Weather-resistant wall painting water-based paint and preparation method thereof

Abstract

The present application relates to a kind of weatherable wall drawing water-based paint and its preparation method, belong to high polymer coating technical field.The present application is by synthesizing N-(trimethylol) methyl acrylamide citrate ester, and it is introduced as comonomer into acrylate polymer main chain.The monomer not only contains polymerizable carbon-carbon double bond, also has multiple hydroxyl and a citrate ester skeleton.In film-forming process, these functional groups promote the formation of more dense, more stable three-dimensional network structure between polymer molecular chains by the form such as physical crosslinking, branching degree promotion and hydrogen bond effect, to improve the comprehensive performance of coating film, especially water resistance, chemical medium resistance and durability.The present application is by the synergistic effect of acrylate polymer emulsion and nano-silica, wood fiber and other fillers, the prepared coating not only has 0 level adhesion, and in anti-sagging construction performance, thixotropy and wear resistance aspect performance is excellent, meet the construction and application requirements of high-quality wall drawing.

Description

Technical Field

[0001] This invention relates to a weather-resistant water-based wall painting coating and its preparation method, belonging to the field of polymer coating technology. Background Technology

[0002] Wall painting, as a personalized decorative art, has been widely used in homes, hotels, exhibition halls, and outdoor public spaces. Wall painting paint not only requires vibrant colors and intricate patterns, but also demands excellent weather resistance, stain resistance, scrub resistance, and strong adhesion to the substrate. Especially for outdoor wall paintings, the coating must withstand long-term exposure to ultraviolet radiation, rain, and temperature changes, making it susceptible to problems such as fading, chalking, cracking, and peeling.

[0003] Traditional wall paints mostly use acrylic emulsions as a base. Although acrylic emulsions have good gloss and color retention, their linear molecular structure limits the density and cross-linking degree of the film formed after coating, resulting in insufficient water resistance, solvent resistance, and stain resistance. Especially under long-term outdoor exposure, the durability of the coating is severely challenged. To improve coating performance, external cross-linking agents (such as aziridine and carbodiimide) are usually added. However, these cross-linking agents often have problems such as high toxicity, short pot life, or poor compatibility with the system.

[0004] Therefore, there is an urgent need to develop a water-based wall painting coating with good weather resistance, stain resistance and mechanical properties. Summary of the Invention

[0005] The purpose of this invention is to provide a weather-resistant water-based wall painting coating and its preparation method, so as to solve the problem of the deviation in weather resistance and stain resistance of current acrylic coatings when used for wall painting.

[0006] This invention provides a weather-resistant water-based wall painting coating, composed of the following components in parts by weight: 40-50 parts of acrylate polymer emulsion; 15-25 parts of water-based pigment paste; 1.5-2.5 parts of nano-silica; 0.3-0.6 parts of associative polyurethane thickener; 0.5-1.0 parts of wood fiber; 0.5-1.0 parts of wetting and dispersing agent; 0.1-0.3 parts of defoamer; 2.0-3.0 parts of film-forming aid; and 20-30 parts of water. The acrylate polymer emulsion is prepared by emulsion polymerization of styrene, butyl acrylate, methyl methacrylate, acrylic acid, and N-(trimethylolpropionic acid)methacrylamide citrate in a mass ratio of 25-35:30-40:10-15:1-3:3-8. The chemical structure of the N-(trimethylolpropionic acid)methacrylamide citrate is as follows:

[0007] .

[0008] Preferably, the method for preparing the acrylate polymer emulsion includes the following steps:

[0009] (1) Styrene, butyl acrylate, methyl methacrylate, acrylic acid and N-(tris(hydroxymethyl)methacrylamide)citrate were prepared into a monomer preemulsion;

[0010] (2) Then, heat and mix a portion of the monomer pre-emulsion and the initiator to obtain a seed emulsion;

[0011] (3) Add the remaining monomer pre-emulsion and initiator to the seed emulsion for mixing and reaction to obtain acrylate polymer emulsion.

[0012] Preferably, in step (1), the method for preparing the monomer preemulsion by styrene, butyl acrylate, methyl methacrylate, acrylic acid and N-(tris(hydroxymethyl)methacrylamide)citrate is as follows: styrene, butyl acrylate, methyl methacrylate, acrylic acid and N-(tris(hydroxymethyl)methacrylamide)citrate are added to a mixture composed of alkyl sulfate, nonylphenol polyoxyethylene ether, alkali metal bicarbonate and water, and mixed evenly to obtain the monomer preemulsion;

[0013] The mass ratio of styrene, butyl acrylate, methyl methacrylate, acrylic acid and N-(trimethylolmethyl)methacrylamide citrate, alkyl sulfate, nonylphenol polyoxyethylene ether, alkali metal bicarbonate and water is 25~35:30~40:10~15:1~3:3~8:0.5~1:0.5~1:0.2~0.5:15~20;

[0014] In step (2), the monomer pre-emulsion accounts for 10-15% of the total mass of the monomer pre-emulsion; the initiator is persulfate, and the temperature for heating and mixing the monomer pre-emulsion and the initiator is 80-85℃, and the time is 30-45min.

[0015] In step (3), the remaining monomer pre-emulsion and initiator are added to the seed emulsion for mixing and reaction at a temperature of 88~90℃ for 1~2h.

[0016] Preferably, the alkyl sulfate is sodium dodecyl sulfate; the alkali metal bicarbonate is sodium bicarbonate; the persulfate is ammonium persulfate; in step (2), the mass ratio of the monomer preemulsion to the initiator is 30~60:1; in step (3), the mass ratio of the remaining monomer preemulsion, initiator and seed emulsion is 80~95:0.3~0.5:15~30.

[0017] Preferably, the preparation method of the associative polyurethane thickener includes the following steps: under the action of a catalyst, isophorone diisocyanate, polyethylene glycol PEG-6000 and tris(hydroxymethyl)phosphine oxide are mixed and reacted, then dimethylolpropionic acid is added for chain extension reaction, and finally a monohydric alcohol compound is added for end capping, followed by neutralization and dispersion with water to obtain the product; the monohydric alcohol compound is n-dodecyl alcohol, n-tridecyl alcohol or n-tetradecyl alcohol; the molar ratio of isophorone diisocyanate, polyethylene glycol PEG-6000, tris(hydroxymethyl)phosphine oxide, dimethylolpropionic acid and monohydric alcohol compound is 0.11~0.12:0.01~0.015:0.01~0.015:0.06~0.07:0.05~0.06.

[0018] Preferably, the average length of the wood fibers is 180~220μm and the average diameter is 10~20μm.

[0019] Preferably, the wood fiber is obtained from bleached wood pulp with an α-cellulose content of ≥90% and a kappa number of ≤1.0 through dissociation, drying, and screening.

[0020] Preferably, the water-based pigment paste is an iron oxide red paste.

[0021] Preferably, the wetting and dispersing agent is BYK-190 wetting and dispersing agent, the defoamer is BYK-024 type defoamer, and the film-forming aid is dodecyl alcohol ester.

[0022] A method for preparing a weather-resistant water-based wall painting coating as described above includes the following steps: mixing an appropriate amount of acrylate polymer emulsion, water-based pigment paste, nano silica, associative polyurethane thickener, wood fiber, wetting and dispersing agent, defoamer, film-forming aid, and water to obtain the coating.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) This invention synthesizes N-(trimethylol)methacrylamide citrate and introduces it as a comonomer into the main chain of an acrylate polymer. This monomer not only contains polymerizable carbon-carbon double bonds, but also has multiple hydroxyl groups and a citrate backbone. During film formation, these functional groups promote the formation of a denser and more stable three-dimensional network structure between polymer molecular chains through physical cross-linking, increased branching, and hydrogen bonding, thereby improving the overall performance of the coating film, especially its resistance to water, chemical media, and durability. In addition, the citrate backbone in the N-(trimethylol)methacrylamide citrate monomer provides rigid support to the polymer main chain, while the multi-hydroxyl structure enhances the intermolecular cohesion by forming a high-density hydrogen bond network and promotes the uniform dispersion of fillers by increasing the affinity with fillers such as wood fibers. The resulting structure, which combines rigidity and flexibility, allows the coating film to maintain good flexibility while having good abrasion resistance. This makes the wall surface effectively resistant to daily cleaning and minor scratches, making it particularly suitable for wall decoration in high-traffic public spaces or children's rooms.

[0025] (2) The coating prepared by the present invention through the synergistic effect of acrylic polymer emulsion and fillers such as nano silica and wood fiber not only has grade 0 adhesion, but also performs well in terms of anti-sagging workability, thixotropy and abrasion resistance, meeting the construction and application requirements of high-quality wall painting.

[0026] (3) This invention utilizes bio-based citric acid derivatives as functional monomers to replace some traditional petroleum-based monomers, thereby reducing the emission of volatile organic compounds. At the same time, the polymer prepared using this monomer promotes the formation of a denser and more stable three-dimensional network structure between polymer molecular chains through physical cross-linking, increased branching degree, and hydrogen bonding, which can effectively inhibit the migration of small molecule additives. This improves the color retention of the coating film under long-term ultraviolet irradiation and temperature and humidity cycling tests, making it less prone to chalking, thus extending the decorative life of the wall and reducing maintenance costs. Attached Figure Description

[0027] Figure 1 The 1H NMR spectrum of N-(tris(hydroxymethyl)methylcitrate monoamide) prepared in Example 1 of this invention;

[0028] Figure 2 The image shows the 1H NMR spectrum of N-(tris(hydroxymethyl)methacrylamide)citrate prepared in Example 1 of this invention. Detailed Implementation

[0029] The following examples are intended to further illustrate the content of the present invention, rather than to limit the scope of protection of the present invention.

[0030] Example 1

[0031] The weather-resistant water-based wall painting coating of this embodiment is composed of the following components in parts by weight: 45 parts acrylic polymer emulsion; 20 parts water-based pigment paste; 2 parts nano silica; 0.4 parts associative polyurethane thickener; 0.8 parts wood fiber; 0.8 parts wetting and dispersing agent; 0.2 parts defoamer; 2.5 parts film-forming aid; and 25 parts deionized water.

[0032] Among them, the water-based pigment paste is BASF Luconyl iron oxide red paste 3396, the nano silica is Degussa white carbon black A200 (AEROSIL 200), the associative polyurethane thickener is Haiming Sideqian RHEOLATE 299 rheology modifier, the wetting and dispersing agent is BYK-190 wetting and dispersing agent, the defoamer is BYK-024 defoamer, and the film-forming aid is dodecyl alcohol ester.

[0033] The preparation method of wood fiber is as follows: bleached wood pulp with α-cellulose content ≥90% and kappa number ≤1.0 is dissociated using a fiber delamination machine, dried, and then screened to obtain fibers with an average length of 200μm and an average diameter of 15μm.

[0034] The preparation method of acrylate polymer emulsion includes the following steps:

[0035] (1) Dissolve 0.09 mol of citric anhydride in 100 mL of anhydrous N,N-dimethylformamide, place in an ice-water bath, cool to 0°C, and then add dropwise 50 mL of anhydrous N,N-dimethylformamide solution containing 0.1 mol of tris(hydroxymethyl)aminomethane. After the addition is complete, raise the temperature to room temperature and stir for 8 h. After the reaction is complete, pour the reaction solution into 500 mL of acetone, stir evenly, and filter. Wash the filter cake three times with acetone. Dry the washed filter cake under vacuum at 40°C for 12 h to obtain a white solid N-(tris(hydroxymethyl)methyl)citric acid monoamide with a yield of 88%. The chemical structure of citric anhydride is as follows:

[0036] ;

[0037] The 1H NMR spectrum of N-(tris(hydroxymethyl)methylcitrate monoamide) is shown below. Figure 1 As shown, the chemical structure is as follows:

[0038] .

[0039] (2) 0.08 mol of N-(tris(hydroxymethyl)methylcitrate) monoamide was dissolved in 150 mL of anhydrous N,N-dimethylformamide, and then 0.2 g hydroquinone and 1.0 g triethylamine were added. Under stirring, 0.08 mol of glycidyl methacrylate was added dropwise. After the addition was completed, the temperature was raised to 90 °C and the reaction was stirred for 5 h. After the reaction was completed, the mixture was cooled to room temperature, and the reaction solution was poured into 1500 mL of diethyl ether. After stirring evenly, the mixture was filtered. The filter cake was washed three times with diethyl ether. The washed filter cake was then vacuum dried at 45 °C for 12 h to obtain N-(tris(hydroxymethyl)methylacrylamide)citrate, with a yield of 79%. The 1H NMR spectrum of N-(tris(hydroxymethyl)methylacrylamide)citrate is shown below. Figure 2 As shown, the chemical structure is as follows:

[0040] .

[0041] (3) 28 parts by weight of styrene, 35 parts by weight of butyl acrylate, 12 parts by weight of methyl methacrylate, 2 parts by weight of acrylic acid and 5 parts by weight of N-(tris(hydroxymethyl)methacrylamide)citrate were added to a mixture consisting of 0.8 parts by weight of sodium dodecyl sulfate, 0.8 parts by weight of nonylphenol polyoxyethylene ether, 0.3 parts by weight of sodium bicarbonate and 18 parts by weight of deionized water, and dispersed at high speed for 30 min to obtain a monomer pre-emulsion.

[0042] (4) In a four-necked flask equipped with a stirrer, condenser, thermometer and constant pressure dropping funnel, add 12 parts by mass of deionized water, 12% of the total mass of the monomer pre-emulsion prepared in step (3) and 0.2 parts by mass of ammonium persulfate, purge with nitrogen and stir evenly, then heat to 82°C and keep warm for 40 min to obtain seed emulsion;

[0043] (5) Under stirring and nitrogen protection, the remaining monomer pre-emulsion and initiator solution (0.4 parts by mass of ammonium persulfate dissolved in 8 parts by mass of deionized water) are added dropwise to the seed emulsion through two constant pressure dropping funnels. During the dropwise addition, the reaction temperature is maintained at 85~87℃, and the dropping rate of monomer pre-emulsion and initiator solution is controlled to ensure that both are added at the same time. The dropwise addition time is 3.5h. After the dropwise addition is completed, the temperature is raised to 89℃ and the reaction is kept at this temperature for 1.5h. After the reaction is completed, the temperature is lowered to below 40℃, the pH is adjusted to 7.5 with ammonia water, and the material is filtered out using a 200-mesh filter to obtain the acrylate polymer emulsion.

[0044] Example 2

[0045] The weather-resistant water-based wall painting coating of this embodiment is composed of the following components in parts by weight: 40 parts acrylic polymer emulsion; 15 parts water-based pigment paste; 1.5 parts nano silica; 0.3 parts associative polyurethane thickener; 0.5 parts wood fiber; 0.5 parts wetting and dispersing agent; 0.1 parts defoamer; 2.0 parts film-forming aid; and 20 parts deionized water.

[0046] Among them, the water-based pigment paste is BASF Luconyl iron oxide red paste 3396, the nano silica is Degussa white carbon black A200 (AEROSIL 200), the associative polyurethane thickener is Haiming Sideqian RHEOLATE 299 rheology modifier, the wetting and dispersing agent is BYK-190 wetting and dispersing agent, the defoamer is BYK-024 defoamer, and the film-forming aid is dodecyl alcohol ester.

[0047] The preparation method of wood fiber is as follows: bleached wood pulp with α-cellulose content ≥90% and kappa number ≤1.0 is dissociated using a fiber delamination machine, dried, and then screened to obtain fibers with an average length of 180μm and an average diameter of 10μm.

[0048] The preparation method of acrylate polymer emulsion includes the following steps:

[0049] (1) Dissolve 0.09 mol of citric anhydride in 100 mL of anhydrous N,N-dimethylformamide, place in an ice-water bath, cool to 0°C, and then add dropwise 50 mL of anhydrous N,N-dimethylformamide solution containing 0.1 mol of tris(hydroxymethyl)aminomethane. After the addition is complete, raise the temperature to room temperature and stir for 8 h. After the reaction is complete, pour the reaction solution into 500 mL of acetone, stir evenly, and filter. Wash the filter cake three times with acetone. Dry the washed filter cake under vacuum at 40°C for 12 h to obtain a white solid N-(tris(hydroxymethyl)methyl)citric acid monoamide. The chemical structure of citric anhydride is as follows:

[0050] ;

[0051] The chemical structure of N-(tris(hydroxymethyl)methylcitrate) monoamide is as follows:

[0052] .

[0053] (2) Dissolve 0.08 mol of N-(tris(hydroxymethyl)methylcitrate) monoamide in 150 mL of anhydrous N,N-dimethylformamide, then add 0.2 g hydroquinone and 1.0 g triethylamine. Under stirring, add 0.08 mol of glycidyl methacrylate dropwise. After the addition is complete, heat to 90 °C and stir for 5 h. After the reaction is complete, cool to room temperature and pour the reaction solution into 1500 mL of diethyl ether. After stirring evenly, filter. Wash the filter cake three times with diethyl ether. Dry the washed filter cake under vacuum at 45 °C for 12 h to obtain N-(tris(hydroxymethyl)methylacrylamide)citrate. The chemical structure of N-(tris(hydroxymethyl)methylacrylamide)citrate is as follows:

[0054] .

[0055] (3) 25 parts by weight of styrene, 30 parts by weight of butyl acrylate, 10 parts by weight of methyl methacrylate, 1 part by weight of acrylic acid and 3 parts by weight of N-(tris(hydroxymethyl)methacrylamide)citrate were added to a mixture consisting of 0.5 parts by weight of sodium dodecyl sulfate, 0.5 parts by weight of nonylphenol polyoxyethylene ether, 0.2 parts by weight of sodium bicarbonate and 15 parts by weight of deionized water, and dispersed at high speed for 30 min to obtain a monomer pre-emulsion.

[0056] (4) In a four-necked flask equipped with a stirrer, condenser, thermometer and constant pressure dropping funnel, add 10 parts by mass of deionized water, 10% of the total mass of the monomer pre-emulsion prepared in step (3) and 0.1 parts by mass of ammonium persulfate, purge with nitrogen and stir evenly, then heat to 80°C and keep warm for 45 min to obtain seed emulsion;

[0057] (5) Under stirring and nitrogen protection, the remaining monomer pre-emulsion and initiator solution (0.3 parts by mass of ammonium persulfate dissolved in 5 parts by mass of deionized water) are added dropwise to the seed emulsion through two constant pressure dropping funnels. During the dropping process, the reaction temperature is maintained at 85~87℃, and the dropping rate of monomer pre-emulsion and initiator solution is controlled to ensure that both are added at the same time. The dropping time is 3h. After the dropping is completed, the temperature is raised to 88℃ and the reaction is kept at this temperature for 2h. After the reaction is completed, the temperature is lowered to below 40℃, the pH is adjusted to 7.0 with ammonia water, and the material is filtered out using a 200-mesh filter to obtain the acrylate polymer emulsion.

[0058] Example 3

[0059] The weather-resistant water-based wall painting coating of this embodiment is composed of the following components in parts by weight: 50 parts acrylic polymer emulsion; 25 parts water-based pigment paste; 2.5 parts nano silica; 0.6 parts associative polyurethane thickener; 1.0 part wood fiber; 1.0 part wetting and dispersing agent; 0.3 parts defoamer; 3.0 parts film-forming aid; and 30 parts deionized water.

[0060] Among them, the water-based pigment paste is BASF Luconyl iron oxide red paste 3396, the nano silica is Degussa white carbon black A200 (AEROSIL 200), the associative polyurethane thickener is Haiming Sideqian RHEOLATE 299 rheology modifier, the wetting and dispersing agent is BYK-190 wetting and dispersing agent, the defoamer is BYK-024 defoamer, and the film-forming aid is dodecyl alcohol ester.

[0061] The preparation method of wood fiber is as follows: bleached wood pulp with α-cellulose content ≥90% and kappa number ≤1.0 is dissociated using a fiber delamination machine, dried, and then screened to obtain fibers with an average length of 220μm and an average diameter of 20μm.

[0062] The preparation method of acrylate polymer emulsion includes the following steps:

[0063] (1) Dissolve 0.09 mol of citric anhydride in 100 mL of anhydrous N,N-dimethylformamide, place in an ice-water bath, cool to 0°C, and then add dropwise 50 mL of anhydrous N,N-dimethylformamide solution containing 0.1 mol of tris(hydroxymethyl)aminomethane. After the addition is complete, raise the temperature to room temperature and stir for 8 h. After the reaction is complete, pour the reaction solution into 500 mL of acetone, stir evenly, and filter. Wash the filter cake three times with acetone. Dry the washed filter cake under vacuum at 40°C for 12 h to obtain a white solid N-(tris(hydroxymethyl)methyl)citric acid monoamide. The chemical structure of citric anhydride is as follows:

[0064] ;

[0065] The chemical structure of N-(tris(hydroxymethyl)methylcitrate) monoamide is as follows:

[0066] .

[0067] (2) Dissolve 0.08 mol of N-(tris(hydroxymethyl)methylcitrate) monoamide in 150 mL of anhydrous N,N-dimethylformamide, then add 0.2 g hydroquinone and 1.0 g triethylamine. Under stirring, add 0.08 mol of glycidyl methacrylate dropwise. After the addition is complete, heat to 90 °C and stir for 5 h. After the reaction is complete, cool to room temperature and pour the reaction solution into 1500 mL of diethyl ether. After stirring evenly, filter. Wash the filter cake three times with diethyl ether. Dry the washed filter cake under vacuum at 45 °C for 12 h to obtain N-(tris(hydroxymethyl)methylacrylamide)citrate. The chemical structure of N-(tris(hydroxymethyl)methylacrylamide)citrate is as follows:

[0068] .

[0069] (3) Add 35 parts by weight of styrene, 40 parts by weight of butyl acrylate, 15 parts by weight of methyl methacrylate, 3 parts by weight of acrylic acid and 8 parts by weight of N-(tris(hydroxymethyl)methacrylamide)citrate to a mixture consisting of 1.0 parts by weight of sodium dodecyl sulfate, 1.0 parts by weight of nonylphenol polyoxyethylene ether, 0.5 parts by weight of sodium bicarbonate and 20 parts by weight of deionized water, and disperse at high speed for 30 min to obtain a monomer pre-emulsion.

[0070] (4) In a four-necked flask equipped with a stirrer, condenser, thermometer and constant pressure dropping funnel, add 15 parts by mass of deionized water, 15% of the total mass of the monomer pre-emulsion prepared in step (3) and 0.3 parts by mass of ammonium persulfate, purge with nitrogen and stir evenly, then heat to 85°C and keep warm for 30 min to obtain seed emulsion;

[0071] (5) Under stirring and nitrogen protection, the remaining monomer pre-emulsion and initiator solution (0.5 parts by mass of ammonium persulfate dissolved in 10 parts by mass of deionized water) are added dropwise to the seed emulsion through two constant pressure dropping funnels. During the dropping process, the reaction temperature is maintained at 85~87℃, and the dropping rate of monomer pre-emulsion and initiator solution is controlled to ensure that both are added at the same time. The dropping time is 4h. After the dropping is completed, the temperature is raised to 90℃ and kept at the temperature for 1h. After the reaction is completed, the temperature is lowered to below 40℃, the pH is adjusted to 8.0 with ammonia water, and the material is filtered out using a 200-mesh filter to obtain the acrylate polymer emulsion.

[0072] Example 4

[0073] The difference between the weather-resistant water-based wall painting coating of this embodiment and the weather-resistant water-based wall painting coating of Example 1 is only that the associative polyurethane thickener in the weather-resistant water-based wall painting coating of this embodiment is prepared by the following method: In a four-necked flask equipped with a stirrer, thermometer and nitrogen delivery tube, 0.11 mol of isophorone diisocyanate and 0.1 g of dibutyltin dilaurate catalyst are added, and the temperature is raised to 55°C. Then, 0.01 mol of polyethylene glycol PEG-6000 that has been vacuum dehydrated at 110°C and 0.01 mol of tris(hydroxymethyl)oxygenate are added. Phosphine was added to a four-necked flask and then stirred at 70°C for 2 hours. The reaction system was then cooled to 55°C, and 0.06 mol of dimethylolpropionic acid and 25 g of butanone were added to adjust the viscosity. The temperature was then raised to 70°C and stirred for 2.5 hours. The system was then cooled to 50°C, and 0.05 mol of n-dodecyl alcohol was added. The reaction was stirred at 60°C for 1.5 hours. Butanone was removed by vacuum distillation, and deionized water was added to adjust the solid content to 25%. The mixture was then neutralized with triethylamine to a pH of 7.0-7.5 to obtain an associative polyurethane thickener.

[0074] Example 5

[0075] The difference between the weather-resistant water-based wall painting coating of this embodiment and the weather-resistant water-based wall painting coating of Example 1 is only that the associative polyurethane thickener in the weather-resistant water-based wall painting coating of this embodiment is prepared by the following method: In a four-necked flask equipped with a stirrer, thermometer and nitrogen delivery tube, 0.11 mol of isophorone diisocyanate and 0.1 g of dibutyltin dilaurate catalyst are added, and the temperature is raised to 55°C. Then, 0.01 mol of polyethylene glycol PEG-6000 that has been vacuum dehydrated at 110°C and 0.01 mol of tris(hydroxymethyl)oxygenate are added. Phosphine was added to a four-necked flask and then stirred at 70°C for 2 hours. The reaction system was then cooled to 55°C, and 0.06 mol of dimethylolpropionic acid and 25 g of butanone were added to adjust the viscosity. The temperature was then raised to 70°C and stirred for 2.5 hours. The system was then cooled to 50°C, and 0.05 mol of n-tetradecyl alcohol was added. The reaction was stirred at 60°C for 1.5 hours. Butanone was removed by vacuum distillation, and deionized water was added to adjust the solid content to 25%. The mixture was then neutralized with triethylamine to a pH of 7.0-7.5 to obtain an associative polyurethane thickener.

[0076] The preparation methods of the weather-resistant water-based wall painting coatings in Examples 1-5 are as follows:

[0077] Add deionized water, BYK-190 wetting and dispersing agent, and BYK-024 defoamer to a dispersion container and stir evenly at 400 r / min. Then, under high-speed dispersion conditions at 2000 r / min, add nano silica (Degussa AEROSIL 200) and wood fiber in sequence and disperse at high speed for 20 min. Subsequently, reduce the speed to 1500 r / min, add acrylate polymer emulsion, BASF Luconyl iron oxide red paste 3396, and dodecyl alcohol ester film-forming aid, and continue stirring for 15 min. Finally, add associative polyurethane thickener and stir evenly at 500 r / min to obtain the final product.

[0078] Comparative Example 1

[0079] The only difference between the weather-resistant water-based wall painting coating of this comparative example and the weather-resistant water-based wall painting coating of Example 1 is that the preparation method of the acrylic polymer emulsion in the weather-resistant water-based wall painting coating of this comparative example includes the following steps:

[0080] (1) Add 30 parts by weight of styrene, 38 parts by weight of butyl acrylate, 12 parts by weight of methyl methacrylate and 2 parts by weight of acrylic acid to a mixture consisting of 0.8 parts by weight of sodium dodecyl sulfate, 0.8 parts by weight of nonylphenol polyoxyethylene ether, 0.3 parts by weight of sodium bicarbonate and 18 parts by weight of deionized water, and disperse at high speed for 30 min to obtain a monomer pre-emulsion.

[0081] (2) In a four-necked flask equipped with a stirrer, condenser, thermometer and constant pressure dropping funnel, add 12 parts by mass of deionized water, 12% of the total mass of the monomer pre-emulsion prepared in step (1) and 0.2 parts by mass of ammonium persulfate, purge with nitrogen and stir evenly, then heat to 82°C and keep warm for 40 min to obtain seed emulsion;

[0082] (3) Under stirring and nitrogen protection, the remaining monomer pre-emulsion and initiator solution (0.4 parts by mass of ammonium persulfate dissolved in 8 parts by mass of deionized water) are added dropwise to the seed emulsion through two constant pressure dropping funnels. During the dropping process, the reaction temperature is maintained at 85~87℃, and the dropping rate of monomer pre-emulsion and initiator solution is controlled to ensure that both are added at the same time. The dropping time is 3.5h. After the dropping is completed, the temperature is raised to 89℃ and kept at the temperature for 1.5h. After the reaction is completed, the temperature is lowered to below 40℃, the pH is adjusted to 7.5 with ammonia water, and the material is filtered out using a 200-mesh filter to obtain the acrylate polymer emulsion.

[0083] Comparative Example 2

[0084] The only difference between the weather-resistant water-based wall painting coating of this comparative example and the weather-resistant water-based wall painting coating of Example 1 is that the preparation method of the acrylic polymer emulsion in the weather-resistant water-based wall painting coating of this comparative example includes the following steps:

[0085] (1) 28 parts by weight of styrene, 35 parts by weight of butyl acrylate, 12 parts by weight of methyl methacrylate, 2 parts by weight of acrylic acid and 5 parts by weight of N-hydroxymethylacrylamide were added to a mixture consisting of 0.8 parts by weight of sodium dodecyl sulfate, 0.8 parts by weight of nonylphenol polyoxyethylene ether, 0.3 parts by weight of sodium bicarbonate and 18 parts by weight of deionized water, and dispersed at high speed for 30 min to obtain a monomer pre-emulsion.

[0086] (2) In a four-necked flask equipped with a stirrer, condenser, thermometer and constant pressure dropping funnel, add 12 parts by mass of deionized water, 12% of the total mass of the monomer pre-emulsion prepared in step (1) and 0.2 parts by mass of ammonium persulfate, purge with nitrogen and stir evenly, then heat to 82°C and keep warm for 40 min to obtain seed emulsion;

[0087] (3) Under stirring and nitrogen protection, the remaining monomer pre-emulsion and initiator solution (0.4 parts by mass of ammonium persulfate dissolved in 8 parts by mass of deionized water) are added dropwise to the seed emulsion through two constant pressure dropping funnels. During the dropping process, the reaction temperature is maintained at 85~87℃, and the dropping rate of monomer pre-emulsion and initiator solution is controlled to ensure that both are added at the same time. The dropping time is 3.5h. After the dropping is completed, the temperature is raised to 89℃ and kept at the temperature for 1.5h. After the reaction is completed, the temperature is lowered to below 40℃, the pH is adjusted to 7.5 with ammonia water, and the material is filtered out using a 200-mesh filter to obtain the acrylate polymer emulsion.

[0088] Comparative Example 3

[0089] The only difference between the weather-resistant water-based wall painting coating of this comparative example and the weather-resistant water-based wall painting coating of Example 1 is that the associative polyurethane thickener in the weather-resistant water-based wall painting coating of this comparative example is prepared by the following method: 0.11 mol of isophorone diisocyanate and 0.1 g of dibutyltin dilaurate catalyst are added to a four-necked flask equipped with a stirrer, thermometer and nitrogen delivery tube, and the temperature is raised to 55°C. Then, 0.01 mol of polyethylene glycol PEG-6000 that has been vacuum dehydrated at 110°C and 0.01 mol of tris(hydroxymethyl)oxygenate are added. Phosphine was added to a four-necked flask and then stirred at 70°C for 2 hours. The reaction system was then cooled to 55°C, and 0.06 mol of dimethylolpropionic acid and 25 g of butanone were added to adjust the viscosity. The temperature was then raised to 70°C and stirred for 2.5 hours. The system was then cooled to 50°C, and 0.05 mol of n-octanol was added. The reaction was stirred at 60°C for 1.5 hours. Butanone was removed by vacuum distillation, and deionized water was added to adjust the solid content to 25%. The mixture was then neutralized with triethylamine to a pH of 7.0-7.5 to obtain an associative polyurethane thickener.

[0090] Comparative Example 4

[0091] The only difference between the weather-resistant water-based wall painting coating of this comparative example and the weather-resistant water-based wall painting coating of Example 1 is that the associative polyurethane thickener in the weather-resistant water-based wall painting coating of this comparative example is prepared by the following method: 0.11 mol of isophorone diisocyanate and 0.1 g of dibutyltin dilaurate catalyst are added to a four-necked flask equipped with a stirrer, thermometer and nitrogen delivery tube, and the temperature is raised to 55°C. Then, 0.01 mol of polyethylene glycol PEG-6000 that has been vacuum dehydrated at 110°C and 0.01 mol of tris(hydroxymethyl)oxygenate are added. Phosphine was added to a four-necked flask and then stirred at 70°C for 2 hours. The reaction system was then cooled to 55°C, and 0.06 mol of dimethylolpropionic acid and 25 g of butanone were added to adjust the viscosity. The temperature was then raised to 70°C and stirred for 2.5 hours. The system was then cooled to 50°C, and 0.05 mol of n-hexadecyl alcohol was added. The reaction was stirred at 60°C for 1.5 hours. Butanone was removed by vacuum distillation, and deionized water was added to adjust the solid content to 25%. The mixture was then neutralized with triethylamine to a pH of 7.0-7.5 to obtain an associative polyurethane thickener.

[0092] Comparative Example 5

[0093] The only difference between the weather-resistant water-based wall painting coating of this comparative example and the weather-resistant water-based wall painting coating of Example 1 is that the associative polyurethane thickener in the weather-resistant water-based wall painting coating of this comparative example is prepared by the following method: 0.11 mol of isophorone diisocyanate and 0.1 g of dibutyltin dilaurate catalyst are added to a four-necked flask equipped with a stirrer, thermometer and nitrogen delivery tube, and the temperature is raised to 55°C. Then, 0.01 mol of polyethylene glycol PEG-6000 which has been vacuum dehydrated at 110°C and 0.015 mol of 1,6-hexanediol are added. Alcohol was added to a four-necked flask and the mixture was stirred at 70°C for 2 hours. The reaction system was then cooled to 55°C, and 0.06 mol of dimethylolpropionic acid and 25 g of butanone were added to adjust the viscosity. The mixture was then heated to 70°C and stirred for 2.5 hours. The mixture was then cooled to 50°C, and 0.05 mol of n-dodecyl alcohol was added. The mixture was stirred at 60°C for 1.5 hours. Butanone was removed by vacuum distillation, and deionized water was added to adjust the solid content to 25%. The mixture was then neutralized with triethylamine to a pH of 7.0-7.5 to obtain an associative polyurethane thickener.

[0094] Comparative Example 6

[0095] The only difference between the weather-resistant water-based wall painting coating of this comparative example and the weather-resistant water-based wall painting coating of Example 1 is that the associative polyurethane thickener in the weather-resistant water-based wall painting coating of this comparative example is prepared by the following method: 0.11 mol of isophorone diisocyanate and 0.1 g of dibutyltin dilaurate catalyst are added to a four-necked flask equipped with a stirrer, thermometer and nitrogen gas delivery tube, and the temperature is raised to 55°C. Then, 0.01 mol of polyethylene glycol PEG-6000 which has been vacuum dehydrated at 110°C and 0.0075 mol of pentaerythritol are added. The mixture was added to a four-necked flask and stirred at 70°C for 2 hours. The reaction mixture was then cooled to 55°C, and 0.06 mol of dimethylolpropionic acid and 25 g of butanone were added to adjust the viscosity. The mixture was then heated to 70°C and stirred for 2.5 hours. The mixture was then cooled to 50°C, and 0.05 mol of n-dodecyl alcohol were added. The mixture was stirred at 60°C for 1.5 hours. Butanone was removed by vacuum distillation, and deionized water was added to adjust the solid content to 25%. The mixture was then neutralized with triethylamine to a pH of 7.0-7.5 to obtain an associative polyurethane thickener.

[0096] Comparative Example 7

[0097] The only difference between the weather-resistant water-based wall painting coating of this comparative example and the weather-resistant water-based wall painting coating of Example 1 is that the associative polyurethane thickener in the weather-resistant water-based wall painting coating of this comparative example is prepared by the following method: 0.11 mol of isophorone diisocyanate and 0.1 g of dibutyltin dilaurate catalyst are added to a four-necked flask equipped with a stirrer, thermometer and nitrogen delivery tube, and the temperature is raised to 55°C. Then, 0.01 mol of polyethylene glycol PEG-6000 that has been vacuum dehydrated at 110°C and 0.01 mol of trimethylolpropane are added. The mixture was added to a four-necked flask and stirred at 70°C for 2 hours. The reaction mixture was then cooled to 55°C, and 0.06 mol of dimethylolpropionic acid and 25 g of butanone were added to adjust the viscosity. The mixture was then heated to 70°C and stirred for 2.5 hours. The mixture was then cooled to 50°C, and 0.05 mol of n-dodecyl alcohol were added. The mixture was stirred at 60°C for 1.5 hours. Butanone was removed by vacuum distillation, and deionized water was added to adjust the solid content to 25%. The mixture was then neutralized with triethylamine to a pH of 7.0-7.5 to obtain an associative polyurethane thickener.

[0098] Experimental Example

[0099] To examine the comprehensive performance of the weather-resistant water-based wall painting coatings in the various embodiments and comparative examples, the thixotropic index, adhesion, water resistance, solvent resistance, scrub resistance, abrasion resistance, stain resistance, and weather resistance of the weather-resistant water-based wall painting coatings were tested. Among them, the test method for the thixotropic index is as follows: the apparent viscosity η6 of the weather-resistant water-based wall painting coating at 6 rpm and the apparent viscosity η60 at 60 rpm were measured using a rotational viscometer, and then the thixotropic index TI value was calculated as η6 / η60. The higher the TI value, the stronger the thixotropy, and the more conducive it is to three-dimensional modeling. Adhesion was tested according to the method specified in standard GB / T 9286-2021. The specific test method is as follows: The weather-resistant water-based wall painting paint was brushed onto the test panel and then allowed to cure and dry at room temperature for 7 days. Five parallel cuts were then made along the long side of the test panel, both parallel and perpendicular, penetrating the coating. Each cut was spaced 1 mm apart. A tear test was then performed using adhesive tape. Based on the degree of coating damage after tearing, the adhesion of the paint was rated according to the provisions of standard GB / T 9286-2021. The test panel material was cement. Each sample was tested three times, and the average of the three test results was taken as the final result. Water resistance and solvent resistance were tested according to the methods specified in standard GB / T 9274-1988 "Determination of Resistance to Liquid Media for Paints and Varnishes". The specific test method is as follows: The weather-resistant water-based wall painting coating was brushed onto a tinplate and allowed to cure and dry at room temperature for 7 days. The edges and back of the tinplate were then sealed with paraffin wax. The tinplate was then immersed in water or the test solvent, sealed, and the time it took for the coating surface to change color, blister, peel, chalk, or soften was observed and recorded. The test solvents were saturated calcium hydroxide solution, 10% acetic acid solution, or ethanol. Each sample was tested three times, and the average of the three test results was taken as the final result. Scrub resistance was determined according to the methods in standard GB / T 9266-2009, measuring the number of scrub cycles the weather-resistant water-based wall painting coating could withstand. Abrasion resistance was tested using an abrasion tester with a rubber grinding wheel under a load of 500g and a rotation speed of 500r. The weight loss of the coating during the test was used to evaluate abrasion resistance. Each sample was tested three times, and the average of the three results was taken as the final result. Stain resistance was tested according to the method in standard GB / T 9780-2013 "Test Method for Stain Resistance of Architectural Coatings". The test result was expressed as the rate of decrease in reflectance; the lower the value, the better the stain resistance. Weather resistance was tested according to the method specified in standard GB / T1865-2009. The specific test method was as follows: the weather-resistant water-based wall painting coating was brushed onto a glass plate, then allowed to cure and dry at room temperature for 7 days. The coated side of the glass plate was then placed in an artificial aging test chamber for weather resistance testing. The absolute value ΔC of the color difference between the coating before aging and after 3000 hours of aging was calculated. Each sample was tested three times, and the average of the three results was taken as the final result.The test results of thixotropic index, adhesion, water resistance, solvent resistance, scrub resistance, abrasion resistance, stain resistance and weather resistance of the weather-resistant water-based wall painting coating are shown in Table 1.

[0100] Table 1. Thixotropic index, adhesion, and other properties of water-based weather-resistant wall painting coatings.

[0101] Water resistance, solvent resistance, washability, abrasion resistance, stain resistance, and weather resistance

[0102]

[0103] A comparison of the data from Example 1 with those from Comparative Examples 1 and 2 shows that the coatings using the self-crosslinking acrylic emulsion prepared in this invention exhibit significantly improved water resistance, washability, and weather resistance.

[0104] In Comparative Example 1, N-(trimethylol)methacrylamide citrate was not added, and in Comparative Example 2, N-(trimethylol)methacrylamide citrate was replaced with N-hydroxymethylacrylamide (NMA). Neither method provided a branched structure and a rigid framework, resulting in a low degree of polymer branching, poor film density, and consequently, lower resistance to media penetration and mechanical strength. This result indicates that the N-(trimethylol)methacrylamide citrate monomer synthesized in this invention plays a crucial role in the polymer emulsion. This monomer not only contains polymerizable carbon-carbon double bonds but also multiple hydroxyl groups and a citrate backbone. During film formation, these functional groups promote the formation of a denser and more stable three-dimensional network structure between polymer molecular chains through physical crosslinking, increased branching, and hydrogen bonding, thereby improving the overall performance of the coating, especially its resistance to water, chemical media, and durability.

[0105] Comparing Examples 1 with Examples 4 and 5, and Comparative Examples 3-7, it can be seen that the structure of the thickener also has a certain impact on the coating performance. Examples 4 and 5 used polyurethane thickeners containing a tri(hydroxymethyl)phosphine oxide structure. Compared with Example 1 (using commercially available thickener RHEOLATE 299) and Comparative Example 7 (using trimethylolpropane chain extender), their thixotropic index and solvent resistance (especially ethanol resistance) were further enhanced. This indicates that the introduction of the phosphorus-containing structure may enhance the hydrophobic association strength between the thickener and emulsion particles and the affinity with pigments and fillers, making the three-dimensional network structure more stable. Comparative Example 3 (n-octanol-terminated) and Comparative Example 4 (n-hexadecylol-terminated) show that hydrophobic segments that are too short or too long are not conducive to establishing an optimal rheological network. If n-octanol is too weakly hydrophobic, the association effect is insufficient; if n-hexadecylol is too strongly hydrophobic, it may lead to a decrease in the solubility of the thickener in the aqueous phase or excessive association, affecting the smoothness and water resistance of the coating film. Comparative Example 5 (1,6-hexanediol chain extension) employed difunctional linear chain extension, which failed to form a three-dimensional network, resulting in a significant decrease in thixotropic index and anti-sagging properties. Comparative Example 6 (pentaerythritol chain extension), although tetrafunctional, had a rigid pentaerythritol core that may have restricted the movement of polyurethane segments, hindering the formation of a dynamically reversible hydrophobic associative structure; therefore, its overall performance was also inferior to Examples 4 and 5. Therefore, the synergistic effect of tris(hydroxymethyl)phosphine oxide and medium- to long-chain alcohols is key to obtaining good thixotropy, leveling, and durability.

[0106] In summary, the present invention synthesizes a monomer with a specific structure, N-(tris(hydroxymethyl)methacrylamide)citrate, and preferably a matching phosphorus-containing associative polyurethane thickener, to prepare a weather-resistant water-based wall painting coating that simultaneously possesses good thixotropic workability, coating density, chemical resistance, and long-term outdoor weather resistance.

Claims

1. A weather-resistant wall-painting water-borne paint, characterized by, The product is composed of the following components in parts by weight: 40-50 parts of acrylate polymer emulsion; 15-25 parts of water-based pigment paste; 1.5-2.5 parts of nano-silica; 0.3-0.6 parts of associative polyurethane thickener; 0.5-1.0 parts of wood fiber; 0.5-1.0 parts of wetting and dispersing agent; 0.1-0.3 parts of defoamer; 2.0-3.0 parts of film-forming aid; and 20-30 parts of water. The acrylate polymer emulsion is prepared by emulsion polymerization of styrene, butyl acrylate, methyl methacrylate, acrylic acid, and N-(trimethylolpropionic acid)methacrylamide citrate in a mass ratio of 25-35:30-40:10-15:1-3:3-8. The chemical structure of the N-(trimethylolpropionic acid)methacrylamide citrate is as follows: 。 2. The weather-resistant water-based wall painting coating as described in claim 1, characterized in that, The preparation method of the acrylate polymer emulsion includes the following steps: (1) Styrene, butyl acrylate, methyl methacrylate, acrylic acid and N-(tris(hydroxymethyl)methacrylamide)citrate were prepared into a monomer preemulsion; (2) Then, heat and mix a portion of the monomer pre-emulsion and the initiator to obtain a seed emulsion; (3) Add the remaining monomer pre-emulsion and initiator to the seed emulsion for mixing and reaction to obtain acrylate polymer emulsion.

3. The weather-resistant water-based wall painting coating as described in claim 2, characterized in that, In step (1), the method for preparing a monomer preemulsion from styrene, butyl acrylate, methyl methacrylate, acrylic acid, and N-(tris(hydroxymethyl)methacrylamide)citrate is as follows: Styrene, butyl acrylate, methyl methacrylate, acrylic acid, and N-(tris(hydroxymethyl)methacrylamide)citrate are added to a mixture composed of alkyl sulfate, nonylphenol polyoxyethylene ether, alkali metal bicarbonate, and water, and mixed evenly to obtain a monomer preemulsion; The mass ratio of styrene, butyl acrylate, methyl methacrylate, acrylic acid and N-(trimethylolmethyl)methacrylamide citrate, alkyl sulfate, nonylphenol polyoxyethylene ether, alkali metal bicarbonate and water is 25~35:30~40:10~15:1~3:3~8:0.5~1:0.5~1:0.2~0.5:15~20; In step (2), the monomer pre-emulsion accounts for 10-15% of the total mass of the monomer pre-emulsion; the initiator is persulfate, and the temperature for heating and mixing the monomer pre-emulsion and the initiator is 80-85℃, and the time is 30-45min. In step (3), the remaining monomer pre-emulsion and initiator are added to the seed emulsion for mixing and reaction at a temperature of 88~90℃ for 1~2h.

4. The weather-resistant water-based wall painting coating as described in claim 3, characterized in that, The alkyl sulfate is sodium dodecyl sulfate; the alkali metal bicarbonate is sodium bicarbonate; the persulfate is ammonium persulfate; in step (2), the mass ratio of the monomer preemulsion to the initiator is 30~60:1; in step (3), the mass ratio of the remaining monomer preemulsion, initiator and seed emulsion is 80~95:0.3~0.5:15~30.

5. The weather-resistant water-based wall painting coating as described in claim 1, characterized in that, The preparation method of the associative polyurethane thickener includes the following steps: under the action of a catalyst, isophorone diisocyanate, polyethylene glycol PEG-6000 and tris(hydroxymethyl)phosphine oxide are mixed and reacted, then dimethylolpropionic acid is added for chain extension reaction, and finally a monohydric alcohol compound is added for end capping. After neutralization and dispersion with water, the product is obtained. The monohydric alcohol compound is n-dodecyl alcohol, n-tridecyl alcohol or n-tetradecyl alcohol. The molar ratio of isophorone diisocyanate, polyethylene glycol PEG-6000, tris(hydroxymethyl)phosphine oxide, dimethylolpropionic acid and monohydric alcohol compound is 0.11~0.12:0.01~0.015:0.01~0.015:0.06~0.07:0.05~0.

06.

6. The weather-resistant water-based wall painting coating as described in claim 1, characterized in that, The average length of the wood fibers is 180~220μm, and the average diameter is 10~20μm.

7. The weather-resistant water-based wall painting coating as described in claim 1, characterized in that, The wood fiber is obtained from bleached wood pulp with an α-cellulose content of ≥90% and a kappa number of ≤1.0 through dissociation, drying, and screening.

8. The weather-resistant water-based wall painting coating as described in claim 1, characterized in that, The water-based pigment paste is an iron oxide red paste.

9. The weather-resistant water-based wall painting coating as described in claim 1, characterized in that, The wetting and dispersing agent is BYK-190 wetting and dispersing agent, the defoamer is BYK-024 type defoamer, and the film-forming aid is dodecyl alcohol ester.

10. A method for preparing a weather-resistant water-based wall painting coating as described in any one of claims 1-9, characterized in that, The process includes the following steps: mixing the formulated amounts of acrylate polymer emulsion, water-based pigment paste, nano silica, associative polyurethane thickener, wood fiber, wetting and dispersing agent, defoamer, film-forming aid, and water to obtain the final product.

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