A para-aramid fiber and its preparation method and application

Abstract

The present invention discloses a para-aramid (PPTA) fiber and its preparation method and application, which belongs to the field of polymer material technology and solves the problem in the prior art that PPTA materials cannot meet the material modulus requirements of ultra-high-end application fields. The preparation method of the para-aramid fiber disclosed by the present invention comprises the following steps: uniformly dispersing a covalent organic framework material in concentrated sulfuric acid at room temperature to obtain a sulfuric acid solution of the covalent organic framework material; dissolving poly(p-phenylene terephthalamide) in the sulfuric acid solution of the covalent organic framework material to obtain a spinning slurry; filtering, degassing and spinning the spinning slurry in sequence; and performing a purification operation to obtain para-aramid fiber. The preparation method provided by the present invention regulates the condensed state of the PPTA molecular chain by adding COFs structural materials, reduces the micro-defects between its molecules, thereby improving the strength and modulus of para-aramid and expanding its application field.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and more particularly to a para-aramid fiber and a preparation method and application thereof. Background Art

[0002] Poly(p-phenylene terephthalamide) (PPTA) boasts exceptional properties such as ultra-high strength, high modulus, high-temperature resistance, acid and alkali resistance, and lightweight. Its strength is 5-6 times that of steel wire, its modulus is 2-3 times that of steel wire or fiberglass, and its toughness is twice that of steel wire, yet its weight is only about one-fifth that of steel wire. It neither decomposes nor melts at temperatures of 560°C. Aramid fiber's exceptional strength, modulus, and excellent acid, alkali, and high-temperature resistance have earned it an irreplaceable position in a variety of applications, including military, aerospace, lightweight optical cables, and automotive weight reduction.

[0003] Due to micro-defects in PPTA's molecular chains, its strength and modulus are relatively limited. Currently, the strength and modulus of standard para-aramid are 19.5 cN / dtex and 85 GPa, respectively, while high-strength and high-modulus para-aramid can reach 23.5 cN / dtex and 110 GPa, respectively. However, this still falls short of the material modulus requirements for ultra-high-end applications such as deep-sea exploration, mooring, and aerospace (where the modulus is required to exceed 120 GPa). Summary of the Invention

[0004] The present invention provides a para-aramid fiber and a preparation method and application thereof, which are used to solve the problem in the prior art that PPTA materials cannot meet the requirements of ultra-high-end application fields on material modulus.

[0005] In a first aspect, the present invention provides a method for preparing para-aramid fiber, comprising the following steps: uniformly dispersing a covalent organic framework material in concentrated sulfuric acid at room temperature to obtain a sulfuric acid solution of the covalent organic framework material; dissolving poly(p-phenylene terephthalamide) in the sulfuric acid solution of the covalent organic framework material to obtain a spinning slurry; filtering, degassing and spinning the spinning slurry in sequence to obtain spun fibers; and purifying the spun fibers to obtain the para-aramid fiber.

[0006] As a possible implementation manner, the covalent organic framework material structure contains NH bonds, O and benzene rings; and / or the structure of the covalent organic framework material is a porous two-dimensional structure.

[0007] As a possible implementation method, the covalent organic framework material is any one of NKCOF-12, COF-3, NKCOF-45 and NKCOF-41; and / or, the uniform dispersion in concentrated sulfuric acid includes the following steps: adding the covalent organic framework material to concentrated sulfuric acid at room temperature and stirring at a rate of 20 to 180 rpm; ultrasonically applying a power of 40 to 200 kHz for 30 to 180 minutes to obtain a sulfuric acid solution of the covalent organic framework material; and / or, the spinning is performed by dry-jet wet spinning, with a spinneret diameter of 0.05 to 0.2 mm, a number of holes of 150 to 1000, and a fiber linear density of 800D to 1500D; and / or, the purification operation includes the following steps: alkali washing, water washing, drying and heat treatment operations are performed on the spun fiber in sequence to obtain the para-aramid fiber.

[0008] As a possible implementation method, the mass ratio of the covalent organic framework material to the poly(p-phenylene terephthalamide) is 0.1 to 8:1000; and / or the viscosity of the poly(p-phenylene terephthalamide) is 5.5 to 7.5 dL / g, and the solid content is 18% to 20%; and / or the poly(p-phenylene terephthalamide) participates in the reaction in the form of a solution, and its concentration is 19.5 wt%; and / or the concentration of the concentrated sulfuric acid is 100%.

[0009] As a possible implementation method, poly(p-phenylene terephthalamide) is dissolved in the sulfuric acid solution of the covalent organic framework material at a dissolution temperature of 30 to 90° C. and a dissolution time of 35 to 60 minutes.

[0010] In a second aspect, the present invention provides a para-aramid fiber prepared by the preparation method described in any possible implementation of the first aspect.

[0011] In a third aspect, the present invention provides an application of a para-aramid fiber prepared by the preparation method described in any possible implementation of the first aspect or the para-aramid fiber described in the second aspect in an ultra-high-end field, wherein the ultra-high-end field is a field that requires the performance of the para-aramid fiber to have a modulus ≥120GPa.

[0012] As a possible implementation method, the ultra-high-end fields include deep-sea exploration, mooring, aviation or aerospace.

[0013] As a possible implementation, the para-aramid fiber is used to prepare 24 mm mooring ropes.

[0014] The present invention provides a method for preparing para-aramid fiber, which regulates the condensed state of PPTA molecular chains by adding COFs structural materials, reduces micro-defects between its molecules, thereby improving the strength and modulus of para-aramid and expanding its application field. COFs are lightweight organic molecular units connected by covalent bonds to form a two-dimensional or three-dimensional network structure, and thus have the advantages of excellent structural tailorability and functional adjustability, as well as low skeleton density, high porosity, and open pore structure. More than 85% of the amide bonds (-CONH-) in the PPTA molecular chain are directly connected to the benzene ring, so it can form a π-π conjugation effect with the benzene ring, and there is a strong interaction force between the molecular chains; at the same time, the macromolecules are arranged in parallel, the free space volume is small, and there is a strong hydrogen bond effect between the PPTA molecular chains.

[0015] COFs, with their NH bonds, O atoms, and benzene rings, form a strong π-π conjugation effect with PPTA chains, enhancing interchain interactions. High internal rotational potential allows the chains to adopt a parallel, rigid, and straight-chain conformation, resulting in relatively complete and higher-crystalline fibers. Furthermore, the NH bonds and O atoms form more hydrogen bonds with PPTA chains, increasing rigidity and enhancing fiber modulus. The porous, three-dimensional COF structure leverages its scaffolding structure to act as a clamp, effectively embedding a large number of PPTA chains within the surface. This enhances lateral interactions between PPTA chains and improves fiber strength and modulus. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 This is the structural formula of the covalent organic framework material NKCOF-12 provided in an embodiment of the present invention.

[0018] Figure 2 This is the structural formula of the covalent organic framework material COF-3 provided in an embodiment of the present invention.

[0019] Figure 3 This is the structural formula of the covalent organic framework material NKCOF-45 provided in an embodiment of the present invention.

[0020] Figure 4 This is the structural formula of the covalent organic framework material NKCOF-41 provided in an embodiment of the present invention.

[0021] Figure 5 This is a SEM image of the para-aramid fiber A provided in an embodiment of the present invention.

[0022] Figure 6 This is a SEM image of the para-aramid fiber E provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] To address the problem in the prior art that PPTA materials cannot meet the material modulus requirements of ultra-high-end applications, an embodiment of the present invention provides a preparation experiment of para-aramid fiber, successfully preparing para-aramid fibers A to D, and preparing para-aramid fiber E for comparison.

[0025] Furthermore, the embodiments of the present invention characterize various properties of para-aramid fibers A to para-aramid fibers E. It can be seen that the para-aramid fibers A to para-aramid fibers D prepared by the present invention have significantly improved linear density, strength and modulus. On the basis of ensuring superior linear density and strength performance, they can also meet the requirements of ultra-high-end application fields for material modulus performance.

[0026] Furthermore, the embodiments of the present invention conducted a test experiment on the application effects of para-aramid fibers A to para-aramid fibers E. It can be seen that the para-aramid fibers A to para-aramid fibers D prepared by the present invention all have relatively significant and superior application effects, and can meet the application needs of ultra-high-end fields.

[0027] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0028] Example 1

[0029] This embodiment provides an experiment for preparing para-aramid fiber.

[0030] 10g NKCOF-12 (structural formula Figure 1100 kg of PPTA was dissolved in the NKCOF-12 sulfuric acid solution A to obtain a spinning slurry A. The spinning slurry A was filtered and degassed with a precision of 20 μm, and then spun by a dry-jet wet spinning method, wherein the spinneret hole specifications used for spinning were 0.05 mm in diameter and 1000 holes. The spinning slurry was passed through a coagulation bath (coagulation bath concentration was 0.5% sulfuric acid) to obtain a spun fiber A. The spun fiber A was then alkali-washed, washed with water, dried, and heat-treated to obtain a para-aramid fiber A.

[0031] 100g NKCOF-41 (structural formula Figure 4 The invention discloses a method for preparing a spun aramid fiber B. The spun aramid fiber B is prepared by dissolving 100 kg of PPTA in the NKCOF-41 sulfuric acid solution B at room temperature and stirring at 80 kHz ultrasonic power and 120 rpm for 50 min. The spun aramid fiber B is prepared by filtering the spun aramid fiber B with a precision of 20 μm to remove air and then spinning the spun aramid fiber B by dry-jet wet spinning. The spinning slurry B has a spinneret hole size of 0.05 mm in diameter and 1000 holes. The spun fiber B is passed through a coagulation bath (coagulation bath concentration of 0.5% sulfuric acid) to obtain a spun fiber B. The spun fiber B is then subjected to alkali washing, water washing, drying, and heat treatment to obtain a para-aramid fiber B.

[0032] 300g COF-3 (structural formula Figure 2 The invention further provides a method for preparing a COF-3 fiber by dissolving 100 kg of PPTA in the COF-3 sulfuric acid solution C at room temperature, and then dispersing the 100 kg of PPTA in the COF-3 sulfuric acid solution C at room temperature. The 100 kg of PPTA was dissolved in the COF-3 sulfuric acid solution C to obtain a spinning slurry C. The spinning slurry C was filtered and degassed with a precision of 20 μm, and then spun by a dry-jet wet spinning method, wherein the spinneret hole specifications used for spinning were 0.05 mm in diameter and 1000 holes. The fiber was passed through a coagulation bath (the coagulation bath concentration was 0.5% sulfuric acid) to obtain a nascent fiber C. The nascent fiber C was subjected to alkali washing, water washing, drying, and heat treatment to obtain a para-aramid fiber C.

[0033] 5 g of COF-3 was dispersed in 412 kg of concentrated sulfuric acid at room temperature and stirred at 80 kHz ultrasonic power and 150 rpm for 60 min to obtain a sulfuric acid solution C1 of COF-3; 100 kg of PPTA was dissolved in the sulfuric acid solution C1 of COF-3 to obtain a spinning slurry C1; the spinning slurry C was filtered and degassed with an accuracy of 20 μm, and then spun by a dry-jet wet spinning method, wherein the spinneret specifications used for spinning were 0.05 mm in diameter and 1000 holes; the spun fiber C1 was obtained by passing through a coagulation bath (the coagulation bath concentration was 0.5% sulfuric acid); the spun fiber C was alkali washed, water washed, dried, and heat treated to obtain a para-aramid fiber C1.

[0034] 800g NKCOF-45 (structural formula Figure 3 The invention discloses a method for preparing a spun aramid fiber D comprising: dispersing 100 kg of PPTA in 412 kg of concentrated sulfuric acid at room temperature, stirring at 80 kHz ultrasonic power and 150 rpm for 80 min, and dissolving 100 kg of PPTA in the NKCOF-45 sulfuric acid solution D to obtain a spinning slurry D. The spinning slurry D is filtered and deaerated with a precision of 20 μm, and then spun by a dry-jet wet spinning method, wherein the spinneret hole specifications used for spinning are 0.05 mm in diameter and 1000 holes. The spinning slurry D is passed through a coagulation bath (coagulation bath concentration is 0.5% sulfuric acid) to obtain a spun fiber D. The spun fiber D is then subjected to alkali washing, water washing, drying, and heat treatment to obtain a para-aramid fiber D.

[0035] 100 kg of PPTA was dissolved in 412 kg of concentrated sulfuric acid to obtain a spinning slurry E; the spinning slurry E was filtered and degassed with an accuracy of 20 μm, and then spun by a dry-jet wet spinning method, wherein the spinneret hole specifications used for spinning were 0.05 mm in diameter and 1000 holes; nascent fibers E were obtained by passing through a coagulation bath (the coagulation bath concentration was 0.5% sulfuric acid); the nascent fibers E were alkali washed, water washed, dried, and heat treated to obtain para-aramid fibers E.

[0036] Example 2

[0037] This embodiment provides a performance characterization experiment of para-aramid fiber.

[0038] The para-aramid fiber A and para-aramid fiber E prepared in the example were subjected to SEM analysis, and the following results were obtained: Figure 5 and Figure 6 As shown in the SEM image, it can be seen that the para-aramid fiber was successfully prepared.

[0039] The para-aramid fibers A to E prepared in Example 1 were tested for linear density, strength, modulus and elongation at break, respectively, and the results shown in Table 1 were obtained.

[0040] Table 1 Performance characterization results of para-aramid fiber

[0041]

[0042] As can be seen from Table 1, compared with the para-aramid fiber E, the para-aramid fibers A to D prepared by the present invention all significantly improve linear density, strength and modulus. On the basis of ensuring superior linear density and strength performance, they can also meet the requirements of ultra-high-end application fields for material modulus performance.

[0043] Example 3

[0044] This embodiment provides an experiment to verify the application effect of para-aramid fiber.

[0045] The fibers to be tested were used to prepare 24 mm mooring ropes using 3,900,000 dtex twisted high-model fibers. In this example, para-aramid fiber C and para-aramid fiber E prepared in Example 1 were used as the test fibers, respectively, to prepare ropes C and E. All other preparation conditions were the same.

[0046] The results show that the modulus of rope C is 11% higher than that of rope E, and the 0.5% breaking strength and elongation (FASE-0.5) is 9% lower; it can be seen that para-aramid fiber C has better application performance.

[0047] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0048] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing para-aramid fiber, characterized in that: The following steps are involved: uniformly dispersing the covalent organic framework material in concentrated sulfuric acid at room temperature to obtain a sulfuric acid solution of the covalent organic framework material; dissolving poly(p-phenylene terephthalamide) in a sulfuric acid solution of the covalent organic framework material to obtain a spinning slurry; The spinning slurry is filtered, degassed, and spun in sequence to obtain nascent fibers; Purifying the spun fibers to obtain the para-aramid fibers; Wherein, the covalent organic framework material is any one of NKCOF-12, COF-3, NKCOF-45 and NKCOF-41.

2. The preparation method according to claim 1, characterized in that The uniform dispersion in concentrated sulfuric acid comprises the following steps: adding the covalent organic framework material to concentrated sulfuric acid at room temperature, stirring at a rate of 20 to 180 rpm; ultrasonicating at a power of 40 to 200 KHz for 30 to 180 minutes to obtain a sulfuric acid solution of the covalent organic framework material; And / or, the spinning is carried out by dry-jet wet spinning, wherein the spinneret diameter is 0.05-0.2 mm, the number of holes is 150-1000, and the fiber linear density is 800D-1500D; And / or, the purification operation includes the following steps: performing alkali washing, water washing, drying and heat treatment operations on the spun fiber in sequence to obtain the para-aramid fiber.

3. The preparation method according to claim 1, characterized in that The mass ratio of the covalent organic framework material to the poly(p-phenylene terephthalamide) is 0.1-8:1000; and / or the poly(p-phenylene terephthalamide) has a viscosity of 5.5 to 7.5 dL / g and a solid content of 18% to 20%; And / or, the poly(p-phenylene terephthalamide) participates in the reaction in the form of a solution with a concentration of 19.5 wt %; And / or, the concentration of concentrated sulfuric acid is 100%.

4. The preparation method according to claim 1, characterized in that The poly(p-phenylene terephthalamide) is dissolved in the sulfuric acid solution of the covalent organic framework material at a dissolution temperature of 30-90° C. and a dissolution time of 35-60 min.

5. A para-aramid fiber prepared by the preparation method according to any one of claims 1 to 4.

6. Use of the para-aramid fiber prepared by the preparation method according to any one of claims 1 to 4 or the para-aramid fiber according to claim 5 in ultra-high-end fields, characterized in that: The ultra-high-end field is a field in which the performance requirement for the para-aramid fiber is a modulus ≥ 120 GPa.

7. The use according to claim 6, characterized in that The ultra-high-end fields include deep-sea exploration, mooring, aviation or aerospace.

8. The use according to claim 6, characterized in that The para-aramid fiber is used to prepare 24 mm mooring ropes.

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