A toughened modified epoxy resin adhesive and preparation method

Abstract

The present invention relates to the technical field of epoxy resin adhesives, and discloses a toughening modified epoxy resin adhesive and a preparation method, 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 defoamer, 64-78 parts by weight of curing agent, etc.; the polyarylether ester contains a flexible ether bond, has a good toughening effect, and is conducive to improving elongation at break and impact toughness. Polyarylether ester has a dendritic three-dimensional structure, and its terminal carboxyl group undergoes a curing reaction with the epoxy resin to form a stable chemical interpenetrating cross-linked network. When the adhesive cured product is subjected to stress, a large amount of energy can be absorbed, thereby further improving toughness, so that the adhesive shows higher elongation at break and impact toughness. Polyarylether ester contains a condensed aromatic ring structure of heat-resistant triphenylbenzene, which is conducive to improving the initial thermal decomposition temperature and high temperature resistance of the adhesive.

Description

Technical Field

[0001] The invention relates to the technical field of epoxy resin adhesives, in particular to a toughened modified epoxy resin adhesive and a preparation method thereof. Background Art

[0002] Epoxy resin adhesives offer excellent bonding properties, high mechanical strength, superior weather resistance, and strong electrical insulation properties, making them important applications in furniture and building materials, sporting goods, electronic appliances, and automotive parts. However, cured epoxy resins suffer from poor toughness and are prone to cracking, which severely impacts the adhesive's impact resistance and bonding properties. Therefore, epoxy resin adhesives require toughening modification. Traditional toughening agents include polyaryletherketones, polyarylethersulfones, polyarylates, nitrile rubber, and polyurethane.

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

[0004] In view of the defects of the prior art, the present invention provides a toughened modified epoxy resin adhesive and a preparation method, which solves the problem of poor toughness of the epoxy resin adhesive and improves the high temperature resistance of the epoxy resin adhesive.

[0005] The technical solution adopted by the present invention is a toughened modified epoxy resin adhesive and a preparation method. 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 defoamer, 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:

[0006] (1) Add diol monomer, 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene, and p-toluenesulfonic acid in a molar ratio of (1.32-1.44):1:(0.005-0.008) to N,N-dimethylformamide to carry out esterification and polycondensation reaction, and distill under reduced pressure. Add the product to methanol, stir, and allow to stand for separation. Remove the methanol layer, collect the oil layer, and dry to obtain polyarylether ester. The reaction formula is:

[0007] .

[0008] (2) Epoxy resin, polyarylether ester, and defoaming agent are added to toluene solvent, and after shearing and dispersion, curing agent and curing accelerator are added to obtain a toughened modified epoxy resin adhesive.

[0009] Furthermore, the structural formula of the diol monomer in step (1) is OH-(CH2) n -OH, n is any integer from 2 to 8, and the diol monomer includes any one of ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, and 1,8-octanediol.

[0010] Furthermore, the reaction in step (1) is carried out at 145-155° C. with stirring and condensation reflux for 6-10 h.

[0011] Furthermore, the curing agent is an acid anhydride curing agent, including methyltetrahydrophthalic anhydride or methylnadic anhydride.

[0012] Furthermore, the curing accelerator is an amine accelerator, including DMP-30, benzyldimethylamine or 2-ethyl-4-methylimidazole.

[0013] Furthermore, the preparation method of 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene is as follows: 1,3,5-tris(4-hydroxyphenyl)benzene and bromoacetic acid are added to 1,4-dioxane, an aqueous solution of a catalyst is added dropwise, the mixture is heated to 100-110°C, stirred and refluxed under condensation for 12-18 hours, 1,4-dioxane is removed by distillation under reduced pressure, water is added to dilute the mixture, a hydrochloric acid solution is added dropwise to adjust the pH to 2-3, a precipitate is precipitated, the precipitate is filtered, and recrystallized from dichloromethane to obtain 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene. The reaction formula is:

[0014] .

[0015] Furthermore, the molar ratio of 1,3,5-tris(4-hydroxyphenyl)benzene, bromoacetic acid, and catalyst is 1:(4.2-5.4):(3-3.6).

[0016] Furthermore, the catalyst is sodium hydroxide or potassium hydroxide.

[0017] The beneficial technical effect of the present invention is that 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene containing three carboxyl groups is subjected to an esterification polycondensation reaction with a diol monomer such as ethylene glycol containing two hydroxyl groups to obtain a polyarylether ester, which is then blended with an epoxy resin, a curing agent, a curing accelerator, etc. to obtain a toughened modified epoxy resin adhesive. The polyarylether ester contains terminal carboxyl groups and can undergo a thermal curing reaction with the epoxy resin. It has excellent compatibility and interfacial bonding strength with the epoxy resin, and contains flexible ether bonds, which have a good toughening effect on the adhesive cured product, which is beneficial for improving elongation at break and impact toughness.

[0018] The polyarylether ester of the present invention has a dendritic three-dimensional structure, and its terminal carboxyl groups undergo a curing reaction with the epoxy resin to form a stable chemical interpenetrating cross-linked network. When the adhesive cured product is subjected to stress, it can absorb a large amount of energy, thereby further improving toughness and making the adhesive exhibit higher elongation at break and impact toughness.

[0019] 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. DETAILED DESCRIPTION

[0020] 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 making any creative efforts are within the scope of protection of the present invention.

[0021] Example 1

[0022] (1) Add 50 mmol of 1,3,5-tris(4-hydroxyphenyl)benzene and 240 mmol of bromoacetic acid to 150 mL of 1,4-dioxane, add dropwise 40 mL of an aqueous solution containing 180 mmol of sodium hydroxide, heat to 100 °C, stir and reflux under condensation for 18 h, remove 1,4-dioxane by distillation under reduced pressure, add water to dilute, add dropwise hydrochloric acid solution to adjust the pH to 3, precipitate, filter and recrystallize the precipitate from dichloromethane to obtain 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene as a light yellow solid with a yield of 20.3 g.

[0023] (2) Add 144 mmol of ethylene glycol, 100 mmol of 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene, and 0.6 mmol of p-toluenesulfonic acid to 0.8 L of N,N-dimethylformamide, heat to 150 °C, stir, condense and reflux for 10 h, and distill under reduced pressure. Add the product to methanol, stir and let it stand to separate the layers, remove the methanol layer, collect the oil layer, and dry to obtain polyarylether ester.

[0024] (3) Add 950 g of epoxy resin E51, 50 g of polyarylether ester, and 5 g of defoamer RhodolineDF 691 to 200 mL of toluene solvent, and after shearing and dispersion, add 780 g of curing agent methyltetrahydrophthalic anhydride and 5.2 g of curing accelerator DMP-30 to obtain a toughened modified epoxy resin adhesive.

[0025] Example 2

[0026] (1) Add 50 mmol of 1,3,5-tris(4-hydroxyphenyl)benzene and 210 mmol of bromoacetic acid to 200 mL of 1,4-dioxane, add dropwise 40 mL of an aqueous solution containing 165 mmol of sodium hydroxide, heat to 100 °C, stir and reflux for 18 h, remove 1,4-dioxane by distillation under reduced pressure, add water to dilute, add dropwise hydrochloric acid solution to adjust the pH to 2, precipitate, filter and recrystallize the precipitate from dichloromethane to obtain 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene as a light yellow solid with a yield of 18.8 g.

[0027] (2) Add 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 to 1 L of N,N-dimethylformamide, heat to 145 °C, stir, condense and reflux for 10 h, and distill under reduced pressure. Add the product to methanol, stir and let it stand to separate the layers, remove the methanol layer, collect the oil layer, and dry to obtain polyarylether ester.

[0028] (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 shearing and 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 modified epoxy resin adhesive.

[0029] Example 3

[0030] (1) Add 50 mmol of 1,3,5-tris(4-hydroxyphenyl)benzene and 240 mmol of bromoacetic acid to 150 mL of 1,4-dioxane, and dropwise add 30 mL of an aqueous solution containing 150 mmol of potassium hydroxide. Heat to 110°C, stir, and reflux under condensation for 12 h. Remove 1,4-dioxane by distillation under reduced pressure, add water to dilute, and dropwise add hydrochloric acid solution to adjust the pH to 2. A precipitate is precipitated. After filtration, the precipitate is recrystallized from dichloromethane to obtain 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene as a light yellow solid with a yield of 21.5 g.

[0031] (2) Add 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 to 1 L of N,N-dimethylformamide, heat to 155 °C, stir, condense and reflux for 6 h, and distill under reduced pressure. Add the product to methanol, stir and let it stand to separate the layers, remove the methanol layer, collect the oil layer, and dry to obtain polyarylether ester.

[0032] (3) 850 g of epoxy resin E51, 150 g of polyarylether ester, and 7 g of defoamer Rhodoline DF 691 were added to 300 mL of toluene solvent. After shearing and dispersion, 680 g of curing agent methyltetrahydrophthalic anhydride and 3 g of curing accelerator benzyldimethylamine were added to obtain a toughened modified epoxy resin adhesive.

[0033] Example 4

[0034] (1) 800 g of epoxy resin E51, 200 g of polyarylether ester (prepared in Example 1), and 7 g of defoamer Rhodoline DF 691 were added to 300 mL of toluene solvent. After shearing and dispersion, 640 g of curing agent methyltetrahydrophthalic anhydride and 3 g of curing accelerator benzyldimethylamine were added to obtain a toughened modified epoxy resin adhesive.

[0035] Comparative Example 1

[0036] (1) Add 950 g of epoxy resin E51 and 5 g of defoamer Rhodoline DF 691 to 200 mL of toluene solvent, shear and disperse, add 780 g of curing agent methyltetrahydrophthalic anhydride and 5.2 g of curing accelerator DMP-30 to obtain epoxy resin adhesive.

[0037] Comparative Example 2

[0038] (1) Add 144mmol of ethylene glycol and 100mmol of hydroquinone-О,О'-diacetic acid (structural formula: , CAS registration number is 2245-53-6), 0.6mmol p-toluenesulfonic acid, heated to 150℃, stirred and refluxed for 10h, distilled under reduced pressure, the product was added to methanol, stirred and allowed to stand for stratification, the methanol layer was removed, the oil layer was collected and dried to obtain polyarylether ester.

[0039] (2) Add 950 g of epoxy resin E51, 50 g of polyarylether ester, and 5 g of defoamer RhodolineDF 691 to 200 mL of toluene solvent, and after shearing and 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.

[0040] Comparative Example 3

[0041] (1) Add 144mmol of ethylene glycol and 100mmol of 1,3,5-tris(carboxymethoxy)benzene (structural formula: , CAS registration number is 215162-34-8), 0.6mmol p-toluenesulfonic acid, heated to 150℃, stirred and refluxed for 10h, distilled under reduced pressure, the product was added to methanol, stirred and allowed to stand for stratification, the methanol layer was removed, the oil layer was collected and dried to obtain polyarylether ester.

[0042] (2) Add 950 g of epoxy resin E51, 50 g of polyarylether ester, and 5 g of defoamer RhodolineDF 691 to 200 mL of toluene solvent, and after shearing and 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.

[0043] Comparative Example 4

[0044] (1) Add 144mmol of ethylene glycol and 100mmol of 1,3,5-tris(4-carboxyphenyl)benzene (structural formula: , CAS registration number is 50446-44-1), 0.6mmol p-toluenesulfonic acid, heated to 150℃, stirred and refluxed for 10h, distilled under reduced pressure, the product was added to methanol, stirred and allowed to stand for stratification, the methanol layer was removed, the oil layer was collected and dried to obtain polyarylate.

[0045] (2) Add 950 g of epoxy resin E51, 50 g of polyarylate, and 5 g of defoamer RhodolineDF 691 to 200 mL of toluene solvent, and after shearing and 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.

[0046] The epoxy resin adhesive was cast into a mold and cured at 100°C for 2 hours, 150°C for 3 hours, and 180°C for 4 hours to make a casting specimen. The tensile properties and impact toughness were tested according to the method specified in GB / T 2567-2021.

[0047] A 5 mg sample of the casting was placed in a thermogravimetric analyzer and subjected to a thermogravimetric performance test in a nitrogen atmosphere by heating from room temperature to 800° C. at a heating rate of 10° C. / min.

[0048] Table 1 Epoxy resin adhesive performance test

[0049]

[0050] As shown in Table 1, the epoxy resin adhesive of Comparative Example 1 has low elongation at break and impact toughness, poor toughness, and a low initial (5% mass loss) thermal decomposition temperature, resulting in poor high-temperature resistance. The epoxy resin adhesives of Examples 1-4 incorporate polyarylether esters, which contain terminal carboxyl groups and can undergo a thermal curing reaction with the epoxy resin. They exhibit excellent compatibility and interfacial bonding strength with the epoxy resin and contain flexible ether bonds, which have a strong toughening effect on the cured adhesive, contributing to improved elongation at break and impact toughness. Furthermore, the polyarylether ester has a dendritic three-dimensional structure, and its terminal carboxyl groups undergo a curing reaction with the epoxy resin, forming a stable chemically interpenetrating cross-linked network. When the cured 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. Furthermore, the polyarylether ester contains a heat-resistant condensed aromatic ring structure of triphenylbenzene, which contributes to improved high-temperature resistance of the adhesive, exhibiting a higher initial thermal decomposition temperature.

[0051] In Comparative Example 2, hydroquinone-О,О'-diacetic acid is used as a raw material, and the polyarylether ester prepared is a linear polymer, which does not contain a dendritic three-dimensional structure and has a poor toughening effect on the epoxy resin adhesive, resulting in low elongation at break and impact toughness. It also does not contain the heat-resistant condensed aromatic ring structure of triphenylbenzene, resulting in poor high temperature resistance of the adhesive and a low initial thermal decomposition temperature.

[0052] Comparative Example 3 uses 1,3,5-tris(carboxymethoxy)benzene as a raw material to prepare a polyarylether ester that does not contain the heat-resistant condensed aromatic ring structure of triphenylbenzene, resulting in poor high-temperature resistance of the adhesive and a low initial thermal decomposition temperature.

[0053] Comparative Example 4 uses 1,3,5-tris(4-carboxyphenyl)benzene as a raw material. The prepared polyarylate does not contain a flexible ether bond and has a poor toughening effect on the epoxy resin adhesive, resulting in low elongation at break and impact toughness.

[0054] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of the present invention.

Claims

1. A toughened modified epoxy resin adhesive, characterized in that: The toughened 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 comprises: adding a diol monomer, 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene, and p-toluenesulfonic acid in a molar ratio of (1.32-1.44):1:(0.005-0.008) to N,N-dimethylformamide, performing reduced pressure distillation after the reaction, adding the product to methanol, stirring, standing and separating, removing the methanol layer, collecting the oil layer, and drying to obtain the polyarylether ester.

2. The toughened modified epoxy resin adhesive according to claim 1, characterized in that: The curing agent is an acid anhydride curing agent, including methyltetrahydrophthalic anhydride or methylnadic anhydride.

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

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

5. The toughened modified epoxy resin adhesive according to claim 1, characterized in that: The reaction was stirred at 145-155°C and refluxed under condensation for 6-10 hours.

6. The toughened modified epoxy resin adhesive according to claim 1, characterized in that: The preparation method of 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene comprises: adding 1,3,5-tris(4-hydroxyphenyl)benzene and bromoacetic acid to 1,4-dioxane, dropwise adding an aqueous solution of a catalyst, heating to 100-110° C., stirring and condensing the mixture under reflux for 12-18 hours, removing 1,4-dioxane by distillation under reduced pressure, adding water for dilution, and dropwise adding a hydrochloric acid solution to adjust the pH to 2-3 to precipitate a precipitate. After filtering the precipitate, the precipitate is recrystallized in dichloromethane to obtain 1,3,5-tris[4-(carboxymethoxy)phenyl]benzene.

7. The toughened modified epoxy resin adhesive according to claim 6, characterized in that: The molar ratio of the 1,3,5-tris(4-hydroxyphenyl)benzene, bromoacetic acid and catalyst is 1:(4.2-5.4):(3-3.6).

8. The toughened modified epoxy resin adhesive according to claim 7, characterized in that: The catalyst is sodium hydroxide or potassium hydroxide.

9. A method for preparing the toughened modified epoxy resin adhesive according to any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: adding epoxy resin, polyarylether ester and defoamer into toluene solvent, and adding curing agent and curing accelerator after shearing and dispersing to obtain toughened modified epoxy resin adhesive.

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