Moisture-curing UV adhesive and its preparation method and application

Abstract

The present invention belongs to the field of UV adhesive technology and relates to a moisture-curing UV adhesive and its preparation method and application. The present invention provides a moisture-curing UV adhesive, which is composed of the following raw materials, measured by mass: 100 parts of a silane-modified base polymer, 10 to 40 parts of a diluent, 10 to 40 parts of a filler, 5 to 10 parts of a thixotropic agent, 1 to 3 parts of an accelerator, 1 to 3 parts of a catalyst, and 1 to 3 parts of a modified photoinitiator. The UV adhesive is prepared by modifying a hydroxyl-containing photoinitiator using γ-glycidyloxysilylpropylsesquioxane. The UV adhesive has excellent oleic acid resistance, a short UV curing time, and high shear strength.

Description

Technical Field

[0001] The invention belongs to the technical field of UV adhesives and relates to a moisture-curing UV adhesive and a preparation method and application thereof. Background Art

[0002] UV light-curing adhesives (abbreviated as UV adhesives) use ultraviolet light as an energy source to irradiate photoinitiators, causing them to produce active species such as free radicals or cations, thereby initiating rapid polymerization and crosslinking reactions of oligomers or monomers to achieve curing. As the most common type of radiation-curing adhesive, UV adhesives offer numerous advantages, such as being solvent-free, virtually pollution-free, energy-efficient and environmentally friendly, and offering fast curing speeds, which facilitate automated production on high-speed production lines. They also offer fast positioning speeds, high production efficiency, room temperature or low-temperature curing capabilities, compact curing equipment, high bonding strength, and compatibility with a variety of substrates. They are widely used in precision industries such as electronics, optical components, and biomedicine.

[0003] Conventional UV adhesives often suffer from incomplete curing due to UV light's difficulty reaching irregularly shaped parts or shadowed areas created by plug-in components when used to bond irregularly shaped parts. Another solution is to address this problem through dual-cure technology. UV / moisture dual-cure adhesives contain both photocurable groups (such as acrylates) and moisture-curable groups (isocyanates or siloxanes) in the photocurable resin. After UV exposure, a photoinitiator triggers polymerization of the acrylate groups, achieving rapid photocuring. The adhesive is then left at room temperature, where moisture in the air reacts with the isocyanate or siloxane groups in the system, resulting in a slow post-cure, further improving the cure and bond strength. Moisture post-cure improves the cure in areas where UV light wasn't sufficient, while also eliminating the need for additional heating, saving energy and equipment. This has led to its popularity in the market and is currently widely used in UV coating adhesives. Since moisture-curing UV adhesives are widely used to bond electronic products that come into long-term contact with the human body, improvements in their oleic acid resistance are crucial. Summary of the Invention

[0004] The present invention aims to provide a moisture-curing UV adhesive that addresses the technical issue of UV adhesive's lack of oleic acid resistance while maintaining or improving its fundamental properties of strength and drop resistance. To this end, the present invention provides a moisture-curing UV adhesive, its preparation method, and its application to address this need in the art.

[0005] In one aspect, the present invention relates to a moisture-curing UV adhesive, which is composed of the following raw materials, calculated by mass: 100 parts of a silane-modified base polymer, 10 to 40 parts of a diluent, 10 to 40 parts of a filler, 5 to 10 parts of a thixotropic agent, 1 to 3 parts of an accelerator, 1 to 3 parts of a catalyst, and 1 to 3 parts of a modified photoinitiator;

[0006] The silane-modified base polymer is a terminal reaction type liquid acrylic resin KANEKA XMAP TM ;

[0007] The preparation method of the modified photoinitiator comprises: mixing a photoinitiator containing a hydroxyl group, γ-glycidyl ether silyl propyl sesquioxane, mercaptosuccinic acid, and azobisisobutyronitrile in an organic solvent, reacting the mixture at 70-80° C. for 18-24 hours, immersing the mixture in water, allowing the mixture to stand, and then filtering the mixture to obtain the modified photoinitiator.

[0008] Furthermore, in the moisture-curing UV adhesive provided by the present invention, the molar ratio of the hydroxyl-containing photoinitiator, γ-glycidyl ether silyl propyl sesquioxane, mercaptosuccinic acid and azobisisobutyronitrile is 10:3-5:2-4:1-3.

[0009] Furthermore, in the moisture-curing UV adhesive provided by the present invention, the diluent is at least one of 4-acryloylmorpholine, isobornyl acrylate, tetrahydrofuran acrylate, cyclotrimethylolpropane formal acrylate, ethoxyphenol acrylate, tripropylene glycol diacrylate, and neopentyl glycol dimethacrylate.

[0010] Furthermore, in the moisture-curing UV adhesive provided by the present invention, the filler is at least one of nano calcium carbonate, heavy calcium carbonate, talc, and light calcium carbonate.

[0011] Furthermore, in the moisture-curing UV adhesive provided by the present invention, the thixotropic agent is fumed silica.

[0012] Furthermore, in the moisture-curing UV adhesive provided by the present invention, the accelerator is aminopropyltriethoxysilane.

[0013] Furthermore, in the moisture-curing UV adhesive provided by the present invention, the catalyst is dibutyltin dilaurate.

[0014] Furthermore, in the moisture-curing UV adhesive provided by the present invention, the hydroxyl-containing photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone and / or hydroxycyclohexane phenone.

[0015] Furthermore, in the moisture-curing UV adhesive provided by the present invention, the shear strength of the UV adhesive after curing is not less than 10 MPa.

[0016] On the other hand, the present invention relates to the use of the moisture-curing UV adhesive in the bonding of electronic components.

[0017] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0018] (1) Excellent oleic acid resistance: By modifying the hydroxyl-containing photoinitiator with γ-glycidyloxysilylpropylsesquioxane, the resulting UV adhesive has significant oleic acid resistance. This is particularly important for bonding electronic products that come into contact with the human body for a long time, such as headphones, to ensure product stability and durability during use.

[0019] (2) Shorter UV curing time: The modified photoinitiator enables the UV adhesive to undergo polymerization and cross-linking reactions more quickly under ultraviolet radiation, thereby achieving rapid curing. This is conducive to improving production efficiency, especially in automated production on high-speed production lines.

[0020] (3) High shear strength: After curing, the moisture-curing UV adhesive provided by the present invention has a shear strength of not less than 10 MPa, which shows high bonding strength. This ensures a strong connection between the bonded materials and improves the overall performance of the product.

[0021] (3) Dual curing mechanism: This UV adhesive contains both light-curable groups (such as acrylates) and moisture-curable groups (such as siloxanes), thus having UV / moisture dual curing properties. This can compensate for the incomplete curing phenomenon when UV light has difficulty reaching irregular shaped parts or shadowed areas formed by plug-in obstructions, further improving the degree of curing and bonding strength.

[0022] Due to the numerous advantages described above, the moisture-curing UV adhesive provided by the present invention has broad application prospects in precision industries such as electronics, optical components, and biomedicine. In particular, it can demonstrate outstanding performance and effectiveness in the bonding of electronic components. In summary, the technical solution provided by the present invention demonstrates significant benefits or advantages in terms of oleic acid resistance, UV curing time, shear strength, dual-curing mechanism, energy conservation and environmental protection, and application areas. DETAILED DESCRIPTION

[0023] The technical solutions of the present invention are described below with reference to the following examples. However, the present invention is not limited to the following examples. The experimental methods and detection methods described in each example are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0024] The silane-modified base polymer in the following examples is a terminal reaction type liquid acrylic resin KANEKAXMAP TM , purchased from Kaneka Co., Ltd.

[0025] The nano-calcium carbonate in the following examples is calcium carbonate particles with a particle size of 100 to 200 nm.

[0026] The model of the fumed silica in the following examples is R972, purchased from Shanghai Haiyi Technology & Trade Co., Ltd.

[0027] The γ-glycidyloxysilylpropylsesquioxane in the following examples has a CAS number of 68611-45-0.

[0028] Example

[0029] This embodiment provides a method for preparing a moisture-curing UV adhesive.

[0030] A hydroxyl-containing photoinitiator, γ-glycidyloxysilylpropylsesquioxane, mercaptosuccinic acid, and azobisisobutyronitrile are added to THF at a molar ratio of 10:3 to 5:2 to 4:1 to 3. For every eq of hydroxyl-containing photoinitiator, add 50 mL of THF. Add the mixture to a 100 mL three-necked flask via an addition funnel. Place the flask on a magnetic stirrer and stir until the mixture completely dissolves in the THF, resulting in a colorless, clear solution with a slight exotherm. Heat the mixture in an oil bath at 75°C for 20 hours. Add the product dropwise to water, completely submerging it, and let it stand overnight. Filter the resulting solid, which is the modified photoinitiator.

[0031] In parts by mass, take silane modified base polymer (terminal reaction type liquid acrylic resin KANEKAXMAP TM ) 100 parts, diluent 10-40 parts, filler 10-40 parts, thixotropic agent 5-10 parts, accelerator 1-3 parts, catalyst 1-3 parts and modified photoinitiator 1-3 parts.

[0032] Silane-modified base polymer and octyl phthalate were added to a planetary mixer and stirred at room temperature to obtain a mixture. Filler was added to the mixture and stirred under vacuum at 90°C to obtain a mixture. After cooling to room temperature, a thixotropic agent, accelerator, catalyst, and modified photoinitiator were quickly added. The mixture was stirred under vacuum at 450 r / min for 30 minutes, and the mixture was discharged and packaged to obtain the UV adhesive.

[0033] Test Case

[0034] This test example provides a performance test of UV adhesives with different compositions.

[0035] With reference to the preparation process of Example 1, different test groups were set up, as follows.

[0036] Test group 1: composed of the following raw materials, in parts by mass: 100 parts of silane-modified base polymer, 10 parts of diluent (4-acryloylmorpholine), 10 parts of filler (nano-calcium carbonate), 5 parts of thixotropic agent (fumed silica), 1 part of accelerator (aminopropyltriethoxysilane), 1 part of catalyst (dibutyltin dilaurate) and 1 part of modified photoinitiator; the molar ratio of 2-hydroxy-2-methyl-1-phenyl-1-propanone, γ-glycidyloxysilylpropylsesquioxane, mercaptosuccinic acid and azobisisobutyronitrile in the modified photoinitiator is 10:3:2:1.

[0037] Experimental Group 2: It is composed of the following raw materials, in parts by mass: 100 parts of silane-modified base polymer, 12 parts of diluent (isobornyl acrylate), 25 parts of filler (nano-calcium carbonate), 7 parts of thixotropic agent (fumed silica), 2 parts of accelerator (aminopropyltriethoxysilane), 2 parts of catalyst (dibutyltin dilaurate) and 2 parts of modified photoinitiator; the molar ratio of hydroxycyclohexane phenone, γ-glycidyl ether silyl propyl sesquioxane, mercaptosuccinic acid and azobisisobutyronitrile in the modified photoinitiator is 10:4:3:2.

[0038] Experimental Group 3: It is composed of the following raw materials, in parts by mass: 100 parts of silane-modified base polymer, 40 parts of diluent (isobornyl acrylate), 40 parts of filler (nano-calcium carbonate), 10 parts of thixotropic agent (fumed silica), 3 parts of accelerator (aminopropyltriethoxysilane), 3 parts of catalyst (dibutyltin dilaurate) and 3 parts of modified photoinitiator; the molar ratio of 2-hydroxy-2-methyl-1-phenyl-1-propanone, hydroxycyclohexane phenone, γ-glycidyloxysilylpropylsesquioxane, mercaptosuccinic acid and azobisisobutyronitrile in the modified photoinitiator is 5:5:5:4:3.

[0039] Comparative Group 1: This comparative group is the same as the experimental group 3, except that the photoinitiator is not modified with γ-glycidyl ether silyl propyl sesquioxane.

[0040] Comparative group 2: This comparative group is the same as experimental group 3, except that the molar ratio of 2-hydroxy-2-methyl-1-phenyl-1-propanone, hydroxycyclohexane phenone, γ-glycidyl ether silyl propyl sesquioxane, mercaptosuccinic acid and azobisisobutyronitrile in the modified photoinitiator is 5:5:10:4:3.

[0041] (1) Curing performance

[0042] The UV adhesives obtained from experimental groups 1 to 3 and comparative groups 1 to 2 were dispensed with a glue gun and then subjected to UV+moisture curing at room temperature. The moisture curing conditions were uniformly set at room temperature and 50±51% RH for 168 hours (one week). The test method is as follows:

[0043] 1. UV curing time: Place the test sample 10 cm below the light source and irradiate it with a UV light intensity of 55 mW / cm 2 , until the sample surface is no longer sticky, and calculate the time required.

[0044] 2. Hardness: Tested in accordance with GB / T 2411-2008 Plastics and hard rubber - Determination of indentation hardness (Shore hardness) using a durometer.

[0045] 3. Tensile strength and elongation at break: Tested in accordance with GB / T 30776-2014 Adhesive tapes - Test method for tensile strength and elongation at break.

[0046] 4. Shear strength: Tested in accordance with GB / T 7124-2008 Adhesives - Determination of tensile shear strength (rigid material to rigid material).

[0047] The test results are shown in Table 1.

[0048] Table 1: Curing properties

[0049]

[0050] As shown in Table 1, modifying the photoinitiator with γ-glycidyloxysilylpropylsesquioxane effectively shortens the UV curing time, achieving high hardness, tensile strength, elongation at break, and shear strength within a relatively short exposure time, significantly reducing the curing time. On the other hand, as shown in Comparative Group 2, when the γ-glycidyloxysilylpropylsesquioxane addition level is too high, while some of it contributes to the bond and improves the colloid strength, the excess remains as an impurity, resulting in a longer UV curing time and a decrease in tensile strength.

[0051] (2) Anti-drop and oleic acid resistance

[0052] 1. Drop resistance: The cured test piece (PC / PC) was dropped from a height of 1 meter onto a marble floor repeatedly until the bond failed. The number of drops at failure was recorded. Each sample was tested 3 times and the average value was taken.

[0053] 2. Oleic acid resistance: Immerse the fully cured adhesive in oleic acid at 60°C, take it out after 7 days, test the bonding strength, and calculate the bonding strength retention rate.

[0054] Table 2: Drop resistance and oleic acid resistance

[0055]

[0056] As shown in Table 2, the modification of the photoinitiator with γ-glycidyl ether silyl propyl sesquioxane can effectively improve the drop resistance and oleic acid resistance of the UV adhesive, and is suitable for improving the bonding performance of electronic products that come into contact with the human body for a long time.

[0057] The embodiments described above are some of the embodiments of the present invention, rather than all of them. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but rather represents only selected embodiments of the present invention. All other embodiments obtained without creative effort and through deduction and substitution by a person of ordinary skill in the art based on the concept of the present invention are within the scope of protection of the present invention.

Claims

1. A moisture-curing UV adhesive, characterized in that: The invention is composed of the following raw materials in parts by mass: 100 parts of silane-modified base polymer, 10 to 40 parts of diluent, 10 to 40 parts of filler, 5 to 10 parts of thixotropic agent, 1 to 3 parts of accelerator, 1 to 3 parts of catalyst and 1 to 3 parts of modified photoinitiator; The silane-modified base polymer is a terminal reaction type liquid acrylic resin KANEKA XMAP TM ; The preparation method of the modified photoinitiator comprises: mixing a photoinitiator containing a hydroxyl group, γ-glycidyl ether silyl propyl sesquioxane, mercaptosuccinic acid, and azobisisobutyronitrile in an organic solvent, reacting the mixture at 70-80° C. for 18-24 hours, immersing the mixture in water, allowing the mixture to stand, and then filtering the mixture to obtain the modified photoinitiator; The molar ratio of the hydroxyl-containing photoinitiator, γ-glycidyl ether silyl propyl sesquioxane, mercaptosuccinic acid and azobisisobutyronitrile is 10:3-5:2-4:1-3; The photoinitiator containing hydroxyl group is 2-hydroxy-2-methyl-1-phenyl-1-propanone and / or hydroxycyclohexane phenone.

2. The moisture-curing UV adhesive according to claim 1, characterized in that: The diluent is at least one of 4-acryloylmorpholine, isobornyl acrylate, tetrahydrofuran acrylate, cyclotrimethylolpropane formal acrylate, ethoxyphenol acrylate, tripropylene glycol diacrylate, and neopentyl glycol dimethacrylate.

3. The moisture-curing UV adhesive according to claim 1, characterized in that: The filler is at least one of nano calcium carbonate, heavy calcium carbonate, talcum powder and light calcium carbonate.

4. The moisture-curing UV adhesive according to claim 1, characterized in that: The thixotropic agent is fumed silica.

5. The moisture-curing UV adhesive according to claim 1, characterized in that: The accelerator is aminopropyltriethoxysilane.

6. The moisture-curing UV adhesive according to claim 1, characterized in that: The catalyst is dibutyltin dilaurate.

7. The moisture-curing UV adhesive according to claim 1, characterized in that: The shear strength of the UV adhesive after curing is not less than 10 MPa.

8. Use of the moisture-curing UV adhesive according to any one of claims 1 to 7 in bonding electronic components.

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