Primary-coating highlight black paint for electrostatic spraying process and preparation method of primary-coating highlight black paint

Abstract

The invention relates to the field of paint, and particularly discloses first-coat highlight black paint for an electrostatic spraying process and a preparation method of the first-coat highlight black paint. The invention discloses one-coat highlight black paint for an electrostatic spraying process. The one-coat highlight black paint is prepared from the following raw materials in parts by weight: 20-30 parts of polyester resin, 30-40 parts of acrylic resin, 15-20 parts of amino resin, 1-3 parts of a leveling wetting aid, 18-22 parts of a diluent, 1-3 parts of an ultraviolet light absorber, 1-3 parts of a light stabilizer and 2-4 parts of color paste, the amino resin is modified by alkyd resin; the one-coat highlight black paint prepared by the invention can be suitable for electrostatic spraying, meanwhile, the surface of a paint film is kept to have relatively good gloss and flatness, the phenomena of pinholes and orange peels are reduced, and compared with a two-coat process, the one-coat highlight black paint has better chemical resistance.

Description

Technical Field

[0001] The present application relates to the field of coatings, and particularly to a one - coat high - gloss black paint for electrostatic spraying process and a preparation method thereof. Background Art

[0002] As a traditional color, black gives people a feeling of solemnity, dignity and seriousness, and has always been the most favored color for official vehicles. For sedans, the higher - end the car is, the more monotonous the color is, with black being the majority. Black is solemn and imposing, and can better highlight one's status. The higher the blackness and the higher the blue phase, the more high - end it appears. With the rapid development of the automotive industry and consumption upgrading, the body colors are becoming increasingly diverse, highlighting the trend of fashion and personalization. Correspondingly, the requirements for the blackness of black sedan bodies are also getting higher and higher.

[0003] Currently, the automotive coating surface mainly consists of electrophoresis, primer surfacer and topcoat. The topcoat mainly consists of color paint and clear topcoat varnish. The color paint provides different colors for the body, and the clear varnish provides high gloss, appearance and protection for the body. These coatings require at least 2 coatings to meet the corresponding performance requirements, with a high defect rate, serious orange peel on the coating being easily caused, and at the same time, the working efficiency of manual spraying is low and the paint utilization rate is low. Summary of the Invention

[0004] In order to improve the existing paint utilization rate and paint film problems, the present application provides a one - coat high - gloss black paint for electrostatic spraying process and a preparation method thereof.

[0005] In the first aspect, the present application provides a one - coat high - gloss black paint for electrostatic spraying process, adopting the following technical solution: A one - coat high - gloss black paint for electrostatic spraying process, comprising the following raw materials in parts by weight: 20 - 30 parts of polyester resin, 30 - 40 parts of acrylic resin, 15 - 20 parts of amino resin, 1 - 3 parts of leveling and wetting agent, 18 - 22 parts of diluent, 1 - 3 parts of ultraviolet absorber, 1 - 3 parts of light stabilizer, 2 - 4 parts of color paste; the amino resin is modified by alkyd resin.

[0006] By adopting the above technical solutions, the polyester resin can improve the flexibility and adhesion of the paint film, while maintaining good gloss of the paint film, and can crosslink and cure with the amino resin. Acrylic acid can improve the hardness and quick-drying property of the paint film, crosslink with the amino resin, improve the leveling property of the paint, and reduce the orange peel phenomenon of the paint film. The amino resin can improve the crosslinking strength in the paint system, improve the hardness and gloss of the paint film. At the same time, the alkyd resin can reduce the brittleness of the amino resin, improve the hardness and weather resistance of the paint film of the paint, improve the leveling property of the paint, and reduce the appearance of pinholes and craters in the coating. Through the crosslinking of the polyester resin, acrylic resin and amino resin, the prepared paint is suitable for electrostatic spraying, has a high paint utilization rate and reduces paint loss. At the same time, adopting a one-component one-coat process can improve the painting efficiency, reduce the orange peel phenomenon of the paint film, and maintain a good appearance of the paint film.

[0007] Preferably, the alkyd resin is a soybean oil alkyd resin, the acid value of the soybean oil alkyd resin is 8 - 20 mgKOH / g, and the oil length of the soybean oil alkyd resin is 31 - 37%.

[0008] By adopting the above technical solutions, using an alkyd resin with a relatively short oil length of 31 - 37% can maintain both good molecular chain rigidity and strong polarity of the alkyd resin, has good miscibility with the amino resin, and improves the reaction rate of the two. At the same time, controlling the oil length of the alkyd resin within a suitable range can reduce the occurrence of crater phenomena in the paint film. If the oil length of the alkyd resin is too short, it is easy to cause too strong polarity of the alkyd resin and reduce the surface effect of the paint film.

[0009] Preferably, the soybean oil alkyd resin comprises the following raw materials in parts by weight: 40 - 45 parts of soybean oil, 36 - 42 parts of trimethylolpropane, 0.01 - 0.05 parts of lithium hydroxide, 40 - 45 parts of phthalic anhydride, 0.5 - 1.5 parts of maleic anhydride, 1 - 3 parts of benzoic acid, 0.5 - 1 part of p-toluenesulfonic acid, and 50 - 55 parts of solvent.

[0010] By adopting the above technical solutions, using trimethylolpropane to enhance the reaction activity with its three primary hydroxyl groups on the molecule, adding phthalic anhydride and maleic anhydride can promote the generation of more branched chains on the main chain of the prepared soybean oil alkyd resin molecule, promote the uniform distribution of active groups of the soybean oil alkyd resin, and improve the crosslinking reaction of the soybean oil alkyd resin with the amino resin. Benzoic acid can promote the shortening of the soybean oil alkyd resin and simultaneously block the end groups of the soybean oil alkyd resin molecules, forming a three-dimensional structure in the paint system, and enhancing the light stability and hardness of the paint film with its own benzene ring. p-Toluenesulfonic acid accelerates the reaction and reduces the baking temperature of the paint.

[0011] Preferably, the preparation method of the soybean oil alkyd resin comprises the following specific steps: Mix soybean oil, trimethylolpropane, and lithium hydroxide, introduce carbon dioxide, heat up for alcoholysis reaction, cool down after the reaction, and then add phthalic anhydride, maleic anhydride, solvent, p-toluenesulfonic acid, and benzoic acid, and continue to heat up for esterification reaction. When the acid value reaches the standard, the soybean oil alkyd resin is obtained.

[0012] Preferably, the alcoholysis reaction temperature is 230-250 °C, the esterification reaction is 220-240 °C, and the temperature is cooled down to less than 180 °C in the reaction system.

[0013] Preferably, the diluent is at least one of xylene, diacetone alcohol, butyl acetate, and n-butanol.

[0014] Preferably, the ultraviolet absorber is a benzotriazole ultraviolet light absorber, and the light stabilizer is a hindered amine light stabilizer.

[0015] In the second aspect, the present application provides a preparation method of a one-coat high-gloss black paint for electrostatic spraying process, adopting the following technical scheme: A preparation method of a one-coat high-gloss black paint for electrostatic spraying process, comprising the following specific steps: High-speed disperse the alkyd resin and amino resin in advance to obtain an alkyd-modified amino resin, and then mix the alkyd-modified amino resin, polyester resin, acrylic resin, leveling and wetting agent, diluent, ultraviolet absorber, light stabilizer, and color paste to obtain a one-coat high-gloss black paint for electrostatic spraying process.

[0016] By adopting the above technical scheme, the prepared paint is suitable for electrostatic spraying, reduces paint loss, and can also be applied to the one-coat process, improving the painting efficiency. Through the synergistic effect of each component, the orange peel on the paint film surface is reduced, and the flatness of the paint film is improved.

[0017] Preferably, the mass ratio of the alkyd resin to the amino resin is (0.5-0.8):1.

[0018] In summary, the present application has the following beneficial effects: 1. Since the present application uses polyester resin, amino resin, and acrylic resin to crosslink with each other, the flexibility, adhesion, and hardness of the paint film are improved, the gloss on the surface of the paint film is maintained well, and the phenomenon of orange peel on the paint film is reduced. The brittleness of the amino resin is reduced by the alkyd resin, the leveling property of the paint is improved, and the phenomena of pinholes and craters on the coating are reduced.

[0019] 2. In the present application, an alkyd resin with a shorter oil length of 31-37% is used, which can maintain both good molecular chain rigidity and strong polarity of the alkyd resin, has good miscibility with the amino resin, reduces the phenomenon of craters on the paint film, and improves the flatness of the paint film surface. DETAILED DESCRIPTION

[0020] The present application is further described in detail below with reference to the embodiments.

[0021] All raw materials in the examples are commercially available. Example

[0022] Example 1 The present embodiment provides a one-coat high-gloss black paint for an electrostatic spraying process, comprising the following raw materials in parts by weight: 25 kg of polyester resin, 35 kg of acrylic resin, 18 kg of amino resin, 2 kg of leveling and wetting aid, 20 kg of diluent, 2 kg of ultraviolet absorber, 2 kg of light stabilizer, and 3 kg of color paste, wherein the amino resin is modified by alkyd resin; wherein the diluent is n-butanol, the weight-average molecular weight of the polyester resin is 18200, and the hydroxyl OH value is 68 mgKOH / g, the acrylic resin is purchased from Setalux 1766VB-64 of Zhanxin Company, the amino resin is purchased from Suzhou Hetai Chemical Company 27-585, the leveling and wetting aid is selected from Dedigo TEGO-2100, the ultraviolet absorber is selected from Tianjin Lianlong New Materials Co., Ltd. THASORB UV-234, and the light stabilizer is selected from Tianjin Lianlong New Materials Co., Ltd. RIASORB UV-292, the color paste is a common commercially available black color paste; the alkyd resin is DSM alkyd resin Novalkyd252, the oil length is 46%, and the hydroxyl OH value is 130 mgKOH / g.

[0023] The method for preparing a high-gloss black paint for electrostatic spraying process comprises the following specific steps: The alkyd resin and the amino resin are uniformly dispersed in advance at a high speed, dispersed at a speed of 2000r / min for 10 minutes, the mass ratio of the alkyd resin to the amino resin is 0.6:1, and the alkyd modified amino resin is obtained. Then the alkyd modified amino resin, polyester resin, acrylic resin, leveling wetting aid, diluent, ultraviolet absorber, light stabilizer, and color paste are mixed to obtain a coat of high gloss black paint for electrostatic spraying process.

[0024] Example 2 The difference between Example 2 and Example 1 is that the amount of polyester resin used in the high-gloss black paint raw materials used in the electrostatic spraying process is 20 kg, the amount of acrylic resin used is 40 kg, the amount of amino resin used is 15 kg, the amount of leveling and wetting aid used is 1 kg, the amount of diluent used is 18 kg, the amount of UV absorber used is 1 kg, the amount of light stabilizer used is 3 kg, and the amount of color paste used is 2 kg.

[0025] Example 3 Example 3 is different from Example 1 in that in the raw materials of the one - coat high - gloss black paint for electrostatic spraying process, the usage amount of polyester resin is 30 kg, the usage amount of acrylic resin is 30 kg, the usage amount of amino resin is 20 kg, the usage amount of leveling and wetting agent is 3 kg, the usage amount of diluent is 22 kg, the usage amount of ultraviolet absorber is 3 kg, the usage amount of light stabilizer is 1 kg, and the usage amount of color paste is 4 kg.

[0026] Example 4 Example 4 is different from Example 1 in that in the raw materials of the one - coat high - gloss black paint for electrostatic spraying process, the alkyd resin is soybean alkyd resin, and the soybean alkyd resin comprises the following raw materials in parts by weight: 43 kg of soybean oil, 39 kg of trimethylolpropane, 0.03 kg of lithium hydroxide, 43 kg of phthalic anhydride, 1 kg of maleic anhydride, 2 kg of benzoic acid, 0.8 kg of p - toluenesulfonic acid, and 53 kg of solvent. Among them, the soybean oil is salad soybean oil, the solvent is xylene, and the trimethylolpropane is selected from Perstorp 39 of Switzerland.

[0027] The preparation method of the one - coat high - gloss black paint for electrostatic spraying process comprises the following specific steps: S1: Mix soybean oil, trimethylolpropane, and lithium hydroxide, introduce carbon dioxide, heat to 240 °C for alcoholysis reaction for 2 h, after the reaction, cool down to 180 °C, then add phthalic anhydride, maleic anhydride, and solvent for reflux for 2 h, then add p - toluenesulfonic acid and benzoic acid and continue to heat up to 230 °C for esterification reaction, and cool down after the acid value reaches the standard to obtain soybean alkyd resin with an acid value of 15 mgKOH / g and an oil length of 34%.

[0028] S2: Predisperse the soybean alkyd resin and amino resin uniformly at a high speed, disperse at a speed of 2000 r / min for 10 min, the mass ratio of soybean alkyd resin to amino resin is 0.65:1 to obtain alkyd - modified amino resin, then mix the alkyd - modified amino resin, polyester resin, acrylic resin, leveling and wetting agent, diluent, ultraviolet absorber, light stabilizer, and color paste to obtain the one - coat high - gloss black paint for electrostatic spraying process.

[0029] Example 5 Example 5 is different from Example 4 in that in the raw materials of soybean alkyd resin, the usage amount of soybean oil is 40 kg, the usage amount of trimethylolpropane is 36 kg, the usage amount of lithium hydroxide is 0.01 kg, the usage amount of phthalic anhydride is 40 kg, the usage amount of maleic anhydride is 0.5 kg, the usage amount of benzoic acid is 1 kg, the usage amount of p - toluenesulfonic acid is 0.5 kg, and the usage amount of solvent is 50 kg.

[0030] Example 6 Example 6 is different from Example 4 in that the amount of soybean oil used in the raw material of soybean oil alkyd resin is 45 kg, the amount of trimethylolpropane used is 42 kg, the amount of lithium hydroxide used is 0.05 kg, the amount of phthalic anhydride used is 45 kg, the amount of maleic anhydride used is 1.5 kg, the amount of benzoic acid used is 3 kg, the amount of p-toluenesulfonic acid used is 1 kg, and the amount of solvent used is 55 kg.

[0031] Example 7 Example 7 is different from Example 4 in that the oil length of the soybean oil alkyd resin is adjusted to 31%.

[0032] Example 8 Example 8 is different from Example 4 in that the oil length of the soybean oil alkyd resin is adjusted to 37%.

[0033] Example 9 Example 9 is different from Example 4 in that the oil length of the soybean oil alkyd resin is adjusted to 28%.

[0034] Example 10 Example 10 is different from Example 4 in that the mass ratio of the soybean oil alkyd resin to the amino resin is 0.5:1.

[0035] Example 11 Example 11 is different from Example 4 in that the mass ratio of the soybean oil alkyd resin to the amino resin is 0.8:1.

[0036] Comparative Example Comparative Example 1 Comparative Example 1 is different from Example 1 in that alkyd resin is not used in the raw material of the one-coat high-gloss black paint for electrostatic spraying process.

[0037] The preparation method of the one-coat high-gloss black paint for electrostatic spraying process includes the following specific steps: Mix the amino resin, polyester resin, acrylic resin, leveling and wetting agent, diluent, ultraviolet absorber, light stabilizer, and color paste to obtain the one-coat high-gloss black paint for electrostatic spraying process.

[0038] Performance Detection Test Perform the following performance detections on the one-coat high-gloss black paint for electrostatic spraying process provided by Examples 1-11 and Comparative Example 1 of the present application. The specific detection results are shown in Table 1.

[0039] Detection Method I. Electrostatic Spraying Effect Use a robot electrostatic rotary cup to spray the one-coat high-gloss black paint for electrostatic spraying process prepared in the present application, bake and cool it. The film thickness is 10 μm, and observe whether there are problems such as orange peel and pinholes on the surface.

[0040] II. Gloss Refer to the standard of GB / T 9754-2007 "Determination of 20°, 60° and 85° specular gloss of paint films of paints and varnishes, paints without metallic pigments", and test the one-coat high-gloss black paint prepared in this application for the electrostatic spraying process. After baking, place it at room temperature for 24 h and measure the gloss of the paint film surface at 20°.

[0041] III. Hardness and Adhesion Refer to the standard of GB / T 6739-2022 "Determination of film hardness by pencil method for paints and varnishes", and test the one-coat high-gloss black paint prepared in this application for the electrostatic spraying process. After baking, place it at room temperature for 24 h and measure the film hardness; refer to the standard of GB / T 9286-2021 "Cross-cut test for paints and varnishes", and test the adhesion effect of the one-coat high-gloss black paint prepared in this application for the electrostatic spraying process.

[0042] Table 1: Data table of performance test results It can be seen from the performance test results that the one-coat high-gloss black paint prepared in this application can be applied to electrostatic spraying. At the same time, using the one-coat process, it has a high paint utilization rate and painting efficiency. The usage amounts of each component in the raw materials of the one-coat high-gloss black paint in Examples 1-2 are different, and the comprehensive performance of Example 1 is better. By comparing Comparative Example 1 with Example 1, it can be seen that in Comparative Example 1, the amino resin is not modified with alkyd resin. Although the paint film made has no problems such as pinholes and orange peel, the flatness and gloss of the paint film surface are significantly reduced, and the hardness also decreases, further indicating that alkyd resin and amino resin can crosslink with each other to improve the hardness and surface flatness of the paint film.

[0043] It can be seen from Examples 4-8 that the soybean alkyd resin and amino resin prepared in Examples 4-8 have better miscibility, further improving the gloss and flatness of the paint film. By comparing Example 9 with Example 4, it can be seen that when the oil length of the soybean alkyd resin is too short, the crosslinking of the soybean alkyd resin and amino resin is affected, which has a certain negative impact on the surface effect and hardness of the paint film.

[0044] This specific embodiment is only an explanation of this application, and it is not a limitation of this application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions according to needs, but as long as they are within the scope of the claims of this application, they are protected by the patent law.

Claims

1. A high gloss black paint for electrostatic spraying process, characterized in that: The invention comprises the following raw materials in parts by weight: 20-30 parts of polyester resin, 30-40 parts of acrylic resin, 15-20 parts of amino resin, 1-3 parts of leveling and wetting assistant, 18-22 parts of diluent, 1-3 parts of ultraviolet absorber, 1-3 parts of light stabilizer and 2-4 parts of color paste; the amino resin is modified by alkyd resin.

2. The one-coat high gloss black paint for electrostatic spraying process according to claim 1, characterized in that: The alkyd resin is soybean oil alkyd resin, the acid value of the soybean oil alkyd resin is 8-20 mgKOH / g, and the oil content of the soybean oil alkyd resin is 31-37%.

3. The one-coat high gloss black paint for electrostatic spraying process according to claim 2, characterized in that: The soybean oil alkyd resin comprises the following raw materials in parts by weight: 40-45 parts of soybean oil, 36-42 parts of trihydroxymethylpropane, 0.01-0.05 parts of lithium hydroxide, 40-45 parts of phthalic anhydride, 0.5-1.5 parts of maleic anhydride, 1-3 parts of benzoic acid, 0.5-1 parts of p-toluenesulfonic acid and 50-55 parts of solvent.

4. The one-coat high gloss black paint for electrostatic spraying process according to claim 3 is characterized in that: The preparation method of soybean oil alkyd resin comprises the following specific steps: soybean oil, trihydroxymethylpropane and lithium hydroxide are mixed, carbon dioxide is introduced, the temperature is raised to carry out alcoholysis reaction, the temperature is lowered after the reaction, phthalic anhydride, maleic anhydride, solvent, p-toluenesulfonic acid and benzoic acid are added, and the temperature is continued to be raised to carry out esterification reaction, and the soybean oil alkyd resin is obtained when the acid value reaches a qualified level.

5. The one-coat high gloss black paint for electrostatic spraying process according to claim 4, characterized in that: The alcoholysis reaction temperature is 230-250°C, the esterification reaction temperature is 220-240°C, and the temperature is lowered to a reaction system temperature of less than 180°C.

6. The one-coat high gloss black paint for electrostatic spraying process according to claim 1, characterized in that: The diluent is at least one of xylene, diacetone alcohol, butyl acetate and n-butanol.

7. The one-coat high gloss black paint for electrostatic spraying process according to claim 1, characterized in that: The ultraviolet light absorber is a benzotriazole ultraviolet light absorber, and the light stabilizer is a hindered amine light stabilizer.

8. A method for preparing a high gloss black paint for electrostatic spraying process as claimed in any one of claims 1 to 7, characterized in that: The specific steps include: The alkyd resin and the amino resin are pre-dispersed at high speed to obtain an alkyd-modified amino resin, and then the alkyd-modified amino resin, polyester resin, acrylic resin, leveling wetting aid, diluent, ultraviolet absorber, light stabilizer, and color paste are mixed to obtain a one-coat high-gloss black paint for an electrostatic spraying process.

9. The method for preparing a high gloss black paint for electrostatic spraying process according to claim 8, characterized in that: The mass ratio of the alkyd resin to the amino resin is (0.5-0.8):1.

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