Silk micro / nanofiber / nonwoven fabric composites, their preparation methods and applications

Abstract

This invention provides a silk micro / nanofiber / nonwoven fabric composite, its preparation method, and its application. The preparation process involves sequentially adding acetic acid and a polysaccharide polymer solution of a predetermined concentration to a silk micro / nanofiber suspension, mixing thoroughly to obtain a silk micro / nanofiber / polysaccharide polymer composite slurry of the predetermined concentration. The obtained silk micro / nanofiber / polysaccharide polymer composite slurry is then coated onto a hydrophilically modified nonwoven fabric using a doctor blade. After drying, a silk micro / nanofiber composite film of a predetermined thickness is formed on the hydrophilically modified nonwoven fabric, resulting in the silk micro / nanofiber / nonwoven fabric composite. This invention first utilizes the synergistic effect of silk micro / nanofibers, acetic acid, and polysaccharide polymer to obtain a uniformly dispersed composite slurry with suitable viscosity. Then, a doctor blade is used to uniformly attach the composite slurry onto the hydrophilic nonwoven fabric. During drying, the bonding structure of the silk fibers, polysaccharide polymer, and active hydroxyl groups on the nonwoven fabric undergoes fine-tuning, resulting in a nanoscale porous structure.

Description

Technical Field

[0001] This invention relates to the field of nanofiber membrane technology, and in particular to a silk micro / nanofiber / nonwoven composite, its preparation method, and its application. Background Technology

[0002] The extremely fine diameter of nanofibers gives them a large specific surface area and high surface adsorption properties. Nanofiber webs, films, or nonwoven fabrics, while possessing extremely small pore sizes, can also maintain a certain porosity, meeting the requirements for gas or liquid flow. Nanofibers and their composites have been widely applied and researched in aerospace, biomedicine, industrial gases, liquid filtration, energy electronics, food packaging, and cosmetics.

[0003] Silk is a natural protein fiber containing a complex hierarchical nanostructure with silk fibrils ranging from tens of nanometers to several micrometers. Due to its excellent mechanical properties, good biocompatibility, and biodegradability, natural silk micro / nanofibers have been studied for membrane and aerogel applications in biomedical materials and filtration materials. Currently, natural silk micro / nanofiber membranes are commonly prepared using vacuum filtration. However, vacuum filtration has significant drawbacks: in terms of process, large-scale, continuous membrane preparation is difficult, and the equipment is costly and energy-intensive; regarding membrane performance, the mechanical properties are poor under humid conditions. Furthermore, when micro / nanofibers are used as filter materials or dressings, it is difficult to simultaneously achieve good mechanical properties and optimal air permeability, moisture permeability, and filtration resistance. Specifically, to obtain good air permeability, moisture permeability, and low filtration resistance, the membrane thickness must be reduced; however, reducing the thickness makes it difficult to achieve the required mechanical strength and self-support for the application.

[0004] To address the aforementioned issues, patent CN105582744B discloses a silk nanofiber filter material, its preparation method, and its application. The method involves dispersing silk nanofibers in deionized water to form a slurry, which is then sprayed onto a non-woven fabric to create a composite membrane of silk nanofibers and non-woven fabric. This involves combining micro / nanofibers and a substrate, with the substrate providing support and the composite micro / nanofiber layer providing functionality. However, this preparation process suffers from poor dispersion uniformity of the silk micro / nanofibers. Furthermore, when using a spraying method, the natural silk micro / nanofibers are difficult to spray evenly under airflow, making thickness control challenging and hindering large-scale, continuous, and controllable preparation. The dehydration process requires filtration and deposition, resulting in high energy consumption and complex equipment.

[0005] In view of this, it is necessary to design an improved silk micro / nanofiber / nonwoven fabric composite, its preparation method and application, in order to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide a silk micro / nanofiber / nonwoven fabric composite, its preparation method, and its application. The preparation process first utilizes the synergistic effect of silk fibers, acetic acid, and polysaccharide polymers to obtain a uniformly dispersed silk micro / nanofiber / polysaccharide polymer composite slurry with appropriate viscosity. Then, a scraper is used to uniformly attach the composite slurry onto a hydrophilic nonwoven fabric. As it dries, the bonding structure of the silk fibers, polysaccharide polymers, and active hydroxyl groups on the nonwoven fabric is finely adjusted, further adjusting the pore structure to obtain a nanoscale porous structure.

[0007] To achieve the above-mentioned objective, this invention provides a method for preparing a silk micro / nanofiber / nonwoven fabric composite, comprising the following steps:

[0008] S1. Add acetic acid and a polysaccharide polymer solution of a preset concentration sequentially to the silk micro-nanofiber suspension, and mix well to obtain a silk micro-nanofiber / polysaccharide polymer composite slurry of a preset concentration;

[0009] S2. Using a scraper, the silk micro / nanofiber / polysaccharide polymer composite slurry obtained in step S1 is coated onto a hydrophilic modified nonwoven fabric. After drying, a silk micro / nanofiber composite film of a predetermined thickness is formed on the hydrophilic modified nonwoven fabric, thus obtaining a silk micro / nanofiber / nonwoven fabric composite.

[0010] As a further improvement of the present invention, in the silk micro / nanofiber / polysaccharide polymer composite slurry of step S1, the mass fraction of the silk micro / nanofiber is 0.5% to 2%, the mass of the polysaccharide polymer is 5% to 15% of the mass of the silk micro / nanofiber, and the volume fraction of acetic acid is 0.5% to 1.5%.

[0011] As a further improvement of the present invention, in step S2, the coating speed of the scraper is 0.01 to 0.8 m / s, and the coating thickness is 50 to 1500 μm; after drying, the thickness of the silk micro / nanofiber composite film formed on the hydrophilic modified nonwoven fabric is 1 to 30 μm.

[0012] As a further improvement of the present invention, the polysaccharide polymer is a high molecular weight polysaccharide polymer; the polysaccharide polymer includes one or more of chitosan, guar gum, modified starch, modified starch, and cellulose derivatives.

[0013] As a further improvement of the present invention, the hydrophilic modification treatment of the nonwoven fabric is one or more of plasma treatment and hydrophilic coating finishing.

[0014] As a further improvement of the present invention, the nonwoven fabric is characterized in that it comprises nonwoven fabric prepared from natural fibers, regenerated fibers, and chemically synthesized fibers, with a basis weight of 20-200 g / m².2 .

[0015] As a further improvement of the present invention, the silk micro-nano fibers are natural silk extracts with a diameter of 30-3000 nm.

[0016] As a further improvement of the present invention, step S1 specifically involves first dissolving the polysaccharide polymer in an acetic acid solution to obtain a polysaccharide polymer solution of a predetermined concentration; then dissolving silk micro / nanofibers in deionized water to obtain a silk micro / nanofiber suspension; and then sequentially adding acetic acid and the polysaccharide polymer solution to the silk micro / nanofiber suspension, and stirring at a speed of 50–50000 r / min for 0.1–24 h to obtain a silk micro / nanofiber / polysaccharide polymer composite slurry of a predetermined concentration.

[0017] The present invention also provides a silk micro / nanofiber / nonwoven fabric composite, which is prepared by the above-described method for preparing the silk micro / nanofiber / nonwoven fabric composite.

[0018] The present invention also provides an application of the above-mentioned silk micro-nanofiber / nonwoven fabric composite, which is used as a filter material and wound dressing.

[0019] The beneficial effects of this invention are:

[0020] (1) The preparation method of the silk micro / nanofiber / nonwoven composite provided by the present invention first prepares a polysaccharide polymer solution, and then adds acetic acid and polysaccharide polymer solution to the silk micro / nanofiber suspension in sequence. The viscosity of the polysaccharide polymer solution is used to uniformly disperse the silk fibers to obtain a composite slurry with a suitable coating viscosity. At the same time, the silk micro / nanofiber, acetic acid and polysaccharide polymer bond with each other to form a spatial network structure, further improving the dispersion uniformity of the silk fibers, and obtaining a silk micro / nanofiber / polysaccharide polymer composite slurry with uniform dispersion and appropriate viscosity.

[0021] Based on this, the composite slurry is uniformly adhered to the hydrophilic nonwoven fabric using a scraper. The spatial network structure formed between the silk micro / nanofibers, acetic acid, and polysaccharide polymer further bonds with the active hydroxyl groups on the nonwoven fabric, firmly adsorbing the silk micro / nanofiber / polysaccharide polymer composite slurry onto the nonwoven fabric. As deionized water continuously evaporates during the drying process, a porous structure is formed; simultaneously, acetic acid also slowly evaporates, and the bonding structure of the silk fibers, polysaccharide polymer, and active hydroxyl groups on the nonwoven fabric is finely adjusted, further modifying the pore structure to obtain a nanoscale porous structure, giving the resulting composite a certain porosity and air permeability.

[0022] (2) The preparation method of the present invention does not involve complex chemical reactions, the materials used are widely available, non-toxic and harmless, simple, low energy consumption, and can achieve large-scale and continuous production. At the same time, the composite material with controllable thickness can be used in applications such as filtration and wound dressing. Attached Figure Description

[0023] Figure 1 A is a SEM image of the surface of the silk micro / nanofiber / nonwoven fabric composite membrane prepared in Example 1, with a scale bar of 10 μm. Figure 1 B. SEM image of the surface of the hydrophilic nonwoven fabric, scale bar is 100μm; Figure 1 C is a cross-sectional SEM image of the silk micro / nanofiber / nonwoven fabric composite, with a scale bar of 50 μm; Figure 1 D is Figure 1 A magnified, scale bar is 2μm; Figure 1 E is Figure 1 B magnified, scale bar is 20μm; Figure 1 F is Figure 1 The scale bar for C is 2μm.

[0024] Figure 2 A is a SEM image of the surface of the hydrophilic PP nonwoven fabric after filtering a 3μm PS microsphere solution, with a scale bar of 100μm. Figure 2 B and 2C are respectively Figure 2 A magnified, with scales of 50μm and 2μm respectively.

[0025] Figure 3 A is a SEM image of the surface of the silk micro-nanofiber / nonwoven fabric composite membrane prepared in Example 1 after filtering a 3μm PS microsphere solution. The scale bar is 20μm. Figure 3 B and 3C are respectively Figure 3 A magnified, with scales of 10μm and 2μm respectively.

[0026] Figure 4 A is a SEM image of the silk micro / nanofiber / nonwoven fabric composite prepared in Comparative Example 2, with a scale bar of 200 μm; Figure 4 B and 4C are respectively Figure 4 A magnified, with scales of 100μm and 20μm respectively. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0029] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0030] This invention provides a method for preparing a silk micro / nanofiber / nonwoven fabric composite. The method involves using acetic acid and a polysaccharide polymer to regulate the dispersion uniformity and viscosity of a silk micro / nanofiber suspension, and then coating the surface of a hydrophilically modified nonwoven fabric substrate with a film-coating process to form the silk micro / nanofiber / nonwoven fabric composite. The method includes the following steps:

[0031] S1. Preparation of silk micro / nanofiber / polysaccharide polymer composite slurry:

[0032] After degumming, the silk was placed in a swelling solution (a mixture of calcium nitrate, ethanol, and water, with a volume ratio of ethanol to water of 1:2–6 and a mass ratio of calcium nitrate to the total volume of ethanol and water of 1–10 g:100 mL) and placed in an oven at 50–80 °C for 60–80 h to swell the silk and weaken the binding force between the nanofibers in the silk. After removal, it was washed three times with deionized water and placed in a crusher at a speed of 7000–9000 r / min with a bath ratio of 1 g:100–200 mL (i.e., 1 g silk: 100–200 mL water) for 80–100 min to mechanically crush the silk fibers. The fibers were then filtered three times and freeze-dried to obtain silk micro / nanofibers.

[0033] The polysaccharide polymer is dissolved in an acetic acid solution, and the polysaccharide polymer molecules and acetic acid molecules bond with each other, so that the polysaccharide polymer molecules are uniformly dispersed in the acetic acid solution, resulting in a polysaccharide polymer solution with a mass fraction of 1% to 5%.

[0034] Next, silk micro / nanofibers were dissolved in deionized water and mixed in a homogenizer to maximize the dispersion of the silk micro / nanofibers in the deionized water, resulting in a silk micro / nanofiber suspension. Then, acetic acid and a polysaccharide polymer solution were added sequentially to the silk micro / nanofiber suspension, and the mixture was stirred at 50–50000 r / min for 0.1–24 h to obtain a silk micro / nanofiber / polysaccharide polymer composite slurry of a predetermined concentration. In this process, the polysaccharide aqueous solution has a certain viscosity, and the viscosity generally increases with increasing molecular weight. Using a high molecular weight polysaccharide polymer to control the viscosity of the natural silk micro / nanofiber slurry makes it easy to achieve a suitable coating viscosity with a small amount of polysaccharide polymer, while also helping to preserve the basic morphology and pore structure of the natural silk micro / nanofiber composite membrane. In addition, acetic acid is added first. Acetic acid is rapidly miscible with water and is uniformly dispersed in the silk micro / nanofiber suspension. At the same time, the carboxyl groups of acetic acid can bond with the active groups such as the hydroxyl groups of silk fibers, improving the dispersion uniformity of silk fibers. Then, a polysaccharide polymer solution is added. The presence of acetic acid can not only prevent the polysaccharide polymer molecules from agglomerating and making them uniformly dispersed, but also allow the silk fibers, acetic acid and polysaccharide polymer to bond with each other, forming a three-dimensional network structure, which is uniformly dispersed in deionized water, resulting in a uniformly dispersed silk micro / nanofiber / polysaccharide polymer composite slurry with appropriate viscosity.

[0035] Specifically, in the silk micro / nanofiber / polysaccharide polymer composite slurry, the mass fraction of silk micro / nanofiber is 0.5% to 2%, the mass fraction of polysaccharide polymer is 1% to 15% of the mass of silk micro / nanofiber, and the volume fraction of acetic acid is 0.5% to 1.5%.

[0036] The polysaccharide polymer is preferably a high molecular weight polysaccharide polymer; the polysaccharide polymer includes one or more of chitosan, guar gum, modified starch, modified starch, and cellulose derivatives.

[0037] Silk micro / nanofibers are natural silk extracts with a diameter of 30–3000 nm. The silk can be domesticated silkworm silk or wild silkworm silk.

[0038] S2. Coating:

[0039] Nonwoven fabrics are hydrophilically modified to achieve a pure water contact angle of less than 90 degrees, resulting in hydrophilically modified nonwoven fabrics. The hydrophilic modification process can be one or more methods, such as plasma treatment or hydrophilic coating finishing.

[0040] Nonwoven fabrics include nonwoven fabrics made from natural fibers, regenerated fibers, and chemically synthesized fibers, with a basis weight of 20–200 g / m². 2 .

[0041] The silk micro / nanofiber / polysaccharide polymer composite slurry obtained in step S1 is coated onto a hydrophilic modified nonwoven fabric using a scraper. After drying, a silk micro / nanofiber composite film with a thickness of 1–30 μm is formed on the hydrophilic modified nonwoven fabric, thus obtaining the silk micro / nanofiber / nonwoven fabric composite.

[0042] Specifically, the coating speed of the scraper is 0.01 to 0.8 m / s, and the coating thickness is 50 to 1500 μm.

[0043] In this process, firstly, at a suitable viscosity, a scraper uniformly adheres the composite slurry of silk micro / nanofibers / polysaccharide polymers onto a hydrophilic nonwoven fabric. The spatial network structure formed between the silk fibers, acetic acid, and polysaccharide polymers further bonds with the active hydroxyl groups on the nonwoven fabric, firmly adsorbing the silk micro / nanofibers / polysaccharide polymer composite slurry onto the nonwoven fabric. Next, a drying process is performed, with deionized water continuously evaporating to form a porous structure. Simultaneously, acetic acid slowly evaporates. With the evaporation of acetic acid, the bonding structure of the silk fibers, polysaccharide polymers, unevaporated trace amounts of acetic acid, and active hydroxyl groups on the nonwoven fabric undergoes fine-tuning, further adjusting the pore structure to obtain a nanoscale porous structure.

[0044] When filtering the prepared silk micro / nanofiber / nonwoven composite solution, it is usually first soaked in a 0.1 mol / L sodium hydroxide solution for 5 minutes, and then washed multiple times with deionized water to remove sodium hydroxide. This operation removes residual trace amounts of acetic acid and, to some extent, fine-tunes the bonding structure formed by the active hydroxyl groups on the silk fibers, polysaccharide polymer, and nonwoven fabric.

[0045] The present invention also provides a silk micro / nanofiber / nonwoven fabric composite, which is prepared by the above-mentioned method for preparing the silk micro / nanofiber / nonwoven fabric composite.

[0046] This invention also provides an application of the silk micro / nanofiber / nonwoven fabric composite, which is used in filter materials and wound dressings.

[0047] The present invention will now be described in detail through specific embodiments.

[0048] Example 1

[0049] A method for preparing a silk micro / nanofiber / nonwoven fabric composite includes the following steps:

[0050] S1. Preparation of silk micro / nanofiber / polysaccharide polymer composite slurry:

[0051] 5g of degummed silk was placed in a swelling solution (a mixture of calcium nitrate, ethanol, and water, with a volume ratio of ethanol to water of 1:3 and a calcium nitrate content of 5g:100mL) and placed in an oven at 60℃ for 72h. After removal, it was washed three times with deionized water and placed in a crusher with a blade speed of 8000r / min at a bath ratio of 1g:200mL for 90min of mechanical treatment. After filtering three times with a filter screen, the silk micro-nano fibers were obtained by freeze drying.

[0052] High molecular weight chitosan was dissolved in a 1% acetic acid solution, and the magnetic stirrer was set to 300 rpm to obtain a chitosan solution with a concentration of 20 mg / mL (approximately 2% by mass).

[0053] Next, 1g of dry silk micro / nanofibers were dissolved in 94.25mL of deionized water and mixed in a homogenizer at 800rpm for 5min to obtain a silk micro / nanofiber suspension. Then, 1mL of acetic acid and 3.75mL of high molecular weight chitosan solution with a concentration of 20mg / mL were added to the silk micro / nanofiber suspension in sequence, and the mixture was slowly stirred at 200rpm for 24h to defoam, thus obtaining a silk micro / nanofiber / polysaccharide polymer composite slurry.

[0054] At this point, in the silk micro / nanofiber / polysaccharide polymer composite slurry, the mass fraction of silk micro / nanofiber is 1%, the mass of polysaccharide polymer is 7.5% of the mass of silk micro / nanofiber, and the volume fraction of acetic acid is 1% (here, acetic acid refers only to the 1 mL of acetic acid added to the silk micro / nanofiber suspension).

[0055] The diameter of silk micro-nano fibers is mainly 500 nm.

[0056] S2. Coating:

[0057] PP nonwoven fabric is hydrophilically modified by plasma treatment, so that the pure water contact angle of the nonwoven fabric is less than 90 degrees, thus obtaining hydrophilically modified nonwoven fabric.

[0058] A 500 μm thick coating was applied to a substrate with a coating weight of 60 g / m² using a doctor blade at a coating speed of 0.02 m / s. 2 The hydrophilically modified PP nonwoven fabric is coated and then dried in a 60℃ oven to form a silk micro-nanofiber composite film with a thickness of about 2.9μm on the hydrophilically modified nonwoven fabric, thus obtaining the silk micro-nanofiber / nonwoven fabric composite.

[0059] Depend on Figure 1 A and Figure 1The SEM image of D shows that chitosan and silk fibers are cross-linked and intertwined, forming a uniform porous structure. Furthermore, chitosan, a positively charged natural alkaline polysaccharide, exhibits stronger bonding with acetic acid and silk micro / nanofibers. Figure 1 C and Figure 1 The SEM image of F shows that the silk micro / nanofiber composite membrane layer and the nonwoven fabric layer are tightly bonded together, while the silk fibers do not excessively adhere to each other, thus improving its porosity and air permeability. Meanwhile, chitosan possesses excellent biocompatibility and slow biodegradability, as well as good antibacterial and hemostatic properties, giving the resulting silk micro / nanofiber / nonwoven fabric composite a variety of properties.

[0060] A 3 μm PS microsphere suspension was filtered using hydrophilically modified PP nonwoven fabric and the silk micro / nanofiber / nonwoven fabric composite prepared in Example 1, respectively. The specific operation of the PS microsphere suspension filtration experiment was as follows: before filtering the PS microsphere solution with the silk micro / nanofiber / nonwoven fabric composite prepared in Example 1, it was first soaked in a 0.1 mol / L sodium hydroxide solution for 5 min, and then washed multiple times with deionized water to remove sodium hydroxide.

[0061] S1. First, prepare a 10 mg / L solution of PS microspheres with a diameter of 3 μm, and then measure the maximum absorption wavelength of the 3 μm PS microsphere solution using UV-Vis spectrophotometry.

[0062] S2. Prepare 3μm PS microsphere solutions of different concentrations, and then measure the absorbance of the corresponding concentration PS microsphere solutions at the maximum absorption wavelength. Plot a standard curve of the concentration versus absorbance of the 3μm PS microsphere solutions.

[0063] S3. The hydrophilically modified PP nonwoven fabric and the silk micro / nanofiber / nonwoven fabric composite prepared in Example 1 were respectively placed in the filter as filter layers to filter a 10 mg / L solution of 3 μm PS microspheres. Then, the absorbance of the filtrate was measured at the maximum absorption wavelength. The filtration efficiency of the hydrophilically modified PP nonwoven fabric and the silk micro / nanofiber / nonwoven fabric composite prepared in Example 1 were calculated according to the standard curve of the concentration and absorbance of the 3 μm PS microsphere solution.

[0064] Depend on Figure 2 As shown in A, 2B, and 2C, the surface of the filtered hydrophilic PP nonwoven fabric shows virtually no intercepted 3μm PS microspheres. This is mainly because the hydrophilic PP nonwoven fabric has a relatively large pore size. Calculations show that the filtration efficiency of the hydrophilic PP nonwoven fabric for a solution containing 3μm PS microspheres is <5%.

[0065] Depend on Figure 3As shown in A, 3B, and 3C, after filtering a solution of 3μm PS microspheres, the silk micro / nanofiber / nonwoven composite prepared in Example 1 exhibits a large number of intercepted 3μm PS microspheres adhering to its surface. This is mainly because the pore size of the silk micro / nanofiber / nonwoven composite surface is generally less than 3μm, resulting in a large number of PS microspheres being intercepted on the surface of the silk micro / nanofiber / nonwoven composite after filtering the 3μm PS microsphere solution. Calculations show that the filtration efficiency of the silk micro / nanofiber / nonwoven composite prepared in Example 1 for the 3μm PS microsphere solution is >99%.

[0066] The silk micro / nanofiber / nonwoven fabric composite prepared in Example 1 was placed under a pressure of 1 bar, and the volume of pure water passing through it over a certain area and time was measured to calculate its water flux. The pure water flux was >90 L·h. -1 ·m -2 ·bar -1 .

[0067] Comparative Example 1

[0068] A method for preparing a silk micro / nanofiber / nonwoven fabric composite differs from Example 1 in that the concentration of chitosan solution in the silk micro / nanofiber / polysaccharide polymer composite slurry is different. Otherwise, it is largely the same as Example 1 and will not be described again here.

[0069] Specifically, 1g of dry silk micro / nanofibers was dissolved in 80.5mL of deionized water and mixed in a homogenizer at 800rpm for 5min to obtain a silk micro / nanofiber suspension. Then, 1mL of acetic acid and 17.5mL of a high molecular weight chitosan solution with a concentration of 20mg / mL were added to the silk micro / nanofiber suspension in sequence. The mixture was then slowly stirred at 200rpm for 24h to remove foam, resulting in a silk micro / nanofiber / polysaccharide polymer composite slurry.

[0070] At this point, in the silk micro / nanofiber / polysaccharide polymer composite slurry, the mass fraction of silk micro / nanofiber is 1%, the mass of polysaccharide polymer is 35% of the mass of silk micro / nanofiber, and the volume fraction of acetic acid is 1%.

[0071] Comparative Example 2

[0072] A method for preparing a silk micro / nanofiber / nonwoven fabric composite differs from Example 1 in that the concentration of chitosan solution in the silk micro / nanofiber / polysaccharide polymer composite slurry is different. Otherwise, it is largely the same as Example 1 and will not be described again here.

[0073] Specifically, 1g of dry silk micro / nanofibers was dissolved in 97.95mL of deionized water and mixed in a homogenizer at 800rpm for 5min to obtain a silk micro / nanofiber suspension. Then, 1mL of acetic acid and 0.05mL of a high molecular weight chitosan solution with a concentration of 20mg / mL were added to the silk micro / nanofiber suspension in sequence, and the mixture was slowly stirred at 200rpm for 24h to remove foam, thus obtaining a silk micro / nanofiber / polysaccharide polymer composite slurry.

[0074] At this point, in the silk micro / nanofiber / polysaccharide polymer composite slurry, the mass fraction of silk micro / nanofiber is 1%, the mass of polysaccharide polymer is 1% of the mass of silk micro / nanofiber, and the volume fraction of acetic acid is 1%.

[0075] The performance of the silk micro / nanofiber / nonwoven fabric composites prepared in Example 1 and Comparative Examples 1-2 was tested, and the results are shown in Table 1:

[0076] Table 1. Silk micro / nanofiber / nonwoven fabric composites prepared in Example 1 and Comparative Examples 1-2

[0077] Example Chitosan concentration (%) water flux Filtration effect Example 1 7.5 <![CDATA[>90L·h -1 ·m -2 ·bar -1 ]]> >99％ Comparative Example 1 35 <![CDATA[<5L·h -1 ·m -2 ·bar -1 ]]> >99％ Comparative Example 2 1 <![CDATA[>5000L·h -1 ·m -2 ·bar -1 ]]> <20％

[0078] Table 1 shows that with increasing chitosan concentration, the water flux of the prepared silk micro / nanofiber / nonwoven composite gradually decreases, while the filtration efficiency gradually increases. When the chitosan concentration is too high, although the filtration efficiency of 3μm PS microspheres remains >99%, the water flux decreases significantly. This is mainly because excessive chitosan severely affects the bonding structure between silk fibers, chitosan, and nonwoven fabric, causing excessive adhesion between silk fibers, reducing the porosity of the silk micro / nanofibers, and decreasing the pore size, thus leading to a significant decrease in water flux, which is detrimental to practical applications. When the chitosan concentration is too low, the viscosity of the silk micro / nanofiber composite slurry decreases, resulting in poor slurry stability and uneven coating. It also affects the bonding structure between silk fibers, chitosan, and nonwoven fabric, causing defects on the surface of the silk micro / nanofiber / nonwoven composite (such as…). Figure 4 (As shown in A, 4B and 4C), which greatly increases its water flux, but reduces its filtration efficiency.

[0079] Example 2

[0080] A method for preparing a silk micro / nanofiber / nonwoven fabric composite differs from Example 1 in that the mass fraction of silk micro / nanofibers in the silk micro / nanofiber / polysaccharide polymer composite slurry is different. Otherwise, it is largely the same as Example 1 and will not be described again here.

[0081] Specifically, 2g of dry silk micro / nanofibers were dissolved in 89.5mL of deionized water and mixed in a homogenizer at 800rpm for 5min to obtain a silk micro / nanofiber suspension. Then, 1mL of acetic acid and 7.5mL of a high molecular weight chitosan solution with a concentration of 20mg / mL were added to the silk micro / nanofiber suspension in sequence, and the mixture was slowly stirred at 200rpm for 24h to remove foam, thus obtaining a silk micro / nanofiber / polysaccharide polymer composite slurry.

[0082] At this point, in the silk micro / nanofiber / polysaccharide polymer composite slurry, the mass fraction of silk micro / nanofiber is 2.0%, the mass of polysaccharide polymer is 7.5% of the mass of silk micro / nanofiber, and the volume fraction of acetic acid is 1%.

[0083] Example 3

[0084] A method for preparing a silk micro / nanofiber / nonwoven fabric composite differs from Example 1 in that the mass fraction of the silk micro / nanofiber is different, while the rest is largely the same as in Example 1 and will not be repeated here.

[0085] Specifically, 0.5g of dry silk micro / nanofibers were dissolved in 96.625mL of deionized water and mixed in a homogenizer at 800rpm for 5min to obtain a silk micro / nanofiber suspension. Then, 1mL of acetic acid and 1.875mL of a high molecular weight chitosan solution with a concentration of 20mg / mL were added to the silk micro / nanofiber suspension in sequence, and the mixture was slowly stirred at 200rpm for 24h to remove foam, thus obtaining a silk micro / nanofiber / polysaccharide polymer composite slurry.

[0086] At this point, in the silk micro / nanofiber / polysaccharide polymer composite slurry, the mass fraction of silk micro / nanofiber is 0.5%, the mass of polysaccharide polymer is 7.5% of the mass of silk micro / nanofiber, and the volume fraction of acetic acid is 1%.

[0087] Comparative Example 3

[0088] A method for preparing a silk micro / nanofiber / nonwoven fabric composite differs from Example 1 in that the mass fraction of the silk micro / nanofiber is different, while the rest is largely the same as in Example 1 and will not be repeated here.

[0089] Specifically, 0.3g of dry silk micro / nanofibers were dissolved in 97.575mL of deionized water and mixed in a homogenizer at 800rpm for 5min to obtain a silk micro / nanofiber suspension. Then, 1mL of acetic acid and 1.125mL of a high molecular weight chitosan solution with a concentration of 20mg / mL were added to the silk micro / nanofiber suspension in sequence, and the mixture was slowly stirred at 200rpm for 24h to remove foam, thus obtaining a silk micro / nanofiber / polysaccharide polymer composite slurry.

[0090] At this point, in the silk micro / nanofiber / polysaccharide polymer composite slurry, the mass fraction of silk micro / nanofiber is 0.3%, the mass of polysaccharide polymer is 7.5% of the mass of silk micro / nanofiber, and the volume fraction of acetic acid is 1%.

[0091] Comparative Example 4

[0092] A method for preparing a silk micro / nanofiber / nonwoven fabric composite differs from Example 1 in that the mass fraction of the silk micro / nanofiber is different, while the rest is largely the same as in Example 1 and will not be repeated here.

[0093] Specifically, 3g of dry silk micro / nanofibers were dissolved in 84.75mL of deionized water and mixed in a homogenizer at 800rpm for 5min to obtain a silk micro / nanofiber suspension. Then, 1mL of acetic acid and 11.25mL of a high molecular weight chitosan solution with a concentration of 20mg / mL were added to the silk micro / nanofiber suspension in sequence. The mixture was then slowly stirred at 200rpm for 24h to remove foam, resulting in a silk micro / nanofiber / polysaccharide polymer composite slurry.

[0094] At this point, in the silk micro / nanofiber / polysaccharide polymer composite slurry, the mass fraction of silk micro / nanofiber is 3%, the mass of polysaccharide polymer is 7.5% of the mass of silk micro / nanofiber, and the volume fraction of acetic acid is 1%.

[0095] The performance of the silk micro / nanofiber / nonwoven fabric composites prepared in Examples 2-3 and Comparative Examples 3-4 was tested, and the results are shown in Table 2.

[0096] Table 2. Silk micro / nanofiber / nonwoven fabric composites prepared in Examples 2-3 and Comparative Examples 3-4

[0097]

[0098] Table 2 shows that when the mass fraction of silk micro / nanofibers is between 0.5% and 2%, the filtration efficiency of the silk micro / nanofiber / nonwoven fabric composite for 3μm PS microspheres is relatively high, and the water flux is also relatively high. When the mass fraction of silk micro / nanofibers is too high, the filtration efficiency decreases significantly. This is mainly because, under the same coating thickness, excessive silk micro / nanofibers in the composite slurry cause a sharp decrease in the fluidity of the composite slurry, and the silk micro / nanofibers even exhibit agglomeration and aggregation. This also severely affects the bonding structure between the silk fibers, chitosan, and nonwoven fabric, resulting in defects on the surface of the silk micro / nanofiber / nonwoven fabric composite and thus a decrease in filtration effect. When the mass fraction of silk micro-nanofibers is too small, the water flux of the silk micro-nanofiber / nonwoven fabric composite will increase, but the filtration efficiency for 3μm PS microspheres will decrease. This is mainly because the silk micro-nanofiber / polysaccharide polymer composite slurry is too thin and has insufficient viscosity, which will cause defects on the surface of the silk micro-nanofiber / nonwoven fabric composite, resulting in a decrease in filtration effect.

[0099] Examples 4-5 and Comparative Example 5

[0100] A method for preparing a silk micro / nanofiber / nonwoven fabric composite differs from Example 1 in that the coating thickness is different in step S2. Otherwise, it is largely the same as Example 1 and will not be described again here.

[0101] The performance of the silk micro / nanofiber / nonwoven fabric composites prepared in Examples 4-5 and Comparative Example 5 were tested, and the results are shown in Table 3.

[0102] Table 3. Silk micro / nanofiber / nonwoven fabric composites prepared in Examples 4-5 and Comparative Example 5.

[0103] Example Coating thickness (μm) water flux Filtration effect Example 1 500 <![CDATA[>90L·h -1 ·m -2 ·bar -1 ]]> >99％ Example 4 1000 <![CDATA[>10L·h -1 ·m -2 ·bar -1 ]]> >99％ Example 5 1500 <![CDATA[>5L·h -1 ·m -2 ·bar -1 ]]> >99％ Comparative Example 5 2000 <![CDATA[<1L·h -1 ·m -2 ·bar -1 ]]> >99％

[0104] As shown in Table 3, the water flux gradually decreases as the coating thickness increases. When the coating thickness reaches 2000 μm, the water flux will be at a low level, which is not satisfactory for practical applications.

[0105] Example 6 and Comparative Example 6

[0106] A method for preparing a silk micro / nanofiber / nonwoven fabric composite differs from Example 1 in that the coating speed is different in step S2. Otherwise, it is roughly the same as Example 1 and will not be described again here.

[0107] The performance of the silk micro / nanofiber / nonwoven fabric composites prepared in Example 6 and Comparative Example 6 was tested, and the results are shown in Table 4.

[0108] Table 4. Silk micro / nanofiber / nonwoven fabric composites prepared in Example 6 and Comparative Example 6.

[0109] Example Speed ​​(m / s) water flux Filtration effect Example 1 0.02 <![CDATA[>90L·h -1 ·m -2 ·bar -1 ]]> >99％ Example 6 0.05 <![CDATA[>95L·h -1 ·m -2 ·bar -1 ]]> >98％ Comparative Example 6 1 <![CDATA[>10000L·h -1 ·m -2 ·bar -1 ]]> <10％

[0110] As shown in Table 4, the water flux gradually increases while the filtration efficiency gradually decreases as the coating speed increases. This is mainly because when the coating speed is too fast, the slurry coated on the surface is not uniform, which affects the bonding structure between the silk fibers, chitosan and nonwoven fabric. As a result, the surface of the silk micro-nano fiber / nonwoven fabric composite is very prone to defects, which greatly reduces the performance of the silk micro-nano fiber / nonwoven fabric composite.

[0111] Comparative Example 7

[0112] A method for preparing a silk micro / nanofiber / nonwoven composite differs from Example 1 in that, in step S1, low molecular weight chitosan is selected for solution preparation. The other steps are largely the same as in Example 1 and will not be repeated here.

[0113] Comparative Example 8

[0114] A method for preparing a silk micro / nanofiber / nonwoven composite differs from Example 1 in that, in step S1, acetic acid is not added during the preparation of the silk micro / nanofiber / polysaccharide polymer composite slurry; instead, 3.75 mL of a high molecular weight chitosan solution with a concentration of 20 mg / mL is directly added to the silk micro / nanofiber suspension. The rest is largely the same as in Example 1 and will not be repeated here.

[0115] Comparative Example 9

[0116] A method for preparing a silk micro / nanofiber / nonwoven fabric composite differs from Example 1 in that, in step S2, the PP nonwoven fabric is not subjected to hydrophilic treatment. The rest is largely the same as in Example 1 and will not be described in detail here.

[0117] Comparative Example 10

[0118] A method for preparing a silk micro / nanofiber / nonwoven fabric composite differs from Example 1 in that, in step S1, high molecular weight chitosan is replaced with high molecular weight sodium alginate. The rest is largely the same as in Example 1 and will not be described again here.

[0119] High molecular weight sodium alginate was dissolved in deionized water to obtain a sodium alginate solution with a concentration of 20 mg / mL.

[0120] Next, 1g of dry silk micro / nanofibers were dissolved in 95.25mL of deionized water and mixed in a homogenizer at 800rpm for 5min to obtain a silk micro / nanofiber suspension. Then, 3.75mL of high molecular weight chitosan solution with a concentration of 20mg / mL was added to the silk micro / nanofiber suspension and the mixture was slowly stirred at 200rpm for 24h to defoam, resulting in a silk micro / nanofiber / polysaccharide polymer composite slurry.

[0121] A 500 μm thick coating was applied to a substrate with a coating weight of 60 g / m² using a doctor blade at a coating speed of 0.02 m / s. 2 A silk micro / nanofiber composite film with a thickness of approximately 2.9 μm was formed on a hydrophilically modified PP nonwoven fabric, and then the coated nonwoven fabric was dried in a 60℃ oven. This resulted in a silk micro / nanofiber / nonwoven fabric composite. The silk micro / nanofiber / nonwoven fabric composite was then immersed in a 1 mol / L calcium chloride solution for 30 min, followed by washing with deionized water and drying.

[0122] The performance of the silk micro / nanofiber / nonwoven fabric composites prepared in Comparative Examples 7-10 was tested, and the results are shown in Table 5.

[0123] Table 5. Silk micro / nanofiber / nonwoven fabric composites prepared in Comparative Examples 7-10

[0124] Example water flux Filtration effect Comparative Example 7 <![CDATA[>800L·h -1 ·m -2 ·bar -1 ]]> <70％ Comparative Example 8 <![CDATA[>700L·h -1 ·m -2 ·bar -1 ]]> <80％ Comparative Example 9 <![CDATA[>20000L·h -1 ·m -2 ·bar -1 ]]> <10％ Comparative Example 10 <![CDATA[>50L·h -1 ·m -2 ·bar -1 ]]> >99％

[0125] As shown in Comparative Example 7 in Table 5, the silk micro / nanofiber / nonwoven composite prepared using low molecular weight chitosan exhibits poor performance. This is mainly because, on the one hand, low molecular weight chitosan has low viscosity, leading to a decrease in the viscosity and poor stability of the silk micro / nanofiber / polysaccharide polymer composite slurry; on the other hand, the molecular structure of low molecular weight chitosan differs from that of high molecular weight chitosan, thus affecting the bonding structure between various substances and resulting in defects on the surface of the silk micro / nanofiber / nonwoven composite, thereby affecting its performance.

[0126] The data from Comparative Example 8 show that when acetic acid is not added during the preparation of the silk micro / nanofiber / polysaccharide polymer composite slurry, chitosan will have uneven dispersion, which will result in defects on the surface of the silk micro / nanofiber / nonwoven fabric composite obtained by coating the nonwoven fabric with the composite slurry, thus affecting its performance.

[0127] As can be seen from the data in Comparative Example 9, when the nonwoven fabric is not treated with hydrophilic treatment, the silk micro-nanofiber / polysaccharide polymer composite slurry coated onto the hydrophobic nonwoven fabric will cause the slurry to separate from the nonwoven fabric, which will seriously damage the surface structure of the silk micro-nanofiber / nonwoven fabric composite and lead to a significant decrease in filtration efficiency.

[0128] The data from Comparative Example 10 show that the silk micro / nanofiber / nonwoven composite prepared using sodium alginate as a polysaccharide polymer can achieve certain required properties, but the overall effect is not as good as that of chitosan.

[0129] In summary, this invention provides a silk micro / nanofiber / nonwoven fabric composite, its preparation method, and its application. The preparation process first utilizes the synergistic effect of silk fibers, acetic acid, and polysaccharide polymers to obtain a uniformly dispersed silk micro / nanofiber / polysaccharide polymer composite slurry with appropriate viscosity. Then, a scraper is used to uniformly adhere the composite slurry onto a hydrophilic nonwoven fabric. As it dries, the bonding structure of the silk micro / nanofibers, polysaccharide polymers, and active hydroxyl groups on the nonwoven fabric is finely adjusted, further modifying the pore structure to obtain a nanoscale porous structure.

[0130] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a silk micro / nanofiber / nonwoven fabric composite, characterized in that, Includes the following steps: S1. Acetic acid and a polysaccharide polymer solution of a predetermined concentration are added sequentially to the silk micro-nanofiber suspension and mixed to obtain a silk micro-nanofiber / polysaccharide polymer composite slurry of a predetermined concentration. In the silk micro-nanofiber / polysaccharide polymer composite slurry, the mass fraction of the silk micro-nanofiber is 0.5%~2%, and the mass of the polysaccharide polymer is 5%~15% of the mass of the silk micro-nanofiber. The polysaccharide polymer is high molecular weight chitosan. S2. The silk micro / nanofiber / polysaccharide polymer composite slurry obtained in step S1 is coated onto a hydrophilic modified nonwoven fabric using a doctor blade. After drying, a silk micro / nanofiber composite film of a predetermined thickness is formed on the hydrophilic modified nonwoven fabric, thus obtaining a silk micro / nanofiber / nonwoven fabric composite. The coating speed of the doctor blade is 0.01~0.8m / s, and the coating thickness is 50~1500μm.

2. The method for preparing the silk micro / nanofiber / nonwoven fabric composite according to claim 1, characterized in that, The volume fraction of acetic acid in step S1 is 0.5% to 1.5%.

3. The method for preparing the silk micro / nanofiber / nonwoven fabric composite according to claim 1, characterized in that, In step S2, after drying, the thickness of the silk micro / nanofiber composite film formed on the hydrophilic modified nonwoven fabric is 1~30μm.

4. The method for preparing the silk micro / nanofiber / nonwoven fabric composite according to claim 1, characterized in that, The hydrophilic modification treatment of nonwoven fabrics is one or more of plasma treatment and hydrophilic coating finishing.

5. The method for preparing the silk micro / nanofiber / nonwoven composite according to claim 1, characterized in that, The nonwoven fabric includes nonwoven fabrics made from natural fibers, regenerated fibers, and chemically synthesized fibers, with a basis weight of 20~200g / m². 2 .

6. The method for preparing the silk micro / nanofiber / nonwoven composite according to claim 1, characterized in that, The silk micro-nano fibers are natural silk extracts with a diameter of 30~3000nm.

7. The method for preparing the silk micro / nanofiber / nonwoven composite according to claim 1, characterized in that, Step S1 specifically involves first dissolving the polysaccharide polymer in an acetic acid solution to obtain a polysaccharide polymer solution of a predetermined concentration; then dissolving silk micro / nanofibers in deionized water to obtain a silk micro / nanofiber suspension; and then sequentially adding acetic acid and the polysaccharide polymer solution to the silk micro / nanofiber suspension, stirring at a speed of 50~50000 r / min for 0.1~24 h to obtain a silk micro / nanofiber / polysaccharide polymer composite slurry of a predetermined concentration.

8. A silk micro / nanofiber / nonwoven fabric composite, characterized in that, The composite material was prepared using the method described in any one of claims 1 to 7.

9. The application of the silk micro / nanofiber / nonwoven fabric composite prepared by the method of any one of claims 1 to 7, or the silk micro / nanofiber / nonwoven fabric composite of claim 8, characterized in that, The silk micro / nanofiber / nonwoven composite is used in filter materials and wound dressings.

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