JP2022159129A - Pipe material for ultrapure water - Google Patents

Abstract

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

Description

TECHNICAL FIELD The present invention relates to piping for ultrapure water. More specifically, the present invention relates to polyolefin resin pipes used as ultrapure water pipes.

2. Description of the Related Art Conventionally, in the manufacture of precision devices such as semiconductor devices and liquid crystal display devices, ultrapure water purified to extremely high purity in wet processes such as washing has been used.

Pipes constituting ultrapure water transport lines are required to have extremely low metal elution and high inner surface smoothness for the purpose of preventing bacteriostatic propagation.

Fluoropolymers, which are chemically inert, have gas barrier properties, are extremely low in elution into ultrapure water, and have high inner surface smoothness, are used as materials for ultrapure water pipes. ing. For example, Patent Document 1 discloses a fluororesin double tube in which two layers of fluororesin are laminated as piping used in semiconductor manufacturing equipment, liquid crystal manufacturing equipment, etc., and the inner layer tube has corrosion resistance and chemical resistance. Excellent fluororesin (e.g., tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), or tetrafluoroethylene-ethylene copolymer (ETFE) ) and the outer layer tube is made of a fluororesin (for example, polyvinylidene fluoride (PVDF)) capable of suppressing gas permeation. Further, Patent Document 2 discloses a multi-layer pipe for piping of ultrapure water, which comprises a first resin layer made of fluororesin and in contact with ultrapure water, and a gas-impermeable resin. and a second resin layer provided on the outer peripheral surface of the resin layer of, furthermore, the outer peripheral surface of the second resin layer protects the second resin layer It is disclosed that a third resin layer is provided and polyethylene is used as the third resin layer.

Polyvinylidene fluoride (PVDF) is one of the materials used for ultrapure water pipes in the semiconductor field. It is used in all transportation pipes that are put into practical use, and has become the technical standard for ultrapure water pipes.

In recent years, as the degree of integration of semiconductor chips has improved, circuit patterns have become more and more fine, and the characteristics required for pipes for ultrapure water are becoming stricter. For example, SEMI F75 has been published as a standard regarding the quality of ultrapure water pipes used in the manufacture of semiconductors, and is updated every two years.

On the other hand, as general tap water piping, in addition to existing cast iron pipes or vinyl chloride pipes, polyethylene pipes with excellent properties such as earthquake resistance, flexibility, corrosion resistance, and lightness are likely to be used. It has become. In particular, for high-density polyethylene, improvements are being made to improve performance while taking advantage of its inherent rigidity. Those having excellent smoothness have also been developed. At present, the high-density polyethylene pipe with the best surface smoothness has a surface roughness Ra of 0.4 μm. It is achieved by improving the non-uniformity of the gel or kneading (Non-Patent Document 1).

JP-A-2004-299808 JP 2010-234576 A

TOSOH Research & Technology Review Vol.44 (2000), p.63-67

Fluororesin piping such as PVDF also has disadvantages in terms of workability and cost compared to other general piping. However, against the background of stricter quality requirements for ultrapure water pipes, fluororesin pipes have become the only option for pipes that meet the required water quality, and outstanding performance that more than compensates for workability and cost. is strongly supported.

Against this background, the present inventor dared to focus on replacing the material of ultrapure water piping with high-density polyolefin resin. However, high-density polyolefin resin lacks surface smoothness for use as a material for ultrapure water tubing. Currently, the limit value of surface smoothness of high-density polyethylene resin pipes is about 0.4 μm, which is far from the level of 0.25 μm or less (outer diameter OD is less than 250 mm) specified by SEMI F57-0314. .

In view of the above points, the object of the present invention is to provide a pipe material for ultrapure water made of high-density polyolefin resin and having excellent surface smoothness with a surface roughness of 0.25 μm or less. do.

As a result of intensive studies, the present inventors have found that by blending a specific lubricant with a high-density polyethylene resin, a pipe material having excellent surface smoothness with a surface roughness of 0.25 μm or less can be obtained. It was also found that the surface smoothness can be further controlled when the high-density polyethylene resin composition is extruded under specific back pressure conditions. The present invention was completed by further studies based on these findings. That is, the present invention provides inventions in the following aspects.

Section 1. An ultrapure water pipe material having an HDPE layer containing high-density polyethylene and a fluorine-based lubricant,
The inner peripheral surface of the HDPE layer constitutes the inner peripheral surface of the pipe material,
The surface roughness of the inner peripheral surface is 0.25 μm or less,
Ultrapure water tubing used to transport ultrapure water.
Section 2. Item 2. The ultrapure water pipe material according to Item 1, wherein the HDPE layer is formed by extruding an HDPE composition containing the high-density polyethylene and the fluorine-based lubricant under a back pressure of 3 to 30 Mpa.
Item 3. Item 3. The pipe material for ultrapure water according to Item 1 or 2, wherein the high-density polyethylene has a molecular weight distribution of 40-80.
Section 4. Item 4. The pipe material for ultrapure water according to any one of Items 1 to 3, wherein the content of the fluorine-based lubricant in the HDPE layer is 0.01 to 5% by weight.
Item 5. Item 5. The pipe material for ultrapure water according to any one of Items 1 to 4, which has a multilayer structure in which another layer is laminated on the outer surface of the HDPE layer.
Item 6. Item 6. The tube material for ultrapure water according to Item 5, wherein the HDPE layer has a layer thickness of 0.3 mm or more.
Item 7. The total amount of elution of aluminum, barium, boron, calcium, chromium, copper, iron, lead, lithium, magnesium, manganese, nickel, potassium, sodium, strontium, and zinc measured based on SEMI F57-0314 is Item 7. The tube material for ultrapure water according to any one of Items 1 to 6, which is 14 μg/m ² or less.
Item 8. The elution amount of calcium is 7 μg/m ² or less, the elution amount of copper is 0.5 μg/m ² or less, and the elution amount of sodium is 1.5 μg/m ² or less, as measured based on SEMI F57-0314. Item 8. The pipe material for ultrapure water according to any one of items 1 to 7, wherein the amount of zinc is 0.5 μg/m ² or less and/or the zinc elution amount is 0.5 μg/m ² or less.
Item 9. Item 9. The tube material for ultrapure water according to any one of Items 1 to 8, wherein the elution amount of fluoride ions measured based on SEMI F57-0314 is 600 μg/m ² or less.
Item 10. Item 10. The tube material for ultrapure water according to any one of Items 1 to 9, wherein the elution amount of all organic components measured based on SEMI F57-0314 is 10000 μg/m ² or less.
Item 11. Item 11. The tube material for ultrapure water according to any one of Items 1 to 10, wherein the ultrapure water is used in a wet treatment process for semiconductor devices or liquid crystals.
Item 12. Item 12. The tube material for ultrapure water according to any one of items 1 to 11, wherein the ultrapure water is used in a wet treatment process for a semiconductor device having a minimum line width of 65 nm or less.
Item 13. It has an HDPE layer containing high-density polyethylene and a fluorine-based lubricant, the inner peripheral surface of the HDPE layer constitutes the inner peripheral surface of the pipe member, and the inner peripheral surface has a surface roughness of 0.25 μm or less. A method for manufacturing a pure water pipe, comprising:
A manufacturing method comprising a step of extruding the HDPE layer from a resin composition containing the high-density polyethylene and the fluorine-based lubricant under a back pressure of 3 to 30 Mpa.

According to the present invention, it is possible to provide a pipe material for ultrapure water made of high-density polyethylene resin and having excellent surface smoothness with a surface roughness of 0.25 μm or less.

1 is a schematic cross-sectional view showing an example of a pipe material for ultrapure water of the present invention; FIG. FIG. 4 is a schematic cross-sectional view showing another example of the pipe material for ultrapure water of the present invention. FIG. 4 is a schematic cross-sectional view showing still another example of the pipe material for ultrapure water of the present invention. FIG. 2 schematically shows a part of a production line for producing the ultrapure water pipe material shown in FIG. 1. FIG. FIG. 3 schematically shows part of a production line for producing the ultrapure water tube shown in FIG. 2 . FIG. 4 schematically shows part of a production line for producing the ultrapure water tube material shown in FIG. 3 .

[1. Tube material for ultrapure water]
The pipe material for ultrapure water of the present invention is a pipe material for ultrapure water having an HDPE layer containing high-density polyethylene and a fluorine-based lubricant, wherein the inner peripheral surface of the HDPE layer constitutes the inner peripheral surface of the pipe material. and the inner peripheral surface has a surface roughness of 0.25 μm or less, and is used for transporting ultrapure water. The details of the pipe material for ultrapure water of the present invention will be described below. In this specification, the numerical range indicated by "-" includes the values at both ends. For example, a notation of 0.5 to 3.0 mm means 0.5 mm or more and 3.0 mm or less.

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

The ultrapure water tubing 100 shown in FIG. 1 consists of a single HDPE layer 210 containing high-density polyethylene and a fluorine-based lubricant. The ultrapure water pipe members 100a and 100b shown in FIGS. 2 and 3 are examples having a multi-layer structure in which another layer is laminated on the outer surface of the HDPE layer 210. FIG. In either case, the inner peripheral surface s of the HDPE layer 210 constitutes the inner peripheral surfaces of the ultrapure water pipe members 100, 100a, and 100b.

The ultrapure water tube 100a shown in FIG. 2 specifically includes an HDPE layer 210 containing high-density polyethylene and a fluorine-based lubricant, and a core layer 220 laminated on the outer peripheral surface side of the HDPE layer 210. . Specifically, the ultrapure water tube 100b shown in FIG. and a gas barrier layer 230 laminated on the outer peripheral surface side of the material layer 220 .

In addition, in the ultrapure water pipe material 100 shown in FIG. 1, one or more layers (for example, a gas barrier layer, etc.) other than the core material layer 220 may be further laminated on the outer peripheral side of the HDPE layer 210. 2 and 3, between the HDPE layer 210 and the core layer 220, between the core layer 220 and the gas barrier layer 230, and/or on the outer peripheral surface of the gas barrier layer 230 may be further laminated with one or more layers (eg, an adhesive layer, etc.).

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

Although the total thickness of the pipe for ultrapure water of the present invention is not particularly limited, it is, for example, 2 to 5 mm, preferably 2.5 to 4 mm, and more preferably 3 to 3.5 mm.

[1-2. HDPE layer]
The HDPE layer is an extruded layer of a resin composition containing high density polyethylene and a fluorolubricant.

[1-2-1. High density polyethylene]
High density polyethylene (HDPE) refers to polyethylene having a density (JIS 6760) of 0.940 g/cm ³ or more. Although the upper limit of the density of HDPE used in the HDPE layer is not particularly limited, it is, for example, 0.970 g/cm ³ or less, preferably 0.965 g/cm ³ or less, more preferably 0.960 g/cm ³ or less, and still more preferably 0.960 g/cm 3 or less. 0.955 g/cm ³ or less, more preferably 0.950 g/cm ³ or less, particularly preferably 0.945 g/cm ³ or less.

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

The molecular weight of the HDPE resin used for the HDPE layer is not particularly limited, and examples thereof include a weight average molecular weight Mw of 1×10 ⁵ to 10×10 ⁵ . From the viewpoint of suppressing elution of organic components into pure water and/or from the viewpoint of further improving surface smoothness, the weight average molecular weight Mw is preferably 3×10 ⁵ to 10×10 ⁵ , more preferably 4. ×10 ⁵ to 9×10 ⁵ , more preferably 6×10 ⁵ to 8.5×10 ⁵ , still more preferably 7×10 ⁵ to 8×10 ⁵ , particularly preferably 7.5×10 ⁵ to 8×10 ⁵ is mentioned. In the present invention, the weight average molecular weight Mw is a value measured in terms of polystyrene by gel permeation chromatography.

The molecular weight distribution (Mw/Mn) of HDPE used in the HDPE layer is, for example, 20 to 80, preferably 40 to 80, more preferably 50 to 78, still more preferably 60 to 76, still more preferably 65 to 74, especially 69 to 72 are preferred. In the present invention, the molecular weight distribution (Mw/Mn) is the value obtained by dividing the weight average molecular weight (Mw) and number average molecular weight (Mn) in terms of polystyrene by gel permeation chromatography, and dividing Mw by Mn. (Mw/Mn). The molecular weight distribution (Mw/Mn) can be controlled by adjusting the amount of the chlorine-based catalyst and/or the polymerization process (single-stage polymerization or multistage polymerization of two or more stages). For example, increasing the amount of chlorine-based catalyst tends to increase the molecular weight distribution (Mw/Mn), and decreasing the amount of the chlorine-based catalyst tends to decrease the molecular weight distribution (Mw/Mn). Further, the molecular weight distribution (Mw/Mn) can be increased by performing multi-stage polymerization of two or more stages, and the molecular weight distribution (Mw/Mn) can be decreased by performing one-stage polymerization.

Also, the calcium concentration in the HDPE layer may be, for example, less than 15 ppb. From the viewpoint of further suppressing the amount of calcium eluted into pure water, the calcium concentration in HDPE is preferably less than 12 ppb, more preferably less than 10 ppb. The calcium concentration is most preferably 0 ppm from this point of view, because the lower the calcium concentration, the smaller the amount of calcium eluted into the pure water. On the other hand, since the pipe material for ultrapure water of the present invention has excellent smoothness of the inner peripheral surface, the Ziegler-Natta catalyst (titanium tetrachloride or titanium trichloride, organoaluminum compound [For example, a catalyst for olefin polymerization prepared by mixing with triethylaluminum or methylaluminoxane, etc.] When using a chlorine-based catalyst such as a catalyst that requires the use of a small amount of neutralizing agent, a trace amount of calcium Even if contamination is unavoidable, elution of calcium into pure water can be effectively suppressed. The calcium concentration in the HDPE layer is directly controlled by adjusting the amount of neutralizing agent added after HDPE polymerization. Also, since the amount of the neutralizing agent is affected by the amount of the chlorine-based catalyst, the calcium concentration can be indirectly controlled by adjusting the amount of the chlorine-based catalyst.

The melt flow rate (MFR) of HDPE used in the HDPE layer is not particularly limited, and examples thereof include 5 to 20 g/10 minutes. From the viewpoint of further improving the impurity elution suppression effect, the MFR of HDPE used in the HDPE layer is preferably 9 to 15 g/10 min, more preferably 11 to 13 g/10 min. In the present invention, МFR is a value measured under the conditions of a temperature of 190°C and a load of 21.6 kg specified in JIS K-6922-2.

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

In the present invention, as the fluorine-containing polymer used in the fluorine-based lubricant, one of the above fluorine-containing polymers may be used alone, or a plurality of types may be used in combination. In the present invention, among the fluorine-containing polymers used in the fluorine-based lubricant, preferred are copolymers, and more preferred are vinylidene fluoride/tetrafluoroethylene/hexafluoropropylene copolymers.

In addition, the fluorine-containing lubricant used in the present invention includes the fluorine-containing polymer described above and an inorganic filler such as calcium carbonate, barium sulfate, talc, and/or silica that does not affect the surface smoothness of the present invention. It is also permissible to add it in a range that does not affect it.

One type of the fluorine-based lubricant may be used alone, or a plurality of types may be used in combination. Among the above fluorine-based lubricants, in the present invention, the fluorine-based lubricant preferably does not contain an inorganic filler other than the fluorine-containing polymer (that is, a fluorine-based lubricant containing 100% fluorine-containing polymer). Particularly preferred is a vinylidene fluoride/tetrafluoroethylene/hexafluoropropylene copolymer.

In the present invention, the content of the fluorine-based lubricant contained in the HDPE layer is not particularly limited as long as it does not impair the effects of the present invention. For example, 0.01 to 5% by weight, preferably 0.05 to 3.5% by weight, more preferably 0.1 to 0.75% by weight, and further from the viewpoint of further improving surface smoothness. Preferably 0.2 to 0.75% by weight, more preferably 0.25 to 0.75% by weight. In addition, from the viewpoint of improving workability during extrusion molding, the %, more preferably 0.01 to 0.55% by weight.

[1-2-3. Surface roughness of inner peripheral surface]
The surface roughness of the inner peripheral surface of the HDPE layer, that is, the inner peripheral surface of the pipe material for ultrapure water of the present invention is 0.25 μm or less. 16 major metals (specifically, aluminum, barium, boron, calcium, chromium, copper, iron, lead, lithium, magnesium, manganese, nickel, potassium, sodium, strontium, and zinc). ), the surface roughness of the inner peripheral surface is preferably 0.23 μm or less, more preferably 0.2 μm or less, from the viewpoint of further reducing the total elution amount and the elution amount of the organic component. More preferably 0.18 μm or less, and still more preferably 0.16 μm or less. In addition, in this invention, surface roughness means arithmetic mean roughness Ra measured based on JISB0601:2001.

The surface roughness of the inner peripheral surface can be controlled by controlling the amount of fluorine-based lubricant blended in the resin composition for the HDPE layer. Specifically, as a method for improving the surface roughness of the inner peripheral surface, there is an increase in the blending amount of the fluorine-based lubricant. The preferred blending amount of the fluorine-based lubricant is as described in the above "2-2. Fluorine-based lubricant". Furthermore, the surface roughness of the inner peripheral surface can also be controlled by controlling the back pressure in the extrusion molding of the pipe material for ultrapure water of the present invention. A preferable back pressure range for improving the surface roughness of the inner peripheral surface is as described in "2-2. Back pressure" below.

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

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

Other additives include antioxidants (eg, phenol antioxidants, phosphorus antioxidants, sulfur antioxidants, aromatic amine antioxidants, lactone antioxidants, etc.). Since the pipe material for ultrapure water of the present invention has an excellent smoothness of the inner peripheral surface, it allows the HDPE layer to further contain an antioxidant, but further suppresses the elution of organic components into the pure water. In view of this, the HDPE layer preferably does not contain other additives such as antioxidants.

[1-2-5. Thickness]
In the case of the HDPE single-layer ultrapure water pipe 100 shown in FIG. is the same as

In the case of the ultrapure water tube materials 100a and 100b having a multilayer structure shown in FIGS. 0.4 to 0.6 mm is preferable.

[1-3. core layer]
In the ultrapure water pipes 100a and 100b of FIGS. 2 and 3, the thickness of the HDPE layer 210 is thinner than that of the ultrapure water pipe 100 of FIG. A further layer 220 is deposited.

Core layer 220 is an extruded layer of any resin composition. From the viewpoint of adhesiveness with the HDPE layer 210, etc., a preferable example of the resin used for the core material layer 220 is a polyolefin resin. The polyolefin-based resin is not particularly limited as long as it is a polymer containing a monomer unit derived from an olefin. Examples of polyolefin resins include polyethylene resins, ethylene-carboxylic acid alkenyl ester copolymer resins, ethylene-α-olefin copolymer resins, polypropylene resins, polybutene resins, poly(4-methyl-1-pentene ) based resins. One of these polyolefin resins may be used alone, or two or more thereof may be used in combination. Among these polyolefin-based resins, polyethylene-based resins and polypropylene-based resins are preferable from the viewpoint of improving the strength of the entire pipe material. Among polyethylene-based resins and polypropylene-based resins, polyethylene-based resins are more preferable from the viewpoint of suppressing the content of low-molecular-weight components and suppressing the elution of organic components into pure water.

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

Examples of carboxylic acid alkenyl esters in the ethylene-carboxylic acid alkenyl ester copolymer resin include vinyl acetate, vinyl propionate, vinyl butyrate, isopropenyl acetate, and allyl acetate, preferably vinyl acetate.

As the ethylene-α-olefin copolymer, an α-olefin such as propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene or 1-octene is copolymerized with ethylene. A copolymer obtained by copolymerization at a rate of about several mol % is mentioned as.

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

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

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

The calcium concentration in the core material layer is not particularly limited, and a calcium concentration that is included in a general-purpose grade resin is allowed.

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

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

[1-4. gas barrier layer]
The gas barrier layer 230 illustrated in the ultrapure water tube 100b of FIG. Alternatively, the gas barrier layer may be provided outside the HDPE layer 210 that constitutes the ultrapure water tube 100 of FIG. The gas barrier layer prevents permeation of oxygen from the outer surface of the pipe member into the inner layer, so that the strength of the pipe member itself can be maintained satisfactorily. Further, the provision of the gas barrier layer is also preferable in that it can satisfactorily prevent the dissolution of gas into pure water. The gas barrier layer is preferably provided for the purpose of blocking oxygen.

The gas barrier layer is an extruded layer of a gas barrier resin composition. Examples of gas barrier materials include polyvinyl alcohol (PVA), ethylene vinyl alcohol copolymer (EVOH), polyvinylidene chloride resin (PVDC), and polyvinylidene chloride resin (PVDC). Acrylonitrile (PAN) and the like, preferably polyvinyl alcohol (PVA) and ethylene vinyl alcohol copolymer (EVOH).

The thickness of the gas barrier layer is, for example, 50-150 μm, preferably 80-120 μm.

[1-5. Impurity elution suppression performance into pure water]
Since the ultrapure water pipe material of the present invention has a highly smooth inner peripheral surface, it is excellent in the ability to suppress elution of impurities into pure water.

Of the impurity elution suppression performance of the ultrapure water pipe material of the present invention, the metal elution suppression performance is measured based on SEMI F57-0314 (this standard refers to SEMI F40 standard), 16 major metals (refers to aluminum, barium, boron, calcium, chromium, copper, iron, lead, lithium, magnesium, manganese, nickel, potassium, sodium, strontium, and zinc), for example, 14 μg/m ² or less , preferably 12 μg/m ² or less, more preferably 10 μg/m ² or less, even more preferably 9 μg/m ² or less, and still more preferably 8.5 μg/m ² or less.

As a more specific example of metal elution inhibition performance, the calcium elution amount measured based on SEMI F57-0314 is, for example, 7 μg/m ² or less, preferably 6 μg/m ² or less, more preferably 5.5 μg/m 2 or less. 5 μg/m ² or less; copper elution amount includes, for example, 0.5 μg/m ² or less, preferably 0.45 μg/m ² or less, more preferably 0.4 μg/m ² or less; The elution amount of zinc is, for example, 1.5 μg/m ² or less, preferably 1.1 μg/m ² or less, more preferably 0.7 μg/m ² or less; ² or less, preferably 0.3 μg/m ² or less, more preferably 0.2 μg/m ² or less.

Among the impurity elution suppressing performances of the ultrapure water pipe material of the present invention, the anion elution amount is, for example, less than 10 μg/m ² as the bromide ion elution amount; less than ² , preferably less than 800 μg/m ² , more preferably less than 700 μg/m ² , and even more preferably less than 600 μg/m ² ; nitrite ions include, for example, less than 10 μg/m ² ; , for example less than 10 μg/m ² .

Among the impurity elution suppression performances of the ultrapure water pipe material of the present invention, the organic component elution suppression performance is, for example, 10000 μg/m ² or less as the total organic component (TOC) elution amount measured based on SEMI F57-0314. , preferably 9000 μg/m ² or less, more preferably 8500 μg/m ² or less, and even more preferably 8000 μg/m ² or less.

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

The pipe material for ultrapure water of the present invention is used for water pipes for nuclear power generation, or for washing in the manufacturing process of pharmaceuticals, semiconductor elements or liquid crystals, more preferably semiconductor elements, where the water quality required for ultrapure water is particularly strict. It is preferably a pipe for transporting ultrapure water used in a wet treatment process. The semiconductor element is preferably one having a higher degree of integration, and more specifically, it is more preferably used in the manufacturing process of a semiconductor element having a minimum line width of 65 nm or less. SEMI F57-0314, for example, is a standard regarding the quality of ultrapure water used in semiconductor manufacturing.

In addition, since the pipe material for ultrapure water of the present invention is excellent in workability, for example, fusion work such as butt (butt) fusion bonding and EF (electrofusion) bonding can be easily performed at a relatively low temperature. .

[2. Manufacturing method of tube material for ultrapure water]
The above-described ultrapure water tube material of the present invention can be manufactured by extruding the resin composition for HDPE layer used for forming the HDPE layer. That is, the method for producing an ultrapure water tube material of the present invention includes a step of extruding a resin composition for an HDPE layer containing high-density polyethylene and a fluorine-based lubricant. Further, when the ultrapure water pipe material to be manufactured has a multilayer structure, the method for manufacturing the ultrapure water pipe material of the present invention comprises a resin composition for the HDPE layer containing high-density polyethylene and a fluorine-based lubricant, and and a step of co-extrusion molding with the resin composition for other layers used for forming the other layers. In the method for producing an ultrapure water pipe material of the present invention, from the viewpoint of easily achieving a surface roughness of 0.25 μm or less on the inner peripheral surface, a resin composition for an HDPE layer containing high-density polyethylene and a fluorine-based lubricant is preferable. It includes extruding the article under a back pressure of 3-30Mpa.

[2-1. Resin composition]
HDPE and fluorine-based lubricant contained in the HDPE layer resin composition containing high-density polyethylene and fluorine-based lubricant, and the composition of the HDPE resin composition (the content or concentration of the components contained in the HDPE layer-use resin composition) is as described as the content or concentration of each component and components contained in the HDPE layer in the above "1-2. HDPE layer".

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

In a specific method for synthesizing HDPE used in the resin composition for the HDPE layer, one-step polymerization is performed using a chlorine-based catalyst, and then an amount of a neutralizing agent (e.g., calcium stearate, hydrocal sites, etc.) can be added. When a neutralizing agent is added in this way, the neutralizing agent can be used singly or in combination. Alternatively, another specific method for synthesizing HDPE used in the resin composition for the HDPE layer may be one-step polymerization using a chromium-based catalyst or metallocene catalyst to eliminate the addition of a neutralizing agent.

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

In addition, when the ultrapure water pipe material to be manufactured has a multi-layer structure including a core material layer, and a polyolefin resin is used for the core material layer, a specific method for synthesizing the polyolefin resin is to use a chlorine catalyst can be used to carry out multi-stage polymerization (preferably two-stage polymerization), and then a neutralizing agent (eg, calcium stearate, hydrocalcite, etc.) can be added in an amount of 15 to 25 ppb in terms of calcium concentration.

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

[2-2. Back pressure]
The back pressure is the force acting in the direction of pushing back the molten material to the extruder side by the die located ahead of the flow path, which is measured in the flow path between the extruder and the die. In the method of manufacturing the pipe material for ultrapure water of the present invention, the HDPE layer is extruded while controlling the back pressure to 3 to 30 MPa, thereby more easily achieving a surface roughness of 0.25 μm on the inner peripheral surface. be able to.

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

In the present invention, the back pressure measurement locations for extrusion molding of the resin composition for the HDPE layer are schematically shown in FIGS. 4 to 6. FIG. In FIGS. 4 to 6, the illustration of a mandrel (metal core) or the like for molding into a tubular shape in a mold is omitted in order to mainly show the extrusion direction of the resin. FIG. 4 schematically shows part of the production line for producing the ultrapure water pipe shown in FIG. 1, and FIG. 5 shows the production line for producing the ultrapure water pipe shown in FIG. FIG. 6 schematically represents a part of the manufacturing line for manufacturing the ultrapure water tube material shown in FIG. In the case shown in FIG. 4, the back pressure refers to the back pressure BP-1 measured in the channel between the HDPE layer extruder (for extruding the HDPE layer resin composition) and the mold. In the case shown in FIGS. 5 and 6, the back pressure means the back pressure BP- Point to 1. In the case shown in FIGS. 5 and 6, the back pressure BP-2 of the resin composition for the HDPE layer and the back pressure BP-2 of the resin composition for the gas barrier layer flowing inside the core material layer in the mold can be equal to the back pressure BP-1. The back pressure equivalent to the back pressure BP-1 is, for example, 0.9 to 1.1 times, preferably 0.95 to 1.05 times the back pressure BP-1.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples.

Tubes for ultrapure water shown in Tables 1 and 2 were produced by extrusion molding. Comparative Example 1 is a PVDF single-layer structure pipe material (total thickness: 2.4 mm, outer diameter: 32.0 mm). Layer structure (HDPE layer 210 of 0.5 mm, core layer 220 of 2.5 mm, gas barrier layer 230 of 0.1 mm, provided that an adhesive layer (not shown) of 0.5 mm is provided between the core layer 220 and the gas barrier layer 230. 1 mm.The outer diameter is 32.0 mm.).

The resin composition shown in Tables 1 and 2 shows the resin composition of the layer forming the inner peripheral surface (the surface in contact with ultrapure water) of the pipe material for ultrapure water. Comparative Examples 2 and 3 and Examples 1 to 8 indicates the resin composition of the HDPE layer 210 . The HDPE shown in Tables 1 and 2 has a density of 0.942 g/cm ³ , a weight average molecular weight of 780,000, a molecular weight distribution (Mw/Mn) of 71, a calcium concentration of less than 10.0 ppb, and an MFR of 12.06 g/10 min. (190° C., 21.6 kg), HDPE polymerized using a Ziegler-Natta catalyst (a clean grade level with a small amount of neutralizer and no antioxidant). In Comparative Examples 2 and 3 and Examples 1 to 8, the material used for the core material layer 220 has a density of 0.941 g/cm ³ , a weight average molecular weight of 730000, a molecular weight distribution (Mw/Mn) of 41, Ziegler-Natta catalyzed HDPE (general purpose grade level with neutralizer and antioxidant) with MFR of 12.88 g/10 min (190° C., 21.6 kg); The material used for the layer is maleic anhydride-modified adhesive polyethylene; the material used for the gas barrier layer is ethylene-vinyl alcohol copolymer, which is an oxygen barrier resin.

The fluorine-based lubricants shown in Tables 1 and 2 are 100% vinylidene fluoride/tetrafluoroethylene/hexafluoropropylene copolymer.

Further, the back pressure shown in Tables 1 and 2 refers to BP1 shown in FIG. 6 (note that BP2 and BP3 had the same back pressure as BP1).

The resulting ultrapure water tubing material was tested for surface roughness (arithmetic mean roughness Ra measured based on JIS B 0601:2001) and major 16 metals (aluminum, barium, boron , calcium, chromium, copper, iron, lead, lithium, magnesium, manganese, nickel, potassium, sodium, strontium, and zinc), total organic content (TOC), and anion elution were measured. Results are shown in Tables 1 and 2.

As is clear from Tables 1 and 2, the ultrapure water tubing material (Examples 1 to 8) having an HDPE layer containing a fluorine-based lubricant satisfies SEMI standards, which has not been achieved with HDPE tubing so far. A surface smoothness could be achieved. Furthermore, even when the blending amount of the fluorine-based lubricant is the same (Examples 1 to 6), the surface smoothness can be further improved by controlling the back pressure (Examples 2 to 5), especially Example 4. In the pipe material for ultrapure water, surface smoothness equivalent to that of the PVDF pipe (Comparative Example 1) could be achieved.

In addition, according to the pipe materials for ultrapure water of Examples 1 to 8, the total elution amount of 16 kinds of metals was significantly higher than that corresponding to the HDPE pipe having the highest surface smoothness ever (Comparative Example 2). Not only is it low, but it is also significantly lower than the PVDF pipe (Comparative Example 1), and it was found to be extremely excellent in terms of elution suppression of 16 kinds of metals. According to the pipe materials for ultrapure water of Examples 1 to 8, among others, it is possible to reduce the elution amounts of calcium, copper, sodium, and zinc contained in HDPE pipes to an extremely low level. In the tube material for ultrapure water of Example 4, the elution amounts of calcium and copper reached levels equivalent to those of the PVDF tube (Comparative Example 1), and the elution amounts of sodium and zinc were lower than those of the PVDF tube (Comparative Example 1). reached up to

Furthermore, in the tube material for ultrapure water of Example 4, the elution amounts of TOC and anions were also reduced to extremely low levels.

Since the elution of impurities is reduced to an extremely low level in this way, the ultrapure water pipes of Examples 1 to 8 are suitable for transporting a semiconductor cleaning liquid suitable for wet processing of semiconductor elements with a minimum line width of 65 nm or less. It was recognized that

100, 100a, 100b ultrapure water pipe 210 HDPE layer 220 core layer 230 gas barrier layer s inner peripheral surface

Claims (13)

An ultrapure water pipe material having an HDPE layer containing high-density polyethylene and a fluorine-based lubricant,
The inner peripheral surface of the HDPE layer constitutes the inner peripheral surface of the pipe material,
The surface roughness of the inner peripheral surface is 0.25 μm or less,
Ultrapure water tubing used to transport ultrapure water. 2. The pipe material for ultrapure water according to claim 1, wherein said HDPE layer is formed by extruding an HDPE composition containing said high-density polyethylene and said fluorine-based lubricant under a back pressure of 3 to 30 Mpa. 3. The pipe material for ultrapure water according to claim 1, wherein the high-density polyethylene has a molecular weight distribution of 40-80. The pipe material for ultrapure water according to any one of claims 1 to 3, wherein the content of said fluorine-based lubricant in said HDPE layer is 0.01 to 5% by weight. The pipe material for ultrapure water according to any one of claims 1 to 4, which has a multilayer structure in which another layer is laminated on the outer surface of the HDPE layer. 6. The pipe material for ultrapure water according to claim 5, wherein the HDPE layer has a layer thickness of 0.3 mm or more. The total amount of elution of aluminum, barium, boron, calcium, chromium, copper, iron, lead, lithium, magnesium, manganese, nickel, potassium, sodium, strontium, and zinc measured based on SEMI F57-0314 is The pipe material for ultrapure water according to any one of claims 1 to 6, which has a weight of 14 µg/m ² or less. The elution amount of calcium is 7 μg/m ² or less, the elution amount of copper is 0.5 μg/m ² or less, and the elution amount of sodium is 1.5 μg/m ² or less, as measured based on SEMI F57-0314. 8. The pipe material for ultrapure water according to any one of claims 1 to 7, wherein the amount of zinc is 0.5 µg/m ² or less and/or the zinc elution amount is 0.5 µg/m ² or less. 9. The pipe material for ultrapure water according to any one of claims 1 to 8, wherein the elution amount of fluoride ions measured according to SEMI F57-0314 is 600 μg/m ² or less. 10. The pipe material for ultrapure water according to any one of claims 1 to 9, wherein the elution amount of all organic components measured based on SEMI F57-0314 is 10000 µg/m ² or less. The tube material for ultrapure water according to any one of claims 1 to 10, wherein said ultrapure water is used in a wet treatment process for semiconductor devices or liquid crystals. The pipe material for ultrapure water according to any one of claims 1 to 11, wherein the ultrapure water is used in a wet treatment process for semiconductor devices having a minimum line width of 65 nm or less. It has an HDPE layer containing high-density polyethylene and a fluorine-based lubricant, the inner peripheral surface of the HDPE layer constitutes the inner peripheral surface of the pipe member, and the inner peripheral surface has a surface roughness of 0.25 μm or less. A method for manufacturing a pure water pipe, comprising:
A manufacturing method comprising a step of extruding the HDPE layer from a resin composition containing the high-density polyethylene and the fluorine-based lubricant under a back pressure of 3 to 30 Mpa.

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