A waterborne sprayable self-drying acrylate adhesive and a preparation method thereof

Abstract

The present application relates to a kind of water-based sprayable self-drying type acrylate adhesive and its preparation method, belong to polymer adhesive technical field.First, the core layer emulsion formed by hard monomer and multi-functional crosslinking monomer is prepared;Then drop the shell monomer including soft monomer, hydrophilic functional monomer and the functional monomer containing beta-dicarbonyl structure on it, form core-shell structure emulsion;Finally, by pH adjustment, add rheological modifier, film-forming aid and the coordination crosslinking agent containing polyvalent metal ions are prepared.The present application combines core-shell structure with beta-dicarbonyl / metal ion room temperature coordination crosslinking system, wherein the core layer provides rigid support, shell layer promotes rapid film formation, functional monomer and metal ion form strong coordination bond network after moisture volatilization.At the same time, self-made bifunctional monomer containing phosphate and silane significantly improves the universal adhesion of adhesive to different substrates.The prepared adhesive has excellent spray atomization, self-drying, high bonding strength and stability.

Description

Technical Field

[0001] This invention belongs to the field of polymer adhesive technology, and relates to a water-based sprayable self-drying acrylic adhesive and its preparation method. Background Technology

[0002] Waterborne acrylic adhesives are water-dispersible adhesives prepared through emulsion polymerization using acrylate monomers as the core raw material. Because they use water as the dispersion medium, they offer significant advantages such as zero volatile organic compound emissions, safety and environmental friendliness, and controllable costs. They have gradually replaced traditional solvent-based adhesives and are widely used in building decoration, furniture manufacturing, packaging printing, and automotive interiors. Their core characteristic stems from the tunability of acrylate monomers; by changing the type and ratio of monomers, the film-forming properties, flexibility, and bonding performance of the adhesive can be flexibly controlled. Furthermore, they possess basic bonding capabilities to various substrates such as wood, plastics, and metals, making them one of the mainstream development directions in the current adhesive industry.

[0003] Currently, the preparation of waterborne acrylic adhesives mainly relies on emulsion polymerization, with core-shell emulsion polymerization and conventional emulsion polymerization being the mainstream processes. Core-shell emulsion polymerization is more widely used due to its ability to precisely control performance. Typically, hard monomers and crosslinking monomers are polymerized under the action of emulsifiers and initiators to form a rigid core layer. Then, a pre-emulsion composed of soft monomers and functional monomers is added dropwise to form a flexible shell layer, constructing a core-shell structure emulsion with a "hard core and soft shell." Conventional emulsion polymerization, on the other hand, directly mixes mixed monomers with water and emulsifiers, and initiates polymerization with an initiator. Subsequent steps require adjusting the pH value and adding thickeners, film-forming aids, and other additives to optimize performance, ultimately yielding the finished adhesive.

[0004] Despite the significant advantages of water-based acrylic adhesives, existing technologies still have several shortcomings: poor water resistance is a core issue, as residual hydrophilic groups in the emulsion easily cause the adhesive film to absorb water and swell, reducing bonding durability; insufficient bonding strength, especially weak interfacial adhesion to polar substrates, making it difficult to meet the requirements of high-strength applications; poor workability, with most products exhibiting poor thixotropy, leading to easy sagging or uneven atomization during spraying, limiting their application to inefficient processes such as brushing; and limited curing methods, with some products requiring high-temperature baking to complete cross-linking, increasing energy consumption and equipment costs, thus restricting their application on large components or heat-sensitive substrates. These problems urgently require technological breakthroughs to solve. Summary of the Invention

[0005] The purpose of this invention is to provide a water-based sprayable self-drying acrylic adhesive and its preparation method, which has excellent spray atomization, rapid room temperature self-drying, high bonding strength and good storage stability, and meets environmental protection requirements.

[0006] The objective of this invention can be achieved through the following technical solutions: A method for preparing a water-based, sprayable, self-drying acrylic adhesive includes the following steps: (1) A core layer emulsion is prepared by polymerizing deionized water, emulsifier and core layer monomer in the presence of an initiator, wherein the core layer monomer mixture contains hard monomer and multifunctional crosslinking monomer; (2) Add shell monomer pre-emulsion to the core layer emulsion for polymerization reaction to obtain an acrylate emulsion with a core-shell structure. The shell monomer includes soft monomer, hydrophilic functional monomer and functional monomer containing β-dicarbonyl structure. (3) Cool down the acrylate emulsion obtained in step (2), adjust the pH value to 7.5-9.0, add rheology modifier, film-forming aid and coordination crosslinking agent containing multivalent metal ions in sequence, mix evenly to obtain the water-based sprayable self-drying acrylate adhesive. The functional monomer containing the β-dicarbonyl structure and the coordination crosslinking agent can undergo a coordination crosslinking reaction at room temperature after the water evaporates.

[0007] As a preferred embodiment of the present invention, the mass ratio of methyl methacrylate, styrene and ethylene glycol dimethacrylate in the core layer monomer is (20-30):(10-20):(1-2).

[0008] As a preferred embodiment of the present invention, the mass ratio of butyl acrylate, ethyl acrylate, functional monomer containing β-dicarbonyl structure, phosphate ester and silane bifunctional monomer and polyethylene glycol methacrylate in the shell monomer is (30-40):(15-25):(2-4):(1-3):(1-3).

[0009] As a preferred embodiment of the present invention, the functional monomer containing the β-dicarbonyl structure is acetylacetoxyethyl methacrylate.

[0010] As a preferred embodiment of the present invention, the coordination crosslinking agent is an organic complex of zirconium, aluminum, or titanium.

[0011] As a preferred embodiment of the present invention, the rheology modifier comprises a nonionic polyurethane associative thickener, a hydrophobically modified alkali-swellable acrylic thickener, and nanocellulose crystals, wherein the mass ratio of the three components is 5-8:2-4:1.

[0012] In this application, a hard monomer with a high glass transition temperature is used as the core layer to impart the necessary cohesive strength, hardness, and heat resistance to the adhesive film. A small amount of multifunctional crosslinking monomers (such as ethylene glycol dimethacrylate) are introduced to form a mild crosslinking network during the polymerization stage, further enhancing the mechanical strength and creep resistance of the core and providing structural support for the entire adhesive film. A soft monomer with a low glass transition temperature is used as the shell layer to ensure that the polymer particles can fully deform and fuse at a lower temperature after moisture evaporation, forming a continuous and dense adhesive film that can be formed at room temperature. This "hard core, soft shell" structure allows the soft shell to fuse first after spraying, achieving rapid surface drying and locking the position of the adhered object; the hard core provides durable support, preventing the adhesive film from creeping and failing under stress. The two work synergistically to achieve a balance between fast drying and strong toughness.

[0013] Traditional water-based adhesives rely on physical film formation through water evaporation or high-temperature crosslinking. This invention introduces a β-dicarbonyl / metal ion room-temperature coordination crosslinking system. The functional monomer acetylacetoxy (-O-CO-CH2-CO-CH3) containing a β-dicarbonyl structure is introduced into the shell layer, which readily enolizes under weakly alkaline conditions, forming a reactive enol structure. Organic complexes of zirconium, aluminum, or titanium are used as crosslinking agents. These multivalent metal ions possess empty electron orbitals. With water evaporation, the oxygen atom in the enolized β-dicarbonyl structure fills the empty orbitals of the metal ions with its lone pair electrons, forming stable chelate cyclic coordination bonds. The strength of these coordination bonds is far greater than that of hydrogen bonds and van der Waals forces, enabling rapid construction of a three-dimensional crosslinked network at room temperature. The self-made phosphate ester and silane bifunctional monomer is key to achieving universally high adhesion. The phosphate ester group has strong polarity and acidity, allowing for chemical adsorption or reaction with oxides or hydroxyl groups on the surface of inorganic substrates such as metals and ceramics, forming a robust phosphate layer. The ethoxy group of the alkoxysilane group can be hydrolyzed to generate silanol groups, which can both condense with hydroxyl groups on the surface of inorganic substrates to form Si-OM covalent bonds, and also self-condense within the film to form a Si-O-Si hydrophobic network, significantly improving water resistance. This monomer is copolymerized onto the polymer chain, causing phosphate esters and silane groups to be directionally enriched at the film-substrate interface, achieving simultaneous and strong adhesion to polar (metal, glass) and non-polar (PP, PE plastic) substrates, eliminating the need for a primer.

[0014] To achieve a well-atomized, non-sagging spraying effect, this invention constructs a three-level synergistic rheology regulation system: the hydrophobic ends of the nonionic polyurethane associative thickener form a dynamic reversible network with the emulsion particles and surfactants through hydrophobic interactions. Under high shear (during spraying), the network is disrupted, causing a sharp drop in viscosity, which facilitates atomization; after the shear force disappears, the network is rapidly rebuilt, preventing sagging. The hydrophobically modified alkali-swellable acrylic thickener mainly provides medium-to-low shear viscosity, improves storage stability, and prevents sedimentation. The high aspect ratio and abundant surface hydroxyl groups of nanocellulose crystals can form a rigid network in the system, providing excellent thixotropy and anti-sagging properties, especially suitable for vertical surface application.

[0015] Furthermore, a water-based, sprayable, self-drying acrylic adhesive is prepared by the aforementioned method.

[0016] Furthermore, a water-based, sprayable, self-drying acrylic adhesive comprises the following components: a) Core-shell structured acrylate emulsion: The core layer of the core-shell structure is formed by copolymerization of hard monomers and multifunctional crosslinked monomers, and the shell layer is formed by copolymerization of soft monomers, hydrophilic functional monomers and functional monomers containing acetylacetoxy groups; b) Rheology modifier system: includes nonionic polyurethane associative thickener, hydrophobically modified alkali-swellable acrylic thickener and nano-cellulose crystals; c) Coordination crosslinking agents: organic complexes of zirconium, aluminum, or titanium; d) Film-forming aids; The acetylacetoxy-containing functional monomer and the coordination crosslinking agent can undergo a coordination crosslinking reaction at room temperature after the water evaporates.

[0017] As a preferred embodiment of the present invention, the functional monomer containing acetylacetoxy groups accounts for 1.5%-5% of the total mass of the monomers based on the emulsion solids, and the molar ratio of the metal ion in the coordination crosslinking agent to the functional monomer containing acetylacetoxy groups is (0.8-1.5):1.

[0018] Furthermore, a method for preparing a bifunctional monomer containing phosphate ester and silane includes the following steps: A1. In the presence of the catalyst tetraisopropyl titanate and the polymerization inhibitor hydroquinone or methoxyphenol, hydroxyethyl methacrylate and diethyl phosphate undergo transesterification to generate phosphate methacrylate intermediate. A2. In the presence of the catalyst dibutyltin dilaurate, the phosphate ester methacrylate intermediate obtained in step A1 is subjected to a condensation reaction with 3-isocyanate-propyltriethoxysilane to obtain the bifunctional monomer containing phosphate ester and silane.

[0019] The beneficial effects of this invention are: (1) This invention achieves functional timing control at the molecular level through a “hard core-soft shell” polymer structure design. After spraying, the soft shell with a low glass transition temperature (Tg) fuses first, achieving rapid surface drying (e.g., ≤10 minutes) and effectively locking the adhered material; the hard core with a high Tg acts as a rigid skeleton, providing long-lasting cohesive strength and creep resistance. This structure unifies “rapid shaping” and “long-term toughness”, fundamentally overcoming the inherent contradiction of traditional water-based adhesives that are brittle when drying quickly and slow to dry when tough.

[0020] (2) This invention abandons the traditional crosslinking method that requires high-temperature heating or releases formaldehyde, and introduces a functional monomer containing a β-dicarbonyl structure and a multivalent metal ion coordination crosslinking agent. After the water evaporates, the two can form a stable chelate coordination bond at room temperature, quickly build a crosslinking network, and significantly improve the final bonding strength, water resistance and heat resistance of the film. At the same time, it achieves rapid drying at room temperature, reducing energy consumption and construction threshold.

[0021] (3) This invention introduces a bifunctional monomer containing both phosphate ester groups and alkoxysilane groups. The phosphate ester groups can strongly adsorb or bond to polar substrates such as metals and ceramics; the silane groups can form Si-OM covalent bonds with inorganic substrates and form a hydrophobic network within the adhesive film. This monomer is copolymerized and fixed to the polymer chain and enriched at the interface, thus exhibiting excellent adhesion to various substrates such as metals, plastics (including difficult-to-adhere PP and PE), wood, and glass. No primer treatment is required, which greatly broadens the application range and simplifies the construction process.

[0022] (4) The rheological behavior of the adhesive was precisely controlled by a three-level synergistic rheology regulation system consisting of a nonionic polyurethane associative thickener, a hydrophobically modified alkali-swellable acrylic thickener, and nanocellulose crystals. This resulted in low viscosity and fine atomization under high shear during spraying; rapid recovery of viscosity and high thixotropy after shear stress elimination, effectively preventing sagging on vertical surfaces. Simultaneously, the system ensured good storage stability of the product, with no sedimentation or stratification. Furthermore, the entire system used water as the dispersion medium, resulting in extremely low volatile organic compound content; the crosslinking system used released no formaldehyde; and the preparation process was mild. Detailed Implementation

[0023] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0024] A method for preparing a water-based, sprayable, self-drying acrylic adhesive includes the following steps: (1) A core layer emulsion is prepared by polymerizing deionized water, emulsifier and core layer monomer in the presence of an initiator, wherein the core layer monomer mixture contains hard monomer and multifunctional crosslinking monomer; (2) Add shell monomer pre-emulsion to the core layer emulsion for polymerization reaction to obtain an acrylate emulsion with a core-shell structure. The shell monomer includes soft monomer, hydrophilic functional monomer and functional monomer containing β-dicarbonyl structure. (3) Cool down the acrylate emulsion obtained in step (2), adjust the pH value to 8.0, add rheology modifier, film-forming aid and coordination crosslinking agent containing multivalent metal ions in sequence, mix evenly to obtain the water-based sprayable self-drying acrylate adhesive. The functional monomer containing the β-dicarbonyl structure and the coordination crosslinking agent can undergo a coordination crosslinking reaction at room temperature after the water evaporates.

[0025] In the core layer monomer, the mass ratio of methyl methacrylate, styrene, and ethylene glycol dimethacrylate is 25:15:1.5.

[0026] The mass ratio of butyl acrylate, ethyl acrylate, acetyl methacrylate, phosphate-containing bifunctional monomers and polyethylene glycol methacrylate in the shell monomer is 35:20:3:2:2.

[0027] The coordination crosslinking agent is ammonium zirconium carbonate.

[0028] The rheology modifiers include a nonionic polyurethane associative thickener (purchased from Xiamen Zuochuan Trading Co., Ltd.), a hydrophobically modified alkali-swellable acrylic thickener (purchased from Dow Chemical Company), and nanocellulose crystals (purchased from Zhejiang Jinjiahao Green Nanomaterials Co., Ltd.), with a mass ratio of 6:3:1.

[0029] A water-based, sprayable, self-drying acrylic adhesive is prepared by the aforementioned method.

[0030] A water-based, sprayable, self-drying acrylic adhesive, comprising the following components: a) Core-shell structured acrylate emulsion: The core layer of the core-shell structure is formed by copolymerization of hard monomers and multifunctional crosslinked monomers, and the shell layer is formed by copolymerization of soft monomers, hydrophilic functional monomers and functional monomers containing acetylacetoxy groups; b) Rheology modifier system: includes nonionic polyurethane associative thickener, hydrophobically modified alkali-swellable acrylic thickener and nano-cellulose crystals; c) Coordination crosslinking agents: organic complexes of zirconium, aluminum, or titanium; d) Film-forming aids; The acetylacetoxy-containing functional monomer and the coordination crosslinking agent can undergo a coordination crosslinking reaction at room temperature after the water evaporates.

[0031] The molar ratio of the metal ions to the acetylacetoxy-containing functional monomers in the coordination crosslinking agent is 1:1.

[0032] A method for preparing a bifunctional monomer containing phosphate ester and silane includes the following steps: A1. In the presence of the catalyst tetraisopropyl titanate and the polymerization inhibitor hydroquinone or methoxyphenol, hydroxyethyl methacrylate and diethyl phosphate undergo transesterification to generate phosphate methacrylate intermediate. A2. In the presence of the catalyst dibutyltin dilaurate, the phosphate ester methacrylate intermediate obtained in step A1 is subjected to a condensation reaction with 3-isocyanate-propyltriethoxysilane to obtain the bifunctional monomer containing phosphate ester and silane.

[0033] Example 2 A method for preparing a water-based, sprayable, self-drying acrylic adhesive includes the following steps: (1) A core layer emulsion is prepared by polymerizing deionized water, emulsifier and core layer monomer in the presence of an initiator, wherein the core layer monomer mixture contains hard monomer and multifunctional crosslinking monomer; (2) Add shell monomer pre-emulsion to the core layer emulsion for polymerization reaction to obtain an acrylate emulsion with a core-shell structure. The shell monomer includes soft monomer, hydrophilic functional monomer and functional monomer containing β-dicarbonyl structure. (3) Cool down the acrylate emulsion obtained in step (2), adjust the pH value to 7.5, add rheology modifier, film-forming aid and coordination crosslinking agent containing multivalent metal ions in sequence, mix evenly to obtain the water-based sprayable self-drying acrylate adhesive. The functional monomer containing the β-dicarbonyl structure and the coordination crosslinking agent can undergo a coordination crosslinking reaction at room temperature after the water evaporates.

[0034] In the core layer monomer, the mass ratio of methyl methacrylate, styrene, and ethylene glycol dimethacrylate is 30:10:1.

[0035] The mass ratio of butyl acrylate, ethyl acrylate, acetoacetoxyethyl methacrylate, phosphate-containing bifunctional monomers and polyethylene glycol methacrylate in the shell monomer is 40:15:2:1:1.

[0036] The coordination crosslinking agent is zirconium acetate.

[0037] The rheology modifiers include a nonionic polyurethane associative thickener (purchased from Xiamen Zuochuan Trading Co., Ltd.), a hydrophobically modified alkali-swellable acrylic thickener (purchased from Dow Chemical Company), and nanocellulose crystals (purchased from Zhejiang Jinjiahao Green Nanomaterials Co., Ltd.), with a mass ratio of 8:2:1.

[0038] A water-based, sprayable, self-drying acrylic adhesive is prepared by the aforementioned method.

[0039] Furthermore, a water-based, sprayable, self-drying acrylic adhesive comprises the following components: a) Core-shell structured acrylate emulsion: The core layer of the core-shell structure is formed by copolymerization of hard monomers and multifunctional crosslinked monomers, and the shell layer is formed by copolymerization of soft monomers, hydrophilic functional monomers and functional monomers containing acetylacetoxy groups; b) Rheology modifier system: includes nonionic polyurethane associative thickener, hydrophobically modified alkali-swellable acrylic thickener and nano-cellulose crystals; c) Coordination crosslinking agents: organic complexes of zirconium, aluminum, or titanium; d) Film-forming aids; The acetylacetoxy-containing functional monomer and the coordination crosslinking agent can undergo a coordination crosslinking reaction at room temperature after the water evaporates.

[0040] The molar ratio of metal ions to acetylacetoxy-containing functional monomers in the coordination crosslinking agent is 0.8:1.

[0041] A method for preparing a bifunctional monomer containing phosphate ester and silane includes the following steps: A1. In the presence of the catalyst tetraisopropyl titanate and the polymerization inhibitor hydroquinone or methoxyphenol, hydroxyethyl methacrylate and diethyl phosphate undergo transesterification to generate phosphate methacrylate intermediate. A2. In the presence of the catalyst dibutyltin dilaurate, the phosphate ester methacrylate intermediate obtained in step A1 is subjected to a condensation reaction with 3-isocyanate-propyltriethoxysilane to obtain the bifunctional monomer containing phosphate ester and silane.

[0042] Example 3 A method for preparing a water-based, sprayable, self-drying acrylic adhesive includes the following steps: (1) A core layer emulsion is prepared by polymerizing deionized water, emulsifier and core layer monomer in the presence of an initiator, wherein the core layer monomer mixture contains hard monomer and multifunctional crosslinking monomer; (2) Add shell monomer pre-emulsion to the core layer emulsion for polymerization reaction to obtain an acrylate emulsion with a core-shell structure. The shell monomer includes soft monomer, hydrophilic functional monomer and functional monomer containing β-dicarbonyl structure. (3) Cool down the acrylate emulsion obtained in step (2), adjust the pH value to 9.0, add rheology modifier, film-forming aid and coordination crosslinking agent containing multivalent metal ions in sequence, mix evenly to obtain the water-based sprayable self-drying acrylate adhesive. The functional monomer containing the β-dicarbonyl structure and the coordination crosslinking agent can undergo a coordination crosslinking reaction at room temperature after the water evaporates.

[0043] In the core layer monomer, the mass ratio of methyl methacrylate, styrene, and ethylene glycol dimethacrylate is 20:20:2.

[0044] The mass ratio of butyl acrylate, ethyl acrylate, acetyl methacrylate, phosphate-containing bifunctional monomers and polyethylene glycol methacrylate in the shell monomer is 30:25:4:3:3.

[0045] The coordination crosslinking agent is basic aluminum chloride.

[0046] The rheology modifiers include a nonionic polyurethane associative thickener (purchased from Xiamen Zuochuan Trading Co., Ltd.), a hydrophobically modified alkali-swellable acrylic thickener (purchased from Dow Chemical Company), and nanocellulose crystals (purchased from Zhejiang Jinjiahao Green Nanomaterials Co., Ltd.), with a mass ratio of 8:2:1.

[0047] A water-based, sprayable, self-drying acrylic adhesive is prepared by the aforementioned method.

[0048] Furthermore, a water-based, sprayable, self-drying acrylic adhesive comprises the following components: a) Core-shell structured acrylate emulsion: The core layer of the core-shell structure is formed by copolymerization of hard monomers and multifunctional crosslinked monomers, and the shell layer is formed by copolymerization of soft monomers, hydrophilic functional monomers and functional monomers containing acetylacetoxy groups; b) Rheology modifier system: includes nonionic polyurethane associative thickener, hydrophobically modified alkali-swellable acrylic thickener and nano-cellulose crystals; c) Coordination crosslinking agents: organic complexes of zirconium, aluminum, or titanium; d) Film-forming aids; The acetylacetoxy-containing functional monomer and the coordination crosslinking agent can undergo a coordination crosslinking reaction at room temperature after the water evaporates.

[0049] The molar ratio of metal ions to acetylacetoxy-containing functional monomers in the coordination crosslinking agent is 1.5:1.

[0050] A method for preparing a bifunctional monomer containing phosphate ester and silane includes the following steps: A1. In the presence of the catalyst tetraisopropyl titanate and the polymerization inhibitor hydroquinone or methoxyphenol, hydroxyethyl methacrylate and diethyl phosphate undergo transesterification to generate phosphate methacrylate intermediate. A2. In the presence of the catalyst dibutyltin dilaurate, the phosphate ester methacrylate intermediate obtained in step A1 is subjected to a condensation reaction with 3-isocyanate-propyltriethoxysilane to obtain the bifunctional monomer containing phosphate ester and silane.

[0051] Example 4 A method for preparing a water-based, sprayable, self-drying acrylic adhesive includes the following steps: (1) A core layer emulsion is prepared by polymerizing deionized water, emulsifier and core layer monomer in the presence of an initiator, wherein the core layer monomer mixture contains hard monomer and multifunctional crosslinking monomer; (2) Add shell monomer pre-emulsion to the core layer emulsion for polymerization reaction to obtain an acrylate emulsion with a core-shell structure. The shell monomer includes soft monomer, hydrophilic functional monomer and functional monomer containing β-dicarbonyl structure. (3) Cool down the acrylate emulsion obtained in step (2), adjust the pH value to 8.0, add rheology modifier, film-forming aid and coordination crosslinking agent containing multivalent metal ions in sequence, mix evenly to obtain the water-based sprayable self-drying acrylate adhesive. The functional monomer containing the β-dicarbonyl structure and the coordination crosslinking agent can undergo a coordination crosslinking reaction at room temperature after the water evaporates.

[0052] In the core layer monomer, the mass ratio of methyl methacrylate, styrene, and ethylene glycol dimethacrylate is 25:15:1.5.

[0053] The mass ratio of butyl acrylate, ethyl acrylate, acetyl methacrylate, phosphate-containing bifunctional monomers and polyethylene glycol methacrylate in the shell monomer is 35:20:3:2:2.

[0054] The coordination crosslinking agent is ammonium zirconium carbonate.

[0055] The rheology modifiers include a nonionic polyurethane associative thickener (purchased from Xiamen Zuochuan Trading Co., Ltd.), a hydrophobically modified alkali-swellable acrylic thickener (purchased from Dow Chemical Company), and nanocellulose crystals (purchased from Zhejiang Jinjiahao Green Nanomaterials Co., Ltd.), with a mass ratio of 8:2:1.

[0056] A water-based, sprayable, self-drying acrylic adhesive is prepared by the aforementioned method.

[0057] Furthermore, a water-based, sprayable, self-drying acrylic adhesive comprises the following components: a) Core-shell structured acrylate emulsion: The core layer of the core-shell structure is formed by copolymerization of hard monomers and multifunctional crosslinked monomers, and the shell layer is formed by copolymerization of soft monomers, hydrophilic functional monomers and functional monomers containing acetylacetoxy groups; b) Rheology modifier system: includes nonionic polyurethane associative thickener, hydrophobically modified alkali-swellable acrylic thickener and nano-cellulose crystals; c) Coordination crosslinking agents: organic complexes of zirconium, aluminum, or titanium; d) Film-forming aids; The acetylacetoxy-containing functional monomer and the coordination crosslinking agent can undergo a coordination crosslinking reaction at room temperature after the water evaporates.

[0058] The molar ratio of metal ions to acetylacetoxy-containing functional monomers in the coordination crosslinking agent is 1.5:1.

[0059] A method for preparing a bifunctional monomer containing phosphate ester and silane includes the following steps: A1. In the presence of the catalyst tetraisopropyl titanate and the polymerization inhibitor hydroquinone or methoxyphenol, hydroxyethyl methacrylate and diethyl phosphate undergo transesterification to generate phosphate methacrylate intermediate. A2. In the presence of the catalyst dibutyltin dilaurate, the phosphate ester methacrylate intermediate obtained in step A1 is subjected to a condensation reaction with 3-isocyanate-propyltriethoxysilane to obtain the bifunctional monomer containing phosphate ester and silane.

[0060] Comparative Example 1 The same monomer types and total mass as in Example 1 were used, but all monomers were added at once for conventional emulsion copolymerization to obtain a random copolymer emulsion. The remaining steps were the same as in Example 1.

[0061] Comparative Example 2 Based on Example 1, acetylacetoxyethyl methacrylate was replaced with an equimolar amount of the crosslinking monomer N-hydroxymethylacrylamide, and the crosslinking agent hexamethoxymethylmelamine was added accordingly, while the rest remained the same as in Example 1.

[0062] Comparative Example 3 Based on Example 1, the nonionic polyurethane associative thickener was removed from the rheology modifier, and only hydrophobically modified alkali-swellable acrylic thickener and nanocellulose crystals were used, while the rest remained the same as in Example 1.

[0063] Comparative Example 4 Based on Example 1, the hydrophobic modified alkali-swellable acrylic thickener was removed from the rheology modifier, and only a nonionic polyurethane associative thickener and nanocellulose crystals were used, while the rest remained the same as in Example 1.

[0064] Comparative Example 5 Based on Example 1, the nanocellulose crystals were removed from the rheology modifier, and only nonionic polyurethane associative thickener and hydrophobically modified alkali-swellable acrylic thickener were used, while the rest remained the same as in Example 1.

[0065] Comparative Example 6 Based on Example 1, the bifunctional monomers containing phosphate esters and silanes were removed, while the rest remained the same as in Example 1.

[0066] Comparative Example 7 Based on Example 1, the phosphate ester and silane bifunctional monomer was replaced with a phosphate ester adhesion promoter, while the rest remained the same as in Example 1.

[0067] Comparative Example 8 Based on Example 1, the phosphate ester and silane bifunctional monomer was replaced with silane coupling agent MP200 adhesion promoter, while the rest remained the same as in Example 1.

[0068] Performance testing: Referring to GB / T 9264-2012 standard, a standard spray gun was used to spray the coating onto white paper. Subjective evaluation was conducted to assess the uniformity of atomization and the absence of stringing, dripping, or other phenomena. A sag tester (multi-groove scraper) was used to prepare wet films of different thicknesses on vertically positioned test cards. The cards were placed vertically, and the wet film thickness at which sag began to appear was observed and recorded. According to GB / T 1728-2020 standard, the surface drying time is determined by finger triggering, and the actual drying time is determined by the filter paper pressing method. The tensile shear strength of stainless steel, polypropylene, and glass was determined after 24 hours according to GB / T 7124-2008 standard.

[0069] The test results show that the examples exhibit excellent sprayability, fast drying, high strength, and high adhesion. Comparative Example 1, although its random copolymer surface dries slightly faster, has a significantly longer actual drying time and lower shear strength across all substrates. Comparative Example 2, using N-hydroxymethylacrylamide crosslinking agent, not only has poor environmental performance but also exhibits low crosslinking rate at room temperature and a long actual drying time. Comparative Examples 3-5 show poor spray atomization when the rheology modifier lacks a nonionic polyurethane associative thickener, a slight decrease in anti-sagging properties when the hydrophobic modified alkali-swellable acrylic thickener is lacking, and a sharp decrease in anti-sagging properties when nanocellulose crystals are missing. Comparative Example 6, lacking a bifunctional monomer containing phosphate esters and silanes, experiences a sharp drop in shear strength to 0.8 MPa for PP. Comparative Examples 7 and 8, using phosphate ester adhesion promoters and silane coupling agent MP200 instead, still show significantly lower performance than the examples.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a water-based, sprayable, self-drying acrylic adhesive, characterized in that, Includes the following steps: (1) A core layer emulsion is prepared by polymerizing deionized water, emulsifier and core layer monomer in the presence of an initiator, wherein the core layer monomer mixture contains hard monomer and multifunctional crosslinking monomer; (2) Add shell monomer pre-emulsion to the core layer emulsion for polymerization reaction to obtain an acrylate emulsion with a core-shell structure. The shell monomer includes soft monomer, hydrophilic functional monomer and functional monomer containing β-dicarbonyl structure. (3) Cool down the acrylate emulsion obtained in step (2), adjust the pH value to 7.5-9.0, add rheology modifier, film-forming aid and coordination crosslinking agent containing multivalent metal ions in sequence, mix evenly to obtain the water-based sprayable self-drying acrylate adhesive. The functional monomer containing the β-dicarbonyl structure and the coordination crosslinking agent can undergo a coordination crosslinking reaction at room temperature after the water evaporates.

2. The method for preparing the water-based sprayable self-drying acrylic adhesive according to claim 1, characterized in that, In the core layer monomer, the mass ratio of methyl methacrylate, styrene and ethylene glycol dimethacrylate is (20-30):(10-20):(1-2).

3. The method for preparing the water-based sprayable self-drying acrylic adhesive according to claim 1, characterized in that, The mass ratio of butyl acrylate, ethyl acrylate, functional monomers containing β-dicarbonyl structure, bifunctional monomers containing phosphate ester and silane and polyethylene glycol methacrylate in the shell monomer is (30-40):(15-25):(2-4):(1-3):(1-3).

4. The method for preparing the water-based sprayable self-drying acrylic adhesive according to claim 3, characterized in that, The functional monomer containing the β-dicarbonyl structure is acetylacetoxyethyl methacrylate.

5. The method for preparing the water-based sprayable self-drying acrylic adhesive according to claim 1, characterized in that, The coordination crosslinking agent is an organic complex of zirconium, aluminum, or titanium.

6. The method for preparing the water-based sprayable self-drying acrylic adhesive according to claim 1, characterized in that, The rheology modifier includes a nonionic polyurethane associative thickener, a hydrophobically modified alkali-swellable acrylic thickener, and nanocellulose crystals, with a mass ratio of 5-8:2-4:

1.

7. A water-based, sprayable, self-drying acrylic adhesive, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

8. A water-based, sprayable, self-drying acrylic adhesive, characterized in that, It consists of the following components: a) Core-shell structured acrylate emulsion: The core layer of the core-shell structure is formed by copolymerization of hard monomers and multifunctional crosslinked monomers, and the shell layer is formed by copolymerization of soft monomers, hydrophilic functional monomers and functional monomers containing acetylacetoxy groups; b) Rheology modifier system: includes nonionic polyurethane associative thickener, hydrophobically modified alkali-swellable acrylic thickener and nano-cellulose crystals; c) Coordination crosslinking agents: organic complexes of zirconium, aluminum, or titanium; d) Film-forming aids; The acetylacetoxy-containing functional monomer and the coordination crosslinking agent can undergo a coordination crosslinking reaction at room temperature after the water evaporates.

9. The water-based sprayable self-drying acrylic adhesive according to claim 8, characterized in that, Based on the emulsion solids, the acetylacetoxy-containing functional monomer accounts for 1.5%-5% of the total monomer mass, and the molar ratio of the metal ion in the coordination crosslinking agent to the acetylacetoxy-containing functional monomer is (0.8-1.5):

1.

10. A method for preparing a bifunctional monomer containing phosphate ester and silane, characterized in that, Includes the following steps: A1. In the presence of the catalyst tetraisopropyl titanate and the polymerization inhibitor hydroquinone or methoxyphenol, hydroxyethyl methacrylate and diethyl phosphate undergo transesterification to generate phosphate methacrylate intermediate. A2. In the presence of the catalyst dibutyltin dilaurate, the phosphate ester methacrylate intermediate obtained in step A1 is subjected to a condensation reaction with 3-isocyanate-propyltriethoxysilane to obtain the bifunctional monomer containing phosphate ester and silane.

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