JPS5992144A - Composition of embedding material for precision casting - Google Patents

Abstract

PURPOSE:To provide a compsn. of an embedding material for precision casting which is formulated to expand largely on curing by mixing ZrSiO4, fused quartz, silica, NH4H2PO4 and MgO and kneading the mixture with a colloidal silica dispersion. CONSTITUTION:An embedding material prepd. by mixing 30-50wt% ZrSiO4, 15-30% fused quartz, 10-40% silica, 5-15% NH4H2PO4, 5-15% MgO is kneaded with a colloidal silica dispersion, whereby a compsn. of an embedding material for precision casting is obtd. The dispersant is mixed preferably at about 14-18cc with 100g, the embedding material. The expansion on curing of such compsn. is increased to about 4%. The expansion on curing is made adjustable by the concn. of the silica in the dispersant. Since there is virtually no expansion with heating, any cracking is not generated in the embedding material and the heating time is reduced.

Description

[Detailed description of the invention] The present invention relates to an investment material composition for precision casting.

In precision casting of dental cast products such as dental crowns, when casting by injecting molten metal into the mold cavity formed by heating, burning out or eluting the wax model embedded in the investment material,
The alloy varies depending on the type, but is approximately 1.4 to 2.3
% heat loss M4, it is necessary to expand the molding cavity beforehand when pouring the molten metal, and this expansion is carried out by the expansion that occurs when the investment material hardens and is heated.

Conventional investment materials include refractory materials such as silica.

Gypsum-based investment material mixed with plaster as a binding material,
Phosphate-based investment materials mixed with monoammonium phosphate and magnesium oxide as a binding material are generally used, and the latter phosphate-based investment materials have a higher performance than plaster-based investment materials. Since it has high heat resistance, it can also be used for casting alloys with high melting points such as nickel-chromium-cobalt alloys, and it also has advantages such as the strength of the investment material during casting. However, when conventional phosphoric acid J4A-based investment materials are kneaded with water, there is almost no hardening expansion and the heating expansion is about 1%, so that the thermal contraction of the alloy cannot be sufficiently compensated for. For this reason, colloidal silica dispersion is used for kneading phosphate-based investment materials.
In this case, the curing expansion can be improved to about 1% by increasing the silica concentration of the colloidal silica dispersion.

In this way, the total expansion rate of the investment material can be increased by kneading the phosphate-based investment material with the colloidal silica dispersion, but if the product speed is increased during heating, the expansion rate will increase and the investment material will be buried. Since cracks occur in the material, it is necessary to gradually raise the temperature and heat it for a long time (for example, 3 to 7 hours). In order to solve the above problems, it is necessary to increase the curing expansion and reduce the heating expansion, and even if the heating rate is increased, the investment material will not crack and can be cast in a short time. What is possible is requested.

- A study on the deformation of a cast body using a prototype non-expandable investment material has been reported (Reporter: Hidekazu Fudeki, Journal of the Japanese Society of Prosthodontics, Vol. 24, No. 2, pp. 165-185, 1972) Published on May 31st).

The investment material composition according to this research report contains 20-40% by weight of zirconium silicate, 5-30% by weight of fused silica, 20% by weight of cristobalite, 45% by weight of cristobalite, and ammonium monophosphate (Nr(,H,PO4) i 0 % by weight, 10% by weight of magnesium oxide (MgO) is mixed into the investment material, and 15% by weight of water is added and kneaded. It is small and was prototyped for the purpose of studying the deformation of the cast body itself.

The present inventors focused on the fact that the thermal expansion of the non-expandable investment material according to the above miscellaneous paper is extremely small7, and a composition obtained by kneading this investment material with a colloidal silica dispersion is superior to conventional phosphate-based investment materials. It was discovered that the curing expansion was much larger than that of a composition kneaded with a colloidal silica dispersion, and the heating expansion was extremely small, up to 1. This led to the achievement of this invention.

That is, this invention mixes 30 to 50% by weight of zirconium silicate, 15 to 30% by weight of fused silica, 10 to 40% by weight of silica, 5 to 15% by weight of monoammonium phosphate, and 5 to 15% by weight of magnesium oxide. This is an investment material composition for precision casting, characterized in that the above investment material is kneaded with a colloidal silica dispersion.

Zirconium silicate in the investment material component in this invention,
Since fused silica has almost no expansion property when heated, it has the effect of eliminating the heating expansion property of silica. The mixing ratio in the total components of the investment material is 30 to 50% by weight of zirconium silicate and 15 to 30% by weight of fused quartz.If they are below the respective lower limits, the expansion property of the investment material will increase when heated, and each If the upper limit of is exceeded, the alloy will shrink when heated and will not be able to compensate for the thermal contraction of the alloy.

The silica in the investment material component is cristobalite or quartz, and the mixing ratio thereof is io to 40% by weight. If the mixing ratio of silica is less than 10% by weight, it will not be possible to compensate for the heat shrinkage of the binding material, and if it exceeds 40% by weight, the thermal expansion property of the investment material will increase. The first component in the investment material
Ammonium phosphate and magnesium oxide are binders, and the mixing ratio of each is 5 to 15% by weight. If the mixing ratio of each is less than 5% by weight, curability decreases.
- It takes a long time for the kneaded composition to harden, and the strength of the investment material after heating decreases.If the amount of kneading exceeds 15% by weight, the strength of the investment material after heating becomes too large, making it difficult to remove the cast product. It becomes difficult.

The proportion of each component in the investment material is appropriately adjusted depending on the expansion property during curing and heating when kneaded with a colloidal silica dispersion. Generally speaking, it is preferable to decrease the ratio of fused silica to zirconium silicate as the mixing ratio of silica increases. Note that the ratio of zirconium silicate to fused silica may be large.

The feature of this invention is that by kneading the above-mentioned buried 4-year-old with a colloidal silica dispersion liquid, curing expansion is increased and heating expansion is almost eliminated. investment material io
The amount of colloidal silica dispersion mixed with o y is 14
~18 cc is preferable; if the mixing amount is too small, it will be difficult to achieve uniform crosstalk, and if the mixing amount is too large, the curing time will become longer and the curing expansion and strength will decrease, which is not preferable. What is important is the concentration of the colloidal silica dispersion,
As the hardness increases, the cure expansion increases, and in the present invention, the cure expansion can be improved to about 4%. Therefore, by appropriately selecting the concentration of the colloidal silica dispersion, it is possible to sufficiently compensate for the different heat shrinkage properties of the alloy. Colloidal silica dispersion is
Since silica concentrations ranging from 20 to 40% are commercially available, to obtain the desired cure expansion, commercially available colloidal silica dispersions can be used at their concentrations or diluted with water 1-1. [Rigetsu] can be done.

According to this invention, the curing expansion can be increased to about 4%, and the curing expansion can be arbitrarily adjusted by the silica content of the crushed colloidal silica dispersion.
Heat shrinkage can be sufficiently compensated even for alloys with high heat shrinkability. Furthermore, since there is almost no thermal expansion, cracks will not occur in the investment material even if the heating rate is increased during heating.

Therefore, the heating time can be shortened,'! ,700
℃ can be fed directly into the kiln, resulting in a short casting process time.

This invention will be explained in detail below.

Example 1 Zirconium silicate (N) 1 degree 74-500 μm, Associated Mineral Consolidated 7.1
)40 city-φ・%, fused silica (sieve 44 μm 90
%panu, 74μ〃z is 92%panu, 14911m is 1%
Residual particle size distribution, trade name Nikkanko-1 W-P, Japan Crucible JT [) 25% by weight, cristobalite (particle size 7411 m or less, Taisei Dental Industry Co., Ltd. survey aQ) i 5% by weight, monobasic ammonium phosphate (particle size 74 μm) below,
(manufactured by Katayama Chemical Co., Ltd.) 10% by weight, magnesium oxide (particle size 7
4 μη2 or less, prepared by Taisei Dental Industry Co., Ltd.) for 30 minutes in a mixer to prepare an investment material, and 100 fI of this investment material was mixed with a colloidal silica-dispersed surface (silica concentration 30%, trade name Chikara Taloid 5C-3Q, catalyst). (manufactured by Kasei Kogyo Co., Ltd.) 16cc
and kneaded at a kneading speed of 350 rpm using a vacuum kneader (manufactured by 0-C).

This investment material composition was prepared according to the research report by Hidekazu Fudeki.
Curing expansion and heating expansion were measured according to standard methods, and the results are shown in the graph of FIG. Graph A in Figure 1 is for a colloidal silica dispersion with a silica concentration of 30%, and the curing expansion rate has improved to 4.0%, and no expansion was observed during heating. Graph B in Figure 1 is , when the above Cataloid 5C-30 is diluted with water and the silica concentration is 20%, the cure expansion coefficient is 1 in graph B.
．． At 7%, no expansion was observed during heating.

Example 2 1 Note! 5+,! In Example 1vc, -h ll o
4 FSC-30 Thornica concentration 15.20.25.
The cure expansion coefficient was measured when the temperature was changed to 30%, and the results are shown in graph C (solid line) in FIG. The above fruit bl
a In Example 1, one volume of the trade name Snowtex 40 (silica concentration 40%, manufactured by Nissan Chemical Industries, Ltd.) was used as a colloidal silica dispersion, and the silica concentration was 10.2 (L80.
Measure the change in cure expansion rate when changing to 40%,
The results are shown in graph 1 (dotted line) in FIG. As shown in the graph of FIG. 2, the cure expansion coefficient increases as the silica concentration of the colloidal silica dispersion increases, and there are slight differences in the cure expansion coefficient depending on the manufacturer.

[Brief explanation of drawings]

FIG. 2 is a graph showing the change in the expansion coefficient of Example 1, and FIG. 2 is a graph showing the relationship between the hardening expansion coefficient and the silica concentration of the colloidal silica dispersion. =277

Claims (1)

[Claims] [l] 30 to 50% by weight of zirconium silicate, 15 to 30% by weight of fused silica, 10 to 40% by weight of silica, 5 to 15% by weight of monoammonium phosphate, 5% by weight of magnesium oxide
An investment material composition for precision casting, characterized in that an investment material containing ~15% by weight is kneaded with a colloidal silica dispersion.