One-component waterborne polyurethane adhesive and preparation method thereof

Abstract

The application discloses a single-component water-based polyurethane adhesive and a preparation method thereof. The single-component water-based polyurethane adhesive comprises the following components in parts by weight: 20-100 parts of a water-based polyurethane dispersion, 20-100 parts of a water-based VAE emulsion, 0.1-0.5 parts of a thickening agent, 0.1-0.5 parts of a wetting agent, and 0.01-0.05 parts of a defoaming agent. The single-component water-based polyurethane adhesive has the characteristics of excellent initial adhesion, low activation temperature, excellent heat resistance, aging resistance and wet heat resistance, and can be single-component brush coated, is very suitable for a manual coating process of an automobile interior steering wheel and other interior parts, and can greatly improve production efficiency and save cost.

Description

Technical Field

[0001] This invention belongs to the field of water-based adhesives technology, specifically relating to a single-component water-based polyurethane automotive interior adhesive and its preparation method. Background Technology

[0002] With increasingly stringent environmental protection requirements, the automotive industry is also raising its standards for controlling VOCs in vehicles. As a result, adhesives used in automotive interiors are gradually shifting from oil-based adhesives to water-based adhesives.

[0003] Currently, water-based adhesives used in automotive interiors are mainly two-component, requiring the adhesive and hardener to be mixed evenly in a specific ratio before use. They must be prepared and used immediately, and have a limited open time. Therefore, in practical use, they suffer from disadvantages such as inconvenient application, short open time, and easy waste. Given this situation, downstream OEMs and automotive interior component manufacturers have an increasingly urgent need for single-component water-based polyurethane adhesives.

[0004] Two-component waterborne polyurethane adhesives are characterized by good initial tack, facilitating the initial positioning and bonding of interior parts, and later forming a cross-linked interpenetrating network structure through the reaction of the curing agent, resulting in excellent long-term durability. Achieving a balance between initial tack and long-term durability is a challenge that needs to be overcome for one-component waterborne polyurethane adhesives.

[0005] CN201811058915.2 discloses the application of a one-component waterborne polyurethane adhesive in automotive interior bonding. This patent uses a combination of a waterborne polyurethane-acrylate copolymer emulsion and a self-crosslinking waterborne polyurethane dispersion to form a one-component waterborne polyurethane adhesive. It argues that the waterborne polyurethane-acrylate copolymer emulsion provides a lower activation temperature, while the self-crosslinking waterborne polyurethane dispersion has a higher activation temperature but offers better later-stage heat resistance and heat aging resistance. However, the introduction of the self-crosslinking structure increases the activation temperature of the polyurethane dispersion. This patent uses activation conditions of 70℃ for 2 minutes, which are still considered high activation temperatures and long activation times in practical applications. Especially in the manual wrapping process of steering wheels and other interior components in automotive interiors, the thermal activation time is only a few seconds or even less. Furthermore, the steering wheel requires complete manual wrapping, demanding higher initial tack, and the high curvature areas of the steering wheel have significant stress concentration, further increasing the requirements for later-stage durability.

[0006] CN201910951834.3 discloses a method to improve initial tack by adjusting the glass transition temperature of EVA emulsion. However, VAE emulsions with low Tg have poor later heat resistance and damp heat resistance, making it difficult to meet the requirements for single-component applications.

[0007] CN201410298003.8 discloses a low-temperature molding waterborne polyurethane adhesive, which uses a blend of polyurethane dispersion, EVA, and acrylic acid. However, the later strength and durability development requires the addition of crosslinking agents such as polycarbodiimide, aziridine, and hydrophilic polyisocyanate, so it cannot be used as a single component.

[0008] CN201510295964.8 discloses a method for improving the water resistance and aging resistance of coatings using organosilicon-modified vinyl acetate-ethylene copolymer. However, for applications in automotive interior adhesives, a lower activation temperature and appropriate bonding strength are required, which cannot be met by the solution of this invention.

[0009] CN201310060849.3 discloses a method for modifying polyvinyl acetate emulsion with organosilane monomers and acrylate monomers to improve the initial tack, water resistance, and cold resistance of cigarette packaging adhesives. However, compared with polyurethane systems, it has the problem of insufficient adhesive strength.

[0010] In summary, how to solve the problems encountered in the bonding of single-component waterborne polyurethane in automotive interiors, such as insufficient adhesion, excessively long thermal activation time, poor manual coating properties, and insufficient durability in the later stages, is a problem that urgently needs to be solved in this technical field. Summary of the Invention

[0011] The purpose of this invention is to provide a single-component waterborne polyurethane automotive interior adhesive, addressing the problems of existing waterborne polyurethane adhesives in automotive interior bonding.

[0012] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0013] A one-component waterborne polyurethane adhesive comprises the following components in parts by weight: 20-100 parts of waterborne polyurethane dispersion, 20-100 parts of waterborne VAE emulsion, 0.1-0.5 parts of thickener, 0.1-0.5 parts of wetting agent, and 0.01-0.05 parts of defoamer; preferably, 50-80 parts of waterborne polyurethane dispersion, 20-50 parts of waterborne VAE emulsion, 0.2-0.4 parts of thickener, 0.2-0.4 parts of wetting agent, and 0.02-0.04 parts of defoamer.

[0014] In one specific embodiment, the aqueous polyurethane dispersion is a silane-modified aqueous polyurethane dispersion, and the raw materials for preparing the aqueous polyurethane dispersion include: aliphatic diisocyanate, polyol, hydrophilic compound, chain extender and silane-modified monomer.

[0015] In one specific embodiment, the aliphatic diisocyanate is selected from one or more of hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate.

[0016] In one specific embodiment, the polyol is selected from one or more of polybutylene adipate diol, polyhexane adipate diol, and polypentylene adipate 1,6-hexanediol diol.

[0017] In one specific embodiment, the hydrophilic compound has hydrophilic groups including ionic or nonionic groups; the hydrophilic compound containing ionic groups is one or more of dimethylolpropionic acid, dimethylolbutyric acid, N-(2-aminoethyl)-2-aminoethanesulfonic acid, and N-(3-aminopropyl)-2-aminoethanesulfonic acid; the hydrophilic compound containing nonionic groups is a monofunctional polyoxyethylene ether containing ethylene oxide repeating units.

[0018] In one specific embodiment, the chain extender is one or more of ethylene glycol, 1,4-butanediol, ethylenediamine, hydroxyethyl ethylenediamine, and isophorone diamine.

[0019] In one specific embodiment, the silane-modified monomer is a siloxane monomer containing two NCO reactive groups, preferably one or more of N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyltriethoxysilane.

[0020] In one specific embodiment, the polyol comprises at least one amorphous polyester polyol and one crystalline polyester polyol, and the proportion of the amorphous polyester polyol is higher than the proportion of the crystalline polyester polyol. The mass ratio of the amorphous polyester polyol to the crystalline polyester polyol is preferably 1-2:1, more preferably 1.2-1.5:1.

[0021] As a preferred embodiment, the raw materials for preparing the waterborne polyurethane dispersion of the present invention include the following components: 5-20 parts of aliphatic diisocyanate, 70-90 parts of polyol, 1-5 parts of hydrophilic compound, 1-5 parts of chain extender, and 0.1-0.5 parts of silane-modified monomer.

[0022] As a preferred embodiment, the method for preparing the waterborne polyurethane dispersion of the present invention includes the following steps: adding a dehydrated polyol, isocyanate, nonionic hydrophilic compound, and an appropriate amount of acetone to a reaction vessel, reacting at 80-90°C to obtain an NCO-terminated prepolymer, diluting with an appropriate amount of acetone, then adding an ionic hydrophilic compound, a chain extender, and a silane-modified monomer to carry out a chain extension reaction at a reaction temperature of 40-50°C, then dispersing with water, removing the organic solvent acetone, and adding an appropriate amount of emulsifier such as Tween 20 or other commonly used emulsifiers in the art to obtain a waterborne polyurethane dispersion with a certain solid content.

[0023] In one specific embodiment, the aqueous VAE emulsion is a silane-modified aqueous VAE emulsion; the glass transition temperature of the silane-modified VAE emulsion is -20℃ to -5℃.

[0024] In one specific implementation, the raw materials for the silane-modified aqueous VAE emulsion include siloxane monomers, vinyl acetate monomers, and acrylic acid monomers.

[0025] In one specific embodiment, the siloxane monomer is a siloxane monomer containing a double bond, preferably one or more of 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, and vinyltrimethoxysilane.

[0026] In one specific implementation, the vinyl acetate monomer is vinyl acetate.

[0027] In one specific embodiment, the acrylate monomer is a monomer with a glass transition temperature below 0°C, such as one or more of isooctyl acrylate, butyl acrylate, and ethyl acrylate.

[0028] In one specific embodiment, the thickener is a polyurethane associative thickener, selected from one or more of Vesmody U604, Vesmody U601, and Vesmody U902 from Wanhua Chemical.

[0029] In one specific embodiment, the defoamer is an organosilicon defoamer, selected from one or more of BYK-020, BYK-022, and BYK-024 from BYK Chemicals.

[0030] In one specific embodiment, the wetting agent is a polyether-modified polysiloxane wetting agent, preferably one or more of TEGO-245 from DIGIC and BYK-349 from BYK Chemical.

[0031] In one specific embodiment, the preparation method of the single-component waterborne polyurethane adhesive includes the following steps: mixing and stirring the waterborne polyurethane dispersion and the waterborne VAE emulsion for 15-30 minutes according to the proportion; adding the defoamer and stirring for 15-30 minutes; adding the wetting agent and stirring for 15-30 minutes; adding the thickener and stirring for 30-40 minutes; and adjusting the viscosity to 2000-5000 cps according to the application requirements.

[0032] Compared with existing technologies, the advantages of the single-component waterborne polyurethane adhesive provided by this invention are as follows: the silane-modified waterborne polyurethane dispersion lowers the activation temperature of the silane-modified waterborne polyurethane dispersion by increasing the proportion of amorphous polyester; the introduction of a low-Tg silane-modified VAE emulsion further enhances the initial tack; simultaneously, the introduction of silane structures in the VAE allows the silane-modified waterborne polyurethane dispersion and the silane-modified VAE emulsion to undergo a cross-linking reaction to form a cross-linked interpenetrating network, further improving later-stage durability. The single-component waterborne polyurethane adhesive obtained by this invention has excellent initial tack, low activation temperature, and excellent later-stage durability, making it highly suitable for single-component manual overlay processes of steering wheels and other interior components in automotive interiors. Detailed Implementation

[0033] To provide a detailed understanding of the technical features and content of this invention, preferred embodiments will be described in more detail below. While preferred embodiments of the invention are described in the examples, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0034] Raw material source:

[0035] PBA2000: Poly(1,4-butanediol adipate) diol, with a number-average molecular weight of approximately 2000 and a functionality of 2, manufactured by Yantai Huada Chemical.

[0036] CMA-654: Poly(neopentyl adipate) hexanediol, with a number-average molecular weight of approximately 1500 and a functionality of 2, manufactured by Yantai Huada Chemical.

[0037] MPEG-1200: A monofunctional epoxy ether with a number-average molecular weight of approximately 1200 and a functionality of 1, produced by Lotte in South Korea.

[0038] IPDI: Isophorone diisocyanate, Wanhua Chemical;

[0039] HDI: 1,6-hexamethylene diisocyanate, Wanhua Chemical;

[0040] A95: Aqueous solution of sodium N-(2-aminoethyl)-2-aminoethanesulfonate, Evonik, Germany;

[0041] EDA-OH Hydroxyethyl ethylenediamine, BASF, Germany;

[0042] IPDA: Isophorone diamine, Wanhua Chemical;

[0043] VAE emulsion: 920, glass transition temperature -20°C, Wacker Chemie;

[0044] VAE emulsion: EN 1689, Glass transition temperature -5°C, Wacker Chemie;

[0045] VAE emulsion: EN 701K, glass transition temperature -10°C, Wacker Chemie;

[0046] VAE emulsion: DH102A, glass transition temperature 0℃, Dalian Chemical;

[0047] Vinyl acetate: Sinopharm Chemicals;

[0048] Isooctyl acrylate: Sinopharm Chemicals;

[0049] N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane: Nanjing Nengde New Materials;

[0050] N-(2-Aminoethyl)-3-aminopropylmethyldimethoxysilane: Nanjing Nengde New Materials;

[0051] 3-Methacryloxypropyltrimethoxysilane: Nanjing Nengde New Materials;

[0052] 3-Methacryloxypropylmethyldimethoxysilane: Nanjing Nengde New Materials;

[0053] Thickener: Vesmody U604, Wanhua Chemical;

[0054] Defoamer: BYK-024, BYK Chemicals;

[0055] Wetting agent: TEGO-245, DIG Chemical.

[0056] Preparation Example 1: Silane-modified waterborne polyurethane dispersion 1

[0057] 150g of dehydrated poly(neopentyl glycol adipate) hexanediol (CMA-654), 100g of dehydrated poly(1,4-butanediol adipate) (PBA2000), 30g of hexamethylene diisocyanate (HDI), 5g of isophorone diisocyanate (IPDI), 2g of dehydrated monofunctional polyvinyl oxide ether (MPEG1200), and 25g of acetone were added to a 1L four-necked round-bottom flask equipped with a nitrogen inlet and outlet. The reaction was carried out at 80-90℃ until the NCO content stopped decreasing. The prepolymer was then dissolved in 400g of acetone and cooled to 50℃. A 35g aqueous solution containing 4.63g A95, 3.26g IPDA, and 0.86g hydroxyethyl ethylenediamine, and a 5g acetone solution containing 0.5g N-(2-aminoethyl)-3-aminopropyltrimethoxysilane were added to the acetone solution containing the prepolymer, respectively, while stirring vigorously for 20 minutes. The polymer was then dispersed by adding 238g water. After removing the acetone by distillation, 4g of emulsifier Tween 20 was added to obtain silane-modified aqueous polyurethane dispersion 1 with a solid content of 50%.

[0058] Preparation Example 2: Silane-modified waterborne polyurethane dispersion 2

[0059] 120g of dehydrated neopentyl glycol adipate diol (CMA-654), 100g of dehydrated 1,4-butanediol adipate diol (PBA2000), 27g of hexamethylene diisocyanate (HDI), 3.5g of isophorone diisocyanate (IPDI), 2g of dehydrated monofunctional polyvinyl oxide ether (MPEG1200), and 25g of acetone were added to a 1L four-necked round-bottom flask equipped with a nitrogen inlet and outlet. The reaction was carried out at 80-90℃ until the NCO content stopped decreasing. The prepolymer was then dissolved in 400g of acetone and cooled to 50℃. A 35g aqueous solution containing 4.63g A95, 3.26g IPDA, and 0.86g hydroxyethyl ethylenediamine, and a 5g acetone solution containing 0.5g N-(2-aminoethyl)-3-aminopropyltrimethoxysilane were added to the acetone solution containing the prepolymer, respectively, while stirring vigorously for 20 minutes. The polymer was then dispersed by adding 238g water. After removing the acetone by distillation, 4g of emulsifier Tween 20 was added to obtain silane-modified aqueous polyurethane dispersion 2 with a solid content of 50%.

[0060] Preparation Example 3: Silane-modified waterborne polyurethane dispersion 3

[0061] 130g of dehydrated neopentyl glycol adipate diol (CMA-654), 100g of dehydrated 1,4-butanediol adipate diol (PBA2000), 28g of hexamethylene diisocyanate (HDI), 4g of isophorone diisocyanate (IPDI), 2g of dehydrated monofunctional polyvinyl oxide ether (MPEG1200), and 25g of acetone were added to a 1L four-necked round-bottom flask equipped with a nitrogen inlet and outlet. The reaction was carried out at 80-90℃ until the NCO content stopped decreasing. The prepolymer was then dissolved in 400g of acetone and cooled to 50℃. A 35g aqueous solution containing 4.63g A95, 3.26g IPDA, and 0.86g hydroxyethyl ethylenediamine, and a 5g acetone solution containing 0.5g N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane were added to the acetone solution containing the prepolymer, respectively, while stirring vigorously for 20 minutes. The polymer was then dispersed by adding 238g water. After removing the acetone by distillation, 4g of emulsifier Tween 20 was added to obtain silane-modified aqueous polyurethane dispersion 3 with a solid content of 50%.

[0062] Comparative Preparation Example 4: Silane-modified waterborne polyurethane dispersion 4 (the ratio of crystalline to amorphous polyester is not within the scope of this invention).

[0063] 50g of dehydrated neopentyl glycol adipate diol (CMA-654), 150g of dehydrated 1,4-butanediol adipate diol (PBA2000), 24g of hexamethylene diisocyanate (HDI), 2.7g of isophorone diisocyanate (IPDI), 2g of dehydrated monofunctional polyvinyl oxide ether (MPEG1200), and 25g of acetone were added to a 1L four-necked round-bottom flask equipped with a nitrogen inlet and outlet. The reaction was carried out at 80-90℃ until the NCO value reached 1.91%. The prepolymer was then dissolved in 400g of acetone and cooled to 50℃. A 35g aqueous solution containing 4.63g A95, 3.26g IPDA, and 0.86g hydroxyethyl ethylenediamine, and a 5g acetone solution containing 0.5g N-(2-aminoethyl)-3-aminopropyltrimethoxysilane were added to the acetone solution containing the prepolymer, respectively, while stirring vigorously for 20 minutes. The polymer was then dispersed by adding 238g water. After removing the acetone by distillation, 4g of emulsifier Tween 20 was added to obtain silane-modified aqueous polyurethane dispersion 4 with a solid content of 50%.

[0064] Comparative Preparation Example 5: Waterborne polyurethane dispersion without silane modification 5

[0065] 150g of dehydrated poly(neopentyl glycol adipate) hexanediol (CMA-654), 100g of dehydrated poly(1,4-butanediol adipate) (PBA2000), 30g of hexamethylene diisocyanate (HDI), 5g of isophorone diisocyanate (IPDI), 2g of dehydrated monofunctional polyethylene oxide ether (MPEG1200), and 25g of acetone were added to a 1L four-necked round-bottom flask equipped with a nitrogen inlet and outlet. The reaction was carried out at 80-90℃ until the NCO content stopped decreasing. The prepolymer was dissolved in 400g of acetone and cooled to 50℃. 35g of an aqueous solution containing 4.63g of A95, 3.26g of IPDA, and 0.86% hydroxyethyl ethylenediamine was added to the acetone solution containing the prepolymer, and the mixture was stirred vigorously for 20 minutes. Then, 238g of water was added to disperse the polymer. After separating the polymer by distillation, the acetone was removed. Adding 4g of emulsifier Tween 20 yielded 5 silane-modified waterborne polyurethane dispersions with a solid content of 50%.

[0066] Preparation Example 6: Silane-modified VAE emulsion 1

[0067] 500g of VAE emulsion with a glass transition temperature of -20℃ was placed in a flask and heated to 45℃. 50g of vinyl acetate monomer, 40g of isooctyl acrylate, and 0.45g of 3-methacryloyloxypropyltrimethoxysilane were added and stirred until homogeneous. Then, 0.1g of tert-butyl hydroperoxide and 0.1g of sodium dithionite were added to initiate polymerization. After reacting at 45℃ for 2 hours, silane-modified VAE emulsion 1 was obtained.

[0068] Preparation Example 7: Silane-modified VAE emulsion 2

[0069] 500g of VAE emulsion with a glass transition temperature of -5℃ was placed in a flask and heated to 45℃. 50g of vinyl acetate monomer, 20g of isooctyl acrylate, and 0.45g of 3-methacryloyloxypropyltrimethoxysilane were added and stirred until homogeneous. Then, 0.1g of tert-butyl hydroperoxide and 0.1g of sodium dithionite were added to initiate polymerization. After reacting at 45℃ for 2 hours, silane-modified VAE emulsion 2 was obtained.

[0070] Preparation Example 8: Silane-modified VAE emulsion 3

[0071] 500g of VAE emulsion with a glass transition temperature of -10℃ was placed in a flask and heated to 45℃. 50g of vinyl acetate monomer, 25g of isooctyl acrylate, and 0.45g of 3-methacryloyloxypropyltrimethoxysilane were added and stirred until homogeneous. Then, 0.1g of tert-butyl hydroperoxide and 0.1g of sodium dithionite were added to initiate polymerization. After reacting at 45℃ for 2 hours, silane-modified VAE emulsion 3 was obtained.

[0072] Comparative Preparation Example 9: Silane-Modified VAE Emulsion 4

[0073] 500g of VAE emulsion with a glass transition temperature of 0℃ was placed in a flask and heated to 45℃. 50g of vinyl acetate monomer, 14g of isooctyl acrylate, and 0.45g of 3-methacryloyloxypropyltrimethoxysilane were added and stirred until homogeneous. Then, 0.1g of tert-butyl hydroperoxide and 0.1g of sodium dithionite were added to initiate polymerization. After reacting at 45℃ for 2 hours, silane-modified VAE emulsion 3 was obtained.

[0074] Example 1

[0075] A one-component water-based automotive interior adhesive consists of the following components:

[0076]

[0077] Mix the silane-modified waterborne polyurethane dispersion 1 and the silane-modified VAE emulsion 1 according to the above ratio and stir for 20 minutes. Add the defoamer and stir for 15 minutes. Add the wetting agent and stir for 15 minutes. Add the thickener and stir for 30 minutes. Adjust the viscosity to about 3000 cps to obtain a one-component waterborne polyurethane adhesive.

[0078] Example 2

[0079] A one-component water-based automotive interior adhesive consists of the following components:

[0080]

[0081] Mix the silane-modified waterborne polyurethane dispersion 2 and the silane-modified VAE emulsion 3 according to the above ratio and stir for 20 minutes. Add the defoamer and stir for 15 minutes. Add the wetting agent and stir for 15 minutes. Add the thickener and stir for 30 minutes. Adjust the viscosity to about 3000 cps to obtain a one-component waterborne polyurethane adhesive.

[0082] Example 3

[0083] A one-component water-based automotive interior adhesive consists of the following components:

[0084]

[0085] According to the above proportions, the waterborne polyurethane dispersion 3 and the silane-modified VAE emulsion 2 are mixed and stirred for 20 minutes. The defoamer is added and stirred for 15 minutes. The wetting agent is added and stirred for 15 minutes. The thickener is added and stirred for 30 minutes. The viscosity is adjusted to about 3000 cps to obtain a one-component waterborne polyurethane adhesive.

[0086] Comparative Example 1 (Silane-free modified VAE emulsion)

[0087] A one-component water-based automotive interior adhesive consists of the following components:

[0088]

[0089] According to the above proportions, add defoamer to silane-modified waterborne polyurethane dispersion 1 and stir for 15 minutes, add wetting agent and stir for 15 minutes, add thickener and stir for 30 minutes, adjust the viscosity to about 3000 cps, and obtain a single-component waterborne polyurethane adhesive.

[0090] Comparative Example 2 (Silane-free modified waterborne polyurethane dispersion)

[0091] A one-component water-based automotive interior adhesive consists of the following components:

[0092]

[0093]

[0094] Add defoamer to silane-modified VAE emulsion 1 according to the above ratio and stir for 15 min, add wetting agent and stir for 15 min, add thickener and stir for 30 min, adjust the viscosity to about 3000 cps, and obtain a single-component water-based adhesive.

[0095] Comparative Example 3 (Silane-modified waterborne polyurethane + unsilane-modified VAE emulsion, Tg: -20℃)

[0096] A one-component water-based automotive interior adhesive consists of the following components:

[0097]

[0098] The silane-modified waterborne polyurethane dispersion 1 and the unmodified VAE emulsion were mixed and stirred for 20 minutes according to the above ratio. The defoamer was added and stirred for 15 minutes. The wetting agent was added and stirred for 15 minutes. The thickener was added and stirred for 30 minutes. The viscosity was adjusted to about 3000 cps to obtain a one-component waterborne polyurethane adhesive.

[0099] Comparative Example 4 (Unmodified waterborne polyurethane + silane VAE emulsion, Tg: -20℃)

[0100] A one-component water-based automotive interior adhesive consists of the following components:

[0101]

[0102] According to the above proportions, the unmodified waterborne polyurethane dispersion 5 and the silane-modified VAE emulsion 1 were mixed and stirred for 20 minutes. The defoamer was added and stirred for 15 minutes. The wetting agent was added and stirred for 15 minutes. The thickener was added and stirred for 30 minutes. The viscosity was adjusted to about 3000 cps to obtain a one-component waterborne polyurethane adhesive.

[0103] Comparative Example 5 (Amorphous / Crystalline ratio not within the specified range)

[0104] A one-component water-based automotive interior adhesive consists of the following components:

[0105]

[0106] According to the above proportions, the silane-modified waterborne polyurethane dispersion 4 and the silane-modified VAE emulsion 1 are mixed and stirred for 20 minutes. The defoamer is added and stirred for 15 minutes. The wetting agent is added and stirred for 15 minutes. The thickener is added and stirred for 30 minutes. The viscosity is adjusted to about 3000 cps to obtain a one-component waterborne polyurethane adhesive.

[0107] Comparative Example 6 (Silane-modified waterborne polyurethane dispersion + silane VAE emulsion, Tg: 0℃)

[0108] A one-component water-based automotive interior adhesive consists of the following components:

[0109]

[0110] According to the above proportions, the silane-modified waterborne polyurethane dispersion 1 and the silane-modified VAE emulsion 4 are mixed and stirred for 20 minutes. The defoamer is added and stirred for 15 minutes. The wetting agent is added and stirred for 15 minutes. The thickener is added and stirred for 30 minutes. The viscosity is adjusted to about 3000 cps to obtain a waterborne single-component waterborne polyurethane adhesive.

[0111] The single-component waterborne polyurethane adhesives prepared in the above examples and comparisons were subjected to the following tests:

[0112] 1) Sample preparation

[0113] Table 1. Composition of composite materials

[0114] Composite materials Substrate 1 Substrate 2 A ABS plastic PVC leather B PU self-skinning foam Genuine Leather

[0115] Cut the substrate from Table 1 into 10×10cm pieces, clean the surface with ethanol, and let it dry. Then, apply adhesive spray to both sides at a rate of 80-100g / m2. After spraying, let it dry. Set the upper mold temperature to 120℃ and the lower mold temperature to 60℃ on the hot press for 18 seconds. The actual adhesive layer temperature should be 45-55 degrees Celsius, and the pressure should be set to 0.1 MPa.

[0116] 2) Peel strength test

[0117] After the specimen prepared in step 1) was placed for 72 hours, the peel strength was tested using a universal tensile testing machine with the clamp moving speed set to 200 mm / min.

[0118] 3) Adhesion test (manual coating properties)

[0119] For the sample that was not hot-pressed in step 1), use a hot air gun at 200-250℃ to blow the adhesive layer for 5-10 seconds, then attach it to the sample, gently press it with your hand, leave it for 1 minute, and test the peel strength.

[0120] 4) Heat resistance test

[0121] After the specimen prepared in step 1) was placed for 72 hours, it was placed in an 80℃ oven with a 200g weight on it for 4 hours, and the distance of glue separation was recorded.

[0122] 5) Heat aging resistance test

[0123] After the specimen prepared in step 1) was placed for 72 hours, it was placed in an oven at 105℃ for 24 hours. The hot peel strength was then tested immediately after the specimen was removed.

[0124] 6) Moisture and heat resistance test

[0125] After the specimen prepared in step 1) was placed for 72 hours, it was then placed under a 200g pendant at 70℃ and 95% RH humidity for 4 hours. The distance of glue separation was recorded.

[0126] The test results are shown in Table 2.

[0127] Table 2. Performance test results of adhesives in the examples and comparative examples.

[0128]

[0129] As shown in Table 2, the data comparison reveals that Examples 1-3, which used a high-amorphous polyester silane-modified waterborne polyurethane dispersion combined with a silane-modified VAE emulsion with a Tg of -20℃ to -5℃, exhibited excellent initial viscosity and high-level durability in the later stages. In Comparative Example 1, compared to Example 1, the high-amorphous polyester silane-modified waterborne polyurethane dispersion alone resulted in insufficient initial viscosity and poor manual coating properties. In Comparative Example 2, compared to Example 1, the silane-modified VAE emulsion with a Tg of -20℃ alone showed good initial viscosity, but poor later-stage heat resistance, heat aging resistance, and damp heat resistance. In Comparative Example 3, compared to Example 1, the high-amorphous polyester silane-modified waterborne polyurethane dispersion combined with unmodified low-Tg VAE resulted in comparable initial viscosity, but significantly reduced later-stage heat resistance and damp heat resistance. Compared to Example 1, Comparative Example 4, using an unmodified high-amorphous polyester aqueous polyurethane dispersion and a silane-modified low-Tg VAE emulsion, showed comparable initial viscosity, but both exhibited a significant decrease in heat and damp heat resistance later on. Comparative Example 5, compared to Example 1, used a high-crystallinity polyester silane-modified aqueous polyurethane dispersion and a low-Tg silane-modified VAE emulsion. Initial viscosity decreased significantly, and insufficient activation led to decreased later-stage resistance. Comparative Example 6, compared to Example 1, used a high-amorphous polyester silane-modified aqueous polyurethane and a silane-modified VAE emulsion with a Tg above -5℃. The improvement in initial viscosity was limited, and insufficient activation again resulted in poor later-stage resistance. In summary, the single-component aqueous automotive interior adhesive provided by this invention features excellent initial viscosity, low activation temperature, excellent hand-applying performance, and excellent heat resistance, heat aging resistance, and damp heat resistance, making it highly suitable for the hand-applying process of automotive steering wheels and other interior components.

[0130] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A single-component waterborne polyurethane adhesive, comprising the following components by weight: waterborne polyurethane dispersion 20-100 parts, waterborne VAE emulsion 20-100 parts, thickening agent 0.1-0.5 parts, wetting agent 0.1-0.5 parts, defoaming agent 0.01-0.05 parts; The aqueous polyurethane dispersion is a silane-modified aqueous polyurethane dispersion, and the raw materials for preparation include: aliphatic diisocyanate, polyol, hydrophilic compound, chain extender and silane modified monomer; the polyol comprises at least one non-crystalline polyester polyol and one crystalline polyester polyol, and the proportion of the non-crystalline polyester polyol is higher than that of the crystalline polyester polyol; the silane modified monomer is a siloxane monomer containing two NCO reactive groups; the waterborne VAE emulsion is a silane modified waterborne VAE emulsion with a glass transition temperature of -20℃ to -5℃; the raw materials of the waterborne VAE emulsion include siloxane monomer containing double bond, vinyl acetate monomer and acrylate monomer; the acrylate monomer is a monomer with a glass transition temperature lower than 0℃.

2. The one-component waterborne polyurethane adhesive according to claim 1, characterized in that, the aliphatic diisocyanate is selected from one or more of hexamethylene diisocyanate, isophorone diisocyanate and dicyclohexylmethane diisocyanate; the hydrophilic group of the hydrophilic compound includes ionic group or non-ionic group, wherein the hydrophilic compound containing ionic group is one or more of dimethylol propionic acid, dimethylol butyric acid, N-(2-aminoethyl)-2-aminoethane sulfonic acid and N-(3-aminopropyl)-2-aminoethane sulfonic acid, and the hydrophilic compound containing non-ionic group is a monofunctional polyethylene oxide ether containing oxirane repeating unit; the chain extender is one or more of ethylene glycol, 1,4-butanediol, ethylenediamine and hydroxyethyl ethylenediamine. 3.The one-component waterborne polyurethane adhesive according to claim 1, characterized in that, comprising the following components by weight: waterborne polyurethane dispersion 50-80 parts, waterborne VAE emulsion 20-50 parts, thickening agent 0.2-0.4 parts, wetting agent 0.2-0.4 parts, defoaming agent 0.02-0.04 parts. 4.The one-component waterborne polyurethane adhesive of claim 1, wherein, the silane modified monomer is one or more of N-(2-aminoethyl)-3-aminopropyl methyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyl trimethoxysilane and N-(2-aminoethyl)-3-aminopropyl methyl triethoxysilane. 5.The one-component waterborne polyurethane adhesive of claim 1, wherein, the mass ratio of the non-crystalline polyester polyol to the crystalline polyester polyol is 1-2:

1. 6.The one-component waterborne polyurethane adhesive of claim 1, wherein, the mass ratio of the non-crystalline polyester polyol to the crystalline polyester polyol is 1.2-1.5:

1.

7. The one-component waterborne polyurethane adhesive according to claim 1, wherein the raw materials for preparing the waterborne polyurethane dispersion include the following components: aliphatic diisocyanate 5-20 parts, polyol 70-90 parts, hydrophilic compound 1-5 parts, chain extender 1-5 parts, silane modified monomer 0.1-0.5 parts. 8.The one-component waterborne polyurethane adhesive according to claim 2, characterized in that, The preparation method of the water-based polyurethane dispersion comprises the following steps: adding a dehydrated polyol, an isocyanate, a hydrophilic compound containing a non-ionic group, and an appropriate amount of acetone into a reaction container in proportion, and then performing a reaction at 80-90 DEG C to obtain an NCO-terminated prepolymer; adding an appropriate amount of acetone for dilution, and then adding a hydrophilic compound containing an ionic group, a chain extender, and a silane-modified monomer to perform a chain extension reaction at a reaction temperature of 40-50 DEG C; then adding water for dispersion, removing the organic solvent acetone, and adding an emulsifier to obtain the water-based polyurethane dispersion. 9.The one-component waterborne polyurethane adhesive of claim 1, wherein, The acrylate monomer is one or more of isooctyl acrylate, butyl acrylate, and ethyl acrylate.

10. A process for the preparation of the one-component waterborne polyurethane adhesive according to any one of claims 1 to 9, comprising the following steps: The water-based polyurethane dispersion and the water-based VAE emulsion are mixed and stirred in proportion for 15-30 min, a defoaming agent is added and stirred for 15-30 min, a wetting agent is added and stirred for 15-30 min, a thickening agent is added and stirred for 30-40 min, and the viscosity is adjusted to 2000-5000 cps according to application requirements.

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