A hydrophobic antifouling waterborne polyurethane coating, and a preparation method and application thereof

Abstract

The present application relates to polyurethane coating and coating technology field, disclose a kind of hydrophobic antifouling waterborne polyurethane coating and its preparation method and application.The raw material composition of the hydrophobic antifouling waterborne polyurethane coating, by mass fraction, including polymeric polyol 6~12 parts, single end double hydroxyl polydimethylsiloxane 8~16 parts, diisocyanate 10~14 parts, hydrophilic chain extender 3~5 parts, small molecule chain extender 1~2 parts, catalyst 0.1~0.2 parts, neutralizing agent 3~5 parts.It is prepared by the method by the common reaction of single end double hydroxyl polydimethylsiloxane and polymeric polyol, diisocyanate, to make the low surface energy organosilicon chain segment into polyurethane main chain in chemical bonding mode, make hydrophobic segment form persistent hydrophobic barrier to surface enrichment when film-forming, solve the problem of poor stain resistance of traditional waterborne polyurethane.The hydrophobic component of the obtained coating is stable and does not migrate, and the antifouling effect can be maintained for a long time, prolonging the service life of leather products.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane coatings and coating technology, specifically relating to a hydrophobic and antifouling waterborne polyurethane coating, its preparation method, and its application. Background Technology

[0002] With the improvement of people's living standards and the enhancement of environmental awareness, leather products are increasingly widely used in fashion, home furnishings, and automotive interiors. However, leather products are easily contaminated by common pollutants such as water stains, oil stains, ink, and coffee during daily use. This not only seriously affects the aesthetic appearance of the products and shortens their service life, but also limits their application in high-end and functional fields. To solve this problem, surface coating of leather has become a crucial step. Polyurethane materials, due to their excellent film-forming properties, abrasion resistance, flexibility, and adhesion, have become one of the most widely used film-forming substances in the field of leather finishing.

[0003] In recent years, with strict global restrictions on volatile organic compound (VOC) emissions, the application of traditional solvent-based polyurethane coatings has been increasingly constrained due to the use of large amounts of organic solvents, which pose hazards to the environment and human health. Against this backdrop, waterborne polyurethane, using water as the dispersion medium, has emerged. Waterborne polyurethane boasts significant advantages such as low VOC emissions, non-toxicity and odorlessness, safety and environmental friendliness, and ease of operation, making it an ideal alternative to solvent-based polyurethane and demonstrating enormous application potential in the leather finishing industry.

[0004] However, waterborne polyurethane still has a significant performance limitation: to achieve stable dispersion in water, a large number of hydrophilic groups (such as carboxyl groups and sulfonic acid groups) must be introduced into its molecular chain. These hydrophilic groups remain inside the coating after film formation, resulting in a high surface energy and generally poor water resistance, stain resistance, and weather resistance. Specifically, when the coating comes into contact with water or oily contaminants, the contaminants easily wet, spread, and penetrate into the coating, causing stains that are difficult to clean. This problem severely restricts the further promotion of waterborne polyurethane in the field of leather finishing, especially in the application of high-end leather products (such as sofas, shoe uppers, and handbags) where high hydrophobic and stain-resistant properties are required. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a hydrophobic and antifouling waterborne polyurethane coating, its preparation method and application, so as to solve the technical problem that the waterborne polyurethane coating has poor water resistance, stain resistance and durability due to the presence of a large number of hydrophilic groups in its molecular chain.

[0006] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a hydrophobic and antifouling waterborne polyurethane coating, wherein the raw material composition of the hydrophobic and antifouling waterborne polyurethane coating, by mass parts, includes 6-12 parts of polymeric polyol, 8-16 parts of single-terminated dihydroxy polydimethylsiloxane, 10-14 parts of diisocyanate, 3-5 parts of hydrophilic chain extender, 1-2 parts of small molecule chain extender, 0.1-0.2 parts of catalyst, and 3-5 parts of neutralizer.

[0007] A further improvement of the present invention is that the polymeric polyol is selected from any one of polypropylene glycol, poly(1,4-butanediol adipate), polytetrahydrofuran ether diol, polypropylene glycol adipate diol, polypentyl adipate diol, polyhexanediol adipate, polycarbonate polyol, or polycaprolactone polyol.

[0008] A further improvement of the present invention is that the diisocyanate is selected from any one of toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,4-di(isocyanate methyl)cyclohexane, 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, isophenyl diisocyanate, tetramethyl diisocyanate, 1,3-di(isocyanate methyl)cyclohexane, phenyl diisocyanate, or isophorone diisocyanate.

[0009] A further improvement of the present invention is that the hydrophilic chain extender is 2,2-dimethylolpropionic acid or 2,2-dimethylolbutyric acid; and the neutralizing agent is diethylamine, triethylamine, diisopropylethylamine or diethylenetriamine.

[0010] A further improvement of the present invention is that the small molecule chain extender is selected from ethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, diethanolamine, diethylene glycol, ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, isophoronediamine, 1,2-cyclohexanediamine, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, or 4,4'-dicyclohexylmethanediamine.

[0011] A further improvement of the present invention is that the catalyst is selected from dimethylaminoethyl ether, pentamethyldiethylenetriamine, dimethylcyclohexylamine, dibutyltin dilaurate, organobismuth or triazine trimer catalyst.

[0012] Secondly, the present invention also provides a method for preparing the hydrophobic and antifouling waterborne polyurethane coating as described above, comprising the following steps: Step 1: The polymer polyol, single-terminated dihydroxy polydimethylsiloxane, diisocyanate and catalyst are mixed and reacted to obtain the first reactant; Step 2: Add a hydrophilic chain extender and a small molecule chain extender to the first reactant to carry out a chain extension reaction, and obtain a polyurethane prepolymer; Step 3: Add a neutralizing agent to the polyurethane prepolymer to carry out a neutralization reaction, and then add water to emulsify and disperse to obtain an aqueous polyurethane emulsion; Step 4: Apply the waterborne polyurethane emulsion to the surface of the substrate and dry it to form a film to obtain the hydrophobic and antifouling waterborne polyurethane coating.

[0013] A further improvement of the present invention is that the temperature of the mixing reaction in step 1 is 70~90℃ and the reaction time is 2~4h; the temperature of the chain extension reaction in step 2 is 50~70℃ and the reaction time is 3~5h; the temperature of the neutralization reaction in step 3 is 30~50℃ and the reaction time is 0.2~0.6h, and the amount of water added is 50~60 parts by mass; and the drying temperature for film formation in step 4 is 50~100℃.

[0014] A further improvement of the present invention is that, in step 3, after adding the neutralizing agent to carry out the neutralization reaction, the step of adding a chain extender is also included; the chain extender is ethylenediamine or isophorone diamine.

[0015] Thirdly, the present invention also provides an application of the hydrophobic and stain-resistant waterborne polyurethane coating as described above in leather finishing. Compared with the prior art, the present invention has the following beneficial effects: This invention provides a hydrophobic and stain-resistant waterborne polyurethane coating. First, the coating contains 8-16 parts by weight of single-terminated dihydroxyl polydimethylsiloxane. This component introduces low surface energy organosilicon segments into the polyurethane backbone through chemical bonding, causing the hydrophobic segments to accumulate on the surface during film formation, forming a durable hydrophobic barrier. This significantly improves the water contact angle and endows the coating with excellent water resistance and resistance to contaminants such as oil stains and inks, fundamentally solving the problem of poor stain resistance caused by hydrophilic groups in traditional waterborne polyurethanes. Second, 6-12 parts of polymeric polyol (such as polyether or polyester polyol) are compounded with the organosilicon segments to achieve synergistic performance enhancement: organosilicon provides hydrophobicity and flexibility, while polyether or polyester soft segments ensure that the coating has excellent mechanical strength and adhesion, allowing the product to maintain good flexibility and strength while possessing high hydrophobicity, perfectly meeting the stringent requirements of leather finishing for material flexibility and durability. In addition, the combined use of 3-5 parts hydrophilic chain extender and 3-5 parts neutralizer enables polyurethane to self-emulsify and form a stable water-based system. The entire product uses water as the dispersion medium, has extremely low VOC content, meets environmental protection requirements, and because the organosilicon segments are covalently attached to the main chain rather than simply blended, the hydrophobic components will not migrate or be lost due to washing or long-term use, ensuring that the coating can maintain a long-lasting and stable hydrophobic and anti-fouling effect, significantly extending the service life of leather products.

[0016] This invention also provides a method for preparing a hydrophobic and stain-resistant waterborne polyurethane coating. This method first involves reacting a single-terminated dihydroxyl polydimethylsiloxane with a polymeric polyol and diisocyanate to precisely integrate low surface energy organosilicon segments into the polyurethane backbone via chemical bonding. This allows the hydrophobic segments to spontaneously accumulate on the surface during subsequent film formation, creating a durable hydrophobic barrier and fundamentally solving the problem of poor stain resistance in traditional waterborne polyurethanes. Furthermore, a chain extension reaction introduces hydrophilic chain extenders and small-molecule chain extenders, achieving molecular-level compounding of organosilicon segments with polyether or polyester soft segments. This ensures that the coating achieves high hydrophobicity while maintaining excellent mechanical strength, flexibility, and adhesion, meeting the comprehensive performance requirements of leather finishing materials. The entire preparation process uses water as the dispersion medium for neutralization and emulsification, resulting in extremely low volatile organic compound content, meeting environmental protection requirements. Moreover, the reaction conditions are mild, requiring no complex equipment, and are easy to industrialize. Most importantly, because the organosilicon segments are covalently attached to the main chain rather than physically blended, the hydrophobic components of the resulting coating are stable and do not migrate, thus maintaining the anti-fouling effect for a long time and significantly extending the service life of leather products. Attached Figure Description

[0017] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely illustrative to aid in understanding the invention and do not specifically limit the shapes and proportions of the components of the invention.

[0018] Figure 1 This diagram illustrates the sliding behavior of common contaminants (water, hexadecane, milk, coffee, and ink) on the surface of a hydrophobic and antifouling waterborne polyurethane coating. Detailed Implementation

[0019] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0020] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0021] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0022] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0023] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0024] This invention provides a hydrophobic and antifouling waterborne polyurethane coating. The raw material composition of the hydrophobic and antifouling waterborne polyurethane coating, by mass parts, includes 6-12 parts of polymeric polyol, 8-16 parts of single-terminated dihydroxy polydimethylsiloxane, 10-14 parts of diisocyanate, 3-5 parts of hydrophilic chain extender, 1-2 parts of small molecule chain extender, 0.1-0.2 parts of catalyst, and 3-5 parts of neutralizer.

[0025] As a preferred embodiment, the polymeric polyol is selected from any one of polypropylene glycol, poly(1,4-butanediol adipate), polytetrahydrofuran ether glycol, polypropylene glycol adipate, polypentyl adipate, polyhexanediol adipate, polycarbonate polyol, or polycaprolactone polyol. Specifically, polyether polyols (such as polypropylene glycol and polytetrahydrofuran ether glycol) possess excellent flexibility and hydrolysis resistance, enabling the coating to exhibit good low-temperature performance and flexibility; polyester polyols (such as poly(1,4-butanediol adipate) and polypropylene glycol adipate) possess higher strength and abrasion resistance. By selecting the above-mentioned polymeric polyols, the mechanical properties of the coating can be adjusted to meet different application requirements. Simultaneously, their terminal hydroxyl groups can react with diisocyanates, introducing flexible segments into the polyurethane backbone, providing the coating with excellent basic mechanical properties.

[0026] As a preferred embodiment, the diisocyanate is selected from any one of toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,4-di(methyl)cyclohexane, 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, isophenyl diisocyanate, tetramethyl diisocyanate, 1,3-di(methyl)cyclohexane, phenylenediamine diisocyanate, or isophorone diisocyanate. Specifically, aromatic diisocyanates (such as toluene diisocyanate and 4,4'-diphenylmethane diisocyanate) have high reactivity and can impart high strength and hardness to the coating; aliphatic and alicyclic diisocyanates (such as hexamethylene diisocyanate, isophorone diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate) have excellent resistance to yellowing and weathering, which can meet the requirements of light-colored or transparent coatings. By selecting the aforementioned diisocyanates, the crosslinking density and hard segment content of the coating can be controlled, thereby optimizing the mechanical properties and durability of the coating.

[0027] As a preferred embodiment, the hydrophilic chain extender is 2,2-dimethylolpropionic acid or 2,2-dimethylolbutyric acid; the neutralizing agent is diethylamine, triethylamine, diisopropylethylamine or diethylenetriamine.

[0028] As a preferred embodiment, the small molecule chain extender is selected from ethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, diethanolamine, diethylene glycol, ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, isophoronediamine, 1,2-cyclohexanediamine, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, or 4,4'-dicyclohexylmethanediamine. Specifically, diol chain extenders (such as ethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, diethanolamine, and diethylene glycol) can react with isocyanates to form urethane bonds, increasing the content of hard segments in the polyurethane molecular chain and improving the coating's strength, hardness, and heat resistance. Diamine chain extenders (such as ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, and isophoronediamine) have even higher reactivity and can react with isocyanates to form urea bonds, further enhancing the coating's mechanical properties and water resistance. By selecting different types of small-molecule chain extenders, the molecular structure and properties of polyurethane can be precisely controlled to meet the needs of different application scenarios.

[0029] As a preferred embodiment, the catalyst is selected from di(dimethylaminoethyl) ether, pentamethyldiethylenetriamine, dimethylcyclohexylamine, dibutyltin dilaurate, organobismuth, or triazine trimerizing catalysts. The catalyst can significantly accelerate the reaction between isocyanate and hydroxyl groups, improving reaction efficiency and shortening reaction time. Specifically, organotin catalysts (such as dibutyltin dilaurate) have high catalytic efficiency and mild reaction conditions; organobismuth catalysts are environmentally friendly and non-toxic; amine catalysts (such as di(dimethylaminoethyl) ether, pentamethyldiethylenetriamine, and dimethylcyclohexylamine) show good selectivity for the reaction between isocyanate and water; and triazine trimerizing catalysts can promote the trimerization of isocyanate, forming a cross-linked structure. By selecting a suitable catalyst, the smooth progress of the reaction can be ensured while avoiding side reactions, thus ensuring product quality.

[0030] This invention also provides a method for preparing a hydrophobic and antifouling waterborne polyurethane coating, comprising the following steps: Step 1: Mix the polymer polyol, mono-dihydroxy polydimethylsiloxane, diisocyanate and catalyst, and stir the mixture at 70~90℃ for 2~4h to obtain the first reactant. Step 2: Add a hydrophilic chain extender and a small molecule chain extender to the first reactant, and stir the reaction at 50~70℃ for 3~5h to carry out the chain extension reaction, and obtain a polyurethane prepolymer; Step 3: Cool the polyurethane prepolymer to 30~50℃, add a neutralizing agent and stir for 0.2~0.6h to carry out the neutralization reaction, then add a chain extender, which is ethylenediamine or isophorone diamine, and then add 50~60 parts by weight of water for high-speed emulsification and dispersion to obtain an aqueous polyurethane emulsion. Step 4: Apply the waterborne polyurethane emulsion to the surface of the substrate and dry it at 50~100℃ to form a film, thereby obtaining the hydrophobic and antifouling waterborne polyurethane coating.

[0031] The present invention also provides an application of a hydrophobic and stain-resistant waterborne polyurethane coating in leather finishing.

[0032] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0033] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" represents weight percentage, "parts" represents parts by weight, and "ratio" represents weight proportion.

[0034] Example 1 This embodiment provides a method for preparing a hydrophobic and antifouling waterborne polyurethane coating, comprising the following steps: (1) In a reactor equipped with a stirrer, a reflux condenser and a thermometer, 10 parts of dehydrated polytetrahydrofuran ether diol, 14 parts of isophorone diisocyanate, 12 parts of single-terminated dihydroxy polydimethylsiloxane and 0.2 parts of dibutyltin dilaurate were added, stirred and heated to 80°C for 2 hours. After the reaction was complete, 4 parts of 2,2-dimethylolbutyric acid and 1 part of 1,4-butanediol were added, and the temperature was raised to 70°C for 4 hours to obtain polyurethane prepolymer; (2) Cool the reactor to 40°C, add 4 parts of triethylamine and stir for 0.5 h, then add 50 parts of water and stir at high speed for 0.5 h to end the reaction and obtain the hydrophobic and antifouling waterborne polyurethane.

[0035] (3) The prepared waterborne polyurethane is applied to the surface of the leather and dried at 60°C to form a film, thus obtaining a hydrophobic and stain-resistant waterborne polyurethane coating.

[0036] Example 2 This embodiment provides a method for preparing a hydrophobic and antifouling waterborne polyurethane coating, comprising the following steps: (1) In a reactor equipped with a stirrer, a reflux condenser and a thermometer, 12 parts of dehydrated polytetrahydrofuran glycol, 10 parts of toluene diisocyanate, 10 parts of single-terminated dihydroxy organosilicon prepolymer and 0.1 parts of dibutyltin dilaurate were added, stirred and heated to 70°C for 2 hours. After the reaction was complete, 4 parts of 2,2-dimethylolbutyric acid and 1 part of 1,4-butanediol were added, and the temperature was raised to 60°C for 4 hours to obtain polyurethane prepolymer. (2) Cool the reactor to 40°C, add 4 parts of triethylamine and stir for 0.5 h, then add 60 parts of water and stir at high speed for 0.5 h to end the reaction and obtain the hydrophobic and antifouling waterborne polyurethane.

[0037] (3) The prepared waterborne polyurethane is applied to the surface of the leather and dried at 60°C to form a film, thus obtaining a hydrophobic and stain-resistant waterborne polyurethane coating.

[0038] Example 3 This embodiment provides a method for preparing a hydrophobic and antifouling waterborne polyurethane coating, comprising the following steps: (1) In a reactor equipped with a stirrer, a reflux condenser and a thermometer, add 8 parts of dehydrated polycaprolactone polyol, 10 parts of 4,4-dicyclohexylmethane diisocyanate, 10 parts of single-terminated dihydroxyl organosilicon prepolymer and 0.1 parts of dibutyltin dilaurate, stir and heat to 80°C for 2 hours. After stirring thoroughly, add 3 parts of 2,2-dimethylolbutyric acid and 1 part of ethylene glycol, heat to 70°C and react for 4 hours to obtain polyurethane prepolymer; (2) Cool the reactor to 45°C, add 3 parts of triethylamine and stir for 0.5 h, then add 60 parts of water and stir at high speed for 0.5 h to end the reaction and obtain the hydrophobic and antifouling waterborne polyurethane.

[0039] (3) The prepared waterborne polyurethane is applied to the surface of the leather and dried at 50°C to form a film, thus obtaining a hydrophobic and stain-resistant waterborne polyurethane coating.

[0040] Example 4 This embodiment provides a method for preparing a hydrophobic and antifouling waterborne polyurethane coating, comprising the following steps: (1) In a reactor equipped with a stirrer, a reflux condenser and a thermometer, 12 parts of dehydrated polycarbonate polyol, 10 parts of hexamethylene diisocyanate, 8 parts of single-terminated dihydroxy organosilicon prepolymer and 0.1 parts of dibutyltin dilaurate were added, stirred and heated to 75°C for 2 hours. After stirring thoroughly, 3.5 parts of 2,2-dimethylolbutyric acid and 1.2 parts of neopentyl glycol were added, and the mixture was heated to 70°C for 3 hours to obtain a polyurethane prepolymer. (2) Cool the reactor to 40°C, add 3.5 parts of triethylamine and stir for 0.6 h, then add 60 parts of water and stir at high speed for 0.5 h to end the reaction and obtain the hydrophobic and antifouling waterborne polyurethane.

[0041] (3) The prepared waterborne polyurethane is applied to the surface of the leather and dried at 55°C to form a film, thus obtaining a hydrophobic and stain-resistant waterborne polyurethane coating.

[0042] Example 5 This embodiment provides a method for preparing a hydrophobic and antifouling waterborne polyurethane coating, comprising the following steps: (1) In a reactor equipped with a stirrer, a reflux condenser and a thermometer, 10 parts of dehydrated poly(1,4-butanediol adipate), 10 parts of 4,4-diphenylmethane diisocyanate, 10 parts of single-terminated dihydroxyl organosilicon prepolymer and 0.1 parts of dibutyltin dilaurate were added, stirred and heated to 65°C for 2 hours. After stirring thoroughly, 3.5 parts of 2,2-dimethylolpropionic acid were added, and the mixture was heated to 60°C for 2 hours to obtain a polyurethane prepolymer. (2) Cool the reactor to 30°C, add 3.5 parts of triethylamine and stir for 0.6h, then add 1.2 parts of ethylenediamine and 60 parts of water and stir at high speed for 1h to end the reaction and obtain the hydrophobic and antifouling waterborne polyurethane.

[0043] (3) The prepared waterborne polyurethane is applied to the surface of the leather and dried at 65°C to form a film, thus obtaining a hydrophobic and stain-resistant waterborne polyurethane coating.

[0044] Example 6 This embodiment provides a method for preparing a hydrophobic and antifouling waterborne polyurethane coating, comprising the following steps: (1) In a reactor equipped with a stirrer, a reflux condenser and a thermometer, 10 parts of dehydrated poly(1,4-butanediol adipate), 10 parts of 4,4-diphenylmethane diisocyanate, 10 parts of single-terminated dihydroxyl organosilicon prepolymer and 0.1 parts of dibutyltin dilaurate were added, stirred and heated to 65°C for 2 hours. After stirring thoroughly, 3.5 parts of 2,2-dimethylolpropionic acid were added, and the mixture was heated to 60°C for 2 hours to obtain a polyurethane prepolymer. (2) Cool the reactor to 30°C, add 3.5 parts of triethylamine and stir for 0.6 h, then add 1.2 parts of isophorone diamine and 60 parts of water and stir at high speed for 1 h to end the reaction and obtain the hydrophobic and antifouling waterborne polyurethane.

[0045] (3) The prepared waterborne polyurethane is applied to the surface of the leather and dried at 50°C to form a film, thus obtaining a hydrophobic and stain-resistant waterborne polyurethane coating.

[0046] Example 7 This embodiment provides a method for preparing a hydrophobic and antifouling waterborne polyurethane coating, comprising the following steps: (1) In a reactor equipped with a stirrer, a reflux condenser and a thermometer, 10 parts of dehydrated poly(1,4-butanediol adipate), 10 parts of 4,4-dicyclohexylmethane diisocyanate, 12 parts of single-terminated dihydroxyl organosilicon prepolymer and 0.1 parts of dibutyltin dilaurate were added, stirred and heated to 80°C for 2 hours. After stirring thoroughly, 4 parts of 2,2-dimethylolpropionic acid were added, and the mixture was heated to 70°C for 2 hours to obtain a polyurethane prepolymer. (2) Cool the reactor to 40°C, add 3.5 parts of triethylamine and stir for 0.6 h, then add 1.2 parts of ethylenediamine and 60 parts of water and stir at high speed for 1 h to end the reaction and obtain the hydrophobic and antifouling waterborne polyurethane.

[0047] (3) The prepared waterborne polyurethane is applied to the surface of the leather and dried at 45°C to form a film, thus obtaining a hydrophobic and stain-resistant waterborne polyurethane coating.

[0048] Performance testing: The waterborne polyurethane coatings of Examples 1-7 were applied to a leather substrate at a coating amount of 50 g / m². 2 Then, it was dried at a certain temperature for 24 hours and the following tests were performed: (1) Stability test method: The hydrophobic and antifouling waterborne polyurethane emulsion is qualified if it is placed at room temperature for 6 months and there is no stratification, precipitation, or significant increase or decrease in viscosity.

[0049] (2) Pencil hardness test method: The pencil hardness of the coating is determined by the ASTM D3363 standard method (hardness grade range is 6B~HB~6H, where 6H is the hardest and 6B is the softest). Specific operation: The hardness tester uses the three-point contact method to test the coating surface (two rollers and one pencil lead). The angle between the pencil and the sample coating surface is 45°. The hardness tester is slid on the coating surface with a pressure of 1±0.05 kg, and the damage to the coating is observed. When the coating breaks no more than twice in 5 tests, the pencil of the next higher hardness grade is replaced for testing. When the coating breaks more than twice, the pencil grade can be read and the next grade next can be recorded.

[0050] (3) Static contact angle: Waterborne polyurethane was applied to a leather substrate, and the contact angle of the water droplets was analyzed using a static contact angle meter. The droplet size was set to 5 μL / droplet, and the measurement temperature was approximately 25°C.

[0051] (4) Adhesion test: Adhesion was determined by the cross-cut test method specified in ASTM D3359.

[0052] The test results are shown in Table 1.

[0053] Table 1 Performance indicators of waterborne polyurethane coatings obtained in Examples 1-7 of this invention

[0054] As shown in Table 1, the hydrophobic and antifouling waterborne polyurethane coatings prepared in Examples 1-7 of this invention all have good storage stability and water contact angles of over 104°, exhibiting excellent hydrophobic properties. At the same time, the coating hardness reaches 3H-5H, and the adhesion is the highest grade 5B, indicating that the coating has both good mechanical strength and excellent bonding with the leather substrate.

[0055] according to Figure 1 As can be seen, the hydrophobic and antifouling waterborne polyurethane coating of the present invention exhibits excellent repellency against a variety of common pollutants. As shown in the figure, droplets such as water, hexadecane, milk, coffee, and ink can all slide freely off the coating surface, and no stains are left on the coating surface after sliding off. This indicates that the coating has a broad-spectrum hydrophobic and antifouling ability and can effectively resist the adhesion and penetration of water-based and oil-based pollutants.

[0056] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A hydrophobic and antifouling waterborne polyurethane coating, characterized in that, The raw material composition of the hydrophobic and antifouling waterborne polyurethane coating, by mass parts, includes 6-12 parts of polymeric polyol, 8-16 parts of single-terminated dihydroxy polydimethylsiloxane, 10-14 parts of diisocyanate, 3-5 parts of hydrophilic chain extender, 1-2 parts of small molecule chain extender, 0.1-0.2 parts of catalyst, and 3-5 parts of neutralizer.

2. The hydrophobic and antifouling waterborne polyurethane coating according to claim 1, characterized in that, The polymer polyol is selected from any one of polypropylene glycol, poly(1,4-butanediol adipate), polytetrahydrofuran ether diol, polypropylene adipate diol, polypentyl adipate diol, polyhexanediol adipate diol, polycarbonate polyol, or polycaprolactone polyol.

3. The hydrophobic and antifouling waterborne polyurethane coating according to claim 1, characterized in that, The diisocyanate is selected from any one of toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,4-di(isocyanate methyl)cyclohexane, 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, isophenyl diisocyanate, tetramethyl diisocyanate, 1,3-di(isocyanate methyl)cyclohexane, phenyl diisocyanate, or isophorone diisocyanate.

4. The hydrophobic and antifouling waterborne polyurethane coating according to claim 1, characterized in that, The hydrophilic chain extender is 2,2-dimethylolpropionic acid or 2,2-dimethylolbutyric acid; the neutralizing agent is diethylamine, triethylamine, diisopropylethylamine or diethylenetriamine.

5. The hydrophobic and antifouling waterborne polyurethane coating according to claim 1, characterized in that, The small molecule chain extender is selected from ethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, diethanolamine, diethylene glycol, ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, isophoronediamine, 1,2-cyclohexanediamine, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, or 4,4'-dicyclohexylmethanediamine.

6. The hydrophobic and antifouling waterborne polyurethane coating according to claim 1, characterized in that, The catalyst is selected from dimethylaminoethyl ether, pentamethyldiethylenetriamine, dimethylcyclohexylamine, dibutyltin dilaurate, organobismuth, or triazine trimer catalyst.

7. A method for preparing a hydrophobic and antifouling waterborne polyurethane coating as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Step 1: The polymer polyol, single-terminated dihydroxy polydimethylsiloxane, diisocyanate and catalyst are mixed and reacted to obtain the first reactant; Step 2: Add a hydrophilic chain extender and a small molecule chain extender to the first reactant to carry out a chain extension reaction, and obtain a polyurethane prepolymer; Step 3: Add a neutralizing agent to the polyurethane prepolymer to carry out a neutralization reaction, and then add water to emulsify and disperse to obtain an aqueous polyurethane emulsion; Step 4: Apply the waterborne polyurethane emulsion to the surface of the substrate and dry it to form a film to obtain the hydrophobic and antifouling waterborne polyurethane coating.

8. The method for preparing a hydrophobic and antifouling waterborne polyurethane coating according to claim 7, characterized in that, The mixing reaction in step 1 is carried out at a temperature of 70-90℃ for 2-4 hours; the chain extension reaction in step 2 is carried out at a temperature of 50-70℃ for 3-5 hours; the neutralization reaction in step 3 is carried out at a temperature of 30-50℃ for 0.2-0.6 hours, and the amount of water added is 50-60 parts by mass; the drying temperature for film formation in step 4 is 50-100℃.

9. The method for preparing a hydrophobic and antifouling waterborne polyurethane coating according to claim 7, characterized in that, Step 3, after adding the neutralizing agent to carry out the neutralization reaction, also includes the step of adding a chain extender; the chain extender is ethylenediamine or isophorone diamine.

10. The application of a hydrophobic and stain-resistant waterborne polyurethane coating as described in any one of claims 1 to 6 in leather finishing.

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