Toughening modified epoxy resin adhesive and preparation method thereof

Abstract

The invention relates to the technical field of epoxy resin adhesives, and discloses a toughened modified epoxy resin adhesive and a preparation method thereof, the epoxy resin adhesive comprises 80-95 parts by weight of epoxy resin, 5-20 parts by weight of polyarylether ester, 0.4-0.7 part by weight of a defoaming agent, 64-78 parts by weight of a curing agent and the like; the polyarylether ester contains flexible ether bonds, has a good toughening effect, and is beneficial to improvement of elongation at break and impact toughness. The polyarylether ester has a dendritic three-dimensional structure, a carboxyl-terminated group of the polyarylether ester and the epoxy resin are subjected to a curing reaction to form a stable chemical interpenetrating cross-linked network, and when an adhesive condensate is stressed, a large amount of energy can be absorbed, so that the toughness is further improved, and the adhesive shows higher elongation at break and impact toughness. The polyarylether ester contains a fused aromatic ring structure of heat-resistant triphenylbenzene, so that the initial thermal decomposition temperature and the high-temperature resistance of the adhesive are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of epoxy resins, and specifically provides a toughened and modified epoxy resin adhesive and a preparation method therefor. Background Art

[0002] Epoxy resin adhesives have good bonding performance, high mechanical strength, excellent weather resistance, and strong electrical insulation performance, and have important applications in furniture building materials, sports goods, electronic appliances, automotive parts, etc. However, the toughness of epoxy resin cured products is poor and prone to cracking, seriously affecting the impact resistance, bonding and other properties of the adhesives. Therefore, it is necessary to toughen and modify epoxy resins. Traditional toughening agents include polyaryletherketone, polyarylethersulfone, polyarylate, nitrile rubber, polyurethane, etc.

[0003] Polyarylate and polyarylether polymers have high heat resistance and mechanical strength and are widely used. The Chinese patent application with publication number CN117659369A provides a phosphorus-containing polyarylate-based active ester flame retardant curing agent, an epoxy resin composition and a preparation method therefor. This patent uses a polyarylate-based active ester polymer containing a DOPO structure as an active ester curing agent, improving the heat resistance, flame retardancy and dielectric properties of epoxy resins. However, the polyarylate-based active ester polymer in this patent does not solve the problem of poor toughness of epoxy resins. Summary of the Invention

[0004] Aiming at the defects of the prior art, the present invention provides a toughened and modified epoxy resin adhesive and a preparation method therefor, which solve the problem of poor toughness of epoxy resin adhesives and at the same time improve the high-temperature resistance of epoxy resins.

[0005] The technical solution adopted by the present invention: A toughened and modified epoxy resin adhesive and a preparation method therefor. The epoxy resin adhesive includes 80 - 95 parts by weight of epoxy resin, 5 - 20 parts by weight of polyarylether ester, 0.4 - 0.7 parts by weight of defoaming agent, 64 - 78 parts by weight of curing agent, and 0.3 - 0.6 parts by weight of curing accelerator. The preparation method is as follows: (1) Add glycol monomer, 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene, and p-toluenesulfonic acid with a molar ratio of (1.32 - 1.44):1:(0.005 - 0.008) to N,N-dimethylformamide, carry out esterification polycondensation reaction, and perform vacuum distillation. Add the product to methanol, stir and then let it stand for layering. Remove the methanol layer, collect the oil layer, and dry to obtain polyarylether ester. The reaction formula is: .

[0006] (2) Add epoxy resin, polyarylether ester, and defoaming agent to toluene solvent, shear and disperse, and then add curing agent and curing accelerator to obtain a toughened and modified epoxy resin adhesive.

[0007] Further, in step (1), the structural formula of the diol monomer is OH-(CH2) n -OH, where n is any integer from 2 to 8, and the diol monomer includes any one of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, and 1,8-octanediol.

[0008] Further, in step (1), the reaction is carried out at 145 - 155 °C, with stirring and reflux condensation for 6 - 10 h.

[0009] Further, the curing agent is an acid anhydride curing agent, including methyltetrahydrophthalic anhydride or methyl nadic anhydride.

[0010] Further, the curing accelerator is an amine accelerator, including DMP-30, benzyldimethylamine, or 2-ethyl-4-methylimidazole.

[0011] Further, the preparation method of 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene is as follows: Add 1,3,5-tris(4-hydroxyphenyl)benzene and bromoacetic acid to 1,4-dioxane, dropwise add an aqueous solution of the catalyst, heat to 100 - 110 °C, stir and reflux for 12 - 18 h, distill off 1,4-dioxane under reduced pressure, add water for dilution, dropwise add hydrochloric acid solution to adjust the pH to 2 - 3, precipitate, filter, and recrystallize the precipitate in dichloromethane to obtain 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene. The reaction formula is: 。

[0012] Further, the molar ratio of 1,3,5-tris(4-hydroxyphenyl)benzene, bromoacetic acid, and the catalyst is 1:(4.2 - 5.4):(3 - 3.6).

[0013] Further, the catalyst is sodium hydroxide or potassium hydroxide.

[0014] The beneficial technical effects of the present invention are as follows: Esterification polycondensation reaction is carried out between 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene containing three carboxyl groups and diol monomers such as ethylene glycol containing two hydroxyl groups to obtain polyarylether ester, and then it is blended with epoxy resin, curing agent, curing accelerator, etc. to obtain a toughened modified epoxy resin adhesive. This polyarylether ester contains terminal carboxyl groups, can undergo thermal curing reaction with epoxy resin, has good compatibility and interfacial bonding strength with epoxy resin, and contains flexible ether bonds, which has a good toughening effect on the cured product of the adhesive, and is beneficial to improving the elongation at break and impact toughness.

[0015] The polyarylether ester of the present invention has a dendritic three-dimensional structure, and its terminal carboxyl groups react with the epoxy resin to form a stable chemical interpenetrating crosslinked network. When the cured adhesive is stressed, it can absorb a large amount of energy, thereby further improving toughness and enabling the adhesive to exhibit a higher elongation at break and impact toughness.

[0016] The polyarylether ester of the present invention contains a heat-resistant condensed aromatic ring structure of triphenylbenzene, which is beneficial to improving the initial thermal decomposition temperature and high-temperature resistance of the adhesive. Specific embodiments

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0018] Example 1 (1) 50 mmol of 1,3,5-tris(4-hydroxyphenyl)benzene and 240 mmol of bromoacetic acid were added to 150 mL of 1,4-dioxane, and 40 mL of an aqueous solution containing 180 mmol of sodium hydroxide was added dropwise. The mixture was heated to 100 °C, stirred and refluxed for 18 h. 1,4-dioxane was removed by distillation under reduced pressure, diluted with water, and the pH was adjusted to 3 by adding hydrochloric acid solution. A precipitate was formed, filtered, and the precipitate was recrystallized from dichloromethane to obtain 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene, a pale yellow solid with a yield of 20.3 g.

[0019] (2) 144 mmol of ethylene glycol, 100 mmol of 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene, and 0.6 mmol of p-toluenesulfonic acid were added to 0.8 L of N,N-dimethylformamide. The mixture was heated to 150 °C, stirred and refluxed for 10 h, and then distilled under reduced pressure. The product was added to methanol, stirred, and allowed to stand for phase separation. The methanol layer was removed, and the oil layer was collected and dried to obtain the polyarylether ester.

[0020] (3) 950 g of epoxy resin E51, 50 g of polyarylether ester, and 5 g of defoamer Rhodoline DF 691 were added to 200 mL of toluene solvent. After shear dispersion, 780 g of curing agent methyltetrahydrophthalic anhydride and 5.2 g of curing accelerator DMP-30 were added to obtain a toughened and modified epoxy resin adhesive.

[0021] Example 2 (1) 50 mmol of 1,3,5-tris(4-hydroxyphenyl)benzene and 210 mmol of bromoacetic acid were added to 200 mL of 1,4-dioxane. An aqueous solution containing 165 mmol of sodium hydroxide in 40 mL was added dropwise. The mixture was heated to 100 °C, stirred, and refluxed for 18 h. 1,4-Dioxane was removed by distillation under reduced pressure. Water was added for dilution, and the pH was adjusted to 2 by dropping hydrochloric acid solution. A precipitate was formed, filtered, and the precipitate was recrystallized from dichloromethane to obtain 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene, a pale yellow solid with a yield of 18.8 g.

[0022] (2) 138 mmol of 1,8-octanediol, 100 mmol of 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene, and 0.8 mmol of p-toluenesulfonic acid were added to 1 L of N,N-dimethylformamide. The mixture was heated to 145 °C, stirred, and refluxed for 10 h. After distillation under reduced pressure, the product was added to methanol, stirred, and allowed to stand for phase separation. The methanol layer was removed, and the oil layer was collected and dried to obtain polyarylether ester.

[0023] (3) 900 g of epoxy resin E51, 100 g of polyarylether ester, and 4 g of defoamer Rhodoline DF 691 were added to 300 mL of toluene solvent. After shear dispersion, 730 g of curing agent methyl nadic anhydride and 6 g of curing accelerator 2-ethyl-4-methylimidazole were added to obtain a toughened and modified epoxy resin adhesive.

[0024] Example 3 (1) 50 mmol of 1,3,5-tris(4-hydroxyphenyl)benzene and 240 mmol of bromoacetic acid were added to 150 mL of 1,4-dioxane. An aqueous solution containing 150 mmol of potassium hydroxide in 30 mL was added dropwise. The mixture was heated to 110 °C, stirred, and refluxed for 12 h. 1,4-Dioxane was removed by distillation under reduced pressure. Water was added for dilution, and the pH was adjusted to 2 by dropping hydrochloric acid solution. A precipitate was formed, filtered, and the precipitate was recrystallized from dichloromethane to obtain 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene, a pale yellow solid with a yield of 21.5 g.

[0025] (2) 132 mmol of 1,4-butanediol, 100 mmol of 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene, and 0.5 mmol of p-toluenesulfonic acid were added to 1 L of N,N-dimethylformamide. The mixture was heated to 155 °C, stirred, and refluxed for 6 h. After distillation under reduced pressure, the product was added to methanol, stirred, and allowed to stand for phase separation. The methanol layer was removed, and the oil layer was collected and dried to obtain polyarylether ester.

[0026] (3) Add 850 g of epoxy resin E51, 150 g of polyarylether ester, and 7 g of defoamer Rhodoline DF 691 to 300 mL of toluene solvent. After shear dispersion, add 680 g of curing agent methyltetrahydrophthalic anhydride and 3 g of curing accelerator benzyldimethylamine to obtain a toughened and modified epoxy resin adhesive.

[0027] Example 4 (1) Add 800 g of epoxy resin E51, 200 g of polyarylether ester (prepared in Example 1), and 7 g of defoamer Rhodoline DF 691 to 300 mL of toluene solvent. After shear dispersion, add 640 g of curing agent methyltetrahydrophthalic anhydride and 3 g of curing accelerator benzyldimethylamine to obtain a toughened and modified epoxy resin adhesive.

[0028] Comparative Example 1 (1) Add 950 g of epoxy resin E51 and 5 g of defoamer Rhodoline DF 691 to 200 mL of toluene solvent. After shear dispersion, add 780 g of curing agent methyltetrahydrophthalic anhydride and 5.2 g of curing accelerator DMP-30 to obtain an epoxy resin adhesive.

[0029] Comparative Example 2 (1) Add 144 mmol of ethylene glycol, 100 mmol of hydroquinone-О,О’-diacetic acid (structural formula is , CAS registration number is 2245-53-6), and 0.6 mmol of p-toluenesulfonic acid to 0.8 L of N,N-dimethylformamide. Heat to 150 °C, stir and reflux for 10 h, carry out vacuum distillation. Add the product to methanol, stir and let it stand for layering. Remove the methanol layer, collect the oil layer, and dry to obtain polyarylether ester.

[0030] (2) Add 950 g of epoxy resin E51, 50 g of polyarylether ester, and 5 g of defoamer Rhodoline DF 691 to 200 mL of toluene solvent. After shear dispersion, add 780 g of curing agent methyltetrahydrophthalic anhydride and 5.2 g of curing accelerator DMP-30 to obtain a modified epoxy resin adhesive.

[0031] Comparative Example 3 (1) Add 144 mmol of ethylene glycol, 100 mmol of 1,3,5-tris(carboxymethoxy)benzene (structural formula is , CAS registration number is 215162-34-8), and 0.6 mmol of p-toluenesulfonic acid to 0.8 L of N,N-dimethylformamide. Heat to 150 °C, stir and reflux for 10 h, carry out vacuum distillation. Add the product to methanol, stir and let it stand for layering. Remove the methanol layer, collect the oil layer, and dry to obtain polyarylether ester.

[0032] (2) Add 950 g of epoxy resin E51, 50 g of polyarylether ester, and 5 g of defoamer Rhodoline DF 691 to 200 mL of toluene solvent. After shear dispersion, add 780 g of curing agent methyltetrahydrophthalic anhydride and 5.2 g of curing accelerator DMP-30 to obtain a modified epoxy resin adhesive.

[0033] Comparative Example 4 (1) Add 144 mmol of ethylene glycol, 100 mmol of 1,3,5-tris(4-carboxyphenyl)benzene (structural formula is , CAS registration number is 50446-44-1), and 0.6 mmol of p-toluenesulfonic acid to 0.8 L of N,N-dimethylformamide. Heat to 150 °C and stir for reflux reaction for 10 h. Carry out vacuum distillation. Add the product to methanol, stir and then let it stand for liquid separation. Remove the methanol layer, collect the oil layer, and dry it to obtain polyarylate.

[0034] (2) Add 950 g of epoxy resin E51, 50 g of polyarylate, and 5 g of defoamer Rhodoline DF 691 to 200 mL of toluene solvent. After shear dispersion, add 780 g of curing agent methyltetrahydrophthalic anhydride and 5.2 g of curing accelerator DMP-30 to obtain a modified epoxy resin adhesive.

[0035] Pour the epoxy resin adhesive into a mold and cure it at 100 °C for 2 h, 150 °C for 3 h, and 180 °C for 4 h in sequence to make a cast specimen. Test the tensile properties and impact toughness according to the method specified in the GB / T 2567-2021 standard.

[0036] Take 5 mg of the cast specimen and put it into a thermogravimetric analyzer to conduct thermogravimetric performance testing in a nitrogen atmosphere. Heat from room temperature to 800 °C at a heating rate of 10 °C / min.

[0037] Table 1 Performance Testing of Epoxy Resin Adhesive

[0038] As can be seen from Table 1, the epoxy resin adhesive of Comparative Example 1 has a low elongation at break and impact toughness, poor toughness, and a low initial (5% mass loss) thermal decomposition temperature, indicating poor high-temperature resistance. In the epoxy resin adhesives of Examples 1-4, polyarylether ester was added. This polyarylether ester contains terminal carboxyl groups, which can undergo a thermal curing reaction with the epoxy resin, has good compatibility and interfacial bonding strength with the epoxy resin, and contains flexible ether bonds, which have a good toughening effect on the cured product of the adhesive, facilitating an increase in the elongation at break and impact toughness. Moreover, the polyarylether ester has a dendritic three-dimensional structure, and its terminal carboxyl groups react with the epoxy resin to form a stable chemical interpenetrating crosslinked network. When the cured product of the adhesive is subjected to stress, it can absorb a large amount of energy, thereby further improving toughness and exhibiting higher elongation at break and impact toughness. Additionally, the polyarylether ester contains a heat-resistant condensed aromatic ring structure of triphenylbenzene, which is beneficial for improving the high-temperature resistance of the adhesive and exhibits a higher initial thermal decomposition temperature.

[0039] In Comparative Example 2, hydroquinone-О,О’-diacetic acid was used as the raw material, and the prepared polyarylether ester was a linear polymer without a dendritic three-dimensional structure, resulting in poor toughening effect on the epoxy resin adhesive, low elongation at break and impact toughness, and no heat-resistant condensed aromatic ring structure of triphenylbenzene, leading to poor high-temperature resistance of the adhesive and a low initial thermal decomposition temperature.

[0040] In Comparative Example 3, 1,3,5-tris(carboxymethoxy)benzene was used as the raw material, and the prepared polyarylether ester did not contain a heat-resistant condensed aromatic ring structure of triphenylbenzene, resulting in poor high-temperature resistance of the adhesive and a low initial thermal decomposition temperature.

[0041] In Comparative Example 4, 1,3,5-tris(4-carboxyphenyl)benzene was used as the raw material, and the prepared polyarylate did not contain flexible ether bonds, resulting in poor toughening effect on the epoxy resin adhesive and low elongation at break and impact toughness.

[0042] The above are only the preferred embodiments of the present invention and do not limit the patent scope of the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the patent protection scope of the present invention.

Claims

1. A toughened modified epoxy resin adhesive, characterized in that, The toughened and modified epoxy resin adhesive comprises 80-95 parts by weight of epoxy resin, 5-20 parts by weight of polyarylether ester, 0.4-0.7 parts by weight of defoamer, 64-78 parts by weight of curing agent, and 0.3-0.6 parts by weight of curing accelerator; The preparation method of the polyarylether ester is as follows: add glycol monomer, 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene, and p-toluenesulfonic acid with a molar ratio of (1.32-1.44):1:(0.005-0.008) to N,N-dimethylformamide, carry out reaction and then distill under reduced pressure, add the product to methanol, stir and then let it stand for layering, remove the methanol layer, collect the oil layer, and dry to obtain the polyarylether ester.

2. The toughened and modified epoxy resin adhesive according to claim 1, wherein, The curing agent is an acid anhydride curing agent, including methyltetrahydrophthalic anhydride or methyl nadic anhydride.

3. The toughened and modified epoxy resin adhesive according to claim 1, wherein The curing accelerator is an amine accelerator, including DMP-30, benzyldimethylamine or 2-ethyl-4-methylimidazole.

4. The toughened and modified epoxy resin adhesive according to claim 1, wherein The structural formula of the diol monomer is OH-(CH2) n -OH, where n is any integer from 2 to 8.

5. The toughened and modified epoxy resin adhesive according to claim 1, wherein The reaction is carried out at 145-155 °C, with stirring and refluxing for 6-10 h.

6. The toughened and modified epoxy resin adhesive according to claim 1, characterized in that The preparation method of 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene is as follows: add 1,3,5-tris(4-hydroxyphenyl)benzene and bromoacetic acid to 1,4-dioxane, dropwise add an aqueous solution of a catalyst, heat to 100-110 °C, stir and reflux for reaction for 12-18 h, distill off 1,4-dioxane under reduced pressure, add water for dilution, dropwise add hydrochloric acid solution to adjust the pH to 2-3, precipitate a precipitate, filter, and recrystallize the precipitate in dichloromethane to obtain 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene.

7. The toughened and modified epoxy resin adhesive according to claim 1, wherein The molar ratio of 1,3,5-tris(4-hydroxyphenyl)benzene, bromoacetic acid, and the catalyst is 1:(4.2-5.4):(3-3.6).

8. The toughened and modified epoxy resin adhesive according to claim 7, wherein The catalyst is sodium hydroxide or potassium hydroxide.

9. A preparation method of the toughened and modified epoxy resin adhesive according to any one of claims 1-8, characterized in that, The preparation method is as follows: add epoxy resin, polyarylether ester, and defoamer to toluene solvent, carry out shear dispersion and then add the curing agent and curing accelerator to obtain the toughened and modified epoxy resin adhesive.

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