High-solid low-viscosity hydroxy acrylic resin based on polyhydroxy monomer and preparation method of high-solid low-viscosity hydroxy acrylic resin

Abstract

The invention relates to the technical field of acrylic resin, and particularly discloses high-solid low-viscosity hydroxy acrylic resin based on a polyhydroxy monomer and a preparation method of the high-solid low-viscosity hydroxy acrylic resin. The invention relates to high-solid low-viscosity hydroxy acrylic resin based on a polyhydroxy monomer. The high-solid low-viscosity hydroxy acrylic resin is prepared from the following raw material components in parts by weight: 10 to 25 parts of the polyhydroxy monomer, 47 to 62 parts of a basic monomer, 1 to 5 parts of an initiator and 23 to 27 parts of a solvent, the polyhydroxy monomer comprises the following raw materials: dimethylolpropionic acid, glycidyl methacrylate, a catalyst and a polymerization inhibitor. A preparation method of high-solid low-viscosity hydroxy acrylic resin based on polyhydroxy monomers comprises the following steps: heating a solvent to 120-130 DEG C for reflux, dropwise adding an initiator solution and a mixed monomer into the solvent at the same time for 3-4 hours, preserving heat and curing for 2 hours after charging is completed, and finally cooling to 60 DEG C or below to obtain the high-solid low-viscosity hydroxy acrylic resin.

Description

Technical Field

[0001] This application relates to the technical field of acrylic resins, and in particular to a high-solids, low-viscosity hydroxyl acrylic resin based on polyhydroxy monomers and its preparation method. Background Technology

[0002] Hydroxyacrylate resins are among the most important film-forming agents in two-component polyurethane coatings. With increasingly stringent environmental regulations, the development of high-solids, low-viscosity hydroxyacrylate resins has become an urgent industry need. Traditional methods reduce viscosity by lowering the resin molecular weight, using reactive diluents, or selecting special solvents, but this often leads to a decrease in film hardness, chemical resistance, and other properties. Furthermore, hydroxyacrylate resins are typically prepared by introducing monohydroxy functional acrylate monomers such as hydroxyethyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl acrylate to provide crosslinking points. These monomers either increase resin viscosity due to their molecular structure or affect the final film's crosslinking density and hardness due to their limited hydroxyl functionality. Summary of the Invention

[0003] To improve the crosslinking density and hardness of high-solids, low-viscosity resin coatings, this application provides a high-solids, low-viscosity hydroxyl acrylic resin based on polyhydroxy monomers and its preparation method.

[0004] In a first aspect, this application provides a high-solids, low-viscosity hydroxyl acrylic resin based on polyhydroxy monomers, which adopts the following technical solution: A high-solids, low-viscosity hydroxyl acrylic resin based on polyhydroxy monomers, wherein the raw materials of the high-solids, low-viscosity hydroxyl acrylic resin include the following components in parts by weight: 10-25 parts of polyhydroxy monomers, 47-62 parts of basic monomers, 1-5 parts of initiator, and 23-27 parts of solvent; wherein the raw materials of the polyhydroxy monomers include dimethylolpropionic acid, glycidyl methacrylate, catalyst, and polymerization inhibitor.

[0005] By employing the above technical solution, under the action of a catalyst, a carboxyl group in dimethylolpropionic acid undergoes a ring-opening reaction with the epoxy group of glycidyl methacrylate. Since dimethylolpropionic acid itself has two primary hydroxyl groups, and the ring-opening reaction generates a new secondary hydroxyl group, the final product is an unsaturated monomer containing three hydroxyl groups and one methacryloyloxy group in a molecule, i.e., a polyhydroxyl monomer. Hydroxy acrylic resin is prepared by solution free radical polymerization of the polyhydroxyl monomer and the basic monomer in the presence of an initiator. Because the polyhydroxyl monomer introduces compact and highly polar polyhydroxyl groups into the polymer side chain, this steric hindrance and polar effect can effectively reduce the entanglement between resin molecular chains, thereby significantly reducing the viscosity of the resin solution while ensuring a high molecular weight and hydroxyl content, achieving "high solids and low viscosity." The methacryloyloxy group contains a double bond that can be used for polymerization. Simultaneously, the highly functional hydroxyl groups on the side chain provide abundant reaction sites for subsequent crosslinking with polyisocyanates, which is beneficial for forming a paint film with high crosslinking density, thus achieving high hardness.

[0006] In one specific implementation, the method for preparing the polyhydroxy monomer includes the following steps: Dimethylolpropionic acid, glycidyl methacrylate, catalyst, and polymerization inhibitor are stirred and mixed evenly. Under nitrogen protection, the mixture is heated to 105-125℃ and the reaction is maintained at this temperature. When the acid value drops below 5 mg KOH / g, the reaction is stopped to obtain the polyhydroxy monomer.

[0007] By adopting the above technical solution, dimethylolpropionic acid, glycidyl methacrylate, catalyst, and polymerization inhibitor are first stirred and mixed evenly, and then the mixture is heated to synthesize a polyhydroxy monomer; the reaction formula is as follows: .

[0008] In one specific implementation, the molar ratio of dimethylolpropionic acid to glycidyl methacrylate is 1.0:(1.0-1.1).

[0009] By adopting the above technical solution, the ratio of dimethylolpropionic acid to glycidyl methacrylate is further limited, which is beneficial to the better synthesis of polyhydroxy monomers.

[0010] In one specific implementation, the catalyst comprises tetrabutylammonium bromide; the polymerization inhibitor comprises p-hydroxyanisole.

[0011] In one specific implementation, the basic monomer comprises a mixture of methyl methacrylate, butyl acrylate, and styrene.

[0012] In one specific embodiment, the initiator comprises tert-butyl peroxide-2-ethylhexanoate; and the solvent comprises n-butyl acetate.

[0013] Secondly, this application provides a method for preparing a high-solids, low-viscosity hydroxyl acrylic resin based on polyhydroxy monomers, which adopts the following technical solution: A method for preparing a high-solids, low-viscosity hydroxyl acrylic resin based on a polyhydroxy monomer includes the following steps: Initiator solution preparation: Dissolve the initiator in a portion of the solvent to obtain an initiator solution; Mixed monomers: The polyhydroxy monomers and basic monomers are stirred and mixed evenly to obtain mixed monomers; Reflux: Heat the remaining solvent to 120-130℃ for reflux, and simultaneously add the initiator solution and mixed monomers dropwise into the solvent. The addition time is 3-4 hours. After the addition is complete, keep it warm for 2 hours. Finally, cool it down to below 60℃ and discharge it to obtain high solids and low viscosity hydroxyl acrylic resin.

[0014] By adopting the above technical solution, the initiator is first dissolved in a portion of the solvent to obtain an initiator solution. Then, the polyhydroxy monomer and the basic monomer are mixed to obtain a mixed monomer. Finally, during the reflux process, the initiator solution and the mixed monomer are slowly added dropwise to the remaining solvent and kept at a warm temperature for curing to obtain a high-solids, low-viscosity hydroxyl acrylic resin.

[0015] In one specific implementation, the high-solids, low-viscosity hydroxyl acrylic resin has a solids content of 74.8-75.1% and a viscosity of 3328-4340 mPa·s at 25°C.

[0016] By adopting the above technical solution and using the preparation method in this application, the obtained hydroxyl acrylic resin has a high solid content and a low viscosity.

[0017] Thirdly, the polyurethane coating provided in this application adopts the following technical solution: A polyurethane coating, wherein the raw materials of the polyurethane coating include the aforementioned high-solids, low-viscosity hydroxyl acrylic resin, propylene glycol methyl ether acetate, and hexamethylene diisocyanate trimer.

[0018] By adopting the above technical solution, the polyurethane coating made from the high-solids, low-viscosity hydroxyl acrylic resin in this application forms a coating film with high crosslinking density and hardness.

[0019] In summary, this application includes at least one of the following beneficial technical effects: In this application, under the action of a catalyst, a carboxyl group in dimethylolpropionic acid undergoes a ring-opening reaction with the epoxy group of glycidyl methacrylate. Since dimethylolpropionic acid itself has two primary hydroxyl groups, and the ring-opening reaction generates a new secondary hydroxyl group, the final product is an unsaturated monomer containing three hydroxyl groups and one methacryloyloxy group in a molecule, i.e., a polyhydroxy monomer. The polyhydroxy monomer and the basic monomer are then subjected to solution free radical polymerization in the presence of an initiator to prepare a hydroxyl acrylic resin. Because the polyhydroxy monomer introduces a compact and highly polar polyhydroxy group into the polymer side chain, this steric hindrance and polar effect can effectively reduce the entanglement between resin molecular chains, thereby significantly reducing the viscosity of the resin solution while ensuring a high molecular weight and hydroxyl content, achieving "high solids and low viscosity." The methacryloyloxy group contains a double bond that can be used for polymerization. Simultaneously, the highly functional hydroxyl groups on the side chain provide abundant reaction sites for subsequent crosslinking with polyisocyanates, which is beneficial for forming a paint film with a high crosslinking density, thus achieving high hardness. The method in this application first dissolves the initiator in a portion of the solvent to obtain an initiator solution, then mixes the polyhydroxy monomer and the basic monomer to obtain a mixed monomer, and finally slowly adds the initiator solution and the mixed monomer to the remaining solvent during reflux, and keeps it at a warm temperature for curing to obtain a high-solids, low-viscosity hydroxyl acrylic resin. The polyurethane coating prepared using the high-solids, low-viscosity hydroxyl acrylic resin of this application forms a film with high crosslinking density and hardness. Detailed Implementation

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

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

[0022] Preparation Example 1 Preparation Example 1 provides a method for preparing a polyhydroxy monomer, comprising the following steps: 134.13g of dimethylolpropionic acid, 149.26g of glycidyl methacrylate, 0.56g of catalyst, and 0.10g of polymerization inhibitor were stirred and mixed evenly. Under nitrogen protection, the mixture was heated to 110℃ and maintained at this temperature. The acid value was monitored during the reaction. When the acid value dropped below 5mg KOH / g, the reaction was stopped to obtain a polyhydroxy monomer. The catalyst was tetrabutylammonium bromide, and the polymerization inhibitor was p-hydroxyanisole. The molar ratio of dimethylolpropionic acid to glycidyl methacrylate was 1:1.05.

[0023] Preparation Example 2 Preparation Example 2 provides a method for preparing a polyhydroxy monomer, comprising the following steps: 134.13g of dimethylolpropionic acid, 135.04g of glycidyl methacrylate, 0.5g of catalyst, and 0.05g of polymerization inhibitor were stirred and mixed evenly. Under nitrogen protection, the mixture was heated to 110℃ and maintained at this temperature. The acid value was monitored during the reaction. When the acid value dropped below 5mg KOH / g, the reaction was stopped to obtain a polyhydroxy monomer. The catalyst was tetrabutylammonium bromide, and the polymerization inhibitor was p-hydroxyanisole. The molar ratio of dimethylolpropionic acid to glycidyl methacrylate was 1:0.95.

[0024] Preparation Example 3 Preparation Example 3 provides a method for preparing a polyhydroxy monomer, comprising the following steps: 134.13g of dimethylolpropionic acid, 142.15g of glycidyl methacrylate, 0.57g of catalyst, and 0.057g of polymerization inhibitor were stirred and mixed evenly. Under nitrogen protection, the mixture was heated to 110℃ and maintained at this temperature. The acid value was monitored during the reaction. When the acid value dropped below 5mg KOH / g, the reaction was stopped to obtain a polyhydroxy monomer. The catalyst was tetrabutylammonium bromide, and the polymerization inhibitor was p-hydroxyanisole. The molar ratio of dimethylolpropionic acid to glycidyl methacrylate was 1:1.

[0025] Preparation Example 4 Preparation Example 4 provides a method for preparing a polyhydroxy monomer, comprising the following steps: 134.13g of dimethylolpropionic acid, 156.37g of glycidyl methacrylate, 0.5g of catalyst, and 0.05g of polymerization inhibitor were stirred and mixed evenly. Under nitrogen protection, the mixture was heated to 110℃ and maintained at this temperature. The acid value was monitored during the reaction. When the acid value dropped below 5mg KOH / g, the reaction was stopped to obtain a polyhydroxy monomer. The catalyst was tetrabutylammonium bromide, and the polymerization inhibitor was p-hydroxyanisole. The molar ratio of dimethylolpropionic acid to glycidyl methacrylate was 1:1.1.

[0026] Preparation Example 5 Preparation Example 5 provides a method for preparing a polyhydroxy monomer, comprising the following steps: 134.13g of dimethylolpropionic acid, 163.47g of glycidyl methacrylate, 0.6g of catalyst, and 0.06g of polymerization inhibitor were stirred and mixed evenly. Under nitrogen protection, the mixture was heated to 110℃ and maintained at this temperature. The acid value was monitored during the reaction. When the acid value dropped below 5mg KOH / g, the reaction was stopped to obtain a polyhydroxy monomer. The catalyst was tetrabutylammonium bromide, and the polymerization inhibitor was p-hydroxyanisole. The molar ratio of dimethylolpropionic acid to glycidyl methacrylate was 1:1.15. Example

[0027] Example 1 Example 1 provides a method for preparing a high-solids, low-viscosity hydroxyl acrylic resin based on polyhydroxy monomers, comprising the following steps: Preparation of initiator solution: Dissolve 3g of initiator in 3g of solvent to obtain initiator solution; wherein the initiator is tert-butyl peroxide-2-ethylhexanoate; and the solvent is n-butyl acetate; Mixed monomers: 10g of the polyhydroxy monomer from Preparation Example 1 and 62g of the basic monomer were stirred and mixed evenly to obtain mixed monomers; wherein the basic monomers were a mixture of methyl methacrylate, butyl acrylate and styrene, and the weight ratio of methyl methacrylate, butyl acrylate and styrene was 22:15:25. Reflux: 22g of solvent was heated to 125℃ for reflux. The initiator solution and mixed monomers were simultaneously added to the solvent through two dropping funnels. The addition time was 3.5h. After the addition was completed, the mixture was kept at the temperature for 2h for curing. Finally, the temperature was lowered to below 60℃ and the mixture was discharged to obtain high solids and low viscosity hydroxyl acrylic resin. The solvent was n-butyl acetate.

[0028] Example 2 Example 2 provides a method for preparing a high-solids, low-viscosity hydroxyl acrylic resin based on a polyhydroxy monomer, comprising the following steps: Preparation of initiator solution: Dissolve 3g of initiator in 3g of solvent to obtain initiator solution; wherein the initiator is tert-butyl peroxide-2-ethylhexanoate; and the solvent is n-butyl acetate; Mixed monomers: 15g of the polyhydroxy monomer from Preparation Example 1 and 57g of the basic monomer were stirred and mixed evenly to obtain mixed monomers; wherein the basic monomers were a mixture of methyl methacrylate, butyl acrylate and styrene, and the weight ratio of methyl methacrylate, butyl acrylate and styrene was 17:15:25. Reflux: 22g of solvent was heated to 125℃ for reflux. The initiator solution and mixed monomers were simultaneously added to the solvent through two dropping funnels. The addition time was 3.5h. After the addition was completed, the mixture was kept at the temperature for 2h for curing. Finally, the temperature was lowered to below 60℃ and the mixture was discharged to obtain high solids and low viscosity hydroxyl acrylic resin. The solvent was n-butyl acetate.

[0029] Example 3 Example 3 provides a method for preparing a high-solids, low-viscosity hydroxyl acrylic resin based on a polyhydroxy monomer, comprising the following steps: Preparation of initiator solution: Dissolve 3g of initiator in 3g of solvent to obtain initiator solution; wherein the initiator is tert-butyl peroxide-2-ethylhexanoate; and the solvent is n-butyl acetate; Mixed monomers: 20g of the polyhydroxy monomer from Preparation Example 1 and 52g of the basic monomer were stirred and mixed evenly to obtain mixed monomers; wherein the basic monomers were a mixture of methyl methacrylate, butyl acrylate and styrene, and the weight ratio of methyl methacrylate, butyl acrylate and styrene was 12:15:25. Reflux: 22g of solvent was heated to 125℃ for reflux. The initiator solution and mixed monomers were simultaneously added to the solvent through two dropping funnels. The addition time was 3.5h. After the addition was completed, the mixture was kept at the temperature for 2h for curing. Finally, the temperature was lowered to below 60℃ and the mixture was discharged to obtain high solids and low viscosity hydroxyl acrylic resin. The solvent was n-butyl acetate.

[0030] Example 4 Example 4 provides a method for preparing a high-solids, low-viscosity hydroxyl acrylic resin based on polyhydroxy monomers, comprising the following steps: Preparation of initiator solution: Dissolve 3g of initiator in 3g of solvent to obtain initiator solution; wherein the initiator is tert-butyl peroxide-2-ethylhexanoate; and the solvent is n-butyl acetate; Mixed monomers: 25g of the polyhydroxy monomer from Preparation Example 1 and 47g of the basic monomer were stirred and mixed evenly to obtain mixed monomers; wherein the basic monomers were a mixture of methyl methacrylate, butyl acrylate and styrene, and the weight ratio of methyl methacrylate, butyl acrylate and styrene was 7:15:25. Reflux: 22g of solvent was heated to 125℃ for reflux. The initiator solution and mixed monomers were simultaneously added to the solvent through two dropping funnels. The addition time was 3.5h. After the addition was completed, the mixture was kept at the temperature for 2h for curing. Finally, the temperature was lowered to below 60℃ and the mixture was discharged to obtain high solids and low viscosity hydroxyl acrylic resin. The solvent was n-butyl acetate.

[0031] Example 5 Example 5 provides a method for preparing a high-solids, low-viscosity hydroxyl acrylic resin based on a polyhydroxy monomer, comprising the following steps: Preparation of initiator solution: Dissolve 1g of initiator in 1g of solvent to obtain initiator solution; wherein the initiator is tert-butyl peroxide-2-ethylhexanoate; and the solvent is n-butyl acetate; Mixed monomers: 25g of the polyhydroxy monomer from Preparation Example 1 and 47g of the basic monomer were stirred and mixed evenly to obtain mixed monomers; wherein the basic monomers were a mixture of methyl methacrylate, butyl acrylate and styrene, and the weight ratio of methyl methacrylate, butyl acrylate and styrene was 7:15:25. Reflux: 26g of solvent was heated to 125℃ for reflux. The initiator solution and mixed monomers were simultaneously added to the solvent through two dropping funnels. The addition time was 3.5h. After the addition was completed, the mixture was kept at the temperature for 2h for curing. Finally, the temperature was lowered to below 60℃ and the mixture was discharged to obtain high solids and low viscosity hydroxyl acrylic resin. The solvent was n-butyl acetate.

[0032] Example 6 Example 6 provides a method for preparing a high-solids, low-viscosity hydroxyl acrylic resin based on a polyhydroxy monomer, comprising the following steps: Preparation of initiator solution: Dissolve 5g of initiator in 5g of solvent to obtain initiator solution; wherein the initiator is tert-butyl peroxide-2-ethylhexanoate; and the solvent is n-butyl acetate; Mixed monomers: 25g of the polyhydroxy monomer from Preparation Example 1 and 47g of the basic monomer were stirred and mixed evenly to obtain mixed monomers; wherein the basic monomers were a mixture of methyl methacrylate, butyl acrylate and styrene, and the weight ratio of methyl methacrylate, butyl acrylate and styrene was 7:15:25. Reflux: 18g of solvent was heated to 125℃ for reflux. The initiator solution and mixed monomers were simultaneously added to the solvent through two dropping funnels. The addition time was 3.5h. After the addition was completed, the mixture was kept at the temperature for 2h for curing. Finally, the temperature was lowered to below 60℃ and the mixture was discharged to obtain high solids and low viscosity hydroxyl acrylic resin. The solvent was n-butyl acetate.

[0033] Example 7 The difference between Example 7 and Example 3 is that the mixed monomers are: 20g of the polyhydroxy monomer from Preparation Example 2 and 52g of the basic monomer are stirred and mixed evenly to obtain the mixed monomers; the remaining steps are the same as in Example 3.

[0034] Example 8 The difference between Example 8 and Example 3 is that the mixed monomers are: 20g of the polyhydroxy monomer from Example 3 and 52g of the basic monomer are stirred and mixed evenly to obtain the mixed monomers; the remaining steps are the same as in Example 3.

[0035] Example 9 The difference between Example 9 and Example 3 is that the mixed monomers are: 20g of the polyhydroxy monomer from Preparation Example 4 and 52g of the basic monomer are stirred and mixed evenly to obtain the mixed monomers; the remaining steps are the same as in Example 3.

[0036] Example 10 The difference between Example 10 and Example 3 is that the mixed monomers are: 20g of the polyhydroxy monomer from Preparation Example 5 and 52g of the basic monomer are stirred and mixed evenly to obtain the mixed monomers; the remaining steps are the same as in Example 3. Comparative Example

[0037] Comparative Example 1 The difference between Comparative Example 1 and Example 3 is that hydroxyethyl methacrylate with an equal number of hydroxyl groups was used to replace all the polyhydroxy monomers in Example 3; the remaining steps were the same as in Example 3.

[0038] Comparative Example 2 The difference between Comparative Example 2 and Example 3 is that a mixture of hydroxyethyl acrylate and hydroxypropyl acrylate is used to replace all the polyhydroxy monomers in Example 3, so that the total hydroxyl functionality in the mixture of hydroxyethyl acrylate and hydroxypropyl acrylate is consistent with that in Example 3; the remaining steps are consistent with those in Example 3. Application examples

[0039] Application Example 1 Application Example 1 provides a method for preparing a polyurethane coating, comprising the following steps: Take the high-solids, low-viscosity hydroxyl acrylic resin from Example 1, add propylene glycol methyl ether acetate to dilute to the application viscosity, which is approximately 20 seconds (French cup 4). Add hexamethylene diisocyanate trimer, stir evenly, and cure for 15 minutes to obtain a polyurethane coating. The NCO content in the hexamethylene diisocyanate trimer is 22%. The amount of hexamethylene diisocyanate trimer added is: number of isocyanate groups: number of hydroxyl groups = 1.1:1.

[0040] Application Example 2 The difference between Application Example 2 and Application Example 1 is that the hydroxy acrylic resin used in Example 2 is selected; the remaining steps are the same as in Application Example 1.

[0041] Application Example 3 The difference between Application Example 3 and Application Example 1 is that the hydroxy acrylic resin used in Example 3 is selected; the remaining steps are the same as in Application Example 1.

[0042] Application Example 4 The difference between Application Example 4 and Application Example 1 is that the hydroxy acrylic resin used in Example 4 is selected; the remaining steps are the same as in Application Example 1.

[0043] Application Example 5 The difference between Application Example 5 and Application Example 1 is that the hydroxy acrylic resin used in Example 5 is selected; the remaining steps are the same as in Application Example 1.

[0044] Application Example 6 The difference between Application Example 6 and Application Example 1 is that the hydroxy acrylic resin used in Example 6 is selected; the remaining steps are the same as in Application Example 1.

[0045] Application Example 7 The difference between Application Example 7 and Application Example 1 is that the hydroxy acrylic resin used in Example 7 is selected; the remaining steps are the same as in Application Example 1.

[0046] Application Example 8 The difference between Application Example 8 and Application Example 1 is that the hydroxy acrylic resin used in Example 8 is selected; the remaining steps are the same as in Application Example 1.

[0047] Application Example 9 The difference between Application Example 9 and Application Example 1 is that the hydroxy acrylic resin used in Example 9 is selected; the remaining steps are the same as in Application Example 1.

[0048] Application Example 10 The difference between Application Example 10 and Application Example 1 is that the hydroxy acrylic resin used in Example 10 is selected; the remaining steps are the same as in Application Example 1. Comparative Application Examples

[0049] Comparative Application Example 1 The difference between Application Example 1 and Application Example 2 is that the hydroxyl acrylic resin used in Comparative Example 1 is selected; the remaining steps are the same as in Application Example 1.

[0050] Comparative Application Example 2 The difference between Application Example 2 and Application Example 1 is that the hydroxyl acrylic resin used in Comparative Example 2 is selected; the remaining steps are the same as in Application Example 1. Performance testing experiment

[0051] Resin testing: The solid content of hydroxyl acrylic resin in each example and comparative example was tested according to GB / T1725-2007, and the viscosity was tested according to GB / T40280-2021.

[0052] Application performance: The polyurethane coatings from each application example and the comparative application example were sprayed onto tinplate. After leveling at room temperature for 20 minutes, they were baked in a 60℃ oven for 2 hours to obtain test panels with a dry film thickness of approximately 40μm. The test panels were then tested. Pencil hardness was tested according to standard GB / T 6739-2022, ethanol wiping resistance according to standard GB / T 23989-2009, paint film adhesion according to standard GB / T 9286-2021, and gloss according to standard GB / T 9754-2007.

[0053] Table 1 Performance test results of hydroxyacrylic resin

[0054] Table 2 Performance test results of polyurethane coatings

[0055] Referring to Table 1, Example 3, and Comparative Examples 1-2, the hydroxyl acrylic resin in Example 3 has a higher solids content and lower viscosity. Referring to Table 2, Application Example 3, and Comparative Application Examples 1-2, the paint film in Application Example 3 has the highest hardness. It can be seen that by using the polyhydroxy monomer in this application, which contains three hydroxyl groups and one methacryloyloxy group, and polymerizing it with a basic monomer in the presence of an initiator via solution free radical polymerization, a hydroxyl acrylic resin is obtained. Because the polyhydroxy monomer introduces compact and highly polar polyhydroxy groups on the polymer side chain, this steric hindrance and polar effect can effectively reduce the entanglement between resin molecular chains, thereby significantly reducing the viscosity of the resin solution while ensuring a high molecular weight and hydroxyl content, achieving "high solids and low viscosity". At the same time, the highly functional hydroxyl groups on the side chain provide abundant reaction sites for subsequent crosslinking with polyisocyanates, which is conducive to forming a paint film with a high crosslinking density and improving the hardness of the paint film.

[0056] Combining Table 2 and Application Examples 1-6, it can be seen that when preparing hydroxyl acrylic resin, according to the raw material ratios in Examples 1-6, the obtained hydroxyl acrylic resin has a high solid content and low viscosity. At the same time, the polyurethane coating film prepared from it has good performance in key properties such as hardness and chemical resistance.

[0057] Based on Table 1, Example 3, and Examples 7-10, the hydroxyl acrylic resins in Examples 3, 8, and 9 have high solid content and low viscosity. This indicates that when preparing polyhydroxy monomers, the preferred molar ratio of dimethylolpropionic acid to glycidyl methacrylate is 1.0:(1.0-1.1), which results in better synthesis of polyhydroxy monomers.

[0058] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high-solids, low-viscosity hydroxyl acrylic resin based on polyhydroxy monomers, characterized in that: The raw materials of the high-solids, low-viscosity hydroxyl acrylic resin include the following components in parts by weight: 10-25 parts of polyhydroxy monomer, 47-62 parts of basic monomer, 1-5 parts of initiator, and 23-27 parts of solvent; the raw materials of the polyhydroxy monomer include dimethylolpropionic acid, glycidyl methacrylate, catalyst, and polymerization inhibitor.

2. The high-solids, low-viscosity hydroxyl acrylic resin based on polyhydroxy monomers according to claim 1, characterized in that: The preparation method of the polyhydroxy monomer includes the following steps: Dimethylolpropionic acid, glycidyl methacrylate, catalyst, and polymerization inhibitor are stirred and mixed evenly. Under nitrogen protection, the mixture is heated to 105-125℃ and the reaction is maintained at this temperature. When the acid value drops below 5 mg KOH / g, the reaction is stopped to obtain the polyhydroxy monomer.

3. The high-solids, low-viscosity hydroxyl acrylic resin based on polyhydroxy monomers according to claim 1, characterized in that: The molar ratio of dimethylolpropionic acid to glycidyl methacrylate is 1.0:(1.0-1.1).

4. The high-solids, low-viscosity hydroxyl acrylic resin based on polyhydroxy monomers according to claim 1, characterized in that: The catalyst comprises tetrabutylammonium bromide; the polymerization inhibitor comprises p-hydroxyanisole.

5. The high-solids, low-viscosity hydroxyl acrylic resin based on polyhydroxy monomers according to claim 1, characterized in that: The basic monomers include a mixture of methyl methacrylate, butyl acrylate, and styrene.

6. The high-solids, low-viscosity hydroxyl acrylic resin based on polyhydroxy monomers according to claim 5, characterized in that: The initiator includes tert-butyl peroxide-2-ethylhexanoate; the solvent includes n-butyl acetate.

7. A method for preparing a high-solids, low-viscosity hydroxyl acrylic resin based on a polyhydroxy monomer as described in any one of claims 1-6, characterized in that: Includes the following steps: Initiator solution preparation: Dissolve the initiator in a portion of the solvent to obtain an initiator solution; Mixed monomers: The polyhydroxy monomers and basic monomers are stirred and mixed evenly to obtain mixed monomers; Reflux: Heat the remaining solvent to 120-130℃ for reflux, and simultaneously add the initiator solution and mixed monomers dropwise into the solvent. The addition time is 3-4 hours. After the addition is complete, keep it warm for 2 hours. Finally, cool it down to below 60℃ and discharge it to obtain high solids and low viscosity hydroxyl acrylic resin.

8. The method for preparing a high-solids, low-viscosity hydroxyl acrylic resin based on a polyhydroxy monomer according to claim 7, characterized in that: The high-solids, low-viscosity hydroxyl acrylic resin has a solids content of 74.8-75.1% and a viscosity of 3328-4340 mPa·s at 25°C.

9. A polyurethane coating, characterized in that: The raw materials for the polyurethane coating include the high-solids, low-viscosity hydroxyl acrylic resin, propylene glycol methyl ether acetate, and hexamethylene diisocyanate trimer as described in any one of claims 1-6.

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