Modified single-component epoxy adhesive and preparation method thereof

Abstract

The invention provides a modified single-component epoxy adhesive and a preparation method thereof. The epoxy resin composition comprises the following components in parts by weight: 100 parts of epoxy resin, 5-20 parts of a multi-beta hydroxyl-carbamate compound, 5-15 parts of a diluent, 3-10 parts of a curing agent, 0.5-1 part of an accelerant, 1-3 parts of a coupling agent and 50-200 parts of inorganic filler. According to the present invention, with the addition of the multi-beta hydroxyl-carbamate compound, the good balance among the performances of the single-component epoxy adhesive is ensured, and particularly the good balance relationship in the shear strength, the impact strength and the temperature resistance is provided so as to well meet the actual requirements;

Description

Technical Field

[0001] The present invention relates to a modified one-component epoxy adhesive and a preparation method thereof, in particular to a modified one-component epoxy adhesive comprising a poly-β-hydroxy-carbamate compound and a preparation method thereof, belonging to the technical field of epoxy resin adhesive production. Background Art

[0002] One-component epoxy adhesives are a type of adhesive product that has a long operating time at room temperature and cures quickly when heated. After curing, it has excellent bonding effect and temperature resistance. It has been widely used in structural bonding and caulking, etc., specifically in the fields of construction, machinery, and electronic and electrical insulation materials. However, the curing system used in conventional one-component epoxy adhesives is mostly latent curing agents, such as dicyandiamide, imidazoles, and aromatic diamine curing agents. The corresponding cured products contain a large number of rigid structures, and the cross-linking density of the cured products is large, which inevitably causes the product to have defects in toughness and poor impact resistance. Therefore, when preparing one-component epoxy adhesives, additional toughening agents are usually added to the mixed system to toughen and modify it, such as nitrile rubber, core-shell structure toughening agents, etc. The use of these toughening agents can improve the toughness and bonding properties of the product, but because these toughening agent structures contain a large number of flexible segments, they will affect the thermal stability of the adhesive product to a certain extent.

[0003] Prior art CN115449324A discloses “a high-strength one-component epoxy adhesive composition and a preparation method thereof”, in which a toughening agent is obtained by condensation reaction of an aromatic diamine and a double-terminal carboxyl liquid nitrile rubber or a double-terminal epoxy liquid nitrile rubber, and the one-component epoxy adhesive toughened by the toughening agent has high impact strength, shear strength and tensile strength, but its mechanical properties under high temperature conditions cannot be guaranteed; CN109593323A discloses “a preparation method of a polyetheramine-epoxy resin adduct for a one-component epoxy structural adhesive”, in which the toughening system of the one-component epoxy adhesive uses blocked polyurethane and core-shell rubber, and the shear strength of the one-component epoxy adhesive involved is ≥20MPa and the impact strength is ≥20KN / m, but due to excessive flexible segments in the system, its Young's modulus is <1000MPa, which will limit its use at higher temperatures.

[0004] Therefore, when preparing a one-component epoxy adhesive, the technical means used to maintain an effective balance between the various properties of the adhesive will determine the actual application scope of the product. Summary of the invention

[0005] The present invention aims to solve the problems of the prior art and proposes a modified one-component epoxy adhesive and a preparation method thereof. The addition of a poly-β-hydroxy-urethane compound ensures that the various properties of the one-component epoxy adhesive are well balanced, especially in terms of shear strength, impact strength and temperature resistance, thereby better meeting actual needs.

[0006] In order to achieve the above technical objectives, the following technical solutions are proposed:

[0007] The first purpose of the technical solution is to propose: a modified one-component epoxy adhesive, which comprises the following components in parts by weight:

[0008] Epoxy resin 100 parts;

[0009] 5 to 20 parts of poly-β-hydroxy-carbamate compound;

[0010] 5-15 parts of diluent;

[0011] 3 to 10 parts of curing agent;

[0012] Accelerator 0.5-1 part;

[0013] 1 to 3 parts of coupling agent;

[0014] 50-200 parts of inorganic filler;

[0015] The structural formula of the poly-β-hydroxy-carbamate compound is as shown in the following formula (I), formula (II) or formula (III):

[0016]

[0017] Among them, R1 is -CH3 or -CH2CH3, and R2 is an alkane group containing C2 to C6.

[0018] Preferably, the epoxy resin is one or a mixture of two or more of bisphenol A epoxy resin, bisphenol F epoxy resin, alicyclic epoxy resin and novolac epoxy resin, wherein the bisphenol A epoxy resin is E51 or E54, and the novolac epoxy resin is F51 or F44.

[0019] Preferably, the poly-β-hydroxy-carbamate compound is prepared by a ring-opening reaction of a polyfunctional cyclic carbonate and a primary amine compound containing Si—O;

[0020] The structural formula of the multifunctional cyclic carbonate is shown below:

[0021]

[0022] The structure of the primary amine compound containing Si-O is shown below:

[0023]

[0024] And the reaction involved is as follows:

[0025]

[0026] Preferably, the multifunctional cyclic carbonate is ethylene glycol diglycidyl ether type cyclic carbonate, 1,4-butanediol diglycidyl ether type cyclic carbonate, 1,6-hexanediol diglycidyl ether type cyclic carbonate or trimethylolpropane triglycidyl ether type cyclic carbonate, and the primary amine compound containing Si-O is aminopropyl triethoxysilane, aminopropyl trimethoxysilane, 2-aminoethyl-aminopropyl trimethoxysilane, diethylene triaminopropyl trimethoxysilane, aminoethyl aminopropyl trimethoxysilane, aminoethyl aminopropyl methyl dimethoxysilane, urea propyl trimethoxysilane or urea propyl triethoxysilane. Among them, the multifunctional cyclic carbonate can be prepared by reacting a common diluent and CO2, and the primary amine compound is a conventional coupling agent, which is cheap and easy to buy. Based on this, the multi-β hydroxy modifier prepared by the technical scheme has a high yield, a simple preparation process, and mild reaction conditions. In addition, since the modifier contains multiple β-hydroxyl and carbamate groups, it can promote the hydrogen bonding between the epoxy adhesive and the substrate, thereby further improving the bonding performance. The modifier structure of the poly-β-hydroxy-carbamate compound contains more hydroxyl and carbamate groups, which can give the adhesive product a higher physical bonding effect with the substrate, increase the hydrogen bonding force, and thus improve its bonding ability.

[0027] Preferably, the diluent is propylene carbonate, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether or polypropylene glycol diglycidyl ether.

[0028] Preferably, the curing agent is a dicyandiamide curing agent, an imidazole curing agent or an aromatic diamine curing agent.

[0029] Preferably, the accelerator is an imidazole accelerator, a tertiary amine accelerator or an organic urea accelerator.

[0030] Preferably, the coupling agent is a silane coupling agent or a titanate coupling agent, wherein more preferably, the coupling agent is KH560.

[0031] Preferably, the inorganic filler is one or a mixture of two or more of kaolin, calcium carbonate, barium sulfate, calcium sulfate, talcum powder, white carbon black, mica powder, wollastonite and red clay. Preferably, the inorganic filler has a particle size of 100 to 300 meshes, and more preferably, the inorganic filler has a particle size of 150 to 200 meshes.

[0032] The second purpose of the technical solution is to propose: a method for preparing a modified one-component epoxy adhesive, comprising the following steps:

[0033] 1) Preparation of a poly-β-hydroxy-carbamate compound: adding a polyfunctional cyclic carbonate to a mono-primary amine compound containing Si-O at a molar ratio of cyclic carbonate functional groups to primary amine groups of 1:1, and controlling the addition time of the polyfunctional cyclic carbonate to be 0.5 to 1 hour; performing a ring-opening reaction at 70 to 100° C. for 1 to 2 hours to obtain a poly-β-hydroxy-carbamate compound;

[0034] 2) Preparation of modified one-component epoxy adhesive: 100 parts of epoxy resin, 5-20 parts of poly-β-hydroxy-urethane compound, 5-15 parts of diluent, 1-3 parts of coupling agent, 50-200 parts of inorganic filler, 3-10 parts of curing agent and 0.5-1 part of accelerator are mixed and stirred evenly. After vacuum degassing, heat curing is performed to obtain poly-β-hydroxy-urethane compound modified adhesive.

[0035] The molar ratio of the multifunctional cyclic carbonate to the Si-O-containing primary amine compound is n (cyclic carbonate group): n (primary amine group) = 1:1, which ensures that the ring-opening reaction is complete, thereby improving the preparation efficiency and quality of the process;

[0036] Since the cyclic carbonate in the multifunctional cyclic carbonate has high reactivity with the primary amine, the reaction can be carried out in a relatively short time. If the feeding time is too short, the two will react rapidly and violently, which will lead to side reactions; if the feeding time is too long, the conversion rate of the reaction will not be greatly improved, and at the same time, the efficiency will be reduced. Therefore, the feeding time of the monofunctional cyclic carbonate is controlled to be 0.5 to 1h;

[0037] Regarding "ring-opening reaction at 70-100°C for 1-2h", the control of the reaction conditions reduces energy consumption while ensuring the conversion rate, but it does not significantly improve the conversion rate. For example, the short reaction time leads to incomplete reaction, and residual cyclic carbonate and primary amine compounds in the modifier system will affect the performance of the product during subsequent use. Among them, the reaction temperature ensures a sufficient reaction, avoids residual cyclic carbonate and primary amine compounds in the system, prevents the impact on subsequent products, and avoids side reactions;

[0038] In addition, the number of the above components is specifically limited, especially the amount of poly-β-hydroxy-carbamate compound added, to ensure the modification effect. For example, if the amount of poly-β-hydroxy-carbamate compound added is too high, it will have an adverse effect on the temperature resistance of subsequent products, for example, the glass transition temperature will be greatly affected.

[0039] In this technical solution, a poly-β-hydroxy-urethane compound is used as a modifier to modify a one-component epoxy adhesive. The working principles involved include:

[0040] When the modifier is added to the epoxy resin adhesive system, the polar groups in the modifier, such as hydroxyl and carbamate groups, can form hydrogen bonds with the polar groups (hydroxyl, ether bonds, etc.) in the epoxy resin chain in the system, thereby improving the physical bonding in the system. When fillers are added to the epoxy resin adhesive system or it is bonded to a substrate, the modifier can form hydrogen bonds with the polar groups (such as hydroxyl, carboxyl, etc.) on the surface of the substrate or filler, thereby further improving its bonding performance.

[0041]

[0042] The beneficial technical effects brought about by adopting this technical solution are:

[0043] 1. In the present invention, the hydroxyl group exists at the β position of the carbamate group in the structure of the modified one-component epoxy adhesive, which can form hydrogen bonds with the polar groups in the resin matrix and the curing agent, effectively improving the intermolecular forces between the epoxy cured product system, thereby enhancing the interfacial bonding ability between the epoxy resin cured product and the substrate, and further increasing its toughness and temperature resistance;

[0044] Second, in the present invention, during the use of the modified one-component epoxy adhesive, the β-hydroxy-urethane compound in the system can interact with the hydroxyl groups on the surface of the inorganic substrate and the long molecular chains in the organic polymer at the same time, thereby coupling materials of different properties;

[0045] 3. In the present invention, the preparation method of the poly-β-hydroxy-carbamate compound is simple and easy to operate; it does not involve the use of organic solvents, avoids subsequent waste liquid treatment, and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is the infrared spectrum of the poly-β-hydroxy-carbamate compound in Example 1-3;

[0047] Figure 2 is a cross-sectional SEM image of the modified one-component epoxy resin adhesive in Example 13;

[0048] Figure 3 is a cross-sectional SEM image of the modified one-component epoxy resin adhesive in Comparative Example 2;

[0049] Figure 4It is a local infrared spectrum of the carbamate group in the modified one-component epoxy adhesive corresponding to Examples 13-14 (wherein a is the C=O infrared peak in the carbamate group corresponding to Example 13, and b is the C=O infrared peak in the carbamate group corresponding to Example 14). DETAILED DESCRIPTION

[0050] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] Examples 1-12

[0052] This embodiment provides a method for preparing a poly-β-hydroxy-carbamate compound, comprising the following steps:

[0053] The multifunctional cyclic carbonate is added to the monoprimary amine compound containing Si-O, and the feeding speed is controlled to be uniform; at a certain temperature, a ring-opening reaction is carried out to obtain a multi-β-hydroxy-carbamate compound.

[0054] Table 1

[0055]

[0056]

[0057] The structural formula of the poly-β-hydroxy-carbamate compound obtained in Example 1 is as follows:

[0058]

[0059] The structural formula of the poly-β-hydroxy-carbamate compound obtained in Example 5 is as follows:

[0060]

[0061] The structural formula of the poly-β-hydroxy-carbamate compound obtained in Example 10 is as follows:

[0062]

[0063] In addition, for the poly-β-hydroxy-carbamate compounds in Examples 1-3, the infrared spectra involved are as follows Figure 1 shown.

[0064] Embodiment 13

[0065] This embodiment is based on the poly-β-hydroxy-urethane compound obtained in Example 1, and proposes a modified one-component epoxy adhesive, which includes the following components in parts by weight:

[0066] 100 parts of bisphenol A epoxy resin (E51), 5 parts of poly-β-hydroxy-urethane compound, 15 parts of propylene carbonate, 3 parts of dicyandiamide curing agent, 0.5 parts of imidazole accelerator, 3 parts of silane coupling agent and 50 parts of high-quality terephthalate (100 mesh).

[0067] The performance indicators of the modified one-component epoxy adhesive include: shear strength 23.7Mpa, impact strength 4.7KJ / m 2 , tensile strength 78Mpa, elongation at break 1.3% and Shore D hardness 89. Moreover, the cross-sectional SEM image of the modified one-component epoxy adhesive is as follows Figure 2 shown.

[0068] Embodiment 14

[0069] This embodiment is based on the poly-β-hydroxy-urethane compound obtained in Example 1, and proposes a modified one-component epoxy adhesive, which includes the following components in parts by weight:

[0070] 100 parts of phenolic epoxy resin (F51), 20 parts of poly-β-hydroxy-urethane compound, 5 parts of polypropylene glycol diglycidyl ether, 3 parts of imidazole curing agent, 1 part of tertiary amine accelerator, 1 part of titanate coupling agent and 200 parts of barium sulfate (150 mesh).

[0071] The performance indicators of the modified one-component epoxy adhesive include: shear strength 21.8Mpa, impact strength 5.9KJ / m 2 , tensile strength 74Mpa, elongation at break 2.5% and Shore D hardness 85.

[0072] Embodiment 15

[0073] This embodiment is based on the poly-β-hydroxy-urethane compound obtained in Example 1, and proposes a modified one-component epoxy adhesive, which includes the following components in parts by weight:

[0074] 100 parts of alicyclic epoxy resin, 10 parts of poly-β-hydroxy-urethane compound, 6 parts of ethylene glycol diglycidyl ether, 5 parts of aromatic diamine curing agent, 0.5 parts of organic urea accelerator, 1.5 parts of KH560 and 80 parts of a mixture of talc powder and white carbon black (1:1, 300 mesh).

[0075] The performance indicators of the modified one-component epoxy adhesive include: shear strength 19Mpa, impact strength 3.8KJ / m 2, tensile strength 80Mpa, elongation at break 1.1% and Shore D hardness 88.

[0076] Example 16

[0077] This embodiment is based on the poly-β-hydroxy-urethane compound obtained in Example 1, and proposes a modified one-component epoxy adhesive, which includes the following components in parts by weight:

[0078] 100 parts of phenolic epoxy resin, 18 parts of poly-β-hydroxy-urethane compound, 11 parts of a mixture of 1,6-hexanediol diglycidyl ether and polyethylene glycol diglycidyl ether (1:2), 8 parts of dicyandiamide curing agent, 1 part of imidazole accelerator, 2 parts of titanate coupling agent and 188 parts of mica powder (200 mesh).

[0079] The performance indicators of the modified one-component epoxy adhesive include: shear strength 21Mpa, impact strength 2.2KJ / m 2 , tensile strength 77Mpa, elongation at break 0.9% and Shore D hardness 90.

[0080] Embodiment 17

[0081] For the modified one-component epoxy adhesive in Examples 13-16, this embodiment provides a method for preparing a modified one-component epoxy adhesive, comprising the following steps: mixing the components in proportion by weight, stirring evenly, vacuum degassing, and heating and curing, i.e., a modified one-component epoxy adhesive of a poly-β-hydroxy-urethane compound.

[0082] Comparative Example 1

[0083] On the basis of Example 1, in order to further discuss the selection of raw materials when preparing the modifier, this comparative example uses epoxy compounds to prepare the modifier, and then applies it to the preparation of epoxy adhesive products and conducts performance tests to further illustrate the technical solution.

[0084] The original "trimethylolpropane triglycidyl ether type cyclic carbonate" was replaced by "trimethylolpropane triglycidyl ether", and the other steps were the same as those in Example 1, and a control modifier was obtained through preparation.

[0085] Comparative Example 2

[0086] Based on Example 17, this control example replaces the "poly-β-hydroxy-urethane compound" with the control modifier prepared by Control Example 1, and the other components and corresponding weight portions are the same as Example 13. Then, epoxy adhesive 1 is prepared.

[0087] Among them, the performance indicators of epoxy adhesive 1 include: shear strength 17.7Mpa, impact strength 0.9KJ / m 2, tensile strength 73Mpa, elongation at break 0.8% and Shore D hardness 89. The cross-sectional SEM image of epoxy adhesive 1 is shown in Figure 3 shown.

[0088] Comparative Example 3

[0089] On the basis of Example 17, this control does not add the "poly-β-hydroxy-urethane compound", and the other components and corresponding weight proportions are the same as Example 13. Then, epoxy adhesive 2 is prepared.

[0090] The performance indicators of the epoxy adhesive 2 include: shear strength 17.4Mpa, impact strength 0.4KJ / m 2 , tensile strength 79Mpa, elongation at break 0.5% and Shore D hardness 91.

[0091] The test results show that the shear strength, impact strength and elongation at break of the epoxy adhesive without adding the poly-β-hydroxy-carbamate compound are lower than the test results of Example 13. This is because the hydroxyl and carbamate groups in the structure of the poly-β-hydroxy-carbamate compound can promote hydrogen bonding in the adhesive system, thereby improving its physical bonding ability, so as to ensure that the various properties of the single-component epoxy adhesive have a good balance, especially in shear strength, impact strength and temperature resistance.

[0092] Comparative Example 4

[0093] Based on Example 1, this comparative example provides a method for preparing a mono-β-hydroxy-carbamate compound, which specifically comprises: slowly adding propylene carbonate in the same molar ratio to aminopropyltriethoxysilane, controlling the addition time to 0.5h and the temperature to 70°C; after the addition is completed, continuing the reaction for 1.5h to obtain a mono-β-hydroxy-carbamate compound with a yield of 98.9%. This is compared with the poly-β-hydroxy-carbamate compound prepared in Example 1.

[0094] Then, on the basis of Example 13, the mono-β-hydroxy-carbamate compound was applied to prepare a modified one-component epoxy adhesive. That is, the "5 parts of poly-β-hydroxy-carbamate compound" in Example 13 was replaced with "5 parts of mono-β-hydroxy-carbamate compound", and the other components and corresponding weight parts were the same as in Example 13, and then, epoxy adhesive 3 was prepared.

[0095] Among them, the performance indicators of epoxy adhesive 3 include: shear strength 21.8Mpa, impact strength 3.3KJ / m 2 , tensile strength 75Mpa, elongation at break 1.2% and Shore D hardness 86.

[0096] The test results show that the shear strength, impact strength and elongation at break of the corresponding epoxy adhesive (epoxy adhesive 3) are lower than those in Example 13. Compared with monofunctional β-hydroxy-carbamate compounds, poly-β-hydroxy-carbamate compounds can provide more hydroxyl and carbamate groups in their structures, which can further promote hydrogen bonding in the adhesive system, thereby improving its physical bonding ability.

[0097] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment according to the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A modified one-component epoxy adhesive, characterized in that: In parts by weight, it includes the following components: Epoxy resin 100 parts; 5 to 20 parts of poly-β-hydroxy-carbamate compound; 5-15 parts of diluent; 3 to 10 parts of curing agent; Accelerator 0.5-1 part; 1 to 3 parts of coupling agent; 50-200 parts of inorganic filler; The structural formula of the poly-β-hydroxy-carbamate compound is as shown in the following formula (I), formula (II) or formula (III): Among them, R1 is -CH3 or -CH2CH3, and R2 is an alkane group containing C2 to C6.

2. The modified one-component epoxy adhesive according to claim 1, characterized in that: The epoxy resin is one of bisphenol A epoxy resin, bisphenol F epoxy resin, alicyclic epoxy resin and novolac epoxy resin, or a mixture of two or more thereof.

3. The modified one-component epoxy adhesive according to claim 1, characterized in that: The poly-β-hydroxy-carbamate compound is prepared by a ring-opening reaction between a polyfunctional cyclic carbonate and a primary amine compound containing Si-O; The structural formula of the multifunctional cyclic carbonate is shown below: The structure of the Si-O-containing primary amine compound is shown below:

4. The modified one-component epoxy adhesive according to claim 3, characterized in that: The multifunctional cyclic carbonate is ethylene glycol diglycidyl ether type cyclic carbonate, 1,4-butanediol diglycidyl ether type cyclic carbonate, 1,6-hexanediol diglycidyl ether type cyclic carbonate or trimethylolpropane triglycidyl ether type cyclic carbonate; The Si-O-containing primary amino compound is aminopropyltriethoxysilane, aminopropyltrimethoxysilane, 2-aminoethyl-aminopropyltrimethoxysilane, diethylenetriaminopropyltrimethoxysilane, aminoethylaminopropyltrimethoxysilane, aminoethylaminopropylmethyldimethoxysilane, ureidopropyltrimethoxysilane or ureidopropyltriethoxysilane.

5. The modified one-component epoxy adhesive according to claim 1, characterized in that: The diluent is propylene carbonate, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether or polypropylene glycol diglycidyl ether.

6. The modified one-component epoxy adhesive according to claim 1, characterized in that: The curing agent is a dicyandiamide curing agent, an imidazole curing agent or an aromatic diamine curing agent.

7. The modified one-component epoxy adhesive according to claim 1, characterized in that: The accelerator is an imidazole accelerator, a tertiary amine accelerator or an organic urea accelerator.

8. The modified one-component epoxy adhesive according to claim 1, characterized in that: The coupling agent is a silane coupling agent or a titanate coupling agent.

9. The modified one-component epoxy adhesive according to claim 1, characterized in that: The inorganic filler is one or a mixture of two or more of kaolin, calcium carbonate, barium sulfate, calcium sulfate, talcum powder, white carbon black, mica powder, wollastonite and red clay, wherein preferably, the particle size of the inorganic filler is 100-300 meshes.

10. A method for preparing a modified one-component epoxy adhesive, characterized in that: The steps include: 1) Preparation of a poly-β-hydroxy-carbamate compound: adding a polyfunctional cyclic carbonate to a mono-primary amine compound containing Si-O at a molar ratio of cyclic carbonate functional groups to primary amine groups of 1:1, and controlling the addition time of the polyfunctional cyclic carbonate to be 0.5 to 1 hour; performing a ring-opening reaction at 70 to 100° C. for 1 to 2 hours to obtain a poly-β-hydroxy-carbamate compound; 2) Preparation of modified one-component epoxy adhesive: 100 parts of epoxy resin, 5-20 parts of poly-β-hydroxy-urethane compound, 5-15 parts of diluent, 1-3 parts of coupling agent, 50-200 parts of inorganic filler, 3-10 parts of curing agent and 0.5-1 part of accelerator are mixed and stirred evenly. After vacuum degassing, heat curing is performed to obtain poly-β-hydroxy-urethane compound modified adhesive.

Images