Secondary pure water device

Abstract

Provided is a secondary pure water device in an ultrapure water production system comprising a primary pure water device and a secondary pure water device. The secondary pure water device includes a non-regenerative ion exchanger and an ultrafiltration membrane in the stated order. At least the downstream side of the non-regenerative ion exchanger is connected by a fluorine-free and chlorine-free synthetic resin tube. A resin tube based on a polyolefin such as polypropylene or polyethylene can be used as the fluorine-free and chlorine-free synthetic resin tube.

Description

Secondary pure water equipment

[0001] This invention relates to a secondary pure water system for an ultrapure water production apparatus.

[0002] Ultrapure water used for semiconductor cleaning is produced by treating raw water (industrial water, city water, well water, etc.) in an ultrapure water production system consisting of a pretreatment device, a primary pure water system, and a secondary pure water system (subsystem).

[0003] Pretreatment devices, consisting of coagulation, pressurized flotation (sedimentation), and filtration systems, remove suspended solids and colloidal substances from the raw water. Primary pure water systems equipped with reverse osmosis (RO) membrane separators, degassing devices, and ion exchange devices (mixed-bed, 2-bed 3-column, or 4-bed 5-column) remove ions and organic components from the raw water. In addition to salt removal, RO membrane separators remove ionic and colloidal total organic oxygen (TOC). In addition to salt removal, ion exchange devices remove TOC components adsorbed or ion-exchanged by ion exchange resins. Degassing devices (nitrogen degassing or vacuum degassing) remove dissolved oxygen.

[0004] In a secondary pure water system (subsystem) equipped with a heat exchanger, low-pressure ultraviolet (UV) oxidation device, mixed-bed ion exchange device, and ultrafiltration (UF) membrane separation device, the purity of the water is further increased to produce ultrapure water. In the low-pressure UV oxidation device, ultraviolet light with a wavelength of 185 nm emitted from a low-pressure UV lamp is used to remove TOC, organic acids, and CO2. ２ It decomposes to the point of breaking down organic acids and CO2. ２ These particles are removed by the ion exchange resin in the subsequent stage. In the UF membrane separation system, fine particles are removed, and particles that flow out of the ion exchange resin are also removed.

[0005] Patent Document 1 describes using synthetic resin for the water-contacting surfaces of equipment in a secondary pure water system. Examples of synthetic resins include fluororesins such as polytetrafluoroethylene and polyvinyl difluoride, as well as polyethylene, polypropylene, polyetheretherketone, polyvinyl chloride, and polysulfone.

[0006] Japanese Patent Publication No. 2004-167308

[0007] In semiconductor factories, maintaining ultrapure water quality is essential, which limits the materials that can be used in various components. On the other hand, the materials used often contain substances subject to environmental regulations (such as fluorine and chlorine).

[0008] For example, in the case of fluoropolymer piping, organic fluorine compounds are released into the environment during the manufacturing and disposal of the piping material, or when ultrapure water is passed through it. In the case of chlorine-based piping, harmful chlorine-based gases (such as dioxins) are generated during the manufacturing and disposal of the piping material, and during installation (heat fusion).

[0009] While polyolefin resin piping, such as polypropylene and polyethylene, can reduce environmental impact for ultrapure water, it has inferior gas barrier properties compared to fluororesin and chlorine resin piping, making it difficult to maintain the quality of ultrapure water. (For example, dissolved oxygen (DO) levels tend to rise.)

[0010] Furthermore, polyolefin resin piping exhibits inferior surface smoothness compared to fluorine-based resin piping and chlorine-based resin piping.

[0011] The present invention aims to provide a secondary pure water system that can reduce environmental impact and maintain the quality of ultrapure water.

[0012] The gist of this invention is as follows:

[0013] [1] A secondary pure water system in an ultrapure water production system comprising a primary pure water system and a secondary pure water system, wherein the secondary pure water system comprises a non-regenerative ion exchange device and an ultrafiltration membrane in that order, and is connected at least downstream of the non-regenerative ion exchange device by non-fluorine and non-chlorine synthetic resin piping.

[0014] [2] The secondary pure water apparatus of [1], wherein the DO concentration of the ultrapure water produced by the ultrapure water production system is 1 μg / L or less.

[0015] [3] The secondary pure water system of [1], wherein the non-fluorine and non-chlorine synthetic resin piping is made of polyolefin resin.

[0016] [4] The secondary pure water system of [3], wherein the polyolefin resin piping is made of polypropylene or polyethylene.

[0017] [5] The polypropylene or polyethylene piping has a capacity of 480 [cc・20 μm / (m ２ A secondary pure water system of [4] having a gas barrier layer of 24hr·atm or less.

[0018] [6] The secondary pure water system of [5], wherein the polypropylene or polyethylene piping is a multilayer piping having a gas barrier layer as the outermost layer.

[0019] [7] The amount of cation component eluted from the inner surface of the polypropylene or polyethylene pipe is 30 μg / m³. ２ One of the following secondary pure water systems: [4] to [6].

[0020] In the secondary pure water system of the present invention, at least the equipment downstream of the non-regenerative ion exchange device is connected with non-fluorine and non-chlorine synthetic resin piping, thereby reducing environmental impact and maintaining the quality of ultrapure water.

[0021] This is a flow diagram of an ultrapure water production apparatus equipped with a secondary pure water system according to an embodiment. This is a flow diagram of a secondary pure water system according to an embodiment. This is a diagram of the piping configuration used in the secondary pure water system according to an embodiment. This is a flow diagram of a secondary pure water system according to an example.

[0022] The embodiments will be described below with reference to the drawings.

[0023] Figure 1 is a flow diagram of an ultrapure water production system equipped with a secondary pure water system, and Figure 2 is a configuration diagram of the secondary pure water system (subsystem).

[0024] Raw water, consisting of industrial water, well water, or municipal water, is sent from the raw water tank 1 to the pretreatment device 2 for treatment. The pretreatment device 2 is equipped with coagulation, pressurized flotation (sedimentation), and filtration devices to remove suspended solids and colloidal substances from the raw water.

[0025] The treated water from the pretreatment device 2 is sent to the primary pure water device 4 via the filtration tank 3 for further treatment. The primary pure water device 4 can be, but is not limited to, (a) a multi-bed ion exchange device + RO (reverse osmosis) device, (b) an RO device + a high-purity ion exchange device, or (c) an RO device + a decarboxylase device + an electrodeionizer. The RO device in (b) and (c) may be a two-stage RO device.

[0026] The pure water obtained from the primary pure water system 4 is introduced into the pure water tank 5. The pure water in the pure water tank 5 is sent through piping 6 to the deaeration membrane system 7, where it is deaerated. The deaerated water is sent through piping 8 to the TOC decomposition unit 10, where it is further treated.

[0027] In this embodiment, the TOC decomposition unit 10 includes a UV oxidizer 11 and an ion exchanger (which may be a mixed-bed type, a two-bed three-column type, or a four-bed five-column type, etc.) 12 located in the subsequent stage.

[0028] A bypass line consisting of piping 13, valve 14, and piping 15 is provided to bypass the degassing membrane device 7 described above. Piping 13 connects piping 6 and valve 14, and piping 15 connects valve 14 and piping 8.

[0029] A DO (dissolved oxygen) meter 9 is installed downstream of the confluence point with pipe 15 in pipe 8. The detection signal from the DO meter 9 is input to a valve controller (not shown). The valve controller controls the opening degree of valve 14 so that the DO detected by the DO meter 9 is 10 ppb or less.

[0030] The high-purity (low TOC) primary pure water processed in the TOC decomposition unit 10 is sent to the sub-tank 17 through piping 16. A branch pipe 16A branches off from piping 16, allowing a portion of the high-purity (low TOC) primary pure water from the TOC decomposition unit 10 to be returned to the pure water tank 5. A flow control valve (not shown) is provided downstream of the branch of piping 16A in piping 16, and the opening of this valve is controlled so that the water level in the sub-tank 17 is within a predetermined range.

[0031] Ultrapure water returning from the use point 36 is also introduced into the sub-tank 17 through the piping 37.

[0032] The water in the sub-tank 17 is sent through the piping 18 to the secondary pure water system (hereinafter sometimes referred to as the subsystem) 20. The ultrapure water produced by processing in the subsystem 20 is sent through the piping 35 to the use point 36, and the unused ultrapure water is returned to the sub-tank 17 through the piping 37.

[0033] Subsystem 20, as shown in Figure 2, includes a sub-pump 19, a cooler (heat exchanger) 21, a low-pressure ultraviolet (UV) oxidizer 22, a non-regenerative ion exchanger 23, a degassing membrane device 24, and an ultrafiltration membrane (UF) device 25. These devices are connected by piping 31 to 34.

[0034] In this embodiment, at least the piping 33, 34, and 35 downstream of the non-regenerative ion exchange device 23 is made of non-fluorine and non-chlorine synthetic resin piping, and preferably all the piping 18, 31-35 is made of non-fluorine and non-chlorine synthetic resin piping.

[0035] For this non-fluorine and non-chlorine synthetic resin piping, polyolefin resin piping is preferred.

[0036] The polyolefin resin can be any polymer containing monomer units derived from olefins. Examples include polypropylene resins, polyethylene resins, ethylene-carboxylic acid alkenyl ester copolymer resins, ethylene-α-olefin copolymer resins, polybutene resins, and poly(4-methyl-1-pentene) resins. These polyolefin resins may be used individually or in combination of two or more. Among these polyolefin resins, polyethylene resins and polypropylene resins are preferred from the viewpoint of improving the strength of ultrapure water piping.

[0037] Examples of the polyethylene resin include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), and high density polyethylene (HDPE). Among these, high density polyethylene (HDPE) is preferred from the viewpoint of suppressing the elution of organic components into ultrapure water.

[0038] Examples of the alkenyl carboxylate in the ethylene-alkenyl carboxylate copolymer resin include vinyl acetate, vinyl propionate, vinyl butyrate, isopropenyl acetate, allyl acetate, etc., and preferably vinyl acetate.

[0039] Examples of the ethylene-α-olefin copolymer include a copolymer obtained by copolymerizing ethylene with an α-olefin such as propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene or 1-octene as a comonomer component at a ratio of about several mol%.

[0040] Examples of the polypropylene resin include homopolypropylene, block polypropylene, and random polypropylene. Examples of the comonomer component in block polypropylene and random polypropylene usually include ethylene. Among these, random polypropylene is preferred from the viewpoint of well-balanced expression of rigidity, strength, etc. of the pipe for ultrapure water. Examples of the polybutene resin include polybutene-1.

[0041] As described above, polypropylene pipes or polyethylene pipes are suitable as the polyolefin resin pipes. However, these polypropylene pipes or polyethylene pipes preferably have a gas barrier layer of 480 cc·20 μm / (m ２ ·24 hr·atm) or less. Therefore, it is preferable to provide a gas barrier layer on the outermost layer of the polypropylene pipe or polyethylene pipe.

[0042] In addition, as the polypropylene pipe or polyethylene pipe, those having an elution amount of cation components from the inner peripheral surface of the pipe of 30 μg / m ２ or less are preferred.

[0043] The subsystem shown in FIG. 2 is an example of the present invention. The secondary pure water apparatus of the present invention may have at least a sub-tank, a sub-pump, a non-regenerative ion exchange apparatus, and an ultrafiltration membrane apparatus (UF apparatus). That is, in the secondary pure water apparatus of the present invention, in the subsystem shown in FIG. 2, other devices may be further provided, some devices may be omitted, or the arrangement of some devices may be different. For example, a hydrogen peroxide removal apparatus may be provided downstream of the UV oxidizer 22. Also, the non-regenerative ion exchange apparatus 23 may be arranged downstream of the deaeration membrane apparatus 24.

[0044] As described above, as the non-fluorine-based and non-chlorine-based synthetic resin pipe, a polyolefin-based resin pipe is preferable, but this polyolefin-based resin pipe generally has a low gas permeability coefficient (high gas permeability). The gas permeability coefficient is determined by the following formula.

[0045] Gas permeability coefficient [cc·20μm / (m ２ ·24hrs·atm)] = Gas permeation amount (volume) × Film thickness / (Pressure difference × Permeation area × Time)

[0046] The gas permeability is determined by the following formula.

[0047] Gas permeability [cc / (m ２ ·24hr·atm)] = Gas permeation amount (volume) / (Pressure difference × Permeation area × Time)

[0048] In the present invention, in order to improve the gas barrier property of a polyolefin-based synthetic resin pipe having poor gas barrier property, it is preferable to have any one of the following configurations (1), (2), and (3).

[0049] (1) It has a single-layer or multi-layer structure and has at least one gas barrier layer. As this gas barrier layer, a synthetic resin gas barrier layer having a gas permeability coefficient of 480 [cc·20μm / (m ２ ·24hrs·atm)] or less and a thickness of 150μm or less, particularly 50 to 150μm, is preferable.

[0050] As this synthetic resin, polyvinyl alcohol, ethylene vinyl alcohol copolymer, polyvinylidene chloride resin, polyacrylonitrile, etc. are preferable.

[0051] This synthetic resin gas barrier layer may be provided on the outer circumference of the pipe, as shown in Figure 3(a). Alternatively, it is preferable to provide a high-density polyethylene (HDPE) layer with reduced elution of Ca and other elements on the inner circumference of the pipe, as shown in Figure 3(b). Each of these layers may be formed integrally with the pipe by extrusion molding.

[0052] (2) Gas permeability coefficient of 480 [cc・20 μm / (m) on the outside of the piping ２ The following materials shall be deployed (24 hours atm): Examples of such materials include metal piping such as SUS, gas barrier resins (polyvinyl alcohol, ethylene vinyl alcohol copolymer, polyvinylidene chloride resin, and polyacrylonitrile, etc.), or piping materials that have been treated with a gas barrier resin.

[0053] (3) Thicken the resin piping to reduce gas permeability. In this case, it is preferable that the ratio of the outer diameter of the piping to the resin thickness is 15% or more.

[0054] In this invention, the amount of metal ions (e.g., Ca, Zn, Al, Fe, Ni, Mg, K, Na, Ba, B, etc.) eluted from the inner surface of the pipe is 30 μg / m³. ２ The following is preferable:

[0055] [Example 1] As shown in Figure 4, a subsystem was used in which a cooler, UV oxidizer, hydrogen peroxide remover, degassing membrane device, non-regenerative ion exchange device, and ultrafiltration membrane device were connected in this order to treat primary pure water of the water quality shown in Table 1 to produce ultrapure water. In the subsystem in Figure 4, at least the piping downstream of the ion exchange device had a gas permeability coefficient of 480 [cc・20 μm / (m ２ The temperature is 24 hours atm or less, and the gas barrier layer on the outer periphery is 150 μm or less in thickness, with a metal ion elution concentration of 30 μg / m³ from the inner surface. ２ The following polyethylene piping was used. The water quality of the ultrapure water produced is shown in Table 1.

[0056]

[0057] As shown in Table 1, the water quality of the produced ultrapure water was good, and the DO concentration of the ultrapure water was 1 μg / L or less.

[0058] Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications are possible within the scope of achieving the effects of the invention. This application is based on Japanese Patent Application No. 2024-175204, filed on 4 October 2024, which is incorporated herein by reference in its entirety.

[0059] 1. Raw water tank 2. Pretreatment unit 4. Primary pure water system 5. Pure water tank 7. Degassing membrane system 10. TOC decomposition unit 17. Sub-tank 20. Secondary pure water system (subsystem) 21. Cooler 22. UV oxidizer 23. Non-regenerative ion exchange system 24. Degassing membrane system 25. Ultrafiltration membrane system 36. Use point

Claims

1. A secondary pure water system in an ultrapure water production system comprising a primary pure water system and a secondary pure water system, wherein the secondary pure water system comprises a non-regenerative ion exchange device and an ultrafiltration membrane in that order, and is connected at least downstream of the non-regenerative ion exchange device by non-fluorine and non-chlorine synthetic resin piping.

2. The secondary pure water apparatus according to claim 1, wherein the DO concentration of the ultrapure water produced by the ultrapure water production system is 1 μg / L or less.

3. The secondary pure water apparatus according to claim 1, wherein the non-fluorine and non-chlorine synthetic resin piping is made of polyolefin resin.

4. The secondary pure water apparatus according to claim 3, wherein the polyolefin resin piping is made of polypropylene or polyethylene.

5. The polypropylene or polyethylene piping has a capacity of 480 [cc・20 μm / (m ２ A secondary pure water apparatus according to claim 4, having a gas barrier layer of 24hr·atm or less.

6. The secondary pure water apparatus according to claim 5, wherein the polypropylene or polyethylene piping is a multilayer piping having a gas barrier layer as its outermost layer.

7. The amount of cation components eluted from the inner surface of the polypropylene or polyethylene piping is 30 μg / m³. ２ The secondary pure water apparatus according to any one of claims 4 to 6, which is as follows:

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