A polyacrylonitrile-based double-layered amidoxime-modified functional fiber and its preparation method

Abstract

The present invention relates to a polyacrylonitrile-based double-layer amidoxime-modified functional fiber and a preparation method thereof, belonging to the technical field of functional polymer materials. The modified functional fiber has a double-layer structure, one layer is a fiber layer formed by partial amidoximation of carboxylated polyacrylonitrile fiber, and the other layer is a compound layer formed by partial or complete amidoximation of carboxylated polyacrylonitrile; the connection between the fiber layer and the compound layer is realized by forming amide bonds between two connection sites of the polyamine compound and the carboxyl groups in the fiber layer and the carboxyl groups in the compound layer respectively; the modified functional fiber is prepared by adjusting the pH value of the polyacrylonitrile salt solution and reacting with amino fibers, and then subjecting the obtained double-layer polyacrylonitrile fiber to amidoximation. Since the polyacrylonitrile in the compound layer bears a part of the amidoxime groups, it can protect the main chain of the polyacrylonitrile fiber in the fiber layer, so that the modified functional fiber has good mechanical properties.

Description

Technical Field

[0001] The present invention relates to a polyacrylonitrile-based double-layer amidoxime-modified functional fiber and a preparation method thereof, belonging to the technical field of functional polymer materials. Background Art

[0002] Uranium is an important raw material for nuclear power. The total amount of uranium in seawater is as high as 4.5 billion tons, which is thousands of times the proven uranium reserves on land. Compared with uranium mining on land, uranium extraction from seawater has less impact on the ecological environment.

[0003] Currently, the research on amidoxime-based ion exchange fibers (abbreviation: amidoxime fibers) in the field of uranium extraction from seawater is relatively extensive. Amidoximated polyacrylonitrile fiber is a kind of amidoxime fiber. In the existing amidoximated polyacrylonitrile fiber material, the nitrile group in the polyacrylonitrile fiber is directly converted into an amidoxime group. This fiber material has problems such as poor mechanical properties, curled and hard morphology, and difficulty in forming. Moreover, the higher the content of the amidoxime group for adsorption in the fiber, the worse the mechanical properties of the fiber, the worse the morphology, and the more difficult it is to form, which is more unfavorable for subsequent textile products such as fabrics woven from the fiber. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a polyacrylonitrile-based double-layer amidoxime-modified functional fiber and a preparation method thereof. The modified functional fiber has a double-layer structure, one layer is the main chain of partially amidoximated polyacrylonitrile fiber, and the other layer is partially or fully amidoximated low-molecular-weight polyacrylonitrile. Therefore, the polyacrylonitrile in the outer layer undertakes a part of the amidoxime group with adsorption function and has a protective effect on the main chain in the inner layer. Compared with the prior art, under the same mechanical strength, the modified functional fiber of the present invention has a higher content of amidoxime group, which is beneficial to the improvement of the adsorption function, and its morphology is good, and the fiber does not curl, so the utilization rate of the amidoxime group is good. Due to the good mechanical properties and morphology of the modified functional fiber, it is beneficial to subsequent textile work and can be woven into textile products such as fabrics, having good application prospects.

[0005] To achieve the purpose of the present invention, the following technical solutions are provided.

[0006] A polyacrylonitrile-based double-layer amidoxime-modified functional fiber, the modified functional fiber has a double-layer structure, one layer is a fiber layer formed by partial amidoximation of carboxylated polyacrylonitrile fiber, and the other layer is a compound layer formed by partial or full amidoximation of carboxylated polyacrylonitrile; the connection between the fiber layer and the compound layer is realized by respectively forming amide bonds between two connection sites of the polyamine compound and the carboxyl groups in the fiber layer and the carboxyl groups in the compound layer;

[0007] When the polyamine compound is a compound containing two or more primary amino groups, the linking site is the nitrogen atom in the primary amino group; when the polyamine compound is a compound containing two or more nitrogen heterocycles, the linking site is the nitrogen atom in the nitrogen heterocycle;

[0008] In the compound layer, the carboxylated polyacrylonitrile is prepared by carboxylating polyacrylonitrile powder with an average molecular weight of 2000 - 20000.

[0009] Preferably, in the fiber layer, the carbonyl content is 1 mmol / g - 3 mmol / g.

[0010] A method for preparing the polyacrylonitrile-based double-layer amidoxime modified functional fiber of the present invention, the steps of the method are as follows:

[0011] (1) Add the polyacrylonitrile powder with an average molecular weight of 2000 - 20000 to an alkali solution, stir evenly to obtain a mixed system containing 0.1 wt% - 10 wt% of polyacrylonitrile powder; that is, in the mixed system, the mass fraction of polyacrylonitrile powder is 0.1% - 10%; react at 70°C - 100°C for 0.5 h - 1 h to obtain a polyacrylonitrile acid salt solution, and adjust the pH value of the polyacrylonitrile acid salt solution to 6 - 10 to obtain a reaction solution;

[0012] The alkali solution is an aqueous solution containing 0.5 wt% - 2 wt% of an alkaline substance; that is, in the alkali solution, the mass fraction of the alkaline substance is 0.5% - 2%;

[0013] (2) Mix the reaction solution and the amino fiber in a mass ratio of (10 - 100):1, reflux and react at 80°C - 100°C for 0.5 h - 2 h, take out the reacted fiber, wash it to obtain a double-layer structured polyacrylonitrile fiber;

[0014] The amino fiber is an aminated product after the reaction of carboxylated polyacrylonitrile fiber and the polyamine compound;

[0015] (3) Add the double-layer structured polyacrylonitrile fiber to a mixed solution composed of hydroxylamine hydrochloride, a weak alkaline substance and water, heat and react at 50°C - 100°C for 0.5 h - 2 h, take out the reacted fiber, wash it, and dry it to obtain a polyacrylonitrile-based double-layer amidoxime modified functional fiber;

[0016] In the mixed solution, the molar ratio of hydroxylamine hydrochloride to sodium ion (Na + ) is (1 - 10):1;

[0017] The molar ratio of the double-layer structured polyacrylonitrile fiber to hydroxylamine hydrochloride is 1:(1 - 10).

[0018] Preferably, in step (1), the basic substance is one or more of sodium hydroxide, sodium carbonate, and 1,8-diazabicyclo[5.4.0]undec-7-ene.

[0019] Preferably, in step (3), the weak basic substance is sodium bicarbonate or sodium carbonate.

[0020] In step (1), the polyacrylonitrile powder can be obtained by a conventional method in the art, and can be one of the following methods:

[0021] I. Commercially available homopolymer or copolymer polyacrylonitrile powder;

[0022] II. In the laboratory, polyacrylonitrile powder obtained by polymerizing acrylonitrile, or by polymerizing acrylonitrile with acrylic acid, or by polymerizing acrylonitrile with itaconic acid.

[0023] Preferably, the particle size of the polyacrylonitrile powder is greater than or equal to 80 mesh.

[0024] Preferably, the amino fiber is prepared by the following method: adding carboxylated polyacrylonitrile fiber to an aqueous polyamine solution, reacting at 60 °C to 100 °C for 1 h to 2 h to obtain the amino fiber; based on the total mass of the carboxylated polyacrylonitrile fiber and the aqueous polyamine solution being 100%, the mass fraction of the carboxylated polyacrylonitrile fiber is greater than 0 and less than or equal to 20%;

[0025] The aqueous polyamine solution is an aqueous solution formed by dissolving the polyamine compound in water, wherein the mass fraction of the polyamine compound is 1% to 20%.

[0026] The carboxylated polyacrylonitrile fiber can be obtained by a conventional method in the art, and can be one of the following three methods:

[0027] I. Carboxylated polyacrylonitrile fiber obtained by hydrolyzing polyacrylonitrile fiber;

[0028] II. Carboxylated polyacrylonitrile fiber obtained by polymerizing and spinning acrylonitrile with acrylic acid, or with itaconic acid;

[0029] III. A fiber containing nitrile groups is obtained by polymerizing and spinning acrylonitrile with the corresponding monomer required by the application requirements, and then hydrolyzing to obtain the carboxylated polyacrylonitrile fiber.

[0030] Beneficial effects

[0031] 1. The present invention provides a polyacrylonitrile-based double-layer amidoxime-modified functional fiber. The modified functional fiber has a double-layer structure. One layer is the main chain of partially amidoximated polyacrylonitrile fiber, i.e., the fiber layer, and the other layer is low-molecular-weight polyacrylonitrile that is partially or fully amidoximated, i.e., the compound layer. Therefore, the polyacrylonitrile in the compound layer bears a part of the amidoxime groups and can protect the main chain of the polyacrylonitrile fiber in the fiber layer, making the modified functional fiber have good mechanical properties.

[0032] 2. The present invention provides a polyacrylonitrile-based double-layer amidoxime-modified functional fiber. Compared with the prior art, under the same mechanical strength, the modified functional fiber of the present invention has a higher content of amidoxime groups, which is beneficial to the improvement of the adsorption function, and its morphology is good, and the morphology of the fiber does not curl. Therefore, the utilization rate of the amidoxime groups is good. Since the modified functional fiber of the present invention has good mechanical properties and morphology, it is beneficial to subsequent textile work and can be woven into textiles such as cloth, having good application prospects.

[0033] 3. The present invention provides a preparation method of a polyacrylonitrile-based double-layer amidoxime-modified functional fiber, which is a solid-liquid heterogeneous reaction. Water is used as the reaction solvent during the reaction process, and the reaction solution can be reused. The preparation process is safe, simple, and environmentally friendly, and has a good basis for scale-up production. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is the reaction mechanism diagram of step (1) in Example 1.

[0035] Figure 2 It is the reaction mechanism diagram of preparing amino fiber in Example 1.

[0036] Figure 3 It is the reaction mechanism diagram of step (2) in Example 1.

[0037] Figure 4 It is the reaction mechanism diagram of step (3) in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0038] The present invention will be further described below in conjunction with the drawings and specific embodiments. Among them, the methods are conventional methods unless otherwise specified, and the raw materials can be obtained from public commercial channels or prepared according to the literature unless otherwise specified.

[0039] In the following test examples, the weight gain method was used to measure the content of amidoxime groups in the polyacrylonitrile-based double-layer amidoxime-modified functional fiber prepared in Example 1 and the fiber directly amidoximated with polyacrylonitrile fiber, that is, the fiber reacting with hydroxylamine hydrochloride was measured for its mass before and after the reaction, and the content of amidoxime groups was calculated by formula (I);

[0040]

[0041] Among them, C 偕胺肟 —— The content of amidoxime groups, in mmol / g;

[0042] W 0 —— The mass of the fiber before reaction, in g;

[0043] W 1 —— The mass of the fiber after reaction, in g.

[0044] Example 1

[0045] A method for preparing a polyacrylonitrile-based double-layer amidoxime-modified functional fiber, the steps of the method are as follows:

[0046] (1) Add 10 g of polyacrylonitrile powder with an average molecular weight of 5000 to 100 mL of an aqueous NaOH solution containing 1% by mass fraction, stir evenly to obtain a mixed system, react at 100 °C for 0.5 h to obtain a sodium polyacrylate solution, and adjust the pH value of the sodium polyacrylate solution to 6 with dilute hydrochloric acid with a HCl concentration of 0.1 mol / L to obtain a reaction solution; the particle size of the polyacrylonitrile powder is 100 mesh.

[0047] The reaction mechanism of this step is as Figure 1 shown. The nitrile group in polyacrylonitrile reacts with NaOH to obtain sodium polyacrylate, and then under the adjustment of dilute hydrochloric acid, a reaction solution is obtained. In this example, the reaction solution is a polyacrylonitrile carboxylic acid solution.

[0048] (2) Mix all the reaction solutions prepared in step (1) with 2 g of amino fiber. In this example, the mass ratio of the reaction solution to the amino fiber is 55:1, reflux and react at 100 °C for 2 h, stir the reactants during the reaction process, take out the reacted fiber, and wash it with deionized water to obtain a double-layer polyacrylonitrile fiber.

[0049] In this step, the amino fiber is prepared by amidation of the carboxyl group in the carboxylated polyacrylonitrile fiber. The specific preparation method is: add the carboxylated polyacrylonitrile fiber to an aqueous solution of triethylenetetramine containing 2% by mass fraction. Among them, based on the sum of the mass of the carboxylated polyacrylonitrile fiber and the aqueous solution of triethylenetetramine being 100%, the mass fraction of the carboxylated polyacrylonitrile fiber is 1%; reflux and react at a temperature of 100 °C for 1 h to obtain the amino fiber.

[0050] The carboxylated polyacrylonitrile fiber is prepared by the following method: Add the polyacrylonitrile fiber to an aqueous solution containing 1% by mass fraction of H 2 SO 4In an aqueous sulfuric acid solution, where the mass fraction of polyacrylonitrile fiber is 1% based on the sum of the masses of polyacrylonitrile fiber and the aqueous sulfuric acid solution being 100%; reflux reaction is carried out for 2 h under boiling conditions to obtain the carboxylated polyacrylonitrile fiber, and the carboxyl content of the carboxylated polyacrylonitrile fiber is measured to be 1.5 mmol / g by acid-base titration.

[0051] The reaction mechanism for the preparation of amino fiber is as Figure 2 shown. The carboxyl group in the carboxylated polyacrylonitrile fiber reacts with the amino group at one end of triethylenetetramine to form an amide bond, and the amino fiber is obtained. Figure 2 In 6 H 14 N 2 , Figure 3 and Figure 4 the R in 6 H 14 N 2 is also C

[0052] The reaction mechanism of step (2) in this example is as Figure 3 shown. The amino group in the amino fiber reacts with the carboxyl group in the reaction solution (in this example, the reaction solution is the polyacrylonitrile carboxylic acid solution) to form an amide bond, realizing the grafting of polyacrylonitrile on the amino fiber, and then forming a polyacrylonitrile fiber with a bilayer structure.

[0053] (3) Add the polyacrylonitrile fiber with a bilayer structure prepared in step (2) to a mixed solution composed of hydroxylamine hydrochloride, sodium bicarbonate and deionized water, heat and react at 100 °C for 2 h, take out the reacted fiber, wash and dry to obtain a polyacrylonitrile-based bilayer amidoxime modified functional fiber;

[0054] In the mixed solution, the concentrations of hydroxylamine hydrochloride and sodium bicarbonate are both 1 mol / L;

[0055] The molar ratio of the polyacrylonitrile fiber with a bilayer structure to hydroxylamine hydrochloride is 1:1.

[0056] The reaction mechanism of step (3) in this example is as Figure 4 shown. The nitrile group in the polyacrylonitrile fiber with a bilayer structure reacts with hydroxylamine hydrochloride to obtain an amidoxime group, and thus the obtained polyacrylonitrile-based bilayer amidoxime modified functional fiber is obtained.

[0057] Take 0.2 g of the polyacrylonitrile-based double-layer amidoxime modified functional fiber prepared in this example, place it in 50 mL of uranyl nitrate aqueous solution with a concentration of 1 mg / L containing uranyl ions, shake and adsorb for 1 h at room temperature. After the shaking adsorption is completed, soak the modified functional fiber in 30 mL of nitric acid aqueous solution with a concentration of 1 mol / L for 1 h, then take out the fiber, and use an inductively coupled plasma mass spectrometer (ICP-MS) with the model ICPMS-2030Series from Shimadzu Corporation to test the concentration of uranyl ions in the soaked nitric acid aqueous solution, and then calculate that the adsorption amount of uranyl ions per unit mass of the modified functional fiber is 8 mg / g; according to the reaction mechanism of the present invention and the above test results, it shows that the polyacrylonitrile-based double-layer amidoxime modified functional fiber is prepared in Example 1, and this fiber has good adsorption performance for uranyl ions.

[0058] Comparative Example 1

[0059] A method for directly amidoximating polyacrylonitrile fiber with hydroxylamine hydrochloride solution to obtain an amidoxime fiber, specifically as follows:

[0060] Put 2.0 g of polyacrylonitrile fiber with dry weight into 100 mL of hydroxylamine hydrochloride aqueous solution with a concentration of 20 g / L to obtain a mixed system, then adjust the pH value of the mixed system to 6 with sodium carbonate, and then heat and react in a water bath at 80 °C for 1 h. Take out the reacted fiber, wash it with deionized water, and dry it at 35 °C to obtain an amidoxime fiber, that is, the fiber obtained by directly amidoximating polyacrylonitrile fiber.

[0061] Test Example 1

[0062] Use a fiber strength and elongation tester with the model XQ-1AN from Shanghai Xinqian Instrument Co., Ltd. to test the breaking strength of the polyacrylonitrile-based double-layer amidoxime modified functional fiber prepared in Example 1 and the amidoxime fiber prepared in Comparative Example 1 respectively.

[0063] The content of amidoxime groups in the polyacrylonitrile-based double-layer amidoxime modified functional fiber prepared in Example 1 and the amidoxime fiber prepared in Comparative Example 1 is both 4.5 mmol / g, and the test results of their breaking strengths are as follows:

[0064] The breaking strength of the polyacrylonitrile-based double-layer amidoxime modified functional fiber prepared in Example 1 is 9.68 cN;

[0065] The breaking strength of the amidoxime fiber prepared in Comparative Example 1 is 7.90 cN;

[0066] It can be seen from this that under the same content of amidoxime groups, the mechanical strength of the polyacrylonitrile-based double-layer amidoxime modified functional fiber prepared in Example 1 is better than that of the fiber obtained by directly amidoximating polyacrylonitrile fiber.

[0067] In addition, the morphology of the fiber obtained by directly amidoximating polyacrylonitrile fiber shows curling and dry hardness; the polyacrylonitrile-based double-layer amidoxime-modified functional fiber obtained in Example 1 has a good morphology, the fiber does not curl, and the appearance is smooth. Therefore, from the perspective of morphology, the polyacrylonitrile-based double-layer amidoxime-modified functional fiber in Example 1 is more conducive to direct textile forming.

[0068] In summary, the polyacrylonitrile-based double-layer amidoxime-modified functional fiber prepared in Example 1 has good adsorption performance for uranyl ions, good mechanical properties and morphology, is conducive to subsequent textile work, and can be woven into textiles such as cloth, having good application prospects.

[0069] The present invention includes but is not limited to the above embodiments. Any equivalent replacement or partial improvement carried out under the principle of the spirit of the present invention will be regarded as within the protection scope of the present invention.

Claims

1. A polyacrylonitrile-based double-layer amidoxime-modified functional fiber, characterized in that: The modified functional fiber has a double-layer structure, one layer is a fiber layer formed by partial amidoximation of carboxylated polyacrylonitrile fiber, and the other layer is a compound layer formed by partial or complete amidoximation of carboxylated polyacrylonitrile; through two connection sites of the polyamine compound to form amide bonds with the carboxyl groups in the fiber layer and amide bonds with the carboxyl groups in the compound layer respectively, the connection between the fiber layer and the compound layer is realized; When the polyamine compound is a compound containing two or more primary amino groups, the connection site is the nitrogen atom in the primary amino group; when the polyamine compound is a compound containing two or more nitrogen heterocycles, the connection site is the nitrogen atom in the nitrogen heterocycle; In the compound layer, the carboxylated polyacrylonitrile is prepared by carboxylating polyacrylonitrile powder with an average molecular weight of 2000 - 20000.

2. A polyacrylonitrile-based double-layer amidoxime-modified functional fiber according to claim 1, characterized in that: In the fiber layer, the carbonyl content is 1 mmol / g - 3 mmol / g.

3. A preparation method of a polyacrylonitrile-based double-layer amidoxime-modified functional fiber as claimed in claim 1 or 2, characterized in that: The method steps are as follows: (1) Add the polyacrylonitrile powder with an average molecular weight of 2000 - 20000 to an aqueous solution containing 0.5 wt% - 2 wt% of an alkaline substance, stir evenly to obtain a mixed system containing 0.1 wt% - 10 wt% of polyacrylonitrile powder; react at 70°C - 100°C for 0.5 h - 1 h to obtain a polyacrylonitrile salt solution, adjust its pH value to 6 - 10 to obtain a reaction solution; (2) Mix the reaction solution with the amino fiber in a mass ratio of (10 - 100):1, reflux and react at 80°C - 100°C for 0.5 h - 2 h, wash the reacted fiber to obtain a double-layer structured polyacrylonitrile fiber; The amino fiber is an aminated product after the reaction of carboxylated polyacrylonitrile fiber with the polyamine compound; (3) Add the double-layer structured polyacrylonitrile fiber to a mixed solution composed of hydroxylamine hydrochloride, a weak alkaline substance and water, heat and react at 50°C - 100°C for 0.5 h - 2 h, wash the reacted fiber and dry it to obtain a polyacrylonitrile-based double-layer amidoxime-modified functional fiber; In the mixed solution, the molar ratio of hydroxylamine hydrochloride to Na + is (1 - 10):1; The molar ratio of the double-layer structured polyacrylonitrile fiber to hydroxylamine hydrochloride is 1:(1 - 10).

4. A preparation method of a polyacrylonitrile-based double-layer amidoxime-modified functional fiber according to claim 3, characterized in that: In step (1), the alkaline substance is one or more of sodium hydroxide, sodium carbonate and diazabicyclo.

5. A preparation method of a polyacrylonitrile-based double-layer amidoxime-modified functional fiber according to claim 4, characterized in that: In step (3), the weak alkaline substance is sodium bicarbonate or sodium carbonate.

6. A preparation method of a polyacrylonitrile-based double-layer amidoxime-modified functional fiber according to claim 5, characterized in that: The particle size of the polyacrylonitrile powder is greater than or equal to 80 mesh.

7. The preparation method of a polyacrylonitrile-based double-layer amidoxime modified functional fiber according to claim 6, characterized in that: the amino fiber is prepared by the following method: adding carboxylated polyacrylonitrile fiber into polyamine aqueous solution, reacting at 60°C to 100°C for 1h to 2h to obtain the amino fiber; based on the total mass of carboxylated polyacrylonitrile fiber and polyamine aqueous solution being 100%, the mass fraction of carboxylated polyacrylonitrile fiber is greater than 0 and less than or equal to 20%; the polyamine aqueous solution is an aqueous solution formed by dissolving the polyamine compound in water, wherein the mass fraction of the polyamine compound is 1% to 20%.

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