High-adhesion and high-weather-resistance varnish coating and preparation method thereof

Abstract

The invention relates to the technical field of coatings, and discloses a varnish coating with high adhesive force and high weather resistance and a preparation method thereof. The preparation method comprises the following steps: S1, heating the polyhydroxy additive, the ethylene glycol, the neopentyl glycol and the isophthalic acid under the protection of nitrogen, uniformly stirring, adding the dibutyltin laurate, keeping the temperature for 1-2 hours, heating to 200-220 DEG C, keeping the temperature until the acid value is less than or equal to 100mg / g, and cooling to 80-85 DEG C; adding neopentyl glycol and maleic anhydride, raising the temperature to 160-170 DEG C, keeping the temperature for 1-2 hours, raising the temperature to 200-220 DEG C, and keeping the temperature until the acid value is less than or equal to 5mg / g to obtain polyester; s2, taking polyester, acrylic resin, a defoaming agent, a dispersing agent, a flatting agent and an anti-sagging auxiliary agent, uniformly mixing, adding the modified silicon dioxide, and uniformly stirring to obtain a component A; mixing cobalt isooctoate and methyl ethyl ketone peroxide to obtain a component B; and mixing the component A and the component B, and adjusting the viscosity to obtain the varnish coating.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and discloses a varnish coating with high adhesion and high weather resistance and a preparation method thereof. Background Art

[0002] With the continuous development of the coating industry, polyester varnish is widely used in various fields due to its excellent hardness, gloss and wear resistance. The polyester varnish for automotive interior and exterior decoration often uses the vertical spraying process, which has the problem of easy sagging. Sagging refers to the phenomenon that after the coating is applied on a vertical surface, under the influence of gravity, the lower part of the wet film becomes thicker and the upper part becomes thinner, resulting in performance degradation.

[0003] At the same time, there are still some deficiencies in the actual application of existing polyester varnishes, especially in terms of adhesion and weather resistance. The film adhesion is insufficient and it is easy to fall off under impact. Insufficient weather resistance leads to problems such as color change, powdering and loss of gloss of the film, seriously affecting the service life. In summary, it is of great significance to study a varnish coating that does not sag, has high adhesion and high weather resistance and its preparation method. Summary of the Invention

[0004] The purpose of the present invention is to provide a varnish coating with high adhesion and high weather resistance and a preparation method thereof to solve the problems raised in the above background art.

[0005] To solve the above technical problems, the present invention provides the following technical solution: A preparation method of a varnish coating with high adhesion and high weather resistance, comprising the following steps: S1: Take triallylphenylsilane, add it to ethanol and stir evenly, add a weather resistance antioxidant, mercapto-polyethylene glycol-hydroxy, 1-thioglycerol, stir evenly, add a photoinitiator, and stir for 5 - 10 min under ultraviolet light irradiation, then remove the solvent to obtain a polyhydroxy additive; S2: Take the polyhydroxy additive, ethylene glycol, neopentyl glycol, isophthalic acid, heat to 160 - 170 °C under nitrogen protection, stir evenly, add dibutyltin dilaurate, keep warm for 1 - 2 h, then heat to 200 - 220 °C and keep warm until the acid value (calculated as KOH) ≤ 100 mg / g, then cool to 80 - 85 °C; add neopentyl glycol and maleic anhydride, heat to 160 - 170 °C and keep warm for 1 - 2 h, then heat to 200 - 220 °C and keep warm until the acid value ≤ 5 mg / g to obtain a polyester; S3: Take the polyester, acrylic resin, defoamer, dispersant, leveling agent, anti-sagging aid (Cabot M-5 from Japan), mix evenly, add modified silica, stir evenly to obtain Component A; take cobalt octoate and methyl ethyl ketone peroxide and mix them to obtain Component B; mix Component A and Component B, and adjust the viscosity as needed to obtain the varnish coating.

[0006] Preferably, the polyhydroxy additive comprises the following raw materials in parts by mass: 2 to 2.5 parts of triallylphenylsilane, 50 to 150 parts of ethanol, 3 to 3.5 parts of weather and aging resistant agent, 8 to 10 parts of mercapto-polyethylene glycol-hydroxy, 1 to 1.5 parts of 1-thioglycerol, 0.01 to 0.015 parts of photoinitiator.

[0007] Preferably, the polyester comprises the following raw materials in parts by mass: 20 to 30 parts of polyhydroxy additive, 2 to 3 parts of ethylene glycol, 30 to 50 parts of neopentyl glycol, 20 to 25 parts of isophthalic acid, 0.1 to 0.2 parts of dibutyltin dilaurate, 15 to 25 parts of maleic anhydride.

[0008] Preferably, for the preparation of the polyester: Take 20 to 30 parts of polyhydroxy additive, 2 to 3 parts of ethylene glycol, 15 to 20 parts of neopentyl glycol, 20 to 25 parts of isophthalic acid, heat up to 160 to 170 °C under nitrogen protection, stir evenly, add 0.1 to 0.2 parts of dibutyltin dilaurate, keep warm for 1 to 2 h, then heat up to 200 to 220 °C and keep warm until the acid value (calculated as KOH) is lower than 100 mg / g, then cool down to 80 to 85 °C; Add 18 to 25 parts of neopentyl glycol and 15 to 25 parts of maleic anhydride, heat up to 160 to 170 °C and keep warm for 1 to 2 h, then heat up to 200 to 220 °C and keep warm until the acid value ≤ 5 mg / g to obtain the polyester.

[0009] Preferably, the component A comprises the following raw materials in parts by mass: 40 to 50 parts of polyester, 6 to 10 parts of acrylic resin, 0.1 to 0.2 parts of defoaming agent, 0.3 to 0.5 parts of dispersant, 0.3 to 0.5 parts of leveling agent, 0.1 to 0.2 parts of anti-sagging agent, 10 to 15 parts of modified silica; Component B comprises cobalt isooctanoate and methyl ethyl ketone peroxide with a mass ratio of 1: (2 to 3); The mass ratio of component A to component B is 100: (1 to 2).

[0010] Preferably, the preparation of the weather and aging resistant agent comprises the following steps: Mix 1-hydroxybenzotriazole, 5-chlorobenzimidazole-2-thiol, sodium carbonate, and tetrahydrofuran evenly, stir at 50 to 60 °C for 4 to 6 h, remove the solvent and unreacted substances to obtain the weather and aging resistant agent.

[0011] Preferably, the weather and aging resistant agent comprises the following raw materials in parts by mass: 10 to 15 parts of 1-hydroxybenzotriazole, 16 to 20 parts of 5-chlorobenzimidazole-2-thiol, 8 to 12 parts of sodium carbonate, 60 to 80 parts of tetrahydrofuran.

[0012] More optimally, the preparation of the modified silica includes the following steps: taking nano-silica and chloromethyltrimethoxysilane, adding them to a 50wt% ethanol aqueous solution, adjusting the pH to 5-6, stirring at 50-60°C for 6-8h, filtering, washing and drying the solid to obtain chlorine-containing silica; taking chlorine-containing silica, adding it to water, adding allyl hydroxyethyl ether and hydroxyethyl acrylate, stirring evenly, stirring at 25-30°C for 8-12h, filtering, washing and drying the solid to obtain modified silica.

[0013] More optimally, the chlorine-containing silica comprises the following raw materials, calculated by mass: 10-15 parts of nano-silicon dioxide, 1-2 parts of chloromethyltrimethoxysilane; the modified silica comprises the following raw materials, calculated by mass: 10-15 parts of chlorine-containing silica, 0.5-1 parts of allyl hydroxyethyl ether, and 1-2 parts of hydroxyethyl acrylate.

[0014] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: the polyester prepared by the present invention contains a polyhydroxy additive, and the preparation steps are as follows: first, 1-hydroxybenzotriazole with anti-ultraviolet performance and 5-chlorobenzimidazole-2-thiol with anti-aging performance are compounded to obtain a thiol-containing weathering and anti-aging agent; then, triallylphenylsilane is used as a matrix, and its double bond structure is utilized to graft the weathering and anti-aging agent, thiol-polyethylene glycol-hydroxyl group, and 1-thioglycerol; triallylphenylsilane itself has good heat resistance and contains multiple active groups, the introduction of thiol-polyethylene glycol-hydroxyl group improves the overall polarity and enhances the adhesion of the coating, and 1-thioglycerol introduces multiple active hydroxyl groups, which is helpful for the next reaction; the addition amount of the above substances needs to be controlled to ensure that the prepared polyhydroxy additive contains multiple hydroxyl groups that can participate in the next reaction and has sufficient weather resistance, aging resistance and adhesion; the method ensures the uniform dispersion of the functional compound in the varnish matrix and reduces the migration problem, thereby improving the adhesion and service life of the varnish; The amount of polyhydroxy additives added to polyester also needs to be controlled. The amount of polyhydroxy additives added determines the degree of branching of polyester. The increase in the degree of branching helps to improve mechanical properties, weather resistance, flexibility and film-forming properties. However, due to its large molecular weight, if too much is introduced, it may affect polymerization or lead to poor dispersibility, which in turn leads to a decrease in performance. In addition, too many benzene rings introduced will cause the varnish to turn yellow easily. The present invention adds a leveling agent and an anti-sagging agent to the varnish, and introduces an acrylic resin to further improve the adhesion. However, the compatibility of the acrylic resin with the polyester is poor, which will affect the leveling property and other properties of the system. Therefore, the present invention controls the amount of acrylic resin added, and introduces modified silica to improve the above problems: first prepare chlorine-containing silica, and then introduce allyl hydroxyethyl ether and hydroxyethyl acrylate to obtain modified silica; wherein hydroxyethyl acrylate has good compatibility with the acrylic resin, and allyl hydroxyethyl ether and polyester contain similar segments, which improves their compatibility. Therefore, the addition of the modified silica helps to improve the compatibility between the acrylic resin and the polyester. At the same time, allyl hydroxyethyl ether and hydroxyethyl acrylate can be used as active diluent monomers, which can reduce the viscosity and improve the performance of the varnish film on the one hand, and improve the dispersibility of silica in the varnish on the other hand. In summary, through the above process, a varnish coating with good anti-sagging properties, good weather resistance and good adhesion can be produced. DETAILED DESCRIPTION

[0015] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] It should be noted that there is no special restriction on the purchase manufacturers of all raw materials involved in the present invention, and illustratively include: ethanol (CAS: 64-17-5); acrylic resin (MW~3000, Aladdin); defoamer (TOYNOLDY-80 defoamer, TL-110D, Jihechang); anti-dripping agent (Japanese Cabot M-5); allyl hydroxyethyl ether (CAS: 111-45-5); hydroxyethyl acrylate (CAS: 818-61-1); 1-hydroxybenzotriazole (CAS: 2592-95-2); 5-chlorobenzimidazole-2-thiol (CAS: 25369-78-2); triallylphenylsilane (CAS: 2633- 57-0); mercapto-polyethylene glycol-hydroxyl (Mn~1000, Tansh); 1-thioglycerol (CAS: 96-27-5); dispersant (coating dispersant CP88, Linyi Guoli Chemical Co., Ltd.); leveling agent (TL-J65A, Jihechang); cobalt isooctanoate (CAS: 136-52-7); methyl ethyl ketone peroxide (CAS: 1338-23-4); nano-silica (ML-SiO2-N12, Manli); chloromethyltrimethoxysilane (CAS: 5926-26-1); sodium carbonate (anhydrous sodium carbonate, CAS: 497-19-8); photoinitiator (photoinitiator 1173, CAS: 7473-98-5); Unless otherwise specified, the following are all parts by mass and mass ratios; Example 1: S1: Take 10 parts of nano-silica and 2 parts of chloromethyltrimethoxysilane, add them to 100 parts of 50 wt% ethanol aqueous solution, adjust the pH to 5, stir at 60 °C for 6 h, filter, wash and dry the solid to obtain chlorine-containing silica; S2: Take 12 parts of chlorine-containing silica, add it to 100 parts of water, add 0.8 part of allyl hydroxyethyl ether and 1.5 parts of hydroxyethyl acrylate, stir evenly, stir at 25 °C for 12 h, filter, wash and dry the solid to obtain modified silica; S3: Mix 13 parts of 1-hydroxybenzotriazole, 18 parts of 5-chlorobenzimidazole-2-thiol, 10 parts of sodium carbonate and 80 parts of tetrahydrofuran evenly, stir at 60 °C for 6 h, remove the solvent to obtain a weather-resistant antioxidant; S4: Take 2.5 parts of triallylphenylsilane, add it to 60 parts of ethanol and stir evenly, add 3 parts of weather-resistant antioxidant, 8 parts of mercapto-polyethylene glycol-hydroxy and 1.5 parts of 1-thioglycerol, stir evenly, add 0.01 part of photoinitiator, stir under ultraviolet light for 6 min, remove the solvent to obtain a polyhydroxy additive; S5: Take 28 parts of polyhydroxy additive, 2 parts of ethylene glycol, 16 parts of neopentyl glycol and 25 parts of isophthalic acid, heat up to 160 °C under nitrogen protection, stir evenly, add 0.1 part of dibutyltin dilaurate, keep warm for 2 h, heat up to 220 °C and keep warm until the acid value is 100 mg / g, then cool down to 85 °C; add 20 parts of neopentyl glycol and 20 parts of maleic anhydride, heat up to 160 °C and keep warm for 1 h, then heat up to 220 °C and keep warm until the acid value is 5 mg / g to obtain a polyester; S6: Take 45 parts of polyester, 8 parts of acrylic resin, 0.1 part of defoamer, 0.3 part of dispersant, 0.3 part of leveling agent, 0.1 part of anti-sagging agent, mix evenly, add 12 parts of modified silica, stir evenly to obtain Component A; take cobalt isooctanoate and methyl ethyl ketone peroxide with a mass ratio of 1:2, mix them to obtain Component B; mix Component A and Component B according to a mass ratio of 100:2 to obtain a varnish coating.

[0017] Example 2: S1: Take 10 parts of nano-silica and 2 parts of chloromethyltrimethoxysilane, add them to 100 parts of 50 wt% ethanol aqueous solution, adjust the pH to 5, stir at 60 °C for 6 h, filter, wash and dry the solid to obtain chlorine-containing silica; S2: Take 10 parts of chlorine-containing silica, add it to 100 parts of water, add 0.5 part of allyl hydroxyethyl ether and 2 parts of hydroxyethyl acrylate, stir evenly, stir at 25 °C for 12 h, filter, wash and dry the solid to obtain modified silica; S3: Mix 10 parts of 1-hydroxybenzotriazole, 16 parts of 5-chlorobenzimidazole-2-thiol, 8 parts of sodium carbonate, and 80 parts of tetrahydrofuran evenly, stir at 60 °C for 6 h, remove the solvent to obtain a weather-resistant antioxidant; S4: Take 2 parts of triallylphenylsilane, add it to 60 parts of ethanol and stir evenly, add 3 parts of the weather-resistant antioxidant, 8 parts of mercapto-polyethylene glycol-hydroxy, 1 part of 1-thioglycerol, stir evenly, add 0.01 part of photoinitiator, stir under ultraviolet light for 5 min, remove the solvent to obtain a polyhydroxy additive; S5: Take 20 parts of the polyhydroxy additive, 2 parts of ethylene glycol, 15 parts of neopentyl glycol, and 20 parts of isophthalic acid, heat up to 160 °C under nitrogen protection and stir evenly, add 0.1 part of dibutyltin dilaurate, keep warm for 2 h, heat up to 220 °C and keep warm until the acid value reaches 100 mg / g, then cool down to 85 °C; add 18 parts of neopentyl glycol and 18 parts of maleic anhydride, heat up to 160 °C and keep warm for 1 h, then heat up to 220 °C and keep warm until the acid value reaches 5 mg / g to obtain a polyester; S6: Take 40 parts of the polyester, 6 parts of acrylic resin, 0.1 part of defoamer, 0.3 part of dispersant, 0.3 part of leveling agent, 0.1 part of anti-sagging agent, mix evenly, add 10 parts of modified silica, stir evenly to obtain Component A; Take cobalt isooctanoate and methyl ethyl ketone peroxide in a mass ratio of 1:2, mix them to obtain Component B; Mix Component A and Component B in a mass ratio of 100:2 to obtain a varnish coating.

[0018] Example 3: S1: Take 10 parts of nano-silica and 2 parts of chloromethyltrimethoxysilane, add them to 100 parts of 50 wt% ethanol aqueous solution, adjust the pH to 5, stir at 60 °C for 6 h, filter, wash and dry the solid to obtain chlorine-containing silica; S2: Take 15 parts of the chlorine-containing silica, add it to 100 parts of water, add 1 part of allyl hydroxyethyl ether and 2 parts of hydroxyethyl acrylate, stir evenly, stir at 25 °C for 12 h, filter, wash and dry the solid to obtain modified silica; S3: Mix 15 parts of 1-hydroxybenzotriazole, 20 parts of 5-chlorobenzimidazole-2-thiol, 12 parts of sodium carbonate, and 80 parts of tetrahydrofuran evenly, stir at 60 °C for 6 h, remove the solvent to obtain a weather-resistant antioxidant; S4: Take 2.5 parts of triallylphenylsilane, add it to 60 parts of ethanol and stir evenly, add 3.5 parts of the weather-resistant antioxidant, 10 parts of mercapto-polyethylene glycol-hydroxy, 1.5 parts of 1-thioglycerol, stir evenly, add 0.01 part of photoinitiator, stir under ultraviolet light for 10 min, remove the solvent to obtain a polyhydroxy additive; S5: Take 30 parts of polyhydroxy additive, 3 parts of ethylene glycol, 20 parts of neopentyl glycol, and 25 parts of isophthalic acid. Under nitrogen protection, heat up to 160 °C, stir evenly, add 0.1 part of dibutyltin laurate, keep warm for 2 h, then heat up to 220 °C and keep warm until the acid value reaches 100 mg / g, and then cool down to 85 °C; add 25 parts of neopentyl glycol and 25 parts of maleic anhydride, heat up to 160 °C and keep warm for 1 h, then heat up to 220 °C and keep warm until the acid value reaches 5 mg / g to obtain the polyester; S6: Take 50 parts of polyester, 10 parts of acrylic resin, 0.1 part of defoamer, 0.3 part of dispersant, 0.3 part of leveling agent, and 0.1 part of anti-sagging agent, mix evenly, add 15 parts of modified silica, stir evenly to obtain Component A; take cobalt isooctanoate and methyl ethyl ketone peroxide with a mass ratio of 1:2, mix them to obtain Component B; mix Component A and Component B according to a mass ratio of 100:2 to obtain the varnish coating.

[0019] Comparative Example 1 (changing the addition amount of raw materials in the polyester, and the other method steps are the same as those in Example 1): S1: Take 10 parts of nano-silica and 2 parts of chloromethyltrimethoxysilane, add them to 100 parts of 50 wt% ethanol aqueous solution, adjust the pH to 5, stir at 60 °C for 6 h, filter, wash and dry the solid to obtain chlorine-containing silica; S2: Take 12 parts of chlorine-containing silica, add it to 100 parts of water, add 0.8 part of allyl hydroxyethyl ether and 1.5 parts of hydroxyethyl acrylate, stir evenly, stir at 25 °C for 12 h, filter, wash and dry the solid to obtain modified silica; S3: Mix 13 parts of 1-hydroxybenzotriazole, 18 parts of 5-chlorobenzimidazole-2-thiol, 10 parts of sodium carbonate, and 80 parts of tetrahydrofuran evenly, stir at 60 °C for 6 h, remove the solvent to obtain the weather-resistant antioxidant; S4: Take 2.5 parts of triallylphenylsilane, add it to 60 parts of ethanol and stir evenly, add 3 parts of weather-resistant antioxidant, 8 parts of mercapto-polyethylene glycol-hydroxy, and 1.5 parts of 1-thioglycerol, stir evenly, add 0.01 part of photoinitiator, stir under ultraviolet light for 6 min, remove the solvent to obtain the polyhydroxy additive; S5: Take 40 parts of polyhydroxy additive, 1 part of ethylene glycol, 16 parts of neopentyl glycol, and 25 parts of isophthalic acid. Under nitrogen protection, heat up to 160 °C, stir evenly, add 0.1 part of dibutyltin laurate, keep warm for 2 h, then heat up to 220 °C and keep warm until the acid value reaches 100 mg / g, and then cool down to 85 °C; add 20 parts of neopentyl glycol and 20 parts of maleic anhydride, heat up to 160 °C and keep warm for 1 h, then heat up to 220 °C and keep warm until the acid value reaches 5 mg / g to obtain the polyester; S6: Take 45 parts of polyester, 8 parts of acrylic resin, 0.1 part of defoamer, 0.3 part of dispersant, 0.3 part of leveling agent, 0.1 part of anti-sagging agent, mix them evenly, add 12 parts of modified silica, stir evenly to obtain Component A; take cobalt isooctanoate and methyl ethyl ketone peroxide in a mass ratio of 1:2, mix them to obtain Component B; mix Component A and Component B in a mass ratio of 100:2 to obtain a varnish coating.

[0020] Comparative Example 2 (changing the addition amount of raw materials in polyester, and the other method steps are the same as those in Example 1): S1: Take 10 parts of nano-silica and 2 parts of chloromethyltrimethoxysilane, add them to 100 parts of 50wt% ethanol aqueous solution, adjust the pH to 5, stir at 60°C for 6h, filter, wash and dry the solid to obtain chlorine-containing silica; S2: Take 12 parts of chlorine-containing silica, add it to 100 parts of water, add 0.8 part of allyl hydroxyethyl ether and 1.5 parts of hydroxyethyl acrylate, stir evenly, stir at 25°C for 12h, filter, wash and dry the solid to obtain modified silica; S3: Mix 13 parts of 1-hydroxybenzotriazole, 18 parts of 5-chlorobenzimidazole-2-thiol, 10 parts of sodium carbonate and 80 parts of tetrahydrofuran evenly, stir at 60°C for 6h, remove the solvent to obtain a weather-resistant antioxidant; S4: Take 2.5 parts of triallylphenylsilane, add it to 60 parts of ethanol and stir evenly, add 3 parts of weather-resistant antioxidant, 8 parts of mercapto-polyethylene glycol-hydroxy and 1.5 parts of 1-thioglycerol, stir evenly, add 0.01 part of photoinitiator, stir under ultraviolet light for 6min, remove the solvent to obtain a polyhydroxy additive; S5: Take 10 parts of polyhydroxy additive, 4 parts of ethylene glycol, 16 parts of neopentyl glycol, 25 parts of isophthalic acid, heat up to 160°C under nitrogen protection, stir evenly, add 0.1 part of dibutyltin dilaurate, keep warm for 2h, heat up to 220°C and keep warm until the acid value reaches 100mg / g, then cool down to 85°C; add 20 parts of neopentyl glycol and 20 parts of maleic anhydride, heat up to 160°C and keep warm for 1h, then heat up to 220°C and keep warm until the acid value reaches 5mg / g to obtain polyester; S6: Take 45 parts of polyester, 8 parts of acrylic resin, 0.1 part of defoamer, 0.3 part of dispersant, 0.3 part of leveling agent, 0.1 part of anti-sagging agent, mix them evenly, add 12 parts of modified silica, stir evenly to obtain Component A; take cobalt isooctanoate and methyl ethyl ketone peroxide in a mass ratio of 1:2, mix them to obtain Component B; mix Component A and Component B in a mass ratio of 100:2 to obtain a varnish coating.

[0021] Comparative Example 3 (changing the preparation method of modified silica, and the other method steps are the same as those in Example 1): S1: Take 10 parts of nano-silica, add 0.8 part of allyl hydroxyethyl ether and 1.5 parts of hydroxyethyl acrylate, stir evenly to obtain modified silica; S2: Mix 13 parts of 1-hydroxybenzotriazole, 18 parts of 5-chlorobenzimidazole-2-thiol, 10 parts of sodium carbonate, and 80 parts of tetrahydrofuran evenly, stir at 60 °C for 6 h, remove the solvent to obtain a weather-resistant antioxidant. S3: Take 2.5 parts of triallylphenylsilane, add it to 60 parts of ethanol and stir evenly, add 3 parts of the weather-resistant antioxidant, 8 parts of mercapto-polyethylene glycol-hydroxy, and 1.5 parts of 1-thioglycerol, stir evenly, add 0.01 part of photoinitiator, stir under ultraviolet light for 6 min, remove the solvent to obtain a polyhydroxy additive. S4: Take 28 parts of the polyhydroxy additive, 2 parts of ethylene glycol, 16 parts of neopentyl glycol, and 25 parts of isophthalic acid, heat up to 160 °C under nitrogen protection and stir evenly, add 0.1 part of dibutyltin dilaurate, keep warm for 2 h, heat up to 220 °C and keep warm until the acid value reaches 100 mg / g, then cool down to 85 °C; add 20 parts of neopentyl glycol and 20 parts of maleic anhydride, heat up to 160 °C and keep warm for 1 h, then heat up to 220 °C and keep warm until the acid value reaches 5 mg / g to obtain a polyester. S5: Take 45 parts of the polyester, 8 parts of acrylic resin, 0.1 part of defoamer, 0.3 part of dispersant, 0.3 part of leveling agent, and 0.1 part of anti-sagging agent, mix evenly, add 12 parts of modified silica, stir evenly to obtain Component A; take cobalt isooctanoate and methyl ethyl ketone peroxide with a mass ratio of 1:2, mix them to obtain Component B; mix Component A and Component B in a mass ratio of 100:2 to obtain a varnish coating.

[0022] Comparative Example 4 (changing the raw material addition amount in Component A, and the other method steps are the same as in Example 1): S1: Take 10 parts of nano-silica and 2 parts of chloromethyltrimethoxysilane, add them to 100 parts of 50 wt% ethanol aqueous solution, adjust the pH to 5, stir at 60 °C for 6 h, filter, wash and dry the solid to obtain chlorine-containing silica. S2: Take 12 parts of the chlorine-containing silica, add it to 100 parts of water, add 0.8 part of allyl hydroxyethyl ether and 1.5 parts of hydroxyethyl acrylate, stir evenly, stir at 25 °C for 12 h, filter, wash and dry the solid to obtain modified silica. S3: Mix 13 parts of 1-hydroxybenzotriazole, 18 parts of 5-chlorobenzimidazole-2-thiol, 10 parts of sodium carbonate, and 80 parts of tetrahydrofuran evenly, stir at 60 °C for 6 h, remove the solvent to obtain a weather-resistant antioxidant. S4: Take 2.5 parts of triallylphenylsilane, add it to 60 parts of ethanol and stir evenly, add 3 parts of the weather-resistant antioxidant, 8 parts of mercapto-polyethylene glycol-hydroxy, and 1.5 parts of 1-thioglycerol, stir evenly, add 0.01 part of photoinitiator, stir under ultraviolet light for 6 min, remove the solvent to obtain a polyhydroxy additive. S5: Take 28 parts of polyhydroxy additive, 2 parts of ethylene glycol, 16 parts of neopentyl glycol, and 25 parts of isophthalic acid. Heat to 160°C under nitrogen protection, stir evenly, add 0.1 part of dibutyltin dilaurate, keep warm for 2 h, then heat to 220°C and keep warm until the acid value reaches 100 mg / g, and then cool to 85°C; add 20 parts of neopentyl glycol and 20 parts of maleic anhydride, heat to 160°C and keep warm for 1 h, then heat to 220°C and keep warm until the acid value reaches 5 mg / g to obtain the polyester. S6: Take 45 parts of polyester, 12 parts of acrylic resin, 0.1 part of defoamer, 0.3 part of dispersant, 0.3 part of leveling agent, and 0.1 part of anti-sagging aid, mix evenly, add 12 parts of modified silica, stir evenly to obtain Component A; take cobalt isooctanoate and methyl ethyl ketone peroxide with a mass ratio of 1:2, mix to obtain Component B; mix Component A and Component B in a mass ratio of 100:2 to obtain the varnish coating.

[0023] Performance test: Take the varnish coatings prepared in Examples 1 to 3 and Comparative Examples 1 to 4, cure to obtain a 50-μm coating, and conduct inspections; (1) Detect its adhesion; (2) Refer to GB / T 1865 to test its gloss 1, then irradiate the coating with a xenon lamp for 1500 h, and test the gloss 2 again, calculate the light retention rate to evaluate its weather resistance; Light retention rate = (Gloss 2 / Gloss 1) × 100%; see Table 1 for details. Table 1: Adhesion Gloss retention rate / % Example 1 5B 74.2 Example 2 5B 72.9 Example 3 5B 73.1 Comparative Example 1 5B 68.2 Comparative Example 2 4B 63.9 Comparative Example 3 4B 66.0 Comparative Example 4 4B 66.7 Conclusion: In Comparative Example 1 and Comparative Example 2, the addition amount of polyhydroxy additive in the polyester was changed, and the performance was inferior to that of the examples. Thus, it can be seen that the degree of branching needs to be strictly controlled; in Comparative Example 3, the preparation method of modified silica was changed. Nanometer silica, allyl hydroxyethyl ether, and hydroxyethyl acrylate were directly stirred evenly to obtain modified silica. Due to the influence of compatibility, etc., the performance decreased; in Comparative Example 4, the addition amount of raw materials in Component A was changed. The amount of acrylic resin increased, the leveling property became poor and there were compatibility problems, resulting in a decrease in performance. Thus, it can be seen that controlling the addition amount of raw materials is of great significance; in summary, the varnish coating prepared by the present invention has good adhesion, good leveling property, no sagging, and good weather resistance.

[0024] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a high - adhesion and high - weather - resistant varnish coating, characterized in that: It includes the following steps: S1: Take triallylphenylsilane, add it to ethanol and stir evenly. Then add a weather and aging resistant agent, mercapto-polyethylene glycol-hydroxy, 1-thioglycerol, and stir evenly. Add a photoinitiator and stir for 5 - 10 min under ultraviolet light irradiation. Remove the solvent to obtain a polyhydroxy additive. S2: Take the polyhydroxy additive, ethylene glycol, neopentyl glycol, isophthalic acid, heat to 160 - 170 °C under nitrogen protection and stir evenly. Add dibutyltin dilaurate, keep warm for 1 - 2 h, then heat to 200 - 220 °C and keep warm until the acid value ≤ 100 mg / g, then cool to 80 - 85 °C. Add neopentyl glycol and maleic anhydride, heat to 160 - 170 °C and keep warm for 1 - 2 h, then heat to 200 - 220 °C and keep warm until the acid value ≤ 5 mg / g to obtain a polyester. S3: Take the polyester, acrylic resin, defoamer, dispersant, leveling agent, anti-sagging aid, mix evenly, add modified silica and stir evenly to obtain Component A. Mix cobalt octoate and methyl ethyl ketone peroxide to obtain Component B. Mix Component A and Component B and adjust the viscosity to obtain a varnish coating.

2. The preparation method of a high-adhesion and high-weather-resistant varnish coating according to claim 1, characterized in that: The polyhydroxy additive includes the following raw materials, by mass: 2 - 2.5 parts of triallylphenylsilane, 50 - 150 parts of ethanol, 3 - 3.5 parts of weather and aging resistant agent, 8 - 10 parts of mercapto-polyethylene glycol-hydroxy, 1 - 1.5 parts of 1-thioglycerol, 0.01 - 0.015 parts of photoinitiator.

3. The preparation method of a high-adhesion and high-weather-resistant varnish coating according to claim 1, characterized in that: The polyester includes the following raw materials, by mass: 20 - 30 parts of polyhydroxy additive, 2 - 3 parts of ethylene glycol, 30 - 50 parts of neopentyl glycol, 20 - 25 parts of isophthalic acid, 0.1 - 0.2 parts of dibutyltin dilaurate, 15 - 25 parts of maleic anhydride.

4. The preparation method of a high-adhesion and high-weather-resistant varnish coating according to claim 1, characterized in that: Component A includes the following raw materials, by mass: 40 - 50 parts of polyester, 6 - 10 parts of acrylic resin, 0.1 - 0.2 parts of defoamer, 0.3 - 0.5 parts of dispersant, 0.3 - 0.5 parts of leveling agent, 0.1 - 0.2 parts of anti-sagging aid, 10 - 15 parts of modified silica; Component B includes cobalt octoate and methyl ethyl ketone peroxide with a mass ratio of 1:(2 - 3); the mass ratio of Component A to Component B is 100:(1 - 2).

5. The preparation method of a high-adhesion and high-weather-resistant varnish coating according to claim 1, characterized in that: The preparation of the weather and aging resistant agent includes the following steps: Mix 1-hydroxybenzotriazole, 5-chlorobenzimidazole-2-thiol, sodium carbonate, and tetrahydrofuran evenly, stir at 50 - 60 °C for 4 - 6 h, remove the solvent to obtain the weather and aging resistant agent.

6. The preparation method of a high-adhesion and high-weather-resistant varnish coating according to claim 5, characterized in that: The weather and aging resistant agent includes the following raw materials, by mass: 10 - 15 parts of 1-hydroxybenzotriazole, 16 - 20 parts of 5-chlorobenzimidazole-2-thiol, 8 - 12 parts of sodium carbonate, 60 - 80 parts of tetrahydrofuran.

7. The preparation method of a high-adhesion and high-weather-resistant varnish coating according to claim 1, characterized in that: The preparation of the modified silica includes the following steps: Take nano-silica and chloromethyltrimethoxysilane, add them to an ethanol aqueous solution, adjust the pH to 5-6, stir at 50-60°C for 6-8 hours, filter, wash and dry the solid to obtain chlorine-containing silica; take chlorine-containing silica, add it to water, add allyl hydroxyethyl ether and hydroxyethyl acrylate, stir evenly, stir at 25-30°C for 8-12 hours, filter, wash and dry the solid to obtain modified silica.

8. The preparation method of a high-adhesion and high-weather-resistant varnish coating according to claim 7, characterized in that: The chlorine-containing silicon dioxide comprises the following raw materials, calculated by weight: 10-15 parts of nano silicon dioxide and 1-2 parts of chloromethyltrimethoxysilane; the modified silicon dioxide comprises the following raw materials, calculated by weight: 10-15 parts of chlorine-containing silicon dioxide, 0.5-1 parts of allyl hydroxyethyl ether and 1-2 parts of hydroxyethyl acrylate.

9. A varnish coating prepared according to the method for preparing a varnish coating with high adhesion and high weather resistance according to any one of claims 1 to 8.