A delayed curing pressure-sensitive adhesive, a pressure-sensitive adhesive tape and a preparation method thereof

Abstract

The invention relates to a delayed curing pressure-sensitive adhesive, a pressure-sensitive adhesive tape and a preparation method thereof, and belongs to the technical field of pressure-sensitive adhesives. The delayed curing pressure-sensitive adhesive is prepared by using a mercapto-modified hyperbranched epoxy resin with a hyperbranched structure, an acrylate polymer containing epoxy groups and a modified photobase generator coated with a mercapto-modified acrylate polymer containing a photosensitizer as raw materials. The prepared delayed curing pressure-sensitive adhesive has a long storage time and can be deeply cured. After being treated with ultraviolet light, the delayed curing pressure-sensitive adhesive has good mechanical properties and high bonding strength.

Description

Technical Field

[0001] The invention belongs to the technical field of pressure-sensitive adhesives, and in particular relates to a delayed-curing pressure-sensitive adhesive, a pressure-sensitive adhesive tape and a preparation method thereof. Background Art

[0002] Pressure-sensitive adhesive is a type of adhesive that is sensitive to pressure and can be firmly bonded to the adherend. Delayed curing pressure-sensitive adhesive is an adhesive that uses ultraviolet light for curing. Its characteristic is that it can be delayed for a period of time before curing under UV light irradiation. In the prior art, cationic photocuring is often used. The photoinitiator used in cationic photocuring has very strong acidity, and its application is limited. Anionic photoinitiator photobase generator is a new type of photoinitiator developed in recent years. It is a type of compound that can release alkaline substances after being excited by radiation, and can achieve effective base-catalyzed reactions under certain conditions. The base-catalyzed photocuring reaction system has the advantages of small material polymerization shrinkage, no oxygen inhibition, and no corrosion to the substrate. However, during the storage of the adhesive, the photobase generator therein will slowly release alkaline substances, and the shelf life is short. At the same time, the delayed curing pressure-sensitive adhesives in the prior art generally have the problem of low bonding strength. Therefore, it is necessary to provide a delayed curing pressure-sensitive adhesive and pressure-sensitive tape that can solve the above problems. Summary of the invention

[0003] The object of the present invention is to provide a delayed curing pressure-sensitive adhesive, a pressure-sensitive adhesive tape and a preparation method thereof. The delayed curing pressure-sensitive adhesive comprises a mercapto-modified hyperbranched epoxy resin having a hyperbranched structure, an acrylate polymer containing an epoxy group and a modified photobase generator coated with a mercapto-modified acrylate polymer containing a photosensitizer as raw materials. The prepared delayed curing pressure-sensitive adhesive has a long storage time and can be deeply cured. The pressure-sensitive adhesive tape obtained after ultraviolet light treatment has good mechanical properties and high bonding strength.

[0004] The technical problem to be solved by the present invention is that during the storage of the adhesive, the photobase generator therein will slowly release alkaline substances, resulting in a short shelf life; at the same time, the delayed curing pressure-sensitive adhesives in the prior art generally have the problem of low bonding strength.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A delayed curing pressure-sensitive adhesive comprises the following components in parts by weight: 1-5 parts of mercapto-modified hyperbranched epoxy resin, 65-90 parts of acrylate polymer and 1-4 parts of modified photobase generator.

[0007] Furthermore, the preparation method of the mercapto-modified hyperbranched epoxy resin comprises the following steps:

[0008] A1. Under nitrogen protection, trimethylolpropane triglycidyl ether and 3,3',5,5'-tetramethylbiphenol are heated and stirred until completely dissolved, and then tetrabutylammonium bromide is added, reacted at 85-90°C for 5-8h, cooled to room temperature, tetrahydrofuran is added and stirred evenly, and then 50-55°C hot water is added, stirred evenly and allowed to stand, an organic phase is separated, and the organic phase is dissolved in tetrahydrofuran, dried over magnesium sulfate, filtered, and the obtained filtrate is added to ether, allowed to stand, an organic phase is separated, and finally vacuum dried to obtain a hyperbranched epoxy resin;

[0009] Furthermore, in step A1, the molar ratio of trimethylolpropane triglycidyl ether to 3,3',5,5'-tetramethylbiphenol is 3-3.2:1.

[0010] A2. Evenly mix the hyperbranched epoxy resin and the dithiol-terminated thiol 1, add a tertiary amine, and then react at 55-60° C. for 8-12 hours. After the reaction, add citric acid and mix and stir for 2-3 hours to obtain a thiol-modified hyperbranched epoxy resin.

[0011] Furthermore, in step A2, the molar ratio of the epoxy functional groups in the hyperbranched epoxy resin to the thiol functional groups in the dithiol-terminated thiol 1 is 1:(2.05-2.1).

[0012] Furthermore, in step A2, the dithiol-terminated thiol 1 is at least one of 3,6-dioxo-1,8-octanedithiol, thiodiglycol mercaptan, 1,4-benzenedimethylenethiol, 1,3-benzenedimethylenethiol, 2,5-dimethylmercapto-1,4-dithiane, and 4,4′-bis(mercaptomethyl)biphenyl.

[0013] In the preparation process of the above-mentioned mercapto-modified hyperbranched epoxy resin, trimethylolpropane triglycidyl ether and 3,3',5,5'-tetramethylbiphenol are first used as raw materials to prepare a hyperbranched epoxy resin, and then the mercapto group in the dithiol-terminated thiol is reacted with the epoxy group of the hyperbranched epoxy resin to obtain the mercapto-modified hyperbranched epoxy resin.

[0014] Furthermore, the acrylate polymer is prepared by copolymerization of non-functional acrylate monomers and epoxy-containing acrylate monomers under the action of an initiator.

[0015] Furthermore, the non-functional acrylic ester monomers include at least two of isooctyl acrylate, butyl acrylate, methyl acrylate, n-octyl acrylate, and isononyl acrylate.

[0016] Furthermore, the epoxy-containing acrylic ester monomer includes glycidyl acrylate.

[0017] Furthermore, the preparation method of the modified photobase generator comprises the following steps:

[0018] B1, methyl methacrylate, isooctyl acrylate, acrylic acid ester monomer containing epoxy group and photosensitizer are mixed evenly, and then ethanol is added and stirred until completely dissolved, initiator 2 is added, the temperature is raised to 70-80°C and kept for 4-7h, and then the temperature is raised to 90-100°C, and the ethanol solvent is removed to obtain an acrylic acid ester polymer containing a photosensitizer;

[0019] Furthermore, in step B1, the photosensitizer is at least one of benzophenone, acetophenone, and ferric acetylacetonate.

[0020] Furthermore, in step B1, the initiator 2 is at least one of benzoyl peroxide, tert-butyl benzoyl peroxide, methyl ethyl ketone peroxide, azobisisobutyronitrile, azobisisoheptanenitrile and dimethyl azobisisobutyrate.

[0021] Furthermore, in step B1, the mass ratio of methyl methacrylate, isooctyl acrylate, acrylic acid ester monomer containing epoxy group, initiator 2, photosensitizer and ethanol is (15-20): (140-155): (2.5-4): (1.5-1.8): (1.6-1.8): (140-200).

[0022] B2, the acrylate polymer containing the photosensitizer and the dithiol-terminated thiol 2 are mixed evenly, a tertiary amine is added, and the mixture is heated at 65-70° C. for reaction for 2-4 hours, and citric acid is added and stirred for 1 hour to obtain a thiol-modified acrylate polymer containing the photosensitizer;

[0023] Furthermore, in step B2, the molar ratio of the epoxy group in the acrylate polymer containing the photosensitizer to the thiol group in the dithiol-terminated thiol 2 is 1:(2.1-2.15).

[0024] Furthermore, in step B2, the dithiol-terminated thiol 2 includes at least one of 3,6-dioxo-1,8-octanedithiol and thiodiglycol mercaptan.

[0025] B3. Dissolve the photobase generator in acetonitrile, then add it to the mercapto-modified acrylate polymer containing the photosensitizer, and let it stand for swelling for 5-7 hours to obtain a modified photobase generator.

[0026] Furthermore, in step B3, the mass ratio of the photobase generator, acetonitrile and the mercapto-modified acrylate polymer containing the photosensitizer is (10-13): (15-20): (80-95).

[0027] Furthermore, in step B3, the photobase generator includes at least one of a carboxylate photobase generator, a borate photobase generator, a carbamate photobase generator and an azacyclic amidine photobase generator.

[0028] In the preparation process of the modified photobase generator, a mercapto-modified acrylate polymer containing a photosensitizer is coated on the surface of the photobase generator, which can improve the stability of the adhesive, avoid the problem of the photobase generator decomposing alkaline substances during storage to cause the curing reaction, and increase the storage time. The mercapto-modified acrylate polymer containing a photosensitizer coated on the surface of the photobase generator can be rapidly depolymerized under UV light, and the photosensitizer present in the polymer can accelerate the decomposition of the polymer and the release rate of the photobase generator. At the same time, the photosensitizer can increase the photosensitivity of the photobase generator in the long wavelength region and accelerate the light initiation rate, thereby accelerating the curing rate. The mercapto-modified acrylate polymer coated on the surface of the photobase generator is rapidly depolymerized under UV light, and the low molecular weight compounds containing mercapto groups generated by depolymerization can click with the epoxy groups on the acrylate polymer, thereby reducing the low molecular weight compounds generated by depolymerization from being free in the adhesive and affecting the comprehensive performance of the adhesive.

[0029] In another aspect, the present invention provides a method for preparing a delayed curing pressure-sensitive adhesive, comprising the following steps:

[0030] S1, mixing a non-functional acrylate monomer and an epoxy-containing acrylate monomer to obtain a mixed monomer;

[0031] S2. Add one third of ethyl acetate into the reactor, introduce inert gas and add two thirds of the mixed monomers, stir evenly and heat to 70-80°C, add two thirds of initiator 1, react for 15-30 minutes, then add the remaining mixed monomers and the remaining mixed solution of ethyl acetate and initiator 1, keep warm and reflux for 3-4 hours to obtain an acrylate polymer.

[0032] Furthermore, in step S2, the mass ratio of the non-functional acrylate monomer, the epoxy-containing acrylate monomer, the initiator 1 and ethyl acetate is (80-100):(1-5):(0.5-1.5):(200-280).

[0033] Further, in step S2, the initiator 1 is at least one of benzoyl peroxide, tert-butyl benzoyl peroxide, methyl ethyl ketone peroxide, azobisisobutyronitrile, azobisisoheptanenitrile and dimethyl azobisisobutyrate.

[0034] S3, uniformly mixing the acrylate polymer, the mercapto-modified hyperbranched epoxy resin and the modified photobase generator, extracting and removing the ethyl acetate to obtain a delayed curing pressure-sensitive adhesive.

[0035] In the above-mentioned preparation process, the thiol-modified hyperbranched epoxy resin has a hyperbranched structure, low viscosity, good rheology, can reduce the viscosity of the adhesive, and help the modified photobase generator to be uniformly dispersed in the adhesive. The thiol-modified hyperbranched epoxy resin has high functionality. Under the catalysis of the alkaline substance generated by the light of the photobase generator, the thiol groups on the thiol-modified hyperbranched epoxy resin and the epoxy groups on the acrylate polymer undergo a click reaction, thereby increasing the crosslinking density of the adhesive. The present invention coats the thiol-modified acrylate polymer containing a photosensitizer on the surface of the photobase generator, improves the compatibility of the photobase generator with the acrylate polymer, and facilitates the uniform dispersion of the modified photobase generator in the adhesive. Thus, it helps the adhesive to be deeply cured, and the pressure-sensitive tape obtained after ultraviolet light treatment has good mechanical properties and high bonding strength.

[0036] The present invention also provides a pressure-sensitive adhesive tape, comprising an adhesive layer, wherein the adhesive layer is composed of the delayed curing pressure-sensitive adhesive.

[0037] Beneficial effects of the present invention:

[0038] (1) In the technical solution of the present invention, the thiol-modified hyperbranched epoxy resin has a hyperbranched structure, low viscosity, and good rheological properties. It can reduce the viscosity of the adhesive and help the modified photobase generator to be evenly dispersed in the adhesive. The thiol-modified hyperbranched epoxy resin has a high functionality. Under the catalysis of the alkaline substance generated by the photobase generator, the thiol groups on the thiol-modified hyperbranched epoxy resin and the epoxy groups on the acrylate polymer undergo a click reaction, thereby increasing the crosslinking density of the adhesive. The present invention coats the thiol-modified acrylate polymer containing a photosensitizer on the surface of the photobase generator, thereby improving the compatibility of the photobase generator and the acrylate polymer, and facilitating the uniform dispersion of the modified photobase generator in the adhesive. As a result, the adhesive is helped to undergo deep curing, and the pressure-sensitive tape obtained after ultraviolet light treatment has good mechanical properties and high bonding strength.

[0039] (2) In the technical solution of the present invention, a mercapto-modified acrylate polymer containing a photosensitizer is coated on the surface of the photobase generator, which can improve the stability of the adhesive and avoid the problem of the photobase generator decomposing alkaline substances during storage to cause a curing reaction, thereby increasing the storage time.

[0040] (3) In the technical solution of the present invention, the mercapto-modified acrylate polymer containing a photosensitizer coated on the surface of the photobase generator can undergo rapid depolymerization under UV light. At the same time, the photosensitizer present in the polymer can accelerate the decomposition of the polymer and the release rate of the photobase generator. At the same time, the photosensitizer can increase the photosensitivity of the photobase generator in the long wavelength region and accelerate the photoinitiation rate, thereby accelerating the curing speed.

[0041] (4) In the technical solution of the present invention, the mercapto-modified acrylate polymer coated on the surface of the photobase generator undergoes rapid depolymerization under UV light, and the low molecular weight compounds containing mercapto groups produced by the depolymerization can undergo a click reaction with the epoxy groups on the acrylate polymer, thereby reducing the low molecular weight compounds produced by the depolymerization from being free in the adhesive and affecting the overall performance of the adhesive. DETAILED DESCRIPTION

[0042] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] Embodiment 1:

[0044] This embodiment provides a method for preparing a mercapto-modified hyperbranched epoxy resin, comprising the following steps:

[0045] A1. Under nitrogen protection, 181.4 g of trimethylolpropane triglycidyl ether and 48.5 g of 3,3',5,5'-tetramethylbiphenol were heated and stirred until completely dissolved, then 9.64 g of tetrabutylammonium bromide was added, and the mixture was reacted at 85° C. for 5 h, cooled to room temperature, 90 mL of tetrahydrofuran was added and stirred evenly, and then 50° C. hot water was added, stirred evenly and allowed to stand, and an organic phase was separated, and the organic phase was dissolved in 90 mL of tetrahydrofuran, dried over magnesium sulfate, filtered, and the obtained filtrate was added to ether, allowed to stand, and an organic phase was separated, and finally vacuum dried to obtain a hyperbranched epoxy resin;

[0046] A2. Mix the hyperbranched epoxy resin and 1,4-benzenedimethylene mercaptan evenly, wherein the molar ratio of the epoxy functional group in the hyperbranched epoxy resin to the thiol functional group in 1,4-benzenedimethylene mercaptan is 1:2.05, add tertiary amine DMP-30 which accounts for 2% of the total amount of the hyperbranched epoxy resin and 1,4-benzenedimethylene mercaptan, and then react at 55°C for 8h. After the reaction, add the hyperbranched epoxy resin and citric acid which accounts for 1.5% of the total amount of 1,4-benzenedimethylene mercaptan, mix and stir for 2h to obtain a thiol-modified hyperbranched epoxy resin.

[0047] Embodiment 2:

[0048] This embodiment provides a method for preparing a mercapto-modified hyperbranched epoxy resin, comprising the following steps:

[0049] A1. Under nitrogen protection, 186.7 g of trimethylolpropane triglycidyl ether and 48.5 g of 3,3',5,5'-tetramethylbiphenol were heated and stirred until completely dissolved, then 9.96 g of tetrabutylammonium bromide was added, and the mixture was reacted at 85° C. for 7 h, cooled to room temperature, 90 mL of tetrahydrofuran was added and stirred, and then 55° C. hot water was added, stirred and allowed to stand, and an organic phase was separated. The organic phase was dissolved in 90 mL of tetrahydrofuran, dried over magnesium sulfate, filtered, and the obtained filtrate was added to ether, allowed to stand, and an organic phase was separated. Finally, the mixture was dried in vacuo to obtain a hyperbranched epoxy resin.

[0050] A2. Mix the hyperbranched epoxy resin and 4,4′-bis(mercaptomethyl)biphenyl evenly, wherein the molar ratio of the epoxy functional group in the hyperbranched epoxy resin to the thiol functional group in 4,4′-bis(mercaptomethyl)biphenyl is 1:2.05, add tertiary amine DMP-30 in an amount of 2% of the total amount of the hyperbranched epoxy resin and 4,4′-bis(mercaptomethyl)biphenyl, and then react at 55°C for 12 hours. After the reaction, add the hyperbranched epoxy resin and citric acid in an amount of 1.5% of the total amount of 4,4′-bis(mercaptomethyl)biphenyl, and mix and stir for 3 hours to obtain a thiol-modified hyperbranched epoxy resin.

[0051] Embodiment 3:

[0052] This embodiment provides a method for preparing a mercapto-modified hyperbranched epoxy resin, comprising the following steps:

[0053] A1. Under nitrogen protection, 193.5 g of trimethylolpropane triglycidyl ether and 48.5 g of 3,3',5,5'-tetramethylbiphenol were heated and stirred until completely dissolved, then 10.31 g of tetrabutylammonium bromide was added, and the mixture was reacted at 90 ° C for 8 h, cooled to room temperature, 100 mL of tetrahydrofuran was added and stirred evenly, and then 55 ° C hot water was added, stirred evenly and allowed to stand, and the organic phase was separated, and the organic phase was dissolved in 100 mL of tetrahydrofuran, and then dried over magnesium sulfate, filtered, and the obtained filtrate was added to ether, allowed to stand, and the organic phase was separated, and finally vacuum dried to obtain a hyperbranched epoxy resin;

[0054] A2. Mix the hyperbranched epoxy resin and 4,4′-bis(mercaptomethyl)biphenyl evenly, wherein the molar ratio of the epoxy functional group in the hyperbranched epoxy resin to the thiol functional group in 4,4′-bis(mercaptomethyl)biphenyl is 1:2.1, add tertiary amine DMP-30 in an amount of 2% of the total amount of the hyperbranched epoxy resin and 4,4′-bis(mercaptomethyl)biphenyl, and then react at 60°C for 12 hours. After the reaction, add citric acid in an amount of 1.5% of the total amount of the hyperbranched epoxy resin and 4,4′-bis(mercaptomethyl)biphenyl, mix and stir for 3 hours to obtain a thiol-modified hyperbranched epoxy resin.

[0055] Embodiment 4:

[0056] This embodiment provides a method for preparing a modified photobase generator, comprising the following steps:

[0057] B1. 15 g of methyl methacrylate, 140 g of isooctyl acrylate, 2.5 g of an acrylate monomer containing an epoxy group and 1.6 g of benzophenone were mixed evenly, 140 g of ethanol was added and stirred until completely dissolved, 1.5 g of benzoyl peroxide was added, the temperature was raised to 70° C. and kept warm for 4 h, then the temperature was raised to 90° C., the ethanol solvent was removed, and an acrylate polymer containing a photosensitizer was obtained;

[0058] B2, the acrylate polymer containing photosensitizer and 3,6-dioxy-1,8-octanedithiol are mixed evenly, wherein the molar ratio of the epoxy group in the acrylate polymer containing photosensitizer to the thiol group in 3,6-dioxy-1,8-octanedithiol is 1:2.1, tertiary amine in an amount of 1.8% of the total amount of the acrylate polymer containing photosensitizer and 3,6-dioxy-1,8-octanedithiol is added, heating the reaction at 65° C. for 2 h, citric acid in an amount of 1.3% of the total amount of the acrylate polymer containing photosensitizer and 3,6-dioxy-1,8-octanedithiol is added, and stirred for 1 h to obtain a thiol-modified acrylate polymer containing photosensitizer;

[0059] B3. Dissolve 10 g of photobase generator PB-D02 in 15 g of acetonitrile, then add to 80 g of mercapto-modified acrylate polymer containing a photosensitizer, and let it stand for swelling for 5 hours to obtain a modified photobase generator.

[0060] Embodiment 5:

[0061] This embodiment provides a method for preparing a modified photobase generator, comprising the following steps:

[0062] B1. 17 g of methyl methacrylate, 148 g of isooctyl acrylate, 3.2 g of an acrylate monomer containing an epoxy group and 1.7 g of acetophenone were mixed evenly, 175 g of ethanol was added and stirred until completely dissolved, 1.7 g of azobisisobutyronitrile was added, the temperature was raised to 70° C. and kept warm for 7 h, then the temperature was raised to 100° C., the ethanol solvent was removed, and an acrylate polymer containing a photosensitizer was obtained;

[0063] B2, the acrylate polymer containing photosensitizer and 3,6-dioxy-1,8-octanedithiol are uniformly mixed, wherein the molar ratio of the epoxy group in the acrylate polymer containing photosensitizer to the thiol group in 3,6-dioxy-1,8-octanedithiol is 1:2.15, tertiary amine is added in an amount of 1.8% of the total amount of the acrylate polymer containing photosensitizer and 3,6-dioxy-1,8-octanedithiol, and the mixture is heated at 70° C. for reaction for 3 h, citric acid is added in an amount of 1.3% of the total amount of the acrylate polymer containing photosensitizer and 3,6-dioxy-1,8-octanedithiol, and stirred for 1 h to obtain a thiol-modified acrylate polymer containing photosensitizer;

[0064] B3. Dissolve 11 g of photobase generator PB-D02 in 17 g of acetonitrile, then add to 89 g of mercapto-modified acrylate polymer containing a photosensitizer, and allow to swell for 6 hours to obtain a modified photobase generator.

[0065] Embodiment 6:

[0066] This embodiment provides a method for preparing a modified photobase generator, comprising the following steps:

[0067] B1, 20g methyl methacrylate, 155g isooctyl acrylate, 4g acrylate monomer containing epoxy group and 1.8g ferric acetylacetonate are mixed evenly, and then 200g ethanol is added and stirred until completely dissolved, and 1.8g azobisisobutyronitrile is added, and the temperature is raised to 80°C and kept for 7h, and then the temperature is raised to 100°C, and the ethanol solvent is removed to obtain an acrylate polymer containing a photosensitizer;

[0068] B2. Evenly mix the acrylate polymer containing a photosensitizer and thiodiglycol mercaptan, wherein the molar ratio of the epoxy group in the acrylate polymer containing a photosensitizer to the thiol group in thiodiglycol mercaptan is 1:2.15, add the acrylate polymer containing a photosensitizer and a tertiary amine in an amount of 1.8% of the total amount of thiodiglycol mercaptan, heat and react at 70°C for 4h, add the acrylate polymer containing a photosensitizer and citric acid in an amount of 1.3% of the total amount of thiodiglycol mercaptan, and stir for 1h to obtain a thiol-modified acrylate polymer containing a photosensitizer;

[0069] B3. Dissolve 13 g of photobase generator TBD·HBPh4 in 20 g of acetonitrile, then add to 95 g of mercapto-modified acrylate polymer containing a photosensitizer, and allow to swell for 7 hours to obtain a modified photobase generator.

[0070] Comparative Example 1:

[0071] Compared with Example 6, the photobase generator in Comparative Example 1 was not coated, and the other steps and raw materials were the same as those in Example 6.

[0072] Comparative Example 2:

[0073] Compared with Example 6, the mercapto-modified acrylate polymer coated on the surface of the modified photobase generator in Comparative Example 2 does not contain a photosensitizer, and the other steps and raw materials are the same as those in Example 6.

[0074] Comparative Example 3:

[0075] Compared with Example 6, the acrylate polymer coated on the surface of the modified photobase generator in Comparative Example 3 was not modified with thiol groups, and the other steps and raw materials were the same as those in Example 6.

[0076] Embodiment 7:

[0077] A delayed curing pressure-sensitive adhesive comprises the following components in parts by weight: 1 part of the mercapto-modified hyperbranched epoxy resin prepared in Example 1, 65 parts of an acrylate polymer, and 1 part of a modified photobase generator prepared in Example 4.

[0078] A method for preparing a delayed curing pressure-sensitive adhesive comprises the following steps:

[0079] S1, 183g of isooctyl acrylate, 57g of butyl acrylate and 3g of glycidyl acrylate are mixed to obtain a mixed monomer;

[0080] S2, add 200g of ethyl acetate into the reactor, introduce nitrogen and add 162g of mixed monomer, stir evenly and heat to 70°C, add 1g of benzoyl peroxide, react for 15min, then add a mixed solution of 81g of mixed monomer, 400g of ethyl acetate and 0.5g of initiator, keep warm and reflux for 3h to obtain acrylate polymer;

[0081] S3. Weigh the above components in parts by weight, mix the acrylate polymer, the mercapto-modified hyperbranched epoxy resin and the modified photobase generator evenly, extract and remove the ethyl acetate to obtain a delayed curing pressure-sensitive adhesive.

[0082] Embodiment 8:

[0083] A delayed curing pressure-sensitive adhesive comprises the following components in parts by weight: 3 parts of the mercapto-modified hyperbranched epoxy resin prepared in Example 2, 78 parts of an acrylate polymer, and 2.7 parts of a modified photobase generator prepared in Example 5.

[0084] A method for preparing a delayed curing pressure-sensitive adhesive comprises the following steps:

[0085] S1, 213g of isooctyl acrylate, 67g of butyl acrylate and 9g of glycidyl acrylate are mixed to obtain a mixed monomer;

[0086] S2. Add 240 g of ethyl acetate into a reactor, introduce nitrogen and add 193 g of mixed monomers, stir evenly and heat to 80°C, add 2 g of azobisisobutyronitrile, react for 20 min, then add a mixed solution of 96 g of mixed monomers, 480 g of ethyl acetate and 1 g of azobisisobutyronitrile, keep warm and reflux for 3.5 h to obtain an acrylate polymer.

[0087] S3. Weigh the above components in parts by weight, mix the acrylate polymer, the mercapto-modified hyperbranched epoxy resin and the modified photobase generator evenly, extract and remove the ethyl acetate to obtain a delayed curing pressure-sensitive adhesive.

[0088] Embodiment 9:

[0089] A delayed curing pressure-sensitive adhesive comprises the following components in parts by weight: 5 parts of the mercapto-modified hyperbranched epoxy resin prepared in Example 3, 90 parts of an acrylate polymer, and 4 parts of a modified photobase generator prepared in Example 6.

[0090] A method for preparing a delayed curing pressure-sensitive adhesive comprises the following steps:

[0091] S1, 228g of isooctyl acrylate, 72g of butyl acrylate and 15g of glycidyl acrylate are mixed to obtain a mixed monomer;

[0092] S2, add 280g of ethyl acetate into the reactor, introduce nitrogen and add 210g of mixed monomer, stir evenly and heat to 80°C, add 3g of azobisisoheptanonitrile, react for 30min, then add a mixed solution of 105g of mixed monomer, 560g of ethyl acetate and 1.5g of azobisisoheptanonitrile, keep warm and reflux for 4h to obtain an acrylate polymer.

[0093] S3. Weigh the above components in parts by weight, mix the acrylate polymer, the mercapto-modified hyperbranched epoxy resin and the modified photobase generator evenly, extract and remove the ethyl acetate to obtain a delayed curing pressure-sensitive adhesive.

[0094] Comparative Example 4:

[0095] Compared with Example 8, the modified photobase generator in Comparative Example 4 uses the substance prepared in Comparative Example 1, and the other steps and raw materials are the same as those in Example 8.

[0096] Comparative Example 5:

[0097] Compared with Example 8, the modified photobase generator in Comparative Example 5 uses the substance prepared in Comparative Example 2, and the other steps and raw materials are the same as those in Example 8.

[0098] Comparative Example 6:

[0099] Compared with Example 8, the modified photobase generator in Comparative Example 6 uses the material prepared in Comparative Example 3, and the other steps and raw materials are the same as those in Example 8.

[0100] Performance testing:

[0101] Peel strength: The delayed curing pressure-sensitive adhesives prepared in Examples 7-9 and Comparative Examples 4-7 were coated on a PET base film with a thickness of 50 μm and then exposed to UV at a dose of about 250 mJ / cm 2 The pressure-sensitive adhesive was irradiated under 400 °C and its peel strength to stainless steel was measured according to ASTM D3330 method.

[0102] Tensile shear strength: The tensile shear strength is tested according to the standard of GB / T 7124-2008;

[0103] Storage stability: record the number of days that the delayed-curing pressure-sensitive adhesive is stored at room temperature without curing and hardening.

[0104]

[0105] It can be seen from the data in Table 1 that the delayed curing pressure-sensitive adhesive prepared by the present invention has good peel strength and shear strength after UV curing, and has good storage stability. It can be seen from the data of Comparative Example 8 and Comparative Example 4 that since the photobase generator is not coated, the peel strength, shear strength and storage stability of the delayed curing pressure-sensitive adhesive after UV curing are all reduced, indicating that the coated photobase generator is more evenly dispersed in the adhesive, which is conducive to deep curing, thereby improving the peel strength and shear strength, and the storage stability is significantly improved after being protected by the polymer. It can be seen from the data of Comparative Example 8 and Comparative Example 5 that since the adhesive does not contain a photosensitizer, the release rate of the photobase generator is reduced and the photosensitivity is reduced, resulting in a decrease in peel strength and shear strength. It can be seen from the data of Comparative Example 8 and Comparative Example 6 that the polymer coated on the surface of the photobase generator is not modified by thiol, resulting in the low molecular weight compounds produced by depolymerization being free in the adhesive, thereby reducing the peel strength and shear strength.

[0106] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0107] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A delayed curing pressure-sensitive adhesive, characterized in that: The invention comprises the following components in parts by weight: 1-5 parts of mercapto-modified hyperbranched epoxy resin, 65-90 parts of acrylate polymer and 1-4 parts of modified photobase generator; The acrylic ester polymer is prepared by copolymerization of a non-functional acrylic ester monomer and an epoxy-containing acrylic ester monomer under the action of an initiator; The preparation method of the mercapto-modified hyperbranched epoxy resin comprises the following steps: A1. Under nitrogen protection, trimethylolpropane triglycidyl ether and 3,3',5,5'-tetramethylbiphenol are heated and stirred until completely dissolved, and then tetrabutylammonium bromide is added, reacted at 85-90°C for 5-8h, cooled to room temperature, tetrahydrofuran is added and stirred evenly, and then 50-55°C hot water is added, stirred evenly and allowed to stand, an organic phase is separated, and the organic phase is dissolved in tetrahydrofuran, dried over magnesium sulfate, filtered, and the obtained filtrate is added to ether, allowed to stand, an organic phase is separated, and finally vacuum dried to obtain a hyperbranched epoxy resin; A2, the hyperbranched epoxy resin and the dithiol-terminated thiol 1 are mixed evenly, a tertiary amine is added, and then the mixture is reacted at 55-60° C. for 8-12 hours. After the reaction is completed, citric acid is added and mixed and stirred for 2-3 hours to obtain a thiol-modified hyperbranched epoxy resin; In the step A1, the molar ratio of trimethylolpropane triglycidyl ether to 3,3',5,5'-tetramethylbiphenol is 3-3.2:1; In the step A2, the molar ratio of the epoxy functional group in the hyperbranched epoxy resin to the thiol functional group in the dithiol-terminated thiol 1 is 1:(2.05-2.1); The preparation method of the modified photobase generator comprises the following steps: B1, methyl methacrylate, isooctyl acrylate, acrylic acid ester monomer containing epoxy group and photosensitizer are mixed evenly, and then ethanol is added and stirred until completely dissolved, initiator 2 is added, the temperature is raised to 70-80°C and kept for 4-7h, and then the temperature is raised to 90-100°C, and the ethanol solvent is removed to obtain an acrylic acid ester polymer containing a photosensitizer; B2, the acrylate polymer containing the photosensitizer and the dithiol-terminated thiol 2 are mixed evenly, a tertiary amine is added, and the mixture is heated at 65-70° C. for reaction for 2-4 hours, and citric acid is added and stirred for 1 hour to obtain a thiol-modified acrylate polymer containing the photosensitizer; B3, dissolving the photobase generator in acetonitrile, then adding it to the mercapto-modified acrylate polymer containing the photosensitizer, and standing it to swell for 5-7 hours to obtain a modified photobase generator; In the step B1, the mass ratio of methyl methacrylate, isooctyl acrylate, acrylic acid ester monomer containing epoxy group, initiator 2, photosensitizer and ethanol is (15-20): (140-155): (2.5-4): (1.5-1.8): (1.6-1.8): (140-200); In the step B2, the molar ratio of the epoxy group in the acrylate polymer containing the photosensitizer to the thiol group in the dithiol-terminated thiol 2 is 1:(2.1-2.15); In the step B3, the mass ratio of the photobase generator, acetonitrile and the mercapto-modified acrylate polymer containing the photosensitizer is (10-13): (15-20): (80-95).

2. A method for preparing the delayed curing pressure-sensitive adhesive according to claim 1, characterized in that: The following steps are involved: S1, mixing a non-functional acrylate monomer and an epoxy-containing acrylate monomer to obtain a mixed monomer; S2. Add one third of ethyl acetate into the reactor, introduce inert gas and add two thirds of the mixed monomers, stir evenly and heat to 70-80°C, add two thirds of initiator 1, react for 15-30 minutes, then add the remaining mixed monomers and the remaining mixed solution of ethyl acetate and initiator 1, keep warm and reflux for 3-4 hours to obtain an acrylate polymer.

3. The method for preparing a delayed curing pressure-sensitive adhesive according to claim 2, characterized in that: In the step S2, the mass ratio of the non-functional acrylate monomer, the epoxy-containing acrylate monomer, the initiator 1 and ethyl acetate is (80-100): (1-5): (0.5-1.5): (200-280). 4 . A pressure-sensitive adhesive tape comprising an adhesive layer, wherein the adhesive layer is composed of the delayed curing pressure-sensitive adhesive according to claim 1 .

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