JPS61117166A - Method of dewaxing ceramic injection molding - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Industrial application field This invention mixes ceramic powder with an organic binder mainly composed of thermoplastic resin, and press-fits the mixture into a mold in a state of good fluidity to give it a shape. The present invention relates to a method of removing resin from a ceramic injection molded body obtained by injection molding after molding.

BACKGROUND OF THE INVENTION When molding ceramic parts with complex shapes, injection molding is applied, which provides molded bodies with good homogeneity, short molding time, and is suitable for large scale production. However, since the ceramic injection molded body obtained by this injection molding method contains an organic binder whose main component is a thermoplastic resin, it cannot be fired as it is, and the organic bonds in the molded body are removed before firing. It is necessary to perform degreasing to remove the agent by thermally decomposing it.

Degreasing is a process in which the thermal decomposition of the organic binder is gradually progressed from the surface of the injection molded object to the inside in a heating T. If the thermal decomposition of the organic binder progresses too quickly, thermal decomposition occurs inside the molded object. The gas cannot escape completely, resulting in various defects in the molded product.

Conventionally, therefore, the thermal decomposition of the troweled binder was gradually progressed by creating an inert gas atmosphere such as N2 gas in the heating furnace.

Problems to be Solved by the Invention However, the above-described conventional method for degreasing an injection molded article has the following problems.

That is, in the conventional method described above, the injection molded article is placed in an inert gas atmosphere from the beginning to the end of degreasing,
Therefore, for an injection molded product having a thick inner part, the center of the thick part is difficult to degrease, and therefore the resin remaining in the center of the thick part is difficult to degrease. There has been a problem in that internal defects called blisters occur in ceramic products after firing with BW.

This invention has been made in view of the above-mentioned conventional circumstances, and is a ceramic injection method that eliminates residual resin and can obtain a fired body without internal defects even in an injection molded body having a thick inner part. The object of the present invention is to provide a method for degreasing a molded article.

A means for solving the problem, that is, a method for degreasing a ceramic injection molded body according to the present invention, is to first heat the ceramic injection molded body in an inert gas atmosphere, and then change the atmosphere to atmospheric air. It is characterized by switching.

The method of the present invention will be explained in more detail below.

In this invention, first, as shown in FIG. 1, a ceramic injection molded body is heated in an inert gas atmosphere.

In FIG. 1, a closed container 2 is disposed inside a heating furnace 1, and a gas introduction pipe 3 for introducing an inert gas from outside the heating furnace 1 into the closed container 2, and a gas introduction pipe 3 from inside the closed container 2. A gas discharge pipe 4 for discharging gas is attached. Further, in the closed container 2, a can 7 is installed in which a ceramic injection molded body 6 is embedded and housed in the ceramic powder 5. Further, a fan 8 is provided on one side of the heating furnace 1, and the fan 8 blows the airtight container 2 into the airtight container 2.
1ffi is sent. N2, Ar, etc. can be used as the inert gas.

Heating in an inert gas atmosphere is preferably carried out until 90% or more of the ceramic injection molded body is degreased. This is because if the inert gas is stopped at a temperature lower than that, degreasing will proceed rapidly thereafter, which will not only have an adverse effect on the molded product, but also pose a danger that the decomposed gas of the organic binder will explode.

Next, in this invention, as shown in FIG. 2, the atmosphere of the molded body after heating in the inert gas atmosphere is switched to the atmospheric atmosphere. That is, as shown in FIG. 2, the introduction of inert gas such as N2 into the closed container 2 through the gas introduction pipe 3 is stopped.

The humidity maintained in the air is preferably 300 to 500°C. Below 300℃, the degreasing efficiency is poor;
This is because if the temperature exceeds C, the oxidation of the raw material composition of the molded body will progress, which will have an adverse effect on the strength of the fired body.In addition, the holding time in the air atmosphere is preferably 2 hours or more.If it is less than 2 hours, This is because degreasing may not be sufficient.

EXAMPLE An example of the method for degreasing a ceramic injection molded body of the present invention will be described below.

EXAMPLE Using the apparatus shown in FIGS. 1 and 2, the injection molded article 6 was degreased according to the degreasing pattern shown in FIG. 3.

The injection molded body 6 is made of silicon nitride (S i3N+ ) 92w
A kneaded product of a ceramic mixed powder consisting of 4 wt% of ittria (Y203) and 4 wt% of spinel (M(]Al204) and 17 wt% of resin was obtained by injection molding into the i-shape of a turbocharging rotor. As shown in Fig. 1, the injection molded body 6 obtained by The heating rate inside the heating furnace 1 was set to 1.
~b and heated to 500°C.

Next, keep the injection molded product under the above conditions for 5 hours until 90% of the 6 to 90%
When the degreasing was completed, the supply of N2 gas was stopped, and the injection molded product 6 was held in the atmospheric atmosphere as shown in FIG.

The holding temperature is in the range of 300 to 500℃, and 2
held for more than an hour.

Finally, after degreasing 98% or more as described above, the obtained degreased body (not shown) was fired at 1750° C. for 5 hours in an N2 gas pressurized atmosphere. The thus obtained fired body was subjected to two-directional X-ray imaging and cut to examine the presence or absence of internal defects.

In addition, degreasing was carried out in the same manner as in the example by setting various temperatures at which the supply of N2 gas was stopped, and the fired bodies obtained after firing were examined for the presence or absence of internal defects.

The above results are shown in Table 1.

Table 1 As shown in Table 1, there were no internal defects in the samples in which the N2 gas was stopped at 300°C, including the samples in which the N2 gas was stopped at 500°C. This shows that, according to the present invention, even a thick injection molded article can be sufficiently degreased to the center. In addition, there are internal defects in those in which N2 gas is stopped at 200°C or 50°C.
It can be seen from the above that it is preferable to heat the injection molded article in an air atmosphere.

Effects of the Invention As described above, according to the method for degreasing a ceramic injection molded body of the present invention, the ceramic injection molded body is heated in an inert gas atmosphere and then heated in an air atmosphere, thereby removing thick parts. Even in the case of a ceramic injection molded body having the following properties, the central part can be sufficiently degreased, and internal defects that occur after firing due to the influence of residual resin can be eliminated.

[Brief explanation of the drawing]

1 and 2 schematically show a heating furnace used for carrying out the present invention, and FIG. 1 shows the inside of the heating furnace during the heating process of an injection molded product in an N2 gas atmosphere, and FIG. FIG. 2 is a diagram showing the inside of the heating furnace during the process of holding the injection molded article in the air atmosphere. FIG. 3 is a diagram showing a degreasing pattern according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Heating furnace, 2... Sealed container, 3... Gas introduction pipe, 4... Gas discharge pipe, 6... Ceramic injection molded body. Applicant Toyota Motor Corporation Representative Patent Attorney Yutaka 1) Hisashi Take (one idiot)

Claims (1)

[Claims] A method for degreasing a ceramic injection molded article, which comprises first heating the ceramic injection molded article in an inert gas atmosphere, and then switching the atmosphere to atmospheric air.