JPS59179145A - Preparation of emulsified slurry - Google Patents

Abstract

PURPOSE:To obtain stable emulsified slurry by stirring a liquid dispersion of inorg. powder, emulsifier, and boric acid in a water-insoluble liq. alcohol after adding a liquid dispersion consisting of inorg. powder, polyvinyl alcohol, and water, thereto. CONSTITUTION:A liquid dispersion W is prepd. by mixing inorg. powder, polyvinyl alcohol and water. Separate liquid dispersion O is prepd. by admixing inorg. powder, emulsifier, and boric acid to a water-insoluble liquid alcohol. An emulsified slurry is obtd. by stirring after pouring said liq. dispersion W into the liq. dispersion O. In the mixing stage of both liq. dispersions, the liq. dispersion W, as soon as it is dispersed in the liq. dispersion O in the particulate state, is surrounded by the emulsifier and boric acid contained in the liq. dispersion O to form gelled film of polyvinyl alcohol. While the intrusion of inorg. Particles into the dispersion O is prevented by the gelled film, the film of the emulsifier is regenerated and restored.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preparing an emulsion-type slurry with excellent emulsion state stability.

In recent years, in the technology of making a composite sintered body starting from a slurry containing two or more substances selected from metals, ceramics, and glasses, each substance contained in the slurry is prepared by adjusting the slurry to an emulsion type. A technology that allows a composite sintered body to inherit only the necessary characteristics of the composite sintered body is attracting attention. One example is a metal-ceramic composite sintered body in which metal particles with good thermal conductivity are bonded through a layer of highly insulating ceramic, and such a sintered body cannot be achieved with each material alone or with a homogeneous compound. It has characteristics that were previously unavailable, namely the combination of high thermal conductivity and high insulation properties. However, the conventional emulsion-type slurry as described above lacks stability in its emulsion state mainly due to the following reasons. That is, by mixing and stirring a water-based slurry and an oil-based slurry containing an emulsifier, an emulsion-type slurry having a structure in which the water-based slurry is emulsified and dispersed in the partial slurry is produced, but the mechanical force applied during stirring is This is because the molecular membrane of the emulsifier is broken and the inorganic powder particles in the aqueous slurry often penetrate into the slurry.

In addition, due to an inappropriate combination of components in the slurry, the emulsion state essentially becomes unstable, and over time, the dispersed aqueous slurry particles begin to coalesce, eventually resulting in the aqueous slurry and oil phase. Sometimes it separated into two layers with the slurry. As described above, the sintered body obtained by starting from the slurry in the emulsion state has lost the properties of the composite sintered body obtained by starting from the emulsion-type slurry. Not only this, but also the basic properties of a sintered body such as mechanical strength and uniformity are inferior. Therefore, according to the conventional emulsion-type slurry preparation method, it is necessary to select a combination of components in the slurry in consideration of their specific gravity and mutual wettability, and to carefully stir the components.

The inventor utilized the phenomenon that polyvinyl alcohol aqueous solution instantaneously gels when it comes into contact with a trace amount of boric acid, and
It has been discovered that a stable emulsion-type slurry can be obtained by mixing a partial slurry containing a certain amount of boric acid with an aqueous slurry containing polyvinyl alcohol and subjecting the mixture to IWM'.

The present invention was obtained based on the above findings, and the gist thereof is (a) inorganic powder, polyvinyl alcohol (hereinafter referred to as rPV),
A process of mixing Aj) and water to create a dispersion W.

(b) Step of adding inorganic powder, emulsifier, and boric acid to non-aqueous liquid alcohol and mixing to create dispersion liquid ○.

(C) A step of pouring the W into O and stirring.

The invention consists in a method for preparing an emulsion-type slurry consisting of:

The reason why the emulsion state of the slurry obtained by the method of the present invention is stable will be explained in detail below.

That is, in step (c) above, W is dispersed in O in the form of particles and at the same time is surrounded by the emulsifier in O and boric acid. Even if the inorganic particles are to be broken and leached into O, at that moment a reaction between PVA molecules and boric acid occurs and a PVA gel film is formed, and this gel film prevents inorganic particles from leaching into O. Because the emulsifier molecular film is regenerated and repaired, W
Stable dispersion of particles is maintained for a long time.

The emulsion-type slurry prepared by the method of the present invention has an extremely stable emulsion state for the above reasons, so the composite sintered body obtained starting from this slurry has good uniformity and excellent characteristics of each component. It becomes something that has both.

Therefore, among such composite sintered bodies, dispersion W containing metals such as molybdenum, tungsten, iron, platinum, and silicon, or highly thermally conductive ceramics such as boron nitride, herria, aluminum nitride, silicon carbide, and magnesia, An emulsion-type slurry starting from a dispersion containing highly insulating ceramics such as alumina, mullite, forsterite, zircon, wollastonite, and glass ceramics is suitable for electronic components such as IC boards and heat sinks. Also, forsterite, mullite, zircon,
Products starting from an emulsion-type slurry consisting of a dispersion W containing ceramics with excellent heat insulation and wear resistance such as zirconia and glass ceramics and a dispersion O containing the above-mentioned metals include gas rings, 7-pieces, seal rings, etc. Suitable for mechanical parts.

Examples are shown below.

Example 1 (a) Distilled water 82cc
PVA (Denka B-17) 3g ferric oxide with an average particle size of 0.3μm 53g manganese dioxide with an average particle size of 0.5μm 3g with an internal volume of 300
The mixture was mixed for 15 hours using a m# polyethylene ball mill, and this was used as a dispersion W1.

Middle) Reagent-grade boric acid 0.5gn
-Butyl alcohol 180cc Forsterite with average particle size of 0.5μm (silane coupling treated product) 7g Emulsifier (Nonion 0P-8OR manufactured by NOF@) 2.
4g ethyl cellulose 2g plasticizer (dioctyl phthalate) 6g internal volume 5
00m1! The mixture was mixed in a polyethylene ball mill for 15 hours, and this was used as Dispersion 01. Dispersion liquid 01 50
The slurry was transferred to a 0 ml beaker, and the dispersion W was poured thereinto while stirring with a propeller stirrer to obtain an emulsion-type slurry S.

The emulsion state of Slurry 81 remained stable even after being left for one day. This Sl was poured onto a polyester carrier film, formed into a sheet using a doctor blade method, and air-dried for 15 hours to produce a green sheet with a thickness of 0.8 mm.The cross section of the sheet was examined using an electron microscope. When observed, it was found that the collection method 1 made of ferric oxide and manganese dioxide was surrounded by forsterite porcelain 2 as shown in the figure. This green sheet was placed in a hydrogen gas atmosphere with a dew point of 15°C.
By firing at a temperature of 1,350°C and a holding time of 1 hour, it has a structure based on sintered forsterite porcelain, in which sintered iron balls produced by reduction of ferric oxide are uniformly dispersed. A metal/ceramic composite sintered body was manufactured.

In this example, a binder and a plasticizer were added to the dispersion liquid 01 in order to facilitate sheet forming, but these are not essential components for the method of the present invention, and the casting shown in Example 2 below. In the case of molding, it is possible to achieve the effects of the present invention without adding these materials even when using thermal theory, spray drying or freeze drying.

Example 2 (al distilled water 82cc
PVA (Denka B-17) 3g Ferric oxide with an average particle size of 0.3 μm 22g Molybdenum trioxide with an average particle size of 0.5 μm 40g Average particle size of 0.
1g of 2μm aluminum oxide has an internal volume of 300m! !
The mixture was mixed for 15 hours using a polyethylene ball mill, and this was used as a dispersion W.

(1)) Reagent-grade boric acid 0.5μ
m-Butyl alcohol 180 cc Aluminum oxide with an average particle size of 0.2 μm (silane coupling treated product) 17 g Reagent special grade aluminum hydroxide (silane coupling treated product) 5 g Reagent -
Grade magnesium calcium silicate g Emulsifier (Nonion 0P-801 manufactured by NOF ■) 2
．． 4 g was mixed for 15 hours in a polyethylene ball mill with an internal volume of 500 m1, and this was used as dispersion liquid 02.

As in Example 1, dispersion W2 was poured into dispersion 02 to obtain emulsion-type slurry S2. This S
2 was poured into a plaster mold, left for 20 minutes, removed from the mold, and baked in a hydrogen atmosphere at a temperature of 1520'C, a dew point of 5°C, and a holding time of 1 hour.
A sintered body was obtained. The obtained sintered body has alumina porcelain as its core, and contains particles of iron and molybdenum with a diameter of 10 to 10.
The metal/ceramic composite sintered body had a structure in which sintered particles of 20 μm were uniformly dispersed.

[Brief explanation of the drawing]

The figure is a partial sectional view of a green sheet obtained according to an embodiment of the emulsion-type slurry preparation method of the present invention.

Claims (1)

[Claims] (a) A step of mixing an inorganic powder, polyvinyl alcohol, and water to prepare a dispersion W. (b) A step of adding an inorganic powder, an emulsifier, and boric acid to a water-insoluble liquid alcohol and mixing them to form a dispersion O. (C) Step of pouring the W into 0 and stirring. A method for preparing an emulsion-type slurry consisting of: