JPH02247037A - Coating composition of molding material - Google Patents

Abstract

PURPOSE:To form protecting layer on molding material by mixing metal oxide of element having the specific grain diameter and powder component consisting of insoluble salt at the specific ratio. CONSTITUTION:Composition mixing the powder component consisting of at least one kind of the metal oxide selected from group composed of ytria, zirconia and magnesia having 1 - 50mum average grain diameter, ytria having 10 - 200Angstrom grain diameter and zirconium soluble salt having 1 - 200Angstrom grain diameter at wt.% of 100 : (0.1-10) : (1 - 30), respectively with water medium, at >=0.15 mixed liquid ratio (vol.(unit cc) of the water medium/wt. (unit g) of the powder component), is manufactured. By using this composition to the coating of the molding material for casting titanium or titanium alloy, the protecting layer having high strength, heat resistance and high temp. stability, can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to casting of titanium or titanium alloys.
The present invention relates to mold material coating compositions used to form a layer that protects the mold material from reaction with molten titanium or titanium alloys.

[Background of the invention] In recent years, titanium or titanium alloys (
The use of castings made of titanium-based metals (hereinafter abbreviated as titanium-based metals) is being considered. Titanium-based metals have high reactivity at high temperatures, so if the silica-silicate-based mold material used in conventional dental mackerel casting is used, it will react with the mold material and cause the mold material to deteriorate. may decompose, making casting difficult, or even if the mold material does not decompose, it may burn onto the cast body.
There is a problem in that the casting surface becomes rough. - In order to solve the problem described in F, it has been proposed to use a mold material that does not easily react with molten titanium metal as a mold material for titanium metal casting. A patent application has already been filed for the mold material (patent application filed in 1986).
3-239237).

On the other hand, silica-phosphate molding material is the most common molding material in the field of dental granular casting, and many dental technicians are familiar with its use, so it is suitable for casting titanium-based metals. It would be advantageous if you could also use it. Therefore, when casting titanium-based metals, zirconia, which is stable at high temperatures and does not easily react with molten titanium-based metals, is added to the surface of the mold made from the silica-phosphate mold material that comes into contact with the molten metal. It has been proposed to protect the mold material by forming a layer of metal oxide powder such as , ittria, or the like.

-F The mold material protective layer made of metal oxide powder is formed from a coating composition containing metal oxide powder serving as an aggregate and fine metal oxide powder even finer than the powder. The metal oxide fine powder acts as a binder in the mold material protective layer described in 1. and binds the metal oxide powders serving as the aggregate to each other. The fine metal oxide powder used as the binder is generally used in the form of a sol dispersed in an aqueous or non-aqueous medium, and the sol is combined with the aggregate in the coating composition. It also acts as a dispersion medium for metal oxides.

In the above coach ink composition, a silica-based binder has conventionally been used. For example, U.S. Patent No. 4,703
, No. 806 discloses a coating composition comprising yttoria powder and a silica-based water-insoluble sol such as silicon alkoxide or ethyl silicate. According to the description in the above specification, when titanium-based metal is cast using a mold in which a protective layer made of yttoria powder is formed using the above-mentioned coach ink composition, α cases on the surface of the cast body are (The embrittled layer formed on the surface of a cast body of the metal due to the reaction of the titanium-based metal) was compared when using a coating composition in which zirconia powder was dispersed in 30% colloidal silica. It is said that it is possible to reduce the thickness by 48 to 92%.

However, it has been reported that when a silica-based binder is used, blackening of the surface of the casting and pinholes always occur (Titanium dental casting conducted at the Skinner Lab, Northwestern University, USA). fundamental research on the use of titanium in dentistry (Kyoto University Hall, August 27, 1986, collection of lecture abstracts), and the coating composition disclosed in the above specification is sufficiently effective in protecting mold materials. may not be obtained. Furthermore, according to the inventor's studies, the protective layer obtained from a coating composition in which ittria powder is dispersed in a silica-based sol such as colloidal silica or ethyl silicate often cracks, making it difficult to obtain a desirable cast body. .

It is also known to use a fine powder of the same kind of metal oxide as the aggregate metal oxide powder as a binder. It is described that a slurry obtained by dispersing itria powder in a sol and a slurry obtained by dispersing itria powder in an itria sol are used as a coating composition. According to the description in the above specification, when the former coating composition is used, the α case tends to increase, and when the latter coach ink composition is used, the α case can be reduced to some extent. It is said that

However, when the present inventor investigated the latter coach ink composition, it was found that in a coating composition in which ittria powder serving as an aggregate is dispersed in a sol of ittria alone, the composition gels when it dries. The protective layer that is formed tends to crack easily because of the rapid rate of curing, and the protective layer that is formed tends to peel off from the mold material because the composition shrinks greatly as it hardens. It has been found that there is a tendency.

Therefore, it is desired to develop a coating composition that can form a metal oxide layer on the mold surface that has sufficient performance to protect the mold material from reaction with molten titanium-based metal.

[Object of the Invention] An object of the present invention is to provide a coating composition that can form a mold material protective layer made of metal oxide on the surface of the mold that comes into contact with molten metal during casting of titanium or titanium alloy. It is in.

[Summary of the Invention] The present inventor has discovered that the performance of a layer made of metal oxide formed to protect the mold material from reaction with titanium-based metal in casting titanium or titanium alloy is We thought that this would depend on the composition of the sol to be dispersed, and conducted repeated studies. As a result, by using a mixture of itria sol and zirconia sol or zirconium insoluble salt sol as a sol for dispersing metal oxide powder, it is possible to control the gelation rate of the coating composition, which is equivalent to that of the mold material. The present invention was completed based on the discovery that a protective layer having a strength of 100% and less shrinkage upon curing can be obtained.

In the present invention, the average particle diameter is 1 to 50 μm, preferably 3 to 50 μm.
0.1 to 10 parts by weight of ittria with an average particle diameter of 10 to 200X, and 1 to 30 parts by weight of at least one metal oxide selected from the group consisting of 10 μm of ittria, zirconia, and magnesia. A powder component consisting of an insoluble salt of zirconia or zirconium having an average particle diameter of 1 to 200^ in parts by weight, and an aqueous medium,
Mixed liquid ratio (body M of aqueous medium (unit: cc)/weight of powder component (unit: g)) o, 15 or more, preferably 0.15 to
0.6, more preferably 0.3 to 0.4.

Preferred embodiments of the coating composition of the present invention are as follows.

(1) The coating composition has an average particle size of 1 to 10
Contains ittria as a μm metal oxide.

(2) The coating composition has an average particle size of 1 to 10
Magnesia should be included as a μm metal oxide together with ittria in a range of 5 to 20 mfJ=% relative to ittria.

(3) The average particle diameter of the metal oxide is in the range of 3 to 10 μm.

(4) The coating composition includes a heat-expandable material.

[Effects of the Invention] Since the coating composition of the present invention has an appropriate gelation rate, it has excellent operability and can advantageously form a coating layer regardless of the shape of the object to be coated. Furthermore, since the coach ink composition of the present invention has little shrinkage upon curing, it is less likely to deform the wax mold to be cast and is less likely to peel off from the mold.

Furthermore, the mold material protective layer formed from the coating composition of the present invention has excellent heat resistance, high temperature stability, and strength.

Therefore, by using the coating composition of the present invention, it is possible to advantageously form a mold material protective layer made of a metal oxide on the surface of a titanium-based metal casting mold that comes into contact with molten metal. Titanium-based metals can be cast using conventionally known general mold materials such as silica-phosphate mold materials or magnesia-based mold materials without using special mold materials such as .

[Detailed Description of the Invention] The coating composition of the mold material for titanium or titanium alloy casting of the present invention comprises at least one metal oxide selected from the group consisting of ittria, zirconia, and magnesia with an average particle size of 1 to 50 μm. With respect to 100 parts by weight, 0.1 to 10 parts by weight of ittria with an average particle size of 10 to 200, and 1 to 30 parts by weight of ittria with an average particle size of 1 to 2
A powder component consisting of 00X zirconia or an insoluble salt of zirconium and an aqueous medium are mixed at a mixing ratio (volume of aqueous medium (unit: cc)/weight of powder component (unit: g))
, 15 or more.

Average particle size contained in the above coating composition: 1 to 50
The μm metal oxide is a metal oxide that serves as an aggregate in the mold material protective layer formed from the coating composition. The metal oxide that serves as the aggregate is stable at high temperatures,
It is a substance that does not easily react with molten titanium metals. The metal oxides used as the aggregate are yttoria, zirconia,
And, it is necessary that the metal oxide is at least one kind of metal oxide selected from the group consisting of magnesia. It is preferable that the coating composition contains magnesia alone or together with itria as the metal oxide serving as the aggregate. By including magnesia together with itria, the fluidity, kneadability, gelation time, and other operability of the coating composition described in (g) can be easily adjusted. The above coating composition is
When magnesia is included along with itria, the content of magnesia is preferably in the range of 5 to 20% by weight based on itria. When the content of magnesia is less than 5% by weight based on itria, it is difficult to obtain a sufficient effect of adjusting the operability of the coating composition;
When it exceeds 0% by weight, the heat resistance and high temperature stability of the resulting metal oxide layer (molding material protective layer) may be low, and the molding material protecting effect against titanium metal may become insufficient.

The average particle size of the metal oxide that becomes the aggregate is 1 to 50 μm
The thickness is preferably in the range of 3 to 10 μm. If the average particle size exceeds 50 μm, a dense metal oxide layer may not be obtained, and the effect of protecting the mold material may become insufficient.

Average particle size contained in the above coating composition: 10-2
The ittria fine powder of 00^ acts as a binder to mutually bind the metal oxide particles in the metal oxide layer formed from the coating composition.

The content of the above-mentioned ittria fine powder is the above-mentioned metal oxide 1
00 parts by weight, it is necessary to be in the range of 0.1 to 10 parts by weight, and preferably in the range of 0.2 to 3 parts by weight. When the content of the ittria fine powder described in (iii) is less than 0.1 part by weight with respect to 100 parts by weight of the metal oxide that becomes the aggregate, it has the effect of caking the metal oxide particles that become the aggregate with each other. If this is not sufficient, a dense metal oxide layer (molding material protective layer) may not be obtained. Furthermore, even if the amount is more than 10 parts by weight, the binder action of the ittria fine powder will not be improved.

Average particle size contained in the above coach ink composition: 1 to 20
The fine powder of zero-pronged zirconia or zirconium insoluble salt acts as a binder to mutually bind the metal oxide particles in the metal oxide layer formed from the coating composition, and also acts as a binder to bind the particles of the metal oxide to each other. It has the function of adjusting the gelation rate of the coating composition when the metal oxide layer (template material protective layer) is formed. The content of the zirconia or zirconium insoluble salt fine powder is 10
With respect to 0 parts by weight, it is necessary to be in the range of 1 to 30 parts by weight, and preferably in the range of 3 to 15 parts by weight. When the content of the fine powder of zirconia or zirconium insoluble salt is less than 1 part by weight based on 100 parts by weight of the metal oxide used as the aggregate, gelation of the coating composition rapidly progresses and formation of a gel occurs. This is not preferable because it tends to cause cracks in the metal oxide layer (molding material protective layer). Moreover, when it exceeds 30 parts by weight, gelation of the coating composition tends to be delayed.

The above-mentioned coating composition contains the above-mentioned aggregate metal oxide, the above-mentioned ittria fine powder, and the above-mentioned zirconia or zirconium insoluble salt fine powder in the above-mentioned range. Shrinkage associated with curing is reduced. If the curing shrinkage of the coating composition is small, the amount of deformation of the wax mold to be cast by the formed metal oxide layer (mold material protective layer) will be reduced in the process of forming the mold material protective layer described below, and the above-mentioned This is advantageous because the metal oxide layer is less likely to separate from the backup-filled mold material.

The coating composition may further contain a thermal expansion material. By adding a thermal expansion material to the above coating composition, the thermal expansion coefficient of the formed metal oxide layer (molding material protective layer) can be made close to that of the backup-filled mold material, which is advantageous. be. It is preferable that the thermal expansion material is added in an amount of 1 to 10 parts by weight based on 100 parts by weight of the metal oxide that serves as the aggregate. Examples of the heat expansion material include zirconium powder.

The above-mentioned coating composition is a composition in which a powder component consisting of the aforementioned metal oxide, fine ittria powder, and fine powder of zirconia or zirconium insoluble salt is mixed with an aqueous medium. The coating composition needs to have a mixing ratio of 0.15 or more, preferably 0.15 to 0.60, and 0.15 to 0.60.
．． It is more preferably in the range of 3 to 0.4. The above-mentioned liquid mixture ratio is an amount expressed by the ratio of the volume (unit: cc) of the aqueous medium to the weight (unit: g) of the powder component (volume M of the aqueous medium/weight of the powder component).

In the above-mentioned coating composition, when the mixing ratio is not within the above-mentioned range, appropriate fluidity may not be obtained.

In the coating composition of the present invention, the powder component consisting of fine ittria powder and fine powder of zirconia or zirconium insoluble salt is preferably used in the form of a sol. By dispersing the aforementioned metal oxide as an aggregate in a mixture of itria sol and a zirconia sol or a sol of a zirconium insoluble salt, a coating composition having the aforementioned powder composition and mixture ratio can be advantageously prepared. can.

The above-mentioned ittriazole has an average particle size of 10 to 200X,
Preferably, it is a sol prepared by dispersing fine ittria powder in an aqueous medium at a concentration of 10 to 20% by weight. The aqueous medium may contain a water-soluble organic solvent such as acetic acid and acetone.

The above sol of zirconia or zirconium insoluble salt is
A sol in which fine powder of zirconia or zirconium insoluble salt having an average particle diameter of 1 to 200×, preferably 5 to 50×, is dispersed in an aqueous medium at a concentration of 10 to 40% by weight is preferred. The aqueous medium may include a water-soluble organic solvent such as acetic acid or acetone, or an aqueous solution of a zirconium compound. The above-mentioned zirconium compounds include compounds having a zirconyl group (ZrO") such as zirconium oxychloride, zirconyl sulfate, zirconyl nitrate, zirconyl phosphate, zirconyl acetate, zirconyl stearate, zirconyl carbonate, and zirconyl ammonium carbonate, or zirconium acetate. can be mentioned.

In the coating composition, the itria sol and the sol of zirconia or zirconium insoluble salt also act as a dispersion medium for the metal oxide. It is believed that the gelation rate of the coating composition has a correlation with the basicity of the sol that acts as the dispersion medium. The above-mentioned coating composition can be obtained by using the zirconia or zirconium insoluble salt vine as a dispersion medium of the metal oxide together with the ittriazole, so that the coating composition can be prepared by using the ittriazole alone or in combination with a metal oxide sol other than zirconia. In comparison, it is presumed that the basicity of the sol acting as a dispersion medium can be adjusted advantageously, and an appropriate gelation rate can be obtained.

The above-mentioned coating composition can usually be advantageously prepared by dispersing the metal oxide aggregate as described above in a mixture of itria sol and zirconia sol or zirconium insoluble salt sol, but if necessary, , and may be further diluted using an aqueous medium. However, in this case, care must be taken to ensure that the mixed liquid ratio falls within the above-mentioned range. - The aqueous medium may contain a water-soluble organic solvent such as acetic acid or acetone, or an aqueous solution of a zirconium compound.

Using the coating composition described above, a mold material protective layer made of a metal oxide can be formed on the surface of the mold that comes into contact with molten metal, for example, by the method described below.

Dental prostheses are generally manufactured by a cast iron casting method using a lost wax method. When casting relatively small objects such as crowns using the lost wax method, the casting mold is made by using wax on a master mold obtained from an impression taken in the oral cavity, and then removing the master model from the wax. Manufacture: The mold to be cast is fixed in a mold, embedded with mold material (backup filling), hardened, and then fired and the wax of the mold to be cast is melted to produce the mold.

In the above-mentioned lost wax method, the protective layer made of the metal oxide powder is formed by applying the coating composition to the wax casting target mold before burying the wax casting target mold in the mold material (backup filling). It can be advantageously formed by inserting a drying step. The coating composition may be applied by directly topping the wax mold to be cast with the coating composition, or the coating composition may be applied to the wax mold by using a brush, brush, etc. .

In addition, when casting a relatively large prosthesis such as a denture base using the lost wax method, the mold is made by taking a double impression from a mother model obtained from an impression taken in the oral cavity, and then using a mold made from the double impression. A mold to be cast is constructed using wax on the model, the wax target mold is buried (backup filling) with mold material together with the duplicate model, the mold material is hardened, and then the wax target mold and the mold material are cured. It is manufactured by firing the mold and melting the wax of the mold to be cast.

In this case, the protective layer made of the metal oxide powder is
In the above-mentioned lost wax method, before embedding the wax casting target mold in a mold material, first, the coating composition is applied on the duplicate model and dried to form the protective layer,
Next, the protective layer can be advantageously formed by forming a mold to be cast using wax, and then applying a coating composition to the wax mold to be cast and drying it. Application of the coating composition can be advantageously carried out by applying the coating composition to a wax casting mold using a brush, brush, or the like.

When the above-mentioned coating composition is applied by topping, it is desirable that the coating composition has high fluidity, and the metal oxide serving as the aggregate contained in the coating composition is preferably composed of ittria and magnesia. preferable. Moreover, it is preferable that the mixing ratio of the coating composition is 0.3 or more. Although there is no particular restriction on the fluidity of the coating composition, it is practically preferable that the mixing ratio is in the range of 0.3 to 0.5.

If the mixing ratio of the coating composition is greater than 0.5, the coating composition tends to be difficult to adhere to during topping, and the curing time of the coating composition tends to be longer.

When applying the above-mentioned coating composition using a brush, brush, etc., the mixture ratio of the above-mentioned coating composition is 0.
．． It is preferably in the range of 3 to 0.4.

- F, in each case application of a coating composition;
It is preferable that the drying is repeated several times to form a coating layer having a thickness of 0.3 to 2 mm.

The hardening of the coating layer can be accelerated by stuccoing metal oxide powder onto the core layer. The above-mentioned metal oxide powder serving as an aggregate can be used for the above-mentioned stucco, and it is particularly preferable to use a mixture of itria powder and magnesia powder.

The mold material used for embedding (backup filling) the wax casting target mold mentioned above can be a conventionally known general mold material such as a silica-phosphate mold material or a magnesia mold material. . However, a calcia-based mold material may also be used.

The coating composition of the present invention may be used not only for protecting mold materials, but also for coating (lining) the surface of a material that comes into contact with molten titanium-based metal to protect the material. For example, it may be used to protect a single crucible used for melting titanium-based metals or a crucible integrally formed with a mold.

A mold in which a metal oxide layer (mold material protective layer) is formed using the coating composition of the present invention can also be cast by cooling the fired mold to room temperature.

The coating composition of the present invention can also be used as a mold material by adjusting the mixing ratio.

Next, examples of the present invention will be shown.

[Example 1] 100 g of Ittria powder with an average particle size of 10.16 μm (manufactured by Mikumi Kinzoku Kogyo ■) was mixed with Ittria sol (manufactured by Tamoto Kagaku ■, containing 15% by weight of Ittria fine powder with an average particle size of 40 μm) and zirconia. Sol (manufactured by Nissan Chemical ■, average particle size 7X
228 containing 20.1% by weight of zirconia fine powder)
(weight ratio) was dispersed in 40 cc of the mixture to produce coating composition A.

A wax mold of a runner was attached to a 1010×10×5 plate-shaped wax mold, and a mold to be cast was prepared, which was set up in a truncated cone. FIG. 1 is a diagram schematically showing a cross section of the mold to be cast.

Next, the coating composition A is applied to the truncated cone 11 of the casting target mold shown in FIG. 1, the wax mold 12 of the runner, and
The wax was applied to a plate-shaped wax mold 13 using a small brush to a thickness of about 1 mm.

The mold to be cast coated with the above coating composition A is fixed in the mold frame, and buried (backup filling) in a phosphate-based investment material (manufactured by WhipMix in the United States, trade name: Hi-Temp Casting Instance), followed by standard method. Therefore, the mold was manufactured by drying, hardening, and firing. For the above firing, the temperature was raised to 800°C in 2 hours using an electric furnace, and after being moored at 800°C for 1 hour, the mold was placed in an arc melting argon gas pressure casting machine (manufactured by Iwatani Sangyo ■, Castmatic). JIS Class 2 pure titanium was cast.

The surface of the obtained cast body was smooth and crisp, no burning of the mold material was observed, and it had a metallic luster.

[Comparative Example 1] 100 g of ittria powder, which was the same as that used in Example 1, was mixed with 50 cc of ittria sol, which was the same as that used in Example 1.
Coating composition B was prepared. No fine powder of zirconia or an insoluble salt of zirconium was added to the above coating composition B.

- Example 1 except that coating composition B described in F was used.
Pure titanium was cast in the same manner.

On the surface of the casting, cracks due to cracks in the protective layer of the mold material were observed.

[Comparative Example 2] 100 g of the same Ittria powder used in Example 1 was dispersed in 40 cc of silica sol (manufactured by Nissan Chemical Company, trade name: Nisnortex) to produce coating composition C.

Pure titanium was cast in the same manner as in Example 1, except that the coating composition C was used.

The molten titanium reacted with the backup phosphate-based investment material (mold material) through cracks in the mold material protective layer, causing the mold material to decompose, making it impossible to obtain a proper cast body.

[Comparative Example 3] 100 g of the same Ittria powder used in Example 1 was dispersed in 55 parts by weight of alumina sol (manufactured by Nissan Chemical Company, trade name: Alumina Sol 1'0O) to produce a coach ink composition.

Pure titanium was cast in the same manner as in Example 1 except that the above coating composition was used.

On the surface of the cast product, there are cracks due to cracks in the protective layer of the mold material.
Burning etc. were observed.

[Usage Example 1] Using coating composition A produced in Example 1, pure titanium was cast in the same manner as in Example 1, except that the mold after firing was cooled to room temperature and then set in the casting machine. I did it.

The surface of the obtained cast body was smooth and firm, no burning of the mold material was observed, and it had a metallic luster.

[Comparative Use Example 1] Pure titanium was cast in the same manner as Use Example 1 except that coating composition A produced in Example 1 was not used at all.

The obtained cast body was strongly baked to the mold material, and the surface of the cast body was discolored black.

[Comparative Use Example 2] Pure titanium was cast in the same manner as in Example 1 except that coating composition A produced in Example 1 was not used at all, but the mold material reacted with the molten titanium. No cast body was obtained because the product was disassembled.

[Example 2] 100 g of a powder prepared by blending 2.0% by weight of metal zirconium powder of 200 mesh pass with Ittria powder (manufactured by Santoku Metal Industries Ltd.) having an average particle diameter of 10.16 μm was mixed with the same Ittria sol used in Example 1. and zirconia sol in a ratio of 2=8 (weight ratio) to 40 cc to prepare coating composition E.

A wax mold of the crown was manufactured using an American Dental Association (ADA) standard crown mold. A wax mold of a runner was attached to the above wax mold to prepare a mold to be cast, which was set up in a truncated cone. FIG. 2 is a diagram schematically showing a cross section of the mold to be cast.

Next, the coating composition E is applied to the truncated cone 21 of the mold to be cast shown in FIG. A wax mold 22 of the runner, and
The wax was applied to the wax mold 23 of the crown using a small brush to a thickness of about 1 mm. The above coating composition E
To the coating layer coated with the same powder as that used in Example 1, 1 part of electric fused magnesia powder manufactured by Tateho Chemical Co., Ltd. was added.
The powder mixed with 0% by weight was stuccoed to accelerate the curing of the coating composition.

The casting target mold subjected to the above-described treatment was treated in the same manner as in Example 1 to produce a mold. Using the above mold, JIS Class 2 pure titanium was cast in the same manner as in Example 1.

The surface of the obtained cast body was smooth, no flaking or burning of the mold material was observed, and it exhibited metallic luster. When the cast body (crown) was fitted into the ADA standard crown mold, a very good fit was obtained.

[Usage Example 2] A mold integrated with a crucible was prepared. FIGS. 3a to 3C are schematic diagrams for explaining a method for manufacturing a green mold of the mold. The formwork formwork 31 shown in FIG. 3a has a convex portion 32 on its bottom surface. 1010X on the upper part of the convex part 32
A runner wax mold 33 to which a 10×5 plate-shaped wax mold 34 was attached was set up and used as a mold to be cast. Next, the coating composition E produced in Example 2 was applied to the wax mold 33 of the runner of the mold to be cast and the plate wax mold 34 shown in FIG. It was applied so that

The mold to be cast coated with the above coating composition E is buried (backup filling) in the same phosphate-based investment material used in Example 1, and dried and hardened according to a standard method to produce a green mold. did.

FIG. 3b schematically shows a cross section of a green mold 35 manufactured by the above-described method. The recess formed in the upper part of the green mold 35 can be used as a crucible. In FIG. 3b, 36 is a metal oxide layer (molding material protective layer) formed from coating composition E by the method described above.
It is.

Next, the coating composition E was applied (lined) to four parts of the upper part of the green mold 35, and was dried and cured. The state of the prototype 35 after the above processing is shown in FIG. 3C.

In FIG. 3C, 37 is a metal oxide layer (template material protective layer) formed from coating composition E by the method described above.

A green mold with a metal oxide layer (mold material protective layer) formed on both the crucible part and the mold part by the above-mentioned treatment,
The mold was fired in the same manner as in Example 1 to produce a mold integrated with the crucible.

The above-mentioned mold was set in a high-frequency casting machine (model Alpatron PC-305 high-frequency unidirectional continuous pressure casting machine, manufactured by Asahi Roentgen ■), and casting was performed using JIS Class 2 pure titanium.

The surface of the obtained cast body was smooth, no burning of the mold material was observed, and it exhibited metallic luster.

[Comparative Use Example 3] Without applying coating composition E to the recessed portion of the upper part of the green mold produced in Use Example 2 (in the state shown in Figure 3b)
Casting was carried out in the same manner as in Use Example 2, except that the mold was manufactured by firing, but the mold material in the crucible part (the upper four parts of the green mold) reacted with the molten titanium and decomposed.
No castings were obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of the mold to be cast used in Example 1. FIG. 2 is a schematic cross-sectional view of the mold to be cast used in Example 2. FIGS. 3a to 30 are schematic diagrams for explaining a method for manufacturing a green mold used in Usage Example 2. FIG. 21: 23: 31: 33: 34 = 36, truncated cone, 22: runner type, crown wax type, formwork, 32: protrusion, runner wax type, plate wax type, 35 : green mold, 37: metal oxide layer. Patent applicant: Takashi Miyazaki Patent applicant: Nippon Lime Industry Co., Ltd.

Claims (1)

[Claims] 1. 0.1 to 1 part by weight of at least one metal oxide selected from the group consisting of yttria, zirconia, and magnesia with an average particle size of 1 to 50 μm
The mixture ratio (aqueous Volume of medium (unit; c
A coating composition for a mold material for casting titanium or a titanium alloy, characterized in that c)/powder component weight (unit: g)) is mixed at a ratio of 0.15 or more.