High-solid, low-viscosity acrylic resin and its preparation method and application

Abstract

The present invention belongs to the technical field of acrylic resins, and specifically relates to a high-solid, low-viscosity acrylic resin and its preparation method and application. The present invention uses a segmented polymerization method to prepolymerize an acrylic acid mixture containing acrylic acid, methyl methacrylate, and hydroxyethyl methacrylate, then add an acrylic acid mixture containing a modified prepolymer, acrylic acid, and butyl acrylate and react with a nano-toughening additive, and finally add deionized water for emulsification to obtain a high-solid, low-viscosity acrylic resin; the nano-toughening additive introduces a rigid furan group to improve the toughening ability and wear resistance of nano-silica; thiolactone acrylamide is prepolymerized with N-isopropyl-N-benzyl-2-acrylamide, and the aminolysis ring is reacted with octadecyl acrylate to obtain a modified prepolymer, which introduces a long-chain alkyl side chain group and a benzene ring structure, thereby improving the flexibility and salt spray resistance of the modified prepolymer. When applied to automotive varnish, the anti-scratch performance of the varnish can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of acrylic resin production, and in particular relates to a high-solid, low-viscosity acrylic resin and a preparation method and application thereof. Background Art

[0002] Acrylic resins refer to polymers and copolymers formed by free radical polymerization of acrylic acid and its esters, and methacrylic acid and its esters. Acrylic resins with a solids content of 60-80% are considered high-solids acrylic resins. In recent years, with increasing environmental awareness and increasingly stringent environmental regulations, restrictions on volatile organic compound (VOC) emissions from resin coatings have become increasingly stringent. High-solids resins with low solvent content have become a research priority. Currently, the development of high-solids, low-viscosity acrylic resins primarily focuses on reducing molecular weight. However, this reduction in molecular weight results in a relative decrease in the hydroxyl content per polymer molecule, affecting crosslinking density and curing speed. Therefore, to ensure the quality of the acrylic resin, most high-solids acrylic resins on the market have a solids content below 65%.

[0003] Chinese invention patent publication number CN116515121B discloses a high-solid, low-viscosity acrylic resin and its application in automotive interior coatings. The high-solid, low-viscosity acrylic resin is formed by reacting a hard segment acrylic resin, a soft segment acrylic resin, and a hyperbranched polysiloxane-grafted β-cyclodextrin. The hard segment acrylic resin is copolymerized with isobornyl methacrylate and hydroxyethyl methacrylate, and the soft segment acrylic resin is copolymerized with butyl methacrylate, behenyl methacrylate, methyl methacrylate, and methacrylic acid. This invention introduces a hard segment acrylic resin, a soft segment acrylic resin, and a hyperbranched polysiloxane-grafted β-cyclodextrin with a specific structure into the high-solid, low-viscosity acrylic resin, resulting in a high-solid, low-viscosity acrylic resin with moderate hardness, good scratch resistance, and good wear resistance. However, the prior art lacks further improvements to the branched components of the acrylic resin prepolymer to enhance the high-solid, low-viscosity performance and cure speed of the acrylic resin, and to expand its application range by increasing the crosslinking density and cure speed. Summary of the Invention

[0004] The object of the present invention is to provide a high-solid, low-viscosity acrylic resin and its preparation method and application, so as to solve the technical problem that the prior art has not further improved the side chain components of the acrylic resin prepolymer to improve the high-solid, low-viscosity performance and curing speed of the acrylic resin, and to expand the application range by increasing the crosslinking density and curing speed.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A high-solid, low-viscosity acrylic resin is prepared from the following components in parts by weight:

[0007] 40-60 parts of acrylic acid mixture 1, 15-25 parts of acrylic acid mixture 2, 10-13 parts of versatile glycidyl carbonate, 10-15 parts of solvent, 0.3-0.5 parts of nano toughening agent, 1-3 parts of azobisisobutyronitrile initiator, 0.5-3 parts of α-methylstyrene dimer chain transfer agent, 5-10 parts of neutralizer and 20-30 parts of deionized water;

[0008] Acrylic acid mixture 1 includes the following raw materials in parts by weight: 12-18 parts of acrylic acid, 20-30 parts of methyl methacrylate, and 12-15 parts of hydroxyethyl methacrylate;

[0009] The second acrylic mixture comprises the following raw materials in parts by weight: 3 to 6 parts of a modified prepolymer, 8 to 10 parts of acrylic acid, and 4 to 8 parts of butyl acrylate;

[0010] The modified prepolymer is prepared by reacting DL-homocysteine thiolactone hydrochloride with acryloyl chloride to generate thiolactone acrylamide, which is then copolymerized with N-isopropyl-N-benzyl-2-acrylamide to obtain a prepolymer, and finally the prepolymer is subjected to aminolysis with triethylamine and then reacted with octadecyl acrylate to obtain the prepolymer.

[0011] The solvent is any one of butyl acetate, isopropyl alcohol, and ethylene glycol butyl ether, and the neutralizer is any one of N,N-dimethylethanolamine and triethanolamine.

[0012] The preparation method of high-solid, low-viscosity acrylic resin comprises the following steps:

[0013] S1. Acrylic acid, methyl methacrylate, and hydroxyethyl methacrylate are mixed to prepare an acrylic acid mixture 1. A solvent and versatile glycidyl carbonate are added to a reaction kettle, nitrogen is introduced to replace the air, the temperature is increased to remove moisture, and then the acrylic acid mixture 1, 0.05-1 parts of azobisisobutyronitrile as an initiator, and 0.3-1.5 parts of α-methylstyrene dimer as a chain transfer agent are added dropwise. The reaction is carried out at this temperature to obtain an intermediate product 1.

[0014] S2, mixing the modified prepolymer, acrylic acid and 4-8 parts of butyl acrylate to prepare acrylic acid mixture 2, adding acrylic acid mixture 2, nano toughening agent, 0.05-1 parts of azobisisobutyronitrile initiator and 0.2-1.5 parts of α-methylstyrene dimer chain transfer agent dropwise to intermediate product 1, and reacting at the same temperature to prepare intermediate product 2;

[0015] S3. After cooling the intermediate product 2, a neutralizing agent is added and stirred evenly, and deionized water is added and stirred and dispersed to obtain a high-solid, low-viscosity acrylic resin.

[0016] Preferably, the temperature of the heat preservation reaction in S1 is raised to 130-140° C. and the heat preservation reaction is carried out for 3-4 hours.

[0017] Preferably, the temperature of the heat preservation reaction in S2 is raised to 130-140° C. and the heat preservation reaction is carried out for 1-2 hours.

[0018] Preferably, the intermediate product 2 in S3 is cooled to 70-80° C., a neutralizing agent is added, and the mixture is stirred at a speed of 2000-3000 rpm for 10-15 minutes to disperse and form an emulsion.

[0019] Preferably, the preparation method of the nano toughening agent comprises the following steps:

[0020] S11, adding 10-20 parts by mass of silica sol to 50-100 parts by mass of ethanol aqueous solution, adding 3-6 parts of 3-aminopropyltrimethoxysilane, heating to react, filtering to collect the solid, washing and drying to obtain grafted nano-silica;

[0021] S12, adding 30-40 parts by mass of 2-vinylfuran to a reaction kettle, adding 35-45 parts of glycidyl acrylate and 0.5-1 part of benzoyl peroxide initiator, and heating the reaction to obtain an epoxy grafted product;

[0022] S13. Add 5 to 6 parts by mass of grafted nano-silica into a reactor, add 50 to 60 parts of N,N-dimethylacrylamide solvent, add 10 to 15 parts of epoxy grafted material and 0.1 to 0.3 parts of benzoyl peroxide initiator, and heat to react to obtain a nano-toughening additive.

[0023] Preferably, the ethanol mass fraction of the ethanol aqueous solution in S11 is 70%, and the temperature is raised to 70-90° C. and the reaction is carried out for 3-4 hours.

[0024] Preferably, the temperature in S12 is raised to 80-90° C. and the reaction is carried out for 1-2 hours.

[0025] Preferably, in S13, the temperature is raised to 60-70° C. and the reaction is carried out for 3-4 hours.

[0026] Preferably, the method for preparing the modified prepolymer comprises the following steps:

[0027] S21. Add 4 to 5 parts of DL-homocysteine thiolactone hydrochloride and 50 to 100 parts of dichloromethane to a reactor, dissolve 2 to 5 parts of acryloyl chloride in dichloromethane and add the mixture to the reactor with stirring in an ice bath. Add 10 to 15 parts of sodium bicarbonate, raise the temperature to room temperature, react for 12 to 24 hours, extract with ethyl acetate, remove water, and dry to obtain thiolactone acrylamide.

[0028] S22. Add 30-40 parts of tetrahydrofuran solvent into a reactor, and add 3-5 parts of thiolactone acrylamide, 10-15 parts of N-isopropyl-N-benzyl-2-acrylamide, 0.1-0.3 parts of methyl styrene dimer chain transfer agent and 0.01-0.5 parts of azobisisobutyronitrile initiator. Raise the temperature to 70-80°C in a nitrogen atmosphere and react for 1-2 hours. Precipitate with ether, collect the solid by filtration, and dry to obtain a prepolymer.

[0029] S23. Add 10-15 parts of prepolymer, 30-40 parts of triethylamine and 40-50 parts of N,N-dimethylacrylamide solvent into a reactor, heat to 50-60°C and react for 12-24 hours to perform aminolysis ring opening, add 20-30 parts of octadecyl acrylate, and react at 30-40°C for 12-24 hours to obtain a modified prepolymer.

[0030] The reaction principle of the modified prepolymer is as follows:

[0031]

[0032] The application of high-solid, low-viscosity acrylic resin is used to prepare automotive varnish, and the preparation method comprises the following steps:

[0033] An automobile clear coat is prepared by mixing, by mass, 75-80 parts of a high-solid, low-viscosity acrylic resin, 10-15 parts of deionized water, 0.5-1 part of dimethylethanolamine, 10-15 parts of ethylene glycol butyl ether, 0.5-2 parts of a leveling agent, 0.5-2 parts of a defoaming agent and 1-5 parts of an ultraviolet absorber.

[0034] Preferably, the leveling agent is any one of BYK-346 and BYK-333.

[0035] Preferably, the defoamer is any one of BYK-141 and BYK-055.

[0036] Preferably, the ultraviolet absorber is any one of UV-400 and UV-1130.

[0037] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0038] 1. The present invention adopts a segmented polymerization method. First, an acrylic acid mixture containing acrylic acid, methyl methacrylate, and hydroxyethyl methacrylate is reacted and prepolymerized. Then, an acrylic acid mixture containing a modified prepolymer, acrylic acid, and butyl acrylate is added and reacted with a nano-toughening additive. Finally, deionized water is added for emulsification to obtain a high-solid, low-viscosity acrylic resin. The long-chain alkyl group of versatate glycidyl carbonate has a large steric hindrance, which increases the distance between molecular chains. The epoxy group can react with the carboxyl group of acrylic acid, which helps to reduce the viscosity of the acrylic resin and increase the solid content and curing speed of the acrylic resin. Methyl methacrylate acts as a hard monomer to increase the hardness of the acrylic resin. Hydroxyethyl methacrylate provides hydroxyl groups to improve the hydrophilicity of the acrylic resin. The modified prepolymer contains long-chain alkyl side chain groups, which have a large steric hindrance and can improve the flexibility and impact resistance of the acrylic resin.

[0039] 2. The present invention prepares grafted nano-silica by grafting an amino-containing silane coupling agent onto silica sol, prepares an epoxy graft by reacting 2-vinylfuran and glycidyl acrylate, and introduces a rigid furan group into the nano-toughening additive prepared by the reaction of the grafted nano-silica and the epoxy graft, thereby improving the toughening ability and wear resistance of the nano-silica.

[0040] 3. The present invention prepares thiolactone acrylamide by reacting thiolactone with acryloyl chloride, which is then prepolymerized with N-isopropyl-N-benzyl-2-acrylamide. Finally, the thiolactone is ring-opened by aminolysis and reacted with octadecyl acrylate to prepare a modified prepolymer. N-isopropyl-N-benzyl-2-acrylamide introduces a benzene ring structure, thereby improving the flexibility and salt spray resistance of the modified prepolymer. The residual thiol group after amino ring opening can form a dynamic disulfide bond under stress, which can improve the scratch resistance of automotive clear coat when applied to the clear coat. The ring-opening grafting of long-chain alkyl side chain groups gives the modified prepolymer greater steric hindrance, avoids gelation caused by excessive polymerization of high-solid content acrylic acid monomers, and enables the high-solid content acrylic resin to have a high molecular weight while having low viscosity, thereby improving the crosslinking density and curing speed of the clear coat. DETAILED DESCRIPTION

[0041] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0042] Example 1: The high-solid, low-viscosity acrylic resin of this embodiment is prepared from the following components:

[0043] 50g of acrylic acid mixture 1, 20g of acrylic acid mixture 2, 11g of versatile glycidyl carbonate, 10g of solvent, 0.5g of nano toughening agent, 1g of azobisisobutyronitrile initiator, 0.5g of α-methylstyrene dimer chain transfer agent, 8g of neutralizer and 20g of deionized water.

[0044] Acrylic acid mixture 1 includes the following raw materials: 15g acrylic acid, 20g methyl methacrylate, 15g hydroxyethyl methacrylate;

[0045] The second acrylic mixture includes the following raw materials: 5 g of modified prepolymer, 9 g of acrylic acid, and 6 g of butyl acrylate.

[0046] The solvent is ethylene glycol butyl ether, and the neutralizer is N,N-dimethylethanolamine.

[0047] The preparation method of the nano toughening agent of this embodiment includes the following steps:

[0048] S11, adding 15 g of silica sol to 50 g of 70% ethanol aqueous solution, adding 3 g of 3-aminopropyltrimethoxysilane, heating to 80° C. for 1 h, filtering and collecting the solid, washing and drying to obtain grafted nano-silica;

[0049] S12, adding 33 g of 2-vinylfuran into a reaction kettle, adding 44 g of glycidyl acrylate and 0.5 g of benzoyl peroxide initiator, raising the temperature to 80° C. and reacting for 2 h to obtain an epoxy grafted product;

[0050] S13. Add 6 g of grafted nano-silica into a reactor, add 60 g of N,N-dimethylacrylamide solvent, add 15 g of epoxy graft and 0.3 g of benzoyl peroxide initiator, raise the temperature to 70° C. and react for 4 h to obtain a nano-toughening additive.

[0051] The preparation method of the modified prepolymer of this embodiment comprises the following steps:

[0052] S21, 4.5g of DL-homocysteine thiolactone hydrochloride and 50g of dichloromethane were added to a reactor, 3g of acryloyl chloride was dissolved in dichloromethane and then added to the reactor, stirred in an ice bath, 15g of sodium bicarbonate was added, the temperature was raised to room temperature and the reaction was carried out for 24h, extracted with ethyl acetate, and dried to obtain thiolactone acrylamide;

[0053] S22. Add 40 g of tetrahydrofuran solvent into the reactor, add 5 g of thiolactone acrylamide, 10 g of N-isopropyl-N-benzyl-2-acrylamide, 0.3 g of methyl styrene dimer chain transfer agent and 0.3 g of azobisisobutyronitrile initiator, raise the temperature to 80 ° C in a nitrogen atmosphere and react for 2 hours, precipitate with ether, collect the solid by filtration, and dry to obtain a prepolymer.

[0054] S23. Add 10 g of prepolymer, 30 g of triethylamine and 40 g of N,N-dimethylacrylamide solvent into a reactor, heat to 60°C and react for 24 h to perform aminolysis ring opening. Add 20 g of octadecyl acrylate and react at 40°C for 24 h to obtain a modified prepolymer.

[0055] The preparation method of the high-solid, low-viscosity acrylic resin of this embodiment comprises the following steps:

[0056] S1. Acrylic acid, methyl methacrylate, and hydroxyethyl methacrylate were mixed to prepare an acrylic acid mixture 1. A solvent and tert-butyl glycidyl carbonate were added to a reaction kettle, nitrogen was introduced to replace the air, the temperature was raised to 130° C. to remove moisture, and the acrylic acid mixture 1, 0.5 g of azobisisobutyronitrile initiator, and 0.3 g of α-methylstyrene dimer chain transfer agent were dropwise added. The reaction was kept warm for 4 h to obtain an intermediate product 1.

[0057] S2, mixing the modified prepolymer, acrylic acid and butyl acrylate to prepare acrylic acid mixture II, adding acrylic acid mixture II, nano toughening agent, 0.5 g of azobisisobutyronitrile initiator and 0.2 g of α-methylstyrene dimer chain transfer agent dropwise to intermediate product 1, and reacting at 140° C. for 2 h to obtain intermediate product 2;

[0058] S3. After cooling the intermediate product 2 to 70° C., a neutralizer was added and stirred evenly, and deionized water was added and stirred at a speed of 3000 rpm for 10 minutes to disperse and form an emulsion, thereby preparing a high-solid, low-viscosity acrylic resin.

[0059] The high-solid, low-viscosity acrylic resin of this embodiment is used to prepare automotive clear coat, and the preparation method comprises the following steps:

[0060] An automotive varnish was prepared by mixing 80 g of a high-solid, low-viscosity acrylic resin, 10 g of deionized water, 0.5 g of dimethylethanolamine, 15 g of ethylene glycol butyl ether, 2 g of a leveling agent BYK-346, 1 g of a defoaming agent BYK-141, and 2 g of an ultraviolet absorber UV-1130.

[0061] Example 2: The high-solid, low-viscosity acrylic resin of this embodiment is prepared from the following components:

[0062] 50g of acrylic acid mixture 1, 15g of acrylic acid mixture 2, 10g of versatile glycidyl carbonate, 10g of solvent, 0.3g of nano toughening agent, 2g of azobisisobutyronitrile initiator, 2g of α-methylstyrene dimer chain transfer agent, 5g of neutralizer and 25g of deionized water.

[0063] Acrylic acid mixture 1 includes the following raw materials by mass: 18g acrylic acid, 20g methyl methacrylate, and 12g hydroxyethyl methacrylate;

[0064] The second acrylic mixture includes the following raw materials: 3 g of modified prepolymer, 8 g of acrylic acid, and 4 g of butyl acrylate.

[0065] The solvent is isopropyl alcohol, and the neutralizing agent is triethanolamine.

[0066] The difference between the nano toughening agent of this embodiment and that of embodiment 1 is that the temperature is raised to 60° C. and the reaction is carried out for 3 hours in step S13.

[0067] The modified prepolymer of this embodiment is prepared in the same manner as in Example 1.

[0068] The preparation method of the high-solid, low-viscosity acrylic resin of this embodiment comprises the following steps:

[0069] S1. Acrylic acid, methyl methacrylate, and hydroxyethyl methacrylate were mixed to prepare acrylic acid mixture 1. A solvent and tert-butyl glycidyl carbonate were added to a reaction kettle, nitrogen was introduced to replace the air, the temperature was raised to 140° C. to remove moisture, and then the acrylic acid mixture 1, 1 g of azobisisobutyronitrile initiator, and 1 g of α-methylstyrene dimer chain transfer agent were added dropwise. The reaction was kept warm for 3 h to obtain intermediate product 1.

[0070] S2, mixing the modified prepolymer, acrylic acid and butyl acrylate to prepare acrylic acid mixture II, adding acrylic acid mixture II, nano toughening agent, 1g of azobisisobutyronitrile initiator and 1g of α-methylstyrene dimer chain transfer agent dropwise to intermediate product 1, and reacting at 140°C for 1h to obtain intermediate product 2;

[0071] S3. After cooling the intermediate product 2 to 80° C., a neutralizer was added and stirred evenly, and deionized water was added and stirred at a speed of 2000 rpm for 15 minutes to disperse and form an emulsion, thereby preparing a high-solid, low-viscosity acrylic resin.

[0072] The high-solid, low-viscosity acrylic resin of this embodiment is used to prepare automotive clear coat, and the preparation method comprises the following steps:

[0073] An automotive varnish was prepared by mixing 75 g of a high-solid, low-viscosity acrylic resin, 10 g of deionized water, 0.5 g of dimethylethanolamine, 10 g of ethylene glycol butyl ether, 0.5 g of a leveling agent BYK-333, 0.5 g of a defoaming agent BYK-055, and 1 g of an ultraviolet absorber UV-400.

[0074] Example 3: The high-solid, low-viscosity acrylic resin of this embodiment is prepared from the following components:

[0075] 60g of acrylic acid mixture 1, 24g of acrylic acid mixture 2, 13g of versatile glycidyl carbonate, 15g of solvent, 0.5g of nano toughening agent, 3g of azobisisobutyronitrile initiator, 3g of α-methylstyrene dimer chain transfer agent, 10g of neutralizer and 30g of deionized water.

[0076] Acrylic acid mixture 1 includes the following raw materials by mass: 18g acrylic acid, 27g methyl methacrylate, and 15g hydroxyethyl methacrylate;

[0077] The second acrylic mixture includes the following raw materials: 6 g of modified prepolymer, 10 g of acrylic acid, and 8 g of butyl acrylate.

[0078] The solvent is butyl acetate, and the neutralizer is N,N-dimethylethanolamine.

[0079] The preparation method of the nano toughening agent in this embodiment is the same as that in Example 1.

[0080] The difference between the modified prepolymer of this embodiment and that of embodiment 1 is that after adding triethanolamine, the temperature is raised to 50° C. and reacted for 12 hours for aminolysis ring opening, and after adding octadecyl acrylate, the temperature is kept at 30° C. and reacted for 12 hours.

[0081] The preparation method of the high-solid, low-viscosity acrylic resin of this embodiment comprises the following steps:

[0082] S1. Acrylic acid, methyl methacrylate, and hydroxyethyl methacrylate were mixed to prepare an acrylic acid mixture 1. A solvent and tert-butyl glycidyl carbonate were added to a reaction kettle, nitrogen was introduced to replace the air, the temperature was raised to 135° C. to remove moisture, and the acrylic acid mixture 1, 0.25 g of azobisisobutyronitrile initiator, and 1.5 g of α-methylstyrene dimer chain transfer agent were dropwise added. The reaction was kept warm for 4 h to obtain an intermediate product 1.

[0083] S2, mixing the modified prepolymer, acrylic acid and butyl acrylate to prepare acrylic acid mixture II, adding acrylic acid mixture II, nano toughening agent, 0.25g of azobisisobutyronitrile initiator and 1.5g of α-methylstyrene dimer chain transfer agent dropwise to intermediate product 1, and reacting at 140°C for 2h to obtain intermediate product 2;

[0084] S3. After cooling the intermediate product 2 to 80° C., a neutralizer was added and stirred evenly, and deionized water was added and stirred at a speed of 2500 rpm for 10 minutes to disperse and form an emulsion, thereby preparing a high-solid, low-viscosity acrylic resin.

[0085] The high-solid, low-viscosity acrylic resin of this embodiment is used to prepare automotive clear coat, and the preparation method comprises the following steps:

[0086] An automotive clear coat was prepared by mixing 80 g of a high-solid, low-viscosity acrylic resin, 15 g of deionized water, 1 g of dimethylethanolamine, 15 g of ethylene glycol butyl ether, 2 g of a leveling agent BYK-346, 0.5-2 g of a defoaming agent BYK-141, and 1-5 g of an ultraviolet absorber UV-400.

[0087] Comparative Example 1: This comparative example differs from Example 1 in that no nano-toughening agent is added.

[0088] Comparative Example 2: This comparative example differs from Example 1 in that the nano-toughening additive is replaced by grafted nano-silica.

[0089] Comparative Example 3: This comparative example differs from Example 1 in that the modified prepolymer is replaced by isobornyl acrylate.

[0090] Comparative Example 4: This comparative example differs from Example 1 in that the modified prepolymer is replaced with thiolactone acrylamide.

[0091] Performance Testing

[0092] The viscosity of the acrylic resins prepared in the examples and comparative examples was tested according to GB / T 1723-1993 “Determination of Coating Viscosity”.

[0093] The solid content of the acrylic resin prepared in each example and comparative example was tested according to GB / T 1725-2007 “Paints, varnishes and plastics - Determination of non-volatile matter content”.

[0094] The acrylic resins prepared in the examples and comparative examples were placed in an oven at 50° C. and stored for 30 days, and the stability of the appearance was observed.

[0095] The test results are shown in Table 1 below:

[0096] Table 1 Acrylic resin performance test

[0097]

[0098] The automotive varnish prepared in each example and comparative example and a curing agent of model HT-500 were mixed uniformly in a mass ratio of 5:1 and then coated on an aluminum plate. The curing time was tested at 25° C. and 60% humidity.

[0099] The impact strength of the cured coating of the automotive clear coat prepared in each embodiment and comparative example was tested according to GB / T 1732-2020 “Determination of impact resistance of paint films”.

[0100] The pencil hardness of the cured automotive varnish coatings prepared in each embodiment and comparative example was tested according to GB / T 6739-2022 “Determination of film hardness of paints and varnishes by pencil method”, using a Zhonghua brand pencil.

[0101] The adhesion grade of the cured coating of the automotive clear coat prepared in each embodiment and comparative example was tested according to GB / T 1720-2020 “Paint film circle test”.

[0102] According to GB / T 10125-2021 "Artificial atmosphere corrosion test - Salt spray test", a 50±5 g / L sodium chloride aqueous solution with a pH value strictly controlled between 6.5 and 7.2 was prepared. The cured automotive clear coat coatings prepared in each embodiment and comparative example were tilted 30° from a vertical plane and completely exposed to the salt spray formed by the sodium chloride aqueous solution for 168 hours. The coating surface was observed to test the salt spray resistance of the cured automotive clear coat coatings prepared in each embodiment and comparative example.

[0103] The test results are shown in Table 2 below:

[0104] Table 2 Car clearcoat performance test

[0105]

[0106] As can be seen from the data in the above table, the solid content of the acrylic resins prepared in Examples 1 to 3 is between 70.0% and 70.3%, the solid content is above 60%, the viscosity is between 1534 and 1587 mPa·s, and no precipitation is produced after storage at 50°C for 30 days, indicating that the acrylic resin prepared by the present invention meets the requirements of high-solid, low-viscosity acrylic resin. In Comparative Example 2, the nano-toughening additive is replaced by grafted nano-silica. The amino group grafted on the surface of the nano-silica is easily over-reacted with the resin monomer in the acrylic resin, resulting in agglomeration. Therefore, a small amount of precipitation is produced after storage at 50°C for 30 days. The curing time of the automotive varnishes prepared in Examples 1 to 3 is between 34 and 35 minutes, the impact strength is 40 kg·cm, the hardness is 3H, the adhesion grade is 0, and the coating has no obvious change, indicating that the acrylic resin prepared by the present invention is used in automotive varnish, has fast curing speed, impact resistance and scratch resistance, and has excellent salt spray resistance.

[0107] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

[0108] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. High solid, low viscosity acrylic resin, characterized in that: It is prepared from the following components in parts by mass: 40-60 parts of acrylic acid mixture 1, 15-25 parts of acrylic acid mixture 2, 10-13 parts of versatile glycidyl carbonate, 10-15 parts of solvent, 0.3-0.5 parts of nano toughening agent, 1-3 parts of azobisisobutyronitrile initiator, 0.5-3 parts of α-methylstyrene dimer chain transfer agent, 5-10 parts of neutralizer and 20-30 parts of deionized water; Acrylic acid mixture 1 includes the following raw materials in parts by weight: 12-18 parts of acrylic acid, 20-30 parts of methyl methacrylate, and 12-15 parts of hydroxyethyl methacrylate; The second acrylic mixture comprises the following raw materials in parts by weight: 3 to 6 parts of a modified prepolymer, 8 to 10 parts of acrylic acid, and 4 to 8 parts of butyl acrylate; The preparation method of the modified prepolymer comprises the following steps: S21. Add 4 to 5 parts of DL-homocysteine thiolactone hydrochloride and 50 to 100 parts of dichloromethane to a reactor, dissolve 2 to 5 parts of acryloyl chloride in dichloromethane and add the mixture to the reactor with stirring in an ice bath. Add 10 to 15 parts of sodium bicarbonate, raise the temperature to room temperature, react for 12 to 24 hours, extract with ethyl acetate, remove water, and dry to obtain thiolactone acrylamide. S22. Add 30-40 parts by mass of tetrahydrofuran solvent to a reactor, add 3-5 parts of thiolactone acrylamide, 10-15 parts of N-isopropyl-N-benzyl-2-acrylamide, 0.1-0.3 parts of methyl styrene dimer chain transfer agent, and 0.01-0.5 parts of azobisisobutyronitrile initiator, raise the temperature to 70-80° C. in a nitrogen atmosphere, react for 1-2 hours, precipitate with diethyl ether, collect the solid by filtration, and dry to obtain a prepolymer; S23, adding 10-15 parts of a prepolymer, 30-40 parts of triethylamine, and 40-50 parts of N,N-dimethylacrylamide solvent into a reaction kettle, heating to 50-60° C. and reacting for 12-24 hours to perform aminolysis ring opening, adding 20-30 parts of octadecyl acrylate, and reacting at 30-40° C. and 12-24 hours to obtain a modified prepolymer; The preparation method of the nano toughening agent comprises the following steps: S11, adding 10-20 parts by mass of silica sol to 50-100 parts by mass of ethanol aqueous solution, adding 3-6 parts of 3-aminopropyltrimethoxysilane, heating to react, filtering to collect the solid, washing and drying to obtain grafted nano-silica; S12, adding 30-40 parts by mass of 2-vinylfuran to a reaction kettle, adding 35-45 parts of glycidyl acrylate and 0.5-1 part of benzoyl peroxide initiator, and heating the reaction to obtain an epoxy grafted product; S13. Add 5 to 6 parts by mass of grafted nano-silica into a reactor, add 50 to 60 parts of N,N-dimethylacrylamide solvent, add 10 to 15 parts of epoxy grafted material and 0.1 to 0.3 parts of benzoyl peroxide initiator, and heat to react to obtain a nano-toughening additive.

2. The high-solid, low-viscosity acrylic resin according to claim 1, characterized in that The solvent is any one of butyl acetate, isopropyl alcohol, and ethylene glycol butyl ether, and the neutralizer is any one of N,N-dimethylethanolamine and triethanolamine.

3. The high-solid, low-viscosity acrylic resin according to claim 1, characterized in that: In the step S11, the temperature is raised to 70-90° C. and the reaction is carried out for 3-4 hours; in the step S12, the temperature is raised to 80-90° C. and the reaction is carried out for 1-2 hours; and in the step S13, the temperature is raised to 60-70° C. and the reaction is carried out for 3-4 hours.

4. The method for preparing a high-solid, low-viscosity acrylic resin according to any one of claims 1 to 3, wherein: The steps include: S1. Acrylic acid, methyl methacrylate, and hydroxyethyl methacrylate are mixed to prepare an acrylic acid mixture 1. A solvent and versatile glycidyl carbonate are added to a reaction kettle, nitrogen is introduced to replace the air, the temperature is increased to remove moisture, and then the acrylic acid mixture 1, 0.05-1 parts of azobisisobutyronitrile as an initiator, and 0.3-1.5 parts of α-methylstyrene dimer as a chain transfer agent are added dropwise. The reaction is carried out at this temperature to obtain an intermediate product 1. S2, mixing the modified prepolymer, acrylic acid and butyl acrylate to prepare acrylic acid mixture 2, adding acrylic acid mixture 2, nano toughening agent, 0.05-1 parts of azobisisobutyronitrile initiator and 0.2-1.5 parts of α-methylstyrene dimer chain transfer agent to intermediate product 1, and keeping the mixture warm to react to prepare intermediate product 2; S3. After cooling the intermediate product 2, a neutralizing agent is added and stirred evenly, and deionized water is added and stirred and dispersed to obtain a high-solid, low-viscosity acrylic resin.

5. The method for preparing a high-solid, low-viscosity acrylic resin according to claim 4, wherein: The temperature of the insulation reaction in S1 is raised to 130-140° C. and the temperature is maintained for 3-4 hours; the temperature of the insulation reaction in S2 is raised to 130-140° C. and the temperature is maintained for 1-2 hours; the intermediate product 2 in S3 is cooled to 70-80° C. and then a neutralizer is added, and the mixture is stirred at a speed of 2000-3000 rpm for 10-15 minutes to disperse and form an emulsion.

6. The use of the high-solid, low-viscosity acrylic resin according to any one of claims 1 to 3, characterized in that: For preparing automobile clearcoat, the method comprises the following steps: An automobile clear coat is prepared by mixing, by mass, 75-80 parts of a high-solid, low-viscosity acrylic resin, 10-15 parts of deionized water, 0.5-1 part of dimethylethanolamine, 10-15 parts of ethylene glycol butyl ether, 0.5-2 parts of a leveling agent, 0.5-2 parts of a defoaming agent and 1-5 parts of an ultraviolet absorber.

7. The use of the high-solid, low-viscosity acrylic resin according to claim 6, characterized in that: The model of the leveling agent is any one of BYK-346 and BYK-333; the model of the defoaming agent is any one of BYK-141 and BYK-055; the model of the ultraviolet absorber is any one of UV-400 and UV-1130.

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