KR20240038046A - Filter material for air filter - Google Patents

Abstract

The object of the present disclosure is to provide a filter medium for an air filter that has renewable raw materials as its main component, is biodegradable, and has sufficient water repellency. In the filter material for an air filter according to the present disclosure, the fibers constituting the filter material include refined fibers and unrefined fibers, the refined fibers are fibrillated lyocell fibers, and the unrefined fibers are biodegradable. It is a fiber, and the mass ratio (purified fiber/unpurified fiber) of the purified fiber and the unrefined fiber is in the range of 3/97 to 20/80, and the filter medium does not contain fluorine in the molecule. It is characterized in that it contains a water repellent agent whose main ingredient is a hydrocarbon-based polymer.

Description

Filter material for air filter

The present disclosure relates to filter media for air filters used in various fields such as factory and building air conditioning, automobile cabins, air conditioners, air purifiers, and personal protective equipment. In particular, the environmental load is small and , It also relates to an air filter filter material that has a small decrease in filtration performance during use.

As medium and high performance filter media for air filters used in building air conditioning, etc., glass fiber filter media and meltblown nonwoven filter media are mainly used. Since glass fiber filter media is non-flammable, it is disposed of in landfill as industrial waste after use. For this reason, the environmental load upon disposal is large. In addition, meltblown nonwoven filter media uses non-renewable and finite fossil resources (PP, etc.) as raw materials, and when disposed of by incineration, carbon dioxide emissions throughout the entire life cycle are large. Additionally, if it is leaked into the environment after use, it does not decompose and continues to remain in the environment. For the above reasons, there is a demand for a filter medium that has a small environmental load, is mainly composed of renewable raw materials, and is biodegradable.

To solve these problems, filter media containing fibrillated lyocell fibers, biodegradable fibers, and regenerated or semi-synthetic fibers have been proposed (see Patent Document 1 or Patent Document 2). However, since cellulose-based fibers such as lyocell fibers have high hygroscopicity and absorbency, when used in a high humidity environment or when air currents or dust containing moisture pass through, swelling of the fibers or changes in the structure of the filter material occur. There is a problem that causes a decrease in the filtration performance of the filter media for air filters, for example, a decrease in the PF value. In addition, the PF value is defined by the equation of number 1, and the higher the PF value, the higher the dust particle collection efficiency, and it means that the filter medium has low pressure loss and high filtration performance.

[Number 1]

Here, transmittance [%] = 100 - collection efficiency [%]

In order to solve the above problems, a method of imparting water repellency to a filter medium is effective, and a method of using a fluorine-based water repellent agent is widely used as a method of imparting water repellency to a filter medium for an air filter (for example, (See Patent Document 3 or Patent Document 4). However, since the perfluoroalkyl compounds constituting the fluorine-based water repellent are poorly degradable and have high bioaccumulation, there is a worldwide movement to regulate their use, and they are not suitable for the purpose of the present invention.

Japanese Patent Publication No. 2006-167659 Japanese Patent Publication No. 2006-326470 Japanese Patent Publication No. 2001-79318 Japanese Patent Publication No. 2014-98082

As described above, there is a demand for a filter medium that has a small environmental load and reduces filtration performance during use. However, with conventional technology, it has been difficult to obtain a filter medium that has both these characteristics. Accordingly, the object of the present disclosure is to provide a filter medium for an air filter that has renewable raw materials as its main component, is biodegradable, and has sufficient water repellency.

In the filter medium for air filter according to the present invention, the fibers constituting the filter medium include refined fibers and unrefined fibers, the refined fibers are fibrillated lyocell fibers, and the unrefined fibers are biodegradable. It is a fiber, and the mass ratio (purified fiber/unpurified fiber) of the purified fiber and the unrefined fiber is in the range of 3/97 to 20/80, and the filter medium does not contain fluorine in the molecule. It is characterized in that it contains a water repellent agent whose main ingredient is a hydrocarbon-based polymer. According to this configuration, it is possible to obtain a filter medium that has a small environmental load and reduces filtration performance during use.

In the filter medium for an air filter according to the present invention, it is preferable that the biodegradable fiber, which is the unrefined fiber, is at least one selected from the group consisting of regenerated cellulose fiber, natural cellulose fiber, and polylactic acid fiber. Accordingly, a filter medium with high filtration performance and biodegradability can be obtained.

In the filter medium for an air filter according to the present invention, it is preferable that the hydrocarbon-based polymer, which is the main component of the water repellent, is an acrylic polymer. Accordingly, high water repellency can be obtained, and deterioration of filtration performance during use can be suppressed.

In the filter medium for an air filter according to the present invention, the filter medium contains a surfactant. Accordingly, high filtration performance can be obtained.

In the filter medium for an air filter according to the present invention, the surfactant is preferably a quaternary ammonium salt. Accordingly, higher filtration performance can be obtained.

In the filter medium for air filters according to the present invention, it is preferable that the water repellency specified in MIL-STD-282 is 100 mm water column height or more. Accordingly, a decrease in filtration performance during use can be suppressed.

In the filter medium for an air filter according to the present invention, the fibrillated lyocell fibers, which are the purified fibers, preferably have an average fiber diameter of 0.3 μm or more, a maximum fiber diameter of 8 μm or less, and a length-weighted average fiber length of 1 mm or more. . Reduction in collection efficiency and tensile strength of the filter medium is unlikely to occur.

In the filter medium for an air filter according to the present invention, the biodegradable fiber, which is the unrefined fiber, preferably has a fiber diameter of 5 μm or more. If the average fiber diameter is 5 μm or more, the voids necessary to uniformly distribute the purified fibers can be maintained, and it is difficult to cause an increase in pressure loss and a decrease in the collection efficiency of the filter medium.

According to the present disclosure, it is possible to obtain a filter medium that has a small environmental load and reduces filtration performance during use. In other words, it is possible to obtain a filter medium for an air filter that has renewable raw materials as its main component, is biodegradable, and has sufficient water repellency to prevent moisture absorption of cellulosic fibers including fibrillated lyocell fibers.

Next, the present invention will be described in detail by showing embodiments, but the present invention should not be construed as being limited to these descriptions. Various modifications may be made to the embodiment as long as the effect of the present invention is achieved.

Lyocell fiber in this embodiment is a regenerated cellulose fiber spun by an organic solvent spinning method using N-methylmorpholine-N-oxide as a solvent. In the organic solvent spinning method, cellulose is dissolved in an organic solvent and spun as is, so there is less cleavage of molecules, the average degree of polymerization is higher than that of other regenerated cellulose fibers, the rigidity of the fiber is high, and the cross-section of the fiber ( It has a shape that is close to a circular shape. This rigidity and cross-sectional shape make it easy to maintain the voids in the filter medium. In addition, the purified fibrillated Lyocell fiber also maintains the above-mentioned characteristics of rigidity and cross-sectional shape. Additionally, when fibrillated by purification, the surface area of the fibers that contribute to particle collection increases, so the collection efficiency increases, and the tensile strength of the filter medium increases because the entanglement of the fibers increases.

The purified fibers in this embodiment are fibrillated lyocell fibers, and the blending amount of the purified fibers is 3 to 20 parts, preferably 5 parts, based on 100 parts of the total fiber mass constituting the filter medium. to 15 parts, more preferably 5 to 13 parts. If the blending amount is less than 3 parts, it is difficult to obtain sufficient collection efficiency, and sufficient tensile strength cannot be obtained because there is little entanglement between the fibers. On the other hand, if the mixing amount is more than 20 parts, the entanglement of the fibers is too much, so the voids are blocked, the pressure loss increases significantly compared to the increase in collection efficiency, and the PF value decreases.

As a purification method for fibrillating Lyocell fibers, purifiers such as Niagara beater, PFI mill, single disc refiner, and double disc refiner can be used. In purification, it is desirable to purify without applying an excessively strong load so as not to excessively shorten the fiber length of Lyocell.

When lyocell fibers are purified, the fibers are cut and the fiber length becomes shorter. If the fiber length is too short, there is a risk that the pressure loss will increase because the voids after sheet formation will be filled. The fibrillated lyocell fiber used in the present invention preferably has a length-weighted average fiber length of 1 mm or more, more preferably 1 to 3 mm, and still more preferably 1 to 2 mm.

In addition, the length-weighted average fiber length of the fibrillated Lyocell fiber was measured according to ISO 16065-2:2007 “Determination of fiber length by automated optical analysis-Part2”.

Lyocell fibers undergo fibrillation through purification and the fiber diameter becomes thinner. The average fiber diameter of the fibril lyocell fiber used in this embodiment is preferably 0.3 μm or more, more preferably 0.3 to 1.0 μm, and still more preferably 0.3 to 0.8 μm. The maximum fiber diameter of the fibrillated Lyocell fiber is preferably 8 μm or less, more preferably 6 μm or less, and even more preferably 4 μm or less. If the average fiber diameter is less than 0.3 μm, the fibers are cut as fibrillation progresses, the tensile strength of the filter medium decreases, voids cannot be maintained, and there is a risk that collection efficiency may decrease. Additionally, if the average fiber diameter exceeds 1.0 μm and the maximum fiber diameter exceeds 8 μm, the surface area of the fibers contributing to particle collection decreases, and there is a risk that collection efficiency may decrease.

In addition, the fiber diameter in this embodiment is obtained by photographing the surface of the filter medium using an electron microscope, drawing a straight line in the transverse direction on the obtained electron microscope photograph, and measuring the fiber diameter at the intersection of the straight line and the fiber. Measured. The average fiber diameter was taken as the arithmetic average of 200 measurements.

The unrefined fibers in this embodiment are unrefined biodegradable fibers, and are preferably at least one selected from the group consisting of regenerated cellulose fibers, natural cellulose fibers, and polylactic acid fibers. Fibers of different fiber diameters may be mixed with the same type of fiber.

The blending amount of unrefined fiber in this embodiment is 80 to 97 parts, assuming that the total mass of fibers constituting the filter medium is 100 parts. If the blending ratio is outside this range, it will be outside the range of the blending amount of the purified fiber.

Regenerated cellulose fibers include viscose rayon fibers spun by a viscose method using cellulose as a raw material, and lyocell fibers spun by an organic solvent spinning method. These are renewable materials made from wood pulp, and have underground biodegradability and marine biodegradability.

Natural cellulose fiber is a fiber mainly made of cellulose extracted from plants, and includes wood pulp, cotton linter pulp, hemp pulp, kenaf pulp, and marcellated pulp obtained by alkali treatment of wood pulp. These are renewable raw materials made from plants, and have biodegradability when buried in the soil.

Polylactic acid fiber is a fiber spun mainly from a polymer obtained by chemically polymerizing lactic acid obtained through saccharification and fermentation using biomass-derived starch as a raw material. This is a renewable material made from corn, etc., and has biodegradability when buried in the soil. In addition, polylactic acid fibers, unlike cellulose fibers, have thermoplasticity, so they can impart tensile strength to the filter medium or thermoformability to the filter medium through heat fusion. Since the raw material of polylactic acid fiber competes with food, it is desirable to keep the blending amount low within a range that allows the physical properties of the filter medium to be tolerated. The compounding amount of polylactic acid fiber is preferably 0 to 30 parts, more preferably 0 to 20 parts, of the total fibers in the filter medium. That is, the blending amount of unrefined fiber is 80 to 97 parts if the total mass of fibers constituting the filter medium is 100 parts, and when polylactic acid fiber is blended n parts, the amount of regenerated cellulose fiber and natural cellulose fiber is 100 parts. Mix the total amount (including the case of only one side) from (80 - n) to (97 - n) parts. However, n is preferably 30 parts or less.

The unrefined fiber in this embodiment preferably has an average fiber diameter of 5 μm or more, more preferably 5 to 40 μm, and still more preferably 7 to 35 μm. If the average fiber diameter is thinner than 5 μm, it becomes difficult to maintain the voids necessary to uniformly distribute the purified fibers, which may lead to an increase in pressure loss. On the other hand, if the average fiber diameter exceeds 40 ㎛, the difference in fiber diameter from the purified fiber is large, so the variation in the pore diameter of the filter medium increases, which may cause a decrease in collection efficiency.

The water repellent in this embodiment is a water repellent whose main component is a hydrocarbon-based polymer that does not contain fluorine in the molecule and is used to provide sufficient water repellency to prevent deterioration of filtration performance during use, and which has acrylic polymer as its main component. desirable. Here, having a hydrocarbon-based polymer that does not contain fluorine in the molecule as the main component means that 50% by mass or more of the polymer component of the water repellent, preferably 80% by mass or more, more preferably 90% by mass or more, is hydrocarbon. It is made of a polymer that has a skeleton and is made of an organic compound containing oxygen, nitrogen, etc. A water repellent agent containing acrylic polymer as a main component can increase water repellency by increasing the carbon number of the ester portion of the raw material monomer, acrylic acid ester or methacrylic acid ester. Here, having an acrylic polymer as the main component means that 50% by mass or more of the polymer component of the water repellent, preferably 80% by mass or more, more preferably 90% by mass or more, is acrylic acid ester and/or methacrylic acid ester. It is made of a polymer polymerized using as the main raw material monomer. Additionally, the number of carbon atoms in the ester portion is preferably 9 or more, and more preferably 12 or more.

The water repellency of the filter medium in this embodiment is preferably 100 mm water column height or higher, more preferably 150 mm water column height or higher, and even more preferably 200 mm water column height or higher. The water repellent content in the filter medium needs to be within a range that achieves the required water repellency and does not impair the biodegradability of the filter medium. The water repellent content in the entire filter medium is preferably 0.3 to 2.0% by mass in terms of solid content, preferably 0.3 to 1.0% by mass, and more preferably 0.3 to 0.5% by mass.

The surfactant in this embodiment is used to improve filtration performance by preventing excessive adhesion of fibers in the filter medium to each other. Surfactants having various compositions and ionic properties can be selected as long as they do not interfere with the effects of the present invention. In particular, quaternary ammonium salts, which are highly effective in improving filtration performance, are preferred. Additionally, since the quaternary ammonium salt has antibacterial properties, it is possible to impart antibacterial properties to the filter medium. The surfactant content in the filter medium needs to be within a range that does not impair the biodegradability of the filter medium. The surfactant content in the entire filter medium is preferably 0 to 1.0 mass% in terms of solid content, preferably 0 to 0.5 mass%, and more preferably 0.1 to 0.5 mass%.

The basis weight of the filter medium in this embodiment is not particularly limited, but is preferably 25 to 350 g/m2, more preferably 50 to 250 g/m2, and still more preferably 70 to 150 g/m2.

The PF value of the filter medium in this embodiment is not particularly limited, but is preferably 5 or more, and more preferably 7 or more.

The tensile strength of the filter medium in this embodiment is not particularly limited as the required tensile strength varies depending on the application or post-processing method, but is preferably 0.4 kN/m or more, more preferably 0.6 kN/m or more. .

The filter medium of this embodiment is manufactured using a wet papermaking method. That is, the fibers constituting the filter medium are dispersed in water using a disperser such as a pulper, the obtained fiber slurry is deposited and dehydrated on a wire to form a sheet, and the obtained wet sheet is dried in a hot air dryer or cylinder. It is dried using a dryer such as a dryer to obtain a filter medium as a dry sheet. When applying a water repellent or a surfactant, the wet sheet before drying is applied through an impregnation treatment such as spraying or dipping in the state of an aqueous dispersion and dried. In addition, when applying only the water repellent, it may be applied to the dry sheet after drying.

Example

Below, the present invention will be described in detail through examples and comparative examples according to the present invention. However, the present invention is not limited to these.

Lyocell fiber (fineness 1.7 dtex (fiber diameter 12 ㎛), fiber length 4 mm, manufacturer: Lenzing AG) was purified using a Niagara beater, and the average fiber diameter was 0.7 ㎛, maximum fiber diameter 3.5 ㎛, and length. Fibrillated lyocell fibers with a weighted average fiber length of 1.1 mm were obtained.

Fibrillated lyocell fibers obtained as purified fibers, and

Unrefined fibers, listed below:

Lyocell fiber (fineness 1.7dtex (fiber diameter 12㎛), fiber length 4mm, manufacturer: Lenzing AG),

Rayon fiber (1) (fineness 0.6dtex (fiber diameter 7㎛), fiber length 4mm, product name: Rayon Corona SD, manufacturer: DAIWABO RAYON CO., LTD.,

Rayon fiber (2) (fineness 2.2dtex (fiber diameter 14㎛), fiber length 5mm, product name: Rayon Corona SB, manufacturer: DAIWABO RAYON CO., LTD.),

Rayon fiber (3) (fineness 9.0dtex (fiber diameter 28㎛), fiber length 8mm, product name: Rayon Corona CD, manufacturer: DAIWABO RAYON CO., LTD.),

Marcelized pulp fiber (average fiber diameter 34㎛, average fiber length 2.8㎜), product name: Porocenia, manufacturer: Rayonier Inc.),

Cotton linter fiber (average fiber diameter 18㎛, average fiber length 2㎜, product name: PS711, manufacturer: Shandong Silver Hawk Chemical Fiber Co.),

Polylactic acid single fiber (fineness 1.7dtex (fiber diameter 13㎛), fiber length 5mm, melting point 170℃, product name: TERRAMAC PL01, manufacturer: UNITIKA LTD.),

Or polylactic acid core sheath fiber (fineness 2.2 dtex (fiber diameter 15㎛), fiber length 5 mm, core melting point 170℃, sheath melting point 130℃, product name: TERRAMAC PL80, manufacturer: UNITIKA LTD.),

Which of the

It was mixed in the mixing ratio shown in Tables 1 to 3, tap water was added so that the slurry concentration was 0.5% by mass, and pulp was used to obtain a fiber slurry. Next, the fiber slurry weighed to have the basis weight shown in Tables 1 to 3 was papered using a water wetting device to obtain a wet sheet. However, in Comparative Example 3, a wet sheet was produced without using fibrillated lyocell fibers.

Next, the obtained wet sheet was impregnated with a water-diluted solution of a water repellent containing acrylic polymer as a main component (product name: UNIDYNE It was applied by treatment and dried in a rotary dryer at 130°C to obtain filter media for air filters of Examples and Comparative Examples. However, in Comparative Example 6, impregnation treatment with a water repellent was not performed. Additionally, the impregnation treatment in Example 17 was performed by the following method.

In Example 17, a water repellent containing acrylic polymer as a main ingredient (product name: UNIDYNE Co. Ltd.) was subjected to an impregnation treatment so that the water repellent content in the filter medium was 0.3% by mass in solids and the surfactant content was 0.2% by mass in solids, dried in a rotary dryer at 130°C, and dried with air. A filter material for a filter was obtained.

[Table 1]

[Table 2]

[Table 3]

The filter media for air filters obtained in the examples and comparative examples were evaluated using the method shown below.

(1) Basis weight [g/㎡]

Measured according to JIS P 8124:2011.

(2) Thickness [㎜]

Measured according to JIS P 8118;1998. Additionally, the measurement pressure was set to 50 kPa.

(3) Density [g/㎤]

Measured according to JIS P 8118;1998.

(4) Pressure loss [Pa]

The differential pressure when the filter medium for an air filter with an effective area of 0.01 m2 was ventilated at a surface wind speed of 5.3 cm/sec was measured using a differential pressure gauge.

(5) Transmittance and collection efficiency [%]

When air containing polydisperse polyalphaolefin (hereinafter abbreviated as PAO) particles generated by a laskin nozzle is ventilated through an air filter filter medium with an effective area of 0.01 m2 at a cotton wind speed of 5.3 cm/sec. The number of PAO particles upstream and downstream of the filter medium was measured using a laser particle counter KC-22B (manufactured by RION CO., LTD.), and the transmittance was calculated from the formula of downstream number/upstream number × 100. . Additionally, the collection efficiency was calculated from the equation of 100 - transmittance. Additionally, the target particle diameter was set to 0.3 μm.

(6) PF value

The PF value was obtained from the measured values of pressure loss and transmittance using the equation (Equation 1). A higher PF value means that the filter medium has high collection efficiency (i.e. low transmittance) with low pressure loss.

[Number 1]

Here, transmittance [%] = 100 - collection efficiency [%]

(7) Water repellency

Measured according to MIL-STD-282.

(8) Tensile strength

Measurements were made according to JIS P 8113-2006 “Paper and Cardboard - Test Method for Tensile Properties - Part 2: Constant Velocity Stretching Method.”

(9) Gurley robber

It was measured according to JAPAN TAPPI pulp test method No. 40:2000.

(10) Biodegradability

The filter medium sample is buried in the soil for 6 months, and then the shape of the filter medium is checked. Those that did not maintain their shape after 6 months were rated as ○, and those with almost no change in shape were rated as ×.

(11) Thermoformability

A thermoforming mold having irregularities with a depth of 3 mm on the top and bottom is heated to 200°C, a filter material is placed between them, and thermoforming is performed by pressing at a pressure of 1 kgf/cm2 for 5 seconds, and the molding depth and tear of the molded filter material are measured. evaluated. Those with a molding depth of 2 mm or more and no tearing were rated as ○, and those with an embossing depth of less than 2 mm or with tearing were rated as ×.

In addition, evaluation of thermoformability was performed only in Examples 2 and 14 to 16.

Tables 1 and 2 show the results showing the influence of the blending amount of refined fiber and the type of unrefined fiber by keeping the basis weight constant, and also show the results in the case of not containing a water repellent and the case of containing a surfactant. there is. From these results, in Comparative Examples 1 and 4 where the blending amount of purified fiber was more than 20 parts, the PF value was low, less than 5. In Comparative Examples 2, 3, and 5 in which the blending amount of purified fiber was less than 3 parts, the tensile strength was low, less than 0.4 kN/m. In Examples 14 to 16, in which polylactic acid fibers were blended as unrefined fibers, tensile strength was high and thermoformability was imparted. In Comparative Example 6 containing no water repellent, water repellency was not developed. In Example 17, which contained a surfactant, the PF value was higher than that in Example 2, which did not contain a surfactant.

Table 3 shows the results showing the effect of basis weight when the ratio of fibers was adjusted so that the maximum value of pressure loss was 40 Pa. Examples 18 to 28 are examples in which the basis weight was adjusted in the range of 25 to 350 g/m 2 , and all of them provided filter media for air filters that were biodegradable and had good PF values and water repellency.

The filter material for air filters of the present invention can be used as a filter material for air filters used in various fields such as factory and building air conditioning, automobile cabins, air conditioners, air purifiers, and personal protective equipment.

Claims (8)

The fibers constituting the filter medium include refined fibers and unrefined fibers,
The purified fiber is fibrillated lyocell fiber,
The unrefined fiber is a biodegradable fiber,
The mass ratio of the refined fiber and the unrefined fiber (refined fiber/unrefined fiber) is in the range of 3/97 to 20/80, and
The filter medium for an air filter is characterized in that it contains a water repellent agent mainly composed of a hydrocarbon polymer that does not contain fluorine in its molecule. According to paragraph 1,
A filter medium for an air filter, wherein the biodegradable fiber, which is the unrefined fiber, is at least one selected from the group consisting of regenerated cellulose fiber, natural cellulose fiber, and polylactic acid fiber. According to claim 1 or 2,
A filter medium for an air filter, characterized in that the hydrocarbon-based polymer, which is the main component of the water repellent, is an acrylic polymer. According to any one of claims 1 to 4,
A filter medium for an air filter, characterized in that the filter medium contains a surfactant. According to paragraph 4,
A filter medium for an air filter, characterized in that the surfactant is a quaternary ammonium salt. According to any one of claims 1 to 5,
A filter material for air filters, characterized in that the water repellency specified in MIL-STD-282 is 100 mm water column height or more. According to any one of claims 1 to 6,
The fibrillated Lyocell fiber, which is the purified fiber, is a filter material for an air filter, characterized in that the average fiber diameter is 0.3 ㎛ or more, the maximum fiber diameter is 8 ㎛ or less, and the length-weighted average fiber length is 1 mm or more. According to any one of claims 1 to 7,
The biodegradable fiber, which is the unrefined fiber, is a filter medium for an air filter, characterized in that the fiber diameter is 5 μm or more.