CN115044996B

CN115044996B - Superfine aramid fiber and preparation method and application thereof

Info

Publication number: CN115044996B
Application number: CN202210740240.XA
Authority: CN
Inventors: 陈克复; 李金鹏
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-06-28
Filing date: 2022-06-28
Publication date: 2023-10-10
Anticipated expiration: 2042-06-28
Also published as: CN115044996A

Abstract

The invention discloses a preparation method of superfine aramid fiber, which comprises the following steps: adding a modifier into the neutral aramid polymer solution, fully mixing and dispersing, and filtering and defoaming to obtain spinning solution; the modifier is a low-melting-point water-soluble polymer; and conveying the spinning solution to a spinneret plate, and sequentially performing spinning, solidification and drafting, washing, drying, hot drafting, heat setting and rolling to obtain the superfine aramid fiber. The invention also discloses the superfine aramid fiber prepared by the preparation method and application thereof. The superfine aramid fiber has small diameter, high strength and linear density of less than 1.0dtex, has rough surface and large specific surface area, has better binding capacity in materials, and has wide application in the fields of papermaking, filtering, spinning, rubber, flexible circuit boards and the like.

Description

Superfine aramid fiber and preparation method and application thereof

Technical Field

The invention relates to the technical field of aramid fibers, in particular to an ultrafine aramid fiber and a preparation method and application thereof.

Background

The poly m-phenylene isophthalamide (meta-aramid) is formed by polycondensation of meta-phenylene diamine and meta-phenylene diacid chloride, amide groups in meta-aramid macromolecules are connected with each other through meta-phenyl groups, covalent bonds of the meta-aramid macromolecules have no conjugate effect, internal rotation energy is lower than that of para-aromatic polyamide fibers, and macromolecular chains are of flexible structures, and the strength and the modulus of the meta-aramid macromolecules are equivalent to those of common polyester and nylon. Meta-aramid fiber is a high-tech special fiber with excellent mechanical properties, stable chemical properties and excellent heat resistance.

Superfine aramid fiber is one of the differential fibers which develop rapidly in recent years, is called as new generation synthetic fiber, is outstanding in various chemical fiber varieties, and is a fiber with high quality and high technology. The aramid fiber maintains excellent mechanical, acid and alkali resistant, high temperature resistant and flame retardant properties, has larger specific surface area and adhesive force due to smaller diameter, has the characteristics of soft hand feeling, high strength, softness, higher hygroscopicity than common aramid fiber and the like, and the fiber and fabric thereof have the advantages of soft hand feeling, light weight, thinness, softness, air permeability, good drapability, self-extinguishing property and the like, so that the application of the superfine aramid fiber in the fields of textile clothing, papermaking, filtering and the like is continuously expanded. The lack of technology for producing superfine aramid fiber at home makes the existing aramid fiber production factory unable to meet the market demand of superfine aramid fiber at home.

In the prior art, no technology for efficiently producing superfine aramid meta-fibers exists at home. For example, chinese patent 202111349941.2 discloses an aramid fiber, a preparation method and application thereof, wherein the aramid fiber is obtained by stretching and washing the fiber for several times, the linear density of the aramid fiber is 2.7dtex, and the single fiber strength is 3.7cN/dtex. Chinese patent 202010191376.0 discloses a modification method of meta-aromatic polyamide spinning solution, which is modified by adding micro polyethylene glycol (0.1-1%) as a spinning solution modifier into meta-aromatic polyamide solution. Chinese patent 202111491249.3 discloses a spinning method of meta-aramid fiber, which is used for obtaining a fiber skin-core-free structure or a very weak skin-core structure, wherein the fiber fineness reaches 1.5dtex, and the single fiber strength reaches 5.10-5.23 cN/dtex at the highest. It is known that the current domestic aramid fiber manufacturing technology focuses on single fiber strength values, and does not aim at solving the superfine fiber (< 1 dtex).

Disclosure of Invention

In order to overcome the defects and shortcomings of the prior art, the invention aims to provide a preparation method of superfine aramid fiber, which realizes efficient production of superfine aramid fiber, and the prepared superfine aramid fiber has linear density of less than 1.0dtex, uniform and compact structure, fewer defects and large specific surface area.

The invention also aims to provide the superfine aramid fiber prepared by the preparation method of the superfine aramid fiber.

It is still another object of the present invention to provide the use of the above ultra fine aramid fiber.

The aim of the invention is achieved by the following technical scheme:

the preparation method of the superfine aramid fiber comprises the following steps:

adding a modifier into the neutral aramid polymer solution, fully mixing and dispersing, and filtering and defoaming to obtain spinning stock solution;

the modifier is a low-melting-point water-soluble polymer;

and conveying the spinning solution to a spinneret plate, and sequentially performing spinning, solidification and drafting, washing, drying, hot drafting, heat setting and rolling to obtain the superfine aramid fiber.

Preferably, the low-melting-point water-soluble polymer is at least one of polyethylene glycol, polyvinylpyrrolidone, N-vinylpyrrolidone and polyoxyethylene lauryl ether.

Preferably, the molecular weight of the polyethylene glycol is 400 to 1500, but is not limited thereto, and for example, the molecular weight may be 4000 or more, and the present invention can be realized.

Preferably, the absolute dry mass ratio of the modifier to the aramid polymer is (5-40) (60-95), and the mixing temperature is 60-150 ℃.

Preferably, the aperture of the spinneret plate is 0.03-0.10 mm.

Preferably, the coagulation drafting includes primary coagulation bath drafting and secondary coagulation bath drafting, specifically:

the primary coagulation bath draft ratio is 1.1-1.8 times, and the temperature is 20-80 ℃; the drawing ratio of the secondary coagulating bath is 1.1-2.5 times, and the temperature is 20-80 ℃.

Preferably, the hot drawing specifically includes: the draft ratio is 1.1-2.0 times, and the temperature is 70-150 ℃.

The water washing is specifically as follows:

the water washing process comprises two sections of water washing: the water temperature of the primary water washing is 50-100 ℃; the water temperature of the second-stage water washing is 20-50 ℃;

the drying is specifically as follows:

the drying temperature is 80-120 ℃;

the heat setting is specifically as follows:

the heat setting temperature is 280-320 ℃.

Preferably, the preparation method of the neutral aramid polymer solution comprises the following steps:

dissolving cosolvent and m-phenylenediamine in N, N-dimethylacetamide at the temperature of 0-20 ℃ under the condition of nitrogen protection, and then adding m-phthaloyl chloride for a plurality of times to obtain a reaction solution; along with the reaction, the temperature of the reaction solution is gradually increased, and after the reaction solution is treated by heat preservation for 0.5 to 10 hours at 50 to 80 ℃, an alkaline agent is added for neutralization, thus obtaining a neutral aramid polymer solution;

the molar ratio of the m-phenylenediamine to the m-phthaloyl chloride is 100: (90-120);

the cosolvent is more than one of lithium bromide, lithium chloride, calcium chloride and calcium bromide;

the alkaline agent is one or more of calcium oxide, calcium hydroxide, magnesium hydroxide, sodium hydroxide and organic amine.

The superfine aramid fiber prepared by the preparation method has the linear density less than 1.0dtex.

The superfine aramid fiber is applied to papermaking, filtering, spinning, rubber and flexible circuit boards.

The principle of the invention is as follows:

the supramolecular microstructure of aramid fibers is characterized by a high degree of orientation with well-aligned long chains, whereas conventional flexible or medium stiffness polymer fibers are typically folded chain supramolecular structures. The invention obviously improves the rheological property of the aramid polymer by adding the modifier, and is favorable for dry-wet spinning. After the modified spinning solution enters the coagulating bath through the spinneret plate, the solvent in the aramid fiber precursor is dissolved in hot water while double diffusion occurs in the coagulating bath, the modifier is gradually dissolved out of the aramid fiber precursor along with the gradual passing of the aramid fiber precursor through the multistage coagulating bath and the water bath, and finally the aramid fiber macromolecules are aligned in a highly oriented manner by combining a multistage multiple drafting process. The above characteristics result in fibers having a high proportion of molecular chains subjected to tensile load and small differences in the length of these molecular chains from each other, and thus have excellent mechanical properties. Under the synergistic effect of solidification and stretching, the intermolecular force is increased, the molecular free volume is relatively reduced along with gradual solidification of the aramid fiber, the orientation and transition diffusion movement of a molecular chain are obviously influenced, a highly ordered and regular chain structure is formed, macromolecules are aligned along the fiber axis, and the strength of the aramid fiber is greatly improved. In addition, the dissolution rate of the modifier can be regulated by controlling different coagulation bath compositions and process temperatures, and finally the superfine high-strength aramid fiber with the adjustable and controllable surface roughness is prepared.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) According to the preparation method of the superfine aramid fiber, the superfine aramid fiber is prepared by adding the modifier and changing the spinning parameters, so that the superfine fiber with small linear density, uniform and compact structure, fewer defects and large specific surface area can be efficiently prepared.

(2) The superfine aramid fiber has small linear density, small diameter and high structural uniformity and compactness; the refinement of the fibers increases the specific surface area of the fibers and the bonding effect of the fibers; the thinning of the aramid fiber reduces the defect content of the fiber precursor in unit area and improves the strength.

(3) The superfine aramid fiber has linear density less than 1.0dtex, rough surface, large specific surface area, better binding capacity in materials and wide application in the fields of papermaking, filtering, spinning, rubber, flexible circuit boards and the like.

Drawings

Fig. 1 is a schematic view of a preparation apparatus for a preparation method of ultra-fine aramid fiber according to an embodiment of the present invention.

Fig. 2 is a cross-sectional SEM image of the ultra-fine aramid fiber prepared in example 5 of the present invention.

Fig. 3 is a surface SEM image of the ultra-fine aramid fiber prepared in example 5 of the present invention.

Fig. 4 is a surface SEM image of the ultra-fine aramid fiber prepared in example 6 of the present invention.

Fig. 5 is a surface SEM image of the ultra-fine aramid fiber prepared in example 7 of the present invention.

Detailed Description

The present invention will be described in further detail with reference to examples, but embodiments of the present invention are not limited thereto.

Example 1

As shown in fig. 1, a preparation device for realizing the preparation method of the superfine aramid fiber of the embodiment comprises a spinneret plate 1, a collecting device 2, a primary coagulation bath drafting device 3, a secondary coagulation bath drafting device 4, a primary water washing device 5, a secondary water washing device 6, a drying device 7, a heat drafting device 8, a heat setting device 9 and a winding device 10.

The preparation method of the superfine aramid fiber in the embodiment is as follows:

(1) Preparation of an aramid polymer: m-phenylenediamine is dissolved in N, N-dimethylacetamide at a low temperature of 15 ℃ under the condition of nitrogen protection, lithium chloride is added, then m-phthaloyl chloride is added for 1 time, and the molar ratio of the m-phenylenediamine to the m-phthaloyl chloride is controlled to be 100:90. the temperature was gradually increased to 50℃as the reaction proceeded, and the incubation time was 10h. And (3) adding calcium oxide for neutralization after heat preservation treatment to prepare the neutral aramid polymer solution.

(2) Preparing an aramid fiber stock solution: adding a proper amount of polyoxyethylene lauryl ether into the neutral aramid polymer obtained in the step (1), wherein the absolute dry mass ratio of the modifier to the aramid polymer is 5:95, and the mixing temperature is 80 ℃. And filtering and defoaming after fully mixing and dispersing to obtain spinning solution.

(3) Preparation of superfine aramid fiber: conveying the spinning solution obtained in the step (2) to a spinneret plate, and sequentially carrying out spinning, solidification drafting, washing, drying, hot drafting, heat setting and winding to finally obtain the superfine aramid fiber, wherein the specific parameters are as follows:

and (3) spinning: the aperture range of the spinneret plate is 0.03mm, and the aperture number is 20000; the distance between the spinneret plate and the coagulating bath is 5cm;

and (3) solidifying and drafting: the primary coagulating bath comprises the following components in percentage by mass: n, N-dimethylacetamide: glycerol: water, etc. =60:20:20; the coagulation bath temperature is 20 ℃, and the draft ratio is 1.1 times; the secondary coagulating bath comprises the following components in percentage by mass: n, N-dimethylacetamide: water=50:50, coagulation bath temperature 50 ℃, second stage coagulation bath draft ratio 1.5 times;

and (3) a water washing process: the water temperature of the first-stage water washing is 20 ℃, and the draft ratio is 1.5 times; the water temperature of the second-stage water washing is 50 ℃;

and (3) drying: the drying temperature is 80 ℃;

and (3) a hot drawing process: the hot drawing temperature is 200 ℃, and the drawing multiplying power is 1.5 times;

and (3) heat setting: the heat setting temperature was 280 ℃.

The properties of the resulting aramid fibers were measured and the test results are shown in Table 1.

Example 2

(1) Preparation of an aramid polymer: m-phenylenediamine is dissolved in N, N-dimethylacetamide at a low temperature of 10 ℃ under the condition of nitrogen protection, lithium chloride is added, and then m-phthaloyl chloride is added for 5 times, wherein the molar ratio of the m-phenylenediamine to the m-phthaloyl chloride is controlled to be 100:110. the temperature was gradually increased to 60℃as the reaction proceeded, and the incubation time was 8h. And (3) after heat preservation treatment, adding calcium hydroxide for neutralization, and thus obtaining the neutral aramid polymer solution.

(2) Preparing an aramid fiber stock solution: adding a proper amount of polyethylene glycol-400 into the neutral aramid polymer obtained in the step (1), wherein the absolute dry mass ratio of the modifier to the aramid polymer is 10:90, and the mixing temperature is 60 ℃. And filtering and defoaming after fully mixing and dispersing to obtain spinning solution.

and (3) spinning: the aperture range of the spinneret plate is 0.08mm, and the aperture number is 5000; the distance between the spinneret and the coagulation bath was 10cm.

And (3) solidifying and drafting: the primary coagulating bath comprises the following components in percentage by mass: n, N-dimethylacetamide: glycerol: water, etc. =70:20:10; the coagulation bath temperature was 50℃and the draft ratio was 1.5 times. The secondary coagulating bath comprises the following components in percentage by mass: n, N-dimethylacetamide: water=60:40, coagulation bath temperature 80 ℃, second stage coagulation bath draft ratio 1.7 times;

and (3) a water washing process: the temperature of the first-stage water washing is 40 ℃, and the draft ratio is 1.3 times; the water temperature of the second-stage water washing is 60 ℃;

and (3) drying: the drying temperature is 100 ℃;

and (3) a hot drawing process: the hot drawing temperature is 260 ℃ and the drawing multiplying power is 1.9 times;

and (3) heat setting: the heat setting temperature is 290 ℃;

Example 3

The preparation method of the superfine aramid fiber of the embodiment is as follows:

(1) Preparation of an aramid polymer: m-phenylenediamine is dissolved in N, N-dimethylacetamide at a low temperature of 5 ℃ under the condition of nitrogen protection, lithium chloride is added, and then m-phthaloyl chloride is added for 3 times, wherein the molar ratio of the m-phenylenediamine to the m-phthaloyl chloride is controlled to be 100:105. the temperature was gradually increased to 70℃as the reaction proceeded, and the incubation time was 5h. And (3) adding calcium oxide for neutralization after heat preservation treatment to prepare the neutral aramid polymer solution.

(2) Preparing an aramid fiber stock solution: adding a proper amount of polyethylene glycol-400 into the neutral aramid polymer obtained in the step (1), wherein the absolute dry mass ratio of the modifier to the aramid polymer is 25:75, and the mixing temperature is 70 ℃. And filtering and defoaming after fully mixing and dispersing to obtain spinning solution.

and (3) spinning: the aperture range of the spinneret plate is 0.05mm, and the aperture number is 8000; the distance between the spinneret plate and the coagulating bath is 20cm;

and (3) a solidification process: the secondary coagulating bath comprises the following components in percentage by mass: n, N-dimethylacetamide: water=60:40, coagulation bath temperature 80 ℃;

and (3) drafting: the primary coagulating bath comprises the following components in percentage by mass: n, N-dimethylacetamide: glycerol: water, etc. =70:15:15; the coagulation bath temperature was 60℃and the draft ratio was 1.8 times. The secondary coagulating bath comprises the following components in percentage by mass: n, N-dimethylacetamide: water=60:40, coagulation bath temperature 80 ℃, second-stage coagulation bath draft ratio 1.8 times; three-stage drafting is hot drafting, the hot drafting temperature is 275 ℃, and the drafting multiplying power is 2.2 times;

and (3) a water washing process: the water temperature of the first section of water washing is 50 ℃, and the draft ratio is 1.1 times; the water temperature of the second-stage water washing is 80 ℃;

and (3) drying: the drying temperature is 105 ℃;

and (3) heat setting: the heat setting temperature was 320 ℃.

Example 4

(1) Preparation of an aramid polymer: m-phenylenediamine is dissolved in N, N-dimethylacetamide at a low temperature of 5 ℃ under the condition of nitrogen protection, lithium chloride is added, and then m-phthaloyl chloride is added for 2 times, wherein the molar ratio of the m-phenylenediamine to the m-phthaloyl chloride is controlled to be 100:103. the temperature was gradually increased to 80℃as the reaction proceeded, and the incubation time was 3h. After heat preservation treatment, adding calcium oxide for neutralization to prepare a neutral aramid polymer solution;

(2) Preparing an aramid fiber stock solution: adding a proper amount of polyethylene glycol-800 into the neutral aramid polymer obtained in the step (1), wherein the absolute dry mass ratio of the modifier to the aramid polymer is 40:60, and the mixing temperature is 70 ℃. Filtering and defoaming after fully mixing and dispersing to obtain spinning solution;

(3) Preparation of superfine aramid fiber: and (3) conveying the spinning solution obtained in the step (2) to a spinneret plate, and sequentially carrying out spinning, solidification drafting, washing, drying, hot drafting, heat setting and winding to finally obtain the superfine aramid fiber. The specific parameters are as follows:

and (3) spinning: the aperture range of the spinneret plate is 0.1mm, and the number of holes is 500; the distance between the spinneret and the coagulation bath was 30cm.

And (3) solidifying and drafting: the primary coagulating bath comprises the following components in percentage by mass: n, N-dimethylacetamide: glycerol: water, etc. =65:25:10; the coagulation bath temperature was 80℃and the draft ratio was 1.6 times. The secondary coagulating bath comprises the following components in percentage by mass: n, N-dimethylacetamide: water=50:50, coagulation bath temperature is 70 ℃, the second-stage coagulation bath draft ratio is 2.0 times;

and (3) a water washing process: the temperature of the first-stage water washing is 45 ℃, and the draft ratio is 2.0 times; the water temperature of the second-stage water washing is 90 ℃;

and (3) a hot drawing process: the hot drawing temperature is 280 ℃, and the drawing multiplying power is 2.4 times;

and (3) heat setting: the heat setting temperature was 300 ℃.

Example 5

(1) Preparation of an aramid polymer: m-phenylenediamine is dissolved in N, N-dimethylacetamide at a low temperature of 5 ℃ under the condition of nitrogen protection, calcium bromide is added, and then m-phthaloyl chloride is added for 3 times, wherein the molar ratio of the m-phenylenediamine to the m-phthaloyl chloride is controlled to be 100:103. the temperature was gradually increased to 80℃as the reaction proceeded, and the incubation time was 3h. And (3) adding calcium oxide for neutralization after heat preservation treatment to prepare the neutral aramid polymer solution.

(2) Preparing an aramid fiber stock solution: adding a proper amount of polyethylene glycol-800 into the neutral aramid polymer obtained in the step (1), wherein the absolute dry mass ratio of the modifier to the aramid polymer is 30:70, and the mixing temperature is 70 ℃. And filtering and defoaming after fully mixing and dispersing to obtain spinning solution.

and (3) spinning: the aperture range of the spinneret plate is 0.05mm, and the aperture number is 8000; the distance between the spinneret plate and the coagulating bath is 15cm;

and (3) solidifying and drafting: the primary coagulating bath comprises the following components in percentage by mass: n, N-dimethylacetamide: glycerol: water, etc. =70:15:15; the coagulation bath temperature was 70℃and the draft ratio was 1.6 times. The secondary coagulating bath comprises the following components in percentage by mass: n, N-dimethylacetamide: water=60:40, coagulation bath temperature is 70 ℃, the second-stage coagulation bath draft ratio is 2.5 times;

and (3) a water washing process: the temperature of the first-stage water washing is 40 ℃, and the draft ratio is 1.5 times; the water temperature of the second-stage water washing is 85 ℃;

and (3) drying: the drying temperature is 110 ℃;

and (3) a hot drawing process: the hot drawing temperature is 285 ℃, and the drawing multiplying power is 2.9 times;

and (3) heat setting: the heat setting temperature is 295 ℃.

The properties of the obtained aramid fiber were measured, and the test results are shown in Table 1; SEM of the fiber cross section and surface are shown in fig. 2-3.

Example 6

This embodiment differs from embodiment 4 in that: the modifier polyethylene glycol-800 in step (1) is replaced by polyvinylpyrrolidone k30. SEM of the fiber surface is shown in fig. 4.

Example 7

This embodiment differs from embodiment 3 in that: the calcium oxide in step (1) is replaced with diethylamine. SEM of the fiber surface is shown in fig. 5.

Example 8

This embodiment differs from embodiment 3 in that: the primary coagulation bath components and the mass ratio in the step (1) are replaced by N, N-dimethylacetamide: ethylene glycol: water=70:15:15.

Comparative example 1

The present comparative example is different from example 1 in that: no modifier is added in step (2).

Detection method

Tensile strength and elongation at break were measured with reference (GB/T14337-2008); the linear density was measured according to GB/T6100-2007.

TABLE 1 test result summary of superfine aramid fiber

Examples	Linear density (dtex)	Tension (cN/dtex)	Elongation (%)
				Example 1	0.98	3.86	28.5
Example 2	0.75	4.15	30.4
				Example 3	0.62	4.83	34.1
Example 4	0.41	5.26	37.5
				Example 5	0.13	5.69	40.6
Example 6	0.55	4.96	35.2
				Example 7	0.65	4.58	33.5
Example 8	0.59	5..03	35.0
				Comparative example 1	2.75	2.82	20.4

As can be seen from Table 1, the superfine aramid fiber added with the modifier of the invention can obviously reduce the diameter of the aramid fiber and improve the strength of the aramid fiber compared with comparative example 1 without the modifier. As is clear from FIGS. 2 to 5, the aramid fiber prepared by the method has the advantages of rough surface, compact structure and no collapse or void generation.

The modifier of the present invention is not limited to polyethylene glycol and polyoxyethylene lauryl ether in the above embodiments, and other modifiers such as polyvinylpyrrolidone and N-vinylpyrrolidone may also be used to realize the present invention.

The invention can be adjusted according to actual production and is suitable for wet spinning or dry-wet spinning; the aramid polymer raw material can be meta-aramid polymer, para-aramid polymer, heterocyclic aramid polymer and the like.

The embodiments described above are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the embodiments described above, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principles of the present invention should be made in the equivalent manner, and are included in the scope of the present invention.

Claims

1. The preparation method of the superfine aramid fiber is characterized by comprising the following steps of:

adding a modifier into the neutral aramid polymer solution, fully mixing and dispersing, and filtering and defoaming to obtain spinning stock solution; the absolute dry mass ratio of the modifier to the aramid polymer is (10-40) to (60-90);

the preparation method of the neutral aramid polymer solution comprises the following steps:

the alkaline agent is more than one of calcium oxide, calcium hydroxide, magnesium hydroxide, sodium hydroxide and organic amine;

the modifier is a low-melting-point water-soluble polymer; the low-melting-point water-soluble polymer is at least one of polyethylene glycol, polyvinylpyrrolidone, N-vinyl pyrrolidone and polyoxyethylene lauryl ether;

conveying the spinning solution to a spinneret plate, and sequentially carrying out spinning, solidification drafting, water washing, drying, hot drafting, heat setting and rolling to obtain superfine aramid fibers;

the coagulation drafting comprises primary coagulation bath drafting and secondary coagulation bath drafting;

the water washing is two sections of water washing.

2. The method for preparing ultra-fine aramid fiber according to claim 1, wherein the mixing temperature is 60 to 150 ℃.

3. The method of producing ultra-fine aramid fiber according to claim 1, wherein the spinneret has a pore diameter of 0.03 to 0.10 and mm.

4. The method for preparing superfine aramid fiber according to claim 1, wherein,

the draft ratio of the primary coagulation bath is 1.1-1.8 times, and the temperature is 20-80 ℃; the drawing ratio of the secondary coagulation bath is 1.1-2.5 times, and the temperature is 20-80 ℃.

5. The method for preparing superfine aramid fiber according to claim 1, wherein the hot drawing specifically comprises: the draft ratio is 1.1-2.0 times, and the temperature is 70-150 ℃.

6. The method for preparing superfine aramid fiber according to claim 1, wherein,

the two sections of water washing are specifically as follows: the water temperature of the primary water washing is 50-100 ℃; the water temperature of the second-stage water washing is 20-50 ℃;

the drying is specifically as follows:

the drying temperature is 80-120 ℃;

the heat setting is specifically as follows:

the heat setting temperature is 280-320 ℃.

7. The superfine aramid fiber prepared by the preparation method of the superfine aramid fiber according to any one of claims 1 to 6, which is characterized in that the linear density is less than 1.0dtex.

8. The use of the ultra-fine aramid fiber of claim 7 in paper making, filtration, spinning, rubber, flexible circuit boards.