A preparation method of high-brightness high-molecular-weight PPTA

Abstract

The present invention provides a method for preparing high-brightness high-molecular-weight PPTA. Under nitrogen protection, N-methylpyrrolidone / calcium chloride solution is added to high-purity liquefied p-phenylenediamine and stirred and mixed, and the stirring temperature is controlled to be 75°C to 95°C. After fully mixing, the temperature is cooled to 30°C to 75°C to form a PPD-NMP-CaCl2 ternary system; the terephthaloyl chloride required for the reaction is added to the PPD-NMP-CaCl2 ternary system obtained in the above steps twice for full reaction, and then subjected to neutralization reaction to obtain a PPTA polymer; the obtained PPTA polymer is ground, washed, and dried to obtain a high-brightness high-molecular-weight PPTA. The present application suppresses side reactions at low temperatures, improves the degree of polymerization of materials, and controls the reaction to be carried out at low temperatures, so that the reaction process is not easy to produce implosion, and finally obtains high-brightness PPTA.

Description

Technical Field

[0001] The invention belongs to the technical field of high molecular polymer preparation, and in particular relates to a method for preparing high-brightness and high-molecular-weight PPTA. Background Art

[0002] Para-aramid is a type of aromatic polyamide, which is characterized by the amide bond directly connected to two aromatic rings. Due to the presence of conjugated benzene rings in the main chain of para-aramid, the molecular chain is not easy to rotate internally, thus presenting a linear rigid structure, which makes it have characteristics such as high modulus and thermal stability.

[0003] The traditional method for preparing PPTA is to mix p-phenylenediamine with N-methylpyrrolidone / calcium chloride, and then react the p-phenylenediamine and N-methylpyrrolidone / calcium chloride mixture with terephthaloyl chloride to finally prepare PPTA polymer. Due to improper control of factors such as reaction temperature, reaction water content, and oxygen content in the traditional preparation of PPTA polymer, there are many side reactions during the reaction, resulting in low brightness of the obtained PPTA polymer. For example, patent application (CN113882030A) discloses a method for preparing colored para-aramid fiber and its fiber product. In the specific implementation of the patent application, it is recorded that the brightness L value of the primary color PPTA fiber is 79.9.

[0004] Therefore, the brightness of para-aramid is currently mainly improved through the PPTA post-treatment process. For example, the patent application (CN106757449A) discloses a method for preparing para-aramid fiber. In this application, the acid-containing fiber bundle from the spinning coagulation bath is introduced into a water washing tank filled with pure water and equipped with an ultrasonic generator for pure water ultrasonic cleaning; the fiber bundle washed with pure water is introduced into a concentrated alkali solution washing tank filled with concentrated alkali solution and equipped with an ultrasonic generator for concentrated alkali solution ultrasonic cleaning; the fiber bundle to be washed with dilute alkali solution is introduced into a dilute alkali solution washing tank filled with dilute alkali solution and equipped with an ultrasonic generator for dilute alkali solution ultrasonic cleaning; the fiber bundle to be dried is introduced into a drying box for drying, and the fiber bundle to be dried is successively oiled and wound out of the drying box to obtain para-aramid fiber. This patent application mainly improves the brightness of PPTA fiber through the cleaning process, and the brightness L value of the obtained PPTA fiber is less than 86. The ability of this method to improve brightness is limited.

[0005] Another example is the authorized patent (KR101675056B1) which discloses a method for making poly(p-phenylene terephthalamide) fiber. The technical solution disclosed in the patent is to control the temperature of the feed water to 50°C to 80°C in the neutralization step and / or the washing step, effectively removing the residual polymerization solvent and inorganic substances in the polymer, thereby obtaining poly(p-phenylene terephthalamide) fiber with small strength change and improved brightness value. The poly(p-phenylene terephthalamide) fiber finally obtained by the patent has a brightness L value between 84 and 86. The technical solution disclosed in the patent is also to improve the brightness of PPTA fiber through the post-treatment process of PPTA fiber.

[0006] It can be seen that the existing technology cannot directly obtain high-brightness PPTA. The obtained PPTA must undergo a special cleaning process to achieve a PPTA with a brightness L value not exceeding 86. This method is not only time-consuming, but also requires the addition of special processing materials, increasing production costs.

[0007] Therefore, it is necessary to provide a new method for preparing high-brightness high-molecular-weight PPTA. Summary of the invention

[0008] In order to obtain a controllable high-brightness high-molecular-weight PPTA, the present invention provides a method for preparing high-brightness high-molecular-weight PPTA, and the present invention specifically comprises the following steps:

[0009] S1. Preparation of PPD-NMP-CaCl2 ternary system: Under nitrogen protection, N-methylpyrrolidone / calcium chloride solution is added to liquefied p-phenylenediamine with a temperature of 150°C to 175°C and a purity of 99.90% to 99.98%, and stirred and mixed, and the stirring temperature is controlled to be 75°C to 95°C. After sufficient mixing, the temperature is lowered to 30°C to 75°C to form a PPD-NMP-CaCl2 ternary system, and the formed PPD-NMP-CaCl2 ternary system is stored in a container at a temperature of 30°C to 75°C;

[0010] S2. Preparation of PPTA: Under nitrogen protection, terephthaloyl chloride required for the reaction is added to the PPD-NMP-CaCl2 ternary system obtained in step S1 twice. The specific feeding reaction control method is:

[0011] Firstly, 30% to 60% of the total mass of terephthaloyl chloride required for the reaction is added and reacted for 3 to 15 seconds, the reaction temperature is controlled at -2°C to 15°C, and the reaction stirring speed is controlled at 30rpm to 50rpm;

[0012] The second time, 40% to 70% of the total mass of terephthaloyl chloride required for the reaction is added, and the reaction is carried out for 10 to 30 minutes, the reaction temperature is controlled at 5°C to 20°C, and the reaction stirring speed is controlled at 20rpm to 60rpm;

[0013] Wherein, the molar ratio of terephthaloyl chloride: p-phenylenediamine is 0.995-1.005:1;

[0014] After the terephthaloyl chloride and the PPD-NMP-CaCl2 ternary system are fully reacted, the reaction product of the terephthaloyl chloride and the PPD-NMP-CaCl2 ternary system is transferred to a neutralization tank through a neutralization reaction, and a NaOH solution is added to neutralize the reaction product to a pH of 1 to 7, thereby obtaining a PPTA polymer.

[0015] S3, post-treatment of PPTA polymer: grind the PPTA polymer obtained in step S2 to obtain a uniform PPTA polymer with a particle size of 70μm to 1000μm accounting for 60% to 95%, then wash the PPTA polymer with deionized water to reduce the ash content of the PPTA polymer to below 500ppm, and after drying, obtain a PPTA with a water content of less than 500ppm, a characteristic viscosity of 6.6dL / g to 7.8dL / g, and a brightness L value of 85 to 91.

[0016] The present application can obtain high-brightness and high-molecular-weight PPTA by controlling the purity of liquefied p-phenylenediamine, the temperature of the liquefied p-phenylenediamine, the temperature of the PPD-NMP-CaCl2 ternary system, the ratio of the PPD-NMP-CaCl2 ternary system to terephthaloyl chloride reaction raw materials and the reaction temperature, neutralization pH value, and grinding particle size.

[0017] Step S1 of the present application is different from the conventional feeding method. In the conventional powder feeding process, the powder will come into contact with air when it is added from the packaging bag to the reactor. The powder is more likely to absorb moisture in the air, which will cause the material to hydrolyze. In the process of preparing the PPD-NMP-CaCl2 ternary system of the present application, the raw materials are transported through pipelines throughout the process and are protected by nitrogen throughout the process, so there is no risk of contact with the outside world, and the raw materials are not easily oxidized. The raw materials in the traditional feeding method are easily oxidized, which will cause a decrease in brightness.

[0018] During the preparation process of the present application, the purpose of setting specific feeding temperature, reaction temperature and storage temperature is to remove heat from the material, delay gelation time, enhance reaction uniformity and reduce side reactions.

[0019] The present application adds materials at low temperature twice, which can improve the cooling efficiency. When the cooling efficiency is improved, side reactions will be reduced. Temperature also affects the particle size of the product particles. If the temperature is too high, an implosion reaction will occur. The implosion reaction will produce a large amount of granular materials, and most of the granular materials will cause a decrease in brightness. The reaction temperature of the first addition of the present application is low and the time is short, which can promote the start of the polymerization reaction and the generation of polymerization chains. During the second addition, the reaction temperature is slightly higher and the time is long, which can achieve the growth and expansion of the polymerization chain, thereby controlling the rate and degree of the polymerization reaction. During the first addition, the low temperature and short time help to reduce the generation of side reactions, and the slightly higher temperature and long time during the second addition are conducive to promoting the generation of polymerization chains, which can further extend the polymerization time and make the reaction more complete, thereby obtaining a polymer product with good uniformity.

[0020] The present application sets the molar ratio of terephthaloyl chloride: p-phenylenediamine to 0.995-1.005:1, so that the terminal group of the polymerization product is an acyl chloride group, and the brightness will be improved. When terephthaloyl chloride is insufficient, the terminal group of the polymerization product is an amino group. Since the amino group is easily oxidized, the brightness of PPTA will decrease.

[0021] Further, in order to obtain PPTA with a brightness L value of 85 to 87, the preferred technical solution adopted is as follows:

[0022] In the step S1, the purity of the liquefied p-phenylenediamine is 99.90% to 99.94% and the temperature is 160° C. to 175° C.;

[0023] The mixing temperature of the liquefied p-phenylenediamine and N-methylpyrrolidone / calcium chloride solution is controlled at 85°C to 95°C. After being fully mixed, the temperature is lowered to 50°C to 75°C to form a PPD-NMP-CaCl2 ternary system, and the formed PPD-NMP-CaCl2 ternary system is stored in a container at a temperature of 50°C to 75°C.

[0024] In the step S2, the terephthaloyl chloride required for the reaction is added to the PPD-NMP-CaCl2 ternary system obtained in the step S1 in two portions, and the specific addition reaction control method is:

[0025] Firstly, 50-60% of the total mass of terephthaloyl chloride required for the reaction is added, and the reaction is carried out for 10-15 seconds, the reaction temperature is controlled at 5°C-15°C, and the reaction stirring speed is controlled at 40rpm-50rpm;

[0026] The second time, 40-50% of the total mass of terephthaloyl chloride required for the reaction is added, and the reaction is carried out for 20-30 minutes, the reaction temperature is controlled at 15-20° C., and the reaction stirring speed is controlled at 40 rpm-60 rpm;

[0027] The neutralization reaction is carried out in the following manner: the reaction product of terephthaloyl chloride and the PPD-NMP-CaCl2 ternary system is transferred to a neutralization tank and a NaOH solution is added thereto to neutralize the reaction product to a pH of 5 to 7.

[0028] The step S3 is to grind the PPTA polymer obtained in step S2 to obtain a uniform PPTA polymer with a particle size of 450 to 1000 μm accounting for 60% to 85%, and then wash the PPTA polymer with deionized water to reduce the ash content of the PPTA polymer to below 500 ppm, and after drying, obtain a PPTA with a water content of less than 500 ppm, a characteristic viscosity of 6.6 dL / g to 6.8 dL / g, and a brightness L value of 85 to 87.

[0029] In another preferred technical solution, in order to obtain PPTA with a brightness L value of 88 to 91, the preferred technical solution adopted has the following characteristics:

[0030] In the step S1, the purity of the liquefied p-phenylenediamine is 99.95% to 99.98% and the temperature is 150° C. to 160° C.;

[0031] The mixing temperature of the liquefied p-phenylenediamine and N-methylpyrrolidone / calcium chloride solution is controlled at 75°C to 85°C. After being fully mixed, the temperature is lowered to 30°C to 50°C to form a PPD-NMP-CaCl2 ternary system, and the formed PPD-NMP-CaCl2 ternary system is stored in a container at a temperature of 30°C to 50°C.

[0032] In the step S2, the terephthaloyl chloride required for the reaction is added to the PPD-NMP-CaCl2 ternary system obtained in the step S1 in two portions, and the specific addition reaction control method is:

[0033] Firstly, 30% to 40% of the total mass of terephthaloyl chloride required for the reaction is added and reacted for 3 to 10 seconds, the reaction temperature is controlled at -2°C to 5°C, and the reaction stirring speed is controlled at 30rpm to 40rpm;

[0034] The second time, 40% to 70% of the total mass of terephthaloyl chloride required for the reaction is added, and the reaction is carried out for 10 to 30 minutes, the reaction temperature is controlled at 5°C to 15°C, and the reaction stirring speed is controlled at 20rpm to 40rpm;

[0035] The neutralization reaction is carried out in the following manner: the reaction product of terephthaloyl chloride and the PPD-NMP-CaCl2 ternary system is transferred to a neutralization tank and a NaOH solution is added thereto to neutralize the reaction product to a pH of 1 to 5.

[0036] The step S3 is replaced by grinding the PPTA polymer obtained in step S2 to obtain a uniform PPTA polymer with a particle size of 70 μm to 850 μm accounting for 80% to 95%, and then washing the PPTA polymer with deionized water to reduce the ash content of the PPTA polymer to below 500 ppm, and after drying, obtaining a PPTA with a water content of less than 500 ppm, an intrinsic viscosity of 7.1 dL / g to 7.8 dL / g, and a brightness L value of 88 to 91.

[0037] The technical effects of this application are:

[0038] 1. Step S1 of the present application is different from the conventional feeding method. In the conventional powder feeding process, the powder will come into contact with air during the process of adding the powder from the packaging bag to the reactor. The powder is more likely to absorb moisture in the air, which will cause the material to hydrolyze. In the process of preparing the PPD-NMP-CaCl2 ternary system of the present application, the raw materials are transported through pipelines throughout the process and are protected by nitrogen throughout the process. Therefore, there is no risk of contact with the outside world, and the raw materials are not easily oxidized. The raw materials in the traditional feeding method are easily oxidized, which will lead to a decrease in brightness.

[0039] 2. During the preparation process of the present application, the purpose of setting specific feeding temperature, reaction temperature and storage temperature is to remove heat from the material, delay the gelation time, enhance the uniformity of the reaction and reduce side reactions.

[0040] 3. The present application adds materials at low temperature twice, which can improve the cooling efficiency. When the cooling efficiency is improved, side reactions will be reduced. Temperature also affects the particle size of the product particles. If the temperature is too high, an implosion reaction will occur. The implosion reaction will produce a large amount of granular materials, and most of the granular materials will cause a decrease in brightness. The reaction temperature of the first addition of the present application is low and the time is short, which can promote the start of the polymerization reaction and the generation of polymerization chains. During the second addition, the reaction temperature is slightly higher and the time is long, which can achieve the growth and expansion of the polymerization chain, thereby controlling the rate and degree of the polymerization reaction. During the first addition, the low temperature and short time help to reduce the occurrence of side reactions, and the slightly higher temperature and long time during the second addition are conducive to promoting the generation of polymerization chains, which can further extend the polymerization time and make the reaction more complete, thereby obtaining a polymer product with good uniformity.

[0041] 4. In the present application, the molar ratio of terephthaloyl chloride: p-phenylenediamine is set to 0.995-1.005:1, so that the terminal group of the polymerization product is the acyl chloride group, and the brightness will be improved. When the terephthaloyl chloride is insufficient, the terminal group of the polymerization product is the amino group. Since the amino group is easily oxidized, the brightness of PPTA will decrease.

[0042] 5. This application solves the technical problem that high-brightness PPTA cannot be directly obtained by traditional preparation methods through process innovation. In the whole process control of this application, a specific temperature is set to suppress side reactions. This application suppresses side reactions at low temperatures to increase the degree of polymerization of materials. And by controlling the reaction to proceed at low temperatures, the reaction process is not prone to implosion, thereby solving the problem of insufficient reaction caused by implosion, which causes the particles of the polymerized materials to become larger. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments 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 creative work are within the scope of protection of this application.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and any variations thereof are intended to cover non-exclusive inclusions.

[0045] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can include or exclude the endpoint values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. In the present application, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, wherein a and b are both real numbers. For example, the numerical range "0-5" represents that all real numbers between "0-5" have been fully listed herein, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a certain parameter is expressed as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0046] To facilitate understanding of this application, the technical terms involved in this application document are explained below.

[0047] PPTA (poly-p-phenylene terephthamide), scientific name: poly-p-phenylene terephthalamide, also known as aramid 1414 and para-aramid.

[0048] PPD (p-Phenylenediamine) is p-phenylenediamine.

[0049] NMP (N-Methylpyrrolidone) is N-methylpyrrolidone.

[0050] CaCl2 is calcium chloride.

[0051] TPC (terephthaloyl chloride) is terephthaloyl chloride.

[0052] Exemplary embodiments of the present application are described below.

[0053] The technical solution of this application is as follows:

[0054] S1. Preparation of PPD-NMP-CaCl2 ternary system: Under nitrogen protection, N-methylpyrrolidone / calcium chloride solution is added to liquefied p-phenylenediamine with a temperature of 150°C to 175°C and a purity of 99.90% to 99.98%, and stirred and mixed, and the stirring temperature is controlled to be 75°C to 95°C. After sufficient mixing, the temperature is lowered to 30°C to 75°C to form a PPD-NMP-CaCl2 ternary system, and the formed PPD-NMP-CaCl2 ternary system is stored in a container at a temperature of 30°C to 75°C;

[0055] S2. Preparation of PPTA: Under nitrogen protection, terephthaloyl chloride required for the reaction is added to the PPD-NMP-CaCl2 ternary system obtained in step S1 twice. The specific feeding reaction control method is:

[0056] Firstly, 30% to 60% of the total mass of terephthaloyl chloride required for the reaction is added and reacted for 3 to 15 seconds, the reaction temperature is controlled at -2°C to 15°C, and the reaction stirring speed is controlled at 30rpm to 50rpm;

[0057] The second time, 40% to 70% of the total mass of terephthaloyl chloride required for the reaction is added, and the reaction is carried out for 10 to 30 minutes, the reaction temperature is controlled at 5°C to 20°C, and the reaction stirring speed is controlled at 20rpm to 60rpm;

[0058] Wherein, the molar ratio of terephthaloyl chloride: p-phenylenediamine is 0.995-1.005:1;

[0059] After the terephthaloyl chloride and the PPD-NMP-CaCl2 ternary system are fully reacted, the reaction product of the terephthaloyl chloride and the PPD-NMP-CaCl2 ternary system is transferred to a neutralization tank through a neutralization reaction, and a NaOH solution is added to neutralize the reaction product to a pH of 1 to 7, thereby obtaining a PPTA polymer.

[0060] The concentration of the added NaOH solution is between 10% and 20%, and the concentration and the amount added can be adjusted according to actual conditions.

[0061] S3, post-treatment of PPTA polymer: grind the PPTA polymer obtained in step S2 to obtain a uniform PPTA polymer with a particle size of 70μm to 1000μm accounting for 60% to 95%, then wash the PPTA polymer with deionized water to reduce the ash content of the PPTA polymer to below 500ppm, and after drying, obtain a PPTA with a water content of less than 500ppm, a characteristic viscosity of 6.6dL / g to 7.8dL / g, and a brightness L value of 85 to 91.

[0062] Please refer to the following embodiments for specific implementations.

[0063] Embodiment 1:

[0064] S1. Preparation of PPD-NMP-CaCl2 ternary system: Under nitrogen protection, 12001 kg of N-methylpyrrolidone / calcium chloride solution was added to 669.5 kg of liquefied p-phenylenediamine with a temperature of 160° C. and a purity of 99.94%, and the mixture was stirred and mixed, and the stirring temperature was controlled to 85° C. After being fully mixed, the mixture was cooled to 75° C. to form a PPD-NMP-CaCl2 ternary system, and the formed PPD-NMP-CaCl2 ternary system was stored in a container at a temperature of 75° C.;

[0065] S2. Preparation of PPTA: Under nitrogen protection, 1302 kg of terephthaloyl chloride was added to 12700.5 kg of PPD-NMP-CaCl2 ternary system obtained in step S1 in two portions, so that the molar ratio of terephthaloyl chloride to p-phenylenediamine was 0.995:1.

[0066] Specifically, 657 kg of terephthaloyl chloride was added for the first time and reacted for 10 seconds, the reaction temperature was controlled at 5°C, and the reaction stirring speed was controlled at 50 rpm; 645 kg of terephthaloyl chloride was added for the second time and reacted for 20 minutes, the reaction temperature was controlled at 15°C, and the reaction stirring speed was controlled at 60 rpm; after sufficient reaction, the reaction product was transferred to a neutralization tank and NaOH solution was added to neutralize to a pH of 5 to obtain a PPTA polymer.

[0067] S3. Post-treatment of PPTA polymer: The PPTA polymer obtained in step S2 is ground to obtain a uniform PPTA polymer with a particle size of 800-1000 μm accounting for 60%, and then washed with deionized water for 9 times to reduce the ash content to 432 ppm. After centrifugal separation, the PPTA polymer solid enters the drying system and is dried with 120°C steam for 30 minutes to obtain a high-brightness PPTA with a water content of 382 ppm and a characteristic viscosity of 6.6 dL / g.

[0068] Embodiment 2:

[0069] S1. Preparation of PPD-NMP-CaCl2 ternary system: Under nitrogen protection, 12003 kg of N-methylpyrrolidone / calcium chloride solution was added to 699.8 kg of liquefied p-phenylenediamine with a temperature of 175° C. and a purity of 99.90%, and the mixture was stirred and mixed, and the stirring temperature was controlled to 95° C. After being fully mixed, the mixture was cooled to 50° C. to form a PPD-NMP-CaCl2 ternary system, and the formed PPD-NMP-CaCl2 ternary system was stored in a container at a temperature of 50° C.;

[0070] S2. Preparation of PPTA: Under nitrogen protection, 1315 kg of terephthaloyl chloride was added to 12702.8 kg of PPD-NMP-CaCl2 ternary system obtained in step S1 in two times to make the molar ratio of terephthaloyl chloride: p-phenylenediamine be 1.005:1, specifically: 789 kg of terephthaloyl chloride was added for the first time to react for 15 seconds, the reaction temperature was controlled at 15°C, and the reaction stirring speed was controlled at 40 rpm; 526 kg of terephthaloyl chloride was added for the second time to react for 30 minutes, the reaction temperature was controlled at 20°C, and the reaction stirring speed was controlled at 40 rpm; after sufficient reaction, the reaction product was transferred to a neutralization tank, NaOH solution was added to neutralize to pH 6, and PPTA polymer was obtained.

[0071] S3. Post-treatment of PPTA polymer: The PPTA polymer obtained in step S2 is ground to obtain a uniform PPTA polymer with a particle size of 500-900 μm accounting for 85%, and then washed with deionized water 11 times to reduce the ash content to 325 ppm. After centrifugal separation, the PPTA polymer solid enters the drying system and is dried with 150°C steam for 25 minutes to obtain a high-brightness PPTA with a water content of 364 ppm and a characteristic viscosity of 6.7 dL / g.

[0072] Embodiment 3:

[0073] S1. Preparation of PPD-NMP-CaCl2 ternary system: Under nitrogen protection, 12004 kg of N-methylpyrrolidone / calcium chloride solution was added to 699.9 kg of liquefied p-phenylenediamine with a temperature of 170° C. and a purity of 99.92%, and the mixture was stirred and mixed, and the stirring temperature was controlled to 90° C. After being fully mixed, the mixture was cooled to 60° C. to form a PPD-NMP-CaCl2 ternary system, and the formed PPD-NMP-CaCl2 ternary system was stored in a container at a temperature of 60° C.;

[0074] S2. Preparation of PPTA: Under nitrogen protection, 1328 kg of terephthaloyl chloride was added to 12703.9 kg of PPD-NMP-CaCl2 ternary system obtained in step S1 in two times to make the molar ratio of terephthaloyl chloride: p-phenylenediamine be 1:1, specifically: 723 kg of terephthaloyl chloride was added for the first time to react for 13 seconds, the reaction temperature was controlled at 10°C, and the reaction stirring speed was controlled at 45 rpm; 605 kg of terephthaloyl chloride was added for the second time to react for 25 minutes, the reaction temperature was controlled at 18°C, and the reaction stirring speed was controlled at 50 rpm; after sufficient reaction, the reaction product was transferred to a neutralization tank, NaOH solution was added to neutralize to pH 7, and PPTA polymer was obtained.

[0075] S3. Post-treatment of PPTA polymer: The PPTA polymer obtained in step S2 is ground to obtain a uniform PPTA polymer with a particle size of 450-700 μm accounting for 70%, and then washed with deionized water for 10 times to reduce the ash content to 363 ppm. After centrifugal separation, the PPTA polymer solid enters the drying system and is dried with 180°C steam for 15 minutes to obtain a high-brightness PPTA with a water content of 372 ppm and a characteristic viscosity of 6.8 dL / g.

[0076] Embodiment 4:

[0077] S1. Preparation of PPD-NMP-CaCl2 ternary system: under nitrogen protection, 12004 kg of N-methylpyrrolidone / calcium chloride solution was added to 700.1 kg of liquefied p-phenylenediamine at a temperature of 150° C. and a purity of 99.95%, and the mixture was stirred and mixed, and the stirring temperature was controlled to be 85° C. After being fully mixed, the mixture was cooled to 50° C. to form a PPD-NMP-CaCl2 ternary system, and the formed PPD-NMP-CaCl2 ternary system was stored in a container at a temperature of 50° C.;

[0078] S2. Preparation of PPTA: Under nitrogen protection, 1328 kg of terephthaloyl chloride was added to 12704.1 kg of PPD-NMP-CaCl2 ternary system obtained in step S1 in two times to make the molar ratio of terephthaloyl chloride: p-phenylenediamine be 0.995:1, specifically: 395 kg of terephthaloyl chloride was added for the first time to react for 3 seconds, the reaction temperature was controlled at 5°C, and the reaction stirring speed was controlled at 30 rpm; 933 kg of terephthaloyl chloride was added for the second time to react for 20 minutes, the reaction temperature was controlled at 15°C, and the reaction stirring speed was controlled at 20 rpm; after sufficient reaction, the reaction product was transferred to a neutralization tank, NaOH solution was added to neutralize to a pH of 1, and a PPTA polymer was obtained.

[0079] S3. Post-treatment of PPTA polymer: The PPTA polymer obtained in step S2 is ground to obtain a uniform PPTA polymer with a particle size of 70-300 μm accounting for 80%, and then washed with deionized water for 10 times to reduce the ash content to 358 ppm. After centrifugal separation, the PPTA polymer solid enters the drying system and is dried with 200°C steam for 10 minutes to obtain a high-brightness PPTA with a water content of 358 ppm and a characteristic viscosity of 7.8 dL / g.

[0080] Embodiment 5:

[0081] S1. Preparation of PPD-NMP-CaCl2 ternary system: under nitrogen protection, 12005 kg of N-methylpyrrolidone / calcium chloride solution was added to 700.1 kg of liquefied p-phenylenediamine at a temperature of 160° C. and a purity of 99.98%, and the mixture was stirred and mixed, and the stirring temperature was controlled to be 80° C. After being fully mixed, the mixture was cooled to 40° C. to form a PPD-NMP-CaCl2 ternary system, and the formed PPD-NMP-CaCl2 ternary system was stored in a container at a temperature of 40° C.;

[0082] S2. Preparation of PPTA: Under nitrogen protection, 1328 kg of terephthaloyl chloride was added to 12705.1 kg of PPD-NMP-CaCl2 ternary system obtained in step S1 in two times to make the molar ratio of terephthaloyl chloride: p-phenylenediamine be 1.005:1, specifically: 461 kg of terephthaloyl chloride was added for the first time to react for 6 seconds, the reaction temperature was controlled at 0°C, and the reaction stirring speed was controlled at 40 rpm; 867 kg of terephthaloyl chloride was added for the second time to react for 20 minutes, the reaction temperature was controlled at 10°C, and the reaction stirring speed was controlled at 30 rpm; after sufficient reaction, the reaction product was transferred to a neutralization tank, NaOH solution was added to neutralize to pH 3, and PPTA polymer was obtained.

[0083] S3. Post-treatment of PPTA polymer: The PPTA polymer obtained in step S2 is ground to obtain a uniform PPTA polymer with a particle size of 250-550 μm accounting for 95%, and then washed with deionized water for 10 times to reduce the ash content to 352 ppm. After centrifugal separation, the PPTA polymer solid enters the drying system and is dried with 150°C steam for 25 minutes to obtain a high-brightness PPTA with a water content of 365 ppm and a characteristic viscosity of 7.5 dL / g.

[0084] Embodiment 6:

[0085] S1. Preparation of PPD-NMP-CaCl2 ternary system: Under nitrogen protection, 12006 kg of N-methylpyrrolidone / calcium chloride solution was added to 700.2 kg of liquefied p-phenylenediamine at a temperature of 165° C. and a purity of 99.96%, and the mixture was stirred and mixed, and the stirring temperature was controlled to 75° C. After being fully mixed, the mixture was cooled to 30° C. to form a PPD-NMP-CaCl2 ternary system, and the formed PPD-NMP-CaCl2 ternary system was stored in a container at a temperature of 30° C.;

[0086] S2. Preparation of PPTA: Under nitrogen protection, 1328 kg of terephthaloyl chloride was added to 12706.2 kg of PPD-NMP-CaCl2 ternary system obtained in step S1 in two times to make the molar ratio of terephthaloyl chloride: p-phenylenediamine be 1:1, specifically: 526 kg of terephthaloyl chloride was added for the first time to react for 10 seconds, the reaction temperature was controlled at -2°C, and the reaction stirring speed was controlled at 50 rpm; 802 kg of terephthaloyl chloride was added for the second time to react for 10 minutes, the reaction temperature was controlled at 5°C, and the reaction stirring speed was controlled at 40 rpm; after sufficient reaction, the reaction product was transferred to a neutralization tank, NaOH solution was added to neutralize to pH 5, and PPTA polymer was obtained.

[0087] S3. Post-treatment of PPTA polymer: The PPTA polymer obtained in step S2 is ground to obtain a uniform PPTA polymer with a particle size of 500-850 μm accounting for 90%, and then washed with deionized water for 10 times to reduce the ash content to 348 ppm. After centrifugal separation, the PPTA polymer solid enters the drying system and is dried with 150°C steam for 25 minutes to obtain a high-brightness PPTA with a water content of 371 ppm and a characteristic viscosity of 7.1 dL / g.

[0088] Comparative Example 1

[0089] The difference between this comparative example and Example 2 is that step S1 adopts the method of adding powder directly, the amount of material added is the same as that of Example 2, and the other processes are the same as those of Example 2, specifically:

[0090] S1. Preparation of PPD-NMP / CaCl2: 699.8 kg of p-phenylenediamine was fully dissolved in 12003 kg of N-methylpyrrolidone / calcium chloride solution to obtain a p-phenylenediamine solution;

[0091] S2. Preparation of PPTA: Under nitrogen protection, 1315 kg of terephthaloyl chloride was added to 12702.8 kg of PPD-NMP-CaCl2 ternary system obtained in step S1 in two times to make the molar ratio of terephthaloyl chloride: p-phenylenediamine be 1.005:1, specifically: 789 kg of terephthaloyl chloride was added for the first time to react for 15 seconds, the reaction temperature was controlled at 15°C, and the reaction stirring speed was controlled at 40 rpm; 526 kg of terephthaloyl chloride was added for the second time to react for 30 minutes, the reaction temperature was controlled at 20°C, and the reaction stirring speed was controlled at 40 rpm; after sufficient reaction, the reaction product was transferred to a neutralization tank, NaOH solution was added to neutralize to pH 6, and PPTA polymer was obtained.

[0092] S3. Post-treatment of PPTA polymer: The PPTA polymer obtained in step S2 is ground to obtain a uniform PPTA polymer with a particle size of 500-900 μm accounting for 85%, and then washed with deionized water 11 times to reduce the ash content to 327 ppm. After centrifugal separation, the PPTA polymer solid enters the drying system and is dried with 150°C steam for 25 minutes to obtain a PPTA with a water content of 364 ppm, a characteristic viscosity of 6.5 dL / g, and a brightness L value of 85.

[0093] Comparative Example 2

[0094] The difference between this comparative example and Example 2 is that in step S2, all the terephthaloyl chloride required for the reaction is added at one time, and the other processes are the same as in Example 2, specifically:

[0095] S1. Preparation of PPD-NMP-CaCl2 ternary system: Under nitrogen protection, 12003 kg of N-methylpyrrolidone / calcium chloride solution was added to 699.8 kg of liquefied p-phenylenediamine with a temperature of 175° C. and a purity of 99.90%, and the mixture was stirred and mixed, and the stirring temperature was controlled to 95° C. After being fully mixed, the mixture was cooled to 50° C. to form a PPD-NMP-CaCl2 ternary system, and the formed PPD-NMP-CaCl2 ternary system was stored in a container at a temperature of 50° C.;

[0096] S2. Preparation of PPTA: At low temperature, 1315 kg of terephthaloyl chloride is added to 12702.8 kg of PPD-NMP-CaCl2 ternary system obtained in step S1 at one time to make the molar ratio of terephthaloyl chloride: p-phenylenediamine be 1.005:1. After sufficient reaction, the reaction product is transferred to a neutralization tank and added with NaOH solution to neutralize to pH 6 to obtain PPTA polymer.

[0097] S3. Post-treatment of PPTA polymer: The PPTA polymer obtained in step S2 is ground to obtain a uniform PPTA polymer with a particle size of 500-900 μm accounting for 85%, and then washed with deionized water 11 times to reduce the ash content to 333 ppm. After centrifugal separation, the PPTA polymer solid enters the drying system and is dried with 150°C steam for 25 minutes to obtain a PPTA with a water content of 368 ppm, a characteristic viscosity of 6.4 dL / g, and a brightness L value of 83.

[0098] Comparative Example 3

[0099] The difference between this comparative example and Example 2 is that the stirring and storage temperature in step S1 is relatively high, and the other processes are the same as in Example 2, specifically:

[0100] S1. Preparation of PPD-NMP-CaCl2 ternary system: Under nitrogen protection, 12003 kg of N-methylpyrrolidone / calcium chloride solution was added to 699.8 kg of liquefied p-phenylenediamine with a temperature of 175° C. and a purity of 99.90%, and the mixture was stirred and mixed, and the stirring temperature was controlled to be 100° C. After being fully mixed, the mixture was cooled to 80° C. to form a PPD-NMP-CaCl2 ternary system, and the formed PPD-NMP-CaCl2 ternary system was stored in a container with a temperature of 80° C.;

[0101] S2. Preparation of PPTA: Under nitrogen protection, 1315 kg of terephthaloyl chloride was added to 12702.8 kg of PPD-NMP-CaCl2 ternary system obtained in step S1 in two times to make the molar ratio of terephthaloyl chloride: p-phenylenediamine be 1.005:1, specifically: 789 kg of terephthaloyl chloride was added for the first time to react for 15 seconds, the reaction temperature was controlled at 15°C, and the reaction stirring speed was controlled at 40 rpm; 526 kg of terephthaloyl chloride was added for the second time to react for 30 minutes, the reaction temperature was controlled at 20°C, and the reaction stirring speed was controlled at 40 rpm; after sufficient reaction, the reaction product was transferred to a neutralization tank, NaOH solution was added to neutralize to pH 6, and PPTA polymer was obtained.

[0102] S3. Post-treatment of PPTA polymer: The PPTA polymer obtained in step S2 is ground to obtain a uniform PPTA polymer with a particle size of 500-900 μm accounting for 85%, and then washed with deionized water 11 times to reduce the ash content to 327 ppm. After centrifugal separation, the PPTA polymer solid enters the drying system and is dried with 150°C steam for 25 minutes to obtain a PPTA with a water content of 373 ppm, a characteristic viscosity of 6.3 dL / g, and a brightness L value of 83.

[0103] Comparative Example 4

[0104] The difference between this comparative example and Example 2 is that the grinding particle size in step S3 is relatively high, and the other processes are the same as Example 2, specifically:

[0105] S1. Preparation of PPD-NMP-CaCl2 ternary system: Under nitrogen protection, 12003 kg of N-methylpyrrolidone / calcium chloride solution was added to 699.8 kg of liquefied p-phenylenediamine with a temperature of 175° C. and a purity of 99.90%, and the mixture was stirred and mixed, and the stirring temperature was controlled to 95° C. After being fully mixed, the mixture was cooled to 50° C. to form a PPD-NMP-CaCl2 ternary system, and the formed PPD-NMP-CaCl2 ternary system was stored in a container at a temperature of 50° C.;

[0106] S2. Preparation of PPTA: Under nitrogen protection, 1315 kg of terephthaloyl chloride was added to 12702.8 kg of PPD-NMP-CaCl2 ternary system obtained in step S1 in two times to make the molar ratio of terephthaloyl chloride: p-phenylenediamine be 1.005:1, specifically: 789 kg of terephthaloyl chloride was added for the first time to react for 15 seconds, the reaction temperature was controlled at 15°C, and the reaction stirring speed was controlled at 40 rpm; 526 kg of terephthaloyl chloride was added for the second time to react for 30 minutes, the reaction temperature was controlled at 20°C, and the reaction stirring speed was controlled at 40 rpm; after sufficient reaction, the reaction product was transferred to a neutralization tank, NaOH solution was added to neutralize to pH 6, and PPTA polymer was obtained.

[0107] S3. Post-treatment of PPTA polymer: The PPTA polymer obtained in step S2 is ground to obtain a uniform PPTA polymer with a particle size of 1000-1300 μm accounting for 80%, and then washed with deionized water 11 times to reduce the ash content to 331 ppm. After centrifugal separation, the PPTA polymer solid enters the drying system and is dried with 150°C steam for 25 minutes to obtain a PPTA with a water content of 361 ppm, a characteristic viscosity of 6.2 dL / g, and a brightness L value of 78.

[0108] Comparative Example 5

[0109] The difference between this comparative example and Example 2 is that the reaction temperature of the terephthaloyl chloride added twice in step S2 is relatively high, and the other processes are the same as Example 2, specifically:

[0110] S1. Preparation of PPD-NMP-CaCl2 ternary system: Under nitrogen protection, 12003 kg of N-methylpyrrolidone / calcium chloride solution was added to 699.8 kg of liquefied p-phenylenediamine with a temperature of 175° C. and a purity of 99.90%, and the mixture was stirred and mixed, and the stirring temperature was controlled to 95° C. After being fully mixed, the mixture was cooled to 50° C. to form a PPD-NMP-CaCl2 ternary system, and the formed PPD-NMP-CaCl2 ternary system was stored in a container at a temperature of 50° C.;

[0111] S2. Preparation of PPTA: Under nitrogen protection, 1315 kg of terephthaloyl chloride was added to 12702.8 kg of PPD-NMP-CaCl2 ternary system obtained in step S1 in two times to make the molar ratio of terephthaloyl chloride: p-phenylenediamine be 1.005:1, specifically: 789 kg of terephthaloyl chloride was added for the first time to react for 15 seconds, the reaction temperature was controlled at 25°C, and the reaction stirring speed was controlled at 40 rpm; 526 kg of terephthaloyl chloride was added for the second time to react for 30 minutes, the reaction temperature was controlled at 25°C, and the reaction stirring speed was controlled at 40 rpm; after sufficient reaction, the reaction product was transferred to a neutralization tank, NaOH solution was added to neutralize to pH 6, and PPTA polymer was obtained.

[0112] S3. Post-treatment of PPTA polymer: The PPTA polymer obtained in step S2 is ground to obtain a uniform PPTA polymer with a particle size of 500-900 μm accounting for 85%, and then washed with deionized water 11 times to reduce the ash content to 329 ppm. After centrifugal separation, the PPTA polymer solid enters the drying system and is dried with 150°C steam for 25 minutes to obtain a PPTA with a water content of 369 ppm, a characteristic viscosity of 6.1 dL / g, and a brightness L value of 79.

[0113] Comparative Example 6

[0114] The difference between this comparative example and Example 2 is that the molar ratio of terephthaloyl chloride: p-phenylenediamine is 0.99:1, and the other processes are the same as those in Example 2, specifically:

[0115] S1. Preparation of PPD-NMP-CaCl2 ternary system: Under nitrogen protection, 12003 kg of N-methylpyrrolidone / calcium chloride solution was added to 699.8 kg of liquefied p-phenylenediamine with a temperature of 175° C. and a purity of 99.90%, and the mixture was stirred and mixed, and the stirring temperature was controlled to 95° C. After being fully mixed, the mixture was cooled to 50° C. to form a PPD-NMP-CaCl2 ternary system, and the formed PPD-NMP-CaCl2 ternary system was stored in a container at a temperature of 50° C.;

[0116] S2, preparation of PPTA: under nitrogen protection, 1300.7 kg of terephthaloyl chloride was added to 12702.8 kg of PPD-NMP-CaCl2 ternary system obtained in step S1 in two times, so that the molar ratio of terephthaloyl chloride: p-phenylenediamine was 1.005:1, specifically: 780.4 kg of terephthaloyl chloride was added for the first time and reacted for 15 seconds, the reaction temperature was controlled at 15°C, and the reaction stirring speed was controlled at 40 rpm; 520.3 kg of terephthaloyl chloride was added for the second time and reacted for 30 minutes, the reaction temperature was controlled at 20°C, and the reaction stirring speed was controlled at 40 rpm; after sufficient reaction, the reaction product was transferred to a neutralization tank, NaOH solution was added to neutralize to pH 6, and PPTA polymer was obtained.

[0117] S3. Post-treatment of PPTA polymer: The PPTA polymer obtained in step S2 is ground to obtain a uniform PPTA polymer with a particle size of 500-900 μm accounting for 85%, and then washed with deionized water 11 times to reduce the ash content to 325 ppm. After centrifugal separation, the PPTA polymer solid enters the drying system and is dried with 150°C steam for 25 minutes to obtain a PPTA with a water content of 364 ppm, a characteristic viscosity of 6.7 dL / g, and a brightness L value of 82.

[0118] Comparative Example 7

[0119] The difference between this comparative example and Example 2 is that the molar ratio of terephthaloyl chloride: p-phenylenediamine is 1.005:1, and the other processes are the same as those in Example 2, specifically:

[0120] S1. Preparation of PPD-NMP-CaCl2 ternary system: Under nitrogen protection, 12003 kg of N-methylpyrrolidone / calcium chloride solution was added to 699.8 kg of liquefied p-phenylenediamine with a temperature of 175° C. and a purity of 99.90%, and the mixture was stirred and mixed, and the stirring temperature was controlled to 95° C. After being fully mixed, the mixture was cooled to 50° C. to form a PPD-NMP-CaCl2 ternary system, and the formed PPD-NMP-CaCl2 ternary system was stored in a container at a temperature of 50° C.;

[0121] S2. Preparation of PPTA: Under nitrogen protection, 1327 kg of terephthaloyl chloride was added to 12702.8 kg of PPD-NMP-CaCl2 ternary system obtained in step S1 in two times to make the molar ratio of terephthaloyl chloride: p-phenylenediamine be 1.01:1, specifically: 796.2 kg of terephthaloyl chloride was added for the first time to react for 15 seconds, the reaction temperature was controlled at 15°C, and the reaction stirring speed was controlled at 40 rpm; 530.8 kg of terephthaloyl chloride was added for the second time to react for 30 minutes, the reaction temperature was controlled at 20°C, and the reaction stirring speed was controlled at 40 rpm; after sufficient reaction, the reaction product was transferred to a neutralization tank, NaOH solution was added to neutralize to pH 6, and PPTA polymer was obtained.

[0122] S3. Post-treatment of PPTA polymer: The PPTA polymer obtained in step S2 is ground to obtain a uniform PPTA polymer with a particle size of 500-900 μm accounting for 85%, and then washed with deionized water 11 times to reduce the ash content to 325 ppm. After centrifugal separation, the PPTA polymer solid enters the drying system and is dried with 150°C steam for 25 minutes to obtain a PPTA with a water content of 364 ppm, a characteristic viscosity of 6.7 dL / g, and a brightness L value of 87.

[0123] The brightness performance test of the above-mentioned embodiments 1-5 and comparative examples 1-7 was carried out, and the test results are shown in Table 1. In Table 1, "L" represents brightness: 0 to 100 represents from black to white; "a" represents red and green: a positive value represents red, and a negative value represents green; "b" represents yellow and blue: a positive value represents yellow, and a negative value represents blue; "YI-E313[D65 / 1]" represents the yellowness index under the D65 standard light source.

[0124] Table 1 Summary of PPTA brightness test results obtained in different embodiments and comparative examples

[0125]

[0126] It can be seen from Examples 1 to 6 that high-brightness and high-molecular-weight PPTA can be obtained by comprehensively controlling parameters such as oxygen content, reaction temperature, storage temperature, feeding method, particle size, and molar ratio of reaction materials.

[0127] It can be seen from Example 2 and Comparative Example 1 that in step S1 of Comparative Example 1, the powder is directly added to obtain the dissolved p-phenylenediamine, and the final product brightness L value is 85, which is lower than the product brightness value of Example 2. This shows that in the conventional powder adding process, the powder will be exposed to air during the addition of the powder from the packaging bag to the reactor. The powder is more likely to absorb moisture in the air, which will cause the material to hydrolyze. In the process of preparing the PPD-NMP-CaCl2 ternary system in the present application, the raw materials are transported through pipelines throughout the process and are protected by nitrogen throughout the process. Therefore, there is no risk of contact with the outside world, and the raw materials are not easily oxidized. The raw materials in the traditional adding method are easily oxidized, which will lead to a decrease in brightness.

[0128] It can be seen from Example 2 and Comparative Example 2 that in step S2 of Comparative Example 2, terephthaloyl chloride is added to the PPD-NMP-CaCl2 ternary system at one time for reaction, and the final product brightness L value is 83, which is lower than the product brightness value of Example 2. It can be inferred that the method of adding terephthaloyl chloride to the PPD-NMP-CaCl2 ternary system at one time for reaction will lead to a slow cooling rate in the reaction system, a high temperature inside the system during the reaction process, and more side reactions, which ultimately affect the product brightness. In Example 2, the low-temperature addition is performed twice, which can improve the cooling efficiency, lower the temperature of the reaction system, reduce side reactions, and obtain PPTA with a high brightness value.

[0129] It can be seen from Example 2 and Comparative Example 3 that in step S1 of Comparative Example 3, the dissolution reaction temperature of liquefied p-phenylenediamine in N-methylpyrrolidone / calcium chloride solution is relatively high, and the final storage temperature is also relatively high. The final product brightness L value is 83, which is lower than the product brightness value of Example 2. It can be inferred that since the dissolution temperature and storage temperature of step S1 of Comparative Example 3 are relatively high, side reactions occur in liquefied p-phenylenediamine and N-methylpyrrolidone / calcium chloride during the storage process, resulting in gelation, which ultimately affects the brightness of the product. By setting specific feeding temperature, reaction temperature, and storage temperature, Example 2 can effectively remove heat from the material, delay the gelation time, enhance the uniformity of the reaction, and reduce the occurrence of side reactions.

[0130] It can be seen from Example 2 and Comparative Example 4 that in the step of grinding the polymer in Comparative Example 4, the particle size of the polymer obtained by grinding is relatively large, and the brightness value of the final product is relatively low, indicating that too large a particle size will lead to reduced product brightness.

[0131] As can be seen from Example 2 and Comparative Example 5, the control of the reaction temperature of adding terephthaloyl chloride twice in step S2 of Comparative Example 5 is high, which eventually leads to a decrease in product brightness. It is inferred that the temperature is too high, which will produce an implosion reaction, and the implosion reaction will produce a large amount of granular materials, which will cause the brightness to decrease. In step S2 of Example 2, the reaction temperature of the first feeding is low and the time is short, which can promote the start-up polymerization chain generation of the polymerization reaction. While the reaction temperature is slightly higher and the time is long during the second feeding process, the growth and expansion of the polymerization chain can be achieved, thereby controlling the rate and degree of the polymerization reaction. During the first feeding process, the low temperature in a short time helps to reduce the generation of side reactions, and the slightly higher temperature and long time during the second feeding process are conducive to promoting the generation of the polymerization chain, which can further extend the polymerization time, so that the reaction is more sufficient, thereby obtaining a high-brightness PPTA polymer with good uniformity.

[0132] From Example 2 and Comparative Examples 6 to 7, it can be seen that in Comparative Example 6, the amount of terephthaloyl chloride is too little, and the brightness of the obtained PPTA decreases significantly. In Comparative Example 7, the amount of terephthaloyl chloride is slightly more, and the brightness does not change significantly. It is speculated that the reason is that when the amount of terephthaloyl chloride is sufficient, the end group of the polymerization product is the acyl chloride group, and the brightness will be improved. When the amount of terephthaloyl chloride is insufficient, the end group of the polymerization product is the amino group. Since the amino group is easily oxidized, the brightness of the PPTA will decrease.

[0133] In summary, through Example 2 and Comparative Examples 1 to 7, it can be found that in the whole process control of Example 2, by controlling the specific reaction temperature, the side reaction is suppressed, and by suppressing the side reaction at low temperature, the polymerization degree of the material is improved. And by controlling the reaction to be carried out in different stages at low temperature, the reaction process is not easy to produce implosion, thereby solving the problem of insufficient reaction caused by implosion, causing the polymer material particles to become larger, and affecting the brightness of the product. Example 2 sets the molar ratio of terephthaloyl chloride to p-phenylenediamine at an appropriate value to ensure that the end group of the polymerization reaction product is an acyl chloride group, and avoids the problem that the end group of the polymerization reaction product is an amino group, and the amino group is oxidized, resulting in a decrease in the brightness of PPTA.

[0134] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing high-brightness and high-molecular-weight PPTA, It is characterized in that The following steps are involved: S1, PPD-NMP-CaCl 2 Preparation of the ternary system: Under nitrogen protection, add N-methylpyrrolidone / calcium chloride solution to liquefied p-phenylenediamine with a temperature of 150℃~175℃ and a purity of 99.90%~99.98%, and stir and mix. Control the stirring temperature to 75℃~95℃. After sufficient mixing, cool to 30℃~75℃ to form PPD-NMP-CaCl 2 The ternary system and the formed PPD-NMP-CaCl 2 The ternary system is stored in a container at a temperature of 30°C to 75°C; S2. Preparation of PPTA: Under nitrogen protection, add the terephthaloyl chloride required for the reaction to the PPD-NMP-CaCl obtained in step S1 in two portions. 2 In the ternary system, the specific feeding reaction control method is: Firstly, 30% to 60% of the total mass of terephthaloyl chloride required for the reaction is added and reacted for 3 to 15 seconds, the reaction temperature is controlled at -2°C to 15°C, and the reaction stirring speed is controlled at 30rpm to 50rpm; The second time, 40% to 70% of the total mass of terephthaloyl chloride required for the reaction is added, and the reaction is carried out for 10 to 30 minutes. The reaction temperature is controlled at 5°C to 20°C, and the reaction stirring speed is controlled at 20rpm to 60rpm. Wherein, the molar ratio of terephthaloyl chloride: p-phenylenediamine is 1:1; Terephthaloyl chloride and PPD-NMP-CaCl 2 After the ternary system is fully reacted, terephthaloyl chloride and PPD-NMP-CaCl are neutralized. 2 The reaction product of the ternary system is transferred to a neutralization tank and a NaOH solution is added thereto to neutralize the mixture to a pH of 1 to 7 to obtain a PPTA polymer. S3, post-treatment of PPTA polymer: grind the PPTA polymer obtained in step S2 to obtain a uniform PPTA polymer with a particle size of 70 μm~1000 μm accounting for 60%~95%, then wash the PPTA polymer with deionized water to reduce the ash content of the PPTA polymer to below 500 ppm, and after drying, obtain a PPTA with a water content of less than 500 ppm, an intrinsic viscosity of 6.6 dL / g~7.8 dL / g, and a brightness L value of 85~91.

2. The method for preparing the high-brightness high-molecular-weight PPTA according to claim 1, It is characterized in that In the step S1, the purity of the liquefied p-phenylenediamine is 99.90% to 99.94% and the temperature is 160° C. to 175° C.; The mixing temperature of the liquefied p-phenylenediamine and N-methylpyrrolidone / calcium chloride solution is controlled at 85°C to 95°C, and after being fully mixed, the temperature is cooled to 50°C to 75°C to form PPD-NMP-CaCl 2 The ternary system and the formed PPD-NMP-CaCl 2 The ternary system is stored in a container at a temperature of 50°C to 75°C.

3. The method for preparing the high-brightness high-molecular-weight PPTA according to claim 1 or 2, It is characterized in that In step S2, the terephthaloyl chloride required for the reaction is added twice to the PPD-NMP-CaCl obtained in step S1. 2 In the ternary system, the specific feeding reaction control method is: Firstly, 50-60% of the total mass of terephthaloyl chloride required for the reaction is added and reacted for 10-15 seconds, the reaction temperature is controlled at 5°C-15°C, and the reaction stirring speed is controlled at 40rpm-50rpm; The second time, 40-50% of the total mass of terephthaloyl chloride required for the reaction is added, and the reaction is carried out for 20-30 minutes, the reaction temperature is controlled at 15-20°C, and the reaction stirring speed is controlled at 40rpm-60rpm; The neutralization reaction is carried out by: mixing terephthaloyl chloride and PPD-NMP-CaCl 2 The reaction product of the ternary system is transferred to a neutralization tank and neutralized with NaOH solution to a pH of 5-7.

4. The method for preparing the high-brightness high-molecular-weight PPTA as claimed in claim 3, It is characterized in that The step S3 is to grind the PPTA polymer obtained in step S2 to obtain a uniform PPTA polymer with a particle size of 450-1000 μm accounting for 60%-85%, and then wash the PPTA polymer with deionized water to reduce the ash content of the PPTA polymer to below 500 ppm, and after drying, obtain a PPTA with a water content of less than 500 ppm, an intrinsic viscosity of 6.6 dL / g-6.8 dL / g, and a brightness L value of 85-87.

5. The method for preparing the high-brightness high-molecular-weight PPTA according to claim 1, It is characterized in that In the step S1, the purity of the liquefied p-phenylenediamine is 99.95% to 99.98% and the temperature is 150° C. to 160° C.; The mixing temperature of the liquefied p-phenylenediamine and N-methylpyrrolidone / calcium chloride solution is controlled at 75°C to 85°C, and after being fully mixed, the temperature is cooled to 30°C to 50°C to form PPD-NMP-CaCl 2 The ternary system and the formed PPD-NMP-CaCl 2 The ternary system is stored in a container at a temperature of 30°C to 50°C.

6. The method for preparing the high-brightness high-molecular-weight PPTA according to claim 1 or 5, It is characterized in that In step S2, the terephthaloyl chloride required for the reaction is added twice to the PPD-NMP-CaCl obtained in step S1. 2 In the ternary system, the specific feeding reaction control method is: Firstly, 30% to 40% of the total mass of terephthaloyl chloride required for the reaction is added and reacted for 3 to 10 seconds, the reaction temperature is controlled at -2°C to 5°C, and the reaction stirring speed is controlled at 30rpm to 40rpm; The second time, 70% to 60% of the total mass of terephthaloyl chloride required for the reaction is added, and the reaction is carried out for 10 to 30 minutes. The reaction temperature is controlled at 5°C to 15°C, and the reaction stirring speed is controlled at 20rpm to 40rpm. The neutralization reaction is carried out by: mixing terephthaloyl chloride and PPD-NMP-CaCl 2 The reaction product of the ternary system is transferred to a neutralization tank and neutralized with NaOH solution to a pH of 1-5.

7. The method for preparing the high-brightness high-molecular-weight PPTA as claimed in claim 6, It is characterized in that The step S3 is replaced by grinding the PPTA polymer obtained in step S2 to obtain a uniform PPTA polymer with a particle size of 70 μm to 850 μm accounting for 80% to 95%, and then washing the PPTA polymer with deionized water to reduce the ash content of the PPTA polymer to below 500 ppm, and after drying, obtaining a PPTA with a water content of less than 500 ppm, an intrinsic viscosity of 7.1 dL / g to 7.8 dL / g, and a brightness L value of 88 to 91.

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