JPH08104535A - Releasing material slurry - Google Patents

Abstract

PURPOSE: To produce a crystallized glass dental material good in dimensional accuracy by forming a uniform and stable reaction suppressing layer containing boron nitride on the surface of a molding mold material. CONSTITUTION: This releasing material slurry is composed of 5-60wt.% boron nitride, 1-20wt.% silica colloid, 1-20wt.% resin soluble to a solvent or uniformly dispersible in the solvent, 50-90wt.% org. solvent consisting of a mixture of high volatile org. solvent and low volatile org. solvent and 2-30wt.% calcium phosphate crystal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold release material slurry, and more particularly to a mold release material slurry for a mold used for molding a dental material made of calcium phosphate type crystallized glass.

[0002]

2. Description of the Related Art Recently, various ceramic-based dental materials have been proposed, and some of them have been put into practical use. Among these, the calcium phosphate-based crystallized glass has characteristics such as excellent moldability and physical properties resembling those of natural teeth.

The calcium phosphate crystallized glass material is
Since the glass melt has a low viscosity and a high fluidity, it is easy to mold, but it easily reacts with the mold material during molding. Therefore,
A method of providing a reaction suppressing layer containing 1% by weight or more of boron nitride on the surface of a mold material has been proposed (Japanese Patent Publication No. 1-104).
No. 47).

Further, when the molded calcium phosphate glass is heat-treated in the mold material and crystallized, the presence of calcium metaphosphate crystals on the surface of the mold material stabilizes the crystallized glass excellent in mechanical properties and aesthetics. (Refer to Japanese Patent Publication No. 2-56291), and in a calcium phosphate-based crystallized glass having a composition further containing strontium oxide, a mold material in which calcium phosphate crystals in which strontium is in solid solution is present is effective ( JP-A-4-231344) is proposed.

[0005]

As a simple method for providing a reaction suppressing layer containing boron nitride on the surface of a molding die, an appropriate binder or aggregate is added to boron nitride, and this is applied to the surface of the die. In the case of coating or by the lost wax method, there is a method of coating on the surface of a mold (wax pattern etc.) of the mold surface, burying the mold with a mold base material, and then removing the mold by an appropriate method. However, in order to use it for such purpose, it is difficult to obtain the homogeneity and stability by simply mixing the necessary components, and the surface property of the molded product tends to have a problem. It is an object of the present invention to provide a release material for providing a reaction suppressing layer containing boron nitride on the surface of a molding die material.

[0006]

SUMMARY OF THE INVENTION The present invention is directed to boron nitride 5
To 60% by weight, silica colloid 1 to 20% by weight, solvent soluble or uniformly dispersible resin 1 to 20% by weight, organic solvent 50 to 90% by weight, and a release agent slurry. .

This mold release material slurry is used to form a layer on the surface of the mold material and improve the mold releasability between the mold material and the material to be molded. The release agent slurry can be fired to remove the organic component, thereby forming a heat-resistant release layer. The molding die and the material to be molded are not particularly limited, but can be preferably used as a die for casting glass, for example.

Boron nitride is indispensable for imparting a releasing effect between the material to be molded and the mold material. Boron nitride content is 5
If it is less than wt%, the releasing effect is insufficient and unsuitable. The higher the content of boron nitride, the better the mold release property.
If it exceeds 0% by weight, the fluidity of the mold release material slurry becomes insufficient and the mechanical strength after curing is lowered, which is not suitable. As the boron nitride, specifically, hexagonal boron nitride powder represented by the composition formula of BN is preferable.

Silica colloid serves as a binding agent for boron nitride when heat-treated, and it is necessary to add 1% by weight or more as a solid content in order to maintain strength. However, if the amount of silica colloid is too large, the releasing action of boron nitride is weakened, so the amount of silica colloid needs to be 20% by weight or less as a solid content. More preferable content of silica colloid is 3 to 10% by weight.
Is.

The silica colloid may be in the form of powder or may be in the state of being dispersed in a solvent. Alcohol-based silica colloid is preferable as the solvent. In the case of powder, the primary particle size is 1 to
It is preferably about 100 nm. In the case of the dispersion liquid, silica having a dispersed particle diameter of about 0.1 to 50 μm is preferable.

The resin component has the function of maintaining the homogeneity of the slurry and improving the operability during coating. Any resin component may be used as long as it is soluble or uniformly dispersed in an organic solvent, and it is preferable to avoid a substance that produces a harmful gas during heat treatment. For example, ethyl cellulose, ethyl hydroxyethyl cellulose, nitrocellulose or polyvinyl butyral having various molecular weights can be preferably used. The amount of the resin component is preferably adjusted so as to have an appropriate viscosity in consideration of the type of resin and the type and amount of the solvent, but when it is less than 1% by weight, the slurry homogeneity improving effect is obtained. Absent.
If it exceeds 20% by weight, the release material after heat treatment tends to collapse, which is not preferable. The more preferable content of the resin component is 2 to 10% by weight. A plurality of resins may be mixed and used for the purpose of adjusting viscosity.

The organic solvent is required in an amount sufficient to uniformly dissolve or disperse the resin and to disperse boron nitride, silica colloid and other components, and 50% by weight or more is necessary. The content of the organic solvent is adjusted according to the material and shape of the mold material or the mold of the mold to be coated, the coating method, etc., but if it exceeds 90% by weight, the uniformity of the slurry will be impaired, which is not suitable. . Organic solvent content is 5
The case of 5 to 70% by weight is particularly preferable.

The organic solvent is preferably used in one kind or a combination of relatively high volatility and low volatility so as to give an appropriate viscosity and drying rate to the slurry.

As the highly volatile organic solvent, the boiling point is 150.
C. or lower, more preferably 100.degree. C. or lower. Specifically, alcohols having 4 or less carbon atoms such as methanol, ethanol, propanol and butanol are preferable.

A low-volatile organic solvent having a boiling point of 150
It is preferably one having a boiling point of 200 ° C. or higher, more preferably 200 ° C. or higher. Specific examples include trimethylpentanediol isobutyrate, diethylene glycol monobutyl ether acetate, and α-terpineol. In addition to pure substances, a mixture of natural products or synthetic or semi-synthetic products such as pine oil (an oily liquid containing α-terpineol as a main component extracted from pine) can be used.

The mixing ratio of the high volatility organic solvent and the low volatility organic solvent is preferably adjusted appropriately so as to obtain a drying speed according to the purpose, but in order to stably disperse the silica colloid. The amount of the highly volatile organic solvent is preferably 10 to 60% by weight of the entire slurry including the amount of alcohol contained in the silica sol, and particularly 20 to 40%.
Weight percent is preferred. The low-volatility organic solvent is preferably 5 to 50% by weight of the whole slurry, and particularly 10 to 40% by weight.
Is preferred.

The mold release material slurry of the present invention can be used for molding various materials such as metal and glass. After glass is cast and molded, it can be crystallized as it is.
When the mold release material slurry of the present invention is used as a mold material for forming and crystallizing calcium phosphate glass, it is preferable that the mold release material slurry contain calcium metaphosphate crystals in an amount of about 2 to 30% by weight. The calcium metaphosphate crystal blended in the mold release material slurry acts as a seed crystal when the crystal precipitates from glass, homogenizes the structure near the surface of the crystallized glass, and obtains a dense and strong crystallized glass. You can A calcium metaphosphate crystal content of less than 2% by weight is not preferable because the effect of uniform crystallization may not be exhibited sufficiently. Compounding amount of calcium metaphosphate crystals is 30% by weight
If it exceeds, the release effect of boron nitride may be impaired, which is not preferable.

Depending on the glass composition, different from calcium metaphosphate, a crystallized glass in which, for example, crystals of calcium metaphosphate in which strontium is solid-dissolved is deposited may be obtained. In such a case, metacrystal as a seed crystal may be obtained. As the calcium phosphate crystal, it is preferable to use the calcium metaphosphate crystal in which strontium is similarly solid-dissolved.

Further, a surfactant or the like may be appropriately added to the release agent slurry for the purpose of improving the dispersibility of boron nitride.

The release agent slurry can be prepared by mixing the above-mentioned components, but it is necessary to sufficiently mix the respective components. Although all the components may be mixed at once, it is preferable that the resin and the silica colloid are not sufficiently mixed simply by stirring, so that they are dissolved or dispersed in an organic solvent in advance and then mixed. As a mixing means, a method using a stirrer, a method using a mortar or a mixer, a method using a ball mill, a roll mill, or the like can be appropriately adopted depending on the viscosity of the slurry. Further, in some cases, the mixing can be promoted by appropriately heating. If alcohol or other solvents may volatilize, use a container with a lid.

As a method for forming a layer having excellent releasability on the surface of the mold material using this mold release material slurry, a method of applying a brush or a trowel or the like to the surface of the mold material, a method of spraying with a spray or the like is used. Various methods such as a method of soaking in the slurry and then pulling it up can be adopted. Further, depending on the case, it is also possible to manufacture the entire mold material with this mold release material. In any case, it is preferable to perform heat treatment at an appropriate temperature in order to increase the strength of the mold surface.

In the lost wax method, which is often used for casting molding of dental materials, the mold release material slurry of the present invention is applied to a paraffin wax master mold (wax pattern), and the mold release material slurry is used in a molding material slurry called investment material. At the same time, the mold material is hardened by heat treatment and the wax pattern is removed, and glass is cast in the voids formed in that portion. Here, when the mold release material slurry is applied to the surface of the wax pattern by various methods before the embedding treatment, the mold release material slurry is also baked when the mold material is hardened by the heat treatment, and the mold base material A release layer is formed on the surface of.

The thickness of the release material layer is preferably adjusted appropriately according to the material, size, shape and molding temperature of the body to be molded, but is preferably in the range of 10 to 300 μm.

The release layer is formed by heat treatment during molding.
It is necessary to remove the organic component. When the organic component remains, air bubbles are entrained in the glass molded body due to the generation of gas, or in the case of glass that is relatively easily reduced at high temperatures such as calcium phosphate-based glass, coloring due to reduction may occur. There are inconveniences such as occurrence. The release material layer after the heat treatment has a structure in which the boron nitride and the seed crystal, in the case of using the seed crystal, are bonded by the silica binder.

[0025]

【Example】

Example 1 Polyvinyl butyral resin (manufactured by Denki Kagaku Kogyo Co., Ltd., polyvinyl butyral 2) in 30 parts by weight of isopropanol
(000 L) was added by 4 parts by weight and dissolved by stirring. This was placed in a mortar, 20 parts by weight of boron nitride powder, 10 parts by weight of calcium metaphosphate crystal powder, 6 parts by weight of colloidal silica powder (manufactured by Catalysts & Chemicals Industry Co., Ltd., trade name OSCAP) were added and mixed, and further 30 parts by weight of pine oil. Parts were added and mixed well to prepare a release agent slurry.

When the above release agent slurry was applied to an acrylic resin rod having a length of 20 mm, a width of 2 mm and a thickness of 2 mm, the slurry was smooth and spread well, and it was possible to apply it thinly and uniformly. This was erected on a rubber base and fixed with a soft wax (manufactured by Meta Dental Industry Co., Ltd., trade name Utility Wax). A metal ring is placed on a rubber base so as to surround the acrylic resin rod coated with the slurry, and a dental investment material (made by Tokuyama Corporation, trade name Blue Vest) powder is dissolved in water inside the ring. After pouring and curing, remove the rubber stand and put in an electric furnace.
A mold was prepared by heat treatment at 0 ° C.

The mold was kept at 650 ° C. and kept at 1100 ° C.
In molten P ₂ O ₅ is 67% by weight, CaO 26% by weight, Al ₂ O ₃ is 4 wt%, the Ce ₂ O ₃ is 3 wt% of the glass was cast by centrifugal casting, as it is, along with the type 7
Crystallization was carried out by keeping at 00 ° C for 16 hours. After crystallization, the temperature was cooled to room temperature, and the crystallized glass was taken out from the mold material. The obtained crystallized glass casting was translucent and crystallized uniformly, the surface was smooth, and the shape of the rod was accurately reproduced.

For the storage stability test of the slurry, the slurry was placed in a container, sealed, and stored in a thermostatic chamber at 40 ° C. for 4 months, and then a mold was prepared in the same manner as in the beginning to cast and crystallize glass. did. Although there was a small amount of supernatant in the slurry, it was possible to easily homogenize it by light stirring, and to apply it as thinly and smoothly as at the beginning. In addition, a crystallized glass cast body having a beautiful appearance similar to that at the beginning was obtained.

Example 2 Two kinds of ethyl cellulose having different molecular weights (trade names N-7 and N-22, manufactured by Hercules, Inc., USA) 1 each
% By weight and 4% by weight and polyvinyl butyral resin (trade name: polyvinyl butyral 2 manufactured by Denki Kagaku Kogyo Co., Ltd.)
000 L) 10% by weight, α-terpineol 55% by weight as a solvent, diethylene glycol monobutyl ether acetate 30% by weight in a liquid 36 parts by weight, about 30
Silica binder liquid containing isopropanol as a solvent containing silica colloid in weight% (manufactured by Catalysts & Chemicals Co., Ltd.,
Product name OSCAL1432) 18 parts by weight, boron nitride 1
9 parts by weight, 50 mol% phosphoric acid and CaO as P ₂ O ₅
As 37 mol% calcium as SrO as 13 mol%
Then, 9 parts by weight of calcium metaphosphate crystal powder in which strontium containing strontium was dissolved and 18 parts by weight of isopropanol were added and sufficiently mixed to prepare a release agent slurry.

An extremely thin coating of the above slurry was applied to a crown-shaped wax pattern and dried, and then a dental embedding material (Matsufu Co., Ltd., trade name Unibest Non Precious) was used to embed and wax according to a conventional method. A mold was prepared by incineration.

This mold material was kept at 650 ° C. and kept at 1100 ° C.
67% by weight of P ₂ O ₅ melted in 16% by weight of CaO,
SrO 10% by weight, Al ₂ O ₃ 4% by weight, Ce ₂ O
Glass with 3% by weight of ₃ was cast by centrifugal casting, and crystallized as it was by keeping it at 700 ° C. for 16 hours together with the mold.
After crystallization, the temperature was cooled to room temperature, and the crystallized glass was taken out from the mold material. The obtained crystallized glass casting was translucent and crystallized uniformly, the surface was smooth, and the shape of the wax pattern was accurately reproduced.

For the storage stability test of the slurry, the slurry was placed in a container, sealed, and stored in a constant temperature bath at 40 ° C. for 4 months, then a mold was prepared in the same manner as in the beginning, and glass was cast and crystallized. did. Although there was a small amount of supernatant in the slurry, it was possible to easily homogenize it by light stirring, and to apply it as thinly and smoothly as at the beginning. In addition, a crystallized glass cast body having a beautiful appearance similar to that at the beginning was obtained.

Example 3 A mold release material slurry was prepared in the same manner as in Example 2 except that the same weight of boron nitride powder was added in place of the calcium metaphosphate of the mold release material slurry of Example 2 to make the total amount of boron nitride 28 parts by weight. Was produced.

The mold release agent slurry is applied to the inside of the mold 7
After firing at 00 ° C for 1 hour, 67% by weight of P ₂ O ₅ melted at 1100 ° C, 16% by weight of CaO, 10% by weight of SrO, 4% by weight of Al ₂ O _{3 and 3} % of Ce ₂ O ₃ were melted. Glass blocks were made by pouring in wt% glass. After cooling, the glass could be easily removed from the mold and a clean glass block was obtained.

[0035]

EFFECTS OF THE INVENTION Since the mold release material slurry of the present invention is smooth and has good coatability, a mold release layer having a thin and uniform thickness can be formed on the mold surface. In addition, it is possible to control the drying speed, and it is possible to solve problems that occur during drying, such as the occurrence of cracks. When calcium phosphate-based crystallized glass is produced using a mold having a release layer formed of this mold release material slurry, a crystallized glass having a high dimensional accuracy and a smooth surface can be obtained as a dental material.

Claims (4)

[Claims] 1. Boron nitride 5 to 60% by weight, silica colloid 1 to 20% by weight, solvent soluble or uniformly dispersible resin 1 to 20% by weight, organic solvent 50 to 90% by weight.
Release agent slurry consisting of. 2. The mold release material slurry according to claim 1, wherein the organic solvent is a mixture of a highly volatile organic solvent and a low volatile organic solvent. 3. The mold release material slurry according to claim 1, which contains 2 to 30% by weight of calcium metaphosphate crystals or calcium phosphate crystals in which strontium is solid-dissolved. 4. The mold release material slurry according to any one of claims 1 to 3, which is used for producing a mold material used for manufacturing a calcium phosphate crystallized glass dental material.