Alkali hydrolysis-resistant polyimide engineering plastic and preparation method thereof

Abstract

The present invention relates to a kind of alkali hydrolysis resistant polyimide engineering plastic and preparation method thereof, belong to the technical field of polyimide engineering plastic preparation.Described by hyperbranched polyamic acid solution, modified polyamic acid solution and dehydrating agent mixing after dehydration reaction is made;Described hyperbranched polyamic acid solution is made by modified nanoparticles, first dianhydride monomer and triamine monomer in a first solvent through in-situ polymerization reaction;Described modified polyamic acid solution is made by second dianhydride monomer, containing branched diamine monomer through polymerization reaction in a second solvent;Described containing branched diamine monomer is made by reaction of aniline and benzaldehyde derivative;Described benzaldehyde derivative is made by reaction of 4 hydroxybenzaldehyde and epoxy silane coupling agent.The polyimide engineering plastic of the present invention contains hyperbranched polyimide and chain polyimide, has good mechanical strength and ultraviolet light resistance and is stable under alkaline conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of polyimide engineering plastic preparation, and in particular relates to an alkali-hydrolysis-resistant polyimide engineering plastic and a preparation method thereof. Background Art

[0002] Polyimide (PI), a polymer containing an imide ring (-CO-NR-CO-) in its backbone, is one of the most comprehensive organic polymer materials. It boasts excellent temperature resistance (high temperatures exceeding 400°C, with a long-term practical temperature range of -200 to 300°C) and excellent electrical insulation properties. Its dielectric constant is 4.0 at 103 Hz, and its dielectric loss is only 0.004 to 0.007, placing it in insulation classes F to H. These exceptional temperature resistance and electrical insulation properties have made it a specialty engineering material widely used in aviation, aerospace, microelectronics, nanotechnology, liquid crystals, separation membranes, and lasers.

[0003] However, polyimide is not resistant to alkaline hydrolysis. In view of the above-mentioned disadvantage of polyimide not being resistant to alkaline hydrolysis, there is an urgent need for an alkaline hydrolysis-resistant polyimide engineering plastic and a preparation method thereof. Summary of the Invention

[0004] The purpose of the present invention is to provide an alkali-hydrolysis-resistant polyimide engineering plastic and a preparation method thereof.

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of existing polyimide in terms of weak mechanical strength and toughness.

[0006] One object of the present invention can be achieved by the following technical solutions:

[0007] An alkali-hydrolysis-resistant polyimide engineering plastic is prepared by mixing a hyperbranched polyamic acid solution, a modified polyamic acid solution and a dehydrating agent and then subjecting the mixture to a dehydration reaction;

[0008] The hyperbranched polyamic acid solution is prepared by in-situ polymerization of modified nanoparticles, a first dianhydride monomer, and a triamine monomer in a first solvent;

[0009] The modified polyamic acid solution is prepared by polymerization of a second dianhydride monomer and a branched diamine monomer in a second solvent;

[0010] The branched diamine monomer is prepared by reacting aniline and benzaldehyde derivatives;

[0011] The benzaldehyde derivative is prepared by reacting 4-hydroxybenzaldehyde and an epoxy silane coupling agent.

[0012] In the present invention, a hyperbranched polyamic acid solution and a chain-type polyamic acid solution are blended and then subjected to imidization treatment (i.e., dehydration operation) to obtain polyimide;

[0013] Among them, the spatial position effect of hyperbranched polyamide is utilized to greatly reduce the interaction force between chain-type polyimide molecules, making the organic solvent solubility of the polyimide obtained by imidization, and improving the application and processability of the final polyimide.

[0014] Furthermore, the modified nanoparticles are nanoparticles modified by a silane coupling agent, and the nanoparticles are nano-titanium dioxide or nano-zinc oxide;

[0015] Here, the present invention utilizes the spatial loading characteristics of hyperbranched polyamide, and obtains a hyperbranched polyamide acid liquid with enhanced ultraviolet light resistance through the form of nano-titanium dioxide modified by a silane coupling agent or nano-zinc oxide modified by a silane coupling agent and in-situ polymerization technology. First, the in-situ polymerization technology is used to improve the stability of the enhanced function, and second, the nano-titanium dioxide or zinc oxide is used to enable the hyperbranched polyamide acid liquid to obtain the intrinsic function of ultraviolet light resistance.

[0016] The nanoparticles modified with silane coupling agents are the surface modification technology of nanoparticles using silane coupling agents well known in the art, and the present invention does not impose any specific limitation thereto.

[0017] Furthermore, the silane coupling agent is one of KH550, KH560, KH570, A151, A171, and A172;

[0018] Preferably, the silane coupling agent is KH550.

[0019] Furthermore, the mass ratio of the hyperbranched polyamic acid solution to the modified polyamic acid solution is 1:1-3.

[0020] Furthermore, the solid content of the hyperbranched polyamic acid solution is 15-30 wt %.

[0021] Preferably, the solid content of the hyperbranched polyamic acid solution is 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt% or 25 wt%.

[0022] Furthermore, the solid content of the modified polyamic acid solution is 25-40 wt %.

[0023] Preferably, the solid content of the modified polyamic acid solution is 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt%, 31wt%, 32wt%, 33wt%, 34wt% or 35wt%.

[0024] Furthermore, the dehydration reaction temperature is 70-130° C., and the reaction time is 5-12 h.

[0025] Furthermore, the molar ratio of the first dianhydride monomer to the triamine monomer is 3.5-4:2.

[0026] Preferably, the molar ratio of the first dianhydride monomer to the triamine monomer is 3.5:2, 3.6:2, 3.7:2, 3.8:2, 3.9:2 or 4:2.

[0027] Furthermore, the reaction temperature in the in-situ polymerization reaction is 0-40° C., and the reaction time is 4-8 hours.

[0028] Furthermore, the modified nanoparticles account for 15-35% of the total mass of the first dianhydride monomer and the triamine monomer.

[0029] Preferably, the modified nanoparticles account for 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34% or 35% of the total mass of the first dianhydride monomer and triamine monomer.

[0030] Furthermore, the first dianhydride monomer is one of 4,4′-phthalic anhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride, and 4,4′-oxydiphthalic anhydride.

[0031] Furthermore, the triamine monomer is 4,4',4''-triaminotriphenylmethane.

[0032] Furthermore, the first solvent is one or more of N,N-methylformamide, N,N-methylacetamide, and N-methylpyrrolidone.

[0033] Furthermore, the molar ratio of the second dianhydride monomer to the branched diamine monomer is 1:1.

[0034] Furthermore, the reaction temperature in the polymerization reaction is 0-40° C., and the reaction time is 4-8 hours.

[0035] Furthermore, the second dianhydride monomer is one of 4,4′-phthalic anhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride, and 4,4′-oxydiphthalic anhydride.

[0036] Furthermore, the second solvent is one or more of N,N-methylformamide, N,N-methylacetamide, and N-methylpyrrolidone.

[0037] Furthermore, the branched diamine monomer is prepared by reacting aniline and a benzaldehyde derivative, comprising:

[0038] After uniformly mixing benzaldehyde derivatives, aniline, aniline hydrochloride and dimethyl sulfoxide, react under nitrogen protection at 100-110°C for 1-3 hours, heat to 130-145°C, keep warm for 2-3 hours, cool to stop the reaction, pour into water, flocculate and precipitate at low temperature, filter to obtain the precipitate, dissolve the precipitate with hydrochloric acid, filter to obtain the filtrate, neutralize the filtrate with sodium hydroxide to produce a precipitate, repeatedly wash the precipitate, and dry to obtain a branched diamine monomer.

[0039] Furthermore, the molar ratio of the benzaldehyde derivative to aniline is 1:2.5-3.

[0040] Furthermore, the added mass of the aniline hydrochloride is 3-6% of the mass of the benzaldehyde derivative and aniline.

[0041] In the above reaction, a coupling dehydration reaction is carried out using the aldehyde group in the benzaldehyde derivative and the hydrogen on the 4-carbon of aniline, that is, 1 mole of the benzaldehyde derivative reacts with 2 moles of aniline to generate a branched diamine monomer, wherein the branch is a siloxane chain. The main chain of the polyamide generated by the reaction of the branched diamine monomer and the second dianhydride monomer is connected to the siloxane chain, thereby improving the stability of the obtained polyimide under alkaline conditions.

[0042] The following is the chemical structure of the branched diamine monomer of epoxy silane coupling agent KH560:

[0043] .

[0044] Furthermore, the benzaldehyde derivative is prepared by reacting 4-hydroxybenzaldehyde with an epoxysilane coupling agent, comprising:

[0045] After 4-hydroxybenzaldehyde, epoxysilane coupling agent and tetrahydrofuran are uniformly mixed, the pH of the system is adjusted to 10-11, heated to reflux under condensation, stirred and reacted for 2-4 hours, cooled to 30-40°C, rotary evaporated, washed and dried to obtain a benzaldehyde derivative.

[0046] Furthermore, the molar ratio of the 4-hydroxybenzaldehyde to the epoxy silane coupling agent is 1:1-1.3.

[0047] The above reaction utilizes the reaction between the hydroxyl group in 4-hydroxybenzaldehyde and the epoxy group in the epoxysilane coupling agent, so that the 4-position of the benzaldehyde is connected to a siloxane chain.

[0048] Another object of the present invention can be achieved by the following technical solutions:

[0049] A method for preparing alkali-hydrolysis-resistant polyimide engineering plastics, comprising:

[0050] The hyperbranched polyamic acid solution, the modified polyamic acid solution and the dehydrating agent are mixed, heated to the dehydration reaction temperature, and kept warm for dehydration. After the dehydration is completed, the mixture is cooled, water or ethanol is added, stirred to precipitate, filtered, and the precipitate is taken and dried to obtain an impact-resistant and high-toughness polyimide.

[0051] Furthermore, the amount of the dehydrating agent added is 3-5 times the total molar mass of the amino monomers provided in the hyperbranched polyamic acid solution and the modified polyamic acid solution, wherein the amino monomers provided are triamine monomers and branched diamine monomers.

[0052] Beneficial effects of the present invention:

[0053] The invention adopts a method of blending a hyperbranched polyamic acid solution and a chain-type polyamic acid solution, and then subjecting the mixture to imidization treatment to obtain a polyimide engineering plastic containing a hyperbranched polyimide and a chain-type polyimide. On the one hand, nanoparticles loaded by the hyperbranched polyimide are utilized to achieve a filling and reinforcing effect of the nanoparticles, thereby improving the mechanical properties of the polyimide engineering plastic finally obtained. On the other hand, the hyperbranched structure of the hyperbranched polyimide and the siloxane side chains in the chain-type polyimide synergistically improve the interpenetrating network of the obtained polyimide-polyimide engineering plastic, thereby further improving the mechanical properties. In addition, the obtained polyimide engineering plastic is stable under alkaline conditions and has good ultraviolet light resistance. DETAILED DESCRIPTION

[0054] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention. Example

[0055] Preparation of branched diamine monomers:

[0056] A1. Evenly mix 0.1 mol of 4-hydroxybenzaldehyde, 0.1 mol of epoxysilane coupling agent (KH560), and 100 mL of tetrahydrofuran, adjust the pH of the system to 10-11, heat to reflux under condensation, stir and react for 2 h, cool to 30-40°C, rotary evaporate, wash, and dry to obtain a benzaldehyde derivative.

[0057] A2. After uniformly mixing 0.1 mol of a benzaldehyde derivative, 0.25 mol of aniline, aniline hydrochloride, and 150 mL of dimethyl sulfoxide, the mixture was reacted at 100° C. under nitrogen protection for 3 h, the temperature was raised to 130° C., the temperature was kept for 3 h, the reaction was stopped by cooling, water was poured into the mixture, flocculated and precipitated at low temperature, the precipitate was filtered out, the precipitate was dissolved in hydrochloric acid, the filtrate was filtered out, the filtrate was neutralized with sodium hydroxide to produce a precipitate, the precipitate was repeatedly washed, and dried to obtain a branched diamine monomer; wherein the mass of the added aniline hydrochloride was 5% of the mass of the benzaldehyde derivative and aniline. Example

[0058] Preparation of branched diamine monomers:

[0059] A1. Evenly mix 0.1 mol of 4-hydroxybenzaldehyde, 0.13 mol of epoxysilane coupling agent (KH560), and 100 mL of tetrahydrofuran, adjust the pH of the system to 10-11, heat to reflux under condensation, stir and react for 4 h, cool to 30-40°C, rotary evaporate, wash, and dry to obtain a benzaldehyde derivative.

[0060] A2. After uniformly mixing 0.1 mol of a benzaldehyde derivative, 0.3 mol of aniline, aniline hydrochloride, and 150 mL of dimethyl sulfoxide, the mixture was reacted at 110° C. under nitrogen protection for 1 h, the temperature was raised to 145° C., the temperature was kept for 2 h, the reaction was stopped by cooling, water was poured into the mixture, flocculated and precipitated at low temperature, the precipitate was filtered out, the precipitate was dissolved in hydrochloric acid, the filtrate was filtered out, the filtrate was neutralized with sodium hydroxide to produce a precipitate, the precipitate was repeatedly washed, and dried to obtain a branched diamine monomer; wherein the added mass of the aniline hydrochloride was 4% of the mass of the benzaldehyde derivative and aniline. Example

[0061] Preparation of polyimide engineering plastics:

[0062] The first step is to prepare a hyperbranched polyamic acid solution: KH550-modified nano-titanium dioxide, 0.35 mol of 4,4'-phthalic anhydride, 0.2 mol of 4,4',4''-triaminotriphenylmethane and N,N-methylformamide are uniformly mixed to prepare a solution with a solid content of 15 wt%. Subsequently, the reaction is carried out at 0°C under nitrogen protection for 8 hours to obtain a hyperbranched polyamic acid solution, wherein the modified nano-titanium dioxide accounts for 20% of the total mass of the 4,4'-phthalic anhydride and 4,4',4''-triaminotriphenylmethane, the particle size of the nano-titanium dioxide is 200-400 nm, and KH550 accounts for 6% of the mass of the nano-titanium dioxide in the KH550-modified nano-titanium dioxide.

[0063] Step 2: Preparation of modified polyamic acid solution: 0.1 mol of 4,4′-phthalic anhydride, 0.1 mol of the branched diamine monomer prepared in Example 1, and N,N-methylformamide were uniformly mixed to prepare a solution with a solid content of 25 wt%. The solution was then reacted at 0° C. under nitrogen protection for 8 h to obtain a modified polyamic acid solution.

[0064] Step 3, preparation of engineering plastics: after mixing the hyperbranched polyamic acid solution obtained in the first step and the modified polyamic acid solution obtained in the second step in a mass ratio of 1:2, add 1 mol of acetic anhydride, stir and heat to 70°C, and keep warm for dehydration for 12 hours. After dehydration, cool, add water or ethanol, stir to precipitate, filter, take the precipitate, and dry to obtain impact-resistant and high-toughness polyimide. Example

[0065] Preparation of polyimide engineering plastics:

[0066] The first step is to prepare a hyperbranched polyamic acid solution: KH550-modified nano-zinc oxide, 0.36 mol of 3,3′,4,4′-benzophenone tetracarboxylic dianhydride, 0.2 mol of 4,4′,4′′-triaminotriphenylmethane and N,N-methylacetamide are uniformly mixed to prepare a solution with a solid content of 20 wt%. Subsequently, the reaction is carried out at 20° C. under nitrogen protection for 6 hours to obtain a hyperbranched polyamic acid, wherein the modified nano-zinc oxide accounts for 25% of the total mass of the 3,3′,4,4′-benzophenone tetracarboxylic dianhydride and 4,4′,4′′-triaminotriphenylmethane, the particle size of the nano-zinc oxide is 200-400 nm, and KH550 accounts for 9% of the mass of the nano-zinc oxide in the KH550-modified nano-zinc oxide.

[0067] Step 2: Preparation of modified polyamic acid solution: 0.1 mol of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, 0.1 mol of the branched diamine monomer prepared in Example 2, and N,N-methylacetamide were uniformly mixed to prepare a solution with a solid content of 30 wt%, and then reacted at 40° C. under nitrogen protection for 4 h to obtain a modified polyamic acid solution.

[0068] Step 3, preparation of engineering plastics: after mixing the hyperbranched polyamic acid solution obtained in the first step and the modified polyamic acid solution obtained in the second step in a mass ratio of 1:1, add 1 mol of acetic anhydride, stir and heat to 100°C, and dehydrate for 8 hours. After dehydration, cool, add water or ethanol, stir to precipitate, filter, take the precipitate, and dry to obtain impact-resistant and high-toughness polyimide. Example

[0069] Preparation of polyimide engineering plastics:

[0070] The first step is to prepare a hyperbranched polyamic acid solution: KH550-modified titanium dioxide, 0.35-0.4 mol of pyromellitic dianhydride, 0.2 mol of 4,4',4''-triaminotriphenylmethane and N-methylpyrrolidone are uniformly mixed to prepare a solution with a solid content of 25 wt%. The solution is then reacted at 40°C under nitrogen protection for 4 hours to obtain a hyperbranched polyamic acid solution, wherein the modified nano-titanium dioxide accounts for 25% of the total mass of the first dianhydride monomer and the triamine monomer, the particle size of the nano-titanium dioxide is 200-400 nm, and KH550 accounts for 12% of the mass of the nano-titanium dioxide in the KH550-modified nano-titanium dioxide.

[0071] Step 2: Preparation of modified polyamic acid solution: 0.1 mol of pyromellitic dianhydride, 0.1 mol of the branched diamine monomer prepared in Example 1, and N-methylpyrrolidone were uniformly mixed to prepare a solution with a solid content of 35 wt%, and then reacted at 0°C under nitrogen protection for 8 h to obtain a modified polyamic acid solution.

[0072] Step 3, preparation of engineering plastics: after mixing the hyperbranched polyamic acid solution obtained in the first step and the modified polyamic acid solution obtained in the second step in a mass ratio of 1:3, 1 mol of acetic anhydride is added, and the mixture is heated to 130°C with stirring and dehydrated for 5 hours. After dehydration, the mixture is cooled, water or ethanol is added, and the precipitate is precipitated with stirring. The precipitate is filtered, taken, and dried to obtain an impact-resistant and high-toughness polyimide.

[0073] Comparative Example 1

[0074] Preparation of polyimide engineering plastics:

[0075] Step 1: Preparation of hyperbranched polyamic acid solution: 0.35 mol of 4,4′-phthalic anhydride, 0.2 mol of 4,4′,4′′-triaminotriphenylmethane and N,N-methylformamide were uniformly mixed to prepare a solution with a solid content of 15 wt%. The solution was then reacted at 0°C under nitrogen protection for 8 hours to obtain a hyperbranched polyamic acid solution.

[0076] Step 2: Preparation of modified polyamic acid solution: Same as the second step in Example 3.

[0077] Step 3: Preparation of engineering plastics: Same as the third step in Example 3.

[0078] Comparative Example 2

[0079] Preparation of polyimide engineering plastics:

[0080] The first step, preparation of hyperbranched polyamic acid solution: the same as the first step in Example 3.

[0081] Step 2: Preparation of polyamic acid solution: 0.1 mol of 4,4′-phthalic anhydride, 2,2′-diphenylenediamine and N,N-methylformamide were uniformly mixed to prepare a solution with a solid content of 25 wt%, and then reacted at 0°C under nitrogen protection for 8 hours to obtain polyamic acid solution;

[0082] Step 3: Preparation of engineering plastics: Same as the third step in Example 3.

[0083] Comparative Example 3

[0084] Preparation of polyimide engineering plastics:

[0085] The first step, preparation of hyperbranched polyamic acid solution: the same as the first step in Comparative Example 1.

[0086] Step 2: Preparation of polyamic acid solution: same as the second step in Comparative Example 2;

[0087] Step 3: Preparation of engineering plastics: Same as the third step in Example 3.

[0088] Comparative Example 4

[0089] Preparation of polyimide engineering plastics:

[0090] Step 1: Preparation of modified polyamic acid solution: 0.1 mol of 4,4′-phthalic anhydride, 0.1 mol of the branched diamine monomer prepared in Example 1, and N,N-methylformamide were uniformly mixed to prepare a solution with a solid content of 25 wt%. The reaction was then carried out at 0°C under nitrogen protection for 8 h to obtain a modified polyamic acid solution.

[0091] Step 2: Preparation of engineering plastics: Add 0.5 mol of acetic anhydride to the modified polyamic acid solution, heat to 70°C with stirring, and dehydrate for 12 hours. After dehydration, cool, add water or ethanol, stir to precipitate, filter, take the precipitate, and dry to obtain polyimide.

[0092] Comparative Example 5

[0093] Preparation of polyimide engineering plastics:

[0094] The first step is to prepare polyamic acid solution: 0.1 mol of 4,4′-phthalic anhydride, 2,2′-diphenylenediamine and N,N-methylformamide are mixed evenly to prepare a solution with a solid content of 25 wt%. Then, the solution is reacted at 0°C under nitrogen protection for 8 hours to obtain polyamic acid solution.

[0095] Step 2: Preparation of engineering plastics: Add 0.4 mol of acetic anhydride to the polyamic acid solution, stir and heat to 70°C, and keep warm for dehydration for 12 hours. After dehydration, cool, add water or ethanol, stir to precipitate, filter, take the precipitate, and dry to obtain polyimide.

[0096] The polyimides obtained in Examples 3-5 and Comparative Examples 1-5 were subjected to physical property tests, and the results are shown in Table 1. Ultraviolet light resistance test: The polyimide sample was placed in a xenon arc lamp box and subjected to accelerated aging using a xenon arc lamp for 1000 hours. The tensile strength of the test sample was taken out, and the tensile strength after accelerated aging with the xenon arc lamp was divided by the tensile strength before being placed in the xenon arc lamp box, i.e., the tensile strength retention rate under ultraviolet light resistance; Alkali resistance: The polyimide sample was immersed in an alkaline solution (a sodium hydroxide solution with a mass concentration of 0.5%) and heated to 85°C in a water bath for 24 hours. The sample was then taken out, washed, and dried. The tensile strength of the sample after immersion was measured, and the tensile strength of the sample after immersion was divided by the tensile strength of the sample before immersion to obtain the tensile strength retention rate under alkali resistance.

[0097] Table 1

[0098] tensile strength Elongation at break Ultraviolet light resistance performance Tensile strength retention rate Alkali resistance tensile strength retention rate unit MPa % % % Example 3 115 18.3 97.4 97.2 Example 4 128 17.5 97.6 97.7 Example 5 137 17.1 98.1 98.0 Comparative Example 1 96 19.6 75.6 97.2 Comparative Example 2 111 15.3 97.4 81.7 Comparative Example 3 106 14.1 75.3 81.6 Comparative Example 4 83 10.2 76.0 97.2 Comparative Example 5 81 7.8 98.4 98.4

[0099] From the data in Table 1, it can be seen that the polyimide obtained in Examples 3-5 has good tensile properties, UV resistance and alkali resistance.

[0100] Throughout the specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0101] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in similar ways. As long as they do not deviate from the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. An alkali-hydrolysis-resistant polyimide engineering plastic, characterized in that: It is prepared by mixing a hyperbranched polyamic acid solution, a modified polyamic acid solution and a dehydrating agent and then undergoing a dehydration reaction; The hyperbranched polyamic acid solution is prepared by in-situ polymerization of modified nanoparticles, a first dianhydride monomer, and a triamine monomer in a first solvent; The modified polyamic acid solution is prepared by polymerization of a second dianhydride monomer and a branched diamine monomer in a second solvent; The branched diamine monomer is prepared by reacting aniline and benzaldehyde derivatives; The benzaldehyde derivative is prepared by reacting 4-hydroxybenzaldehyde and an epoxy silane coupling agent; The chemical structural formula of the branched diamine monomer is as follows: ； The mass ratio of the hyperbranched polyamic acid solution to the modified polyamic acid solution is 1:1-3; the solid content of the hyperbranched polyamic acid solution is 15-30 wt %; and the solid content of the modified polyamic acid solution is 25-40 wt %.

2. The alkali-hydrolysis-resistant polyimide engineering plastic according to claim 1, characterized in that: The dehydration reaction temperature is 70-130° C., and the reaction time is 5-12 hours.

3. The alkali-hydrolysis-resistant polyimide engineering plastic according to claim 1, characterized in that: The molar ratio of the first dianhydride monomer to the triamine monomer is 3.5-4:2; the reaction temperature in the in-situ polymerization reaction is 0-40° C., and the reaction time is 4-8 hours; the modified nanoparticles account for 15-35% of the total mass of the first dianhydride monomer and the triamine monomer.

4. The alkali-hydrolysis-resistant polyimide engineering plastic according to claim 1, characterized in that: The first dianhydride monomer is one of 4,4′-phthalic anhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride, and 4,4′-oxydiphthalic anhydride; the triamine monomer is 4,4′,4′′-triaminotriphenylmethane; and the first solvent is one or more of N,N-methylformamide, N,N-methylacetamide, and N-methylpyrrolidone.

5. The alkali-hydrolysis-resistant polyimide engineering plastic according to claim 1, characterized in that: The molar ratio of the second dianhydride monomer and the branched diamine monomer is 1:1; the reaction temperature in the polymerization reaction is 0-40°C, and the reaction time is 4-8 hours; the second dianhydride monomer is one of 4,4′-phthalic anhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride, and 4,4′-oxydiphthalic anhydride; and the second solvent is one or more of N,N-methylformamide, N,N-methylacetamide, and N-methylpyrrolidone.

6. The alkali-hydrolysis-resistant polyimide engineering plastic according to claim 1, characterized in that: The branched diamine monomer is obtained by reacting aniline and benzaldehyde derivatives, including: After uniformly mixing benzaldehyde derivative, aniline, aniline hydrochloride and dimethyl sulfoxide, reacting at 100-110°C under nitrogen protection for 1-3 hours, raising the temperature to 130-145°C, keeping the temperature for 2-3 hours, stopping the reaction, and post-processing to obtain a branched diamine monomer; The molar ratio of the benzaldehyde derivative to aniline is 1:2.5-3, and the added mass of the aniline hydrochloride is 3-6% of the mass of the benzaldehyde derivative and aniline.

7. The alkali-hydrolysis-resistant polyimide engineering plastic according to claim 1, characterized in that: The benzaldehyde derivative is prepared by reacting 4-hydroxybenzaldehyde with an epoxy silane coupling agent, comprising: After 4-hydroxybenzaldehyde, epoxysilane coupling agent and tetrahydrofuran are uniformly mixed, the pH of the system is adjusted to 10-11, heated to reflux under condensation, stirred and reacted for 2-4 hours, the reaction is stopped, and the benzaldehyde derivative is obtained through post-treatment; The molar ratio of the 4-hydroxybenzaldehyde to the epoxy silane coupling agent is 1:1-1.

3.

8. The alkali-hydrolysis-resistant polyimide engineering plastic according to claim 1, characterized in that: The dehydrating agent is acetic anhydride.

9. The method for preparing an alkali-hydrolysis-resistant polyimide engineering plastic according to any one of claims 1 to 8, characterized in that: include: The hyperbranched polyamic acid solution, the modified polyamic acid solution and the dehydrating agent are mixed, heated to a dehydration reaction temperature, and kept warm for dehydration. After the dehydration is completed, the mixture is post-treated to obtain polyimide.

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