Acrylate pressure-sensitive adhesive for high-temperature electric appliance insulation and preparation method thereof

Abstract

The invention discloses an acrylate pressure-sensitive adhesive for high-temperature electric appliance insulation and a preparation method thereof. The prepolymer participates in the reaction of the urethane-based epoxy resin, and the urethane-based epoxy resin forms a cross-linked structure due to active groups, so that the cohesion strength, the adhesive force and the electrical strength of the pressure-sensitive adhesive can be effectively improved; the hydroxyl donor is added into the prepolymer, so that the reaction process is favorably controlled, and the molecular structure stability is improved; a hydrogen peroxide-ferrous chloride system is used as an initiator, so that generation of free radicals can be adjusted, and a polymer molecular chain structure is optimized; and combining the soft monomer, the hard monomer and the functional monomer, and polymerizing to obtain the pressure-sensitive adhesive. The prepared pressure-sensitive adhesive has high quality, high reliability and excellent electrical insulation performance, and can meet the requirements of different fields on high-performance pressure-sensitive adhesives.

Description

Technical Field

[0001] The invention relates to the technical field of adhesives, in particular to an acrylic pressure-sensitive adhesive for high-temperature electrical insulation and a preparation method thereof. Background Art

[0002] Currently, there are many problems to be solved in the fields of consumer electronics, new energy and family life. Most acrylic pressure-sensitive adhesive products generally have the problem of being unable to balance the heat-resistant and durable properties under high temperature conditions.

[0003] The prior art CN114921202A obtains a low-cost, heat-resistant and long-lasting acrylic pressure-sensitive adhesive by organically combining non-amide polymers with carbon nanotubes and polymerizing them with commonly used acrylic soft and hard monomers and functional monomers.

[0004] Prior art CN111471145A discloses an emulsion-type epoxy-modified acrylate pressure-sensitive adhesive having good initial adhesion, lasting adhesion and peel strength, and being resistant to high temperature and aging and environmentally friendly. Summary of the Invention

[0005] In view of the problem that existing acrylic pressure-sensitive adhesives are difficult to balance in terms of heat resistance and durability at high temperatures, the present invention involves a prepolymer in a reaction with a urethane-based epoxy resin. The cross-linked structure formed by the active groups of the urethane-based epoxy resin can effectively improve the cohesive strength, adhesion and electrical strength of the pressure-sensitive adhesive. The addition of a hydroxyl donor to the prepolymer helps control the reaction process and improve the stability of the molecular structure. The hydrogen peroxide-ferrous chloride system acts as an initiator to regulate the generation of free radicals and optimize the polymer molecular chain structure. Soft monomers, hard monomers and functional monomers are polymerized to produce a high-performance acrylic pressure-sensitive adhesive for high-temperature electrical insulation, which can meet the needs of different fields for high-performance pressure-sensitive adhesives.

[0006] The specific technical solutions are as follows: An acrylic pressure-sensitive adhesive for high-temperature electrical insulation, comprising the following components in parts by mass: 50-80 parts of ethyl acetate, 8-12 parts of butyl acrylate, 8-12 parts of urethane-based epoxy resin, 3-8 parts of methyl methacrylate, 1-3 parts of glycidyl methacrylate, and 0.3-0.9 parts of initiator.

[0007] The initiator is any one of benzoyl peroxide and a hydrogen peroxide-ferrous chloride mixture.

[0008] Preferably, the preparation method of the urethane-based epoxy resin is as follows: 20-50g of the prepolymer is added to 200-300mL of N,N-dimethylformamide, and stirred at 100-1200r / min for 20min at -5-0°C under nitrogen conditions; 70-80g of 3-chloroperoxybenzoic acid is dissolved in 300-800mL of N,N-dimethylformamide, and stirred at 100-200r / min for 20-30min at -5-0°C; after mixing the above two solutions, stir at 100-200r / min for 5-10min, heat to 30-50°C, react for 12-36h, wash with 100mL of 10% sodium bisulfite aqueous solution 1-3 times, wash with 100mL of 5% sodium bicarbonate aqueous solution 1-3 times, wash with 100mL of deionized water 1-3 times, and freeze-dry at 0-5°C for 12-36h.

[0009] Preferably, the preparation method of the prepolymer is as follows: 10-30g of aliphatic diisocyanate and 20-50g of hydroxyl donor are dissolved in 100-300mL of toluene, and stirred at 100-200r / min for 8-12min; 0.5-3g of triethylenediamine is added, and the mixture is heated in a water bath at 60-80°C for 1-2h; cooled to 0°C and allowed to stand for 1-2h, the precipitate is washed 1-3 times with 100mL of ethanol, and dried in an oven at 60-80°C for 3-5h.

[0010] The aliphatic diisocyanate is any one of hexamethylene diisocyanate and isophorone diisocyanate.

[0011] The hydroxyl donor is any one of polyethylene glycol, p-cresol, eugenol and cardanol.

[0012] The present invention also discloses a method for preparing the acrylic pressure-sensitive adhesive for high-temperature electrical insulation, which is specifically as follows: Add 50-80 parts of ethyl acetate, 8-12 parts of butyl acrylate, 8-12 parts of urethane epoxy resin, 3-8 parts of methyl methacrylate, and 1-3 parts of glycidyl methacrylate into a reactor, stir at 100-200 r / min under a nitrogen atmosphere for 1-3 minutes, continue to add 0.1-0.3 parts of initiator under a nitrogen atmosphere, continue to stir at 100-200 r / min for 8-12 minutes, heat to 60-80°C and react for 90 minutes, add 0.1-0.3 parts of initiator, add it within 8-12 minutes, and keep it warm for 1-3 hours; add 0.1-0.3 parts of initiator, add it slowly within 8-12 minutes, and keep it warm at 60-80°C for 3-8 hours to obtain the product.

[0013] Beneficial effects of the present invention: 1. Compared to the prior art, the urethane-based epoxy resin prepolymer used in this invention undergoes an addition polymerization reaction in a toluene solvent environment via isocyanate groups and the hydroxyl groups in the hydroxyl donor molecules. Furthermore, flexible polyurethane segments are introduced into the subsequent epoxy resin to form an interpenetrating network structure, effectively improving the toughness and impact resistance of the epoxy resin, reducing its brittleness, and further enhancing the product's mechanical properties in higher temperature environments.

[0014] 2. Compared to existing technologies, the urethane-based epoxy resin of the present invention further stabilizes and improves the structure of the pressure-sensitive adhesive through hydrogen bonding within the reaction system and interactions with other monomers and polymer chains. In actual applications, when temperatures rise, the crosslinked network prevents relative slippage and displacement between molecular chains, allowing the pressure-sensitive adhesive to maintain its optimal shape and performance even at high temperatures. Furthermore, the strength of the intramolecular chemical bonds is enhanced, thereby improving overall thermal stability, making the resulting pressure-sensitive adhesive less susceptible to decomposition and aging in high-temperature environments.

[0015] 3. The acrylic pressure-sensitive adhesive prepared by the present invention has a relatively pure, high-molecular-weight polymer structure. The hydroxyl donors in the amino-epoxy resin form a pressure-sensitive adhesive with mostly non-polar or weakly polar molecules, reducing charge accumulation and conduction within the material. Consequently, the pressure-sensitive adhesive exhibits excellent insulating properties, expanding its application range and enabling wider market adoption. DETAILED DESCRIPTION

[0016] An acrylic pressure-sensitive adhesive for high-temperature electrical insulation comprises the following components, calculated by mass: 50-80 parts of ethyl acetate, 8-12 parts of butyl acrylate, 8-12 parts of urethane-based epoxy resin, 3-8 parts of methyl methacrylate, 1-3 parts of glycidyl methacrylate, and 0.3-0.9 parts of an initiator.

[0017] The preparation method comprises the following steps: adding 50-80 parts of ethyl acetate, 8-12 parts of butyl acrylate, 8-12 parts of urethane epoxy resin, 3-8 parts of methyl methacrylate and 1-3 parts of glycidyl methacrylate into a reaction kettle, stirring the mixture at 100-200 r / min under a nitrogen atmosphere for 1-3 minutes, continuously adding 0.1-0.3 parts of initiator under a nitrogen atmosphere, continuously stirring the mixture at 100-200 r / min for 8-12 minutes, heating the mixture to 60-80°C for reaction for 90 minutes, adding 0.1-0.3 parts of initiator over 8-12 minutes, and keeping the temperature for 1-3 hours; adding 0.1-0.3 parts of initiator over 8-12 minutes, and keeping the temperature at 60-80°C for 3-8 hours to obtain the product.

[0018] The preparation method of the above-mentioned urethane-based epoxy resin is as follows: 20-50g of the prepolymer is added to 200-500mL of N,N-dimethylformamide, and stirred at 100-1200r / min for 20min at -5-0°C under a nitrogen atmosphere; 70-80g of 3-chloroperoxybenzoic acid is dissolved in 300-800mL of N,N-dimethylformamide, and stirred at 100-200r / min for 20-30min at -5-0°C; after mixing the above-mentioned two solutions, the mixture is stirred at 100-200r / min for 5-10min, then heated to 30-50°C, reacted for 12-36h, washed, and dried to obtain the product.

[0019] Preferably, the preparation method of the prepolymer involved in the urethane-based epoxy resin is as follows: 10-30g of isophorone diisocyanate and 20-50g of polyethylene glycol are dissolved in 100-300mL of toluene, and stirred at 100-200r / min for 8-12min; 0.5-3g of triethylenediamine is added, and the mixture is heated in a water bath at 60-80°C for 1-2h; cooled to 0°C and allowed to stand for 1-2h, and the precipitate is taken, washed with ethanol, and then dried.

[0020] Butyl acrylate: A soft monomer whose long-chain alkyl structure gives the pressure-sensitive adhesive good flexibility and viscosity, enabling the pressure-sensitive adhesive to maintain good adhesion properties over a wide temperature range.

[0021] Methyl methacrylate: It is a hard monomer with a relatively regular structure and high rigidity. It can increase the hardness and cohesive strength of the pressure-sensitive adhesive, making it less likely to deform and break when subjected to external forces, thereby improving the mechanical properties and heat resistance of the pressure-sensitive adhesive.

[0022] Urethane epoxy resin: The ester group in the molecule can interact with other monomers and polymer chains through hydrogen bonding in the reaction system; forming a cross-linked structure between polymer molecular chains, which can prevent relative sliding and displacement between molecular chains in high temperature environments, improve the rigidity, heat resistance, cohesive strength and other properties of the pressure-sensitive adhesive, and stabilize and improve the structure of the pressure-sensitive adhesive.

[0023] Glycidyl methacrylate: Contains epoxy groups, which can copolymerize with other monomers during the polymerization reaction to introduce epoxy functional groups into the polymer molecular chain. The epoxy groups react with the amino active groups in the urethane epoxy resin to further cross-link the polymer molecular chain, thereby increasing the cross-linking density and cohesive strength of the pressure-sensitive adhesive, and also improving the heat resistance of the pressure-sensitive adhesive.

[0024] 3-Chloroperoxybenzoic acid: It is a key reaction reagent for the preparation of urethane-based epoxy resins. It is used to oxidize the prepolymer and cause structural changes to produce urethane-based epoxy resins.

[0025] Hydrogen peroxide-ferrous chloride system: As an initiator, the ferrous ions in ferrous chloride undergo redox reaction with hydrogen peroxide to produce active free radicals such as hydroxyl radicals and hydroperoxyl radicals, which initiate the polymerization reaction of monomers, converting monomer molecules into active free radical species, and then triggering chain growth reaction to form polymer chains. By controlling the amount of initiator and the method of addition, the speed and degree of the polymerization reaction can be adjusted, thereby achieving the regulation of the performance of the pressure-sensitive adhesive.

[0026] Triethylenediamine: As a catalyst in the prepolymer preparation process, it can reduce the activation energy of the reaction between isophorone diisocyanate and polyethylene glycol, improve the reaction efficiency, and does not change the chemical structure of the reaction product.

[0027] The parameters and sources of some substances in the examples are as follows: Butyl acrylate: CAS number: 141-32-2.

[0028] Isophorone diisocyanate: CAS number: 4098-71-9.

[0029] Methyl methacrylate: CAS number: 80-62-6.

[0030] 3-Chloroperoxybenzoic acid: CAS number: 937-14-4.

[0031] Cardanol: Model: NX-2024; Kalede.

[0032] Epoxy resin: Bisphenol A epoxy resin: Model: EPIKOTE™ 6520-WH-53A; Hexion.

[0033] Polyethylene glycol: average molecular weight 600; serial number: 010-62935; Kaixida Chemical.

[0034] Example 1 A method for preparing an acrylic pressure-sensitive adhesive for high-temperature electrical insulation is as follows: Add 500g of ethyl acetate, 100g of butyl acrylate, 100g of urethane epoxy resin, 50g of methyl methacrylate, and 20g of glycidyl methacrylate to the reactor, stir at 200r / min for 1min under a nitrogen atmosphere, continue to add 1g of benzoyl peroxide under a nitrogen atmosphere, continue to stir at 200r / min for 10min, heat to 80℃ and react for 90min, add 2g of benzoyl peroxide, add it over 10min, and keep it warm for 3h; add 1g of benzoyl peroxide, add it over 10min, and keep it warm at 80℃ for 5h.

[0035] The preparation method of the urethane-based epoxy resin is as follows: 30 g of prepolymer is added to 300 mL of N,N-dimethylformamide, and stirred at 0°C, 200 r / min, and 20 min under a nitrogen atmosphere; 75 g of 3-chloroperoxybenzoic acid is dissolved in 500 mL of N,N-dimethylformamide, and stirred at 0°C, 200 r / min, and 30 min; the two solutions are mixed, stirred at 200 r / min for 8 min, and then heated to 40°C for reaction for 24 h. After filtering, the mixture is washed three times with 100 mL of 10% sodium bisulfite aqueous solution, three times with 100 mL of 5% sodium bicarbonate aqueous solution, and three times with 100 mL of deionized water, and freeze-dried at 0°C for 24 h.

[0036] The preparation method of the above-mentioned prepolymer is as follows: 20g of isophorone diisocyanate and 30g of polyethylene glycol are dissolved in 200mL of toluene, and stirred at 200r / min for 10min; 1g of triethylenediamine is added, and after heating in an 80°C water bath for 2h, it is cooled to 0°C and allowed to stand for 2h. The precipitate is washed three times with 100ml of ethanol and dried in an 80°C oven for 5h.

[0037] Example 2 A method for preparing an acrylic pressure-sensitive adhesive for high-temperature electrical insulation is as follows: Add 500g of ethyl acetate, 100g of butyl acrylate, 100g of urethane epoxy resin, 50g of methyl methacrylate, and 20g of glycidyl methacrylate into a reactor, stir at 200r / min under a nitrogen atmosphere for 1min, continue to add 1g of benzoyl peroxide under a nitrogen atmosphere, continue to stir at 200r / min for 10min, heat to 80℃ and react for 90min, add 2g of benzoyl peroxide, add it over 10min, and keep it warm for 3h; add 1g of benzoyl peroxide, add it over 10min, and keep it warm at 80℃ for 5h.

[0038] The preparation method of the urethane-based epoxy resin is as follows: 30 g of prepolymer is added to 300 mL of N,N-dimethylformamide, and stirred at 0°C, 200 r / min, and 20 min under a nitrogen atmosphere; 75 g of 3-chloroperoxybenzoic acid is dissolved in 500 mL of N,N-dimethylformamide, and stirred at 0°C, 200 r / min, and 30 min; the two solutions are mixed, stirred at 200 r / min for 8 min, heated to 40°C, reacted for 24 h, filtered, washed three times with 100 mL of 10% sodium bisulfite aqueous solution, washed three times with 100 mL of 5% sodium bicarbonate aqueous solution, washed three times with 100 mL of deionized water, and freeze-dried at 0°C for 24 h.

[0039] The preparation method of the above-mentioned prepolymer is as follows: 20g of isophorone diisocyanate and 30g of p-cresol are dissolved in 200mL of toluene, and stirred at 200r / min for 10min; 1g of triethylenediamine is added, and the mixture is heated in an 80°C water bath for 2h; cooled to 0°C, allowed to stand for 2h, and the precipitate is washed three times with 100mL of ethanol and dried in an oven at 80°C for 5h.

[0040] Example 3 A method for preparing an acrylic pressure-sensitive adhesive for high-temperature electrical insulation is as follows: Add 500g of ethyl acetate, 100g of butyl acrylate, 100g of urethane epoxy resin, 50g of methyl methacrylate, and 20g of glycidyl methacrylate into a reactor, stir at 200r / min under a nitrogen atmosphere for 1min, continue to add 1g of benzoyl peroxide under a nitrogen atmosphere, continue to stir at 200r / min for 10min, heat to 80℃ and react for 90min, add 2g of benzoyl peroxide, add it over 10min, and keep it warm for 3h; add 1g of benzoyl peroxide, add it over 10min, and keep it warm at 80℃ for 5h.

[0041] The preparation method of the urethane-based epoxy resin is as follows: 30 g of prepolymer is added to 300 mL of N,N-dimethylformamide, and stirred at 0°C, nitrogen atmosphere, and 200 r / min for 20 minutes; 75 g of 3-chloroperoxybenzoic acid is dissolved in 500 mL of N,N-dimethylformamide, and stirred at 0°C, 200 r / min for 30 minutes; the two solutions are mixed, stirred at 200 r / min for 8 minutes, heated to 40°C, reacted for 24 hours, filtered, washed three times with 100 mL of 10% sodium bisulfite aqueous solution, washed three times with 100 mL of 5% sodium bicarbonate aqueous solution, washed three times with 100 mL of deionized water, and freeze-dried at 0°C for 24 hours.

[0042] The preparation method of the above-mentioned prepolymer is as follows: 20g of isophorone diisocyanate and 30g of eugenol are dissolved in 200mL of toluene, and stirred at 200r / min for 10min; 1g of triethylenediamine is added, and heated in an 80°C water bath for 2h; cooled to 0°C, allowed to stand for 2h, and the precipitate is washed three times with 100mL of ethanol and dried in an 80°C oven for 5h.

[0043] Example 4 A method for preparing an acrylic pressure-sensitive adhesive for high-temperature electrical insulation is as follows: Add 500g of ethyl acetate, 100g of butyl acrylate, 100g of urethane epoxy resin, 50g of methyl methacrylate, and 20g of glycidyl methacrylate into a reactor, stir at 200r / min under a nitrogen atmosphere for 1min, continue to add 1g of benzoyl peroxide under a nitrogen atmosphere, continue to stir at 200r / min for 10min, heat to 80℃ and react for 90min, add 2g of benzoyl peroxide, add it over 10min, and keep it warm for 3h; add 1g of benzoyl peroxide, add it over 10min, and keep it warm at 80℃ for 5h.

[0044] The urethane-based epoxy resin is prepared by adding 30 g of prepolymer to 300 mL of N,N-dimethylformamide, stirring at 200 r / min at 0°C under a nitrogen atmosphere for 20 minutes, dissolving 75 g of 3-chloroperoxybenzoic acid in 500 mL of N,N-dimethylformamide, and stirring at 200 r / min at 0°C for 30 minutes; mixing the two solutions, stirring at 200 r / min for 8 minutes, heating to 40°C, reacting for 24 hours, filtering, washing with 100 mL of 10% sodium bisulfite aqueous solution three times, washing with 100 mL of 5% sodium bicarbonate aqueous solution three times, washing with 100 mL of deionized water three times, and freeze-drying at 0°C for 24 hours.

[0045] The preparation method of the above-mentioned prepolymer is as follows: 20g of isophorone diisocyanate and 30g of cardanol are dissolved in 200mL of toluene, and stirred at 200r / min for 10min; 1g of triethylenediamine is added, and heated in an 80°C water bath for 2h; cooled to 0°C and allowed to stand for 2h, the precipitate is washed three times with 100mL of ethanol, and dried in an oven at 80°C for 5h.

[0046] Example 5 A method for preparing an acrylic pressure-sensitive adhesive for high-temperature electrical insulation is as follows: Add 500g of ethyl acetate, 100g of butyl acrylate, 100g of urethane epoxy resin, 50g of methyl methacrylate, and 20g of glycidyl methacrylate into the reactor, stir at 200r / min under a nitrogen atmosphere for 1min, continue to add 1g of benzoyl peroxide under a nitrogen atmosphere, continue to stir at 200r / min for 10min, heat to 80℃ and react for 90min, add 2g of benzoyl peroxide, add it over 10min, and keep it warm for 3h; add 1g of benzoyl peroxide, add it over 10min, and keep it warm at 80℃ for 5h.

[0047] The urethane-based epoxy resin is prepared by adding 30 g of prepolymer to 300 mL of N,N-dimethylformamide, stirring at 0°C, nitrogen, and 200 r / min for 20 minutes; dissolving 75 g of 3-chloroperoxybenzoic acid in 500 mL of N,N-dimethylformamide, and stirring at 0°C, 200 r / min for 30 minutes; mixing the two solutions, stirring at 200 r / min for 5-10 minutes, heating to 40°C and reacting for 24 hours, washing three times with 100 mL of 10% sodium bisulfite aqueous solution, filtering, washing three times with 100 mL of 5% sodium bicarbonate aqueous solution, washing three times with 100 mL of deionized water, and freeze-drying at 0°C for 24 hours.

[0048] The preparation method of the above-mentioned prepolymer is as follows: 20g of hexamethylene diisocyanate and 30g of p-cresol are dissolved in 200mL of toluene, and stirred at 200r / min for 10min; 1g of triethylenediamine is added, and the mixture is heated in an 80°C water bath for 2h, cooled to 0°C, and allowed to stand for 2h. The precipitate is washed three times with 100ml of ethanol, and dried in an 80°C oven for 5h.

[0049] Example 6 A method for preparing an acrylic pressure-sensitive adhesive for high-temperature electrical insulation is as follows: 500 g of ethyl acetate, 100 g of butyl acrylate, 100 g of urethane epoxy resin, 50 g of methyl methacrylate, and 20 g of glycidyl methacrylate were added to a reactor, stirred at 200 r / min under a nitrogen atmosphere for 1 min, 0.1 mL of a hydrogen peroxide-ferrous chloride mixed solution was added under a nitrogen atmosphere, and stirring was continued at 200 r / min for 10 min. The mixture was heated to 80° C. and reacted for 90 min. 0.2 mL of a hydrogen peroxide-ferrous chloride mixed solution was added over 10 min and kept warm for 3 h. 0.1 mL of a hydrogen peroxide-ferrous chloride mixed solution was slowly added over 10 min and kept warm at 80° C. for 5 h to obtain the product.

[0050] The above-mentioned hydrogen peroxide-ferrous chloride mixed solution was prepared by dissolving 1.27 g of ferrous chloride in 50 mL of deionized water and diluting the volume to 100 mL; then, 0.306 mL of a 30% aqueous hydrogen peroxide solution was mixed and the volume was diluted to 100 mL with deionized water.

[0051] The urethane-based epoxy resin is prepared by: adding 30 g of prepolymer to 300 mL of N,N-dimethylformamide, stirring at 0°C, nitrogen atmosphere, and 200 r / min for 20 minutes; dissolving 78 g of 3-chloroperoxybenzoic acid in 500 mL of N,N-dimethylformamide, and stirring at 0°C and 200 r / min for 30 minutes; mixing the two solutions, stirring at 200 r / min for 8 minutes, heating to 40°C, and reacting for 24 hours; filtering, washing with 100 mL of 10% sodium bisulfite aqueous solution three times, washing with 100 mL of 5% sodium bicarbonate aqueous solution three times, and washing with 100 mL of deionized water three times, and distilling under reduced pressure to obtain a white solid, dissolving the white solid in 100 mL of toluene, and freeze-drying at 0°C for 24 hours.

[0052] The preparation method of the above-mentioned prepolymer is as follows: 20g of isophorone diisocyanate and 30g of p-cresol are dissolved in 200mL of toluene, and stirred at 200r / min for 10min; 1g of triethylenediamine is added, and heated in an 80°C water bath for 2h; cooled to about 0°C, allowed to stand for 2h, the precipitate is filtered, washed three times with 100mL of ethanol, and dried in an 80°C oven for 5h.

[0053] Comparative Example 1 A method for preparing an acrylic pressure-sensitive adhesive for high-temperature electrical insulation is as follows: Add 500g of ethyl acetate, 100g of butyl acrylate, 100g of epoxy resin, 50g of methyl methacrylate, and 20g of glycidyl methacrylate into a reactor, stir at 200r / min under a nitrogen atmosphere for 1min, add 1g of benzoyl peroxide under a nitrogen atmosphere, continue stirring at 200r / min for 10min, heat to 80℃ and react for 90min, add 2g of benzoyl peroxide, add it over 10min, and keep it warm for 3h; add 1g of benzoyl peroxide, add it slowly over 10min, and keep it warm at 80℃ for 5h to obtain the product.

[0054] Test Example 1 Peel test Peel strength was determined according to the test method for peel strength of adhesive tapes in accordance with GB / T 2792-2014. The acrylic pressure-sensitive adhesives prepared in Examples 1-6 and Comparative Example 1 were coated on a 50 μm PVC film with a thickness of 10±1 μm. The film was dried at 110° C. for 2 min to obtain test samples.

[0055] The test samples were placed in an accelerated aging chamber at a temperature of (120 ± 5)°C and a relative humidity of (80 ± 5)%. After 72 hours, the samples were removed and tested for 180° peel strength. The samples were also observed for any defects such as bubbles, delamination, adhesive overflow, and yellowing. The results are shown in Table 1.

[0056] Table 1 Test results

[0057] Compared to Comparative Example 1, the pressure-sensitive adhesive tapes prepared using urethane-based epoxy resins in Examples 1-6 maintained a substantially smooth appearance, without cracking, blistering, or discoloration. This is likely due to the improved heat and moisture resistance of urethane-based epoxy resins. Their unique structure enhances molecular chain stability in high-temperature and high-humidity environments, making them less susceptible to hydrolysis and degradation, thereby maintaining the tape's overall appearance. This also suggests that the reactive groups, such as amino and ester groups, in urethane-based epoxy resins react with monomers such as acrylates to form crosslinks between polymer chains, enhancing the cohesive strength of the pressure-sensitive adhesive. During aging, this crosslinking effectively prevents molecular chain slippage and breakage, allowing the tapes to maintain high peel strength even after aging. Conventional epoxy resins, lacking these reactive groups and crosslinking, weaken the interchain forces during aging, resulting in a significant decrease in peel strength. Conventional epoxy resins, exposed to high temperatures and high humidity, may experience structural changes due to the brittle nature of the chemical bonds within their molecular chains, leading to blistering and discoloration.

[0058] Further Example 2 relates to a prepolymer of a urethane-based epoxy resin. The added p-cresol has a benzene ring structure, and the conjugated system can effectively disperse the electron cloud, allowing the resulting prepolymer to withstand high temperatures without significant degradation or deformation during the subsequent epoxy resin synthesis and curing process. The benzene ring may participate in the subsequent cross-linking reaction, further improving the mechanical properties and chemical stability of the urethane-based epoxy resin. In contrast, polyethylene glycol has more hydroxyl groups and higher reactivity, which may lead to an uneven molecular structure of the prepolymer or excessive cross-linking. The reactive sites and spatial environment around the phenolic hydroxyl groups of eugenol are more complex, which is not conducive to the access of isocyanate groups. Although cardanol also has certain activity, due to its complex long-chain alkyl structure, there may be uncertain factors during the reaction process, affecting the performance of the prepolymer.

[0059] In contrast, the hydrogen peroxide-ferrous chloride system of Example 6 exhibits superior low-temperature initiation capability, likely due to the generation of hydroxyl radicals during the reaction, which react with functional groups in the monomers, introducing additional crosslinking points into the molecular chain, thereby enhancing the cohesive strength and adhesion of the pressure-sensitive adhesive and increasing its peel strength. However, the polymer chain structure generated by the polymerization reaction initiated by benzoyl peroxide is relatively simple, limiting its ability to modulate the properties of the pressure-sensitive adhesive.

[0060] Test Example 2 Electrical performance test The acrylic pressure-sensitive adhesive prepared in Examples 1-6 and Comparative Example 1 was coated on a 50 μm PVC film at a coating weight of 30 g / cm 2 After drying at 110°C for 2 minutes, the test sample was obtained.

[0061] The prepared test sample, 100 mm long and 10 mm wide, was placed in an electrical strength tester (GB1408) (Source: Beijing Aerospace Zongheng Testing Instrument Co., Ltd.). Both ends were connected to electrodes. Voltage was applied at a typical rate of 1 kV / s. The current change was measured and the electrical strength at the time of electrical breakdown was recorded. The results are shown in Table 2.

[0062] The electric strength formula is:

[0063] Where V is the breakdown voltage (kV) and d is the thickness of the sample (mm).

[0064] Table 2 Electric strength test results

[0065] As shown in Table 2, the electrical strength of the tapes prepared in Examples 1-6 was higher than that of the tape prepared in the comparative example. This indicates that the addition of urethane-based epoxy resin to the pressure-sensitive adhesive has a positive effect on improving the electrical strength of the tape. During the polymerization process, the urethane bonds react with the acrylate monomers to form a more compact and complex cross-linked network structure, effectively restricting the movement of molecular chains and reducing carrier migration channels, thereby improving the electrical strength. Conventional epoxy resins, on the other hand, have a relatively simple molecular structure and may not have the same degree of cross-linking as urethane-based epoxy resins, resulting in their inferior electrical performance.

[0066] In Examples 2 and 5, the prepolymers involved the addition of p-cresol, whose benzene ring structure, likely through π-π stacking, allows for a more regular and compact arrangement of molecular chains. During the subsequent polymerization and curing processes, this regular and compact molecular structure helps improve the stability and performance of the urethane-based epoxy resin, thereby positively impacting the performance of the subsequent acrylic pressure-sensitive adhesive. The molecular structure of the hexamethylene diisocyanate added to Example 5, during the preparation of the prepolymer with p-cresol and the subsequent formation of the urethane-based epoxy resin and pressure-sensitive adhesive, results in a less dense crosslinked network. The weak intermolecular interactions under the action of an electric field make carriers more easily migrated, preventing the molecular arrangement and interactions that improve electrical performance, as seen with isophorone diisocyanate. Consequently, the electrical strength and breakdown voltage are inferior to those of Example 2, which uses isophorone diisocyanate.

[0067] Further, embodiment 6 can relatively easily control the generation speed and quantity of free radicals by regulating the concentration of hydrogen peroxide and ferrous chloride, and then accurately regulate the process of polymerization reaction, so that the polymer molecular chain generated has more suitable length and cross-linking degree.By contrast, the decomposition temperature of benzoyl peroxide is higher, and initiated polymerization at a higher temperature may cause reaction rate too fast, and molecular chain growth is uneven, producing more defects and weak points.In embodiment 6, uniform polymer molecular chain structure can more effectively disperse electric field stress under electric field action, reduce local electric field concentration, thereby improving electrical strength.

[0068] The urethane-based epoxy resin, specific initiator, acrylic monomer and other components in Examples 1-6 work synergistically to enable the prepared pressure-sensitive tape to exhibit advantages over the comparative examples in terms of electrical properties, thereby improving the electrical strength of the tape to meet the higher requirements for the electrical insulation performance of the tape in different application scenarios.

Claims

1. An acrylic pressure-sensitive adhesive for high-temperature electrical insulation, characterized in that: The invention is composed of the following components, calculated in parts by mass: 50-80 parts of ethyl acetate, 8-12 parts of butyl acrylate, 8-12 parts of urethane-based epoxy resin, 3-8 parts of methyl methacrylate, 1-3 parts of glycidyl methacrylate, and 0.3-0.9 parts of initiator.

2. The acrylic pressure-sensitive adhesive for high-temperature electrical insulation according to claim 1, characterized in that: The preparation method of the urethane-based epoxy resin is as follows: 20-50 g of a prepolymer is added to 200-500 mL of N,N-dimethylformamide, and stirred at -5-0° C., a nitrogen atmosphere, and 100-1200 r / min for 10-20 minutes; 70-80 g of 3-chloroperoxybenzoic acid is dissolved in 300-800 mL of N,N-dimethylformamide, and stirred at -5-0° C., 100-200 r / min for 20-30 minutes; the two solutions are mixed, stirred at 100-200 r / min for 5-10 minutes, and then heated to 30-50° C., reacted for 12-36 hours, washed, and dried to obtain the urethane-based epoxy resin.

3. The acrylic pressure-sensitive adhesive for high-temperature electrical insulation according to claim 2, characterized in that: The preparation method of the prepolymer is: Dissolve 10-30g of aliphatic diisocyanate and 20-50g of hydroxyl donor in 100-300mL of toluene, stir at 100-200r / min for 8-12min; add 0.5-3g of triethylenediamine, heat in a water bath at 60-80℃ for 1-2h; cool to 0℃ and let stand for 1-2h, take the precipitate, wash with ethanol and then dry.

4. The acrylic pressure-sensitive adhesive for high-temperature electrical insulation according to claim 3, characterized in that: The aliphatic diisocyanate substance is isophorone diisocyanate or hexamethylene diisocyanate.

5. The acrylic pressure-sensitive adhesive for high-temperature electrical insulation according to claim 3, characterized in that: The hydroxyl donor is any one of polyethylene glycol, p-cresol, eugenol, and cardanol.

6. The acrylic pressure-sensitive adhesive for high-temperature electrical insulation according to claim 1, characterized in that: The initiator is any one of benzoyl peroxide or a hydrogen peroxide-ferrous chloride mixed solution.

7. The method for preparing an acrylic pressure-sensitive adhesive for high-temperature electrical insulation according to any one of claims 1 to 6, characterized in that: Add 50-80 parts of ethyl acetate, 8-12 parts of butyl acrylate, 8-12 parts of urethane epoxy resin, 3-8 parts of methyl methacrylate, and 1-3 parts of glycidyl methacrylate into a reactor, stir for 1-3 minutes at 100-200 r / min under a nitrogen atmosphere, continue to add 0.1-0.3 parts of initiator under a nitrogen atmosphere, continue to stir for 8-12 minutes at 100-200 r / min, heat to 60-80°C and react for 90 minutes, add 0.1-0.3 parts of initiator, add within 8-12 minutes, and keep warm for 1-3 hours; add 0.1-0.3 parts of initiator, add within 8-12 minutes, and keep warm at 60-80°C for 3-8 hours to obtain the product.

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