JP3420786B2 - Manufacturing method of molded body - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a uniaxial pressure molding method in which a liquid additive is added to a raw material comprising a plurality of granules and a granule material containing short fibers. The present invention relates to a method for producing a molded article, in which a molded article is obtained by obtaining a molded article by a preliminary molding method or an injection molding method and then firing the molded article. 2. Description of the Related Art Conventionally, in order to obtain a compact using a granular raw material, a preform having a predetermined shape is preliminarily molded and then fired. As a method of forming the preformed body, a method of performing a hydrostatic pressing state using a uniaxial pressing method, a hydrostatic pressing method (CIP), or a uniaxial pressing method is known. In this type of method, for example, the present applicant discloses that a mixture obtained by adding a liquid additive to a raw material in the form of powder and granules in advance is subjected to a hydrostatic pressing state by a uniaxial pressing method. A method has been proposed in which a preformed body is obtained by discharging a suitable liquid additive (see Japanese Patent Application Laid-Open No. 4-212904). As a result, various advantages such as a hydrostatic pressure molding method, which could be conventionally achieved only by using a rubber mold as a liquid pressure medium, can be realized by a uniaxial pressure molding method using a mold. Has been obtained. [0004] In recent years, fine particles of raw materials, that is, those having a particle size of from μm to submicron or less, have been used.
It is desired to obtain a preform using such a raw material. However, when the raw material is finely divided, the mold clearance for obtaining the preform is reduced to 70 μm,
It is necessary to reduce the thickness from 100 μm to 100 μm to 10 μm to 30 μm, and especially in a mold having a complicated shape, the production cost becomes enormous. Furthermore, if the rheological properties of the raw materials and the liquid additive are thixotropic,
Leakage from the mold clearance may be significant. The present invention has been made to solve this kind of problem. In particular, when preforming a finely divided raw material, the raw material can be prevented from leaking and has excellent strength and quality. It is an object of the present invention to provide a method for producing a molded article capable of obtaining a molded article. [0006] In order to solve the above problems, the present invention is flat
The uniform particle size is one of the clearance between the fixed mold and the movable mold.
/ 20-1 / 50 feedstock comprising a plurality of particulate material is
On the other hand, a liquid additive and stearic acid, stearic acid
, Aluminum stearate, magnesium stearate
, One or two of ammonium stearate
Added individually and the temporary binder consisting of more complex, the liquid
Dissolved layer formed by the reaction of the state additive and the temporary binder
The liquid additive and the temporary binder through
And a first step of surrounding each powder and granular material of the raw material with the combined liquid additive and the temporary binder to expand the apparent particle diameter of the powder and granular material, and the first step. A second step of removing the excess liquid additive from the obtained mixture by a uniaxial pressure molding method or an injection molding method to obtain a preform, and firing and molding the preform obtained in the second step. And a third step of obtaining a body. The preform is obtained through a hydrostatic pressing state by a uniaxial pressure molding method or an injection molding method in the second step. In the method for producing a molded article according to the present invention, when a liquid additive and a temporary binder are added to a raw material comprising a plurality of powders, the temporary binder is added to the liquid additive. And reacts with each other to surround each of the particles of the raw material. For this reason, the apparent particle diameter of the granular material expands, and even if the granular material itself is fine particles, it effectively prevents leakage from the mold clearance when filled in the cavity of the molding apparatus. be able to. Furthermore, when performing uniaxial pressure molding or injection molding with a molding device, a granular material bridge in which each granular material of the raw material bridges its vertices and ridges in a gap between a wall surface forming a cavity and a punch or a plunger. Is formed, and then a preform is formed through an isostatic pressing state while removing excess liquid additive from the gap between the particulate bridges. As a result, a preform having a uniform density is obtained. An embodiment of the method for producing a molded article according to the present invention will be described below in detail with reference to the accompanying drawings. In FIG. 1, reference numeral 10 indicates a molding apparatus for performing the method of manufacturing a molded body according to the present embodiment. The molding apparatus 10 includes a mold 12, and the mold 1
A lower punch 16 and an upper punch 18 are arranged on the cavity 14 formed in the second so as to be uniaxially pressurizable. A clearance 19 is provided between the cavity 14, the lower punch 16 and the upper punch 18. ing. EXPERIMENTAL EXAMPLE 1 In the method for manufacturing a compact according to Experimental Example 1, the maximum value of the clearance 19 is obtained by precisely measuring the dimensions of the mold 12, and various powders are prepared, and the average particle diameter and the clearance 19 are determined. The relationship with the presence or absence of the outflow of the granular material from the food was detected. Therefore, first, 17 parts by weight of ethyl alcohol and 0.08 parts by weight of ammonium stearate as a temporary binder are added to 100 parts by weight of the granular material.
Two types of mixtures (raw materials) 20 were added in an amount of 0 parts by weight. The two mixtures 20 were filled in the cavities 14 of the mold 12, respectively, and the relationship between the clearance 19 and the average particle diameter of the powder particles flowing out of the clearance 19 was tested. The result is shown in FIG. In FIG. 2, for example, when the clearance 19 is 60 μm, when the amount of ammonium stearate added is 0.08 parts by weight, powder having an average particle size of 1.6 μm or less flows out. In order to prevent outflow, an average particle size of 1.6 μm or more was required. When the clearance 19 is 120 μm, when the addition amount of ammonium stearate is 0.08 parts by weight, powder having an average particle size of 5.6 μm or less flows out, while the addition amount of ammonium stearate is In the case of 0.10 parts by weight, it was recognized that powder having an average particle diameter of 2.4 μm or more did not flow out and could be molded. [0013] In this case, in the case where the stearic acid compound as a temporary binder is not added, the clearance 19
By using a powder having an average particle diameter of 1/5 to 1/10 of the above, molding was possible without flowing out of the clearance 19. On the other hand, in the case where only 0.08 parts by weight of ammonium stearate as the temporary binder is added, it becomes possible to form a powder having an average particle diameter of 1/20 to 1/35 as compared with the conventional one. In addition, when only 0.10 part by weight of ammonium stearate was added, it was possible to form a powder having an average particle diameter of 1/30 to 1/50 as compared with the conventional one. That is, as shown in FIG.
When a liquid additive (e.g., ethyl alcohol) 32 and a temporary binder (e.g., ammonium stearate) 34 are added to the gap 0, the temporary binder 34 reacts with the liquid additive 32 to form a dissolution layer (reaction layer). 36 was obtained. For this reason, the temporary binder 34 and the liquid additive 32 are bonded to each other via the dissolving layer 36, and the apparent particle diameter of each of the powders 30 is expanded so as to surround each powder 30 (FIG. 3, two-dot chain line). Therefore, even if the powder 30 itself is a fine particle, the apparent particle diameter expands, and it can be effectively prevented from leaking from the clearance 19. It should be noted that almost the same results were obtained when stearic acid amide was used instead of ammonium stearate. Experimental Example 2 In the method for producing a molded body according to Experimental Example 2, first, silicon nitride powder (average particle diameter 0.4 μm) obtained by an imide decomposition method
Is 90 parts by weight, 7 parts by weight of ceric oxide (average particle size 1 μm), and 3 parts by weight of lanthanum oxide (average particle size 1 μm). (Temporary binder) was added in an amount of 0.07 parts by weight, and was sufficiently mixed by a ball mill. Further, after defoaming, only 25 parts by weight of water was added to 100 parts by weight of the mixed powder, and the mixture was sufficiently mixed, whereby a mixture 20 was obtained. The mixture 20 was introduced into an injection molding machine (not shown) and molded at an injection pressure of 80 MPa to 200 MPa to obtain a preform having a diameter (diameter) of 20 × 100 mm. This preform had no molding defects, and only the moisture was discharged from the mold without the powders leaking from the mold. In this case, when an injection pressure is applied to the mixture 20 by an injection molding method, the frictional resistance between the powder and granules constituting the mixture 20 and the wall surface of the mold is higher than that between the powders and granules. Therefore, the fluidity of the powdery granules was better in the central part than in the part close to the mold. Therefore,
The largest stress is applied to the edge of the mixture 20, and the densification of the powders starts from this edge. With the increase of the pressing force, the densification is caused between the edge and the wall surface of the mold. The connected granules were crosslinked to form a bridge. The bridge portion prevents the powder and granules constituting the mixture 20 from flowing out of the cavities, and maintains the hydrostatic pressure state by an appropriate amount of the liquid additive. A uniform pressure was applied. At that time, while the excess liquid additive is being discharged, the mixture 20 is further densified by the pressing force within the elastic deformation pressure range through the hydrostatic pressurizing state, and the preform becomes homogeneous at any part. Since the density became a certain constant, and the granular material was in the elastic deformation region, the state of the open pore was also maintained in the gap between the granular material. Comparative Example 1 1 of a granule having the same components and the same composition as Experimental Example 2
With respect to 00 parts by weight, 0.001 part by weight of ammonium alginate as a dispersant, 0.02 part by weight of an acrylic resin emulsion as a binder and only 40 parts by weight of water were added, and they were sufficiently mixed by a ball mill. Further, after defoaming, only 25 parts by weight of water was added to 100 parts by weight of the mixed powder, and the mixture was sufficiently mixed to obtain a mixture. This mixture was injection molded under the same conditions as in Experimental Example 2. At that time, the injection pressure did not rise to a predetermined pressure, and the mixture leaked from the mold mating surface, making molding impossible. The mold was divided into two parts, and the precise measurement of the mating surfaces of the molds revealed that the maximum clearance was only 0.1 mm in the non-pressurized state. EXPERIMENTAL EXAMPLE 3 In the method for producing a molded body according to Experimental Example 3, first, powder particles composed of 97.5% by weight of electrolytic copper powder (average particle diameter of 10 μm) and 2.5% by weight of chromium powder (particle diameter of 10 μm) A mixture obtained by adding only 17 parts by weight of ethyl alcohol to 100 parts by weight of the body and mixing well (hereinafter referred to as mixture A), and further containing 0.03 parts by weight of stearamide as a temporary binder.
0.5 parts by weight added and mixed well (hereinafter referred to as mixture B), and ammonium stearate (temporary binder) added by 0.03 parts by weight to 0.5 parts by weight and mixed well (Hereinafter referred to as mixture C), a mixture obtained by adding only 0.03 to 0.5 parts by weight of stearic acid (temporary binder) (hereinafter referred to as mixture D), stearic acid Aluminum (temporary binder) added in an amount of 0.03 to 0.5 parts by weight and mixed well (hereinafter referred to as mixture E), and magnesium stearate (temporary binder) of 0.03 parts by weight A mixture that was sufficiently mixed by adding only 0.5 part by weight (hereinafter, referred to as mixture F) was prepared. Then, the above-mentioned mixtures A to F are filled in the cavities 14 of the mold 12, respectively, and are formed by a uniaxial press molding method at a molding pressure of 100 MPa and 120 × 24 × 24 mm.
Was obtained. The result is shown in FIG.
Here, in the mixture A to which ethyl alcohol was added without adding the stearic acid compound as the temporary binder, the withdrawal pressure was about 3 MPa (30.6 kgf / cm ² ) to 4 MPa.
a (40.7 kgf / cm ² ). On the other hand, in the case of adding a stearic acid compound in addition to ethyl alcohol (mixtures B to F),
The withdrawal pressure suddenly decreased, and even with the addition amount of only 0.3 parts by weight, the withdrawal pressure was 1 MPa (10.2 kgf /
cm ² ). No molding defects were found in any of the preforms. Here, although the type of the stearic acid compound has a slight effect on the extraction pressure, it is 0.5MPa.
It was in the range of a to 1 MPa and did not cause any problem. When an experiment was conducted by adding methyl alcohol, hexane, toluene and methyl chloride instead of adding ethyl alcohol, the same results as in the case of the above ethyl alcohol were obtained. Next, the obtained preform is held at 650 ° C. for 30 minutes in a nitrogen atmosphere or under vacuum, then at 1000 ° C. for 1 hour, and further at 1050 ° C. for 2 hours. C. for 4 hours and fired. The result is shown in FIG. The density was measured by the Archimedes method. In this case, in the mixtures B and C, the relative density was 100% when the addition amount of stearamide and ammonium stearate was 0.1 parts by weight or less. The amount of stearic acid added to the mixture D was 0.06.
In the case where the addition amount of aluminum stearate in the mixture E was 0.02 parts by weight or less and the amount of magnesium stearate in the mixture F was 0.02 parts by weight or less, the relative density was 100%. Comparative Example 2 One of the granules having the same components and the same composition as Experimental Example 3
Only 0.5 part by weight of zinc stearate was added to 00 parts by weight, and a preform was obtained by a usual dry molding method. The withdrawal pressure at that time was 7 MPa. In addition, molding defects such as lamination cracks were observed in all the preforms. On the other hand, 17 parts by weight of dimethyl ketone and 0.
Only a part by weight of from 0.3 to 0.5 parts by weight was added, and a preform was obtained by a usual dry molding method. In this preformed body, although no molding defects were found in all, the ejection pressure was 2.5 MPa to 2.8 MPa (see FIG. 4). As described above, according to the method of manufacturing a molded article according to the present invention, when a liquid additive and a temporary binder are added to a raw material composed of a plurality of powders, this temporary binding An agent reacts and binds with the liquid additive to surround each granule of the raw material. For this reason, the apparent particle diameter of the granular material expands,
Even if the granular material itself is fine particles, it can be effectively prevented from leaking from the mold clearance when filled into the cavity of the molding apparatus. In addition, when performing uniaxial pressure molding or injection molding with a molding device, a granular material bridge in which each granular material of the raw material bridges the vertices and ridges in a gap between a cavity forming wall surface and a punch or a plunger. Is formed, and then a preform is formed through an isostatic pressing state while removing the excess liquid additive from the gap between the particulate bridges. As a result, a preform having a uniform density is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view of a molding apparatus used in a method for manufacturing a molded article according to the present embodiment. FIG. 2 is a diagram showing the relationship between the clearance of a mold and the average particle size of a powder material flowing out. FIG. 3 is a schematic view illustrating an operation state of the method for manufacturing a molded body according to the present embodiment. FIG. 4 is a graph showing the relationship between the amount of various additives and the extraction pressure. FIG. 5 is a diagram showing the relationship between the amount of various additives and the density. BRIEF DESCRIPTION OF THE SYMBOLS 10 ... Molding device 12 ... Mold 14 ... Cavity 16 ... Lower punch 18 ... Upper punch 19 ... Clearance 20 ... Mixture 30 ... Powder and granular material 32 ... Liquid additive 34 ... Temporary binder 36 ... Dissolution layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-211904 (JP, A) JP-A-64-31903 (JP, A) JP-A-57-198202 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B22F 3/02 B28B 1 / 24,3 / 02 C04B 35/632

Claims (1)

(57) [Claims] [Claim 1] The average particle diameter is smaller than the distance between the fixed mold and the movable mold.
To 1 / 20-1 / 50 feedstock comprising a plurality of particulate material which is the clearance, and a liquid additive, stearic acid, scan
Tearamide, aluminum stearate, steer
Magnesium phosphate, ammonium stearate
Separately with a temporary binder consisting of one or more complex
In addition, the liquid additive and the temporary binder react to form
The liquid additive and the temporary binder are exchanged via the formed dissolution layer.
Together with the liquid additive and the temporary
A first step of enlarging the apparent particle diameter of the granular material by surrounding each granular material of the raw material with a binder, and a uniaxial pressing method of the mixture obtained in the first step or A second step of obtaining a preformed body by removing an excess liquid additive by an injection molding method; and a third step of firing the preformed body obtained in the second step to obtain a formed body, A method for producing a molded body, wherein the preformed body is obtained through a hydrostatic pressure state by a uniaxial pressure molding method or an injection molding method in the second step.