Water-borne wood paint suitable for high-pressure mechanical spraying and preparation method of water-borne wood paint

Abstract

The invention provides a water-borne wood paint suitable for high-pressure mechanical spraying and a preparation method thereof, and belongs to the technical field of wood paints.The preparation method comprises the following steps that beet-based polyol, hexamethylene diisocyanate and auxiliaries are mixed to react, perfluoropolyether alcohol is added to react, the mixture is cooled and kept, reduced pressure distillation is conducted, epoxidized soybean oil acrylate is added to be evenly mixed, and the water-borne wood paint suitable for high-pressure mechanical spraying is obtained. A composite polyurethane emulsion is prepared; the preparation method comprises the following steps: dispersing nano titanium dioxide powder in methylbenzene, adding lactic acid, carrying out ultrasonic treatment, stirring for reaction, centrifuging, discarding supernate, adding chloroform, carrying out ultrasonic treatment, centrifuging, discarding supernate, and preparing a polylactic acid-titanium dioxide photoinitiator; and mixing the composite polyurethane emulsion with a polylactic acid-titanium dioxide photoinitiator, and stirring at a high speed to obtain the water-based wood paint. The water-based wood paint prepared by the invention can improve water resistance and heat resistance, and meanwhile, achieves the purposes of environmental protection, high efficiency and energy conservation.

Description

Technical Field

[0001] The invention relates to the technical field of wood paint, and in particular to a water-based wood paint suitable for high-pressure mechanical spraying and a preparation method thereof. Background Art

[0002] Water-based wood paint uses water as the dispersion medium and is popular for its non-toxic, environmentally friendly, and harmless characteristics. However, there is still a gap between water-based resins and oily resins in terms of resistance and construction properties. Therefore, the development of high-performance resin emulsions for use in water-based wood paints is a research hotspot.

[0003] Polyurethane resin is a material with excellent chemical and mechanical properties and is used in the chemical field. Polyurethane paints are used in wood coatings due to their excellent wear resistance, flexibility, and low-humidity film-forming properties. As the environmental protection trend of wood coatings becomes stronger and stronger, water-based polyurethane wood coatings are developed and used because of their low VOC and environmentally friendly properties. At the same time, the shortcomings of water-based polyurethane wood coatings are gradually exposed. Due to the introduction of hydrophilic groups, water-based polyurethanes have defects such as poor water resistance and heat resistance. As wood coatings, wood materials are flammable and easily corroded when exposed to water. It is necessary to improve the water resistance and thermal stability of water-based polyurethane wood coatings. In the prior art, hydroxypropyl polydimethylsiloxane is used as a modifier to prepare polysiloxane-modified polyurethane emulsions to improve their hydrophobicity and thermal stability. However, when hydroxypropyl polydimethylsiloxane is embedded in the molecular chain of polyurethane, its room temperature tensile strength, toughness and brittleness are all low. In addition, in water-based polyurethanes, the water phase itself and the water vapor in the air will produce carbon dioxide during the film formation process, resulting in bubbles in the paint film during the curing process, which needs further research and resolution.

[0004] When water-based wood paint is sprayed with high-pressure spray equipment, it can be evenly sprayed on the wood surface, making it smooth and has good adhesion.

[0005] Therefore, it is necessary to provide a water-based wood paint suitable for high-pressure mechanical spraying and a preparation method thereof to solve the problems existing in the above-mentioned prior art. Summary of the invention

[0006] In view of this, the present invention provides a water-based wood paint suitable for high-pressure mechanical spraying and a preparation method thereof, which can improve water resistance and heat resistance while achieving the purpose of reducing bubbles.

[0007] To achieve the above object, the present invention provides a method for preparing a water-based wood paint suitable for high-pressure mechanical spraying, comprising the following steps: S1. After beet-based polyol, hexamethylene diisocyanate and an auxiliary agent are mixed and reacted, perfluoropolyether alcohol is added to react, the temperature is lowered and maintained, vacuum distillation is performed, and epoxy soybean oil acrylate is added and mixed to obtain a composite polyurethane emulsion; S2. Disperse the nano-titanium dioxide powder in toluene, slowly add lactic acid under stirring, after ultrasonic treatment, stir and react, centrifuge to discard the supernatant, add chloroform, perform ultrasonic treatment, centrifuge to discard the supernatant, and prepare a polylactic acid-titanium dioxide photoinitiator; S3. After mixing the composite polyurethane emulsion and the polylactic acid-titanium dioxide photoinitiator, stir at high speed to prepare a waterborne wood lacquer.

[0008] The present invention is different from the traditional use of trace betaine as a surfactant. In the present invention, betaine-based polyols are prepared as raw materials for producing polyurethane prepolymers. When the multi-branched structure of betaine-based polyols and the residual lignin aromatic ring fragments that are not completely converted react with hexamethylene diisocyanate, it promotes the formation of a three-dimensional cross-linked network of polyurethane, reduces the penetration of water, and improves water resistance; in addition, during the high-pressure spraying process, the broad molecular weight distribution of betaine-based polyols and the inverse emulsion process make the emulsion have excellent shear thinning properties, and can maintain good atomization uniformity under the spraying pressure of 10-20 MPa, and the viscosity quickly recovers after spraying, avoiding the phenomenon of sagging. Furthermore, the waterborne wood lacquer prepared by the preparation method of the present invention is more suitable for high-pressure mechanical spraying and is not easy to block the nozzle of the spray gun. In addition, the hydroxyl groups in perfluoropolyether alcohol are used to encapsulate the isocyanate groups in the remaining system, so as to form a hydrophobic layer on the coating surface, significantly improving water resistance. And the rigid aromatic ring structure in lignin and the double bond cross-linking of epoxy soybean oil acrylate endow the wood lacquer with heat resistance.

[0009] The present invention prepares polylactic acid-titanium dioxide as a photoinitiator. Titanium dioxide is an excellent photoactive compound, non-toxic, inert and inexpensive. Using titanium dioxide as a photoinitiator for ultraviolet-curing composite polyurethane emulsion, hydroxyl radicals can be generated in the photoreaction under aerobic conditions, so as to initiate polymerization by opening the double bond of the acrylic group in epoxy soybean oil acrylate. In addition, the isocyanate groups in polyurethane will also react with the generated free radicals and participate in cross-linking to form a cured network; through the introduction of the photoinitiator, the composite polyurethane emulsion can be rapidly polymerized and cross-linked, and also limits the formation and growth of bubbles during the curing process, avoiding their retention in the paint film. However, nano-titanium dioxide itself is prone to agglomeration and has poor dispersibility. To solve this problem, polylactic acid-grafted nano-titanium dioxide is introduced. The carboxyl and hydroxyl groups in polylactic acid form hydrogen bonds and non-covalent interactions with the TiO2 surface. Due to the bidentate coordination between the titanium atom and the carboxyl group of lactic acid (the way in which a ligand forms a coordination bond with a metal center through two atoms), the molecular chain of polylactic acid is grafted onto TiO2, providing hydroxyl groups for the whole, increasing its compatibility with the composite polyurethane emulsion, and enhancing its dispersibility in the waterborne wood lacquer.

[0010] Optionally, the beet-based polyol is prepared by mixing polyethylene glycol 400 and glycerol, adding beet pulp powder and stirring for 3 - 5 min, heating to 150 - 200 °C, adding concentrated sulfuric acid, continuing the reaction at 200 rmp for 70 - 150 min, cooling, adding an aqueous solution of 1,4-dioxane and stirring for 2 h, and then drying in an oven at 105 °C for 24 h.

[0011] In the present invention, the beet-based polyol is prepared. First, cellulose / hemicellulose in the beet pulp is decomposed into monosaccharides by acid hydrolysis, and a condensation reaction is carried out in a composite solvent system of glycerol and polyethylene glycol to form a polyol with a multi-branched structure. Catalyzed by sulfuric acid, the functional groups of monosaccharides react with those of glycerol and polyethylene glycol to generate a bio-based polyol with rigidity and flexibility.

[0012] Optionally, the volume ratio of 1,4-dioxane to water in the aqueous solution of 1,4-dioxane is 4:1; the volume concentration of the concentrated sulfuric acid is 95%.

[0013] Optionally, the beet pulp powder is prepared by drying the beet pulp at 70 °C for 48 h, grinding, and then sieving to obtain a beet pulp powder with a particle size less than 60 μm.

[0014] Optionally, in step S1, vanillin is added while adding the beet-based polyol.

[0015] In the process of preparing the composite polyurethane emulsion in the present invention, a small amount of vanillin is added to improve the raw material odor of the polyurethane material, and the phenolic hydroxyl group therein can react with free radicals to play a role in capturing free radicals, thereby slowing down the oxidation reaction and improving the overall antioxidant property.

[0016] Optionally, in step S1, after mixing the beet-based polyol and vanillin, hexamethylene diisocyanate is added and reacted at 70 °C for 3 h, then an auxiliary agent is added and reacted for 4 h, then perfluoropolyether alcohol is added and reacted at 80 °C for 2 - 3 h, the temperature is lowered to 60 °C and maintained for 2 h, then methyl ethyl ketone is added, the temperature is further lowered to 40 °C, glacial acetic acid is added to adjust the pH value to 7.0 - 7.2, then under a negative pressure of -0.1 KPa and a temperature of 40 °C, it is maintained for 0.5 - 1 h for vacuum distillation, epoxy soybean oil acrylate is added and mixed evenly, then the temperature is raised to 60 - 80 °C and maintained for 0.5 - 1 h, and then ammonium persulfate is added dropwise within 4 h, and then maintained for 1 - 2 h to obtain the composite polyurethane emulsion.

[0017] In the process of preparing the composite polyurethane emulsion in the present invention, methyl ethyl ketone diluent is added to adjust the viscosity of the system to avoid too high viscosity, and ammonium persulfate can promote the closer combination of epoxy soybean oil acrylate and polyurethane.

[0018] Optionally, the auxiliary agent is 1,4-butanediol, trimethylolpropane, and triethylamine.

[0019] In the process of preparing the composite polyurethane emulsion of the present invention, 1,4-butanediol is used as a chain extender to react with isocyanate to extend the polymerization chain, and trimethylolpropane is used as a crosslinking agent to increase the compactness of the polymer, thereby making the internal structure more stable and improving the overall stability and durability.

[0020] Optionally, in step S2, the nano-titanium dioxide powder is dispersed in toluene, lactic acid is slowly added under stirring, then ultrasonic treatment is carried out at 90 °C for 40 - 60 min, stirring reaction is carried out at 150 °C for 24 - 36 h under a nitrogen atmosphere, centrifugation is carried out at a speed of 5000 rpm for 0.5 - 1 h, the supernatant is discarded, chloroform is added, ultrasonic treatment is carried out for 20 - 30 min, and then centrifugation is carried out at a speed of 5000 rpm for 0.5 - 1 h, and the supernatant is discarded to obtain the polylactic acid-titanium dioxide photoinitiator.

[0021] Optionally, in step S3, after mixing the composite polyurethane emulsion and the polylactic acid-titanium dioxide photoinitiator, high-speed stirring is carried out at a rate of 3000 - 5000 rpm for 10 - 15 min, then the ground pigment and filler are added, stirring is carried out at a rate of 200 - 500 rpm for 20 - 30 min, and then deionized water is added for high-speed inverse phase emulsification for 30 - 50 min to obtain the waterborne wood lacquer.

[0022] The present invention also provides a waterborne wood lacquer prepared by the preparation method of a waterborne wood lacquer suitable for high-pressure mechanical spraying as described above, which comprises the following raw materials in parts by mass: 40 - 60 parts of composite polyurethane emulsion, 0.4 - 1 part of polylactic acid-titanium dioxide photoinitiator, 1 - 5 parts of pigment and filler, and 40 - 50 parts of deionized water.

[0023] The present invention can obtain the best comprehensive performance by using the raw materials in these parts by mass, and can meet the requirements of high-pressure mechanical spraying.

[0024] The above technical solutions of the present invention at least include the following beneficial effects: 1. The present invention innovatively uses beet pulp to prepare beet-based polyol as a raw material for polyurethane prepolymer. Its multi-branched structure and residual lignin aromatic ring fragments react with hexamethylene diisocyanate to form a dense three-dimensional cross-linked network, significantly improving water resistance. The broad molecular weight distribution of beet-based polyol endows the emulsion with excellent shear-thinning properties, atomizes uniformly under high-pressure spraying of 10 - 20 MPa and quickly recovers viscosity, avoiding sagging, and is especially suitable for mechanical spraying. Perfluoropolyether alcohol encapsulates isocyanate groups to form a surface hydrophobic layer, which synergistically strengthens the water and heat resistance with the rigidity of the lignin aromatic ring and the cross-linking of epoxy soybean oil acrylate. Compared with the application of traditional betaine surfactants, the present invention realizes the unity of spraying applicability and functionality through the improvement of raw materials.

[0025] 2. The present invention prepares polylactic acid-titanium dioxide as a photoinitiator. The photocatalytic reaction of titanium dioxide under aerobic conditions can generate hydroxyl radicals, which can initiate polymerization by opening the double bond of the acrylic group in epoxy soybean oil acrylate. In addition, the isocyanate groups in polyurethane will also react with the generated radicals and participate in cross-linking to form a curing network. By introducing the photoinitiator, the composite polyurethane emulsion can polymerize and cross-link rapidly, and also limits the formation and growth of bubbles during the curing process, avoiding their retention in the paint film. Using polylactic acid grafted TiO2 can increase its compatibility with the composite polyurethane emulsion and improve its dispersibility in wood coatings. Detailed implementation mode

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present invention.

[0027] Example 1 After drying 100 parts of beet pulp at 70 °C for 48 h, it was ground for 10 min and then screened to a particle size of less than 60 μm to obtain beet pulp powder. 80 parts of polyethylene glycol 400 and 40 parts of glycerol were mixed evenly, 80 parts of beet pulp powder were added and mixed and stirred for 5 min. After heating to 200 °C, 15 parts of sulfuric acid with a volume concentration of 95% were added, and the reaction was continued at 200 rmp for 150 min and then cooled to terminate the reaction. 100 parts of an aqueous solution of 1,4-dioxane (volume ratio of 1,4-dioxane to water is 4:1) were added and stirred for 2 h, and then dried in an oven at 105 °C for 24 h to obtain beet-based polyol.

[0028] After mixing 50 parts of beet-based polyol and 0.12 parts of vanillin evenly, 20 parts of hexamethylene diisocyanate were added and reacted at 70 °C for 3 h. Then 3 parts of 1,4-butanediol, 1 part of trimethylolpropane, and 2 parts of triethylamine were added and reacted for 4 h. 5 parts of perfluoropolyether alcohol were added and reacted at 80 °C for 2 h. After cooling to 60 °C and maintaining for 2 h, 10 parts of methyl ethyl ketone were added, the temperature was lowered to 40 °C, and glacial acetic acid was added to adjust the pH value to 7.0. Then, under a negative pressure of -0.1 KPa and a temperature of 40 °C, it was maintained for 0.5 h for vacuum distillation. 30 parts of epoxy soybean oil acrylate were added and mixed evenly, then the temperature was raised to 60 °C and kept for 0.5 h. Then, 2 parts of ammonium persulfate were added dropwise within 4 h and kept for 1 h to obtain the composite polyurethane emulsion.

[0029] Disperse 2 parts of nano-titanium dioxide powder in 16 parts of toluene, slowly add 4 parts of lactic acid under stirring, then perform ultrasonic treatment at 90 °C for 40 min, stir and react at 150 °C for 24 h under a nitrogen atmosphere, centrifuge at a speed of 5000 rpm for 0.5 h, discard the supernatant, add 10 parts of chloroform, perform ultrasonic treatment for 20 min, then centrifuge at a speed of 5000 rpm for 0.5 h, discard the supernatant to obtain a polylactic acid-titanium dioxide photoinitiator.

[0030] Mix 40 parts of composite polyurethane emulsion and 0.4 part of polylactic acid-titanium dioxide photoinitiator, stir at a rate of 3000 rpm for 10 min, add 1 part of ground pigment and filler, stir at a rate of 200 rpm for 20 min, then add 40 parts of deionized water, and perform high-speed inverse phase emulsification for 30 min to obtain a waterborne wood lacquer.

[0031] Example 2 Dry 100 parts of beet pulp at 70 °C for 48 h, grind for 6 min, and then screen to a particle size less than 60 μm to obtain beet pulp powder; mix 80 parts of polyethylene glycol 400 and 40 parts of glycerol evenly, add 60 parts of beet pulp powder and mix and stir for 3 min, heat to 150 °C, then add 10 parts of sulfuric acid with a volume concentration of 95%, continue to react at 200 rmp for 70 min and then cool to terminate the reaction, add 80 parts of an aqueous solution of 1,4-dioxane (volume ratio of 1,4-dioxane to water is 4:1) and stir for 2 h, and then dry in an oven at 105 °C for 24 h to obtain beet-based polyol.

[0032] Mix 35 parts of beet-based polyol and 0.15 part of vanillin evenly, then add 30 parts of hexamethylene diisocyanate and react at 70 °C for 3 h, add 5 parts of 1,4-butanediol, 3 parts of trimethylolpropane, and 4 parts of triethylamine and react for 4 h, add 5 parts of perfluoropolyether alcohol, react at 80 °C for 3 h, then cool to 60 °C and keep for 4 h, add 10 parts of methyl ethyl ketone, lower the temperature to 40 °C, add glacial acetic acid to adjust the pH value to 7.2, keep under negative pressure of -0.1 KPa and at a temperature of 40 °C for 1 h for vacuum distillation, add 50 parts of epoxy soybean oil acrylate and mix evenly, then heat to 80 °C, keep warm for 1 h, and dropwise add 5 parts of ammonium persulfate within 4 h, then keep warm for 2 h to obtain a composite polyurethane emulsion.

[0033] Disperse 5 parts of nano-titanium dioxide powder in 20 parts of toluene, slowly add 8 parts of lactic acid under stirring, then perform ultrasonic treatment at 90 °C for 60 min, keep stirring and reacting at 150 °C for 36 h under a nitrogen atmosphere, centrifuge at a speed of 5000 rpm for 1 h, discard the supernatant, add 10 parts of chloroform, perform ultrasonic treatment for 30 min, then centrifuge at a speed of 5000 rpm for 1 h, discard the supernatant to obtain a polylactic acid-titanium dioxide photoinitiator.

[0034] After mixing 60 parts of the composite polyurethane emulsion and 1 part of the polylactic acid-titanium dioxide photoinitiator, stirring at a rate of 5000 rpm for 15 min, adding 5 parts of the ground pigment and filler, stirring at a rate of 500 rpm for 30 min, adding 50 parts of deionized water, and carrying out high-speed inverse emulsification for 50 min, a waterborne wood lacquer is prepared.

[0035] Example 3 After drying 100 parts of sugar beet pulp at 70 °C for 48 h, grinding for 7 min, and then screening to a particle size less than 60 μm, sugar beet pulp powder is prepared; 80 parts of polyethylene glycol 400 and 40 parts of glycerol are mixed evenly, 70 parts of sugar beet pulp powder is added and stirred for 3 min, heated to 180 °C, 12 parts of sulfuric acid with a volume concentration of 95% is added, and the reaction is continued at 200 rmp for 120 min and then cooled to terminate the reaction. 90 parts of an aqueous solution of 1,4-dioxane (volume ratio of 1,4-dioxane to water is 4:1) is added and stirred for 2 h, and then dried in an oven at 105 °C for 24 h to obtain sugar beet-based polyol.

[0036] After mixing 45 parts of sugar beet-based polyol and 0.2 part of vanillin evenly, adding 40 parts of hexamethylene diisocyanate and reacting at 70 °C for 3 h, adding 5 parts of 1,4-butanediol, 2 parts of trimethylolpropane, and 3 parts of triethylamine and reacting for 4 h, adding 5 parts of perfluoropolyether alcohol, reacting at 80 °C for 2.5 h, cooling to 60 °C and maintaining for 5 h, adding 10 parts of methyl ethyl ketone, reducing the temperature to 40 °C, adjusting the pH value to 7.1 with glacial acetic acid, carrying out vacuum distillation at a negative pressure of -0.1 KPa and a temperature of 40 °C for 1 h, adding 60 parts of epoxy soybean oil acrylate and mixing evenly, heating to 70 °C, maintaining for 1 h, dropping 4 parts of ammonium persulfate within 4 h, and maintaining for 1.5 h to obtain the composite polyurethane emulsion.

[0037] Disperse 3 parts of nano-titanium dioxide powder in 15 parts of toluene, slowly add 6 parts of lactic acid under stirring, carry out ultrasonic treatment at 90 °C for 50 min, maintain stirring reaction at 150 °C in a nitrogen atmosphere for 30 h, centrifuge at a speed of 5000 rpm for 1 h, discard the supernatant, add 10 parts of chloroform, carry out ultrasonic treatment for 25 min, centrifuge at a speed of 5000 rpm for 1 h, and discard the supernatant to obtain the polylactic acid-titanium dioxide photoinitiator.

[0038] After mixing 50 parts of the composite polyurethane emulsion and 0.6 part of the polylactic acid-titanium dioxide photoinitiator, stirring at a rate of 4000 rpm for 12 min, adding 2 parts of the ground pigment and filler, stirring at a rate of 300 rpm for 25 min, adding 45 parts of deionized water, and carrying out high-speed inverse emulsification for 40 min, a waterborne wood lacquer is prepared.

[0039] Example 4 After drying 100 parts of beet pulp at 70 °C for 48 h, grinding for 8 min, and then screening to a particle size less than 60 μm, beet pulp powder was obtained; 80 parts of polyethylene glycol 400 was mixed evenly with 40 parts of glycerol, 75 parts of beet pulp powder was added and mixed and stirred for 4 min, after heating to 160 °C, 14 parts of sulfuric acid with a volume concentration of 95% was added, and the reaction was continued at 200 rmp for 90 min and then cooled to terminate the reaction. 85 parts of an aqueous solution of 1,4-dioxane (volume ratio of 1,4-dioxane to water was 4:1) was added and stirred for 2 h, and then dried in an oven at 105 °C for 24 h to obtain beet-based polyol.

[0040] After mixing 40 parts of beet-based polyol and 0.12 part of vanillin evenly, 35 parts of hexamethylene diisocyanate was added and reacted at 70 °C for 3 h, then 4 parts of 1,4-butanediol, 3 parts of trimethylolpropane, and 4 parts of triethylamine were added and reacted for 4 h. 5 parts of perfluoropolyether alcohol was added and reacted at 80 °C for 3 h, then the temperature was lowered to 60 °C and maintained for 5 h, 10 parts of methyl ethyl ketone was added, the temperature was lowered to 40 °C, acetic acid was added to adjust the pH value to 7.2, and then vacuum distillation was carried out at a negative pressure of -0.1 KPa and a temperature of 40 °C for 1 h. 45 parts of epoxy soybean oil acrylate was added and mixed evenly, then the temperature was raised to 75 °C and kept warm for 1 h, and 3 parts of ammonium persulfate was added dropwise within 4 h, and then kept warm for 2 h to obtain a composite polyurethane emulsion.

[0041] 3 parts of nano-titanium dioxide powder was dispersed in 18 parts of toluene, and 6 parts of lactic acid was slowly added under stirring. After ultrasonic treatment at 90 °C for 60 min, the reaction was stirred at 150 °C in a nitrogen atmosphere for 30 h, centrifuged at 5000 rpm for 1 h, and the supernatant was discarded. 10 parts of chloroform was added, ultrasonic treatment was carried out for 30 min, and then centrifuged at 5000 rpm for 1 h and the supernatant was discarded to obtain a polylactic acid-titanium dioxide photoinitiator.

[0042] After mixing 55 parts of the composite polyurethane emulsion and 0.6 part of the polylactic acid-titanium dioxide photoinitiator, stirring was carried out at a rate of 4000 rpm for 15 min, then 2 parts of ground pigment and filler was added, stirring was carried out at a rate of 500 rpm for 30 min, and then 45 parts of deionized water was added, and high-speed reverse phase emulsification was carried out for 40 min to obtain a waterborne wood lacquer.

[0043] Example 5 After drying 100 parts of beet pulp at 70 °C for 48 h, grinding for 6 min, and then sieving to a particle size of less than 60 μm, beet pulp powder was obtained; 80 parts of polyethylene glycol 400 was mixed evenly with 40 parts of glycerol, 65 parts of beet pulp powder was added and mixed and stirred for 3 min, after heating to 170 °C, 11 parts of sulfuric acid with a volume concentration of 95% was added, and the reaction continued at 200 rmp for 100 min and then cooled to terminate the reaction. 85 parts of an aqueous solution of 1,4-dioxane (the volume ratio of 1,4-dioxane to water was 4:1) was added and stirred for 2 h, and then dried in an oven at 105 °C for 24 h to obtain beet-based polyol.

[0044] After mixing 45 parts of beet-based polyol and 0.15 part of vanillin evenly, 30 parts of hexamethylene diisocyanate was added and reacted at 70 °C for 3 h, then 3 parts of 1,4-butanediol, 2 parts of trimethylolpropane, and 3 parts of triethylamine were added and reacted for 4 h. 5 parts of perfluoropolyether alcohol was added and reacted at 80 °C for 2.5 h, then the temperature was lowered to 60 °C and maintained for 3 h, 10 parts of methyl ethyl ketone was added, the temperature was lowered to 40 °C, acetic acid was added to adjust the pH value to 7.0, and then vacuum distillation was carried out at a negative pressure of -0.1 KPa and a temperature of 40 °C for 0.5 h. 40 parts of epoxy soybean oil acrylate was added and mixed evenly, then the temperature was raised to 70 °C and kept warm for 1 h, and 3 parts of ammonium persulfate was added dropwise within 4 h, and then kept warm for 1.5 h to obtain a composite polyurethane emulsion.

[0045] 2 parts of nano-titanium dioxide powder was dispersed in 16 parts of toluene, and 4 parts of lactic acid was slowly added under stirring. After ultrasonic treatment at 90 °C for 50 min, it was stirred and reacted at 150 °C in a nitrogen atmosphere for 28 h, centrifuged at a speed of 5000 rpm for 1 h, the supernatant was discarded, 10 parts of chloroform was added, ultrasonic treatment was carried out for 20 min, and then centrifuged at a speed of 5000 rpm for 0.5 h, and the supernatant was discarded to obtain a polylactic acid-titanium dioxide photoinitiator.

[0046] After mixing 45 parts of the composite polyurethane emulsion and 0.7 part of the polylactic acid-titanium dioxide photoinitiator, it was stirred at a rate of 4000 rpm for 13 min, then 2 parts of ground pigment and filler were added, stirred at a rate of 400 rpm for 25 min, and then 50 parts of deionized water was added, and high-speed reverse phase emulsification was carried out for 35 min to obtain a waterborne wood paint.

[0047] The present invention also carried out comparative examples and related tests.

[0048] Comparative Example 1 Compared with Example 1, the difference was that methoxypolyethylene glycol was directly used as the raw material of the composite polyurethane emulsion instead of beet-based polyol, and other components and preparation steps were exactly the same, and finally a waterborne wood paint was obtained.

[0049] Comparative Example 2 Compared with Example 1, the difference is that perfluoropolyether alcohol was not added during the preparation of the composite polyurethane emulsion for reaction, and other components and preparation steps are exactly the same, and a waterborne wood lacquer was prepared.

[0050] Comparative Example 3 Compared with Example 1, the difference is that nano-titanium dioxide was directly used as a photoinitiator, and the polylactic acid-titanium dioxide photoinitiator was not prepared, and other components and preparation steps are exactly the same, and a waterborne wood lacquer was prepared.

[0051] Comparative Example 4 Compared with Example 1, the difference is that commercially available photoinitiator 1173 was directly used, and the polylactic acid-titanium dioxide photoinitiator was not prepared, and other components and preparation steps are exactly the same, and a waterborne wood lacquer was prepared.

[0052] Performance detection test For the waterborne wood lacquers obtained in Examples 1 to 5 and Comparative Examples 1 to 4, basic performance tests were carried out on fineness, non-volatile matter, storage stability, gloss, abrasion resistance, and adhesion in accordance with the national standard requirements of GB / T 23999-2009 for waterborne wood coatings for interior decoration and renovation. The test results are shown in Table 1.

[0053] Table 1

[0054] It can be seen from Table 1 that the fineness of the waterborne wood lacquers prepared in Examples 1 to 5 ≤25μm, abrasion resistance ≤0.02g, non-volatile matter ≥40%, and adhesion ≤Grade 1 all meet the national standards specified in GB / T 23999-2009 for waterborne wood coatings for interior decoration and renovation.

[0055] Combined with Table 1, it can be seen that compared with Comparative Example 1 (using methoxypolyethylene glycol), Example 1 shows better performance in adhesion, abrasion resistance, and gloss, indicating that betaine-based polyols can enhance the crosslinking density and film-forming properties of polyurethane emulsions. In Comparative Examples 3 and 4, due to the non-use of the polylactic acid-titanium dioxide photoinitiator, the poor dispersion of the individual nano-titanium dioxide powder or photoinitiator 1173 in the emulsion resulted in the appearance of hard lumps, which in turn affected the fineness and gloss problems. This is because the polylactic acid-titanium dioxide photoinitiator improved the dispersion through chemical bonding, while also enhancing the photocuring efficiency and coating uniformity; in Comparative Example 2, the abrasion resistance decreased significantly due to the non-addition of perfluoropolyether alcohol, which also indicates that perfluoropolyether alcohol improved the abrasion resistance and hydrophobicity of the coating by introducing fluorine elements; in summary, the basic performance of the waterborne wood lacquer prepared by the present invention has been significantly improved.

[0056] Examples 1 to 5 and Comparative Examples 1 to 4 were tested for drying time, water resistance, dry heat resistance, and film appearance according to the implementation standard of HG / T 3655-1999 UV-curable wood coatings. The test results are shown in Table 2.

[0057] Table 2

[0058] As can be seen from Table 2, in Comparative Example 1, the lack of use of beet-based polyols led to a low crosslinking density and slow curing, and also caused blistering at the film edges; compared with Comparative Example 2, the addition of perfluoropolyether alcohol in Example 1 significantly improved the water resistance and dry heat resistance; compared with Comparative Examples 3 and 4, the addition of polylactic acid-titanium dioxide photoinitiator in Example 1 resulted in high UV curing efficiency, significantly shortened curing time, and further prevented the generation of bubbles. In Comparative Example 3, nano-titanium dioxide was directly added, resulting in agglomeration due to poor dispersibility, delayed curing, and large-area blistering due to film defects; and both the curing speed and dry heat resistance reached the standard of HG / T 3655-1999 UV-curable wood coatings.

[0059] The above are the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a water-based wood lacquer suitable for high-pressure mechanical spraying, characterized in that, It includes the following steps: S1. Mix beet-based polyol, hexamethylene diisocyanate and an auxiliary agent for reaction, then add perfluoropolyether alcohol for reaction, cool and maintain the temperature, conduct vacuum distillation, add epoxy soybean oil acrylate and mix evenly to obtain a composite polyurethane emulsion; S2. Disperse nano-titanium dioxide powder in toluene, slowly add lactic acid under stirring, conduct ultrasonic treatment, then stir and react, centrifuge and discard the supernatant, add chloroform, conduct ultrasonic treatment, centrifuge and discard the supernatant to obtain a polylactic acid-titanium dioxide photoinitiator; S3. Mix the composite polyurethane emulsion and the polylactic acid-titanium dioxide photoinitiator, and conduct high-speed stirring to obtain a waterborne wood lacquer.

2. The preparation method of a water-based wood lacquer suitable for high-pressure mechanical spraying according to claim 1, characterized in that, The beet-based polyol is prepared by mixing polyethylene glycol 400 and glycerol evenly, adding beet pulp powder and mixing and stirring for 3 - 5 min, heating to 150 - 200 °C, adding concentrated sulfuric acid, continuing to react at 200 rmp for 70 - 150 min, then cooling, adding an aqueous solution of 1,4-dioxane and stirring for 2 h, and then drying in an oven at 105 °C for 24 h.

3. The preparation method of a water-based wood lacquer suitable for high-pressure mechanical spraying according to claim 2, wherein In the aqueous solution of 1,4-dioxane, the volume ratio of 1,4-dioxane to water is 4:1; the volume concentration of the concentrated sulfuric acid is 95%.

4. The preparation method of a water-based wood lacquer suitable for high-pressure mechanical spraying according to claim 2, characterized in that, The beet pulp powder is obtained by drying beet pulp at 70 °C for 48 h, grinding, and then sieving to obtain beet pulp powder with a particle size less than 60 μm.

5. The preparation method of a water-based wood lacquer suitable for high-pressure mechanical spraying according to claim 2, characterized in that, In step S1, vanillin is added while adding the beet-based polyol.

6. The preparation method of a water-based wood lacquer suitable for high-pressure mechanical spraying according to claim 1, characterized in that In step S1, after mixing the beet-based polyol and vanillin evenly, add hexamethylene diisocyanate and mix and react at 70 °C for 3 h, then add the auxiliary agent and react for 4 h, add perfluoropolyether alcohol and react at 80 °C for 2 - 3 h, cool to 60 °C and maintain for 2 h, add methyl ethyl ketone, then lower the temperature to 40 °C, add glacial acetic acid to adjust the pH value to 7.0 - 7.2, then conduct vacuum distillation at a negative pressure of -0.1 KPa and a temperature of 40 °C for 0.5 - 1 h, add epoxy soybean oil acrylate and mix evenly, then heat to 60 - 80 °C, keep warm for 0.5 - 1 h, then dropwise add ammonium persulfate within 4 h, and keep warm for 1 - 2 h to obtain a composite polyurethane emulsion.

7. The preparation method of a waterborne wood lacquer suitable for high-pressure mechanical spraying according to claim 6, characterized in that, The auxiliary agent is 1,4-butanediol, trimethylolpropane and triethylamine.

8. The preparation method of a water-based wood lacquer suitable for high-pressure mechanical spraying according to claim 1, characterized in that, In step S2, disperse nano-titanium dioxide powder in toluene, slowly add lactic acid under stirring, then conduct ultrasonic treatment at 90 °C for 40 - 60 min, maintain stirring reaction at 150 °C under a nitrogen atmosphere for 24 - 36 h, centrifuge at a speed of 5000 rpm for 0.5 - 1 h, discard the supernatant, add chloroform, conduct ultrasonic treatment for 20 - 30 min, then centrifuge at a speed of 5000 rpm for 0.5 - 1 h, discard the supernatant to obtain a polylactic acid-titanium dioxide photoinitiator.

9. The preparation method of a water-based wood paint suitable for high-pressure mechanical spraying according to claim 1, characterized in that, In step S3, after mixing the composite polyurethane emulsion and the polylactic acid-titanium dioxide photoinitiator, conduct high-speed stirring at a rate of 3000 - 5000 rpm for 10 - 15 min, then add the ground pigment and filler, stir at a rate of 200 - 500 rpm for 20 - 30 min, add deionized water, and conduct high-speed reverse phase emulsification for 30 - 50 min to obtain a waterborne wood lacquer.

10. An aqueous wood lacquer suitable for high-pressure mechanical spraying, characterized in that, Prepared by the preparation method of an aqueous wood lacquer suitable for high-pressure mechanical spraying according to any one of claims 1 to 9, and comprising the following raw materials in parts by mass: 40 to 60 parts of a composite polyurethane emulsion, 0.4 to 1 part of a polylactic acid-titanium dioxide photoinitiator, 1 to 5 parts of a pigment filler, and 40 to 50 parts of deionized water.

Images