Double-layered pipe

Abstract

We provide a multilayer pipe with a polypropylene resin innermost layer that can be used as piping for transporting ultrapure water. [Solution] The multilayered pipes 1 and 1' are multilayered pipes used for transporting ultrapure water, and comprise a first layer 11, a second layer 12, and a third layer 13. The first layer 11 constitutes the innermost layer and is mainly composed of polypropylene resin. The second layer 12 is located outside the first layer 11 and is mainly composed of adhesive polyolefin resin. The third layer 13 has gas barrier properties and is located outside the second layer 12.

Description

[Technical Field]

[0001] This disclosure relates to multi-layered pipes. [Background technology]

[0002] In the manufacturing of precision devices such as semiconductor devices or liquid crystal displays, ultrapure water purified to extremely high purity is used in wet processes such as cleaning. If metal ions or other impurities are present in the water above a certain concentration, the metal will adsorb onto the wafer surface, adversely affecting the quality of the precision device. Therefore, strict control over impurities in ultrapure water is carried out.

[0003] The contamination of ultrapure water with impurities can also occur in the piping that makes up the ultrapure water transport line. While metals such as stainless steel, which have excellent gas barrier properties, have been used as the material for the piping, it is considered preferable to use resin considering the effects of metal leaching from the piping.

[0004] For example, Patent Document 1 discloses a multilayer pipe for piping ultrapure water, characterized by comprising a first resin layer made of fluororesin that comes into contact with ultrapure water, and a second resin layer made of a gas-impermeable resin that is provided on the outer surface of the first resin layer. Furthermore, it is disclosed that a third resin layer is provided on the outer surface of the second resin layer to protect the second resin layer, and that polyethylene is used as the third resin layer.

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

[0006] Fluoropolymer piping, such as PVDF, has disadvantages in terms of ease of installation and cost compared to other common types of piping. Furthermore, ultra-high-purity cleaning solutions often contain dialuminoalkanes such as 3-dialuminopropane, and because they are used at 60°C, they deteriorate quickly.

[0007] Therefore, for example, a pipe material has been proposed in which an HDPE layer containing high-density polyethylene and a fluorine-based lubricant is used in the innermost layer, as shown in Patent Document 2. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2010-234576 [Patent Document 2] Japanese Patent Publication No. 2022-159129 [Overview of the project] [Problems that the invention aims to solve]

[0009] As described in Patent Document 2 above, while the use of polyethylene resin for the innermost layer of ultrapure water piping has been studied, sufficient studies have not been conducted on the use of polypropylene resin for the innermost layer.

[0010] This disclosure aims to provide a multilayer pipe that uses a polypropylene resin in its innermost layer and can be used as piping for transporting ultrapure water. [Means for solving the problem]

[0011] To achieve the above objective, the multilayered tube according to the first disclosure is a multilayered tube used for transporting ultrapure water, and comprises a first layer, a second layer, and a third layer. The first layer constitutes the innermost layer and is mainly composed of a polypropylene resin. The second layer is located outside the first layer and is mainly composed of an adhesive polyolefin resin. The third layer has gas barrier properties and is located outside the second layer.

[0012] Thus, even when the multilayer tube of the present disclosure uses a layer mainly composed of a polypropylene-based resin for the innermost layer, by disposing a layer having gas barrier properties on the outside, it is possible to secure an oxygen barrier property that can be used for transporting semiconductor cleaning liquid, and it can be used as a pipe for ultrapure water.

[0013] The multilayer tube according to the second disclosure is the multilayer tube according to the first disclosure, and the calcium elution amount measured in accordance with SEMI F-57 is 30 μg / m

[0017] Less than.

[0014] Thereby, it is possible to provide a multilayer tube that can be used as a pipe for ultrapure water.

[0015] The multilayer tube according to the third disclosure is the multilayer tube according to the first disclosure, and the thickness of the third layer is 80 μm or more and 500 μm or less.

[0016] By setting the thickness of the third layer having gas barrier properties to 80 μm or more, the oxygen permeability can be reduced so that it can be used for transporting ultrapure water. Although the oxygen permeability can be reduced by increasing the thickness of the third layer, 500 μm is set as the upper limit value when used as an actual product.

[0017] The multilayer tube according to the fourth disclosure is the multilayer tube according to the first disclosure, and further includes a core material layer. The core material layer is disposed between the first layer and the second layer and is mainly composed of a polypropylene-based resin.

[0018] For example, by using a material with a lower cost than the first layer for the core material layer, the cost can be reduced while ensuring the strength of the multilayer tube.

[0019] The multilayer tube according to the fifth disclosure is the multilayer tube according to the first disclosure, and the third layer contains an ethylene vinyl alcohol copolymer as a main component.

[0020] Thereby, the moldability of the multilayer tube can be improved. [Effects of the Invention]

[0021] According to this disclosure, a multi-layer pipe can be provided that uses a polypropylene resin for the innermost layer and can be used as piping for transporting ultrapure water. [Brief explanation of the drawing]

[0022] [Figure 1] (a) Cross-sectional view of a multilayer pipe in an embodiment of the present disclosure, (b) Cross-sectional view of a multilayer pipe in another example of an embodiment of the present disclosure. [Modes for carrying out the invention]

[0023] Embodiments relating to this disclosure will be described below with reference to the drawings.

[0024] (Double-layered pipe 1) Figure 1(a) is a cross-sectional view of a double-layered pipe 1. Figure 2(b) is a cross-sectional view showing another example of a double-layered pipe 1, which is a double-layered pipe 1'.

[0025] The multilayered pipe 1 shown in Figure 1(a) includes a first layer 11, a second layer 12, and a third layer 13. The first layer 11 constitutes the innermost layer of the multilayered pipe 1. The first layer 11 constitutes the inner surface 1b of the multilayered pipe 1. The first layer 11 mainly contains polypropylene resin. The second layer 12 is located outside the first layer 11. The second layer 12 mainly contains adhesive polyolefin resin. The third layer 13 is a gas barrier layer with gas barrier properties. The third layer 13 constitutes the outer surface 1c of the multilayered pipe 1.

[0026] The multilayered pipe 1' shown in Figure 1(b) includes a first layer 11, a core material layer 14, a second layer 12, and a third layer 13. In the multilayered pipe 1', the core material layer 14 is positioned between the first layer 11 and the second layer 12 of the multilayered pipe 1. The first layer 11 constitutes the innermost layer of the multilayered pipe 1'. The first layer 11 constitutes the inner surface 1b' of the multilayered pipe 1'. The third layer 13 constitutes the outer surface 1c' of the multilayered pipe 1'.

[0027] (1st layer 11) The first layer 11 mainly contains polypropylene resin. The main component is the component that is present in the largest quantity by mass. The main component is a component that is present in a quantity of at least 50%. The lower limit of the polypropylene resin content in the first layer 11 is preferably 50% by mass, more preferably 70% by mass, even more preferably 80% by mass, and may also be 90% by mass, and may also be 95% by mass.

[0028] The polypropylene resin included as the main component in the first layer 11 is not particularly limited, and examples include homopolypropylene, block polypropylene, and random polypropylene. In block polypropylene and random polypropylene, ethylene is typically used as the copolymer component.

[0029] The calcium elution amount measured in Layer 11 according to SEMI F-57 is 30 μg / m². 2 The calcium concentration in the first layer 11 is adjusted so that it is less than 360 ppm. The calcium concentration in the first layer 11 is 360 ppm or less, preferably 55 ppm or less, and more preferably 50 ppm or less. If the calcium concentration exceeds 60 ppm, the amount of calcium leached into the ultrapure water will be excessive, and it may not be possible to meet the required quality of the ultrapure water.

[0030] From the perspective of further suppressing the amount of calcium leached into ultrapure water, it is preferable to keep the calcium concentration in the first layer 11 as low as possible. However, from the perspective of obtaining good thermal stability and long-term strength for the polypropylene resin composition, the inclusion of trace amounts of calcium is unavoidable.

[0031] In other words, if the amount of neutralizing agent added to the polypropylene resin polymerized using the Ziegler catalyst is insufficient, the catalyst residue may remain active in the resin, potentially reducing the thermal stability and long-term strength of the polypropylene resin composition.

[0032] Therefore, in this embodiment, it is essential to add the minimum necessary amount of neutralizing agent to neutralize the catalyst residue. Considering the above, the calcium concentration of the first layer 11 is 10 ppm or more, preferably 13 ppm or more, more preferably 15 ppm or more, and even more preferably 20 ppm or more.

[0033] The oxidation induction time (OIT) of the first layer 11 at 210°C is preferably 20 minutes or more from the viewpoint of ensuring thermal stability. If the oxidation induction time at 210°C is less than 20 minutes, the polypropylene resin may deteriorate when heat-processed, which may lead to a decrease in long-term strength or an increase in particles derived from the deteriorated material, and this is undesirable in this embodiment.

[0034] From the viewpoint of ensuring sufficient long-term strength of piping materials for ultrapure water, when the first layer 11 is formed as piping material, it is preferable that the hot internal pressure creep performance is such that the piping material does not break for 3,000 hours or more when a circumferential stress of 5.0 MPa is applied to the piping material at 80°C.

[0035] The first layer 11 may or may not contain an antioxidant. Examples of antioxidants include phenolic antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, aromatic amine-based antioxidants, and lactone-based antioxidants.

[0036] Examples of phenolic antioxidants include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and N,N'-hexane-1,6-diylbis[3-(3,5- [Di-tert-butyl-4-hydroxyphenyl)propionamide], benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy, C7-C9 side-chain alkyl ester, 3,3',3'',5,5',5''-hexa-tert-butyl-a,a',a''-(mesitylene-2,4,6-triyl)tri-p-cresol, 4,6-bis(dodecylthiomethyl)-o-cresol, 4,6-bis(octyl Luthiomethyl)-o-cresol, ethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1 Examples include 3,5-tris[(4-tert-butyl-3-hydroxy-2,6-xylyl)methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 2,6-di-tert-butyl-4-[4,6-bis(octylthio)-1,3,5-triazine2-ylamino]phenol, and diethyl[{3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl}methyl]phosphonate.

[0037] When using phenolic antioxidants, one type may be used alone, or two or more types may be used in combination. However, from the viewpoint of preventing calcium elution, it is preferable that the antioxidant does not contain oxygen derived from a group other than the phenol group. Examples include 3,3',3'',5,5',5''-hexa-tert-butyl-a,a',a''-(mesitylene-2,4,6-triyl)tri-p-cresol, 2,6-di-tert-butyl-4-[4,6-bis(octylthio)-1,3,5-triazine2-ylamino]phenol, 4,4',4''-(1-methylpropanyl-3-ylidene)tris(6-tert-butyl-m-cresol), and 6,6'-di-tert-butyl-4,4'-butylidenebis-m-cresol. Furthermore, when using a phenolic antioxidant that contains oxygen derived from a group other than the phenol group, it is preferable that the calcium concentration in the polyethylene resin be 50 ppm or less. Examples of functional groups containing oxygen derived from groups other than phenol groups include ester groups, carbonyl groups, carboxyl groups, ether groups, nitro groups, nitroso groups, amide groups, azixy groups, and sulfo groups.

[0038] Examples of phosphorus-based antioxidants include tris(2,4-di-tert-butylphenyl) phosphite, tris[2-[[2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphefin-6-yl]oxy]ethyl]amine, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, bis[2,4-bis(1,1-dimethylethyl)-6-methylphenyl]ethyl ester phosphorous acid, and tetrakis(2,4-di-tert-butylphenyl)(1,1-biphenyl)-4,4'-diylbisphosphonate.

[0039] Examples of sulfur-based antioxidants include dilaurylthiodipropionate, dimyristylthiodipropionate, distearylthiodipropionate, and pentaerythrityltetrakis(3-laurylthiopropionate).

[0040] Examples of aromatic amine antioxidants include monoamine compounds such as diphenylamine compounds, quinoline compounds, and naphthylamine compounds, as well as diamine compounds such as phenylenediamine compounds and benzimidazole compounds.

[0041] Examples of diphenylamine compounds include p-(p-toluenesulfonylamide)-diphenylamine, 4,4'-(α,α-dimethylbenzyl)diphenylamine, and 4,4'-dioctyl diphenylamine derivatives. Examples of quinoline compounds include 2,2,4-trimethyl-1,2-dihydroquinoline polymers.

[0042] Examples of naphthylamine compounds include phenyl-α-naphthylamine and N,N'-di-2-naphthyl-p-phenylenediamine.

[0043] Examples of phenylenediamine compounds include N-N'-diphenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, mixtures of N-N'-diphenyl-p-phenylenediamine, diaryl-p-phenylenediamine derivatives or mixtures thereof.

[0044] Examples of benzimidazole compounds include 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, zinc salt of 2-mercaptobenzimidazole, and zinc salt of 2-mercaptomethylbenzimidazole.

[0045] Examples of lactone-based antioxidants include reaction products of 3-hydroxy-5,7-di-tert-butylfuran-2-one and o-xylene. The antioxidant content in the first layer 11 is, for example, 0.01% by weight or more, preferably 0.03% by weight or more, and more preferably 0.05% by weight or more, from the viewpoint of suppressing the effect of oxygen and ensuring desirable strength. The upper limit of the antioxidant content is, for example, 5% by weight or less, preferably 1% by weight or less, and more preferably 0.5% by weight or less.

[0046] The first layer 11 may or may not contain a light stabilizer, but it is preferable that it does not contain a light stabilizer from the viewpoint of preventing total organic carbon (TOC) elution. Examples of light stabilizers include hindered amine light stabilizers (HALS). Furthermore, it is preferable that the first layer 11 of this embodiment is substantially free of light stabilizers. Here, substantially free means that light stabilizers are not actively added, and that unavoidable contamination as impurities is acceptable. The lower the concentration of light stabilizers that are inevitably present as impurities, the better.

[0047] Examples of hindered amine-based light stabilizers include NH-type hindered amine compounds, NR-type hindered amine compounds, and N-OR-type hindered amine compounds.

[0048] Examples of NH-type hindered amine compounds include Tinuvin 770DF, Kimasove 2020FDL, Kimasove 944FDL (all trade names, manufactured by BASF), Adeka Stab LA-68, Adeka Stab LA-57 (both trade names, manufactured by Adeka), Siasorb UV-3346, Siasorb UV-3853 (both trade names, manufactured by Sun Chemical Co., Ltd.).

[0049] Examples of NR-type hindered amine compounds include tinubine 622SF, tinubine 765, tinubine PA144, kimasoub 119, tinubine 111 (all trade names, manufactured by BASF), savostab UV119 (trade name, manufactured by Savo), adekastab LA-63P, and adekastab LA-52 (all trade names, manufactured by adeka).

[0050] Examples of N-OR type hindered amine compounds include tinuvin 123, tinuvin 5100, tinuvin NOR371FF, and flame stub NOR116FF (all trade names, manufactured by BASF).

[0051] The first layer 11 may or may not contain a UV absorber (UVA). Examples of UV absorbers include benzophenone-based UV absorbers, salmalate-based UV absorbers, benzocoat-based UV absorbers, benzotriazole-based UV absorbers, cyanoacrylate-based UV absorbers, and quenchers. For polyethylene or polypropylene, benzophenone-based UV absorbers and benzotriazole-based UV absorbers are particularly preferred.

[0052] Examples of benzophenone-based UV absorbers include 2-hydroxy-4-methoxy-benzophenone.

[0053] Examples of benzotriazole-based UV absorbers include 2-(2-hydroxy-5-methylphenyl)benzotriazole (Sumisorb 200, manufactured by Sumika Chemtex Co., Ltd.), 2-(2-hydroxy-5-t-butyl-5-methylphenyl)-5-chlorobenzotriazole (Tinuvin 326, manufactured by BASF), 2-(2-hydroxy-3,5-di-t-butylphenyl)-5-chlorobenzotriazole (Tinuvin 327, manufactured by BASF), and 2-(2-hydroxy-3,5-di-t-amylphenyl)benzotriazole (Tinuvin 328, manufactured by BASF).

[0054] From the viewpoint of obtaining good rigidity of the polypropylene resin composition, the density of the first layer 11 is preferably 0.900 g / cm³. 3 More preferably 0.901 g / cm³ 3 More preferably 0.902 g / cm³ 3 The above points are listed above. Furthermore, from the viewpoint of obtaining good long-term durability and flexibility of the polypropylene resin composition, the density is preferably 0.910 g / cm³. 3 More preferably, 0.909 g / cm³ 3 More preferably, 0.908 g / cm³ 3 These are some examples. The density is a value determined in accordance with JIS K6922-2:1997.

[0055] The inner surface smoothness (arithmetic mean roughness Ra) of the first layer 11 is not particularly limited, and for example, it can be 0.50 μm or less. From the viewpoint of obtaining good low elution properties of the piping, the inner surface smoothness of the first layer 11 is preferably 0.40 μm or less, and more preferably 0.35 μm or less.

[0056] The thickness t1 of the first layer 11 is preferably, for example, 0.5 mm or more and 16 mm or less. More specifically, in the case of a double-layered pipe 1 with a diameter of 25A, the thickness t1 is preferably 2 mm or more and 3.5 mm or less. In the case of a double-layered pipe 1' with a diameter of 25A, the thickness t1 is preferably 0.5 mm or more and 1.5 mm or less. In the case of a double-layered pipe 1 with a diameter of 75A, the thickness t1 is preferably 4 mm or more and 7 mm or less. In the case of a double-layered pipe 1' with a diameter of 75A, the thickness t1 is preferably 0.5 mm or more and 3 mm or less. In the case of a double-layered pipe 1 with a diameter of 200A, the thickness t1 is preferably 12 mm or more and 16 mm or less. In the case of a double-layered pipe 1' with a diameter of 200A, the thickness t1 is preferably 0.5 mm or more and 3 mm or less.

[0057] (Core material layer 14) As shown in Fig. 1(b), the core material layer 14 is disposed outside the first layer 11. The core material layer 14 is mainly composed of a polypropylene-based resin. The main component refers to the component with the highest content on a mass basis. The main component is a component with a content of at least 50%. The lower limit of the content of the polypropylene-based resin in the core material layer 14 is preferably 50% by mass, more preferably 70% by mass, still more preferably 80% by mass, even more preferably 90% by mass, and even more preferably 95% by mass.

[0058] The polypropylene-based resin used for the core material layer 14 may be of the same type or different types from the polypropylene-based resin used for the first layer 11. However, when the two layers are in contact with each other and laminated, from the viewpoint of improving the adhesion between the two layers and exhibiting preferable strength, it is more preferable that they are polypropylene-based resins of the same type.

[0059] Regarding the calcium elution amount of the material (polypropylene-based resin composition) of the core material layer 14 measured in accordance with EMIF-57, from the viewpoint of ensuring the strength of the pipe for semiconductor cleaning liquid in a usage environment of 60°C, it is preferably 30 μg / m 2 or more, more preferably 50 μg / m 2 or more, still more preferably 70 μg / m 2 or more, even more preferably 80 μg / m 2 or more, particularly preferably 90 μg / m 2 or more, even more particularly preferably 95 μg / m 2 or more.

[0060] Since the multi-layer pipe 1' of the present invention is excellent in the effect of suppressing the elution of calcium and organic components, even if the material of the core material layer 14 contains a large amount of calcium, the elution of calcium can be effectively suppressed. From such a viewpoint, as preferable examples of the above calcium elution amount, among the above ranges, 80 μg / m 2 or more, 90 μg / m 2 or more, or 95 μg / m 2 or more can be mentioned. Also, the upper limit of the above calcium elution amount is not particularly limited, but from the viewpoint of suppressing the elution of calcium, 120 μg / m2 Below, 110μg / m 2 The following, or 100 μg / m² 2 The following are examples. Furthermore, the calcium concentration in the core material layer 14 (polyolefin resin composition) is not particularly limited as long as it satisfies the above-mentioned calcium elution amount, but from the viewpoint of ensuring the strength of the semiconductor cleaning solution piping in a 60°C operating environment, for example, 20 ppm or more, preferably 30 ppm or more, more preferably 40 ppm or more, even more preferably 50 ppm or more, and even more preferably 60 ppm or more. Furthermore, as an upper limit for the above-mentioned calcium concentration range, from the viewpoint of suppressing insufficient strength due to the calcium itself acting as the starting point for fracture, and from the viewpoint of suppressing the elution of calcium and organic components, for example, 200 ppm or less, preferably 150 ppm or less, more preferably 130 ppm or less, and even more preferably 100 ppm or less.

[0061] For the core layer 14 material (polyolefin resin composition), the amount of organic components (TOC) eluted, as measured in accordance with EMIF-57, is, for example, 30,000 μg / m². 2 One example is the multilayer tube 1' of the present invention, which has excellent effect in suppressing the elution of calcium and organic components. Therefore, even if the core material layer 14 contains a large amount of organic components, the elution of organic components can be effectively suppressed. From this viewpoint, a suitable example of the amount of organic components eluted is 31,000 μg / m². 2 Preferably, the above is 31500 μg / m². 2 The above points are listed. Furthermore, there is no particular limit to the upper limit of the amount of organic components eluted, but from the viewpoint of suppressing the elution of organic components, for example, 35,000 μg / m³ is used. 2 Preferably, 34,000 μg / m² 2 More preferably, 33,000 μg / m² 2 More preferably, 32,000 μg / m² 2 The following are listed:

[0062] The core material layer 14 may contain a pigment. This allows for a different color from the first layer 11, and makes it possible to confirm whether the inside of the core material layer 14 is covered by the first layer 11. Furthermore, when the multilayer tube 1' is fusion-joined, visually confirming that the colored core material layer 14 does not protrude from the inner surface of the joint makes it possible to confirm whether the inner surface of the joint is covered by the low-eluting material of the first layer 11, thus facilitating quality control. Any conventionally known organic pigment, inorganic pigment, or extender pigment can be used as the pigment, and is not particularly limited. Examples of organic pigments include phthalocyanine-based, azo-based, condensed azo-based, anthraquinone-based, perinone / perylene-based, indigo / thioindigo-based, isoindolinone-based, azomethine azo-based, dioxazine-based, quinacridone-based, aniline black-based, and triphenylmethane-based pigments. Examples of inorganic pigments include carbon black-based, titanium dioxide-based, iron oxide-based, iron hydroxide-based, chromium oxide-based, spinel-type calcined pigments, lead chromate-based, vermilion chromate-based, Prussian blue-based, aluminum powder, and bronze powder. Examples of extender pigments include calcium carbonate-based, barium sulfate-based, silicon dioxide-based, and aluminum hydroxide-based pigments. The pigments are used individually or in combination so that the core material layer 14 becomes a predetermined color.

[0063] The pigment content in the core material layer 14 is not particularly limited as long as the above-mentioned color difference can be achieved, but it is preferably 0.05 wt% or more and 1.00 wt% or less.

[0064] The core material layer 14 preferably contains an antioxidant. Examples of antioxidants include phenolic antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, aromatic amine-based antioxidants, and lactone-based antioxidants, similar to those used in the first layer 11. From the viewpoint of suppressing the effects of oxygen and ensuring desirable strength, the antioxidant content in the core material layer 14 is, for example, 0.01% by weight or more, preferably 0.1% by weight or more. The upper limit of the antioxidant content is, for example, 5% by weight or less, preferably 1% by weight or less, and more preferably 0.5% by weight or less.

[0065] Furthermore, the thickness of the core material layer 14 is preferably 0.5 mm or more and 15.5 mm or less. Specifically, for a 25A diameter double-layered pipe 1', the thickness t4 of the core material layer 14 is preferably 0.5 mm or more and 3 mm or less. For a 75A diameter double-layered pipe 1', the thickness t4 of the core material layer 14 is preferably 1 mm or more and 6.5 mm or less. For a 200A diameter double-layered pipe 1', the thickness t4 of the core material layer 14 is preferably 9 mm or more and 15.5 mm or less.

[0066] (2nd layer 12) As shown in Figure 1(a), the second layer 12 is positioned outside the first layer 11. The second layer 12 adheres the third layer 13 to the outside of the first layer 11. As shown in Figure 1(b), the second layer 12 is positioned outside the core material layer 14. The second layer 12 adheres the third layer 13 to the outside of the core material layer 14. As the material for the second layer 12, which functions as an adhesive layer, an adhesive polyolefin resin is preferred. The second layer 12 contains an adhesive polyolefin resin as its main component. The main component refers to the component with the highest mass content. The main component is a component with a content of at least 50%. The lower limit of the content of the adhesive polyolefin resin in the second layer 12 is preferably 50% by mass, more preferably 70% by mass, even more preferably 80% by mass, and may also be 90% by mass, and may also be 95% by mass. As the adhesive polyolefin resin, for example, maleic anhydride-modified adhesive polyethylene can be used.

[0067] The thickness t2 of the second layer 12 is not particularly limited as long as it is thick enough to bond the third layer 13 to the first layer 11 or the core material layer 14, but it is preferably 50 μm or more and 500 μm or less. Note that the preferred range of thickness t2 is the same even if the type and diameter of the multilayer tubes 1 and 1' are different.

[0068] (3rd layer 13) By providing the third layer 13, which acts as a gas barrier layer, the dissolution of gas into ultrapure water can be effectively suppressed. Furthermore, the third layer 13 prevents oxygen from the outer surfaces 1c and 1c' of the multilayered pipes 1 and 1' from penetrating into the innermost first layer 11 or the core material layer 14, thereby improving the long-term strength of the multilayered pipes 1 and 1'. Providing a gas barrier layer is also preferable because it effectively suppresses the dissolution of gas into ultrapure water.

[0069] Examples of materials for the third layer 13 include ethylene vinyl alcohol copolymer (EVOH), polyvinylidene chloride resin (PVDC), and nylon resin. The third layer 13 mainly contains ethylene vinyl alcohol copolymer (EVOH), polyvinylidene chloride resin (PVDC), or nylon resin. The main component is a component that makes up at least 50% of the total content. The lower limit of the content of ethylene vinyl alcohol copolymer (EVOH), polyvinylidene chloride resin (PVDC), or nylon resin in the third layer 13 is preferably 50% by mass, more preferably 70% by mass, even more preferably 80% by mass, and may also be 90% by mass, and may also be 95% by mass. From the viewpoint of moldability, it is preferable to use ethylene vinyl alcohol copolymer (EVOH) as the adhesive polyolefin resin for the third layer 13.

[0070] The thickness t3 of the gas barrier layer is not particularly limited as long as it is thick enough to ensure the gas barrier properties of at least the polypropylene resin, but it is preferably 80 μm or more and 500 μm or less, and more preferably 100 μm or more and 270 μm or less. In order to obtain an oxygen permeability equivalent to that obtained when PVDF is used in the innermost layer of the pipe, the thickness t3 of the third layer 13 is preferably 100 μm or more. Note that the preferred range of thickness t3 is the same even if the type and diameter of the multilayer pipes 1 and 1' are different.

[0071] (Applications of piping materials for ultrapure water) The multilayered pipes 1 and 1' of the embodiment of the present invention can be used for transporting ultrapure water. Specifically, the multilayered pipes 1 and 1' of the embodiment of the present invention can be used as piping within an ultrapure water production apparatus, piping for transporting ultrapure water from the ultrapure water production apparatus to a point of use, and piping for returning ultrapure water from a point of use. In this invention, ultrapure water is defined as having a resistivity of 10 MΩ·cm or more at 25°C, more precisely, a resistivity of 15 MΩ·cm or more at 25°C, and even more precisely, a resistivity of 18 MΩ·cm or more at 25°C.

[0072] The multilayer pipes 1 and 1' of the embodiments of the present invention are preferably transport pipes for ultrapure water used in water piping for nuclear power plants, or in wet processing processes such as cleaning in the manufacturing of pharmaceuticals, semiconductor devices, or liquid crystals, and more preferably in the manufacturing of semiconductor devices, where the required water quality for ultrapure water is particularly stringent. The semiconductor device is preferably one with a higher degree of integration, and more specifically, it is more preferably used in the manufacturing process of a semiconductor device with a minimum line width of 65 nm or less. Examples of standards related to the quality of ultrapure water used in semiconductor manufacturing include SEMI F75.

[0073] Furthermore, since the multilayer pipes 1 and 1' of the embodiment of the present invention have layers mainly composed of polypropylene resin, they offer excellent workability. For example, fusion bonding work such as butt fusion bonding and EF (electrofusion) bonding can be easily performed at relatively low temperatures.

[0074] (Manufacturing of multi-layered pipes) The multilayered pipes 1 and 1' according to the embodiment of the present invention can be manufactured by co-extruding a polypropylene resin, which is the main component of the first layer 11 forming the inner surface 1b of the piping material, and a polypropylene resin, which is optionally the main component of the core material layer 14, preparing an adhesive polyolefin resin, which is the material for the second layer 12, and preparing a coating resin that constitutes the outer third layer 13, so that the thickness of each layer is a predetermined thickness. Since the multilayered pipe according to the embodiment of the present invention is made of polypropylene resin, it can be manufactured at low cost.

[0075] (Other embodiments) Although one embodiment of the present disclosure has been described above, the present disclosure is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the invention.

[0076] (A) In the multilayer pipe 1' of the above embodiment, the first layer 11, the core material layer 14, the second layer 12, and the third layer are arranged in that order, but the arrangement is not limited to this, and another layer may be placed between the core material layer 14 and the second layer 12.

[0077] (B) In the multilayered pipes 1 and 1' of the above embodiment, the third layer 13, which is a gas barrier layer, constitutes the outer surfaces 1c and 1c', but another layer may be provided on the outside of the third layer 13.

[0078] (C) The layer structure of the multi-layered pipes 1 and 1' in the above embodiment may be applied to joints used when connecting resin pipes (elbow joints, straight joints, tee joints, cross joints, flange joints, etc.), or to electrofusion joints.

[0079] (Examples) Next, the multi-layer pipe of this embodiment will be described in detail using examples.

[0080] In Examples 1 to 6, the oxygen barrier performance was measured for the multilayer tube 1 described in the above embodiment by changing the diameter and the thickness of the third layer. For the first layer 11, Novatec PP, EA9FTD, manufactured by Nippon Polypropylene Co., Ltd., was used as the polypropylene resin material (indicated as PP in the table). For the second layer 12, maleic anhydride-modified adhesive polyethylene (indicated as adhesive PE in the table) was used. For the third layer 13, ethylene vinyl alcohol copolymer (indicated as EVOH in the table) was used. The thickness of the third layer is shown below (Table 1).

[0081] For the oxygen barrier performance test, oxygen permeability was measured using the isobaric method in accordance with JIS K7126-2. The oxygen barrier performance values ​​in Table 1 below represent the oxygen permeability per unit area of ​​the piping.

[0082] (Table 1) TIFF2026045910000002.tif47153

[0083] In Comparative Example 1, the oxygen barrier performance of a single-layer tube composed solely of layers formed from polyvinylidene fluoride (PVDF) (Kureha KF Polymer, manufactured by Kureha Corporation) was measured.

[0084] In Comparative Example 2, the oxygen barrier performance of a single-layer tube composed solely of layers formed from polyethylene resin was measured. Novatec PP, EA9FTD, manufactured by Nippon Polypropylene Co., Ltd., was used as the polyethylene resin.

[0085] (Table 2) TIFF2026045910000003.tif45154

[0086] An oxygen permeability of 0.5 or less is considered acceptable (〇), and 0.35 or less is considered good (◎). As shown in Examples 1 to 6, it can be seen that the oxygen permeability decreases as the thickness of the third layer increases. In Examples 1 to 5, the oxygen permeability was 0.35 or less, so it was good. In Example 6, the thickness of the third layer was 50 μm, and the oxygen permeability was 0.48, which is outside the good range but within the acceptable range. Also, as shown in Comparative Example 2, if the third layer is not provided, the oxygen permeability exceeds 0.5, which is poor. Furthermore, in order to ensure oxygen barrier properties equivalent to those of a single-layer PVDF tube shown in Comparative Example 1 (oxygen permeability of 0.29), it can be seen that a thickness of 100 μm or more for the third layer is preferable.

[0087] From the above, it can be seen that a multilayer pipe using polypropylene resin as the innermost layer can be used as a piping for transporting ultrapure water by adding a third layer with gas barrier properties. [Explanation of symbols]

[0088] 1, 1': Double-layered pipe 11: 1st layer 12: 2nd layer 13:Third layer 14: Core material layer

Claims

1. A double-layered tube used for transporting ultrapure water, The innermost layer consists of a first layer mainly composed of polypropylene resin, A second layer, which is disposed on the outside of the first layer and mainly consists of an adhesive polyolefin resin, A third layer, which is disposed on the outside of the second layer and has gas barrier properties, is provided. Double-layered pipe.

2. The calcium elution amount measured according to SEMI F-57 is 30 μg / m³. ２ Less than, The multilayer pipe according to claim 1.

3. The thickness of the third layer is 80 μm or more and 500 μm or less. The multilayer pipe according to claim 1.

4. The first layer and the second layer are further provided with a core material layer mainly composed of polypropylene resin, The multilayer pipe according to claim 1.

5. The third layer contains an ethylene vinyl alcohol copolymer as its main component. The multilayer pipe according to claim 1.

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