KR101955404B1 - nonwoven for high efficiency-filtering and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a nonwoven fabric for high-efficiency filtration having excellent filtration efficiency and improved durability and a method for producing the same, and more particularly, to a nonwoven fabric for high- Wherein the nonwoven fabric comprises 90.0 to 99.5% by weight of a non-conductive thermoplastic polymer and 0.5 to 10.0% by weight of an acidic polymer containing an acid group and having an acid value of 50 to 1,000, .
The nonwoven fabric for filtration according to the present invention can be used as a filter material having a high charging voltage at a charging point and a high charging rate with an absolute value of 100 V or higher and a high collection rate and being usable for a long period of time.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a nonwoven fabric for high-

The present invention relates to a nonwoven fabric for high-efficiency filtration having excellent filtration efficiency and improved durability and a method for producing the same.

The nonwoven fabric for high-efficiency filtration is a filter material that is usefully used for removing contaminants present in air or water. Especially, it is a filter material which is excellent in removing dust, fine dust, bacteria, (HEPA filter, high efficiency particulate air filter). These HEPA filters have been applied to health masks, various households requiring air purification, vehicles, industrial air conditioners, and air cleaners.

A number of technologies and products have been developed to produce such high-efficiency nonwoven fabrics for filtration.

The most important characteristics of the main filter, ie, the HEPA filter to which the high-efficiency filtration nonwoven fabric is applied, include a higher filtration efficiency, an effective trapping of fine particles, and a technique for reducing the pressure difference after filtration. The factors on the characteristics have also been studied and revealed by many people over a long period of time.

The permeability P (penetration, filtration efficiency = 1 - P) of the particles passing through the filter media in the filtration filter is given as follows,

α _f : filter packing desisity

d _f : fiber diameter

η: particle collection efficiency

Z: filter thickness

The pressure drop ΔP in the filter media is given by:

μ: gas dynamic viscosity

V ₀ : filteration velocity

F: drag coefficient

L _f : length of fiber per unit area

("Modeling Pressure Drop in HEPA Filters during Dynamic Filtration"

J. Aerosol Sci. Vol. 30, NO. 2, pp. 235-246,1999)

In order to improve the performance of such a HEPA filter, development of fibers constituting nonwoven fabric and nonwoven fabric constituting filter media (media) is proceeding in various aspects.

The filter paper or the nonwoven fabric is mainly used as the hemofilter filter material. The nonwoven fabric manufactured by the melt blowing method is made of ultrafine microfine fibers and exhibits characteristics as a high-performance filter, and is more preferably used.

However, it is difficult to miniaturize the microfine fibers and to miniaturize the air holes due to the limitation of fineness, which makes it difficult to exhibit high filtration efficiency and permeability, and the durability is deteriorated due to miniaturization.

In order to solve such a problem, there is a method of coating an electrostatic resin on a nonwoven fabric.

However, such a coating method is complicated in the production process, and the waste liquid is generated during the process, so that the environment is contaminated, the manufacturing cost is high, and the pressure loss is low.

To solve these problems, techniques for electretizing the nonwoven fabric itself have been developed.

In this case, the electret refers to a dielectric material showing a semi-permanent charge, and the electret nonwoven fabric is a nonwoven fabric in which the electrification of the yin and yang is continuously polarized so as to be semi-permanent.

No. 4,215,682 discloses a technique for forming a nonwoven fabric by a meltblowing method in connection with an electretized nonwoven fabric and charging it to provide an electret filter. In this document, fibers are formed using a "meltblown" process, and impact is applied to the charged particles when the fibers are discharged from the die orifices. Meltblown fibers impacted with charged particles are randomly deposited on a collector to form electret meltblown nonwoven fabrics. This document discloses that the filtration efficiency can be improved by two or more factors when the meltblown fibers are charged.

In addition, as a method of charging the nonwoven fabric to produce a hepafilter, there is a method in which the nonwoven fabric is corona charged (U.S. Patent No. 4,588,537) or the nonwoven fabric is brought into close contact with the ground electrode on the smooth surface (US Pat. No. 4,592,815).

In addition, a mechanical method has been proposed as a method of imparting electric charge to the fibers. U.S. Patent No. 4,798,850 discloses a technique in which two different types of crimped synthetic polymer fibers produced by carding and needling with a fleece are mixed well to allow the fibers to be charged during carding. The method described in this document is commonly referred to as " triboelectric charging ".

In addition, water is used to charge the nonwoven fibrous web (U.S. Pat. No. 5,496,507). The pressurized jet or water flow impinges on the nonwoven web containing non-conductive microfibers to generate charge. The formed charge provides filtration enhancement properties. The air corona discharge treatment of the nonwoven fabric before the hydrocharging operation can further improve the charging.

On the other hand, a method of improving filtration performance of a filter by adding a specific additive to improve charging performance has also been proposed.

For example, an oil mist resistive electret filter is prepared by incorporating a fluorinated additive into meltblown polypropylene microfibers (US Pat. Nos. 5,411,576 and 5,472,481). U.S. Patent No. 5,908,598 discloses a heat-stable organic compound or oligomer containing (i) at least one perfluorinated component, (ii) a thermally stable organic triazine compound containing at least one triazine group and at least one nitrogen atom Or an oligomer, or (iii) a mixture of (i) and (ii). Also, U.S. Patent No. 5,057,710 discloses a polypropylene electret nonwoven fabric to which at least one stabilizer selected from hindered amines, nitrogen-containing hindered phenols and metal-containing hindered phenols is added. In addition, U.S. Patent Nos. 4,652,282 and 4,789,504 disclose a method of mixing a fatty acid metal salt with an insulating polymer to maintain a high vibration damping performance over a long period of time, and Japanese Patent Publication No. 60-947 discloses a method of mixing poly- (1) a compound selected from the group consisting of (a) a compound containing a phenol and a phenol hydroxyl group, (b) a higher aliphatic carboxylic acid and a metal salt thereof, (c) a thiocarboxylate compound, Disclose electrets containing more than two kinds of compounds.

On the other hand, pollutants such as dust in the air have been known to be charged. Therefore, various techniques have been developed to charge the nonwoven fabric to act electrostatic attraction force for effective removal of charged particles, and research on the charging state of the polypropylene and the performance of the filter using the nonwoven fabric have been actively carried out (Electret properties of polypropylene, Journal of Electrostatics, 51-52 (2001) 232-238, Bozena Lowkis, Edmund Motyl).

Thus, various technologies and products related to the nonwoven fabric for high-efficiency filtration have been developed. However, it is also clear that the pollution of the atmosphere, water and soil, which is the environment in which human beings live, is continuously increasing, and the pollution of the environment is adversely affecting human health. In the field of nonwoven fabrics for high-efficiency filtration, there is a continuing need to develop technologies that exhibit higher efficiency and performance.

The present invention provides a non-woven fabric for high-efficiency filtration and a method for manufacturing the same, which are improved in performance by easily and uniformly charging the non-woven fabric and having an improved charging state for the granular papermaking continuously and stably .

The present invention provides a nonwoven fabric comprising 90.0 to 99.5% by weight of a non-conductive thermoplastic polymer and 0.5 to 10.0% by weight of an acidic polymer containing an acid group and having an acid value of 50 to 1,000, wherein the nonwoven fabric has a non- A nonwoven fabric for high-efficiency filtration characterized in that the ratio of the charging point charged and the charging point having an absolute value of the charging voltage of 100 V or more is 90% or more.

Also, the present invention provides a method for producing a non-conductive thermoplastic polymer composition, comprising: preparing a raw material having a composition of 90.0 to 99.5% by weight of a non-conductive thermoplastic polymer and 0.5 to 10.0% by weight of an acidic polymer containing an acid group and having an acid value of 50 to 1,000; Forming a web of short fibers prepared by a melt blowing method using a composition containing the raw material; And charging the nonwoven fabric made of the web by at least one method selected from friction charging, corona charging and hydro charging method.

The nonwoven fabric for filtration according to the present invention can be used as a filter material having a high charging voltage at a charging point and a high charging rate with a large ratio of charging points having an absolute value of 100 V or more.

Further, even if the composition is used for a long period of time, the decrease in the collection rate is suppressed, and the composition can be used for a long period of time.

The nonwoven fabric for high-efficiency filtration of the present invention is characterized in that the surface potential (electric potential, V) is not constant and is discontinuously charged, and the charge voltage at the charging point on the one surface of the nonwoven fabric has an absolute value of 100V or more Of 90% or more.

The nonwoven fabric for high-efficiency filtration of the present invention is charged with an uneven discrete dislocation which is different in the value of the potential or the sign when the dislocation is measured at various portions of the surface.

This is different from what happens when a charge on a conductive material or a charge on a non-conductive material occurs when the charges are equilibrated with adjacent charges, such as charging by polarization.

As a result, the charging voltage is high, and even if there are not many charging points, it is possible to have a sufficient amount of charge for collection, and the charging state can be maintained for a long time.

In addition, the charging voltage at the charging point on one surface of the nonwoven fabric has an absolute value of 100 V or more and a value exceeding 150 V, which is generally much higher than the charge amount per unit area required by the HEPA filter of 1 × 10 ^-6 C / Level, it is possible to have a charge amount sufficiently high enough to perform high-efficiency filtration even if there are not many charge points.

Electretization in a general electret filter is based on the polarization of electric charge, and the voltage is close to zero. However, in the present invention, since a large voltage is high at the charging point, particles capable of attracting ions Therefore, the filtration efficiency can be increased.

In order to exhibit such electrical characteristics, the nonwoven fabric of the present invention may be composed of a short fiber composed of a fiber material composition containing 90 to 99.5% by weight of a non-conductive thermoplastic polymer and 0.5 to 10% by weight of an acidic polymer having an acid value of 50 to 1,000 have.

The non-conductive thermoplastic polymer is a main constituent of the nonwoven fabric. The non-conductive thermoplastic polymer should have sufficient physical properties to form a nonwoven fabric, thermoplasticity and fiber formability that can be produced in the form of a nonwoven fabric, and have a resistivity exceeding 10 ¹² ohm- It should be possible to suppress the movement of the charged charges.

Examples of the non-conductive thermoplastic polymer include polyolefins such as polyethylene, polypropylene, poly-4-methyl-1-pentene, polyvinyl chloride and the like; polystyrene; Polycarbonate; Polyesters such as polyethylene terephthalate and polylactic acid; Polyamides, and copolymers thereof. Preferably, polypropylene is a more useful material in terms of price, formability, and electret state.

The inventors of the present invention have found through long studies that the absolute value of the applied voltage at the charging point is high and thus the charged voltage is sufficiently high and the charging voltage is not uniformly distributed discontinuously and the charging point I have been testing the possibility of augmentation.

It has been found that structural changes such as ionization of molecular species are more effective than simple polarization of non-conductive materials in order to continuously and stably obtain an improved charged state for trapping particles in a high-efficiency filtration nonwoven fabric.

Accordingly, in order to select a compound having an acid group that can be most easily ionized and to maintain a more uniform and stable dispersion state and a charged state on the web, Was used. In the present invention, a polymer having an acid group is represented by an acidic polymer. In addition, electrical energy (corona charging), physical energy (triboelectrification), or collision energy (hydrostatic charging) applied to the nonwoven fabric to charge the nonwoven fabric during the production process of the high efficiency filtration nonwoven fabric using the acidic polymer, And the present invention has been completed.

The acidic polymer may be at least one selected from the group consisting of a sulfonic acid group, a sulfonic acid ester group, a carboxylic acid group, a carboxylic acid ester group, a thiocarboxylic acid group, a thiocarboxylic acid ester group, a dithiocarboxylic acid group, a dithiocarboxylic acid ester group, And an anhydride group. The acidic properties of the acidic polymer differ depending on the acidity. Therefore, the acidic polymer can be used in a variety of ways depending on the non-conductive thermoplastic polymer as the main component.

The acidic polymer may be at least one selected from the group consisting of a sulfonic acid group, a sulfonic acid ester group, a carboxylic acid group, a carboxylic acid ester group, a thiocarboxylic acid group, a thiocarboxylic acid ester group, a dithiocarboxylic acid group, a dithiocarboxylic acid ester group, An olefin polymer obtained by using at least one monomer selected from the group consisting of anhydride groups can be used.

Examples of the monomer having such a functional group include vinylsulfonic acid, fumaric acid, itaconic acid, crotonic acid, maleic acid, acrylic acid, methacrylic acid, vinylthiocarboxylic acid, vinyldithiocarboxylic acid and esters thereof. Monomers can be used. The acidic polymer can be prepared through emulsion polymerization or solution polymerization used for general olefin polymerization with such monomers, and general addition polymerization catalyst and additives can be used for the polymerization reaction. In order to control the acid value, melting point, and other physical properties of the acidic polymer, common monomers such as vinyltoluene, styrene, acrylamide, and vinyl acetate used for olefin polymerization may be used.

If the acid value of the acidic polymer is less than 50, sufficient electrification is not performed and the filtration efficiency is not good. If the acid value exceeds 1,000, the flowability of the acidic polymer drops rapidly and the mechanical performance of the nonwoven fabric is not good. And preferably has an acid value of 100 to 500. [

When the weight average molecular weight of the acidic polymer is less than 1,000, the number of charging points decreases in the nonwoven fabric, and when the acidic polymer is more than 20,000, the absolute value of the voltage may be lowered. And preferably from 2,000 to 10,000.

The acidic polymer is a thermoplastic polymer. Generally, in the case of a polymer having a high acid value, there is no flowability of the molecule due to strong polarity or may be greatly deteriorated. Therefore, when a polymer having no thermoplasticity is used, compatibility with a non-conductive thermoplastic polymer as a main component is lost and high- It is difficult to do. Accordingly, in the present invention, a thermoplastic polymer is used, and a melt viscosity of 100 to 80,000 poise at 200 DEG C can be used.

When the content of the acidic polymer of the present invention is less than 0.5% by weight, sufficient electrification is not carried out. When the content of the acidic polymer exceeds 10% by weight, various characteristics of the nonwoven fabric are greatly reduced. It is preferable to use 1 to 5% by weight.

An additive may be added to the fiber material of the present invention to improve charging characteristics and improve the ability of the fiber material.

It is preferable that the additive contains at least one hindered amine-based additive or a triazine additive. By containing this additive in the fiber material, it is possible to maintain particularly high charging performance.

Examples of the hindered amine additive include poly [((6- (1,1,3,3-tetramethylbutyl) imino-1,3,5-triazine-2,4- (2,2,6,6-tetramethyl-4-piperidyl) imino)] (Ciba Geigy < (R) > , Chimassov 944LD), dimethyl-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate (Chinobi- , 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonic acid bis (1,2,2,6,6-pentamethyl- Shiba Kagija, Chinupin 114), and the like.

Examples of the triazine-based additive include poly ([(6- (1,1,3,3-tetramethylbutyl) imino-1,3,5-triazine-2,4- (2,2,6,6, -tetramethyl-4-piperidyl) imino)] (Ciba) (4-aminophenyl) -1,3,5-triazine-2-yl) -5 - ((hexyl) oxy) -phenol NUPHIN 1577FF). Among them, it is particularly preferable to use a hindered amine-based additive.

At this time, the content of the charging property improving additive is preferably 0.5 to 5% by weight.

When the addition amount is less than 0.5% by weight, it is difficult to obtain a desired high charging performance. When the addition amount is more than 5% by weight, the yarn quality is deteriorated and the strength of the fiber or nonwoven fabric is remarkably decreased And it is disadvantageous in terms of cost.

In the fiber material of the present invention, commonly known additives such as heat stabilizers, weatherability agents, polymerization inhibitors and the like can be used in addition to the above additives.

The nonwoven fabric can be formed into a fiber by using the above-mentioned fiber material.

It is more preferable that the nonwoven fabric of the present invention is produced by a melt-blow method.

The melt blowing method is a manufacturing method in which a melt base polymer is melted and spun through a nozzle, stretched and cooled by high-temperature and high-pressure air, and laminated on a web forming apparatus to have a nonwoven fabric form.

The nonwoven fabric by the melt blowing method can produce fibers of various sizes depending on the nozzle size, discharge amount, and process conditions, and it is possible to produce nonwoven webs of tens to hundreds of gsm (gram per square meter) The nonwoven fabric web of various structures can be formed. Therefore, it is very suitable for the production of filtration media such as filters, and is advantageous in cost competitiveness compared to other types of nonwoven fabric manufacturing methods due to relatively simple process control.

In particular, the permeability to gas can be enhanced by the numerous micropores formed by the dispersion of fibers having high homogeneity.

In the present invention, the web is configured to have fine pores formed by fine fibers having a monofilament fineness of 0.1 to 10 占 퐉, so that the nonwoven fabric has permeability and can filter a large surface area per unit weight and fine contaminants, .

In particular, since the fiber material is not a single component in the present invention, if the single fiber fineness deviates from the above range, the mechanical strength may deteriorate or the sacrifice may be deteriorated.

However, in order to improve the mechanical strength required for the pressure resistance when the non-woven fabric has fineness and fine pores as described above and the nonwoven fabric is more easily manufactured and actually filtered, a web is formed under the following manufacturing conditions, To 12-fold lamination, whereby the micropores can be controlled while improving the mechanical strength.

The manufacturing conditions of the web are as follows: the spinning temperature is 30 to 120 ° C or higher relative to the melting point of the non-conductive thermoplastic polymer; the blowing air temperature is ± 40 ° C relative to the spinning temperature; (die to collector distance) of 100 to 300 mm and a collector speed of 1 to 50 mpm (meter per minute).

In order to ensure that the monofilament fineness and the average pore size of the nonwoven fabric produced by the melt blowing method are within the above range, it is important to precisely set the lamination processing conditions of the nonwoven fabric. The laminated nonwoven fabric is heated at a temperature of 110 to 180 ° C, To 30 MPa for 60 to 180 seconds, so that the above performance can be satisfied.

If the pressing temperature, pressure, and time are less than the above range, there is a fear that the laminated layers are separated from each other due to insufficient adhesive force. If the pressing temperature exceeds the above range, fusion between the nonwoven fabrics occurs and pore size and pore distribution are uniformly formed The filtration efficiency is lowered, which is not preferable.

Through such lamination and pressing, it is possible to prevent the fiber material from forming even if the fiber material contains the acidic polymer and to suppress the lowering of the formability and the mechanical strength to have a uniform fineness, and the micropores of the nonwoven fabric are uniformly formed It is possible to manufacture a nonwoven fabric having a tensile strength of 40 N or more and a tensile strength per unit area of 4 MPa or more, which is excellent in pressure resistance, exhibits excellent filtration efficiency even when the amount of permeation is increased, suppresses reduction in charging value, and can maintain a charged state for a long period of time.

The melt blown nonwoven fabric manufacturing apparatus has a melt flow emitter for spinning very fine staple fibers together with an injection stream of ejected air from a spinning hole of a fiber material composition and a melt blowing radiator and a net conveyor for collecting the fibers discharged from the melt blow spinning machine in the form of a sheet-like fiber sheet.

The die for melt blowing has a plurality of pores for discharging the molten fiber material composition at its tip lip portion, and usually has a width of 1000 to 2000 mm, and the pore is generally perforated with 1,000 to 10,000 pores at its tip lip portion, And is usually about 0.1 to 0.5 mm.

Further, from the die for melt blowing, the fiber material composition is brought into contact with the heating gas at a high speed, and the fiber material composition stream is divided and simultaneously grafted to the melted state to be drawn in the fiber length direction, For this purpose, the melt blowing die is a device for introducing a high-speed heating gas stream (blowing air) and forming a fine discontinuous staple fiber by contacting the melted fiber material composition with the heated gas stream inside or outside the die.

The nonwoven fabric thus produced is composed of staple fibers having an average fiber diameter of 0.1 to 10 mu m and has a basis weight of 5 to 100 g / m 2.

Thereafter, the formed nonwoven fabric can be charged to form a charged nonwoven fabric.

As the charging method, any standard charging method known in the art can be used. For example, triboelectric (utilizing physical energy), corona charging (using electrical energy), and hydro charging (using collision energy).

Hydrocharging is performed by contacting the fibers with water in a manner sufficient to impart charge to the fibers, followed by drying the nonwoven.

An example of hydrocharging involves impinging a water jet or water droplet stream onto a nonwoven fabric at a pressure sufficient to provide a charge to the nonwoven fabric, followed by drying the nonwoven fabric. The pressure required to achieve optimal results depends on the type of sprayer used, the type of polymer forming the nonwoven, the type and concentration of the additive to the polymer, the thickness and density of the nonwoven, and the pretreatment, e.g., It depends on what you did before. In general, water pressures in the range of 10 to 500 psi (69 to 3450 psi) are suitable. The water jet or water droplet stream may be provided by any suitable atomizing apparatus. An example of a useful spray device is a device that is used to hydraulically entangling fibers. An example of a suitable hydro-charging method is described in U.S. Patent No. 5,496,507 (Angadjivand et al.).

The average surface charge density of the charged nonwoven fabric of the present invention may be 0.5 to 5 × 10 ^-5 C / m 2.

The effect of improving the filtration efficiency can not be obtained when the electrification charge amount in the electrified nonwoven fabric is too small, and the dust collection performance is hardly changed even when it is too large.

The filter of the present invention in which the nonwoven fabric for high-efficiency filtration is provided as the filter media material has an initial high collection ability and can maintain its performance for a long time.

Since the nonwoven fabric for high-efficiency filtration of the present invention is intended to remove fine dust, it can be suitably used as an air filter for air conditioners, air cleaners, cleaners, fan heaters, general air conditioners, .

Hereinafter, the present invention will be described in more detail with reference to the following Production Examples, Examples and Comparative Examples.

It is to be understood, however, that the invention is not to be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Will be apparent to those skilled in the art to which the present invention pertains.

[Production Examples 1 to 5]

180.0 parts by weight of water and monomers such as vinyl sulfonic acid (VSA), fumaric acid (FMA), methyl methacrylate (MMA) and vinyl toluene (VTN) were charged into a reactor capable of heating, stirring and refluxing as shown in Table 1 , 0.5 part by weight of t-butylperoxy 2-ethylhexanoate as an initiator and 1.2 parts by weight of sodium laurylbenzene sulfate as an emulsifier were charged, the temperature of the reactor was raised to 60 ° C and the temperature was maintained at 6 Time reaction. Thereafter, water was removed, and the obtained reaction product was dried at 100 DEG C for 8 hours and then pulverized to obtain a powdery acidic polymer.

The properties of the obtained acidic polymer are shown in Table 1 below.

division Production Example 1 Production Example 2 Production Example 3 Production Example 4 Production Example 5 Monomer
input
(Parts by weight) VSA 42.0 64.0 0 0 12.0 FMA 24.0 0 43.0 0 84.0 MMA 34.0 11.0 45.0 38.0 4.0 VTN 0 25.0 12.0 62.0 0 Manufactured
acid
Polymer Acid value (mg KOH / g) 382 261 423 32 1,024 Molecular Weight 5,500 3,400 10,200 8,800 1,600 Melting point
(poise, 200 < 0 > C) 8,400 4,600 12,000 2,200 60,000

[Example 1]

Polypropylene and acidic polymer having MFR of 95 Og / 10 min (ASTM D 1238, 230 DEG C, 2.16 Kg) were mixed in a tumbler mixer as shown in Table 2 below to prepare a fiber material composition.

The fiber material composition was fed into an extruder, melted at 265 ° C, and discharged from a melt blowing die connected to the end of the extruder for spinning. The temperature of the blown air was 275 ° C, the amount of air to be blown was 5.8 Nm 3 / min, distance was 300 ㎜, the melt velocity nonwoven fabric having an average fiber diameter of 3 탆 and a basis weight of 20 g / ㎡ was obtained.

The formed nonwoven fabric was continuously passed at a speed of 20 m / min while applying a DC voltage of -30 kV to the electrodes constituted by arranging the needle electrodes in two rows at intervals of 12 mm in the lengthwise direction at a rate of 20 m / min.

The average surface charge amount of the prepared electrified nonwoven fabric was measured and found to be 1.8 × 10 ^-5 C / m 2. At this time, the average surface charge amount was measured by bringing an electrode probe having an area of 1 cm ² into contact with the surface of the non-woven fabric using a surface charge density measuring apparatus manufactured by the Physical Chemistry Laboratories.

On the other hand, the properties of the thus-prepared electrified nonwoven fabric were evaluated using the following evaluation methods.

[Examples 2 to 4], [Comparative Examples 1 to 4]

A charging nonwoven fabric was produced in the same manner as in Example 1, except that the content of the fiber material composition in Example 1 was changed as shown in Table 2 below.

Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Polypropylene content
(weight%) 98.5 95.0 98.5 98.5 98.5 98.5 99.6 89.0 acid
Polymer Kinds Production Example 1 Production Example 1 Production Example 2 Production Example 3 Production Example 4 Production Example 5 Production Example 1 Production Example 1 content
(weight%) 1.5 5.0 1.5 1.5 1.5 1.5 0.4 11.0

[Example 5]

The fiber material composition of Example 1 was put into an extruder and melted at 220 캜 and spun out from a melt blowing die connected to the end of the extruder and spun to obtain a blown air temperature of 230 캜, melt-blown nonwoven web was obtained under conditions of a die to collector distance of 170 mm and a collector speed of 3 mpm (meter per minute).

The obtained melt blown nonwoven web had a thickness of 0.11 mm, a basis weight of 7.2 g / m 2, and an average pore size of 11.4 탆. The fibers constituting the nonwoven fabric were observed with a microscope and the average fiber diameter was measured to be 4 탆.

The resultant nonwoven web was laminated with four layers of laminate, and thermocompression-bonded at a temperature of 120 DEG C and a pressure of 6 MPa for 2 minutes to form a nonwoven fabric.

The average pore size of the formed nonwoven fabric was 8.5 탆.

The formed nonwoven fabric was continuously passed at a speed of 20 m / min while applying a DC voltage of -35 kV to the electrodes constituted by arranging the needle electrodes in two rows at intervals of 12 mm in the longitudinal direction at a rate of 20 m / min to prepare a charging nonwoven fabric .

[Examples 6 to 7], [Comparative Example 5, Comparative Example 6]

Table 3 shows the evaluation results of the pore and the strength of the prepared electrified nonwoven fabric by using the same method as in Example 5 except that the number of laminated layers was changed as shown in Table 3 in Example 5 Respectively.

division Example 5 Example 6 Example 7 Comparative Example 5 Comparative Example 6 Number of layers (layer) 6 8 12 3 13 Average pore size
(One layer before lamination, 占 퐉) 11.4 11.4 11.4 11.4 11.4 Average pore size
(Mu m after lamination) 7.9 7.4 7.3 10.5 7.2 Thickness (mm) 0.21 0.26 0.32 0.17 0.33 Tensile strength (N) 40 48 68 31 69

From the results of Table 3, it can be seen that when the number of layers is 4 or more, the average pore size becomes smaller and the filtration efficiency of the fine material is further increased. Also, in the filtration process using the filter material continuously for a long time under the pressure condition, It can be confirmed that the improvement is suppressed.

As the number of layers increases, the average pore size decreases and the tensile strength increases. However, the degree of such improvement is insignificant, and the appearance of the nonwoven fabric gradually deteriorates without being uniform due to fusion of the multilayers.

<Evaluation method>

1. Voltage

Measure using an electrostatic voltmeter (model no. 244, manufactured by Monroe Electronics, USA).

After the nonwoven web sample was adhered and fixed on an iron plate of a grounded electrostatic voltmeter, a sensor of an electrostatic voltmeter was placed on an arbitrary portion of the sample, and a magnitude of 50 charge points was measured at intervals of 5 cm in length and width, The magnitude of the measured voltage and the ratio of the charging point are evaluated.

2. Filtration efficiency (%)

The nonwoven web was placed in a filter state using a filter tester (Model No. 8130, TSI, USA) and measured under the conditions of a filter member area of 100 cm 2, NaCl particles of 0.3 탆 and air volume of 32 LPM.

Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Daejeon
ratio(%) Less than 100V 0 0 0 0 92 100 98 100 100 ~ 150V 38 6 44 0 8 0 2 0 Over 150V 62 94 56 100 0 0 0 0 Filtration efficiency (%) 99.93 99.94 99.92 99.96 82.38 89.21 74.45 91.26

Example 5 Example 6 Example 7 Comparative Example 5 Comparative Example 6 Daejeon
ratio(%) Less than 100V 0 0 0 6 0 100 ~ 150V 42 38 36 38 38 Over 150V 58 62 64 56 62 Filtration Efficiency (%) - Initial 99.99 99.99 99.99 99.27 99.99 Filtration efficiency (%) * 99.89 99.92 99.95 98.43 99.90 * Measured after 7 days under the condition of air volume 32LPM

From the results of Tables 4 and 5, it is confirmed that the filtration efficiency of the electretonized nonwoven fabric according to the present invention is excellent and the excellent filtration efficiency is maintained even after the filtration time has elapsed.

This can be interpreted as a result of the fact that the electrification nonwoven fabric according to the present invention has a high voltage at the charging point of the surface.

On the other hand, in Comparative Example 6, appearance failure phenomenon occurred, which indicates an uneven outer surface due to the occurrence of wrinkles on the surface of the nonwoven fabric.

Claims (11)

A nonwoven fabric comprising 90.0 to 99.5% by weight of a non-conductive thermoplastic polymer and 0.5 to 10.0% by weight of an acidic polymer having an acid value of 50 to 1,000,
The nonwoven fabric is charged at a nonuniform surface potential and the ratio of the charging point having an absolute value of the charging voltage by the charging of 100 V or higher is 90%
The acidic polymer may be selected from the group consisting of a sulfonic acid group, a sulfonic acid ester group, a carboxylic acid group, a carboxylic acid ester group, a thiocarboxylic acid group, a thiocarboxylic acid ester group, a dithiocarboxylic acid group, a dithiocarboxylic acid ester group, Wherein the polymer is polymerized by using a monomer containing at least one group selected from the group consisting of a hydrogen atom, The method according to claim 1,
The acidic polymer may be at least one selected from the group consisting of a sulfonic acid group, a sulfonic acid ester group, a carboxylic acid group, a carboxylic acid ester group, a thiocarboxylic acid group, a thiocarboxylic acid ester group, a dithiocarboxylic acid group, a dithiocarboxylic acid ester group, And at least one acid group selected from the group consisting of an alkyl group, The method according to claim 1,
Wherein the acidic polymer is a thermoplastic polymer having a weight average molecular weight of 1,000 to 20,000. delete The method according to claim 1,
Wherein the non-conductive thermoplastic polymer is selected from the group consisting of polyolefins selected from polyethylene, polypropylene, poly-4-methyl-1-pentene and polyvinyl chloride; polystyrene; Polycarbonate; Polyester; Polyamide, and copolymers thereof. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt; Preparing a raw material having a composition of 90.0 to 99.5% by weight of a non-conductive thermoplastic polymer and 0.5 to 10.0% by weight of an acidic polymer having an acid value of 50 to 1,000;
Forming a web of short fibers prepared by a melt blowing method using a composition containing the raw material; And
Charging the nonwoven fabric made of the web by at least one method selected from triboelectrification, corona charging, and hydrocharging method,
The acidic polymer may be at least one selected from the group consisting of a sulfonic acid group, a sulfonic acid ester group, a carboxylic acid group, a carboxylic acid ester group, a thiocarboxylic acid group, a thiocarboxylic acid ester group, a dithiocarboxylic acid group, a dithiocarboxylic acid ester group, Wherein the polymer is polymerized by using a monomer having at least one functional group selected from the group consisting of an alkyl group and a hydrocarbon group. delete The method according to claim 6,
In the forming of the web, the spinning temperature is a temperature of 30 to 120 ° C or more relative to the melting point of the non-conductive thermoplastic polymer, the temperature of the blowing air is ± 40 ° C relative to the spinning temperature, the blowing air amount is 0.5 to 2.0 Nm 3 / Wherein the web is formed on a condition of a die to collector distance (DCD) of 100 to 300 mm and a collector speed of 1 to 50 mpm (meter per minute). The method according to claim 6,
Wherein the staple fiber has an average fiber diameter of 0.1 to 10 占 퐉. The method according to claim 6,
After the step of forming the web,
Laminating the web to form a nonwoven fabric; And
And thermally bonding the laminated nonwoven fabric to the nonwoven fabric. 11. The method of claim 10,
Wherein the lamination is a lamination of 4 to 12 layers and the thermocompression bonding is performed at a temperature of 110 to 180 DEG C and a pressure of 6 to 30 MPa for 60 to 180 seconds.