A water-based paint suitable for the surface of leather

Abstract

The application discloses an anti-aging water-based paint suitable for a leather surface and belongs to the technical field of paints. The anti-aging water-based paint is composed of A component, B component, a free radical capturing agent, a leveling agent and a defoaming agent, wherein the A component is an acrylate copolymer emulsion containing a weather-resistant functional monomer, and the B component is a silane-terminated water-based polyurethane emulsion. The weather-resistant functional monomer is synthesized through three-step reaction and integrates ultraviolet absorption, light energy conversion and crosslinking functions; the A component is prepared through pre-emulsified semi-continuous seed polymerization, the B component is prepared through pre-polymerization, hydrophilic chain extension, silane termination and emulsification, and the two are hybridized in proportion, then additives are added, pH and viscosity are adjusted, and finally the finished product is obtained. The application constructs a complete anti-aging protection system, has excellent adhesion, flexibility and friction resistance, is suitable for leather working conditions and has low VOC content, can avoid yellowing and peeling of the coating, and prolongs the service life of leather products.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to an aging-resistant water-based paint suitable for leather surfaces. Background Technology

[0002] In the field of coating technology, leather surface finishing is a key step in enhancing the appearance, texture, durability, and added value of leather products. With increasingly stringent global environmental regulations and the popularization of green consumption concepts, traditional solvent-based leather finishing agents are gradually being replaced by water-based paints due to problems such as high emissions of volatile organic compounds (VOCs) and serious environmental pollution. Water-based coatings have become the core development trend of leather finishing materials. Currently, the mainstream water-based coatings for leather in the industry mainly include acrylic esters, polyurethanes, and hybrid systems of the two. Each system achieves its coating function through specific processes: Acrylic ester water-based coatings typically use emulsion polymerization, with methacrylates, butyl acrylates, etc., as comonomers. The rigidity and flexibility of the coating are controlled by adjusting the monomer ratio. They are widely used due to their low cost and good weather resistance. Polyurethane water-based coatings use polyether glycols, polyester glycols, or polycarbonate glycols and diisocyanates as raw materials, and are prepared through prepolymerization, hydrophilic chain extension, emulsification, and other steps. They have excellent flexibility and adhesion, and can adapt to the frequent deformation requirements of leather. In order to take into account the advantages of the two systems, some technologies prepare acrylic-polyurethane hybrid water-based coatings through physical blending or simple chemical modification, attempting to achieve complementary performance.

[0003] To improve the aging resistance of water-based paints for leather, existing technologies generally employ the addition of small-molecule additives such as UV absorbers and hindered amine light stabilizers (HALS). UV absorbers, primarily benzotriazoles and benzophenones, absorb some UV light to reduce coating degradation. HALS, on the other hand, delay yellowing and loss of gloss by capturing free radicals and breaking the degradation chain reaction. Simultaneously, to address issues of insufficient coating adhesion and abrasion resistance, some solutions introduce modifiers such as silane coupling agents and multifunctional chain extenders, or optimize the type and dosage of emulsifiers to improve emulsion dispersibility and film density. Furthermore, to meet the flexibility requirements of leather substrates, engineers attempt to balance the rigidity and flexibility of the coating by adjusting the proportion of soft-segment monomers and controlling the crosslinking density.

[0004] However, existing water-based coatings for leather still have many unresolved technical shortcomings: First, the performance of single systems is obviously limited. Acrylic ester coatings have poor flexibility and adhesion, and are prone to peeling off due to leather deformation after long-term use; polyurethane coatings have weak UV aging resistance and are prone to molecular chain degradation under UV irradiation, resulting in defects such as yellowing and cracking; hybrid systems often have poor two-phase compatibility and microphase separation, leading to unstable coating performance. Second, the effect of aging resistance modification is limited. Small molecule UV absorbers and HALS are prone to migration and precipitation after film formation, causing the protective effect to decay rapidly over time. In addition, some HALS may interact with free radicals in the acrylic ester polymerization system, interfering with the normal polymerization reaction and affecting the integrity of the coating structure. Third, it is difficult to achieve a balance of performance across all dimensions. Existing technologies often focus on improving a single performance, such as excessive cross-linking to pursue aging resistance, which increases the brittleness of the coating, or sacrificing the density and abrasion resistance of the coating to ensure flexibility, failing to meet the comprehensive requirements of leather products for aging resistance, adhesion, flexibility, and abrasion resistance. These problems severely restrict the application scope and effectiveness of water-based paints for leather. Therefore, developing a comprehensive, stable, and reliable water-based paint for leather has significant industry value. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing an aging-resistant water-based paint suitable for leather surfaces.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: an aging-resistant water-based paint suitable for leather surfaces, comprising the following components by weight: Component A: 12-32 parts; Component B: 60-80 parts; free radical scavenger: 0.1-0.3 parts; leveling agent: 0.2-0.3 parts; defoamer: 0.1-0.3 parts;

[0007] The specific formulation of component A is as follows, by weight: methyl methacrylate: 40-50 parts, butyl acrylate: 35-45 parts, weather-resistant functional monomer: 5-10 parts, acrylic acid: 5-8 parts, compound emulsifier: 2-3 parts, ammonium persulfate: 0.5-1.0 parts, and deionized water: 90-110 parts.

[0008] The specific formulation of component B is as follows, by weight: polycarbonate diol: 90-110 parts, isophorone diisocyanate: 30-40 parts, pentaerythritol: 3-6 parts, 2,2-dimethylolpropionic acid: 4-7 parts, γ-aminopropyltriethoxysilane: 6-10 parts, dibutyltin dilaurate: 0.05-0.15 parts, deionized water: 180-240 parts;

[0009] The chemical structural formula of the weather-resistant functional monomer is as follows:

[0010] ;

[0011] The preparation method of the weather-resistant functional monomer includes the following steps:

[0012] (1) Add 2-(2H-benzotriazol-2-yl)-4-methyl-6-(2-propenyl)phenol and epichlorohydrin to a reaction apparatus equipped with a reflux condenser, heat to 80-90℃, and add 50% sodium hydroxide solution dropwise with stirring for 30-60 min. After the addition is complete, keep the reaction at the temperature for 1-3 h, cool to room temperature, wash three times with deionized water, dry the organic phase with anhydrous sodium sulfate, remove excess epichlorohydrin by vacuum distillation, and recrystallize the remaining product in ethanol to obtain intermediate M1; the chemical reaction equation is as follows:

[0013] ; the product passes through 1 Characterized by 1H NMR; in this step, the phenolic hydroxyl group of 2-(2H-benzotriazol-2-yl)-4-methyl-6-(2-propenyl)phenol has a certain acidity. The 50% sodium hydroxide solution, as a base, will remove the hydrogen atom on the phenolic hydroxyl group, converting the phenolic hydroxyl group into a more nucleophilic phenoxy anion. This phenoxy anion, as a nucleophile, attacks the saturated carbon atom connected to the chlorine atom in the epichlorohydrin molecule, resulting in a nucleophilic substitution reaction. The chlorine atom is replaced as a leaving group, while the three-membered epoxy ring structure of epichlorohydrin is retained, ultimately generating intermediate M1 containing a phenoxy linker segment and residual epoxy group and aliphatic hydroxyl group;

[0014] (2) Under nitrogen protection, intermediate M1 and 4-aminoxylenone were added to dimethyl sulfoxide. The pH of the system was adjusted to 9-10 with triethylamine, and the temperature was raised to 45-55℃. The mixture was stirred for 6-10 h. After the reaction was completed, the reaction solution was poured into deionized water and extracted three times with ethyl acetate. The organic phase was dried over anhydrous sodium sulfate and the solvent was removed by vacuum distillation. The residue was purified by gradient elution using silica gel column chromatography to obtain intermediate M2. The chemical reaction equation is as follows:

[0015] ; the product passes through 1 Characterized by ¹H NMR; in this step, under nitrogen protection and a weakly alkaline environment, the three-membered epoxy ring retained in the intermediate M1 molecule has ring strain and electron-deficient characteristics, while the amino group of 4-aminoxylenone has a lone pair of electrons, making it a strong nucleophile. The lone pair of electrons of the amino group attacks the electron-deficient carbon atom of the epoxy ring, causing the epoxy ring to break and undergo a ring-opening reaction, forming a new CN covalent bond. At the same time, a new aliphatic hydroxyl group is generated at the rupture site of the epoxy ring. The weakly alkaline environment can enhance the nucleophilic activity of the amino group (avoiding protonation deactivation of the amino group) and inhibit non-specific hydrolysis of the epoxy group, ensuring the selectivity of the reaction; finally, intermediate M2 is obtained.

[0016] (3) Under nitrogen protection, intermediate M2 and isocyanate-based propyltriethoxysilane were added to anhydrous tetrahydrofuran, followed by dibutyltin dilaurate. The mixture was heated to 40-60℃ and reacted at a constant temperature for 1-3 hours. After the reaction was completed, excess solvent was removed by vacuum distillation. Then, the mixture was washed three times with petroleum ether under stirring. After each wash, the lower oil phase was separated by a separatory funnel. After the last wash, the oil phase was dried under vacuum to obtain the weather-resistant functional monomer. The chemical reaction equation is as follows:

[0017] ; the product passes through 1 Characterized by ¹H NMR; in this step, under the catalysis of dibutyltin dilaurate, the aliphatic hydroxyl group in the intermediate M2 molecule reacts with the isocyanate group of isocyanate-propyltriethoxysilane. This reaction produces no byproducts and directly forms a stable urethane bond, thereby covalently grafting the siloxane group to the end of the molecule. This siloxane group is the key group for subsequent coating crosslinking. It can hydrolyze and condense during the film formation process of waterborne paint to form a siloxane crosslinking network, thereby improving the coating's aging resistance, hydrolysis resistance and adhesion.

[0018] More preferably, the preparation method of the weather-resistant functional monomer includes the following steps:

[0019] (1) 2-(2H-benzotriazol-2-yl)-4-methyl-6-(2-propenyl)phenol and epichlorohydrin were added to a reaction apparatus equipped with a reflux condenser. The temperature was raised to 85°C, and 50% sodium hydroxide solution was added dropwise with stirring for 45 min. After the addition was completed, the reaction was kept at the temperature for 2 h. After cooling to room temperature, the mixture was washed three times with deionized water. The organic phase was dried with anhydrous sodium sulfate and the excess epichlorohydrin was removed by vacuum distillation. The remaining product was recrystallized in ethanol to obtain intermediate M1.

[0020] (2) Under nitrogen protection, intermediate M1 and 4-aminoxylenone were added to dimethyl sulfoxide, the pH of the system was adjusted to 9-10 with triethylamine, the temperature was raised to 50°C, and the reaction was stirred for 8 hours. After the reaction was completed, the reaction solution was poured into deionized water and extracted three times with ethyl acetate. The organic phase was dried with anhydrous sodium sulfate and the solvent was removed by vacuum distillation. The residue was purified by gradient elution by silica gel column chromatography to obtain intermediate M2.

[0021] (3) Under nitrogen protection, intermediate M2 and isocyanate-based propyltriethoxysilane were added to anhydrous tetrahydrofuran, followed by dibutyltin dilaurate. The mixture was heated to 60°C and reacted at a constant temperature for 2 hours. After the reaction was completed, excess solvent was removed by vacuum distillation. Then, the mixture was washed three times with petroleum ether under stirring. After each wash, the lower oil phase was separated by a separatory funnel. After the last wash, the oil phase was dried under vacuum to obtain the weather-resistant functional monomer.

[0022] Preferably, the free radical scavenger refers to light stabilizer 944.

[0023] Preferably, the leveling agent refers to BYK-333.

[0024] Preferably, the defoamer is BYK-024.

[0025] Preferably, the compound emulsifier refers to a mixture of sodium dodecyl sulfate and nonylphenol polyoxyethylene ether in a weight ratio of 1:1.

[0026] Preferably, the average Mn of the polycarbonate diol is 2000.

[0027] Preferably, in (1), the molar ratio of 2-(2H-benzotriazol-2-yl)-4-methyl-6-(2-propenyl)phenol, epichlorohydrin and sodium hydroxide is 1:4-6:1-1.4.

[0028] More preferably, in (1), the molar ratio of 2-(2H-benzotriazol-2-yl)-4-methyl-6-(2-propenyl)phenol, epichlorohydrin and sodium hydroxide is 1:5:1.2.

[0029] Preferably, in (2), the molar ratio of intermediate M1 and 4-aminoxylene is 1:1-1.2.

[0030] More preferably, in (2), the intermediate M1 and 4-aminoxylenone are in a molar ratio of 1:1.2.

[0031] Preferably, in (2), the intermediate M1, dimethyl sulfoxide and deionized water are in a weight ratio of 1:8-12:10-15.

[0032] More preferably, in (2), the intermediate M1, dimethyl sulfoxide and deionized water are in a weight ratio of 1:10:12.

[0033] Preferably, in step (2), gradient elution refers to the volume ratio of petroleum ether to ethyl acetate in each eluent step being 20:1, 10:1, 8:1 to 2:1.

[0034] Preferably, in (3), the intermediate M2 and isocyanate-propyltriethoxysilane are in a weight ratio of 1:1-1.2.

[0035] More preferably, in (3), the intermediate M2 and isocyanate-based propyltriethoxysilane are in a weight ratio of 1:1.1.

[0036] Preferably, in (3), the intermediate M2, anhydrous tetrahydrofuran and dibutyltin dilaurate are in a weight ratio of 1:8-12:0.001-0.005.

[0037] More preferably, in (3), the intermediate M2, anhydrous tetrahydrofuran and dibutyltin dilaurate are in a weight ratio of 1:10:0.003.

[0038] Preferably, the preparation method of component A includes the following steps:

[0039] At room temperature, methyl methacrylate, butyl acrylate, weather-resistant functional monomers, acrylic acid, compound emulsifier, and half the volume of deionized water are added to an emulsification kettle. High-speed stirring is started, and the speed is adjusted to 1000-2000 rpm for 20-40 minutes to obtain a pre-emulsion. Then, in a three-necked reaction flask equipped with a reflux condenser, a stirrer, and a dropping funnel, the remaining deionized water is added, along with 1 / 5 of the volume of ammonium persulfate. Stirring is started, and the temperature is raised to 60-80°C. The mixture is then added to the reaction mixture through the dropping funnel. Add 1 / 10 of the above pre-emulsion to the bottle, with a dropping time of 10-30 minutes. After the dropping is completed, keep the temperature constant for 20-40 minutes. Prepare the remaining ammonium persulfate into an ammonium persulfate aqueous solution and place it and the remaining pre-emulsion in two separate dropping funnels. Add the pre-emulsion and the ammonium persulfate aqueous solution simultaneously. After all the materials have been added, continue the reaction at a constant temperature for 2-3 hours. After the reaction is completed, allow the system temperature to cool naturally to 30-40℃, stop stirring, and filter through a 100-mesh filter to obtain component A.

[0040] Component A employs a pre-emulsified semi-continuous seeded emulsion polymerization process. Through free radical copolymerization, aging-resistant functional monomers are uniformly grafted onto the acrylate polymer backbone while ensuring emulsion stability. In the pre-emulsification stage, a compounded emulsifier forms micelles in water under high-speed stirring, encapsulating oil-soluble monomers such as methyl methacrylate, butyl acrylate, weather-resistant functional monomers, and acrylic acid, forming a stable pre-emulsion. This prevents monomer stratification and provides a "reaction site" for subsequent uniform polymerization. In the seed polymerization stage, when the system is heated to 60-80℃, ammonium persulfate thermally decomposes to generate sulfate free radicals. These free radicals initiate free radical polymerization of monomers within a small number of micelles in the pre-emulsion, forming fine seed latex particles. The presence of these seed latex particles controls the particle size distribution in subsequent polymerization, preventing explosive polymerization. In the semi-continuous polymerization stage, the remaining pre-emulsion and 5-10 wt% ammonium persulfate aqueous solution are added dropwise simultaneously. The initiator continuously decomposes to generate free radicals, and the monomers gradually polymerize and grow on the surface of the seed latex particles. Methyl methacrylate provides polymer rigidity, butyl acrylate imparts flexibility, and acrylic acid introduces carboxyl groups to enhance the compatibility of the emulsion with other components. Weather-resistant functional monomers participate in free radical copolymerization through allyl double bonds in the molecule and are covalently grafted onto the acrylate backbone. Finally, after cooling and filtration to remove a small amount of gel impurities, an acrylate copolymer emulsion with uniform particle size and containing weather-resistant groups is obtained.

[0041] Preferably, the concentration of the ammonium sulfate aqueous solution in the preparation method of component A is 5-10 wt%.

[0042] Preferably, the synchronous dripping time in the preparation method of component A is 1-2.5 h.

[0043] Preferably, the preparation method of component B includes the following steps:

[0044] Polycarbonate diol, after vacuum dehydration, is added to a three-necked reaction flask equipped with a reflux condenser, a stirrer, and a nitrogen delivery tube under nitrogen protection. The temperature is raised to 70-80°C, and isophorone diisocyanate and pentaerythritol are added and stirred until homogeneous. Then, dibutyltin dilaurate is added, and the reaction is maintained at a constant temperature for 2-2.5 hours. The prepolymerization reaction is stopped when the isocyanate group content in the prepolymer reaches 5.0-5.5% by di-n-butylamine titration. The reaction system is then cooled to 60-65°C, and... Add 2,2-dimethylolpropionic acid and stir continuously for 1-2 hours. Then, continue to cool to 40-45℃, add triethylamine to adjust the pH of the system to 8-9, and then add γ-aminopropyltriethoxysilane. Stir at a constant temperature for 1-2 hours, maintaining the system temperature at 40-45℃. Add deionized water to the system while stirring at a high speed of 800-1000 r / min, and keep stirring for 20-40 min. Allow to cool naturally to room temperature and filter through a 120-mesh filter to obtain component B.

[0045] The polycarbonate diol in component B is first dehydrated under vacuum to remove trace amounts of water. Then, at 70-80℃ and under the catalysis of dibutyltin dilaurate, its hydroxyl groups react with the -NCO groups of isophorone diisocyanate to undergo a polyurethane prepolymerization reaction. Pentaerythritol, as a multifunctional chain extender, forms a branched structure by reacting with the -NCO groups through its four hydroxyl groups. In the hydrophilic chain extension stage, after cooling to 60-65℃, 2,2-dimethylolpropionic acid is added. Its hydroxyl groups react with the remaining -NCO groups in the prepolymer to introduce carboxyl groups into the polyurethane molecular chain, providing a hydrophilic structural basis for subsequent aqueous emulsification. In the silane end-capping stage, triethylamine is added after cooling to 40-45℃ to neutralize the carboxyl group of 2,2-dimethylolpropionic acid and form a hydrophilic carboxyl group, maintaining the pH of the system at 8-9. Subsequently, the amino group of γ-aminopropyltriethoxysilane undergoes an addition reaction with the remaining -NCO, completing the silane end-capping of the molecular chain and introducing siloxane groups to improve the aging resistance and adhesion of the subsequent coating. In the in-situ emulsification stage, deionized water is added under high-speed stirring at 800-1000 r / min. The hydrophilic carboxyl group disperses the polyurethane molecular chain in water to form a stable oil-in-water emulsion. Continuous stirring ensures the homogeneity of the emulsion. After cooling and filtration to remove gel impurities, an aqueous emulsion with both polyurethane flexibility and silane function is obtained.

[0046] Furthermore, the present invention also provides a method for preparing an aging-resistant water-based paint suitable for leather surfaces, comprising the following steps:

[0047] First, add component B to a reactor equipped with a stirrer and heat it to 40-60℃ while stirring at 1000-1500 rpm. Then, add component A to component B and stir at a constant temperature for 1-2 hours. Subsequently, add the free radical scavenger, leveling agent, and defoamer in sequence and continue stirring for 10-20 minutes. Then, adjust the pH of the system to 7.5-9.5 and use a Forecast 4 cup to adjust the viscosity to 20-30 seconds at 25℃. After cooling to room temperature, filter through a 120-mesh filter to obtain an aging-resistant water-based paint suitable for leather.

[0048] Preferably, the pH value of the system is adjusted by ammonia, and the viscosity is adjusted by adding deionized water or evaporating deionized water.

[0049] Preferably, the mechanism of action of the anti-aging water-based paint suitable for leather surfaces in this invention is explained as follows:

[0050] The aging resistance of this invention stems from a synergistic mechanism of "multiple UV light blocking + precise free radical capture." The weather-resistant functional monomer is covalently grafted onto the acrylate backbone of component A. The benzotriazole group in its molecule forms a dual UV absorption system with the 4-aminoxylene fragment. Benzotriazole can efficiently absorb UV light in the 290-400nm range (this wavelength is the main UV region that causes degradation of leather coatings), while 4-aminoxylene undergoes an intramolecular structural transformation after absorbing UV light, converting the absorbed light energy into heat energy and preventing light energy from causing polymer chain breakage. The coating reduces free radical generation at the source by cracking; the physically added free radical scavenger acts as a "back-end protection" agent, which can quickly capture the small amount of alkyl free radicals and peroxy free radicals generated by the coating under ultraviolet irradiation, interrupt the free radical chain degradation reaction, and prevent the coating from yellowing, losing gloss, cracking and other aging phenomena; at the same time, the siloxane groups at the end of the weather-resistant functional monomers hydrolyze and condense to form a cross-linked network during the film formation process, which not only improves the density of the coating structure and reduces the penetration depth of ultraviolet light, but also fixes the weather-resistant groups and free radical scavengers, preventing their migration and loss, and ensuring the long-term aging resistance effect is stable.

[0051] The film-forming process of water-based paint is a process of in-situ hybridization and synergistic cross-linking of component A and component B, which ultimately forms a high-performance coating adapted to leather substrates. After mixing component A (acrylate copolymer emulsion) and component B (silane-terminated aqueous polyurethane emulsion), molecular-level compatibility is achieved under constant temperature stirring at 40-60℃. The carboxyl groups of component A and the urethane groups of component B have hydrogen bonding, which promotes uniform dispersion of the two phases and avoids delamination. During the film-forming stage, the siloxane groups at the ends of component B hydrolyze under the action of water to generate silanol groups. The silanol groups undergo condensation reactions with each other and with the hydroxyl groups of component A to form a three-dimensional siloxane cross-linking network, which tightly connects the acrylate segments and the polyurethane segments. This not only compensates for the lack of flexibility in the acrylate coating, but also improves the weather resistance and abrasion resistance of the polyurethane coating. In addition, the rigidity provided by methyl methacrylate in component A and the flexibility imparted by butyl acrylate, combined with the hydrolysis resistance of the polycarbonate diol segments in component B, make the film-forming coating have sufficient hardness to resist external friction, and also have good elasticity to adapt to the bending and stretching deformation of leather, so that the coating will not peel off or crack due to leather deformation.

[0052] This invention ensures that water-based paints are suitable for application and use on leather surfaces through component design and process control. During the application phase, the compound emulsifier ensures the stability of the emulsion after mixing components A and B. The leveling agent BYK-333 reduces the surface tension of the coating, allowing the paint to spread quickly on the leather surface and preventing pinholes and brush marks. The defoamer BYK-024 effectively eliminates air bubbles generated during application, ensuring a smooth and even coating surface. The pH value of the system is adjusted to 7.5-9.5, which maintains the stability of the emulsion and enhances the adhesion between the coating and the leather substrate. The viscosity is controlled at 20-30s (Ford cup 4, 25℃), suitable for conventional leather finishing processes such as spraying and brushing, avoiding excessively thin or thick paint that is difficult to apply. During the usage phase, the cross-linked network structure of the coating gives it excellent abrasion and hydrolysis resistance, resisting daily friction and temperature and humidity changes during leather use. At the same time, the good compatibility of each functional component with the system ensures that the coating does not precipitate or have haze, maintaining its appearance integrity and aging resistance even after long-term use, meeting the service life requirements of leather products.

[0053] Compared with the prior art, the beneficial effects of the present invention are:

[0054] 1. This invention designs a weather-resistant functional monomer structure that integrates ultraviolet absorption, light energy conversion, and cross-linking fixation, forming a "physical blocking-light energy conversion-functional fixation" protection mechanism. It can intercept ultraviolet light that causes degradation of leather coatings across the entire wavelength range, converting excess light energy into heat energy for release. In addition, the siloxane cross-linking network fixes the functional groups, avoiding the migration and loss problems of traditional small molecule additives. This allows the coating to effectively resist yellowing, loss of gloss, chalking, and cracking even when exposed to complex environments for a long time, significantly extending the service life of leather products.

[0055] 2. This invention, through in-situ hybridization and interpenetrating network construction of components A and B, perfectly integrates the weather resistance of acrylate, the flexibility of polyurethane, and the density of siloxane. The coating possesses sufficient surface hardness and abrasion resistance to withstand frictional wear during daily use, while also exhibiting excellent flexibility and elasticity to adapt to the frequent bending and stretching deformations of leather, preventing coating peeling or cracking due to substrate deformation. Simultaneously, the hydrogen bonding and chemical cross-linking between components A and B synergistically enhance the adhesion between the coating and the leather substrate, ensuring that the coating maintains structural integrity throughout long-term use, without defects such as peeling or flaking.

[0056] 3. This invention, through precise parameter control of the pre-emulsified semi-continuous seed polymerization process, ensures efficient grafting of functional monomers onto the polymer backbone, with no free monomers or additive residues, thus giving the emulsion system excellent stability. During application, the coating exhibits excellent leveling properties, effectively avoiding defects such as pinholes, brush marks, and bubbles, and is compatible with conventional leather finishing processes such as spraying and brushing. After film formation, the coating structure is dense and uniform, free of pores or micro-defects, improving both abrasion and hydrolysis resistance while ensuring a smooth and even coating appearance, meeting the high-quality surface decoration requirements of leather products.

[0057] 4. This invention employs a water-based system design, using water as the dispersion medium throughout the process. It has extremely low volatile organic compound content, no irritating odor, and complies with current environmental regulations and green production concepts. It has no adverse effects on the environment or human health during use. Furthermore, the components exhibit excellent compatibility, with no issues such as precipitation or stratification during long-term storage and use. It is suitable for various substrates, including natural and synthetic leather. The product combines environmental friendliness, practicality, and durability, addressing the performance shortcomings of existing water-based leather paints while meeting market demand for high-quality leather finishing materials, thus possessing broad application prospects. Attached Figure Description

[0058] Figure 1 The intermediate M1 prepared in the preparation example of the present invention 1 H NMR spectrum;

[0059] Figure 2 The intermediate M2 prepared in the preparation example of this invention 1 H NMR spectrum;

[0060] Figure 3 The anti-aging functional monomer prepared in the preparation example of this invention 1 H NMR spectrum. Detailed Implementation

[0061] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0062] Preparation example: The specific preparation method of the aging-resistant functional monomer includes the following steps:

[0063] (1) 0.1 mol (26.53 g) of 2-(2H-benzotriazol-2-yl)-4-methyl-6-(2-propenyl)phenol and 0.5 mol (46.26 g) of epichlorohydrin were added to a reaction apparatus equipped with a reflux condenser. The temperature was raised to 85 °C, and 9.6 g of 50% sodium hydroxide solution (0.12 mol sodium hydroxide content) was added dropwise with stirring over a period of 45 min. After the addition was complete, the reaction was kept at this temperature for 2 h. After cooling to room temperature, the product was washed three times with deionized water. The organic phase was dried with anhydrous sodium sulfate, and excess epichlorohydrin was removed by vacuum distillation. The remaining product was recrystallized in ethanol to obtain intermediate M1. The product was then subjected to... 1 The structure was confirmed by H NMR;

[0064] (2) Under nitrogen protection, 0.1 mol (32.14 g) of intermediate M1 and 0.12 mol (23.67 g) of 4-aminoxylenone were added to 321.4 g of dimethyl sulfoxide. The pH of the system was adjusted to 9-10 with triethylamine, the temperature was raised to 50 °C, and the mixture was stirred for 8 h. After the reaction was completed, the reaction solution was poured into 385.68 g of deionized water and extracted three times with ethyl acetate. The organic phase was dried over anhydrous sodium sulfate and the solvent was removed by vacuum distillation. The residue was purified by gradient elution using silica gel column chromatography. The volume ratio of petroleum ether to ethyl acetate in each eluent was 20:1, 10:1, 8:1 to 2:1, respectively, to obtain intermediate M2. The product was purified by... 1 The structure was confirmed by H NMR;

[0065] (3) Under nitrogen protection, 0.1 mol (51.86 g) of intermediate M2 and 0.11 mol (27.21 g) of isocyanate-propyltriethoxysilane were added to 518.6 g of anhydrous tetrahydrofuran, followed by 0.16 g of dibutyltin dilaurate. The mixture was heated to 60 °C and reacted at a constant temperature for 2 h. After the reaction, excess solvent was removed by vacuum distillation, and then the mixture was washed three times with petroleum ether under stirring. After each wash, the lower oil phase was separated by a separatory funnel. After the last wash, the oil phase was dried under vacuum to obtain the weather-resistant functional monomer. The product was then processed through... 1 The structure was confirmed by H NMR.

[0066] Comparative Preparation Example 1: The difference between Comparative Preparation Example 1 and Preparation Example 2 is that steps (1) and (2) are omitted. 2-(2H-benzotriazol-2-yl)-4-methyl-6-(2-propenyl)phenol is directly reacted with isocyanate-propyltriethoxysilane in anhydrous tetrahydrofuran via dibutyltin dilaurate catalysis to obtain a weather-resistant functional monomer.

[0067] Comparative preparation example 2: The difference between comparative preparation example 2 and preparation example is that step (3) is omitted. The intermediate M2 obtained in step (2) is the aging-resistant functional monomer.

[0068] Comparative Preparation Example 3: The difference between Comparative Preparation Example 3 and the Preparation Example is that 4-aminoxyleneone in step (2) is replaced with 2,2,6,6-tetramethylpiperidineamine.

[0069] Example 1: A specific preparation method for an aging-resistant water-based paint suitable for leather surfaces, comprising the following steps:

[0070] S1. At room temperature, 400g of methyl methacrylate, 350g of butyl acrylate, 50g of the weather-resistant functional monomer prepared according to the preparation example, 50g of acrylic acid, 20g of the compound emulsifier (a mixture of sodium dodecyl sulfate and nonylphenol polyoxyethylene ether in a weight ratio of 1:1) and 450g of deionized water were added to an emulsification kettle. High-speed stirring was started, and the speed was adjusted to 1000r / min. Stirring was carried out for 20min to obtain a pre-emulsion. Then, 450g of deionized water and 1g of ammonium persulfate were added to a three-necked reaction flask equipped with a reflux condenser, a stirrer, and a dropping funnel. Stirring was started. The temperature was raised to 60°C, and 1 / 10 of the pre-emulsion was added dropwise to the reaction flask through a dropping funnel over a period of 10 minutes. After the addition was completed, the reaction was kept at a constant temperature for 20 minutes. The remaining 4g of ammonium persulfate was prepared into a 5wt% ammonium persulfate aqueous solution, and placed in two separate dropping funnels along with the remaining pre-emulsion. The pre-emulsion and the ammonium persulfate aqueous solution were added dropwise simultaneously over a period of 1 hour. After all the materials were added, the reaction was kept at a constant temperature for another 2 hours. After the reaction was completed, the system temperature was naturally cooled to 30°C, stirring was stopped, and the mixture was filtered through a 100-mesh filter to obtain component A.

[0071] S2. After vacuum dehydration, 900g of polycarbonate diol (average Mn=2000) was added to a three-necked reaction flask equipped with a reflux condenser, a stirrer, and a nitrogen delivery tube under nitrogen protection. The temperature was raised to 70°C, and 300g of isophorone diisocyanate and 30g of pentaerythritol were added and stirred until homogeneous. Then, 0.5g of dibutyltin dilaurate was added, and the reaction was maintained at a constant temperature for 2 hours. The prepolymerization reaction was stopped when the isocyanate group content in the prepolymer reached 5.0-5.5% by titration with di-n-butylamine. The reaction system was then cooled to 60°C, and 40g of 2,2-dimethylolpropionic acid was added. The reaction was stirred continuously for 1 hour, and then the temperature was further lowered to 40°C. Triethylamine was added to adjust the pH of the system to 8-9, and then 60g of... γ-aminopropyltriethoxysilane was reacted at a constant temperature with stirring for 1 hour, maintaining the system temperature at 40°C. 1.8 kg of deionized water was added to the system while stirring at a high speed of 800 r / min. The mixture was stirred for 20 minutes and then allowed to cool naturally to room temperature. The mixture was then filtered through a 120-mesh filter to obtain component B.

[0072] S3. First, add 600g of component B to a reactor equipped with a stirrer, heat to 40℃ while stirring at 1000rpm, add 120g of component A to component B, stir at a constant temperature for 1h, then add 1g of light stabilizer 944, 2g of BYK-333 and 1g of BYK-024 in sequence, continue stirring for 10min, then adjust the pH of the system to 7.5-9.5 with ammonia, and adjust the viscosity of the system to 20-30s by adding or evaporating deionized water at 25℃ using a Forte 4 cup; after cooling to room temperature, filter through a 120-mesh filter to obtain an aging-resistant water-based paint suitable for leather.

[0073] Example 2: A specific preparation method for an aging-resistant water-based paint suitable for leather surfaces, comprising the following steps:

[0074] S1. At room temperature, 450g of methyl methacrylate, 400g of butyl acrylate, 80g of the weather-resistant functional monomer prepared according to the preparation example, 65g of acrylic acid, 25g of compound emulsifier (a mixture of sodium dodecyl sulfate and nonylphenol polyoxyethylene ether in a weight ratio of 1:1) and 500g of deionized water were added to an emulsification kettle. High-speed stirring was started, and the speed was adjusted to 1500r / min. Stirring was carried out for 30min to obtain a pre-emulsion. Subsequently, 500g of deionized water and 1.2g of ammonium persulfate were added to a three-necked reaction flask equipped with a reflux condenser, a stirrer, and a dropping funnel. Stirring was started and the temperature was increased. The temperature was raised to 70℃. One-tenth of the pre-emulsion was added dropwise to the reaction flask through a dropping funnel over a period of 20 minutes. After the addition was completed, the reaction was kept at a constant temperature for 30 minutes. The remaining 4.8g of ammonium persulfate was prepared into an 8wt% ammonium persulfate aqueous solution. This solution and the remaining pre-emulsion were placed in two separate dropping funnels. The pre-emulsion and the ammonium persulfate aqueous solution were added dropwise simultaneously over a period of 1.5 hours. After all the materials were added, the reaction was kept at a constant temperature for another 2.5 hours. After the reaction was completed, the system temperature was naturally cooled to 35℃. Stirring was stopped. The mixture was then filtered through a 100-mesh filter to obtain component A.

[0075] S2. After vacuum dehydration, 1 kg of polycarbonate diol (average Mn = 2000) was added to a three-necked reaction flask equipped with a reflux condenser, a stirrer, and a nitrogen delivery tube under nitrogen protection. The temperature was raised to 75°C, and 350 g of isophorone diisocyanate and 45 g of pentaerythritol were added. The mixture was stirred until homogeneous, and then 1 g of dibutyltin dilaurate was added. The reaction was maintained at a constant temperature for 2.3 h. The prepolymerization reaction was stopped when the isocyanate group content in the prepolymer reached 5.0-5.5% by titration with di-n-butylamine. The reaction system was then cooled to 62°C, and 50 g of 2,2-dimethylolpropionic acid was added. The reaction was stirred continuously for 1.5 h, and then the temperature was further lowered to 43°C. Triethylamine was added to adjust the pH of the system to 8-9, and then 80 g of... γ-aminopropyltriethoxysilane was reacted under constant temperature stirring for 1.5 h, maintaining the system temperature at 43 °C. 2.1 kg of deionized water was added to the system under high-speed stirring at 900 r / min, and stirring was maintained for 30 min. The mixture was then allowed to cool naturally to room temperature and filtered through a 120-mesh filter to obtain component B.

[0076] S3. First, add 700g of component B to a reactor equipped with a stirrer, heat to 50℃ while stirring at 1200rpm, add 220g of component A to component B, and stir at a constant temperature for 1.5h. Then, add 2g of light stabilizer 944, 2.5g of BYK-333 and 2g of BYK-024 in sequence, and continue stirring for 15min. Then, adjust the pH of the system to 7.5-9.5 with ammonia water, and adjust the viscosity of the system to 20-30s at 25℃ by adding or evaporating deionized water using a Forte 4 cup. After cooling to room temperature, filter through a 120-mesh filter to obtain an aging-resistant water-based paint suitable for leather.

[0077] Example 3: A specific preparation method for an aging-resistant water-based paint suitable for leather surfaces, comprising the following steps:

[0078] S1. At room temperature, 500g of methyl methacrylate, 450g of butyl acrylate, 100g of the weather-resistant functional monomer prepared according to the preparation example, 80g of acrylic acid, 30g of compound emulsifier (a mixture of sodium dodecyl sulfate and nonylphenol polyoxyethylene ether in a weight ratio of 1:1) and 550g of deionized water were added to an emulsification kettle. High-speed stirring was started, and the speed was adjusted to 2000 rpm for 40 minutes to obtain a pre-emulsion. Subsequently, 550g of deionized water and 2g of ammonium persulfate were added to a three-necked reaction flask equipped with a reflux condenser, a stirrer, and a dropping funnel. Stirring was started and... Heat the mixture to 80°C, and add 1 / 10 of the pre-emulsion to the reaction flask through a dropping funnel over a period of 30 minutes. After the addition is complete, maintain the temperature and react for 40 minutes. Prepare a 10 wt% ammonium persulfate aqueous solution and place it and the remaining pre-emulsion in two separate dropping funnels. Add the pre-emulsion and the ammonium persulfate aqueous solution simultaneously over a period of 2.5 hours. After all the materials have been added, continue the reaction at a constant temperature for 3 hours. After the reaction is complete, allow the system to cool naturally to 40°C, stop stirring, and filter through a 100-mesh filter to obtain component A.

[0079] S2. After vacuum dehydration, 1.1 kg of polycarbonate diol (average Mn = 2000) was added to a three-necked reaction flask equipped with a reflux condenser, a stirrer, and a nitrogen delivery tube under nitrogen protection. The temperature was raised to 80°C, and 400 g of isophorone diisocyanate and 60 g of pentaerythritol were added and stirred until homogeneous. Then, 1.5 g of dibutyltin dilaurate was added, and the reaction was maintained at a constant temperature for 2.5 h. The prepolymerization reaction was stopped when the isocyanate group content in the prepolymer reached 5.0-5.5% by titration with di-n-butylamine. The reaction system was then cooled to 65°C, and 70 g of 2,2-dimethylolpropionic acid was added. The reaction was stirred continuously for 2 h, and then the temperature was further lowered to 45°C. Triethylamine was added to adjust the pH of the system to 8-9, and then 100 g of... γ-aminopropyltriethoxysilane was reacted at a constant temperature and stirred for 2 hours. The system temperature was maintained at 45°C. Deionized water was added to the system under high-speed stirring at 1000 r / min. The stirring was maintained for 40 min. The mixture was then naturally cooled to room temperature and filtered through a 120-mesh filter to obtain component B.

[0080] S3. First, add 800g of component B to a reactor equipped with a stirrer, and heat to 60℃ while stirring at 1500rpm. Then, add 320g of component A to component B and stir at a constant temperature for 2 hours. Subsequently, add 3g of light stabilizer 944, 3g of BYK-333, and 3g of BYK-024 in sequence, and continue stirring for 20 minutes. Then, adjust the pH of the system to 7.5-9.5 with ammonia water, and adjust the viscosity of the system to 20-30s at 25℃ by adding or evaporating deionized water using a Forte 4 cup. After cooling to room temperature, filter through a 120-mesh filter to obtain an aging-resistant water-based paint suitable for leather.

[0081] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that the aging-resistant functional monomer prepared according to the preparation example is replaced with 2-(2H-benzotriazol-2-yl)-4-methyl-6-(2-propenyl)phenol.

[0082] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that the aging-resistant functional monomer prepared according to the preparation example is replaced with the aging-resistant functional monomer prepared according to Comparative Preparation Example 1.

[0083] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that the aging-resistant functional monomer prepared according to the preparation example is replaced with the aging-resistant functional monomer prepared according to Comparative Preparation Example 2.

[0084] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that the aging-resistant functional monomer prepared according to the preparation example is replaced with the aging-resistant functional monomer prepared according to Comparative Preparation Example 3, and light stabilizer 944 is not added.

[0085] Comparative Example 5: The difference between Comparative Example 5 and Example 2 is that γ-aminopropyltriethoxysilane is not added in step S2.

[0086] Performance testing:

[0087] 1. UV Aging Resistance Test: The test was conducted using a QUV UV aging test chamber, referring to GB / T 14522-2008 "Artificial Climate Aging Test Methods for Plastics, Coatings and Rubber Materials for Mechanical Industry Products". Water-based paints from Examples 1-3 and Comparative Examples 1-5 were uniformly coated onto pigskin substrates (wet film thickness 80 μm, dried at 100℃ for 30 min). Samples measuring 50 mm × 50 mm were cut and placed in the test chamber. The irradiation conditions were set to UVA-340 lamps with an irradiance of 0.68 W / m². 2 The temperature was 60℃, and the cycle consisted of 4 hours of light exposure and 4 hours of condensation. The cumulative test time was 1000 hours. Before and after the test, the yellowing index (ΔE*) of the sample was measured by a colorimeter, and the gloss rate was measured by a gloss meter (60° angle). At the same time, the sample surface was observed by the naked eye to see if cracking, powdering, peeling and other phenomena appeared. The experimental results are shown in Table 1.

[0088] Table 1. Results of UV aging resistance test

[0089]

[0090] 2. Coating Adhesion Test: Referring to QB / T 2724-2018 "Test Method for Adhesive Fastness of Leather Coatings", the cross-cut adhesion test-tape peeling method was used. Pigskin samples coated with water-based paints from Examples 1-3 and Comparative Examples 1-5 and cured were laid flat and fixed. A 10×10 grid with a 1mm spacing was cut on the coating surface using a cross-cut adhesion tester (penetrating the coating to the leather substrate). After removing debris from the grid with a brush, 3M 610 tape was smoothly applied to the grid area. The tape was pressed firmly with a finger to ensure complete adhesion to the coating. The tape was then quickly peeled off at a 180° angle. This process was repeated three times. The coating peeling area was graded as follows: Grade 0 (no peeling), Grade 1 (peeling area ≤ 5%), Grade 2 (peeling area 5%-15%), Grade 3 (peeling area 15%-35%), Grade 4 (peeling area 35%-65%), and Grade 5 (peeling area > 65%). The experimental results are shown in Table 2.

[0091] 3. Coating Flexibility Test: Referring to GB / T 1731-1993 "Determination of Coating Film Flexibility", strips of 15mm × 100mm were cut from pigskin samples coated with water-based paints of Examples 1-3 and Comparative Examples 1-5 and cured. These strips were placed at 25℃ and 50% relative humidity for 24 hours. Then, using the cylindrical shaft bending method, the sample was bent slowly at a 180° angle around cylindrical shafts with diameters of 2mm, 4mm, 6mm, 8mm, and 10mm, with the coating facing outwards. After holding the bend for 10 seconds, the sample was returned to its original shape. The presence of cracks, creases, or peeling was observed. The minimum diameter of the cylindrical shaft without damage was recorded; a smaller diameter indicates better flexibility. A repeated bending test was also performed, bending the sample repeatedly at a frequency of 30 times / min (bending angle ±90°) for a total of 10,000 times. The coating integrity was then observed. The experimental results are shown in Table 2.

[0092] 4. Abrasion resistance test: Referring to GB / T 15102-2017 "Leather Physical and Mechanical Tests - Determination of Color Fastness to Abrasion", a Martindale abrasion tester was used. Pig leather samples coated with water-based paints from Examples 1-3 and Comparative Examples 1-5 and cured were fixed in the lower clamp of the instrument. The friction media were standard wool cloth (dry friction) and wet wool cloth (wet friction, 100% moisture content). The load weight was set to 500g, the friction speed to 40 times / min, the friction stroke to 24mm, and the cumulative friction to 5000 times. After the test, the coating surface was observed for wear, exposure of the base material, and discoloration. The experimental results are shown in Table 2.

[0093] Table 2. Test results of coating adhesion, coating flexibility and abrasion resistance

[0094]

[0095] Data Analysis:

[0096] As can be seen from the experimental data in Table 1-2, the anti-aging water-based paint prepared by the present invention in Examples 1-3 is significantly better than the comparative examples in terms of UV aging resistance, coating adhesion, flexibility and abrasion resistance; among them, Example 2 achieves the optimal balance of various performance dimensions and comprehensive performance.

[0097] Example 2 exhibits optimal UV aging resistance, likely because the benzotriazole group in its weather-resistant functional monomer can efficiently absorb 290-400nm UV light, while 4-aminoxylenecone converts the absorbed light energy into heat energy, reducing free radical generation at the source. The siloxane crosslinking network not only enhances the coating's density and reduces UV light penetration depth but also firmly fixes the weather-resistant groups, preventing their migration and loss. The physically mixed light stabilizer 944 precisely captures a small amount of residual free radicals in the coating, interrupting the polymer degradation chain reaction. The three components form a complete protective chain of "front-end blocking - structural fixation - back-end removal."

[0098] Compared with Example 2, each comparative example had problems with broken protective systems or insufficient structural support: Comparative Example 1 used a single benzotriazole to replace the complete weather-resistant functional monomer, lacking the auxiliary conversion function of 4-aminoxylene and the siloxane crosslinking network, making the weather-resistant groups easy to lose and unable to resist long-term UV exposure; Comparative Example 2 omitted the first two steps of the weather-resistant functional monomer reaction, lacking 4-aminoxylene, relying solely on benzotriazole to absorb UV light, resulting in a significant decrease in protection efficiency; Comparative Example 3 omitted the silane grafting step of the weather-resistant functional monomer, lacking a crosslinking network to fix the weather-resistant groups, and the migration of groups during the test led to a decrease in the protective effect; In Comparative Example 4, the HALS fragment preferentially captured free radicals during the polymerization stage of component A, terminating the polymerization reaction, resulting in component A not forming a complete copolymer, a loose coating structure, and no effective protective system, with UV light directly causing rapid degradation of the coating; In Comparative Example 5, component B was not silane-terminated, failing to form a dense crosslinking network, allowing UV light to easily penetrate the coating and cause polymer chain degradation, exacerbating gloss loss and yellowing.

[0099] The coating adhesion in Example 2 reached an optimal level, which may be due to the molecular-level compatibility and strong interaction of its A / B components: Component A, through a pre-emulsified semi-continuous seed polymerization process, forms an acrylate copolymer emulsion with uniform particle size. The carboxyl groups in the molecular chain form stable hydrogen bonds with the urethane groups in the polyurethane molecular chain of Component B, promoting uniform dispersion of the two phases. At the same time, the siloxane groups of Component B undergo a condensation reaction with the hydroxyl groups of Component A to form a three-dimensional siloxane crosslinking network, which tightly connects the acrylate segments and the polyurethane segments, enabling the coating to form a dual effect of "physical adsorption + chemical bonding" with the leather substrate, resulting in extremely strong adhesion.

[0100] The adhesion of each comparative example was weaker than that of Example 2. The core reason was the lack of key binding sites or failure of structural formation: In Comparative Example 1, the weather-resistant functional monomer lacked siloxane groups and the polar effect of 4-aminoxylene ketone, resulting in weakened interaction between components A and B, and the coating adhered to the substrate only through physical adsorption; Although Comparative Examples 2 and 3 retained some crosslinking groups, the incomplete structure of the weather-resistant functional monomer reduced compatibility with components A and B, resulting in insufficient adhesion; In Comparative Example 4, the polymerization of component A failed, failing to form a complete copolymer chain, and thus could not form an effective bond with component B. The coating only physically covered the surface of the substrate and was easily detached; In Comparative Example 5, component B lacked silane end capping and the tight connection effect of the crosslinking network was missing. Components A and B were only bonded by hydrogen bonds, resulting in significantly reduced adhesion.

[0101] The coating in Example 2 exhibits the best flexibility due to the precise matching between the polymer segment characteristics and the crosslinking network structure: butyl acrylate in component A provides suitable flexible segments, while methyl methacrylate provides rigid support. The ratio of these two components is synergistically controlled with the polymerization temperature and pre-emulsification speed, enabling the polymer segments to possess both flexibility and stability. Meanwhile, the siloxane crosslinking network formed by silane end-capping in component B is a "flexible crosslinking," which not only enhances the integrity of the coating structure but also does not restrict the elastic deformation of the segments, allowing the coating to adapt to the bending and stretching conditions of leather.

[0102] The flexibility of each comparative example was inferior to that of Example 2, which was essentially due to an imbalance in chain segment characteristics or cross-linking structure: Comparative Example 1 lacked weather-resistant functional monomers, resulting in insufficient cross-linking of the coating and excessive rigidity of the polymer chain segments, making it unable to adapt to deformation; Comparative Examples 2-3 had incomplete weather-resistant functional monomer structures, causing the cross-linking network's flexibility adjustment function to fail, resulting in decreased flexibility; Component A of Comparative Example 4 did not form effective polymer chains, resulting in a loose and fragile coating structure with no elasticity, making it unable to withstand bending deformation; Component B of Comparative Example 5 lacked silane end capping, increasing the rigidity of the cross-linking network, limiting the elastic deformation of the chain segments, and deteriorating flexibility.

[0103] Example 2 exhibits excellent abrasion resistance, likely due to its dense and wear-resistant coating structure: the three-dimensional siloxane crosslinked network formed after the hybridization of components A and B results in a dense and uniform coating structure without loose pores, effectively resisting the impact of external frictional forces; the polycarbonate diol segments in component B possess excellent abrasion and hydrolysis resistance properties, which synergistically enhance the wear resistance of the coating with the acrylate segments; simultaneously, the stable presence of weather-resistant groups does not compromise the structural integrity of the coating, ensuring that the coating does not peel off or expose the substrate during friction.

[0104] The friction resistance of each comparative example was inferior to that of Example 2. The main reason was that the coating structure was loose or the wear-resistant components failed to function: Comparative Example 1 had insufficient cross-linking and a loose structure, and the surface layer was easily worn off during friction; Comparative Examples 2 and 3 had incomplete weather-resistant functional monomer structures and reduced cross-linking network density, resulting in weakened wear resistance; the coating of Comparative Example 4 had no effective structural support due to the failure of A component polymerization, and the substrate was directly worn off during friction; the B component of Comparative Example 5 was not silane-capped, the coating structure lacked density, the wear-resistant layer could not withstand long-term friction, and wear and discoloration were easy to occur.

[0105] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An aging-resistant water-based paint suitable for a leather surface, characterized by, The components include the following weight parts: component A: 12-32 parts; component B: 60-80 parts; free radical trapping agent: 0.1-0.3 parts, leveling agent: 0.2-0.3 parts; Defoaming agent: 0.1-0.3 parts; The specific formulation of the A component is, in parts by weight: methyl methacrylate: 40-50 parts, butyl acrylate: 35-45 parts, weather-resistant functional monomer: 5-10 parts, acrylic acid: 5-8 parts, compounded emulsifier: 2-3 parts, ammonium persulfate: 0.5-1.0 parts, deionized water 90-110 parts; The specific formulation of the B component is, in parts by weight: polycarbonate diol: 90-110 parts, isophorone diisocyanate: 30-40 parts, pentaerythritol: 3-6 parts, 2,2-dimethylol propionic acid: 4-7 parts, gamma-aminopropyl triethoxysilane: 6-10 parts, dibutyltin dilaurate: 0.05-0.15 parts, deionized water: 180-240 parts; The preparation method of the weather-resistant functional monomer comprises the following steps: (1) 2-(2H-benzotriazole-2-yl)-4-methyl-6-(2-propenyl) phenol and epichlorohydrin are added to a reaction device with a reflux condenser, heated to 80-90℃, and 50% sodium hydroxide solution is added dropwise under stirring, the dropwise adding time is 30-60 min, after the dropwise adding is completed, the reaction is kept for 1-3 h, cooled to room temperature, washed with deionized water three times, the organic phase is dried with anhydrous sodium sulfate, the excess epichlorohydrin is removed by reduced pressure distillation, the remaining product is recrystallized in ethanol to obtain intermediate M1; (2) Under nitrogen protection, intermediate M1 and 4-aminoditolyl ketone are added to dimethyl sulfoxide, the pH of the system is adjusted to 9-10 with triethylamine, heated to 45-55℃, and stirred for 6-10 h, after the reaction is completed, the reaction liquid is poured into deionized water, extracted with ethyl acetate three times, the organic phase is dried with anhydrous sodium sulfate, the solvent is removed by reduced pressure distillation, and the remaining material is purified by silica gel column chromatography with gradient elution to obtain intermediate M2; (3) Under nitrogen protection, intermediate M2 and isocyanate propyl triethoxysilane are added to anhydrous tetrahydrofuran, and then dibutyltin dilaurate is added, heated to 40-60℃, and kept for 1-3 h, after the reaction is completed, the excess solvent is removed by reduced pressure distillation, then washed with petroleum ether three times under stirring, after each washing, the lower oil phase is separated through a separatory funnel, after the last washing, the oil phase is vacuum dried to obtain the weather-resistant functional monomer.

2. The water-based paint for a leather surface according to claim 1, characterized by, The free radical trapping agent refers to light stabilizer 944; the leveling agent refers to BYK-333; the defoaming agent refers to BYK-024; the compounded emulsifier refers to a mixture of sodium dodecyl sulfate and nonylphenol polyoxyethylene ether in a weight ratio of 1:1; the average Mn of polycarbonate diol is 2000.

3. The water-based paint for a leather surface according to claim 1, characterized by, In the (1), 2-(2H-benzotriazole-2-yl)-4-methyl-6-(2-propenyl) phenol, epichlorohydrin and sodium hydroxide are in a molar ratio of 1:4-6:1-1.

4.

4. The water-based paint for a leather surface according to claim 1, characterized by, The intermediate M1 and 4-amino xylene ketone in the (2) are in a molar ratio of 1:1-1.2; the intermediate M1, dimethyl sulfoxide and deionized water are in a weight ratio of 1:8-12:10-15; the gradient elution refers to the volume ratio of petroleum ether and ethyl acetate in each step eluent is in turn from 20:1, 10:1, 8:1 to 2:

1.

5. The water-based paint for a leather surface according to claim 1, characterized by, The intermediate M2 and isocyanate propyl triethoxysilane in the (3) are in a weight ratio of 1:1-1.2; the intermediate M2, anhydrous tetrahydrofuran and dibutyltin dilaurate are in a weight ratio of 1:8-12:0.001-0.

005.

6. The water-based, age-resistant paint suitable for leather surfaces according to claim 1, characterized in that, The preparation method of the A component comprises the following steps: At room temperature, methyl methacrylate, butyl acrylate, weather-resistant functional monomer, acrylic acid, compound emulsifier and half of the amount of deionized water are added into an emulsifying kettle, high-speed stirring is started, the rotating speed is adjusted to 1000-2000 r / min, and stirring is performed for 20-40 min to obtain a pre-emulsion; then, in a three-necked reaction flask provided with a reflux condenser, a stirring paddle and a dropping funnel, the remaining deionized water and 1 / 5 of the amount of ammonium persulfate are added, stirring is started and the temperature is raised to 60-80℃, 1 / 10 of the pre-emulsion is added dropwise into the reaction flask through the dropping funnel, the dropping time is 10-30 min, after the dropping is completed, constant temperature reaction is performed for 20-40 min; the remaining ammonium persulfate is configured into an ammonium sulfate aqueous solution, and the remaining pre-emulsion is placed in two dropping funnels respectively, the pre-emulsion and the ammonium sulfate aqueous solution are synchronously added dropwise, after all the materials are added dropwise, constant temperature reaction is continuously performed for 2-3 h, after the reaction is completed, the system temperature is naturally cooled to 30-40℃, stirring is stopped, filtration is performed through a 100-mesh filter screen, and the A component is obtained.

7. The water-based, ageing-resistant paint suitable for leather surfaces according to claim 6, characterized in that, In the preparation method of the A component, the concentration of the ammonium sulfate aqueous solution is 5-10 wt%; the synchronous dropping time is 1-2.5 h.

8. The water-based paint for a leather surface according to claim 1, wherein The preparation method of the B component comprises the following steps: After the polycarbonate diol is vacuum dehydrated, it is added into a three-necked reaction flask provided with a reflux condenser, a stirring paddle and a nitrogen conduit under the protection of nitrogen, the temperature is raised to 70-80℃, isophorone diisocyanate and pentaerythritol are added, stirring is performed for mixing, then dibutyltin dilaurate is added, constant temperature reaction is performed for 2-2.5 h, the pre-polymer is monitored by di-n-butylamine titration until the isocyanate group content in the pre-polymer reaches 5.0-5.5%, then the reaction system is cooled to 60-65℃, 2,2-dimethylol propionic acid is added, stirring reaction is continuously performed for 1-2 h, then the temperature is continuously lowered to 40-45℃, triethylamine is added to make the pH value of the system 8-9, then γ-aminopropyl triethoxysilane is added, constant temperature stirring reaction is performed for 1-2 h, the system temperature is maintained at 40-45℃, deionized water is added into the system under the condition of high-speed stirring of 800-1000 r / min, stirring is maintained for 20-40 min, the system is naturally cooled to room temperature, filtration is performed through a 120-mesh filter screen, and the B component is obtained.

9. A process for the preparation of an anti-ageing water-based paint suitable for leather surfaces according to any one of claims 1-8, characterized in that, The preparation method comprises the following steps: Firstly, the B component is added into a reaction kettle with stirring paddle, and heated to 40-60℃ under stirring at 1000-1500rpm. Then the A component is added into the B component, and constant temperature stirring is carried out for 1-2h. Subsequently, the radical scavenger, leveling agent and defoaming agent are added in sequence, and stirring is continued for 10-20min. Then the pH value of the system is adjusted to 7.5-9.5, and the viscosity is adjusted to 20-30s at 25℃ using a coating-4 cup. After cooling to room temperature, filtration is carried out through a 120 mesh filter screen, to obtain an aging-resistant water-based paint suitable for leather.

10. The process for the preparation of an anti-aging water-based paint suitable for leather surfaces according to claim 9, characterized by the fact that, The pH value of the system is adjusted by ammonia water, and the viscosity is adjusted by adding deionized water or evaporating deionized water.

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