Preparation method of water-based single-component plastic paint

Abstract

The present application relates to the technical field of curing glue paint, in particular to a preparation method of water-based single-component plastic paint. The water-based single-component plastic paint prepared by the present application overcomes the problems of poor environmental protection and difficult balance of comprehensive performance of paint film. The water-based single-component plastic paint is prepared by optimizing the preparation method and raw material system; the alicyclic isocyanate is selected and step-by-step reaction is combined with ring-opening epoxy resin, quercetin and disulfide to form a dense coating, so as to improve corrosion resistance and adhesion; hydrolyzed KH560 and polyurethane-polyurea composite system are used to introduce fluorine-containing monomers, so as to enhance water resistance and low-temperature stability; a three-dimensional network is constructed by free radical copolymerization, triethylamine is added to inhibit polymerization, and the feeding and post-ripening steps are optimized to balance the hardness, drying speed and surface state after cooking. The water-based single-component plastic paint of the present application is suitable for various plastic substrates such as automobile interior and exterior trim and 3C products, and has significant advantages in protection performance and construction adaptability.

Description

Technical Field

[0001] This invention relates to the field of curing adhesives and coatings, specifically to a method for preparing a water-based single-component plastic paint. Background Technology

[0002] Traditional plastic paints are mostly solvent-based coatings. Although they perform well in terms of adhesion, hardness, and durability, they contain a large amount of volatile organic compounds (VOCs), which have a serious impact on the environment and human health. With increasingly stringent environmental regulations and people's growing environmental awareness, water-based plastic paints have emerged and developed rapidly.

[0003] Currently, most water-based plastic paints on the market, especially water-based acrylic plastic paints, are two-component systems that require the addition of a hardener before use. This not only increases the complexity of application but also results in a limited activation period for the mixed paint, leading to waste. While single-component water-based plastic paints are convenient to apply, their performance, particularly in terms of corrosion resistance, stability, and freeze-thaw resistance, often falls short of solvent-based or two-component water-based paints. This is especially true in demanding fields such as automotive interiors and exteriors, 3C electronics, and home appliances, where the overall performance of the paint film is extremely critical, requiring excellent adhesion and hardness on the substrates.

[0004] Some waterborne single-component acrylic coating systems used in paint preparation may introduce small amounts of organic solvents as film-forming aids or leveling agents to improve performance, which contradicts the current advocacy of "zero VOC" or "ultra-low VOC" environmental protection concepts. Therefore, developing a waterborne single-component acrylic plastic paint coating that is free of organic solvents, purely water-based, has good surface condition after cooking before use, and exhibits excellent corrosion resistance, adhesion, and freeze-thaw resistance after curing has significant practical importance and market value.

[0005] Therefore, a method for preparing water-based single-component plastic paint is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing water-based single-component plastic paint. By optimizing the selection of isocyanate types and the stepwise reaction method, alicyclic isocyanates combined with open-ring epoxy resins are used to significantly improve the corrosion resistance and adhesion of the water-based single-component plastic paint. Dynamic disulfide bonds and phenolic hydroxyl groups synergistically delay oxidative degradation, and vacuum dehydration avoids bubble defects. For waterproofing and low-temperature stability, a hydrophobic silanol layer is formed by hydrolysis of a silane coupling agent, combined with a polyurethane-polyurea composite system. The rigid-flexible chain segment complementarity and fluorinated monomers enhance the hydrophobic and antifreeze capabilities, ensuring the coating maintains density during freeze-thaw cycles. A three-dimensional cross-linked network is constructed through free radical copolymerization, and a neutralizing agent is used to regulate the surface state after cooking. Stepwise chain extension and post-curing steps optimize drying efficiency, and dynamic bonds relieve internal stress, achieving a balance between high hardness, fast drying, and long-term stability. This technology is suitable for automotive interior and exterior trim, 3C electronics, home appliances, and other plastics, as well as acrylonitrile-butadiene-styrene copolymer (ABS), polycarbonate (PC), and carbon fiber substrates, exhibiting excellent comprehensive performance.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for preparing a water-based single-component plastic paint, the preparation method being as follows:

[0009] The dried polyurethane prepolymer and polyurea prepolymer are thoroughly mixed to obtain a water-based one-component plastic paint precursor; the water-based one-component plastic paint precursor is added to the dispersed mixture for emulsification and dispersion, and after standing to defoam, the water-based one-component plastic paint is obtained; the water-based one-component plastic paint is heated and kept at a constant temperature for post-curing process before use; the VOCs content of the water-based one-component plastic paint is less than 5g / L.

[0010] The raw materials for preparing the mixture include deionized water, hydrolyzed KH560, 1,4-butanediol, tripropylene glycol diacrylate, potassium persulfate, and triethylamine.

[0011] The polyurethane prepolymer was prepared from diisocyanate, quercetin, 2-hydroxyethyl disulfide and ring-opening epoxy resin;

[0012] Polyurea prepolymers are obtained by reacting diisocyanates with diamines.

[0013] Preferably, by weight, the amount of polyurethane prepolymer is 80-100 parts; the amount of polyurea prepolymer is 24-40 parts; the amount of hydrolyzed KH560 is 5.5-7.5 parts; the amount of 1,4-butanediol is 4.0-5.5 parts; the amount of tripropylene glycol diacrylate is 7.2-8.0 parts; and the amount of deionized water is 100-1000 parts.

[0014] Further preferred, the amount of deionized water used is 420-500 parts.

[0015] Preferably, the post-curing temperature is 65-75℃, the curing time is 3-7h, and the dispersion speed is 1500-2500r / min.

[0016] Preferably, the preparation method of polyurethane prepolymer is as follows: Diisocyanate and N,N-dimethylformamide are added to a four-necked flask, heated, and then dibutyltin dilaurate, 1 / 2 mass of quercetin, and 1 / 2 mass of 2-hydroxyethyl disulfide are added and reacted. The remaining quercetin and 2-hydroxyethyl disulfide are added and the temperature is raised and reacted. The temperature is lowered, and then ring-opening epoxy resin is added and reacted to obtain a polyurethane prepolymer precursor. After cooling, the prepolymer is neutralized to obtain a polyurethane prepolymer. The method for determining the -NCO content in the reaction degree is based on ASTM D2572-87 "Standard Test Method for Isocyanate Groups in Carbamate Materials or Prepolymers".

[0017] Preferably, the diisocyanate is one of 4,4-diisocyanate dicyclohexylmethane and isophorone diisocyanate; the amount of diisocyanate is 68.9-84.0 parts; the total amount of quercetin is 30.2-36.3 parts; and the total amount of 2-hydroxyethyl disulfide is 15.4-18.5 parts.

[0018] Preferably, the preparation method of the open-ring epoxy resin is as follows: Epoxy resin is added to a four-necked flask equipped with a thermometer, stirrer and reflux condenser. After heating, glycidyl methacrylate and boron trifluoride-amine complex are added dropwise. The mixture is stirred, hydroquinone is added, and the reaction continues after heating to obtain a modified epoxy resin. The modified epoxy resin is cooled, and N,N-dimethylformamide is added. The mixture is stirred to obtain the open-ring epoxy resin. The hydroxyl value of the epoxy resin E55 is 40-60 mg KOH / g.

[0019] Preferably, the preparation method of polyurea prepolymer is as follows: diisocyanate and N,N-dimethylformamide are added to a four-necked flask, the temperature is raised, and then a diamine solution is added dropwise. After the addition is completed, the temperature is raised to react and the polyurea prepolymer is obtained; the diamine solution is obtained by mixing and dissolving diamine and N,N-dimethylformamide.

[0020] Preferably, the diamine is one of isophorone diamine, diethyltoluene diamine, 4,4'-diaminodicyclohexylmethane, and 2,2'-di(trifluoromethyl)diaminobiphenyl.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. By optimizing the selection of isocyanate types and the stepwise reaction method, the corrosion resistance and adhesion of water-based single-component plastic paint are significantly improved. Alicyclic isocyanates are used instead of traditional aliphatic isocyanates. Combined with a staged feeding strategy, the crosslinking density and reaction process are precisely controlled to form a highly dense coating structure. The resulting polyurethane and polyurea polymers—isocyanate-quercetin-isocyanate-2-hydroxyethyl disulfide-isocyanate-open-ring epoxy resin—effectively block the penetration of corrosive media. The introduction of open-ring epoxy resin allows its hydroxyl groups to react with isocyanate groups to form urethane bonds. Simultaneously, the double bonds participate in subsequent free radical crosslinking, not only filling the micropores of the paint film but also enhancing interfacial adhesion. The synergistic effect of the phenolic hydroxyl groups of quercetin and the dynamic disulfide bonds of 2-hydroxyethyl disulfide delays oxidative degradation and improves coating flexibility, further inhibiting the decrease in adhesion caused by stress cracking. Vacuum dehydration during raw material pretreatment prevents the generation of carbon dioxide bubbles from the source, ensuring the integrity of the paint film and long-term protective performance.

[0023] 2. To enhance the coating's waterproofness and low-temperature stability, a hydrophobic silanol layer is generated through the hydrolysis of a silane coupling agent, which, combined with a polyurethane-polyurea composite system, achieves synergistic performance. Hydrolyzed KH560 forms a covalently bonded silanol network on the substrate surface under weakly acidic conditions, significantly reducing the surface energy of the coating film and blocking moisture penetration. Simultaneously, the epoxy groups of hydrolyzed KH560 react with the isocyanates of polyurethane and polyurea. The rigid structure of the polyurea prepolymer complements the flexible segments of the polyurethane, suppressing microcracks caused by thermal shrinkage stress in low-temperature environments and maintaining the coating's density. The introduction of fluorinated monomers and dynamic chain extenders further optimizes the hydrophobic effect and freeze-thaw resistance. The high bond energy of the polyurea bonds synergistically with the elasticity of the polyurethane ensures that the coating film does not undergo phase separation or interfacial peeling during repeated freeze-thaw cycles, thus balancing waterproof performance and low-temperature adaptability.

[0024] 3. Achieving a high-efficiency balance through free radical polymerization and cross-linking network design enables the application of water-based single-component plastic paints in automotive interior and exterior trims, 3C electronic products, home appliances, and on substrates such as ABS, PC, and carbon fiber. The unsaturated double bonds of tripropylene glycol diacrylate and ring-opening epoxy resin undergo free radical copolymerization initiated by potassium persulfate, forming a three-dimensional interpenetrating network structure that imparts high hardness and wear resistance to the coating. The addition of the neutralizing agent triethylamine effectively inhibits the self-polymerization reaction of the silane coupling agent and blocks the runaway free radical chain reaction by neutralizing the acidic environment, ensuring the stability of the prepolymer. Furthermore, the stepwise feeding chain extension method and post-curing treatment optimize the cross-linking density and solvent evaporation path, shortening drying time while avoiding film defects. The synergistic cross-linking design of polyurethane and polyurea not only improves mechanical strength but also alleviates internal stress through dynamic disulfide bonds, ultimately achieving a unified high hardness, fast drying, and surface condition after long-term boiling. Attached Figure Description

[0025] Figure 1 The graph shows the test results of surface drying time and actual drying time for Examples 7-10, Comparative Examples 3, 5, 6, 8, 10 and 14-21 of the water-based single-component plastic paint of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Please see Figure 1 This invention provides a method for preparing a water-based single-component plastic paint, the technical solution of which is as follows:

[0028] The substances involved in this invention have the following information: isophorone diisocyanate (IPDI) CAS: 4098-71-9; quercetin CAS: 117-39-5; 2-hydroxyethyl disulfide CAS: 1892-29-1; glycidyl methacrylate CAS: 106-91-2; isophorone diamine CAS: 2855-13-2; diethyltoluene diamine CAS: 68479-98-1; 1,2-propanediamine CAS: 78-90-0; 4,4'-di... Aminodicyclohexylmethane CAS: 1761-71-3; 2,2'-Di(trifluoromethyl)diaminobiphenyl CAS: 341-58-2; 1,4-Butanediol CAS: 110-63-4; Tripropylene glycol diacrylate CAS: 42978-66-5; 4,4-Diisocyanate dicyclohexylmethane (HMDI) CAS: 5124-30-1; Boron trifluoride-amine complex CAS: 75-23-0; Defoamer purchased from Guangdong Shierli New Materials Co., Ltd. 5010s emulsion defoamer.

[0029] Example 1

[0030] Raw material pretreatment: Epoxy resin E55 was vacuum dried at 110℃ for 3 hours, cooled, and sealed for later use; isophorone diamine, quercetin, and 2-hydroxyethyl disulfide were vacuum dried at 80℃ for 4 hours for later use; glycidyl methacrylate and isophorone diisocyanate were pretreated before use. Molecular sieve dehydration treatment;

[0031] Preparation of open-ring epoxy resin: 37.0 g of epoxy resin E55 was added to a four-necked flask equipped with a thermometer, stirrer and reflux condenser. The temperature was raised to 70 °C, and 7.1 g of glycidyl methacrylate and 0.2 g of boron trifluoride-amine complex were slowly added dropwise over a period of 30 min. The mixture was stirred at 80 °C for 1 h, and 0.1 g of hydroquinone was added. The temperature was raised to 95 °C and the reaction was continued for 4 h to obtain modified epoxy resin. After cooling the modified epoxy resin, 50 mL of N,N-dimethylformamide was added to obtain open-ring epoxy resin.

[0032] Preparation of polyurethane prepolymer: 68.9 g of IPDI and 50 mL of N,N-dimethylformamide were added to a four-necked flask, heated to 60 °C, and 0.08 g of dibutyltin dilaurate, half the mass of quercetin, and half the mass of 2-hydroxyethyl disulfide were added. The mixture was reacted for 0.5 h. The remaining quercetin and 2-hydroxyethyl disulfide were added, and the mixture was heated to 90 °C and reacted for 3 h until the -NCO content reached the theoretical value. The temperature was then lowered to 75 °C, and the ring-opening epoxy resin obtained above was added. The mixture was reacted for 2 h until the -NCO content reached the theoretical value. The temperature was then lowered to below 40 °C, and 0.5 g of TEA was added for a neutralization reaction for 5 min to obtain the polyurethane prepolymer. The amounts of quercetin and 2-hydroxyethyl disulfide were 30.2 g and 15.4 g, respectively.

[0033] Preparation of polyurea prepolymer: 48.9 g IPDI and 50 mL N,N-dimethylformamide were added to a four-necked flask, and the temperature was raised to 70 °C. Isoflurane diamine solution was added dropwise over 0.5 h, and the temperature was controlled to remain below 80 °C. After the addition was completed, the temperature was raised to 80 °C and reacted for 4 h to obtain polyurea prepolymer. The isoflurane diamine solution was obtained by dissolving 17.0 g isoflurane diamine and 50 mL N,N-dimethylformamide.

[0034] 16.4g KH560 was added to a flask, and 2mL of 35% acetic acid aqueous solution was added dropwise while stirring. After the addition was complete, the mixture was stirred at 40℃ for 2h to hydrolyze the solution. The pH of the reaction was 3. The solution was then dried to remove water to obtain hydrolyzed KH560.

[0035] The polyurethane prepolymer and polyurea prepolymer were vacuum dried to remove N,N-dimethylformamide and water. 90g of the dried polyurethane prepolymer and 30g of the polyurea prepolymer were thoroughly mixed to obtain a water-based single-component plastic paint precursor. The water-based single-component plastic paint precursor was added to the mixture, which was dispersed at 2000 r / min, and emulsified and dispersed for 10 min. After standing and defoaming, the water-based single-component plastic paint was obtained. The mixture contained 450 mL of deionized water, 6.0g of hydrolyzed KH560, 4.5g of 1,4-butanediol, 7.5g of tripropylene glycol diacrylate, 1.0g of defoamer, 2.5g of Tween 80, 0.5g of potassium persulfate, and 1.0g of triethylamine.

[0036] The application method of water-based single-component plastic paint is as follows: Before coating, pre-treat the plastic surface by wiping it with organic solvents such as alcohol to remove surface oil, dust and other impurities; Coating: After completing the surface pre-treatment, spray the water-based single-component plastic paint to enhance the wetting and adhesion of the plastic surface. The spray gun pressure is 0.3Pa, the spray thickness is 10 micrometers, and after a post-curing process of keeping it at 70℃ for 40 minutes, the paint film is obtained by natural drying.

[0037] Examples 2-4

[0038] Unlike Example 1, the preparation method of the polyurethane prepolymer was changed, as shown in Table 1. The initial addition amounts of quercetin and 2-hydroxyethyl disulfide were the mass ratios of their total addition amounts.

[0039] Table 1. Preparation methods of polyurethane prepolymers

[0040]

[0041] Unless otherwise specified, the other steps of the comparative example are consistent with the preparation method of Example 1.

[0042] Comparative Example 1 replaced IPDI with an equal mass of hexamethylene diisocyanate.

[0043] In Comparative Example 2, IPDI was not added in two separate additions, but rather added together with N,N-dimethylformamide during the initial feed of raw materials.

[0044] Comparative Example 3 did not contain any ring-opening epoxy resin.

[0045] In Comparative Example 4, the epoxy resin was not treated with glycidyl methacrylate. Instead, diethylamine (approximately 7.3 g) and N,N-dimethylformamide (50 mL) were directly added to it. The mixture was stirred at 60 °C for 4 h, cooled, and then sealed for storage to obtain an open-ring epoxy resin.

[0046] Comparative Example 5 did not contain quercetin.

[0047] Comparative Example 6 did not contain 2-hydroxyethyl disulfide.

[0048] Comparative Example 7: Quercetin and 2-hydroxyethyl disulfide were added simultaneously with dibutyltin dilaurate, rather than in a stepwise manner.

[0049] In Comparative Example 8, no polyurethane prepolymer was added during the preparation of the water-based single-component plastic paint precursor, and the amount of polyurea prepolymer added was 120g.

[0050] Experimental Example 1

[0051] The water-based single-component plastic paints obtained in the above examples and comparative examples were subjected to corrosion resistance and mechanical property tests. The corrosion resistance performance of the paint film was evaluated by the salt spray test method. The corrosion resistance performance was tested according to ISO 9227-2017. After the water-based single-component plastic paint was sprayed onto the plastic and dried, the plastic was placed in a salt spray chamber and continuously sprayed with 5.0wt% NaCl solution at 35℃±1℃. The paint film was observed regularly for blistering, rusting and other phenomena, and the time when blistering and rusting occurred was recorded.

[0052] The adhesion was tested according to the method in GB / T9286-1998, using the cross-cut adhesion test, where a cross-cut is made with a scalpel (1 mm apart). The adhesion was graded as 0, 1, 2, 3, 4, and 5, with grade 0 being the best. The final test results are shown in Table 2.

[0053] Table 2 Results of corrosion resistance and adhesion tests

[0054] Salt spray tolerance time (h) Adhesion rating (level) Example 1 240 0 Example 2 216 0 Example 3 192 0 Example 4 192 0 Comparative Example 1 72 2 Comparative Example 2 96 1 Comparative Example 3 48 3 Comparative Example 4 72 1 Comparative Example 5 48 4 Comparative Example 6 48 3 Comparative Example 7 120 2 Comparative Example 8 24 5

[0055] The polyurethane prepolymer prepared according to the preparation method of the present invention, and the water-based single-component plastic paint prepared therefrom, have good corrosion resistance and good adhesion. Firstly, the raw materials are dehydrated to prevent the formation of carbon dioxide bubbles from the reaction of water and isocyanate during later reactions, which could lead to defects in the paint. In the preparation of the ring-opening epoxy resin, glycidyl methacrylate and epoxy resin E55 undergo ring-opening under the catalysis of BF3·amine complex, and the epoxy groups react with the hydroxyl groups of glycidyl methacrylate to form a modified epoxy resin. The introduction of double bonds enhances crosslinking ability and improves the weather resistance and adhesion of the paint film. In the preparation of polyurethane, diisocyanate groups react with the phenolic hydroxyl groups of quercetin and the hydroxyl groups of 2-hydroxyethyl disulfide to form polyurethane. By adding the ring-opening epoxy resin, which reacts with the isocyanate groups through hydroxyl groups, epoxy groups and unsaturated double bonds are introduced into the system. Adjusting the order of diisocyanate addition further results in a polyurethane polymer of isocyanate-quercetin-isocyanate-2-hydroxyethyl disulfide-isocyanate-ring-opening epoxy resin. After mixing with the prepared polyurea polymer and undergoing a curing reaction, a water-based single-component plastic paint is obtained. Examples 1-4 optimized and adjusted the type and amount of diisocyanate used, the reaction temperature at different stages, and the amounts of quercetin and 2-hydroxyethyl disulfide, thereby enabling the water-based single-component plastic paint to have good adhesion, salt spray resistance for 192-240 hours, and good corrosion resistance.

[0056] Comparative Example 1, by replacing the alicyclic isocyanate of the previous example with an aliphatic one, resulted in insufficient crosslinking density, reduced salt spray resistance time, and poor adhesion. In Comparative Example 2, IPDI was not added in two stages but rather simultaneously with N,N-dimethylformamide during the initial raw material addition. This prevented the polyurethane prepolymer from having completely isocyanate end groups, hindering crosslinking with 1,4-butanediol and hydrolyzed KH560 during later curing, thus degrading overall performance. Comparative Example 3 lacked epoxy resin crosslinking sites, leading to increased film porosity, reduced salt spray resistance time, and minimal adhesion. Comparative Example 4 did not use glycidyl methacrylate to treat the epoxy resin, resulting in a final system lacking unsaturated acrylates and unable to react with tripropylene glycol dipropylene. Crosslinking and curing of esters reduces corrosion resistance and adhesion; Comparative Example 5, lacking quercetin, suffers from the absence of phenolic hydroxyl groups, leading to the inability to terminate free radicals, resulting in easy oxidation and degradation of the paint film, reduced salt spray resistance time, and decreased adhesion; Comparative Example 6, lacking 2-hydroxyethyl disulfide, fails to introduce dynamic disulfide bonds into the system, resulting in insufficient flexibility and oxidation resistance, increased brittleness of the paint film, and decreased overall corrosion resistance and performance; Comparative Example 7, with the simultaneous addition of quercetin, 2-hydroxyethyl disulfide, and dibutyltin dilaurate, exhibits incomplete reaction, increased byproducts, and uneven crosslinking structure; Comparative Example 8, lacking polyurethane prepolymer and using only rigid polyurea, suffers from excessively high rigidity, mismatched with the thermal expansion coefficient of the substrate, resulting in poor adhesion and easy detachment, exhibiting the worst adhesion and the shortest salt spray resistance time.

[0057] Example 5

[0058] Unlike Example 1, the preparation method of the polyurea prepolymer was changed, in which the isoflurane diamine solution was replaced with diethyltoluene diamine solution; the diethyltoluene diamine solution was obtained by dissolving 17.8g of diethyltoluene diamine and 50mL of N,N-dimethylformamide.

[0059] Example 6

[0060] Unlike Example 1, the preparation method of the polyurea prepolymer was changed, in which the isoflurane diamine solution was replaced with a 4,4'-diaminodicyclohexylmethane solution; the 4,4'-diaminodicyclohexylmethane solution was obtained by dissolving 21.0 g of 4,4'-diaminodicyclohexylmethane and 50 mL of N,N-dimethylformamide.

[0061] Example 7

[0062] Unlike Example 1, the preparation method of the polyurea prepolymer was changed, wherein the isophorone diamine solution was replaced with 2,2'-di(trifluoromethyl)diaminobiphenyl solution; the 2,2'-di(trifluoromethyl)diaminobiphenyl solution was obtained by dissolving 32.0 g of 2,2'-di(trifluoromethyl)diaminobiphenyl and 50 mL of N,N-dimethylformamide.

[0063] Comparative Example 9

[0064] Unlike Example 1, the preparation method of the polyurea prepolymer was changed, in which the isoflurane diamine solution was replaced with a 1,2-propanediamine solution; the 1,2-propanediamine solution was obtained by dissolving 7.4 g of 1,2-propanediamine and 50 mL of N,N-dimethylformamide.

[0065] Comparative Example 10

[0066] Unlike Example 1, no polyurea prepolymer was added during the preparation of the water-based single-component plastic paint, and the amount of polyurethane prepolymer was adjusted to 120g.

[0067] Comparative Example 11

[0068] Unlike Example 1, hydrolyzed KH560 was not added.

[0069] Comparative Example 12

[0070] Unlike Example 1, in the preparation of the polyurea prepolymer, 48.9 g of IPDI was replaced with an equal mass of hexamethylene diisocyanate.

[0071] Comparative Example 13

[0072] Unlike Example 1, in the preparation of the polyurea prepolymer, the temperature was directly raised to 80°C for reaction; and the isophorone diamine solution was added directly instead of being slowly added dropwise over 0.5 hours.

[0073] Experiment Example 2

[0074] The water-based single-component plastic paints prepared in Examples 1, 5-7, and Comparative Examples 3, 5, 6, and 8-13 were tested for waterproofing and freeze-thaw resistance. The freeze-thaw resistance of the water-based single-component plastic paint emulsions was tested according to GB / T9268-2008, involving freeze-thaw cycle testing. The emulsions were placed in a freezer at -10℃ for 18 hours, then removed and placed at 25℃ for 6 hours, repeating this cycle 10 times. The emulsion's condition was then observed. A 150μm layer of semi-cured water-based single-component plastic paint was applied using a four-sided applicator and dried in an 80℃ oven for 24 hours. The water contact angle was measured using a contact angle meter. The final test results are shown in Table 3.

[0075] Observe the emulsion in the bottle for any clumping, sedimentation, or layering. If there is no change, the emulsion has passed the freeze-thaw stability test.

[0076] Table 3 Results of Waterproofing and Freeze-Thaw Resistance Tests

[0077]

[0078]

[0079] The polyurea prepolymer prepared according to the method of this invention is mixed with a polyurethane prepolymer and then with other substances in the mixture. The resulting waterborne single-component plastic paint precursor exhibits good freeze-thaw resistance. After cross-linking and curing, the resulting waterborne single-component plastic paint exhibits good hydrophobicity. Under the conditions of Examples 1 and 5-7, the water contact angle is 90.2°-98.1°, and the waterborne single-component plastic paint precursor emulsion remains normal after cyclic freeze-thaw cycles. During the preparation of the polyurea polymer, polyurea bonds are generated through the reaction of diisocyanate and amino groups. These bonds, combined with polyurethane, have a higher bond energy than polyurethane, resulting in superior hydrolysis resistance and stability. Hydrolyzing KH560 to silanol under acidic conditions and then co-polymerizing it in the system further enhances the waterproofing effect. Under the conditions of Example 1, hydrolysis of KH560 forms a hydrophobic silanol layer, and the polyurethane-polyurea synergistic cross-linking enhances density. The balance between the flexibility of polyurethane and the rigidity of polyurea results in a stable cross-linked network. No phase separation at low temperatures; In Example 5, isoflurane diamine for preparing polyurea prepolymer was replaced with diethyltoluene diamine, introducing benzene rings to increase crosslinking density, but the hydrophobicity was slightly lower than in Example 1; In Example 6, 4,4'-diaminodicyclohexyl was used to prepare polyurea prepolymer. The alicyclic amine structure enhanced hydrophobicity, the crosslinking network was denser, and the cyclohexyl structure was resistant to low-temperature shrinkage, resulting in uniform emulsion dispersion; In Example 7, 2,2'-di(trifluoromethyl)diaminobiphenyl was used as a reactant. The trifluoromethyl strong hydrophobic group significantly improved the surface energy, and in synergy with hydrolyzed KH560, the contact angle reached its maximum. The fluorinated structure inhibited ice crystal formation, resulting in excellent freeze-thaw stability.

[0080] Comparative Example 3 lacks epoxy resin crosslinking sites, resulting in high film porosity, enhanced hydrophilicity, and incomplete crosslinking, leading to emulsion phase separation during freeze-thaw cycles. Comparative Example 5, lacking quercetin, suffers from slight oxidative degradation of the film due to the absence of phenolic hydroxyl groups, decreased hydrophobicity, unterminated free radicals, and aggregation of by-reaction products, resulting in precipitation during freeze-thaw cycles. Comparative Example 6 lacks thioether bonds (-SS-), resulting in insufficient dynamic crosslinking, reduced film density, and insufficient flexibility, leading to microphase separation during freeze-thaw cycles. Comparative Example 8, with only polyurea prepolymer added, exhibits excessive rigidity, surface microcracks causing a slight decrease in hydrophobicity, and a mismatch with the thermal expansion coefficient of the substrate, resulting in interfacial peeling during freeze-thaw cycles. Comparative Example 9 uses 1,2-propanediamine short-chain amine. The following results were observed: Low polyurea crosslinking density, hydrophilic paint film, short molecular chains, and uneven emulsion dispersion. Comparative Example 10, without polyurea prepolymer, exhibited excessively strong flexibility and insufficient density in pure polyurethane, with a normal emulsion. The polyurethane showed resistance to low-temperature shrinkage but weak protective properties. Comparative Example 11 lacked silane coupling agent, resulting in poor adhesion between the paint film and substrate, strong hydrophilicity, insufficient interfacial adhesion, and peeling during freeze-thaw cycles. Comparative Example 12 had low HDI crosslinking density, resulting in a loose paint film, decreased hydrophobicity, poor low-temperature resistance of the aliphatic isocyanate, and insufficient emulsion stability. Comparative Example 13 directly added isoflurane diamine, leading to rapid reaction, uneven crosslinking, a rough and hydrophilic surface, and localized over-crosslinking, resulting in the worst emulsion dispersion.

[0081] Examples 8-10

[0082] Unlike Example 7, the preparation method of the water-based single-component plastic paint and the heat preservation temperature and time used have been adjusted, as shown in Table 4.

[0083] Table 4. Preparation methods and application conditions of water-based single-component plastic paint

[0084]

[0085] Unless otherwise specified, the preparation methods in the comparative examples are the same as those in Example 7, except for the following changes in conditions.

[0086] The high-speed dispersion speed of Comparative Example 14 was 1000 r / min.

[0087] Comparative Example 15 used 1L of deionized water.

[0088] Comparative Example 16 used 100 mL of deionized water.

[0089] Comparative Example 17 did not undergo a heat preservation and post-curing process, i.e., it was cured at room temperature.

[0090] The insulation temperature for Comparative Example 18 was 100℃.

[0091] Comparative Example 19 did not contain 1,4-butanediol.

[0092] Comparative Example 20: Tripropylene glycol diacrylate was not added.

[0093] Comparative Example 21 did not contain potassium persulfate or triethylamine.

[0094] Experimental Example 3

[0095] The water-based single-component plastic paints prepared in Examples 7-10 and Comparative Examples 3, 5, 6, 8, 10, and 14-21 were tested for drying time, surface hardness, film condition, and surface condition after boiling. The paint films were dried in a forced-air drying oven at 25°C for 7 days, and then the film hardness was tested according to the test method specified in GB / T 6739-2006. Surface drying and complete drying time tests were performed according to GB 1728-79(89). The surface condition was observed after boiling at 80°C for 4 hours. The final test results are shown in Table 5. Figure 1 As shown, the hardness results decrease in the order of H, HB, B, and 2B.

[0096] Table 5. Overall Performance Test Results

[0097]

[0098]

[0099] The water-based paint film prepared according to the method of the present invention has good comprehensive properties, as shown in Table 5 and Figure 1As shown, under the conditions of Examples 7-10, the hardness was H, the surface drying time was 18-30 min, and the complete drying time was 15-25 h. After steaming, the surface was normal. The paint film surfaces of the examples were all normal, while the paint films of the comparative examples all showed varying degrees of blistering, loss of gloss, and paint peeling. By optimizing the preparation methods of polyurethane prepolymer, polyurea prepolymer, and the mixture, a water-based single-component plastic paint with excellent comprehensive performance is achieved. Hydrolyzed KH560 and 1,4-butanediol added to the mixture react with the terminal isocyanate groups in the polyurethane and polyurea prepolymers during post-curing and drying, forming a tightly linked cross-linked structure. The added tripropylene glycol diacrylate copolymerizes with the unsaturated double bonds of the ring-opening epoxy resin in the polyurethane prepolymer. Potassium persulfate decomposes during post-curing at 70°C, generating sulfate free radicals that attack the unsaturated double bonds (C=C) in the tripropylene glycol diacrylate and ring-opening epoxy resin, initiating a free radical polymerization reaction. After the reaction, monomer molecules are continuously added to the free radical chains, causing the polymer chains to grow continuously and ultimately promoting the formation of a cross-linked network structure. By adding triethylamine, the aggregation phenomenon caused by the hydrolysis of KH560 is avoided, ensuring the stability of the water-based single-component plastic paint. The reaction of KH560 is carried out under acidic conditions. Triethylamine (an alkaline substance) can neutralize the residual acetic acid, adjust the pH of the system to weakly alkaline, inhibit the further condensation reaction of silanol, and prevent the silane coupling agent from self-polymerizing into gel during storage. In addition, triethylamine, as an electron donor, can capture the residual free radicals in the system and the chain-terminating free radicals after the reaction of acrylate, blocking the continuation of the free radical chain reaction, preventing the double bonds in the prepolymer from polymerizing prematurely during storage, ensuring the single-component stability of the coating, and improving the water resistance of the final paint film at high temperatures.

[0100] Comparative Example 3, without the addition of open-ring epoxy resin, suffers from missing crosslinking sites, resulting in high coating porosity, decreased mechanical strength, incomplete crosslinking, and excessive solvent residue, hindering evaporation and thus prolonging surface drying and complete drying times. Uneven emulsion dispersion, the absence of the heat-resistant effect of open-ring epoxy resin, and the inability of dipropylene glycol diacrylate in the mixture to polymerize via unsaturated double bonds further degrade the final surface condition after cooking. Comparative Example 5, without the addition of quercetin, suffers from the absence of phenolic hydroxyl groups, leading to easy oxidative degradation of the paint film, increased coating brittleness, decreased hardness, and prolonged drying time. While the benzene ring structure of quercetin enhances heat resistance, its absence reduces cooking resistance. Comparative Example 6, lacking 2-hydroxyethyl disulfide, suffers from missing thioether bonds, insufficient dynamic crosslinking, reduced density, decreased hardness, and insufficient chain segment flexibility, resulting in slower film formation and a deteriorated surface condition after cooking. Comparative Example 8, with only polyurea prepolymer, exhibits excessively high rigidity, leading to a mismatch between the polyurea and the substrate's thermal expansion, resulting in surface microcracks and the lowest hardness. The lack of flexible polyurethane chains obstructs solvent evaporation pathways, prolonging drying time. Comparative Example 10, with only polyurethane prepolymer, suffers from excessively high flexibility and insufficient rigidity. Furthermore, the low self-crosslinking efficiency of polyurethane chains prolongs film formation time, leaving solvent residue in undispersed areas and causing uneven evaporation. Comparative Example 14 exhibits insufficient dispersion speed, resulting in incomplete dispersion and a small emulsion particle size. The film was large, rough, and had reduced surface hardness. Solvent residue remained in undispersed areas, and evaporation was uneven. In Comparative Example 15, excessive dilution led to insufficient crosslinking density, resulting in a loose film and significantly reduced hardness. The excessive amount of deionized water prolonged the solvent evaporation path, significantly increasing drying time. In Comparative Example 16, insufficient water resulted in excessively high emulsion viscosity, uneven dispersion, and reduced hardness compared to Example 7. The drying time was significantly shorter than in Example 7, but the surface condition of the water-based single-component plastic paint after cooking was significantly worse. In Comparative Example 17, the lack of heat preservation and post-curing processes resulted in incomplete crosslinking, a loose film, prolonged curing time, and severe blistering, loss of gloss, and paint peeling after cooking. In Comparative Example 18, high temperature caused some chain segments to... Thermal decomposition and structural damage, rapid solvent evaporation but excessive crosslinking shrinkage, resulted in microcracks and numerous paint bubbles, leading to a decline in the overall performance of the paint film. Comparative Example 19 lacked a chain extender, resulting in short molecular chains, low crosslinking density, and failure to form a stable network. Solvent retention caused blistering, loss of gloss, and paint peeling on the paint film surface after cooking. Comparative Example 20 did not add tripropylene glycol diacrylate, resulting in missing double bond crosslinking sites, insufficient coating density, and impact on subsequent free radical polymerization, leading to a decrease in film formation rate. Comparative Example 21 lacked an initiator, preventing polymerization between unsaturated double bonds and lacking inhibitors. Hydrolysis of KH560 led to agglomeration, free radical self-polymerization, and a chaotic crosslinking pathway, resulting in a decline in the overall performance of the paint film and a significant deterioration in surface condition after cooking.

[0101] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a water-based single-component plastic paint, characterized in that: The preparation method is as follows: The dried polyurethane prepolymer and polyurea prepolymer are thoroughly mixed to obtain a water-based one-component plastic paint precursor; the water-based one-component plastic paint precursor is added to the dispersed mixture for emulsification and dispersion, and after standing to defoam, the water-based one-component plastic paint is obtained; after heating and holding at a certain temperature, it is used for post-curing process. The raw materials for preparing the mixture include deionized water, hydrolyzed KH560, 1,4-butanediol, tripropylene glycol diacrylate, potassium persulfate, and triethylamine. The polyurethane prepolymer is prepared from diisocyanate, quercetin, 2-hydroxyethyl disulfide and ring-opening epoxy resin; The polyurea prepolymer is obtained by reacting diisocyanate with diamine; The preparation method of the open-ring epoxy resin is as follows: Epoxy resin is added to a four-necked flask equipped with a thermometer, stirrer and reflux condenser. After heating, glycidyl methacrylate and boron trifluoride-amine complex are added dropwise. After stirring, hydroquinone is added. After heating, the reaction continues to obtain modified epoxy resin. The modified epoxy resin is cooled, N,N-dimethylformamide is added, and the mixture is stirred to obtain the open-ring epoxy resin.

2. The method for preparing a water-based single-component plastic paint according to claim 1, characterized in that: The amount of the polyurethane prepolymer is 80-100 parts by weight; the amount of the polyurea prepolymer is 24-40 parts; the amount of hydrolyzed KH560 is 5.5-7.5 parts; the amount of 1,4-butanediol is 4.0-5.5 parts; the amount of tripropylene glycol diacrylate is 7.2-8.0 parts; and the amount of deionized water is 420-500 parts.

3. The method for preparing a water-based single-component plastic paint according to claim 1, characterized in that: The post-curing temperature is 65-75℃, and the curing time is 3-7h; the dispersion speed is 1500-2500r / min.

4. The method for preparing a water-based single-component plastic paint according to claim 1, characterized in that: The preparation method of the polyurethane prepolymer is as follows: the diisocyanate and N,N-dimethylformamide are added to a four-necked flask, heated, and then dibutyltin dilaurate, 1 / 2 mass of the quercetin and 1 / 2 mass of the 2-hydroxyethyl disulfide are added and reacted. The remaining quercetin and the 2-hydroxyethyl disulfide are added and the temperature is raised and reacted. The temperature is lowered, and the ring-opening epoxy resin is added and reacted to obtain the polyurethane prepolymer precursor. After cooling, the mixture is neutralized to obtain the polyurethane prepolymer.

5. The method for preparing a water-based single-component plastic paint according to claim 4, characterized in that: The diisocyanate used to prepare the polyurethane prepolymer is one of 4,4-diisocyanate dicyclohexylmethane and isophorone diisocyanate; the amount of the diisocyanate used to prepare the polyurethane prepolymer is 68.9-84.0 parts; the total amount of quercetin is 30.2-36.3 parts; and the total amount of 2-hydroxyethyl disulfide is 15.4-18.5 parts.

6. The method for preparing a water-based single-component plastic paint according to claim 1, characterized in that: The preparation method of the polyurea prepolymer is as follows: the diisocyanate and N,N-dimethylformamide are added to a four-necked flask, the temperature is raised, and the diamine solution is added dropwise. After the addition is completed, the temperature is raised to react and the polyurea prepolymer is obtained; the diamine solution is obtained by mixing and dissolving the diamine and N,N-dimethylformamide.

7. The method for preparing a water-based single-component plastic paint according to claim 6, characterized in that: The diamine is one of isoflurane diamine, diethyltoluene diamine, 4,4'-diaminodicyclohexylmethane, and 2,2'-di(trifluoromethyl)diaminobiphenyl.

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