Antibacterial polyurethane surface layer resin for automobile leather and preparation method of antibacterial polyurethane surface layer resin

Abstract

The invention discloses antibacterial polyurethane surface layer resin for automobile leather and a preparation method of the antibacterial polyurethane surface layer resin, and relates to the technical field of high-molecular polymers. 1 to 20 parts of polyisocyanate; 4.5 to 12.5 parts of a hydrophilic chain extender; 0.5 to 2 parts of a small molecular alcohol chain extender; 1-10 parts of an amine chain extender; 0.01 to 0.5 part of a catalyst; 2-5 parts of a salt forming agent; wherein the hydrophilic chain extender is caffeic acid; the caffeic acid is adopted to replace a carboxylic acid type hydrophilic chain extender, so that the wear resistance, weather resistance and mechanical strength of the prepared waterborne polyurethane are greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of high molecular polymers, in particular to an antibacterial polyurethane surface layer resin for automobile leather and a preparation method thereof. Background Art

[0002] Leather products have become a necessity in human life, with large consumption and wide applications. However, since the raw leather is composed of collagen and a large amount of animal and plant oils or their modified products are added during the processing, it provides a rich source of nutrition for the growth and reproduction of microorganisms; in addition, the natural multi-porous structure of leather is easy to absorb moisture from the air, and it is a natural breeding ground for microbial reproduction. Therefore, leather products are prone to mildew during use, which greatly affects the performance of leather and its products. Leather mildew usually starts from the outer surface of the leather product, and its outer surface is the surface resin. If the surface resin of the leather has anti-mildew properties, it can effectively protect the leather and its products and extend its service life. Therefore, the anti-mildew technology of the leather surface resin is very important in the leather industry. Waterborne polyurethane materials are becoming more and more familiar to people due to their environmental protection and safety properties. At present, the main preparation method of waterborne polyurethane mainly relies on hydrophilic chain extenders such as dimethylolpropionic acid (DMPA) and dimethylolbutyric acid (DMBA). However, these two hydrophilic chain extenders require external antibacterial agents to prevent mildew during the production process, and the effect is not good. They are easy to precipitate on the surface during use, resulting in surface mottling.

[0003] The prior art discloses an aqueous surface polyurethane resin for automobile leather and a preparation method thereof, which has the characteristics of abrasion resistance, weather resistance, and anti-pollution of the automobile leather surface. The above-mentioned prior art solutions have the following defects: the prior art has the problem that abrasion resistance, weather resistance, and anti-pollution cannot be achieved at the same time, that is, the automobile leather surface cannot be truly and effectively antibacterial, and cannot effectively protect the leather and its products and extend their service life. Summary of the invention

[0004] The present invention aims to solve the shortcomings existing in the background technology, and provides an antibacterial polyurethane surface layer resin for automobile leather and a preparation method thereof, which at least solves some technical problems in the prior art.

[0005] To achieve the above object, the present invention provides the following technical solutions: An antibacterial polyurethane surface resin for automobile leather comprises the following raw material components and weight parts: 70-85 parts of macromolecular polyol; 1-20 parts of polyisocyanate; 4.5-12.5 parts of hydrophilic chain extender; 0.5-2 parts of small molecule alcohol chain extender; 1-10 parts of amine chain extender; 0.01-0.5 parts of catalyst; 2-5 parts of salt-forming agent; Wherein, the hydrophilic chain extender is caffeic acid.

[0006] Further, the macromolecular polyol is any one or more of polyester polyol, polycarbonate polyol, polytetramethylene ether polyol, polyethylene oxide polyol, polypropylene oxide polyol, polyester ether polyol and polysiloxane polyol; The molecular weight of the macromolecular polyol is 1000-3000.

[0007] Furthermore, the polyisocyanate is any one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, xylylene diisocyanate, naphthalene-1,5-diisocyanate, polymethylene polyphenyl isocyanate, tetramethylxylylene diisocyanate, methylcyclohexyl diisocyanate and dicyclohexylmethane diisocyanate.

[0008] Furthermore, the small molecule alcohol chain extender is any one or more of ethylene glycol, 2-methyl-1,3-propanediol, 1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, glycerol, sorbitol, trimethylolpropane and dimethylolcyclohexane.

[0009] Furthermore, the amine chain extender is one or more of ethylenediamine, 1,6-hexanediamine, isophoronediamine and polyetheramine.

[0010] Further, the catalyst is an organic bismuth catalyst; The salt-forming agent includes any one or more of triethylamine, ammonia water and sodium hydroxide.

[0011] On the other hand, the present invention also provides a method for preparing an antibacterial polyurethane surface layer resin for automobile leather, comprising the following steps: reacting a macromolecular polyol with the polyisocyanate; Adding the hydrophilic chain extender and the small molecule alcohol chain extender into the reaction; Then, the catalyst is added, and after the catalytic reaction, the temperature is lowered and the salt-forming agent is added for neutralization; After adding water, the amine chain extender is added, and the mixture is distilled under reduced pressure to obtain a waterborne polyurethane resin.

[0012] Preferably, the method comprises the following steps: Reacting the macromolecular polyol and the polyisocyanate at 85-95° C. for 2-3 hours; Then, the hydrophilic chain extender and the small molecule alcohol chain extender are added and reacted at 75-85° C. for 1.5-2.5 hours; Then add the catalyst, react at 65-75°C for 2-3h, cool to -5-5°C, add the salt-forming agent for neutralization; After adding water, the amine chain extender is added, and the mixture is distilled under reduced pressure to obtain a waterborne polyurethane resin.

[0013] Preferably, the preparation steps are specifically as follows: Dehydrate the macromolecular polyol at 10-110°C for 1-2 hours, then cool to 65-75°C, add 15g of polyisocyanate, heat to 80-95°C and keep warm for 2-3 hours; Then add a hydrophilic chain extender and a small molecule alcohol chain extender and react at 75-85°C for 1.5-2.5h and then cool to 55-65°C; Then add a catalyst to adjust the viscosity, react at 65-75°C for 2-3h, then cool to -5-5°C, add a salt-forming agent for neutralization, and neutralize for 30-60min; Deionized water is added under high-speed shearing, dispersed for 1-5 minutes, and then an amine chain extender is slowly added, and vacuum distillation is performed to obtain a waterborne polyurethane resin emulsion.

[0014] Preferably, acetone is added simultaneously with the addition of the catalyst.

[0015] Beneficial effects of the present invention: (1) The present invention uses caffeic acid to replace the traditional carboxylic acid type hydrophilic chain extender, which greatly improves the wear resistance, weather resistance and mechanical strength of the prepared waterborne polyurethane. The source of caffeic acid is safe, environmentally friendly and pollution-free. Caffeic acid is used as a hydrophilic chain extender to react with polyisocyanate to improve the stability of the polymerization reaction. Caffeic acid has antibacterial and antiviral effects, and can make leather products more effectively antibacterial and antiviral. (2) In the present invention, acetone is added at the same time as the catalyst. Acetone can adjust the viscosity of the reaction solution. The acetone is removed by distillation during the reduced pressure distillation stage. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0017] The disclosure below provides many different embodiments or examples for implementing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are only examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numbers and / or reference letters in different examples. This repetition is for the purpose of simplicity and clarity, and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but a person of ordinary skill in the art may be aware of the application of other processes and / or the use of other materials.

[0018] The invention adopts caffeic acid to replace the carboxylic acid type hydrophilic chain extender. Caffeic acid is an organic acid with a chemical formula of C9H8O4. It is a yellow crystalline powder, soluble in hot water and ethanol, slightly soluble in acetone, can be safely used in cosmetics and leather finishing, and has a wide range of antibacterial and antiviral activities.

[0019] It can be used as a chain extender, hydrophilic agent and cross-linking agent, greatly improving the friction resistance, weather resistance and anti-pollution properties of waterborne polyurethane. Caffeic acid is safe, environmentally friendly and pollution-free.

[0020] Caffeic acid is used as a hydrophilic chain extender, which can react better with polyisocyanate and improve the stability of the polymerization reaction.

[0021] In addition, caffeic acid has antibacterial and antiviral effects, so that water-based polyurethane can be obtained without the addition of an external bactericide, and the prepared leather can achieve the effect of antiseptic and sterilization.

[0022] Example 1 Dehydrate 78 g of polytetrahydrofuran ether polyol (molecular weight 3000) at 105° C. for 1 h, then cool to 70° C.; Add 15g of toluene diisocyanate, heat to 85℃ and keep warm for 2 hours, measure the NCO content after 2 hours, and cool to 60℃ after reaching the theoretical value; Then add 6g of caffeic acid and 1.5g of ethylene glycol and react at 80℃ for 2h, then cool to 60℃; Then, 0.2 g of organic bismuth Coscat83 and 2 ml of acetone were added to adjust the viscosity, and the mixture was reacted at 70°C for 2.5 h. After the reaction, the NCO content was measured, and then the temperature was lowered to 0°C. 2.32 g of triethylamine was added for neutralization. After neutralization for 30 min, deionized water was added under high-speed shearing and dispersed for 2 min. Then, 2 g of ethylenediamine was slowly added, and the acetone in the system was removed by distillation under reduced pressure to obtain a waterborne polyurethane resin emulsion sample with a solid content of 39.8%.

[0023] Production process of automobile leather surface layer: take 100g water-based polyurethane sample, add 0.5g water-based wetting agent, 0.2g water-based defoaming agent, 1g water-based leveling agent, 0.8g water-based thickener, configure the water-based polyurethane sample 1 to 3000-4000Cps viscosity, use No. 13 coating rod to scrape on DE-7 model release paper, then put it into a drying oven at 110℃, place it on a water platform, take it out after it is completely dried, and obtain the surface layer sample.

[0024] Example 2 Dehydrate 80 g of polyethylene oxide polyol (molecular weight 3000) at 105 °C for 1 h, then cool to 70 °C; Add 15g of isophorone diisocyanate, raise the temperature to 90℃ and keep it for 2 hours, measure the NCO content after two hours, and cool it down to 60℃ after reaching the theoretical value; Then add 8g of caffeic acid and 1.5g of glycerol and react at 80℃ for 2h, then cool to 60℃; Then, 0.15 g of organic bismuth 1610 and 2 ml of acetone were added to adjust the viscosity, and the mixture was reacted at 70°C for 2.5 h. After the reaction, the NCO content was measured, and then the temperature was lowered to 0°C. 2.12 g of triethylamine was added for neutralization. After neutralization for 30 min, deionized water was added under high-speed shearing and dispersed for 2 min. Then, 8 g of polyetheramine was slowly added, and the acetone in the system was removed by distillation under reduced pressure to obtain a waterborne polyurethane resin sample with a solid content of 40.8%.

[0025] Production process of automobile leather surface layer: take 100g water-based polyurethane sample, add 0.5g water-based wetting agent, 0.2g water-based defoaming agent, 1g water-based leveling agent, 0.8g water-based thickener, configure the water-based polyurethane sample 1 to 3000-4000Cps viscosity, use No. 13 coating rod to scrape on DE-7 model release paper, then put it into a drying oven at 110℃, place it on a water platform, take it out after it is completely dried, and obtain the surface layer sample.

[0026] Example 3 Dehydrate 75 g of polyester ether polyol (molecular weight 3000) at 105 °C for 1 h, then cool to 70 °C; Add 15g of 1,6-hexamethylene diisocyanate, raise the temperature to 90℃ and keep it for 2 hours, measure the NCO content after two hours, and cool it down to 60℃ after reaching the theoretical value; Then add 7.2g of caffeic acid and 1.5g of ethylene glycol and react at 80℃ for 2h, then cool to 60℃; Then, 0.2 g of organic bismuth 2010 and 2 ml of acetone were added to adjust the viscosity, and the mixture was reacted at 70°C for 2.5 h. After the reaction, the NCO content was measured, and then the temperature was lowered to 0°C. 2.51 g of triethylamine was added for neutralization. After neutralization for 30 min, deionized water was added under high-speed shearing and dispersed for 2 min. Then, 5 g of isophorone diamine was slowly added, and the acetone in the system was removed by reduced pressure distillation to obtain a waterborne polyurethane resin sample with a solid content of 40.6%.

[0027] Production process of automobile leather surface layer: take 100g water-based polyurethane sample, add 0.5g water-based wetting agent, 0.2g water-based defoaming agent, 1g water-based leveling agent, 0.8g water-based thickener, configure the water-based polyurethane sample 1 to 3000-4000Cps viscosity, use No. 13 coating rod to scrape on DE-7 model release paper, then put it into a drying oven at 110℃, place it on a water platform, take it out after it is completely dried, and obtain the surface layer sample.

[0028] Example 4 80 g of polypropylene oxide polyol (molecular weight 4000) was dehydrated at 105°C for 1 h, and then cooled to 70°C; Add 15g of xylylene diisocyanate, raise the temperature to 90℃ and keep it for 2 hours, measure the NCO content after two hours, and cool it down to 60℃ after reaching the theoretical value; Then add 6.8g of caffeic acid and 1.5g of ethylene glycol and react at 80℃ for 2h, then cool to 60℃; Then, 0.2 g of organic bismuth Coscat83 and 2 ml of acetone were added to adjust the viscosity, and the mixture was reacted at 70°C for 2.5 h. After the reaction, the NCO content was measured, and then the temperature was lowered to 0°C. 2.32 g of triethylamine was added for neutralization. After neutralization for 30 min, deionized water was added under high-speed shearing and dispersed for 2 min. Then, 6 g of 1,6-hexanediamine was slowly added, and the acetone in the system was removed by distillation under reduced pressure to obtain a waterborne polyurethane resin sample with a solid content of 40.2%.

[0029] Production process of automobile leather surface layer: take 100g water-based polyurethane sample, add 0.5g water-based wetting agent, 0.2g water-based defoaming agent, 1g water-based leveling agent, 0.8g water-based thickener, configure the water-based polyurethane sample 1 to 3000-4000Cps viscosity, use No. 13 coating rod to scrape on DE-7 model release paper, then put it into a drying oven at 110℃, place it on a water platform, take it out after it is completely dried, and obtain the surface layer sample.

[0030] Example 5 Dehydrate 83 g of polysiloxane polyol (molecular weight 3000) at 105 °C for 1 h, then cool to 70 °C; Add 15g of methylcyclohexyl diisocyanate, raise the temperature to 90℃ and keep it for 2 hours, measure the NCO content after two hours, and cool it down to 60℃ after reaching the theoretical value; Then, 7.6 g of caffeic acid and 1.6 g of butanediol were added and reacted at 80 °C for 2 h, and then the temperature was lowered to 60 °C; Then, 0.2 g of organic bismuth Coscat83 and 3 ml of acetone were added to adjust the viscosity, and the mixture was reacted at 70°C for 3 h. After the reaction, the NCO content was measured, and then the temperature was lowered to 0°C. 2.32 g of triethylamine was added for neutralization. After neutralization for 30 min, deionized water was added under high-speed shearing and dispersed for 2 min. Then, 2.3 g of ethylenediamine was slowly added, and the acetone in the system was removed by distillation under reduced pressure to obtain a waterborne polyurethane resin sample with a solid content of 39.8%.

[0031] Production process of automobile leather surface layer: take 100g water-based polyurethane sample, add 0.5g water-based wetting agent, 0.2g water-based defoaming agent, 1g water-based leveling agent, 0.8g water-based thickener, configure the water-based polyurethane sample 1 to 3000-4000Cps viscosity, use No. 13 coating rod to scrape on DE-7 model release paper, then put it into a drying oven at 110℃, place it on a water platform, take it out after it is completely dried, and obtain the surface layer sample.

[0032] Comparative Example 1 Dehydrate 80 g of polytetrahydrofuran ether polyol (molecular weight 3000) at 105° C. for 1 h, then cool to 70° C.; Add 15g of toluene diisocyanate, raise the temperature to 90℃ and keep it for 2 hours, measure the NCO content after two hours, and cool it down to 60℃ after reaching the theoretical value; Then add 6g of dimethylolpropionic acid and 1.5g of ethylene glycol and react at 80°C for 2h, then cool to 60°C; Then, 0.2 g of organic bismuth Coscat83 and 2 ml of acetone were added to adjust the viscosity, and the mixture was reacted at 70°C for 2.5 h. After the reaction, the NCO content was measured, and then the temperature was lowered to 0°C. 2.32 g of triethylamine was added for neutralization. After neutralization for 30 min, deionized water was added under high-speed shearing and dispersed for 2 min. Then, 2 g of ethylenediamine was slowly added, and the acetone in the system was removed by distillation under reduced pressure to obtain a waterborne polyurethane resin sample with a solid content of 41%.

[0033] Production process of automobile leather surface layer: take 100g water-based polyurethane sample, add 0.5g water-based wetting agent, 0.2g water-based defoaming agent, 1g water-based leveling agent, 0.8g water-based thickener, configure the water-based polyurethane sample 1 to 3000-4000Cps viscosity, use No. 13 coating rod to scrape on DE-7 model release paper, then put it into a drying oven at 110℃, place it on a water platform, take it out after it is completely dried, and obtain the surface layer sample.

[0034] Comparative Example 2 Dehydrate 83 g of polysiloxane polyol (molecular weight 3000) at 105 °C for 1 h, then cool to 70 °C; Add 15g of methylcyclohexyl diisocyanate, raise the temperature to 90℃ and keep it for 2 hours, measure the NCO content after two hours, and cool it down to 60℃ after reaching the theoretical value; Then, 7.6 g of dimethylolbutyric acid and 1.6 g of butanediol were added and reacted at 80°C for 2 h, and the temperature was lowered to 60°C; Then, 0.2 g of organic bismuth Coscat83 and 3 ml of acetone were added to adjust the viscosity, and the mixture was reacted at 70°C for 3 h. After the reaction, the NCO content was measured, and then the temperature was lowered to 0°C. 2.32 g of triethylamine was added for neutralization. After neutralization for 30 min, deionized water was added under high-speed shearing and dispersed for 2 min. Then, 2.3 g of ethylenediamine was slowly added, and the acetone in the system was removed by distillation under reduced pressure to obtain a waterborne polyurethane resin sample with a solid content of 40.12%.

[0035] Production process of automobile leather surface layer: take 100g water-based polyurethane sample, add 0.5g water-based wetting agent, 0.2g water-based defoaming agent, 1g water-based leveling agent, 0.8g water-based thickener, configure the water-based polyurethane sample 1 to 3000-4000Cps viscosity, use No. 13 coating rod to scrape on DE-7 model release paper, then put it into a drying oven at 110℃, place it on a water platform, take it out after it is completely dried, and obtain the surface layer sample.

[0036] Performance Testing: The aqueous surface polyurethane resins for automobile leather prepared in Examples 1-5 and Comparative Examples 1 and 2 were respectively tested for the antibacterial rate of aqueous emulsions, and the prepared automobile leather surface layers were tested for performance such as normal low temperature folding resistance, Martindale abrasion resistance, and weather resistance, and the test methods for each performance are as follows: Test method for antibacterial rate of water-based emulsion: Paper method, a method used, using paper, membrane, film, etc. as a culture medium carrier, attaching a specific culture medium and color-developing substance on it, and determining the microorganisms in food by observing the growth and color development of microorganisms on the test piece (the test standard is ASTME2315-03) Test method for folding resistance of automobile leather surface layer at room and low temperature: take surface layer sample, and laminate it with genuine leather or microfiber bass by transfer coating method, test standard QB / T 2714 2005. It is qualified if it can withstand 100,000 times of folding at room temperature and 25,000 times of folding at low temperature.

[0037] Martindale abrasion resistance test: Take the surface sample and use the transfer coating method to laminate it with leather or microfiber bass. The test standard is Martindale method ASTM D4966 fabric friction resistance test. It is qualified if the number of abrasion times is 100,000 times.

[0038] Weather resistance test: Take the surface sample and use the transfer coating method to laminate it with genuine leather or microfiber base. The test standard is the sample standard provided by FAW-Volkswagen. After one month in the environmental circulation box, no obvious change in color or thickness is considered excellent.

[0039] Antibacterial rate test of automobile leather surface: Cut the automobile leather surface into 3*3CM size, then inoculate the mold on the sample to be tested, and observe the mold growth on the sample surface under constant temperature (28℃) and constant humidity (95%) for 7 days (QB / T4199-2011): No growth – Level 0 slight growth (<10%) + Level 1 small growth (10~30%) ++ Level 2 moderate growth (30 ~ 60%) ++ Level 3 severe growth (60% to complete coverage) +++4.

[0040] The test results are shown in Table 1: Table 1

[0041] It can be seen from Table 1 that the waterborne polyurethane provided in Examples 1-5 has good antibacterial properties, and the applied surface layer has excellent folding resistance at room temperature and low temperature, good wear resistance, excellent weather resistance, and excellent antibacterial rate.

[0042] As antibacterial resin for automobile leather, the resin is superior to the resin for automobile leather on the market. Therefore, the waterborne polyurethane prepared by the present invention is a polyurethane with strong antibacterial property, and has excellent antibacterial and antimicrobial properties when applied to the surface layer of automobile leather.

[0043] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of the above disclosed technical contents without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. An antibacterial polyurethane surface resin for automobile leather, characterized in that: The invention comprises the following raw material components and weight parts: 70-85 parts of macromolecular polyol; 1-20 parts of polyisocyanate; 4.5-12.5 parts of hydrophilic chain extender; 0.5-2 parts of small molecule alcohol chain extender; 1-10 parts of amine chain extender; 0.01-0.5 parts of catalyst; 2-5 parts of salt-forming agent; Wherein, the hydrophilic chain extender is caffeic acid.

2. The antimicrobial polyurethane surface layer resin for automobile leather according to claim 1, characterized in that: The macromolecular polyol is any one or more of polyester polyol, polycarbonate polyol, polytetramethylene ether polyol, polyethylene oxide polyol, polypropylene oxide polyol, polyester ether polyol and polysiloxane polyol; The molecular weight of the macromolecular polyol is 1000-3000.

3. The antimicrobial polyurethane surface layer resin for automobile leather according to claim 1, characterized in that: The polyisocyanate is any one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, xylylene diisocyanate, naphthalene-1,5-diisocyanate, polymethylene polyphenyl isocyanate, tetramethylxylylene diisocyanate, methylcyclohexyl diisocyanate and dicyclohexylmethane diisocyanate.

4. The antimicrobial polyurethane surface layer resin for automobile leather according to claim 1, characterized in that: The small molecule alcohol chain extender is any one or more of ethylene glycol, 2-methyl-1,3-propanediol, 1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, glycerol, sorbitol, trimethylolpropane and dimethylolcyclohexane.

5. The antimicrobial polyurethane surface layer resin for automobile leather according to claim 1, characterized in that: The amine chain extender is one or more of ethylenediamine, 1,6-hexanediamine, isophoronediamine and polyetheramine.

6. The antimicrobial polyurethane surface layer resin for automobile leather according to claim 1, characterized in that: The catalyst is an organic bismuth catalyst; The salt-forming agent includes any one or more of triethylamine, ammonia water and sodium hydroxide.

7. A method for preparing an antibacterial polyurethane surface layer resin for automobile leather, characterized in that: The following steps are involved: reacting a macromolecular polyol with the polyisocyanate; Adding the hydrophilic chain extender and the small molecule alcohol chain extender into the reaction; Then, the catalyst is added, and after the catalytic reaction, the temperature is lowered and the salt-forming agent is added for neutralization; After adding water, the amine chain extender is added, and distillation is performed under reduced pressure to obtain a waterborne polyurethane resin.

8. The method for preparing the antimicrobial polyurethane surface layer resin for automobile leather according to claim 7, characterized in that: The following steps are involved: Reacting the macromolecular polyol and the polyisocyanate at 85-95° C. for 2-3 hours; Then, the hydrophilic chain extender and the small molecule alcohol chain extender are added and reacted at 75-85° C. for 1.5-2.5 hours; Then add the catalyst, react at 65-75°C for 2-3h, cool to -5-5°C, add the salt-forming agent for neutralization; After adding water, the amine chain extender is added, and distillation is performed under reduced pressure to obtain a waterborne polyurethane resin.

9. The method for preparing the antibacterial polyurethane surface layer resin for automobile leather according to claim 8, characterized in that: The specific preparation steps are: Dehydrate the macromolecular polyol at 10-110°C for 1-2 hours, then cool to 65-75°C, add 15g of polyisocyanate, heat to 80-95°C and keep warm for 2-3 hours; Then add a hydrophilic chain extender and a small molecule alcohol chain extender and react at 75-85°C for 1.5-2.5h and then cool to 55-65°C; Then add a catalyst to adjust the viscosity, react at 65-75°C for 2-3h, then cool to -5-5°C, add a salt-forming agent for neutralization, and neutralize for 30-60min; Deionized water is added under high-speed shearing, dispersed for 1-5 minutes, and then an amine chain extender is slowly added, and vacuum distillation is performed to obtain a waterborne polyurethane resin emulsion.

10. The method for preparing the antimicrobial polyurethane surface layer resin for automobile leather according to claim 8 or 9, characterized in that: Acetone was added simultaneously with the catalyst.

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