Ultraviolet curable positioning temporary masking adhesive and processing technology

Abstract

This invention relates to the field of photocurable adhesives, specifically to a UV-curable, positionable temporary masking adhesive and its processing technology. It addresses the problems of slow curing speed, low mechanical properties, and poor peel strength in existing temporary masking adhesives. Modified photosensitive polyurethane is used as the core film-forming resin. Its rigid oligocellulose skeleton imparts excellent modulus and thermal stability to the adhesive layer. The chain extender introduces amide groups that form a dense, strong hydrogen bond network between molecular chains, enhancing cohesive strength and tear resistance. Simultaneously, the pyrimidine ring provided by 2,4-dihydroxypyrimidine-5-carboxylic acid forms dynamic coordination bonds with zinc ions dissociated from zinc acetate, enhancing the mechanical properties after curing. A rapid decrease in viscosity can be achieved under secondary triggering. The highly efficient hydrogen abstraction initiation capability of the nano-photoinitiator enables rapid photocuring. Its cage-like rigid skeleton nano-sizes the photoinitiator and utilizes steric hindrance to reduce migration rate. These two elements work synergistically to achieve rapid positioning curing, high strength, and full-sheet peeling.

Description

Technical Field

[0001] This invention relates to the field of light-curing adhesive technology, specifically to a temporary masking adhesive that can be cured and positioned under ultraviolet light and its processing technology. Background Technology

[0002] Photopolymerization is a technology that uses light sources such as ultraviolet or visible light to cause a rapid chemical reaction in adhesives, forming a strong bond or hardening. It is particularly suitable for fields such as electronic component packaging, precision component bonding, and craft manufacturing. In the current field of photopolymer adhesives, some products can meet the requirements for rapid bonding. Photopolymer adhesives are widely used in many fields due to their excellent curing speed, low pollution, and superior performance, especially in the electronics, optics, and decorative industries. In these industries, photopolymer adhesives are widely used for processes such as device fixing and coating formation.

[0003] However, traditional bonding processes often require a long curing time, resulting in low efficiency. Furthermore, the process requires avoiding interference from external environments such as air and moisture, which increases the complexity and cost of the process. Existing temporary masking adhesives have slow curing speeds, low mechanical properties, and poor peel strength, making it particularly difficult to meet the requirements of rapid positioning, high-strength masking, and full-sheet peeling for materials such as self-adhesive rubber asphalt in production and construction.

[0004] Therefore, developing a UV-curable, positionable temporary masking adhesive and its processing technology is of great significance in the field of UV-curable adhesive technology. Summary of the Invention

[0005] In order to overcome the above-mentioned technical problems, the purpose of this invention is to provide a UV-curable and positionable temporary masking adhesive and its processing technology, which solves the problems of slow curing speed, low mechanical properties and poor peel strength of existing temporary masking adhesives.

[0006] The objective of this invention can be achieved through the following technical solutions: In a first aspect, this application provides a UV-curable and positionable temporary masking adhesive, comprising the following components in parts by weight: 50-70 parts of modified photosensitive polyurethane, 10-20 parts of epoxidized acrylate soybean oil ester, 10-20 parts of polyisobutylene, 1-3 parts of compounded photoinitiator, 0.5-2 parts of zinc acetate, and 5-10 parts of reactive diluent. The CAS number of the epoxidized acrylate soybean oil ester is 91722-14-4; the polyisobutylene is produced by Sigma-Aldrich and its product number is 181463-100G; the compound photoinitiator is a mixture of nano-photoinitiator and photoinitiator TPO at a mass ratio of 1:2; and the reactive diluent is isobornyl acrylate.

[0007] In a preferred embodiment of the present invention, the modified photosensitive polyurethane is prepared by the following steps: Step a1: Add microcrystalline cellulose and deionized water to a three-necked flask equipped with a stirrer and thermometer, mix and stir at 25°C for 10-15 min, add phosphoric acid solution pre-cooled to -15°C, continue stirring for 2 h, transfer to an oil bath at 60°C and continue stirring for 2-3 h, add anhydrous ethanol, vacuum filter, retain the filtrate, let stand for 1 h, centrifuge, and vacuum dry at 60°C to obtain oligocellulose; under nitrogen protection, add isophthalic acid dihydrazide and N,N-dimethylacetamide to a beaker, heat to 60°C, add isophorone diisocyanate and dibutyltin dilaurate, mix and stir to react for 4 h, distill under reduced pressure to obtain chain extender; Step a2: Oligocellulose, chain extender, 2,4-dihydroxypyrimidine-5-carboxylic acid and N,N-dimethylacetamide are added to a three-necked flask equipped with a stirrer and thermometer. The mixture is stirred for 30 min, then dibutyltin dilaurate is added. The mixture is stirred and reacted at 80 °C for 3 h. The temperature is then lowered to 60 °C, hydroxyethyl acrylate and 4-methoxyphenol are added, and the reaction is continued for 2-3 h. After the reaction is completed, the mixture is distilled under reduced pressure to obtain modified photosensitive polyurethane.

[0008] In a preferred embodiment of the present invention, the ratio of microcrystalline cellulose, deionized water, phosphoric acid solution, anhydrous ethanol, diisophthalic acid dihydrazide, N,N-dimethylacetamide, isophorone diisocyanate, and dibutyltin dilaurate in step a1 is 3-5g:10-30mL:100mL:1000mL:2.8-3g:30mL:13-15mL:0.01mL; the microcrystalline cellulose is manufactured by Maclean, catalog number M909921; and the phosphoric acid solution has a mass fraction of 85%.

[0009] In a preferred embodiment of the present invention, the ratio of oligocellulose, chain extender, 2,4-dihydroxypyrimidine-5-carboxylic acid, N,N-dimethylacetamide, dibutyltin dilaurate, hydroxyethyl acrylate and 4-methoxyphenol in step a2 is 8-9g:9-10mL:6-7g:50mL:0.01mL:6-8mL:0.1g.

[0010] In a preferred embodiment of the present invention, the nano-photoinitiator is prepared by the following steps: Step b1: Add sulfuric acid solution and thiosalicylic acid to a three-necked flask equipped with a stirrer and thermometer, mix and stir for 15-30 min, add phenoxyacetic acid, seal and protect from light, stir and react at 25℃ for 72 h, filter, add the filter cake to 1,4-dioxane at 40℃, mix and stir for 30 min, let stand for 1-2 h, take the supernatant, dilute with distilled water to precipitate the precipitate, filter, dry at 60-80℃ for 2-4 h, add thionyl chloride, purge with nitrogen for protection, react at 25℃ under sealed and light-protected conditions for 12 h to obtain the precursor; Step b2: Add n-propanol, acetonitrile, tetraethylammonium hydroxide, and deionized water to a three-necked flask equipped with a thermometer and stirrer. Mix and stir at 400-500 r / min for 3-4 h. Under nitrogen protection, add aminopropyltriethoxysilane and heat to 50℃ for 24 h. Filter and wash the precipitate 2-3 times with distilled water and cyclohexane, respectively. Vacuum dry for 24 h to obtain functionalized nanoparticles. Add the functionalized nanoparticles and N,N-dimethylformamide to a beaker and mix and stir for 30 min. Under a nitrogen atmosphere at 50℃, add the precursor and continue stirring for 12 h. Add saturated sodium chloride solution and extract with ethyl acetate, retaining the organic phase. Continue extraction with hydrochloric acid solution, retaining the organic phase. Add anhydrous magnesium sulfate, filter, and dry at 50-60℃ for 3-5 h to obtain the nano-photoinitiator.

[0011] In a preferred embodiment of the present invention, the ratio of sulfuric acid solution, thiosalicylic acid, phenoxyacetic acid, 1,4-dioxane and thionyl chloride in step b1 is 60-70 mL: 1-2 g: 1-2 g: 30-50 mL: 1-2 mL; the mass fraction of the sulfuric acid solution is 98%.

[0012] In a preferred embodiment of the present invention, the ratio of n-propanol, acetonitrile, tetraethylammonium hydroxide, deionized water, aminopropyltriethoxysilane, N,N-dimethylformamide, precursor, saturated sodium chloride solution, and anhydrous magnesium sulfate in step b2 is 4-5 mL: 1-2 mL: 0.1-0.3 mL: 9-10 mL: 20-25 mL: 20-30 mL: 0.4-0.5 g: 50 mL: 3-5 g.

[0013] Secondly, this application provides a processing technology for a UV-curable and positionable temporary masking adhesive, comprising the following steps: Step 1: Weigh out 50-70 parts of modified photosensitive polyurethane, 10-20 parts of epoxidized acrylate soybean oil, 10-20 parts of polyisobutylene, 1-3 parts of compounded photoinitiator, 0.5-2 parts of zinc acetate, and 5-10 parts of reactive diluent according to the following weight proportions. Step 2: Under light-protected conditions, add modified photosensitive polyurethane, epoxidized acrylate soybean oil ester, polyisobutylene, reactive diluent, and zinc acetate to a reaction vessel. Stir at 300-500 r / min for 30-45 min in a 60℃ water bath. Cool down to 40-50℃, add the compounded photoinitiator, stir in the dark for 15-20 min, transfer to a vacuum degassing machine, and degas for 10-15 min under a vacuum of -0.095 MPa. Discharge the material to obtain a temporary masking adhesive that can be cured and positioned under ultraviolet light.

[0014] The beneficial effects of this invention are: This invention discloses a UV-curable temporary masking adhesive and its processing technology. Under light-protected conditions, modified photosensitive polyurethane, epoxidized acrylate soybean oil ester, polyisobutylene, reactive diluent, and zinc acetate are mixed and stirred in a water bath. A compounded photoinitiator is added, and the mixture is stirred in the dark, followed by vacuum degassing to obtain the UV-curable temporary masking adhesive. This temporary masking adhesive can be rapidly cured by UV light, achieving instant positioning and efficient fixation during processing. The cured masking adhesive exhibits excellent resistance to cutting fluids, acids and alkalis, wide temperature range stability, and strong peel strength. After processing, the peel strength can be reduced by secondary UV irradiation or gentle heating, achieving non-destructive and residue-free whole-sheet peeling, effectively avoiding damage to precision components. The cured adhesive layer can utilize its characteristic fluorescence response for residue detection and precise positioning, significantly improving process yield and operational convenience.

[0015] In the preparation of a UV-curable, positionable temporary masking adhesive, a modified photosensitive polyurethane was first prepared. Microcrystalline cellulose was swollen with phosphoric acid at low temperature and hydrolyzed at elevated temperature. The β-1,4-glycosidic bonds were broken via acid catalysis to generate oligocellulose. Isophthalic acid dihydrazide and isophorone diisocyanate underwent a nucleophilic addition reaction catalyzed by dibutyltin dilaurate. The hydrazide group reacted with the isocyanate group to generate a chain extender containing an amide group. The active hydroxyl groups on the surface of the oligocellulose, the amide group in the chain extender, and 2,4-dihydroxypyrimidine-5-carboxylic acid simultaneously underwent addition reactions with isophorone diisocyanate, constructing a polyurethane prepolymer with oligocellulose as the rigid backbone, the chain extender providing hydrogen bond reinforcement, and the pyrimidine ring as the coordination site. Subsequently, hydroxyethyl acrylate reacted with the terminal isocyanate groups of the prepolymer. The reaction introduces photosensitive acrylate double bonds to obtain modified photosensitive polyurethane. The oligocellulose backbone provides the material with a bio-based source, and its rigid pyran ring structure significantly improves the modulus and thermal stability of the adhesive layer. The amide urea groups introduced by the chain extender can form a dense and strong hydrogen bond network between molecular chains, enhancing the cohesive strength and tear resistance of the adhesive layer. The pyrimidine ring provided by 2,4-dihydroxypyrimidine-5-carboxylic acid forms a dynamic coordination bond with the zinc ions dissociated from zinc acetate. During photocuring, it forms an interpenetrating structure with the acrylate crosslinking network, improving mechanical properties. The viscosity can be rapidly reduced through the reversible dissociation of coordination bonds during heating or secondary UV irradiation. The polyurethane main chain also contains polycyclic structures such as benzene rings and cyclohexane, which enhances the chemical inertness and solvent resistance of the adhesive layer, effectively resisting the corrosion of cutting fluids and acid and alkali cleaning solutions.

[0016] In the preparation of a UV-curable and positionable temporary masking adhesive, a nano-photoinitiator was first prepared. Thiosyl salicylic acid and phenoxyacetic acid under sulfuric acid catalysis underwent a condensation cyclization reaction, forming a carboxylated thioxanthrone core with a conjugated structure through intermolecular dehydration, yielding a carboxylated thioxanthrone. This carboxylated thioxanthrone then underwent an acyl chloride reaction with thionyl chloride, converting the carboxyl group into a more reactive acyl chloride group, yielding the precursor. Aminopropyltriethoxysilane underwent a hydrolysis condensation reaction in an aqueous phase catalyzed by tetraethylammonium hydroxide, forming functionalized nanoparticles with a three-dimensional cage-like structure through the construction of Si-O-Si bonds. In N,N-dimethylformamide solvent, the precursor reacted with the ammonia on the surface of the functionalized nanoparticles... The photoinitiator undergoes an amidation condensation reaction, covalently grafting thioxanthone photosensitive units onto the surface of nanoparticles to form a core-shell structured nanophotoinitiator. The thioxanthone structure exhibits characteristic absorption in the 365-405 nm ultraviolet region, enabling it to efficiently absorb light energy and generate free radicals through a hydrogen abstraction mechanism. This initiates rapid crosslinking of acrylate double bonds, achieving rapid curing and localization of the adhesive layer. The cage-like rigid framework of the functionalized nanoparticles increases the molecular size of the photoinitiator, and the steric hindrance effect generated by its three-dimensional structure reduces mobility, preventing contamination of precision devices. The rigid structure can also serve as physical crosslinking points to participate in the construction of the polymer network, synergistically enhancing the modulus and tear resistance of the adhesive layer. Detailed Implementation

[0017] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1:

[0018] This embodiment describes a process for processing a UV-curable, positionable temporary masking adhesive, including the following steps: Step S1: Add 3g of microcrystalline cellulose and 10mL of deionized water to a three-necked flask equipped with a stirrer and thermometer. Mix and stir at 25°C for 10min. Add 100mL of 85% phosphoric acid solution pre-cooled to -15°C and continue stirring for 2h. Transfer to an oil bath at 60°C and continue stirring for 2h. Add 1000mL of anhydrous ethanol, vacuum filter, retain the filtrate, let stand for 1h, centrifuge, and vacuum dry at 60°C to obtain oligocellulose. Under nitrogen protection, add 2.8g of isophthalic acid dihydrazide and 30mL of N,N-dimethylacetamide to a beaker, heat to 60°C, add 13mL of isophorone diisocyanate and 0.01mL of dibutyltin dilaurate, mix and stir for 4h, and distill under reduced pressure to obtain a chain extender. The microcrystalline cellulose is produced by Maclean, catalog number M909921. Step S2: Add 8g of oligocellulose, 9mL of chain extender, 6g of 2,4-dihydroxypyrimidine-5-carboxylic acid, and 50mL of N,N-dimethylacetamide to a three-necked flask equipped with a stirrer and thermometer. Mix and stir for 30min. Add 0.01mL of dibutyltin dilaurate and continue stirring at 80℃ for 3h. Cool down to 60℃, add 6mL of hydroxyethyl acrylate and 0.1g of 4-methoxyphenol, and continue reacting for 2h. After the reaction is complete, distill under reduced pressure to obtain modified photosensitive polyurethane. Step S3: Add 60 mL of 98% sulfuric acid solution and 1 g of thiosalicylic acid to a three-necked flask equipped with a stirrer and thermometer. Mix and stir for 15 min. Add 1 g of phenoxyacetic acid. Seal and protect from light. Stir and react at 25 °C for 72 h. Filter. Add the filter cake to 30 mL of 1,4-dioxane at 40 °C. Mix and stir for 30 min. Let stand for 1 h. Take the supernatant. Dilute with distilled water to precipitate the precipitate. Filter. Dry at 60 °C for 2 h. Add 1 mL of thionyl chloride. Purge with nitrogen for protection. React at 25 °C under sealed and light-protected conditions for 12 h to obtain the precursor. Step S4: Add 4 mL of n-propanol, 1 mL of acetonitrile, 0.1 mL of tetraethylammonium hydroxide, and 9 mL of deionized water to a three-necked flask equipped with a thermometer and a stirrer. Mix and stir at 400 r / min for 3 h. Under nitrogen protection, add 20 mL of aminopropyltriethoxysilane and heat to 50 °C for 24 h. Filter and wash the precipitate twice with distilled water and cyclohexane, respectively. Vacuum dry for 24 h to obtain functionalized nanoparticles. Add the functionalized nanoparticles and 20 mL of N,N-dimethylformamide to a beaker and mix and stir for 30 min. Under a nitrogen atmosphere at 50 °C, add 0.4 g of precursor and continue stirring for 12 h. Add 50 mL of saturated sodium chloride solution and extract with ethyl acetate, retaining the organic phase. Continue extraction with hydrochloric acid solution, retaining the organic phase. Add 3 g of anhydrous magnesium sulfate, filter, and dry at 50 °C for 3 h to obtain nano-photoinitiator. Step S5: Weigh out 50 parts by weight of modified photosensitive polyurethane, 10 parts by weight of epoxidized soybean oil acrylate, 10 parts by weight of polyisobutylene, 1 part by weight of compound photoinitiator, 0.5 parts by weight of zinc acetate, and 5 parts by weight of reactive diluent; the CAS number of the epoxidized soybean oil acrylate is 91722-14-4; the polyisobutylene is produced by Sigma-Aldrich, catalog number 181463-100G; the compound photoinitiator is a mixture of nano-photoinitiator and photoinitiator TPO at a mass ratio of 1:2; the reactive diluent is isobornyl acrylate. Step S6: Under light-protected conditions, the modified photosensitive polyurethane, epoxidized acrylate soybean oil ester, polyisobutylene, reactive diluent, and zinc acetate are added to the reaction vessel and stirred at 300 r / min for 30 min in a 60°C water bath. The mixture is then cooled to 40°C, and the compounded photoinitiator is added. The mixture is stirred in the light-protected environment for 15 min and then transferred to a vacuum degassing machine. The mixture is degassed under a vacuum of -0.095 MPa for 10 min and then discharged to obtain a temporary masking adhesive that can be cured and positioned under ultraviolet light. Example 2:

[0019] This embodiment describes a process for processing a UV-curable, positionable temporary masking adhesive, including the following steps: Step S1: Add 4g of microcrystalline cellulose and 20mL of deionized water to a three-necked flask equipped with a stirrer and thermometer. Mix and stir at 25°C for 13min. Add 100mL of 85% phosphoric acid solution pre-cooled to -15°C and continue stirring for 2h. Transfer to an oil bath at 60°C and continue stirring for 2.5h. Add 1000mL of anhydrous ethanol, vacuum filter, retain the filtrate, let stand for 1h, centrifuge, and vacuum dry at 60°C to obtain oligocellulose. Under nitrogen protection, add 2.9g of isophthalic acid dihydrazide and 30mL of N,N-dimethylacetamide to a beaker, heat to 60°C, add 14mL of isophorone diisocyanate and 0.01mL of dibutyltin dilaurate, mix and stir for 4h, and distill under reduced pressure to obtain a chain extender. The microcrystalline cellulose is produced by Maclean, catalog number M909921. Step S2: Add 8.5g of oligocellulose, 9.5mL of chain extender, 6.5g of 2,4-dihydroxypyrimidine-5-carboxylic acid, and 50mL of N,N-dimethylacetamide to a three-necked flask equipped with a stirrer and thermometer. Mix and stir for 30min. Add 0.01mL of dibutyltin dilaurate and continue stirring at 80℃ for 3h. Cool down to 60℃, add 7mL of hydroxyethyl acrylate and 0.1g of 4-methoxyphenol, and continue reacting for 2.5h. After the reaction is complete, distill under reduced pressure to obtain modified photosensitive polyurethane. Step S3: Add 65 mL of 98% sulfuric acid solution and 1.5 g of thiosalicylic acid to a three-necked flask equipped with a stirrer and thermometer. Mix and stir for 20 min. Add 1.5 g of phenoxyacetic acid. Seal and protect from light. Stir and react at 25 °C for 72 h. Filter. Add the filter cake to 40 mL of 1,4-dioxane at 40 °C. Mix and stir for 30 min. Let stand for 1.5 h. Take the supernatant. Dilute with distilled water to precipitate the precipitate. Filter. Dry at 70 °C for 3 h. Add 1.5 mL of thionyl chloride. Purge with nitrogen for protection. React at 25 °C under sealed and light-protected conditions for 12 h to obtain the precursor. Step S4: Add 4.5 mL of n-propanol, 1.5 mL of acetonitrile, 0.2 mL of tetraethylammonium hydroxide, and 9.5 mL of deionized water to a three-necked flask equipped with a thermometer and a stirrer. Mix and stir at 450 r / min for 3.5 h. Under nitrogen protection, add 23 mL of aminopropyltriethoxysilane and heat to 50 °C for 24 h. Filter and wash the precipitate three times with distilled water and cyclohexane, respectively. Vacuum dry for 24 h to obtain functionalized nanoparticles. Add the functionalized nanoparticles and 25 mL of N,N-dimethylformamide to a beaker and mix and stir for 30 min. Under a nitrogen atmosphere at 50 °C, add 0.45 g of precursor and continue stirring for 12 h. Add 50 mL of saturated sodium chloride solution and extract with ethyl acetate, retaining the organic phase. Continue extraction with hydrochloric acid solution, retaining the organic phase. Add 4 g of anhydrous magnesium sulfate, filter, and dry at 55 °C for 4 h to obtain nano-photoinitiator. Step S5: Weigh out 60 parts by weight of modified photosensitive polyurethane, 15 parts by weight of epoxidized soybean oil acrylate, 15 parts by weight of polyisobutylene, 2 parts by weight of compound photoinitiator, 1 part by weight of zinc acetate, and 8 parts by weight of reactive diluent; the CAS number of the epoxidized soybean oil acrylate is 91722-14-4; the polyisobutylene is produced by Sigma-Aldrich, catalog number 181463-100G; the compound photoinitiator is a mixture of nano-photoinitiator and photoinitiator TPO at a mass ratio of 1:2; the reactive diluent is isobornyl acrylate. Step S6: Under light-protected conditions, the modified photosensitive polyurethane, epoxidized acrylate soybean oil ester, polyisobutylene, reactive diluent, and zinc acetate are added to the reaction vessel and stirred at 400 r / min for 40 min in a 60℃ water bath. The mixture is then cooled to 45℃, and the compounded photoinitiator is added. The mixture is stirred in the light-protected environment for 18 min and then transferred to a vacuum degassing machine. The mixture is degassed under a vacuum of -0.095 MPa for 13 min and then discharged to obtain a temporary masking adhesive that can be cured and positioned under ultraviolet light. Example 3:

[0020] This embodiment describes a process for processing a UV-curable, positionable temporary masking adhesive, including the following steps: Step S1: Add 5g of microcrystalline cellulose and 30mL of deionized water to a three-necked flask equipped with a stirrer and thermometer. Mix and stir at 25°C for 15min. Add 100mL of 85% phosphoric acid solution pre-cooled to -15°C. Continue stirring for 2h. Transfer to an oil bath at 60°C and continue stirring for 3h. Add 1000mL of anhydrous ethanol. Vacuum filter, retain the filtrate, let stand for 1h, centrifuge, and vacuum dry at 60°C to obtain oligocellulose. Under nitrogen protection, add 3g of isophthalic acid dihydrazide and 30mL of N,N-dimethylacetamide to a beaker. Heat to 60°C, add 15mL of isophorone diisocyanate and 0.01mL of dibutyltin dilaurate. Mix and stir for 4h. Distill under reduced pressure to obtain a chain extender. The microcrystalline cellulose is produced by Maclean, catalog number M909921. Step S2: Add 9g of oligocellulose, 10mL of chain extender, 7g of 2,4-dihydroxypyrimidine-5-carboxylic acid and 50mL of N,N-dimethylacetamide to a three-necked flask equipped with a stirrer and thermometer, mix and stir for 30min, add 0.01mL of dibutyltin dilaurate, continue stirring and reacting at 80℃ for 3h, cool to 60℃, add 8mL of hydroxyethyl acrylate and 0.1g of 4-methoxyphenol and continue reacting for 3h. After the reaction is completed, distill under reduced pressure to obtain modified photosensitive polyurethane; Step S3: Add 70 mL of 98% sulfuric acid solution and 2 g of thiosalicylic acid to a three-necked flask equipped with a stirrer and thermometer. Mix and stir for 30 min. Add 2 g of phenoxyacetic acid, seal and protect from light. Stir and react at 25 °C for 72 h. Filter and add the filter cake to 50 mL of 1,4-dioxane at 40 °C. Mix and stir for 30 min. Let stand for 2 h. Take the supernatant, dilute with distilled water to precipitate the precipitate, filter, dry at 80 °C for 4 h, add 2 mL of thionyl chloride, purge with nitrogen for protection, and react at 25 °C under sealed and light-protected conditions for 12 h to obtain the precursor. Step S4: Add 5 mL of n-propanol, 2 mL of acetonitrile, 0.3 mL of tetraethylammonium hydroxide, and 10 mL of deionized water to a three-necked flask equipped with a thermometer and a stirrer. Mix and stir at 500 r / min for 4 h. Under nitrogen protection, add 25 mL of aminopropyltriethoxysilane and heat to 50 °C for 24 h. Filter and wash the precipitate three times with distilled water and cyclohexane, respectively. Vacuum dry for 24 h to obtain functionalized nanoparticles. Add the functionalized nanoparticles and 30 mL of N,N-dimethylformamide to a beaker and mix and stir for 30 min. Under a nitrogen atmosphere at 50 °C, add 0.5 g of precursor and continue stirring for 12 h. Add 50 mL of saturated sodium chloride solution and extract with ethyl acetate, retaining the organic phase. Continue extraction with hydrochloric acid solution, retaining the organic phase. Add 5 g of anhydrous magnesium sulfate, filter, and dry at 60 °C for 5 h to obtain nano-photoinitiator. Step S5: Weigh out 70 parts by weight of modified photosensitive polyurethane, 20 parts by weight of epoxidized soybean oil acrylate, 20 parts by weight of polyisobutylene, 3 parts by weight of compound photoinitiator, 2 parts by weight of zinc acetate, and 10 parts by weight of reactive diluent; the CAS number of the epoxidized soybean oil acrylate is 91722-14-4; the polyisobutylene is produced by Sigma-Aldrich, catalog number 181463-100G; the compound photoinitiator is a mixture of nano-photoinitiator and photoinitiator TPO at a mass ratio of 1:2; the reactive diluent is isobornyl acrylate. Step S6: Under light-protected conditions, the modified photosensitive polyurethane, epoxidized acrylate soybean oil ester, polyisobutylene, reactive diluent, and zinc acetate are added to the reaction vessel and stirred at 500 r / min for 45 min in a 60°C water bath. The mixture is then cooled to 50°C, and the compounded photoinitiator is added. The mixture is stirred in the light-protected environment for 20 min and then transferred to a vacuum degassing machine. The mixture is degassed under a vacuum of -0.095 MPa for 15 min and then discharged to obtain a temporary masking adhesive that can be cured and positioned under ultraviolet light.

[0021] Comparative Example 1: This comparative example illustrates a UV-curable, positionable temporary masking adhesive processing technology, including the following steps: Step S1: Weigh out 60 parts by weight of polyurethane acrylate HY-7902, 15 parts by weight of epoxidized acrylate soybean oil ester, 15 parts by weight of polyisobutylene, 2 parts by weight of photoinitiator TPO, 1 part by weight of zinc acetate, and 8 parts by weight of reactive diluent; the CAS number of the epoxidized acrylate soybean oil ester is 91722-14-4; the polyisobutylene is produced by Sigma-Aldrich, catalog number 181463-100G; the reactive diluent is isobornyl acrylate. Step S2: Under light-protected conditions, polyurethane acrylate HY-7902, epoxidized acrylate soybean oil ester, polyisobutylene, reactive diluent, and zinc acetate were added to a reaction vessel and stirred at 400 r / min for 40 min in a 60°C water bath. The mixture was then cooled to 45°C, and photoinitiator TPO was added. The mixture was stirred in the light-protected environment for 18 min and then transferred to a vacuum degassing machine. The mixture was degassed under a vacuum of -0.095 MPa for 13 min and then discharged to obtain a temporary masking adhesive that can be cured and positioned under ultraviolet light.

[0022] Comparative Example 2: This comparative example illustrates a UV-curable, positionable temporary masking adhesive processing technology, including the following steps: Step S1: Add 4g of microcrystalline cellulose and 20mL of deionized water to a three-necked flask equipped with a stirrer and thermometer. Mix and stir at 25°C for 13min. Add 100mL of 85% phosphoric acid solution pre-cooled to -15°C and continue stirring for 2h. Transfer to an oil bath at 60°C and continue stirring for 2.5h. Add 1000mL of anhydrous ethanol, vacuum filter, retain the filtrate, let stand for 1h, centrifuge, and vacuum dry at 60°C to obtain oligocellulose. Under nitrogen protection, add 2.9g of isophthalic acid dihydrazide and 30mL of N,N-dimethylacetamide to a beaker, heat to 60°C, add 14mL of isophorone diisocyanate and 0.01mL of dibutyltin dilaurate, mix and stir for 4h, and distill under reduced pressure to obtain a chain extender. The microcrystalline cellulose is produced by Maclean, catalog number M909921. Step S2: Add 8.5g of oligocellulose, 9.5mL of chain extender, 6.5g of 2,4-dihydroxypyrimidine-5-carboxylic acid, and 50mL of N,N-dimethylacetamide to a three-necked flask equipped with a stirrer and thermometer. Mix and stir for 30min. Add 0.01mL of dibutyltin dilaurate and continue stirring at 80℃ for 3h. Cool down to 60℃, add 7mL of hydroxyethyl acrylate and 0.1g of 4-methoxyphenol, and continue reacting for 2.5h. After the reaction is complete, distill under reduced pressure to obtain modified photosensitive polyurethane. Step S3: Weigh out 60 parts by weight of modified photosensitive polyurethane, 15 parts by weight of epoxidized soybean oil acrylate, 15 parts by weight of polyisobutylene, 2 parts by weight of photoinitiator TPO, 1 part by weight of zinc acetate, and 8 parts by weight of reactive diluent; the CAS number of the epoxidized soybean oil acrylate is 91722-14-4; the polyisobutylene is produced by Sigma-Aldrich, catalog number 181463-100G; the reactive diluent is isobornyl acrylate. Step S4: Under light-protected conditions, the modified photosensitive polyurethane, epoxidized acrylate soybean oil ester, polyisobutylene, reactive diluent, and zinc acetate are added to the reaction vessel and stirred at 400 r / min for 40 min in a 60℃ water bath. The mixture is then cooled to 45℃, and the photoinitiator TPO is added. The mixture is stirred in the light-protected environment for 18 min and then transferred to a vacuum degassing machine. The mixture is degassed under a vacuum of -0.095 MPa for 13 min and then discharged to obtain a temporary masking adhesive that can be cured and positioned under ultraviolet light.

[0023] Comparative Example 3: This comparative example illustrates a UV-curable, positionable temporary masking adhesive processing technology, including the following steps: Step S1: Add 65 mL of 98% sulfuric acid solution and 1.5 g of thiosalicylic acid to a three-necked flask equipped with a stirrer and thermometer. Mix and stir for 20 min. Add 1.5 g of phenoxyacetic acid, seal and protect from light, and stir at 25 °C for 72 h. Filter and add the filter cake to 40 mL of 1,4-dioxane at 40 °C. Mix and stir for 30 min, let stand for 1.5 h, take the supernatant, dilute with distilled water to precipitate the precipitate, filter, dry at 70 °C for 3 h, add 1.5 mL of thionyl chloride, purge with nitrogen for protection, and react at 25 °C under sealed and light-protected conditions for 12 h to obtain the precursor. Step S2: Add 4.5 mL of n-propanol, 1.5 mL of acetonitrile, 0.2 mL of tetraethylammonium hydroxide, and 9.5 mL of deionized water to a three-necked flask equipped with a thermometer and a stirrer. Mix and stir at 450 r / min for 3.5 h. Under nitrogen protection, add 23 mL of aminopropyltriethoxysilane and heat to 50 °C for 24 h. Filter and wash the precipitate three times with distilled water and cyclohexane, respectively. Vacuum dry for 24 h to obtain functionalized nanoparticles. Add the functionalized nanoparticles and 25 mL of N,N-dimethylformamide to a beaker and mix and stir for 30 min. Under a nitrogen atmosphere at 50 °C, add 0.45 g of precursor and continue stirring for 12 h. Add 50 mL of saturated sodium chloride solution and extract with ethyl acetate, retaining the organic phase. Continue extraction with hydrochloric acid solution, retaining the organic phase. Add 4 g of anhydrous magnesium sulfate, filter, and dry at 55 °C for 4 h to obtain nano-photoinitiator. Step S3: Weigh out 60 parts by weight of polyurethane acrylate HY-7902, 15 parts by weight of epoxidized acrylate soybean oil ester, 15 parts by weight of polyisobutylene, 2 parts by weight of compound photoinitiator, 1 part by weight of zinc acetate, and 8 parts by weight of reactive diluent; the CAS number of the epoxidized acrylate soybean oil ester is 91722-14-4; the polyisobutylene is produced by Sigma-Aldrich, catalog number 181463-100G; the compound photoinitiator is a mixture of nano-photoinitiator and photoinitiator TPO at a mass ratio of 1:2; the reactive diluent is isobornyl acrylate. Step S4: Under light-protected conditions, polyurethane acrylate HY-7902, epoxidized acrylate soybean oil ester, polyisobutylene, reactive diluent, and zinc acetate are added to a reaction vessel and stirred at 400 r / min for 40 min in a 60°C water bath. The mixture is then cooled to 45°C, and a compounded photoinitiator is added. The mixture is stirred in the light-protected environment for 18 min and then transferred to a vacuum degassing machine. The mixture is degassed under a vacuum of -0.095 MPa for 13 min and then discharged to obtain a temporary masking adhesive that can be cured and positioned under ultraviolet light.

[0024] The UV-curable and positionable temporary masking adhesives prepared in Examples 1-3 and Comparative Examples 1-3 were injected into screw caps and irradiated with UV light. When the UV energy reached 6000 mJ / cm², the solution was applied to the screw caps. 2 The UV-curable temporary masking adhesive was peeled off, and the peel integrity, tensile strength, and elongation at break of the UV-curable temporary masking adhesive were tested. Surface dryness was tested by touch, and the stickiness of the adhesive film was observed when the finger touched it. The test results are shown in the table below: Comparing Examples 1-3 with Comparative Examples 1-3: Examples 1-3 all achieved completely dry and non-sticky films after UV curing, and could be peeled off completely without residue. Example 2 showed the best overall performance. Comparing Example 2 with Comparative Example 1: Comparative Example 1 used commercial polyurethane acrylate + photoinitiator TPO, which lacked the hydrogen bond reinforcement of modified polyurethane and the low migration characteristics of nano-photoinitiators. After curing, the cohesive strength was insufficient, and the film broke and some residue remained during peeling. Comparing Example 2 with Comparative Example 2: Comparative Example 2 used modified photosensitive polyurethane + photoinitiator TPO, which had good mechanical properties. However, it did not use nano-photoinitiators, and the high migration rate of the photoinitiator TPO led to slight interface contamination and trace residue. Comparing Example 2 with Comparative Example 3: Comparative Example 3 used commercial polyurethane acrylate + compounded nano-photoinitiators, which improved peel integrity, but lacked oligocellulose backbone and hydrogen bond / coordination bond reinforcement, resulting in lower tensile strength and elongation at break.

[0025] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0026] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in this application, they should all fall within the protection scope of the present invention.

Claims

1. A temporary masking adhesive that can be cured and positioned under ultraviolet light, characterized in that, Includes the following components by weight: 50-70 parts of modified photosensitive polyurethane, 10-20 parts of epoxidized acrylate soybean oil ester, 10-20 parts of polyisobutylene, 1-3 parts of compounded photoinitiator, 0.5-2 parts of zinc acetate, and 5-10 parts of reactive diluent. The modified photosensitive polyurethane is prepared by the following steps: Step a1: Mix microcrystalline cellulose and deionized water, add pre-cooled phosphoric acid solution, continue stirring, transfer to an oil bath and continue stirring, add anhydrous ethanol, vacuum filter, retain the filtrate, let stand, centrifuge, and dry to obtain oligocellulose; mix isophthalic acid dihydrazide, N,N-dimethylacetamide, isophorone diisocyanate and dibutyltin dilaurate, stir and react, and distill under reduced pressure to obtain chain extender; Step a2: Mix oligocellulose, chain extender, 2,4-dihydroxypyrimidine-5-carboxylic acid and N,N-dimethylacetamide, add dibutyltin dilaurate and continue stirring, cool down and add hydroxyethyl acrylate and 4-methoxyphenol to continue the reaction, distill under reduced pressure to obtain modified photosensitive polyurethane.

2. The UV-curable and positionable temporary masking adhesive according to claim 1, characterized in that, The CAS number of the epoxidized acrylate soybean oil ester is 91722-14-4; the compound photoinitiator is composed of a nano photoinitiator and a photoinitiator TPO mixed at a mass ratio of 1:2; the reactive diluent is isobornyl acrylate.

3. The UV-curable and positionable temporary masking adhesive according to claim 1, characterized in that, In step a1, the ratio of microcrystalline cellulose, deionized water, phosphoric acid solution, anhydrous ethanol, isophthalic acid dihydrazide, N,N-dimethylacetamide, isophorone diisocyanate, and dibutyltin dilaurate is 3-5g:10-30mL:100mL:1000mL:2.8-3g:30mL:13-15mL:0.01mL; the product number of the microcrystalline cellulose is M909921; and the mass fraction of the phosphoric acid solution is 85%.

4. The UV-curable and positionable temporary masking adhesive according to claim 1, characterized in that, The ratio of oligocellulose, chain extender, 2,4-dihydroxypyrimidine-5-carboxylic acid, N,N-dimethylacetamide, dibutyltin dilaurate, hydroxyethyl acrylate, and 4-methoxyphenol in step a2 is 8-9g:9-10mL:6-7g:50mL:0.01mL:6-8mL:0.1g.

5. The UV-curable and positionable temporary masking adhesive according to claim 2, characterized in that, The nano-photoinitiator was prepared by the following steps: Step b1: Mix sulfuric acid solution and thiosalicylic acid, add phenoxyacetic acid, seal and protect from light, stir and react, filter, add filter cake to 1,4-dioxane and mix, let stand, take the supernatant, dilute with distilled water to precipitate, filter, dry, add thionyl chloride, react under sealed and light-protected conditions to obtain the precursor. Step b2: Mix and stir n-propanol, acetonitrile, tetraethylammonium hydroxide and deionized water, add aminopropyltriethoxysilane, heat to react, filter, wash the precipitate, and vacuum dry to obtain functionalized nanoparticles; mix and stir functionalized nanoparticles and N,N-dimethylformamide, add precursor, continue stirring to react, add saturated sodium chloride solution and extract with ethyl acetate, retain the organic phase, continue extraction with hydrochloric acid solution, retain the organic phase, add anhydrous magnesium sulfate, filter, and dry to obtain nano-photoinitiator.

6. The UV-curable and positionable temporary masking adhesive according to claim 5, characterized in that, In step b1, the ratio of sulfuric acid solution, thiosalicylic acid, phenoxyacetic acid, 1,4-dioxane and thionyl chloride is 60-70 mL: 1-2 g: 1-2 g: 30-50 mL: 1-2 mL; the mass fraction of the sulfuric acid solution is 98%.

7. The UV-curable and positionable temporary masking adhesive according to claim 5, characterized in that, The ratio of n-propanol, acetonitrile, tetraethylammonium hydroxide, deionized water, aminopropyltriethoxysilane, N,N-dimethylformamide, precursor, saturated sodium chloride solution, and anhydrous magnesium sulfate in step b2 is 4-5 mL: 1-2 mL: 0.1-0.3 mL: 9-10 mL: 20-25 mL: 20-30 mL: 0.4-0.5 g: 50 mL: 3-5 g.

8. A processing method for a UV-curable, positionable temporary masking adhesive as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Weigh out 50-70 parts of modified photosensitive polyurethane, 10-20 parts of epoxidized acrylate soybean oil, 10-20 parts of polyisobutylene, 1-3 parts of compounded photoinitiator, 0.5-2 parts of zinc acetate, and 5-10 parts of reactive diluent according to the following weight proportions. Step 2: Under light-protected conditions, add modified photosensitive polyurethane, epoxidized acrylate soybean oil ester, polyisobutylene, reactive diluent and zinc acetate to the reaction vessel, stir in a water bath, cool down and add compound photoinitiator, stir in the dark, transfer to a vacuum degassing machine, degas under vacuum, and discharge to obtain a temporary masking adhesive that can be cured and positioned under ultraviolet light.

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