Modified poly(p-phenyleneterephthalamide) fibers having high elongation at break and methods for making the same

Abstract

The present application relates to the technical field of aromatic polyamide polymer, in particular to a modified poly-p-phenyleneterephthalamide fiber with high elongation at break and a preparation method thereof.The present application introduces a small amount of 3,4'-diamino diphenyl ether and a fourth monomer containing a bis-amino phenoxy functional group during polymerization, and controls the molar ratio of the third monomer and the fourth monomer in the total amount of diamine monomer, thereby to a certain extent, the rigid molecular chain structure of the conventional p-aramid is destroyed, while the breaking strength of the fiber is maintained, the elongation at break of the polymer fiber is enhanced, the modified poly-p-phenyleneterephthalamide can still be prepared by dry spraying wet spinning process, the cost of building a new production line in the factory is saved, the process conditions and parameters are optimized, the fiber with stable elongation at break index is obtained, and the prepared fiber has an elongation at break of more than 3.6%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aromatic polyamide, in particular to a modified poly-p-phenyleneterephthalamide fiber with high elongation at break and a preparation method thereof. BACKGROUND

[0002] Poly-p-phenyleneterephthalamide (PPTA) is a straight-chain molecule with regular molecular arrangement. Therefore, the aramid fiber 1414 prepared from poly-p-phenyleneterephthalamide has very strong rigidity, high modulus itself, and low elongation at break compared to other flexible molecular materials. The fiber material used in the crown cover ply of the automobile tire needs to overcome the fatigue of high frequency rolling of the tire, that is, it needs to have high disc fatigue resistance, and thus needs to have high elongation at break. In the application of conveyor belt, aramid fiber is first woven into a canvas, and then used as a skeleton material of the conveyor belt, which also needs to have bending and compression fatigue resistance. Such bending and compression fatigue resistance requires improving the elongation at break of the material. The high strength and low density of aramid 1414 are very suitable for application in tires and conveyor belts, which can significantly reduce the weight of tires and conveyor belts. However, the elongation at break of the ordinary type of aramid 1414 is usually less than 3.6%, which is not suitable for use in these fields.

[0003] Patent JP2023020354A discloses a preparation method of a copolyaramid fiber, which introduces a large number of meta-structure units into the rigid structure of para-aramid. The prepared copolyaramid fiber has high heat resistance, balanced tensile strength and high elongation at break. However, the introduction of a large number of meta-structure units destroys the liquid crystal properties 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 production line in a para-aramid factory. Patent CN112695390A optimizes the polymerization process and spinning process parameters of PPTA. The para-aramid fiber obtained based on the above preparation method has an elongation at break of ≥3.5%. However, the preparation method described in the invention has high requirements for the precision of the equipment, and 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-phenyleneterephthalamide fiber with high elongation at break. SUMMARY

[0005] In view of the problem that the breaking elongation of poly-p-phenyleneterephthalamide fiber is relatively low compared with other flexible molecular materials in the prior art, the breaking elongation is usually less than 3.6%, and the application of the poly-p-phenyleneterephthalamide fiber in some fields requiring high breaking elongation is affected, the present application aims to provide a modified poly-p-phenyleneterephthalamide fiber with high breaking elongation and a preparation method thereof, the modified poly-p-phenyleneterephthalamide fiber can be dry-jet wet-spun, the prepared poly-p-phenyleneterephthalamide fiber has high breaking elongation, 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 the above object, the present application adopts the following technical solutions:

[0007] The first aspect of the present application provides a modified poly-p-phenyleneterephthalamide fiber with high breaking elongation, and the specific technical solutions are as follows:

[0008] The modified poly-p-phenyleneterephthalamide fiber with high breaking elongation has the following molecular structure formula:

[0009]

[0010] In the formula, Ar1 is a residual group of a diamine containing a bis-aminophenoxy functional group except for an amino group; 80≤m≤90, 5≤n≤17, and 3≤p≤5.

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

[0012]

[0013] The second aspect of the present application provides a preparation method of the modified poly-p-phenyleneterephthalamide fiber with high breaking elongation, and the preparation method comprises the following steps:

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

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

[0016] In some embodiments of the present application, the low-temperature polycondensation process comprises: dissolving the p-phenylenediamine, the third monomer and the fourth monomer in a solvent system to form a premixture; adding part of the terephthaloyl chloride to perform pre-polymerization to form a prepolymer; and performing polymerization of the prepolymer with the remaining terephthaloyl chloride to obtain the modified polyterephthaloyl p-phenylenediamine fiber.

[0017] In some embodiments of the present application, the dry-jet wet spinning process specifically comprises: forming nascent filaments by passing the spinning dope through a spinneret, and then entering a coagulation bath to coagulate and form, and the coagulated and formed fibers are washed, neutralized, dried, oiled, and wound into products.

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

[0019] 1. The modified polyterephthaloyl p-phenylenediamine fiber provided by the present application introduces a diamine monomer containing a bisaminophenoxy functional group, thereby to a certain extent destroying the rigid molecular chain structure of conventional para-aramid fibers, and further enhancing the breaking elongation thereof; the introduction of a small amount of monomer 3,4'-diamino diphenyl ether, in addition to further increasing the flexible structure in the molecular chain, its asymmetric staggered 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 drawing, so that the modified polyterephthaloyl p-phenylenediamine fiber can maintain the breaking strength of the fiber while improving the breaking elongation thereof; at the same time, by controlling the total mole percentage of the third monomer and the fourth monomer in the total mole of the diamine monomer, the modified polyterephthaloyl p-phenylenediamine fiber can still be produced by the dry-jet wet spinning process, thereby saving the cost of building a new production line in a factory.

[0020] 2. The modified polyterephthaloyl p-phenylenediamine fiber preparation method provided by the present application, by strongly stirring the modified aramid fiber in a double-screw reactor with concentrated sulfuric acid with a mass fraction of 98wt%-100wt% and heating to 78-82℃, a spinning dope with a concentration of 19.0wt%-19.5wt% is prepared; within the above temperature range, the polymer can be well dissolved, and will not be degraded due to too high temperature; under the condition of a concentration of 19.0-19.5%, the spinning dope presents good spinnability; by controlling the filtration accuracy of the spinning dope to be less than 10 microns, gel particles and solid insoluble particles can be effectively filtered out; because the spinning plate aperture used for spinning is very small, therefore, all the large insoluble particles need to be removed, so as to ensure that the spinning dope strip is continuous during the spinning process, the fiber structure has few defects, a more compact structure is formed, and the arrangement is more regular, so that a fiber with high elongation can be obtained.

[0021] 3、The modified poly-p-phenyleneterephthalamide fiber preparation method provided by the application selects a spinneret with a suitable spinneret hole diameter, avoids the situation that the ratio between the spinneret hole of the spinning plate and the final fiber diameter is too large, which causes the stretching ratio to be too large, reduces the generation of fiber structure defects, controls the tension of the spinning process to be 0.2-0.5 g / d, and is beneficial to obtaining a fiber with a more stable breaking elongation index under the above process conditions. DETAILED DESCRIPTION

[0022] The modified poly-p-phenyleneterephthalamide fiber with high breaking elongation and the preparation method of the fiber are described in detail below.

[0023] The first aspect of the application provides a modified poly-p-phenyleneterephthalamide fiber with high breaking elongation, and the specific technical solutions are as follows.

[0024] The modified poly-p-phenyleneterephthalamide fiber with high breaking elongation has a molecular structure as follows.

[0025]

[0026] In the formula, Ar1 is a residual group of a diamine containing an amino phenoxy functional group except for an amino group; 80≤m≤90, 5≤n≤17, and 3≤p≤5.

[0027] In the application, the fourth monomer containing a double amino phenoxy functional group damages the rigid molecular chain structure of the conventional p-aramid to some extent, and thus the breaking elongation is enhanced; the introduction of a small amount of the third monomer 3,4'-diamino diphenyl ether further increases the flexible structure in the molecular chain, and the asymmetric staggered structure thereof 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-phenyleneterephthalamide fiber can maintain the breaking strength while the breaking elongation is improved; meanwhile, the total mole ratio of the third monomer and the fourth monomer to the total mole of the diamine monomer is controlled, so that the modified poly-p-phenyleneterephthalamide fiber can still be prepared by using the dry-jet wet spinning process, and the cost of building a new production line in a factory is saved.

[0028] In the application, the "diamine containing a double amino phenoxy functional group" refers to a diamine containing two amino phenoxy functional groups.

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

[0030] In the application, the "phenoxy group" generally refers to a phenyl-O- group, and the bond with the parent part is through an ether oxygen.

[0031] In some embodiments of the present application, 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 application provides a method for preparing the modified poly-p-phenyleneterephthalamide fiber with high elongation at break, comprising the following steps:

[0034] (1) performing a low-temperature polycondensation reaction on p-phenylenediamine, terephthaloyl chloride, a third monomer, and a fourth monomer in a solvent system to obtain a modified poly-p-phenyleneterephthalamide; 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-phenyleneterephthalamide obtained in step (1) as a raw material, concentrated sulfuric acid as a solvent, preparing a spinning solution, and using a dry-jet wet spinning process to prepare the modified poly-p-phenyleneterephthalamide fiber with high elongation at break.

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

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

[0038] In some embodiments of the present application, the total molar amount of the third monomer and the fourth monomer accounts for 10-20% of the total molar amount of the diamine monomers. By controlling the total molar amount of the third monomer and the fourth monomer to be not more than 20% of the total molar amount of the diamine monomers, the preparation of the modified poly-p-phenyleneterephthalamide fiber can still use the dry-jet wet spinning process, thereby saving the cost of building a new production line in a factory.

[0039] In some embodiments of the present application, the molar amount of the part of the terephthaloyl chloride is 35%-65% of the total molar amount of the terephthaloyl chloride, which can be 35%-40%, 40%-45%, 45%-50%, 50%-55%, 55%-60%, or 60%-65%.

[0040] In some embodiments of the present application, the temperature of the prepolymerization is -10-5℃, which can be -10--8℃, -8--6℃, -6--4℃, -4--2℃, -2-0℃, 0-2℃, or 2-5℃, preferably -10-0℃.

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

[0042] In some embodiments of the present application, the solvent system comprises a solvent and a cosolvent, the solvent is selected from N-methyl pyrrolidone (NMP), and the cosolvent is calcium chloride (CaCl2), the content of CaCl2 in the NMP-CaCl2 solvent system is 8wt%, the molar ratio of CaCl2 to the total moles of diamine monomers is 1.5-1.7:1, which can be 1.5-1.6:1 or 1.6-1.7:1.

[0043] In some embodiments of the present application, the mass fraction of the concentrated sulfuric acid is 98wt%-100wt%, which can be 98wt%-98.5wt%, 98.5wt%-99wt%, 99wt%-99.5wt%, or 99.5wt%-100wt%.

[0044] In some embodiments of the present application, the preparation of the spinning dope is carried out in a twin-screw reactor, and sufficient engagement or shear strength is required during the preparation process.

[0045] In some embodiments of the present application, the spinning dope needs to be precisely filtered. Preferably, the precision of the precise filtration is 8-10μm, which can effectively filter out gel particles and solid insoluble particles. Since the spinning plate aperture is very small, it is necessary to remove all the larger insoluble particles to ensure that the spinning slurry is continuous during the spinning process, the fiber structure has fewer defects, forms a more compact structure, and is more regularly arranged, thereby obtaining a fiber with high elongation.

[0046] In some embodiments of the present application, the dry-jet wet spinning process specifically comprises: forming a primary filament by passing the spinning dope through a spinning plate, then entering a coagulation bath to coagulate and form, and the coagulated and formed fiber is washed, neutralized, dried, and oiled, and then wound into a product.

[0047] In some embodiments of the present application, the concentration of the modified poly-p-phenyleneterephthalamide in the spinning dope is 19.0wt%-19.5wt%, which can be 19.0wt%-19.1wt%, 19.1wt%-19.2wt%, 19.2wt%-19.3wt%, 19.3wt%-19.4wt%, or 19.4wt%-19.5wt%. When the concentration of the modified poly-p-phenyleneterephthalamide is within the above range, the spinning dope exhibits good spinnability.

[0048] In some embodiments of the present application, strong stirring is performed during the preparation of the spinning dope, and the temperature is controlled at 78-82°C. Within the above temperature range, the polymer can be well dissolved, and degradation does not occur 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 application, the yarn tension is controlled at 0.2-0.5g / d during the washing, neutralization, drying, oiling, and winding processes, which is beneficial to obtaining fibers with more stable elongation at break.

[0050] In some embodiments of the present application, the diameter of the spinning hole of the spinneret is 0.065mm, which avoids the phenomenon that the ratio between the diameter of the spinning hole of the spinneret and the diameter of the final fiber is too large, thereby reducing the generation of fiber structure defects.

[0051] The specific embodiments of the present application are further described in detail below with reference to the preferred embodiments. When numerical ranges are given, it should be understood that, unless otherwise specified by the present application, each numerical range has two endpoints and any number between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present application have the same meanings as commonly understood by those skilled in the art. In addition to the specific methods, devices, and materials described in the embodiments, any methods, devices, and materials similar or equivalent to those described in the embodiments of the present application can be used to implement the present application, as long as they are within the knowledge and skills of those skilled in the art and are described in the present application.

[0052] Embodiment 1

[0053] The structure of the fourth monomer selected in the present embodiment is as follows:

[0054]

[0055] The preparation method of the modified poly-p-phenyleneterephthalamide fiber in the present embodiment includes the following steps:

[0056] (1) Polymerization process

[0057] The p-phenylenediamine (PPD), 3,4'-diaminodiphenyl ether (3,4'-ODA) (third monomer), and fourth monomer are mixed and dissolved in the NMP-CaCl2 solvent system (CaCl2 accounts for 8wt% in the NMP-CaCl2 solvent system), wherein the molar ratio of PPD:3,4'-ODA: fourth monomer is 80:3:17, and the molar ratio of CaCl2: total amount of diamine monomers is 1.5:1; then, a certain amount of terephthaloyl chloride (TPC) is added in the prepolymerization reactor to perform polycondensation reaction to form a prepolymer, wherein the added amount of TPC is 35% of the total TPC added molar amount, and the prepolymerization temperature is controlled to be -10-0°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-phenyleneterephthalamide (PPTA) polymer, wherein the total added amount of TPC and the total amount of diamine monomers have a molar ratio of 1.015:1, and the polymerization temperature is controlled to be 10-30°C during the reaction. The polymer is neutralized, washed, and dried by using 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 to be less than 0.5wt%, and the total amount of other possible impurities cannot exceed 50ppm.

[0058] (2) Preparation of the spinning dope

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

[0060] (3) Spinning

[0061] The above filtered spinning dope is sprayed from the spinneret after being metered by a gear pump, the spinneret aperture is 0.065mm, and the spun slurry is formed after being sprayed from the spinning hole. After passing through a 6mm air layer, the spun slurry enters the coagulation system, and flows out from the pipe under the coagulation tank. The coagulation bath temperature is 0-10°C, and the acid content of the coagulation liquid is 10%. After passing through the coagulation pipe, the sulfuric acid contained in the spinning slurry is partially extracted to become a wet yarn containing sulfuric acid. The wet yarn is continuously washed, neutralized, and then dried on a 135°C drying drum after being sequentially washed and neutralized in a multi-stage drum in the order of water washing / alkali washing / alkali washing. The speed of the roller is controlled during the process of wet yarn water washing / alkali washing / alkali washing / drying and winding. The speed of the roller in the later stage is slightly greater than that in the former stage to form a spinning tension, so that the fiber remains in a taut state throughout the process. After oil finishing, the dry yarn is wound on a paper tube by a winding machine. The yarn tension is controlled to be 0.2-0.5g / d throughout the process.

[0062] Example 2

[0063] The fourth monomer structure selected in this example is as follows:

[0064]

[0065] The preparation method of the modified poly-p-phenyleneterephthalamide fiber of this example comprises the following steps:

[0066] (1) Polymerization process

[0067] P-phenylenediamine (PPD), 3,4'-diamino diphenyl ether (3,4'-ODA), and the fourth monomer are fully mixed and dissolved in an NMP-CaCl2 solvent system (CaCl2 accounts for 8wt% in the NMP-CaCl2 solvent system), wherein the molar ratio of PPD:3,4'-ODA:the fourth monomer is 89:4:7, and the molar ratio of CaCl2:total amount of diamine monomer is 1.7:1; then a certain amount of terephthaloyl chloride (TPC) is added for condensation reaction in a prepolymerization reactor to form a prepolymer, wherein the addition amount of TPC is 50% of the total TPC addition molar amount, and the prepolymerization temperature is controlled at -10-0°C during the reaction; the prepolymer and the remaining TPC are subjected to a second polymerization reaction in a double screw reactor to obtain a modified PPTA polymer, wherein the total addition amount of TPC and the total amount of diamine monomer are in a molar ratio of 1.006:1, and the polymerization temperature is controlled at 10-30°C during the reaction. The polymer is neutralized, washed, and dried by using a 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 dope

[0069] The above modified PPTA polymer is added to 99wt% sulfuric acid, and after strong stirring and heating to 81°C, a spinning dope with a concentration of 19.3% is prepared. The spinning dope is deaerated and filtered before being delivered to the spinning metering pump. The filter precision is controlled at 8 microns to ensure that insoluble impurities and gel particles are completely filtered. The prepared spinning dope needs to be spun in time, and the residence process cannot exceed 4 hours, otherwise the viscosity will decrease, thereby affecting the fiber performance.

[0070] (3) Spinning

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

[0072] Example 3

[0073] The fourth monomer structure used in this example is as follows:

[0074]

[0075] The preparation method of the modified poly-p-phenyleneterephthalamide fiber of this example comprises the following steps:

[0076] (1) Polymerization process

[0077] P-phenylenediamine (PPD), 3,4'-diamino diphenyl ether (3,4'-ODA), and the fourth monomer are fully mixed and dissolved in an NMP-CaCl2 solvent system (CaCl2 accounts for 8wt% in the NMP-CaCl2 solvent system), wherein the molar ratio of PPD:3,4'-ODA:the fourth monomer is 82:5:13, and the molar ratio of CaCl2:total amount of diamine monomer is 1.6:1; then a certain amount of terephthaloyl chloride (TPC) is added to the pre-polymerization reactor for condensation reaction to form a prepolymer, wherein the addition amount of TPC is 40% of the total TPC addition molar amount, and the pre-polymerization temperature is controlled at-10-0℃ during the reaction; the prepolymer and the remaining TPC are subjected to a second polymerization reaction in a double screw reactor to obtain a modified poly-p-phenyleneterephthalamide (PPTA) polymer, wherein the total addition amount of TPC and the total amount of diamine monomer have a molar ratio of 1.005:1, and the polymerization temperature is controlled at 10-30℃ during the reaction. The polymer is neutralized, washed, and dried by using a sodium hydroxide solution. Finally, a pure and dry polymer is obtained, 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 stock solution

[0079] The modified PPTA polymer is added to 98wt% sulfuric acid, stirred vigorously and heated to 82°C to form a 19.3% concentration of the spinning dope. The spinning dope is degassed and filtered and then fed to a metering pump. The filter is set to 9 microns to ensure that insoluble impurities and gel particles are completely filtered. The spinning dope is spun immediately and the residence time should not exceed 4 hours, otherwise the viscosity will decrease and the fiber properties will be affected.

[0080] (3) Spinning

[0081] The above slurry is filtered and then fed from a gear metering pump through a spinneret with a 0.065mm diameter. The slurry is spun through the spinneret and then passes through a 6mm air layer and into a coagulation system. The coagulation bath temperature is 0-10°C and the coagulation liquid contains 10% acid. The sulfuric acid in the spinning slurry is partially extracted through the coagulation tube and the resulting wet yarn contains sulfuric acid. The wet yarn is washed, neutralized and dried in the order of water washing / alkali washing / alkali washing on a multi-stage drum. The yarn is then dried on a 135°C drying drum. The yarn is controlled on the water washing / alkali washing / alkali washing / drying drums until it is wound. The speed of the drums is controlled so that the speed of the last drum is slightly greater than the speed of the previous drum to create a spinning tension. The dry yarn is oiled and then wound on a paper tube using a winder. The yarn tension is controlled at 0.2-0.5g / d during the entire process.

[0082] Example 4

[0083] The fourth monomer used in this example has the following structure:

[0084]

[0085] The method for preparing the modified poly-p-phenyleneterephthalamide fiber of this example includes the following steps:

[0086] (1) Polymerization process

[0087] The p-phenylenediamine (PPD), 3,4'-diaminodiphenyl ether (3,4'-ODA), and the fourth monomer are mixed and dissolved in the NMP-CaCl2 solvent system (CaCl2 accounts for 8wt% in the NMP-CaCl2 solvent system), wherein the molar ratio of PPD:3,4'-ODA:the fourth monomer is 90:5:5, and the molar ratio of CaCl2:total amount of diamine monomers is 1.7:1; then, a certain amount of terephthaloyl chloride TPC is added in the prepolymerization reactor to perform polycondensation reaction to form a prepolymer, wherein the addition amount of TPC is 65% of the total TPC addition molar amount, and the prepolymerization temperature is controlled to be-10~0℃ during the reaction; the prepolymer and the remaining TPC are subjected to a second polymerization reaction in a double screw reactor to obtain a modified PPTA polymer, wherein the total addition amount of TPC and the total amount of diamine monomers have a molar ratio of 1.002:1, and the polymerization temperature is controlled to be 10~30℃ during the reaction. The polymer is neutralized, washed, and dried by using a 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 the spinning dope

[0089] The above modified PPTA polymer is added into sulfuric acid with a concentration of 100%, and after being stirred intensively and heated to 78℃, a spinning dope with a concentration of 19.0% is prepared. The spinning dope is deaerated and filtered, and then is delivered to a spinning metering pump. The filtering accuracy of the filter is controlled to be 10 microns, so as to ensure that the insoluble impurities and gel particles are completely filtered. The prepared spinning dope needs to be spun in time, and the residence time cannot exceed 4 hours, otherwise the viscosity will decrease, thereby affecting the fiber performance.

[0090] (3) Spinning

[0091] The above spinning dope is filtered and then is sprayed from a spinneret by a gear metering pump, the spinneret has a pore diameter of 0.065mm, and the spinning dope is sprayed from the spinning hole to become a spinning yarn, passes through a 6mm air layer, enters a coagulation system, and flows out from a coagulation pipe at the center of a coagulation tank. The coagulation bath temperature is 0-10℃, and the acid content of the coagulation liquid is 10%. After passing through the coagulation pipe, the sulfuric acid contained in the spinning dope is partially extracted to become a wet yarn containing sulfuric acid. The wet yarn is continuously washed, neutralized, and then dried on a 135℃ drying drum after being sequentially washed and neutralized in a multi-stage drum in the order of water washing / alkali washing / alkali washing. The wet yarn is controlled in the process of water washing / alkali washing / alkali washing / drying and winding. The speed of the rear-stage roller is slightly greater than that of the front-stage roller, so as to form a spinning tension and keep the fiber in a taut state in the whole process. After oil finishing, the dry yarn is wound on a paper tube by a winding machine. The yarn tension is controlled to be 0.2-0.5g / d in the whole process.

[0092] Comparative Example 1

[0093] The present comparative example differs from Example 1 in that the fourth monomer is not added, and the fourth monomer is replaced by equimolar amount of p-phenylenediamine (PPD), and the rest of the conditions remain unchanged as in Example 1.

[0094] Comparative Example 2

[0095] The present comparative example differs from Example 1 in that the third monomer 3,4'-diaminodiphenyl ether (3,4'-ODA) is not added, and the third monomer is replaced by equimolar amount of p-phenylenediamine (PPD), and the rest of the conditions remain unchanged as in Example 1.

[0096] The poly-p-phenyleneterephthalamide fibers prepared in the above examples and comparative examples are subjected to performance tests, and the test method refers to GB / T 14344-2022, and the test results are shown in Table 1 below.

[0097] Table 1 Performance test results of modified poly-p-phenyleneterephthalamide fibers obtained in examples and comparative examples

[0098]

[0099]

[0100] From the test results in Table 1, it can be seen that the preparation method of the modified poly-p-phenyleneterephthalamide fiber with high elongation at break provided by the present application introduces a small amount of 3,4'-diaminodiphenyl ether and a fourth monomer containing a bis-aminophenoxy functional group during polymerization, and by optimizing the process conditions and parameters, the elongation at break of the prepared fiber is more than 3.6%, and the breaking strength is greater than 21.5 cN / dtex, which can be applied in the fields of tires and conveyor belts.

[0101] The above examples only illustrate the principles and effects of the present application, and are not used to limit the present application. Any person skilled in the art can modify or change the above examples without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical idea disclosed by the present application should be covered by the claims of the present application.

Claims

1. A modified poly-para-phenyleneterephthalamide fiber having a high elongation at break, characterized in that, The molecular structure of the modified poly(p-phenylene terephthalamide) fiber is as follows: ； Ar1 is the residual group other than the amino group in a diamine containing a diaminophenoxy functional group; 80≤m≤90, 5≤n≤17, 3≤p≤5; Its preparation method includes the following steps: (1) p-Phenylenediamine, terephthaloyl chloride, a third monomer, and a fourth monomer are subjected to a low-temperature polycondensation reaction in a solvent system to obtain modified poly(p-phenylenediamine terephthalamide); the third monomer is 3,4'-diaminodiphenyl ether, and the fourth monomer is a diamine containing a diaminophenoxy functional group; 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; (2) Using the modified poly(p-phenylene terephthalamide) obtained in step (1) as raw material and concentrated sulfuric acid as solvent, a spinning solution is prepared. The modified poly(p-phenylene terephthalamide) fiber with high elongation at break is prepared by dry-jet wet spinning process.

2. The modified poly(p-phenylene terephthalamide) fiber with high elongation at break as described in claim 1, characterized in that, The diamine containing the diaminophenoxy functional group is selected from one or more of the following compounds: 。 3. The modified poly(p-phenylene terephthalamide) fiber with high elongation at break as described in claim 1 or 2, characterized in that, 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 modified poly(p-phenylenediamine terephthalamide) fiber.

4. The modified poly(p-phenylene terephthalamide) fiber with high elongation at break as described in claim 3, 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 molar amount of the terephthaloyl chloride is 35% to 65% of the total molar amount of terephthaloyl chloride.

5. The modified poly(p-phenylene terephthalamide) fiber with high elongation at break as described in claim 3, characterized in that, The prepolymerization temperature is -10 to 5 °C; and / or the polymerization temperature is 0 to 50 °C.

6. The modified poly(p-phenylene terephthalamide) fiber with high elongation at break as described in claim 1 or 2, characterized in that, The solvent system includes a solvent and a co-solvent. The solvent is selected from N-methylpyrrolidone, and the co-solvent is calcium chloride. CaCl2 accounts for 8 wt% of the NMP-CaCl2 solvent system.

7. The modified poly(p-phenylene terephthalamide) fiber with high elongation at break as described in claim 6, characterized in that, The molar ratio of CaCl2 to the total molar ratio of diamine monomer is 1.5-1.7:

1.

8. The modified poly(p-phenylene terephthalamide) fiber with high elongation at break as described in claim 1 or 2, characterized in that, Step (2) includes one or more of the following features: 1) The concentrated sulfuric acid has a mass fraction of 98wt%~100wt%; 2) The spinning solution is prepared in a twin-screw reactor; 3) The spinning solution needs to be precision filtered; 4) The dry-jet wet spinning process specifically includes: passing the spinning solution through a spinneret to form nascent filaments, which are then coagulated in a coagulation bath. The coagulated fibers are then washed, neutralized, dried, and oiled before being wound into a product. 5) The concentration of modified poly(p-phenylene terephthalamide) in the spinning solution is 19.0 wt% to 19.5 wt%.

9. The modified poly(p-phenylene terephthalamide) fiber with high elongation at break as described in claim 8, characterized in that, Includes one or more of the following characteristics: a) Vigorous stirring is carried out during the preparation of the spinning solution, and the temperature is controlled at 78-82 ℃; b) The filtration accuracy of the precision filter is 8-10 μm; c) The filament tension is controlled at 0.2-0.5 g / d during washing, neutralization, drying, oiling, and winding. d) The diameter of the spinneret orifice is 0.065 mm.

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