Preparation and low-temperature bleaching method of primary-color alginate fiber

Abstract

The invention belongs to the technical field of textile chemical industry, and particularly relates to a preparation and low-temperature bleaching method of primary-color alginate fibers, in particular to a low-temperature bleaching process. Aiming at the problems of non-uniform whiteness, large damage caused by traditional oxidation bleaching and the like of alginate fibers due to raw material difference, a reduction bleaching process is innovatively adopted, thiourea dioxide or sodium hydrosulfite is used as a bleaching agent, a mixed solution of sodium metasilicate and sodium hydroxide is used as an alkaline agent, and bleaching is performed under the conditions that the pH is 7-11 and the temperature is 40-80 DEG C. According to the method, through the synergistic effect of the alkaline agent and the bleaching agent and in combination with a calcium chloride protection mechanism, fiber damage is remarkably reduced, the whiteness is stably larger than or equal to 50, process wastewater pollution is low, and clean production is achieved. According to the invention, the technical bottleneck of alginate fiber bleaching is broken through, and the application range of alginate fiber in high-grade textiles is widened.

Description

Technical Field

[0001] This invention belongs to the field of textile chemical technology, specifically relating to a method for preparing natural-colored seaweed fiber and a low-temperature bleaching method, with particular emphasis on the low-temperature bleaching process. Background Technology

[0002] Seaweed fiber is a novel green, biodegradable fiber made from sodium alginate extracted from natural seaweed through a wet spinning process. With its excellent moisture absorption, film-forming and fiber-forming properties, as well as outstanding biodegradability and biocompatibility, this fiber has been widely used in medical dressings and also shows great potential in high-end clothing, underwear fabrics, and decorative textiles. While its smooth feel enhances wearing comfort, it also increases the difficulty of spinning.

[0003] Due to differences in raw materials, the whiteness of seaweed fibers varies considerably. Therefore, seaweed fibers require bleaching to facilitate subsequent dyeing. Traditional bleaching processes cause significant damage to seaweed fibers, making bleaching a critical technological bottleneck for the industrial application of seaweed fibers, and a mature and reliable bleaching process has yet to be developed. Most sodium alginate bleaching involves bleaching the sodium alginate concentrate during production. However, this process degrades the large molecular chains of sodium alginate, and if not properly controlled, can lead to instability in the molecular weight of sodium alginate, resulting in significant fluctuations in the properties of seaweed fibers made from sodium alginate. Currently, there are some research reports on the bleaching of seaweed fiber blended fabrics, but most focus on bleaching components other than seaweed; reports on bleaching techniques for pure seaweed fibers are rare.

[0004] For example, CN202410097019.6 proposes a bleaching method for blended fabrics containing seaweed fibers. Its core principle is to use a specially formulated compound alkali agent and hydrogen peroxide to bleach the blended fabrics containing seaweed fibers, focusing primarily on bleaching the blended fibers other than the seaweed. Its limitation lies in the excessively high requirements for bleaching temperature and pH value, focusing only on the bleaching of the blended fibers and neglecting the bleaching of the seaweed fibers themselves. High process temperature and pH value can potentially affect the properties of the seaweed fibers.

[0005] For example, CN202310255066.4 proposes a dyeing method for seaweed fiber blended yarn without alkali or salt, and its application. The core technology is a dyeing method for seaweed fiber blended yarn without alkali or salt. The patent does not mention bleaching technology for seaweed fibers or their blended fabrics, focusing only on dyeing. This suggests that the cotton fibers used have undergone scouring and bleaching pretreatment. Furthermore, it does not mention bleaching of the seaweed fibers and does not address the influence of the seaweed fiber's inherent color on the dyeing process.

[0006] For example, the paper published by Gu Dongya et al. on the bio-enzymatic pretreatment of seaweed fiber / cotton blended fabrics (Dyeing and Printing, 2015, Vol. 41, No. 02, 19-21) uses a combined process of boiling enzyme and hydrogen peroxide for desizing, boiling, and bleaching. The principle is that hydrogen peroxide decomposes to produce active oxygen and hydroxyl radicals, which react with the pigments in cotton fibers to generate colorless substances. The limitations of this method are: (1) the bleaching pH value (8.5) leads to insufficient hydrogen peroxide activity, resulting in limited improvement in the whiteness of seaweed fiber; (2) the lack of protective measures for seaweed fiber makes the fiber susceptible to damage and gelation during bleaching.

[0007] Traditional bleaching processes for pure cotton fabrics and animal fibers primarily use bleaching agents such as hydrogen peroxide, sodium hypochlorite, and sodium chlorite. During the bleaching process, the active substances produced by the decomposition of these bleaching agents can significantly damage seaweed fibers. Without protective measures, the structure of seaweed fibers is easily eroded by these active substances, leading to weight loss, damage, and even dissolution. Therefore, bleaching seaweed fibers using traditional processes easily triggers gelation, resulting in fiber morphology damage, reduced strength, and significant losses. Summary of the Invention

[0008] Technical issues Traditional bleaching processes cause significant damage to seaweed fibers, and existing bleaching research mostly focuses on seaweed fiber blends, not pure seaweed fibers. Therefore, there is a need to propose a bleaching method for seaweed fibers that minimizes damage to pure seaweed fibers and achieves good bleaching results.

[0009] Technical content To address the aforementioned technical problems, this invention aims to provide a method for preparing natural-colored seaweed fibers and a low-temperature weak alkali bleaching method. The core of this method lies in resolving the critical technical contradiction of significantly improving the whiteness of seaweed fibers while minimizing damage to their physicochemical structure.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: The preparation of the original color seaweed fiber of the present invention includes the following steps: Solution preparation: Dissolve industrial-grade colored sodium alginate granules to prepare a spinning solution with a mass concentration of 3%; Spinning: The raw solution is extruded through a spinneret into a calcium chloride coagulation bath with a concentration of 5% and a temperature of 40°C for solidification; Post-processing: The formed fibers are stretched by 1.5 times, then washed and dried to obtain the finished product.

[0011] The present invention provides a bleaching solution for unbleached seaweed fibers, wherein the unbleached seaweed fiber bleaching solution contains 0.01~0.1 mol / L sodium metasilicate, 0.05~0.5 mol / L sodium hydroxide, and 1~10 g / L reducing bleaching agent.

[0012] Furthermore, the concentration of the sodium metasilicate is 0.02~0.07 mol / L.

[0013] Furthermore, the concentration of the sodium hydroxide is 0.1~0.3 mol / L.

[0014] Furthermore, the concentration of the reducing bleaching agent is 1~5 g / L.

[0015] Furthermore, the reducing bleaching agent includes thiourea dioxide and / or sodium dithionite.

[0016] Furthermore, the seaweed fiber bleaching solution may also contain 0.1-0.5 g / L of calcium chloride.

[0017] Furthermore, the seaweed fiber bleaching solution can control the weight loss rate of the bleached seaweed fiber to within 10% and the whiteness to above 50.

[0018] A low-temperature weak alkali bleaching method for unbleached seaweed fibers includes the following steps: (1) Preparation of bleaching solution: Take water at a bath ratio of 1:10 to 1:50, add a reducing bleaching agent with a mass concentration of 1-10 g / L, and add an alkaline agent to form a mixed bleaching solution; (2) Bleaching treatment: Put the original color seaweed fiber into the mixed bleaching solution and add 0.1-0.5 g / L of calcium chloride. Then, heat the system to 40-80℃ at a slow heating rate of 1-1.5 ℃ / min and then keep it at the temperature for 30-60 minutes. (3) Post-treatment: Wash the bleached seaweed fiber with water and then dry it.

[0019] Furthermore, the alkaline agent in step (1) is 0.01~0.1 mol / L sodium metasilicate and 0.05~0.5 mol / L sodium hydroxide.

[0020] Furthermore, the water washing in step (3) is performed using hot water at 50~60℃ and / or room temperature water; the washing time is 5~20 minutes.

[0021] Furthermore, the drying in step (3) includes baking, air drying, or static drying.

[0022] A type of seaweed fiber obtained by bleaching according to the above-described bleaching method.

[0023] Beneficial effects Compared with the prior art, the breakthrough innovation and significant advantages of this invention are as follows: 1. Innovative Bleaching System: Abandoning the traditional oxidative bleaching method, which is highly destructive to seaweed fibers, this system innovatively employs a reduction bleaching system. This system removes pigments from the fibers through reduction, fundamentally preventing the attack and degradation of the seaweed fiber macromolecular chains by reactive oxygen free radicals.

[0024] 2. Synergistic Protection Mechanism: A composite alkali buffer system: Utilizing a specific ratio of sodium metasilicate and sodium hydroxide mixture, this system not only provides an optimal and stable pH environment for reductive bleaching, but its buffering effect also prevents excessively high local pH levels, thus protecting the fibers from strong alkali corrosion. Calcium ion protectant: An innovative small amount of calcium chloride is introduced into the bleaching solution. Calcium ions can bind to the carboxyl groups on the seaweed fiber molecular chains, stabilizing its unique "egg-box" gel structure, thereby effectively inhibiting fiber swelling, weight loss, and gelation during the bleaching process, greatly reducing fiber damage.

[0025] 3. Mild Processing Conditions: The entire process is carried out under low temperature (≤80℃) and weakly alkaline (pH 7-11) conditions, ensuring a mild and controllable process that is friendly to fibers. High Whiteness: The whiteness of the treated seaweed fibers consistently reaches over 50, meeting the requirements of subsequent textile processing. Low Damage: Fiber weight loss can be controlled within 10%, with high strength retention, intact morphology and structure, and excellent hand feel.

[0026] 4. Green and environmentally friendly: The process is simple, the chemicals used have low environmental impact, and the subsequent washing wastewater causes little pollution, which is in line with the modern industrial development direction of cleaner production. Detailed Implementation

[0027] This invention proposes a low-temperature bleaching method for natural-colored seaweed fibers. To make the advantages and technical solutions of this invention clearer and more explicit, the invention will be described in detail below with reference to specific embodiments.

[0028] The preparation method of natural-colored seaweed fiber is as follows: Solution preparation: Dissolve industrial-grade colored sodium alginate granules to prepare a spinning solution with a mass concentration of 3%; Spinning: The raw solution is extruded through a spinneret into a calcium chloride coagulation bath with a concentration of 5% and a temperature of 40°C for solidification; Post-processing: The formed fibers are stretched by 1.5 times, then washed and dried to obtain the finished product.

[0029] Example 1 Take distilled water at a bath ratio of 1:50, add a mixed alkali of sodium metasilicate and sodium hydroxide, adjust the pH to 8, and add thiourea dioxide to prepare a bleaching solution, wherein the concentration of sodium metasilicate is 0.05 mol / L, the concentration of sodium hydroxide is 0.2 mol / L, and the concentration of thiourea dioxide is 2 g / L.

[0030] The unbleached seaweed fibers were immersed in a bleaching solution with 0.1 g / L of calcium chloride added. The temperature was increased to 40°C at a rate of 1°C / min and maintained for 30 minutes. Subsequently, the fibers were washed for 10 minutes each in 60°C hot water and room temperature water, and then dried at 60°C.

[0031] Example 2 Take distilled water at a bath ratio of 1:50, add a mixed alkali of sodium metasilicate and sodium hydroxide, adjust the pH to 9, and add thiourea dioxide to prepare a bleaching solution, wherein the concentration of sodium metasilicate is 0.05 mol / L, the concentration of sodium hydroxide is 0.2 mol / L, and the concentration of thiourea dioxide is 4 g / L.

[0032] The unbleached seaweed fibers were immersed in a bleaching solution with 0.1 g / L of calcium chloride added. The temperature was increased to 60°C at a rate of 1°C / min and maintained for 30 minutes. Subsequently, the fibers were washed for 10 minutes each in 60°C hot water and room temperature water, and then dried at 60°C.

[0033] Example 3 Take distilled water at a bath ratio of 1:50, add a mixed alkaline agent of sodium metasilicate and sodium hydroxide, adjust the pH to 11, and add thiourea dioxide to prepare a bleaching solution, wherein the concentration of sodium metasilicate is 0.05 mol / L, the concentration of sodium hydroxide is 0.2 mol / L, and the concentration of thiourea dioxide is 6 g / L.

[0034] The unbleached seaweed fibers were immersed in a bleaching solution with 0.1 g / L of calcium chloride added. The temperature was increased to 80°C at a rate of 1°C / min and maintained for 30 minutes. Subsequently, the fibers were washed for 10 minutes each in 60°C hot water and room temperature water, and then dried at 60°C.

[0035] Example 4 Take distilled water at a bath ratio of 1:50, add a mixed alkaline agent of sodium metasilicate and sodium hydroxide, adjust the pH to 8, and add sodium dithionite to prepare a bleaching solution, wherein the concentration of sodium metasilicate is 0.05 mol / L, the concentration of sodium hydroxide is 0.2 mol / L, and the concentration of sodium dithionite is 2 g / L.

[0036] The unbleached seaweed fibers were immersed in a bleaching solution with 0.3 g / L of calcium chloride added. The temperature was increased to 60°C at a rate of 1°C / min and maintained for 30 minutes. Subsequently, the fibers were washed for 10 minutes each in 60°C hot water and room temperature water, and then dried at 60°C.

[0037] Example 5 Take distilled water at a bath ratio of 1:50, add a mixed alkaline agent of sodium metasilicate and sodium hydroxide, adjust the pH to 9, and add sodium dithionite to prepare a bleaching solution, wherein the concentration of sodium metasilicate is 0.05 mol / L, the concentration of sodium hydroxide is 0.2 mol / L, and the concentration of sodium dithionite is 4 g / L.

[0038] The unbleached seaweed fibers were immersed in a bleaching solution with 0.1 g / L of calcium chloride added. The temperature was increased to 80°C at a rate of 1°C / min and maintained for 30 minutes. Subsequently, the fibers were washed for 10 minutes each in 60°C hot water and room temperature water, and then dried at 60°C.

[0039] Example 6 Take distilled water at a bath ratio of 1:50, add a mixed alkali of sodium metasilicate and sodium hydroxide, adjust the pH to 10, and add thiourea dioxide and sodium dithionite to prepare a bleaching solution, wherein the concentration of sodium metasilicate is 0.05 mol / L, the concentration of sodium hydroxide is 0.2 mol / L, and the concentrations of thiourea dioxide and sodium dithionite are both 2 g / L.

[0040] The unbleached seaweed fibers were immersed in a bleaching solution with 0.2 g / L of calcium chloride added. The temperature was increased to 70°C at a rate of 1°C / min and maintained for 30 minutes. Subsequently, the fibers were washed for 10 minutes each in 60°C hot water and room temperature water, and then dried at 60°C.

[0041] Comparative Example 1 This comparative example uses traditional hydrogen peroxide bleaching. 2.00g of the same batch of unbleached seaweed fiber was weighed and added to distilled water at a bath ratio of 1:50. Hydrogen peroxide (H2O2, 30wt%) was added to achieve an H2O2 concentration of 5g / L, and the pH was adjusted to 10.5 with sodium hydroxide. The bleaching solution was heated to 90℃ at a rate of 1.5℃ / min and held at that temperature for 45 minutes. The fiber was then washed for 10 minutes each in 60℃ hot water and room temperature water, and finally dried in a 60℃ oven.

[0042] The seaweed fibers obtained in Examples 1, 2, 3, 4, 5, 6 and the comparative examples were weighed and tested for whiteness. The performance after bleaching is shown in Table 1.

[0043] Table 1. Properties of seaweed fiber after bleaching

[0044] The whiteness of the unbleached seaweed fiber is 5.3. Results Analysis As shown in Table 1, regarding fiber damage comparison: the comparative example using traditional hydrogen peroxide bleaching showed a fiber weight loss rate as high as 17.5%, and obvious gelation was observed, indicating severe damage to the fiber structure. In contrast, the weight loss rate of all embodiments of the present invention was controlled within 10%, and the fiber morphology remained intact with a soft feel, fully demonstrating the superior effect of the reduction bleaching system and protective mechanism of the present invention in reducing fiber damage.

[0045] Whiteness Comparison: The comparative example, under conditions of severe fiber damage, achieved a whiteness of only 48.50, failing to meet the application requirement (≥50). In contrast, the embodiments of this invention, while exhibiting minimal damage, consistently maintained a whiteness above 50, reaching a maximum of 55.42, achieving the dual goals of whiteness enhancement and fiber protection.

[0046] In summary, the low-temperature weak alkali reduction bleaching method provided by this invention is superior to the traditional oxidation bleaching process in all key technical indicators, and successfully solves the long-standing technical problem in the field of seaweed fiber bleaching.

[0047] It should be noted that the above embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the guidance of the above-described invention content still fall within the scope of protection of the present invention.

Claims

1. A bleaching solution for unbleached seaweed fibers, characterized in that, The original color seaweed fiber bleaching solution contains 0.01~0.1 mol / L sodium metasilicate, 0.05~0.5 mol / L sodium hydroxide, and 1~10 g / L reducing bleaching agent.

2. The bleaching solution according to claim 1, characterized in that, The concentration of sodium metasilicate is 0.02~0.07 mol / L.

3. The bleaching solution according to claim 1, characterized in that, The concentration of sodium hydroxide is 0.1~0.3 mol / L.

4. The bleaching solution according to claim 1, characterized in that, The concentration of the reducing bleaching agent is 1~5 g / L.

5. The bleaching solution according to claim 1, characterized in that, The reducing bleaching agent includes thiourea dioxide and / or sodium dithionite.

6. The bleaching solution according to any one of claims 1 to 5, characterized in that, The original color seaweed fiber bleaching solution contains 0.1-0.5 g / L of calcium chloride.

7. A low-temperature weak alkali bleaching method for unbleached seaweed fibers, characterized in that, Includes the following steps: (1) Preparation of bleaching solution: Take water at a bath ratio of 1:10 to 1:50, add a reducing bleaching agent with a mass concentration of 1-10 g / L, and add an alkaline agent to form a mixed bleaching solution; the alkaline agent is 0.01~0.1 mol / L sodium metasilicate and 0.05~0.5 mol / L sodium hydroxide; (2) Bleaching treatment: Put the original color seaweed fiber into the mixed bleaching solution and add 0.1-0.5 g / L of calcium chloride. Then, heat the system to 40-80℃ at a slow heating rate of 1-1.5 ℃ / min and then keep it at the temperature for 30-60 minutes. (3) Post-treatment: Wash the bleached seaweed fiber with water and then dry it.

8. The low-temperature weak alkali bleaching method according to claim 7, characterized in that, The water washing in step (3) is performed using hot water at 50~60℃ and / or room temperature water; the washing time is 5~20 minutes.

9. The low-temperature weak alkali bleaching method according to claim 7, characterized in that, The drying process described in step (3) includes baking, air drying, or static drying.

10. A type of seaweed fiber, characterized in that, The seaweed fiber is obtained by bleaching using the low-temperature weak alkali bleaching method according to any one of claims 7 to 9.

Images