Low-voc high-solid content waterborne polyurethane adhesive and preparation method and application thereof

Abstract

The application provides a low-VOC high-solid-content water-based polyurethane adhesive and a preparation method and application thereof, and belongs to the technical field of fine chemical industry.The application takes diisocyanate, sulfonate polyester polyol, polypropylene glycol, hydrophilic chain extender, non-hydrophilic chain extender and acrylic ester monomer as raw materials, uses the acrylic ester monomer and an organic solvent as a diluent, then is polymerized and dispersed into an acrylic ester modified water-based polyurethane dispersion, the speed of removing VOC is increased by using the method of inert gas bubbling in a vacuum rotary evaporator, finally, a leveling agent, a defoaming agent, a wetting agent and the like without volatile organic compounds are added, and the water-based polyurethane adhesive for automobiles is prepared.The water-based polyurethane adhesive prepared by the application can be used for bonding automobile interior and exterior plastic and metal parts, can reduce the content and smell intensity of VOC without reducing the bonding performance, and achieves the effect of environmental protection.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical technology, and in particular relates to a low-VOC, high-solids-content waterborne polyurethane adhesive, its preparation method, and its application. Background Technology

[0002] With the continuous innovation of automotive technology, adhesives, as an essential auxiliary material for automobile production, are subject to increasingly higher requirements for their bonding performance and environmental performance. As a result, adhesive research and development is becoming increasingly active, product upgrades and replacements are accelerating, and the application scope in automobiles is becoming wider and wider. The innovation and development of adhesives that meet the requirements of bonding performance and automobile production processes are also becoming more and more stringent.

[0003] Solvent-based adhesives are frequently used in automobile manufacturing due to their excellent bonding properties. However, their preparation and use involve the use of large amounts of volatile organic solvents, which harm the environment and human health. With societal progress and increased environmental awareness, the requirements for volatile organic compounds (VOCs) in automobiles are becoming increasingly stringent. Therefore, reducing the use of solvent-based adhesives in automobiles and accelerating the promotion and application of environmentally friendly adhesives such as solvent-free, low-VOC adhesives, water-based adhesives, and hot melt adhesives have become urgent issues.

[0004] Water-based adhesives, using water as a dispersion medium, have seen the fastest growth in recent years. They offer advantages such as environmental friendliness, low cost, non-flammability and non-explosiveness, safe production and use, and easily adjustable viscosity. Water-based polyurethane adhesives, as a category of water-based adhesives, possess excellent environmental performance. Compared to traditional organic solvent-based adhesives, they contain fewer harmful volatile organic compounds, thus reducing environmental pollution and aligning with the concept of green environmental protection. Furthermore, water-based polyurethane adhesives have strong adhesion and bonding properties, making them widely applicable to various materials such as paper, fabrics, rubber, plastics, and metals. Whether in home decoration, footwear manufacturing, woodworking, or automotive manufacturing, water-based polyurethane adhesives can meet the bonding needs of diverse fields. Additionally, unlike traditional adhesives, they do not require drying or heating; simply apply them to the materials to be bonded, then press the two materials together with slight pressure. Moreover, being water-based, they do not damage the materials themselves, protecting the integrity of the bonded materials. Finally, waterborne polyurethane adhesives also possess certain weather resistance properties. After appropriate curing time, they can exhibit water resistance, moisture resistance, and high-temperature resistance, making them effective for outdoor use or applications in extreme environments. Therefore, waterborne polyurethane adhesives are a green, environmentally friendly, and high-performance adhesive. Their wide applicability and excellent bonding properties make them the preferred choice for automotive bonding needs.

[0005] However, due to the high surface tension and polarity of water, water-based adhesives have poor wetting properties for non-polar or weakly polar plastic materials, resulting in poor bonding performance. Furthermore, commonly used water-based adhesives typically contain 40-50 g / L or higher VOCs, which harm the environment and human health. Therefore, there is a need to develop and synthesize more environmentally friendly, healthier water-based adhesives with lower VOC content. However, the synthesis of water-based adhesives with lower VOC content, higher solids content, and excellent bonding performance still faces challenges due to the complexity of the synthesis process, requiring multiple steps, equipment, investment, and numerous experiments.

[0006] Therefore, the development of ultra-low VOC, high solids content waterborne polyurethane adhesives for automobiles has significant application and innovative implications in preparation, production, and application. Summary of the Invention

[0007] To address the environmental issue of residual VOCs in waterborne polyurethane adhesives, further reduce the content of volatile organic compounds, and meet the special requirements for waterborne adhesives used in automobiles, this invention proposes a low-VOC, high-solids-content waterborne polyurethane adhesive, its preparation method, and its application.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] One of the technical solutions of the present invention:

[0010] A method for preparing an aqueous polyurethane dispersion includes the following steps:

[0011] Sulfonate polyester polyol, polypropylene glycol, diisocyanate, and catalyst were mixed and heated and stirred at 60℃-80℃ for 2-4 hours. Then, a hydrophilic chain extender was added, and the mixture was heated and stirred at 60℃-90℃ for 2-4 hours. The reaction temperature was then lowered to 50℃, and a non-hydrophilic chain extender was added. The mixture was heated and stirred at 60℃-80℃ for 2-4 hours. During the heating and stirring process, an organic solvent, acrylate monomer, and polymerization inhibitor were added. After the heating and stirring were completed, the reaction temperature was lowered to 50℃, and the acrylate monomer was added. The mixture was heated and stirred at 60℃-80℃ for 2-4 hours. Finally, a neutralizing agent was added to obtain the prepolymer.

[0012] After emulsifying and dispersing the prepolymer, an amine chain extender is added, and the mixture is stirred to obtain an intermediate product of an aqueous polyurethane dispersion.

[0013] A heating initiator is added dropwise to the intermediate product of the aqueous polyurethane dispersion, and the mixture is heated and stirred at a temperature of 60℃-80℃ for 2-5 hours. Then the temperature is increased to 80℃-90℃ and the mixture is heated and stirred for 2-4 hours to obtain an acrylate-modified aqueous polyurethane dispersion.

[0014] The acrylate-modified waterborne polyurethane dispersion was heated and stirred under vacuum to obtain the waterborne polyurethane dispersion.

[0015] Furthermore, the preparation method of the aqueous polyurethane dispersion specifically includes the following steps:

[0016] Sulfonate polyester polyol and polypropylene glycol are added to a reaction vessel and heated and stirred at 40°C for half an hour. After uniform mixing, diisocyanate and catalyst are added, and the mixture is heated and stirred at 60°C-80°C for 2-4 hours. After the content of unreacted -NCO groups is found to be within acceptable limits (the conversion rate of hydroxyl groups in sulfonate polyester polyol and polypropylene glycol is 90-100%), a hydrophilic chain extender containing carboxyl-COOH groups is added, and the mixture is heated and stirred at 60°C-90°C for 2-4 hours. During the reaction, organic solvents are added to adjust the viscosity of the prepolymer. After the content of unreacted -NCO groups is found to be within acceptable limits (the conversion rate of hydroxyl groups in the hydrophilic chain extender is 90-100%), a non-hydrophilic chain extender is added, and the mixture is heated and stirred at 60°C-80°C. Heat and stir for 2-4 hours. During the heating and stirring process, add organic solvent, acrylate monomer, and polymerization inhibitor to adjust the viscosity of the prepolymer. After the content of unreacted -NCO groups is found to be qualified (the conversion rate of hydroxyl groups in the non-hydrophilic chain extender is 90-100%), reduce the reaction temperature to 50°C, add acrylate monomer, and heat and stir at 60°C-80°C for 2-4 hours. During the reaction process, add organic solvent, acrylate monomer, and polymerization inhibitor to adjust the viscosity of the prepolymer. After the content of unreacted -NCO groups is found to be qualified (the conversion rate of hydroxyl groups in the acrylate monomer is 90-100%), reduce the reaction temperature to 40°C, add acrylate monomer and polymerization inhibitor, and stir for 30 minutes. Finally, add a neutralizing agent to neutralize and obtain the prepolymer.

[0017] The prepolymer was transferred to an emulsification reactor, and deionized water was added under stirring to emulsify and disperse for 0.5-1 hours. Then, an amine chain extender was added, and the mixture was dispersed at high speed for 0.5-1 hours to obtain an intermediate product of waterborne polyurethane dispersion.

[0018] The intermediate product of the aqueous polyurethane dispersion was heated and stirred at 70℃-80℃ for 1 hour. Then, a thermal initiator was added dropwise using a peristaltic pump for 2-5 hours. After that, the temperature was raised to 80℃-90℃ and heated and stirred for 2-4 hours to complete the polymerization of the acrylate monomer. After filtration, the acrylate-modified aqueous polyurethane dispersion was obtained.

[0019] The acrylate-modified waterborne polyurethane dispersion was placed in a vacuum rotary evaporator and heated and stirred under vacuum to obtain the waterborne polyurethane dispersion.

[0020] This invention uses a mixture of organic solvent and acrylate monomer for dilution, ensuring low viscosity of the prepolymer in the reactor, thereby reducing the need for organic solvent during the polymerization of acrylate monomer.

[0021] Furthermore, the organic solvent is acetone or butanone, preferably acetone;

[0022] The average molecular weight of the sulfonate polyester polyol is 1000-2000;

[0023] The average molecular weight of the polypropylene glycol is 1000-3000;

[0024] The diisocyanate includes 2,4-toluene diisocyanate and / or isoflurone diisocyanate, preferably 2,4-toluene diisocyanate;

[0025] The catalyst comprises one or more of dibutyltin dilaurate, dimethylethanolamine and triethanolamine, preferably dibutyltin dilaurate;

[0026] The thermal initiator includes one or more of benzoyl peroxide, azobisisobutyronitrile, or azobisisoheptanenitrile, preferably azobisisobutyronitrile;

[0027] The acrylate monomer is one or more of methyl methacrylate and hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, or hydroxypropyl acrylate. More specifically, the acrylate monomer comprises two components, one of which is methyl methacrylate, and the other component is one of hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, or hydroxypropyl acrylate. The molar ratio of methyl methacrylate to the other component in the acrylate monomer is (20-70):1. During the preparation process, each component of the acrylate monomer is added in batches as appropriate.

[0028] The hydrophilic chain extender includes dimethylolpropionic acid and / or dimethylolbutyric acid, preferably dimethylolpropionic acid;

[0029] The non-hydrophilic chain extender includes 1,4-butanediol and / or neopentyl glycol, preferably 1,4-butanediol;

[0030] The amine chain extender includes ethylenediamine and / or isophorone diamine, preferably ethylenediamine;

[0031] The neutralizing agent includes one or more of triethylamine, tripropylamine, tributylamine, sodium hydroxide, and ammonia water, preferably triethylamine;

[0032] The polymerization inhibitor includes one or more of p-hydroxyanisole, hydroquinone, and tert-butylcatechol, preferably p-hydroxyanisole.

[0033] Furthermore, the amount of the acrylate monomer used is 15%-35% of the total mass of the aqueous polyurethane dispersion;

[0034] The amount of the thermal initiator is 0.2%-1.2% of the mass of the acrylate monomer.

[0035] The amount of diisocyanate used is 10%-30% of the total mass of diisocyanate, hydrophilic chain extender, non-hydrophilic chain extender, sulfonate polyester polyol, polypropylene glycol and acrylate monomer.

[0036] The amount of the hydrophilic chain extender is 2.5%-4.5% of the total mass of diisocyanate, hydrophilic chain extender, non-hydrophilic chain extender, sulfonate polyester polyol, polypropylene glycol and acrylate monomers.

[0037] The total amount of the sulfonate polyester polyol and polypropylene glycol is 45%-70% of the total mass of diisocyanate, hydrophilic chain extender, non-hydrophilic chain extender, sulfonate polyester polyol, polypropylene glycol and acrylate monomer.

[0038] The sulfonate polyester polyol accounts for 20%-85% of the mass of polypropylene glycol;

[0039] The total amount of the organic solvent and acrylate monomer is 25%-60% of the total mass of diisocyanate, hydrophilic chain extender, non-hydrophilic chain extender, sulfonate polyester polyol, polypropylene glycol and acrylate monomer.

[0040] The catalyst is used in an amount of 0.1%-0.2% of the total mass of diisocyanate, hydrophilic chain extender, sulfonate polyester polyol, polypropylene glycol and acrylate monomer.

[0041] The amount of the polymerization inhibitor is 0.01%-0.2% of the mass of the acrylate monomer.

[0042] Furthermore, an inert gas is introduced into the acrylate-modified waterborne polyurethane dispersion to create a vacuum of 0.04 MPa-0.06 MPa, and the mixture is heated and stirred at 60°C for 2-6 hours.

[0043] Furthermore, the inert gas is nitrogen and / or air. Agitation using nitrogen or air bubbling increases the removal efficiency and proportion of organic solvents, unreacted acrylate monomers, and other volatile organic compounds from the aqueous polyurethane dispersion in a vacuum.

[0044] The second technical solution of the present invention:

[0045] An aqueous polyurethane dispersion prepared by the above method has a VOC content of less than 5 g / L and a solid content of 50%.

[0046] The third technical solution of the present invention:

[0047] The above-mentioned waterborne polyurethane dispersion is used in the preparation of waterborne polyurethane adhesives for automobiles.

[0048] The fourth technical solution of the present invention:

[0049] An automotive waterborne polyurethane adhesive, by weight, comprises the following components: 80-90 parts of the waterborne polyurethane dispersion, 0-10 parts of deionized water, 0.1-1 parts of defoamer, 0.1-1 parts of leveling agent, and 0.1-1 parts of wetting agent.

[0050] Furthermore, the preparation method of the waterborne polyurethane adhesive for automobiles includes the following steps: in the waterborne polyurethane dispersion, deionized water, leveling agent, defoamer and wetting agent are added respectively at a rotation speed of 500 r / min. After all are added, the mixture is stirred for 0.5 hours to obtain the waterborne polyurethane adhesive for automobiles.

[0051] This invention uses diisocyanate and sulfonate polyester polyol, polypropylene glycol, hydrophilic chain extender, non-hydrophilic chain extender, acrylate monomer, etc. as raw materials, and uses acrylate monomer and organic solvent as diluents. Then, it is polymerized and dispersed to form an acrylate-modified waterborne polyurethane dispersion. The removal rate of VOCs is increased by inert gas bubbling in a vacuum rotary evaporator. Finally, leveling agents, defoamers, wetting agents, etc. that do not contain volatile organic compounds are added to formulate a waterborne polyurethane adhesive for automobiles.

[0052] Compared with the prior art, the present invention has the following advantages and technical effects:

[0053] (1) The preparation method of the waterborne polyurethane dispersion of the present invention is simple to operate and easy to control. It does not require the addition of benzene solvents or other high-boiling-point non-volatile solvents as in traditional methods. It is safe and environmentally friendly. The prepared product has the advantages of suitable viscosity and ultra-low VOC volatility. It can be used to formulate waterborne polyurethane adhesives for automobiles.

[0054] (2) The present invention uses nitrogen, air or a mixture thereof as a bubbling agent to increase the mass transfer area of ​​VOC in vacuum and increase the volatilization rate of VOC. This allows waterborne polyurethane to remove a large amount of VOC and unreacted monomers in a short time. On the other hand, it also removes odorous organic compounds, achieving the effect of deodorization.

[0055] (3) The waterborne polyurethane adhesive of the present invention has a VOC content of less than 5 g / L, low odor intensity, no irritating odor, good bonding performance, and can be used for automotive bonding with environmental protection requirements and high quality.

[0056] (4) The waterborne polyurethane dispersion of the present invention is used to formulate adhesives for automobiles, resulting in a low water content in the adhesive layer after drying, a short drying time, good bonding strength and heat resistance, low odor, and a VOC content of less than 0.1% after drying and film formation, thus exhibiting excellent adhesive performance. Attached Figure Description

[0057] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0058] Figure 1 The infrared spectrum of the waterborne polyurethane adhesive for automobiles prepared in Example 1 of this invention. Detailed Implementation

[0059] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0060] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0061] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0062] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0063] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0064] All raw materials used in the embodiments of this invention were purchased commercially available. Specific purchase information is as follows:

[0065] 2,4-Toluene diisocyanate (TDI): Bayer MaterialScience (China) Co., Ltd., industrial grade;

[0066] Isoflurone diisocyanate (IPDI): Bayer MaterialScience (China) Co., Ltd., industrial grade;

[0067] Sulfonate polyester polyols: Beijing Baiyuan Chemical Co., Ltd., industrial grade;

[0068] Dimethylolpropionic acid: Perstor, Sweden, industrial grade;

[0069] Dimethylolbutyric acid (DMPO): Jiangxi Hongdu Chemical Development Technology Co., Ltd., industrial grade;

[0070] Polypropylene glycol 200 / 400 / 600 / 1000 / 2000: Sinopharm Chemical Reagent Co., Ltd., chemically pure;

[0071] Hydroxyethyl acrylate: Shanghai Maclean Biochemical Technology Co., Ltd., chemically pure;

[0072] Hydroxypropyl acrylate: Shanghai Maclean Biochemical Technology Co., Ltd., chemically pure;

[0073] Hydroxyethyl methacrylate: Shanghai Maclean Biochemical Technology Co., Ltd., chemically pure;

[0074] Hydroxypropyl methacrylate: Shanghai Maclean Biochemical Technology Co., Ltd., chemically pure;

[0075] Methyl methacrylate: Shanghai Maclean Biochemical Technology Co., Ltd., chemically pure;

[0076] p-Hydroxyanisole: Aladdin Reagent (Shanghai) Co., Ltd., analytical grade;

[0077] Dibutyltin dilaurate: Tianjin Damao Chemical Reagent Factory, analytical grade;

[0078] Ethylenediamine: Sinopharm Chemical Reagent Co., Ltd., chemically pure;

[0079] Isopropanol: Sinopharm Chemical Reagent Co., Ltd., analytical grade;

[0080] Acetone: Guangzhou Chemical Reagent Factory, analytical grade;

[0081] Butanone: Guangzhou Chemical Reagent Factory, analytical grade;

[0082] Sodium hydroxide: Guangzhou Chemical Reagent Factory, analytical grade;

[0083] Ammonia solution: Guangzhou Chemical Reagent Factory, analytical grade;

[0084] Defoamers: BYK-012, BYK-016, BYK-022 and BYK-093, BYK Additives (Shanghai) Co., Ltd., industrial grade;

[0085] Leveling agents: BYK-333, BYK-345, BYK-348 and BYK-348, BYK Additives (Shanghai) Co., Ltd., industrial grade;

[0086] Wetting agents: BYK-3410, BYK-3450 and BYK-3451, BYK Additives (Shanghai) Co., Ltd., industrial grade.

[0087] Unless otherwise specified, the term "parts" used in the embodiments of this invention refers to "parts by weight".

[0088] In this embodiment of the invention, room temperature refers to 25±2℃.

[0089] The technical solution of the present invention will be further illustrated by the following embodiments.

[0090] Example 1

[0091] Sulfonate polyester polyol (BY-3305), polypropylene glycol (PPG-2000) and hydrophilic chain extender (dimethylolpropionic acid) were placed in a vacuum drying oven and dehydrated at 100°C and 0.06 MPa for 2 hours, then cooled to room temperature for later use.

[0092] Accurately weigh the following raw materials: 128g polypropylene glycol, 54g sulfonate polyester polyol, 34.9g diisocyanate, 0.3g catalyst, 9g hydrophilic chain extender, 60g organic solvent (10g + 20g + 20g + 10g), 1.8g non-hydrophilic chain extender, 95.9g acrylate monomer (20g methyl methacrylate + 30g methyl methacrylate + 1.9g hydroxyethyl methacrylate + 44g methyl methacrylate), 0.1g polymerization inhibitor (0.03g + 0.03g + 0.04g), 6.3g neutralizer, 320g deionized water, 0.3g amine chain extender, and 1g thermal initiator.

[0093] 128g of polypropylene glycol (PPG-2000) and 54g of sulfonate polyester polyol (BY-3305) were added to a reactor and heated and stirred at 40°C for half an hour. After uniform mixing, 34.9g of diisocyanate (2,4-toluene diisocyanate) and 0.3g of catalyst (dibutyltin dilaurate) were added, and the mixture was heated and stirred at 70°C for 3 hours. After the content of unreacted -NCO groups was found to be within acceptable limits, the reaction proceeded (sulfonate polyester polyol, polypropylene glycol, sulfonate polyester polyol ... The hydroxyl groups of the glycol are converted to 90-100%. Add 9g of a hydrophilic chain extender (dimethylolpropionic acid) and 10g of an organic solvent (acetone, to adjust the viscosity of the prepolymer). Heat and stir at 75°C for 2 hours. After confirming the unreacted -NCO group content is within acceptable limits (the hydroxyl group conversion rate of the hydrophilic chain extender is 90-100%), add 1.8g of a non-hydrophilic chain extender (1,4-butanediol), 20g of an organic solvent (acetone), and 20g of acrylate. Monomer (methyl methacrylate) and 0.03g polymerization inhibitor (p-hydroxyanisole) were used to adjust the viscosity of the prepolymer. The mixture was heated and stirred at 80°C for 1 hour. After confirming the unreacted -NCO group content was within acceptable limits (the conversion rate of hydroxyl groups in the non-hydrophilic chain extender was 90-100%), the reaction temperature was lowered to 50°C. Then, 20g of organic solvent (acetone), acrylate monomer (30g methyl methacrylate + 1.9g hydroxyethyl methacrylate), and 0.03g polymerization inhibitor were added. The reaction was carried out at 70°C with stirring for 3 hours. After the content of unreacted -NCO groups was found to be within acceptable limits (the conversion rate of hydroxyl groups in the acrylate monomer was 90-100%), the reaction temperature was lowered to 40°C, 44g of acrylate monomer (methyl methacrylate) and 0.04g of polymerization inhibitor (p-hydroxyanisole) were added, and after stirring for 30 minutes, 6.3g of neutralizing agent (triethylamine) was added for neutralization. The degree of neutralization was 100%, and the prepolymer was obtained.

[0094] The prepolymer was transferred to an emulsification reactor, stirred for 5 minutes at 2000 rpm, then 320 g of deionized water was added and stirred for 0.5 hours at 2000 rpm. Then 0.3 g of amine chain extender (ethylenediamine) was added and dispersed at 1000 rpm for 0.5 hours to obtain an intermediate product of waterborne polyurethane dispersion.

[0095] The intermediate product of the aqueous polyurethane dispersion was added to a reactor and heated and stirred at 60°C for 1 hour. Then, 1 g of thermal initiator (azobisisobutyronitrile) and 10 g of acetone were added dropwise using a peristaltic pump. The reactor was stirred during the dropwise addition, and the dropwise addition time was 5 hours. The temperature in the reactor was maintained at 60°C during the dropwise addition. After the dropwise addition was completed, the temperature was raised to 90°C and heated and stirred for 2 hours to complete the polymerization of acrylate monomers. After filtration, the acrylate-modified aqueous polyurethane dispersion was obtained.

[0096] The acrylate-modified waterborne polyurethane dispersion was placed in a vacuum rotary evaporator with a vacuum of 0.06 MPa. Nitrogen and / or air were continuously introduced and the vacuum was maintained at 0.06 MPa. The mixture was heated and stirred at 60°C for 2 hours until the measured VOC content was lower than 5 g / L. The solid content was adjusted to 50% by adding deionized water according to the solid content, thus obtaining the waterborne polyurethane dispersion.

[0097] In an aqueous polyurethane dispersion, deionized water, leveling agent (BYK-333), defoamer (BYK-016), and wetting agent (BYK-3450) were added at a speed of 500 r / min. After all the ingredients were added, the mixture was stirred for another 0.5 hours to obtain an aqueous polyurethane adhesive for automobiles.

[0098] Example 2

[0099] Sulfonate polyester polyol (BY-3305B), polypropylene glycol (PPG-1000) and hydrophilic chain extender (dimethylolpropionic acid) were placed in a vacuum drying oven and dehydrated at 100°C and 0.06 MPa for 2 hours, then cooled to room temperature for later use.

[0100] Accurately weigh the following raw materials: 64g polypropylene glycol, 50g sulfonate polyester polyol, 33g diisocyanate, 0.2g catalyst, 9g hydrophilic chain extender, 10g + 20g + 20g + 10g organic solvent = 60g, 1.8g non-hydrophilic chain extender, 61.8g acrylate monomer (20g methyl methacrylate + 20g methyl methacrylate + 1.8g hydroxyethyl acrylate + 20g methyl methacrylate) = 61.8g, 0.02g + 0.02g + 0.02g = 0.06g polymerization inhibitor, 6.3g neutralizer, 220g deionized water, 0.3g amine chain extender, and 0.7g thermal initiator.

[0101] Add 64g of polypropylene glycol (PPG-1000) and 50g of sulfonate polyester polyol (BY-3305B) to a reactor. Heat and stir at 40°C for half an hour. After mixing evenly, add 33g of diisocyanate (2,4-toluene diisocyanate) and 0.2g of catalyst (dibutyltin dilaurate). Heat and stir at 60°C for 4 hours. After confirming that the content of unreacted -NCO groups is within acceptable limits, (sulfonate polyester polyol, polypropylene glycol...) The conversion rate of the hydroxyl groups of the alcohol is 90-100%. Add 9g of a hydrophilic chain extender (dimethylolpropionic acid) and 10g of an organic solvent (acetone, to adjust the viscosity of the prepolymer). Heat and stir at 75°C for 4 hours. After confirming that the content of unreacted -NCO groups is within acceptable limits (the conversion rate of the hydroxyl groups of the hydrophilic chain extender is 90-100%), add 1.8g of a non-hydrophilic chain extender (1,4-butanediol), 20g of an organic solvent (acetone), and acrylate monomer (methyl methacrylate). The prepolymer viscosity was adjusted by adding 20g of methyl methacrylate and 0.02g of polymerization inhibitor (p-hydroxyanisole). The mixture was heated and stirred at 80°C for 4 hours. After confirming the unreacted -NCO group content was within acceptable limits (the conversion rate of hydroxyl groups in the non-hydrophilic chain extender was 90-100%), the reaction temperature was lowered to 50°C. Then, 20g of organic solvent (acetone), acrylate monomer (20g methyl methacrylate + 1.8g hydroxyethyl acrylate), and 0.02g of polymerization inhibitor (p-hydroxyanisole) were added. p-Hydroxyanisole was heated and stirred at 70°C for 4 hours. After the content of unreacted -NCO groups was found to be within acceptable limits (the conversion rate of hydroxyl groups in the acrylate monomer was 90-100%), the reaction temperature was lowered to 40°C, 20g of acrylate monomer (methyl methacrylate) and 0.02g of polymerization inhibitor (p-hydroxyanisole) were added, and after stirring for 30 minutes, 6.3g of neutralizing agent (triethylamine) was added for neutralization. The degree of neutralization was 100%, and the prepolymer was obtained.

[0102] The prepolymer was transferred to an emulsification reactor, stirred for 5 minutes at 2000 rpm, then 220 g of deionized water was added and stirred for 0.5 hours at 2000 rpm. Then 0.3 g of amine chain extender (ethylenediamine) was added and dispersed at 1000 rpm for 0.5 hours to obtain an intermediate product of waterborne polyurethane dispersion.

[0103] The intermediate product of the aqueous polyurethane dispersion was added to a reactor and heated and stirred at 70°C for 1 hour. Then, 0.7 g of thermal initiator (azobisisobutyronitrile) and 10 g of acetone were added dropwise using a peristaltic pump. The reactor was stirred during the dropwise addition, and the dropwise addition time was 3 hours. The temperature in the reactor was maintained at 70°C during the dropwise addition. After the dropwise addition was completed, the temperature was raised to 80°C and heated and stirred for 4 hours to complete the polymerization of acrylate monomers. After filtration, the acrylate-modified aqueous polyurethane dispersion was obtained.

[0104] The acrylate-modified waterborne polyurethane dispersion was placed in a vacuum rotary evaporator with a vacuum of 0.04 MPa. Nitrogen and / or air were continuously introduced and the vacuum was maintained at 0.04 MPa. The mixture was heated and stirred at 60°C for 6 hours until the measured VOC content was lower than 5 g / L. The solid content was adjusted to 50% by adding deionized water according to the solid content, thus obtaining the waterborne polyurethane dispersion.

[0105] In an aqueous polyurethane dispersion, deionized water, leveling agent (BYK-345), defoamer (BYK-012), and wetting agent (BYK-3410) were added at a speed of 500 r / min. After all the ingredients were added, the mixture was stirred for another 0.5 hours to obtain an aqueous polyurethane adhesive for automobiles.

[0106] Example 3

[0107] Sulfonate polyester polyol (BY-3303), polypropylene glycol (PPG-3000) and hydrophilic chain extender (dimethylolpropionic acid) were placed in a vacuum drying oven and dehydrated at 100°C and 0.06 MPa for 2 hours, then cooled to room temperature for later use.

[0108] Accurately weigh the following raw materials: 120g polypropylene glycol, 50g sulfonate polyester polyol, 33.5g diisocyanate, 0.2g catalyst, 9g hydrophilic chain extender, 60g organic solvent (10g + 20g + 20g + 10g), 1.8g non-hydrophilic chain extender, 42.5g acrylate monomer (10g methyl methacrylate + 20g methyl methacrylate + 2.5g hydroxypropyl methacrylate + 10g methyl methacrylate), 0.01g + 0.02g + 0.01g = 0.04g polymerization inhibitor, 6.3g neutralizer, 260g deionized water, 0.3g amine chain extender, and 0.5g thermal initiator.

[0109] 120g of polypropylene glycol (PPG-3000) and 50g of sulfonate polyester polyol (BY-3303) were added to a reactor and heated and stirred at 40°C for half an hour. After uniform mixing, 33.5g of diisocyanate (2,4-toluene diisocyanate) and 0.2g of catalyst (dibutyltin dilaurate) were added, and the mixture was heated and stirred at 80°C for 3 hours. After the content of unreacted -NCO groups was found to be within acceptable limits, the reaction proceeded (sulfonate polyester polyol, polypropylene glycol, sulfonate polyester polyol ... The hydroxyl conversion rate of the glycol is 90-100%. Add 9g of hydrophilic chain extender (dimethylolpropionic acid) and 10g of organic solvent (acetone, to adjust the prepolymer viscosity). Heat and stir at 90℃ for 3 hours. After confirming the unreacted -NCO group content is within acceptable limits (the hydroxyl conversion rate of the hydrophilic chain extender is 90-100%), add 1.8g of non-hydrophilic chain extender (1,4-butanediol), 20g of organic solvent (acetone), and 10g of acrylate monoacrylate. The prepolymer viscosity was adjusted by adding methyl methacrylate (Mmethacrylate) and 0.01g of polymerization inhibitor (p-hydroxyanisole). The mixture was heated and stirred at 80°C for 3 hours. After confirming the unreacted -NCO group content was within acceptable limits (the conversion rate of hydroxyl groups in the non-hydrophilic chain extender was 90-100%), the reaction temperature was lowered to 50°C. Then, 20g of organic solvent (acetone), acrylate monomer (20g Mmethacrylate + 2.5g hydroxypropyl methacrylate), and 0.02g of polymerization inhibitor were added. (p-hydroxyanisole) was heated and stirred at 80°C for 3 hours. After the content of unreacted -NCO groups was found to be qualified (the conversion rate of hydroxyl groups in the acrylate monomer was 90-100%), the reaction temperature was reduced to 40°C, 10g of acrylate monomer (methyl methacrylate) and 0.01g of polymerization inhibitor (p-hydroxyanisole) were added, and after stirring for 30 minutes, 6.3g of neutralizing agent (triethylamine) was added for neutralization. The degree of neutralization was 100%, and the prepolymer was obtained.

[0110] The prepolymer was transferred to an emulsification reactor, stirred for 5 minutes at 2000 rpm, then 260 g of deionized water was added and stirred for 0.5 hours at 2000 rpm. Then 0.3 g of amine chain extender (ethylenediamine) was added and dispersed at 1000 rpm for 0.5 hours to obtain an intermediate product of waterborne polyurethane dispersion.

[0111] The intermediate product of the aqueous polyurethane dispersion was added to a reactor and heated and stirred at 80°C for 1 hour. Then, 0.5 g of thermal initiator (azobisisobutyronitrile) and 10 g of acetone were added dropwise using a peristaltic pump. The reactor was stirred during the dropwise addition, and the dropwise addition time was 2 hours. The temperature in the reactor was maintained at 80°C during the dropwise addition. After the dropwise addition was completed, the temperature was raised to 90°C and heated and stirred for 2 hours to complete the polymerization of acrylate monomers. After filtration, the acrylate-modified aqueous polyurethane dispersion was obtained.

[0112] The acrylate-modified waterborne polyurethane dispersion was placed in a vacuum rotary evaporator with a vacuum of 0.05 MPa. Nitrogen and / or air were continuously introduced and the vacuum was maintained at 0.05 MPa. The mixture was heated and stirred at 60°C for 5 hours until the measured VOC content was lower than 5 g / L. The solid content was adjusted to 50% by adding deionized water according to the solid content, thus obtaining the waterborne polyurethane dispersion.

[0113] In an aqueous polyurethane dispersion, deionized water, leveling agent (BYK-348), defoamer (BYK-022), and wetting agent (BYK-3451) were added at a speed of 500 r / min. After all the ingredients were added, the mixture was stirred for another 0.5 hours to obtain an aqueous polyurethane adhesive for automobiles.

[0114] Example 4

[0115] Sulfonate polyester polyol (BY-3305), polypropylene glycol (PPG-2000) and hydrophilic chain extender (dimethylolpropionic acid) were placed in a vacuum drying oven and dehydrated at 100°C and 0.06 MPa for 2 hours, then cooled to room temperature for later use.

[0116] Accurately weigh the following raw materials: 146g polypropylene glycol, 40g sulfonate polyester polyol, 35g diisocyanate, 0.2g catalyst, 9g hydrophilic chain extender, 60g organic solvent (10g + 20g + 20g + 10g), 1.8g non-hydrophilic chain extender, 91.8g acrylate monomer (30g methyl methacrylate + 30g methyl methacrylate + 1.8g hydroxypropyl acrylate + 30g methyl methacrylate) = 91.8g, 0.03g + 0.03g + 0.03g = 0.09g polymerization inhibitor, 6.3g neutralizer, 326g deionized water, 0.3g amine chain extender, and 1g thermal initiator.

[0117] 146g of polypropylene glycol (PPG-2000) and 40g of sulfonate polyester polyol (BY-3305) were added to a reactor and heated and stirred at 40°C for half an hour. After the mixture was homogeneous, 35g of diisocyanate (2,4-toluene diisocyanate) and 0.2g of catalyst (dibutyltin dilaurate) were added. The mixture was then heated and stirred at 60°C for 4 hours. After the content of unreacted -NCO groups was found to be within acceptable limits, the reaction proceeded (sulfonate polyester polyol, polypropylene glycol...). The conversion rate of the hydroxyl groups of the alcohol is 90-100%. Add 9g of a hydrophilic chain extender (dimethylolpropionic acid) and 10g of an organic solvent (acetone, to adjust the viscosity of the prepolymer). Heat and stir at 90°C for 3 hours. After confirming that the content of unreacted -NCO groups is within acceptable limits (the conversion rate of the hydroxyl groups of the hydrophilic chain extender is 90-100%), add 1.8g of a non-hydrophilic chain extender (1,4-butanediol), 20g of an organic solvent (acetone), and 30g of acrylate monoacrylate. The prepolymer viscosity was adjusted by adding methyl methacrylate (Methyl methacrylate) and 0.03g of polymerization inhibitor (p-hydroxyanisole). The mixture was heated and stirred at 60°C for 4 hours. After confirming the unreacted -NCO group content was within acceptable limits (the conversion rate of hydroxyl groups in the non-hydrophilic chain extender was 90-100%), the reaction temperature was lowered to 50°C. Then, 20g of organic solvent (acetone), acrylate monomer (30g methyl methacrylate + 1.8g hydroxypropyl acrylate), and 0.03g of polymerization inhibitor (p-hydroxyanisole) were added. p-Hydroxyanisole was heated and stirred at 60°C for 2 hours. After the content of unreacted -NCO groups was found to be within acceptable limits (the conversion rate of hydroxyl groups in the acrylate monomer was 90-100%), the reaction temperature was lowered to 40°C, 30g of acrylate monomer (methyl methacrylate) and 0.03g of polymerization inhibitor (p-hydroxyanisole) were added, and after stirring for 30 minutes, 6.3g of neutralizing agent (triethylamine) was added for neutralization. The degree of neutralization was 100%, and the prepolymer was obtained.

[0118] The prepolymer was transferred to an emulsification reactor, stirred at 2000 r / min for 5 min, 326 g of deionized water was added, and stirred at 2000 r / min for 0.5 h. Then 0.3 g of amine chain extender (ethylenediamine) was added, and dispersed at 1000 r / min for 0.5 h to obtain an intermediate product of waterborne polyurethane dispersion.

[0119] The intermediate product of the aqueous polyurethane dispersion was added to a reactor and heated and stirred at 75°C for 1 hour. Then, 1 g of thermal initiator (azobisisobutyronitrile) and 10 g of acetone were added dropwise using a peristaltic pump. The reactor was stirred during the dropwise addition, and the dropwise addition time was 3 hours. The temperature in the reactor was maintained at 75°C during the dropwise addition. After the dropwise addition was completed, the temperature was raised to 90°C and heated and stirred for 3 hours to complete the polymerization of acrylate monomers. After filtration, the acrylate-modified aqueous polyurethane dispersion was obtained.

[0120] The acrylate-modified waterborne polyurethane dispersion was placed in a vacuum rotary evaporator with a vacuum of 0.04 MPa. Nitrogen and / or air were continuously introduced and the vacuum was maintained at 0.04 MPa. The mixture was heated and stirred at 60°C for 5 hours until the measured VOC content was lower than 5 g / L. The solid content was adjusted to 50% by adding deionized water according to the solid content, thus obtaining the waterborne polyurethane dispersion.

[0121] In an aqueous polyurethane dispersion, deionized water, leveling agent (BYK-349), defoamer (BYK-093), and wetting agent (BYK-3410) were added at a speed of 500 r / min. After all the ingredients were added, the mixture was stirred for another 0.5 hours to obtain an aqueous polyurethane adhesive for automobiles.

[0122] Comparative Example 1

[0123] The commercially available 2849XP 50% waterborne polyurethane dispersion was placed in a vacuum rotary evaporator, and the vacuum degree was increased to 0.05 MPa. Nitrogen and / or air were continuously introduced into the dispersion while maintaining the vacuum degree at 0.05 MPa. The dispersion was heated and stirred at 60°C for 6 hours. The solid content was adjusted to 50% by adding deionized water according to the solid content, thus obtaining the waterborne polyurethane dispersion.

[0124] In the aqueous polyurethane dispersion prepared in Comparative Example 1, deionized water, leveling agent (BYK-333), defoamer (BYK-016), and wetting agent (BYK-3450) were added at a speed of 500 r / min. After all the additions were completed, the mixture was stirred for another 0.5 hours to obtain the aqueous polyurethane adhesive.

[0125] Performance testing

[0126] The infrared spectrum of the waterborne polyurethane adhesive for automobiles prepared in Example 1 of this invention is shown below. Figure 1 ,Depend on Figure 1 As can be seen from the infrared spectrum, the synthesized product is a typical polyurethane / acrylate composite polymer.

[0127] The aqueous polyurethane adhesives prepared in Examples 1-4 and Comparative Example 1 were tested:

[0128] The VOC content in water-based adhesives was determined by gas chromatography according to the national standard GB 33372-2020.

[0129] The content of nonvolatile matter (solid content) shall be determined in accordance with the national standard GB / T 2793-1995.

[0130] The odor level of waterborne polyurethane adhesives was determined according to the odor level method in T / CAS 598—2022 "Standard for Odor Pollutant Control in Passenger Cars" issued by the China Association for Standardization.

[0131] The average particle size and zeta potential of the waterborne polyurethane adhesive were determined using a Mastersizer 3000 laser particle size analyzer. The particle size of the blue dispersion diluted at 1:1000 was tested at a temperature of 25℃.

[0132] Tensile strength and elongation at break were tested according to the national standard GB / T 528-2009. The film was molded and dried in a polytetrafluoroethylene mold. The prepared film was cut into dumbbell-shaped test pieces with a length of 25 mm and a width of 6 mm. The test was conducted using an intelligent electronic tensile testing machine. Three tests were performed and the average value was taken. The tensile speed was 50 mm / min.

[0133] Prepare samples on steel plates, dry them, press them together, and test the initial tack strength and T-peel strength according to the national standard GB / T 2790-1995 Adhesives T-peel strength test method;

[0134] The shelf life of waterborne polyurethane adhesives shall be determined in accordance with the national standard GB / T 7123.2-2002.

[0135] The surface water contact angle of the composite film was tested using an OCA20 contact angle meter at a temperature of 25°C.

[0136] A coating was applied to a glass slide, and the water resistance of the coating was tested by immersion in water according to the national standard GB / T 1733-1993.

[0137] Water absorption rate: A film is formed inside a polytetrafluoroethylene mold. The film is cut into 2.5cm*2.5cm pieces, weighed, and the mass is recorded as m0. Then, it is soaked in deionized water for 24 hours. The film is then removed, the surface moisture is wiped off with filter paper, and weighed again, and the mass is recorded as m1. The water absorption rate W (%) is then calculated as follows:

[0138]

[0139] The performance test results are shown in Table 1.

[0140] Table 1. Performance test results of the waterborne polyurethane adhesives prepared in Examples 1-4 and Comparative Example 1

[0141] Solid content (%) 50.4 50.8 50.6 50.3 50.2 VOC content (g / L) 1.7 1.9 1.8 1.7 32.5 Odor rating 1 1 1 1 4 Zeta potential (mV) -47 -46 -47 -48 -43 Average particle size (nm) 205 210 200 207 283 Storage stability (months) ＞6 ＞6 ＞6 ＞6 ＞6 Tensile strength (MPa) 3.6 3.2 3.4 3.5 1.2 Elongation at break (%) 2432 2348 2299 2247 1247 Initial tack strength (N / mm) 1.8 1.7 1.9 1.6 0.5 T-peel strength (N / mm) 3.1 3.0 2.9 3.2 1.0 Water resistance (24h) Almost no change Almost no change Almost no change Almost no change Slight whitening Water contact angle (°) 70.5 71.2 70.9 70.3 71.4 Water absorption rate (%) 15.7 15.3 13.6 15.8 22.2

[0142] As can be seen from Table 1, compared with Comparative Example 1 and Example 1, the waterborne polyurethane adhesive prepared in Example 1 of the present invention has a significantly reduced VOC content of more than 94%, a significantly reduced odor level to level 1 with almost no odor, a significantly increased tensile strength of about 3 times, an increased elongation at break of about 2 times, an increased initial tack strength of more than 3 times, an increased T-peel strength of about 3 times, and a reduced water absorption rate of more than 30%.

[0143] The solid content of the waterborne polyurethane adhesives of the present invention all exceed 50%, the zeta potential meets the requirements for storage stability, the average particle size measured by Malvern particle size analyzer is about 200 nanometers, they can be stored for more than 6 months and still maintain good bonding performance, have good water resistance, and the water contact angle meets the hydrophilic characteristics of waterborne polyurethane.

[0144] Therefore, after testing the waterborne polyurethane adhesive prepared by this invention, it was found that it can be used for bonding plastics and metals in automotive parts. It has the characteristics of being environmentally friendly, low VOC, pollution-free, having high bonding strength, high peel strength, and high tensile strength, and its performance is significantly improved compared with commercially available waterborne polyurethane adhesives.

[0145] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing an aqueous polyurethane dispersion, characterized in that, Includes the following steps: Sulfonate polyester polyol, polypropylene glycol, diisocyanate, and catalyst are mixed and heated and stirred at 60℃-80℃ for 2-4 hours. Then, a hydrophilic chain extender is added and the mixture is heated and stirred at 60℃-90℃ for 2-4 hours. The reaction temperature is then lowered to 50℃, a non-hydrophilic chain extender is added, and the mixture is heated and stirred at 60℃-80℃ for 2-4 hours. During the heating and stirring process, an organic solvent, acrylate monomer, and polymerization inhibitor are added. The reaction temperature is then lowered to 50℃, acrylate monomer is added, and the mixture is heated and stirred at 60℃-80℃ for 2-4 hours. Finally, a neutralizing agent is added to obtain the prepolymer. After emulsifying and dispersing the prepolymer, an amine chain extender is added, and the mixture is stirred to obtain an intermediate product of an aqueous polyurethane dispersion. A heating initiator is added dropwise to the intermediate product of the aqueous polyurethane dispersion, and the mixture is heated and stirred at a temperature of 60℃-80℃ for 2-5 hours. Then the temperature is increased to 80℃-90℃ and the mixture is heated and stirred for 2-4 hours to obtain an acrylate-modified aqueous polyurethane dispersion. The acrylate-modified waterborne polyurethane dispersion was vacuum heated and stirred to obtain the waterborne polyurethane dispersion. The mass ratio of the sulfonate polyester polyol to polypropylene glycol is 20%-85%. The non-hydrophilic chain extender includes 1,4-butanediol and / or neopentyl glycol; The polymerization inhibitor includes one or more of p-hydroxyanisole, hydroquinone, and tert-butylcatechol; The acrylate monomer is one or more of methyl methacrylate and hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate or hydroxypropyl acrylate. An inert gas is introduced into the acrylate-modified waterborne polyurethane dispersion to create a vacuum of 0.04 MPa to 0.06 MPa, and the mixture is heated and stirred at 60°C for 2 to 6 hours.

2. The method for preparing the aqueous polyurethane dispersion according to claim 1, characterized in that, The average molecular weight of the sulfonate polyester polyol is 1000-2000; the average molecular weight of the polypropylene glycol is 1000-3000. The diisocyanate includes 2,4-toluene diisocyanate and / or isoflurone diisocyanate; The catalyst includes one or more of dibutyltin dilaurate, dimethylethanolamine, and triethanolamine; The thermal initiator includes one or more of benzoyl peroxide, azobisisobutyronitrile, or azobisisoheptanenitrile.

3. The method for preparing the aqueous polyurethane dispersion according to claim 1, characterized in that, The hydrophilic chain extender includes dimethylolpropionic acid and / or dimethylolbutyric acid; The amine chain extender includes ethylenediamine and / or isophorone diamine; The neutralizing agent includes one or more of triethylamine, tripropylamine, tributylamine, sodium hydroxide, and ammonia.

4. The method for preparing the aqueous polyurethane dispersion according to claim 1, characterized in that, The amount of the acrylate monomer used is 15%-35% of the total mass of diisocyanate, hydrophilic chain extender, non-hydrophilic chain extender, sulfonate polyester polyol, polypropylene glycol and acrylate monomer. The amount of the thermal initiator is 0.2%-1.2% of the mass of the acrylate monomer.

5. The method for preparing the aqueous polyurethane dispersion according to claim 1, characterized in that, The amount of diisocyanate used is 10%-30% of the total mass of diisocyanate, hydrophilic chain extender, non-hydrophilic chain extender, sulfonate polyester polyol, polypropylene glycol and acrylate monomer. The amount of the hydrophilic chain extender is 2.5%-4.5% of the total mass of diisocyanate, hydrophilic chain extender, non-hydrophilic chain extender, sulfonate polyester polyol, polypropylene glycol and acrylate monomers. The sum of the amounts of the sulfonate polyester polyol and polypropylene glycol is 45%-70% of the total mass of diisocyanate, hydrophilic chain extender, non-hydrophilic chain extender, sulfonate polyester polyol, polypropylene glycol and acrylate monomer.

6. The method for preparing the aqueous polyurethane dispersion according to claim 1, characterized in that, The total amount of the organic solvent and acrylate monomer is 25%-60% of the total mass of diisocyanate, hydrophilic chain extender, non-hydrophilic chain extender, sulfonate polyester polyol, polypropylene glycol and acrylate monomer. The catalyst is used in an amount of 0.1%-0.2% of the total mass of diisocyanate, hydrophilic chain extender, sulfonate polyester polyol, polypropylene glycol and acrylate monomer. The amount of the polymerization inhibitor is 0.01%-0.2% of the mass of the acrylate monomer.

7. An aqueous polyurethane dispersion prepared by the preparation method according to any one of claims 1-6.

8. The use of the waterborne polyurethane dispersion according to claim 7 in the preparation of waterborne polyurethane adhesives for automobiles.

9. A water-based polyurethane adhesive for automobiles, characterized in that, The product comprises, by weight, the following components: 80-90 parts of the aqueous polyurethane dispersion of claim 7, 0-10 parts of deionized water, 0.1-1 parts of defoamer, 0.1-1 parts of leveling agent, and 0.1-1 parts of wetting agent.

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