Amino hyperbranched polysiloxane modified unsaturated polyimide high-temperature-resistant adhesive and preparation method thereof

Abstract

The invention discloses a preparation method of an amino hyperbranched polysiloxane modified unsaturated polyimide high-temperature-resistant adhesive, which comprises the following steps: mixing and reacting a dianhydride compound, diamine and unsaturated monoanhydride in a polar solvent to obtain an unsaturated anhydride terminated polyamide acid solution; adding amino hyperbranched polysiloxane into the unsaturated polyamide acid solution for reaction to obtain an amino hyperbranched polysiloxane modified unsaturated polyamide acid solution; adding an excessive amount of a mixed solution of triethylamine and acetic anhydride for reaction to obtain an amino hyperbranched polysiloxane modified unsaturated polyimide solution; after cooling to room temperature, pouring into an alcohol solvent, washing, filtering and drying to obtain amino hyperbranched polysiloxane modified unsaturated polyimide solid powder; the preparation method comprises the following steps: dissolving amino hyperbranched polysiloxane modified unsaturated polyimide solid powder into an organic solvent; the adhesive prepared by the preparation method disclosed by the invention is excellent in adhesive property and mechanical property, excellent in high-temperature resistance and good in long-time adhesion stability.

Description

Technical Field

[0001] The invention relates to an adhesive and a preparation method thereof, in particular to an amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive and a preparation method thereof. Background Art

[0002] With the continuous development of various industries, the demand for high-temperature resistant amino adhesives is also increasing. As a high-performance adhesive, polyimide (PI) adhesive has excellent thermal stability, chemical resistance and mechanical properties, and has been widely used in aerospace, electronics, electrical and other fields.

[0003] According to the processing method of PI adhesives, they can be divided into three categories: polycondensation PI adhesives, thermoplastic PI adhesives and addition PI adhesives. Polycondensation PI adhesives are generally prepared from aromatic dianhydrides and aromatic diamines in organic solvents. However, water, solvents, etc. often evaporate during the curing process of the adhesive, resulting in bubbles and bonding defects. Therefore, it is often necessary to apply appropriate pressure during the curing process to remove bubbles. Therefore, polycondensation PI adhesives are not suitable for large-area bonding. Thermoplastic PI adhesives have the characteristics of softening after heating and hardening again after cooling, so they have unique advantages in many applications of repeated heating and cooling. However, most traditional thermoplastic PI adhesives contain flexible segments in the main chain, resulting in a low glass transition temperature and a heat resistance temperature of only 200°C, which limits the further application of PI adhesives in the field of high-temperature resistant amino.

[0004] Thermosetting PI adhesives can undergo an irreversible curing reaction after heating to form structural adhesives with high strength, high heat resistance and high chemical stability, so they have excellent high temperature amino resistance, chemical resistance and dimensional stability. However, due to the high crosslinking density of conventional thermosetting PI adhesives, the cured material is brittle, and the curing temperature and pressure are high while the room temperature shear strength of the adhesive is low, which limits the further application of thermosetting PI adhesives. Based on this, Chinese patent CN 108641665 B discloses a polyimide adhesive and a preparation method thereof, which introduces an aromatic diamine containing a siloxane structure into the polymer main chain to solve the problem of heat instability and decreased bonding performance of polyimide adhesives when the temperature is higher than 350°C in the prior art, but the synthesis process is complicated, the bonding is unstable for a long time, and the heat resistance is poor. Chinese patent CN 111793208 A discloses a polyimide material modified by three-dimensional graphene hollow spheres, its preparation method and modified polyimide adhesive. It is found that adding modified spherical silica as a template to prepare the graphene hollow spheres solves the problem that two-dimensional graphene is easy to agglomerate and difficult to disperse in the adhesive, and also gives the adhesive excellent conductive properties, but its high-temperature bonding performance is poor. At the same time, Chinese patent CN 106566462 A discloses a method for preparing a high-temperature resistant amino polyimide adhesive. After uniformly mixing a polyamic acid solution and 10 to 150 mass parts of an inorganic filler, a polyimide adhesive that can maintain good bonding performance at a high temperature of 1000°C is obtained. However, the adhesive is rigid and debonding occurs during long-term use.

[0005] Based on the existing research results, it can be found that although the high-temperature bonding performance of polyimide adhesives can be improved to a certain extent through structural design and filler addition, there are often problems such as complex synthesis process, long-term unstable bonding, and poor heat resistance, which cannot meet the future aerospace field's demand for the use of higher temperature-resistant adhesives. Summary of the invention

[0006] Purpose of the invention: In order to overcome the deficiencies in the prior art, the purpose of the present invention is to provide a method for preparing an amino-hyperbranched polysiloxane-modified unsaturated polyimide high-temperature resistant adhesive which is simple to prepare and easy to use. Another purpose of the present invention is to provide an amino-hyperbranched polysiloxane-modified unsaturated polyimide high-temperature resistant adhesive which has good bonding properties and good mechanical properties.

[0007] Technical solution: The preparation method of an amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive described in the present invention comprises the following steps:

[0008] Step 1, mixing a dianhydride compound, a diamine, and an unsaturated monoanhydride in a polar solvent to obtain an unsaturated anhydride-terminated polyamic acid solution;

[0009] Step 2, adding amino hyperbranched polysiloxane to the unsaturated anhydride terminated polyamic acid solution to react, to obtain amino hyperbranched polysiloxane modified unsaturated polyamic acid solution;

[0010] Step 3, adding an excess of a mixed solution of triethylamine and acetic anhydride to the amino hyperbranched polysiloxane-modified unsaturated polyamic acid solution to react to obtain an amino hyperbranched polysiloxane-modified unsaturated polyimide solution;

[0011] Step 4, after the product obtained in step 3 is cooled to room temperature, pouring it into an alcohol solvent, washing, filtering and drying, to obtain an amino-hyperbranched polysiloxane-modified unsaturated polyimide solid powder;

[0012] Step 5: dissolving the amino hyperbranched polysiloxane modified unsaturated polyimide solid powder in an organic solvent to obtain a homogeneous solution; applying the homogeneous solution to the surface of the adherend, removing the organic solvent, and curing to obtain the amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive.

[0013] Further, in step 1, the dianhydride compound is one or more of pyromellitic dianhydride, 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride, 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, and hexafluoro dianhydride; the specific general formula is as follows:

[0014]

[0015] The diamine is one or more of 4,4'-diaminodiphenyl ether, 2,6-diaminopyridine, 4,4'-diaminodiphenyl sulfone, m-phenylenediamine, p-phenylenediamine, 4,4'-bis(3-aminophenoxy)biphenyl, 2,5-bis(4-aminophenyl)pyridine, bisphenol A diether diamine, and 1,3-bis(3-aminopropyl)tetramethyldisiloxane; the specific general formula is as follows:

[0016]

[0017] The unsaturated monoanhydride is one or more of maleic anhydride, dimethylmaleic anhydride, methylmaleic anhydride, 2,3-dichloromaleic anhydride, nadic anhydride, methylnadic anhydride, dimethylnadic anhydride, 2-hexyl-3-methylmaleic anhydride, 4-phenylindole phthalic anhydride, and 5-ethynylisobenzofuran-1,3-dione;

[0018] The polar solvent is one or more of N-methylpyrrolidone, N-ethylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, toluene, m-cresol, and methylamine.

[0019] Further, in step 1, the reaction temperature is -10 to 80°C, the reaction time is 1 to 24 hours, the molar ratio of the dianhydride compound, the diamine, and the unsaturated monoanhydride is 1:1.01 to 10:0.02 to 18, and the mass percentage of the polar solvent is 5wt% to 30wt%. Preferably, the reaction temperature is 0 to 60°C, the reaction time is 4 to 18 hours, the molar ratio of the dianhydride compound, the diamine, and the unsaturated monoanhydride is 1:1.2 to 8:0.4 to 16, and the mass percentage of the polar solvent is preferably 10wt% to 20wt%.

[0020] Further, in step 2, the general formula of the amino hyperbranched polysiloxane is:

[0021]

[0022] Among them, R 1 , R 2 It is one or more of methyl, ethyl, phenyl, trifluoromethyl and propyl.

[0023] Furthermore, in step 2, the mass ratio of the unsaturated anhydride-terminated polyamic acid to the amino hyperbranched polysiloxane is 1:0.01-0.2, the reaction temperature is -20-60°C, and the reaction time is 1-24h. Preferably, the mass ratio of the unsaturated anhydride-terminated polyamic acid to the amino hyperbranched polysiloxane is 1:0.05-0.15, the reaction temperature is 0-40°C, and the reaction time is 4-18h.

[0024] Further, in step 3, the molar ratio of triethylamine, acetic anhydride, and amino hyperbranched polysiloxane modified unsaturated polyamic acid is 1:1:0.1-0.5, the reaction temperature is 80-250°C, and the reaction time is 1-12h. Preferably, the molar ratio of triethylamine, acetic anhydride, and amino hyperbranched polysiloxane modified unsaturated polyamic acid is 1:1:0.2-0.4, the reaction temperature is 100-200°C, and the reaction time is 2-10h.

[0025] Furthermore, in step 4, the alcohol solvent is one or more of methanol, ethanol, isopropanol, isobutanol, tert-butanol, and n-butanol.

[0026] Furthermore, in step five, the organic solvent is one or more of chloroform, toluene, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

[0027] Furthermore, in step 5, the curing temperature is 100-400° C., and the curing time is 1-12 hours. Preferably, the curing temperature is 200-350° C., and the curing time is 2-10 hours.

[0028] The amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive obtained by the preparation method comprises C, O, N and Si elements.

[0029] The reaction equation is as follows:

[0030]

[0031] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0032] 1. The obtained amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive has excellent bonding performance and mechanical properties, and due to the addition of amino hyperbranched polysiloxane, the modified polyimide adhesive has excellent high temperature resistance and bonding strength, and good long-term bonding stability;

[0033] 2. It is simple to prepare and easy to use, which can further expand the application of polyimide adhesives in aerospace, electronic insulation and optical fiber communications. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a physical picture of the amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive of the present invention;

[0035] Figure 2 It is an infrared image of the amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive of the present invention;

[0036] Figure 3 It is a dynamic thermomechanical performance diagram of the amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive of the present invention;

[0037] Figure 4 It is a thermal stability diagram of the amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive of the present invention;

[0038] Figure 5 It is the XPS spectrum of the amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive of the present invention. Figure 6 It is a stress-strain change diagram of the amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive after high temperature ablation. DETAILED DESCRIPTION

[0039] Unless otherwise specified, the materials, reagents, instruments, etc. used in the following examples can be obtained from commercial sources. Experimental methods without specific conditions in the examples are usually carried out under conventional conditions or under conditions recommended by the manufacturer.

[0040] Example 1

[0041] A method for preparing an amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive comprises the following steps:

[0042] (1) In a 1L three-necked flask equipped with a mechanical stirrer, 21.81 g (0.1 mol) of pyromellitic anhydride, 20.22 g (0.101 mol) of 4,4-diaminodiphenyl ether, 1.96 g (0.002 mol) of maleic anhydride and 835.81 g (5 wt%) of N-methylpyrrolidone were added, and after mixing evenly, the mixture was reacted at -10°C for 24 h to obtain an unsaturated anhydride-terminated polyamic acid.

[0043] (2) 0.218 g of amino hyperbranched polysiloxane was added to the unsaturated anhydride-terminated polyamic acid solution and reacted at -20°C for 24 hours to obtain an amino hyperbranched polysiloxane-modified unsaturated polyamic acid solution, wherein the amino hyperbranched polysiloxane has the following structural formula:

[0044]

[0045] (3) A mixed solution of 101.19 g (1 mol) of triethylamine and 102.09 g (1 mol) of acetic anhydride was added to the amino hyperbranched polysiloxane-modified polyamic acid solution and reacted at 80° C. for 12 h to obtain an amino hyperbranched polysiloxane-modified unsaturated polyimide solution.

[0046] (4) After the reaction mixture is cooled to room temperature, it is poured into methanol and washed, filtered, and dried to obtain amino hyperbranched polysiloxane-modified unsaturated polyimide solid powder.

[0047] (5) dissolving the amino hyperbranched polysiloxane modified polyimide solid powder in N-methylpyrrolidone to obtain a homogeneous solution; applying the homogeneous solution to the surface of the adherend, removing the organic solvent, and curing at 100° C. for 12 hours to obtain the amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive, thereby completing the bonding of the adherend.

[0048] Figure 1 This is a physical picture of a homogeneous solution (amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive). Figure 1 It can be seen that the adhesive solution is orange-yellow and has a low viscosity, which is conducive to large-scale construction.

[0049] Figure 2 It is an infrared ray-cured unsaturated polyimide high temperature resistant adhesive modified by amino hyperbranched polysiloxane. Figure 2 It can be seen that at 1100cm -1 The infrared peak of Si-O-Si appeared at 1371cm -1 The infrared peak of CN appeared at 1710 cm -1 and 1680cm -1 The infrared peak of C=O appeared at , which indicated the successful synthesis of amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive.

[0050] Figure 3 The dynamic thermomechanical properties of amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive are shown in Figure 2. Figure 3 It can be seen that the storage modulus of the adhesive at 100°C is as high as 2.7 GPa, and the glass transition temperature is 253°C, showing excellent mechanical properties.

[0051] Figure 4 The thermal stability diagram of amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive is shown in Figure 2. Figure 4 It can be seen that the initial thermal decomposition temperature of the adhesive is 518°C, showing excellent thermal stability, which can ensure the bonding strength of the adhesive material at high temperatures.

[0052] Figure 5 This is the XPS spectrum of amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive. Figure 5 It can be seen that there are four elements, C, O, N and Si, in the adhesive, which indicates the successful introduction of Si element.

[0053] Figure 6 The stress-strain change diagram of amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive after high temperature ablation. Figure 6 It can be seen that after 5 minutes of ablation with an alcohol lamp, the bonding strength can still be maintained at 20MPa, showing excellent bonding performance.

[0054] The amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive obtained in Example 1 was aged at 25°C and 350°C for 4 hours, and then its bonding strength was tested according to ASTMD1002-10, as shown in Table 1. It can be seen from Table 1 that the adhesive of this example has high bonding strength on the iron-iron, iron-stainless steel, and iron-stainless steel interfaces.

[0055] Table 1 Adhesive properties of the adhesive obtained in Example 1

[0056] Iron-Iron Iron-Stainless Steel Stainless steel-stainless steel 25℃ bonding strength / MPa 20±1.2 23.2±1.5 25.3±0.95 Adhesion strength after aging at 350℃ for 4h / MPa 18±1.09 21.9±0.83 23.2±1.3 Bond strength after aging at 350℃ for 24h / MPa 18.39±2.03 20.8±0.39 21.5±0.95

[0057] Example 2

[0058] A method for preparing an amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive comprises the following steps:

[0059] (1) In a 2L three-necked flask equipped with a mechanical stirrer, 32.22 g (0.1 mol) of 3,3',4,4'-benzophenone tetracarboxylic anhydride, 108.14 g (1 mol) of p-phenylenediamine, 295.48 g (1.8 mol) of nadic anhydride and 1016.96 g (30 wt%) of N-ethylpyrrolidone were added, and after mixing evenly, the mixture was reacted at 80° C. for 1 h to obtain an unsaturated anhydride-terminated polyamic acid.

[0060] (2) 6.44 g of amino-hyperbranched polysiloxane was added to the unsaturated anhydride-terminated polyamic acid solution and reacted at 60° C. for 24 h to obtain an amino-hyperbranched polysiloxane-modified unsaturated polyamic acid solution, wherein the amino-hyperbranched polysiloxane has the same structural formula as that of Example 1.

[0061] (3) A mixed solution of 20.24 g (0.2 mol) of triethylamine and 20.42 g (0.2 mol) of acetic anhydride was added to the amino hyperbranched polysiloxane-modified unsaturated polyamic acid solution and reacted at 250° C. for 1 h to obtain an amino hyperbranched polysiloxane-modified unsaturated polyimide solution.

[0062] (4) After the reaction mixture is cooled to room temperature, it is poured into tert-butyl alcohol and washed, filtered and dried to obtain amino hyperbranched polysiloxane modified unsaturated polyimide solid powder.

[0063] (5) dissolving the amino hyperbranched polysiloxane modified unsaturated polyimide solid powder in N-ethylpyrrolidone to obtain a homogeneous solution; applying the homogeneous solution to the surface of the adherend, removing the organic solvent, and curing at 400° C. for 1 hour to obtain the amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive, thereby completing the bonding of the adherend.

[0064] Table 2 Adhesive properties of the adhesive obtained in Example 2

[0065] Iron-Iron Iron-Stainless Steel Stainless steel-stainless steel 25℃ bonding strength / MPa 24.1±0.56 20.3±2.5 23.4±2.31 Adhesion strength after aging at 350℃ for 4h / MPa 22.3±1.23 21.3±1.45 20.5±1.57 Bond strength after aging at 350℃ for 24h / MPa 11.3±1.3 12.5±2.0 17.6±2.31

[0066] Example 3

[0067] A method for preparing an amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive comprises the following steps:

[0068] (1) In a 1L three-necked flask equipped with a mechanical stirrer, 44.42 g (0.1 mol) of hexafluorodianhydride, 13.10 g (0.12 mol) of 2,6-diaminopyridine, 7.13 g (0.04 mol) of nadic anhydride and 581.85 g (10 wt%) of N,N-dimethylformamide were added, and after mixing evenly, the mixture was reacted at 0°C for 18 h to obtain an unsaturated anhydride-terminated polyamic acid.

[0069] (2) Add 2.221 g of amino-hyperbranched polysiloxane to the unsaturated anhydride-terminated polyamic acid solution and react at 0° C. for 18 h to obtain an amino-hyperbranched polysiloxane-modified unsaturated polyamic acid solution, wherein the amino-hyperbranched polysiloxane has the same structural formula as that of Example 1.

[0070] (3) A mixed solution of 5.06 g (0.05 mol) of triethylamine and 5.105 g (0.05 mol) of acetic anhydride was added to the amino hyperbranched polysiloxane-modified unsaturated polyamic acid solution and reacted at 100° C. for 10 h to obtain an amino hyperbranched polysiloxane-modified unsaturated polyimide solution.

[0071] (4) After the reaction mixture is cooled to room temperature, it is poured into n-butanol and washed, filtered, and dried to obtain amino hyperbranched polysiloxane-modified unsaturated polyimide solid powder.

[0072] (5) dissolving the amino hyperbranched polysiloxane modified unsaturated polyimide solid powder in chloroform to obtain a homogeneous solution; applying the homogeneous solution to the surface of the adherend, removing the organic solvent, and curing at 200° C. for 10 hours to obtain the amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive, thereby completing the bonding of the adherend.

[0073] Table 3 Adhesive properties of the adhesive obtained in Example 3

[0074] Iron-Iron Iron-Stainless Steel Stainless steel-stainless steel 25℃ bonding strength / MPa 18.92±2.36 28.3±1.72 25.2±2.83 Bond strength after aging at 350℃ for 4h / MPa 17.25±2.48 26.2±2.36 26.1±1.85 Bond strength after aging at 350℃ for 24h / MPa 10.43±1.24 6.32±0.65 8.42±0.32

[0075] Example 4

[0076] A method for preparing an amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive comprises the following steps:

[0077] (1) In a 2L three-necked flask equipped with a mechanical stirrer, 35.83 g (0.1 mol) of 3,3',4,4'-diphenylsulfone tetracarboxylic acid dianhydride, 209.06 g (0.8 mol) of 2,5-di(4-aminophenyl)pyridine, 233.76 g (1.4 mol) of 2,3-dichloromaleic anhydride and 1914.6 g (20 wt%) of N,N-dimethylformamide were added, and after being uniformly mixed, the mixture was reacted at 60° C. for 4 h to obtain an unsaturated anhydride-terminated polyamic acid.

[0078] (2) 5.375 g of amino hyperbranched polysiloxane was added to the unsaturated anhydride-terminated polyamic acid solution and reacted at 40° C. for 4 h to obtain an amino hyperbranched polysiloxane-modified unsaturated polyamic acid solution, wherein the amino hyperbranched polysiloxane has the same structural formula as that of Example 1.

[0079] (3) A mixed solution of 25.30 g (0.25 mol) of triethylamine and 25.52 g (0.25 mol) of acetic anhydride was added to the amino hyperbranched polysiloxane-modified unsaturated polyamic acid solution and reacted at 200° C. for 2 h to obtain an amino hyperbranched polysiloxane-modified unsaturated polyimide solution.

[0080] (4) After the reaction mixture is cooled to room temperature, it is poured into ethanol and washed, filtered, and dried to obtain amino hyperbranched polysiloxane-modified unsaturated polyimide solid powder.

[0081] (5) dissolving the amino hyperbranched polysiloxane modified unsaturated polyimide solid powder in toluene to obtain a homogeneous solution; applying the homogeneous solution to the surface of the adherend, removing the organic solvent, and curing at 350° C. for 2 hours to obtain the amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive, thereby completing the bonding of the adherend.

[0082] Table 4 Adhesive properties of the adhesive obtained in Example 4

[0083] Iron-Iron Iron-Stainless Steel Stainless steel-stainless steel 25℃ bonding strength / MPa 26.3±1.5 23.2±1.28 28.4±3.12 Bond strength after aging at 350℃ for 4h / MPa 15.79±2.63 19.56±1.26 25.7±3.43 Bond strength after aging at 350℃ for 24h / MPa 5.28±0.36 7.52±1.36 5.32±2.6

[0084] Example 5

[0085] A method for preparing an amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive comprises the following steps:

[0086] (1) In a 2L three-necked flask equipped with a mechanical stirrer, 17.92 g (0.05 mol) of 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride, 6.204 g (0.02 mol) of 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, 15.61 g (0.03 ml) of bisphenol A type diether dianhydride, 104.53 g (0.4 mol) of 2,5-bis(4-aminophenyl)pyridine, 193.90 g (0.4 mol) of bisphenol A diether diamine, 233.76 g (1.4 mol) of 2,3-dichloromaleic anhydride and 1914.6 g (20 wt%) of N,N-dimethylformamide were added, and after being uniformly mixed, the mixture was reacted at 60° C. for 4 h to obtain an unsaturated anhydride-terminated polyamic acid.

[0087] (2) 5.375 g of amino hyperbranched polysiloxane was added to the unsaturated anhydride-terminated polyamic acid solution and reacted at 40° C. for 4 h to obtain an amino hyperbranched polysiloxane-modified unsaturated polyamic acid solution, wherein the amino hyperbranched polysiloxane has the same structural formula as that of Example 1.

[0088] (3) A mixed solution of 25.30 g (0.25 mol) of triethylamine and 25.52 g (0.25 mol) of acetic anhydride was added to the amino hyperbranched polysiloxane-modified unsaturated polyamic acid solution and reacted at 200° C. for 2 h to obtain an amino hyperbranched polysiloxane-modified unsaturated polyimide solution.

[0089] (4) After the reaction mixture is cooled to room temperature, it is poured into ethanol and washed, filtered, and dried to obtain amino hyperbranched polysiloxane-modified unsaturated polyimide solid powder.

[0090] (5) dissolving the amino hyperbranched polysiloxane modified polyimide solid powder in toluene to obtain a homogeneous solution; applying the homogeneous solution to the surface of the adherend, removing the organic solvent, and curing at 350° C. for 2 h to obtain the amino hyperbranched polysiloxane modified polyimide high temperature resistant adhesive, thereby completing the bonding of the adherend.

[0091] Table 5 Adhesive properties of the adhesive obtained in Example 5

[0092] Iron-Iron Iron-Stainless Steel Stainless steel-stainless steel 25℃ bonding strength / MPa 23.5±1.35 26.5±1.36 25.6±2.67 Bond strength after aging at 350℃ for 4h / MPa 26.2±1.69 23.6±1.58 23.81±2.45 Bond strength after aging at 350℃ for 24h / MPa 12.6±1.53 10.3±2.2 9.56±3.1

[0093] In the above embodiments, the best embodiment is embodiment 1. Due to the presence of amino hyperbranched siloxane, the crosslinking density of the PI adhesive material is enhanced, so that the bonding strength of the amino hyperbranched polysiloxane modified unsaturated polyimide adhesive at room temperature can be as high as 20±1.2MPa. When amino hyperbranched siloxane is introduced into the adhesive material, an organic-inorganic hybrid structure can be formed. After aging at 350°C for 24h, the inorganic siloxane structure can inhibit the further decomposition of the PI segment, thereby maintaining a high shear strength.

[0094] Comparative Example 1

[0095] The remaining steps of this comparative example are the same as those of Example 1, except that amino hyperbranched polysiloxane is replaced with aminopropyl-terminated polydimethylsiloxane. The bonding performance is tested, and the results show that compared with Example 1, the bonding performance of Comparative Example 1 for iron-iron after aging at 350° C. for 24 hours is only 1.23±0.83 MPa.

[0096] Comparative Example 2

[0097] The remaining steps of this comparative example are the same as those of Example 1, except that the amino hyperbranched polysiloxane is replaced by silica nanoparticles. The bonding performance is tested, and it is found that compared with Example 1, the bonding performance of Comparative Example 2 for iron-iron after aging at 350° C. for 24 hours is only 0.81±0.14 Mpa.

[0098] Comparative Example 3

[0099] A method for preparing an amino-hyperbranched polysiloxane-modified unsaturated polyimide solution comprises the following steps:

[0100] (1) In a 1L three-necked flask equipped with a mechanical stirrer, 21.81 g (0.1 mol) of pyromellitic anhydride, 20.22 g (0.101 mol) of 4,4-diaminodiphenyl ether, 1.96 g (0.002 mol) of maleic anhydride and 835.81 g (5 wt%) of N-methylpyrrolidone were added, and after mixing evenly, the mixture was reacted at -10°C for 24 h to obtain an unsaturated anhydride-terminated polyamic acid.

[0101] (2) 0.218 g of amino hyperbranched polysiloxane was added to the unsaturated anhydride-terminated polyamic acid solution and reacted at -20°C for 24 h to obtain an amino hyperbranched polysiloxane-modified unsaturated polyamic acid solution, wherein the amino hyperbranched polysiloxane has the same structural formula as in Example 1.

[0102] (3) A mixed solution of 101.19 g (1 mol) of triethylamine and 102.09 g (1 mol) of acetic anhydride was added to the amino hyperbranched polysiloxane-modified polyamic acid solution and reacted at 80° C. for 12 h to obtain an amino hyperbranched polysiloxane-modified unsaturated polyimide solution.

[0103] Compared with Example 1, step (4) and step (5) were omitted in this comparative example. As a result, it was found that due to the presence of residual solvent and residual acetic anhydride from chemical imidization, the amino hyperbranched polysiloxane-modified unsaturated polyimide solution was directly used as an adhesive, and the bonding performance was poor.

Claims

1. A method for preparing an amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive, It is characterized in that The following steps are involved: Step 1, mixing a dianhydride compound, a diamine, and an unsaturated monoanhydride in a polar solvent to obtain an unsaturated anhydride-terminated polyamic acid solution; Step 2, adding amino hyperbranched polysiloxane to the unsaturated anhydride terminated polyamic acid solution to react, to obtain amino hyperbranched polysiloxane modified unsaturated polyamic acid solution; Step 3, adding an excess of a mixed solution of triethylamine and acetic anhydride to the amino hyperbranched polysiloxane-modified unsaturated polyamic acid solution to react to obtain an amino hyperbranched polysiloxane-modified unsaturated polyimide solution; Step 4, after the product obtained in step 3 is cooled to room temperature, pouring it into an alcohol solvent, washing, filtering and drying, to obtain an amino-hyperbranched polysiloxane-modified unsaturated polyimide solid powder; Step 5: dissolving the amino-hyperbranched polysiloxane-modified unsaturated polyimide solid powder in an organic solvent.

2. The method for preparing the amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive according to claim 1, Features: In the step 1, the dianhydride compound is one or more of pyromellitic dianhydride, 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride, 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, and hexafluoro dianhydride; The diamine is one or more of 4,4'-diaminodiphenyl ether, 2,6-diaminopyridine, 4,4'-diaminodiphenyl sulfone, m-phenylenediamine, p-phenylenediamine, 4,4'-bis(3-aminophenoxy)biphenyl, 2,5-bis(4-aminophenyl)pyridine, bisphenol A diether diamine, and 1,3-bis(3-aminopropyl)tetramethyldisiloxane.

3. The method for preparing the amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive according to claim 1, Features: In the step 1, the unsaturated monoanhydride is one or more of maleic anhydride, dimethylmaleic anhydride, methylmaleic anhydride, 2,3-dichloromaleic anhydride, nadic anhydride, methylnadic anhydride, dimethylnadic anhydride, 2-hexyl-3-methylmaleic anhydride, 4-phenylindole phthalic anhydride, and 5-ethynylisobenzofuran-1,3-dione; The polar solvent is one or more of N-methylpyrrolidone, N-ethylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, toluene, m-cresol, and methylamine.

4. The method for preparing the amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive according to claim 1, Features: In the step 1, the reaction temperature is -10 to 80°C, and the reaction time is 1 to 24 hours; the molar ratio of the dianhydride compound, diamine, and unsaturated monoanhydride is 1:1.01 to 10:0.02 to 18, and the mass percentage of the polar solvent is 5 wt% to 30 wt%.

5. The method for preparing the amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive according to claim 1, Features: In the step 2, the general formula of the amino hyperbranched polysiloxane is: Among them, R 1 , R 2 It is one or more of methyl, ethyl, phenyl, trifluoromethyl and propyl.

6. The method for preparing the amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive according to claim 1, Features: In the step 2, the mass ratio of the unsaturated anhydride-terminated polyamic acid to the amino hyperbranched polysiloxane is 1:0.01-0.2, the reaction temperature is -20-60°C, and the reaction time is 1-24h.

7. The method for preparing the amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive according to claim 1, Features: In the step 3, the molar ratio of triethylamine, acetic anhydride and amino hyperbranched polysiloxane modified unsaturated polyamic acid is 1:1:0.1-0.5, the reaction temperature is 80-250° C., and the reaction time is 1-12 hours.

8. The method for preparing the amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive according to claim 1, Features: In step 4, the alcohol solvent is one or more of methanol, ethanol, isopropanol, isobutanol, tert-butanol, and n-butanol.

9. The method for preparing the amino hyperbranched polysiloxane modified unsaturated polyimide high temperature resistant adhesive according to claim 1, Features: In the step 5, the organic solvent is one or more of chloroform, toluene, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

10. The amino-hyperbranched polysiloxane-modified unsaturated polyimide high temperature resistant adhesive obtained by the preparation method of the amino-hyperbranched polysiloxane-modified unsaturated polyimide high temperature resistant adhesive according to any one of claims 1 to 9, Features: Including C, O, N, and Si elements.

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