JP2008007811A - Method for manufacturing metal porous body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a metal porous body for producing a metal porous body having high porosity and uniform skeletal structure with high productivity. <P>SOLUTION: This manufacturing method comprises: a slurry preparation step; a skeletal structure forming step; a step of forming a multilayer construction of skeletal structure; a precursor heating step; and a sintering step. The metal porous body can be obtained by preparing a slurry where metal powder of ≤15μm average particle size and insoluble thermoplastic resin powder are contained in a dispersion medium, applying the slurry to the periphery of a resin foam, evaporating the dispersion medium to allow a fusion layer composed of the thermoplastic resin powder to bridge mutual particles of the metal powder so as to form a skeletal structure around the resin foam, applying the slurry again to the periphery of the resultant skeletal structure to form a multilayer construction of skeletal structure, heating a subsequently obtained precursor and then sintering the metal powder. The multilayer construction of skeletal structure can be attained by repeating the above step of forming the multilayer construction of skeletal structure. As the metal powder, that of stainless steel material is preferred. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is, for example, a metal that can be used for various filters such as a filter for removing soot contained in exhaust gas of diesel engines such as automobiles, a water treatment filter such as sewage and industrial water, and a catalyst carrier part for fuel cells. The present invention relates to a method for producing a porous body.

A metal porous body manufactured using a foamed resin foam as a base material is composed of a skeleton portion made of metal and a void portion which is a space, and a series of skeletons and one void portion surrounded by the skeleton portion are also called cells. For example, when a fluid, that is, a gas or liquid is passed through a porous metal body, foreign particles mixed in the fluid are adsorbed or collected by the skeleton and removed, and the fluid from which foreign particles have been removed passes through the cell. I will do it. In this case, the size of the cell is selected according to the size of the foreign particle to be removed. Metal porous bodies having such functions are used as various filter members.
For example, when using a metal porous body for catalyst carrier parts such as a fuel cell, the catalyst is supported on the surface of the skeleton to increase the contact area with the reactants, thereby increasing the reaction. used. In addition, the metal porous body is excellent in ductility, toughness, and impact resistance as compared with nonmetals, and has an effect of protecting a fragile catalyst.

  Conventionally, as one of the methods for forming a metal porous body as described above, for example, a porous foamed resin foam disclosed in Patent Document 1 is subjected to conductive treatment, electroplated with Ni or Cr, and then heat-treated to foam. A method for removing a resin foam and obtaining a metal porous body is known. Such electroplating methods have the inconvenience of being limited to components such as Ni and Cr that can be electroplated, but in the case of parts that react electrically or parts that require a certain degree of corrosion resistance, etc. It is a suitable method.

  In addition to the above-described method for obtaining a metal porous body by electroplating, for example, Patent Document 2 discloses a dispersion medium, a metal powder, a dispersion medium such as gelled cellulose, polyvinyl alcohol, epoxy resin, and silicone resin. It is known that a porous foamed resin foam is impregnated with a slurry containing a soluble binder and dried, and then the foamed resin foam is removed to sinter metal powder to obtain a porous metal body. Yes.

JP-A-57-174484 JP-A-38-17554

  However, in the case of the above-described electroplating method, a metal porous body having a high Ni purity has a low mechanical strength and may not be used as a structural component. In addition, there are metal porous bodies in which Cr is plated on Ni in order to improve mechanical strength. However, in general, the environmental load of Cr plating is a problem, and technical development that does not perform Cr plating has been conducted. It is desired.

  Further, in the case of the method in which the above-mentioned slurry is infiltrated into the foamed resin foam, the mechanical strength is generally low as compared with the metal porous body obtained by the above-described electroplating method, and thus it cannot be used as a structural component. For this reason, it was studied to increase the mechanical strength by increasing the thickness of the metal porous body. For example, we considered the formation of a thick skeleton by infiltrating a slurry having a high blending ratio of metal powder into the foamed resin foam, and the metal powder was adjusted to the upper limit of the viscosity at which the slurry can sufficiently penetrate into the foamed resin foam. A slurry blended in a large amount was used. However, although a slight improvement in strength was observed, a thick skeleton reaching the desired strength could not be formed. Also, for example, when a skeleton once fixed with an appropriate amount of slurry was formed and an attempt was made to form a thick skeleton by adding a slurry to this skeleton again, the skeleton once formed was softened. A healthy skeleton could not be formed because it melted away.

  An object of the present invention is to solve the above-described problems and to provide a method for producing a metal porous body for producing a metal porous body having a high porosity and excellent mechanical strength with high productivity. .

  The present inventor applied a slurry added with an insoluble thermoplastic resin powder to a dispersion medium around a foamed resin foam and then dried to form a skeleton. After applying the slurry around the skeleton again, the slurry was dried. The inventors have found that the above-mentioned problems can be solved by forming a skeleton in multiple layers, and have arrived at the present invention.

  That is, the present invention provides a slurry production process for producing a slurry comprising a dispersion medium, a metal powder having an average particle diameter of 15 μm or less, and a thermoplastic resin powder insoluble in the dispersion medium and having an average particle diameter of 10 μm or less, From the applied slurry after coating around a foamed resin foam having a porosity of 90% or more and an average number of pores intersecting with a straight line in an arbitrary direction having a length of 25 mm and having a cell number of 5 to 30 The dispersion medium is evaporated, the thermoplastic resin powder is fused by the evaporation to form a fused layer, and the fused layer is cross-linked with the metal powder to form a skeleton around the foamed resin foam. A skeleton forming step, and after re-coating the slurry around the obtained skeleton, the dispersion medium is evaporated from the re-coated slurry, and the thermoplastic resin powder is fused by the evaporation to form a fused layer. Formed and melted A skeleton multilayering process in which the metal powder is cross-linked with each other to multilayer the skeleton, and the precursor obtained after the skeleton multilayering process is heated to remove the foamed resin foam and the fusion layer And a sintering step of forming a metal porous body by sintering metal powder after the precursor heating step.

  In the production method of the present invention, it is desirable to further stratify the skeleton by repeating the skeleton multilayering step. Further, it is desirable to use a stainless material for the metal powder.

  According to the present invention, the mechanical strength of the metal porous body can be remarkably improved. Therefore, it is useful for putting various members such as exhaust gas and water treatment filter members and fuel cells into practical use where high mechanical strength is desired by utilizing the filter function and support function of the metal porous body. Technology.

  One of the important features in the method for producing a porous metal body of the present invention is the skeleton formation step. The thermoplastic resin powder contained in the slurry used in the skeleton forming process is mixed in the dispersion medium, and the dispersion medium evaporates to fuse the resin particles together, forming an insoluble fused layer with respect to the dispersion medium. To do. In the present invention, an insoluble skeleton can be formed in the dispersion medium by cross-linking the fused layers formed by fusing the thermoplastic resin powder as described above with the metal powders. As a result, the skeleton once formed becomes insoluble in the dispersion medium, and even if the slurry is applied to the skeleton again, there is no problem that the skeleton once formed is softened and melted down.

  In addition, an important feature different from the above in the production method of the present invention is the skeleton multilayering step. Specifically, in the skeleton multilayering step, the slurry containing the thermoplastic resin powder is re-applied around the skeleton formed in the skeleton formation step, and then the dispersion medium is evaporated from the re-applied slurry. By evaporating the dispersion medium, the thermoplastic resin powder is fused to form a fused layer, and the fused layer is cross-linked with the metal powder, and the skeleton formed in the skeleton forming step is multilayered to obtain a precursor. Form. As a result, a skeleton is further formed on the existing skeleton previously formed, and a precursor in which the skeleton is multilayered is obtained. The precursor becomes a material for sintering a metal powder to form a metal porous body, and the multilayered precursor significantly improves the mechanical strength compared to a conventional precursor composed of a single layer skeleton. be able to. In the present invention, since the skeleton formed in the skeleton multilayering process is also insoluble in the dispersion medium, the mechanical strength of the precursor can be further improved by multilayering the skeleton by repeating the skeleton multilayering process. it can.

Hereinafter, the manufacturing method of the metal porous body of the present invention will be described for each manufacturing process.
The slurry production step in the present invention is a step of producing a slurry containing a dispersion medium, a metal powder having an average particle size of 15 μm or less, and a thermoplastic resin powder insoluble in the dispersion medium and having an average particle size of 10 μm or less. Specifically, a reference amount of the dispersion medium is put in a suitable stirring tank, and the above-mentioned metal powder and thermoplastic resin powder are added to the dispersion medium, mixed and stirred, and dispersed almost uniformly. And can be produced by means such as slurry.

The slurry is a suspension in which a fine solid is dispersed in a liquid, and is generally called a mixture having fluidity that can be pumped. The slurry in the present invention contains a dispersion medium, a metal powder having an average particle diameter of 15 μm or less, and a thermoplastic resin powder insoluble in the dispersion medium and having an average particle diameter of 10 μm or less. The dispersion medium contained in the slurry has a function of suspending and dispersing the metal powder or thermoplastic resin powder to be dispersed and adding appropriate fluidity to the slurry.

  When the dispersion medium is evaporated from the slurry, the thermoplastic resin powder contained in the slurry can be fused together to form a fused layer, and the fused powder can crosslink the metal powder to each other. That is, it is a binder for bonding metal powders to each other. In the present invention, a thermoplastic resin powder having an average particle size of 10 μm or less that is insoluble in the dispersion medium is used. By making it insoluble in the dispersion medium, even if the slurry is applied again around the skeleton once formed, the skeleton does not soften and melt down. For this reason, it becomes possible to form a precursor in which the skeleton described above is multilayered. Further, by making the thermoplastic resin powder to be used have an average particle size of 10 μm or less, it is possible to disperse the resin powder without floating with respect to the dispersion medium, and an amount sufficient to crosslink the fusion layer between the metal powders. Can be supplied between the metal powders, but a thermoplastic resin powder having an average particle size of 0.01 μm or more is easily available, which is preferable.

  The metal powder contained in the slurry is a material that forms the skeleton of the metal porous body. A metal powder having an average particle size of 15 μm or less is used in the present invention because the metal powder has an extremely large density compared to the dispersion medium and fast sedimentation in the slurry. When the average particle diameter of the metal powder used exceeds 15 μm, the metal powder may settle and separate while the slurry is applied to the foamed resin foam and dried. Further, the average particle size of the metal powder can be densely formed as a skeleton part of the sintered metal porous body as the particle size becomes finer, for example, 10 μm or less, 5 μm or less, 3 μm or less, but the average particle size is 1 μm or more. These metal powders are preferred because they are readily available and easy to handle.

  In the skeleton formation step in the present invention, the slurry produced in the above-described slurry production step has a porosity of 90% or more and the number of cells which is an average number of pores intersecting a straight line in an arbitrary direction having a length of 25 mm is 5 to 5 After coating around 30 foamed resin foams, the dispersion medium is evaporated from the applied slurry, and by this evaporation, the thermoplastic resin powder is fused to form a fused layer. It is set as the process of mutually cross-linking and forming frame | skeleton around a foamed resin foam.

  Specifically, first, the slurry produced in the slurry production process is applied around the foamed resin foam. For example, the foamed resin foam may be immersed in the slurry, or the foamed resin foam may be impregnated with the slurry or directly sprayed. Thereby, the slurry containing the metal powder and the thermoplastic resin powder is adhered around the foamed resin foam.

  Next, the foamed resin foam to which the slurry is attached is dried, for example, in a warm air atmosphere of 40 to 100 ° C. so as not to cause cracking or peeling, and a skeleton containing metal powder is formed around the foamed resin foam. As a result of the drying, the dispersion medium evaporates from the slurry applied around the foamed resin foam as described above, and the thermoplastic resin powder is fused to form a fused layer. Crosslink to form a skeleton.

  The foamed resin foam used in the skeleton forming step is, for example, a resinous solid having a sponge-like surface and a large number of pores inside. The cell in the foamed resin foam determines the size of the pores of the metal porous body, and affects the mechanical strength of the metal porous body. A cell is a series of skeletons and a single hole surrounded by them. Further, the number of cells is generally an index indicating the number of pores of the foamed resin foam and is used to identify the structure of the foamed resin foam. In the foamed resin foam, a straight line having a length of 25 mm is assumed in an arbitrary direction. It is defined as the average number of holes that intersect this straight line.

  In the present invention, the number of cells of the foamed resin foam is 5 to 30. When the number of cells is less than 5, the size of the pores becomes excessive. For example, when a metal porous body is used for a filter, foreign matters may not be removed with an excessive filter mesh. For example, when a metal porous body is used for a catalyst carrier, the total surface area of the skeleton may be too narrow to support a sufficient amount of catalyst. On the other hand, if the number of cells exceeds 30, the size of the pores becomes too small, and it becomes difficult to apply and infiltrate the slurry, and the pores are easily clogged. In addition, when the above-mentioned number of cells is converted into the average diameter of the holes, it is 4.2 to 6.2 mm if the number of cells is 5, and 0.81 to 0.86 mm if the number of cells is 30.

  In the present invention, the foamed resin foam has a porosity of 90% or more. The porosity is determined by the density (mass / volume) of the foamed resin foam and the specific gravity of the material forming the foamed resin foam, and is an index indicating the composition ratio of the space portion in the foamed resin foam. When the porosity of the foamed resin foam is less than 90%, the slurry does not sufficiently permeate when the skeleton is multilayered, causing variations in the thickness of the multilayered skeleton, and the mechanical strength of the formed precursor May be damaged. Further, the formed porous metal body has a small number of pores, and may not be used in applications such as filters and catalyst carriers. Note that the porosity and the number of cells described above have a relationship in which, for example, when the number of cells is the same, the skeleton portion becomes thicker as the porosity decreases.

  Next, in the skeleton multilayering step in the present invention, the slurry is re-applied around the skeleton formed in the above-described skeleton formation step, and then the dispersion medium is evaporated from the re-applied slurry. A fusion layer is formed by fusing, and the fusion layer is cross-linked with metal powders to form a precursor by multilayering the skeleton.

  Specifically, using the same means as in the skeleton formation step, the slurry is re-applied around the existing skeleton, and the slurry containing the metal powder and the thermoplastic resin powder is adhered. Thereafter, using the same means as in the skeleton formation step, the reattached slurry is dried. As a result, a new skeleton containing metal powder is formed around the existing skeleton formed around the foamed resin foam, and the skeleton is multilayered to obtain a precursor that becomes a material for the metal porous body. Preferably, as the precursor, the skeleton multilayering step is repeated to multilayer the skeleton, whereby the mechanical strength of the metal porous body can be remarkably improved.

  Next, the precursor formed in the skeleton multilayering step is heated to remove the foamed resin foam and the fusion layer, and the metal powder is sintered to form a metal porous body. As a means for removing the foamed resin foam and the fused layer, for example, a sintering furnace may be used and included in the sintering of the metal powder. As a means for sintering such a metal powder, for example, the precursor is left standing in a sintering furnace in a vacuum or an inert gas atmosphere and the temperature is raised. First, the foamed resin foam or the fused layer is vaporized or decomposed. And remove. Then, after this, the temperature can be raised to the sintering temperature to sinter the metal powder. Moreover, what is necessary is just to select conditions which do not produce a crack and peeling in frame | skeleton of a precursor about various conditions, such as a temperature increase rate and holding temperature.

  Further, when a metal powder having a value of (tap density / true density) of about 0.5 is sintered, generally shrinkage of approximately 2% to 20% occurs. For this reason, the shape dimension of the sintered metal porous body is reduced more than the shape dimension of the used foamed resin foam. Specifically, the holes are reduced and the number of cells is increased. For example, when a foamed resin foam having 30 cells is used and shrinkage of 20% occurs during sintering, a porous metal body having 37 to 38 cells is obtained.

Next, a preferable configuration in the present invention will be described.
As the dispersion medium, ultrapure water or pure water containing very little foreign matter such as contamination and impurities is preferable. The pure water here is water having a purity that substantially cannot detect impurities, and can be produced by a method such as further distillation of water from which contained ions have been removed. In addition to ultrapure water and pure water, ion exchange water, distilled water, clean water, etc., which are slightly disadvantageous compared to pure water in terms of contained ions and impurities, can also be used. Alternatively, alcohols such as ethanol or a mixed solution of pure water and ethanol can be used.

  Examples of the thermoplastic resin powder include the above-mentioned various water and alcohol-insoluble acrylate copolymers, vinyl acetate polymers, vinyl acetate and acrylate copolymers, styrene and acrylate copolymers, and the like. The resin powder which combined these, or these can be used. And it is preferable to add 5 to 15% by mass% in the slurry. Moreover, when using the above-mentioned water as a dispersion medium, you may use the emulsion which disperse | distributed powders, such as an acrylic resin insoluble in water, to the above-mentioned water, and when the resin solid content is 50%, the emulsion is 10%. It is preferable to add ~ 30%. In general, the smaller the average particle size, the easier the thermoplastic resin powder forms a fused layer. Therefore, the average particle size is preferably 5 μm or less, more preferably 1 μm or less.

  The slurry is preferably a slurry having a low viscosity and good fluidity so that the metal powder does not settle or flow down so that it can be uniformly applied to the foamed resin foam. For example, the viscosity measured with a B-type viscometer is preferably 0.2 to 5 Pa · s. If the viscosity is less than 0.2 Pa · s, it becomes difficult to attach the metal powder to the foamed resin foam, and the viscosity is 5 Pa · s. If it exceeds 1, the fluidity of the slurry is insufficient and it becomes difficult to apply the slurry to the foamed resin foam. It is also preferable to add various additives to the slurry. For example, polyvinyl alcohol, water-soluble gum arabic that expresses the effect of improving the adhesive strength of the metal powder attached around the foamed resin foam, various dispersants that prevent aggregation of the metal powder, surfactants, etc. Good.

  The metal powder is preferably added in an amount of 60 to 80% in terms of mass% when the mass of the slurry is 100%, thereby imparting suitable fluidity to the slurry. The fluidity of the slurry is mainly determined by the dispersion medium and the shape, particle size distribution, tap density (T / D), etc. of the metal powder to be used. By adding the metal powder within the above range, the foamed resin foam can be obtained. The slurry can be suitably applied. The metal powder can be made of any material as long as it can be sintered. For example, a metal such as Fe, Ni, Al, Cu, Ti, or an alloy made of these can be used. The use of stainless steel excellent in heat resistance and oxidation resistance such as SUS310S and SUS316L is also preferable. In addition, although there are problems such as environmental load, Ni—Cr-based or Ni—Cr—Al-based alloy powder containing Cr can also be used.

  For example, in water treatment applications, austenitic stainless steel such as SUS316L containing 12.0% or more of Ni, 16.0% or more of Cr, and 2.0% or more of Mo is used in consideration of corrosion resistance. It is preferable to do. Further, for example, in exhaust gas treatment applications of diesel engines, austenitic stainless steel such as SUS310S containing 19.0% or more of Ni and 24.0% or more of Cr in mass% is considered in consideration of heat resistance and oxidation resistance. It is preferable to use it. For example, carbonyl Ni can be used for a pure Ni porous body containing 99.0% or more of Ni by mass% used for battery electrodes and reaction base materials.

  As the foamed resin foam, for example, an easily available foamed urethane foam, a thermoplastic resin such as polyethylene, polypropylene, polystyrene, or a phenol resin that is a thermosetting resin is preferable. By adopting these foamed resin foams, it is difficult to break during slurry application or handling of foamed resin foams, and suppresses problems such as deterioration of the mechanical strength of the metal porous body due to residual carbon etc. during sintering of the metal powder. it can.

  Moreover, when applying the slurry around the foamed resin foam or around the existing skeleton, it is preferable to adjust the thickness of the adhered slurry layer to be uniform. A skeleton can be formed healthy. Specifically, for example, it is preferable to adopt means such as filling the slurry in the space of the foamed resin foam and then reducing the atmosphere to remove bubbles remaining inside the foamed resin foam. For example, means for removing excess slurry on the surface of the foamed resin foam by blowing pressurized air or the like may be employed. In the skeleton formation process, while the slurry adhering to the foamed resin foam is not dried, the foamed resin foam is compressed by a pressing means such as sandwiching the foamed resin foam between flat plates or passing between parallel rolls. It is also possible to adopt means such as processing.

As an example related to the multilayering of the skeleton in the present invention, a metal porous body P1 which is an example of the present invention shown in Table 1 manufactured by the following manufacturing procedure will be described as an example.
Slurry manufacturing process:
LDM7512 (Nichigo Mobile) is an emulsion liquid in which ultrapure water is dispersed as a dispersion medium, SUS310S having an average particle diameter of 7 μm as a metal powder, and an acrylate copolymer having an average particle diameter of 0.25 μm is dispersed as a thermoplastic resin powder. (Made by Co., Ltd., resin solid content 50%) was used, and the respective blending ratios were 7%, 71%, and 21% by mass% and put into the container. Then, the mixture was sufficiently mixed and stirred to obtain a slurry (hereinafter referred to as slurry A) in which the metal powder and the thermoplastic resin powder were dispersed almost uniformly in the dispersion medium.

Framework formation process:
Using slurry A and foamed urethane foam as foamed resin foam with a porosity of 97%, 8 cells, 130 mm in length, 130 mm in width, and 20 mm in thickness (hereinafter referred to as urethane foam U), A skeleton in which a fusion layer made of an acrylate copolymer was cross-linked with each other of SUS310S powder was formed. An example of the structure of the used urethane foam U is shown in FIG. Specifically, the procedure was as follows. First, the urethane foam U was immersed in the container while stirring the slurry A, and the slurry A was sufficiently permeated into the inside of the urethane foam U. After this, the urethane foam U is taken out, and before the ultrapure water evaporates from the slurry A attached around the urethane foam U, the excess slurry A is removed from the urethane foam U by a pressure device using a parallel roller. . Then, the urethane foam U to which the slurry A was adhered was allowed to stand for 20 minutes in a hot-air circulating drier having a tank internal temperature of 80 ° C. to evaporate ultrapure water. As a result, the acrylic ester copolymer powder was fused to form an adhesive layer, and this adhesive layer was cross-linked with each other of the SUS310S powder to form a single layer skeleton around the urethane foam U.

Skeleton multilayering process:
Using the above-mentioned slurry A and foamed urethane U having a single layer skeleton, a new fusion layer in which an acrylate copolymer copolymer of SUS310S powder is cross-linked around the existing single layer skeleton. A skeleton was formed, and the skeleton had two layers. Specifically, the procedure was as follows. First, the urethane foam U having a single layer skeleton was immersed in the container while stirring the slurry A, and the slurry A was sufficiently infiltrated around the skeleton formed inside the urethane foam U. Thereafter, foamed urethane U having a single layer skeleton was taken out, and excess slurry A was removed by blowing pressurized air before the ultrapure water evaporated from the slurry A attached around the existing skeleton. Then, the urethane foam U having a skeleton with the slurry A attached thereto was allowed to stand for 20 minutes in a hot-air circulating dryer having a tank temperature of 80 ° C. to evaporate ultrapure water. As a result, the acrylic ester copolymer powder is fused to form an adhesive layer, and this adhesive layer is cross-linked with the SUS310S powder to form a new skeleton around the existing skeleton. A precursor was obtained.

Precursor heating process:
The obtained precursor having a two-layer skeleton was left standing in a sintering furnace in a hydrogen gas atmosphere, heated to 600 ° C. at a heating rate of 60 ° C./h, heated, held for 2 h, and urethane foam U The pressure-sensitive adhesive layer made of an acrylic ester copolymer was removed by vaporization or decomposition.

Sintering process:
Subsequent to the precursor heating step, using a sintering furnace in a vacuum atmosphere, heated to 1250 ° C. at a heating rate of 150 ° C./h, heated, held for 2 h, SUS310S powder was sintered and porous metal A body P1 was obtained.

The metal porous body P1 obtained by the above-described production procedure has a porosity of 97.7%, a cell number of 9, a length of 111 mm, a width of 110 mm, and a thickness of 17.2 mm. It was a good metal porous body in which defects such as pore clogging could not be confirmed.
As described above, the metal porous body P1 serving as an example of the present invention could be manufactured through the slurry manufacturing process, the skeleton forming process, the skeleton multilayering process, the precursor heating process, and the sintering process. .

  Next, the metal porous bodies P2 to P4 shown in Table 1, which are examples of the present invention, use the slurry A and the urethane foam U in the same manner as when the metal porous body P1 is manufactured. It was manufactured through a skeleton formation step, a skeleton multilayering step, a precursor heating step, and a sintering step. The metal porous bodies P2, P3, and P4 are manufactured using precursors having skeletons of 4 layers, 6 layers, and 7 layers, respectively. Repeated 6 times. Any of the obtained metal porous bodies P2 to P4 were good metal porous bodies in which defects such as metal skeleton defects and cracks and pore clogging could not be confirmed by visual observation. An example of the structure of a porous metal body P3 obtained from a precursor having a skeleton having six layers is shown in FIG. 1, and an example of the structure of a porous metal body P1 obtained from a precursor having a skeleton having two layers is shown in FIG. .

  Moreover, the metal porous body Q1 shown in Table 1 was manufactured as a comparative example. As shown in Table 1, the metal porous body Q1 uses a slurry based on polyvinyl alcohol, which is a water-soluble resin, and urethane foam U, and a precursor having a skeleton of one layer through a slurry manufacturing process and a skeleton formation process. Then, it was manufactured through a precursor heating step and a sintering step. The obtained metal porous body Q1 has a porosity equivalent to that of the metal porous body P1 having the above-mentioned skeleton in two layers, and defects such as metal skeleton defects and cracks and clogging of the pores are visually observed. It was a favorable metal porous body which cannot be confirmed.

Using metal porous bodies P1 to P4, which are examples of the present invention obtained by the above-described manufacturing method, and metal porous body Q1, which is a comparative example, a disk-shaped test body having a diameter of 50 mm is cut out and compressed from each. The strength was measured. The measurement results are shown in Table 2.
The compressive strength of the metal porous bodies P1 to P4 obtained from the precursors having the skeletons of 2, 4, 6, and 7 layers, which are examples of the present invention, is higher than that of the metal porous body Q1 that is a comparative example. The metal porous body P1 was 1.6 times, and the other metal porous bodies P2 to P4 were 2.6 times, 4.4 times, and 8.6 times. Also, the compressive strength increased as the number of skeleton layers formed in the precursor increased. As a result, the method for producing a metal porous body of the present invention having the feature of multilayering the precursor skeleton is effective for producing a metal porous body having a high porosity and excellent mechanical strength with high productivity. It was confirmed that.

As an example relating to the material of the metal powder in the present invention, a metal porous body P5 having a porosity of 88.5%, a cell number of 9, a length of 104 mm, a width of 104 mm, and a thickness of 30.5 mm manufactured by the following manufacturing procedure. And the above-described metal porous body P3 obtained from a precursor having the same six-layer skeleton as the metal porous body P5 will be described.
For the metal porous body P5 that is an example of the present invention, a slurry (hereinafter referred to as slurry B) in which the material of the metal powder to be used is replaced with SUS316L in the slurry A described above. That is, the slurry B is an emulsion liquid in which ultrapure water is dispersed as a dispersion medium, SUS316L having an average particle diameter of 7 μm is dispersed as a metal powder, and an acrylic acid ester copolymer having an average particle diameter of 0.25 μm is dispersed as a thermoplastic resin powder. A certain LDM7512 (manufactured by Nichigo Movinyl Co., Ltd., resin solid content: 50%) was used, and the blending ratios thereof were 7%, 71%, and 21% by mass%.

  And the slurry B is used, and the urethane foam U is used similarly to the case where the metal porous body P3 is manufactured, and the slurry manufacturing process, the skeleton forming process, the skeleton multilayering process, the precursor heating process, and the sintering process are performed. Produced by going through. In addition, the metal porous body P5 used the precursor which has 6 frame | skeleton, and repeated the frame | skeleton multilayering process 5 times. The obtained metal porous body P5 was a good metal porous body in which defects such as metal skeleton defects and cracks and pore clogging could not be confirmed by visual observation.

A test specimen having a disk shape with a diameter of 50 mm was cut out from the metal porous body P5 obtained by the above-described manufacturing method, and the compressive strength was measured. The measurement results are shown in Table 3 together with the metal porous body P3.
The metal porous body P5 using SUS316L as the metal powder had a compressive strength of 6.3 MPa. Compared to this, the compression strength of the porous metal body P3 using the same six-layered precursor skeleton and using SUS310S as the metal powder was 2.2 MPa, and the difference was 2.8 times. From this result, it was found that the compressive strength of the obtained metal porous body can be adjusted by appropriately selecting the material of the metal powder to be used.

  In addition, the metal porous body P5 has a high residual C value, that is, the amount of carbon contained, which is considered to be related to the fact that Mo is contained in SUS316L. For this reason, although compressive strength is high, it is thought that it is inferior to metal porous body P3 as buckling strength. From this, it was found that it is preferable to select the material of the metal powder according to the use of the metal porous body.

It is a figure which shows an example of the structure of the metal porous body obtained from the precursor which made frame | skeleton 6 layers in this invention. It is a figure which shows an example of the structure of the metal porous body obtained from the precursor which made 2 layer | skeleton the frame | skeleton in this invention. It is a figure which shows an example of the structure of the foamed resin foam used in the Example in this invention.

Claims (3)

  A slurry production step of producing a slurry comprising a dispersion medium, a metal powder having an average particle size of 15 μm or less, and a thermoplastic resin powder having an average particle size of 10 μm or less that is insoluble in the dispersion medium; After coating around a foamed resin foam having an average number of vacancies of 90% or more and a length of 25 mm and intersecting a straight line in an arbitrary direction and having 5 to 30 cells, the dispersion medium is evaporated from the coated slurry. A skeleton forming step of fusing the thermoplastic resin powder by the evaporation to form a fusing layer, and cross-linking the fusing layer with the metal powder to form a skeleton around the foamed resin foam; Then, after re-applying the slurry around the obtained skeleton, the dispersion medium is evaporated from the re-applied slurry, and the thermoplastic resin powder is fused by the evaporation to form a fused layer, and the fused layer is formed. The metal powder A skeleton multilayering step in which the skeletons are multilayered by crosslinking each other, and a precursor heating step in which the precursor obtained after the skeleton multilayering step is heated to remove the foamed resin foam and the fusion layer; And a sintering step of forming a metal porous body by sintering the metal powder after the precursor heating step.   The method for producing a porous metal body according to claim 1, wherein the skeleton multilayering step is repeated to stratify the skeleton. The method for producing a metal porous body according to claim 1, wherein a stainless material is used for the metal powder.