water filter

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

Technical Field

[0001] The present invention relates to a water purification filter.

Background Art

[0002] For the disinfection of tap water, sodium hypochlorite is mainly used. Hypochlorous acid and hypochlorite ions generated when the 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 the reaction between ammonia and nitrogen oxides present in natural water and the added hypochlorous acid and hypochlorite ions. Combined residual chlorine and free residual chlorine are collectively called residual chlorine. Depending on the state of the raw water taken, the amount of free residual chlorine added, and further the amount of chloramine, odor often becomes a problem.

[0003] Water purifiers are used to remove these residual chlorines 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 optionally an organic polymer membrane for filtration. In recent years, with the demand for higher performance of water purifiers and air purifiers, activated carbon is widely used in these filters and the like.

[0004] For example, a residual chlorine removal filter body for removing residual chlorine in water, which is obtained by mixing an activated carbon adsorbent, a fibrillated fiber binder, and calcium sulfite in water to form a mixed slurry-like substance, adsorbing and depositing the mixed slurry-like substance while sucking it from the side surface of a hollow cylindrical core member to form an adsorbed deposit, and heating and drying the adsorbed deposit. The activated carbon adsorbent is composed of either granular activated carbon or fibrous activated carbon or both. Based on 100 parts by weight of the activated carbon 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 (see, for example, Patent Document 1). According to this filter body, it has good water permeability and is said to be able to highly maintain the removal performance of residual chlorine including both free residual chlorine and combined residual chlorine. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-179374 [Overview of the project] [Problems that the invention aims to solve]

[0006] In the filter of the embodiment described in Patent Document 1 above, drinking water with a combined residual chlorine concentration of 0.2 ppm (mg / L) is used, the water temperature is set to 20°C, and the water flow rate is set to 2.5 L / min, with an SV value of 500hr. -1 The amount of combined residual chlorine filtered water after water was passed through and measured was at most 1.1 m³. 3 Therefore, its ability to filter out combined residual chlorine was insufficient.

[0007] Therefore, the main objective of the present invention is to provide a water purification filter that can solve the above problems and achieve both the filtration capacity for bound residual chlorine and free residual chlorine. [Means for solving the problem]

[0008] To solve the above problems, the inventors considered using activated carbon with a high amount of acidic functional groups. However, the inventors found that simply using activated carbon with a high amount of acidic functional groups did not result in a good filtration capacity for free residual chlorine, although it did result in a good filtration capacity for bound residual chlorine.

[0009] Here, the inventors investigated the reasons why it was difficult to achieve excellent filtration capacity for free residual chlorine. The following oxidation-reduction reaction is considered to be the filtration mechanism of free residual chlorine by activated carbon. HClO (free residual chlorine) + C (activated carbon) → CO + HCl

[0010] In other words, C (activated carbon) acts as a reducing agent and decomposes free residual chlorine. Here, activated carbon with a high amount of acidic functional groups includes activated carbon into which acidic functional groups such as cyclic and chain carboxyl groups, lactone groups, phenol groups, hydroxyl groups, ketone groups, and sulfone groups have been introduced to the carbon atoms. It is thought that on the surface of activated carbon into which acidic functional groups have been introduced, the portion that acts as a reducing agent is reduced, so the above oxidation-reduction reaction proceeds less easily compared to activated carbon without acidic functional groups. That is, it is thought that the greater the amount of acidic functional group in the activated carbon, and the higher the acidity of the acidic functional group, the more the above oxidation-reduction reaction is inhibited.

[0011] Therefore, the inventors further investigated and found that, for example, by using activated carbon with a high acidic functional group content and activated carbon with a low acidic functional group content and a specific surface area within a certain range, the average particle size and blending ratio of these materials were such that the acidic functional group content of the water purification filter was 0.8 to 3.0 mmol / g and the specific surface area of ​​the water purification filter was 1600 to 1900 m². 2 We discovered that the above problems can be solved by adjusting the activated carbon layer to a value of / g. This invention was completed through diligent research based on this finding.

[0012] In other words, the present invention provides inventions in the following embodiments. Item 1. A water purification filter containing an activated carbon layer, wherein the specific surface area of ​​the activated carbon layer is 1600 to 1900 m². 2 A water purification filter having a concentration of 0.8 to 3.0 mmol / g, and the amount of acidic functional groups in the activated carbon layer, as measured by the following measurement method, being 0.8 to 3.0 mmol / g. (Method for measuring the amount of acidic functional groups) A portion of the activated carbon layer is scraped off with a utility knife, and the scraped material is finely ground and classified until the particle size distribution is 2 mm or less. 1.0 g of this material is taken and used as the sample for measurement. A 0.1 mol / L sodium hydroxide solution is used as the alkaline solution. waterAdd the sample to 50 mL of the solution, shake for 30 minutes, and then allow to stand at 25°C for 24 hours. After that, filter using glass fiber filter paper (Whatman GF / C), and 10 mL of the resulting filtrate is titrated with 0.1 mol / L hydrochloric acid solution to determine the amount of acidic functional groups (mmol / g). Item 2. The water filter comprises a cylindrical core and a cover layer included on the outer periphery of the activated carbon layer, wherein the activated carbon layer is included on the outer periphery of the core, and the ratio of the thickness of the activated carbon layer to the thickness of the water filter (thickness of the activated carbon layer / thickness of the water filter) is 0.7 to 0.9. The water purification filter described in item 1, wherein the pressure loss A measured by the following measurement method of the water purification filter is 0.010 to 0.040 MPa. (Method for measuring pressure loss A) After sealing both ends of the water purification filter with foamed polyethylene caps using hot melt or silicone sealant, fill it into a resin housing and empty it with pure water. between The water is passed from the outside to the inside at a velocity (SV) of 2781 / h, and this flow rate is maintained for 10 minutes. Then, the pressure loss X1 (MPa) is measured using a Bourdon tube pressure gauge. Similarly, the pressure loss X2 (MPa) is measured in a blank state with the water purification filter removed. The value obtained by subtracting the pressure loss X2 from the pressure loss X1 is defined as the water flow pressure loss A (MPa) through the water purification filter. Item 3. The combined residual chlorine filtration volume of the water filter measured by the following measurement method is 20 to 100 m³. 3 Therefore, the amount of free residual chlorine filtered water measured by the following measurement method of the water purification filter is 40 to 140 m³. 3 A water filter as described in item 1 or 2. (Method for measuring the amount of combined residual chlorine filtered water) The ends of the water purification filter are sealed by bonding foamed polyethylene caps using hot melt or silicone sealant, and then filled into a stainless steel housing. In accordance with Article 4 of the Water Supply Act of Japan, raw water is prepared by adding ammonium chloride and sodium hypochlorite to tap water that conforms to the water quality standards stipulated in the "Ministerial Ordinance Concerning Water Quality Standards (Ministry of Health, Labour and Welfare Ordinance No. 101 of May 30, 2003)," stirring and mixing, to achieve a combined residual chlorine concentration of 0.5 mg / L. between The raw water is passed through the water filter from the outside to the inside at a flow rate of 2.0 L / min so that the velocity (SV) is 370 / h. The concentration of combined residual chlorine is quantitatively measured using DPD reagent spectrophotometric method before and after passing through the water filter. The breakthrough point is defined as the point at which the concentration of combined residual chlorine in the effluent (filtered water) relative to the influent (raw water) exceeds 20% initially. The total amount of filtered water up to this breakthrough point (m³) is then calculated. 3 ) (Method for measuring the amount of free residual chlorine filtered water) The ends of the water purification filter are sealed by bonding foamed polyethylene caps using hot melt or silicone sealant, and then filled into a stainless steel housing. Based on Article 4 of the Water Supply Act of Japan, the adjusted raw water is prepared by adding sodium hypochlorite to tap water that conforms to the water quality standards stipulated in the "Ministerial Ordinance Concerning Water Quality Standards (Ministry of Health, Labour and Welfare Ordinance No. 101 of May 30, 2003)" so that the free residual chlorine concentration is 2.0 ± 0.2 mg / L. between The treated raw water is passed through the water filter from the outside to the inside at a rate (SV) of 741 / h. The concentration of free residual chlorine is quantitatively measured using DPD reagent spectrophotometric method before and after passing through the water filter. The breakthrough point is defined as the point at which the concentration of free residual chlorine in the effluent (filtered liquid) relative to the influent (treated raw water) exceeds 20% initially. The total amount of filtered water up to this breakthrough point (m³) is then calculated. 3 ) [Effects of the Invention]

[0013] According to the water purification filter of the present invention, it is possible to achieve a balance between the filtration capacity for bound residual chlorine and free residual chlorine.

Brief Description of the Drawings

[0014] [Figure 1] It is a schematic diagram for explaining an example of a manufacturing apparatus for a water purification filter of the present invention by a slurry suction method.

Embodiments for Carrying Out the Invention

[0015] <Configuration of the water purification filter of the present invention> The water purification filter of the present invention is a water purification filter containing an activated carbon layer, wherein the specific surface area of the activated carbon layer is 1600 - 1900 m 2 / g, and the amount of acidic functional groups measured by the following measurement method of the activated carbon layer is 0.8 - 3.0 mmol / g.

[0016] (Measurement method for the amount of acidic functional groups) A part of the activated carbon layer is scraped out with a cutter knife, and the scraped material is finely pulverized and classified until the particle size distribution becomes 2 mm or less, and 1.0 g is collected and used as a measurement sample. As an alkaline solution, 0.1 mol / L sodium hydroxide water solution 50 mL, the measurement sample is added, shaken for 30 minutes, and then left standing at 25 °C for 24 hours. Then, filtration is performed using a glass fiber filter paper (GF / C manufactured by Whatman), and 10 mL of the obtained filtrate is subjected to neutral titration with 0.1 mol / L hydrochloric acid solution to determine the amount of acidic functional groups (mmol / g).

[0017] As a preferable configuration of the water purification filter of the present invention, it 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.

[0018] Hereinafter, each member constituting the water purification filter of the present invention will be described in detail.

[0019] 1. Activated carbon layer The water purification filter of the present invention includes an activated carbon layer.

[0020] In the water purification filter of the present invention, the activated carbon layer has a specific surface area of ​​1600 to 1900 m². 2 The specific surface area is 1700-1900m². This specific surface area means that there are many carbon atoms in the activated carbon layer. Furthermore, setting the specific surface area within the above range, and the amount of acidic functional groups (described later) within a specific range, means that the activated carbon layer contains specific amounts of carbon atoms with acidic functional groups introduced and carbon atoms without acidic functional groups introduced. As a result, the resulting water filter has excellent combined residual chlorine filtration capacity and free residual chlorine filtration capacity. This specific surface area range, along with the amount of acidic functional groups (described later), can be achieved, for example, by using activated carbon with a high amount of acidic functional groups (e.g., 2 mmol / g or more) and activated carbon with a low amount of acidic functional groups (e.g., 0.2 mmol / g or less) in combination and adjusting their mixing ratio. From the viewpoint of achieving superior combined residual chlorine filtration capacity, the specific surface area is set to 1700-1900m². 2 / g is preferable.

[0021] In this invention, the specific surface area of ​​the activated carbon layer is calculated based on the nitrogen adsorption isotherm at 77.4 K. Specifically, first, using an automatic gas adsorption amount measuring device (product name "AUTOSORB-1-MP", manufactured by QUANTCHROME), the sample (activated carbon layer) is cooled to 77.4 K (boiling point of nitrogen), nitrogen gas is introduced, and the amount of nitrogen gas adsorbed V [cc / g] is measured by the volumetric method. At this time, the pressure P [hPa] of the introduced nitrogen gas 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 a nitrogen adsorption isotherm is created by plotting the amount of adsorption for each relative pressure. Using the analysis program attached to the above device, the specific surface area is determined according to the BET method based on the obtained nitrogen adsorption isotherm. The sample is sampled so that its mass is 0.1 g.

[0022] In the water purification filter of the present invention, the activated carbon layer has an acidic functional group content of 0.8 to 3.0 mmol / g, as measured by the following measurement method. (Method for measuring the amount of acidic functional groups) A portion of the activated carbon layer is scraped off with a utility knife, and the scraped material is finely ground and classified until the particle size distribution is 2 mm or less. 1.0 g of this material is taken and used as the sample for measurement. A 0.1 mol / L sodium hydroxide solution is used as the alkaline solution. water Add the sample to 50 mL of the solution, shake for 30 minutes, and then allow to stand at 25°C for 24 hours. After that, filter using glass fiber filter paper (Whatman GF / C), and 10 mL of the resulting filtrate is titrated with 0.1 mol / L hydrochloric acid solution to determine the amount of acidic functional groups (mmol / g).

[0023] The particle size distribution of the crushed and classified activated carbon layer is the volume-based particle size distribution of granular activated carbon, measured using a laser diffraction / scattering particle size distribution analyzer (product name LA-920, manufactured by Horiba, Ltd.).

[0024] As mentioned above, setting the specific surface area within the specified range and the amount of acidic functional groups, as described later, within a specific range means that the activated carbon layer contains specific amounts of carbon atoms with acidic functional groups introduced and carbon atoms without acidic functional groups introduced. As a result, the resulting water purification filter has excellent combined residual chlorine filtration capacity and free residual chlorine filtration capacity. Setting the specific surface area within the specified range and the amount of acidic functional groups, as described later, can be achieved, for example, by using activated carbon with a high amount of acidic functional groups (e.g., 2 mmol / g or more) and activated carbon with a low amount of acidic functional groups (e.g., 0.5 mmol / g or less) in combination and adjusting their mixing ratio. From the viewpoint of achieving even better combined residual chlorine filtration capacity, the amount of acidic functional groups is preferably 1.5 to 3.0 mmol / g.

[0025] The acidic functional groups present in the activated carbon layer of the present invention are not particularly limited, but examples include cyclic and linear carboxyl groups, lactone groups, phenol groups, hydroxyl groups, ketone groups, and sulfone groups.

[0026] The apparent density of the activated carbon layer is, for example, 0.25 to 0.5 g / cm³. 3These include 0.3-0.45 g / cm³. 3 The following are preferred. Furthermore, when the activated carbon layer is cylindrical, the thickness of the activated carbon layer can be, for example, 5 to 30 mm, with 10 to 25 mm being preferred.

[0027] <Examples of preferred raw materials for 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 preferably contains activated carbon with a high acidic functional group content, specifically activated carbon with an acidic functional group content of 2 mmol / g or more, as a raw material. This makes it easier to adjust the acidic functional group content of the activated carbon layer to 0.8 to 3.0 mmol / g. The above acidic functional group content is more preferably 2 to 4 mmol / g, and even more preferably 2.5 to 3.5 mmol / g.

[0028] In this invention, the amount of acidic functional groups in activated carbon is measured as follows. (Measurement method) Take 1.0 g of activated carbon and use it as the sample for measurement. Prepare a 0.1 mol / L sodium hydroxide solution as the alkaline solution. water Add the sample to 50 mL of the solution, shake for 30 minutes, and then allow to stand at 25°C for 24 hours. After that, filter using glass fiber filter paper (Whatman GF / C), and 10 mL of the resulting filtrate is titrated with 0.1 mol / L hydrochloric acid solution to determine the amount of acidic functional groups (mmol / g).

[0029] Furthermore, the specific surface area of ​​activated carbon with a high acidic functional group content is 1800-2500 m². 2 / g is preferred, and 2000~2300m 2 A value of / g is more preferable. This allows for a greater number of carbon atoms with acidic functional groups to be present on the surface, making it easier to improve the combined residual chlorine filtration capacity of the water filter. The method for measuring the specific surface area of ​​activated carbon is the same as that for measuring the specific surface area of ​​the water filter.

[0030] Furthermore, activated carbon with a high acidic functional group content is preferably granular activated carbon, with an average particle size of 150 to 200 μm, and more preferably 160 to 200 μm. By using such an average particle size, the resulting water purification filter can be more easily kept within the pressure loss range described later. The average particle size of granular activated carbon refers to the particle size at which the cumulative volume value in the particle size distribution of granular activated carbon accounts for 50%, as measured using a laser diffraction / scattering particle size distribution analyzer (product name LA-920, manufactured by Horiba, Ltd.).

[0031] In the activated carbon layer of the water purification filter of the present invention, the content of activated carbon with a high acidic functional group content can be 20 to 90% by mass, and from the viewpoint of making it easier to further balance the filtration capacity of the water purification filter for both bound residual chlorine and free residual chlorine, 45 to 90% by mass is preferred.

[0032] (2) Activated carbon with low acidic functional group content In the water purification filter of the present invention, the activated carbon layer preferably contains activated carbon with a low acidic functional group content, specifically activated carbon with an acidic functional group content of 0.5 mmol / g or less, as a raw material. This makes it easier to adjust the acidic functional group content of the activated carbon layer to 0.8 to 3.0 mmol / g. The above acidic functional group content is more preferably 0.3 mmol / g or less, and even more preferably 0.2 mmol / g or less.

[0033] Furthermore, the specific surface area of ​​activated carbon with a low acidic functional group content is 1400-2000 m². 2 / g is preferred, and 1500~1900m 2 / g is more preferable. This allows for a greater number of carbon atoms on the surface that do not have acidic functional groups introduced, making it easier to improve the free residual chlorine filtration capacity of the water filter.

[0034] Furthermore, activated carbon with a low acidic functional group content is preferably granular activated carbon, with an average particle size of 120 μm to 300 μm being preferred, and 130 to 280 μm being more preferred. By using such an average particle size, the resulting water purification filter can be more easily made to conform to the pressure loss range described later. Moreover, from the viewpoint of further making the resulting water purification filter conform to the pressure loss range described later, it is more preferable to use a combination of activated carbon with an average particle size of 130 to 170 μm and activated carbon with an average particle size of 200 to 300 μm.

[0035] In the activated carbon layer of the water purification filter of the present invention, the content of activated carbon with a low acidic functional group content can be 5 to 70% by mass, and from the viewpoint of making it easier to further balance the filtration capacity of the water purification filter for both bound residual chlorine and free residual chlorine, 5 to 50% by mass is preferred.

[0036] (3) Other ingredients The activated carbon layer in the water purification filter of the present invention may contain, as raw materials, other components besides the activated carbon with a high acidic functional group content and the activated carbon with a low acidic functional group content mentioned above. Examples of such other components include binder fibers. Binder fibers are formed by integrating with the granular activated carbon, thereby intertwining the granular activated carbon and shaping it into a cylindrical form. In the activated carbon layer of the water purification filter of the present invention, the granular activated carbon may be fused to the binder fibers. Known fibrillated binder fibers used in activated carbon layers can be used as binder fibers. Specific examples of such fibrillated binder fiber types include acrylic fibers, acrylic fibers, polyethylene fibers, cellulose fibers, and aramid fibers. Binder fibers may be used individually or in combination of two or more types.

[0037] 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.

[0038] 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 as a core member, it plays a role in increasing the strength of the water purification filter and also plays a role in reducing the shedding of carbon dust from the activated carbon layer.

[0039] As for the core material, known materials can be used, such as porous ceramics, porous metal filters, and nonwoven fabrics. Alternatively, a cylindrical member with pores may be molded from resin, metal, etc., and used as the core. Among these, nonwoven fabric is preferred, and nonwoven fabric obtained by compression molding is more preferred. Furthermore, there are no particular limitations on the fibrous material constituting the nonwoven fabric, but polyester fibers are preferred.

[0040] For example, the basis weight of the nonwoven fabric used to form the core is 30-100 g / m². 2 These include 50-90g / m². 2 The following are preferred. The core thickness can be, for example, 1 to 5 mm, with 2 to 4 mm being more preferred. The apparent density of the core is 0.2 to 0.6 g / cm³. 3 These include 0.25-0.35 g / cm³. 3 These are preferred.

[0041] 3. Cover layer The water purification filter of the present invention may include a cover layer on the outer periphery 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 the shedding of carbon dust from the activated carbon layer.

[0042] The cover layer is not particularly limited, but woven fabrics, knitted fabrics, nonwoven fabrics, and other types of fabrics are preferred, with nonwoven fabrics being particularly preferred. Among these, nonwoven fabrics made of long fibers or continuous fibers are preferred from the viewpoint of having relatively high tear strength and superior handling and processing properties.

[0043] The nonwoven fabric consisting of long fibers or continuous fibers is not particularly limited, but a spunbond nonwoven fabric is preferred. Examples of long fibers or continuous fibers constituting the spunbond nonwoven fabric include core-sheath type heat-fusible fibers in which a heat-fusible component is arranged in the sheath portion and a synthetic resin component having a melting point 20°C or more, more preferably 30°C or more, higher than the melting point of the sheath portion is arranged in the core portion. Examples of the core portion of the above core-sheath type heat-fusible fiber include a synthetic resin component having a melting point of 150 to 300°C, more preferably 200 to 300°C, and having a melting point 20°C or more higher than the melting point of the sheath portion, and more specifically, polyethylene terephthalate. Examples of the sheath portion of the above core-sheath type heat-fusible fiber include those having a melting point 80 to 170°C, more preferably 80 to 140°C, and more specifically, polyester resins such as olefin resins such as polypropylene and polyethylene, or copolymerized polyethylene terephthalate copolymerized with copolymerized components such as isophthalic acid. Among these, polyolefin resins are preferred, and polyethylene is more preferred, from the viewpoint of superior flexibility and heat-sealability to activated carbon molded bodies, as well as superior handling and processability.

[0044] For example, the basis weight of the cover layer is 20-100 g / m². 2 These include 40-60g / m 2 The following are preferred. The thickness of the cover layer can be, for example, 0.03 to 1.0 mm, and preferably 0.05 to 0.6 mm. The apparent density of the cover layer is 0.05 to 0.5 g / cm³. 3 These include 0.08~0.4 g / cm³. 3 These are preferred.

[0045] 4. Water filter The water purification filter of the present invention may include a cylindrical core, an activated carbon layer included on the outer circumference of the core, and a cover layer included on the outer circumference of the activated carbon layer. Preferably, the ratio of the thickness of the activated carbon layer to the thickness of the water purification filter (thickness of the activated carbon layer / thickness of the water purification filter) is 0.7 to 0.9.

[0046] 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 measurement method. (Method for measuring pressure loss) (Method for measuring pressure loss A) After sealing both ends of the water purification filter with foamed polyethylene caps using hot melt or silicone sealant, fill it into a resin housing and empty it with pure water. between The water is passed from the outside to the inside at a velocity (SV) of 2781 / h, and this flow rate is maintained for 10 minutes. Then, the pressure loss X1 (MPa) is measured using a Bourdon tube pressure gauge. Similarly, the pressure loss X2 (MPa) is measured in a blank state with the water purification filter removed. The value obtained by subtracting the pressure loss X2 from the pressure loss X1 is defined as the water flow pressure loss A (MPa) through the water purification filter.

[0047] The above pressure loss A indicates that the average particle size of activated carbon with a high acidic functional group content (e.g., 2 mmol / g or more) and the average particle size of activated carbon with a low acidic functional group content (e.g., 0.2 mmol / g or less) are both within specific ranges. As a result, the resulting water purification filter tends to have better combined residual chlorine filtration capacity and free residual chlorine filtration capacity. In other words, by setting the pressure loss A within the above range, the activated carbon layer has an appropriate density, and a flow path that better exhibits combined residual chlorine filtration capacity and free residual chlorine filtration capacity is maintained within the activated carbon layer, resulting in better combined residual chlorine filtration capacity and free residual chlorine filtration capacity. From the viewpoint of further improving the combined residual chlorine filtration capacity, it is preferable that the above pressure loss A be 0.015 to 0.028 MPa.

[0048] The water purification filter of the present invention preferably has a pressure loss B measured by the following measurement method of 0.010 to 0.030 MPa, and more preferably 0.010 to 0.018 MPa. (Method for measuring pressure loss B) After sealing both ends of the water purification filter with foamed polyethylene caps using hot melt or silicone sealant, fill it into a resin housing and empty it with pure water. between The water is passed from the outside to the inside at a velocity (SV) of 1854 / h, and this flow rate is maintained for 10 minutes. Then, the pressure loss Y1 (MPa) is measured using a Bourdon tube pressure gauge. Similarly, the pressure loss Y2 (MPa) is measured in a blank state with the water purification filter 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) through the water purification filter.

[0049] The water purification filter of the present invention has a combined residual chlorine filtration volume of 20 to 100 m³ as measured by the following measurement method. 3 Preferably, the amount of free residual chlorine filtered water measured by the following measurement method is 40 to 140 m³. 3 It is preferable that this be the case.

[0050] (Method for measuring the amount of combined residual chlorine filtered water) The ends of the water purification filter are sealed by bonding foamed polyethylene caps using hot melt or silicone sealant, and then filled into a stainless steel housing. In accordance with Article 4 of the Water Supply Act of Japan, raw water is prepared by adding ammonium chloride and sodium hypochlorite to tap water that conforms to the water quality standards stipulated in the "Ministerial Ordinance Concerning Water Quality Standards (Ministry of Health, Labour and Welfare Ordinance No. 101 of May 30, 2003)," stirring and mixing, to achieve a combined residual chlorine concentration of 0.5 mg / L. between The raw water is passed through the water filter from the outside to the inside at a flow rate of 2.0 L / min so that the velocity (SV) is 370 / h. The concentration of combined residual chlorine is quantitatively measured using DPD reagent spectrophotometric method before and after passing through the water filter. The breakthrough point is defined as the point at which the concentration of combined residual chlorine in the effluent (filtered water) relative to the influent (raw water) exceeds 20% initially. The total amount of filtered water up to this breakthrough point (m³) is then calculated. 3 )

[0051] (Method for measuring the amount of free residual chlorine filtered water) The ends of the water purification filter are sealed by bonding foamed polyethylene caps using hot melt or silicone sealant, and then filled into a stainless steel housing. Separately, in accordance with Article 4 of the Water Supply Act of Japan, sodium hypochlorite is added to tap water that conforms to the water quality standards stipulated in the "Ministerial Ordinance Concerning Water Quality Standards (Ministry of Health, Labour and Welfare Ordinance No. 101 of May 30, 2003)" to prepare the raw water for adjustment, so that the free residual chlorine concentration is 2.0 ± 0.2 mg / L. between The treated raw water is passed through the water filter from the outside to the inside at a rate (SV) of 741 / h. The concentration of free residual chlorine is quantitatively measured using DPD reagent spectrophotometric method before and after passing through the water filter. The breakthrough point is defined as the point at which the concentration of free residual chlorine in the effluent (filtered liquid) relative to the influent (treated raw water) exceeds 20% initially. The total amount of filtered water up to this breakthrough point (m³) is then calculated. 3 )

[0052] As mentioned above, activated carbon with a high acidic functional group content and activated carbon with a low acidic functional group content and a specific surface area within a certain range are used in combination, and the mixing ratio of these is such that the acidic functional group content of the activated carbon layer is 0.8 to 3.0 mmol / g and the specific surface area of ​​the activated carbon layer is 1600 to 1900 m². 2 By adjusting the ratio to / g, or by adjusting the average particle size to fall within the range of pressure loss A and / or pressure loss B mentioned above, it becomes possible to further achieve a balance between the combined residual chlorine and free residual chlorine filtration volumes. From the perspective of further ensuring a balance between the combined residual chlorine and free residual chlorine filtration capacities, the combined residual chlorine filtration volume and the free residual chlorine filtration volume are set to 50-100 m³. 3 It is preferable that this be the case.

[0053] The height of the water purification filter of the present invention (the length from one bottom surface to the other bottom surface) can be set appropriately depending on the type of water purifier used, but examples include 10 to 300 mm.

[0054] The thickness of the water purification filter of the present invention can be appropriately set according to the type of water purifier used, but from the viewpoint of water purification performance and water permeability, for example, a thickness of 2.5 to 50 mm is recommended. 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. The inner diameter is the diameter of the space that connects 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. 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.

[0055] When the water purification filter of the present invention is cylindrical, its inner diameter and outer diameter can be appropriately set to satisfy the thickness described above, but specifically, an inner diameter of 5 mm or more and an outer diameter of 15 to 150 mm are examples.

[0056] <Method of manufacturing a water purification filter> The method for manufacturing the water purification filter of the present invention is not particularly limited, and examples include the following methods.

[0057] First, a core and preferred raw materials for the activated carbon layer described above are prepared, and an intermediate in which the core and activated carbon layer are integrated is produced by slurry suction. Specifically, a slurry is obtained by mixing granular activated carbon with a high acidic functional group content, granular activated carbon with a low acidic functional group content, and binder fibers with water. Next, for example, a double-tubular container having an inner tube and an outer tube with numerous small holes is used, the core is set on the outer circumference of the inner tube, the slurry is poured between the core and the outer tube, and a cylindrical molded body is obtained by suctioning the slurry from the center. The intermediate is obtained by drying this molded body. The molded body may be subjected to heat treatment and compression treatment as needed. The ratio of powdered activated carbon to binder fibers in the slurry can be set to the ratio described above 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 the shape of the water purification filter can be made into various shapes by changing the shape of the container. Next, a cover layer is wrapped around the outer circumference of the obtained intermediate to manufacture the water purification filter of the present invention.

[0058] Another specific example of a method for producing an intermediate in which a core and an activated carbon layer are integrated by the slurry suction method described above will be explained. Figure 1 is a schematic diagram illustrating an example of a production apparatus for the intermediate in which the core and activated carbon layer are integrated by the slurry suction method. The production apparatus in Figure 1 comprises a mold 6 having a cylindrical core 62 having numerous suction holes 61 on its surface, and flanges that are detachable from the core and arranged at both ends of the core 62, a suction tube 7 that is connected to the inside of the cylinder of the core 62 so as to be able to pass air and liquid, and a container 9 containing a slurry 8 obtained by mixing the above-mentioned granular activated carbon with a high acidic functional group content, the above-mentioned granular activated carbon with a low acidic functional group content, and the above-mentioned binder fibers with water.

[0059] First, a uniform aqueous slurry is prepared containing granular activated carbon with a high acidic functional group content, granular activated carbon with a low acidic functional group content, and binder fibers in a predetermined proportion. The solid content concentration in the aqueous slurry is not particularly limited, but it is preferably about 0.1 to 4% by mass from the viewpoint of ease of handling and ease of molding. Mechanical dispersion, stirring, and beating can be performed when preparing the slurry using a beater or the like.

[0060] The obtained slurry 8 is placed in a container 9. Next, one flange of the mold 6 is removed, the aforementioned cylindrical core is inserted into the core body 62, the flange is reattached, and the mixture is immersed in the slurry 8. Then, using a pump, the inside of the core body 62 is depressurized through the suction tube 7, causing the granular activated carbon with a high acidic functional group content in the slurry, the granular activated carbon with a low acidic functional group content, and the binder fibers to be deposited on the surface of the core inserted into the core body 62.

[0061] Then, the mold 6 is lifted from the slurry 8, the intermediate in which the core and activated carbon layer are integrated is extracted, and it is dried. The drying temperature can be, for example, around 80 to 150°C. Although not shown in the figures, it is preferable to include a step of compressing the layer containing granular activated carbon with a high amount of acidic functional groups, granular activated carbon with a low amount of acidic functional groups, and binder fibers that has been deposited on the mold 6, either while the slurry is being aspirated or after the mold 6 has been lifted from the slurry 8. The method of compression is not particularly limited, but for example, a rotating roller may be pressed against the layer so that the activated carbon layer reaches a predetermined apparent density, and the activated carbon layer containing granular activated carbon with a high amount of acidic functional groups, granular activated carbon with a low amount of acidic functional groups, and binder fibers deposited on the mold 6 may be compressed while the mold 6 is also rotated around its long axis. After drying, a cover layer is wrapped around the outer circumference of the obtained intermediate to manufacture the water purification filter of the present invention.

[0062] <Uses of water purification 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 hemodialysis. [Examples]

[0063] The present invention will be described in detail below with reference to examples and comparative examples. However, the present invention is not limited to the examples.

[0064] <Example 1> (1) Preparation of raw materials for the activated carbon layer The following ingredients were prepared. • Activated carbon with a high acidic functional group content: A carbide made from phenolic resin and potassium hydroxide were mixed in a mass ratio (potassium hydroxide / carbide) of 3. This mixture was placed in a furnace and heated to 800°C at a rate of 10°C / min under a nitrogen flow (1 L / min), then held for 2 hours for alkaline activation treatment. Next, it was boiled in a 5.25 wt% hydrochloric acid (HCl) aqueous solution and then filtered. The filtered sample was washed with 60°C hot water and vacuum filtered, and the washing and dewatering were repeated until the pH of the filtrate was 6.5 or higher, and then dried at 115°C. After drying, it was heated to 300°C in an air atmosphere (heating rate 10°C / min) and held for 24 hours for oxidation treatment. After oxidation treatment, it was ground in a ball mill and adjusted to an average particle size of 180 μm. When the acidic functional group content and specific surface area of ​​this activated carbon were measured, the acidic functional group content was 2.73 mmol / g and the specific surface area was 2180 m². 2 It was / g. • Activated carbon A with low acidic functional group content: Carbonized material made from coconut shells was placed in a furnace and heated to 900°C (10°C / min). While maintaining this temperature, steam was circulated into the furnace along with nitrogen (1 L / min) (steam concentration 70 vol%) to activate it with steam. Next, it was crushed in a ball mill and adjusted to an average particle size of 250 μm. The acidic functional group content and specific surface area of ​​this activated carbon were measured, and the acidic functional group content was 0.13 mmol / g, and the specific surface area was 1700 m². 2 It was / g. • Activated carbon B with low acidic functional group content: The aforementioned activated carbon A with low acidic functional group content was pulverized in a ball mill to prepare it so that the average particle size was 150 μm, thereby obtaining activated carbon B with low acidic functional group content. When the acidic functional group content and specific surface area of ​​this activated carbon were measured, the acidic functional group content was 0.13 mmol / g and the specific surface area was 1700 m². 2 It was / g. • Binder fiber: Fibrillated acrylic fiber, manufactured by Nippon Exlan Industries Co., Ltd., product name: Vipal (registered trademark)

[0065] (2) Manufacturing of water purification filters (2-1) Preparation of nonwoven core A thin web was formed by carding 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.). This web was then subjected to needle punching, heat-treated at 163°C, and cooled to obtain a nonwoven fabric. This nonwoven fabric has a basis weight of 80 g / m². 2 Thickness 0.32 mm, apparent density 0.25 g / cm³ 3 The following was done: A cylindrical iron pipe with an outer diameter of 30.0 mm was prepared as the core, and the nonwoven fabric was wound around the core so that the outer diameter of the core was 37 mm. The pipe was then placed in a furnace and heat-treated at an ambient temperature of 150°C for 2 hours, after which it was allowed to cool naturally. After that, the core was removed, and the pipe was cut into lengths of 124 mm and 248 mm using a cutting machine to obtain nonwoven fabric cores. The obtained nonwoven fabric cores 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 / cm³. 3 That was the case.

[0066] (2-2) Manufacturing of water purification filters A slurry was obtained by mixing activated carbon with a high acidic functional group content, activated carbon A with a low acidic functional group content, activated carbon B with a low acidic functional group content, and binder fibers with water to obtain the composition shown in Table 1. The prepared 124 mm core was set in the core body of a mold, the slurry was sucked out from the center, and the material was drawn out. By drying in a 120°C drying oven for 15 hours, an intermediate was obtained in which the core and activated carbon layer were integrated, with an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of 124 mm. A nonwoven fabric (Elves S0503, manufactured by Unitika Ltd., a spunbond nonwoven fabric made of continuous fibers which are core-sheath type composite fibers with a polyester resin core and a polyolefin resin sheath, and the deposited continuous fibers are partially pressed together by heat embossing to form an integrated nonwoven fabric, with a basis weight of 50 g / m²) was used as a cover layer on this intermediate. 2 Thickness 0.34 mm, apparent density 0.15 g / cm³ 3 A water purification filter 1A was obtained by wrapping a material around the core to cover the outer layer and heat-sealing the beginning and end of the wrapping with an iron heated to 150°C. Similarly, using a prepared core with a length of 248 mm, an intermediate body in which the core and activated carbon layer were integrated was obtained with an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of 248 mm. A nonwoven fabric (Elves S0503, manufactured by Unitika Ltd.) was wrapped around the core as a cover layer to cover the outer layer, and heat-sealing the beginning and end of the wrapping with an iron heated to 150°C was obtained to obtain a water purification filter 1B. The volume of water purification filter 1A was 324 cm³. 3 Therefore, the volume of water filter 1B is 648 cm³. 3 Furthermore, the outer diameter of water filters 1A and 1B was 65 mm, the inner diameter was 30 mm, and the thickness was 17.5 mm. The nonwoven fabric core in water filters 1A and 1B 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 / cm³. 3 The activated carbon layer in water filter 1A has a mass of 100g, the activated carbon layer in water filter 1B has a mass of 199g, the outer diameter of the activated carbon layer in water filters 1A and 1B is 64.32mm, the thickness is 13.66mm, and the apparent density is 0.37g / cm³. 3The ratio of the thickness of the activated carbon layer to the thickness of the water purification filters 1A and 1B (thickness of the activated carbon layer / thickness of the water purification filter) was 0.78.

[0067] <Example 2> (1) Preparation of raw materials for the activated carbon layer The same raw materials as in Example 1 were prepared.

[0068] (2) Manufacturing of water purification filters (2-1) Preparation of nonwoven core A nonwoven fabric core identical to that used in Example 1 was prepared.

[0069] (2-2) Manufacturing of water purification filters A slurry was obtained by mixing activated carbon with a high acidic functional group content, activated carbon A with a low acidic functional group content, activated carbon B with a low acidic functional group content, and binder fibers with water to obtain the composition shown in Table 1. The prepared 124 mm core was set in the core body of a mold, the slurry was sucked out from the center, and the material was drawn out. By drying in a 120°C drying oven for 15 hours, an intermediate was obtained in which the core and activated carbon layer were integrated, with an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of 124 mm. A nonwoven fabric (Elves S0503, manufactured by Unitika Ltd., a spunbond nonwoven fabric made of continuous fibers which are core-sheath type composite fibers with a polyester resin core and a polyolefin resin sheath, and the deposited continuous fibers are partially pressed together by heat embossing to form an integrated nonwoven fabric, with a basis weight of 50 g / m²) was used as a cover layer on this intermediate. 2 Thickness 0.34 mm, apparent density 0.15 g / cm³ 3 A water purification filter 2A was obtained by wrapping a material around the core to cover the outer layer and heat-sealing the beginning and end of the wrapping with an iron heated to 150°C. Similarly, using a prepared core with a length of 248 mm, an intermediate body in which the core and activated carbon layer were integrated was obtained with an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of 248 mm. A nonwoven fabric (Elves S0503, manufactured by Unitika Ltd.) was wrapped around the core as a cover layer to cover the outer layer, and heat-sealing the beginning and end of the wrapping with an iron heated to 150°C was obtained to obtain a water purification filter 2B. The volume of water purification filter 2A was 324 cm³.3 Therefore, the volume of water filter 2B is 648 cm³. 3 Furthermore, the outer diameter of water filters 2A and 2B was 65 mm, the inner diameter was 30 mm, and the thickness was 17.5 mm. The nonwoven fabric core in water filters 2A and 2B 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 / cm³. 3 The activated carbon layer in water filter 2A has a mass of 100g, the activated carbon layer in water filter 2B has a mass of 200g, the outer diameter of the activated carbon layer in water filters 2A and 2B is 64.32mm, the thickness is 13.66mm, and the apparent density is 0.37g / cm³. 3 The ratio of the thickness of the activated carbon layer to the thickness of the water purification filters 2A and 2B (thickness of the activated carbon layer / thickness of the water purification filter) was 0.78.

[0070] <Example 3> (1) Preparation of raw materials for the activated carbon layer The same raw materials as in Example 1 were prepared.

[0071] (2) Manufacturing of water purification filters (2-1) Preparation of nonwoven core A nonwoven fabric core identical to that used in Example 1 was prepared.

[0072] (2-2) Manufacturing of water purification filters A slurry was obtained by mixing activated carbon with a high acidic functional group content, activated carbon A with a low acidic functional group content, activated carbon B with a low acidic functional group content, and binder fibers with water to obtain the composition shown in Table 1. The prepared 124 mm core was set in the core body of a mold, the slurry was sucked out from the center, and the material was drawn out. By drying in a 120°C drying oven for 15 hours, an intermediate was obtained in which the core and activated carbon layer were integrated, with an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of 124 mm. A nonwoven fabric (Elves S0503, manufactured by Unitika Ltd., a spunbond nonwoven fabric made of continuous fibers which are core-sheath type composite fibers with a polyester resin core and a polyolefin resin sheath, and the deposited continuous fibers are partially pressed together by heat embossing to form an integrated nonwoven fabric, with a basis weight of 50 g / m²) was used as a cover layer on this intermediate.2 Thickness 0.34 mm, apparent density 0.15 g / cm³ 3 A water purification filter 3A was obtained by wrapping a material around the core to cover the outer layer and heat-sealing the beginning and end of the wrapping with an iron heated to 150°C. Similarly, using a prepared core with a length of 248 mm, an intermediate body in which the core and activated carbon layer were integrated was obtained with an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of 248 mm. A nonwoven fabric (Elves S0503, manufactured by Unitika Ltd.) was wrapped around the core as a cover layer to cover the outer layer, and heat-sealing the beginning and end of the wrapping with an iron heated to 150°C was obtained to obtain a water purification filter 3B. The volume of water purification filter 3A was 324 cm³. 3 Therefore, the volume of the water purification filter 3B is 648 cm³. 3 Furthermore, the outer diameter of water filters 3A and 3B was 65 mm, the inner diameter was 30 mm, and the thickness was 17.5 mm. The nonwoven fabric core in water filters 3A and 3B 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 / cm³. 3 The activated carbon layer in water filter 3A has a mass of 100g, the activated carbon layer in water filter 3B has a mass of 201g, the outer diameter of the activated carbon layer in water filters 3A and 3B is 64.32mm, the thickness is 13.66mm, and the apparent density is 0.37g / cm³. 3 The ratio of the thickness of the activated carbon layer to the thickness of the water purification filters 3A and 3B (thickness of the activated carbon layer / thickness of the water purification filter) was 0.78.

[0073] <Example 4> (1) Preparation of raw materials for the activated carbon layer The same raw materials as in Example 1 were prepared.

[0074] (2) Manufacturing of water purification filters (2-1) Preparation of nonwoven core A nonwoven fabric core identical to that used in Example 1 was prepared.

[0075] (2-2) Manufacturing of water purification filters A slurry was obtained by mixing activated carbon with a high acidic functional group content, activated carbon A with a low acidic functional group content, activated carbon B with a low acidic functional group content, and binder fibers with water to obtain the composition shown in Table 1. The prepared 124 mm core was set in the core body of a mold, the slurry was sucked out from the center, and the material was drawn out. By drying in a 120°C drying oven for 15 hours, an intermediate was obtained in which the core and activated carbon layer were integrated, with an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of 124 mm. A nonwoven fabric (Elves S0503, manufactured by Unitika Ltd., a spunbond nonwoven fabric made of continuous fibers which are core-sheath type composite fibers with a polyester resin core and a polyolefin resin sheath, and the deposited continuous fibers are partially pressed together by heat embossing to form an integrated nonwoven fabric, with a basis weight of 50 g / m²) was used as a cover layer on this intermediate. 2 Thickness 0.34 mm, apparent density 0.15 g / cm³ 3 A water purification filter 4A was obtained by wrapping a material around the core to cover the outer layer and heat-sealing the beginning and end of the wrapping with an iron heated to 150°C. Similarly, using a prepared core with a length of 248 mm, an intermediate body in which the core and activated carbon layer were integrated was obtained with an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of 248 mm. A nonwoven fabric (Elves S0503, manufactured by Unitika Ltd.) was wrapped around the core as a cover layer to cover the outer layer, and heat-sealing the beginning and end of the wrapping with an iron heated to 150°C was obtained to obtain a water purification filter 4B. The volume of water purification filter 4A was 324 cm³. 3 Therefore, the volume of the water purification filter 4B is 648 cm³. 3 Furthermore, the outer diameter of water filters 4A and 4B was 65 mm, the inner diameter was 30 mm, and the thickness was 17.5 mm. The nonwoven fabric core in water filters 4A and 4B 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 / cm³. 3 The activated carbon layer in water filter 4A has a mass of 98g, the activated carbon layer in water filter 4B has a mass of 197g, the outer diameter of the activated carbon layer in water filters 4A and 4B is 64.32mm, the thickness is 13.66mm, and the apparent density is 0.37g / cm³. 3The ratio of the thickness of the activated carbon layer to the thickness of the water purification filters 4A and 4B (thickness of the activated carbon layer / thickness of the water purification filter) was 0.78.

[0076] <Example 5> (1) Preparation of raw materials for the activated carbon layer The same raw materials as in Example 1 were prepared.

[0077] (2) Manufacturing of water purification filters (2-1) Preparation of nonwoven core A nonwoven fabric core identical to that used in Example 1 was prepared.

[0078] (2-2) Manufacturing of water purification filters A slurry was obtained by mixing activated carbon with a high acidic functional group content, activated carbon A with a low acidic functional group content, activated carbon B with a low acidic functional group content, and binder fibers with water to obtain the composition shown in Table 1. The prepared 124 mm core was set in the core body of a mold, the slurry was sucked out from the center, and the material was drawn out. By drying in a 120°C drying oven for 15 hours, an intermediate was obtained in which the core and activated carbon layer were integrated, with an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of 124 mm. A nonwoven fabric (Elves S0503, manufactured by Unitika Ltd., a spunbond nonwoven fabric made of continuous fibers which are core-sheath type composite fibers with a polyester resin core and a polyolefin resin sheath, and the deposited continuous fibers are partially pressed together by heat embossing to form an integrated nonwoven fabric, with a basis weight of 50 g / m²) was used as a cover layer on this intermediate. 2 Thickness 0.34 mm, apparent density 0.15 g / cm³ 3 A water purification filter 5A was obtained by wrapping a material around the core to cover the outer layer and heat-sealing the beginning and end of the wrapping with an iron heated to 150°C. Similarly, using a prepared core with a length of 248 mm, an intermediate body in which the core and activated carbon layer were integrated was obtained with an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of 248 mm. A nonwoven fabric (Elves S0503, manufactured by Unitika Ltd.) was wrapped around the core as a cover layer to cover the outer layer, and heat-sealing the beginning and end of the wrapping with an iron heated to 150°C was obtained to obtain a water purification filter 5B. The volume of water purification filter 5A was 324 cm³.3 Therefore, the volume of the water purification filter 5B is 648 cm³. 3 Furthermore, the outer diameter of water filters 5A and 5B was 65 mm, the inner diameter was 30 mm, and the thickness was 17.5 mm. The nonwoven fabric core in water filters 5A and 5B 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 / cm³. 3 The activated carbon layer in water filter 5A has a mass of 100g, the activated carbon layer in water filter 5B has a mass of 200g, the outer diameter of the activated carbon layer in water filters 5A and 5B is 64.32mm, the thickness is 13.66mm, and the apparent density is 0.37g / cm³. 3 The ratio of the thickness of the activated carbon layer to the thickness of the water purification filters 5A and 5B (thickness of the activated carbon layer / thickness of the water purification filter) was 0.78.

[0079] <Example 6> (1) Preparation of raw materials for the activated carbon layer The following ingredients were prepared. • Activated carbon with a high acidic functional group content: A carbide made from phenolic resin and potassium hydroxide were mixed in a mass ratio (potassium hydroxide / carbide) of 3. This mixture was placed in a furnace and heated to 800°C at a rate of 10°C / min under a nitrogen flow (1 L / min), then held for 2 hours for alkaline activation treatment. Next, it was boiled in a 5.25 wt% hydrochloric acid (HCl) aqueous solution and then filtered. The filtered sample was washed with 60°C hot water and vacuum filtered, and the washing and dewatering were repeated until the pH of the filtrate was 6.5 or higher, and then dried at 115°C. After drying, it was heated to 300°C in an air atmosphere (heating rate 10°C / min) and held for 24 hours for oxidation treatment. After oxidation treatment, it was ground in a ball mill and adjusted to an average particle size of 180 μm. When the acidic functional group content and specific surface area of ​​this activated carbon were measured, the acidic functional group content was 2.73 mmol / g and the specific surface area was 2180 m². 2 It was / g. • Activated carbon B with low acidic functional group content: The aforementioned activated carbon A with low acidic functional group content was pulverized in a ball mill to prepare it so that the average particle size was 150 μm, thereby obtaining activated carbon B with low acidic functional group content. When the acidic functional group content and specific surface area of ​​this activated carbon were measured, the acidic functional group content was 0.13 mmol / g and the specific surface area was 1700 m². 2 It was / g. • Binder fiber: Fibrillated acrylic fiber, manufactured by Nippon Exlan Industries Co., Ltd., product name: Vipal (registered trademark)

[0080] (2) Manufacturing of water purification filters (2-1) Preparation of nonwoven core A nonwoven fabric core identical to that used in Example 1 was prepared.

[0081] (2-2) Manufacturing of water purification filters A slurry was obtained by mixing activated carbon with a high acidic functional group content, activated carbon B with a low acidic functional group content, and binder fibers with water to obtain the composition shown in Table 1. A 124 mm core prepared was set in the core body of a mold, the slurry was sucked out from the center, and the material was pulled out. By drying in a 120°C drying oven for 15 hours, an intermediate was obtained in which the core and activated carbon layer were integrated, with an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of 124 mm. A nonwoven fabric (Elves S0503, manufactured by Unitika Ltd., a spunbond nonwoven fabric made of continuous fibers which are core-sheath type composite fibers in which the core part is made of polyester resin and the sheath part is made of polyolefin resin, and the deposited continuous fibers are partially pressed together by heat embossing to form an integrated nonwoven fabric, with a basis weight of 50 g / m²) was used as a cover layer on this intermediate. 2 Thickness 0.34 mm, apparent density 0.15 g / cm³ 3A water purification filter 6A was obtained by wrapping a nonwoven fabric (Elves S0503, manufactured by Unitika Ltd.) around the core to cover the outer layer, and heat-sealing the beginning and end of the wrapping with an iron heated to 150°C. Similarly, using a prepared core with a length of 248 mm, an intermediate body in which the core and activated carbon layer were integrated was obtained with an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of 248 mm. A water purification filter 6B was obtained by wrapping a nonwoven fabric (Elves S0503, manufactured by Unitika Ltd.) around the core as a cover layer to cover the outer layer, and heat-sealing the beginning and end of the wrapping with an iron heated to 150°C. The volume of water purification filter 6A was 324 cm³. 3 Therefore, the volume of the water purification filter 6B is 648 cm³. 3 Furthermore, the outer diameter of water filters 6A and 6B was 65 mm, the inner diameter was 30 mm, and the thickness was 17.5 mm. The nonwoven fabric core in water filters 6A and 6B 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 / cm³. 3 The activated carbon layer in water filter 6A has a mass of 100g, the activated carbon layer in water filter 6B has a mass of 199g, the outer diameter of the activated carbon layer in water filters 6A and 6B is 64.32mm, the thickness is 13.66mm, and the apparent density is 0.37g / cm³. 3 The ratio of the thickness of the activated carbon layer to the thickness of the water purification filters 6A and 6B (thickness of the activated carbon layer / thickness of the water purification filter) was 0.78.

[0082] <Comparative Example 1> (1) Preparation of raw materials for the activated carbon layer The following ingredients 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. (Amount of acidic functional groups: 0.13 mmol / g, specific surface area: 1700 m²) 2 / g, average particle size 250μm) • Activated carbon B with a low amount of acidic functional groups: Activated carbon B with a low amount of acidic functional groups was prepared in the same manner as in Example 1. (Amount of acidic functional groups: 0.13 mmol / g, specific surface area: 1700 m²) 2 / g, average particle size 150μm) • Activated carbon fiber: Manufactured by Adore Co., Ltd., product name A-15 (Acidic functional group content: 0.37 mmol, specific surface area 1700 m²)2 ( / g, average fiber diameter 16μm) • Binder fiber: Fibrillated acrylic fiber, manufactured by Nippon Exlan Industries Co., Ltd., product name: Vipal (registered trademark)

[0083] (2) Manufacturing of water purification filters (2-1) Preparation of nonwoven core A nonwoven fabric core identical to that used in Example 1 was prepared. (2-2) Manufacturing of water purification filters A slurry was obtained by mixing activated carbon A, activated carbon B, activated carbon fibers, and binder fibers with water to obtain the composition shown in Table 1, with the above-mentioned low acidic functional group content of activated carbon A, activated carbon B, activated carbon fibers, and binder fibers. A 124 mm core prepared was set in the core body of a mold, the slurry was sucked out from the center, and the material was pulled out. By drying in a 120°C drying oven for 15 hours, an intermediate was obtained in which the core and activated carbon layer were integrated, with an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of 124 mm. A nonwoven fabric (Elves S0503, manufactured by Unitika Ltd., a spunbond nonwoven fabric made of continuous fibers which are core-sheath type composite fibers in which the core part is made of polyester resin and the sheath part is made of polyolefin resin, and the deposited continuous fibers are partially pressed together by heat embossing to form a nonwoven fabric, with a basis weight of 50 g / m²) was used as a cover layer on this intermediate. 2 Thickness 0.34 mm, apparent density 0.15 g / cm³ 3 A water purification filter 7A was obtained by wrapping a material around the core to cover the outer layer and heat-sealing the beginning and end of the wrapping with an iron heated to 150°C. Similarly, using a prepared core with a length of 248 mm, an intermediate was obtained in which a core with an outer diameter of 64.32 mm, an inner diameter of 30 mm, and a length of 248 mm was integrated with an activated carbon layer. A water purification filter 7B was obtained by wrapping a nonwoven fabric (Elves S0503, manufactured by Unitika Ltd.) as a cover layer to cover the outer layer and heat-sealing the beginning and end of the wrapping with an iron heated to 150°C. The volume of water purification filter 7A was 324 cm³. 3 Therefore, the volume of the water purification filter 7B is 648 cm³. 3Furthermore, the outer diameter of water filters 7A and 7B was 65 mm, the inner diameter was 30 mm, and the thickness was 17.5 mm. The nonwoven fabric core in water filters 7A and 7B 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 / cm³. 3 The activated carbon layer in water filter 7A has a mass of 98g, the activated carbon layer in water filter 7B has a mass of 196g, the outer diameter of the activated carbon layer in water filters 7A and 7B is 64.32mm, the thickness is 13.66mm, and the apparent density is 0.37g / cm³. 3 The ratio of the thickness of the activated carbon layer to the thickness of the water purification filters 7A and 7B (thickness of the activated carbon layer / thickness of the water purification filter) was 0.78.

[0084] <Measurement methods for various physical properties, etc.> (1) Amount of acidic functional groups in activated carbon and activated carbon layer The measurements were taken as described above.

[0085] (2) Pressure loss A and pressure loss B of the water purification filter Using water purification filters 1B, 2B, 3B, 4B, 5B, 6B, and 7B, pressure loss A and pressure loss B were measured as described above.

[0086] (3) Specific surface area of ​​activated carbon and activated carbon layer The measurements were taken as described above.

[0087] (4) Average particle size of activated carbon The measurements were taken as described above.

[0088] (5) Combined residual chlorine filtration volume The measurements were taken using water purification filters 1A, 2A, 3A, 4A, 5A, 6A, and 7A, as described above.

[0089] (6) Free residual chlorine filtration volume The measurements were taken using water purification filters 1A, 2A, 3A, 4A, 5A, 6A, and 7A, as described above.

[0090] (7) Evaluation of the degree of carbon dust generation in the water purification filter After sealing both ends of water purification filters 1B, 2B, 3B, 4B, 5B, 6B, and 7B by bonding foamed polyethylene caps using hot melt or silicone sealant, fill them into resin housings and empty them with pure water. between The water was passed from the outside to the inside at a velocity (SV) of 463 / h. After 5 minutes, 0.5 L of water that had passed through the water purification filter was collected and filtered using a white membrane filter (pore size 0.45 μm). The amount of carbon dust remaining on the membrane filter was evaluated according to the following criteria. A score of △ or higher was considered acceptable. ○: No coal dust was visible to the naked eye. △: A small amount of coal dust can be seen with the naked eye. ×: Coal dust is clearly visible to the naked eye.

[0091] The results are shown in Table 1.

[0092] [Table 1]

[0093] As is clear from Table 1, the water purification filters of Examples 1 to 6 are water purification filters that include an activated carbon layer, and the specific surface area of ​​the activated carbon layer is 1600 to 1900 m². 2 Since the acidic functional group content of the activated carbon layer, as measured by the following measurement method, is 0.8 to 3.0 mmol / g, it was possible to achieve a balance between the filtration capacity of bound residual chlorine and free residual chlorine.

[0094] On the other hand, the water purification filter of Comparative Example 1 had an acidic functional group content of less than 0.8 mmol / g in the activated carbon layer, resulting in inferior combined residual chlorine filtration capacity.

Claims

1. A water purification filter containing an activated carbon layer, The specific surface area of ​​the activated carbon layer measured by the following measurement method is 1600 to 1900 m². ２ / g, A water purification filter wherein the amount of acidic functional groups in the activated carbon layer, as measured by the following measurement method, is 0.8 to 3.0 mmol / g, The activated carbon layer is Activated carbon having an acidic functional group content of 2 mmol / g or more as measured by the following measurement method, and a specific surface area of ​​1800 to 2500 m² / g as measured by the following measurement method, Activated carbon having an acidic functional group content of 0.5 mmol / g or less as measured by the following measurement method, and a specific surface area of ​​1400 to 2000 m² / g as measured by the following measurement method, A water filter containing fibrillated binder fibers. (Method for measuring the amount of acidic functional groups in the activated carbon layer) A portion of the activated carbon layer is scraped off with a utility knife, and the scraped material is finely ground and classified until the particle size distribution is 2 mm or less. 1.0 g of this material is taken and used as the sample for measurement. The sample is added to 50 mL of a 0.1 mol / L sodium hydroxide aqueous solution as the alkaline solution, shaken for 30 minutes, and then allowed to stand at 25°C for 24 hours. After that, the solution is filtered using glass fiber filter paper, and 10 mL of the resulting filtrate is titrated with a 0.1 mol / L hydrochloric acid solution to determine the amount of acidic functional groups (mol / g). (Method for measuring the amount of acidic functional groups in activated carbon) Take 1.0 g of activated carbon and use it as the sample for measurement. Add the sample to 50 mL of 0.1 mol / L sodium hydroxide aqueous solution as the alkaline solution, shake for 30 minutes, and then let stand at 25°C for 24 hours. After that, filter using glass fiber filter paper, and 10 mL of the resulting filtrate is titrated with 0.1 mol / L hydrochloric acid solution to determine the amount of acidic functional groups (mol / g). (Method for measuring the specific surface area of ​​the activated carbon layer) 0.1 g of activated carbon is sampled, and using an automated gas adsorption measurement device, the activated carbon is cooled to 77.4 K (the boiling point of nitrogen), and nitrogen gas is introduced. The amount of nitrogen gas adsorbed, V [cc / g], is measured by volumetric method. At this time, the pressure P [hPa] of the introduced nitrogen gas is gradually increased, and the value obtained by dividing it by the saturated vapor pressure P0 [hPa] of the nitrogen gas is defined as the relative pressure P / P0. A nitrogen adsorption isotherm is created by plotting the amount of adsorption for each relative pressure. Based on the obtained nitrogen adsorption isotherm, the specific surface area is determined according to the BET method. (Method for measuring the specific surface area of ​​activated carbon) 0.1 g of activated carbon is taken, and using an automated gas adsorption measurement device, the activated carbon is cooled to 77.4 K (the boiling point of nitrogen), nitrogen gas is introduced, and the amount of nitrogen gas adsorbed, V [cc / g], is measured by the volumetric method. At this time, the pressure P [hPa] of the introduced nitrogen gas is gradually increased, and the value obtained by dividing by the saturated vapor pressure P0 [hPa] of the nitrogen gas is defined as the relative pressure P / P0. A nitrogen adsorption isotherm is created by plotting the amount of adsorption for each relative pressure. Based on the obtained nitrogen adsorption isotherm, the specific surface area is determined according to the BET method.

2. A cylindrical core, The activated carbon layer includes a cover layer laminated on the outer periphery of the activated carbon layer, The activated carbon layer is stacked on the outer periphery of the core. The ratio of the thickness of the activated carbon layer to the thickness of the water purification filter (thickness of the activated carbon layer / thickness of the water purification filter) is 0.7 to 0.

9. The water purification filter according to claim 1, wherein the pressure loss A measured by the following measurement method of the water purification filter is 0.010 to 0.040 MPa. (Method for measuring pressure loss A) The ends of the water purification filter are sealed by bonding foamed polyethylene caps using hot melt or silicone sealant, then filled into a resin housing, and pure water is passed through from the outside to the inside at a space velocity (SV) of 2781 / h. After maintaining this flow rate for 10 minutes, the pressure loss X1 (MPa) is measured using a Bourdon tube pressure gauge. Similarly, the pressure loss X2 (MPa) is measured in a blank sample with the water purification filter removed. The value obtained by subtracting the pressure loss X2 from the pressure loss X1 is defined as the water flow pressure loss A (MPa) through the water purification filter.

3. The combined residual chlorine filtered water volume of the aforementioned water filter, as measured by the following measurement method, is 20 to 100 m³. ３ And, The amount of free residual chlorine filtered water from the aforementioned water filter, as measured by the following measurement method, is 40 to 140 m³. ３ The water filter according to claim 1 or 2. (Method for measuring the amount of combined residual chlorine filtered water) The ends of the water purification filter are sealed by attaching foamed polyethylene caps using hot melt or silicone sealant, and then filled into a stainless steel housing. In accordance with Article 4 of the Water Supply Act of Japan, raw water is prepared by adding ammonium chloride and sodium hypochlorite to tap water that conforms to the water quality standards stipulated in the "Ministerial Ordinance Concerning Water Quality Standards (Ministry of Health, Labour and Welfare Ordinance No. 101 of May 30, 2003)" and stirring and mixing it to a combined residual chlorine concentration of 0.5 mg / L. The adjusted raw water is passed through the water purification filter from the outside to the inside at a flow rate of 2.0 L / min so that the space velocity (SV) is 370 / h. The concentration of combined residual chlorine is quantitatively measured using the DPD reagent spectrophotometric method before and after passing through the water purification filter, and the point at which the water concentration of combined residual chlorine in the effluent (filtered liquid) relative to the influent (adjusted raw water) is initially 20% or more is defined as the breakthrough point, and the total filtered water volume (m³) up to the breakthrough point is defined. ３ ) (Method for measuring the amount of free residual chlorine filtered water) The ends of the water purification filter are sealed by attaching 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 Act of Japan, the adjusted raw water is prepared by adding sodium hypochlorite to tap water that conforms to the water quality standards stipulated in the "Ministerial Ordinance Concerning Water Quality Standards (Ministry of Health, Labour and Welfare Ordinance No. 101 of May 30, 2003)" so that the free residual chlorine concentration is 2.0 ± 0.2 mg / L. The adjusted raw water is passed from the outside to the inside of the water purification filter so that the space velocity (SV) is 741 / h. The concentration of free residual chlorine is quantitatively measured using the DPD reagent spectrophotometric method before and after passing through the water purification filter, and the point at which the water concentration of free residual chlorine in the effluent (filtered liquid) becomes 20% or more relative to the influent (adjusted raw water) is defined as the breakthrough point, and the total filtered water volume (m³) up to the breakthrough point is defined. ３ )

4. A cylindrical core, An activated carbon layer is stacked on the outer circumference of the cylindrical core, A water purification filter comprising a cover layer laminated on the outer periphery 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 the activated carbon layer / thickness of the water purification filter) is 0.7 to 0.

9. The pressure loss A of the aforementioned water purification filter, as measured by the following measurement method, is 0.010 to 0.040 MPa. The specific surface area of ​​the activated carbon layer, as measured by the following measurement method, is 1600 to 1900 m² / g. A method for manufacturing a water purification filter, wherein the amount of acidic functional groups in the activated carbon layer, as measured by the following measurement method, is 0.8 to 3.0 mmol / g, As raw materials constituting the activated carbon layer, Activated carbon having an acidic functional group content of 2 mmol / g or more as measured by the following measurement method, and a specific surface area of ​​1800 to 2500 m² / g as measured by the following measurement method, Activated carbon having an acidic functional group content of 0.5 mmol / g or less as measured by the following measurement method, and a specific surface area of ​​1400 to 2000 m² / g as measured by the following measurement method, A method for manufacturing a water purification filter, comprising the steps of preparing fibrillated binder fibers. (Method for measuring the amount of acidic functional groups in the activated carbon layer) A portion of the activated carbon layer is scraped off with a utility knife, and the scraped material is finely ground and classified until the particle size distribution is 2 mm or less. 1.0 g of this material is taken and used as the sample for measurement. The sample is added to 50 mL of a 0.1 mol / L sodium hydroxide aqueous solution as the alkaline solution, shaken for 30 minutes, and then allowed to stand at 25°C for 24 hours. After that, the solution is filtered using glass fiber filter paper, and 10 mL of the resulting filtrate is titrated with a 0.1 mol / L hydrochloric acid solution to determine the amount of acidic functional groups (mol / g). (Method for measuring the amount of acidic functional groups in activated carbon) Take 1.0 g of activated carbon and use it as the sample for measurement. Add the sample to 50 mL of 0.1 mol / L sodium hydroxide aqueous solution as the alkaline solution, shake for 30 minutes, and then let stand at 25°C for 24 hours. After that, filter using glass fiber filter paper, and 10 mL of the resulting filtrate is titrated with 0.1 mol / L hydrochloric acid solution to determine the amount of acidic functional groups (mol / g). (Method for measuring the specific surface area of ​​the activated carbon layer) 0.1 g of activated carbon is sampled, and using an automated gas adsorption measurement device, the activated carbon is cooled to 77.4 K (the boiling point of nitrogen), and nitrogen gas is introduced. The amount of nitrogen gas adsorbed, V [cc / g], is measured by volumetric method. At this time, the pressure P [hPa] of the introduced nitrogen gas is gradually increased, and the value obtained by dividing it by the saturated vapor pressure P0 [hPa] of the nitrogen gas is defined as the relative pressure P / P0. A nitrogen adsorption isotherm is created by plotting the amount of adsorption for each relative pressure. Based on the obtained nitrogen adsorption isotherm, the specific surface area is determined according to the BET method. (Method for measuring the specific surface area of ​​activated carbon) 0.1 g of activated carbon is taken, and using an automated gas adsorption measurement device, the activated carbon is cooled to 77.4 K (the boiling point of nitrogen), nitrogen gas is introduced, and the amount of nitrogen gas adsorbed, V [cc / g], is measured by the volumetric method. At this time, the pressure P [hPa] of the introduced nitrogen gas is gradually increased, and the value obtained by dividing by the saturated vapor pressure P0 [hPa] of the nitrogen gas is defined as the relative pressure P / P0. A nitrogen adsorption isotherm is created by plotting the amount of adsorption for each relative pressure. Based on the obtained nitrogen adsorption isotherm, the specific surface area is determined according to the BET method. (Method for measuring pressure loss A) The ends of the water purification filter are sealed by bonding foamed polyethylene caps using hot melt or silicone sealant, then filled into a resin housing, and pure water is passed through from the outside to the inside at a space velocity (SV) of 2781 / h. After maintaining this flow rate for 10 minutes, the pressure loss X1 (MPa) is measured using a Bourdon tube pressure gauge. Similarly, the pressure loss X2 (MPa) is measured in a blank sample with the water purification filter removed. The value obtained by subtracting the pressure loss X2 from the pressure loss X1 is defined as the water flow pressure loss A (MPa) through the water purification filter.

Images