JPS6219236A - Dispersing method of boron nitride into base material - Google Patents

Abstract

PURPOSE:To increase the dispersion properties and also to prevent the reflocculation by dispersing boron nitride for a base material such as gypsum in the presence of a surfactant. CONSTITUTION:A uniformly mixed slurry is easily obtained by mixing 1-90wt% boron nitride and 0.001-10wt% surfactant as a mold release agent to a base material for a mold such as gypsum and silica and stirring the mixture. Further as the surfactant, the effect is recognized in spite of the kind but especially an anionic and a nonionic surfactants are effective. In case of the nonionic surfactant, HLB is at least 5 and preferably >=8.

Description

[Detailed description of the invention] (Industrial application field) The present invention is a method for dispersing boron nitride into a substrate.

In particular, the present invention relates to a method for improving the dispersibility of boron nitride present as a mold release material on the surface of a mold.

(Prior Art) It is necessary for the surfaces of various molds to have high mold releasability from the cast product, and for this purpose various mold release means have been proposed.

Among these measures, the provision of a layer of boron nitride has been proposed, and some have been implemented, for various molds.

(Problems to be solved by the invention) Boron nitride has a large surface smoothness and is chemically stable, so it has the advantage of having a wide range of applications, but has the disadvantage of poor dispersibility in other materials. ing.

For example, even in a typical case where a small amount of powdered boron nitride is dispersed in a base material such as gypsum slurry, it takes a great deal of energy and time to uniformly disperse the powder, and only one dispersion is required. The viscosity of the slurry becomes quite high, making the subsequent molding operation difficult, and since it contains a large amount of fine bubbles, the molded product itself has various problems and defects, such as defects caused by the bubbles. Furthermore, the boron nitride powder dispersed in this manner is likely to reagglomerate, and the effect of adding boron nitride is not very effective.

(Means for Solving the Problems) The present inventor has solved these various drawbacks, made boron nitride easily and uniformly dispersed in the base material, and furthermore, the boron nitride after dispersion does not cause re-agglomeration. As a result of various studies and examinations aimed at finding an f-stage that eliminates the
It has been found that the above object can be achieved, and this is the gist of the present invention.

In the present invention, the base material in which boron nitride is dispersed includes:
For example, 1 gypsum, silica, magnesium phosphate, aluminum phosphate, magnesium oxide.

Calcium silicate, etc., and these include materials used for dental investment materials, metal molds, crucibles, lubricants, and the like.

The amount of boron nitride dispersed in such a base material is preferably about 1 to 90 g per 100 g (dry amount) of the base material to be mixed, when it imparts surface smoothness to a mold, etc. be.

In the present invention, a surfactant is used when dispersing boron nitride into the base material. The amount of surfactant to be used is generally from o,oot to 10% by weight based on the base material, so that boron nitride can be easily and uniformly dispersed in the base material and the amount of boron nitride after dispersion can be reduced. Aggregation can also be sufficiently suppressed.

Although such surfactants are effective regardless of their type, particularly high effects can be expected when anionic surfactants and nonionic surfactants are employed.

Examples of anionic surfactants used include higher alcohol sulfate ester salts, fatty acid salts, alkylbenzenesulfonate salts, and nonionic surfactants such as polyoxyethylene alkyl ether,
Polyoxyethylene rubitan fatty acid ester and the like may be appropriately employed.

When using a nonionic surfactant, its HLB
When the ratio is at least 5, preferably 8 or more, high effects can be expected.

Depending on the purpose of use, boron nitride can be dispersed throughout the base material, or it can be concentrated in the vicinity of the mold surface that comes into contact with the object to be molded, such as in a casting mold. The following aspect may be adopted.

In addition, in the present invention, the above-mentioned materials can be used as the base material, but in addition, binders and extenders for the base material such as ethyl silicate, filler 1 colorants, etc. may be used in combination as appropriate as long as they do not impede the purpose of the present invention. I can do it.

(Example) Example 1 Nonionic surfactant (Nonipol 55 manufactured by Sanyo Chemical Co., Ltd.
HL B 10.5) 0.5g) was added to 100g of a dedicated investment material solution containing silica sol as the main ingredient, 100g of phosphate-based investment material (Blue Best manufactured by Tokuyama Kinken Co., Ltd.) powder and 40g of boron nitride powder were added, and Yoshida The mixture was stirred and degassed for 20 seconds at 740 rpm under a vacuum of tOtorr using a Tsu'acumina type stirrer manufactured by Kogyo Co., Ltd., to obtain a uniformly mixed and smooth slurry. Then, the defoamed slurry is filled into a ring with a chevron-shaped wax pattern planted in the center,
Hardened.

These were then heated at 700° C. for 1 hour to burn out the wax pattern and obtain cavities therein. On the other hand, CaO2
A composition consisting of 5% by weight, 2% by weight of Al2O, and 573% by weight of P2O was melted at 1250°C, introduced into the cavity by centrifugal casting, cast, and kept at 700°C for 2 hours to form a crystallized glass. Obtained. After that, I cooled it down for an hour, broke the mold, took out the crystallized glass molded body, and brushed it with a toothbrush. All the investment material that had adhered to it was easily removed! After separating A, no reaction area with the molding material was observed on the surface of the molded product, and a white molded product with translucent texture was obtained.

Example 2 Anionic surfactant (Neoperex manufactured by Kajosha) 0
．． 10 g of phosphate-based investment material (Blue Best manufactured by Yayama Seidai Co., Ltd.) powder was added to 15 g of a dedicated investment material solution mainly composed of silica sol in which 01 g of boron nitride powder and 5 g of boron nitride powder were added and dispersed. Using a stirrer, ? 40rps
After stirring at + for 20 seconds and defoaming under vacuum, a smooth, uniformly mixed slurry was obtained.

This slurry was applied to the surface of a tooth-shaped wax pattern fixed to a sprue wire set in advance in a rubber cone T to a thickness of 0.1 to 0.5 layers. Then, this wax pattern was stacked at the center of the ring, and a slurry of a phosphate-based investment material (Blue Best, manufactured by Tokuyama Teidai Co., Ltd.) was filled into the ring and allowed to harden.

Next, heat treatment, glass casting, and crystallization were performed in the same manner as in Example 1 to obtain a molded body. As in Example 1, the obtained molded product had no reaction with the mold material and had the same appearance.

Comparative Example The same procedure as in Example 1 was carried out except that no surfactant was used, and stirring was carried out in the same manner as in Example 1.
After a few minutes, I finally got a fairly sticky slurry that appeared to be almost homogeneous.

When a glass molded body was obtained using this slurry in the same manner as in Example 1, there were reaction products with the mold material in the shape of irregular protrusions of about 80 μm at several places on the surface of the molded body.

This is because some boron nitride was not dispersed in the mold material, and that portion of the mold material was missing. From these facts, it seems that either a uniform investment material slurry was not produced, or that some of the boron nitride in the uniform slurry that was once produced re-agglomerated.
r Procedural amendment (formula, Showa 60, 11 JJlq

Claims (1)

[Claims] 1. A method for dispersing boron nitride into a substrate, which comprises dispersing boron nitride into the substrate in the presence of a surfactant. 2. The dispersion method according to claim (1), wherein the amount of boron nitride dispersed in the base material is 1 to 90% by weight based on the base material. 3. The amount of surfactant present is 0.001 to 1% relative to the base material.
The dispersion method according to claim (1), wherein the dispersion method is 0% by weight. 4. The dispersion method according to claim (1), wherein the base material is gypsum, silica, magnesium phosphate, aluminum phosphate, magnesium oxide, or calcium silicate. 5. The dispersion method according to claim (1) or (3), wherein the surfactant is an anionic surfactant. 6. The dispersion method according to claim (1) or (3), wherein the surfactant is a nonionic surfactant. 7. The dispersion method according to claim (6), wherein the nonionic surfactant has an HLB of at least 5.