A catalyst and preparation of a saturated resin for molding

Abstract

The application relates to a catalyst and preparation and molding of saturated resin, and belongs to the technical field of resin material preparation. The catalyst is composed of a solute and an organic solvent, the solute is composed of a titanium catalyst and a potassium / aluminum catalyst mixed according to a weight ratio of 1:0.5-2.0; the preparation steps are as follows: 1) respectively dehydrating polyhydric alcohol, saturated dibasic acid and epoxy resin; 2) adding the products and the catalyst of step 1) into a reactor, under nitrogen protection, heating to 175-180 DEG C and keeping warm, then heating to 200-205 DEG C and keeping warm, until the acid value is 11-13 mgKOH / g, and dehydrating in the whole process; 3) cooling to 80-100 DEG C, adding styrene and a polymerization inhibitor and mixing uniformly; and saturated resin is obtained. The saturated resin for molding prepared by the application has the characteristics of light color, transparency and zero shrinkage, and the catalyst can shorten the esterification polycondensation period.

Description

Technical Field

[0001] This invention belongs to the field of resin material preparation technology, specifically relating to a catalyst and the preparation of a saturated resin for molding. Background Technology

[0002] Saturated resin for molding is the core material for the molding process. It refers to a resin system with a saturated molecular structure that can be cured into a solid product through molding. It is mainly used to prepare various molded structural parts and decorative parts, and is widely used in the automotive, electronics, and building materials industries. Its performance directly determines the quality and performance of the molded products.

[0003] Existing industrial molding saturated resins have many drawbacks: they are prone to volume shrinkage during curing, leading to warping, cracking, and surface depressions in the products, failing to meet mid-to-high-end demands; the finished products have a dark color and low transparency, limiting their application range. In their preparation, the synthetic raw materials have low reactivity, and commonly used tin, acid, and amine catalysts have limitations, resulting in slow esterification and polycondensation reactions with a cycle of 8-12 hours. High-temperature reactions can also trigger oxidative degradation and side reactions of the raw materials, exacerbating appearance defects and affecting the mechanical properties of the products.

[0004] Furthermore, its molecular structure lacks suitable active groups, resulting in poor compatibility with other components in the system. It is prone to layering and precipitation, leading to surface mottling, insufficient smoothness, and reduced service life. Existing optimization methods are not very effective. Increasing the amount of catalyst can easily lead to excessive resin crosslinking and increased brittleness, while adding compatibilizers results in uneven dispersion, failing to fundamentally solve the core problems.

[0005] A Chinese invention patent entitled "A Saturated Polyester Resin for Use as a Low Shrinkage Agent in Molding Plastics and Its Preparation Method" (publication number CN101508828A) describes the preparation of a low-shrinkage saturated polyester resin by polymerizing propylene glycol, ethylene glycol, dipropylene glycol and aliphatic diacids in styrene. Although this resin can achieve low shrinkage, good water resistance and toughness, and is suitable for white coloring, it still has problems such as uneven dispersion and easy separation when compounded with unsaturated resins and calcium powder, making it difficult to meet the needs of high-end transparent and high-gloss molded products.

[0006] A Chinese invention patent entitled "A Saturated Polyester Thickening Low-Shrinkage Resin for SMC / BMC" (publication number CN115926061A) describes the synthesis of a thickening low-shrinkage resin by using saturated polyacids, aliphatic polyols, and crosslinking agents to participate in the SMC / BMC thickening system. While this can solve the problems of low-shrinkage resin precipitation, poor product appearance, and low strength, the resin synthesis requires strict control of the staged heating rate and acid value range. Excessive thickening speed can easily lead to a surge in material viscosity, and the shrinkage rate control of some formulations is unstable, resulting in large fluctuations in mechanical properties. This makes it difficult to adapt to high-end molded products with high requirements for shrinkage precision and appearance.

[0007] In summary, the catalysts used in the existing methods for preparing saturated resins for molding have problems such as low reaction efficiency and easy initiation of side reactions. Furthermore, the saturated resins for molding themselves have performance defects and shortcomings in the preparation process, which cannot meet the needs of high-end molded products. Therefore, optimizing the preparation process of saturated resins for molding, improving their performance, and developing efficient catalysts that are suitable for their synthesis requirements have become technical challenges that urgently need to be overcome in this field. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a catalyst and preparation method for saturated resin for molding. The saturated resin for molding prepared by the present invention has the characteristics of light color, transparency and zero shrinkage, and the catalyst can shorten the esterification polycondensation cycle.

[0009] To achieve the above objectives, this invention provides a catalyst composed of a solute and an organic solvent. The solute is a mixture of a titanium-based catalyst and a potassium / aluminum-based catalyst in a weight ratio of 1:0.5~2.0. The combination of the titanium-based and potassium / aluminum-based catalysts creates a synergistic catalytic effect, which both increases the reaction rate and improves the color of the finished product.

[0010] Excessive use of titanium-based catalysts can lead to excessively rapid reaction rates, easily causing runaway reactions and direct solidification of materials within the reactor, preventing normal resin preparation. Insufficient use of titanium-based catalysts results in insufficient catalytic activity, significantly prolonging the esterification and polycondensation cycle, and causing the finished product to darken in color. Excessive use of potassium / aluminum-based catalysts disrupts the synergistic catalytic balance, significantly darkening the finished product and affecting its transparency. Insufficient use of potassium / aluminum-based catalysts fails to effectively suppress the oxidative degradation of raw materials and side reactions, also causing the finished product to darken in color and prolonging the reaction time. Titanium-based catalysts and potassium / aluminum-based catalysts must be mixed in a ratio of 1:0.5 to 2.0 to achieve the desired effects of rapid reaction, light color, and high compatibility of this invention.

[0011] The titanium-based catalyst is at least one selected from isopropyl titanate, tetrabutyl titanate, and tetraethyl titanate; the potassium / aluminum-based catalyst is at least one selected from potassium isooctanoate, alumina, and aluminum hydroxide. Isopropyl titanate is preferred as the titanium-based catalyst due to its high catalytic activity, which can significantly accelerate the esterification and polycondensation reaction; potassium / aluminum-based catalysts are preferred as potassium isooctanoate and aluminum hydroxide due to their good stability, ability to inhibit the oxidative degradation of raw materials, and reduction of yellowing in the finished product.

[0012] Preferably, the titanium-based catalyst is isopropyl titanate; preferably, the potassium / aluminum-based catalyst is a mixture of aluminum hydroxide and potassium isooctanoate in a weight ratio of 1:0.68~2.10. The weight ratio of isopropyl titanate, aluminum hydroxide, and potassium isooctanoate is 1.68~3.10:1:0.68~2.10. Excessive aluminum hydroxide will darken the color of the finished product; insufficient aluminum hydroxide will inhibit oxidative degradation, have insufficient color protection, and result in a significantly darker color and decreased catalytic stability. Excessive potassium isooctanoate will darken the color of the finished product and decrease its transparency; insufficient potassium isooctanoate will fail to effectively inhibit yellowing and stabilize the reaction system, resulting in a darker color and poorer reaction stability. The above ratio range can achieve the optimal reaction time and the best color. When the weight ratio of isopropyl titanate, potassium isooctanoate, and aluminum hydroxide is too high, the color will deepen. When the weight ratio of isopropyl titanate, potassium isooctanoate, and aluminum hydroxide is too low, the reaction time will increase and the color will deepen.

[0013] The weight ratio of solute to organic solvent is 0.1~0.2:1; the solute concentration is appropriate to avoid agglomeration or insufficient activity, ensure catalytic efficiency, and shorten the reaction cycle; it forms a uniform and stable system, which is easy to disperse subsequently, contributing to the stability of the finished product's color and compatibility; the amount of organic solvent is reasonable, balancing cost and effect, and adapting to large-scale production; it takes into account both catalytic activity and stability. Excessive solute can easily lead to agglomeration, uneven dispersion, and locally excessive catalytic activity, triggering side reactions, resulting in a darker resin color and decreased reaction stability. Insufficient solute results in insufficient effective catalytic components, reduced catalytic efficiency, prolonged esterification polycondensation cycle, and inability to achieve rapid reaction. Excessive organic solvent leads to over-dilutation, a low effective catalytic concentration, and a slower reaction rate; increased residual solvent affects the resin's solid content and subsequent curing performance; insufficient organic solvent leads to incomplete dissolution, an uneven system, difficulty in stable catalyst dispersion, locally excessive / insufficient catalysis, resulting in reaction fluctuations and a worsened finished product color.

[0014] The organic solvent is methanol or ethanol; the ethanol is anhydrous ethanol; the organic solvent of the present invention can ensure the uniformity of subsequent dispersion and help the reaction proceed stably; the preferred organic solvent is methanol, which has less residue and does not affect the color and compatibility of the finished product; it has stronger dissolving power and a more stable catalyst system.

[0015] Another aspect of the present invention provides a method for preparing a catalyst, comprising the following steps: mixing a titanium-based catalyst and a potassium / aluminum-based catalyst at a weight ratio under conditions of 20–30°C; then adding an organic solvent and mixing and dissolving the mixture to obtain the catalyst.

[0016] Preferably, the saturated resin for molding, by weight, comprises the following components: 434.7-603.7 parts of polyol, 876.0-905.2 parts of saturated diacid, 40.9-135.8 parts of epoxy resin, 0.20-0.24 parts of polymerization inhibitor, 755-780 parts of styrene, and 9.50-10.66 parts of catalyst; the polyol is at least one selected from ethylene glycol, propylene glycol, and diethylene glycol; preferably, ethylene glycol and propylene glycol are the optimal diol combination, which allows the resin to achieve the best results in terms of comprehensive performance, color, reaction efficiency, and compatibility. The saturated diacid is adipic acid; the polymerization inhibitor is at least one selected from methylhydroquinone, trimethylhydroquinone, and hydroquinone; preferably, methylhydroquinone is the polymerization inhibitor. Because no maleic anhydride or fumaric acid is added to the saturated resin for molding, the prepared saturated resin has the characteristic of zero shrinkage.

[0017] The present invention also provides a method for preparing a saturated resin for molding using the above-mentioned catalyst, comprising the following steps: (1) Dehydrate the polyol, saturated dicarboxylic acid and epoxy resin respectively until the water content is ≤0.1% to obtain the product; (2) Add the product and catalyst described in step (1) into the reactor, and under nitrogen protection, heat to 175~180℃ and keep warm for 1~1.5h; then heat to 200~205℃ at a heating rate of 10~15℃ / h and keep warm until the acid value is 11~13mgKOH / g; dehydrate the entire process of step (2) to obtain the product; (3) Cool the product from step (2) to 80~100℃, add styrene and polymerization inhibitor, and mix well to obtain saturated resin for molding.

[0018] The weight ratio between the epoxy resin added in step (1) and the polyol and saturated diacid added is 0.03 to 0.09:1. The above-mentioned epoxy resin dosage range can coordinate the interaction between the components, achieve the best compatibility effect, and ensure a stable state without stratification or precipitation. When the epoxy resin addition is too low, due to insufficient epoxy group content, it cannot achieve sufficient compatibility with the unsaturated resin, resulting in stratification. When the epoxy resin addition is too high, the excessive epoxy groups will react excessively with the hydroxyl and carboxyl groups of the molding saturated resin and the active groups of the unsaturated resin, resulting in a significant reduction in the proportion of effective groups that can combine with the unsaturated polyester resin in the system, leading to stratification. Step (1) Dehydrate using an oven at 90~105℃.

[0019] The epoxy resin mentioned in step (1) is a bisphenol A type epoxy resin with an epoxy value of 0.4~0.6 eq / 100g; the epoxy groups can react with the hydroxyl and carboxyl groups of the zero-shrinkage material and the active groups of the unsaturated resin to form an interfacial transition layer, thereby improving compatibility; and its light color and good compatibility ensure that the saturated resin used for molding is transparent and light in color.

[0020] The molar ratio of the polyol to the saturated diacid in step (1) is 1.03~1.07:1, referred to as the alkyd-acid ratio; that is, the molar ratio of the amount of polyol added in step (1) to the amount of saturated diacid added is 1.03~1.07:1. If the alkyd-acid ratio is too low, the esterification reaction will be incomplete, the reaction time will be significantly prolonged, the color of the product will be darker, and it will separate and precipitate when compounded with unsaturated polyester resin; if the alkyd-acid ratio is too high, the esterification will be incomplete, the purity of the product will decrease, the reaction time will be prolonged, the color will be darker, and it will also separate and precipitate, resulting in poor compatibility. The alkyd-acid ratio within the above range can balance reaction efficiency and quality, thereby obtaining the optimal reaction time and color, and achieving the best compatibility effect of no separation and no precipitation. When the alkyd-acid ratio exceeds the range of this invention, it will cause incomplete esterification, resulting in prolonged reaction time, darker color of the product, and separation and precipitation problems during the compounding process with unsaturated polyester resin.

[0021] The top-temperature holding time in this application refers to the holding time under the highest temperature condition during the entire reaction process. The purpose of the top-temperature holding time is to allow the esterification polycondensation reaction to proceed fully until the acid value reaches 11-13 mgKOH / g, which is a core parameter determining the reaction cycle and resin quality.

[0022] Step (2) involves dehydration throughout to promote the forward reaction; the reaction temperature is 200~205℃. At this temperature, the water generated by the esterification reaction turns into water vapor and is discharged with nitrogen. Step (2) under nitrogen protection can prevent the raw materials and products from being oxidized. Heating to 200~205℃ at a rate of 10~15℃ / h can reduce the occurrence of side reactions. Epoxy resin is added at the beginning of the synthesis to participate in the polymerization reaction and is uniformly grafted onto the molecular chain of the saturated resin used for molding, which fundamentally solves the compatibility with unsaturated resin and avoids uneven dispersion caused by physical mixing in the later stage. In step (2), the temperature is further increased to 200~205℃ at a rate of 10~15℃ / h and held for 3~4h, with an acid value of 11~13mgKOH / g. The catalyst of this invention is used at a temperature of 175~205℃, and the heating rate from 175~180℃ to 200~205℃ during the use of the catalyst needs to be controlled within the range of 10~15℃ / h.

[0023] In step (2), the weight ratio of the product from step (1) to the catalyst is 222~256:1. If this ratio is too high, the esterification polycondensation cycle will be greatly extended, the raw material oxidation degradation and side reactions will increase, the color of the finished product will be greatly deepened, the transparency will decrease, the reaction will be incomplete, the resin performance will decrease, and the compatibility with unsaturated resin and calcium powder will deteriorate. If this ratio is too low, the local catalysis will be too strong, the side reactions will be aggravated, the resin color will be deepened, the brittleness will increase, the crosslinking will be excessive, and the subsequent molding and mechanical properties of the product will be affected.

[0024] Compared with the prior art, the beneficial effects of this invention are: 1. The zero-shrinkage saturated resin for molding prepared by this invention is characterized by its light color, transparency, and zero shrinkage. Furthermore, the synergistic effect of titanium-based and potassium / aluminum-based catalysts shortens the esterification polycondensation cycle. The titanium-based catalyst and potassium / aluminum-based catalyst are compounded at a ratio of 1:0.5~2.0, producing a synergistic effect that significantly accelerates the esterification polycondensation reaction, reducing the top-temperature holding time to 3~4 hours, far superior to the traditional 8~12 hours. The synthesis cycle of the saturated resin for molding prepared by this invention is 4~5 hours; the color is ≤1 Gardner; and no stratification occurs when mixed with unsaturated resin and calcium powder and allowed to stand for 24 hours.

[0025] 2. The molding saturated resin preparation method of the present invention produces resin with light color, high transparency, zero shrinkage after curing, and the product does not warp, crack, or sink, meeting the requirements of high-end molding; the epoxy resin participates in polymerization in the early stage and is grafted onto the molecular chain, and there is no stratification or precipitation when it is left to stand with unsaturated resin and calcium powder for 24 hours, and the surface is smooth and bright.

[0026] 3. The catalyst of this application is simple to prepare, and the synthesis of zero-shrinkage saturated resin for molding does not require complex equipment. The reaction parameters are easy to control, the cost is controllable, and it is suitable for large-scale industrial production with broad application prospects.

[0027] 4. The catalyst of this invention has a working temperature range of 175~205℃ and a heating rate of 10~15℃ / h. Using the catalyst of this invention improves the stability of the resin preparation process and the yield of the finished product. Detailed Implementation

[0028] Example 2 is the preferred embodiment of the present invention. The present invention will be further described below with reference to specific embodiments and comparative examples.

[0029] The chemical additives used in the embodiments and comparative examples of this invention are all commercially available, and the specific information is as follows: Ethylene glycol: Lijin Leo Chemical Co., Ltd.; Propylene glycol: Cangzhou Jinzhan Chemical Co., Ltd.; Diethylene glycol: Changzhou Chemical and Light Industrial Materials Corporation; Adipic acid: Ningbo Zhongxing New Material Technology Co., Ltd.; Bisphenol A type epoxy resin: Jiangyin Jizhan Chemical Trade Co., Ltd.; CAS: 1675-54-3; Isopropyl titanate: Shanghai Maclean Biochemical Technology Co., Ltd.; Potassium isooctanoate: Shandong Yousuo Chemical Technology Co., Ltd.; Aluminum hydroxide: Henan Jinhuoban Chemical Products Co., Ltd.; Methanol: Zouping Jinyi Chemical Co., Ltd.; Anhydrous ethanol: Pingyuan Xuxin Experimental Instrument Co., Ltd.; Styrene: Zhejiang Sunrise Basic Chemical Co., Ltd.; Methylhydroquinone: Changzhou Yurong Chemical Co., Ltd.; Hydroquinone: Changzhou Yurong Chemical Co., Ltd.; Tetrabutyl titanate: Shanghai Maclean Biochemical Technology Co., Ltd.; Tetraethyl titanate: Shanghai Maclean Biochemical Technology Co., Ltd.; Alumina: Shanghai Maclean Biochemical Technology Co., Ltd.; Calcium powder is heavy calcium carbonate: Wenzhou Junyi Building Materials Co., Ltd.

[0030] Table 1. Raw materials used in the examples (by weight). .

[0031] Example 1 A method for preparing a catalyst, comprising the following steps: At 20°C, titanium-based catalyst and potassium / aluminum-based catalyst were mixed in a weight ratio; then an organic solvent was added and the mixture was dissolved to obtain the catalyst. A method for preparing a saturated resin for molding comprises the following steps: (1) Dehydrate the polyol, saturated dicarboxylic acid and epoxy resin respectively until the water content is ≤0.1%; Step (1) Dehydrate using an oven at 90℃; (2) Add the product and catalyst described in step (1) into the reactor, and under nitrogen protection, heat to 175°C and keep warm for 1.5 h; then heat to 200°C at a rate of 10°C / h and keep warm for 4 h until the acid value is 11 mg KOH / g; dehydration is carried out throughout the entire process of step (2); (3) Cool the product from step (2) to 80°C, add styrene and polymerization inhibitor, and mix well to obtain a saturated resin for molding.

[0032] Example 2 A method for preparing a catalyst, comprising the following steps: At 25°C, titanium-based catalyst and potassium / aluminum-based catalyst were mixed in a weight ratio; then an organic solvent was added and the mixture was dissolved to obtain the catalyst. A method for preparing a saturated resin for molding comprises the following steps: (1) Dehydrate the polyol, saturated dicarboxylic acid and epoxy resin respectively until the water content is ≤0.1%; Step (1) uses an oven to dehydrate at 103℃; (2) Add the product and catalyst described in step (1) into the reactor, and under nitrogen protection, heat to 177°C and keep warm for 1.3h; then heat to 203°C at a rate of 13°C / h and keep warm for 3.5h until the acid value is 12mgKOH / g; the entire process of step (2) is dehydrated; (3) Cool the product from step (2) to 90°C, add styrene and polymerization inhibitor, and mix well to obtain a saturated resin for molding.

[0033] Example 3 A method for preparing a catalyst, comprising the following steps: At 30°C, titanium-based catalyst and potassium / aluminum-based catalyst were mixed in a weight ratio; then an organic solvent was added and the mixture was dissolved to obtain the catalyst. A method for preparing a saturated resin for molding comprises the following steps: (1) Dehydrate the polyol, saturated dicarboxylic acid and epoxy resin respectively until the water content is ≤0.1%; Step (1) Dehydrate using an oven at 105℃; (2) Add the product and catalyst described in step (1) into the reactor, and under nitrogen protection, heat to 180°C and keep warm for 1.5 h; then heat to 205°C at a rate of 15°C / h and keep warm for 3 h until the acid value is 13 mg KOH / g; dehydration is carried out throughout the entire process of step (2); (3) Cool the product from step (2) to 100°C, add styrene and polymerization inhibitor, and mix well to obtain a saturated resin for molding.

[0034] Example 4 A method for preparing a catalyst, comprising the following steps: At 25°C, titanium-based catalyst and potassium / aluminum-based catalyst were mixed in a weight ratio; then an organic solvent was added and the mixture was dissolved to obtain the catalyst. A method for preparing a saturated resin for molding comprises the following steps: (1) Dehydrate the polyol, saturated dicarboxylic acid and epoxy resin respectively until the water content is ≤0.1%; Step (1) uses an oven to dehydrate at 103℃; (2) Add the product and catalyst described in step (1) into the reactor, and under nitrogen protection, heat to 177°C and keep warm for 1.3h; then heat to 203°C at a rate of 13°C / h and keep warm for 3.5h until the acid value is 12mgKOH / g; the entire process of step (2) is dehydrated; (3) Cool the product from step (2) to 90°C, add styrene and polymerization inhibitor, and mix well to obtain a saturated resin for molding.

[0035] Example 5 A method for preparing a catalyst, comprising the following steps: At 25°C, titanium-based catalyst and potassium / aluminum-based catalyst were mixed in a weight ratio; then an organic solvent was added and the mixture was dissolved to obtain the catalyst. A method for preparing a saturated resin for molding comprises the following steps: (1) Dehydrate the polyol, saturated dicarboxylic acid and epoxy resin respectively until the water content is ≤0.1%; Step (1) uses an oven to dehydrate at 103℃; (2) Add the product and catalyst described in step (1) into the reactor, and under nitrogen protection, heat to 177°C and keep warm for 1.3h; then heat to 203°C at a rate of 13°C / h and keep warm for 3.5h until the acid value is 12mgKOH / g; the entire process of step (2) is dehydrated; (3) Cool the product from step (2) to 90°C, add styrene and polymerization inhibitor, and mix well to obtain a saturated resin for molding.

[0036] Table 2 shows the raw materials used in Comparative Examples 1-6 (in parts by weight). .

[0037] Table 3 shows the raw materials used in Comparative Examples 7-13 (in parts by weight). .

[0038] Comparative Example 1 The preparation method of the saturated resin for molding described in this comparative example is the same as that in Example 2, except that the amount of bisphenol A epoxy resin used is too low; see Table 2 for the specific formula.

[0039] Comparative Example 2 The preparation method of the saturated resin for molding described in this comparative example is the same as that in Example 2, except that the amount of bisphenol A epoxy resin used is too high; see Table 2 for the specific formula.

[0040] Comparative Example 3 The preparation method of the saturated resin for molding described in this comparative example is the same as that in Example 2, except that the alkyd-acid ratio is too low. For the specific formulation, please refer to Table 2.

[0041] Comparative Example 4 The preparation method of the saturated resin for molding described in this comparative example is the same as that in Example 2, except that the alkyd-acid ratio is too high. For the specific formulation, please refer to Table 2.

[0042] Comparative Example 5 The preparation method of the saturated resin for molding described in this comparative example is the same as that in Example 2, except that the amount of catalyst used is too low. For the specific formula, please refer to Table 2.

[0043] Comparative Example 6 The preparation method of the saturated resin for molding described in this comparative example is the same as that in Example 2, except that the amount of catalyst used is too high. For the specific formula, please refer to Table 2.

[0044] Comparative Example 7 The preparation method of the saturated resin for molding described in this comparative example is the same as that in Example 2, except that the weight ratio of isopropyl titanate, potassium isooctanoate, and aluminum hydroxide is too high and the amount of organic solvent used is different. For the specific formula, please refer to Table 3.

[0045] Comparative Example 8 The preparation method of the saturated resin for molding described in this comparative example is the same as that in Example 2, except that the weight ratio of isopropyl titanate, potassium isooctanoate, and aluminum hydroxide is too low and the amount of organic solvent is different. For the specific formula, please refer to Table 3.

[0046] Comparative Example 9 The preparation method of the saturated resin for molding described in this comparative example is the same as that in Example 2, except that aluminum hydroxide is not added. For the specific formula, please refer to Table 3.

[0047] Comparative Example 10 The preparation method of the saturated resin for molding described in this comparative example is the same as that in Example 2, except that potassium isooctanoate is not added. For the specific formula, please refer to Table 3.

[0048] Comparative Example 11 The preparation method of the saturated resin for molding described in this comparative example is the same as that in Example 2, except that isopropyl titanate is not added. For the specific formulation, please refer to Table 3.

[0049] Comparative Example 12 The formulation of the saturated resin for molding described in this comparative example is the same as that in Example 2, except that the heating rate in step (2) is lower than that in this invention. For the specific formulation, please refer to Table 3. The specific preparation method for step (2) is as follows: Add the product and catalyst described in step (1) into the reactor, raise the temperature to 177°C under nitrogen protection, and keep it at that temperature for 1.3 h; then raise the temperature to 203°C at a rate of 9°C / h and keep it at that temperature for 3.5 h until the acid value is 12 mg KOH / g; dehydration is carried out in the entire process of step (2).

[0050] Comparative Example 13 The formulation of the saturated resin for molding described in this comparative example is the same as that in Example 2, except that the heating rate in step (2) is higher than that in this invention. For the specific formulation, please refer to Table 3. The specific preparation method for step (2) is as follows: Add the product and catalyst described in step (1) into the reactor, raise the temperature to 177°C under nitrogen protection, and keep it at that temperature for 1.3 h; then raise the temperature to 203°C at a rate of 16°C / h and keep it at that temperature for 3.5 h until the acid value is 12 mg KOH / g; dehydration is carried out in the entire process of step (2).

[0051] Performance testing The performance of the saturated resins prepared in the examples and comparative examples was tested, and the specific test results are shown in Table 4.

[0052] Color comparison is based on Gardner's colorimetric method.

[0053] Compatibility test: Under the condition of 20~30℃, saturated resin, unsaturated polyester resin and calcium powder are mixed in a weight ratio of 10~30:70:150 and allowed to stand for 24h to obtain a compound resin paste; the calcium powder is heavy calcium carbonate.

[0054] Shrinkage test: The compatibility test results of the compound resin paste without stratification are tested according to GB / T 2567.

[0055] Table 4. Test results of the examples and comparative examples .

[0056] The titanium-based and potassium / aluminum-based catalysts of this invention are compounded at a weight ratio of 1:0.5~2.0, and combined with an organic solvent, significantly shortening the esterification polycondensation cycle. Compared to the traditional 6~10h top-temperature holding time, the top-temperature holding time of the saturated resin for molding in this embodiment is 3~4h, and it can inhibit the oxidative degradation of raw materials and reduce yellowing of finished products. The saturated resin for molding of this invention has the characteristics of ≤1 color Gardner, transparency, and zero shrinkage, and has excellent compatibility with unsaturated resins, solving the pain points of poor compatibility and dark color of traditional zero-shrinkage materials. This invention improves compatibility by using epoxy resin to participate in the polymerization reaction to achieve molecular linking. It is suitable for high-end molded products with high requirements for dimensional accuracy and appearance quality, such as pressed ping-pong tables and automotive plastic sheets.

[0057] If stratification occurs, the shrinkage rate cannot be tested. In this application, the shrinkage rate must be less than 0.05% to be considered zero shrinkage. In Comparative Example 1, the amount of bisphenol A epoxy resin was too low, resulting in insufficient epoxy group content and an inability to form an effective interfacial transition layer, leading to poor compatibility. In Comparative Example 2, the amount of bisphenol A epoxy resin was too high. Excessive epoxy groups react excessively with the hydroxyl, carboxyl, and active groups of the unsaturated resin in the zero-shrinkage material, significantly reducing the proportion of effective groups that can combine with the unsaturated polyester resin in the system, ultimately causing stratification and affecting compatibility. In Comparative Example 3, the alkyd-acid ratio was too low, prolonging the synthesis cycle; the color deepened; and stratification and precipitation occurred. In Comparative Example 4, the alkyd-acid ratio was too high. Excess polyol caused a shift in reaction equilibrium, incomplete esterification, decreased purity, and problems with color, compatibility, and reaction efficiency. In Comparative Example 5, the amount of catalyst was too low, prolonging the synthesis cycle and causing a deeper color. In Comparative Example 6, the excessive catalyst dosage led to an overly rapid reaction rate, causing runaway and direct solidification of the material within the reactor, making color and compatibility testing impossible. In Comparative Example 7, the excessive weight ratio of isopropyl titanate, potassium isooctanoate, and aluminum hydroxide resulted in a darker color. In Comparative Example 8, the excessively low weight ratio of isopropyl titanate, potassium isooctanoate, and aluminum hydroxide prolonged the synthesis cycle and darkened the color. In Comparative Example 9, the absence of aluminum hydroxide in the catalyst resulted in a darker color in the finished product. In Comparative Example 10, the absence of potassium isooctanoate in the catalyst also resulted in a darker color in the finished product. In Comparative Example 11, the absence of isopropyl titanate in the catalyst slowed the reaction rate, and the longer synthesis cycle also affected the color to some extent. In Comparative Example 12, controlling the heating rate to 9℃ / h during the preparation of saturated resin resulted in a darker color. In Comparative Example 13, controlling the heating rate to 16℃ / h during the preparation of saturated resin resulted in stratification.

[0058] The saturated resin for molding of the present invention has a synthesis cycle of 4-5 hours; its color is ≤1 Gardner; and it shows no stratification when mixed with unsaturated resin and calcium powder and left to stand for 24 hours.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A catalyst, characterized in that: It consists of two parts: a solute and an organic solvent. The solute is composed of a mixture of titanium-based catalyst and potassium / aluminum-based catalyst in a weight ratio of 1:0.5~2.

0.

2. The catalyst according to claim 1, characterized in that: The titanium-based catalyst is at least one of isopropyl titanate, tetrabutyl titanate, and tetraethyl titanate; the potassium / aluminum-based catalyst is at least one of potassium isooctanoate, alumina, and aluminum hydroxide.

3. A catalyst according to claim 1 or 2, characterized in that: The titanium-based catalyst is isopropyl titanate; the potassium / aluminum-based catalyst is a mixture of aluminum hydroxide and potassium isooctanoate in a weight ratio of 1:0.68~2.

10.

4. The catalyst according to claim 1, characterized in that: The weight ratio of the solute to the organic solvent is 0.1~0.2:

1.

5. The catalyst according to claim 1, characterized in that: The organic solvent is methanol or ethanol.

6. A method for preparing a catalyst according to any one of claims 1 to 5, characterized in that, The process includes the following steps: at 20–30°C, titanium-based catalyst and potassium / aluminum-based catalyst are mixed in a weight ratio; then an organic solvent is added and the mixture is dissolved to obtain the catalyst.

7. A method for preparing a saturated resin for molding, characterized in that, Includes the following steps: (1) Dehydrate the polyol, saturated dicarboxylic acid and epoxy resin respectively until the water content is ≤0.1% to obtain the product; (2) Add the product described in step (1) and the catalyst described in any one of claims 1 to 5 into the reactor, and under nitrogen protection, heat to 175 to 180°C and keep warm for 1 to 1.5 h; then heat to 200 to 205°C at a heating rate of 10 to 15°C / h and keep warm until the acid value is 11 to 13 mg KOH / g; dehydrate the entire process of step (2) to obtain the product; (3) Cool the product from step (2) to 80~100℃, add styrene and polymerization inhibitor, and mix well to obtain saturated resin for molding.

8. The method for preparing a saturated resin for molding according to claim 7, characterized in that: The weight ratio between the amount of epoxy resin added in step (1) and the amount of polyol and saturated dicarboxylic acid added is 0.03 to 0.09:

1.

9. The method for preparing a saturated resin for molding according to claim 7, characterized in that: The molar ratio of the polyol to the saturated dicarboxylic acid in step (1) is 1.03~1.07:

1.

10. A method for preparing a saturated resin for molding according to claim 7, characterized in that: In step (2), the weight ratio of the product from step (1) to the catalyst is 222~256:1.