Heat-resistant strong adhesive and preparation method thereof

Abstract

This invention discloses a method for preparing a heat-resistant, high-strength adhesive, belonging to the field of adhesive preparation technology. First, a modified phenolic resin is prepared by co-condensation of 1,4-naphthyldiamine with phenol and formaldehyde. The introduction of aromatic amine structures improves the heat resistance of the adhesive. Second, an epoxy-phenolic resin is generated by reacting epoxypropane with the modified phenolic resin. The epoxy groups and phenolic hydroxyl groups undergo a cross-linking reaction to form a three-dimensional network structure. Simultaneously, 1,4-naphthyldiamine undergoes a ring-opening reaction with the epoxy groups, giving the epoxy-phenolic resin a more stable network structure. N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane-enriched amino-modified nano-silica is used as a composite filler, undergoing ring-opening cross-linking with the epoxy groups to form a more complex three-dimensional network structure. Furthermore, the alkoxy moieties of the modifier form stable Si-O-Si bonds, improving the overall heat resistance and structural stability of the adhesive. This invention exhibits excellent heat resistance, stability, and shear strength.

Description

Technical Field

[0001] This invention relates to the field of adhesive preparation technology, specifically to a heat-resistant high-strength adhesive and its preparation method. Background Technology

[0002] Adhesives are an important industrial raw material, widely used in automobile manufacturing, packaging, construction, furniture manufacturing, and other fields. The invention of phenolic resin in the early 20th century marked the beginning of the era of synthetic adhesives. Subsequently, the development of high-performance synthetic resins such as epoxy resins, polyurethanes, and acrylates greatly expanded the application range of adhesives. With the development of high-tech industries such as automobiles, electronics, and aerospace, improving temperature resistance, enhancing adhesive performance, increasing toughness, and improving mechanical strength have become the development direction of synthetic resin adhesives.

[0003] Phenolic resin adhesives, due to their phenolic hydroxyl and methylene structures, are prone to oxidation, resulting in a brittle and easily broken adhesive layer, especially exhibiting poor heat resistance when the degree of cross-linking is insufficient. In practical applications, phenolic resin adhesives also suffer from high curing temperatures, slow curing speeds, low production efficiency, and high energy consumption, limiting their wider application. However, phenolic resins have good compatibility. Modification through a composite of organic and inorganic substances can enhance the toughness of phenolic resins, improve the heat resistance of modified adhesives, and impart better adhesive properties to meet the requirements of high-tech fields. Summary of the Invention

[0004] The purpose of this invention is to provide a heat-resistant, high-strength adhesive and its preparation method to solve the problems mentioned in the background art.

[0005] A heat-resistant high-strength adhesive comprising epoxy-phenolic resin and modified nano-silica.

[0006] Preferably, the epoxy-phenolic resin is prepared by co-condensation of 1,4-naphthyldiamine, phenol and formaldehyde to obtain a modified phenolic resin, which is then crosslinked with epoxybromopropane.

[0007] Preferably, the modified nano-silica is prepared by modification with N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane.

[0008] Preferably, the method for preparing the heat-resistant high-strength adhesive includes the following specific steps:

[0009] (1) Add 0.3-0.6 mol of phenol and 0.2-0.3 mol of sodium hydroxide with a concentration of 20-30 wt% to a three-necked flask. Stir at 50 r / min for 10 min until homogeneous. Keep warm at 35-45℃ for 20 min. Add 0.6 mol of formaldehyde and 0.1-0.3 mol of 1,4-naphthyldiamine to the three-necked flask and mix to undergo a condensation reaction. The reaction temperature is 60℃. Stir at 80 r / min for 20 min. Then raise the temperature to 75-80℃ and add 0.4 mol of formaldehyde and 0.1-0.2 mol of 1,4-naphthyldiamine. Stir at 100 r / min for 20 min until homogeneous. Keep warm for 40 min to obtain modified phenolic resin.

[0010] (2) After cooling the modified phenolic resin to 70°C, add epoxy propane and 50-70 wt% sodium hydroxide as a catalyst. Raise the temperature of the system where the cross-linking reaction occurs to 85-90°C, stir at 100-120 r / min for 20 min to mix evenly, and keep it at the temperature for 1 h to obtain epoxy-phenolic resin.

[0011] (3) Disperse silica with a particle size of 20 nm in ammonia water with a concentration of 5-10 wt% at a ratio of 1-1.5 mg / mL, then add N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, stir at 45-60 r / min for 12 h at room temperature, centrifuge to collect the solid, wash with deionized water and anhydrous ethanol respectively, centrifuge 3-5 times, and dry in a 60℃ forced-air oven for 2 h to obtain modified nano silica;

[0012] (4) Modified nano-silica is added to epoxy-phenolic resin, and after mixing at a constant temperature of 80-90℃ for 20-30 min at 80 r / min, it is refluxed at 95-100℃ for 45-60 min, cooled to 70℃ and degassed for 10 min, and then cooled to 30-40℃ to discharge the material to obtain the heat-resistant strong adhesive.

[0013] Preferably, in step (1) above, the molar ratio of formaldehyde, 1,4-naphthyldiamine, phenol and sodium hydroxide is 1:0.2-0.5:0.3-0.6:0.2-0.3.

[0014] Preferably, in step (2) above, the molar ratio of sodium hydroxide to modified phenolic resin is 1:0.14.

[0015] Preferably, in step (2) above, the molar ratio of modified phenolic resin to epichlorohydrin is 1:1.5 to 2.

[0016] Preferably, in step (3) above, the mass ratio of N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane to nano-silica is 1 to 1.2:2.

[0017] Preferably, in step (3) above: the centrifugation conditions are 8000-10000 r / min and the centrifugation time is 10 min.

[0018] Preferably, in step (4) above, the mass ratio of modified nano-silica to modified epoxy-phenolic resin is 1:45-55.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0020] This invention uses modified phenolic resin and epoxy propane containing epoxy groups to prepare a heat-resistant and strong adhesive, thereby achieving excellent heat resistance, stability and shear strength.

[0021] First, the present invention prepares a modified phenolic resin by co-condensation of 1,4-naphthyldiamine with phenol and formaldehyde. 1,4-naphthyldiamine has a naphthalene ring and two amino functional groups. The naphthalene ring provides good stability, while the introduction of a thermally stable aromatic amine structure into the main chain of the phenolic resin adhesive increases the glass transition temperature, thereby improving the heat resistance of the present invention and maintaining good adhesion and structural stability within the operating temperature range.

[0022] Secondly, epoxy-phenolic resin is generated by reacting epoxy propane with modified phenolic resin under the action of an alkaline catalyst. The epoxy groups can undergo cross-linking reactions with the phenolic hydroxyl groups. The phenolic hydroxyl groups act as nucleophiles, inserting their oxygen atoms into the epoxy ring, forming a new CO bond after ring opening. This creates cross-linking points between molecules, transforming the original linear or branched molecular structure into a three-dimensional network structure. Simultaneously, based on the nucleophilic addition reaction between amine compounds and epoxy groups, 1,4-naphthyldiamine can undergo ring-opening reactions with the epoxy groups of epoxy compounds, forming new chemical bonds. This results in a more stable network structure for the epoxy-phenolic resin, improving the shear strength and peel strength of the invention. The nano-silica is modified with N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, which, as a composite filler rich in amino groups, improves the dispersibility of the nano-silica in the resin while simultaneously forming a more complex three-dimensional network structure through ring-opening crosslinking with epoxy groups. Furthermore, the alkoxy groups of the modifier are partially hydrolyzed to generate silanol groups, forming stable Si-O-Si bonds, thereby improving the overall heat resistance and structural stability of the invention. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] To more clearly illustrate the method provided by the present invention, the following embodiments are provided in detail. The test methods for various indicators of the heat-resistant strong adhesives prepared in the following embodiments and comparative examples are as follows:

[0025] 180° peel strength: The adhesives prepared in the examples and comparative examples were applied to the surface of a PI film with a width of 25 mm and a length of 200 mm. After bonding with metal, the peel strength of the adhesive was tested according to standard GB / T2790. The tensile speed of the universal electronic tensile testing machine was 200 mm / min, and the average value was calculated after 5 measurements.

[0026] Heat resistance: The adhesives prepared in the examples and comparative examples were coated onto the surface of a PI film with a width of 25 mm and a length of 200 mm. After bonding with the metal, the test piece for peel strength testing was placed in an oven at 250°C. After 48 hours, it was taken out and cooled. The peel strength of the adhesive was tested according to standard GB / T2790. The tensile speed of the universal electronic tensile testing machine was 200 mm / min. The test was performed 5 times and the average value was calculated.

[0027] Example 1; (1) 0.3 mol of phenol and 0.2 mol of 20 wt% sodium hydroxide were added to a three-necked flask and stirred at 50 r / min for 10 min until homogeneous. After being kept at 40°C for 20 min, 0.6 mol of formaldehyde and 0.1 mol of 1,4-naphthyldiamine were added to the three-necked flask and mixed to undergo a condensation reaction. The reaction temperature was 60°C and the mixture was stirred at 80 r / min for 20 min. Then the temperature was raised to 75°C and 0.4 mol of formaldehyde and 0.2 mol of 1,4-naphthyldiamine were added. The mixture was stirred at 100 r / min for 20 min until homogeneous. After being kept at 40 min, modified phenolic resin was obtained.

[0028] (2) After cooling the modified phenolic resin to 70°C, add epoxy propane and 50wt% sodium hydroxide as a catalyst. Raise the temperature of the system where the cross-linking reaction occurs to 85°C, stir at 100r / min for 20min to mix evenly, and keep it at the temperature for 1h to obtain epoxy-phenolic resin.

[0029] (3) Disperse silica with a particle size of 20 nm in a 5 wt% ammonia solution at a ratio of 1 mg / mL, then add N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, stir at 45 r / min for 12 h at room temperature, centrifuge to collect the solid, wash with deionized water and anhydrous ethanol respectively, centrifuge 3-5 times, and dry in a 60℃ forced-air oven for 2 h to obtain modified nano silica;

[0030] (4) Modified nano-silica was added to epoxy-phenolic resin, stirred at 80 r / min for 20 min under constant temperature of 80℃, refluxed at 95℃ for 45 min, cooled to 70℃ and degassed for 10 min, and then cooled to 35℃ to discharge the material to obtain the heat-resistant strong adhesive.

[0031] Example 2; (1) 0.5 mol of phenol and 0.25 mol of 24 wt% sodium hydroxide were added to a three-necked flask and stirred at 50 r / min for 10 min until homogeneous. After being kept at 40°C for 20 min, 0.6 mol of formaldehyde and 0.15 mol of 1,4-naphthyldiamine were added to the three-necked flask and mixed to undergo a condensation reaction. The reaction temperature was 60°C and the mixture was stirred at 80 r / min for 20 min. Then the temperature was raised to 75°C and 0.4 mol of formaldehyde and 0.2 mol of 1,4-naphthyldiamine were added. The mixture was stirred at 100 r / min for 20 min until homogeneous. After being kept at 40 min, modified phenolic resin was obtained.

[0032] (2) After cooling the modified phenolic resin to 70°C, add epoxy propane and 60wt% sodium hydroxide as a catalyst. Raise the temperature of the system where the cross-linking reaction occurs to 90°C, stir at 120r / min for 20min to mix evenly, and keep it at the temperature for 1h to obtain epoxy-phenolic resin.

[0033] (3) Silica with a particle size of 20 nm was dispersed in ammonia water with a concentration of 8 wt% at a ratio of 1.4 mg / mL, and then N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane was added. After stirring at 50 r / min for 12 h at room temperature, the solid was centrifuged and washed with deionized water and anhydrous ethanol respectively, centrifuged 3-5 times, and dried in a 60℃ forced-air oven for 2 h to obtain modified nano silica.

[0034] (4) Modified nano-silica was added to epoxy-phenolic resin, stirred at 80 r / min for 30 min under constant temperature of 85℃, refluxed at 95℃ for 60 min, cooled to 70℃ and degassed for 10 min, and then cooled to 35℃ to discharge the material to obtain the heat-resistant strong adhesive.

[0035] Example 3; (1) 0.6 mol of phenol and 0.3 mol of 30 wt% sodium hydroxide were added to a three-necked flask and stirred at 50 r / min for 10 min until homogeneous. After being kept at 45°C for 20 min, 0.6 mol of formaldehyde and 0.3 mol of 1,4-naphthyldiamine were added to the three-necked flask and mixed to undergo a condensation reaction. The reaction temperature was 60°C and the mixture was stirred at 80 r / min for 20 min. The temperature was then raised to 80°C and 0.4 mol of formaldehyde and 0.1 mol of 1,4-naphthyldiamine were added. The mixture was stirred at 100 r / min for 20 min until homogeneous. After being kept at 40 min, modified phenolic resin was obtained.

[0036] (2) After cooling the modified phenolic resin to 70°C, add epoxy propane and 70wt% sodium hydroxide as a catalyst. Raise the temperature of the system where the crosslinking reaction occurs to 90°C, stir at 120r / min for 20min to mix evenly, and keep it at the temperature for 1h to obtain epoxy-phenolic resin.

[0037] (3) Silica with a particle size of 20 nm was dispersed in ammonia water with a concentration of 10 wt% at a ratio of 1.5 mg / mL, and then N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane was added. After stirring at 60 r / min for 12 h at room temperature, the solid was centrifuged and washed with deionized water and anhydrous ethanol respectively, centrifuged 3-5 times, and dried in a 60℃ forced-air oven for 2 h to obtain modified nano silica.

[0038] (4) Modified nano-silica was added to epoxy-phenolic resin, stirred at 80 r / min for 30 min under constant temperature of 90℃, refluxed at 100℃ for 60 min, cooled to 70℃ and degassed for 10 min, and then cooled to 40℃ to discharge the material to obtain the heat-resistant strong adhesive.

[0039] Comparative Example 1; The difference between Comparative Example 1 and Example 2 lies in step (1). Step (1) is changed as follows: 0.5 moles of phenol and 0.25 moles of 10 wt% sodium hydroxide are added to a three-necked flask, stirred at 50 r / min for 10 min until homogeneous, and kept at 40°C for 20 min. Then, 0.6 moles of formaldehyde and 0.1 moles of 1,4-naphthyldiamine are added to the three-necked flask to react and undergo a condensation reaction at 60°C. After stirring at 80 r / min for 20 min, the temperature is raised to 75°C, 0.4 moles of formaldehyde are added, and stirred at 100 r / min for 20 min until homogeneous. The mixture is then kept at 40 min to obtain the modified phenolic resin. The remaining steps are the same as in Example 2.

[0040] Comparative Example 2; The difference between Comparative Example 2 and Example 2 lies in step (1). Step (1) is changed as follows: 0.5 moles of phenol and 0.25 moles of sodium hydroxide with a concentration of 24 wt% are added to a three-necked flask, stirred at 50 r / min for 10 min until homogeneous, and kept at 40°C for 20 min. Then, 0.5 moles of formaldehyde and 0.15 moles of 1,4-naphthyldiamine are added to the three-necked flask to mix and undergo a condensation reaction. The reaction temperature is 60°C, and the mixture is stirred at 80 r / min for 20 min. Then, the temperature is raised to 75°C, and 0.2 moles of 1,4-naphthyldiamine are added. The mixture is stirred at 100 r / min for 20 min until homogeneous, and kept at 40 min to obtain modified phenolic resin. The remaining steps are the same as in Example 2.

[0041] Comparative Example 3; The difference between Comparative Example 3 and Example 2 is the difference in step (2). Step (2) is changed to: after cooling the modified phenolic resin to 70°C, add epoxybromopropane and 24wt% sodium hydroxide as a catalyst, raise the temperature of the system in which the crosslinking reaction occurs to 75°C, stir at 50r / min for 20min to mix evenly, and keep it at the temperature for 1h to obtain epoxy-phenolic resin; the remaining steps are the same as in Example 2.

[0042] Comparative Example 4; The difference between Comparative Example 4 and Example 2 is that step (3) is omitted, and step (4) is changed to: adding nano-silica with a particle size of 20nm to epoxy-phenolic resin, stirring at 80r / min for 30min under constant temperature of 85℃, refluxing at 95℃ for 60min, cooling to 70℃ and degassing for 10min, and then cooling to 35℃ to discharge the material to obtain the heat-resistant strong adhesive; the remaining steps are the same as in Example 2.

[0043] Example of effect

[0044] Table 1 below shows the performance analysis results of the heat-resistant and strong adhesives of Examples 1 to 3 and Comparative Examples 1 to 4 of the present invention.

[0045] Table 1

[0046]

[0047]

[0048] A comparison of the experimental data on 180° peel strength and 180° peel strength after 48 hours at high temperature between the examples and comparative examples reveals that the present invention, through the co-condensation of 1,4-naphthyldiamine with phenol and formaldehyde, prepares a modified phenolic resin. This introduces a thermally stable aromatic amine structure into the main chain of the phenolic resin adhesive, thereby increasing the glass transition temperature and improving the heat resistance of the invention, thus maintaining good adhesion and structural stability within the operating temperature range. Furthermore, the modification of the phenolic resin using epichlorohydrin allows the phenolic hydroxyl group to act as a nucleophile, inserting its oxygen atom into the epoxy ring. After ring opening, a new CO bond is formed, creating crosslinking points between molecules. This transforms the original linear or branched molecular structure into a three-dimensional network structure, improving the shear strength and adhesive properties of the adhesive. Viscosity strength; simultaneously, based on the nucleophilic addition reaction between amine compounds and epoxy groups, 1,4-naphthyldiamine can undergo ring-opening reaction with the epoxy groups of epoxy compounds to form new chemical bonds, thereby giving the epoxy-phenolic resin a more stable network structure, further improving the shear strength and peel strength of the present invention; N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane-modified nano-silica, as a composite filler with amino-rich surface, improves the dispersibility of nano-silica in the resin, while forming a more complex three-dimensional network structure through ring-opening crosslinking with epoxy groups, and the alkoxy portion of the modifier hydrolyzes to generate silanol groups, forming stable Si-O-Si bonds, thereby improving the overall heat resistance and structural stability of the present invention.

[0049] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A heat-resistant, high-strength adhesive, characterized in that, The heat-resistant high-strength adhesive comprises epoxy-phenolic resin and modified nano-silica; The epoxy-phenolic resin is prepared by co-condensation of 1,4-naphthyldiamine, phenol and formaldehyde to obtain a modified phenolic resin, which is then crosslinked with epoxybromopropane. The modified nano-silica was prepared by modification with N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane; The preparation method of the heat-resistant high-strength adhesive includes the following preparation steps: (1) Add 0.3~0.6 mol of phenol and 0.2~0.3 mol of sodium hydroxide with a concentration of 20~30wt% to a three-necked flask, stir at 50 r / min for 10 min until uniform, keep warm at 35~45℃ for 20 min, add 0.6 mol of formaldehyde and 0.1~0.3 mol of 1,4-naphthyldiamine to the three-necked flask and mix to undergo a condensation reaction. The reaction temperature is 60℃, stir at 80 r / min for 20 min, then raise the temperature to 75~80℃, add 0.4 mol of formaldehyde and 0.1~0.2 mol of 1,4-naphthyldiamine, stir at 100 r / min for 20 min until uniform, keep warm for 40 min to obtain modified phenolic resin; (2) After cooling the modified phenolic resin to 70°C, add epoxy propane and 50-70 wt% sodium hydroxide as a catalyst. Raise the temperature of the system where the cross-linking reaction occurs to 85-90°C, stir at 100-120 r / min for 20 min to mix evenly, and keep warm for 1 h to obtain epoxy-phenolic resin. (3) Disperse silica with a particle size of 20 nm in ammonia water with a concentration of 5-10 wt% at a ratio of 1-1.5 mg / mL, then add N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, stir at 45-60 r / min for 12 h at room temperature, centrifuge to collect the solid, wash with deionized water and anhydrous ethanol respectively, centrifuge 3-5 times, and dry in a 60℃ forced-air oven for 2 h to obtain modified nano silica; (4) Modified nano-silica is added to epoxy-phenolic resin. After mixing at a constant temperature of 80~90℃ for 20~30min at 80r / min, it is refluxed at 95~100℃ for 45~60min, cooled to 70℃ and degassed for 10min. Then, it is cooled to 30~40℃ and discharged to obtain the heat-resistant strong adhesive.

2. The method for preparing a heat-resistant high-strength adhesive according to claim 1, characterized in that, In step (1), the molar ratio of formaldehyde, 1,4-naphthyldiamine, phenol and sodium hydroxide is 1:0.2~0.5:0.3~0.6:0.2~0.

3.

3. The method for preparing a heat-resistant high-strength adhesive according to claim 1, characterized in that, In step (2), the molar ratio of sodium hydroxide to modified phenolic resin is 1:0.

14.

4. The method for preparing a heat-resistant high-strength adhesive according to claim 1, characterized in that, In step (2), the molar ratio of modified phenolic resin to epichlorohydrin is 1:1.5~2.

5. The method for preparing a heat-resistant high-strength adhesive according to claim 1, characterized in that, In step (3), the mass ratio of N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane to nano-silica is 1~1.2:

2.

6. The method for preparing a heat-resistant high-strength adhesive according to claim 1, characterized in that, In step (3), the centrifugation conditions are 8000~10000 r / min and the centrifugation time is 10 min.

7. The method for preparing a heat-resistant high-strength adhesive according to claim 1, characterized in that, In step (4), the mass ratio of modified nano-silica to modified epoxy-phenolic resin is 1:45~55.

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