Preparation method of high-molecular-weight heterocyclic aromatic polyamide powder, powder product and application

Abstract

The invention discloses a preparation method of high-molecular-weight heterocyclic aromatic polyamide powder, a powder product and application of the high-molecular-weight heterocyclic aromatic polyamide powder. 2-(4-aminophenyl)-5-aminobenzimidazole, p-phenylenediamine and other aromatic diamine monomers which are metered according to a proportion are dissolved in an organic solvent containing a cosolvent, then paraphthaloyl chloride is added, stirring is carried out, and the high-molecular-weight heterocyclic aromatic polyamide powder is obtained. The solid content of the bulk or granular polymer is 6-15%, and the logarithmic viscosity of the obtained polymer can reach more than 8dL / g, and the maximum logarithmic viscosity can reach more than 12dL / g. The heterocyclic aromatic polyamide powder prepared by the method can be dissolved in concentrated sulfuric acid, methanesulfonic acid and other strong acids to prepare a high-viscosity solution, the solution is processed into a high-performance fiber or film material, and large-scale popularization and application of heterocyclic aramid fibers can be realized.

Description

Technical Field

[0001] The invention relates to a method for preparing heterocyclic aromatic polyamide powder. The prepared heterocyclic aromatic polyamide powder can be used for preparing fibers or films with excellent mechanical properties, and belongs to the field of high-performance organic fiber and film preparation. Background Art

[0002] Heterocyclic aromatic polyamide fiber, also known as heterocyclic aramid or aramid III, is prepared by introducing aromatic diamines containing heterocycles on the basis of para-aramid (aramid II, aramid 1414). The mechanical properties of heterocyclic aramid are 30% to 50% higher than those of para-aramid. It is one of the high-performance organic fibers with the best comprehensive performance. It has significant application advantages and broad application potential in the fields of aerospace, vehicles, protection, ropes and cables. However, the cost of heterocyclic aramid is about 10 times that of para-aramid, which greatly restricts its large-scale promotion and application.

[0003] Low production efficiency is one of the key factors for the high cost of heterocyclic aramid. Existing heterocyclic aramid is made of terephthaloyl chloride (TPC), p-phenylenediamine (PPDA), 2-(4-aminophenyl)-5-aminobenzimidazole (DAPBI), and sometimes other small amounts of modified diamine monomers are added as needed, in DMAc / LiCl or NMP / CaCl 2 The polymer is polymerized in an organic solvent system to obtain a viscous polymer solution (such as Figure 1 As shown), and then prepared by wet spinning or dry-wet spinning. The former has a spinning speed of about 10-20 m / min, and the latter has a spinning speed of about 30-40 m / min, with low production efficiency. This type of technology is well known, and can be found in patents such as CN106757452B, CN104357939B, and CN104278338B. In contrast, para-aramid uses liquid crystal dry-wet spinning technology, and the spinning speed can reach 300 m / min-800 m / min, or even higher. First, terephthaloyl chloride (TPC) and p-phenylenediamine (PPDA) are reacted in DMAc / LiCl or NMP / CaCl 2 The polymer is polymerized in an organic solvent system to obtain "crumb"-like polymer gel particles, which are then ground, washed, dried, and other processes to obtain para-aramid polymer powder. The polymer powder is then redissolved in concentrated sulfuric acid to form a high-concentration liquid crystal solution, and then the para-aramid fiber is prepared by dry-wet spinning. Although the preparation process of para-aramid is longer and more complicated than that of heterocyclic aramid, the liquid crystal spinning solution can achieve high-speed spinning, which significantly improves production efficiency. If heterocyclic aramid is prepared using liquid crystal spinning technology similar to para-aramid, the production efficiency of heterocyclic aramid will be greatly improved, and the production cost will be significantly reduced, which will play an important role in promoting the large-scale application of heterocyclic aramid.

[0004] The preparation of heterocyclic aramid polymer powder is a prerequisite for realizing liquid crystal dry-wet spinning. As is well known, the solubility of aramid in organic solvents such as NMP or DMAc is related to the content of cosolvents such as CaCl 2 or LiCl. For example, if no cosolvent is added to NMP or DMAc, the polymer will precipitate at a relatively low molecular weight in the early stage of the polymerization reaction, resulting in an excessively low molecular weight of the final polymer. Due to the regular structure and strong intermolecular forces of para-aramid, as the polymerization reaction proceeds, when the molecular weight increases to a certain extent, even with a high content of cosolvent, it will still precipitate from the solvent to form a polymer in the shape of breadcrumbs. However, due to the introduction of DAPBI monomers in heterocyclic aramid on the basis of para-aramid, its solubility is improved and it will not precipitate from organic solvents at a high cosolvent content. Therefore, it is impossible to prepare a polymer gel powder similar to the breadcrumb-like para-aramid by using the existing heterocyclic aramid polymerization process, and only a viscoelastic rubber-like polymer can be obtained. The patent US20070083032A1 of Teijin Limited discloses a method for preparing heterocyclic aramid polymer powder. This invention prepares heterocyclic aramid polymer powder by adjusting the relationship between the molar content (b%) of DAPBI in the polymer structure and the cosolvent concentration (c%). The key to this invention is that when the DAPBI content (b%) is low, the polymer solubility is poor, and by appropriately increasing the cosolvent (c%) content, precipitation in the early stage of polymerization is avoided to obtain a low molecular weight polymer; when the DAPBI content (b%) is high, the polymer solubility is good, and by appropriately reducing the cosolvent content (c%), the formation of a viscoelastic rubber-like polymer is avoided. By controlling b*c between 50 and 215, a heterocyclic aramid polymer that can be crushed into powder and does not stick together is obtained, and the inherent viscosity of this polymer is 4-7 dL / g. The patents WO2013019581A1 and WO2013019598A1 of DuPont Company have made improvements on the basis of the Teijin patent. By increasing the solid content to promote precipitation in the later stage of the polymerization reaction to form a crushable gel, the preparation of heterocyclic aramid polymer with a relatively high molecular weight at a high solid content (12%-15%) is realized. This invention controls b*c≥225, the cosolvent content c% is controlled between 5% and 10%, and the inherent viscosity of the polymer is 4-8 dL / g. However, high-solid-content polymerization easily leads to uneven molecular weight distribution of the polymer and high cosolvent content, resulting in difficult washing.

[0005] As is well known, the mechanical properties of fibers are closely related to their molecular weight. Especially in the process of liquid crystal spinning, the amide bonds of aramid will degrade under the action of concentrated sulfuric acid. Therefore, to obtain high-performance heterocyclic aramid, it is necessary to increase the initial molecular weight of the polymer, but the molecular weight of the heterocyclic aramid powder prepared by the existing technology is relatively low. Summary of the Invention

[0006] The object of the present invention is to provide a method for preparing a heterocyclic aromatic polyamide powder with high molecular weight, a powder product and its application, aiming at the disadvantage of the heterocyclic aromatic polyamide powder prepared by the prior art having a relatively low molecular weight. The molecular weight of the heterocyclic aromatic polyamide powder is mainly determined by its solubility in the organic solvent in addition to factors such as monomer purity and water content of the organic solvent. As the polymerization reaction proceeds, when the molecular weight increases to a certain extent, due to the strong interaction between heterocyclic aromatic polyamide molecules, it will precipitate from the organic solvent. The worse the solubility of the heterocyclic aromatic polyamide powder in the organic solvent, the lower the molecular weight at which it precipitates from the solvent, resulting in premature termination of the polymerization reaction and a lower molecular weight of the product; if the solubility is too good, the polymer cannot precipitate from the organic solvent, resulting in a highly viscous solution of the polymer obtained by polymerization, which cannot be pulverized into powder. Therefore, controlling the solubility of the heterocyclic aromatic polyamide powder in the organic solvent is the key to preparing a polymer with high molecular weight and easy powder formation. The solubility of the heterocyclic aromatic polyamide in organic solvents such as DMAc or NMP is related to factors such as its molecular structure, the content of cosolvents (CaCl 2 or LiCl) and the solid content. Patent US20070083032A1 prepares a powdery polymer by controlling the molecular structure (DAPBI content) and the content of cosolvent, but the molecular weight of the obtained polymer powder needs to be improved; Patent WO2013019581A1 promotes the precipitation of the polymer in a solvent with a high cosolvent content by increasing the solid content, and the molecular weight of the obtained polymer is improved to some extent, but still needs to be further improved.

[0007] Starting from the molecular structure design, the present invention appropriately increases the solubility of the polymer itself by introducing modified monomers such as p-chloro-phenylenediamine, 2,5-diaminobenzonitrile, m-phenylenediamine, 4,4'-diaminodiphenyl ether and 3,4'-diaminodiphenyl ether into the molecular structure, so that it has a more appropriate solubility in a solvent with a low cosolvent content, thereby preparing a heterocyclic aromatic polyamide with high molecular weight and easy powder formation.

[0008] The object of the present invention is achieved by the following technical solutions:

[0009] A method for preparing a heterocyclic aromatic polyamide powder with high molecular weight, dissolving proportionally metered 2-(4-aminophenyl)-5-aminobenzimidazole, p-phenylenediamine and other aromatic diamine monomers in an organic solvent containing a cosolvent, then adding terephthaloyl chloride (TPC), and reacting under nitrogen protection to obtain a polymer gel block or gel particles with a solid content of 6% to 15%, and pulverizing them into powder.

[0010] The organic solvent is one of NMP and DMAc.

[0011] The cosolvent is CaCl2 and one of LiCl; when the cosolvent used is CaCl 2 , its mass fraction in the total amount of the NMP / CaCl 2 solvent system is 1% - 5%, preferably 2% - 3%; when the cosolvent used is LiCl, its mass fraction in the total amount of the DMAc / LiCl solvent system is 0.5% - 3%, preferably 1% - 2%.

[0012] The molar percentages of the three monomers of 2-(4-aminophenyl)-5-aminobenzimidazole, p-phenylenediamine and other aromatic diamines are 40 - 90%:8 - 50%:2 - 30%.

[0013] The other aromatic diamines are one or more of m-phenylenediamine, 2,5-diaminobenzonitrile, 2,5-dichlorop-phenylenediamine, 2-chlorop-phenylenediamine, 2,6-dichlorop-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether.

[0014] The polymer gel block or gel particle refers to a reaction product formed after polymerization, which is a non-flowing and non-sticking block or granular solid. The size of the gel block or particle is related to the structure and form of the polymerization equipment; the gel block or gel particle can be further broken into finer powders by mechanical methods such as a grinder or a crusher, and the specific diameter is related to the grinding or crushing equipment used.

[0015] The inherent viscosity of the heterocyclic aromatic polyamide powder product prepared by the above method is ≥8 dL / g. The powder product can be dissolved in strong acids such as concentrated sulfuric acid, methanesulfonic acid, and chlorosulfonic acid to prepare a high-viscosity solution, and processed into fiber or film materials.

[0016] The high-molecular-weight heterocyclic aromatic polyamide powder product is formed by arbitrarily connecting the repeating units with the following structural formula

[0017]

[0018] Among them,

[0019] Ar in the repeating unit Ⅲ 1 is at least one of;

[0020] The molar percentage contents of each repeating unit in the molecular composition structure are as follows:

[0021] The content of the repeating unit Ⅰ is 40 - 90%;

[0022] The content of the repeating unit Ⅱ is 8 - 50%;

[0023] The content of the repeating unit Ⅲ is 2-30%.

[0024] Compared with the prior art, the present invention has the following advantages and effects:

[0025] (1) As is well known, the properties of aramid fibers are closely related to their molecular weight. Within a certain range, the fiber properties improve with the increase of the molecular weight. For relevant literature, reference can be made to "Research on Ultra-High Molecular Weight PPTA Resin and Its High-Modulus Aramid, High-Tech Fibers & Applications, 2014, 39(3): 15-20" and "Research on Direct Wet Spinning of PPTA Copolymers by Low-Temperature Solution Polycondensation, Synthetic Fiber Industry, 2014, 37(5): 1-5", etc. The molecular weight of the heterocyclic aromatic polyamide powder prepared by the prior art is relatively low, which affects the preparation of high-performance heterocyclic aramid fibers. Especially during the dissolution of the heterocyclic aromatic polyamide in concentrated sulfuric acid, the molecular weight will also decrease significantly. Therefore, it is necessary to use a resin with a sufficiently high molecular weight for spinning to make up for the influence of the reduction of the polymer molecular weight caused by dissolution and the like. The heterocyclic aromatic polyamide powder prepared by the present invention has a higher molecular weight, and the inherent viscosity can reach more than 8 dL / g, and can reach up to more than 12 dL / g at most, which is helpful for preparing higher-strength heterocyclic aramid.

[0026] (2) The present invention prepares a polymer with a higher molecular weight at a lower cosolvent concentration. The reduction of the cosolvent content helps to reduce the washing difficulty and reduce the ash residue in the polymer powder.

[0027] (3) The present invention appropriately introduces modified monomers such as p-chlorophenylenediamine, 2,5-diaminobenzonitrile, m-phenylenediamine, 4,4'-diaminodiphenyl ether, and 3,4'-diaminodiphenyl ether into the molecular structure, and by controlling the usage amount of the cosolvent, that is, CaCl 2 accounts for 1%-5% of the mass of the solvent, or LiCl accounts for 0.5%-3% of the mass of the solvent, so that a crushable gel powder can be prepared, reducing the production cost of heterocyclic aramid, and further realizing the large-scale popularization and application of heterocyclic aramid. Description of the Drawings

[0028] Figure 1 It is a picture of the heterocyclic aramid polymer solution used in the existing wet spinning.

[0029] Figure 2 It is a picture of the polymer gel block / particle prepared in Example 1 of the present invention.

[0030] Figure 3 It is a picture of the polymer powder product prepared in Example 1 of the present invention.

[0031] Figure 4 It is a picture of the highly viscous polymer product prepared in Comparative Example 4. Detailed implementation mode

[0032] To better explain the present invention, the present invention will be specifically described below in conjunction with embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention still fall within the protection scope of the present invention.

[0033] Example 1

[0034] 175.7575 g (0.7837 mol) of DAPBI, 7.53335 g (0.0697 mol) of PPDA and 3.4874 g of 4,4'-diaminodiphenyl ether (0.0174 mol) were dissolved in 1636.4 g of NMP / CaCl 2 solvent with a mass fraction of 3%, then 106.0741 g of TPC (0.5225 mol) was added. After reacting for 30 min under nitrogen protection, 70.7161 g of TPC (0.3483 mol) was added again and stirred rapidly for another 20 min to obtain a polymer gel block / particle with a solid content of 15% (as 2 shown); the polymer gel block / particle was pulverized to 60-mesh particles by a pulverizer and then washed and dried to obtain a powder (as Figure 2 shown) for the measurement of reduced viscosity in terms of logarithm. The test results are shown in Table 1. Figure 3 shown) for the measurement of reduced viscosity in terms of logarithm. The test results are shown in Table 1.

[0035] Example 2

[0036] 117.9414 g (0.5259 mol) of DAPBI, 16.2492 g (0.1503 mol) of PPDA and 8.1246 g of m-phenylenediamine (0.0751 mol) were dissolved in 1705.2 g of DMAc / LiCl solvent with a mass fraction of 2% of LiCl. Then 91.5180 g of TPC (0.4508 mol) was added. After reacting for 30 min under nitrogen protection, 61.0120 g of TPC (0.3005 mol) was added again and stirred rapidly for another 20 min to obtain a polymer gel block / particle with a solid content of 12%; the polymer gel block / particle was pulverized to 60-mesh particles by a pulverizer and then washed and dried to obtain a powder for the measurement of reduced viscosity in terms of logarithm. The test results are shown in Table 1.

[0037] Example 3

[0038] 97.5210 g (0.4349 mol) of DAPBI, 13.4358 g (0.1242 mol) of PPDA and 8.2716 g of 2,5-diaminobenzonitrile (0.0621 mol) were dissolved in 1754.7 g of CaCl 2 NMP / CaCl with a mass fraction of 2% 2 The solvent was then added with 75.6726 g of TPC (0.3727 mol), and the mixture was reacted for 30 min under nitrogen protection. Then, 50.4484 g of TPC (0.2485 mol) was added again, and the mixture was rapidly stirred and reacted for another 20 min to obtain polymer gel blocks / particles with a solid content of 10%. The polymer gel blocks / particles were crushed into 60-mesh particles by a crusher, and then washed and dried to obtain a powder for inherent viscosity test. The test results are shown in Table 1.

[0039] Example 4

[0040] 68.4063 g (0.3050 mol) of DAPBI, 10.9954 g (0.1017 mol) of PPDA and 14.4981 g of 2-chloro-p-phenylenediamine (0.1017 mol) were dissolved in 1802.9 g of DMAc / LiCl solvent with a mass fraction of 1% of LiCl, and then 61.9274 g of TPC (0.3050 mol) was added. After reacting for 30 minutes under nitrogen protection, 41.2849 g of TPC (0.2034 mol) was added again and the mixture was stirred rapidly and reacted for another 20 minutes to obtain a polymer gel block / particle with a solid content of 8%. The polymer gel block / particle was crushed into 60 mesh particles by a crusher, and then washed and dried to obtain a powder for inherent viscosity test. The test results are shown in Table 1.

[0041] Example 5

[0042] 68.4065 g (0.3050 mol) of DAPBI, 16.4931 g (0.1525 mol) of PPDA and 9.0000 g of 2,5-dichloro-p-phenylenediamine (0.0508 mol) were dissolved in 1802.9 g of DMAc / LiCl solvent with a mass fraction of 0.5% of LiCl, and then 61.9276 g of TPC (0.3050 mol) was added. After reacting for 30 minutes under nitrogen protection, 41.2851 g of TPC (0.2034 mol) was added again and stirred rapidly and continued to react for 20 minutes to obtain a polymer gel block / particle with a solid content of 8%; the polymer gel block / particle was crushed into 60 mesh particles by a crusher, and then washed and dried to obtain a powder for logarithmic viscosity test. The test results are shown in Table 1.

[0043] Example 6

[0044] 138.9678 g (0.6197 mol) of DAPBI, 12.5646 g (0.1162 mol) of PPDA and 7.7552 g of 3,4'-diaminodiphenyl ether (0.0387 mol) were dissolved in 1683.5 g of NMP / CaCl 2 solvent with a mass fraction of 2.5%, and then 94.3545 g of TPC (0.4648 mol) was added. After reacting for 30 min under nitrogen protection, 62.9030 g of TPC (0.3098 mol) was added again and the mixture was rapidly stirred and continued to react for 20 min to obtain a polymer gel block / particle with a solid content of 13%; the polymer gel block / particle was pulverized to 60-mesh particles by a pulverizer and then washed and dried, and the obtained powder was used for the measurement of inherent viscosity, and the measurement results are shown in Table 1. 2 solvent with a mass fraction of 2.5%, and then 94.3545 g of TPC (0.4648 mol) was added. After reacting for 30 min under nitrogen protection, 62.9030 g of TPC (0.3098 mol) was added again and the mixture was rapidly stirred and continued to react for 20 min to obtain a polymer gel block / particle with a solid content of 13%; the polymer gel block / particle was pulverized to 60-mesh particles by a pulverizer and then washed and dried, and the obtained powder was used for the measurement of inherent viscosity, and the measurement results are shown in Table 1.

[0045] Example 7

[0046] 96.5423 g (0.4305 mol) of DAPBI, 8.7288 g (0.0807 mol) of PPDA and 4.7631 g of 2,6-dichlorophenylenediamine (0.0269 mol) were dissolved in 1780.7 g of DMAc / LiCl solvent with a mass fraction of 2.5% of LiCl, and then 65.5490 g of TPC (0.3229 mol) was added. After reacting for 30 min under nitrogen protection, 43.6993 g of TPC (0.2152 mol) was added again and the mixture was rapidly stirred and continued to react for 20 min to obtain a polymer gel block / particle with a solid content of 8%; the polymer gel block / particle was pulverized to 60-mesh particles by a pulverizer and then washed and dried, and the obtained powder was used for the measurement of inherent viscosity, and the measurement results are shown in Table 1.

[0047] Example 8

[0048] 87.7859 g (0.3914 mol) of DAPBI, 16.9324 g (0.1566 mol) of PPDA and 33.4898 g of 2-chlorophenylenediamine (0.2349 mol) were dissolved in 1702.8 g of DMAc / LiCl solvent with a mass fraction of 1.0% of LiCl, and then 95.3659 g of TPC (0.4697 mol) was added. After reacting for 30 min under nitrogen protection, 63.5772 g of TPC (0.3132 mol) was added again and the mixture was rapidly stirred and continued to react for 20 min to obtain a polymer gel block / particle with a solid content of 12%; the polymer gel block / particle was pulverized to 60-mesh particles by a pulverizer and then washed and dried, and the obtained powder was used for the measurement of inherent viscosity, and the measurement results are shown in Table 1.

[0049] Example 9

[0050] Dissolve 72.3424 g (0.3226 mol) of DAPBI, 20.9305 g (0.1935 mol) of PPDA, and 22.8427 g of 2,5-dichlorophenylenediamine (0.1290 mol) in 1752.9 g of CaCl 2 NMP / CaCl with a mass fraction of 2.0% 2 in the solvent. Then add 78.5889 g of TPC (0.3871 mol). After reacting for 30 min under nitrogen protection, add 52.3926 g of TPC (0.2581 mol) again and continue to react with rapid stirring for 20 min to obtain polymer gel blocks / particles with a solid content of 10%. The polymer gel blocks / particles are pulverized to 60-mesh particles by a pulverizer and then washed and dried. The obtained powder is used for the measurement of the reduced viscosity, and the test results are shown in Table 1.

[0051] Example 10

[0052] Dissolve 37.3698 g (0.1666 mol) of DAPBI, 22.5250 g (0.2083 mol) of PPDA, and 5.9402 g of 2-chlorophenylenediamine (0.0417 mol) in 1849.6 g of DMAc / LiCl solvent with a mass fraction of 3.0% of LiCl. Then add 50.7457 g of TPC (0.2500 mol). After reacting for 30 min under nitrogen protection, add 33.8304 g of TPC (0.1666 mol) again and continue to react with rapid stirring for 20 min to obtain polymer gel blocks / particles with a solid content of 6%. The polymer gel blocks / particles are pulverized to 60-mesh particles by a pulverizer and then washed and dried. The obtained powder is used for the measurement of the reduced viscosity, and the test results are shown in Table 1.

[0053] Example 11

[0054] Dissolve 37.4311 g (0.1669 mol) of DAPBI, 22.5620 g (0.2086 mol) of PPDA, 2.9750 g (0.0209 mol) of 2-chlorophenylenediamine, and 2.7780 g (0.0209 mol) of 2,5-diaminobenzonitrile in 1852.3 g of CaCl 2 NMP / CaCl with a mass fraction of 5.0% 2In a solvent, 50.8289 g of TPC (0.2504 mol) was then added. After reacting for 30 min under nitrogen protection, 33.8860 g of TPC (0.1669 mol) was added again and the mixture was rapidly stirred and continued to react for 20 min to obtain polymer gel blocks / particles with a solid content of 6%. The polymer gel blocks / particles were crushed into 60-mesh particles by a crusher and then washed and dried. The obtained powder was used for the measurement of reduced viscosity, and the test results are shown in Table 1.

[0055] Comparative Example 1

[0056] This comparative example was compared with Example 3. The main difference from Example 3 was that 2,5-diaminobenzonitrile diamine monomer was not added, and other conditions were the same. Specifically as follows:

[0057] 98.2845 g (0.4383 mol) of DAPBI and 20.3115 g (0.1878 mol) of PPDA were dissolved in 1754.3 g of CaCl 2 NMP / CaCl with a mass fraction of 2.0% 2 In the solvent, then 76.2650 g of TPC (0.3757 mol) was added. After reacting for 30 min under nitrogen protection, 50.8433 g of TPC (0.2504 mol) was added again and the mixture was rapidly stirred and continued to react for 20 min to obtain polymer gel blocks / particles with a solid content of 10%. The polymer gel blocks / particles were crushed into 60-mesh particles by a crusher and then washed and dried. The obtained powder was used for the measurement of reduced viscosity, and the test results are shown in Table 1.

[0058] Comparative Example 2

[0059] This comparative example was compared with Example 9. The main difference from Example 9 was that 2-chloro-p-phenylenediamine was not added, and other conditions were the same. Specifically as follows:

[0060] 75.7072 g (0.3376 mol) of DAPBI and 36.5067 g (0.3376 mol) of PPDA were dissolved in 1750.7 g of CaCl 2 NMP / CaCl with a mass fraction of 2.0% 2 In the solvent, then 82.2443 g of TPC (0.4051 mol) was added. After reacting for 30 min under nitrogen protection, 54.8295 g of TPC (0.2701 mol) was added again and the mixture was rapidly stirred and continued to react for 20 min to obtain polymer gel blocks / particles with a solid content of 10%. The polymer gel blocks / particles were crushed into 60-mesh particles by a crusher and then washed and dried. The obtained powder was used for the measurement of reduced viscosity, and the test results are shown in Table 1.

[0061] Comparative Example 3

[0062] This comparative example is for comparison with Example 6. The main difference from Example 6 is that 3,4'-diaminodiphenyl ether diamine monomer is not added, and other conditions are the same. Specifically as follows:

[0063] Dissolve 140.9009 g (0.6283 mol) of DAPBI and 16.9859 g (0.1571 mol) of PPDA in 1682.7 g of CaCl 2 NMP / CaCl with a mass fraction of 2.5% 2 solvent, then add 95.6670 g of TPC (0.4712 mol). After reacting for 30 min under nitrogen protection, add 63.7780 g of TPC (0.3141 mol) again and continue to react with rapid stirring for 20 min to obtain a polymer gel block / particle with a solid content of 13%; the polymer gel block / particle is crushed into 60-mesh particles by a crusher and then washed and dried, and the obtained powder is used for the measurement of reduced viscosity. The test results are shown in Table 1.

[0064] Comparative Example 4

[0065] This comparative example is for comparison with Example 2. The main difference from Example 2 is that the mass fraction of the cosolvent LiCl in the total amount of the DMAc / LiCl solvent system is 4%, and other conditions are the same. Specifically as follows:

[0066] Dissolve 117.9414 g (0.5259 mol) of DAPBI, 16.2492 g (0.1503 mol) of PPDA, and 8.1246 g of m-phenylenediamine (0.0751 mol) in 1705.2 g of DMAc / LiCl solvent with a LiCl mass fraction of 4.0%, then add 91.5180 g of TPC (0.4508 mol). After reacting for 30 min under nitrogen protection, add 61.0120 g of TPC (0.3005 mol) again and continue to react with rapid stirring for 20 min to obtain a polymer (as Figure 4 shown) with a solid content of 12% and in a viscoelastic state; the polymer is washed and dried and then used for the measurement of reduced viscosity. The test results are shown in Table 1.

[0067] Comparative Example 5

[0068] This comparative example is for comparison with Example 4. The main difference from Example 4 is that the mass fraction of the cosolvent LiCl in the total amount of the DMAc / LiCl solvent system is 4%, and other conditions are the same. Specifically as follows:

[0069] 68.4063 g (0.3050 mol) of DAPBI, 10.9954 g (0.1017 mol) of PPDA and 14.4981 g of 2-chlorophenylenediamine (0.1017 mol) were dissolved in 1802.9 g of DMAc / LiCl solvent with 4.0% mass fraction of LiCl. Then 61.9274 g of TPC (0.3050 mol) was added. After reacting for 30 min under nitrogen protection, 41.2849 g of TPC (0.2034 mol) was added again and the mixture was rapidly stirred and reacted for another 20 min to obtain a polymer with a solid content of 8%. The polymer was washed and dried and then used for the measurement of inherent viscosity. The test results are shown in Table 1.

[0070] Explanation of the experiment for measuring inherent viscosity:

[0071] 1. Since aramid cannot be dissolved in organic solvents, it is difficult to directly measure the molecular weight by means such as gel permeation chromatography (GPC). In the industry, inherent viscosity is often used to indirectly express and reflect the molecular weight of aramid polymers.

[0072] 2. The inherent viscosity of the polymer of the present invention was measured according to the method specified in GB / T 1632.1-2008 Plastics - Determination of viscosity of dilute solutions of polymers using capillary viscometers - Part 1: General principles. The solvent used was concentrated sulfuric acid with a concentration of (96.5 ± 0.2)%, and the test temperature was (25 ± 0.1)°C.

[0073] Table 1 Polymerization conditions and test results of inherent viscosity of polymers in Examples 1-11 and Comparative Examples 1-5

[0074]

[0075] In Table 1, from the experimental results of Example 3 and Comparative Example 1, Example 6 and Comparative Example 3, Example 9 and Comparative Example 2, it can be seen that at a lower cosolvent content, crushable gel powders can be formed, but the introduction of repeating unit Ⅲ can increase the molecular weight of the polymer; from the experimental results of Example 2 and Comparative Example 4, Example 4 and Comparative Example 5, it can be seen that at an excessive cosolvent content, the heterocyclic aromatic polymer obtained in the present invention is a viscoelastic polymer and cannot be crushed into powder. Further, from Figure 2-3 It can also be seen that the present invention can obtain a polymer with a high molecular weight and easy to form powder at a lower solid content, which can be used to prepare fibers or films with excellent mechanical properties, and can realize the large-scale popularization and application of heterocyclic aramid.

Claims

1. A method for preparing a high molecular weight heterocyclic aromatic polyamide powder, characterized in that: Weigh 2-(4-aminophenyl)-5-aminobenzimidazole, p-phenylenediamine and other aromatic diamine monomers in proportion, dissolve them in an organic solvent containing a co-solvent, then add terephthaloyl chloride, and react under nitrogen protection to obtain a polymer gel block or gel particles with a solid content of 6% - 15%, and then crush them into powder; The organic solvent is one of NMP and DMAc; The cosolvent is one of CaCl 2 and LiCl; when the cosolvent used is CaCl 2 , its mass fraction in the total amount of the NMP / CaCl 2 solvent system is 1% to 5%; when the cosolvent used is LiCl, its mass fraction in the total amount of the DMAc / LiCl solvent system is 0.5% to 3%. The molar percentages of the three monomers of 2-(4-aminophenyl)-5-aminobenzimidazole, p-phenylenediamine and other aromatic diamines are 40 - 90%: 8 - 50%: 2 - 30%; The other aromatic diamines are one or more of m-phenylenediamine, 2,5-diaminobenzonitrile, 2,5-dichlorop-phenylenediamine, 2-chlorop-phenylenediamine, 2,6-dichlorop-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether.

2. The method for preparing a high molecular weight heterocyclic aromatic polyamide powder according to claim 1, characterized in that: When the cosolvent used is CaCl 2 when, its mass fraction in the total amount of the NMP / CaCl 2 solvent system is 2% to 3%.

3. The method for preparing a high molecular weight heterocyclic aromatic polyamide powder according to claim 1, characterized in that: When the co-solvent used is LiCl, its mass fraction in the total amount of the DMAc / LiCl solvent system is 1% - 2%.

4. The method for preparing a high molecular weight heterocyclic aromatic polyamide powder according to claim 1, characterized in that: The polymer gel block or gel particles refer to the reaction products formed after polymerization, which are non-flowing and non-sticky blocky or granular solids, and the size of the gel block or particles is related to the structure and form of the polymerization equipment.

5. A high molecular weight heterocyclic aromatic polyamide powder product, characterized in that: It is prepared by the method described in any one of claims 1 - 3, and the inherent viscosity of the heterocyclic aromatic polyamide powder is ≥8 dL / g.

6. The high molecular weight heterocyclic aromatic polyamide powder product according to claim 5, characterized in that: The molecular structure of the high molecular weight heterocyclic aromatic polyamide powder is formed by the random connection of repeating units with the following structural formula, wherein, Ar in repeating unit Ⅲ 1 is at least one of; The molar percentage content of each repeating unit in the molecular composition structure is as follows: The content of repeating unit I is 40 - 90%; The content of repeating unit II is 8 - 50%; The content of repeating unit III is 2 - 30%.

7. The high molecular weight heterocyclic aromatic polyamide powder product according to claim 5, characterized in that: Dissolve it in concentrated sulfuric acid, methanesulfonic acid, or chlorosulfonic acid to prepare a high-viscosity solution, and process it into fiber or film materials.

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