Multi-layer pipe

Abstract

A multilayer tube is provided which suppresses the amount of calcium and organic component leaching to a low level and which can be realized as a tube that has mechanical properties at 60°C. This multilayer tube includes a first polyolefin resin layer configuring the innermost layer, and a second polyolefin resin layer arranged outside of the first polyolefin resin layer; the amount of calcium leaching, measured in accordance with SEMI F-57, of the material of the first polyolefin resin layer is less than 30 μg / m2; the ratio of the thickness of the first polyolefin resin layer to the total thickness of the first polyolefin resin layer and the second polyolefin resin layer is 0.011-0.17. By means of this configuration, it is possible to suppress the amount of leaching of calcium and organic substances to a low level, and to realize a pipe having a strength that takes into account a 60°C use environment.

Description

[Technical field]

[0001] The present invention relates to a multi-layer pipe, and more specifically, to a multi-layer pipe made of a polyolefin resin, which is useful as a piping for a semiconductor cleaning solution. [Background technology]

[0002] Conventionally, in the manufacture of semiconductor precision devices, a semiconductor cleaning solution is used in wet processes such as cleaning, which is a suitable mixture of ultrapure water purified to an extremely high degree of purity and an ultrapure cleaning solution purified to an extremely high degree of purity containing necessary components. If metal ions and / or organic substances are present in the semiconductor cleaning solution at a concentration above a certain level, the metals and / or organic substances will be adsorbed onto the wafer surface or the like, adversely affecting the quality of the precision device, and therefore, the impurities in the semiconductor cleaning solution are strictly controlled.

[0003] Impurities can also get mixed into the semiconductor cleaning solution in the piping that constitutes the transport line of the semiconductor cleaning solution. Although 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 in consideration of the influence of metal elution from the piping.

[0004] Resins used as materials for semiconductor cleaning liquid piping are fluororesins that are chemically inactive, have gas barrier properties, and are very little eluted into semiconductor cleaning liquids. 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, 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 piping for semiconductor cleaning solutions, polyvinylidene fluoride (PVDF) is used in all practical applications in the semiconductor field, including piping within semiconductor cleaning solution manufacturing equipment and piping for transporting semiconductor cleaning solutions from semiconductor cleaning solution manufacturing equipment to use points, and has become the technical standard for piping for semiconductor cleaning solutions.

[0006] Recently, with the increase in the 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 semiconductor cleaning fluids have become increasingly strict. For example, the standard for the quality of semiconductor cleaning fluids used in semiconductor manufacturing has been published as SEMI F75, and is 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] In the context of increasingly strict quality requirements for semiconductor cleaning fluids, fluororesin piping such as PVDF is the only option that meets the required water quality, and its outstanding performance is strongly supported. However, due to the special nature of its use, it is disadvantageous in terms of construction and cost compared to other general piping. In addition, there are problems such as rapid deterioration because ultra-high purity cleaning fluids often contain diaminoalkanes such as 3-diaminopropane and are used under conditions of 60°C.

[0009] Therefore, the present inventors have dared to focus on replacing the material of the pipe for the semiconductor cleaning liquid. Specifically, in view of the fact that polyolefin-based resins, which are excellent in workability and cost, are used as general piping materials, the inventors have attempted to replace the material of the pipe for the semiconductor cleaning liquid with polyolefin-based resins.

[0010] However, polyolefin resins, which are widely used as piping materials, are synthesized by polymerization using a chlorine-based catalyst, and it is necessary to mix neutralizing agents such as calcium stearate and hydrocalcite to neutralize the catalyst residue after polymerization. For this reason, polyolefin resin pipes dissolve calcium and organic substances derived from the neutralizing agent into the water they transport. Furthermore, the level of dissolution of these calcium and organic substances is far below the quality required for semiconductor cleaning fluids.

[0011] The inventors attempted to dramatically reduce the amount of calcium and organic matter elution to a level that had previously only been achieved with fluororesin piping such as PVDF by using a material for polyolefin resin pipes in which the amount of neutralizing agent added to the catalyst in the polyolefin resin is extremely small compared to the original amount intended for neutralizing the catalyst residue. However, on the other hand, the inventors also faced a new problem in that the catalyst residue in such polyolefin resins maintains its activity, accelerating oxidative deterioration, and as a result, the mechanical strength (specifically, long-term durability against internal pressure) that piping should have cannot be met, and the deterioration is particularly noticeable in the environment of semiconductor cleaning solutions at 60°C.

[0012] In other words, it was found that if the material for piping for semiconductor cleaning solutions is replaced with polyolefin-based resins, there is a unique issue in that it is not possible to simultaneously suppress the amount of calcium and organic substance elution and to provide piping with mechanical properties that take into account the operating environment of 60°C.

[0013] In view of the above, an object of the present invention is to provide a piping made of a polyolefin resin which can be used as a piping that suppresses the amount of calcium and organic substances eluted into a transported liquid to a low level and has mechanical properties (specifically, this refers to long-term durability against internal pressure; hereinafter, this may also be simply referred to as "strength") that take into account a usage environment of 60°C. [Means for solving the problem]

[0014] As a result of intensive research, the present inventors have found that by forming a polyolefin resin pipe into a multi-layer structure, disposing an inner layer of a polyolefin resin made of a polyolefin resin material that suppresses the amount of calcium and organic substance elution to a predetermined amount, and designing the thickness of the inner layer of the polyolefin resin to be within a predetermined range, it is possible to achieve a pipe that has mechanical properties that take into account the usage environment of 60°C while suppressing the amount of calcium and organic substance elution to an extremely low level. The present invention has been completed based on this finding and through further research. That is, the present invention provides the following aspects of the invention.

[0015] Item 1. A thermal insulation film comprising a first polyolefin-based resin layer constituting an innermost layer and a second polyolefin-based resin layer disposed on the outer side of the first polyolefin-based resin layer, The amount of calcium elution of the material of the first polyolefin resin layer, as measured in accordance with SEMI F-57, is 30 μg / m 2 is less than A multi-layer pipe, wherein the ratio of the thickness of the first polyolefin resin layer to the total thickness of the first polyolefin resin layer and the second polyolefin resin layer is 0.011 to 0.17. Item 2. The multi-layer pipe according to Item 1, which is used for transporting a semiconductor cleaning liquid. Item 3. The multi-layer pipe according to Item 1 or 2, wherein the first polyolefin resin layer has a thickness of 0.07 mm or more. Item 4. The multi-layer pipe according to any one of Items 1 to 3, wherein the first polyolefin resin layer has a thickness of 0.94 mm or less, or 0.07 mm or less. Item 5. The amount of calcium elution of the material of the second polyolefin resin layer, as measured in accordance with SEMI F-57, is 30 μg / m 2 5. The multi-layer pipe according to any one of items 1 to 4, wherein: Item 6. A multi-layer pipe according to any one of Items 1 to 5, wherein the proportion of components having a molecular weight of 1000 or less is 0.15% or more in an integrated molecular weight distribution curve of the polyolefin resin in the first polyolefin resin layer measured by gel permeation chromatography. Item 7. The multi-layer pipe according to any one of Items 1 to 6, further comprising a gas barrier layer on the outside of the second polyolefin resin layer. Item 8. The multi-layer tube according to any one of Items 2 to 7, wherein the semiconductor cleaning liquid is used in a wet processing step of a semiconductor element having a minimum line width of 65 nm or less. Item 9. The method includes a step of co-extruding a polyolefin-based resin composition for an innermost layer and a polyolefin-based resin composition for an outer layer to produce a multi-layer pipe, and a step of cleaning at least the inner surface of the produced multi-layer pipe, the polyolefin-based resin composition for the innermost layer is disposed on the outer side of the innermost layer, The calcium elution amount of the polyolefin resin composition for the innermost layer is 30 μg / m as measured in accordance with SEMI F-57. 2 is less than A method for producing a multi-layer pipe, wherein a ratio of a thickness of the innermost layer to a total thickness of the innermost layer and the outer layer is 0.011 to 0.17. Effect of the Invention

[0016] The multi-layer pipe made of polyolefin resin of the present invention can suppress the amount of calcium and organic substances eluted into the transported liquid to a low level, and can be used as a piping having strength sufficient to withstand an operating environment of 60°C. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a multi-layer pipe of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing another example of the multi-layer pipe of the present invention. [Diagram 3] FIG. 2 is a schematic cross-sectional view showing still another example of the multi-layer pipe of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] [1. Layer configuration] The multi-layer pipe of the present invention includes a first polyolefin resin layer constituting the innermost layer, and a second polyolefin resin layer disposed on the outer side of the first polyolefin resin layer. Examples of the multi-layer pipe of the present invention are shown in Figures 1 to 3.

[0019] The multi-layer pipe 100 shown in Fig. 1 includes a first polyolefin-based resin layer 210 and a second polyolefin-based resin layer 220. The first polyolefin-based resin layer 210 constitutes the innermost layer of the multi-layer pipe 100, and the second polyolefin-based resin layer 220 is laminated in contact with the first polyolefin-based resin layer 210. The multi-layer pipe 100a shown in Fig. 2 includes a first polyolefin-based resin layer 210a and a second polyolefin-based resin layer 220. The first polyolefin-based resin layer 210a has a multi-layer structure. Although not shown, the multi-layer pipe of the present invention may include a first polyolefin resin layer having a single layer structure and a second polyolefin resin layer having a multi-layer structure; may include a first polyolefin resin layer having a multi-layer structure and a second polyolefin resin layer having a multi-layer structure; or may include another layer between the first polyolefin resin layer 210 and the second polyolefin resin layer 220. The multi-layer pipe 100b shown in FIG. 3 includes a first polyolefin resin layer 210, a second polyolefin resin layer 220, and a gas barrier layer 300. The gas barrier layer 300 may be laminated on the outside of the second polyolefin resin layer 220. The gas barrier layer 300 may constitute the outermost layer of the multi-layer pipe 100b, or another layer may be provided further outside the gas barrier layer 300.

[0020] [2. First polyolefin resin layer] The polyolefin resin contained in the first polyolefin resin layer is not particularly limited, and may be a polymer containing a monomer unit derived from an olefin. Examples include polyethylene resins, ethylene-alkenyl carboxylate ester copolymer resins, ethylene-α-olefin copolymer resins, polypropylene resins, polybutene resins, and poly(4-methyl-1-pentene) resins. These polyolefin resins may be used alone or in combination of two or more. Among these polyolefin resins, polyethylene resins and polypropylene resins are preferred from the viewpoint of improving the strength of the multi-layered pipe. Furthermore, among the polyethylene resins and polypropylene resins, polyethylene resins are more preferred from the viewpoint of suppressing the content of low molecular weight components and suppressing the elution of organic components into the transport liquid.

[0021] 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 the transport liquid.

[0022] 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.

[0023] 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 %.

[0024] Examples of polypropylene resins include homopolypropylene, block polypropylene, and random polypropylene. The copolymerization component in block polypropylene and random polypropylene usually includes ethylene. Examples of polybutene resins include polybutene-1.

[0025] The proportion of components with a molecular weight of 1000 or less in the integral molecular weight distribution curve of the polyolefin resin contained in the first polyolefin resin layer measured by gel permeation chromatography (polystyrene equivalent) is, for example, 0.15% or more. Furthermore, from the viewpoint of obtaining good processability during pipe molding, the proportion of components with a molecular weight of 1000 or less in the integral molecular weight distribution curve is preferably 0.45% or more, more preferably 0.65% or more, and even more preferably 0.7% or more. The upper limit of the proportion of components with a molecular weight of 1000 or less in the integral molecular weight distribution curve is not particularly limited, but is, for example, 0.9% or less, preferably 0.8% or less.

[0026] The molecular weight of the polyolefin resin contained in the first polyolefin resin layer is not particularly limited, and may be, for example, 1×10 5 ~10×10 5 From the viewpoint of suppressing the elution of organic components into the transport liquid and obtaining surface smoothness, for example, the weight average molecular weight Mw is preferably 3×10 5 ~10×10 5 , more preferably 4 × 10 5 ~9×10 5 The weight average molecular weight Mw is a value measured by gel permeation chromatography in terms of polystyrene.

[0027] The molecular weight distribution (Mw / Mn) of the polyolefin resin contained in the first polyolefin resin layer is 2 or more, for example, 2 to 30, from the viewpoint of processability during pipe molding. Furthermore, from the viewpoint of also suppressing the elution of organic components into the transport liquid, the molecular weight distribution (Mw / Mn) is preferably 2 to 28. From the viewpoint of obtaining these effects more effectively, the molecular weight distribution (Mw / Mn) of the polyolefin resin contained in the first polyolefin resin layer is preferably 6 to 26, more preferably 10 to 24, and even more preferably 18 to 23. The molecular weight distribution (Mw / Mn) is a value (Mw / Mn) obtained by dividing the weight average molecular weight (Mw) and number average molecular weight (Mn) in terms of polystyrene by gel permeation chromatography measurement.

[0028] The amount of calcium elution of the material (polyolefin resin composition) of the first polyolefin resin layer, measured in accordance with EMI F-57, is 30 μg / m 2 The amount of calcium elution is less than 30 μg / m 2 If a material having a calcium solubility of 200 μg / m or more is used, the amount of calcium eluted into the semiconductor cleaning liquid during use of the multi-layer pipe becomes excessive, and the required quality of the semiconductor cleaning liquid cannot be met, particularly when the multi-layer pipe is used for transporting the semiconductor cleaning liquid. From the viewpoint of further suppressing the amount of calcium eluted into the transport liquid, the calcium elution amount of the material for the first polyolefin resin layer is preferably 29 μg / m 2 Less than or equal to 28 μg / m 2 The lower the amount of calcium elution from the material of the first polyolefin resin layer, the more preferable it is. Therefore, the most preferable lower limit is 0 μg / m 2 However, when a chlorine-based catalyst such as a Ziegler-Natta catalyst is used in the synthesis of the polyolefin resin used in the first polyolefin resin layer, and a small amount of neutralizing agent is further used, it is inevitable that a small amount of calcium is mixed in. In this case, the amount of calcium elution from the material of the first polyolefin resin layer is, for example, 1 μg / m 2 More than 5μg / m 2 More than 10μg / m 2 More than 15μg / m2 More than 20μg / m 2 or more than 25 μg / m 2 The above can be mentioned.

[0029] The calcium concentration in the material (polyolefin resin composition) of the first polyolefin resin layer is not particularly limited as long as it satisfies the above calcium elution amount, but may be, for example, 10 ppm or less. From the viewpoint of further suppressing the amount of calcium elution into the transport liquid, the calcium concentration in the material of the first polyolefin resin layer is preferably 8 ppm or less, more preferably 7 ppm or less, and even more preferably 6 ppm or less. The lower the calcium concentration in the first polyolefin resin layer, the less the amount of calcium elution into the transport liquid. From this viewpoint, the calcium concentration is most preferably 0 ppm. However, when a chlorine-based catalyst such as a Ziegler-Natta catalyst is used in the synthesis of the polyolefin resin used in the first polyolefin resin layer and a small amount of neutralizing agent is used, in the case where the inclusion of a trace amount of calcium is unavoidable, the calcium concentration in the first polyolefin resin layer may be, for example, 0.3 ppm or more, or 0.5 ppm or more.

[0030] The amount of organic components (total organic carbon; TOC) eluted from the material (polyolefin resin composition) of the first polyolefin resin layer, as measured in accordance with EMI F-57, is, for example, 800 μg / m 2 In order to further suppress the amount of organic components eluted into the transport liquid, the amount of organic components eluted from the material of the first polyolefin resin layer is preferably 600 μg / m 2 Less than or equal to 400 μg / m 2 Less than 360 μg / m 2 The lower the amount of organic components dissolved from the material of the first polyolefin resin layer, the more preferable it is. Therefore, the most preferable lower limit is 0 μg / m 2However, when a chlorine-based catalyst such as a Ziegler-Natta catalyst is used in the synthesis of the polyolefin resin used in the first polyolefin resin layer, and a small amount of a neutralizing agent is further used, it is inevitable that a trace amount of organic components will be mixed in. In this case, the amount of organic components eluted from the material of the first polyolefin resin layer is, for example, 5 μg / m 2 More than 10μμg / m 2 More than 100μg / m 2 More than 200μg / m 2 or more than 300 μg / m 2 The above can be mentioned.

[0031] In addition, when the first polyolefin resin layer 210a is multi-layered, such as in the multi-layer pipe 100a, the calcium elution amount, calcium concentration, and / or organic component elution amount of the material of the innermost layer of the multi-layered first polyolefin resin layer 210a can be designed to be lower than the materials of the other layers of the first polyolefin resin layer 210a.

[0032] In addition, by providing a degassing device for removing oxygen in the multi-layer pipe, an antioxidant is not required in the first polyolefin resin layer. By not including an antioxidant in the first polyolefin resin layer, it is possible to further suppress the elution of organic components into the transport liquid. In addition, the unnecessary antioxidant is not particularly limited as long as it is one used in ordinary polyolefin resins, and examples thereof include phenol-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, aromatic amine-based antioxidants, and lactone-based antioxidants.

[0033] The thickness t1 of the first polyolefin resin layer is, for example, 0.07 mm or more, preferably 0.2 mm or more, from the viewpoint of further suppressing the amount of calcium and / or organic components eluted into the transport liquid. In addition, depending on the thickness of the second polyolefin resin layer, for example, when the thickness t2 of the second polyolefin resin layer is 4 mm or more, the thickness t1 of the first polyolefin resin layer is more preferably 0.4 mm or more, more preferably 0.6 mm or more, even more preferably 0.8 mm or more, and particularly preferably 0.85 mm or more, from the viewpoint of further improving the strength of the multi-layer pipe against a 60°C use environment and further suppressing the amount of calcium and / or organic components eluted into the transport liquid. The upper limit of the range of the thickness t1 of the first polyolefin resin layer is, for example, 0.94 mm or less, preferably 0.92 mm or less, from the viewpoint of further improving the strength of the multi-layer pipe against a 60°C use environment and further suppressing the amount of calcium and / or organic components eluted into the transport liquid.

[0034] The ratio t1 [t1 / (t1+t2)] of the thickness of the first polyolefin resin layer to the sum of the thickness t1 of the first polyolefin resin layer and the thickness t2 of the second polyolefin resin layer is 0.11 to 0.17. If the lower limit of the ratio is below 0.11, the migration of calcium and organic components contained in the second polyolefin resin layer into the transport liquid during use cannot be sufficiently prevented, and the amount of calcium and organic components eluted into the semiconductor cleaning liquid becomes excessive, making it impossible to meet the required quality of the semiconductor cleaning liquid. Also, if the upper limit of the ratio is above 0.17, the strength of the multi-layer pipe cannot be ensured in a 60°C environment.

[0035] From the viewpoint of further suppressing the amount of calcium and organic components eluted, the lower limit of the above ratio is preferably 0.013 or more, more preferably 0.04 or more, even more preferably 0.08 or more, even more preferably 0.12 or more, particularly preferably 0.135 or more, and most preferably 0.15 or more. From the viewpoint of further improving the strength of the multi-layer pipe in a 60°C environment, the upper limit of the above ratio is preferably 0.165 or less, more preferably 0.16 or less.

[0036] Furthermore, it is more preferable that the thickness of the first polyolefin resin layer is adjusted so that the SDR (standard outer diameter / minimum wall thickness) is within a range of 7 to 17. An SDR of 7 or more is preferable because it is easy to ensure the transport amount of the transport liquid by ensuring a sufficient inner diameter of the pipe relative to the outer diameter. Also, an SDR of 17 or less is preferable because it ensures the thickness of the second polyolefin resin layer, compensates for the lack of strength of the first polyolefin resin layer itself, and provides the multi-layer pipe as a whole with a more preferable strength suitable for practical use.

[0037] [3. Second polyolefin resin layer] The polyolefin resin contained in the second polyolefin resin layer is not particularly limited, and can be appropriately selected from those listed as the polyolefin resin contained in the first polyolefin resin layer. Among the above-mentioned polyolefin resins, high density polyethylene (HDPE) is preferred from the viewpoint of suppressing the elution of low molecular weight components and / or from the viewpoint of durability when pipes are washed with chemicals. The polyolefin resin used in the second polyolefin resin layer may be the same or different from the polyolefin resin used in the first polyolefin resin layer, but when both layers are laminated in contact with each other, it is more preferable that the polyolefin resin is the same from the viewpoint of improving the adhesion between the two layers and expressing a preferable strength.

[0038] The molecular weight of the polyolefin resin contained in the second polyolefin resin layer is not particularly limited. From the viewpoint of strength, the molecular weight of the polyolefin resin used in the first polyolefin resin layer is preferably larger than that of the polyolefin resin used in the second polyolefin resin layer. For example, the weight average molecular weight Mw is preferably 5×10 5 ~12×10 5 , preferably 5.5 x 10 5 ~10×10 5 , more preferably 7 × 10 5 ~9.5×10 5 , and more preferably 8 × 10 5 ~9×10 5From the viewpoint of strength, the weight average molecular weight of the polyolefin resin used in the second polyolefin resin layer is 1.5 to 4 times, and preferably 2 to 4 times, the weight average molecular weight of the polyolefin resin used in the first polyolefin resin layer.

[0039] The molecular weight distribution (Mw / Mn) of the polyolefin resin contained in the second polyolefin resin layer is not particularly limited, and may be 20 to 180. The molecular weight distribution (Mw / Mn) of the polyolefin resin contained in the second polyolefin resin layer is 20 or more, particularly when the weight average molecular weight of the polyolefin resin contained in the second polyolefin resin layer is 1.5 to 4 times, preferably 1.8 to 3 times, more preferably 2 to 2.5 times, of the weight average molecular weight of the polyolefin resin contained in the first polyolefin resin. In other words, the molecular weight distribution (Mw / Mn) of the polyolefin resin contained in the second polyolefin resin layer is 20 or more, which is preferable from the viewpoint of obtaining good strength by sufficiently securing low molecular weight components at the layer interface with the first polyolefin resin layer (i.e., by sufficiently securing the overlapping portion of the molecular weight distribution between both layers), thereby improving adhesion, and the molecular weight distribution of 180 or less is preferable from the viewpoint of obtaining the strength of the second polyolefin resin layer itself. To obtain these effects more effectively, the molecular weight distribution (Mw / Mn) of the polyolefin resin used in the second polyolefin resin layer is preferably 22 to 170, more preferably 45 to 160, even more preferably 60 to 155, still more preferably 80 to 150, even more preferably 100 to 145, and particularly preferably 120 to 140.

[0040] The amount of calcium elution from the material of the second polyolefin resin layer (polyolefin resin composition) measured in accordance with EMI F-57 is set to 30 μg / m2 from the viewpoint of ensuring the strength of the multi-layer pipe in a 60°C environment. 2 or more, preferably 50 μg / m 2 More preferably, 70 μg / m 2 More preferably, 80 μg / m 2More preferably, 90 μg / m 2 More preferably, 95 μg / m 2 The above are some of the examples. The multi-layer pipe of the present invention has an excellent effect of suppressing the elution of calcium and organic components, and therefore can effectively suppress the elution of calcium even if the material of the second polyolefin resin layer contains a large amount of calcium. From this viewpoint, a suitable example of the amount of calcium elution is 80 μg / m2 within the above range. 2 More than 90μg / m 2 or more than 95 μg / m 2 The upper limit of the amount of calcium elution is not particularly limited, but from the viewpoint of suppressing calcium elution, it is preferably 120 μg / m 2 Below, 110μg / m 2 or less than 100μg / m 2 The following are included:

[0041] The calcium concentration in the material (polyolefin resin composition) of the second polyolefin resin layer is not particularly limited as long as it satisfies the above calcium elution amount, but from the viewpoint of ensuring the strength of the multi-layer pipe against a use environment of 60 ° C., for example, 20 ppm or more, preferably 100 ppm or more, more preferably 500 ppm or more, even more preferably 800 ppm or more, even more preferably 1000 ppm or more, even more preferably 1200 ppm or more, and particularly preferably 1400 ppm or more. The upper limit of the calcium concentration range is, for example, 2000 ppm or less, preferably 1800 ppm or less, more preferably 1600 ppm or less, from the viewpoint of suppressing the lack of strength caused by the contained calcium itself becoming the starting point of destruction, and from the viewpoint of suppressing the elution of calcium and organic components.

[0042] The amount of organic components (TOC) eluted from the material (polyolefin resin composition) of the second polyolefin resin layer, as measured in accordance with EMI F-57, is, for example, 30,000 μg / m 2The multi-layer pipe of the present invention has an excellent effect of suppressing the elution of calcium and organic components, and therefore can effectively suppress the elution of organic components even if the material of the second polyolefin resin layer contains a large amount of organic components. From this perspective, a suitable example of the amount of eluted organic components is 31,000 μg / m 2 or more, preferably 31500 μg / m 2 The upper limit of the amount of eluted organic components is not particularly limited, but from the viewpoint of suppressing elution of organic components, it is preferably, for example, 35,000 μg / m 2 Less than or equal to 34000 μg / m 2 Less than or equal to 33,000 μg / m 2 More preferably, 32000 μg / m 2 The following are included:

[0043] The second polyolefin resin 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. The content of the antioxidant in the second polyolefin resin layer is, for example, 0.01% by weight or more, preferably 0.1% by weight or more, from the viewpoint of suppressing the influence of oxygen and ensuring a preferable strength, and the upper limit of the content of the antioxidant is, for example, 5% by weight or less, preferably 1% by weight or less, more preferably 0.5% by weight or less.

[0044] [4. Gas barrier layer] When the multi-layer pipe of the present invention has a gas barrier layer, the gas barrier layer is provided on the outside of the second polyolefin resin layer. The gas barrier layer can improve the strength of the multi-layer pipe by preventing oxygen from the outer surface of the multi-layer pipe from penetrating into the second polyolefin resin layer and further into the first polyolefin resin layer. In addition, providing a gas barrier layer is also preferable in that it can effectively suppress gas dissolution in the transport liquid.

[0045] Examples of materials for the gas barrier layer 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).

[0046] The thickness of the gas barrier layer is not particularly limited as long as it is a thickness that can ensure gas barrier properties to the extent that at least the strength reduction due to oxidative degradation of the polyolefin resin is suppressed, and examples of the thickness include 50 to 300 μm, preferably 100 to 250 μm, and more preferably 150 to 250 μm.

[0047] [5. Uses of multi-layer pipes] The multi-layer pipe of the present invention is particularly useful for transporting semiconductor cleaning liquids, since it suppresses the amount of calcium and organic substances eluted into the transport liquid to a low level and has a strength that takes into account the usage environment of 60°C. As the semiconductor cleaning liquid, ultrapure water that has been refined to an extremely high purity and from which unnecessary substances have been strictly removed, and / or ultra-high purity cleaning liquid from which unnecessary substances other than necessary components have been strictly removed, is used. In other words, in the present invention, the semiconductor cleaning liquid is intended to include ultrapure water and high purity cleaning liquid.

[0048] Since the multi-layer pipe of the present invention has excellent strength against an operating environment of 60° C., when used to transport an ultra-high purity cleaning solution, even when used to transport an ultra-high purity cleaning solution obtained by diluting a cleaning stock solution containing at least an amino compound (for example, a cleaning stock solution containing an amino compound such as diaminoalkane, a chelating agent, a surfactant, and a pH adjuster, etc.) with ultra-pure water, the multi-layer pipe of the present invention has excellent strength against an operating environment of 60° C. Note that, although a high purity cleaning solution is itself composed of various organic components as exemplified above as necessary compositions, by transporting the high purity cleaning solution using the multi-layer pipe of the present invention, which has excellent TOC elution suppression ability, contamination by unnecessary organic components derived from the piping material other than the necessary components can be suppressed.

[0049] The multi-layer pipe of the present invention can be used as piping in a semiconductor cleaning liquid manufacturing apparatus, piping for transporting a semiconductor cleaning liquid from the semiconductor cleaning liquid manufacturing apparatus to a use point, piping for returning the semiconductor cleaning liquid from the use point, etc. The semiconductor cleaning piping of the present invention may also be used as piping for transporting the semiconductor cleaning liquid after semiconductor cleaning for purification and reuse.

[0050] The multi-layer pipe of the present invention can be used in the wet cleaning process in the manufacturing process of semiconductor devices. The semiconductor device is preferably one having a higher integration degree, specifically, a semiconductor device having a minimum line width of 65 nm or less. For example, SEMI F75 is an example of a standard regarding the quality of semiconductor cleaning liquid used in semiconductor manufacturing, and the multi-layer pipe of the present invention can maintain the quality of the semiconductor cleaning liquid being transported at a level that meets the above standard even when used to transport the semiconductor cleaning liquid.

[0051] In addition, the multi-layer pipe of the present invention is easy to join pipes to each other and has excellent workability. Furthermore, since both the line used for transporting ultrapure water and the line used for transporting ultrapure cleaning solution can be made of polyolefin resin, the lines can be easily joined to each other and has excellent workability. In joining the multi-layer pipe of the present invention, for example, fusion joining such as butt fusion joining and EF (electrical fusion) joining can be easily performed at a relatively low temperature.

[0052] [6. Manufacturing of multi-layer pipes] The multi-layer pipe of the present invention can be produced by preparing a material for the first polyolefin resin layer, a material for the second polyolefin resin layer, and, if necessary, a material for the gas barrier layer, and co-extrusion molding the materials so that each layer has a predetermined thickness. Since the multi-layer pipe of the present invention is made of polyolefin resin, it can be produced inexpensively.

[0053] That is, the present invention includes a step of producing a multi-layer pipe by co-extruding a polyolefin-based resin composition for an innermost layer and a polyolefin-based resin composition for an outer layer, and a step of cleaning at least the inner surface of the produced multi-layer pipe, the polyolefin-based resin composition for the innermost layer is disposed on the outer side of the innermost layer, The calcium elution amount of the polyolefin resin composition for the innermost layer is 30 μg / m as measured in accordance with SEMI F-57. 2 is less than The present invention also provides a method for producing a multi-layer pipe, wherein the ratio of the thickness of the innermost layer to the total thickness of the innermost layer (first polyolefin resin layer) and the outer layer (second polyolefin resin layer) is 0.011 to 0.17.

[0054] The polyolefin resin composition for the innermost layer is as described above in "2. First polyolefin resin layer" as "Material for the first polyolefin resin layer (polyolefin resin composition)". The polyolefin resin composition for the outer layer is as described above in "3. Second polyolefin resin layer" as "Material for the second polyolefin resin layer (polyolefin resin composition)".

[0055] Furthermore, the polyolefin resins contained in the materials of the first polyolefin resin layer and the second polyolefin resin layer can both be synthesized by polymerization using a chlorine-based catalyst such as the commonly used Ziegler-Natta catalyst (a catalyst made of triethylaluminum and titanium tetrachloride).

[0056] The amount of calcium and organic components eluted from each polyolefin resin layer can be directly controlled by adjusting the amount of neutralizing agent added after polymerization. In addition, since the amount of neutralizing agent is affected by the amount of chlorine-based catalyst, the amount of calcium and organic components eluted can also be indirectly controlled by adjusting the amount of chlorine-based catalyst. In addition, the molecular weight distribution (Mw / Mn) in each polyolefin resin layer 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, by increasing the amount of chlorine-based catalyst, the molecular weight distribution (Mw / Mn) tends to become larger. In addition, by performing multi-stage polymerization of two or more stages, the molecular weight distribution (Mw / Mn) can be increased.

[0057] More specifically, the polyolefin resin used as the material for the first polyolefin resin layer can be prepared by, for example, polymerizing (e.g., one-stage polymerization) using a chlorine-based catalyst in an amount appropriately determined by a person skilled in the art, and then adding a predetermined amount of a neutralizing agent (e.g., calcium stearate, hydrocalcite, etc.) to a calcium concentration of 10 ppm or less. Alternatively, a neutralizing agent may not be added. The polyolefin resin used for the first polyolefin resin layer may also be polymerized using a polymerization catalyst other than the above chlorine-based catalyst, such as a chromium-based catalyst or a metallocene catalyst. In this case, it is not necessary to add a neutralizing agent.

[0058] In addition, the polyolefin resin used as the material for the second polyolefin resin layer can be prepared by polymerizing (multi-stage polymerization, preferably two-stage polymerization) using a chlorine-based catalyst in an amount appropriately determined by a person skilled in the art, and then adding a predetermined amount (e.g., 20 to 2000 ppm in terms of calcium concentration) of a neutralizing agent (e.g., calcium stearate, hydrocalcite, etc.), and preferably an antioxidant as well. EXAMPLES

[0059] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0060] (1) Fabrication of multi-layered pipes The polyolefin (HDPE1) for the first polyolefin resin layer (first PO layer) was a completely additive-free high density polyethylene that did not contain any antioxidants. The calcium concentration in the polyolefin for the first PO layer was 5.5 ppm, the molecular weight distribution (ratio [Mw / Mn] determined from the weight average molecular weight [Mw] and number average molecular weight [Mn] in terms of polystyrene by gel permeation chromatography measurement; the same applies below) was 22.2, and Mw was 4.1×10 5 In the integrated molecular weight distribution curve using standard polystyrene measured by gel permeation chromatography, the proportion of components with a molecular weight of 1000 or less was 0.75%. Furthermore, the amounts of calcium elution and organic components eluted from the material of the first polyolefin resin layer (first PO layer) are as shown in Reference Example 1.

[0061] The polyolefin (HDPE2) for the second polyolefin resin layer (second PO layer) was a PE100 grade high density polyethylene containing an antioxidant. The calcium concentration of the polyolefin for the second PO layer was 1500 ppm, the molecular weight distribution (Mw / Mn) was 132.5, and Mw was 8.4×10 5 Furthermore, the amounts of calcium elution and organic components eluted from the material of the second polyolefin resin layer (second PO layer) were as shown in Reference Example 2.

[0062] Each resin composition was extrusion molded to the thickness shown in Tables 1 and 2, and the entire surface of the molded pipe, including the inner surface, was washed with water. Comparative Examples 1 and 2 were extrusion molded into single-layer pipes, while Examples 1 to 5 were co-extrusion molded into multi-layer pipes.

[0063] (2) Performance evaluation (2-1) Measurement of calcium elution amount and organic matter (TOC) elution amount The obtained multi-layer pipe was cut to a length of 200 mm, ultrapure water was sealed inside, both ends were plugged with polytetrafluoroethylene (PTFE), and the test sample was obtained by fixing it with a wire from the outside. The ultrapure water used was one in which the calcium concentration and TOC amount were below the detection limit of the measuring device (ISP-MS device and TOC meter described below). The test sample was left to stand for 7 days under the condition of 85°C ± 5°C to allow dissolution. After dissolution, the amount of calcium and TOC in the water of the test sample were measured using an ISP-MS device (Agilent Technologies, model number Agilent7500cs) and a TOC meter (Thermo Fisher Scientific, model number ICS2000), respectively. The standard value that must be met for the amount of calcium dissolution is 30 μg / m 2 based on the SEMI F57 standard. 2 The TOC elution standard is 30,000 μg / m 2 The results are shown in Tables 1 and 2.

[0064] (3-2) Strength (internal pressure creep performance) measurement A multi-layer pipe with an outer diameter of 60 mm was prepared, cut to a length of 300 mm, and both ends were sealed with metal fixtures to obtain a test sample. In accordance with the internal pressure creep test method described in JIS K6761, the sample was subjected to conditions of 60°C and 1 MPa for 165 hours, and it was examined whether or not it broke. If it broke, it was evaluated as ×, and if it did not break, it was evaluated as ○. The results are shown in Tables 1 and 2.

[0065] [Table 1]

[0066] [Table 2]

[0067] As shown in the table above, the calcium elution amount is 30 μg / m 2 In the case of piping made of materials less than 1000 g / m2 (Reference Example 1), the amount of calcium elution and TOC elution in ultrapure water was small, but the strength was not sufficient in a 60°C environment, and the amount of calcium elution was 30 μg / m2. 2The pipe made of the above materials (Reference Example 2) had sufficient strength in a 60°C environment, but had excessive calcium elution into ultrapure water and could not meet the quality requirements for semiconductor cleaning fluids. The TOC elution amount also did not meet the standards of this test. Calcium elution amount: 30 μg / m 2 The inner layer is made of materials with a calcium elution rate of 30 μg / m 2 In the case of a multi-layer pipe composed of an inner layer and an outer layer composed of the above materials, when the thickness ratio of the inner layer was more than 0.17 (Comparative Example 1), a significant decrease in the amount of calcium elution was observed, but in the internal pressure creep measurement, destruction occurred in 133 hours, and strength was not obtained in an environment of 60° C. Furthermore, when the thickness ratio of the inner layer was less than 0.011 (Comparative Example 2), although strength was obtained in an environment of 60° C., calcium was excessively eluted into ultrapure water, and the required quality of a semiconductor cleaning solution could not be met, and the amount of TOC elution did not meet the standard of this test.

[0068] In contrast, when the thickness ratio of the inner layer was 0.011 to 0.17 (Examples 1 to 5), not only was the amount of calcium elution suppressed to a level that satisfied the required quality of the semiconductor cleaning liquid, but strength in a 60° C. environment was also obtained.

[0069] Although the same resin composition was used in Examples 1 to 5, Comparative Examples 1 and 2, and Reference Example 1, the reason why the amount of calcium elution was reduced in the Examples is unclear, but the following mechanism is assumed.

[0070] Additives such as calcium compounds contained in the inner layer material have the property of precipitating when exposed to high temperatures, and the inner layer material in a molten state in the extruder has a higher calcium compound content than other parts due to the precipitation of additives, especially in the part in contact with the inner wall of the extruder, which is at a high temperature. When the inner layer material in such a state in which calcium compounds are unevenly distributed is extruded into a hot die, the part in contact with the inner wall of the extruder with a large amount of calcium compounds is exposed on the inner surface of the multi-layer pipe. In this case, as in Examples 1 to 5 and Comparative Example 1, if the thickness of the extruded inner layer is thin, the thickness of the part with a large amount of calcium compounds is also thin, and the calcium compounds are densely concentrated in a narrower area, so the amount of calcium compounds exposed on the inner surface of the multi-layer pipe is large. When the inner surface of the multi-layer pipe obtained in this way is washed, the exposed calcium compounds are washed away, so that almost no calcium compounds are present on the inner surface and the part close to it after washing (the part very shallow from the inner surface). It is considered that this is the reason for the decrease in the amount of calcium elution in Examples 1 to 5 and Comparative Example 1.

[0071] On the other hand, when the thickness of the extruded inner layer is thick as in Reference Example 1, the thickness of the part containing a large amount of calcium compounds is also thick, and the calcium compounds are present in a sparser form in this part than in Examples 1 to 5 and Comparative Example 1, so the amount of calcium compounds exposed on the inner surface of the multi-layered pipe is less than in Examples 1 to 5. When the inner surface of the multi-layered pipe obtained in this way is washed, the exposed calcium compounds are washed away, but the amount of calcium compounds washed away is less than in Examples 1 to 5, and calcium compounds still remain even in the part close to the inner surface after washing (the part very shallow from the inner surface). It is believed that the amount of calcium elution was large in Reference Example 1 due to the elution of such remaining calcium compounds.

[0072] Furthermore, when the thickness of the extruded inner layer is too thin as in Comparative Example 2, it is not possible to ensure a thickness that allows the uneven distribution of calcium compounds in parts with a large amount of calcium compounds and parts without calcium compounds as in Examples 1 to 5 and Comparative Example 1, so it is considered that the obtained multi-layer pipe does not have any parts with almost no calcium compounds even if the inner surface is washed. Alternatively, even if it is assumed that the uneven distribution of calcium compounds in parts with a large amount of calcium compounds and parts without calcium compounds as in Examples 1 to 5 and Comparative Example 1 is possible in Comparative Example 2, it is also considered that the thickness of the part with almost no calcium compounds obtained by washing the inner surface of the obtained multi-layer pipe is too thin, and the calcium compounds present in the part close to the inner surface (the part very shallow from the inner surface) gradually eluted, resulting in a large amount of calcium elution. As another consideration, it is also considered that only when the thickness of the inner layer is too thin as in Comparative Example 2, the calcium present in the outer layer penetrates through the layer and elutes from the inner surface.

[0073] In addition to the reduction in calcium elution and the improvement in strength, a reduction in the amount of TOC elution was also observed in Examples 1 to 5. In view of the levels of calcium and TOC elution, it was found that the multi-layer pipes of Examples 1 to 5 are suitable for transporting semiconductor cleaning solutions suitable for wet processing of semiconductor elements with a minimum line width of 65 nm or less. [Explanation of symbols]

[0074] 100, 100a, 100b Multi-layer pipe 210, 210a First polyolefin resin layer 220 Second polyolefin resin layer 300 Gas barrier layer t1 Thickness of the first polyolefin resin layer t2 Thickness of the second polyolefin resin layer

Claims

1. The present invention includes a first polyolefin resin layer constituting an innermost layer, and a second polyolefin resin layer disposed on an outer side of the first polyolefin resin layer, The amount of calcium elution of the material of the first polyolefin resin layer measured in accordance with SEMI F-57 is 30 μg / m 2 is less than A multi-layer pipe, wherein a ratio of a thickness of the first polyolefin resin layer to a total thickness of the first polyolefin resin layer and the second polyolefin resin layer is 0.011 to 0.

17.

2. The multi-layer pipe according to claim 1 , which is used for transporting a semiconductor cleaning liquid.

3. The multi-layer pipe according to claim 1 or 2, wherein the first polyolefin resin layer has a thickness of 0.07 mm or more.

4. The multi-layer pipe according to any one of claims 1 to 3, wherein the first polyolefin resin layer has a thickness of 0.94 mm or less.

5. The amount of calcium elution of the material of the second polyolefin resin layer measured in accordance with SEMI F-57 is 30 μg / m 2 The multi-layer pipe according to any one of claims 1 to 4.

6. The multi-layer pipe according to any one of claims 1 to 5, wherein in an integrated molecular weight distribution curve of the polyolefin resin in the first polyolefin resin layer measured by gel permeation chromatography, the proportion of components having a molecular weight of 1000 or less is 0.15% or more.

7. The multi-layer pipe according to any one of claims 1 to 6, further comprising a gas barrier layer on the outside of the second polyolefin resin layer.

8. 3. The multi-layer tube according to claim 2, wherein the semiconductor cleaning solution is used in a wet processing step for semiconductor elements having a minimum line width of 65 nm or less.

9. The method includes a step of producing a multi-layer pipe by co-extruding a polyolefin-based resin composition for an innermost layer and a polyolefin-based resin composition for an outer layer, and a step of cleaning at least an inner surface of the produced multi-layer pipe, the polyolefin-based resin composition for the innermost layer is disposed on the outer side of the innermost layer, The calcium elution amount of the polyolefin resin composition for the innermost layer, measured in accordance with SEMI F-57, is 30 μg / m 2 is less than A method for producing a multi-layer pipe, wherein a ratio of a thickness of the innermost layer to a total thickness of the innermost layer and the outer layer is 0.011 to 0.17.

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