JP4786080B2 - Dental rapid heating phosphate investment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dental phosphate-based investment material for casting a high melting point metal.
In particular, the present invention relates to a rapid heating type phosphate-based investing material in which a ring buried 20 to 30 minutes after being buried is directly put into a furnace at 800 to 1000 ° C.
[0002]
[Prior art]
Phosphate-based investment has been used to cast 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, etc. as a refractory material (aggregate), and is kneaded with colloidal silica as a dedicated liquid. It is also characteristic.
As an advantage of this investment material, by adjusting the concentration of the colloidal silica in the dedicated liquid, it is possible to obtain an overall expansion commensurate with the casting shrinkage of various metals. For example, it can be widely used from a precious alloy mainly composed of gold to a non-precious alloy mainly composed of nickel and cobalt.
[0003]
Complementing the casting shrinkage of the non-precious alloy requires a total expansion of 2.5% or more. As a normal phosphate-based investment material, it is difficult to increase the thermal expansion amount by 1.5% or more, and therefore, it is necessary to expect a curing expansion obtained from a dedicated liquid. When kneaded with only the exclusive liquid, in addition to the amount of thermal expansion of the phosphate-based investment material, the expansion of curing is adjusted to expand 1.5% or more, and diluted according to the amount of metal expansion / contraction. It is common to use it.
[0004]
In addition, there is a gypsum-based investment material as a typical investment material, which cannot be used at a high temperature because it decomposes at a high temperature. However, since it is relatively inexpensive, a gypsum-based investment material is used for a metal having a low melting point (1000 to 1100 ° C), and a phosphate-based investment material is used for a metal having a high melting point (1100 ° C or higher). It is customary.
In recent years, a gypsum-based investment material has become a mainstream of a short-time casting method, that is, a rapid heating type investment material. Normally, gypsum-based investment is performed by normal heating casting.
[0005]
The normal heating casting method is to leave it for about 1 hour after burying, then put it in the furnace and heat it from room temperature to reach 700 ° C over 1.5 to 2 hours. It is. Recently, however, 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 a method in which a ring is directly put into a 700 ° C. furnace 20 to 30 minutes after burying for the purpose of greatly shortening the technical work.
In recent years, rapid heating technology has also been developed in gypsum-based investment materials, overcoming many problems, designed to have strength in a short time, and imparting rapid curability. became.
[0006]
In terms of surface properties, in the case of gypsum-based investment materials, the binder is mainly composed of hemihydrate gypsum, so that a coagulation reaction occurs mainly by a hydration reaction. Therefore, even if the investment material is subjected to thermal shock in a short time, it only accelerates the hydration reaction rapidly, so that it was not a problem to cause rough casting of the casting.
[0007]
On the other hand, although the phosphate-based investment material still has many conventional normal heating casting methods, the rapid heating casting method is rapidly spreading.
Normal heating of phosphate-based investment material is allowed to stand for about 1 hour after completion of the investment, and then heated to reach a temperature of 800 to 900 ° C. over 1.5 to 2 hours from room temperature for 30 minutes. It is cast after mooring.
[0008]
On the other hand, in the rapid heating casting method, a ring is directly put into a furnace at 800 to 900 ° C. 20 to 30 minutes after being buried.
However, since the phosphate-based investment material uses the above-mentioned magnesium oxide and primary ammonium phosphate as a binder, it needs to be cured in a short time in order to be put into the furnace in a short time. When the phosphate-based investment material was rapidly heated, the problem was that the surface properties were not smoother than when heated normally.
[0009]
Further, when the binder is reduced, the amount of hardening expansion is reduced, and it is difficult to compensate for the casting shrinkage of the non-precious alloy.
Conventional methods using inorganic salts such as phosphates have a problem in reactivity, and when rapid heating is performed, they have problems that surface properties are deteriorated and that they are vulnerable to heat shock.
[0010]
A method for improving the surface properties and a method for increasing the fire resistance are typically disclosed in Japanese Patent Application Laid-Open No. 59-181203, which is solved by adding acid aluminum phosphate to a hemihydrate gypsum as a base. .
However, it has a problem that it has poor curability and cracks and cracks caused by rapid heating cause it to be vulnerable to heat shock.
[0011]
A method aimed at obtaining a high overall expansion is disclosed in Japanese Patent Laid-Open No. 63-141906. Based on a hemihydrate gypsum or phosphate-based binder, a refractory material for increasing the fire resistance is added, and the expansion material As a method of adding natural starch and carbides, nitrides, borides, silicides and sulfides of group IV, V and VI transition metals of the periodic table.
However, the addition of starch has the problem that the expansion becomes unstable.
[0012]
A method for obtaining heat resistance and smooth surface properties is disclosed in JP-A-2-207010. A calcium phosphate compound having a molar ratio of calcium to phosphorus of 1.5 to 2.0 is converted into α-type tricalcium phosphate and phosphorus. Tetracalcium acid is used as a binder.
However, this method also has a problem that the curability is poor and cracks are caused by rapid heating.
[0013]
A method for overcoming metal seizure on the surface is disclosed in JP-A-4-327514, in which aluminum oxide is added to a normal phosphate-based investment, and the average particle size of cristobalite and aluminum oxide is 2 to 40 μm. It is solved by that.
However, surface burn-in can be prevented, but the surface properties are not sufficiently improved.
[0014]
Japanese Laid-Open Patent Application No. 9-220638 discloses an attempt to cast a high melting point metal by preventing a pyrolysis gas of gypsum in a gypsum investment material.
However, the method of increasing the fire resistance based on hemihydrate gypsum has a problem in that sufficient curing and expansion cannot be obtained, and the surface properties are deteriorated due to the dissolved state of the high melting point metal.
In addition, various attempts have been made to prevent pyrolysis gas, but the present situation is that the solution has not yet reached normal use.
[0015]
In thermal expansion, since it is adjusted with a kneading liquid, an investment material that has a certain degree of thermal expansion is desired, but in the case of phosphate-based investment materials, there are reports of investment materials that have simultaneously solved other demands. It has not been.
Furthermore, rapid heating type technology has not been developed with phosphate-based investment materials, and there are a number of problems, and none of them can solve heat shock, cracks, surface properties, etc. at the same time. In particular, in a method of obtaining a cast body having a stable surface property, it is not easy to solve.
[0016]
It was difficult to ensure the total expansion, especially the amount of thermal expansion, and there were many cracks and cracks 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 nothing to solve them.
In addition to solving these problems, there is a need for curing in a short time, but none has good curability.
It has not been solved to combine surface prevention with good surface properties.
[0017]
[Problems to be solved by the invention]
The present invention provides sufficient expansion, there is no risk of metal seizure on the surface, improves the surface properties of the phosphate-based investment material, provides high overall expansion, and enables rapid heating This is a problem.
In phosphate-based investment materials, it is desired to improve surface properties and obtain sufficient curing expansion.
Moreover, a dental rapid heating type phosphate-based investing material that is resistant to heat shock without cracks or cracks even after rapid heating has not been developed.
[0018]
Furthermore, it is desired to be able to cast a precise casting in a short time, to be resistant to heat shock and to obtain a large overall expansion, to be able to be used for a wider range of metals, and to obtain a casting having a smooth surface property. There is no conventional investment material, and it is desired to solve these problems.
In addition to the advantages of conventional investment materials, it has good curability, enables rapid heating, provides a cast with stable surface properties, secures the amount of expansion, and ensures stable expansion without cracks or cracks due to heat shock. It develops, does not cause cracks, cracks, and after kneading, after imparting the form of the mold, it is cured in a short period of time, the form is stable, surface baking does not occur, and the surface properties are good Is an issue.
Another object of the present invention is to create an investment material that has a suitable curing time for rapid heating, has a high compressive strength during casting, and is easy to dig after casting.
[0019]
[Means for solving problems]
As a result of intensive studies on these problems, the present inventors have reached the present invention.
The present invention is an investment for dental casting, in (a) magnesium oxide, (b) a phosphate-based investment containing a first ammonium phosphate (c) aggregate,
(A) Magnesium oxide having an average particle diameter of 10 to 40 μm (b) 25 μm or less of primary ammonium phosphate is 10 to 45% by weight based on the total primary ammonium phosphate It is a rapid heating type phosphate investment.
[0020]
A preferred dental rapid heating phosphate-based investment material according to the present invention is (a) magnesium oxide having an average particle size of 20 to 30 μm and particles having a particle size of 100 μm or more within 1%, and (b) first phosphorus It is a dental rapid heating type phosphate-based investing material characterized in that ammonium acid is 60 μm or less, and 25 μm or less is 20 to 35% by weight based on the total primary ammonium phosphate.
The present invention is preferably a dental rapid heating type phosphate-based investment, wherein (a) magnesium oxide is 5 to 15% by weight and (b) primary ammonium phosphate is 10 to 20% by weight. It is a phosphate investment.
[0021]
The present invention is a dental rapid heating phosphate-based investment material, wherein (c) the aggregate contains one or more selected from zirconia, zirconium silicate, fused quartz, mullite, and alumina. It is a rapid heating type phosphate-based investment material.
Furthermore, the present invention uses a colloidal silica solution as a dedicated liquid for kneading dental rapid heating phosphate-based investing materials, and the rapid heating dental phosphate having an average particle size of the colloidal silica of 70 to 100 nm. It is preferable that it is a system investment material.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
The dental rapid heating phosphate-based investment material according to the present invention will be specifically described below. It does not specifically limit regarding what is illustrated.
Although it is the magnesium oxide which is (a) constituent requirements of this invention, the higher the purity, the more preferable the magnesium oxide generally used for dentistry is preferable. Particles of 100 μm or more are preferably within 1% in the particle size distribution. More preferably, it does not contain particles of 100 μm or more.
Moreover, it is preferable that an average particle diameter is 10-40 micrometers, and it is still more preferable that it is 20-30 micrometers.
The blending amount of the entire phosphate-based investment material is preferably 5 to 15% by weight.
[0023]
Next, although it is the 1st ammonium phosphate which is the structural requirements of (b) of this invention, 1st ammonium phosphate is soluble, but when using it as a binding material of an investment material, it is preferable that a maximum particle size is small. . From the surface smoothness of the phosphate-based investment material, it is preferable that there is no particle having a particle size of 60 μm or more. Further, among the particles of 60 μm or less, the particles of 25 μm or less are preferably 10 to 45% by weight, and more preferably 20 to 35% by weight.
The blending amount of the entire phosphate-based investment material is preferably 10 to 20% by weight.
[0024]
Next, it is preferable that the compounding ratio of the (a) constituent requirement and the (b) constituent requirement of the present invention is (a) / (b) = 0.3 to 1.0 by weight ratio. More preferably, (a) / (b) = 0.4 to 0.8.
[0025]
Next, (c) the aggregate which is a constituent requirement for blending these binders may be any refractory material used for dental casting investment, specifically quartz, cristobalite, fused quartz, There are alumina, zirconia, zirconium silicate, calcia, yttria and the like. Zirconia, zirconium silicate, quartz and cristobalite are particularly preferred.
[0026]
In addition, regarding the amount of these aggregates, it is better that the amount of cristobalite is small in the rapid heating type phosphate investment. The amount of cristobalite is preferably 15 to 45%, particularly preferably 25 to 35%. The blending amount of zirconia and zirconium silicate is preferably 5 to 15%.
[0027]
Furthermore, although it is a liquid material which kneads the powder material as these investment materials, colloidal silica aqueous solution is raised. In order to achieve the present invention, it is preferable to use large particle size colloidal silica in order to achieve both high curing expansion and rapid heating. The average particle size of the colloidal silica is preferably 10 nm to 120 nm, particularly preferably 70 nm to 100 nm.
The colloidal silica concentration is preferably 20 to 50% by weight, particularly preferably 35 to 45% by weight.
[0028]
As an effect obtained by the present invention, it can be directly put into a furnace at 800 ° C. to 1000 ° C. within 30 minutes, a curing expansion of 1.5% or more can be obtained, and a smooth surface property can be obtained.
[0029]
【Example】
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 measurement of magnesium oxide used the Nikkiso Microtrac HRA type | mold, and the 1st ammonium phosphate sieve used the JIS standard sieve.
[0030]
The adjusted magnesium oxide raw material of Sample 1 was pulverized and classified to adjust the frequency of particles having an average particle diameter of 25 μm and 100 μm or more to within 1%.
[0031]
Preparation of Sample 2 Monobasic ammonium phosphate was pulverized and adjusted so that 250 mesh (60 μm) was passed through and the particles under a 25 μm (500 mesh) sieve were 30% by weight.
[0032]
Sample 3 Grinding of Magnesium Oxide Raw material of magnesium oxide was crushed and classified to adjust the frequency of particles having an average particle diameter of 45 μm and 100 μm or more to 1% or less.
[0033]
Preparation of Sample 4 Monobasic ammonium phosphate was pulverized and adjusted so that 125 mesh (125 μm) was completely passed and particles under a 25 μm (500 mesh) sieve were 5% by weight.
[0034]
Preparation of Sample 5 Monobasic ammonium phosphate was pulverized and adjusted so that 125 mesh (125 μm) was passed through and the particles under a 25 μm (500 mesh) sieve were 50% by weight.
[0035]
Cristobalite (all 200 mesh (77 μm)), quartz (200 mesh (77 μm) all), zirconium silicate (200 mesh (77 μm) all), zirconia (200 mesh (77 μm) all) and samples 1-5 Was blended in the following composition.
[0036]
[Table 1]
[0037]
[Table 2]
[0038]
[Table 3]
[0039]
As the kneading liquid, Snowtex ZL (anhydrous silicic acid 40% by weight, average particle size 90 nm) manufactured by Nissan Chemical Co., Ltd. and Snowtex 30 (anhydrous silicic acid 30% by weight, average particle size 30 nm) manufactured by Nissan Chemical Co., Ltd. were used.
The test method for the mold was in accordance with Japanese Industrial Standard “Gypsum investment for dental casting” T6601-1998. That is, the curing time and compressive strength were based on this, and the thermal expansion was increased to 800 ° C. and the values were read.
The investment material kneading method was a mixture ratio of 22 mL / 100 g powder, Snowtex ZL was used as Kneading liquid A, and Snowtex 30 was used as Kneading liquid B. The vacuum stirrer was a Matsukaze power lift mixer, and the kneading time was 30 seconds.
[0040]
Curing and expansion test Rings with pine wind non-asbestos were lined and coated with petroleum jelly on a ring with a diameter of 40 mm and an inner diameter of 40 mm. Pour kneaded mud into the ring, place a glass plate, read the cured expansion value with a vertical dial gauge (reading 1/100 mm), and calculate the expansion rate.
The total expansion is an expansion amount obtained by adding hardening expansion to thermal expansion.
[0041]
Heat shock test A ring having a diameter of 55 mm and an inner diameter of 40 mm was lined with pine-style non-asbestos and coated with petrolatum. The kneaded mud was poured into the ring, and after 20 minutes from the start of kneading, the kneaded mud was put in a furnace heated to 800 ° C., and cracks were confirmed. The case where casting was impossible was marked with x, the case where cracks were generated was marked with △, and the case where there were no cracks was marked with ◯.
[0042]
Confirmation of cast surface A ring having a height of 55 mm and an inner diameter of 40 mm was lined with pine-style non-asbestos and coated with petroleum jelly. The kneaded mud was poured into the ring, put into a furnace heated to 800 ° C. 20 minutes after the start of kneading, moored for 30 minutes, cast pine wind unimetal, and confirmed its surface properties. The case where surface polishing was not necessary was marked with ◯, the surface which could be used by polishing the surface was marked with △, and the case where there were significant protrusions on the cast body surface was marked with ×.
[0043]
[Table 4]
[0044]
【effect】
As described above, according to the present invention, a dental rapid heating mold that can be widely cast from a precious alloy to a non-precious alloy, has good surface properties, is resistant to heat shock even after rapid heating, and does not crack or crack. A phosphate-based investment was obtained.
[0045]
According to the present invention, in a phosphate-based investment material, a dental rapid heating phosphate that can improve surface properties, obtain sufficient curing expansion, and is resistant to heat shock without cracking or cracking even when rapidly heated. A system investment material was obtained.
The present invention creates an investment material that can cast a precise casting in a short time, is resistant to heat shock, can be used for a wide range of metals by obtaining a large overall expansion, and can obtain a casting with a smooth surface property. It is to be.
Further, by utilizing the present invention, a product having sufficient compressive strength at the time of casting and easily excavating a cast body was obtained.

Claims (3)

A dental casting investment material comprising (a) magnesium oxide, (b) monobasic ammonium phosphate, and (c) a phosphate-based investment material including aggregate, wherein (a) the average particle diameter is 10 to 40 μm 5-15 wt% of certain magnesium oxide, (b) 10-20 wt% of monobasic ammonium phosphate ,
A dental rapid heating phosphate-based investing material, wherein among the first ammonium phosphate , the first ammonium phosphate having a particle size of 25 μm or less is 10 to 45% by weight. The dental rapid heating phosphate-based investment material according to claim 1, wherein (c) the aggregate contains one or more selected from zirconia, zirconium silicate, fused quartz, mullite, and alumina. A fast-acting phosphate-based investment for dental use. A colloidal silica solution is used as the exclusive liquid for kneading the dental rapid heating phosphate-based investment material according to claim 1, and the dental rapid heating phosphor having an average particle diameter of 70 to 100 nm. Acid salt investment.