[0042] Performance evaluation procedure for titanium-magnesium bimetallic catalyst: Weigh 153.0 g of dimethyl naphthalene, 97.0 g of ethylene glycol, and 0.75 g of titanium-magnesium bimetallic catalyst into a stainless steel reactor. Heat to 220℃ and react for 2 h to carry out transesterification reaction, releasing methanol as a byproduct from the system. Continue heating to 300℃ and reduce the pressure of the reaction system to 100 Pa. React under these conditions for 2 h, then discharge the material while hot, granulate it, and obtain PEN resin.

[0043] Example 2

[0044] 33.6 g of tetrabutyl titanate, 16.4 g of magnesium acetate, 0.01 g of ammonia and 150 g of water were added to a high-pressure reactor. After stirring evenly, the mixture was heated to 200°C and reacted statically for 24 h to obtain a bimetallic gel. 200 g of ethylene glycol was added to the system, and the mixture was heated to 120°C and stirred for 4 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in an oven at 200°C and dried for 2 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0045] The catalyst performance evaluation procedure is the same as in Example 1.

[0046] Example 3

[0047] 27.6 g of tetrabutyl titanate, 22.4 g of magnesium acetate, 0.01 g of ammonia and 150 g of water were added to a high-pressure reactor. After stirring evenly, the mixture was heated to 200°C and reacted statically for 24 h to obtain a bimetallic gel. 200 g of ethylene glycol was added to the system, and the mixture was heated to 120°C and stirred for 4 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in an oven at 200°C and dried for 2 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0048] The catalyst performance evaluation procedure is the same as in Example 1.

[0049] Example 4

[0050] 30.6 g of tetrabutyl titanate, 19.4 g of magnesium acetate, 0.005 g of ammonia, 0.005 g of sodium bicarbonate, and 150 g of water were added to a high-pressure reactor. After stirring evenly, the mixture was heated to 200°C and reacted statically for 24 h to obtain a bimetallic gel. 200 g of ethylene glycol was added to the system, and the mixture was heated to 120°C and stirred for 4 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in a 200°C oven and dried for 2 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0051] The catalyst performance evaluation procedure is the same as in Example 1.

[0052] Example 5

[0053] 30.6 g of tetrabutyl titanate, 19.4 g of magnesium acetate, 0.005 g of ammonia, 0.005 g of pyridine, and 150 g of water were added to a high-pressure reactor. After stirring evenly, the mixture was heated to 200°C and reacted statically for 24 h to obtain a bimetallic gel. 200 g of ethylene glycol was added to the system, and the mixture was heated to 120°C and stirred for 4 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in an oven at 200°C and dried for 2 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0054] The catalyst performance evaluation procedure is the same as in Example 1.

[0055] Example 6

[0056] 30.6 g of tetrabutyl titanate, 19.4 g of magnesium acetate, 0.02 g of ammonia and 150 g of water were added to a high-pressure reactor. After stirring evenly, the mixture was heated to 200°C and reacted statically for 24 h to obtain a bimetallic gel. 200 g of ethylene glycol was added to the system, and the mixture was heated to 120°C and stirred for 4 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in an oven at 200°C and dried for 2 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0057] The catalyst performance evaluation procedure is the same as in Example 1.

[0058] Example 7

[0059] 30.6 g of tetrabutyl titanate, 19.4 g of magnesium acetate, 0.01 g of ammonia and 100 g of water were added to a high-pressure reactor. After stirring evenly, the mixture was heated to 200°C and reacted statically for 24 h to obtain a bimetallic gel. 200 g of ethylene glycol was added to the system, and the mixture was heated to 120°C and stirred for 4 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in an oven at 200°C and dried for 2 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0060] The catalyst performance evaluation procedure is the same as in Example 1.

[0061] Example 8

[0062] 30.6 g of tetrabutyl titanate, 19.4 g of magnesium acetate, 0.01 g of ammonia and 150 g of water were added to a high-pressure reactor. After stirring evenly, the temperature was raised to 260℃ and the static reaction was carried out for 24 h to obtain a bimetallic gel. 200 g of ethylene glycol was added to the system, the temperature was raised to 120℃ and the reaction was stirred for 4 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the above suspension was placed in an oven at 200℃ and dried for 2 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0063] The catalyst performance evaluation procedure is the same as in Example 1.

[0064] Example 9

[0065] 30.6 g of tetrabutyl titanate, 19.4 g of magnesium acetate, 0.01 g of ammonia and 150 g of water were added to a high-pressure reactor. After stirring evenly, the mixture was heated to 200°C and reacted statically for 36 h to obtain a bimetallic gel. 200 g of ethylene glycol was added to the system, and the mixture was heated to 120°C and stirred for 4 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in an oven at 200°C and dried for 2 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0066] The catalyst performance evaluation procedure is the same as in Example 1.

[0067] Example 10

[0068] 30.6 g of tetrabutyl titanate, 19.4 g of magnesium acetate, 0.01 g of ammonia and 150 g of water were added to a high-pressure reactor. After stirring evenly, the mixture was heated to 200°C and reacted statically for 24 h to obtain a bimetallic gel. 400 g of ethylene glycol was added to the system, and the mixture was heated to 120°C and stirred for 4 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in a 200°C oven and dried for 2 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0069] The catalyst performance evaluation procedure is the same as in Example 1.

[0070] Example 11

[0071] 30.6 g of tetrabutyl titanate, 19.4 g of magnesium acetate, 0.01 g of ammonia and 150 g of water were added to a high-pressure reactor. After stirring evenly, the mixture was heated to 200°C and reacted statically for 24 h to obtain a bimetallic gel. 200 g of ethylene glycol was added to the system, and the mixture was heated to 160°C and stirred for 4 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in an oven at 200°C and dried for 2 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0072] The catalyst performance evaluation procedure is the same as in Example 1.

[0073] Example 12

[0074] 30.6 g of tetrabutyl titanate, 19.4 g of magnesium acetate, 0.01 g of ammonia and 150 g of water were added to a high-pressure reactor. After stirring evenly, the mixture was heated to 200°C and reacted statically for 24 h to obtain a bimetallic gel. 200 g of ethylene glycol was added to the system, and the mixture was heated to 120°C and stirred for 6 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in an oven at 200°C and dried for 2 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0075] The catalyst performance evaluation procedure is the same as in Example 1.

[0076] Example 13

[0077] Titanium chloride (30.6 g), magnesium acetate, and sodium acetate were weighed into a high-pressure reactor at a molar ratio of 0.5:1.5:0.005. Water, with a mass twice the total mass of the mixture, was added. After stirring evenly, the mixture was heated to 100°C and allowed to react statically for 48 h to obtain a bimetallic gel. Ethylene glycol solvent, with a mass three times the mass of the bimetallic gel, was added to the system. The mixture was heated to 100°C and stirred for 5 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in an oven at 150°C and dried for 25 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0078] Example 14

[0079] Tetrabutyl titanate, magnesium nitrate, and methylamine were weighed into a high-pressure reactor at a molar ratio of 1.0:1.01:0.02. Water, with a mass four times the total mass of the mixture, was added. After stirring until homogeneous, the mixture was heated to 300°C and allowed to react statically for 12 h to obtain a bimetallic gel. Ethylene glycol solvent, with a mass twice the mass of the bimetallic gel, was added to the system. The mixture was heated to 180°C and stirred for 3 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in an oven at 220°C and dried for 2 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0080] Example 15

[0081] Tetrabutyl titanate, magnesium chloride, and pyridine were weighed into a high-pressure reactor at a molar ratio of 1.5:3.0:0.01. Water, with a mass three times the total mass of the mixture, was added. After stirring until homogeneous, the mixture was heated to 150°C and allowed to react statically for 30 h to obtain a bimetallic gel. Ethylene glycol solvent, with a mass equal to the mass of the bimetallic gel, was added to the system. The mixture was heated to 80°C and stirred for 6 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in an oven at 100°C and dried for 3 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0082] Comparative Example 1

[0083] 40.0 g of tetrabutyl titanate, 10.0 g of magnesium acetate, 0.01 g of ammonia and 150 g of water were added to a high-pressure reactor. After stirring evenly, the mixture was heated to 200°C and reacted statically for 24 h to obtain a bimetallic gel. 200 g of ethylene glycol was added to the system, and the mixture was heated to 120°C and stirred for 4 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in an oven at 200°C and dried for 2 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0084] The catalyst performance evaluation procedure is the same as in Example 1.

[0085] Comparative Example 2

[0086] 30.6 g of tetrabutyl titanate, 19.4 g of magnesium acetate, and 150 g of water were added to a high-pressure reactor. After stirring evenly, the temperature was raised to 200°C, and the mixture was allowed to react statically for 24 h to obtain a bimetallic gel. 200 g of ethylene glycol was added to the system, and the temperature was raised to 120°C. The mixture was stirred for 4 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in a 200°C oven and dried for 2 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0087] The catalyst performance evaluation procedure is the same as in Example 1.

[0088] Comparative Example 3

[0089] 30.6 g of tetrabutyl titanate, 19.4 g of magnesium acetate, 0.01 g of ammonia and 220 g of water were added to a high-pressure reactor. After stirring evenly, the mixture was heated to 200°C and reacted statically for 24 h to obtain a bimetallic gel. 200 g of ethylene glycol was added to the system, and the mixture was heated to 120°C and stirred for 4 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in a 200°C oven and dried for 2 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0090] The catalyst performance evaluation procedure is the same as in Example 1.

[0091] Comparative Example 4

[0092] 30.6 g of tetrabutyl titanate, 19.4 g of magnesium acetate, 0.01 g of ammonia and 150 g of water were added to a high-pressure reactor. After stirring evenly, the mixture was heated to 80°C and reacted statically for 24 h to obtain a bimetallic gel. 200 g of ethylene glycol was added to the system, and the mixture was heated to 120°C and stirred for 4 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in an oven at 200°C and dried for 2 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0093] The catalyst performance evaluation procedure is the same as in Example 1.

[0094] Comparative Example 5

[0095] 30.6 g of tetrabutyl titanate, 19.4 g of magnesium acetate, 0.01 g of ammonia and 150 g of water were added to a high-pressure reactor. After stirring evenly, the mixture was heated to 200°C and reacted statically for 60 h to obtain a bimetallic gel. 200 g of ethylene glycol was added to the system, and the mixture was heated to 120°C and stirred for 4 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in an oven at 200°C and dried for 2 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0096] The catalyst performance evaluation procedure is the same as in Example 1.

[0097] Comparative Example 6

[0098] 30.6 g of tetrabutyl titanate, 19.4 g of magnesium acetate, 0.01 g of ammonia and 150 g of water were added to a high-pressure reactor. After stirring evenly, the mixture was heated to 200°C and reacted statically for 24 h to obtain a bimetallic gel. 700 g of ethylene glycol was added to the system, and the mixture was heated to 120°C and stirred for 4 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in an oven at 200°C and dried for 2 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0099] The catalyst performance evaluation procedure is the same as in Example 1.

[0100] Comparative Example 7

[0101] 30.6 g of tetrabutyl titanate, 19.4 g of magnesium acetate, 0.01 g of ammonia and 150 g of water were added to a high-pressure reactor. After stirring evenly, the mixture was heated to 200°C and reacted statically for 24 h to obtain a bimetallic gel. 200 g of ethylene glycol was added to the system, and the mixture was heated to 200°C and stirred for 4 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in a 200°C oven and dried for 2 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0102] The catalyst performance evaluation procedure is the same as in Example 1.

[0103] Comparative Example 8

[0104] 30.6 g of tetrabutyl titanate, 19.4 g of magnesium acetate, 0.01 g of ammonia and 150 g of water were added to a high-pressure reactor. After stirring evenly, the mixture was heated to 200°C and reacted statically for 24 h to obtain a bimetallic gel. 200 g of ethylene glycol was added to the system, and the mixture was heated to 120°C and stirred for 2 h to obtain a bimetallic catalyst suspension. The filter cake obtained after filtering the suspension was placed in an oven at 200°C and dried for 2 h to obtain a titanium-magnesium bimetallic catalyst for polymerization.

[0105] The catalyst performance evaluation procedure is the same as in Example 1.

[0106] The preparation conditions for Examples 1-12 and Comparative Examples 1-8 are shown in Table 1, and the performance comparison is shown in Table 2.

[0107] Table 1. Overview of synthetic data for examples and comparative examples

[0108]

[0109] Table 2 Comparison of PEN resin properties obtained in the examples and comparative examples

[0110]

[0111] As can be seen from Examples 1-13 and Comparative Examples 1-8, in Comparative Example 1, the proportions of titanium and magnesium sources exceeded the range specified in this invention, resulting in an altered proportion of metal atoms in the catalyst. This made it difficult for the catalyst to form multi-ring intermediates with the active groups of the polymer, leading to poor catalytic performance and the inability to obtain PEN polymers with high intrinsic viscosity. In Comparative Example 2, excessive amounts of hydrolysis promoter resulted in the formation of inert metal oxides, failing to exhibit good catalytic performance. In Comparative Example 3, excessive water usage exceeded the scope of the claims, leading to a decrease in the concentration of metal atoms per unit volume and hindering effective catalysis of PEN polymerization. In Comparative Example 4, the static reaction temperature was too low. In Comparative Example 5, the catalyst substrate could not react completely, resulting in an imperfect catalyst structure and ineffective catalysis of the polymerization reaction. In Comparative Example 6, the static reaction time was too long, exceeding the reaction time range of this invention, causing the formation of inert metal oxides in the system, thus leading to poor catalytic performance. In Comparative Example 7, the excessive amount of ethylene glycol destroyed the structure of the bimetallic gel, resulting in reduced catalyst performance. In Comparative Example 8, the excessively high stirring temperature destroyed the formed gel structure at high temperatures, reducing the catalytic effect. In Comparative Example 8, the insufficient stirring time prevented the complete formation of the catalyst microstructure, leading to reduced catalytic efficiency. This invention can solve the problem of product yellowing caused by the etherification side reaction induced by traditional titanium-based catalysts. The PEN resin synthesized using the titanium-magnesium bimetallic catalyst exhibits excellent performance, with an intrinsic viscosity of 0.45-1.10 dL / g, a diethylene glycol content of 0.05%-1%, a yellowness value (YI) of 0.05-0.50, and a transmittance of 89%-93%, showing broad industrial application prospects and commercial value.

[0112] The above description is only of the preferred embodiment of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All variations made within the scope of the independent claims of the present invention are also within the scope of protection of the present invention.

[0113] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. A method for preparing a titanium-magnesium bimetallic catalyst for the synthesis of polyethylene naphthalate resin, characterized in that, Includes the following steps: Titanium salt, magnesium salt, hydrolysis accelerator and water were subjected to a static reaction at 100-300℃ for 12-48 h to obtain a bimetallic gel. Ethylene glycol was added to the bimetallic gel and reacted at 80-180℃ for 3-6 h. The mixture was then filtered and dried to obtain a titanium-magnesium bimetallic catalyst for polymerization. The molar ratio of titanium salt, magnesium salt, and hydrolysis accelerator is 0.5-1.5:1.0-3.0:0.005-0.02; The mass of water is 2-4 times the total mass of titanium salt, magnesium salt, and hydrolysis accelerator; The mass of ethylene glycol is 1-3 times the mass of the bimetallic gel.

2. The method for preparing the titanium-magnesium bimetallic catalyst for synthesizing polyethylene naphthalate resin according to claim 1, characterized in that, The titanium salt is tetrabutyl titanate or titanium chloride.

3. The method for preparing the titanium-magnesium bimetallic catalyst for synthesizing polyethylene naphthalate resin according to claim 1, characterized in that, Magnesium salts are magnesium acetate, magnesium nitrate, or magnesium chloride.

4. The method for preparing the titanium-magnesium bimetallic catalyst for synthesizing polyethylene naphthalate resin according to claim 1, characterized in that, The hydrolysis accelerator is one or a mixture of two of the following: ammonia, sodium bicarbonate, sodium acetate, methylamine, and pyridine.

5. The method for preparing the titanium-magnesium bimetallic catalyst for synthesizing polyethylene naphthalate resin according to claim 4, characterized in that, When the hydrolysis accelerator is a mixture of two substances from ammonia, sodium bicarbonate, sodium acetate, methylamine, and pyridine, the mass ratio of the two substances is 1:

1.

6. A titanium-magnesium bimetallic catalyst for synthesizing polyethylene naphthalate resin prepared by the method according to any one of claims 1-5, characterized in that, The catalyst has an intrinsic viscosity of 0.65-1.10 dL / g, a diethylene glycol content of 0.05%-1%, a yellowness value (YI) of 0.05-0.5, and a transmittance of >89%.

7. The application of a titanium-magnesium bimetallic catalyst prepared according to any one of claims 1-5 for the synthesis of polyethylene naphthalate resin in the synthesis of PEN resin.

Images