KR20240083284A - A Composite nonwoven fabric for air purification and manufacturing method thereof - Google Patents

Abstract

In the present invention, a mixture of polyvinyl alcohol (PVA) and polytetrafluoroethylene (PTFE), an aliphatic hydrocarbon having a divalent or higher carboxyl group, is electrospun on a fiber substrate and then an ester bond is induced in polyvinyl alcohol. Provided is a composite nonwoven fabric for air purification, which includes a composite fiber layer that promotes crosslink formation and is poorly water-soluble, and a method for manufacturing the same.

Description

Composite nonwoven fabric for air purification and manufacturing method thereof}

The present invention relates to a composite nonwoven fabric for air purification and a method of manufacturing the same. More specifically, the present invention relates to a composite nonwoven fabric for air purification and a method of manufacturing the same. More specifically, the present invention relates to a mixture of polyvinyl alcohol and polytetrafluoroethylene, electrospun on a fiber base, and then heat treated to induce an ester bond in the polyvinyl alcohol. It relates to a composite nonwoven fabric for purification and a method of manufacturing the same.

Due to the recent large-scale spread of infectious diseases, the demand for face filtering health masks is rapidly increasing, and fiber filters are mainly used to block the route of infection transmitted to the respiratory tract through airborne pollutants (viruses, droplets). .

In addition, as air pollution has recently worsened, there has been an issue regarding disease induction by pollutants such as heavy metals, fine dust, and volatile organic compounds in the air, so fabric filters are receiving a lot of attention in the field of air filtration.

Polypropylene (PP), a non-degradable polymer with excellent processing stability, is used as the main raw material for meltblown and spunbond nonwoven fabrics, which are used as the core material of the filtration layer of health masks.

Increasing the filter weight of meltblown nonwovens or forming a denser structure of the nonwovens are common approaches to achieve high filtration efficiency, but they significantly increase air flow resistance (differential pressure).

In addition, high filtration performance is provided through a charging process, and electrostatic charging and hydrocharging are mainly used in the charging process.

The electrostatic charging method is a dry corona method that introduces charges to the surface of a dielectric polymer material through the formation of high voltage, turning the non-woven fabric into an electrostatic material (electret). It shows highly efficient filter performance through mechanical collection and electrostatic force collection during filtration.

However, the electrostatic effect provided in this way had the problem of reduced filtration performance due to increased temperature and humidity, adsorption of volatile organic compounds, physical changes in the surface of the fiber, and long-term storage.

Specifically, the meltblown nonwoven fabric according to the prior art is difficult to use for a long period of time, and its performance is reduced due to adsorption of volatile organic compounds, physical changes on the fiber surface, and long-term storage, and the charge given to the surface is neutralized by increased humidity. There was a problem in which efficiency decreased more rapidly.

Recently, fiber microfiltration technology has been actively researched to increase filtration efficiency while maintaining low airflow resistance, and common methods of making such microfiber filtration materials include melt-blown and wet nonwoven fabrics ( wet-laid, spun bonding, needle punching, electrospinning, etc.

Compared to existing melt blown, nanofiber nonwoven fabric manufactured through electrospinning has high aspect ratio, high specific surface area, and small pore size, showing high filtration efficiency even in small amounts without electrostatic effect. However, it has the disadvantage of having a high differential pressure due to its dense physical structure. In addition, polyvinylidene fluoride, which has been mainly used as a filter material recently, is an insoluble material with ferroelectric properties and shows excellent filtration efficiency even without a separate charging process. However, due to the use of mixed solvents based on organic solvents (DMAc, DMF, Acetone, etc.) during the manufacturing process, there are problems such as the generation of a large amount of waste solution and the difficulty in removing the solvent remaining in the nonwoven fabric, so its use as a filter medium is limited. .

(Patent Document 0001) Korean Patent Publication No. 0-2022-0027313 (2022.03.08.)

The purpose of the present invention to solve the above problems is to heat-treat the composite fiber layer formed after electrospinning a mixture of an aqueous solution of polyvinyl alcohol in water and an emulsion in which polytetrafluoroethylene is dispersed on a fiber substrate, thereby producing polyvinyl alcohol. By inducing an ester bond to vinyl alcohol, it improves heat resistance, dust collection efficiency (PFE), surface roughness and structural stability, and is a composite fiber (=nano) that has high efficiency filtration performance even in a small amount compared to the melt blown of the prior art. To provide a composite nonwoven fabric for air purification made of (fiber) and a method for manufacturing the same.

The technical problem to be achieved by the present invention is not limited to the technical problem mentioned above, and other technical problems not mentioned can be clearly understood by those skilled in the art from the description below. There will be.

The configuration of the present invention to achieve the above object includes a fiber base; and a composite fiber layer that is poorly soluble in water by electrospinning a mixture of polyvinyl alcohol (PVA) and polytetrafluoroethylene (PTFE) on the fiber substrate and then inducing ester bonds in polyvinyl alcohol to promote the formation of crosslinks; It provides a composite nonwoven fabric for air purification, comprising:

In an embodiment of the present invention, the mixing ratio of polyvinyl alcohol (PVA) and polytetrafluoroethylene (PTFE) may be 95:5 or 60:40.

In an embodiment of the present invention, the mixed solution may be characterized as a mixture of an aqueous solution in which the polyvinyl alcohol is dissolved in water and an emulsion in which polytetrafluoroethylene is dispersed.

In an embodiment of the present invention, the mixed solution further includes a catalyst, and the catalyst has a content of 5 parts by weight (wt%) to 50 parts by weight (wt%) relative to the aliphatic hydrocarbon having a carboxyl group of two or more valences. It can be characterized.

In an embodiment of the present invention, the content of the aliphatic hydrocarbon having a divalent or higher carboxyl group may be 5 parts by weight (wt%) to 30 parts by weight (wt%) based on 100 parts of the composite fiber layer.

In an embodiment of the present invention, as the content of polytetrafluoroethylene increases, heat resistance and dust collection efficiency (PFE) may be improved.

In an embodiment of the present invention, the composite fiber layer may be characterized in that it is ester bonded by an aliphatic hydrocarbon compound having a divalent or higher carboxyl group.

In an embodiment of the present invention, the aliphatic hydrocarbon compound having a divalent or higher carboxyl group is citric acid, butane-1,2,3,4-tetracarboxylic acid, succinic acid, maleic acid, or two of them. It may be characterized as including the above.

In an embodiment of the present invention, the melting point of the fiber substrate may be 200°C or higher.

In an embodiment of the present invention, the fiber substrate may be any one of non-woven fabric, fabric, and knitted fabric.

In an embodiment of the present invention, the fiber substrate may be a spunbond nonwoven fabric.

In an embodiment of the present invention, the composite nonwoven fabric for air purification may be a filter element or filter unit product applied as a face filtration mask or a filter medium for air purification.

In addition, the present invention for achieving the above object includes the steps of (a) preparing an aqueous solution of polyvinyl alcohol and an aliphatic hydrocarbon having a divalent or higher carboxyl group dissolved in water; (b) forming a mixed solution by mixing an emulsion in which polytetrafluoroethylene is dispersed and the aqueous solution at a preset ratio; (c) electrospinning the mixed solution onto a fiber substrate to produce a composite fiber layer; and (d) heat treating the composite fiber layer to induce an ester bond in polyvinyl alcohol.

In an embodiment of the present invention, in step (d), the mixed solution may further include a catalyst.

In an embodiment of the present invention, in step (d), the composite fiber layer may be heat treated at a temperature of 160°C to 200°C.

The effect of the present invention according to the above configuration is that a mixture of an aqueous solution of polyvinyl alcohol and an aliphatic hydrocarbon having a divalent or higher carboxyl group dissolved in water and an emulsion in which polytetrafluoroethylene is dispersed is electrospun on a fiber substrate. By heat treating the formed composite fiber layer to induce an ester bond to polyvinyl alcohol, heat resistance, dust collection efficiency (PFE), surface roughness, and structural stability can be improved.

The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the configuration of the invention described in the detailed description or claims of the present invention.

1 is a flowchart showing a method of manufacturing a composite nonwoven fabric for air purification according to an embodiment of the present invention.
Figure 2 is a graph showing the results of a heat and moisture resistance cycle test of a nonwoven fabric for air purification manufactured by a method for manufacturing a composite nonwoven fabric for air purification according to an embodiment of the present invention.
Figure 3 is an image showing that surface roughness increases as the content of polytetrafluoroethylene (PTFE) increases in the method of manufacturing a composite nonwoven fabric for air purification according to an embodiment of the present invention.
Figure 4 is a graph showing weight loss according to temperature in the method of manufacturing a composite nonwoven fabric for air purification according to an embodiment of the present invention.
Figures 5 (a) and (b) are graphs showing dust collection efficiency (PFE) and resistance according to surface speed in the method of manufacturing a composite nonwoven fabric for air purification according to an embodiment of the present invention.
Figure 6 shows dust collection of NaCl particles and paraffin-oil particles of the filter medium manufactured according to the content of polyvinyl alcohol and polytetrafluoroethylene (PTFE) in the method of manufacturing a composite nonwoven fabric for air purification according to an embodiment of the present invention. This is a graph showing efficiency (PFE) and resistance.

Hereinafter, the present invention will be described with reference to the attached drawings. However, the present invention may be implemented in various different forms and, therefore, is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts unrelated to the description are omitted, and similar parts are given similar reference numerals throughout the specification.

Throughout the specification, when a part is said to be “connected (connected, contacted, combined)” with another part, this means not only “directly connected” but also “indirectly connected” with another member in between. "Includes cases where it is. Additionally, when a part "includes" a certain component, this does not mean that other components are excluded, but that other components can be added, unless specifically stated to the contrary.

The terms used herein are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that it does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

1. Composite nonwoven fabric for air purification

A composite nonwoven fabric for air purification according to an embodiment of the present invention includes a fiber base and a composite fiber layer.

The fiber substrate may be in the form of a single fiber or a plurality of fiber bundles, or may be a fiber bonding structure in which a plurality of fibers are regularly or irregularly bonded to each other.

Specifically, the fiber substrate is a microfiber and may be a fabric, knitted fabric, spun yarn, filament, or non-woven fabric. More preferably, the fiber substrate may be a spunbond nonwoven fabric, and as a result, it may be advantageous in maintaining physical strength.

Illustratively, the fiber base is a microfiber, which may include a polymer with a melting point of 200°C or higher, or 200 to 600°C or 300 to 500°C, or may include a metal material (e.g., SUS mesh or wire mesh, etc.) .

The above-described fiber substrate may be either a spunbond nonwoven fabric or a meltblown nonwoven fabric.

The composite fiber layer is a nano-fiber layer, and a mixture of polyvinyl alcohol (PVA) and polytetrafluoroethylene (PTFE) is electrospun on a fiber base and then induces ester bonds in polyvinyl alcohol to promote the formation of cross-links to protect against water damage. It is dissolved.

Here, the mixed solution is a mixture of an aqueous solution of polyvinyl alcohol (PVA) dissolved in water and an emulsion in which polytetrafluoroethylene (PTFE) is dispersed.

At this time, the mixing ratio of polyvinyl alcohol (PVA) and polytetrafluoroethylene (PTFE) may be 95:5 or 60:40.

In particular, it may be desirable to mix polyvinyl alcohol (PVA) and polytetrafluoroethylene (PTFE) at 80:20 to 70:30.

When mixed at other mixing ratios, there is difficulty in uniformly forming polyvinyl alcohol (PVA) into fibers.

In addition, the mixed solution may further include a catalyst, and the catalyst may have a content of 5 parts by weight (wt%) to 50 parts by weight (wt%) relative to the aliphatic hydrocarbon having a carboxyl group of two or more valences.

Additionally, the content of the aliphatic hydrocarbon having a divalent or higher carboxyl group may be 5 parts by weight (wt%) to 30 parts by weight (wt%) based on 100 parts of the composite fiber layer.

In addition, polytetrafluoroethylene particles are ferroelectric inorganic particles that enhance the hydrophobicity of polyvinyl alcohol composite fibers (=nanofibers) and are used as reinforcing materials for high-temperature filter applications by improving the performance and heat resistance of fiber filters.

Specifically, the composite fiber layer is ester bonded by an aliphatic hydrocarbon compound having a divalent or higher carboxyl group.

Here, the aliphatic hydrocarbon compound having a divalent or higher carboxyl group includes citric acid, butane-1,2,3,4-tetracarboxylic acid, succinic acid, maleic acid, or two or more of these.

Specifically, based on 100 parts by weight of the composite fiber layer, the content of the aliphatic hydrocarbon group having at least a divalent carboxyl group may be 5 to 30 parts by weight, or 5 to 20 parts by weight, or 7 to 12 parts by weight. In addition, when the content of the aliphatic hydrocarbon group having at least a divalent or higher carboxyl group satisfies this range, it is advantageous in terms of maintaining the nanofiber form and maintaining filtration performance even when exposed to a humidified environment.

Preferably, the aliphatic hydrocarbon compound may be an aliphatic hydrocarbon compound having a trivalent or higher carboxyl group. When the aliphatic hydrocarbon compound is an aliphatic hydrocarbon compound having a trivalent or higher carboxyl group, the hydroxyl groups of the composite fiber (=nanofiber) form more ester bonds with polyvinyl alcohol through the aliphatic hydrocarbon compound, leading to the suffering of polyvinyl alcohol. The degree of pulverization can be controlled.

The fiber base of the above-described composite nonwoven fabric for air purification is combined with a polyvinyl alcohol composite fiber layer that is poorly water-soluble by ester bonding, thereby preventing physical damage to the composite fiber layer and serving to supplement physical strength.

When the fiber base contains a polymer or metal material having a melting point in this range, the properties of the fiber base can be prevented from changing even when subjected to heat treatment of 160°C or higher during the manufacturing process of the composite nonwoven fabric for air purification described later.

Polymers included in the fiber base for this may include polyethylene terephthalate, nylon, polybutylene terephthalate, or two or more of these.

Specifically, the above-described fiber substrate may include polyethylene terephthalate spunbond nonwoven fabric, nylon spunbond nonwoven fabric, polybutylene terephthalate spunbond nonwoven fabric, or two or more thereof.

The above-described fiber substrate can be combined with a poorly water-soluble composite fiber layer in a physically bonded structure.

The composite nonwoven fabric for air purification of the present invention is a composite nonwoven fabric having a composite fiber layer made of poorly water-soluble polyvinyl alcohol bonded to a fiber base. It has poor water solubility and has a dust collection efficiency before exposure to a humidified environment even after exposure to a humidified environment. Maintain more than 80% of

Since air purification materials such as respiratory protective masks are easily exposed to humidified environments, it is very important to not only have poor water solubility but also maintain filtration efficiency.

The filtration efficiency maintenance rate before and after humidification refers to the ratio of the dust collection efficiency after exposure to the dust collection efficiency before exposing the filtration efficiency evaluation object to the humidifying environment. The dust collection efficiency after humidification, that is, the degree of maintenance of filtration efficiency before and after humidification. This is the number by which to judge. Therefore, the filtration efficiency maintenance rate before and after humidification can be referred to as the dust collection efficiency maintenance rate before and after humidification.

The composite nonwoven fabric for air purification of the present invention has a filtration efficiency maintenance rate before and after humidification of 80% or more, specifically 82% or more, 85% or more, 87% or more, 88.3% or more, 89.6% or more, 100% or less, 95% or less, 89.6% or more. % or less, and may be 80% to 100%, or 85% to 95%, or 80% to 90%, or 80% to 89.6%, or 88.3% to 89.6%.

If the filtration efficiency maintenance rate before and after humidification of the air purifying composite nonwoven fabric is less than 80%, when the air purifying composite nonwoven fabric is exposed to a humidifying environment, it will still dissolve in water and cannot be used for air purification, or even if it is not soluble in water, it will not be used for air purification. When pressure is applied, the shape of the pore structure within the nonwoven fabric easily deforms, which is undesirable because the dust collection efficiency is significantly reduced.

The filtration efficiency maintenance rate before and after humidification described above is defined as [Equation 1]:

[Equation 1]

Filtration efficiency maintenance rate before and after humidification (%) = (Dust collection efficiency after humidification) / (Dust collection efficiency before humidification) × 100

In the above [Equation 1], the humidification conditions are treated in a constant temperature and humidity chamber set at 38 ± 2.5°C and 85 ± 5% RH for 25 ± 1 hours.

At this time, dust collection efficiency can be measured by a method applicable to the relevant technical field, for example, using an automated filter tester based on the 42 CFR 84 evaluation method, which is a NIOSH (National Institute for Industry and Health) standard. , TSI 8130, TSI company) can be used to measure. At this time, the measurement method using an automated filter tester involves fixing the composite nonwoven fabric to a sample holder with a round hole and then mounting it on an automatic filter tester to measure dust collection efficiency under the condition of a face velocity of 10.4 cm/sec. It is possible to use sodium chloride (polydisperse solid NaCl) aerosol with a mass median diameter of 0.26㎛ as the test aerosol.

In the present invention, poorly water-soluble means that it does not dissolve when in contact with water. This water solubility is evaluated by gel fraction, and when the gel fraction is 90% or more, it can be defined as poor water solubility.

For example, the poorly water-soluble composite fiber layer may have a gel fraction of 90% or more, 92% or more, 93.5% or more, 95% or more, 97.5% or less, 98% or less, 99% or less, and 100% or less. When the gel fraction of the composite fiber layer satisfies this range, the polyvinyl alcohol composite fiber does not dissolve even when exposed to a humidified environment, which can be advantageous because the composite fiber layer with micropores can be maintained.

At this time, the gel fraction of the poorly water-soluble composite fiber layer can be calculated using the following [Equation 2].

[Equation 2]

Gel fraction (%) = Ws/Wi * 100

(Where, Wi = weight (g) of polyvinyl alcohol nonwoven fabric (polyvinyl alcohol composite fiber layer poorly soluble in water) before immersion in distilled water, Ws = polyvinyl alcohol nonwoven fabric (polyvinyl alcohol poorly soluble in water) dried after immersion in distilled water Weight of composite fiber layer (g)

As described above, the present invention has surface characteristics of poor water solubility/hydrophobicity, shows color/shape stability even when exposed to a long-term environment (0 to 80°C temperature/20 to 90% humidity, 96 hours), and reduces 80% of the filtration efficiency before exposure. Maintain above-mentioned performance.

In the present invention as described above, heat resistance and dust collection efficiency (PFE) are improved as the content of polytetrafluoroethylene (PTFE) increases, and a detailed description of this will be provided later.

The above-described composite nonwoven fabric for air purification may be a filter element or filter unit article applied as a face filtration mask or a filter media for air purification.

2. Method for manufacturing composite nonwoven fabric for air purification

Hereinafter, a method for manufacturing a composite nonwoven fabric for air purification according to an embodiment of the present invention will be described with reference to FIGS. 1 to 5.

1 is a flowchart showing a method of manufacturing a composite nonwoven fabric for air purification according to an embodiment of the present invention.

Referring to Figure 1, the method for manufacturing a composite nonwoven fabric for air purification according to an embodiment of the present invention includes the steps of (a) preparing an aqueous solution in which polyvinyl alcohol (PVA) and an aliphatic hydrocarbon compound having a divalent or higher carboxyl group are dissolved in water; (S100), (b) forming a mixed solution by mixing an emulsion in which polytetrafluoroethylene (PTFE) is dispersed and an aqueous solution at a preset ratio (S200), (c) electrospinning the mixed solution on a fiber substrate to form a composite fiber layer It includes a step of manufacturing (S300) and (d) heat treating the composite fiber layer to induce an ester bond to polyvinyl alcohol (S400).

In step (a), an aqueous solution is prepared by dissolving polyvinyl alcohol (PVA) in water.

In general, polyvinyl alcohol (PVA) has hydroxyl groups with high hydrophilicity and has high solubility in water, so it can easily produce composite fibers through electrospinning by preparing a solution using water, and can easily produce composite fibers with carboxyl groups of more than two valences. After adding an aliphatic hydrocarbon compound to the solution, the obtained composite fiber (=nanofiber) can be modified to be poorly water-soluble by inducing an ester reaction through heat treatment. Polyvinyl alcohol composite fibers that have poor water solubility do not dissolve even when exposed to a humidified environment and maintain their shape stably, thereby maintaining a high level of filtration efficiency.

The weight average molecular weight of polyvinyl alcohol (PVA) is not particularly limited, and any polyvinyl alcohol that can dissolve in distilled water can be used.

For example, the weight average molecular weight (MW) of polyvinyl alcohol (PVA) may be 8,000 to 250,000 g/mol, or 9,000 to 200,000 g/mol, particularly 9,000 to 10,000 g/mol, or 31,000 to 31,000 g/mol. Polyvinyl alcohols having a weight average molecular weight of 50,000 g/mol, 85,000 to 146,000 g/mol, and 124,000 to 186,000 g/mol can be applied.

Additionally, the degree of saponification of the polyvinyl alcohol may be 80 to 90 or 87 to 90%. At this time, when the weight average molecular weight and saponification degree of the polyvinyl alcohol satisfy these ranges, it is advantageous in terms of securing solubility in water and manufacturing composite fibers (=nanofibers) through electrospinning.

If the degree of saponification of polyvinyl alcohol rises to 90% or more, electrospinning does not occur at all, so it is preferable that the degree of saponification of polyvinyl alcohol has the above-mentioned range.

Aliphatic hydrocarbon compounds having a divalent or higher carboxyl group that serve to make the polyvinyl alcohol composite fiber poorly soluble in water include citric acid, butane-1,2,3,4-tetracarboxylic acid, succinic acid, and maleic acid. acid, or two or more of these. At this time, when citric acid or butane-1,2,3,4-tetracarboxylic acid is applied as the aliphatic hydrocarbon compound having a trivalent or higher carboxyl group, the aliphatic hydrocarbon compound having two carboxyl groups Compared to this, even if the same amount is applied, it is advantageous because more divalent or higher ester bonds can be induced and water solubility can be further promoted.

At this time, the polyvinyl alcohol in the mixed solution may be 1 to 20 parts by weight, or 5 to 20 parts by weight, or 8 to 15 parts by weight, based on 100 parts by weight of the solvent. When the polyvinyl alcohol content satisfies this range, it can be advantageous in terms of stably producing composite fibers (=nanofibers).

Additionally, the content of the aliphatic hydrocarbon having a divalent or higher carboxyl group may be 5 parts by weight (wt%) to 30 parts by weight (wt%) based on 100 parts of the composite fiber layer.

Specifically, based on 100 parts by weight of the polyvinyl alcohol composite fiber, the content of the aliphatic hydrocarbon compound having a divalent or higher carboxyl group is 5 to 30 parts by weight, or 5 to 20 parts by weight, or 5 to 15 parts by weight, or 7 to 12 parts by weight. It could be wealth. When the content of the aliphatic hydrocarbon compound having a divalent or higher carboxyl group satisfies this range, it is advantageous in terms of maintaining filtration performance in a humidified environment without impairing the spinnability of the composite fiber.

Next, in step (b), a mixed solution is formed by mixing an emulsion in which polytetrafluoroethylene (PTFE) is dispersed and an aqueous solution at a preset ratio.

In step (c), a composite fiber layer is manufactured by electrospinning the mixed solution onto a fiber substrate.

At this time, the fiber substrate may be a fabric, knitted fabric, spun yarn, filament, or non-woven fabric. More preferably, the fiber substrate may be a spunbond nonwoven fabric, and as a result, it may be advantageous in maintaining physical strength. According to one embodiment of the present invention, the fiber substrate may include polyethylene terephthalate spunbond nonwoven fabric, nylon spunbond nonwoven fabric, polybutylene terephthalate spunbond nonwoven fabric, or two or more thereof.

For more detailed information regarding the fiber substrate, refer to the above.

The electrospinning method is a technology that can produce fibers ranging in size from several micrometers to several nanometers by charging a polymer solution using an electric field. Compared to template synthesis, phase separation, and self-assembly methods using existing electric fields, the manufacturing method and device are simple, and various properties can be exhibited depending on the composition ratio of the polymer material. fibers can be manufactured. Fibers obtained by electrospinning are very flexible and have a high specific surface area, so they have the advantage of being widely used in various fields such as filters and mask sheets.

Electrospinning can be performed under the conditions of a mixed solution concentration of 5 to 20% by weight, a voltage of 5 to 100 kV, a solution discharge rate of 0.1 to 10 mL/h, and a spinning distance of 3 to 50 cm.

Next, the composite fiber layer is heat treated at a temperature of 160° C. or higher to induce an ester bond between polyvinyl alcohol and an aliphatic hydrocarbon compound having a divalent or higher carboxyl group.

In step (d), the composite nonwoven fabric for air purification according to the present invention is manufactured by crosslinking the fiber base and the composite fiber layer by heat treating the composite fiber layer to induce ester bonding.

At this time, in step (d), the composite fiber layer is heat treated at a temperature of 160°C to 200°C.

In more detail, the carboxyl group of the aliphatic hydrocarbon compound and the hydroxyl group of the polyvinyl alcohol composite fiber (=nanofiber) undergo an ester reaction, and the aliphatic hydrocarbon compound combines with the polyvinyl alcohol composite fiber through an ester linker, causing the polyvinyl alcohol composite fiber to suffer. It is dissolved.

Specifically, heat treatment conditions may be performed at 160°C to 200°C, 160°C to 180°C, or 160°C to 170°C for 1 minute to 30 minutes, or 3 minutes to 10 minutes. When step (d) satisfies the above-mentioned conditions, it can be advantageous in that ester bonding occurs easily, the work speed can be increased, and deformation of the base fiber layer by heat can be minimized.

Additionally, in step (d), a catalyst may be further included in the mixed solution to increase the efficiency of the ester reaction.

The catalyst may include sodium acetate, sodium hypophosphite, etc., of which sodium acetate may be more preferably applied.

In actual experiments, the catalyst may have a content of 5 parts by weight (wt%) to 50 parts by weight (wt%) compared to the aliphatic hydrocarbon having the divalent or higher carboxyl group.

Specifically, the catalyst content is 1 to 20 parts by weight, or 5 to 15 parts by weight, or 8 to 15 parts by weight, or 8 to 20 parts by weight, or 1 to 8 parts by weight, based on 100 parts by weight of an aliphatic hydrocarbon compound having a carboxyl group. , or 5 to 8 parts by weight. When the content of the catalyst satisfies this range, it can be advantageous in terms of promoting ester bonding.

In step (d), when the heat treatment temperature is 160 to 180 ℃ and the content of the aliphatic hydrocarbon compound having the carboxyl group is 10 to 20 parts by weight based on 100 parts by weight of polyvinyl alcohol, ester crosslinking and By recrystallizing polyvinyl alcohol, a high gel fraction of more than 90% can be effectively soluble in water, and further, a network structure can be formed by multiple ester bonds, greatly improving shape stability. , when exposed to a humidified environment, dust collection efficiency is maintained after humidification treatment compared to before humidification treatment, and excellent filtration efficiency maintenance rate before and after humidification can be achieved.

Example 1

A 10 wt% polyvinyl alcohol aqueous solution was prepared by dissolving polyvinyl alcohol polymer (weight average molecular weight 85,000 to 124,000 g/mol, 87 to 89% hydrolyzed, Sigma-Aldrich) in distilled water at 80°C for about 12 hours. After cooling the polyvinyl alcohol aqueous solution to room temperature, 100 parts by weight of polyvinyl alcohol, 12 parts by weight of citric acid, and 8% by weight of sodium acetate (sodium acetate) as an ester reaction catalyst relative to citric acid were added and stirred to mix polyvinyl alcohol. An aqueous solution was prepared.

Thereafter, the mixed aqueous solution was electrospun on a current collector to which a flat polyethylene terephthalate spunbond nonwoven fabric was attached using an electrospinning device to produce polyvinyl alcohol having a composite fiber layer (=nanofiber layer) attached to the base fiber layer. A composite nonwoven fabric was prepared. At this time, during electrospinning, the applied voltage was 25 kV, the spinning distance (distance between the syringe tip and the current collector plate) was 15 cm, the spinning speed (fluid speed) was 0.3 mL/hr, and a 25-gauge needle was used.

Afterwards, the formed polyvinyl alcohol composite nonwoven fabric was heat-treated at 170°C for 10 minutes using a convection oven to produce a heat-treated polyvinyl alcohol composite nonwoven fabric.

Example 2

Afterwards, a heat-treated polyvinyl alcohol composite nonwoven fabric was manufactured in the same manner as in Example 1, except that the formed polyvinyl alcohol composite nonwoven fabric was heat-treated at 160° C. using a convection oven.

Comparative Example 1

A heat-treated polyvinyl alcohol composite nonwoven fabric was prepared in the same manner as Example 1, except that an aqueous polyvinyl alcohol solution was prepared without adding citric acid and sodium acetate.

Comparative Example 2

A heat-treated polyvinyl alcohol composite nonwoven fabric was prepared in the same manner as in Example 1, except that 100 parts by weight of polyvinyl alcohol and 4 parts by weight of citric acid were added to prepare a polyvinyl alcohol mixed aqueous solution and heat treatment was performed at 150°C. .

Comparative Example 3

A heat-treated polyvinyl alcohol composite nonwoven fabric was prepared in the same manner as in Example 1, except that 100 parts by weight of polyvinyl alcohol and 4 parts by weight of citric acid were added to prepare a polyvinyl alcohol mixed aqueous solution and heat treatment was performed at 160°C. .

Comparative Example 4

A heat-treated polyvinyl alcohol composite nonwoven fabric was prepared in the same manner as in Example 1, except that 100 parts by weight of polyvinyl alcohol and 4 parts by weight of citric acid were added to prepare a polyvinyl alcohol mixed aqueous solution.

Comparative Example 5

A heat-treated polyvinyl alcohol composite nonwoven fabric was prepared in the same manner as in Example 1, except that 100 parts by weight of polyvinyl alcohol and 8 parts by weight of citric acid were added to prepare a polyvinyl alcohol mixed aqueous solution and heat treatment was performed at 150°C. .

Comparative Example 6

A heat-treated polyvinyl alcohol composite nonwoven fabric was prepared in the same manner as in Example 1, except that 100 parts by weight of polyvinyl alcohol and 8 parts by weight of citric acid were added to prepare a polyvinyl alcohol mixed aqueous solution and heat treatment was performed at 160°C. .

Comparative Example 7

A heat-treated polyvinyl alcohol composite nonwoven fabric was prepared in the same manner as in Example 1, except that 100 parts by weight of polyvinyl alcohol and 8 parts by weight of citric acid were added to prepare a polyvinyl alcohol mixed aqueous solution.

Comparative Example 8

A heat-treated polyvinyl alcohol composite nonwoven fabric was prepared in the same manner as in Example 1, except that 100 parts by weight of polyvinyl alcohol and 12 parts by weight of citric acid were added to prepare a polyvinyl alcohol mixed aqueous solution and heat treatment was performed at 150°C. .

Comparative Example 9

Add 100 parts by weight of polyvinyl alcohol and 12 parts by weight of citric acid to make polyvinyl

A heat-treated polyvinyl alcohol composite nonwoven fabric was prepared in the same manner as in Example 1, except that an alcohol mixed aqueous solution was prepared and heat treatment was performed at 150°C.

(Experimental example)

Gel fraction measurement

After measuring the weight (Wi) of the polyvinyl alcohol composite fiber (=nanofiber) nonwoven fabric, it was immersed in 20 mL of distilled water and incubated at 60 rpm for 24 hours using a shaking incubator (VS-8480 TSI, Vision Scientific). I shook it. Afterwards, the swollen polyvinyl alcohol sample is removed from distilled water, dried at 105°C using a convection oven, and the dried weight (Ws) is measured. The gel fraction is calculated from the following equation: To evaluate the water solubility of the composite fiber (=nanofiber) nonwoven fabric, the gel fraction was measured using only the composite fiber (=nanofiber) nonwoven fabric layer without the polyethylene terephthalate spunbond nonwoven fabric.

Gel fraction (%) = Ws/Wi * 100

Wi; Weight of dried sample before immersion in distilled water

Ws; Weight of sample dried after immersion in distilled water

Filtration performance evaluation (dust collection efficiency evaluation)

The dust collection efficiency (filtration efficiency (PFE)) of heat-treated polyvinyl alcohol composite nonwoven fabric was measured using an automated filter tester (TSI8130, TSI) based on the 42 CFR84 evaluation method, which is a NIOSH (National Institute for Industry and Health) standard. ) was measured using.

The composite nonwoven fabric was fixed to a sample holder with a round hole and then mounted on an automatic filter tester to measure dust collection efficiency under the condition of a face velocity of 10.4 cm/sec. Sodium chloride (polydisperse solid NaCl) aerosol with a mass median diameter of 0.26㎛ was used as the aerosol for testing.

Filtration performance evaluation after humidification environment treatment and filtration efficiency maintenance rate before and after humidification

The heat-treated polyvinyl alcohol composite nonwoven fabric was humidified by placing it in a constant temperature and humidity chamber set at 38 ± 2.5°C and 85 ± 5% RH for 25 ± 1 hours.

The dust collection efficiency of samples exposed to a humidified environment was measured according to the filtration performance evaluation method, and the filtration efficiency maintenance rate before and after humidification was calculated from the following equation.

Filtration efficiency maintenance rate before and after humidification (%) = (Dust collection efficiency after humidification) / (Dust collection efficiency before humidification) × 100

Correlation between measured air pressure and air flow rate

Using heat-treated polyvinyl alcohol composite nonwoven fabric, the correlation between measured air pressure (airflow resistance) and air flow rate (flow rate) was analyzed using a PMI capillary flow porometer (CFP-1500AEX, Porous Materials) in dry conditions. did. Samples before exposure to the humidified environment and samples after exposure to the humidified environment were compared and evaluated.

Gel fraction (%) Before humidification
Dust collection efficiency
[B (%)] After humidification
Dust collection efficiency
[A (%)] Before and after humidification
filtration efficiency
retention rate
[A/B (%)] Example 1 97.5 73.6 65.0 88.3 Example 2 93.5 78.7 70.5 89.6 Comparative Example 1 72.6 76.3 25.9 33.9 Comparative example 2 6.9 71.8 27.0 37.6 Comparative example 3 74.5 75.6 51.4 68.0 Comparative Example 4 91.4 73.0 35.4 48.5 Comparative Example 5 53.6 83.4 21.2 25.4 Comparative Example 6 88.1 81.7 52.7 64.5 Comparative example 7 95.3 71.7 47.1 65.7 Comparative example 8 74.2 70.5 40.1 56.9 Comparative Example 9 4.3 83.2 13.0 15.7

As shown in [Table 1], as the amount of citric acid added increases, the gel fraction increases even at the same heat treatment temperature, and even if the amount of citric acid added is the same, the gel fraction increases as the heat treatment temperature increases. From this, it can be seen that water solubility increases as an ester bond is formed through heat treatment after adding citric acid.

Heat and moisture resistance cycle experiment of composite nonwoven fabric for air purification

Figure 2 is a graph showing the results of a heat and moisture resistance cycle test of a nonwoven fabric for air purification manufactured by a method for manufacturing a composite nonwoven fabric for air purification according to an embodiment of the present invention.

In the heat resistance cycle experiment shown in Figure 2, various environmental conditions were set using heat resistance equipment (IS-16-SF1200, IS Bio). The experiment was conducted under the following temperature and humidity conditions, and the experiment was repeated approximately three times. First, the conditions for one cycle are to increase the temperature from an initial temperature in the chamber of 20 ℃ to a temperature of 80 ± 2 ℃ and 0% humidity within 2 hours, then continue for 8 hours, and then again within 2 hours to a temperature of 20 ± 2 ℃ and humidity of 90%. After moving, it was set to be maintained for 8 hours under stabilized conditions. This cycle takes approximately 20 hours, and the manufactured composite nonwoven fabric (PVA/PTFE 7:3 ratio condition) was placed in the chamber and repeated a total of three times to confirm the dust collection efficiency of the treated nonwoven fabric.

The dust collection efficiency (filtration efficiency (PFE)) of heat-treated polyvinyl alcohol composite nonwoven fabric was measured using an automated filter tester (TSI8130, TSI) based on the 42 CFR84 evaluation method, which is a NIOSH (National Institute for Industry and Health) standard. ) was measured using.

The composite nonwoven fabric was fixed to a sample holder with a round hole and then mounted on an automatic filter tester to measure dust collection efficiency under the condition of a face velocity of 10.4 cm/sec. Sodium chloride (polydisperse solid NaCl) aerosol with a mass median diameter of 0.26㎛ was used as the aerosol for testing.

As shown in Figure 2, it can be confirmed that the dust collection efficiency is maintained at more than 80% even after treatment for more than 48 hours in a high temperature environment of 80℃ and 0% humidity and a high humidity environment of 0℃ and 90% humidity. .

In more detail, compared to before the test, it was confirmed that the dust collection efficiency was more than 90% compared to the initial sample.

In particular, when the heat treatment temperature was 170°C as in Example 2, Comparative Example 4, and Comparative Example 7, all samples to which citric acid was added showed a gel fraction of more than 90%, indicating that water solubleness was effectively achieved. On the other hand, when citric acid is not added even though the heat treatment temperature is 170°C as in Comparative Example 1, it can be seen that the gel fraction is not sufficient at 72.6%.

In addition, even when 12% by weight of citric acid was added as in Comparative Examples 8 and 9, the gel fraction was low when heat treatment was not performed or heat treatment was insufficient.

Respiratory protective masks are easily exposed to high temperature and humidity due to body temperature and moisture contained in the breathed air, and air purification filters are often used in humid environments. Therefore, maintaining filtration efficiency even in a humid environment is very important as a filter material for air purification.

In Comparative Examples 4 and 7, although the gel fraction was more than 90% and had poor water solubility, when exposed to a humidified environment, the dust collection efficiency decreased significantly compared to before humidification treatment, and the filtration efficiency maintenance rate before and after humidification was less than 70%. On the other hand, in Examples 1 and 2, even after exposure to a humidified environment, the filtration efficiency was maintained at a high level of approximately 90% compared to the dust collection efficiency before exposure to the humidified environment.

A scanning electron microscope (SEM) photograph of the composite nonwoven fabric prepared in Example 2 after exposure to a humidified environment shows that the shape of the polyvinyl alcohol fiber layer on the base fiber layer is well maintained even after exposure to a humidified environment. On the other hand, a scanning electron microscope photograph of the composite nonwoven fabric prepared in Comparative Example 1 after exposure to a humidified environment shows that the polyvinyl alcohol nonwoven fabric layer on the base fiber layer has a fibrous shape even though there is a significant portion that does not dissolve as a result of exposure to the humidified environment. You can see that most of it can be lost.

In the case of the sample prepared in Example 1, it can be seen that there is little difference in the correlation between the measured air pressure and flow rate before and after exposure to the humidified environment. On the other hand, in the case of the sample prepared in Comparative Example 4 and exposed to a humidified environment, it can be seen that the flow rate increases rapidly as the measurement pressure increases from a low measurement pressure of 2 mmAq or less.

This means that in the case of Example 1, little structural change occurs due to air pressure even when exposed to a humidified environment, whereas in the case of Comparative Example 4, a large shape deformation occurs even when exposed to a small amount of air pressure due to exposure to a humidified environment. This suggests that if a large amount of shape deformation occurs, the deformation may easily occur even if a small amount of air pressure is applied when measuring filtration efficiency, which could easily result in a decrease in filtration efficiency.

Hereinafter, the effect of the nonwoven fabric for air purification manufactured by the method for controlling the nonwoven fabric for air purification according to the above will be described with reference to FIGS. 3 to 6.

Figure 3 is an image showing that surface roughness increases as the content of polytetrafluoroethylene (PTFE) increases in the method of manufacturing a composite nonwoven fabric for air purification according to an embodiment of the present invention.

The two images at the top and bottom on the leftmost in Figure 3 are images showing the surface roughness of the composite nonwoven fabric when polyvinyl alcohol (PVA) is 100%, and the two images at the top and bottom from the left in Figure 3 are images showing the surface roughness of the composite nonwoven fabric when polyvinyl alcohol (PVA) is 100%. is an image showing the surface roughness of a composite nonwoven fabric mixed with polyvinyl alcohol (PVA) and polytetrafluoroethylene (PTFE) at a mixing ratio of 9:1, and in Figure 3, 2 is the third top and bottom from the left. The image shows the surface roughness of a composite nonwoven fabric mixed with polyvinyl alcohol (PVA) and polytetrafluoroethylene (PTFE) at a mixing ratio of 8:2, and is 2 at the top and bottom rightmost in Figure 3. The image shows the surface roughness of a composite nonwoven fabric containing polyvinyl alcohol (PVA) and polytetrafluoroethylene (PTFE) mixed at a mixing ratio of 7:3.

As shown in Figure 3, it can be seen that the surface roughness of the composite nonwoven fabric increases as the mixing ratio of polytetrafluoroethylene (PTFE) increases compared to when the polyvinyl alcohol (PVA) is 100%, which is This means that as the mixing ratio of polytetrafluoroethylene (PTFE) increases, the dust collection efficiency (PFE) increases.

Figure 4 is a graph showing weight loss according to temperature in a method of manufacturing a composite nonwoven fabric for air purification according to an embodiment of the present invention.

In Figure 4, PV means polyvinyl alcohol (PVA), PT means polytetrafluoroethylene (PTFE), and H means heat treatment (crosslinking by heat treatment).

As shown in Figure 4, it can be seen that as the content of polytetrafluoroethylene (PTFE) in polyvinyl alcohol (PVA) increases, heat resistance (=heat resistance characteristics) improves.

Figures 5 (a) and (b) are graphs showing dust collection efficiency (PFE) and resistance according to surface speed in the method of manufacturing a composite nonwoven fabric for air purification according to an embodiment of the present invention. am.

In Figures 5 (a) and (b), PV means polyvinyl alcohol (PVA), and PF means polytetrafluoroethylene (PTFE).

In addition, face velocity refers to the flow rate of air when measured, and while efficiency generally decreases as the flow rate increases, nanofibers are not significantly affected by the flow rate, so they are more stable than existing melt blown.

Referring to (a) of FIG. 5, it can be seen that the dispersion capture efficiency (PFE) increases as the content of polytetrafluoroethylene (PTFE) mixed with polyvinyl alcohol (PVA) increases.

On the other hand, referring to (b) of FIG. 5, the differential pressure (=resistance) is affected by the flow rate and increases as polytetrafluoroethylene (PTFE) particles are reinforced.

Figure 6 is a graph showing the efficiency in a dry environment and a wet environment in a method for manufacturing a composite nonwoven fabric for air purification according to an embodiment of the present invention according to an embodiment of the present invention.

The general test is considered to be a tool to check the decrease in efficiency in the dry environment (Nacl) shown on the left of Figure 6 and the wet environment (Praffin oil) (inside the mask) shown on the right of Figure 6, but the existing PP-based melt blown (MB) has a significant decrease in efficiency on paraffin oil.

On the other hand, composite fibers (=nanofibers) are not greatly affected by the properties of the particles, and the more polytetrafluoroethylene (PTFE) particles are added to polyvinyl alcohol (PVA), the more stable the results are.

The description of the present invention described above is for illustrative purposes, and those skilled in the art will understand that the present invention can be easily modified into other specific forms without changing the technical idea or essential features of the present invention. will be. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive. For example, each component described as unitary may be implemented in a distributed manner, and similarly, components described as distributed may also be implemented in a combined form.

The scope of the present invention is indicated by the patent claims described below, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention.

Claims (15)

fiber substrate; and
A mixture of aliphatic hydrocarbons, polyvinyl alcohol (PVA), and polytetrafluoroethylene (PTFE) having a divalent or higher carboxyl group is electrospun on the fiber substrate, and then an ester bond is induced in the polyvinyl alcohol to form a crosslink. A composite nonwoven fabric for air purification comprising a composite fiber layer that promotes and becomes poorly soluble in water.
According to claim 1,
A composite nonwoven fabric for air purification, characterized in that the mixing ratio of the polyvinyl alcohol (PVA) and the polytetrafluoroethylene (PTFE) is 95:5 or 60:40.
According to claim 1,
The mixed solution is a composite nonwoven fabric for air purification, characterized in that an aqueous solution of an aliphatic hydrocarbon compound having a carboxyl group of more than 2 valence and polyvinyl alcohol dissolved in water, and an emulsion in which polytetrafluoroethylene is dispersed.
According to claim 1,
The mixed solution further contains a catalyst,
The catalyst is a composite nonwoven fabric for air purification, characterized in that the catalyst has a content of 5 parts by weight (wt%) to 50 parts by weight (wt%) relative to the aliphatic hydrocarbon having a carboxyl group of more than two valence.
According to claim 1,
A composite nonwoven fabric for air purification, wherein the content of the aliphatic hydrocarbon having a divalent or higher carboxyl group is 5 parts by weight (wt%) to 30 parts by weight (wt%) based on 100 of the composite fiber layer.
According to claim 1,
A composite nonwoven fabric for air purification, characterized in that heat resistance and dust collection efficiency (PFE) improve as the content of polytetrafluoroethylene increases.
According to claim 1,
The composite nonwoven fabric for air purification, characterized in that the composite fiber layer is ester bonded to polyvinyl alcohol by an aliphatic hydrocarbon compound having a divalent or higher carboxyl group.
According to clause 7,
The aliphatic hydrocarbon compound having a divalent or higher carboxyl group is characterized in that it includes citric acid, butane-1,2,3,4-tetracarboxylic acid, succinic acid, maleic acid, or two or more of these. Composite non-woven fabric for air purification.
According to claim 1,
A composite nonwoven fabric for air purification, characterized in that the melting point of the fiber base is 200°C or higher.
According to claim 1,
A composite nonwoven fabric for air purification, wherein the fiber substrate is any one of nonwoven fabric, fabric, and knitted fabric.
According to claim 1,
A composite nonwoven fabric for air purification, wherein the fiber substrate is a spunbond nonwoven fabric.
According to claim 1,
The composite nonwoven fabric for air purification is a composite nonwoven fabric for air purification, characterized in that it is a filter element or filter unit product applied as a face filtration mask or a filter media for air purification.
(a) preparing an aqueous solution of an aliphatic hydrocarbon compound having a divalent or higher carboxyl group and polyvinyl alcohol dissolved in water;
(b) forming a mixed solution by mixing an emulsion in which polytetrafluoroethylene is dispersed and the aqueous solution at a preset ratio;
(c) electrospinning the mixed solution onto a fiber substrate to produce a composite fiber layer; and
(d) heat treating the composite fiber layer to induce an ester bond to polyvinyl alcohol.
According to claim 13,
In step (d) above,
A method for producing a composite nonwoven fabric for air purification, characterized in that the mixed solution further contains a catalyst.
According to claim 13,
In step (d) above,
A method of manufacturing a composite nonwoven fabric for air purification, characterized in that the composite fiber layer is heat treated at a temperature of 160 ℃ to 200 ℃.

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