Titanium porous body and titanium porous body manufacturing method

Abstract

This titanium porous body according to the present invention is in a sheet shape and has a thickness t of 0.50 mm or less. The projected area of the surface on a plane is 28000 mm2 or more, the irreversible deformation amount after pressurization at 100 MPa is 1.0% or less, the air permeance P (μm / Pa·S) satisfies a relationship of P ≥ I with an index value I, and the index value I is represented as I = 1.6 × (1 / t)1.3.

Description

Titanium porous body and method for producing titanium porous body

[0001] The present invention relates to a sheet-shaped porous titanium body and a method for producing the porous titanium body.

[0002] Porous titanium bodies produced by sintering titanium powder or the like have air or liquid permeability due to their fine pores, electrical conductivity, and also high corrosion resistance due to the formation of a passivation film on the surface.

[0003] Porous titanium having such properties is being considered for use in porous transport layers (PTLs) in polymer electrolyte membrane (PEM)-type water electrolysis devices, which are in environments where corrosion may occur. In particular, hydrogen produced in PEM-type or other water electrolysis devices using electricity derived from renewable energy is called "green hydrogen," and great expectations are being placed on it in recent years as efforts to realize a decarbonized society accelerate.

[0004] In this regard, Patent Document 1 discloses a "method for producing a porous titanium sintered body, comprising: a slurry preparation step of mixing at least one of titanium powder and titanium hydride powder with an organic binder, a foaming agent, a plasticizer, water, and, if necessary, a surfactant to prepare a slurry; a molding step of applying the slurry to a first support to form a molded body; a foaming step of heating and drying the molded body to foam it, to produce a foamed molded body; a degreasing step of heating and degreasing the foamed molded body that has been separated from the first support and placed on a second support; a first sintering step of heating the degreased foamed molded body in a non-oxidizing atmosphere to produce a conductive primary sintered body; and a second sintering step of sintering the primary sintered body in a non-oxidizing atmosphere at a temperature higher than that in the first sintering step to produce a porous titanium sintered body."

[0005] JP 2009-102701 A

[0006] In the above-mentioned water electrolysis apparatus, from the viewpoint of miniaturization of the apparatus, a thin sheet-like titanium porous body that has excellent compression resistance is sometimes required. This is because a titanium porous body with poor compression resistance will not be able to maintain the required thickness or shape against the compressive force that may act when incorporated into an apparatus such as a PEM-type water electrolysis apparatus, and there is a concern that the air permeability or liquid permeability will be reduced.

[0007] One way to obtain a porous titanium body with high compression resistance is to increase the sintering temperature during production. However, when producing a porous titanium body with a relatively large surface area (projected area on a plane), if the heating temperature during sintering is raised to a certain extent, wrinkles will appear on the surface of the sintered porous titanium body, making it more likely to produce defective products and reducing production yields.

[0008] Patent Document 1 does not consider at all how to improve the compression resistance of the porous titanium body.

[0009] An object of the present invention is to provide a porous titanium body that has a relatively large surface area, is excellent in compression resistance, and is capable of exhibiting the required air and liquid permeability, and a method for producing such a porous titanium body that can be produced with a relatively high yield.

[0010] After extensive research, the inventors devised a method for sequentially drying a paste containing titanium powder, removing the binder from the resulting molded body, and sintering the titanium powder. The method involves inverting the molded body after drying to remove the binder. This allows the organic binder, which accumulates on the lower mounting surface of the paste during drying, to be positioned on the upper side of the molded body after the drying process. This allows the organic binder to volatilize efficiently during debinding. As a result, even if the molded body is heated to a relatively high temperature during sintering, defects such as surface wrinkles in the sintered porous titanium body can be suppressed, improving yield. Furthermore, the porous titanium body produced in this manner has excellent compression resistance and relatively high air and liquid permeability. The organic binder accumulates on the lower mounting surface of the paste during drying. This is thought to be due to the organic solvent preferentially volatilizing from the upper side (opposite the mounting surface) during drying. As drying progresses, the organic binder from the upper side dissolves and accumulates in the organic solvent on the lower side, which is less likely to volatilize. If the binder is then removed without turning the compact over, the organic binder on the lower side will remain, preventing the titanium powder from coming into close proximity or contact during sintering, resulting in the formation of slightly larger holes, which is thought to make it difficult to improve compression resistance.

[0011] The porous titanium body of the present invention is in the form of a sheet, having a thickness t of 0.50 mm or less and a surface area projected onto a flat surface of 28,000 mm. 2 or more, the irreversible deformation amount after pressurization at 100 MPa is 1.0% or less, the air permeability P (μm / Pa S) satisfies the relationship P≧I with the index value I, and the index value I is I=1.6×(1 / t) 1.3 It is expressed as follows.

[0012] The titanium porous body preferably has a titanium content of 97% by mass or more and an oxygen content of 0.9% by mass or more and 2.0% by mass or less.

[0013] The titanium porous body has a surface with a projected area of ​​600,000 mm 2 It is preferable that:

[0014] The porous titanium body preferably has a thickness t of 0.04 mm or more.

[0015] The porous titanium body preferably has a ten-point average roughness Rz of at least one surface of 9 μm or less.

[0016] The method for producing a titanium porous body of this invention is a method for producing a sheet-like titanium porous body, and includes the steps of: a drying step in which a paste containing titanium powder, an organic binder, and an organic solvent, but not containing water or a foaming agent, is heated on a mounting surface to dry, thereby obtaining a sheet-like molded body; a binder removal step in which the molded body is heated on the mounting surface in an orientation reversed from the orientation on the mounting surface in the drying step, thereby volatilizing the organic binder in the molded body; and a sintering step in which the molded body after the binder removal step is heated to sinter the titanium powder in the molded body, and the sheet-like titanium porous body has a thickness of 0.50 mm or less and a projected area on a surface plane of 28,000 mm. 2 The porous titanium body described above is produced.

[0017] In the above manufacturing method, it is preferable to use a pulverized titanium powder having an average particle size D50 of 10 μm or more and 45 μm or less. Alternatively, it is possible to use a pulverized titanium powder having an average particle size D50 of 10 μm or more and 20 μm or less.

[0018] In the drying step, the paste is preferably heated to a temperature of 80° C. or higher and 150° C. or lower in an oxygen-containing atmosphere.

[0019] In the binder removal step, the compact is preferably heated to a temperature of 320° C. or higher and 450° C. or lower in an oxygen-containing atmosphere.

[0020] In the sintering step, the compact is preferably heated in a reduced pressure atmosphere or an inert gas atmosphere.

[0021] In the sintering step, the compact is preferably heated to 750°C to 1000°C, and in the sintering step, the compact is preferably heated to 775°C to 950°C.

[0022] The porous titanium body of the present invention has a relatively large surface area, is excellent in compression resistance, and exhibits the required air and liquid permeability. The method for producing the porous titanium body of the present invention allows such porous titanium bodies to be produced with a relatively high yield.

[0023] The following is a detailed description of an embodiment of the present invention. The porous titanium body of one embodiment of the present invention is in the form of a sheet having a thickness t of 0.50 mm or less, and a projected area (apparent area in plan view) of 28,000 mm when the surface is projected onto a plane. 2 This porous titanium body has an irreversible deformation of 1.0% or less after being pressurized at 100 MPa, and the air permeability P (μm / Pa·S) satisfies the relationship P≧I with the index value I, so it has excellent compression resistance and can exhibit the required air and liquid permeability. The index value I depends on the thickness t (mm), and is expressed as I=1.6×(1 / t) 1.3 It is expressed as:

[0024] To produce such a titanium porous body, for example, a paste containing titanium powder is dried, followed by a binder removal process and a titanium powder sintering process. In the drying process, the paste is heated and dried on a mounting surface to obtain a sheet-like molded body. In the manufacturing method of this embodiment, in the subsequent binder removal process, the molded body is heated on the mounting surface in an inverted orientation relative to the orientation on the mounting surface in the drying process.

[0025] The inventors conducted various studies and came to the following conjecture. That is, when the paste is heated on the mounting surface in the drying process, as mentioned above, much of the organic binder in the paste migrates to the lower mounting surface, and a large amount of organic binder may be present on the lower side of the molded body obtained in the drying process. If the binder removal process is carried out in this orientation, the organic binder on the lower side of the molded body may not be sufficiently removed and may remain. If the molded body is then heated in the sintering process, the titanium porous body is likely to become a defective product due to the formation of wrinkles or ridges on its surface caused by the evaporation of the organic binder during the sintering process. This is particularly true for porous titanium bodies with a surface projection area of ​​28,000 mm2 or less. 2 This problem becomes apparent when producing a porous titanium body having a size larger than 1000 mm or larger. Furthermore, in this case, the organic binder remaining on the lower side during sintering prevents the titanium powder from bonding together, which tends to result in the formation of relatively large holes (pores) there, and the compression resistance of the porous titanium body cannot be significantly improved.

[0026] In contrast, as described above, by turning the compact over after the drying process, the organic binder that was located on the lower side of the compact after the drying process is now located on the upper side (i.e., the side opposite the mounting surface), making it easier to volatilize during the subsequent binder removal process. This reduces the occurrence of defective products during the sintering process and improves production yield. Furthermore, because the organic binder volatilizes well during the binder removal process, the formation of relatively large holes (pores) due to residual organic binder is suppressed during the sintering process. Furthermore, the organic binder is well separated from the compact used in the sintering process, and the titanium powder particles are properly positioned in the compact during sintering, ensuring the required air permeability and liquid permeability. This results in a porous titanium body that is excellent in compression resistance and maintains the required air permeability and liquid permeability even during compression.

[0027] (Titanium porous body) The titanium porous body is made of titanium. If it is made of titanium, a titanium porous body having high electrical conductivity at a certain relative density can be obtained. The titanium content of the titanium porous body is preferably 97% by mass or more, and more preferably 98% by mass or more. The upper limit of the titanium content is not limited to this, but may be, for example, 99.8% by mass or less, or 99% by mass or less. This titanium content refers to the purity of titanium taking into account not only the metal components but also impurities such as gas components such as oxygen. Therefore, the titanium content can be calculated by subtracting the total content of impurities, including metal components and gas components, from 100% by mass.

[0028] The titanium porous body may contain Fe as an impurity, and the Fe content may be, for example, 0.25 mass% or less. The titanium porous body may also contain Ni, Cr, Al, Cu, Zn, and Sn as unavoidable impurities resulting from the manufacturing process. It is preferable that the content of each of Ni, Cr, Al, Cu, Zn, and Sn is less than 0.10 mass%, and that the total content of these elements is less than 0.30 mass%.

[0029] The oxygen content of the porous titanium body is not particularly limited, but may be 0.9% by mass or more and 2.0% by mass or less. If the drying step and / or the binder removal step are carried out in an oxygen-containing atmosphere, as in the production method described below, the oxygen content of the porous titanium body may increase to some extent. The oxygen content can be measured by inert gas fusion-infrared absorption spectroscopy.

[0030] The titanium porous body may have a purity equivalent to pure titanium grades 1 to 4, typically grades 1 to 2, of JIS H4600 (2012), excluding the oxygen content.

[0031] The thickness t of the sheet-shaped porous titanium body is 0.50 mm or less, and may be 0.04 mm or more. For example, a porous titanium body with such a thickness t may be required for the porous transport layer of a PEM-type water electrolysis device. If the thickness t is too large, the PEM-type water electrolysis device may become large. The thickness t of the porous titanium body is, for example, 0.40 mm or less, 0.35 mm or less, 0.30 mm or less, 0.25 mm or less, or 0.20 mm or less, and may be 0.04 mm or more, or 0.08 mm or more.

[0032] The thickness t is measured at five points, four points on the periphery and one point in the center, of the titanium porous body using a digital thickness gauge with a flat probe having a diameter of 10 mm and a measurement accuracy of 0.001 to 0.01 mm, such as a Mitutoyo digital thickness gauge (model number 547-321), and is taken as the average of these measurements. When the sheet-like titanium porous body has a rectangular shape in plan view, the four peripheral points are the four corners.

[0033] The projected surface area of ​​the sheet-shaped porous titanium body in plan view is 28,000 mm 2 or more, for example, 600,000 mm 2 The following may be used: A porous titanium body with a surface projected area that is relatively large can be cut and used as needed, making it suitable for mass production. On the other hand, attempts to manufacture porous titanium bodies with a large surface projected area tend to result in a large number of defective products, but the embodiments described here can prevent the occurrence of such defective products. The projected area here refers to the area of ​​the surface of the porous titanium body projected onto a plane.

[0034] The term "sheet-like" in reference to a porous titanium body refers to a plate or foil shape having a thickness small relative to its dimensions in a plan view. The shape of the porous titanium body in a plan view is not particularly limited, but may be a square, a rectangle with an aspect ratio of 1:1 to 1:3, a rhombus, or other polygonal shape. The corners of a polygonal porous titanium body may be chamfered.

[0035] Porous titanium bodies are formed by bonding titanium powder particles together, and have a three-dimensional network structure in which pores are formed between the bonded titanium powder particles. As an example, porous titanium bodies may have a skeleton with a three-dimensional network structure similar to that of titanium sponge. Note that porous titanium bodies manufactured using titanium fibers tend to have a three-dimensional network structure similar to that of nonwoven fabric. In many cases, the interior of the skeleton of porous titanium bodies, which is made up of titanium powder particles bonded together, is solid rather than hollow.

[0036] When the porous titanium body is subjected to a compression operation of 100 MPa in the thickness direction for 3 minutes, followed by unloading, twice, the irreversible deformation, which is the ratio of change in thickness before and after the operation, is 1.0% or less.

[0037] As a result, when the porous titanium body is incorporated into a device such as a PEM water electrolysis device, it will maintain a certain degree of thickness and shape when a compressive force is applied, and will be able to exhibit the required air and liquid permeability. The amount of irreversible deformation is preferably 1.0% or less. The amount of irreversible deformation may be, for example, 0.6% or less, or may be, for example, 0.5% or less. The smaller the amount of irreversible deformation, the better, so the lower limit is not particularly limited and can be set appropriately depending on the purpose.

[0038] More specifically, the irreversible deformation amount Dc is calculated by measuring the thickness T1 of the porous titanium body before applying a pressure of 100 MPa and the thickness T2 of the porous titanium body after applying and unloading the pressure, using the formula: Dc = (1 - T2 / T1) x 100. To measure the irreversible deformation amount Dc, the thickness T1 of a square sample of the porous titanium body (projected area 20 mm x 20 mm) in plan view is first measured. The sample is then sandwiched between the flat surfaces of two flat plates or the like in the thickness direction, and the flat surfaces are displaced toward each other, so that a pressure of 100 MPa is applied evenly to the surface of the sample in the thickness direction for three minutes. The displacement rate can be constant at 0.1 mm / min. After applying the pressure, the pressure is released. This pressure application and unloading operation is repeated twice, for a total of two times. The thickness T2 of the sample is then measured after removal from the flat surfaces. Here, various compression testing devices or other devices capable of applying pressure to the sample can be used. To measure the thicknesses T1 and T2 of the sample, the thickness is measured at one point at the center of gravity of the sample in a plan view. This measurement is performed on five different samples, and the average value is used as the irreversible deformation amount Dc.

[0039] A porous titanium body with a relatively high air permeability P can be said to have good air permeability or liquid permeability. However, the air permeability P of a porous titanium body can vary depending on its thickness. Therefore, the air permeability or liquid permeability of a porous titanium body is evaluated here by comparing the air permeability P of the porous titanium body with an index value I that depends on the thickness t (mm). The index value I is calculated using the formula: I = 1.6 × (1 / t) 1.3 The value is expressed as:

[0040] Specifically, the porous titanium body of this embodiment has an air permeability P that satisfies the relationship P≧I with the index value I. Such a porous titanium body can exhibit good air and liquid permeability, particularly in a PEM-type water electrolysis device.

[0041] The air permeability P (μm / Pa·S) is measured in accordance with the Gurley tester method, but here the volume of air passed through the titanium porous body is 300 mL. Specifically, for example, a Gurley densometer conforming to ISO 5635-5, such as a Gurley densometer (product number: G-B3C) manufactured by Toyo Seiki Seisakusho, is used to measure the time (s) required for the air to pass through a measurement hole diameter of 6 mm and an air volume of 300 mL, and the ISO air permeability (μm / Pa·S) thus obtained is defined as the air permeability P.

[0042] The ten-point mean roughness Rz of at least one surface of the porous titanium body is preferably 9 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less. The ten-point mean roughness Rz of the surface is measured, for example, using a Mitutoyo SJ-210 in accordance with JIS B0601 (2001).

[0043] The porous titanium body is particularly suitable for use in a porous transport layer of a PEM-type water electrolysis device. A PEM-type water electrolysis device may include an anode, a cathode, an electrolyte membrane such as a perfluorocarbon sulfonic acid membrane disposed between the anode and the cathode and having electrode catalyst layers of a platinum group metal or the like on both sides, and a porous transport layer disposed between each electrode catalyst layer of the electrolyte membrane and the anode or cathode.

[0044] In a PEM-type water electrolysis device, when water is supplied to the anode and a voltage is applied, the water moves through the porous transport layer on the anode side and reaches the electrode catalyst layer, where it decomposes to produce oxygen and protons (H + The protons pass through the anode electrolyte membrane to move from the anode to the cathode, where they acquire electrons at the cathode catalyst layer, generating hydrogen at the cathode. Meanwhile, oxygen passes through the porous transport layer to the discharge channel and is discharged outside the device.

[0045] In such a PEM-type water electrolysis device, the space where the porous transport layer is placed, particularly on the anode side, is subject to strongly acidic and strongly oxidizing conditions, but a titanium porous body with high corrosion resistance can be used successfully as a porous transport layer in such an extremely harsh environment. Note that the titanium porous body of this embodiment may have a large number of fine pores formed on at least one surface, and may be able to achieve a surface with a small ten-point average roughness Rz, which may prevent damage to the electrolyte membrane when the surface side is pressed against the electrolyte membrane in a PEM-type water electrolysis device.

[0046] In addition to the PEM-type water electrolysis devices described above, the use of porous titanium materials in organic electrolysis synthesis using PEM-type reactors is also being considered. In such devices, electrolysis is carried out by passing protons through a proton exchange membrane. The porous titanium materials described here may also be well suited for organic electrolysis synthesis using PEM-type reactors, and are considered to be usable as a porous transport layer (PTL) on the anode side of electrolysis devices that use proton exchange membranes.

[0047] (Manufacturing Method) The above-described porous titanium body can be manufactured, for example, by carrying out the following steps in this order: paste preparation, paste application, drying, binder removal, and sintering. However, if the paste has already been prepared or applied in sheet form, the paste preparation and paste application steps may be omitted.

[0048] First, in a paste preparation step, a paste containing titanium powder, an organic binder, and an organic solvent is prepared.

[0049] The average particle size D50 of the titanium powder contained in the paste can be 10 μm or more and 45 μm or less. The average particle size D50 of the titanium powder can also be 10 μm or more and 30 μm or less, or 10 μm or more and 20 μm or less. This allows the use of relatively inexpensive titanium powder, suppressing increases in production costs and facilitating handling of the titanium powder. Using titanium powder with a small average particle size D50 tends to smooth the surface of the sheet-shaped titanium porous body. Furthermore, by producing a titanium porous body using the production conditions described herein, it is possible to produce a titanium porous body with a small amount of irreversible deformation while ensuring the required air or liquid permeability. The average particle size D50 refers to the particle size at which the cumulative volume distribution obtained by laser diffraction scattering reaches 50%.

[0050] High-purity titanium powder is preferred, and pure titanium powder can be used. The titanium powder may have a titanium content of 99% by mass or more. The titanium powder can be a pulverized powder, a spherical powder such as atomized powder, or any other powder. Titanium hydride powder obtained by hydrogenating and pulverizing a titanium raw material such as sponge titanium can also be used. In this case, the hydrogen content of the titanium hydride powder is preferably 5% by mass or less. When using titanium hydride powder, dehydrogenation treatment may be performed between the binder removal step and the sintering step described below in a reduced pressure atmosphere such as vacuum at a temperature range of 500°C to 650°C. Furthermore, hydrogenated and dehydrogenated titanium powder (so-called HDH powder) obtained by dehydrogenating the above-mentioned titanium hydride powder can also be used.

[0051] The organic binder used in the paste can be selected from a variety of materials, including methyl cellulose, polyvinyl alcohol, ethyl cellulose, acrylic, and polyvinyl butyral. Hydrophobic organic binders are preferred. However, they are not limited to the materials listed here. The organic solvent is alcohol (ethanol, isopropanol, terpineol, butyl carbitol, etc.). For example, the organic binder may be polyvinyl butyral and the organic solvent may be isopropyl alcohol. The paste may further contain a plasticizer (glycerin, ethylene glycol, etc.) or a surfactant (alkylbenzene sulfonate, etc.).

[0052] The paste does not contain water as a solvent. It is also preferable that the paste does not contain a foaming agent. This is because, if the paste contains water, aggregation of the titanium powder in the paste due to the difference in drying behavior between organic solvents and water during drying and the generation of pinholes on the surface of the titanium porous body are suppressed. Furthermore, if the paste does not contain a foaming agent, large localized voids caused by foaming of the foaming agent are not formed in the titanium porous body. As a result, the titanium porous body is likely to have a smooth surface and is less likely to crack during handling. Therefore, a foaming treatment that generates bubbles in the paste is not performed here. It is sufficient that the paste does not contain water as a solvent, and the inclusion of water that may be unintentionally mixed into the paste due to moisture absorption or the like is permitted.

[0053] The paste can be prepared by mixing the titanium powder, organic binder, organic solvent, and the like as described above using, for example, a mixer with an agitator, a rotary mixer, a triple roll mill, etc. At this time, the mixture may be pulverized using a vibration mill, a bead mill, or other pulverizing mixer, etc.

[0054] In the paste application step, the paste is applied relatively thinly onto a mounting surface of a substrate or the like. A release layer may be provided on the substrate in advance. In this case, the paste is applied onto the substrate via the release layer. When a release layer is provided on the substrate, it becomes easier to separate the molded body obtained by drying the paste from the substrate after the drying step.

[0055] The substrate is preferably a resin substrate, which is relatively inexpensive and readily available. Resin substrates also have the advantage of being flexible and therefore easy to handle. Specific materials for the resin substrate include polyesters such as PET (polyethylene terephthalate) and PEN (polyethylene naphthalate), and polyvinyls such as polyethylene, polypropylene, polystyrene, and polyvinyl alcohol. PET is particularly preferred because it is inexpensive and allows the molded body to be easily separated from the substrate after the drying process.

[0056] It is optional to provide a release layer on the substrate. If a release layer is provided, a silicone coating or the like can be used as the release layer. For example, a release layer can be provided on the substrate by selecting a substrate pre-coated with such a material, such as Cerapeel (registered trademark) manufactured by Toray Industries, Inc. By providing a release layer on the substrate, the thin sheet-like molded product obtained after the drying process can be easily separated from the substrate.

[0057] In the drying step, the paste is dried on the mounting surface in, for example, a furnace or a dryer, etc. This causes the organic solvent in the paste to evaporate, and a sheet-like molded body is obtained on the substrate.

[0058] The heating temperature during drying can be 80°C or higher and 150°C or lower. Alternatively, the heating temperature during drying can be 100°C or higher and 140°C or lower. By drying the paste at a temperature within this range, it is possible to complete drying in a relatively short time while suppressing boiling of components such as organic solvents in the paste. The drying time is not particularly limited and may be determined appropriately, and can be, for example, 5 minutes or higher and 300 minutes or lower. Drying is preferably carried out in an oxygen-containing atmosphere, such as air. This can prevent an increase in manufacturing costs.

[0059] After the drying step is completed, the molded body obtained by drying the paste is separated from the mounting surface by peeling or the like, and the molded body is turned over, followed by the binder removal step. In other words, the term "turning over the molded body" as used herein means turning the surface of the molded body that faced the lower mounting surface in the drying step over to face the upper side in the binder removal step, and also turning the surface that faced the upper side in the drying step over to face the lower mounting surface in the binder removal step.

[0060] In the drying process, the organic binder tends to be concentrated on the lower mounting surface where the organic solvent in the paste is less likely to volatilize, but by turning the compact over, the organic binder is located on the upper side and volatilizes well in the debinding process, which makes it possible to suppress the generation of defective products after the sintering process described below, in which the compact is heated at a relatively high temperature.

[0061] In the drying process and the binder removal process, the same substrate can be used as the member on which the paste or the molded body is placed, but different substrates can also be used. In this way, the placement surface in the drying process and the placement surface in the binder removal process do not necessarily coincide.

[0062] Next, in the binder removal step, the compact is heated in a furnace to volatilize and remove the organic binder in the compact. By turning the compact upside down as described above, the organic binder located on the upper side of the compact can be efficiently volatilized, and the organic binder remaining after the binder removal step is reduced.

[0063] In the binder removal process, the compact is preferably heated to a temperature of 320°C or higher and 450°C or lower, or 360°C or higher and 400°C or lower. This makes it possible to remove the organic binder while suppressing sintering of the titanium powder due to heating. In this way, the appropriate position of each titanium powder in the compact can be maintained. The heating time is not particularly limited, but may be set to 3 hours or higher and 12 hours or lower. The heating atmosphere is preferably an oxygen-containing atmosphere, such as air. It is presumed that an oxygen-containing atmosphere not only suppresses cost increases but also allows an oxide film to grow well on the surface of the titanium powder.

[0064] Thereafter, the compact that has undergone the binder removal step is subjected to a sintering step to sinter the titanium powder in the compact. In the sintering step, the compact is heated to a temperature of 750°C to 1000°C, preferably 775°C to 950°C. In the sintering step, the compact may be heated at the above temperature for 1 hour or more and 4 hours or less. The sintering atmosphere may be, for example, 1.0 x 10 -2 The atmosphere may be a vacuum or reduced pressure atmosphere of 10 Pa or less, or an inert gas atmosphere of Ar or He.

[0065] By carrying out the binder removal step in an oxygen-containing atmosphere and then carrying out the sintering step in a reduced pressure or inert gas atmosphere, the oxygen in the oxide film that grew on the surface of the titanium powder in the binder removal step is incorporated into the titanium powder in the sintering step, strengthening the sintered porous titanium body and resulting in a porous titanium body with excellent compression resistance. Note that if the sintering step is also carried out in an oxygen-containing atmosphere, the oxygen in the atmosphere will also be incorporated into the titanium powder in the sintering step, potentially resulting in an excessive oxygen content.

[0066] After the sintering step, a porous titanium body is obtained. As mentioned above, this porous titanium body has high compression resistance and can exhibit the required air and liquid permeability. In this case, the thickness is 0.50 mm or less, and the projected area of ​​the surface onto a flat surface is 28,000 mm. 2 The porous titanium body having the above dimensions is manufactured. In order to achieve these dimensions, the area and thickness of the paste to be applied in the paste application step can be adjusted.

[0067] Next, a prototype of the porous titanium body of the present invention was produced and its effects were confirmed, which will be described below. However, the description here is for illustrative purposes only and is not intended to be limiting.

[0068] A paste was prepared by mixing titanium powder (HDH powder) having an average particle size D50 shown in Table 1 and a titanium content of 99% by mass or more with polyvinyl butyral as an organic binder and isopropyl alcohol as an organic solvent. The paste prepared in this manner does not contain water or a foaming agent.

[0069] The paste was applied in the form of a sheet onto the mounting surface of a PET resin substrate, which was then dried to form a compact. This compact was then debindered and sintered to produce a porous titanium body having a rectangular shape in plan view (aspect ratio within the range of 1:1 to 1:3). Drying was performed by heating the paste to 120°C in an air atmosphere. Debindering was performed by heating the compact to 380°C in an air atmosphere. Sintering was performed in a vacuum atmosphere (1 x 10 -2 The heating temperature is as shown in Table 1.

[0070] In Examples 1 to 7, after drying, the molded body was peeled from the resin substrate and placed upside down on the mounting surface of a graphite setter, and then debindering was performed. In Comparative Examples 1 to 3, after drying, the molded body was peeled from the resin substrate, but was not turned upside down, and was placed on the mounting surface of a graphite setter in the same orientation as during drying, and then debindering was performed.

[0071] As a result, after sintering, Examples 1 to 7 and Comparative Example 2 produced porous titanium bodies with good flat surfaces, whereas Comparative Examples 1 and 3 produced porous titanium bodies with wrinkles that protruded from the surface, resulting in defective products. This shows that, in order to produce porous titanium bodies with a large projected area on a flat surface like Examples 1 to 7, the occurrence of defective products can be suppressed by turning the body over after drying and before removing the binder. The projected areas and thicknesses shown in Table 1 were measured according to the methods described above.

[0072] Furthermore, for each of the titanium porous bodies of Examples 1 to 7, the amount of irreversible deformation, air permeability P, and index value I were measured or calculated using the methods described above. The results are shown in Table 1. The titanium porous bodies of Examples 1 to 7 all had a titanium content of 97% by mass or more and an oxygen content in the range of 0.9% by mass or more and 2.0% by mass or less.

[0073] As shown in Table 1, all of the porous titanium bodies of Examples 1 to 7 had excellent compression resistance due to a sufficiently small amount of irreversible deformation, and P≧I, providing the required air or liquid permeability. This is thought to be due to the good volatilization of the organic binder in the binder removal process and the high heating temperature during sintering. In particular, in Examples 2 and 3, in which the heating temperature during sintering was further increased, and in Examples 6 and 7, in which titanium powder with a small average particle size D50 was used, the amount of irreversible deformation of the porous titanium bodies was smaller, and in some cases, as in Examples 6 and 7, it was essentially zero. Since the results for Examples 6 and 7 were below the lower limit of the measuring device, they were classified as "less than 0.4%." Comparative Example 2 was a porous titanium body with a small surface projected area.

[0074]

[0075] From the above, it has been suggested that this invention may enable the production, with high yield, of porous titanium bodies that have a relatively large surface area, excellent compression resistance, and the required air or liquid permeability.

Claims

1. A sheet-shaped porous titanium body having a thickness t of 0.50 mm or less and a projected area of ​​the surface on a flat surface of 28,000 mm 2 or more, the irreversible deformation amount after pressurization at 100 MPa is 1.0% or less, the air permeability P (μm / Pa·S) satisfies the relationship P≧I with the index value I, and the index value I is I=1.6×(1 / t) 1.3 The titanium porous body is represented by the formula:

2. A titanium porous body according to claim 1, having a titanium content of 97% by mass or more and an oxygen content of 0.9% by mass or more and 2.0% by mass or less.

3. The projected area of ​​the surface is 600,000 mm 2 3. The titanium porous body according to claim 1 or 2, wherein:

4. The titanium porous body according to claim 1 or 2, which has a thickness t of 0.04 mm or more.

5. A porous titanium body according to claim 1 or 2, wherein the ten-point average roughness Rz of at least one surface is 9 μm or less.

6. A method for producing a sheet-like porous titanium body, comprising: a drying step in which a paste containing titanium powder, an organic binder and an organic solvent, but not containing water or a foaming agent, is heated and dried on a mounting surface to obtain a sheet-like molded body; a binder removal step in which the molded body is heated on the mounting surface in an orientation inverted from the orientation on the mounting surface in the drying step to volatilize the organic binder in the molded body; and a sintering step in which the molded body after the binder removal step is heated to sinter the titanium powder in the molded body, and the thickness of the molded body is 0.50 mm or less and the projected area on the surface plane is 28,000 mm. 2 A method for producing a porous titanium body, comprising the steps of: producing the porous titanium body described above; 7. The method for producing a porous titanium body according to claim 6, wherein the titanium powder used is a crushed powder having an average particle size D50 of 10 μm or more and 45 μm or less.

8. A method for producing a porous titanium body according to claim 6 or 7, wherein the titanium powder has an average particle size D50 of 10 μm or more and 20 μm or less.

9. A method for producing a porous titanium body according to claim 6 or 7, wherein in the drying step, the paste is heated to a temperature of 80° C. or higher and 150° C. or lower in an oxygen-containing atmosphere.

10. A method for producing a porous titanium body as described in claim 6 or 7, wherein in the binder removal step, the molded body is heated to a temperature of 320°C or higher and 450°C or lower in an oxygen-containing atmosphere.

11. The method for producing a porous titanium body according to claim 6 or 7, wherein in the sintering step, the molded body is heated in a reduced pressure atmosphere or an inert gas atmosphere.

12. A method for producing a porous titanium body according to claim 6 or 7, wherein the green body is heated to 750°C to 1000°C in the sintering step.

13. The method for producing a porous titanium body according to claim 12, wherein the molded body is heated to 775°C to 950°C in the sintering step.