Polymer aerogel fiber as well as preparation method and application thereof

Abstract

The invention discloses a polymer aerogel fiber as well as a preparation method and application thereof. A polymer nascent fiber is prepared from a polymer solution in a wet spinning manner through a phase separation bath and a coagulating bath according to a non-solvent induced phase separation principle, and the polymer nascent fiber is dried to obtain the polymer aerogel fiber. The preparation method of the polymer aerogel fiber has the advantages of being simple, safe, environmentally friendly, rapid and low in cost, a feasible scheme is provided for large-scale preparation of the aerogel fiber at the room temperature and under the normal pressure, and the obtained aerogel fiber has huge application prospects in the aspects of heat insulation, fire resistance, flame retardance and the like.

Description

Technical Field

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

[0002] Aerogel is a new type of material with high porosity, low density, large specific surface area and good thermal insulation performance, while aerogel fiber combines the advantages of aerogel and fiber materials. It is a lightweight, porous, flexible and multifunctional material with broad application prospects in thermal insulation, pollution adsorption, biomedicine, energy storage and aerospace. Compared with bulk aerogel, aerogel fiber is highly flexible and weavable, and can be more easily integrated into applications of various shapes and sizes.

[0003] The existing preparation of aerogel fibers still continues the traditional process similar to that of bulk aerogels, namely the sol-gel method, followed by freeze drying or supercritical drying. This process has two major defects. On the one hand, this type of preparation method and drying method are non-continuous methods, and the drying conditions take a long time, making the process difficult to operate continuously, and there is no prospect of large-scale continuous production. On the other hand, freeze drying and supercritical drying methods are expensive and require high equipment, which greatly limits the low-cost large-scale application of aerogel fibers. Summary of the invention

[0004] In view of the defect that freeze drying or supercritical drying is inevitably required for the preparation of aerogel fibers in the prior art, the present invention provides a method for preparing polymer aerogel fibers, which overcomes the problems of cumbersome, discontinuous, high cost and many restrictive conditions in the traditional aerogel fiber process.

[0005] One of the technical solutions of the present invention is to provide a method for preparing polymer aerogel fibers, by decomposing the traditional coagulation bath into two steps: a phase separation bath and a coagulation bath, wherein the phase separation bath uses a higher concentration of solvent to promote the delayed phase separation behavior of the polymer in the bath and avoid instantaneous phase separation, thereby forming a uniform submicron sponge pore structure; the coagulation bath composed of a pure non-solvent can effectively maintain the sponge pore structure, so that no additional freeze drying or supercritical drying is required, and the polymer aerogel can be obtained by drying at room temperature and normal pressure, thereby achieving large-scale continuous spinning. In addition, compared with the existing freeze-drying method to fix the pore structure, the present invention can maintain a continuous sponge pore structure and ensure the strength of the aerogel fiber.

[0006] Specifically, the method includes: extruding a polymer solution and passing it through a phase separation bath to obtain a gel-state fiber, then passing the gel-state fiber through a coagulation bath to obtain a nascent fiber, and drying the nascent fiber to obtain an aerogel fiber; the phase separation bath is a mixed solution of a solvent and a non-solvent for the polymer, and the mass fraction of the solvent for the polymer is 40% to 90%; the phase separation time is 2 min to 10 min; and the coagulation bath is a non-solvent for the polymer.

[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 50µm~500µm and a strength of 10Mpa~40Mpa.

[0012] Furthermore, the pores inside the polymer aerogel fibers are micron-scale sponge pores or nano-scale sponge pores, and the average pore size is 500nm~5µm.

[0013] The third technical solution of the present invention is to provide the application of the above-mentioned polymer aerogel fiber in the field of heat resistance and fire prevention.

[0014] A fourth technical solution of the present invention is to provide a tow prepared from the above-mentioned polymer aerogel fiber.

[0015] The beneficial effects of the present invention are as follows: compared with the preparation of traditional aerogel fibers, this process does not require solvent replacement or freeze-drying, and the prepared fibers have uniform sponge pores, which, on the one hand, allow the fibers to maintain better mechanical properties and flexibility at a lower density, and on the other hand, the structure of the sponge pores is better maintained during the drying and heat treatment process. 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 the SEM image of the polyimide aerogel fiber obtained in Example 1; Figure 3 This is the pore size distribution diagram of the polyimide aerogel obtained in Example 1; Figure 4 Fire resistance test of polyimide aerogel in Example 1; Figure 5 This is a picture of knotting the polyimide aerogel in Example 1; Figure 6 This is the SEM image of the polyimide aerogel fiber in Example 2; Figure 7 This is the SEM image of the polyimide aerogel fiber in Example 4; Figure 8 This is the SEM image of the polyimide aerogel fiber obtained in Comparative Example 1. DETAILED DESCRIPTION

[0017] Non-solvent induced phase separation is a common basic scientific principle in the field of polymer membrane materials. Its process is to dissolve the polymer in the solvent to form a homogeneous solution, then slowly add a reagent that is more miscible with the solvent (called an extractant) to extract the solvent, forming a two-phase structure with the polymer as the continuous phase and the solvent as the dispersed phase. Then, the solvent is removed by normal pressure drying to obtain a polymer with a certain pore structure. This method is widely used in the preparation of phase separation membranes and hollow fiber membranes. The use of the non-solvent induced phase separation principle for wet spinning and normal pressure drying can well realize the continuous production of aerogel fibers.

[0018] The selection of polymer solvent and non-solvent is common knowledge in the art. Generally, the solvent of the polymer is generally selected from one or more of DMF, DMAC, NMP, DMSO, HMPA, TEP, TMP, TMU, and the non-solvent is generally selected from one or more of water, ethanol, isopropanol, methanol, ether, ethyl acetate, ethylene glycol, and glycerol.

[0019] Sponge pore structure refers to a type of three-dimensional porous structure with uniform small pores similar to a sponge. 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.

[0020] 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.

[0021] The embodiments of the present invention are further described below with reference to a plurality of embodiments.

[0022] 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.

[0023] 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.

[0024] Example 1 (1) A 15 wt% polyimide acid N,N-dimethylacetyl solution was extruded into a phase separation bath using a spinning needle with an inner diameter of 340 µm (corresponding to the national standard 23G), and then pulled into a coagulation bath to obtain polyimide acid primary fibers. The phase separation bath consisted of N,N-dimethylacetyl and water in a mass ratio of 1:1, the phase separation time was 2 minutes, and the coagulation bath was water.

[0025] (2) Drying the polyimide acid fiber at room temperature and normal pressure to obtain a polyimide acid aerogel fiber, such as Figure 1 shown.

[0026] (3) The polyimide acid aerogel fiber is thermally imidized to obtain polyimide aerogel. The imidization temperature is 300 °C and the imidization time is 1 h. Figure 2 shown.

[0027] Figure 3 The porosity distribution diagram of the polyimide aerogel fiber in Example 1 shows that the pores of the aerogel fiber are normally distributed as a whole, and the proportion in the range of 1.5-3 μm is greater than 70%. The polyimide aerogel fiber in Example 1 was subjected to an ablation test, and the results are as follows: Figure 4 The polyimide aerogel fibers in Example 1 were knotted, and the results were as shown in Figure 5 As shown, the aerogel fiber has good flexibility and weavability Example 2 The difference between Example 2 and Example 1 is that the composition of the phase separation bath is N, N-dimethylacetyl and water in a mass ratio of 4:6. The microscopic morphology of the obtained aerogel fiber is as follows: Figure 6 As shown, the phase separation time is 10 minutes, the pore size is relatively uniform, and the overall normal distribution is greater than 70% in the range of 400nm-600nm, and the average pore size is 500nm. The fiber thickness is 50µm and the strength is 10Mpa.

[0028] Example 3 (1) The difference from Example 1 is that a spinneret with a pore size of 240 µm and a number of holes of 20 is used instead of a spinning needle to extrude into a phase separation bath, and then pulled into a coagulation bath to obtain a polyimide acid primary fiber bundle. The phase separation bath is composed of N,N-dimethylacetyl and water in a mass ratio of 1:1, the phase separation time is 2 minutes, and the coagulation bath is water.

[0029] (2) Drying the polyimide acid fiber bundle at room temperature and normal pressure to obtain a polyimide acid aerogel fiber bundle.

[0030] (3) The polyimide acid aerogel fiber bundle is thermally imidized to obtain a polyimide aerogel bundle, the imidization temperature is 300°C, and the imidization time is 1 h.

[0031] (4) The obtained polyimide aerogel filaments are woven into plain fabrics. The obtained fabrics have good thermal insulation properties in the vertical direction, and the thermal conductivity is 44 mW / m·K.

[0032] Example 4 Compared with Example 1, this embodiment uses multiple spinning needles with different inner diameters (corresponding to national standards 22G, 24G, 28G, and 32G) for spinning, and successfully achieves the preparation of aerogel fibers with different diameters. The microscopic morphology of the obtained aerogel fibers of different thicknesses is as follows: Figure 7 shown.

[0033] Example 5 The only difference from Example 1 is that a 10 wt % polyimide acid solution is used.

[0034] Example 6 (1) A 0.1wt% heterocyclic aramid N,N-dimethylacetyl solution was extruded into a phase separation bath using a national standard 21G spinning needle, and then pulled into a coagulation bath to obtain heterocyclic aramid nascent fibers. The mass composition of the phase separation bath was 80% dimethyl sulfoxide and 20% water, the phase separation time was 2 minutes, and the composition of the coagulation bath was ethanol.

[0035] (2) The heterocyclic aramid fibers were dried at room temperature and pressure to obtain heterocyclic aramid aerogel fibers, the pore size of which was normally distributed in the range of 500nm~1µm, with a proportion greater than 70%. The fiber thickness was 500µm, the strength was 40Mpa, and the average pore size was 5µm.

[0036] Example 7 The only difference from Example 6 is that 2.5 wt % heterocyclic aramid solution is used.

[0037] Example 8 (1) A 15 wt% polyurethane dimethyl sulfoxide solution is extruded into a phase separation bath using a national standard 26G spinning needle, and then pulled into a coagulation bath to obtain polyurethane primary fibers. The mass composition of the phase separation bath is 40% N,N-dimethylacetamide solution and 60% water, the phase separation time is 5 minutes, and the coagulation bath is composed of ethanol and water in a ratio of 1:1.

[0038] (2) The polyurethane primary fibers were dried at room temperature and pressure to obtain polyurethane aerogel fibers, the pore size of which was normally distributed in the range of 2.5µm to 3.5µm, with a proportion greater than 70%. The fiber thickness was 200µm and the strength was 40Mpa.

[0039] Example 9 The only difference from Example 8 is that a 25 wt % polyurethane solution is used.

[0040] Example 10 (1) 15 wt% polyacrylonitrile N,N-dimethylformamide was extruded into a phase separation bath using a national standard 32G spinning needle, and then pulled into a coagulation bath to obtain polyurethane primary fibers. The mass composition of the phase separation bath was 90% N-methylpyrrolidone solution and 10% water, the phase separation time was 2 minutes, and the coagulation bath was composed of water.

[0041] (2) The polyacrylonitrile primary fibers are dried at room temperature and normal pressure to obtain polyacrylonitrile aerogel fibers, the pore sizes of which are normally distributed in the range of 1 µm to 2 µm, with a proportion greater than 70%.

[0042] Embodiment 11 The only difference from Example 10 is that a 25 wt % polyacrylonitrile solution is used.

[0043] Example 12 The only difference from Example 10 is that the phase separation bath is 80% N-methylpyrrolidone solution and 20% water.

[0044] Comparative Example 1 The only difference from Example 1 is that the composition of the phase separation bath is N, N-dimethylacetyl and water in a mass ratio of 1:4, the phase separation time is 2 minutes, and the coagulation bath is N, N-dimethylacetyl solution and water in a mass ratio of 1:9. The microscopic morphology of the obtained aerogel fiber is as follows: Figure 8 As shown in the figure, most of the aerogel is uneven finger-like pores with a length of 50µm, and the fiber strength is low and the flexibility is poor. The tensile strength is about 5Mpa and the elongation at break is about 10%. It can be seen that the appropriate concentration of phase separation bath and coagulation bath is the key to constructing uniform submicron sponge pores.

[0045] Comparative Example 2 The difference from Example 1 is that after the phase separation bath of Example 1, the fiber is directly freeze-dried without entering the coagulation bath. The pore size of the obtained aerogel fiber is widely distributed, ranging from 1 to 10 μm, which is not conducive to its industrial application.

[0046] 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 a polymer aerogel fiber, characterized in that: The polymer solution is extruded and first passed through a phase separation bath to obtain gel fibers, and then the gel fibers are passed through a coagulation bath to obtain nascent fibers, and the nascent fibers are dried to obtain aerogel fibers; the phase separation bath is a mixed solution of a solvent and a non-solvent for the polymer, and the mass fraction of the solvent for the polymer is 40% to 90%; the phase separation time is 2 min to 10 min; and the coagulation bath is a non-solvent for the polymer.

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, and 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. A polymer aerogel fiber prepared by the preparation method according to claim 1, characterized in that: The polymer aerogel fiber has a thickness of 50µm to 500µm and a strength of 10Mpa to 40Mpa.

6. The polymer aerogel fiber according to claim 5, characterized in that: The pores inside the polymer aerogel fibers are micron-scale sponge pores or nano-scale sponge pores, and the average pore size is 500nm~5µm.

7. Use of the polymer aerogel fiber as claimed in claim 6 in the field of heat resistance and fire prevention.

8. A tow consisting of the polymer aerogel fiber according to any one of claims 1 to 7.

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