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

Abstract

A pure water filter capable of significantly suppressing iron elution for a long period, and an ultrapure water production system and an ultrapure water production method using the same. The pure water production filter (1) has a filter body (11) in a cylindrical shape with both ends open and a plurality of filter holes on the side surface, and a cover member (12) liquid-tightly bonded to one end of the filter body (11), the filter body (11) having a filter body main body composed of metal and a fluororesin film provided on the entire surface of the filter body main body, the cover member (12) being convex toward the outside of the filter body main body (11), and the entire liquid receiving surface being composed of fluororesin.

Description

Technical Field

[0001] This invention relates to filters for producing pure water, ultrapure water production systems using such filters, and ultrapure water production methods. Background Technology

[0002] In semiconductor manufacturing processes such as cleaning semiconductor wafers, ultrapure water with highly purified impurities is widely used. Ultrapure water is produced by an ultrapure water production system, which integrates water treatment devices according to the desired water quality. This system includes a pretreatment unit, a primary pure water unit, and a secondary pure water unit. Raw water, such as tap water, well water, and industrial water, is processed sequentially by each unit to produce ultrapure water. The produced ultrapure water is then supplied to the point of use (POU) via a supply pipeline.

[0003] For ultrapure water used in semiconductor manufacturing processes, in order to cope with the high miniaturization of semiconductor products, the concentration of metals (Fe, Cr, Ni, Mo, etc.) is required to be below 1 ng / L, and sometimes below 0.1 ng / L.

[0004] To improve the quality of ultrapure water, a non-regenerative mixed-bed ion exchange resin unit (fine treatment unit) is installed near the end (downstream) of the secondary pure water system to remove residual ions. Furthermore, to suppress water quality deterioration caused by trace amounts of resin from the fine treatment unit, especially leakage from damaged resin within the fine treatment unit, a filter is sometimes installed downstream of the fine treatment unit to capture the resin. From the perspective of strength and corrosion resistance, this filter is generally made of SUS (stainless steel). However, if an SUS filter is used for a long period, metallic components such as iron (Fe), nickel (Ni), and chromium (Cr), especially iron (Fe), may dissolve into the water. Since the downstream section of the filter lacks a device to remove the dissolved iron, this can lead to deterioration of the ultrapure water quality.

[0005] To address the aforementioned issues, a filter has been proposed where the water inlet is made of a low-leaching material, such as titanium, titanium alloys, or nickel alloys (see, for example, Patent Document 1). Furthermore, an ion exchange tower with a container and its lid lined with a synthetic resin has also been proposed (see, for example, Patent Document 2).

[0006] Existing technical documents Patent documents Patent Document 1: International Publication No. 2023 / 053572 Patent Document 2: Japanese Patent Application Publication No. 2011-67793 Summary of the Invention

[0007] The problem that the invention aims to solve As mentioned above, in order to meet the requirements of highly miniaturized semiconductor products, ultrapure water requires a metal (Fe, Cr, Ni, Mo, etc.) concentration of less than 0.1 ng / L to less than 1 ng / L. In particular, when heating and cooling pure water in a secondary pure water unit, and in the long-term production of ultrapure water, it has been found that the contamination of iron (Fe) is difficult to avoid.

[0008] In addition, titanium, titanium alloys, nickel alloys, etc. are generally expensive, which increases the manufacturing cost of filters and ultrapure water produced using these filters.

[0009] The present invention was made to solve the above-mentioned problems, and its purpose is to provide a filter for producing pure water that can significantly suppress iron leaching over a long period of time, as well as an ultrapure water production system and ultrapure water production method using the filter for producing pure water.

[0010] Methods for solving problems As mentioned above, further research is needed to suppress iron from mixing into the pure water in the secondary pure water device. The inventors have discovered that by using fluororesin to form the surface of the filter located at the downstream end of the non-regenerative mixed bed ion exchange resin device (fine treatment device), it is possible to suppress the leaching of iron from the filter and significantly reduce the iron concentration in the ultrapure water over a long period of time.

[0011] The pure water production filter, ultrapure water production system, or ultrapure water production method according to embodiments of the present invention are as follows.

[0012] [1] A filter for producing pure water, comprising a cylindrical filter body with openings at both ends and multiple filter holes on the sides, and a cover member liquid-tightly bonded to one end of the filter body. The filter body comprises a filter body body made of metal and a fluoropolymer membrane disposed on the entire surface of the filter body body. The cover component is convex towards the outside of the filter body, and the entire liquid contact surface is made of fluororesin.

[0013] [2] The filter for producing pure water according to [1], wherein, It also has a cylindrical outer shell. The outer casing has a water outlet at one end and a water inlet at the other end. The housing accommodates the filter body and the cover member with the cover member facing the water inlet of the housing. The opening of the filter body is connected to the water outlet of the outer shell.

[0014] [3] The filter for producing pure water according to [2], wherein, The outer shell and the filter body are cylindrical. The cover component is a solid cone or a solid hemisphere.

[0015] [4] A filter for producing pure water according to [2] or [3], wherein, The open end of the filter body is connected to the water outlet of the outer casing.

[0016] [5] A filter for producing pure water according to any one of [1] to [4], wherein, The filter for producing pure water has a connecting portion that connects the filter body and the cover member.

[0017] [6] The filter for producing pure water according to [5], wherein, The connecting part has a threaded member that passes through the end face of the cover member and the filter body.

[0018] [7] A filter for producing pure water according to any one of [1] to [6], wherein, The fluoropolymer membrane and the fluoropolymer contain polytetrafluoroethylene.

[0019] [8] A filter 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 filter for pure water production is less than 0.1 ng / L.

[0020] [9] An ultrapure water production system, comprising a primary pure water unit and a secondary pure water unit, in sequence. Secondary pure water systems include non-regenerative mixed-bed ion exchange resin systems. The ultrapure water production system includes a pure water production filter, as described in any one of [1] to [8], downstream of the non-regenerative mixed-bed ion exchange resin device.

[0021]

[10] According to the ultrapure water manufacturing system described in [9], wherein, The iron (Fe) concentration in the pure water that has passed through the filter for pure water production is less than 0.1 ng / L.

[0022]

[11] A method for producing ultrapure water, wherein raw water is treated sequentially using a primary pure water unit and a secondary pure water unit. The secondary pure water system includes a non-regenerative mixed-bed ion exchange resin device and a pure water production filter attached to and configured downstream of the non-regenerative mixed-bed ion exchange resin device. The pure water production filter has a cylindrical filter body with openings at both ends and multiple filter holes on the sides, and a cover member liquid-tightly bonded to one end of the filter body. The filter body comprises a filter body body made of metal and a fluoropolymer membrane disposed on the entire surface of the filter body body. The cover component is convex towards the outside of the filter body, and the entire liquid-contacting surface is made of fluororesin. The ultrapure water manufacturing method produces ultrapure water with an iron (Fe) concentration of less than 0.1 ng / L.

[0023] It should be noted that the symbol "~" indicates the range of values ​​to its left and right.

[0024] Invention Effects The filter for producing pure water according to the embodiment can significantly suppress iron leaching over a long period of time.

[0025] Furthermore, according to the ultrapure water production system and method of the pure water production filter according to the usage implementation method, it is possible to produce high-quality ultrapure water with extremely low iron concentration for a long period of time. Attached Figure Description

[0026] Figure 1 This is a schematic cross-sectional view of a pure water production filter 1 according to an embodiment.

[0027] Figure 2 This is a schematic cross-sectional view of the first connection 13 in other ways.

[0028] Figure 3 This is a flowchart that schematically illustrates the manufacturing method of a filter for producing pure water according to an embodiment.

[0029] Figure 4 This is a block diagram that schematically represents an ultrapure water production system. Detailed Implementation

[0030] [Filter for pure water production] Hereinafter, a filter for producing pure water according to an embodiment of the present invention will be described with reference to the accompanying drawings. Figure 1 This is a schematic cross-sectional view of a pure water production filter 1 according to an embodiment. The pure water production filter 1 of this embodiment includes a cylindrical filter body 11 with openings at both ends and a cover member 12. The side surface of the filter body 11 has multiple filter holes, forming a filter surface 11a. In the pure water production filter 1, as the water to be treated flows from the filter surface 11a on the side surface of the filter body 11 into the interior of the filter body 11, impurities such as resin in the water are removed, and the treated water flows out from the opening at the downstream end of the filter body 11. Hereinafter, the two ends of the filter body 11 will be referred to as the upstream end and the downstream end according to the flow of water through the filter body 11.

[0031] The filter element 11 comprises a filter body made of metal and a fluoropolymer membrane disposed on its entire surface. The fluoropolymer membrane spans the entire surface of the filter body; specifically, the liquid-contacting surfaces of the filter element 11, such as the filter surface, the surface of the filter pores, and the inner wall surface of the filter element, are all covered by the fluoropolymer membrane. Regarding the metal constituting the filter body, stainless steel (SUS) such as SUS304, SUS316, SUS316L, and SUS304L can be cited as examples; SUS316 or SUS316L is more preferred in terms of strength and corrosion resistance. The filter body is, for example, composed of a filter element and multiple rod-shaped support members. The filter element is composed of a spirally wound wire, and the multiple rod-shaped support members are arranged along the spiral length direction of the filter element and are separated in the circumferential direction of the spiral. The cross-sectional shape of the wire is, for example, triangular, and the wire is arranged with the apex of the triangle facing inwards towards the filter body, forming a gap between the spiral wire and the support members that functions as filter pores. The diameter of the filter pores only needs to be small enough that the ion exchange resin cannot pass through, for example, the diameter (inner diameter) is about 0.3 mmφ. In addition, the filter body 11 is, for example, a cylindrical shape with an outer diameter of 15 mmφ to 220 mmφ or 15 mmφ to 165 mmφ.

[0032] The pure water production filter 1 of this embodiment, for example, is manufactured as described later in the method for manufacturing a pure water production filter. A fluoropolymer membrane is formed on the surface of the filter body 11, which is open at both ends, and then the rear cover member 12 is connected, thereby making it easy to line or coat the surface of the filter body 11. Therefore, even for complex shapes with many filter holes, the fluoropolymer membrane can be formed easily and uniformly. If the lining or coating is insufficient and the fluoropolymer membrane has defects such as pinholes, even small defects can lead to the deterioration of the ultrapure water quality. However, for example, by forming a fluoropolymer membrane on the surface of the filter body 11, which is open at both ends, a fluoropolymer membrane without the above-mentioned defects can be formed by lining or coating, and the entire liquid-contacting surface of the filter body 11 can be covered with the fluoropolymer membrane.

[0033] It should be noted that, for example, the presence of the fluoropolymer membrane on the entire surface of the filter body 11 can be confirmed by the following methods. First, in an ultrapure water production system, the pure water production filter 1 of the embodiment is attached to a non-regenerating mixed-bed ion exchange resin device and placed downstream of it. During continued ultrapure water production, for example, it can be confirmed whether ultrapure water with an iron concentration of less than 1.0 ng / L can be obtained within a period of 30 days or more after rinsing. Second, as an accelerated test, for example, the pure water production filter is immersed in ultrapure water for 7 days, and the iron concentration in the immersed ultrapure water is measured. Simultaneously, under the same conditions, the iron concentration in the immersed ultrapure water is measured when a fluoropolymer sheet with the same or equal (error ±5%) surface area as the pure water production filter, or an SUS sheet that has been lined or coated with fluoropolymer (hereinafter, both are referred to as "comparative samples") has been immersed. Alternatively, this can be confirmed by comparing the measured values ​​obtained from the pure water production filter with those from the comparative sample, thus determining whether there is a significant difference in the iron concentration in the ultrapure water impregnated with the pure water production filter compared to the iron concentration in the ultrapure water impregnated with the comparative sample. In this case, for example, if the iron concentration is determined by separately measuring the iron concentration in ultrapure water impregnated with multiple comparative samples, and the determination is performed at a significance level of 2.5%, then if the iron concentration in the ultrapure water impregnated with the pure water production filter is set as F... samp The average value calculated based on the iron concentration in the ultrapure water impregnated with the comparative sample is denoted as F. ave If the standard deviation is set as σ, then in F samp ≤F ave With a value of +1.96×σ, it can be determined that a fluoropolymer membrane is present on the entire surface of the filter body 11. Alternatively, this can be determined by repeatedly measuring the iron concentration in ultrapure water containing a comparative sample. It should be noted that the test method is preferably based on, for example, the leaching test method for piping materials for ultrapure water according to UC standard specifications (UCS12 Semiconductor Industry Development and UCS12 Results, edited by the Semiconductor Baseboard Technology Research Association, published September 28, 2002, ISBN 4898080278, pp. 1181-1188). Using this method, since it is a non-flowing system, the leaching material can dissolve in a small amount of ultrapure water, thus making it an accelerated test and easy to measure. Thirdly, as a further accelerated test, it can also be confirmed by using an aqueous solution of hydrogen peroxide or sulfuric acid or a mixture thereof instead of ultrapure water in the second method, otherwise using the same method as the second method. In this case, the immersion time can be measured, for example, at approximately one day.

[0034] In the pure water production filter 1, the cover member 12 is liquid-tightly bonded to the upstream end of the filter body 11. The cover member 12 has a convex shape extending outward from the upstream end of the filter body 11, and at least the liquid-contact surface is made of fluororesin. The cover member 12 may also be composed of a cover member body made of metal such as SUS and a fluororesin membrane provided on the surface of the cover member body, and the entire cover member may also be made of fluororesin. Due to its light weight and ease of operation, it is preferable that the entire cover member 12 is made of fluororesin. The cover member may be hollow or solid, but from the perspective of ease of manufacture, a solid cover member is preferred, and more preferably, the entire cover member 12 is made of solid fluororesin.

[0035] The cover member 12 preferably has at least a bottom surface and a side surface that rises from the bottom surface. The bottom surface of the cover member 12, i.e., the opposite side of the convexity, is connected to the opening at the upstream end of the filter body 11 via the first connecting portion 13. As for the convex shape of the cover member 12, examples include a convex cross section, i.e., a cross section perpendicular to the bottom surface and passing through the point farthest from the bottom surface that is a polygon, quadrilateral, triangle, semicircle, etc.

[0036] Preferably, the convex shape of the cover member 12 is such that it does not generate flow deviation or eddies in the water flow on the surface of the cover member 12. If flow deviation or eddies are generated in the water flow on the convex surface of the cover member 12, the filter will vibrate due to the water flow. Since the ultrapure water production system operates continuously for at least one year, and sometimes for several years, the long-term vibration of the filter will cause deterioration of the fluoropolymer membrane on the filter surface, potentially leading to the generation of resin fragments and the leaching of iron from the SUS surface covered by the resin. Specifically, a triangular, semi-circular, or semi-elliptical convex cross-section is preferred as the convex cross-section that does not generate such flow deviation or eddies. In the case of a triangular convex cross-section, for example, one side of the triangle is located on the upstream end side of the filter body 11. In the case of a semi-circular convex cross-section, for example, the diameter of the semicircle is located on the upstream end side of the filter body 11. In the case of a semi-elliptical convex cross-section, for example, the major or minor axis of the semi-ellipse is located on the upstream end side of the filter body 11. Regarding the convex shape of the cover member 12, for example, when the opening of the filter body 11 is circular, a hemisphere, a semi-ellipsoid, or a cone is preferred from the viewpoint that it is less likely to cause flow deviation on the surface of the cover member 12. In particular, when the shape of the cover member 12 is conical, the inclination of the side from the apex to the bottom surface is fixed, so a straightening effect on the treated water can also be obtained, which is more preferable. Furthermore, water accumulation on the surface of the cover member 12 causes impurities such as those dissolved from various components to be retained and accumulated in the accumulation. In this case, with changes in the treated water flow rate, such as a sharp increase or decrease, or the opening and closing of valves, a large amount of impurities may flow into the pure water, leading to water quality deterioration.

[0037] Preferably, the outer diameter of the cover member 12 is the same as or approximately the same as the outer diameter of the opening of the filter body 11 and is larger than the outer diameter of the opening of the filter body 11. This allows for adjustment of the water flow around the first connection portion 13 between the filter body 11 and the cover member 12, thereby suppressing the deterioration of the lining or coating as described above.

[0038] The fluororesin used in the cover member 12 and the fluororesin membrane on the surface of the filter body 11 are not particularly limited. Examples include tetrafluoroethylene and perfluoroether copolymer (PFA, perfluoroalkoxyalkane), polytetrafluoroethylene (PTFE), and ethylene / tetrafluoroethylene copolymer (ETFE). The fluororesin in the cover member 12 and the fluororesin membrane on the surface of the filter body 11 can be the same or different, but they are preferably the same.

[0039] When using ETFE as a fluoropolymer, to control crystallinity, ETFE is preferably a product obtained by copolymerizing ethylene and tetrafluoroethylene with other fluorinated monomers. As for the other fluorinated monomers, there are no particular limitations as long as they can be added to both ethylene and tetrafluoroethylene, but fluorinated vinyl monomers with 3 to 8 carbon atoms are readily used; examples include hexafluoroisobutylene and CH2=CFC3F6H. From the viewpoint of not impairing heat resistance, flame retardancy, and chemical resistance, the other fluorinated monomers are preferably 5 mol% or less of the total monomer content of the ETFE.

[0040] When ETFE is a substance obtained by copolymerizing other fluorinated monomers, the fluorine content in ETFE is preferably 50% by mass or more. A fluorine content of 50% by mass or more provides excellent heat resistance, flame retardancy, and chemical resistance. For example, the fluorine content of ETFE is 70% by mass or less. The fluorine content can be adjusted by appropriately regulating the ratio of ethylene, tetrafluoroethylene, and the other monomers mentioned above used as needed. The aforementioned fluorine content is obtained by burning the fluoropolymer, causing the fluorine contained therein to be absorbed into alkaline water, etc., and then measuring it using an ion chromatograph or similar instrument.

[0041] Among the aforementioned fluororesins, tetrafluoroethylene and perfluoroether copolymer (PFA, perfluoroalkoxyalkane) and polytetrafluoroethylene (PTFE) resin are widely and commonly used raw materials in ultrapure water production equipment due to their excellent heat resistance and chemical resistance, and can be appropriately used for fluororesin membranes on cover component 12 and filter body 11.

[0042] The first connecting portion 13 is not particularly limited as long as it can liquid-tightly connect the filter body 11 and the cover member 12. Examples of the first connecting portion 13 include those formed by soldering, fusion welding, or welding, where the material state of the connecting portion changes during connection. Alternatively, it can be a mechanically constructed connection that does not involve a change in the material state of the connecting portion, for example, using a screw or one or more threaded components. The first connecting portion 13 is preferably a mechanically constructed connecting portion so as not to cause defects in the fluoropolymer film on the surface of the filter body 11 when connecting the filter body 11 and the cover member 12.

[0043] like Figure 1 As shown, for example, a first connector 131 with a mountain-shaped portion 131a on its outer surface is connected to the bottom surface of the cover member 12, and a cylindrical second connector 132 with a spiral groove 132a on its inner wall that engages with the mountain-shaped portion is connected to the upstream end of the filter body 11. The filter body 11 and the cover member 12 can be connected by the engagement of the mountain-shaped portion of the first connector 131 and the groove of the second connector 132. In this case, the first connector 13 includes a first connector 131, a mountain-shaped portion 131a provided in the first connector 131, a second connector 132, and a groove 132a provided in the second connector 132. Alternatively, instead of having a mountain-shaped portion in the first connector 131 and a groove in the second connector 132, the first connector 131 may have a groove, and the inner wall of the second connector 132 may have a mountain-shaped portion. To improve the liquid tightness between the filter body 11 and the cover member 12, a sealing member such as an O-ring made of resin can be sandwiched between the end face of the second connector 132 of the filter body 11 and the outer periphery of the bottom surface of the cover member 12.

[0044] Figure 2 This is a schematic cross-sectional view of the first connection portion 13 in other configurations. For example... Figure 2 As shown, a third connector 133 is provided on the end face of the upstream end of the filter body 11. The third connector 133, for example, is arranged along the periphery of the upstream end of the filter body 11 and is a solid annular shape with thickness in both the axial and circumferential directions. A plurality of threaded holes 134 are provided near the outer periphery of the cover member 12, through which threaded members 142, etc., pass through the cover member 12 and the third connector 133, thus connecting the filter body 11 and the cover member 12. In this case, the first connecting portion 13 includes the cover member 12 and the threaded member 142 that passes through the cover member 12 and is inserted into the third connector 133. It should be noted that, in order to improve the liquid tightness between the filter body 11 and the cover member 12, a sealing member such as an O-ring formed of resin may also be sandwiched between the end face of the upstream end of the third connector 133 and the bottom surface of the cover member 12. In this case, the first connecting portion 13 also includes a sealing member.

[0045] like Figure 2As shown, when using threaded member 142 to connect filter body 11 and cover member 12, water may accumulate on or near the surface (thread head) of threaded member 142, and iron may leach from the threaded member if it is metal. However, since the size of threaded member 142 is tiny compared to filter body 11, their impact on the quality of treated water is minimal. If there are depressions on or near the surface of threaded member 142, it is preferable to fill these depressions with fluoropolymer to form a protective portion, thereby improving the quality of ultrapure water obtained as treated water. In this case, the protective portion can be made of a different fluoropolymer than that used in cover member 12, or it can be the same fluoropolymer, but the same fluoropolymer is preferred.

[0046] Figure 1 The pure water production filter 1 shown also includes a cylindrical outer shell 15 that houses the filter element 11. The outer shell 15 internally houses the entire filter element 11. At both ends of the outer shell 15, a discharge port 15a is opened at the downstream end, and a water inlet 15b is opened at the upstream end. The outer shell 15 can be a continuous cylindrical shape with a fixed inner diameter, or it can be a shape in which multiple cylindrical sections with different inner diameters are continuously connected. In addition, a portion of the cylinder, particularly at both ends or one end, may have a tapered shape with the diameter decreasing towards the end. It should be noted that a fluoropolymer membrane is preferably provided on the inner surface of the outer shell 15, and, if necessary, on the liquid-contacting surface outside the inner surface. The fluoropolymer membrane on the inner surface of the outer shell 15, like that of the filter element 11, can be formed by lining or coating.

[0047] In the pure water production filter 1, the filter body 11 and the cover member 12 are arranged and housed within the housing 15 with the cover member 12 facing the water inlet 15b of the housing 15. Furthermore, the opening at the downstream end of the filter body 11 communicates with the water outlet 15a of the housing 15, and the treated water that has passed through the filter surface 11a of the filter body 11 is discharged from the water outlet 15a of the housing.

[0048] The filter element 11 and the outer casing 15 are connected via a second connecting portion 18. The second connecting portion 18 is not particularly limited as long as it allows for a liquid-tight connection between the filter element 11 and the outer casing 15. Figure 1In the pure water production filter 1 shown, the outlet pipe 20 is connected to the housing 15 via a second connecting portion 18. The outlet pipe 20 has an outlet pipe body 24 and a flange portion 22 that is continuously disposed along the outer circumferential direction from the upstream end of the outlet pipe body 24. A threaded hole is provided in the flange portion 22. The housing 15 has a flange portion 151 that is continuously disposed along the outer circumferential direction from the downstream end of the housing 15, and a threaded hole is provided in the flange portion 151. Furthermore, a fourth connecting body 148 is connected to the downstream end of the filter body 11. The fourth connecting body 148 is disposed along the periphery of the downstream end of the filter body 11 and is a solid annular shape with thickness in both the axial and circumferential directions. A portion of the outer diameter of the downstream end side of the outer periphery of the fourth connecting body 148 (the side opposite to the side connected to the downstream end of the filter body 11) is larger than that of the upstream end, and a cutout is provided for the flange portion 151 to fit into.

[0049] In the pure water production filter 1, a cutout of a fourth connector 148 is provided between the flange portion 151 and the flange portion 22, allowing a threaded member 144a to pass through the threaded holes of the flange portion 151 and the flange portion 22. The threaded member 144a is fixed by a threaded fixing member 144b, thus forming a second connection portion 18. That is, the second connection portion 18 includes the flange portion 151 and the fourth connector 148, the flange portion 22, the threaded member 144a passing through the flange portion 151 and the flange portion 22, and the threaded fixing member 144b. It should be noted that sealing members such as O-rings formed of resin can also be sandwiched between the cutout of the flange portion 151 and the fourth connector 148, and between the downstream end face of the fourth connector 148 and the flange portion 22, respectively, to improve the liquid tightness of the second connection portion 18. At this time, the second connection part 18 also includes sealing members 146a and 146b.

[0050] Next, other connection methods between the filter body 11 and the housing 15 will be described. In this method, a connection with... Figure 1 The filter body 11 and the cover member 12 shown have the same connection structure. That is, a cylindrical sixth connector with a spiral groove on its inner wall is connected to the upstream end of the outlet pipe 20, and a cylindrical fifth connector with a bevel on its outer surface that screws into the groove is connected to the downstream end of the filter body 11, and the connection is achieved by the screwing of the groove and the bevel. In this case, the second connection part 18 includes a fifth connector, a bevel provided on the fifth connector, a sixth connector, and a groove provided on the inner wall of the sixth connector. Alternatively, instead of having a bevel on the inner wall of the fifth connector and a groove on the sixth connector, the inner wall of the fifth connector may have a groove, and the sixth connector may have a bevel. To improve the liquid tightness between the filter body 11 and the outer shell 15, a sealing member such as an O-ring formed of resin may be sandwiched between the end face of the downstream end of the fifth connector and the end face of the upstream end of the sixth connector. In this case, the second connection part 18 also includes a sealing member.

[0051] Preferably, the pure water production filter 1 in this embodiment is a non-regenerative mixed-bed ion exchange resin device (fine treatment device) attached to a secondary pure water unit and disposed downstream therefrom. In this case, the Fe concentration in the pure water passing through the pure water production filter can be obtained to be 0.1 ng / L or less.

[0052] [Manufacturing method of filter for pure water production] The manufacturing method of the filter for pure water production according to this embodiment will be described. Figure 3 This is a flowchart that schematically illustrates the manufacturing method of a filter for producing pure water according to an embodiment. Figure 3 The method for manufacturing a pure water filter shown includes: an assembly step S80, assembling a filter body 11; a fluoropolymer membrane formation step S82, forming a fluoropolymer membrane on the surface of the filter body; and a connection step S84, connecting a cover member 12 and each connector (a first connector, a second connector, or a third connector) to the filter body 11 on which the fluoropolymer membrane is formed.

[0053] First, in assembly step S80, the filter body 11 is assembled. In assembly step S80, a commercially available bag-shaped filter with a sealed upstream end and an open downstream end can also be used as raw material, and the filter body 11 of the embodiment is obtained by opening the upstream end of the filter.

[0054] Next, in the fluoropolymer membrane formation step S82, the aforementioned fluoropolymer membrane is formed on the surface of the filter body. The method for forming the fluoropolymer membrane can be a coating method such as dip coating, spray coating, electrostatic coating, brush coating, or roller coating, or a lining method such as electrostatic powder coating or sheet lining. Spray coating is preferred in terms of uniformly forming the fluoropolymer membrane on the inner surface of the filter pores of the filter surface 11a. The thickness of the fluoropolymer membrane formed on the surface of the filter body 11 is typically about 200 μm to 300 μm.

[0055] Next, the cover member 12 and each connector are connected to the filter body 11 as described above. Furthermore, the filter body 11 with the cover member 12 attached is housed in the outer casing 15 as needed. When using a hollow or solid cover member 12 made of fluororesin, the cover member 12 can be obtained by machining the fluororesin block using a machine tool or the like after the fluororesin has been formed into a block. More specifically, a cylindrical fluororesin rod can be cut from the fluororesin block, or the desired shape can be manufactured by machining the fluororesin rod after it has been formed into a cylindrical shape. It should be noted that since the cover member 12 is solid, pure water can be prevented from stagnating inside the cover. Therefore, since the cover member 12 is solid, it does not contribute to the main factors of water quality deterioration, and is therefore preferred. The cover member can also be made of stainless steel, polypropylene, or polyethylene. In these cases, it is preferable to coat or line the surface with a fluorine-based raw material.

[0056] It should be noted that, in the above description, the scheme of connecting each connector after forming a fluoropolymer membrane on the filter body 11 has been explained. However, it is also possible to form a fluoropolymer membrane after connecting each connector to the filter body 11. In the manufacturing method of the pure water production filter of this embodiment, by forming a fluoropolymer membrane on the surface of the filter body 11 which is open at both ends, lining or coating can be easily performed. Therefore, even for complex shapes with many filter holes, a fluoropolymer membrane can be formed easily and uniformly. If the lining or coating is insufficient and the fluoropolymer membrane has defects such as pinholes, even small defects can lead to the deterioration of the ultrapure water quality. However, by forming a fluoropolymer membrane on the surface of the filter body 11 which is open at both ends, a fluoropolymer membrane without the aforementioned defects can be formed by lining or coating, and a pure water production filter suitable for the production of ultrapure water can be obtained.

[0057] [Ultrapure water production system and ultrapure water production method] Next, the ultrapure water manufacturing system and ultrapure water manufacturing method of this embodiment will be described.

[0058] The ultrapure water production system of this embodiment includes: a primary pure water device for performing primary pure water treatment to convert raw water or pretreated water into primary pure water; and a secondary pure water device, including the above-mentioned pure water production filter, for performing secondary pure water treatment to convert primary pure water into secondary pure water.

[0059] Figure 4This is a block diagram schematically illustrating the ultrapure water production system 100 of this embodiment. The ultrapure water production system 100 comprises a pretreatment unit 112, a primary pure water unit 114, a pure water tank 116, and a secondary pure water unit 117. The secondary pure water unit 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 device (fine treatment device) 126, and an ultrafiltration (UF) device 128. Furthermore, a pure water production filter 1 of the above embodiment is provided downstream of the non-regenerative mixed-bed ion exchange resin device 126.

[0060] (Pretreatment device) Raw water is supplied to the pretreatment unit 112. The pretreatment unit 112 is equipped with a coagulation sedimentation device, a sand filtration device, a membrane filtration device, etc., to remove turbidity from the raw water and produce pretreated water in which some of the suspended solids and organic matter have been removed. Examples of raw water include industrial water, tap water, groundwater, and river water.

[0061] (Pure water system) The primary pure water unit 114 further purifies the pretreated water, removing impurities to produce primary pure water. Specifically, the primary pure water unit 114 includes various devices such as a desalination device for removing impurity ions, a reverse osmosis membrane device for removing inorganic ions, organic matter, particles, etc., a vacuum degassing device or membrane degassing device for removing dissolved gases such as dissolved oxygen, and a regenerative mixed bed desalination device for removing residual ions, etc.

[0062] (Pure water tank) The primary purified water obtained from the primary purified water unit 114 is conveyed to the pure water tank 116. The primary purified water obtained from the primary purified water unit 114 is temporarily stored in the pure water tank 116. The material and shape of the pure water tank 116 are not particularly limited, as long as it does not rust, has minimal leaching of components from the container, and can stably store the primary purified water. The material of the pure water tank 116 is preferably, for example, fiber-reinforced plastic (FRP), polyethylene, SUS304, or materials lined with Teflon (registered trademark). Furthermore, to prevent the absorption of impurity gases such as carbon dioxide and dissolved oxygen, the upper part of the pure water tank 116 is preferably purged with pure nitrogen. As described later, when circulating unused ultrapure water from the produced ultrapure water, the pure water tank 116 can also store the aforementioned primary purified water mixed with ultrapure water.

[0063] (Water pump) The water pump 118 delivers primary purified water from the purified water tank 116 to the heat exchanger 120. The composition of the water pump is not particularly limited. For example, even if the part in contact with the primary purified water is made of a material from which trace amounts of metallic components, such as stainless steel, are dissolved, these dissolved metallic components are adsorbed by the ion exchange resin in the non-regenerative mixed-bed ion exchange resin unit (refining unit) 126. Therefore, the material of the part of the water pump 118 in contact with the primary purified water has virtually no impact on the quality of the produced ultrapure water. Therefore, a water pump commonly used in the production of pure water can be used as the water pump 118.

[0064] (Heat exchanger) In heat exchanger 120, the temperature of pure water is adjusted once by heat exchange (heating or cooling). For example, a flat-plate heat exchanger can be used as heat exchanger 120, but its specific construction is not particularly limited. Generally, the heat exchanger adjusts the water temperature to room temperature, for example, around 20°C. However, sometimes it is adjusted to 60–80°C; in this case, the produced ultrapure water is called hot ultrapure water. It should be noted that in the case of producing hot ultrapure water, in addition to heat exchanger 120, a heat exchanger can also be provided. In this case, the heat exchanger is, for example, located between the pure water production filter 1 and the ultrafiltration (UF) device 128.

[0065] (Ultraviolet irradiation device) The purified water, after being conditioned by the heat exchanger 120, is conveyed to the ultraviolet irradiation device 122. In the ultraviolet irradiation device 122, the purified water is irradiated with ultraviolet light to decompose organic matter and inactivate bacteria (sterilize). The ultraviolet irradiation device 122 is equipped with ultraviolet lamps capable of irradiating wavelengths around 185 nm and 254 nm, reliably decomposing organic matter and sterilizing the purified water. The ultraviolet lamp used in the ultraviolet irradiation device 122 is not particularly limited, but a low-pressure mercury lamp is preferred for ease of operation. Furthermore, examples of ultraviolet irradiation devices 122 include a flow-through type where the ultraviolet lamp is arranged inside the housing along the flow path of the treated water, or an immersion type where the ultraviolet lamp is immersed in a tank storing the treated water; however, from the viewpoint of treatment efficiency, a flow-through type is preferred.

[0066] (Membrane degassing device) The membrane degassing device 124 uses a gas separation membrane that allows gas to pass through but not water to remove gas from primary pure water, especially dissolved oxygen.

[0067] (Non-regenerative mixed-bed ion exchange resin device) The purified water, after having its dissolved oxygen concentration removed by the membrane degassing device 124, is then transported to the 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 by the ultraviolet irradiation device 122, or impurity ions such as metal ions remaining in the water.

[0068] (Filter for pure water production) In the ultrapure water production system 100, a pure water production filter 1 is provided downstream of the non-regenerative mixed-bed ion exchange resin device 126, attached to the non-regenerative mixed-bed ion exchange resin device 126. This suppresses the leaching of Fe from the metal constituting the filter, thereby improving the quality of the treated water.

[0069] (Ultrafiltration device) Primary purified water, after impurity ions have been removed by the non-regenerating mixed-bed ion exchange resin unit 126, is conveyed to the ultrafiltration (UF) unit 128. The ultrafiltration (UF) unit 128 removes particulates to produce ultrapure water. The ultrafiltration (UF) unit 128 is located at the end of the secondary purified water unit 117.

[0070] It should be noted that in the secondary pure water unit 117, for example, in order to remove hydrogen peroxide that is generated secondarily in the ultraviolet irradiation device, other treatment devices such as catalyst resin filling towers may be installed as needed to obtain ultrapure water with the desired purity.

[0071] Furthermore, to increase the water supply pressure to the ultrafiltration unit 128, a booster pump can 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 dissolve, resulting in an increase in metal concentration. Therefore, in the case of producing ultrapure water with lower metal concentration, it is preferable not to install a booster pump, or to use a booster pump whose contact part with the treated water is made of a material in which metal components do not dissolve or are not easily dissolved. Alternatively, it is preferable to install the booster pump upstream of the non-regenerative mixed-bed ion exchange resin unit 126.

[0072] The secondary purified water (ultrapure water) obtained through the aforementioned devices (processes) and the secondary purified water device 117 is sent to the usage location (usage point) 160, such as the process point in the semiconductor manufacturing process, through the water supply pipe 162. The ultrapure water sent out, the unused ultrapure water, is circulated to the pure water tank 116 through the circulation pipe 164 and stored in the pure water tank 116 together with the primary purified water.

[0073] Based on the aforementioned pure water production filter 1 and ultrapure water production system 100, ultrapure water with an iron content of less than 1 ng / L can be obtained, and further, ultrapure water with an iron content of less than 0.1 ng / L. This is particularly suitable for the production of ultrapure water supplied to process points in semiconductor manufacturing processes. Furthermore, ultrapure water with nickel and chromium content of less than 0.1 ng / L can be produced. These nickel and chromium components are mainly derived from stainless steel.

[0074] Example Hereinafter, embodiments of this implementation will be described, but this implementation is not limited to the following embodiments.

[0075] (Example 1) In Figure 4 In the same ultrapure water production system shown, ultrapure water is produced using a filter manufactured by the method described above, which has a solid conical cap member at the upstream end of the filter body. It should be noted that the water flow conditions are as follows.

[0076] Filter: Linear velocity 1.2m / h Products coated with PTFE with both ends open. (The width of the grooves (filter holes) on the filter surface is 0.3mm. This is a prototype manufactured by Nomura Microscience Co., Ltd.) (Comparative Example 1) Ultrapure water was produced under the same conditions, except that the following filter was used instead of the filter used in Example 1.

[0077] Filter: Made of SUS steel, with an opening on only one side. (The groove width of the filter surface is 0.3mm; this is a prototype manufactured by Nomura Microscience Co., Ltd.) (Comparative Example 2) Ultrapure water was produced under the same conditions as in Comparative Example 1, except that a filter with a PTFE-coated surface was used instead of the filter used in Comparative Example 1.

[0078] Table 1 shows the water quality at the outlet (i.e., filter inlet) and filter outlet of the non-regenerative mixed-bed ion exchange resin unit (fine treatment unit) after 30 days under the above conditions. It should be noted that the iron concentration is the value determined by inductively coupled plasma mass spectrometry (ICP-MS) after evaporating and concentrating samples collected from various locations.

[0079] [Table 1] Based on the above results, it can be confirmed that coating the existing single-sided open filter of Comparative Example 2 with fluororesin does not yield sufficient performance. The reason is believed to be as follows: Although the filter of Comparative Example 2 is a single-sided open filter coated with fluororesin, this process is not easy, and while it appears uniformly coated to the naked eye, extremely small areas are not coated or are insufficiently coated. On the other hand, it is believed that if the method of the embodiment is used, the fluororesin coating is formed uniformly and without defects, thus effectively suppressing iron leaching.

[0080] Explanation of reference numerals in the attached figures 1: Filter for pure water production; 11: Filter body; 11a: Filter surface; 12: Cover component; 13: First connecting part; 131: First connecting body; 131a: Mountain part; 132: Second connecting body; 132a: Groove part; 133: Third connecting body; 134: Threaded hole; 146a, 146b: Sealing component; 142: Threaded component; 15: Outer shell; 15a: Water outlet; 15b: Water inlet; 18: Second connecting part; 20: Water outlet pipe; 24: Water outlet pipe body; 22, 151: Flange part; 144a: Threaded component; 144b: Threaded fixing component; 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 (fine treatment device); 128: Ultrafiltration (UF) device; 160: Application site (point of use); 162: Water supply piping; 164: Circulation piping; S80: Assembly process; S82: Fluoropolymer membrane formation process; S84: Connection process.

Claims

1. A filter for producing pure water, comprising a cylindrical filter body open at both ends and having multiple filter holes on its sides, and a cover member liquid-tightly bonded to one end of the filter body. The filter body comprises a filter body body made of metal and a fluoropolymer membrane disposed on the entire surface of the filter body body. The cover component is convex towards the outside of the filter body, and the entire liquid contact surface is made of fluororesin.

2. The filter for pure water production according to claim 1, wherein, It also has a cylindrical outer shell. The outer casing has a water outlet at one end and a water inlet at the other end. The housing accommodates the filter body and the cover member with the cover member facing the water inlet of the housing. The opening of the filter body is connected to the water outlet of the outer shell.

3. The filter for pure water production according to claim 2, wherein, The outer shell and the filter body are cylindrical. The cover component is a solid cone or a solid hemisphere.

4. The filter for pure water production according to claim 2 or 3, wherein, The open end of the filter body is connected to the water outlet of the outer shell.

5. The filter for pure water production according to claim 1 or 2, wherein, The filter for producing pure water has a connecting portion that connects the filter body and the cover member.

6. The filter for pure water production according to claim 5, wherein, The connecting part has a threaded member that passes through the end face of the cover member and the filter body.

7. The filter for pure water production according to claim 1 or 2, wherein, The fluoropolymer membrane and the fluoropolymer contain polytetrafluoroethylene.

8. The filter for pure water production according to claim 1 or 2, wherein, The iron (Fe) concentration in the pure water that has passed through the filter for pure water production is less than 0.1 ng / L.

9. An ultrapure water production system, comprising a primary pure water unit and a secondary pure water unit, respectively. Secondary pure water systems include non-regenerative mixed-bed ion exchange resin systems. The ultrapure water production system includes a pure water production filter as described in claim 1 or 2 at the downstream end of the non-regenerative mixed-bed ion exchange resin device.

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

11. A method for producing ultrapure water, comprising treating raw water sequentially using a primary pure water unit and a secondary pure water unit. The secondary pure water system includes a non-regenerative mixed-bed ion exchange resin device and a pure water production filter attached to and configured downstream of the non-regenerative mixed-bed ion exchange resin device. The pure water production filter has a cylindrical filter body with openings at both ends and multiple filter holes on the sides, and a cover member liquid-tightly bonded to one end of the filter body. The filter body comprises a filter body body made of metal and a fluoropolymer membrane disposed on the entire surface of the filter body body. The cover component is convex towards the outside of the filter body, and the entire liquid-contacting surface is made of fluororesin. The ultrapure water manufacturing method produces ultrapure water with an iron (Fe) concentration of less than 0.1 ng / L.

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