High-strength water-soaking-resistant orthophthalic unsaturated resin and synthesis method thereof

Abstract

The invention relates to a high-strength water-soaking-resistant orthophthalic unsaturated resin and a synthesis method thereof. The formula comprises the following components in parts by mass: 45-56 parts of phthalic anhydride; 20 to 28 parts of dihydric alcohol; 17 to 20 parts of styrene; 3-6 parts of polyethylene glycol adipate; 1.5 to 4 parts of gamma-aminopropyltriethoxysilane (gamma-aminopropyltriethoxysilane); according to the orthophthalic unsaturated resin disclosed by the invention, through a chain extension reaction of the polyethylene glycol adipate, the molecular weight and tensile strength of the resin are remarkably improved, low viscosity is maintained, and the problems that the viscosity is easy to increase and the processing is difficult when the strength is improved by a traditional method are solved; the unique structure of the gamma-aminopropyltriethoxysilane is utilized to enhance the interface bonding force between the resin and the inorganic filler, the amino group of the gamma-aminopropyltriethoxysilane reacts with the carboxyl group in the resin to form a chemical bond, and is combined with the hydroxyl group on the surface of the inorganic filler to form dual interface protection, so that the permeation of water is effectively reduced, and the water resistance of the resin is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, and in particular to a high-strength water-immersion-resistant ortho-phthalic unsaturated resin and a synthesis method thereof. BACKGROUND

[0002] The ortho-phthalic unsaturated resin is widely used in the fields of infrastructure, water conservancy facilities, ocean engineering, industrial equipment, etc., and its performance advantages are due to the carefully designed formula and rigorous production synthesis process.

[0003] The existing ortho-phthalic unsaturated resin has problems such as hydrolysis, aging, and interface debonding with inorganic fillers such as glass fibers in environments that need to be in contact with water for a long time, such as ocean engineering and water conservancy facilities, which leads to a decline in material performance and affects the service life. In addition, the traditional ortho-phthalic unsaturated resin not only has a large curing shrinkage rate and high molding stress, which affects the dimensional stability of the product, but also has high energy consumption and large volatile organic compound (VOC) emissions in the production process, which does not meet the environmental protection requirements.

[0004] Therefore, the present application proposes a high-strength water-immersion-resistant ortho-phthalic unsaturated resin and a synthesis method thereof to solve the above problems. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a high-strength water-immersion-resistant ortho-phthalic unsaturated resin and a synthesis method thereof to solve the problems of insufficient water-immersion-resistant aging performance and mechanical strength of the ortho-phthalic unsaturated resin in the application of composite materials, hydrolysis, aging, interface debonding, and poor processing performance.

[0006] To solve the above technical problems, the technical solution of the present application is as follows: a high-strength water-immersion-resistant ortho-phthalic unsaturated resin, the innovative point of which is that the formula components and their mass fractions of the ortho-phthalic unsaturated resin include: 45-56 parts of phthalic anhydride; 20-28 parts of dihydric alcohol; 17-20 parts of styrene; 3-6 parts of polyethylene glycol adipate; 1.5-4 parts of gamma-aminopropyl triethoxysilane.

[0007] Further, the dihydric alcohol uses one or more of propylene glycol, neopentyl glycol, or diethylene glycol.

[0008] Further, the dihydric alcohol uses a mixture of neopentyl glycol and diethylene glycol, and the addition ratio of neopentyl glycol to diethylene glycol in the mixture is 1:1.

[0009] The synthesis method of the above high-strength water-immersion-resistant ortho-phthalic unsaturated resin includes the following steps: Step 1, esterification reaction stage: According to the formula components and their mass fractions, phthalic anhydride, maleic anhydride and dihydric alcohol are added to the reaction kettle; The reaction kettle is stirred by a stirrer, and is heated at a certain rate to 160-180℃, and the esterification reaction is started. During the reaction process, the water generated by the reaction is continuously separated out by using a water trap. As the esterification reaction proceeds, the acid value of the reaction system is periodically detected by sampling. When the acid value decreases to a first acid value, the reaction temperature is increased to 200-220℃, and the esterification reaction is continued. When the acid value reaches a second acid value, the esterification reaction is completed, and a resin is obtained; Step 2, dilution stage: The temperature in the reaction kettle is reduced to 120-140℃, and styrene and a polymerization inhibitor are slowly added under stirring. After the addition is completed, stirring is continued for 1-2h to make the resin and styrene fully mixed and uniform, and a resin solution is obtained; Step 3, additive compounding stage: The temperature of the resin solution is reduced to 60-80℃, and functional additives, γ-aminopropyl triethoxysilane and polyethylene glycol adipate are sequentially added, and stirring is continued for 0.5-1h to make the functional additives, γ-aminopropyl triethoxysilane and polyethylene glycol adipate uniformly dispersed in the resin solution; Step 4, filtration stage: The compounded resin solution is filtered through a filter screen to remove impurities and gel particles, and a high-strength water-immersion-resistant ortho-phenyl unsaturated resin is obtained.

[0010] Further, in the step 1, the first acid value is 30-50mgKOH / g, and the second acid value is 15-30mgKOH / g.

[0011] Further, in the step 1, the rate of heating the reaction kettle to 160-180℃ is 8-12℃ / min.

[0012] Further, in the step 1, the addition amount of maleic anhydride is controlled to be 33.3%-55.5% of the addition amount of phthalic anhydride.

[0013] Further, in the step 2, styrene and the polymerization inhibitor are added in a dropwise manner, and the dropwise addition speed is 50-60 drops / min.

[0014] Further, the polymerization inhibitor is hydroquinone, p-benzoquinone or p-hydroxyanisole.

[0015] Further, the functional additives include antioxidants and ultraviolet absorbers.

[0016] The advantages of the present application are: (1) The ortho-phthalic unsaturated resin of the present application improves the molecular weight and tensile strength of the resin significantly through chain extension reaction of polyethylene adipate, maintains low viscosity, overcomes the problem of increasing viscosity and processing difficulty caused by traditional method in improving strength, and utilizes the unique structure of gamma-aminopropyl triethoxysilane to enhance the interfacial adhesion of the resin and inorganic filler, the amino group reacts with the carboxyl group in the resin to form a chemical bond, and at the same time combines with the hydroxyl group on the surface of the inorganic filler to form a double interface protection, effectively reducing the penetration of moisture and improving the water resistance of the resin.

[0017] (2) The ortho-phthalic unsaturated resin of the present application utilizes the synergistic effect of the branched structure of neopentyl glycol and the linear structure of diethylene glycol to balance the rigidity and flexibility of the resin, and inhibit the diffusion of water molecules, thereby further improving the water resistance of the resin.

[0018] (3) The ortho-phthalic unsaturated resin of the present application has significantly improved strength, water immersion aging resistance, shrinkage rate and curing speed compared with existing ortho-phthalic unsaturated resin; while the existing ortho-phthalic unsaturated resin is difficult to meet the high requirements in strength and water resistance at the same time, the ortho-phthalic unsaturated resin of the present application realizes the unity of high strength and high water resistance through unique formula design and process optimization.

[0019] (4) The synthesis method of the ortho-phthalic unsaturated resin of the present application strictly controls the reaction temperature at each stage to avoid slow reaction rate and long reaction time caused by too low temperature, and color change and gelation of the resin caused by too high temperature, and uses acid value as an evaluation index to quantitatively evaluate the esterification reaction degree, thereby improving the synthesis rate and product quality.

[0020] (5) The ortho-phthalic unsaturated resin of the present application adopts green synthesis process, reduces energy consumption and generation of phenolic by-products, reduces styrene content and VOC emissions, and is more in line with environmental protection requirements. BRIEF DESCRIPTION OF DRAWINGS

[0021] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0022] Figure 1 The figure is a comparison chart of the bending strength of the ortho-phthalic unsaturated resin of the present application before fresh water immersion.

[0023] Figure 2 The figure is a comparison chart of the bending strength of the ortho-phthalic unsaturated resin of the present application after fresh water immersion.

[0024] Figure 3 The figure is a comparison chart of the bending strength loss rate of the ortho-phthalic unsaturated resin of the present application in fresh water immersion.

[0025] Figure 4 The figure is a comparison chart of the bending strength of the ortho-phthalic unsaturated resin of the present application before sea water immersion.

[0026] Figure 5 This is a comparison diagram of the bending strength of the present invention after immersion in seawater.

[0027] Figure 6 This is a comparison chart of the flexural strength loss rate under fresh seawater immersion of the present invention.

[0028] Figure 7 This is a physical image of the high-strength, water-resistant, phthalic unsaturated resin of the present invention. Detailed Implementation

[0029] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0030] Example 1 This embodiment provides a high-strength, water-resistant phthalic unsaturated resin, the formulation components and their mass fractions of which include: 45 parts of phthalic anhydride; 23 parts of propylene glycol; 19 parts of styrene; 4 parts of polyethylene adipate; 3 parts of γ-aminopropyltriethoxysilane.

[0031] The method for synthesizing the above-mentioned high-strength, water-resistant phthalic unsaturated resin includes the following steps: Step 1, Esterification Reaction Stage: According to the formula components and their mass fractions, 450g of phthalic anhydride, 180g of maleic anhydride and 230g of propylene glycol were added to a reaction vessel equipped with a stirrer, thermometer, reflux condenser and water separator. Turn on the stirrer and heat the reactor to 175°C at a rate of 11°C / min to begin the esterification reaction. Water will be produced during the reaction, and it should be continuously separated out through a water separator to promote the reaction in the forward direction. During the reaction, the temperature and water output should be closely monitored. As the esterification reaction proceeds, the acid value of the reaction system should be sampled and tested periodically. When the acid value drops to the first acid value of 30-50 mgKOH / g, the reaction temperature should be increased to 205°C to continue the esterification reaction. When the acid value reaches the second acid value of 15-30 mgKOH / g, the esterification reaction is complete, and the resin is obtained. Step 2, Dilution Stage: The temperature inside the reactor was lowered to 125°C. Under stirring, 190g of styrene and 5g of hydroquinone inhibitor were slowly added dropwise at a rate of 50-60 drops / min. After the addition was completed, stirring was continued for 1 hour to ensure that the resin and styrene were fully mixed and homogeneous, thus obtaining a resin solution. Step 3, Additive compounding stage: The temperature of the resin solution was lowered to 75℃, and then 0.05~0.15g of antioxidant p-benzoquinone, 0.02~0.10g of ultraviolet absorber 2,4-dihydroxybenzophenone, 30g of γ-aminopropyltriethoxysilane, and 40g of polyethylene adipate were added sequentially. The mixture was stirred for 0.5h to ensure that the antioxidant, ultraviolet absorber, γ-aminopropyltriethoxysilane, and polyethylene adipate were uniformly dispersed in the resin solution. Step 4, Filtering stage: The compounded resin solution is filtered through a filter screen to remove impurities and gel particles, resulting in a high-strength, water-resistant phthalic unsaturated resin. This resin is then placed in a clean, dry container and sealed for storage.

[0032] Example 2 This embodiment provides a high-strength, water-resistant phthalic unsaturated resin, the formulation components and their mass fractions of which include: 53 parts of phthalic anhydride; 27 parts of neopentyl glycol; 17 parts of styrene; Three parts of polyethylene adipate; 1.5 parts of γ-aminopropyltriethoxysilane.

[0033] The method for synthesizing the above-mentioned high-strength, water-resistant phthalic unsaturated resin includes the following steps: Step 1, Esterification Reaction Stage: According to the formula components and their mass fractions, 530g of phthalic anhydride, 210g of maleic anhydride and 270g of neopentyl glycol were added to a reaction vessel equipped with a stirrer, thermometer, reflux condenser and water separator. Turn on the stirrer and heat the reactor to 160°C at a rate of 8°C / min to begin the esterification reaction. Water will be produced during the reaction, and it should be continuously separated out through a water separator to promote the reaction in the forward direction. During the reaction, the temperature and water output should be closely monitored. As the esterification reaction proceeds, the acid value of the reaction system should be sampled and tested periodically. When the acid value drops to the first acid value of 30-50 mgKOH / g, the reaction temperature should be increased to 200°C to continue the esterification reaction. When the acid value reaches the second acid value of 15-30 mgKOH / g, the esterification reaction is complete, and the resin is obtained. Step 2, Dilution Stage: The temperature inside the reactor was lowered to 120°C. Under stirring, 170g of styrene and 4.5g of the polymerization inhibitor p-hydroxyanisole were slowly added dropwise at a rate of 50-60 drops / min. After the addition was completed, stirring was continued for 2 hours to ensure that the resin and styrene were fully mixed and homogeneous, thus obtaining a resin solution. Step 3, Additive compounding stage: The temperature of the resin solution was lowered to 60℃, and then 0.06~0.18g of antioxidant hydroquinone, 0.03~0.12g of ultraviolet absorber 2-hydroxy-4-methoxybenzophenone, 15g of γ-aminopropyltriethoxysilane, and 30g of polyethylene adipate were added sequentially. The mixture was stirred for 0.5h to ensure that the antioxidant, ultraviolet absorber, γ-aminopropyltriethoxysilane, and polyethylene adipate were uniformly dispersed in the resin solution. Step 4, Filtering stage: The compounded resin solution is filtered through a filter screen to remove impurities and gel particles, resulting in a high-strength, water-resistant phthalic unsaturated resin. This resin is then placed in a clean, dry container and sealed for storage.

[0034] Example 3 This embodiment provides a high-strength, water-resistant phthalic unsaturated resin, the formulation components and their mass fractions of which include: 56 parts of phthalic anhydride; 21 parts of diethylene glycol; 20 parts styrene; 6 parts of polyethylene adipate; 4 parts of γ-aminopropyltriethoxysilane.

[0035] The method for synthesizing the above-mentioned high-strength, water-resistant phthalic unsaturated resin includes the following steps: Step 1, Esterification Reaction Stage: According to the formula components and their mass fractions, 560g of phthalic anhydride, 220g of maleic anhydride and 210g of diethylene glycol were added to a reaction vessel equipped with a stirrer, thermometer, reflux condenser and water separator. Turn on the stirrer and heat the reactor to 180°C at a rate of 12°C / min to begin the esterification reaction. Water will be produced during the reaction, and it should be continuously separated out through a water separator to promote the reaction in the forward direction. During the reaction, the temperature and water output should be closely monitored. As the esterification reaction proceeds, the acid value of the reaction system should be sampled and tested periodically. When the acid value drops to the first acid value of 30-50 mgKOH / g, the reaction temperature should be increased to 220°C to continue the esterification reaction. When the acid value reaches the second acid value of 15-30 mgKOH / g, the esterification reaction is complete, and the resin is obtained. Step 2, Dilution Stage: The temperature inside the reactor was lowered to 140℃. Under stirring, 200g of styrene and 5g of the polymerization inhibitor p-hydroxyanisole were slowly added dropwise at a rate of 50-60 drops / min. After the addition was completed, stirring was continued for 2 hours to ensure that the resin and styrene were fully mixed and homogeneous, thus obtaining a resin solution. Step 3, Additive compounding stage: The temperature of the resin solution was lowered to 80℃, and then 0.06~0.18g of antioxidant hydroquinone, 0.03~0.12g of ultraviolet absorber 2-hydroxy-4-methoxybenzophenone, 40g of γ-aminopropyltriethoxysilane, and 60g of polyethylene adipate were added sequentially. The mixture was stirred for 0.5h to ensure that the antioxidant, ultraviolet absorber, γ-aminopropyltriethoxysilane, and polyethylene adipate were uniformly dispersed in the resin solution. Step 4, Filtering stage: The compounded resin solution is filtered through a filter screen to remove impurities and gel particles, resulting in a high-strength, water-resistant phthalic unsaturated resin. This resin is then placed in a clean, dry container and sealed for storage.

[0036] Example 4 This embodiment provides a high-strength, water-resistant phthalic unsaturated resin, the formulation components and their mass fractions of which include: 50 parts of phthalic anhydride; 25 parts of a mixture of neopentyl glycol and diethylene glycol, wherein the ratio of neopentyl glycol to diethylene glycol in the mixture is 1:1; 18 parts of styrene; 5 parts of polyethylene adipate; Two parts of γ-aminopropyltriethoxysilane.

[0037] The method for synthesizing the above-mentioned high-strength, water-resistant phthalic unsaturated resin includes the following steps: Step 1, Esterification Reaction Stage: According to the formula components and their mass fractions, 500g of phthalic anhydride, 200g of maleic anhydride, and 250g of a mixture of neopentyl glycol and diethylene glycol (the ratio of neopentyl glycol to diethylene glycol is 1:1) were added to a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and water separator. Turn on the stirrer and heat the reactor to 170°C at a rate of 10°C / min to begin the esterification reaction. Water will be produced during the reaction, and it should be continuously separated out through a water separator to promote the reaction in the forward direction. During the reaction, the temperature and water output should be closely monitored. As the esterification reaction proceeds, the acid value of the reaction system should be sampled and tested periodically. When the acid value drops to the first acid value of 30-50 mgKOH / g, the reaction temperature should be increased to 210°C to continue the esterification reaction. When the acid value reaches the second acid value of 15-30 mgKOH / g, the esterification reaction is complete, and the resin is obtained. Step 2, Dilution Stage: The temperature inside the reactor was lowered to 130℃ (120~140℃). Under stirring, 180g of styrene and 4g of catechol (polymerization inhibitor) were slowly added dropwise at a rate of 50~60 drops / min. After the addition was completed, stirring was continued for 1.5h to ensure that the resin and styrene were fully mixed and homogeneous to obtain a resin solution. Step 3, Additive compounding stage: Lower the temperature of the resin solution to 70°C, and then add 0.05~0.15g of antioxidant TBC, 0.05~0.15g of ultraviolet absorber phenyl phthalate, 20g of γ-aminopropyltriethoxysilane, and 50g of polyethylene adipate in sequence. Continue stirring for 1 hour to ensure that the antioxidant, ultraviolet absorber, γ-aminopropyltriethoxysilane, and polyethylene adipate are uniformly dispersed in the resin solution. Step 4, Filtering stage: The compounded resin solution is filtered through a filter screen to remove impurities and gel particles, resulting in a high-strength, water-resistant phthalic unsaturated resin. This resin is then placed in a clean, dry container and sealed for storage.

[0038] The phthalic unsaturated resin of this invention uses phthalic anhydride as the basic resin skeleton to ensure the molecular rigidity and thermal stability of the resin at the microscopic level. Diol is used to optimize the flexibility and water resistance of the resin. Styrene is used as an active diluent to reduce the resin viscosity, giving it good flowability and promoting rapid and complete curing. Polyethylene adipate (PAEG) is used as a polymer chain extender to significantly increase the molecular weight and tensile strength of the resin through chain extension reaction, while maintaining a low viscosity, so that the resin has good processability while possessing high strength. γ-aminopropyltriethoxysilane (KH-550) is used as a coupling agent to enhance the interfacial adhesion between the resin and inorganic fillers (such as glass fiber). The addition amount is 1.5%-4%. Its amino groups react with the carboxyl groups in the resin to form chemical bonds, and at the same time combine with the hydroxyl groups on the surface of the glass fiber to form a double interfacial protection, effectively reducing water penetration and improving the water resistance of the resin.

[0039] (a) Performance testing of liquid resin The basic performance of the liquid resins of the phthalic unsaturated resins synthesized in Examples 1-4 was tested and compared. The comparison results are shown in Table 1. Table 1. Liquid resin performance results of the phthalic unsaturated resins synthesized in Examples 1-4 According to the performance results table, the acid value, viscosity, and solids content of the liquid resins of the phthalic unsaturated resins synthesized in Examples 1-4 all meet the index requirements. Based on the macroscopic measurement of gel time and the microscopic hinge mechanism analysis, Example 4 has the shortest gel time. The mixture of neopentyl glycol and diethylene glycol used in Example 4 plays an important role in optimizing the flexibility and water resistance of the resin. The branched structure of neopentyl glycol can effectively reduce the permeation channels of water molecules, while the linear structure of diethylene glycol works synergistically to effectively balance the rigidity and flexibility of the resin, thereby inhibiting the diffusion of water molecules.

[0040] (II) Performance comparison with existing phthalic unsaturated resins The liquid resin properties and resin casting properties of existing phthalic unsaturated resins S901, FX191, JH5019, JN196, HR192, and the phthalic unsaturated resin synthesized in Example 4 were tested respectively. The test results were compared with the performance results, which are shown in Tables 2 and 3. Among them, the phthalic unsaturated resin S901 is from Nanjing Feilong Composite Materials Co., Ltd., FX191 is from Nantong Fangxin Chemical Co., Ltd., JH5019 and JN196 are both from Jiangyin Jianheng Chemical Co., Ltd., and HR192 is from Changzhou Huari New Materials Co., Ltd.

[0041] Table 2. Comparison of the properties of liquid resins of phthalic unsaturated resins Table 3. Performance Comparison of Resin Castings Based on Phthalic Unsaturated Resin Compared with existing phthalic unsaturated resins, the phthalic unsaturated resin of the present invention exhibits stable performance through optimized formulation and synthesis method, and shows significant improvements in strength and shrinkage.

[0042] (III) Water immersion resistance test and comparison (1) Simulation of the corrosion environment for detection: Water selection in water corrosion test: (1) Soak in pure water; (2) Prepare water with simulated seawater salinity, add 35g sodium chloride to 1000ml of water and control the salinity at a concentration of 3.5%.

[0043] (2) Testing process and results Six specimen strips were made from existing phthalic unsaturated resins S901, FX191, HR192, and the phthalic unsaturated resin synthesized in Example 4, respectively. After testing the flexural strength, the specimen strips were immersed in a 60°C constant temperature water bath for more than 14 days. After immersion, they were removed and placed in a 25°C constant temperature condition for more than 1 hour. After natural drying, the flexural strength after immersion was tested. The comparison of the flexural strength test results is shown in Table 4. Table 4 Comparison of Water Immersion Resistance Tests According to Table 4 and Figures 1-6 Analysis shows that the phthalic unsaturated resin synthesized in this invention exhibits superior flexural strength compared to existing phthalic unsaturated resins, whether immersed in pure water or seawater. Furthermore, compared to existing phthalic unsaturated resins, the phthalic unsaturated resin of this invention demonstrates an increase of over 8% in both resistance to pure water immersion corrosion and resistance to seawater immersion corrosion.

[0044] Compared with existing phthalic unsaturated resins, the phthalic unsaturated resin of the present invention has significantly improved strength, water immersion aging resistance, shrinkage rate and curing speed; while existing phthalic unsaturated resins are difficult to meet high requirements in terms of both strength and water resistance at the same time, the present invention achieves the unity of high strength and high water resistance through unique formulation design and process optimization.

[0045] This invention employs a green synthesis process, reducing energy consumption and the generation of phenolic byproducts, while also lowering styrene content and VOC emissions, thus better meeting environmental protection requirements. The diol can also be replaced with a bio-based source, enhancing the resin's sustainability and environmental friendliness.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations 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 scope of the present invention.

Claims

1. A high-strength, water-resistant, phthalic unsaturated resin, characterized in that: The formulation components and their mass fractions of the phthalic unsaturated resin include: Phthalic anhydride 45-56 parts; 20-28 parts of diol; 17-20 parts styrene; 3-6 parts of polyethylene adipate; 1.5 to 4 parts of γ-aminopropyltriethoxysilane.

2. The high-strength, water-resistant, phthalic unsaturated resin according to claim 1, characterized in that: The diol is one or more of propylene glycol, neopentyl glycol, or diethylene glycol.

3. The high-strength, water-resistant, phthalic unsaturated resin according to claim 2, characterized in that: The diol is a mixture of neopentyl glycol and diethylene glycol, with a ratio of 1:1 between the two.

4. The method for synthesizing the high-strength, water-resistant, phthalic unsaturated resin according to any one of claims 1-3, characterized in that: Includes the following steps: Step 1, Esterification Reaction Stage: According to the formula components and their mass fractions, phthalic anhydride, maleic anhydride and diol were added to the reaction vessel; The reaction vessel is stirred with a stirrer and heated to 160-180°C at a certain rate to start the esterification reaction. During the reaction, the water produced by the reaction is continuously separated out using a water separator. As the esterification reaction proceeds, the acid value of the reaction system is sampled and tested periodically. When the acid value drops to the first acid value, the reaction temperature is raised to 200-220°C to continue the esterification reaction. When the acid value reaches the second acid value, the esterification reaction is completed and the resin is obtained. Step 2, Dilution Stage: Reduce the temperature inside the reactor to 120-140℃, and slowly add styrene and polymerization inhibitor while stirring. After the addition is complete, continue stirring for 1-2 hours to ensure that the resin and styrene are fully mixed and homogeneous to obtain a resin solution. Step 3, Additive compounding stage: Lower the temperature of the resin solution to 60-80℃, then add the functional additive, γ-aminopropyltriethoxysilane, and polyethylene adipate in sequence, and continue stirring for 0.5-1h to ensure that the functional additive, γ-aminopropyltriethoxysilane, and polyethylene adipate are evenly dispersed in the resin solution. Step 4, Filtering stage: The compounded resin solution is filtered through a filter screen to remove impurities and gel particles, thereby obtaining a high-strength, water-resistant phthalic unsaturated resin.

5. The method for synthesizing the high-strength, water-resistant, phthalic unsaturated resin according to claim 4, characterized in that: In step 1, the first acid value is 30-50 mg KOH / g, and the second acid value is 15-30 mg KOH / g.

6. The method for synthesizing the high-strength, water-resistant, phthalic unsaturated resin according to claim 4, characterized in that: In step 1, the rate at which the temperature inside the reactor is raised to 160-180°C is 8-12°C / min.

7. The method for synthesizing the high-strength, water-resistant, phthalic unsaturated resin according to claim 4, characterized in that: In step 1, the amount of maleic anhydride added is controlled to be 33.3% to 55.5% of the amount of phthalic anhydride added.

8. The method for synthesizing the high-strength, water-resistant, phthalic unsaturated resin according to claim 4, characterized in that: In step 2, styrene and polymerization inhibitor are added by dropping, at a rate of 50-60 drops / min.

9. The method for synthesizing the high-strength, water-resistant, phthalic unsaturated resin according to claim 8, characterized in that: The polymerization inhibitor is catechol, hydroquinone, or p-hydroxyanisole.

10. The method for synthesizing the high-strength, water-resistant, phthalic unsaturated resin according to claim 4, characterized in that: The functional additives include antioxidants and ultraviolet absorbers.

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