JP2001303103A - Method for producing sintered powder molded body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously and uniformly produce a material for molding composed of sinterable powders and an organic binder by a process in a short time. SOLUTION: This method for producing a sintered powder molded body includes a step 4 in which an organic binder composed of one or more kinds of organic compound powders 2 or the one obtained by adding a luquid organic compound 1 to the above compound powders and sinterable powders 3 for sintering composed of any one kind among the powders of ceramics, metal and cermet or a mixture of two or more kinds among the above sinterable powders are mixed in a stage heated to a temperature in which the organic compound having the lowest melting point in the above organic binder is melted, a granulating step 5 in which the mixture taken out of the above stage is mechanically treated and granulated and steps 6 and 7 in which the granular material obtained through the above granulating step is subjected to extrusion molding to obtain a molded body as a final product or a molded body as a molding material for a final product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a powder compact using a sinterable powder such as ceramics, metal or cermet.

[0002]

2. Description of the Related Art Sinterable ceramics, metal or cermet powders are extruded or injection-molded, and the products obtained by sintering the compacts are compared with metal products or the like obtained by conventional pressing or other processing methods. As a result, since a complicated shape can be obtained with high dimensional accuracy, the production amount is steadily increasing. However, these powders must be kneaded with an organic binder to form a kneaded product. Generally, since a plurality of types of organic compounds having various melting points, shapes and particle diameters are used as the organic binder, they are made uniform. Conventionally, a kneading treatment for a long time was usually performed using a batch type kneader having a relatively small capacity in order to obtain a mixed phase. Since it takes a long time to obtain only a small volume of molding material, increasing the size of the kneading machine will increase the throughput of each batch, but in this case, the problem of taking longer time for uniform kneading is a problem. is there.

[0003] Conventionally, in order to shorten the kneading time on the premise of using such a batch type kneader, for example, in the invention of Japanese Patent No. 2779319, first, a high-viscosity polymer compound and a metal powder are kneaded to form a metal. By dispersing the agglomerated portion of the powder in a short time, then adding a low molecular compound binder and continuing to knead, kneading is completed in about 30 minutes. As another solution, a method of pulverizing an organic binder and adding the powder to a metal powder is disclosed in, for example,
No. 6950 discloses this. This method
All the organic materials used as a binder are powdered, and after mixing these powders, they are added to the metal powder with a kneader and kneaded, and the kneading time itself is shorter than that of a non-powder solid or liquid organic binder. .

However, in a batch type kneader, the size of the material obtained after kneading is about the size of a human fist, and in order to use the kneaded material for molding, the material must be taken out of the kneader and pulverized. It is necessary to further pelletize after pulverization. In the case of pulverization, since the shape of the pulverized molding material is not uniform, there is a disadvantage that the molding material cannot be continuously supplied at the time of molding, and the plasticization time is not uniform. Further, since the pulverized material has pores, when the pulverized material is used for molding, the molded body may have pores. Therefore, if a method of pulverizing the material after kneading and further pelletizing can be used, the disadvantage of only pulverization can be avoided, but because of batch-type kneading, it is possible to obtain molding pellets in a continuous and uniform phase state. Is still difficult.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to produce a molding material comprising a sinterable powder and an organic binder continuously and uniformly in a short time.

Another object of the present invention is to continuously produce molding pellets in a uniform phase that can be subjected to both injection molding and extrusion molding to obtain a final product.

[0007]

According to the present invention, there is provided an organic binder comprising a) one or more kinds of organic compound powders or a liquid organic compound added to those compound powders. And a sinterable powder of one of ceramic, metal and cermet powders or a mixture of two or more of these powders, and the organic compound having the lowest melting point in the organic binder is melted. A step of mixing in a stage heated to a temperature higher than or equal to a predetermined temperature, b) a granulating step of mechanically treating and granulating the mixture discharged from the stage, and c) a granulating step obtained by the granulating step. A step of obtaining a molded product as a final product or a molded product as a molding material of the final product by extruding the granular material. .

The present invention also relates to a method of continuously extruding a molded product as a molding material of the final product as a pellet from a continuous extruder, and extruding or injection molding the pellet material. And a method for producing a sintered powder compact as a final product.

In the method of the present invention, when the average particle size of the powdery organic compound is 500 μm or less, a uniform molding material can be produced in a very short time. In this case, the powdery organic compound having an average particle size of 500 μm or less is subjected to an integration step such as heating and melting, dissolving in an organic solvent, or alloying the one or more organic compounds used as an organic binder, It can be obtained by pulverizing this integrated organic compound.

Further, in the method of the present invention, the average particle diameter of the granules obtained through the above-mentioned granulation step is 0.5 mm to 10 mm.
By setting the thickness in mm, extrusion molding of a final product or continuous extrusion molding of pellets as a final molding material can be uniformly performed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In the flowchart shown in FIG. 1, the liquid organic binder 1 is of a suitable type only when it is considered that the powdery organic binder 2 made of at least one kind of organic compound is advantageous for promoting the mixing and granulating treatment. And the amount are prepared and added to the powdery organic binder 2. Powdered organic binder 2
The average particle size of the organic compound used as the above should be 500 μm or less, preferably 200 μm or less. This is because, if the average particle size is larger than 500 μm, it becomes difficult to obtain a uniform granulated body, and thus to finally obtain a uniform molding material (pellet) in a short time.

[0012] Powdered organic binders include thermoplastic resins, waxes, fatty acid-based lubricants and the like, and those used as liquids include phthalic acid-based plasticizers.
Defoamers, liquid paraffin, polyethylene glycol and the like. In order to make the former powdery, it is heated and melted, or dissolved in an organic solvent, or integrated through a process such as alloying, and this integrated product is made into a powder having an average particle diameter of 500 μm or less.

The sintering powder 3 made of any one of ceramic, metal and cermet powders which are sinterable powders or a mixture of two or more of these sinterable powders is
The powdery organic binder 2 is supplied together with the powdery organic binder 2 to a heating / mixing stage 4 preferably formed of a receiving powder mixing section in a granulating apparatus. As the sinterable powder, any one of ceramics such as alumina and zirconia, metal powder such as iron, stainless steel and titanium, and cermet material, or 2
Mixtures of more than one species can be used. The heating temperature of the stage 4 is equal to or higher than the temperature at which the lowest melting organic compound in the organic binder is melted. Note that, before the heating and mixing 4, preliminary mixing of the organic binder and the sintering powder may be performed.

The mixture coming out of the heating and mixing stage 4 is mechanically treated and granulated in a granulation stage 5 of a granulator. In this case, as a granulation device, a mixing granulator,
A mixing stirrer, a mechanochemical granulator, a briquetting / compacting machine and the like are used. The granules formed through the granulation stage 5 are formed by an extrusion step 6 for directly forming a final molded product, or a pellet comprising a continuous extruder for forming pellets, which are preferable molding materials for obtaining the final molded product. Is supplied to the chemical conversion step 7. The average particle size of the granular material supplied to these steps is 0.5 to 1
Should be 0 mm. If the particle size is out of this range, efficient supply to an extruder, particularly an extruder for pelletizing, cannot be performed.

When the compact as a molding material of the final product is a pellet which is continuously extruded through a pelletizing step 7, these pellets are subjected to a molding treatment by either the extrusion molding 8 or the injection molding 9 step. , It is possible to continuously produce a desired end product. The form of the pellet is typically 2 to 3 mm in diameter and 2 to 5 in length.
It has a cylindrical shape of about mm.

[0016]

EXAMPLES Examples and comparative examples of the present invention will be described below. The following materials were used as the raw materials for the examples . 1. 1. Sinterable powder: SUS316L (average particle size 9 μm) Organic binder: (1) Resin powder 20.0 vol% of powdered polyoxymethylene 7.0 vol% of powdered polybutyl methacrylate 20.0 vol% of powdered polyvinyl butyral The average particle diameter of each of the above three types of resin powder is 100 μm. . (2) Wax, etc. Paraffin wax 43.0 vol% Carnauba wax 5.0 vol% Stearic acid 5.0 vol% After the above-mentioned three substances were integrated by melting, they were powdered to have an average particle size of 80 μm.

The mixing ratio between the sintering powder and the organic binder is as follows. SUS316L powder 100.0 parts by weight Total organic binder amount 7.8 parts by weight

First, a powdered organic binder and a powder for sintering are charged into a mixing stirrer, and the mixed portion is heated to 100 ° C.
And mixed for 30 minutes. This temperature is such that the melting temperature of paraffin wax, which is the lowest melting point component in the organic binder, is about 38 to 65 ° C, and the melting point of the next lowest carnauba wax is about 78 to 84 ° C,
It has been determined to exceed these. In the mixing stirrer, the kneaded material generated by mixing in this manner is:
Granulated and sieved in the agitation granulator, average particle size 5m
and discharged as m particles. This is the average particle size,
Naturally, those exceeding 5 mm are included, but the particle size is 10 mm.
The above is pulverized and sieved and extracted again. The granules thus obtained were fed to a twin screw extruder heated to 180 ° C. and pelletized at a rate of 50 kg per hour.

COMPARATIVE EXAMPLE The organic binder used in the above example was not granulated, but was granulated as it was and extruded under the same conditions to obtain pellets. Polyoxymethylene: average particle size about 3 mm Polybutyl methacrylate: average particle size about 3 mm Polyvinyl butyral: average particle size about 2 mm Paraffin wax: block-shaped carnauba wax: scaly stearic acid about 1 mm thick and about 4 mm in size: Average particle size about 2mm

Using the pellet-shaped molding materials obtained in Examples and Comparative Examples, a strip-shaped molded product having a thickness of 3.5 mm, a width of 10 mm and a length of 100 mm was prepared by an injection molding method. Under a nitrogen atmosphere, the temperature was raised at a rate of 30 ° C./hour to a maximum temperature of 500 ° C., and the degreased body was depressurized in an argon atmosphere to a maximum temperature of 1350 °
C and sintered. Table 1 shows the quality or physical properties at each stage after the above-mentioned molded body was made.

[0021]

[Table 1]

As is clear from Table 1, the molded articles according to the examples have no internal defects as a result of uniform kneading and have a fluidity (melt flow rate) of 30 g / 10 mi.
n. However, in the comparative example, there is an unmelted portion of the resin inside the molded body, and the fluidity is also 15 g / 10 min. And obviously inferior. As a result, in the example, there is no defect at the time of degreasing, and it is possible to obtain a sintered body as a uniform phase with a relative density of 97.5%. However, in the comparative example, the resin is melted and thermally decomposed during degreasing. It causes swelling, cracks and other defects in the molded body. As is apparent from such comparison results, it will be understood that pulverizing the organic material used as the organic binder through integration and other processes greatly contributes to labor saving in the process from kneading to molding. .

Further, a test piece extruded using the pellet-shaped molding material obtained in the example and a granule obtained in the granulation step before the pelletizing step in the example were directly extruded and formed into the same shape. Table 2 shows the quality or physical properties at the same stage as in Table 1 for the test pieces of Table 1.

[0024]

[Table 2]

As is clear from Table 2, the final extruding from the pellet-shaped molded article according to the example and the direct final extruding using the non-pelletized granules have a fluidity of 30 g / 10 min. . To 28 g / 10 min. No substantial difference was observed except for slightly lower.

[0026]

As described above, the present invention solves the problems of conventional kneading and the problem of prolonged kneading, and provides a new sintered powder compact that can continuously produce a high-quality sintered compact. It is intended to provide a manufacturing method.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a procedure for implementing a method for producing a sintered powder compact of the present invention.

Claims (5)

[Claims] 1. An organic binder comprising one or more kinds of organic compound powders or a liquid organic compound added to these compound powders, and a ceramic, metal or cermet powder which is a sinterable powder. Mixing a sintering powder composed of any one or a mixture of two or more of these sinterable powders in a stage heated to a temperature at which an organic compound having the lowest melting point in the organic binder is melted or higher. B) a granulation step of mechanically treating and granulating the mixture discharged from the stage; and c) extruding the granules obtained through the granulation step to obtain a final product. Obtaining a molded product or a molded product as a molding material of a final product. 2. A molding as a molding material of the final product is a pellet continuously extruded by a continuous extruder, and the pellet is obtained by extrusion or injection molding to obtain a final product. The method of claim 1, wherein 3. The powdery organic compound having an average particle size of 5
The method according to claim 1, wherein the thickness is not more than 00 μm. 4. An integrated process such as heating and melting, dissolving in an organic solvent, or alloying the one or more organic compounds used as an organic binder, or a compound obtained by adding a liquid organic compound to the compounds. 4. The apparatus according to claim 3, wherein the powdered organic compound having an average particle diameter of 500 [mu] m or less is obtained by treating and pulverizing the integrated organic compound. 5. The method according to claim 1, wherein an average particle diameter of the granules obtained through the granulation step is 0.5 mm to 10 mm.