A carbon five petroleum resin for improving the leveling of paint and a method for preparing the same

Abstract

The application discloses a kind of carbon five petroleum resin for improving paint leveling and preparation method thereof, and specifically relates to petroleum resin technical field.The method comprises the following steps: refining carbon five petroleum resin, mixed with organic solvent under nitrogen protection and heated to carry out thermal polymerization;After cooling, polar modified monomer and composite catalyst are added, and catalytic polymerization and grafting reaction are carried out;Add alkaline terminator to terminate the reaction, and the finished product is obtained after washing, solvent removal and granulation.The composite catalyst is prepared by loading tin tetrachloride-phosphorus tributyl ester complex on activated clay.The application solves the problems of poor leveling, poor weather resistance, halogen residue and other problems of traditional resin through raw material refining, step-by-step polymerization and synergistic effect of polarity grafting.The obtained resin can significantly improve the leveling of paint, improve the gloss and weather resistance of coating film, has good compatibility and high stability, is suitable for various coating systems, and the process is environmentally friendly and easy to industrialize.

Description

Technical Field

[0001] This invention relates to the field of petroleum resins, and in particular to a C5 petroleum resin for improving the leveling properties of coatings and a method for preparing the same. Background Technology

[0002] C5 petroleum resins, as an important functional additive in the coatings industry, have long been the focus of research on improving coating leveling properties. With the coatings industry's increasing emphasis on high performance and environmental friendliness, problems such as orange peel, pinholes, and decreased gloss caused by poor coating leveling have become key factors restricting the appearance quality of coatings. Leveling essentially depends on the surface tension gradient and viscoelastic relaxation behavior of the coating film during film formation. C5 petroleum resins, with their suitable glass transition temperature, good compatibility with various film-forming resins, and controllable molecular weight distribution, can effectively regulate the viscoelastic properties of coating systems, suppress the formation of Bénard vortices, and thus promote uniform film spreading. They have found important applications in solvent-based coatings, high-solids coatings, and some powder coating systems.

[0003] C5 petroleum resin is a thermoplastic oligomer obtained by polymerizing pyrolyzed C5 fractions. Its preparation process mainly focuses on two aspects: polymerization methods and molecular structure regulation. Regarding polymerization processes, cationic polymerization is widely used due to its mild reaction conditions and high conversion rate. Commonly used catalytic systems include boron trifluoride and its complexes, and Lewis acids such as aluminum trichloride. Thermal polymerization utilizes high temperatures to induce Diels-Alder addition and free radical polymerization of olefin components. In terms of molecular structure regulation, researchers have attempted to improve the compatibility of the resin with polar coating bases by introducing polar monomers such as maleic anhydride and acrylic acid through copolymerization modification. Other studies have explored hydrogenation modification processes, using unsaturated double bonds in saturated molecules to enhance the resin's weather resistance and lightness, thereby expanding its application range in light-colored topcoats and outdoor coatings.

[0004] However, existing methods for preparing C5 petroleum resins still have many shortcomings. Using halogen-containing Lewis acid catalysts such as boron trifluoride easily leaves halogen residues in the resin, which, upon hydrolysis, produce acidic substances that corrode the substrate and cause yellowing and chalking of the coating. Resins obtained through traditional thermal polymerization processes have a wide molecular weight distribution; low molecular weight components easily cause film re-adhesion, while high molecular weight components significantly increase melt viscosity, hindering sufficient film flow and limiting the improvement in leveling properties. Resins obtained through conventional preparation methods have high color and high unsaturated bond content, resulting in poor weather resistance and easy yellowing and loss of gloss when used outdoors. Insufficient raw material pretreatment leads to residual light components, resulting in a strong resin odor and high volatile organic compound content, making it difficult to meet increasingly stringent environmental protection requirements. Furthermore, traditional C5 petroleum resins have low polarity, resulting in poor compatibility with mainstream coating bases such as acrylic resins and polyester resins, easily causing problems such as cloudiness and decreased gloss, and the softening point fluctuates significantly, adversely affecting the stability of coating formulations. Summary of the Invention

[0005] The main objective of this invention is to provide a method for preparing C5 petroleum resin for improving the leveling properties of coatings, which can effectively solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a C5 petroleum resin for improving the leveling properties of coatings includes the following steps:

[0008] S1: The five-carbon petroleum resin is refined, and under nitrogen protection, the refined five-carbon petroleum resin is mixed with an organic solvent and heated to carry out a thermal polymerization reaction to obtain a thermally polymerized product.

[0009] S2: Cool the thermally polymerized product, add polar modified monomers and composite catalysts, and carry out catalytic polymerization and grafting reaction at 50-80℃ for 2-4 hours to obtain the polymerization reaction solution;

[0010] S3: Add an alkaline terminator to the polymerization reaction solution to terminate the reaction. After washing, solvent removal, and granulation, C5 petroleum resin is obtained.

[0011] Preferably, in step S1, the amount of organic solvent used accounts for 30-70% of the total amount of solvent used; the temperature of the thermal polymerization reaction is 220-240℃, and the time is 3-4 hours; in step S2, the thermal polymerization product is cooled to 50-80℃, and the catalytic polymerization and grafting reaction are carried out at 50-80℃ for 2-4 hours.

[0012] Preferably, the nitrogen gas introduction rate is 0.5-1.5 L / min, the pressure of the thermal polymerization reaction is controlled at 0.1-0.3 MPa, and the heating rate is 5-10 °C / min.

[0013] Preferably, the composite catalyst in step S2 is prepared by the following method:

[0014] S21: Tin tetrachloride and tributyl phosphate are complexed in cyclohexane at 30-70°C for 1-3 hours to obtain tin tetrachloride-tributyl phosphate complex.

[0015] S22: The tin tetrachloride-tributyl phosphate complex is loaded onto activated clay and reacted at 60-90℃ for 2-5 hours. After washing and drying, the composite catalyst is obtained.

[0016] Preferably, the amount of cyclohexane used is 2-5 times the total mass of tin tetrachloride and tributyl phosphate, the drying temperature is 80-100℃, the drying time is 2-3 hours, and anhydrous ethanol is used for washing, with the number of washing cycles being 2.

[0017] Preferably, the molar ratio of tin tetrachloride to tributyl phosphate in step S21 is 1:(0.8-1.5).

[0018] Preferably, the mass ratio of tin tetrachloride-tributyl phosphate complex to activated clay in step S22 is 1:(3-10).

[0019] Preferably, the particle size of the activated clay is 100-200 mesh, the stirring rate of the loading reaction is 200-400 r / min, and the activated clay needs to be activated at 110-130℃ for 2-3 hours before use.

[0020] Preferably, the refining process in step S1 includes removing light components below C4 from the C5 petroleum resin and heat-treating it at 120-140°C for 1-2 hours to dimerize cyclopentadiene into dicyclopentadiene.

[0021] Preferably, the amount of composite catalyst added in step S2 is 2.0-5.0% of the thermal polymerization product; the polar modifying monomer in step S2 is one or more of maleic anhydride, acrylic acid or methacrylic acid, and its amount added is 3.0-8.0% of the mass of the thermal polymerization product.

[0022] Preferably, the catalytic polymerization and grafting reaction in step S2 takes 3-4 hours and the reaction temperature is 55-70℃.

[0023] Preferably, in step S2, the organic solvent is a combination of toluene and xylene, with a mass ratio of 1:(0.5-1.4); the total amount of organic solvent used is in a mass ratio of (0.6-1.3):1 to the thermal polymerization product.

[0024] Preferably, the alkaline terminator in step S3 is an aqueous solution of sodium hydroxide or potassium hydroxide, and the amount added is such that the pH value of the reaction system reaches 6-8.

[0025] Preferably, the mass concentration of the alkaline terminator is 5-15%, the dropping rate is 1-3 mL / min, the washing is done with deionized water, the washing is done 2-3 times, and the amount of water used for each washing is 30-50% of the mass of the polymerization reaction solution; the solvent is removed by vacuum distillation, the distillation temperature is 120-150℃, the distillation pressure is 0.01-0.05 MPa, the granulation temperature is 100-120℃, the particle size is 0.5-2 mm, and the granulation is cooled to room temperature by air cooling.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. In the technical solution of this invention, the composite catalyst exhibits a supported Lewis acid-base complex structure at the microscopic level. This structure uses a tin tetrachloride-tributyl phosphate complex, formed by coordination bonds between tin tetrachloride and tributyl phosphate, as the active center. This complex is anchored within the interlayer domains and surface pores of activated clay through multiple interactions including ion exchange, hydrogen bonding, and van der Waals forces. Activated clay is a layered silicate mineral with nanoscale interlayer spacing and a high specific surface area. Its surface is rich in silanol and aluminol hydroxyl groups, and its interlayer contains exchangeable cations. During preparation, tin tetrachloride and tributyl phosphate undergo a coordination reaction in a cyclohexane medium. The oxygen atom in the phosphorus-oxygen double bond of tributyl phosphate acts as an electron pair donor, forming a coordination bond with the empty 5d orbital of the central tin atom in tin tetrachloride. This increases the coordination number of the tin atom, redistributes the electron cloud density, and moderately reduces the Lewis acidity. Subsequently, the complex reacts with activated clay under heating conditions. The complex enters the clay interlayer through cation exchange and simultaneously forms a hydrogen bond network with surface hydroxyl groups, thereby achieving a high degree of dispersion and immobilization of the active center.

[0028] 2. In the technical solution of this invention, the synergistic effect of the coordination passivation effect and steric hindrance of the composite catalyst controls the generation rate of carbocations within a mild range, allowing the chain growth step to proceed fully while significantly suppressing chain transfer and premature termination. This results in a resin product with a narrow molecular weight distribution, and the content of both low-molecular-weight oligomers and high-molecular-weight gels is reduced to very low levels, solving the problem of simultaneously achieving good leveling, coating hardness, and anti-tack properties. Simultaneously, because the active centers are firmly anchored on the clay support, and the coordination effect enhances the stability of the Sn-Cl bonds, the catalyst and product can be separated by simple filtration after the reaction. The halogen residue in the resin is extremely low, avoiding substrate corrosion, coating yellowing, and chalking caused by the generation of corrosive acids through hydrolysis in humid and hot environments. This significantly improves the weather resistance and adhesion retention of the coating. Furthermore, the recyclability of the heterogeneous catalyst simplifies the post-processing steps, reduces the generation of acid and alkali washing wastewater, and meets environmental protection requirements.

[0029] 3. The technical solution of this invention further incorporates several technical measures, including raw material refining, stepwise polymerization, and polar monomer grafting modification. By pre-removing the light components below C4 in the C5 petroleum resin and subjecting it to heat treatment to dimerize cyclopentadiene into dicyclopentadiene, the probability of side reactions is reduced. The resulting resin has a light color, low unsaturated bond content, low odor, and its volatile organic compound content meets environmental protection standards. A stepwise reaction mode of high-temperature thermal polymerization followed by low-temperature catalytic polymerization and grafting is adopted. During the catalytic polymerization stage, polar monomers such as maleic anhydride, acrylic acid, or methacrylic acid are added. Utilizing the nano-confining effect and electrostatic guiding effect of the interlayer pores of activated clay, the polar monomers are efficiently grafted onto the resin molecular chain, introducing carboxyl groups, anhydrides, and other polar functional groups into the resin. This significantly improves the compatibility of the resin with polar coating bases such as acrylic resin and polyester resin, effectively reduces the surface tension gradient of the coating film, and inhibits the formation of leveling defects such as orange peel and pinholes. Meanwhile, the synergistic effect of stepwise polymerization and heterogeneous catalysis significantly narrows the range of resin softening point fluctuations and improves batch-to-batch consistency, providing a stable leveling improvement effect for coating formulations. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating the preparation process of the present invention. Detailed Implementation

[0031] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise range thresholds, and these range thresholds should be understood to include values ​​close to these range thresholds. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0032] The following describes in detail, with reference to the accompanying drawings, a method for preparing a C5 petroleum resin for improving the leveling properties of coatings, as provided in the embodiments of this specification.

[0033] like Figure 1 As shown, a method for preparing a C5 petroleum resin for improving the leveling properties of coatings.

[0034] Preparation Example 1

[0035] The composite catalyst was prepared by the following method: 8g of tin tetrachloride and 7.8g of tributyl phosphate were added to 31.6g of cyclohexane, and the complexation reaction was carried out at 30℃ for 1 hour to obtain the tin tetrachloride-tributyl phosphate complex.

[0036] The complex prepared above was loaded onto 47.4 g of activated clay and reacted at 60 °C for 2 hours. After washing twice with anhydrous ethanol, it was dried at 80 °C for 2 hours to obtain the composite catalyst.

[0037] Preparation Example 2

[0038] The composite catalyst was prepared by the following method: 10g of tin tetrachloride and 12.2g of tributyl phosphate were added to 66.6g of cyclohexane, and the complexation reaction was carried out at 50℃ for 2 hours to obtain the tin tetrachloride-tributyl phosphate complex.

[0039] The complex prepared above was loaded onto 111g of activated clay and reacted at 75℃ for 3.5 hours. After washing twice with anhydrous ethanol, it was dried at 90℃ for 2.5 hours to obtain the composite catalyst.

[0040] Preparation Example 3

[0041] The composite catalyst was prepared by the following method: 9g of tin tetrachloride and 13.4g of tributyl phosphate were added to 112g of cyclohexane, and the complexation reaction was carried out at 70℃ for 3 hours to obtain the tin tetrachloride-tributyl phosphate complex.

[0042] The complex prepared above was loaded onto 224g of activated clay, reacted at 90℃ for 5 hours, washed twice with anhydrous ethanol, and dried at 100℃ for 3 hours to obtain the composite catalyst.

[0043] Example 1

[0044] This embodiment provides a method for preparing a C5 petroleum resin for improving the leveling properties of coatings. The specific steps are as follows:

[0045] S1: Take 200g of C5 petroleum resin and remove light components below C4 using vacuum distillation at a distillation temperature of 85℃, a distillation pressure of 0.06MPa, and a reflux ratio of 1:2 to obtain refined C5 petroleum resin for later use. Under nitrogen protection, mix the refined C5 petroleum resin with a solvent of 90g toluene and 90g xylene in a 1:1 ratio and heat to carry out a thermal polymerization reaction. The total amount of organic solvent used to the mass ratio of the thermally polymerized product is 0.8:1. The thermal polymerization reaction temperature is 220℃, and the reaction time is 4 hours to obtain the thermally polymerized product.

[0046] S2: Cool the thermally polymerized product to 55°C, add 6g of maleic anhydride, take 4g of the composite catalyst from Preparation Example 1 (accounting for 2.0% of the mass of the thermally polymerized product), disperse it with 10g of toluene and add it to the reaction system, catalyze polymerization and grafting reaction at 55°C for 3 hours to obtain the polymerization reaction solution.

[0047] S3: Add 10% sodium hydroxide aqueous solution as an alkaline terminator to the polymerization reaction solution at a dropping rate of 1.5 mL / min, adjust the pH of the reaction system to 6, and terminate the reaction. Filter to remove the composite catalyst, and after washing, solvent removal, and granulation, obtain C5 petroleum resin.

[0048] Example 2

[0049] This embodiment provides a method for preparing a C5 petroleum resin for improving the leveling properties of coatings. The specific steps are as follows:

[0050] S1: Take 200g of C5 petroleum resin and refine it. First, remove the lighter components below C4. Under nitrogen protection, mix the refined C5 petroleum resin with a mixed solvent consisting of 100g of toluene and 100g of xylene in a 1:1 mass ratio and heat to carry out a thermal polymerization reaction. The total amount of organic solvent used is in a 1:1 mass ratio to the thermally polymerized product. The thermal polymerization reaction temperature is 230℃, and the reaction time is 3.5 hours to obtain the thermally polymerized product.

[0051] S2: Cool the thermally polymerized product to 65°C, add 11g of acrylic acid, take the composite catalyst from Preparation Example 2, disperse it with 16g of xylene and add it to the reaction system, catalyze polymerization and grafting reaction at 60°C for 3.5 hours to obtain the polymerization reaction solution.

[0052] S3: Add 10% potassium hydroxide aqueous solution to the polymerization reaction solution as an alkaline terminator to adjust the pH of the reaction system to 7 and terminate the reaction. Filter to remove the composite catalyst, wash three times with deionized water, remove the solvent by vacuum distillation at 130℃, and granulate at 110℃ to obtain C5 petroleum resin.

[0053] Example 3

[0054] This embodiment provides a method for preparing a C5 petroleum resin for improving the leveling properties of coatings. The specific steps are as follows:

[0055] S1: 200g of C5 petroleum resin was purified at a distillation temperature of 100℃ and a distillation pressure of 0.1MPa to remove light components below C4. Under nitrogen protection, the purified C5 petroleum resin was mixed with a solvent prepared by mixing 109g of toluene and 131g of xylene at a mass ratio of 1:1.2, and the mixture was heated to 240℃ and held at that temperature for 4 hours to obtain the thermally polymerized product.

[0056] S2: Cool the thermally polymerized product to 80°C, add 16g of methacrylic acid, take 10g of the composite catalyst from Preparation Example 3, disperse it in 20g of toluene / xylene mixed solvent, add it to the reaction system, and catalyze polymerization and grafting reaction at 70°C for 4 hours to obtain the polymerization reaction solution.

[0057] S3: Add 15% sodium hydroxide aqueous solution to the polymerization reaction solution as an alkaline terminator, adjust the pH of the reaction system to 8, and terminate the reaction. Filter to remove the composite catalyst, wash three times with deionized water, remove the solvent by vacuum distillation at 150℃, and granulate at 120℃ to obtain the modified C5 petroleum resin.

[0058] Comparative Example 1

[0059] In this comparative example, step S2 does not use a composite catalyst. Instead, a boron trifluoride diethyl ether complex, commonly used in traditional cationic polymerization, is used as the catalyst, with an addition amount of 0.5% of the mass of the thermally polymerized product. The remaining steps and parameters are the same as in Example 2. That is, after cooling the thermally polymerized product to 65°C, the boron trifluoride diethyl ether complex and acrylic acid monomer are directly added, and the reaction is carried out at 65°C for 3 hours. Then, an alkaline terminator is added to adjust the pH to 7. After washing, solvent removal, and granulation, C5 petroleum resin is obtained.

[0060] Comparative Example 2

[0061] In this comparative example, no polar modified monomers are added in step S2; only catalytic polymerization is carried out. The remaining steps are the same as in Example 2.

[0062] Comparative Example 3

[0063] In this comparative example, the thermal polymerization reaction in step S1 is omitted. The refined C5 petroleum resin is directly mixed with an organic solvent and catalytically polymerized at a single temperature. The remaining steps are the same as in Example 2.

[0064] Comparative Example 4

[0065] In this comparative example, the refining process in step S1 is omitted. That is, the C5 petroleum raw material is not subjected to the removal of light components below C4, nor is it subjected to heat treatment at 120-140°C to dimerize cyclopentadiene. The untreated C5 petroleum resin is directly mixed with an organic solvent, and the remaining steps are the same as in Example 2.

[0066] Comparative Example 5

[0067] The difference between this comparative example and Example 2 is that the catalyst used in step S2 is a tin tetrachloride-tributyl phosphate complex that is not supported on activated clay. That is, only step S21 of the composite catalyst preparation method is completed, but the loading operation in step S22 is not performed. The remaining steps are the same as in Example 2.

[0068] Coating leveling performance test: The C5 petroleum resins prepared in Examples 1-3 and Comparative Examples 1-5 were formulated into coatings according to a unified formula, with acrylic resin as the main film-forming substance, combined with mixed solvents, defoamers, and conventional leveling agents. After high-speed dispersion and uniform dispersibility, the coatings were allowed to stand to defoam, and then uniformly coated in one go on a horizontal glass plate cleaned with ethanol using a 100μm wet film preparation device. The coatings were then dried in a constant temperature and humidity environment of 25℃ and 50% relative humidity for 24 hours. The leveling effect was graded by visual rating according to GB / T1750-1979. At the same time, the gloss was measured at different positions of the coating using a 60° gloss meter, and the average value was taken. The gloss level was used to assist in evaluating the leveling performance. Defects such as orange peel and pinholes were recorded for each group of samples.

[0069] (2) Weather resistance test: The same coating as above was evenly applied to a degreased and sanded tinplate. The wet film thickness was controlled at 100 μm. After surface drying at room temperature, it was baked at 60℃ for 30 min and then fully cured at room temperature for 72 h. Accelerated aging test was conducted using an artificial climate aging chamber with UV-A 340nm lamps. One cycle was set as 8 h of light exposure at 60℃ and 4 h of condensation at 50℃, and the test was conducted continuously for 300 h. Before and after the test, the Lab value of the coating was measured using a colorimeter and the color difference value ΔE was calculated. At the same time, the gloss was measured using a 60° gloss meter and the gloss retention rate was calculated. The appearance changes such as yellowing, chalking, and loss of gloss of the coating were observed and recorded to comprehensively evaluate the weather resistance performance. The results are shown in Table 1:

[0070] Table 1. Leveling and weathering test results of each embodiment and comparative example.

[0071]

[0072] Table 1 shows that the leveling grades of Examples 1-3 are 1-2, the gloss at 60° is greater than 87 GU, the color difference ΔE after 300h aging is less than 1.0, and the gloss retention rate is higher than 90%. This indicates that the C5 petroleum resin prepared by this invention can significantly improve the leveling properties of the coating and give the coating film high gloss and excellent weather resistance. Comparative Example 1 uses a traditional boron trifluoride catalyst, resulting in poor leveling, low gloss, large color difference after aging, and low gloss retention rate. This indicates that traditional catalysts easily lead to uneven resin structure and halogen residues, which are detrimental to leveling and weather resistance. Comparative Example 2 does not add polar modified monomers, resulting in low leveling grade, poor gloss, and poor weather resistance. This indicates that the lack of polar grafting reduces resin compatibility and aggravates film formation defects. Comparative Example 3 does not use stepwise thermal polymerization, resulting in insufficient structural control. Its leveling and weather resistance are weaker than those of the examples. Comparative Example 4 does not undergo raw material refining, resulting in the worst leveling properties and the most obvious yellowing and loss of gloss. This indicates that light components and by-products can seriously damage the coating film performance. Comparative Example 5 uses an unsupported complex catalyst, which has insufficient stability, and its performance is between that of the examples and other comparative examples.

[0073] In summary, the modified C5 petroleum resin used in Examples 1-3 is superior to the comparative example in terms of leveling, gloss and weather resistance, and can significantly improve the film quality and outdoor durability of the coating.

[0074] In the description of this specification, the reference to terms such as "embodiment," "various embodiments," etc., indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment or preparation example is included in at least one embodiment of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments.

[0075] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a C5 petroleum resin for improving the leveling properties of coatings, characterized in that, Includes the following steps: S1: The five-carbon petroleum resin is refined, and under nitrogen protection, the refined five-carbon petroleum resin is mixed with an organic solvent and heated to carry out a thermal polymerization reaction to obtain a thermally polymerized product. S2: Cool the thermally polymerized product to 50-80℃ under nitrogen protection, add polar modified monomers, and add the composite catalyst after dispersing it in an organic solvent. Carry out the catalytic polymerization reaction for 2-4 hours to obtain the polymerization reaction solution. S3: Add an alkaline terminator to the polymerization reaction solution to terminate the reaction, filter to remove the composite catalyst, and then wash, remove the solvent, and granulate to obtain C5 petroleum resin. The composite catalyst in step S2 is prepared by the following method: S21: Tin tetrachloride and tributyl phosphate are complexed in cyclohexane at 30-70°C for 1-3 hours to obtain tin tetrachloride-tributyl phosphate complex. S22: The tin tetrachloride-tributyl phosphate complex was loaded onto activated clay and reacted at 60-90℃ for 2-5 hours. After washing and drying, the composite catalyst was obtained.

2. The method for preparing a C5 petroleum resin for improving the leveling properties of coatings according to claim 1, characterized in that, In step S1, the amount of organic solvent used accounts for 30-70% of the total amount of solvent used; the temperature of the thermal polymerization reaction is 220-240℃ and the time is 3-4 hours; in step S2, the thermal polymerization product is cooled to 50-80℃, and the catalytic polymerization and grafting reaction are carried out at 50-80℃ for 2-4 hours.

3. The method for preparing a C5 petroleum resin for improving the leveling properties of coatings according to claim 1, characterized in that, In step S21, the molar ratio of tin tetrachloride to tributyl phosphate is 1:(0.8-1.5).

4. The method for preparing a C5 petroleum resin for improving the leveling properties of coatings according to claim 1, characterized in that, The mass ratio of the tin tetrachloride-tributyl phosphate complex added in step S22 to the activated clay is 1:(3-10).

5. The method for preparing a C5 petroleum resin for improving the leveling properties of coatings according to claim 1, wherein the refining process in step S1 includes removing light components below C4 from the C5 petroleum resin.

6. The method for preparing a C5 petroleum resin for improving the leveling properties of coatings according to claim 1, wherein the amount of composite catalyst added in step S2 is 2.0-5.0% of the thermally polymerized product; and the polar modifying monomer in step S2 is one or more of maleic anhydride, acrylic acid or methacrylic acid, and its addition amount is 3.0-8.0% of the mass of the thermally polymerized product.

7. A method for preparing a C5 petroleum resin for improving the leveling properties of coatings according to claim 1, characterized in that, The catalytic polymerization and grafting reaction in step S2 takes 3-4 hours and the reaction temperature is 55-70℃.

8. A method for preparing a C5 petroleum resin for improving the leveling properties of coatings according to claim 1, characterized in that, In step S2, the organic solvent is a combination of toluene and xylene, with a mass ratio of 1:(0.5-1.4); the total amount of organic solvent used is in a mass ratio of (0.6-1.3):1 to the thermal polymerization product.

9. A method for preparing a C5 petroleum resin for improving the leveling properties of coatings according to claim 1, characterized in that, In step S3, the alkaline terminator is an aqueous solution of sodium hydroxide or potassium hydroxide, and the amount added is such that the pH value of the reaction system reaches 6-8.

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