Preparation method of silicon oxide aerogel modified low-thermal-conductivity cotton fiber

Abstract

The invention provides a preparation method of a silicon oxide aerogel modified low-heat-conductivity cotton fiber, which comprises the following steps: by taking an N-methylmorpholine-N-oxide aqueous solution with a specific concentration as a solvent, swelling the cotton fiber at a specific temperature and reacting with silicon oxide aerogel to prepare the cotton fiber with a complete fiber structure and a low heat conductivity coefficient. According to the low-heat-conduction cotton fiber obtained through the method, the fiber structure is kept complete, and the heat conduction coefficient is as low as 0.028 W / m.K. The invention has the characteristics of low raw material cost, simple preparation process, excellent product performance and easy realization of industrial large-scale production, and can be widely used for production of various high-performance thermal insulation cotton products.

Description

TECHNICAL FIELD

[0001] The present application relates to the synthesis of new materials, in particular to a method for preparing a silica aerogel modified low thermal conductivity cotton fiber with intact fiber structure. BACKGROUND

[0002] Cotton, as the largest natural fiber in the world, is widely used in the manufacture of various textiles. Although cotton fibers have good tensile properties, skin-friendliness and water absorption, their thermal conductivity is relatively high (0.05 W / m·K-0.08 W / m·K), which significantly limits their application in high-performance thermal textiles compared to wool, down and silk.

[0003] Aerogel is a nano-porous structure with a porosity of more than 90%, and its nanopore size is less than the free path of air (about 70 nanometers), thus having extremely low density and thermal conductivity. Common aerogels are mainly divided into three categories: inorganic oxide aerogels, organic polymer aerogels and carbon aerogels; only silica aerogel has achieved commercial production, and its composite products, such as aerogel felt, aerogel pad and aerogel coating, are commonly used as various high-performance thermal insulation materials.

[0004] By compounding textile fibers with silica aerogel, the thermal conductivity of the fibers can be effectively reduced while maintaining the integrity of the fiber structure, which is an important technology to improve the thermal performance of textile fibers. CN201610838980.1 reports the preparation of low thermal conductivity cellulose composite silica aerogel fibers by mixing cellulose with silica aerogel precursor solution, followed by mechanical spinning, aging, vacuum drying and other post-processing. CN201911316358.4 and CN202010736877.2 report the preparation of various synthetic fibers and silica aerogel composites by melt spinning after mixing silica aerogel with polyester fibers, polyamide fibers, polyacrylonitrile fibers or polypropylene fibers, which have significantly reduced thermal conductivity. CN202411711147.1 reports a method for preparing low thermal conductivity textile fibers by electrospinning and post-annealing treatment of silica aerogel and polyacrylonitrile.

[0005] However, the reported compounding of various natural or synthetic fibers with silica aerogel basically adopts the spinning method, but the preparation of silica aerogel dispersed fiber spinning solution requires high technical content and complex and expensive spinning equipment, resulting in high cost and great difficulty in the process of preparing silica aerogel modified low thermal conductivity textile fibers by spinning, which is not conducive to large-scale industrial production. SUMMARY

[0006] The present application aims at overcoming the deficiencies of the prior art, and provides a preparation method of silica aerogel modified low-thermal-conductivity cotton fiber, which is simple in process, low in cost and capable of large-scale industrial production.

[0007] The present application solves the above technical problems by using the following technical solutions:

[0008] The method for preparing the silica aerogel modified low-thermal-conductivity cotton fiber does not go through a traditional spinning process, directly uses a specific concentration of N-methylmorpholine-N-oxide aqueous solution with strong polarity to substitute the intermolecular hydrogen bond of the cellulose of the cotton fiber at a specific reaction temperature, so as to cause the swelling of the cotton fiber and the dehydration reaction between the cellulose hydroxyl group and the terminal hydroxyl group of the silica aerogel at a specific temperature, and thus the silica aerogel is efficiently modified to the surface of the cotton fiber; after the reaction is completed, the N-methylmorpholine-N-oxide aqueous solution is only diluted with water to reduce the concentration of the N-methylmorpholine-N-oxide, so that the N-methylmorpholine-N-oxide cannot form a hydrogen bond with the cellulose hydroxyl group, and the cellulose hydroxyl group of the cotton fiber forms a hydrogen bond again, so that the cotton fiber shrinks and returns to the original fiber state, that is, the silica aerogel modified low-thermal-conductivity cotton fiber with complete fiber structure is prepared.

[0009] Preferably, the concentration of the specific concentration of N-methylmorpholine-N-oxide aqueous solution is at least one of 75% to 85%.

[0010] Preferably, the specific reaction temperature is at least one of 85°C to 95°C.

[0011] The present application has the following beneficial effects:

[0012] The silica aerogel modified low-thermal-conductivity cotton fiber prepared by the present application uses a specific concentration of N-methylmorpholine-N-oxide aqueous solution as a cotton fiber swelling agent, and directly reacts with the silica aerogel after the cotton fiber is swelled at a specific temperature, so that the silica aerogel is efficiently modified to the surface of the cotton fiber; after being diluted with water, the concentration of the N-methylmorpholine-N-oxide aqueous solution is reduced, and the swelled cotton fiber shrinks to the normal fiber state, that is, the silica aerogel modified low-thermal-conductivity cotton fiber is prepared. The present application avoids a complex and expensive spinning method, the synthesis raw material is easy to obtain, the preparation process is simple, the N-methylmorpholine-N-oxide aqueous solution can be recycled without loss after vacuum dehydration, which is beneficial to industrial production; the silica aerogel modified cotton fiber has complete fiber structure and a significantly reduced thermal conductivity, and can be used for the production of various high-performance thermal insulation cotton products. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 Field emission scanning electron micrograph and energy spectrum of the product of Example 1.

[0014] Figure 2 Infrared spectrum and X-ray diffraction pattern of the product of Example 1.

[0015] Figure 3 Field emission scanning electron micrograph and energy spectrum of the product of Comparative Example 1.

[0016] Figure 4 Infrared spectrum and X-ray diffraction pattern of the product of Comparative Example 1.

[0017] Figure 5 Field emission scanning electron micrograph and energy spectrum of the product of Comparative Example 4.

[0018] Figure 6 Infrared spectrum and X-ray diffraction pattern of the product of Comparative Example 4. DETAILED DESCRIPTION

[0019] The application will be further described in conjunction with the drawings and specific embodiments, but the scope and application of the application are not limited thereto.

[0020] Example 1

[0021] In a single-neck flask with mechanical stirring, 3 g of cotton fiber, 0.5 g of silica aerogel and 150 ml of 80% concentration N-methyl morpholine-N-oxide aqueous solution were added respectively, heated to 90°C for 30 minutes under stirring, diluted with 300 ml of water and naturally cooled, the product was repeatedly washed with water, and dried at 80°C for 6 hours, to obtain silica aerogel modified low thermal conductivity cotton fiber, which had no difference in appearance from unmodified cotton fiber, and the thermal conductivity coefficient was 0.032 W / m·K.

[0022] Example 2

[0023] In a single-neck flask with mechanical stirring, 3 g of cotton fiber, 0.5 g of silica aerogel and 150 ml of 85% concentration N-methyl morpholine-N-oxide aqueous solution were added respectively, heated to 95°C for 30 minutes under stirring, diluted with 300 ml of water and naturally cooled, the product was repeatedly washed with water, and dried at 80°C for 6 hours, to obtain silica aerogel modified low thermal conductivity cotton fiber, which had no difference in appearance from unmodified cotton fiber, and the thermal conductivity coefficient was 0.028 W / m·K.

[0024] Example 3

[0025] In a single-neck flask with mechanical stirring, 3 g of cotton fiber, 0.5 g of silica aerogel and 150 ml of 75% concentration N-methyl morpholine-N-oxide aqueous solution were added respectively, heated to 85°C for 30 minutes under stirring, diluted with 300 ml of water and cooled naturally, the product was washed with water repeatedly, dried at 80°C for 6 hours, and low thermal conductivity cotton fiber modified by silica aerogel was obtained, which had no difference in appearance from unmodified cotton fiber, and the thermal conductivity coefficient was 0.036 W / m·K.

[0026] Example 4

[0027] In a single-neck flask with mechanical stirring, 3 g of cotton fiber, 0.5 g of silica aerogel and 150 ml of 75% concentration N-methyl morpholine-N-oxide aqueous solution were added respectively, heated to 85°C for 30 minutes under stirring, diluted with 300 ml of water and cooled naturally, the product was washed with water repeatedly, dried at 80°C for 6 hours, and low thermal conductivity cotton fiber modified by silica aerogel was obtained, which had no difference in appearance from unmodified cotton fiber, and the thermal conductivity coefficient was 0.036 W / m·K.

[0028] Example 5

[0029] In a single-neck flask with mechanical stirring, 3 g of cotton fiber, 0.5 g of silica aerogel and 150 ml of 75% concentration N-methyl morpholine-N-oxide aqueous solution were added respectively, heated to 85°C for 30 minutes under stirring, diluted with 300 ml of water and cooled naturally, the product was washed with water repeatedly, dried at 80°C for 6 hours, and low thermal conductivity cotton fiber modified by silica aerogel was obtained, which had no difference in appearance from unmodified cotton fiber, and the thermal conductivity coefficient was 0.036 W / m·K.

[0030] Example 6

[0031] In a single-neck flask with mechanical stirring, 3 g of cotton fiber, 0.5 g of silica aerogel and 150 ml of 75% concentration N-methyl morpholine-N-oxide aqueous solution were added respectively, heated to 85°C for 30 minutes under stirring, diluted with 300 ml of water and cooled naturally, the product was washed with water repeatedly, dried at 80°C for 6 hours, and low thermal conductivity cotton fiber modified by silica aerogel was obtained, which had no difference in appearance from unmodified cotton fiber, and the thermal conductivity coefficient was 0.036 W / m·K.

[0032] Comparative Example 1

[0033] In a single-neck flask with mechanical stirring, 3 g of cotton fiber, 0.5 g of silica aerogel and 150 ml of 70% concentration N-methyl morpholine-N-oxide aqueous solution were added respectively, heated to 95°C for 30 minutes under stirring, diluted with 300 ml of water and naturally cooled, the product was repeatedly washed with water and dried at 80°C for 6 hours, to obtain a product with appearance indistinguishable from unmodified cotton fiber, with thermal conductivity of 0.072 W / m·K.

[0034] Comparative Example 2

[0035] In a single-neck flask with mechanical stirring, 3 g of cotton fiber, 0.5 g of silica aerogel and 150 ml of 90% concentration N-methyl morpholine-N-oxide aqueous solution were added respectively, heated to 85°C for 30 minutes under stirring, diluted with 300 ml of water and naturally cooled, the product was repeatedly washed with water and dried at 80°C for 6 hours, to obtain a product with appearance of powder, with thermal conductivity of 0.026 W / m·K.

[0036] Comparative Example 3

[0037] In a single-neck flask with mechanical stirring, 3 g of cotton fiber, 0.5 g of silica aerogel and 150 ml of 85% concentration N-methyl morpholine-N-oxide aqueous solution were added respectively, heated to 80°C for 30 minutes under stirring, diluted with 300 ml of water and naturally cooled, the product was repeatedly washed with water and dried at 80°C for 6 hours, to obtain a product with appearance indistinguishable from unmodified cotton fiber, with thermal conductivity of 0.066 W / m·K.

[0038] Comparative Example 4

[0039] In a single-neck flask with mechanical stirring, 3 g of cotton fiber, 0.5 g of silica aerogel and 150 ml of 75% concentration N-methyl morpholine-N-oxide aqueous solution were added respectively, heated to 100°C for 30 minutes under stirring, diluted with 300 ml of water and naturally cooled, the product was repeatedly washed with water and dried at 80°C for 6 hours, to obtain a product with appearance of powder, with thermal conductivity of 0.025 W / m·K.

[0040] Figure 1 The field emission scanning electron microscope image and energy spectrum diagram of the product of Example 1. The field emission scanning electron microscope image shows that the product of Example 1 has complete fiber structure in micro-morphology; the energy spectrum diagram detects three elements of carbon, oxygen and silicon, in which the carbon and oxygen elements mainly come from cotton fiber, and the silicon element only comes from silica aerogel, indicating that the product of Example 1 is silica aerogel modified cotton fiber with complete fiber structure.

[0041] Figure 2 The infrared spectrum and X-ray diffraction diagram of the product of Example 1. In the infrared spectrum, 1000 cm -1-1200 cm -1 C-O and C-H characteristic vibration peaks of cellulose of cotton fiber, 1260 cm -1 Si-C characteristic vibration peak of silica aerogel, indicating that the product of Example 1 has both the structure of cellulose of cotton fiber and silica aerogel; in the X-ray diffraction spectrum, 14.94°, 16.46°, 22.72° and 34.26° correspond to 101, 002 and 004 crystal faces of cellulose of cotton fiber respectively, and 20.46° is a characteristic diffuse peak of silica aerogel, indicating that the product of Example 1 has a complete fiber structure of cotton fiber and also has the structure of silica aerogel.

[0042] Figure 3 The field emission scanning electron microscope image and energy spectrum diagram of the product of Comparative Example 1. The field emission scanning electron microscope image shows that the product of Comparative Example 1 has a complete fiber structure in the micro-morphology; in the energy spectrum diagram, carbon and oxygen elements of cotton fiber are detected, and silicon element of silica aerogel is not detected, indicating that the product of Comparative Example 1 is cotton fiber with a complete fiber structure, but the silica aerogel has not modified it.

[0043] Figure 4 The infrared spectrum and X-ray diffraction spectrum of the product of Comparative Example 1. In the infrared spectrum, 1000 cm -1 -1200 cm -1 C-O and C-H characteristic vibration peaks of cellulose of cotton fiber, and no Si-C characteristic vibration peak of silica aerogel is detected, indicating that the product of Comparative Example 1 has the structure of cellulose of cotton fiber, but the silica aerogel has not modified it; in the X-ray diffraction spectrum, 14.94°, 16.46°, 22.72° and 34.26° correspond to 101, 002 and 004 crystal faces of cellulose of cotton fiber respectively, and no characteristic diffuse peak of silica aerogel is detected, indicating that the product of Comparative Example 1 is cotton fiber with a complete fiber structure, but the silica aerogel has not modified it.

[0044] Figure 5 The field emission scanning electron microscope image and energy spectrum diagram of the product of Comparative Example 4. The field emission scanning electron microscope image shows that the product of Comparative Example 4 has a completely destroyed fiber structure in the micro-morphology; in the energy spectrum diagram, carbon, oxygen and silicon elements are detected, in which the carbon and oxygen elements mainly come from cotton fiber, and the silicon element only comes from silica aerogel, indicating that the product of Comparative Example 4 has realized the modification of cotton fiber by silica aerogel, but the fiber structure of cotton fiber has been completely destroyed.

[0045] Figure 6 The infrared spectrum and X-ray diffraction spectrum of the product of Comparative Example 4. In the infrared spectrum, 1000 cm -1 -1200 cm-1 The fine structure of C-O and C-H characteristic vibration peaks of the product of Example 1 completely disappeared, but the characteristic vibration peak of Si-C of the silica aerogel was detected at 1260 cm -1 The Si-C characteristic vibration peak of the silica aerogel was detected, indicating that the product of Comparative Example 4 achieved modification of the cotton fiber by the silica aerogel, but the cellulose structure of the cotton fiber was destroyed; only the characteristic diffraction peak of the silica aerogel at 20.46° was detected in the X-ray diffraction spectrum, and the four characteristic crystal face peaks of the cellulose of the cotton fiber at 14.94°, 16.46°, 22.72° and 34.26° completely disappeared, indicating that the product of Comparative Example 4 achieved modification of the cotton fiber by the silica aerogel, but the fiber structure of the cotton fiber was completely destroyed.

[0046] Although the present application has been illustrated and described with reference to specific embodiments, the foregoing is merely intended to illustrate the best mode of the present application, and is not to be taken in a limiting sense. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A method for preparing low thermal conductivity cotton fiber modified with silica aerogel, characterized in that: Using a specific concentration of N-methylmorpholine-N-oxide aqueous solution as the solvent and silica aerogel as the high-performance thermal insulation material, the cotton fiber was swollen at a specific temperature and reacted with the silica aerogel for 30 minutes. The silica aerogel was then modified onto the surface of the cotton fiber to prepare low thermal conductivity cotton fiber with complete fiber structure.

2. According to claim 1, a method for preparing a low thermal conductivity cotton fiber modified with silica aerogel, characterized in that: include: (1) Cotton fiber, silica aerogel, and a specific concentration of N-methylmorpholine-N-oxide aqueous solution are added to a reactor at the same time, and stirred at a specific temperature for 30 minutes to allow the cotton fiber to swell and react with the silica aerogel; (2) After the reaction is completed, water is added to dilute the N-methylmorpholine-N-oxide aqueous solution to shrink the swollen cotton fibers. After cooling to room temperature, the fibers are washed and dried to obtain silica aerogel-modified low thermal conductivity cotton fibers with complete fiber structure.

3. According to claim 1, it is characterized in that The concentration of the N-methylmorpholine-N-oxide aqueous solution, which can make the cotton fiber swell and react with the silicon oxide aerogel and keep the cotton fiber structure intact, is at least one of 75% and 85%.

4. According to claim 1, it is characterized in that The cotton fibers can be swollen and react with the silica aerogel, and the reaction temperature for maintaining the integrity of the cotton fiber structure is between 85°C and 95°C.

5. A method for preparing low thermal conductivity cotton fiber modified with silica aerogel, characterized in that: The silica aerogel-modified low thermal conductivity cotton fiber material is prepared by the method described in any one of claims 1 to 4.

6. The low thermal conductivity cotton fiber material modified with silica aerogel according to claim 5, characterized in that: The low thermal conductivity cotton fiber material has a complete fiber structure and a thermal conductivity coefficient of 0.036 W / m·K-0.028 W / m·K.

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