JP2013194328A - Nanocomposite-nanofiber and filter element for nanofiber-air filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new nanocomposite-nanofiber, and a new filter element for a nanofiber-air filter.SOLUTION: When forming a nanofiber by using a spinning solution of polyether sulfone with an electrospinning method, a powder of a scallop is added to reduce a diameter of a nanofiber formed from polyether sulfone and produce the nanofiber having a small fiber diameter distribution. When the obtained nanocomposite-nanofiber is used for a filter element for a filter, a high-functional nanofiber-air filter that has low pressure loss, high particle trapping efficiency and a high bacteriostatic activity value is obtained.

Description

The present invention relates to a novel nanocomposite nanofiber.
The present invention also relates to a novel filter medium for a nanofiber air filter using the nanocomposite nanofiber.

  Electrospinning is widely known as a method for producing nanofibers (nanofibers) having a fiber diameter of less than 1 μm (see, for example, Patent Document 1 and Patent Document 2). In a typical method for producing nanofibers by electrospinning, first, a polymer constituting the fiber is dissolved in a solvent, and this solution is filled into a syringe as a spinning solution. Then, a high DC voltage of several kV to several tens of kV is applied between the needle-type electrode attached to the syringe and the collector electrode for depositing nanofibers, and strong between the needle-type electrode and the collector electrode. Generate an electric field. In this environment, when the spinning solution is released from the needle-type electrode toward the collector electrode, the solvent that dissolved the polymer evaporates in the electric field, and the polymer is stretched while solidifying to be nano-ordered ultrafine fibers ( Nanofibers) are deposited on the collector electrode. By changing the spinning conditions, ultrafine fibers with a scale of nm to μm are formed.

The spinning solution is not limited to a single polymer solution, and a mixed solution of different polymers, or a mixed solution of a polymer, an inorganic material, and the like can be used, so that nanohybrid fibers and nanocomposite nanofibers can be produced.
Nanofibers have characteristics such as “high specific surface area”, “molecular arrangement effect”, and “nanosize effect”, and can be expected to exhibit unique functions due to nanostructures.

On the other hand, in recent years, fiber products and resin molded products subjected to antibacterial processing have attracted attention, and for example, clothing, medical supplies, sanitary products, and the like that are given antibacterial properties are commercially available.
These conventional antibacterial products require special antibacterial processing to impart antibacterial properties to the resin. As an antibacterial substance used for this antibacterial processing, conventionally, an inorganic antibacterial agent having a metal ion such as copper, silver or zinc, or an organic antibacterial agent such as benzalkonium chloride, organic silicon or quaternary ammonium salt. Etc. are widely used.

  However, inorganic antibacterial agents have the disadvantage that they are deteriorated by heat and other factors when added to polymers to form fibers and the like, and the product value is significantly reduced. On the other hand, organic antibacterial agents are weather resistant, It has the disadvantages of poor chemical resistance and high acute oral toxicity.

  Since nanofibers can be obtained by electrospinning, the manufacturing process of the fiber itself is simple. However, in order to develop an antibacterial effect, a process for supporting or imparting an antibacterial agent or the like has been required so far. Therefore, it takes time and cost.

  Conventionally, the fiber diameter and form when polymer nanofibers are produced by electrospinning are the types of polymer materials used, the molecular weight, the concentration of the polymer materials in the spinning solution, the viscosity, the solvent used, the surface tension, the conductivity. It is known to be affected by various factors such as the degree, the distance between the needle-type electrode and the collector electrode, the voltage difference, the discharge amount, the needle diameter, the environmental temperature, the humidity, and the pressure (Non-Patent Document 1, Non-Patent Document 1, Patent Document 2).

  Non-Patent Document 1 reports that polyethersulfone (PES) is dissolved in an N, N-dimethylformamide (DMF) solution, and nanofibers having a diameter of 550 nm to 1.3 μm are formed by electrospinning. . Non-Patent Document 2 reports that nanofibers having an average diameter of 260 nm can be obtained by selecting conditions during electrospinning. By selecting the conditions in this way, the fiber diameter can be changed.

  On the other hand, it is also described that the average diameter decreases when an electrolyte or the like is added to the polymer solution. In particular, Patent Document 3 describes that nanofiber diameter is reduced by adding a quaternary ammonium salt to polyimide, and Non-Patent Document 3 is adding an electrolyte such as sodium carbonate. .

As described above, in the production of nanofibers, it is known that the diameter of the formed nanofibers is affected by the production conditions.
On the other hand, it is known to add functionality by adding inorganic or organic nanoparticles to nanofibers (see Non-Patent Document 4). Non-Patent Document 4 discloses that the functionality of a separation membrane is imparted by adding titanium oxide nanoparticles to polyethersulfone nanofibers.
In addition, scallop powder exhibits antibacterial properties and is applied to various sanitary products (see Non-Patent Document 5).

Japanese Patent Laying-Open No. 2005-330624 JP 2005-264386 A JP 2009-270210 A

Polymer, 50, (2009), 2893-2899. Journal of Membrane Science, 365, (2010), 68-77. Polymer Journal, 41, (2009), 1124-1128. Defect and Diffusion Forum Vol. 312-315, (2011), 613-619. Health December issue (2004) 184-189

  When forming the polyethersulfone nanofibers, which are engineering plastics, by electrospinning, even if the diameter is usually 500 nm and various conditions are devised, the diameter of 200 to 300 nm is the limit when trying to produce a fiber having a uniform diameter. there were.

  Therefore, in order to produce an air filter with low pressure loss and high collection efficiency and to further develop the function of the nanofiber, the average diameter of the polyethersulfone nanofiber is made smaller and the nanometer with a smaller diameter distribution is used. There is a need for fibers, and there is also a demand for nanofibers that are simultaneously provided with functionality such as antibacterial properties.

This invention is made | formed in view of such a subject, and it aims at providing a novel nanocomposite nanofiber.
Another object of the present invention is to provide a novel filter medium for a nanofiber air filter using the nanocomposite nanofiber.

  In order to solve the above problems and achieve the object of the present invention, the nanocomposite nanofiber of the present invention is characterized by containing polyethersulfone and scallop powder.

  Here, although not necessarily limited, it is preferable that the content of the scallop powder is in the range of 0.01 to 25% by mass with respect to the mass of the polyethersulfone. Moreover, although not necessarily limited, it is preferable that content of a scallop powder exists in the range of 0.1-20 weight% with respect to the mass of polyethersulfone. Moreover, although not necessarily limited, it is preferable that the average particle diameter of a scallop powder exists in the range of 1-1000 nm. Moreover, although not necessarily limited, it is preferable that the average particle diameter of a scallop powder exists in the range of 1-200 nm. Moreover, although it is not necessarily limited, it is preferable that the average diameter of a nanocomposite nanofiber exists in the range of 5-200 nm. Moreover, although it is not necessarily limited, it is preferable that the average diameter of a nanocomposite nanofiber exists in the range of 30-150 nm.

  Moreover, the nanofiber air filter medium of the present invention is characterized by using the above-mentioned nanocomposite nanofiber.

  Here, although not limited, it is preferable that the collection efficiency of 0.1 μm particles is 99.8% or more. Moreover, although not necessarily limited, it is preferable that a bacteriostatic activity value is 2.0 or more. Moreover, although not necessarily limited, it is preferable that a pressure loss is 150 Pa or less.

  The present invention has the following effects.

  Since the nanocomposite nanofiber of the present invention contains polyethersulfone and scallop powder, a novel nanocomposite nanofiber can be provided.

  Since the above-mentioned nanocomposite nanofiber is used for the nanofiber air filter filter of the present invention, a novel nanofiber air filter filter can be provided.

  Hereinafter, the present invention will be described in detail. The nanocomposite nanofiber of the present invention can be formed using an electrospinning apparatus similar to the conventional one. The electrospinning apparatus includes a syringe, a needle-type electrode nozzle, a collector electrode, and the like. The collector electrode may be a flat plate or other form such as a cylindrical shape. A high voltage, for example, a voltage of about several kV to several tens of kV, is applied between the needle electrode and the collector electrode, and a certain amount of the spinning solution is released from the syringe. This constant amount can be released by applying a constant pressure in the syringe.

  The diameter of the fiber formed by the electrospinning method depends on the viscosity of the solution, the type of polymer used, the degree of polymerization, the composition of the solution, the applied voltage, the flow rate, etc. When the degree of polymerization is large, when the applied voltage is low, or when the flow rate is large, the fiber diameter is usually large.

  In electrospinning, the spinning atmosphere is generally carried out in air at room temperature, but depending on the spinning conditions, it is carried out at a temperature lower than room temperature or higher than room temperature. Further, since the electric field is affected by moisture in the atmosphere, it is necessary to stabilize the humidity in order to stabilize the diameter.

  The polyethersulfone used for the production of the nanocomposite nanofiber of the present invention has the following molecular structure. Polyethersulfone is an aromatic polymer having an ether group and a sulfone group in the repeating unit.

  For the polyethersulfone of the present invention, a polymer material known to be spinnable by the conventional electrospinning method may be used as long as the effect of the present invention is exhibited, if necessary. Examples of such polymer materials include, for example, polybenzimidazole, polysulfone, polyarylene ether sulfone, polyarylate, polyvinylidene fluoride, polyurethane, polystyrene, polyvinylpyrrolidone, polyacrylonitrile, polycaprolactam, polylactic acid, nylon 6 , Nylon 66, ethylene-vinyl alcohol copolymer, cellulose acetate, polyvinyl chloride, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyethylene terephthalate, polymethacrylate, polyvinyl pyrrolidone, polyacrylamide, etc. However, it is not particularly limited to those exemplified here as long as it does not reduce the performance of polyethersulfone as an original engineering plastic. .

  Examples of the solvent used for dissolving the polyether sulfone to form a spinning solution include N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N, N-dimethylacetamide (DMAc) and the like. However, this is not the case. Moreover, you may mix and use these.

  In the nanocomposite / nanofiber manufacturing method of the present invention, other polymer additives are added to the spinning solution conventionally used for manufacturing nanofibers within the range in which the effects of the present invention are exhibited. Also good.

  Moreover, you may use fiberization promoters, such as polyethyleneglycol (PEG), polyethylene oxide (PEO), and polyvinylpyrrolidone (PVP) as needed. The concentration of the fiberization accelerator is preferably in the range of 0.01 to 10% by mass and more preferably in the range of 0.1 to 5% by mass with respect to the mass of the polyethersulfone.

  In the present invention, scallop powder is used in the spinning solution. The content is preferably 0.01 to 25% by mass, more preferably 0.1 to 20% by mass with respect to the mass of the polyethersulfone.

  There exists an advantage that antibacterial expression becomes clear that content is 0.01 mass% or more. When the content is 0.1% by mass or more, this effect becomes more remarkable.

  There exists an advantage that the intensity | strength of a nanofiber layer can maintain the intensity | strength as a filter medium for filters as content is 25 mass% or less. When the content is 20% by mass or less, this effect becomes more remarkable.

  The average particle size of the scallop powder is preferably in the range of 1 nm to 1000 nm. The average particle size is more preferably in the range of 1 nm to 200 nm. The average particle size is still more preferably in the range of 1 nm to 100 nm.

  When the average particle diameter is 1 nm or more, there is an advantage that the viscosity of the solution can be conveniently maintained for electrospinning.

  When the average particle size is 1000 nm or less, there is an advantage that the dispersibility with the nanofiber is excellent and the antibacterial property is excellent. When the average particle size is 200 nm or less, this effect becomes more remarkable. When the average particle size is 100 nm or less, this effect becomes more remarkable.

  The distance between the nozzle and the collector electrode is preferably in the range of 10 to 500 mm. When the distance between the nozzle and the collector electrode is 10 mm or more, there is an advantage that no corona discharge occurs between the nozzle and the collector electrode. When the distance between the nozzle and the collector electrode is 500 mm or less, there is an advantage that the electric field strength necessary for electrospinning can be obtained.

  The spinning voltage is preferably in the range of 2 to 100 kV. When the spinning voltage is 2 kV or more, there is an advantage that electric field strength necessary for electrospinning can be obtained. When the spinning voltage is 100 kV or less, there is an advantage that the spinning state of the spinning solution can be prevented from becoming unstable due to the influence of corona discharge.

  The spinning humidity is preferably in the range of 0 to 70% relative humidity. When the relative humidity is 70% or less, there is an advantage that induction of electric charge necessary for electrospinning occurs at the nozzle tip.

  The spinning temperature is usually room temperature, but is preferably in the range of 5 ° C. to the boiling point of the solvent. When the spinning temperature is 5 ° C. or higher, there is an advantage that the solvent of the spinning solution does not coagulate. When the spinning temperature is lower than the boiling point of the solvent, there is an advantage that the solvent of the spinning solution can be prevented from evaporating.

  Moreover, it is preferable that the density | concentration of the solution of polyethersulfone exists in the range of 1-50 mass%. More preferably, it is in the range of 10 to 30% by mass. When the concentration of the polyethersulfone is 1% by mass or more, there is an advantage that generation of particulate matter such as beads is suppressed and uniform fibers are easily generated. This effect becomes more prominent when the concentration of the polyethersulfone is 10% by mass or more. When the concentration of the polyethersulfone is 50% by mass or less, there is an advantage that it is possible to prevent the solution viscosity from becoming excessively high and spraying from not occurring when a voltage is applied. This effect becomes more prominent when the concentration of the polyethersulfone is 30% by mass or less.

  The supply flow rate of the spinning solution is controlled by air pressure. The pressure at this time is preferably in the range of 1 to 200 kPa. When the supply pressure of the spinning solution is 1 kPa or more, there is an advantage that a stable spray state can be maintained for a long time without insufficient solution supply at the nozzle tip. When the supply flow rate of the spinning solution is 200 kPa or less, there is an advantage that liquid dripping from the nozzle tip does not occur.

  The average diameter of the nanocomposite nanofiber is preferably in the range of 5 nm to 200 nm. The average diameter is more preferably in the range of 30 nm to 150 nm.

  When the average diameter is 5 nm or more, the strength of the nanofiber fiber is sufficient, and when the average diameter is 30 nm or more, there is an advantage that the strength of the nanofiber fiber is more sufficient.

When the average diameter is 200 nm or less, there is an advantage that there is an effect of reducing the pressure loss due to the slip flow effect. When the average diameter is 150 nm or less, this effect becomes more remarkable.
When the average diameter is 30 to 150 nm, a reduction in pressure loss due to the slip flow effect and an improvement in nanofiber strength due to an increase in fiber diameter can be obtained simultaneously.

  When the nanocomposite nanofiber of the present invention is used as a filter medium for an air filter, the effect can be further exerted. Therefore, the electrospinning is laminated on a glass nonwoven fabric or a polypropylene nonwoven fabric that is a base material of the air filter.

  The thickness of the nanofiber layer is preferably 100 nm or more, and more preferably 1 μm or more. When the thickness of the nanofiber layer is 100 nm or more, there is an advantage that the collection efficiency is improved. This effect becomes more remarkable when the thickness of the nanofiber layer is 1 μm or more.

  The thickness of the nanofiber layer on the substrate is a slight thickness of about one-fifth or less of the substrate, but dominates the filter performance of pressure loss and collection efficiency. A suitable nanofiber filter medium has a low pressure loss and a high collection efficiency, and since the thickness hardly becomes a bottleneck, the thickness obtained as a result of obtaining suitable filter performance can be accepted. When a new technology called nanofiber filter is used, the thickness is selected so that the pressure loss is 150 Pa or less.

  The collection efficiency of 0.1 μm particles in the nanofiber / air filter medium is preferably 99.8% or more. When the collection efficiency of 0.1 μm particles is 99.8% or more, there is an advantage that the particle collection performance is equivalent to that of a HEPA filter.

  The bacteriostatic activity value of the nanofiber air filter medium is preferably 2.0 or more. When the bacteriostatic activity value is 2.0 or more, there is an advantage that an effect of inhibiting and preventing the growth of a certain amount of bacteria is exhibited.

  The pressure loss of the nanofiber air filter medium is preferably 150 Pa or less. When the pressure loss is 150 Pa or less, the pressure loss is about 50% or less of a filter made of a conventional filter medium, and there is an advantage that a large energy saving effect can be exhibited.

From the above, according to the embodiment for carrying out the present invention, the following effects can be obtained.
The nanocomposite nanofiber of the present invention can be produced by an electrospinning method using a spinning solution obtained by adding scallop powder to a polyethersulfone solution.
The nanocomposite nanofiber of the present invention has a finer diameter than the conventional method and is excellent in the uniformity of the fiber diameter. The reason why a fine diameter can be obtained is thought to be due to the involvement of pH, Ca ions, active oxygen, and the like.
Thereby, a high function can be expressed by “high specific surface area” and “nano-size effect”, and the nanocomposite nanofiber of the present invention also has bacteriostatic activity.
The nanocomposite nanofiber of the present invention has a very large surface area compared to a normal fiber, and thus can provide special functions such as highly efficient bacteriostatic activity. These functions are strongly dependent on the diameter of the nanofiber, and the above characteristics are improved by reducing the diameter of the nanofiber.
The nanocomposite / nanofiber of the present invention is suitable for a filter material for a nanofiber / air filter. An air filter using the nanocomposite / nanofiber has high nanoparticle collection efficiency and extremely low pressure loss. Furthermore, since it has a function of high bacteriostatic activity, it is suitable for air filters such as hospitals, pharmaceutical factories and food factories.

  Note that the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage, and a plurality of components disclosed in the embodiments. Various modifications can be made by an appropriate combination of the above.

  Next, specific examples of the present invention will be described. However, it goes without saying that the present invention is not limited to these examples.

<Electrospinning>
As the electrospinning apparatus, ES-200 manufactured by FUEENCE was used. As electrospinning conditions when using this apparatus, an applied voltage of 0 to 50 kV, a nozzle-electrode distance of 2 to 20 cm, and a syringe solution supply pressure of 5 to 100 kPa can be employed.

<Observation / Measurement Method>
The spinning state was observed using a scattered image by irradiating a metal halide lamp light source (manufactured by Sumita Optical Glass Co., Ltd., LS-M210) to the nozzle tip. Further, the structure of the fiber was observed using a scanning electron microscope (SEM, JEOL JMC-5700). Observation was performed under the condition of an acceleration voltage of 10 kV. As an observation sample, a platinum-coated film having a thickness of about 5 nm using a fine coater (manufactured by JEOL Ltd., JFC-1600) was used. The fiber diameters at 20 arbitrary points on the fiber were measured from the obtained secondary electron image, and the average fiber diameter was determined.

<Observation and measurement results>
After application of the electric field, continuous spinning of the solution from the tip of the nozzle was confirmed, and the nanofibers were collected on the glass nonwoven fabric. By spinning for about 200 minutes, a filter medium in which fibers were laminated could be obtained.

<Measurement of collection efficiency>
Measurement of pressure loss was performed using a device manufactured by Japan Air Filter Co., Ltd. based on JIS-B9927, and at the same time, MSP Wide-Range Particle Spectrometer 1000XP attached to this device was used to collect nanoparticles. Was measured.

<Measurement of bacteriostatic activity value>
The bacteriostatic activity value was measured by JIS L1902 bacterial solution absorption method, test bacteria: Staphylococcus aureus.

Example 1
Polyethersulfone (Sumitomo Chemical, Sumika Excel PES5200P; reduced non-viscosity 0.52) was dissolved in N, N-dimethylformamide (Wako Reagent Special Grade) to 22.5% by mass. After confirming dissolution, nano scallop powder (manufactured by Tokyo Nano Biotechnology, average particle size 70 nm) was uniformly dispersed in an amount of 20% by mass with respect to the mass of the polyethersulfone. The electrospinning apparatus (manufactured by Fuence, ES-200) was used. Electrospinning was performed on a glass nonwoven fabric (manufactured by H & V, 0120) with a syringe needle inner diameter of 0.41 mm, an applied voltage of 25 kV, a nozzle-main electrode distance of 160 mm, and a syringe solution supply pressure of 5 kPa. Thereafter, this laminate was taken out and the pressure loss was measured at a wind speed of 5.3 cm / sec. As a result, the pressure loss was 107 Pa. The collection efficiency of 0.1 μm particles of this filter medium was 99.8%. When the SEM observation of this nanocomposite nanofiber was performed, the average diameter was 105 nm. When the bacteriostatic activity value of the laminate separately produced under the same conditions was measured, it was 5.1.

Comparative Example 1
In the same manner as in Example 1, polyethersulfone (manufactured by Sumitomo Chemical Co., Ltd., SUMIKAEXCEL PES5200P; reduced non-viscosity 0.52) was dissolved in N, N-dimethylformamide (special grade of Wako Reagent) to 22.5% by mass. After confirming dissolution, this solution was used for electrospinning using the electrospinning apparatus (manufactured by Fuence, ES-200). Electrospinning was performed on a glass nonwoven fabric (H & V, 0121) at an applied voltage of 25 kV, a nozzle-main electrode distance of 160 mm, a syringe needle inner diameter of 0.41 mm, and a syringe solution supply pressure of 5 kPa. Thereafter, this laminate was taken out and, similarly, the pressure loss was measured at a wind speed of 5.3 cm / sec. As a result, the pressure loss was 161 Pa. The collection efficiency of 0.1 μm particles of this filter medium was 99.5%. When this nanocomposite nanofiber was observed with an SEM, the average diameter was 155 nm. Separately, the bacteriostatic activity value of the laminate prepared under the same conditions was not different from the control.

Example 2
In the same manner as in Example 1, the amount of nanoscallop powder was 8% by mass based on the mass of the polyethersulfone, and electrospinning was performed using the electrospinning apparatus (ES-200, manufactured by Fuence). Electrospinning was performed on a glass nonwoven fabric (manufactured by H & V, 0120) with a syringe needle inner diameter of 0.41 mm, an applied voltage of 20 kV, a nozzle-main electrode distance of 160 mm, and a syringe solution supply pressure of 5 kPa. When the pressure loss, the collection efficiency, the average diameter, and the bacteriostatic activity value at that time were measured, they were 105 Pa, 99.9%, 110 nm, and 3.0, respectively.

  In the industry dealing with air conditioning filters, filters with low pressure loss, high collection efficiency and long life have been pursued. However, since these performances have contradictory performances, it has been difficult to create an ideal one. Therefore, in recent years, the development of air conditioning filters with ideal performance in the filter industry has attracted attention as a result of technological developments in the textile industry that have led to the development of ultra-fine fibers. Therefore, the present invention is intended to solve these problems, to provide a filter medium having a high antibacterial property, exhibiting high-efficiency and long-life performance with low pressure loss, undeniably exhibiting the ultrafine fiber effect. Demand for safety and health will continue to increase in the future, and it has extremely high utility value in the industry.

Claims (11)

A nanocomposite nanofiber comprising polyethersulfone and scallop powder. 2. The nanocomposite nanofiber according to claim 1, wherein the content of scallop powder is in the range of 0.01 to 25% by mass with respect to the mass of the polyethersulfone. 2. The nanocomposite nanofiber according to claim 1, wherein the scallop powder content is in the range of 0.1 to 20 wt% with respect to the mass of the polyethersulfone. The nanocomposite nanofiber according to any one of claims 1 to 3, wherein the average particle size of the scallop powder is in the range of 1 to 1000 nm. The average particle diameter of scallop powder is in the range of 1 to 200 nm. The nanocomposite nanofiber according to any one of claims 1 to 3. The nanocomposite nanofiber according to any one of claims 1 to 5, wherein the average diameter is in the range of 5 to 200 nm. The nanocomposite nanofiber according to any one of claims 1 to 5, wherein an average diameter is in a range of 30 to 150 nm. The nanocomposite nanofiber according to any one of claims 1 to 7 is used. A nanofiber air filter medium. The filter medium for a nanofiber air filter according to claim 8, wherein the collection efficiency of 0.1 µm particles is 99.8% or more. 10. The nanofiber air filter medium according to claim 8, wherein the bacteriostatic activity value is 2.0 or more. The pressure loss is 150 Pa or less. The nanofiber air filter medium according to any one of claims 8 to 10, wherein the pressure loss is 150 Pa or less.