Unsaturated polyester resin for imitation jade handicrafts and preparation method of unsaturated polyester resin

Abstract

The invention discloses unsaturated polyester resin for imitation jade handicrafts and a preparation method thereof, and belongs to the technical field of polyester resin. Comprising the following components: diethylene glycol, methylpropanediol, propylene glycol, maleic anhydride, phthalic anhydride, an antioxidant, a polymerization inhibitor, paraffin, a stabilizer, an ultraviolet light absorber, a whitening agent and a diluent. The weight ratio of the propylene glycol to the methyl propylene glycol is (1.0-1.3): 1, and the methyl propylene glycol accounts for 20-22% of the total amount of the dihydric alcohol; the weight ratio of maleic anhydride to phthalic anhydride is (0.46-0.52): 1; the preparation method comprises 1) adding the raw materials and the antioxidant into a reactor, carrying out heating, carrying out heat preservation for 0.5-1.0 h and continuing heating, 2) carrying out a reaction for 2-3 h after heating, carrying out dehydration until an acid value is 20-25 mgKOH / g, and 3) carrying out cooling, adding the auxiliary agent and carrying out uniform mixing so that the unsaturated polyester resin is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of polyester resins, and particularly relates to an unsaturated polyester resin for jade-like handicrafts and a preparation method thereof. Background Art

[0002] Unsaturated polyester resins are widely used in a wide range of fields due to their excellent low-temperature curing properties, simple operation procedures, and reasonable prices. Using unsaturated polyester resin as a matrix, these resins are thoroughly mixed with various fillers and auxiliary materials, then cast into a mold. Demolding, grinding, and polishing processes produce exquisitely shaped and lifelike resin crafts. With the continuous improvement of modern living standards, people's demand for handicrafts is growing, and the resin craft market continues to unleash its potential, showing extremely broad development prospects. At the same time, market requirements for the quality of resin crafts are also constantly increasing, especially in the field of jade imitation crafts, which impose more stringent standards on resin performance.

[0003] The resin used in jade-like crafts must be colorless or light-colored to facilitate coloring, and after curing, exhibit brilliant colors and an attractive luster. Furthermore, the resin must possess high hardness and toughness, as well as good impact and heat resistance. However, existing unsaturated polyester resins for crafts made from jade-like crafts suffer from the problem of unstable chemical bonds within the resin molecules absorbing ultraviolet light, which triggers photodegradation reactions, leading to molecular chain breakage and the formation of chromophores. This results in yellowing, reduced gloss, and decreased physical strength. Therefore, existing unsaturated polyester resins do not meet the requirements for jade-like crafts. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide an unsaturated polyester resin for imitation jade handicrafts and a preparation method thereof. The resin of the present invention is water white, and its liquid indicators and physical properties can meet the requirements of imitation jade handicrafts.

[0005] In order to achieve the above object, the present invention provides an unsaturated polyester resin for imitation jade handicrafts, which is composed of the following components, calculated by weight: 16.2-16.8 parts of diethylene glycol, 6.0-6.6 parts of methyl propylene glycol, 6.6-7.8 parts of propylene glycol, 11.73-13 parts of maleic anhydride, 25-25.53 parts of phthalic anhydride, 0.052-0.058 parts of antioxidant, 0.0038-0.0043 parts of polymerization inhibitor, 0.052-0.058 parts of paraffin wax, 0.0009-0.0012 parts of stabilizer, 0.03-0.035 parts of ultraviolet absorber, 0.0025-0.0035 parts of brightener and 31.8418-32.6215 parts of diluent; The weight ratio of propylene glycol to methyl propylene glycol is 1.0-1.3:1, and methyl propylene glycol accounts for 20-22% of the total amount of diols; the weight ratio of maleic anhydride to phthalic anhydride is 0.46-0.52:1.

[0006] Preferably, the unsaturated polyester resin for imitation jade handicrafts comprises the following components, by mass percentage: 16.5 parts of diethylene glycol, 6.3 parts of methylpropylene glycol, 7.2 parts of propylene glycol, 12.4 parts of maleic anhydride, 25.3 parts of phthalic anhydride, 0.055 parts of triphenyl phosphite, 0.004 parts of hydroquinone, 0.055 parts of paraffin, 0.001 parts of cobalt isooctanoate, 32.15 parts of methylstyrene, 0.032 parts of 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, and 0.003 parts of 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene; the weight ratio of propylene glycol to methylpropylene glycol is 1.14:1, and methylpropylene glycol accounts for 21% of the total amount of diols; and the weight ratio of maleic anhydride to phthalic anhydride is approximately 0.49:1.

[0007] Due to its strong water absorption, propylene glycol can improve the wettability of resins and promote adhesion between resins and substrates. However, excessive amounts of propylene glycol can increase the hydroxyl density, accelerating oxidation side reactions during high-temperature stages to form chromophores. Increasing the amount of propylene glycol used results in a pale yellowish color in the resin, which can affect the quality of handicrafts. The branched structure of methylpropanediol reduces molecular symmetry, inhibiting crystallization and imparting high stability to the resin. However, excessive branching increases molecular chain steric hindrance. It offers a balance of strength and flexibility, exhibiting excellent chemical, weather, and UV resistance. Diethylene glycol, a long-chain diol, has ether bonds in its molecular structure that increase the flexibility of the resin chain and reduce crosslinking density, thereby imparting enhanced toughness to the resin. Toughness is related to tensile strength and elongation at break.

[0008] When the weight ratio of propylene glycol to methylpropylene glycol is within the range of 1.0 to 1.3, the resin appears watery white, and the color difference of the handicraft is less than 0.5. When the weight ratio of propylene glycol to methylpropylene glycol exceeds the range of 1.0 to 1.3, the resin color gradually changes to light yellow to yellow, and the color difference increases significantly. Excessive methylpropylene glycol content can increase molecular chain rigidity, restrict the cross-linking network, and cause fluctuations in the exothermic peak temperature.

[0009] The weight ratio of propylene glycol to methylpropylene glycol is 1.0 to 1.3:1. Propylene glycol optimizes the fluidity of the resin, and methylpropylene glycol enhances weather resistance and chemical resistance. A balance is achieved between process performance and long-term stability within the weight ratio of 1.0 to 1.3:1.

[0010] Methylpropanediol accounts for 20 to 22% of the total diols. This proportion range ensures that the long-chain flexible structure of methylpropanediol is fully integrated into the resin network, giving the product sufficient toughness to simulate the texture of jade, while avoiding excessive amounts that lead to a decrease in tensile strength; when the proportion of methylpropanediol exceeds 22%, the resin's hydrolysis resistance is improved but the viscosity increases, affecting the uniformity of filler dispersion; below 20%, the UV aging resistance is insufficient, making it difficult to meet the long-term outdoor use needs of imitation jade crafts.

[0011] The weight ratio of maleic anhydride to phthalic anhydride is 0.46 to 0.52:1. When the weight ratio of maleic anhydride to phthalic anhydride is lower than 0.46, the reaction activity and reaction rate will decrease. When the cooling acid value reaches 20 to 25 mgKOH / g, the gel time will be longer, the post-curing time will be extended, and the exothermic peak will be low, resulting in poor curing effect of the handicraft, reduced physical properties, and low shrinkage after curing, which is not conducive to demolding. When the weight ratio of maleic anhydride to phthalic anhydride is higher than 0.52, the reaction activity and reaction rate will increase, the crosslinking density will be too high, the impact strength will decrease, the gel time will be faster, the post-curing time will be shortened, and the exothermic peak will be high, resulting in rapid heat release during the production of handicrafts, causing deformation or cracks, or even cracking. The high exothermic peak and rapid heat release will also lead to increased shrinkage, affecting the product effect.

[0012] Preferably, the weight ratio of maleic anhydride to phthalic anhydride is 0.47 to 0.51:1, which can avoid curing delay caused by a low ratio or rapid curing caused by a high ratio, thereby improving physical properties and structural stability.

[0013] Maleic anhydride contains double bonds, increasing the resin's crosslinking density and hardness, but excessive amounts can make the resin more brittle. Phthalic anhydride's benzene ring structure enhances heat resistance and rigidity, simulating the luster of jade. A ratio of 0.46 to 0.52:1 ensures the resin retains the texture of jade while also withstanding the mechanical stresses of processing.

[0014] The antioxidant is triphenyl phosphite, which decomposes hydroperoxides to block oxidative chain reactions, reducing yellowing of polymer materials caused by aging. The polymerization inhibitors are hydroquinone, p-benzoquinone, methylhydroquinone, tert-butylhydroquinone, or tert-butylcatechol. Phenol-based polymerization inhibitors capture free radicals within their benzene ring structure, blocking chain polymerization reactions. All polymerization inhibitors are compatible with unsaturated resins, and unreacted residues do not interfere with the transparency and mechanical properties of jade-like products, meeting the required surface gloss. Hydroquinone effectively slows resin self-polymerization by capturing free radicals and also acts as an antioxidant, inhibiting yellowing. The introduction of a tert-butyl group into tert-butylhydroquinone enhances thermal stability through a significant steric hindrance. The methyl group in methylhydroquinone enhances molecular solubility, improving compatibility with resin systems and making it suitable for complex formulations. p-Benzoquinone maintains stable polymerization inhibition activity even at high temperatures, making it particularly suitable for jade-like resin processes requiring heat curing. p-Benzoquinone can inhibit the early polymerization, and tert-butylhydroquinone can delay the late gelation.

[0015] The stabilizer is copper octoate or copper naphthenate; it has a stable molecular structure, high thermal stability, good compatibility with the resin system, and no residue affecting transparency. The stabilizer also has anti-corrosion properties, making it suitable for applications requiring long-term corrosion resistance.

[0016] The weight ratio of copper octanoate to copper naphthenate is 1.5 to 4:1. A synergistic effect is achieved within this range, primarily based on molecular structural complementarity and redox synergy. Copper octanoate improves the dispersibility of copper naphthenate. A preferred weight ratio of 3:1 ensures a more stable exotherm during the curing process, optimizing mechanical properties and gloss.

[0017] The paraffin wax is 52# paraffin wax or 54# paraffin wax; it has high purity, high chemical inertness, strong processing applicability, and small volume shrinkage.

[0018] The diluent is styrene or methylstyrene; styrene can effectively reduce resin viscosity and improve filler wettability. As a traditional diluent, styrene is inexpensive and has high copolymerization activity with unsaturated polyesters. It can quickly initiate a curing reaction at room temperature, shortening the production cycle of handicrafts. Methylstyrene has a lower volatile organic compound content, reducing the release of irritating gases during processing, which is in line with the environmental trend of styrene-free resins. The methyl substituent enhances the thermal stability of the molecule and can reduce bubble formation during high-temperature curing processes. It is particularly suitable for high-transparency imitation jade products that require heat molding. Styrene reduces viscosity, and methylstyrene retards gelation. When the two are mixed, they can achieve a viscosity-reactivity balance.

[0019] The UV absorber is 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole or 2-(2'-hydroxy-3,5'-di-tert-amylphenyl)benzotriazole. 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole absorbs UV light in the 270-340nm wavelength range, providing particularly effective protection against long-wave UV rays. It converts UV energy into heat through intramolecular hydrogen bonding, reducing resin photodegradation. It disperses evenly in a variety of polymers and minimally affects resin transparency, making it suitable for transparent or light-colored products. The disubstituted groups in 2-(2'-hydroxy-3,5'-di-tert-amylphenyl)benzotriazole enhance absorption efficiency. The di-tert-amyl groups ortho to the hydroxyl group increase molecular steric hindrance, enhancing short-wave UV absorption and making it suitable for use in more demanding UV exposure environments.

[0020] The whitening agent is 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene. The bisbenzoxazolyl group significantly enhances fluorescence emission efficiency through conjugation, giving the jade-like resin a luster closer to that of natural jade. The 5-tert-butyl substituent effectively inhibits molecular thermal motion, reducing the risk of side reactions with free radicals or oxidation products in the resin system, and maintains whitening stability even during curing processes at temperatures above 120°C. This whitening agent absorbs 290-400nm ultraviolet light generated during resin aging and emits blue light, reducing yellowing of the product after long-term exposure. The whitening agent's molecular structure matches the polarity of the diluent styrene, reducing its migration tendency. Combined with the hydrophobic effect of the tert-butyl group, the whitening agent's migration rate in the styrene dilution system is reduced.

[0021] The weight ratio of UV absorber to brightener is 8.75 to 14.0:1. Within this ratio, the synergistic effect of the two is primarily manifested in optimizing gloss, balancing cure and mechanical properties, and improving weather resistance. The brightener enhances the resin's initial gloss by scattering UV and visible light, while the UV absorber inhibits photodegradation by absorbing high-energy UV rays. A UV absorber content of 0.03 to 0.035 parts does not significantly interfere with the curing reaction, and the brightener does not affect the resin's crosslink density. This synergistic effect maintains gloss retention after light exposure and inhibits discoloration caused by molecular chain breakage, thereby extending the resin's service life.

[0022] When the ratio of the two exceeds the above range, the synergistic effect is destroyed, the curing efficiency and reaction activity are unbalanced, and the mechanical properties conflict with the optical stability. When the UV absorber is excessive, its heat absorption characteristics interfere with the curing heat release; when the UV absorber is added in insufficient parts by weight, it accelerates surface oxidation and increases color difference. When the whitening agent is excessive, it causes abnormal refractive index inside the resin, resulting in microfluorescence; when the whitening agent is added in insufficient parts by weight, it exacerbates uneven light scattering, resulting in increased color difference.

[0023] According to another aspect of the present invention, there is also provided a method for preparing the unsaturated polyester resin for the above-mentioned jade-like handicraft, comprising the following steps: (1) Add diethylene glycol, methyl propylene glycol, propylene glycol, maleic anhydride, phthalic anhydride and antioxidant into the reactor according to weight, heat to 155-165°C, keep the temperature for 0.5-1.0h, and then continue to heat to 200-210°C; (2) React at 200-210°C for 2-3 hours; when the acid value reaches 50-55 mgKOH / g, dehydrate; (3) Cooling the mixture and adding a polymerization inhibitor and paraffin wax by weight; cooling the mixture again and adding a stabilizer and a diluent by weight; continuing to cool the mixture and adding an ultraviolet absorber and a brightener by weight, and mixing the mixture; and obtaining an unsaturated polyester resin for jade-like handicrafts.

[0024] The heating rate for further heating to 200-210°C in step (1) is 12-14°C / h. The heating rate of 12-14°C / h is used to prevent local overheating that may cause isomerization failure of maleic anhydride and to avoid sudden cooling that may cause resin phase separation or component segregation.

[0025] Step (2) The reaction is carried out at 200-210° C. for 2-3 hours. When the acid value reaches 50-55 mgKOH / g, dehydration is carried out at 200-210° C. until the acid value reaches 20-25 mgKOH / g. The water generated by the reaction is removed by dehydration, which promotes the reaction toward polyester chain growth, thereby reducing the acid value from 50-55 mgKOH / g to 20-25 mgKOH / g and improving the esterification rate. The acid value of 20-25 mgKOH / g improves water resistance by reducing the hydrophilic carboxyl groups while retaining sufficient cross-linking sites.

[0026] The specific operation of step (3) is to cool the mixture and add the polymerization inhibitor and paraffin wax by weight; cool the mixture again and add the stabilizer and diluent by weight; continue to cool the mixture and add the ultraviolet absorber and brightener by weight; mix the mixture to obtain the unsaturated polyester resin for jade imitation crafts.

[0027] The polymerization inhibitor must disperse rapidly in a molten state at 170-190°C to ensure full contact with the polyester molecular chains and form an effective free radical capture network. Paraffin wax is liquid at high temperatures, and its liquid coating on the resin surface inhibits premature gelation. Adding a diluent by weight at 90-110°C reduces volatility and prevents premature decomposition of the stabilizer. Adding a UV absorber by weight at 50-60°C maintains the stability of its UV absorption peak. Brighteners undergo an esterification side reaction with residual anhydride at high temperatures; low temperatures can control their degradation rate.

[0028] If the temperature is lowered to 50-60°C at one time and inhibitor, paraffin, stabilizer, diluent, UV absorber and brightener are added by weight at the same time, the viscosity of the polyester in the reactor is high, the inhibitor is unevenly dispersed, resulting in gel after the diluent is added, and the paraffin solidifies at 50-60°C, resulting in uneven dispersion. The amount of UV absorber and brightener added is small, and the wall adhesion will affect the adding effect.

[0029] According to another aspect of the present invention, the present invention also provides the use of the unsaturated polyester resin described above or the unsaturated polyester resin prepared by the above method in imitation jade crafts. The imitation jade craft preparation method includes: uniformly mixing the resin described in each embodiment and comparative example with aluminum hydroxide powder, adding cobalt isooctanoate, a special accelerator for crafts, and methyl ethyl ketone peroxide, a special curing agent for crafts. After thorough mixing, the mixture is poured into a mold, which is placed in a constant temperature and humidity chamber. After curing, the mold is removed and demolded to obtain a casting, which is the imitation jade craft. Preferably, the resin and aluminum hydroxide powder are uniformly mixed in a weight ratio of 1:1.3 to 1.7. More preferably, the resin and aluminum hydroxide powder are uniformly mixed in a weight ratio of 1:1.5.

[0030] Compared with the prior art, the present invention has the following beneficial effects: 1. The present application optimizes the ratio of propylene glycol, methyl propylene glycol and diethylene glycol, uses an appropriate ratio of phthalic anhydride to maleic anhydride, and reacts until the acid value reaches 20-25 mgKOH / g. The viscosity and curing time of the finished resin are beneficial to the production and processing of handicrafts. After adding fillers, the resin is evenly distributed and the heat release is slow and uniform, avoiding cracks or cracks caused by excessive heat release during product curing. The appropriate shrinkage rate is beneficial to demoulding and does not affect the product effect. The present application achieves a comprehensive breakthrough in the processing adaptability, mechanical strength and appearance quality of the resin through the coordinated control of molecular structure optimization and process parameters. The present invention is water white, and the hardness, tensile strength, elongation at break, flexural strength and impact strength can all meet the requirements of handicrafts. Toughness is related to tensile strength and elongation at break.

[0031] 2. In this application, the compounding of copper octanoate and copper naphthenate in a weight ratio of 1.5 to 4:1 can exert a synergistic effect, release heat steadily during the curing process, and improve mechanical properties and gloss.

[0032] 3. The synergistic effect of UV absorbers and brighteners optimizes gloss, balances curing and mechanical properties, and makes the processed crafts have excellent gloss, stable color and physical properties, and maintains good gloss after long-term light exposure, thereby improving weather resistance. DETAILED DESCRIPTION

[0033] Example 9 is the best embodiment of the present invention. The present invention will be further described below with reference to specific examples and comparative examples.

[0034] The chemical additives used in the examples and comparative examples of the present invention are all commercially available, and their specific information is as follows: Diethylene glycol: industrial grade, purchased from Ningbo Hongyixin Import and Export Co., Ltd. Methylpropanediol: industrial grade, purchased from Nanjing Deze Chemical Co., Ltd. Propylene glycol: industrial grade, purchased from Guangdong Hongjiu New Materials Co., Ltd. Maleic anhydride: industrial grade, purchased from Shandong Dechuan New Materials Co., Ltd. Phthalic anhydride: industrial grade, purchased from Hubei Nengtai Technology Co., Ltd. Triphenyl phosphite: industrial grade, purchased from Changhe Chemical New Materials (Jiangsu) Co., Ltd. Hydroquinone: industrial grade, purchased from Changzhou Yurong Chemical Co., Ltd. p-Benzoquinone: industrial grade, purchased from Jinan Xichuan Chemical Technology Co., Ltd. Methylhydroquinone: industrial grade, purchased from Wuxi Qianfeng Chemical Technology Co., Ltd. 4-tert-Butylhydroquinone: industrial grade, purchased from Changzhou Yurong Chemical Co., Ltd. 52# paraffin wax: industrial grade, purchased from Jingmen Weijia Industrial Co., Ltd.; 54# paraffin wax: industrial grade, purchased from Jingmen Weijia Industrial Co., Ltd.; Cobalt 2-ethylhexanoate: industrial grade, purchased from Shanghai Pudong Tongzhou Chemical Co., Ltd. Copper naphthenate: industrial grade, purchased from Shanghai Pudong Tongzhou Chemical Co., Ltd. Styrene: industrial grade, purchased from Aolid International Trading Co., Ltd., Zhangjiagang Free Trade Zone; Methyl styrene: industrial grade, purchased from Shandong Jinghao Chemical Co., Ltd. 2-(2'-Hydroxy-5'-tert-octylphenyl)benzotriazole: industrial grade, purchased from Changzhou Yurong Chemical Co., Ltd. 2-(2'-Hydroxy-3,5'-di-tert-pentylphenyl)benzotriazole: industrial grade, purchased from Changzhou Yurong Chemical Co., Ltd. 2,5-Bis(5-tert-butyl-2-benzoxazolyl)thiophene: industrial grade, purchased from Changzhou Yurong Chemical Co., Ltd. Cobalt 2-ethylhexanoate: industrial grade, purchased from Shanghai Taoyuan Cobalt Industry Co., Ltd. Methyl ethyl ketone peroxide: CAS number 131-11-3, purchased from Tianjin Nouryon Peroxide Co., Ltd. Constant temperature and humidity incubator: Shaoxing Bowei Instrument Equipment Co., Ltd.

[0035] Example 1 The present embodiment is a formula of unsaturated polyester resin for imitation jade handicraft, which is composed of the following ingredients: 16.8 parts of diethylene glycol, 6.6 parts of methylpropylene glycol, 6.6 parts of propylene glycol, 12 parts of maleic anhydride, 25.53 parts of phthalic anhydride, 0.052 parts of triphenyl phosphite, 0.0043 parts of hydroquinone, 0.058 parts of 52# paraffin, 0.0012 parts of copper isooctanoate, 32.321 parts of styrene, 0.03 parts of 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, and 0.0035 parts of 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene; the weight ratio of propylene glycol to methylpropylene glycol is 1:1, and methylpropylene glycol accounts for 22% of the total diols; the weight ratio of maleic anhydride to phthalic anhydride is 0.47:1; The preparation method of this embodiment comprises the following steps: (1) Diethylene glycol, methyl propylene glycol, propylene glycol, maleic anhydride, phthalic anhydride and triphenyl phosphite were added into the reactor according to weight, heated to 155°C, kept warm for 0.5h, and then continued to heat to 200°C; (2) At 200°C, react for 2 h until the acid value reaches 50 mgKOH / g; then dehydrate at 200°C until the acid value reaches 20 mgKOH / g; (3) Cooling the mixture to 170°C and adding polymerization inhibitor and paraffin wax by weight; then cooling the mixture to 90°C and adding stabilizer and diluent by weight; further cooling the mixture to 50°C and adding ultraviolet absorber and brightener by weight, and mixing the mixture; and obtaining unsaturated polyester resin for jade imitation crafts.

[0036] Example 2 The present embodiment is a formula of unsaturated polyester resin for imitation jade handicraft, which is composed of the following ingredients: 16.2 parts of diethylene glycol, 6 parts of methylpropylene glycol, 7.8 parts of propylene glycol, 12 parts of maleic anhydride, 25.53 parts of phthalic anhydride, 0.058 parts of triphenyl phosphite, 0.0038 parts of p-benzoquinone, 0.052 parts of 54# paraffin wax, 0.0009 parts of copper naphthenate, 32.3178 parts of methyl styrene, 0.035 parts of 2-(2'-hydroxy-3,5'-di-tert-amylphenyl)benzotriazole, and 0.0025 parts of 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene; the weight ratio of propylene glycol to methylpropylene glycol is 1.3:1, and methylpropylene glycol accounts for 20% of the total diols; the weight ratio of maleic anhydride to phthalic anhydride is 0.47:1; The preparation method of this embodiment comprises the following steps: (1) Diethylene glycol, methyl propylene glycol, propylene glycol, maleic anhydride, phthalic anhydride and triphenyl phosphite were added into the reactor according to weight, heated to 165°C, kept warm for 1.0h, and then continued to heat to 210°C; (2) At 210°C, react for 3 h until the acid value reaches 55 mgKOH / g; then dehydrate at 210°C until the acid value reaches 25 mgKOH / g; (3) Cooling the mixture to 190°C and adding an inhibitor and paraffin wax by weight; then cooling the mixture to 110°C and adding a stabilizer and a diluent by weight; further cooling the mixture to 60°C and adding an ultraviolet absorber and a whitening agent by weight, and mixing the mixture; and obtaining an unsaturated polyester resin for jade-like crafts.

[0037] Example 3 The present embodiment is a formula of unsaturated polyester resin for imitation jade handicraft, which is composed of the following ingredients: 16.8 parts of diethylene glycol, 6.6 parts of methylpropylene glycol, 6.6 parts of propylene glycol, 11.73 parts of maleic anhydride, 25.5 parts of phthalic anhydride, 0.052 parts of triphenyl phosphite, 0.0038 parts of methylhydroquinone, 0.058 parts of 52# paraffin, 0.0012 parts of copper isooctanoate, 32.6215 parts of styrene, 0.03 parts of 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, and 0.0035 parts of 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene; the weight ratio of diols to methylpropylene glycol is 1:1, and methylpropylene glycol accounts for 22% of the total diols; the weight ratio of maleic anhydride to phthalic anhydride is approximately 0.46:1; The preparation method of this embodiment comprises the following steps: (1) Diethylene glycol, methyl propylene glycol, propylene glycol, maleic anhydride, phthalic anhydride and triphenyl phosphite were added into the reactor according to weight, heated to 160°C, kept warm for 0.8h, and then continued to heat to 205°C; (2) At 205°C, the reaction was continued for 2.5 h until the acid value reached 53 mgKOH / g, and then dehydrated at 205°C until the acid value reached 23 mgKOH / g; (3) Cooling the mixture to 180°C and adding polymerization inhibitor and paraffin wax by weight; cooling the mixture to 100°C and adding stabilizer and diluent by weight; continuing to cool the mixture to 55°C and adding ultraviolet absorber and brightener by weight; mixing the mixture to obtain unsaturated polyester resin for jade imitation crafts.

[0038] Example 4 The present embodiment is a formula of unsaturated polyester resin for imitation jade handicraft, which is composed of the following ingredients: 16.2 parts of diethylene glycol, 6 parts of methylpropylene glycol, 7.8 parts of propylene glycol, 12 parts of maleic anhydride, 25.53 parts of phthalic anhydride, 0.058 parts of triphenyl phosphite, 0.0043 parts of tert-butylhydroquinone, 0.052 parts of 54# paraffin, 0.0009 parts of copper isooctanoate, 32.3173 parts of styrene, 0.035 parts of 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, and 0.0025 parts of 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene; the weight ratio of propylene glycol to methylpropylene glycol is 1.3:1, and methylpropylene glycol accounts for approximately 20% of the total diols; the weight ratio of maleic anhydride to phthalic anhydride is approximately 0.47:1; The preparation method of this embodiment comprises the following steps: (1) Diethylene glycol, methyl propylene glycol, propylene glycol, maleic anhydride, phthalic anhydride and triphenyl phosphite were added into the reactor according to weight, heated to 160°C, kept warm for 0.8h, and then continued to heat to 205°C; (2) At 205°C, react for 2.5 hours until the acid value reaches 53 mgKOH / g; then dehydrate at 205°C until the acid value reaches 23 mgKOH / g; (3) Cooling down and adding polymerization inhibitor and paraffin wax by weight; cooling down again and adding stabilizer and diluent by weight; continuing to cool down and adding ultraviolet absorber and brightener by weight, and mixing well; obtaining unsaturated polyester resin for imitation jade crafts.

[0039] Example 5 The present embodiment is a formula of unsaturated polyester resin for imitation jade handicraft, which is composed of the following ingredients: 16.8 parts of diethylene glycol, 6.6 parts of methylpropylene glycol, 6.6 parts of propylene glycol, 12.8 parts of maleic anhydride, 25.09 parts of phthalic anhydride, 0.058 parts of triphenyl phosphite, 0.0043 parts of tert-butylcatechol, 0.052 parts of 52# paraffin wax, 0.0009 parts of copper isooctanoate, 31.9573 parts of methyl styrene, 0.035 parts of 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, and 0.0025 parts of 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene; the weight ratio of propylene glycol to methylpropylene glycol is 1:1, and methylpropylene glycol accounts for 22% of the total amount of diols; the weight ratio of maleic anhydride to phthalic anhydride is approximately 0.51:1; The preparation method of this embodiment comprises the following steps: (1) Diethylene glycol, methyl propylene glycol, propylene glycol, maleic anhydride, phthalic anhydride and triphenyl phosphite were added into the reactor according to weight, heated to 160°C, kept warm for 0.8h, and then continued to heat to 205°C; (2) At 205°C, the reaction was continued for 2.5 hours until the acid value reached 53 mgKOH / g; then the mixture was dehydrated at 205°C until the acid value reached 23 mgKOH / g; (3) Cooling the mixture to 180°C and adding polymerization inhibitor and paraffin wax by weight; then cooling the mixture to 100°C and adding stabilizer and diluent by weight; further cooling the mixture to 55°C and adding ultraviolet absorber and brightener by weight, and mixing the mixture; and obtaining unsaturated polyester resin for jade imitation crafts.

[0040] Example 6 The present embodiment is a formula of unsaturated polyester resin for imitation jade handicraft, which is composed of the following ingredients: 16.2 parts of diethylene glycol, 6 parts of methylpropylene glycol, 7.8 parts of propylene glycol, 13 parts of maleic anhydride, 25 parts of phthalic anhydride, 0.058 parts of triphenyl phosphite, 0.0038 parts of tert-butylcatechol, 0.058 parts of 54# paraffin, 0.0009 parts of copper isooctanoate, 31.8418 parts of methyl styrene, 0.035 parts of 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, and 0.0025 parts of 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene; the weight ratio of propylene glycol to methylpropylene glycol is 1.3:1, and methylpropylene glycol accounts for approximately 20% of the total diols; the weight ratio of maleic anhydride to phthalic anhydride is 0.52:1; The preparation method of this embodiment comprises the following steps: (1) Diethylene glycol, methyl propylene glycol, propylene glycol, maleic anhydride, phthalic anhydride and triphenyl phosphite were added to a reactor, heated to 160°C, maintained at this temperature for 0.8 h, and then continued to heat to 205°C; (2) At 205°C, the reaction was carried out for 2.5 hours until the acid value reached 53 mgKOH / g; dehydration was carried out at 205°C until the acid value reached 23 mgKOH / g; (3) Cooling the mixture to 180°C and adding polymerization inhibitor and paraffin wax by weight; then cooling the mixture to 100°C and adding stabilizer and diluent by weight; further cooling the mixture to 55°C and adding ultraviolet absorber and brightener by weight, and mixing the mixture; and obtaining unsaturated polyester resin for jade imitation crafts.

[0041] Example 7 The present embodiment is a formula of unsaturated polyester resin for imitation jade handicraft, which is composed of the following ingredients: 16.8 parts of diethylene glycol, 6.6 parts of methylpropylene glycol, 6.6 parts of propylene glycol, 12.8 parts of maleic anhydride, 25.09 parts of phthalic anhydride, 0.052 parts of triphenyl phosphite, 0.0038 parts of hydroquinone, 0.058 parts of 52# paraffin, 0.0012 parts of copper isooctanoate, 31.9615 parts of methyl styrene, 0.03 parts of 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, and 0.0035 parts of 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene; the weight ratio of propylene glycol to methylpropylene glycol is 1:1, and methylpropylene glycol accounts for 22% of the total diols; the weight ratio of maleic anhydride to phthalic anhydride is approximately 0.51:1; The preparation method of this embodiment comprises the following steps: (1) Diethylene glycol, methyl propylene glycol, propylene glycol, maleic anhydride, phthalic anhydride and triphenyl phosphite were added into the reactor according to weight, and the temperature was raised to 160°C and kept at this temperature for 0.8h, and then raised to 205°C; (2) At 205°C, react for 2.5 hours until the acid value reaches 53 mgKOH / g; then dehydrate at 205°C until the acid value reaches 23 mgKOH / g; (3) Cooling the mixture to 180°C and adding polymerization inhibitor and paraffin wax by weight; then cooling the mixture to 100°C and adding stabilizer and diluent by weight; further cooling the mixture to 55°C and adding ultraviolet absorber and brightener by weight, and mixing the mixture; and obtaining unsaturated polyester resin for jade imitation crafts.

[0042] Example 8 The present embodiment is a formula of unsaturated polyester resin for imitation jade handicraft, which is composed of the following ingredients: 16.2 parts of diethylene glycol, 6 parts of methylpropylene glycol, 7.8 parts of propylene glycol, 12.8 parts of maleic anhydride, 25.09 parts of phthalic anhydride, 0.052 parts of triphenyl phosphite, 0.0043 parts of hydroquinone, 0.052 parts of 52# paraffin, 0.0012 parts of copper isooctanoate, 31.967 parts of styrene, 0.03 parts of 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, and 0.0035 parts of 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene; the weight ratio of propylene glycol to methylpropylene glycol is 1.3:1, and methylpropylene glycol accounts for 20% of the total diols; the weight ratio of maleic anhydride to phthalic anhydride is approximately 0.51:1; The preparation method of this embodiment comprises the following steps: (1) Add diethylene glycol, methyl propylene glycol, propylene glycol, maleic anhydride, phthalic anhydride and triphenyl phosphite into the reactor, heat it to 160°C, keep it warm for 0.8h, and then continue to heat it to 205°C; (2) At 205°C, the reaction was continued for 2.5 h until the acid value reached 53 mgKOH / g, and then dehydrated at 205°C until the acid value reached 23 mgKOH / g; (3) Cooling the mixture to 180°C and adding polymerization inhibitor and paraffin wax by weight; then cooling the mixture to 100°C and adding stabilizer and diluent by weight; further cooling the mixture to 55°C and adding ultraviolet absorber and brightener by weight, and mixing the mixture; and obtaining unsaturated polyester resin for jade imitation crafts.

[0043] Example 9 The present embodiment is a formula of unsaturated polyester resin for imitation jade handicraft, which is composed of the following ingredients: 16.5 parts of diethylene glycol, 6.3 parts of methylpropylene glycol, 7.2 parts of propylene glycol, 12.4 parts of maleic anhydride, 25.3 parts of phthalic anhydride, 0.055 parts of triphenyl phosphite, 0.004 parts of hydroquinone, 0.055 parts of 54# paraffin, 0.00075 parts of copper isooctanoate, 0.00025 parts of copper naphthenate, 32.15 parts of methyl styrene, 0.032 parts of 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, and 0.003 parts of 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene; the weight ratio of propylene glycol to methylpropylene glycol is 1.14:1, and methylpropylene glycol accounts for 21% of the total diols; the weight ratio of maleic anhydride to phthalic anhydride is approximately 0.49:1; The preparation method of this embodiment comprises the following steps: (1) Diethylene glycol, methyl propylene glycol, propylene glycol, maleic anhydride, phthalic anhydride and triphenyl phosphite were added to the reactor, heated to 160°C, kept at this temperature for 0.8h and then continued to heat to 205°C; (2) React at 205°C for 2.5 hours until the acid value reaches 53 mgKOH / g, and then dehydrate at 205°C until the acid value reaches 23 mgKOH / g; (3) Cooling the mixture to 180°C and adding polymerization inhibitor and paraffin wax by weight; then cooling the mixture to 100°C and adding stabilizer and diluent by weight; further cooling the mixture to 55°C and adding ultraviolet absorber and brightener by weight, and mixing the mixture; and obtaining unsaturated polyester resin for jade imitation crafts.

[0044] Comparative Example 1 The preparation method of an unsaturated polyester resin for imitation jade handicrafts described in this comparative example is the same as that in Example 9, except that the whitening agent and the ultraviolet absorber are not added in parts by weight in step (3).

[0045] Comparative Example 2 The preparation method of an unsaturated polyester resin for imitation jade handicrafts described in this comparative example is the same as that in Example 9, except that 0.032 parts by weight of ultraviolet absorber is added in step (3), and no whitening agent is added.

[0046] Comparative Example 3 The preparation method of an unsaturated polyester resin for imitation jade handicrafts described in this comparative example is the same as that in Example 9, except that 0.003 parts by weight of a brightener is added in step (3), and no ultraviolet absorber is added.

[0047] Comparative Example 4 The preparation method of an unsaturated polyester resin for imitation jade handicrafts described in this comparative example is the same as that in Example 9, except that 0.0036 parts of a brightener and 0.029 parts of an ultraviolet absorber are added in parts by weight in step (3).

[0048] Comparative Example 5 The preparation method of an unsaturated polyester resin for imitation jade handicrafts described in this comparative example is the same as that in Example 9, except that 0.0024 parts of a brightener and 0.036 parts of an ultraviolet absorber are added in parts by weight in step (3).

[0049] Comparative Example 6 The preparation method of an unsaturated polyester resin for jade-like handicrafts described in this comparative example is the same as that in Example 9, except that methyl propylene glycol is not added by weight in step (1).

[0050] Comparative Example 7 The preparation method of an unsaturated polyester resin for imitation jade handicrafts described in this comparative example is the same as that in Example 9, except that propylene glycol is not added by weight in step (1).

[0051] Comparative Example 8 The preparation method of an unsaturated polyester resin for imitation jade handicrafts described in this comparative example is the same as that in Example 9, except that 0.00082 parts of copper isooctanoate and 0.00018 parts of copper cyclohexane are added in step (3).

[0052] Comparative Example 9 The preparation method of an unsaturated polyester resin for imitation jade handicrafts described in this comparative example is the same as that in Example 9, except that 0.00055 parts of copper isooctanoate and 0.00055 parts of copper cyclohexane are added in step (3).

[0053] Comparative Example 10 The preparation method of an unsaturated polyester resin for imitation jade handicrafts described in this comparative example is the same as that in Example 9, except that the weight ratio of propylene glycol to methyl propylene glycol in step (1) is 0.5.

[0054] Comparative Example 11 The preparation method of an unsaturated polyester resin for imitation jade handicrafts described in this comparative example is the same as that in Example 9, except that the weight ratio of propylene glycol to methyl propylene glycol in step (1) is 0.6.

[0055] Comparative Example 12 The preparation method of an unsaturated polyester resin for imitation jade handicrafts described in this comparative example is the same as that in Example 9, except that the weight ratio of propylene glycol to methylpropylene glycol in step (1) is 0.7.

[0056] Comparative Example 13 The preparation method of an unsaturated polyester resin for imitation jade handicrafts described in this comparative example is the same as that in Example 9, except that the weight ratio of propylene glycol to methyl propylene glycol in step (1) is 0.8.

[0057] Comparative Example 14 The preparation method of an unsaturated polyester resin for imitation jade handicrafts described in this comparative example is the same as that in Example 9, except that the weight ratio of propylene glycol to methylpropylene glycol in step (1) is 0.9.

[0058] Comparative Example 15 The preparation method of an unsaturated polyester resin for imitation jade handicrafts described in this comparative example is the same as that in Example 9, except that the weight ratio of propylene glycol to methyl propylene glycol in step (1) is 0.95.

[0059] Comparative Example 16 The preparation method of an unsaturated polyester resin for imitation jade handicrafts described in this comparative example is the same as that in Example 9, except that the weight ratio of propylene glycol to methyl propylene glycol in step (1) is 1.1.

[0060] Comparative Example 17 The preparation method of an unsaturated polyester resin for imitation jade handicrafts described in this comparative example is the same as that in Example 9, except that the weight ratio of propylene glycol to methylpropylene glycol in step (1) is 1.2.

[0061] Comparative Example 18 The preparation method of an unsaturated polyester resin for imitation jade handicrafts described in this comparative example is the same as that in Example 9, except that the weight ratio of propylene glycol to methylpropylene glycol in step (1) is 1.35.

[0062] Comparative Example 19 The preparation method of an unsaturated polyester resin for imitation jade handicrafts described in this comparative example is the same as that in Example 9, except that the weight ratio of propylene glycol to methylpropylene glycol in step (1) is 1.4.

[0063] Comparative Example 20 The preparation method of an unsaturated polyester resin for imitation jade handicrafts described in this comparative example is the same as that in Example 9, except that the weight ratio of propylene glycol to methyl propylene glycol in step (1) is 1.5.

[0064] Performance Testing The performance tests were carried out on the examples and comparative examples. The specific test results are shown in Tables 1, 2, 3 and 4. The unsaturated polyester resins prepared in Examples 1 to 9 and Comparative Examples 1 to 9 were subjected to liquid index tests. The specific test results are shown in Table 1. The performance tests were conducted on the unsaturated polyester resin cast products prepared in Examples 1 to 9 and Comparative Examples 1 to 9. The specific test results are shown in Table 2. The cooling acid value refers to the time when the target acid value is reached and the temperature is lowered, which represents the end point of the reaction. In Example 9, other conditions remain unchanged. Different cooling acid values represent different reaction degrees. The lower the acid value, the higher the reaction degree. Synthesis was carried out using different cooling acid values, and the viscosity, exothermic peak, oil absorption value and color difference of the handicraft were tested. The specific test results are shown in Table 3. Based on the formula of Example 9, the weight ratio of propylene glycol to methylpropylene glycol was adjusted to obtain Comparative Examples 10 to 20. The viscosity, exothermic peak, oil absorption value and color difference of the handicraft were tested. The specific test results are shown in Table 4.

[0065] The tensile strength of unsaturated polyester resin used in imitation jade crafts is tested in accordance with GB / T2567-2021; The tensile elastic modulus of unsaturated polyester resin used in imitation jade crafts is tested in accordance with GB / T2567-2021; The elongation at break of unsaturated polyester resin used in imitation jade crafts is tested in accordance with GB / T2567-2021; The flexural strength of unsaturated polyester resin used in imitation jade crafts is tested with reference to GB / T2567-2021; The flexural elastic modulus of unsaturated polyester resin used in imitation jade crafts is tested in accordance with GB / T2567-2021; The impact strength of unsaturated polyester resin used in imitation jade crafts is tested with reference to GB / T2567-2021; The Barcol hardness of unsaturated polyester resin used in imitation jade crafts is tested in accordance with GB / T3854-2017; The heat deformation temperature of unsaturated polyester resin used in imitation jade crafts is tested with reference to GB / T1643-2019; The viscosity of unsaturated polyester resin used in imitation jade crafts is tested with reference to GB / T7193-2008; The gel time of unsaturated polyester resin used in imitation jade crafts is tested with reference to GB / T7193-2008; The exothermic peak of unsaturated polyester resin used in imitation jade crafts is tested with reference to GB / T7193-2008; The oil absorption value of unsaturated polyester resin used in imitation jade crafts is tested with reference to GB / T7193-2008.

[0066] Post-curing time: The gel time of unsaturated polyester resin used in imitation jade crafts is tested with reference to GB / T7193-2008. The post-curing time refers to the time interval from the gel state of unsaturated polyester resin, when the material is jelly-like and soft in texture, to the temperature reaching the exothermic peak and maintaining a stable temperature for 30 seconds. During this process, the resin completes the transition from gel state to complete curing and finally presents a higher hardness state.

[0067] Oil absorption value test: The oil absorption value of unsaturated polyester resin used in imitation jade handicrafts is the resin adsorption amount, which is an index indicating the amount of resin absorbed by the filler. As the oil absorption value increases, the viscosity of the resin increases, which seriously affects the dispersibility and rheological properties, and deteriorates the molding process performance. When obtaining the same viscosity, more resin needs to be added, which invisibly increases the cost. The same proportion of fillers is added to each embodiment and comparative example, and the American BROOKFIELDDV2T viscometer is used to select the same speed to test the oil absorption value viscosity of the samples at the same temperature.

[0068] Color Difference Test: Gloss reflects the combined properties of an object's surface smoothness, cleanliness, and specular reflectivity. Higher gloss indicates brighter and more wear-resistant surfaces. The gloss of the crafts produced in the Examples and Comparative Examples was tested using Lichen Technology's universal 60-degree gloss meter, the WGG-60. Gloss comparison tests were conducted after the craft samples were exposed to LED UV light (wavelength 280-400nm) for 168 hours. Color difference was also tested using the Linshang Technology LS173 colorimeter.

[0069] Color difference ΔE * ab The calculation formula is: ; in: ‌ΔL * ‌: Luminance difference (brightness change); ‌Δa * ‌: chromaticity difference between red and green axes; ‌Δb * ‌: chromaticity difference between yellow and blue axes; Preparation method of imitation jade: The resin and aluminum hydroxide powder described in each embodiment and comparative example are mixed and stirred evenly in a weight ratio of 1:1.5, and at a room temperature of 25°C and a humidity of 50%, 0.3 parts of cobalt isooctanoate, a special accelerator for handicrafts, and 1.5 parts of methyl ethyl ketone peroxide, a special curing agent for handicrafts, are added respectively. After fully stirring for 1 minute, the mixture is poured into a mold. The mold is placed in a constant temperature and humidity incubator, maintained at a temperature of 30°C and a humidity of 40%, and cured at a constant temperature for 30 minutes, then taken out and demolded. The demolded handicraft is placed in a constant temperature and humidity box, maintained at a temperature of 30°C and a humidity of 40%, and continued to cure for 1 hour, then taken out and tested for glossiness.

[0070] Cooling acid value: Cooling acid value is when the temperature starts to drop when the acid value at the end point of the reaction is reached; in Example 9, other conditions remain unchanged, and different cooling acid values represent different reaction degrees, and the lower the acid value, the higher the reaction degree.

[0071] Oil absorption viscosity: After adding filler to the resin, the viscosity obtained by testing in accordance with GB / T7193-2008 is the oil absorption viscosity. When the test temperature is the same, the higher the oil absorption value, the lower the adsorption capacity.

[0072] Resin color was determined by visual inspection.

[0073] Table 1 Performance test results of Examples 1 to 9 and Comparative Examples 1 to 9 in liquid state .

[0074] Table 2 Test results of resin castings of Examples 1 to 9 and Comparative Examples 1 to 9 .

[0075] Table 3 Comparison of viscosity of acid value, exothermic peak and oil absorption value at different temperature drops in Example 9 .

[0076] Table 4 Performance test results of the embodiments and comparative examples .

[0077] As shown in Tables 1 to 3, the comprehensive performance is best when methyl propylene glycol accounts for 20 to 22% of the total amount of diols. The viscosity of Examples 1 to 9 is 320 to 350 mPa·s, the gel time is 3'38" to 3'55", and the exothermic peak temperature is 156 to 160°C, indicating that the resin system has excellent process controllability; the water-white appearance and the acid value of 19.13 to 21.38 mgKOH / g indicate that the raw material purity is high; the post-curing time is 9'16 to 9'45" and the oil absorption value is 2010 to 2088 cP. The formulations of Examples 1-9 achieve a balance between curing rate and fluidity, achieving tensile strengths of 60-65 MPa and flexural strengths of 106-112 MPa, reaching the level of engineering plastics. The combined impact strength of 12-15 kJ / m² and elongation at break of 4.02-4.95 parts per million demonstrates the material's combined impact resistance and moderate plastic deformation capacity. Example 9 exhibits the best overall performance, with a tensile strength of 65 MPa and a flexural strength of 112 MPa; a tensile modulus of elasticity of 3188 MPa and a flexural modulus of 3357 MPa.

[0078] This application addresses the conflict between mechanical strength and weather resistance in traditional resins through molecular structure design and stabilizer formulation. A synergistic curing system controls the exothermic peak temperature between 156°C and 160°C to prevent internal stress accumulation. UV absorbers transfer light energy through intramolecular hydrogen bonds, reducing UV penetration and photodegradation rates. Interface enhancement technology, with an oil absorption range of 2010 to 2088 cP, ensures full filler wetting and enhances interfacial bonding.

[0079] As shown in Table 3, when the acid value is 15 mgKOH / g, the viscosity increases, resulting in poor filler dispersion; the oil absorption value increases, the molecular chain is too long or the cross-linking network is loose; the exothermic peak temperature is too high, resulting in stress concentration during curing and inducing microcracks.

[0080] When the acid value is 30 mgKOH / g, the viscosity is too low, accompanied by incomplete reaction, resulting in an exothermic peak of only 151°C, insufficient curing cross-linking density, and decreased mechanical properties; the oil absorption value is low, but the surface density of the cured product is insufficient, and weather resistance is limited.

[0081] Table 3 shows that when the acid value drops to 15 mgKOH / g, the resin viscosity becomes too high and the oil absorption increases significantly, which affects filler dispersion. Furthermore, the excessively high exothermic peak can easily lead to cracking during curing. At an acid value of 30 mgKOH / g, while the viscosity and oil absorption are lower, the low exothermic peak affects curing. Overall, the optimal acid value range is 20-25 mgKOH / g, achieving moderate resin viscosity, reasonable oil absorption, and an appropriate exothermic peak temperature, ensuring good processing properties and product quality.

[0082] As shown in Tables 1 and 2, Comparative Example 1 has the worst gloss retention and color difference. The results of Comparative Example 1 indicate that the lack of a brightener affects the resin's initial gloss and exacerbates color difference after illumination. The lack of a UV absorber reduces weather resistance. The gloss of Comparative Example 2, 52.6 GU before illumination, is lower than the 73.8 GU of Example 9. After illumination, this drops to 37.5 GU, indicating that the absence of a brightener reduces the resin's surface gloss and light resistance. While brighteners improve initial gloss by reducing internal light scattering, their absence reduces the surface's reflective properties. Without a brightener, the resin's UV shielding ability weakens, accelerating light-induced molecular chain breakage and oxidation reactions, leading to a decrease in gloss and an increase in color difference. Comparative Example 3, with a gloss of 62.8 GU before illumination, drops to 39.8 GU after illumination, indicating significant color shift due to UV aging. The absence of a UV absorber reduces the resin's UV protection and accelerates photodegradation. Ultraviolet absorbers protect the surface structure of the resin by shielding ultraviolet radiation and delaying the breakage of molecular chains. Their absence directly leads to a decrease in gloss and an increase in color difference after exposure to light.

[0083] In Comparative Example 4, insufficient addition of UV absorber and excessive addition of brightener resulted in a decrease in gloss after illumination, indicating that insufficient UV absorber resulted in reduced weather resistance and inability to effectively inhibit photodegradation; excessive brightener interfered with curing, resulting in the post-curing time being extended to 10 minutes and 5 seconds, and the brightener molecules occupied the cross-linking sites, hindering the free radical chain growth reaction; the color difference ΔE*ab reached 0.99, the excessive addition of brightener resulted in poor color stability, and the insufficient addition of UV absorber accelerated the color change after illumination.

[0084] In Comparative Example 5, excessive UV absorber and insufficient brightener hindered the curing reaction, deteriorating mechanical properties, reducing optical stability, increasing defects in the resin crosslink network, and lowering the heat distortion temperature. The gel time and post-cure time in Comparative Example 5 were prolonged, indicating that the excessive UV absorber inhibited the curing reaction activity, resulting in reduced crosslinking efficiency. The exothermic peak temperature dropped to 147°C, indicating that excessive UV absorber interfered with the absorption of resin reaction heat and the curing process. The GU value dropped from 58.4 before irradiation to 40.6 after irradiation, indicating that insufficient brightener resulted in an imbalance in UV protection and signs of photodegradation on the resin surface. The color difference ΔE*ab reached 0.92, indicating that the imbalance in the additive ratio exacerbated the color shift after irradiation.

[0085] The results of Comparative Examples 1-5 show that within the ratio range of 0.03-0.035 parts of UV absorber and 0.0025-0.0035 parts of brightener, the UV absorber preferentially absorbs the UVB wavelength range of 280-320nm, while the brightener absorbs the UVA wavelength range of 320-400nm and emits blue light through fluorescence, reducing resin yellowing. The synergistic effect of the two is mainly manifested in: optimizing gloss, balancing curing and mechanical properties, and improving weather resistance. When the additive ratio exceeds this range, the synergistic effect is destroyed, and the functions of the two will antagonize each other, resulting in reduced curing efficiency and an imbalance between mechanical properties and weather resistance.

[0086] In Comparative Example 6, no methylpropylene glycol was added, resulting in the resin being yellow in color. The lack of methylpropylene glycol resulted in decreased flexibility of the molecular chain and insufficient filler infiltration; the color was 33.6 GU before irradiation and dropped to 18.1 GU after irradiation, and the color difference ΔE*ab reached 1.27, indicating that the lack of methylpropylene glycol resulted in a significant decrease in its UV aging resistance; the oil absorption value reached 2248 cP, indicating that the flexibility of the molecular chain was abnormal, and the oil absorption increased due to the loose cross-linking network; the gel time and post-curing time were shortened, but the exothermic peak was 150°C, indicating that the curing reaction activity was insufficient and the cross-linking density decreased.

[0087] In Comparative Example 7, no propylene glycol was added, resulting in a light yellow resin color, 35.1 GU before illumination and 19.9 GU after illumination, with a color difference ΔE*ab reaching 1.24, indicating that the lack of propylene glycol caused its UV aging resistance to decrease significantly; the viscosity and oil absorption value both increased, indicating that the flexibility of the molecular chain was abnormal or the cross-linked network was loose.

[0088] As shown in Table 4, when the weight ratio of propylene glycol to methylpropylene glycol is within the range of 1.0 to 1.3:1, the resin exhibits the best water white color, the color difference ΔE*ab is less than 0.71, and the oil absorption value is 2022 to 2170 cP. At this ratio, the exothermic peak temperature is stable at 154 to 159°C, indicating that the reaction activity is moderate and the resin viscosity is maintained in the optimal processing range of 300 to 350 mPa·s.

[0089] When the weight ratio of propylene glycol to methylpropylene glycol exceeds 1.3:1, significant performance degradation will occur, the color will turn light yellow to yellow, the color difference of the handicraft will increase, the oil absorption value will increase, and the exothermic peak temperature will decrease. When the weight ratio of propylene glycol to methylpropylene glycol is less than 1:1, the process performance will deteriorate, the color stability will decrease, and the exothermic peak temperature will decrease.

[0090] In Comparative Example 8, the weight ratio of copper isooctanoate to copper naphthenate was greater than 4:1, resulting in prolonged gel time and post-curing time, increased oil absorption, decreased curing efficiency and gloss, and failure to achieve a synergistic effect. In Comparative Example 9, the weight ratio of copper isooctanoate to copper naphthenate was less than 1.5:1, resulting in prolonged gel time and post-curing time, increased oil absorption, and decreased tensile strength, flexural strength, and gloss.

[0091] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. An unsaturated polyester resin for imitation jade handicrafts, characterized in that: The invention comprises the following ingredients in parts by weight: 16.2-16.8 parts of diethylene glycol, 6.0-6.6 parts of methyl propylene glycol, 6.6-7.8 parts of propylene glycol, 11.73-13 parts of maleic anhydride, 25-25.53 parts of phthalic anhydride, 0.052-0.058 parts of antioxidant, 0.0038-0.0043 parts of polymerization inhibitor, 0.052-0.058 parts of paraffin wax, 0.0009-0.0012 parts of stabilizer, 0.03-0.035 parts of ultraviolet absorber, 0.0025-0.0035 parts of brightener and 31.8418-32.6215 parts of diluent; The weight ratio of propylene glycol to methyl propylene glycol is 1.0-1.3:1, and methyl propylene glycol accounts for 20-22% of the total amount of diols; the weight ratio of maleic anhydride to phthalic anhydride is 0.46-0.52:

1.

2. The unsaturated polyester resin for imitation jade handicraft according to claim 1, wherein: The weight ratio of maleic anhydride to phthalic anhydride is 0.47-0.51:

1.

3. The unsaturated polyester resin for imitation jade handicraft according to claim 1, wherein: The stabilizer is at least one of copper isooctanoate or copper naphthenate.

4. The unsaturated polyester resin for imitation jade handicraft according to claim 3, wherein: The weight ratio of the copper isooctanoate to the copper naphthenate is 1.5-4:

1.

5. The unsaturated polyester resin for imitation jade handicraft according to claim 1, wherein: The weight ratio of the ultraviolet absorber to the whitening agent is 8.75-14.0:

1.

6. The unsaturated polyester resin for imitation jade handicraft according to claim 1 or 5, wherein: The ultraviolet absorber is 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole or 2-(2'-hydroxy-3,5'-di-tert-amylphenyl)benzotriazole; the whitening agent is 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene.

7. The method for preparing an unsaturated polyester resin for imitation jade handicraft according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Add diethylene glycol, methyl propylene glycol, propylene glycol, maleic anhydride, phthalic anhydride and antioxidant into the reactor according to weight, heat to 155-165°C, keep the temperature for 0.5-1.0h, and then continue to heat to 200-210°C; (2) React at 200-210°C for 2-3 hours; dehydrate; (3) Cooling down and adding polymerization inhibitor and paraffin wax by weight; cooling down again and adding stabilizer and diluent by weight; continuing to cool down and adding ultraviolet absorber and brightener by weight; mixing well to obtain unsaturated polyester resin for imitation jade handicrafts.

8. The method for preparing an unsaturated polyester resin for imitating jade handicraft according to claim 7, wherein: The heating rate for further heating to 200-210° C. in step (1) is 12-14° C. / h.

9. The method for preparing an unsaturated polyester resin for imitating jade handicraft according to claim 7, wherein: Step (2) reacts at 200-210°C for 2-3 hours; dehydrates until the acid value reaches 20-25 mgKOH / g.

10. The method for preparing an unsaturated polyester resin for imitation jade handicraft according to claim 7, wherein: The specific operation of step (3) is to cool the mixture to 170-190°C, add a polymerization inhibitor and paraffin wax by weight; cool the mixture to 90-110°C, add a stabilizer and a diluent by weight; cool the mixture to 50-60°C, add an ultraviolet absorber and a whitening agent by weight, and mix well; and obtain an unsaturated polyester resin for imitation jade crafts.