Ultrapure water piping

Abstract

To provide a high-density polyolefin resin-based pipe material for ultrapure water with a reduced elution amount of ammonium ions.SOLUTION: A pipe material for ultrapure water having an HDPE layer containing high-density polyethylene, is used to transport ultrapure water, where the inner peripheral surface of the HDPE layer constitutes the inner peripheral surface of the pipe material, and an amount of ammonium ions eluted from the inner peripheral surface is 800 μg / m2 or less. With this configuration, it is possible to establish a high-density polyolefin resin-based pipe material for ultrapure water in which an elution amount of ammonium ions is reduced.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a pipe for ultrapure water, and more specifically, to a polyolefin resin pipe used as a pipe for ultrapure water. [Background technology]

[0002] Conventionally, in the manufacture of precision devices such as semiconductor devices or liquid crystal display devices, ultrapure water that has been refined to an extremely high purity has been used in wet processes such as cleaning. If metal ions or the like are present in the water at a concentration above a certain level, the metals are adsorbed onto the wafer surface or the like, adversely affecting the quality of the precision device, and therefore, the amount of impurities in the ultrapure water is strictly controlled.

[0003] Impurities can also get mixed into ultrapure water in the piping that makes up the ultrapure water transport line. Although metals such as stainless steel, which have excellent gas barrier properties, have been used as piping materials, it is considered preferable to use resins in consideration of the effect of metal elution from the piping.

[0004] Resins used as materials for ultrapure water piping are fluororesins that are chemically inactive, have gas barrier properties, and are very little eluted into ultrapure water. For example, Patent Document 1 discloses a fluororesin double tube in which two layers of fluororesin are laminated as piping used in semiconductor manufacturing equipment, liquid crystal manufacturing equipment, etc., in which an inner layer tube is made of a fluororesin that is excellent in corrosion resistance and chemical resistance (e.g., tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), or tetrafluoroethylene-ethylene copolymer (ETFE)), and an outer layer tube is made of a fluororesin that can suppress gas permeation (e.g., polyvinylidene fluoride (PVDF)). Patent Document 2 discloses a multi-layer pipe for piping ultrapure water, characterized in that it comprises a first resin layer made of a fluororesin that comes into contact with the ultrapure water, and a second resin layer made of a gas-impermeable resin that is provided on the outer peripheral surface of the first resin layer, and further discloses that a third resin layer that protects the second resin layer is provided on the outer peripheral surface of the second resin layer, and that polyethylene is used for the third resin layer.

[0005] Among the resins used as materials for ultrapure water piping, polyvinylidene fluoride (PVDF) is used in all practical applications in the semiconductor industry, such as piping within ultrapure water production equipment and piping for transporting ultrapure water from ultrapure water production equipment to use points, and has become the technical standard for ultrapure water piping.

[0006] Recently, with the increasing integration density of semiconductor chips, circuit patterns have become finer and finer, making them more susceptible to even low-level impurities. Therefore, the quality requirements for ultrapure water are becoming increasingly strict. For example, standards for the quality of ultrapure water used in semiconductor manufacturing are published as SEMI F75, and are updated every two years. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2004-299808 A [Patent Document 2] JP 2010-234576 A Summary of the Invention [Problem to be solved by the invention]

[0008] Fluororesin piping such as PVDF has some disadvantages in terms of ease of construction and cost compared to other general piping, but in the context of increasingly strict water quality requirements for ultrapure water, fluororesin piping is the only option that meets the required water quality, and its outstanding performance, which more than compensates for the disadvantages of ease of construction and cost, is strongly supported.

[0009] Against this background, the present inventors have dared to focus on alternative materials for ultrapure water piping. For example, polyolefin resins, which are excellent in workability and cost, are used as pipe materials for general water pipes, and among them, efforts have been made to improve high-density polyethylene, which has excellent properties such as earthquake resistance, flexibility, corrosion resistance, and light weight, in the development of pipe materials for water pipes.

[0010] The present inventors attempted to use high density polyethylene as a material for ultrapure water piping, but were faced with a significant problem in that a large amount of ammonium ions, which are a source of corrosion, were eluted from the polyethylene.

[0011] In view of the above, an object of the present invention is to provide a pipe material for ultrapure water made of a high-density polyolefin resin in which the amount of ammonium ion eluted is reduced. [Means for solving the problem]

[0012] The present invention provides the following aspects. Item 1. An ultrapure water pipe material having an HDPE layer containing high density polyethylene, The inner circumferential surface of the HDPE layer constitutes the inner circumferential surface of the pipe material, The amount of ammonium ions eluted from the inner peripheral surface is 800 μg / m 2 is as follows: Ultrapure water pipe material used for transporting ultrapure water. Item 2. The ultrapure water pipe material according to Item 1, wherein the HDPE layer is vented by extrusion molding. Item 3. The ultrapure water pipe material according to Item 2, wherein the HDPE layer is vented by extrusion molding at a suction pressure of 10 KPa or more. Item 4. The ultrapure water pipe material according to any one of Items 1 to 3, wherein the high-density polyethylene has a molecular weight distribution of 40 to 80. Item 5. The ultrapure water pipe material according to any one of Items 1 to 4, wherein the HDPE layer further contains a fluorine-based lubricant. Item 6. The ultrapure water pipe according to any one of Items 1 to 5, wherein the ultrapure water is used in a wet processing step of a semiconductor element or a liquid crystal. Item 7. The ultrapure water pipe according to any one of Items 1 to 6, wherein the ultrapure water is used in a wet processing step of a semiconductor device having a minimum line width of 65 nm or less. Item 8. A pipe material having an HDPE layer containing high density polyethylene, the inner circumferential surface of the HDPE layer constitutes the inner circumferential surface of the pipe material, and the amount of ammonium ion eluted from the inner circumferential surface is 800 μg / m 2 A method for producing a pipe material for ultrapure water, comprising the steps of: a vented extrusion of said HDPE layer. Effect of the Invention

[0013] According to the present invention, it is possible to provide a pipe material for ultrapure water made of a high-density polyolefin resin in which the amount of ammonium ion elution is reduced. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of an ultrapure water pipe material of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing another example of the ultrapure water pipe material of the present invention. [Diagram 3] FIG. 2 is a schematic cross-sectional view showing still another example of the ultrapure water pipe material of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] [1. Ultrapure water pipe material] The ultrapure water pipe material of the present invention is a pipe material for ultrapure water having an HDPE layer containing high density polyethylene, the inner peripheral surface of the HDPE layer constitutes the inner peripheral surface of the pipe material, and the amount of ammonium ions eluted from the inner peripheral surface is 800 μg / m 2 The pipe material for ultrapure water according to the present invention has a diameter of 0.5 mm or less and is characterized in that it is used for transporting ultrapure water. Details of the pipe material for ultrapure water according to the present invention will be described below. In this specification, the numerical range indicated by "-" includes both ends of the range. For example, the expression "0.5-3.0 mm" means 0.5 mm or more and 3.0 mm or less.

[0016] [1-1. Layer configuration] The pipe material for ultrapure water of the present invention has an HDPE layer containing high density polyethylene. Examples of the pipe material for ultrapure water of the present invention are shown in Figures 1 to 3.

[0017] The ultrapure water pipe material 100 shown in Fig. 1 is composed of a single layer of HDPE layer 210 containing high density polyethylene. The ultrapure water pipe materials 100a and 100b shown in Fig. 2 and Fig. 3 are examples of multi-layer structures in which other layers are laminated on the outer surface of the HDPE layer 210. In either case, the inner circumferential surface s of the HDPE layer 210 constitutes the inner circumferential surface of the ultrapure water pipe materials 100, 100a, and 100b.

[0018] The ultrapure water pipe material 100a shown in Fig. 2 specifically includes an HDPE layer 210 containing high density polyethylene, and a core layer 220 laminated on the outer peripheral surface side of the HDPE layer 210. The ultrapure water pipe material 100b shown in Fig. 3 specifically includes an HDPE layer 210 containing high density polyethylene, a core layer 220 laminated on the outer peripheral surface side of the HDPE layer 210, and a gas barrier layer 230 laminated on the outer peripheral surface side of the core layer 220.

[0019] In addition, in the ultrapure water pipe material 100 shown in Figure 1, one or more layers other than the core layer 220 (e.g., a gas barrier layer, etc.) may be further laminated on the outer circumferential side of the HDPE layer 210, and in the ultrapure water pipe materials 100a, 100b shown in Figures 2 and 3, one or more layers (e.g., an adhesive layer, etc.) may be further laminated between the HDPE layer 210 and the core layer 220, between the core layer 220 and the gas barrier layer 230, and / or on the outer circumferential surface of the gas barrier layer 230.

[0020] The outer diameter of the ultrapure water pipe material of the present invention is not particularly limited, but preferably, the outer diameter (OD) required for the surface roughness of the inner peripheral surface to be 0.25 μm or less according to SEMI F57-0314 is less than 250 mm. More specifically, the outer diameter of the ultrapure water pipe material of the present invention is preferably 20 to 180 mm, more preferably 25 to 100 mm, even more preferably 28 to 50 mm, even more preferably 30 to 40 mm, and particularly preferably 30 to 35 mm.

[0021] The total thickness of the ultrapure water piping of the present invention is not particularly limited, but may be, for example, 2 to 5 mm, preferably 2.5 to 4 mm, and more preferably 3 to 3.5 mm.

[0022] [1-2. HDPE layer] The HDPE layer is an extrusion layer of a resin composition containing high density polyethylene.

[0023] [1-2-1. High density polyethylene] High density polyethylene (HDPE) has a density (JIS 6760) of 0.940 g / cm 3 The upper limit of the density of the HDPE used in the HDPE layer is not particularly limited, but is, for example, 0.970 g / cm 3 Less than 0.965 g / cm 3 Less than or equal to 0.960 g / cm 3 More preferably, 0.955 g / cm 3 More preferably 0.950 g / cm 3 Below 0.945 g / cm, particularly preferably 0.3 The following are included:

[0024] Specific examples of HDPE used in the HDPE layer include HDPE synthesized by polymerization with a chlorine-based catalyst such as a widely used Ziegler-Natta catalyst, and HDPE synthesized with a chromium-based catalyst or a metallocene catalyst.

[0025] The molecular weight of the HDPE resin used in the HDPE layer is not particularly limited, and may be, for example, 1×10 as the weight average molecular weight Mw. 5 ~10×10 5 From the viewpoint of further improving the effect of suppressing the elution of ammonium ions, the weight average molecular weight Mw is preferably 3×10 5 ~10×10 5 , more preferably 4 × 10 5 ~9×10 5 , and more preferably 6 × 10 5 ~8.5×10 5 , more preferably 7×10 5 ~8×10 5 , and particularly preferably 7.5×10 5 ~8×10 5 In the present invention, the weight average molecular weight Mw is a value measured by gel permeation chromatography in terms of polystyrene.

[0026] The molecular weight distribution (Mw / Mn) of the HDPE used in the HDPE layer is, for example, 20 to 80, preferably 40 to 80, more preferably 50 to 78, further preferably 60 to 76, even more preferably 65 to 74, and particularly preferably 69 to 72. In the present invention, the molecular weight distribution (Mw / Mn) is a value (Mw / Mn) obtained by dividing the weight average molecular weight (Mw) and the number average molecular weight (Mn) in terms of polystyrene by gel permeation chromatography measurement. The molecular weight distribution (Mw / Mn) can be controlled by adjusting the amount of the chlorine-based catalyst and / or the polymerization process (single-stage polymerization or multi-stage polymerization of two or more stages). For example, by increasing the amount of the chlorine-based catalyst, the molecular weight distribution (Mw / Mn) tends to be large, and by decreasing the amount of the chlorine-based catalyst, the molecular weight distribution (Mw / Mn) tends to be small. Moreover, by carrying out multi-stage polymerization such as two or more stages, the molecular weight distribution (Mw / Mn) can be increased, and by carrying out single-stage polymerization, the molecular weight distribution (Mw / Mn) can be decreased.

[0027] The melt flow rate (MFR) of the HDPE used in the HDPE layer is not particularly limited, and may be, for example, 5 to 20 g / 10 min. From the viewpoint of further improving the effect of suppressing ammonium ion elution, the MFR of the HDPE used in the HDPE layer is preferably 9 to 15 g / 10 min, more preferably 11 to 13 g / 10 min. In the present invention, MFR is a value measured under the conditions of a temperature of 190° C. and a load of 21.6 kg as specified in JIS K-6922-2.

[0028] [1-2-2. Fluorine-based lubricants] In order to further improve the effect of suppressing the elution of ammonium ions, it is preferable that the HDPE layer further contains a fluorine-based lubricant. The fluorine-based lubricant used in the present invention is a fluorine-containing polymer. Such a fluorine-containing polymer is generally a homopolymer or copolymer of a fluoroolefin having a ratio of fluorine atoms to carbon atoms (F:C) of at least 1:2. Examples of the homopolymer include a homopolymer of vinylidene fluoride and a homopolymer of vinyl fluoride. Examples of the copolymer include a copolymer of vinylidene fluoride and a fluorinated olefin having at least one type of terminal double bond and containing at least one fluorine atom on the double-bonded carbon atom. Specific examples of the fluorinated olefin, which is a comonomer from which the copolymer is derived, include tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, and pentafluoropropylene.

[0029] In the present invention, the fluorine-containing polymer used in the fluorine-based lubricant may be one of the above fluorine-containing polymers or a combination of two or more of them. Among the above fluorine-containing polymers used in the fluorine-based lubricant in the present invention, copolymers are preferred, and vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymers are more preferred.

[0030] In addition, the fluorine-based lubricant used in the present invention may further contain inorganic fillers such as calcium carbonate, barium sulfate, talc, and / or silica in addition to the above-mentioned fluorine-containing polymer, within the range that does not affect the surface smoothness that is the object of the present invention.

[0031] The above-mentioned fluorine-based lubricants may be used alone or in combination of two or more kinds. Among the above-mentioned fluorine-based lubricants, in the present invention, the fluorine-based lubricant is preferably one that does not contain inorganic fillers other than the above-mentioned fluorine-containing polymer (i.e., a fluorine-based lubricant that is 100% fluorine-containing polymer), and particularly preferably one that is made of vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer.

[0032] In the present invention, the content of the fluorine-based lubricant contained in the HDPE layer is not particularly limited as long as it does not impair the effects of the present invention. For example, the content may be 0.01 to 0.75% by weight, and from the viewpoint of further improving the effect of suppressing ammonium ion elution, the content may be preferably 0.05 to 0.75% by weight, more preferably 0.1 to 0.75% by weight, even more preferably 0.2 to 0.75% by weight, and even more preferably 0.25 to 0.75% by weight. In addition, from the viewpoint of improving the workability during extrusion molding, the content may be preferably 0.01 to 0.7% by weight, more preferably 0.01 to 0.65% by weight, even more preferably 0.01 to 0.6% by weight, and even more preferably 0.01 to 0.55% by weight.

[0033] [1-2-4. Other ingredients] The ultrapure water pipe material of the present invention is allowed to further contain other components in the HDPE layer other than those described above. The other components include resin components other than HDPE and additives other than the fluorine-based lubricant.

[0034] The other resin components are not particularly limited, and examples thereof include one or more types selected from polyolefin resins other than HDPE (such as polypropylene), polyether methyl ketone, acetal resins, polyvinyl chloride, etc. In the HDPE layer used in the present invention, the proportion of the other resin components per 100 parts by weight of the total amount of HDPE and other resin components is, for example, 30 parts by weight or less, preferably 20 parts by weight or less, more preferably 10 parts by weight or less, even more preferably 5 parts by weight or less, still more preferably 1 part by weight or less, even more preferably 0.1 parts by weight or less, and most preferably 0 part by weight.

[0035] Examples of other additives include antioxidants (e.g., phenol-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, aromatic amine-based antioxidants, lactone-based antioxidants, etc.). However, from the viewpoint of suppressing elution of organic components, it is preferable that the HDPE layer does not contain other additives such as antioxidants.

[0036] [1-2-5. Thickness] In the case of the single-layer HDPE pipe material 100 for ultrapure water shown in FIG. 1, the thickness of the HDPE layer 210 (ie, the thickness of the pipe material 100 for ultrapure water) is the same as the total thickness described above in "1-1. Layer structure."

[0037] In the case of the multi-layered ultrapure water pipe materials 100a, 100b shown in Figs. 2 and 3, the thickness of the HDPE layer 210 is, for example, 0.1 to 1 mm, preferably 0.2 to 0.8 mm, and more preferably 0.4 to 0.6 mm.

[0038] [1-3. Core layer] In the ultrapure water pipe materials 100a and 100b of Figures 2 and 3, the thickness of the HDPE layer 210 is made thinner than that of the ultrapure water pipe material 100 of Figure 1, while a core layer 220 is further laminated to ensure the rigidity of the entire pipe material.

[0039] The core layer 220 is an extrusion layer of any resin composition. From the viewpoint of adhesion to the HDPE layer 210, etc., a preferred example of the resin used for the core layer 220 is a polyolefin-based resin. The polyolefin-based resin is not particularly limited, and may be a polymer containing a monomer unit derived from an olefin. Examples of the polyolefin-based resin include polyethylene-based resin, ethylene-alkenyl carboxylate ester copolymer resin, ethylene-α-olefin copolymer resin, polypropylene-based resin, polybutene-based resin, poly(4-methyl-1-pentene)-based resin, etc. These polyolefin-based resins may be used alone or in combination of two or more. Among these polyolefin-based resins, polyethylene-based resin and polypropylene-based resin are preferred from the viewpoint of improving the strength of the entire pipe material, etc. Furthermore, among the polyethylene-based resin and polypropylene-based resin, polyethylene-based resin is more preferred from the viewpoint of suppressing the content of low molecular weight components and suppressing the elution of organic components into pure water.

[0040] The polyethylene resin is not particularly limited, but examples thereof include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), etc. Among these, high-density polyethylene (HDPE) is preferred from the viewpoint of suppressing the elution of organic components into pure water.

[0041] Examples of the alkenyl carboxylate in the ethylene-alkenyl carboxylate copolymer resin include vinyl acetate, vinyl propionate, vinyl butyrate, isopropenyl acetate, and allyl acetate, and preferably vinyl acetate.

[0042] Examples of ethylene-α-olefin copolymers include copolymers in which ethylene is copolymerized with an α-olefin such as propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, or 1-octene as a copolymerization component at a ratio of about several mol %.

[0043] The molecular weight of the polyolefin resin used in the core layer is not particularly limited, but is preferably the same as that of the HDPE used in the HDPE layer, which is the inner layer. Specifically, the molecular weight of the polyolefin resin used in the core layer can be selected from the weight average molecular weights described in "1-2-1. High density polyethylene" above. The weight average molecular weight of the polyolefin resin used in the core layer is 0.8 to 1.2 times, preferably 0.85 to 1 times, and more preferably 0.9 to 0.95 times, of the weight average molecular weight of the HDPE used in the HDPE layer, which is the inner layer.

[0044] The molecular weight distribution (Mw / Mn) of the polyolefin resin contained in the core layer is not particularly limited, but may be, for example, 25-60, more preferably 30-55, even more preferably 35-48, and particularly preferably 40-43.

[0045] The MFR of the resin used in the core layer is not particularly limited, but is preferably the same as the MFR of the HDPE used in the HDPE layer, which is the inner layer. Specifically, the MFR of the resin used in the core layer can be selected from the MFRs described in "1-2-1. High-density polyethylene" above. The weight-average molecular weight of the polyolefin resin used in the core layer is 0.8 to 1.2 times, preferably 0.9 to 1.1 times, of the weight-average molecular weight of the HDPE used in the HDPE layer, which is the inner layer.

[0046] The core layer preferably contains an antioxidant. Examples of the antioxidant include phenol-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, aromatic amine-based antioxidants, and lactone-based antioxidants. From the viewpoint of suppressing the influence of oxygen and ensuring a preferable strength, the content of the antioxidant in the core layer is, for example, 0.01% by weight or more, preferably 0.1% by weight or more, and the upper limit of the content of the antioxidant is, for example, 5% by weight or less, preferably 1% by weight or less, and more preferably 0.5% by weight or less.

[0047] The thickness of the core layer is, for example, 1.5 mm or more, preferably 2 mm or more, more preferably 2.3 mm or more, from the viewpoint of ensuring the rigidity of the pipe material itself. The upper limit of the thickness of the core layer is, for example, 3.5 mm or less, preferably 3 mm or less, more preferably 2.7 mm or less.

[0048] [1-4. Gas barrier layer] The gas barrier layer 230 exemplified in the ultrapure water pipe material 100b in FIG. 3 is provided on the outside of the core layer 220. Alternatively, the gas barrier layer may be provided on the outside of the HDPE layer 210 constituting the ultrapure water pipe material 100 in FIG. 1. The gas barrier layer prevents oxygen from the outer surface of the pipe material from penetrating into the inner layers, so that the strength of the pipe material itself can be well maintained. In addition, providing a gas barrier layer is also preferable in that it can effectively suppress the dissolution of gas into pure water. The gas barrier layer is preferably provided for the purpose of blocking oxygen.

[0049] The gas barrier layer is an extrusion-molded layer of a gas barrier resin composition. Examples of gas barrier materials include polyvinyl alcohol (PVA), ethylene-vinyl alcohol copolymer (EVOH), polyvinylidene chloride resin (PVDC), and polyacrylonitrile (PAN), and preferably polyvinyl alcohol (PVA) and ethylene-vinyl alcohol copolymer (EVOH).

[0050] The thickness of the gas barrier layer is, for example, 50 to 150 μm, and preferably 80 to 120 μm.

[0051] [1-5. Suppression of impurities leaching into pure water] The ultrapure water pipe material of the present invention has an ammonium ion elution rate of 800 μg / m from the inner circumferential surface. 2 In the case where the ultrapure water pipe material of the present invention has a more preferable elution suppression property, the amount of ammonium ion eluted from the inner peripheral surface thereof is preferably 750 μg / m or less. 2 Less than or equal to 700 μg / m 2Less than 660 μg / m 2 Less than 610 μg / m 2 More preferably, 550 μg / m 2 Less than 500 μg / m 2 The amount of ammonium ion elution is a value obtained by preparing an analytical material according to SEMI F40, which is referenced in the SEMI F57-0314 standard, immersing it in ultrapure water at 85°C for 72 hours, and measuring the ammonium ions in the leachate according to ASTM D4327.

[0052] The amount of ammonium ion leaching can be controlled by vented extrusion of the HDPE layer, preferably by controlling the suction pressure in vented extrusion of the HDPE layer and / or by incorporating a fluorine-based lubricant in the HDPE layer.

[0053] A preferred example of the suction pressure in the vented extrusion molding of the HDPE layer to further improve the effect of suppressing ammonium ion elution is as described in "2-2. Suction Pressure" below. Also, a preferred amount of fluorine-based lubricant to further improve the effect of suppressing ammonium ion elution is as described in "1-2-2. Fluorine-based lubricant" above.

[0054] [1-6.Application] The ultrapure water pipe material of the present invention is used for transporting ultrapure water. Specifically, the ultrapure water pipe material of the present invention can be used as piping in an ultrapure water production apparatus, piping for transporting ultrapure water from an ultrapure water production apparatus to a use point, piping for returning ultrapure water from a use point, etc.

[0055] The ultrapure water pipe material of the present invention is preferably used as water piping for nuclear power generation, where the required quality of ultrapure water is particularly strict, or as ultrapure water transport piping used in wet processing steps such as washing in the manufacturing process of pharmaceuticals, semiconductor devices or liquid crystals, and more preferably in the manufacturing process of semiconductor devices. The semiconductor devices are preferably those with a higher integration density, and more specifically, are more preferably used in the manufacturing process of semiconductor devices with a minimum line width of 65 nm or less. Standards relating to the quality of ultrapure water used in semiconductor manufacturing include, for example, SEMI F57-0314.

[0056] Furthermore, the ultrapure water pipe material of the present invention has excellent workability, and therefore, for example, fusion joining such as butt fusion joining and EF (electrical fusion) joining can be easily carried out at a relatively low temperature.

[0057] [2. Manufacturing method of ultrapure water pipe material] The above-mentioned ultrapure water pipe material of the present invention can be produced by extrusion molding the resin composition for the HDPE layer used to form the HDPE layer. That is, the method for producing the ultrapure water pipe material of the present invention is as follows: The method for producing an ultrapure water pipe of the present invention includes a step of extruding a resin composition for an HDPE layer containing high density polyethylene. When the ultrapure water pipe to be produced has a multi-layer structure, the method for producing an ultrapure water pipe of the present invention includes a step of co-extrusion molding a resin composition for an HDPE layer containing high density polyethylene and a resin composition for another layer used to form a layer other than the HDPE layer. The ... amount of ammonium ion eluted from the inner peripheral surface of the ultrapure water pipe of the present invention is 800 μg / m. 2 From the viewpoint of more easily achieving the following, it is preferable to include a step of vented extrusion of a resin composition for the HDPE layer containing high density polyethylene.

[0058] [2-1. Resin composition] The HDPE contained in the resin composition for HDPE layer containing high density polyethylene, and the fluorine-based lubricant further contained in a preferred embodiment, as well as the composition of the resin composition for HDPE (the content or concentration of the components contained in the resin composition for HDPE layer) are as described above in "1-2. HDPE Layer" as the content or concentration of each component and the components contained in the HDPE layer.

[0059] The HDPE used in the resin composition for the HDPE layer may be synthesized, for example, by polymerization using a chlorine-based catalyst such as a widely used Ziegler-Natta catalyst, or may be synthesized using a chromium-based catalyst or a metallocene catalyst.

[0060] The resin composition for the HDPE layer can be prepared by using the HDPE synthesized as described above or a commercially available product thereof, and further mixing a fluorine-based lubricant as necessary.

[0061] Furthermore, when the ultrapure water pipe material to be manufactured has a multi-layer structure including a core layer, and a polyolefin-based resin is used for the core layer, a specific method for synthesizing the polyolefin-based resin is to use a chlorine-based catalyst and carry out multi-stage polymerization (preferably two-stage polymerization).

[0062] The resin composition for the core layer can be prepared by using the polyolefin resin synthesized as described above or a commercially available product thereof, and preferably further blending an antioxidant.

[0063] [2-2. Suction pressure] The suction pressure in the vented extrusion molding of the HDPE layer resin composition is preferably 10 kPa or more, more preferably 54 kPa or more, even more preferably 70 kPa or more, still more preferably 90 kPa or more, even more preferably 95 kPa or more, and particularly preferably 100 kPa or more, from the viewpoint of further improving the effect of suppressing ammonium ion elution. The suction pressure in the vented extrusion molding of the HDPE layer resin composition is the pressure required for suction to degas the inside of the cylinder through a vent hole opening in the cylinder wall constituting the extruder used for extruding the HDPE layer resin composition. EXAMPLES

[0064] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0065] The ultrapure water pipe materials shown in Table 1 were produced by extrusion molding. Reference Example 1 is a pipe material with a single layer structure of PVDF (total thickness 2.4 mm, outer diameter 32.0 mm), and Comparative Examples 1 and 2 and Examples 1 to 6 are pipe materials with a multilayer structure shown in FIG. 3 (HDPE layer 210 is 0.5 mm, core layer 220 is 2.5 mm, gas barrier layer 230 is 0.1 mm, but there is an additional adhesive layer of 0.1 mm not shown between the core layer 220 and the gas barrier layer 230. The outer diameter is 32.0 mm). The resin composition shown in Table 1 indicates the resin composition of the layer that forms the inner surface (surface that comes into contact with ultrapure water) of the ultrapure water pipe material, and for Comparative Examples 1 and 2 and Examples 1 to 6, the resin composition of the HDPE layer 210 is shown. The HDPE shown in Table 1 has a density of 0.942 g / cm 3 The material used for the core layer 220 in Comparative Examples 1 and 2 and Examples 1 to 6 is HDPE (clean grade level without antioxidants) polymerized using a Ziegler-Natta catalyst, with a weight average molecular weight of 780,000, a molecular weight distribution (Mw / Mn) of 71, and an MFR of 12.06 g / 10 min (190°C, 21.6 kg). 3 The material used for the adhesive layer is maleic anhydride-modified adhesive polyethylene; and the material used for the gas barrier layer is an ethylene-vinyl alcohol copolymer, an oxygen barrier resin.

[0066] In addition, the fluorine-based lubricant shown in Table 1 is 100% vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer.

[0067] Furthermore, the suction pressure shown in Table 1 is the pressure required for suction to degas the inside of the cylinder through a vent hole opening in the cylinder wall constituting the extruder used for extruding the resin composition for the HDPE layer.

[0068] For the obtained ultrapure water pipe material, an analytical material was prepared according to SEMI F40, which is referenced in the SEMI F57-0314 standard, and immersed in ultrapure water at 85°C for 72 hours, and the ammonium ions in the leachate were measured according to ASTM D4327. In addition, the ratio of the amount of ammonium ions eluted by each comparative example and example when the amount of ammonium ions eluted by the pipe material of Comparative Example 1 was set to 1 was calculated as the effect of reducing the amount of ammonium ions eluted (the smaller the ratio, the higher the effect of reducing the amount of ammonium ions eluted). The results are shown in Table 1.

[0069] [Table 1]

[0070] As is clear from Table 1, the ultrapure water pipe materials of Examples 1 to 6 had an ammonium ion elution amount of 800 μg / m 2 The above was achieved. Furthermore, by using a vent-type extruder, controlling the suction pressure, or by adding a fluorine-based lubricant in addition to the suction pressure, the amount of ammonium ion elution could be further suppressed. In particular, as is clear from the results of Examples 1 to 6, even though the amount of fluorine-based lubricant blended is the same, the effect of reducing the amount of ammonium ion elution when a fluorine-based lubricant is blended increases as the suction pressure increases, and the amount of ammonium ion elution in the ultrapure water pipe material of Example 6 was reduced to about half that in Comparative Example 1. Since the amount of ammonium ion elution was reduced to an extremely low level in this way, it was recognized that the ultrapure water pipes of Examples 1 to 6 are suitable for transporting semiconductor cleaning liquid suitable for wet processing of semiconductor elements with a minimum line width of 65 nm or less. [Explanation of symbols]

[0071] 100,100a,100b Ultrapure water piping 210 HDPE layers 220 Core layer 230 Gas Barrier Layer s Inner surface

Claims

1. A pipe material for ultrapure water having an HDPE layer containing high density polyethylene, The inner circumferential surface of the HDPE layer constitutes the inner circumferential surface of the pipe material, The HDPE layer is vented by extrusion at a suction pressure of 10 kPa or more; The amount of ammonium ions eluted from the inner peripheral surface is 800 μg / m 2 is as follows: Ultrapure water pipe material used for transporting ultrapure water.

2. 2. The ultrapure water pipe material according to claim 1, wherein the molecular weight distribution of said high density polyethylene is 40 to 80.

3. The ultrapure water pipe material according to claim 1 or 2, wherein the HDPE layer further contains a fluorine-based lubricant.

4. 4. The ultrapure water pipe according to claim 1, wherein the ultrapure water is used in a wet processing step for semiconductor devices or liquid crystals.

5. 5. The ultrapure water pipe according to claim 1, wherein the ultrapure water is used in a wet processing step of a semiconductor device having a minimum line width of 65 nm or less.

6. The pipe material has an HDPE layer containing high density polyethylene, the inner circumferential surface of the HDPE layer constitutes the inner circumferential surface of the pipe material, and the amount of ammonium ions eluted from the inner circumferential surface is 800 μg / m 2 A method for producing a pipe material for ultrapure water, comprising the steps of: The method includes the step of vented extrusion of the HDPE layer at a suction pressure of 10 kPa or greater.

Images