Superfine aerogel fiber as well as preparation method and application thereof

Abstract

The invention discloses a superfine aerogel fiber as well as a preparation method and application thereof. A polymer solution passes through a gradient phase separation bath and step-by-step drafting in a wet spinning mode, is coagulated by a coagulating bath, and is dried at normal temperature and normal pressure to obtain the superfine polymer aerogel fiber. The average diameter of the polymer aerogel fiber is smaller than 10 microns, the polymer aerogel fiber has good mechanical properties and good weaving performance, the internal average pore size is smaller than 60 nm, and gas heat conduction can be effectively reduced. The preparation method has the advantages of being simple, safe, environmentally friendly, rapid and low in cost, and the heat insulation textile based on the superfine fibers has the advantages of being light in weight, high in strength, good in heat insulation performance and good in flexibility and has a huge application prospect in the field of heat preservation and heat insulation.

Description

Technical Field

[0001] The invention relates to the technical field of aerogel preparation, and in particular to an ultrafine aerogel fiber and a preparation method and application thereof. Background Art

[0002] Aerogel fiber is a new type of material with high porosity, low density and good thermal insulation performance. Due to its rich functions and easy weaving or integration into textiles and composite materials, it is suitable for thermal insulation clothing, filter materials, personal protective fabrics and smart textiles. In addition, aerogel fibers with fine diameters can be woven into denser fabrics that can effectively isolate external cold air and reflect human heat at a high density. Textiles based on such fine fibers have better thermal insulation performance.

[0003] The aerogel fibers currently prepared by freeze spinning have low porous skeleton strength, low pore wall orientation, and poor mechanical properties. The strength of the gel fibers during the preparation process is not enough to withstand the tension of industrial spinning equipment, and the fragile mechanical properties limit its continuous preparation. Therefore, it is difficult to achieve a high draft ratio in the preparation process of such fibers to prepare ultrafine fibers, and their weaving performance is poor. The fibers prepared by one-step drafting in the ordinary wet spinning process, due to the extremely strong interchain interaction between polymers, the instantaneous solidification and rapid hardening of the gel precursor inhibits the post-stretching and thinning process, resulting in the final fiber showing a diameter of more than 10 microns. Such a large diameter also greatly reduces the mechanical properties of the polymer fiber. The aerogel fibers currently prepared have a large pore size, a narrow processing range, and are difficult to optimize thermal insulation performance. Summary of the invention

[0004] In view of the problem that it is difficult to prepare ultrafine aerogel fibers with small pore size and excellent mechanical properties in the prior art, the present invention provides an ultrafine aerogel fiber and a preparation method and application thereof, so as to prepare aerogel fibers with good mechanical strength, flexibility and thermal insulation properties.

[0005] One of the technical solutions of the present invention is to provide a method for preparing ultrafine aerogel fibers, which is drawn and stretched in a phase separation bath with a high solvent content. Since the fiber has a low degree of phase separation, the distance between polymer chains is far, and the intermolecular interaction is weak, the polymer chains can be partially oriented under the drawing force, and then further stretched in a phase separation bath with a lower solvent content, so that the arrangement of the polymer chains is more dense, thereby improving the strength of the polymer porous fiber skeleton. The drawing force in the step-by-step phase separation process effectively suppresses the nucleation size of the polymer lean phase and ensures the fine pore size inside the aerogel fiber. After testing, the present invention can effectively control the internal pore size of the aerogel within 60nm. The average pore size inside the aerogel fiber is less than 60 nm, which effectively reduces gas heat conduction and has good thermal insulation performance.

[0006] Specifically, the method comprises: extruding a polymer solution, stretching it in a multi-stage phase separation bath system, then coagulating it in a coagulation bath to obtain nascent fibers, and drying the nascent fibers to obtain ultrafine polymer aerogel fibers; the multi-stage phase separation bath system comprises a plurality of phase separation baths, the phase separation baths are mixed solutions of a solvent and a non-solvent for the polymer, wherein the mass fraction of the solvent is between 30% and 90%, the mass fraction of the solvent in the first phase separation bath is not less than 40%, and the mass fraction of the solvent in each phase separation bath decreases successively; the coagulation bath is a non-solvent for the polymer; and the stretching ratio in each phase separation bath is between 30% and 200%.

[0007] Furthermore, the polymer solution is a 10wt% to 15wt% polyimide acid solution, a 0.1wt% to 2.5wt% heterocyclic aramid solution, a 15wt% to 25wt% polyurethane solution or a 15wt% to 25wt% polyacrylonitrile solution.

[0008] Furthermore, the solvent is one or more of DMF, DMAC, NMP, DMSO, HMPA, TEP, TMP, and TMU; and the non-solvent is one or more of water, ethanol, isopropanol, methanol, ether, ethyl acetate, ethylene glycol, and glycerol.

[0009] Furthermore, the drying process is carried out at room temperature and normal pressure.

[0010] In some embodiments of the present invention, polyimide acid is used as a polymer solution to prepare polyimide aerogel fibers. After drying, the polyimide acid aerogel fibers need to be moved to a tubular furnace for imidization at 300° C. for one hour to obtain polyimide aerogel fibers.

[0011] The second technical solution of the present invention is to provide a polymer aerogel fiber prepared by the above method, wherein the polymer aerogel fiber has a thickness of 3µm~10µm, a strength of 40Mpa~200Mp, and a porosity of 40%~70%.

[0012] Furthermore, the pores inside the polymer aerogel fiber are nanopores with an average pore size of less than 60 nm. The air in these small pores is generally static, which can effectively reduce gas heat conduction and play a huge role in thermal insulation.

[0013] The third technical solution of the present invention is to provide a tow composed of the above-mentioned ultrafine aerogel fibers.

[0014] A fourth technical solution of the present invention is to provide a woven fabric prepared from the above-mentioned yarn bundle.

[0015] The beneficial effects of the present invention are: the aerogel pore structure is finely regulated by preparing through multi-stage phase separation bath and step-by-step drawing, and the prepared polymer aerogel fiber has a fine diameter, good mechanical strength and flexibility, thereby giving the aerogel fiber good weavability. On the other hand, the average pore size inside the aerogel fiber is less than 60 nm, which effectively reduces gas heat conduction and has good thermal insulation performance. The preparation method of the present invention is simple and efficient, and provides a feasible solution for large-scale preparation of weavable aerogel fibers at room temperature and normal pressure. It has strong repeatability and shows broad application prospects in the field of thermal insulation textiles. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the SEM image of the polyimide acid aerogel fiber obtained in Example 1; Figure 2 This is a picture of the knotting of the polyimide aerogel in Example 1. DETAILED DESCRIPTION

[0017] The following examples are used to further illustrate the present invention, and their purpose is to illustrate the present invention and should not be construed as limiting the scope of the present invention. Unless otherwise specified, all parts by weight and weight percentages are used below.

[0018] The raw materials used in the present invention, unless otherwise specified, are conventional commercially available products; the methods used in the present invention, unless otherwise specified, are conventional methods in the art.

[0019] The embodiments of the present invention are further described below with reference to a plurality of embodiments.

[0020] The spinning needle of the present invention is a commercially available national standard needle.

[0021] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0022] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings. Example 1

[0023] (1) A 15% mass fraction polyimide N,N-dimethylacetamide solution was extruded through a 34G needle, passed through a three-stage gradient phase separation bath and stretched, and finally passed through a pure water coagulation bath wet spinning to obtain polyimide acid primary fibers. The mass ratios of N,N-dimethylacetamide and water in the gradient phase separation bath were 9:1, 1:1, and 3:7, respectively, and the corresponding stretching ratios in each bath were 50%, 200%, and 100%, respectively.

[0024] (2) The polyimide acid fiber is placed at room temperature and atmospheric pressure to dry to obtain a polyimide acid aerogel fiber, which is then thermally imidized to obtain a polyimide aerogel. The imidization temperature is 300°C and the imidization time is 1 hour. The prepared fiber diameter is about 9 μm. The microscopic morphology of the obtained aerogel fiber is as follows: Figure 1 As shown, the average pore size is 37nm, the orientation degree is 0.72, the porosity is 70%, and the tensile strength is 157MPa. The polyimide aerogel fiber in Example 1 is knotted, and the result is as follows Figure 2 The fibers in Example 1 were prepared into tows and then woven into fabrics, and the thermal conductivity in the vertical direction was 39 mw / mK at room temperature. Example 2

[0025] The only difference from Example 1 is that 10 wt % polyimide acid N,N-dimethylacetamide solution is used. Example 3

[0026] (1) A 0.1% mass fraction of heterocyclic aramid N,N-dimethylacetamide solution was extruded through a 32G needle, passed through a three-stage gradient phase separation bath and stretched, and finally wet-spun in a pure ethanol coagulation bath to obtain heterocyclic aramid primary fibers. The mass ratios of dimethyl sulfoxide and ethanol in the gradient phase separation bath were 8:2, 6:4, and 4:6, respectively, and the corresponding stretching ratios in each bath were 30%, 150%, and 100%, respectively.

[0027] (2) The heterocyclic aramid fibers were dried at room temperature and atmospheric pressure to obtain heterocyclic aramid aerogel fibers. The average pore size was 51 nm, the fiber diameter was 3 μm, the orientation degree was 0.75, the porosity was 40%, and the tensile strength was 200 MPa. The fibers in Example 2 were prepared into tows and then woven into fabrics. The thermal conductivity in the vertical direction was 55 mw / mK at room temperature. Example 4

[0028] The only difference from Example 3 is that 2.5 wt % heterocyclic aramid N,N-dimethylacetamide solution is used. Example 5

[0029] (1) A 15% polyurethane N,N-dimethylformamide solution was extruded through a 30G needle, passed through a four-stage gradient phase separation bath and stretched, and finally wet-spun in a pure ethanol coagulation bath to obtain polyurethane primary fibers. The mass ratios of N,N-dimethylformamide to water in the gradient phase separation bath were 8:2, 6:4, 4:6, and 3:7, respectively, and the corresponding stretching ratios in each bath were 80%, 200%, 100%, and 100%, respectively. The composition of the coagulation bath was ethanol and water miscible in a ratio of 1:1.

[0030] (2) Drying the polyurethane primary fibers at room temperature and normal pressure to obtain polyurethane aerogel fibers. The average pore size is 60 nm, the fiber diameter is 10 microns, the orientation degree is 0.87, and the tensile strength is 40 MPa. The fibers in Example 3 are prepared into tows and then woven into fabrics. The thermal conductivity in the vertical direction at room temperature is 45 mw / mK. Example 6

[0031] The only difference from Example 5 is that a 25% by mass polyurethane N,N-dimethylformamide solution is used. Example 7

[0032] (1) A 15% polyacrylonitrile dimethyl sulfoxide solution was extruded through a 34G needle, passed through a three-stage gradient phase separation bath and stretched, and finally wet-spun through a pure water coagulation bath to obtain polyacrylonitrile primary fibers. The mass ratio of N-methylpyrrolidone solution to water in the gradient phase separation bath was 8:2, 6:4, and 1:1, and the corresponding stretching ratios in each bath were 50%, 200%, and 100%, respectively.

[0033] (2) The polyacrylonitrile primary fibers were dried at room temperature and normal pressure to obtain polyacrylonitrile aerogel fibers. The average pore size was 37 nm, the fiber diameter was 6 microns, the orientation degree was 0.77, and the strength was 125 MPa. The fibers in Example 4 were prepared into tows and then woven into fabrics. The thermal conductivity in the vertical direction at room temperature was 38 mw / mK. Example 8

[0034] The only difference from Example 7 is that a polyacrylonitrile dimethyl sulfoxide solution with a mass fraction of 25% is used. Example 9

[0035] (1) A 15% polyacrylonitrile dimethyl sulfoxide solution was extruded through a 34G needle, passed through a three-stage gradient phase separation bath and stretched, and finally wet-spun through a pure water coagulation bath to obtain polyacrylonitrile primary fibers. The mass ratio of N-methylpyrrolidone solution to water in the gradient phase separation bath was 4:6, 7:13, and 3:7, and the corresponding stretching ratios in each bath were 50%, 200%, and 100%, respectively.

[0036] (2) Drying the polyacrylonitrile primary fibers at room temperature and normal pressure to obtain polyacrylonitrile aerogel fibers.

[0037] Comparative Example 1 The difference from Example 1 is that the mass ratios of N,N-dimethylacetamide and water in the three-stage gradient phase separation bath are 3:7, 2:8, and 1:9, respectively, and the corresponding stretching ratios in each bath are 50%, 200%, and 100%, respectively. The prepared fibers are solid fibers without porous structures.

[0038] The above embodiments describe in detail the structure, features and effects of the present invention. The above are only preferred embodiments of the present invention. Any changes made in accordance with the concept of the present invention, or modifications to equivalent embodiments with equivalent changes, which do not exceed the scope covered by the specification, should be within the protection scope of the present invention.

Claims

1. A method for preparing ultrafine aerogel fibers, characterized in that: The polymer solution is extruded, stretched in a multi-stage phase separation bath system, and then coagulated in a coagulation bath to obtain nascent fibers, and the nascent fibers are dried to obtain ultrafine polymer aerogel fibers; the multi-stage phase separation bath system includes multiple phase separation baths, the phase separation baths are mixed solutions of a solvent and a non-solvent for the polymer, wherein the mass fraction of the solvent is 30% to 90%, the mass fraction of the solvent in the first phase separation bath is not less than 40%, and the mass fraction of the solvent in each phase separation bath decreases successively; the coagulation bath is a non-solvent for the polymer; and the stretching ratio in each phase separation bath is 30% to 200%.

2. The preparation method according to claim 1, characterized in that: The polymer solution is a 10wt% to 15wt% polyimide acid solution, a 0.1wt% to 2.5wt% heterocyclic aramid solution, a 15wt% to 25wt% polyurethane solution or a 15wt% to 25wt% polyacrylonitrile solution.

3. The preparation method according to claim 1, characterized in that: The solvent is one or more of DMF, DMAC, NMP, DMSO, HMPA, TEP, TMP, and TMU; the non-solvent is one or more of water, ethanol, isopropanol, methanol, ether, ethyl acetate, ethylene glycol, and glycerol.

4. The preparation method according to claim 1, characterized in that: The drying process is carried out at room temperature and normal pressure.

5. An ultrafine aerogel fiber prepared by the preparation method according to claim 1, characterized in that: The polymer aerogel fiber has a diameter of 3µm to 10µm, a strength of 40Mpa to 200Mpa, and a porosity of 40% to 70%.

6. The ultrafine aerogel fiber according to claim 7, characterized in that: The pores inside the polymer aerogel fibers are nanopores with an average pore size of less than 60 nm.

7. A tow consisting of the ultrafine aerogel fiber according to any one of claims 1 to 6.

8. A braided fabric prepared from the yarn bundle according to claim 7.

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