KR102752742B1 - Nano fiber and the method for manufacturing the same - Google Patents

Abstract

The present invention relates to nanofibers in which relatively thin bacterial cellulose forms a network structure between thick polymer nanofibers, and a method for producing the same, and an air filter including nanofibers produced by the method can have high efficiency and low differential pressure.

Description

{NANO FIBER AND THE METHOD FOR MANUFACTURING THE SAME}

The present invention relates to nanofibers and a method for producing the same.

Recently, as interest in air quality has increased, the demand for indoor air purification has also increased, and accordingly, various filters are being developed to remove foreign substances in the air. A filter is a filtration device that filters foreign substances in a fluid, and among them, air filters can be used in devices such as air purifiers, air conditioners, air conditioners, and vehicle air circulators to remove fine dust, etc. in indoor air at home, offices, etc., and in personal hygiene tools such as face masks, and can also be used in clean rooms installed to prevent product defects in the manufacturing process of advanced products.

In particular, ULPA (ultra low penetration air) or HEPA (high efficiency particulate air) filters are attracting attention as next-generation materials in the global filter market to block ultrafine dust that is harmful to the human body. ULPA and HEPA filters are high-efficiency filters and are mainly manufactured using glass fibers. However, glass fiber materials can break into fine glass fragments over time. The occurrence of glass fragments increases the defect rate of high-precision products, and there is a problem that users may inhale glass fragments.

In response, research on polymer nanofibers as a new filter material is being conducted. Polymer nanofibers, which are ultrafine fibers, have a higher surface area to volume ratio and higher porosity than conventional fibers, so they are expected to be able to efficiently remove harmful particles and gases.

Meanwhile, the smaller the diameter of the polymer nanofiber, the lower the pressure loss, which is advantageous for increasing the efficiency of the filter. Therefore, efforts to manufacture nanofibers with small diameters are ongoing, and for example, fibers with a netting structure are attracting attention.

In particular, development is underway on nano-fibers/nets (NFN) composed of general electrospun nano-fibers and ultrafine nano-nets. The fibers have a form in which relatively thinner nano-fibers form a network structure between nano-fibers, and because they have a very small diameter, they are in the spotlight as a material for reducing the size of structures, and because they have high porosity and excellent filtration function, they are expected to be used as a filter that blocks nano-sized viruses. In addition, NFN membranes are difficult to transport in the air due to the length of the fibers and the area of the network structure, and therefore cannot penetrate the body and are expected to be harmless to the human body.

The present invention provides a nanofiber in which relatively thin bacterial cellulose forms a network structure between polymer nanofibers, and a method for producing the same.

In addition, the present invention provides an air filter advantageous in efficiency and differential pressure, including nanofibers manufactured by the above method.

The present invention comprises a polymer binder and bacterial cellulose,

The above polymer binder comprises at least one polymer resin selected from the group consisting of polyvinyl alcohol and polyvinyl butyral.

Provides nano fibers.

In addition, the present invention provides a method for producing the nanofiber comprising the following steps:

A step of preparing a spinning solution comprising a polymer binder, bacterial cellulose and a solvent;

A step of radiating the above-mentioned radiation solution by electrospinning, and

Comprising a step of removing the solvent from the above-mentioned radiation solution,

The above polymer binder includes at least one polymer resin selected from the group consisting of polyvinyl alcohol and polyvinyl butyral.

In addition, the present invention provides an air filter including a nonwoven layer containing the nanofibers.

Hereinafter, the present invention will be described in detail.

The nanofiber of the present invention comprises a polymer binder and bacterial cellulose, and the polymer binder comprises at least one polymer resin selected from the group consisting of polyvinyl alcohol and polyvinyl butyral.

The above nanofibers can form a netting structure in which relatively thin bacterial cellulose is connected between relatively thick polymer nanofibers.

In the past, in order to manufacture a fabric composed of two types of nanofibers with different diameters, a mixture of two or more different polymers was spun. In this case, only a form in which nanofibers with different diameters were laminated was observed, and a form in which thinner nanofibers connected thicker nanofibers as in the present invention was not observed. Therefore, in order to manufacture a network structure of nanofibers, additional efforts were required, such as adding salt or using an acid solvent.

On the other hand, the present invention makes it possible to form the network structure by using bacterial cellulose instead of the conventional polymer binder. The bacterial cellulose is a cellulose produced by bacterial species, and is the only natural cellulose that can be obtained in a film form. The gel-like film-like bacterial cellulose sheet not only has properties very similar to pulp, but is also denser than pulp and has a three-dimensional network structure and excellent mechanical strength. Therefore, when bacterial cellulose is used to produce nanofibers, it is possible to form nanofibers having a diameter of several nm to several tens nm, which are difficult to produce by electrospinning a polymer solution, and when applied to an air filter, the efficiency of the air filter increases and the differential pressure is lowered.

Preferably, the bacterial cellulose may be present in an amount of 0.1 to 20 parts by weight, or 0.1 to 15 parts by weight, or 0.1 to 13 parts by weight, or 0.1 to 10 parts by weight, relative to 100 parts by weight of the total polymer binder.

When the content of the bacterial cellulose is less than 0.1 parts by weight based on 100 parts by weight of the total polymer binder, the amount of bacterial cellulose required for forming a network structure is insufficient, and when it exceeds 20 parts by weight, aggregation occurs between bacterial cellulose, making it difficult to disperse in a solvent, and the viscosity increases, making electrospinning difficult.

Meanwhile, the polymer binder of the nanofibers includes at least one polymer resin selected from the group consisting of polyvinyl alcohol and polyvinyl butyral. The bacterial cellulose included in the nanofibers together with the polymer binder is easily dispersed in a polar protic solvent such as water or ethanol. Accordingly, the polymer resin to be used in the production of the nanofibers should also be easily soluble in a polar protic solvent, and thus, the polyvinyl alcohol or polyvinyl butyral can be used as a polymer applicable to the electrospinning of the present invention.

In another embodiment of the present invention, a method for manufacturing nanofibers is provided, comprising the steps of preparing a spinning solution including a polymer binder, bacterial cellulose, and a solvent, spinning the spinning solution by electrospinning, and removing the solvent in the spinning solution, wherein the polymer binder includes at least one polymer resin selected from the group consisting of polyvinyl alcohol and polyvinyl butyral.

Among the conventional methods for manufacturing fabrics made of different nanofibers, there is a method of manufacturing nanofibers by first spinning a polymer solution and then electrospinning another polymer a second time to laminate the nanofibers. This method has the disadvantage of being complicated because it requires two electrospinning operations.

On the other hand, even if a solution containing two types of polymers is electrospun at the same time, it is impossible to manufacture a network structure in which thin nanofibers connect relatively thick nanofibers.

Accordingly, in the present invention, a manufacturing method of electrospinning a spinning solution containing a polymer binder and bacterial cellulose was used to manufacture nanofibers in which small-diameter nanofibers form a network structure between large-diameter nanofibers with only one electrospinning.

As described above, in the above manufacturing method, the polymer binder may be polyvinyl alcohol and/or polyvinyl butyral, which are polymers that dissolve well in polar protic solvents.

Preferably, the polymer binder may be present in an amount of 5 to 15 parts by weight, or 5 to 10 parts by weight, or 5 to 8 parts by weight, relative to 100 parts by weight of the total solvent.

If the content of the polymer binder is less than 5 parts by weight based on 100 parts by weight of the total solvent, the viscosity is too low and not suitable for spinning, and if it exceeds 15 parts by weight, the viscosity is too high and not suitable for spinning.

Preferably, the bacterial cellulose may be present in an amount of 0.1 to 20 parts by weight, or 0.1 to 15 parts by weight, or 0.1 to 13 parts by weight, or 0.1 to 10 parts by weight, relative to 100 parts by weight of the total polymer binder.

The above solvent can be used without special restrictions as long as it is a polar protic solvent, and preferably, it can be water or ethanol.

Meanwhile, in the step of preparing the above-mentioned radiation solution, a step of grinding and preparing the bacterial cellulose may be included. If the bacterial cellulose is not ground, it exists in the form of a gel sheet and the bacterial cellulose is not dispersed in the radiation solution. Therefore, it is preferable to include a step of grinding and preparing it for easy dispersion of the bacterial cellulose.

At this time, there is no limitation on the device commonly used for grinding to grind bacterial cellulose, and for example, a mixer grinder or blender can be used.

Electrospinning is a method of obtaining a nonwoven fiber assembly by directly spinning a polymer solution into fibers on or without a substrate using electrostatic force.

In this electrospinning, the spinning solution may include, in addition to the polymer binder and solvent described above, a dispersant, additives, etc.

Unless specifically limited in this specification, process conditions, materials, etc., generally used in the technical field to which the present invention pertains for manufacturing fibrous nonwoven fabrics using a radiation process, such as dispersants or other additives, may be applied to the present invention without any particular limitation.

Meanwhile, according to another embodiment of the invention, the present invention provides an air filter including a nonwoven layer containing nanofibers manufactured by the above method.

The nanofibers of the present invention form a network structure of relatively thin bacterial cellulose between thick polymer nanofibers, and an air filter including the nanofibers has the characteristics of high efficiency and low differential pressure.

Figure 1 is an image of the slurries manufactured in each of the Manufacturing Examples and Comparative Manufacturing Examples, observed in the order of Manufacturing Example 1, Manufacturing Example 2, Comparative Manufacturing Example 1, Comparative Manufacturing Example 2, and Comparative Manufacturing Example 3 from the left.
Figure 2 is a SEM image of the nanofiber nonwoven layer manufactured in Example 1.
Figure 3 is a SEM image of the nanofiber nonwoven layer manufactured in Example 2.
Figure 4 is a SEM image of the nanofiber nonwoven layer manufactured in Example 3.
Figure 5 is a SEM image of the nanofiber nonwoven fabric layer manufactured in Comparative Example 1.

Hereinafter, the present invention will be described in more detail to help understand the present invention. However, the following examples are only intended to illustrate the present invention, and the content of the present invention is not limited to the following examples.

Manufacturing example 1

Bacterial cellulose sheets and water were placed in a general blender and ground sufficiently at 15,000 rpm or higher for 3 minutes or longer to produce a 1 wt% bacterial cellulose slurry using water as a solvent. Afterwards, water was removed as much as possible using a vacuum filter, and the bacterial cellulose slurry was added to ultrapure water so that it became 1 wt%, and dispersed using an impeller at 600 rpm for 1 minute.

Manufacturing example 2

A bacterial cellulose slurry was prepared using the same method as in Manufacturing Example 1, except that ethanol was used instead of ultrapure water as the solvent after using a pressure reducing filter.

Comparative manufacturing example 1

A bacterial cellulose slurry was prepared using the same method as in Manufacturing Example 1, except that acetone was used instead of ultrapure water as the solvent after using a pressure reducing filter.

Comparative manufacturing example 2

A bacterial cellulose slurry was prepared using the same method as in Manufacturing Example 1, except that dimethyl sulfoxide (DMSO) was used instead of ultrapure water as the solvent after using a pressure reducing filter.

Comparative manufacturing example 3

A bacterial cellulose slurry was prepared using the same method as in Manufacturing Example 1, except that NMP (N-methyl-2-pyrrolidone) was used instead of ultrapure water as the solvent after using a pressure reducing filter.

Example 1

Bacterial cellulose sheets were added to ultrapure water at 0.4 to 0.8 wt%, ground using a mixer, dehydrated by filtration, and stirred sufficiently in ethanol as a solvent. This process was repeated three times to produce a 2 wt% bacterial cellulose slurry.

Polyvinyl butyral (PVB) was dispersed in ethanol as a solvent at 8 wt%, and the slurry was added so that the content of bacterial cellulose was 0.1 wt% relative to PVB, and stirred at a temperature of about 40°C for about 1 hour to prepare a spinning solution.

As a device for electrospinning, a flat collector electrospinning device from NanoNC was used to produce a nanofiber nonwoven layer. The spinning conditions were as follows.

Nozzle: single metal nozzle(18 gauge); Radiation speed: 0.03 ml/min; Radiation distance: 25 cm; Voltage: 20 kV; Radiation time: 30 min

Example 2

A nanofiber nonwoven layer was manufactured in the same manner as in Example 1, except that the slurry was added so that the content of bacterial cellulose was 5 wt% relative to PVB.

Example 3

A nanofiber nonwoven layer was manufactured in the same manner as in Example 1, except that the slurry was added so that the content of bacterial cellulose was 10 wt% relative to PVB.

Comparative Example 1

A nanofiber nonwoven layer was prepared in the same manner as in Example 1 except that the bacterial cellulose slurry was not added.

Experimental example

(1) Comparison of bacterial cellulose dispersion according to solvent

The degree of dispersion of the bacterial cellulose slurries manufactured in the above manufacturing examples and comparative manufacturing examples was compared, and the results of photographing each slurry are shown in Figure 1.

Figure 1 is an image of the slurries manufactured in each of the Manufacturing Examples and Comparative Manufacturing Examples, observed in the order of Manufacturing Example 1, Manufacturing Example 2, Comparative Manufacturing Example 1, Comparative Manufacturing Example 2, and Comparative Manufacturing Example 3.

Referring to Figure 1, it was confirmed that bacterial cellulose was most easily dispersed in water, and that it was dispersed at a similar level in ethanol as in water. On the other hand, in the case of acetone, bacterial cellulose and acetone separated into layers (circled) over time, causing cellulose to precipitate, and in the case of DMSO and NMP, it was confirmed that bacterial cellulose was dispersed to some extent compared to water, but was not dispersed and formed lumps (circled).

From the above results, it can be seen that in the case of solvents such as acetone, DMSO, or NMP, bacterial cellulose is relatively difficult to disperse and thus is not suitable as a solvent for the present invention. Based on this, it can be inferred that resins such as PTFE, PVDF, and PET that dissolve in the above solvents are also difficult to use as a polymer binder for the present invention.

(2) Observation of the appearance of the nanofiber nonwoven layer

The nanofiber nonwoven fabric layers manufactured in the above examples and comparative examples were observed using SEM.

FIG. 2 is an SEM image of a nanofiber nonwoven layer manufactured in Example 1, FIG. 3 is an SEM image of a nanofiber nonwoven layer manufactured in Example 2, FIG. 4 is an SEM image of a nanofiber nonwoven layer manufactured in Example 3, and FIG. 5 is an SEM image of a nanofiber nonwoven layer manufactured in Comparative Example 1.

Referring to FIGS. 2 to 4, it can be confirmed that the spaces between relatively thick PVB fibers are connected by small-diameter bacterial cellulose, forming a network structure.

On the other hand, in the case of Fig. 5, the nanofiber nonwoven layer of Comparative Example 1, which was electrospun using a spinning solution that did not contain bacterial cellulose, did not form a network structure.

Considering that the length of the white bar shown for size comparison in FIGS. 2 to 5 is 1 μm, it can be seen that the diameter of the PVB fiber is several hundred nm, and the diameter of the bacterial cellulose is several tens nm.

Claims (9)

Containing a polymer binder and bacterial cellulose,
The above polymer binder contains polyvinyl butyral,
The bacterial cellulose is present in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the polymer binder.
Nano fibers.
In the first paragraph,
The above nanofibers are a netting structure in which relatively thin bacterial cellulose is connected between relatively thick polymer nanofibers, which are polymer binders.
Nano fibers.
delete A step of preparing a spinning solution comprising a polymer binder, bacterial cellulose and a solvent;
A step of radiating the above-mentioned radiation solution by electrospinning, and
Comprising a step of removing the solvent from the above-mentioned radiation solution,
The above polymer binder comprises polyvinyl butyral.
A method for producing nanofibers of the first paragraph.
In paragraph 4,
The polymer binder is present in an amount of 5 to 15 parts by weight relative to 100 parts by weight of the total solvent.
Method for producing nanofibers.
In paragraph 4,
The bacterial cellulose is present in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the polymer binder.
Method for producing nanofibers.
In paragraph 4,
The above solvent is water or ethanol,
Method for producing nanofibers.
In paragraph 4,
The step of preparing the above-mentioned radiation solution includes the step of grinding and preparing the above-mentioned bacterial cellulose.
Method for producing nanofibers.
Comprising a nonwoven layer containing the nano fibers of the first clause,
Air filter.