JP5177506B2 - Filter and liquid treatment method - Google Patents

Description

  The present invention relates to a filter suitably used for processing a liquid such as water, an aqueous solution, and an organic solvent, and a liquid processing method using the filter.

  Pleated ion exchange filters are widely used for high purity treatment of ultrapure water used in semiconductor manufacturing processes. This pleated ion exchange filter is a flat membrane such as a nonwoven fabric or a porous membrane made into a pleated shape.

  In the pleated ion exchange filter, the flow tends to be biased at the pleat folding portion, and a sufficient removal rate cannot be obtained in the extremely low concentration region as described above. Further, since the film thickness is thin, breakthrough is quick and the life is short. From the viewpoint of particle removal, as described above, long life and high removal performance are problems. If the film thickness is increased or the pores of the film are reduced in order to improve the ion removal rate, there is a problem that water permeability is sacrificed.

An electrospinning method (electrostatic spinning method) is known as a method for producing ultrafine nanofibers having a fiber diameter on the order of nanometers (Patent Documents 1 and 2 below). In this electrospinning method, an electric field is formed between a nozzle and a target, and spinning is performed by discharging a liquid raw material from the nozzle in the form of fine fibers.
JP2007-92237 JP 2006-144138 A

  Conventional pleated ion exchange filters have a short lifetime and are required to have a long lifetime.

  An object of the present invention is to solve the above-mentioned conventional problems, and to provide a filter that has excellent filtration performance and can extend the life, and a liquid treatment method using the filter.

Filter according to claim 1, in the filter for filtering liquids, a substrate layer made of ultrafine fibers of fluorine resins, laminated to the substrate layer, the average of the polymeric material having a sulfo group as an ion-exchange group A composite layer composed of fine particles having a particle size (c) of 1 to 1000 μm and / or an ion-exchange material layer made of nanofibers (provided that 1000 layers or less) is provided, and the equivalent diameter (a) of the nanofiber is 10 to 10 The ratio b / a of the equivalent diameter (b) of the ultrafine fiber to the equivalent diameter (a) is 1-1000.

  The filter according to claim 2 is characterized in that, in claim 1, the ultrafine fibers or the nanofibers are electrospun.

A filter according to a third aspect is the filter according to the first or second aspect, wherein the number of stacked composite layers is 35 to 500 .

Filter according to claim 4, in any one of claims 1 to 3, the ratio c / b of the equivalent diameter (b) of the ultrafine fiber flat Hitoshitsubu径and (c) of the fine particles in the 2 to 1000 It is characterized by being.

A filter according to a fifth aspect is the filter according to any one of the first to fourth aspects, wherein the base material layer is further provided on the ion exchange material layer positioned at an end in a stacking direction from the base material layer toward the ion exchange material layer. It is characterized by being laminated.

A liquid processing method according to a sixth aspect is characterized in that a processing liquid is obtained by allowing the liquid to be processed to pass through the filter according to any one of the first to fifth aspects.

According to a seventh aspect of the present invention, in the sixth aspect , the liquid to be treated is ultrapure water having a metal ion concentration of 0.5 to 5 ng / L.

The liquid treatment method according to an eighth aspect is characterized in that, in the sixth or seventh aspect , the temperature of the liquid to be treated is 50 to 100 ° C.

  The filter of the present invention (invention 1) has a composite layer in which an ion exchange material layer made of fine particles and / or nanofibers is laminated on a base material layer made of ultrafine fibers. Since this filter uses fine particles and / or nanofibers having a large specific surface area as an ion exchange material, the ion exchange capacity is large. By laminating this ion exchange material layer on the base material layer, the outflow of the ion exchange material is prevented. In addition, this filter has not only an ion exchange function but also excellent filtration performance.

  The filter of the present invention allows the liquid to permeate in the thickness direction of the composite layer and is used for filtration. At this time, water passes in the direction from the ion exchange material layer of the composite layer to the base material layer. Such a water-pass filter does not have a drift like a pleated filter and has a long life. And permeation flux can be kept high over a long period of time.

  The filter of the present invention is suitable for use in the production of ultrapure water or the like. In recent years, treatment of high-temperature water at 50 ° C. or higher may be required in the electronic component manufacturing process. By using materials having high heat resistance as the fine particles and nanofibers, it is possible to sufficiently treat such high-temperature water.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 (a) is a cross-sectional view in the direction perpendicular to the thickness direction of the filter according to the embodiment.

  The filter 1 includes a base material layer 2 made of ultrafine fibers of a polymer material B having no ion exchange group, and a polymer material A having an ion exchange group such as a sulfo group laminated on the base material layer 2. And an ion exchange material layer (a cation exchange material layer in this embodiment) 3 made of fine particles and / or nanofibers.

  As the ultrafine fibers of the base material layer 2 made of the polymer material B, extremely fine fibers having an equivalent diameter of about 1 to 1000 nm, particularly about 10 to 700 nm are suitable. The “equivalent diameter” is a value calculated from the cross-sectional area of one fiber (fiber) and the outer circumferential length of the cross-sectional area by (equivalent diameter) = 4 × (cross-sectional area) / (outer circumferential length of the cross-section) It is. The length of the ultrafine fiber is preferably 1 μm or more. In addition, when produced by electrospinning, the length can be several tens of centimeters, and since continuous spinning is possible, the length can be increased without an upper limit.

  The polymer material B is not particularly limited as long as predetermined water permeability and strength are ensured.

  Examples of the polymer material B include polyolefins such as polyethylene and polypropylene, polyethers such as polyethylene oxide and polypropylene oxide, PTFE, CTFE, PFA, fluororesins such as polyvinylidene fluoride (PVDF), halogenated polyolefins such as polyvinyl chloride, Polyamide such as nylon-6, nylon-66, urea resin, phenol resin, melamine resin, polystyrene, cellulose, cellulose acetate, cellulose nitrate, polyetherketone, polyetherketoneketone, polyetheretherketone, polysulfone, polyethersulfone, Polyimide, polyetherimide, polyamideimide, polybenzimidazole, polycarbonate, polyethylene terephthalate, polybutylene terephthalate Polyphenylene sulfide, polyacrylonitrile, polyether nitrile, but polyvinyl alcohol and materials including these copolymers can be used, not limited thereto. In particular, it is not limited to one kind of material, and various materials can be selected as necessary. However, when used for the treatment of high-temperature water at 50 ° C. or higher, a fluororesin having heat resistance is suitable. In addition, you may mix other polymers, such as polyolefin and polyether, with a fluororesin.

  The base material layer 2 is preferably made of a fine fiber or a non-woven fabric obtained by electrospinning the polymer material B.

  The thickness of the base material layer 2 is preferably about 1 to 1000 μm, particularly about 10 to 100 μm.

  The ion exchange material layer 3 is made of fine particles and / or nanofibers of the polymer material A having an ion exchange group such as a sulfo group. The polymer material A preferably has fluorine. Specifically, the polymer material A includes at least a material having a sulfo group by reacting polystyrene sulfonic acid, polysulfonic acid, glycidyl methacrylate with sulfurous acid, a fluorine resin having a sulfo group, and the like. One type is exemplified. Examples of the fluororesin having a sulfo group introduced include commercially available Nafion (registered trademark). The ion exchange group may be a carboxyl group, a phosphate group, a primary to quaternary amino group, or the like.

  As the fine particles of the ion exchange material layer 3, those having an average particle diameter of 1 to 1000 μm, particularly 10 to 700 μm are suitable. In addition, this average particle diameter is calculated | required from the imaging of an electron microscope. The method for producing the fine particles is not particularly limited, but the electric field granulation method is suitable. In the electric field granulation method, fine particles are produced by applying a voltage and discharging a liquid raw material based on the same principle as the electrospinning method.

The nanofibers of the ion exchange material layer 3 are preferably electrospun with an equivalent diameter (a) of 10 to 1000 nm, particularly 50 to 700 nm. Such extremely thin fibers have a large specific surface area and a high ability to remove substances to be separated from the water to be treated.
In the present invention, the ratio c / b between the average particle diameter (c) of the fine particles constituting the ion exchange material layer 3 and the equivalent diameter (b) of the ultrafine fibers constituting the substrate layer is 2 to 1000, particularly 5 to 100. It is preferable to do this. If the ultrafine fiber is too thick, the fine particles flow out, which is not preferable. If it is too thin, sufficient water permeability cannot be obtained.
When the ion exchange material layer is composed of nanofibers, the ratio b / a between the equivalent diameter (b) of the ultrafine fibers and the equivalent diameter (a) of the nanofibers is set to 1 to 1000 times, particularly 1 to 100 times the thickness. Is preferred. In addition, when the nanofiber of the ion exchange material layer is excessively thin, the water flow resistance increases, and when the nanofiber is excessively thick, the ion exchange performance is low.

  The ion exchange material layer 3 may be composed of only fine particles or only nanofibers, or may be composed of a mixture of both. When the ion exchange material layer 3 is composed of nanofibers and fine particles, it is preferable to use ultrafine fibers having a thickness that satisfies both the above-mentioned conditions.

  The thickness of the ion exchange material layer 3 is preferably about 1 to 1000 μm, particularly about 10 to 100 μm.

  The fine particles or nanofibers made of a polymer material having an ion exchange group of the ion exchange material layer 3 may be produced by granulating or spinning the polymer material having an ion exchange group. The fine particles or nanofibers may be subjected to a treatment for imparting ion exchange groups.

As a method for introducing the ion exchange group, it is preferable to select an appropriate method according to the material of the material. For example, when a sulfo group is introduced into polystyrene, the sulfo group can be introduced by adding an appropriate amount of paraformaldehyde to the sulfuric acid solution and carrying out heat crosslinking.
In the present invention, the ion-exchange material layer may enter a little inside the base material layer.

  When water treatment is performed using the filter 1 configured in this way, the water to be treated passes through the filter 1 in the thickness direction of the composite layer and is taken out as filtered water. At this time, the downstream end of the filter is Water is passed to form a base material layer.

In FIG. 1 (a), the filter 1 is composed of only one composite layer 4. However, like the filter 1A of FIG. 1 (b), a plurality of composite layers 4 are laminated. May be. Also in this case, water is passed from the upper side to the lower side in the drawing, that is, in the direction from the ion exchange material layer 3 to the base material layer 2 in each composite layer 4. The number of laminated composite layers 4 is appropriately set in consideration of water pressure loss, but is usually 1000 or less, particularly 500 or less.
The material, thickness, etc. of each layer 2, 3, 4 are the same as in FIG. 1 (a).

  In the present invention, the base material layer 2 may be laminated on the ion exchange material layer 3 on the end side in the laminating direction from the base material layer 2 toward the ion exchange material layer 3 as in the filter 1B of FIG. 1 (c). Good. According to this filter 1B, it can be used for both the usage method of passing water from the upper side of the figure and the usage method of passing water from the lower side.

  In FIG. 1 (c), in the embodiment of FIG. 1 (b) in which a plurality of composite layers 4 are stacked, the base material layer 2 is stacked on the uppermost ion exchange material layer 3. A filter having a sandwich structure in which the base material layer 2 is laminated on the ion exchange material layer 3 of the layer 4 (a three-layer structure in which the base material layer 2, the ion exchange material layer 3 and the base material layer 2 are laminated in this order) may be used. .

  The present invention is suitable for use in the case where ultrapure water having a metal ion concentration of 0.5 to 5 ng / L is subjected to filtration treatment to reduce the metal ion concentration to about 0.1 ng / L or less.

  The filter of the present invention can also be used for processing liquids other than water.

[Example 1]
<Structure of base material layer 2>
Electrospinning with a polymer dope prepared by dissolving Aldrich PVDF (Mw = 273,000) in DMA (dimethylacetamide) at 17 wt% as a polymer material B and applying a voltage of 50 kV (manufactured by Panasonic Factory Solutions Co., Ltd.) Thus, an ultrafine fiber having an equivalent diameter of 100 nm was obtained. A base material layer 2 made of a nonwoven fabric having a thickness of 50 μm was manufactured by spraying the ultrafine fibers while moving the discharge port.

<Manufacture of ion exchange material layer 3>
20 parts by weight of commercially available Nafion (sulfo group-introduced polytetrafluoroethylene. Registered trademark) is dissolved in a mixed solvent of 35 parts by weight of water and 45 parts by weight of 1-propanol (a total of 80 parts by weight) to produce a polymer for producing fine particles or nanofibers A dope was prepared.

  The polymer dope was granulated by an electric field granulator (manufactured by Panasonic Factory Solutions Co., Ltd.) with an applied voltage of 50 kV to produce fine particles having an average particle diameter of 2 μm. By spraying the fine particles onto the base material layer 2 while moving the discharge port, an ion exchange material layer 3 made of the fine particles is laminated on the base material layer 2 to form a composite layer 4, and the filter thickness is further increased. A filter 1A was manufactured by laminating 35 composite layers 4 so as to be 2 mm, and laminating a base material layer on the uppermost layer.

The produced filter 1A was thoroughly washed with 5% hydrochloric acid, and then the hydrochloric acid was washed away with ultrapure water. This was attached to a filter holder having a membrane area of 13 cm ² . Thereafter, a normal temperature test in which a standard solution for atomic absorption was added to ultrapure water so that the metal (Na, Mg, Al, K, Ca, Cr, Fe, Cu, Zn) concentration of the water to be treated was 10 ng / L. The water was treated for 20 L at 30 KPa. The results of measuring the metal concentration in the treated water are shown in Table 1. The measurement was performed by concentrating the sampling water and then analyzing with ICPMS (Yokogawa Analytical Systems Agilent-4500).

[Example 2]
Ultrafine fibers having an average fiber diameter of 500 nm were obtained in the same manner as in Example 1 except that the polymer dope concentration of the polymer material B was 20 wt% and the applied voltage was 20 kV. From this, a substrate layer 2 having a thickness of 50 μm was produced in the same manner as described above.
As polymer material A, 20 parts by weight of the above-mentioned Nafion was dissolved in a mixed solvent of 34 parts by weight of water and 45 parts by weight of 1-propanol (total 80 parts by weight), and 1 part by weight of polyethylene oxide was further dissolved to produce nanofibers. A polymer dope was prepared.

The polymer dope was electrospun by an electrospinning apparatus with an applied voltage of 50 kV to obtain nanofibers having an average fiber diameter of 500 nm. By spraying the nanofibers onto the base material layer 2 while moving the discharge port, a composite layer 4 is formed by laminating the ion exchange material layer 3 made of nanofibers on the base material layer 2, and the thickness of the filter. the composite layer 4 so as to Saga 2mm were produced filter 1A and the product layer.

The produced filter 1A was thoroughly washed with 5% hydrochloric acid, and then the hydrochloric acid was washed away with ultrapure water. Thereafter, a water passage test was conducted in the same manner as in Example 1. The results are shown in Table 1.
In addition, the SEM photograph when the ion exchange material layer 3 is laminated on the base material layer 2 to form the composite layer 4 is shown in FIG. FIG. 3 is an SEM photograph in the middle of producing ultrafine fibers of the polymer material B under the conditions of Example 2 and attaching the fine particles of the polymer material A under the conditions of Example 1.

[Comparative Example 1]
An ion exchange nonwoven fabric, a polysulfone porous membrane, and a polypropylene nonwoven fabric (channel material) were laminated to produce a filter having a thickness of 2 mm. The test water was passed through the filter in the same manner. The results are shown in Table 1.

  As shown in Table 1, according to the present invention, metal ions can be sufficiently removed with a high permeation flux. This high permeation flux was maintained over 30 days.

[Reference example]
Reference example 1
A filter made of a nonwoven fabric having a thickness of 40 μm, 75 μm, and 110 μm was manufactured in the same manner except that the manufacturing condition of the base material layer 2 in Example 1 was changed to a polymer dope concentration of 25 wt%. This filter consists only of the base material layer 2.

Reference example 2
Fine particles having an average particle diameter of 10 μm were produced by changing the polymer dope concentration of the ultrafine fiber production conditions in Reference Example 1 to 10 wt%. The fine particles were formed in layers so that the film thickness was the same as in Reference Example 1 to obtain a filter.

  For these filters of Reference Examples 1 and 2, pure water was passed at 0.4 KPa, and the permeation flux was measured. The results are shown in FIG.

  As shown in FIG. 2, it is recognized that the permeation flux is remarkably increased when the electrospun fiber is used.

It is a typical sectional view of a filter concerning an embodiment. It is a graph which shows the measurement result of the permeation | transmission flux of the filter of a reference example. It is a SEM photograph of the composite layer in the middle of manufacture.

Explanation of symbols

1,1A, 1B filter 2 base material layer 3 ion exchange material layer 4 composite layer

Claims (8)

In the filter for filtering liquids,
Fine particles and / or nano particles having an average particle diameter (c) of 1 to 1000 μm of a base material layer made of ultrafine fibers of fluororesin and a polymer material having a sulfo group as an ion exchange group laminated on the base material layer Provided with multiple layers (but 1000 layers or less) composed of an ion exchange material layer made of fiber,
The equivalent diameter (a) of the nanofiber is 10 to 1000 nm, and the ratio b / a between the equivalent diameter (b) of the ultrafine fiber and the equivalent diameter (a) is 1-1000. filter.   The filter according to claim 1, wherein the ultrafine fiber or the nanofiber is electrospun.   3. The filter according to claim 1, wherein the composite layer has a stack number of 35 to 500. 4. In any one of claims 1 to 3, the ratio c / b of the equivalent diameter (b) of the ultrafine fiber flat Hitoshitsubu径and (c) of the fine particles is characterized in that 2 to 1,000 filters . In any one of claims 1 to 4, characterized in that further said base layer in said ion-exchange material layer located at the end in the stacking direction toward the ion-exchange material layer from the substrate layer are laminated Filter. Liquid processing method characterized by obtaining the treating solution by passing liquid to be treated filter according to any one of claims 1 to 5. 7. The liquid treatment method according to claim 6, wherein the liquid to be treated is ultrapure water having a metal ion concentration of 0.5 to 5 ng / L. The liquid processing method according to claim 6 or 7, wherein the temperature of the liquid to be processed is 50 to 100 ° C.

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