Safe and environment-friendly water-based paint for toys and preparation method thereof

Abstract

The invention relates to a safe and environment-friendly water-based paint for toys and a preparation method of the safe and environment-friendly water-based paint, and belongs to the technical field of paints.The paint is prepared from bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer, dynamic covalent bond self-repairing resin, functional filler, antibacterial agent and the like. The bio-based waterborne polyurethane-acrylic interpenetrating network polymer is prepared by the following steps: carrying out a reaction on castor oil modified polyol, lysine diisocyanate, ethylhexyl palmitate and dimethylolpropionic acid to prepare a prepolymer, and then carrying out a reaction on the prepolymer, butyl acrylate, methyl methacrylate and hydroxyethyl methylacrylate to prepare the bio-based waterborne polyurethane-acrylic interpenetrating network polymer. The dynamic covalent bond self-repairing resin is prepared by the following steps: reacting 3, 3 '-thiodipropionic acid, glycidyl methacrylate and isobutyl palmitate to obtain a product, reacting the product with methyl methacrylate and ethylene glycol dimethacrylate to obtain an oligomer, and finally reacting the oligomer with water-based acrylic resin. All the components are matched for use, so that the coating has good adhesiveness, crack resistance, water resistance, wear resistance and self-repairing capability, and is safe and environment-friendly.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and in particular relates to a safe and environmentally friendly water-based coating for toys and a preparation method thereof. Background Art

[0002] In the field of children's products, toys, as essential companions in children's growth, have always attracted much attention for their safety and environmental friendliness. With socioeconomic development and improvements in living standards, parents have increasingly high expectations for toy quality, focusing not only on the toys' fun and educational aspects but also on safety as a primary consideration. The performance of toy surface coatings, as the part that comes into direct contact with children, directly impacts their health. Traditional solvent-based coatings, containing large amounts of volatile organic compounds (VOCs), heavy metals, and other harmful substances, are increasingly unable to meet market demand. Against this backdrop, safe and environmentally friendly water-based coatings have emerged as a research hotspot and development direction in the toy coatings field.

[0003] Traditional solvent-based coatings once dominated toy manufacturing. These coatings use organic solvents such as benzene, toluene, and xylene as dispersion media. During the coating process, large amounts of these solvents evaporate into the air, causing serious air pollution and posing a health risk to operators. Furthermore, organic solvents are flammable and explosive, posing a significant safety hazard. More critically, traditional solvent-based coatings often contain heavy metals such as lead, cadmium, and mercury, as well as harmful substances such as formaldehyde. Children, while playing, may chew or suck on the surface of toys, causing these harmful substances to enter their bodies. Long-term accumulation can cause irreversible damage to children's nervous and immune systems.

[0004] Water-based paints use water as their primary solvent or dispersion medium and offer significant advantages such as environmental friendliness, safety, and low toxicity. Compared to traditional solvent-based paints, water-based paints produce virtually no VOCs during production and use, effectively reducing atmospheric pollution and aligning with the concept of green development. Furthermore, water-based paints contain no organic solvents, eliminating flammable and explosive safety hazards and reducing risks during production and storage. In terms of safety, water-based paints utilize non-toxic and harmless film-forming substances, pigments, and additives to avoid the introduction of harmful substances such as heavy metals. This ensures the safety of toys coming into contact with children from the very beginning, providing strong support for children's healthy growth.

[0005] Despite their numerous advantages, water-based coatings still face some technical challenges in practical application. For example, their water resistance and abrasion resistance still lag behind those of solvent-based coatings, requiring further improvement through formulation optimization and process refinement. Summary of the Invention

[0006] To meet the requirements for the use of toys and products, while ensuring human health and improving the various performance properties of water-based coatings, the present invention provides a safe and environmentally friendly water-based coating for toys and its preparation method. A special method is used to prepare a bio-based water-based polyurethane-acrylic acid interpenetrating network polymer and a dynamic covalent bond self-healing resin. Water is used as a solvent to effectively reduce VOC volatility. When used in combination with functional fillers, antibacterial agent-grade and other ingredients in a certain proportion, it has excellent adhesion, crack resistance, water resistance and wear resistance, and has excellent self-healing ability. The specific technical solution is as follows:

[0007] A safe and environmentally friendly water-based paint for toys, the paint comprising the following raw materials in parts by weight: 40 to 45 parts of a bio-based waterborne polyurethane-acrylic interpenetrating network polymer, 8 to 10 parts of a dynamic covalent bond self-healing resin, 20 to 25 parts of a functional filler, 6 to 8 parts of an antibacterial agent, 0.5 to 1 part of a thickener, 1 to 2 parts of a dispersant, 0.2 to 0.5 parts of a leveling agent, 8 to 12 parts of a pigment, 0.5 to 1 part of a defoaming agent, and the balance being deionized water. The solid content is 45% to 55%.

[0008] The bio-based waterborne polyurethane-acrylic interpenetrating network polymer is a product obtained by reacting a bio-based waterborne polyurethane prepolymer with castor oil-modified polyol, lysine diisocyanate, ethylhexyl palmitate, and dimethylolpropionic acid, and then reacting the prepolymer with butyl acrylate, methyl methacrylate, and hydroxyethyl methacrylate.

[0009] The dynamic covalent bond self-healing resin is a product obtained by reacting 3,3'-thiodipropionic acid, glycidyl methacrylate, and isobutyl palmitate to obtain a product A, which is then reacted with methyl methacrylate and ethylene glycol dimethacrylate to obtain an oligomer, and finally reacted with a water-based acrylic resin to obtain a product;

[0010] The antibacterial agent is a catechin beta-cyclodextrin inclusion compound.

[0011] In the above coating, the preparation method of the bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer comprises:

[0012] S1: Add 100 to 120 parts of castor oil-modified polyol to 80 to 100 parts of acetone, stir well, add 35 to 40 parts of lysine diisocyanate, 10 to 15 parts of ethylhexyl palmitate, and 0.1 to 0.2 parts of dibutyltin dilaurate in sequence, and reflux at 80 to 85°C for 3 to 4 hours. Add 8 to 10 parts of dimethylolpropionic acid, reflux at 50 to 60°C for 1 to 1.5 hours, and add triethylamine (1 to 1.1 times the mass of the dimethylolpropionic acid) for neutralization and stirring well to obtain a prepolymer solution.

[0013] S2: adding the prepolymer solution to deionized water 2.5 to 3.5 times the mass of the prepolymer solution under stirring, stirring and emulsifying, and removing acetone and part of the deionized water by vacuum distillation to achieve a solid content of 45 wt% to 50 wt% to obtain a bio-based waterborne polyurethane prepolymer;

[0014] S3: Add 100 to 120 parts of bio-based waterborne polyurethane prepolymer to 50 to 80 parts of deionized water, stir evenly, add 30 to 35 parts of butyl acrylate, 20 to 25 parts of methyl methacrylate, and 5 to 8 parts of hydroxyethyl methacrylate in sequence, stir evenly, add dropwise 10 to 12 parts of a 4 wt% to 6 wt% aqueous solution of ammonium persulfate, and reflux the reaction at 75°C to 80°C for 3h to 4h to obtain a bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer.

[0015] In the above-mentioned method for preparing the bio-based waterborne polyurethane-acrylic interpenetrating network polymer, in S1, the stirring is performed at 200 r / min to 300 r / min for 15 to 20 min, and the stirring speed of the reflux reaction is 250 rpm to 300 rpm.

[0016] In the above-mentioned method for preparing the bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer, in S2, the stirring speed is 1000 r / min to 1200 r / min, and the stirring and emulsification time is 30 min to 40 min.

[0017] In the above-mentioned method for preparing the bio-based waterborne polyurethane-acrylic interpenetrating network polymer, in S3, the stirring is at 200 r / min to 300 r / min for 15 min to 20 min, and the rotation speed of the reflux reaction is 250 rp m to 300 rpm.

[0018] In the above-mentioned coating, the preparation method of the dynamic covalent bond self-repairing resin includes:

[0019] N1: Under nitrogen protection, 20 to 25 parts by mass of 3,3'-thiodipropionic acid, 40 to 45 parts of glycidyl methacrylate, 10 to 12 parts of isobutyl palmitate, 50 to 60 parts of ethyl acetate and 2 to 3 parts of triethylamine were refluxed at 80 to 85°C for 3 to 4 hours, cooled to room temperature, and the filtrate was filtered to obtain product A; under nitrogen protection, all of product A, 30 to 35 parts of methyl methacrylate, 5 to 8 parts of ethylene glycol dimethacrylate, 0.8 to 1.2 parts of azobisisobutyronitrile and 60 to 80 parts of ethyl acetate were refluxed at 75 to 80°C for 6 to 8 hours, cooled to room temperature to obtain product B; product B was poured into cold methanol for precipitation, and the solid was collected by filtration; washed with methanol, and dried in vacuo to obtain an oligomer;

[0020] N2: By mass, add 100 to 120 parts of water-based acrylic resin to 15 to 25 parts of deionized water, stir evenly, add 13 to 17 parts of oligomer, stir evenly, add 8 to 10 parts of a 4 wt% to 6 wt% aqueous potassium persulfate solution dropwise, and reflux the reaction at 80°C to 85°C for 3h to 4h to obtain a dynamic covalent bond self-healing resin.

[0021] In the preparation method of the above-mentioned dynamic covalent bond self-healing resin, in N1, the stirring speed of the reflux reaction is 250 rpm to 300 rpm, the mesh number of the sieve for filtering the filtrate is 100 mesh to 200 mesh, the temperature of the cold methanol is 2°C to 6°C, the amount of the cold methanol is 10 times to 12 times the volume of the product B, the mesh number of the sieve for filtering and collecting the solid is 200 mesh to 325 mesh, the number of methanol washings is 3 times to 5 times, and the vacuum drying is vacuum drying at 35°C to 40°C for 24h to 30h.

[0022] In the preparation method of the dynamic covalent bond self-healing resin, in N2, the stirring speed is 200 r / min to 300 r / min for 15 min to 20 min; the stirring speed of the reflux reaction is 250 rpm to 300 rpm.

[0023] In the above-mentioned coating, the preparation method of the catechin β-cyclodextrin inclusion complex comprises: preparing a 15g / L-18g / L β-cyclodextrin water mixture; preparing a 4.5g / L-5.0g / L catechin ethanol solution; in a volume ratio of β-cyclodextrin water mixture: catechin ethanol solution = (4-5): (1-1.2), under stirring, dropwise adding the catechin ethanol solution to the β-cyclodextrin water mixture, stirring the inclusion reaction at 30°C-40°C for 2h-4h, standing at 4°C-6°C to precipitate the inclusion complex, centrifuging at 4000rpm-6000rpm for 10min-15min, collecting the precipitate, vacuum drying at 40°C-50°C to constant weight, and breaking it up to obtain the catechin β-cyclodextrin inclusion complex.

[0024] In the above coating, the mass ratio of the functional filler is calcium carbonate: talc: kaolin: titanium dioxide = (30-35): (20-25): (8-12): (5-10); the functional filler is sieved through 325-460 mesh.

[0025] In the above coating, the thickener is hydroxyethyl cellulose or xanthan gum.

[0026] In the above coating, the dispersant is lecithin.

[0027] In the above coating, the leveling agent is an acrylic leveling agent.

[0028] In the above coating, the pigment is a natural plant pigment.

[0029] In the above coating, the defoamer is a polyether defoamer.

[0030] The method for preparing the above-mentioned safe and environmentally friendly water-based paint for toys comprises the following steps:

[0031] The bio-based waterborne polyurethane-acrylic interpenetrating network polymer was added into a reactor according to the mass ratio, and stirred at a low speed of 200 rpm to 250 rpm. The dynamic covalent self-healing resin, functional filler, antibacterial agent and pigment were added in sequence, and the stirring was continued for 30 min to 40 min to obtain a mixture A; the dispersant, leveling agent and thickener were added to 8 to 10 parts of deionized water and mixed evenly to obtain a mixture B; the mixture B and defoaming agent were added to the mixture A, and the mixture was stirred at 800 r / min to 1200 r / min for 30 min to 40 min. The solid content of the coating was adjusted to 45 wt% to 55 wt% with deionized water, and the coating was filtered through a 150 mesh to 200 mesh sieve to obtain the coating.

[0032] The present invention provides a safe and environmentally friendly water-based paint for toys and a preparation method thereof, which has the following beneficial effects:

[0033] 1. The preparation method and parameter design can achieve complete reaction and improve the reasonable adjustment of polymerization, with good structural uniformity. The solvent evaporates more completely during the preparation process, the monomer residue is small, and the VOC emissions are reduced.

[0034] Second, bio-based waterborne polyurethane-acrylic interpenetrating polymer networks contain numerous reactive groups, such as hydroxyl and carboxyl groups. During film formation, these reactive groups chemically react with oxides or other polar groups on the substrate surface, forming covalent bonds. Simultaneously, through intermolecular van der Waals forces and hydrogen bonding, they achieve strong physical adsorption to the substrate. Furthermore, with the appropriate proportion and increased dosage of functional fillers, they can fill the voids in the resin network, enhancing the density and cohesion of the coating and strengthening the bond between the coating and the substrate.

[0035] 3. Dynamic Covalent Bonds: The dynamic covalent bonds within the self-healing resin (including disulfide bonds and dynamic chemical bonds related to ester exchange reactions) have unique reversible properties. During temperature changes or bending, when the coating is subjected to stress, the dynamic covalent bonds can break and recombine, alleviating stress concentration through the movement and rearrangement of molecular chains. At the same time, the combination with a bio-based waterborne polyurethane-acrylic interpenetrating network polymer increases the flexibility of the coating, allowing the coating to maintain structural integrity even when subjected to greater deformation. After drying and film formation, the formed coating is denser and the porosity is significantly reduced, effectively blocking the penetration channel of water molecules. The bio-based waterborne polyurethane-acrylic interpenetrating network polymer and the dynamic covalent bond self-healing resin work synergistically to construct a stable three-dimensional network structure, enhancing the coating's resistance to water erosion. The catechin β-cyclodextrin inclusion complex is evenly dispersed in the system, not only exerting an antibacterial effect, but also stabilizing the coating structure through interactions with the resin molecules, reducing the destructive effects of water molecules on the coating.

[0036] Fourth, the optimized ratio of the bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer and functional fillers significantly alters the coating's microstructure. The functional fillers are evenly dispersed within the resin matrix, reinforcing the backbone and improving the coating's surface hardness and wear resistance. The continuous phase formed by the bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer possesses excellent toughness and cohesive strength, effectively dispersing stress and reducing wear of the coating when subjected to abrasive friction.

[0037] 5. The optimized preparation and rational proportioning of the dynamic covalent self-healing resin significantly increase the number of dynamic covalent bonds in the coating. When scratches appear on the coating surface, the dynamic covalent bonds break and rebond under the influence of ambient temperature and molecular thermal motion, prompting the molecular chains to diffuse and migrate toward the scratched area. Through the mutual entanglement and crosslinking of the molecular chains, the scratch gap is gradually filled, achieving self-healing function. At the same time, the bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer provides a favorable matrix environment, which is conducive to the function of the dynamic covalent self-healing resin.

[0038] 5. In the bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer reaction system, an appropriate amount of ethylhexyl palmitate can promote monomer reaction, improve the stability and homogeneity of the reaction system, achieve a suitable molecular weight, enhance subsequent crosslinking, reduce monomer residue, and effectively reduce VOC volatility. If added in too little, the improvement effect is insufficient, the internal plasticization effect of the molecular chain is weak, and the flexibility and impact resistance of the coating are not effectively improved. If added in excess, ethylhexyl palmitate will reduce the crosslinking density of the polymer, resulting in a decrease in the mechanical properties of the coating and poor water resistance.

[0039] 6. In the synthesis of dynamic covalent bond self-healing resins, an appropriate amount of isobutyl palmitate promotes monomer reactions and significantly impacts the flexibility and fluidity of the molecular chain. If added too little, the improvement is minimal, limiting the mobility of the molecular chain and hindering the exchange and recombination of dynamic covalent bonds, resulting in suboptimal self-healing properties and crack resistance. If added too much, it interferes with thioester bond exchange, resulting in a loss of dynamic response and reduced hardness and wear resistance of the coating. DETAILED DESCRIPTION

[0040] The present invention will be further described below with reference to specific implementation cases, but the present invention is not limited to these embodiments.

[0041] Example 1

[0042] A safe and environmentally friendly water-based paint for toys. The paint comprises the following raw materials in parts by weight: 40 parts bio-based waterborne polyurethane-acrylic interpenetrating network polymer, 8 parts dynamic covalent bond self-healing resin, 20 parts functional filler, 6 parts antimicrobial agent, 0.5 parts thickener, 1 part dispersant, 0.2 parts leveling agent, 8 parts pigment, 0.5 parts defoamer, and the balance is deionized water. The solid content is 45%. The weight ratio of the functional filler is calcium carbonate: talc: kaolin: titanium dioxide = 30:20:8:5; the functional filler is sieved through a 325-mesh sieve. The antimicrobial agent is a catechin β-cyclodextrin inclusion complex. The thickener is hydroxyethyl cellulose. The dispersant is lecithin. The leveling agent is an acrylic ester leveling agent. The pigment is a natural plant pigment. The defoamer is a polyether defoamer.

[0043] The preparation method of the bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer includes:

[0044] S1: 100 parts of castor oil-modified polyol were added to 80 parts of acetone, stirred at 200 r / min for 15 min, 35 parts of lysine diisocyanate, 10 parts of ethylhexyl palmitate and 0.1 parts of dibutyltin dilaurate were added in sequence, and the mixture was refluxed at 80°C and 250 rpm for 3 h. 8 parts of dimethylolpropionic acid were added, and the mixture was refluxed at 50°C for 1 h. Triethylamine (1 times the mass of the dimethylolpropionic acid) was added for neutralization, and the mixture was stirred at 200 r / min for 15 min to obtain a prepolymer solution;

[0045] S2: adding the prepolymer solution to deionized water (2.5 times the mass of the prepolymer solution) under stirring at 1000 r / min, stirring and emulsifying at 1000 r / min for 30 min, and removing acetone and part of the deionized water by vacuum distillation to achieve a solid content of 45 wt% to obtain a bio-based waterborne polyurethane prepolymer;

[0046] S3: Add 100 parts of bio-based waterborne polyurethane prepolymer to 50 parts of deionized water, stir at 200 r / min for 15 minutes, add 30 parts of butyl acrylate, 20 parts of methyl methacrylate, and 5 parts of hydroxyethyl methacrylate in sequence, stir at 200 r / min for 15 minutes, add 10 parts of 4 wt% ammonium persulfate aqueous solution dropwise, and reflux at 75°C and 250 rpm for 3 hours to obtain a bio-based waterborne polyurethane-acrylic interpenetrating network polymer.

[0047] The preparation method of the dynamic covalent bond self-healing resin includes:

[0048] N1: Under nitrogen protection, 20 parts of 3,3'-thiodipropionic acid, 40 parts of glycidyl methacrylate, 10 parts of isobutyl palmitate, 50 parts of ethyl acetate and 2 parts of triethylamine were refluxed at 80°C and 250 rpm for 3 hours, cooled to room temperature, and filtered through a 100-mesh sieve to obtain the filtrate to obtain product A; under nitrogen protection, all of product A, 30 parts of methyl methacrylate, 5 parts of ethylene glycol dimethacrylate, 0.8 parts of azobisisobutyronitrile and 60 parts of ethyl acetate were refluxed at 75°C and 250 rpm for 6 hours, cooled to room temperature to obtain product B; product B was poured into 2°C cold methanol with a volume 10 times that of product B to precipitate, and the solid was collected by filtration through a 200-mesh sieve; washed with methanol three times, and dried in vacuo at 35°C for 24 hours to obtain an oligomer;

[0049] N2: By mass, 100 parts of water-based acrylic resin were added to 15 parts of deionized water, stirred at 200 r / min for 18 minutes, 13 parts of oligomer were added, stirred at 200 r / min for 18 minutes, 8 parts of a 4 wt% aqueous solution of potassium persulfate were added dropwise, and the mixture was refluxed at 80°C and 250 rpm for 3 hours to obtain a dynamic covalent bond self-healing resin.

[0050] The preparation method of the catechin β-cyclodextrin inclusion complex comprises: preparing a 15 g / L β-cyclodextrin water mixture; preparing a 4.5 g / L catechin ethanol solution; adding the catechin ethanol solution dropwise to the β-cyclodextrin water mixture at a volume ratio of β-cyclodextrin water mixture: catechin ethanol solution = 4:1 under stirring, stirring the mixture at 30° C. for inclusion reaction for 2 hours, standing at 4° C. to precipitate the inclusion complex, centrifuging at 4000 rpm for 10 minutes, collecting the precipitate, vacuum drying at 40° C. to constant weight, and breaking it up to obtain the catechin β-cyclodextrin inclusion complex.

[0051] The method for preparing the above-mentioned safe and environmentally friendly water-based paint for toys comprises the following steps:

[0052] The bio-based waterborne polyurethane-acrylic interpenetrating network polymer was added to the reactor in parts by mass and stirred at a low speed of 200 rpm. The dynamic covalent bond self-healing resin, functional filler, antibacterial agent and pigment were added in sequence and stirred for 30 minutes to obtain a mixture A. The dispersant, leveling agent and thickener were added to 8 parts of deionized water and mixed evenly to obtain a mixture B. The mixture B and defoaming agent were added to the mixture A, stirred at 800 r / min for 30 minutes, the solid content of the coating was adjusted to 45wt% with deionized water, and filtered through a 150-mesh sieve to obtain the coating.

[0053] Example 2

[0054] A safe and environmentally friendly water-based paint for toys. The paint comprises the following raw materials in parts by weight: 43 parts of a bio-based waterborne polyurethane-acrylic interpenetrating network polymer, 9 parts of a dynamic covalent self-healing resin, 22 parts of a functional filler, 7 parts of an antimicrobial agent, 0.7 parts of a thickener, 1.5 parts of a dispersant, 0.35 parts of a leveling agent, 10 parts of a pigment, and 0.7 parts of a defoamer. The balance is deionized water. The solids content is 50%. The weight ratio of the functional filler is calcium carbonate: talc: kaolin: titanium dioxide = 32:23:10:8; the functional filler is sieved through a 400-mesh sieve. The antimicrobial agent is a catechin-β-cyclodextrin inclusion complex. The thickener is hydroxyethyl cellulose. The dispersant is lecithin. The leveling agent is an acrylic ester leveling agent. The pigment is a natural plant pigment. The defoamer is a polyether defoamer.

[0055] The preparation method of the bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer includes:

[0056] S1: Add 110 parts of castor oil-modified polyol to 90 parts of acetone, stir at 250 r / min for 18 min, add 38 parts of lysine diisocyanate, 13 parts of ethylhexyl palmitate and 0.15 parts of dibutyltin dilaurate in sequence, and reflux at 82°C and 280 rpm for 3.5 h. Add 9 parts of dimethylolpropionic acid, reflux at 55°C for 1 h, neutralize with triethylamine (1 times the mass of the dimethylolpropionic acid), and stir at 250 r / min for 18 min to obtain a prepolymer solution;

[0057] S2: adding the prepolymer solution to deionized water (3 times the mass of the prepolymer solution) under stirring at 1100 r / min, stirring and emulsifying at 1100 r / min for 35 min, and removing acetone and part of the deionized water by vacuum distillation to achieve a solid content of 48 wt % to obtain a bio-based waterborne polyurethane prepolymer;

[0058] S3: Add 110 parts of bio-based waterborne polyurethane prepolymer to 65 parts of deionized water, stir at 250 r / min for 20 min, add 32 parts of butyl acrylate, 23 parts of methyl methacrylate, and 6.5 parts of hydroxyethyl methacrylate in sequence, stir at 250 r / min for 20 min, add 11 parts of 5 wt% ammonium persulfate aqueous solution dropwise, and reflux at 78°C and 280 rpm for 3.5 h to obtain a bio-based waterborne polyurethane-acrylic interpenetrating network polymer.

[0059] The preparation method of the dynamic covalent bond self-healing resin includes:

[0060] N1: Under nitrogen protection, 22 parts of 3,3'-thiodipropionic acid, 43 parts of glycidyl methacrylate, 11 parts of isobutyl palmitate, 55 parts of ethyl acetate and 2.5 parts of triethylamine were refluxed at 82°C and 280 rpm for 3.5 hours, cooled to room temperature, and filtered through a 150-mesh sieve to obtain the filtrate to obtain product A; under nitrogen protection, all of product A, 32 parts of methyl methacrylate, 7 parts of ethylene glycol dimethacrylate, 1 part of azobisisobutyronitrile and 70 parts of ethyl acetate were refluxed at 78°C and 280 rpm for 7 hours, cooled to room temperature to obtain product B; product B was poured into 11 times the volume of product B in 4°C cold methanol for precipitation, and the solid was collected by filtration through a 250-mesh sieve; washed with methanol 4 times, and dried in vacuo at 38°C for 26 hours to obtain an oligomer;

[0061] N2: By mass, 110 parts of water-based acrylic resin were added to 20 parts of deionized water, stirred at 250 r / min for 15 minutes, 15 parts of oligomer were added, stirred at 250 r / min for 15 minutes, 9 parts of a 5 wt% aqueous solution of potassium persulfate were added dropwise, and the mixture was refluxed at 82°C and 280 rpm for 3.5 hours to obtain a dynamic covalent bond self-healing resin.

[0062] The preparation method of the catechin β-cyclodextrin inclusion complex comprises: preparing a 16 g / L β-cyclodextrin water mixture; preparing a 4.8 g / L catechin ethanol solution; adding the catechin ethanol solution dropwise to the β-cyclodextrin water mixture at a volume ratio of β-cyclodextrin water mixture: catechin ethanol solution = 4.5:1.1 under stirring, carrying out an inclusion reaction at 35° C. with stirring for 3 hours, standing at 5° C. to precipitate the inclusion complex, centrifuging at 5000 rpm for 12 minutes, collecting the precipitate, vacuum drying at 45° C. to constant weight, and breaking it up to obtain the catechin β-cyclodextrin inclusion complex.

[0063] The method for preparing the above-mentioned safe and environmentally friendly water-based paint for toys comprises the following steps:

[0064] The bio-based waterborne polyurethane-acrylic interpenetrating network polymer was added to the reactor in parts by mass, stirred at a low speed of 220 rpm, and dynamic covalent self-healing resin, functional filler, antibacterial agent, and pigment were added in sequence, and stirring was continued for 35 minutes to obtain mixture A; the dispersant, leveling agent, and thickener were added to 9 parts of deionized water and mixed evenly to obtain mixture B; mixture B and defoaming agent were added to mixture A, stirred at 1000 r / min for 35 minutes, the solid content of the coating was adjusted to 50wt% with deionized water, and filtered through a 150-mesh sieve to obtain the coating.

[0065] Example 3

[0066] A safe and environmentally friendly water-based paint for toys. The paint comprises the following raw materials in parts by weight: 45 parts bio-based waterborne polyurethane-acrylic interpenetrating network polymer, 10 parts dynamic covalent bond self-healing resin, 25 parts functional filler, 8 parts antibacterial agent, 1 part thickener, 2 parts dispersant, 0.5 parts leveling agent, 12 parts pigment, 1 part defoamer, and the balance is deionized water. The solids content is 55%. The weight ratio of the functional filler is calcium carbonate: talc: kaolin: titanium dioxide = 35:25:12:10; the functional filler is sieved through a 460-mesh sieve. The antibacterial agent is a catechin β-cyclodextrin inclusion complex. The thickener is xanthan gum. The dispersant is lecithin. The leveling agent is an acrylic ester leveling agent. The pigment is a natural plant pigment. The defoamer is a polyether defoamer.

[0067] The preparation method of the bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer includes:

[0068] S1: 120 parts by mass of castor oil-modified polyol were added to 100 parts of acetone, stirred at 300 r / min for 20 min, 40 parts of lysine diisocyanate, 15 parts of ethylhexyl palmitate and 0.2 parts of dibutyltin dilaurate were added in sequence, and the mixture was refluxed at 85°C and 300 rpm for 4 h. 10 parts of dimethylolpropionic acid were added, and the mixture was refluxed at 60°C for 1.5 h. Triethylamine (1.1 times the mass of the dimethylolpropionic acid) was added for neutralization, and the mixture was stirred at 300 r / min for 20 min to obtain a prepolymer solution;

[0069] S2: adding the prepolymer solution to deionized water (3.5 times the mass of the prepolymer solution) under stirring at 1200 r / min, stirring and emulsifying at 1200 r / min for 40 min, and removing acetone and part of the deionized water by vacuum distillation to achieve a solid content of 50 wt% to obtain a bio-based waterborne polyurethane prepolymer;

[0070] S3: Add 120 parts of bio-based waterborne polyurethane prepolymer to 80 parts of deionized water, stir at 300 r / min for 18 minutes, add 35 parts of butyl acrylate, 25 parts of methyl methacrylate, and 8 parts of hydroxyethyl methacrylate in sequence, stir at 300 r / min for 18 minutes, add 12 parts of 6 wt% ammonium persulfate aqueous solution dropwise, and reflux at 80°C and 300 rpm for 4 hours to obtain a bio-based waterborne polyurethane-acrylic interpenetrating network polymer.

[0071] The preparation method of the dynamic covalent bond self-healing resin includes:

[0072] N1: Under nitrogen protection, 25 parts of 3,3'-thiodipropionic acid, 45 parts of glycidyl methacrylate, 12 parts of isobutyl palmitate, 60 parts of ethyl acetate and 3 parts of triethylamine were refluxed at 85°C and 300 rpm for 4 hours, cooled to room temperature, and filtered through a 200-mesh sieve to obtain the filtrate to obtain product A; under nitrogen protection, all of product A, 35 parts of methyl methacrylate, 8 parts of ethylene glycol dimethacrylate, 1.2 parts of azobisisobutyronitrile and 80 parts of ethyl acetate were refluxed at 80°C and 300 rpm for 8 hours, cooled to room temperature to obtain product B; product B was poured into 12 times the volume of product B in 6°C cold methanol for precipitation, and the solid was collected by filtration through a 325-mesh sieve; washed with methanol 5 times, and dried in vacuo at 40°C for 30 hours to obtain an oligomer;

[0073] N2: By mass, 120 parts of water-based acrylic resin were added to 25 parts of deionized water, stirred at 300 r / min for 20 min, 17 parts of oligomer were added, stirred at 300 r / min for 20 min, 10 parts of a 6 wt% aqueous solution of potassium persulfate were added dropwise, and the mixture was refluxed at 85°C and 300 rpm for 4 h to obtain a dynamic covalent bond self-healing resin.

[0074] The preparation method of the catechin β-cyclodextrin inclusion complex comprises: preparing 18 g / L of a β-cyclodextrin water mixture; preparing 5.0 g / L of a catechin ethanol solution; adding the catechin ethanol solution dropwise to the β-cyclodextrin water mixture at a volume ratio of β-cyclodextrin water mixture: catechin ethanol solution = 5:1.2 under stirring, carrying out an inclusion reaction at 40° C. with stirring for 4 hours, standing at 6° C. to precipitate the inclusion complex, centrifuging at 6000 rpm for 15 minutes, collecting the precipitate, vacuum drying at 50° C. to constant weight, and breaking it up to obtain the catechin β-cyclodextrin inclusion complex.

[0075] The method for preparing the above-mentioned safe and environmentally friendly water-based paint for toys comprises the following steps:

[0076] The bio-based waterborne polyurethane-acrylic interpenetrating network polymer was added to the reactor in parts by mass, stirred at a low speed of 250 rpm, and dynamic covalent self-healing resin, functional filler, antibacterial agent, and pigment were added in sequence, and stirring was continued for 40 minutes to obtain mixture A; the dispersant, leveling agent, and thickener were added to 10 parts of deionized water and mixed evenly to obtain mixture B; mixture B and defoaming agent were added to mixture A, stirred at 1200 r / min for 40 minutes, the solid content of the coating was adjusted to 55wt% with deionized water, and filtered through a 200-mesh sieve to obtain the coating.

[0077] Sources of raw materials in the above examples: Calcium carbonate was sourced from Shijiazhuang Jingsen Mineral Products Co., Ltd. (light calcium carbonate). Talc was sourced from Lingshou County Qiangdong Mineral Products Processing Plant (high white talc). Kaolin was sourced from Shijiazhuang Qiantong Mineral Products Co., Ltd. (calcined kaolin). Titanium dioxide was sourced from Xinhao Energy Saving Technology (Tianjin) Co., Ltd. (rutile titanium dioxide). Catechin was sourced from Xi'an Ruiying Biotechnology Co., Ltd. (98% purity). β-Cyclodextrin was sourced from Henan Anrui Biotechnology Co., Ltd. (beta-cyclodextrin). Hydroxyethyl cellulose was sourced from Zou Ping'an Lan Chemical Co., Ltd. (beta-xanthan gum). Xanthan gum was sourced from Zhengzhou Xinke Chemical Products Co., Ltd. (beta-xanthan gum). Lecithin was sourced from Anhui Weimao Biotechnology Co., Ltd. (soybean lecithin). The acrylate leveling agent was BYK-381 from Germany. The natural plant pigment was madder pigment. The polyether defoamer was sourced from Guangdong Nanhui New Materials Co., Ltd. (model Cl-318). The castor oil-modified polyol was Polycin D290. Lysine diisocyanate was sourced from Wuhan Huaxiang Kejie Biotechnology Co., Ltd. (L-lysine diisocyanate). Ethylhexyl palmitate was sourced from Shanghai Xiangu Chemical Co., Ltd. Dibutyltin dilaurate was sourced from Shanghai Gaoming Chemical Co., Ltd. Tin-based dibutyltin dilaurate. Dimethylolpropionic acid was sourced from Guangzhou Tengli Chemical Co., Ltd. 2,2-Dimethylolpropionic acid was sourced from Guangzhou Tengli Chemical Co., Ltd. Triethylamine was sourced from Shandong Chongcheng Energy Technology Co., Ltd. Butyl acrylate was sourced from Jinan Yuansite New Materials Technology Co., Ltd. Methyl methacrylate was sourced from Shandong Xinheng Chemical Co., Ltd. Hydroxyethyl methacrylate was sourced from Shanghai Yuanye Biotechnology Co., Ltd. Ammonium persulfate was sourced from Changzhou Jiaye Chemical Co., Ltd. 3,3'-Thiodipropionic acid was sourced from Wuhan Xinxin Jiali Biotechnology Co., Ltd. Glycidyl methacrylate was sourced from Shanghai Yuanye Biotechnology Co., Ltd. Isobutyl palmitate was sourced from Hubei Rishengchang New Materials Technology Co., Ltd. Ethyl acetate was sourced from Jinan Bada Chemical Co., Ltd. Ethylene glycol dimethacrylate was sourced from Hubei Zhenbo Chemical Co., Ltd. Azobisisobutyronitrile was sourced from Shandong Yukang Chemical Co., Ltd. Water-based acrylic resin was sourced from Dongguan Taikang Polymer Technology Co., Ltd. The water-based acrylic resin emulsion had a solids content of 36±2%. Potassium persulfate was sourced from Hubei Xinrunde Chemical Co., Ltd.

[0078] Comparative Example 1

[0079] The bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer is replaced by waterborne acrylic resin; other parameters and methods are the same as in Example 1.

[0080] Comparative Example 2

[0081] In the preparation method S1 of the bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer, ethylhexyl palmitate was not added; other parameters and methods were the same as in Example 1.

[0082] Comparative Example 3

[0083] In the preparation method S1 of the bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer, 3 parts of ethylhexyl palmitate were added (too little); other parameters and methods were the same as in Example 1.

[0084] Comparative Example 4

[0085] In the preparation method S1 of the bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer, 25 parts of ethylhexyl palmitate (excessive) were added; other parameters and methods were the same as in Example 1.

[0086] Comparative Example 5

[0087] In the preparation method S1 of the bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer, 2 parts of dimethylolpropionic acid (too little) were added; other parameters and methods were the same as in Example 1.

[0088] Comparative Example 6

[0089] In the preparation method S1 of the bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer, 20 parts of dimethylolpropionic acid are added (excessive); other parameters and methods are the same as in Example 1.

[0090] Comparative Example 7

[0091] In the preparation method S3 of the bio-based waterborne polyurethane-acrylic interpenetrating network polymer, 50 parts of the bio-based waterborne polyurethane prepolymer is added (too little); other parameters and methods are the same as in Example 1.

[0092] Comparative Example 8

[0093] In the preparation method S3 of the bio-based waterborne polyurethane-acrylic interpenetrating network polymer, 200 parts (excessive) of the bio-based waterborne polyurethane prepolymer are added; other parameters and methods are the same as in Example 1.

[0094] Comparative Example 9

[0095] The dynamic covalent bond self-healing resin is replaced by water-based acrylic resin; other parameters and methods are the same as in Example 1.

[0096] Comparative Example 10

[0097] 30 parts of dynamic covalent self-healing resin were added (excessive); other parameters and methods were the same as in Example 1.

[0098] Comparative Example 11

[0099] In the preparation method N1 of the dynamic covalent bond self-healing resin, isobutyl palmitate is not added; other parameters and methods are the same as in Example 1.

[0100] Comparative Example 12

[0101] In the preparation method N1 of the dynamic covalent bond self-healing resin, 3 parts of isobutyl palmitate was added (too little); other parameters and methods were the same as in Example 1.

[0102] Comparative Example 13

[0103] In the preparation method N1 of the dynamic covalent bond self-healing resin, 20 parts of isobutyl palmitate are added (excessive); other parameters and methods are the same as in Example 1.

[0104] Comparative Example 14

[0105] In the preparation method N2 of the dynamic covalent bond self-healing resin, 3 parts of oligomer are added (too little); other parameters and methods are the same as in Example 1.

[0106] Comparative Example 15

[0107] In the preparation method N2 of the dynamic covalent bond self-healing resin, 30 parts of oligomer are added (excessive); other parameters and methods are the same as in Example 1.

[0108] Comparative Example 16

[0109] The catechin β-cyclodextrin inclusion complex was replaced by catechin; other parameters and methods were the same as those in Example 1.

[0110] (1) VOC emission detection:

[0111] A 150mm×75mm×0.8mm glass plate was sprayed with the coating to form a wet film with a thickness of 100±5μm. The plate was then placed in an environment with a temperature of 25°C and a relative humidity of 50% to dry for 7 days to ensure that the coating was completely cured. The dried sample was placed in a 100L environmental test chamber with a temperature of 25°C and a relative humidity of 50%. After equilibration for 1 hour, a gas chromatography-mass spectrometry (GC-MS) was used to collect gas samples in the chamber. Gas chromatography conditions: a DB-5MS capillary column (30m×0.25mm×0.25μm) was used, the injection port temperature was 250°C, the column oven had an initial temperature of 40°C, was maintained for 2 minutes, and then the temperature was increased to 250°C at a rate of 5°C / min and maintained for 5 minutes. Mass spectrometry conditions: an electron impact source (EI), an electron energy of 70eV, an ion source temperature of 230°C, and a scanning range of 35-350m / z. VOC emissions (in mg / m 3 ).

[0112] (2) Adhesion test:

[0113] In accordance with GB / T 9286, "Cross-cut Test for Paints and Varnishes," the coating was applied to ABS plastic panels (dry film thickness 80 ± 2 μm) and dried for 7 days at 25°C and 50% relative humidity. The cross-cut method (1 mm spacing, 6 × 6 squares) was used to assess the degree of peeling. The scale is as follows: 0 indicates completely smooth cut edges with no peeling; 1 indicates slight flaking at the intersection of the cuts, with no more than 5% of the cross-cut area significantly affected; and 5 indicates peeling greater than 65%.

[0114] (3) Crack resistance test:

[0115] The coating was applied to a soft polyvinyl chloride (PVC) substrate (dry film thickness 80 ± 2 μm) and dried at 25°C and 50% relative humidity for 7 days. A bending test was performed using a 3 mm diameter mandrel to observe the maximum crack length (in mm).

[0116] (IV) Water resistance test:

[0117] The coating was applied to an aluminum panel to a wet film thickness of 120 ± 5 μm and dried at 25°C and 50% relative humidity for 7 days. The dried sample was completely immersed in deionized water at 25°C, with the water level 20 mm above the sample. After immersion for 240 hours, the sample was removed and the coating surface was observed for blistering, shedding, discoloration, or gloss loss. The severity of the blistering is as follows: Level 0: The coating surface exhibits no blistering, shedding, discoloration, or gloss loss, remaining completely intact. Level 1: The coating surface exhibits slight discoloration or gloss loss, but no blistering or shedding. Level 2: The coating surface exhibits a small number of fine bubbles (diameter ≤ 0.5 mm, area ≤ 5%), with no shedding, but noticeable discoloration or gloss loss. Level 3: The coating surface exhibits a significant number of bubbles (diameter ≤ 1 mm, area ≤ 15%), with minor localized shedding (area ≤ 10%), and severe discoloration or gloss loss. Level 4: There are a large number of bubbles (diameter > 1mm, area > 15%) on the coating surface, and there is obvious shedding (area > 10%), which seriously affects the integrity of the coating. Level 5: The coating fails (bubbling, shedding area > 50%, substrate exposed), and loses its protective properties.

[0118] (5) Wear resistance test:

[0119] The test was conducted in accordance with GB / T 1768, "Paints and varnishes - Determination of abrasion resistance." The coating was applied to an aluminum panel (dry film thickness 80 ± 2 μm) and cured at room temperature for 7 days. A Taber abrader (CS-10 wheel, 500 g load, 1000 revolutions) was used to record the mass loss (in mg).

[0120] (6) Self-repair performance testing:

[0121] The coating was applied to an ABS panel (dry film thickness 80 μm) and dried at 25°C and 50% relative humidity for 7 days. A vertical scratch with a blade was made: 50 μm deep, 30 μm wide, and 10 mm long. The panel was then heated in a 60°C oven for 30 minutes. The average width of the repaired scratch (in μm) was measured using a microscope.

[0122] Table 1 Performance test results

[0123]

[0124] It can be seen from the above results that the coatings of Examples 1 to 3 have more excellent performance, complete reaction and reasonable improvement and regulation of polymerization, good structural uniformity, more complete solvent volatilization during the preparation process, less monomer residue, and reduced VOC emissions. Bio-based waterborne polyurethane-acrylic interpenetrating network polymer contains a large number of active groups such as hydroxyl and carboxyl groups. During the film-forming process of the coating, these active groups can react chemically with oxides or other polar groups on the surface of the substrate material to form covalent bonds; at the same time, through the van der Waals force and hydrogen bond between molecules, strong physical adsorption is produced with the substrate. In addition, with the reasonable proportion and increase in the amount of functional fillers, they can fill the gaps in the resin network, enhance the density and cohesion of the coating, and make the coating and the substrate more firmly bonded. The dynamic covalent bonds (including disulfide bonds and dynamic chemical bonds related to ester exchange reactions) inside the dynamic covalent bond self-healing resin have unique reversible properties. When the coating is subjected to stress during temperature fluctuations or bending, dynamic covalent bonds can break and recombine, alleviating stress concentrations through molecular chain movement and rearrangement. The addition of a bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer enhances the coating's flexibility, allowing it to maintain structural integrity even under greater deformation. After drying, the resulting film becomes denser and has significantly reduced porosity, effectively blocking the permeation pathways of water molecules. The bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer and the dynamic covalent self-healing resin synergistically construct a stable three-dimensional network structure, enhancing the coating's resistance to water erosion. The catechin β-cyclodextrin inclusion complex is uniformly dispersed throughout the system, not only exerting its antimicrobial properties but also stabilizing the coating structure through interactions with the resin molecules, reducing the destructive effects of water molecules. The optimized ratio of the bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer and functional filler significantly alters the coating's microstructure. The functional filler is evenly dispersed within the resin matrix, reinforcing the backbone and improving the coating's surface hardness and wear resistance. The continuous phase formed by the bio-based waterborne polyurethane-acrylic interpenetrating network polymer has good toughness and cohesive strength. When subjected to abrasive friction, it can effectively disperse stress and reduce wear of the coating. The increase in the content of dynamic covalent bond self-healing resin significantly increases the number of dynamic covalent bonds in the coating. When scratches appear on the surface of the coating, under the influence of ambient temperature and molecular thermal motion, the dynamic covalent bonds can break and rebond, prompting the molecular chains to diffuse and migrate to the scratched area. Through the mutual entanglement and cross-linking of the molecular chains, the scratch gaps are gradually filled, realizing the self-healing function. At the same time, the bio-based waterborne polyurethane-acrylic interpenetrating network polymer provides a good matrix environment, which is conducive to the dynamic covalent bond self-healing resin to function.

[0125] Comparative Example 1: Ordinary acrylic resin was used as a substitute, but no interpenetrating network was formed. The conversion rate of the residual monomers in the acrylic resin itself was low, and volatile monomers were present, which increased VOC volatilization. After replacing the bio-based waterborne polyurethane-acrylic interpenetrating network polymer with ordinary waterborne acrylic resin, the coating system lost the unique advantages of bio-based materials. Ordinary waterborne acrylic resin has a relatively simple molecular chain structure and lacks active groups that can form strong chemical bonds with the substrate, resulting in decreased adhesion. Its cross-linking density is low, the intermolecular force is weak, and it performs poorly in terms of wear resistance, crack resistance, and water resistance. Acrylic resin has high rigidity, insufficient flexibility, and is prone to cracking.

[0126] Comparative Examples 2 to 4: Ethylhexyl palmitate promotes monomer reaction. Its absence or inadequate amount will result in an increase in residual unreacted monomer and higher VOC emissions. Excessive ethylhexyl palmitate will migrate to the surface, causing some ester volatilization, further increasing VOC emissions. In the synthesis of bio-based waterborne polyurethane-acrylic interpenetrating network polymers, ethylhexyl palmitate plays a key role in plasticization, improving compatibility, and enhancing polymerizability. Without ethylhexyl palmitate in Comparative Example 2, the interactions between the polymer chains were too strong, restricting the movement of the molecular segments. This resulted in poor coating flexibility and reduced abrasion resistance due to the lack of a flexible buffer within the molecular chains. In Comparative Example 3, too little was added, resulting in insufficient improvement, weak internal plasticization of the molecular chains, and ineffective improvement in the coating's flexibility and impact resistance. In Comparative Example 4, excessive ethylhexyl palmitate reduced the polymer's crosslinking density, leading to decreased mechanical properties, poor water resistance, and film swelling.

[0127] Comparative Examples 5 and 6: Insufficient dimethylolpropionic acid results in incomplete neutralization and volatilization of residual triethylamine; excessive dimethylolpropionic acid introduces excess carboxylic acid groups, requiring more triethylamine for neutralization, and volatilization of residual amines. Dimethylolpropionic acid is an important raw material for introducing hydrophilic groups and plays a role in regulating water dispersibility and cross-linking structure in polymer synthesis. In Comparative Example 5, the amount added was too little, resulting in insufficient hydrophilic groups on the polymer molecular chains. During the water dispersion process, a stable emulsion system could not be formed, resulting in numerous defects in the coating film, affecting the density and mechanical properties of the coating film, and reducing both adhesion and water resistance. In Comparative Example 6, excessive addition caused excessive branching of the polymer molecular chains, increased entanglement between the molecular chains, hindered the uniformity of the cross-linking reaction, and formed an uneven cross-linked network structure, resulting in reduced flexibility and crack resistance of the coating film. It also affected the bonding strength between the coating film and the substrate, resulting in reduced adhesion.

[0128] Comparative Examples 7 to 8: The amount of bio-based polyurethane prepolymer added was reduced, resulting in an incomplete interpenetrating network structure and an increase in unreacted monomer residues; at the same time, insufficient prepolymer affected the emulsification effect, and the residual solvents such as acetone increased. Excessive prepolymer hindered the reaction of acrylic monomers, resulting in a large amount of residual monomers. In Comparative Example 7, the amount of bio-based waterborne polyurethane prepolymer added was too small, and the effective ingredients participating in the subsequent acrylic ester copolymerization reaction were insufficient, and a complete interpenetrating network structure could not be formed. This resulted in a decrease in the mechanical properties and stability of the coating. In the wear resistance test, due to the lack of sufficient polymer support, the coating was more easily damaged by abrasives, and the mass loss increased. In Comparative Example 8, too much was added, and the viscosity of the system increased significantly. During the reaction, the materials were unevenly mixed, resulting in difficulty in fully proceeding the reaction. The molecular weight distribution of the formed polymer was uneven, and the performance of the coating became unstable. Phase separation led to an uneven structure and stress concentration, and various performance indicators declined to varying degrees.

[0129] Comparative Example 9: The dynamic covalent bond resin is replaced by ordinary acrylic resin, which loses the dynamic stability of the thioester bond, and the unreacted glycidyl methacrylate monomer residues in the resin synthesis increase; the residual monomers of the acrylic resin itself volatilize. After the dynamic covalent bond self-healing resin is replaced by ordinary water-based acrylic resin, the coating almost loses its self-healing ability. The coating film formed by ordinary water-based acrylic resin is a static cross-linked structure. When scratches appear on the surface of the coating film, the molecular chains cannot move and recombine independently to repair the damage. At the same time, the mechanical properties and environmental resistance of this resin are relatively weak. In the wear resistance, crack resistance and water resistance tests, it performs worse than the coating containing dynamic covalent bond self-healing resin.

[0130] In Comparative Example 10, excessive addition of dynamic covalent bond self-healing resin results in excessively high crosslinking degree of the coating, causing the coating to become hard. Excessive dynamic bonds inhibit the continuity of the acrylic resin, limiting the repair efficiency, and resulting in inferior self-healing performance to that of Example 1. The crack resistance is poor, and excessive crosslinking also affects the bonding between the coating and the substrate, causing decreased adhesion. In the wear resistance test, due to the increased brittleness of the coating, cracks and peeling are more likely to occur, resulting in increased mass loss.

[0131] Comparative Examples 11 to 13: Isobutyl palmitate promotes monomer reaction. Its absence or insufficient amount will lead to an increase in the residual unreacted monomers, a decrease in the flexibility of the chain segments in the synthesis of dynamic bond resins, and at the same time, reduced plasticity leads to poor emulsion stability and increased ethyl acetate solvent residues. Excessive isobutyl palmitate will migrate to the surface, some esters will volatilize, and VOC volatilization will increase. In the synthesis of dynamic covalent bond self-healing resins, isobutyl palmitate has an important influence on the flexibility and fluidity of the molecular chain. In Comparative Example 11, isobutyl palmitate is not added, and the synthesized oligomer molecular chain is relatively rigid. When subsequently copolymerized with a water-based acrylic resin, it is difficult to form a uniform network structure, resulting in a decrease in the mechanical properties and self-healing properties of the coating. In Comparative Example 12, the amount added is too little, the improvement effect is not obvious, the mobility of the molecular chain is limited, and the exchange and recombination of dynamic covalent bonds are affected, and the self-healing properties and crack resistance are not ideal. In comparative example 13, too much was added, which interfered with the thioester bond exchange, lost the dynamic response ability, and reduced the hardness and wear resistance of the coating. In the wear resistance test, the mass loss increased.

[0132] Comparative Examples 14 to 15: Too little oligomer was added, resulting in an incomplete dynamic bond network, insufficient cross-linking, and volatilization of residual monomers. Insufficient oligomers also resulted in uneven dispersion of fillers and increased volatiles. Excessive oligomers resulted in an overly dense dynamic bond network, with some thioester bonds remaining unreacted. Excessive oligomers also hindered the emulsification process, causing uneven dispersion and cross-linking, and increased volatiles. In Comparative Example 14, too little oligomer was added, and when copolymerized with the water-based acrylic resin, the number of dynamic covalent bonds provided was insufficient, preventing effective self-repair. Furthermore, due to the low oligomer content, the improvement in the mechanical properties of the coating was limited, affecting wear resistance and crack resistance. Adding too much oligomer in Comparative Example 15 resulted in an excessively high cross-linking density in the coating, reducing the flexibility of the molecular chains, and making the coating hard and brittle. Cracks easily appeared in crack resistance tests, and adhesion decreased due to poor compatibility between the coating and the substrate.

[0133] Comparative Example 16: After replacing the catechin β-cyclodextrin inclusion complex with catechin, the stability of catechin in the coating system decreased. Catechins are prone to oxidation or aggregation during the water dispersion process. The free state of catechins can react adversely with the resin molecules, destroying the cross-linked structure of the resin and reducing the water resistance and self-healing properties of the coating.

Claims

1. A safe and environmentally friendly water-based paint for toys, characterized in that: The coating comprises the following raw materials in parts by weight: 40 to 45 parts of bio-based waterborne polyurethane-acrylic interpenetrating network polymer, 8 to 10 parts of dynamic covalent bond self-healing resin, 20 to 25 parts of functional filler, 6 to 8 parts of antibacterial agent, 0.5 to 1 part of thickener, 1 to 2 parts of dispersant, 0.2 to 0.5 parts of leveling agent, 8 to 12 parts of pigment, 0.5 to 1 part of defoaming agent, and the balance is deionized water. The solid content is 45% to 55%. The bio-based waterborne polyurethane-acrylic interpenetrating network polymer is a product obtained by reacting a bio-based waterborne polyurethane prepolymer with castor oil-modified polyol, lysine diisocyanate, ethylhexyl palmitate, and dimethylolpropionic acid, and then reacting the prepolymer with butyl acrylate, methyl methacrylate, and hydroxyethyl methacrylate. The dynamic covalent bond self-healing resin is a product obtained by reacting 3,3'-thiodipropionic acid, glycidyl methacrylate, and isobutyl palmitate to obtain a product A, which is then reacted with methyl methacrylate and ethylene glycol dimethacrylate to obtain an oligomer, and finally reacted with a water-based acrylic resin to obtain a product; The antibacterial agent is a catechin beta-cyclodextrin inclusion compound.

2. A safe and environmentally friendly water-based paint for toys according to claim 1, characterized in that: The preparation method of the bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer comprises: S1: Add 100 to 120 parts of castor oil-modified polyol to 80 to 100 parts of acetone, stir well, add 35 to 40 parts of lysine diisocyanate, 10 to 15 parts of ethylhexyl palmitate, and 0.1 to 0.2 parts of dibutyltin dilaurate in sequence, and reflux at 80 to 85°C for 3 to 4 hours. Add 8 to 10 parts of dimethylolpropionic acid, reflux at 50 to 60°C for 1 to 1.5 hours, and add triethylamine (1 to 1.1 times the mass of the dimethylolpropionic acid) for neutralization and stirring well to obtain a prepolymer solution. S2: adding the prepolymer solution to deionized water 2.5 to 3.5 times the mass of the prepolymer solution under stirring, stirring and emulsifying, and removing acetone and part of the deionized water by vacuum distillation to achieve a solid content of 45 wt% to 50 wt% to obtain a bio-based waterborne polyurethane prepolymer; S3: Add 100 to 120 parts of bio-based waterborne polyurethane prepolymer to 50 to 80 parts of deionized water, stir evenly, add 30 to 35 parts of butyl acrylate, 20 to 25 parts of methyl methacrylate, and 5 to 8 parts of hydroxyethyl methacrylate in sequence, stir evenly, add dropwise 10 to 12 parts of a 4 wt% to 6 wt% aqueous solution of ammonium persulfate, and reflux the reaction at 75°C to 80°C for 3h to 4h to obtain a bio-based waterborne polyurethane-acrylic acid interpenetrating network polymer.

3. The safe and environmentally friendly water-based paint for toys according to claim 2, characterized in that: In S1, the stirring is at 200r / min~300r / min for 15min~20min, and the stirring speed of the reflux reaction is 250rpm~300rpm; in S2, the stirring speed is 1000r / min~1200r / min, and the stirring emulsification time is 30min~40min; in S3, the stirring is at 200r / mi n~300r / min for 15min~20min, and the stirring speed of the reflux reaction is 250rpm~300rpm.

4. The safe and environmentally friendly water-based paint for toys according to claim 1, characterized in that: The preparation method of the dynamic covalent bond self-repairing resin comprises: N1: Under nitrogen protection, 20 to 25 parts by mass of 3,3'-thiodipropionic acid, 40 to 45 parts of glycidyl methacrylate, 10 to 12 parts of isobutyl palmitate, 50 to 60 parts of ethyl acetate and 2 to 3 parts of triethylamine were refluxed at 80 to 85°C for 3 to 4 hours, cooled to room temperature, and the filtrate was filtered to obtain product A; under nitrogen protection, all of product A, 30 to 35 parts of methyl methacrylate, 5 to 8 parts of ethylene glycol dimethacrylate, 0.8 to 1.2 parts of azobisisobutyronitrile and 60 to 80 parts of ethyl acetate were refluxed at 75 to 80°C for 6 to 8 hours, cooled to room temperature to obtain product B; product B was poured into cold methanol for precipitation, and the solid was collected by filtration; washed with methanol, and dried in vacuo to obtain an oligomer; N2: By mass, add 100 to 120 parts of water-based acrylic resin to 15 to 25 parts of deionized water, stir evenly, add 13 to 17 parts of oligomer, stir evenly, add 8 to 10 parts of a 4 wt% to 6 wt% aqueous potassium persulfate solution dropwise, and reflux the reaction at 80°C to 85°C for 3h to 4h to obtain a dynamic covalent bond self-healing resin.

5. The safe and environmentally friendly water-based paint for toys according to claim 4, characterized in that: In N1, the stirring speed of the reflux reaction is 250 rpm to 300 rpm, the mesh number of the sieve used to filter the filtrate is 100 mesh to 200 mesh, the temperature of the cold methanol is 2°C to 6°C, the amount of the cold methanol is 10 to 12 times the volume of the product B, the mesh number of the sieve used to filter and collect the solid is 200 mesh to 325 mesh, the number of methanol washings is 3 to 5 times, and the vacuum drying is vacuum drying at 35°C to 40°C for 24 h to 30 h.

6. The safe and environmentally friendly water-based paint for toys according to claim 4, characterized in that: In N2, the stirring speed is 200 r / min~300 r / min for 15 min~20 min; the stirring speed of the reflux reaction is 250 rpm~300 rpm.

7. The safe and environmentally friendly water-based paint for toys according to claim 1, characterized in that: The preparation method of the catechin β-cyclodextrin inclusion complex comprises: preparing a 15 g / L to 18 g / L β-cyclodextrin water mixture; preparing a 4.5 g / L to 5.0 g / L catechin ethanol solution; and adding the catechin ethanol solution dropwise to the β-cyclodextrin water mixture in a volume ratio of β-cyclodextrin water mixture: catechin ethanol solution = (4 to 5): (1 to 1.2) under stirring, performing an inclusion reaction at 30° C. to 40° C. with stirring for 2 to 4 hours, allowing the inclusion complex to precipitate, centrifuging at 4000 rpm to 6000 rpm for 10 to 15 minutes, collecting the precipitate, vacuum drying at 40° C. to 50° C. to constant weight, and breaking it up to obtain the catechin β-cyclodextrin inclusion complex.

8. The safe and environmentally friendly water-based paint for toys according to claim 1, characterized in that: The mass ratio of the functional filler is calcium carbonate: talc: kaolin: titanium dioxide = (30-35): (20-25): (8-12): (5-10); the functional filler is sieved through a 325-460 mesh sieve.

9. The safe and environmentally friendly water-based paint for toys according to claim 1, characterized in that: The thickener is hydroxyethyl cellulose or xanthan gum; the dispersant is lecithin; the leveling agent is an acrylate leveling agent; the pigment is a natural plant pigment; and the defoaming agent is a polyether defoaming agent.

10. The method for preparing a safe and environmentally friendly water-based paint for toys according to claim 1, characterized in that: The steps include: The bio-based waterborne polyurethane-acrylic interpenetrating network polymer was added into a reactor according to the mass ratio, and stirred at a low speed of 200 rpm to 250 rpm. The dynamic covalent self-healing resin, functional filler, antibacterial agent and pigment were added in sequence, and the stirring was continued for 30 min to 40 min to obtain a mixture A; the dispersant, leveling agent and thickener were added to 8 to 10 parts of deionized water and mixed evenly to obtain a mixture B; the mixture B and defoaming agent were added to the mixture A, and the mixture was stirred at 800 r / min to 1200 r / min for 30 min to 40 min. The solid content of the coating was adjusted to 45 wt% to 55 wt% with deionized water, and the coating was filtered through a 150 mesh to 200 mesh sieve to obtain the coating.

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