JPS62105945A - Binder composition for 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 [Technical Field of the Invention] The present invention relates to an injection molding binder particularly suitable for molding fine ceramics.

[Technical background of the invention and its problems]

Generally, fine ceramic products are manufactured by putting raw material powder prepared by adding a forming aid and a sintering aid into a mold, shaping it, and then firing it. Dry processing molding is used to mold the above raw material powder.

Various methods have been used, such as rocking molding, potter's wheel molding, and mud casting molding, but they have the disadvantage of poor IT productivity. Therefore, injection molding has been developed as a method for efficiently molding fine ceramics.

However, the thermal conductivity of the molten resin containing ceramic powder is much higher than that of +8 melting point resin alone, so it is difficult to cool and solidify.

It has the disadvantage of extremely poor liquidity.

By the way, paraffin-based or resin-based binders have conventionally been used as injection molding binders for ceramics. However, the former paraffin binder is difficult to mold due to paraffin crystallization. Furthermore, paraffin binders have poor wettability with ceramic powder and poor compatibility with resins, so they are easily separated. On the other hand, the latter resin binder has dilatancy (D
i 1atancy; the property that a viscous suspension becomes difficult to flow due to the influence of shear stress. ). However, when both paraffin-based and resin-based binders have high thermal decomposition properties, the mechanical strength of the molded product after degreasing,
In particular, it has poor scratch resistance and is prone to surface defects in the sintered body.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances.

It is an object of the present invention to provide a binder for injection molding that can improve the fluidity of a mixture of ceramic powder and a molding binder during injection molding, and further improve the mechanical strength after degreasing.

[Summary of the invention]

The present invention is a binder composition for ceramic injection molding, in which a polyamide hot melt adhesive is blended with a paraffin binder or a resin binder that is kneaded when ceramic powder is injection molded.

[Embodiments of the invention]

Hereinafter, details of the present invention will be explained by way of examples with reference to FIGS. 1 to 8.

100 parts by weight of silicon nitride powder was mixed into the following composition.

Knead according to the mixing ratio and make a test piece (thickness 10M1lli).
After injection molding a disc with a diameter of 50 mm, degreasing conditions (room temperature to 120℃ 5℃/H, 120°○ to 260"03°0
7H, 260"0~400℃5'./H, 400℃~6
Degreasing was carried out at 00°C (10" O/H). Thereafter, thermogravimetric analysis of the contaminants of each example and cavilograph (described later) were carried out.
Toyo Seiki! The viscosity was measured by The fluidity evaluation of the mixed substance is performed using Cavillograph cD loyη (viscosity) v
Dilatancy and thixotropy were determined from the s1ofSR (shear rate) measurement results, and load fluctuations during measurement under certain conditions were read from a recorder, and in addition to the above-mentioned determination, a comprehensive evaluation was made.

The scratch resistance of the degreased body was evaluated using a stereoscopic microscope (10x magnification) to determine the presence or absence of surface scratches that occur during cleaning with a paintbrush or air blow.

Margin below Table 7 EVA in Nao 1 table is ethylene vinyl acetate.

DOP is dioctyl 7 tallate, APP is actiic polypropylene, PMMA is polymethyl methacrylate, Metrose is cellulose non-resin manufactured by Shin-Etsu Chemical, and Polyester is polyester resin manufactured by Nippon Gosei Chemical.

In addition, the Cabilograph is a measuring device manufactured by Toyosei and Iku Co., Ltd., which applies pressure to the liquid in the cylinder, causes the liquid to flow out from Oriais, and measures the viscosity from the relationship between the applied pressure and the flow rate. Figures 1 to 7 are measurements taken using the above-mentioned cavilograph, and sample positive 1 (
(black circle) Viscosity η vs. shear rate SR of sample No. 3 (white circle)
FIG. 1 is for the first embodiment, and similarly, FIG. 7 is for the seventh embodiment. Furthermore, Figure 8 shows the results of thermogravimetric analysis (TGA) of polyamide hot melt adhesives.
J is a diagram showing the degree of mass on the axis and the weight loss on the vertical axis. 3.6% remains.

TGA measurement conditions are nitrogen atmosphere, temperature rise rate constant 8"Q/min
It is.

〔Effect of the invention〕

As detailed above, the binder composition for ceramic injection molding of the present invention is composed of a paraffin binder or a resin binder and a polyamide hot melt adhesive. Various excellent effects can be obtained.

That is, in Figures 1 to 7, -1, the measurement results (measured temperature so'a) by Yapirograph (manufactured by Toyo Seiki) are 1a.
it 1 (viscosity) vslops 几 (shear series! f:
), when the polyamide hot melt is not added (each example Nn1), the viscosity curve is not linear but curved (giratancy). When polyamide-based hot melt is added, if 1 to 10 parts by weight is added to 100 parts by weight of ceramic powder, the above lopη vs 1opBR becomes a linear relationship (thixotropy), and it does not flow into the mold during injection molding. The liquidity of
A good degreased body and sintered body can be obtained. In addition, polyamide-based hot melt adhesives have a low melt viscosity, have an affinity for ceramic powders, especially silicon nitride powders, and have good compatibility with various resins, so they have the effect of improving the fluidity of mixed materials of ceramic powders. Furthermore, as a result of thermogravimetric analysis, polyamide hot melt adhesive
This is because the weight loss component in the temperature range of 25°C is heat resistant, and the thermal decomposition residue at 600°C is 3.6%.

It is effective in preventing cracks in the degreased body due to low-temperature thermal decomposition and volatilization during degreasing. Furthermore, the carbon residue in the degreased body contributes to improving the mechanical strength of the degreased body, which has the effect of improving the scratch resistance of the surface.

Note that the resin binder is not limited to this embodiment, and may be an olefin wax resin, a polyurethane resin, a phenol resin, or the like, as long as it can be used as a binder.

[Brief explanation of drawings]

Figures 1 to 7 are embodiments of the present invention to embodiment 7.
FIG. 8 is a diagram showing the relationship between viscosity and shear rate in , and FIG. 8 is a diagram showing the relationship between weight loss and heating temperature of polyamide hot melt. Agent Patent Attorney Noriyuki Chika Yudo Kikuo Takehana Figure 1 Figure 3 Figure 2 @ Figure 4

Claims (9)

[Claims] (1) A binder composition for ceramic injection molding, characterized in that a polyamide hot melt adhesive is blended with a paraffin binder or a resin binder as an injection molding binder that is kneaded into ceramic powder. (2) 100 parts by weight of ceramic powder to 30 parts by weight of paraffin binder or resin binder
Parts by weight, and 1 out of 23 parts by weight to 30 parts by weight
2. A binder composition for ceramic injection molding according to claim 1, characterized in that from 10 parts by weight is a polyamide hot melt adhesive. (3) The binder composition for ceramic injection molding according to claim 1 or 2, wherein the paraffin binder contains paraffin and ethylene vinyl acetate. (4) The binder composition for ceramic injection molding according to claim 1 or 2, wherein the resin binder contains polystyrene, polybutyl methacrylate, and paraffin. (5) The binder composition for ceramic injection molding according to claim 1 or 2, wherein the resin binder contains atactic polypropylene, ethylene vinyl acetate, and paraffin. (6) The binder set for injection molding of ceramics according to claim 1 or 2, wherein the resin binder contains polyethylene wax, ethylene vinyl acetate, and paraffin. (7) The resin binder is polymethyl methacrylate,
The binder composition for ceramic injection molding according to claim 1 or 2, characterized in that it contains polybutyl methacrylate and paraffin. (8) The binder composition for ceramic injection molding according to claim 1 or 2, wherein the resin binder contains a cellulose resin, ethylene vinyl acetate, and paraffin. (9) The binder composition for ceramic injection molding according to claim 1 or 2, wherein the resin binder contains a polyester resin, ethylene vinyl acetate, and paraffin.