Modified aramid fiber and preparation method thereof

Abstract

The invention provides a modified aramid fiber and a preparation method thereof. The preparation method comprises the following steps: S1, adding an organic solvent A and acetate into a reactor; s2, adding m-phenylenediamine into the mixed solution obtained in the step S1; s3, adding isophthaloyl dichloride into the mixed solution obtained in the step S2 in batches; s4, neutralizing hydrogen chloride in the reaction liquid obtained in the step S3 by adopting a neutralizing agent; s5, dissolving the polyisophthaloyl metaphenylene diamine obtained in the step S4 and white carbon black of which the mass is 0.05-0.15% of that of the polyisophthaloyl metaphenylene diamine into concentrated sulfuric acid to prepare a spinning solution, and finally obtaining polyisophthaloyl metaphenylene diamine fibers; s5, dissolving acyl chloride and aluminum trichloride in an organic solvent B to obtain a mixed solution; and S6, adding the polyisophthaloyl metaphenylene diamine fiber obtained in the step S5 into the mixed solution obtained in the step S5, and modifying to obtain the modified aramid fiber. According to the modified aramid fiber prepared by the method, the breaking strength is greater than 7.1 cN.dtex-1, the elongation at break is greater than 14.7%, and the surface free energy is better.

Description

Technical Field

[0001] The invention relates to the field of aramid fibers, and in particular to a modified aramid fiber and a preparation method thereof. Background Art

[0002] As a high-performance synthetic fiber, aramid has shown unparalleled application potential in aerospace, defense and military, automobile manufacturing, sports equipment and other fields due to its excellent high temperature resistance, high strength, high modulus, good chemical stability and wear resistance. However, in order to further broaden the application scope of aramid materials and optimize their specific properties to meet the special needs of different fields, researchers are constantly exploring new methods and technologies for aramid modification, aiming to adjust its microstructure and surface properties through physical or chemical means, so as to obtain new materials with better comprehensive performance.

[0003] In the study of aramid modification, chemical modification is one of the most widely used methods, including copolymerization, grafting, cross-linking, functionalization and other strategies. Copolymerization modification can effectively regulate the regularity and polarity of the molecular chain by introducing other monomers during the aramid synthesis process, thereby affecting the crystallinity, thermal stability and mechanical properties of the material. For example, incorporating fluorinated monomers into the aramid molecular chain can not only improve the material's resistance to chemical corrosion, but also enhance its hydrophobicity and self-cleaning ability, which is particularly important for the development of high-performance protective clothing and filtration materials.

[0004] Grafting modification refers to grafting other functional groups or polymer segments onto the aramid skeleton, which can not only improve the interfacial compatibility of the material, but also introduce new functionality, such as conductivity, fluorescence or bioactivity. By grafting hydrophilic polymers such as polyethylene glycol (PEG), the wettability and biocompatibility of aramid fibers can be significantly improved, providing new material solutions for medical implants and biomedical textiles.

[0005] Crosslinking modification can effectively improve the thermal stability and dimensional stability of the material by forming stable chemical bonds between aramid molecules, which is particularly important in high-temperature application environments. In addition, proper crosslinking can also enhance the mechanical strength and creep resistance of the material, which is of great significance for the preparation of composite materials in the aerospace field.

[0006] Functional modification focuses on giving aramid specific functionality, such as introducing nanoparticles (such as nano-silicon dioxide, carbon nanotubes, etc.) through surface coating or impregnation, which can not only enhance the mechanical properties of the material, but also realize advanced functions such as electromagnetic shielding, sensing or catalysis. For example, carbon nanotube-reinforced aramid composites exhibit excellent electrical and thermal conductivity while maintaining light weight, making them an ideal choice for the development of smart textiles and lightweight electronic devices.

[0007] Aramid modification technology is the key to promoting the application of this high-performance material in a wider range of fields. Through precisely designed modification strategies, it is not only possible to overcome the limitations of original aramid in certain applications, but also to give it new properties and functions to meet the growing demand for diversified material performance in high-tech fields. With the continuous progress and innovation of materials science, the research on aramid modified materials will be more in-depth in the future, and its application prospects will be broader.

[0008] CN110130101B discloses a method for surface functional modification of meta-aramid fabric, belonging to the field of textile technology. The method refers to treating meta-aramid fabric with a modified liquid composed of N, N-dimethylacetamide, LiCl, and inorganic functional nanoparticles under low temperature positive pressure conditions, so that the fiber surface macromolecules react with N, N-dimethylacetamide and LiCl to form a slightly soluble layer, and the inorganic functional nanoparticles on the fiber surface are squeezed into the slightly soluble layer under the action of positive pressure, and then under high temperature negative pressure conditions, N, N-dimethylacetamide in the slightly soluble layer is volatilized and extracted, and the inorganic functional nanoparticles are solidified on the surface of the meta-aramid fiber, enhancing the flame retardant, antistatic, radiation resistance and other functions of the meta-aramid surface. The present invention effectively improves the efficiency and durability of the functional modification of the meta-aramid surface such as flame retardant, antistatic, and radiation resistance under the premise of preserving the fiber main structure without damage and no obvious decrease in mechanical properties, and the method has no sewage output, reducing production costs. However, the performance of the prepared aramid still needs to be improved, and the preparation process conditions are harsh. Summary of the invention

[0009] In view of the deficiencies of the prior art, the present invention provides a modified aramid fiber with excellent performance and a preparation method thereof.

[0010] To achieve the above objectives, the present invention is implemented through the following technical solutions: A method for preparing modified aramid fiber comprises the following steps: S1: adding organic solvent A and acetate into a reactor, then blowing nitrogen into the reactor and stirring to make the mixture uniform; S2: adding m-phenylenediamine to the mixed solution obtained in step S1, stirring to dissolve the m-phenylenediamine, and cooling to -8 to -3°C; S3: adding isophthaloyl chloride to the mixed solution obtained in step S2 in batches, the addition time is 1-2 hours, and after the addition is completed, the reaction is continued for 3-4 hours, and the reaction temperature is 2-8°C; S4: neutralize the reaction solution obtained in step S3 with a neutralizer to obtain hydrogen chloride to obtain an aramid spinning solution, and then separate the generated polymer, wash and dry it to obtain poly(m-phenylene isophthalamide); S5: dissolving the poly(m-phenylene isophthalamide) obtained in step S4 and 0.05-0.15% of white carbon black by weight in concentrated sulfuric acid to prepare a spinning solution, uniformly dispersing by ultrasonication, and then spinning, coagulating, washing, drying, dry-heat drawing, and heat-setting to obtain the poly(m-phenylene isophthalamide) fiber. Adding a small amount of white carbon black will not affect the performance of the aramid fiber, but will be more conducive to modification, because the white carbon black on the surface will enhance its reaction activity during modification and increase its surface active sites. The white carbon black can be well dispersed in the concentrated sulfuric acid only by ultrasonic dispersion, because the density of white carbon black is small and it is difficult to mix evenly by general stirring. The white carbon black is preferably fumed white carbon black. S5 dissolving the acyl chloride and aluminum chloride in an organic solvent B to obtain a mixed solution; S6: adding the poly(m-phenylene isophthalamide) fiber obtained in step S5 to the mixed solution of step S5, and reacting at a temperature between 20°C and 40°C for 2 to 3 hours; after the modification in steps S5 and S6, new active groups can be introduced on the surface of the aramid fiber, so that the performance is better and the application field is wider; S7: Filter, wash and dry the reaction solution obtained in step S6 to obtain modified aramid fiber.

[0011] Furthermore, in step S1, the organic solvent A is N,N-dimethylformamide or N,N-dimethylacetamide, the mass of the solvent is 500g, the acetate is calcium acetate or lithium acetate, and the mass of the acetate is 3-5g. Calcium chloride or lithium chloride is replaced by calcium acetate or lithium acetate, because acetate contains organic groups, has good solubility and compatibility, and has the function of buffering pH value, which not only increases the reaction rate and promotes the polymerization reaction, but also accelerates the chemical reaction between m-phenylenediamine and isophthaloyl chloride, can better adjust the ionic strength of the solution, control the solubility of the polymer and the phase behavior during the polymerization process, and is conducive to obtaining a good fiber structure.

[0012] Furthermore, in step S1, nitrogen is respectively blown into four positions at the bottom of the reactor. By blowing nitrogen into four positions at the bottom of the reactor, hydrogen chloride generated during the reaction can be taken away, the reaction speed can be accelerated, and less neutralizing agent can be used in the later stage.

[0013] Furthermore, the amount of interphenylenediamine added in step S2 is 1 mol, 108 g.

[0014] Furthermore, in the step S3, the amount of phthaloyl chloride added is 0.99 mol, 201 g.

[0015] Furthermore, in step S4, the neutralizing agent is m-phenylenediamine, and the amount of the neutralizing agent added is 0.05 mol, 5.4 g. The neutralizing agent is m-phenylenediamine. The salt produced after neutralization can be regenerated into a neutralizing agent, m-phenylenediamine, after adding alkali, and recycled to save costs.

[0016] Furthermore, in step S5, the organic solvent B is tetrahydrofuran or diethyl ether, the mass of the acyl chloride is 30 g, the mass of the organic solvent B is 120-150 g, and the mass of the aluminum chloride is 10 g. The organic solvent B selected in the present invention has good solubility for aluminum chloride and other reaction raw materials, the reaction can be completed smoothly, and the reaction activity is good.

[0017] Furthermore, in step S5, the acyl chloride is acetyl chloride or p-fluorobenzoyl chloride, preferably p-fluorobenzoyl chloride, because the fluorine atom further imparts more excellent properties to the prepared aramid.

[0018] At the same time, the present invention also provides a modified aramid fiber prepared by any of the above methods, wherein the prepared modified aramid fiber has excellent performance and a breaking strength greater than 7.1 cN·dtex -1 , the elongation at break is greater than 14.7%, and the surface free energy is large and better. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0020] Embodiment 1: A method for preparing modified aramid fiber, comprising the following steps: S1: 500 g of N,N-dimethylacetamide and 4 g of lithium acetate are added into a reactor, and then nitrogen is blown into the reactor at four locations at the bottom of the reactor, and stirred to make the mixture uniform; S2: adding 108 g of m-phenylenediamine to the mixed solution obtained in step S1, stirring to dissolve the m-phenylenediamine, and cooling to -8 to -3°C; S3: Add 201 g of isophthaloyl chloride to the mixed solution obtained in step S2 in batches, and the addition time is 2 h. After the addition is completed, continue the reaction for 3 h, and the reaction temperature is 2-8 ° C; S4: neutralize the reaction solution obtained in step S3 with 5.4 g of m-phenylenediamine to obtain aramid spinning solution, and then separate the generated polymer, wash and dry it to obtain polymethylene terephthalamide; S5: dissolving the poly(m-phenylene isophthalamide) obtained in step S4 and 0.24 g of white carbon black in concentrated sulfuric acid to prepare a spinning solution, uniformly dispersing the solution by ultrasonication, and then spinning, coagulating, washing, drying, dry-heat drawing, and heat-setting the solution to obtain poly(m-phenylene isophthalamide) fibers; S5 Dissolve 30 g of p-fluorobenzoyl chloride and 10 g of aluminum chloride in 130 g of ether to obtain a mixed solution; S6. Add the poly(m-phenylene isophthalamide) fiber obtained in step S5 to the mixed solution in step S5, and react at a temperature between 30° C. and 40° C. for 2 hours; S7: Filter, wash and dry the reaction solution obtained in step S6 to obtain modified aramid fiber.

[0021] The modified aramid fiber prepared by the method has good performance.

[0022] Embodiment 2: A method for preparing modified aramid fiber, comprising the following steps: S1: 500 g of N,N-dimethylformamide and 3 g of calcium acetate are added into a reactor, and then nitrogen is blown into the reactor and stirred to make the mixture uniform; S2: adding 108 g of m-phenylenediamine to the mixed solution obtained in step S1, stirring to dissolve the m-phenylenediamine, and cooling to -8 to -3°C; S3: Add 201 g of isophthaloyl chloride to the mixed solution obtained in step S2 in batches. The addition time is 1 hour. After the addition is completed, continue the reaction for 4 hours. The reaction temperature is 2-8°C. S4: neutralize the reaction solution obtained in step S3 with 5.4 g of m-phenylenediamine to obtain aramid spinning solution, and then separate the generated polymer, wash and dry it to obtain polymethylene terephthalamide; S5: dissolving the poly(m-phenylene isophthalamide) obtained in step S4 and 0.24 g of white carbon black in concentrated sulfuric acid to prepare a spinning solution, uniformly dispersing the solution by ultrasonication, and then spinning, coagulating, washing, drying, dry-heat drawing, and heat-setting the solution to obtain poly(m-phenylene isophthalamide) fibers; S5: dissolving 30 g of acetyl chloride and 10 g of aluminum chloride in 130 g of tetrahydrofuran to obtain a mixed solution; S6. Add the poly(m-phenylene isophthalamide) fiber obtained in step S5 to the mixed solution in step S5, and react at a temperature between 20° C. and 30° C. for 3 hours; S7: Filter, wash and dry the reaction solution obtained in step S6 to obtain modified aramid fiber.

[0023] The modified aramid fiber prepared by the method has good performance.

[0024] Embodiment 3: A method for preparing modified aramid fiber, comprising the following steps: S1: 500 g of N,N-dimethylformamide and 3 g of lithium acetate are added into a reactor, and then nitrogen is blown into the reactor and stirred to make the mixture uniform; S2: adding 108 g of m-phenylenediamine to the mixed solution obtained in step S1, stirring to dissolve the m-phenylenediamine, and cooling to -8 to -3°C; S3: Add 201 g of isophthaloyl chloride to the mixed solution obtained in step S2 in batches, and the addition time is 2 h. After the addition is completed, continue the reaction for 4 h, and the reaction temperature is 2-8 ° C; S4: neutralize the reaction solution obtained in step S3 with 5.4 g of m-phenylenediamine to obtain aramid spinning solution, and then separate the generated polymer, wash and dry it to obtain polymethylene terephthalamide; S5: dissolving the poly(m-phenylene isophthalamide) obtained in step S4 and 0.24 g of white carbon black in concentrated sulfuric acid to prepare a spinning solution, uniformly dispersing the solution by ultrasonication, and then spinning, coagulating, washing, drying, dry-heat drawing, and heat-setting the solution to obtain poly(m-phenylene isophthalamide) fibers; S5: dissolve 30 g of acetyl chloride and 10 g of aluminum chloride in 130 g of ether to obtain a mixed solution; S6. Add the poly(m-phenylene isophthalamide) fiber obtained in step S5 to the mixed solution in step S5, and react at a temperature between 20° C. and 30° C. for 2 hours; S7: Filter, wash and dry the reaction solution obtained in step S6 to obtain modified aramid fiber.

[0025] The modified aramid fiber prepared by the method has good performance.

[0026] Comparative Example 1 Only the white carbon black component in step S5 of Example 2 is removed, and the rest is the same as Example 2 and will not be described in detail.

[0027] Comparative Example 2 Only calcium acetate in step S1 of Example 2 is replaced by calcium chloride, and the rest is the same as Example 2 and will not be described in detail.

[0028] The modified aramid fiber prepared by the present invention has good breaking strength and breaking elongation, and good surface free energy. The performance of Example 1 is better due to the presence of fluorine atoms. The data of Comparative Examples 1 and 2 show that the technical solution of the present invention has better technical effects.

Claims

1. A method for preparing modified aramid fiber, characterized in that: The following steps are involved: S1: adding organic solvent A and acetate into a reactor, then blowing nitrogen into the reactor and stirring to make the mixture uniform; S2: adding m-phenylenediamine to the mixed solution obtained in step S1, stirring to dissolve the m-phenylenediamine, and cooling to -8 to -3°C; S3: adding isophthaloyl chloride to the mixed solution obtained in step S2 in batches, the addition time is 1-2 hours, and after the addition is completed, the reaction is continued for 3-4 hours, and the reaction temperature is 2-8°C; S4: neutralize the hydrogen chloride in the reaction solution obtained in step S3 with a neutralizer to obtain an aramid spinning solution, and then separate the generated polymer, wash and dry it to obtain poly(m-phenylene isophthalamide); S5: dissolving the poly(m-phenylene isophthalamide) obtained in step S4 and 0.05-0.15% by weight of white carbon black in concentrated sulfuric acid to prepare a spinning solution, uniformly dispersing the solution by ultrasonication, and then spinning, coagulating, washing, drying, dry-heat drawing, and heat-setting the solution to obtain poly(m-phenylene isophthalamide) fibers; S5 dissolving the acyl chloride and aluminum chloride in an organic solvent B to obtain a mixed solution; S6. Add the poly(m-phenylene isophthalamide) fiber obtained in step S5 to the mixed solution in step S5, and react at a temperature between 20° C. and 40° C. for 2 to 3 hours; S7: Filter, wash and dry the reaction solution obtained in step S6 to obtain modified aramid fiber.

2. The method for preparing modified aramid fiber according to claim 1, characterized in that: In step S1, the organic solvent A is N,N-dimethylformamide or N,N-dimethylacetamide, the mass of the solvent is 500g, the acetate is calcium acetate or lithium acetate, and the mass of the acetate is 3-5g.

3. The method for preparing modified aramid fiber according to claim 1, characterized in that: In step S1, nitrogen is blown into four locations at the bottom of the reactor.

4. The method for preparing modified aramid fiber according to claim 1, characterized in that: The amount of interphenylenediamine added in step S2 is 1 mol, 108 g.

5. The method for preparing modified aramid fiber according to claim 1, characterized in that: In the step S3, the amount of phthaloyl chloride added is 0.99 mol, 201 g.

6. The method for preparing modified aramid fiber according to claim 1, characterized in that: In step S4, the neutralizing agent is m-phenylenediamine, and the amount of the neutralizing agent added is 0.05 mol, 5.4 g.

7. The method for preparing modified aramid fiber according to claim 1, characterized in that: In step S5, the organic solvent B is tetrahydrofuran or diethyl ether, the mass of the acyl chloride is 30 g, the mass of the organic solvent B is 120-150 g, and the mass of the aluminum chloride is 10 g.

8. The method for preparing modified aramid fiber according to claim 1, characterized in that: In step S5, the acyl chloride is acetyl chloride or p-fluorobenzoyl chloride.

9. A modified aramid fiber prepared by the method according to any one of claims 1 to 8.