Bi-crosslinking cyanate ester-epoxy blended adhesive and preparation method thereof

Abstract

The invention relates to a bi-crosslinking cyanate ester-epoxy blended adhesive and a preparation method thereof, and relates to the technical field of high polymer materials, the adhesive comprises the following components in parts by weight: 45-85 parts of cyanate ester resin, 5-35 parts of epoxy resin, 0-20 parts of a reactive diluent, 2-6 parts of a bi-crosslinking curing agent and 0-50 parts of a functional filler, the bi-crosslinking curing agent has the following structure: R is alkyl, aliphatic amine or aryl; r'is a primary amino group and / or a secondary amino group, R ''is-C = N and / or-OCN, m is an integer from 1 to 3, and n is an integer from 1 to 2. By adding the double-crosslinking curing agent containing the amino group and the cyano group, the technical problems of high curing temperature, large stress after curing, poor temperature resistance of epoxy resin and the like of the existing cyanate ester resin system are solved, and the curing temperature, the bonding strength and the temperature resistance of the adhesive are balanced. The adhesive can be cured at the temperature lower than 90 DEG C, and has high glass transition temperature, low thermal weight loss and excellent adhesive property.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a double crosslinked cyanate ester-epoxy blend adhesive and its preparation method. Background Technology

[0002] With the rapid development of modern industry, the demand for high-performance adhesives is increasing. Especially in the electronics, aerospace, and automotive industries, adhesives not only need excellent mechanical properties but also need to maintain stable electrical properties under extreme environments such as high temperature and high humidity. While traditional epoxy resin adhesives possess good mechanical properties and chemical resistance, their performance remains insufficient in certain high-performance applications, such as electronic packaging and aerospace. For example, epoxy resins have a relatively low glass transition temperature (Tg), typically between 100-150°C, which limits their application in high-temperature environments. Furthermore, the dielectric properties of epoxy resins are insufficient to meet the requirements of high-frequency electronic devices. To overcome these limitations, researchers have begun exploring new resin systems. Cyanate ester resins have attracted attention due to their excellent thermal stability and dielectric properties. During curing, cyanate ester resins can form a highly cross-linked triazine ring network structure, exhibiting a high glass transition temperature (typically between 240-300°C) and a low dielectric constant. These characteristics make cyanate ester resins a promising candidate for high-performance adhesives.

[0003] Despite the many excellent properties of cyanate ester resins, they still have some drawbacks and limitations in practical applications. First, cyanate ester resins have a slow curing speed, which limits their application in fast-paced production environments. Second, cyanate ester resins lack toughness and are prone to brittle fracture under stress. Furthermore, cyanate ester resins have poor processability and require high-temperature curing, which increases production costs. On the other hand, while epoxy resins possess good mechanical and processability properties, their glass transition temperature is low and their dielectric properties are not ideal. Therefore, using either cyanate ester resin or epoxy resin alone cannot meet the requirements for high-performance adhesives. By combining cyanate ester resins with epoxy resins, the advantages of both can be combined to develop an adhesive that combines rapid curing, high mechanical properties, and excellent dielectric properties. This composite system has broad application prospects in fields such as electronic packaging and aerospace structural component bonding.

[0004] Despite the significant advantages of cyanate ester-epoxy adhesives, several technical challenges remain in practical applications. First, the different curing mechanisms of cyanate ester and epoxy resins make simultaneous curing difficult. Cyanate ester resins typically require high temperatures for curing, while epoxy resins can cure at lower temperatures. This temperature difference makes it challenging to find suitable curing conditions that meet the curing requirements of cyanate ester resins without causing premature curing of the epoxy resin. Second, the significant differences in chemical structures between cyanate ester and epoxy resins result in poor compatibility. In composite systems, the two resins are prone to phase separation, affecting the overall performance of the adhesive. Furthermore, the cured products of cyanate ester resins exhibit high crosslinking density, which, while improving thermal stability and mechanical properties, also increases brittleness. In practical applications, this brittleness can lead to adhesive breakage upon impact or bending. Finally, the curing reactions of cyanate ester and epoxy resins require different catalysts. Cyanate ester resins typically require transition metal catalysts or active hydrogen catalysts, while epoxy resins require basic catalysts. The incompatibility of these catalysts makes it difficult to achieve efficient curing of both resins simultaneously in a composite system.

[0005] Clearly, neither a single epoxy nor cyanate ester system can simultaneously achieve the aforementioned properties, while simple blending faces a triple bottleneck: catalyst incompatibility, enrichment of interfacial polar groups, and metal ion migration. Therefore, developing a cyanate ester-epoxy adhesive that simultaneously completes the triazineation of cyanate ester and the ring-opening of epoxy, forming a covalent bridge at the two-phase interface, has become a key technology urgently needing breakthroughs for high-performance, high-reliability cyanate ester-epoxy adhesive systems. Summary of the Invention

[0006] In view of the above analysis, the present invention aims to provide a double crosslinked cyanate ester-epoxy blend adhesive and its preparation method to solve at least one of the following problems: (1) The chemical structures of cyanate ester resin and epoxy resin are quite different. Simple blending is prone to phase separation, which weakens the interfacial bonding strength and affects the adhesiveness and mechanical properties of the adhesive; (2) In the prior art, cyanate ester resin often uses active hydrogen catalysts or transition metal catalysts that require the addition of cosolvents, while epoxy resin relies on amine or imidazole catalysts. These catalysts or cosolvents are prone to volatilization or decomposition at high temperatures, which affects the adhesiveness and thermal stability of the adhesive; (3) Traditional cyanate ester resin requires high temperature curing, while epoxy resin can be cured at a lower temperature. The curing temperature windows of the two are not matched, which makes it difficult to achieve synchronous curing in practical applications, affecting the comprehensive performance and process adaptability of the adhesive.

[0007] To achieve the above objectives, the first aspect of the present invention provides a double crosslinked cyanate ester-epoxy blend adhesive, wherein the raw materials for preparing the adhesive include, by weight, 45-85 parts of cyanate ester resin, 5-35 parts of epoxy resin, 0-20 parts of reactive diluent, 2-6 parts of double crosslinked curing agent, and 0-50 parts of functional filler. The dual crosslinking curing agent has the structure shown in Formula I: Formula I Where R is a hydrocarbon group, aliphatic amine, or aryl group, R' is a primary amine group and / or a secondary amine group, R'' is –CN and / or –OCN, m is an integer from 1 to 3, and n is an integer from 1 to 2.

[0008] Furthermore, in the dual crosslinking curing agent, R is an aryl group, m is an integer from 2 to 3, and the aryl group is selected from at least one of benzene, biphenyl, naphthalene, anthracene, pyridine, pyrimidine, furan, or thiophene.

[0009] Furthermore, in the dual crosslinking curing agent, R' and R'' are located at the para, ortho, meta, or biphenyl bridging positions of the aryl group.

[0010] Further, the dual crosslinking curing agent is selected from at least one of 1,4-diamino-2,5-dicyanophenyl, 2,5-diaminobenzonitrile, 4,4'-diamino-[1,1'-biphenyl]-3,3'-dicarboxynitrile and 4,4'-diamino-[1,1'-biphenyl]-3-carboxynitrile.

[0011] Further, the dual crosslinking curing agent is selected from at least one of 6-aminohexanonitrile, 11-aminoundecanonitrile, 1,4-diaminobutane-2-nitrile, 5-amino-4-methylpentanonitrile, N-(2-cyanoethyl)ethylenediamine and terminal aminonitrile oligomers.

[0012] Furthermore, the cyanate resin is selected from monomers or prepolymers of at least one compound selected from bisphenol A cyanate, bisphenol E cyanate, bisphenol M cyanate, phenolic cyanate, dicyclopentadiene cyanate, and bisphenol F cyanate.

[0013] Furthermore, the epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenolic epoxy resin, aliphatic epoxy resin, organosilicon epoxy resin and multifunctional epoxy resin.

[0014] Furthermore, the reactive diluent is selected from butyl glycidyl ether, diglycidyl tetrahydrophthalate, and C... 12 -C 14At least one of alkyl glycidyl ether, phenyl glycidyl ether, 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, cashew phenol glycidyl ether, epoxidized vegetable oil, and epoxidized soybean oil.

[0015] Furthermore, the functional filler is at least one selected from nano-SiO2, carbon nanotubes, SiC whiskers, AlN, BN, Al2O3, graphite, carbon fiber, aluminum hydroxide, magnesium hydroxide, mica powder, boehmite, ferrite, iron carbonyl, FeSiAl, and graphene.

[0016] A second aspect of the present invention provides a method for preparing a double-crosslinked cyanate ester-epoxy blend adhesive, the method comprising: S1. Mix epoxy resin and reactive diluent to obtain epoxy diluent; S2: Heat the epoxy diluent to the first temperature, add cyanate ester resin and mix to obtain cyanate ester-epoxy blend; S3: Cool the cyanate ester-epoxy blend to a second temperature and add a double crosslinking curing agent to obtain a double crosslinked cyanate ester-epoxy blend adhesive; The dual crosslinking curing agent has the structure shown in Formula I: Formula I Where R is a hydrocarbon group, aliphatic amine, or aryl group, R' is a primary amine group and / or a secondary amine group, R'' is –CN and / or –OCN, m is an integer from 1 to 3, and n is an integer from 1 to 2.

[0017] Furthermore, the method further includes step S4: adding functional fillers to the double crosslinked cyanate ester-epoxy blend adhesive at room temperature.

[0018] Furthermore, the first temperature is 50~120℃.

[0019] Furthermore, the second temperature is 25~80℃.

[0020] Further, by weight, 45-85 parts cyanate ester resin, 5-35 parts epoxy resin, 0-20 parts reactive diluent, 2-6 parts dual crosslinking curing agent, and 0-50 parts functional filler.

[0021] A third aspect of the present invention provides a double crosslinked cyanate ester-epoxy blend adhesive, wherein the double crosslinked cyanate ester-epoxy blend adhesive is prepared according to the method described in the second aspect.

[0022] The fourth aspect of this invention provides the application of the double crosslinked cyanate-epoxy blend adhesive described in the third aspect in high-reliability electronic packaging and aerospace structural component bonding.

[0023] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: 1. The dual-crosslinking curing agent of the present invention integrates primary amine groups and / or secondary amine groups with cyano groups and / or cyanate groups on the same molecular backbone. The primary amine groups and / or secondary amine groups catalyze the ring-opening of epoxy resin at a lower temperature (≤100℃), while the cyano groups and / or cyanate groups copolymerize with cyanate esters to participate in triazine cyclization. This achieves simultaneous low-temperature curing of cyanate esters and epoxy in a single component, improving process adaptability and avoiding the incompatibility problem between metal catalysts and amine / imidazolium catalysts in traditional systems. It fundamentally eliminates defects such as asynchronous curing and uneven network structure caused by catalytic system conflicts. Furthermore, since the dual-crosslinking curing agent of the present invention does not contain metal, it avoids adhesive aging and mechanical property degradation caused by metal residues.

[0024] 2. The cyanate ester resin in the curing agent of this invention, after curing, forms a highly cross-linked network dominated by a triazine ring structure. This structure provides excellent thermal stability and a high glass transition temperature (typically reaching 240~260℃, and even up to 400℃). Simultaneously, primary and / or secondary amine groups react with epoxy to form an epoxy network, contributing to adhesive performance and excellent chemical stability. The two phases are covalently bridged by the same molecule, forming a chemically cross-linked interpenetrating network structure, achieving complementary advantages and creating a synergistic enhancement effect. This results in excellent performance across multiple performance dimensions, effectively suppressing phase separation caused by poor compatibility between cyanate ester and epoxy, avoiding the enrichment of polar groups at the interface, thereby significantly improving the adhesive strength and mechanical properties.

[0025] 3. In this invention, when selecting cyanate ester resin or epoxy resin with high viscosity, an active diluent is used instead of a traditional solvent. This can reduce the viscosity of the cyanate ester-epoxy blend and improve the handling performance, while reacting with the blend without sacrificing the bonding performance and mechanical properties.

[0026] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0027] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0028] Figure 1 This is a schematic diagram of the preparation of the double crosslinked cyanate-epoxy blend adhesive with a highly crosslinked network structure in Example 1. Detailed Implementation

[0029] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0030] Currently, single epoxy resin or cyanate ester resin systems are insufficient to meet the requirements of high-frequency electronic devices, while simple blending faces a triple bottleneck of "catalyst incompatibility, enrichment of interfacial polar groups, and metal ion migration." Based on this, in order to solve the above problems, the first aspect of the present invention provides a double crosslinked cyanate ester-epoxy blend adhesive, wherein the raw materials for preparing the adhesive include, by weight, 45-85 parts of cyanate ester resin, 5-35 parts of epoxy resin, 0-20 parts of reactive diluent, 2-6 parts of double crosslinked curing agent, and 0-50 parts of functional filler; The dual crosslinking curing agent has the structure shown in Formula I: Formula I Where R is a hydrocarbon group, aliphatic amine, or aryl group, R' is a primary amine group and / or a secondary amine group, R'' is –CN and / or –OCN, m is an integer from 1 to 3, and n is an integer from 1 to 2.

[0031] In this invention, the dual-crosslinking curing agent integrates primary amine groups and / or secondary amine groups with cyano groups and / or cyanate groups on the same molecular backbone. The primary amine groups and / or secondary amine groups catalyze the ring-opening of epoxy resin at a lower temperature (≤100℃), while the cyano groups and / or cyanate groups copolymerize with cyanate ester to participate in triazine cyclization. This achieves simultaneous low-temperature curing of cyanate ester and epoxy in a single component, improving process adaptability and avoiding the incompatibility problem between metal catalysts and amine / imidazolium catalysts in traditional systems. It fundamentally eliminates defects such as asynchronous curing and uneven network structure caused by catalytic system conflicts. Furthermore, since the dual-crosslinking curing agent of this invention does not contain metal, it avoids adhesive aging and mechanical property degradation caused by metal residues.

[0032] Furthermore, to ensure the integrity of the structure, stability of the performance, and reliability of the process of the prepared adhesive, m is taken as an integer from 1 to 3. However, if R is aryl, n is taken as an integer from 2 to 3. This is because the inventors found that when n=1, the crosslinking points of the curing agent are insufficient, making it difficult to form a dense interpenetrating network, resulting in low crosslinking density of the cured product and a decrease in heat resistance and mechanical properties. At the same time, the molecular weight is small and easy to migrate and volatilize, affecting the compatibility and storage stability of the components, and the curing efficiency is insufficient, which disrupts the synchronous curing of the two phases.

[0033] Specifically, this system achieves multiple synergies through precise matching of the content ranges of each component: cyanate ester and epoxy resin are uniformly blended at a suitable viscosity adjusted by the reactive diluent, creating a homogeneous environment for the simultaneous catalysis of the dual crosslinking curing agent. The dual crosslinking curing agent simultaneously catalyzes the curing of the two phases at the above dosage, constructing a dense triazine interpenetrating network. Functional fillers are uniformly dispersed in this network and form interfacial bonds, further enhancing the integrity of the triazine network while improving functionality.

[0034] Furthermore, the content of the cyanate resin can be 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, or any two of the above values. If the content of the cyanate resin is less than 45 parts, the triazine network density is insufficient, resulting in a significant decrease in heat resistance (Tg); if it is more than 80 parts, the brittleness increases dramatically, and the unreacted cyanate is prone to phase separation, affecting the interfacial bonding and process adaptability. In order to obtain better results, the content of the cyanate resin is preferably 65 to 80 parts.

[0035] Furthermore, the content of the epoxy resin can be 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, or any combination of two of the above values. If the epoxy resin content is less than 5 parts, the toughening effect is insufficient, the curing stress is high, and cracking is easy; if it is more than 35 parts, the heat resistance of the adhesive will decrease. To obtain better results, preferably, the content of the epoxy resin is 10 to 25 parts.

[0036] Further, the content of the reactive diluent can be 0 parts, 2 parts, 3 parts, 5 parts, 8 parts, 10 parts, 15 parts, 20 parts, or any combination of two of the above values. In this invention, if the types of cyanate ester resin and epoxy resin selected are sufficiently mixed to form a homogeneous interface, the amount of reactive diluent can be 0 parts. However, for this invention, regardless of the type of cyanate ester resin and epoxy resin selected, if the amount of reactive diluent exceeds 20 parts, it will excessively dilute the resin concentration, reduce the crosslinking density, and lead to a significant decrease in mechanical strength and heat resistance. Preferably, the content of the reactive diluent is preferably 0 to 15 parts.

[0037] Furthermore, the content of the dual-crosslinking curing agent can be 2 parts, 2.5 parts, 3 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, or any combination of two of the above values. As a key component for simultaneous catalysis and crosslinking, the dual-crosslinking curing agent, when present in amounts below 2 parts, results in insufficient catalytic efficiency, making it difficult for the curing reaction to proceed simultaneously with the cyanate ester resin and epoxy resin; when present in amounts above 6 parts, excessive crosslinking leads to system embrittlement, and the increased residue of small-molecule curing agents further reduces thermomechanical properties. To achieve even better results, the content of the dual-crosslinking curing agent is preferably 2.5 to 5 parts.

[0038] Furthermore, the content of the functional filler can be 5 parts, 10 parts, 15 parts, 20 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, or any two of the above values. In this invention, adding an appropriate amount of functional filler can fully utilize its functional role by forming an interface with the triazine network and enhancing the integrity of the triazine network, thereby improving the overall performance of the adhesive. However, when the content exceeds 50 parts, the functional filler is difficult to disperse evenly and may even damage the structure of the triazine network, leading to a decrease in mechanical properties. To further obtain better results, preferably, the content of the functional filler is 10 to 40 parts.

[0039] According to some embodiments of the present invention, the aryl group is selected from at least one of benzene, biphenyl, naphthalene, anthracene, pyridine, pyrimidine, furan or thiophene, preferably benzene, biphenyl or naphthalene.

[0040] In this invention, the aryl group serves as the core skeleton, and its conjugated structure regulates the electronic effects of primary and / or secondary amines with cyano and / or cyanate groups, preferably benzene, biphenyl, or naphthalene, thereby ensuring high activity while endowing the system with excellent storage and thermal stability.

[0041] According to some embodiments of the present invention, in the dual crosslinking curing agent, R' and R'' are located at the para, ortho, meta, or biphenyl bridging positions of the aryl group. The position of the functional groups modulates the intensity of electronic effects through spatial arrangement such as para and meta positions, achieving a precise balance between curing rate and storage stability, and providing flexibility for process design.

[0042] According to some preferred embodiments of the present invention, specifically, the dual crosslinking curing agent is selected from at least one of 1,4-diamino-2,5-dicyanophenylene, 2,5-diaminobenzonitrile, 4,4'-diamino-[1,1'-biphenyl]-3,3'-dicarboxynitrile, 4,4'-diamino-[1,1'-biphenyl]-3-carboxynitrile, 6-aminohexanonitrile, 11-aminoundecanonitrile, 1,4-diaminobutane-2-nitrile, 5-amino-4-methylpentanonitrile, and N-(2-cyanoethyl)ethylenediamine.

[0043] According to some embodiments of the present invention, the cyanate resin is selected from monomers or prepolymers of at least one compound selected from bisphenol A cyanate, bisphenol E cyanate, bisphenol M cyanate, phenolic cyanate, dicyclopentadiene cyanate, and bisphenol F cyanate.

[0044] In this invention, when the cyanate ester is selected from the above-mentioned types, it can precisely synergize with the dual crosslinking curing agent to ensure efficient curing by primary and / or secondary amines at low temperatures. At the same time, its own -OCN functional group can copolymerize with the cyano group of the dual crosslinking curing agent to jointly construct a dense and thermally stable triazine network, which is the basis for achieving a balance between low-temperature processing and heat resistance.

[0045] According to some embodiments of the present invention, the epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenolic epoxy resin, aliphatic epoxy resin, organosilicon epoxy resin and multifunctional epoxy resin.

[0046] In this invention, when the epoxy resin is selected from the above-mentioned types, it can form a complementary relationship with cyanate ester. The epoxy phase improves toughness and reduces overall curing stress. Its abundant reaction sites and the double crosslinking curing agent synergistically construct a dense interpenetrating network, jointly achieving a comprehensive improvement in high strength, toughness, and high temperature resistance.

[0047] According to some embodiments of the present invention, the reactive diluent is selected from butyl glycidyl ether, diglycidyl tetrahydrophthalate, C... 12 -C 14 At least one of alkyl glycidyl ether, phenyl glycidyl ether, 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, cashew phenol glycidyl ether, epoxidized vegetable oil, and epoxidized soybean oil.

[0048] In this invention, the above-mentioned reactive diluent is used to replace the traditional solvent, which can reduce the viscosity of the cyanate ester-epoxy blend and improve the handling performance, while reacting with the blend without sacrificing the bonding performance and mechanical properties.

[0049] According to some embodiments of the present invention, the functional filler is at least one selected from nano-SiO2, carbon nanotubes, SiC whiskers, AlN, BN, Al2O3, graphite, carbon fiber, aluminum hydroxide, magnesium hydroxide, mica powder, boehmite, ferrite, carbonyl iron, FeSiAl, and graphene. In the present invention, mica powder is preferred in view of improving the temperature resistance of the final adhesive.

[0050] In this invention, nanofillers (such as nano-SiO2) enhance the interfacial bonding with the triazine-trinitrile / epoxy interpenetrating network through surface effects, thereby improving mechanical properties and inhibiting crack propagation. Thermally / electrically conductive fillers (such as BN and graphene) construct efficient permeation pathways in the cured network and form an interfacial polarization layer with the resin phase, synergistically optimizing dielectric and thermal conductivity. Flame-retardant fillers (such as ATH) couple with the resin carbonization layer during decomposition, forming a dense protective layer and improving flame-retardant efficiency. The fillers not only perform their intrinsic functions but also participate in network construction through physical interweaving and chemical bonding, achieving integrated structure-function enhancement.

[0051] A second aspect of the present invention provides a method for preparing a double-crosslinked cyanate ester-epoxy blend adhesive, the method comprising: S1. Mix epoxy resin and reactive diluent to obtain epoxy diluent; S2: Heat the epoxy diluent to the first temperature, add cyanate ester resin and mix to obtain cyanate ester-epoxy blend; S3: Cool the cyanate ester-epoxy blend to a second temperature and add a double crosslinking curing agent to obtain a double crosslinked cyanate ester-epoxy blend adhesive; The dual crosslinking curing agent has the structure shown in Formula I: Formula I Where R is a hydrocarbon group, aliphatic amine, or aryl group, R' is a primary amine group and / or a secondary amine group, R'' is –CN and / or –OCN, m is an integer from 2 to 3, and n is an integer from 1 to 2.

[0052] In this invention, the reactive diluent is preferentially mixed with the epoxy resin, which effectively reduces the initial viscosity of the system and improves the uniformity of the epoxy phase, laying the foundation for the subsequent dispersion of cyanate ester.

[0053] According to some embodiments of the present invention, considering the needs of different application scenarios, the method further includes step S4: adding functional fillers to the double crosslinked cyanate ester-epoxy blend adhesive at room temperature.

[0054] In this invention, by adding the functional fillers described herein, adhesives can be endowed with additional functional properties, such as electrical conductivity, thermal conductivity, and electromagnetic shielding. This functional integration capability transforms adhesives from simple bonding materials into an important component of multifunctional composite material systems.

[0055] According to some embodiments of the present invention, the first temperature is 50~120°C, and the second temperature is 25~80°C.

[0056] In this invention, heating to a first temperature allows the cyanate ester resin to be fully melted and dispersed in a low-viscosity epoxy diluent, avoiding local agglomeration and forming a homogeneous blend precursor; cooling to a second temperature and then adding a dual crosslinking curing agent can ensure uniform diffusion of curing agent molecules in the system while avoiding premature gelation.

[0057] According to some embodiments of the present invention, the amount of cyanate ester resin is 45-85 parts by weight, the amount of epoxy resin is 5-35 parts, the amount of reactive diluent is 0-20 parts, the amount of dual crosslinking curing agent is 2-6 parts, and the amount of functional filler is 5-50 parts.

[0058] According to some embodiments of the present invention, the dual crosslinking curing agent has the structure shown in Formula I: Formula I Where R is a hydrocarbon group, aliphatic amine, or aryl group, R' is a primary amine group and / or a secondary amine group, R'' is –C≡N and / or –OCN, m is an integer from 1 to 3, and n is an integer from 1 to 2.

[0059] According to some embodiments of the present invention, m takes the integer value of 1 to 3, but if R is an aryl group, n takes the integer value of 2 to 3.

[0060] According to some embodiments of the present invention, the content of the cyanate resin can be 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, or any two of the above values. If the content of the cyanate resin is less than 45 parts, the triazine network density is insufficient, resulting in a significant decrease in heat resistance (Tg); if the content is greater than 80 parts, the brittleness increases dramatically, and unreacted cyanate is prone to phase separation, affecting interfacial bonding and process adaptability. In order to obtain better results, the content of the cyanate resin is preferably 65 to 80 parts.

[0061] According to some embodiments of the present invention, the content of the epoxy resin can be 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, or any combination of two of the above values. If the content of epoxy resin is less than 5 parts, the toughening effect is insufficient, the curing stress is high, and cracking is easy; if it is more than 35 parts, the heat resistance of the adhesive will decrease. To further obtain better results, preferably, the content of the epoxy resin is 10 to 25 parts.

[0062] According to some embodiments of the present invention, the content of the active diluent may be 0 parts, 2 parts, 3 parts, 5 parts, 8 parts, 10 parts, 15 parts, 20 parts, or any combination of two of the above values, preferably 0 to 15 parts.

[0063] According to some embodiments of the present invention, the content of the dual crosslinking curing agent can be 2 parts, 2.5 parts, 3 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, or any combination of the above two values, preferably 2.5 to 5 parts.

[0064] According to some embodiments of the present invention, the content of the functional filler can be 5 parts, 10 parts, 15 parts, 20 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, or any two of the above values, preferably 10 to 40 parts.

[0065] According to some embodiments of the present invention, the aryl group is selected from at least one of benzene, biphenyl, naphthalene, anthracene, pyridine, pyrimidine, furan or thiophene, preferably benzene, biphenyl or naphthalene.

[0066] According to some embodiments of the present invention, in the dual crosslinking curing agent, R' and R'' are located at the para, ortho, meta, or biphenyl bridging positions of the aryl group. The position of the functional groups modulates the intensity of electronic effects through spatial arrangement such as para and meta positions, achieving a precise balance between curing rate and storage stability, and providing flexibility for process design.

[0067] According to some preferred embodiments of the present invention, specifically, the dual crosslinking curing agent is selected from at least one of 1,4-diamino-2,5-dicyanophenylene, 2,5-diaminobenzonitrile, 4,4'-diamino-[1,1'-biphenyl]-3,3'-dicarboxynitrile, 4,4'-diamino-[1,1'-biphenyl]-3-carboxynitrile, 6-aminohexanonitrile, 11-aminoundecanonitrile, 1,4-diaminobutane-2-nitrile, 5-amino-4-methylpentanonitrile, and N-(2-cyanoethyl)ethylenediamine.

[0068] According to some embodiments of the present invention, the cyanate resin is selected from monomers or prepolymers of at least one compound selected from bisphenol A cyanate, bisphenol E cyanate, bisphenol M cyanate, phenolic cyanate, dicyclopentadiene cyanate, and bisphenol F cyanate.

[0069] According to some embodiments of the present invention, the epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenolic epoxy resin, aliphatic epoxy resin, organosilicon epoxy resin and multifunctional epoxy resin.

[0070] According to some embodiments of the present invention, the active diluent is selected from at least one of butyl glycidyl ether, diglycidyl tetrahydrophthalate, C12-C14 alkyl glycidyl ether, phenyl glycidyl ether, 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, cashew phenol glycidyl ether, epoxidized vegetable oil, and epoxidized soybean oil.

[0071] According to some embodiments of the present invention, the functional filler is at least one selected from nano-SiO2, carbon nanotubes, SiC whiskers, AlN, BN, Al2O3, graphite, carbon fiber, aluminum hydroxide, magnesium hydroxide, mica powder, boehmite, ferrite, carbonyl iron, FeSiAl, and graphene. In the present invention, mica powder is preferred in view of improving the temperature resistance of the final adhesive.

[0072] A third aspect of the present invention provides a double crosslinked cyanate-epoxy blend adhesive prepared by the method described in the second aspect.

[0073] In this invention, the adhesive comprises as follows: Figure 1The highly cross-linked network structure shown specifically utilizes a bifunctional curing agent integrating primary and / or secondary amine groups with cyano and / or cyanate groups. This agent simultaneously catalyzes the curing reaction of cyanate ester and epoxy resin at low temperatures and forms a dense interpenetrating network structure through covalent bridging. This fundamentally solves the technical problems of asynchronous curing, poor compatibility, and weak interfaces in traditional blending systems, achieving a balance between low-temperature curing and high comprehensive performance of the adhesive. After curing at ≤90℃, the adhesive exhibits excellent comprehensive performance with a glass transition temperature ≥210℃, a thermal weight loss of ≤2wt% at 300℃, an adhesive strength ≥17MPa, and a tensile strength ≥90MPa.

[0074] The fourth aspect of this invention provides the application of the double crosslinked cyanate-epoxy blend adhesive described in the third aspect in electronic packaging and aerospace structural component bonding.

[0075] To more clearly describe the present invention, the following embodiments and comparative examples are provided for further illustration.

[0076] In the following examples and comparative examples, the thermal stability of the double crosslinked cyanate ester-epoxy blend adhesive was characterized by mass loss at 300°C, which was measured by TGA (thermogravimetric analysis) at 300°C in a nitrogen atmosphere. Curing temperature: The curing exothermic peak temperature was measured by DSC (differential scanning calorimetry).

[0077] Glass transition temperature (Tg): Measured by DSC or DMA (Dynamic Mechanical Analysis).

[0078] The bond strength was measured in accordance with GB / T 7124-2008; Tensile strength and elongation at break were measured in accordance with GB / T 1040.2-2022.

[0079] Example 1 S1. Slowly add 25g of E44 epoxy resin to 10g of diglycidyl tetrahydrophthalate and stir thoroughly until completely mixed to obtain epoxy dilution. S2. Heat the epoxy diluent to 80°C, and slowly add 35g of 1,1-bis(4-cyanoxyphenyl)ethane and 40g of 2,2-bis(4-cyanoxyphenyl)propane, stirring thoroughly until the resin is completely mixed to obtain the blend. S3. Then cool the blend to 30°C and add 3g of 2,4-diaminobenzonitrile, stirring thoroughly until the curing agent dissolves. S4. Cool the mixture system obtained in step S3 to room temperature and add 30g of 800-mesh mica powder. Stir thoroughly until the mica powder is evenly mixed to obtain a double crosslinked cyanate ester-epoxy blend adhesive.

[0080] Example 2 S1. Slowly add 16g of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate to 5g of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, and stir thoroughly until completely mixed to obtain an epoxy diluent. S2. Heat the epoxy diluent to 30°C, and slowly add 35g of 1,1-bis(4-cyanoxyphenyl)ethane and 45g of 2,2-bis(4-cyanoxyphenyl)propane, stirring thoroughly until the resin is completely mixed to obtain the blend. S3. Then cool the blend to 25°C and add 3g of 2,4-diaminobenzonitrile, stirring thoroughly until the curing agent dissolves. S4. Cool the mixture system obtained in step S3 to room temperature and add 30g of 800-mesh mica powder. Stir thoroughly until the mica powder is evenly mixed to obtain a double crosslinked cyanate ester-epoxy blend adhesive.

[0081] Example 3 S1. Slowly add 20g of E51 epoxy resin to 10g of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester and stir thoroughly until completely mixed to obtain epoxy dilution. S2. Heat the epoxy diluent to 80°C and slowly add 50g of 1,1-bis(4-cyanoxyphenyl)ethane and 20g of 4,4'-methylenebis(2,6-dimethylphenyl cyanate), stirring thoroughly until the resin is completely mixed to obtain the blend. S3. Then cool the blend to 30°C and add 4g of 2,4-diaminobenzonitrile, stirring thoroughly until the curing agent dissolves. S4. Cool the mixture system obtained in step S3 to room temperature and add 30g of BN with a diameter of 25μm to obtain a double crosslinked cyanate ester-epoxy blend adhesive.

[0082] Example 4 The method of Example 2 is followed, except that the cyanate ester resin is replaced with 80g of 1,1-bis(4-cyanoxyphenyl)ethane.

[0083] Example 5 S1. Slowly add 10g of E51 epoxy resin and 5g of E54 epoxy resin to 3g of 1,4-butanediol diglycidyl ether, and stir thoroughly until completely mixed to obtain epoxy dilution. S2. Heat the epoxy diluent to 90°C and slowly add 50g of 4,4'-[1,3-phenylbis(1-methyl-ethylidene)]bisphenyl cyanate and 20g of 2,2-bis(4-cyanoxyphenyl)propane. Stir thoroughly until the resin is completely mixed to obtain the blend. S3. Then cool the blend to 30°C and add 2.5g of 4,4'-diamino-[1,1'-biphenyl]-3-carboxynitrile, and stir thoroughly until the curing agent is dissolved; S4. Cool the mixture system obtained in step S3 to room temperature and add 25g of AlN with a length of 20μm to obtain a double crosslinked cyanate ester-epoxy blend adhesive.

[0084] Example 6 The method is the same as in Example 2, except that the amount of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate is 22g, the amount of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester is 5g, the amount of 1,1-bis(4-cyanooxyphenyl)ethane is 35g, the amount of 2,2-bis(4-cyanooxyphenyl)propane is 35g, the amount of 2,4-diaminobenzonitrile is 2g, and the amount of mica powder is 35g.

[0085] Example 7 The method is the same as in Example 2, except that the amount of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate is 30g, the amount of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester is 1g, the amount of 1,1-bis(4-cyanooxyphenyl)ethane is 25g, the amount of 2,2-bis(4-cyanooxyphenyl)propane is 35g, the amount of 2,4-diaminobenzonitrile is 6g, and the amount of mica powder is 15g.

[0086] Example 8 The method is the same as in Example 2, except that the amount of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate is 25g, no reactive diluent is used, 1,1-bis(4-cyanooxyphenyl)ethane is 60g, and 2,2-bis(4-cyanooxyphenyl)propane is 25g.

[0087] Example 9 The method is the same as in Example 1, except that no mica powder filler is added.

[0088] Comparative Example 1 The method is the same as in Example 1, except that the curing agent is 4-aminobenzonitrile.

[0089] Comparative Example 2 The method is the same as in Example 1, except that the curing agent is 4-cyanobiphenyl.

[0090] Comparative Example 3 The method is the same as in Example 1, except that the curing agent is replaced with an equal amount of isophorone diisocyanate.

[0091] Comparative Example 4 The method is the same as in Example 1, except that the curing agent is replaced with p-phenylenediamine.

[0092] Comparative Example 5 The method is the same as in Example 1, except that the amount of curing agent used is 10g.

[0093] Comparative Example 6 The method is the same as in Example 2, except that the amount of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate is 40g, the amount of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester is 20g, the amount of 1,1-bis(4-cyanooxyphenyl)ethane is 25g, the amount of 2,2-bis(4-cyanooxyphenyl)propane is 15g, the amount of 2,4-diaminobenzonitrile is 8g, and the amount of mica powder is 5g.

[0094] Test case The properties of the adhesives prepared in the examples and comparative examples were tested, specifically as follows: Initial curing temperature: 10 mg of adhesive was placed in a sealed aluminum crucible and scanned from room temperature to 250 °C at a rate of 10 °C / min under nitrogen at a rate of 50 mL / min. The DSC curve was recorded and the initial curing temperature was characterized by the exothermic peak temperature. The results are shown in Table 1.

[0095] Mass loss (thermal weight loss): 10 mg of adhesive was placed in a ceramic crucible and heated from 30 °C to 400 °C at a rate of 10 °C / min under air at a rate of 25 mL / min. The initial mass and the remaining mass at 300 °C were recorded, and the percentage of mass loss at 300 °C was calculated. The results are shown in Table 1.

[0096] Glass transition temperature: The adhesive was placed in an oven and heated at 80℃ for 2 hours and then at 300℃ for 1 hour to allow it to fully cure. 10 mg of the cured resin was taken and heated from 30℃ to 400℃ at a rate of 10℃ / min under nitrogen at a rate of 50 mL / min. The DSC curve was recorded, and the glass transition temperature was represented by the characteristic peak. The results are shown in Table 1.

[0097] The bond strength was tested in accordance with GB / T 7124-2008 "Determination of Tensile Bond Strength of Adhesives (Rigid Material to Rigid Material)". Mechanical properties were tested in accordance with GB / T 1040.2-2022 "Determination of tensile properties of plastics".

[0098]

[0099] The data above shows that, within the scope of the claims, by adjusting the proportions and types of cyanate ester resin (65-80 parts), epoxy resin (10-30 parts), reactive diluent (0-10 parts), dual crosslinking curing agent (2-6 parts), and functional filler (15-30 parts), all examples exhibit excellent comprehensive performance: thermal weight loss at 300℃ ≤1.32%, curing temperature ≤90℃, glass transition temperature ≥218℃, bond strength ≥17.6MPa, and tensile strength ≥90.5MPa, achieving a balance between low-temperature curing, high thermal stability, and high strength.

[0100] When Comparative Example 1 used a monofunctional curing agent, and Comparative Examples 2-4 used curing agents without active amino groups or curing agents containing only amino groups without cyano groups, the product showed an increase in curing temperature and a significant decrease in heat resistance (Tg dropped to 156-212℃) and mechanical properties. Comparative Examples 5-6 proved that excessive curing agent or excessive epoxy resin, or insufficient filler, would lead to a significant deterioration in bond strength and tensile strength.

[0101] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A double-crosslinked cyanate ester-epoxy blend adhesive, characterized in that, The raw materials for preparing the adhesive include, by weight, 45-85 parts of cyanate ester resin, 5-35 parts of epoxy resin, 0-20 parts of reactive diluent, 2-6 parts of dual crosslinking curing agent, and 0-50 parts of functional filler. The dual crosslinking curing agent has the structure shown in Formula I: Equation I R is a hydrocarbon group, aliphatic amine, or aryl group; R' is a primary amine group and / or a secondary amine group; R'' is –C≡N and / or –OCN; m is an integer from 1 to 3; and n is an integer from 1 to 2.

2. The adhesive according to claim 1, characterized in that, In the dual crosslinking curing agent, R is an aryl group, m is an integer from 2 to 3, and the aryl group is selected from at least one of benzene, biphenyl, naphthalene, anthracene, pyridine, pyrimidine, furan or thiophene. And / or, in the dual crosslinking curing agent, R' and R'' are located at the para, ortho, meta, or biphenyl bridging position of the aryl group.

3. The adhesive according to claim 1, characterized in that, The dual crosslinking curing agent is selected from at least one of 1,4-diamino-2,5-dicyanophenyl, 2,5-diaminobenzonitrile, 4,4'-diamino-[1,1'-biphenyl]-3,3'-dicarboxynitrile and 4,4'-diamino-[1,1'-biphenyl]-3-carboxynitrile; And / or, the dual crosslinking curing agent is selected from at least one of 6-aminohexanonitrile, 11-aminoundecanonitrile, 1,4-diaminobutane-2-nitrile, 5-amino-4-methylpentanonitrile, N-(2-cyanoethyl)ethylenediamine and terminal aminonitrile oligomers.

4. The adhesive according to claim 1, characterized in that, The cyanate resin is selected from monomers or prepolymers of at least one of the following compounds: bisphenol A cyanate, bisphenol E cyanate, bisphenol M cyanate, phenolic cyanate, dicyclopentadiene cyanate, and bisphenol F cyanate. And / or, the epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenolic epoxy resin, aliphatic epoxy resin, organosilicon epoxy resin and multifunctional epoxy resin.

5. The adhesive according to any one of claims 1-4, characterized in that, The active diluent is selected from at least one of butyl glycidyl ether, diglycidyl tetrahydrophthalate, C12-C14 alkyl glycidyl ether, phenyl glycidyl ether, 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, cashew phenol glycidyl ether, epoxidized vegetable oil, and epoxidized soybean oil. And / or, the functional filler is at least one selected from nano-SiO2, carbon nanotubes, SiC whiskers, AlN, BN, Al2O3, graphite, carbon fiber, aluminum hydroxide, magnesium hydroxide, mica powder, boehmite, ferrite, iron carbonyl, FeSiAl, and graphene.

6. A method for preparing a double-crosslinked cyanate ester-epoxy blend adhesive, characterized in that, The method includes: S1. Mix epoxy resin and reactive diluent to obtain epoxy diluent; S2: Heat the epoxy diluent to the first temperature, add cyanate ester resin and mix to obtain cyanate ester-epoxy blend; S3: Cool the cyanate ester-epoxy blend to a second temperature and add a double crosslinking curing agent to obtain a double crosslinked cyanate ester-epoxy blend adhesive; The dual crosslinking curing agent has the structure shown in Formula I: Equation I Where R is a hydrocarbon group, aliphatic amine, or aryl group, R' is a primary amine group and / or a secondary amine group, R'' is –CN and / or –OCN, m is an integer from 1 to 3, and n is an integer from 1 to 2.

7. The preparation method according to claim 6, characterized in that, The method further includes step S4: adding functional fillers to the double crosslinked cyanate ester-epoxy blend adhesive at room temperature; And / or, the first temperature is 50~120℃; And / or, the second temperature is 25~80℃.

8. The preparation method according to claim 6, characterized in that, Used to prepare the double crosslinked cyanate-epoxy blend adhesive according to any one of claims 1-5.

9. A double-crosslinked cyanate ester-epoxy blend adhesive, characterized in that, Prepared according to the method described in claims 6-8.

10. The application of the double crosslinked cyanate-epoxy blend adhesive of claim 9 in high-reliability electronic packaging and aerospace structural component bonding.

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