A ethylene glycol antimony catalyst, its preparation method and application

Abstract

This invention belongs to the field of polyester synthesis catalyst technology, and particularly relates to an antimony glycolate catalyst, its preparation method, and its application. A protective structure is constructed by preparing antimony-modified aliphatic tricarboxylic acid oligomers and trimethylolpropane-succinate. The small molecule trimethylolpropane-succinate preferentially diffuses to the surface of the antimony glycolate crystals, forming a pre-adsorption layer through hydrogen bonding and covalent anchoring of defect sites. The large molecule antimony-modified aliphatic tricarboxylic acid oligomer is then deposited, covalently bridged to the pre-adsorption layer, and cross-linked to form a film. The grafted C... 18 Alkyl chains are oriented to form a hydrophobic barrier, creating a composite protective structure of covalent anchoring layer, cross-linked film and hydrophobic barrier, which synergistically inhibits the hydrolysis of antimony sites on the surface and the deterioration of catalyst by hydrolysis.

Description

Technical Field

[0001] This invention relates to the field of polyester synthesis catalyst technology, and in particular to an antimony glycol catalyst, its preparation method, and its application. Background Technology

[0002] In the industrial production of polyester, antimony glycolate (SGA) has become a mainstream catalyst with extremely high application rates in polyester polycondensation reactions due to its outstanding advantages such as high catalytic activity, stable polymerization reaction control, low side reaction formation, and low interference with the color and hue of finished polyester products. It is widely used in the production of various polyester products, including chemical fiber chips, bottle-grade polyester, and engineering plastic polyester. Currently, the industry generally uses the basic synthetic route of reacting antimony trioxide with ethylene glycol to prepare antimony glycol. After impurity removal, crystallization, solvent washing, and conventional drying processes, the finished product is obtained. Given the inherent hydrolytic nature of antimony glycolate, existing technologies mostly rely on conventional methods to optimize storage performance, such as strictly controlling the packaging environment, reducing contact time with humid environments, vacuum sealing, adjusting crystal particle morphology, or using physical coating and isolation. However, these traditional treatment methods only achieve shallow, passive protection and cannot structurally stabilize the active antimony sites on the catalyst surface. They are insufficient to prevent surface hydrolysis and deterioration of the catalyst during drying and storage, ultimately resulting in insufficient solubility and light transmittance of the finished catalyst and delayed catalytic response, which adversely affects polyester production efficiency and the overall quality of the finished product. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide an antimony glycolate catalyst, its preparation method, and its application. A protective structure is constructed by preparing antimony-modified aliphatic tricarboxylic acid oligomers and trimethylolpropane-succinate. The small molecule trimethylolpropane-succinate preferentially diffuses to the surface of the antimony glycolate crystals, forming a pre-adsorption layer through hydrogen bonding and covalent anchoring of defect sites. The large molecule antimony-modified aliphatic tricarboxylic acid oligomer is then deposited, covalently bridged to the pre-adsorption layer, and cross-linked to form a film. The grafted C... 18 Alkyl chains are oriented to form a hydrophobic barrier, creating a composite protective structure of covalent anchoring layer, cross-linked film, and hydrophobic barrier, which synergistically inhibits the hydrolysis of antimony sites on the surface and suppresses the hydrolytic degradation of the catalyst.

[0004] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a method for preparing an antimony glycol catalyst, comprising the following steps: S1. Trimethylolpropane is heated to melt, succinic acid and p-toluenesulfonic acid are added, the reaction is carried out, and the mixture is kept warm for later use to obtain trimethylolpropane-succinate. S2. Under nitrogen protection, aliphatic tricarboxylic acid and octadecyl alcohol are added to ethylene glycol, p-toluenesulfonic acid is added, and after the first reaction, modified aliphatic tricarboxylic acid is obtained; antimony trioxide and adipic acid are added to the modified aliphatic tricarboxylic acid, and after the second reaction, the mixture is kept at a certain temperature for later use to obtain antimony-modified aliphatic tricarboxylic acid oligomer. S3. Mix antimony trioxide and ethylene glycol, introduce nitrogen gas, heat up, react, filter, collect the filtrate in a preheated crystallization vessel, cool down in stages to crystallize, and obtain a suspension containing antimony glycol crystals. S4. Centrifuge the suspension containing antimony glycol crystals to obtain wet crystals; add trimethylolpropane-succinate to antimony-modified aliphatic tricarboxylic acid oligomer, disperse, add to wet crystals, impregnate and dry to obtain antimony glycol catalyst.

[0005] In one feasible implementation, in step S1, the mass ratio of trimethylolpropane, succinic acid, and p-toluenesulfonic acid is (1.6-2.4):(2.0-2.8):(0.006-0.01); the target heating temperature is 60-70°C; the reaction temperature is 100-120°C; the reaction time is 3-5 hours; and the temperature for heat preservation is 80-100°C.

[0006] Trimethylolpropane (TMP) contains three primary hydroxyl groups arranged radially outward in a trigonal pyramidal pattern from the central carbon atom; succinic acid contains two carboxyl groups located at both ends of the carbon chain. Under heating conditions, the carboxyl groups of succinic acid undergo dehydration condensation with the hydroxyl groups of TMP to form ester bonds. Because the three hydroxyl groups are symmetrically distributed in space, when succinic acid esterifies with any one of the hydroxyl groups, the remaining hydroxyl groups still maintain a regular spatial arrangement. By controlling the reaction temperature and reaction time, the esterification reaction can be made incomplete, thus retaining both free hydroxyl and free carboxylic acid groups in the product, forming a structure with TMP as the core and succinic acid as the connecting arm.

[0007] This structure endows trimethylolpropane-succinate with two key functional groups: the free carboxylic acid group can, on the one hand, form a strong anchoring Sb-OC=O covalent bond with the antimony-hydroxyl groups exposed at crystal surface defect sites during subsequent drying; on the other hand, it can form a Sb-OC=O covalent bond with the antimony-hydroxyl groups of the oligomer, serving as the main bridging pathway between the two layers. The free hydroxyl group can, on the one hand, form a hydrogen bond network with the hydroxyl groups of ethylene glycol molecules on the crystal surface, allowing the molecule to spread and adsorb on flat areas to achieve full surface coverage; on the other hand, it can form a COC=O ester bond with the free carboxylic acid group of the oligomer, serving as an auxiliary bridging pathway. Simultaneously, the molecule has a small molecular weight and preferentially diffuses to the crystal surface in the early stages of drying, providing reaction sites for subsequent covalent bridging of the oligomer, forming a pre-adsorption layer in the triple-protection structure, and filling the gaps between oligomer macromolecules to increase film density.

[0008] In one feasible implementation, in S2, the aliphatic tricarboxylic acid is selected from one or more of 1,2,4-butanetricarboxylic acid and citric acid, preferably 1,2,4-butanetricarboxylic acid.

[0009] In one feasible implementation, in step S2, the mass ratio of the aliphatic tricarboxylic acid, octadecyl alcohol, ethylene glycol, p-toluenesulfonic acid, antimony trioxide, and adipic acid is (0.06-0.15):(0.084-0.213):(5-10):(0.001-0.005):(0.11-0.35):(0.012-0.03); the temperature of the first reaction is 100-110℃, and the time of the first reaction is 2-3 hours; the temperature of the second reaction is 120-130℃, and the time of the second reaction is 4-8 hours; the temperature for heat preservation is 60-80℃.

[0010] Citric acid contains three carboxyl groups that can be grafted with hydrophobic alkyl groups, but it has a tertiary hydroxyl group at the 2 position. Under acidic heating conditions, intramolecular cyclization may occur to form lactones, which reduces the yield of the target monoesterification product. The hydroxyl group can assist in coordinating with antimony ions to participate in crosslinking, but its C3 branched backbone makes the oligomer segments relatively rigid. When spreading on the crystal surface, it tends to form local agglomerates rather than spread uniformly, affecting the coverage uniformity of the crosslinked film.

[0011] 1,2,4-Butanetricarboxylic acid is a straight-chain aliphatic tricarboxylic acid without hydroxyl groups. Its molecule contains unshielded terminal methylene carboxyl groups at positions 1 and 4, and a tertiary carbon carboxyl group surrounded by alkyl groups at position 2. This steric hindrance difference results in natural regioselectivity. Under p-toluenesulfonic acid catalysis, equimolar amounts of octadecyl alcohol preferentially attack either the sterically less hindrance terminal carboxyl group at positions 1 or 4 for monoesterification. However, due to the combined constraints of material metering and the steric hindrance of the grafted long alkyl chain, it is difficult for it to simultaneously esterify with both carboxyl groups at positions 1 and 4. By grafting C... 18 The hydrophobic long-chain alkyl group forms a spatial barrier at the molecular end, increasing the activation energy for secondary esterification of the remaining carboxyl groups. Simultaneously, the abundant ethylene glycol in the system acts as a polar solvent for the dihydroxyl groups, enabling continuous solvation coating on the unreacted free carboxyl groups through multi-point hydrogen bonding, suppressing secondary esterification side reactions and stabilizing the reaction system at the monoesterification stage. Furthermore, 1,2,4-butanetricarboxylic acid has a C4 straight-chain backbone, and its oligomer segments are more flexible, allowing for easier and more uniform spreading on the crystal surface to form a dense, continuous cross-linked film. Higher film uniformity results in longer water vapor permeation paths and lower permeation rates, thus providing superior protection.

[0012] Antimony trioxide gradually dissolves under the acidic action of the carboxylic acid groups of the modified aliphatic tricarboxylic acid, exposing antimony-hydroxyl groups. The free carboxylic acid groups of the modified aliphatic tricarboxylic acid condense and esterify with antimony-hydroxyl groups to form Sb-OC=O ester bonds. Some carboxylic acid groups coordinate with antimony ions to form Sb←O=C coordinate bonds. Excess antimony centers act as cross-linking nodes, connecting the modified aliphatic tricarboxylic acid molecules into a network of condensed oligomers. At the same time, adipic acid acts as a bifunctional bridging agent, with its carboxyl groups at both ends esterifying with antimony-hydroxyl groups of different antimony centers, introducing C6 flexible straight-chain segments between antimony atoms, increasing the flexibility of the oligomer molecular chains and making it easier for them to spread evenly on the crystal surface.

[0013] In one feasible implementation, in step S3, the flow rate of nitrogen gas is 1-3 L / min; the mass ratio of antimony trioxide to ethylene glycol is 100:(500-800); the heating rate is 4-6 °C / min; the target temperature is 130-150 °C; the reaction time is 2-4 h; the filtration medium is a microporous filter with a pore size of 5-10 μm; the preheating temperature is 110 °C; the step of segmented cooling crystallization is as follows: first, rapidly cool from 110 °C to 50-60 °C at a cooling rate of 10-20 °C / h, then slowly cool from 50-60 °C to 0-10 °C at a cooling rate of 2-5 °C / h, and after cooling, keep at this temperature for 1-2 h.

[0014] Antimony trioxide reacts with ethylene glycol under heating conditions. The hydroxyl oxygen atom of ethylene glycol replaces the bridging oxygen atom in antimony trioxide to generate antimony glycolate with ethylene glycol as the chelating ligand. After the reaction is complete, the mixture is filtered while hot to remove unreacted solid impurities. The temperature control during hot filtration aims to prevent antimony glycolate from crystallizing at low temperatures and clogging pipelines and equipment. The filtrate is crystallized by staged cooling to control the crystal growth rate and particle size distribution: first, the temperature is rapidly cooled to an intermediate temperature to create a supersaturated environment that promotes the generation of a large number of crystal nuclei; then, the temperature is slowly cooled to a low temperature and kept at that temperature to allow the crystals to grow fully under a lower degree of supersaturation, resulting in antimony glycolate crystals with uniform particle size and high purity. During crystallization, antimony sites on the crystal surface lack ligand coverage in the direction of the lattice termination face facing outward, resulting in coordination vacancies. In the ethylene glycol medium, these vacancies are occupied by oxygen atoms of ethylene glycol molecules to form a surface ethylene glycol coordination layer. Among them, the ethylene glycol coordination at the defect sites is relatively weak, which provides a chemical basis for the selective desorption and surface modification of weakly coordinated ethylene glycol during the subsequent vacuum drying process.

[0015] In one feasible implementation, in step S4, the amount of trimethylolpropane-succinate added is 0.18-0.26 g; the centrifugation speed is 3000-4000 rpm, and the centrifugation time is 8-10 min; the impregnation step is: impregnating under a vacuum of -0.08 MPa for 5-10 min; the drying is vacuum drying, and the drying steps are: heating to 100-120°C at a heating rate of 2-3°C / min, maintaining for 1-2 h under a vacuum of ≤100 Pa, then heating to 130-150°C at a heating rate of 2-3°C / min, maintaining for 2-4 h under a vacuum of ≤100 Pa, and finally cooling to 80-100°C, maintaining for 1-2 h under a vacuum of ≤100 Pa.

[0016] Centrifugation of antimony glycol suspension yields wet crystals that retain a weakly coordinated solvent structure on the surface. When mixed and impregnated with trimethylolpropane-succinate and antimony-modified 1,2,4-butanetricarboxylic acid oligomers, ordered layered adhesion is achieved based on the molecular weight difference between the two modified components. The smaller molecule trimethylolpropane-succinate diffuses faster; its free hydroxyl groups form hydrogen bonds with the surface ethylene glycol, covering flat areas. Its free carboxylic acid esterifies with the antimony-hydroxyl groups at defect sites to form Sb-OC=O covalent bonds, achieving strong anchoring of defect sites and forming a uniform and robust pre-adsorbed substructure on the crystal surface. The macromolecular antimony-modified 1,2,4-butane tricarboxylic acid oligomer has a relatively slow migration rate and is subsequently uniformly deposited on the outside of the pre-adsorption layer. Its antimony-hydroxyl groups esterify with the carboxylic acid exposed in the pre-adsorption layer to form Sb-OC=O covalent bonds, which serve as the main bridging pathway to covalently connect the two layers. At the same time, its free carboxylic acid esterifies with the free hydroxyl groups of trimethylolpropane-succinate to form COC=O ester bonds to assist bridging. Meanwhile, intermolecular esterification and cross-linking reactions continue to occur between oligomer molecules, forming a continuous film.

[0017] By employing a programmed temperature-controlled vacuum drying process, weakly bound ethylene glycol molecules on the crystal surface can be selectively removed, fully exposing highly active antimony-hydroxyl unsaturated sites on the crystal surface and enhancing the stability and density of the protective structure. Simultaneously, long alkyl hydrophobic segments grafted onto the oligomer spontaneously align on the film surface, constructing a low-surface-energy hydrophobic barrier. Ultimately, a composite protective structure consisting of a covalent anchoring layer, a cross-linked film layer, and a hydrophobic barrier layer is formed on the surface of the antimony glycolate particles. This structure effectively prevents moisture intrusion under ambient temperature storage conditions, inhibiting the chain hydrolysis reaction at the antimony sites at its source, eliminating the generation of antimony trioxide impurities, and stabilizing the catalyst surface activity. When applied to polyester synthesis systems, this composite protective structure can naturally peel off along with the layer-by-layer dissolution of the antimony glycolate lattice in the ethylene glycol medium. Furthermore, the ester bond network of the protective layer can undergo transesterification reactions with ethylene glycol and terephthalic acid monomers under high-temperature polycondensation conditions, completely integrating into the polyester polymerization system without generating any foreign impurities. This fully ensures the normal functioning of the catalytic activity and rapid response performance of the antimony glycolate itself.

[0018] After centrifugation, the surface of the antimony glycol crystals is covered with a large amount of free ethylene glycol, and the interparticle spaces are also filled with ethylene glycol. This needs to be gradually removed through programmed temperature rise and vacuum drying. During the drying process, trimethylolpropane-succinate and antimony-modified aliphatic tricarboxylic acid oligomers migrate sequentially to the crystal surface under the drive of the temperature gradient. First, preliminary heating evaporates and removes the free ethylene glycol from the interparticle spaces, causing the liquid film on the crystal surface to gradually concentrate. Trimethylolpropane-succinate, due to its small molecular weight and fast diffusion rate, preferentially reaches the crystal surface. In flat areas, its free hydroxyl groups form hydrogen bonds with the surface lattice ethylene glycol to achieve coverage; its free carboxylic acid esterifies with antimony-hydroxyl groups at defect sites to achieve strong anchoring, forming a pre-adsorption layer that provides initial protection to the crystal surface. Meanwhile, the antimony-modified aliphatic tricarboxylic acid oligomers, due to their large molecular weight and slow diffusion rate, concentrate in the outer layer of the liquid film.

[0019] Further heating causes selective thermal desorption of weakly coordinated ethylene glycol at surface defect sites, exposing unsaturated antimony-hydroxyl groups. The oligomers are deposited onto the outer layer of the pre-adsorption layer in a further concentrated liquid film. Their free carboxylic acid esterifies with surface antimony-hydroxyl groups to form Sb-OC=O covalent bonds, achieving direct strong anchoring. The oligomers are bridged by Sb-OC=O covalent bonds formed through esterification of the free carboxylic acid in trimethylolpropane-succinate in the pre-adsorption layer with antimony-hydroxyl groups, while COC=O ester bonds are formed through esterification of the free carboxylic acid in trimethylolpropane-succinate to assist bridging. Subsequently, the oligomer molecules continue to cross-link through esterification of free carboxylic acid and antimony-hydroxyl groups, forming a continuous cross-linked film covering the pre-adsorption layer. The C atoms in the oligomer molecules... 18Alkyl chains spontaneously align on the outer surface of the film, forming a low-surface-energy hydrophobic barrier. Finally, cooling is performed, and residual ethylene glycol is further removed under vacuum. This stage utilizes the difference in desorption energy barriers between different bond types to achieve selective desorption. The bond energies of the Sb-OC=O and COC=O ester bonds are much higher than the coordination bond energies of the weakly coordinated ethylene glycol. At this temperature, the ester bonds remain stable, and only the residual weakly coordinated ethylene glycol continues to be removed, stabilizing and solidifying the protective structure, ultimately yielding a surface-modified antimony glycol catalyst.

[0020] In a second aspect, the present invention provides an antimony glycol catalyst, which is prepared by the preparation method described in the first aspect.

[0021] Thirdly, the present invention provides an application of antimony glycolate catalyst in polyester synthesis.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: This scheme prepares an antimony glycolate catalyst by generating antimony-modified 1,2,4-butanetricarboxylic acid oligomers and trimethylolpropane-succinate, exhibiting both high solubility and light transmittance and rapid catalytic response. The 1,2,4-butanetricarboxylic acid is modified by using hydrophobic C... 18 Long chains are grafted onto the 1,2,4-butanetricarboxylic acid backbone via ester bonds, and further condense with antimony trioxide to form a network oligomer. Adipic acid acts as a bridging agent, with its carboxyl groups at both ends esterified with antimony-hydroxyl groups, forming flexible segments between antimony atoms and increasing the flexibility of the oligomer segments. The antimony sites on the surface of antimony glycol crystals are located at the lattice termination plane, lacking ligands in the direction towards the outer edge of the lattice, thus possessing coordination vacancies. In solution, these vacancies can be occupied by the lone pair electrons of oxygen atoms in ethylene glycol. Through programmed temperature drying, the weakly coordinated ethylene glycol at surface defect sites is selectively desorbed, exposing stable and strongly electrophilic antimony-hydroxyl coordinated unsaturated sites. In the initial stage of drying, trimethylolpropane-succinate, due to its small molecular weight, diffuses rapidly to the crystal surface. Its free hydroxyl groups form hydrogen bonds with surface ethylene glycol, covering flat areas. Its free carboxylic acid esterifies with the antimony-hydroxyl groups at defect sites to form Sb-OC=O covalent bonds, achieving strong anchoring of defect sites and thus forming a pre-adsorption layer.

[0023] Subsequently, the antimony-modified 1,2,4-butanetricarboxylic acid oligomer, due to its large molecular weight and slow migration, is deposited and concentrated on the outer layer of the pre-adsorption layer. Its antimony-hydroxyl groups esterify with the exposed carboxylic acid in the pre-adsorption layer to form Sb-OC=O covalent bonds, serving as the main bridging pathway to covalently connect the two layers. Simultaneously, its free carboxylic acid esterifies with the free hydroxyl groups of trimethylolpropane-succinate to form COC=O ester bonds, assisting in bridging. Based on this, the oligomer molecules continue to cross-link through esterification between the free carboxylic acid and antimony-hydroxyl groups, forming a continuous film. The C18 alkyl chains grafted onto the periphery of the oligomers spontaneously align on the outer surface of the film, constructing a low surface energy hydrophobic barrier. This creates a triple protective structure on the particle surface: a covalent anchoring layer, a cross-linked film, and a hydrophobic barrier. Under room temperature storage conditions, this synergistically inhibits the chain hydrolysis reaction, fundamentally preventing the formation of an antimony trioxide thin layer and maintaining the catalyst surface activity. When the catalyst is added to the polyester synthesis system, the surface protective layer is naturally peeled off as the ethylene glycol antimony lattice dissolves layer by layer in ethylene glycol. The ester bond network therein undergoes transesterification reaction with ethylene glycol and terephthalic acid at the polycondensation temperature and is integrated into the system without generating foreign impurities. This solves the problems of existing ethylene glycol antimony catalysts, such as easy decomposition when exposed to moisture, low solubility and light transmittance, and catalytic response lag, caused by the exposed antimony sites on the particle surface and hydrolysis. Attached Figure Description

[0024] Figure 1 This is a physical image of the antimony glycol catalyst prepared in Example 1 of the present invention. Detailed Implementation

[0025] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the application will be further described in detail below with reference to embodiments. However, this should not be construed as limiting the scope of this application to the following examples. All other embodiments obtained by those skilled in the art without creative effort without departing from the above-described methodological spirit of this application are within the scope of protection of this application.

[0026] The singular forms “for,” “or,” “a,” “any,” and “described” used in this application are intended to include the plural forms unless the context clearly indicates otherwise. Furthermore, the terms “first” and “second” are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0027] Example 1 A method for preparing an antimony glycolate catalyst includes the following steps: S1. Heat 2g of trimethylolpropane to 65°C until it is completely melted, add 2.4g of succinic acid and 0.008g of p-toluenesulfonic acid, raise the temperature to 110°C under nitrogen protection, stir at 250rpm for 4h to obtain trimethylolpropane-succinate, and keep warm at 90°C for later use.

[0028] S2. 0.105 g of 1,2,4-butanetricarboxylic acid and 0.149 g of octadecyl alcohol were added to 7.5 g of ethylene glycol, and 0.003 g of p-toluenesulfonic acid was added as a catalyst. The mixture was stirred at 250 rpm at 105 °C for 2.5 h under nitrogen protection to obtain modified 1,2,4-butanetricarboxylic acid. 0.23 g of antimony trioxide and 0.021 g of adipic acid were added to the modified 1,2,4-butanetricarboxylic acid. The mixture was stirred at 250 rpm at 125 °C for 6 h under nitrogen protection to obtain antimony-modified 1,2,4-butanetricarboxylic acid oligomer, which was kept at 70 °C for later use.

[0029] S3. 100g of antimony trioxide and 650g of ethylene glycol were added to a 1L reactor equipped with a stirrer and reflux condenser. Under a nitrogen atmosphere, nitrogen was continuously introduced at a flow rate of 2L / min, and the temperature was raised to 140℃ at a rate of 5℃ / min. The reaction was carried out at this temperature with stirring at 250rpm for 3 hours to obtain an antimony glycolate solution. The antimony glycolate solution was filtered while hot through a microporous filter with a pore size of 7.5μm and a steam-heated insulation jacket. The filtrate was collected in a 500mL crystallization vessel preheated to 110℃. The filtrate was subjected to staged cooling crystallization under stirring at 150rpm. First, the temperature was rapidly reduced from 110℃ to 55℃ at a cooling rate of 15℃ / h, and then slowly reduced from 55℃ to 5℃ at a cooling rate of 3.5℃ / h. After cooling, the solution was kept at this temperature and allowed to stand for 1.5 hours to obtain a suspension containing antimony glycolate crystals.

[0030] S4. Centrifuge the suspension containing antimony glycolate crystals at 3500 rpm for 9 min to obtain wet crystals. Place the wet crystals at 27°C for 25 min under nitrogen protection to allow them to warm up. Add 0.22 g of trimethylolpropane-succinate to the insulated antimony-modified 1,2,4-butanetricarboxylic acid oligomer while hot, stir at 150 rpm for 5 min, add to the wet crystals, stir at 150 rpm for 7.5 min, and then impregnate under a vacuum of -0.08 MPa for 7 min to obtain the mixed wet crystals. The mixed wet crystals were transferred to a sealed vacuum dryer, with a packing thickness not exceeding 3 cm. A three-stage programmed temperature-controlled vacuum drying process was performed under a nitrogen atmosphere. The first stage involved heating to 110 °C at a rate of 2.5 °C / min and holding at a vacuum level ≤100 Pa for 1.5 h. The second stage involved heating to 140 °C at a rate of 2.5 °C / min and holding at a vacuum level ≤100 Pa for 3 h. The third stage involved cooling to 90 °C and holding at a vacuum level ≤100 Pa for 1.5 h. After drying, the mixture was cooled to 27.5 °C under a nitrogen atmosphere to obtain the antimony glycolate catalyst.

[0031] The antimony glycol catalyst prepared in this embodiment is as follows: Figure 1As shown, it appears as a uniform white powder, with fine and loose particles and no obvious agglomeration or clumping, indicating that the modified antimony glycolate crystal particles have good dispersibility.

[0032] Example 2 A method for preparing an antimony glycolate catalyst includes the following steps: S1. Heat 1.6g of trimethylolpropane to 60℃ to melt it completely, add 2.0g of succinic acid and 0.006g of p-toluenesulfonic acid, and heat to 100℃ under nitrogen protection and stir at 220rpm for 3h to obtain trimethylolpropane-succinate, which is then kept at 80℃ for later use.

[0033] S2. Add 0.06g of citric acid and 0.084g of octadecyl alcohol to 5g of ethylene glycol, add 0.001g of p-toluenesulfonic acid as a catalyst, and react under nitrogen protection at 100℃ with stirring at 200rpm for 2h to obtain modified citric acid; add 0.11g of antimony trioxide and 0.012g of adipic acid to the modified citric acid, and react under nitrogen protection at 120℃ with stirring at 200rpm for 4h to obtain antimony-modified citric acid oligomer, and keep it at 60℃ for later use.

[0034] S3. 100g of antimony trioxide and 500g of ethylene glycol were added to a 1L reactor equipped with a stirrer and reflux condenser. Under a nitrogen atmosphere, nitrogen was continuously introduced at a flow rate of 1L / min, and the temperature was raised to 130℃ at a rate of 4℃ / min. The reaction was carried out at this temperature with stirring at 200rpm for 2 hours to obtain an antimony glycolate solution. The antimony glycolate solution was filtered while hot through a microporous filter with a pore size of 5μm and a steam-heated insulation jacket. The filtrate was collected in a 500mL crystallization vessel preheated to 110℃. The filtrate was subjected to staged cooling crystallization under stirring at 100rpm. First, the temperature was rapidly reduced from 110℃ to 50℃ at a cooling rate of 10℃ / h, and then slowly reduced from 50℃ to 0℃ at a cooling rate of 2℃ / h. After cooling, the solution was kept at this temperature and allowed to stand for 1 hour to obtain a suspension containing antimony glycolate crystals.

[0035] S4. Centrifuge the suspension containing antimony glycolate crystals at 3000 rpm for 8 min to obtain wet crystals. Place the wet crystals at 25°C for 20 min under nitrogen protection to allow them to warm up. Add 0.18 g of trimethylolpropane-succinate to the insulated antimony-modified citric acid oligomer while hot, stir at 150 rpm for 5 min, add to the wet crystals, stir at 100 rpm for 5 min, and then impregnate under a vacuum of -0.08 MPa for 5 min to obtain the mixed wet crystals. The mixed wet crystals were transferred to a sealed vacuum dryer, with a packing thickness not exceeding 3 cm. A three-stage programmed temperature-controlled vacuum drying process was performed under a nitrogen atmosphere. The first stage involved heating to 100 °C at a rate of 2 °C / min and holding for 1 hour under a vacuum ≤100 Pa. The second stage involved heating to 130 °C at a rate of 2 °C / min and holding for 2 hours under a vacuum ≤100 Pa. The third stage involved cooling to 80 °C and holding for 1 hour under a vacuum ≤100 Pa. After drying, the mixture was cooled to 25 °C under a nitrogen atmosphere to obtain the antimony glycolate catalyst.

[0036] Example 3 A method for preparing an antimony glycolate catalyst includes the following steps: S1. Heat 2.4g of trimethylolpropane to 70°C until it is completely melted, add 2.8g of succinic acid and 0.01g of p-toluenesulfonic acid, raise the temperature to 120°C under nitrogen protection, and stir at 280rpm for 5h to obtain trimethylolpropane-succinate, and keep it at 90°C for later use.

[0037] S2. Add 0.15g of 1,2,4-butanetricarboxylic acid and 0.213g of octadecyl alcohol to 10g of ethylene glycol, add 0.005g of p-toluenesulfonic acid as an esterification catalyst, and react under nitrogen protection at 110℃ with stirring at 300rpm for 3h to obtain modified 1,2,4-butanetricarboxylic acid; add 0.35g of antimony trioxide and 0.03g of adipic acid to the modified 1,2,4-butanetricarboxylic acid, and react under nitrogen protection at 130℃ with stirring at 300rpm for 8h to obtain antimony-modified 1,2,4-butanetricarboxylic acid oligomer, and keep it at 80℃ for later use.

[0038] S3. 100g of antimony trioxide and 800g of ethylene glycol were added to a 1L reactor equipped with a stirrer and reflux condenser. Under a nitrogen atmosphere, nitrogen was continuously introduced at a flow rate of 3L / min, and the temperature was raised to 150℃ at a rate of 6℃ / min. The reaction was carried out at this temperature with stirring at 300rpm for 4 hours to obtain an antimony glycolate solution. The antimony glycolate solution was filtered while hot through a microporous filter with a pore size of 10μm and a steam-heated insulation jacket. The filtrate was collected in a 500mL crystallization vessel preheated to 110℃. The filtrate was subjected to staged cooling crystallization under stirring at 200rpm. First, the temperature was rapidly reduced from 110℃ to 60℃ at a cooling rate of 20℃ / h, and then slowly reduced from 60℃ to 10℃ at a cooling rate of 5℃ / h. After cooling, the solution was kept at this temperature and allowed to stand for 2 hours to obtain a suspension containing antimony glycolate crystals.

[0039] S4. Centrifuge the suspension containing antimony glycol crystals at 4000 rpm for 10 min to obtain wet crystals. Place the wet crystals at 30°C for 30 min under nitrogen protection to allow them to warm up. Add 0.26 g of trimethylolpropane-succinate to the heat-insulated antimony-modified 1,2,4-butanetricarboxylic acid oligomer while hot, stir at 150 rpm for 5 min, add to the wet crystals, stir at 200 rpm for 10 min, and then impregnate under a vacuum of -0.08 MPa for 10 min to obtain the mixed wet crystals. The mixed wet crystals were transferred to a sealed vacuum dryer, with a packing thickness not exceeding 3 cm. A three-stage programmed temperature-controlled vacuum drying process was performed under a nitrogen atmosphere. The first stage involved heating to 120 °C at a rate of 3 °C / min and holding for 2 hours under a vacuum ≤100 Pa. The second stage involved heating to 150 °C at a rate of 3 °C / min and holding for 4 hours under a vacuum ≤100 Pa. The third stage involved cooling to 100 °C and holding for 2 hours under a vacuum ≤100 Pa. After drying, the mixture was cooled to 30 °C under a nitrogen atmosphere to obtain the antimony glycolate catalyst.

[0040] Comparative Example 1 A method for preparing an antimony glycol catalyst differs from Example 1 in that the antimony-modified 1,2,4-butane tricarboxylic acid oligomer and trimethylolpropane succinate are not prepared; the remaining steps and parameters are the same as in Example 1.

[0041] Comparative Example 2 A method for preparing an antimony glycolate catalyst differs from Example 1 in that trimethylolpropane-succinate is not prepared; the remaining steps and parameters are the same as in Example 1.

[0042] Comparative Example 3 A method for preparing an antimony glycol catalyst differs from Example 1 in that the antimony-modified 1,2,4-butanetricarboxylic acid oligomer was not prepared; the remaining steps and parameters are the same as in Example 1.

[0043] Performance testing: Dissolution and transmittance test: Take 0.25g of the antimony glycolate catalyst samples prepared in Examples 1-3 and Comparative Examples 1-3 respectively and place them in conical flasks. Add 25g of ethylene glycol and stir magnetically at 200rpm for 30min in a 60℃ constant temperature water bath to dissolve the catalyst. After dissolution, cool the solution to 25℃ and transfer it to a 25mL volumetric flask. Wash the conical flask three times with a small amount of ethylene glycol and transfer the washings to the volumetric flask. Dilute to the mark with ethylene glycol, shake well, and let stand in a 25℃ constant temperature bath for 10min to allow the temperature to equalize. Transfer the solution to a 1cm cuvette and measure the transmittance at a wavelength of 500nm using a UV-Vis spectrophotometer. Dilute to the same volume with pure ethylene glycol as a reference. Each sample is measured in parallel three times and the average value is taken.

[0044] Catalytic response time test: 80g of terephthalic acid and 53.8g of ethylene glycol were weighed and added to the reaction vessel. 0.083g of the ethylene glycol antimony catalyst samples prepared in Examples 1-3 and Comparative Examples 1-3 were added respectively. The reaction was carried out under nitrogen protection, with the temperature increased to 250℃ at a rate of 5℃ / min and the stirring speed continuously at 80rpm. After the reaction proceeded for 90min, a vacuum was drawn. The vacuum was reduced to 50kPa within 10min and maintained for 10min, then reduced to 10kPa within another 10min and maintained for 10min. n, and finally the pressure was reduced to ≤100 Pa within 10 min, while the temperature was increased to 275 °C at a rate of 3 °C / min to carry out the polycondensation reaction. During the polycondensation stage, the stirring speed was switched to 40 rpm. The time when the vacuum degree reached ≤100 Pa and the temperature reached 275 °C was recorded as the start time of polycondensation. The power reading of the stirring motor at the start of polycondensation was taken as the initial power P0. The power reading of the stirring motor was recorded every 5 min. The time required for the power reading of the stirring motor to reach 3P0 was taken as the catalytic response time. Each sample was measured twice in parallel and the average value was taken.

[0045] Color b-value test: Weigh 80.0g of terephthalic acid and 53.8g of ethylene glycol into the reaction vessel, and add 0.083g of the ethylene glycol antimony catalyst samples prepared in Examples 1-3 and Comparative Examples 1-3 respectively. Under nitrogen protection, the temperature is increased to 250℃ at a rate of 5℃ / min and reacted for 90min. After esterification, the vacuum is gradually reduced to ≤100Pa according to the same vacuum gradient as the catalytic response time test. At the same time, the temperature is increased to 275℃ at a rate of 3℃ / min to carry out polycondensation reaction. During the polycondensation stage, the stirring speed is 40rpm. When the stirring motor power reaches 4P0, the material is discharged (P0 is constant). (For the catalytic response time test), the polyester melt was rapidly poured into ice water for rapid cooling and granulation. Within 5 minutes after granulation, the polyester chips were transferred to a vacuum dryer and dried for 4 hours at 120℃ and a vacuum degree ≤50Pa. The dried polyester chips were then hot-pressed at 260℃ and 5MPa for 5 minutes to form a transparent sheet with a thickness of 2.0mm. After hot pressing, the sheet was quickly demolded and allowed to cool naturally at room temperature. Three qualified sheets were selected and the hue b value was measured using a colorimeter under a D65 light source. Three different positions were measured on each sheet, and the average of the nine measured values ​​of the three sheets was taken as the hue b value of the sample.

[0046] Storage stability test: The antimony glycolate catalyst samples prepared in Examples 1-3 and Comparative Examples 1-3 were uniformly spread in glass petri dishes with a diameter of 90 mm and a layer thickness of 3 mm. The petri dishes were placed horizontally in a single layer in a constant temperature and humidity chamber and stored openly for 30 days at a temperature of 25°C and a relative humidity of 60%. At the same time, standard antimony glycolate samples with a known solubility transmittance ≥98% were stored synchronously in the same conditions and location with the same layer thickness as controls. Before storage, the initial solubility transmittance of all samples and controls was uniformly measured. After 30 days of storage, samples were uniformly taken from within 2 mm of the sample surface and the solubility transmittance after storage was measured according to the above solubility transmittance test method. The difference between the transmittance after storage and the initial transmittance was calculated as the transmittance decrease value. The measurements were performed in parallel for 3 times and the average value was taken. The transmittance decrease value of the control sample was used to correct for systematic errors.

[0047] Table 1. Performance test results of the antimony glycolate catalysts prepared in Examples 1-3 and Comparative Examples 1-3

[0048] As shown in Table 1, the antimony glycolate catalysts prepared in Examples 1-3 have higher solubility and solubility after storage than those in Comparative Examples 1-3. Furthermore, their catalytic response time, hue b value, and transmittance decrease are lower than those in Comparative Examples 1-3. This indicates that the antimony glycolate catalysts prepared in Examples 1-3 have better solubility, transmittance, catalytic response, and storage stability than those in Comparative Examples 1-3.

[0049] In Comparative Example 1, without the preparation of antimony-modified 1,2,4-butanetricarboxylic acid oligomers and trimethylolpropane-succinate, the antimony sites on the surface of the antimony glycol particles were exposed to air during vacuum drying due to desorption from weakly coordinated ethylene glycol. During subsequent storage, these sites underwent a chain hydrolysis reaction upon direct contact with moisture in the air, resulting in the formation of a thin layer of antimony trioxide on the surface. This thin layer acts as a dissolution barrier, hindering the dissolution and diffusion of the catalyst in ethylene glycol, leading to a significant decrease in dissolution transmittance. Furthermore, it reduces the effective antimony concentration available for polycondensation, prolonging the catalytic response time. Simultaneously, the trivalent antimony oxides in the hydrolysis products exhibit a color interference effect at the polycondensation temperature, causing a significant increase in the b-value of the polyester hue. After 30 days of storage, continuous chain hydrolysis caused the antimony trioxide thin layer to thicken further, and the dissolution transmittance decreased further, indicating that surface hydrolysis of the unprotected antimony glycol catalyst under normal storage conditions is an irreversible and continuous deterioration process.

[0050] Comparative Example 2 did not prepare trimethylolpropane-succinate, and the particle surface lacked the bridging effect of a pre-adsorption layer. The oligomer could only be directly anchored at defect sites via Sb-OC=O ester bonds. However, in the flat areas occupying most of the particle surface, the surface antimony sites were still occupied by chelated ethylene glycol, preventing effective anchoring of the oligomer. Coverage was achieved only through physical adsorption, resulting in weak bonding. This point-strong, area-weak coverage state led to incomplete and weak bonding of the oligomer film in flat areas. Moisture could penetrate along the gaps between the film and the surface to the exposed antimony sites in the flat areas, triggering hydrolysis. This resulted in a significant decrease in transmittance, prolonged catalytic response time, increased hue b-value, and decreased transmittance after storage. This indicates that without the bridging effect of a pre-adsorption layer, the oligomer film cannot achieve complete planar coverage, significantly weakening the protective effect.

[0051] Comparative Example 3 did not prepare antimony-modified 1,2,4-butanetricarboxylic acid oligomers; the particle surface only had a pre-adsorption layer without a cross-linked film or hydrophobic barrier. Although trimethylolpropane-succinate could achieve full surface coverage in flat areas through hydrogen bonding adsorption and in defect sites through esterification anchoring, it is a monolayer structure with weak hydrogen bonding and no barrier to water vapor. Water vapor can directly penetrate the pre-adsorption layer to reach the antimony sites on the surface and trigger hydrolysis. Simultaneously, the pre-adsorption layer itself does not contain hydrophobic alkyl chains and cannot provide a hydrophobic barrier. Dissolution transmittance decreased significantly, catalytic response time was significantly prolonged, hue b-value increased, and the transmittance decrease after storage increased significantly. This indicates that the protective effect of the pre-adsorption layer alone is extremely limited; it solves the coverage problem but not the barrier problem. Water vapor penetration triggers chain hydrolysis, demonstrating the decisive role of the cross-linked film and hydrophobic barrier in protection.

[0052] Comparative Examples 1-3, due to the absence of antimony-modified 1,2,4-butanetricarboxylic acid oligomer and trimethylolpropane-succinate, resulted in the direct chain hydrolysis of antimony sites on the particle surface under the action of water vapor, forming a thin layer of antimony trioxide. The oligomer film was not sufficiently anchored in flat areas, allowing water vapor to penetrate along the gaps in the film and causing local hydrolysis. The pre-adsorption layer could not block water vapor penetration, and the surface antimony sites continued to hydrolyze under the direct invasion of water vapor. All of these factors resulted in varying degrees of deterioration in solubility, light transmittance, catalytic responsiveness, and storage stability.

[0053] The above results demonstrate and describe the basic principles and main features of this application, as well as its advantages.

[0054] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for preparing an antimony glycolate catalyst, characterized in that, Includes the following steps: S1. Trimethylolpropane is heated to melt, succinic acid and p-toluenesulfonic acid are added, the reaction is carried out, and the mixture is kept warm for later use to obtain trimethylolpropane-succinate. S2. Add aliphatic tricarboxylic acid and octadecyl alcohol to ethylene glycol, add p-toluenesulfonic acid, and after the first reaction, obtain modified aliphatic tricarboxylic acid; add antimony trioxide and adipic acid to the modified aliphatic tricarboxylic acid, and after the second reaction, keep warm for later use, to obtain antimony-modified aliphatic tricarboxylic acid oligomer. S3. Mix antimony trioxide and ethylene glycol, heat, react, filter, collect the filtrate in a preheated crystallization vessel, and crystallize by cooling in stages to obtain a suspension containing antimony glycol crystals. S4. Centrifuge the suspension containing antimony glycolate crystals to obtain wet crystals; Trimethylolpropane-succinate was added to antimony-modified aliphatic tricarboxylic acid oligomer, dispersed, added to wet crystals, impregnated and dried to obtain antimony glycolate catalyst.

2. The method for preparing an antimony glycolate catalyst according to claim 1, characterized in that, In step S1, the mass ratio of trimethylolpropane, succinic acid, and p-toluenesulfonic acid is (1.6-2.4):(2.0-2.8):(0.006-0.01); the target heating temperature is 60-70℃; the reaction temperature is 100-120℃; and the reaction time is 3-5 hours.

3. The method for preparing an antimony glycolate catalyst according to claim 1, characterized in that, In S2, the aliphatic tricarboxylic acid is selected from one or more of 1,2,4-butanetricarboxylic acid and citric acid; the mass ratio of the aliphatic tricarboxylic acid, octadecyl alcohol, ethylene glycol, p-toluenesulfonic acid, antimony trioxide and adipic acid is (0.06-0.15):(0.084-0.213):(5-10):(0.001-0.005):(0.11-0.35):(0.012-0.03).

4. The method for preparing an antimony glycolate catalyst according to claim 1, characterized in that, In step S2, the temperature of the first reaction is 100-110℃ and the reaction time is 2-3 hours; the temperature of the second reaction is 120-130℃ and the reaction time is 4-8 hours.

5. The method for preparing an antimony glycolate catalyst according to claim 1, characterized in that, In step S3, the mass ratio of antimony trioxide to ethylene glycol is 100:(500-800); the target temperature for heating is 130-150℃; and the reaction time is 2-4 hours.

6. The method for preparing an antimony glycolate catalyst according to claim 1, characterized in that, In step S3, the filtration medium is a microporous filter with a pore size of 5-10 μm; the preheating temperature is 110℃; the step of segmented cooling crystallization is as follows: first, the temperature is lowered from 110℃ to 50-60℃ at a cooling rate of 10-20℃ / h, and then slowly lowered from 50-60℃ to 0-10℃ at a cooling rate of 2-5℃ / h. After the cooling is completed, the temperature is maintained and left to stand for 1-2 hours.

7. The method for preparing an antimony glycolate catalyst according to claim 1, characterized in that, In step S4, the amount of trimethylolpropane-succinate added is 0.18-0.26g; the centrifugation speed is 3000-4000rpm, and the centrifugation time is 8-10min; the impregnation step is: impregnation under vacuum conditions of -0.08MPa for 5-10min.

8. The method for preparing an antimony glycolate catalyst according to claim 1, characterized in that, In step S4, the drying is vacuum drying, and the drying steps are as follows: heating to 100-120℃ at a heating rate of 2-3℃ / min and holding for 1-2 hours, then heating to 130-150℃ at a heating rate of 2-3℃ / min and holding for 2-4 hours, and finally cooling to 80-100℃ and holding for 1-2 hours.

9. An antimony glycol catalyst, characterized in that, It is obtained by the preparation method according to any one of claims 1-8.

10. The application of the antimony glycol catalyst as described in claim 9 in polyester synthesis.

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