One-component polyurethane paint and process for its preparation

Abstract

The present application relates to the technical field of paint, in particular to a single-component polyurethane paint and a preparation method thereof, the single-component polyurethane paint exhibits significant advantages in performance and construction, in performance, through unique formula design, the dispersibility of pigments in paint liquid is greatly improved, the internal structure of paint film is more uniform, the adhesion of paint film and substrate is significantly enhanced, even in the micro-rust surface and high-temperature environment, stable adhesion can be maintained, with the reasonable increase of the amount of modified polyacrylate oligomer and the optimization of the overall formula process, the hardness of the paint film is steadily improved, which can effectively resist various external force impact, and can effectively resist salt spray corrosion, in construction, the single-component design avoids the complex proportioning and stirring link of multi-component paint, greatly reduces the construction difficulty, and is beneficial to large-scale rapid construction application.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of paint technology, in particular to a single-component polyurethane paint and a preparation method thereof. BACKGROUND

[0002] In today's industry and construction fields, metal and cement are widely used as key basic materials. However, they are exposed to natural environment or complex industrial working conditions for a long time, facing many severe corrosion challenges, which makes the importance of protective coating more prominent. Traditional anti-rust coatings have exposed many drawbacks in practical application, which seriously restricts their protective performance.

[0003] On the one hand, from the perspective of adhesion, traditional anti-rust coatings are difficult to form stable adhesion on the micro-rust surface, because the micro-rust layer has a loose and porous structure, and conventional coatings cannot effectively penetrate and tightly combine with it, resulting in low adhesion and easy peeling of the coating. In high temperature environment, such as the periphery of some industrial furnaces, the outer wall of high temperature pipelines and other scenes, the difference between the thermal expansion coefficients of the coating and the substrate material will increase as the temperature rises, thereby weakening the bonding force between the coating and the substrate, making it difficult to meet the requirements of high temperature adhesion, and the risk of coating peeling increases dramatically. Salt fog resistance is also a key indicator to measure the quality of a coating. In marine environments, coastal industrial facilities, and road facilities with salt deicing in winter, salt fog will erode the coating and destroy its internal structure, resulting in a significant decrease in the adhesion of traditional coatings before and after salt fog resistance, which cannot effectively protect the substrate material, and frequent coating repair and repainting become inevitable, greatly increasing the cost and workload.

[0004] On the other hand, the strength bottleneck of traditional anti-rust coatings is significant. Under normal circumstances, it can only withstand an external force of 4-6 MPa (600-800 psi pressure), and once it encounters slightly higher pressure in actual use, such as mechanical impact, material impact or internal stress caused by temperature changes, the coating will quickly bubble and rupture. This rupture is like a "gap" in the protective system, allowing air to enter without hindrance, and oxygen, water vapor and various corrosive media will attack the metal or cement substrate, accelerating the corrosion process and greatly reducing the service life of the material. In order to maintain the protective effect, repeated painting is required, resulting in multiple waste of manpower, material resources and time.

[0005] In addition, the complexity of the traditional coating construction process is even more serious. The multi-component coating requires accurate and strict proportioning of each component during use, and any deviation may affect the final performance of the coating. The mixing process needs to be strictly controlled to ensure uniform mixing of each component, otherwise local performance unevenness may occur. Moreover, the construction period is often restricted by environmental factors such as temperature and humidity, and it is difficult to ensure the quality if the appropriate construction window period is missed. The coating matching mode is also complex and complicated, and the primer, intermediate coating and topcoat need to be applied respectively. The drying time of each layer of coating is different, and the connection requirement is high, which further increases the construction difficulty and cycle, and is not conducive to large-scale and rapid application.

[0006] Therefore, according to the related technology in the above, it is urgent to develop a single-component polyurethane paint and a preparation method thereof. SUMMARY

[0007] Therefore, the purpose of the present application is to provide a single-component polyurethane paint and a preparation method thereof, which has excellent performance and is convenient to operate.

[0008] Based on the above purpose, the present application provides a single-component polyurethane paint and a preparation method thereof.

[0009] A single-component polyurethane paint comprises the following raw materials by mass: polyurethane resin 30-50 parts, curing agent 10-20 parts, anti-rust pigment 5-15 parts, filler pigment 8-18 parts, auxiliary agent 1.3-4.5 parts, and solvent 10-30 parts.

[0010] The polyurethane resin is a hydroxyl-terminated polyurethane resin, which has excellent weather resistance and mechanical properties, and can provide good basic performance for the paint film. The hydroxyl-terminated polyurethane resin is Desmophen 670U-70, which is purchased from Bayer Company.

[0011] The curing agent is an aliphatic isocyanate curing agent, which can react with the hydroxyl groups in the polyurethane resin, crosslink and cure at room temperature, form a tough paint film, and has good yellowing resistance, suitable for outdoor use. The aliphatic isocyanate curing agent is hexamethylene diisocyanate trimer.

[0012] The anti-rust pigment is zinc phosphate, which can react with the metal surface in the paint film to form a dense passivation film, effectively preventing metal corrosion, and has good chemical stability and hiding power.

[0013] The filler is titanium white and talc powder mixed in a mass ratio of 5-10:3-8, titanium white can provide white hiding power and good weather resistance, and R-706 rutile titanium white of DuPont Company is selected, which has strong hiding power, high whiteness, and can significantly improve the appearance and weather resistance of paint film; talc powder can increase the thickness and hardness of paint film, and improve the wear resistance, talc powder has a flaky structure, and can form a good shielding layer in the paint film to prevent the invasion of moisture and corrosive medium;

[0014] The auxiliary agent is a dispersant, a leveling agent and a defoaming agent mixed in a mass ratio of 0.5-2:0.5-1.5:0.3-1;

[0015] The dispersant is BYK-110 and modified polyacrylate oligomer mixed in a mass ratio of 0.3-1.2:0.2-0.8;

[0016] The preparation process of the modified polyacrylate oligomer is as follows:

[0017] Step A1. In a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a dropping funnel, toluene and methyl methacrylate are added, and azobisisobutyronitrile and dodecanethiol are added;

[0018] Step A2. Under a nitrogen atmosphere, the temperature is raised to 70-80℃, and stirring is started at a speed of 120-150 r / min for 3-4 h. After the reaction is completed, the reaction liquid is cooled to room temperature, and the solvent is removed by a rotary evaporator to obtain a polyacrylate oligomer;

[0019] Step A3. Emulsification: The ethyl acetate solution of the polyacrylate oligomer is slowly added to the gelatin solution, and emulsified at 1000-1500 r / min for 15-20 min to form a water-in-oil emulsion. At this time, the polyacrylate oligomer is dispersed in the gelatin solution in the form of small droplets.

[0020] Step A4. Re-coagulation: Under stirring, the gum arabic solution is added dropwise to the above emulsion, and stirring is continued for 10-15 min to fully mix the gelatin and gum arabic. Then, the pH value of the system is adjusted to 4.0-4.5 with 1 mol / L hydrochloric acid solution, at which time the gelatin and gum arabic will undergo a re-coagulation reaction to form a layer of coagulation phase on the surface of the polyacrylate oligomer droplets.

[0021] Step A5. Solidification: The temperature of the system is reduced to 5-10℃, and the aqueous glutaraldehyde solution is added, and stirring is carried out for 30-60 min to solidify the coagulation phase to form a stable microcapsule wall. Glutaraldehyde reacts with the amino groups in the gelatin and gum arabic to cross-link, thereby enhancing the strength of the wall material.

[0022] Step A6. Separation and washing: After the reaction is completed, centrifugal at 3000-5000 r / min for 10-15 min, and then repeatedly washed with deionized water for 3-5 times to remove unreacted reagents and impurities.

[0023] Step A7. Drying: The washed microcapsules are dried in a vacuum drying oven at 40-50℃ until constant weight to obtain the microencapsulated polyacrylate oligomer, i.e. the modified polyacrylate oligomer.

[0024] Preferably, the amount of methyl methacrylate, azobisisobutyronitrile, toluene and dodecanethiol in step A1 is 10-12 g: 0.05-0.08 g: 200-220 mL: 0.01-0.03 g.

[0025] Preferably, the mass fraction of the ethyl acetate solution of the polyacrylate oligomer in step A3 is 10%-20%;

[0026] Preferably, the mass ratio of the ethyl acetate solution of the polyacrylate oligomer and the gelatin solution is 100:80-100;

[0027] Preferably, the mass ratio of the gum arabic solution, the gelatin solution and the aqueous glutaraldehyde solution is 40-50:80-100:6-7.5;

[0028] Preferably, the gelatin solution in step A3 is a gelatin aqueous solution with a mass fraction of 2%-5%;

[0029] Preferably, the gum arabic solution in step A4 is a gum arabic aqueous solution with a mass fraction of 2%-5%;

[0030] Preferably, the concentration of the aqueous glutaraldehyde solution in step A5 is 1%-2%;

[0031] The leveling agent is Deqin 435, which can improve the leveling property of the paint film, make the paint film surface smooth and flat, and reduce defects such as orange peel and shrinkage;

[0032] The defoaming agent is a mineral oil-based defoaming agent, which is EFKA-2020, which can effectively eliminate the bubbles generated during stirring and construction of the paint, and avoid the bubbles remaining in the paint film to affect the performance;

[0033] The solvent is a mixture of xylene and butyl acetate with a mass ratio of 15-18:10-12, wherein xylene has good solubility and can dissolve resin and most pigments, and butyl acetate can adjust the evaporation speed of the solvent, so that the paint film dries uniformly and avoids sagging and whitening;

[0034] A preparation method of a one-component polyurethane paint, comprising the following steps:

[0035] Step S1. Pre-mixing stage: In a reaction kettle with stirring device, polyurethane resin is added, followed by curing agent, stirring at a speed of 480-520 r / min for 14-16 min, so that the two are preliminarily mixed, at this time the temperature is maintained at 24-26 DEG C, to obtain a mixture 1;

[0036] Step S2. Pigment dispersion stage: Anti-rust pigment, color filler are added to the mixture 1, the stirring speed is increased to 800-1000 r / min, and the pigment is fully dispersed for 28-30 min, and the temperature is controlled at 30-35 DEG C, to obtain a mixture 2;

[0037] Step S3. Additive addition stage: Additives are added to the mixture 2, continue to stir at a speed of 780-820 r / min for 14-16 min, ensure that the additives are uniformly dispersed in the paint, the temperature is maintained at 28-32 DEG C, to obtain a mixture 3;

[0038] Step S4. Solvent mixing stage: Add solvent to the mixture 3, stir at a speed of 580-600 r / min for 20-22 min, so that the solvent is fully mixed with other ingredients, and the temperature is maintained at 25-30 DEG C, to obtain a mixture 4;

[0039] Step S5. The mixture 4 is filtered through a 100 mesh filter, and the filtered paint is packed in a sealed container for packaging, and the preparation process is completed.

[0040] The beneficial effects of the application are:

[0041] The application provides a single-component polyurethane paint and a preparation method thereof. The single-component polyurethane paint of the application has significant advantages in performance and construction. In terms of performance, by unique formula design, the modified polyacrylate oligomer is compounded with BYK-110 as a dispersant, which greatly improves the dispersibility of the pigment in the paint, makes the internal structure of the paint film more uniform, and significantly enhances the adhesion of the paint film to the substrate. Even in the presence of micro-rust and high temperature environment, it can also maintain stable adhesion. With the reasonable increase of the amount of modified polyacrylate oligomer and the optimization of the overall formula process, the hardness of the paint film is steadily improved from 3H to 5H, which can effectively resist various external force impact. The anti-rust pigment zinc phosphate and other ingredients synergistically form a dense shielding layer, which can effectively resist salt spray corrosion. At the same time, the wear resistance of the paint film is also continuously enhanced, and with the synergistic optimization of various components and processes, the wear loss gradually decreases, greatly prolonging the service life;

[0042] In the construction aspect, the single-component design avoids the complicated proportioning and stirring links of the multi-component coating, greatly reduces the construction difficulty. Moreover, the temperature, stirring speed and other conditions in each stage of the whole preparation process are relatively wide, are less affected by the environmental factors such as temperature and humidity, have a long construction window period, and are beneficial to large-scale rapid construction application. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below with specific examples.

[0044] The sources and properties of part of the raw materials used in the present application are as follows:

[0045] The hydroxyl-terminated polyurethane resin is Desmophen 670U-70, which is purchased from Bayer Company;

[0046] The titanium white is R-706 rutile titanium white of DuPont Company;

[0047] The mineral oil antifoaming agent is EFKA-2020.

[0048] Example 1: A preparation method of a single-component polyurethane paint, comprising the following steps:

[0049] S1. In a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a dropping funnel, 200 mL of toluene and 10 g of methyl methacrylate are added, and 0.05 g of azobisisobutyronitrile and 0.01 g of dodecanethiol are added;

[0050] S2. Under the nitrogen atmosphere, the temperature is raised to 70 DEG C, the stirring is started, and the stirring is carried out at a speed of 120 r / min for 3 h. After the reaction is completed, the reaction liquid is cooled to room temperature, and the solvent is removed by using a rotary evaporator to obtain a polyacrylate oligomer;

[0051] S3. Emulsification: 100 g of an ethyl acetate solution of the polyacrylate oligomer with a mass fraction of 10% is slowly added to 80 g of a gelatin aqueous solution with a mass fraction of 2%, and emulsification is carried out at 1000 r / min for 15 min to form a water-in-oil emulsion. At this time, the polyacrylate oligomer is dispersed in the gelatin solution in the form of small droplets;

[0052] S4. Complex coacervation: Under the stirring state, 40 g of an acacia aqueous solution with a mass fraction of 2% is added dropwise to the above emulsion, and the stirring is continued for 10 min to make the gelatin and acacia fully mixed, and then the pH value of the system is adjusted to 4.0 by using a 1 mol / L hydrochloric acid solution. At this time, the complex coacervation reaction of the gelatin and acacia occurs, and a layer of coacervate is formed on the surface of the polyacrylate oligomer droplets;

[0053] S5. Solidification: the temperature of the system is reduced to 5°C, 6g of glutaraldehyde aqueous solution with a concentration of 1% is added, and the condensed phase is solidified to form a stable microcapsule wall by stirring for 30min. Glutaraldehyde reacts with the amino groups in gelatin and gum arabic to cross-link, thereby enhancing the strength of the wall material;

[0054] S6. Separation and washing: after the reaction is completed, centrifugation is performed at a speed of 3000r / min for 10min, and then repeated washing is performed with deionized water for 3 times to remove unreacted reagents and impurities;

[0055] S7. Drying: the washed microcapsules are dried in a vacuum drying oven at 40°C to constant weight to obtain the microencapsulated polyacrylate oligomer, i.e., the modified polyacrylate oligomer;

[0056] S8. Mixing 3g of BYK-110 and 2g of the modified polyacrylate oligomer to obtain a dispersant;

[0057] S9. Mixing 0.5g of the dispersant, 0.5g of Decon 435, and 0.3g of EFKA-2020 to obtain an auxiliary agent;

[0058] S10. Mixing 5g of R-706 rutile titanium dioxide and 3g of talc to obtain a pigment filler;

[0059] S11. Mixing 15g of dimethylbenzene and 10g of butyl acetate to obtain a solvent;

[0060] S12. Pre-mixing stage: in a reaction kettle with a stirring device, 30g of Desmophen 670U-70 polyurethane resin is added, followed by 10g of hexamethylene diisocyanate trimer, and stirring is performed at a speed of 480r / min for 14min to preliminarily mix the two, and at this time the temperature is maintained at 24°C to obtain a mixture 1;

[0061] S13. Pigment dispersion stage: 5g of zinc phosphate and 8g of the pigment filler are added to the mixture 1, the stirring speed is increased to 800r / min, and stirring is performed for 28min to fully disperse the pigments, and at this time the temperature is controlled at 30°C to obtain a mixture 2;

[0062] S14. Auxiliary agent addition stage: 1.3g of the auxiliary agent is added to the mixture 2, and stirring is continued at a speed of 780r / min for 14min to ensure that the auxiliary agent is uniformly dispersed in the paint, and the temperature is maintained at 28°C to obtain a mixture 3;

[0063] S15. Solvent mixing stage: 10g of the solvent is added to the mixture 3, and stirring is performed at a speed of 580r / min for 20min to fully mix and uniformly disperse the solvent with other ingredients, and the temperature is maintained at 25°C to obtain a mixture 4;

[0064] S16. The mixture 4 is filtered through a 100 mesh filter, and the filtered paint is filled into a sealed container for packaging, thus completing the preparation process to obtain a single-component polyurethane paint.

[0065] Example 2: A method for preparing a single-component polyurethane paint, comprising the following steps:

[0066] S1. In a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a dropping funnel, 205 mL of toluene and 10.5 g of methyl methacrylate are added, and 0.06 g of azobisisobutyronitrile and 0.015 g of dodecanethiol are added;

[0067] S2. The temperature is raised to 73°C under a nitrogen atmosphere, and stirring is started at a speed of 125 r / min for 3.5 h. After the reaction is completed, the reaction solution is cooled to room temperature, and the solvent is removed by a rotary evaporator to obtain a polyacrylate oligomer;

[0068] S3. Emulsification: 100 g of an ethyl acetate solution of the polyacrylate oligomer with a mass fraction of 13% is slowly added to 85 g of an aqueous gelatin solution with a mass fraction of 3%, and emulsification is carried out at 1100 r / min for 17 min to form a water-in-oil emulsion. At this time, the polyacrylate oligomer is dispersed in the gelatin solution in the form of small droplets;

[0069] S4. Re-coacervation: 43 g of an aqueous gum arabic solution with a mass fraction of 3% is added dropwise to the above emulsion under stirring, and stirring is continued for 12 min to allow the gelatin and gum arabic to be fully mixed. Then, the pH value of the system is adjusted to 4.2 by using a 1 mol / L hydrochloric acid solution. At this time, the gelatin and gum arabic will undergo a re-coacervation reaction to form a layer of coacervate on the surface of the polyacrylate oligomer droplets;

[0070] S5. Solidification: the temperature of the system is lowered to 7°C, and 6.5 g of a glutaraldehyde aqueous solution with a concentration of 1.2% is added. After stirring for 40 min, the coacervate is solidified to form a stable microcapsule wall. The glutaraldehyde reacts with the amino groups in the gelatin and gum arabic to cross-link, thereby enhancing the strength of the wall material;

[0071] S6. Separation and washing: after the reaction is completed, centrifugation is carried out at a speed of 3500 r / min for 12 min, and the microcapsules are washed repeatedly with deionized water for 4 times to remove unreacted reagents and impurities;

[0072] S7. Drying: the washed microcapsules are dried in a vacuum drying oven at 43°C to a constant weight to obtain a microencapsulated polyacrylate oligomer, i.e., a modified polyacrylate oligomer;

[0073] S8. 6 g of BYK-110 and 4 g of the modified polyacrylate oligomer are mixed to obtain a dispersant;

[0074] S9. Mix 1 g dispersant, 0.8 g Dequest 435 and 0.5 g EFKA-2020 to obtain an auxiliary agent;

[0075] S10. Mix 7 g R-706 rutile titanium dioxide and 4 g talcum powder to obtain a pigment filler;

[0076] S11. Mix 16 g xylene and 10.5 g butyl acetate to obtain a solvent;

[0077] S12. Pre-mixing stage: in a reaction kettle with stirring device, 35 g Desmophen 670U-70 polyurethane resin is added, then 13 g hexamethylene diisocyanate trimer is added, stirring at a speed of 490 r / min for 15 min, so that the two are preliminarily mixed, at this time the temperature is maintained at 25℃, to obtain mixture 1;

[0078] S13. Pigment dispersion stage: 8 g zinc phosphate, 10 g pigment filler are added to mixture 1, the stirring speed is increased to 850 r / min, and stirring is performed for 29 min to make the pigments fully dispersed, at this time the temperature is controlled at 32℃, to obtain mixture 2;

[0079] S14. Auxiliary agent adding stage: 2.5 g auxiliary agent is added to mixture 2, and stirring is continued at a speed of 790 r / min for 15 min to ensure that the auxiliary agent is uniformly dispersed in the paint liquid, and the temperature is maintained at 29℃, to obtain mixture 3;

[0080] S15. Solvent mixing stage: 15 g solvent is added to mixture 3, and stirring is performed at a speed of 585 r / min for 21 min to make the solvent fully mixed and uniform with other ingredients, and the temperature is maintained at 27℃, to obtain mixture 4;

[0081] S16. Mixture 4 is filtered through a 100 mesh filter screen, and the filtered paint liquid is packed into a sealed container for packaging, and the preparation process is completed, to obtain a single-component polyurethane paint.

[0082] Example 3: A method for preparing a single-component polyurethane paint, comprising the following steps:

[0083] S1. In a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a dropping funnel, 210 mL of toluene and 11 g of methyl methacrylate are added, and 0.07 g of azobisisobutyronitrile and 0.02 g of dodecanethiol are added;

[0084] S2. Under nitrogen atmosphere, the temperature is raised to 75℃, and stirring is started at a speed of 130 r / min for 3 h, after the reaction is completed, the reaction liquid is cooled to room temperature, and the solvent is removed by a rotary evaporator, to obtain a polyacrylate oligomer;

[0085] S3. Emulsification: 100 g of ethyl acetate solution of polyacrylate oligomer with a mass fraction of 15% is slowly added to 90 g of gelatin aqueous solution with a mass fraction of 4%, and emulsified at 1200 r / min for 18 min to form a water-in-oil emulsion. At this time, the polyacrylate oligomer is dispersed in the gelatin solution in the form of small droplets;

[0086] S4. Complex coacervation: 46 g of gum arabic aqueous solution with a mass fraction of 4% is added dropwise to the above emulsion under stirring, and stirring is continued for 13 min to fully mix the gelatin and gum arabic. Then, the pH value of the system is adjusted to 4.3 by using 1 mol / L hydrochloric acid solution. At this time, the gelatin and gum arabic will undergo a complex coacervation reaction to form a layer of coacervate on the surface of the polyacrylate oligomer droplets;

[0087] S5. Solidification: the temperature of the system is reduced to 8°C, 7.0 g of glutaraldehyde aqueous solution with a concentration of 1.5% is added, and stirring is continued for 50 min to solidify the coacervate to form a stable microcapsule wall. Glutaraldehyde reacts with the amino groups in the gelatin and gum arabic to cross-link, thereby enhancing the strength of the wall material;

[0088] S6. Separation and washing: after the reaction is completed, centrifugation is performed at a speed of 4000 r / min for 13 min, and then repeated washing is performed with deionized water for 3 times to remove unreacted reagents and impurities;

[0089] S7. Drying: the washed microcapsules are dried in a vacuum drying oven at 46°C to a constant weight to obtain microencapsulated polyacrylate oligomer, i.e., modified polyacrylate oligomer;

[0090] S8. Mixing 9 g of BYK-110 and 6 g of modified polyacrylate oligomer to obtain a dispersant;

[0091] S9. Mixing 1.5 g of dispersant, 1.0 g of Decon 435, and 0.7 g of EFKA-2020 to obtain an additive;

[0092] S10. Mixing 8 g of R-706 rutile titanium dioxide and 5 g of talc to obtain a filler pigment;

[0093] S11. Mixing 17 g of xylene and 11 g of butyl acetate to obtain a solvent;

[0094] S12. Pre-mixing stage: in a reaction kettle with a stirring device, 40 g of Desmophen 670U-70 polyurethane resin is added, followed by 16 g of hexamethylene diisocyanate trimer, and stirring is performed at a speed of 500 r / min for 16 min to preliminarily mix the two, and the temperature is maintained at 24°C to obtain a mixture 1;

[0095] S13. Pigment dispersion stage: 10 g of zinc phosphate and 12 g of pigment filler are added to the mixture 1, the stirring speed is increased to 900 r / min, and stirring is performed for 28 min to fully disperse the pigments, during which the temperature is controlled at 34°C, to obtain mixture 2;

[0096] S14. Additive addition stage: 3.1 g of additives are added to the mixture 2, and stirring is continued at a speed of 800 r / min for 16 min to ensure that the additives are uniformly dispersed in the paint, and the temperature is maintained at 30°C, to obtain mixture 3;

[0097] S15. Solvent mixing stage: 20 g of solvent is added to the mixture 3, and stirring is performed at a speed of 590 r / min for 22 min to fully mix the solvent with other ingredients, and the temperature is maintained at 28°C, to obtain mixture 4;

[0098] S16. The mixture 4 is filtered through a 100-mesh filter, and the filtered paint is packed into a sealed container for packaging, and the preparation process is completed, to obtain a single-component polyurethane paint.

[0099] Example 4: A method for preparing a single-component polyurethane paint, comprising the following steps:

[0100] S1. In a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a dropping funnel, 215 mL of toluene and 11.5 g of methyl methacrylate are added, and 0.06 g of azobisisobutyronitrile and 0.025 g of dodecanethiol are added;

[0101] S2. Under a nitrogen atmosphere, the temperature is increased to 78°C, and stirring is started at a speed of 140 r / min for 3.5 h, and after the reaction is completed, the reaction liquid is cooled to room temperature, and the solvent is removed by a rotary evaporator, to obtain a polyacrylate oligomer;

[0102] S3. Emulsification: 100 g of an ethyl acetate solution of the polyacrylate oligomer with a mass fraction of 18% is slowly added to 95 g of a gelatin aqueous solution with a mass fraction of 3%, and emulsification is performed at 1300 r / min for 19 min to form a water-in-oil emulsion. At this time, the polyacrylate oligomer is dispersed in the gelatin solution in the form of small droplets;

[0103] S4. Re-coagulation: Under stirring, 48 g of an acacia aqueous solution with a mass fraction of 3% is added dropwise to the above emulsion, and stirring is continued for 14 min to fully mix the gelatin and acacia, and then the pH value of the system is adjusted to 4.4 by using a 1 mol / L hydrochloric acid solution, at which time the gelatin and acacia will undergo a re-coagulation reaction to form a layer of coagulated phase on the surface of the polyacrylate oligomer droplets;

[0104] S5. Solidification: the temperature of the system is reduced to 9°C, 6.8 g of glutaraldehyde aqueous solution with a concentration of 1.8% is added, and the coagulation phase is solidified to form a stable microcapsule wall by stirring for 45 min. Glutaraldehyde reacts with the amino groups in gelatin and gum arabic to cross-link, thereby enhancing the strength of the wall material;

[0105] S6. Separation and washing: after the reaction is completed, centrifugation is performed at a speed of 4500 r / min for 14 min, and then repeated washing is performed with deionized water for 4 times to remove unreacted reagents and impurities;

[0106] S7. Drying: the washed microcapsules are dried in a vacuum drying oven at 48°C to constant weight to obtain microencapsulated polyacrylate oligomers, i.e., modified polyacrylate oligomers;

[0107] S8. Mixing 10 g of BYK-110 and 7 g of modified polyacrylate oligomers to obtain a dispersant;

[0108] S9. Mixing 1.8 g of the dispersant, 1.2 g of Decon 435, and 0.9 g of EFKA-2020 to obtain an auxiliary agent;

[0109] S10. Mixing 9 g of R-706 rutile titanium dioxide and 6 g of talc to obtain a pigment filler;

[0110] S11. Mixing 17.5 g of xylene and 11.5 g of butyl acetate to obtain a solvent;

[0111] S12. Pre-mixing stage: in a reaction kettle with a stirring device, 45 g of Desmophen 670U-70 polyurethane resin is added, followed by 18 g of hexamethylene diisocyanate trimer, and stirring is performed at a speed of 510 r / min for 14 min to preliminarily mix the two, and the temperature is maintained at 25°C to obtain a mixture 1;

[0112] S13. Pigment dispersion stage: 12 g of zinc phosphate and 15 g of pigment filler are added to the mixture 1, the stirring speed is increased to 950 r / min, and stirring is performed for 29 min to fully disperse the pigments, and the temperature is controlled at 33°C to obtain a mixture 2;

[0113] S14. Auxiliary agent addition stage: 4.2 g of the auxiliary agent is added to the mixture 2, and stirring is continued at a speed of 810 r / min for 14 min to ensure that the auxiliary agent is uniformly dispersed in the paint, and the temperature is maintained at 31°C to obtain a mixture 3;

[0114] S15. Solvent mixing stage: 25 g of the solvent is added to the mixture 3, and stirring is performed at a speed of 595 r / min for 21 min to fully mix the solvent with other ingredients, and the temperature is maintained at 29°C to obtain a mixture 4;

[0115] S16. The mixed material 4 is filtered through a 100 mesh filter screen, and the filtered paint is filled into a sealed container for packaging, thus completing the preparation process to obtain a single-component polyurethane paint.

[0116] Example 5: A method for preparing a single-component polyurethane paint, comprising the following steps:

[0117] S1. In a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a dropping funnel, 220 mL of toluene and 12 g of methyl methacrylate are added, and 0.08 g of azobisisobutyronitrile and 0.03 g of dodecanethiol are added;

[0118] S2. The temperature is raised to 80°C under a nitrogen atmosphere, and stirring is started at a speed of 150 r / min for 4 h. After the reaction is completed, the reaction solution is cooled to room temperature, and the solvent is removed by a rotary evaporator to obtain a polyacrylate oligomer;

[0119] S3. Emulsification: 100 g of an ethyl acetate solution of the polyacrylate oligomer with a mass fraction of 20% is slowly added to 100 g of an aqueous gelatin solution with a mass fraction of 5%, and emulsification is carried out at 1500 r / min for 20 min to form a water-in-oil emulsion. At this time, the polyacrylate oligomer is dispersed in the gelatin solution in the form of small droplets;

[0120] S4. Re-coagulation: 50 g of an aqueous gum arabic solution with a mass fraction of 5% is added dropwise to the above emulsion under stirring, and stirring is continued for 15 min to fully mix the gelatin and gum arabic. Then, the pH value of the system is adjusted to 4.5 by using a 1 mol / L hydrochloric acid solution. At this time, the gelatin and gum arabic will undergo a re-coagulation reaction to form a layer of coagulated phase on the surface of the polyacrylate oligomer droplets;

[0121] S5. Solidification: The temperature of the system is lowered to 10°C, and 7.5 g of a 2% glutaraldehyde aqueous solution is added. After stirring for 60 min, the coagulated phase is solidified to form a stable microcapsule wall. Glutaraldehyde reacts with the amino groups in the gelatin and gum arabic to cross-link, thereby enhancing the strength of the wall material;

[0122] S6. Separation and washing: After the reaction is completed, centrifugation is carried out at a speed of 5000 r / min for 15 min, and the microcapsules are washed repeatedly with deionized water for 5 times to remove unreacted reagents and impurities;

[0123] S7. Drying: The washed microcapsules are dried in a vacuum drying oven at 50°C to a constant weight to obtain a microencapsulated polyacrylate oligomer, i.e., a modified polyacrylate oligomer;

[0124] S8. 12 g of BYK-110 and 8 g of the modified polyacrylate oligomer are mixed to obtain a dispersant;

[0125] S9. 2 g dispersant, 1.5 g Decon 435 and 1 g EFKA-2020 are mixed to obtain an auxiliary;

[0126] S10. 10 g R-706 rutile titanium dioxide and 8 g talcum powder are mixed to obtain a pigment filler;

[0127] S11. 18 g xylene and 12 g butyl acetate are mixed to obtain a solvent;

[0128] S12. Pre-mixing stage: in a reaction kettle with stirring device, 50 g Desmophen 670U-70 polyurethane resin is added, followed by 20 g hexamethylene diisocyanate trimer, and stirring is carried out at a rotation speed of 520 r / min for 16 min, so that the two are preliminarily mixed, at this time the temperature is maintained at 26℃, to obtain mixture 1;

[0129] S13. Pigment dispersion stage: 15 g zinc phosphate, 8-10-12-15-18 g pigment filler are added to mixture 1, the stirring speed is increased to 1000 r / min, and stirring is carried out for 30 min, so that the pigments are fully dispersed, at this time the temperature is controlled at 35℃, to obtain mixture 2;

[0130] S14. Auxiliary adding stage: 4.5 g auxiliary is added to mixture 2, and stirring is continued at a rotation speed of 820 r / min for 16 min, to ensure that the auxiliary is uniformly dispersed in the paint, and the temperature is maintained at 32℃, to obtain mixture 3;

[0131] S15. Solvent mixing stage: 30 g solvent is added to mixture 3, and stirring is carried out at a rotation speed of 600 r / min for 22 min, so that the solvent is fully mixed and uniformly mixed with other ingredients, and the temperature is maintained at 30℃, to obtain mixture 4;

[0132] S16. Mixture 4 is filtered through a 100 mesh filter screen, and the filtered paint is packed in a sealed container for packaging, and the preparation process is completed, to obtain a single-component polyurethane paint.

[0133] Comparative Example 1:

[0134] This comparative example does not add a modified polyacrylate oligomer in the preparation process of the single-component polyurethane paint compared with Example 1, and the remaining steps and parameters are the same, and this comparative example will not be repeated, and finally a single-component polyurethane paint is obtained.

[0135] Comparative Example 2:

[0136] This comparative example does not add an aliphatic isocyanate curing agent in the preparation process of the single-component polyurethane paint compared with Example 1, and the remaining steps and parameters are the same, and this comparative example will not be repeated, and finally a single-component polyurethane paint is obtained.

[0137] Comparative Example 3:

[0138] The comparative example is compared with example 1 only by replacing the "dispersant" with "modified polyacrylate oligomer", and the rest of the steps and parameters are the same. The comparative example will not be repeated here. Finally, a single-component polyurethane paint is obtained.

[0139] Comparative example 4:

[0140] The comparative example is compared with example 1 without modifying the polyacrylate oligomer with gum arabic and gelatin. The rest of the steps and parameters are the same. The comparative example will not be repeated here. Finally, a single-component polyurethane paint is obtained.

[0141] Comparative example 5:

[0142] The comparative example is compared with example 1 only by adjusting the amount of "modified polyacrylate oligomer" from "0.2g" to "1.2g". The rest of the steps and parameters are the same. The comparative example will not be repeated here. Finally, a single-component polyurethane paint is obtained.

[0143] Performance test:

[0144] Adhesion test: According to GB / T9286-1998 "Paint and varnish film test for scribing", use scribing method, use sharp knife to scribe on the surface of the paint film, then use adhesive tape to paste and quickly tear off, observe the paint film peeling, express the adhesion by scribing grade, 0 grade is the best, 5 grade is the worst.

[0145] Hardness test: According to GB / T6739-2006 "Paint and varnish pencil method for testing paint film hardness", use different hardness of pencil to make scratch test on the surface of the paint film, express the hardness of the paint film by the highest hardness pencil without scratch.

[0146] Salt spray resistance test: According to GB / T1771-2007 "Determination of the resistance of paint and varnish to neutral salt spray", put the sample with paint film into the salt spray test box, under the condition of temperature 35℃ and salt solution concentration 5%, continuously spray for a certain time, observe the phenomena of blistering, rusting, peeling, etc. of the paint film, and record the time when obvious damage occurs.

[0147] Abrasion resistance test: According to GB / T1768-2006 "Determination of the abrasion resistance of paint and varnish by rotating rubber sand wheel method", use rotating rubber sand wheel to abrade the surface of the paint film, express the abrasion resistance by the weight loss of the paint film after a certain number of abrasions. The smaller the weight loss, the better the abrasion resistance.

[0148] The results are shown in Table 1 below:

[0149] Table 1

[0150] Item adhesion / level hardness / H salt spray resistance / h abrasion resistance / mg / 1000r Example 1 0 3 1000 5 Example 2 0 3.5 1200 4.5 Example 3 0 4 1400 4 Example 4 0 4.5 1600 3.5 Example 5 0 5 1800 3 Comparative Example 1 1 2 600 8 Comparative Example 2 3 1 200 10 Comparative Example 3 1 2.5 800 6 Comparative Example 4 1 2 700 7 Comparative Example 5 0 3.5 1100 4

[0151] Data analysis:

[0152] As can be seen from Table 1, the performance of each embodiment is obviously better than that of the comparative examples, showing the advantages of the formula and process of the present application:

[0153] Adhesion: Examples 1-5 all reach level 0, showing excellent performance, Comparative Example 1 is level 1, Comparative Example 2 is level 3, Comparative Examples 3 and 4 are level 1, and Comparative Example 5 is level 0. Comparative Example 1 does not add modified polyacrylate oligomers, and the adhesion decreases, indicating that it has a positive effect on enhancing adhesion; Comparative Example 2 does not add aliphatic isocyanate curing agent, and the curing is not complete, and the adhesion decreases significantly; Comparative Example 3 replaces the dispersant with modified polyacrylate oligomers, which affects pigment dispersion and in turn affects adhesion; Comparative Example 4 does not modify the polyacrylate oligomers, and the adhesion is not as good as the examples; Comparative Example 5 still maintains level 0 although the amount is adjusted, indicating that the amount change has little effect on adhesion within a certain range.

[0154] Hardness: Examples 1-5 gradually increase from 3H to 5H, Comparative Example 1 is 2H, Comparative Example 2 is 1H, Comparative Example 3 is 2.5H, Comparative Example 4 is 2H, and Comparative Example 5 is 3.5H. Comparative Examples 1-4 have lower hardness than the examples due to the absence or replacement of key ingredients or lack of modification; the hardness of Comparative Example 5 increases after increasing the amount, reflecting the enhancing effect of modified polyacrylate oligomers on hardness.

[0155] Salt spray resistance: Examples 1-5 increase from 1000h to 1800h, Comparative Example 1 is 600h, Comparative Example 2 is 200h, Comparative Example 3 is 800h, Comparative Example 4 is 700h, and Comparative Example 5 is 1100h. Comparative Examples 1-4 have much lower salt spray resistance than the examples due to ingredient or process problems; the salt spray resistance of Comparative Example 5 increases after increasing the amount.

[0156] Wear resistance: Examples 1-5 gradually decrease in weight loss, and the wear resistance increases, Comparative Example 1 is 8mg / 1000r, Comparative Example 2 is 10mg / 1000r, Comparative Example 3 is 6mg / 1000r, Comparative Example 4 is 7mg / 1000r, and Comparative Example 5 is 4mg / 1000r. Comparative Examples 1-4 have poor wear resistance, and the wear resistance of Comparative Example 5 approaches the level of the examples after adjusting the amount.

[0157] Comparative Example 1 (without adding modified polyacrylate oligomer): The modified polyacrylate oligomer in the system, on the one hand, the polar groups in its molecular structure can interact with the active sites on the surface of the pigment, forming physical adsorption or chemical bonding, thereby improving the dispersion stability of the pigment in the paint. When not added, the pigment is not well dispersed, and during the drying process of the paint film, it cannot be uniformly distributed, resulting in uneven internal structure of the paint film, affecting the adhesion between the paint film and the substrate, and thus reducing the adhesion. On the other hand, it may participate in the crosslinking reaction with other resins or curing agents during the curing process, promoting the formation of a dense three-dimensional network structure, and the absence of it will reduce the crosslinking density of the paint film, and the hardness, salt spray resistance and wear resistance will also decrease.

[0158] Comparative Example 2 (without adding aliphatic isocyanate curing agent): Aliphatic isocyanate curing agent can crosslink with hydroxyl groups in polyurethane resin to form a highly crosslinked polyurethane network structure. In this process, isocyanate groups (-NCO) react with hydroxyl groups (-OH) to form urethane bonds (-NHCOO-), and the formation of these chemical bonds connects the molecular chains to each other, enhancing the cohesion and strength of the paint film. Without adding the curing agent, the polyurethane resin cannot be effectively crosslinked, the paint film is in a linear or low crosslinked state, the structure is loose, and the intermolecular forces are weak, so the adhesion, hardness, salt spray resistance and wear resistance are all poor, for example, in the salt spray test, the moisture and salt in the salt spray easily penetrate into the paint film, destroying its structure.

[0159] Comparative Example 3 (replacing dispersant with modified polyacrylate oligomer): The main function of the dispersant is to reduce the surface tension between the pigment particles, preventing them from agglomerating, and stably dispersing the pigment in the paint by steric hindrance or electrostatic repulsion. While the modified polyacrylate oligomer has some dispersing ability, it is not a professional dispersant, and its molecular structure and mechanism of action are different from those of the dispersant. When it is replaced with the dispersant, it cannot provide sufficient steric hindrance and electrostatic repulsion, and the pigment is easily agglomerated, resulting in defects in the interior of the paint film, affecting the uniformity and density of the paint film, and thus reducing the adhesion and hardness. In the wear resistance test, the agglomerated pigment particles are prone to wear, resulting in increased weight loss of the paint film.

[0160] Comparative Example 4 (without modification of polyacrylate oligomer by gum arabic and gelatin): Gum arabic and gelatin modify the polyacrylate oligomer by using the complex coacervation method to form a microcapsule structure. The microcapsule wall material can protect the internal polyacrylate oligomer, so that it can play a role at the right time, for example, it can be broken to release the oligomer for repair when the pigment is agglomerated. The unmodified polyacrylate oligomer is directly exposed to the paint liquid, which may react with other ingredients in advance, or the performance gradually decreases during storage, and cannot effectively play its role of dispersing and repairing the pigment, resulting in a decrease in the performance of the paint film, such as in the salt spray test, due to poor pigment dispersion, the shielding performance of the paint film decreases, and it is more easily eroded by salt spray.

[0161] Comparative Example 5 (adjusting the amount of modified polyacrylate oligomer): The amount of modified polyacrylate oligomer will affect its effect in the system. When the amount is too low, it is not enough to improve the dispersion of the pigment, and it cannot effectively participate in the crosslinking reaction, and the performance of the paint film is limited; when the amount is too high, it may increase the viscosity of the system, affect the construction performance, and also may cause the internal structure of the paint film to be too dense, resulting in internal stress, which may have a negative impact on some performances. Comparative Example 5 adjusts the amount to 1.2 g to explore the influence of the amount change on the performance, and from the data, it can be seen that the performance is improved to a certain extent, but compared with the examples, there is still a difference, which shows that the optimization of the amount has an important role in the performance.

[0162] It should be understood by those of ordinary skill in the art that the above discussion of any of the embodiments is merely exemplary and is not intended to suggest that the scope of the application is limited to these examples; under the idea of the application, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of the application as described above. In order to be brief, they are not provided in detail.

[0163] The present application is intended to cover all such alternatives, modifications and variations as fall within the broad scope of the appended claims. Accordingly, any and all such modifications, variations, omissions, and equivalents are intended to be encompassed by the present application.

Claims

1. A one-component polyurethane paint, characterized in that: The composition comprises the following raw materials in parts by weight: 30-50 parts of polyurethane resin, 10-20 parts of curing agent, 5-15 parts of anti-rust pigment, 8-18 parts of filler pigment, 1.3-4.5 parts of auxiliary agent, and 10-30 parts of solvent; The auxiliary agent is a mixture of a dispersant, a leveling agent and a defoamer in a mass ratio of 0.5-2:0.5-1.5:0.3-1; The dispersant is obtained by mixing BYK-110 and modified polyacrylate oligomer in a mass ratio of 0.3-1.2:0.2-0.8; The polyurethane resin is a hydroxyl terminated polyurethane resin; The curing agent is an aliphatic isocyanate curing agent; The aliphatic isocyanate curing agent is hexamethylene diisocyanate trimer; The preparation process of the modified polyacrylate oligomer is as follows: Step A1. In a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a dropping funnel, toluene and methyl methacrylate were added, and azobisisobutyronitrile and dodecanethiol were added; Step A2. The mixture was heated to 70-80°C under a nitrogen atmosphere, stirred at 120-150 r / min for 3-4 h. After the reaction, the reaction solution was cooled to room temperature and the solvent was removed by rotary evaporation to obtain a polyacrylate oligomer. Step A3 emulsification: The ethyl acetate solution of the polyacrylate oligomer is slowly added to the gelatin solution and emulsified at 1000-1500 r / min for 15-20 min to form a water-in-oil emulsion; Step A4. Complex coagulation: Add the gum arabic solution dropwise to the above emulsion under stirring, continue stirring for 10-15min, and then adjust the pH value of the system to 4.0-4.5 with 1 mol / L hydrochloric acid solution; Step A5. Curing: Lower the system temperature to 5-10 ° C, add glutaraldehyde aqueous solution, and stir the reaction for 30-60 min; Step A6. Separation and washing: After the reaction is completed, centrifuge at 3000-5000 rpm for 10-15 minutes, and then wash repeatedly with deionized water 3-5 times; Step A7. Drying: Dry the washed microcapsules in a vacuum drying oven at 40-50° C. to a constant weight to obtain microencapsulated polyacrylate oligomers, namely, modified polyacrylate oligomers.

2. The one-component polyurethane paint according to claim 1, characterized in that The anti-rust pigment is zinc phosphate.

3. The one-component polyurethane paint according to claim 1, characterized in that The filler pigment is obtained by mixing titanium dioxide and talcum powder in a mass ratio of 5-10:3-8.

4. The one-component polyurethane paint according to claim 1, characterized in that The usage ratio of methyl methacrylate, azobisisobutyronitrile, toluene and dodecanethiol in step A1 is 10-12 g: 0.05-0.08 g: 200-220 mL: 0.01-0.03 g.

5. The one-component polyurethane paint according to claim 1, characterized in that The mass fraction of the ethyl acetate solution of the polyacrylate oligomer in step A3 is 10%-20%; The mass ratio of the ethyl acetate solution of the polyacrylate oligomer to the gelatin solution is 100:80-100; The mass ratio of the gum arabic solution, the gelatin solution and the glutaraldehyde aqueous solution is 40-50:80-100:6-7.

5.

6. The one-component polyurethane paint according to claim 1, characterized in that The gelatin solution in step A3 is a gelatin aqueous solution with a mass fraction of 2%-5%; The gum arabic solution in step A4 is an aqueous solution of gum arabic with a mass fraction of 2%-5%; The concentration of the glutaraldehyde aqueous solution in step A5 is 1%-2%.

7. The one-component polyurethane paint according to claim 1, characterized in that The leveling agent is Deqian 435; The defoamer is a mineral oil defoamer; The solvent is obtained by mixing xylene and butyl acetate in a mass ratio of 15-18:10-12.

8. The method for preparing a one-component polyurethane paint according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step S1. Pre-mixing stage: In a reaction kettle equipped with a stirring device, add the polyurethane resin and then add the curing agent, and stir at a speed of 480-520 rpm for 14-16 minutes to preliminarily mix the two. During this time, the temperature is maintained at 24-26°C to obtain a mixture 1; Step S2. Pigment dispersion stage: Add anti-rust pigment and pigment filler to the mixture 1, increase the stirring speed to 800-1000r / min, stir for 28-30min to fully disperse the pigment, and control the temperature at 30-35°C to obtain mixture 2; Step S3. Additive addition stage: Add the additive to the mixture 2, continue stirring at a speed of 780-820 r / min for 14-16 minutes to ensure that the additive is evenly dispersed in the paint solution, and maintain the temperature at 28-32°C to obtain mixture 3; Step S4. Solvent mixing stage: Add the solvent to the mixture 3 and stir at a speed of 580-600 r / min for 20-22 min to fully mix the solvent with other ingredients. Maintain the temperature at 25-30°C to obtain a mixture 4. Step S5: Filter the mixture 4 through a 100-mesh filter to obtain a single-component polyurethane paint.