JP2022155561A - Water purification filter - Google Patents

Abstract

To provide a water purification filter that can have the ability to filter both of bound residual chlorine and free residual chlorine.SOLUTION: A water purification filter containing an activated carbon layer, wherein the specific surface area of the activated carbon layer is 1600 to 1900 m2/g, and the amount of acidic functional groups is 0.8 to 3.0 mmol/g as measured by the method of the following: (Method of measuring the amount of acidic functional groups) A part of the activated carbon layer is shaved off, the shaved material is finely pulverized and classified until the particle size distribution is reduced to 2 mm or less, and 1.0 g is collected and used as a sample for the measurement. The sample is added to 50 mL of 0.1 mol/L sodium hydroxide alkaline solution, shaken for 30 minutes, and then allowed to stand at 25°C for 24 hours. The filtrate is then filtered through glass fiber filter paper, and 10 mL of the resulting filtrate is subjected to neutralization titration with a 0.1 mol/L hydrochloric acid solution to determine the amount of acidic functional groups (mmol/g).SELECTED DRAWING: Figure 1

Description

The present invention relates to water purification filters.

Sodium hypochlorite is mainly used for disinfection of tap water, and hypochlorous acid and hypochlorite ions generated when sodium hypochlorite dissolves in water are called free residual chlorine. Free residual chlorine has a bactericidal or disinfecting effect. However, combined residual chlorine such as chloramine is generated from reactions between ammonia and nitrogen oxides present in natural water and added hypochlorous acid and hypochlorite ions. Combined residual chlorine and free residual chlorine are called residual chlorine. Odor often becomes a problem depending on the condition of raw water taken, the amount of free residual chlorine added, and the amount of chloramine.

A water purifier is used for the purpose of removing residual chlorine from drinking water such as tap water. Such a water purifier has a structure including an adsorption member made of an inorganic material such as activated carbon or ceramic, and an organic polymer membrane for filtration, if necessary. In recent years, along with the demand for higher performance of water purifiers and air purifiers, activated carbon is often used in these filters and the like.

For example, an activated carbon adsorbent, a fibrillated fiber binder, and calcium sulfite are mixed in water to form a mixed slurry. and a residual chlorine removal filter body for removing residual chlorine in water obtained by heating and drying the adsorption deposit, wherein the activated carbon adsorbent is made of either one or both of granular activated carbon and fibrous activated carbon, and the activated carbon With 100 parts by weight of the adsorbent as the adsorbent, 7 to 22 parts by weight of the fibrillated fiber binder and 10 to 100 parts by weight of the calcium sulfite are blended based on the weight of the activated carbon adsorbent. (See Patent Document 1, for example). According to this filter body, it has good water permeability and is said to be able to maintain a high level of performance for removing residual chlorine containing both free residual chlorine and combined residual chlorine.

JP 2020-179374 A

In the filter of the example of Patent Document 1, drinking water with a combined residual chlorine concentration of 0.2 ppm (mg / L) was set at a water temperature of 20 ° C. and a water flow rate of 2.5 L / min, and an SV value of 500 hr. The amount of ^filtered water with combined residual chlorine measured was 1.1 m ³ at most, indicating that the ability to filter out combined residual chlorine was insufficient.

Accordingly, the main object of the present invention is to provide a water purifying filter that solves the above problems and is capable of filtering both combined residual chlorine and free residual chlorine.

In order to solve the above problems, the present inventors studied using activated carbon with a high amount of acidic functional groups. However, as a result of investigations by the present inventors, it has been found that even though the ability to filter bound residual chlorine can be improved simply by using activated carbon with a high amount of acidic functional groups, the ability to filter free residual chlorine can be improved. it was difficult to

Here, the inventors of the present invention have investigated the cause of the difficulty in improving the ability to filter free residual chlorine. The following oxidation-reduction reaction can be considered as a mechanism of filtration of free residual chlorine by activated carbon.
HClO (free residual chlorine) + C (activated carbon) → CO + HCl

That is, C (activated carbon) acts as a reducing agent and decomposes free residual chlorine. Activated carbon having a high amount of acidic functional groups includes activated carbon in which acidic functional groups such as cyclic and chain carboxyl groups, lactone groups, phenol groups, hydroxyl groups, ketone groups and sulfone groups are introduced into carbon atoms. Then, on the surface of the activated carbon introduced with the acidic functional group, the portion that acts as a reducing agent is reduced, so it was thought that the oxidation-reduction reaction would be less likely to proceed compared to the activated carbon not introduced with the acidic functional group. That is, it is considered that the oxidation-reduction reaction is inhibited as the amount of acidic functional groups of activated carbon increases and as the acidity of the acidic functional groups increases.

Therefore, as a result of further studies by the present inventors, for example, activated carbon with a high amount of acidic functional groups and activated carbon with a low amount of acidic functional groups and a specific surface area within a certain range are used in combination, and their average particle diameter and the mixing ratio is adjusted so that the amount of acidic functional groups in the water purification filter is 0.8 to 3.0 mmol/g, and the specific surface area of the water purification filter is 1600 to 1900 m ² /g to form the activated carbon layer. I found that the problem can be solved. The present invention is an invention that has been completed through intensive studies based on such findings.

That is, the present invention provides inventions in the following aspects.
Section 1. A water purification filter including an activated carbon layer, wherein the activated carbon layer has a specific surface area of 1600 to 1900 m ² /g, and the amount of acidic functional groups of the activated carbon layer measured by the following measuring method is 0.8 to 3.0 mmol/ g, a water purification filter.
(Method for measuring the amount of acidic functional groups)
A part of the activated carbon layer is cut out with a cutter knife, and the cut-out part is finely pulverized and classified until the particle size distribution becomes 2 mm or less, and 1.0 g is taken as a sample for measurement. A measurement sample is added to 50 mL of a 0.1 mol/L sodium hydroxide solution as an alkaline solution, shaken for 30 minutes, and then allowed to stand at 25° C. for 24 hours. Thereafter, filtration is performed using glass fiber filter paper (GF/C manufactured by Whatman), 10 mL of the obtained filtrate is subjected to neutralization titration with 0.1 mol / L hydrochloric acid solution, and the amount of acidic functional groups (mmol / g) is determined. Ask.
Section 2. A cylindrical core and a cover layer included on the outer peripheral side of the activated carbon layer, wherein the activated carbon layer is included on the outer peripheral side of the core, and the ratio of the thickness of the activated carbon layer to the thickness of the water purification filter (thickness of activated carbon layer/thickness of water purification filter) is 0.7 to 0.9,
Item 2. The water purifying filter according to item 1, wherein the water purifying filter has a pressure loss A of 0.010 to 0.040 MPa measured by the following measuring method.
(Method for measuring pressure loss A)
After sealing both end faces of the water purification filter by adhering foamed polyethylene caps using hot melt or silicone sealant, the resin housing is filled, and pure water is added so that the superficial velocity (SV) becomes 2781 / h. After holding the flow rate for 10 minutes, the pressure loss X1 (MPa) is measured with a Bourdon tube pressure gauge. Similarly, the pressure loss X2 (MPa) in a blank from which the water purification filter is previously removed is measured. The value obtained by subtracting the pressure loss X2 from the pressure loss X1 is defined as the water flow pressure loss A (MPa) of the water purification filter.
Item 3. Item 1, wherein the water purification filter has a combined residual chlorine filtered water amount measured by the following measuring method of 20 to 100 m ³ and a free residual chlorine filtered water amount measured by the following measuring method of the water purifying filter is 40 to 140 m ³ . Or the water purification filter according to 2.
(Method for measuring combined residual chlorine filtered water volume)
Both end faces of the water purification filter are sealed by adhering foamed polyethylene caps using hot-melt or silicone sealant, and then filled into a stainless steel housing. Based on the provisions of Article 4 of the Water Supply Law of Japan, ammonium chloride and Sodium chlorite is added and mixed with stirring to prepare raw water so that the concentration of combined residual chlorine is 0.5 mg/L. Adjusted raw water is passed from the outside to the inside of the water purification filter at a flow rate of 2.0 L/min so that the superficial velocity (SV) is 370/h. Quantitatively measure the concentration of combined residual chlorine before and after passing through the water filter using the DPD reagent absorption photometry method, and the concentration of combined residual chlorine in the effluent (filter-passing liquid) relative to the influent (adjusted raw water) becomes 20% or more at the initial stage. The point is defined as the breakthrough point, and the total filtered water volume (m ³ ) up to the breakthrough point is determined.
(Method for measuring amount of free residual chlorine filtered water)
Both end faces of the water purification filter are sealed by adhering foamed polyethylene caps using hot-melt or silicone sealant, and then filled into a stainless steel housing. Based on the provisions of Article 4 of the Water Supply Law of Japan, the free residual chlorine concentration is Sodium hypochlorite is added so that the concentration is 2.0±0.2 mg/L, and the raw water is prepared as adjusted raw water. Adjusted raw water is passed from the outside to the inside of the water purification filter so that the superficial velocity (SV) becomes 741/h. Quantitatively measure the concentration of free residual chlorine before and after passing through the water purification filter using the DPD reagent absorption photometry method, and the concentration of free residual chlorine in the effluent (filter-passing liquid) relative to the influent (adjusted raw water) becomes 20% or more at the initial stage. The point is defined as the breakthrough point, and the total filtered water volume (m ³ ) up to the breakthrough point is determined.

According to the water purification filter of the present invention, it is possible to achieve both filtering capacity for combined residual chlorine and free residual chlorine.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram explaining an example of the manufacturing apparatus by a slurry suction method of the water-purifying filter of this invention.

<Configuration of the water purification filter of the present invention>
The water purification filter of the present invention includes an activated carbon layer, the specific surface area of the activated carbon layer is 1600 to 1900 m ² /g, and the amount of acidic functional groups of the activated carbon layer measured by the following measuring method is 0. .8 to 3.0 mmol/g.

(Method for measuring the amount of acidic functional groups)
A part of the activated carbon layer is cut out with a cutter knife, and the cut-out part is finely pulverized and classified until the particle size distribution becomes 2 mm or less, and 1.0 g is taken as a sample for measurement. A measurement sample is added to 50 mL of a 0.1 mol/L sodium hydroxide solution as an alkaline solution, shaken for 30 minutes, and then allowed to stand at 25° C. for 24 hours. Thereafter, filtration is performed using glass fiber filter paper (GF/C manufactured by Whatman), 10 mL of the obtained filtrate is subjected to neutralization titration with 0.1 mol / L hydrochloric acid solution, and the amount of acidic functional groups (mmol / g) is determined. Ask.

A preferable configuration of the water purification filter of the present invention includes a cylindrical core and a cover layer included on the outer peripheral side of the activated carbon layer, and the activated carbon layer is included on the outer peripheral side of the core. In this case, the activated carbon layer is preferably cylindrical.

Hereinafter, each member constituting the water purification filter of the present invention will be described in detail.

1. Activated carbon layer The water purification filter of the present invention includes an activated carbon layer.

In the water purification filter of the present invention, the activated carbon layer has a specific surface area of 1600-1900 m ² /g. The specific surface area means that the activated carbon layer contains a large number of carbon atoms. In addition, the range of the specific surface area and the specific range of the amount of the acidic functional group described later means that the carbon atoms to which the acidic functional group has been introduced and the carbon atoms to which the acidic functional group has not been introduced are added to the activated carbon layer. Atoms are present in specific amounts, respectively, so that the obtained water purification filter has excellent combined residual chlorine filtering capacity and free residual chlorine filtering capacity. The range of the specific surface area and the specific range of the amount of acidic functional groups described later can be achieved by, for example, using activated carbon with a high amount of acidic functional groups (for example, 2 mmol / g or more) and the amount of acidic functional groups, which will be described later. It can be realized by using together with activated carbon having a low molecular weight (for example, 0.2 mmol/g or less) and adjusting their compounding ratio. The specific surface area is preferably 1,700 to 1,900 m ² /g from the viewpoint of improving the ability to filter combined residual chlorine.

In the present invention, the specific surface area of the activated carbon layer is calculated based on the nitrogen adsorption isotherm at 77.4K. Specifically, first, the sample (activated carbon layer) was cooled to 77.4 K (the boiling point of nitrogen) using an automatic gas adsorption amount measuring device (trade name “AUTOSORB-1-MP” manufactured by QUANTCHROME). A gas is introduced and the adsorption amount V [cc/g] of nitrogen gas is measured by the volumetric method. At this time, the pressure P [hPa] of the nitrogen gas to be introduced is gradually increased, and the value obtained by dividing by the saturated vapor pressure P0 [hPa] of the nitrogen gas is taken as the relative pressure P/P0, and the adsorption amount is plotted against each relative pressure. Create a nitrogen adsorption isotherm by Using the analysis program attached to the above apparatus, the specific surface area is determined according to the BET method based on the obtained nitrogen adsorption isotherm. As for the above sample, sampling is performed so that the mass becomes 0.1 g.

In the water purification filter of the present invention, the activated carbon layer has an amount of acidic functional groups of 0.8 to 3.0 mmol/g as measured by the following measuring method.
(Method for measuring the amount of acidic functional groups)
A part of the activated carbon layer is cut out with a cutter knife, and the cut-out part is finely pulverized and classified until the particle size distribution becomes 2 mm or less, and 1.0 g is taken as a sample for measurement. A measurement sample is added to 50 mL of a 0.1 mol/L sodium hydroxide solution as an alkaline solution, shaken for 30 minutes, and then allowed to stand at 25° C. for 24 hours. Thereafter, filtration is performed using glass fiber filter paper (GF/C manufactured by Whatman), 10 mL of the obtained filtrate is subjected to neutralization titration with 0.1 mol / L hydrochloric acid solution, and the amount of acidic functional groups (mmol / g) is determined. Ask.

The particle size distribution of the pulverized and classified activated carbon layer was measured using a laser diffraction/scattering particle size distribution analyzer (trade name LA-920 manufactured by Horiba, Ltd.), based on the volume of granular activated carbon. is the particle size distribution of

As described above, the range of the specific surface area and the specific range of the amount of the acidic functional group described later means that the activated carbon layer contains carbon atoms into which the acidic functional group is introduced, and carbon atoms into which the acidic functional group is introduced. It means that the carbon atoms that are not present are present in specific amounts, respectively, and as a result, the resulting water purification filter is said to have excellent combined residual chlorine filtering capacity and free residual chlorine filtering capacity. Become. The range of the specific surface area and the specific range of the amount of acidic functional groups described later can be achieved by, for example, using activated carbon with a high amount of acidic functional groups (for example, 2 mmol / g or more) and the amount of acidic functional groups, which will be described later. It can be realized by using together with activated carbon having a low molecular weight (for example, 0.5 mmol/g or less) and adjusting their compounding ratio. The amount of acidic functional groups is preferably 1.5 to 3.0 mmol/g from the viewpoint of improving the ability to filter combined residual chlorine.

The acidic functional groups provided in the activated carbon layer of the present invention are not particularly limited, and examples thereof include cyclic and chain carboxyl groups, lactone groups, phenol groups, hydroxyl groups, ketone groups, and sulfone groups.

The apparent density of the activated carbon layer is, for example, 0.25 to 0.5 g/cm ³ , preferably 0.3 to 0.45 g/cm ³ . When the activated carbon layer has a cylindrical shape, the thickness of the activated carbon layer is, for example, 5 to 30 mm, preferably 10 to 25 mm.

<Examples of preferred raw materials for composing the activated carbon layer>
(1) Activated carbon with a high amount of acidic functional groups In the water purification filter of the present invention, the activated carbon layer may contain activated carbon with a high amount of acidic functional groups, specifically activated carbon with an amount of acidic functional groups of 2 mmol/g or more, as a raw material. preferable. This makes it easier to adjust the amount of acidic functional groups in the activated carbon layer to 0.8 to 3.0 mmol/g. The amount of the acidic functional group is more preferably 2 to 4 mmol/g, still more preferably 2.5 to 3.5 mmol/g.

In the present invention, the amount of acidic functional groups in activated carbon is measured as follows.
(Measuring method)
1.0 g of activated carbon is sampled and used as a sample for measurement. A measurement sample is added to 50 mL of a 0.1 mol/L sodium hydroxide solution as an alkaline solution, shaken for 30 minutes, and then allowed to stand at 25° C. for 24 hours. Thereafter, filtration is performed using glass fiber filter paper (GF/C manufactured by Whatman), 10 mL of the obtained filtrate is subjected to neutralization titration with 0.1 mol / L hydrochloric acid solution, and the amount of acidic functional groups (mmol / g) is determined. Ask.

Further, the specific surface area of activated carbon having a high amount of acidic functional groups is preferably 1800 to 2500 m ² /g, more preferably 2000 to 2300 m ² /g. As a result, more carbon atoms to which an acidic functional group has been introduced can be present on the surface, making it easier to improve the combined residual chlorine filtering ability of the water purification filter. The method for measuring the specific surface area of activated carbon is the same as that for the water purification filter.

The activated carbon having a high amount of acidic functional groups is preferably granular activated carbon, and the average particle size is preferably 150 to 200 μm, more preferably 160 to 200 μm. By setting it as such an average particle diameter, it becomes easy to make the water-purifying filter obtained the range of the pressure loss mentioned later. The average particle size of the granular activated carbon is measured using a laser diffraction/scattering particle size distribution analyzer (trade name LA-920 manufactured by Horiba, Ltd.), and the cumulative volume value in the particle size distribution of the granular activated carbon is It refers to the particle size that becomes 50%.

In the activated carbon layer contained in the water purification filter of the present invention, the content of activated carbon with a high amount of acidic functional groups is 20 to 90% by mass, and the filtering ability of the water purification filter for combined residual chlorine and free residual chlorine is further enhanced. 45 to 90% by mass is preferable from the viewpoint of making it easier to achieve both.

(2) Activated carbon with a low amount of acidic functional groups In the water purification filter of the present invention, the activated carbon layer contains activated carbon with a low amount of acidic functional groups, specifically activated carbon with an amount of acidic functional groups of 0.5 mmol/g or less, as a raw material. is preferred. This makes it easier to adjust the amount of acidic functional groups in the activated carbon layer to 0.8 to 3.0 mmol/g. The amount of acidic functional groups is more preferably 0.3 mmol/g or less, even more preferably 0.2 mmol/g or less.

The specific surface area of activated carbon having a low amount of acidic functional groups is preferably 1400 to 2000 m ² /g, more preferably 1500 to 1900 m ² /g. As a result, more carbon atoms to which no acidic functional group has been introduced can be present on the surface, and the ability of the water purification filter to filter free residual chlorine can be easily improved.

Further, the activated carbon having a low amount of acidic functional groups is preferably granular activated carbon, and the average particle size is preferably 120 μm to 300 μm, more preferably 130 to 280 μm. By setting it as such an average particle diameter, it becomes easy to make the water-purifying filter obtained the range of the pressure loss mentioned later. In addition, from the viewpoint of making the water purification filter to be obtained more easily in the range of pressure loss described later, the activated carbon with a low amount of acidic functional groups has an average particle size of 130 to 170 μm and an activated carbon with an average particle size of 200 to 300 μm. It is more preferable to use a certain activated carbon together.

In the activated carbon layer contained in the water purification filter of the present invention, the content of activated carbon with a low amount of acidic functional groups is 5 to 70% by mass, and the filtering ability of the water purification filter for combined residual chlorine and free residual chlorine is further enhanced. From the viewpoint of making it easier to achieve both, 5 to 50% by mass is preferable.

(3) Other components The activated carbon layer contained in the water purification filter of the present invention can contain other components as raw materials other than the above-described activated carbon with a high amount of acidic functional groups and activated carbon with a low amount of acidic functional groups. The other component includes binder fibers. The binder fiber is integrated with the granular activated carbon to form a cylindrical shape by entangling the granular activated carbon. Granular activated carbon may be fused to binder fibers in the activated carbon layer contained in the water purification filter of the present invention. As binder fibers, known fibrillated binder fibers used for activated carbon layers can be used. Specific examples of such fibrillated binder fibers include acrylic fibers, acrylic fibers, polyethylene fibers, cellulose fibers, and aramid fibers. Binder fibers may be used singly or in combination of two or more.

In the activated carbon layer contained in the water purification filter of the present invention, the binder fiber content is, for example, about 2 to 7% by mass, preferably about 3 to 5% by mass.

2. Core The water purification filter of the present invention may include a cylindrical core. The core has pores through which the water to be purified can pass, and serves as a core member to increase the strength of the water purification filter and to reduce the shedding of coal dust from the activated carbon layer.

Known materials can be used for the core, and examples thereof include porous ceramics, porous metal filters, and non-woven fabrics. Alternatively, a cylindrical member having pores may be molded from resin, metal, or the like, and used as the core. Among them, nonwoven fabrics are preferred, and those obtained by compression-molding nonwoven fabrics are more preferred. Moreover, the fiber material that constitutes the nonwoven fabric is not particularly limited, but preferably includes polyester fiber.

The basis weight of the nonwoven fabric for molding the core is, for example, 30 to 100 g/m ² , preferably 50 to 90 g/m ² . The thickness of the core is, for example, 1 to 5 mm, more preferably 2 to 4 mm. The apparent density of the core is 0.2 to 0.6 g/cm ³ , preferably 0.25 to 0.35 g/cm ³ .

3. Cover Layer The water purification filter of the present invention may include a cover layer on the outer peripheral side of the activated carbon layer. The cover layer has pores through which the water to be purified can pass, and plays a role in reducing falling-off of coal dust from the activated carbon layer.

The cover layer is not particularly limited, but fabrics such as woven fabrics, knitted fabrics, and nonwoven fabrics are preferred, and nonwoven fabrics are preferred. Among them, a nonwoven fabric made of long fibers or continuous fibers is preferable from the viewpoint of relatively high tear strength and excellent handleability and workability.

The nonwoven fabric made of long fibers or continuous fibers is not particularly limited, but a spunbond nonwoven fabric is preferred. As the long fibers or continuous fibers constituting the spunbond nonwoven fabric, the heat-fusible component in the sheath and the synthetic resin in the core whose melting point is preferably 20°C or more, more preferably 30°C or more higher than the melting point of the sheath A core-sheath type heat-fusible fiber in which components are arranged is exemplified. As the core of the core-sheath type heat-fusible fiber, for example, a synthetic resin component having a melting point of 150 to 300° C., more preferably 200 to 300° C., and a melting point higher than that of the sheath by 20° C. or more. and more specifically polyethylene terephthalate. The sheath portion of the core-sheath type heat-fusible fiber preferably has a melting point of 80 to 170°C, more preferably 80 to 140°C. Olefin-based resins or polyester-based resins such as copolymerized polyethylene terephthalate obtained by copolymerizing copolymer components such as isophthalic acid can be used. Among them, polyolefin-based resins are preferable, and polyethylene is more preferable, from the viewpoints of superior flexibility and heat-sealability to the activated carbon molded body, and superior handleability and workability.

The basis weight of the cover layer is, for example, 20 to 100 g/m ² , preferably 40 to 60 g/m ² . The thickness of the cover layer is, for example, 0.03 to 1.0 mm, preferably 0.05 to 0.6 mm. The apparent density of the cover layer is 0.05 to 0.5 g/cm ³ , preferably 0.08 to 0.4 g/cm ³ .

4. Water Purification Filter The water purification filter of the present invention can include a cylindrical core, an activated carbon layer included on the outer peripheral side of the core, and a cover layer included on the outer peripheral side of the activated carbon layer. The ratio of the thickness of the activated carbon layer to the thickness of the water purification filter (thickness of activated carbon layer/thickness of water purification filter) is preferably 0.7 to 0.9.

The water purification filter of the present invention preferably has a pressure loss A of 0.010 to 0.040 MPa as measured by the following measuring method.
(Method for measuring pressure loss)
(Method for measuring pressure loss A)
After sealing both end faces of the water purification filter by adhering foamed polyethylene caps using hot melt or silicone sealant, the resin housing is filled, and pure water is added so that the superficial velocity (SV) becomes 2781 / h. After holding the flow rate for 10 minutes, the pressure loss X1 (MPa) is measured with a Bourdon tube pressure gauge. Similarly, the pressure loss X2 (MPa) in a blank from which the water purification filter is previously removed is measured. The value obtained by subtracting the pressure loss X2 from the pressure loss X1 is defined as the water flow pressure loss A (MPa) of the water purification filter.

The pressure drop A is the average particle size of activated carbon with a high amount of acidic functional groups (e.g., 2 mmol/g or more) and the average particle size of activated carbon with a low amount of acidic functional groups (e.g., 0.2 mmol/g or less). and are within specific ranges, which makes it easier for the obtained water purification filter to have more excellent combined residual chlorine filtering capacity and free residual chlorine filtering capacity. That is, by setting the pressure loss A within the above range, the activated carbon layer has an appropriate density, and a flow path that exhibits the combined residual chlorine filtration ability and the free residual chlorine filtration ability is maintained in the activated carbon layer. The residual chlorine filtration ability and the free residual chlorine filtration ability become more excellent. The pressure loss A is preferably 0.015 to 0.028 MPa from the viewpoint of further improving the combined residual chlorine filtering ability.

The water purification filter of the present invention preferably has a pressure loss B of 0.010 to 0.030 MPa, more preferably 0.010 to 0.018 MPa, as measured by the following measuring method.
(Method for measuring pressure loss B)
After sealing both end faces of the water purification filter by adhering foamed polyethylene caps using hot melt or silicone sealant, the resin housing is filled, and pure water is added so that the superficial velocity (SV) becomes 1854 / h. After maintaining the flow rate for 10 minutes, the pressure loss Y1 (MPa) is measured with a Bourdon tube pressure gauge. Similarly, the pressure loss Y2 (MPa) is measured in a blank from which the water purification filter has been previously removed. The value obtained by subtracting the pressure loss Y2 from the pressure loss Y1 is defined as the water flow pressure loss B (MPa) of the water purification filter.

The water purification filter of the present invention preferably has a combined residual chlorine filtered water amount of 20 to 100 m ³ measured by the following measuring method, and a free residual chlorine filtered water amount of 40 to 140 m ³ measured by the following measuring method. is preferred.

(Method for measuring combined residual chlorine filtered water volume)
Both end faces of the water purification filter are sealed by adhering foamed polyethylene caps using hot-melt or silicone sealant, and then filled into a stainless steel housing. Based on the provisions of Article 4 of the Water Supply Law of Japan, ammonium chloride and Sodium chlorite is added and mixed with stirring to prepare raw water so that the concentration of combined residual chlorine is 0.5 mg/L. Adjusted raw water is passed from the outside to the inside of the water purification filter at a flow rate of 2.0 L/min so that the superficial velocity (SV) is 370/h. Quantitatively measure the concentration of combined residual chlorine before and after passing through the water filter using the DPD reagent absorption photometry method, and the concentration of combined residual chlorine in the effluent (filter-passing liquid) relative to the influent (adjusted raw water) becomes 20% or more at the initial stage. The point is defined as the breakthrough point, and the total filtered water volume (m ³ ) up to the breakthrough point is determined.

(Method for measuring amount of free residual chlorine filtered water)
Both end faces of the water purification filter are sealed by adhering foamed polyethylene caps using hot-melt or silicone sealant, and then filled into a stainless steel housing. Separately, based on the provisions of Article 4 of the Water Supply Law of Japan, free residue is added to tap water that meets the water quality standards stipulated in the "Ministerial Ordinance on Water Quality Standards (Ministry of Health, Labor and Welfare Ordinance No. 101, May 30, 2003)". Adjusted raw water is prepared by adding sodium hypochlorite so that the chlorine concentration becomes 2.0±0.2 mg/L. Adjusted raw water is passed from the outside to the inside of the water purification filter so that the superficial velocity (SV) becomes 741/h. Quantitatively measure the concentration of free residual chlorine before and after passing through the water purification filter using the DPD reagent absorption photometry method, and the concentration of free residual chlorine in the effluent (filter-passing liquid) relative to the influent (adjusted raw water) becomes 20% or more at the initial stage. The point is defined as the breakthrough point, and the total filtered water volume (m ³ ) up to the breakthrough point is determined.

As described above, activated carbon having a high amount of acidic functional groups and activated carbon having a low amount of acidic functional groups and having a specific surface area within a certain range are used in combination, and the blending ratio thereof is adjusted so that the amount of acidic functional groups in the activated carbon layer is 0.8 to 3.0 mmol/g, the specific surface area of the activated carbon layer is adjusted to 1600 to 1900 m ² /g, or the average particle size thereof is adjusted to the pressure loss A and / or pressure loss B range described above. By adjusting so as to be, it is possible to achieve both the combined residual chlorine and free residual chlorine filtered water amounts as described above. From the viewpoint of further securing both combined residual chlorine and free residual chlorine filtration capabilities, the combined residual chlorine filtered water amount and the free residual chlorine filtered water amount are preferably 50 to 100 m ³ .

The height (length from one bottom surface to the other bottom surface) of the water purification filter of the present invention may be appropriately set according to the type of water purifier used, and is, for example, 10 to 300 mm.

The thickness of the water purification filter of the present invention may be appropriately set according to the type of water purifier to be used. mentioned. In the present invention, the thickness of the cylindrical water purification filter is the value obtained by subtracting the inner diameter from the outer diameter. In addition, the inner diameter is the diameter of the space that communicates from the center of one bottom surface to the center of the other bottom surface in a cross section perpendicular to the height direction of the water purification filter. In addition, the outer diameter is the diameter of the water purification filter including the space in a cross section perpendicular to the height direction of the water purification filter.

When the water purification filter of the present invention is cylindrical, its inner and outer diameters may be appropriately set so as to satisfy the thickness described above. Specifically, the inner diameter is 5 mm or more and the outer diameter is 15 to 150 mm can be mentioned.

<Manufacturing method of water purification filter>
The method for producing the water purification filter of the present invention is not particularly limited, and includes, for example, the following methods.

First, the core and the above-mentioned preferred raw materials for forming the activated carbon layer are prepared, and an intermediate body in which the core and the activated carbon layer are integrated is manufactured by a slurry suction method. Specifically, the granular activated carbon having a high amount of acidic functional groups, the granular activated carbon having a low amount of acidic functional groups, and the binder fibers are mixed with water to obtain a slurry. Next, for example, using a double tubular container having an inner tube and an outer tube in which a large number of small holes are formed, a core is set on the outer peripheral side of the inner tube, and the slurry is placed between the core and the outer tube. A cylindrical compact is obtained by pouring and sucking the slurry from the center. By drying this molded product, the intermediate is obtained. The molded body may be subjected to heat treatment and compression treatment as necessary. The ratio of the powdery activated carbon and the binder fiber in the slurry can be set so as to be the above ratio in the water purification filter. In addition, in the slurry suction method, the shape of the water purification filter corresponds to the shape of the container into which the slurry is poured, so by changing the shape of the container, the shape of the water purification filter can be made into various shapes. . Then, a cover layer is wound around the outer peripheral side of the obtained intermediate to manufacture the water purification filter of the present invention.

Another specific example of the method for producing the intermediate in which the core and the activated carbon layer are integrated by the slurry suction method will be described. FIG. 1 is a schematic diagram illustrating an example of an apparatus for producing an intermediate body in which the core and the activated carbon layer are integrated by a slurry suction method. The manufacturing apparatus of FIG. 1 includes a cylindrical core body 62 having a large number of small suction holes 61 on its surface, and flanges arranged at both ends of the core body 62 and detachable from the core body. A mold 6, a suction tube 7 connected to the cylindrical interior of a core 62 so as to allow ventilation and liquid flow, and the granular activated carbon with a high amount of acidic functional groups, the granular activated carbon with a low amount of acidic functional groups, and the above A container 9 containing a slurry 8 obtained by mixing binder fibers with water is provided.

First, a uniform aqueous slurry is prepared containing granular activated carbon with a high amount of acidic functional groups, the aforementioned granular activated carbon with a low amount of acidic functional groups, and the aforementioned binder fibers in a predetermined ratio. The solid content concentration in the aqueous slurry is not particularly limited, but is preferably about 0.1 to 4% by mass from the viewpoint of ease of handling, ease of molding, and the like. When preparing the slurry, mechanical dispersion, stirring and beating can be performed using a beater or the like.

The resulting slurry 8 is placed in container 9 . Next, one flange of the molding die 6 is removed, the above-described cylindrical core is inserted into the core body 62 , the flange is attached again, and immersed in the slurry 8 . Then, by using a pump to reduce the pressure inside the core 62 through the suction pipe 7, the granular activated carbon having a high amount of acidic functional groups in the slurry, the granular activated carbon having a low amount of acidic functional groups, and the binder fibers are transferred to the core. It is deposited on the surface of the core inserted at 62 .

Then, the molding die 6 is pulled up from the slurry 8, and the intermediate body in which the core and the activated carbon layer are integrated is pulled out and dried. The drying temperature is, for example, about 80 to 150°C. Although not shown, during the suction of the slurry described above or after the mold 6 is lifted from the slurry 8, granular activated carbon with a high amount of acidic functional groups deposited on the mold 6, granular activated carbon with a low amount of acidic functional groups, etc. It is preferable to include the step of compressing the layer containing activated carbon and the binder fibers described above. The method of compression is not particularly limited, but for example, a rotating roller is pressed against the layer so that the activated carbon layer has a predetermined apparent density, and the mold 6 is also rotated around the long axis of the cylinder while the mold 6 is pressed. Compressing the activated carbon layer containing the granular activated carbon having a high amount of acidic functional groups deposited on the surface, the granular activated carbon having a low amount of acidic functional groups, and the binder fiber. Then, after drying, a cover layer is wound around the outer peripheral side of the obtained intermediate to manufacture the water purification filter of the present invention.

<Uses of water filters>
Applications of the water purification filter of the present invention include water purifiers that filter raw water such as tap water to make it drinking water, and water purifiers that filter raw water to obtain dialysis water for performing artificial dialysis.

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples. However, the invention is not limited to the examples.

<Example 1>
(1) Preparation of raw materials for activated carbon layer The following raw materials were prepared.
・Activated carbon with a high amount of acidic functional groups: Carbide made from phenolic resin and potassium hydroxide are mixed so that the mass ratio (potassium hydroxide/carbide) is 3, the mixture is placed in a furnace, and nitrogen is circulated ( 1 L/min), the temperature was raised to 800° C. at a rate of temperature rise of 10° C./min, and then held for 2 hours for alkali activation treatment. Next, it was boiled in a 5.25% by weight hydrochloric acid (HCl) aqueous solution and then filtered. The sample after filtration was washed with hot water at 60°C and vacuum filtered, repeatedly washed and dehydrated until the pH of the filtrate reached 6.5 or higher, and then dried at 115°C. After drying, the temperature was raised to 300° C. in an air atmosphere (heating rate: 10° C./min), and then held for 24 hours for oxidation treatment. After the oxidation treatment, it was pulverized with a ball mill and adjusted to have an average particle size of 180 μm. When the amount of acidic functional groups and the specific surface area of this activated carbon were measured, the amount of acidic functional groups was 2.73 mmol/g and the specific surface area was 2180 m ² /g.
- Activated carbon A with a low amount of acidic functional groups: Charcoal made from coconut shells is placed in a furnace and heated to 900°C (10°C/min). It was circulated in the furnace together (steam concentration 70 vol%) to perform steam activation. Next, it was pulverized with a ball mill and adjusted to have an average particle size of 250 μm. When the amount of acidic functional groups and the specific surface area of this activated carbon were measured, the amount of acidic functional groups was 0.13 mmol/g and the specific surface area was 1700 m ² /g.
- Activated carbon B with a low amount of acidic functional groups: Activated carbon A with a low amount of acidic functional groups was pulverized with a ball mill to prepare an average particle size of 150 µm to obtain activated carbon B with a low amount of acidic functional groups. When the amount of acidic functional groups and the specific surface area of this activated carbon were measured, the amount of acidic functional groups was 0.13 mmol/g and the specific surface area was 1700 m ² /g.
・ Binder fiber: Trade name Vipal (registered trademark) manufactured by Nihon Exlan Kogyo Co., Ltd., fibrillated acrylic fiber

(2) Production of water purification filter (2-1) Preparation of nonwoven fabric core Polyester fiber A (Tetron polyester staple (Safmet), manufactured by Toray Industries, Inc.) and polyester fiber B (Tetron polyester staple (SD), manufactured by Toray Industries, Inc.) and was carded to form a thin web, and the web was subjected to needle punching, heat treatment at a temperature of 163° C., and cooling to obtain a nonwoven fabric. This nonwoven fabric had a basis weight of 80 g/m ² , a thickness of 0.32 mm and an apparent density of 0.25 g/cm ³ . An iron cylindrical pipe with an outer diameter of 30.0 mm is prepared as a core, and the nonwoven fabric is wound around the core so that the core has an outer diameter of 37 mm, placed in a furnace, and heat-treated at an atmospheric temperature of 150 ° C. for 2 hours. After applying, it was naturally cooled. Then, after removing the core, it was cut into lengths of 124 mm and 248 mm with a cutting machine to obtain nonwoven fabric cores. The resulting nonwoven core had an inner diameter of 30.0 mm, an outer diameter of 37.0 mm, a thickness of 3.5 mm and an apparent density of 0.30 g/cm ³ .

(2-2) Production of water purification filter: activated carbon having a high amount of acidic functional groups, activated carbon A having a low amount of acidic functional groups, activated carbon B having a low amount of acidic functional groups, and binder fibers, so as to have the composition shown in Table 1; Mixed with water to obtain a slurry. The prepared 124 mm core was set on the core of the molding die, the slurry was sucked from the center, pulled out, and dried in a drying oven at 120 ° C. for 15 hours to obtain an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of An intermediate of 124 mm in which the core and the activated carbon layer were integrated was obtained. A nonwoven fabric (Elves S0503, manufactured by Unitika Ltd., a spunbond nonwoven fabric made of continuous fibers that are core-sheath type composite fibers with a core made of a polyester resin and a sheath made of a polyolefin resin) is used as a cover layer for this intermediate. , A nonwoven fabric in which stacked continuous fibers are partially pressed together by heat embossing to be integrated, and the nonwoven fabric has a basis weight of 50 g/m ² , a thickness of 0.34 mm, and an apparent density of 0.15 g/cm ³ . ) was wound to cover the outer layer, and the beginning and end of winding were thermally bonded with an iron heated to 150° C. to obtain a water purification filter 1A. In the same way, using a prepared core with a length of 248 mm, an intermediate having an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of 248 mm, in which the core and the activated carbon layer are integrated, is obtained. Elves S0503, manufactured by Unitika Ltd.) was wound to cover the outer layer, and the beginning and end of winding were thermally bonded with an iron heated to 150°C to obtain a water purification filter 1B. The volume of water purification filter 1A was 324 cm ³ and the volume of water purification filter 1B was 648 cm ³ . The water purification filters 1A and 1B have an outer diameter of 65 mm, an inner diameter of 30 mm, and a thickness of 17.5 mm. .5 mm, apparent density is 0.30 g/cm ³ , mass of activated carbon layer in water purification filter 1A is 100 g, mass of activated carbon layer in water purification filter 1B is 199 g, outer diameter of activated carbon layers in water purification filters 1A and 1B is 64.32 mm , the thickness is 13.66 mm, the apparent density is 0.37 g/cm ³ , the ratio of the thickness of each activated carbon layer to the thickness of the water purification filters 1A and 1B (thickness of activated carbon layer/thickness of water purification filter) is was 0.78.

<Example 2>
(1) Preparation of Raw Materials for Activated Carbon Layer The same raw materials as in Example 1 were prepared.

(2) Production of water purification filter (2-1) Preparation of nonwoven fabric core The same nonwoven fabric core as in Example 1 was prepared.

(2-2) Production of water purification filter: activated carbon having a high amount of acidic functional groups, activated carbon A having a low amount of acidic functional groups, activated carbon B having a low amount of acidic functional groups, and binder fibers, so as to have the composition shown in Table 1; Mixed with water to obtain a slurry. The prepared 124 mm core was set on the core of the molding die, the slurry was sucked from the center, pulled out, and dried in a drying oven at 120 ° C. for 15 hours to obtain an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of An intermediate of 124 mm in which the core and the activated carbon layer were integrated was obtained. A nonwoven fabric (Elves S0503, manufactured by Unitika Ltd., a spunbond nonwoven fabric made of continuous fibers that are core-sheath type composite fibers with a core made of a polyester resin and a sheath made of a polyolefin resin) is used as a cover layer for this intermediate. , A nonwoven fabric in which stacked continuous fibers are partially pressed together by heat embossing to be integrated, and the nonwoven fabric has a basis weight of 50 g/m ² , a thickness of 0.34 mm, and an apparent density of 0.15 g/cm ³ . ) was wound to cover the outer layer, and the beginning and end of winding were thermally bonded with an iron heated to 150° C. to obtain a water purification filter 2A. In the same way, using a prepared core with a length of 248 mm, an intermediate having an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of 248 mm, in which the core and the activated carbon layer are integrated, is obtained. Elbes S0503, manufactured by Unitika Ltd.) was wound to cover the outer layer, and the beginning and end of winding were thermally bonded with an iron heated to 150°C to obtain a water purification filter 2B. The volume of the water purification filter 2A was 324 cm ³ and the volume of the water purification filter 2B was 648 cm ³ . The water purification filters 2A and 2B have an outer diameter of 65 mm, an inner diameter of 30 mm, and a thickness of 17.5 mm. .5 mm, apparent density 0.30 g/cm ³ , mass of activated carbon layer in water purification filter 2A: 100 g, mass of activated carbon layer in water purification filter 2B: 200 g, outer diameter of activated carbon layers in water purification filters 2A and 2B: 64.32 mm , the thickness is 13.66 mm, the apparent density is 0.37 g/cm ³ , the ratio of the thickness of each activated carbon layer to the thickness of the water purification filters 2A and 2B (thickness of activated carbon layer/thickness of water purification filter) is was 0.78.

<Example 3>
(1) Preparation of Raw Materials for Activated Carbon Layer The same raw materials as in Example 1 were prepared.

(2) Production of water purification filter (2-1) Preparation of nonwoven fabric core The same nonwoven fabric core as in Example 1 was prepared.

(2-2) Production of water purification filter: activated carbon having a high amount of acidic functional groups, activated carbon A having a low amount of acidic functional groups, activated carbon B having a low amount of acidic functional groups, and binder fibers, so as to have the composition shown in Table 1; Mixed with water to obtain a slurry. The prepared 124 mm core was set on the core of the molding die, the slurry was sucked from the center, pulled out, and dried in a drying oven at 120 ° C. for 15 hours to obtain an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of An intermediate of 124 mm in which the core and the activated carbon layer were integrated was obtained. A nonwoven fabric (Elves S0503, manufactured by Unitika Ltd., a spunbond nonwoven fabric made of continuous fibers that are core-sheath type composite fibers with a core made of a polyester resin and a sheath made of a polyolefin resin) is used as a cover layer for this intermediate. , A nonwoven fabric in which stacked continuous fibers are partially pressed together by heat embossing to be integrated, and the nonwoven fabric has a basis weight of 50 g/m ² , a thickness of 0.34 mm, and an apparent density of 0.15 g/cm ³ . ) was wound to cover the outer layer, and the beginning and end of winding were thermally bonded with an iron heated to 150° C. to obtain water purification filter 3A. In the same way, using a prepared core with a length of 248 mm, an intermediate having an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of 248 mm, in which the core and the activated carbon layer are integrated, is obtained. Elves S0503, manufactured by Unitika Ltd.) was wound to cover the outer layer, and the beginning and end of winding were thermally bonded with an iron heated to 150°C to obtain water purification filter 3B. The volume of water purification filter 3A was 324 cm ³ and the volume of water purification filter 3B was 648 cm ³ . The water purification filters 3A and 3B have an outer diameter of 65 mm, an inner diameter of 30 mm, and a thickness of 17.5 mm. .5 mm, apparent density is 0.30 g/cm ³ , mass of activated carbon layer in water purification filter 3A is 100 g, mass of activated carbon layer in water purification filter 3B is 201 g, outer diameter of activated carbon layers in water purification filters 3A and 3B is 64.32 mm , the thickness is 13.66 mm, the apparent density is 0.37 g/cm ³ , the ratio of the thickness of each activated carbon layer to the thickness of the water purification filters 3A and 3B (thickness of activated carbon layer/thickness of water purification filter) is was 0.78.

<Example 4>
(1) Preparation of Raw Materials for Activated Carbon Layer The same raw materials as in Example 1 were prepared.

(2) Production of water purification filter (2-1) Preparation of nonwoven fabric core The same nonwoven fabric core as in Example 1 was prepared.

(2-2) Production of water purification filter: activated carbon having a high amount of acidic functional groups, activated carbon A having a low amount of acidic functional groups, activated carbon B having a low amount of acidic functional groups, and binder fibers, so as to have the composition shown in Table 1; Mixed with water to obtain a slurry. The prepared 124 mm core was set on the core of the molding die, the slurry was sucked from the center, pulled out, and dried in a drying oven at 120 ° C. for 15 hours to obtain an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of An intermediate of 124 mm in which the core and the activated carbon layer were integrated was obtained. A nonwoven fabric (Elves S0503, manufactured by Unitika Ltd., a spunbond nonwoven fabric made of continuous fibers that are core-sheath type composite fibers with a core made of a polyester resin and a sheath made of a polyolefin resin) is used as a cover layer for this intermediate. , A nonwoven fabric in which stacked continuous fibers are partially pressed together by heat embossing to be integrated, and the nonwoven fabric has a basis weight of 50 g/m ² , a thickness of 0.34 mm, and an apparent density of 0.15 g/cm ³ . ) was wound to cover the outer layer, and the beginning and end of winding were thermally bonded with an iron heated to 150° C. to obtain a water purification filter 4A. In the same way, using a prepared core with a length of 248 mm, an intermediate having an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of 248 mm, in which the core and the activated carbon layer are integrated, is obtained. Elbes S0503, manufactured by Unitika Ltd.) was wound to cover the outer layer, and the beginning and end of winding were thermally bonded with an iron heated to 150°C to obtain water purification filter 4B. The volume of the water purification filter 4A was 324 cm ³ and the volume of the water purification filter 4B was 648 cm ³ . The water purification filters 4A and 4B have an outer diameter of 65 mm, an inner diameter of 30 mm, and a thickness of 17.5 mm. .5 mm, apparent density is 0.30 g/cm ³ , mass of activated carbon layer in water purification filter 4A is 98 g, mass of activated carbon layer in water purification filter 4B is 197 g, outer diameter of activated carbon layers in water purification filters 4A and 4B is 64.32 mm , the thickness is 13.66 mm, the apparent density is 0.37 g/cm ³ , the ratio of the thickness of each activated carbon layer to the thickness of the water purification filters 4A and 4B (thickness of activated carbon layer/thickness of water purification filter) is was 0.78.

<Example 5>
(1) Preparation of Raw Materials for Activated Carbon Layer The same raw materials as in Example 1 were prepared.

(2) Production of water purification filter (2-1) Preparation of nonwoven fabric core The same nonwoven fabric core as in Example 1 was prepared.

(2-2) Production of water purification filter: activated carbon having a high amount of acidic functional groups, activated carbon A having a low amount of acidic functional groups, activated carbon B having a low amount of acidic functional groups, and binder fibers, so as to have the composition shown in Table 1; Mixed with water to obtain a slurry. The prepared 124 mm core was set on the core of the molding die, the slurry was sucked from the center, pulled out, and dried in a drying oven at 120 ° C. for 15 hours to obtain an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of An intermediate of 124 mm in which the core and the activated carbon layer were integrated was obtained. A nonwoven fabric (Elves S0503, manufactured by Unitika Ltd., a spunbond nonwoven fabric made of continuous fibers that are core-sheath type composite fibers with a core made of a polyester resin and a sheath made of a polyolefin resin) is used as a cover layer for this intermediate. , A nonwoven fabric in which stacked continuous fibers are partially pressed together by heat embossing to be integrated, and the nonwoven fabric has a basis weight of 50 g/m ² , a thickness of 0.34 mm, and an apparent density of 0.15 g/cm ³ . ) was wound to cover the outer layer, and the beginning and end of winding were thermally bonded with an iron heated to 150° C. to obtain a water purification filter 5A. In the same way, using a prepared core with a length of 248 mm, an intermediate having an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of 248 mm, in which the core and the activated carbon layer are integrated, is obtained. Elves S0503, manufactured by Unitika Ltd.) was wound to cover the outer layer, and the beginning and end of winding were thermally bonded with an iron heated to 150°C to obtain water purification filter 5B. The volume of the water purification filter 5A was 324 cm ³ and the volume of the water purification filter 5B was 648 cm ³ . The water purification filters 5A and 5B have an outer diameter of 65 mm, an inner diameter of 30 mm, and a thickness of 17.5 mm. .5 mm, apparent density is 0.30 g/cm ³ , mass of activated carbon layer in water purification filter 5A is 100 g, mass of activated carbon layer in water purification filter 5B is 200 g, outer diameter of activated carbon layers in water purification filters 5A and 5B is 64.32 mm , the thickness is 13.66 mm, the apparent density is 0.37 g/cm ³ , and the ratio of the thickness of each activated carbon layer to the thickness of the water purification filters 5A and 5B (thickness of activated carbon layer/thickness of water purification filter) is was 0.78.

<Example 6>
(1) Preparation of raw materials for activated carbon layer The following raw materials were prepared.
・Activated carbon with a high amount of acidic functional groups: Carbide made from phenolic resin and potassium hydroxide are mixed so that the mass ratio (potassium hydroxide/carbide) is 3, the mixture is placed in a furnace, and nitrogen is circulated ( 1 L/min), the temperature was raised to 800° C. at a rate of temperature rise of 10° C./min, and then held for 2 hours for alkali activation treatment. Next, it was boiled in a 5.25% by weight hydrochloric acid (HCl) aqueous solution and then filtered. The sample after filtration was washed with hot water at 60°C and vacuum filtered, repeatedly washed and dehydrated until the pH of the filtrate reached 6.5 or higher, and then dried at 115°C. After drying, the temperature was raised to 300° C. in an air atmosphere (heating rate: 10° C./min), and then held for 24 hours for oxidation treatment. After the oxidation treatment, it was pulverized with a ball mill and adjusted to have an average particle size of 180 μm. When the amount of acidic functional groups and the specific surface area of this activated carbon were measured, the amount of acidic functional groups was 2.73 mmol/g and the specific surface area was 2180 m ² /g.
- Activated carbon B with a low amount of acidic functional groups: Activated carbon A with a low amount of acidic functional groups was pulverized with a ball mill to prepare an average particle size of 150 µm to obtain activated carbon B with a low amount of acidic functional groups. When the amount of acidic functional groups and the specific surface area of this activated carbon were measured, the amount of acidic functional groups was 0.13 mmol/g and the specific surface area was 1700 m ² /g.
・ Binder fiber: Trade name Vipal (registered trademark) manufactured by Nihon Exlan Kogyo Co., Ltd., fibrillated acrylic fiber

(2) Production of water purification filter (2-1) Preparation of nonwoven fabric core The same nonwoven fabric core as in Example 1 was prepared.

(2-2) Production of Water Purification Filter The activated carbon having a high amount of acidic functional groups, the activated carbon B having a low amount of acidic functional groups, and binder fibers were mixed with water so as to have the composition shown in Table 1 to obtain a slurry. The prepared 124 mm core was set on the core of the molding die, the slurry was sucked from the center, pulled out, and dried in a drying oven at 120 ° C. for 15 hours to obtain an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of An intermediate of 124 mm in which the core and the activated carbon layer were integrated was obtained. A nonwoven fabric (Elves S0503, manufactured by Unitika Ltd., a spunbond nonwoven fabric made of continuous fibers that are core-sheath type composite fibers with a core made of a polyester resin and a sheath made of a polyolefin resin) is used as a cover layer for this intermediate. , A nonwoven fabric in which stacked continuous fibers are partially pressed together by heat embossing to be integrated, and the nonwoven fabric has a basis weight of 50 g/m ² , a thickness of 0.34 mm, and an apparent density of 0.15 g/cm ³ . ) was wound to cover the outer layer, and the beginning and end of winding were thermally bonded with an iron heated to 150° C. to obtain a water purification filter 6A. In the same way, using a prepared core with a length of 248 mm, an intermediate having an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of 248 mm, in which the core and the activated carbon layer are integrated, is obtained. Elves S0503, manufactured by Unitika Ltd.) was wound to cover the outer layer, and the beginning and end of winding were thermally bonded with an iron heated to 150° C. to obtain a water purification filter 6B. The volume of the water purification filter 6A was 324 cm ³ and the volume of the water purification filter 6B was 648 cm ³ . The water purification filters 6A and 6B have an outer diameter of 65 mm, an inner diameter of 30 mm, and a thickness of 17.5 mm. 0.5 mm, apparent density of 0.30 g/cm ³ , mass of activated carbon layer in water purification filter 6A: 100 g, mass of activated carbon layer in water purification filter 6B: 199 g, outer diameter of activated carbon layers in water purification filters 6A and 6B: 64.32 mm , the thickness is 13.66 mm, the apparent density is 0.37 g/cm ³ , the ratio of the thickness of each activated carbon layer to the thickness of the water purification filters 6A and 6B (thickness of activated carbon layer/thickness of water purification filter) is was 0.78.

<Comparative Example 1>
(1) Preparation of raw materials for activated carbon layer The following raw materials were prepared.
• Activated carbon A with a low amount of acidic functional groups: Activated carbon A with a low amount of acidic functional groups was prepared in the same manner as in Example 1. (Acidic functional group content: 0.13 mmol/g, specific surface area: 1700 m ² /g, average particle size: 250 µm)
- Activated carbon B having a low amount of acidic functional groups: Activated carbon B having a low amount of acidic functional groups was prepared in the same manner as in Example 1. (Acidic functional group content: 0.13 mmol/g, specific surface area: 1700 m ² /g, average particle size: 150 µm)
- Activated carbon fiber: trade name A-15 manufactured by Ador Co., Ltd. (Amount of acidic functional groups: 0.37 mmol, specific surface area: 1700 m ² /g, average fiber diameter: 16 μm)
・ Binder fiber: Trade name Vipal (registered trademark) manufactured by Nihon Exlan Kogyo Co., Ltd., fibrillated acrylic fiber

(2) Production of water purification filter (2-1) Preparation of nonwoven fabric core The same nonwoven fabric core as in Example 1 was prepared.
(2-2) Production of water purification filter The activated carbon A having a low amount of acidic functional groups, the activated carbon B having a low amount of acidic functional groups, the activated carbon fiber and the binder fiber are mixed with water so as to have the composition shown in Table 1, A slurry was obtained. The prepared 124 mm core was set on the core of the molding die, the slurry was sucked from the center, pulled out, and dried in a drying oven at 120 ° C. for 15 hours to obtain an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of An intermediate of 124 mm in which the core and the activated carbon layer were integrated was obtained. A nonwoven fabric (Elves S0503, manufactured by Unitika Ltd., a spunbond nonwoven fabric made of continuous fibers that are core-sheath type composite fibers with a core made of a polyester resin and a sheath made of a polyolefin resin) is used as a cover layer for this intermediate. , A nonwoven fabric in which stacked continuous fibers are partially pressed together by heat embossing to be integrated, and the nonwoven fabric has a basis weight of 50 g/m ² , a thickness of 0.34 mm, and an apparent density of 0.15 g/cm ³ . ) was wound to cover the outer layer, and the beginning and end of winding were thermally bonded with an iron heated to 150° C. to obtain water purification filter 7A. Similarly, using a prepared core with a length of 248 mm, an intermediate was obtained by integrating a core with an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of 248 mm with an activated carbon layer. S0503, manufactured by Unitika Ltd.) was wound to cover the outer layer, and the start and end of winding were thermally bonded with an iron heated to 150°C to obtain water purification filter 7B. The volume of the water purification filter 7A was 324 cm ³ and the volume of the water purification filter 7B was 648 cm ³ . The water purification filters 7A and 7B have an outer diameter of 65 mm, an inner diameter of 30 mm, and a thickness of 17.5 mm. .5 mm, apparent density is 0.30 g/cm ³ , mass of activated carbon layer in water purification filter 7A is 98 g, mass of activated carbon layer in water purification filter 7B is 196 g, outer diameter of activated carbon layers in water purification filters 7A and 7B is 64.32 mm , the thickness is 13.66 mm, the apparent density is 0.37 g / cm ³ The ratio of the thickness of each activated carbon layer to the thickness of water purification filters 7A and 7B (thickness of activated carbon layer / thickness of water purification filter) is 0 0.78.

<Methods for measuring various physical properties>
(1) Amount of acidic functional groups in activated carbon and activated carbon layer Measured as described above.

(2) Water purification filter pressure loss A and pressure loss B
Using the water purification filters 1B, 2B, 3B, 4B, 5B, 6B and 7B, pressure drop A and pressure drop B were measured as described above.

(3) Specific Surface Area of Activated Carbon and Activated Carbon Layer Measured as described above.

(4) Average particle size of activated carbon Measured as described above.

(5) Amount of combined residual chlorine in filtered water Measured as described above using water purification filters 1A, 2A, 3A, 4A, 5A, 6A and 7A.

(6) Amount of Free Residual Chlorine in Filtrated Water Measured as described above using water purification filters 1A, 2A, 3A, 4A, 5A, 6A and 7A.

(7) Evaluation of the degree of coal dust generation of water purification filters Both end faces of water purification filters 1B, 2B, 3B, 4B, 5B, 6B and 7B are sealed by adhering foamed polyethylene caps using hot melt or silicone sealant. After that, it is filled in a resin housing, pure water is passed from the outside to the inside so that the superficial velocity (SV) is 463 / h, and after 5 minutes, 0.5 L of water that has passed through the water purification filter is sampled, It was filtered using a white membrane filter (pore size 0.45 μm), and the amount of coal dust remaining on the membrane filter was evaluated according to the following criteria. △ or more was set as the pass.
O: Coal dust cannot be visually confirmed.
Δ: Coal dust can be slightly confirmed visually.
x: Coal dust can be clearly confirmed visually.

Table 1 shows the results.

As is clear from Table 1, the water purification filters of Examples 1 to 6 include an activated carbon layer, the specific surface area of the activated carbon layer is 1600 to 1900 m ² /g, and the following measurements of the activated carbon layer Since the amount of acidic functional groups measured by the method was 0.8 to 3.0 mmol/g, it was possible to achieve both the ability to filter bound residual chlorine and free residual chlorine.

On the other hand, the water purifying filter of Comparative Example 1 had an amount of acidic functional groups of less than 0.8 mmol/g in the activated carbon layer, and thus was inferior in filtering ability of combined residual chlorine.

Claims (3)

A water purification filter including an activated carbon layer,
The activated carbon layer has a specific surface area of 1600 to 1900 m ² /g,
A water purification filter, wherein the amount of acidic functional groups in the activated carbon layer measured by the following measuring method is 0.8 to 3.0 mmol/g.
(Method for measuring the amount of acidic functional groups)
A part of the activated carbon layer is cut out with a cutter knife, and the cut-out part is finely pulverized and classified until the particle size distribution becomes 2 mm or less, and 1.0 g is taken as a sample for measurement. A measurement sample is added to 50 mL of a 0.1 mol/L sodium hydroxide solution as an alkaline solution, shaken for 30 minutes, and then allowed to stand at 25° C. for 24 hours. Thereafter, filtration is performed using glass fiber filter paper (GF/C manufactured by Whatman), 10 mL of the obtained filtrate is subjected to neutralization titration with 0.1 mol / L hydrochloric acid solution, and the amount of acidic functional groups (mmol / g) is determined. Ask. a cylindrical core;
and a cover layer included on the outer peripheral side of the activated carbon layer,
The activated carbon layer is included on the outer peripheral side of the core,
The ratio of the thickness of the activated carbon layer to the thickness of the water purification filter (thickness of activated carbon layer/thickness of water purification filter) is 0.7 to 0.9,
2. The water purifying filter according to claim 1, wherein the water purifying filter has a pressure loss A of 0.010 to 0.040 MPa measured by the following measuring method.
(Method for measuring pressure loss A)
After sealing both end faces of the water purification filter by adhering foamed polyethylene caps using hot melt or silicone sealant, the resin housing is filled, and pure water is added so that the superficial velocity (SV) becomes 2781 / h. After holding the flow rate for 10 minutes, the pressure loss X1 (MPa) is measured with a Bourdon tube pressure gauge. Similarly, the pressure loss X2 (MPa) in a blank from which the water purification filter is previously removed is measured. The value obtained by subtracting the pressure loss X2 from the pressure loss X1 is defined as the water flow pressure loss A (MPa) of the water purification filter. The combined residual chlorine filtered water amount of the water purification filter measured by the following measuring method is 20 to 100 m ³ ,
3. The water purifying filter according to claim 1, wherein the filtered water amount of free residual chlorine measured by the following measuring method of the water purifying filter is 40 to 140 m ³ .
(Method for measuring combined residual chlorine filtered water volume)
Both end faces of the water purification filter are sealed by adhering foamed polyethylene caps using hot-melt or silicone sealant, and then filled into a stainless steel housing. Based on the provisions of Article 4 of the Water Supply Law of Japan, ammonium chloride and Sodium chlorite is added and mixed with stirring to prepare raw water so that the concentration of combined residual chlorine is 0.5 mg/L. Adjusted raw water is passed from the outside to the inside of the water purification filter at a flow rate of 2.0 L/min so that the superficial velocity (SV) is 370/h. Quantitatively measure the concentration of combined residual chlorine before and after passing through the water filter using the DPD reagent absorption photometry method, and the concentration of combined residual chlorine in the effluent (filter-passing liquid) relative to the influent (adjusted raw water) becomes 20% or more at the initial stage. The point is defined as the breakthrough point, and the total filtered water volume (m ³ ) up to the breakthrough point is determined.
(Method for measuring amount of free residual chlorine filtered water)
Both end faces of the water purification filter are sealed by adhering foamed polyethylene caps using hot-melt or silicone sealant, and then filled into a stainless steel housing. Based on the provisions of Article 4 of the Water Supply Law of Japan, the free residual chlorine concentration is Sodium hypochlorite is added so that the concentration is 2.0±0.2 mg/L, and the raw water is prepared as adjusted raw water. Adjusted raw water is passed from the outside to the inside of the water purification filter so that the superficial velocity (SV) becomes 741/h. Quantitatively measure the concentration of free residual chlorine before and after passing through the water purification filter using the DPD reagent absorption photometry method, and the concentration of free residual chlorine in the effluent (filter-passing liquid) relative to the influent (adjusted raw water) becomes 20% or more at the initial stage. The point is defined as the breakthrough point, and the total filtered water volume (m ³ ) up to the breakthrough point is determined.

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