Method for preparing nano-silver-loaded antibacterial fibrilia through gaseous reduction

Abstract

The invention provides a method for preparing nano-silver-loaded antibacterial fibrilia through gaseous reduction. The method comprises the following steps: soaking fibrilia in a silver ion-containing aqueous solution; freezing the obtained fibrilia adsorbing the silver ions, and then performing vacuum freeze drying to obtain freeze-dried fibers; and reducing the freeze-dried fibers with gaseous sulfur dioxide to obtain the nano-silver loaded hemp fibers. According to the method, the fibrilia is impregnated and adsorbed with silver ions, so that the silver ions permeate into a fibrilia skeleton along with water, and then moisture in the fibrilia is removed through vacuum freeze drying, so that the process that liquid water flows from the interior of a fibrilia structure to the surface is avoided. And finally, silver ions are reduced into nano-silver particles by adopting a gas-solid reaction method, and the nano-silver particles are uniformly dispersed in a fiber structure and cannot be dissolved out too quickly due to procedures such as washing. According to the method, the original physical properties (such as strength, elongation and the like) of the fibrilia can be kept, the utilization rate of silver ions and the distribution uniformity of nano-silver can be improved, and 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 antibacterial hemp fiber loaded with nano-silver by gaseous reduction. Background Art

[0002] Bacterial infection is one of the most serious risks in public health. As an important functional material, antibacterial fiber has the functions of blocking the spread of diseases and preventing textile deterioration. It plays an irreplaceable and important role in the health and safety of personnel in combat, duty, firefighting and disaster relief. Resource shortage and environmental degradation are serious problems facing the world today. The polymer synthetic fibers we use in our daily lives are made of petroleum. With the reduction of petroleum resources, sustainable development fibers have received more and more attention. Therefore, the research and development of new, efficient, durable and environmentally friendly antibacterial renewable functional fiber materials has great social significance and economic application value.

[0003] Hemp fiber is a fiber extracted from hemp plants and is a kind of natural renewable fiber. Hemp fiber usually needs to be degummed before processing to remove the colloid and other non-cellulose components in the fiber and improve the purity and spinnability of the fiber. The degummed hemp fiber can be spun, weaved and other subsequent processing to make various hemp fiber products. However, degumming will cause most of the antibacterial components to be lost, resulting in the loss of antibacterial properties of hemp fiber after combing, which cannot meet human antibacterial needs for fiber. As an antibacterial agent, nanosilver has significant advantages such as high efficiency sterilization, long-lasting antibacterial, low toxicity and safety, and no drug resistance, and has been used in medical fields such as promoting wound healing.

[0004] At present, the commonly used method 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: Perform necessary pretreatment on the hemp fiber, such as cleaning and impurity removal, to improve the binding effect of nanosilver. (3) Impregnation treatment: Immerse the pretreated hemp fiber in the nanosilver sol to allow the nanosilver particles to adhere to the fiber surface or penetrate into the fiber. Parameters such as impregnation time and temperature need to be optimized according to specific circumstances. (4) Drying and curing: Dry the impregnated hemp fiber to firmly fix the nanosilver particles on the fiber. 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 antibacterial hemp fiber loaded with nanosilver by gaseous reduction, which method improves the utilization rate and distribution uniformity of nanosilver, 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 fiber is immersed in an aqueous solution containing silver ions to obtain the hemp fiber adsorbing the 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 hemp fiber contains >90 wt% cellulose, 2-3 wt% hemicellulose and <1 wt% lignin.

[0020] The invention provides a preparation method of nano-silver loaded antibacterial hemp fiber by gaseous reduction, comprising the following steps: immersing hemp fiber in a silver ion-containing aqueous solution to obtain hemp fiber adsorbing silver ions; freezing the hemp fiber adsorbing silver ions and then vacuum freeze-drying to obtain freeze-dried fiber; reducing the freeze-dried fiber by gaseous sulfur dioxide to obtain nano-silver loaded hemp fiber. The method first allows the hemp fiber to be impregnated with silver ions, so that the silver ions penetrate into the hemp fiber skeleton with water, and then removes the water in the hemp fiber by freeze-drying technology to avoid the process of liquid water flowing from the inside of the fiber structure to the surface, 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. Finally, the silver ions are reduced into nano-silver particles by a gas-solid reaction method of gaseous reduction, and are evenly dispersed in the fiber structure, and will not be dissolved too quickly due to washing and other procedures. The preparation method is not only conducive to maintaining the original physical properties of the hemp fiber (such as strength, elongation, etc.), but also can improve the utilization rate and distribution uniformity of nano-silver, and the prepared fiber has excellent antibacterial durability. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0024] Figure 4 This is the Ag3d spectrum of the silver-loaded nano-hemp fiber (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 fiber is immersed in an aqueous solution containing silver ions to obtain the hemp fiber adsorbing the 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 has the characteristics of simple operation, high efficiency, low pollution, etc. The nano-silver loaded hemp fiber prepared by this process not only effectively protects the original physical properties of the hemp fiber, but also significantly improves the utilization efficiency of nano-silver and greatly enhances the durability of its antibacterial performance.

[0030] The present invention immerses hemp fiber in an aqueous solution containing silver ions to obtain hemp fiber adsorbing silver ions. The hemp fiber in the present invention has the following physical properties: (1) It has good moisture absorption, moisture dissipation and air permeability functions, because the cellulose cells of the hemp fiber are arranged in parallel and bonded together by pectin in the fiber to form a capillary effect, which is helpful for moisture conduction and sweat removal; (2) It has fast heat transfer and heat conduction, and is cool and crisp when worn, and does not stick to the body when sweating; (3) It is light in texture, strong, insect-proof and mildew-proof, has low static electricity, and is not easy to be contaminated by the fabric; (4) The color is soft, generous and rough, which is suitable for the excretion and secretion of human skin. Hemp fiber has the following chemical and biological characteristics: (1) The main component of hemp fiber is cellulose, and the molecular chain contains a large number of hydrophilic groups-hydroxyl groups, which makes it have good hygroscopicity; (2) Hemp fiber also contains hemicellulose, lignin, pectin and other substances, 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 because its components contain a variety of natural antibacterial substances, 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 is about 5cm, and the average length is about 20mm; the 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 0.1-0.5 mol / L. 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.

[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 rate 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 rate is 180 rpm.

[0033] After obtaining the hemp fiber adsorbing silver ions, the present invention freezes the hemp fiber adsorbing silver ions and then freeze-dries it in a vacuum to obtain freeze-dried fiber. The present invention squeezes the hemp fiber adsorbing silver ions and 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 temperature of the vacuum freeze-drying is -40°C to -50°C for 0.5 to 2 hours; in the sublimation stage, the temperature of the vacuum freeze-drying is -35°C to -10°C, the vacuum degree is 1.3 to 13Pa, and the drying time is controlled to ensure that the moisture in the material is completely sublimated. The present invention adopts a drying method that converts ice into steam under a relatively high vacuum and removes it, thereby avoiding the process of liquid water flowing from the inside of the fiber structure to the surface, 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 obtain nano-silver loaded hemp fiber. The reduced nano-silver exists both inside and on the surface of the fiber. The volume concentration of the gaseous sulfur dioxide used in the present invention is 0.1-100%; in a specific embodiment, 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 1g:(0.2-1)mmol. The reduction time is 1-10h, preferably 3-8h.

[0035] The present invention reduces silver ions by adopting a gas-solid reaction method of reducing with gaseous sulfur dioxide. Since the silver ions are uniformly dispersed in the fiber structure, the correspondingly generated nano-silver particles are also uniformly dispersed in the fiber structure and will not be dissolved too quickly due to washing during use. In addition, since the generated nano-silver particles are uniformly dispersed in the fiber structure, the generated nano-silver particles are not easy to agglomerate due to the barrier of the hemp fiber structure, and the reducing microenvironment formed by the rich hydroxyl groups in the hemp fiber structure can significantly reduce the oxidation of nano-silver by oxygen molecule penetration, thereby enhancing the stability of the nano-silver particles.

[0036] After reduction, the fiber was taken out, washed in pure water until neutral, and dried in vacuum at 60°C to obtain 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, which can reduce wastewater discharge and further improve the utilization rate of silver ions.

[0038] The 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 use 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 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 fibers: The damage to hemp fibers caused by high temperature treatment is avoided during the whole process, and the original excellent mechanical properties of hemp fibers are maintained;

[0043] (4) Environmental protection and energy saving: Compared with the traditional high-temperature treatment method, 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] In order to further illustrate the present invention, a method for preparing antibacterial hemp fiber loaded with nano-silver by gaseous reduction provided by the present invention is described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0045] Example 1

[0046] Weigh 1.0g of hemp fiber, soak it in 0.2M silver nitrate solution at 25℃ for 12h, shake it at 180rpm overnight, and the fiber will be impregnated and adsorb silver ions;

[0047] The fiber was fished out, squeezed to 4g, 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 -40℃ and the time was 2h; in the sublimation stage, the vacuum freeze drying temperature was -35℃ and the vacuum degree was 1.3Pa, so that the water in the material was completely sublimated;

[0048] The fiber was placed in 3L 0.3% (v / v) sulfur dioxide gas, reacted for 3 hours, taken out, washed in pure water until neutral, and vacuum dried at 60°C to obtain yellow nano-silver-loaded hemp fiber. The silver content in the fiber was tested by microwave digestion-inductively coupled plasma technology and was 58.5 mg / g.

[0049] Example 2

[0050] Weigh 1.0 g of hemp fiber, soak it in 0.5 M silver nitrate solution at 30 °C for 6 h, shake it at 180 rpm overnight, and the fiber will be impregnated and adsorb silver ions;

[0051] The fiber was fished out, squeezed to 4g, 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 -50℃ and the time was 0.5h; in the sublimation stage, the vacuum freeze drying temperature was -10℃ and the vacuum degree was 13Pa, so that the water in the material was completely sublimated;

[0052] The fiber was placed in 2L 0.5% (v / v) sulfur dioxide gas, reacted for 5 hours, taken out, washed in pure water until neutral, and dried to obtain yellow nano-silver loaded hemp fiber. The silver content in the fiber was tested by microwave digestion-inductively coupled plasma technology and was 115.1 mg / g.

[0053] Example 3

[0054] Weigh 1.0g of hemp fiber, soak it in 0.1M silver nitrate solution at 20℃ for 24h, shake it at 180rpm overnight, and the fiber will be impregnated and adsorb 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, so that the water in the material was completely sublimated;

[0056] The fiber was placed in 2L 0.5% (v / v) sulfur dioxide gas, reacted for 1 hour, taken out, washed in pure water until neutral, and dried to obtain yellow nano-silver loaded hemp fiber. The silver content in the fiber was tested by microwave digestion-inductively coupled plasma technology and was 40.9 mg / g.

[0057] Comparative Example 1

[0058] Weigh 1.0g of hemp fiber, soak it in 0.2M silver nitrate solution at 25℃ for 12h, shake it at 180rpm overnight, and the fiber will be impregnated and adsorb silver ions;

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

[0060] The fiber was placed in 3L 0.3% (v / v) sulfur dioxide gas, reacted for 3 hours, taken out, washed in pure water until neutral, and vacuum dried at 60°C to obtain yellow nano-silver loaded hemp fiber. The silver content in the fiber was tested by microwave digestion-inductively coupled plasma technology and was 10.5 mg / g.

[0061] The present invention performs SEM test on the loaded nano silver hemp fibers 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-hemp fiber (before cleaning) prepared in Example 1; Figure 3 This is the SEM image of the nano-silver-hemp fiber (before cleaning) prepared in Comparative Example 1.

[0062] Depend on Figure 2 and Figure 3 It can be seen that: there are many wrinkles on the surface of the fiber prepared in Example 1, and there are many nanosilver particles in the gaps between the wrinkles after magnification, and they are evenly distributed; while there are many rod-shaped crystals on the surface of the fiber prepared in Comparative Example 1, which is mainly due to the fact that the silver nitrate solution that penetrates the fiber structure flows to the fiber surface during the drying process, and crystallizes on the fiber surface to form rod-shaped silver nitrate crystals after dehydration. When sulfur dioxide is used for reduction, only the silver ions on the surface of the crystals will be reduced, and the nanosilver generated by the reduction will still remain in the silver nitrate crystals. When pure water is used for post-washing treatment, the silver nitrate crystals on the surface of the fiber dissolve into the water, and as the silver nitrate crystals dissolve, the nanosilver contained in them also enters the water body, which 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 loaded nano silver hemp fiber (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 368.2 eV and 374.2 eV represent singlet silver, and the binding energies of 367.9 eV and 373.9 eV represent monovalent silver ions. These peaks demonstrate that Ag and Ag + Coexistence on the surface of hemp fibers.

[0064] The present invention conducts 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 Washability 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 Washability test results of the nano silver hemp fiber prepared in Comparative Example 1

[0072]

[0073] The present invention tests the breaking strength and breaking elongation of the loaded nano silver 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 nano-silver hemp fibers prepared in Examples 1 to 3 and Comparative Example 1

[0075]

[0076] As can be seen from the above embodiments, the present invention provides a method for preparing nano-silver-loaded antibacterial hemp fiber by gaseous reduction, comprising the following steps: immersing hemp fiber in an aqueous solution containing silver ions to obtain hemp fiber adsorbing silver ions; freezing the hemp fiber adsorbing silver ions and then vacuum freeze-drying to obtain freeze-dried fiber; reducing the freeze-dried fiber with gaseous sulfur dioxide to obtain nano-silver-loaded hemp fiber. The method first allows hemp fiber to be impregnated with adsorbed silver ions, and then removes the moisture in the hemp fiber by freeze-drying technology, and the silver ions are still retained in the fiber structure after freeze-drying. Finally, the silver ions are reduced to nano-silver particles by a gas-solid reaction method of gaseous reduction, and are evenly dispersed in the fiber structure, and will not be dissolved too quickly due to washing and other procedures. During the preparation process, the original physical properties of the hemp fiber (such as breaking strength, elongation at break, etc.) are maintained. The method improves the utilization rate and distribution uniformity of nano-silver, and the prepared fiber has excellent antibacterial durability. The nano-silver particles are evenly dispersed in the fiber structure and form a good combination with the fiber to enhance the mechanical strength of the fiber, or remain unchanged. Due to the high temperature treatment, the fiber in comparative example 1 is in poor condition, easy to fall off, and the mechanical strength is greatly reduced. The experimental results show that after washing 50 times, the antibacterial rate of E. coli, S. aureus and C. albicans is 92-95%, 95.93-99.13% and 79.95-85.98% respectively; the breaking strength is 5.19-5.25 cN / dtex; the breaking elongation is 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 principle of the present invention. These improvements and modifications should also be regarded as 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 fiber is immersed in an aqueous solution containing silver ions to obtain the hemp fiber adsorbing the silver ions; Freezing the hemp fiber adsorbing the silver ions and then freeze-drying it in a vacuum to obtain freeze-dried fiber; The freeze-dried fibers are reduced with gaseous sulfur dioxide to obtain nano-silver-loaded hemp fibers.

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 to 30° C., and the immersion time is 6 to 24 hours; The shaking speed is 100-180 rpm.

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

5. The preparation method according to claim 1, characterized in that: In the pre-freezing stage, the temperature of vacuum freeze drying is -40℃~-50℃, and the time is 0.5~2h; in the sublimation stage, the temperature of vacuum freeze drying is -35℃~-10℃, and the vacuum degree is 1.3~13Pa.

6. The preparation method according to claim 1, characterized in that: The molar ratio of the mass of the freeze-dried fiber to gaseous sulfur dioxide is 1 g: (0.2-1) mmol.

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

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

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

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

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