A waterborne polyurethane hybrid emulsion, a preparation method and application thereof

Abstract

The present application belongs to the technical field of paint, and particularly relates to a water-based polyurethane composite emulsion, a preparation method and application thereof. The preparation raw materials of the water-based polyurethane composite emulsion include polyol, isocyanate, main chain extender, catalyst, neutralizing agent, acrylic ester monomer, emulsifier, initiator, post chain extender and water. The main chain extender includes hydrophilic chain extender, hard segment chain extender and functional chain extender. The hydrophilic chain extender includes sulfonic acid type chain extender and fluorine-containing chain extender. The hard segment chain extender includes cyclic chain extender and side chain type chain extender. The functional chain extender includes acetoacetic acid diol and adipic acid dihydrazide. The emulsifier includes anionic reactive emulsifier and non-ionic surfactant. The isocyanate includes aliphatic isocyanate. The water-based polyurethane composite emulsion has small particle size and good stability, and the prepared finish paint has excellent properties such as yellowing resistance, aging resistance, water resistance, self-repairing ability and spraying performance.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, and specifically relates to an aqueous polyurethane composite emulsion, its preparation method, and its application. Background Technology

[0002] With the deepening of urbanization and the public's increasing demands for a better life, purely functional pavements can no longer meet the comprehensive requirements of modern cities in terms of aesthetics, safety, and ecology. Road surface color modification technology is a key technological field that has emerged in response to this demand. It achieves a dual upgrade in both the appearance and performance of pavements by applying a colored functional coating to existing asphalt, concrete, or permeable pavements. After more than half a century of development, this technology has become an indispensable tool for urban renewal, traffic management, and spatial beautification.

[0003] Currently, the main raw materials for road surface color changing on the market are methyl methacrylate (MMA) topcoat and water-based acrylic topcoat. MMA topcoat is characterized by its extremely fast curing speed and short construction window, which requires strict control over the substrate preparation and construction rhythm. Moreover, the curing process has a strong monomer odor and poor environmental performance. Water-based acrylic topcoat uses water as the dispersion medium, has low VOC, and is safe and environmentally friendly, but it requires high-quality spraying equipment. After continuous immersion in water, the coating is prone to problems such as blistering, whitening, and decreased adhesion.

[0004] Therefore, it is of great significance to provide a topcoat with excellent resistance to yellowing, water resistance, adhesion, and self-healing ability. Summary of the Invention

[0005] The present invention aims to solve one or more technical problems existing in the prior art, and at least provide a beneficial solution. Specifically, the present invention provides a waterborne polyurethane composite emulsion with fine particle size and good stability; the prepared waterborne polyurethane-acrylic resin topcoat has excellent resistance to yellowing, water resistance, and adhesion, and also has good self-healing ability and sprayability.

[0006] The inventive concept of this invention: The raw materials for preparing the waterborne polyurethane composite emulsion of this invention include polyols, isocyanates, main chain extenders, catalysts, neutralizers, acrylate monomers, emulsifiers, initiators, post-chain extenders, and water; the main chain extenders include hydrophilic chain extenders, hard segment chain extenders, and functional chain extenders; the hydrophilic chain extenders include sulfonic acid chain extenders and fluorinated chain extenders; the hard segment chain extenders include cyclic chain extenders and side-chain chain extenders; the functional chain extenders include acetoacetic acid glycol and adipic acid dihydrazide; the emulsifiers include anionic reactive emulsifiers and nonionic surfactants; and the isocyanates include aliphatic isocyanates.

[0007] This invention utilizes the combined action of components such as polyols, isocyanates, main chain extenders, and acrylate monomers to form a core-shell emulsion with an aliphatic polyurethane as the "soft core" and an acrylate polymer as the "hard shell." The emulsion has a fine particle size and good stability. The prepared topcoat exhibits excellent resistance to yellowing, water resistance, self-healing ability, adhesion, and spraying performance. Furthermore, the improved resistance to yellowing also gives it good aging resistance.

[0008] The addition of acetoacetic acid diol and adipic acid dihydrazide in this invention can introduce acylhydrazone bonds, forming a large number of dynamic and reversible acylhydrazone crosslinking networks inside the polyurethane soft core, completing the core layer self-healing matrix, realizing the self-healing function, and solving the problem of irreversible coating scratches.

[0009] This invention employs a dual crosslinking design using cyclic chain extenders and side-chain chain extenders to achieve core self-crosslinking and shell grafting crosslinking, thereby improving the rigidity and density of the coating film and ensuring the bonding force at the core-shell interface. It can effectively solve the problem in the prior art where ordinary physical core-shell structures rely solely on physical encapsulation for bonding, resulting in weak interfacial bonding force and easy phase separation and coating peeling.

[0010] This invention employs a combination of sulfonic acid chain extenders and fluorinated chain extenders. During the emulsion synthesis stage, the sulfonic acid groups provide strong hydrophilicity and easy emulsification, ensuring the stability of the emulsion. During the coating film formation stage, the surface of the fluorinated chain segments segregates hydrophobicity, which can block the problem of increased water absorption caused by hydrophilic groups, thus solving the pain point that waterborne polyurethane (WPU) cannot simultaneously achieve both hydrophilic emulsification and water resistance.

[0011] Therefore, a first aspect of the present invention provides an aqueous polyurethane composite emulsion.

[0012] Specifically, the raw materials for preparing the waterborne polyurethane composite emulsion include polyol, isocyanate, main chain extender, catalyst, neutralizer, acrylate monomer, emulsifier, initiator, post-chain extender, and water; The main chain extender includes hydrophilic chain extenders, hard segment chain extenders, and functional chain extenders; The hydrophilic chain extender includes sulfonic acid chain extenders and fluorinated chain extenders; the hard segment chain extender includes cyclic chain extenders and side-chain chain extenders; the functional chain extender includes acetoacetic acid diol and adipic acid dihydrazide; The emulsifier includes anionic reactive emulsifiers and nonionic surfactants; The isocyanate includes aliphatic isocyanates.

[0013] Preferably, the mass ratio of the hydrophilic chain extender, the hard segment chain extender, and the functional chain extender is 1:(0.7-1):(1.2-1.5).

[0014] Preferably, the mass ratio of the sulfonic acid chain extender to the fluorinated chain extender is 1:(0.4-0.8); for example, the mass ratio is 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, etc.

[0015] Preferably, the sulfonic acid chain extender includes at least one of 2-aminoethyl sulfonate (AAS) and isophorone diisocyanate sulfonate diol (IPDU-S).

[0016] Preferably, the fluorinated chain extender includes at least one of polytetrafluoroethylene glycol, fluorinated hexanediol, and short-chain fluorinated alkyl glycol.

[0017] Preferably, the mass ratio of the cyclic chain extender to the side-chain chain extender is 1:(0.7-1.1); for example, the mass ratio is 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, etc.

[0018] Preferably, the cyclic chain extender comprises 1,4-cyclohexanediethanol (CHDM).

[0019] Preferably, the side-chain chain extender comprises trimethylolpropane monoallyl ether (TMPME).

[0020] Specifically, the dual crosslinking design of 1,4-cyclohexanediethanol and trimethylolpropane monoallyl ether enables core self-crosslinking and shell grafting crosslinking, improving the rigidity and density of the coating and ensuring the bonding force at the core-shell interface. At the same time, the trimethylolpropane monoallyl ether has double bonds attached to its side, enabling covalent grafting crosslinking between the polyurethane soft core and the acrylate shell. The core and shell are tightly bonded, with no phase separation or delamination issues, and the coating is not easy to peel off.

[0021] Preferably, the molar ratio of acetoacetic acid diol (DAA) to adipic dihydrazide (ADH) is 1:(0.8-1.2); for example, the molar ratio is 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, etc.

[0022] Preferably, the mass ratio of the anionic reactive emulsifier to the nonionic surfactant is (2-3):1; for example, the mass ratio is 2:1, 2.5:1, 3:1, etc.

[0023] Preferably, the anionic reactive emulsifier includes at least one of nonylphenol polyoxyethylene ether sulfate (SE-10N) and sodium allyloxyhydroxypropyl sulfonate (HAPS).

[0024] Preferably, the nonionic surfactant includes alkyl glycosides (APG).

[0025] Preferably, the polyol includes at least one of castor oil diol, cashew nut shell oil diol, and soybean oil polyol.

[0026] Specifically, the hydroxyl value of the polyol is 35-250 mgKOH / g. All polyols in this invention are derived from vegetable oil polyols, which are made from renewable vegetable oils (castor oil, soybean oil, etc.), making them natural and renewable resources that can be recycled, completely eliminating dependence on non-renewable petroleum resources. Furthermore, vegetable oil polyols themselves have no irritating odor and extremely low volatile organic compound (VOC) content, requiring no additional environmentally friendly additives. The prepared emulsions and coatings have no toxic or harmful residues and can naturally degrade after disposal, meeting environmental protection coating standards. They are suitable for environmentally friendly use scenarios such as indoor and outdoor humidity-regulating topcoats, and are especially suitable for the construction and home furnishing sectors with high environmental requirements.

[0027] Preferably, the aliphatic isocyanate includes at least one of isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI).

[0028] Specifically, by using an aliphatic raw material system, the yellowing resistance and aging resistance of the topcoat can be guaranteed.

[0029] Preferably, the acrylate monomers include hard monomers and soft monomers.

[0030] Preferably, the hard monomer includes at least one of methyl methacrylate, methyl acrylate, acrylic acid, methacrylic acid, and acrylonitrile.

[0031] Preferably, the soft monomer includes at least one of ethyl acrylate, butyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, isooctyl acrylate, and n-octyl acrylate.

[0032] Preferably, the chain extender comprises ethylenediamine.

[0033] Preferably, the catalyst includes at least one of dibutyltin dilaurate and stannous octoate.

[0034] Preferably, the neutralizing agent comprises triethylamine.

[0035] Preferably, the initiator includes at least one of ammonium persulfate, potassium persulfate, sodium persulfate, sodium bisulfite, and sodium metabisulfite.

[0036] Preferably, before use, the initiator is dissolved in water to prepare an aqueous solution with a mass concentration of 5-10%, which is then used as the initiator solution.

[0037] Preferably, the raw materials for preparing the waterborne polyurethane composite emulsion, by weight, include 18-25 parts of polyol, 4-9 parts of isocyanate, 1.5-3 parts of main chain extender, 0.01-0.05 parts of catalyst, 0.8-2 parts of neutralizer, 10-20 parts of acrylate monomer, 0.1-0.5 parts of emulsifier, 0.05-0.3 parts of initiator, 0.05-0.2 parts of post-chain extender, and 45-60 parts of water.

[0038] Preferably, the raw materials for preparing the waterborne polyurethane composite emulsion also include organic solvents.

[0039] Preferably, the organic solvent includes acetone.

[0040] Preferably, the raw materials for preparing the waterborne polyurethane composite emulsion, by weight, include 18-25 parts of polyol, 4-9 parts of isocyanate, 1.5-3 parts of main chain extender, 0.01-0.05 parts of catalyst, 0.8-2 parts of neutralizer, 10-20 parts of acrylate monomer, 0.1-0.5 parts of emulsifier, 0.05-0.3 parts of initiator, 0.05-0.2 parts of post-chain extender, 3.5-6 parts of organic solvent, and 45-60 parts of water.

[0041] A second aspect of the present invention provides a method for preparing the aqueous polyurethane composite emulsion described in the first aspect of the present invention.

[0042] Specifically, the preparation method of the waterborne polyurethane composite emulsion includes the following steps: The waterborne polyurethane composite emulsion is prepared by emulsion polymerization of the raw materials.

[0043] Preferably, the preparation method of the waterborne polyurethane composite emulsion includes the following steps: (1) The polyol, catalyst, and isocyanate are mixed in an organic solvent and reacted. An organic solution of the remaining main chain extender, except for adipic dihydrazide, is added. Finally, adipic dihydrazide is added and reacted to obtain a polyurethane prepolymer. (2) The polyurethane prepolymer is neutralized with a neutralizing agent, the neutralized polyurethane prepolymer is mixed with the first part of water and shear pre-emulsified, and the chain extender is added after vacuum distillation to obtain polyurethane seed emulsion. (3) The initiator and the second portion of water are mixed to obtain an initiator solution; (4) Mix the acrylate monomer, emulsifier and the remaining water, and emulsify to obtain a monomer pre-emulsion; (5) After the polyurethane seed emulsion is heated, the monomer pre-emulsion and initiator solution are added dropwise simultaneously, and the reaction is carried out under heat to obtain the product.

[0044] Specifically, this invention first prepares a polyurethane seed emulsion, then adds acrylate monomers. The monomers preferentially polymerize on the surface of the polyurethane latex particles, inhibiting the formation of new nuclei in the aqueous phase and gradually forming a coating structure. Simultaneously, a side-chain chain extender (such as TMPME chain extender containing double bonds) is introduced onto the polyurethane chain, which can covalently graft with the acrylate chain, strengthening the interfacial bonding between the two phases and stabilizing the core-shell morphology. Furthermore, due to the difference in physical properties between the flexible polyurethane chain and the rigid acrylate chain, a structurally stable "soft core-hard shell" composite emulsion is ultimately formed.

[0045] Preferably, in step (1), the polyol and the main chain extender other than adipic acid dihydrazide are first subjected to dehydration treatment to make them reach the polyurethane grade.

[0046] Preferably, the vacuum degree of the dehydration treatment is ≥-0.095MPa.

[0047] Preferably, the temperature of the dewatering treatment is 105-115℃.

[0048] Preferably, the water removal treatment time is 2.0-3.0 hours.

[0049] Preferably, the material undergoes dehydration treatment to achieve a moisture content of ≤0.05%. That is, polyurethane grade refers to a material with a moisture content of ≤0.05% after dehydration treatment.

[0050] Preferably, in step (1), the polyol, catalyst, isocyanate and part of the organic solvent are mixed and reacted; after cooling, a mixture consisting of the remaining main chain extender except for adipic dihydrazide and the remaining organic solvent is added.

[0051] Preferably, the amount of the organic solvent used accounts for 45-55% of the total amount of organic solvent used; for example, it can be any value in the range of 45-55%, such as 45%, 50%, 55%, etc.

[0052] Preferably, the organic solvent includes acetone.

[0053] Preferably, the polyol, catalyst, isocyanate and a portion of organic solvent are mixed and then heated to 83-87°C for reaction. For example, the temperature after heating can be any value within the range of 83-87°C, such as 83°C, 84°C, 85°C, 86°C, 87°C, etc.

[0054] Preferably, the reaction time after heating is 55-65 min; for example, the reaction time after heating can be any value within the range of 55-65 min, such as 55 min, 60 min, 65 min, etc.

[0055] Preferably, the temperature after cooling is 55-65℃; for example, the temperature after cooling can be any value within the range of 55-65℃, such as 55℃, 60℃, 65℃, etc.

[0056] Preferably, the addition rate of the mixture is 1.1-2.2 mL / min; for example, the addition rate can be any value within the range of 1.1-2.2 mL / min, such as 1.1 mL / min, 1.5 mL / min, 1.7 mL / min, 2.0 mL / min, 2.2 mL / min, etc.

[0057] Specifically, by controlling the dropping rate of the mixture and adding it slowly, the system temperature is kept stable.

[0058] Preferably, in step (1), after the mixture is added dropwise, the -NCO value is monitored by di-n-butylamine titration. When it approaches the theoretical value, the temperature is lowered to 40-50℃, and adipic acid dihydrazide is added to construct the dynamic bond in the nucleus.

[0059] Preferably, in step (1), the reaction time after adding adipic dihydrazide is 110-130 min; for example, 110 min, 115 min, 120 min, 125 min, 130 min, etc.

[0060] Specifically, after adding adipic dihydrazide, the reaction is carried out for 110-130 minutes without further heating, i.e., a mild reaction for 110-130 minutes.

[0061] Preferably, in step (2), the neutralization temperature is 30-35℃; for example, the neutralization temperature can be any value in the range of 30-35℃, such as 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, etc.

[0062] Preferably, in step (2), the neutralization time is 20-30 minutes to ensure that the sulfonic acid groups are completely neutralized; for example, the neutralization time is 20 minutes, 25 minutes, 30 minutes, etc.

[0063] Preferably, in step (2), stirring is performed during the neutralization process, and the stirring speed is 300-500 rpm.

[0064] Preferably, in step (2), the rotation speed of the shear pre-emulsification is >2500 rpm.

[0065] Preferably, in step (2), the shear pre-emulsification process is as follows: at a stirring speed of >2500 rpm, the neutralized polyurethane prepolymer is poured into the first part of water within 5-10 minutes.

[0066] Preferably, the temperature of the first portion of water is 0-2℃; for example, it can be any value within the range of 0-2℃.

[0067] Preferably, when the temperature of the first portion of water (H2O) is 0°C, it is preferably in the form of an ice-water mixture at 0°C.

[0068] Preferably, the mass ratio of the first portion of water to the neutralized polyurethane prepolymer is (1-1.5):1; for example, the mass ratio can be any value in the range of (1-1.5):1, such as 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, etc.

[0069] Preferably, in step (2), the temperature of the vacuum distillation is 40-50℃, and the vacuum degree of the vacuum distillation is above -0.095MPa. Acetone is recovered by vacuum distillation, and the endpoint is determined by observing the distillation rate and the foaming of the system.

[0070] Specifically, in step (2), the molecular weight is increased by adding a chain extender to react with the residual -NCO in the polyurethane chain and then performing secondary chain extension in water.

[0071] Preferably, in step (3), the mass fraction of the initiator solution is 5-10%; for example, it can be any value within the range of 5-10%. That is, the initiator and the second part of water are mixed to obtain an initiator solution with a mass fraction of 5-10%.

[0072] Preferably, in step (4), the mass ratio of the remaining water to the acrylate monomer is (0.9-1.1):1; for example, the mass ratio can be any value in the range of (0.9-1.1):1, such as 0.9:1, 1:1, 1.1:1, etc.

[0073] Preferably, in step (4), the amount of emulsifier is 1.5-2.5% of the total amount of acrylate monomers; for example, it can be any value in the range of 1.5-2.5%, such as 1.5%, 2%, 2.5%, etc.

[0074] Preferably, in step (4), the emulsification temperature is 45-55℃. For example, the emulsification temperature can be any value in the range of 45-55℃, such as 45℃, 50℃, 55℃, etc.

[0075] Preferably, in step (4), the stirring rate of the emulsification is 800-1200 r / min; for example, the stirring rate can be any value in the range of 800-1200 r / min, such as 800 r / min, 1000 r / min, 1200 r / min, etc.

[0076] Preferably, in step (4), the emulsification time is 30-45 min; for example, the emulsification time can be any value in the range of 30-45 min, such as 30 min, 35 min, 40 min, 45 min, etc.

[0077] Specifically, by optimizing the emulsification process, such as using appropriate emulsifiers, emulsification temperatures, emulsification times, and rotation speeds, it is ensured that the seed emulsion (monomer pre-emulsion) has a uniform particle size and is free of coarse particles.

[0078] Specifically, there is no sequential relationship between steps (3) and (4), which is only for the convenience of description.

[0079] Preferably, in step (5), the dropping time of the monomer preemulsion and the initiator solution is 2-3 hours; for example, the dropping time can be any value in the range of 2-3 hours, such as 2 hours, 2.5 hours, 3 hours, etc.

[0080] Specifically, seed emulsion polymerization is carried out using polymerization kinetics control, that is, the polyurethane seed emulsion is heated to 65-75℃ (any value within the range of 65-75℃), and the monomer pre-emulsion and initiator solution are added dropwise simultaneously but independently and slowly, with the addition time controlled at 2-3 hours, during which uniform speed and good stirring are maintained.

[0081] Preferably, in step (5), the amount of the initiator is 0.3-1.2% of the total amount of acrylate monomers, for example, any value in the range of 0.3-1.2%, so as to control the initiator to be continuously added dropwise at a low steady-state concentration.

[0082] Specifically, in step (5), the dropping rate of the monomer pre-emulsion is matched with the polymerization rate to maintain a starved state of <5% for the aqueous monomer (unreacted monomer in the aqueous phase). The polymerization temperature is controlled at 65-75℃ and kept constant at ±1℃ to achieve a stable match between the free radical concentration, chain growth rate and particle nucleation rate. This can effectively inhibit the formation of new nuclei in the aqueous phase, ensure that the latex particles form a regular core-shell structure, and ensure that the latex particles are uniform and small in size with a strong core-shell interface.

[0083] Preferably, in step (5), the temperature after heating is 65-75℃; for example, the temperature after heating can be any value in the range of 65-75℃, such as 65℃, 68℃, 70℃, 72℃, 75℃, etc.

[0084] Preferably, in step (5), the heat preservation reaction is carried out after the addition is completed.

[0085] Preferably, in step (5), the temperature of the heat preservation reaction is 75-85°C, and the time of the heat preservation reaction is 1-2 hours, so as to ensure complete conversion of the monomer.

[0086] Preferably, in step (5), after the heat preservation reaction is completed, the temperature is lowered and the mixture is filtered to obtain the water-based polyurethane composite emulsion.

[0087] A third aspect of the present invention provides a waterborne polyurethane-acrylic resin topcoat.

[0088] Specifically, the waterborne polyurethane-acrylic resin topcoat includes component A and component B; component A includes the waterborne polyurethane composite emulsion described in the first aspect of the present invention; and component B includes a hydrophilic modified isocyanate curing agent.

[0089] Preferably, component A further includes filler, additives, colorant, and water.

[0090] Preferably, by mass parts, component A comprises 35-60 parts of waterborne polyurethane composite emulsion, 5-15 parts of filler, 1.55-9 parts of additives, 2-10 parts of color paste and 20-40 parts of water.

[0091] Preferably, the additives include at least one of film-forming aids, thickeners, wetting agents, dispersants, defoamers, bactericides, pH buffers, and light stabilizers.

[0092] Preferably, the additives include film-forming aids, thickeners, wetting agents, dispersants, defoamers, bactericides, pH buffers, and light stabilizers; and by mass parts, component A includes 35-60 parts of aqueous polyurethane composite emulsion, 5-15 parts of filler, 0.5-2 parts of film-forming aid, 0.1-1 part of thickener, 0.1-0.5 parts of wetting agent, 0.1-0.5 parts of dispersant, 0.1-0.5 parts of defoamer, 0.05-0.5 parts of bactericide, 0.1-1 part of pH buffer, 0.5-3 parts of light stabilizer, 2-10 parts of colorant, and 20-40 parts of water.

[0093] Preferably, the filler includes at least one of calcium carbonate, barium sulfate, silica powder, and talc.

[0094] Preferably, the film-forming aid comprises a dodecyl alcohol ester.

[0095] Preferably, the thickener includes at least one of associative polyurethane, ethyl hydroxyethyl cellulose, and carboxymethyl cellulose.

[0096] Preferably, the wetting agent includes at least one of polyether-modified siloxane solution (such as at least one of BYK-346 and MOK-2617) and ionic polyacrylate solution (such as BYK-381).

[0097] Preferably, the dispersant comprises at least one of the following: a salt solution of unsaturated polyamine amide and acidic polyester (such as BYK-W980), a solution of unsaturated polycarboxylic acid polymer and polysiloxane copolymer (such as BYK-W940), and a nonylphenol polyoxyethylene ether dispersant (such as SURFYNOL®CT-131).

[0098] Preferably, the defoamer includes an organosilicon defoamer; for example, at least one of BYK-028, BYK-024, and S-124.

[0099] Preferably, the bactericide includes at least one of 1,2-benzisothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, and octyl-4-isothiazolin-3-one; for example, at least one of ROCIMA 562, BIT-20, and KQ-208.

[0100] Preferably, the pH buffer includes at least one of ammonia, sodium bicarbonate, and sodium dihydrogen phosphate.

[0101] Preferably, the light stabilizer comprises at least one of benzotriazole mixtures (such as Tinuvin 1130, etc.), triazine compounds (such as Tinuvin 1577, etc.), and piperidine-triazine polymers (such as Chimassorb 2020, etc.).

[0102] Specifically, the present invention does not impose any particular limitation on the type of pigment, and those skilled in the art can select it according to actual needs.

[0103] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows: (1) This invention forms a core-shell emulsion with aliphatic polyurethane as the "soft core" and acrylate polymer as the "hard shell" through the combined action of components such as polyol, aliphatic isocyanate, functional chain extender, cyclic chain extender, side chain chain extender, sulfonic acid chain extender, fluorinated chain extender, compound emulsifier, and acrylate monomer. The emulsion has a small particle size and good stability. The prepared topcoat has excellent properties such as yellowing resistance, aging resistance, water resistance, self-healing ability, spraying performance, hardness, and adhesion.

[0104] (2) This invention uses an aliphatic raw material system, which can improve the yellowing resistance and aging resistance of the topcoat. The acylhydrazone bonds introduced by acetoacetic acid diol and adipic acid dihydrazide form a large number of dynamic reversible acylhydrazone crosslinking networks inside the polyurethane soft core, completing the core layer self-healing matrix, realizing the self-healing function, and solving the problem of irreversible coating scratches. The dual crosslinking design of cyclic chain extender and side-chain chain extender realizes core self-crosslinking and shell grafting crosslinking, improving the rigidity and density of the coating film, and ensuring the core-shell interface bonding force, thereby improving the water resistance, hardness, adhesion, etc. of the coating film. By compounding sulfonic acid chain extender and fluorinated chain extender, the pain point of waterborne polyurethane's inability to simultaneously achieve hydrophilic emulsification and water resistance can be solved.

[0105] (3) The polyurethane core forms a dual cross-linking network through permanent rigid cross-linking (isocyanate, cyclic chain extender, and side-chain chain extender) and dynamic reversible cross-linking (acetoacetic acid glycol and adipic acid dihydrazide), giving the core-shell particles excellent structural density. During the film formation stage, after the latex particles soften, the short molecular chains, strong mobility, and extremely low surface energy of the long alkyl hydrophobic segments (vegetable oil polyols, such as castor oil polyols, have multiple long alkyl side chains of fatty acids that are incorporated into the polyurethane soft segments; the side chains have weak entanglement and good mobility, continuously migrating to the coating surface) and the fluorocarbon flexible chains with extremely low surface energy and strong hydrophobic properties can penetrate the gaps between the outer acrylate molecules and spontaneously accumulate on the coating surface, forming a hydrophobic barrier layer on the coating surface. The dense structure and hydrophobic barrier layer of the coating film give it good water resistance.

[0106] (4) By introducing hydrophilic groups such as sulfonic acid groups, this invention optimizes the emulsification process (such as controlling emulsification temperature, emulsification time, monomer dosage, emulsifier type, and compound emulsifier mass ratio) and polymerization kinetics control (such as initiator dosage, monomer pre-emulsion dripping rate, polymerization temperature, etc.), resulting in a waterborne polyurethane composite emulsion with fine particles and good stability. This enables the waterborne polyurethane-acrylic resin topcoat to achieve good atomization effect during spraying, making it particularly suitable for spraying construction, reducing equipment requirements and reducing equipment investment costs.

[0107] (5) All polyols in this invention are derived from vegetable oil polyols. Vegetable oil polyols use renewable vegetable oils (castor oil, soybean oil, etc.) as raw materials, which are natural renewable resources that can be recycled. This completely eliminates the dependence on non-renewable petroleum resources. Compared with traditional petroleum-based polyols, using the traditional waterborne polyurethane-polyacrylate composite emulsion (PUA emulsion) process as a reference, and according to the current national energy consumption standards (GB / T 2589-2020 General Rules for Calculating Comprehensive Energy Consumption and GB / T 12723-2013 General Rules for Compiling Energy Consumption Limits for Unit Products) and carbon emission standards (GB / T 32150-2025 General Rules for Accounting and Reporting of Greenhouse Gas Emissions of Industrial Enterprises and GB / T 32151.40-2025 Requirements for Accounting and Reporting of Greenhouse Gas Emissions Part 40: Building Waterproofing Material Production Enterprises), the comprehensive energy consumption per unit product of this invention is reduced by 23%, the consumption of non-renewable resources is reduced by 61%, and the emission of greenhouse gases into the atmosphere is reduced by 36%. Meanwhile, the plant oil polyols themselves have no irritating odor and extremely low VOC content, so there is no need to add additional environmentally friendly additives. The emulsions and coatings prepared have no toxic or harmful residues and can be naturally degraded after disposal, meeting environmental protection coating standards. They are suitable for environmentally friendly use scenarios of indoor and outdoor humidity-regulating topcoats, and are especially suitable for the construction and home furnishing fields with high environmental protection requirements.

[0108] (6) Compared with methyl methacrylate (MMA) topcoat, the waterborne polyurethane-acrylic resin topcoat of the present invention has better environmental protection and construction window period; compared with waterborne acrylic topcoat, the waterborne polyurethane-acrylic resin topcoat of the present invention has better water resistance, aging resistance, adhesion and spraying effect. Detailed Implementation

[0109] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0110] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0111] The source information of the raw materials in the embodiments and comparative examples of this invention is as follows: Castor oil diol: purchased from Shanghai Jingri New Materials Technology Co., Ltd., models AN2010 and A4812; Cashew nut shell oil diol: purchased from Cardlä, model NX-9203LP; Soybean oil polyols: purchased from Guangzhou Haierma Company, model number HM-10100; IPDI: Purchased from Bayer, model Desmodur®I; HDI: Purchased from Bayer, model number Desmodur®H; Diphenylmethane diisocyanate (MDI): Purchased from Bayer, model Desmodur® 44C; Sodium 2-[(2-aminoethyl)amino]ethanesulfonate (2-aminoethyl sulfonate, AAS salt, 50% aqueous solution by mass) was purchased from Hubei Xinrun Chemical Co., Ltd. Polytetrafluoroether diol: purchased from Solvay, model Fomblin Z-DOL 2000; 1,4-Cyclohexanediethanol (CHDM, purity ≥99%), purchased from Guangzhou Yuanda New Materials Co., Ltd. Trimethylolpropane monoallyl ether (TMPME, purity ≥98%) was purchased from Guangzhou Daixun Trading Co., Ltd. Diacetoacetate (i.e., 1,7-dihydroxy-3,5-heptadecylone, structural formula HOCH2CH2COCH2COCH2CH2OH): purchased from BASF, model DAA-Diol 280; Anionic reactive emulsifier: purchased from Adico, model SE-10N; Nonionic emulsifier: purchased from Jinan Xinguang Chemical Products Co., Ltd., model APG0810; Emulsifier: Purchased from Renda Chemical Co., Ltd., model CO-436; Thickener: Purchased from Dow, model RM-8W; Wetting agents, dispersants and defoamers: all purchased from BYK AG, Germany, models BYK-346, BYK-W940 and BYK-024 respectively; Bactericide: Purchased from Dow, model ROCIMA 562; Light stabilizer: purchased from BASF, model Tinuvin 1130; pH buffer ammonia solution: purchased from Binhua Group Co., Ltd.; Aqueous acrylic emulsion: purchased from Wanhua, model number Archsol® 8035; Waterborne polyurethane dispersion: purchased from Wanhua, model Leasys® 5531; Color paste (501 resin-free black paste), purchased from Jiangmen Maolian Chemical Co., Ltd.; The hydrophilic modified isocyanate curing agent, purchased from Wanhua, is model Aquolin®278.

[0112] Example 1 This embodiment provides an aqueous polyurethane composite emulsion, which is composed of the following raw materials by mass: Castor oil diol AN2010 18.7 parts, catalyst dibutyltin dilaurate (DBTDL) 0.02 parts, IPDI 8.0 parts, acetone 4 parts, sulfonic acid chain extender 2-aminoethyl sulfonate 0.4 parts, fluorinated chain extender polytetrafluoroethylene glycol 0.25 parts, functional chain extender acetoacetic acid glycol 0.5 parts, cyclic chain extender 1,4-cyclohexanediethanol 0.25 parts, side-chain chain extender trimethylolpropane monoallyl ether 0.25 parts, functional chain extender adipate dihydrazide 0. 36 parts, neutralizer triethylamine 1.13 parts, chain extender ethylenediamine 0.14 parts, methyl methacrylate 8.33 parts, butyl acrylate 5.0 parts, hydroxyethyl acrylate 0.67 parts, acrylic acid 0.33 parts, emulsifier 0.27 parts (mass ratio of SE-10N to APG0810 is 2.5:1), 51.23 parts deionized water (including 34 parts of ice water mixture at 0°C), initiator ammonium persulfate (APS) 0.17 parts.

[0113] The specific steps for preparing the above-mentioned waterborne polyurethane composite emulsion are as follows: (1) First, castor oil diol, 2-aminoethyl sulfonate, polytetrafluoroethylene diol, acetoacetic acid diol, 1,4-cyclohexanediol, and trimethylolpropane monoallyl ether were dehydrated (vacuum dehydration for 2.5 h under vacuum conditions of -0.095 MPa and 110 °C) to achieve polyurethane grade (water content of 0.05%). Then, castor oil diol, catalyst DBTDL, IPDI, and 2 parts of acetone were added to the reactor, and dry nitrogen gas was introduced for protection. The temperature was raised to 85 °C and reacted for 1 h. The temperature was lowered to 60℃, and an acetone solution containing 2-aminoethyl sulfonate, polytetrafluoroethylene glycol, acetoacetic acid glycol, 1,4-cyclohexanediol, and trimethylolpropane monoallyl ether was slowly added dropwise at a rate of 1.7 mL / min (acetone volume was 2 parts). The -NCO value was monitored every 30 min using the di-n-butylamine titration method. When the mass fraction of -NCO dropped to 2%, the reaction endpoint was reached. The temperature was lowered to 45℃, adipic acid dihydrazide was added, and the reaction was carried out gently for 2 h to obtain a polyurethane (PU) preform and complete the construction of dynamic bonds in the core. (2) At 32°C, triethylamine was added to the PU prepolymer obtained in step (1), and the mixture was stirred at a medium speed of 400 rpm for 25 min to ensure complete neutralization of the carboxyl groups. Under the stirring of a high-speed disperser (3000 rpm), the neutralized PU prepolymer was slowly poured into 34 parts of an ice-water mixture at 0°C for shear preemulsification. The operation time of the slow pouring was controlled at 8 min. After the shear preemulsification was completed, the mixture was distilled under reduced pressure at 45°C and -0.095 MPa to recover acetone. The endpoint was determined by observing the distillation rate and the foaming of the system. After the acetone recovery was completed, ethylenediamine was added and the reaction was continued for 30 min to obtain the PU seed emulsion. (3) Mix methyl methacrylate, butyl acrylate, hydroxyethyl acrylate, acrylic acid, emulsifier and 14 parts of deionized water, and shear at 1000 rpm for 40 min at 50°C to form a stable monomer pre-emulsion. The PU seed emulsion was heated to 70°C, and monomer pre-emulsion and initiator aqueous solution (0.17 parts initiator dissolved in 3.23 parts water) were added dropwise simultaneously but independently and slowly, with the addition time controlled at 2.5 h. During this period, uniform speed and good stirring were maintained (stirring speed controlled at 300 rpm). After the addition was completed, the mixture was kept at 80°C for 1.5 h to ensure complete monomer conversion. Then the temperature was lowered to 30°C, and the mixture was filtered through a 200-mesh nylon screen to obtain the waterborne polyurethane composite emulsion.

[0114] This embodiment also provides a waterborne polyurethane-acrylic resin topcoat, which is composed of component A and component B in a mass ratio of 100:4; By weight, component A consists of the following raw material components: 46.3 parts of the aqueous polyurethane composite emulsion of Example 1, 0.2 parts of thickener RM-8W, 7.0 parts of calcium carbonate, 1.4 parts of film-forming aid dodecyl alcohol ester, 0.3 parts of wetting agent BYK-346, 0.4 parts of dispersant BYK-W940, 0.2 parts of defoamer BYK-024, 0.2 parts of bactericide ROCIMA 562, 34.5 parts of deionized water, 1.0 part of light stabilizer Tinuvin 1130, 8.0 parts of colorant and 0.5 parts of pH buffer ammonia water; Component B is the hydrophilic modified isocyanate curing agent Aquolin® 278.

[0115] This embodiment also provides a method for preparing the above-mentioned waterborne polyurethane-acrylic resin topcoat, the specific steps of which are as follows: The aqueous polyurethane composite emulsion, thickener, calcium carbonate, film-forming aid, wetting agent, dispersant, defoamer, bactericide, deionized water, light stabilizer and color paste of Example 1 were added to the reaction vessel and stirred evenly. Finally, a pH buffer was added to adjust the pH to 8 to obtain component A. Components A and B constitute a waterborne polyurethane-acrylic resin topcoat.

[0116] Example 2 The only difference between Example 2 and Example 1 is that the amount of castor oil diol (A4812) used in Example 2 is 21.5 parts and the amount of IPDI is 5.2 parts. The rest is the same as in Example 1.

[0117] Specifically, the aqueous polyurethane composite emulsion of Example 2 is composed of the following raw materials by mass: Castor oil diol (A4812) 21.5 parts, catalyst DBTDL 0.02 parts, IPDI 5.2 parts, 4 parts acetone, 0.4 parts sulfonic acid chain extender 2-aminoethyl sulfonate, 0.25 parts fluorinated chain extender polytetrafluoroethylene glycol, 0.5 parts functional chain extender acetoacetic acid glycol, 0.25 parts cyclic chain extender 1,4-cyclohexanediethanol, 0.25 parts side-chain chain extender trimethylolpropane monoallyl ether, 0.36 parts functional chain extender adipate dihydrazide, 1.13 parts neutralizer triethylamine, 0.14 parts post-chain extender ethylenediamine, 8.33 parts methyl methacrylate, 5.0 parts butyl acrylate, 0.67 parts hydroxyethyl acrylate, 0.33 parts acrylic acid, 0.27 parts emulsifier (the mass ratio of SE-10N and APG0810 is 2.5:1), 51.23 parts deionized water (including 34 parts of ice water mixture at 0°C), and 0.17 parts initiator APS.

[0118] Example 2: The preparation method of the waterborne polyurethane composite emulsion is the same as that in Example 1, except that the raw materials and dosages are different.

[0119] This embodiment also provides a waterborne polyurethane-acrylic resin topcoat and its preparation method. The only difference between this and the waterborne polyurethane-acrylic resin topcoat of Example 1 is that the waterborne polyurethane composite emulsion prepared in Example 2 is used. All other aspects are the same as the waterborne polyurethane-acrylic resin topcoat of Example 1.

[0120] Example 3 The only difference between Example 3 and Example 1 is that Example 3 uses soybean oil polyol (HM-10100) in an amount of 21.5 parts and IPDI in an amount of 5.2 parts. The rest is the same as Example 1.

[0121] Specifically, the aqueous polyurethane composite emulsion of Example 3 is composed of the following raw materials by mass: Soybean oil polyol (HM-10100) 21.5 parts, catalyst DBTDL 0.02 parts, IPDI 5.2 parts, 4 parts acetone, 0.4 parts sulfonic acid chain extender 2-aminoethyl sulfonate, 0.25 parts fluorinated chain extender polytetrafluoroethylene glycol, 0.5 parts functional chain extender acetoacetic acid glycol, 0.25 parts cyclic chain extender 1,4-cyclohexanediol, 0.25 parts side-chain chain extender trimethylolpropane monoallyl ether, 0.36 parts functional chain extender adipate dihydrazide, 1.13 parts neutralizer triethylamine, 0.14 parts post-chain extender ethylenediamine, 8.33 parts methyl methacrylate, 5.0 parts butyl acrylate, 0.67 parts hydroxyethyl acrylate, 0.33 parts acrylic acid, 0.27 parts emulsifier (the mass ratio of SE-10N and APG0810 is 2.5:1), 51.23 parts deionized water (including 34 parts of ice-water mixture at 0°C), and 0.17 parts initiator APS.

[0122] Example 3: The preparation method of the waterborne polyurethane composite emulsion is the same as that in Example 1, except that the raw materials and dosages are different.

[0123] This embodiment also provides a waterborne polyurethane-acrylic resin topcoat and its preparation method. The only difference between this and the waterborne polyurethane-acrylic resin topcoat of Example 1 is that the waterborne polyurethane composite emulsion prepared in Example 3 is used. All other aspects are the same as the waterborne polyurethane-acrylic resin topcoat of Example 1.

[0124] Example 4 The only difference between Example 4 and Example 1 is that Example 4 uses cashew nut shell oil diol (NX-9203LP) in an amount of 20.5 parts and HDI in an amount of 6.2 parts. The rest is the same as Example 1.

[0125] Specifically, the aqueous polyurethane composite emulsion of Example 4 is composed of the following raw materials by mass: Cashew nut shell oil diol (NX-9203LP) 20.5 parts, catalyst DBTDL 0.02 parts, HDI 6.2 parts, 4 parts acetone, 0.4 parts sulfonic acid chain extender 2-aminoethyl sulfonate, 0.25 parts fluorinated chain extender polytetrafluoroethylene glycol, 0.5 parts functional chain extender acetoacetic acid glycol, 0.25 parts cyclic chain extender 1,4-cyclohexanediethanol, 0.25 parts side-chain chain extender trimethylolpropane monoallyl ether, 0.36 parts functional chain extender adipate dihydrazide, 1.13 parts neutralizer triethylamine, 0.14 parts post-chain extender ethylenediamine, 8.33 parts methyl methacrylate, 5.0 parts butyl acrylate, 0.67 parts hydroxyethyl acrylate, 0.33 parts acrylic acid, 0.27 parts emulsifier (the mass ratio of SE-10N and APG0810 is 2.5:1), 51.23 parts deionized water (including 34 parts of ice-water mixture at 0°C), and 0.17 parts initiator APS.

[0126] Example 4: The preparation method of the waterborne polyurethane composite emulsion is the same as that in Example 1, except that the raw materials and dosages are different.

[0127] This embodiment also provides a waterborne polyurethane-acrylic resin topcoat and its preparation method. The only difference between this and the waterborne polyurethane-acrylic resin topcoat of Example 1 is that the waterborne polyurethane composite emulsion prepared in Example 4 is used. All other aspects are the same as the waterborne polyurethane-acrylic resin topcoat of Example 1.

[0128] Example 5 Example 5, the waterborne polyurethane composite emulsion, differs from Example 1 only in that methacrylic acid is used to replace acrylic acid in an equal amount; otherwise, they are the same as in Example 1.

[0129] Specifically, the aqueous polyurethane composite emulsion of Example 5 is composed of the following raw materials by mass: Castor oil diol AN2010 18.7 parts, catalyst dibutyltin dilaurate (DBTDL) 0.02 parts, IPDI 8.0 parts, acetone 4 parts, sulfonic acid chain extender 2-aminoethyl sulfonate 0.4 parts, fluorinated chain extender polytetrafluoroethylene glycol 0.25 parts, functional chain extender acetoacetic acid glycol 0.5 parts, cyclic chain extender 1,4-cyclohexanediethanol 0.25 parts, side-chain chain extender trimethylolpropane monoallyl ether 0.25 parts, functional chain extender adipic acid 0.36 parts of dihydrazide, 1.13 parts of triethylamine (neutralizing agent), 0.14 parts of ethylenediamine (chain extender), 8.33 parts of methyl methacrylate, 5.0 parts of butyl acrylate, 0.67 parts of hydroxyethyl acrylate, 0.33 parts of methacrylic acid, 0.27 parts of emulsifier (the mass ratio of SE-10N to APG0810 is 2.5:1), 51.23 parts of deionized water (including 34 parts of ice-water mixture at 0°C), and 0.17 parts of APS (initiator).

[0130] Example 5: The preparation method of the waterborne polyurethane composite emulsion is the same as that in Example 1, except that the raw materials are different.

[0131] This embodiment also provides a waterborne polyurethane-acrylic resin topcoat and its preparation method. The only difference between this and the waterborne polyurethane-acrylic resin topcoat of Example 1 is that the waterborne polyurethane composite emulsion prepared in Example 5 is used. All other aspects are the same as the waterborne polyurethane-acrylic resin topcoat of Example 1.

[0132] Example 6 The only difference between Example 6 and Example 1 is that Example 6 uses an equal amount of methacrylic acid to replace acrylic acid and an equal amount of hydroxypropyl acrylate to replace hydroxyethyl acrylate. The rest is the same as Example 1.

[0133] Specifically, the aqueous polyurethane composite emulsion of Example 6 is composed of the following raw materials by mass: Castor oil diol AN2010 18.7 parts, catalyst dibutyltin dilaurate (DBTDL) 0.02 parts, IPDI 8.0 parts, acetone 4 parts, sulfonic acid chain extender 2-aminoethyl sulfonate 0.4 parts, fluorinated chain extender polytetrafluoroethylene glycol 0.25 parts, functional chain extender acetoacetic acid glycol 0.5 parts, cyclic chain extender 1,4-cyclohexanediethanol 0.25 parts, side-chain chain extender trimethylolpropane monoallyl ether 0.25 parts, functional chain extender adipic acid 0.36 parts of dihydrazide, 1.13 parts of triethylamine (neutralizing agent), 0.14 parts of ethylenediamine (chain extender), 8.33 parts of methyl methacrylate, 5.0 parts of butyl acrylate, 0.67 parts of hydroxypropyl acrylate, 0.33 parts of methacrylic acid, 0.27 parts of emulsifier (the mass ratio of SE-10N to APG0810 is 2.5:1), 51.23 parts of deionized water (including 34 parts of ice-water mixture at 0°C), and 0.17 parts of APS (initiator).

[0134] Example 6: The preparation method of the waterborne polyurethane composite emulsion is the same as that in Example 1, except that the raw materials are different.

[0135] This embodiment also provides a waterborne polyurethane-acrylic resin topcoat and its preparation method. The only difference between this and the waterborne polyurethane-acrylic resin topcoat of Example 1 is that the waterborne polyurethane composite emulsion prepared in Example 6 is used. All other aspects are the same as the waterborne polyurethane-acrylic resin topcoat of Example 1.

[0136] Example 7 Example 7: Aqueous polyurethane composite emulsion, composed of the following raw materials by mass: Castor oil diol AN2010 18.7 parts, catalyst dibutyltin dilaurate (DBTDL) 0.02 parts, IPDI 8.0 parts, acetone 4 parts, sulfonic acid chain extender 2-aminoethyl sulfonate 0.4 parts, fluorinated chain extender polytetrafluoroethylene glycol 0.25 parts, functional chain extender acetoacetic acid glycol 0.5 parts, cyclic chain extender 1,4-cyclohexanediethanol 0.25 parts, side-chain chain extender trimethylolpropane monoallyl ether 0.25 parts, functional chain extender adipate dihydrazide 0. 36 parts, neutralizer triethylamine 1.13 parts, chain extender ethylenediamine 0.14 parts, methyl methacrylate 8.33 parts, butyl acrylate 5.0 parts, hydroxyethyl acrylate 0.67 parts, acrylic acid 0.33 parts, emulsifier 0.27 parts (mass ratio of SE-10N to APG0810 is 2.5:1), 51.23 parts deionized water (including 34 parts of ice water mixture at 0°C), initiator ammonium persulfate (APS) 0.17 parts.

[0137] Example 7 The preparation method of the waterborne polyurethane composite emulsion is the same as that of Example 1.

[0138] This embodiment also provides a waterborne polyurethane-acrylic resin topcoat, which is composed of component A and component B in a mass ratio of 100:4; By weight, component A consists of the following raw material components: 45.2 parts of the aqueous polyurethane composite emulsion of Example 7, 0.3 parts of thickener RM-2W, 8.0 parts of filler silica powder, 1.4 parts of film-forming aid dodecyl alcohol ester, 0.3 parts of wetting agent BYK-346, 0.4 parts of dispersant BYK-W940, 0.2 parts of defoamer BYK-024, 0.2 parts of bactericide ROCIMA 562, 34.5 parts of deionized water, 1.0 part of light stabilizer Tinuvin 1130, 8.0 parts of color paste and 0.5 parts of pH buffer ammonia water; Component B is the hydrophilic modified isocyanate curing agent Aquolin® 278.

[0139] Example 7: The preparation method of the waterborne polyurethane-acrylic resin topcoat is the same as that of Example 1.

[0140] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that Comparative Example 1 uses MDI instead of IPDI in its waterborne polyurethane composite emulsion, and the amount of MDI is 8.6 parts, the amount of castor oil diol (AN2010) is 18.1 parts, and no catalyst is added. Otherwise, it is the same as Example 1.

[0141] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the waterborne polyurethane composite emulsion in Comparative Example 2 uses the conventional emulsifier CO-436 to replace the combined emulsifier of SE-10N and APG0810 in equal amounts; otherwise, it is the same as in Example 1.

[0142] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that the aqueous polyurethane composite emulsion in Comparative Example 3 uses 2-aminoethyl sulfonate to replace polytetrafluoroether diol in an equal amount, that is, the amount of 2-aminoethyl sulfonate is 0.65 parts, and it does not contain polytetrafluoroether diol. Otherwise, it is the same as Example 1.

[0143] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that the aqueous polyurethane composite emulsion in Comparative Example 4 does not contain acetoacetic acid glycol and adipic acid dihydrazide, and the amount of 1,4-cyclohexanediethanol is 0.68 parts and the amount of trimethylolpropane monoallyl ether is 0.68 parts. The rest is the same as in Example 1.

[0144] Comparative Example 5 Comparative Example 5 used commercially available waterborne acrylic emulsion Wanhua Archsol® 8035 (30 parts by weight) and waterborne polyurethane dispersion Wanhua Leasys® 5531 (16.3 parts by weight) as a composite emulsion. The preparation process was physical mixing, and other aspects were the same as in Example 1.

[0145] Comparative Example 6 The only difference between Comparative Example 6 and Example 1 is that the aqueous polyurethane composite emulsion in Comparative Example 6 uses trimethylolpropane monoallyl ether to replace 1,4-cyclohexanediethanol in an equal amount, that is, 1,4-cyclohexanediethanol is not added. Otherwise, it is the same as Example 1.

[0146] Comparative Example 7 The only difference between Comparative Example 7 and Example 1 is that the aqueous polyurethane composite emulsion in Comparative Example 7 uses an equal amount of 1,4-cyclohexanediethanol to replace trimethylolpropane monoallyl ether, that is, trimethylolpropane monoallyl ether is not added. Otherwise, it is the same as Example 1.

[0147] Performance testing The particle size and stability of the waterborne polyurethane composite emulsions of Examples 1-7 and Comparative Examples 1-7 were tested, and the performance of the waterborne polyurethane-acrylic resin topcoat of Examples 1-7 and Comparative Examples 1-7 was tested. The relevant test items and test methods are as follows: Tensile shear strength: Tested in accordance with GB / T 7124-2008 "Determination of tensile shear strength of adhesives (rigid material to rigid material)"; Yellowing resistance: Tested according to GB / T 16422.3-2022 "Plastics Laboratory Light Source Exposure Part 3: Fluorescent UV Lamps"; Spraying performance: The atomization effect of the sample after spraying was observed using a 100mL spray bottle. Composite emulsion particle size / D50: Tested according to GB / T 11175-2021 "Test Methods for Synthetic Resin Emulsions"; Water resistance (water absorption rate): According to GB / T 1034-2008, the film was immersed in deionized water at 25℃ for 24 hours. After taking it out, the surface moisture was absorbed with filter paper, and the water absorption rate was weighed and calculated. Repair rate: Tested according to T / CSCP 0003-2023 "Evaluation Method for Self-Healing Performance of Organic Coatings"; Pencil hardness: Tested according to GB / T 6739-2022 "Determination of Hardness of Paints and Varnishes by Pencil Method"; Adhesion (Adhesion Grade): Tested according to GB / T 9286-2021 "Paints and Varnishes - Cross-cut Test" (Cross-cut Method); Emulsion stability: The mechanical stability was tested in accordance with GB / T 11175-2021 "Test Methods for Synthetic Resin Emulsions".

[0148] The particle size and stability of the waterborne polyurethane composite emulsions in Examples 1-7 and Comparative Examples 1-7, as well as the performance test results of the waterborne polyurethane-acrylic resin topcoat, are shown in Table 1.

[0149] Table 1: Particle size, stability, and performance test results of waterborne polyurethane composite emulsions in Examples 1-7 and Comparative Examples 1-7, and waterborne polyurethane-acrylic resin topcoat.

[0150] As can be seen from Table 1, the waterborne polyurethane composite emulsion of the present invention has fine particle size and good stability. The waterborne polyurethane-acrylic resin topcoat prepared by the invention has excellent water resistance, yellowing resistance, self-healing ability, spraying effect, adhesion, tensile shear strength and hardness.

[0151] In Comparative Example 1, MDI was used instead of IPDI in the composite emulsion, resulting in a larger emulsion particle size than in Example 1. This also resulted in significantly worse tensile shear strength and yellowing resistance of the topcoat compared to Example 1. This demonstrates that the use of aliphatic isocyanates in this invention helps to obtain emulsions with fine particle sizes and improves the tensile shear strength and yellowing resistance of waterborne polyurethane-acrylic resin topcoats.

[0152] Comparative Example 2 uses a conventional emulsifier in its composite emulsion, resulting in a significantly larger particle size than that of Example 1, poorer stability, and inferior tensile shear strength and spraying performance of the topcoat in Comparative Example 2 compared to Example 1. This demonstrates that the present invention, by combining anionic reactive emulsifiers and nonionic surfactants, can refine the emulsion particle size and improve the tensile shear strength and spraying performance of waterborne polyurethane-acrylic resin topcoats.

[0153] Comparative Example 3, lacking the fluorinated chain extender polytetrafluoroethylene glycol, exhibited significantly worse water resistance than Example 1 in its topcoat. This demonstrates that fluorinated chain extenders can improve the water resistance of topcoats, and also indicates that using conventional single hydrophilic systems (such as sulfonic acid chain extenders) without introducing fluorinated hydrophobic modification cannot effectively resolve the contradiction between strong hydrophilicity and poor water resistance.

[0154] Comparative Example 4, without the addition of acetoacetic acid diol and 2,2-adipic acid dihydrazide, showed a significantly lower repair rate for its topcoat compared to Example 1. This indicates that the acylhydrazone bonds introduced by acetoacetic acid diol and adipic acid dihydrazide can achieve self-healing function, improve the repair rate, and solve the problem of irreversible coating scratches.

[0155] Comparative Example 5 used a simple physical mixture of commercially available waterborne acrylic emulsion and waterborne polyurethane dispersion as a composite emulsion. This resulted in a significantly larger emulsion particle size than Example 1, significantly lower stability, and a marked reduction in the tensile shear strength, yellowing resistance, water resistance, spraying performance, pencil hardness, adhesion, and repair rate of the topcoat in Comparative Example 5. This demonstrates that compared to the physical mixing of waterborne acrylic emulsion and waterborne polyurethane dispersion, the core-shell structured polyurethane composite emulsion used in this invention plays a crucial role in refining particle size, improving the stability of the waterborne polyurethane composite emulsion, and consequently enhancing the overall performance of the waterborne polyurethane-acrylic resin topcoat, including tensile shear strength, yellowing resistance, water resistance, spraying performance, and repair rate.

[0156] Comparative Example 6, without the addition of 1,4-cyclohexanediethanol, exhibited lower water resistance, pencil hardness, and repair rate compared to Example 1. Comparative Example 7, without the addition of trimethylolpropane monoallyl ether, also showed lower water resistance, pencil hardness, repair rate, and adhesion compared to Example 1. This demonstrates that the dual crosslinking design using a cyclic chain extender and a side-chain chain extender enables core self-crosslinking and shell graft crosslinking, improving coating rigidity and density while ensuring core-shell interface bonding, thereby enhancing the coating's water resistance, hardness, and adhesion. Furthermore, 1,4-cyclohexanediethanol improves the coating's toughness and stability, making repair easier and more stable; trimethylolpropane monoallyl ether regulates crosslinking density and introduces hydrogen bonding, making crack closure easier and improving repair efficiency and stability.

[0157] In summary, this invention utilizes the combined effects of polyols, aliphatic isocyanates, functional chain extenders, cyclic chain extenders, side-chain chain extenders, sulfonic acid chain extenders, fluorinated chain extenders, anionic reactive emulsifiers, nonionic surfactant compound emulsifiers, and acrylate monomers to form a core-shell emulsion with aliphatic polyurethane as the "soft core" and acrylate polymer as the "hard shell." The emulsion has fine particle size and good stability. The prepared waterborne polyurethane-acrylic resin topcoat exhibits excellent resistance to yellowing, aging, water resistance, self-healing ability, spraying performance, hardness, shear strength, and adhesion. It can meet the requirements of applying colored functional coatings to existing asphalt, concrete, or permeable pavements, achieving a dual upgrade in both the appearance and performance of the pavement.

[0158] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A waterborne polyurethane composite emulsion, characterized in that, The raw materials for preparing the waterborne polyurethane composite emulsion consist of polyol, isocyanate, main chain extender, catalyst, neutralizer, acrylate monomer, emulsifier, initiator, post-chain extender, water, and organic solvent. The main chain extender is a hydrophilic chain extender, a hard segment chain extender, and a functional chain extender; The hydrophilic chain extender is a sulfonic acid type chain extender and a fluorinated chain extender; the hard segment chain extender is a cyclic chain extender and a side chain type chain extender; the functional chain extender is acetoacetic acid diol and adipic acid dihydrazide; The mass ratio of the hydrophilic chain extender, hard segment chain extender, and functional chain extender is 1:(0.7-1):(1.2-1.5). The sulfonic acid chain extender includes 2-aminoethyl sulfonate; The fluorinated chain extender includes at least one of polytetrafluoroethylene glycol and fluorinated hexanediol. The cyclic chain extender includes 1,4-cyclohexanediethanol; The side-chain chain extender includes trimethylolpropane monoallyl ether; The emulsifier includes anionic reactive emulsifiers and nonionic surfactants; The isocyanate includes aliphatic isocyanates; The acetoacetic acid diol is 1,7-dihydroxy-3,5-heptanedione; The anionic reactive emulsifier is a nonylphenol polyoxyethylene ether sulfate reactive emulsifier.

2. The aqueous polyurethane composite emulsion according to claim 1, characterized in that, The mass ratio of the sulfonic acid chain extender to the fluorinated chain extender is 1:(0.4-0.8). And / or, the mass ratio of the cyclic chain extender to the side-chain chain extender is 1:(0.7-1.1). And / or, the molar ratio of the acetoacetic acid diol and adipic acid dihydrazide is 1:(0.8-1.2); And / or, the mass ratio of the anionic reactive emulsifier to the nonionic surfactant is (2-3):

1.

3. The aqueous polyurethane composite emulsion according to claim 1, characterized in that, The polyols include at least one of castor oil diol, cashew nut shell oil diol, and soybean oil polyol; And / or, the aliphatic isocyanate includes at least one of isophorone diisocyanate and hexamethylene diisocyanate; And / or, the acrylate monomers include hard monomers and soft monomers.

4. The aqueous polyurethane composite emulsion according to claim 3, characterized in that, The hard monomer includes at least one of methyl methacrylate, methyl acrylate, acrylic acid, methacrylic acid, and acrylonitrile; And / or, the soft monomer includes at least one of ethyl acrylate, butyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, isooctyl acrylate, and n-octyl acrylate.

5. The aqueous polyurethane composite emulsion according to claim 1, characterized in that, The raw materials for preparing the waterborne polyurethane composite emulsion, by weight, include 18-25 parts of polyol, 4-9 parts of isocyanate, 1.5-3 parts of main chain extender, 0.01-0.05 parts of catalyst, 0.8-2 parts of neutralizer, 10-20 parts of acrylate monomer, 0.1-0.5 parts of emulsifier, 0.05-0.3 parts of initiator, 0.05-0.2 parts of post-chain extender, and 45-60 parts of water.

6. The method for preparing the aqueous polyurethane composite emulsion according to any one of claims 1-5, characterized in that, Includes the following steps: The waterborne polyurethane composite emulsion is prepared by emulsion polymerization of the raw materials.

7. The preparation method according to claim 6, characterized in that, The method for preparing the aqueous polyurethane composite emulsion includes the following steps: (1) The polyol, catalyst, and isocyanate are mixed in an organic solvent and reacted. An organic solution of the remaining main chain extender, except for adipic dihydrazide, is added. Finally, adipic dihydrazide is added and reacted to obtain a polyurethane prepolymer. (2) The polyurethane prepolymer is neutralized with a neutralizing agent, the neutralized polyurethane prepolymer is mixed with the first part of water and shear pre-emulsified, and the chain extender is added after vacuum distillation to obtain polyurethane seed emulsion. (3) The initiator and the second portion of water are mixed to obtain an initiator solution; (4) Mix the acrylate monomer, emulsifier and the remaining water, and emulsify to obtain a monomer pre-emulsion; (5) After the polyurethane seed emulsion is heated, the monomer pre-emulsion and initiator solution are added dropwise simultaneously, and the reaction is carried out under heat to obtain the product; The monomer preemulsion and initiator solution are added over a period of 2-3 hours.

8. A water-based polyurethane-acrylic resin topcoat, characterized in that, The waterborne polyurethane-acrylic resin topcoat comprises component A and component B; component A comprises the waterborne polyurethane composite emulsion according to any one of claims 1-5; and component B comprises a hydrophilic modified isocyanate curing agent.

9. The waterborne polyurethane-acrylic resin topcoat according to claim 8, characterized in that, Component A also includes fillers, additives, color pastes, and water.

10. The waterborne polyurethane-acrylic resin topcoat according to claim 9, characterized in that, By mass, component A comprises 35-60 parts of waterborne polyurethane composite emulsion, 5-15 parts of filler, 1.55-9 parts of additives, 2-10 parts of color paste, and 20-40 parts of water.

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