Low-precipitation epoxy adhesive for bonding as well as preparation method and application of low-precipitation epoxy adhesive

Abstract

The invention relates to the technical field of epoxy adhesives, in particular to a low-precipitation epoxy adhesive for bonding and a preparation method and application thereof. The low-precipitation epoxy adhesive is prepared from the following components in parts by weight: 30 to 40 parts of toughened epoxy resin, 5 to 15 parts of polyfunctional epoxy resin, 5 to 15 parts of low-viscosity epoxy resin, 23 to 27 parts of curing agent, 3 to 5 parts of accelerant, 4 to 6 parts of stabilizer, 15 to 30 parts of filler, 0.5 to 2 parts of pigment and 0.5 to 5 parts of thixotropic agent, according to the low-precipitation epoxy adhesive for bonding, disclosed by the invention, the combination of the acrylic rubber toughened epoxy resin, the tetrafunctional glycidyl amine epoxy resin and the tert-butyl catechol glycidyl ether is adopted, so that the curing rate and the overall performance of the adhesive are improved.

Description

Technical Field

[0001] The invention relates to the technical field of epoxy adhesives, and in particular to a low-precipitation epoxy adhesive for bonding, and a preparation method and application thereof. Background Art

[0002] With the rapid development of modern science and technology, especially the progress in 5G communications, electronic appliances, optical devices, automotive industry, aerospace, and mechanical manufacturing, the requirements for material performance are increasing. LCP (liquid crystal polymer), as a polymer material that can exist in a liquid crystal state under specific conditions, has become one of the key materials in these high-tech fields due to its high temperature resistance, high modulus, low melt viscosity, low thermal expansion coefficient and excellent dielectric properties. In particular, in the application of 5G high-frequency antennas, LCP is considered to be an ideal substrate material.

[0003] However, in actual application, the problem of difficult bonding of LCP materials has gradually emerged. LCP does not refer to a single material, but a general term for a class of materials. The differences in its synthetic monomers, processing technology, and filler types and proportions will lead to significant differences in the performance and characteristics of LCP materials. Therefore, the bonding effect of the same adhesive on different LCP materials is often very different. Traditional epoxy resin adhesives can hardly guarantee effective bonding of all types of LCP materials, which limits the wider application of LCP materials.

[0004] In addition, for the assembly and bonding of certain precision electronic, optical devices and semiconductor components, more stringent requirements are placed on adhesives - low precipitation. The so-called precipitation refers to the phenomenon that a thin layer of colorless transparent or colored transparent oily substance appears at the edge of the glue after the adhesive is cured. This phenomenon will not only cause component contamination and reduce product yield, but also increase the cost of cleaning and rework. In order to reduce precipitation, many users choose to perform heat curing operations quickly after applying the glue, but this method increases the complexity and difficulty of the glue application process.

[0005] Currently available epoxy adhesives usually focus on reducing resin precipitation through rapid curing, or try to use different chemical composition combinations in order to obtain better bonding effects. However, these methods are often accompanied by some defects: although rapid curing can reduce precipitation to a certain extent, it increases the difficulty of process implementation and is not suitable for all production environments; changing the chemical composition of the adhesive can improve the bonding performance, but may introduce new problems, such as reduced storage stability, shortened operation time or increased costs. Moreover, many improved adhesives are only effective for specific types of LCP materials and lack universal applicability.

[0006] In summary, there is an urgent need to develop a new adhesive that can effectively bond a variety of LCP materials and maintain a low level of precipitation without immediate thermal curing, so as to simplify the sizing process and improve product quality and production efficiency. Summary of the invention

[0007] The present application discloses a low-precipitation epoxy adhesive for bonding, a preparation method and an application thereof, which adopts a combination of acrylic rubber toughened epoxy resin, tetrafunctional glycidylamine epoxy resin and tert-butyl catechol glycidyl ether to improve the curing rate and overall performance of the adhesive, and solve the problems of easy precipitation of the adhesive, reduced storage stability and shortened operation time.

[0008] The purpose of the present invention is achieved through the following technical solutions: In a first aspect of the present application, a low precipitation epoxy adhesive for bonding is provided, comprising the following components in parts by weight: 30-40 parts of toughened epoxy resin, 5-15 parts of multifunctional epoxy resin, 5-15 parts of low-viscosity epoxy resin, 23-27 parts of curing agent, 3-5 parts of accelerator, 4-6 parts of stabilizer, 15-30 parts of filler, 0.5-2 parts of pigment, 0.5-5 parts of thixotropic agent; The toughened epoxy resin is an acrylic rubber toughened epoxy resin; The multifunctional epoxy resin is a tetrafunctional glycidylamine epoxy resin; The low-viscosity epoxy resin is tert-butylcatechol glycidyl ether.

[0009] In one or more technical solutions, the viscosity of the acrylic rubber toughened epoxy resin is 100000 mPa•S; The viscosity of the tetrafunctional glycidylamine epoxy resin is 3000-6000 mPa•S; The viscosity of the tert-butyl catechol glycidyl ether is 1500 mPa•S and the epoxy equivalent is 214 g / mol.

[0010] In one or more technical solutions, the curing agent is trimethylolpropane tris(3-mercaptopropionate).

[0011] In one or more technical solutions, the accelerator is an imidazole adduct accelerator.

[0012] In one or more technical solutions, the stabilizer is an epoxy resin adduct stabilizer.

[0013] In one or more technical solutions, the filler is any one or more of nano calcium carbonate, talcum powder and glass powder.

[0014] In one or more technical solutions, the pigment is one or both of carbon black and fluorescent whitening agent.

[0015] In one or more technical solutions, the thixotropic agent is hydrophobic fumed silica.

[0016] The second aspect of the present application provides a method for preparing the low precipitation epoxy adhesive for bonding described in the first aspect, comprising the following steps: S1. Prepare the corresponding raw materials according to the weight composition of the low precipitation epoxy adhesive for bonding; Mixing a toughened epoxy resin, a multifunctional epoxy resin and a low-viscosity epoxy resin to obtain a mixed resin; S2. Add filler and pigment to the mixed resin and mix to obtain a resin-filler mixture; S3. Add a curing agent, a accelerator and a thixotropic agent to the resin-filler mixture and mix to form a base mixture; S4. Add a stabilizer to the above base mixture, and after vacuum treatment, obtain a low-precipitation epoxy adhesive for bonding.

[0017] Step S1, adding toughened epoxy resin, multifunctional epoxy resin and low-viscosity epoxy resin in proportion into a stirring kettle of a planetary mixer equipped with a vacuum pump and a cooling water supply device, and passing cooling water at about 15°C, and during the preparation process, the cooling water is continuously passed. Stirring at a stirring speed of 50-70rpm under normal pressure for 10 minutes, then increasing the stirring speed to 110-130rpm, stirring at normal pressure for 30 minutes, to obtain a mixed resin; Step S2, adding fillers and pigments in proportion to the mixed resin obtained in step S1, stirring at a stirring speed of 50-70 rpm under normal pressure for 10 minutes, then increasing the stirring speed to 110-130 rpm, stirring at normal pressure for 30 minutes, to obtain a resin-filler mixture; Step S3, adding a curing agent, an accelerator and a thixotropic agent into the resin-filler mixture obtained in step S2 in proportion, stirring at a stirring speed of 50-70 rpm under normal pressure for 10 minutes, then increasing the stirring speed to 110-130 rpm, stirring at normal pressure for 30 minutes, to obtain a basic mixture; Step S4, add the stabilizer to the basic mixture obtained in step S3 in proportion, stir for 5 minutes at a stirring speed of 50-70rpm under normal pressure, then increase the stirring speed to 110-130rpm, stir for 10 minutes under normal pressure, then turn on the vacuum equipment, reduce the stirring speed to 20-30rpm, and stir for 20 minutes. Finally, stop stirring, turn off the vacuum equipment, and after the stirring kettle returns to normal pressure, discharge the material, and obtain a low-precipitation medium-temperature curing single-component epoxy adhesive for LCP bonding. After discharging, the cooling water can be turned off.

[0018] The third aspect of the present application provides an application of a low precipitation epoxy adhesive for bonding, wherein the low precipitation epoxy adhesive for bonding described in the first aspect or the low precipitation epoxy adhesive for bonding prepared by the preparation method described in the second aspect is applied to the bonding of any one or more of LCP, steel, and PC.

[0019] The beneficial effects of this application are: The low precipitation epoxy adhesive for bonding described in the present application adopts a combination of acrylic rubber toughened epoxy resin, tetrafunctional glycidylamine epoxy resin and tert-butyl catechol glycidyl ether to improve the curing rate and overall performance of the adhesive. Among them, the tetrafunctional glycidylamine epoxy resin and tert-butyl catechol glycidyl ether both have high reactivity and can react at a faster rate during the curing process, thereby reducing or avoiding resin precipitation.

[0020] The low-precipitation epoxy adhesive for bonding described in the present application also has good storage stability and a long operating time to meet the needs of different application scenarios.

[0021] The low-precipitation epoxy adhesive for bonding described in the present application can not only effectively bond materials such as LCP, steel (SS) and PC, but also can ensure that only a small amount of resin precipitates are produced after curing even if the thermal curing process is not immediately performed after the gluing is completed, thereby reducing the difficulty of the gluing process and improving the product yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0023] Figure 1 A summary diagram of specific raw material compositions of the epoxy adhesives of the embodiments and comparative examples described in this application; Figure 2 A summary diagram of performance test results of the epoxy adhesives of the embodiments and comparative examples described in the present application; Figure 3 This is the actual damage performance diagram of the substrate when the LCP-LCP shear strength test result is the substrate fracture; Figure 4 It is a schematic diagram of the state of the adhesive and the substrate when the precipitation phenomenon occurs; Figure 5 Schematic diagram showing the actual situation of the precipitation degree, where (a) no precipitation; (b) slight precipitation; (c) severe precipitation. DETAILED DESCRIPTION

[0024] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with embodiments, and the contents mentioned in the implementation modes are not intended to limit the present invention.

[0025] As used herein, "and / or" includes the term of any and all combinations of one or more associated listed items. The terms used herein are only used to describe specific embodiments and are not intended to limit the present invention. As used herein, the singular forms "a", "an", "an" and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise. It is further understood that "including", when used in this specification, specifies the stated features, integers, steps, operations, elements and / or compositions, but does not exclude the existence or addition of one or more other features, integers, steps, operations, elements, compositions and / or combinations thereof.

[0026] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. It is further understood that terms, such as defined in commonly used dictionaries, are interpreted in accordance with their meanings in the context of the relevant art and are not idealized or overly formal meanings unless explicitly defined as such herein.

[0027] The exemplary invention described herein may appropriately lack any one or more element limitations that are not specifically disclosed herein. Therefore, the terms "comprise", "include", "contain", etc. should be understood broadly and non-restrictively. In addition, the terminology used herein is used as a description, not a limitation, and it is unintentional to use these terminology expressions that do not include any equivalent characteristics, but only describe some of their characteristics, but various modifications are possible within the scope of the present invention according to the rights. Therefore, although the present invention has been specifically disclosed by preferred embodiments and optional features, the modifications disclosed herein to embody the changes of the present invention may be recorded by those skilled in the art, and such modifications and changes will be considered to be within the scope of the present invention.

[0028] The raw materials or reagents used in the embodiments of the present invention and the comparative examples are all purchased from mainstream manufacturers in the market. The manufacturer or concentration is not specified, and they are all analytically pure raw materials or reagents that can be routinely obtained. As long as the expected effect can be achieved, there is no particular restriction. The instruments and equipment used in the present embodiment are all purchased from major manufacturers in the market. As long as the expected effect can be achieved, there is no particular restriction. If specific techniques or conditions are not specified in the present embodiment, the techniques or conditions described in the literature in this area or according to the product specification are carried out.

[0029] In view of the problem that LCP materials are difficult to bond and traditional adhesives are prone to resin precipitation during the curing process, the present application provides a low precipitation epoxy adhesive for bonding, comprising the following components in parts by weight: 30-40 parts of toughened epoxy resin, 5-15 parts of multifunctional epoxy resin, 5-15 parts of low-viscosity epoxy resin, 23-27 parts of curing agent, 3-5 parts of accelerator, 4-6 parts of stabilizer, 15-30 parts of filler, 0.5-2 parts of pigment, 0.5-5 parts of thixotropic agent; The toughened epoxy resin is an acrylic rubber toughened epoxy resin; The multifunctional epoxy resin is a tetrafunctional glycidylamine epoxy resin; The low-viscosity epoxy resin is tert-butylcatechol glycidyl ether.

[0030] Specifically, the viscosity of the acrylic rubber toughened epoxy resin is 100000 mPa•S (50°C); The viscosity of the tetrafunctional glycidylamine epoxy resin is 3000-6000 mPa•S (50°C); The viscosity of the tert-butyl catechol glycidyl ether is 1500 mPa•S and the epoxy equivalent is 214 g / mol.

[0031] Specifically, in the present application, the acrylic rubber toughened epoxy resin can improve the toughness, impact resistance and thermal cycling resistance of the adhesive. The acrylic rubber toughened epoxy resin contains dispersed phase rubber particles, which absorb energy and inhibit crack propagation when impacted, thereby enhancing the overall strength and durability of the adhesive layer.

[0032] In one or more embodiments, the weight of the toughened epoxy resin is 30-40 parts, ensuring sufficient toughness to cope with mechanical stress in practical applications; for example, the weight of the toughened epoxy resin can be any value of 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, 35 parts, 36 parts, 37 parts, 38 parts, 39 parts, and 40 parts, as long as it is within 30-40 parts. If the weight of the toughened epoxy resin exceeds 40 parts, the cured adhesive layer may be too soft, reducing the bonding strength; if the weight of the toughened epoxy resin is less than 30 parts, it may not provide sufficient toughness, making the adhesive easily break when impacted.

[0033] Specifically, in the present application, the multifunctional epoxy resin can provide more crosslinking points, increase the mechanical strength, corrosion resistance and adhesion of the cured product, and at the same time improve the heat resistance of the system. The tetrafunctional glycidylamine epoxy resin is synthesized from 4,4'-diaminodiphenylmethane and epichlorohydrin, and its general formula is:

[0034] in, .

[0035] In one or more embodiments, the weight of the multifunctional epoxy resin is 5-15 parts, ensuring that there are enough multifunctional groups to participate in the reaction and form a solid network structure. If the weight of the multifunctional epoxy resin exceeds 15 parts, the adhesive may become too viscous, difficult to apply evenly, and the curing time is prolonged. If the weight of the multifunctional epoxy resin is less than 5 parts, it may not be enough to form a stable cross-linked network, affecting the performance of the final product. Therefore, the weight of the multifunctional epoxy resin can be any value of 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, and 15 parts, as long as it meets the requirements of 5-15 parts.

[0036] Specifically, the low-viscosity epoxy resin is tert-butyl catechol glycidyl ether, with a viscosity of 1,500 mPa·S (25°C) and an epoxy equivalent of 214 g / mol. Its general formula is:

[0037] in, .

[0038] In this application, the low viscosity epoxy resin can reduce the initial viscosity of the overall mixture, facilitate construction, and help improve fluidity, ensuring that the adhesive can fully penetrate into small gaps on the bonded surfaces.

[0039] In one or more embodiments, the weight of the low-viscosity epoxy resin is 5-15 parts to ensure appropriate fluidity for construction operations. If the weight of the low-viscosity epoxy resin exceeds 15 parts, the adhesive may be too thin, difficult to control the coating thickness, and may also affect the final bonding strength. If the weight of the low-viscosity epoxy resin is less than 5 parts, the mixture will be too viscous and difficult to apply evenly. Therefore, the weight of the low-viscosity epoxy resin can be any value of 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, and 15 parts, as long as it meets the requirements of 5-15 parts.

[0040] It can be understood that in the present application, by adding a combination of a tetrafunctional glycidylamine epoxy resin and the tert-butyl catechol glycidyl ether to the toughened epoxy resin, the following beneficial effects can be achieved: The tetrafunctional glycidylamine epoxy resin and the tert-butyl catechol glycidyl ether both have high reactivity and can undergo a curing reaction at a faster rate during the curing process, thereby increasing the overall curing rate and thereby reducing or avoiding resin precipitation.

[0041] There are multiple epoxy groups and aromatic rings in the molecular structure of tetrafunctional glycidylamine epoxy resin, which can not only improve the mechanical strength, corrosion resistance and adhesion of the system, but also greatly improve the heat resistance of the system, making the overall performance of the adhesive more excellent.

[0042] Tert-butyl catechol glycidyl ether has a lower viscosity than bisphenol A and bisphenol F epoxy resins, while the tetrafunctional glycidyl amine epoxy resin has a higher viscosity. By adjusting the ratio of the two, the overall viscosity can be controlled within a wider range without significantly increasing the thixotropy of the system.

[0043] Specifically, the curing agent is trimethylolpropane tris(3-mercaptopropionate).

[0044] In this application, trimethylolpropane tris(3-mercaptopropionate) reacts with epoxy groups to generate flexible thioether single bonds, which accelerates the curing process and improves impact resistance and thermal cycling performance. In addition, it belongs to a thiol curing system, which helps to reduce or avoid resin precipitation.

[0045] In one or more embodiments, the weight portion of the curing agent is 23-27 parts, ensuring that there is a sufficient amount of curing agent to completely cure the epoxy resin and form a stable cross-linked network. If the weight portion of the curing agent exceeds 27 parts, it may cause the curing rate to be too fast, causing the problem of violent polymerization, and affecting product quality. If the weight portion of the curing agent is less than 23 parts, the curing is incomplete, and the adhesive may fail to achieve the expected physical properties. Therefore, the weight portion of the curing agent can be any one of 23 parts, 24 parts, 25 parts, 26 parts, and 27 parts, meeting the requirement of 23-27 parts.

[0046] Specifically, the accelerator is an imidazole adduct accelerator. More specifically, the imidazole adduct accelerator can be any one or more of PN-23, MY-24, PN-23J and PN-40J of Ajinomoto Co., Ltd.

[0047] In the present application, the accelerator can accelerate the curing reaction of the epoxy resin, shorten the curing time, and improve production efficiency.

[0048] In one or more embodiments, the weight of the accelerator is 3-5 parts, ensuring that the curing reaction can be completed within a reasonable time. If the weight of the accelerator exceeds 5 parts, the curing speed is too fast, which may cause the local temperature to be too high or even violent polymerization. If the weight of the accelerator is less than 3 parts, the curing speed is slow, which prolongs the process cycle and increases the production cost. Therefore, the weight of the accelerator can be any value of 3 parts, 4 parts, 5 parts, 3.5 parts, and 4.5 parts, which meets the requirement of 3-5 parts.

[0049] Specifically, the stabilizer is an epoxy resin adduct stabilizer. More specifically, the epoxy resin adduct stabilizer is Shanghai Shengyi's L-02B epoxy resin adduct stabilizer.

[0050] In the present application, the stabilizer can improve the storage stability and operating time of the adhesive and prevent problems such as delamination or premature curing during long-term storage.

[0051] In one or more embodiments, the weight of the stabilizer is 4-6 parts, ensuring sufficient stability to meet transportation and storage requirements. If the weight of the stabilizer exceeds 6 parts, it may interfere with the normal curing reaction and affect the performance after curing. If the weight of the stabilizer is less than 4 parts, the adhesive may undergo adverse changes during storage, such as delamination or premature curing. Therefore, the weight of the stabilizer can be any value of 4 parts, 5 parts, 6 parts, and 4.5 parts, as long as it meets the requirements of 4-6 parts.

[0052] Specifically, the filler is any one or more of nano calcium carbonate, talcum powder and glass powder; more specifically, the specific surface area of ​​nano calcium carbonate is 17 m² / g, and the talcum powder is preferably HD25 of Shanghai Fushi.

[0053] In the present application, fillers play the role of filling spaces, increasing solid content, adjusting thixotropy and hardness, and improving certain physical properties such as wear resistance.

[0054] In one or more embodiments, the weight of the filler is 15-30 parts, providing the necessary filling effect and optimizing the physical properties. If the weight of the filler exceeds 30 parts, the fluidity and bonding performance of the adhesive may be reduced; if the weight of the filler is less than 15 parts, the filler effect is not obvious and the physical properties cannot be effectively improved. Therefore, the weight of the filler can be any value of 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, and 30 parts, as long as it meets the requirement of 15-30 parts.

[0055] Specifically, the pigment is one or both of carbon black and fluorescent whitening agent.

[0056] In this application, the pigment gives the product a specific color for easy identification and aesthetics, without affecting the main properties of the adhesive.

[0057] In one or more embodiments, the weight of the pigment is 0.5-2 parts, providing sufficient color depth for visual identification. If the weight of the pigment exceeds 2 parts: it may cause the color to be too dark or the covering power to be too strong, affecting the appearance evaluation. If the weight of the pigment is less than 0.5 parts: the color is not bright enough, and it is difficult to achieve the desired visual effect. Therefore, the weight of the pigment can be any value of 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, and 2.0 parts, which meets the requirement of 0.5-2 parts.

[0058] Specifically, the thixotropic agent is hydrophobic fumed silica. More specifically, the hydrophobic fumed silica is one or any of R805 and R202 from Evonik, TS720 from Cabot, and HB620 from Huifu.

[0059] In the present application, the thixotropic agent forms a network structure through hydrogen bonds to improve the thixotropy of the adhesive, that is, it maintains a higher viscosity in a static state and exhibits a lower viscosity when stirred or applied, which is beneficial for construction.

[0060] In one or more embodiments, the weight portion of the thixotropic agent is 0.5-5 parts, ensuring that there is enough thixotropy to support good construction performance. If the weight portion of the thixotropic agent exceeds 5 parts, the adhesive may be too viscous and difficult to apply evenly. If the weight portion of the thixotropic agent is less than 0.5 parts, the thixotropy is insufficient, and the adhesive may sag during construction. Therefore, the weight portion of the thixotropic agent can be 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts, 1.2 parts, 2.0 parts, 2.4 parts, 2.5 parts, 3.1 parts, 3.7 parts, 3.8 parts, 3.9 parts, 4.5 parts, 4.6 parts, 4.7 parts, 4.8 parts, 4.9 parts, any value in 5.0, which meets the requirement of 0.5-5 parts.

[0061] The second aspect of the present application provides a method for preparing the low precipitation epoxy adhesive for bonding, comprising the following steps: S1. Prepare the corresponding raw materials according to the weight composition of the low precipitation epoxy adhesive for bonding; Mixing a toughened epoxy resin, a multifunctional epoxy resin and a low-viscosity epoxy resin to obtain a mixed resin; S2. Add filler and pigment to the mixed resin and mix to obtain a resin-filler mixture; S3. Add a curing agent, a accelerator and a thixotropic agent to the resin-filler mixture and mix to form a base mixture; S4. Add a stabilizer to the above base mixture, and after vacuum treatment, obtain a low-precipitation epoxy adhesive for bonding.

[0062] Specifically, the preparation method of the low precipitation epoxy adhesive for bonding comprises the following steps: Step S1, adding toughened epoxy resin, multifunctional epoxy resin and low-viscosity epoxy resin in proportion into a stirring kettle of a planetary mixer equipped with a vacuum pump and a cooling water supply device, and passing cooling water at about 15°C, and during the preparation process, the cooling water is continuously passed. Stirring at a stirring speed of 50-70rpm under normal pressure for 10 minutes, then increasing the stirring speed to 110-130rpm, stirring at normal pressure for 30 minutes, to obtain a mixed resin; Step S2, adding fillers and pigments in proportion to the mixed resin obtained in step S1, stirring at a stirring speed of 50-70 rpm under normal pressure for 10 minutes, then increasing the stirring speed to 110-130 rpm, stirring at normal pressure for 30 minutes, to obtain a resin-filler mixture; Step S3, adding a curing agent, an accelerator and a thixotropic agent into the resin-filler mixture obtained in step S2 in proportion, stirring at a stirring speed of 50-70 rpm under normal pressure for 10 minutes, then increasing the stirring speed to 110-130 rpm, stirring at normal pressure for 30 minutes, to obtain a basic mixture; Step S4, adding the stabilizer to the basic mixture obtained in step S3 in proportion, stirring at a stirring speed of 50-70 rpm under normal pressure for 5 minutes, then increasing the stirring speed to 110-130 rpm, stirring at normal pressure for 10 minutes, then turning on the vacuum pumping device, and reducing the stirring speed to 20-30 rpm, stirring for 20 minutes. Finally, stopping the stirring, turning off the vacuum pumping device, and after the stirring kettle returns to normal pressure, the material can be discharged, and a low-precipitation medium-temperature curing one-component epoxy adhesive for LCP bonding is obtained.

[0063] The third aspect of the present application provides an application of a low precipitation epoxy adhesive for bonding, wherein the low precipitation epoxy adhesive for bonding described in the first aspect or the low precipitation epoxy adhesive for bonding prepared by the preparation method described in the second aspect is applied to bonding between any one or more of LCP, steel, and PC.

[0064] The low precipitation epoxy adhesive for bonding of the present invention is further described below in conjunction with specific embodiments and comparative examples: In the following examples and comparative examples, the specifications and sources of some raw materials are as follows: Example 1 A low precipitation epoxy adhesive for bonding, the raw material composition includes, by weight: 34 parts of toughened epoxy resin, 5 parts of multifunctional epoxy resin, 10 parts of low-viscosity epoxy resin, 24 parts of curing agent, 2 parts of accelerator 1, 2 parts of accelerator 2, 5 parts of stabilizer, 10 parts of nano calcium carbonate, 14 parts of talc, 1 part of carbon black, 0.5 parts of fluorescent whitening agent, and 0.5 parts of fumed silica.

[0065] Specifically, the toughened epoxy resin is an acrylic rubber toughened epoxy resin.

[0066] Specifically, the multifunctional epoxy resin is a tetrafunctional glycidylamine epoxy resin.

[0067] Specifically, the low-viscosity epoxy resin is tert-butylcatechol glycidyl ether.

[0068] Specifically, the curing agent is trimethylolpropane tris(3-mercaptopropionate).

[0069] Specifically, the first accelerator is PN-23J.

[0070] Specifically, the second accelerator is PN-40J.

[0071] Specifically, the stabilizer is L-02B.

[0072] The specific raw material composition of the epoxy adhesive obtained in this embodiment is shown in Figure 1 , performance test results see Figure 2 .

[0073] Example 2 A low precipitation epoxy adhesive for bonding, the raw material composition includes, by weight: 32 parts of toughened epoxy resin, 5 parts of multifunctional epoxy resin, 12 parts of low-viscosity epoxy resin, 24 parts of curing agent, 2 parts of accelerator 1, 2 parts of accelerator 2, 5 parts of stabilizer, 24 parts of nano calcium carbonate, 1 part of carbon black, 0.5 parts of fluorescent whitening agent, and 0.5 parts of fumed silica.

[0074] Specifically, the toughened epoxy resin is an acrylic rubber toughened epoxy resin.

[0075] Specifically, the multifunctional epoxy resin is a tetrafunctional glycidylamine epoxy resin.

[0076] Specifically, the low-viscosity epoxy resin is tert-butylcatechol glycidyl ether.

[0077] Specifically, the curing agent is trimethylolpropane tris(3-mercaptopropionate).

[0078] Specifically, the first accelerator is PN-23J.

[0079] Specifically, the second accelerator is PN-40J.

[0080] Specifically, the stabilizer is L-02B.

[0081] The specific raw material composition of the epoxy adhesive obtained in this embodiment is shown in Figure 1 , performance test results see Figure 2 .

[0082] Example 3 A low precipitation epoxy adhesive for bonding, the raw material composition of which is calculated by weight: 30 parts of toughened epoxy resin, 14 parts of multifunctional epoxy resin, 5 parts of low-viscosity epoxy resin, 26 parts of curing agent, 2 parts of accelerator I, 1.5 parts of accelerator II, 4 parts of stabilizer, 24 parts of talc, 1 part of carbon black, 0.5 parts of fluorescent whitening agent and 0.5 parts of fumed silica.

[0083] Specifically, the toughened epoxy resin is an acrylic rubber toughened epoxy resin.

[0084] Specifically, the multifunctional epoxy resin is a tetrafunctional glycidylamine epoxy resin.

[0085] Specifically, the low-viscosity epoxy resin is tert-butylcatechol glycidyl ether.

[0086] Specifically, the curing agent is trimethylolpropane tris(3-mercaptopropionate).

[0087] Specifically, the first accelerator is PN-23J.

[0088] Specifically, the second accelerator is PN-40J.

[0089] Specifically, the stabilizer is L-02B.

[0090] The specific raw material composition of the epoxy adhesive obtained in this embodiment is shown in Figure 1 , performance test results see Figure 2 .

[0091] Example 4 A low precipitation epoxy adhesive for bonding, the raw material composition includes, by weight: 31 parts of toughened epoxy resin, 9 parts of multifunctional epoxy resin, 9 parts of low-viscosity epoxy resin, 26 parts of curing agent, 2 parts of accelerator 1, 1.5 parts of accelerator 2, 4 parts of stabilizer, 12 parts of nano calcium carbonate, 12 parts of talc, 1 part of carbon black, 0.5 parts of fluorescent whitening agent, and 0.5 parts of fumed silica.

[0092] Specifically, the toughened epoxy resin is an acrylic rubber toughened epoxy resin.

[0093] Specifically, the multifunctional epoxy resin is a tetrafunctional glycidylamine epoxy resin.

[0094] Specifically, the low-viscosity epoxy resin is tert-butylcatechol glycidyl ether.

[0095] Specifically, the curing agent is trimethylolpropane tris(3-mercaptopropionate).

[0096] Specifically, the first accelerator is PN-23J.

[0097] Specifically, the second accelerator is PN-40J.

[0098] Specifically, the stabilizer is L-02B.

[0099] The specific raw material composition of the epoxy adhesive obtained in this embodiment is shown in Figure 1 , performance test results see Figure 2 .

[0100] Comparative Example 1 A low precipitation epoxy adhesive for bonding, the raw material composition includes, by weight: 34 parts of toughened epoxy resin, 5 parts of multifunctional epoxy resin, 10 parts of low-viscosity epoxy resin, 24 parts of curing agent, 1.5 parts of accelerator 1, 2.5 parts of accelerator 2, 5 parts of stabilizer, 10 parts of nano calcium carbonate, 14 parts of talc, 1 part of carbon black, 0.5 parts of fluorescent whitening agent, and 0.5 parts of fumed silica.

[0101] Specifically, the toughened epoxy resin is an acrylic rubber toughened epoxy resin.

[0102] Specifically, the multifunctional epoxy resin is a tetrafunctional glycidylamine epoxy resin.

[0103] Specifically, the low-viscosity epoxy resin is tert-butylcatechol glycidyl ether.

[0104] Specifically, the curing agent is trimethylolpropane tris(3-mercaptopropionate).

[0105] Specifically, the first accelerator is PN-23J.

[0106] Specifically, the second accelerator is PN-40J.

[0107] Specifically, the stabilizer is L-02B.

[0108] The specific raw material composition of the epoxy adhesive obtained in this comparative example is shown in Figure 1 , performance test results see Figure 2 .

[0109] The difference between this comparative example and Example 1 is that the addition amount of PN-23J in this comparative example is 1.5 parts by mass, and the addition amount of PN-40J is 2.5 parts by mass.

[0110] Comparative Example 2 A low precipitation epoxy adhesive for bonding, the raw material composition of which is calculated by weight: 34 parts of toughened epoxy resin, 5 parts of multifunctional epoxy resin, 10 parts of low-viscosity epoxy resin, 24 parts of curing agent, 14 parts of accelerator, 5 parts of stabilizer, 10 parts of nano calcium carbonate, 14 parts of talc, 1 part of carbon black, 0.5 parts of fluorescent whitening agent and 0.5 parts of fumed silica.

[0111] Specifically, the toughened epoxy resin is an acrylic rubber toughened epoxy resin.

[0112] Specifically, the multifunctional epoxy resin is a tetrafunctional glycidylamine epoxy resin.

[0113] Specifically, the low-viscosity epoxy resin is tert-butylcatechol glycidyl ether.

[0114] Specifically, the curing agent is trimethylolpropane tris(3-mercaptopropionate).

[0115] Specifically, the first accelerator is PN-23J.

[0116] Specifically, the stabilizer is L-02B.

[0117] The specific raw material composition of the epoxy adhesive obtained in this comparative example is shown in Figure 1 , performance test results see Figure 2 .

[0118] The difference between this comparative example and Example 1 is that the addition amount of PN-23J in this comparative example is 4 parts by mass, and the addition amount of PN-40J is 0 parts by mass.

[0119] Comparative Example 3 A low precipitation epoxy adhesive for bonding, the raw material composition includes, by weight: 34 parts of toughened epoxy resin, 5 parts of multifunctional epoxy resin, 10 parts of low-viscosity epoxy resin, 24 parts of curing agent, 1.5 parts of accelerator 1, 2.5 parts of accelerator 2, 5 parts of stabilizer, 10 parts of nano calcium carbonate, 12 parts of talc, 1 part of carbon black, 0.5 parts of fluorescent whitening agent, and 2.5 parts of fumed silica.

[0120] Specifically, the toughened epoxy resin is an acrylic rubber toughened epoxy resin.

[0121] Specifically, the multifunctional epoxy resin is a tetrafunctional glycidylamine epoxy resin.

[0122] Specifically, the low-viscosity epoxy resin is tert-butylcatechol glycidyl ether.

[0123] Specifically, the curing agent is trimethylolpropane tris(3-mercaptopropionate).

[0124] Specifically, the first accelerator is PN-23J.

[0125] Specifically, the second accelerator is PN-40J.

[0126] Specifically, the stabilizer is L-02B.

[0127] The specific raw material composition of the epoxy adhesive obtained in this comparative example is shown in Figure 1 , performance test results see Figure 2 .

[0128] The difference between this comparative example and comparative example 1 is that the added amount of talc in this comparative example is 12 parts by mass, and the added amount of fumed silica is 2.5 parts by mass.

[0129] Comparative Example 4 A low precipitation epoxy adhesive for bonding, the raw material composition includes, by weight: 34 parts of toughened epoxy resin, 5 parts of multifunctional epoxy resin, 10 parts of low-viscosity epoxy resin, 24 parts of curing agent, 2 parts of accelerator 1, 2 parts of accelerator 2, 5 parts of stabilizer, 11.5 parts of nano calcium carbonate, 14 parts of talc, and 0.5 parts of fumed silica.

[0130] Specifically, the toughened epoxy resin is an acrylic rubber toughened epoxy resin.

[0131] Specifically, the multifunctional epoxy resin is a tetrafunctional glycidylamine epoxy resin.

[0132] Specifically, the low-viscosity epoxy resin is tert-butylcatechol glycidyl ether.

[0133] Specifically, the curing agent is trimethylolpropane tris(3-mercaptopropionate).

[0134] Specifically, the first accelerator is PN-23J.

[0135] Specifically, the second accelerator is PN-40J.

[0136] Specifically, the stabilizer is L-02B.

[0137] The specific raw material composition of the epoxy adhesive obtained in this comparative example is shown in Figure 1 , performance test results see Figure 2 .

[0138] The difference between this comparative example and Example 1 is that the addition amount of nano-calcium carbonate in this comparative example is 11.5 parts by mass, the addition amount of carbon black is 0 parts by mass, and the addition amount of fluorescent whitening agent is 0 parts by mass.

[0139] Comparative Example 5 A low precipitation epoxy adhesive for bonding, the raw material composition includes, by weight: 34 parts of toughened epoxy resin, 24 parts of curing agent, 2 parts of accelerator 1, 2 parts of accelerator 2, 5 parts of stabilizer, 10 parts of nano calcium carbonate, 14 parts of talcum powder, 1 part of carbon black, 0.5 parts of fluorescent brightener, and 0.5 parts of fumed silica.

[0140] Specifically, the toughened epoxy resin is an acrylic rubber toughened epoxy resin.

[0141] Specifically, the curing agent is trimethylolpropane tris(3-mercaptopropionate).

[0142] Specifically, the first accelerator is PN-23J.

[0143] Specifically, the second accelerator is PN-40J.

[0144] Specifically, the stabilizer is L-02B.

[0145] The specific raw material composition of the epoxy adhesive obtained in this comparative example is shown in Figure 1 , performance test results see Figure 2 .

[0146] Comparative Example 6 A low precipitation epoxy adhesive for bonding, the raw material composition includes, by weight: 34 parts of toughened epoxy resin, 10 parts of low-viscosity epoxy resin, 24 parts of curing agent, 2 parts of accelerator 1, 2 parts of accelerator 2, 5 parts of stabilizer, 10 parts of nano calcium carbonate, 14 parts of talc, 1 part of carbon black, 0.5 parts of fluorescent whitening agent, and 0.5 parts of fumed silica.

[0147] Specifically, the toughened epoxy resin is an acrylic rubber toughened epoxy resin.

[0148] Specifically, the low-viscosity epoxy resin is tert-butylcatechol glycidyl ether.

[0149] Specifically, the curing agent is trimethylolpropane tris(3-mercaptopropionate).

[0150] Specifically, the first accelerator is PN-23J.

[0151] Specifically, the second accelerator is PN-40J.

[0152] Specifically, the stabilizer is L-02B.

[0153] The specific raw material composition of the epoxy adhesive obtained in this comparative example is shown in Figure 1 , performance test results see Figure 2 .

[0154] Comparative Example 7 A low precipitation epoxy adhesive for bonding, the raw material composition includes, by weight: 34 parts of toughened epoxy resin, 5 parts of multifunctional epoxy resin, 24 parts of curing agent, 2 parts of accelerator 1, 2 parts of accelerator 2, 5 parts of stabilizer, 10 parts of nano calcium carbonate, 14 parts of talcum powder, 1 part of carbon black, 0.5 parts of fluorescent whitening agent, and 0.5 parts of fumed silica.

[0155] Specifically, the toughened epoxy resin is an acrylic rubber toughened epoxy resin.

[0156] Specifically, the multifunctional epoxy resin is a tetrafunctional glycidylamine epoxy resin.

[0157] Specifically, the curing agent is trimethylolpropane tris(3-mercaptopropionate).

[0158] Specifically, the first accelerator is PN-23J.

[0159] Specifically, the second accelerator is PN-40J.

[0160] Specifically, the stabilizer is L-02B.

[0161] The specific raw material composition of the epoxy adhesive obtained in this comparative example is shown in Figure 1 , performance test results see Figure 2 .

[0162] Comparative Example 8 A low precipitation epoxy adhesive for bonding, the raw material composition includes, by weight: 34 parts of toughened epoxy resin, 5 parts of multifunctional epoxy resin, 10 parts of low-viscosity epoxy resin, 24 parts of curing agent, 2 parts of accelerator 1, 2 parts of accelerator 2, 5 parts of stabilizer, 10 parts of nano calcium carbonate, 14 parts of talc, 1 part of carbon black, 0.5 parts of fluorescent whitening agent, and 0.5 parts of fumed silica.

[0163] Specifically, the toughened epoxy resin is an acrylic rubber toughened epoxy resin.

[0164] Specifically, the multifunctional epoxy resin is a tetrafunctional glycidylamine epoxy resin.

[0165] Specifically, the low-viscosity epoxy resin is tert-butylcatechol glycidyl ether.

[0166] Specifically, the curing agent is methyltetrahydrophthalic anhydride.

[0167] Specifically, the first accelerator is PN-23J.

[0168] Specifically, the second accelerator is PN-40J.

[0169] Specifically, the stabilizer is L-02B.

[0170] The specific raw material composition of the epoxy adhesive obtained in this comparative example is shown in Figure 1 , performance test results see Figure 2 .

[0171] The above-mentioned Example 1 to Example 4 and Comparative Example 1 to Comparative Example 8, the corresponding epoxy adhesive preparation method is carried out according to the following preparation method: The preparation method of the low precipitation epoxy adhesive for bonding comprises the following steps: Step S1, adding toughened epoxy resin, multifunctional epoxy resin and low-viscosity epoxy resin in proportion into a stirring kettle of a planetary mixer equipped with a vacuum pump and a cooling water supply device, and passing cooling water at about 15°C, and during the preparation process, the cooling water is continuously passed. Stirring at a stirring speed of 50-70rpm under normal pressure for 10 minutes, then increasing the stirring speed to 110-130rpm, stirring at normal pressure for 30 minutes, to obtain a mixed resin; Step S2, adding fillers and pigments in proportion to the mixed resin obtained in step S1, stirring at a stirring speed of 50-70 rpm under normal pressure for 10 minutes, then increasing the stirring speed to 110-130 rpm, stirring at normal pressure for 30 minutes, to obtain a resin-filler mixture; Step S3, adding a curing agent, an accelerator and a thixotropic agent into the resin-filler mixture obtained in step S2 in proportion, stirring at a stirring speed of 50-70 rpm under normal pressure for 10 minutes, then increasing the stirring speed to 110-130 rpm, stirring at normal pressure for 30 minutes, to obtain a basic mixture; Step S4, adding the stabilizer to the basic mixture obtained in step S3 in proportion, stirring at a stirring speed of 50-70 rpm under normal pressure for 5 minutes, then increasing the stirring speed to 110-130 rpm, stirring at normal pressure for 10 minutes, then turning on the vacuum pumping device, and reducing the stirring speed to 20-30 rpm, stirring for 20 minutes. Finally, stopping the stirring, turning off the vacuum pumping device, and after the stirring kettle returns to normal pressure, the material can be discharged, and a low-precipitation medium-temperature curing one-component epoxy adhesive for LCP bonding is obtained.

[0172] The epoxy adhesives prepared in Examples 1-4 and Comparative Examples 1-8 were tested according to the following test method. The results are summarized as follows: Figure 2 middle.

[0173] The test method is as follows: 1. Shear strength and breaking load The test was conducted according to the GB / T 7124-2008 standard, with a tensile rate of 10 mm / min.

[0174] 2. Degree of precipitation Take a medium-speed qualitative filter paper, place 0.1g of sample in the center of the filter paper, let it stand at room temperature for 30 minutes, and then bake it at 90℃ for 30 minutes. After baking, take out the filter paper and observe the precipitation distance by electron microscope or other means.

[0175] If no resin precipitation is observed, the degree of precipitation is "none"; if resin precipitation is observed and the precipitation distance is ≤0.7mm, the degree of precipitation is "mild"; if resin precipitation is observed and the precipitation distance is >0.7mm, the degree of precipitation is "severe".

[0176] Therefore, from Figure 1 , Figure 2 as well as Figure 3-Figure 5 It can be seen that: The fracture of LCP substrate is as follows Figure 3 It should be noted that in order to make the damage of the adhesive layer easier to show in the picture, when testing the tensile shear strength of the black LCP substrate, the sample without adding pigment was used, and when testing the shear strength of SS-SS, the sample with normal adding pigment was used. The two only differ in color, and there is no obvious difference in performance. Figure 2 The test results of Example 1 and Comparative Example 4 can also illustrate this point.

[0177] Depend on Figure 2 It can be seen that Examples 1-4 all show relatively excellent bonding effects on LCP, steel and PC substrates, and at the same time, they also have good performance in resin precipitation. By comparing the precipitation degree of Example 1 and the comparative example, it is found that the precipitation degree of Example 1 is "none", while that of Comparative Example 1 is "serious". The difference between Comparative Example 1 and Example 1 is that the proportion of the accelerators of the two is different, and the other settings are the same. The reason for the difference in precipitation degree between the two is that the activity of PN-23J is higher than that of PN-40J. Higher activity means faster curing rate. The faster the curing rate, the lower the precipitation degree. The addition ratio of PN-23J in Comparative Example 1 is less than that of Example 1, so "serious" precipitation occurs.

[0178] By comparing the precipitation degree of Example 1, Comparative Example 1 and Comparative Example 2, it is found that the precipitation degree of Example 1 and Comparative Example 2 is "none", but only Comparative Example 2 has a "violent aggregation" phenomenon among the three, because the addition ratio of PN-23J in Comparative Example 2 is the largest among the three, and the reaction rate is too fast, resulting in the "violent aggregation" phenomenon. By comparing the precipitation degree of Comparative Example 1 and Comparative Example 3, it is found that the precipitation degree of both is "serious". The difference between Comparative Example 1 and Comparative Example 3 is that the addition ratio of fumed silica is different in the two, and fumed silica can form a network structure through hydrogen bonds, thereby improving the thixotropy of the system.

[0179] In summary, the low precipitation epoxy adhesive for LCP bonding of the present invention has certain practical application value in bonding materials such as LCP, steel and PC, as well as in the low precipitation bonding scenario of these materials.

[0180] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention may also be implemented in other ways. Any obvious replacement without departing from the concept of the present invention is within the protection scope of the present invention.

Claims

1. A low precipitation epoxy adhesive for bonding, characterized in that: The invention comprises the following components in parts by weight: 30-40 parts of toughened epoxy resin, 5-15 parts of multifunctional epoxy resin, 5-15 parts of low-viscosity epoxy resin, 23-27 parts of curing agent, 3-5 parts of accelerator, 4-6 parts of stabilizer, 15-30 parts of filler, 0.5-2 parts of pigment, 0.5-5 parts of thixotropic agent; The toughened epoxy resin is an acrylic rubber toughened epoxy resin; The multifunctional epoxy resin is a tetrafunctional glycidylamine epoxy resin; The low-viscosity epoxy resin is tert-butylcatechol glycidyl ether.

2. The low precipitation epoxy adhesive for bonding according to claim 1, characterized in that: The viscosity of the acrylic rubber toughened epoxy resin is 100000 mPa•S; The viscosity of the tetrafunctional glycidylamine epoxy resin is 3000-6000 mPa•S; The viscosity of the tert-butyl catechol glycidyl ether is 1500 mPa•S and the epoxy equivalent is 214 g / mol.

3. The low precipitation epoxy adhesive for bonding according to claim 1, characterized in that: The curing agent is trimethylolpropane tris(3-mercaptopropionate).

4. The low precipitation epoxy adhesive for bonding according to claim 1, characterized in that: The accelerator is an imidazole adduct accelerator.

5. The low precipitation epoxy adhesive for bonding according to claim 1, characterized in that: The stabilizer is an epoxy resin adduct stabilizer.

6. The low precipitation epoxy adhesive for bonding according to claim 1, characterized in that: The filler is any one or any combination of nano calcium carbonate, talcum powder and glass powder.

7. The low precipitation epoxy adhesive for bonding according to claim 1, characterized in that: The pigment is one or both of carbon black and fluorescent whitening agent.

8. The low precipitation epoxy adhesive for bonding according to claim 1, characterized in that: The thixotropic agent is hydrophobic fumed silica.

9. The method for preparing the low precipitation epoxy adhesive for bonding according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. Prepare the corresponding raw materials according to the weight composition of the low precipitation epoxy adhesive for bonding; Mixing a toughened epoxy resin, a multifunctional epoxy resin and a low-viscosity epoxy resin to obtain a mixed resin; S2. Add filler and pigment to the mixed resin and mix to obtain a resin-filler mixture; S3. Add a curing agent, a accelerator and a thixotropic agent to the resin-filler mixture and mix to form a base mixture; S4. Add a stabilizer to the above base mixture, and after vacuum treatment, obtain a low-precipitation epoxy adhesive for bonding.

10. Application of low precipitation epoxy adhesive for bonding, characterized in that: The low precipitation epoxy adhesive for bonding described in any one of claims 1 to 8 or the low precipitation epoxy adhesive for bonding prepared by the preparation method described in claim 9 is applied to bonding any one or more of LCP, steel, and PC.

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