A water-boiling self-detaching ultraviolet light curing adhesive as well as a preparation method and application thereof

Abstract

The application belongs to the field of ultraviolet light curing adhesive, and particularly relates to a water-boiling self-falling ultraviolet light curing adhesive as well as a preparation method and application thereof. The water-boiling self-falling ultraviolet light curing adhesive provided by the application comprises the following components in parts by weight: polyurethane acrylate resin 40-70 parts, active diluent 20-60 parts, polythiol 1-6 parts, expanding agent 2-5 parts, photoinitiator 1-5 parts, coupling agent 0.5-3 parts and thixotropic agent 1-5 parts. The key of the application lies in preparing specific polythiol, which can make the surface of the cured adhesive dry and non-sticky, and also can make the ultraviolet light curing adhesive extremely easy to absorb water during the water boiling process, and meanwhile, the adhesive layer can be quickly and effectively made to fail in bonding and automatically fall off by cooperating with the expanding agent.

Description

Technical Field

[0001] This invention belongs to the field of ultraviolet curable adhesives, specifically relating to a water-boiling self-removing ultraviolet curable adhesive, its preparation method, and its application. Background Technology

[0002] In today's internet age, mobile devices such as laptops, tablets, and mobile phones are developing at an increasingly rapid pace. The aluminum materials widely used in the casings and keyboard frames of laptops, as well as the casings of tablets and mobile phones, require anodizing treatment. The principle of anodizing is to use aluminum or aluminum alloy products as the anode, placing them in an electrolyte solution and passing an electric current through them. This electrolysis causes a thin film of aluminum oxide to form on the surface, a process known as anodizing of aluminum and aluminum alloys. After anodizing, an oxide film ranging from a few micrometers to hundreds of micrometers can be formed on the aluminum surface. Compared to the natural oxide film of aluminum alloys, its corrosion resistance, wear resistance, and decorative properties are significantly improved.

[0003] During the anodizing process, the screw holes and tapped structures of aluminum parts need to be temporarily protected to prevent the anodizing solution from corroding these structures and causing dimensional deviations. At the same time, some special areas on the aluminum surface that do not require anodizing also need to be temporarily protected.

[0004] Currently, UV-curable adhesives used for temporary protection during the anodizing of aluminum parts rely primarily on manual removal for subsequent peeling. This method is inefficient, labor-intensive, and prone to breakage within screw holes during removal, hindering yield. This inefficient approach increasingly fails to meet the rapid and efficient production demands of the electronics industry. Furthermore, UV-curable adhesives exhibit oxygen inhibition on the adhesive surface during curing, resulting in a curing underlayer while the surface remains sticky or even dry, negatively impacting subsequent processing.

[0005] Therefore, there is an urgent need to design a temporary protective adhesive that leaves the cured adhesive surface dry and easy to peel off, enabling rapid adhesive removal, improving the efficiency and yield of the entire process, and reducing costs. Summary of the Invention

[0006] One of the objectives of this invention is to address the problems of high labor costs, low efficiency, and low yield associated with the current UV-curable adhesives used for temporary protection during aluminum anodizing, which leave the adhesive surface sticky after curing and require manual removal. This invention proposes a water-cooking self-removing UV-curable adhesive that ensures a dry, non-sticky surface after curing, without affecting subsequent anodizing processes. Furthermore, it allows for rapid and thorough removal of the adhesive under boiling conditions at 90-100°C, effectively improving production efficiency and reducing labor costs.

[0007] Specifically, the water-boiling self-removing UV-curable adhesive provided by the present invention comprises the following components in parts by weight: 40-70 parts of polyurethane acrylate resin, 20-60 parts of reactive diluent, 1-6 parts of polythiol, 2-5 parts of expanding agent, 1-5 parts of photoinitiator, 0.5-3 parts of coupling agent, and 1-5 parts of thixotropic agent; the structure of the polythiol is shown in formula (1);

[0008]

[0009] In formula (1), R1 is a group derived from a hydrophilic oligomeric diol and whose side chain includes at least one hydroxyl group, and R2 is a substituted or unsubstituted C1-C2 group. 12 Alkylene, substituted or unsubstituted C6-C 30 aryl, substituted or unsubstituted C6-C 30 arylene alkyl, substituted or unsubstituted C6-C 30 alkylaryl, R3 is a group derived from polythiol compounds, and n is an integer from 1 to 10.

[0010] The second objective of this invention is to provide a method for preparing the above-mentioned water-cooking self-removing UV-curable adhesive. The method includes mixing and stirring polyurethane acrylate resin, reactive diluent, polythiol, expanding agent, photoinitiator, coupling agent and thixotropic agent evenly, and then discharging the mixture in the dark to obtain the water-cooking self-removing UV-curable adhesive.

[0011] The third objective of this invention is to provide the application of the above-mentioned water-boiling self-removing UV-curable adhesive in the surface anodizing treatment of aluminum.

[0012] The key to this invention lies in the synergistic combination of polyurethane acrylic resin, reactive diluent, specific polythiol, expanding agent, photoinitiator, coupling agent, and thixotropic agent in specific amounts to form a UV-curable adhesive. The resulting UV-curable adhesive, through the specific combination of polythiol and expanding agent, enables the adhesive layer to rapidly detach under boiling conditions at 90-100°C. Furthermore, during UV curing, oxygen inhibition occurs on the adhesive surface. This inhibition is primarily due to the formation of peroxy radicals from free radicals and oxygen in the system, leading to a slower photocuring reaction on the colloid surface, resulting in low molecular weight and low modulus. Macroscopically, this manifests as a sticky, non-drying surface. However, the active hydrogen in the polythiol can react with the peroxy radicals, and the resulting hydrogen-free polythiol forms new free radicals that continue to participate in the curing addition reaction, increasing the molecular weight and making the cured adhesive surface essentially non-sticky, or even dry. Therefore, the water-boiling self-detaching UV-curing adhesive provided by the present invention not only makes the surface of the adhesive dry and non-sticky after curing, but also causes the adhesive layer to fail under boiling conditions and fall off quickly, reducing labor costs and improving production efficiency. Furthermore, the preparation process of the water-boiling self-detaching UV-curing adhesive provided by the present invention is simple and suitable for industrial production. Detailed Implementation

[0013] The water-repellent, self-removing, UV-curable adhesive provided by this invention comprises polyurethane acrylate resin, reactive diluent, polythiol, expanding agent, photoinitiator, coupling agent, and thixotropic agent. The polyurethane acrylate resin content is 40-70 parts by weight, such as 40, 42, 45, 48, 50, 52, 55, 58, 60, 62, 65, 68, or 70 parts by weight, or any value between them; the polythiol content is 1-6 parts by weight, such as 1, 2, 3, 4, 5, or 6 parts by weight, or any value between them; the diluent content is 20-60 parts by weight, such as 20, 25, 30, 35, 40, 45, 50, 55, or 60 parts by weight, or any value between them. The content of the expanding agent is 2 to 5 parts by weight, such as 2, 3, 4, 5 parts by weight or any value between them; the content of the photoinitiator is 1 to 5 parts by weight, such as 1, 2, 3, 4, 5 parts by weight or any value between them; the content of the coupling agent is 0.5 to 3 parts by weight, such as 0.5, 0.8, 1, 1.5, 2, 2.5, 3 or any value between them; the content of the thixotropic agent is 1 to 5 parts by weight, such as 1, 2, 3, 4, 5 parts by weight or any value between them.

[0014] In a preferred embodiment, the polythiol has the structure shown in formula (1);

[0015]

[0016] In formula (1), R1 is a group derived from a hydrophilic oligomeric diol and whose side chain includes at least one hydroxyl group, and R2 is a substituted or unsubstituted C1-C2 group. 12 Alkylene, substituted or unsubstituted C6-C 30 aryl, substituted or unsubstituted C6-C 30 arylene alkyl, substituted or unsubstituted C6-C 30 The compound is an alkylene aryl group, where R3 is a group derived from polythiol compounds, and n is an integer from 1 to 10. The C1 to C2 groups are... 12 The alkylene group can be at least one selected from methylene, ethylene, n-propylene, isopropylene, n-butylene, secondary butylene, isobutylene, tert-butylene, n-pentylene, isopentylene, tert-pentylene, neopentylene, n-hexylene, n-heptylene, n-octylene, n-nonylene, n-decylene, and n-dodecylene. The C6-C... 30 The arylene group can be at least one selected from phenylene, biphenylene, bitolylene, and naphthylene. The C6-C6 group... 30 The arylene alkyl group can be tolyl. The C6-C6 group... 30 The alkylene aryl group can be phenylene dimethyl and / or phenylene methyl. n is an integer from 1 to 10, such as 1, 2, 4, 6, 8, 10, etc.

[0017] In a preferred embodiment, the polythiol is prepared by a method comprising the following steps:

[0018] S1. A hydrophilic oligomer diol and a polyisocyanate are subjected to an addition reaction to obtain a prepolymer with isocyanate double-terminated ends;

[0019] S2. The isocyanate-double-terminated prepolymer is subjected to a termination reaction with a polythiol compound to obtain polythiol.

[0020] In the preparation process of the above-mentioned polythiol, in step S1, the conditions for the addition reaction include a temperature preferably of 80 to 120°C, such as 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C or any value between them; and a time preferably of 1 to 5 hours, such as 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours or any value between them.

[0021] In the preparation process of the above-mentioned polythiol, in step S2, the conditions of the end-capping reaction include a temperature preferably of 30 to 60°C, such as 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C or any value between them; and a time preferably of 2 to 10 hours, such as 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours or any value between them.

[0022] In the preparation of the aforementioned polythiols, isocyanates are sensitive to moisture. Therefore, to ensure the smooth reaction of polyisocyanates with hydrophilic oligomer diols and polythiols, the reaction vessel and reactants need to be dehydrated before the reaction is initiated, and the reaction should be carried out under an inert atmosphere. Specifically, the reaction vessel can be dehydrated by drying it at 130–150°C for 2–4 hours. The reactants can be dehydrated using methods such as heating and vacuuming, freeze-drying, molecular sieve dehydration, and glove box ventilation. The polymerization reaction is carried out under an inert atmosphere by introducing a chemical inert gas into the reaction vessel, evacuating the vessel, and filling it with an inert gas to maintain the reaction system under this atmosphere. Specifically, the chemical inert gas can be nitrogen or argon, preferably nitrogen.

[0023] In one specific embodiment, the preparation method of the above-mentioned polythiol can be as follows: heating a hydrophilic oligomeric diol to 100-130°C and dehydrating it under vacuum for 0.5-2 hours, cooling it to 80-120°C, adding the dehydrated diisocyanate, and stirring the reaction under an inert gas atmosphere for 1-5 hours; continuing to add the dehydrated polythiol and initiator, and stirring the reaction under 30-60°C for 2-10 hours, and terminating the reaction by controlling the thiol content at 5-20 wt%.

[0024] In the preparation process of the above-mentioned polythiol, the content of thiol groups is determined according to the test method provided in CN201711190623.X. That is, after dissolving the sample in acetonitrile solvent, an iodine-ethanol solution containing the same mass as the sample to be tested and a KI aqueous solution containing twice the mass of the sample are added to react with the thiol groups. Finally, the remaining iodine is determined with a sodium thiosulfate standard solution, thereby determining the content of thiol groups.

[0025] In a preferred embodiment, the molar ratio of the hydrophilic oligomeric diol, polyisocyanate, and polythiol compound is 1:(1.1–1.5):(0.5–1.0). Based on 1 mol of the hydrophilic oligomeric diol, the amount of the polyisocyanate is 1.1–1.5 mol, such as 1.1 mol, 1.2 mol, 1.3 mol, 1.4 mol, 1.5 mol, or any value between therewith; the amount of the polythiol compound is 0.5–1.0 mol, such as 0.5 mol, 0.6 mol, 0.7 mol, 0.8 mol, 0.9 mol, 1.0 mol, or any value between therewith.

[0026] In a preferred embodiment, the initiator is added in an amount of 0.1 to 0.25 wt% of the total mass of the reactants, such as 0.1 wt%, 0.12 wt%, 0.15 wt%, 0.18 wt%, 0.20 wt%, 0.22 wt%, 0.25 wt%, or any value between therewith. The reactants include hydrophilic oligomeric diols, polyisocyanates, and polythiols.

[0027] In a preferred embodiment, the polyisocyanate is a compound with two or more isocyanate groups at the molecular chain terminal, and its specific structure is shown in formula (5), wherein R is a substituted or unsubstituted C1-C1 group. 12 Alkylene, substituted or unsubstituted C6-C 30 aryl, substituted or unsubstituted C6-C 30 arylene alkyl, substituted or unsubstituted C6-C 30 alkylene aryl. Specifically, the C1-C1... 12 The alkylene group can be at least one selected from methylene, ethylene, n-propylene, isopropylene, n-butylene, secondary butylene, isobutylene, tert-butylene, n-pentylene, isopentylene, tert-pentylene, neopentylene, n-hexylene, n-heptylene, n-octylene, n-nonylene, n-decylene, and n-dodecylene. The C6-C... 30 The arylene group can be at least one selected from phenylene, biphenylene, bitolyl, and naphthylene. The C6-C6 group... 30 The arylene alkyl group can be tolyl. The C6-C6 group... 30 The alkylene aryl group can be diphenylenemethyl and / or diphenylenemethyl. From the perspective of readily available raw materials, the polyisocyanate is selected from at least one of toluene diisocyanate, norbornene diisocyanate, isophorone diisocyanate, isophenylene diisocyanate, 4,4-dicyclohexylmethane diisocyanate, pentamethylene diisocyanate, and hexamethylene diisocyanate, preferably at least one of isophorone diisocyanate, hexamethylene diisocyanate, and 4,4-dicyclohexylmethane diisocyanate.

[0028] NCO-R-NCO formula (5)

[0029] In a preferred embodiment, the polythiol compound is a trifunctional and / or tetrafunctional polythiol, specifically selected from at least one of trimethylolpropane tris(3-mercaptoacetic acid), trimethylolpropane tris(3-mercaptopropionate), trimethylolpropane tris(3-mercaptobutyrate), pentaerythritol tetra(mercaptoacetic acid), pentaerythritol tetra(3-mercaptopropionic acid), and pentaerythritol tetra(3-mercaptobutyrate).

[0030] In a preferred embodiment, the initiator is selected from at least one of dibutyltin dichloride, dibutyltin dilaurate, butyltin oxide, and dioctyltin dilaurate.

[0031] In a preferred embodiment, the hydrophilic oligomer diol has the structure shown in formula (2):

[0032]

[0033] In formula (2), R4 is a C1-C6 alkylene group with at least one hydroxyl group in its side chain, R5 is a C1-C6 alkylene group, and m is an integer from 1 to 25. Specific examples of the C1-C6 alkylene group include, but are not limited to, at least one of methylene, ethylene, n-propylene, isopropylene, n-butylene, isobutylene, tert-butylene, n-pentylene, isopentylene, tert-pentylene, neopentylene, and n-hexylene. m is an integer from 1 to 25, such as 1, 5, 10, 15, 20, 25, or any value between them.

[0034] In a preferred embodiment, the hydrophilic oligomeric diol has a hydroxyl value of 86–180 mg KOH / g, such as 86 mg KOH / g, 90 mg KOH / g, 100 mg KOH / g, 110 mg KOH / g, 120 mg KOH / g, 130 mg KOH / g, 140 mg KOH / g, 150 mg KOH / g, 160 mg KOH / g, 170 mg KOH / g, 180 mg KOH / g, or any value between them.

[0035] In a preferred embodiment, the hydrophilic oligomeric diol has a molecular weight of 500–3000 g / mol, such as 500 g / mol, 800 g / mol, 1000 g / mol, 1200 g / mol, 1500 g / mol, 1800 g / mol, 2000 g / mol, 2500 g / mol, 3000 g / mol, or any value between them.

[0036] In a preferred embodiment, the hydrophilic oligomer diol is obtained by polycondensation of a dicarboxylic acid having the structure shown in formula (3) and a diol having the structure shown in formula (4) in the presence of a catalyst.

[0037] HO-R5-OH Formula (4)

[0038] In formula (3), R4 is a C1 to C6 alkylene group and the side chain includes at least one hydroxyl group;

[0039] In formula (4), R5 is a C1 to C6 alkylene group;

[0040] In formulas (3) and (4), specific examples of the C1 to C6 alkylene groups include, but are not limited to, at least one of methylene, ethylene, n-propylene, isopropylene, n-butylene, isobutylene, tert-butylene, n-pentylene, isopentylene, tert-pentylene, neopentylene, and n-hexylene.

[0041] In a preferred embodiment, the molar ratio of the diacid to the diol is 1:(1.8 to 2.1). The amount of the diol is 1.8 to 2.1 mol, such as 1.8 mol, 1.9 mol, 2.0 mol, 2.1 mol, or any value between them, based on 1 mol of the diacid.

[0042] In a preferred embodiment, the catalyst is added in an amount of 0.2 to 1 wt% of the total mass of the dicarboxylic acid and diol, such as 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, or any value between them.

[0043] In a preferred embodiment, the preparation method of the hydrophilic oligomeric diol specifically involves heating a diacid, a portion of the diol, and a catalyst to 60–80°C under inert gas protection, stirring the reaction for 1–5 hours, and controlling the top temperature of the condenser to be below 100°C during the heating process; during this period, the reaction system is evacuated for approximately 5–10 minutes every 0.5 hours to remove small molecule byproducts, allowing the reaction to reach equilibrium until the weight of the reaction system no longer changes significantly (the mass of the extracted small molecules essentially no longer increases); the remaining diol is added and stirring is continued for 0.5–2 hours, then the temperature is raised to 130–180°C and evacuated to a vacuum degree of not less than 0.095 MPa, and the reaction is continued for 0.5–1 hour. The hydroxyl value is tested to reach 86–180 mg KOH / g, thus obtaining the hydrophilic oligomeric diol. The molar ratio of the diacid to a portion of the diol can be 1:1.5; the molar ratio of the diacid to the remaining diol can be 1:(0.3 to 0.6), such as 1:0.3, 1:0.4, 1:0.5, 1:0.6 or any value between them.

[0044] In a preferred embodiment, the dicarboxylic acid is a compound with carboxyl groups at both ends of its molecular chain and at least one hydroxyl group on its side chain, as shown in formula (3), wherein R4 is a C1-C6 alkylene group and the side chain includes at least one hydroxyl group. Specifically, specific examples of the C1-C6 alkylene group include, but are not limited to, at least one of the following: methylene, ethylene, n-propylene, isopropylene, n-butylene, isobutylene, tert-butylene, n-pentylene, isopentylene, tert-pentylene, neopentylene, and n-hexylene. From the perspective of readily available raw materials, the dicarboxylic acid is selected from at least one of tartaric acid, tartaric acid, 2-hydroxysuccinic acid, 3-hydroxyglutaric acid, 2-hydroxyhexanoic acid, and 3-hydroxyoctanoic acid.

[0045]

[0046] In a preferred embodiment, the diol is selected from at least one of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentanediol, and 1,6-hexanediol.

[0047] In a preferred embodiment, the catalyst is selected from at least one of sodium bisulfate, p-toluenesulfonic acid, concentrated sulfuric acid, and concentrated hydrochloric acid.

[0048] In a preferred embodiment, the polyurethane acrylate is a difunctional aliphatic polyurethane acrylate. The viscosity of the polyurethane acrylate at 25°C is 20,000–80,000 cps, preferably 25,000–65,000 cps, such as 25,000 cps, 30,000 cps, 40,000 cps, 45,000 cps, 50,000 cps, 55,000 cps, 60,000 cps, 65,000 cps, or any value between them. Specifically, the polyurethane acrylate is selected from at least one of UV-3000B, UV-30008, UV-32008, UV-3520TL, U600, U603, 230TH, Trust 7200, Trust 7205, Trust 7080, Trust 7060, Trust 7050, 7296-1, 7221, 7230B and 7206.

[0049] In a preferred embodiment, the reactive diluent is a monofunctional acrylate monomer, specifically selected from at least one of tetrahydrofuran (meth)acrylate, isobornyl (meth)acrylate, butyl acrylate, isooctyl acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, dicyclopentadiene acrylate, bisphenol A di(meth)acrylate, lauryl acrylate, lauryl methacrylate, 2-phenoxyethyl acrylate, isodecyl acrylate, N,N-dimethylacrylamide, and 4-acryloylmorpholine.

[0050] In a preferred embodiment, the expanding agent is selected from at least one of ettringite, alunite, and anhydrous gypsum.

[0051] In a preferred embodiment, the photoinitiator is selected from at least one of Irgacure 1173, Irgacure 184, Irgacure 651, Irgacure 819, Irgacure 907 and TPO.

[0052] In a preferred embodiment, the coupling agent is selected from at least one of methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, γ-mercaptopropyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, and bis(γ-triethoxysilylpropyl)-tetrasulfide.

[0053] In a preferred embodiment, the thixotropic agent is fumed silica, specifically selected from at least one of H8, H20, H30, TS-530, TS720, R972, R974, R976, R202 and R8200.

[0054] This invention also provides a method for preparing the above-mentioned water-curable self-removing UV-curable adhesive. The method includes mixing and stirring polyurethane acrylate resin, reactive diluent, polythiol, expanding agent, photoinitiator, coupling agent, and thixotropic agent until homogeneous, then discharging the mixture in the dark to obtain the water-curable self-removing UV-curable adhesive. In one specific embodiment, the method includes the following steps: weighing appropriate weights of polyurethane acrylate resin, reactive diluent, polythiol, photoinitiator, and coupling agent and sequentially adding them to a dual planetary hybrid reactor, stirring for 1–3 hours; after homogeneous stirring, weighing appropriate weights of expanding agent and thixotropic agent and adding them to the reactor, stirring for 0.5–1.5 hours, performing wall scraping treatment, continuing stirring for another 0.5–1.5 hours, then vacuum degassing, discharging, and sealing for packaging. Furthermore, in the preparation process of the above-mentioned water-curable self-removing UV-curable adhesive, especially during the stirring process, it is crucial to strictly avoid white light.

[0055] The present invention also provides the application of the above-mentioned water-boiling self-removing UV-curable adhesive in the surface anodizing treatment of aluminum.

[0056] The present invention will be described in detail below through specific embodiments.

[0057] In the following examples and comparative examples, the parts of raw materials refer to parts by weight.

[0058] Preparation Example 1: Preparation of hydrophilic oligomer diols

[0059] A four-necked flask equipped with a magnetic stirrer, thermometer, N2 inlet pipe, and air-cooled condenser was placed in a covered resistance heater. 120.1 g (0.8 mol) tartaric acid, 125 g (1.2 mol) neopentyl glycol, and 1 g concentrated sulfuric acid were added and stirred for 2 hours under nitrogen protection. The temperature of the flask was controlled at 70 °C for the dehydration and polycondensation reaction. During the heating process, the temperature of the top of the condenser was controlled to be below 100 °C. During this period, the reaction system was evacuated for about 5 minutes every 0.5 hours to remove small molecule byproducts. The reaction was allowed to reach equilibrium until there was no significant change in the weight of the reaction system. 41.6 g (0.4 mol) neopentyl glycol was added and the reaction was continued for 1 hour. The temperature was then gradually increased to 150 °C and the vacuum degree was ≥0.095 MPa. The reaction was continued until the hydroxyl value reached 112 mg KOH / g, and a hydrophilic oligomeric diol with a molecular weight of 1000 g / mol was obtained, denoted as A.

[0060] Preparation Example 2: Preparation of Polythiol

[0061] 200 g (0.2 mol) of hydrophilic oligomeric diol A was added to a three-necked flask equipped with a stirrer, heated to 120 °C and dehydrated under vacuum for 1 h, then cooled to 90 °C. 50.4 g (0.3 mol) of hexamethylene diisocyanate was added in two separate additions, and the mixture was stirred for 2 h under an inert gas atmosphere. Then, 79.7 g (0.2 mol) of trimethylolpropane tris(3-mercaptopropionate) and 0.35 g (0.11 wt%) of dibutyltin dichloride catalyst were added, and the mixture was reacted at 40 °C for 3.5 h. The reaction was terminated when the thiol content was found to be around 15%, yielding a viscous liquid, which is polythiol, denoted as A-1.

[0062] Preparation Example 3: Preparation of Polythiol

[0063] 240 g (0.24 mol) of hydrophilic oligomeric diol A was added to a three-necked flask equipped with a stirrer, heated to 130 °C and dehydrated under vacuum for 0.6 h, then cooled to 110 °C, and 78.6 g (0.30 mol) of dicyclohexylmethane-4,4-diisocyanate was added. The mixture was stirred for 3 h under an inert gas atmosphere. Then, 73.4 g (0.15 mol) of pentaerythritol tetrakis(3-mercaptopropionic acid) and 0.59 g (0.15 wt%) of dibutyltin dichloride catalyst were added, and the mixture was reacted at 50 °C for 4 h. The mercapto content was measured to be around 17%, and the reaction was terminated to obtain a viscous liquid, which is polythiol, denoted as A-2.

[0064] Preparation Example 4: Preparation of Polythiol

[0065] 240 g (0.24 mol) of hydrophilic oligomeric diol A was added to a three-necked flask equipped with a stirrer. The mixture was heated to 120 °C and dehydrated under vacuum for 1 h. After cooling to 100 °C, 71.14 g (0.32 mol) of isophorone diisocyanate was added, and the mixture was stirred for 3.5 h under an inert gas atmosphere. Then, 79.7 g (0.2 mol) of trimethylolpropane tris(3-mercaptopropionate) and 0.98 g (0.25 wt%) of dibutyltin dilaurate catalyst were added, and the mixture was reacted at 45 °C for 4 h. The mercapto content was measured to be around 13%, and the reaction was terminated to obtain a viscous liquid, which is polythiol, denoted as A-3.

[0066] Example 1: Preparation of a water-boiling self-removing UV-curable adhesive

[0067] 45 parts of difunctional aliphatic polyurethane acrylate UV-3000B (purchased from Arkema, France, the same below), 32 parts of dicyclopentadienyl acrylate, 10 parts of hydroxyethyl methacrylate, 3.5 parts of polythiol A-1, 3 parts of photoinitiator Irgacure 1173, 1 part of photoinitiator TPO, and 1 part of γ-aminopropyltriethoxysilane were sequentially added to a dual planetary hybrid reactor and stirred for 2 hours. Then, 3 parts of calcium vanadate and 1.5 parts of fumed silica R202 were added and stirred for 1 hour. After wall scraping, stirring was continued for 1 hour. After vacuum degassing, the product was discharged, and the water-removing UV-curable adhesive was obtained, denoted as A1.

[0068] Example 2: Preparation of a water-boiling self-removing UV-curable adhesive

[0069] 42 parts of difunctional aliphatic polyurethane acrylate U603 (purchased from DSM, Netherlands), 30 parts of lauryl methacrylate, 13 parts of N,N-dimethylacrylamide, 5 parts of polythiol A-2, 3 parts of photoinitiator Irgacure 184, 1 part of photoinitiator TPO, and 1 part of γ-aminopropyltriethoxysilane were sequentially added to a double planetary hybrid reactor and stirred for 1.5 h. Then, 4 parts of calcium vanadium stone and 3 parts of fumed silica H30 were added and stirred for 1 h. After wall scraping, stirring was continued for 1 h. After vacuum degassing, the product was discharged, and the self-removing UV-curable adhesive was obtained, denoted as A2.

[0070] Example 3: Preparation of a water-boiling self-removing UV-curable adhesive

[0071] 45 parts of difunctional aliphatic polyurethane acrylate Trust 7080 (purchased from Shenzhen Youyang Technology Co., Ltd.), 36 parts of bisphenol A di(meth)acrylate, 5 parts of isobornyl methacrylate, 4 parts of polythiol A-3, 3 parts of photoinitiator Irgacure 651, 1 part of photoinitiator TPO, and 1 part of γ-mercaptopropyltriethoxysilane were sequentially added to a double planetary hybrid reactor and stirred for 2 hours. Then, 3 parts of calcium vanadium stone and 2 parts of fumed silica H2O were added and stirred for 1 hour. After wall scraping, stirring was continued for 1 hour. After vacuum degassing, the product was discharged, and the self-removing UV-curable adhesive was obtained, denoted as A3.

[0072] Example 4: Preparation of a water-boiling self-removing UV-curable adhesive

[0073] 55 parts of difunctional aliphatic polyurethane acrylate UV-3000B, 50 parts of dicyclopentadienyl acrylate, 10 parts of hydroxyethyl methacrylate, 6 parts of polythiol A-1, 3 parts of photoinitiator Irgacure 1173, 1 part of photoinitiator TPO, and 1 part of γ-aminopropyltriethoxysilane were sequentially added to a dual planetary hybrid reactor and stirred for 2 hours. Then, 3 parts of calcium vanadate and 1.5 parts of fumed silica R202 were added and stirred for 1 hour. After wall scraping, stirring was continued for 1 hour. The mixture was then degassed under vacuum and discharged to obtain a water-removable, self-removing UV-curable adhesive, denoted as A4.

[0074] Example 5: Preparation of a water-boiling self-removing UV-curable adhesive

[0075] 70 parts of difunctional aliphatic polyurethane acrylate Trust 7080, 15 parts of bisphenol A di(meth)acrylate, 5 parts of isobornyl methacrylate, 1 part of polythiol A-3, 3 parts of photoinitiator Irgacure 651, 1 part of photoinitiator TPO, and 1 part of γ-mercaptopropyltriethoxysilane were sequentially added to a dual planetary hybrid reactor and stirred for 2 hours. Then, 5 parts of calcium vanadium stone and 2 parts of fumed silica H2O were added and stirred for 1 hour. After wall scraping, stirring was continued for 1 hour. The mixture was then degassed under vacuum and discharged to obtain a water-removable, UV-curable adhesive, denoted as A5.

[0076] Comparative Example 1: Preparation of Reference UV-Curable Adhesive

[0077] A reference UV-curable adhesive was prepared according to the method of Example 1, except that polythiol A-1 was replaced with the same amount of difunctional aliphatic polyurethane acrylate UV-3000B, and the other conditions were the same as in Example 1. This adhesive is denoted as DA1.

[0078] Comparative Example 2: Preparation of Reference UV-Curable Adhesive

[0079] A reference UV-curable adhesive was prepared according to the method of Example 2, except that polythiol A-2 was replaced with the same amount of difunctional aliphatic polyurethane acrylate U603, and the other conditions were the same as in Example 2. This adhesive was denoted as DA2.

[0080] Preparation of the reference UV-curable adhesive in Comparative Example 3

[0081] A reference UV-curable adhesive was prepared according to the method of Example 3, except that polythiol A-3 was replaced by the same weight of a difunctional aliphatic polyurethane acrylate, brand name Trust 7080, and the other conditions were the same as in Example 3, denoted as DA3.

[0082] Preparation of the reference UV-curable adhesive in Comparative Example 4

[0083] A reference UV-curable adhesive was prepared according to the method of Example 1, except that polythiol A-1 was replaced with the same amount of trimethylolpropane tris(3-mercaptopropionate) by weight, and the other conditions were the same as in Example 1. This adhesive is denoted as DA4.

[0084] Preparation of the reference UV-curable adhesive (Comparative Example 5)

[0085] A reference UV-curable adhesive was prepared according to the method of Example 1, except that calcium vanadate was replaced with the same amount of fumed silica R202 by weight, and the other conditions were the same as in Example 1. This adhesive is denoted as DA5.

[0086] Test case

[0087] (1) Curing conditions: Ultraviolet light curing was performed using an LED lamp with a wavelength of 365nm, and the radiation intensity was 3000mj / cm². 2 .

[0088] (2) Shear strength test: The shear strength of anodized aluminum bonded to tempered glass was tested according to the method in GB7124-86 "Determination of Tensile Shear Strength of Adhesives (Metal-Metal)". During sample preparation, a 365nm wavelength LED lamp was used for ultraviolet curing, with a radiation intensity of 3000 mJ / cm². 2 The results are shown in Table 1.

[0089] (3) Water absorption rate: The water absorption rate was tested according to the method in GB / T1034-2008 "Determination of Water Absorption of Plastics". The cured adhesive was made into a square sample of 60mm×60mm×1mm. During the sample preparation process, a 365nm wavelength LED lamp was used for ultraviolet curing, and the radiation intensity was 3000mj / cm. 2 The water absorption of the test sample after immersion in water at 90℃ for 1 hour was measured, and the water absorption mass fraction (%) was recorded. The results are shown in Table 1.

[0090] (4) Adhesive peeling time test: The UV-curable adhesives obtained in the above embodiments and the reference UV-curable adhesives obtained in the comparative examples were applied to the surface of the anode aluminum samples, and then UV-cured using a 365nm wavelength LED lamp with a radiation intensity of 3000mj / cm². 2 To allow the adhesive to fully cure, the sample was then placed in hot water at 90–100°C, and the time from immersion in the hot water to the automatic detachment of the adhesive from the anode aluminum part was calculated. The results are shown in Table 1.

[0091] (5) Surface drying condition: A 0.2mm layer of adhesive was applied to the glass slide, and ultraviolet light curing was performed using a 365nm wavelength LED lamp with a radiation intensity of 3000mj / cm². 2 After curing, touch the surface of the glue with a cotton swab and check if the surface sticks to the cotton swab to determine the degree of surface drying.

[0092] Table 1

[0093]

[0094]

[0095] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A water-boiling self-removing UV-curing adhesive, characterized in that, The water-removable, UV-curable adhesive comprises the following components by weight: 40-70 parts polyurethane acrylate resin, 20-60 parts reactive diluent, 1-6 parts polythiol, 2-5 parts expanding agent, 1-5 parts photoinitiator, 0.5-3 parts coupling agent, and 1-5 parts thixotropic agent; the structure of the polythiol is shown in formula (1). Equation (1) In formula (1), R1 is a group derived from a hydrophilic oligomeric diol and whose side chain includes at least one hydroxyl group, and R2 is a substituted or unsubstituted C1~C2 group. 12 Alkylene, substituted or unsubstituted C6~C 30 aryl, substituted or unsubstituted C6~C 30 arylene alkyl, substituted or unsubstituted C6~C 30 alkylene aryl, R3 is a group derived from polythiol compounds, and n is an integer from 1 to 10; The hydrophilic oligomer diol has the structure shown in formula (2): Equation (2) In formula (2), R4 is a C1~C6 alkylene group and the side chain includes at least one hydroxyl group, R5 is a C1~C6 alkylene group, and m is an integer from 1 to 25.

2. The water-boiling self-removing UV-curing adhesive according to claim 1, characterized in that, The polythiol is prepared by a method comprising the following steps: S1. A hydrophilic oligomer diol and a polyisocyanate are subjected to an addition reaction to obtain a prepolymer with isocyanate double-terminated ends; S2. The isocyanate-double-terminated prepolymer is reacted with a polythiol compound in the presence of an initiator to obtain polythiol.

3. The water-boiling self-removing UV-curing adhesive according to claim 2, characterized in that, The molar ratio of the hydrophilic oligomeric diol, polyisocyanate, and polythiol compound is 1:(1.1~1.5):(0.5~1.0); the amount of the initiator added is 0.1~0.25wt% of the total mass of the reaction raw materials; and the thiol content of the polythiol is 5~20wt%.

4. The water-boiling self-removing UV-curing adhesive according to claim 2, characterized in that, The hydrophilic oligomer diol has a hydroxyl value of 86~180 mg KOH / g and a number-average molecular weight of 500~3000 g / mol.

5. The water-boiling self-removing UV-curable adhesive according to claim 1, characterized in that, The hydrophilic oligomer diol is obtained by polycondensation reaction of a dicarboxylic acid having the structure shown in formula (3) and a diol having the structure shown in formula (4) in the presence of a catalyst. Equation (3), Equation (4) In formula (3), R4 is a C1~C6 alkylene group and the side chain includes at least one hydroxyl group; In formula (4), R5 is a C1~C6 alkylene group.

6. The water-boiling self-removing UV-curing adhesive according to claim 5, characterized in that, The molar ratio of the dicarboxylic acid to the diol is 1:(1.8~2.1).

7. The water-boiling self-removing UV-curing adhesive according to claim 5, characterized in that, The catalyst is added at a rate of 0.2 to 1 wt% of the total mass of the dicarboxylic acid and diol.

8. The water-boiling self-removing UV-curing adhesive according to claim 5, characterized in that, The dicarboxylic acid is selected from at least one of tartaric acid, tartaric acid, 2-hydroxysuccinic acid, 3-hydroxyglutaric acid, 2-hydroxyadipic acid, and 3-hydroxyoctanoic acid.

9. The water-boiling self-removing UV-curing adhesive according to claim 5, characterized in that, The diol is selected from at least one of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentanediol, and 1,6-hexanediol.

10. The water-boiling self-removing UV-curing adhesive according to claim 5, characterized in that, The catalyst is selected from at least one of sodium bisulfate, p-toluenesulfonic acid, concentrated sulfuric acid, and concentrated hydrochloric acid.

11. The water-boiling self-removing UV-curing adhesive according to claim 2, characterized in that, The polyisocyanate is selected from at least one of toluene diisocyanate, norbornene diisocyanate, isophorone diisocyanate, isophenyl dimethyl diisocyanate, 4,4-dicyclohexylmethane diisocyanate, pentamethylene diisocyanate, and hexamethylene diisocyanate.

12. The water-boiling self-removing UV-curing adhesive according to claim 2, characterized in that, The polythiol compound is a trifunctional and / or tetrafunctional polythiol compound; the polythiol compound is selected from at least one of trimethylolpropane tris(3-mercaptoacetate), trimethylolpropane tris(3-mercaptopropionate), trimethylolpropane tris(3-mercaptobutyrate), pentaerythritol tetra(mercaptoacetate), pentaerythritol tetra(3-mercaptopropionic acid) ester, and pentaerythritol tetra(3-mercaptobutyrate) ester.

13. The water-boiling self-removing UV-curing adhesive according to claim 1, characterized in that, The polyurethane acrylate is a difunctional aliphatic polyurethane acrylate; the viscosity of the polyurethane acrylate at 25 °C is 20,000~80,000 cps; the expanding agent is selected from at least one of ettringite, alunite and anhydrous gypsum.

14. The method for preparing the water-boiling self-removing ultraviolet-curable adhesive according to any one of claims 1 to 13, characterized in that, The method involves mixing and stirring polyurethane acrylate resin, reactive diluent, polythiol, expanding agent, photoinitiator, coupling agent and thixotropic agent evenly, and then discharging the mixture in the dark to obtain a water-boiling self-removing UV-curable adhesive.

15. The application of the water-boiling self-removing UV-curing adhesive according to any one of claims 1 to 13 in the surface anodizing treatment of aluminum.

Images