Preparation method of polyurethane-acrylate dispersion and application of polyurethane-acrylate dispersion in coating

Abstract

The invention discloses a preparation method of a polyurethane-acrylate dispersoid and application of the polyurethane-acrylate dispersoid in a coating, and belongs to the technical field of chemical engineering, and the preparation method comprises the following steps: S1, preparation of a bifunctional prepolymer: reacting glycidyl phenyl ether with adipic acid to generate a polyfunctional acrylate derivative, and then reacting with a sulfydryl-terminated thio-polyurethane prepolymer to obtain the bifunctional prepolymer; a difunctional prepolymer is obtained; s2, preparation of a mixed solution A: mixing the thio-urethane acrylate prepolymer with a viscosity reduction solvent, a hydrophilic chain extender and dihydroxy propionate, fully and uniformly stirring, and reacting hydroxyl in the dihydroxy propionate with isocyanate groups in the thio-urethane acrylate prepolymer to generate an isocyanate-terminated prepolymer; the problems that in the prior art, a polyurethane-acrylate dispersion is poor in stability and insufficient in comprehensive performance are solved, and the polyurethane-acrylate dispersion has the advantages of being good in weather resistance and efficient in processing.

Description

Technical Field

[0001] The invention relates to the technical field of chemical engineering, and in particular to a preparation method of a polyurethane-acrylate dispersion and application thereof in coatings. Background Art

[0002] As a highly efficient and environmentally friendly coating, powder coating has developed rapidly in recent years. Compared with traditional liquid coatings, powder coatings have the advantages of being pollution-free, resource-saving and highly efficient, so they are widely used in many fields.

[0003] Although powder coatings have many advantages, there are still some problems in practical applications, which limit their wider promotion and use: (1) Limitations of single resin: Polyurethane resin: Although it has excellent mechanical properties, cold resistance and wear resistance, its high temperature resistance, weather resistance and hydrolysis resistance are poor, which limits its application in some harsh environments. Polyacrylate resin: Although it has good gloss, water resistance and outdoor aging resistance, its hardness is high, and its adhesion and flexibility are poor, which affects the comprehensive performance of the coating. (2) Insufficient coating performance: Weather resistance: Many existing powder coatings are prone to aging and fading after long-term exposure to outdoor environments. Chemical resistance: In some special applications, the coating needs to withstand the erosion of various chemicals, and some existing powder coatings do not perform well in this regard. Adhesion: The adhesion between the coating and the substrate is insufficient, which easily causes the coating to fall off and affects the service life. Flexibility: The coating is prone to cracking when subjected to external forces, especially when the substrate is deformed. (3) Construction difficulty: Leveling: The existing powder coatings have poor leveling during the construction process and are prone to defects such as orange peel and pinholes. (4) Curing speed: Too fast or too slow curing speed will affect the quality of the coating and construction efficiency. (5) Environmental issues: VOC emissions: Although powder coatings themselves do not contain volatile organic compounds, other harmful substances may still be produced during the production and construction process, affecting the environment and health.

[0004] Therefore, there is an urgent need for a method for preparing polyurethane-acrylate dispersions, which not only retains the excellent mechanical properties, cold resistance and wear resistance of polyurethane, but also improves its high temperature resistance, weather resistance and hydrolysis resistance. At the same time, it is applied to coatings to improve the gloss, water resistance and outdoor aging resistance of the coatings, overcoming the shortcomings of high hardness, poor adhesion and flexibility. Summary of the invention

[0005] To this end, the present invention provides a method for preparing a polyurethane-acrylate dispersion and application thereof in a coating, so as to solve the problems of poor stability and insufficient comprehensive performance of the polyurethane-acrylate dispersion in the prior art, improve its adhesion, chemical resistance, flexibility, weather resistance and leveling, thereby preparing a coating with excellent comprehensive performance and efficient processing performance.

[0006] In order to achieve the above object, the present invention provides the following technical solutions: According to a first aspect of the present invention, there is provided a method for preparing a polyurethane-acrylate dispersion, comprising the following steps: S1. Preparation of bifunctional prepolymer: glycidyl phenyl ether is reacted with adipic acid to generate a multifunctional acrylate derivative, which is then reacted with a thiourethane prepolymer having a thiol group at the end to obtain a bifunctional prepolymer; S2. Preparation of mixed solution A: 80-120 parts of thiourethane acrylate prepolymer, 10-20 parts of viscosity reducing solvent, 8-10 parts of hydrophilic chain extender and 10-13 parts of dihydroxypropionate are mixed, stirred evenly, and reacted at 60-80° C. for 1.5-2.5 hours, and the hydroxyl groups in the dihydroxypropionate react with the isocyanate groups in the thiourethane acrylate prepolymer to form an isocyanate-terminated prepolymer; S3. Preparation of a double bond-terminated polyurethane prepolymer: Determine the content of isocyanate groups in the mixed solution A, and mix the epoxy resin and the mixed solution A with the isocyanate group and the like, and react to obtain a double bond-terminated polyurethane prepolymer; S4. Preparation of mixed solution B: dissolving the double-bond terminated polyurethane prepolymer in toluene and removing the solvent to obtain a polyurethane dispersion containing a terminal carboxyl group, and diluting the polyurethane dispersion containing a terminal carboxyl group to a solid content of 20-30% of the mixed solution B; S5. Preparation of polyurethane-acrylate dispersion: The mixed solution B is mixed with adipic anhydride for emulsification, and the obtained emulsion is mixed with an initiator solution for reaction to obtain a carboxyl-terminated polyurethane dispersion.

[0007] Furthermore, S1 includes the following specific steps: S11. Synthesis of multifunctional acrylate derivatives: 80-120 parts of glycidyl phenyl ether and 100-135 parts of adipic acid are mixed, 1-4 parts of an esterification catalyst are added, and the mixture is reacted at 80-120° C. until the acid value reaches 5 mg KOH / g or less; Add 3-6 parts of epoxidation catalyst and 180-220 parts of dichloromethane to the reaction solution, add 145-160 parts of adipic anhydride dropwise under nitrogen atmosphere and ice water bath, warm to room temperature and react for 10-12 hours after the addition is complete, filter, wash with saturated sodium carbonate solution, dry the organic phase with anhydrous calcium chloride, filter and evaporate the solvent to obtain a multifunctional acrylate derivative; S12. Synthesis of thiopolyurethane prepolymer: under nitrogen atmosphere and ice water bath, 85-125 parts of polyisocyanate are added dropwise to 118-126 parts of dithiol, and 1-3 parts of isocyanate reaction catalyst are added simultaneously. After the addition is completed, the temperature is raised to room temperature until the polyisocyanate and dithiol react completely to obtain a thiopolyurethane prepolymer having a thiol terminal; S13. Synthesis of bifunctional prepolymer: Mix 90-112 parts of thiourethane prepolymer with terminal mercapto groups, 115-125 parts of multifunctional acrylate derivatives and 22-35 parts of adipic acid, control the molar ratio of mercapto to carboxyl functional groups to be between 1:1-1:3, and wait for the mercapto groups to react completely to obtain a bifunctional prepolymer.

[0008] Further, the esterification reaction catalyst is one or more of tetrabutyl titanate, sodium bisulfate, N,N-dimethylaminopyridine, and 1,8-diazabicycloundec-7-ene; The epoxidation reaction catalyst is one or more of boron trifluoride ether complex, peracetic acid, N,N-diisopropylethylamine, and 1,5-diazabicyclo[4.3.0]non-5-ene; The isocyanate reaction catalyst is one or more of dibutyltin diacetate, dioctyltin dilaurate, di-n-butyltin dilaurate, di-n-octyltin oxide, and N,N-dimethylaminopyridine.

[0009] Furthermore, in S2, the viscosity reducing solvent accounts for 5-15% of the mass of the mixed solution A; the hydrophilic chain extender accounts for 6-8% of the solid content of the mixed solution A; and the dihydroxypropionic acid ester accounts for 6-10% of the solid content of the mixed solution A.

[0010] Furthermore, the viscosity reducing solvent includes at least one of dimethyl sulfoxide, N,N-dimethylformamide, methyl acetate, isopropyl acetate, nitrogen methyl pyrrolidone, cyclohexane, toluene, xylene and 1,4-dioxane.

[0011] Furthermore, the hydrophilic chain extender includes at least one of diethanolamine, dimethylol propionic acid, dimethylol butyric acid, tartaric acid, 11,3-propylene glycol-2-sodium sulfonate and 1,2-butanediol-3-sodium sulfonate.

[0012] According to a second aspect of the present invention, there is provided a polyurethane-acrylate dispersion, which is prepared by the above-mentioned preparation method.

[0013] According to a third aspect of the present invention, there is provided a coating comprising the above-mentioned polyurethane-acrylate dispersion.

[0014] Further, the following components in parts by weight are included: 70-80 parts of hydroxyl-containing epoxy resin, 50-60 parts of polyurethane-acrylate dispersion, 5-10 parts of low-temperature curing agent, 0.5-2.5 parts of leveling agent, 0.5-1.5 parts of wetting agent, 4-8 parts of precipitated barium sulfate, 10-22 parts of titanium dioxide, 1-3 parts of curing accelerator, 0.1-0.5 parts of photoinitiator, 0.1-0.5 parts of anti-settling agent and 0.1-0.5 parts of solid paraffin.

[0015] According to a fourth aspect of the present invention, there is provided a method for preparing the above-mentioned coating, comprising the following steps: S1. Weigh the materials according to the formula and grind them in a grinder for 1-2h to obtain a mixed material; S2. The mixed material is transported to the blending extruder by a screw conveyor for melt mixing and extrusion, and is cold pressed into sheets by a cooling roller, and the cold pressed sheets are crushed by a crusher and transported to a jet mill for fine grinding; S3. The crushed semi-finished product is collected by a cyclone separator, and then passed through a 100-mesh powder sifter to remove impurities and coarse powder to obtain a finished coating product.

[0016] The present invention has the following advantages: 1. The polyurethane-acrylate dispersion of the present application provides excellent flexibility, weather resistance and chemical resistance through the combination of multifunctional acrylate derivatives and thiourethane prepolymers. The polyurethane part gives the coating good flexibility and impact resistance, while the acrylate part enhances the weather resistance and chemical resistance of the coating, making it perform well under various environmental conditions. The dispersion has good stability and dispersibility, is not prone to sedimentation and stratification, and ensures the uniformity and consistency of the coating during storage and use. The isocyanate-terminated prepolymer has good reactivity with the substrate, ensuring that the coating has excellent adhesion and improving the durability and durability of the coating.

[0017] 2. This application uses a reasonable ratio of epoxy resin, polyurethane-acrylate dispersion and other additives, and the coating has excellent adhesion, chemical resistance, flexibility, weather resistance, leveling and surface performance, and is suitable for a variety of substrates and application scenarios. The use of viscosity-reducing solvents and hydrophilic chain extenders effectively reduces the viscosity of the mixed liquid and improves the processing performance and construction convenience of the coating. The addition of leveling agents and wetting agents further improves the surface quality and leveling of the coating, and reduces defects such as orange peel and pinholes.

[0018] 3. This application ensures the uniformity and stability of the coating through optimized preparation process and equipment, improves production efficiency and product quality. The finished coating has good construction performance and excellent use effect, and is suitable for various indoor and outdoor coating needs. DETAILED DESCRIPTION

[0019] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are 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 creative work are within the scope of protection of the present invention.

[0020] The present invention provides a method for preparing a polyurethane-acrylate dispersion, comprising the following steps: S1. Preparation of bifunctional prepolymer: glycidyl phenyl ether is reacted with adipic acid to generate a multifunctional acrylate derivative, which is then reacted with a thiourethane prepolymer having a thiol group at the end to obtain a bifunctional prepolymer; S2. Preparation of mixed solution A: 80-120 parts of thiourethane acrylate prepolymer, 10-20 parts of viscosity reducing solvent, 8-10 parts of hydrophilic chain extender and 10-13 parts of dihydroxypropionate are mixed, stirred evenly, and reacted at 60-80° C. for 1.5-2.5 hours, and the hydroxyl groups in the dihydroxypropionate react with the isocyanate groups in the thiourethane acrylate prepolymer to form an isocyanate-terminated prepolymer; S3. Preparation of a double bond-terminated polyurethane prepolymer: Determine the content of isocyanate groups in the mixed solution A, and mix the epoxy resin and the mixed solution A with the isocyanate group and the like, and react to obtain a double bond-terminated polyurethane prepolymer; S4. Preparation of mixed solution B: dissolving a double-bond terminated polyurethane prepolymer in toluene and removing the solvent to obtain a polyurethane dispersion containing a terminal carboxyl group, and diluting the polyurethane dispersion containing a terminal carboxyl group to a solid content of 20-30% of the mixed solution B; S5. Preparation of polyurethane-acrylate dispersion: Mixed solution B and adipic anhydride are mixed and emulsified, and the obtained emulsion is mixed and reacted with an initiator solution to obtain a carboxyl-terminated polyurethane dispersion.

[0021] Among them, S1 includes the following specific steps: S11. Synthesis of multifunctional acrylate derivatives: 80-120 parts of glycidyl phenyl ether and 100-135 parts of adipic acid are mixed, 1-4 parts of an esterification catalyst are added, and the mixture is reacted at 80-120° C. until the acid value reaches 5 mg KOH / g or less; Add 3-6 parts of epoxidation catalyst and 180-220 parts of dichloromethane to the reaction solution, add 145-160 parts of adipic anhydride dropwise under nitrogen atmosphere and ice water bath, warm to room temperature and react for 10-12 hours after the addition is complete, filter, wash with saturated sodium carbonate solution, dry the organic phase with anhydrous calcium chloride, filter and evaporate the solvent to obtain a multifunctional acrylate derivative; S12. Synthesis of thiopolyurethane prepolymer: under nitrogen atmosphere and ice water bath, 85-125 parts of polyisocyanate are added dropwise to 118-126 parts of dithiol, and 1-3 parts of isocyanate reaction catalyst are added simultaneously. After the addition is completed, the temperature is raised to room temperature until the polyisocyanate and dithiol react completely to obtain a thiopolyurethane prepolymer having a thiol terminal; S13. Synthesis of bifunctional prepolymer: Mix 90-112 parts of thiourethane prepolymer with terminal mercapto groups, 115-125 parts of multifunctional acrylate derivatives and 22-35 parts of adipic acid, control the molar ratio of mercapto to carboxyl functional groups to be between 1:1-1:3, and wait for the mercapto groups to react completely to obtain a bifunctional prepolymer.

[0022] Specifically, the esterification reaction catalyst is one or more of tetrabutyl titanate, sodium bisulfate, N,N-dimethylaminopyridine, and 1,8-diazabicycloundec-7-ene; preferably, tetrabutyl titanate is selected in the present application.

[0023] The epoxidation reaction catalyst is one or more of boron trifluoride ether complex, peracetic acid, N,N-diisopropylethylamine, and 1,5-diazabicyclo[4.3.0]non-5-ene; preferably, peracetic acid is used in this application.

[0024] The isocyanate reaction catalyst is one or more of dibutyltin diacetate, dioctyltin dilaurate, di-n-butyltin dilaurate, di-n-octyltin oxide, and N,N-dimethylaminopyridine. Preferably, dibutyltin diacetate is used in the present application.

[0025] Specifically, in S2, the viscosity reducing solvent accounts for 5-15% of the mass of the mixed solution A; the hydrophilic chain extender accounts for 6-8% of the solid content of the mixed solution A; and the dihydroxypropionic acid ester accounts for 6-10% of the solid content of the mixed solution A.

[0026] Specifically, the viscosity reducing solvent includes at least one of dimethyl sulfoxide, N,N-dimethylformamide, methyl acetate, isopropyl acetate, nitrogen methyl pyrrolidone, cyclohexane, toluene, xylene and 1,4-dioxane. Preferably, the present application uses N,N-dimethylformamide.

[0027] Specifically, the hydrophilic chain extender includes at least one of diethanolamine, dimethylolpropionic acid, dimethylolbutyric acid, tartaric acid, 11,3-propylene glycol-2-sodium sulfonate and 1,2-butanediol-3-sodium sulfonate. Preferably, dimethylolpropionic acid is used in the present application.

[0028] The invention provides a polyurethane-acrylate dispersion, which is prepared by the above-mentioned preparation method.

[0029] The present invention provides a coating comprising the polyurethane-acrylate dispersion.

[0030] Specifically, the coating includes the following components in parts by weight: 70-80 parts of hydroxyl-containing epoxy resin, 50-60 parts of polyurethane-acrylate dispersion, 5-10 parts of low-temperature curing agent, 0.5-2.5 parts of leveling agent, 0.5-1.5 parts of wetting agent, 4-8 parts of precipitated barium sulfate, 10-22 parts of titanium dioxide, 1-3 parts of curing accelerator, 0.1-0.5 parts of photoinitiator, 0.1-0.5 parts of anti-settling agent and 0.1-0.5 parts of solid paraffin.

[0031] Among them, the low temperature curing agent is one or more of an amine curing agent, an imidazole curing agent, and a modified amine curing agent. Preferably, polyamide amine is selected in this application; The leveling agent is one or more of an organic silicon leveling agent, an acrylate leveling agent, and a fluorocarbon leveling agent. Preferably, BYK-333 is used in this application; The wetting agent is one or more of a silicone wetting agent, a fluorocarbon wetting agent, a nonionic surfactant, and an anionic surfactant. Preferably, BYK-190 is used in this application; The curing accelerator is one or more of tertiary amines, imidazoles, and metal salts. Preferably, triethylamine is used in this application; The photoinitiator is one or more of benzophenone, dibenzophenone and thioxanthone. Preferably, BP-1 is used in this application. The anti-settling agent is one or more of organic bentonite, hydrogenated castor oil, polyamide wax, and fumed silica. Preferably, the present application uses organic bentonite.

[0032] The present invention provides a method for preparing a coating, comprising the following steps: S1. Weigh the materials according to the formula and grind them in a grinder for 1-2h to obtain a mixed material; S2. The mixed material is transported to the blending extruder by a screw conveyor for melt mixing and extrusion, and is cold pressed into sheets by a cooling roller, and the cold pressed sheets are crushed by a crusher and transported to a jet mill for fine grinding; S3. The crushed semi-finished product is collected by a cyclone separator, and then passed through a 100-mesh powder sifter to remove impurities and coarse powder to obtain a finished coating product.

[0033] Example 1 This embodiment provides a method for preparing a polyurethane-acrylate dispersion, comprising the following steps: S1. Preparation of bifunctional prepolymer: S11. Synthesis of multifunctional acrylate derivatives: 100 g of glycidyl phenyl ether was mixed with 120 g of adipic acid, 2 g of tetrabutyl titanate was added, and the mixture was reacted at 120 ° C until the acid value reached 5 mg KOH / g or less; Add 5 g of peracetic acid and 200 mL of dichloromethane to the reaction solution, and dropwise add 150 g of adipic anhydride under a nitrogen atmosphere and an ice-water bath. After the dropwise addition, warm the temperature to room temperature and react for 12 h. Finally, filter, wash with a saturated sodium carbonate solution, dry the organic phase with anhydrous calcium chloride, filter, and evaporate the solvent to obtain a multifunctional acrylate derivative. S12. Synthesis of thiopolyurethane prepolymer: Under nitrogen atmosphere and ice water bath, 100 g of polyisocyanate was added dropwise to 120 g of dithiol, and 2 g of dibutyltin diacetate was added. After the addition, the temperature was raised to room temperature until the polyisocyanate and dithiol were completely reacted to obtain a thiopolyurethane prepolymer having a thiol terminal; S13. Synthesis of a bifunctional prepolymer: 100 g of a thiopolyurethane prepolymer having a thiol terminal was mixed with 120 g of a multifunctional acrylate derivative and 30 g of adipic acid, and the molar ratio of the thiol to carboxyl functional groups was controlled to be 1:3, and the thiol was completely reacted to obtain a bifunctional prepolymer; S2. Preparation of mixed solution A: 100 g of thiourethane acrylate prepolymer was mixed with N, N-dimethylformamide, dimethylol propionic acid and dihydroxypropionate, stirred well, and reacted at 80 ° C for 2 h. The hydroxyl groups in the dihydroxypropionate reacted with the isocyanate groups in the thiourethane acrylate prepolymer to form an isocyanate-terminated prepolymer; S3. Preparation of a double bond-terminated polyurethane prepolymer: Determine the content of isocyanate groups in the mixed solution A, and mix the epoxy resin and the mixed solution A with the isocyanate group and the like, and react to obtain a double bond-terminated polyurethane prepolymer; S4. Preparation of mixed solution B: dissolving a double-bond terminated polyurethane prepolymer in toluene and removing the solvent to obtain a polyurethane dispersion containing a terminal carboxyl group, and diluting the polyurethane dispersion containing a terminal carboxyl group to a solid content of 30% of mixed solution B; S5. Preparation of polyurethane-acrylate dispersion: Mixed solution B and adipic anhydride are mixed and emulsified, and the obtained emulsion is mixed and reacted with the initiator solution to obtain a carboxyl-terminated polyurethane-acrylate dispersion.

[0034] In S2, N,N-dimethylformamide accounts for 10% of the mass of the mixed solution A; dihydroxymethylpropionic acid accounts for 8% of the solid content of the mixed solution A; and dihydroxypropionic acid ester accounts for 8% of the solid content of the mixed solution A.

[0035] This embodiment provides a polyurethane-acrylate dispersion, which is prepared by the above-mentioned preparation method.

[0036] This embodiment provides a coating comprising the above-mentioned polyurethane-acrylate dispersion.

[0037] The above-mentioned coating comprises the following components: Modified bisphenol A epoxy resin 80g, polyurethane-acrylate dispersion 60g, polyamide amine 7g, BYK-3331.5g, BYK-190 1g, heavy barium sulfate 6g, rutile titanium dioxide 16g, triethylamine 2g, BP-1 0.3g, organic bentonite 0.3g, microcrystalline wax 0.5g.

[0038] This embodiment provides a method for preparing the above-mentioned coating, comprising the following steps: S1. Weigh the materials according to the formula and grind them in a grinder for 2 hours to obtain a mixed material; S2. The mixed material is transported to the blending extruder by a screw conveyor for melt mixing and extrusion, and is cold pressed into sheets by a cooling roller, and the cold pressed sheets are crushed by a crusher and transported to a jet mill for fine grinding; S3. The crushed semi-finished product is collected by a cyclone separator, and then passed through a 100-mesh powder sifter to remove impurities and coarse powder to obtain a finished coating product.

[0039] Example 2 This embodiment provides a method for preparing a polyurethane-acrylate dispersion, comprising the following steps: S1. Preparation of bifunctional prepolymer: S11. Synthesis of multifunctional acrylate derivatives: 100 g of glycidyl phenyl ether was mixed with 120 g of adipic acid, 2 g of tetrabutyl titanate was added, and the mixture was reacted at 120 ° C until the acid value reached 5 mg KOH / g or less; Add 5 g of peracetic acid and 200 mL of dichloromethane to the reaction solution, and dropwise add 150 g of adipic anhydride under a nitrogen atmosphere and an ice-water bath. After the dropwise addition, warm the temperature to room temperature and react for 12 h. Finally, filter, wash with a saturated sodium carbonate solution, dry the organic phase with anhydrous calcium chloride, filter, and evaporate the solvent to obtain a multifunctional acrylate derivative. S12. Synthesis of thiopolyurethane prepolymer: Under nitrogen atmosphere and ice water bath, 100 g of polyisocyanate was added dropwise to 120 g of dithiol, and 2 g of dibutyltin diacetate was added. After the addition, the temperature was raised to room temperature until the polyisocyanate and dithiol were completely reacted to obtain a thiopolyurethane prepolymer having a thiol terminal; S13. Synthesis of a bifunctional prepolymer: 100 g of a thiopolyurethane prepolymer having a thiol terminal was mixed with 120 g of a multifunctional acrylate derivative and 30 g of adipic acid, and the molar ratio of the thiol to carboxyl functional groups was controlled to be 1:3, and the thiol was completely reacted to obtain a bifunctional prepolymer; S2. Preparation of mixed solution A: 100 g of thiourethane acrylate prepolymer was mixed with N, N-dimethylformamide, dimethylol propionic acid and dihydroxypropionate, stirred well, and reacted at 80 ° C for 2 h. The hydroxyl groups in the dihydroxypropionate reacted with the isocyanate groups in the thiourethane acrylate prepolymer to form an isocyanate-terminated prepolymer; S3. Preparation of a double bond-terminated polyurethane prepolymer: Determine the content of isocyanate groups in the mixed solution A, and mix the epoxy resin and the mixed solution A with the isocyanate group and the like, and react to obtain a double bond-terminated polyurethane prepolymer; S4. Preparation of mixed solution B: dissolving a double-bond terminated polyurethane prepolymer in toluene and removing the solvent to obtain a polyurethane dispersion containing a terminal carboxyl group, and diluting the polyurethane dispersion containing a terminal carboxyl group to a solid content of 30% of mixed solution B; S5. Preparation of polyurethane-acrylate dispersion: Mixed solution B and adipic anhydride are mixed and emulsified, and the obtained emulsion is mixed and reacted with the initiator solution to obtain a carboxyl-terminated polyurethane-acrylate dispersion.

[0040] In S2, N,N-dimethylformamide accounts for 10% of the mass of the mixed solution A; dihydroxymethylpropionic acid accounts for 8% of the solid content of the mixed solution A; and dihydroxypropionic acid ester accounts for 8% of the solid content of the mixed solution A.

[0041] This embodiment provides a polyurethane-acrylate dispersion, which is prepared by the above-mentioned preparation method.

[0042] This embodiment provides a coating comprising the above-mentioned polyurethane-acrylate dispersion.

[0043] The above coating comprises the following components in parts by weight: Modified bisphenol A epoxy resin 80g, polyurethane-acrylate dispersion 55g, polyamide amine 7g, BYK-3331.5g, BYK-190 1g, heavy barium sulfate 6g, rutile titanium dioxide 16g, triethylamine 2g, BP-1 0.3g, organic bentonite 0.3g, microcrystalline wax 0.5g.

[0044] This embodiment provides a method for preparing the above-mentioned coating, comprising the following steps: S1. Weigh the materials according to the formula and grind them in a grinder for 2 hours to obtain a mixed material; S2. The mixed material is transported to the blending extruder by a screw conveyor for melt mixing and extrusion, and is cold pressed into sheets by a cooling roller, and the cold pressed sheets are crushed by a crusher and transported to a jet mill for fine grinding; S3. The crushed semi-finished product is collected by a cyclone separator, and then passed through a 100-mesh powder sifter to remove impurities and coarse powder to obtain a finished coating product.

[0045] Example 3 This embodiment provides a method for preparing a polyurethane-acrylate dispersion, comprising the following steps: S1. Preparation of bifunctional prepolymer: S11. Synthesis of multifunctional acrylate derivatives: 100 g of glycidyl phenyl ether was mixed with 120 g of adipic acid, 2 g of tetrabutyl titanate was added, and the mixture was reacted at 120 ° C until the acid value reached 5 mg KOH / g or less; Add 5 g of peracetic acid and 200 mL of dichloromethane to the reaction solution, and dropwise add 150 g of adipic anhydride under a nitrogen atmosphere and an ice-water bath. After the dropwise addition, warm the temperature to room temperature and react for 12 h. Finally, filter, wash with a saturated sodium carbonate solution, dry the organic phase with anhydrous calcium chloride, filter, and evaporate the solvent to obtain a multifunctional acrylate derivative. S12. Synthesis of thiopolyurethane prepolymer: Under nitrogen atmosphere and ice water bath, 100 g of polyisocyanate was added dropwise to 120 g of dithiol, and 2 g of dibutyltin diacetate was added. After the addition, the temperature was raised to room temperature until the polyisocyanate and dithiol were completely reacted to obtain a thiopolyurethane prepolymer having a thiol terminal; S13. Synthesis of a bifunctional prepolymer: 100 g of a thiopolyurethane prepolymer having a thiol terminal was mixed with 120 g of a multifunctional acrylate derivative and 30 g of adipic acid, and the molar ratio of the thiol to carboxyl functional groups was controlled to be 1:3, and the thiol was completely reacted to obtain a bifunctional prepolymer; S2. Preparation of mixed solution A: 100 g of thiourethane acrylate prepolymer was mixed with N, N-dimethylformamide, dimethylol propionic acid and dihydroxypropionate, stirred well, and reacted at 80 ° C for 2 h. The hydroxyl groups in the dihydroxypropionate reacted with the isocyanate groups in the thiourethane acrylate prepolymer to form an isocyanate-terminated prepolymer; S3. Preparation of a double bond-terminated polyurethane prepolymer: Determine the content of isocyanate groups in the mixed solution A, and mix the epoxy resin and the mixed solution A with the isocyanate group and the like, and react to obtain a double bond-terminated polyurethane prepolymer; S4. Preparation of mixed solution B: dissolving a double-bond terminated polyurethane prepolymer in toluene and removing the solvent to obtain a polyurethane dispersion containing a terminal carboxyl group, and diluting the polyurethane dispersion containing a terminal carboxyl group to a solid content of 30% of mixed solution B; S5. Preparation of polyurethane-acrylate dispersion: Mixed solution B and adipic anhydride are mixed and emulsified, and the obtained emulsion is mixed and reacted with the initiator solution to obtain a carboxyl-terminated polyurethane-acrylate dispersion.

[0046] In S2, N,N-dimethylformamide accounts for 10% of the mass of the mixed solution A; dihydroxymethylpropionic acid accounts for 8% of the solid content of the mixed solution A; and dihydroxypropionic acid ester accounts for 8% of the solid content of the mixed solution A.

[0047] This embodiment provides a polyurethane-acrylate dispersion, which is prepared by the above-mentioned preparation method.

[0048] This embodiment provides a coating comprising the above-mentioned polyurethane-acrylate dispersion.

[0049] The above coating comprises the following components in parts by weight: Modified bisphenol A epoxy resin 70g, polyurethane-acrylate dispersion 50g, polyamide amine 7g, BYK-3331.5g, BYK-190 1g, heavy barium sulfate 6g, rutile titanium dioxide 16g, triethylamine 2g, BP-1 0.3g, organic bentonite 0.3g, microcrystalline wax 0.5g.

[0050] This embodiment provides a method for preparing the above-mentioned coating, comprising the following steps: S1. Weigh the materials according to the formula and grind them in a grinder for 2 hours to obtain a mixed material; S2. The mixed material is transported to the blending extruder by a screw conveyor for melt mixing and extrusion, and is cold pressed into sheets by a cooling roller, and the cold pressed sheets are crushed by a crusher and transported to a jet mill for fine grinding; S3. The crushed semi-finished product is collected by a cyclone separator, and then passed through a 100-mesh powder sifter to remove impurities and coarse powder to obtain a finished coating product.

[0051] Comparative Example 1 This example is used as a comparative example of Example 1, except that the polyurethane-acrylate dispersion in the coating formulation is replaced with a pure acrylate dispersion, and the other steps and parameters are the same as those in Example 1.

[0052] Comparative Example 2 This example is used as a comparative example of Example 1, except that the modified bisphenol A epoxy resin in the coating formula is replaced with ordinary epoxy resin, and the other steps and parameters are the same as those in Example 1.

[0053] Test Example 1 The polyurethane-acrylate dispersion prepared in Example 1 was tested with reference to GB / T11175-2002 "Test Methods for Synthetic Resin Emulsions", wherein the test items include the appearance, pH, solid content, and viscosity of the polyurethane-acrylate dispersion, and the average particle size of the dispersion was measured using a nanoparticle size analyzer (ZSNanoS); at the same time, the heat storage stability of the polyurethane-acrylate dispersion at 50°C was tested. The test results are shown in Table 1.

[0054] Table 1

[0055] in conclusion: During the test, the appearance of the polyurethane-acrylate dispersion remained semi-transparent, indicating that the dispersion maintained good stability for a long time without obvious turbidity, precipitation or stratification, indicating that the dispersion has good physical stability. The pH value changed slightly, gradually decreasing from 8.5 at 7 days to 8.0 at 180 days, indicating that the dispersion had good chemical stability during storage and no significant acid-base changes occurred, which was conducive to maintaining the long-term stability of the dispersion. The solid content gradually increased from 45.6% at 7 days to 46.8% at 180 days, with a small overall change, indicating that the solid content of the dispersion remained relatively stable for a long time. The viscosity gradually increased from 1490mPa·s at 7 days to 1600mPa·s at 180 days, and the particle size gradually increased from 93nm at 7 days to 98nm at 180 days, indicating that the particles in the dispersion remained well dispersed for a long time without significant aggregation or sedimentation, indicating that the dispersion had good particle size stability. The ethanol content remained below 0.1% throughout the testing period, indicating that the ethanol content in the dispersion was sufficiently low to have a negative impact on the properties of the dispersion.

[0056] In summary, the polyurethane-acrylate dispersion prepared in Example 1 exhibits good physical and chemical stability over a long period of time, stable particle size, changes in solid content and viscosity within a reasonable range, and low ethanol content. The above results show that the polyurethane-acrylate dispersion has excellent comprehensive properties, is suitable for the application of high-performance coatings, and has superiority in practical applications.

[0057] Test Example 2 The powder coatings prepared in Examples 1-3 and Comparative Examples 1-2 were applied to an aluminum substrate and then cured at about 200-270° C. for 10-30 min. The coated aluminum substrates were subjected to the following performance tests, and the test results are shown in Table 3.

[0058] 1. Coating adhesion test (1) Prepare tools and materials: Sharp blade (blade angle 20-30°, blade thickness 0.43±0.03mm), test sample, brush, adhesive tape with adhesion of 10±1N / 25mm (NICHIBAN CT405AP-24 adhesive tape), magnifying glass (5x).

[0059] (2) Marking: Use a sharp blade to mark 10×10 small grids of 2 mm×2 mm on the surface of the test sample; use a brush to thoroughly clean the debris in the test area to ensure that the surface is flat and free of residue.

[0060] (3) Apply tape: Firmly stick a tape with an adhesion of 10±1N / 25mm (NICHIBAN CT405AP-24 tape) on the small grid to be tested. Gently squeeze the tape with your fingernails to ensure that there are no bubbles between the tape and the coating to increase the contact area and adhesion between the tape and the tested area.

[0061] (4) Resting step: Allow the tape to rest on the test area for 90 ± 30 seconds to ensure that the tape is fully adhered.

[0062] (5) Tearing off the tape: After the standing time is over, grab one end of the tape with your hand and quickly tear off the tape at an angle of 60° within 0.5-1s.

[0063] (6) Inspection steps: Use a 5x magnifying glass to check for coating shedding.

[0064] Table 2 shows the judgment criteria, as follows:

[0065] 2. Re-coating adhesion: For the aluminum substrate that has been sprayed with powder coating and cured, spray the same powder coating again in the same way and bake it to cure. Then test the adhesion in the same way as in 1 above.

[0066] 3. Pencil hardness: The pencil hardness of the coatings formed in Examples 1-3 and Comparative Examples 1-2 was determined according to ISO 15184.

[0067] 4. Gloss: The gloss of the aluminum substrate coated with the powder coating was measured at an angle of 60° using a haze-gloss meter (Byk-Gardner).

[0068] 5. Heat resistance: The heat resistance of the coatings formed in Examples 1-3 and Comparative Examples 1-2 was tested according to GB / T 1735. The heat resistance in the present application is reflected by the gloss retention rate (the ratio of the gloss of the coating after high-temperature baking to the gloss before baking of the substrate coated with the coating of the present application).

[0069] 6. Impact resistance: The impact resistance of the coatings formed in Examples 1-3 and Comparative Examples 1-2 was measured according to GB / T 1732-93.

[0070] Table 3. Performance test results

[0071] in conclusion: The adhesion of Examples 1-3 is ≥5B, while the adhesion of Comparative Examples 1 and 2 is ≥4B, indicating that the addition of polyurethane-acrylate dispersion significantly improves the adhesion of the coating, making it reach the highest adhesion level (5B), while the adhesion of pure acrylate dispersion and ordinary epoxy resin coating is slightly lower. The recoating adhesion of Examples 1-3 is ≥5B, while the recoating adhesion of Comparative Examples 1 and 2 is only ≥0B. It shows that the addition of polyurethane-acrylate dispersion significantly improves the recoating adhesion of the coating, so that it can still maintain good adhesion after multiple spraying, while the adhesion of pure acrylate dispersion and ordinary epoxy resin coating decreases significantly after recoating. The pencil hardness of all samples is 2H, indicating that there is no significant difference in hardness. At 280℃, 310℃ and 350℃, the gloss retention rate of Examples 1-3 is ≥50%. At 280℃, 310℃ and 350℃, the gloss retention rate of Comparative Examples 1 and 2 is ≥100%. Although the gloss retention rates of Comparative Examples 1 and 2 are higher, the gloss retention rates of Examples 1-3 also reach a relatively high level, indicating that the polyurethane-acrylate dispersion performs well in terms of heat resistance and can meet the application requirements in high temperature environments. All samples performed well in the 100-grid test, with no obvious coating shedding, indicating that the coating has good scratch resistance and wear resistance. All samples performed consistently in the impact strength test, indicating that the coating has good impact resistance when subjected to external force.

[0072] From the above, it can be seen that the polyurethane-acrylate dispersion significantly improves the adhesion and recoat adhesion of the coating, making it reach the highest adhesion grade (5B), and can still maintain good adhesion after multiple spraying. The adhesion and recoat adhesion of pure acrylate dispersion and ordinary epoxy resin are slightly lower, especially the recoat adhesion is significantly reduced. Polyurethane-acrylate dispersion shows good heat resistance in high temperature environment and has a high gloss retention rate, which can meet the application requirements in high temperature environment. Although pure acrylate dispersion and ordinary epoxy resin have a higher gloss retention rate, the heat resistance of polyurethane-acrylate dispersion has also reached a high level.

[0073] In summary, the addition of polyurethane-acrylate dispersion significantly improves the adhesion and recoating adhesion of the coating, allowing it to maintain good adhesion after multiple spraying. In addition, polyurethane-acrylate dispersion also shows good performance in improving the heat resistance, pencil hardness, scratch resistance, wear resistance and impact resistance of the coating. These results show that polyurethane-acrylate dispersion has significant advantages in high-performance coatings and is suitable for application requirements in a variety of complex environments. The superiority of polyurethane-acrylate dispersion is further verified by comparison with the comparative example.

[0074] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A method for preparing a polyurethane-acrylate dispersion, characterized in that: The following steps are involved: S1. Preparation of bifunctional prepolymer: glycidyl phenyl ether is reacted with adipic acid to generate a multifunctional acrylate derivative, which is then reacted with a thiourethane prepolymer having a thiol group at the end to obtain a bifunctional prepolymer; S2. Preparation of mixed solution A: 80-120 parts of thiourethane acrylate prepolymer, 10-20 parts of viscosity reducing solvent, 8-10 parts of hydrophilic chain extender and 10-13 parts of dihydroxypropionate are mixed, stirred evenly, and reacted at 60-80° C. for 1.5-2.5 hours, and the hydroxyl groups in the dihydroxypropionate react with the isocyanate groups in the thiourethane acrylate prepolymer to form an isocyanate-terminated prepolymer; S3. Preparation of a double bond-terminated polyurethane prepolymer: Determine the content of isocyanate groups in the mixed solution A, and mix the epoxy resin and the mixed solution A with the isocyanate group and the like, and react to obtain a double bond-terminated polyurethane prepolymer; S4. Preparation of mixed solution B: dissolving the double-bond terminated polyurethane prepolymer in toluene and removing the solvent to obtain a polyurethane dispersion containing a terminal carboxyl group, and diluting the polyurethane dispersion containing a terminal carboxyl group to a solid content of 20-30% of the mixed solution B; S5. Preparation of polyurethane-acrylate dispersion: The mixed solution B is mixed with adipic anhydride for emulsification, and the obtained emulsion is mixed with an initiator solution for reaction to obtain a carboxyl-terminated polyurethane dispersion.

2. The method for preparing a polyurethane-acrylate dispersion according to claim 1, characterized in that: S1 includes the following specific steps: S11. Synthesis of multifunctional acrylate derivatives: 80-120 parts of glycidyl phenyl ether and 100-135 parts of adipic acid are mixed, 1-4 parts of an esterification catalyst are added, and the mixture is reacted at 80-120° C. until the acid value reaches 5 mg KOH / g or less; Add 3-6 parts of epoxidation catalyst and 180-220 parts of dichloromethane to the reaction solution, add 145-160 parts of adipic anhydride dropwise under nitrogen atmosphere and ice water bath, warm to room temperature and react for 10-12 hours after the addition is complete, filter, wash with saturated sodium carbonate solution, dry the organic phase with anhydrous calcium chloride, filter and evaporate the solvent to obtain a multifunctional acrylate derivative; S12. Synthesis of thiopolyurethane prepolymer: under nitrogen atmosphere and ice water bath, 85-125 parts of polyisocyanate are added dropwise to 118-126 parts of dithiol, and 1-3 parts of isocyanate reaction catalyst are added simultaneously. After the addition is completed, the temperature is raised to room temperature until the polyisocyanate and dithiol react completely to obtain a thiopolyurethane prepolymer having a thiol terminal; S13. Synthesis of bifunctional prepolymer: Mix 90-112 parts of thiourethane prepolymer with terminal mercapto groups, 115-125 parts of multifunctional acrylate derivatives and 22-35 parts of adipic acid, control the molar ratio of mercapto to carboxyl functional groups to be between 1:1-1:3, and wait for the mercapto groups to react completely to obtain a bifunctional prepolymer.

3. The method for preparing a polyurethane-acrylate dispersion according to claim 2, characterized in that: The esterification reaction catalyst is one or more of tetrabutyl titanate, sodium bisulfate, N,N-dimethylaminopyridine, and 1,8-diazabicycloundec-7-ene; The epoxidation reaction catalyst is one or more of boron trifluoride ether complex, peracetic acid, N,N-diisopropylethylamine, and 1,5-diazabicyclo[4.3.0]non-5-ene; The isocyanate reaction catalyst is one or more of dibutyltin diacetate, dioctyltin dilaurate, di-n-butyltin dilaurate, di-n-octyltin oxide, and N,N-dimethylaminopyridine.

4. The method for preparing a polyurethane-acrylate dispersion according to claim 1, characterized in that: In the S2, the viscosity reducing solvent accounts for 5-15% of the mass of the mixed solution A; the hydrophilic chain extender accounts for 6-8% of the solid content of the mixed solution A; and the dihydroxypropionic acid ester accounts for 6-10% of the solid content of the mixed solution A.

5. The method for preparing a polyurethane-acrylate dispersion according to claim 4, characterized in that: The viscosity reducing solvent includes at least one of dimethyl sulfoxide, N,N-dimethylformamide, methyl acetate, isopropyl acetate, nitrogen methyl pyrrolidone, cyclohexane, toluene, xylene and 1,4-dioxane.

6. The method for preparing a polyurethane-acrylate dispersion according to claim 4, characterized in that: The hydrophilic chain extender includes at least one of diethanolamine, dimethylol propionic acid, dimethylol butyric acid, tartaric acid, 11,3-propylene glycol-2-sodium sulfonate and 1,2-butanediol-3-sodium sulfonate.

7. A polyurethane-acrylate dispersion, characterized in that: The method is prepared according to any one of claims 1 to 6.

8. A coating, characterized in that: Contains the polyurethane-acrylate dispersion as claimed in claim 7.

9. The coating according to claim 8, characterized in that The composition comprises the following components in parts by weight: 70-80 parts of hydroxyl-containing epoxy resin, 50-60 parts of polyurethane-acrylate dispersion, 5-10 parts of low-temperature curing agent, 0.5-2.5 parts of leveling agent, 0.5-1.5 parts of wetting agent, 4-8 parts of precipitated barium sulfate, 10-22 parts of titanium dioxide, 1-3 parts of curing accelerator, 0.1-0.5 parts of photoinitiator, 0.1-0.5 parts of anti-settling agent and 0.1-0.5 parts of solid paraffin.

10. A method for preparing a coating, for producing the coating as claimed in claim 9, characterized in that: The following steps are included: S1. Weigh the materials according to the formula and grind them in a grinder for 1-2h to obtain a mixed material; S2. The mixed material is transported to the blending extruder by a screw conveyor for melt mixing and extrusion, and is cold pressed into sheets by a cooling roller, and the cold pressed sheets are crushed by a crusher and transported to a jet mill for fine grinding; S3. The crushed semi-finished product is collected by a cyclone separator, and then passed through a 100-mesh powder sifter to remove impurities and coarse powder to obtain a finished coating product.

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