Ultraviolet curing resin, preparation method thereof, photosensitive adhesive and application thereof

Abstract

The invention relates to the technical field of photosensitive resin materials, in particular to ultraviolet curing resin and a preparation method thereof, and photosensitive adhesive and application thereof. The molecular structural formula of the ultraviolet curing resin is high in functionality, the ultraviolet curing resin further contains alkenyl and hydroxyl and can further contain epoxy groups, the alkenyl can generate free radicals under the action of ultraviolet light, and the curing speed is high. Hydroxyl is beneficial to hydrogen-bond interaction with other molecules and is beneficial to combination with a base material, so that the stability and the adhesive force are improved, and volume shrinkage is not easy to occur. When the epoxy group is contained, cation curing can be initiated, the curing degree is high, and the generated hydroxyl group can further reduce volume shrinkage in the film forming process. And the crosslinking degree during curing is high due to higher functionality, so that the formed film has higher compactness. Therefore, the ultraviolet curing resin has higher curing rate and curing degree, high compactness, strength and adhesive force after film formation, is not easy to generate volume shrinkage, has good sealing property and waterproofness, and can be used for photosensitive adhesives.

Description

Technical Field

[0001] This application relates to the technical field of photosensitive resin materials, and particularly to ultraviolet curable resins and their preparation methods, photosensitive adhesives and their applications. Background Art

[0002] Ultraviolet curable resin technology can excite photosensitizers in the resin through ultraviolet irradiation, quickly initiate polymerization reactions, and cure the resin in a short time. Traditional ultraviolet curable resins are divided into free radical-initiated and cation-initiated photocuring materials, which decompose to generate free radicals or cations respectively under ultraviolet irradiation, and then achieve curing.

[0003] On the one hand, free radical curing is fast, but the presence of a large number of ester groups makes its water resistance poor, and the volume shrinkage is large during the curing of acrylate. When used for bonding and sealing, the shrinkage after curing may cause problems such as defects or bubbles at the interface fitting, and the effect of preventing water vapor is not good, which cannot meet the use requirements of bonding and sealing adhesives. In addition, after the curing light source is removed, the polymerization reaction of the free radical polymerization system immediately terminates without a post-curing process, and the reaction is incomplete at the light-blocked part, and it is easy to have problems with low curing degree. On the other hand, cationic curing is still in an "active" polymerization state after the curing light source is removed, with dark reactions, and the proportion of active groups participating in the reaction is high, so the curing degree is high. However, its curing speed is slow, the curing depth is limited, and the reaction products are relatively hard and brittle, with limited applications. In addition, the curing is prone to yellowing and explosive polymerization, and the high prices of cationic initiators and sensitizers also restrict their applications.

[0004] Therefore, the prior art often combines the two curing methods and uses dual-curing resins to improve various properties, taking into account both the curing speed and the crosslinking curing degree. However, due to the introduction of acrylate groups, when used for curing and sealing, there is still a phenomenon of volume shrinkage, resulting in problems such as poor sealing and waterproof performance, and new ultraviolet curable resin materials need to be developed. Summary of the Invention

[0005] The purpose of this application is to provide an ultraviolet curable resin and its preparation method, a photosensitive adhesive and its application, aiming to solve the technical problem that dual-curing resins in the prior art are difficult to balance comprehensive performance, especially the volume will shrink during curing, resulting in poor sealing performance.

[0006] To achieve the above application purpose, the technical solution adopted in this application is as follows:

[0007] In the first aspect, this application provides an ultraviolet curable resin, whose molecular structural formula is shown as the following general formula (I):

[0008]

[0009] Among them, R1 is a soft segment group, and R2 to R5 are the same or different groups containing epoxy groups or alkenyl groups, and at least one of the groups R2 to R5 contains an alkenyl group, and at least one of the groups R2 to R5 contains a hydroxyl group.

[0010] The ultraviolet curable resin of the present application can be used for ultraviolet curing. First, at least one of the groups R2 to R5 contains an alkenyl group, which can generate free radicals under the action of ultraviolet light and can crosslink and cure with free radical reactive diluents, and the curing speed is fast. Second, at least one of the groups R2 to R5 contains a hydroxyl group, which is beneficial to form hydrogen bond interactions with other molecules in the curing components, and the hydroxyl group is beneficial to bind to the substrate, improving the stability and adhesion during the film-forming process and not easily undergoing volume shrinkage. Moreover, when R2 to R5 also contain epoxy groups, cationic curing can be further initiated, the curing degree is high, and the generated hydroxyl groups will further reduce the volume shrinkage during the film-forming process. Then, the ultraviolet curable resin molecular structural formula (I) contains R2 to R5 and has a high functionality, so the crosslinking degree during crosslinking curing is high, giving a high density after film formation. Finally, R2 to R5 are respectively bonded to two benzene rings, and the benzene ring is a rigid group, improving the strength after film formation. R1 connects the two benzene rings, and R1 is a soft segment group, which is beneficial to form a three-dimensional crosslinked spatial structure during curing. Therefore, the ultraviolet curable resin of the present application has a high curing rate and curing degree, high density, strength, and adhesion after film formation, is not easily subject to volume shrinkage, and has good sealing and waterproof properties.

[0011] In a second aspect, the present application provides a method for preparing the above ultraviolet curable resin of the present application, including the following steps:

[0012] Perform a ring-opening esterification reaction on the epoxy group-containing raw material and the acrylic acid-based raw material to generate an ultraviolet curable resin;

[0013] Among them, the molecular structural formula of the epoxy group-containing raw material is shown as the following general formula (IX):

[0014]

[0015] Among them, A1 is a soft segment group, and A2 to A5 are the same or different groups containing epoxy groups.

[0016] The raw materials for the preparation method of the present application include epoxy group-containing raw materials and acrylic acid-based raw materials. The molecular structural formula of the epoxy group-containing raw material is shown in the general formula (IX). During the reaction, the epoxy group in the epoxy group-containing raw material is ring-opened to form a hydroxyl group, and an esterification reaction occurs with the carboxyl group of the acrylic acid-based raw material, connecting the acrylic acid-based raw material and the epoxy group-containing raw material through an ester group, and the vinyl group is also introduced into the product molecule to generate the above-mentioned ultraviolet curable resin, which can be used for ultraviolet curing. This preparation method can control the proportion of reaction raw materials and reaction conditions to obtain different types of ultraviolet curable resins shown in the general formula (I), and the preparation method has controllable process.

[0017] In a third aspect, the present application provides a photosensitive adhesive, which includes the ultraviolet curable resin of the present application above or the ultraviolet curable resin prepared by the preparation method of the present application above.

[0018] Since the ultraviolet curable resin of the present application has a high curing rate and curing degree, high density and strength after film formation, is not prone to volume shrinkage, and has good sealing performance, it can be used in photosensitive adhesives. The photosensitive adhesive can be quickly cured under the action of ultraviolet light, and has high film density, high strength, strong adhesion, and is not prone to volume shrinkage, so it has good sealing and waterproof properties.

[0019] In a fourth aspect, the present application provides an application of the above photosensitive adhesive of the present application, and the photosensitive adhesive is applied to at least one of electronic sealing, optical fiber devices, coatings, and 3D printing inks.

[0020] Since the photosensitive adhesive of the present application can be quickly cured under the action of ultraviolet light, and has high film density, high strength, strong adhesion, is not prone to volume shrinkage, and has good sealing and waterproof properties, it can be widely used in fields such as electronic sealing, optical fiber devices, coatings, and 3D printing inks. During application, it can be first coated or filled, and then irradiated with ultraviolet light to initiate free radical and cationic curing. Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1 is the nuclear magnetic resonance hydrogen spectrum of the ultraviolet curable resin of Example A1 of the present application;

[0023] Figure 2 is the infrared spectrum of the ultraviolet curable resin of Example A1 of the present application. Detailed Embodiments

[0024] In order to make the technical problems to be solved, technical solutions and beneficial effects of the present application clearer and more understandable, the present application will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0025] In the present application, the term "and / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. Among them, A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0026] In the present application, "at least one" means one or more, and "a plurality" means two or more. "At least one of the following" or its similar expressions refer to any combination of these items, including any combination of single items or plural items.

[0027] It should be understood that in various embodiments of the present application, the magnitudes of the serial numbers of the above processes do not mean the order of execution. Some or all of the steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0028] The weight of the relevant components mentioned in the specification of the embodiments of the present application not only can refer to the specific content of each component, but also can represent the proportional relationship of the weights between the components. Therefore, as long as the content of the relevant components in the specification of the embodiments of the present application is enlarged or reduced in proportion, it is within the scope disclosed in the specification of the embodiments of the present application. Specifically, the mass in the specification of the embodiments of the present application can be μg, mg, g, kg and other mass units well-known in the chemical industry.

[0029] The terms "first" and "second" are only used for descriptive purposes to distinguish objects such as substances from each other, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX can also be referred to as the second XX. Similarly, the second XX can also be referred to as the first XX. Thus, the features defined with "first" and "second" can explicitly or implicitly include one or more of such features.

[0030] The first aspect of the embodiments of the present application provides an ultraviolet curable resin, and its molecular structural formula is shown as the following general formula (I):

[0031]

[0032] Among them, R1 is a soft segment group, and R2 to R5 are the same or different groups containing epoxy groups or vinyl groups, and at least one of R2 to R5 contains a vinyl group, and at least one of R2 to R5 contains a hydroxyl group.

[0033] The ultraviolet curable resin of the embodiment of the present application can be used for ultraviolet curing. First, at least one of R2 to R5 contains a vinyl group, which can generate free radicals under the action of ultraviolet light and can crosslink and cure with free radical active diluents, and the curing speed is fast. Secondly, at least one of R2 to R5 contains a hydroxyl group, which is beneficial to form hydrogen bond interactions with other molecules in the curing components, and the hydroxyl group is beneficial to combine with the substrate, improving the stability and adhesion during the film formation process and not easily undergoing volume shrinkage. Moreover, when R2 to R5 also contain epoxy groups, cationic curing can be further initiated, the curing degree is high, and the generated hydroxyl groups will further reduce the volume shrinkage during the film formation process. Then, the ultraviolet curable resin molecular structural formula (I) contains R2 to R5 and has a high functionality, so the crosslinking degree during crosslinking curing is high, giving a high density after film formation. Finally, R2 to R5 are respectively bonded to two benzene rings. The benzene ring is a rigid group, which improves the strength after film formation. R1 connects the two benzene rings, and R1 is a soft segment group, which is beneficial to form a three-dimensional crosslinked spatial structure during curing. Therefore, the ultraviolet curable resin of the embodiment of the present application has a high curing rate and curing degree, high density, strength, and adhesion after film formation, is not prone to volume shrinkage, and has good sealing and waterproof properties.

[0034] In the general formula (I), the groups of R2 to R5 can be the same or different. One, two, three, or four of R2 to R5 can contain vinyl groups, one, two, three, or four of R2 to R5 can contain hydroxyl groups, one, two, three, or four of R2 to R5 can contain epoxy groups, or none of them contain epoxy groups.

[0035] In some embodiments, R2 to R5 can be the same or different groups represented by the following general formulas (II), (III), (IV), or (V), and at least one of R2 to R5 is a group represented by the general formula (IV) or (V):

[0036]

[0037] Among them, R6 and R7 are the same or different and are oxygen atoms or C1 - C4 alkyl groups, and R8 and R9 are the same or different and are hydrogen atoms or C1 - C5 alkyl groups.

[0038] The above four general formulas represent typical groups containing epoxy groups or vinyl groups. Among them, the groups shown in general formulas (II) and (III) contain epoxy groups and can be cationically cured. During curing, it is beneficial to improve the degree of curing, and the hydroxyl groups generated after ring-opening will further reduce the volume shrinkage during the film-forming process. The hydroxyl groups are also beneficial for binding to the substrate, improving the stability during the film-forming process, and enhancing the sealing property of curing.

[0039] The epoxy group and the benzene ring can be connected through an alkyl group. For example, the epoxy group in general formula (III) is connected to the benzene ring in general formula (I) through a methylene group. When R6 in general formula (II) is an alkyl group with 1 to 4 carbon atoms, the epoxy group is connected to the benzene ring in general formula (I) through other alkyl groups. The group connecting the epoxy group and the benzene ring can also contain an oxygen atom. For example, when R6 in general formula (II) is an oxygen atom, an oxygen atom is directly bonded to the benzene ring, and then a methylene group and an epoxy group are further connected. Compared with the direct connection through an alkyl group, this method is beneficial for the electron cloud of the carbon atom in the epoxy group to be denser, further enhancing the inductive effect and making it easier to undergo ring-opening nucleophilic reaction and then curing.

[0040] The groups shown in general formulas (IV) and (V) contain vinyl groups and can be free-radically cured with a fast curing speed. Moreover, the vinyl groups therein are all vinyl ester groups, further increasing the curing rate. And they all contain hydroxyl groups, which are beneficial for reducing the volume shrinkage during the film-forming process, and are also beneficial for binding to the substrate, improving the stability and adhesion during the film-forming process, and enhancing the sealing property of the cured film. When R7 in general formula (IV) is an oxygen atom, similar to when R6 is an oxygen atom, it is also beneficial for promoting the cross-linking reaction of the vinyl ester groups.

[0041] R1 is a soft segment group. During curing, it is beneficial for the molecules of this ultraviolet-curable resin to rotate, bend, etc., enabling the groups on the two benzene rings to better contact and react with other molecules to form a three-dimensional cross-linked spatial structure. In some embodiments, R1 can be a group shown in the following general formula (VI):

[0042]

[0043] In some embodiments, R1 can also be a group shown in the following general formula (VII):

[0044]

[0045] In some embodiments, R1 can also be a group shown in the following general formula (VIII):

[0046]

[0047] Among them, R 10 and R 11 are the same or different alkyl chains with 1 to 4 carbon atoms.

[0048] The group represented by the general formula (VI), (VII) or (VIII) is a soft segment group, which is beneficial to the formation of a three-dimensional cross-linked spatial structure between the ultraviolet curable resin and other molecules during curing. And this type of ultraviolet curable resin is easy to prepare and has a relatively low cost.

[0049] In summary, in the exemplary examples, the ultraviolet curable resin of the general formula (I) may include the following typical molecular structural formulas:

[0050] Such as:

[0051]

[0052] Such as:

[0053]

[0054] These ultraviolet curable resin molecules have a high functionality, contain vinyl groups and hydroxyl groups, and further contain epoxy groups. Therefore, they have a high curing rate and curing degree, high density, strength and adhesion after film formation, are not prone to volume shrinkage, and have good sealing and waterproof properties.

[0055] The second aspect of the embodiments of the present application provides a method for preparing the ultraviolet curable resin of the above embodiments of the present application, including the following steps:

[0056] S10: Perform a ring-opening esterification reaction on the epoxy group-containing raw material and the acrylic acid-based raw material to generate an ultraviolet curable resin;

[0057] Among them, the molecular structural formula of the epoxy group-containing raw material is as shown in the following general formula (IX):

[0058]

[0059] Among them, A1 is a soft segment group, and A2 to A5 are the same or different groups containing epoxy groups.

[0060] The raw materials for the preparation method of the embodiments of the present application include an epoxy group-containing raw material and an acrylic acid-based raw material. The molecular structural formula of the epoxy group-containing raw material is as shown in the general formula (IX). During the reaction, the epoxy group in the epoxy group-containing raw material is opened to form a hydroxyl group, and an esterification reaction occurs with the carboxyl group of the acrylic acid-based raw material. The acrylic acid-based raw material and the epoxy group-containing raw material are connected through an ester group, and the vinyl group is also introduced into the product molecule to generate the above-mentioned ultraviolet curable resin, which can be used for ultraviolet curing. This preparation method can control the ratio of reaction raw materials and reaction conditions to obtain different types of ultraviolet curable resins as shown in the general formula (I), and the preparation method process is controllable.

[0061] Step S10 can be further divided into step S11 and step S12:

[0062] S11: Provide the above raw material containing epoxy groups;

[0063] S12: Carry out ring-opening esterification reaction on the raw material containing epoxy groups and the acrylic acid-based raw material.

[0064] The raw material containing epoxy groups in step S11 is rich in epoxy groups. In the exemplary embodiment, phenolic raw materials and epichlorohydrin-based raw materials can be selected for preparation. The two can generate phenoxy epoxy compounds in the presence of a catalyst (such as tetrabutylammonium bromide) and an alkaline environment (such as 16% sodium hydroxide). In the exemplary embodiment, styrene-based raw materials and peroxy acid-based raw materials can be selected, and the unsaturated bonds can be reacted to form epoxy groups through an oxidation reaction. The raw material containing epoxy groups with the molecular structural formula shown in general formula (IX) can be obtained through the above various methods, which is rich in epoxy groups.

[0065] In some embodiments, in general formula (IX), A2 to A5 can be the same or different groups shown in the following general formula (X) or (XI):

[0066]

[0067] Among them, A6 is an oxygen atom or an alkyl group with 1 to 4 carbon atoms.

[0068] General formula (X) or (XI) is a typical group containing epoxy groups. Among them, the epoxy group in general formula (XI) is connected to the benzene ring in general formula (IX) through a methylene group. When A6 in general formula (X) is an alkyl group with 1 to 4 carbon atoms, the epoxy group is connected to the benzene ring in general formula (IX) through other alkyl groups. The group connecting the epoxy group and the benzene ring can also contain an oxygen atom. For example, when A6 in general formula (X) is an oxygen atom, an oxygen atom is directly bonded to the benzene ring, and then a methylene group and an epoxy group are further connected. Compared with the direct connection method through an alkyl group, this method is beneficial to making the electron cloud of the carbon atom in the epoxy group denser, further improving the inductive effect, and is more beneficial to the ring-opening esterification reaction between the epoxy group and the acrylic acid-based raw material, and is beneficial to introducing an alkenyl group into the molecule; if the epoxy group does not undergo ring-opening esterification reaction, it will also be retained in the prepared ultraviolet curable resin, which is beneficial to subsequent ring-opening nucleophilic reaction and then curing.

[0069] A1 is a soft segment group, which is beneficial to the prepared ultraviolet curable resin to undergo changes such as rotation and bending, and improves the degree of three-dimensional crosslinking during curing. In some embodiments, A1 can refer to the above R1 group and can be a group shown in general formula (VI) or (VII) or (VIII).

[0070] In summary, the raw material containing epoxy groups can include the following typical molecular structural formulas:

[0071] Such as: 2,2′-[(1-methylethylidene)bis[[6-(2-oxiranylmethoxy)-3,1-phenylene]methylene]]bis[oxirane], and the molecular structural formula is:

[0072]

[0073] Such as:

[0074]

[0075] In step S12, the above epoxy group-containing raw material and the acrylic acid-based raw material are further subjected to a ring-opening esterification reaction. In some embodiments, the acrylic acid-based raw material includes at least one of acrylic acid-based, vinyl acid, and crotonic acid. Among them, the acrylic acid-based includes at least one of acrylic acid, acryloyl chloride, methacrylic acid, methacryloyl chloride, ethylacrylic acid, propylacrylic acid, butylacrylic acid, and 3,3-dimethylacrylic acid. Crotonic acid may include 2-butenoic acid or 3-butenoic acid. In addition, acrylate, styrene, etc. can also be added. The carboxyl group in these acrylic acid-based raw materials can undergo a ring-opening esterification reaction with the epoxy group of the epoxy group-containing raw material, and the alkenyl group in the acrylic acid-based raw material is also introduced into the product molecule, enabling the subsequent free radical polymerization of the ultraviolet curable resin. In some embodiments, the mass ratio of the epoxy group-containing raw material to the acrylic acid-based raw material can be (20-85):(20-50). In the exemplary embodiments, it can include, but is not limited to, any ratio or the range between any two ratios of (20 or 35 or 50 or 65 or 85):(20 or 30 or 40 or 50). By adjusting the mass ratio of the two raw materials, the degree of the ring-opening esterification reaction can be adjusted, and the degree of introduction of the alkenyl group in the product molecule can be adjusted.

[0076] In some embodiments, the reaction temperature of the ring-opening esterification reaction can be 70-180°C. In the exemplary embodiments, it can include, but is not limited to, any value or the range between any two values of 70°C, 100°C, 130°C, 150°C, 180°C, and the reaction time can be 1-24 hours. Optionally, the reaction temperature is 70-120°C and the reaction time is 1-5 hours. The above reaction temperature and time can adjust the progress and speed of the reaction.

[0077] In some embodiments, the ring-opening esterification reaction may further include adding a catalyst and / or an inhibitor. The mass of the added catalyst and inhibitor can be added according to the mass ratio of the epoxy group-containing raw material: catalyst: inhibitor of (20-85):(0.01-0.5):(0.01-0.5).

[0078] The catalyst can promote the ring-opening esterification reaction in cooperation with parameters such as temperature. In the demonstration example, the catalyst can include at least one of triethylamine, N,N-dimethylbenzylamine, N,N-dimethylaniline, trimethylbenzylammonium chloride, triphenylphosphine, triphenylantimony, chromium acetylacetonate, and tetraethylammonium bromide. The inhibitor can prevent the polymerization and curing between acrylic acid-based raw materials and between acrylic acid-based raw materials and epoxy group-containing raw materials, which is beneficial to obtaining ultraviolet-curable resin molecules without premature polymerization. In the demonstration example, the inhibitor can include at least one of p-methoxyphenol, hydroquinone, 2,6-di-tert-butyl-p-cresol, and 2,5-dimethylhydroquinone.

[0079] The third aspect of the embodiments of the present application provides a photosensitive adhesive, which includes the ultraviolet-curable resin of the above embodiments of the present application or the ultraviolet-curable resin prepared by the preparation method of the above embodiments of the present application.

[0080] Since the ultraviolet-curable resin of the embodiments of the present application has a high curing rate and curing degree, high density and strength after film formation, is not prone to volume shrinkage, and has good sealing performance, it can be used in photosensitive adhesives. The photosensitive adhesive can be quickly cured under the action of ultraviolet light, and has high film density, high strength, strong adhesion, and is not prone to volume shrinkage, so it has good sealing and waterproof properties.

[0081] In some embodiments, the photosensitive adhesive includes the following components in parts by mass:

[0082] Ultraviolet-curable resin 80-120 parts

[0083] Free radical active diluent 30-70 parts

[0084] Photoinitiator 1-5 parts.

[0085] Among them, the free radical active diluent contains a large number of unsaturated bonds, and under the action of ultraviolet light and photoinitiator, a large number of free radicals are generated, which can crosslink and cure with the ultraviolet curable resin. In some embodiments, the free radical active diluent includes at least one of acrylate compounds, styrene compounds, and vinyl acetate. Among them, the acrylate compounds include at least one of butyl acrylate, isooctyl acrylate, isodecyl acrylate, lauryl acrylate, ethoxyethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, glycidyl methacrylate, isobornyl methacrylate, tetrahydrofurfuryl acrylate, phenoxyethyl acrylate, styrene, vinyl acetate, N-vinylpyrrolidone, diethylene glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, ethylene glycol phthalate diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol tetraacrylate. The mass parts of the free radical active diluent can include but are not limited to any value of 30 parts, 40 parts, 50 parts, 60 parts, 70 parts or the range between any two values.

[0086] The photoinitiator can initiate free radical polymerization under the action of ultraviolet light. In some embodiments, the photoinitiator includes at least one of benzoin compounds, α-hydroxyalkylacetophenone, α-aminoalkylacetophenone, acylphosphine oxides, benzophenone compounds, anthraquinone compounds, thioxanthone compounds, or sulfur-containing photoinitiators. The mass parts of the photoinitiator can include but are not limited to any value of 1 part, 2 parts, 3 parts, 4 parts, 5 parts or the range between any two values.

[0087] Under the action of ultraviolet light, the photosensitive adhesive will undergo a free radical polymerization reaction. With the action of ultraviolet light and the increase of temperature, the epoxy group will also undergo ring-opening polymerization, having a double-curing effect of free radical curing and cationic curing. In the demonstration example, the ultraviolet curable resin, free radical active diluent, and photoinitiator in the photosensitive adhesive can be composed of the following mass parts: 100 parts, 30 parts, 1 part, or 100 parts, 40 parts, 2 parts, or 100 parts, 50 parts, 3 parts, or 100 parts, 60 parts, 4 parts, or 100 parts, 70 parts, 5 parts.

[0088] Mixing the above components evenly will obtain the photosensitive adhesive. In some embodiments, the photosensitive adhesive may further include additives, and the additives may include at least one of stabilizers, leveling agents, defoaming agents, dispersants, plasticizers, and coupling agents, which can improve the properties such as the stability and film-forming flatness of the photosensitive adhesive. According to the above, when the mass parts of the ultraviolet resin are 100 parts, the mass parts of the additives can be 1 to 10 parts.

[0089] The fourth aspect of the embodiments of the present application provides an application of the photosensitive adhesive in the above embodiments of the present application, and the photosensitive adhesive is applied to at least one of electronic sealing, optical fiber devices, coatings, and 3D printing inks.

[0090] Since the photosensitive adhesive in the embodiments of the present application can be quickly cured under the action of ultraviolet light, and has a high film density, high strength, strong adhesion, and is not prone to volume shrinkage, and has good sealing and waterproof properties, it can be widely applied in fields such as electronic sealing, optical fiber devices, coatings, and 3D printing inks. During application, it can be first coated or filled, and then irradiated with ultraviolet light to initiate free radical and cationic curing.

[0091] The following will be described in conjunction with specific embodiments.

[0092] Example A1

[0093] This example provides an ultraviolet curable resin and a preparation method thereof. The preparation method includes the following steps S1 to S2:

[0094] S1: Prepare the epoxy group-containing raw material

[0095] Take the raw material 4,4'-(propane-2,2-diyl)bis(2-allylphenol), also known as o-diallylbisphenol A, and react it with epichlorohydrin under the action of the catalyst tetrabutylammonium bromide (TBAB). During the reaction, 16% sodium hydroxide is added to neutralize the reaction product hydrogen chloride and keep the reaction going. After the reaction is completed, sodium tungstate dihydrate, phosphoric acid, sulfuric acid, toluene, trioctylmethylammonium sulfate, and hydrogen peroxide are added for reaction to obtain 2,2′-[(1-methylethylidene)bis[[6-(2-oxiranylmethoxy)-3,1-phenylene]methylene]]bis[oxirane]; the reaction process is as follows:

[0096]

[0097] S2: Prepare the ultraviolet curable resin

[0098] In a 2000 ml three-necked glass bottle equipped with a stirrer and a condenser, add 450 g of 2,2′-[(1-methylethylidene)bis[[6-(2-oxiranylmethoxy)-3,1-phenylene]methylene]]bis[oxirane] prepared in step S1, 150 g of acrylic acid, 1 g of p-methoxyphenol as a polymerization inhibitor, and 4 g of triethylamine as a catalyst. Then reflux and heat at 90 °C and stir for 150 min to carry out ring-opening esterification reaction. The reaction process is as follows:

[0099]

[0100] The main product is ultraviolet curable resin 1, and the molecular structural formula is as follows:

[0101]

[0102] Among them, two epoxy groups undergo ring-opening esterification reactions to generate hydroxyl groups and introduce vinyl groups. Of course, in the product, there are inevitably products in which 0, 1, 3, and 4 epoxy groups in the molecule undergo ring-opening esterification reactions. However, by controlling the amount of acrylic acid used, the main product is still the above-mentioned ultraviolet-curable resin 1. Moreover, observing the substitution situation on the benzene ring, compared with the epoxy group directly bonded to the benzene ring through a methylene group, the way of directly bonding to the benzene ring through an oxygen atom, then combining with a methylene group and an epoxy group, is more likely to undergo a ring-opening reaction and then an esterification reaction.

[0103] Example A2

[0104] This example provides an ultraviolet-curable resin and its preparation method. The difference from Example A1 is only that: in step S2, the acrylic acid is changed from 150 g to 230 g, and the others are the same. The main product is ultraviolet-curable resin 2, and its molecular structural formula is as follows:

[0105]

[0106] Example A3

[0107] This example provides an ultraviolet-curable resin and its preparation method. The difference from Example A1 is only that: in step S2, the acrylic acid is changed from 150 g to 300 g, the temperature is changed to 120 °C, and the others are the same. The main product is ultraviolet-curable resin 3, and its molecular structural formula is as follows:

[0108]

[0109] Example A4

[0110] This example provides an ultraviolet-curable resin and its preparation method. The difference from Example A1 is only that: in step S2, the acrylic acid is changed to methacrylic acid, from 150 g to 172 g, the inhibitor and the catalyst are both changed to 10 g, the temperature is changed to 140 °C, and it is heated and stirred for 360 min, and the others are the same. The main product is ultraviolet-curable resin 4, and its molecular structural formula is as follows:

[0111]

[0112] Comparative Example A1

[0113] This comparative example provides an ultraviolet-curable resin. The difference from Example A1 is only that: in step S2, 2,2′-[(1-methylethylidene)bis[[6-(2-oxiranylmethoxy)-3,1-phenylene]methylene]]bis[oxirane] is changed to bisphenol A epoxy resin, and the others are the same.

[0114] The main product is ultraviolet curable resin 5, and its molecular structural formula is as follows:

[0115]

[0116] Performance testing of ultraviolet curable resin

[0117] Each case was tested with a nuclear magnetic resonance spectrometer. Among them, the nuclear magnetic resonance hydrogen spectrum of the ultraviolet curable resin in Example A1 is as Figure 1 shown. According to Figure 1 it can be seen that the resin contains characteristic peaks of vinyl protons and epoxy group protons, and the integral area ratio is consistent with the theoretical value of the product in Example A1.

[0118] Each case was tested with an infrared spectrometer. Among them, the infrared spectrum of the ultraviolet curable resin in Example A1 is as Figure 2 shown. According to Figure 2 it can be seen that the resin contains acrylic carbon-carbon double bonds and epoxy groups, further proving that the target product was successfully obtained.

[0119] Examples of photosensitive adhesives

[0120] Take 100 grams of the ultraviolet curable resin in Example A1, add a radical active diluent (40 grams), a coupling agent KBM-5103 (2 grams), a leveling agent BYK-310 (2 grams), a dispersant BYK-9077 (2 grams), a plasticizer 184 (3 grams), and an initiator 819 (1 gram), and stir evenly at room temperature to obtain the photosensitive adhesive of Example A1. Among them, the radical active diluent is 20 grams each of dipentaerythritol hexaacrylate (DPHA) and isobornyl acrylate (IBOA).

[0121] Similarly, the ultraviolet curable resin in Example A2 correspondingly obtains the photosensitive adhesive of Example B2, and so on, until the ultraviolet curable resin in Comparative Example A1 correspondingly obtains the photosensitive adhesive of Comparative Example B1. The differences between the photosensitive adhesives of each example and comparative example are shown in Table 1 below:

[0122] Table 1

[0123] Material Name or Model Example B1 Example B2 Example B3 Example B4 Comparative Example B1 Each UV-Curable Resin 100 g 100g 100g 100g 100g DPHA 20g 40g 55g 45g 35g IBOA 20g 30g 30g 25g 20g Coupling Agent KBM-5103 2g 2g 2g 2g 2g Leveling Agent BYK-310 2g 2g 3g 2g 2g Dispersant BYK-9077 2g 2g 2g 2g 2g Plasticizer 184 3g 3g 4g 4g 3g Initiator 819 1g 1g 1g 1g 1g

[0124] Performance testing of photosensitive adhesives

[0125] Take the photosensitive adhesives of the above Examples B1 to B4 and Comparative Example B1, cure them under the condition of 365 nm ultraviolet light wavelength to produce test pieces; and use the standard test methods in the art to test the performance of the photosensitive adhesives, the curing process, and the test pieces. Among them, the viscosity (25 °C) of the photosensitive adhesive in Example B1 is 5400 cps, the curing time is 45 min. It is measured that the volume shrinkage rate of the test piece made of the photosensitive adhesive in Example B1 is only 4%, the Shore hardness is 82D, the elongation at break is 185%, the bonding strength is 14 MPa, and the glass transition temperature (Tg) is 93 °C. The test results of each case are shown in Table 2.

[0126] Table 2

[0127] Test Items Example B1 Example B2 Example B3 Example B4 Comparative Example B1 Viscosity / cps @ 25°C 5400 3800 4000 3500 3600 Curing Duration (min) 45 30 30 58 70 Volume Shrinkage Rate (%) 4 2 1.5 5 10 Shore D Hardness 82 85 88 80 65 Elongation at Break (%) 185 180 160 180 160 Adhesion Strength (MPa) 14 18 20 13 10 Tg / °C (DMA) 93 105 110 90 70

[0128] Combined with Table 1 and Table 2, it can be seen that the curing time of the photosensitive adhesives in Examples B1 to B4 is short, and the properties such as hardness, toughness, and bonding strength after film formation are better than those of the photosensitive adhesive in Comparative Example B1. Moreover, the volume shrinkage rate of the film formed in each example is low, so the film has good sealing and waterproof properties. This shows that the ultraviolet-curable resin of the present application has excellent performance, proving that high functionality, containing alkenyl and hydroxyl groups, or further containing epoxy groups is beneficial to improving the comprehensive performance, and even if acrylate groups are introduced, the volume shrinkage rate is relatively low.

[0129] At the same time, it can be seen that among the various examples, the performance of Examples B2 and B3 is relatively excellent, proving that introducing more alkenyl groups into the ultraviolet-curable resin is more beneficial to improving the comprehensive performance.

[0130] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An ultraviolet curable resin, characterized in that, Its molecular structural formula is shown as the following general formula (I): Wherein, R1 is a soft segment group, and R2 to R5 are the same or different groups containing epoxy groups or alkenyl groups, and at least one of R2 to R5 contains an alkenyl group, and at least one of R2 to R5 contains a hydroxyl group.

2. The ultraviolet curable resin according to claim 1, wherein: R2 to R5 are the same or different groups shown as the following general formula (II), (III), (IV) or (V), and at least one of R2 to R5 is a group shown as general formula (IV) or (V): Wherein, R6 and R7 are the same or different and are oxygen atoms or C1-C4 alkyl groups, and R8 and R9 are the same or different and are hydrogen atoms or C1-C5 alkyl groups.

3. The ultraviolet curable resin according to claim 1 or 2, characterized in that: R1 is a group shown as the following general formula (VI) or (VII) or (VIII): Among them, R 10 , R 11 which are the same or different, are alkyl chains of C1 to C4.

4. The ultraviolet curable resin according to claim 1 or 2, characterized in that: The general formula (I) is the following molecular structural formula: or The general formula (I) is the following molecular structural formula:

5. A method for preparing an ultraviolet curable resin according to any one of claims 1 to 4, characterized in that, It includes the following steps: Carry out a ring-opening esterification reaction on the epoxy group-containing raw material and the acrylic acid raw material to generate an ultraviolet curable resin; Wherein, the molecular structural formula of the epoxy group-containing raw material is shown as the following general formula (IX): Wherein, A1 is a soft segment group, and A2 to A5 are the same or different groups containing epoxy groups.

6. The preparation method according to claim 5, characterized in that: In the general formula (VII), A2 to A5 are the same or different and are groups shown as the following general formula (X) or (XI): Wherein, A6 is an oxygen atom or a C1-C4 alkyl group; and / or A1 is the group shown as the general formula (VI) or (VII) or (VIII).

7. The preparation method according to claim 5 or 6, characterized in that: The mass ratio of the epoxy group-containing raw material to the acrylic acid raw material is (20-85):(20-50); and / or The acrylic acid raw material includes at least one of acrylic acid, vinyl acid, and crotonic acid; and / or The reaction temperature of the ring-opening esterification reaction is 70-180°C; and / or The ring-opening esterification reaction includes adding a catalyst and / or an inhibitor.

8. A photosensitive adhesive, characterized in that: It includes the ultraviolet curable resin according to any one of claims 1 to 4 or the ultraviolet curable resin prepared by the preparation method according to any one of claims 5 to 7.

9. The photosensitive adhesive according to claim 8, characterized in that: It includes the following components in parts by mass: 80-120 parts of the ultraviolet curable resin 30-70 parts of a free radical active diluent 1-5 parts of a photoinitiator; wherein, The free radical active diluent includes at least one of acrylate compounds, styrene compounds, and vinyl acetate; and / or The photoinitiator includes at least one of benzoin compounds, α-hydroxyalkylacetophenones, α-aminoalkylacetophenones, acylphosphine oxides, benzophenone compounds, anthraquinone compounds, thioxanthone compounds, or sulfur-containing photoinitiators.

10. Use of a photosensitive adhesive as described in claim 8 or 9, characterized in that: Apply the photosensitive adhesive to at least one of electronic sealing, optical fiber devices, coatings, and 3D printing inks.

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