Environment-friendly water-based adhesive and preparation method thereof

Abstract

The invention relates to the technical field of adhesives, and discloses an environment-friendly water-based adhesive and a preparation method thereof.The environment-friendly water-based adhesive is prepared by taking a modified polyurethane matrix as a base material and taking a wetting agent, a defoaming agent, a thickening agent and a photoinitiator as auxiliary materials, jointly adding the materials into deionized water and mixing the materials, the modified polyurethane matrix is prepared from a soft segment monomer and a modified monomer, and a high-temperature-resistant silica skeleton and a hydrophilic sulfonic acid group are introduced into the soft segment monomer through chemical bonding, so that the adhesive is endowed with good high-temperature resistance and hydrophilicity; a modified monomer is prepared by introducing a water-soluble phenolic resin polymer with good heat resistance, bonding strength and other properties into an olefinic bond, and the olefinic bond in the modified monomer is initiated to generate a free radical polymerization reaction under the conditions of a photoinitiator and ultraviolet irradiation, so that quick crosslinking curing can be realized, and the adhesive has good adhesion. The adhesive is endowed with the characteristics of high bonding strength and rapid curing.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and in particular to an environmentally friendly water-based adhesive and a preparation method thereof. Background Art

[0002] Adhesives, key materials for joining materials in industrial production, are widely used in aerospace, electronics, automotive, and machinery manufacturing. Traditional adhesives are primarily solvent-based, but their reliance on organic solvents as a dispersion medium presents drawbacks such as volatility, flammability, explosiveness, toxicity, and harmfulness. These adhesives not only pose a threat to the operating environment and human health, but also face increasingly stringent environmental regulations. With the global adoption of green manufacturing concepts, the development of environmentally friendly, water-based adhesives has become a core development direction for the industry.

[0003] Water-based adhesives, using water as their primary dispersion medium, are formed by dissolving or dispersing high-molecular-weight polymers in water. They offer significant advantages such as being non-flammable, low-odor, low-pollution, energy-efficient, and easy to apply. Compared to solvent-based products, they avoid the atmospheric pollution and fire risks associated with the volatilization of organic solvents, while also reducing safety and protective costs during the production process, meeting the sustainable development needs of the current "dual carbon" goals. Therefore, the replacement of solvent-based adhesives with water-based adhesives has become an irreversible industry trend, particularly in areas with stringent environmental requirements such as food packaging, medical devices, and automotive interiors, where the penetration of water-based adhesives continues to increase.

[0004] Among them, polyurethane water-based adhesives introduce hydrophilic groups into polyurethane molecules. In a high-temperature bonding environment, the active groups in the macromolecular structure of polyurethane water-based adhesives are prone to chemical reactions such as hydrolysis and oxidation with active medium molecules, resulting in the destruction and cracking of the main valence bonds of the macromolecules, which in turn causes a decrease in bond strength and leads to problems such as acid and alkali resistance and water resistance. In addition, the presence of large amounts of water in water-based polyurethane adhesives dilutes the concentration of the polymer's active ingredients. During the curing process, as the water evaporates, the polymer particles need to approach each other and fuse to form a continuous film. However, the presence of water makes it difficult to increase the effective cross-linking density between polymer molecular chains, and the intermolecular forces are weak, resulting in insufficient cohesion of the formed film and an inability to provide sufficient support for bonding. Therefore, compared with structural adhesives with fast curing and high strength characteristics, the gap between water-based polyurethane adhesives in bond strength and curing rate greatly limits their use in applications that require higher bond strength and curing speed.

[0005] Given the performance limitations of existing water-based polyurethane adhesives, there is an urgent need to develop a water-based polyurethane adhesive that has excellent high-temperature resistance, high bonding strength and fast curing properties to meet the demand for long-term and stable use of adhesives in multiple application scenarios. Summary of the Invention

[0006] The object of the present invention is to provide an environmentally friendly water-based adhesive and a preparation method thereof.

[0007] The purpose of the present invention can be achieved through the following technical solutions: An environmentally friendly water-based adhesive comprises the following components, calculated by weight: 65-75 parts of a modified polyurethane matrix, 2-4 parts of a wetting agent, 0.2-0.5 parts of a defoaming agent, 0.1-0.5 parts of a thickener, 0.3-0.6 parts of a photoinitiator, and 30-50 parts of deionized water.

[0008] Furthermore, the preparation method of the modified polyurethane matrix is ​​specifically as follows: Under nitrogen protection, add soft segment monomer, diphenylmethane diisocyanate and catalyst into the reactor, react at 80-85°C for 2-3h, then add modified monomer and continue to react for 6-7h. After the reaction is completed, the modified polyurethane matrix is ​​obtained.

[0009] Furthermore, the catalyst is any one of dibutyltin dilaurate, stannous octoate, and dibutyltin diacetate.

[0010] Furthermore, the preparation method of the soft segment monomer comprises the following steps: S1: Under nitrogen protection, add hydroxyl-terminated polydimethylsiloxane, epichlorohydrin, and boron trifluoride ether complex to the reactor while stirring, then adjust the temperature to 50-65°C, react for 5-6 hours, and obtain an intermediate after the reaction is completed; S2: Under nitrogen protection, add the intermediate and 2-aminoethanesulfonic acid into the reactor, heat and react. After the reaction is completed, purify the mixture to obtain the soft segment monomer.

[0011] Furthermore, in step S1, the molar ratio of the hydroxyl-terminated polydimethylsiloxane to epichlorohydrin is 1:1-2; and the number average molecular weight of the hydroxyl-terminated polydimethylsiloxane is 2000.

[0012] Furthermore, in step S2, the reaction temperature is 70-75° C., and the reaction time is 5-6 h.

[0013] Through the above technical solution, under the catalysis of boron trifluoride etherate complex, the epoxy group in epichlorohydrin and the terminal hydroxyl group of hydroxyl-terminated polydimethylsiloxane undergo a ring-opening reaction to generate an intermediate containing hydroxyl groups and halogen substituents. The halogen substituents in the intermediate structure can further react with the amino group in 2-aminoethanesulfonic acid to generate a soft segment monomer having both an active hydroxyl substituent and a sulfonic acid group at the end of the structure.

[0014] Furthermore, the preparation method of the modified monomer comprises the following steps: T1: Under nitrogen protection, phenol is added to the reactor, heated to melt the phenol, then the temperature is set to 50-55°C, potassium hydroxide aqueous solution is added, stirred, then formaldehyde solution is added, the temperature is raised to 62-65°C, and the reaction is carried out for 1-1.5 hours, potassium hydroxide aqueous solution is added again, the temperature is raised to 70-75°C, and the reaction is carried out for 30-45 minutes, and finally formaldehyde solution and polyvinyl alcohol are added, the temperature is raised to 86-90°C, and the reaction is carried out for 2.5-3 hours, and then the reaction solution is rapidly cooled and the unreacted matter is removed to obtain a water-soluble phenolic resin polymer; T2: Under nitrogen protection, add toluene, water-soluble phenolic resin polymer, and 3-isopropyl-dimethylbenzyl isocyanate into the reactor while stirring, then add dibutyltin dilaurate, set the temperature to 70-75°C, and react for 5-6 hours. After the reaction is completed, remove the unreacted materials and solvent, and obtain the modified monomer after purification.

[0015] Furthermore, in step T1, the mass fraction of the potassium hydroxide aqueous solution is 50-60%; the mass concentration of the formaldehyde solution is 37 g / 100 mL; and the number average molecular weight of the polyvinyl alcohol is 10,000-20,000.

[0016] Through the above technical scheme, phenol, formaldehyde and polyvinyl alcohol are used as reactants to prepare a water-soluble phenolic resin polymer under the catalysis of potassium hydroxide. Then, under the catalysis of dibutyltin dilaurate, the hydroxymethyl group in the water-soluble phenolic resin polymer reacts with the isocyanate group in 3-isopropyl-dimethylbenzyl isocyanate to introduce an unsaturated bond into the water-soluble phenolic resin polymer to obtain a modified monomer.

[0017] Furthermore, the wetting agent is BYK-349 or TEGO-KL245; the defoaming agent is AFE-7610 or AFE-7820; the thickener is any one of methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl methyl cellulose; and the photoinitiator is any one of benzoin ethyl ether, benzoin dimethyl ether, and photoinitiator 1173.

[0018] A method for preparing an environmentally friendly water-based adhesive comprises the following steps: Step 1: Prepare all raw materials according to mass proportion; Step 2: Add the modified polyurethane matrix into deionized water, then add the wetting agent, thickener, and photoinitiator, and disperse them evenly at a temperature of 40-60°C and a rotation speed of 2500-5000r / min. Then add the defoaming agent, stir for 10-30 minutes, and let it stand for 2-3 hours to obtain an environmentally friendly water-based adhesive.

[0019] Beneficial effects of the present invention: (1) The soft segment monomer prepared in the present invention has the dual excellent properties of high temperature resistance and hydrophilicity; the soft segment monomer has a relatively high bond energy silicon-oxygen bond to construct a stable chemical structure, which can still maintain the integrity of the molecular chain in a high temperature environment, inhibit the breakage and degradation of the chain segment, and has excellent high temperature resistance; in addition, the soft segment monomer also has a highly hydrophilic sulfonic acid group, which can be quickly dissolved to form a uniform transparent solution; the polyurethane adhesive further prepared based on the soft segment monomer fully inherits its performance advantages, maintains good bonding strength and flexibility under high temperature conditions, and can also be uniformly dispersed in an aqueous solution to form a stable emulsion system, achieving a balance between high temperature resistance and good water solubility, greatly broadening the application range of water-soluble polyurethane adhesives in high temperature environments.

[0020] (2) The present invention adopts a multi-step synthesis process to prepare the modified monomer. The rigid benzene ring structure of the phenolic resin in the modified monomer has good heat resistance, bonding strength, chemical resistance and other properties. The introduction of the polyethylene group gives it flexibility and hydrophilicity, so that it can be quickly dissolved in water and compatible with the emulsion; after adding the photoinitiator, under ultraviolet light irradiation, the photoinitiator decomposes to produce free radicals, which trigger the free radical polymerization reaction of the olefinic bond, so that the modified monomer can be quickly cross-linked and cured, thereby greatly shortening the curing time of the water-soluble polyurethane adhesive; finally, the high strength characteristics of the phenolic resin and the dense cross-linked network formed by the rapid curing of the olefinic bond work synergistically to give the adhesive good bonding strength.

[0021] (3) The present invention integrates silicon-oxygen bonds, sulfonic acid groups, phenolic resin structures and olefinic bonds into a polyurethane matrix through molecular design to construct a high-performance adhesive system with synergistic effects; silicon-oxygen bonds give the material excellent high-temperature resistance and anti-aging properties; sulfonic acid groups provide good water solubility and water dispersibility; the phenolic resin structure enhances bonding strength, has chemical corrosion resistance and electrical insulation properties; the olefinic bonds are rapidly cross-linked and cured by ultraviolet light under the action of photoinitiators, significantly shortening the curing time; this multi-functional group synergistic structural design enables the water-based polyurethane adhesive to have excellent high-temperature resistance, high-strength bonding performance and fast curing characteristics, while meeting environmental protection requirements and being suitable for high-temperature environments and the needs of rapid bonding in multiple scenarios.

[0022] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0024] Figure 1is the infrared spectrum of the soft segment monomer of the present invention; Figure 2 is the infrared spectrum of the modified monomer of the present invention. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0026] Example 1 An environmentally friendly water-based adhesive comprising the following components, calculated by weight: 65 parts of a modified polyurethane matrix, 2 parts of BYK-349, 0.2 parts of AFE-7610, 0.1 parts of methyl cellulose, 0.3 parts of a photoinitiator 1173, and 30 parts of deionized water; The preparation method of the environmentally friendly water-based adhesive comprises the following steps: Step 1: Prepare all raw materials according to mass proportion; Step 2: Add the modified polyurethane matrix to deionized water, then add BYK-349, AFE-7610, methyl cellulose, and photoinitiator 1173, and disperse them evenly at a temperature of 40°C and a rotation speed of 2500r / min. Then add the defoamer, stir for 10 minutes, and let it stand for 2 hours to obtain an environmentally friendly water-based adhesive.

[0027] The preparation method of the modified polyurethane matrix is ​​specifically as follows: Under nitrogen protection, 10.2 g of soft segment monomer, 8.4 g of diphenylmethane diisocyanate, and 0.02 g of dibutyltin dilaurate were added to a 500 mL reactor, and the mixture was stirred and reacted at 80°C for 3 h. Then, 1.8 g of modified monomer was slowly added dropwise and the reaction was continued for 6 h. After the reaction was completed, a modified polyurethane matrix was obtained.

[0028] The preparation method of the soft segment monomer comprises the following steps: S1: Under nitrogen protection, 24.8 g of hydroxyl-terminated polydimethylsiloxane with a number average molecular weight of 2000, 2.3 g of epichlorohydrin, and 0.4 g of boron trifluoride ether complex were added to a 250 mL reactor while stirring, and then the temperature was adjusted to 50 ° C. and heated to react for 5 h. After the reaction was completed, an intermediate was obtained; S2: Under nitrogen protection, 19.5 g of the intermediate and 1.2 g of 2-aminoethanesulfonic acid were added to a 500 mL reactor, and the mixture was reacted at 70°C for 5 h. After the reaction was completed, the mixture was purified to obtain the soft segment monomer.

[0029] Figure 1 is the infrared spectrum of the soft segment monomer, where 3445 cm -1 It is the characteristic absorption peak of oxygen-hydrogen bond in hydroxyl group, 3320cm -1 It is the characteristic absorption peak of nitrogen hydrogen bond in secondary amine, 3000~2890cm -1 The characteristic absorption peak of saturated carbon-hydrogen bond is 1168 cm -1 The characteristic absorption peak of the sulfur-oxygen double bond in the sulfonic acid group is 1052 cm -1 It is the characteristic absorption peak of carbon-oxygen bond in ether bond, 1025cm -1 It is the characteristic absorption peak of silicon-oxygen-silicon bond.

[0030] The preparation method of the modified monomer comprises the following steps: T1: Under nitrogen protection, 10.8 g of phenol was added to a 500 mL reactor, heated to 45 ° C to melt the phenol, and then the temperature was set to 50 ° C, 14 mL of a 50% potassium hydroxide aqueous solution was added, stirred for 30 min, and then 14 mL of formaldehyde solution was added, the temperature was raised to 62 ° C, and the reaction was carried out for 1 h. Then, 7 mL of a 50% potassium hydroxide aqueous solution was added, and the reaction was carried out at 70 ° C for 30 min. Finally, 7.3 mL of formaldehyde solution and 1.3 g of polyvinyl alcohol with a number average molecular weight of 10,000 were added, the temperature was set to 86 ° C, and the reaction was carried out for 2.5 h. The reaction solution was then rapidly cooled and the unreacted matter was removed to obtain a water-soluble phenolic resin polymer; T2: Under nitrogen protection, toluene, 14.4 g of water-soluble phenolic resin polymer, and 7.5 g of 3-isopropyl-dimethylbenzyl isocyanate were added to a 500 mL reactor while stirring, and then 0.06 g of dibutyltin dilaurate was added. The temperature was set to 70°C and the reaction was carried out for 5 h. The unreacted materials and solvent were removed and the modified monomer was obtained after purification.

[0031] Figure 2 is the infrared spectrum of the modified monomer, where 3398 cm -1 It is the characteristic absorption peak of oxygen-hydrogen bond in hydroxyl group, 3038cm -1 It is the characteristic absorption peak of the carbon-hydrogen bond in the unsaturated bond, 3000~3100cm -1 It is the characteristic absorption peak of the carbon-hydrogen bond in the benzene ring, 1738 cm -1 It is the characteristic absorption peak of the carbon-oxygen double bond in the ester group, 1685 cm -1 The characteristic absorption peak of the carbon-oxygen double bond in the amine ester group is 1647 cm -1 is the characteristic absorption peak of carbon-carbon double bond, 1560 cm -1 The characteristic absorption peak of nitrogen-hydrogen bond in amide, 1260 cm -1 is the characteristic absorption peak of the carbon-oxygen bond connected to the carbonyl group, 1115 cm-1 It is the characteristic absorption peak of the carbon-oxygen bond in the ether bond.

[0032] Example 2 An environmentally friendly water-based adhesive comprising the following components, calculated by weight: 72 parts of a modified polyurethane matrix, 3 parts of BYK-349, 0.3 parts of AFE-7610, 0.2 parts of methyl cellulose, 0.4 parts of a photoinitiator 1173, and 35 parts of deionized water; The preparation method of the environmentally friendly water-based adhesive comprises the following steps: Step 1: Prepare all raw materials according to mass proportion; Step 2: Add the modified polyurethane matrix to deionized water, then add BYK-349, AFE-7610, methyl cellulose, and photoinitiator 1173, and disperse them evenly at a temperature of 50°C and a rotation speed of 3000 r / min. Then add the defoamer, stir for 15 minutes, and let it stand for 2.5 hours to obtain an environmentally friendly water-based adhesive.

[0033] The preparation method of the modified polyurethane matrix is ​​the same as that of Example 1.

[0034] Example 3 An environmentally friendly water-based adhesive, comprising the following components, calculated by weight: 75 parts of a modified polyurethane matrix, 4 parts of BYK-349, 0.5 parts of AFE-7610, 0.5 parts of methyl cellulose, 0.6 parts of a photoinitiator 1173, and 50 parts of deionized water; The preparation method of the environmentally friendly water-based adhesive comprises the following steps: Step 1: Prepare all raw materials according to mass proportion; Step 2: Add the modified polyurethane matrix to deionized water, then add BYK-349, AFE-7610, methyl cellulose, and photoinitiator 1173, and disperse them evenly at a temperature of 60°C and a rotation speed of 5000 r / min. Then add the defoamer, stir for 30 minutes, and let it stand for 3 hours to obtain an environmentally friendly water-based adhesive.

[0035] The preparation method of the modified polyurethane matrix is ​​the same as that of Example 1.

[0036] Comparative Example 1 An environmentally friendly water-based adhesive comprising the following components, calculated by weight: 66 parts of a modified polyurethane matrix, 3 parts of BYK-349, 0.3 parts of AFE-7610, 0.2 parts of methyl cellulose, 0.4 parts of a photoinitiator 1173, and 35 parts of deionized water; The preparation method of the environmentally friendly water-based adhesive comprises the following steps: Step 1: Prepare all raw materials according to mass proportion; Step 2: Add the modified polyurethane matrix to deionized water, then add BYK-349, AFE-7610, methyl cellulose, and photoinitiator 1173, and disperse them evenly at a temperature of 50°C and a rotation speed of 3000 r / min. Then add the defoamer, stir for 15 minutes, and let it stand for 2.5 hours to obtain an environmentally friendly water-based adhesive.

[0037] The preparation method of the modified polyurethane matrix is ​​different from that of Example 1 in that no soft segment monomer is added, and the rest are the same.

[0038] Comparative Example 2 An environmentally friendly water-based adhesive comprising the following components, calculated by weight: 66 parts of a modified polyurethane matrix, 3 parts of BYK-349, 0.3 parts of AFE-7610, 0.2 parts of methyl cellulose, 0.4 parts of a photoinitiator 1173, and 35 parts of deionized water; The preparation method of the environmentally friendly water-based adhesive comprises the following steps: Step 1: Prepare all raw materials according to mass proportion; Step 2: Add the modified polyurethane matrix to deionized water, then add BYK-349, AFE-7610, methyl cellulose, and photoinitiator 1173, and disperse them evenly at a temperature of 50°C and a rotation speed of 3000 r / min. Then add the defoamer, stir for 15 minutes, and let it stand for 2.5 hours to obtain an environmentally friendly water-based adhesive.

[0039] The preparation method of the modified polyurethane matrix is ​​different from that of Example 1 in that no modifying monomer is added, and the rest are the same.

[0040] Comparative Example 3 An environmentally friendly water-based adhesive, comprising the following components, calculated by weight: 66 parts of water-based polyurethane, 3 parts of BYK-349, 0.3 parts of AFE-7610, 0.2 parts of methyl cellulose, 0.4 parts of photoinitiator 1173, and 35 parts of deionized water; The preparation method of the environmentally friendly water-based adhesive comprises the following steps: Step 1: Prepare all raw materials according to mass proportion; Step 2: Add water-based polyurethane to deionized water, then add BYK-349, AFE-7610, methyl cellulose, and photoinitiator 1173, and disperse them evenly at a temperature of 50°C and a rotation speed of 3000 r / min. Then add defoamer, stir for 15 minutes, and let it stand for 2.5 hours to obtain an environmentally friendly water-based adhesive.

[0041] Among them, water-based polyurethane was purchased from Shanghai MacLean Biochemical Technology Co., Ltd. with product number A909856.

[0042] Test Example The prepared water-based adhesive in Example 1-Example 3 and Comparative Example 1-Comparative Example 3 was stirred uniformly, and then uniformly coated on the surface of a clean PP substrate, with single-sided brushing, a coating amount of 2 g / cm 2 A test sample was made, and placed in an oven at 120°C, while using a 100W, 365nm wavelength ultraviolet lamp to irradiate it, until it was completely cured, and the required time was recorded. The evaluation standard for complete curing was that using a fingernail to scratch the cured product, there was no trace at all; According to the national standard GB / T 2791-1995 (Adhesive T-peel strength test method flexible material against flexible material), a sample was prepared, and the "T" peel strength was tested; another test sample of the same batch and same specification was taken out after being placed in an environment at a temperature of 85°C for 10 days, and after natural cooling, the peel strength was tested again, to evaluate the high temperature resistance of the adhesive; the test results are shown in the following table: According to the analysis of the test data, the adhesive prepared in Example 1-Example 3 has good bonding performance and faster curing speed, and good high temperature resistance, because the adhesive prepared in Example 1-Example 3 has soft segment monomers and modified monomers; Comparative Example 2 contains soft segment monomers, so its high temperature resistance is stronger than that of Comparative Example 1 and Comparative Example 3; Comparative Example 1 contains modified monomers, so its curing characteristics and bonding strength are stronger than those of Comparative Example 2 and Comparative Example 3; Comparative Example 3 does not have soft segment monomers and modified monomers, so its high temperature resistance, bonding strength and curing characteristics are the worst.

[0043] The above content is only an example and description of the concept of the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace, as long as they do not deviate from the concept of the present application or exceed the scope defined by the present claims, and should belong to the protection scope of the present application.

Claims

1. An environmentally friendly water-based adhesive, characterized in that: Calculated by mass, it includes the following components: 65-75 parts of modified polyurethane matrix, 2-4 parts of wetting agent, 0.2-0.5 parts of defoaming agent, 0.1-0.5 parts of thickener, 0.3-0.6 parts of photoinitiator, 30-50 parts of deionized water.

2. The environmentally friendly water-based adhesive according to claim 1, characterized in that: The preparation method of the modified polyurethane matrix is ​​specifically as follows: Under nitrogen protection, add soft segment monomer, diphenylmethane diisocyanate and catalyst into the reactor, react at 80-85°C for 2-3h, then add modified monomer and continue to react for 6-7h. After the reaction is completed, the modified polyurethane matrix is ​​obtained.

3. The environmentally friendly water-based adhesive according to claim 2, characterized in that: The catalyst is any one of dibutyltin dilaurate, stannous octoate and dibutyltin diacetate.

4. The environmentally friendly water-based adhesive according to claim 2, characterized in that: The preparation method of the soft segment monomer comprises the following steps: S1: Under nitrogen protection, add hydroxyl-terminated polydimethylsiloxane, epichlorohydrin, and boron trifluoride ether complex to the reactor while stirring, then adjust the temperature to 50-65°C, react for 5-6 hours, and obtain an intermediate after the reaction is completed; S2: Under nitrogen protection, add the intermediate and 2-aminoethanesulfonic acid into the reactor, heat and react. After the reaction is completed, purify the mixture to obtain the soft segment monomer.

5. The environmentally friendly water-based adhesive according to claim 4, characterized in that: In step S1, the molar ratio of the hydroxyl-terminated polydimethylsiloxane to epichlorohydrin is 1:1-2; and the number average molecular weight of the hydroxyl-terminated polydimethylsiloxane is 2000.

6. The environmentally friendly water-based adhesive according to claim 4, characterized in that: In step S2, the reaction temperature is 70-75° C., and the reaction time is 5-6 h.

7. The environmentally friendly water-based adhesive according to claim 2, characterized in that: The preparation method of the modified monomer comprises the following steps: T1: Under nitrogen protection, phenol is added to the reactor, heated to melt the phenol, then the temperature is set to 50-55°C, potassium hydroxide aqueous solution is added, stirred, then formaldehyde solution is added, the temperature is raised to 62-65°C, and the reaction is carried out for 1-1.5 hours, potassium hydroxide aqueous solution is added again, the temperature is raised to 70-75°C, and the reaction is carried out for 30-45 minutes, and finally formaldehyde solution and polyvinyl alcohol are added, the temperature is raised to 86-90°C, and the reaction is carried out for 2.5-3 hours, and then the reaction solution is rapidly cooled and the unreacted matter is removed to obtain a water-soluble phenolic resin polymer; T2: Under nitrogen protection, add toluene, water-soluble phenolic resin polymer, and 3-isopropyl-dimethylbenzyl isocyanate into the reactor while stirring, then add dibutyltin dilaurate, set the temperature to 70-75°C, and react for 5-6 hours. After the reaction is completed, remove the unreacted materials and solvent, and obtain the modified monomer after purification.

8. The environmentally friendly water-based adhesive according to claim 6, characterized in that: In step T1, the mass fraction of the potassium hydroxide aqueous solution is 50-60%; the mass concentration of the formaldehyde solution is 37 g / 100 mL; and the number average molecular weight of the polyvinyl alcohol is 10,000-20,000.

9. The environmentally friendly water-based adhesive according to claim 1, characterized in that: The wetting agent is BYK-349 or TEGO-KL245; the defoaming agent is AFE-7610 or AFE-7820; the thickener is any one of methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl methyl cellulose; and the photoinitiator is any one of benzoin ethyl ether, benzoin dimethyl ether, and photoinitiator 1173.

10. A method for preparing the environmentally friendly water-based adhesive according to claim 1, characterized in that: The following steps are involved: Step 1: Prepare all raw materials according to mass proportions; Step 2: Add the modified polyurethane matrix into deionized water, then add the wetting agent, thickener, and photoinitiator, and disperse them evenly at a temperature of 40-60°C and a rotation speed of 2500-5000r / min. Then add the defoaming agent, stir for 10-30 minutes, and let it stand for 2-3 hours to obtain an environmentally friendly water-based adhesive.

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