A method for improving the carbon yield of viscose-based carbon fiber

Abstract

The present invention belongs to the field of new material technology, and relates to the preparation of carbon fiber, and specifically to a method for improving the carbon yield of viscose-based carbon fiber. The method comprises the following steps: (1) soaking the viscose yarn in water at 80 to 90°C, ultrasonically cleaning it after soaking, and then soaking it in triethanolamine and diammonium phosphate solution in turn for catalytic treatment; (2) drying the catalytically treated viscose yarn, and then pre-oxidizing and stretching it at 220 to 280°C to obtain pre-oxidized yarn; (3) carbonizing and stretching the pre-oxidized yarn in a nitrogen atmosphere, and then cooling it to room temperature to obtain viscose-based carbon fiber. The present invention inhibits the production of L-glucose tar substances during the pre-oxidation and carbonization process, reduces the amount of tar during fiber carbonization, thereby reducing the decomposition loss of carbon and improving the carbon yield of viscose-based carbon fiber.

Description

Technical Field

[0001] The invention belongs to the technical field of new materials, relates to the preparation of carbon fibers, and specifically relates to a method for improving the carbon yield of viscose-based carbon fibers. Background Art

[0002] Carbon fiber is a fiber material with a carbon content of more than 90%. It has the properties of "lightweight and high strength", high temperature resistance, corrosion resistance, good electrical and thermal conductivity, etc. It is widely used in many fields. Viscose fiber is a regenerated cellulose fiber. It is made from natural fibers such as wood, hemp and cotton through pulping, sulfonation, aging and spinning. Its chemical formula is (C6H 10 O5)n, carbon content is 44.4%, oxygen content is 49.39%, and hydrogen content is 6.17%. The theoretical carbon yield of viscose-based carbon fiber is 44.4%, but in the production process, due to the presence of impurities such as oil agent on the surface of the raw silk and the production of by-product levulose tar at high temperature, the decomposition loss of carbon increases and the carbon yield decreases. The theoretical carbon yield is far from the actual production carbon yield.

[0003] During the production process, viscose yarn usually needs to be oiled and sized before processing to reduce static friction and improve spinnability and performance. At the same time, a small amount of impurities such as alkali metals will inevitably remain in the viscose yarn during production. In the preparation method of viscose-based carbon fiber proposed by China Publication No. CN116427058A, the method for removing impurities is to simply treat the impurities by hot water rinsing, and the yield of the prepared carbon fiber is not ideal.

[0004] When preparing viscose-based carbon fibers, a catalyst needs to be used to pre-treat the viscose filaments to reduce the generation of by-products. In the preparation method for preparing viscose-based carbon fibers proposed in China Publication No. CN101158063A, an inorganic catalyst is used to pre-treat the viscose filaments. In the production process, the inorganic catalyst is easily loaded on the fiber surface and is difficult to penetrate into the fiber core, resulting in reduced carbon fiber performance and carbon yield.

[0005] At present, there is an urgent need to provide a more effective method for improving the carbon yield of viscose-based carbon fibers. The present invention uses organic and inorganic catalysts to synergistically pretreat the precursor, thereby improving the carbon yield of viscose-based carbon fibers. Summary of the invention

[0006] In view of the problems and shortcomings of the prior art, the present invention provides a method for improving the carbon yield of viscose-based carbon fibers.

[0007] Based on the above purpose, the present invention adopts the following technical solution:

[0008] The present invention provides a method for improving the carbon yield of viscose-based carbon fibers, comprising the following steps:

[0009] (1) Soak the viscose thread in water at 80-90°C, perform ultrasonic cleaning after soaking, and then soak it in triethanolamine and diammonium dihydrogen phosphate solutions in turn for catalytic treatment;

[0010] (2) drying the catalytically treated viscose yarn, and then pre-oxidizing and drawing it at 220-280° C. to obtain pre-oxidized yarn;

[0011] (3) The pre-oxidized fiber is carbonized and stretched in a nitrogen atmosphere, and then cooled to room temperature to obtain viscose-based carbon fiber.

[0012] Preferably, the step (1) is sequentially immersed in triethanolamine and diammonium phosphate solutions, wherein the triethanolamine is immersed at room temperature for 0.5 to 1.5 hours, and the diammonium phosphate solution is immersed at 60 to 80° C. for 0.5 to 1.5 hours. Furthermore, the concentration of the diammonium phosphate solution is 5wt% to 15wt%.

[0013] Preferably, the carbonization treatment temperature in step (3) is 1000-1200°C

[0014] Preferably, the soaking time in water in step (1) is 25 to 30 minutes.

[0015] Preferably, the ultrasonic cleaning power in step (1) is 240 to 480 W, and the time is 2 to 8 min.

[0016] Preferably, the drying temperature in step (2) is 70-100°C.

[0017] Preferably, the pre-oxidation in step (2) is carried out in an air atmosphere.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The present invention uses organic and inorganic catalysts to catalyze the viscose yarn. The hydroxyl end group of triethanolamine has great activity and can form intermolecular hydrogen bonds with a large number of hydroxyl groups in the viscose fiber molecules at room temperature, thereby destroying the original intramolecular bonds of cellulose and making the cellulose macromolecules in an open (swelling) state, making it easy for the inorganic ammonium salt catalyst molecules to penetrate into the fiber core, thus avoiding the inorganic catalyst being loaded only on the fiber surface, thereby improving the uniformity of the inorganic catalyst dispersion inside and outside the fiber; inhibiting the generation of L-glucose tar substances during the pre-oxidation and carbonization process, reducing the amount of tar during fiber carbonization, thereby reducing the decomposition loss of carbon and improving the carbon yield of viscose-based carbon fibers; making the thermal decomposition of viscose fibers proceed in a wider temperature range and at a relatively low temperature, resulting in a longer oxidation decomposition time and a reduction in hole defects on the fiber surface.

[0020] 2. The present invention rinses the viscose yarn with hot water to remove the oil and impurities on the surface of the viscose yarn, and then uses ultrasonic cleaning to act on the surface of the viscose yarn with high-frequency vibration and powerful shock waves, which helps to completely remove impurities attached to the fiber. It can more efficiently and thoroughly remove impurities on the surface of the viscose yarn, improve the purity of the raw yarn, and make the raw yarn better impregnated and catalyzed.

[0021] 3. The present invention stretches the viscose yarn during the pre-oxidation process, and the shrinkage of the viscose yarn in a hot oxygen environment can be reduced by stretching; the viscose yarn is stretched during the carbonization process, and the stretching can improve the orientation of the fiber along the fiber direction, reduce the formation of fiber defects, and thus improve the carbon yield and strength of the carbon fiber. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the present invention clearer and more specific, the present invention is further described in detail by examples below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] Example 1

[0024] A viscose-based carbon fiber, and a preparation method thereof, the specific steps are as follows:

[0025] (1) Soak the viscose thread in 90°C water for 30 minutes, put it in an ultrasonic cleaning machine, and perform ultrasonic cleaning at 360W for 4 minutes, then soak it in triethanolamine at room temperature for 1 hour, and then soak it in a 5wt% diammonium dihydrogen phosphate solution at 70°C for 1 hour for catalytic treatment;

[0026] (2) placing the catalytically treated viscose yarn in an oven at 80°C for drying, and then placing it in a pre-oxidation furnace for pre-oxidation at 250°C in an air atmosphere and stretching to obtain pre-oxidized yarn;

[0027] (3) The pre-oxidized fiber is placed in a carbonization furnace, carbonized at 1000°C in a nitrogen atmosphere and stretched, and then cooled to room temperature to obtain viscose-based carbon fiber.

[0028] Example 2

[0029] A viscose-based carbon fiber, whose components and preparation method are basically the same as those in Example 1, except that the concentration of the diammonium dihydrogen phosphate solution is 10wt%.

[0030] Example 3

[0031] A viscose-based carbon fiber, whose components and preparation method are basically the same as those in Example 1, except that the concentration of the diammonium dihydrogen phosphate solution is 15wt%.

[0032] Comparative Example 1

[0033] A viscose-based carbon fiber, and a preparation method thereof, the specific steps are as follows:

[0034] (1) Soak the viscose thread in 90°C water for 30 minutes. After soaking, put it into an ultrasonic cleaning machine and perform ultrasonic cleaning at 360W for 4 minutes;

[0035] (2) placing the viscose yarn after ultrasonic cleaning in an oven to dry at 80°C, and then placing it in a pre-oxidation furnace, pre-oxidizing it at 250°C in an air atmosphere and stretching it to obtain pre-oxidized yarn;

[0036] (3) The pre-oxidized fiber is placed in a carbonization furnace, carbonized at 1000°C in a nitrogen atmosphere and stretched, and then cooled to room temperature to obtain viscose-based carbon fiber.

[0037] Comparative Example 2

[0038] A viscose-based carbon fiber, and a preparation method thereof, the specific steps are as follows:

[0039] (1) Soak the viscose yarn in 90°C water for 30 minutes, put it into an ultrasonic cleaning machine, and perform ultrasonic cleaning at 360W for 4 minutes, and then soak it in a 10wt% diammonium phosphate solution at 70°C for 1 hour for catalytic treatment;

[0040] (2) placing the catalytically treated viscose yarn in an oven at 80°C for drying, and then placing it in a pre-oxidation furnace for pre-oxidation at 250°C in an air atmosphere and stretching to obtain pre-oxidized yarn;

[0041] (3) The pre-oxidized fiber is placed in a carbonization furnace, carbonized at 1000°C in a nitrogen atmosphere and stretched, and then cooled to room temperature to obtain viscose-based carbon fiber.

[0042] Comparative Example 3

[0043] A viscose-based carbon fiber, and a preparation method thereof, the specific steps are as follows:

[0044] (1) Soak the viscose thread in 90°C water for 30 minutes. After soaking, put it in an ultrasonic cleaning machine and perform ultrasonic cleaning at 360W for 4 minutes. Then, soak it in triethanolamine at room temperature for 1 hour for catalytic treatment.

[0045] (2) placing the catalytically treated viscose yarn in an oven at 80°C for drying, and then placing it in a pre-oxidation furnace for pre-oxidation at 250°C in an air atmosphere and stretching to obtain pre-oxidized yarn;

[0046] (3) The pre-oxidized fiber is placed in a carbonization furnace, carbonized at 1000°C in a nitrogen atmosphere and stretched, and then cooled to room temperature to obtain viscose-based carbon fiber.

[0047] The carbon yields of the viscose-based carbon fibers prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were measured, and the measurement results are shown in Table 1.

[0048]

[0049] As can be seen from Table 1, the carbon fiber yield of the viscose yarn in Comparative Example 1 was only 19.76% when it was not pretreated. The carbon fiber yield was improved when triethanolamine and diammonium phosphate were used to pretreat the viscose yarn in Comparative Examples 2-3. In Examples 1-3, triethanolamine and diammonium phosphate were used to pretreat the viscose yarn in coordination. Triethanolamine formed intermolecular hydrogen bonds with a large number of hydroxyl groups rich in viscose fiber molecules, so that the cellulose macromolecules were in a swollen state, and the diammonium phosphate molecules were easily immersed in the fiber core. Therefore, the catalytic efficiency was improved, the generation of by-products during the pre-oxidation and carbonization process was reduced, and finally the carbon yield of viscose-based carbon fibers was significantly improved.

[0050] The above is a description of a preferred embodiment of the present invention, but it should be understood that the invention is not limited to the contents disclosed herein. As long as non-substantial improvements are made using the method concept and technical solution of the present invention, or the method concept and technical solution of the present invention are applied to other occasions, they are all within the scope of protection of the present invention.

Claims

1. A method for improving the carbon yield of viscose-based carbon fibers, characterized in that: The following steps are involved: (1) Soak the viscose yarn in water at 80-90°C, perform ultrasonic cleaning after soaking, and then soak it in triethanolamine and diammonium dihydrogen phosphate solutions in turn for catalytic treatment; (2) drying the catalytically treated viscose yarn, and then pre-oxidizing and drawing it at 220-280° C. to obtain pre-oxidized yarn; (3) The pre-oxidized fiber is carbonized and stretched in a nitrogen atmosphere, and then cooled to room temperature to obtain a viscose-based carbon fiber; The step (1) is sequentially immersed in triethanolamine and diammonium phosphate solutions, wherein the triethanolamine is immersed at room temperature for 0.5 to 1.5 hours, and the diammonium phosphate solution is immersed at 60 to 80° C. for 0.5 to 1.5 hours; The concentration of the diammonium phosphate solution is 5wt% to 15wt%.

2. The method for improving the carbon yield of viscose-based carbon fibers according to claim 1, characterized in that: The carbonization treatment temperature in step (3) is 1000-1200°C.

3. The method for improving the carbon yield of viscose-based carbon fibers according to claim 1, characterized in that: The soaking time in water in step (1) is 25 to 30 minutes.

4. The method for improving the carbon yield of viscose-based carbon fibers according to claim 3, characterized in that: The ultrasonic cleaning power in step (1) is 240 to 480 W, and the time is 2 to 8 minutes.

5. The method for improving the carbon yield of viscose-based carbon fibers according to claim 1, characterized in that: The drying temperature in step (2) is 70-100°C.

6. The method for improving the carbon yield of viscose-based carbon fibers according to claim 5, characterized in that: The pre-oxidation in step (2) is carried out in an air atmosphere.

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