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US20140127031A1 - Screw rotor for exhaust pump, method for manufacturing the same, gas exhaust pump having screw rotor, and manufacturing method and assembly method of the same - Google Patents

Screw rotor for exhaust pump, method for manufacturing the same, gas exhaust pump having screw rotor, and manufacturing method and assembly method of the same Download PDF

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Publication number
US20140127031A1
US20140127031A1 US14/233,427 US201214233427A US2014127031A1 US 20140127031 A1 US20140127031 A1 US 20140127031A1 US 201214233427 A US201214233427 A US 201214233427A US 2014127031 A1 US2014127031 A1 US 2014127031A1
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United States
Prior art keywords
pfa
film
screw rotor
temperature
screw
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US14/233,427
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English (en)
Inventor
Masamichi IWAKI
Tadahiro Ohmi
Kenji Ohyama
Isao Akutsu
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Tohoku University NUC
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Tohoku University NUC
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Assigned to TOHOKU UNIVERSITY reassignment TOHOKU UNIVERSITY ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: OHMI, TADAHIRO, OHYAMA, Kenji, AKUTSU, ISAO, IWAKI, Masamichi
Publication of US20140127031A1 publication Critical patent/US20140127031A1/en
Abandoned legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D129/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Coating compositions based on hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Coating compositions based on derivatives of such polymers
    • C09D129/10—Homopolymers or copolymers of unsaturated ethers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C18/00—Rotary-piston pumps specially adapted for elastic fluids
    • F04C18/08—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing
    • F04C18/12—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type
    • F04C18/14—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons
    • F04C18/16—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons with helical teeth, e.g. chevron-shaped, screw type
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B05D3/02—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by baking
    • B05D3/0209—Multistage baking
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B05D3/02—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by baking
    • B05D3/0254—After-treatment
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01C—ROTARY-PISTON OR OSCILLATING-PISTON MACHINES OR ENGINES
    • F01C21/00—Component parts, details or accessories not provided for in groups F01C1/00 - F01C20/00
    • F01C21/08—Rotary pistons
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2/00—Rotary-piston machines or pumps
    • F04C2/08—Rotary-piston machines or pumps of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing
    • F04C2/12—Rotary-piston machines or pumps of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type
    • F04C2/126—Rotary-piston machines or pumps of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with radially from the rotor body extending elements, not necessarily co-operating with corresponding recesses in the other rotor, e.g. lobes, Roots type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2230/00—Manufacture
    • F04C2230/60—Assembly methods
    • F04C2230/602—Gap; Clearance
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2230/00—Manufacture
    • F04C2230/90—Improving properties of machine parts
    • F04C2230/91—Coating
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C27/00—Sealing arrangements in rotary-piston pumps specially adapted for elastic fluids
    • F04C27/001—Radial sealings for working fluid
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
    • F05C2225/00—Synthetic polymers, e.g. plastics; Rubber
    • F05C2225/04—PTFE [PolyTetraFluorEthylene]

Definitions

  • the present invention relates to a screw rotor for a gas exhaust pump used in an apparatus for manufacturing semiconductor devices and electronic devices which use semiconductor-related technology, such as liquid crystal display devices, solar cells, organic FL devices, and LEDs (hereinafter referred to as “semiconductor application electronic devices”), or in an apparatus for manufacturing electronic components for the electronic devices, a method for manufacturing the screw rotor for a gas exhaust pump, a gas exhaust pump having the screw rotor, and a manufacturing method and an assembling method of the gas exhaust pump having the screw rotor.
  • semiconductor-related technology such as liquid crystal display devices, solar cells, organic FL devices, and LEDs
  • various types of pumps are used in an apparatus for manufacturing display devices which use semiconductor devices, liquid crystal, organic EL, and the like, and functional devices such as solar cell devices, due to limitations of application ranges depending on the pumping performance. Since the above-mentioned pump has a wide range of application of decompression and the pumping performance does not depend on the type of exhaust gas, there is no need to perform complicated works, such as replacement of a pump depending on the type of gas, placement of a pump in accordance with a change in pressure conditions, or preparation of a pump suitable for each pumping position in a production system having a plurality of pumping positions.
  • a pump does not depend on a pumping speed, the same type of pump can be used, thereby eliminating troublesome selection of a pump for each pumping position. If the above type of pump becomes commercially available at low costs, it can be easily expected that such a type of pump will become widely popular and greatly contribute to the development of the industry.
  • FIG. 1 is a schematic view of an exemplary pump of the above-mentioned type.
  • FIG. 2 is an enlarged schematic view of a portion shown by II in FIG. 1 .
  • a gas exhaust pump 100 with variable-lead/variable-inclination-angle screws includes an variable-lead/variable-inclination-angle female screw rotor 101 and an variable-lead/variable-inclination-angle male screw rotor 102 .
  • a screw engaging portion 104 is formed between the screw rotors 101 and 102 , in which teeth and grooves are engaged with each other with a predetermined clearance to obtain a safe and smooth rotary motion.
  • the screw rotors 101 and 102 are installed in a stator 106 with a predetermined gap provided between tooth top ends of the screw rotors 101 and 102 and an inner wall of the stator 106 .
  • the rotating shaft 105 is rotatably mounted to a bearing body 116 via a holding means such as an angular bearing 107 ( FIG. 1 shows four angular bearings 107 a, 107 b, 107 c, and 107 d for convenience).
  • the male screw rotor 102 is fixed to the rotating shaft 105 and is rotated by the rotation of the rotating shaft 105 .
  • a lubricating oil supply path 109 is provided in the rotating shaft 105 .
  • a lubricating oil 111 is stored in a lubricating oil reservoir 112 provided at a predetermined position under a base plate 110 .
  • the rotating shaft 105 When the rotating shaft 105 receives a rotational force of a motor (not shown) via a rotary gear (not shown) and rotates, the rotation generates a centrifugal force so that the lubricating oil 111 rises by suction through the lubricating oil supply path 109 to be supplied to the angular bearing 107 .
  • An oil seal member 113 for preventing the lubricating oil from diffusing is provided all around the rotating shaft 105 so as to seal a gap between the rotating shaft 105 and a seal housing 108 (they form an axis seal mechanism) as shown in FIG. 1 so that the lubricating oil 111 does not diffuse into a portion other than the angular bearing 107 through the gap between the rotating shaft 105 and the seal housing 108 .
  • a seal gas such as N 2 is supplied to the gap between the rotating shaft 105 and the seal housing 108 through a seal gas supply path 114 as shown by arrows in FIG.
  • the seal gas is supplied from the seal gas supply path 114 , flows through a predetermined passage, and is discharged outside from a discharge path (not shown) with other gases used in semiconductor processes such as film deposition and etching.
  • the female and male screw rotors 101 and 102 are engaged with each other. More specifically, a top end surface of a tooth of one screw rotor (a top end surface 201 of a tooth of the screw rotor 102 ) is engaged with a bottom end surface of the other screw rotor (a bottom end surface 202 of a groove of the screw rotor 101 , which corresponds to a bottom end surface 202 of a groove of the screw rotor 102 ) with a small gap therebetween so that the screw rotors can smoothly rotate.
  • a top end surface of a tooth of one screw rotor (a top end surface 201 of a tooth of the screw rotor 102 ) is engaged with a bottom end surface of the other screw rotor (a bottom end surface 202 of a groove of the screw rotor 101 , which corresponds to a bottom end surface 202 of a groove of the screw rotor 102 ) with a small gap therebetween so that the screw rotors can smoothly rotate.
  • an inner surface of the groove of one screw rotor is generally configured to face an outer surface of the tooth of the other screw rotor with a small gap therebetween so as to maintain smooth rotation of the screw rotors.
  • a side surface of a tooth and groove of the first screw rotor smoothly contacts a side surface of a tooth and groove of the second screw rotor so that the rotation driving force is smoothly and efficiently transmitted to the second screw rotor.
  • the screw pump of FIG. 1 has a pair of (twin) screw rotors. There is also a screw pump having a single screw rotor and configured to rotate the screw rotor for pumping in a state where a gap is provided between a top end surface of a tooth of the screw rotor and an inner wall surface of a stator (see PTL 1).
  • NPL 1 “Innovative Manufacturing Techniques in Semiconductor and Display Industries (1)”, Technology Alliance Group, Inc., pp. 443-447
  • a width of a gap between a screw portion 103 and the stator 106 greatly influence the pumping performance of a pump. Accordingly, it is considered that a smaller width of a gap is preferable in order to increase a pumping speed.
  • the gaps must be designed to have a certain width under the present circumstances.
  • the present invention has been made to solve the above problems, and in a gas exhaust pump having a screw rotor, a rotating shaft of the screw rotor, and a stator containing the rotatably-mounted screw rotor therein, it is an object of the present invention to provide a screw rotor that can ensure safe rotation even if a gap between the screw rotor and the stator is particularly smaller than that of a conventional one and can greatly increase a pumping performance of the pump, and a manufacturing method of the screw rotor.
  • a first aspect of the present invention is a screw rotor for a gas exhaust pump, the pump including a screw rotor, a rotating shaft fixed to the screw rotor or formed integrally with the screw rotor and rotatably engaging with a rotation driving means so as to rotate the screw rotor, and a holding means having a structure of rotatably holding the rotating shaft to allow high-speed rotation of the rotating shaft, wherein the screw rotor has a screw portion, and at least a top end surface of the screw portion facing an inner wall surface of a stator has a film of perfluoro alkoxy alkane (hereinafter referred to as “PFA”) of the structural formula 1:
  • PFA perfluoro alkoxy alkane
  • Rf is a perfluoro alkyl group and m and n are both positive integers (a first screw rotor).
  • the PFA film in the first aspect is a film formed through a remelting process (a second screw rotor).
  • a manufacturing method of a screw rotor for a gas exhaust pump including preparing a screw rotor having a coating film of PFA of the structural formula 1 on a top end surface of a tooth of a screw portion of the screw rotor, exposing the coating film to an atmosphere with a temperature higher than a melting temperature of PFA so as to melt at least a free surface area of the coating film, then exposing the coating film to an atmosphere with a temperature lower than the melting temperature of PFA so as to solidify at least a portion to be a free surface area, then exposing the coating film to an atmosphere with a temperature equal to the melting temperature of PFA or higher than the melting temperature of PFA so as to remelt at least the portion to be a free surface area, and then lowering the temperature of the atmosphere to a temperature sufficiently lower than the melting temperature of PFA so as to increase smoothness of the free surface of a solid film consisting of PFA (a manufacturing method of the first screw rotor).
  • a manufacturing method of a gas exhaust pump includes the processes defined in the manufacturing method of the screw rotor of the third aspect (a manufacturing method of a first pump).
  • an assembling method of a gas exhaust pump includes using the screw rotor of any one of the first to fourth aspects as an assembly part (an assembling method of the first pump).
  • a gas exhaust pump has the screw rotor of the first aspect.
  • a gas exhaust pump has the screw rotor of the second aspect.
  • the pumping performance is particularly high as compared to a conventional pump of a similar type and it is possible to maintain a certain rotation performance without causing erroneous rotation by high-speed, continuous, and longtime operation.
  • FIG. 1 illustrates a conventional gas exhaust pump and a feature of a gas exhaust pump of the present invention along with the conventional gas exhaust pump;
  • FIG. 2 is a schematic enlarged view of a portion shown by II in FIG. 1 ;
  • FIG. 3 illustrates measurement areas of smoothness in Experiment 1.
  • the screw rotor of the present invention When installed in a pump, the screw rotor of the present invention is placed with a gap between a top end surface 201 of a tooth of a screw portion 103 and an inner wall surface 203 of a stator 106 .
  • a PFA film (not shown) is provided on the top end surface 201 . If the PFA film of the present invention is provided in a predetermined manner, the width of the gap between the free surface of the PFA film and the inner wall surface 203 of the stator 106 can be made significantly smaller than that of a conventional one, so that the pumping performance is greatly improved. In addition, even with a little foreign matter entering the gap, the PFA film can prevent the occurrence of erroneous rotation due to the biting and damage to the pump.
  • the PFA film After coating at least the top end surface 201 of the screw rotor with PFA, followed by melting and remelting processes, the PFA film is formed to have a high smoothness on its free surface.
  • the PFA film may be provided not only on the top end surface 201 , but also on a bottom end surface 202 or side inner wall surfaces 204 , 205 of the screw portion 103 .
  • the pumping performance can be increased by providing the PFA film on the top end surface and the side inner surface or the screw portions of the female and male screw rotors.
  • the PFA of the structural formula 1 used in the present invention is manufactured by and available from many companies. Under the circumstances, it is desirable that the PFA of the present invention preferably have a melting point of 298° to 310° C. and a density of 2.12 to 2.17. Further, in a case where it is necessary to consider use under high temperature conditions, it is desirable that the PFA of the present invention be selected from PFA having a highest temperature for continuous use preferably of at least 260° C.
  • the PFA of the present invention have a thermal conductivity equal to or higher than, for example, 0.25 W/m k.
  • PFA of the AC type includes AC-5600, ACX-21, ACX-31, ACX-31WH, ACX-34, and ACX-41.
  • AD-2CRE coating film thickness: 10 to 15 ⁇ m
  • AW-5000L coating film thickness: 30 to 40 ⁇ m
  • the manufacturer recommends that AD-2CRE and AW-5000L be used with a wire netting having 100 to 150 meshes and a wire netting having 60 to 80 meshes, respectively, for coating after filtration.
  • air spraying conditions preferably include a spray gun having a nozzle diameter of 1.0 mm ⁇ and a spraying pressure of 0.2 MPa.
  • air spraying conditions preferably include a spray gun having a nozzle diameter of 1.0 to 1.2 mm ⁇ and a spraying pressure of 0.2 to 0.4 MPa.
  • Examples of preferable primers used in the present invention available from Daikin Industries LTD. include: ED-1939D21L, EK-1908S21L, EK-1909S21L, EK-1959S21L, EK-1983S21L, EK-1208M1L, EK-1209BKEL, EK-1209M10L, and EK-1283S1L as aqueous primers; and TC-1509M1, TC-1559M2, and TC-11000 as solvent-based primers.
  • EM-500CL for aqueous topcoat
  • EM-500GN for aqueous topcoat
  • EM-700CL for aqueous topcoat
  • EM-700GN for aqueous topcoat
  • EM-700GY for aqueous topcoat
  • the following PFA can also be used in the present invention: MP-102 (micropowder for topcoat), MP-103 (micropowder for topcoat), MP-300 (fluorinated powder for topcoat), MP-310 (fluorinated powder for topcoat), MP-630 (conductive powder), MP-642 (conductive powder), MP-620 (having a high thermal conductivity), MP-621 (having a high thermal conductivity), MP-622 (having a high thermal conductivity), MP-623 (having a high thermal conductivity), MP-501 (suitable for products to which electrostatic coating cannot be applied due to their complicated shapes), MP-502 (suitable for products to which electrostatic coating cannot be applied due to their complicated shapes), SL-800BK (including a carbon filler), and SL-800LT (including a glass filler).
  • MP-102 micropowder for topcoat
  • MP-103 micropowder for topcoat
  • MP-300 fluorinated powder for topcoat
  • MP-310 fluorinated powder for topcoat
  • MP-103, MP-300, and MP-310 are preferable in the present invention since the obtained film has an excellent surface smoothness.
  • MP-310 is especially preferable since it has control of a spherulite diameter of about 5 ⁇ m and is excellent in terms of size and uniformity.
  • SL-800BK is preferable in the present invention in terms of heat dissipation properties since it has a good thermal conductivity and excellent heat dissipation properties.
  • MP-630, 642 conductive micropowder are also used in the present invention as a preferable PFA material.
  • an especially preferable PFA includes Rf of “—CF2CF2CF3” in the structural formula 1 and has a molecular weight of several hundreds of thousands to one million, a melting point of 300° to 310° C., a viscosity of 104 to 105 poise (380° C.), and a highest temperature for continuous use of 260° C.
  • Preferable primers are PFA Primer PL-902 Series sold as aqueous primers for general use and PFA Primer PL-910 Series sold as primers having excellent heat resistance and corrosion resistance. Their specific brand names are PL-902YL, PL-902BN, PL-902AL, PL-910YL, PL-910BN, PL-910AL, and PL-914AL.
  • NK-108 lubricant, standard film thickness: 50 ⁇ m, heat resistant temperature: 260° C.
  • NK-372, 379 lubricant, antistatic, standard film thickness: 100, 300 ⁇ m, heat resistant temperature: 260° C.
  • NK-013, 013C wear resistant, standard film thickness: 300 ⁇ m, heat resistant temperature: 150° C.
  • NF-015 standard film thickness: 50 ⁇ m
  • NF-015EC standard film thickness: 40 ⁇ m, antistatic
  • NF-020AC standard film thickness: 600 ⁇ m, antistatic
  • a metal-based material having a good thermal conductivity and being suitable for the processing for workpieces is adopted, preferably stainless steel or an aluminum-based metal such as aluminum alloys.
  • the rotating shaft and the seal housing are engaged with each other via the angular bearing so that the rotating shaft is rotatable. Since the long-time, high-speed rotation generates frictional heat between the rotating shaft and the angular bearing, a base material with a good thermal conductivity is preferably selected to improve a heat dissipation effect of the rotating shaft and the seal housing.
  • a light aluminum-based metal is preferably selected. At the same time, it is preferable to select an aluminum-based metal that is as hard as possible and has a smaller thermal expansion coefficient.
  • an aluminum-based material an aluminum alloy containing a metal other than aluminum in a pure aluminum is adopted in the present invention.
  • the aluminum alloy used in the present invention is made of metal containing aluminum as a main component. It is desirable that the metal containing aluminum as a main component be a metal containing normally 50% by mass or more of aluminum, preferably 80% by mass or more of aluminum, more preferably 90% by mass or more of aluminum, and still more preferably 94% by mass or more of aluminum.
  • the metal containing aluminum as a main component be a metal containing normally 50% by mass or more of aluminum, preferably 80% by mass or more of aluminum, more preferably 90% by mass or more of aluminum, and still more preferably 94% by mass or more of aluminum.
  • at least one metal is selected from the group consisting of magnesium, titanium, and zirconium.
  • magnesium is especially preferable since it increases the strength of the aluminum alloy.
  • the aluminum alloy used in the present invention may also be a metal containing a high-purity aluminum as a main component having a decreased content of specific elements (iron, copper, manganese, zinc, and chromium).
  • the total content of specific elements is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, and still more preferably 0.3% by mass or less.
  • the aluminum alloy including a high-purity aluminum as a main component may contain one or more other metals that may form an alloy with aluminum as necessary.
  • Preferable metals include at least one metal selected from the group consisting of magnesium, titanium, and zirconium, but are not limited thereto, as long as they are other than the specific elements.
  • magnesium is especially preferable since it increases the strength of the aluminum alloy.
  • the concentration of magnesium is not particularly limited as long as it is in a range in which magnesium and aluminum can form an alloy, but is normally 0.5% by mass or more, preferably 1.0% by mass or more, and more preferably 1.5% by mass or more, to contribute to the sufficient increase in the strength.
  • the concentration of magnesium is preferably 6.5% by mass or less, more preferably 5.0% by mass or less, still more preferably 4.5% by mass or less, and most preferably 3.0% by mass or less.
  • the aluminum alloy used in the present invention may contain other metallic elements as a crystal regulator.
  • the metallic elements are not particularly limited as long as they have a sufficient effect of crystal control, but zirconium or the like is preferably used.
  • the content of each metal other than aluminum actively contained in the aluminum alloy be normally 0.01% by mass or more, preferably 0.05% by mass or more, and more preferably 0.1% by mass or more relative to the entire aluminum alloy.
  • the lower limit of the content defines a required amount of the metal to fully exhibit its properties.
  • the content of each metal is normally 20% by mass or less, preferably 10% by mass or less, more preferably 6% by mass or less, particularly preferably 4.5% by mass or less, and most preferably 3% by mass or less.
  • the upper limit defines a required amount of the metal to form a uniform solid solution of aluminum and other metallic elements to maintain excellent material properties.
  • a base material formed of stainless steel SUS316 is preferably used for corrosion resistance, SUS316L for low-carbon steel, and SUS316L-EP which has a mirror-finished surface by electrolytic polishing for a base material with a smooth surface.
  • the base material formed of stainless steel is not limited to the above-mentioned materials as long as a material suitable for purposes and conditions of use is selected.
  • iron-based alloy materials such as SCM 440, S45 are occasionally used for hardness.
  • a base material also referred to as a “workpiece” processed for the screw rotor for the screw pump of the present invention
  • the smoothness of the polished surface at this stage preferably be equal to or smaller than an average particle size of the PFA powder.
  • the smoothness is not limited to this in a case where the PFA film is provided not directly on the polished surface of the base material.
  • a film of Al 2 O 3 , Ni, or Nif 2 (referred to as a “base film”) be provided beforehand on the PFA film-provided surface.
  • Providing beforehand a film of Ni or Nif 2 on the PFA film-provided surface can produce an effect of reducing pyrolysis of PFA when melting or remelting the PFA film provided on the surface, and therefore a film having a better quality can be obtained even if a higher melting temperature is set as compared to other base materials.
  • an Ni film has a high corrosion resistance and a high adhesion to the PFA film, it is preferably used as a base film for the PFA film.
  • a base film for the PFA film.
  • electroless nickel plating and plasma sputtering for depositing Ni by sputtering, but also MOCVD using an organic Ni complex.
  • a plating solution includes a reducing agent, and P (phosphorus) or B (boron) map be included in the obtained Ni film depending on the reducing agent to be used.
  • hypophosphite In a case where hypophosphite is used for the reducing agent, it is possible to include P (phosphorus) in the obtained Ni film, while in a case where dimethylamineborane (DMAB) is used, it is possible to include B (boron) in the Ni film.
  • DMAB dimethylamineborane
  • B (boron) in the Ni film can increase hardness of the film and decrease electrical resistance of the film as compared to the case of including P (phosphorus) in the Ni film, and therefore it is possible to decide whether to include P (phosphorus) or B (boron) in the Ni film depending on the use of reaction vessels.
  • Using hydrazine for the reducing agent provides an advantage that hydrogen gas is not generated during reaction unlike the case of using hypophosphorous acid or DMAB.
  • the amount of P (phosphorus) contained in the Ni film is appropriately determined according to the use of a reaction vessel. It is desirable that the chemical compositions be preferably 83 to 98% of Ni, 2 to 15% of P, and 0 to 2% of others. In the case of B (boron), it is desirable that the chemical compositions be preferably 97 to 99.7% of Ni, 0.3 to 3% of B, and 0 to 2.7% of others.
  • Electroless nickel plating may be conducted by our since an electroless nickel plating solution itself is commercially available and the solution may be prepared by our, but it is also possible to have a third party conduct the electroless nickel plating based on specifications to achieve the objects of the present invention.
  • Electroless nickel plating solutions are manufactured by or commercially available from, for example, Tool System Co., Ltd., World Metal Co., Ltd., Metal Finishing Laboratory Co., Ltd., OKUNO CHEMICAL INDUSTRIES CO., LTD., and Uyemura & CO., LTD.
  • Examples of companies conducting electroless nickel plating include Japan Kanigen Co., Ltd., Hitachi Kyowa Engineering Co., Ltd., SANWA PLATING INDUSTRY INCORPORATED COMPANY, Kodama Co., Shimizucho Metal Plating Industry Co., Ltd., Yamato Denki Ind. Co., Ltd., Nishina Industrial Co., LTD., and TOMASEIREN CO., LTD.
  • a free surface of the Ni film provided on the PFA film-provided surface of the workpiece should be fluorinated.
  • a base material having the Ni film on its surface is placed in a vacuum vessel, and then F 2 gas is supplied to the vacuum vessel after reaching a predetermined degree of vacuum to expose the surface of the Ni film to the F 2 gas.
  • F 2 gas is supplied to the vacuum vessel after reaching a predetermined degree of vacuum to expose the surface of the Ni film to the F 2 gas.
  • the Nif 2 film obtained by fluorinating the Ni film including P (phosphorus) or B (boron) as described above includes P (phosphorus) or B (boron) in the above chemical compositions.
  • the film is annealed at a predetermined temperature for a predetermined time in an atmosphere such as a noble gas or nitrogen gas, so that adhesion strength of the film to the base material and hardness of the film are greatly increased. Therefore, this is a preferable post-treatment method of the base film in the present invention.
  • annealing be performed for about one hour in a nitrogen atmosphere at a temperature in the range of 260° to 350° C., for example.
  • an anodic oxidation method capable of forming a non-porous Al 2 O 3 film is preferably used.
  • a film formed by the anodic oxidation method is formed at least on the PFA film-provided surface of the workpiece by the anodic oxidation method which will be described later.
  • the Al 2 O 3 anodic oxide film is a film of metal oxide including aluminum as a main component, and a film having a thickness of 10 nm or larger can be easily formed. Since this film is a passive film, it exhibits high performance as a protective film when formed on an inner surface of an aluminum reaction vessel body.
  • the thickness of the Al 2 O 3 anodic oxide film is preferably 100 ⁇ m or smaller.
  • the thickness of the Al 2 O 3 anodic oxide film is preferably 10 ⁇ m or smaller, more preferably 1 ⁇ m or smaller, still more preferably 0.8 ⁇ m or smaller, and particularly preferably 0.6 ⁇ m or smaller.
  • the lower limit of the film thickness is 10 nm or larger. If the film thickness is smaller than 10 nm, it becomes impossible to obtain sufficient corrosion resistance.
  • the thickness of the Al 2 O 3 anodic oxide film is preferably 20 nm or larger, more preferably 30 nm or larger.
  • This method has another advantage that a dense smooth anodic oxide film can be formed since the method has a function of repairing a defect caused by unevenness of a metal surface.
  • the lower limit of the pH of the chemical conversion solution be 4 or greater as described above, preferably 5 or greater, and more preferably 6 or greater.
  • the upper limit of the pH of the chemical conversion solution be normally 10 or smaller, preferably 9 or smaller, and more preferably 8 or smaller.
  • the pH of the chemical conversion solution be neutral or nearly neutral, or as close to neutral as possible.
  • the chemical conversion solution preferably has a pH in the range of 4 to 10 so as to maintain the pH within a predetermined range by buffering variation in concentration of various substances during the anodic oxidation (buffering action).
  • a compound hereinafter also referred to as “compound (A)”
  • compound (A) such as an acid or a salt that exhibits a buffering action.
  • the type of such a compound is not particularly limited, but at least one selected from the group consisting of preferably boric acid, phosphoric acid, organic carboxylic acid, and salts thereof is preferable in terms of high solubility in the chemical conversion solution and high solution stability.
  • the compound is an organic carboxylic acid or its salt with almost no residual boron or phosphorus element in the anodic oxide film.
  • the chemical conversion solution used in the present invention preferably contains a non-aqueous solvent. If the chemical conversion solution containing the non-aqueous solvent is used, there is an advantage that the treatment can be carried out with high throughput since the time required for constant electric current chemical conversion can be shortened as compared with the case where an aqueous-based chemical conversion solution is used. If an aqueous solution is used as the chemical conversion solution, the anodic oxide film is etched by OH ions generated by electrolysis of water to become porous, and therefore it is preferable to use a main solvent having a low dielectric constant to suppress the electrolysis of water.
  • non-aqueous solvent is not particularly limited as long as it is capable of favorable anodic oxidization and has a sufficient solubility to solute, but is preferably a solvent having one or more alcoholic hydroxy groups and/or one or more phenolic hydroxy groups or an aprotic organic solvent.
  • a solvent having one or more alcoholic hydroxy groups is preferable in terms of storage stability.
  • Examples of compounds having one or more alcoholic hydroxy groups include a monohydric alcohol such as methanol, ethanol, propanol, isopropanol, 1-butanol, 2-ethyl-1-hexanol, and cyclohexanol; a dihydric alcohol such as ethylene glycol, propylene glycol, butane-1, 4-diol , diethylene glycol, triethylene glycol, and tetraethylene glycol; and a trihydric or higher polyhydric alcohol such as glycerin and pentaerythritol. It is also possible to use a solvent having a functional group other than an alcoholic hydroxy group in a molecule.
  • a monohydric alcohol such as methanol, ethanol, propanol, isopropanol, 1-butanol, 2-ethyl-1-hexanol, and cyclohexanol
  • a dihydric alcohol such as ethylene glycol, propylene glycol
  • a compound having two or more alcoholic hydroxy groups in terms of miscibility with water and vapor pressure more preferably a dihydric alcohol and a trihydric alcohol, and particularly preferably ethylene glycol, propylene glycol, and diethylene glycol.
  • the compounds having alcoholic hydroxy groups and/or phenolic hydroxy groups may have other functional groups in the molecule.
  • a solvent having alkoxy groups as well as alcoholic hydroxy groups, such as methyl cellosolve and cellosolve.
  • aprotic organic solvent either a polar solvent or a non-polar solvent may be used.
  • polar solvent examples include, but are not limited to, cyclic carboxylic acid esters such as ⁇ -butyrolactone, ⁇ -valerolactone, and ⁇ -valerolactone; chain carboxylic acid esters such as methyl acetate, ethyl acetate, and methyl propionate; cyclic carbonate esters such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate; chain carbonate esters such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; amides such as N-methylformamide, N-ethylformamide, N,N-dimethylformamide, N,N-diethylformamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpyrrolidone; nitriles such as acetonitrile, glutaronitrile, adiponitrile, methoxy acetonitrile, and 3-
  • non-polar solvent examples include, but are not limited to, hexane, toluene, and silicone oil.
  • the content of the water relative to the entire chemical conversion solution is normally 1% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more, and particularly preferably 15% by mass or more, while, as the upper limit, is normally 85% by mass or less, preferably 50% by mass or less, and particularly preferably 40% by mass or less.
  • the ratio of the water to the non-aqueous solvent is preferably 1% by mass or more, preferably 5% by mass or more, more preferably 7% by mass or more, and particularly preferably 10% by mass or more, while, as the upper limit, is normally 90% by mass or less, preferably 60% by mass or less, more preferably 50% by mass or less, and particularly preferably 40% by mass or less.
  • the chemical conversion solution may contain another additive as needed.
  • an additive for improving film formation properties and film properties of the anodic oxide film may be contained.
  • the additive is not particularly limited, but may be a known additive used in chemical conversion solutions, or one or more components may be selected and added from the components other than a component of the known additive.
  • the amount of the additive is not particularly limited, but may be any appropriate amount in view of its effect, cost, or the like.
  • a method of controlling current and voltage of the anodic oxidation is not particularly limited. It is possible to appropriately combine the conditions for forming the oxide film on the inner surface of an aluminum alloy vessel body 1.
  • anodic oxidation is preferably carried out at a constant current and at a constant voltage. That is, it is preferable that chemical conversion be carried out at a constant current until a predetermined chemical conversion voltage Vf is reached and, after the chemical conversion voltage is reached, anodic oxidation be carried out with the reached chemical conversion voltage maintained for a fixed time.
  • the current density is normally set to 0.001 mA/cm 2 or more, preferably to 0.01 mA/cm 2 or more.
  • the current density is normally set to 100 mA/cm 2 less, preferably to 10 mA/cm 2 or less.
  • the chemical conversion voltage Vf is normally set to 3 V or more, preferably to 10 V or more, and more preferably to 20 V or more. Since the thickness of the oxide film to be obtained is related to the chemical conversion voltage Vf, it is preferable to apply the above voltage or higher in order to give a certain thickness to the oxide film. However, it is normally set to 1000 V or less, preferably to 700 V or less, and more preferably to 500 V or less. Since the oxide film to be obtained has high dielectric properties, it is preferable to perform the anodic oxidation at the above voltage or less in order to form the high-quality oxide film without causing dielectric breakdown.
  • the temperature at the time of anodic oxidization is set within a range in which a chemical conversion solution stably exists as a solution.
  • the temperature is normally ⁇ 20° C. or higher, preferably 5° C. or higher, and more preferably 10° C. or higher.
  • the temperature is normally 150° C. or lower, preferably 100° C. or lower, and more preferably 80° C. or lower.
  • the constant voltage application in an appropriate time and perform heat treatment (annealing) in a subsequent step. It is desirable that the heat treatment be performed at a temperature of preferably 150° C. or higher, more preferably about 300° C., for 0.5 to one hour. Although a duration time of the residual electric current depends on the duration of the residual electric current, the constant voltage application may be continued if the duration time of the residual electric current is not too long. If the duration time is long, the constant voltage application may be switched to the heat treatment.
  • a current of normally 0.01 to 100 mA, preferably 0.1 to 10 mA, and more preferably 0.5 to 2 mA is caused to flow per square centimeter.
  • the voltage in the third step is set to, as already described, a voltage at which electrolysis of the chemical conversion solution does not occur.
  • the non-porous Al 2 O 3 anodic oxide film formed in the chemical conversion has an amorphous structure across the film and has almost no crystal grain boundaries or the life based on the knowledge of the present inventors. It is presumed that, by further adding a compound having the buffering action and using the non-aqueous solvent as a solvent, a very small quantity of carbon component is trapped into the anodic oxide film to weaken the Al—O binding strength, thereby stabilizing the amorphous structure of the entire film.
  • the temperature of the heat treatment is not particularly limited, but is normally 100° C. or higher, preferably 200° C. or higher, and more preferably 250° C. or higher. In order to sufficiently remove water on the surface of and inside the Al 2 O 3 anodic oxide film by the heat treatment, it is preferable to perform the treatment at a temperature not lower than the above-mentioned temperature. However, the temperature of the heat treatment is normally 600° C. or lower, preferably 550° C. or lower, and more preferably 500° C. or lower. It is preferable to perform the treatment at the above-mentioned temperature in order to hold the amorphous structure of the Al 2 O 3 anodic oxide film and maintain the flatness of the surface.
  • the heat treatment time is not particularly limited, and may be appropriately set in consideration of the surface roughness due to the heat treatment, the productivity, and the like.
  • the heat treatment time is normally one minute or more, preferably five minutes or more, and particularly preferably 15 minutes or more.
  • the heat treatment time is normally 180 minutes or less, preferably 120 minutes or less, more preferably 60 minutes or less. It is preferable to perform the heat treatment for the time not more than the above-mentioned time in order to maintain the Al 2 O 3 anodic oxide film structure and the surface flatness.
  • a gas atmosphere in a furnace during the annealing is not particularly limited, and normally, nitrogen, oxygen, a mixed gas thereof, or the like may appropriately be used.
  • the oxygen concentration of the atmosphere is preferably 18% by volume or more, more preferably 20% by volume or more, and most preferably 100% by volume.
  • the thickness of a base film is appropriately selected in view of smoothness of the PFA film-provided surface of the base material, an average particle size of the PFA powder to be used, and an average particle size of PFA particles diffused in the PFA coating.
  • the thickness of the base film be preferably 0.1 to 30 ⁇ m, more preferably 1 to 20 ⁇ m, and more preferably 2 to 15 ⁇ m.
  • PFA film formation surface a PFA film on the PFA film-provided surface of a workpiece or on the surface of the base film (collectively referred to as a “PFA film formation surface”) in the following manner, as in Experiments 1 and 2 and the example which will be described later.
  • the forms of PFA to be prepared for forming a PFA film include: a fine powder for use in electrostatic coating and a liquid as the general coating.
  • the fine powder for use in electrostatic coating is preferable since a coating film having a uniform thickness can be easily formed even if the workpiece is relatively complex and rough in shape.
  • spray coating is preferably used in the case of applying a liquid coating as the general coating.
  • dip coating, dip spin coating, roll coating, or spin flow coating is appropriately used.
  • Electrostatic powder coating or an electrostatic fluidized bed method is preferably used for applying a powder coating.
  • the PFA coating applied in such a manner is baked on the PFA film formation surface of the workpiece. At the same time, melting and remelting steps are given, and finally, a PFA coating film having a desirable smoothness can be obtained.
  • a method for forming a coating film on the PFA film formation surface of the workpiece depends on the type of base material, uses, and the type of selected coating, but preferably includes the following steps:
  • topcoat (PFA) coating In the case of providing a thick topcoat layer, the above steps of “(7) Topcoat (PFA) coating, (8) Predrying, and (9) Primary firing (melting)” are repeated to form a topcoat layer having a desirable thickness.
  • a coating thickness per process is appropriately set depending on the form (powder or coating) of PFA to be used, viscosity at the time of melting treatment, and in the case of coating, dispersion concentration and particle size, while in the case of powder, particle size of the powder, or the like.
  • a coating thickness of 1 to 100 ⁇ m is preferable.
  • a primary firing temperature in the first and intermediate coating is set as an intermediate primary firing temperature
  • a primary firing temperature in the final coating is set as a final primary firing temperature
  • the intermediate primary firing temperature and the final primary firing temperature are occasionally set to the same temperature, but it is desirable that the intermediate primary firing temperature preferably be set to a temperature lower than the final primary firing temperature.
  • Steps (3), (5), and (6) are occasionally omitted.
  • steps (3), (5), and (6) may be omitted.
  • primer coating allows the base material to firmly adhere to the topcoat via the primer, step (3) may be omitted.
  • the primary firing temperature and firing time in the present invention are important factors in the secondary firing to obtain a sufficient smoothness to achieve the objects of the present invention, and are appropriately determined depending on the PFA and metal workpiece to be used and determination of the primer to be adopted as needed.
  • the primary firing temperature and firing time in the present invention be set to a sufficient temperature and time to discharge impurities (low molecular weight components, components having unfluorinated terminal groups, products in the middle of synthesis, additives such as a surfactant, or the like) contained in PFA materials (available in the form of powder or coating) from the coated PFA film by the primary firing.
  • the upper limit of the primary firing temperature be set to a temperature at which the PFA having a molecular weight required for forming a PFA film giving a high smoothness is not decomposed (expressed as “PFA decomposition temperature”), or a temperature slightly higher than the decomposition temperature (expressed as “Th”). Th is determined in connection with the time for keeping the PFA coating film at the primary firing temperature.
  • Th in the present invention is preferably set to a temperature higher than the melting point of the PFA to be used by 30° to 70° C. If the set temperature is too low, a sufficient smoothness may not be obtained in the secondary firing, while if the set temperature is too high, decomposition of the PFA may be promoted. It is desirable to set a temperature of preferably 35° to 60° C., more preferably 40° to 50° C.
  • the primary firing time in the present invention consists of a time required to increase the temperature up to the primary firing temperature (primary firing heat-up time) and a time required to hold the primary firing temperature (primary firing temperature holding time).
  • the heat-up speed is controlled by a control device so that heat is equally transmitted across the PFA coating film and the PFA coating film is uniformly fired.
  • the entire free surface of the PFA coating film is controlled to be dissolved as uniformly as possible to minimize the visual recognition of positional nonuniformity.
  • the primary firing temperature holding time varies depending on the thickness and size of the PFA coating film
  • the primary firing temperature holding time is appropriately set each time based on the thickness and size of the PFA coating film.
  • the primary firing temperature holding time is set to preferably 10 to 50 minutes, more preferably 15 to 40 minutes.
  • the primary firing is performed in a mixed gas atmosphere of a noble gas and oxygen, such as a gas atmosphere of 20% by volume of O 2 /Ar.
  • a mixed gas of a noble gas and oxygen as the atmosphere gas in the primary firing, but the atmosphere gas in the present invention is not limited thereto.
  • An oxygen gas alone or a mixed gas of nitrogen and oxygen may be used.
  • a sample is cooled to a temperature not higher than the melting point of the PFA to be used (expressed as “Tl”) and solidified (primary cooling and solidification).
  • Tl the melting point of the PFA to be used
  • a desirable primary firing temperature is appropriately selected within the above range relative to the lowest temperature in the temperature range of the various melting points.
  • the heat-up speed from the temperature Tl (primary cooling and solidification temperature) below the melting point up to the secondary firing temperature and the holding time for keeping the secondary firing temperature are set so as to ensure a sufficient smoothness of the free surface of the PFA film to be obtained after the secondary cooling down to room temperature.
  • the secondary firing temperature is a temperature required for remelting the solidified PFA film after the primary firing and for promoting the smoothing of the PFA film during the solidification after the process in which the temperature is lowered to room temperature at which the PFA coating film is subjected to the next treatment after the primary firing.
  • the secondary firing is preferably performed at a high temperature equal to the melting point of the PFA to be used or at most 15° C. higher than the melting point. More preferably, the secondary firing is performed at a temperature equal to the melting point of the PFA to be used or slightly lower or higher than the melting point.
  • the melting and remelting steps will be described.
  • Rf in the structural formula 1 is “—CF 2 CF 2 CF 3 ” (the melting point is 310° C.)
  • the PFA film formation surface of the workpiece is coated with PFA fine powder by using electrostatic coating to form a PFA film having a predetermined thickness, heated to 345° C. at a programmed heating rate, and held for 30 minutes at a temperature of 345° C. (melting step).
  • the melting step is performed in a gas atmosphere of 20% by volume of O 2 /Ar. Then, the atmosphere is switched to an atmosphere of 100% by volume of argon, and the temperature is lowered to 280° C.
  • the PFA film is heated again to 310° C. at a predetermined rate (remelting step) and the temperature is held at 310° C. for 30 minutes. After holding the temperature at 310° C. for 30 minutes, heating is stopped and the PFA film is left by itself until the temperature is lowered to room temperature. After such melting and remelting steps, a PFA film having a free surface of an excellent smoothness can be obtained.
  • the melting starts at a temperature between 295° and 305° C., although it is said that the melting point is 310° C. Accordingly, as the temperature in the remelting step, a temperature in the range of 295° to 315° C. can be selected. It is preferable to select a temperature in the range of 305° to 315° C.
  • the largest smoothness can be obtained at a temperature of 310° C. or slightly lower or higher than the melting point of 310° C.
  • base materials 1 and 2 Two plate-like SUS-based materials (SUS316L-EP: 10 ⁇ 10 mm 2 , thickness: 2 mm) (base materials 1 and 2) were prepared on which predetermined cleaning was performed after mirror polishing. Surface smoothness of mirror finished surfaces of these base materials was measured by using a commercially available profilometer (Dektak 6M available from Veeco Instruments Inc.). Both base materials had a surface roughness Ra of 0.006 ⁇ m.
  • Ni film thickness: 2 ⁇ m
  • the base material 1 was immersed in a commercially available activation liquid (OPC-505 Accelerator (trademark) available from OKUNO CHEMICAL INDUSTRIES CO., LTD.) at 35° C. for five minutes. Then, the base material 1 was taken out of the activation liquid and its mirror finished surface was sufficiently cleaned with ultrapure water for semiconductors.
  • OPC-505 Accelerator (trademark) available from OKUNO CHEMICAL INDUSTRIES CO., LTD.
  • the base material 1 treated in the above manner was immersed in the electroless plating solution (A) for 70 minutes. Then, the terse material 1 was taken out of the electroless plating solution (A) and sufficiently cleaned with ultrapure water for semiconductors. In visual observation, the Ni film was uniformly formed on the entire mirror finished surface, and its free surface was extremely smooth when touched by fingers.
  • the base materials 1 and 2 on which the Ni film was provided in the above manner were immersed for degreasing in the commercially available degreasing agent (OPC-370 Condiclean M (trademark) available from OKUNO CHEMICAL INDUSTRIES CO., LTD.) at 60° C. for five minutes. Then, the base materials 1 and 2 were taken out of the degreasing agent and sufficiently cleaned with ultrapure water for semiconductors.
  • a precoat material was applied and dried under the following conditions:
  • a film of PFA powder was provided to have a thickness of 20 ⁇ m by using electrostatic coating under the following conditions, and then, the base materials were placed in a vessel made of quartz (quartz vessel) installed in an infrared heating furnace.
  • thermocouple In the infrared heating furnace, a thermocouple is installed on the periphery of the quarts vessel, and an output of an infrared light source is controlled by a temperature controller to obtain a programmed temperature based on the temperature information from the thermocouple.
  • the temperature was kept at 345° C. for 30 minutes.
  • the atmosphere was switched to a gas of 100% by volume of argon, and the gas was allowed to flow at a flow rate of 5 l/min for ten minutes to have the temperature in the quartz vessel reach 280° C. This condition was kept for 30 minutes.
  • the flow rate of the gas of 100% by volume of argon was switched to 1 l/min, and the temperature was raised from 280° to 310° C. in six minutes.
  • the output of the infrared light source was controlled, and the condition was kept for 30 minutes.
  • the quartz vessel was taken outside, and the base materials 1 and 2 were placed in a desiccator to cool naturally.
  • the base materials 1 and 2 were set on a surface roughness measurement device to measure smoothness of the PFA surface.
  • the PFA film on the base material 1 and the PFA film on the base material 2 were called a sample 1-1 and a sample 1-2, respectively.
  • the free surface of the PFA film of each sample was divided into five for each side per 2 cm in a horizontal direction (referred to as “in an X-axis direction” for convenience), and the divided surfaces of the sample were measured on the straight line from one end to the other end.
  • the free surface of the PFA film of each sample was divided into five per 2 cm also in a vertical direction (referred to as “in a Y-axis direction” for convenience), and smoothness was measured for each divided area (see FIG. 3 ).
  • Examples 3-1 and 3-2 Two plate-like SUS substrates (SUS316L-EP: 2 cm ⁇ 5 cm) (samples 3-1 and 3-2) were prepared on which mirror polishing was performed, and an Ni film was provided on the mirror-polished surfaces of the SUS substrates in the same manner as in Experiment 1. Surface smoothness of the mirror-polished surfaces of the two SUS substrates and surface smoothness of the Ni film surface were measured in the same manner as in Experiment 1, and substantially the same results as those in Experiment 1 were obtained.
  • Ni films on the two SUS substrates each having the Ni film provided thereon were coated with PFA by outsourcing according to the specification.
  • the SUS substrates on which a quartz grating was coated with PFA powder by electrostatic coating were placed in the quartz vessel, and firing was performed on the two samples in the following manner:
  • the temperature program is shown in the following table.
  • the female and male screw rotors thus processed were installed in the stator instead of female and male screw rotors of a screw pump used for an operating test, and the pump was assembled.
  • the width of the gap between the inner wall surface of the stator and the top end surface of the screw rotor was 20 ⁇ m.
  • the pump of the present invention prepared in this manner was tested for its pumping performance and the longtime, continuous rotation. The results are shown in Table 5.
  • the pumps having screw rotors of samples 11 to 16 individually installed therein each maintained their initial smooth rotation even by the continuous rotation at 10,000 rotation/sec for 3,000 hours, without any trouble.
  • the pump having the screw rotor of sample 17 installed therein did not have any trouble in rotation even by the continuous rotation at 10,000 rotation/sec for 3,000 hours within a range of general use as a pump.
  • the pump having the screw rotor of sample 18 installed therein did not have any trouble in rotation even by the continuous rotation at 5,000 rotation/sec for 3,000 hours within a range of general use as a pump.
  • the pump developed a trouble in rotation after a lapse of 1,000 hours. Accordingly, the rotation was canceled immediately.
  • the pump having the screw rotor of sample 19 installed therein developed a trouble in rotation after a lapse of 1,000 hours by the continuous rotation at 5,000 rotation/sec. Accordingly, the operation was canceled immediately.
  • the pumping performance is particularly high as compared to a conventional pump of a similar type and it is possible to maintain a certain pumping performance without causing erroneous rotation by high-speed, continuous, and longtime operation, and therefore maintenance and inspection of the pump can be significantly reduced. Accordingly, since the production cost can be reduced, the present invention has a high industrial applicability.

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WO2013011635A1 (fr) 2013-01-24
US20150225593A1 (en) 2015-08-13
JPWO2013011635A1 (ja) 2015-02-23
US9957406B2 (en) 2018-05-01

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