Photobase generator, adhesive composition and preparation method thereof

Abstract

The invention discloses an imino photobase generator, and the imino photobase generator is a complex formed by an imine intermediate and a photobase generator, the molar ratio of the imine intermediate to the photobase generator is 1: 1. The invention also discloses an adhesive composition containing the imino photobase generator and a preparation method of the imino photobase generator. The adhesive composition prepared by adopting the imino photobase generator has a window period for delaying curing, and can be used for bonding low ultraviolet light transmission base materials.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of photocuring, and particularly relates to a photoalkaline agent, an adhesive composition and a preparation method thereof. BACKGROUND

[0002] UV glue is a kind of adhesive that can be cured by ultraviolet irradiation. The curing principle is that the active species (free radicals, hydrogen ions, amines) generated by the photoinitiator under light irradiation initiate the polymerization of monomers. UV glue has many advantages, such as safety, environmental protection, no pollution, fast curing speed, excellent compatibility, and high bonding strength, and is widely used in the field of precision electronic device packaging. However, the current UV glue still has many disadvantages, for example, when the substrate to be bonded cannot transmit ultraviolet light, the photoinitiator cannot be activated and the final curing cannot be achieved.

[0003] An effective method is to develop UV glue that can provide a certain operation time after light irradiation and then bond. In recent years, based on specific formula design, resin structure design and other methods, people have been able to prepare some UV-delayed curing glues. For example, CN118307767A can achieve a certain delay time by structural design of epoxy compounds. Zhu et al. used multifunctional glycidyl ethers to achieve the characteristics of slow curing speed, and also developed a delayed curing glue (RSC Adv. 2017, 7, 4046-4053). Harikrishna added amine compounds to the cationic curing composition, which can consume the generated hydrogen ions at the initial stage of the reaction, so as to delay the gel time (Journal of Photochemistry and Photobiology A: Chemistry 2015, 303, 17). However, most of these strategies are effective for some specific formula range, and when the formula contains high-reactivity resins (such as alicyclic epoxy resins), the system will still quickly cure. Moreover, the above-mentioned glues belong to cationic polymerization systems, which have the problem of corrosion to the substrate.

[0004] In summary, there is an urgent need in the art for a delayed curing platform that can achieve delayed curing effect for glues containing high-reactivity resins, and can artificially control the delay window according to actual process requirements. SUMMARY

[0005] Based on the above analysis, the present application aims to provide a photoalkaline agent, an adhesive composition and a preparation method thereof.

[0006] In a first aspect, the present application provides an imine-based photo-base generator, wherein the imine-based photo-base generator is a complex of an imine intermediate and a photo-base generator, the molar ratio of the imine intermediate to the photo-base generator is 1:1; the structure of the imine intermediate is as follows: , wherein each R1, R2 is independently selected from an aromatic ring group, a heteroaromatic group, or each pair of R1 and R2 is connected to each other to form an aromatic ring group or a heteroaromatic group, the aromatic ring group or the heteroaromatic group is a 5-7 membered ring; n is an integer selected from 1-10, preferably an integer selected from 1-5.

[0007] In a second aspect, the present application provides a method for preparing the imine-based photo-base generator of the first aspect. The method comprises the following steps: (1) preparing an imine intermediate; (2) mixing a photo-base generator with a solution of the imine intermediate to obtain the imine-based photo-base generator; wherein the molar ratio of the photo-base generator to the imine intermediate is 1:1; preferably, the reaction temperature of the step (2) is -20-100℃, more preferably 0-70℃. Further, the imine intermediate is prepared by reacting an imine compound containing an active functional group with a chloroether compound under alkaline conditions in the step (1); preferably, the alkaline conditions are preferably sodium hydride, sodium tert-butoxide, lithium diisopropylamide; preferably, the reaction temperature of the step (1) is -20-100℃.

[0008] In a third aspect, the present application provides an adhesive composition, comprising: 0.01-1 parts by mass of the imine-based photo-base generator of the first aspect of the present application or the imine-based photo-base generator prepared by the method of the second aspect of the present application; 1-10 parts by mass of a resin; 1-10 parts by mass of a thiol curing agent; 0.01-1 parts by mass of a silane coupling agent; 0.01-1 parts by mass of a photosensitizer, and 0-1 parts by mass of a free radical polymerization inhibitor; wherein the resin is an epoxy resin, an acrylic resin, or a combination thereof.

[0009] In a fourth aspect, the present application provides a use of the adhesive composition of the third aspect for bonding substrates.

[0010] The adhesive composition comprising the imine-based photo-base generator provided by the present application has a delayed curing function and can be used for bonding substrates with low ultraviolet (UV) transmittance. Moreover, by adjusting the size of the side polyether chain in the imine intermediate, the delayed curing window can be artificially controlled. BRIEF DESCRIPTION OF DRAWINGS

[0011] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings described below only constitute some embodiments of the present application, and for those skilled in the art, other embodiments can also be obtained from these drawings without creative labor.

[0012] Figure 1 A schematic diagram of an imine-based photobase generator is shown.

[0013] Figure 2 A1H NMR spectrum of imine-PBG-1 is shown. 1 H NMR spectrum. DETAILED DESCRIPTION

[0014] Hereinafter, the present application will be described in detail. It is to be understood that the following description is only illustrative of the present application and is not intended to limit the scope of the present application, which is defined by the appended claims. Moreover, those skilled in the art will appreciate that modifications can be made to the technical solutions of the present application without departing from the spirit and scope of the present application. If not specifically indicated, the technical means used in the embodiments are conventional means known to those skilled in the art.

[0015] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the subject matter described herein belongs. The following definitions are provided to better define the present application.

[0016] In the context of the present application, many embodiments use the expressions "comprising", "including" or "consisting essentially of". The expressions "comprising", "including" or "consisting essentially of" should be understood as open-ended expressions, meaning that not only the elements, components, components, method steps, etc. specifically listed after the expressions are included, but also other elements, components, components, method steps, etc. are included. In addition, in this document, the expressions "comprising", "including" or "consisting essentially of" can also be understood as closed expressions in some cases, meaning that only the elements, components, components, method steps, etc. specifically listed after the expressions are included, and any other elements, components, components, method steps, etc. are not included. At this time, the expression is equivalent to the expression "consisting of".

[0017] It is noted that for numerical values or numerical ranges mentioned herein, unless the context clearly dictates otherwise, are defined in terms of the term "about". In the present context, the term "about" with respect to a numerical value means ± 5%, such as ± 4%, ± 3%, ± 2%, or ± 1%, with respect to a numerical range, the term "about" means ± 5%, such as ± 4%, ± 3%, ± 2%, or ± 1% of the upper and lower limit of the numerical range.

[0018] In the present context, sometimes the ordinal adjectives "first", "second", "third", etc. are used to modify or identify an element, component, step, solution, solvent, temperature, system, etc. It is noted that these adjectives are used only to identify or distinguish the elements, components, steps, solutions, solvents, temperatures, systems, etc. to which they are modifying or identifying, and do not imply any particular order or importance.

[0019] In order to solve at least one of the above-mentioned problems, the present application aims to provide a novel photobase generator, an adhesive composition and a preparation method thereof.

[0020] In a first aspect, the present application provides an imine-based photobase generator, wherein the imine-based photobase generator is a complex of an imine intermediate and a photobase generator (PBG), the molar ratio of the imine intermediate to the PBG is 1:1; the structural formula of the imine intermediate is as follows: , wherein each R1, R2 is independently selected from an aromatic ring group, a heteroaromatic group, or each pair of R1 and R2 is connected to each other to form an aromatic ring group or a heteroaromatic group, the aromatic ring group or the heteroaromatic group is a 5-7 membered ring; n is an integer selected from 1-10, preferably an integer selected from 1-5.

[0021] The photobase generator (PBG) of the present application is a kind of photosensitive compound that can release organic base (such as amine, amidine, guanidine, etc.) by intramolecular bond breaking or electron transfer under ultraviolet-visible light irradiation. The released organic base abstracts proton or attacks nucleophilically, so that epoxy, thiol-epoxy, siloxane and other monomers undergo ring-opening or step polymerization to form a crosslinked network, thereby realizing curing.

[0022] It is worth noting that the PBG of the present application can be any known type of photobase generator in the prior art, preferably, the PBG is selected from the group consisting of tetraphenylborate and its substituted derivatives on the benzene ring, quaternary ammonium salt, oxime ester, carbamate, carboxylate and / or triphenyl-n-butyl borate.

[0023] The imine-based photobase generator is a complex formed by an imine intermediate and a photobase generator. As shown in the structural formula of the imine intermediate, the imine intermediate is a cyclic polyether structure having a cavity in the structural skeleton which can accommodate a photobase generator. In the process of forming the complex, the photobase generator is occluded in the cavity of the imine intermediate. Therefore, compared with the conventional PBG, the polarity of the imine-based photobase generator is significantly reduced, and the affinity of the imine-based photobase generator with the resin is significantly improved. By adjusting the size of the polyether chain in the imine intermediate, different sizes of cavities can be obtained, and thus different sizes of photobase generator molecules can be accommodated. The base generating performance of the imine-based photobase generator of the present application is not only related to the type of PBG, but also related to the occlusion structure of the imine intermediate and the PBG. When n in the structural formula of the imine intermediate is an integer selected from 1-10 (such as n is 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, preferably 1-5), the imine intermediate and the occluded PBG can form a stable occlusion structure and can slowly release the PBG, thereby delaying the photobase process and forming a delayed curing window period.

[0024] It is worth noting that the occlusion of the present application refers to the process that the molecule having a cavity wraps the occluded molecule in the cavity of the structural skeleton, and forms a stable occluded compound with the occluded molecule through van der Waals force, hydrophobic interaction and hydrogen bond, etc. Therefore, the complex of the present application can also be called an inclusion compound or an occluded complex.

[0025] The structural diagram of the complex formed by the imine intermediate and the photobase generator is shown in FIG. 1. Figure 1 In the figure, the molar ratio of the imine intermediate to the photobase generator is 1:1.

[0026] Further, the imine-based photobase generator of the present application also contains an imine structure, which can undergo cis-trans isomerization under light, causing changes in molecular configuration, and is widely used in the fields of optical switches, molecular machines, etc. Based on this, the imine-based photobase generator prepared by the present application with imine structure as the mother nucleus (as shown in FIG. 2, it is worth noting that PBGs in FIG. 2 represent a class of photobase generators, in which s represents that different types of photobase generators can be accommodated by adjusting the size of the polyether chain of the imine intermediate) can undergo cis-trans isomerization under light, causing changes in the configuration of the polyether chain hanging on the side group, and the photobase generator molecules cannot be coated, so that the photobase generator molecules are free, and the photobase generator molecules are further photolyzed to obtain an organic superbase, which induces the anionic polymerization of the thiol-epoxy resin or thiol-acrylic resin composition. Figure 1 Figure 1 When the imine intermediate structure formula of the present application is used to prepare the imine-based photobase generator, the imine intermediate and the occluded PBG can form a stable occlusion structure, and the PBG can be slowly released, thereby delaying the photobase process and forming a delayed curing window period.​ .

[0027] In some embodiments, the imine intermediate can be any organic substituent, such as R1 and R2, which can be independently selected from aryl groups, heteroaryl groups, or a group of R1 and R2 linked together to form an aryl group or a heteroaryl group. The group of R1 and R2 refers to R1 and R2 attached to adjacent groups.

[0028] In a preferred embodiment, the set of R1 and R2 are interconnected to form an aromatic ring or a heteroaryl group, wherein the aromatic ring or heteroaryl group is a 5-7 membered ring, such as a five-membered ring, a six-membered ring, or a seven-membered ring.

[0029] In a preferred embodiment, R1 and R2 are interconnected to form a heteroaryl group. It is worth noting that the heteroaryl group in this invention refers to an aryl group containing heteroatoms (such as nitrogen atoms, oxygen atoms, sulfur atoms, or phosphorus atoms). The heteroaryl group is preferably a nitrogen-containing heteroaryl group, and more preferably, the heteroaryl group is a five-membered nitrogen-containing heteroaryl group, such as pyrrole, imidazolyl, or pyrazolyl.

[0030] Those skilled in the art will understand that heteroaryl or aryl cyclic groups substituted with substituents are also within the scope of protection of this invention.

[0031] In one specific embodiment, R1 and R2 are interconnected to form a pyrrole group, n is 1, and the photoalkali-generating agent is tetramethylguanidine tetraphenylborate. The structure of the imine-based photoalkali-generating agent formed at this time is as follows: .

[0032] By testing its alkali-producing performance, when phenol red is used as a pH indicator, the imine-based photoalkali-producing agent changes color in 20 minutes after light exposure.

[0033] In another specific embodiment, R1 and R2 are interconnected to form a pyrrole group, n is 2, and the photoalkali-generating agent is 1,2-diisopropyl-4,4,5,5-tetramethylbiguanide butyltriphenylborate. The structure of the imine photoalkali-generating agent formed in this case is as follows: .

[0034] By testing its alkali-producing performance, when phenol red is used as a pH indicator, the imine-based photoalkali-producing agent changes color in 10 minutes after light exposure.

[0035] In yet another specific embodiment, R1 and R2 are interconnected to form a pyrrole group, n is 3, and the photoalkali-generating agent is tetra(m-fluorophenyl)borate of 1,2-dicyclohexyl-4,4,5,5-tetramethylbiguanide (WPBG-345). The structure of the imine photoalkali-generating agent formed in this case is as follows: .

[0036] By testing its alkali-producing performance, when phenol red is used as a pH indicator, the imine-based photoalkali-producing agent changes color in 15 minutes after light exposure.

[0037] The imine-based photoalkali-generating agent prepared by this invention can form a complex by selecting a suitable imine intermediate according to the size of the PBG molecule. Specifically, by adjusting the size of the side polyether chains in the imine intermediate, imine intermediates with cavity structures of different sizes are obtained, which can accommodate different types of photoalkali-generating agents, thereby providing a delayed window period that can adapt to different curing requirements.

[0038] The imine-based photoalkali-generating agent of this invention is a complex formed by the PBG and the imine intermediate, i.e., the PBG is encapsulated within the cavity of the imine intermediate. Therefore, compared with conventional PBG, the polarity of the imine-based photoalkali-generating agent is significantly reduced, and the affinity between the imine-based photoalkali-generating agent and the resin is significantly improved. Therefore, adhesive compositions prepared using the imine-based photoalkali-generating agent of this invention exhibit better compatibility.

[0039] In a second aspect, the present invention provides a method for preparing the imine-based photoalkali-generating agent described in the first aspect. The method comprises the following steps: (1) preparing an imine intermediate; (2) mixing PBG with a solution of the imine intermediate and reacting to obtain the imine-based photoalkali-generating agent; wherein the molar ratio of the photoalkali-generating agent to the imine intermediate is 1:1. It is worth noting that the solution of the imine intermediate can be prepared using any solvent capable of dissolving the imine intermediate, including but not limited to methanol, ethanol, acetone, chloroform, water, diethyl ether, toluene, benzene, 1,4-dioxane, N,N-dimethylacetamide, tetrahydrofuran, acetonitrile, dichloromethane, ethyl acetate, petroleum ether, n-hexane, isopropanol, tert-butanol, etc. In a preferred embodiment, the stirring speed in step (2) is 10-2000 rpm, and the reaction temperature is -20-100°C; more preferably, the reaction temperature is 0-70°C.

[0040] In some embodiments, step (1) involves reacting an imine compound containing an active functional group with a chlorinated ether compound under alkaline conditions. Preferably, the alkaline conditions are sodium hydride, sodium tert-butoxide, or lithium diisopropylamine. Preferably, the stirring speed in step (1) is 10-2000 rpm, and the reaction temperature is -20-100°C; more preferably, the reaction temperature is 0-70°C. It is worth noting that the active functional group in the imine compound reacts with the chlorine atom in the chlorinated ether compound to form the imine intermediate structure.

[0041] In a third aspect, the present invention provides an adhesive composition comprising: The imine-based photoalkali-generating agent of the first aspect is 0.01-1 parts by weight, or the imine-based photoalkali-generating agent prepared by the method of the second aspect; Resin in parts by weight of 1-10; Thiol curing agent in parts by weight of 1-10; Silane coupling agent in parts by weight of 0.01 to 1; A photosensitizer in parts by weight of 0.01-1 parts, and Free radical polymerization inhibitor in parts by weight of 0-1; The resin is epoxy resin, acrylic resin, or a combination thereof.

[0042] It is worth noting that, under light irradiation, the adhesive composition of the present invention first produces alkali through a photoalkali-generating agent, which then promotes the reaction and curing of the thiol curing agent with the resin. When the resin is an epoxy resin, no free radical polymerization inhibitor needs to be added to the adhesive composition. However, when the resin is an acrylic resin, acrylic acid is more prone to free radical polymerization. Therefore, in order to induce anionic polymerization of the acrylic resin, a free radical polymerization inhibitor needs to be added. The added free radical polymerization inhibitor is 0.01-1 part by mass, for example, 0.01 part, 0.1 part, 0.2 part, 0.3 part, 0.4 part, 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part, or 1 part, preferably 0.1-0.5 parts.

[0043] In the adhesive composition, the imine-based photoalkali-generating agent is present in a mass fraction of 0.01-1 part, such as 0.01, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1 part, preferably 0.1-1 part. The resin is present in a mass fraction of 1-10 parts, such as 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 parts, preferably 1-8 parts. The thiol curing agent is present in a mass fraction of 1-10 parts, such as 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 parts, preferably 1-8 parts. The silane coupling agent is present in a mass fraction of 0.01-1 part, such as 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1 part, preferably 0.01-0.5 parts. The photosensitizer is present in a mass fraction of 0.01-1 part, such as 0.01, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1 part, preferably 0.1-0.5 parts.

[0044] The epoxy resin described in this invention can be any epoxy resin in the prior art. Preferably, the epoxy resin is selected from the group consisting of bisphenol A type glycidyl ether epoxy resin, bisphenol F type glycidyl ether epoxy resin, a mixture of bisphenol A type and bisphenol F type glycidyl ether epoxy resin, rubber toughening type glycidyl ether epoxy resin, aliphatic epoxy resin, alicyclic epoxy resin, benzyl glycidyl ether and its derivatives, alkyl glycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, allyl glycidyl ether, trifunctional glycidyl ether and / or tetrafunctional glycidyl ether.

[0045] The thiol curing agent of the present invention can be any thiol compound in the prior art. Preferably, the thiol curing agent is selected from the group consisting of alkyl thiols, trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptopropionic acid) ester, pentaerythritol tetrakis(3-mercaptobutyrate), inositol hexa(mercaptopropionate) and / or tris[2-(3-mercaptopropionyloxy)ethyl]isocyanurate.

[0046] The acrylic resin described in this invention can be any acrylic resin in the prior art. Preferably, the acrylic resin is selected from the group consisting of norborneol acrylate, acrylic acid, methyl methacrylate, dicyclopentadiene acrylate, tetrahydrofuran acrylate, 1,4-butanediol dimethacrylate, di(trimethylolpropane)tetraacrylate, pentaerythritol tetraacrylate, and / or dipentaerythritol hexaacrylate.

[0047] The silane coupling agent described in this invention can be any silane coupling agent in the prior art. Preferably, the silane coupling agent is selected from the group consisting of 3-glycidoxypropyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, (3-epoxypropylpropoxy)trimethoxysilane, (3-epoxypropylpropoxy)triethoxysilane, and / or 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

[0048] The photosensitizer described in this invention can be any photosensitizer in the prior art. Preferably, the photosensitizer is selected from the group consisting of 2-isopropylthioxanthone, camphorquinone, anthraquinones and their derivatives, methylene blue and / or porphyrins and their derivatives.

[0049] The free radical polymerization inhibitor described in this invention can be any free radical polymerization inhibitor in the prior art. Preferably, the free radical polymerization inhibitor is selected from the group consisting of benzoquinone, phenol and its derivatives and / or tetramethylpiperidine derivatives.

[0050] In a fourth aspect, the present invention provides an application of the adhesive composition of the third aspect for bonding substrates.

[0051] include: (1) The adhesive composition is irradiated with ultraviolet light and initiated, and the adhesive composition enters a delayed curing window; (2) During the window period, the adhesive composition is bonded to the substrate.

[0052] The adhesive composition of the present invention is applicable to a variety of substrates (such as glass, crystalline materials, plastics, etc.). Because the adhesive composition of the present invention has a delayed curing window, it also achieves good adhesion to substrates with low ultraviolet (UV) transmittance.

[0053] The low UV transmittance substrates described in this invention generally refer to substrates with a UV transmittance of less than 20%, such as non-transparent substrates (e.g., metals, ceramics, carbon fibers, black / dark plastics, etc.), substrates containing UV absorbers (e.g., certain weather-resistant coatings, sun-protective packaging materials, optical protective films, etc.), and multilayer composite substrates (e.g., glass with a UV shielding layer, UV-resistant films, etc.).

[0054] It should be noted that there is no particular limitation on the adhesive application thickness; it depends on the bonding requirements. The UV irradiation time can be determined for different adhesive application thicknesses. In a preferred embodiment, the adhesive composition of the present invention, with an application thickness of 0.2-1 mm, uses a wavelength of 200-500 nm and a curing energy of 100-100000 mJ / cm². 2 After irradiation with ultraviolet (UV) light, the adhesive undergoes delayed curing, with a delayed curing window of 5 min to 30 min, for example, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min, and 30 min. The source of the UV light can be any light source capable of producing the aforementioned wavelength and curing energy, such as a mercury lamp, LED light source, or xenon lamp light source.

[0055] The adhesive composition of the present invention has at least one of the following beneficial effects: The imine-based photoalkali-generating agent of this invention, through the inclusion and slow-release effect of the imine intermediate on the photoalkali-generating agent, prevents the immediate rapid induced polymerization of its initiating target, thus creating a delayed curing window. Furthermore, by adjusting the size of the polyether chains on the side groups of the imine intermediate, its internal cavity can accommodate different photoalkali-generating agents, thereby achieving artificial control of the delayed window. This allows for different operating windows to be provided according to specific process requirements, greatly improving the convenience and user-friendliness of construction.

[0056] The adhesive composition containing an imine-based photoalkali-generating agent described in this invention can be pre-applied to the surface of a substrate. After being excited by ultraviolet light, the adhesive composition does not immediately cure but remains in a fluid state within a certain window. During this period, it can bond low UV transmittance substrates, solving the problem that low UV transmittance substrates cannot be cured with UV adhesives.

[0057] Compared with traditional ionic photoalkali generators, imine-based photoalkali generators have a stronger affinity for resins and are therefore more easily soluble in adhesive formulations, solving the problem of poor solubility of some ionic initiators.

[0058] The sources of reagents and solvents used in the following specific examples and comparative examples are explained: The chloroether compounds used in the following examples were prepared in-house with reference to prior literature (Fordyce, Reid.; Lovell, Edwin L.; Hibbert, Harold. (1939). Studies on Reactions Relating to Carbohydrates and Polysaccharides. LVI. The Synthesis of the Higher Polyoxyethylene Glycols. Journal of the American Chemical Society, 61(7), 1905-1910. DOI: 10.1021 / ja01876a072). All other reagents and solvents were commercially available.

[0059] Example Example 1: Synthesis of imine-based photoalkali-producing agent (1) Synthesis of imine-PBG-1 The synthetic route for imine-PBG-1 is shown below: .

[0060] The synthesis steps of imine-PBG-1 were as follows: 2 mmol of 2-aldehyde pyrrole and 2 mmol of 2-amino pyrrole were dissolved in methanol, and the mixture was then heated to 60 °C and stirred for 5 h. After the reaction was complete, methanol was removed by rotary evaporation. The crude product obtained did not require further purification and was directly dissolved in tetrahydrofuran. 4 mmol of sodium hydride was added at 0 °C, and the mixture was stirred in an ice bath for 1 h. Subsequently, 1 mmol of the chloroether compound 1,18-dichloro-2,5,8,11,14,17-hexaoxabalane was added dropwise to the reaction solution. After reacting overnight, the reaction was quenched with methanol. The mixture was washed with water, extracted with dichloromethane, dried over anhydrous sodium sulfate, and then evaporated to dryness. The product was subjected to column chromatography to obtain 758 mg of an imine intermediate. The yield was 90%. 1 ¹H NMR (CDCl₃, 400MHz): 6.13–8.1 (7H), 5.93 (4H), 3.54 (20H), NMR spectrum attached. Figure 2 As shown.

[0061] The imine intermediate obtained above was dissolved in methanol at room temperature, followed by the addition of 2 mmol of tetramethylguanidine tetraphenylborate, resulting in crystal precipitation. After the reaction was complete, methanol was removed by rotary evaporation. The mixture was cooled to room temperature, hexane was added, and the mixture was filtered. The filter cake was washed three times with a small amount of methanol. Finally, it was dried in a vacuum oven to obtain colorless crystalline imine-PBG-1, a photoalkali-producing agent. Elemental analysis results: Theoretical value: C 50 H 65 BN6O6:%C (70.08), %H (7.65), actual value:%C (69.99),%H (7.55).

[0062] (2) Synthesis of imine-PBG-2 The synthetic route for imine-PBG-2 is shown below: .

[0063] The synthesis steps of imine-PBG-2 are as follows: 884 mg of imine-PBG-2 imine intermediate was prepared using the same synthesis method as imine-PBG-1 (1), with a yield of 95%. The chloro ether compound used was 1,21-dichloro-2,5,8,11,14,17,20-heptaoxhexane. 1 H NMR (CDCl3, 400 MHz): 8.12-6.2 (7H), 5.93 (4H), 3.54 (24H).

[0064] The imine intermediate obtained above was dissolved in methanol at room temperature, followed by the addition of 2 mmol of 1,2-diisopropyl-4,4,5,5-tetramethylbiguanide butyltriphenylborate, resulting in crystal precipitation. After the reaction was complete, methanol was removed by rotary evaporation. The mixture was cooled to room temperature, hexane was added, and the mixture was filtered. The filter cake was washed three times with a small amount of methanol. Finally, it was dried in a vacuum oven to obtain colorless crystalline imine-PBG-2, a photoalkali-producing agent. Elemental analysis results: Theoretical value: C 57 H 87 BN8O7: %C (67.97), %H (8.71), actual value: %C (67.91), %H (8.59).

[0065] (3) Synthesis of imine-PBG-3 The synthetic route for imine-PBG-3 is shown below: .

[0066] The synthesis steps of imine-PBG-3 are as follows: 764 mg of imine-PBG-3 imine intermediate was prepared using the same synthesis method as imine-PBG-1 (1), with a yield of 75%. The chloro ether compound used was 1,24-dichloro-2,5,8,11,14,17,20,23-octaoxetane. 1 H NMR (CDCl3, 400 MHz): 8.12-6.2 (7H), 5.93 (4H), 3.54 (28H). The imine intermediate obtained above was dissolved in methanol at room temperature, followed by the addition of 2 mmol of tetra(m-fluorophenyl)borate of 1,2-dicyclohexyl-4,4,5,5-tetramethylbiguanide (WPBG-345), resulting in crystal precipitation. After the reaction was complete, methanol was removed by rotary evaporation. The mixture was cooled to room temperature, hexane was added, and the mixture was filtered. The filter cake was washed three times with a small amount of methanol. Finally, it was dried in a vacuum oven to obtain colorless crystalline imine-PBG-3, a photoalkali-producing agent. Elemental analysis: Theoretical value: C 67 H 91 BF4N8O8: %C (65.78), %H (7.50), actual value: %C (65.55), %H (7.44).

[0067] Example 2 Preparation of adhesive composition Test Example 1 An adhesive composition prepared using the compound imine-PBG-1 prepared in Example 1 of this invention as a photoinitiator is provided.

[0068] The preparation method is as follows: 0.4 parts imine-PBG-1, 0.2 parts photosensitizer 2-isopropylthioxanthraquinone (ITX), 2 parts bisphenol F epoxy resin NPEF-170, 2 parts pentaerythritol tetrakis(3-mercaptopropionic acid) ester thiol curing agent, and 0.05 parts silane coupling agent A-187 are thoroughly mixed in a high-speed mixer to obtain an adhesive composition.

[0069] Test Example 2 The adhesive composition was prepared using the same method as in Test Example 1, except that 0.25 parts of imine-PBG-2 were used as the photoinitiator.

[0070] Test Example 3 The adhesive composition was prepared using the same method as in Test Example 1, except that 0.3 parts of imine-PBG-3 were used as the photoinitiator.

[0071] Test Example 4 The adhesive composition was prepared using the same method as in Test Example 2, except that 2 parts of bisphenol A epoxy resin NPEL-128 were used instead of Test Example 2.

[0072] Test Example 5 The adhesive composition was prepared using the same method as in Test Example 2, except that 0.4 parts of imine-PBG-2 was used as the photoinitiator.

[0073] Test Example 6 The adhesive composition was prepared using the same method as in Test Example 2, except that 2 parts of pentaerythritol tetra(3-mercaptobutyrate) were used as the thiol curing agent.

[0074] Test Example 7 The adhesive composition was prepared using the same method as in Test Example 2. The difference from Test Example 2 was that an acrylic resin and a free radical polymerization inhibitor were added to the reaction system. The acrylic resin used was 1.5 parts of pentaerythritol tetraacrylate, and the free radical polymerization inhibitor used was 0.2 parts of p-benzoquinone.

[0075] Test Example 8 The adhesive composition was prepared using the same method as in Test Example 2, except that 0.6 parts of imine-PBG-2 were used as the photoinitiator, and 4 parts of pentaerythritol tetrakis(3-mercaptopropionic acid) ester were used as the thiol curing agent. Additionally, acrylic resin and a free radical polymerization inhibitor were added to the reaction system, wherein 1.5 parts of pentaerythritol tetraacrylate were used as the acrylic resin, and 0.2 parts of p-benzoquinone were used as the free radical polymerization inhibitor.

[0076] Comparative Example Comparative Example 1 The adhesive composition was prepared using the same method as in Test Example 2, except that 0.13 parts of 1,2-diisopropyl-4,4,5,5-tetramethylbiguanide butyltriphenylborate was used as the photoinitiator.

[0077] Comparative Example 2 The adhesive composition was prepared using the same method as in Test Example 2, except that a combination of 0.13 parts of 1,2-diisopropyl-4,4,5,5-tetramethylbiguanide butyltriphenylborate and 0.12 parts of an imine intermediate (specifically, the imine intermediate in imine-PBG-2) was used as a photoinitiator.

[0078] Alkali-producing performance test of photo-alkali-producing agent: The alkali-producing properties of the imine-based photoalkali-producing agents (imine-PBG-1, imine-PBG-2, and imine-PBG-3) synthesized in Example 1 and the photoinitiators used in Comparative Examples 1-2 (combinations of butyltriphenylborate of 1,2-diisopropyl-4,4,5,5-tetramethylbiguanide and imine intermediates, respectively) were evaluated as follows: Using phenol red as a pH indicator, the photoinitiator was recorded as the imine-based photoalkalogen prepared in Example 1 and the photoinitiator used in Comparative Examples 1-2 (the concentration of the imine-based photoalkalogen prepared in Example 1 and the photoinitiator used in Comparative Examples 1-2 was 2 × 10⁻⁶). -4 mol / L, ITX concentration is 10 -4 The color change time of the indicator (mol / L) after illumination, wherein the illumination conditions are 365nm ultraviolet light with a light intensity of 900 mW / cm². 2 The test results are shown in Table 1.

[0079] Table 1. Color change time of different photoinitiators

[0080] As shown in Table 1, the imine-based photoalkali-generating agents (imine-PBG-1, imine-PBG-2, and imine-PBG-3) synthesized in Example 1 exhibited color-changing times of over 10 minutes after UV irradiation, demonstrating a significant delay effect compared to the photoinitiators in Comparative Examples 1-2. This is mainly due to the inclusion and sustained-release effect of the cyclic polyether structure imine intermediate in the imine-based photoalkali-generating agents. Furthermore, the cavity size of the imine intermediate can be adjusted by controlling the size of the side-chain polyether groups, thereby accommodating different types of photoalkali-generating agents to provide a delayed window period suitable for varying curing requirements.

[0081] Performance evaluation of adhesive compositions: The adhesive compositions obtained in Test Examples 1-8 and Comparative Examples 1-2 were evaluated as follows: 1. Delay window: A 0.5 mm thick adhesive layer was prepared using a coating machine and placed under 365 nm ultraviolet light (light intensity: 900 mW / cm²). 2 Irradiate for 30 seconds. Gently stir the adhesive layer with a toothpick every 1 minute. The time it takes for the adhesive layer to start to string is defined as the delay time (unit: min).

[0082] 2. Initial bond strength: Samples were prepared using the chip shearing method, with glass substrates bonded to each other, and the bonding area was 3 mm × 3 mm. The shear strength (unit: MPa) was tested and recorded after 30 minutes using a Dage chip pusher.

[0083] 3. Final strength: The test method is the same as the test method for initial bond strength, except that the Dage chip thrust tester is used to test and record the shear strength (unit: MPa) after 24 hours.

[0084] The performance test results of the adhesive compositions prepared in Test Examples 1-8 and Comparative Examples 1-2 are detailed in Table 2.

[0085] Table 2. Performance test results of the adhesive compositions prepared in Test Examples 1-8 and Comparative Examples 1-2

[0086] Table 2 shows that, compared with Comparative Examples 1 and 2, Test Examples 1-8 all exhibit a significant delay window, demonstrating that the imine-based photoalkali-generating agent prepared in this invention possesses significant delayed curing performance. The cavity size can be adjusted by controlling the side group polyether chain size, thereby accommodating different types of photoalkali-generating agents and ultimately allowing for artificial control of the delay window. Comparative Example 2 shows that simply combining the imine intermediate with 1,2-diisopropyl-4,4,5,5-tetramethylbiguanide butyltriphenylborate and adding it to the formulation does not significantly delay curing ability; it is clearly inferior to the effect obtained by the complexation of the two. This indicates that the inclusion structure formed by the imine intermediate and PBG, as well as the cis-trans isomerism of the imine bond, are important factors determining the delay capability.

[0087] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Any modifications, substitutions, improvements, etc., made within the spirit and principles of the present invention shall be protected by the present invention.

Claims

1. An imine-based photoalkali-generating agent, wherein, The imine-based photoalkalizing agent is a complex formed by an imine intermediate and a photoalkalizing agent; the molar ratio of the imine intermediate to the photoalkalizing agent is 1:1; the structural formula of the imine intermediate is as follows: ， Each R1 and R2 is independently selected from aryl or heteroaryl groups, or each pair of R1 and R2 is connected to each other to form an aryl or heteroaryl group, wherein the aryl or heteroaryl group is a 5-7 membered ring; n is an integer selected from 1 to 10.

2. The imine-based photoalkali-generating agent according to claim 1, wherein, n is an integer selected from 1 to 5.

3. The imine-based photoalkali-generating agent according to claim 1 or 2, wherein, The photoalkali-producing agent is selected from the group consisting of tetraphenylborates and their benzene ring-substituted derivatives, quaternary ammonium salts, oxime esters, carbamates, carboxylates and / or triphenyl-n-butylborates.

4. A method for preparing the imine-based photoalkali-generating agent according to any one of claims 1-3, comprising the following steps: (1) Preparation of imine intermediates; (2) The photoalkalizing agent is mixed with a solution of the imine intermediate to react and obtain the imine-based photoalkalizing agent; wherein, The molar ratio of the photoalkalizing agent to the imine intermediate is 1:1; Preferably, the reaction temperature of step (2) is -20 to 100°C.

5. The method of claim 4, wherein, In step (1), the imine intermediate is prepared by reacting an imine compound containing an active functional group with a chloro ether compound under alkaline conditions; preferably, the alkaline conditions are sodium hydride, sodium tert-butoxide, and lithium diisopropylamine; preferably, the reaction temperature of step (1) is -20 to 100°C.

6. An adhesive composition comprising: The imine-based photoalkali-generating agent according to any one of claims 1-3, or the imine-based photoalkali-generating agent prepared by the method described in claim 4 or 5, is present in parts by weight of 0.01-1 parts. Resin in parts by weight of 1-10; Thiol curing agent in parts by weight of 1-10; Silane coupling agent in parts by weight of 0.01 to 1; A photosensitizer in parts by weight of 0.01-1 parts, and Free radical polymerization inhibitor in parts by weight of 0-1; The resin is epoxy resin, acrylic resin, or a combination thereof.

7. The adhesive composition of claim 6, wherein the epoxy resin is selected from the group consisting of bisphenol A type glycidyl ether epoxy resin, bisphenol F type glycidyl ether epoxy resin, a mixture of bisphenol A type and bisphenol F type glycidyl ether epoxy resin, rubber toughening type glycidyl ether epoxy resin, aliphatic epoxy resin, alicyclic epoxy resin, benzyl glycidyl ether and its derivatives, alkyl glycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, allyl glycidyl ether, trifunctional glycidyl ether and / or tetrafunctional glycidyl ether; The thiol curing agent is selected from the group consisting of alkyl thiols, trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptopropionic acid) ester, pentaerythritol tetrakis(3-mercaptobutyrate), inositol hexa(mercaptopropionate) and / or tris[2-(3-mercaptopropionyloxy)ethyl]isocyanurate; The acrylic resin is selected from the group consisting of norborneol acrylate, acrylic acid, methyl methacrylate, dicyclopentadiene acrylate, tetrahydrofuran acrylate, 1,4-butanediol dimethacrylate, di(trimethylolpropane)tetraacrylate, pentaerythritol tetraacrylate and / or dipentaerythritol hexaacrylate. The silane coupling agent is selected from the group consisting of 3-glycidoxypropyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, (3-epoxypropylpropoxy)trimethoxysilane, (3-epoxypropylpropoxy)triethoxysilane and / or 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. The photosensitizer is selected from the group consisting of 2-isopropylthioxanthone, camphorquinone, anthraquinones and their derivatives, methylene blue and / or porphyrins and their derivatives; and / or The free radical polymerization inhibitor is selected from the group consisting of benzoquinone, phenol and its derivatives and / or tetramethylpiperidine derivatives.

8. An application of the adhesive composition of claim 6 or 7 for bonding substrates.

9. The application of claim 8, wherein the substrate is a low ultraviolet light transmittance substrate.

10. The application according to claim 8 or 9, comprising: (1) The adhesive composition is irradiated with ultraviolet light and initiated, and the adhesive composition enters a delayed curing window; (2) During the window period, the adhesive composition is bonded to the substrate; Preferably, the adhesive composition has an application thickness of 0.2-1 mm, the ultraviolet light wavelength is 200-500 nm, and the curing energy is 100-100000 mJ / cm². 2 .

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