Aerogel for adhesives and method of preparation and use thereof

Abstract

The present application belongs to the technical field of aerogel materials, and particularly relates to an aerogel for adhesives, a preparation method and application thereof. The present application prepares active polyimide aerogel by taking amide group-containing diamine monomer and phenolic hydroxyl-containing diamine monomer as raw materials. Due to the presence of phenolic hydroxyl, polyimide powder can react with epoxy groups of epoxy resin to form covalent bonds, thereby improving the compatibility of the two, and making the epoxy resin system achieve good toughening effect. The introduction of amide group-containing diamine monomer breaks the regularity of the polyimide main chain, not only improves the mechanical properties of the polyimide material, but also helps the formation of the gel network, improves the gel porosity, is conducive to the infiltration of the adhesive resin, and further improves the mechanical strength of the adhesive.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aerogel materials, and particularly relates to an aerogel for adhesives, a preparation method and application thereof. BACKGROUND

[0002] An adhesive is a kind of organic or inorganic, natural or synthetic substance that can connect the same kind / two or more than two kinds of homogeneous or heterogeneous parts or materials together, and has sufficient strength after solidification. The adhesive is combined with the bonded material through surface adhesion, chemical bond, diffusion, physical adsorption and other effects, and compared with other bonding methods, has the characteristics of high strength, convenient use, etc., and is widely used in the fields of automobile industry, aerospace, household appliances, biomedicine and dentistry, etc.

[0003] At present, in the manufacturing industry, adhesives are widely used in the bonding of various materials due to their unique properties such as curing period, bonding strength, weather resistance and moisture resistance. The research focus of adhesives is to enhance the bonding strength and tensile stress, improve the corrosion resistance, reduce the curing period and reduce the use thickness of the adhesive, etc. These research progresses greatly meet the diversified needs of the market for adhesive applications.

[0004] The adhesives used on the market mainly include inorganic adhesives and organic adhesives. The inorganic adhesives are mainly composed of inorganic salts, inorganic alkali metals, inorganic acids, metal oxides and hydroxides, etc. According to the types of inorganic salts, the inorganic adhesives can be divided into sulfate, phosphate, silicate and borate adhesives. Due to the outstanding advantages of inorganic materials, inorganic adhesives have excellent high and low temperature resistance, can be used in the range of-180℃-3000℃, have small curing shrinkage, simple construction process, low cost and are widely used in the fields of mechanical manufacturing and maintenance, building coatings, etc. However, the inorganic adhesives have low acid and alkali resistance, high brittleness, poor impact resistance and low bonding strength, and the performance is difficult to improve, which limits the application of inorganic adhesives.

[0005] CN117659920A provides a high shear strength silver nanosheet / epoxy resin conductive adhesive and a preparation method thereof. The components of the conductive adhesive include silver nanosheet 60-70 parts by weight, epoxy resin 30-40 parts by weight, curing agent 1-2 parts by weight, defoaming agent 0.05-0.1 parts by weight, diluent 8-12 parts by weight, ferrocene derivative 1-5 parts by weight. The ferrocene derivative is prepared by reacting ferrocene formaldehyde with 3,3'-dimercapto benzidine. The ferrocene derivative has good conductivity, and can react with the epoxy group of the substrate through -SH and -NH3, and strong interaction can be formed between S and Ag, so that the addition of the ferrocene derivative can improve the shear strength and conductivity of the silver nanosheet / epoxy resin conductive adhesive. CN115181524A solves the problem that the existing epoxy resin adhesive preparation method cannot simultaneously consider normal temperature shear strength and medium-high temperature shear strength. The method is: first, add a cosolvent into a reaction bottle, then add a silicate and a silane coupling agent, then add a catalyst, after heating, add an acid aqueous solution dropwise, heat and react, then add an epoxy resin, vacuum rotary evaporation, to obtain a SiO2 hybrid epoxy resin; second, mix the SiO2 hybrid epoxy resin and an equivalent amount of an amine curing agent uniformly to obtain a SiO2 hybrid epoxy resin adhesive. The method significantly improves the compatibility of SiO2 inorganic nanoparticles and the epoxy resin, and the formed IPN structure significantly improves the comprehensive performance of the epoxy adhesive. Although the above-mentioned patents improve the mechanical properties of the adhesive to some extent, there are compatibility problems in the modification of a large amount of inorganic fillers. SUMMARY

[0006] The present application provides an aerogel for adhesives and a preparation method and application thereof. The preparation process is simple, low in cost, easy to operate, and the raw materials are easy to obtain, which is conducive to industrial production. The mechanical properties of the adhesive modified by the aerogel are excellent, and the application prospect is broad, especially in the field of epoxy resin adhesives.

[0007] The object of the application is achieved by the following technical scheme:

[0008] A preparation method of an aerogel for adhesives, comprising the following steps:

[0009] (1) adding an amide-containing diamine monomer and a phenolic hydroxyl-containing diamine monomer into an organic solvent to obtain a diamine monomer mixed solution; the molar ratio of the amide-containing diamine monomer to the phenolic hydroxyl-containing diamine monomer is (0-0.5):1; the amount of the amide-containing diamine monomer is not 0;

[0010] (2) adding a dianhydride monomer into the diamine monomer mixed solution in batches, and obtaining a polyamic acid after reaction;

[0011] (3) adding the polyamic acid into deionized water, and obtaining a polyamic acid powder after precipitation.

[0012] (4) Polyamic acid powder and organic alkaline compound are added to deionized water, and polyamic acid hydrogel is obtained after sol-gelation.

[0013] (5) Dry the polyamic acid hydrogel, partially heat imidize it, and pulverize it to obtain an aerogel for adhesives.

[0014] Polyimide typically cannot be directly fused with epoxy resin, while polyamic acid, the precursor of polyimide, is a liquid substance with a certain viscosity that can be uniformly mixed in epoxy resin, making the process extremely simple. The inventors previously used polyamic acid to modify adhesives. However, polyamic acid is mostly in a liquid state, exhibiting extremely poor stability and requiring immediate preparation, which limits its large-scale application. Aerogel materials, as lightweight materials with porous structures, are widely used as reinforcing stabilizers in bonding resin composites. Traditional inorganic aerogel materials have low strength, are brittle, and are difficult to process. Although common polymer aerogels are easier to process than inorganic aerogels, they still suffer from poor heat resistance. In contrast, polyimide-based aerogels retain the general properties of aerogel materials and, thanks to the excellent mechanical properties and high-temperature thermal stability of polyimide, overcome the shortcomings of traditional aerogels, such as low strength.

[0015] Therefore, this invention prepares an active polyimide aerogel using amide-containing diamine monomers and phenolic hydroxyl-containing diamine monomers as raw materials. Due to the presence of phenolic hydroxyl groups, the polyimide powder can react with the epoxy groups of the epoxy resin to form covalent bonds, thereby improving the compatibility between the two and enabling the epoxy resin system to achieve a good toughening effect. However, the introduction of a large number of phenolic hydroxyl groups also leads to a decrease in the mechanical strength of the polyimide itself. To solve this problem, this invention selects to add a certain amount of amide-containing diamine monomers. The introduction of amide-containing diamine monomers breaks the regularity of the polyimide main chain, which not only improves the mechanical properties of the polyimide material but also helps in the formation of a gel network, increases gel porosity, and facilitates the wetting of the adhesive resin. Furthermore, the amide-containing diamine monomers contain a large number of active amide bonds, which are conducive to further forming hydrogen bonds with the epoxy resin, promoting the formation of the hydrogen bond network of the adhesive, and further improving the mechanical strength of the adhesive.

[0016] Further, the phenolic hydroxy diamine monomer mentioned in step (1) is one or more of the following: 2,2-bis(3-amino-4-hydroxyphenyl)propane, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 3,3-diamino-4,4-dihydroxydiphenyl sulfone, 9,9-bis(3-amino-4-hydroxyphenyl)fluorene, 3,3-diamino-4,4-dihydroxybiphenyl, 3,3-dihydroxy-4,4-diaminodiphenylmethane, 4,4-diamino-4-hydroxytriphenylmethane, bis(5-amino-2-hydroxyphenyl)methane, 3,3-diamino-4,4-dihydroxydiphenyl sulfide, and 3,3-diamino-4,4-dihydroxydiphenyl ether.

[0017] Furthermore, the amide-containing diamine monomer mentioned in step (1) is one or more of 4,4-diaminobenzoyl aniline, 2-chloro-4,4-diaminobenzoyl aniline, 3,4-diaminobenzoyl aniline, 2-methyl-4,4-diaminobenzoyl aniline, and 3-methyl-4,4-diaminobenzoyl aniline;

[0018] Furthermore, the organic solvent mentioned in step (1) is one or more of N,N-dimethylacetamide, dimethyl sulfoxide, N,N-dimethylformamide, and N-methylpyrrolidone;

[0019] Further, the dianhydride monomers mentioned in step (2) are pyromellitic dianhydride, 3,3,4,4-diphenyl ether tetracarboxylic dianhydride, 3,3,4,4-biphenyl tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride, 4,4-hexafluoroisopropylphthalic anhydride, 2,3,3,4-benzophenone tetracarboxylic dianhydride, 3,3,4,4-benzophenone tetracarboxylic dianhydride, 3,3,4,4-biphenyl tetracarboxylic dianhydride, and p- One or more of the following: phenylene-bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)phenyl dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)phenyl dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, and 2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride. Specifically, the dianhydride monomer is pyromellitic dianhydride, 3,3,4,4-diphenyl ether tetracarboxylic dianhydride, 3,3,4,4-biphenyltetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride, 4,4-hexafluoroisopropylphthalic anhydride, 2,3,3,4-benzophenone tetracarboxylic dianhydride, 3,3,4,4-benzophenone tetracarboxylic dianhydride, 3,3,4,4-biphenyltetracarboxylic dianhydride, and p-phenylene-bisphenyltrilate dianhydride. Further, it is selected from biphenyl dianhydrides and ester-based dianhydrides. Further, the dianhydride is selected from 3,3,4,4-biphenyltetracarboxylic dianhydride and p-phenylene-bisphenyltrilate dianhydride. Furthermore, the molar ratio of 3,3,4,4-biphenyltetracarboxylic dianhydride to p-phenylene-bisphenyltriester dianhydride is (0.1-1):1; further, it is (0.3-0.5):1. By selecting ester-containing dianhydrides and biphenyl dianhydrides, the formation of hydrogen bonds in the system can be further promoted, improving the stability of the aerogel structure; and the combination of flexible ester-containing dianhydrides and rigid biphenyl dianhydrides can improve the stiffness and toughness of the aerogel network, thereby enhancing the mechanical properties of the adhesive.

[0020] Furthermore, in step (2), the dianhydride monomer is added to the diamine monomer mixture in 2-6 portions (evenly distributed among the dianhydride monomer mixture), with an interval of 2-6 minutes between each addition; the molar ratio of the dianhydride monomer to the diamine monomer is (1-1.04):1.

[0021] Furthermore, the reaction temperature in step (2) is 25-35℃, and the reaction time is 6-10h;

[0022] Furthermore, the precipitation process described in step (3) also includes subsequent washing and drying processes.

[0023] Furthermore, the organic alkaline compound mentioned in step (4) is at least one of triethylamine, tripropylamine, diethylenetriamine, triethylenetetramine, and triethylenediamine; the mass ratio of the polyamic acid powder to the organic alkaline compound is 1:(0.1-1).

[0024] Furthermore, the drying process described in step (5) is freeze-drying or supercritical drying.

[0025] Furthermore, the partial thermal imidization described in step (5) involves holding at 100-180℃ for 1-3 hours. Specifically, it involves holding at 140-160℃ for 1.5-2.5 hours. In particular, the carboxyl groups on the partially imidized aerogel mainly react with the epoxy groups. Each unit has two active hydrogens at different positions, which may react simultaneously, thus forming a complex macromolecular ester graft copolymer and an interpenetrating network structure. When the temperature reaches 200-300℃, the carboxyl groups that have not reacted with the epoxy and the amino groups on the adjacent benzene ring undergo a condensation reaction to form a five-membered ring group. The formation of this stable five-membered ring further improves the stability of the system, which is particularly beneficial to the improvement of heat resistance. Due to the presence of imide groups, the heat resistance of the system can be improved by using partially imidized aerogel to modify epoxy resin adhesives.

[0026] On the other hand, the present invention also provides an aerogel for adhesives and its application, which uses modified aerogel in the field of adhesives, wherein the adhesive comprises a bonding resin and an aerogel, which can greatly improve the mechanical properties of resin adhesives.

[0027] Specifically, the adhesive may optionally contain components such as bonding resin, aerogel, curing agent, and a small amount of diluent.

[0028] Specifically, the adhesive resin is polyurethane, epoxy resin, phenolic resin, silicone resin, acrylic resin, etc.

[0029] Beneficial effects:

[0030] (1) Polyimide-based aerogels retain the general properties of aerogel materials and benefit from the excellent mechanical properties and high-temperature thermal stability of polyimide, thus overcoming the shortcomings of traditional aerogels such as low strength.

[0031] (2) An active polyimide aerogel was prepared using amide-containing diamine monomers and phenol-hydroxyl-containing diamine monomers as raw materials. Due to the presence of phenolic hydroxyl groups, the polyimide powder can react with the epoxy groups of the epoxy resin to form covalent bonds, thereby improving the compatibility between the two and enabling the epoxy resin system to achieve a good toughening effect. The introduction of amide-containing diamine monomers breaks the regularity of the polyimide main chain, which not only improves the mechanical properties of the polyimide material, but also helps to form a gel network, increases the gel porosity, and facilitates the wetting of the adhesive resin. In addition, the amide-containing diamine monomers contain a large number of active amide bonds, which are conducive to further forming hydrogen bonds with the epoxy resin, promoting the formation of the hydrogen bond network of the adhesive, and further improving the mechanical strength of the adhesive. Detailed Implementation

[0032] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0033] Unless otherwise specified, the raw material types and specific process parameters of the following examples and comparative examples are consistent. The product performance testing method is as follows: under the same conditions, the effect of the aerogel prepared in Examples 1-10 and Comparative Example 1 on the performance of the epoxy resin adhesive is tested. The epoxy resin adhesive comprises: 100 parts E-51 epoxy resin, 4.5 parts aerogel, 20 parts 4,4'-diaminodiphenyl sulfone, etc. After the epoxy resin and aerogel are mixed evenly, the curing agent 4,4'-diaminodiphenyl sulfone is added, and the mixture is stirred at 95°C for 0.6 hours to obtain the epoxy resin adhesive. The epoxy resin adhesive is uniformly coated on the treated aluminum alloy surface and cured at 120°C for 0.5 hours, 150°C for 0.5 hours, 170°C for 1.5 hours, 210°C for 1.5 hours, and 250°C for 1.5 hours; the curing pressure is 0.2 MPa. The shear strength is tested according to GB7124-86.

[0034] Example 1

[0035] A method for preparing an aerogel for adhesives includes the following steps:

[0036] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenol-hydroxy diamine monomer to the organic solvent N,N-dimethylacetamide to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer and the phenol-hydroxy diamine monomer is 0.1:1; the phenol-hydroxy diamine monomer is 2,2-bis(3-amino-4-hydroxyphenyl)propane;

[0037] (2) The dianhydride monomer is added in batches to the mixed solution of diamine monomers, and polyamic acid is obtained after the reaction; the dianhydride monomer is 3,3,4,4-diphenyl ether tetracarboxylic dianhydride; the dianhydride monomer is added to the mixed solution of diamine monomers in three batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.01:1; the reaction temperature is 25℃ and the reaction time is 10h;

[0038] (3) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0039] (4) Polyamic acid powder and triethylamine, an organic alkaline compound, are added to deionized water, and polyamic acid hydrogel is obtained after sol-gelation; the mass ratio of polyamic acid powder to organic alkaline compound is 1:0.4.

[0040] (5) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 145℃ for 3 hours, and then pulverized to obtain an aerogel for adhesives. The shear strength of the aerogel-modified adhesive was tested to be 24.8 MPa.

[0041] Example 2

[0042] A method for preparing an aerogel for adhesives includes the following steps:

[0043] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenol-hydroxy diamine monomer to the organic solvent N-methylpyrrolidone to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer to the phenol-hydroxy diamine monomer is 0.5:1; the phenol-hydroxy diamine monomer is 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane;

[0044] (2) The dianhydride monomer is added in batches to the mixed solution of diamine monomers, and polyamic acid is obtained after the reaction; the dianhydride monomer is a mixture of pyromellitic dianhydride and 3,3,4,4-diphenyl ether tetracarboxylic dianhydride in a molar ratio of 1:1; the dianhydride monomer is added to the mixed solution of diamine monomers in three batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.01:1; the reaction temperature is 35℃ and the reaction time is 6h;

[0045] (3) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0046] (4) Polyamic acid powder and triethylamine, an organic alkaline compound, are added to deionized water, and polyamic acid hydrogel is obtained after sol-gelation; the mass ratio of polyamic acid powder to organic alkaline compound is 1:0.8.

[0047] (5) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 160℃ for 1 hour, and then pulverized to obtain an aerogel for adhesives. The shear strength of the aerogel-modified adhesive was tested to be 27.5 MPa.

[0048] Example 3

[0049] A method for preparing an aerogel for adhesives includes the following steps:

[0050] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenol-hydroxy diamine monomer to the organic solvent N,N-dimethylacetamide to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer to the phenol-hydroxy diamine monomer is 0.3:1; the phenol-hydroxy diamine monomer is 3,3-diamino-4,4-dihydroxydiphenyl sulfone;

[0051] (2) The dianhydride monomer is added in batches to the mixed solution of diamine monomers, and polyamic acid is obtained after the reaction; the dianhydride monomer is 3,3,4,4-biphenyltetracarboxylic dianhydride; the dianhydride monomer is added to the mixed solution of diamine monomers in three batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.01:1; the reaction temperature is 30℃ and the reaction time is 8h;

[0052] (3) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0053] (4) Polyamic acid powder and triethylamine, an organic alkaline compound, are added to deionized water, and polyamic acid hydrogel is obtained after sol-gelation; the mass ratio of polyamic acid powder to organic alkaline compound is 1:0.6.

[0054] (5) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 152℃ for 2 hours, and then pulverized to obtain an aerogel for adhesives. The shear strength of the aerogel-modified adhesive was tested to be 26.0 MPa.

[0055] Example 4

[0056] A method for preparing an aerogel for adhesives includes the following steps:

[0057] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenol-hydroxy diamine monomer to the organic solvent N,N-dimethylacetamide to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer and the phenol-hydroxy diamine monomer is 0.5:1; the phenol-hydroxy diamine monomer is 3,3-diamino-4,4-dihydroxydiphenyl sulfone;

[0058] (2) The dianhydride monomer is added in batches to the mixed solution of diamine monomers, and polyamic acid is obtained after the reaction; the dianhydride monomer is 2,2-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride; the dianhydride monomer is added to the mixed solution of diamine monomers in three batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.01:1; the reaction temperature is 25℃ and the reaction time is 6h;

[0059] (3) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0060] (4) Polyamic acid powder and triethylamine, an organic alkaline compound, are added to deionized water, and polyamic acid hydrogel is obtained after sol-gelation; the mass ratio of polyamic acid powder to organic alkaline compound is 1:0.5.

[0061] (5) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 150°C for 1.3 h, and then pulverized to obtain an aerogel for adhesives. The shear strength of the aerogel-modified adhesive was tested to be 25.1 MPa.

[0062] Example 5

[0063] A method for preparing an aerogel for adhesives includes the following steps:

[0064] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenol-hydroxy diamine monomer to the organic solvent N,N-dimethylacetamide to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer to the phenol-hydroxy diamine monomer is 0.3:1; the phenol-hydroxy diamine monomer is 3,3-diamino-4,4-dihydroxydiphenyl sulfone;

[0065] (2) The dianhydride monomer is added in batches to the mixed solution of diamine monomers, and polyamic acid is obtained after the reaction; the dianhydride monomer is p-phenylene-bisphenyltriester dianhydride; the dianhydride monomer is added to the mixed solution of diamine monomers in three batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.01:1; the reaction temperature is 30℃ and the reaction time is 8h;

[0066] (3) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0067] (4) Polyamic acid powder and triethylamine, an organic alkaline compound, are added to deionized water, and polyamic acid hydrogel is obtained after sol-gelation; the mass ratio of polyamic acid powder to organic alkaline compound is 1:0.6.

[0068] (5) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 152℃ for 2 hours, and then pulverized to obtain an aerogel for adhesives. The shear strength of the aerogel-modified adhesive was tested to be 25.3 MPa.

[0069] Example 6

[0070] A method for preparing an aerogel for adhesives includes the following steps:

[0071] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenol-hydroxy diamine monomer to the organic solvent N-methylpyrrolidone to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer to the phenol-hydroxy diamine monomer is 0.2:1; the phenol-hydroxy diamine monomer is 3,3-diamino-4,4-dihydroxybiphenyl;

[0072] (2) The dianhydride monomer is added in batches to the diamine monomer mixture solution, and polyamic acid is obtained after the reaction; the dianhydride monomer is a mixture of 2,3,3,4-benzophenone tetracarboxylic dianhydride and 3,3,4,4-biphenyltetracarboxylic dianhydride in a molar ratio of 1:1; the dianhydride monomer is added to the diamine monomer mixture solution in three batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.01:1; the reaction temperature is 28℃ and the reaction time is 9h;

[0073] (3) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0074] (4) Polyamic acid powder and triethylamine, an organic alkaline compound, are added to deionized water, and polyamic acid hydrogel is obtained after sol-gelation; the mass ratio of polyamic acid powder to organic alkaline compound is 1:0.5.

[0075] (5) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 149℃ for 2.8h, and then pulverized to obtain an aerogel for adhesives. The shear strength of the aerogel-modified adhesive was tested to be 25.8MPa.

[0076] Example 7

[0077] A method for preparing an aerogel for adhesives includes the following steps:

[0078] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenol-hydroxy diamine monomer to the organic solvent N,N-dimethylacetamide to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer to the phenol-hydroxy diamine monomer is 0.3:1; the phenol-hydroxy diamine monomer is 3,3-diamino-4,4-dihydroxydiphenyl sulfone;

[0079] (2) The dianhydride monomer is added in batches to the mixed solution of diamine monomers, and polyamic acid is obtained after the reaction; the dianhydride monomer is a mixture of 3,3,4,4-biphenyltetracarboxylic dianhydride and p-phenylene-bisphenyltrilate dianhydride in a molar ratio of 1:0.5; the dianhydride monomer is added to the mixed solution of diamine monomers in three batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.01:1; the reaction temperature is 30℃ and the reaction time is 8h;

[0080] (3) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0081] (4) Polyamic acid powder and triethylamine, an organic alkaline compound, are added to deionized water, and polyamic acid hydrogel is obtained after sol-gelation; the mass ratio of polyamic acid powder to organic alkaline compound is 1:0.6.

[0082] (5) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 152℃ for 2 hours, and then pulverized to obtain an aerogel for adhesives. The shear strength of the aerogel-modified adhesive was tested to be 26.2 MPa.

[0083] Example 8

[0084] A method for preparing an aerogel for adhesives includes the following steps:

[0085] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenol-hydroxy diamine monomer to the organic solvent N,N-dimethylacetamide to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer to the phenol-hydroxy diamine monomer is 0.4:1; the phenol-hydroxy diamine monomer is 2,2-bis(3-amino-4-hydroxyphenyl)propane;

[0086] (2) The dianhydride monomer is added in batches to the diamine monomer mixture solution, and polyamic acid is obtained after the reaction; the dianhydride monomer is a mixture of pyromellitic dianhydride and 3,3,4,4-biphenyltetracarboxylic dianhydride in a molar ratio of 1:1; the dianhydride monomer is added to the diamine monomer mixture solution in three batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.01:1; the reaction temperature is 31℃ and the reaction time is 7h;

[0087] (3) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0088] (4) Polyamic acid powder and triethylamine, an organic alkaline compound, are added to deionized water, and polyamic acid hydrogel is obtained after sol-gelation; the mass ratio of polyamic acid powder to organic alkaline compound is 1:0.7.

[0089] (5) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 155℃ for 2.5h, and then pulverized to obtain an aerogel for adhesives. The shear strength of the aerogel-modified adhesive was tested to be 26.7MPa.

[0090] Example 9

[0091] A method for preparing an aerogel for adhesives includes the following steps:

[0092] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenol-hydroxy diamine monomer to the organic solvent N,N-dimethylacetamide to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer to the phenol-hydroxy diamine monomer is 0.2:1; the phenol-hydroxy diamine monomer is 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane;

[0093] (2) The dianhydride monomer is added in batches to the mixed solution of diamine monomers, and polyamic acid is obtained after the reaction; the dianhydride monomer is a mixture of 3,3,4,4-benzophenone tetracarboxylic dianhydride and 3,3,4,4-biphenyltetracarboxylic dianhydride in a molar ratio of 1:1; the dianhydride monomer is added to the mixed solution of diamine monomers in three batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.01:1; the reaction temperature is 29°C and the reaction time is 7.5 h;

[0094] (3) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0095] (4) Polyamic acid powder and triethylamine, an organic alkaline compound, are added to deionized water, and polyamic acid hydrogel is obtained after sol-gelation; the mass ratio of polyamic acid powder to organic alkaline compound is 1:0.6.

[0096] (5) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 155℃ for 2.2 h, and then pulverized to obtain an aerogel for adhesives. The shear strength of the aerogel-modified adhesive was tested to be 27.3 MPa.

[0097] Example 10

[0098] A method for preparing an aerogel for adhesives includes the following steps:

[0099] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenol-hydroxy diamine monomer to the organic solvent N,N-dimethylacetamide to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer to the phenol-hydroxy diamine monomer is 0.3:1; the phenol-hydroxy diamine monomer is 3,3-diamino-4,4-dihydroxydiphenyl sulfone;

[0100] (2) The dianhydride monomer is added in batches to the mixed solution of diamine monomers, and polyamic acid is obtained after the reaction; the dianhydride monomer is a mixture of 3,3,4,4-biphenyltetracarboxylic dianhydride and p-phenylene-bisphenyltrilate dianhydride in a molar ratio of 0.5:1; the dianhydride monomer is added to the mixed solution of diamine monomers in three batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.01:1; the reaction temperature is 30℃ and the reaction time is 8h;

[0101] (3) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0102] (4) Polyamic acid powder and triethylamine, an organic alkaline compound, are added to deionized water, and polyamic acid hydrogel is obtained after sol-gelation; the mass ratio of polyamic acid powder to organic alkaline compound is 1:0.6.

[0103] (5) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 152℃ for 2 hours, and then pulverized to obtain an aerogel for adhesives. The shear strength of the aerogel-modified adhesive was tested to be 28.8 MPa.

[0104] Comparative Example 1

[0105] A method for preparing an aerogel for adhesives includes the following steps:

[0106] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenol-hydroxy diamine monomer to the organic solvent N,N-dimethylacetamide to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer to the phenol-hydroxy diamine monomer is 1:1; the phenol-hydroxy diamine monomer is 3,3-diamino-4,4-dihydroxydiphenyl sulfone;

[0107] (2) The dianhydride monomer is added in batches to the mixed solution of diamine monomers, and polyamic acid is obtained after the reaction; the dianhydride monomer is a mixture of 3,3,4,4-biphenyltetracarboxylic dianhydride and p-phenylene-bisphenyltrilate dianhydride in a molar ratio of 0.5:1; the dianhydride monomer is added to the mixed solution of diamine monomers in three batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.01:1; the reaction temperature is 30℃ and the reaction time is 8h;

[0108] (3) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0109] (4) Polyamic acid powder and triethylamine, an organic alkaline compound, are added to deionized water, and polyamic acid hydrogel is obtained after sol-gelation; the mass ratio of polyamic acid powder to organic alkaline compound is 1:0.6.

[0110] (5) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 152℃ for 2 hours, and then pulverized to obtain an aerogel for adhesives. The shear strength of the aerogel-modified adhesive was tested to be 18.8 MPa.

[0111] As can be seen from the above examples and comparative examples, this invention prepares an active polyimide aerogel using amide-containing diamine monomers and phenolic hydroxyl-containing diamine monomers as raw materials. Due to the presence of phenolic hydroxyl groups, the polyimide powder can react with the epoxy groups of the epoxy resin to form covalent bonds, thereby improving the compatibility between the two and enabling the epoxy resin system to achieve a good toughening effect. However, the introduction of a large number of phenolic hydroxyl groups also leads to a decrease in the mechanical strength of the polyimide itself. To solve this problem, this invention selects to add a certain amount of amide-containing diamine monomers. The introduction of amide-containing diamine monomers breaks the regularity of the polyimide main chain, which not only improves the mechanical properties of the polyimide material but also helps in the formation of a gel network, increases gel porosity, and facilitates the wetting of the adhesive resin. Furthermore, the amide-containing diamine monomers contain a large number of active amide bonds, which are beneficial for further forming hydrogen bonds with the epoxy resin, promoting the formation of the hydrogen bond network of the adhesive, and further improving the mechanical strength of the adhesive. However, the amount of amide-diamine monomer used should not be excessive, otherwise it will lead to the formation of polyimide with amide-diamine monomer as the main structure, affecting the interaction between phenolic hydroxyl diamine monomer and epoxy adhesive, and hindering the improvement of mechanical properties. Compared with Example 10, the amount of amide-diamine monomer used in Comparative Example 1 was excessive, affecting the interaction between phenolic hydroxyl diamine monomer and epoxy adhesive, resulting in a decrease in the shear strength of the adhesive.

[0112] The above description is merely a preferred embodiment of the invention and is not intended to limit the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should be considered within the technical scope of this invention.

Claims

1. A method for preparing an aerogel for adhesives, characterized in that, Includes the following steps: (1) Add the amide-containing diamine monomer and the phenol-hydroxyl-containing diamine monomer to an organic solvent to obtain a mixed solution of diamine monomers; The amide-containing diamine monomer is one or more of 4,4-diaminobenzoyl aniline, 2-chloro-4,4-diaminobenzoyl aniline, 3,4-diaminobenzoyl aniline, 2-methyl-4,4-diaminobenzoyl aniline, and 3-methyl-4,4-diaminobenzoyl aniline. The phenol-hydroxy diamine monomer is one or more of the following: 2,2-bis(3-amino-4-hydroxyphenyl)propane, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 3,3-diamino-4,4-dihydroxydiphenyl sulfone, 9,9-bis(3-amino-4-hydroxyphenyl)fluorene, 3,3-diamino-4,4-dihydroxybiphenyl, 3,3-dihydroxy-4,4-diaminodiphenylmethane, 4,4-diamino-4-hydroxytriphenylmethane, bis(5-amino-2-hydroxyphenyl)methane, 3,3-diamino-4,4-dihydroxydiphenyl sulfide, and 3,3-diamino-4,4-dihydroxydiphenyl ether. The molar ratio of the amide-containing diamine monomer to the phenol-hydroxyl-containing diamine monomer is (0-0.5):1, and the amount of the amide-containing diamine monomer is not 0. (2) The dianhydride monomer is added in batches to the mixed solution of diamine monomers, and polyamic acid is obtained after the reaction; (3) Add polyamic acid to deionized water and precipitate to obtain polyamic acid powder; (4) Polyamic acid powder and organic alkaline compound are added to deionized water, and polyamic acid hydrogel is obtained after sol-gelation. (5) Dry the polyamic acid hydrogel, partially heat imidize it, and pulverize it to obtain an aerogel for adhesives.

2. The method for preparing an aerogel for adhesives as described in claim 1, characterized in that, The organic solvent mentioned in step (1) is one or more of N,N-dimethylacetamide, dimethyl sulfoxide, N,N-dimethylformamide, and N-methylpyrrolidone.

3. The method for preparing an aerogel for adhesives as described in claim 1, characterized in that, The dianhydride monomer described in step (2) is added to the diamine monomer mixture in 2-6 portions, with an interval of 2-6 minutes between each addition.

4. The method for preparing an aerogel for adhesives as described in claim 1, characterized in that, The reaction temperature in step (2) is 25-35℃ and the reaction time is 6-10h.

5. The method for preparing an aerogel for adhesives as described in claim 1, characterized in that, The precipitation process described in step (3) also includes subsequent washing and drying processes.

6. The method for preparing an aerogel for adhesives as described in claim 1, characterized in that, The mass ratio of the polyamic acid powder to the organic alkaline compound in step (4) is 1:(0.1-1).

7. An aerogel for adhesives, characterized in that, It is prepared by the method for preparing an adhesive aerogel according to any one of claims 1-6.

8. An adhesive containing an aerogel for adhesives, characterized in that, It comprises epoxy resin and aerogel, wherein the aerogel is the aerogel for adhesives as described in claim 7.