Waterborne polyurethane surface treatment agent with antifouling and anti-migration functions

Abstract

The present application relates to the technical field of waterborne polyurethane, in particular to a waterborne polyurethane surface treatment agent with antifouling and anti-migration functions.The surface treatment agent comprises 100 parts of modified waterborne polyurethane emulsion, 0.2-0.5 parts of defoaming agent, 0.2-0.5 parts of wetting agent, 1.5-2.5 parts of thickening agent and 3-7 parts of deionized water by mass fraction.The modified waterborne polyurethane emulsion is prepared by introducing a tertiary amine dihydroxyl chain extender obtained by the reaction of 2-(dimethylamino)ethyl methacrylate and 3-mercapto-1,2-propanediol into polyurethane segments in two states of pre-saponification and non-saponification, and then performing post-saponification after the introduction of monohydroxyl-terminated polydimethylsiloxane.The sulfobetaine structure and polydimethylsiloxane segments in the surface treatment agent are fixed in the polyurethane molecular chain, and when the surface treatment agent is used for the finishing of polyurethane synthetic leather, the antifouling attenuation and contact migration risk after wet rubbing can be reduced.

Description

Technical Field

[0001] This invention relates to the field of waterborne polyurethane technology, and more specifically to a waterborne polyurethane surface treatment agent with antifouling and anti-migration functions. Background Technology

[0002] Waterborne polyurethane surface treatment agents are characterized by flexible film formation, good adhesion, and environmentally friendly application. They are commonly used for surface coating of polyurethane synthetic leather, automotive interior leather, medical mattress leather, public seating leather, and synthetic leather for children's products. These materials are in prolonged contact with sweat, sebum, clothing dyes, cleaning solutions, and airborne dust during use, requiring the coating to possess good tactile feel, abrasion resistance, stain resistance, and appearance stability even at relatively thin thicknesses.

[0003] To improve initial antifouling properties, existing technologies typically add silicone oil, wax emulsions, fluorinated additives, or low surface energy lubricants to waterborne polyurethane to reduce the adhesion of contaminants to the coating surface. However, these components mostly exist through physical dispersion or compatibility, lacking a stable and fixed relationship. They are prone to migration during hot pressing, repeated friction, wet cleaning, and long-term pressure contact, leading to surface stickiness, dust accumulation, oil stain transfer, and reduced antifouling properties.

[0004] To improve the performance of water-based stains, sweat salts, and dye residues, existing systems often incorporate hydrophilic additives, surfactants, or amphoteric components. While these components enhance ease of cleaning, if present only as additives, they are prone to leaching or extraction in humid environments, during alcohol-based cleaning, or during rinsing. Excessive dosage may also increase the coating's hygroscopicity, leading to re-adhesion, decreased stain resistance, and reduced coating integrity.

[0005] Meanwhile, the low surface energy components and hydrophilic components have different mechanisms of action. Simple blending is prone to local phase separation due to polarity differences, resulting in component enrichment, hydrophilic component precipitation, or uneven micro-region distribution on the coating surface. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a waterborne polyurethane surface treatment agent with antifouling and anti-migration functions, so as to solve the problem that existing waterborne polyurethane surface treatment agents usually rely on free antifouling additives, and the antifouling effect decreases and contact migration is obvious after long-term use and wet cleaning.

[0007] To achieve the above objectives, the present invention provides a waterborne polyurethane surface treatment agent with antifouling and anti-migration functions, comprising, by weight: 100 parts modified waterborne polyurethane emulsion, 0.2-0.5 parts defoamer, 0.2-0.5 parts wetting agent, 1.5-2.5 parts thickener and 3-7 parts deionized water;

[0008] Preferably, the defoamer is selected from one or more of polyether defoamers, mineral oil defoamers, polymer-type non-silicone defoamers, organosilicone defoamers, and polyether-modified siloxane defoamers; further, the defoamer is a polymer-type non-silicone defoamer.

[0009] Preferably, the wetting agent is selected from one or more of acetylenic diol wetting agents, polyether modified wetting agents, nonionic surfactants, anionic surfactants, polyether modified siloxane wetting agents, and fluorine-free dynamic wetting agents; further, the wetting agent is an acetylenic diol dynamic wetting agent.

[0010] Preferably, the thickener is selected from one or more of nonionic associative polyurethane thickeners, alkali-swellable acrylic thickeners, hydrophobically modified alkali-swellable acrylic thickeners, cellulose ether thickeners, polyether thickeners, and inorganic layered silicate thickeners; further, the thickener is a nonionic associative polyurethane thickener.

[0011] The preparation steps of the modified waterborne polyurethane emulsion are as follows:

[0012] (1) Preparation of tertiary amine dihydroxy chain extender;

[0013] (2) Preparation of pre-beet alkalization dihydroxy chain extender solution;

[0014] (3) Preparation of modified waterborne polyurethane emulsion;

[0015] Preferably, the tertiary amine dihydroxy chain extender in step (1) is obtained by a mercapto-Michael addition reaction of 2-(dimethylamino)ethyl methacrylate and 3-mercapto-1,2-propanediol.

[0016] Preferably, the tertiary amine dihydroxy chain extender in step (1) is obtained by reacting 15-17 parts of 2-(dimethylamino)ethyl methacrylate and 10-12 parts of 3-mercapto-1,2-propanediol by mass.

[0017] Preferably, the addition reaction in step (1) is carried out in a nitrogen atmosphere under light-protected conditions, first stirred at 25-35°C for 6-10 hours, and then heated to 40-50°C to continue the reaction for 1-3 hours.

[0018] Preferably, the pre-beet alkalization dihydroxy chain extender solution in step (2) is obtained by reacting a tertiary amine dihydroxy chain extender with 1,3-propanesulfonyl lactone.

[0019] Preferably, the pre-beet alkalization dihydroxy chain extender solution in step (2) is obtained by reacting 12-14 parts of tertiary amine dihydroxy chain extender and 5-7 parts of 1,3-propanesulfonyl lactone by mass.

[0020] Preferably, the mass fraction of the pre-beet alkalization dihydroxy chain extender solution in step (2) is 45%-55%.

[0021] Preferably, the reaction temperature in step (2) is 40-50℃ and the reaction time is 6-10h.

[0022] Preferably, step (3) of preparing the modified waterborne polyurethane emulsion includes: dehydrating polytetramethylene ether glycol and mixing it with isophorone diisocyanate and dibutyltin dilaurate, reacting at 68-72°C for 70-120 min; then adding 2,2-dimethylolpropionic acid, and continuing the reaction at 70-78°C to obtain a carboxyl-containing isocyanate-terminated polyurethane prepolymer; cooling the carboxyl-containing isocyanate-terminated polyurethane prepolymer to 55-65°C, adding a pre-beet alkalized dihydroxy chain extender solution dropwise, and then cooling at 55-65°C after the addition is complete. Continue the reaction for 30-60 min; then add the tertiary amine dihydroxy chain extender dropwise to the reaction system, and continue the reaction for 45-90 min after the addition is complete; separately add the monohydroxy-terminated polydimethylsiloxane dropwise to the reaction system, controlling the system temperature at 50-65℃, and continue the reaction for 40-80 min after the addition is complete; then add 1,3-propanesulfonyl lactone to the reaction system, and continue the reaction at 50-60℃ for 3-5 h; finally, cool the reaction system to 35-45℃, add triethylamine, and remove acetone under reduced pressure to obtain the modified waterborne polyurethane emulsion;

[0023] Preferably, the weight ratio of polytetramethylene ether glycol, isophorone diisocyanate, 2,2-dimethylolpropionic acid, pre-beet alkalized dihydroxy chain extender solution, tertiary amine dihydroxy chain extender, monohydroxy-terminated polydimethylsiloxane, 1,3-propane sulfonyl lactone, and triethylamine is 78-82 parts: 30-32 parts: 4.5-5.5 parts: 5-8 parts: 1.5-2.5 parts: 2.5-3.5 parts: 0.7-1.1 parts: 4.7-6.2 parts.

[0024] Preferably, the polytetramethylene ether glycol has a molecular weight of 1991-2011, a hydroxyl value of 53-59 mgKOH / g, and a moisture content of no more than 0.02%.

[0025] Preferably, the monohydroxy-terminated polydimethylsiloxane is an asymmetric monohydroxy-terminated polydimethylsiloxane with a number-average molecular weight of 900-1200 and a viscosity of 15-20 cSt at 25°C.

[0026] Preferably, the modified waterborne polyurethane emulsion has a solid content of 29wt%-31wt%.

[0027] The beneficial effects of this invention are:

[0028] This invention introduces a sulfobetaine structure formed by a tertiary amine dihydroxy chain extender into the molecular chain of waterborne polyurethane, fixing the hydrophilic antifouling unit within the hard segments of the polyurethane, rather than allowing it to exist as a free hydrophilic additive. This structure can form stable hydration fixation points within the coating, reducing the persistent residue of sweat, salt, water-based dyes, and cleaning media, and lowering the risk of precipitation during wet wiping and alcohol-water cleaning processes.

[0029] This invention enables monohydroxy-terminated polydimethylsiloxane to react with residual isocyanate groups and enter the polyurethane molecular chain via chemical bonding. Compared with external silicone oil or silicone lubricants, this method can reduce the migration of polydimethylsiloxane to adjacent materials under hot pressing, friction and long-term contact conditions while maintaining low surface energy and antifouling effect, thereby reducing the risk of surface stickiness, oil stain transfer and dust accumulation.

[0030] This invention enables the un-betained tertiary amine dihydroxy chain extender to enter the polyurethane system during the later chain extension stage, and performs post-positioning betaine alkalization after the incorporation of monohydroxy-terminated polydimethylsiloxane, resulting in a stable micro-region distribution of sulfobetaine units and polydimethylsiloxane segments on the film surface. This structure allows the low surface energy orientation layer and the inner hydration anchoring layer to work together, achieving both antifouling and anti-migration properties.

[0031] The non-silicone defoamer, dynamic wetting agent, and nonionic associative polyurethane thickener in this invention are mainly used to improve construction leveling, defoaming, and rheological stability. Their antifouling and anti-migration effects primarily originate from the fixed sulfobetaine structure and polydimethylsiloxane segments in the polyurethane molecular chain. Therefore, the resulting surface treatment agent is suitable for applications requiring repeated wet wiping, such as medical mattress leather, public seating leather, synthetic leather for children's products, and automotive interior leather.

[0032] Compared to existing waterborne polyurethane surface treatment agents that rely on free silicone oil, wax emulsions, fluorinated additives, or added hydrophilic additives, this invention fixes a hydrophilic antifouling structure and a low surface energy structure within the polyurethane molecular chain, and forms a stable surface structure through post-positioning beetroot alkalization. When used for finishing synthetic leather, it helps reduce the risk of antifouling degradation, contact migration, surface stickiness, and oil stain transfer after wet rubbing, and improves long-term cleanliness stability and appearance retention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0034] Polytetramethylene ether glycol: Dalian Chemical PTG2000, molecular weight 2000, hydroxyl value 55mgKOH / g, moisture content not exceeding 0.02%;

[0035] Single-hydroxyl-terminated polydimethylsiloxane: Gelest product code MCR-C12, the structure is asymmetric single-hydroxyl-terminated polydimethylsiloxane, the number average molecular weight is 1000, and the viscosity at 25℃ is 20cSt.

[0036] Defoamer: BYK-012;

[0037] Wetting agent: Evonik DYNOL 607;

[0038] Thickener: Elementis RHEOLATE HX6010IF.

[0039] Example 1: A method for preparing a waterborne polyurethane surface treatment agent with antifouling and anti-migration functions, comprising the following steps:

[0040] Preparation of tertiary amine dihydroxy chain extender using S1:

[0041] 40g of acetone, 16g of 2-(dimethylamino)ethyl methacrylate, 11g of 3-mercapto-1,2-propanediol, and 30mg of hydroquinone were added to a four-necked flask equipped with a mechanical stirrer, thermometer, condenser, and nitrogen inlet. Nitrogen gas was introduced for 15 minutes to purge air, and the mixture was stirred at 30°C for 8 hours in the dark. The temperature was then raised to 45°C and the reaction was continued for 2 hours. After the reaction was completed, the acetone was removed under reduced pressure below 45°C to obtain a light yellow viscous liquid, which is the tertiary amine dihydroxy chain extender.

[0042] S2 Preparation of pre-beet alkalized dihydroxy chain extender solution:

[0043] 20g of N-methylpyrrolidone and 13g of tertiary amine dihydroxy chain extender were added to a reaction flask equipped with a mechanical stirrer, thermometer, and nitrogen inlet. The mixture was heated to 40°C under nitrogen protection, and 6g of 1,3-propanesulfonyl lactone was added in three portions, with each addition 20min apart. After all the contents were added, the temperature was raised to 45°C and the reaction was continued for 8h to obtain a pre-beet alkalization dihydroxy chain extender solution with a mass fraction of 50%.

[0044] S3 is used to prepare modified waterborne polyurethane emulsions:

[0045] 80g of polytetramethylene ether glycol was dehydrated at 110℃ and under a vacuum of not less than -0.08MPa for 2 hours, then cooled to 70℃ and kept under nitrogen protection. 31g of isophorone diisocyanate and 35mg of dibutyltin dilaurate were added, and the mixture was reacted at 70℃ for 90 minutes. Subsequently, 5g of 2,2-dimethylolpropionic acid and 15g of N-methylpyrrolidone were added, and the reaction continued at 75℃ until the mass fraction of isocyanate groups in the system was determined to be 4% to 5% by di-n-butylamine-hydrochloric acid back titration, yielding a carboxyl-containing isocyanate-terminated polyurethane prepolymer. The obtained carboxyl-containing isocyanate-terminated polyurethane prepolymer was cooled to 60℃, and 6g of pre-betaine alkalized dihydroxy chain extender solution was added dropwise over 20 minutes. After the addition was complete, the reaction was continued at 60℃ for 40 minutes. Separately, 2g of tertiary amine dihydroxy chain extender and 2g... 1,4-Butanediol and 10g of acetone were mixed thoroughly and added dropwise to the reaction system over 25 minutes, maintaining the system temperature at 60°C. After the addition was complete, the reaction continued for 60 minutes. Then, 3g of monohydroxy-terminated polydimethylsiloxane was mixed thoroughly with 10g of acetone and added dropwise to the reaction system over 20 minutes, maintaining the system temperature at 60°C. After the addition was complete, the reaction continued for 60 minutes. Finally, 5g of N-methylpyrrolidone and 0.9g of... were added to the reaction system. 1,3-Propanesulfonyl lactone was reacted at 55°C for 4 hours. After the reaction was completed, the reaction system was cooled to 40°C, and 4g of triethylamine was added and stirred for 30 minutes to neutralize the carboxyl groups introduced by 2,2-dimethylolpropionic acid into carboxylates. Then, under stirring at 1200 r / min, the obtained prepolymer was slowly added to 240g of deionized water, and the addition time was controlled at 40 minutes to obtain an aqueous dispersion. Then, 1.4g of ethylenediamine was dissolved in 20g of deionized water and added dropwise to the aqueous dispersion over 20 minutes. After the addition was completed, stirring was continued for 60 minutes. Finally, acetone was removed under conditions below 40°C and a vacuum degree not lower than -0.08MPa to obtain a modified waterborne polyurethane emulsion with a solid content of 30wt%.

[0046] S4 is used to formulate water-based polyurethane surface treatment agents:

[0047] Take 100g of modified waterborne polyurethane emulsion, add 0.3g of defoamer, 0.3g of wetting agent, 2g of thickener and 5g of deionized water in sequence, stir at 500r / min for 30min, adjust the pH value to 7 to 8, and obtain a waterborne polyurethane surface treatment agent with antifouling and anti-migration functions.

[0048] The difference between Example 2 and Example 1 is as follows:

[0049] In step S1, the raw materials used are 35g acetone, 15g 2-(dimethylamino)ethyl methacrylate, 10g 3-mercapto-1,2-propanediol, and 20mg hydroquinone; in step S2, the raw materials used are 18g N-methylpyrrolidone, 12g tertiary amine dihydroxy chain extender, and 5g 1,3-propane sulfonyl lactone; in step S3, the 6g pre-beet alkalization dihydroxy chain extender solution is adjusted to 5g; the 2g tertiary amine dihydroxy chain extender is adjusted to 1.5g; the 3g monohydroxy-terminated polydimethylsiloxane is adjusted to 2.5g monohydroxy-terminated polydimethylsiloxane with a number average molecular weight of 900; and the 0.9g 1,3-propane sulfonyl lactone is adjusted to 0.7g. 1,3-Propanesulfonyl lactone; 1.4g ethylenediamine was adjusted to 1.7g ethylenediamine; 240g deionized water was adjusted to 230g deionized water; the water dispersion stirring speed was controlled at 1200r / min; in step S4, the amount of defoamer was 0.5g, the amount of wetting agent was 0.5g, the amount of thickener was 2.5g and the amount of deionized water was 7g; the remaining conditions were the same as in Example 1.

[0050] The difference between Example 3 and Example 1 is as follows:

[0051] In step S1, the raw materials used are 45g acetone, 17g 2-(dimethylamino)ethyl methacrylate, 12g 3-mercapto-1,2-propanediol, and 40mg hydroquinone; in step S2, the raw materials used are 22g N-methylpyrrolidone, 14g tertiary amine dihydroxy chain extender, and 7g 1,3-propane sulfonyl lactone; in step S3, the 6g pre-beet alkalization dihydroxy chain extender solution is adjusted to 8g; the 2g tertiary amine dihydroxy chain extender is adjusted to 2.5g; the 3g monohydroxy-terminated polydimethylsiloxane is adjusted to 3.5g monohydroxy-terminated polydimethylsiloxane with a number average molecular weight of 1200; and the 0.9g 1,3-propane sulfonyl lactone is adjusted to 1.1g. 1,3-Propanesulfonyl lactone; adjust 1.4g ethylenediamine to 1.2g ethylenediamine; adjust 240g deionized water to 250g deionized water; control the water dispersion stirring speed at 1300r / min; in step S4, the amount of defoamer is 0.2g, the amount of wetting agent is 0.2g, the amount of thickener is 1.5g and the amount of deionized water is 3g; the remaining conditions are the same as in Example 1.

[0052] The difference between Example 4 and Example 1 is as follows: In S1, the preparation conditions of the tertiary amine dihydroxy chain extender were adjusted to stirring at 25°C for 10 hours, followed by heating to 40°C and continuing the reaction for 3 hours; in S2, the preparation conditions of the pre-betain alkalized dihydroxy chain extender solution were adjusted to adding 1,3-propanesulfonyl lactone in batches at 35°C, and after all the solution was added, heating to 40°C and continuing the reaction for 10 hours; in S3, the dehydration time of polytetramethylene ether glycol was adjusted to 2.5 hours, and the initial reaction time after the addition of isophorone diisocyanate was adjusted to 120 minutes. The reaction time after the addition of the beet alkalization dihydroxy chain extender solution was adjusted to 60 min, the reaction time after the addition of the tertiary amine dihydroxy chain extender and 1,4-butanediol was adjusted to 90 min, the reaction time after the addition of the monohydroxy-terminated polydimethylsiloxane was adjusted to 80 min, the reaction temperature of the beet alkalization reaction was adjusted to 50℃ and the reaction time was adjusted to 5 h, the prepolymer addition and dispersion time was adjusted to 50 min, and the stirring time after the addition of ethylenediamine was adjusted to 75 min; the remaining conditions were the same as in Example 1.

[0053] The difference between Example 5 and Example 1 is as follows: In S1, the preparation conditions of the tertiary amine dihydroxy chain extender were adjusted to stirring at 35°C for 6 hours, followed by heating to 50°C and continuing the reaction for 1 hour; in S2, the preparation conditions of the pre-beet alkalization dihydroxy chain extender solution were adjusted to adding 1,3-propanesulfonyl lactone in batches at 45°C, and then heating to 50°C and continuing the reaction for 6 hours after all the 1,3-propanesulfonyl lactone was added; in S3, the initial reaction time after the addition of isophorone diisocyanate was adjusted to 70 minutes, and the reaction time after the pre-beet alkalization dihydroxy chain extender solution was added was adjusted to 30 minutes. The reaction time after the chain extender and 1,4-butanediol were added was adjusted to 45 min, the reaction time after the monohydroxy-terminated polydimethylsiloxane was added was adjusted to 40 min, the temperature of the subsequent beet alkalization reaction was adjusted to 60 °C and the reaction time was adjusted to 3 h, the prepolymer addition and dispersion time was adjusted to 30 min, and the stirring time after the ethylenediamine was added was adjusted to 45 min; the stirring speed when preparing the waterborne polyurethane surface treatment agent in S4 was adjusted to 600 r / min and the stirring time was adjusted to 20 min; the remaining conditions were the same as in Example 1.

[0054] The difference between Comparative Example 1 and Example 1 is that: the pre-beet alkalization dihydroxy chain extender solution is not used; the step of adding 6g of pre-beet alkalization dihydroxy chain extender solution dropwise over 20 minutes in S3 is changed to adding a mixture of 2g of tertiary amine dihydroxy chain extender and 4g of N-methylpyrrolidone dropwise over 20 minutes; and the 0.9g of 1,3-propanesulfonyl lactone is adjusted to 1.8g of 1,3-propanesulfonyl lactone, so that the total amount of 1,3-propanesulfonyl lactone required for beet alkalization is basically the same as in Example 1; the other conditions are the same as in Example 1.

[0055] The difference between Comparative Example 2 and Example 1 is as follows: In S3, the 6g pre-beet alkalization dihydroxy chain extender solution was adjusted to 12g pre-beet alkalization dihydroxy chain extender solution; subsequently, 2g tertiary amine dihydroxy chain extender was not added, and its hydroxyl equivalent was replaced with 0.7g 1,4-butanediol, while 1.3g N-methylpyrrolidone was added to maintain the total mass of the materials added in this step being basically consistent; subsequently, 0.9g 1,3-propanesulfonyl lactone was not added, only 5g N-methylpyrrolidone was added and kept at 55°C for 4h; the remaining conditions were the same as in Example 1.

[0056] The difference between Comparative Example 3 and Example 1 is as follows: In S3, 2g of tertiary amine dihydroxy chain extender, 2g of 1,4-butanediol and 10g of acetone were first mixed evenly and added dropwise to the reaction system over 25 minutes, while the system temperature was controlled at 60°C. After the addition was completed, the reaction continued for 60 minutes. Then, 6g of pre-beet alkalized dihydroxy chain extender solution was added dropwise and the reaction continued at 60°C for 40 minutes. The remaining conditions were the same as in Example 1.

[0057] The difference between Comparative Example 4 and Example 1 is as follows: In S3, after adding 6g of pre-beet alkalization dihydroxy chain extender solution and continuing the reaction for 40min, 3g of monohydroxy-terminated polydimethylsiloxane and 10g of acetone were mixed and added dropwise to the reaction system, and the reaction was continued at 60°C for 60min; then, a mixture of 2g of tertiary amine dihydroxy chain extender, 2g of 1,4-butanediol and 10g of acetone was added, and the reaction was continued under the conditions of Example 1; subsequently, 5g of N-methylpyrrolidone and 0.9g of 1,3-propanesulfonyl lactone were added for beet alkalization; the remaining conditions were the same as in Example 1.

[0058] The difference between Comparative Example 5 and Example 1 is that: in S3, 3g of monohydroxy-terminated polydimethylsiloxane is not added, but the corresponding residual isocyanate groups are consumed by 1,4-butanediol with an equivalent amount of hydroxyl groups; in S4, when preparing the surface treatment agent, an equal amount of monohydroxy-terminated polydimethylsiloxane is added according to the theoretical mass of monohydroxy-terminated polydimethylsiloxane contained in 100g of modified waterborne polyurethane emulsion in Example 1, so that it exists in the form of physical blend; the other conditions are the same as in Example 1.

[0059] The difference between Comparative Example 6 and Example 1 is as follows: In S3, after the mixture of 2g tertiary amine dihydroxy chain extender, 2g 1,4-butanediol and 10g acetone was added dropwise and the reaction continued for 60min, 5g N-methylpyrrolidone and 0.9g 1,3-propanesulfonyl lactone were added first, and the reaction continued at 55°C for 4h; then 3g monohydroxy-terminated polydimethylsiloxane and 10g acetone were mixed and added dropwise to the reaction system, and the reaction continued at 55-60°C for 60min; the remaining conditions were the same as in Example 1.

[0060] Performance testing

[0061] The waterborne polyurethane surface treatment agents obtained in Examples 1 to 5 and Comparative Examples 1 to 6 were used as test samples. Polyurethane synthetic leather with a thickness of 1.0 mm from the same batch was used as the substrate. The substrate was cut into 100 mm × 100 mm test pieces, and the surface was wiped with anhydrous ethanol and then placed at 23°C and 50% relative humidity for 24 hours. Following the scraping method of GB / T1727-2021, each test sample was coated onto the surface of the polyurethane synthetic leather using a wire rod, with a wet coating amount of 30 g / m². 2 The film was dried at 80℃ for 5 min, and then conditioned at 50℃ for 24 h. The dry film thickness was measured according to GB / T13452.2-2008 and controlled to be 6 μm ± 1 μm. Before all tests, the film was conditioned for 24 h at 23℃ and 50% relative humidity according to GB / T9278-2008.

[0062] Water contact angle test: The water contact angle was tested according to GB / T30693-2014 using an optical contact angle meter. 4 μL of deionized water was dropped onto the coating surface, and the initial water contact angle was recorded 2 seconds after the drop, and the dynamic water contact angle was recorded 30 seconds after the drop. Five different locations were selected for testing for each sample, and the average value was taken.

[0063] Anti-fouling durability test: The color difference was evaluated according to the drop test principle of GB / T9274-1988 and in accordance with GB / T11186-2025. Artificial sebum, coffee liquid, and methylene blue aqueous solution were used as the contamination media. Artificial sebum was prepared by mixing 70g oleic acid, 20g palmitic acid, and 10g cholesterol. Coffee liquid was prepared by dissolving 10g of commercially available instant coffee in 90g deionized water. The methylene blue aqueous solution had a mass fraction of 0.1%. 0.2mL of the contamination media was dropped onto the surface of each sample, and the samples were placed at 23℃ for 2 hours. Then, the samples were wiped 20 times with a non-woven fabric moistened with deionized water and wrung until it was no longer dripping. The color difference between the contaminated and uncontaminated areas was measured according to GB / T11186-2025, and the overall color difference of the three contamination media was calculated. Subsequently, following the reciprocating friction method of GB / T40920-2021, the sample surface was rubbed 1000 times with a 500g load and wet friction medium. The above contamination and wiping process was repeated, and the overall color difference after 1000 wet wiping cycles was recorded.

[0064] Anti-migration test: Surface-treated polyurethane synthetic leather was laminated with a 50μm thick polyethylene terephthalate film, ensuring direct contact between the coated surface and the polyethylene terephthalate film. The test was conducted at 70℃ / 1kg with a contact area of ​​25cm². 2 Hot-pressed under load for 24 hours. After hot pressing, observe whether oil spots appear on the surface of the polyethylene terephthalate film, and cut a sample with a contact area of ​​25 cm².2 Polyethylene terephthalate (PET) films were digested with 5 mL of nitric acid and 2 mL of hydrogen peroxide. The digestion solution was brought to a final volume of 50 mL. The silicon content was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) according to GB / T23942-2009 and converted to silicon transfer amount in μg / dm³. 2 Another 50mm×50mm sample was weighed and immersed in 50mL of 50% ethanol aqueous solution. It was soaked at 40℃ for 24h, then removed and vacuum dried at 60℃ to constant weight. The extraction weight loss rate was calculated.

[0065] Solvent resistance wiping test: Solvent resistance wiping was evaluated according to GB / T23989-2009. The wiping medium was a 50% (w / w) ethanol aqueous solution, the wiping cloth was white cotton cloth, the wiping load was 500g, and the number of wiping cycles was 200. After wiping, the coating surface was observed to see if it became sticky, white, peeled off, or significantly lost its gloss. The color difference of the coating surface before and after wiping was measured according to GB / T11186-2025.

[0066] Adhesion and pencil hardness tests: Adhesion was tested according to GB / T9286-2021 with a cross-cut test and a cross-cut spacing of 1 mm. The cross-cut grade was recorded after the tape was peeled off. Pencil hardness was tested according to GB / T6739-2022. The test sample was a coating film prepared on a glass plate under the same coating, drying and curing conditions. The angle between the pencil and the coating surface was 45°. The highest pencil hardness that did not produce visible scratches was recorded after pushing the pencil forward 6 mm.

[0067] Table 1 Performance Test Results

[0068] Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Initial water contact angle / ° 96.4 92.7 99.1 95.8 93.6 88.4 91.5 94.2 101.5 106.8 100.2 30s water contact angle / ° 81.8 83.5 77.6 80.7 82.2 71.9 69.8 76.5 90.1 100.4 87.6 Initial overall color difference ΔE 1.5 1.9 1.3 1.6 1.8 2.7 2.3 2.2 2.1 1.8 2.4 Overall color difference ΔE after 1000 wet rubs 2.3 3.0 2.6 2.4 2.8 7.2 5.6 4.8 5.9 8.6 6.4 Color difference ΔE after solvent-resistant wiping 1.1 1.6 1.4 1.2 1.5 3.6 3.1 2.5 3.0 4.7 3.4 Oil spots after hot pressing No visible oil spots No visible oil spots No visible oil spots No visible oil spots No visible oil spots Mild oil spots Mild oil spots No obvious oil spots Mild oil spots Obvious oil spots Mild oil spots <![CDATA[Silicon element transfer amount / μg / dm 2 > 31.6 43.2 36.8 33.9 41.5 82.5 112.4 76.7 139.3 420.8 156.2 Loss of weight during extraction with 50% ethanol aqueous solution / % 0.5 0.8 0.7 0.6 0.8 2.4 1.8 1.4 2.2 5.6 2.6 Grid rating / level 0 0 0 0 0 1 1 1 1 2 1 Pencil hardness H H HB H H HB HB H H HB HB

[0069] As shown in Table 1, Examples 1-5 all exhibited good antifouling durability and anti-migration properties. This indicates that the pre-beet alkalized dihydroxy chain extender first enters the polyurethane hard segment, followed by the un-beet alkalized tertiary amine dihydroxy chain extender entering the later hard segment, and then the monohydroxy-terminated polydimethylsiloxane is covalently incorporated, followed by post-positioning beet alkalization. This sequential design can form a low surface energy orientation layer and an inner hydration anchoring layer in the coating. In contrast, Comparative Example 1 lacks early hydration fixing points, Comparative Example 2 lacks later tertiary amine reaction sites, Comparative Examples 3 and 4 disrupt the order of addition of the two types of chain extenders or polydimethylsiloxane, Comparative Example 5 changes the polydimethylsiloxane to physical blending, and Comparative Example 6 performs beet alkalization in advance. All of these weaken the antifouling retention after wet wiping and the anti-migration properties after hot pressing.

[0070] Therefore, this invention is not simply a combination of sulfobetaine structure and polydimethylsiloxane segments, but rather achieves a synergistic effect through the dual-state distribution of homologous chain extenders, covalent access at chain ends, and post-positioning hydration anchoring. This surface treatment agent is suitable for medical mattress leather, public seating leather, synthetic leather for children's products, and automotive interior leather, and can reduce the risk of stain residue, surface stickiness, and additive migration during long-term contact use.

[0071] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A water-based polyurethane surface treatment agent with antifouling and anti-migration functions, characterized in that, By weight, it includes: 100 parts modified waterborne polyurethane emulsion, 0.2-0.5 parts defoamer, 0.2-0.5 parts wetting agent, 1.5-2.5 parts thickener and 3-7 parts deionized water; The preparation steps of the modified waterborne polyurethane emulsion are as follows: (1) Preparation of tertiary amine dihydroxy chain extender; (2) Preparation of pre-beet alkalization dihydroxy chain extender solution; (3) Preparation of modified waterborne polyurethane emulsion; The tertiary amine dihydroxy chain extender in step (1) is obtained by a mercapto-Michael addition reaction of 2-(dimethylamino)ethyl methacrylate and 3-mercapto-1,2-propanediol. The pre-beet alkalization dihydroxy chain extender solution in step (2) is obtained by reacting a tertiary amine dihydroxy chain extender with 1,3-propanesulfonyl lactone; Step (3) involves preparing the modified waterborne polyurethane emulsion by: dehydrating polytetramethylene ether glycol and reacting it with isophorone diisocyanate and dibutyltin dilaurate; then sequentially adding 2,2-dimethylolpropionic acid, pre-betaine alkalized dihydroxy chain extender solution, tertiary amine dihydroxy chain extender, monohydroxy-terminated polydimethylsiloxane, 1,3-propane sulfonyl lactone, and finally adding triethylamine, followed by deacetone removal under reduced pressure to obtain the modified waterborne polyurethane emulsion; The weight ratio of polytetramethylene ether glycol, isophorone diisocyanate, 2,2-dimethylolpropionic acid, pre-beet alkalized dihydroxy chain extender solution, tertiary amine dihydroxy chain extender, monohydroxy-terminated polydimethylsiloxane, 1,3-propane sulfonyl lactone, and triethylamine, by mass, is 78-82 parts: 30-32 parts: 4.5-5.5 parts: 5-8 parts: 1.5-2.5 parts: 2.5-3.5 parts: 0.7-1.1 parts: 4.7-6.2 parts.

2. The waterborne polyurethane surface treatment agent with antifouling and anti-migration functions according to claim 1, characterized in that, The defoamer is selected from one or more of polyether defoamers, mineral oil defoamers, polymer-type non-silicone defoamers, organosilicone defoamers, and polyether-modified siloxane defoamers.

3. The waterborne polyurethane surface treatment agent with antifouling and anti-migration functions according to claim 1, characterized in that, The wetting agent is selected from one or more of the following: acetylenic diol wetting agents, polyether modified wetting agents, nonionic surfactants, anionic surfactants, polyether modified siloxane wetting agents, and fluorine-free dynamic wetting agents.

4. The waterborne polyurethane surface treatment agent with antifouling and anti-migration functions according to claim 1, characterized in that, The thickener is selected from one or more of the following: nonionic associative polyurethane thickener, alkali-swellable acrylic thickener, hydrophobically modified alkali-swellable acrylic thickener, cellulose ether thickener, polyether thickener, and inorganic layered silicate thickener.

5. The waterborne polyurethane surface treatment agent with antifouling and anti-migration functions according to claim 1, characterized in that, The tertiary amine dihydroxy chain extender in step (1) is obtained by reacting 15-17 parts of 2-(dimethylamino)ethyl methacrylate and 10-12 parts of 3-mercapto-1,2-propanediol by mass.

6. The waterborne polyurethane surface treatment agent with antifouling and anti-migration functions according to claim 1, characterized in that, The pre-beet alkalization dihydroxy chain extender solution in step (2) is obtained by reacting 12-14 parts of tertiary amine dihydroxy chain extender and 5-7 parts of 1,3-propanesulfonyl lactone by mass.

7. The waterborne polyurethane surface treatment agent with antifouling and anti-migration functions according to claim 1, characterized in that, The polytetramethylene ether glycol has a molecular weight of 1991-2011, a hydroxyl value of 53-59 mgKOH / g, and a moisture content of no more than 0.02%.

8. The waterborne polyurethane surface treatment agent with antifouling and anti-migration functions according to claim 1, characterized in that, The monohydroxy-terminated polydimethylsiloxane is an asymmetric monohydroxy-terminated polydimethylsiloxane with a number-average molecular weight of 900-1200 and a viscosity of 15-20 cSt at 25°C.

9. The waterborne polyurethane surface treatment agent with antifouling and anti-migration functions according to claim 1, characterized in that, The modified waterborne polyurethane emulsion has a solid content of 29wt%-31wt%.