Porous membrane roll, substrate for filter, and cartridge filter

Abstract

To provide a porous membrane roll in which defect is suppressed from occurring.SOLUTION: A porous membrane roll comprises a porous membrane having graft chains, and a core material around which a porous membrane having graft chains is wound, wherein the porous membrane having graft chains satisfies the following equation (1) and has a Gurley value of 0.5 seconds / 100 mL to 500 seconds / 100 mL. (Standard deviation of the graft rate of the porous membrane having graft chains) / (Average graft rate of the porous membrane having graft chains)×100≤15.0 (1).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a porous membrane roll, a filter substrate, and a cartridge filter. [Background technology]

[0002] Graft polymerization is one of the technologies for creating functional polymer materials. This is a very useful technique that can impart desired functionality to a polymer material (base material) while maintaining its shape and properties.

[0003] For example, Patent Document 1 describes a filter cartridge that is characterized by being composed of a fiber material in which ion exchange groups and / or chelating groups are introduced into an organic polymer fiber substrate having an average fiber diameter of 0.1 μm to 20 μm and an average pore diameter of 1 μm to 20 μm. Patent Document 2 describes an ion exchange membrane comprising a porous polymer support and an organic portion in which an ion exchange group is covalently bonded to the organic portion, in which the organic portion is grafted to the porous polymer support. Patent Document 3 describes a polyethylene porous substrate having a graft chain fixed to the polyethylene porous substrate and having a functional group, and a basis weight of 30 to 120 g / m 2 The metal-removing filter medium is characterized in that the graft chain has a graft rate of 40 to 150%, and the functional group is selected from a quaternary ammonium group, a primary, secondary or tertiary amino group, an iminodiacetic acid group, a phosphate group, and an iminodiethanol group. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-251118 [Patent Document 2] Special Publication No. 2001-515113 [Patent Document 3] International Publication No. 2022 / 176355 Summary of the Invention [Problem to be solved by the invention]

[0005] One known method for introducing functional groups into polymer chains is to directly introduce the functional groups into the polymer by graft polymerization. However, when a hydrophobic polymer is used as the substrate, it is difficult to react with a hydrophilic monomer. Therefore, a known method is to first polymerize a reactive monomer onto the hydrophobic polymer to form a graft chain, and then react a compound containing the functional group to introduce the functional group. Graft polymerization onto a polymer substrate generally results in changes in mass and volume, and similarly, the introduction of functional groups also results in changes in mass and volume. Furthermore, while this is not a problem when using porous membranes made of fibers, specifically hollow fibers, nonwoven fabrics, and knitted fabrics, when using polymer porous membranes with a porous structure, the introduction of functional groups tends to cause embrittlement. Needless to say, from an industrial and productivity perspective, continuous production is preferable. Patent Document 1 uses a polyethylene nonwoven fabric as the porous membrane, but it suffers from issues such as poor uniformity (thickness, basis weight, and gaps between fibers) specific to nonwoven fabrics and a small contact area. In addition, Patent Document 2 uses a polyethylene porous membrane roll as the porous membrane, but γ-ray irradiation is carried out in a reaction vessel for 60 hours, and roll-to-roll graft polymerization is not carried out, resulting in poor productivity. Patent Document 3 describes that the porous membrane may be produced by continuously processing a roll of polyethylene porous membrane, but there is no description of a porous membrane wound body as a continuous body, and it is impossible to stably produce a continuous body.

[0006] An object of one embodiment of the present disclosure is to provide a porous membrane roll in which the occurrence of defects is suppressed. Another problem to be solved by another embodiment of the present disclosure is to provide a filter substrate and a cartridge filter using the porous membrane wound body. [Means for solving the problem]

[0007] The present disclosure includes the following aspects. <1> A porous membrane having graft chains and a core material around which the porous membrane having graft chains is wound, A porous membrane roll, in which the porous membrane having graft chains satisfies the following formula (1) and has a Gurley value of 0.5 seconds / 100 mL to 1000 seconds / 100 mL. (Standard deviation of grafting rate of porous membrane having graft chains) / (Average grafting rate of porous membrane having graft chains)×100≦15.0 … (1) <2> The porous membrane having graft chains is a polyethylene porous membrane having graft chains. <1> The porous membrane roll according to claim 1. <3> The width of the porous membrane having graft chains is 100 mm to 1600 mm. <1> or <2> The porous membrane roll according to claim 1. <4> The roll length of the porous membrane having graft chains is 10 m to 5000 m. <1> ~ <3> 10. The porous membrane roll according to any one of the above items. <5> The graft ratio of the porous membrane having graft chains is 10% to 300%. <1> ~ <4> 10. The porous membrane roll according to any one of the above items. <6> The graft chain contains at least one functional group selected from the group consisting of an ion exchange group and a chelate exchange group. <1> ~ <5> 10. The porous membrane roll according to any one of the above items. <7> <1> ~ <6> 1. A filter substrate comprising a porous membrane having graft chains in the porous membrane roll according to any one of 1 to 8. <8> A filter substrate comprising a porous membrane having graft chains that satisfy the following formula (1) and have a Gurley value of 0.5 seconds / 100 mL to 1000 seconds / 100 mL: (Standard deviation of grafting rate of porous membrane having graft chains) / (Average grafting rate of porous membrane having graft chains)×100≦15.0 … (1) <9> <7> or <8> A cartridge filter comprising the filter substrate according to claim 1. [Effects of the Invention]

[0008] According to one embodiment of the present disclosure, a porous membrane roll in which the occurrence of defects is suppressed is provided. According to another embodiment of the present disclosure, there are provided a filter substrate and a cartridge filter using the porous membrane wound body. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present disclosure will be described in detail below. The following description of the components may be based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments. In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in an example. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

[0010] In the present disclosure, when a plurality of substances corresponding to each component are present in the composition, the amount of each component in the composition means the total amount of the plurality of substances present in the composition, unless otherwise specified. In the present disclosure, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved. In the present disclosure, the "width direction of the porous membrane" means a direction perpendicular to the longitudinal direction of the porous membrane.

[0011] [Porous membrane roll] The porous membrane roll according to the present disclosure comprises a porous membrane having graft chains and a core material around which the porous membrane having graft chains is wound, wherein the graft-polymerized porous membrane satisfies the following formula (1) and has a Gurley value of 0.5 seconds / 100 mL to 1000 seconds / 100 mL: (Standard deviation of grafting rate of porous membrane having graft chains) / (Average grafting rate of porous membrane having graft chains)×100≦15.0 … (1)

[0012] The porous membrane roll according to the present disclosure satisfies the above formula (1), and therefore has excellent uniformity of the porous membrane, and the occurrence of defects is suppressed.

[0013] The porous membrane roll according to the present disclosure will be described in detail below.

[0014] <Porous membrane with grafted chains> The porous membrane roll according to the present disclosure includes a porous membrane having graft chains. A porous membrane having graft chains can be produced, for example, by subjecting a porous membrane to graft polymerization.

[0015] (porous membrane) In the present disclosure, a porous membrane refers to a membrane that has a large number of micropores inside, has a structure in which the micropores are connected, and allows gas or liquid to pass from one surface to the other.

[0016] The porous membrane preferably contains a resin, and from the viewpoint of having graft chains, it preferably contains a resin that generates reactive species (radicals). The resin that generates reactive species (radicals) is not particularly limited as long as it can generate reactive species (radicals), and examples thereof include polyolefin resins, halogenated polyolefin resins, fluorine-based resins (polytetrafluoroethylene, polychlorotrifluoroethylene, ethylene fluoride, polyhexafluoropropylene, polyvinylidene fluoride, etc.), polyvinyl alcohol resins, polyvinyl alcohol-ethylene copolymer resins, polyvinyl chloride resins, polyester resins (polyethylene terephthalate, etc.), polyamide resins (nylon, etc.), polyacrylate resins, polysulfone resins, polyethersulfone resins, polyarylsulfonamide resins, cellulose resins, cellulose ester resins, polycarbonate resins, polyimide resins, ethylene-tetrafluoroethylene resins, and ethylene-vinyl alcohol resins. These resins may be homopolymers or copolymers, or multiple resins may be used in combination.

[0017] Examples of polyolefins include homopolymers (i.e., polyethylene, polypropylene, polybutylene, polymethylpentene, etc.) or copolymers of ethylene, propylene, butylene, methylpentene, etc., and mixtures thereof. Among these, polyethylene is preferred as the polyolefin, and high-density polyethylene or a mixture of high-density polyethylene and ultra-high-molecular-weight polyethylene is more preferred.

[0018] The porous membrane is preferably formed using two or more polyolefins that differ from each other in at least one of the type of monomer, degree of polymerization, degree of branching, crystallinity, stretchability, and molecular orientation. By using two or more polyolefins, a network structure is easily formed in the porous membrane by fibrillation during stretching.

[0019] The weight average molecular weight (Mw) of the polyolefin contained in the polyolefin porous membrane is preferably 500,000 to 5,000,000. When the Mw of the polyolefin is 500,000 or more, the porous membrane can be imparted with sufficient mechanical properties. When the Mw of the polyolefin is 5,000,000 or less, the porous membrane can be easily formed. The weight average molecular weight of the entire polyolefin constituting the polyolefin porous membrane is preferably 800,000 or more, more preferably 850,000 or more, even more preferably 900,000 or more, even more preferably 950,000 or more, and particularly preferably 970,000 or more, from the viewpoint of densifying the polyolefin porous membrane. From the viewpoint of increasing the porosity of the porous membrane, the weight-average molecular weight of the polyethylene contained in the polyolefin porous membrane is preferably 4.9 million or less, more preferably 4.8 million or less, and even more preferably 4.7 million or less. When the polyethylene porous membrane contains two or more types of polyethylene, it is preferable that the weight-average molecular weight of the mixture of two or more types of polyethylene is in the above range.

[0020] In the present disclosure, the weight-average molecular weight is determined by dissolving a polyolefin porous membrane in o-dichlorobenzene under heating and measuring the weight-average molecular weight by gel permeation chromatography (system: Alliance GPC 2000 manufactured by Waters, columns: GMH6-HT and GMH6-HTL) at a column temperature of 135°C and a flow rate of 1.0 mL / min. Monodisperse polystyrene (Tosoh Corporation) is used to calibrate the molecular weight.

[0021] The polyolefin constituting the polyolefin porous film is preferably polyethylene. That is, the polyolefin porous film is preferably a polyethylene porous film. In the present disclosure, the polyethylene porous film means a porous film in which polyethylene is the resin that accounts for the largest mass proportion of the total resin.

[0022] In the polyethylene porous film, polyethylene preferably accounts for 90% by mass or more of the polyethylene porous film, more preferably 95% by mass or more, and even more preferably 99% by mass or more. The polyethylene porous film may contain an organic filler, an inorganic filler, a surfactant, etc., within a range that does not affect the effects of the present disclosure.

[0023] The polyethylene porous membrane is preferably a porous membrane formed using two or more polyethylenes that differ from each other in at least one of degree of polymerization, degree of branching, crystallinity, stretchability, and molecular orientation. By using two or more polyethylenes, a network structure is easily formed in the polyethylene porous membrane by fibrillation during stretching.

[0024] Examples of polyethylene constituting the porous polyethylene film include ultra-high molecular weight polyethylene, high density polyethylene, and a mixture of ultra-high molecular weight polyethylene and high density polyethylene.

[0025] From the viewpoint of densifying the polyethylene porous membrane, the polyethylene porous membrane preferably contains ultra-high molecular weight polyethylene having a weight-average molecular weight of 900,000 or more. The polyethylene porous membrane preferably contains 5% by mass to 90% by mass, more preferably 10% by mass to 88% by mass, and even more preferably 15% by mass to 85% by mass of ultra-high molecular weight polyethylene having a weight-average molecular weight of 900,000 or more.

[0026] The polyethylene porous membrane is made of ultra-high molecular weight polyethylene with a weight-average molecular weight of 900,000 and polyethylene with a weight-average molecular weight of 200,000 to 800,000 and a density of 0.92 g / cm. 3 ~0.98g / cm 3 The mass ratio of the two polyethylenes contained in the polyethylene microporous membrane (ultra-high molecular weight polyethylene:high density polyethylene) is preferably 5:95 to 95:5, more preferably 10:90 to 90:10, and even more preferably 15:85 to 85:15.

[0027] The polyethylene porous membrane can be produced, for example, by the following method. The method for producing the porous polyethylene film is preferably a method comprising the following steps (1) to (5): The polyethylene used as the raw material is as described above.

[0028] (1) Preparation of polyethylene solution A polyethylene solution is prepared by dissolving polyethylene in a solvent. Examples of the solvent include paraffin, liquid paraffin, paraffin oil, mineral oil, castor oil, tetralin, ethylene glycol, glycerin, decalin, toluene, xylene, diethyltriamine, ethyldiamine, dimethyl sulfoxide, and hexane. In this case, the solvent may be used alone or in combination of two or more. Among the solvents, volatile solvents include solvents with a boiling point of less than 300°C under atmospheric pressure, such as decalin, toluene, xylene, diethyltriamine, ethyldiamine, dimethyl sulfoxide, hexane, tetralin, ethylene glycol, glycerin, etc. Non-volatile solvents include solvents with a boiling point of 300°C or higher under atmospheric pressure, such as paraffin, liquid paraffin, paraffin oil, mineral oil, castor oil, etc. A mixed solvent may be a combination of decalin and liquid paraffin. When liquid paraffin is used as a solvent, the average pore size of the polyethylene porous membrane tends to be smaller. When decalin is used alone as a solvent, the average pore size of the polyethylene porous membrane tends to be larger than when liquid paraffin is used in combination. However, the average pore size can also be controlled by other process parameters, and this is not limited to this.

[0029] The polyethylene concentration of the polyethylene solution is preferably 1% by mass to 45% by mass, more preferably 10% by mass to 40% by mass. When the polyethylene concentration is 1% by mass or more, the gel composition obtained by cooling gelation can be maintained without being significantly swollen by the solvent, making it less likely to deform and easier to handle. On the other hand, when the polyethylene concentration is 45% by mass or less, the pressure during extrusion can be suppressed, making it possible to maintain the discharge rate and resulting in excellent productivity.

[0030] (2) Extrusion of polyethylene solution The prepared polyethylene solution is kneaded in a single-screw extruder or twin-screw extruder and extruded through a T-die, cross-hanger die, or I-die at a temperature above the melting point and below the melting point + 70° C. In this case, a twin-screw extruder is preferably used. The polyolefin solution extruded from the die is then passed through a chill roll or a cooling bath to form a gel composition. At this time, it is preferable to rapidly cool the polyethylene solution to a temperature below its gelling temperature to cause gelation.

[0031] (3) Desolvent treatment Next, the solvent is removed from the gel composition. If a volatile solvent is used in preparing the polyethylene solution, the solvent can be removed from the gel composition by evaporation by heating or the like, which also serves as a preheating step. If a non-volatile solvent is used in preparing the polyethylene solution, the solvent can be removed by squeezing it out under pressure, for example. It is not necessary to completely remove the solvent.

[0032] (4) Stretching of the gel composition Following the solvent removal treatment, the gel composition is stretched. A relaxation treatment may be performed before the stretching treatment. In the stretching treatment, the gel composition is heated and stretched uniaxially or biaxially at a predetermined magnification by a conventional tenter method, roll method, rolling method, or a combination of these methods. Biaxial stretching may be performed simultaneously or sequentially. Multi-stage longitudinal stretching or three- or four-stage stretching may also be used. The stretching temperature is preferably 80°C or higher and lower than the melting point of the polyethylene used in production, more preferably 90°C to 130°C. If the heating temperature is lower than the melting point, the gel composition is less likely to dissolve, allowing for good stretching. If the heating temperature is 80°C or higher, the gel composition is sufficiently softened, allowing for high-magnification stretching without film rupture. The stretching ratio varies depending on the thickness of the raw film, but is preferably at least 2 times or more, and more preferably 4 to 20 times in one axial direction. After stretching, heat setting is carried out as necessary to provide thermal dimensional stability.

[0033] (5) Extraction and removal of solvent The stretched gel composition is immersed in an extraction solvent to extract the solvent, particularly the nonvolatile solvent. Examples of the extraction solvent include easily volatile solvents such as hydrocarbons (e.g., pentane, hexane, heptane, cyclohexane, decalin, tetralin), chlorinated hydrocarbons (e.g., methylene chloride, carbon tetrachloride, methylene chloride), fluorinated hydrocarbons (e.g., trifluoroethane), and ethers (e.g., diethyl ether, dioxane). These solvents are appropriately selected depending on the solvent (e.g., the nonvolatile solvent) used in preparing the polyethylene solution, and can be used alone or in combination. The solvent extraction removes the solvent in the polyethylene porous membrane to less than 1% by mass.

[0034] (Physical properties of porous membrane) From the viewpoint of increasing the strength of the porous membrane, the average thickness of the porous membrane is preferably 0.01 μm or more, more preferably 3 μm or more, even more preferably 3.5 μm or more, particularly preferably 4 μm or more, and most preferably 5 μm or more. From the viewpoint of maintaining liquid permeability, the average thickness of the porous membrane is preferably 500 μm or less, more preferably 400 μm or less, even more preferably 350 μm or less, particularly preferably 300 μm or less, and most preferably 280 μm or less. The average thickness of the porous membrane is preferably 0.01 μm to 500 μm, more preferably 3 μm to 400 μm, even more preferably 3.5 μm to 350 μm, particularly preferably 4 μm to 300 μm, and most preferably 5 to 280 μm.

[0035] From the viewpoint of mechanical strength, the Gurley value of the porous membrane is preferably 0.1 sec / 100 mL or more, more preferably 0.2 sec / 100 mL or more, even more preferably 0.5 sec / 100 mL or more, and particularly preferably 1 sec / 100 mL or more. From the viewpoint of liquid permeability, the Gurley value of the porous membrane is preferably 500 seconds / 100 mL or less, more preferably 450 seconds / 100 mL or less, even more preferably 400 seconds / 100 mL or less, and particularly preferably 300 seconds / 100 mL or less. The Gurley value of the porous membrane is preferably 0.1 sec / 100 mL to 500 sec / 100 mL, more preferably 0.2 sec / 100 mL to 450 sec / 100 mL, further preferably 0.5 sec / 100 mL to 400 sec / 100 mL, and particularly preferably 1 sec / 100 mL to 300 sec / 100 mL. The Gurley value of the porous membrane is a value measured in accordance with JIS P8117:2009.

[0036] The basis weight of the porous membrane is set at 0.5 g / m from the viewpoint of mechanical strength. 2 More than 0.7g / m is preferable. 2 More preferably, 1.0 g / m or more 2 More preferably, 1.5 g / m 2 The above is particularly preferred. The basis weight of the porous membrane is set to 50.0 g / m from the viewpoint of handling. 2 Less than 45.0 g / m 2 Less than 40.0 g / m is more preferable. 2 More preferably, 30.0 g / m or less 2 The following are particularly preferred: The weight of the porous membrane is 0.5g / m 2 ~50.0g / m 2 is preferred, and 0.7 g / m 2 ~45.0g / m 2 More preferably, 1.0 g / m 2 ~40.0g / m 2 More preferably, 1.5 g / m 2 ~30.0g / m 2 The following are particularly preferred: The basis weight of the porous membrane can be determined by measuring the weight of a sample of a certain size and dividing the weight by the area.

[0037] (graft chain) The method of graft polymerization to the porous membrane is not particularly limited, and examples thereof include a method in which reactive species (radicals) are generated, and then the resulting product is brought into contact with a monomer having a vinyl group, and polymerization is carried out using the radicals as the reaction initiation point.

[0038] Examples of radical generating means include methods using chemical initiators, plasma treatment, visible light, ultraviolet light, far ultraviolet light, and radiation (electron beams, X-rays). Among these, the method using radiation is preferred from the viewpoints that graft chains can be introduced into the interior of the porous membrane, there is no contamination such as a reaction initiator, and a porous membrane of any shape can be used. Examples of radiation include α-rays, β-rays, γ-rays, electron beams, and ultraviolet rays. Among these, γ-rays and electron beams are suitable. Radiation-induced graft polymerization methods include pre-irradiation graft polymerization, in which a grafting substrate is first irradiated with radiation and then contacted with a polymerizable monomer (graft monomer) to allow reaction, and simultaneous irradiation graft polymerization, in which the grafting substrate and polymerizable monomer are irradiated with radiation in the presence of both. Either method may be used. The method for contacting the polymerizable monomer with the grafting substrate is not particularly limited. Examples include liquid-phase graft polymerization, in which polymerization is carried out while the grafting substrate is immersed in a polymerizable monomer solution; gas-phase graft polymerization, in which polymerization is carried out by contacting the grafting substrate with vapor of the polymerizable monomer; and impregnation-gas-phase graft polymerization, in which the grafting substrate is immersed in a polymerizable monomer solution and then removed from the polymerizable monomer solution to allow reaction in the gas phase. Any of these methods may be used. The dose of the electron beam is preferably 10 kGy to 500 kGy, and more preferably 20 kGy to 500 kGy.

[0039] After the porous membrane is immersed in the polymerizable monomer, it is preferable to control the impregnation amount in the width direction of the porous membrane so that it is uniform.The means for controlling the impregnation amount so that it is uniform is not particularly limited, but it is preferable to control it by, for example, the polymerizable monomer concentration, the shape of the porous membrane conveying roll, the porous membrane conveying speed, the porous membrane conveying tension, the nip, etc.

[0040] The polymerizable monomer is preferably a radical polymerizable monomer, more preferably a monomer having a vinyl group. As the polymerizable monomer, for example, either a method of graft polymerizing a polymerizable monomer having an ion exchange group and / or a chelating group, or a method of graft polymerizing a polymerizable monomer that does not itself have an ion exchange group and / or a chelating group but has a functional group that can be converted into an ion exchange group and / or a chelating group onto a porous membrane, and then converting the functional group on the graft chain into an ion exchange group and / or a chelating group can be used. Examples of polymerizable monomers having an ion exchange group include polymerizable monomers having a sulfonic acid group such as styrene sulfonic acid, vinyl sulfonic acid, and their sodium salts and ammonium salts; polymerizable monomers having a carboxy group such as acrylic acid and methacrylic acid; polymerizable monomers having an amine ion exchange group such as vinylbenzyltrimethylammonium chloride (VBTAC), dimethylaminoethyl methacrylate (DMAEMA), dimethylaminopropylacrylamide (DMAPAA), etc.; and polymerizable monomers having an amine ion exchange group such as acrylamide, hydroxyethyl methacrylate, N-vinylacetamide, N-vinylpyrrolidone, etc. Furthermore, examples of polymerizable monomers that do not themselves have an ion exchange group and / or a chelating group but have a functional group that can be converted into an ion exchange group and / or a chelating group include glycidyl methacrylate, styrene, acrylonitrile, acrolein, and chloromethylstyrene.

[0041] For example, after graft polymerizing glycidyl methacrylate onto a porous membrane, iminodiacetic acid groups, which are chelate exchange groups, can be introduced onto the graft chains by reacting with a sodium iminodiacetate solution.Furthermore, after graft polymerizing styrene onto a porous membrane, sulfonic acid groups, which are strongly acidic cation exchange groups, can be introduced onto the graft chains by sulfonating the membrane with sulfuric acid or chlorosulfonic acid. The selection of the polymerizable monomer is not particularly limited. In the case of a highly hydrophobic resin, however, a method is preferred in which a polymerizable monomer which does not itself have an ion exchange group and / or a chelating group but has a functional group which can be converted into these groups is graft-polymerized onto a porous membrane, and then the functional group on the graft chain is converted into an ion exchange group and / or a chelating group. When a polyethylene porous membrane is used as the porous membrane, a method is preferred in which glycidyl methacrylate and / or styrene are graft polymerized, and then the functional groups on the graft chains are exchanged with ion exchange groups and / or chelating groups.

[0042] The reaction temperature in the graft polymerization can be, for example, from −20° C. to the decomposition temperature of the resin constituting the porous membrane, but is preferably 20° C. to 120° C., more preferably 25° C. to 80° C., and particularly preferably 30° C. to 70° C. The reaction time varies depending on, for example, how the porous membrane and the polymerizable monomer are combined, but is preferably 1 minute to 24 hours, more preferably 5 minutes to 12 hours, and particularly preferably 10 minutes to 2 hours.

[0043] The graft chain preferably contains at least one functional group selected from the group consisting of an ion exchange group and a chelate exchange group.

[0044] The ion exchange group may be a cation exchange group or an anion exchange group. Examples of the cation exchange group include strongly acidic cation exchange groups such as sulfonic acid groups; and weakly acidic cation exchange groups such as phosphate groups and carboxy groups. Examples of anion exchange groups include strongly basic anion exchange groups such as quaternary ammonium groups, and weakly basic anion exchange groups such as primary, secondary, or tertiary amino groups.

[0045] Examples of the chelating group include functional groups derived from iminodiacetic acid and its sodium salt, functional groups derived from various amino acid groups such as glutamic acid, aspartic acid, lysine, and proline, functional groups derived from iminodiethanol, functional groups derived from ethylenediaminetriacetic acid, dithiocarbamic acid groups, and thiourea groups.

[0046] From the viewpoint of functionality, the amount of the functional group introduced is preferably 10 mmol / sqm to 1,000 mmol / sqm.

[0047] When the functional group is an iminodiacetic acid group, the amount of the functional group introduced is measured by the following method.

[0048] The porous membrane with grafted chains is cut into a 10cm x 10cm sample. The sample is immersed in a 7% by mass aqueous solution of hydrochloric acid and stirred for 30 minutes. It is then washed with pure water until the wash water becomes neutral. The sample is placed in 50mL of a 0.05mol / L aqueous solution of sodium hydroxide to convert the H-form to the Na-form. 10mL of the resulting liquid is taken and subjected to neutralization titration using 0.05mol / L hydrochloric acid. The capacity of weak acid groups in the sample is calculated from the amount of sodium hydroxide consumed, and the amount introduced is calculated taking into account the number of functional groups.

[0049] (Physical Properties) The porous membrane having grafted chains satisfies formula (1). (Standard deviation of grafting rate of porous membrane having graft chains) / (Average grafting rate of porous membrane having graft chains)×100≦15.0 … (1)

[0050] The graft ratio refers to the mass ratio of graft chains formed on the surface of the porous membrane by graft polymerization to the porous membrane before graft polymerization (= mass of graft chains / mass of porous membrane × 100; mass %).

[0051] In the present disclosure, the graft ratio is calculated using the basis weight before and after graft polymerization using the following formula. (Basis weight after graft polymerization - Basis weight before graft polymerization) / Basis weight before graft polymerization x 100 Specifically, 10 cm x 10 cm samples are prepared by cutting the surface layer (within 2 m from the surface layer of the porous membrane roll) and the inner layer (within 2 m from the core) of the graft-polymerized porous membrane roll, and at least four samples are taken from each surface, for a total of eight samples, and the mass of each sample is measured. The measured mass is multiplied by 100 to calculate the basis weight after graft polymerization. The graft rate is calculated using the above formula from the obtained basis weight after polymerization and the basis weight before graft polymerization, and the arithmetic mean value and arithmetic standard deviation of at least four samples from each surface, for a total of eight samples, are calculated to obtain the average graft rate and the standard deviation of the graft rate. In addition, after confirming the correlation between the characteristic peak of the monomer polymerized by graft polymerization and the graft ratio calculated from the weight before and after graft polymerization in FTIR analysis, it can also be calculated from the characteristic peak of FTIR. Specifically, in the case of glycidyl methacrylate, the characteristic peak of the carbonyl group (1730 cm -1 It is possible to correlate the area of ​​the polymer (near the center) with the grafting rate. In addition, the carbonyl group at 1730cm -1 and 1470 cm for polyethylene -1 It is also possible to obtain a correlation with the graft ratio by measuring the peak imaging of each of the above and normalizing by dividing the carbonyl group peak intensity by the polyethylene peak intensity.

[0052] When the value of the left side of the formula (1) is 15.0 or less, the thickness of the porous membrane having graft chains is uniform in the width direction, and the occurrence of defects in the porous membrane roll is suppressed. The above value is preferably 14.5 or less, and more preferably 14.0 or less.

[0053] The graft ratio of the porous membrane having graft chains is preferably 10% to 300%, more preferably 20% to 200%. The graft ratio refers to the mass ratio of the graft chains formed on the surface of the porous membrane by graft polymerization to the porous membrane before graft polymerization (=mass of graft chains / mass of porous membrane × 100; mass %).

[0054] When the grafting rate is 10% or more, functionality can be imparted. When the graft ratio is 300% or less, the strength is maintained and the polymer is less likely to break.

[0055] The porous membrane having graft chains has a Gurley value of 0.5 seconds / 100 mL to 1000 seconds / 100 mL, and preferably 1 second / 100 mL to 500 seconds / 100 mL in terms of liquid permeability and / or breathability. A Gurley value of 0.5 seconds / 100 mL to 1000 seconds / 100 mL indicates that the porous membrane has a large number of micropores inside.

[0056] In this disclosure, the Gurley value is measured using a Gurley densometer manufactured by Toyo Seiki Seisaku-sho in accordance with JIS P8117: 2009. The measurement is performed by measuring the time it takes for 200 mL of air to pass through a 28.6 mm diameter sample, and then halving that time to convert it to a value per 100 mL.

[0057] The thickness of the porous membrane having graft chains is measured using a contact-type film thickness meter (Mitutoyo Corporation, ABS Digimatic Indicator, Model ID: ID-S112X). Specifically, measurements are taken at 18 points in each of the outer and inner layers of the porous membrane roll in the width direction. The outer layer refers to the portion within 2 m from the outer end of the porous membrane roll. The inner layer refers to the portion within 2 m from the inner end of the porous membrane roll. The arithmetic mean value of the 36 points in total is taken as the average film thickness. A cylindrical terminal with a bottom diameter of 6.5 mm is used as the contact terminal.

[0058] The width of the porous membrane having graft chains is preferably 100 mm to 1600 mm, more preferably 200 mm to 1500 mm. In the present disclosure, the width of the porous membrane having grafted chains is measured using a JIS Class 1 straight scale measurement.

[0059] The roll length of the porous membrane having graft chains is preferably 10 m to 5000 m, more preferably 20 m to 3000 m. In the present disclosure, the roll length of the porous membrane having grafted chains is measured using a roll length counter.

[0060] The basis weight of the porous membrane with graft chains is 1 g / m 2 ~200g / m 2 It is preferable that the density is 1.5 g / m 2 ~100g / m 2 It is more preferable that: In the present disclosure, the basis weight of a porous membrane having graft chains is measured by the following method. The outer layer and inner layer of the porous membrane roll are cut to prepare 10cm x 10cm samples. The outer layer refers to the portion within 2m from the outer end of the porous membrane roll. The inner layer refers to the portion within 2m from the inner end of the porous membrane roll. The arithmetic mean value of four points on each sample, for a total of eight points, is calculated. The basis weight of the sample is the value obtained by multiplying the measured mass of the sample by 100.

[0061] <Core material> The porous membrane roll according to the present disclosure includes a core material around which a porous membrane having graft chains is wound.

[0062] The shape of the core material is not particularly limited, and a cylindrical shape such as a prismatic shape, a cylindrical shape, or an elliptical cylindrical shape is suitable, and a cylindrical shape is preferable. The material of the core is not particularly limited, but metal, resin, etc. are suitable, and resin is preferred.

[0063] The porous membrane roll according to the present disclosure may include a configuration other than the porous membrane having graft chains and the core material. For example, the porous membrane roll according to the present disclosure may include an interleaf between the porous membranes having graft chains. In particular, it is preferable to include an interleaf when the graft chains contain at least one functional group selected from the group consisting of an ion exchange group and a chelate exchange group. The interleaf is preferably a porous film that does not react with the functional group.

[0064] [Filter substrate] The filter substrate according to the present disclosure includes the porous membrane having graft chains in the porous membrane roll. That is, the filter substrate according to the present disclosure includes a porous membrane having graft chains that satisfy the following formula (1) and have a Gurley value of 0.5 seconds / 100 mL to 1000 seconds / 100 mL. (Standard deviation of grafting rate of porous membrane having graft chains) / (Average grafting rate of porous membrane having graft chains)×100≦15.0 … (1) The details of the porous membrane having graft chains are as described above.

[0065] The filter substrate is used as a filter medium for a filter. For example, a porous membrane having grafted chains can be pleated to form a filter substrate.

[0066] [Cartridge filter] The cartridge filter according to the present disclosure includes the filter substrate. A cartridge filter according to the present disclosure includes, for example, the filter substrate and a cylindrical housing, with the filter substrate housed inside the housing. The cartridge filter according to the present disclosure is of a cartridge type and is detachably attachable to, for example, a filtering device.

[0067] The cartridge filter according to the present disclosure is suitable for removing fine particles having a particle size of about several nanometers from a liquid to be treated. The cartridge filter according to the present disclosure can be used, for example, in the manufacturing process of semiconductors and displays. [Example]

[0068] The present disclosure will be specifically described below with reference to examples, but the present disclosure is not limited to these examples in any way.

[0069] [Preparation of porous membrane] 15 parts by mass of ultra-high molecular weight polyethylene (UHMWPE) with a weight average molecular weight (Mw) of 4.6 million and 15 parts by mass of polyethylene terephthalate (PE) with a weight average molecular weight (Mw) of 560,000 and a density of 950 kg / m 3 A polyethylene composition was prepared by mixing 85 parts by mass of high-density polyethylene (HDPE) containing 1,000 parts of polyethylene glycol fluoride (PEF) and 85 parts by mass of high-density polyethylene (HDPE). Next, the polyethylene composition was mixed with decalin as a solvent so that the concentration of the polyethylene composition was 30% by mass, thereby preparing a polyethylene solution.

[0070] The polyethylene solution was extruded from a die at a temperature of 169°C into a sheet, and the extrudate was then cooled in a water bath at a water temperature of 15°C to obtain a first gel-like sheet.

[0071] The first gel-like sheet was pre-dried at 60°C for 13 minutes, then stretched in the MD direction at 1.3 times its original size, and then dried at 55°C for 9 minutes to obtain a second gel-like sheet. The residual solvent content in the second gel-like sheet was less than 1% by mass.

[0072] Next, as the second stretching, the second gel-like sheet was stretched in the MD direction at a stretching ratio of 2.5 at a temperature of 80° C., and then stretched in the TD direction at a stretching ratio of 6.0 at a temperature of 125° C. Immediately after the second stretching, a heat treatment (heat setting) at 134° C. was carried out.

[0073] The heat-set sheet was immersed in a methylene chloride bath for a total of 2.0 minutes to extract the solvent from the sheet. After removing the sheet from the methylene chloride bath, the sheet was dried on a heated roll at 40°C to remove the methylene chloride. The sheet was then annealed in a heated atmosphere at 80°C.

[0074] Through the above steps, a porous membrane substrate made of a polyethylene porous membrane was obtained. The obtained porous membrane substrate was slit to obtain an untreated porous membrane roll of 280 mm x 550 m. The basis weight is 17.7g / m 2 The average membrane thickness was 105 μm, and the Gurley value was 10 seconds / 100 mL.

[0075] <Example 1-1> The untreated porous membrane roll was unwound, irradiated with an electron beam at a dose of 50 kGy under a nitrogen atmosphere, and immersed in a 100% glycidyl methacrylate solution. After adjusting the nip roll so that the amount of solution impregnated was uniform across the width, the mixture was reacted at 60°C for 40 minutes, and then wound around a 3-inch core (made of polyethylene, inner diameter: 76.2 mm) to obtain a porous membrane roll having graft chains. The winding tension was adjusted to 30N to 50N to prevent misalignment of the wound end and to prevent wrinkles from forming inside the wound body.

[0076] <Example 1-2> A porous membrane roll having graft chains was obtained in the same manner as in Example 1-1, except that the pressure of the nip rolls was adjusted to be higher than that in Example 1-1 so as to reduce the amount of impregnation.

[0077] <Examples 1-3> A porous membrane roll having graft chains was obtained in the same manner as in Example 1-1, except that the dose of electron beam was changed to 40 kGy.

[0078] <Examples 1-4> A porous membrane roll having graft chains was obtained in the same manner as in Example 1-3, except that the reaction time was changed to 60 minutes.

[0079] <Examples 1-5> A porous membrane roll having graft chains was obtained in the same manner as in Example 1-2, except that the pressure of the nip rolls was adjusted to be higher than that in Example 1-2 so as to reduce the amount of impregnation.

[0080] <Examples 1-6> A porous membrane roll having graft chains was obtained in the same manner as in Example 1-4, except that it was immersed in a 30% by mass ethanol solution of glycidyl methacrylate.

[0081] <Comparative Example 1-1> A porous membrane roll having graft chains was obtained in the same manner as in Example 1-1, except that the amount of solution impregnated in the width direction was not adjusted.

[0082] The obtained porous membrane roll having graft chains was evaluated for appearance and continuous conveyability by the following methods.

[0083] <Appearance> After drying the porous membrane roll having graft chains, the presence or absence of defects (reaction spots, bands, and notches) was visually confirmed. The evaluation criteria were as follows: A: No defects were found. B: Defects confirmed.

[0084] <Continuous conveyance> It was confirmed whether or not the porous membrane roll having graft chains was broken during transportation. A: It did not break. B: Broken.

[0085] The evaluation results are shown in Table 1. In Table 1, σ represents the standard deviation. In the graft ratio column, "σ / average" represents "(standard deviation of the graft ratio of the porous membrane having graft chains) / (average graft ratio of the porous membrane having graft chains)."

[0086] [Table 1]

[0087] As shown in Table 1, it was found that in Examples 1-1 to 1-6, the porous membranes having graft chains satisfied formula (1), and therefore the occurrence of defects was suppressed.

[0088] <Example 2-1> The porous membrane roll having graft chains obtained in Example 1-1 was co-wound with a polyethylene porous substrate as an insert sheet. It was immersed in a mixture of iminodiacetic acid, aqueous sodium hydroxide solution, and 2-propanol at a mass ratio of 8:72:20. After reacting at 80°C for 10 hours, it was washed with ultrapure water and dried to obtain a porous membrane roll containing iminodiacetic acid groups and graft chains.

[0089] <Example 2-2> A porous membrane roll containing iminodiacetic acid groups and having graft chains was obtained in the same manner as in Example 2-1, except that the porous membrane roll having graft chains obtained in Example 1-2 was used.

[0090] <Comparative Example 2-1> An attempt was made to obtain a porous membrane roll containing iminodiacetic acid groups and having graft chains in the same manner as in Example 2-1, except that the porous membrane roll having graft chains obtained in Comparative Example 1-1 was used.

[0091] The appearance and continuous conveyability were evaluated in the same manner as in Example 1-1. In Comparative Example 2-1, the porous membrane was broken during the drying process, and a porous membrane roll containing functional groups could not be obtained.

[0092] In Examples 2-1 and 2-2, the amount of functional groups introduced into the porous membrane roll containing iminodiacetic acid groups and having graft chains was calculated by the following calculation method. A porous membrane roll containing iminodiacetic acid groups and grafted chains was cut into a 10 cm x 10 cm sample. The sample was immersed in a 7% by mass aqueous solution of hydrochloric acid and stirred for 30 minutes. It was then washed with pure water until the wash water became neutral. The sample was placed in 50 mL of a 0.05 mol / L aqueous solution of sodium hydroxide to convert the H-form to the Na-form. 10 mL of the resulting solution was taken and subjected to neutralization titration using 0.05 mol / L hydrochloric acid. The capacity of weak acid groups in the sample was calculated from the amount of sodium hydroxide consumed, and the amount introduced was calculated taking into account the number of functional groups.

[0093] The evaluation results are shown in Table 2.

[0094] [Table 2]

[0095] As shown in Table 2, it was found that in Examples 2-1 and 2-2, the porous membranes having graft chains satisfied formula (1), and therefore the occurrence of defects was suppressed.

Claims

1. A porous membrane having graft chains and a core material around which the porous membrane having graft chains is wound, The porous membrane having graft chains satisfies the following formula (1) and has a Gurley value of 0.5 seconds / 100 mL to 1000 seconds / 100 mL. (Standard deviation of graft ratio of porous membrane having graft chains) / (Average graft ratio of porous membrane having graft chains)×100≦15.0 (1)

2. The porous membrane roll according to claim 1 , wherein the porous membrane having graft chains is a polyethylene porous membrane having graft chains.

3. The porous membrane roll according to claim 1, wherein the width of the porous membrane having graft chains is 100 mm to 1600 mm.

4. The porous membrane roll according to claim 1, wherein the wound length of the porous membrane having the graft chains is 10 m to 5000 m.

5. The porous membrane roll according to claim 1, wherein the graft ratio of the porous membrane having the graft chains is 10% to 300%.

6. The porous membrane roll according to claim 1 , wherein the graft chains contain at least one functional group selected from the group consisting of an ion exchange group and a chelate exchange group.

7. A filter substrate comprising the porous membrane having the graft chains in the porous membrane roll according to any one of claims 1 to 6.

8. A filter substrate comprising a porous membrane having graft chains that satisfy the following formula (1) and have a Gurley value of 0.5 seconds / 100 mL to 1000 seconds / 100 mL: (Standard deviation of graft ratio of porous membrane having graft chains) / (Average graft ratio of porous membrane having graft chains)×100≦15.0 (1)

9. A cartridge filter comprising the filter substrate according to claim 8.

Images