JPH06234613A - Dental investing material - Google Patents

Abstract

PURPOSE:To enable elimination of gas defect on the surface of a mold composed of titanium or a titanium alloy in a dental investing material using a phosphate- based dental investing material and magnesia as a refractory and alumina cement as a binder. CONSTITUTION:In a dental investing material composed of at least two kinds of refractories, a binder and a blending solution, aluminum titanate is contained in the refractories and the amount of the aluminum titanate is 1-30wt.% based on the total of the refractories and the binder. In a dental mold material comprising refractory, a phosphate, a metal oxide and a colloidal silica sol, ammonium primary phosphate is used as the phosphate, the amount of the phosphate blended is set 3-5wt.% the whole mixture except the colloidal silica sol and colloidal silica having >=40mum particle diameter is used for the colloidal silica sol.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dental investment material suitable for casting metals having a high melting point such as titanium and titanium alloys.

[0002]

2. Description of the Related Art In dental casting, gold alloy, silver alloy,
Co-Cr alloys, Ni-Cr alloys, etc. have been used, but recently, pure titanium and titanium alloys have come to be widely used because of their excellent affinity with cell tissues. And, as the casting mold material of this high melting point pure titanium or titanium alloy, calcia is kneaded with methyl alcohol, magnesia cement is used as the binder, and phosphate (for example, first phosphorus) is used as the binder. Ammonium salts, monobasic sodium phosphate, etc.) and basic metal oxides (eg, magnesia, calcia, zinc oxide, etc.) that easily react with phosphate ions,
Known are refractory materials that use alumina, zircon, zirconia, calcia, spinel, mullite, magnesia, and the like, and refractory materials that use silica, such as silica, cristobalite, and tridymite.

[0003]

[Problems to be Solved by the Invention] The template material obtained by kneading calcia with methyl alcohol is difficult to handle because of lack of storage stability because calcia reacts with moisture in the air to change to calcium hydroxide. It was Further, the mold material using magnesia cement as a binder was difficult to handle because magnesium chloride, which is a component of magnesia cement, decomposes at a high temperature to generate chlorine gas, which causes the electric furnace to fail. .

Further, in the case where a mixture of a phosphate and a metal oxide is used as a binder, phosphorus in the phosphate penetrates into the surface of the casting to form a thick reaction layer, which has a high surface hardness and is brittle. Then, there is a problem that the properties of titanium are deteriorated.
Further, ammonium phosphate and sodium monophosphate are used as phosphates, but the latter has the drawback of deliquescent by binding with moisture in the air. Then, the three components of the above refractory material, phosphate and metal oxide are kneaded with water or colloidal silica sol to form a mold,
In each case, the surface of the cast body was rough.

Further, the one using alumina as a refractory material is thermodynamically stable with respect to titanium and titanium alloys, but since the coefficient of thermal expansion is small, it is necessary to compensate for thermal contraction of titanium and titanium alloys. However, there is a problem that the cast product becomes smaller than the required size. It is known that metal powders such as zirconium and aluminum are added to a template material, and the thermal contraction of titanium and the like is compensated by utilizing the oxidative expansion of the metal powders during heating and firing, but zirconium is expensive. It is not practical because the expansion becomes non-uniform due to the non-uniformity of its oxidation degree. On the other hand, the metal powder other than zirconium reacts with water to generate bubbles in the mold, and when the mold is heated and baked. There are cracks, the casting surface becomes defective, and there is ignition depending on the type of metal,
It wasn't practical.

[0006] Further, a material using silicic acid anhydride such as quartz as the refractory material has a large thermal expansion and can easily compensate for the thermal contraction of titanium and titanium alloy, but on the other hand, it is easily wetted by the molten titanium and reacts with it. Therefore, there is a problem that the reaction layer is formed on the surface of the cast product to increase the surface hardness, the titanium is fragile and the property is deteriorated, and the casting surface defect and the gas defect are likely to occur. It was

In order to solve the above problems, in a so-called phosphate-based dental investment material consisting of a refractory material, a phosphate and a basic metal oxide, a monoammonium phosphate as a phosphate is used. Of the colloidal silica used in the kneading liquid is smaller than that of the conventional refractory material, the ammonium phosphate monobasic and the basic metal oxide, and the particle size of the colloidal silica is smaller than that of the conventional one. Also big 40
Attempts were made to make it more than mμ, and the reaction layer on the surface of the cast body could be made thinner, the surface roughness could be made smaller, and the dimensional accuracy could be improved, but gas defects, that is, depressions on the surface of the cast body, occurred. Could not be prevented.

According to the present invention, magnesium titanate is added to a refractory material in the above-mentioned phosphate-based dental investment material and magnesia as a refractory material, and in the dental investment material using alumina cement as a binder. As a result, the gas defects on the surface of the cast product made of titanium or titanium alloy are significantly improved.

[0009]

That is, the present invention is
In a dental investment material consisting of at least two types of refractory material, binder and kneading liquid, the above refractory material contains aluminum titanate, and its compounding amount is 1 with respect to the total amount of refractory material and binder. -30% by weight, preferably 1-1
The dental investment material is characterized by being 5% by weight.

The investment material of the present invention may be a phosphate-based investment material in which the binder comprises a phosphate and a basic metal oxide, and a colloidal silica sol is used in the kneading liquid, and the refractory material is mainly magnesia. The binder may be alumina cement and the kneading liquid may be water. When alumina cement is used as the binder, its content is 1 with respect to the total amount of refractory and binder.
0 to 20% by weight is preferred.

When a phosphate-based investment material is used, ammonium phosphate is used as the phosphate and magnesia is used as the basic metal oxide, and the content of the ammonium phosphate is set to the refractory material and the binder. It is preferable to use 3 to 5% by weight, which is less than the conventional 7 to 20% by weight, and to use colloidal silica having a particle size of 40 mμ or more, which is larger than the conventional 10 to 20 mμ. . In addition, it is preferable that the refractory material in this case uses at least one of quartz, cristobalite and tridymite as a main component, and slightly adds one or more of alumina, zircon, zirconia, mullite and spinel.

[0012]

When 1 to 30% by weight, especially 15% by weight or less of aluminum titanate is added to the total amount of the refractory material and the binder, the aluminum titanate has a low thermal expansion property, a low thermal conductivity and a heat resistance. In addition to being excellent in impact resistance, its melting point is extremely high, and it is 1860 ° C. Therefore, even in a casting material using quartz, cristobalite, tridymite, etc., the wettability with the molten titanium is lowered, resulting in defective casting surface and generation of gas defects. To prevent. However, if the content of aluminum titanate is less than 1%, there is no effect. On the other hand, if it exceeds 30%, the thermal expansion of the mold material becomes small, the dimensional accuracy of the cast product cannot be ensured, and the mold becomes expensive. .

When a phosphate-based investment material is used and ammonium phosphate monobasic is used as the phosphate, and the amount thereof is reduced to 3 to 5% by weight of the total amount of the refractory material and the binder, The amount of phosphorus infiltrated into the surface of the cast body made of titanium or titanium alloy is small, the thickness of the reaction layer becomes thin, and the performance of titanium does not deteriorate. In this case, the colloidal silica sol acts as a binder by using the colloidal silica sol as the kneading liquid, and therefore the strength of the template is compensated even though the compounding amount of ammonium monophosphate is reduced. . Then, by using a colloidal silica having a particle size of 40 mμ or more, the concave portion on the surface of the mold generally made of a refractory material having a particle size of 10 to 170 μ is filled with colloidal silica, and the generation of the reaction layer is suppressed. In addition, the surface roughness of the cast product becomes small, and a cast product with a smooth surface can be obtained.

However, when the content of the ammonium monophosphate is less than 3% by weight, the strength of the obtained mold is insufficient, the casting pressure at the time of casting cannot be endured, and casting becomes impossible.
On the other hand, when it exceeds 5% by weight, the reaction layer on the surface of the cast product becomes thick when the titanium or titanium alloy is cast, the surface becomes hard and brittle, and the characteristics of the titanium cast product are not exhibited. When the particle size of colloidal silica is less than 40 mμ, the reaction layer on the surface of the cast product becomes thick and the surface roughness becomes large.

When magnesia is used as the metal oxide, both stability in the air and heat resistance are improved as compared with the case of using calcia or zinc oxide. Further, if one or more of quartz, cristobalite and tridymite is used as a main component as a refractory material, thermal expansion of these is large, so that the thermal contraction of titanium and titanium alloy can be easily compensated, and alumina, By adding a slight amount of one or more of zircon, zirconia, mullite and spinel, the above-mentioned drawbacks of quartz, cristobalite and tridymite (which are easily wet with a molten titanium and easily react with titanium) can be compensated.

On the other hand, when magnesia is mainly used as the refractory material and alumina cement is used as the binder, the magnesia does not react with the molten titanium at all, so that the surface shines a beautiful metallic color and the surface roughness is low. Is obtained. However, when the content of magnesia decreases and the content of alumina cement exceeds 30% by weight, the above characteristics are lost.

[0017]

Example An experiment was carried out using a phosphate-based investment material. That is, ammonium phosphate monobasic and magnesia are prepared as the binder, and zircon, alumina, zirconia, mullite, spinel, quartz and cristobalite are prepared as the refractory material, and the combination and blending amount (% by weight) thereof are variously set. , The mixture was kneaded with water or colloidal silica sol to form a mold, a titanium crown was cast, and the thickness, gas defect, surface roughness, and dimensional accuracy of the reaction layers of the obtained cast products were compared. Table 1 shows the results of Experimental Examples 1 to 5 in which the compounding amount of the primary ammonium phosphate was increased.

Table 1 Experimental example number 1 2 3 4 5 Ammonium phosphate (%) 15 10 10 10 10 Magnesia (%) 15 10 10 10 10 Zircon (%) − 40 40 40 40 Quartz (%) 50 20 20 20 20 Cristobalite (%) 20 20 20 20 20 Mixing liquid type and particle size (mμ) Water Water 10-20 40-50 50 80-100 Reaction layer × × × △ ○ Gas defect × × × × × Surface roughness of cast body × × △ △ △ ○ Dimensional accuracy △ ○ ◎ ◎ ◎ ◎

However, the numbers in the column of the type of kneading liquid and particle size in the table indicate the particle size (mμ) of colloidal silica.
In addition, the reaction layers are indicated by ⊚ for those that require almost no polishing, ◯ for those that require slight polishing, Δ for those that require considerable polishing, and x for those that cannot be used because the reaction layer is too thick. . In addition, regarding gas defects, ⊚ indicates that there are almost no depressions on the surface, ◯ indicates that the depressions are extremely small, Δ indicates that the depressions are slightly large, and × indicates that they are too large to be used.
And In addition, the surface roughness was evaluated as follows: 10-point average roughness Rz of less than 10 μ: ⊚, 10 μ or more and less than 15 μ: ◯, 15 μ or more and less than 20 μ: Δ, and 20 μ or more: x. The dimensional accuracy was rated as ◎, that is slightly smaller than that of the design, ◯, that of which it was extremely small was rated as Δ, and that of which it was too small to be used was rated as x.

As is apparent from Table 1 above, in Experimental Example 1, since water was used as the kneading liquid, the surface roughness of the cast body was large and the dimensional accuracy was low. Then, in Experimental Examples 3 to 5 in which the colloidal silica sol was used as the kneading liquid, the surface roughness and the dimensional accuracy were improved, and the reaction layer was improved as the particle size of the colloidal silica was increased. In particular, the particle size was 80 to 1
In Experimental Example 5 using 00 mμ of colloidal silica, improvement was recognized in both the reaction layer and the surface roughness. However, the gas defects were all bad.

Next, the casting amounts of the first ammonium phosphate, magnesia, and zircon in Experimental Example 5 described above were decreased, and the compounding amounts of quartz were increased to perform the casting of Experimental Examples 6 to 8, and the casting was performed in the same manner as above. The performance of the products was compared. The results are shown in Table 2.

Table 2 Experimental Example No. 6 7 8 Ammonium phosphate (%) 5 3 2 Magnesia (%) 5 4 3 Zircon (%) 10 10 10 Quartz (%) 20 65 68 Cristobalite (%) 15 15 15 Mixing Liquid type, particle size (mμ) 80 to 100 80 to 100 80 to 100 Reaction layer ◎ ◎ Casting gas defect × × Manufacturing surface roughness of casting ◎ ◎ Non-dimensional accuracy ◎ ◎ Performance

As is apparent from Table 3 above, Experimental Examples 6 and 7 in which the compounding amount of ammonium monophosphate was 3 to 5%.
The reaction layer, surface roughness and dimensional accuracy were all good, while the amount of ammonium monophosphate mixed was 2%.
In Experimental Example 8 in which the amount was extremely reduced, the strength of the mold was insufficient and casting was impossible. However, no improvement regarding gas defects was observed.

Next, casting experiments of Experimental Examples 9 to 12 were carried out by substituting a part of the quartz in Experimental Example 6 with another refractory material. The results are shown in Table 3 below.

Table 3 Experimental Example No. 9 10 11 12 Ammonium phosphate (%) 5 Same as same Magnesia (%) 5 Same as same Same zircon (%) 10 Same as same Alumina (%) 5 --- Zirconia (%) − 5 − − Mullite (%) − − 5 − Spinel (%) − − − 5 Quartz (%) 60 Same as the same Cristobalite (%) 15 Same as the same Kind of mixing liquid, particle size (mμ) 80 to 100 Same Same Same Reaction layer 〇 ◎ ◎ ◎ ◎ Gas defects △ △ △ △ Cast surface roughness ◎ ◎ ◎ ◎ Dimensional accuracy ◎ ◎ ◎ ◎ ◎

As is clear from Table 3 above, substituting part of the quartz with alumina, zirconia, mullite or spinel slightly improved the gas defects. However, the improvement was insufficient regarding gas defects.

Then, casting experiments of Experimental Examples 13 to 18 were carried out by substituting a part of quartz in Experimental Example 10 with aluminum titanate. The results are shown in Table 4 below.

Table 4 Experimental Example No. 13 14 15 16 17 18 Ammonium Phosphate (%) 5 Same Same Same Same Same Magnesia (%) 5 Same Same Same Same Same Same Zircon (%) 10 Same Same Same Same Same Same Zirconia (%) 5 Same as above Same as same Same as aluminum titanate (%) 2 5 8 10 20 30 Quartz (%) 58 55 52 50 40 30 Cristobalite (%) 15 Same as same Same as same Kind of mixing liquid, particle size (mμ) 80 〜 100 ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎

As can be seen in Table 4 above, the addition of aluminum titanate significantly reduces gas defects. It should be noted that when the amount of the mixture increased and the amount of the quartz mixed decreased, the dimensional accuracy tended to decrease.
This could be compensated by designing the prototype slightly larger.

Next, casting experiments of Experimental Examples 19 to 23 were carried out by adding aluminum titanate to an investment material using magnesia as a refractory material and alumina cement as a binding material. However, water was used as the kneading liquid in each case. The results are shown in Table 5 below.

Table 5 Experimental example number 19 20 21 22 23 Magnesia (%) 88 78 68 78 90 Alumina cement (%) 10 20 30 10 10 Alumina (%) − − − 10 − Aluminum titanate (%) 2 2 2 2-Reaction layer ◎ ◎ × △ ◎ Gas defects ◎ ◎ △ 〇 △ Cast surface roughness ◎ ◎ × 〇 ◎ Dimensional accuracy × × × × ×

As is clear from Table 5 above, it was confirmed that the addition of aluminum titanate almost eliminates the surface depression caused by the gas defects.
However, when the amount of alumina cement increases and reaches 30% by weight, gas defects are generated again. Further, in this case, the dimensional accuracy is poor, but this can be compensated by designing the prototype slightly larger.

[0033]

As described above, the dental investment material according to claim 1 contains aluminum titanate in the refractory material in an amount of 1 to 30% by weight based on the total amount of the refractory material and the binder. Since this aluminum titanate has a low thermal expansion property, low thermal conductivity, excellent thermal shock resistance, and a very high melting point, quartz, cristobalite,
Even in a mold material using tridymite or the like, the wettability with the molten titanium is lowered, and it is possible to prevent defective casting surface and generation of gas defects.

The invention described in claim 2 is the same as the invention described in claim 1, except that the investment material is made of phosphate and colloidal silica sol is used in the kneading liquid. The roughness can be reduced, the dimensional accuracy can be improved, and the amount of phosphate used can be reduced, so that the reaction layer can be thinned and the performance of titanium in the titanium cast product can be exhibited. Further, claim 3
In the invention described in 1), ammonium phosphate is used as the phosphate, magnesia is used as the basic metal oxide, and the content of ammonium phosphate is 3 to 5% by weight with respect to the total amount of the refractory material and the binder. Since the particle size of the colloidal silica is 40 mμ or more, the reaction layer of the cast body,
The surface roughness and dimensional accuracy can be further improved.

According to a fourth aspect of the present invention, in the phosphate-based investment material, any one or more of quartz, cristobalite and tridymite, and alumina, zircon, zirconia, mullite and spinel are used as the refractory material. Since it is a mixture of one or more, the thermal expansion of quartz and cristobalite is large and the thermal contraction of titanium and titanium alloy is easily compensated to improve the dimensional accuracy, and this quartz and cristobalite is easily wet by the molten titanium, It is possible to suppress the formation of the reaction layer by compensating for the drawbacks such as easy reaction with titanium by the above alumina or the like.

In the invention described in claim 5, magnesia is used as the refractory material, alumina cement is used as the binder, and water is used as the kneading liquid. Since magnesia does not react with titanium at all, A titanium cast product with excellent gloss can be obtained.

Claims (5)

[Claims] 1. A dental investment material comprising at least two types of refractory material, binder and kneading liquid, wherein the refractory material contains aluminum titanate, and the compounding amount thereof is the total of the refractory material and the binder. A dental investment material, which is 1 to 30% by weight based on the amount. 2. The dental investment material according to claim 1, wherein the binder comprises a phosphate and a basic metal oxide, and the kneading liquid is colloidal silica sol. 3. The phosphate is ammonium phosphate,
The basic metal oxide is magnesia, the content of the ammonium phosphate is 3 to 5% by weight with respect to the total amount of the refractory material and the binder, and the particle diameter of the colloidal silica is 40.
The dental investment material according to claim 2, having a size of mμ or more. 4. A refractory material comprising at least one selected from quartz, cristobalite and tridymite, and at least one selected from alumina, zircon, zirconia, mullite and spinel. The listed dental investment material. 5. The refractory material is mainly made of magnesia,
The dental investment material according to claim 1, wherein the binder is alumina cement and the kneading liquid is water.