Strainer for pure water production, ultrapure water production system using the same, and ultrapure water production method

Abstract

To provide a strainer for pure water which can remarkably suppress elution of iron over a long period of time, an ultrapure water production system using the same, and an ultrapure water production method.SOLUTION: A strainer 1 for pure water production has a cylindrical filtration body 11 whose both ends are opened, and having a plurality of filtration holes on its side face, and a cap member 12 which is bonded to one end of the filtration body 11 in a liquid-tight manner, where the filtration body 11 includes a filtration body composed of metal, and a fluorine resin film provided on the whole surface of the filtration body, the cap member 12 projects to the outside of the filtration body 11, and the whole liquid contact surface of the filtration body is composed of a fluorine resin.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a strainer for producing pure water, an ultrapure water producing system using the same, and a method for producing ultrapure water. [Background technology]

[0002] Ultrapure water, which has had impurities highly removed, is often used in semiconductor manufacturing processes, such as for cleaning semiconductor wafers. Ultrapure water is produced in an ultrapure water production system that combines water treatment equipment depending on the desired water quality. An ultrapure water production system is equipped with a pretreatment device, a primary water purification device, and a secondary water purification device, and raw water, such as city water, well water, or industrial water, is treated in turn in each device to produce ultrapure water. The produced ultrapure water is supplied to the point of use (POU) via a supply line for use.

[0003] The ultrapure water used in the semiconductor manufacturing process must have a metal (Fe, Cr, Ni, Mo, etc.) concentration of 1 ng / L or less, and sometimes 0.1 ng / L or less, in order to accommodate the advanced miniaturization of semiconductor products.

[0004] To improve the quality of ultrapure water, a non-regenerative mixed-bed ion exchange resin unit (polisher) is installed near the end (most downstream) of the secondary deionization system to remove residual ionic components. Furthermore, to prevent water quality deterioration due to the leakage of trace amounts of resin from the polisher, especially resin damaged within the polisher, a strainer to capture the resin is sometimes installed downstream of the polisher. These strainers are typically made of stainless steel (SUS) for their strength and corrosion resistance. However, when SUS strainers are used for extended periods, metal components contained in the SUS, such as iron (Fe), nickel (Ni), and chromium (Cr), especially iron (Fe), can leach into the water. Since there is no device downstream to remove the leached iron, this can lead to a deterioration in the quality of the ultrapure water.

[0005] To solve the above problems, strainers have been proposed in which the water-contacting parts are made of low-elution materials, such as titanium, titanium alloys, and nickel alloys (see, for example, Patent Document 1). Also proposed is an ion exchange column in which the liquid-contacting surfaces of the container and container top lid are lined with synthetic resin (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2023 / 053572 [Patent Document 2] Patent Publication No. 2011-67793 Summary of the Invention [Problem to be solved by the invention]

[0007] As mentioned above, ultrapure water is required to have a metal (Fe, Cr, Ni, Mo, etc.) concentration of 0.1 ng / L or less to 1 ng / L or less in order to accommodate the advanced miniaturization of semiconductor products. In particular, it has been found that there is a problem in that it is difficult to avoid the contamination of iron (Fe) when the purified water is heated or cooled in the secondary purified water equipment or when ultrapure water is produced over a long period of time.

[0008] Furthermore, titanium, titanium alloys, nickel alloys, etc. are generally expensive, which poses a problem of high production costs for strainers and the ultrapure water produced using them.

[0009] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a strainer for producing pure water that can significantly suppress iron elution over a long period of time, and an ultrapure water production system and method using the same. [Means for solving the problem]

[0010] As described above, further investigation was needed to prevent iron from being mixed into the pure water in the secondary pure water treatment system. The inventors discovered that by constructing the surface of the strainer installed downstream of the non-regenerative mixed-bed ion exchange resin treatment system (polisher) from a fluororesin, it is possible to prevent iron from eluting from the strainer and significantly reduce the iron concentration in the ultrapure water for a long period of time.

[0011] The strainer for producing pure water, the ultrapure water producing system, and the ultrapure water producing method according to the embodiment of the present invention are as follows. [1] A cylindrical filter body having both ends open and a plurality of filter holes on the side surface, and a cap member liquid-tightly adhered to one end of the filter body, The filter body includes a filter body body made of metal and a fluororesin membrane provided on the entire surface of the filter body body, The cap member is convex toward the outside of the filter body, and the entire liquid-contacting surface is made of fluororesin. [2] Further, the device has a cylindrical housing, The housing has a water outlet at one end and a water inlet at the other end, The housing accommodates the filter body and the cap member such that the cap member faces the water inlet of the housing; The opening of the filter body is in communication with the water outlet of the housing. [1] A strainer for producing pure water according to the present invention. [3] The housing and the filter body are cylindrical, The strainer for producing pure water described in [2], wherein the cap member has a solid cone or solid hemisphere shape. [4] A strainer for producing pure water according to [2] or [3], wherein the open end of the filter body is connected to the outlet of the housing.

[0012] [5] A strainer for producing pure water according to any one of [1] to [4], which has a connecting portion that connects the filter body and the cap member. [6] The connection part is The strainer for producing pure water described in [5], comprising the cap member and a screw member that penetrates the end face of the filter body. [7] A strainer for producing pure water according to any one of [1] to [6], wherein the fluororesin membrane and the fluororesin contain polytetrafluoroethylene. [8] A strainer for producing pure water according to any one of [1] to [7], wherein the iron (Fe) concentration in the pure water that has passed through the strainer for producing pure water is 0.1 ng / L or less. [9] A primary water purification system and a secondary water purification system are provided in this order; the secondary water purification system includes a non-regenerative mixed-bed ion exchange resin system; An ultrapure water production system comprising a strainer for producing pure water according to any one of [1] to [8], disposed downstream of the non-regenerative mixed-bed ion exchange resin device.

[10] The ultrapure water producing system according to [9], wherein the iron (Fe) concentration in the pure water that has passed through the strainer for producing pure water is 0.1 ng / L or less.

[0013]

[11] A method for producing ultrapure water in which raw water is treated in a primary water purification system and a secondary water purification system in this order, the secondary water purification system includes a non-regenerative mixed-bed ion exchange resin system and a pure water production strainer attached to the non-regenerative mixed-bed ion exchange resin system and arranged downstream of the non-regenerative mixed-bed ion exchange resin system; The strainer for producing pure water includes a cylindrical filter body that is open at both ends and has a plurality of filter holes on a side surface, and a cap member that is liquid-tightly adhered to one end of the filter body, The filter body includes a filter body body made of metal and a fluororesin membrane provided on the entire surface of the filter body body, The cap member has a convex shape facing outward from the filter body, and the entire liquid-contacting surface is made of fluororesin, producing ultrapure water with an iron (Fe) concentration of 0.1 ng / L or less. The symbol "~" indicates a range of values including the values before and after it. [Effects of the Invention]

[0014] According to the strainer for producing pure water of the embodiment, the elution of iron can be significantly suppressed for a long period of time. Furthermore, according to the ultrapure water production system and ultrapure water production method using the pure water production strainer of the embodiment, high-quality ultrapure water with an extremely low iron concentration can be produced over a long period of time. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view schematically showing a strainer 1 for producing pure water according to an embodiment. [Figure 2] FIG. 10 is a cross-sectional view schematically showing a first connection portion 13 in another embodiment. [Figure 3] FIG. 2 is a flow chart schematically illustrating a method for manufacturing a pure water strainer according to an embodiment. [Figure 4] 1 is a block diagram showing an ultrapure water manufacturing system according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0016] [Strainer for pure water production] A pure water producing strainer according to an embodiment of the present invention will now be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically illustrating a pure water producing strainer 1 according to the embodiment. The pure water producing strainer 1 according to the embodiment includes a cylindrical filter body 11 with both ends open, and a cap member 12. The side surface of the filter body 11 has a plurality of filter holes to form a filter surface 11a. In the pure water producing strainer 1, as the water to be treated flows from the filter surface 11a on the side surface of the filter body 11 into the filter body 11, impurities such as resin in the water to be treated are removed, and the treated water flows out from the opening at the downstream end of the filter body 11. Hereinafter, the opposite ends of the filter body 11 will be referred to as the upstream end and the downstream end, depending on the flow of water passing through the filter body 11.

[0017] The filter body 11 includes a metal filter body and a fluororesin membrane disposed over the entire surface of the filter body. The fluororesin membrane is disposed over the entire surface of the filter body. Specifically, all liquid-contacting surfaces of the filter body 11, such as the filtration surface, the surfaces of the filter pores, and the inner wall surface of the filter body, are covered with the fluororesin membrane. Examples of metals constituting the filter body include stainless steel (SUS) such as SUS304, SUS316, SUS316L, and SUS304L. From the viewpoints of strength and corrosion resistance, SUS316 or SUS316L is more preferable. The filter body includes, for example, a filter element formed of a spirally wound wire and multiple rod-shaped support members disposed in the longitudinal direction of the spiral of the filter element and spaced apart in the circumferential direction of the spiral. The cross-sectional shape of the wire is, for example, triangular, and the wire is disposed so that the apex of the triangle faces the interior of the filter body. The gaps between the spiral wire and the support members function as filter pores. The diameter of the filter holes may be any size that does not allow the ion exchange resin to pass through, for example, a diameter (inner diameter) of about 0.3 mm. The filter body 11 is cylindrical, for example, with an outer diameter of 15 mm to 220 mm or 15 mm to 165 mm.

[0018] The pure water producing strainer 1 of this embodiment can be easily lined or coated on the surface of the filter body 11 by forming a fluororesin membrane on the surface of the filter body 11, which is open at both ends, and then connecting the cap member 12, as in the method of manufacturing a pure water producing strainer described below. Therefore, it is possible to easily and uniformly form a fluororesin membrane even on a complex shape with numerous filter holes. If the lining or coating is insufficient and the fluororesin membrane has defects such as pinholes, even if the defects are small, they can lead to a deterioration in the quality of ultrapure water. However, by forming a fluororesin membrane on the surface of the filter body 11, which is open at both ends, a fluororesin membrane without such defects can be formed by lining or coating, and the entire liquid-contacting surface of the filter body 11 can be covered with the fluororesin membrane.

[0019] The presence of a fluororesin membrane over the entire surface of the filter body 11 can be confirmed, for example, by the following method: First, when the strainer 1 for producing pure water according to the embodiment is attached to a non-regenerative mixed-bed ion exchange resin apparatus and installed downstream of the apparatus in an ultrapure water production system, and ultrapure water production is continued, it can be confirmed by checking whether ultrapure water having an iron concentration of 1.0 ng / L or less can be obtained for 30 days or more after, for example, 30 days of flushing. Second, as an accelerated test, for example, a strainer for producing pure water is immersed in ultrapure water for seven days, and the iron concentration in the ultrapure water after immersion is measured. At the same time, under the same conditions, a piece of fluororesin or a piece of SUS with a fluororesin lining or coating (hereinafter both are referred to as "comparison sample") having the same or equivalent surface area (with an error of ±5%) as the strainer for producing pure water is immersed, and the iron concentration in the ultrapure water after immersion is measured. The measured values are compared to determine whether the iron concentration in the ultrapure water in which the strainer for producing pure water is immersed is significant compared to the iron concentration in the ultrapure water in which the comparison sample is immersed. In this case, for example, when testing the iron concentrations measured in ultrapure water in which multiple comparison samples are immersed at a significance level of 2.5%, the iron concentration in the ultrapure water in which the strainer for producing pure water is immersed is determined as F samp The average value calculated from the iron concentration in the ultrapure water in which the comparison sample was immersed was F ave , and the standard deviation is σ, F samp ≦F aveIf the value is +1.96 × σ, it can be determined that a fluororesin film is formed over the entire surface of the filter body 11. Alternatively, the iron concentration in ultrapure water in which a single comparative sample has been immersed can be measured multiple times to make a similar determination. The test method is preferably based on, for example, the UC Standard, "Elution Test Method for Ultrapure Water Piping Materials" (UCS12 Semiconductor Industry Development and UCS12 Results, edited by the Semiconductor Fundamental Technology Research Group, pp. 1181-1188). This method is a non-flow system, and since eluates are eluted in a small amount of ultrapure water, it constitutes an accelerated test, and measurement is easy. Third, as a further accelerated test, confirmation can be made by using the same method as the second method, except that an aqueous solution of hydrogen peroxide, sulfuric acid, or a mixture thereof is used instead of ultrapure water. In this case, measurement can be performed after an immersion time of, for example, about one day.

[0020] In the strainer 1 for producing pure water, the cap member 12 is liquid-tightly adhered to the upstream end of the filter body 11. The cap member 12 has a convex shape extending outward from the upstream end of the filter body 11, and at least the liquid-contacting surface is made of fluororesin. The cap member 12 may be made of a metal cap member body such as SUS and a fluororesin film provided on the surface of the cap member body, or the entire cap member may be made of fluororesin. It is preferable that the entire cap member 12 be made of fluororesin because it is lightweight and easy to handle. The cap member may be hollow or solid, but a solid cap member is preferable because it is easy to manufacture, and it is particularly preferable that the entire cap member 12 be made of a solid fluororesin.

[0021] The cap member 12 preferably has at least a bottom surface and side surfaces rising from the bottom surface. The bottom surface, i.e., the side opposite the convex surface, of the cap member 12 is connected to the opening at the upstream end of the filter body 11 via a first connecting part 13. Examples of the convex shape of the cap member 12 include those in which the convex cross section, i.e., the cross section perpendicular to the bottom surface and passing through the point farthest from the bottom surface, is polygonal, rectangular, triangular, semicircular, etc.

[0022] The convex shape of the cap member 12 is preferably such that the water flow on the surface of the cap member 12 does not cause unidirectional flow or vortexes. If unidirectional flow or vortexes occur on the surface of the convex cap member 12, the strainer will vibrate. Because ultrapure water production systems are continuously operated for at least one year, and in some cases for several years, long-term strainer vibration can accelerate deterioration of the fluororesin film on the strainer's filtering surface, potentially causing resin fragments and iron leaching from the SUS surface that was previously covered by the resin. Convex cross-sections that do not cause unidirectional flow or vortexes are preferably triangular, semicircular, or semi-elliptical. When the convex cross-section is triangular, for example, one side of the triangle is located on the upstream end of the filter body 11. When the convex cross-section is semicircular, for example, the diameter of the semicircle is located on the upstream end of the filter body 11. When the convex cross-section is semi-elliptical, for example, the major axis or minor axis of the semi-ellipse is located on the upstream end of the filter body 11. For example, when the opening of the filter body 11 is circular, the convex shape of the cap member 12 is preferably a hemisphere, a semi-elliptical sphere, or a cone, since this reduces the likelihood of one-sided flow on the surface of the cap portion 12. In particular, a conical shape of the cap member 12 is more preferable because the side surface has a constant slope from the apex to the base, thereby achieving a rectifying effect on the treated water. Furthermore, water stagnation may occur on the surface of the cap member 12, and impurities eluted from each component may accumulate and accumulate in this stagnation. In this case, fluctuations in the treated water flow rate, such as sudden increases or decreases in volume or the opening and closing of valves, may result in a large amount of impurities being released into the pure water, potentially leading to a deterioration in water quality.

[0023] The outer diameter of the cap member 12 is preferably the same as the outer diameter of the opening of the filter body 11, or approximately the same as but larger than the outer diameter of the opening of the filter body 11. This makes it possible to adjust the water flow around the first connecting portion 13 between the filter body 11 and the cap member 12, thereby suppressing the deterioration of the lining or coating as described above.

[0024] The fluororesin used for the fluororesin of the cap member 12 and the fluororesin film on the surface of the filter body 11 is not particularly limited, and examples thereof include tetrafluoroethylene and perfluoroether copolymer (PFA, perfluoroalkoxyalkane), polytetrafluoroethylene (PTFE), ethylene / tetrafluoroethylene copolymer (ETFE), etc. The fluororesin of the cap member 12 and the fluororesin of the fluororesin film on the surface of the filter body 11 may be the same or different, but are preferably the same type.

[0025] When ETFE is used as the fluororesin, for the purpose of controlling crystallinity, the ETFE is preferably one obtained by copolymerizing ethylene and tetrafluoroethylene with other fluorine-containing monomers. The other fluorine-containing monomers are not particularly limited as long as they can be added to both ethylene and tetrafluoroethylene, but fluorine-containing vinyl monomers having 3 to 8 carbon atoms are easy to use, such as hexafluoroisobutylene and CH2=CFC3F6H. The other fluorine-containing monomers are preferably 5 mol% or less of the total monomers of the ETFE, so as not to impair heat resistance, flame retardancy, and chemical resistance.

[0026] When ETFE is obtained by copolymerizing other fluorine-containing monomers, the fluorine content in ETFE is preferably 50% by mass or more. A fluorine content of 50% by mass or more results in excellent heat resistance, flame retardancy, and chemical resistance. The fluorine content of ETFE is, for example, 70% by mass or less. The fluorine content can be adjusted by appropriately adjusting the ratio of ethylene, tetrafluoroethylene, and the other monomers used as desired. The fluorine content is a value obtained by burning a fluororesin, absorbing the fluorine contained therein into alkaline water, etc., and measuring the resultant by ion chromatography, etc.

[0027] Among the above-mentioned fluororesins, tetrafluoroethylene and perfluoroether copolymer (PFA, perfluoroalkoxyalkane) and polytetrafluoroethylene (PTFE) resin are materials that are widely and generally used in ultrapure water production systems due to their excellent heat resistance and chemical resistance, and can also be suitably used for the cap member 12 and the fluororesin membrane on the filter body 11.

[0028] The first connecting portion 13 is not particularly limited as long as it can connect the filter body 11 and the cap member 12 liquid-tightly. Examples of the first connecting portion 13 include a connecting portion formed by soldering, welding, or the like, which undergoes a change in the state of the material of the connecting portion when connected. Alternatively, the first connecting portion 13 may be a connecting portion formed by a mechanical structure without undergoing a change in the state of the material of the connecting portion when connected, for example, a connecting portion using threaded engagement or one or more screw members. It is preferable that the first connecting portion 13 be a connecting portion formed by a mechanical structure, since the fluororesin film on the surface of the filter body 11 is not damaged when the filter body 11 and the cap member 12 are connected.

[0029] 1 , for example, a first connector 131 having ridges 131a on its outer surface can be connected to the bottom surface of the cap member 12, and a cylindrical second connector 132 having a spiral groove 132a on its inner wall that screws with the ridges can be connected to the upstream end of the filter body 11, and the filter body 11 and the cap member 12 can be connected by screwing the ridges of the first connector 131 into the groove of the second connector 132. In this case, the first connector 13 includes the first connector 131, the ridges 131a provided on the first connector 131, the second connector 132, and the groove 132a provided on the second connector 132. Furthermore, instead of the embodiment in which the first connector 131 has ridges and the second connector 132 has grooves, the first connector 131 may have grooves and the inner wall of the second connector 132 may have ridges. In order to improve the liquid-tightness between the filter body 11 and the cap member 12, a sealing member such as an O-ring made of resin or the like may be interposed between the end face of the second connector 132 of the filter body 11 and the vicinity of the outer periphery of the bottom surface of the cap member 12.

[0030] FIG. 2 is a cross-sectional view schematically illustrating another embodiment of the first connecting portion 13. As shown in FIG. 2, a third connecting body 133 is provided on the end face of the upstream end of the filter body 11. The third connecting body 133 is, for example, arranged along the periphery of the upstream end of the filter body 11 and has a solid ring shape with thickness in the axial and circumferential directions. The filter body 11 and the cap member 12 can be connected by providing a plurality of screw holes 134 near the outer periphery of the cap member 12 and inserting a screw member 142 or the like through the screw holes 134 into the cap member 12 and the third connecting body 133. In this case, the first connecting portion 13 includes the cap member 12 and the screw member 142 that penetrates the cap member 12 and is inserted into the third connecting body 133. To improve the liquid-tightness between the filter body 11 and the cap member 12, a seal member 141, such as an O-ring made of resin, may be interposed between the end face of the upstream end of the third connecting body 133 and the bottom surface of the cap member 12. In this case, the first connecting portion 13 further includes a sealing member 141 .

[0031] 2, when the filter body 11 and the cap member 12 are connected using the screw member 142, there is a possibility that water may pool on the surface (screw head) of the screw member 142 or in the vicinity thereof, or that iron may leach out from the screw member if the screw member 142 is made of metal. However, because the size of the screw member 142 is much smaller than that of the filter body 11, the impact of these factors on the quality of the treated water is extremely small. If the surface of the screw member 142 or in the vicinity thereof has a depression, it is preferable to form a protective part by filling the depression with a fluororesin in order to improve the quality of the ultrapure water obtained as treated water. In this case, the material of the protective part may be a different fluororesin from or the same fluororesin as the cap member 12, but it is preferable that it be the same fluororesin.

[0032] The strainer 1 for producing pure water shown in FIG. 1 further includes a cylindrical housing 15 that houses the filter body 11. The housing 15 houses the entire filter body 11. The housing 15 has a water outlet 15a at the downstream end and a water inlet 15b at the upstream end. The housing 15 may be a continuous cylinder with a constant inner diameter, or may have a shape in which multiple cylindrical sections with different inner diameters are connected in series. Furthermore, a portion of the cylinder, particularly both ends or one end, may have a tapered shape with a diameter that decreases toward the end. It is preferable that a fluororesin membrane be provided on the inner surface of the housing 15 and, if necessary, on liquid-contacting surfaces other than the inner surface. The fluororesin membrane on the inner surface of the housing 15, etc., can be formed by lining or coating, similar to the filter body 11.

[0033] In the strainer 1 for producing pure water, the filter body 11 and the cap member 12 are arranged and housed in the housing 15 so that the cap member 12 faces the water inlet 15b of the housing 15. In addition, the opening at the downstream end of the filter body 11 communicates with the water outlet 15a of the housing 15, so that treated water that has passed through the filtration surface 11a of the filter body 11 is discharged from the water outlet 15a of the housing.

[0034] The filter body 11 and the housing 15 are connected via a second connecting part 18. The second connecting part 18 is not particularly limited as long as it can connect the filter body 11 and the housing 15 liquid-tightly. In the strainer 1 for producing pure water shown in FIG. 1 , a discharge pipe 20 is connected to the housing 15 via the second connecting part 18. The discharge pipe 20 has a discharge pipe main body 22 and a flange portion 24 that is provided circumferentially and contiguous with the upstream end of the discharge pipe main body 22. A threaded hole is provided in the flange portion 24. The housing 15 has a flange portion 151 that is provided circumferentially and contiguous with the housing 15 at its downstream end, and the flange portion 151 is provided with a threaded hole. Furthermore, a fourth connecting part 148 is connected to the downstream end of the filter body 11. The fourth connecting part 148 is arranged along the periphery of the downstream end of the filter body 11 and has a solid ring shape that is thick in both the axial and circumferential directions. The outer diameter of a part of the downstream end side of the outer periphery of the fourth connector 148 (opposite the side that contacts the downstream end of the filter body 11) is larger than that of the upstream end, and a notch into which the flange portion 151 fits is provided.

[0035] In the pure water producing strainer 1, the second connecting portion 18 can be configured by arranging the notch of the fourth connecting body 148 between the flange portion 151 and the flange portion 24, passing a screw member 144a through the threaded holes in the flange portion 151 and the flange portion 24, and fastening the passing screw member 144a with a screw member 144b. That is, the second connecting portion 134 includes the flange portion 151, the fourth connecting body 148, the flange portion 24, and the screw member 144a and screw member 144b that pass through the flange portion 151 and the flange portion 24. Note that, in order to improve the liquid-tightness of the second connecting portion 18, sealing members 146a, 146b such as O-rings made of resin or the like may be interposed between the flange portion 151 and the notch of the fourth connecting body 148 and between the end face of the downstream end of the fourth connecting body 148 and the flange portion 24. In this case, the second connecting portion 18 further includes sealing members 146a and 146b.

[0036] Next, another method for connecting the filter body 11 and the housing 15 will be described. This method uses a structure similar to that of the filter body 11 and the cap member 12 shown in FIG. 1 . Specifically, a cylindrical sixth connector having a spiral groove on its inner wall is connected to the upstream end of the discharge pipe 20, and a cylindrical fifth connector having a ridge on its outer surface that threadably engages with the groove is connected to the downstream end of the filter body 11, allowing the connection to be achieved by threading the groove and the ridge. In this case, the second connector 18 includes a fifth connector, a ridge provided on the fifth connector, a sixth connector, and a groove provided on the inner wall of the sixth connector. Alternatively, instead of the fifth connector having a ridge on its inner wall and the sixth connector having a groove, the fifth connector may have a groove on its inner wall and the sixth connector may have a ridge. To improve the liquid-tightness between the filter body 11 and the housing 15, a sealing member such as an O-ring made of resin or the like may be interposed between the downstream end face of the fifth connector and the upstream end face of the sixth connector. In this case, the second connection portion 18 further includes a sealing member.

[0037] The strainer 1 for producing pure water of this embodiment is preferably attached to a regenerative mixed-bed ion exchange resin device (polisher) in a secondary pure water system and placed after the device. In this case, the Fe concentration in the pure water that has passed through the strainer for producing pure water can be reduced to 0.1 ng / L or less.

[0038] [Manufacturing method for pure water strainers] A method for manufacturing a strainer for producing pure water according to this embodiment will now be described. Fig. 3 is a flow chart that schematically illustrates a method for manufacturing a strainer for producing pure water according to this embodiment. The method for manufacturing a strainer for producing pure water shown in Fig. 3 includes an assembly step S80 for assembling a filter body 11, a fluororesin film forming step S82 for forming a fluororesin film on the surface of the filter body, and a connection step S84 for connecting a cap member 12 and each connector (first connector and second connector, or third connector) to the filter body 11 having the fluororesin film formed on its surface.

[0039] First, in an assembly step S80, the filter body 11 is assembled and manufactured. In the assembly step S80, a commercially available bag-shaped strainer having a sealed upstream end and an open downstream end may be used as a raw material, and the upstream end of the strainer may be opened to obtain the filter body 11 of the embodiment.

[0040] Subsequently, in the fluororesin film forming step S82, the above-mentioned fluororesin film is formed on the surface of the filter body. The fluororesin film may be formed by a coating method such as dip coating, spray coating, electrostatic painting, brush painting, or roll coating, or by a lining method such as electrostatic powder painting or sheet lining. Spray coating is preferred because it allows the fluororesin film to be formed uniformly on the inner surfaces of the filter pores 11a. The thickness of the fluororesin film formed on the surface of the filter body 11 in this manner is usually about 200 μm to 300 μm.

[0041] The cap member 12 and each connector are then connected to the filter body 11 as described above. If necessary, the filter body 11 with the cap member 12 connected thereto is housed in the housing 15. When using a hollow or solid cap member 12 made of fluororesin, the cap member 12 can be obtained by forming the fluororesin into a block and then cutting the block of fluororesin using a machine tool or the like. More specifically, the cap member 12 can be manufactured into the desired shape by cutting a cylindrical fluororesin rod from a block of fluororesin, or by forming the fluororesin into a cylindrical fluororesin rod and then cutting it. The solid cap member 12 prevents pure water from stagnating inside the cap. Therefore, a solid cap member 12 is preferable because it does not cause deterioration of water quality. The cap member may be made of stainless steel, polypropylene, or polyethylene. In these cases, it is preferable to coat or line the surface with a fluorine-based material.

[0042] Although the above describes an embodiment in which the fluororesin membrane is formed on the filter body 11 and then the connectors are connected, the fluororesin membrane may also be formed after the connectors are connected to the filter body 11. In the method for manufacturing a strainer for pure water production according to this embodiment, forming a fluororesin membrane on the surface of the filter body 11, which is open at both ends, allows for easy lining or coating. Therefore, it is possible to easily and uniformly form a fluororesin membrane even on a complex shape with numerous filter holes. If the lining or coating is insufficient and the fluororesin membrane has defects such as pinholes, even minor defects can lead to deterioration of the quality of ultrapure water. However, by forming a fluororesin membrane on the surface of the filter body 11, which is open at both ends, a fluororesin membrane without such defects can be formed by lining or coating, resulting in a strainer for pure water production suitable for producing ultrapure water.

[0043] [Ultrapure water production system and ultrapure water production method] Next, an ultrapure water producing system and an ultrapure water producing method according to this embodiment will be described. The ultrapure water production system of this embodiment comprises a primary water purification device that performs primary water purification treatment to convert raw water or pretreated water into primary pure water, and a secondary water purification device that includes the above-mentioned pure water production strainer and performs secondary water purification treatment to convert the primary pure water into secondary pure water.

[0044] 4 is a block diagram showing an outline of an ultrapure water producing system 100 according to this embodiment. The ultrapure water producing system 100 includes a pretreatment device 112, a primary pure water system 114, a pure water tank 116, and a secondary pure water system 117. The secondary pure water system 117 includes a water pump 118, a heat exchanger 120, an ultraviolet irradiation device 122, a membrane degassing device 124, a non-regenerative mixed-bed ion exchange resin system (polisher) 126, and an ultrafiltration (UF) device 128. The strainer 1 for producing pure water according to the embodiment described above is provided downstream of the non-regenerative mixed-bed ion exchange resin system 126.

[0045] (Pretreatment device) Raw water is supplied to the pretreatment device 112. The pretreatment device 112 is equipped with a coagulation sedimentation device, a sand filter, a membrane filter, etc., and clarifies the raw water supplied thereto, producing pretreated water from which suspended solids and a portion of organic matter have been removed. Examples of raw water include industrial water, tap water, groundwater, and river water.

[0046] (Primary pure water equipment) The primary deionized water system 114 further purifies the pretreated water to remove impurities from the pretreated water and produce primary deionized water. Specifically, the primary deionized water system 114 includes various devices such as a demineralizer that removes impurity ions, a reverse osmosis membrane device that removes inorganic ions, organic matter, fine particles, etc., a vacuum degassing device or membrane degassing device that removes dissolved gases such as dissolved oxygen, and a regenerative mixed-bed demineralizer that removes remaining ions, etc.

[0047] (Pure water tank) The primary pure water obtained in the primary pure water system 114 is sent to the pure water tank 116. The pure water tank 116 temporarily stores the primary pure water obtained in the primary pure water system 114. The material and shape of the pure water tank 116 are not particularly limited as long as it is free from rust, causes little elution of components from the container, and can stably store the primary pure water. Preferred materials for the pure water tank 116 include fiber reinforced plastics (FRP), polyethylene, SUS304, and Teflon (registered trademark)-lined versions of these materials. The upper part of the pure water tank 116 is preferably purged with pure nitrogen to prevent absorption of impurity gases such as carbon dioxide and dissolved oxygen. As described below, the pure water tank 116 can also store a mixture of the primary pure water and ultrapure water when circulating unused ultrapure water produced.

[0048] (Water pump) The water pump 118 sends primary pure water from the pure water tank 116 to the heat exchanger 120. The configuration of the water pump is not particularly limited. For example, even if the part that comes into contact with the primary pure water is made of a material that elutes small amounts of metal components, such as stainless steel, the eluted metal components are adsorbed by the ion exchange resin in the non-regenerative mixed-bed ion exchange resin device (polisher) 126. Therefore, the material of the part of the water pump 118 that comes into contact with the primary pure water has almost no effect on the quality of the ultrapure water produced. Therefore, a water pump that is commonly used in the production of pure water can be used as the water pump 118.

[0049] (heat exchanger) The heat exchanger 120 adjusts the temperature of the primary pure water by heat exchange (heating or cooling). The heat exchanger 120 may be, for example, a plate-type heat exchanger, but the specific structure is not particularly limited. The heat exchanger generally adjusts the water temperature to room temperature, for example, about 20°C. However, it may also be adjusted to, for example, 60 to 80°C, in which case the produced ultrapure water is called hot ultrapure water. When producing hot ultrapure water, a further heat exchanger may be installed in addition to the heat exchanger 120. In this case, the heat exchanger is installed, for example, between the pure water producing strainer 1 and the ultrafiltration (UF) device 128.

[0050] (Ultraviolet irradiation device) The primary pure water whose temperature has been adjusted by the heat exchanger 120 is sent to the ultraviolet irradiation device 122. The ultraviolet irradiation device 122 irradiates the primary pure water with ultraviolet light to decompose organic matter in the primary pure water and kill (sterilize) live bacteria. The ultraviolet irradiation device 122 is equipped with an ultraviolet lamp capable of irradiating, for example, with a wavelength of around 185 nm or 254 nm, thereby ensuring the decomposition and sterilization of organic matter in the primary pure water. The ultraviolet lamp of the ultraviolet irradiation device 122 is not particularly limited, but a low-pressure mercury lamp is preferred from the viewpoint of ease of handling. The ultraviolet irradiation device 122 may be a flow-through type in which an ultraviolet lamp is arranged inside a housing along the flow path of the water to be treated, or an immersion type in which an ultraviolet lamp is immersed in a tank that stores the water to be treated, but the flow-through type is preferred from the viewpoint of treatment efficiency.

[0051] (Membrane degassing device) The membrane degassing device 124 removes gases, particularly dissolved oxygen, from the primary pure water using a gas separation membrane that is impermeable to water but permeable to gases.

[0052] (Non-regenerative mixed-bed ion exchange resin device) The primary pure water from which the dissolved oxygen concentration has been removed by the membrane degassing device 124 is sent to a non-regenerative mixed-bed ion exchange resin device 126. The non-regenerative mixed-bed ion exchange resin device 126 adsorbs and removes organic acids produced by the decomposition of organic matter in the ultraviolet irradiation device 122, as well as impurity ions such as metal ions remaining in the water.

[0053] (Strainer for producing pure water) In the ultrapure water production system 100, the strainer 1 for pure water production described above is provided downstream of the non-regenerative mixed bed ion exchange resin apparatus 126. This prevents Fe from leaching out from the metal constituting the strainer, improving the quality of the treated water.

[0054] (Ultrafiltration device) The primary pure water from which impurity ions have been removed by the non-regenerative mixed-bed ion exchange resin device 126 is sent to an ultrafiltration (UF) device 128. The ultrafiltration (UF) device 128 removes fine particles to produce ultrapure water. The ultrafiltration (UF) device 128 is located at the end of the secondary pure water device 117. In addition, in the secondary pure water system 117, other treatment devices such as a catalytic resin packed tower may be installed as needed to remove hydrogen peroxide generated secondarily in the ultraviolet irradiation system, thereby obtaining ultrapure water of the desired purity.

[0055] Furthermore, in order to increase the water supply pressure to the ultrafiltration unit 128, for example, a booster pump may be installed between the non-regenerative mixed-bed ion exchange resin unit 126 and the ultrafiltration (UF) unit 128. However, contact with the booster pump may cause metal components to elute, increasing the metal concentration. Therefore, when producing ultrapure water with a lower metal concentration, it is preferable to either not install a booster pump or to use a booster pump whose contact portion with the water to be treated is made of a material that does not or does not easily elute metal components. Alternatively, it is preferable to install the booster pump upstream of the non-regenerative mixed-bed ion exchange resin unit 126.

[0056] The secondary pure water (ultrapure water) obtained by the secondary pure water device 117 after passing through the above-mentioned devices (steps) is sent to a use point 160, such as a process point in a semiconductor manufacturing process, via a water supply pipe 162. Unused ultrapure water from the sent ultrapure water is circulated to the pure water tank 116 via a circulation pipe 164 and stored in the pure water tank 116 together with the primary pure water.

[0057] The above-described pure water producing strainer 1 and ultrapure water producing system 100 can produce ultrapure water with an iron content of 1 ng / L or less, and even 0.1 ng / L or less, making them particularly suitable for use in producing ultrapure water to be supplied to process points in semiconductor manufacturing processes. Furthermore, it is possible to produce ultrapure water with an iron content of 0.1 ng / L or less, such as nickel and chromium. These nickel and chromium components are primarily derived from stainless steel. [Example]

[0058] Examples of this embodiment will be described below, but this embodiment is not limited to the following examples.

[0059] Example 1 In an ultrapure water production system similar to that shown in Fig. 4, ultrapure water was produced using a strainer equipped with a solid conical cap member at the upstream end of the filter body, which was produced by the method of the above-mentioned embodiment. The water flow conditions were as follows: Strainer: Linear velocity 1.2m / h : PTFE coated with open ends (filter surface slot width: 0.3 mm, prototype manufactured by Nomura Micro Science Co., Ltd.)

[0060] (Comparative Example 1) Ultrapure water was produced under the same conditions as in Example 1, except that the following strainer was used instead of the strainer used in Example 1. Strainer: Made of stainless steel, open on one side only. (Slot width on filter surface: 0.3 mm, prototype manufactured by Nomura Micro Science Co., Ltd.)

[0061] (Comparative Example 2) Ultrapure water was produced under the same conditions as in Comparative Example 1, except that the strainer used in Comparative Example 1 was replaced with a strainer whose surface had been PTFE-coated.

[0062] The water quality at the outlet of the non-regenerative mixed-bed ion exchange resin device (polisher) (i.e., strainer inlet) and at the strainer outlet after 30 days in the above cases is shown in Table 1. The iron concentration was measured by evaporating and concentrating samples taken from each location and using inductively coupled plasma mass spectrometry (ICP-MS).

[0063] [Table 1]

[0064] From the above results, it was confirmed that sufficient performance could not be obtained with the existing strainer of Comparative Example 2, which is open on one side and coated with a fluororesin. The strainer of Comparative Example 2 is a strainer open on one side that has been coated with a fluororesin, but this process is not easy, and although the coating appears uniform to the naked eye, it is thought that very small areas are not coated or that the coating is insufficient. On the other hand, when the method of the embodiment was used, the fluororesin coating was uniform and formed without defects, so it is thought that iron elution was sufficiently suppressed. [Explanation of symbols]

[0065] 1...strainer for producing pure water, 11...filter body, 11a...filter surface, 12...cap member, 13...first connecting portion, 131...first connecting body, 131a...groove portion, 132...second connecting body, 132a...ridge portion, 133...third connecting body, 134...screw hole, 141, 146a, 146b...sealing member, 142...screw member, 15...housing, 15a...water outlet, 15b...water inlet, 18...second connecting portion, 20...discharge pipe, 22...discharge pipe main body, 24, 151...flange portion, 144a...screw member, 144b...screw fastening member, 14 8...fourth connector, 100...ultrapure water production system, 112...pretreatment device, 114...primary pure water device, 116...pure water tank, 117...secondary pure water device, 118...water pump, 120...heat exchanger, 122...ultraviolet irradiation device, 124...membrane degassing device, 126...non-regenerative mixed bed ion exchange resin device (polisher), 128...ultrafiltration (UF) device, 160...point of use (use point), 162...water supply piping, 164...circulation piping, S80...assembly process, S82...fluororesin membrane formation process, S84...connection process

Claims

1. The filter includes a cylindrical filter body that is open at both ends and has a plurality of filter holes on a side surface, and a cap member that is liquid-tightly adhered to one end of the filter body, The filter body includes a filter body body made of metal and a fluororesin membrane provided on the entire surface of the filter body body, The cap member is convex toward the outside of the filter body, and the entire liquid-contacting surface is made of fluororesin.

2. Further, the device has a cylindrical housing, The housing has a water outlet at one end and a water inlet at the other end, The housing accommodates the filter body and the cap member such that the cap member faces the water inlet of the housing; The opening of the filter body is in communication with the water outlet of the housing. The strainer for producing pure water according to claim 1.

3. The housing and the filter body are cylindrical, 3. The strainer for producing pure water according to claim 2, wherein the cap member has a solid cone or a solid hemisphere shape.

4. 4. A strainer for producing pure water according to claim 2, wherein the open end of the filter body is connected to the outlet of the housing.

5. 3. The strainer for producing pure water according to claim 1, further comprising a connecting portion for connecting the filter body and the cap member.

6. The connection portion is The strainer for producing pure water according to claim 5, further comprising a screw member that penetrates the cap member and the end face of the filter body.

7. 3. The strainer for producing pure water according to claim 1, wherein the fluororesin membrane and the fluororesin contain polytetrafluoroethylene.

8. 3. The strainer for producing pure water according to claim 1, wherein the concentration of iron (Fe) in the pure water passed through the strainer for producing pure water is 0.1 ng / L or less.

9. The system is equipped with a primary deionizer and a secondary deionizer in this order, the secondary water purification system includes a non-regenerative mixed-bed ion exchange resin system; 3. An ultrapure water producing system comprising the strainer for producing pure water according to claim 1 or 2, disposed downstream of the non-regenerative mixed-bed ion exchange resin device.

10. 10. The ultrapure water producing system according to claim 9, wherein the iron (Fe) concentration in the pure water that has passed through the strainer for producing pure water is 0.1 ng / L or less.

11. A method for producing ultrapure water in which raw water is treated in a primary water purification system and a secondary water purification system in this order, the secondary water purification system includes a non-regenerative mixed-bed ion exchange resin system and a pure water production strainer attached to the non-regenerative mixed-bed ion exchange resin system and arranged downstream of the non-regenerative mixed-bed ion exchange resin system; The strainer for producing pure water includes a cylindrical filter body that is open at both ends and has a plurality of filter holes on a side surface, and a cap member that is liquid-tightly adhered to one end of the filter body, The filter body includes a filter body body made of metal and a fluororesin membrane provided on the entire surface of the filter body body, the cap member has a convex shape facing the outside of the filter body, and the entire liquid-contacting surface is made of fluororesin; A method for producing ultrapure water having an iron (Fe) concentration of 0.1 ng / L or less.

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