JPS59203763A - Injection molding composition - 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 The present invention relates to an injection molding composition used as a raw material in an injection molding process, which is one process for manufacturing ceramic molded products.

Conventionally, ceramic molded products are produced by mixing ceramic powder and an organic binder, injection molding the mixture to form a molded product of a certain shape, and then removing the organic binder in a degreasing process.
After that, it was manufactured by sintering. As the organic binder, for example, polystyrene, polypropylene, etc. have been used. In addition, in this case, the organic binder is diT-thilphthalene 1.
~, plasticizers such as diallyl phthalate, and lubricants such as paraffin, wax, and stearic acid were added.

However, conventional ceramic molded products produced by MA using the injection molding compositions described above have the following drawbacks.

First, the dimensional accuracy during injection molding is poor, making it difficult to obtain ceramic molded products with complex shapes with high precision.
It was 1. This is due to the poor flow of the injection molding composition.

Second, in the degreasing step of removing the organic binder from the molded product after injection molding, defects such as blistering, cracking, and peeling of the surface layer tend to occur in the molded product. In order to prevent such defects, for example, there is a method of slowing down the temperature increase rate during degreasing, but this takes a long time and poses problems in manufacturing. Furthermore, defects such as cracks and peeling of the surface layer tended to further expand during the sintering process.

The present invention was devised in view of the above circumstances, and aims to improve the accuracy of usage during injection molding by changing the composition of the injection molding composition, and to degrease or degrease ceramic products with complex shapes. The purpose is to do so without producing defects such as cracks during sintering.

The first invention is an injection molding composition comprising a ceramic powder and an organic binder, the organic binder being mainly polybutene.

The organic binder has the function of imparting fluidity to the ceramic powder and allowing prompt injection molding. A plasticizer and a lubricant are added to the organic binder at a weight ratio of 5 to 20 parts of polybutene to 100 parts of ceramic powder.
The amount of plasticizer and lubricant is preferably 5 parts or less each. Polybutene is a colorless and transparent random copolymer produced by a low-level catalytic reaction between isobutylene and normal butylene in the butane-butylene fraction produced by naphtha decomposition. This has good compatibility with lubricants such as wax and paraffin, and also has good wetting with ceramic powder. Also, compared to conventionally used thermoplastic resins,
Due to its low viscosity and low surface tension, it has good fluidity when mixed with ceramic powder.

As the ceramic powder, silicon nitride, alumina, zirconia, silicon carbide, aluminum nitride, -4-tungsten carbide, boron nitride, boron carbide, cordierite, metallic silicon, etc. can be used.

The particle size is preferably about 0.1 to 10 parts.

The molecular weight of polybutene can be selected depending on the particle size of the ceramic powder. When the molecular weight of polybutene is small when the particle size of the ceramic powder is relatively small, and when it is large when the particle size is relatively large, the yield rate after sintering and the condition after degreasing are improved.

A second invention is a composition for injection molding, comprising a ceramic powder and an organic binder, the organic binder being mainly polybutene, and containing a sublimable substance having a sublimation temperature lower than the melting temperature of the polybutene. It is a thing.

As the sublimable substance, at least one of naphthalene, anthracene, camphor, zenatrene, anthraquinone, benzoic acid, phthalic anhydride, and salicylic acid can be used. During the degreasing process, the sublimable substance sublimates at a low temperature before the polybutene is thermally decomposed, forming many fine pores in the molded body, and releasing cracked gas, which is a thermal decomposition product of polybutene, into the molded body. It has the function of making it easier to release the liquid to the outside.

However, if the amount of the substance ↑↑1 is too large, it will inhibit the adhesiveness of polybutene and impair moldability. Therefore, the amount of the sublimable substance to be blended varies depending on the type of the sublimable substance, but is generally about 30 parts by weight or less per 100 parts by weight of polybutene. Note that adding paraffin to the organic binder can compensate for the deterioration in moldability caused by sublimable substances.

When the injection molding composition of the first invention is used, it has good fluidity during injection molding, and therefore molded products with complex shapes can be made with dimensional accuracy. Moreover, since the molecular weight of polybutene can be changed according to the particle size of the ceramic powder, the fluidity is good.Furthermore, the pyrolysis gas of polybutene is released quickly during degreasing, so there is no cracking, The incidence of defects such as surface layer peeling 1 is also low. Moreover, when the injection molding composition of the second invention is used, in the degreasing step,
Since the sublimable substance first volatilizes and forms fine pores in the molded product, the thermal decomposition gas of polybutene is released more quickly than the fine pores. Therefore, the occurrence of defects such as cracks, peeling of the surface layer, and swelling during the degreasing process is effectively prevented.

The present invention will be explained in detail below.

First Example of the Invention First Example Ceramic powder contains 90 mol% of silicon nitride (Si3N4) with an average particle size of 0.8 microns and 11% of magnesila.
Aluminum spinel (M(IO・Al2O3)10
After wet mixing the mole %, a dry product was prepared. To 100 parts by weight of the ceramic powder, 12 parts by weight of polybutene, 2 parts by weight of paraffin as a lubricant, and 1 to 1 part by weight of diethyl phtathy as a plasticizer,
This was the composition for extrusion molding of the first example. In addition, as shown in Table 1, polybutene has 5 different molecular lengths.
Type-b was used. A ceramic molded article is manufactured using the composition for cutting molding having such a composition according to the following steps. 1
child .

First, the injection molding composition comprising ceramic powder and an organic binder was kneaded in a high-temperature kneader at 18-7-0°C for 30 minutes, then re-kneaded using a twin-screw high-dry extrusion machine, and pelletized. . Next, the jqed pellets are heated at 160 to 200°C and 90°C using an injection molding machine.
A cup-shaped test piece and a rotor part for a gas turbine were molded by injection into a mold under a strip 1 of 0 k(]/cm2. Each test piece produced by this injection molding was heated to 2°C/cm2.
The sample was degreased by heating from room temperature to 400° C. at a heating rate of 1 hour, and then kept at 1750° C. for 4 hours in a nitrogen atmosphere to sinter, yielding the desired ceramic sintered body. Table 1 summarizes the formability, condition after degreasing, and yield rate after sintering of each test piece.

Second Example In the second example, a ceramic powder consisting of 95 mol % of alumina (A1203) with an average particle size of 3 microns and 5 mol % of kaolinite was used. The compositions of polybutene, lubricant, and plasticizer are the same as in the first example. 1st
Ceramic molded products were manufactured in the same manner as in the examples, and their moldability, condition after degreasing, yield rate after sintering, etc. were compared. The results are shown in Table 2.

Second Example of the Invention Third Example Ceramic powder contains 90 mol% of silicon nitride (St 3N4) with an average particle size of 0.8 microns, and 10 mol% of magnesium aluminum spinel (MgO-Al2O2).
A mixture consisting of the following was wet mixed and a dry mixture was prepared. As an organic binder, 0 to 40 parts by weight of naphthalene as a sublimable substance per 100 parts by weight of polybutene (Nos. 01 to 10 in Table 3) and a lubricant to 100 parts by weight of the combined polybutene and naphthalene. A composition consisting of 10 parts of paraffin was added to prepare a composition for extrusion molding. The ratio of the ceramic powder to the organic binder was such that the organic binder was 45% by volume.

Ceramic molded products were manufactured using the injection molding compositions having the above compositions according to the following procedure, and their moldability, condition after degreasing, yield rate after sintering, etc. were compared.

First, from ceramic powder and organic binder -〇
- After kneading the composition consisting of the following compositions at 180° C. for 1 hour in a high-temperature kneader, it was re-kneaded and pelletized using a twin-screw high-dry extruder. Next, the jqed pellets were injected into a mold using an injection molding machine under conditions of 160 to 200°C and 900 kg/cm' to mold rectangular test pieces of 10 mm x 60 mm x 5 mm and rotor parts for a gas turbine. 1
The injection molded product thus prepared was degreased by heating from room temperature to 400°C at a heating rate of 4°C/hour, and then sintered by keeping it at 1750°C for 4 hours in a nitrogen atmosphere. Table 3 shows the results.

The bending strength in Table 3 is the average value of 10 samples each obtained by a three-point bending test with a span of 30 mm and a loading rate of 0.5 mm/min.

Fourth Embodiment The fourth embodiment is substantially the same as the third embodiment. The fourth embodiment differs from the third embodiment in that an1-hracene was used as the sublimable substance. Table 4 shows a comparison of moldability, state after degreasing, and food grade after sintering of ceramic molded products manufactured using the injection molding composition of Example 4.

-10- According to Table 1, for ceramic powder with an average particle size of about 0.8 microns, the molecular weight of polybutene is 550 to 980.
It can be seen that the moldability, the condition after degreasing, and the yield rate after firing are all good. Also, from a comparison of Tables 1 and 2, it is decided that when the particle size of the ceramic powder changes, the molecular weight of the polybutene will be changed accordingly.In other words, if the average particle size increases, the molecular weight of the polybutene It can be seen that when the molecular weight is large and the average particle size is small, the moldability, the condition after degreasing, and the yield rate after firing can be improved by reducing the molecular weight of polybutene.

Also, from Table 3, naphthalene, which is a sublimable substance, is added to polybutene, which is an organic binder, and 7. - case, formability,
Both the condition after degreasing and the bending strength are good, and the effect is remarkable when the amount of naphthalene added is 30 parts by weight or less, preferably 2 to 20 parts by weight, based on 100 parts by weight of polybutene. I understand. In addition, when paraffin is further added to polybutene and naphthalene, N in Table 1
A comparison of samples No. 4, No. 10, and No. 10 shows that the forming property can be improved. That is, deterioration in moldability caused by naphthalene can be compensated for by paraffin. Next, from Table 4, it can be seen that when anthracene is used as the leather material, the amount added may be slightly smaller than that of naphthalene.

To summarize as above, the first invention is an injection molding composition consisting of ceramic powder and an organic binder, and using polybutene as the main organic binder, and the second invention is
The organic binder is mainly composed of polybutene and further contains a sublimable substance whose sublimation temperature is lower than the melting temperature of polybutene.1!1. : A composition for injection molding. J: Sea urchin, which is clear from the description in the Examples, the first invention and the second invention
When a ceramic molded article is manufactured using the injection molding composition of the invention, the ceramic molded article has a complicated shape due to precision dimensions, and defects such as cracks, surface peeling, and swelling occur. You can get it without.

-12- Table 1 Table 2 13- Table 3-1/l - Table 4-15-Continued from page 1 ■Inventor Masa Asai 23, Iwasaku, Mukaihata, Nagakute-machi, Aichi-gun, Aichi Prefecture■ Requester: Toyota Central Research Institute Co., Ltd. 41-1 Yokodori, Nagato, Nagakute-machi, Aichi-gun, Aichi Prefecture

Claims (4)

[Claims] (1) An injection molding composition comprising a ceramic powder and an organic binder, wherein the organic binder contains polybutene as a main component. (2) The organic binder is composed of polybutene, a plasticizer, and a lubricant, and the weight ratio in the injection molding composition is 5 to 20 parts of polybutene to 100 parts of ceramic powder;
The injection molding composition according to claim 1, wherein the composition contains 5 parts or less of a plasticizer and 5 parts or less of a lubricant. (3) An injection molding composition comprising ceramic powder and an organic binder, the organic binder containing polybutene as a main component and a sublimable substance having a sublimation temperature lower than the melting temperature of the polybutene. An injection molding composition characterized by: -1- (4) The injection molding according to claim 3, wherein the flowering substance is at least one of naphthalene, anthracene, camphor, phenanthrene, anthraquinone, benzoic acid, phthalic anhydride, and salicylic acid. Composition for use.