Polyimide material with high temperature resistance and high toughness, preparation method thereof, molded part and application thereof

Abstract

This invention relates to the field of polyimide synthesis technology, specifically to polyimide materials possessing both high temperature resistance and high toughness, their preparation methods, molded parts, and applications; comprising the following monomers obtained through aqueous phase polymerization: rigid dianhydride monomer, rigid diamine monomer, flexible diamine monomer, and crosslinking monomer; wherein the rigid dianhydride monomer is selected from pyromellitic dianhydride and biphenyl dianhydride; the rigid diamine monomer is selected from diaminodiphenyl ether and phenylenediamine; the flexible diamine monomer is selected from diaminodiphenyl sulfone and bis[(aminophenoxy)phenyl]propane; and the crosslinking monomer is triaminobenzene; the material of this invention uses aromatic rigid groups as the main chain, introduces flexible segments into the side chains, and combines a small amount of crosslinking units, using green aqueous phase polymerization to obtain polyimide that can achieve both high temperature resistance and high toughness, and the mechanical strength and molding performance are superior to existing aqueous phase polymerized products and commercial products, and the toughness can be improved without the addition of toughening agents.

Description

Technical Field

[0001] This invention relates to the field of polyimide synthesis technology, specifically to polyimide materials with both high temperature resistance and high toughness, their preparation methods, molded parts, and applications. Background Technology

[0002] Polyimide (PI), as a high-performance engineering plastic, possesses irreplaceable application value in high-end fields such as aerospace, microelectronics, and precision machinery due to its excellent thermal stability, chemical corrosion resistance, and electrical insulation. However, traditional polyimide materials generally suffer from the technical bottleneck of "the incompatibility between high temperature resistance and toughness." While its rigid aromatic structure endows it with excellent high-temperature resistance, it also results in high brittleness and low elongation at break, making it difficult to meet the stringent toughness requirements of high-speed rotating components and complex molded parts.

[0003] Currently, there are two main types of common methods to improve the toughness of polyimide: one is to add toughening agents (such as rubber and nanoparticles), but this will significantly reduce the high temperature resistance and mechanical strength of the material, and there are problems such as uneven dispersion and poor compatibility; the other is to introduce flexible segments through copolymerization, but traditional copolymerization processes often use toxic high-boiling-point organic solvents such as N-methylpyrrolidone (NMP) and dimethylformamide (DMF), which have the disadvantages of environmental pollution, difficulty in solvent recovery, and high production costs. Moreover, the introduction of flexible segments can easily destroy the regularity of molecular chains, resulting in a significant decrease in high temperature resistance, and it is impossible to balance high temperature resistance and toughness.

[0004] Aqueous-phase polymerization, as a green and environmentally friendly synthesis process, uses distilled water as the reaction medium, which can completely solve the environmental and cost problems caused by organic solvents, and has become a research hotspot in the field of polyimide synthesis in recent years. However, existing aqueous-phase polymerization technology has obvious limitations: the monomer solubility in the aqueous system is poor, the polymerization reaction has low controllability, and problems such as incomplete imidization and uneven cross-linking of molecular chains are prone to occur, resulting in large fluctuations in product performance. Moreover, although the post-processing process is simple, most of them adopt the constant rate heating method, which cannot achieve the ordered growth of molecular chains and precise control of crystallinity, further exacerbating the contradiction between high temperature resistance and toughness. In addition, the sintering performance, molding performance and mechanical properties of polyimide powder prepared by existing aqueous-phase polymerization are difficult to match synergistically, and the pressed molded parts are prone to defects such as cracking and delamination, which limits its application in high-end fields.

[0005] Therefore, developing a polyimide material that is based on precise molecular structure design, uses a green aqueous phase polymerization process, and achieves both high temperature resistance and high toughness, as well as stable performance and easy industrial production, is a technical problem that urgently needs to be solved in this field. It has important industrial application value and innovative significance. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a polyimide material possessing both high temperature resistance and high toughness, along with its preparation method, molded parts, and applications. This invention uses rigid aromatic groups as the main chain, introduces flexible segments into the side chains, and combines a small number of crosslinking units. The polyimide obtained through green aqueous phase polymerization achieves a balance between high temperature resistance and high toughness, with superior mechanical strength and molding performance compared to existing aqueous phase polymerized products and commercial products. Toughness enhancement is achieved without the need for toughening agents.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0008] The first aspect of this invention provides a polyimide material with both high temperature resistance and high toughness, which is prepared by aqueous polymerization of monomers in the following molar percentages: 40%-55% rigid dianhydride monomer, 25%-40% rigid diamine monomer, 15%-25% flexible diamine monomer, and 1%-3% crosslinking monomer;

[0009] The rigid dianhydride monomer is selected from a mixture of pyromellitic dianhydride and biphenyl dianhydride in a molar ratio of 1-1.2:1; the rigid diamine monomer constructs a highly aromatic main chain structure to ensure the high temperature resistance of the material.

[0010] The rigid diamine monomer is selected from a mixture of diaminodiphenyl ether and phenylenediamine in a molar ratio of 1-1.4:1;

[0011] The flexible diamine monomer is selected from diaminodiphenyl sulfone and bis[(aminophenoxy)phenyl]propane mixed in a molar ratio of 1-1.35:1; as a comonomer, by precisely controlling the molar ratio of the flexible diamine monomer, flexible groups are introduced into the rigid main chain, thereby enhancing the mobility of the molecular chain and improving the toughness of the material.

[0012] The crosslinking monomer is triaminobenzene, which restricts excessive slippage of the molecular chain through crosslinking, while simultaneously controlling the crystallinity to 25%-35%, avoiding the decrease in high-temperature resistance caused by the introduction of flexible segments, and achieving a synergistic balance of "rigidity-flexibility-crosslinking". Through molecular design, the polyimide molecular chain possesses both the high-temperature resistant framework of the rigid main chain and the toughness adjustment capability of the flexible side chains. At the same time, the crystallinity is optimized through crosslinking, solving the technical problem of "the incompatibility between high-temperature resistance and toughness".

[0013] Furthermore, the diaminodiphenyl ether is selected from one or more of 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl ether, and 3,3'-diaminodiphenyl ether.

[0014] The phenylenediamine is selected from p-phenylenediamine and / or m-phenylenediamine;

[0015] The diaminodiphenyl sulfone is selected from one or more of 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, and 4,4'-bis(3-aminophenoxy)diphenyl sulfone;

[0016] The bis[(aminophenoxy)phenyl]propane is selected from one or both of 2,2'-bis[4-(4-aminophenoxyphenyl)]propane (BAPP or p-BAPP) and 2,2'-bis[4-(3-aminophenoxy)phenyl)]propane (m-BAPP).

[0017] Furthermore, the polyimide material has a crystallinity of 25%-35% and an intrinsic viscosity of 0.6-0.8 dL / g.

[0018] Furthermore, the polyimide material is a powder with a specific surface area of ​​35-45 m² / g, an average particle size D50 of 60-90 μm, and no organic solvent residue.

[0019] Furthermore, the properties of the polyimide material satisfy the following two conditions:

[0020] The elongation at break under GB / T 1040.1 standard shall be at least 10%;

[0021] The 5% weight loss thermal decomposition temperature is at least 580℃.

[0022] Furthermore, the properties of the polyimide material also satisfy at least one of the following conditions:

[0023] The tensile strength under GB / T 1040.1 standard shall be at least 160 MPa;

[0024] The impact strength under GB / T 1843 standard shall be at least 110 kJ / m².

[0025] The heat distortion temperature under GB / T 1634.1 standard shall be at least 330℃;

[0026] The residual carbon content at 700℃ should be at least 58%;

[0027] Density 1.38-1.40 g / cm³.

[0028] A second aspect of the present invention provides a method for preparing a polyimide material that combines high temperature resistance and high toughness, comprising the following steps:

[0029] S1. Preparation of polyamic acid (PAA) suspension by aqueous suspension polymerization: Using distilled water as the reaction solvent, under a protective atmosphere and with continuous stirring, at a temperature below 60°C, rigid diamine, flexible diamine, and crosslinking monomer are added according to the formula. After complete dissolution, rigid dianhydride monomer is added in multiple batches. The reaction temperature of the reaction system is controlled at 55~65°C and the reaction is maintained at this temperature to obtain polyamic acid suspension. Adding rigid dianhydride monomer in batches can avoid excessively vigorous local reactions, improve the uniformity of the polymerization reaction, and solve the problem of poor monomer solubility in the aqueous system.

[0030] S2. Preparation of crude PI powder by aqueous in-situ imidization: The pH of the polyamic acid suspension is adjusted to alkaline, and an aqueous in-situ imidization reaction is carried out under a protective atmosphere. After filtration, washing and drying, crude PI powder is obtained.

[0031] S3. Post-processing: The coarse PI powder is placed in a muffle furnace and subjected to gradient heating heat treatment under a protective atmosphere. After cooling, crushing, and sieving, a polyimide material with both high temperature resistance and high toughness is obtained.

[0032] Furthermore, the total monomer in S1 constitutes 10%-15% by mass in the reaction system; nitrogen is used as the protective atmosphere, with a nitrogen flow rate of 30-50 mL / min; and the stirring speed is 250-350 rpm.

[0033] Furthermore, the rigid dianhydride monomer described in S1 is added in at least three batches, with an interval of at least 15 minutes between each batch; the heat preservation reaction time described in S1 is 4-6 hours.

[0034] Furthermore, in S2, the pH value is adjusted using ammonia water with a mass fraction of 25%-28% to a pH value of 8-9. This alkaline condition accelerates the catalytic imide process.

[0035] Furthermore, the aqueous in-situ imidization reaction described in S2 is carried out at a temperature of 120-130℃, with a reaction time of 3-4 hours at this temperature and a heating rate of 2-3℃ / min. The protective atmosphere is nitrogen, with a nitrogen flow rate of 40-60 mL / min. Performing the aqueous in-situ imidization reaction at this temperature avoids molecular chain breakage caused by high temperatures and ensures that the imidization reaction proceeds fully, achieving a degree of imidization ≥99%.

[0036] Furthermore, the protective atmosphere used in S3 is nitrogen, with a nitrogen flow rate of 50-70 mL / min;

[0037] The gradient heating heat treatment includes a first stage treatment, a second stage treatment, and a third stage treatment.

[0038] The first stage of treatment is the dehydration and degassing stage: the temperature is increased to 80-120℃ at 3-4℃ / min and kept at 1-1.5h to remove the adsorbed moisture and residual trace gases from the powder;

[0039] The second stage of treatment is the molecular chain regularization stage: the temperature is increased to 180-250℃ at 1-2℃ / min and held for 1.5-2h to promote the orderly arrangement of molecular chains and improve the uniformity of crystallinity;

[0040] The third stage of treatment is the cross-linking curing and performance optimization stage: the temperature is increased to 300-320℃ at 0.5-1℃ / min and held for 2-2.5h to achieve full cross-linking of the cross-linking monomers, adjust the crystallinity to 25-35%, and repair the molecular chain defects generated during the polymerization process.

[0041] The third aspect of the present invention provides a molded part, which is prepared by cold pressing preforming-stepwise high-temperature sintering process from the polyimide material provided in the first aspect or the polyimide material prepared by the method of the second aspect; the cold pressing preforming conditions are: room temperature, pressurization rate of 40-50 MPa / min, pressure of 600-650 MPa, and holding pressure for 6-8 min; the stepwise high-temperature sintering is carried out under nitrogen protection by sequentially heating to 100°C and holding for 30 min, heating to 200°C and holding for 30 min, heating to 300°C and holding for 30 min, and heating to 380-400°C and holding for 1-1.5 h.

[0042] Furthermore, the nitrogen flow rate during the stepwise high-temperature sintering process is 60-80 mL / min, and the heating rates for each stage are as follows: 8-10℃ / min for the 100℃ stage, 5-6℃ / min for the 200℃ stage, 3-4℃ / min for the 300℃ stage, and 2-3℃ / min for the 380-400℃ stage.

[0043] The final aspect of the present invention provides the application of the polyimide material provided according to the first aspect, or the polyimide material prepared according to the preparation method of the second aspect, or the molded part provided according to the third aspect in high-end equipment manufacturing materials;

[0044] The high-end equipment manufacturing system includes at least one of the following: materials for aerospace, materials for mechanical parts, materials for chip packaging, materials for microelectromechanical systems, and materials for semiconductor equipment.

[0045] Beneficial technical effects: This invention uses aromatic rigid groups as the main chain, introduces flexible segments into the side chains, and combines a small number of crosslinking units. It adopts a green aqueous phase polymerization process with distilled water as the only reaction medium, without adding any organic solvents. By precisely controlling the ratio of flexible monomers and crosslinking monomers, as well as adjusting the polymerization parameters and segmented post-processing, the orderly growth of molecular chains and the synergistic matching of performance parameters are achieved. The resulting polyimide material has excellent high temperature resistance (5% thermal decomposition temperature at least 580℃) and high toughness (elongation at break at least 10%). Moreover, its mechanical strength and molding performance are superior to existing commercial products. Toughness improvement can be achieved without adding toughening agents, avoiding the performance degradation problem caused by toughening agents.

[0046] This invention improves the solubility of monomers and the uniformity of polymerization in an aqueous polymerization system by adding dianhydride monomers in batches and controlling the reaction temperature, thereby achieving a green synthesis with high imidization degree. Subsequently, a segmented post-heat treatment process is used to precisely control the crystallinity and molecular chain structure, thereby improving the product performance stability. Detailed Implementation

[0047] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] Unless otherwise specifically stated, the numerical values ​​set forth in these embodiments do not limit the scope of the invention. Techniques and methods known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques and methods should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that values ​​expressed, for example, as "within the range of ab" or "between the range of ab," do not include the endpoint values ​​a and b; values ​​expressed as "for ab," "is ab," or "ab" include the endpoint values ​​a and b.

[0049] Furthermore, it should be noted that the use of terms such as "first" and "second" to define the post-processing stages is merely for the purpose of distinguishing the processing steps. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0050] Experimental methods not specified in the following examples are generally performed according to national standards; if there is no corresponding national standard, they are performed according to general standard requirements or general methods.

[0051] Example 1

[0052] A method for preparing polyimide materials that combine high temperature resistance and high toughness includes the following steps:

[0053] S1. Preparation of PAA precursor by aqueous suspension polymerization: 200 mL of distilled water was added to the reactor, nitrogen gas was introduced (flow rate 40 mL / min), and the mixture was continuously stirred (stirring rate 300 r / min) until the temperature reached 55 °C. Then, 8.62 g of 4,4'-diaminodiphenyl ether (ODA, 200.24 g / mol, 0.043 mol), 3.48 g of p-phenylenediamine (PPD, 108.14 g / mol, 0.032 mol), 5.28 g of 4,4'-diaminodiphenyl sulfone (DDS, 248.30 g / mol, 0.021 mol), and 6.72 g of 2,2'-bis[4-(4-aminophenoxyphenyl)]propane were added. 0.42 g of 1,3,5-triaminobenzene (BAPP, 410.51 g / mol, 0.016 mol) and 0.42 g of 1,3,5-triaminobenzene (TAP, 123.16 g / mol, 0.0034 mol) were stirred until completely dissolved. Then, 10.92 g of pyromellitic dianhydride (PMDA, 218.12 g / mol, 0.050 mol) and 12.96 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA, 294.22 g / mol, 0.044 mol) were added in batches, 15 min apart, at a time. The reaction temperature was maintained at 60 °C for 5 h to obtain a PAA suspension.

[0054] S2. Aqueous in-situ imidization reaction: Ammonia (25wt%) was added to the PAA suspension to adjust the pH of the system to 8.5. The temperature was increased to 125℃ at 2.5℃ / min for aqueous in-situ imidization reaction, with a nitrogen flow rate of 50mL / min. The reaction was maintained at this temperature for 3.5h. After cooling, the mixture was centrifuged and filtered, washed four times with distilled water, and dried under vacuum at 105℃ for 10h to obtain crude PI powder.

[0055] S3. Post-processing: The coarse PI powder is placed in a muffle furnace and subjected to gradient heating heat treatment under a nitrogen atmosphere (nitrogen flow rate 60 mL / min). After cooling, it is crushed and passed through a 150-mesh sieve to obtain PI powder.

[0056] The gradient heating heat treatment includes a first stage treatment, a second stage treatment, and a third stage treatment.

[0057] The first stage of treatment: the temperature is increased to 100℃ at a rate of 3.5℃ / min and held for 1.2 hours;

[0058] The second stage of treatment: the temperature is increased to 200℃ at a rate of 1.5℃ / min and held for 1.8 hours;

[0059] The third stage of treatment involves heating to 310℃ at a rate of 1℃ / min and holding at that temperature for 2.2 hours.

[0060] The PI powder prepared above was used to make molded parts. The preparation process is as follows: PI powder was added to a 200×155mm rectangular mold, and the pressure was increased from 5MPa / min to 62MPa at room temperature and held for 7min. Then, under nitrogen protection (nitrogen flow rate 70mL / min), stepwise high-temperature sintering was carried out: the temperature was increased to 100℃ at 10℃ / min and held for 30min, the temperature was increased to 200℃ at 6℃ / min and held for 30min, the temperature was increased to 300℃ at 3.5℃ / min and held for 30min, the temperature was increased to 390℃ at 2.5℃ / min and held for 1.2h. After cooling, the molded parts were obtained.

[0061] Example 2

[0062] A method for preparing polyimide materials that combine high temperature resistance and high toughness includes the following steps:

[0063] S1. Preparation of PAA precursor by aqueous suspension polymerization: Add 200 mL of distilled water to the reactor, purge with nitrogen (flow rate 30 mL / min), and continuously stir (stirring rate 250 r / min). Heat to 50 °C, add 7.76 g of 4,4'-diaminodiphenyl ether (ODA), 3.13 g of p-phenylenediamine (PPD), 4.40 g of 4,4'-diaminodiphenyl sulfone (DDS), 5.60 g of 2,2'-bis[4-(4-aminophenoxyphenyl)]propane (BAPP), and 0.28 g of 1,3,5-triaminobenzene (TAP), and stir until completely dissolved; add in batches 9.84 g of pyromellitic dianhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA). 11.68g (divided into 5 batches, with an interval of 20min between each batch), the reaction temperature of the reaction system was controlled at 55℃, and the reaction was kept at this temperature for 4h to obtain PAA suspension;

[0064] S2. Aqueous in-situ imidization reaction: Ammonia (25wt%) was added to the PAA suspension to adjust the pH of the system to 8.0. The aqueous in-situ imidization reaction was carried out at 120℃ with a nitrogen flow rate of 40mL / min and the reaction was maintained at this temperature for 4h. After cooling, the mixture was centrifuged and filtered, washed three times with distilled water, and dried under vacuum at 120℃ for 12h to obtain crude PI powder.

[0065] S3. Post-processing: The coarse PI powder is placed in a muffle furnace and subjected to gradient heating heat treatment under a nitrogen atmosphere (nitrogen flow rate 50 mL / min). After cooling, it is crushed and passed through a 100-mesh sieve to obtain PI powder.

[0066] The gradient heating heat treatment includes a first stage treatment, a second stage treatment, and a third stage treatment.

[0067] The first stage of treatment: the temperature is increased to 100℃ at a rate of 3℃ / min and held for 1.5 hours;

[0068] Second stage treatment: Increase the temperature to 200℃ at a rate of 1℃ / min and hold for 2 hours;

[0069] The third stage of treatment involves heating to 300℃ at a rate of 1℃ / min and holding at that temperature for 2.5 hours.

[0070] The PI powder prepared above was used to make molded parts. The preparation process is as follows: PI powder was added to a 200×155mm rectangular mold, and the pressure was increased to 60MPa at 4MPa / min at room temperature and held for 8min. Then, under nitrogen protection (nitrogen flow rate 60mL / min), stepwise high-temperature sintering was carried out: the temperature was increased to 100℃ at 8℃ / min and held for 30min, the temperature was increased to 200℃ at 5℃ / min and held for 30min, the temperature was increased to 300℃ at 3℃ / min and held for 30min, the temperature was increased to 380℃ at 2℃ / min and held for 1.5h, and the molded parts were obtained after cooling.

[0071] Example 3

[0072] A method for preparing polyimide materials that combine high temperature resistance and high toughness includes the following steps:

[0073] S1. Preparation of PAA precursor by aqueous suspension polymerization: Add 200 mL of distilled water to the reactor, purge with nitrogen (flow rate 50 mL / min), and continuously stir (stirring rate 350 r / min). Heat to 60 °C, add 9.48 g of 4,4'-diaminodiphenyl ether (ODA), 3.82 g of p-phenylenediamine (PPD), 6.16 g of 4,4'-diaminodiphenyl sulfone (DDS), 7.84 g of 2,2'-bis[4-(4-aminophenoxyphenyl)]propane (BAPP), and 0.56 g of 1,3,5-triaminobenzene (TAP), and stir until completely dissolved; add pyromellitic dianhydride (PMDA) in batches. 11.99 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 14.24 g of BPDA were mixed in 5 batches, with an interval of 15 min between each batch. The reaction temperature of the reaction system was controlled at 65 °C and the reaction was maintained at this temperature for 6 h to obtain a PAA suspension.

[0074] S2. Aqueous in-situ imidization reaction: Ammonia (28wt%) was added to the PAA suspension to adjust the pH of the system to 9.0. The aqueous in-situ imidization reaction was carried out at 130℃ with a nitrogen flow rate of 60mL / min and the reaction was maintained at this temperature for 3h. After cooling, the mixture was centrifuged and filtered, washed 5 times with distilled water, and dried under vacuum at 110℃ for 8h to obtain crude PI powder.

[0075] S3. Post-processing: The coarse PI powder is placed in a muffle furnace and subjected to gradient heating heat treatment under a nitrogen atmosphere (nitrogen flow rate 70 mL / min). After cooling, it is crushed and passed through a 200-mesh sieve to obtain PI powder.

[0076] The gradient heating heat treatment includes a first stage treatment, a second stage treatment, and a third stage treatment.

[0077] First stage treatment: heat up to 100℃ at 4℃ / min and hold for 1 hour;

[0078] The second stage of treatment: the temperature is increased to 200℃ at a rate of 2℃ / min, and held at that temperature for 1.5 hours;

[0079] The third stage of treatment involves heating to 320°C at a rate of 1°C / min and holding at that temperature for 2 hours.

[0080] The PI powder prepared above was used to make molded parts. The preparation process is as follows: PI powder was added to a 200×155mm rectangular mold, and the pressure was increased from 5MPa / min to 80MPa at room temperature and held for 6min. Then, under nitrogen protection (nitrogen flow rate 80mL / min), stepwise high-temperature sintering was carried out: the temperature was increased to 100℃ at 10℃ / min and held for 30min, the temperature was increased to 200℃ at 6℃ / min and held for 30min, the temperature was increased to 300℃ at 4℃ / min and held for 30min, the temperature was increased to 400℃ at 3℃ / min and held for 1h, and the molded parts were obtained after cooling.

[0081] Comparative Example 1

[0082] In this case, the polyimide preparation process only uses PMDA, BPDA, ODA, and PPD for aqueous suspension polymerization, without adding flexible diamine monomers (DDS, BAPP) and crosslinking monomers (TAP). The remaining steps are the same as in Example 1.

[0083] Comparative Example 2

[0084] The preparation process of the polyimide in this case is the same as in Example 1, except that the specific feed quantities are as follows: 8.62 g of 4,4'-diaminodiphenyl ether (ODA), 3.48 g of p-phenylenediamine (PPD), 8.80 g of 4,4'-diaminodiphenyl sulfone (DDS), 11.20 g of 2,2'-bis[4-(4-aminophenoxyphenyl)]propane (BAPP), 0.42 g of 1,3,5-triaminobenzene (TAP), 10.92 g of pyromellitic dianhydride (PMDA), and 12.96 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA). The difference between this case and Example 1 is the higher proportion of flexible monomers, with the proportion of flexible diamine monomers increased to approximately 27%.

[0085] Comparative Example 3

[0086] The preparation process of the polyimide in this case is the same as in Example 1, except that the specific feed quantities are as follows: 8.62 g of 4,4'-diaminodiphenyl ether (ODA), 3.48 g of p-phenylenediamine (PPD), 2.20 g of 4,4'-diaminodiphenyl sulfone (DDS), 2.80 g of 2,2'-bis[4-(4-aminophenoxyphenyl)]propane (BAPP), 0.42 g of 1,3,5-triaminobenzene (TAP), 10.92 g of pyromellitic dianhydride (PMDA), and 12.96 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA). The difference between this case and Example 1 is the lower proportion of flexible monomers; the proportion of flexible diamine monomers is reduced to approximately 8%.

[0087] Comparative Example 4

[0088] The preparation process of the polyimide in this case is the same as that in Example 1, except that no crosslinking monomer (TAP) is added.

[0089] Comparative Example 5

[0090] In this case, NMP was used as the reaction solvent, and other conditions were the same as in Example 1.

[0091] Comparative Example 6

[0092] The polyimide preparation method in this case is the same as that in Example 1, except that the S3 post-treatment uses a constant rate of heating to 320°C at 10°C / min and holding at that temperature for 2.2 hours.

[0093] In the above comparative examples, except for the clearly changed monomer ratio / addition amount, all processes such as reaction temperature, time, heating program, atmosphere, and post-treatment are completely consistent with those in Example 1.

[0094] Test case

[0095] The performance of the molded parts in the above cases was tested, and the results are shown in Table 1.

[0096] Table 1. Specifications of polyimide materials in the examples and comparative examples

[0097]

[0098] As shown in Table 1, the material in Comparative Example 1 has extremely poor toughness and cannot meet the requirements of high-end applications; the material in Comparative Example 2 has significantly reduced high-temperature resistance and cannot balance high-temperature resistance and toughness; the material in Comparative Example 5 has similar performance to that in Example 1, but has residual organic solvents, resulting in high production costs and serious environmental pollution, which does not meet the requirements of green production; the material in Comparative Example 6 has uneven crystallinity (20%-40%) and large performance fluctuations, with both toughness and mechanical strength decreasing.

[0099] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A polyimide material possessing both high temperature resistance and high toughness, characterized in that, The monomers are prepared by aqueous phase polymerization in the following molar percentages: 40%-55% rigid dianhydride monomer, 25%-40% rigid diamine monomer, 15%-25% flexible diamine monomer, and 1%-3% crosslinking monomer. The rigid dianhydride monomer is selected from a mixture of pyromellitic dianhydride and biphenyl dianhydride in a molar ratio of 1-1.2:1; The rigid diamine monomer is selected from a mixture of diaminodiphenyl ether and phenylenediamine in a molar ratio of 1-1.4:1; The flexible diamine monomer is selected from diaminodiphenyl sulfone and bis[(aminophenoxy)phenyl]propane mixed in a molar ratio of 1-1.35:1; The crosslinking monomer is triaminobenzene.

2. The polyimide material with both high temperature resistance and high toughness according to claim 1, characterized in that, The diaminodiphenyl ether is selected from one or more of 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl ether, and 3,3'-diaminodiphenyl ether; The phenylenediamine is selected from p-phenylenediamine and / or m-phenylenediamine; The diaminodiphenyl sulfone is selected from one or more of 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, and 4,4'-bis(3-aminophenoxy)diphenyl sulfone; The bis[(aminophenoxy)phenyl]propane is selected from one or both of 2,2'-bis[4-(4-aminophenoxyphenyl)]propane and 2,2'-bis[4-(3-aminophenoxy)phenyl)]propane.

3. The polyimide material with both high temperature resistance and high toughness according to claim 1, characterized in that, The physicochemical properties of the polyimide material satisfy at least two of the following conditions I to III: I. Crystallinity is 25%-35%; II. Inherent viscosity is 0.6-0.8 dL / g; III. Powder form, with a specific surface area of ​​35-45 m² / g and an average particle size D50 of 60-90 μm, and no organic solvent residue.

4. The polyimide material with both high temperature resistance and high toughness according to claim 1, characterized in that, The polyimide material satisfies both conditions (1) and (2) below, and also satisfies one of the conditions (3) to (7) below: (1) The elongation at break under GB / T 1040.1 standard shall be at least 10%; (2) The 5% weight loss thermal decomposition temperature is at least 580℃; (3) The tensile strength under GB / T 1040.1 standard is at least 160 MPa; (4) The impact strength under GB / T 1843 standard shall be at least 110 kJ / m²; (5) The heat distortion temperature under GB / T 1634.1 standard is at least 330℃; (6) The carbon residue at 700℃ is at least 58%; (7) Density 1.38-1.40 g / cm³.

5. A method for preparing a polyimide material possessing both high temperature resistance and high toughness, applicable to the preparation of the polyimide material as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Preparation of polyamic acid suspension by aqueous suspension polymerization: Using distilled water as the reaction solvent, under a protective atmosphere and continuous stirring, at a temperature below 60°C, rigid diamine, flexible diamine and crosslinking monomer are added according to the ratio. After complete dissolution, rigid dianhydride monomer is added. The reaction temperature of the reaction system is controlled at 55-65°C and the reaction is maintained at this temperature to obtain polyamic acid suspension. S2. Preparation of crude PI powder by aqueous in-situ imidization: The pH of the polyamic acid suspension is adjusted to be alkaline, and an aqueous in-situ imidization reaction is carried out under a protective atmosphere to obtain crude PI powder. S3. Post-processing: The coarse PI powder is subjected to gradient heating heat treatment under a protective atmosphere to obtain a polyimide material with both high temperature resistance and high toughness.

6. The method for preparing the polyimide material with both high temperature resistance and high toughness according to claim 5, characterized in that, The total monomer in S1 is 10%-15% by mass in the reaction system; nitrogen is used as the protective atmosphere, and the nitrogen flow rate is 30-50 mL / min. The rigid dianhydride monomer described in S1 is added in at least 3 batches, with an interval of at least 15 minutes between each batch; the heat preservation reaction time described in S1 is 4-6 hours.

7. The method for preparing the polyimide material with both high temperature resistance and high toughness according to claim 5, characterized in that, In S2, the pH value is adjusted using ammonia water with a mass fraction of 25%-28% to a pH value of 8-9. The aqueous in-situ imidization reaction described in S2 is carried out at a temperature of 120-130℃, with a reaction time of 3-4 h at this temperature, a heating rate of 2-3℃ / min, and a nitrogen atmosphere of 40-60 mL / min.

8. The method for preparing the polyimide material with both high temperature resistance and high toughness according to claim 5, characterized in that, The protective atmosphere used in S3 is nitrogen, and the flow rate of nitrogen is 50-70 mL / min; The gradient heating heat treatment includes a first stage treatment, a second stage treatment, and a third stage treatment. The first stage of treatment involves heating to 80-120℃ at a rate of 3-4℃ / min and holding at that temperature for 1-1.5 hours. The second stage of treatment: heat up to 180-250℃ at a rate of 1-2℃ / min, and hold at that temperature for 1.5-2 hours; The third stage of treatment involves heating to 300-320℃ at a rate of 0.5-1℃ / min and holding at that temperature for 2-2.5 hours.

9. A molded part, characterized in that, The polyimide material is prepared by a cold-pressing preforming-step-high-temperature sintering process, comprising the polyimide material according to any one of claims 1-5 or the polyimide material prepared by any one of claims 6-8. The cold-pressing preforming conditions are: room temperature, pressurization rate of 40-50 MPa / min, pressure of 600-650 MPa, and holding pressure for 6-8 min. The stepwise high-temperature sintering is carried out under nitrogen protection by sequentially heating to 100℃ at a rate of 8-10℃ / min and holding for 30 min, heating to 200℃ at a rate of 5-6℃ / min and holding for 30 min, heating to 300℃ at a rate of 3-4℃ / min and holding for 30 min, and heating to 380-400℃ at a rate of 2-3℃ / min and holding for 1-1.5 h.

10. Application, characterized in that, This includes the application of the polyimide material according to any one of claims 1-5, or the polyimide material prepared by the preparation method according to any one of claims 6-8, or the molded part according to claim 9 in high-end equipment manufacturing materials; The high-end equipment manufacturing system includes materials for aerospace, materials for mechanical parts, materials for chip packaging, materials for microelectromechanical systems, and materials for semiconductor equipment.

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