Quick-drying varnish for automobile repair and preparation method of quick-drying varnish

Abstract

The invention relates to the field of coating materials, and particularly discloses quick-drying varnish for automobile repair and a preparation method of the quick-drying varnish. The invention discloses quick-drying varnish for repairing automobiles. The quick-drying varnish is prepared from the following raw materials in parts by weight: 10 to 20 parts of hydroxy acrylic resin, 40 to 50 parts of polyether polyol, 40 to 60 parts of isocyanate, 0.1 to 0.3 part of organic silicon additive, 0.1 to 0.5 part of flatting agent, 0.02 to 0.04 part of organic tin, 0.03 to 0.05 part of organic amine, 1 to 3 parts of silane coupling agent, 5 to 8 parts of xylene, 5 to 8 parts of butyl ester and 6.9 to 9.9 parts of propylene glycol methyl ether acetate. According to the invention, propylene glycol methyl ether acetate, butyl ester and xylene with different boiling points are compounded, and acrylic resin is introduced into a polyurethane matrix, so that a prepared paint film has relatively short drying time and relatively strong hardness and toughness.

Description

Technical Field

[0001] The present application relates to the field of coating materials, and in particular, to a fast-drying clear varnish for automotive repair and its preparation method. Background Art

[0002] Automotive repair clear varnish is an essential material in the field of automotive repair. Its main function is to form a protective layer on the surface of the vehicle to prevent corrosion, oxidation, and damage to the vehicle body by the external environment. With the rapid development of the automotive industry and the increasing requirements of consumers for the appearance of automobiles, automotive repair clear varnish has played an important role in enhancing the aesthetics, durability, and environmental friendliness of vehicles. Currently, there are a wide variety of automotive repair clear varnishes on the market, covering traditional solvent-based clear varnishes, waterborne clear varnishes, and UV-curable clear varnishes. While meeting different needs, these products have also promoted the technological progress of the entire industry.

[0003] Traditional polyacrylic resins have good adhesion properties, but they cannot withstand the action of dynamic loads for a long time, and also have disadvantages such as poor resistance to organic solvents and brittleness at low temperatures. Polyurethane resins form a dense paint film through the cross-linking of isocyanate groups with hydroxyl groups or other groups, so they have relatively high hardness, better stain resistance and chemical resistance, etc. However, they still have the drawbacks of short storage period and long drying time. Summary of the Invention

[0004] In order to improve the deficiencies of existing paint materials, the present application provides a fast-drying clear varnish for automotive repair and its preparation method.

[0005] In a first aspect, the present application provides a fast-drying clear varnish for automotive repair, adopting the following technical solution: A fast-drying clear varnish for automotive repair, comprising the following raw materials in parts by weight: 10 - 20 parts of hydroxyl acrylic resin, 40 - 50 parts of polyether polyol, 40 - 60 parts of isocyanate, 0.1 - 0.3 part of organosilicon additive, 0.1 - 0.5 part of leveling agent, 0.02 - 0.04 part of organotin, 0.03 - 0.05 part of organic amine, 1 - 3 parts of silane coupling agent, 5 - 8 parts of xylene, 5 - 8 parts of butyl ester, and 6.9 - 9.9 parts of propylene glycol methyl ether acetate.

[0006] By adopting the above technical solution, the hydroxyl group of the acrylic resin reacts with the isocyanate group of the isocyanate to undergo addition polymerization to form a polyurethane-acrylate network structure, introducing the acrylic resin into the polyurethane matrix, thereby improving the yellowing resistance and adhesion of the varnish. On the other hand, the acrylic resin can form urethane hard segments in the polyurethane matrix and introduce its own carboxyl group, which can absorb moisture to form hydrogen bonds, shortening the drying time of the paint film. The compounding of organotin and organic amine can improve the curing speed of the paint film without affecting the storage stability. The three solvents with different boiling points, namely propylene glycol methyl ether acetate, butyl acetate, and xylene, are compounded. The low-boiling propylene glycol methyl ether acetate can quickly volatilize to take away heat, promoting the rapid surface formation of the paint film in the initial stage. The medium-boiling butyl acetate balances the volatilization speed, avoiding surface defects caused by too fast surface drying of the paint film. The high-boiling xylene delays the later drying, ensuring the leveling property of the coating, and at the same time preventing pinholes caused by solvent retention, enabling the paint film to have both a relatively fast surface drying speed and good paint film flatness.

[0007] Preferably, the hydroxyl acrylic resin is pre-modified with polyhedral oligomeric silsesquioxane, including the following specific steps: mixing polyhedral oligomeric silsesquioxane with a solvent, heating under the protection of nitrogen, and then adding a hydroxyl-containing acrylic monomer, N-(isobutoxy)methylacrylamide, and an initiator for heat preservation reaction to obtain polyhedral oligomeric silsesquioxane-modified acrylic resin.

[0008] By adopting the above technical solution, polyhedral oligomeric silsesquioxane is introduced into the main chain of the acrylic resin, which can reduce the surface tension of the paint film, improve the roughness and stiffness of the paint film surface, and enhance the initial quick-drying property and hydrolysis resistance of the paint film. Adding N-(isobutoxy)methylacrylamide to the polymerization reaction of acrylic monomers can also react with isocyanate to form a three-dimensional network structure, which can increase the crosslinking degree in the paint system and enhance the quick-drying performance of the paint film.

[0009] Preferably, the reaction temperature is 140 - 160 °C.

[0010] Preferably, the polyhedral oligomeric silsesquioxane-modified acrylic resin comprises the following raw materials in parts by weight: 5 - 10 parts of polyhedral oligomeric silsesquioxane, 25 - 35 parts of hydroxyl-containing acrylic monomer, 1 - 3 parts of N-(isobutoxy)methylacrylamide, 0.01 - 0.03 parts of initiator, and 30 - 40 parts of solvent.

[0011] Preferably, the hydroxyl-containing acrylic monomer is styrene, isobutyl acrylate, isooctyl acrylate, 2-hydroxypropyl methacrylate, or acrylic acid.

[0012] Preferably, the mass ratio of styrene, isobutyl acrylate, isooctyl acrylate, 2-hydroxypropyl methacrylate, and acrylic acid is (1 - 2) : (1 - 2) : (3 - 5) : (3 - 4) : 2.

[0013] Preferably, the polyether polyol is a mixture of polyether triol and polyether diol, and the mass ratio of the polyether triol to the polyether diol is 1 : (3 - 4).

[0014] By adopting the above technical solution, the polyether triol and polyether diol are compounded. The bifunctional polyether polyol is used to improve the elasticity and elongation at break of the paint film, and the trifunctional polyether polyol is used to improve the tensile strength and hardness of the paint film. The trifunctional polyether polyol can enhance the crosslinking density with isocyanate, thereby reducing the drying time of the paint film.

[0015] Preferably, the organosilicon additive is a hydroxyl-terminated polysiloxane.

[0016] In a second aspect, the present application provides a preparation method for a fast-drying clear varnish for automotive repair, adopting the following technical solution: A preparation method for a fast-drying clear varnish for automotive repair includes the following specific steps: Vacuum-dry the acrylic resin and polyether polyol respectively. Mix the polyether polyol, xylene, butyl ester, isocyanate, and organosilicon additive, then add organotin and organic amine and heat for reaction. Then add the acrylic resin, propylene glycol methyl ether acetate, and silane coupling agent and mix for heat preservation reaction to obtain a fast-drying clear varnish for automotive repair.

[0017] By adopting the above technical solution, under the synergistic effect of each component of the prepared clear varnish, the drying time of the paint film is significantly shortened, and at the same time, the clear varnish still maintains good weather resistance.

[0018] Preferably, the reaction temperature is 80 - 90 °C.

[0019] In summary, the present application has the following beneficial effects: 1. Since the present application introduces acrylic resin into the polyurethane matrix, it improves the yellowing resistance and weather resistance of the clear varnish, and at the same time retains the quick-drying performance of the acrylic resin. The combination of propylene glycol methyl ether acetate, butyl ester, and xylene with different boiling points promotes the rapid surface drying of the paint film in the initial stage, while preventing pinholes caused by solvent retention, balancing the evaporation rate, and avoiding surface defects caused by too fast surface drying.

[0020] 2. In the present application, the acrylic resin is pre-modified with polyhedral oligomeric silsesquioxane. Introducing polyhedral oligomeric silsesquioxane into the main chain of the acrylic resin can reduce the surface tension of the paint film, improve the surface roughness and stiffness of the paint film, and improve the initial quick-drying property and hydrolysis resistance of the paint film. Detailed implementation mode

[0021] The following further elaborates on the present application in conjunction with embodiments.

[0022] All raw materials in the embodiments can be obtained commercially. Embodiment

[0023] Embodiment 1 This embodiment provides a fast-drying clear varnish for automobile repair, comprising the following raw materials in parts by weight: 15 kg of hydroxy acrylic resin, 45 kg of polyether polyol, 50 kg of isocyanate, 0.2 kg of organosilicon auxiliary, 0.3 kg of leveling agent, 0.03 kg of organotin, 0.04 kg of organic amine, 2 kg of silane coupling agent, 7 kg of xylene, 7 kg of butyl ester, and 8.5 kg of propylene glycol methyl ether acetate. The organosilicon auxiliary is hydroxy-terminated polysiloxane with a number-average molecular weight of 500; the hydroxy content in the hydroxy acrylic resin is 130 mgKOH / g; the polyether polyol is polyether diol with a number-average molecular weight of 2000, the isocyanate is toluene diisocyanate, the organotin is dibutyltin dilaurate, the organic amine is triethylamine, the silane coupling agent is KH550, and the leveling agent is BYK-306.

[0024] The preparation method of the fast-drying clear varnish for automobile repair comprises the following specific steps: Vacuum-dry the acrylic resin and polyether polyol respectively, mix the dried polyether polyol, xylene, butyl ester, isocyanate, and organosilicon auxiliary, then add organotin and organic amine and heat to 85 °C for constant-temperature reaction for 2 h, and then add hydroxy acrylic resin, propylene glycol methyl ether acetate, and silane coupling agent and mix for reaction at 80 °C for 1 h to obtain the fast-drying clear varnish for automobile repair.

[0025] Embodiment 2 The difference between Embodiment 2 and Embodiment 1 is that in the raw materials of the fast-drying clear varnish for automobile repair, the usage amount of hydroxy acrylic resin is 10 kg, the usage amount of polyether polyol is 40 kg, the usage amount of isocyanate is 40 kg, the usage amount of organosilicon auxiliary is 0.1 kg, the usage amount of leveling agent is 0.3 kg, the usage amount of organotin is 0.02 kg, the usage amount of organic amine is 0.05 kg, the usage amount of silane coupling agent is 1 kg, the usage amount of xylene is 5 kg, the usage amount of butyl ester is 8 kg, and the usage amount of propylene glycol methyl ether acetate is 6.9 kg.

[0026] Embodiment 3 Example 3 is different from Example 1 in that the usage amount of hydroxy acrylic resin in the raw materials of the fast-drying clear varnish for automobile repair is 20 kg, the usage amount of polyether polyol is 50 kg, the usage amount of isocyanate is 60 kg, the usage amount of organosilicon auxiliary is 0.3 kg, the usage amount of leveling agent is 0.5 kg, the usage amount of organotin is 0.04 kg, the usage amount of organic amine is 0.03 kg, the usage amount of silane coupling agent is 3 kg, the usage amount of xylene is 8 kg, the usage amount of butyl ester is 5 kg, and the usage amount of propylene glycol methyl ether acetate is 9.9 kg.

[0027] Example 4 Example 4 is different from Example 1 in that the polyether polyol in the raw materials of the fast-drying clear varnish for automobile repair is a mixture of polyether triol and polyether diol, and the mass ratio of polyether triol to polyether diol is 1:3.5. Among them, the polyether triol is polyether triol N-303, and the hydroxyl content is 450 mgKOH / g.

[0028] Example 5 Example 5 is different from Example 4 in that the mass ratio of polyether triol to polyether diol in the raw materials of the fast-drying clear varnish for automobile repair is 1:3.

[0029] Example 6 Example 6 is different from Example 4 in that the mass ratio of polyether triol to polyether diol in the raw materials of the fast-drying clear varnish for automobile repair is 1:4.

[0030] Example 7 Example 7 is different from Example 4 in that the hydroxy acrylic resin in the raw materials of the fast-drying clear varnish for automobile repair is pre-modified with polyhedral oligomeric silsesquioxane. Among them, the polyhedral oligomeric silsesquioxane-modified acrylic resin includes the following raw materials in parts by weight: 8 kg of polyhedral oligomeric silsesquioxane, 30 kg of hydroxy-containing acrylic monomer, 2 kg of N-(isobutoxy)methylacrylamide, 0.02 kg of initiator, and 35 kg of solvent; among them, the polyhedral oligomeric silsesquioxane is allyl heptaisobutyl-POSS, the initiator is di-tert-butyl peroxide, and the solvent is mesitylene; the hydroxy-containing acrylic monomer includes styrene, isobutyl acrylate, isooctyl acrylate, 2-hydroxypropyl methacrylate, and acrylic acid, and the mass ratio of styrene, isobutyl acrylate, isooctyl acrylate, 2-hydroxypropyl methacrylate, and acrylic acid is 1.5:1.5:4:3.5:2.

[0031] The preparation method of the fast-drying clear varnish for automobile repair includes the following specific steps: S1: Mix the polyhedral oligomeric silsesquioxane with a solvent, heat it to 150 °C under the protection of nitrogen, then add the hydroxy acrylic monomer, N-(isobutoxy) methacrylamide, and initiator, and keep the reaction at a constant temperature for 4 h to obtain the polyhedral oligomeric silsesquioxane modified acrylic resin.

[0032] S2: Vacuum dry the polyhedral oligomeric silsesquioxane modified acrylic resin and the polyether polyol respectively. Mix the dried polyether polyol, xylene, butyl ester, isocyanate, and silicone additive, then add organotin and organic amine, heat to 85 °C and keep the reaction at a constant temperature for 2 h. Then add the hydroxy acrylic resin, propylene glycol methyl ether acetate, and silane coupling agent, and react at 80 °C for 1 h to obtain the fast-drying clear varnish for automotive repair.

[0033] Example 8 The difference between Example 8 and Example 7 is that in the raw materials of the polyhedral oligomeric silsesquioxane modified acrylic resin, the usage amount of polyhedral oligomeric silsesquioxane is 5 kg, the usage amount of the hydroxy acrylic monomer is 25 kg, the usage amount of N-(isobutoxy) methacrylamide is 3 kg, the usage amount of the initiator is 0.01 kg, and the usage amount of the solvent is 30 kg.

[0034] Example 9 The difference between Example 9 and Example 7 is that in the raw materials of the polyhedral oligomeric silsesquioxane modified acrylic resin, the usage amount of polyhedral oligomeric silsesquioxane is 10 kg, the usage amount of the hydroxy acrylic monomer is 35 kg, the usage amount of N-(isobutoxy) methacrylamide is 1 kg, the usage amount of the initiator is 0.03 kg, and the usage amount of the solvent is 40 kg.

[0035] Example 10 The difference between Example 10 and Example 7 is that in the hydroxy acrylic monomer, the mass ratio of styrene, isobutyl acrylate, isooctyl acrylate, 2-hydroxypropyl methacrylate, and acrylic acid is 1:2:3:4:2.

[0036] Example 11 The difference between Example 11 and Example 7 is that in the hydroxy acrylic monomer, the mass ratio of styrene, isobutyl acrylate, isooctyl acrylate, 2-hydroxypropyl methacrylate, and acrylic acid is 2:1:5:3:2.

[0037] Comparative Example Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that in the raw materials of the fast-drying clear varnish for automotive repair, the hydroxy acrylic resin is not used.

[0038] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that an equal amount of xylene is used to replace butyl ester in the raw materials of the fast-drying clear varnish for automotive repair.

[0039] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that an equal amount of xylene is used to replace butyl ester and propylene glycol methyl ether acetate in the raw materials of the fast-drying clear varnish for automotive repair.

[0040] Performance detection test For the fast-drying clear varnish for automotive repair provided in Examples 1-11 and Comparative Examples 1-3 of the present application, the following performance detections were carried out, and the specific detection results are shown in Table 1.

[0041] Detection method I. Surface drying time Referring to the standard of GB / T 1728-2020 "Determination of drying time of paint film and putty film", the surface drying time of the fast-drying clear varnish for automotive repair prepared in the present application was detected at 25°C.

[0042] II. Tensile strength and elongation at break Using an AL-70005 electronic universal testing machine, according to the standard of GB / T 528—2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber", the tensile strength, elongation at break were detected at -18°C and 25°C, and the displacement rate was 500 mm / min.

[0043] III. Solvent resistance test Referring to the standard of GB / T 23989-2009 "Determination method for solvent rub resistance of coatings", wiping with 99% mass fraction of alcohol, the number of wiping times of the fast-drying clear varnish for automotive repair prepared in the present application was detected, and it could maintain no color fading and no loss of gloss.

[0044] Table 1: Data table of performance detection results It can be seen from the performance detection results that the fast-drying clear varnish for automotive repair prepared in the present application has a fast surface drying speed, and can also maintain good strength and toughness at low temperatures. By comparing Comparative Examples 1-3 with Example 1, it can be seen that in Comparative Example 1, no hydroxyl acrylic resin is used, in Comparative Example 2, an equal amount of xylene is used to replace butyl ester, and in Comparative Example 3, an equal amount of xylene is used to replace butyl ester and propylene glycol methyl ether acetate. It can be seen from the performance detection results that the surface drying time of Comparative Example 1 decreased significantly, and the comprehensive performance of the strength, toughness and surface drying time of the paint films prepared in Comparative Examples 2-3 decreased significantly. It further shows that the present application introduces acrylic resin into the polyurethane matrix to improve the drying time of the paint film, and the use of solvents with different boiling points in combination can also promote the paint film to have both a fast surface drying speed and good paint film flatness.

[0045] As can be seen from Examples 4-6, the polyether polyol is a mixture of polyether triol and polyether diol. From the performance test results, it can be known that it can effectively enhance the crosslinking density of the polyether polyol and the isocyanate, thereby reducing the drying time of the paint film.

[0046] As can be seen from Examples 7-10, the hydroxyl acrylic resin is pre-modified with polyhedral oligomeric silsesquioxane to reduce the surface tension of the paint film, improve the initial drying speed of the paint film and the solvent resistance of the paint film.

[0047] This specific embodiment is only an explanation of the present application, and it does not limit the present application. Those skilled in the art can make modifications to this embodiment without creative contributions according to needs after reading this specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A quick-drying clearcoat for automotive refinishing, characterized in that, It comprises the following raw materials in parts by weight: 10 - 20 parts of hydroxyl acrylic resin, 40 - 50 parts of polyether polyol, 40 - 60 parts of isocyanate, 0.1 - 0.3 part of silicone auxiliary agent, 0.1 - 0.5 part of leveling agent, 0.02 - 0.04 part of organotin, 0.03 - 0.05 part of organic amine, 1 - 3 parts of silane coupling agent, 5 - 8 parts of xylene, 5 - 8 parts of butyl ester, and 6.9 - 9.9 parts of propylene glycol methyl ether acetate.

2. The quick-drying clear varnish for automotive repair according to claim 1, characterized in that, The hydroxyl acrylic resin is pre - modified by polyhedral oligomeric silsesquioxane, and it includes the following specific steps: Mix polyhedral oligomeric silsesquioxane with a solvent, after heating under the protection of nitrogen, add hydroxyl - containing acrylic monomers, N - (isobutoxy) methacrylamide, and an initiator for heat - preservation reaction to obtain polyhedral oligomeric silsesquioxane - modified acrylic resin.

3. The quick-drying clear varnish for automotive repair according to claim 2, characterized in that, The reaction temperature is 140 - 160 °C.

4. The quick-drying clear varnish for automotive repair according to claim 2, characterized in that, The polyhedral oligomeric silsesquioxane - modified acrylic resin comprises the following raw materials in parts by weight: 5 - 10 parts of polyhedral oligomeric silsesquioxane, 25 - 35 parts of hydroxyl - containing acrylic monomers, 1 - 3 parts of N - (isobutoxy) methacrylamide, 0.01 - 0.03 part of initiator, and 30 - 40 parts of solvent.

5. The quick-drying clear varnish for automotive repair according to claim 3, characterized in that, The hydroxyl - containing acrylic monomers are styrene, isobutyl acrylate, isooctyl acrylate, 2 - hydroxypropyl methacrylate, and acrylic acid.

6. The quick-drying clear varnish for automotive repair according to claim 5, characterized in that, The mass ratio of styrene, isobutyl acrylate, isooctyl acrylate, 2 - hydroxypropyl methacrylate, and acrylic acid is (1 - 2):(1 - 2):(3 - 5):(3 - 4):

2.

7. The quick-drying clear varnish for automobile repair according to claim 1, characterized in that, The polyether polyol is a mixture of polyether triol and polyether diol, and the mass ratio of polyether triol to polyether diol is 1:(3 - 4).

8. The quick-drying clear varnish for automobile repair according to claim 1, wherein The silicone auxiliary agent is hydroxyl - terminated polysiloxane.

9. A preparation method of a quick-drying clear varnish for automobile repair as described in any one of claims 1-8, characterized in that, It includes the following specific steps: Vacuum - dry the acrylic resin and polyether polyol respectively, mix the polyether polyol, xylene, butyl ester, isocyanate, and silicone auxiliary agent, then add organotin and organic amine for heating reaction, and then add the acrylic resin, propylene glycol methyl ether acetate, and silane coupling agent for mixing and heat - preservation reaction to obtain a quick - drying clear varnish for automotive refinishing.

10. The preparation method of the fast-drying clear varnish for automotive repair according to claim 9, wherein, The reaction temperature is 80 - 90 °C.

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