JPH02311374A - Degreasing - Google Patents

Abstract

PURPOSE:To reduce occurrence of cracks by packing an inorganic granular material into an inner diameter part of a cylindrical molded article having specific dimension and shape, comprising a sintering substance-containing mixture having a binder, and sintering after degreasing thereof. CONSTITUTION:100 pts.wt. sintering substance selected from a metal having >=800 deg.C decomposition temperature and 1 to 500mum particle diameter and an inorganic compound such as SiC having 0.1 to 200mum particle diameter is blended in a molten state with <=20 pts.wt. sintering auxiliary, 3 to 40 pts.wt. binder such as ethylene-based hydrocarbon having, 2,000 to 500,000 number-average molecular weight and <=20 pts.wt. processing auxiliary and pelletized. The pellets are molded at 70 to 300 deg.C to give a cylindrical molded article having 10 to 150mm height, 5 to 100mm inner diameter, 3 to 20mm thickness, 1 to 10 ratio of height/inner diameter and 0.1 to 1.0 ratio of thickness/inner diameter. An inorganic granular material such as Al2O3 having 0.5 to 100mum particle diameter, not causing chemical change, not melting and not reacting during degreasing is packed into the inner diameter part on a supporting material such as sintered material of ZrO2. The cylindrical molded article is heated at 10 to 100 deg.C/hour rate of heating to decompose and remove the binder. The molded article is sintered and then the inorganic granular material is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for sintering a mixture containing a sinterable substance. More specifically, the degreasing method not only significantly shortens the degreasing time and sintering time, but also obtains a sintered product of a molded body of a sinterable substance-containing mixture that is free from deformations such as blisters and cracks that occur during sintering. The present invention relates to a method, and in particular to a method for degreasing a cylindrical molded body.

[Prior art] Currently, several percent of water-soluble substances such as polyvinyl alcohol are mixed with powders of ceramic materials such as alumina, silicon carbide, phyllite, barium titanate, and silicon nitride, and metals such as nickel, titanium, and iron. The granulated powder is shaped using a press method, then degreased and sintered, or an organic substance such as polyvinyl butyral is mixed with an organic solvent such as toluene to produce a sheet using a doctor blade method. However, after this sheet is dried, it is generally punched out with a punching die, degreased and dried to obtain a molded product. However, in such a method,
It was not possible to obtain a molded product that was three-dimensional and had a complicated shape. Recently, a method for obtaining green bodies by injection molding has been developed in order to obtain molded articles having complex three-dimensional shapes. In order to obtain a green body having a complicated shape by this injection molding method, 10 to 30% by weight of a low polymer of various polymers such as wax, styrene polymer, acrylic polymer, etc. is added to the ceramic material or metal. This is done by filling a mixture of the above into a mold using an injection molding machine. In order to sinter the green body thus obtained, a degreasing step is required to remove the polymeric substances and organic substances used in shaping the green body. After the polymeric substances and organic substances have been removed, a sintered body can be obtained through a sintering process, but conventional methods such as the pressing method and doctor blade method do not allow blisters, cracks, etc. in the molded body during the degreasing process. Furthermore, no harmful deformation occurs and the time required for degreasing is short.

[Problems to be Solved by the Invention] However, molded bodies obtained by molding methods such as injection molding and extrusion molding have a high content of polymeric substances and organic substances, so the degreasing process is difficult compared to conventional methods. It will make your hair last much longer. Furthermore, during the degreasing process, there are problems such as blisters and cracks on the surface of the green body, and further, deformation of the molded body.

In addition to these problems, especially in the case of cylindrical bodies, when degreasing the cylindrical body is set on a support in the usual way,
When heated at a constant temperature increase rate, there is a problem in that cracks, splits, and peeling occur inside the cylindrical body.

From the above, the present invention does not have these problems (defects), and can be made more efficiently by injection molding, extrusion molding, etc. The purpose is to obtain a product by a method that shortens the process and does not cause harmful deformations such as curls and cracks during degreasing.

[Means and effects for solving the problems] According to the present invention, these problems are such that the height is 10 to 150 mm, the inner diameter is 5 to 10 mm, and the wall thickness is 3 to 20 mm.
mm, the height to inner diameter ratio is 1-10, and the inner diameter to wall thickness ratio is 0.1-, -1.0. 3.
It is a sinterable substance containing 0 to 40% by weight, and when the cylindrical molded body is degreased on a support, the inside of the cylindrical body has an average particle size of 0.
．． It is characterized by being filled with inorganic granules that have a diameter of 5 to 100 μm, do not chemically change during the degreasing stage, do not melt during the degreasing stage, and do not react with the sinterable substance present in the molded body. It can be solved by degreasing method. The present invention will be explained in detail below.

The sinterable substance-containing mixture in the present invention essentially consists of the following sinterable substance and a binder.

fA) Sinterable substance The melting point, decomposition temperature or sublimation point of the sinterable substance of the present invention is usually 800°C or higher, preferably 1,000°C or higher,
In particular, a temperature of 1.4000°C or higher is suitable. If metals or inorganic compounds with a melting point, decomposition temperature or sublimation point below 800° C. are used as sinterable substances, harmful deformation and blistering will occur during degreasing (calcination).

Further, the average particle size is 0.1 to 500 μm. This average particle size varies depending on the type of sinterable substance, but in the case of metals, it is usually 1 to 500 μm, preferably 1 to 300 μm, and most preferably 1 to 200 μm. When a metal with an average particle size of less than 1 μm is used, crosstalk is difficult. On the other hand, if a metal with a diameter exceeding 500 μm is used, the mechanical properties of the molded product obtained by sintering will deteriorate. Also,
In the case of inorganic compounds, it is generally 0.1 to 200 μm, preferably 0.1 to 150 μm, particularly 0.1 to 1
00 μm is suitable. If an inorganic compound having an average particle size of less than 0.111 m is used, it is difficult to uniformly disperse the inorganic compound during crosstalk during production of the composition.

On the other hand, if an inorganic compound with a diameter exceeding 200 μm is used, shape retention will deteriorate when sintering a molded product of the composition, the density after sintering will decrease, and the mechanical strength of the sintered body will decrease. .

Representative examples of metals used as sinterable materials in the present invention include metals such as aluminum, iron, copper, titanium, molybdenum, zirconium, cobalt, nickel, and black metal, and metals containing these metals as a main component (at least 50% by weight). ). Powders of these metals and alloys are widely used as bearing base metals, free-cutting steel, heat-resistant materials, wear-resistant materials, etc., and are usually referred to as powder metallurgy materials. Typical examples include ceramic materials such as alumina, silicon carbide, silicon nitride, zirconia, cordierite, tungsten carbide, ferrite, and aluminum nitride.In addition, as sintering aids, boron, beryllium, carbon, and oxidized Add a small amount of yttrium, cerium oxide, magnesium oxide, lithium oxide, etc. (generally 10
(at most 20 parts by weight per 0 parts by weight of inorganic compound).

(B) Binder Resins that can be used as binders include ethylene polymers, styrene polymers, propylene polymers, ethylene-vinyl acetate copolymers, and alkyl (6 or less carbon atoms) methacrylates as main components. (50% by weight or more) (e.g., polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate)
and polymers (for example, polymethyl acrylate, polyethyl acrylate, polybutyl acrylate) having an alkyl (carbon number of 6 or less) acrylate as a main component (50% by weight or more). In the above description, the term "°-based polymer" means a homopolymer of the monomer and a copolymer containing the monomer as a main component (at least 50% by weight) and other monomers. The number average molecular weight of these binders (preferably higher than vapor). These binders are widely used in the field of producing sintered materials by mixing with ceramic materials.

(Production of C1 mixture In producing the mixture of the present invention, the sinterable substance 1
The mixing ratio of binder to 00 parts by weight is generally 3
．． The amount is 0 to 40 parts by weight, preferably 5.0 to 40 parts by weight, and particularly preferably 5.0 to 30 parts by weight. The mixing ratio of the binder to 100 parts by weight of the sinterable material is 3.
If the amount is less than 0 parts by weight, not only will the crosstalk, moldability and dispersibility of the mixture be poor, but it will also be difficult to produce a homogeneous mixture, and even if a homogeneous mixture is obtained,
It is not possible to obtain a good green body. On the other hand, if it exceeds 40 parts by weight, the physical properties of the green body (strength, shape retention) are good, but the density after removing the binder is low, and furthermore, it is difficult to sinter.

Furthermore, if necessary, halogen-free processing aids such as fatty acid amides, fatty acids or their esters, fatty alcohols, phthalates, aliphatic ethers, paraffin waxes, silane-based or titanate-based coupling agents are added. be able to. At this time, the amount of processing aid added is at most 2 parts by weight of the sinterable material.
The amount is preferably 0 weight, particularly 10 parts by weight or less.

The sinterable substance-containing mixture of the present invention can be produced by uniformly mixing the above sinterable substance and the binder or these and the processing aid. As a mixing method, it can be produced by tri-blending using a mixer such as a Henschel mixer, which is commonly used in the field of thermoplastic resins, or by using a bar mixer, kneader, roll mill, and screw extruder. Like,
It can also be obtained by melt-kneading using a mixer.

At this time, a homogeneous mixture can be obtained by triblending in advance and melt-kneading the resulting mixture. In this case, -1i19 is melted and kneaded, then molded into pellets, and subjected to the molding described later.

(Dl molded body The molded body of the sinterable substance-containing mixture used in the degreasing method of the present invention is made using an injection molding machine, extrusion molding machine, press molding machine, etc. at a temperature where the binder in the mixture melts. It is obtained by molding at a temperature that does not decompose.The molding temperature cannot be limited by the type of binder in the sinterable substance-containing mixture, but is generally 70°C.
~300°C. The obtained molded bodies of the sinterable substance-containing mixture in various shapes are subjected to degreasing described later.

The height of the molded body obtained in this way is 10 to 150 m.
m, 15 to 1.5 [1 mm is preferable, 20 to 1
50 mm is suitable. The height of this molded body is 150mm
If the degreasing is performed as described below, the lower part of the molded article will be deformed at that stage. Also, the inner diameter is 5 to 10
0 mm, preferably 5 to 90 mm, particularly preferably 5 to 80 mm. The inner diameter of the cylindrical molded body is 100
If it exceeds mm, degreasing can be carried out without filling the inside of the cylindrical molded body with the inorganic particulate matter described below.

Furthermore, the wall thickness is 3 to 20 mm, preferably 3 to 18 mm, and particularly preferably 3 to 15 mm. If the wall thickness of the cylindrical molded body exceeds 20 mm, cracks, splits, peeling, etc. may occur in the molded body during degreasing described later. On the other hand, if the height, inner diameter, and wall thickness are each less than the lower limit, the effect cannot be exhibited even if the degreasing described later is carried out.

Furthermore, the height to inner diameter ratio is between 1 and 10;
A value of 1 to 9 is desirable, and a value of 2 to 9 is particularly preferred. Also, the ratio of wall thickness to inner diameter is 0.1-1.0, and 0.
1 to 0.9 is preferable, and 0.2 to 0.9 is particularly preferable. Even if the ratio of the height to the inner diameter and the ratio of the wall thickness to the inner diameter are both less than the lower limit or exceed the upper limit, the resulting cylindrical molded product, its degreased product and sintered product will not have cracks, cracks, peeling, etc. This is not preferable because deformation may occur.

[E] Support Also, the support on which the molded body used in the degreasing method of the present invention is installed is a plate-shaped sintered body molded from any of various alumina, zirconia, silica, magnesia-based compounds, etc. , the thickness is not particularly limited.

fFl Inorganic Particulate Material Furthermore, the inorganic particulate material used in the present invention does not chemically change during degreasing described later. That is,
It does not undergo dehydration or decarboxylation. Furthermore, it does not melt during the degreasing step described later. Furthermore, it does not chemically react with the sinterable substance present in the molded body. Of course, if there is a chemical change or reaction during degreasing, there will be problems.

Its average particle size is 0.5 to 100 μm, and 1 to 100 μm.
The thickness is preferably 1 to 80 μm.

If the average particle size of the inorganic granules is less than 0.5 μm, there is a problem in that when the cylindrical molded body is filled with the granules for degreasing, the filling becomes uneven. On the other hand, if it exceeds 100μm, cracks, cracks, etc. may occur inside the cylindrical molded body during degreasing.
Peeling may occur. Examples of such inorganic particulates include alumina, silica, graphite, carbon, zirconia, and magnesia.

(Gl degreasing process In carrying out the degreasing process of the present invention, it is necessary to fill the cylindrical interior of the cylindrical molded body with the inorganic granules. At this time, if too much pressure is applied when filling the inorganic granules, the cylinder This is undesirable because cracks will occur on the inner surface of the shaped product.A cylindrical molded product filled with inorganic particulates can be heated at a temperature increase rate of 10 to 100°C per hour. The binder inside is completely decomposed and volatilized.Here, the end of degreasing is when the binder in the molded body is completely removed. "Instrumental Analysis" (Shokabo, published September 20, 1975) No. 308
The decomposition end temperature may be set as [see pages 317 to 317].

This degreasing step may be carried out in an atmosphere of inert gas (for example, argon gas, helium gas, nitrogen gas) using a degreasing furnace such as an electric furnace or a gas furnace.
The degreasing may be carried out in oxygen or air, but it must not react with the sinterable substance during degreasing.

By directly sintering the degreased cylindrical molded body in this way, harmful deformations such as blisters, cracks, and deformation do not occur on the surface or inner surface of the molded body, and in addition to sintering, degreasing is also possible. time can be significantly reduced.

[H) Sintering Step The molded body thus degreased is sintered according to a commonly used method. Oxide systems such as alumina are sintered in air at temperatures ranging from 500 to 700°C, each determined by the type of sinterable material. In addition, non-oxides such as silicon nitride and silicon carbide are nitrogen,
Sintering is performed in an atmosphere such as argon at a temperature in the range of 1500 to 2500°C, again determined by the type of sinterable material.

In carrying out this sintering, it is a matter of course that it is necessary to completely remove the inorganic particulates from the cylindrical molded body filled with the inorganic particulates degreased as described above.

[Examples and Comparative Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Examples 1 to 6, Comparative Examples 1 to 5 Alumina having an average particle size of 2.0 μm and silicon carbide having an average particle size of 0°6 μm were used as sinterable materials.

9 of each of these sinterable substances shown in Table 1.
0 parts by weight, 10 parts by weight of polymethyl acrylate having a number average molecular weight of about 350,000, 2.0 parts by weight of dibutyl phthalate, and 1.0 parts by weight of stearic acid were pre-triblended for 5 minutes using a Henschel mixer. I did it. The composition (
Beret) was manufactured. Each of the obtained pellets was molded at 150°C using an injection molding machine (mold clamping pressure of 100 tons) to produce a cylindrical plate-shaped molded product whose height, inner diameter, and wall thickness are shown in Table 1. did.

Each of the obtained molded bodies was placed on the support plate shown in Table 1, the inner diameter of the molded body was filled with inorganic granules whose type and average particle size were shown in Table 1, and 15° at
The temperature was raised to 600° C. at a heating rate of C/hour, and it was confirmed that the binder had been removed. In all of the Examples, no abnormalities were observed in the appearance of the degreased molded articles thus obtained. However, in Comparative Example 5, blisters occurred on the outer surface. Also, Comparative Examples 1 and 2
And in 5, the circle side! A crack occurred.

Furthermore, in Comparative Example 3, the lower part of the cylindrical molded body was deformed.

Each of the molded bodies degreased in this way was placed in an incinerator, and the temperature was raised to 1600°C under a nitrogen atmosphere (however, in Example 6 and Comparative Example 5, it was up to 2100°C under an argon atmosphere) at a temperature increase rate of 10°C/ The temperature was raised over time to perform sintering. No abnormality was observed in any of the sintered bodies obtained in all Examples.

However, all of the sintered bodies obtained in the other comparative examples had cracks on their inner surfaces, and in Comparative Example 4, blisters occurred on their inner surfaces.

(The following is a blank space) [Effects of the Invention 1 According to the method of the present invention, the following effects (characteristics) are exhibited.

Since the fil degreasing is performed uniformly, cracks, cracks, etc. do not occur on the inner surface of the sintered cylindrical body.

(2) Even if the degreasing time is shortened, a good molded product can be obtained.

According to the method of the present invention, the cylindrical molded product obtained to exhibit the above-mentioned effects can be used in fields such as machine parts such as various bottles, electronic equipment parts, home appliance parts, and automobile parts. Ru.

Claims (1)

[Claims] The height is 10-150mm and the inner diameter is 5-10mm.
and has a wall thickness of 3 to 20 mm, a height to inner diameter ratio of 1 to 10, and a cylindrical molded body having a wall thickness to inner diameter ratio of 0.1 to 1.0. , and the molded body is a sinterable material containing 3.0 to 40% by weight of a binder, and when the cylindrical molded body is degreased on a support,
An inorganic material with an average particle size of 0.5 to 100 μm inside the cylindrical shape, which does not chemically change during the degreasing stage, does not melt during the degreasing stage, and does not react with the sinterable substance present in the molded body. A degreasing method characterized by filling with granules.