Method for reducing residual quantity of viscose sulfide in fiber processing

Abstract

The invention belongs to the field of fiber processing, and particularly relates to a method for reducing residual quantity of viscose sulfide in fiber processing, which comprises the following steps: adding water into a viscose sulfur and smell removal agent to prepare liquid with the mass percent of 0.5-2.5%, and then adjusting the pH value to 8.5-10.5 to obtain sulfur removal agent treatment liquid; after the sulfur removal agent treatment liquid is heated to 78 + / -10 DEG C, the sulfur removal agent treatment liquid serves as a first water bath, viscose fibers are guided into the water bath to be soaked, and the soaking time is 1-3 min; the viscose fiber desulfurizing and deodorizing agent is prepared from a hydrotalcite catalyst and alkali metal oxide. Viscose fibers processed by the method are low in residual sulfur content and free of peculiar smell.

Description

Technical Field

[0001] This invention belongs to the field of fiber processing, and specifically relates to a method for reducing the residual amount of sulfides in viscose fibers during fiber processing. Background Technology

[0002] Viscose fiber is an important type of regenerated cellulose fiber, widely used in textiles, clothing, and home textiles due to its excellent moisture absorption, breathability, and dyeability. During the production of viscose fiber, carbon disulfide (CS2) is used as a solvent, inevitably resulting in a certain amount of sulfides remaining in the fiber, mainly in the form of hydrogen sulfide (H2S) and carbon disulfide (CS2). These sulfide residues not only produce a pungent odor, affecting the sensory quality of the fiber, but also pose potential hazards to human health and the environment. For example, hydrogen sulfide is a toxic gas that can damage the respiratory and nervous systems with prolonged exposure; carbon disulfide is irritating and can harm the skin and eyes. Furthermore, sulfide residues also affect the dyeing properties and subsequent processing performance of viscose fiber.

[0003] Currently, the main methods for reducing the residual amount of sulfides in viscose fibers include: 1) Strengthening desulfurization during the spinning process: For example, patent CN201810460170.6, which involves extending the residence time of fibers in the spinning bath, increasing the spinning bath temperature, and increasing the concentration of desulfurizing agent. However, these methods often lead to problems such as decreased fiber strength and reduced production efficiency.

[0004] 2) Post-treatment of finished fiber products: For example, oxidizing agents (such as hydrogen peroxide or sodium hypochlorite, which oxidize sulfides to sulfates effectively but cause significant damage to the fibers), reducing agents (such as sodium sulfite, which reduce sulfides to elemental sulfur or hydrogen sulfide), or alkali treatment (which dissolves sulfides, but wastewater treatment is costly) can be used to treat the finished fiber products to remove residual sulfides. However, these methods are usually complex, costly, and may adversely affect fiber properties.

[0005] Therefore, developing an efficient, environmentally friendly, and low-cost method for deodorizing viscose fibers is of great practical significance.

[0006] Invention CN111545162B, entitled "A Sulfur Dioxide Adsorbent and Its Preparation Method," provides a method for preparing a sulfur dioxide adsorbent. The method includes: dissolving 0.5g-15g of an oxidized metal salt, 0.5g-15g of a transition metal salt, and 0.01g-5g of an alkali metal salt in water to obtain a mixed salt solution; mixing 65g-99g of a magnesium-aluminum compound and 0.5g-5g of an extrusion aid with the mixed salt solution to obtain an intermediate material; kneading and extruding the intermediate material, followed by drying and calcination to obtain the sulfur dioxide adsorbent. The magnesium-aluminum compound is magnesium aluminum hydrotalcite. The alkali metal salt is selected from at least one of lithium chloride, sodium chloride, sodium sulfate, and potassium chloride. This sulfur dioxide adsorbent is used for gas adsorption in a dry state. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method for reducing the residual amount of sulfides in viscose fibers during fiber processing, thereby achieving the goal of reducing the residual amount of sulfides in viscose fibers.

[0008] To solve the above-mentioned technical problems, the present invention provides a method for reducing the residual amount of sulfur compounds in viscose fibers during fiber processing. The method involves adding water to a viscose fiber desulfurizing and deodorizing agent to prepare a liquid (suspension) with a mass percentage of 0.5% to 2.5%, and then adjusting the pH value to 8.5 to 10.5 to obtain a desulfurizing agent treatment solution. After heating the above desulfurizing agent solution to 78±10℃, it is used as the first water washing bath (the first water washing bath after fiber formation on the viscose fiber production line, i.e., for the first water washing). The viscose fiber is immersed in this water washing bath for 1~3 minutes (preferably 1.5 minutes). The viscose fiber desulfurization and deodorization agent (a desulfurization agent that reduces the residual amount of sulfides in viscose fibers) is composed of hydrotalcite catalyst and alkali metal oxides; The mass ratio of hydrotalcite catalyst to alkali metal oxide is 3~10:1 (preferably 3~9:1).

[0009] Note: The pH value mentioned above can be adjusted, for example, using 1 M sodium hydroxide.

[0010] As an improvement to the method for reducing the residual amount of sulfides in viscose fibers during fiber processing according to the present invention: the hydrotalcite catalyst is magnesium aluminum hydrotalcite, wherein the molar ratio of magnesium to aluminum in the magnesium aluminum hydrotalcite is 3~7:1 (preferably 3~6:1).

[0011] As a further improvement to the method for reducing the residual amount of sulfides in viscose fibers during fiber processing of the present invention, the alkali metal oxide is at least one of CaO and MgO.

[0012] As a further improvement to the method for reducing the residual sulfur content of viscose fibers in fiber processing according to the present invention: the viscose fiber desulfurization and deodorization agent is composed of Mg6Al2(OH) 16 It is composed of CO3·4H2O and MgO, Mg6Al2(OH) 16 The mass ratio of CO3·4H2O to MgO is 5:1.

[0013] The working principle of the desulfurizing agent of this invention is as follows: using magnesium aluminum hydrotalcite catalyst, the residual sulfides (H2S, CS2) on the fiber (viscose fiber) are hydrolyzed into H2S in the water bath, and then the alkali metal oxide reacts with H2S to generate precipitate, thereby removing the volatile sulfides on the fiber in the water bath, and finally reducing the residual sulfur content of the fiber and removing the odor of the fiber.

[0014] This invention reduces the residual sulfur content in fibers by scientifically designing the desulfurizing agent formula and rationally applying desulfurization process conditions and treatment stages, thereby efficiently catalyzing the degradation and absorption of sulfides. The treatment stage specified in this invention is a fiber water washing bath (one-water wash), with a treatment time of 1-3 minutes. The desulfurizing agent of this invention (viscose fiber desulfurizing and deodorizing agent) is highly efficient and environmentally friendly, and can be directly used in conventional viscose fiber production lines. Viscose fibers processed using the method of this invention have low residual sulfur content and no odor, making them suitable for various nonwoven fabrics and medical supplies fields, exhibiting significant performance advantages. Detailed Implementation

[0015] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto: In this invention, the preparation of viscose fiber adopts a conventional production process, namely, the following steps are performed in sequence: cellulose pulp → alkalization → xanthation → dissolution → aging → filtration → spinning → fiber formation → drawing → first water washing (in a first water washing bath) → desulfurization → second water washing → bleaching → third water washing → drying → finished product storage.

[0016] The improvement of this invention is that a viscose fiber desulfurizing and deodorizing agent is prepared by adding water to a water wash to form a liquid with a mass percentage of 0.5% to 2.5%.

[0017] Generally speaking: Desulfurization: Use a 1.8 g / L sodium hydroxide aqueous solution at a temperature of 75~80℃; immerse the solution by guiding the wire roller and remove it after 30 seconds.

[0018] Second wash: Water with a pH of 8-9 and a temperature of 65-70℃ is used; the water is immersed in the water by the guide roller and treated for 15-20 seconds before being removed.

[0019] Bleaching: Sodium hypochlorite at a concentration of 5.0 g / L is used; the solution is immersed in the solution by the guide roller and then removed after 30 seconds.

[0020] Three-water wash: A citric acid aqueous solution with pH 5-6 is used. The solution is immersed in the solution by the guide roller and treated for 15-20 seconds before being removed.

[0021] Drying: After mechanical extrusion and dehydration, heat-dry at 110℃ for 5 minutes.

[0022] In this invention, the magnesium aluminum hydrotalcite used is: Magnesium aluminum hydrotalcite with a magnesium / aluminum molar ratio of 6:1, such as TMZ-05 magnesium aluminum hydrotalcite (Shanxi Tengmao Technology Co., Ltd.). Magnesium-aluminum hydrotalcite with a magnesium / aluminum molar ratio of 3.2:1, such as FM-300 magnesium-aluminum hydrotalcite (Jingjiang Kanggaote New Material Technology Co., Ltd.). The structural formula is Mg6Al2(OH). 16 CO3·4H2O, magnesium aluminum hydrotalcite with a magnesium / aluminum molar ratio of 3:1, such as H302201 magnesium aluminum hydrotalcite (Shanghai Aladdin Biochemical Technology Co., Ltd.). DHT-4A magnesium-aluminum hydrotalcite with a magnesium / aluminum molar ratio of 1:3 (Shenzhen Longlifeng Materials Co., Ltd.); The structural formula is Mg4Al2(OH). 12 CO3·3H2O, HT-1 magnesium aluminum hydrotalcite with a magnesium / aluminum molar ratio of 2:1 (Sakai Chemical Co., Ltd., Japan).

[0023] Example 1: A desulfurizing and deodorizing agent for viscose fibers (a desulfurizing agent that reduces the residual amount of sulfides in viscose fibers, hereinafter referred to as a desulfurizing agent): Magnesium aluminum hydrotalcite (magnesium / aluminum molar ratio of 6:1) and CaO were weighed out at a mass ratio of 9:1 and mixed evenly to form a desulfurizing agent.

[0024] Experiment 1: The desulfurizing agent obtained in Example 1 was mixed with water to prepare a liquid (suspension) with a mass percentage of 0.5%, and the pH value was adjusted to 10.5 (for example, using 1 M sodium hydroxide) to obtain the desulfurizing agent treatment solution.

[0025] The only difference between this process and the conventional production process for viscose fiber preparation is that a desulfurizing agent solution is used during the "first wash." The desulfurizing agent solution is heated to 78°C and then introduced into the first wash tank. The temperature of the wash is maintained at 78°C as per standard settings. The viscose fiber is immersed in the first wash tank for 90 seconds, also a standard setting.

[0026] Example 2: A viscose fiber desulfurization and deodorization agent (hereinafter referred to as desulfurizer): Magnesium aluminum hydrotalcite (magnesium / aluminum molar ratio of 3.2:1) and CaO were weighed out at a mass ratio of 7:1 and mixed evenly to form a desulfurizing agent.

[0027] Experiment 2: The desulfurizing agent obtained in Example 2 was mixed with water to prepare a liquid with a mass percentage of 1.2%, and the pH value was adjusted to 10.2 to obtain the desulfurizing agent treatment solution.

[0028] The rest is the same as Experiment 1.

[0029] Example 3: A viscose fiber desulfurization and deodorization agent (hereinafter referred to as desulfurizer): Weigh out magnesium aluminum hydrotalcite (Mg6Al2(OH)) at a mass ratio of 5:1. 16 CO3·4H2O (with a magnesium / aluminum molar ratio of 3:1) and MgO are mixed evenly to form a desulfurizing agent.

[0030] Experiment 3: The desulfurizing agent obtained in Example 3 was mixed with water to prepare a liquid with a mass percentage of 2.0%, and the pH value was adjusted to 9.8 to obtain the desulfurizing agent treatment solution.

[0031] The rest is the same as Experiment 1.

[0032] Example 4: A desulfurizing and deodorizing agent for viscose fibers (hereinafter referred to as desulfurizer): Weigh out magnesium aluminum hydrotalcite (Mg6Al2(OH)) at a mass ratio of 3:1. 16 CO3·4H2O (with a magnesium / aluminum molar ratio of 3:1) and MgO are mixed evenly to form a desulfurizing agent.

[0033] Experiment 4: The desulfurizing agent obtained in Example 4 was mixed with water to prepare a liquid with a mass percentage of 2.5%, and the pH value was adjusted to 8.5 to obtain the desulfurizing agent treatment solution.

[0034] The rest is the same as Experiment 1.

[0035] Example 5: A viscose fiber desulfurization and deodorization agent (hereinafter referred to as desulfurizer): Magnesium aluminum hydrotalcite (magnesium / aluminum molar ratio of 6:1) and CaO were weighed out at a mass ratio of 4:1 and mixed evenly to form a desulfurizing agent.

[0036] Experiment 5: The desulfurizing agent obtained in Example 5 was mixed with water to prepare a liquid with a mass percentage of 2.5%, and the pH value was adjusted to 8.5 to obtain the desulfurizing agent treatment solution.

[0037] The rest is the same as Experiment 1.

[0038] The fiber products obtained from the above experiments were tested for residual sulfur content according to FZ / T 50014-2008; the residual amounts of H2S and CS2 in the fibers were tested according to the method described in patent 202411993331X (for example, refer to Example 2); the odor of the fibers was evaluated according to the subjective evaluation method: about 5 g of fiber was placed in a 150 mL water cup, 70 mL of hot water at 65°C was added to the cup, and the smell emitted from the cup was immediately smelled with the nose about 20 mm away from the mouth of the cup.

[0039] The test results are shown in Table 1. The residual sulfur content of all fibers obtained in the experiments was below 5.3 mg / 100g, far below the national standard GB / T 14463-2022's limit of 12.0 mg / 100g for superior grade viscose fiber. After soaking in hot water, the fibers showed no obvious odor. In contrast, the viscose fibers produced without this desulfurizing agent (the first wash used a conventional alkaline hot water bath at 78℃ and pH 10, with the fibers soaked for 1.5 min; the rest of the experiment was the same as described in this invention) had measured residual sulfur, volatile sulfur oxide (H2S) residue, and CS2 residue values ​​of 8.8 mg / 100g, 0.008 μg / g, and 0.035 μg / g, respectively. Furthermore, the viscose fibers produced without this desulfurizing agent had a very noticeable odor. Therefore, this desulfurizing agent has a significant deodorizing effect.

[0040] Table 1. Properties of the fibers obtained in Experiments 1-5

[0041] Comparative Example 1: The mass ratio of magnesium aluminum hydrotalcite to CaO in Example 1 was changed to 13:1, while other parameters remained unchanged. The fiber was treated in accordance with Experiment 1, and the properties of the obtained fiber are shown in Table 2.

[0042] The fiber has a relatively high residual sulfur content and volatile sulfur content, and the fiber has a more obvious odor. It can be seen that desulfurizing agents with a mass ratio of magnesium aluminum hydrotalcite and alkali metal oxides higher than the range set in this invention cannot achieve a good deodorization effect.

[0043] Comparative Example 2: The mass ratio of magnesium aluminum hydrotalcite to CaO in Example 1 was changed to 2:1, while other parameters remained unchanged. The fiber was treated in accordance with Experiment 1, and the properties of the obtained fiber are shown in Table 2.

[0044] The fiber has a relatively high residual sulfur content and volatile sulfur content, and the fiber has a more obvious odor. It can be seen that desulfurizing agents with a mass ratio of magnesium aluminum hydrotalcite and alkali metal oxides below the range set in this invention cannot achieve a good deodorization effect.

[0045] Comparative Example 3: The mass percentage of the desulfurizing agent in Experiment 1 was changed to 0.25%, while other parameters remained unchanged. The properties of the obtained fibers are shown in Table 2.

[0046] The fiber has a relatively high residual sulfur content and volatile sulfur content, and the fiber also has a slight odor. It can be seen that even if the addition range of the desulfurizer in this invention is lower than the range, a good deodorization effect cannot be obtained.

[0047] The comparison between Comparative Examples 1 to 3 and Example 1 is shown in Table 2 below.

[0048] Table 2

[0049] Comparative Example 4: The pH value of the desulfurizing agent treatment solution in Experiment 4 was changed to 7.0, while other parameters remained unchanged. The properties of the obtained fibers are shown in Table 3.

[0050] The fiber has a relatively high residual sulfur content and volatile sulfur content, and the fiber has a noticeable odor, indicating that a good deodorization effect cannot be obtained at this pH value.

[0051] Comparative Example 5: The pH value of the desulfurizing agent treatment solution in Experiment 4 was changed to 5.5, while other parameters remained unchanged. The properties of the obtained fibers are shown in Table 3.

[0052] It is evident that desulfurizers are essentially ineffective under acidic conditions and have no deodorizing effect.

[0053] The comparison between Comparative Examples 4-5 and Example 4 (Experiment 4) is shown in Table 3 below.

[0054] Table 3

[0055] Comparative Example 6: The magnesium-aluminum hydrotalcite (magnesium / aluminum molar ratio of 3.2:1) in Example 2 was replaced with another magnesium-aluminum hydrotalcite (magnesium / aluminum molar ratio of 1:3), which did not meet the magnesium / aluminum molar ratio requirement specified in this invention. Other parameters remained unchanged, and the treatment was carried out in accordance with Experiment 2. The properties of the obtained fibers are shown in Table 4.

[0056] The fiber has a relatively high residual sulfur content and volatile sulfur content, resulting in a noticeable odor and poor deodorization effect.

[0057] Comparative Example 7: The magnesium aluminum hydrotalcite (magnesium / aluminum molar ratio of 3.2:1) in Example 2 was replaced with another magnesium aluminum hydrotalcite (with the structural formula Mg4Al2(OH)). 12 The reaction mixture (CO3·3H2O, with a magnesium / aluminum molar ratio of 2:1) does not meet the requirements for magnesium-aluminum hydrotalcite specified in this invention. With other parameters unchanged and treated according to Experiment 2, the properties of the obtained fibers are shown in Table 4.

[0058] The fiber has a relatively high residual sulfur content and volatile sulfur content, and the fiber has a slight odor, which is not effectively removed by desulfurizing agents.

[0059] The comparison between Comparative Examples 6-7 and Example 2 (Experiment 2) is shown in Table 4 below.

[0060] Table 4

[0061] Comparative Example 8-1: In Example 3, “MgO” was replaced with “lithium oxide”, the weight remained the same, and the rest was the same as in Example 3.

[0062] Furthermore, following the example of Experiment 3 above, the results showed that the resulting fiber had a noticeable odor. This may be because lithium oxide reacts with water to produce lithium hydroxide, which, as a strong alkali, can only react and digest some of the sulfides and cannot precipitate or eliminate them. Moreover, lithium hydroxide is highly corrosive, limiting its practical application.

[0063] Comparative Example 8-2: In Example 3, “MgO” was replaced with “sodium oxide”, the weight remained the same, and the rest was the same as in Example 3.

[0064] Furthermore, following the example of Experiment 3 above, the results showed that the obtained fiber had a noticeable odor, possibly because sodium oxide reacts with water to produce sodium hydroxide, which, as a strong alkali, can only react to digest some of the sulfides and cannot play a role in precipitating and eliminating sulfides. Its function is similar to that of a strong alkali in a desulfurization bath.

[0065] Comparative Example 8-3: In Example 3, “MgO” was replaced with “zinc oxide”, the weight remained the same, and the rest was the same as in Example 3.

[0066] Furthermore, referring to Experiment 3 above, the results were as follows: the fiber had a distinct odor, similar to the odor of viscose fiber produced without this desulfurizing and deodorizing agent. This is because zinc oxide reacts with H2S to form zinc sulfide, but the zinc sulfide remaining in the fiber is easily reduced to H2S under subsequent acidic conditions, producing an odor.

[0067] Comparative Example 8-4: In Example 3, “MgO” was replaced with “iron oxide”, the weight remained the same, and the rest was the same as in Example 3.

[0068] Furthermore, following the example of Experiment 3 above, the results showed that the fiber had a distinct odor, similar to that of viscose fiber produced without the addition of desulfurizing and deodorizing agents. This may be because the reaction between iron oxide and hydrogen sulfide produces insoluble elemental sulfur that is adsorbed into the pores inside the fiber, making it more difficult to remove later.

[0069] Comparative Examples 8-5: In Example 3, “MgO” was replaced with “lithium chloride”, “magnesium chloride” or “magnesium sulfate”, while the weight remained unchanged, and the rest was the same as in Example 3.

[0070] Furthermore, following the same procedure as Experiment 3 above, the results were all: the fiber had a noticeable odor and almost no effect.

[0071] Finally, it should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of this invention should be considered within the scope of protection of this invention.

Claims

1. A method for reducing the residual amount of sulfides in viscose fibers during fiber processing, characterized in that: The viscose fiber desulfurizing and deodorizing agent is mixed with water to prepare a liquid with a mass percentage of 0.5% to 2.5%, and then the pH value is adjusted to 8.5 to 10.5 to obtain the desulfurizing agent treatment solution. After heating the above desulfurizing agent treatment solution to 78±10℃, it is used as the first water bath. The viscose fiber is introduced into the water bath for immersion for 1~3 minutes. The viscose fiber desulfurization and deodorization agent is composed of hydrotalcite catalyst and alkali metal oxide; Hydrotalcite catalyst: alkali metal oxide = 3~10:1 mass ratio.

2. The method for reducing the residual amount of sulfides in viscose fibers during fiber processing according to claim 1, characterized in that: The hydrotalcite catalyst is magnesium aluminum hydrotalcite, wherein the molar ratio of magnesium to aluminum in the magnesium aluminum hydrotalcite is 3 to 7 to 1.

3. The method for reducing the residual amount of sulfides in viscose fibers during fiber processing according to claim 2, characterized in that: The alkali metal oxide is at least one of CaO and MgO.

4. The method for reducing the residual amount of sulfides in viscose fibers during fiber processing according to claim 2, characterized in that: The desulfurization and deodorization agent for viscose fibers is made of Mg6Al2(OH). 16 It is composed of CO3·4H2O and MgO, Mg6Al2(OH) 16 The mass ratio of CO3·4H2O to MgO is 5:1.

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