Ultrapure water pipes

Abstract

To provide a high-density polyolefin resin-based pipe material for ultrapure water with excellent surface smoothness whose surface roughness is equal to or less than 0.25 μm.SOLUTION: A pipe material for ultrapure water having an HDPE layer containing high-density polyethylene and a fluorine-based lubricant, 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 the surface roughness of the inner peripheral surface is 0.25 μm or less. With this configuration, it is possible to establish a pipe having excellent surface smoothness with a surface roughness of 0.25 μm or less, even though it is a high-density polyolefin resin-based pipe material for ultrapure water.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] 2. Description of the Related Art Ultrapure water refined to an extremely high purity has conventionally been used in wet processes such as cleaning in the manufacture of precision devices such as semiconductor devices and liquid crystal display devices.

[0003] Piping that constitutes an ultrapure water transport line is required to have extremely low metal elution and high inner surface smoothness for the purpose of preventing the growth of bacteria.

[0004] Fluororesin is used as a material for ultrapure water piping because it is chemically inert, has gas barrier properties, is very little eluted in ultrapure water, and has a high degree of inner surface smoothness. 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 the inner layer tube is made of a fluororesin that is highly corrosion-resistant and chemical-resistant (e.g., tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), or tetrafluoroethylene-ethylene copolymer (ETFE)) and the 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 fluororesin that comes into contact with the ultrapure water, and a second resin layer made of gas-impermeable resin that is provided on the outer 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 surface of the second resin layer, and that polyethylene is used for the third resin layer.

[0005] Among the materials used for ultrapure water piping, polyvinylidene fluoride (PVDF) is used in all practical applications in the semiconductor industry, including 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, as the integration density of semiconductor chips has increased, circuit patterns have become increasingly finer, and the characteristics required for ultrapure water piping have become increasingly strict. For example, the standard for the quality of ultrapure water piping used in semiconductor manufacturing has been published as SEMI F75, and is updated every two years.

[0007] Meanwhile, polyethylene pipes, which offer excellent properties such as earthquake resistance, flexibility, corrosion resistance, and light weight, are increasingly being used as general tap water piping in addition to conventional cast iron pipes or polyvinyl chloride pipes. High-density polyethylene in particular has been improved to enhance its performance while maintaining its inherent rigidity. Some high-density polyethylene pipes have been developed with excellent surface smoothness to reduce friction with the internal fluid and prevent the adhesion of limescale and other deposits. Currently, the highest surface smoothness of high-density polyethylene pipes has a surface roughness Ra of 0.4 μm, and this excellent surface smoothness has been achieved by improving the polymerization catalyst and process technology to reduce the gel or non-uniformity of the kneaded mixture present in the resin (Non-Patent Document 1). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-299808 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-234576 [Non-patent literature]

[0009] [Non-Patent Document 1] TOSOH Research & Technology Review Vol.44(2000),p.63-67 Summary of the Invention [Problem to be solved by the invention]

[0010] Fluororesin piping such as PVDF has some disadvantages in terms of ease of installation and cost compared to other common piping. However, with the background of increasingly strict quality requirements for ultrapure water piping, fluororesin piping has become the only option for piping that meets the required water quality, and its outstanding performance, which more than makes up for the disadvantages of ease of installation and cost, is strongly supported.

[0011] Against this background, the present inventors have deliberately focused on replacing the material of ultrapure water piping with high-density polyolefin resin. However, high-density polyolefin resins lack the surface smoothness required for use as ultrapure water piping. Currently, the surface smoothness limit of high-density polyethylene resin pipes is approximately 0.4 μm, which is far from the level of 0.25 μm or less (outer diameter OD less than 250 mm) specified in SEMI F57-0314.

[0012] 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, which has an excellent surface smoothness with a surface roughness of 0.25 μm or less. [Means for solving the problem]

[0013] As a result of extensive research, the present inventors have found that blending a specific lubricant with a high-density polyethylene resin results in a pipe material with excellent surface smoothness, with a surface roughness of 0.25 μm or less. They have also found that extrusion molding a high-density polyethylene resin composition under specific back pressure conditions allows for further control of surface smoothness. Based on these findings and through further research, the present invention has been completed. Specifically, the present invention provides the following aspects:

[0014] Item 1. An ultrapure water pipe material having an HDPE layer containing high density polyethylene and a fluorine-based lubricant, The inner circumferential surface of the HDPE layer constitutes the inner circumferential surface of the pipe material, The surface roughness of the inner peripheral surface is 0.25 μm or less, Ultrapure water pipe material used to transport ultrapure water. Item 2. The ultrapure water pipe material according to Item 1, wherein the HDPE layer is formed by extrusion molding an HDPE composition containing the high-density polyethylene and the fluorine-based lubricant under a back pressure of 3 to 30 MPa. Item 3. The ultrapure water pipe material according to Item 1 or 2, wherein the high-density polyethylene has a molecular weight distribution of 40 to 80. term 4. The pipe material for ultrapure water according to any one of items 1 to 3, wherein the content of the fluorine-based lubricant in the HDPE layer is 0.01 to 5% by weight. Item 5. The pipe material for ultrapure water according to any one of Items 1 to 4, which has a multi-layer structure in which another layer is laminated on the outer surface of the HDPE layer. Item 6. The ultrapure water pipe material according to Item 5, wherein the HDPE layer has a thickness of 0.3 mm or more. Item 7. The total amount of elution of aluminum, barium, boron, calcium, chromium, copper, iron, lead, lithium, magnesium, manganese, nickel, potassium, sodium, strontium, and zinc measured in accordance with SEMI F57-0314 is 14 μg / m 2 Item 7. A pipe material for ultrapure water according to any one of Items 1 to 6, which is as follows: Item 8. The amount of calcium elution measured based on SEMI F57-0314 is 7 μg / m 2 Below, the copper elution amount is 0.5 μg / m 2 Below, the sodium elution amount is 1.5 μg / m 2 The elution amount is 0.5 μg / m or less. 2 or less, and / or zinc elution is 0.5 μg / m 2 8. A pipe material for ultrapure water according to any one of items 1 to 7, which is as follows: Item 9. The amount of fluoride ion elution measured in accordance with SEMI F57-0314 is 600 μg / m 2 Item 9. A pipe material for ultrapure water according to any one of Items 1 to 8, which is as follows: Item 10. The elution amount of all organic components measured in accordance with SEMI F57-0314 is 10,000 μg / m 2 Item 10. A pipe material for ultrapure water according to any one of Items 1 to 9, which is as follows: Item 11. A pipe for ultrapure water according to any one of Items 1 to 10, wherein the ultrapure water is used in a wet processing step for semiconductor devices or liquid crystals. Item 12. A pipe for ultrapure water according to any one of Items 1 to 11, wherein the ultrapure water is used in a wet processing step for semiconductor devices having a minimum line width of 65 nm or less. Item 13. A method for manufacturing a pipe material for ultrapure water, the pipe material having an HDPE layer containing high-density polyethylene and a fluorine-based lubricant, the inner surface of the HDPE layer forming the inner surface of the pipe material, and the surface roughness of the inner surface being 0.25 μm or less, The manufacturing method includes a step of extruding the HDPE layer from a resin composition containing the high-density polyethylene and the fluorine-based lubricant under a back pressure of 3 to 30 MPa. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a pipe material for ultrapure water made of high-density polyethylene resin, which has excellent surface smoothness with a surface roughness of 0.25 μm or less. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic cross-sectional view showing an example of a pipe material for ultrapure water of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view showing another example of a pipe material for ultrapure water according to the present invention. [Figure 3] FIG. 2 is a schematic cross-sectional view showing yet another example of the ultrapure water pipe material of the present invention. [Figure 4] 2 is a schematic diagram showing a part of a production line for manufacturing the ultrapure water pipe material shown in FIG. 1. [Figure 5] 3 is a schematic diagram showing a part of a production line for manufacturing the ultrapure water pipe material shown in FIG. 2. [Figure 6] 4 is a schematic diagram showing a part of a manufacturing line for manufacturing the ultrapure water pipe material shown in FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0017] [1.Pipe material for ultrapure water] The ultrapure water pipe material of the present invention is a pipe material for ultrapure water having an HDPE layer containing high-density polyethylene and a fluorine-based lubricant, wherein the inner circumferential surface of the HDPE layer constitutes the inner circumferential surface of the pipe material, the surface roughness of the inner circumferential surface is 0.25 μm or less, and the pipe material is used for transporting ultrapure water. Details of the ultrapure water pipe material of the present invention are described below. In this specification, numerical ranges indicated by "to" include both ends of the range. For example, the expression "0.5 to 3.0 mm" means 0.5 mm or more and 3.0 mm or less.

[0018] [1-1. Layer configuration] The pipe material for ultrapure water of the present invention has an HDPE layer containing high density polyethylene and a fluorine-based lubricant. Figures 1 to 3 show examples of the pipe material for ultrapure water of the present invention.

[0019] The ultrapure water pipe material 100 shown in Figure 1 is made of a single layer of HDPE layer 210 containing high-density polyethylene and a fluorine-based lubricant. The ultrapure water pipe materials 100a and 100b shown in Figures 2 and 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 peripheral surface s of the HDPE layer 210 forms the inner peripheral surface of the ultrapure water pipe materials 100, 100a, and 100b.

[0020] The ultrapure water pipe material 100a shown in Fig. 2 specifically includes an HDPE layer 210 containing high-density polyethylene and a fluorine-based lubricant, and a core layer 220 laminated on the outer peripheral surface 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 and a fluorine-based lubricant, a core layer 220 laminated on the outer peripheral surface of the HDPE layer 210, and a gas barrier layer 230 laminated on the outer peripheral surface of the core layer 220.

[0021] In addition, in the ultrapure water pipe material 100 shown in Figure 1, one or more layers other than the core material layer 220 (e.g., a gas barrier layer, etc.) may be laminated on the outer circumferential side of the HDPE layer 210, and in the ultrapure water pipe materials 100a and 100b shown in Figures 2 and 3, one or more layers (e.g., an adhesive layer, etc.) may be laminated between the HDPE layer 210 and the core material layer 220, between the core material layer 220 and the gas barrier layer 230, and / or on the outer circumferential surface of the gas barrier layer 230.

[0022] The outer diameter of the ultrapure water pipe material of the present invention is not particularly limited, but is preferably less than 250 mm, which is the outer diameter (OD) required for an inner surface surface roughness of 0.25 μm or less according to SEMI F57-0314. 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.

[0023] 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.

[0024] [1-2. HDPE layer] The HDPE layer is an extrusion-molded layer of a resin composition containing high-density polyethylene and a fluorine-based lubricant.

[0025] [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 for example, it is 0.970 g / cm 3 or less, preferably 0.965 g / cm 3 or less, more preferably 0.960 g / cm 3 or less, more preferably 0.955 g / cm 3 More preferably 0.950 g / cm or less 3 Below 0.945 g / cm, particularly preferably3 The following are included:

[0026] Specific examples of HDPE used in the HDPE layer include HDPE synthesized by polymerization using a chlorine-based catalyst such as a commonly used Ziegler-Natta catalyst, and HDPE synthesized using a chromium-based catalyst or metallocene catalyst.

[0027] The molecular weight of the HDPE resin used in the HDPE layer is not particularly limited, and for example, the weight average molecular weight Mw is 1×10 5 ~10×10 5 From the viewpoint of suppressing the elution of organic components into pure water and / or further improving the surface smoothness, 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 , 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.

[0028] 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, even more 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 determined by measuring the weight-average molecular weight (Mw) and number-average molecular weight (Mn) in terms of polystyrene by gel permeation chromatography, and then dividing Mw by Mn (Mw / Mn). The molecular weight distribution (Mw / Mn) can be controlled by adjusting the amount of chlorine-based catalyst and / or the polymerization process (single-stage polymerization or multi-stage polymerization of two or more stages). For example, increasing the amount of chlorine-based catalyst tends to increase the molecular weight distribution (Mw / Mn), while decreasing the amount of chlorine-based catalyst tends to decrease the molecular weight distribution (Mw / Mn). Furthermore, by using multi-stage polymerization such as two or more stages, the molecular weight distribution (Mw / Mn) can be increased, and by using single-stage polymerization, the molecular weight distribution (Mw / Mn) can be decreased.

[0029] The calcium concentration in the HDPE layer can be, for example, less than 15 ppb. To further suppress calcium elution into pure water, the calcium concentration in HDPE is preferably less than 12 ppb, more preferably less than 10 ppb. The lower the calcium concentration, the less calcium elution into pure water, so 0 ppm is most preferable. On the other hand, the ultrapure water pipe material of the present invention has an excellent inner surface smoothness, so it can effectively suppress calcium elution into pure water even when trace amounts of calcium are unavoidable, such as when a chlorine-based catalyst such as a Ziegler-Natta catalyst (an olefin polymerization catalyst prepared by mixing titanium tetrachloride or titanium trichloride with an organoaluminum compound [e.g., triethylaluminum or methylaluminoxane]) is used to synthesize the HDPE used in the HDPE layer, requiring the use of a small amount of neutralizing agent. The calcium concentration in the HDPE layer can be directly controlled by adjusting the amount of neutralizing agent added after HDPE polymerization. Furthermore, since the amount of neutralizing agent is affected by the amount of chlorine-based catalyst, the calcium concentration can also be controlled indirectly by adjusting the amount of chlorine-based catalyst.

[0030] 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 impurity 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.

[0031] [1-2-2. Fluorine-based lubricants] The fluorine-based lubricant used in the present invention is a fluorine-containing polymer. Such fluorine-containing polymers are generally homopolymers and copolymers of fluoroolefins having a fluorine atom to carbon atom ratio (F:C) of at least 1:2. Examples of such homopolymers include homopolymers of vinylidene fluoride and homopolymers of vinyl fluoride. Examples of such copolymers include copolymers of vinylidene fluoride and fluorinated olefins 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 olefins that are comonomers from which such copolymers are derived include tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, and pentafluoropropylene.

[0032] In the present invention, the fluorine-containing polymer used in the fluorine-based lubricant may be one of the above-mentioned fluorine-containing polymers or a combination of two or more of them. Among the above-mentioned 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.

[0033] Furthermore, the fluorine-based lubricant used in the present invention may further contain an inorganic filler such as calcium carbonate, barium sulfate, talc, and / or silica in addition to the above-mentioned fluorine-containing polymer, within a range that does not affect the surface smoothness that is the object of the present invention.

[0034] The above-mentioned fluorine-based lubricants may be used alone or in combination of two or more. Among the above-mentioned fluorine-based lubricants, in the present invention, preferred are those that do not contain any inorganic filler other than the above-mentioned fluorine-containing polymer (i.e., fluorine-based lubricants that are 100% fluorine-containing polymer), and particularly preferred are those that consist of vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer.

[0035] 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, it can be 0.01 to 5 wt %, and from the viewpoint of further improving surface smoothness, it is preferably 0.05 to 3.5 wt %, more preferably 0.1 to 0.75 wt %, even more preferably 0.2 to 0.75 wt %, and even more preferably 0.25 to 0.75 wt %. Furthermore, from the viewpoint of improving workability during extrusion molding, it is preferably 0.01 to 0.7 wt %, more preferably 0.01 to 0.65 wt %, even more preferably 0.01 to 0.6 wt %, and even more preferably 0.01 to 0.55 wt %.

[0036] [1-2-3. Surface roughness of inner surface] The surface roughness of the inner circumferential surface of the HDPE layer, i.e., the inner circumferential surface of the ultrapure water pipe material of the present invention, is 0.25 μm or less. To further reduce the total amount of elution of the 16 major metals (specifically, aluminum, barium, boron, calcium, chromium, copper, iron, lead, lithium, magnesium, manganese, nickel, potassium, sodium, strontium, and zinc; hereinafter, also referred to simply as "metals") and the amount of elution of organic components, the surface roughness of the inner circumferential surface is preferably 0.23 μm or less, more preferably 0.2 μm or less, even more preferably 0.18 μm or less, and even more preferably 0.16 μm or less. In the present invention, "surface roughness" refers to the arithmetic mean roughness Ra measured in accordance with JIS B 0601:2001.

[0037] The surface roughness of the inner peripheral surface can be controlled by adjusting the amount of fluorine-based lubricant blended into the resin composition for the HDPE layer. Specifically, one method for improving the surface roughness of the inner peripheral surface is to increase the blend amount of fluorine-based lubricant. The preferred blend amount of fluorine-based lubricant is as described above in "2-2. Fluorine-based lubricant." Furthermore, the surface roughness of the inner peripheral surface can also be controlled by controlling the back pressure during extrusion molding of the ultrapure water pipe material of the present invention. The preferred range of back pressure for improving the surface roughness of the inner peripheral surface is as described below in "2-2. Back pressure."

[0038] [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 than those described above, such as resin components other than HDPE and additives other than fluorine-based lubricants.

[0039] The other resin component is not particularly limited, and examples include one or more selected from polyolefin resins other than HDPE (such as polypropylene), polyether methyl ketone, acetal resin, polyvinyl chloride, etc. In the HDPE layer used in the present invention, the proportion of the other resin component per 100 parts by weight of the total amount of HDPE and the 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.

[0040] 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.) Because the ultrapure water pipe material of the present invention has excellent smoothness on the inner circumferential surface, it is permissible to further contain an antioxidant in the HDPE layer. However, from the viewpoint of further suppressing the elution of organic components into pure water, it is preferable that the HDPE layer does not contain other additives such as antioxidants.

[0041] [1-2-5. Thickness] In the case of the HDPE single-layer ultrapure water pipe material 100 shown in FIG. 1, the thickness of the HDPE layer 210 (ie, the thickness of the ultrapure water pipe material 100) is the same as the total thickness described above in "1-1. Layer structure."

[0042] In the case of the multi-layered ultrapure water pipe materials 100a and 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.

[0043] [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 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.

[0044] The core layer 220 is an extrusion-molded layer made of any resin composition. From the viewpoint of adhesion to the HDPE layer 210, a preferred example of a resin used for the core layer 220 is a polyolefin-based resin. The polyolefin-based resin is not particularly limited, and any polymer containing a monomer unit derived from an olefin may be used. Examples of polyolefin-based resins include polyethylene-based resins, ethylene-alkenyl carboxylic acid ester copolymer resins, ethylene-α-olefin copolymer resins, polypropylene-based resins, polybutene-based resins, and poly(4-methyl-1-pentene)-based resins. These polyolefin-based resins may be used alone or in combination. Among these polyolefin-based resins, polyethylene-based resins and polypropylene-based resins are preferred from the viewpoint of improving the overall strength of the pipe material. Furthermore, among polyethylene-based resins and polypropylene-based resins, polyethylene-based resins are more preferred from the viewpoint of suppressing the content of low-molecular-weight components and thereby suppressing the elution of organic components into pure water.

[0045] The polyethylene resin is not particularly limited, but examples thereof 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 pure water.

[0046] Examples of the alkenyl carboxylic acid ester in the ethylene-alkenyl carboxylic acid ester copolymer resin include vinyl acetate, vinyl propionate, vinyl butyrate, isopropenyl acetate, and allyl acetate, with vinyl acetate being preferred.

[0047] 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 %.

[0048] 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 serving as 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 above in "1-2-1. High-density polyethylene." 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 time, and more preferably 0.9 to 0.95 times, the weight-average molecular weight of the HDPE used in the HDPE layer serving as the inner layer.

[0049] The molecular weight distribution (Mw / Mn) of the polyolefin resin contained in the core layer is not particularly limited, but is, for example, 25-60, more preferably 30-55, even more preferably 35-48, and particularly preferably 40-43.

[0050] The MFR of the resin used in the core layer is not particularly limited, but it 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 above in "1-2-1. High-density polyethylene." 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, the weight-average molecular weight of the HDPE used in the HDPE layer, which is the inner layer.

[0051] The calcium concentration in the core layer is not particularly limited, and a calcium concentration of the same level as that contained in general-purpose grade resins is acceptable.

[0052] The core layer preferably contains an antioxidant. Examples of antioxidants include phenol-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, aromatic amine-based antioxidants, and lactone-based antioxidants. From the viewpoint of suppressing the effects of oxygen and ensuring desirable 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.

[0053] 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 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.

[0054] [1-4. Gas barrier layer] The gas barrier layer 230 illustrated in the ultrapure water pipe material 100b of 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 of FIG. 1. The gas barrier layer prevents oxygen from penetrating from the outer surface of the pipe material into the inner layers, thereby maintaining the strength of the pipe material itself. The provision of a gas barrier layer is also preferable because it effectively prevents gas dissolution into pure water. The gas barrier layer is preferably provided for the purpose of blocking oxygen.

[0055] 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).

[0056] The thickness of the gas barrier layer is, for example, 50 to 150 μm, and preferably 80 to 120 μm.

[0057] [1-5. Performance in preventing impurities from leaching into pure water] The ultrapure water pipe material of the present invention has a highly smooth inner peripheral surface and is therefore excellent in the ability to inhibit the elution of impurities into pure water.

[0058] The metal elution suppression performance of the ultrapure water pipe material of the present invention, among the impurity elution suppression performance, is, for example, 14 μg / m as the total amount of elution of 16 major metals (aluminum, barium, boron, calcium, chromium, copper, iron, lead, lithium, magnesium, manganese, nickel, potassium, sodium, strontium, and zinc) measured based on SEMI F57-0314 (which refers to the SEMI F40 standard). 2 or less, preferably 12 μg / m 2 Less than 10 μg / m 2 or less, more preferably 9 μg / m 2 or less, more preferably 8.5 μg / m 2 The following are included:

[0059] A more specific example of metal elution suppression performance is, for example, 7 μg / m as the amount of calcium elution measured in accordance with SEMI F57-0314. 2 Less than 6 μg / m 2 or less, more preferably 5.5 μg / m 2 The following can be mentioned: the amount of copper eluted is, for example, 0.5 μg / m 2 or less, preferably 0.45 μg / m 2 Less than or equal to 0.4 μg / m 2 The following can be mentioned: for example, the amount of sodium eluted is 1.5 μg / m 2 or less, preferably 1.1 μg / m 2 Less than or equal to 0.7 μg / m 2 The following can be mentioned: the amount of zinc eluted is, for example, 0.5 μg / m 2 Less than or equal to 0.3 μg / m 2 Less than or equal to 0.2 μg / m2 The following are included:

[0060] Regarding the impurity elution suppression performance of the ultrapure water pipe material of the present invention, the amount of anion elution is, for example, 10 μg / m as the elution amount of bromide ions. 2 The amount of fluoride ions eluted is, for example, 1000 μg / m 2 Less than 800 μg / m 2 less than 700 μg / m 2 less than 600 μg / m 2 as nitrite ions, for example, 10 μg / m 2 as sulfate ions, for example, 10 μg / m 2 Examples include:

[0061] The impurity elution suppression performance of the ultrapure water pipe material of the present invention, with respect to the organic component elution suppression performance, is, for example, 10,000 μg / m as the elution amount of total organic components (TOC) measured in accordance with SEMI F57-0314. 2 or less, preferably 9000 μg / m 2 Less than or equal to 8500 μg / m 2 or less, more preferably 8000 μg / m 2 The following are included:

[0062] [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 within an ultrapure water production system, piping for transporting ultrapure water from an ultrapure water production system to a use point, piping for returning ultrapure water from a use point, etc.

[0063] The ultrapure water pipe material of the present invention is preferably used as water piping for nuclear power generation, which requires particularly strict water quality for ultrapure water, or as ultrapure water transport piping used in pharmaceutical manufacturing processes, or in wet processing steps such as cleaning in the manufacturing process of semiconductor devices or liquid crystals, more preferably semiconductor devices. The semiconductor devices in question are preferably those with a higher degree of integration, and more specifically, those used in the manufacturing process of semiconductor devices with a minimum line width of 65 nm or less. Standards for the quality of ultrapure water used in semiconductor manufacturing include, for example, SEMI F57-0314.

[0064] Furthermore, the ultrapure water pipe material of the present invention has excellent workability, and therefore, for example, fusion welding such as butt fusion welding and EF (electrofusion) welding can be easily carried out at a relatively low temperature.

[0065] [2. Manufacturing method of ultrapure water pipe material] The above-described ultrapure water pipe of the present invention can be produced by extruding a resin composition for an HDPE layer used to form the HDPE layer. That is, 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 and a fluorinated lubricant. Furthermore, 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 fluorinated lubricant and a resin composition for another layer used to form layers other than the HDPE layer. To more easily achieve a surface roughness of 0.25 μm or less on the inner circumferential surface, the method for producing an ultrapure water pipe of the present invention preferably includes a step of extruding a resin composition for an HDPE layer containing high-density polyethylene and a fluorinated lubricant under a back pressure of 3 to 30 MPa.

[0066] [2-1. Resin composition] The HDPE and fluorine-based lubricant contained in the resin composition for HDPE layer, which contains high-density polyethylene and a fluorine-based lubricant, 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.

[0067] The HDPE used in the resin composition for the HDPE layer may be synthesized by polymerization using a chlorine-based catalyst such as a commonly used Ziegler-Natta catalyst, or may be synthesized using a chromium-based catalyst or a metallocene catalyst.

[0068] In a specific synthesis method for HDPE used in the resin composition for the HDPE layer, a chlorine-based catalyst is used for single-stage polymerization, followed by the addition of a neutralizing agent (e.g., calcium stearate, hydrocalcite, etc.) in an amount equivalent to a calcium concentration of less than 15 ppb. When a neutralizing agent is added in this manner, one type of neutralizing agent can be used alone or in combination with multiple types. Alternatively, in another specific synthesis method for HDPE used in the resin composition for the HDPE layer, a chromium-based catalyst or a metallocene catalyst can be used for single-stage polymerization, eliminating the need for a neutralizing agent.

[0069] 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 blending a fluorine-based lubricant therein.

[0070] Furthermore, when the ultrapure water pipe material to be manufactured has a multi-layer structure including a core layer, and when a polyolefin resin is used for the core layer, a specific method for synthesizing the polyolefin resin involves multi-stage polymerization (preferably two-stage polymerization) using a chlorine-based catalyst, followed by the addition of a neutralizing agent (e.g., calcium stearate, hydrocalcite, etc.) in an amount equivalent to a calcium concentration of 15 to 25 ppb.

[0071] 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.

[0072] [2-2. Back pressure] Back pressure is the force measured in the flow path between the extruder and the mold, acting in the direction in which the mold at the end of the flow path pushes the molten material back toward the extruder. In the method for producing a pipe material for ultrapure water of the present invention, by extruding the HDPE layer while controlling the back pressure to 3 to 30 MPa, it is possible to more easily achieve a surface roughness of 0.25 μm on the inner surface.

[0073] Furthermore, from the viewpoint of further reducing the surface roughness of the inner peripheral surface (i.e., further improving the surface smoothness of the inner peripheral surface), the back pressure for extrusion molding the resin composition for the HDPE layer is preferably 5 to 25 MPa, more preferably 9 to 24 MPa, even more preferably 13 to 23 MPa, even more preferably 17 to 22 MPa, and particularly preferably 19 to 21 MPa.

[0074] In the present invention, the measurement locations of the back pressure for extrusion molding of the resin composition for the HDPE layer are shown in Figures 4 to 6. In Figures 4 to 6, the mandrel (metal core) used to form the pipe in the mold is omitted to mainly show the extrusion direction of the resin. Figure 4 shows a part of the production line for manufacturing the ultrapure water pipe material shown in Figure 1, Figure 5 shows a part of the production line for manufacturing the ultrapure water pipe material shown in Figure 2, and Figure 6 shows a part of the production line for manufacturing the ultrapure water pipe material shown in Figure 3. In Figure 4, the back pressure refers to the back pressure BP-1 measured in the flow path between the HDPE layer extruder (which extrudes the resin composition for the HDPE layer) and the mold. In Figures 5 and 6, the back pressure refers to the back pressure BP-1 measured in the flow path between the core layer extruder (which extrudes the resin composition for the core layer) and the mold. 5 and 6, the back pressure BP-2 of the resin composition for the HDPE layer that flows inside the core layer in the mold and the back pressure BP-2 of the resin composition for the gas barrier layer can both be set to the same value as the back pressure BP-1. Examples of back pressures that are equivalent to the back pressure BP-1 include back pressures that are 0.9 to 1.1 times, and preferably 0.95 to 1.05 times, the back pressure BP-1. [Example]

[0075] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0076] The ultrapure water pipe materials shown in Tables 1 and 2 were produced by extrusion molding. Comparative Example 1 is a pipe material with a single-layer structure made of PVDF (total thickness 2.4 mm, outer diameter 32.0 mm), while Comparative Examples 2 and 3 and Examples 1 to 8 are pipe materials with a multi-layer structure as shown in Fig. 3 (HDPE layer 210: 0.5 mm, core layer 220: 2.5 mm, gas barrier layer 230: 0.1 mm, with an additional 0.1 mm adhesive layer (not shown) between core layer 220 and gas barrier layer 230. Outer diameter: 32.0 mm).

[0077] The resin compositions shown in Tables 1 and 2 indicate the resin compositions of the layer that forms the inner circumferential surface (surface that comes into contact with ultrapure water) of the ultrapure water pipe material, and for Comparative Examples 2 and 3 and Examples 1 to 8, the resin compositions are those of the HDPE layer 210. The HDPE shown in Tables 1 and 2 has a density of 0.942 g / cm 3 The HDPE polymerized using a Ziegler-Natta catalyst had a weight average molecular weight of 780,000, a molecular weight distribution (Mw / Mn) of 71, a calcium concentration of less than 10.0 ppb, and an MFR of 12.06 g / 10 min (190°C, 21.6 kg) (clean grade level with a trace amount of neutralizer and no antioxidant added). In Comparative Examples 2 and 3 and Examples 1 to 8, the material used for the core layer 220 had a density of 0.941 g / cm. 3 The material is HDPE (general-grade, neutralized and formulated with antioxidants) polymerized using a Ziegler-Natta catalyst, with a weight-average molecular weight of 730,000, a molecular weight distribution (Mw / Mn) of 41, and an MFR of 12.88 g / 10 min (190°C, 21.6 kg); 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.

[0078] The fluorine-based lubricants shown in Tables 1 and 2 are 100% vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymers.

[0079] Furthermore, the back pressures shown in Tables 1 and 2 refer to BP1 shown in FIG. 6 (note that BP2 and BP3 were also the same back pressure as BP1).

[0080] The surface roughness (arithmetic mean roughness Ra measured according to JIS B 0601:2001) of the obtained ultrapure water pipe material and the amount of elution of 16 major metals (aluminum, barium, boron, calcium, chromium, copper, iron, lead, lithium, magnesium, manganese, nickel, potassium, sodium, strontium, and zinc), total organic components (TOC), and anions based on the SEMI F57-0314 standard were measured. The results are shown in Tables 1 and 2.

[0081] [Table 1] [Table 2]

[0082] As is clear from Tables 1 and 2, the ultrapure water pipe material having an HDPE layer blended with a fluorine-based lubricant (Examples 1 to 8) was able to achieve a surface smoothness that complies with SEMI standards, something that had not been achieved with previous HDPE pipes. Furthermore, even when the blending amount of fluorine-based lubricant was the same (Examples 1 to 6), controlling the back pressure further improved the surface smoothness (Examples 2 to 5), and in particular, the ultrapure water pipe material of Example 4 was able to achieve a surface smoothness equivalent to that of a PVDF pipe (Comparative Example 1).

[0083] Furthermore, the ultrapure water pipe materials of Examples 1 to 8 not only showed a significantly lower total elution amount of the 16 metals than the HDPE pipe (Comparative Example 2), which had the highest surface smoothness to date, but also significantly lower than the PVDF pipe (Comparative Example 1), demonstrating excellent suppression of elution of the 16 metals. The ultrapure water pipe materials of Examples 1 to 8 made it possible to reduce the elution amounts of calcium, copper, sodium, and zinc contained in HDPE pipes to extremely low levels, and the ultrapure water pipe material of Example 4 achieved the same levels of calcium and copper elution as the PVDF pipe (Comparative Example 1), and the elution amounts of sodium and zinc were lower than those of the PVDF pipe (Comparative Example 1).

[0084] Furthermore, in the ultrapure water pipe material of Example 4, the amounts of TOC and anions eluted were also reduced to extremely low levels.

[0085] Since the elution of impurities was reduced to an extremely low level, it was confirmed that the ultrapure water piping of Examples 1 to 8 was suitable for transporting semiconductor cleaning solutions suitable for wet processing processes of semiconductor elements with a minimum line width of 65 nm or less. [Explanation of symbols]

[0086] 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 and a fluorine-based lubricant, The inner circumferential surface of the HDPE layer constitutes the inner circumferential surface of the pipe material, The surface roughness of the inner circumferential surface is 0.25 μm or less, Ultrapure water pipe material used to transport ultrapure water.

2. 2. The pipe material for ultrapure water according to claim 1, wherein the HDPE layer is formed by extrusion molding an HDPE composition containing the high-density polyethylene and the fluorine-based lubricant under a back pressure of 3 to 30 MPa.

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

4. 4. The pipe material for ultrapure water according to claim 1, wherein the content of said fluorine-based lubricant in said HDPE layer is 0.01 to 5% by weight.

5. 5. The pipe material for ultrapure water according to claim 1, which has a multi-layer structure in which another layer is laminated on the outer surface of the HDPE layer.

6. 6. The ultrapure water pipe according to claim 5, wherein the HDPE layer has a thickness of 0.3 mm or more.

7. The total amount of elution of aluminum, barium, boron, calcium, chromium, copper, iron, lead, lithium, magnesium, manganese, nickel, potassium, sodium, strontium, and zinc measured in accordance with SEMI F57-0314 is 14 μg / m 2 The ultrapure water pipe material according to any one of claims 1 to 6, wherein:

8. The amount of calcium elution measured based on SEMI F57-0314 is 7 μg / m 2 Below, the amount of copper eluted is 0.5 μg / m 2 The sodium elution amount is 1.5 μg / m 2 The elution amount is 0.5 μg / m or less. 2 or less, and / or the amount of zinc eluted is 0.5 μg / m 2 The ultrapure water pipe material according to any one of claims 1 to 7, wherein:

9. The amount of fluoride ions eluted is 600 μg / m as measured based on SEMI F57-0314. 2 The ultrapure water pipe material according to any one of claims 1 to 8, wherein:

10. The amount of eluted total organic components measured according to SEMI F57-0314 is 10,000 μg / m 2 The ultrapure water pipe material according to any one of claims 1 to 9, wherein:

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

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

13. A method for manufacturing a pipe material for ultrapure water, the pipe material having an HDPE layer containing high-density polyethylene and a fluorine-based lubricant, the inner circumferential surface of the HDPE layer constituting the inner circumferential surface of the pipe material, and the surface roughness of the inner circumferential surface being 0.25 μm or less, The manufacturing method includes a step of extruding the HDPE layer from a resin composition containing the high-density polyethylene and the fluorine-based lubricant under a back pressure of 3 to 30 MPa.

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