A method for preparing high-performance poly(p-phenylene terephthalamide) fiber

Abstract

The present invention relates to the technical field of man-made fibers, and in particular to a method for preparing high-performance poly(p-phenylene terephthalamide) fibers. The present invention improves the fluidity of the spinning solution by adding a spinning aid during the preparation of the spinning solution, thins the retention layer of the spinning solution in the pipeline, is not easy to form a dead zone, significantly reduces the amount of spinning solution that is degraded due to long-term retention, narrows the molecular weight distribution in the spinning solution, and narrows the molecular weight distribution of the formed fiber, which is more conducive to obtaining fibers with better performance and more uniformity; after the fluidity of the spinning solution is improved, the inner wall adhesion is significantly reduced when passing through the spinneret, and the fiber molding is more uniform and stable; after the spinnability of the spinning solution is enhanced, the extrusion swell ratio is reduced, the fiber molding is easier and more stable, the fiber formation rate is higher, the hair fibers are less, and the mechanical properties are improved.

Description

Technical Field

[0001] The invention relates to the technical field of artificial fibers, in particular to a method for preparing high-performance poly(p-phenylene terephthalamide) fibers. Background Art

[0002] In 1965, DuPont Company of the United States synthesized poly(p-phenylene terephthalamide) (PPTA) fiber by low-temperature solution polycondensation reaction. Then, the dry-jet wet spinning method was invented by taking advantage of the liquid crystal behavior of PPTA / H2SO4 solution, thereby obtaining high-performance poly(p-phenylene terephthalamide) fiber (referred to as "aramid 1414"). Patents for related technologies were successively published in the United States from 1970 to 1985, such as patent numbers: 3671542, 3819587, 19730361818, 3767756, 3869429, 3849430, 4726922, 5001219, 5009830, 19760720849, 19880182826, 1980012088, 19970950250, etc.

[0003] DuPont of the United States began to develop the market for PPTA fiber production in small quantities in 1972, and began industrial production in 1982, with the product name Kevlar. In 1985, Akzo of the Netherlands started to produce PPTA aramid fiber, with the product name Twaron. Kelon of South Korea also tried to produce PPTA and pulp in 1985, and built a large-scale production plant in 2006.

[0004] There are many commercial varieties of aramid 1414 fiber products. According to GB / T42823-2023 "Para-aramid Filament", they are divided into conventional type, high model and high strength type. Among them, conventional type superior products: strength ≥20CN / dtex, elongation at break is about 3.5%, modulus is about 75Gpa; high model superior products: strength ≥18CN / dtex, elongation at break is about 2.5%, modulus ≥100Gpa; high strength superior products: strength ≥23.5CN / dtex, elongation at break is about 3.7%, modulus is about 75Gpa;

[0005] The industrial production of aramid 1414 fiber adopts a two-step process, namely polymerization and then spinning.

[0006] First, a poly(p-phenylene terephthalamide) polymer is prepared, and then the polymer is neutralized, washed, and dried to obtain a poly(p-phenylene terephthalamide) polymer. The polymerization reaction for preparing the poly(p-phenylene terephthalamide) polymer is shown in the following formula:

[0007]

[0008] The specific preparation process is as follows: calcium chloride (CaCl2) is dissolved in N-methylpyrrolidone to prepare a CaCl2-NMP solvent. p-phenylenediamine (PPDA) is dissolved in the CaCl2-NMP solvent, and then an equal molar ratio of TPC is added to obtain poly(p-phenylene terephthalamide) polymer by a low temperature solution method under high-speed shearing, which can be achieved by continuous polymerization or intermittent polymerization.

[0009] The properties and quality of poly(p-phenylene terephthalamide) polymers directly affect the spinning process, fiber performance, industrial efficiency and production cost. The polymer properties include the end group form of the molecular chain (-NH or -CO end group), molecular weight, molecular weight distribution, bulk density, moisture content, particle size, ash content, etc.

[0010] Then the polymer is used for spinning. The currently recognized spinning method in the industry is dry-jet wet spinning, which is to dissolve poly(p-phenylene terephthalamide) polymer in concentrated sulfuric acid. When the concentration is 12-20%, a liquid crystal solution (Anisctropic Solution) can be formed. After this solution passes through the spinneret, it is coagulated by air and then exchanged in a coagulation bath to precipitate the sulfuric acid in the spinning solution, thus obtaining high-performance aramid fiber. The process characteristics of dry-jet wet spinning are: during spinning, there is a certain height of air layer gap between the spinneret and the coagulation liquid surface. After the spinning solution is ejected from the spinneret, it passes through the air layer, enters the coagulation bath, and is discharged from the coagulation tube. The filamentous spinning solution ejected from the spinneret is extracted by the coagulation liquid when entering the coagulation bath, and the polymer is precipitated into fibers. The coagulated primary fibers are wound and formed after washing, neutralization, drying and other processes.

[0011] Poly(p-phenylene terephthalamide) polymer is a rigid structure polymer. On the one hand, the polymer is difficult to dissolve in various organic substances and can only be dissolved in superacids such as concentrated sulfuric acid and fluorosulfuric acid. Moreover, the solubility is very poor and requires a certain temperature and strong shearing to fully dissolve. On the other hand, the polymer is very easy to degrade after dissolution. At about 75°C, the polymer intrinsic viscosity is characterized (see Figure 1 ), the degradation rate of spinning solution is about 0.2-0.5 / hour. This will lead to two problems: First, during the dissolution process, the polymer that is dissolved first forms a viscous spinning solution that wraps part of the polymer to form particles, and sulfuric acid is difficult to penetrate into it, which leads to serious differences in the degree of polymer dissolution. In extreme cases, the outer spinning solution begins to degrade, and the inner polymer has not yet begun to dissolve (see Figure 2 ); second, the dissolved spinning solution has a very high dynamic viscosity (about 200,000 cp) and strong adhesion. During the pipeline transportation, the solution adheres to the pipe wall in large quantities and degrades over time. The dynamic viscosity and intrinsic viscosity of the degraded spinning solution are reduced, and it gradually falls off from the pipe wall and mixes into the fresh spinning solution (see Figure 3 ). The above two situations will lead to the presence of a large number of polymers that have been degraded into small molecular weight in the spinning solution, and the molecular weight distribution will become wider. This will lead to a decrease in fiber performance; thirdly, the dynamic viscosity of the para-aramid spinning solution with concentrated sulfuric acid as the solvent is relatively high. Due to the viscosity, the fluid particles adhere to the surface of the object, forming a fluid non-slip phenomenon, poor fluidity, and the yarns in the spinning hole are prone to curling, filaments, and broken yarns. As a result, the mechanical properties of the finished fiber are reduced and there are more filaments. It is because of the above problems that the aramid fibers obtained in industrial production are significantly different from their theoretical performance. In the production process, there are very high requirements for dissolution equipment and processes, material residence time, pipeline design, spindle design, etc., and the production difficulty is relatively high. Summary of the invention

[0012] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for preparing high-performance poly(p-phenylene terephthalamide) fiber, by adding specific additives to improve the flow characteristics of the spinning solution, and ultimately achieve the purpose of increasing the spinnability of the spinning solution, reducing filaments, and improving fiber performance during the dry-jet wet spinning process.

[0013] To achieve this object, the present invention adopts the following technical solutions:

[0014] The present invention provides a method for preparing high-performance poly(p-phenylene terephthalamide) fiber, and the specific technical scheme is as follows:

[0015] A method for preparing high-performance poly(p-phenylene terephthalamide) fiber comprises the following steps:

[0016] (1) Using terephthaloyl chloride and p-phenylenediamine as raw materials, a polymer is prepared by a low temperature solution polymerization method;

[0017] (2) Using 96wt~100wt% concentrated sulfuric acid as solution, polymer and spinning aid are prepared into modified spinning solution; using dry-jet wet spinning process to prepare high-performance poly(p-phenylene terephthalamide) fiber from the modified spinning solution; the spinning aid is selected from any one of polyethylene glycol, alkylphenol polyoxyethylene ether, ethylene bisoleamide, fatty acid glyceride, white oil, polyvinyl pyrrolidone, butynediol diethoxy ether, or a combination of several of them.

[0018] In some embodiments of the present invention, in step (2), the polymer and the spinning aid are used to prepare a modified spinning solution, and the specific operation includes adding the mixture obtained by mixing the polymer and the spinning aid or adding the two separately to a concentrated sulfuric acid solution to dissolve them to obtain the modified spinning solution.

[0019] In some embodiments of the present invention, in step (2), the amount of the spinning aid added is 0.001 wt% to 0.05 wt% of the mass of the poly(p-phenylene terephthalamide) polymer.

[0020] In some embodiments of the present invention, in step (2), the spinning aid is compounded by a long-chain macromolecular aid and a low-molecular aid.

[0021] In some embodiments of the present invention, in step (2), the spinning aid is a compound of polyethylene glycol and ethylene bisoleamide. Preferably, the mass ratio of polyethylene glycol to ethylene bisoleamide is 1:0.5-5, more preferably 1:0.5-2.

[0022] In some embodiments of the present invention, in step (1), the solvent in the polymerization solvent system is N-methylpyrrolidone, and the co-solvent is calcium chloride.

[0023] In some embodiments of the present invention, the mass fraction of calcium chloride in the polymerization solvent system is 5 wt % to 10 wt %, and the water content is less than 0.02 wt %.

[0024] In some embodiments of the present invention, in step (2), stirring or meshing is performed during the dissolution process; and / or, the solid content of the obtained modified spinning solution is 18 wt% to 20 wt%.

[0025] In some embodiments of the present invention, in step (1), the inherent viscosity of the polymer is 4.5 to 7.5; and / or, in step (2), the modified spinning solution is filtered before spinning with a filtration accuracy of 10 μm.

[0026] In some embodiments of the present invention, in step (2), the dry-jet wet spinning process includes the following steps: passing the modified spinning solution through a spinneret to form primary filaments, which are then put into a coagulation bath for coagulation and forming; the coagulated fibers are washed, neutralized, dried and oiled, and then wound into products.

[0027] In some embodiments of the present invention, in step (2), the diameter of the spinneret holes of the spinneret is 0.05 to 0.07 mm; and / or the spinning speed in the dry-jet wet spinning process is 200 to 750 m / min.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The present invention adopts a low-temperature solution polymerization method to obtain a polymer, and prepares the polymer and a spinning aid into a modified spinning solution. Compared with the spinning solution without a spinning aid, the surface tension of the mobile phase can be effectively improved, the leveling and uniformity can be improved, the flow driving force can be increased, the retention layer of the spinning solution in the pipeline can be thinned, and the spinning solution degraded due to long-term retention can be significantly reduced, thereby improving the fiber performance.

[0030] 2. The present invention improves the fluidity of the spinning solution by adding a spinning aid. The inner wall adhesion of the spinning solution when passing through the spinneret is significantly reduced, the apparent viscosity and the structural viscosity index are significantly reduced, the shear thinning behavior is increased, the spinnability is enhanced, the extrusion expansion ratio is reduced, and the shear orientation is more obvious. Therefore, the fiber molding is easier and more stable, and the macroscopic performance is that the fiber formation rate is higher, the fiber has less lint, and the mechanical properties are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The variation of the logarithmic viscosity of the spinning solution with the dissolution time (70-80°C).

[0032] Figure 2 Schematic diagram of PPTA resin dissolving in liquid sulfuric acid.

[0033] Figure 3 Schematic diagram of the degradation and shedding of PPTA during viscous flow. DETAILED DESCRIPTION

[0034] The preparation method of the high-performance poly(p-phenylene terephthalamide) fiber of the present invention is described in detail below.

[0035] The para-aramid spinning solution with concentrated sulfuric acid as solvent has a high dynamic viscosity of about 150,000-200,000 cp, poor fluidity, severe friction and adhesion with the pipe wall, forming a thick retention layer, and material dead zones appearing in local areas such as equipment and filter components; on the other hand, the para-aramid spinning solution with concentrated sulfuric acid as solvent system has the characteristics of fast degradation speed, and the degradation rate Δη at 70-80°C controlled by normal production can reach 0.2 / hour, and the degradation rate increases further with the increase of temperature, and the dynamic viscosity decreases significantly after degradation; the spinning solution in the pipe wall and dead zone is continuously degraded and collapsed into the solution system, so that the average molecular weight of the polymer in the spinning solution is reduced and the molecular weight distribution is widened, resulting in a decrease in the performance of the fiber. The inventors of the present invention have found that by adding a specific spinning aid in the preparation process of the spinning solution, the fluidity of the spinning solution is improved, the degradation rate is reduced, the inner wall adhesion of the spinning solution is significantly reduced when passing through the spinneret, the fiber formation rate of the fiber is higher, the hair is less, and the mechanical properties are improved, and the present invention is completed on this basis.

[0036] The present invention provides a method for preparing high-performance poly(p-phenylene terephthalamide) fiber, and the specific technical scheme is as follows:

[0037] A method for preparing high-performance poly(p-phenylene terephthalamide) fiber comprises the following steps:

[0038] (1) Using terephthaloyl chloride and p-phenylenediamine as raw materials, a polymer is prepared by a low temperature solution polymerization method;

[0039] (2) Using 96wt~100wt% concentrated sulfuric acid as solution, polymer and spinning aid are prepared into modified spinning solution; using dry-jet wet spinning process to prepare high-performance poly(p-phenylene terephthalamide) fiber from the modified spinning solution; the spinning aid is selected from any one of polyethylene glycol, alkylphenol polyoxyethylene ether, ethylene bisoleamide, fatty acid glyceride, white oil, polyvinyl pyrrolidone, butynediol diethoxy ether, or a combination of several of them.

[0040] The spinning aid in the present invention is selected from chemicals that can be dissolved in concentrated sulfuric acid solution, have good stability in concentrated sulfuric acid solution, usually have a degradation time of more than 6 hours, and can improve the fluidity and spinnability of the spinning solution. The present invention does not need to change the polymerization process and dissolution process of the polymer. By adding the spinning aid to physically modify the spinning solution, the fluidity of the spinning solution can be significantly improved, the degradation rate of the polymer is greatly reduced, the fiber formation rate of the fiber is higher, the hair is less, the mechanical properties are improved, and a high-performance poly(p-phenylene terephthalamide) fiber product is obtained.

[0041] The low temperature solution polymerization method of the present invention is not particularly limited and can be a commonly used method in the art, which can be intermittent polymerization or continuous polymerization. The polymer of the present invention refers to the pure polymer obtained after washing and drying the product obtained by the polymerization reaction.

[0042] In some embodiments of the present invention, in step (2), the specific operation of preparing the modified spinning solution from the polymer and the spinning aid includes mixing the polymer and the spinning aid to obtain a mixture or adding the two separately to a concentrated sulfuric acid solution, dissolving, and obtaining a modified spinning solution. The first method is to first mix the polymer and the spinning aid to obtain a mixture, and then add the mixture to a concentrated sulfuric acid solution, dissolve, and prepare the modified spinning solution, which is convenient for operation; specifically, the polymer and the spinning aid can be mixed at any stage after the product obtained by the polymerization reaction is washed to before the preparation of the spinning solution, for example, a) the spinning aid is dissolved in water, the spinning aid is prepared into an aqueous solution and mixed with the polymer, and then dried together to obtain a mixture; b) the spinning aid is in a solid block or powder form, and the spinning aid is directly mixed with the dried polymer to obtain a mixture. The second method is to add the polymer and the spinning aid separately to a concentrated sulfuric acid solution, dissolve, and prepare the modified spinning solution.

[0043] In some embodiments of the present invention, in step (2), the added amount of the spinning aid is 0.001wt% to 0.05wt% of the mass of the poly(p-phenylene terephthalamide) polymer, which can be 0.001wt% to 0.002wt%, 0.002wt% to 0.003wt%, 0.003wt% to 0.004wt%, 0.04wt% to 0.005wt%, 0.005wt% to 0.01wt%, 0.01wt% to 0.02wt%, 0.02wt% to 0.03wt%, 0.03wt% to 0.04wt%, and can also be 0.04wt% to 0.05wt%.

[0044] In the present invention, the polyethylene glycol (PEG) is a high molecular polymer with good water solubility, and is often used as an antistatic agent and softener. The alkylphenol polyoxyethylene ether (APEO) is an important polyoxyethylene nonionic surfactant, which can be nonylphenol polyoxyethylene ether (NPEO), octylphenol polyoxyethylene ether (OPEO), dodecyl polyoxyethylene ether (DPEO) and dinonylphenol polyoxyethylene ether. The ethylene bisoleamide (EBO) is a light yellow waxy solid, which is used as a lubricant, brightener, slip agent, anti-adhesive agent and release agent in plastics, and an antistatic agent for cellophane. The fatty acid glyceride is a nonionic surfactant, which is mainly divided into monoglyceride (monoglyceride), diglyceride (diglyceride) and triglyceride (triglyceride) according to the number of fatty acid molecules. Monoglyceride (MAC) includes monostearate glyceryl (MG), monooleate glyceryl, monolaurate glyceryl, etc. It is a white or light yellow solid at room temperature and is often used as an emulsifier. The white oil is a white mineral oil, and the molecular weight is usually in the range of 250 to 450, and it is an industrial grade white oil. The polyvinyl pyrrolidone (PVP) is a non-ionic polymer compound, which is a white or nearly white powder. As a polymer surfactant, polyvinyl pyrrolidone can be used as a dispersant, emulsifier, thickener, leveling agent, particle size regulator, anti-reprecipitation agent, coagulant, cosolvent and detergent in different dispersion systems. The butynediol diethoxy ether (EBO) is a yellow to orange-yellow transparent liquid, which is mainly used as a brightener and weak leveling agent for nickel electroplating in industry.

[0045] In some embodiments of the present invention, in step (2), the spinning aid is compounded by a long-chain macromolecular aid and a low-molecular aid. The long-chain macromolecular aid is selected from polyethylene glycol or polyvinyl pyrrolidone, and the molecular weight is 30,000 to 50,000; the low-molecular aid is selected from any one of alkylphenol polyoxyethylene ether, ethylene bisoleamide, fatty acid glyceride, white oil, and butynediol diethoxy ether. Specifically, the spinning aid includes but is not limited to a compound of polyethylene glycol and alkylphenol polyoxyethylene ether, a compound of polyethylene glycol and white oil, a compound of polyethylene glycol and ethylene bisoleamide, and fatty acid glyceride, and can also be a compound of polyvinyl pyrrolidone and butynediol diethoxy ether. During the spinning process, low molecular weight additives can migrate to the liquid-solid interface, reduce the surface tension between the mobile phase and the pipe wall, make the spinning solution have good wettability in the pipe, and help leveling; long-chain macromolecular additives form an extremely thin monomolecular layer on the surface of the system, and then accumulate in the trough to form a high surface energy state, generating a driving force for the PPTA resin to flow here, making the retention layer of the spinning solution in the pipe thinner and less likely to form a dead zone, which significantly reduces the amount of spinning solution degraded due to long-term retention. Therefore, the use of a spinning aid compounded with long-chain macromolecular additives and low molecular weight additives can greatly improve the performance of the fiber.

[0046] In some embodiments of the present invention, in step (2), the spinning aid is a compound of polyethylene glycol and ethylene bisoleamide. In the present invention, polyethylene glycol and ethylene bisoleamide can be compounded in any ratio, and can achieve a good effect of improving the fluidity of the spinning solution and the fiber performance. In some preferred embodiments of the present invention, the mass ratio of polyethylene glycol to ethylene bisoleamide is 1:0.5-5, more preferably 1:0.5-2.

[0047] In some embodiments of the present invention, in step (1), the solvent in the polymerization solvent system is N-methylpyrrolidone, and the cosolvent is calcium chloride. In some embodiments of the present invention, the mass fraction of calcium chloride in the polymerization solvent system is 5wt% to 10wt%, and can be 5wt% to 6wt%, 6wt% to 7wt%, 7wt% to 8wt%, 8wt% to 9wt%, or 9wt% to 10wt%. The water content is less than 0.02wt%.

[0048] In some embodiments of the present invention, in step (2), stirring or meshing is performed during the dissolution process. The above preparation process can be prepared in a twin-screw reactor or in other containers. The stirring described in the present invention can provide higher shear strength. When prepared in a twin-screw reactor, sufficient meshing or shear strength needs to be provided. The temperature control during the dissolution process in the present invention is generally adapted to the type of reactor used for dissolution. According to the type of reactor, segmented temperature control or unified temperature control can be adopted, as long as the temperature requirements of the dissolution process can be met. In some specific embodiments of the present invention, the segmented temperature control is divided into four sections from feeding to discharging, the temperature of the first section is controlled at 10-20°C, the temperature of the second section is controlled at 20-40°C, the temperature of the third section is controlled at 40-60°C, and the temperature of the fourth section is controlled at 60-80°C. In other specific embodiments of the present invention, the unified temperature control is specifically to control the system temperature within the range of 70-80°C. In the present invention, there is no special restriction on the solid content of the modified spinning solution, as long as the requirements of the spinning process can be achieved. Preferably, the solid content of the modified spinning solution is 18wt% to 20wt%, may be 18wt% to 18.5wt%, 18.5wt% to 19wt%, 19wt% to 19.5wt%, or 19.5wt% to 20wt%, preferably 18.5wt% to 19.5wt%, and more preferably 19wt%.

[0049] In some embodiments of the present invention, in step (1), the polymer has a logarithmic viscosity of 4.5 to 7.5. The polymer in this viscosity range is suitable for spinning, has a suitable molecular weight, and is also easy to dissolve. The more preferred range is 6.0 to 6.5. Within this viscosity range, the spinning solution is reasonably prepared, and the fiber obtained by spinning has a logarithmic viscosity of 5.5 to 6.0 and excellent mechanical properties.

[0050] In some embodiments of the present invention, in step (2), the modified spinning solution is filtered before spinning with a filtration accuracy of 10 μm, which is conducive to removing gel particles and solid insoluble particles in the spinning solution.

[0051] In some embodiments of the present invention, in step (2), the diameter of the spinneret holes of the spinneret is 0.05 to 0.07 mm.

[0052] In some embodiments of the present invention, in step (2), the spinning speed in the dry-jet wet spinning process is 200-750 m / min, which can be 200-250 m / min, 250-300 m / min, 300-350 m / min, 350-400 m / min, 400-450 m / min, 450-500 m / min, 500-550 m / min, 550-600 m / min, 600-650 m / min, 650-700 m / min, or 700-750 m / min.

[0053] The specific embodiments of the present invention are further described in detail below in conjunction with preferred embodiments. When the embodiments provide numerical ranges, it should be understood that, unless otherwise specified in the present invention, the two endpoints of each numerical range and any numerical value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those generally understood by those skilled in the art. In addition to the specific methods, equipment, and materials used in the embodiments, as those skilled in the art grasp the prior art and record the present invention, any methods, equipment, and materials of the prior art similar or equivalent to the methods, equipment, and materials described in the embodiments of the present invention can also be used to realize the present invention.

[0054] Example 1

[0055] The method for preparing high-performance poly(p-phenylene terephthalamide) fiber in this embodiment comprises the following steps:

[0056] S1. Using terephthaloyl chloride (10 kg) and p-phenylenediamine (5.32 kg) as raw materials, calcium chloride is dissolved in NMP solvent to form NMP-CaCl2 mixed solvent (101.92 kg), wherein calcium chloride accounts for 9 wt% in the mixed solvent, as a polymerization solvent system, and a low-temperature solution polymerization method is adopted to carry out polymerization reaction to obtain a polymerization product, and the polymerization product is washed and dried to obtain a polymer (11.72 kg).

[0057] S2, using 100wt% concentrated sulfuric acid as a solution, a spinning aid ethylene bisoleic acid amide (1.1724g) and a polymer (11.72kg) were uniformly mixed (the amount of ethylene bisoleic acid amide was 0.01% of the mass of the polymer) to obtain a mixture, and the mixture was added to concentrated sulfuric acid and stirred vigorously to prepare a modified spinning solution with a solid content of 19wt%;

[0058] S3. The dry-jet wet spinning process is adopted to pass the filtered modified spinning solution through a spinneret (spinneret hole diameter is 0.06 mm) to form primary filaments at a spinning speed of 500 m / min. The filaments then enter a coagulation bath for coagulation. The coagulated fibers are washed, neutralized, dried and oiled, and then wound into aramid fiber products.

[0059] Example 2

[0060] The spinning aid was replaced with polyethylene glycol (PEG 40000), and the remaining steps were the same as those in Example 1 to obtain aramid fibers.

[0061] Example 3

[0062] The spinning aid was replaced with a mixture of polyethylene glycol (PEG 40000) and ethylene bisoleamide in a mass ratio of 2:1 (PEG=0.7816 g, EBO=0.3908 g), and the remaining operating steps were the same as those in Example 1 to obtain aramid fibers.

[0063] Example 4

[0064] The spinning aid was replaced with a mixture of polyethylene glycol (PEG 40000) and ethylene bisoleamide in a mass ratio of 1:1 (PEG=0.5862 g, EBO=0.5862 g), and the remaining operating steps were the same as those in Example 1 to obtain aramid fibers.

[0065] Example 5

[0066] The spinning aid was replaced with a mixture of polyethylene glycol (PEG 40000) and ethylene bisoleamide in a mass ratio of 1:2 (PEG=0.3908 g, EBO=0.7816 g), and the remaining operating steps were the same as those in Example 1 to obtain aramid fibers.

[0067] Example 6

[0068] The spinning aid was replaced with a mixture of polyethylene glycol (PEG 40000) and ethylene bisoleamide in a mass ratio of 1:3 (PEG=0.2931 g, EBO=0.8793 g), and the remaining operating steps were the same as those in Example 1 to obtain aramid fibers.

[0069] Example 7

[0070] The method for preparing high-performance poly(p-phenylene terephthalamide) fiber in this embodiment comprises the following steps:

[0071] S1. Using terephthaloyl chloride (10 kg) and p-phenylenediamine (5.32 kg) as raw materials, calcium chloride is dissolved in NMP solvent to form NMP-CaCl2 mixed solvent (101.92 kg), wherein calcium chloride accounts for 9 wt% in the mixed solvent, as a polymerization solvent system, and a low-temperature solution polymerization method is adopted to carry out polymerization reaction to obtain a polymerization product, and the polymerization product is washed and dried to obtain a polymer (11.72 kg).

[0072] S2, taking 100wt% concentrated sulfuric acid as solution, adding polymer (11.72kg) and ethylenebisoleamide (1.1724g) into concentrated sulfuric acid (the amount of ethylenebisoleamide is 0.01% of the mass of the polymer) to prepare a modified spinning solution with a solid content of 19wt%;

[0073] S3. The dry-jet wet spinning process is adopted to pass the filtered modified spinning solution through a spinneret (spinneret hole diameter is 0.06 mm) to form primary filaments at a spinning speed of 500 m / min. The filaments then enter a coagulation bath for coagulation. The coagulated fibers are washed, neutralized, dried and oiled, and then wound into aramid fiber products.

[0074] Example 8

[0075] The spinning aid was replaced with nonylphenol polyoxyethylene ether (NPEO), and the remaining operating steps were the same as those in Example 1 to obtain aramid fiber.

[0076] Example 9

[0077] The spinning aid was replaced with glyceryl monostearate (MG), and the remaining operating steps were the same as those in Example 1 to obtain aramid fiber.

[0078] Example 10

[0079] The spinning aid was replaced with white oil (industrial grade), and the remaining operating steps were the same as those in Example 1 to obtain aramid fiber.

[0080] Embodiment 11

[0081] The spinning aid was replaced with polyvinyl pyrrolidone (PVP 30000), and the remaining steps were the same as those in Example 1 to obtain aramid fibers.

[0082] Example 12

[0083] The spinning aid was replaced with butynediol diethoxy ether, and the remaining steps were the same as those in Example 1 to obtain aramid fiber.

[0084] Comparative Example 1

[0085] No spinning aid was added, and the remaining steps were the same as in Example 1 to obtain aramid fiber.

[0086] The spinning conditions of Examples 1 to 12 and Comparative Example 1 and the performance characterization results of the obtained aramid fibers are shown in Table 1 below.

[0087] Table 1 Spinning conditions of Examples 1 to 12 and Comparative Example 1 and performance characterization results of the obtained aramid fibers

[0088]

[0089] *Note: Aramid fiber has a natural moisture content of about 5%, so the theoretical maximum fiber yield is 105%. The fiber yield here is defined as the fiber with a certain weight collected onto the paper core.

[0090] Result analysis: From the data in Table 1, it can be seen that the spinning solutions added with spinning aids in Examples 1 to 12 have improved spinnability and fiber performance compared with Comparative Example 1, mainly due to the improvement of spinning solution leveling, thinning of the retention layer on the pipe wall, increased spinning solution fluidity, reduced proportion of degraded materials, and increased fiber mechanical properties. The spinning aids in Examples 3 to 6 are a combination of long-chain macromolecular aids and low-molecular aids. In addition to improving spinnability, they also greatly improve the comprehensive mechanical properties of the fiber, and the effect of improving fiber mechanical properties is better than that of Examples 1 to 2 and Examples 7 to 12 using only one spinning aid. From the data of Examples 3 to 6, as the amount of low-molecular-weight additives used increases, the mechanical properties of the fiber first increase and then decrease. When the spinning aids in Examples 1 and 7 to 12 are all low-molecular-weight additives, the mechanical properties of the fiber are not as good as those in Examples 3 to 6. This may be due to the excessive addition of low-molecular-weight additives, which will affect the molecular structure of PPTA and form defects, resulting in a decrease in the mechanical properties of the fiber. Therefore, when the low-molecular-weight additives and long-chain macromolecules are compounded in a suitable proportion (for example, the mass ratio of polyethylene glycol to ethylene bisoleamide is 1:0.5 to 2), fibers with optimal performance can be obtained.

[0091] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for preparing high-performance poly(p-phenylene terephthalamide) fiber, characterized in that: The following steps are involved: (1) Using terephthaloyl chloride and p-phenylenediamine as raw materials, the polymer is prepared by low-temperature solution polymerization; (2) Using 96wt~100wt% concentrated sulfuric acid as solution, polymer and spinning aid are prepared to obtain modified spinning solution; The high-performance poly(p-phenylene terephthalamide) fiber is prepared by using a dry-jet wet spinning process to modify the spinning solution; the spinning aid is compounded by a long-chain macromolecular aid and a low-molecular aid; the long-chain macromolecular aid is selected from polyethylene glycol, and the low-molecular aid is selected from ethylene bisoleamide; the mass ratio of polyethylene glycol to ethylene bisoleamide is 1:0.5-5; The polymer and the spinning aid are used to prepare a modified spinning solution. The specific operation includes adding the mixture obtained by mixing the polymer and the spinning aid or adding the two separately into a concentrated sulfuric acid solution to dissolve them to obtain a modified spinning solution; The added amount of the spinning aid is 0.01wt% of the mass of the poly(p-phenylene terephthalamide) polymer.

2. The preparation method according to claim 1, characterized in that The mass ratio of polyethylene glycol to ethylene bisoleamide is 1:0.5~2.

3. The preparation method according to claim 1, characterized in that: In step (1), the polymerization solvent system of the low-temperature solution polymerization method includes a solvent and a co-solvent, the solvent is N-methylpyrrolidone, and the co-solvent is calcium chloride.

4. The preparation method according to claim 3, characterized in that: The mass fraction of calcium chloride in the polymerization solvent system is 5wt%-10wt%, and the water content is less than 0.02wt%.

5. The preparation method according to claim 1, characterized in that: In step (2), stirring or meshing is performed during the dissolution process; and / or, the solid content of the obtained modified spinning solution is 18wt%~20wt%.

6. The preparation method according to claim 1, characterized in that: In step (1), the inherent logarithmic viscosity of the polymer is 4.5-7.5; and / or, in step (2), the modified spinning solution is filtered before spinning with a filtration accuracy of 10 μm.

7. The preparation method according to claim 1, characterized in that: In step (2), the dry-jet wet spinning process includes the following steps: passing the modified spinning solution through a spinneret to form primary filaments, which are then put into a coagulation bath for coagulation and forming; the coagulated fibers are washed, neutralized, dried and oiled, and then wound into products.

8. The preparation method according to claim 7, characterized in that: The spinneret hole diameter of the spinneret is 0.05-0.07 mm; and / or the spinning speed in the dry-jet wet spinning process is 200-750 m / min.

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