JP2003034608A - Flash heating-type phosphate investment for dental use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flash heating-type phosphate investment for dental use having an improved surface characteristics which can expand sufficiently, has no danger of metal burn on its surface, can achieve a high overall expansion, and enables flash heating. SOLUTION: A phosphate investment for dental casting investment contains (a) magnesium oxide, (b) ammonium primary phosphate and (c) an aggregate. The flash heating-type phosphate investment for dental use is characterized by that it contains (a) magnesium oxide having an average diameter of 10-40 μm and (b) ammonium primary phosphate having an average diameter of 25 μm or less in a proportion of 10-45 wt.% with respect to total ammonium primary phosphate.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a dental phosphate-based investment material for casting a metal having a high melting point. Especially after burial 2
The present invention relates to a rapid heating type phosphate-based investment material in which a ring buried after 0 to 30 minutes is directly put into a furnace at 800 to 1000 ° C.

[0002]

2. Description of the Related Art Phosphate-based investment materials have been used for casting high melting point metals used as porcelain baking alloys. The composition of the phosphate-based investment material includes magnesium oxide and primary ammonium phosphate as a binder, silica, alumina, zircon as a refractory material (aggregate), and is mixed with colloidal silica as a dedicated liquid. That is also characteristic. As an advantage of this investment material, by adjusting the concentration of colloidal silica in the dedicated liquid, it is possible to obtain a total expansion that matches casting shrinkage of various metals.
For example, it can be widely used from precious alloys mainly composed of gold to non-precious alloys mainly composed of nickel and cobalt.

A total expansion of 2.5% or more is required to compensate for the casting shrinkage of the non-precious alloy. Since it is difficult to increase the thermal expansion amount by 1.5% or more for a normal phosphate-based investment material, it is necessary to expect a hardening expansion obtained from a dedicated liquid. When kneaded only with the dedicated liquid, the thermal expansion amount of the phosphate-based investment material plus the hardening expansion of 1.5%
It is customary to adjust the above so that it expands and dilute it according to the amount of expansion and contraction of the metal.

In addition to this, a typical investment material is a gypsum investment material, which cannot be used at high temperatures because it decomposes at high temperatures. However, since it is relatively inexpensive, it has a low melting point (1
It is customary to use a gypsum-based investment material for metals of 000 to 1100 ° C. and a phosphate-based investment material for metals of high melting point (1100 ° C. or higher). In recent years, as the gypsum-based investment material, a short-time casting method, that is, an investment material called a rapid heating type is becoming mainstream. Normally, the gypsum-based investment material is produced by the normal heating casting method.

What is the normal heating casting method? After the burial is completed, it is left for about 1 hour, then put in a furnace and from room temperature to 1.
It is heated for 5 to 2 hours to reach a temperature of 700 ° C., moored for 30 minutes, and then cast. However, recently, a casting method called a short time casting method (hereinafter referred to as a rapid heating casting method) has become mainstream. The rapid heating casting method is used for the purpose of drastically shortening the technical work, and it is 20 ~ 3
It is a method of directly inserting the ring into the furnace at 700 ° C. after 0 minutes. In recent years, even in gypsum-based investment materials,
Rapid heating type technology has been developed, overcomes various problems, is designed to have strength in a short time, and has been rapidly hardened.

Regarding the surface properties, in the case of a gypsum-based investment material, the binder mainly contains hemihydrate gypsum, so that a solidification reaction mainly occurs by a hydration reaction. Therefore, even if a heat shock is applied to the investment material for a short time, the hydration reaction is only accelerated rapidly, so that the roughening of the casting surface of the cast body is not a serious problem.

On the other hand, as for the phosphate-based investment material, although there are still many conventional normal heating casting methods, the rapid heating casting method is rapidly becoming popular. Normal heating of phosphate-based investment material is left for about 1 hour after the investment is completed, then put in a furnace and heated from room temperature to 800-900 ° C over 1.5-2 hours, 30 minutes It is moored and then cast.

On the other hand, in the rapid heating casting method, 20 hours after burial
After about 30 minutes, the ring is directly put into the furnace at 800 to 900 ° C. However, since the phosphate-based investment material uses the above-described magnesium oxide and the first ammonium phosphate as a binder, it needs to be hardened in a short time in order to put it in the furnace in a short time. When the phosphate-based investment material was rapidly heated, there was a problem that the surface texture was less smooth than when it was normally heated.

Further, when the amount of the binder is reduced, the amount of hardening expansion is reduced, and it is difficult to compensate the casting shrinkage of the non-precious alloy. The conventional methods using inorganic salts such as phosphates have problems in reactivity, and when rapid heating is performed, they have problems in that the surface properties deteriorate and they are weak against heat shock.

A method for improving the surface properties and a method for increasing the fire resistance are typically disclosed in JP-A-59-181203, which is solved by adding hemihydrate gypsum as a base and adding acidic aluminum phosphate. is doing. However, it has a problem that it is poor in curability, cracks and cracks are formed when it is rapidly heated, and it is susceptible to heat shock.

A method aiming at obtaining a high total expansion is disclosed in Japanese Patent Laid-Open No. 63-141906, and a refractory material for increasing the fire resistance is added based on a hemihydrate gypsum or phosphate binder. There is a method of adding natural starch as an expansive material and carbides, nitrides, borides, silicides and sulfides of transition metals of Groups IV, V and VI of the Periodic Table. However, the addition of starch has a problem that the expansion becomes unstable.

A method for obtaining heat resistance and a smooth surface property is disclosed in JP-A-2-207010, and a calcium phosphate compound having a molar ratio of calcium to phosphorus of 1.5 to 2.0 is used as an α-type triphosphate. Calcium and tetracalcium phosphate are used as binders. However, even with this method, the curability is poor, and there is a problem in that cracks are formed by rapid heating.

A method for overcoming the seizure of metal on the surface is disclosed in JP-A-4-327514, and aluminum oxide is added to a usual phosphate-based investment material, and the average particle size of cristobalite and aluminum oxide is 2 to. 40μ
It is solved by being m. However, although the seizure of the surface can be prevented, the improvement of the surface property was not sufficient.

Japanese Unexamined Patent Publication No. 9-220638 discloses a method of casting a high melting point metal in a gypsum-based investment material by preventing pyrolysis gas of the gypsum. However, the method of increasing the fire resistance based on hemihydrate gypsum has a problem that sufficient hardening expansion cannot be obtained and the surface quality is deteriorated due to the molten state of the metal having a high melting point. In addition, various attempts have been made to prevent thermal decomposition gas, but the present situation is that it has not been solved yet for normal use.

In the thermal expansion, an investment material having a certain degree of suitable thermal expansion is desired because it is adjusted by a kneading liquid, but in the case of the phosphate-based investment material, an investment material which has solved other needs at the same time. No timber has been reported. Furthermore, the rapid heating type technology of phosphate-based investment materials has not been developed and has various problems, and there is no one that can simultaneously solve heat shock, cracking, surface texture and the like. In particular, it is not easy to solve the problem in a method of obtaining a cast body having stable surface properties.

Total expansion It is difficult to secure a particular amount of thermal expansion, and cracks and cracks often occur due to heat shock. Even if it was adjusted to some extent, the expansion became unstable and it could not be used stably. There were many cracks and cracks, and there was no solution to them. In addition to solving these problems, it was necessary to cure them in a short time, but none of them had good curability. It has not been solved to prevent the surface from being baked and to have a good surface property.

[0017]

DISCLOSURE OF THE INVENTION According to the present invention, sufficient expansion is obtained, there is no risk of metal sticking to the surface, the surface properties of the phosphate-based investment material are improved, and a high overall expansion is obtained. And to enable rapid heating. In a phosphate-based investment material, it is desired to improve the surface properties and obtain sufficient curing expansion. Moreover, no rapid-heating dental phosphate-based investment material for dental use, which is resistant to heat shock without cracks or cracks even when rapidly heated, has not been developed.

Furthermore, it is desired that a precision cast body can be cast in a short time, it is resistant to heat shock, and a large total expansion is obtained. It can be used for a wider range of metals and has a smooth surface property. There is no investment material that can be obtained, and it is desired to solve these problems. In addition to the advantages of conventional investment materials, it has a good hardening property, enables rapid heating, can obtain a cast product with stable surface properties, secures an expansion amount, does not crack or crack due to heat shock, and has a stable expansion It develops, cracks, and without kneading, after kneading, after imparting the morphology of the mold, the morphology is stable in a short period of time, the morphology is stable, surface baking does not occur, and it also has a good surface property. Is an issue. Further, the present invention is to create an investment material that has an appropriate curing time for performing rapid heating, has high compressive strength during casting, and is easy to dig after casting.

[0019]

Means for Solving the Problems As a result of earnest research on these problems, the present inventors were able to reach the present invention. The present invention relates to a dental casting investment material, which is (a) magnesium oxide, (b) a first ammonium phosphate (c) a phosphate-based investment material containing an aggregate, wherein (a) the average particle size is 10: ~ 40
The rapid heating type phosphate-based investment material for dental use, wherein 25 μm or less of the magnesium oxide (b) monobasic ammonium phosphate having a diameter of 10 μm is 10 to 45% by weight with respect to the total ammonium phosphate. Is.

The preferred dental rapid heating phosphate-based investment material of the present invention comprises (a) magnesium oxide having an average particle size of 20.
˜30 μm and 100 μm or more of particles are 1% or less, (b) ammonium monophosphate is 60 μm or less, and 25 μm or less is 20 to 35% by weight with respect to the total ammonium monophosphate. A rapid-heating dental phosphate-based investment material for dental use. The present invention is preferably a dental rapid heating phosphate-based investment material,
(A) 5 to 15% by weight of magnesium oxide (b) 10 to 20% by weight of ammonium monobasic phosphate, which is a rapid heating phosphate-type investment material for dental use.

The present invention is a rapid heating phosphate-type investment material for dental use, wherein the aggregate (c) contains at least one selected from zirconia, zirconium silicate, fused silica, mullite and alumina. It is a rapid heating type phosphate-based investment material for dentistry. Further, the present invention uses a colloidal silica solution as a dedicated liquid for kneading a dental rapid heating phosphate-based investment material, and the average particle size of the colloidal silica is 70 to 1
It is preferably a rapid heating type phosphate-based investment material for dentin having a size of 00 nm.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The dental rapid heating type phosphate-based investment material according to the present invention will be specifically described below. The exemplified ones are not particularly limited. Regarding the magnesium oxide which is the constituent factor (a) of the present invention, the purity of magnesium oxide generally used for dentistry is preferably high, and it is preferable that it is finely divided.
Particles of 100 μm or more preferably have a particle size distribution of 1% or less. More preferably, it does not contain particles of 100 μm or more. The average particle size is 10-40
The thickness is preferably μm, more preferably 20 to 30 μm. The compounding amount in the whole phosphate-based investment material is
It is preferably 5 to 15% by weight.

Next, the first feature which is the (b) constituent requirement of the present invention
Although it is ammonium phosphate, the first ammonium phosphate is soluble, but when it is used as a bonding material for an investment material, it is preferable that the maximum particle size is small. Due to the surface lubricity of the phosphate-based investment material, it is preferable that there is no particle having a particle size of 60 μm or more. Further, of the particles of 60 μm or less, the amount of particles of 25 μm or less is preferably 10 to 45% by weight, and 20 to 20%
More preferably, it is 35% by weight. The content of the phosphate-based investment material in the whole is preferably 10 to 20% by weight.

Next, the preferable composition ratio of (a) constituents and (b) constituents of the present invention is (a) / (b) = weight ratio.
It is preferably 0.3 to 1.0. More preferably, (a) / (b) = 0.4 to 0.8.

Next, the aggregate (c), which is a constituent of the binder, is a refractory material used as an investment material for dental casting. Specifically, quartz, cristobalite, Examples include fused silica, alumina, zirconia, zirconium silicate, calcia, and yttria. Zirconia, zirconium silicate, quartz and cristobalite are particularly preferred.

Regarding the content of these aggregates, it is preferable that the content of cristobalite be small in the rapid heating type phosphate investment material. The amount of cristobalite is 1
5 to 45% is preferable, and 25 to 35% is particularly preferable.
The amount of zirconia and zirconium silicate is 5 to 15%
Is preferred.

Further, a colloidal silica aqueous solution is a liquid material for kneading these powder materials as an investment material. In order to achieve the present invention, it is preferable to use a large particle size colloidal silica because high curing expansion and rapid heating are performed in parallel. The average particle size of colloidal silica is 10n
m-120 nm is preferable and 70 nm-100 nm is especially preferable. The colloidal silica concentration is 20 to 50.
%, Preferably 35 to 45% by weight.

The effect obtained by the present invention is 30
Within a minute, it can be directly put into a furnace at 800 to 1000 ° C., curing expansion of 1.5% or more can be obtained, and smooth surface properties can be obtained.

[0029]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In addition, the particle size of magnesium oxide was measured using a Nikkiso Microtrac HRA type, and the first ammonium phosphate sieve was a JIS standard sieve.

Preparation of Sample 1 The magnesium oxide raw material was pulverized and classified to adjust the frequency of particles having an average particle diameter of 25 μm and 100 μm or more within 1%.

Preparation of Sample 2 The first ammonium phosphate was crushed to obtain 250 mesh (6
0 μm) was passed through, and the amount of particles under a 25 μm (500 mesh) sieve was adjusted to 30% by weight.

Preparation of Sample 3 Magnesium Oxide Grinding A magnesium oxide raw material was crushed and classified to adjust the frequency of particles having an average particle diameter of 45 μm and 100 μm or more within 1%.

Preparation of Sample 4 First ammonium phosphate was pulverized to 125 mesh (1
25 μm), and the particles under a 25 μm (500 mesh) sieve were adjusted to be 5% by weight.

Preparation of Sample 5 First ammonium phosphate was pulverized to 125 mesh (1
25 μm), and the amount of particles under a 25 μm (500 mesh) sieve was adjusted to 50% by weight.

Cristobalite (200 mesh (77
μm) all through), quartz (200 mesh (77 μm) all through), zirconium silicate (200 mesh (77 μm)
m) all through), zirconia (200 mesh (77 μm)
All) and Samples 1 to 5 were blended in the following composition.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

The kneading solution is Snowtex ZL manufactured by Nissan Kagaku.
(Silica anhydride 40% by weight, average particle diameter 90 nm), and Nissan Chemical's Snowtex 30 (silicic acid anhydride 30% by weight, average particle diameter 30 nm) were used. The test method of the mold is Japanese Industrial Standards "Gypsum-based investment material for dental casting" T6601.
-1998. That is, the curing time and the compressive strength complied with this, and the thermal expansion was raised to 800 ° C., and the numerical values were read. Mixing method for investment materials is 2
Snowtex ZL was made into a kneading liquid A and Snowtex 30 was made into a kneading liquid B with 2 mL / 100 g of powder. A Matsukaze power lift mixer was used as the vacuum stirrer, and the kneading time was 30 seconds.

Curing expansion test ring A ring having a diameter of 40 mm and an inner diameter of 40 mm was lined with Matsukaze non-asbestos and applied with vaseline. The kneading mud is poured into the ring, a glass plate is placed on the ring, the hardening expansion value is read with a vertical dial gauge (1/100 mm reading), and the expansion coefficient is calculated. The total expansion is an expansion amount obtained by adding hardening expansion to thermal expansion.

Heat Shock Test Ring A ring having a diameter height of 55 mm and an inner diameter of 40 mm was lined with Matsukaze non-asbestos and applied with vaseline. The kneaded mud was poured into the ring, and 20 minutes after the kneading was started, the kneaded mud was put into a furnace heated to 800 ° C., and cracking was confirmed. When casting was impossible, it was marked with X, when cracks were found, it was marked with Δ, and when there were no cracks, it was marked with ◯.

Confirmation of Cast Surface A ring having a ring diameter of 55 mm and an inner diameter of 40 mm was lined with Matsukaze non-asbestos and coated with vaseline. The kneaded mud was poured into the ring, and 20 minutes after the kneading was started, the kneaded mud was put into a furnace heated to 800 ° C., and after 30 minutes of mooring, Matsukaze unimetal was cast, and its surface properties were confirmed. Those that did not require surface polishing were marked with ◯, those that could be used after polishing the surface were marked with Δ, and those with significant protrusions on the surface of the casting were marked with x.

[0043]

[Table 4]

[0044]

[Effects] As described above, according to the present invention, it is possible to cast a wide range of materials from precious alloys to non-precious alloys, has good surface properties, is resistant to heat shock even when subjected to rapid heating, and is free from cracks and cracks. A rapid heating type phosphate investment material could be obtained.

According to the present invention, in a phosphate-based investment material, a rapid heating type for dental use, which has improved surface properties, sufficient curing expansion, and is resistant to heat shock without cracks or cracks even when rapidly heated. A phosphate-based investment material could be obtained. The present invention creates an investment material that can cast a precision casting in a short time, is resistant to heat shock, can be used for a wide range of metals by obtaining a large total expansion, and can obtain a casting with smooth surface properties. It is to be. Further, by utilizing the present invention, a product having sufficient compressive strength during casting and easily digging out a cast body was obtained.

Claims (4)

[Claims] 1. An investment material for dental casting, comprising: (a) magnesium oxide, (b) ammonium phosphate monobasic, and (c) a phosphate-based investment material containing aggregate, wherein (a) average particle size. Of 10 to 40 μm of magnesium oxide (b) monobasic ammonium phosphate, 25 μm or less is 10 to 45% by weight based on the total ammonium monobasic phosphate, dental rapid heating phosphoric acid Salt-based investment material. 2. The dental rapid heating phosphate-based investment material according to claim 1, wherein (a) magnesium oxide is 5 to 15.
% By weight (b) 10 to 20% by weight of primary ammonium phosphate
A rapid heating type phosphate-based investment material for dentistry. 3. The dental rapid heating type phosphate-based investment material according to claim 1, wherein the aggregate (c) is one selected from zirconia, zirconium silicate, fused silica, mullite and alumina. A rapid-heating dental phosphate-based investment material for dental use, which comprises the above. 4. A colloidal silica solution is used as a dedicated liquid for kneading the rapid-heating dental phosphate-based investment material according to any one of claims 1 to 3, and the average particle diameter of the colloidal silica is 70 to 70.
Dental rapid heating phosphate-based investment material with a thickness of 100 nm.