A method for preparing nano-silver-loaded antibacterial hemp fiber by gaseous reduction

Abstract

The present invention provides a method for preparing nanosilver-loaded antibacterial hemp fiber by gaseous reduction. The method comprises: impregnating the hemp fiber with an aqueous solution containing silver ions; freezing the resulting silver-ion-adsorbed hemp fiber and then vacuum freeze-drying it to obtain freeze-dried fiber; and reducing the freeze-dried fiber with gaseous sulfur dioxide to obtain the nanosilver-loaded hemp fiber. This method first allows the hemp fiber to be impregnated with silver ions, allowing the silver ions to penetrate into the hemp fiber skeleton along with the water. The water in the hemp fiber is then removed by vacuum freeze-drying, thereby preventing the flow of liquid water from the interior of the fiber structure to the surface. Finally, a gas-solid reaction method is used to reduce the silver ions to nanosilver particles, which are evenly dispersed in the fiber structure and prevent rapid dissolution due to washing or other procedures. This method not only helps maintain the original physical properties of the hemp fiber (such as strength and elongation), but also improves the utilization rate of the silver ions and the uniformity of the distribution of the nanosilver. The prepared fiber has excellent antibacterial durability.

Description

Technical Field

[0001] The invention belongs to the technical field of nano-silver and fiber combination, and in particular relates to a method for preparing nano-silver loaded antibacterial hemp fiber through gaseous reduction. Background Art

[0002] Bacterial infection is one of the most serious risks to public health. Antimicrobial fibers, as important functional materials, can block the spread of disease and prevent textile deterioration. They play an irreplaceable role in protecting the health and safety of personnel in combat, on-duty operations, firefighting, and disaster relief. Resource shortages and environmental degradation are serious issues facing the world today. The polymer synthetic fibers we use in our daily lives are all made from petroleum. As petroleum resources dwindle, sustainable fiber development is gaining increasing attention. Therefore, the research and development of new, highly efficient, durable, and environmentally friendly antimicrobial, renewable functional fiber materials has significant social significance and economic application value.

[0003] Hemp fiber is extracted from the hemp plant and is a naturally renewable fiber. Before processing, hemp fiber typically undergoes a degumming process to remove colloids and other non-cellulose components, thereby improving its purity and spinnability. Degummed hemp fiber can then be spun, woven, and made into a variety of hemp fiber products. However, degumming results in the loss of most antimicrobial components, resulting in a loss of antimicrobial properties after combing, making it unable to meet human antimicrobial needs. Nanosilver, as an antimicrobial agent, offers significant advantages, including high bactericidal efficiency, long-lasting antimicrobial activity, low toxicity, safety, and resistance to drug resistance. It has been applied in medical fields, such as promoting wound healing.

[0004] The commonly used method at present is to use the impregnation (rolling) method to attach nanosilver particles to the surface or inside of hemp fibers. The specific steps include: (1) Preparation of nanosilver sol: First, prepare nanosilver sol, usually by chemical reduction and other methods to obtain a colloidal solution containing nanosilver particles. (2) Fiber pretreatment: The hemp fibers are subjected to necessary pretreatment, such as cleaning and impurity removal, to improve the binding effect of nanosilver. (3) Impregnation treatment: The pretreated hemp fibers are immersed in the nanosilver sol to allow the nanosilver particles to adhere to the fiber surface or penetrate into the fiber interior. Parameters such as impregnation time and temperature need to be optimized according to specific circumstances. (4) Drying and curing: The impregnated hemp fibers are dried to firmly fix the nanosilver particles on the fibers. The above method has a low utilization rate of nanosilver, and the nanosilver is only distributed on the fiber surface, and the antibacterial durability is not ideal. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a method for preparing nano-silver loaded antibacterial hemp fiber by gaseous reduction, which improves the utilization rate and distribution uniformity of nano-silver, and the prepared fiber has excellent antibacterial durability.

[0006] The present invention provides a method for preparing nano-silver-loaded antibacterial hemp fiber by gaseous reduction, comprising the following steps:

[0007] The hemp fibers are immersed in an aqueous solution containing silver ions to obtain hemp fibers adsorbing silver ions;

[0008] Freezing the hemp fiber adsorbing the silver ions and then freeze-drying it in a vacuum to obtain freeze-dried fiber;

[0009] The freeze-dried fibers are reduced with gaseous sulfur dioxide to obtain nano-silver loaded hemp fibers.

[0010] Preferably, the molar ratio of the mass of the hemp fiber to the silver ions in the silver ion-containing aqueous solution is (0.1-10) g:(0.1-10) mol.

[0011] Preferably, the impregnation is carried out under shaking conditions; the impregnation temperature is 20 to 30° C., and the impregnation time is 6 to 24 hours;

[0012] The shaking speed is 100-180 rpm.

[0013] Preferably, the freezing temperature is 0 to -80°C, and the freezing time is 1 to 24 hours.

[0014] Preferably, in the pre-freezing stage, the vacuum freeze drying temperature is -40°C to -50°C, and the time is 0.5 to 2 hours; in the sublimation stage, the vacuum freeze drying temperature is -35°C to -10°C, and the vacuum degree is 1.3 to 13Pa.

[0015] Preferably, the molar ratio of the mass of the freeze-dried fiber to gaseous sulfur dioxide is 1 g: (0.2-1) mmol.

[0016] Preferably, the volume concentration of gaseous sulfur dioxide is 0.1 to 100%.

[0017] Preferably, the reduction time is 1 to 10 hours.

[0018] Preferably, the silver ion-containing aqueous solution is a silver nitrate aqueous solution.

[0019] Preferably, the cellulose in the hemp fiber is greater than 90 wt%, the hemicellulose is 2-3 wt% and the lignin is less than 1 wt%.

[0020] The present invention provides a method for preparing nanosilver-loaded antibacterial hemp fiber by gaseous reduction, comprising the following steps: immersing hemp fiber in an aqueous solution containing silver ions to obtain silver-ion-adsorbed hemp fiber; freezing the silver-ion-adsorbed hemp fiber and then freeze-drying it in a vacuum to obtain freeze-dried fiber; and reducing the freeze-dried fiber with gaseous sulfur dioxide to obtain nanosilver-loaded hemp fiber. This method first allows the hemp fiber to be impregnated with silver ions, allowing the silver ions to penetrate into the hemp fiber skeleton along with the water. Freeze-drying is then used to remove moisture from the hemp fiber, preventing liquid water from flowing from the fiber structure to the surface. This means that the silver ions do not flow out of the fiber structure with the liquid water, but remain within the fiber structure after freeze-drying. Finally, a gas-solid reaction method is used to reduce the silver ions to nanosilver particles, which are evenly dispersed throughout the fiber structure and prevent rapid dissolution due to washing or other procedures. This preparation method not only helps maintain the original physical properties of the hemp fiber (such as strength and elongation), but also improves the utilization rate and uniformity of the nanosilver. The resulting fiber exhibits excellent antibacterial durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The morphology of raw hemp fiber (A) and hemp fiber loaded with nanosilver (B);

[0022] Figure 2 This is the SEM image of the nano-silver-loaded hemp fiber (before cleaning) prepared in Example 1;

[0023] Figure 3 This is the SEM image of the nano-silver-loaded hemp fiber (before cleaning) prepared in Comparative Example 1;

[0024] Figure 4 This is the Ag3d spectrum of the silver nanofiber (before cleaning) prepared in Example 1. DETAILED DESCRIPTION

[0025] The present invention provides a method for preparing nano-silver-loaded antibacterial hemp fiber by gaseous reduction, comprising the following steps:

[0026] The hemp fibers are immersed in an aqueous solution containing silver ions to obtain hemp fibers adsorbing silver ions;

[0027] Freezing the hemp fiber adsorbing the silver ions and then freeze-drying it in a vacuum to obtain freeze-dried fiber;

[0028] The freeze-dried fibers are reduced with gaseous sulfur dioxide to obtain nano-silver loaded hemp fibers.

[0029] The process technology of the present invention is characterized by simple operation, high efficiency, and low pollution. The nano-silver-loaded hemp fiber prepared using this process not only effectively preserves the original physical properties of the hemp fiber, but also significantly improves the utilization efficiency of the nano-silver and greatly enhances the durability of its antibacterial properties.

[0030] The present invention immerses hemp fibers in an aqueous solution containing silver ions to obtain hemp fibers that adsorb silver ions. The hemp fibers described in the present invention have the following physical properties: (1) good moisture absorption and dissipation and breathability. This is because the cellulose cells of the hemp fibers are arranged in parallel and bonded together by pectin and other substances in the fibers, forming a capillary effect that helps to conduct moisture and perspiration; (2) fast heat conduction, cool and crisp wearing, and no sweating sticking to the skin; (3) light texture, strong strength, insect and mildew resistance, low static electricity, and fabric pollution-resistant; (4) soft and elegant color, rugged, suitable for human skin excretion and secretion. Hemp fiber has the following chemical and biological properties: (1) The main component of hemp fiber is cellulose, which contains a large number of hydrophilic groups (hydroxyl groups) in the molecular chain, making it have good hygroscopicity; (2) Hemp fiber also contains substances such as hemicellulose, lignin, and pectin, which affect the performance and processing methods of hemp fiber to varying degrees; (3) Hemp fiber has natural antibacterial and deodorizing functions, which is mainly due to the presence of a variety of natural antibacterial substances in its composition, such as flavonoids, organic acids, steroids, and phenolic substances. The main components of the hemp fiber described in the present invention are: cellulose>90wt%, hemicellulose 2-3wt%, lignin<1wt%, pectin<1wt%, lipid<1wt%, length of about 5cm, average length of about 20mm; fiber count is 1568Nm.

[0031] The silver ion-containing aqueous solution is preferably a silver nitrate aqueous solution; the concentration of silver ions in the silver ion-containing aqueous solution is 0.1 to 0.5 mol / L; and the molar ratio of the mass of the hemp fiber to the silver ions in the silver ion-containing aqueous solution is (0.1 to 10) g:(0.1 to 10) mol.

[0032] In the present invention, the immersion is carried out under shaking conditions; the immersion temperature is 20-30°C, the immersion time is 6-24 hours, and the shaking speed is 100-180 rpm. In a specific embodiment, the immersion temperature is 23°C, the immersion time is overnight, preferably 10-12 hours, and the shaking speed is 180 rpm.

[0033] After obtaining the hemp fiber that adsorbs silver ions, the present invention freezes the hemp fiber that adsorbs silver ions and then freeze-dries it in a vacuum to obtain freeze-dried fiber. The present invention squeezes the hemp fiber that adsorbs silver ions and then freezes it at 0 to -20°C for 1 to 24 hours. After freezing, the frozen fiber is placed in a vacuum freeze-drying instrument to freeze-dry the fiber; in the pre-freezing stage, the vacuum freeze-drying temperature is -40°C to -50°C and the time is 0.5 to 2 hours; in the sublimation stage, the vacuum freeze-drying temperature is -35°C to -10°C and the vacuum degree is 1.3 to 13 Pa. The drying time is controlled to ensure that the moisture in the material is completely sublimated. Since the present invention adopts a drying method that converts ice into vapor under a relatively high vacuum and removes it, the process of liquid water flowing from the inside of the fiber structure to the surface is avoided. That is, the silver ions will not flow out of the fiber structure with the flow of liquid water, but will remain in the fiber structure after freeze-drying.

[0034] After obtaining the freeze-dried fiber, the present invention reduces the freeze-dried fiber with gaseous sulfur dioxide to produce nanosilver-loaded hemp fiber. The reduced nanosilver is present both within and on the surface of the fiber. The volume concentration of the gaseous sulfur dioxide used in the present invention is 0.1 to 100%; in specific embodiments, the volume concentration of the gaseous sulfur dioxide is 0.3% or 0.5%. The molar ratio of the mass of the freeze-dried fiber to the gaseous sulfur dioxide is 1 g: (0.2 to 1) mmol. The reduction time is 1 to 10 hours, preferably 3 to 8 hours.

[0035] The present invention reduces silver ions through a gas-solid reaction method using gaseous sulfur dioxide. Since the silver ions are uniformly dispersed within the fiber structure, the resulting nanosilver particles are also uniformly dispersed within the fiber structure, preventing them from dissolving rapidly during washing. Furthermore, since the resulting nanosilver particles are uniformly dispersed within the fiber structure, they are less likely to agglomerate due to the barrier provided by the hemp fiber structure. Furthermore, the abundant hydroxyl groups within the hemp fiber structure create a reducing microenvironment that significantly reduces oxidation of the nanosilver particles by oxygen molecule penetration, thereby enhancing the stability of the nanosilver particles.

[0036] After reduction, the fiber was taken out and washed in pure water until neutral, and then dried in vacuum at 60°C to obtain the antibacterial hemp fiber loaded with nano-silver. The hemp fiber loaded with nano-silver prepared by the present invention is yellow ( Figure 1 Middle B).

[0037] When the present invention adopts pure water for washing, the washing liquid mainly contains a small amount of unreduced silver ions and a small amount of nano-silver particles generated on the fiber surface. The washing liquid can be directly reused in the impregnation liquid after simple centrifugal precipitation of nano-silver. This can not only reduce wastewater discharge, but also further improve the utilization rate of silver ions.

[0038] The present invention adopts microwave digestion-inductively coupled plasma technology to test the silver content in the fiber.

[0039] The nano-silver loaded antibacterial hemp fiber prepared by the above preparation method of the present invention has the following advantages:

[0040] (1) Efficient utilization of nanosilver: By first adsorbing silver ions and then reducing them in a gaseous state, the generation location and quantity of nanosilver particles can be precisely controlled, thereby improving the utilization rate and distribution uniformity of nanosilver;

[0041] (2) Excellent antibacterial durability: Since the nanosilver particles are formed in the in-situ chemical gas reduction process and are firmly fixed in the hemp fiber structure, they have stronger binding force and stability and can maintain excellent antibacterial properties for a long time;

[0042] (3) Protect the quality of hemp fiber: The damage to hemp fiber caused by high temperature treatment is avoided during the whole process, and the original excellent mechanical properties of hemp fiber are maintained;

[0043] (4) Environmental protection and energy saving: Compared with traditional high-temperature treatment methods, the process of the present invention is more environmentally friendly, reduces energy consumption and waste gas emissions, and meets the requirements of sustainable development;

[0044] To further illustrate the present invention, a method for preparing nano-silver-loaded antibacterial hemp fiber by gaseous reduction provided by the present invention is described in detail below in conjunction with examples, but they should not be construed as limiting the scope of protection of the present invention.

[0045] Example 1

[0046] Weigh 1.0 g of hemp fiber and soak it in 0.2 M silver nitrate solution at 25°C for 12 h, shaking at 180 rpm overnight to allow the fiber to absorb silver ions.

[0047] The fiber was fished out, squeezed to 4 g, frozen at -20°C overnight, and then placed in a vacuum freeze dryer to freeze-dry the fiber: in the pre-freezing stage, the vacuum freeze drying temperature was -40°C and the time was 2 hours; in the sublimation stage, the vacuum freeze drying temperature was -35°C and the vacuum degree was 1.3 Pa to completely sublime the water in the material;

[0048] The fibers were exposed to 3L of 0.3% (v / v) sulfur dioxide gas for 3 hours. The fibers were then removed, rinsed in pure water until neutral, and dried under vacuum at 60°C to yield yellow nanosilver-loaded hemp fibers. Microwave digestion-inductively coupled plasma analysis revealed a silver content of 58.5mg / g.

[0049] Example 2

[0050] Weigh 1.0 g of hemp fiber and soak it in 0.5 M silver nitrate solution at 30°C for 6 h, shaking at 180 rpm overnight to allow the fiber to absorb silver ions.

[0051] The fiber was fished out, squeezed to 4 g, frozen at -20°C overnight, and then placed in a vacuum freeze dryer to freeze-dry the fiber: in the pre-freezing stage, the vacuum freeze drying temperature was -50°C and the time was 0.5 h; in the sublimation stage, the vacuum freeze drying temperature was -10°C and the vacuum degree was 13 Pa to completely sublime the water in the material;

[0052] The fibers were exposed to 2L of 0.5% (v / v) sulfur dioxide gas for 5 hours, then removed, rinsed in pure water until neutral, and dried to yield yellow nanosilver-loaded hemp fibers. Microwave digestion-inductively coupled plasma analysis revealed a silver content of 115.1mg / g.

[0053] Example 3

[0054] Weigh 1.0 g of hemp fiber and soak it in 0.1 M silver nitrate solution at 20°C for 24 h, shaking at 180 rpm overnight to allow the fiber to absorb silver ions.

[0055] The fiber was fished out, squeezed to 5g, frozen at -20℃ overnight, and then placed in a vacuum freeze dryer to freeze-dry the fiber: in the pre-freezing stage, the vacuum freeze drying temperature was -45℃ and the time was 1.0h; in the sublimation stage, the vacuum freeze drying temperature was -25℃ and the vacuum degree was 10Pa to completely sublime the water in the material;

[0056] The fibers were exposed to 2L of 0.5% (v / v) sulfur dioxide gas for 1 hour, then removed, rinsed in pure water until neutral, and dried to obtain yellow nanosilver-loaded hemp fibers. Microwave digestion-inductively coupled plasma analysis revealed a silver content of 40.9mg / g.

[0057] Comparative Example 1

[0058] Weigh 1.0 g of hemp fiber and soak it in 0.2 M silver nitrate solution at 25°C for 12 h, shaking at 180 rpm overnight to allow the fiber to absorb silver ions.

[0059] Take out the fiber, squeeze it to 4g, and dry it at 60℃ to constant weight;

[0060] The fibers were exposed to 3L of 0.3% (v / v) sulfur dioxide gas for 3 hours. The fibers were then removed, rinsed in pure water until neutral, and dried under vacuum at 60°C to yield yellow, nanosilver-loaded hemp fibers. Microwave digestion-inductively coupled plasma analysis revealed a silver content of 10.5mg / g.

[0061] The present invention carries out SEM test on the nano silver hemp fiber prepared in Example 1 and Comparative Example 1, and the results are shown in FIG. Figure 2 and Figure 3 ; Figure 2This is the SEM image of the nano-silver-loaded hemp fiber (before cleaning) prepared in Example 1; Figure 3 This is the SEM image of the nano-silver-loaded hemp fiber (before cleaning) prepared in Comparative Example 1.

[0062] Depend on Figure 2 and Figure 3 It can be seen that the fiber prepared in Example 1 has many wrinkles on its surface, and after magnification, many nanosilver particles are found in the gaps between the wrinkles, and they are evenly distributed. In contrast, the fiber prepared in Comparative Example 1 has many rod-shaped crystals on its surface. This is mainly because the silver nitrate solution that permeates the fiber structure during the drying process flows to the fiber surface and crystallizes on the fiber surface after dehydration to form rod-shaped silver nitrate crystals. When sulfur dioxide is used for reduction, only the silver ions on the crystal surface are reduced, and the nanosilver generated by the reduction remains in the silver nitrate crystals. When pure water is used for post-washing treatment, the silver nitrate crystals on the fiber surface dissolve into the water. As the silver nitrate crystals dissolve, the nanosilver contained in them also enters the water. This is also the main reason why the silver content of the fiber in Comparative Example 1 is much lower than that in Example 1.

[0063] Figure 4 This is the Ag3d spectrum of the silver nanofiber (before cleaning) prepared in Example 1. It can be seen that Ag3d is mainly composed of two orbitals, Ag3d 5 / 2 and Ag3d 3 / 2 The binding energies of 368.2eV and 374.2eV represent singlet silver, and the binding energies of 367.9eV and 373.9eV represent monovalent silver ions. These peaks demonstrate that Ag and Ag + Coexistence on the surface of hemp fibers.

[0064] The present invention conducted a wash resistance test on the nano-silver loaded antibacterial hemp fibers prepared in Examples 1 to 3 and Comparative Example 1. The results are shown in Tables 1 to 3:

[0065] Table 1 Washing resistance test results of nanosilver-loaded antibacterial hemp fibers prepared in Example 1

[0066]

[0067] Table 2 Washability test results of the loaded nano silver hemp fibers prepared in Example 2

[0068]

[0069] Table 3 Washability test results of the loaded nano silver hemp fibers prepared in Example 3

[0070]

[0071] Table 4 Washing resistance test results of nano-silver hemp fibers prepared in Comparative Example 1

[0072]

[0073] The present invention tests the breaking strength and breaking elongation of the nano-silver-loaded hemp fibers prepared in Examples 1 to 3 and Comparative Example 1, and the results are shown in Table 5:

[0074] Table 5 Mechanical properties test results of nanosilver-loaded fibers prepared in Examples 1 to 3 and Comparative Example 1

[0075]

[0076] As can be seen from the above examples, the present invention provides a method for preparing nanosilver-loaded antibacterial hemp fibers by gaseous reduction, comprising the following steps: impregnating hemp fibers with an aqueous solution containing silver ions to obtain silver-ion-adsorbed hemp fibers; freezing the silver-ion-adsorbed hemp fibers and then freeze-drying them under vacuum to obtain freeze-dried fibers; and reducing the freeze-dried fibers with gaseous sulfur dioxide to obtain nanosilver-loaded hemp fibers. This method first allows the hemp fibers to be impregnated with silver ions for adsorption, then removes moisture from the fibers through freeze-drying. The silver ions remain in the fiber structure after freeze-drying. Finally, the silver ions are reduced to nanosilver particles by a gas-solid reaction method using gaseous reduction. These particles are evenly dispersed in the fiber structure, preventing them from dissolving rapidly due to washing or other procedures. During the preparation process, the original physical properties of the hemp fibers (such as breaking strength and elongation at break) are maintained. This method improves the utilization rate and uniformity of the nanosilver distribution, resulting in fibers with excellent antibacterial durability. The nanosilver particles are evenly dispersed in the fiber structure and form a good bond with the fibers, enhancing or maintaining the mechanical strength of the fibers. Due to the high-temperature treatment, the fibers in Comparative Example 1 were in poor condition, easily shed, and had significantly reduced mechanical strength. Experimental results showed that after 50 washes, the nanosilver-loaded antibacterial hemp fibers had an antibacterial rate of 92-95% against E. coli, 95.93-99.13% against S. aureus, and 79.95-85.98% against C. albicans. The breaking strength was 5.19-5.25 cN / dtex, and the elongation at break was 3.35-3.82%.

[0077] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing nano-silver-loaded antibacterial hemp fiber by gaseous reduction, comprising the following steps: The hemp fibers are immersed in an aqueous solution containing silver ions to obtain hemp fibers adsorbing silver ions; The hemp fiber adsorbing silver ions is frozen and then vacuum freeze-dried to obtain freeze-dried fiber; in the pre-freezing stage, the vacuum freeze-drying temperature is -50°C to -40°C and the time is 0.5 to 2 hours; in the sublimation stage, the vacuum freeze-drying temperature is -35°C to -10°C and the vacuum degree is 1.3 to 13 Pa; Reducing the freeze-dried fibers with gaseous sulfur dioxide to obtain nano-silver loaded hemp fibers; The molar ratio of the mass of the freeze-dried fiber to gaseous sulfur dioxide is 1g:(0.2~1)mmol.

2. The preparation method according to claim 1, characterized in that The molar ratio of the mass of the hemp fiber to the silver ions in the silver ion-containing aqueous solution is (0.1-10) g: (0.1-1) mol.

3. The preparation method according to claim 1, characterized in that The immersion is carried out under shaking conditions; the immersion temperature is 20-30°C and the immersion time is 6-24 hours; The oscillation speed is 100~180rpm.

4. The preparation method according to claim 1, characterized in that The freezing temperature is -80°C to 0°C, and the freezing time is 1 to 24 hours.

5. The preparation method according to claim 1, characterized in that The volume concentration of gaseous sulfur dioxide is 0.1~100%.

6. The preparation method according to claim 1, characterized in that The reduction time is 1 to 10 hours.

7. The preparation method according to claim 1, characterized in that The silver ion-containing aqueous solution is a silver nitrate aqueous solution.

8. The preparation method according to claim 1, characterized in that Hemp fiber contains cellulose > 90wt%, hemicellulose 2~3wt% and lignin <1wt%.

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