Damp-heat-resistant single-component thiol epoxy adhesive

Abstract

The invention relates to a damp-heat-resistant single-component thiol epoxy adhesive, which is prepared from the following components in parts by weight: 100 parts of epoxy resin, 60 to 100 parts of polyfunctional group thiol (sulfydryl) silane coupling agent, 0.5 to 10 parts of latent curing agent and 0.1 to 5 parts of stabilizer. The thiol compound structure adopted by the invention does not contain ester bonds, and a cured product has elasticity and excellent heat and humidity resistance, and still keeps good bonding strength after high-temperature and high-humidity treatment.

Description

Technical Field

[0001] The invention belongs to epoxy resin adhesive, in particular to a single-component epoxy resin which can be cured at low temperature and in a short time (80°C for 20 minutes), and belongs to the technical field of adhesives. Background Art

[0002] About 80% of semiconductor devices are encapsulated with epoxy resin, including transistors, integrated circuits, scale integrated circuits and ultra-large-scale integrated circuits. The wide application of epoxy resin is mainly due to its high bonding strength, good corrosion resistance and excellent electrical insulation performance. However, the main disadvantages of single-component epoxy resin adhesives are high curing temperature and long curing time, and the cured product is relatively brittle, has no elasticity and toughness, and is prone to stress cracking, which affects the quality of the product.

[0003] At present, the epoxy resin system based on thiol compound curing is mainly used to meet the requirements of low temperature and short time curing epoxy adhesives and sealants. CN105324363A discloses a thiol-containing compound and a one-component epoxy resin composition, which is composed of bisphenol A epoxy resin, a multifunctional thiol compound with an ester bond (see formula-1 and 2), a latent epoxy resin curing agent and a stabilizer. It has a storage stability of 4 days at room temperature of 25°C, and a gel time of less than 5 minutes at 80°C. It has good storage stability while having low temperature and fast curing characteristics. However, the multifunctional thiol compound with an ester bond is easily hydrolyzed in a high temperature and high humidity environment, resulting in the epoxy resin cured product obtained from it experiencing high temperature and high humidity (such as: 85°C 85%RH). After that, the bonding strength is greatly reduced or even fails, and it cannot be used for electronic and electrical components and other uses that require high temperature and high humidity environments.

[0004]

[0005] CN113736403A discloses a one-component heat-resistant epoxy resin composition and its preparation method and application, wherein the composition comprises 20-30 parts of bisphenol A epoxy resin, 20-30 parts of epoxy resin containing rigid ring, 30-50 parts of isocyanurate type polythiol compound (see molecular formula-3), 1-5 parts of latent curing agent, and 0.1-10 parts of auxiliary agent. It can realize low-temperature rapid curing, and the cured product has good moisture and heat resistance and hot bonding strength. Since the isocyanurate type polythiol compound does not contain ester bond structure, it is not easy to hydrolyze and has good moisture and heat resistance. However, this type of material is extremely expensive and difficult to obtain. At the same time, the cured product is very brittle and lacks toughness and elasticity, is not resistant to falling, and is also prone to stress in cold and hot shock environmental tests, thereby causing a decrease in bonding strength.

[0006]

[0007] CN115029092A discloses a heat-resistant one-component epoxy resin adhesive and its preparation method and application. The one-component epoxy resin adhesive comprises a combination of epoxy resin, toughening resin, mercaptan curing agent (molecular formula-4), curing accelerator and nano calcium carbonate. By limiting the curing agent to a mercaptan curing agent without an ester bond, the hydrolysis resistance of the adhesive is greatly enhanced, and its heat-resistant aging performance is improved. However, although the polyfunctional mercaptan containing an ether bond has excellent hydrolysis resistance, it is difficult to accept electronic and electrical appliances used in a closed environment because of its relatively small molecular weight, strong volatility and extremely unpleasant odor.

[0008]

[0009] CN115232585A discloses a single-component epoxy resin composition resistant to wet and hot hydrolysis, and its preparation method and application. The composition comprises: 40-60 parts of epoxy resin, 20-60 parts of non-ester bond thiol compound (molecular formula-5), 0.5-10 parts of curing accelerator, 0.1-5 parts of stabilizer, 0.1-5 parts of silane coupling agent, and 0.1-40 parts of filler. Since the thiol compound structure does not contain ester bonds and contains two benzene ring structures, it has good wet and hot resistance after curing, and can still maintain good bonding strength after wet and hot treatment. However, the synthesis steps of the thiol compound used in this invention patent are extremely cumbersome, a large amount of solvent is used, the reaction time is very long, and complex process flows such as alkali washing, water washing, solvent extraction, distillation and purification are required, a large amount of waste water and waste solvent are generated, the synthesis process is environmentally unfriendly, the target product yield is low, the cost is very high, and it is not suitable for packaging and bonding and sealing of ordinary electronic components.

[0010] Summary of the invention

[0011] The purpose of the present invention is to provide a one-component epoxy resin composition that is elastic and elongated and can be cured by heating at low temperature and in a short time (80°C for 20 minutes). The thiol compound used in the present invention does not contain an ester bond in its structure, and the cured product is elastic and has excellent resistance to moisture and heat, and still maintains good bonding strength after high temperature and high humidity treatment.

[0012] The technical solution for achieving the purpose of the present invention is: a moisture and heat resistant one-component thiol epoxy adhesive, which comprises the following components in parts by weight: 100 parts of epoxy resin, 60 to 100 parts of multifunctional thiol (mercapto) silane coupling agent, 0.5 to 10 parts of latent curing agent, and 0.1 to 5 parts of stabilizer.

[0013] Furthermore, the epoxy resin described in the present invention is selected from one or a mixture of bisphenol A epoxy resin, bisphenol F epoxy resin, novolac epoxy resin, glycidyl ester epoxy resin, alicyclic epoxy resin, oxetane, etc., preferably one or two of bisphenol A epoxy resin and bisphenol F epoxy resin.

[0014] Furthermore, the multifunctional thiol (mercapto) silane coupling agent is synthesized by hydrolysis of mercaptopropylmethyldimethoxysilane coupling agent and / or mercaptopropyltrimethoxysilane coupling agent in the presence of a catalyst, and has the following structure:

[0015]

[0016] Wherein, R represents a methyl group or a methoxy group, and n is an integer of 0 to 100.

[0017] Specifically, the catalyst for hydrolysis synthesis is selected from any one or more of inorganic acids and organic acids, organic tin compounds, titanate compounds, α-silane coupling agents, Lewis acids or Lewis base compounds, and the weight ratio of mercaptopropylmethyldimethoxysilane coupling agent and / or mercaptopropyltrimethoxysilane coupling agent to the catalyst is 100:0.05~2.

[0018] Specifically, the catalyst for hydrolysis synthesis is one or more of inorganic acids, organic acids and organotin compounds, and the inorganic acids and organic acids include hydrochloric acid, sulfuric acid, phosphoric acid, methanesulfonic acid, trifluoromethanesulfonic acid, toluenesulfonic acid, etc.; the organotin compounds include dibutyltin dibutyl ketoxime silicon, dibutyltin diacetylacetonate, dibutyltin diacetylacetate, dibutyltin dilaurate, dibutyltin bistriethoxysilicate, dioctyltin bistriethoxysilicate, and tetravalent tin compounds which are the reaction products of diketoxime tin oxide and silicate compounds.

[0019] Furthermore, the latent curing agent described in the present invention includes any one or more of boron trifluoride-amine complexes, dicyandiamide, imidazole compounds and their derivatives or adducts thereof, fatty amine adducts, organic acid hydrazides, melamine and its derivatives, imide compounds or microencapsulated curing agents.

[0020] Furthermore, the latent curing agent is selected from PN-23, MY-24 of Ajinomoto, FXE-1000, FXR-1020, FXR-1030, FXR-1081 of Fuji Chemical Industry, EH-3293, H-3615 of Asahi Denka, or HX-3721 of Asahi Chemical, etc., or a mixture of several of them, but not limited to these. The above latent curing agents can be used alone or in combination of two or more.

[0021] Furthermore, the stabilizer of the present invention is a Lewis acid compound, such as one or more of a carboxylic acid compound, a liquid borate compound, and an aluminum chelating agent. From the perspective of versatility, safety, and storage stability, a liquid borate compound is preferred.

[0022] Specifically, the carboxylic acid compound includes saturated fatty monobasic acids such as propionic acid, butyric acid, valeric acid, caproic acid, and octanoic acid, unsaturated monobasic acids such as acrylic acid, methacrylic acid, and crotonic acid, and aliphatic polybasic acids such as oxalic acid, malonic acid, and maleic acid; the liquid borate compound includes one or more of L-07N of Shikoku Chemical of Japan, trimethyl borate, triethyl borate, tri-n-propyl borate, triisopropyl borate, tri-n-butyl borate, tri-n-pentyl borate, triallyl borate, trihexyl borate, tricyclohexyl borate, trioctyl borate, trinonyl borate, tridecyl borate, tridodecyl borate, trihexadecyl borate, trioctadecyl borate, triphenyl borate, or triethanolamine borate, preferably one or more of triethyl borate, tri-n-propyl borate, triisopropyl borate, and tri-n-butyl borate.

[0023] Furthermore, the adhesive of the present invention may also contain a silane coupling agent, specifically including but not limited to: one or more of γ-methacryloxypropyltrimethoxysilane, vinyltri(β-methoxyethoxy)silane, vinyltrimethoxysilane, vinyltriethoxysilane, anilinemethyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and γ-ureapropyltriethoxysilane.

[0024] Furthermore, the adhesive of the present invention may also contain various fillers, including but not limited to: one or more of silicon dioxide, aluminum oxide, aluminum hydroxide, mica powder, talcum powder, calcium carbonate, glass fiber powder, glass microspheres, hollow microspheres, titanium dioxide, and metal powders.

[0025] Furthermore, the adhesive of the present invention may also contain antioxidants, flame retardants, diluents, adhesion promoters, dyes, pigments, defoaming agents, leveling agents, etc., which are well known to those skilled in the art and will not be elaborated herein.

[0026] Compared with the prior art, the advantages of the present invention are:

[0027] (1) After curing, the thiol epoxy resin adhesive of the present invention has slight elasticity and a certain elongation, which is beneficial to improving the anti-seismic and anti-drop performance of the bonded components.

[0028] (2) The thiol epoxy resin adhesive of the present invention has excellent moisture and heat resistance, and after high temperature and high humidity tests, the original bonding strength is still maintained without decrease. DETAILED DESCRIPTION

[0029] The epoxy resin of the present invention is selected from one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, novolac epoxy resin, glycidyl ester epoxy resin, alicyclic epoxy resin, oxetane, etc. to achieve the required viscosity, hardness or reaction speed.

[0030] The reaction rate of mercapto groups and epoxy groups is extremely slow, and usually requires the addition of organic amine curing agents or curing accelerators.

[0031] The present invention adopts powdered latent curing agent as a catalyst for the reaction between thiol and epoxy groups, so that it has good preservation at room temperature. Once heated, the active amine of the latent curing agent is exposed to immediately catalyze the reaction between thiol and epoxy groups. Therefore, the system has the characteristics of low-temperature rapid curing and can be cured at 80°C for 20 minutes.

[0032] In order to improve the storage properties of the adhesive at room temperature or in refrigerated conditions, a stabilizer needs to be added. The amount of stabilizer added should not affect the curing speed.

[0033] The following is the hydrolysis synthesis method of the multifunctional thiol silane coupling agent and the formula of the one-component epoxy resin adhesive.

[0034] [Mercaptosilane coupling agent-1] In a three-necked glass flask with a reflux condenser, add 100 g of mercaptopropylmethyldimethoxysilane coupling agent (commercially available chemical reagent), 5 g of deionized water, 50 g of ethanol, and 0.5 g of dibutyltin bistriethoxysilicate. Stir and heat to 60°C for 5 h. Rotary evaporate to remove unreacted water, ethanol solvent and generated methanol to obtain a multifunctional mercaptosilane coupling agent-1 with a viscosity of 5.8 mPas.

[0035] [Mercaptosilane coupling agent-2] In a three-necked glass flask with a reflux condenser, add 100g of mercaptopropylmethyldimethoxysilane coupling agent, 15g of deionized water, 50g of ethanol, and 0.1g of trifluoromethanesulfonic acid. Stir and heat to 60°C for 5h, then cool to room temperature. Add excess sodium carbonate to neutralize the residual trifluoromethanesulfonic acid, filter out the solid sodium carbonate by sedimentation, and remove the ethanol solvent and the generated methanol by rotary evaporation to obtain a multifunctional mercaptosilane coupling agent-2 with a viscosity of 45mPas.

[0036] [Mercaptosilane coupling agent-3] In a three-necked glass flask with a reflux condenser, add 100 g of mercaptopropylmethyldimethoxysilane coupling agent, 10 g of deionized water, and 0.5 g of dibutyltin dilaurate. Stir and heat to 60°C for 5 h. Rotary evaporate to remove unreacted water and generated methanol to obtain a multifunctional mercaptosilane coupling agent-3 with a viscosity of 90 mPas.

[0037] [Mercaptosilane coupling agent-4] In a three-necked glass flask with a reflux condenser, add 90g of mercaptopropylmethyldimethoxysilane coupling agent, 10g of mercaptopropyltrimethoxysilane coupling agent, 10g of deionized water, and 0.5g of dibutyltin dilaurate. Stir and heat to 60°C for 5h. Rotary evaporation is used to remove unreacted water and generated methanol to obtain a multifunctional mercaptosilane coupling agent-4 with a viscosity of 155mPas.

[0038] [Example 1] - [Example 4] The formula is shown in Table 1, and the preparation process is the same. Epoxy resin, thiol silane coupling agent, latent curing agent, stabilizer, etc. are added to a planetary mixer and mixed uniformly under vacuum.

[0039] [Comparative Example 1] - [Comparative Example 3] The formulas are shown in Table 1, and the preparation processes are the same.

[0040] The test results of various embodiments and comparative examples are shown in Table 1.

[0041] Table 1

[0042]

[0043] Note: 850S is bisphenol A epoxy resin of Zhonglan International Chemical, 830S is bisphenol F epoxy resin of Zhonglan International Chemical, PEMP is a tetrafunctional thiol of molecular formula-2, TSIC is an isocyanurate polythiol compound of molecular formula-3, PN-23 and MY-24 are latent epoxy resin curing agents of Ajinomoto, FXR-1081 is a latent epoxy resin curing agent of Fuji Chemical, L-07N is a borate ester compound of Shikoku Chemical, and n-butyl borate uses a reagent grade compound.

[0044] Comparative Examples 1 to 4 show that the multifunctional thiol silane coupling agent synthesized by hydrolysis can be cured at low temperature and in a short time (i.e., 80°C 20min curing) by combining different latent curing agents MY-24, PN-23, and FXR-1081. The cured product has a relatively good elongation and a certain elasticity. Although the initial shear strength is not very high, the shear strength decreases little or even does not decrease after high temperature and high humidity (85°C 85% RH*500h). Although the initial shear strength of Comparative Examples 1 and 3 is relatively large, the shear strength decreases sharply after high temperature and high humidity, indicating that the thiol compound containing an ester bond structure is severely hydrolyzed under high temperature and high humidity conditions, resulting in molecular chain breakage, and is difficult to be applied to applications such as bonding or sealing of electronic and electrical components that require harsh moisture resistance. The thiol compound of Comparative Example 2 does not contain an ester bond structure, and the shear strength decreases much less after high temperature and high humidity than Comparative Examples 1 and 2 containing an ester bond structure, but there is still a 36% decrease. In addition, the cured product is very hard and brittle, and the elongation is very low, which is not conducive to anti-drop experiments.

Claims

1. A heat and moisture resistant one-component mercaptan epoxy adhesive, characterized in that: The invention comprises the following components in parts by weight: 100 parts of epoxy resin, 60-100 parts of multifunctional thiol (mercapto) silane coupling agent, 0.5-10 parts of latent curing agent and 0.1-5 parts of stabilizer.

2. The adhesive according to claim 1, characterized in that The epoxy resin is selected from one or a mixture of bisphenol A epoxy resin, bisphenol F epoxy resin, novolac epoxy resin, glycidyl ester epoxy resin, alicyclic epoxy resin, and oxetane, preferably one or two of bisphenol A epoxy resin and bisphenol F epoxy resin.

3. The adhesive according to claim 1, characterized in that The multifunctional thiol (mercapto) silane coupling agent is synthesized by hydrolysis of mercaptopropylmethyldimethoxysilane coupling agent and / or mercaptopropyltrimethoxysilane coupling agent in the presence of a catalyst, and has the following structure: Wherein, R represents a methyl group or a methoxy group, and n is an integer of 0 to 100.

4. The adhesive according to claim 3, characterized in that The catalyst is selected from any one or more of inorganic acid and organic acid, organic tin compound, titanate compound, α-silane coupling agent, Lewis acid or Lewis base compound, and the weight ratio of mercaptopropylmethyldimethoxysilane coupling agent and / or mercaptopropyltrimethoxysilane coupling agent to the catalyst is 100:0.05-2.

5. The adhesive according to claim 4, characterized in that The inorganic acid and organic acid are hydrochloric acid, sulfuric acid, phosphoric acid, methanesulfonic acid, trifluoromethanesulfonic acid, and toluenesulfonic acid; the organotin compound is dibutyltin dibutyl ketoxime silicon, dibutyltin diacetylacetonate, dibutyltin diacetylacetate, dibutyltin dilaurate, dibutyltin bistriethoxysilicate, dioctyltin bistriethoxysilicate, and the reaction product of diketoxime tin oxide and silicate compound, which is a tetravalent tin compound.

6. The adhesive according to claim 1, characterized in that The latent curing agent is any one or more of boron trifluoride-amine complex, dicyandiamide, imidazole compounds and their derivatives or adducts, fatty amine adducts, organic acid hydrazides, melamine and its derivatives, imide compounds or microencapsulated curing agents.

7. The adhesive according to claim 1, characterized in that The latent curing agent is selected from one or a mixture of PN-23, MY-24 of Ajinomoto of Japan, FXE-1000, FXR-1020, FXR-1030, FXR-1081 of Fuji Chemical Industry of Japan, EH-3293, H-3615 of Asahi Denka of Japan or HX-3721 of Asahi Kasei of Japan.

8. The adhesive according to claim 1, characterized in that The stabilizer is a Lewis acid compound, such as one or more of a carboxylic acid compound, a liquid borate compound, and an aluminum chelating agent, preferably a liquid borate compound.

9. The adhesive according to claim 8, characterized in that The carboxylic acid compound is a saturated fatty monoacid selected from one or more of propionic acid, butyric acid, valeric acid, caproic acid, and octanoic acid; an unsaturated monoacid selected from one or more of acrylic acid, methacrylic acid, and crotonic acid; an aliphatic polyacid selected from one or more of oxalic acid, malonic acid, and maleic acid; the liquid borate compound is one or more of L-07N produced by Shikoku Chemical of Japan, trimethyl borate, triethyl borate, tri-n-propyl borate, triisopropyl borate, tri-n-butyl borate, tri-n-pentyl borate, triallyl borate, trihexyl borate, tricyclohexyl borate, trioctyl borate, trinonyl borate, tridecyl borate, tridodecyl borate, trihexadecyl borate, trioctadecyl borate, triphenyl borate, or triethanolamine borate, preferably one or more of triethyl borate, tri-n-propyl borate, triisopropyl borate, and tri-n-butyl borate.

10. The adhesive according to claim 8, characterized in that The adhesive further comprises a silane coupling agent, which is selected from one or more of γ-methacryloxypropyltrimethoxysilane, vinyltri(β-methoxyethoxy)silane, vinyltrimethoxysilane, vinyltriethoxysilane, anilinemethyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and γ-ureapropyltriethoxysilane.

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