CN107469645B - Small-aperture high-porosity bacterial cellulose nanofiber composite membrane and preparation method thereof - Google Patents

Abstract

The invention discloses a small-aperture high-porosity bacterial cellulose nanofiber composite membrane and a preparation method thereof. The preparation method comprises the following steps: mechanically dissociating the bacterial cellulose membrane, dispersing the bacterial cellulose membrane in an insoluble solvent, and adding a dispersing agent to form a stable bacterial cellulose nanofiber suspension; spreading the bacterial cellulose nanofiber suspension on the surface of the porous fiber base material by adopting a synchronous ultrasonic filtration method to form a wet composite membrane; and removing the residual solvent in the wet composite membrane to obtain the small-aperture high-porosity bacterial cellulose nanofiber composite membrane with a continuous two-dimensional reticular structure completely covered on the surface. The surface of the composite membrane is a completely covered continuous two-dimensional reticular structure formed by bacterial cellulose nanofibers. The invention has the advantages of continuous two-dimensional network structure with completely covered surface and higher porosity.

Description

Small pore size high porosity bacterial cellulose nanofiber composite membrane and preparation method thereof

technical field

The invention relates to a small pore size and high porosity bacterial cellulose nanofiber composite membrane and a preparation method thereof, belonging to the technical field of nanofiber composite membrane materials.

Background technique

Fiber membrane materials have become the most widely used class of materials due to their wide range of raw material sources, strong structural adjustability, and good aggregate continuity. However, because the diameter of fiber membrane materials is mostly in the micron level, it has the problem of large pore size, which seriously limits the improvement of its application performance in the fields of environmental governance, biomedicine, and clean energy. Therefore, reducing the pore size of fiber membranes becomes the key to effectively improve their application performance in related fields. Compared with conventional micron-scale fiber materials, the diameter of electrospun fiber membranes is relatively small, which reduces the pore size to a certain extent. Practical applications in related fields cannot be realized. In order to prepare small-pore fiber membranes, the patents "Preparation Method of Nano Spider Web/Nanofiber Composite Protective Materials" (CN101564914) and "Preparation Method of Multi-component Reticulated Nanofiber Membrane" (CN103806221A) propose that in medium and low humidity environments. However, due to the limited coverage of the spider web, it is difficult to obtain a two-dimensional network material with continuous structure, and the close packing of the spider web leads to low porosity of the material. Another patent "High-throughput and high-efficiency nanofibrous membrane and its preparation method" (CN102481527A), literature [Novel nanofibrousscaffolds for water filtration with bacteria and virus removal capability[J]. Journal of Electron Microscopy, 2011, 60(3): 201-209] and [Nanofibrous microfiltration membrane based on cellulose nanowhiskers[J]. Biomacromolecules, 2012, 13, 180-186] proposed to use oxidized cellulose nanocrystals to form a non-woven structure layer on the surface of electrospun fiber membrane to reduce the pore size of the fiber membrane, but This method is only suitable for electrospinning fiber substrates, and because the length of oxidized cellulose nanocrystals is less than 1 μm and the diameter is 5-50 nm, it is easy to agglomerate, and it is difficult to form a uniform and continuous non-woven structure on the surface of electrospun fibers, which penetrates into The oxidized cellulose nanocrystals inside the electrospun fiber membrane lead to the blockage of the connected pores of the fiber membrane and the decrease of the porosity of the fiber membrane. Therefore, there is an urgent need for a method that is widely applicable and can effectively prepare small-pore fiber membranes with a fully covered continuous two-dimensional network structure and high porosity.

SUMMARY OF THE INVENTION

The problem to be solved by the present invention is to provide a bacterial cellulose nanofiber composite membrane with small pore size and high porosity and a preparation method thereof.

In order to solve the above-mentioned problems, the present invention provides a method for preparing a bacterial cellulose nanofiber composite membrane with small pore size and high porosity, which is characterized by comprising the following specific steps:

Step 1): mechanically dissociate and disperse the bacterial cellulose membrane in an insoluble solvent, and form a stable bacterial cellulose nanofiber suspension by adding a dispersant;

Step 2): using the synchronous ultrasonic filtration method to spread the bacterial cellulose nanofiber suspension obtained in step 1) on the surface of the porous fiber substrate to form a wet composite membrane;

Step 3): Removing the residual solvent in the wet composite membrane obtained in Step 2) to obtain a bacterial cellulose nanofiber composite membrane with small pore size and high porosity with a fully covered continuous two-dimensional network structure on the surface.

Preferably, in the step 1), the mechanical dissociation adopts any one or a combination of high-speed stirring dissociation, ultrasonic dissociation, high-pressure homogeneous dissociation, high-speed grinding dissociation and freezing grinding dissociation.

Preferably, the insoluble solvent in the step 1) is any one or more of water, methanol, ethanol, propanol, isopropanol, tert-butanol, acetone and butanone.

Preferably, in the step 1), the dispersing agent is alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, fatty acid polyoxyethylene ester, fatty acid methyl ester ethoxylate, polyoxyethylene amine, polyoxyethylene amide , sodium stearate, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium hexametaphosphate, sodium polysilicate, potassium pyrophosphate, anhydrous sodium carbonate, sodium thiocarbonate and sodium borate any one or more.

Preferably, in the step 1), the average length of the bacterial cellulose nanofibers in the bacterial cellulose nanofiber suspension is 1-300 μm, the average diameter is 10-100 nm, and the mass percentage of the fibers is 0.0005-1 wt %.

Preferably, the synchronous ultrasonic filtration method in the step 2) is as follows: ultrasonically treat the bacterial cellulose nanofiber suspension while filtering, the ultrasonic output power is 100-1500W, and the applied pressure during filtration is positive pressure or negative pressure, The applied pressure ranges from 0.5 to 50 kPa.

Preferably, the porous fiber substrate is a combination of one or more of electrospun fiber membrane, non-woven fabric, cellulose filter paper, woven fabric, and knitted fabric.

Preferably, the pore size of the porous fiber substrate in the step 2) is 1-300 μm.

Preferably, the specific method for removing in the step 3) is any one of vacuum drying, blast drying, supercritical drying, freeze drying, microwave drying and infrared drying.

The present invention also provides a small pore size and high porosity bacterial cellulose nanofiber composite membrane prepared by using the above method for preparing a small pore size and high porosity bacterial cellulose nanofiber composite membrane, characterized in that the surface of the composite membrane is The fully covered continuous two-dimensional network structure formed by the bacterial cellulose nanofibers has an average pore diameter of 0.01-2 μm and a composite membrane porosity of 70-98%.

Compared with the prior art, the beneficial effects of the present invention are:

Different from the nano-arachnoid small-pore fiber membrane prepared by the electrospinning method, the surface of the small-pore fiber membrane prepared by the present invention is a continuous two-dimensional network structure layer that is completely covered by bacterial cellulose nanofibers, which effectively avoids the need for nano-fiber membranes. The limited coverage area of arachnids leads to the discontinuous two-dimensional network structure and the close packing of arachnoid layers leads to the problem of low porosity of the fibrous membrane.

The invention is different from the method of using oxidized cellulose nanocrystals for coating. The prepared bacterial cellulose nanofibers have a long length, which can effectively avoid the penetration of short nanocrystals into the fiber membrane, resulting in decreased pore connectivity and porosity of the fiber membrane. And the problem of discontinuous nonwoven structure on the surface. In addition, the adopted synchronous ultrasonic filtration method can effectively adjust the mesh uniformity of the two-dimensional network structure layer of bacterial cellulose nanofibers.

The bacterial cellulose nanofiber composite membrane with small pore size and high porosity prepared by the invention simultaneously has a continuous two-dimensional network structure with complete surface coverage and high porosity, and has broad application in the fields of environmental treatment, biomedicine, clean energy and the like. application prospects.

The method provided by the present invention is not limited by environmental conditions and has a wide variety of substrates, and meanwhile, the preparation process is simple, the operability is strong, and the time-consuming is short.

Description of drawings

Fig. 1 is the schematic diagram of synchronous ultrasonic filtering device;

Fig. 2 is the electron microscope photograph of the bacterial cellulose nanofiber composite membrane with small pore size and high porosity prepared in Example 12; in the figure: a is bacterial cellulose nanofiber; b is porous fiber receiving substrate.

Detailed ways

In order to make the present invention more obvious and comprehensible, preferred embodiments are described in detail below with reference to the accompanying drawings.

The synchronous ultrasonic filtration device adopted in Example 1-15 is shown in Figure 1, and a porous fiber-receiving substrate 3 is placed on the filter device 4, and the porous fiber-receiving substrate 3 is above the bacterial cellulose nanofiber suspension 1. The cellulose nanofiber suspension 1 is surrounded by an ultrasound system 2 .

Example 1

A preparation method of a bacterial cellulose nanofiber composite membrane with small pore size and high porosity:

Step 1: The bacterial cellulose membrane was mechanically dissociated into bacterial cellulose nanofibers with an average length of 300 μm and an average diameter of 100 nm by high-speed stirring and dissociation, and dispersed in water. forming a stable bacterial cellulose nanofiber suspension; the mass percentage of bacterial cellulose nanofibers in the suspension is 0.05wt%;

Step 2: The above bacterial cellulose nanofiber suspension is spread on the surface of cellulose filter paper with a pore size of 300 μm by means of synchronous ultrasonic filtration (as shown in Figure 1) to form a wet composite membrane; The ultrasonic output power is 1000W, the pressure applied during filtration is positive pressure, and the pressure size is 40kPa;

Step 3: vacuum drying at 80° C. for 30 minutes to remove the residual water in the wet composite membrane to obtain a small pore size and high porosity bacterial cellulose nanofiber composite membrane with a fully covered continuous two-dimensional network structure on the surface. The average pore size of the mesh in the composite membrane is 2 μm, and the porosity of the composite membrane is 80%.

Example 2

A preparation method of a bacterial cellulose nanofiber composite membrane with small pore size and high porosity:

Step 1: The bacterial cellulose membrane was mechanically dissociated into bacterial cellulose nanofibers with an average length of 200 μm and an average diameter of 80 nm by ultrasonic dissociation and dispersed in methanol, and formed by adding a dispersant fatty alcohol polyoxyethylene ether. Stable bacterial cellulose nanofiber suspension; the mass percentage of bacterial cellulose nanofibers in the suspension is 0.002wt%;

Step 2: using the synchronous ultrasonic filtration method to spread the above bacterial cellulose nanofiber suspension on the surface of the polyethylene terephthalate spunbond non-woven fabric with a pore size of 150 μm to form a wet composite membrane; the synchronous ultrasonic filtration process The ultrasonic output power used in the filter is 800W, the pressure applied during filtration is negative pressure, and the pressure size is 5kPa;

Step 3: use 50° C. blast drying for 20 minutes to remove residual methanol in the wet composite membrane, and obtain a small pore size and high porosity bacterial cellulose nanofiber composite membrane with a fully covered continuous two-dimensional network structure on the surface. The average pore size of the mesh in the composite membrane is 1.5 μm, and the porosity of the composite membrane is 70%.

Example 3

A preparation method of a bacterial cellulose nanofiber composite membrane with small pore size and high porosity:

Step 1: The bacterial cellulose membrane is mechanically dissociated into bacterial cellulose nanofibers with an average length of 100 μm and an average diameter of 50 nm by the method of high-pressure homogeneous dissociation and dispersed in ethanol, and formed by adding dispersant sodium stearate. Stable bacterial cellulose nanofiber suspension; the mass percentage of bacterial cellulose nanofibers in the suspension is 0.001wt%;

Step 2: using the synchronous ultrasonic filtration method to spread the above bacterial cellulose nanofiber suspension on the polypropylene melt-blown non-woven surface with a pore size of 80 μm to form a wet composite membrane; the ultrasonic output power used in the synchronous ultrasonic filtration process is: 500W, the pressure applied during filtration is positive pressure, and the pressure is 30kPa;

Step 3: Freeze the above wet composite membrane in liquid nitrogen at -196°C for 1 min, freeze-dry to remove residual ethanol, and obtain bacterial cellulose nanoparticles with small pore size and high porosity with a fully covered continuous two-dimensional network structure on the surface. The fiber composite membrane, the average pore size of the mesh in the composite membrane is 1 μm, and the porosity of the composite membrane is 85%.

Example 4

A preparation method of a bacterial cellulose nanofiber composite membrane with small pore size and high porosity:

Step 1: The bacterial cellulose membrane was mechanically dissociated into bacterial cellulose nanofibers with an average length of 80 μm and an average diameter of 80 nm by high-speed grinding and dissociation, and dispersed in a mixed solvent of water and propanol. Sodium dodecylbenzene sulfonate forms a stable bacterial cellulose nanofiber suspension; the mass percentage of bacterial cellulose nanofibers in the suspension is 0.005wt%;

Step 2: using the synchronous ultrasonic filtration method to spread the above bacterial cellulose nanofiber suspension on the surface of a polysulfone electrospinning fiber membrane with a pore size of 50 μm to form a wet composite membrane; the ultrasonic output power used in the synchronous ultrasonic filtration process is: 300W, the pressure applied during filtration is negative pressure, and the pressure is 10kPa;

Step 3: use the supercritical drying method to remove the residual water and propanol in the above wet composite membrane to obtain a small pore size and high porosity bacterial cellulose nanofiber composite membrane with a fully covered continuous two-dimensional network structure on the surface. The average pore size of the mesh in the composite membrane is 0.8 μm, and the porosity of the composite membrane is 90%.

Example 5

A preparation method of a bacterial cellulose nanofiber composite membrane with small pore size and high porosity:

Step 1: The bacterial cellulose membrane was mechanically dissociated into bacterial cellulose nanofibers with an average length of 50 μm and an average diameter of 30 nm by a combination of high-speed stirring dissociation and freeze-grinding dissociation, and dispersed in water and isopropanol. In the mixed solvent, a stable bacterial cellulose nanofiber suspension is formed by adding a dispersant sodium hexametaphosphate; the mass percentage of bacterial cellulose nanofibers in the suspension is 1wt%;

Step 2: using the synchronous ultrasonic filtration method to spread the above bacterial cellulose nanofiber suspension on the surface of a silica electrospinning fiber membrane with a pore size of 30 μm to form a wet composite membrane; the ultrasonic output power used in the synchronous ultrasonic filtration process is 1500W, the pressure applied during filtration is positive pressure, and the pressure is 50kPa;

Step 3: The residual water and isopropanol in the wet composite membrane are removed by microwave drying method to obtain a small pore size and high porosity bacterial cellulose nanofiber composite membrane with a fully covered continuous two-dimensional network structure on the surface. The average pore size of the mesh in the composite membrane is 0.2 μm, and the porosity of the composite membrane is 80%.

Example 6

A preparation method of a bacterial cellulose nanofiber composite membrane with small pore size and high porosity:

Step 1: The bacterial cellulose membrane was mechanically dissociated into bacterial cellulose nanofibers with an average length of 1 μm and an average diameter of 10 nm by a combination of high-speed stirring dissociation, ultrasonic dissociation and high-pressure homogenization dissociation, and dispersed in water. In a mixed solvent with tert-butanol, a stable bacterial cellulose nanofiber suspension is formed by adding a dispersant fatty acid polyoxyethylene ester; the mass percentage of bacterial cellulose nanofibers in the suspension is 0.0005wt%;

Step 2: using the synchronous ultrasonic filtration method to spread the above bacterial cellulose nanofiber suspension on the surface of an electrospun fiber membrane with a pore size of 1 μm formed by multi-jet blending of chitosan and gelatin to form a wet composite membrane; The ultrasonic output power used in the ultrasonic filtration process is 100W, the pressure applied during the filtration is negative pressure, and the pressure size is 0.5kPa;

Step 3: using the infrared drying method to remove the residual water and tert-butanol in the wet composite membrane to obtain a bacterial cellulose nanofiber composite membrane with small pore size and high porosity with a fully covered continuous two-dimensional network structure on the surface, The average pore size of the mesh in the composite membrane is 0.01 μm, and the porosity of the composite membrane is 98%.

Example 7

A preparation method of a bacterial cellulose nanofiber composite membrane with small pore size and high porosity:

Step 1: The bacterial cellulose membrane was mechanically dissociated into bacterial cellulose nanofibers with an average length of 30 μm and an average diameter of 20 nm by a combination of ultrasonic dissociation and high-pressure homogenization dissociation, and dispersed in a mixed solvent of water and ethanol , a stable bacterial cellulose nanofiber suspension is formed by adding a dispersant sodium polysilicate; the mass percentage of bacterial cellulose nanofibers in the suspension is 0.003wt%;

Step 2: using the synchronous ultrasonic filtration method to spread the above bacterial cellulose nanofiber suspension on the surface of a double-layer fiber membrane to form a wet composite membrane, the upper layer of the double-layer fiber membrane is a polyacrylonitrile electrospinning fiber membrane with a pore size of 20 μm, The lower layer is a polypropylene melt-blown non-woven fabric with a pore size of 80 μm; the ultrasonic output power used in the synchronous ultrasonic filtration process is 180W, the pressure applied during filtration is positive pressure, and the pressure size is 5kPa;

Step 3: vacuum drying at 60° C. for 15 minutes to remove residual water and ethanol in the wet composite membrane to obtain a bacterial cellulose nanofiber composite membrane with small pore size and high porosity with a fully covered continuous two-dimensional network structure on the surface, The average pore size of the mesh in the composite membrane is 0.2 μm, and the porosity of the composite membrane is 95%.

Example 8

A preparation method of a bacterial cellulose nanofiber composite membrane with small pore size and high porosity:

Step 1: The bacterial cellulose membrane was mechanically dissociated into bacterial cellulose nanofibers with an average length of 20 μm and an average diameter of 30 nm by high-speed stirring and dissociation, and dispersed in a mixed solvent of water and methanol. Potassium phosphate forms a stable bacterial cellulose nanofiber suspension; the mass percentage of bacterial cellulose nanofibers in the suspension is 0.05wt%;

Step 2: Using the synchronous ultrasonic filtration method, the above bacterial cellulose nanofiber suspension is spread on the surface of a double-layer fiber membrane to form a wet composite membrane. The upper layer of the double-layer fiber membrane is a polyurethane electrospinning fiber membrane with a pore size of 10 μm, and the lower layer is a Hemp fiber woven fabric with a pore size of 300 μm; the ultrasonic output power used in the synchronous ultrasonic filtration process is 800W, the pressure applied during filtration is negative pressure, and the pressure size is 20kPa;

Step 3: Freeze the above wet composite membrane in liquid nitrogen at -196°C for 2 min, freeze-dry to remove residual water and methanol, and obtain bacterial fibers with small pore size and high porosity with a continuous two-dimensional network structure covered on the surface. A plain nanofiber composite membrane, the average pore size of the mesh in the composite membrane is 0.5 μm, and the composite porosity is 85%.

Example 9

A preparation method of a bacterial cellulose nanofiber composite membrane with small pore size and high porosity:

Step 1: The bacterial cellulose membrane was mechanically dissociated into bacterial cellulose nanofibers with an average length of 60 μm and an average diameter of 50 nm by a combination of freeze-grinding dissociation and ultrasonic dissociation and dispersed in a mixed solvent of water and acetone , by adding a dispersant polyoxyethylene amine to form a stable bacterial cellulose nanofiber suspension; the mass percentage of bacterial cellulose nanofibers in the suspension is 0.2wt%;

Step 2: using the synchronous ultrasonic filtration method to spread the above bacterial cellulose nanofiber suspension on the surface of a double-layer fiber membrane to form a wet composite membrane, and the upper layer of the double-layer fiber membrane is formed by blending polylactic acid and polycaprolactone. The electrospun nanofibers with a pore size of 50 μm, and the lower layer is a wool fiber knitted fabric with a pore size of 300 μm; the ultrasonic output power used in the synchronous ultrasonic filtration process is 1000W, and the pressure applied during filtration is positive pressure, and the pressure size is 30kPa;

Step 3: vacuum drying at 40° C. for 60 min to remove residual water and acetone in the wet composite membrane to obtain a small pore size and high porosity bacterial cellulose nanofiber composite membrane with a fully covered continuous two-dimensional network structure on the surface, The average pore size of the mesh in the composite membrane is 0.2 μm, and the porosity of the composite membrane is 90%.

Example 10

A preparation method of a bacterial cellulose nanofiber composite membrane with small pore size and high porosity:

Step 1: The bacterial cellulose membrane was mechanically dissociated into bacterial cellulose nanofibers with an average length of 80 μm and an average diameter of 80 nm by high-speed stirring and dissociation, and dispersed in water. By adding a dispersant fatty acid methyl ester ethoxylate forming a stable bacterial cellulose nanofiber suspension; the mass percentage of bacterial cellulose nanofibers in the suspension is 0.5wt%;

Step 2: using the synchronous ultrasonic filtration method to spread the above bacterial cellulose nanofiber suspension on the surface of a double-layer fiber membrane to form a wet composite membrane, the upper layer of the double-layer fiber membrane is a cellulose acetate electrospinning fiber membrane with a pore size of 50 μm, The lower layer is cellulose filter paper with a pore size of 100 μm; the ultrasonic output power used in the synchronous ultrasonic filtration process is 1000W, the pressure applied during filtration is positive pressure, and the pressure size is 30kPa;

Step 3: Use blast drying at 80° C. for 20 minutes to remove the residual water in the wet composite membrane, and obtain a bacterial cellulose nanofiber composite membrane with small pore size and high porosity with a continuous two-dimensional network structure that is completely covered on the surface. The average pore size of the mesh in the composite membrane is 0.5 μm, and the porosity of the composite membrane is 90%.

Example 11

A preparation method of a bacterial cellulose nanofiber composite membrane with small pore size and high porosity:

Step 1: The bacterial cellulose membrane was mechanically dissociated into bacterial cellulose nanofibers with an average length of 10 μm and an average diameter of 50 nm by a combination of high-speed stirring dissociation and freeze-grinding dissociation, and dispersed in water by adding a dispersant. Anhydrous sodium carbonate forms a stable bacterial cellulose nanofiber suspension; the mass percentage of bacterial cellulose nanofibers in the suspension is 0.002wt%;

Step 2: using the synchronous ultrasonic filtration method to spread the above bacterial cellulose nanofiber suspension on the surface of a double-layer fiber membrane to form a wet composite membrane, the upper layer of the double-layer fiber membrane is a polyamide 6 electrospinning fiber membrane with a pore size of 8 μm, The lower layer is a polyacrylonitrile electrospinning fiber membrane with a pore size of 20 μm; the ultrasonic output power used in the synchronous ultrasonic filtration process is 100W, the pressure applied during filtration is negative pressure, and the pressure size is 10kPa;

Step 3: use vacuum drying at 100° C. for 10 minutes to remove the residual water in the wet composite membrane, and obtain a bacterial cellulose nanofiber composite membrane with small pore size and high porosity with a continuous two-dimensional network structure that is completely covered on the surface. The average pore size of the mesh in the composite membrane is 0.1 μm, and the porosity of the composite membrane is 90%.

Example 12

A preparation method of a bacterial cellulose nanofiber composite membrane with small pore size and high porosity:

Step 1: The bacterial cellulose membrane was mechanically dissociated into bacterial cellulose nanofibers with an average length of 5 μm and an average diameter of 20 nm by a combination of high-speed stirring dissociation and ultrasonic dissociation, and dispersed in water. Sodium metaphosphate and sodium borate form a stable bacterial cellulose nanofiber suspension; the mass percentage of bacterial cellulose nanofibers in the suspension is 0.005wt%;

Step 2: using the synchronous ultrasonic filtration method to spread the above bacterial cellulose nanofiber suspension on the surface of the three-layer fiber membrane to form a wet composite membrane, the upper layer of the three-layer fiber membrane is a polyacrylonitrile electrospinning fiber membrane with a pore size of 3 μm, The middle layer is a polysulfone electrospinning fiber with a pore size of 10 μm, and the lower layer is a polypropylene melt-blown non-woven fabric with a pore size of 50 μm; the ultrasonic output power used in the synchronous ultrasonic filtration process is 500W, and the pressure applied during filtration is negative pressure, The pressure is 40kPa;

Step 3: Use blast drying at 60° C. for 40 minutes to remove the residual water in the wet composite membrane to obtain a small pore size and high porosity bacterial cellulose nanofiber composite membrane with a fully covered continuous two-dimensional network structure on the surface (such as 2), the average pore size of the mesh in the composite membrane is 0.2 μm, and the porosity of the composite membrane is 80%.

Example 13

A preparation method of a bacterial cellulose nanofiber composite membrane with small pore size and high porosity:

Step 1: The bacterial cellulose membrane was mechanically dissociated into bacterial cellulose nanofibers with an average length of 10 μm and an average diameter of 20 nm by a combination of high-pressure homogeneous dissociation and ultrasonic dissociation and dispersed in a mixture of water and butanone In the solvent, a stable bacterial cellulose nanofiber suspension is formed by adding a dispersant polyoxyethylene amide; the mass percentage of the bacterial cellulose nanofibers in the suspension is 0.05wt%;

Step 2: using the synchronous ultrasonic filtration method to spread the above bacterial cellulose nanofiber suspension on the surface of a three-layer fiber membrane to form a wet composite membrane, the upper layer of the three-layer fiber membrane is a polyurethane electrospinning fiber membrane with a pore size of 5 μm, and the middle layer is It is a polypropylene non-woven fabric with a pore size of 80 μm, and the lower layer is a cotton fiber knitted fabric with a pore size of 300 μm; the ultrasonic output power used in the synchronous ultrasonic filtration process is 1000W, and the pressure applied during filtration is positive pressure, and the pressure size is 30kPa;

Step 3: Use blast drying at 60° C. for 60 minutes to remove residual water and butanone in the wet composite membrane, and obtain a small pore size and high porosity bacterial cellulose nanofiber composite with a fully covered continuous two-dimensional network structure on the surface The average pore size of the mesh in the composite membrane is 0.1 μm, and the porosity of the composite membrane is 85%.

Example 14

A preparation method of a bacterial cellulose nanofiber composite membrane with small pore size and high porosity:

Step 1: The bacterial cellulose membrane is mechanically dissociated into bacterial cellulose nanofibers with an average length of 50 μm and an average diameter of 30 nm by ultrasonic dissociation and dispersed in water, and stable bacteria are formed by adding dispersant sodium hexametaphosphate Cellulose nanofiber suspension; the mass percentage of bacterial cellulose nanofibers in the suspension is 0.001wt%;

Step 2: using the synchronous ultrasonic filtration method to spread the above bacterial cellulose nanofiber suspension on the surface of the three-layer fiber membrane to form a wet composite membrane, the upper layer of the three-layer fiber membrane is a polyvinylidene fluoride electrospun fiber membrane with a pore size of 30 μm , the middle layer is a polypropylene melt-blown non-woven fabric with a pore size of 80 μm, and the lower layer is a polyacrylonitrile woven fabric with a pore size of 200 μm; the ultrasonic output power used in the synchronous ultrasonic filtration process is 500W, and the pressure applied during filtration is negative pressure , the pressure is 20kPa;

Step 3: using a microwave drying method to remove the residual water in the wet composite membrane to obtain a small pore size and high porosity bacterial cellulose nanofiber composite membrane with a fully covered continuous two-dimensional network structure on the surface, the composite membrane The average pore size of the middle mesh is 0.5 μm, and the porosity of the composite membrane is 90%.

Example 15

A preparation method of a bacterial cellulose nanofiber composite membrane with small pore size and high porosity:

Step 1: The bacterial cellulose membrane is mechanically dissociated into bacterial cellulose nanofibers with an average length of 80 μm and an average diameter of 80 nm by high-speed stirring and dissociation, and dispersed in water, and stable bacteria are formed by adding dispersant potassium pyrophosphate. Cellulose nanofiber suspension; the mass percentage of bacterial cellulose nanofibers in the suspension is 0.1 wt%;

Step 2: using the synchronous ultrasonic filtration method to spread the above bacterial cellulose nanofiber suspension on the surface of the three-layer fiber membrane to form a wet composite membrane, the upper layer of the three-layer fiber membrane is a polypropylene melt-blown non-woven fabric with a pore size of 50 μm, The middle layer is a wool knitted fabric with a pore size of 100 μm, and the lower layer is a cotton woven fabric with a pore size of 300 μm; the ultrasonic output power used in the synchronous ultrasonic filtration process is 1000W, and the pressure applied during the filtration is positive pressure, and the pressure size is 30kPa;

Step 3: use 50° C. vacuum drying for 60 minutes to remove the residual water in the wet composite membrane to obtain a small pore size and high porosity bacterial cellulose nanofiber composite membrane with a fully covered continuous two-dimensional network structure on the surface. The average pore size of the mesh in the composite membrane is 0.2 μm, and the porosity of the composite membrane is 80%.

Claims (6)

1. A preparation method of a small-aperture high-porosity bacterial cellulose nanofiber composite membrane is characterized by comprising the following specific steps of:

step 1): mechanically dissociating the bacterial cellulose membrane, dispersing the bacterial cellulose membrane in an insoluble solvent, and adding a dispersing agent to form a stable bacterial cellulose nanofiber suspension;

step 2): spreading the bacterial cellulose nanofiber suspension prepared in the step 1) on the surface of a porous fiber substrate by adopting a synchronous ultrasonic filtration method to form a wet composite membrane;

step 3): removing residual solvent in the wet composite membrane prepared in the step 2) to obtain a small-aperture high-porosity bacterial cellulose nanofiber composite membrane with a continuous two-dimensional reticular structure completely covered on the surface;

the insoluble solvent in the step 1) is any one or more of water, methanol, ethanol, propanol, isopropanol, tert-butanol, acetone and butanone;

the dispersing agent in the step 1) is any one or more of alkylphenol ethoxylates, fatty alcohol-polyoxyethylene ethers, fatty acid-polyoxyethylene esters, fatty acid methyl ester ethoxylates, polyoxyethylene amines, polyoxyethylene amides, sodium stearate, sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, sodium hexametaphosphate, sodium polysilicate, potassium pyrophosphate, anhydrous sodium carbonate, sodium thiosulfate and sodium borate;

the average length of the bacterial cellulose nanofibers in the bacterial cellulose nanofiber suspension in the step 1) is 1-300 mu m, the average diameter is 10-100 nm, and the mass percentage of the fibers is 0.0005-1 wt%;

the aperture of the porous fiber base material in the step 2) is 1-300 mu m.

2. The preparation method of the small-aperture high-porosity bacterial cellulose nanofiber composite membrane as claimed in claim 1, wherein the mechanical dissociation in the step 1) is any one or a combination of a plurality of materials selected from the group consisting of high-speed stirring dissociation, ultrasonic dissociation, high-pressure homogeneous dissociation, high-speed grinding dissociation and freeze grinding dissociation.

3. The preparation method of the small-aperture high-porosity bacterial cellulose nanofiber composite membrane as claimed in claim 1, wherein the synchronous ultrasonic filtration method in the step 2) is as follows: and (3) treating the bacterial cellulose nanofiber suspension by using ultrasonic waves while filtering, wherein the output power of the ultrasonic waves is 100-1500W, the applied pressure during filtering is positive pressure or negative pressure, and the applied pressure range is 0.5-50 kPa.

4. The method for preparing the small-aperture high-porosity bacterial cellulose nanofiber composite membrane as claimed in claim 1, wherein the porous fiber substrate is one or a combination of more of an electrostatic spinning fiber membrane, a non-woven fabric, a cellulose filter paper, a woven fabric and a knitted fabric.

5. The preparation method of the small-aperture high-porosity bacterial cellulose nanofiber composite membrane as claimed in claim 1, wherein the specific method for removing in the step 3) is as follows: any one of vacuum drying, forced air drying, supercritical drying, freeze drying, microwave drying and infrared drying.

6. The small-aperture high-porosity bacterial cellulose nanofiber composite membrane prepared by the preparation method of the small-aperture high-porosity bacterial cellulose nanofiber composite membrane as claimed in any one of claims 1 to 5, wherein the surface of the composite membrane is a completely covered continuous two-dimensional reticular structure formed by bacterial cellulose nanofibers, the average aperture of meshes is 0.01-2 μm, and the porosity of the composite membrane is 70-98%.

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