Modified poly (p-phenylene terephthamide) fiber with high elongation at break and preparation method of modified poly (p-phenylene terephthamide) fiber

Abstract

The invention relates to the technical field of aromatic polyamide high polymers, in particular to a modified poly-p-phenylene terephthamide fiber with high elongation at break and a preparation method of the modified poly-p-phenylene terephthamide fiber. According to the invention, a small amount of 3, 4-difluorobenzene is introduced According to the preparation method, the third monomer containing 4, 4 '-diaminodiphenyl ether and the fourth monomer containing a diaminophenoxy functional group are added, and the molar ratio of the third monomer and the fourth monomer in the total amount of the diamine monomer is controlled, so that the rigid molecular chain structure of the conventional para-aramid fiber is destroyed to a certain extent, the breaking strength of the fiber is maintained, the elongation at break of the polymer fiber is enhanced, and the service life of the polymer fiber is prolonged. The prepared modified poly-p-phenylene terephthamide can still adopt a dry-jet wet spinning process, the cost of a new production line of a factory is saved, the fiber with stable elongation at break index is obtained by optimizing process conditions and parameters, and the elongation at break of the prepared fiber is 3.6% or above.

Description

Technical Field

[0001] The invention relates to the technical field of aromatic polyamide polymers, in particular to a modified poly(p-phenylene terephthalamide) fiber with high elongation at break and a preparation method thereof. Background Art

[0002] Poly(p-phenylene terephthalamide) (PPTA) is a linear molecule with regular molecular arrangement. Therefore, the aramid 1414 fiber prepared from poly(p-phenylene terephthalamide) is very rigid, has a high modulus, and has a lower elongation at break than other flexible molecular materials. The fiber material used in the crown cord of automobile tires needs to overcome the fatigue of high-frequency rolling of tires, that is, it needs a higher anti-disc fatigue performance, which requires a higher elongation at break. In conveyor belt applications, aramid fibers must first be woven into canvas and then used as the skeleton material of the conveyor belt, which also requires bending and compression fatigue resistance. This bending and compression fatigue resistance requires an increase in the elongation at break of the material. The high strength and low density of aramid 1414 is very suitable for use in tires and conveyor belts, which can significantly reduce the weight of tires and conveyor belts. However, the elongation at break of ordinary types of aramid 1414 is usually less than 3.6%, which is not suitable for use in these fields.

[0003] Patent JP2023020354A discloses a method for preparing copolymerized aramid fiber, which introduces a large number of meta-structure units into the rigid structure of para-aramid. The prepared copolymerized aramid fiber has high heat resistance, balanced tensile strength and high elongation at break. However, the introduction of a large number of meta-structures destroys the liquid crystal characteristics of para-aramid, and the spinning process is changed from dry-jet wet spinning to wet spinning, which increases the cost of building a new spinning line in the para-aramid factory. Patent CN112695390A optimizes the polymerization process and spinning process parameters of PPTA. The elongation at break of the para-aramid fiber obtained based on the above preparation method is ≥3.5%. However, the preparation method described in the invention has high requirements on the precision of the equipment. During long-term operation, the wear and aging of the equipment itself will affect the consistency and stability of the product.

[0004] Therefore, it is of great significance to develop a poly(p-phenylene terephthalamide) fiber with high elongation at break. Summary of the invention

[0005] In view of the fact that the elongation at break of poly(p-phenylene terephthalamide) fiber in the prior art is lower than that of other flexible molecular materials, and the elongation at break is usually lower than 3.6%, and its application in some fields requiring high elongation at break is affected, the object of the present invention is to provide a modified poly(p-phenylene terephthalamide) fiber with high elongation at break and a preparation method thereof. The modified poly(p-phenylene terephthalamide) fiber can be dry-jet wet-spun, and the prepared poly(p-phenylene terephthalamide) fiber has high elongation at break, is suitable for industrial-scale production, has excellent impact resistance and fatigue resistance, and can be applied to the fields of conveyor belts and tires.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention provides a modified poly(p-phenylene terephthalamide) fiber with high elongation at break, and the specific technical scheme is as follows:

[0008] A modified poly(p-phenylene terephthalamide) fiber with high elongation at break, wherein the molecular structure of the modified poly(p-phenylene terephthalamide) fiber is as follows:

[0009]

[0010] Among them, Ar 1 It is the residual group other than the amino group in the diamine containing the bisaminophenoxy functional group; 80≤m≤90, 5≤n≤17, 3≤p≤5.

[0011] In some embodiments of the present invention, the diamine containing a bisaminophenoxy functional group is selected from one or more of the following compounds:

[0012]

[0013] The second aspect of the present invention provides a method for preparing the modified poly(p-phenylene terephthalamide) fiber having high elongation at break, comprising the following steps:

[0014] (1) subjecting p-phenylenediamine, terephthaloyl chloride, a third monomer and a fourth monomer to a low-temperature polycondensation reaction in a solvent system to obtain modified poly(p-phenylene terephthalamide); the third monomer is 3,4'-diaminodiphenyl ether, and the fourth monomer is a diamine containing a bisaminophenoxy functional group;

[0015] (2) Using the modified poly(p-phenylene terephthalamide) obtained in step (1) as a raw material and concentrated sulfuric acid as a solvent to prepare a spinning solution, and adopting a dry-jet wet spinning process to prepare a modified poly(p-phenylene terephthalamide) fiber with a high elongation at break.

[0016] In some embodiments of the present invention, the low-temperature polycondensation reaction process includes: dissolving paraphenylenediamine, a third monomer and a fourth monomer in a solvent system to form a premix; adding a portion of terephthaloyl chloride to perform prepolymerization to form a prepolymer; and polymerizing the prepolymer with the remaining terephthaloyl chloride to obtain modified poly(p-phenylene terephthalamide) fiber.

[0017] In some embodiments of the present invention, the dry-wet spinning process specifically includes: passing the 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.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The modified poly(p-phenylene terephthalamide) fiber provided by the present invention introduces a diamine monomer containing a bisaminophenoxy functional group, thereby destroying the rigid molecular chain structure of conventional para-aramid to a certain extent, thereby enhancing its elongation at break; the introduction of a small amount of monomer 3,4'-diaminodiphenyl ether, in addition to further increasing the flexible structure in the molecular chain, its asymmetric dislocation structure can be used as a connection point for adjusting the conformation of the molecular chain, which is beneficial to making the molecular chain present a straight conformation during spinning and stretching, so that the modified poly(p-phenylene terephthalamide) fiber maintains the breaking strength of the fiber while improving the elongation at break; at the same time, by controlling the proportion of the total molar amount of the third monomer and the fourth monomer in the total molar amount of the diamine monomer, the modified poly(p-phenylene terephthalamide) can still adopt the dry-jet wet spinning process, saving the cost of building a new production line in the factory.

[0020] 2. The modified poly(p-phenylene terephthalamide) fiber preparation method provided by the present invention comprises the following steps: the modified aramid is vigorously stirred with concentrated sulfuric acid having a mass fraction of 98wt% to 100wt% in a twin-screw reactor and the temperature is raised to 78-82°C to prepare a spinning solution with a concentration of 19.0wt% to 19.5wt%. Within the above temperature range, the polymer can be well dissolved and will not be degraded due to excessive temperature. At a concentration of 19.0-19.5%, the slurry exhibits good spinnability. By controlling the filtration accuracy of the spinning solution to be less than 10 microns, gel particles and solid insoluble particles can be effectively filtered out. Since the aperture of the spinning spinneret is very small, all larger insoluble particles need to be removed to ensure that the slurry strips are continuous during the spinning process, the fiber structure has fewer defects, a denser structure is formed, and a more regular arrangement is formed, thereby obtaining fibers with high elongation.

[0021] 3. The method for preparing modified poly(p-phenylene terephthalamide) fiber provided by the present invention selects a spinneret with a suitable spinneret hole diameter to avoid excessive stretching ratio caused by a large ratio between the spinneret hole of the spinneret and the final fiber diameter, thereby reducing the generation of fiber structural defects and controlling the tension of the spinning process to 0.2-0.5 g / d. Under the above process conditions, it is beneficial to obtain fibers with more stable elongation at break index. DETAILED DESCRIPTION

[0022] The modified poly(p-phenylene terephthalamide) fiber with high elongation at break and the preparation method of the fiber are described in detail below.

[0023] The first aspect of the present invention provides a modified poly(p-phenylene terephthalamide) fiber with high elongation at break, and the specific technical scheme is as follows:

[0024] A modified poly(p-phenylene terephthalamide) fiber with high elongation at break, wherein the molecular structure of the modified poly(p-phenylene terephthalamide) fiber is as follows:

[0025]

[0026] Among them, Ar 1 It is the residual group other than the amino group in the diamine containing the aminophenoxy functional group; 80≤m≤90, 5≤n≤17, 3≤p≤5.

[0027] The present invention destroys the rigid molecular chain structure of conventional para-aramid to a certain extent by introducing a fourth monomer containing a bisaminophenoxy functional group, thereby enhancing its elongation at break; the introduction of a small amount of monomer 3,4'-diaminodiphenyl ether, in addition to further increasing the flexible structure in the molecular chain, its asymmetric dislocation structure can be used as a connection point for adjusting the conformation of the molecular chain, which is beneficial to making the molecular chain present a straight conformation during spinning and stretching, so that the elongation at break of the modified poly(p-phenylene terephthalamide) fiber is improved while maintaining the fiber's breaking strength; at the same time, the proportion of the total molar amount of the third monomer and the fourth monomer in the total molar amount of the diamine monomer is controlled, so that the preparation of the modified poly(p-phenylene terephthalamide) fiber can still adopt a dry-jet wet spinning process, saving the cost of building a new production line in the factory.

[0028] In the present invention, the "diamine containing a bisaminophenoxy functional group" refers to a diamine containing two aminophenoxy functional groups.

[0029] In the present invention, the amino group and the phenoxy group in the "aminophenoxy functional group" are on the same benzene ring.

[0030] As used herein, the term "phenoxy" generally refers to a phenyl-O- group, the bond to the parent moiety being through the ether oxygen.

[0031] In some embodiments of the present invention, the diamine containing a bisaminophenoxy functional group is selected from one or more of the following compounds:

[0032]

[0033] The second aspect of the present invention provides a method for preparing the modified poly(p-phenylene terephthalamide) fiber having high elongation at break, comprising the following steps:

[0034] (1) subjecting p-phenylenediamine, terephthaloyl chloride, a third monomer and a fourth monomer to a low-temperature polycondensation reaction in a solvent system to obtain modified poly(p-phenylene terephthalamide); the third monomer is 3,4'-diaminodiphenyl ether, and the fourth monomer is a diamine containing an aminophenoxy functional group;

[0035] (2) Using the modified poly(p-phenylene terephthalamide) obtained in step (1) as a raw material and concentrated sulfuric acid as a solvent to prepare a spinning solution, and adopting a dry-jet wet spinning process to prepare a modified poly(p-phenylene terephthalamide) fiber with a high elongation at break.

[0036] In some embodiments of the present invention, in step (1), the low-temperature polycondensation reaction process includes: dissolving p-phenylenediamine, the third monomer and the fourth monomer in a solvent system to form a premix; adding a portion of terephthaloyl chloride to perform prepolymerization to form a prepolymer; and polymerizing the prepolymer with the remaining terephthaloyl chloride to obtain a modified poly(p-phenylene terephthalamide) fiber. The polymerization production process of the low-temperature polycondensation reaction in the present invention is not particularly limited, and the process commonly used in the art can be used, and intermittent polymerization or continuous polymerization can be used.

[0037] In some embodiments of the present invention, the molar ratio of the terephthaloyl chloride to the total amount of the diamine monomers is 1-1.015:1, may be 1.000-1.005:1, 1.005-1.010:1, or may be 1.010-1.015:1.

[0038] In some embodiments of the present invention, the total molar amount of the third monomer and the fourth monomer accounts for 10-20% of the total molar amount of the diamine monomer. By controlling the total molar amount of the third monomer and the fourth monomer not to exceed 20% of the total molar amount of the diamine monomer, the preparation of the modified poly(p-phenylene terephthalamide) fiber can still adopt the dry-jet wet spinning process, saving the cost of building a new production line in the factory.

[0039] In some embodiments of the present invention, the molar amount of the partial terephthaloyl chloride is 35% to 65% of the total molar amount of terephthaloyl chloride, and can be 35% to 40%, 40% to 45%, 45% to 50%, 50% to 55%, 55% to 60%, or 60% to 65%.

[0040] In some embodiments of the present invention, the prepolymerization temperature is -10 to 5°C, -10 to -8°C, -8 to -6°C, -6 to -4°C, -4 to -2°C, -2 to 0°C, 0 to 2°C, or 2 to 5°C, preferably -10 to 0°C.

[0041] In some embodiments of the present invention, the polymerization temperature is 0-50°C, and can be 0-5°C, 5-10°C, 10-15°C, 15-20°C, 20-25°C, 25-30°C, 30-35°C, 35-40°C, 40-45°C, or 45-50°C, preferably 10-30°C.

[0042] In some embodiments of the present invention, the solvent system comprises a solvent and a co-solvent, the solvent is selected from N-methylpyrrolidone (NMP), and the co-solvent is calcium chloride (CaCl 2 ), CaCl 2 In NMP-CaCl 2 The solvent system accounts for 8wt%. The CaCl 2 The ratio of the molar amount of to the total molar amount of the diamine monomers is 1.5-1.7:1, can be 1.5-1.6:1, or can be 1.6-1.7:1.

[0043] In some embodiments of the present invention, the mass fraction of the concentrated sulfuric acid is 98wt% to 100wt%, may be 98wt% to 98.5wt%, 98.5wt% to 99wt%, 99wt% to 99.5wt%, or 99.5wt% to 100wt%.

[0044] In some embodiments of the present invention, the spinning solution is prepared in a twin-screw reactor, and sufficient meshing or shearing strength needs to be provided during the preparation process.

[0045] In some embodiments of the present invention, the spinning solution needs to be finely filtered. Preferably, the fine filtration accuracy of the fine filtration is 8-10 μm, which can effectively filter out gel particles and solid insoluble particles. Because the aperture of the spinning spinneret is very small, it is necessary to remove all the larger insoluble particles to ensure that the spinning pulp strips are continuous during the spinning process, with fewer fiber structural defects, forming a denser structure and a more regular arrangement, thereby obtaining fibers with high elongation.

[0046] In some embodiments of the present invention, the dry-wet spinning process specifically includes: passing the 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.

[0047] In some embodiments of the present invention, the concentration of the modified poly(p-phenylene terephthalamide) in the spinning solution is 19.0wt% to 19.5wt%, and can be 19.0wt% to 19.1wt%, 19.1wt% to 19.2wt%, 19.2wt% to 19.3wt%, 19.3wt% to 19.4wt%, or 19.4wt% to 19.5wt%. When the concentration of the modified poly(p-phenylene terephthalamide) is within the above range, the spinning solution exhibits good spinnability.

[0048] In some embodiments of the present invention, strong stirring is performed during the preparation of the spinning solution and the temperature is controlled at 78-82°C. Within the above temperature range, the polymer can be well dissolved and will not be degraded due to excessively high temperature. Specifically, the temperature can be 78-79°C, 79-80°C, 80-81°C, or 81-82°C.

[0049] In some embodiments of the present invention, the filament tension is controlled at 0.2-0.5 g / d during washing, neutralization, drying, oiling and winding, which is beneficial for obtaining fibers with more stable elongation at break index.

[0050] In some embodiments of the present invention, the diameter of the spinneret hole of the spinneret is 0.065 mm, which avoids the phenomenon of excessive stretching ratio caused by the large ratio between the spinneret hole of the spinneret and the final fiber diameter, thereby reducing the occurrence of fiber structure defects.

[0051] 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.

[0052] Example 1

[0053] The fourth monomer structural formula selected in this embodiment is as follows:

[0054]

[0055] The preparation method of the modified poly(p-phenylene terephthalamide) fiber of this embodiment comprises the following steps:

[0056] (1) Polymerization process

[0057] PPD, 3,4'-diaminodiphenyl ether (3,4'-ODA) (third monomer), and fourth monomer were mixed in NMP-CaCl 2 Solvent system (CaCl 2 In NMP-CaCl 2 The molar ratio of PPD: 3,4'-ODA: the fourth monomer is 80:3:17, and the CaCl 2 : The total molar ratio of diamine monomers is 1.5:1; then a condensation reaction is carried out with a certain amount of terephthaloyl chloride (TPC) in a prepolymerization reactor to form a prepolymer, wherein the amount of TPC added is 35% of the total TPC added molar amount, and the prepolymerization temperature is controlled to be -10 to 0°C during the reaction; the prepolymer and the remaining TPC are subjected to a second polymerization reaction in a twin-screw reactor to obtain a modified poly(p-phenylene terephthalamide) (PPTA) polymer, wherein the total amount of TPC added and the total molar ratio of diamine monomers is 1.015:1, and the polymerization temperature is controlled to be 10 to 30°C during the reaction. The polymer is neutralized, washed and dried with a sodium hydroxide solution to finally obtain a pure and dry modified PPTA polymer; the moisture content of the modified PPTA polymer needs to be controlled within 0.5wt%, and the total amount of other possible impurities cannot exceed 50ppm.

[0058] (2) Preparation of spinning solution

[0059] The modified PPTA polymer is added to concentrated sulfuric acid with a mass fraction of 99.8wt%, and after strong stirring and heating to 81°C, a spinning solution with a concentration of 19.35wt% is prepared. The spinning solution is degassed and filtered and then transported to the spinning metering pump. The filtration accuracy of the filter is controlled at 10 microns to ensure that insoluble impurities and gel particles are completely filtered. The prepared spinning solution needs to be spun in time, and the residence process cannot exceed 4 hours, otherwise it will cause a decrease in viscosity, thereby affecting the fiber performance.

[0060] (3) Spinning

[0061] The filtered spinning solution is ejected from the spinneret by a gear metering pump. The spinneret aperture is 0.065mm. The spinning slurry is ejected from the spinning hole to form slurry. After passing through a 6mm air layer, it enters the coagulation system, passes through the coagulation tube in the center of the coagulation tank, and flows out from the bottom of the tube. The coagulation bath temperature is 0-10°C, the acid content of the coagulation solution is 10%, and the sulfuric acid contained in the spinning slurry has been partially extracted after passing through the coagulation tube to become wet yarn containing sulfuric acid. The wet yarn is continuously washed and neutralized in the order of water washing / alkali washing / alkali washing on a multi-stage drum, and then dried on a drying drum at 135°C. The roller speed is controlled during the process of water washing / alkali washing / alkali washing / drying until the winding of the wet yarn. The speed of the roller at the latter stage is slightly greater than that of the roller at the previous stage, forming a spinning tension to keep the fiber taut throughout the process. The dry yarn is oiled and wound on a paper drum with a winder. The tension of the filaments is controlled at 0.2-0.5g / d throughout the process.

[0062] Example 2

[0063] The fourth monomer structural formula selected in this embodiment is as follows:

[0064]

[0065] The preparation method of the modified poly(p-phenylene terephthalamide) fiber of this embodiment comprises the following steps:

[0066] (1) Polymerization process

[0067] PPD, 3,4'-diaminodiphenyl ether (3,4'-ODA), and the fourth monomer were mixed in NMP-CaCl 2 Solvent system (CaCl 2 In NMP-CaCl 2 The molar ratio of PPD: 3,4'-ODA: the fourth monomer is 89:4:7, and CaCl 2 : The total molar ratio of diamine monomer is 1.7:1; then, a condensation reaction is carried out with a certain amount of terephthaloyl chloride TPC in a prepolymerization reactor to form a prepolymer, wherein the amount of TPC added is 50% of the total molar amount of TPC added, and the prepolymerization temperature is controlled to be -10 to 0°C during the reaction; the prepolymer and the remaining TPC are subjected to a second polymerization reaction in a twin-screw reactor to obtain a modified PPTA polymer, wherein the total molar ratio of TPC added to the total amount of diamine monomer is 1.006:1, and the polymerization temperature is controlled to be 10 to 30°C during the reaction. The polymer is neutralized, washed and dried with sodium hydroxide solution. Finally, a pure and dry polymer is obtained, and the moisture content of the polymer needs to be controlled within 0.5wt%, and the total amount of other possible impurities cannot exceed 50ppm.

[0068] (2) Preparation of spinning solution

[0069] The modified PPTA polymer is added to 99wt% sulfuric acid, stirred vigorously and heated to 81°C to prepare a spinning solution with a concentration of 19.3%. The spinning solution is degassed and filtered before being transported to a spinning metering pump. The filter accuracy is controlled at 8 microns to ensure that insoluble impurities and gel particles are completely filtered. The prepared spinning solution needs to be spun in time, and the residence time cannot exceed 4 hours, otherwise the viscosity will decrease, thereby affecting the fiber performance.

[0070] (3) Spinning

[0071] After filtering, the slurry is sprayed out from the spinneret by a gear metering pump. The spinneret aperture is 0.065mm. After the spinning slurry is sprayed out of the spinning hole, it becomes slurry. After passing through a 6mm air layer, it enters the coagulation system, passes through the coagulation tube in the center of the coagulation tank, and flows out from the bottom of the tube. The coagulation bath temperature is 0-10℃, the acid content of the coagulation liquid is 10%, and the sulfuric acid contained in the spinning slurry has been partially extracted after passing through the coagulation tube to become wet yarn containing sulfuric acid. The wet yarn is continuously washed and neutralized in the order of water washing / alkali washing / alkali washing on a multi-stage drum, and then dried on a drying drum at 135℃. The roller speed is controlled during the process of water washing / alkali washing / alkali washing / drying until the winding of the wet yarn. The speed of the roller at the next stage is slightly greater than that of the roller at the previous stage, forming a spinning tension to keep the fiber taut throughout the process. After the dry yarn is oiled and finished, it is wound on a paper drum with a winder. The tension of the filaments is controlled at 0.2-0.5g / d throughout the process.

[0072] Example 3

[0073] The fourth monomer structural formula used in this embodiment is as follows:

[0074]

[0075] The preparation method of the modified poly(p-phenylene terephthalamide) fiber of this embodiment comprises the following steps:

[0076] (1) Polymerization process

[0077] PPD, 3,4'-diaminodiphenyl ether (3,4'-ODA), and the fourth monomer were mixed in NMP-CaCl 2 Solvent system (CaCl 2 In NMP-CaCl 2 The molar ratio of PPD: 3,4'-ODA: the fourth monomer is 82:5:13, and the CaCl 2: The total molar ratio of diamine monomers is 1.6:1; then a condensation reaction is carried out with a certain amount of terephthaloyl chloride TPC in a prepolymerization reactor to form a prepolymer, wherein the amount of TPC added is 40% of the total TPC added molar amount, and the prepolymerization temperature is controlled to be -10 to 0°C during the reaction; the prepolymer and the remaining TPC are subjected to a second polymerization reaction in a twin-screw reactor to obtain a modified poly(p-phenylene terephthalamide) (PPTA) polymer, wherein the total amount of TPC added to the total molar ratio of diamine monomers is 1.005:1, and the polymerization temperature is controlled to be 10 to 30°C during the reaction. The polymer is neutralized, washed and dried with sodium hydroxide solution. Finally, a pure and dry polymer is obtained, and the moisture content of the polymer needs to be controlled within 0.5wt%, and the total amount of other possible impurities cannot exceed 50ppm.

[0078] (2) Preparation of spinning solution

[0079] The modified PPTA polymer is added to 98wt% sulfuric acid, stirred vigorously and heated to 82°C to prepare a spinning solution with a concentration of 19.3%. The spinning solution is degassed and filtered before being transported to a spinning metering pump. The filter accuracy is controlled at 9 microns to ensure that insoluble impurities and gel particles are completely filtered. The prepared spinning solution needs to be spun in time, and the residence process cannot exceed 4 hours, otherwise it will cause a decrease in viscosity, thereby affecting the fiber performance.

[0080] (3) Spinning

[0081] After filtering, the slurry is sprayed out from the spinneret by a gear metering pump. The spinneret aperture is 0.065mm. After the spinning slurry is sprayed out of the spinning hole, it becomes slurry. After passing through a 6mm air layer, it enters the coagulation system, passes through the coagulation tube in the center of the coagulation tank, and flows out from the bottom of the tube. The coagulation bath temperature is 0-10℃, the acid content of the coagulation liquid is 10%, and the sulfuric acid contained in the spinning slurry has been partially extracted after passing through the coagulation tube to become wet yarn containing sulfuric acid. The wet yarn is continuously washed and neutralized in the order of water washing / alkali washing / alkali washing on a multi-stage drum, and then dried on a drying drum at 135℃. The roller speed is controlled during the process of water washing / alkali washing / alkali washing / drying until the winding of the wet yarn. The speed of the roller at the next stage is slightly greater than that of the roller at the previous stage, forming a spinning tension. After the dry yarn is oiled and finished, it is wound on a paper drum with a winder. During the whole process, the yarn tension is controlled at 0.2-0.5g / d.

[0082] Example 4

[0083] The fourth monomer structural formula used in this embodiment is as follows:

[0084]

[0085] The preparation method of the modified poly(p-phenylene terephthalamide) fiber of this embodiment comprises the following steps:

[0086] (1) Polymerization process

[0087] PPD, 3,4'-diaminodiphenyl ether (3,4'-ODA), and the fourth monomer were mixed in NMP-CaCl 2 Solvent system (CaCl 2 In NMP-CaCl 2 The molar ratio of PPD: 3,4'-ODA: the fourth monomer is 90:5:5, and CaCl 2 : The total molar ratio of diamine monomer is 1.7:1; then, a condensation reaction is carried out with a certain amount of terephthaloyl chloride TPC in a prepolymerization reactor to form a prepolymer, wherein the amount of TPC added is 65% of the total molar amount of TPC added, and the prepolymerization temperature is controlled at -10 to 0°C during the reaction; the prepolymer and the remaining TPC are subjected to a second polymerization reaction in a twin-screw reactor to obtain a modified PPTA polymer, wherein the total molar ratio of TPC added to the total amount of diamine monomer is 1.002:1, and the polymerization temperature is controlled at 10 to 30°C during the reaction. The polymer is neutralized, washed and dried with sodium hydroxide solution. Finally, a pure and dry polymer is obtained, and the moisture content of the polymer needs to be controlled within 0.5wt%, and the total amount of other possible impurities cannot exceed 50ppm.

[0088] (2) Preparation of spinning solution

[0089] The modified PPTA polymer is added to 100% sulfuric acid, stirred vigorously and heated to 78°C to prepare a 19.0% spinning pulp. The spinning solution is degassed and filtered before being transported to the spinning metering pump. The filter accuracy is controlled at 10 microns to ensure that insoluble impurities and gel particles are completely filtered. The prepared spinning solution needs to be spun in time, and the residence process cannot exceed 4 hours, otherwise it will cause a decrease in viscosity, thereby affecting the fiber performance.

[0090] (3) Spinning

[0091] After filtering, the slurry is sprayed out from the spinneret by a gear metering pump. The spinneret aperture is 0.065mm. After the spinning slurry is sprayed out of the spinning hole, it becomes slurry. After passing through a 6mm air layer, it enters the coagulation system, passes through the coagulation tube in the center of the coagulation tank, and flows out from the bottom of the tube. The coagulation bath temperature is 0-10℃, the acid content of the coagulation liquid is 10%, and the sulfuric acid contained in the spinning slurry has been partially extracted after passing through the coagulation tube to become wet yarn containing sulfuric acid. The wet yarn is continuously washed and neutralized in the order of water washing / alkali washing / alkali washing on a multi-stage drum, and then dried on a drying drum at 135℃. The roller speed is controlled during the process of water washing / alkali washing / alkali washing / drying until the winding of the wet yarn. The speed of the roller at the next stage is slightly greater than that of the roller at the previous stage, forming a spinning tension to keep the fiber taut throughout the process. After the dry yarn is oiled and finished, it is wound on a paper drum with a winder. The tension of the filaments is controlled at 0.2-0.5g / d throughout the process.

[0092] Comparative Example 1

[0093] The difference between this comparative example and Example 1 is that the fourth monomer is not added, and the fourth monomer is replaced by an equimolar amount of p-phenylenediamine (PPD), and the other conditions remain the same as those in Example 1.

[0094] Comparative Example 2

[0095] The difference between this comparative example and Example 1 is that the third monomer 3,4'-diaminodiphenyl ether (3,4'-ODA) is not added, and the third monomer is replaced by an equimolar amount of p-phenylenediamine (PPD), and the other conditions remain the same as in Example 1.

[0096] The performance of the poly(p-phenylene terephthalamide) fibers prepared in the above embodiments and comparative examples was tested according to GB / T 14344-2022. The test results are shown in Table 1 below.

[0097] Table 1 Performance test results of modified poly(p-phenylene terephthalamide) fibers obtained in Examples and Comparative Examples

[0098]

[0099]

[0100] It can be seen from the test results in Table 1 that the method for preparing the modified poly(p-phenylene terephthalamide) fiber with high elongation at break provided by the present invention is to introduce a small amount of 3,4'-diaminodiphenyl ether and a fourth monomer containing a bisaminophenoxy functional group during polymerization, and optimize the process conditions and parameters. The obtained fiber has an elongation at break of more than 3.6% and a breaking strength of more than 21.5 cN / dtex, and can be applied to the fields of tires and conveyor belts.

[0101] 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 modified poly(p-phenylene terephthalamide) fiber having high elongation at break, characterized in that: The molecular structural formula of the modified poly(p-phenylene terephthalamide) fiber is as follows: Wherein, Ar1 is the residual group other than the amino group in the diamine containing the bisaminophenoxy functional group; 80≤m≤90, 5≤n≤17, 3≤p≤5.

2. The modified poly(p-phenylene terephthalamide) fiber with high elongation at break according to claim 1, characterized in that: The diamine containing a bisaminophenoxy functional group is selected from one or more of the following compounds:

3. The method for preparing modified poly(p-phenylene terephthalamide) fiber with high elongation at break according to claim 1 or 2, characterized in that: The steps include: (1) subjecting p-phenylenediamine, terephthaloyl chloride, a third monomer and a fourth monomer to a low-temperature polycondensation reaction in a solvent system to obtain modified poly(p-phenylene terephthalamide); the third monomer is 3,4'-diaminodiphenyl ether, and the fourth monomer is a diamine containing a bisaminophenoxy functional group; (2) Using the modified poly(p-phenylene terephthalamide) obtained in step (1) as a raw material and concentrated sulfuric acid as a solvent to prepare a spinning solution, and adopting a dry-jet wet spinning process to prepare a modified poly(p-phenylene terephthalamide) fiber with a high elongation at break.

4. The method for preparing modified poly(p-phenylene terephthalamide) fiber with high elongation at break according to claim 3, characterized in that: In step (1), the low-temperature polycondensation reaction process comprises: dissolving p-phenylenediamine, the third monomer and the fourth monomer in a solvent system to form a premix; adding a portion of terephthaloyl chloride to perform prepolymerization to form a prepolymer; The prepolymer is polymerized with the remaining terephthaloyl chloride to obtain modified poly(p-phenylene terephthalamide) fiber.

5. The method for preparing modified poly(p-phenylene terephthalamide) fiber with high elongation at break according to claim 4, characterized in that: Includes one or more of the following characteristics: 1) The molar ratio of the terephthaloyl chloride to the total amount of the diamine monomer is 1-1.015:1; 2) the total molar amount of the third monomer and the fourth monomer accounts for 10-20% of the total molar amount of the diamine monomer; 3) The molar amount of the partial terephthaloyl chloride is 35% to 65% of the total molar amount of terephthaloyl chloride.

6. The method for preparing modified poly(p-phenylene terephthalamide) fiber with high elongation at break according to claim 4, characterized in that: The prepolymerization temperature is -10 to 5°C; and / or the polymerization temperature is 0 to 50°C.

7. The method for preparing modified poly(p-phenylene terephthalamide) fiber with high elongation at break according to claim 3, characterized in that: The solvent system includes a solvent and a co-solvent, the solvent is selected from N-methylpyrrolidone, the co-solvent is calcium chloride, and CaCl2 accounts for 8wt% in the NMP-CaCl2 solvent system.

8. The method for preparing modified poly(p-phenylene terephthalamide) fiber with high elongation at break according to claim 7, characterized in that: The ratio of the molar amount of CaCl2 to the total molar amount of diamine monomers is 1.5-1.7:

1.

9. The method for preparing modified poly(p-phenylene terephthalamide) fiber with high elongation at break according to claim 3, characterized in that: In step (2), one or more of the following features are included: 1) The mass fraction of the concentrated sulfuric acid is 98wt% to 100wt%; 2) The spinning solution is prepared in a twin-screw reactor; 3) The spinning solution needs to be finely filtered; 4) The dry-jet wet spinning process specifically includes: passing the spinning solution through a spinneret to form primary filaments, which are then put into a coagulation bath for coagulation and forming, and the coagulated fibers are washed, neutralized, dried and oiled, and then wound into products; 5) The concentration of the modified poly(p-phenylene terephthalamide) in the spinning solution is 19.0wt% to 19.5wt%.

10. The method for preparing modified poly(p-phenylene terephthalamide) fiber with high elongation at break according to claim 9, characterized in that: Includes one or more of the following features: a) During the preparation of the spinning solution, strong stirring is performed and the temperature is controlled at 78-82°C; b) The filtration accuracy of the precision filtration is 8-10 μm; c) The tension of the yarn is controlled at 0.2-0.5g / d during washing, neutralization, drying, oiling and winding; d) The diameter of the spinneret hole of the spinneret is 0.065 mm.

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