Aliphatic polyurethane finish paint with high adhesion resistance and water resistance and preparation method of aliphatic polyurethane finish paint

Abstract

The invention discloses an aliphatic polyurethane finish paint with high stain adhesion resistance and water resistance and a preparation method thereof, relates to the technical field of coatings, and aims to solve the technical problems that the existing waterborne polyurethane finish paint is easy to stain in a high-humidity environment, the water resistance is insufficient, the stain resistance of the surface is quickly attenuated and the like. By synergistically introducing the carbon dioxide copolymer polyol and the soybean oil polyol, the environmental protection property, the flexibility and the water whitening resistance of a paint film are improved; hydroxyl-terminated organic silicone oil is used for regulating and controlling surface free energy, so that a lasting and efficient anti-sticking function is realized; on the basis, an acrylate monomer is introduced for in-situ emulsion polymerization, a polyurethane / acrylate interpenetrating network structure is formed, and the water resistance, chemical resistance and comprehensive antifouling performance of a paint film are remarkably improved. The process is mild and environment-friendly, and the obtained paint film is suitable for high-durability and high-antifouling surface coating of metal, plastic, wood, building interior and exterior walls, tunnel side walls, concrete anti-collision guardrails and the like.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to a highly stain-resistant and water-resistant aliphatic polyurethane topcoat and its preparation method. Background Technology

[0002] Waterborne polyurethane coatings, due to their environmental friendliness and low VOC emissions, have become an important development direction for replacing solvent-based coatings. However, existing waterborne polyurethane topcoats still face many technical challenges in practical applications. First, in high-humidity or highly polluted environments, traditional waterborne polyurethane coatings easily adsorb pollutants, leading to film contamination and affecting their appearance and protective function. Second, due to the presence of hydrophilic groups in waterborne systems, the water resistance of existing waterborne polyurethane coatings is generally inferior to that of solvent-based products, making them prone to hydrolysis or swelling, thus reducing the service life of the coating. Furthermore, the surface stain resistance of the coating often declines over time, making it difficult to maintain long-term cleanliness and aesthetics. Finally, some waterborne polyurethane systems exhibit poor batch stability and have high requirements for the construction environment and operation, affecting their applicability in application.

[0003] To improve the performance of waterborne polyurethane coatings, the industry has conducted extensive research. For example, weather resistance has been improved by introducing aliphatic isocyanates; surface properties have been enhanced through silicone modification; and overall performance has been improved by copolymerizing with acrylates to form an interpenetrating network structure. However, these individual improvement solutions often fail to comprehensively address the aforementioned multiple complex problems, or they may introduce new problems while solving one aspect. For instance, silicone modification may affect the mechanical properties of the coating film or its compatibility with other components, and the introduction of acrylates may sometimes sacrifice the flexibility of the coating film.

[0004] Based on research on polyurethane topcoats, existing technology CN116376415A discloses a method for preparing a wall paint with strong antibacterial and stain-resistant properties. This patent involves a simple mixture of acidified chitosan-modified polyurethane emulsion and polysiloxane-modified acrylic emulsion with active vinyl groups. This approach primarily addresses the specific needs of the wall coating field, and its modification method merely involves the physical mixing of two modified emulsions, lacking the formation of a deep chemical interpenetrating network structure. Therefore, this coating exhibits significant shortcomings in long-term durability under conditions such as alternating humid and hot environments, high-intensity mechanical impact, and heavy pollution conditions such as oil stains and chemicals.

[0005] In conclusion, developing a new material that can achieve multi-dimensional synergistic optimization and comprehensively improve the anti-fouling, water resistance, weather resistance, and application adaptability of waterborne polyurethane topcoats in high humidity environments has become a pressing technical challenge in the coatings industry. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a highly stain-resistant and water-resistant aliphatic polyurethane topcoat and its preparation method. The purpose of this invention is to provide a topcoat that, while solving the technical problems of existing water-based polyurethane topcoats such as easy staining in high-humidity environments, insufficient water resistance, rapid degradation of surface stain resistance, and poor application adaptability, possesses excellent environmental friendliness, flexibility, water-whitening resistance, high durability, high decorative properties, and excellent anti-fouling performance.

[0007] The specific technical solution is as follows: A highly stain-resistant and water-resistant aliphatic polyurethane topcoat comprises a bio-based polyurethane backbone and a reinforcing phase. The bio-based polyurethane backbone utilizes a non-petroleum-based polyol raw material during the prepolymer formation stage. The reinforcing phase includes covalently grafted organosilicon functional groups and a polyurethane / acrylate interpenetrating network structure. The organosilicon functional groups are covalently bonded to the polyurethane backbone during the prepolymer modification stage. The polyurethane / acrylate interpenetrating network structure is formed by in-situ emulsion polymerization of acrylate monomers in a polyurethane emulsion, resulting in an interpenetrating network between the acrylate phase and the polyurethane backbone.

[0008] Furthermore, the highly stain-resistant and water-resistant aliphatic polyurethane topcoat comprises the following components in parts by weight: Carbon dioxide copolymer polyol: 60-80 parts; Soybean oil polyols: 20-40 parts; Aliphatic diisocyanates: 30-70 parts; Crosslinking agent: 1-10 parts; Hydrophilic chain extender: 4-20 parts; Hydroxyl-containing silicone oil: 30-60 parts; Neutralizing agent: 1-15 parts; Hydroxyacrylates: 1-15 parts; Deionized water: 100-400 parts; Chain extender: 1-10 parts; Acrylate monomer: 10-40 parts; Initiator: 0.01-0.5 parts.

[0009] Furthermore, the carbon dioxide copolymer polyol is a polycarbonate diol with an average molecular weight of 2000; the soybean oil polyol is a self-made bio-based polyol with a hydroxyl value of 50 mg KOH / g; and the hydroxyl-containing organosilicon oil is a hydroxyl-terminated polydimethylsiloxane.

[0010] Furthermore, the hydroxyl-containing acrylate is hydroxyethyl acrylate, which is used to introduce double bond active sites on the polyurethane chain that can participate in subsequent in-situ emulsion polymerization; the acrylate monomer is any two of butyl acrylate, methyl methacrylate or isobornyl acrylate, which are used to construct an acrylate network structure that interpenetrates with the polyurethane, thereby improving the hardness, water resistance and chemical resistance of the coating film.

[0011] Furthermore, the aliphatic diisocyanate is isophorone diisocyanate or hexamethylene diisocyanate; the crosslinking agent is a polyol having three hydroxyl groups, specifically including trimethylolpropane or glycerol; the hydrophilic chain extender is 2,2-dimethylolpropionic acid or 2,2-dimethylolbutyric acid; the neutralizing agent is triethylamine; and the chain extender is ethylenediamine or isophorone diamine.

[0012] Furthermore, the preparation method of the aforementioned highly stain-resistant and water-resistant aliphatic polyurethane topcoat includes the following steps: S1: Under nitrogen protection, carbon dioxide copolymer polyol, soybean oil polyol and crosslinking agent are added to the reactor, heated to dehydrate, cooled to 50°C, and aliphatic diisocyanate is added to carry out prepolymerization reaction until the NCO content of the system reaches the theoretical value ±0.2% to obtain polyurethane prepolymer. S2: Cool the polyurethane prepolymer prepared in S1 to 50-60℃, add a hydrophilic chain extender, and react for 0.5-1.5 hours to introduce the hydrophilic carboxyl structure into the polyurethane chain segment; after the NCO content in the system tends to stabilize, adjust the temperature to 60-70℃ and add hydroxyl-containing organosilicon oil in batches to graft the organosilicon chain segment onto the polyurethane prepolymer. S3: Add a neutralizing agent to the system in step S2 at 40-50℃ and stir for 30 minutes to neutralize the polyurethane prepolymer; after neutralization, add hydroxyl-containing acrylate and heat to 55-65℃ to react for 1-2 hours to graft it onto the polyurethane chain segment. S4: The neutralized polyurethane prepolymer is added to deionized water under high-speed stirring to form an aqueous polyurethane dispersion. The dispersion temperature is controlled at 25-45℃. After dispersion, the stirring speed is turned to medium speed, and a chain extender is added to extend the chain through water inlet to obtain an aqueous polyurethane emulsion. S5: Add acrylate monomers and initiators to the emulsion in step S4 to carry out in-situ emulsion polymerization to form a polyurethane / acrylate interpenetrating network structure; after the polymerization reaction is completed, cool the system to room temperature, filter, and obtain a highly stain-resistant and water-resistant aliphatic polyurethane topcoat.

[0013] Furthermore, the heating and dehydration temperature in step S1 is 60°C, and the time is 1 hour; the temperature of the prepolymerization reaction is 75-85°C.

[0014] Furthermore, the batch method described in step S2 is as follows: after each addition of hydroxyl-containing silicone oil, stir for 10-30 minutes to ensure full dispersion and reaction; the entire grafting stage reaction lasts for 1-3 hours.

[0015] Furthermore, the reaction conditions for water-injected chain extension in step S4 are: the reaction temperature is room temperature, and the reaction time is 1-2 hours.

[0016] Furthermore, the reaction conditions for the in-situ emulsion polymerization reaction in step S5 are: a reaction temperature of 50-80℃ and a reaction time of 3-5 hours.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) Improved environmental friendliness and flexibility: This invention introduces carbon dioxide copolymer polyol and soybean oil polyol, which reduces the dependence on petroleum-based raw materials and improves environmental friendliness. The synergistic effect of these two polyols gives the coating film better flexibility and water-whitening resistance, solving the problem that traditional waterborne polyurethane coating films are prone to brittleness and whitening in low temperature or high humidity environments.

[0018] (2) Surface anti-fouling function: The present invention adjusts the surface free energy of the paint film by introducing and grafting hydroxyl-containing silicone oil. During the curing process of the paint film, silicone tends to migrate to the surface to form a hydrophobic and oleophobic layer with low surface energy, which significantly reduces the adhesion of pollutants, thereby achieving excellent anti-fouling and easy-to-clean functions, and this function is stable and durable.

[0019] (3) Composite Interpenetrating Network Structure: In this invention, acrylate monomers are introduced in situ into the polyurethane dispersion for emulsion polymerization to form a polyurethane / acrylate interpenetrating network structure. This network structure allows the two polymer chains to intertwine and solidify, effectively combining the flexibility and abrasion resistance of polyurethane with the hardness, water resistance, and chemical resistance of acrylate, thereby significantly improving the overall protective performance of the coating film, including water resistance, chemical corrosion resistance, and anti-fouling properties.

[0020] (4) Mild and environmentally friendly preparation process: The entire preparation process of this invention is carried out in an aqueous environment, which reduces the use of organic solvents and meets environmental protection requirements. The reaction conditions are mild, which is easy to industrialize and reduces production costs. Attached Figure Description

[0021] Figure 1 This is a flowchart of the preparation method of the high anti-fouling and water-resistant aliphatic polyurethane topcoat of the present invention; Figure 2 This is a synthesis route diagram for Embodiment 1 of the present invention; Figure 3 This is a comparison diagram of the tensile bond strength results of the embodiments and comparative examples of the present invention; Figure 4This is a comparison chart showing the anti-slip performance and wear resistance results of embodiments and comparative examples of the present invention. Detailed Implementation

[0022] The following embodiments further explain and illustrate the technical solutions of the present invention. It should be specifically noted that each specific embodiment is a concretization and explanation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention.

[0023] The high stain-resistant and water-resistant aliphatic polyurethane topcoat of this invention is prepared by a prepolymer method combined with in-situ emulsion polymerization technology. The preparation process is shown in the attached figure. Figure 1 As shown. The formula is in the following parts by weight: Carbon dioxide copolymer polyol: 60-80 parts; Soybean oil polyols: 20-40 parts; Aliphatic diisocyanates: 30-70 parts; Crosslinking agent: 1-10 parts; Hydrophilic chain extender: 4-20 parts; Hydroxyl-containing silicone oil: 30-60 parts; Neutralizing agent: 1-15 parts; Hydroxyacrylates: 1-15 parts; Deionized water: 100-400 parts; Chain extender: 1-10 parts; Acrylate monomer: 10-40 parts; Initiator: 0.01-0.5 parts.

[0024] The specific steps are as follows: 1. Preparation of polyurethane prepolymer: In a four-necked flask equipped with a stirrer, condenser, thermometer, and inert gas inlet, precisely weighed carbon dioxide copolymer polyol, soybean oil polyol, and crosslinking agent are first added. Under nitrogen protection, stirring is started, and the mixture is heated to 60°C and kept at this temperature for 1 hour to dehydrate.

[0025] Subsequently, the system was cooled to 50°C, and a measured amount of aliphatic diisocyanate was slowly added. After adding the isocyanate, the temperature was gradually increased to 75-85°C to carry out the prepolymerization reaction. Simultaneously, samples were taken periodically to detect the NCO content of the system. When the NCO content reached the theoretically calculated value ±0.2%, heating was stopped, and the mixture was kept at this temperature and stirred for another 15-30 minutes to ensure complete reaction, thus obtaining the polyurethane prepolymer. This stage of the reaction involves the addition polymerization of hydroxyl groups in the polyol with NCO groups in the isocyanate, forming a low molecular weight polymer with specific terminal NCO groups.

[0026] The carbon dioxide copolymer polyol is a polycarbonate diol with an average molecular weight of 2000; the soybean oil polyol has a hydroxyl value of 50 mg KOH / g; the crosslinking agent is trimethylolpropane (TMP) or glycerol; and the aliphatic diisocyanate is isophorone diisocyanate (IPDI) or hexamethylene diisocyanate (HDI).

[0027] The determination of the hydroxyl value of soybean oil polyols: The sample is heated in a mixed solvent of acetic anhydride / pyridine to induce esterification of the polyol hydroxyl groups. After the reaction, water is added to hydrolyze the unreacted acetic anhydride, and the released acetic acid is titrated with standard KOH solution. The hydroxyl value of each gram of sample is calculated by measuring the amount of KOH consumed by the sample and subtracting the amount consumed in the blank titration, in mgKOH / g.

[0028] 2. Introduction of hydrophilic carboxyl groups and organosilicon grafting modification: The polyurethane prepolymer prepared above is cooled to 50-60°C. At this temperature, an accurately weighed hydrophilic chain extender is slowly added. The two hydroxyl groups in the hydrophilic chain extender react with the NCO groups in the prepolymer, introducing carboxyl groups into the polyurethane segments. The reaction is allowed to proceed for 0.5-1.5 hours until the NCO content in the system tends to stabilize. Subsequently, the temperature is adjusted to 60-70°C, and hydroxyl-containing silicone oil is added in batches, stirring for 10-30 minutes after each addition to ensure thorough dispersion and reaction. The entire grafting stage takes 1-3 hours to ensure sufficient reaction between the silicone oil and the polyurethane segments, achieving effective grafting of the silicone segments. This process aims to covalently bond the low surface energy silicone structure to the polyurethane chain, preventing later migration and precipitation, and ensuring the durability of the anti-fouling function.

[0029] The hydrophilic chain extender is 2,2-dimethylolpropionic acid (DMPA) or 2,2-dimethylolbutyric acid (DMBA); the hydroxyl-containing silicone oil is hydroxyl-terminated polydimethylsiloxane.

[0030] 3. Neutralization and introduction of hydroxyl-containing acrylates: A measured amount of neutralizing agent is added to the reaction system at 40-50℃ and stirred for 30 minutes to allow it to fully react with the carboxyl groups introduced by the hydrophilic chain extender, forming a hydrophilic carboxylate structure, thereby improving the hydrophilicity and emulsifying ability of the polyurethane prepolymer. After neutralization, a hydroxyl-containing acrylate is added, and the system is heated to 55-65℃ and reacted for 1-2 hours. The hydroxyl-containing acrylate reacts with the NCO groups in the polyurethane chain through its hydroxyl groups, grafting them onto the polyurethane backbone. Its acrylate groups then serve as active sites for subsequent in-situ polymerization.

[0031] The neutralizing agent is triethylamine (TEA); the hydroxyl-containing acrylate is hydroxyethyl acrylate (HEA).

[0032] 4. Water dispersion and influent chain extension: Prepare a dispersion tank filled with deionized water and turn on high-speed stirring. While stirring, slowly and evenly pour the polyurethane prepolymer into the deionized water. Control the dispersion temperature between 25-45℃ to avoid excessively high temperatures causing emulsion instability or triggering unnecessary side reactions. Through strong shear action, the polyurethane prepolymer forms a stable water-in-oil emulsion in water and gradually transforms into an oil-in-water dispersion.

[0033] After dispersion, stop high-speed stirring and switch to medium-speed stirring. Slowly add the metered chain extender and react at room temperature for 1-2 hours to perform water-based chain extension. During this process, the amino groups of the chain extender react with the residual NCO groups in the polyurethane prepolymer, further extending the polyurethane molecular chains, increasing the molecular weight, and forming a stable waterborne polyurethane emulsion (WPU).

[0034] The chain extender is ethylenediamine (EDA) or isoflurane diamine (IPDA).

[0035] 5. In-situ emulsion polymerization of acrylates: In the aforementioned organosilicon-grafted modified system, acrylate monomers and a water-soluble initiator are added. The system is heated to 50-80℃ and maintained at this temperature for in-situ emulsion polymerization for 3-5 hours. During this process, the acrylate monomers polymerize within and around the polyurethane emulsion particles under the action of the initiator, ultimately forming a polyurethane / acrylate (PUA) interpenetrating network structure. This structure maximizes the synergistic effect of the two polymers, improving the overall performance of the coating film, particularly water resistance, hardness, and chemical resistance.

[0036] After the polymerization reaction is complete, the system is cooled to room temperature. Any gel or impurities that may be present are removed by filtration to obtain a stable, highly stain-resistant, and water-resistant aliphatic polyurethane topcoat emulsion.

[0037] The acrylate monomer is any two of butyl acrylate (BA), methyl methacrylate (MMA), or isobornyl acrylate (IBOA); the water-soluble initiator is ammonium persulfate (APS) or potassium persulfate (KPS).

[0038] The theoretical formula for calculating the NCO content of the prepolymer mentioned above is as follows: NCO content (%) = (NCO total- OH total )×M NCO ×100% / M prep NCO total It is the total number of moles of NCO added, in mol; OH total It is the total number of moles of hydroxyl groups added; M NCO The molar mass of the NCO group is 42.0 g / mol; M prep This is the total mass of the prepolymer, expressed in grams (g).

[0039] The above method for determining NCO content involves di-n-butylamine back titration, and the specific steps are as follows: (1) Reagent preparation: Di-n-butylamine standard solution: Prepare a 0.5 mol / L di-n-butylamine standard solution using a mixture of analytical grade di-n-butylamine and anhydrous toluene, and then standardize it with a 0.1 mol / L hydrochloric acid standard solution.

[0040] (2) Sample weighing: Based on the theoretical NCO content, accurately weigh the polyurethane prepolymer sample to an accuracy of 0.0001 g and place it in a 250 mL Erlenmeyer flask with a ground glass stopper.

[0041] (3) Adsorption reaction: Add approximately 20 mL of anhydrous toluene to the conical flask and shake well to dissolve the sample. Accurately add 50.00 mL of the standardized di-n-butylamine standard solution using a pipette, stir well, immediately seal the flask tightly, and allow it to stand at room temperature in the dark for 15 minutes. The di-n-butylamine will react quantitatively with the NCO groups in the sample.

[0042] Blank experiment: In another 250mL Erlenmeyer flask, add 20mL of anhydrous toluene and 50.00mL of di-n-butylamine standard solution of the same precise volume. Do not add the sample. Seal the flask tightly and allow it to stand for reaction at the same time as the sample.

[0043] (4) Back titration: After the adsorption reaction is complete, add 3-5 drops of bromophenol blue indicator solution to the conical flask and the blank experimental group. Titrate the excess di-n-butylamine with 0.1 mol / L hydrochloric acid standard solution. Record the volume of hydrochloric acid standard solution consumed by the sample (V1, mL) and the volume of hydrochloric acid standard solution consumed by the blank sample (V0, mL).

[0044] (5) Calculation: NCO content (%) = (V 1- V0)×C HCl ×M NCO ×F×100% / (1000×m), where C HCl M represents the concentration of the hydrochloric acid standard solution, in mol / L. NCO is the molar mass of the NCO group, which is 42.0 g / mol; F is the conversion factor, which is 1; m is the mass of the sample taken, in g.

[0045] Table 1 shows the reagents used in the following examples and comparative examples:

[0046] Example 1: In this example, a highly stain-resistant and water-resistant aliphatic polyurethane topcoat was prepared according to the following parts by weight: PCDL: 70 copies; Soybean oil polyols: 30 parts; HDI: 50 portions; TMP: 5 servings; DMPA: 10 copies; Hydroxyl-terminated polydimethylsiloxane: 45 parts; TEA: 10 servings; HEA: 8.5 copies; Deionized water: 250 parts; IPDA: 5.6 copies; BA: 20 copies; MMA: 10 copies; APS: 0.25 copies.

[0047] Preparation process: The preparation route is shown in the appendix. Figure 2As shown, under nitrogen protection, 70 parts PCDL, 30 parts soybean oil polyol, and 5 parts TMP were added to a reactor and heated to 60°C for 1 hour to dehydrate. The temperature was then lowered to 50°C, and 50 parts HDI were added. The theoretical NCO content of the prepolymer in this system was 9.0%. The temperature was then raised to 80°C and reacted for 3 hours. At this point, the NCO content of the system was measured to be 8.7%. Heating was stopped, and the mixture was kept at this temperature and stirred for another 22 minutes to obtain the prepolymer. The prepolymer was cooled to 55°C, and 10 parts DMPA were added, reacting for 1 hour. 45 parts hydroxyl-terminated polydimethylsiloxane were added, and the reaction temperature was raised to 65°C, stirring for 2 hours. The system temperature was lowered to 45°C, and 10 parts TEA were added, stirring for 30 minutes. After neutralization, 8.5 parts HEA were added, and the mixture was stirred at 60°C for 1.5 hours. Under high-speed stirring, the prepolymer was slowly dispersed in 250 parts deionized water, with the dispersion temperature controlled at 35°C, to form an aqueous polyurethane dispersion. Add 5.6 parts of IPDA for water-based chain extension and react at room temperature for 1.5 hours. Add 20 parts of BA, 10 parts of MMA, and 0.25 parts of APS, and heat to 70°C for polymerization for 4 hours. Cool to room temperature, filter, and obtain the topcoat of Example 1.

[0048] Example 2: In this example, a highly stain-resistant and water-resistant aliphatic polyurethane topcoat was prepared according to the following parts by weight: PCDL: 60 copies; Soybean oil polyols: 20 parts; IPDI: 30 copies; Glycerin: 1 part; DMBA: 4 copies; Hydroxyl-terminated polydimethylsiloxane: 30 parts; TEA: 3 servings; HEA: 1 copy; Deionized water: 100 parts; EDA: 1 copy; BA: 6.7 servings; MMA: 3.3 copies; KPS: 0.01 copies.

[0049] Preparation process: Under nitrogen protection, 60 parts PCDL, 20 parts soybean oil polyol, and 1 part glycerol were added to a reactor and heated to 60°C for 1 hour to dehydrate. The temperature was then lowered to 50°C, and 30 parts IPDI were added. The theoretical NCO content of the prepolymer in this system was 4.6%. The temperature was raised to 75°C and reacted for 2.5 hours. At this point, the NCO content of the system was measured to be 4.5%. Heating was stopped, and the mixture was kept at this temperature and stirred for another 15 minutes to obtain the prepolymer. The prepolymer was cooled to 50°C, and 4 parts DMBA were added, reacting for 0.5 hours. 30 parts hydroxyl-terminated polydimethylsiloxane were added, and the reaction temperature was raised to 60°C and stirred for 1 hour. The system temperature was lowered to 40°C, and 3.0 parts TEA were added, stirring for 30 minutes. After neutralization, 1 part HEA was added, and the mixture was stirred at 55°C for 1 hour. Under high-speed stirring, the neutralized prepolymer was slowly dispersed in 100 parts deionized water, with the dispersion temperature controlled at 25°C, to form an aqueous polyurethane dispersion. Add 1 part EDA for water-based chain extension and react at room temperature for 1 hour. Add 6.7 parts BA, 3.3 parts MMA and 0.01 parts KPS, and heat to 50°C for polymerization for 3 hours. Cool to room temperature, filter, and obtain the topcoat of Example 2.

[0050] Example 3: In this example, a highly stain-resistant and water-resistant aliphatic polyurethane topcoat was prepared according to the following parts by weight: PCDL: 80 copies; Soybean oil polyols: 40 parts; HDI: 70 portions; TMP: 10 servings; DMBA: 20 copies; Hydroxyl-terminated polydimethylsiloxane: 60 parts; TEA: 15 servings; HEA: 10 copies; Deionized water: 400 parts; IPDA: 10 copies; IBOA: 20 copies; BA: 20 copies; APS: 0.5 copies.

[0051] Preparation process: Under nitrogen protection, 80 parts PCDL, 40 parts soybean oil polyol, and 10 parts TMP were added to a reactor and heated to 60°C for dehydration for 1 hour. The temperature was then lowered to 50°C, and 70 parts HDI were added. The theoretical NCO content of the prepolymer in this system was 8.9%. The temperature was raised to 85°C and reacted for 4 hours. At this point, the NCO content of the system was measured to be 8.7%. Heating was stopped, and the mixture was kept at this temperature and stirred for another 30 minutes to obtain the prepolymer. The prepolymer was cooled to 60°C, and 20 parts DMBA were added, reacting for 1.5 hours. 60 parts hydroxyl-terminated polydimethylsiloxane were added, and the reaction temperature was raised to 70°C, stirring for 3 hours. The system temperature was lowered to 50°C, and 15 parts TEA were added, stirring for 30 minutes. After neutralization, 10 parts HEA were added, and the mixture was stirred at 65°C for 2 hours. Under high-speed stirring, the neutralized prepolymer was slowly dispersed in 400 parts deionized water, with the dispersion temperature controlled at 45°C, to form an aqueous polyurethane dispersion. Add 10 parts of IPDA for water-based chain extension and react at room temperature for 1 hour. Add 20 parts of IBOA, 20 parts of BA, and 0.5 parts of APS, and heat to 80°C for polymerization for 5 hours. Cool to room temperature, filter, and obtain the topcoat of Example 3.

[0052] Comparative Example 1: This comparative example aims to investigate the effects of carbon dioxide copolymer polyol and soybean oil polyol on the film properties. No carbon dioxide copolymer polyol or soybean oil polyol was added to the formulation. The formulation by weight parts is as follows: poly(1,4-butanediol adipate) polyol: 100 parts; IPDI: 60 parts; TMP: 5 parts; DMPA: 10 parts; TEA: 8 parts; deionized water: 250 parts; EDA: 3 parts; hydroxyl-terminated polydimethylsiloxane: 31 parts; HEA: 8.5 parts; BA: 20 parts; MMA: 15 parts; APS: 0.25 parts. The preparation method is the same as in Example 1.

[0053] Comparative Example 2: This comparative example aims to investigate the effects of the introduction and grafting of hydroxyl-containing silicone oil on the film properties. No hydroxyl-containing silicone oil was added to the formulation. The formulation consisted of the following parts by weight: PCDL: 70 parts; soybean oil polyol: 30 parts; IPDI: 50 parts; TMP: 5 parts; DMPA: 10 parts; TEA: 8 parts; deionized water: 250 parts; EDA: 3 parts; HEA: 8.5 parts; BA: 20 parts; MMA: 15 parts; APS: 0.25 parts. The preparation method was the same as in Example 1, except that the silicone grafting modification step was omitted.

[0054] Comparative Example 3: This comparative example aims to investigate the contribution of the PUA interpenetrating network structure to the film performance. No acrylate monomers or initiators were added to the formulation, and no PUA interpenetrating network was formed. The formulation by weight parts is as follows: PCDL: 70 parts; soybean oil polyol: 30 parts; IPDI: 50 parts; TMP: 5 parts; DMPA: 10 parts; TEA: 8 parts; deionized water: 250 parts; EDA: 3 parts; hydroxyl-terminated polydimethylsiloxane: 31 parts; HEA: 8.5 parts. The preparation method is the same as in Example 1, except that the in-situ polymerization step of the acrylate is omitted.

[0055] Detection method: Refer to GB / T 22374-2018 "Floor Coating Materials" (Basic Physical Properties of Topcoat and Coating Systems) (Light Load R Type).

[0056] 1. Container status detection: Instructions: Open the packaging container and stir with the stirring rod; Judgment criteria: Observe whether the stirred paint is in a uniform flow state, whether there are any lumps or sediments, whether the color is uniform, and whether there are any obvious color separation or other abnormalities. Acceptable standard: The paint is uniform after stirring and has no lumps.

[0057] 2. Paint film appearance inspection: Procedure: Apply the sample to the sample plate and cure for 2 days at a temperature of 23±2℃ and a relative humidity of 50±5% until the paint film is completely dry. Visually observe the paint film surface under diffused sunlight. Judgment criteria: Observe whether the paint film surface is smooth and whether there are any obvious visible pinholes, floating color, mottling, wrinkles, bubbles, cracks, peeling, etc. Acceptable standard: The surface is smooth, without pinholes, visible particles, floating color, mottling, wrinkles, pinholes, cracks, etc.

[0058] 3. Drying time determination: Procedure: Surface Drying Time: Apply the paint evenly to a glass plate to form a film of standard thickness. Within a specified time interval, gently touch the surface of the paint film with your finger. If the finger does not stick to the paint film when touched, it is surface dry. Complete Drying Time: After surface drying, place a load on the paint film. After a certain period of time, remove the load and observe the surface of the paint film for any indentations or adhesion. When the surface of the paint film is free of any damage or indentations, it is complete dry. Judgment criteria: Surface drying time ≤ 8 hours; actual drying time ≤ 48 hours.

[0059] 4. Abrasion resistance test (750g / 500r): Equipment: abrasion tester, grinding wheel, load; Operation: Uniformly coat the paint sample on a metal plate of standard size, prepare a paint film of specified thickness and fully cure it. Weigh the initial mass m1 of the sample plate. Fix the sample plate on the abrasion tester, select a suitable grinding wheel, apply a load of 750 g, set the number of grinding rotations to 500 r, conduct the abrasion test. After the test, remove the abrasion debris on the surface of the sample plate and weigh the mass m of the sample plate again. 2； Calculation: Abrasion resistance (weight loss) = m1 - m2, unit: g; Judgment criterion: Weight loss ≤ 0.030 g is considered qualified.

[0060] 5. Determination of tensile bond strength: Equipment: Pull-off tester; Operation: (1) Standard conditions: The sample is cured for 4 days under the conditions of temperature 23 ± 2 °C and relative humidity 50 ± 5%. Coat the paint sample on the specified substrate, prepare a paint film of a certain thickness and fully cure it. Bond a standard pull-off head on the surface of the paint film with a high-strength adhesive, and the bonding area is A, unit: mm 2 . After the adhesive is fully cured, fix the sample plate with the pull-off head on the pull-off tester, apply a tensile stress perpendicular to the surface of the paint film at a tensile speed of 5 mm / min until the paint film peels off from the substrate or internal damage occurs. Record the maximum stress value F at the time of failure, unit: N. Conduct multiple tests and take the average value. Calculate the tensile bond strength P = F / A, and the result is accurate to 0.1 MPa; (2) After immersion in water: Prepare the sample plate according to the above operation, immerse the sample plate in deionized water at 23 ± 2 °C for the specified time of 7 days, take it out and dry the surface moisture, and immediately conduct the tensile bond strength test according to the operation method under standard conditions; Judgment criterion: ≥ 2.0 MPa under standard conditions; ≥ 2.0 MPa after immersion in water is considered qualified.

[0061] 6. Determination of impact resistance: Equipment: Impact tester, 500 g steel ball; Operation: Uniformly coat the paint sample on a metal plate of standard size, prepare a paint film of specified thickness and fully cure it. Fix the sample plate on the base of the impact tester with the paint film surface facing up. Drop a 500 g steel ball freely from a height of 100 cm to impact the surface of the paint film; Judgment criterion: Visually inspect the impact area, and the paint film surface without cracks and peeling is considered qualified.

[0062] 7. Determination of skid resistance (dry friction coefficient): Equipment: Friction coefficient tester; Procedure: Apply the paint sample onto a standard-sized test board to prepare a paint film of the specified thickness and allow it to fully cure. Fix the test board onto the coefficient of friction meter and conduct the test according to the instrument's operating procedures. Measure at multiple points and take the average value. Judgment criterion: Dry friction coefficient ≥ 0.50.

[0063] 8. Water resistance test (168h): Procedure: Apply the paint sample to the specified substrate to prepare a paint film of the specified thickness and allow it to fully cure. Immerse the sample in a container of deionized water at 23±2℃, ensuring partial immersion of the paint film. Immersion time is 168 hours. After immersion, remove the sample, wipe the surface dry with a soft cloth, immediately observe the condition of the paint film, and observe again after 2 hours of recovery. Number of specimens: Three specimens per experiment group; Judgment criteria: Visually inspect the paint film for defects such as blistering, peeling, and discoloration. Acceptance criteria: Two out of three test pieces should not blister or peel, and slight discoloration is permissible; no slight discoloration is considered a better result.

[0064] 9. Chemical resistance test: Procedure: Alkali resistance (20% NaOH, 72h): Apply the coating sample to a specified substrate to prepare a paint film of the specified thickness and allow it to fully cure. Immerse the sample in a container filled with 20% NaOH solution at 23±2℃ for 72 hours. After immersion, remove the sample, wipe the surface dry with a soft cloth, immediately observe the paint film condition, and observe again after 2 hours of recovery. Oil resistance (120# solvent oil, 72h): Prepare samples according to the same procedure described above. Immerse the samples in a container filled with 120# solvent oil at 23±2℃ for 72 hours. After immersion, remove the samples, wipe the surface dry with a soft cloth, observe the paint film condition immediately, and observe again after 2 hours of recovery. Number of specimens: Three specimens per experiment group; Judgment criteria: Visually inspect the paint film for blistering, peeling, and swelling. Acceptance criteria: Two out of three test pieces should not blister or peel, and slight discoloration is permissible; no slight discoloration is considered a better performance.

[0065] Table 2 Comparison of the state, coating appearance, and drying time results in the containers of each embodiment and comparative example:

[0066] Table 3 Comparison of tensile bond strength, anti-slip properties, and abrasion resistance results for each embodiment and comparative example:

[0067] Table 4 compares the impact resistance, water resistance, and chemical resistance results of each example and comparative example:

[0068] Results analysis: (1) Film-forming properties and appearance: As shown in Table 2, the surface drying time and actual drying time of Examples 1-3 were 2.0-4.0 hours and 24-36 hours, respectively, which were significantly faster than those of the comparative examples. Meanwhile, the paint films of the examples exhibited a smooth surface, free from visible pinholes, floating color, mottling, wrinkling, and cracking, far superior to the slight floating color, pinholes, slightly lower gloss, and pinholes observed in the comparative examples. This indicates that the formulation design of the present invention, especially the formation of the PUA interpenetrating network structure, not only facilitates film formation and leveling but also significantly improves the overall aesthetics and initial film quality of the paint film, laying a solid foundation for the subsequent realization of protective performance.

[0069] (2) Mechanical and protective properties: as shown in Table 3, Table 4, and Appendix Figure 3 Appendix Figure 4 As shown, the tensile bond strength, abrasion resistance, anti-slip properties, and impact resistance of Examples 1-3 are far superior to those of the comparative examples, meeting or even exceeding the technical requirements. This is mainly attributed to the excellent flexibility imparted by the introduction of carbon dioxide copolymer polyol and soybean oil polyol, as well as the synergistic effect of the composite PUA interpenetrating network structure on strength, hardness, toughness, and abrasion resistance.

[0070] (3) Durability: As shown in Tables 3 and 4, no blistering, peeling, or discoloration was observed in Examples 1-3 during water immersion, alkali resistance, and oil resistance tests, demonstrating excellent water resistance and chemical resistance, far exceeding the comparative examples. This is due to the composite PUA interpenetrating network structure effectively reducing the water absorption rate and chemical penetration of the paint film. At the same time, the grafting of hydroxyl-containing silicone oil may also synergistically enhance the hydrophobic properties of the surface, comprehensively improving the long-term protective capability of the paint film.

[0071] In summary, the products of the embodiments of the present invention have achieved significant improvements over traditional products in terms of film-forming performance, mechanical strength, durability, environmental friendliness, and special functionalities. These superior properties demonstrate that the introduction of bio-based polyols, the grafting of organosilicon, and the construction of a unique polyurethane / acrylate interpenetrating network structure have successfully achieved a comprehensive performance enhancement of waterborne protective coatings, enabling them to meet environmental requirements while possessing excellent overall protective capabilities.

Claims

1. A highly stain-resistant and water-resistant aliphatic polyurethane topcoat, comprising a bio-based polyurethane backbone and a reinforcing phase, characterized in that, In the prepolymer formation stage, the bio-based polyurethane backbone uses non-petroleum-based polyol raw materials; the reinforcing phase includes covalently grafted organosilicon functional groups and a polyurethane / acrylate interpenetrating network structure, wherein the organosilicon functional groups are covalently bonded to the polyurethane backbone in the prepolymer modification stage; the polyurethane / acrylate interpenetrating network structure is formed by in-situ emulsion polymerization of acrylate monomers in a polyurethane emulsion, thereby forming an interpenetrating network between the acrylate phase and the polyurethane backbone.

2. The highly stain-resistant and water-resistant aliphatic polyurethane topcoat as described in claim 1, characterized in that, The aliphatic polyurethane topcoat comprises the following components in parts by weight: Carbon dioxide copolymer polyol: 60-80 parts; Soybean oil polyols: 20-40 parts; Aliphatic diisocyanates: 30-70 parts; Crosslinking agent: 1-10 parts; Hydrophilic chain extender: 4-20 parts; Hydroxyl-containing silicone oil: 30-60 parts; Neutralizing agent: 1-15 parts; Hydroxyacrylates: 1-15 parts; Deionized water: 100-400 parts; Chain extender: 1-10 parts; Acrylate monomer: 10-40 parts; Initiator: 0.01-0.5 parts.

3. The highly stain-resistant and water-resistant aliphatic polyurethane topcoat as described in claim 2, characterized in that, The carbon dioxide copolymer polyol is a polycarbonate diol with an average molecular weight of 2000; the soybean oil polyol is a self-made bio-based polyol with a hydroxyl value of 50 mg KOH / g; and the hydroxyl-containing organosilicon oil is a hydroxyl-terminated polydimethylsiloxane.

4. The highly stain-resistant and water-resistant aliphatic polyurethane topcoat as described in claim 2, characterized in that, The hydroxyl-containing acrylate is hydroxyethyl acrylate, used to introduce double bond active sites on the polyurethane chain that can participate in subsequent in-situ emulsion polymerization; the acrylate monomer is any two of butyl acrylate, methyl methacrylate or isobornyl acrylate, used to construct an acrylate network structure that interpenetrates with the polyurethane, thereby improving the hardness, water resistance and chemical resistance of the coating film.

5. The highly stain-resistant and water-resistant aliphatic polyurethane topcoat as described in claim 2, characterized in that, The aliphatic diisocyanate is isophorone diisocyanate or hexamethylene diisocyanate; the crosslinking agent is a polyol having three hydroxyl groups, specifically including trimethylolpropane or glycerol; the hydrophilic chain extender is 2,2-dimethylolpropionic acid or 2,2-dimethylolbutyric acid; the neutralizing agent is triethylamine; and the chain extender is ethylenediamine or isophorone diamine.

6. A method for preparing a highly stain-resistant and water-resistant aliphatic polyurethane topcoat according to any one of claims 1-5, characterized in that, Includes the following steps: S1: Under nitrogen protection, carbon dioxide copolymer polyol, soybean oil polyol and crosslinking agent are added to the reactor, heated to dehydrate, cooled to 50°C, and aliphatic diisocyanate is added to carry out prepolymerization reaction until the NCO content of the system reaches the theoretical value ±0.2% to obtain polyurethane prepolymer. S2: Cool the polyurethane prepolymer prepared in S1 to 50-60℃, add a hydrophilic chain extender, and react for 0.5-1.5 hours to introduce the hydrophilic carboxyl structure into the polyurethane chain segment; after the NCO content in the system tends to stabilize, adjust the temperature to 60-70℃ and add hydroxyl-containing organosilicon oil in batches to graft the organosilicon chain segment onto the polyurethane prepolymer. S3: Add a neutralizing agent to the system in step S2 at 40-50℃ and stir for 30 minutes to neutralize the polyurethane prepolymer; after neutralization, add hydroxyl-containing acrylate and heat to 55-65℃ to react for 1-2 hours to graft it onto the polyurethane chain segment. S4: The neutralized polyurethane prepolymer is added to deionized water under high-speed stirring to form an aqueous polyurethane dispersion. The dispersion temperature is controlled at 25-45℃. After dispersion, the stirring speed is turned to medium speed, and a chain extender is added to extend the chain through water inlet to obtain an aqueous polyurethane emulsion. S5: Add acrylate monomers and initiators to the emulsion in step S4 to carry out in-situ emulsion polymerization to form a polyurethane / acrylate interpenetrating network structure; after the polymerization reaction is completed, cool the system to room temperature, filter, and obtain a highly stain-resistant and water-resistant aliphatic polyurethane topcoat.

7. The preparation method of a highly stain-resistant and water-resistant aliphatic polyurethane topcoat as described in claim 6, characterized in that, The heating and dehydration temperature in step S1 is 60°C for 1 hour; the prepolymerization reaction temperature is 75-85°C.

8. The method for preparing a highly stain-resistant and water-resistant aliphatic polyurethane topcoat as described in claim 6, characterized in that, The batching method described in step S2 is as follows: after each addition of hydroxyl-containing silicone oil, stir for 10-30 minutes to ensure full dispersion and reaction; the entire grafting stage reaction takes 1-3 hours.

9. The method for preparing a highly stain-resistant and water-resistant aliphatic polyurethane topcoat as described in claim 6, characterized in that, The reaction conditions for water-injected chain extension in step S4 are: the reaction temperature is room temperature, and the reaction time is 1-2 hours.

10. The method for preparing a highly stain-resistant and water-resistant aliphatic polyurethane topcoat as described in claim 6, characterized in that, The reaction conditions for the in-situ emulsion polymerization reaction in step S5 are: a reaction temperature of 50-80℃ and a reaction time of 3-5 hours.

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