A kind of porous aramid fiber and preparation method thereof

Abstract

The present invention relates to a porous aramid fiber and a preparation method thereof, which is prepared from heterocyclic aramid resin slurry containing imidazole groups and metal ions. The porous aramid fiber of the present invention has a uniform cavity structure, high porosity, high specific surface area, good mechanical strength, low thermal conductivity, and good thermal stability, and has good application prospects in the field of thermal insulation and protective materials.

Description

Technical Field

[0001] The invention belongs to the field of high-performance fiber manufacturing, and particularly relates to a porous aramid fiber and a preparation method thereof. Background Art

[0002] Porous materials have the characteristics of high specific surface area, high porosity and low density, and have broad application prospects in the fields of thermal insulation, energy storage and conversion, photoelectric catalysis, shock absorption and explosion protection. Traditional porous materials are mainly block materials, which have the disadvantages of high brittleness, easy cracking, and difficult molding and processing, making it difficult to meet their application in wearable and flexible protective equipment. Fibrous porous materials have excellent flexibility and weavability, which broadens their application in wearable fabrics and other fields.

[0003] However, the porous fiber preparation methods reported so far, such as phase separation method, template method, and ice crystal growth method, are all difficult to obtain porous fibers with uniform structure, resulting in uneven cavities, low porosity, small specific surface area, and poor mechanical properties. After the spinning solution is extruded through the spinneret, it is expected to continuously prepare porous fibers with uniform structure through sol-gel transformation. However, if the sol-gel transformation is too fast, the spinneret hole will be blocked and cannot be formed, while if the transformation is too slow, phase separation and uneven structure will easily occur during the coagulation process of the coagulation bath. Therefore, how to develop a suitable sol-gel system to continuously prepare porous fibers with uniform structure is still a difficult problem. On the other hand, aramid fiber has the advantages of excellent mechanical properties, high and low temperature resistance, good flame retardancy, and good chemical corrosion resistance. Processing aramid fiber into porous structure fiber is more conducive to its application in high-temperature insulation protective clothing and other flexible protective equipment. However, aramid itself has poor solubility and difficult molding and processing, and it is difficult to produce porous aramid fiber with uniform structure in the prior art. Patent CN113463375A first etches aramid fibers in an organic alkaline solvent to form aramid nanofibers, and then uses the aramid nanofibers as raw materials to obtain porous aramid fibers by wet spinning through the principle of phase separation. However, this method is time-consuming and complicated to operate, and the obtained porous aramid fibers have poor mechanical properties and a small specific surface area. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a porous aramid fiber and a preparation method thereof. The prepared porous aramid fiber has a uniform void structure, high porosity, high specific surface area, good mechanical strength, low thermal conductivity, and good thermal stability, and has good application prospects in the field of thermal insulation and protective materials.

[0005] The present invention provides a porous aramid fiber, which is prepared from a heterocyclic aramid resin slurry containing imidazole groups and a metal ion compound; wherein the heterocyclic aramid containing imidazole groups has a structural formula of:

[0006]

[0007] The range of m and n is 50-300.

[0008] The metal ion compound includes one or more of copper acetate, zinc acetate, cobalt acetate and nickel acetate.

[0009] The porous aramid fiber has the following technical parameters and properties:

[0010] Density 0.03~0.13g / cm 3 , porosity 90.5~97.8%, specific surface area 281~350m 2 / g, breaking strength 8.6~13.0MPa, breaking elongation 15.1~61.2%, thermal conductivity 0.0262~0.0416W / (m·K).

[0011] The present invention also provides a method for preparing porous aramid fiber, comprising the following steps:

[0012] (1) Using anhydrous calcium chloride as a cosolvent and anhydrous N-methylpyrrolidone as a solvent, p-phenylenediamine, 5(6)-amino-2-(4-aminophenyl)benzimidazole, and terephthaloyl chloride as raw materials are used to synthesize a heterocyclic aramid resin slurry containing imidazole groups through solution polymerization; the solution polymerization reaction conditions are: temperature -5 to 0°C, reaction time 15 to 40 minutes;

[0013] (2) adding a metal ion compound to the resin slurry synthesized in step (1), adding a solvent to dilute the mixture, and mixing the mixture uniformly by magnetic stirring to obtain a mixed slurry; wherein the molar ratio of the metal ion compound to the imidazole group in the heterocyclic aramid resin containing imidazole groups is 1:2 to 1:4;

[0014] (3) using the mixed slurry obtained in step (2) as a spinning solution, preparing organogel primary fibers by wet spinning;

[0015] (4) The organic gel primary fibers obtained in step (3) are replaced by gradient solvents to obtain organic gel fibers, which are then dried to obtain porous aramid fibers.

[0016] The sum of the moles of p-phenylenediamine and 5(6)-amino-2-(4-aminophenyl)benzimidazole in step (1) is equal to the mole of terephthaloyl chloride; the molar ratio of p-phenylenediamine to 5(6)-amino-2-(4-aminophenyl)benzimidazole is 1:0.6-4; and the mole of anhydrous calcium chloride is equal to the mole of amino groups in the system.

[0017] The solid content of the resin slurry in step (1) is 5-10%.

[0018] The solvent in step (2) is one or both of N'N-dimethylformamide and N'N-dimethylacetamide.

[0019] The concentration of the mixed slurry in step (2) is 0.5-2.5 wt%.

[0020] The wet spinning conditions in step (3) are as follows: the spinneret diameter is 80-500 μm, the spinning speed is 2-10 m / min; the volume ratio of the organic solvent to water in the coagulation bath is 1:1, the coagulation bath temperature is 60-80° C.; and the negative stretching ratio is -70 to -20%.

[0021] The solvent used for the solvent replacement in step (4) is acetone or tert-butanol.

[0022] The gradient solvent is specifically: water, a mixed solution of water and acetone or tert-butanol in a volume ratio of 1:1, acetone or tert-butanol.

[0023] The drying method in step (4) is supercritical carbon dioxide drying or freeze drying.

[0024] The present invention introduces benzimidazole units into the aramid main chain to enable it to have the ability to coordinate with a variety of metal ions, and can construct a cross-linked system of aramid and metal ions through metal coordination bonds. Through the coordination of metal ions with imidazole groups on the aramid main chain, the metal ion-aramid resin solution system can form a physical cross-linked network, and through the adjustment of the reaction temperature, the sol-gel transition speed of the system can be conveniently regulated to match the dynamic spinning process, and the sol-gel transition of the filaments can be achieved in the wet spinning process to form a uniform three-dimensional cross-linked network, thereby obtaining a porous fiber with a uniform structure. In addition, the cross-linking effect of the metal coordination bond can further improve the mechanical strength and thermal stability of the fiber, develop a class of high-performance porous aramid fibers, and provide a new idea for the continuous preparation of other high-performance porous fibers.

[0025] Beneficial Effects

[0026] (1) The metal coordination bond cross-linked aramid system of the present invention can undergo a sol-gel transition rapidly and uniformly during the wet spinning process to form a uniform three-dimensional cross-linked structure, and finally obtain a porous aramid fiber with uniform structure, thereby further achieving high porosity, high specific surface area, low thermal conductivity and good thermodynamic properties.

[0027] (2) Due to the reversible cross-linking characteristics of the metal coordination bonds, the aramid porous fiber of the present invention is also recyclable. (3) The present invention is easy to operate and can achieve continuous preparation of porous aramid fibers through traditional wet spinning technology, making it easier to achieve large-scale production of products.

[0028] (4) The present invention can be extended to the preparation of other high-performance porous fibers. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a digital photo of the porous aramid fiber prepared in Example 1 of the present invention;

[0030] Figure 2 This is a scanning electron microscope photograph of a cross section of a porous aramid fiber prepared in Example 1 of the present invention;

[0031] Figure 3 This is a scanning electron microscope photograph of the surface of the porous aramid fiber prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0033] Example 1

[0034] 150 mL of anhydrous N-methylpyrrolidone was added to a 500 mL three-necked flask, and then 3.329 g of anhydrous calcium chloride was added, stirred, and after it was completely dissolved, 1.622 g of p-phenylenediamine and 3.364 g of 5 (6) -amino-2- (4-aminophenyl) benzimidazole were added, stirred, and after it was completely dissolved, the solution was cooled to -5 to 0 ° C, and then 6.091 g of terephthaloyl chloride was added, and after vigorous stirring for 30 minutes, a heterocyclic aramid resin slurry containing imidazole groups was obtained. Subsequently, 1.370 g of copper acetate was added to the slurry, and anhydrous N'N-dimethylacetamide was added to dilute the slurry concentration to 0.5 wt%, and the mixture was mixed evenly by magnetic stirring to obtain a mixed slurry. The obtained mixed slurry is used as a spinning slurry for wet spinning, wherein the spinneret diameter is 80 μm, the spinning speed is 4 m / min, the negative stretch ratio is -50%, the coagulation bath composition is a mixed solvent of N'N-dimethylacetamide and water (volume ratio 1:1), and the coagulation bath temperature is 70°C. The spinning solution is extruded through the spinneret and enters the coagulation bath, and under the temperature condition of the coagulation bath, the filaments undergo a sol-gel transition to form an organic gel primary fiber. Finally, the primary fiber obtained is subjected to gradient solvent replacement, and finally replaced with acetone, and then dried by supercritical carbon dioxide drying to prepare porous aramid fiber.

[0035] The obtained porous aramid fiber is as follows Figure 1 As shown, its surface SEM image and cross-section SEM image are as follows Figure 2 shown.

[0036] The obtained porous aramid fiber structural parameters and properties are as follows: density 0.0384g / cm 3 , porosity 97.31%, specific surface area 331m 2 / g, breaking strength 8.59MPa, breaking elongation 35.9%, thermal conductivity 0.0306W / (m·K).

[0037] Example 2

[0038] 500 mL of anhydrous N-methylpyrrolidone was added to a 1000 mL three-necked flask, and then 13.316 g of anhydrous calcium chloride was added, and stirred. After complete dissolution, 6.488 g of p-phenylenediamine and 13.456 g of 5 (6) -amino-2- (4-aminophenyl) benzimidazole were added, and stirred. After complete dissolution, the solution was cooled to -5 to 0 ° C, and then 24.364 g of terephthaloyl chloride was added. After vigorous stirring for 40 minutes, a heterocyclic aramid resin slurry containing imidazole groups was obtained. Subsequently, 5.480 g of copper acetate was added to the slurry, and anhydrous N'N-dimethylacetamide was added to dilute the slurry concentration to 1 wt%, and the mixture was mixed evenly by magnetic stirring to obtain a mixed slurry. The obtained mixed slurry is used as a spinning slurry for wet spinning, wherein the spinneret diameter is 80 μm, the spinning speed is 6 m / min, the negative stretch ratio is -70%, the coagulation bath composition is a mixed solvent of N'N-dimethylacetamide and water (volume ratio 1:1), and the coagulation bath temperature is 80°C. The spinning solution is extruded through the spinneret and enters the coagulation bath, and under the temperature condition of the coagulation bath, the filaments undergo a sol-gel transition to form an organic gel primary fiber. Finally, the primary fiber obtained is subjected to gradient solvent replacement, and finally replaced with acetone, and then dried by supercritical carbon dioxide drying to prepare porous aramid fiber.

[0039] The obtained porous aramid fiber structural parameters and properties are as follows: density 0.0619g / cm 3 , porosity 95.67%, specific surface area 312m 2 / g, breaking strength 11.21MPa, breaking elongation 53.3%, thermal conductivity 0.0317W / (m·K).

Claims

1. A porous aramid fiber, characterized in that: It is prepared from heterocyclic aramid resin slurry containing imidazole groups and metal ion compounds; wherein the heterocyclic aramid containing imidazole groups has the structural formula: The range of m, n is 50-300; The preparation method comprises the following steps: (1) Using anhydrous calcium chloride as a cosolvent and anhydrous N-methylpyrrolidone as a solvent, p-phenylenediamine, 5(6)-amino-2-(4-aminophenyl)benzimidazole, and terephthaloyl chloride as raw materials are used to synthesize a heterocyclic aramid resin slurry containing imidazole groups through solution polymerization; the solution polymerization reaction conditions are: temperature -5 to 0°C, reaction time 15 to 40 minutes; (2) adding a metal ion compound to the resin slurry synthesized in step (1), adding a solvent to dilute the mixture, and mixing the mixture uniformly by magnetic stirring to obtain a mixed slurry; wherein the molar ratio of the metal ion compound to the imidazole group in the heterocyclic aramid resin containing imidazole groups is 1:2 to 1:4; (3) using the mixed slurry obtained in step (2) as a spinning solution, preparing organic gel primary fibers by wet spinning; wherein the wet spinning conditions are: a spinneret diameter of 80-500 μm, a spinning speed of 2-10 m / min; a volume ratio of organic solvent to water in a coagulation bath of 1:1, a coagulation bath temperature of 60-80° C.; and a negative stretch ratio of -70 to -20%; (4) The organic gel primary fibers obtained in step (3) are replaced by gradient solvents to obtain organic gel fibers, which are then dried to obtain porous aramid fibers.

2. The porous aramid fiber according to claim 1, characterized in that: The metal ion compound includes one or more of copper acetate, zinc acetate, cobalt acetate and nickel acetate.

3. A method for preparing the porous aramid fiber according to claim 1, comprising the following steps: (1) Using anhydrous calcium chloride as a cosolvent and anhydrous N-methylpyrrolidone as a solvent, p-phenylenediamine, 5(6)-amino-2-(4-aminophenyl)benzimidazole, and terephthaloyl chloride as raw materials are used to synthesize a heterocyclic aramid resin slurry containing imidazole groups through solution polymerization; the solution polymerization reaction conditions are: temperature -5 to 0°C, reaction time 15 to 40 minutes; (2) adding a metal ion compound to the resin slurry synthesized in step (1), adding a solvent to dilute, and mixing uniformly by magnetic stirring to obtain a mixed slurry; wherein, The molar ratio of the metal ion compound to the imidazole group in the heterocyclic aramid resin containing imidazole groups is 1:2 to 1:4; (3) using the mixed slurry obtained in step (2) as a spinning solution, preparing organic gel primary fibers by wet spinning; wherein the wet spinning conditions are: a spinneret diameter of 80-500 μm, a spinning speed of 2-10 m / min; a volume ratio of organic solvent to water in a coagulation bath of 1:1, a coagulation bath temperature of 60-80° C.; and a negative stretch ratio of -70 to -20%; (4) The organic gel primary fibers obtained in step (3) are replaced by gradient solvents to obtain organic gel fibers, which are then dried to obtain porous aramid fibers.

4. The preparation method according to claim 3, characterized in that: The sum of the moles of p-phenylenediamine and 5(6)-amino-2-(4-aminophenyl)benzimidazole in step (1) is equal to the mole of terephthaloyl chloride; the molar ratio of p-phenylenediamine to 5(6)-amino-2-(4-aminophenyl)benzimidazole is 1:0.6-4; and the mole of anhydrous calcium chloride is equal to the mole of amino groups in the system.

5. The preparation method according to claim 3, characterized in that: The solid content of the resin slurry in step (1) is 5-10%.

6. The preparation method according to claim 3, characterized in that: The solvent in step (2) is one or both of N'N-dimethylformamide and N'N-dimethylacetamide.

7. The preparation method according to claim 3, characterized in that: The concentration of the mixed slurry in step (2) is 0.5-2.5 wt%.

8. The preparation method according to claim 3, characterized in that: The solvent used for the solvent replacement in step (4) is acetone or tert-butanol.

9. The preparation method according to claim 3, characterized in that: The drying method in step (4) is supercritical carbon dioxide drying or freeze drying.

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