An epoxy resin adhesive, its preparation method and application

Abstract

This invention relates to an epoxy resin adhesive, its preparation method, and its application. The adhesive comprises 100 parts by weight of epoxy resin, 1-10 parts by weight of dicyandiamide micronized curing agent, 3-20 parts by weight of metal micronized powder, and 10-30 parts by weight of thermoplastic acrylic resin. The adhesive preparation process of this invention does not use solvents, and the adhesive has no irritating odor, meeting environmental protection requirements. It is chemically stable at room temperature, and once used, there is a strong interaction between the adhesive and the composite material, making it difficult to detach. The bonding time is short, and it is easy to manufacture into various shapes, with good adaptability to the bonding site. The adhesive is in a solid state, can be stacked, and can be arbitrarily adapted to the bonding spacing of composite materials, facilitating the bonding process. The composite material bonded by the adhesive is resistant to high temperatures; after high-temperature use, there are no cracks or detachment at the bonding joints, and it still possesses good mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of adhesive technology, and in particular relates to an epoxy resin adhesive, its preparation method, and its application. Background Technology

[0002] With the scaling up of modern industry and the increasing complexity and integration of production technologies, there is a growing demand for materials to be manufactured into large-sized or complex-shaped components. This demand has greatly driven the development of joining technologies, leading to the emergence of many new joining technologies that have achieved excellent results. Carbon fiber products, with their outstanding high-temperature thermophysical properties, are widely used in aerospace, nuclear industry, metallurgy, automotive and other industries. The main methods for joining and fixing carbon fiber composite materials include: (1) mechanical fastening; (2) welding / fusion; (3) adhesive bonding, etc.

[0003] Mechanical fastening requires drilling holes in material components, which can lead to localized performance degradation, stress concentration, and increased equipment weight after connection. Welding / fusion requires high-temperature heating of the connection area, making it difficult to avoid the effects of thermal stress. It also places strict requirements on brazing equipment and connection processes, and the construction time is relatively long. Adhesive bonding can overcome the above defects, which is conducive to reducing the weight of the whole machine, improving the overall structure of the equipment, and increasing the reliability of the structure.

[0004] There are two types of bonding materials for composite materials: one is organic material binders, such as phenolic resin and tetraethyl orthosilicate. These binders have strong bonding properties, but their preparation is complex and their heat resistance is not ideal. The other type is inorganic material binders, such as Al2O3-B2O3-SiO2, Si, and some metallic material binders. Among them, Al2O3-B2O3-SiO2 generates an alumina-borosilicate bonding layer after high-temperature heat treatment, but this binder relies on physical bonding with the composite matrix, so its bonding performance is not ideal and it is easy to fall off after bonding. Si and metallic material binders can directly react with the carbon matrix to form a carbide bonding transition layer, so this binder has strong bonding properties. However, the coefficient of thermal expansion (CTE) of these carbides is much greater than that of the carbon matrix, making them prone to forming many cracks during thermal cycling, resulting in a decrease in overall performance after bonding and causing the bonded parts to fall off.

[0005] See patent CN102352190A, which discloses an adhesive that uses microwave treatment for bonding to avoid the formation of an alumina-borosilicate bonding layer. However, when the adhesive is applied to the composite material, it needs to wait at room temperature for 3 hours, which is time-consuming and prolongs the bonding process operation time. Summary of the Invention

[0006] One object of the present invention is to provide an epoxy resin adhesive, particularly an epoxy resin adhesive with high bonding strength, superior mechanical properties, high temperature resistance, and ease of use.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] An epoxy resin adhesive comprising the following components:

[0009] 100 parts by weight of epoxy resin;

[0010] 1-10 parts by weight of dicyandiamide micro powder curing agent;

[0011] 3-20 parts by weight of metallic micro powder;

[0012] 10-30 parts by weight of thermoplastic acrylic resin.

[0013] The epoxy resin is the main component of the adhesive. The epoxy resin is a high molecular compound containing epoxy groups in its molecular structure. It has excellent bonding strength to the surfaces of metal and non-metal materials, good dielectric properties, low shrinkage, good dimensional stability, high hardness, good flexibility, and is stable to alkalis and most solvents.

[0014] The dicyandiamide micro powder curing agent is a dimer powder of cyanamide, with the following structural formula:

[0015]

[0016] The dicyandiamide micro powder curing agent can rapidly cure softened epoxy resin adhesive after microwave heating, reducing the bonding process operation time.

[0017] The metal micro powder is a powder with metal as the main component. It can heat up quickly during microwave heating, which improves the speed and convenience of use, and can effectively improve the mechanical properties of epoxy resin adhesive after curing.

[0018] The thermoplastic acrylic resin is a type of thermoplastic resin polymerized from acrylic acid, methacrylic acid and their derivatives (such as esters, nitriles and amides), which can effectively bond epoxy resin, dicyandiamide micro powder curing agent and metal micro powder.

[0019] Preferably, in the above technical solution, the epoxy resin adhesive further includes 3 to 20 parts by weight of metal oxide micropowder, based on 100 parts by weight of epoxy resin. The metal oxide micropowder is a powder whose main material is metal oxide. Adding the metal oxide micropowder can improve the bonding strength of the adhesive, increase heat transfer efficiency, and reduce the bonding process operation time.

[0020] More preferably, the metal oxide micro powder is used in amounts of 8-15 parts by weight. Insufficient metal oxide micro powder results in slow microwave heating, increasing the curing time of the binder and prolonging the bonding process, while also leading to poor mechanical properties. Excessive metal micro powder can easily decompose the epoxy resin, thereby reducing its strength and causing the bonded joints to break.

[0021] More preferably, the metal oxide micro powder includes one or more of aluminum oxide, copper oxide, and magnesium oxide.

[0022] More preferably, the metal oxide micro powder is alumina micro powder. The alumina micro powder includes flake alumina and needle-shaped alumina, with a weight ratio of 1 to 2:1. The flake alumina is produced by calcining industrial alumina at high temperature, resulting in a flake-like crystal morphology with a certain thickness; the needle-shaped alumina has a linear crystal morphology, which can better improve the heat transfer rate and mechanical properties.

[0023] Preferably, in the above technical solution, the epoxy resin adhesive further includes carbon fiber, wherein the carbon fiber comprises 3 to 20 parts by weight of 100 parts by weight of epoxy resin.

[0024] More preferably, the carbon fiber comprises 5 to 15 parts by weight to improve bonding strength and heating uniformity.

[0025] More preferably, the carbon fiber is selected from carbon fiber micro powder, carbon fiber short fibers, carbon fiber long fibers, carbon fiber filaments, and carbon fiber cloth. Even more preferably, the carbon fiber is carbon fiber micro powder to improve heating uniformity.

[0026] Preferably, the epoxy resin in the above technical solution includes one or more of biphenyl-type epoxy resin and naphthalene-type epoxy resin. The biphenyl-type epoxy resin is an epoxy resin containing biphenyl groups; the naphthalene-type epoxy resin is an epoxy resin containing naphthalene ring structural units. More preferably, the epoxy resin is a naphthalene-type epoxy resin.

[0027] Preferably, in the above technical solution, the Vicat softening point of the epoxy resin is 90℃~110℃. The Vicat softening point is the temperature at which a sample is pressed into a depth of 1mm by a 1mm² indenter in a liquid heat transfer medium under a certain load and a certain constant rate of heating. Epoxy resin with a Vicat softening point of 90℃~110℃ can better improve the bonding strength and mechanical properties of the bonded joint.

[0028] Preferably, in the above technical solution, the dicyandiamide micro powder curing agent is 3-7 parts by weight. If the amount of dicyandiamide micro powder curing agent is too small, the curing time of the epoxy resin adhesive after microwave softening will be prolonged, and the bonding process operation time will be extended accordingly; if the amount of dicyandiamide micro powder curing agent is too large, the mechanical properties of the bonded joint will be reduced after bonding.

[0029] Preferably, in the above technical solution, the average particle size of the dicyandiamide micro powder curing agent is 1-5 μm.

[0030] More preferably, the average particle size of the dicyandiamide micro powder curing agent is 3-4 μm. If the average particle size of the dicyandiamide micro powder curing agent is too small, it will easily cause dust pollution. If the average particle size of the dicyandiamide micro powder curing agent is too large, it will not be conducive to the uniform mixing of the dicyandiamide micro powder curing agent with other components.

[0031] Preferably, the amount of metal micro powder used in the above technical solution is 8 to 15 parts by weight. If the amount of metal micro powder is too small, the microwave heating will be slow, increasing the curing time of the adhesive and prolonging the bonding operation time. If the amount of metal micro powder is too large, the epoxy resin will easily decompose, thereby reducing the strength of the epoxy resin and causing the joint to break.

[0032] Preferably, the metal powder mentioned above includes one or more of aluminum powder, copper powder, gold powder, silver powder, tantalum powder, and iron powder.

[0033] More preferably, the metal powder is one or more of aluminum powder and copper powder, and aluminum powder and copper powder can better improve the mechanical properties of epoxy resin adhesive after curing than other metal powders.

[0034] More preferably, the metal powder is aluminum powder and copper powder, and the weight ratio of aluminum powder to copper powder is 1 to 2:1; the average particle size of the aluminum powder is greater than 8 μm, and the average particle size of the copper powder is less than 8 μm. This can improve the heating rate and uniformity of microwave irradiation.

[0035] Preferably, in the above technical solution, the amount of thermoplastic acrylic resin is 15-25 parts by weight. If the amount of thermoplastic acrylic resin is too small, the bonding effect with epoxy resin, dicyandiamide micronized curing agent, and metal micronized powder will be poor, leading to reduced mechanical properties and even separation of the bonded parts after prolonged use. If the amount of thermoplastic acrylic resin is too large, the thermoplastic acrylic resin will soften under high-temperature conditions, resulting in reduced mechanical properties of the bonded parts and separation of the bonded parts.

[0036] Preferably, in the above technical solution, the melt flow index of the thermoplastic acrylic resin at 230°C is 5–10 g / 10 min, in order to improve the bonding strength.

[0037] Preferably, the thermoplastic acrylic resin described above is polymethyl methacrylate.

[0038] Another objective of this invention is to provide a method for preparing an epoxy resin adhesive, which has a certain regular shape and is convenient for bonding and construction.

[0039] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0040] A method for preparing an epoxy resin adhesive includes: weighing epoxy resin, dicyandiamide micro powder curing agent, metal micro powder, and thermoplastic acrylic resin, mixing them evenly at 100-150°C, and molding them into an adhesive sheet of a predetermined shape by molding, extrusion, or injection molding.

[0041] Another object of the present invention is to provide a method of using an epoxy resin adhesive.

[0042] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0043] A method of using an epoxy resin adhesive includes:

[0044] 1) Clean and dry the bonding surfaces of bonding units M and N; cut the epoxy resin adhesive to fit the bonding surfaces.

[0045] 2) Stack the bonding surfaces in the order of M (M bonding surface), epoxy resin adhesive, and N (N bonding surface), apply a pressure of 5-15 MPa, and microwave in a microwave reactor at 2400-2500 MHz and 500-550 W for 10-20 minutes. Then remove and cool to obtain the adhesive.

[0046] Preferably, in the above technical solution, the bonding unit M and the bonding unit N are the same type of epoxy resin or carbon fiber composite material.

[0047] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0048] 1. No solvents are used in the preparation process of the adhesive, and the adhesive has no irritating odor, meeting environmental protection requirements;

[0049] 2. The adhesive has stable chemical properties at room temperature. Once used, there is a strong interaction between the adhesive and the composite material, making it difficult to detach.

[0050] 3. The adhesive is in solid state, can be used in layers, and can be adapted to the bonding spacing of composite materials, making the bonding process convenient;

[0051] 4. The adhesive has a shorter bonding time and is easy to make into various shapes, making it more adaptable to the bonding area;

[0052] 5. Composite materials bonded by adhesives are resistant to high temperatures. After high-temperature use, there are no cracks or detachment at the bonding points of the composite materials, and they still have good mechanical properties. Detailed Implementation

[0053] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] The raw materials used in each embodiment and comparative example are as follows:

[0055] Epoxy Resin

[0056] A1: Biphenyl type epoxy resin, Mitsubishi Chemical YX4000H, Vicat softening point 105℃, epoxy equivalent 193g / eq.

[0057] A2: Naphthalene-type epoxy resin, DIC HP-9500, Vicat softening point 110℃, epoxy equivalent 230g / eq.

[0058] A3: Naphthalene-type epoxy resin, DIC HP-4700, Vicat softening point 90℃, epoxy equivalent 160g / eq.

[0059] A4: Naphthalene-type epoxy resin, DIC HP-4710, Vicat softening point 100℃, epoxy equivalent 170g / eq.

[0060] Dicyandiamide micro powder curing agent

[0061] B1: Mitsubishi Chemical's DICY7, with an average particle size of 3.5 μm.

[0062] B2: Mitsubishi Chemical's DICY50, with an average particle size of 50μm.

[0063]

Metal micro powders

[0064] C1: Aluminum powder, spherical aluminum powder produced by Hunan Jinhao New Material Technology Co., Ltd., with an average particle size of 10μm.

[0065] C2: Aluminum powder, spherical aluminum powder produced by Hunan Jinhao New Material Technology Co., Ltd., with an average particle size of 6μm.

[0066] C3: Copper powder, spherical copper powder produced by Bohuas Nanotechnology (Ningbo) Co., Ltd., with an average particle size of 6μm.

[0067] Thermoplastic acrylic resin

[0068] D1: Polymethyl methacrylate, Mitsubishi Chemical IRS404, melt index 8.5 g / 10 min at 230℃.

[0069] D2: Polymethyl methacrylate, Mitsubishi Chemical IRS204, melt index 14.5 g / 10 min at 230℃.

[0070] D3: Polymethyl methacrylate, Mitsubishi Chemical IRS309, melt index 3.0 g / 10 min at 230℃.

[0071] Carbon fiber

[0072] E1: MLD-30, carbon fiber micro powder produced by Toray Industries, Inc. of Japan, with a fiber length of 30μm.

[0073] E2: MLD-300, carbon fiber micro powder produced by Toray Industries, Inc. of Japan, with a fiber length of 130μm.

[0074] Metal oxide micro powder

[0075] F1: Flake alumina: Produced by Kawai Lime Industry Co., Ltd., model BMF, average particle size 5μm, length / thickness ratio 25.

[0076] F2: Needle-shaped alumina: produced by Kawai Lime Industry Co., Ltd., model BMI, average particle size 6μm, aspect ratio 40.

[0077] F3: Blocky alumina: Produced by Kawai Lime Industry Co., Ltd., model BMB, average particle size 2μm, aspect ratio 2.

[0078] Prepare the adhesive using the following method:

[0079] Weigh each raw material according to the formula shown in Table 1 and mix them in a mixer at 110°C for 30 minutes. After the material is mixed evenly, pour it into a mold and press it at 110°C to form a sheet with a thickness of 200μm.

[0080] Perform the bonding process as follows:

[0081] The bonding surfaces of bonding unit M and bonding unit N are washed and dried. The epoxy resin adhesive is cut to fit the bonding surfaces. Then, the bonding surfaces of M, epoxy resin adhesive and N are stacked in that order. A pressure of 10 MPa is applied. Then, the mixture is microwaved in a microwave reactor at 2450 MHz and 528 W for 15 min. After cooling, the adhesive is obtained.

[0082] The following tests were performed on the adhesive. Unless otherwise specified, all tests were performed at 25°C.

[0083] Tensile shear strength: tested according to national standard (GB / T 7124-2008).

[0084] Fracture growth rate: Tested according to national standard (GB / T 30776-2014).

[0085] Impact strength: Tested according to national standard (GB / T 1043.1-2008).

[0086] Table 1:

[0087]

[0088]

[0089] Table 2:

[0090]

[0091] As shown in Tables 1 and 2, compared with the comparative examples, the adhesive prepared in the examples has a stronger interaction with the composite material, the adhesive has better mechanical properties and is not easy to fall off; the adhesive prepared in the examples has a shorter curing time, reduces the bonding process time, and is easy to make into various shapes, with better adaptability to the bonding parts.

[0092] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An epoxy resin binder, characterized by consists of: 100 parts by weight of an epoxy resin, the epoxy resin being a biphenyl type epoxy resin or a naphthalene type epoxy resin, the Vicat softening point being 90-110°C; 1-10 parts by weight of a dicyanamide micro powder curing agent, the average particle size of the dicyanamide micro powder curing agent being 1-5 μm; 3-20 parts by weight of a metal micro powder, the metal micro powder being aluminum powder and copper powder, the weight ratio of the aluminum powder and the copper powder being 1-2:1, the average particle size of the aluminum powder being greater than 8 μm, and the average particle size of the copper powder being less than 8 μm; 10-30 parts by weight of a thermoplastic acrylic resin, the thermoplastic acrylic resin being polymethyl methacrylate, the 230°C melt index being 5-10 g / 10 min; 3-20 parts by weight of a metal oxide micro powder, the metal oxide micro powder being aluminum oxide micro powder, the aluminum oxide micro powder including flaky aluminum oxide and needle-like aluminum oxide, the weight ratio of the flaky aluminum oxide and the needle-like aluminum oxide being 1-2:1; 3-20 parts by weight of a carbon fiber, the carbon fiber being carbon fiber micro powder.

2. A method of preparing the epoxy resin binder of claim 1, characterized in that, It includes: weighing the epoxy resin, the dicyanamide micro powder curing agent, the metal micro powder, and the thermoplastic acrylic resin, mixing them uniformly at 100-150°C, and forming the adhesive sheet with a set shape by mold pressing, or extruding, or injection molding.

3. Use of the epoxy resin binder as claimed in claim 1, characterized in that: It includes: 1) washing and drying the bonding surfaces of the bonding unit M and the bonding unit N; cutting the epoxy resin adhesive to a size suitable for the bonding surfaces, 2) stacking them in the order of the M bonding surface, the epoxy resin adhesive, and the N bonding surface, applying a pressure of 5-15 MPa, and treating them in a microwave reactor at 2400-2500 MHz and 500-550 W for 10-20 min, and then taking them out and cooling to obtain the bonding body.

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