JP2859723B2 - Method for producing artificial pearl nucleus - Google Patents

Description

The present invention relates to a method for producing an artificial pearl nucleus used for producing cultured pearls and artificial pearls.

[Conventional technology]

Cultured pearls are produced by inserting nuclei into mother oysters such as pearl oysters and cultivating them to form a nacre around the nuclei. For this purpose, nuclei conventionally existed in the Mississippi River in the United States. Natural shells, typically scallops, are cut into dice and then finished into spheres.

However, in this method, since the thickness of the shell is not constant, it is difficult to obtain one having a uniform particle size, and it is difficult to obtain a product having a diameter of 7 mm or more, which has a high product value. Furthermore, in order to obtain good quality pearls,
It is necessary to have a clear, white and glossy sphere, but many shells have a streaky colored layer, and together with the shape problem, the processing yield from the shell is low. There was a problem of low. Furthermore, recently, the depletion of natural resources has raised concerns about the availability of shells suitable for pearl nuclei, and there has been a demand for superior artificial pearl nuclei that are easy to manufacture and can be stably obtained.

Under such circumstances, various methods for producing artificial nuclei for pearls using various organic and inorganic materials, resins, and the like have been proposed.

For example, JP-A-48-52594 discloses powders of light calcium carbonate obtained by a chemical treatment or heavy calcium carbonate obtained by a physical pulverization treatment.
10 parts of a water-resistant adhesive or a water-resistant synthetic resin are added to each part and mixed to form flakes or pastes, and then granulated to produce smooth pearl cores having a diameter of 10 mm or less by granulation. The method described in JP-A-63-219325 discloses a molded product comprising calcium carbonate, a synthetic resin, and a pigment, wherein the linear expansion coefficient of the molded product is 0.5 × 10 ^{−5 to} 2.0 × 10 ^−5. / ℃
A method for culturing pearls using artificial nuclei, such as those described in the above, is disclosed. Furthermore, Japanese Patent Publication No. 2-12537 proposes a pearl core material made of free-cutting crystallized glass having a Knoop hardness of 250 to 50.

By the way, the following characteristics are required as the material of the core for cultured pearls. 1) Bulk density is close to that of pearls
It should be around 2.75 g / cm ³ . If this value deviates significantly,
During breeding, the rate of mother shellfish spitting out nuclei and uneven formation of nacre around the nuclei increases. 2) It must be plain white. Pearl shine is the result of light reflection, refraction and interference. It is said that the minimum thickness of the nacre in order not to be affected by the nucleus is 0.3 mm, but if a colored nucleus is used, it is necessary to make this nacre even thicker, which increases the time required for aquaculture. I will. 3) The organization is dense. The surface roughness of the nucleus made from shellfish is Ra
Is 0.02 μm or less. For materials with a porous structure,
The surface roughness of the pearl nucleus increases, making it difficult to obtain pearls with good spheres and bright pearls. 4) The hardness is appropriate. The Mohs hardness of the pearl is 3-4, and the hardness of the shell of the shell is almost the same, 3-4. Pearls are drilled or molded and used in the form of necklaces, earrings, rings and the like. The shells of shells and the structure of nacre have a structure in which hexagonal plate-like calcium carbonate crystals of several μm are stacked in a mosaic pattern by proteins. Therefore, the shear energy applied to the tip of the tool is absorbed by the protein layer, and the processing can be easily performed in combination with the low Mohs hardness.
Therefore, if the hardness of the material is too high, the processing cost at the time of manufacturing the core is increased, and it is difficult to process the obtained pearl, which is not preferable. 5) Thermal expansion coefficient is 5 × 10 ^-6 to 15
× 10 ⁻⁶ / ° C. The shells and nacres of the shells have almost the same structure, and the coefficients of thermal expansion are approximately 10 × 10 ^{-6 to} 11 × 10 ^-6 / ° C. If the core and nacre have different coefficients of thermal expansion, the temperature changes during a long period of use may cause distortion and cause cracking or peeling, which may reduce the commercial value.
6) No harmful components are eluted by seawater. Elution of harmful components during aquaculture may inhibit the growth of the shellfish or even kill it.

[Problems to be solved by the invention]

It is considered that a material that satisfies the above characteristics can be sufficiently used as a cultured pearl core. However, any of the conventionally proposed materials has advantages and disadvantages, and few are satisfactory in all aspects. For example, metals and resins are unsuitable in terms of bulk density and coefficient of thermal expansion,
Glass, ceramic, alumina, and zirconia ceramic balls have problems in bulk density, hardness, workability, and the like. In addition, white limestone, marble, coral, etc. are expected from the similarity of tissues, but limestone has problems in workability, marble is colored, and coral is problematic in terms of resource protection. The one hardened with an adhesive has a very similar property, but generally, when immersed in seawater for a long time, many resins elute components harmful to the growth of the mother shellfish, which is not preferable. Among the above prior arts, glass ceramics in which mica crystals are precipitated in molten glass, which is listed as a free-cutting crystallized glass, have fairly good properties, but have a bulk density of 2.5 to 2.6. At g / cm ³ , it is slightly smaller than the bulk density of pearls. Furthermore, since this material is heat-treated in a molten state at a high temperature to precipitate crystals, it can be produced only in a large shape and is usually commercially available as a large columnar or plate-like material. Therefore, in order to obtain a small spherical pearl nucleus, it is necessary to process a plate-like material into a dice shape and finish it into a spherical shape by three to four stages of polishing, resulting in high processing cost and material loss. There is a major drawback of many.

An object of the present invention is to solve such a problem and to create an artificial pearl nucleus that satisfies the characteristics required for a cultured pearl nucleus and that can be manufactured at a low cost by a simple process.

[Means for solving the problem]

The present inventors have studied various materials as a core material for pearls, and found that the fluorphlogopite mica glass ceramics produced by a specific method was subjected to HIP (Hot Isostatic Pressing) treatment to obtain extremely good properties. The present inventors have found that a pearl core material having the following formula is obtained, and arrived at the present invention.

In the present invention, SiO ₂ is 40 to 50% by weight in terms of oxide,
Al ₂ O ₃ is 10 to 20%, MgO is 10~20%, K ₂ O is 5~15%, B ₂ O
₃ is 0 to 15% and F is 5 to 15%.
The raw material powder mixture containing the compounds of i, Al, Mg, K, B and F is subjected to heat treatment at a maximum temperature of 1000 to 1100 ° C. to precipitate crystals of fluorophlogopite, and the obtained heat-treated product is averaged. After pulverizing so that the particle diameter becomes 5 μm or less, the one molded into a desired shape is sintered at 1100 to 1300 ° C., and the obtained sintered body is HIPed and then polished to obtain an artificial pearl nucleus. This is a method for producing an artificial pearl nucleus.

The raw material powder mixture used here must have good sintering properties capable of producing a fluorophlogopite-containing glass ceramic without melting in a glassy state. Raw material powder mixtures satisfying such requirements include alkoxide compounds of various metal components (Si, Al, Mg, K) (some of these alkoxide compounds can be replaced with other metal compounds soluble in polar solvents). Water) to a mixed solution of fluorinated compounds and water, hydrolyzed, dehydrated and dried, and crushed to about 100 μm or less, or containing kaolin and activated clay as main raw materials, and containing Mg, K, and F-containing compounds. As an auxiliary material, B ₂ O ₃ is further added as a sintering aid, and a raw material powder mixture of about 10 μm or less prepared so that the component composition at the time of forming a sintered body falls within the above range is preferably used. it can.

In the production method of the present invention, first, the raw material mixture, the maximum temperature is heat-treated under a temperature condition of 1000 ~ 1100 ° C. 30 ~
60% by weight of crystals of fluorophlogopite are precipitated. In this heat treatment step, after the volatile components are volatilized, a solid phase reaction occurs at the grain boundaries of each particle, and fine particles of fluorophlogopite crystals are precipitated. If the maximum temperature during this heat treatment is less than 1000 ° C., the amount of crystals generated is not sufficient, and the shrinkage in the subsequent firing step is increased, resulting in poor machinability. Also the maximum temperature
If the temperature exceeds 1100 ° C., sintering proceeds too much and the pulverizability of the heat-treated product deteriorates, and the crystal growth of fluorophlogopite becomes too advanced, which makes uniform dispersion of the crystals difficult.

Next, the obtained heat-treated product is pulverized so that the average particle diameter becomes 5 μm or less, and is shaped into a sphere close to the shape of the target pearl core. When a pearl nucleus having a special shape such as a polygon is desired, it is needless to say that the pearl nucleus may be formed into an arbitrary shape close thereto. In the present invention, since the sintering has partially progressed in the heat treatment step, the shape can be made close to the shape of the product at this stage. The molding method is not particularly limited. However, in order to obtain a dense sintered body without pores, a molding method capable of uniform filling such as CIP (rubber press) is desirable. If the average particle size exceeds 5 μm, it is not preferable because a dense sintered body cannot be obtained. In the molding process, if necessary, a small amount of binder,
A molding aid such as a dispersant and a release agent may be added.

The obtained molded body was placed in a box, heated at 1100 to 1300 ° C. for about 3 to 12 hours, and sintered, whereby fine crystals of fluorophlogopite were entangled with each other, and the gap was filled with a vitreous matrix. Fluorphlogopite mica glass ceramics are obtained. The fluorophlogopite mica glass-ceramics can obtain different crystal sizes and ratios depending on the ratio of raw materials to be used, reaction conditions, and the like. It is preferable that crystals having a size of 3 to 15 μm in an amount corresponding to 6060% by weight are uniformly dispersed. If the size or amount of the fluorophlogopite crystal is out of this range, the machinability of the obtained product is deteriorated, which is not preferable.

The sintered body thus obtained has a bulk density of 2.5 to 2.6 g /
Although it is a white sphere of cm ^3, the density and surface gloss are slightly insufficient for pearl nuclei. Therefore, in the production method of the present invention, the sintered body is further subjected to a pressure of 500 to 1500 kg /
HIP treatment is performed under the conditions of cm ² and a temperature of 900 to 1100 ° C. This increases the density and significantly improves the surface gloss. The HIP treated product is polished, such as by tumbling using abrasives such as cerium or silicon carbide used for glass polishing, so that the bulk density is 2.65 to 2.75 g / cm ³ and the surface is translucent. It is possible to obtain an artificial pearl nucleus having a characteristic very close to a natural white pearl nucleus with gloss. This artificial pearl nucleus has a Mohs hardness of 3-4 and a coefficient of thermal expansion of 5 × 10
^-6 to 15 × 10 ^-6 / ° C, with good machinability, and does not require high-performance cutting and polishing equipment like ordinary ceramics processing. In addition, it is possible to perform sufficient processing using tools and tools, and it is also easy to perform processing such as drilling of the obtained pearl.

This glass ceramics can be formed to any size by molding,
Shapes can be made. Therefore, it is possible to stably produce large cores having a high commercial value, such as a diameter of 7 to 10 mm, which are difficult to obtain from conventional shells and having a uniform grain shape. Also, since a sintered body having a shape close to a product can be obtained, there is almost no loss of material, and the material cost is minimized. Further, generally, fluorophlogopite glass ceramics have an affinity for living organisms, as can be seen from studies on the application to artificial bones and artificial dental roots, and the material obtained according to the present invention also has strong adhesion with nacre. Thus, it does not crack or peel off during processing or during long-term use, and is also suitable as a material for cultured pearl nuclei from this point.

The artificial pearl nucleus produced by the production method of the present invention can be produced as a pearl for cultured pearls, because it is possible to produce pearls of good quality with good yield by inserting and culturing the pearl nucleus in mother oysters such as pearl oysters. Although it is excellent, it can be suitably used also as a core for artificial pearls produced by applying several layers of paint that forms a pearl-like layer around the core.

In addition, this artificial pearl nucleus has a beautiful glossy white color and is suitable for producing a so-called pearl-colored pearl, but pearls of any color are produced by coloring with a pigment or the like. You can also.

〔Example〕

Example 1 As a starting material, silicon tetraethoxide (Si (OC
₂ H _{5) 4)} 163g, magnesium methoxide _{(Mg (OCH 3) 2)} 36
g, potassium methoxide (KOCH ₃ ) 16 g, 3-aminobenzotrifluoride (NH ₂ C ₆ H ₄ CF ₃ ) 25 g, methanol 1200 g
Dissolved in aluminum isopropoxide (Al (iso-OC ₃
H ₇ ) ₃ ) A solution prepared by dissolving 64 g in 300 g of benzene was added and mixed. Then, 204 g of water adjusted to pH 11 was added dropwise and hydrolyzed. When the solution is completely white gelled, remove
It was dried at ℃ to obtain 130 g of a dried product. 100μ of this dried body
After crushing to less than 400 m
Heat treatment was performed at 4 ° C. for 4 hours to obtain 103 g of a heat-treated product. This is pulverized to 5 μm or less, granulated, and packed in a rubber mold.
CIP molding was performed under a pressure of 00 kg / cm ² to form a sphere-shaped body having a diameter of 8.0 mm, and the body was further sintered at 1250 ° C. for 4 hours. This sintered body contains 47.0% of SiO ₂ , 16% of Al ₂ O ₃ , MgO
Had a component composition of 17%, K ₂ O of 11.0%, and F of 9.0%, had a bulk density of 2.62 g / cm ³ , and had an opaque white surface. This sintered body is pressured at 1000kg / cm ² at 1000 ℃ for 2 hours
As a result of the HIP treatment, the bulk density became 2.73 g / cm ³ , and the surface became glossy translucent white. This HIP processed product is 1
Polishing was performed using a 000 mesh cerium powder as a polishing material using a plate-type rolling polisher to obtain an artificial pearl nucleus having a diameter of 7.0 mm.

Example 2 830 g of kaolin, 466 g of activated clay, 326 g of MgO, K ₂ SiF ₆ 234
g, 138 g of KF and 40 g of B ₂ O ₃ are mixed and pulverized, and the average particle size is 5 μm.
After drying with a spray dryer, the mixture was heated in an electric furnace and heat-treated at 380 to 420 ° C for 4 hours, 730 to 770 ° C for 6 hours, and further at 1060 to 1090 ° C for 3 hours. This heat-treated product
After adding 1.0% by weight of PVA-based binder and water, pulverizing to an average particle diameter of 5 μm or less by wet pulverization, granulating, filling in a rubber mold, and CIP molding under a pressure of 2000 kg / cm ² to form a 8.0 mm diameter.
And sintered at 1250 ° C. for 4 hours. This sintered body contains 45.7% of SiO _{2 in} terms of oxide and Al
₂ O ₃ is 16.1%, MgO is 16.7%, K ₂ O is 10.9%, F has a 8.5% and B ₂ O ₃ 2.0% of the component composition, a volume density of 2.55 g / cm ³ surface opaque Had a very white color. 1000 kg of this sintered body
HIP treatment at 1000 ° C. for 2 hours at a pressure of / cm ² resulted in a bulk density of 2.70 g / cm ³ and a glossy translucent white surface. This HIP treated product is polished using a 1000-mesh cerium powder as an abrasive using a flat-plate type rolling polisher,
An artificial pearl nucleus with a diameter of 7.0 mm was obtained.

When the artificial pearl nuclei of Examples 1 and 2 were nucleated and cultured in pearl oysters, it was confirmed that a nacre was generated as inferior to a natural pearl nucleus.

〔The invention's effect〕

According to the production method of the present invention, without using shells such as shellfish, which is a natural resource, it is possible to form a core of any size and shape that is difficult to obtain with shellfish, and uniform particle size.
The bulk density is 2.65 to 2.75 g / cm ^3, which is close to that of a pearl, and a white artificial pearl nucleus having a translucent luster can be efficiently produced. This method differs from the glass melting method, which is a method for producing ordinary glass ceramics, in that the raw material can be molded into a shape very close to the pearl nucleus of the final product and sintered, so that there is almost no loss of material, and this point This is a very industrially advantageous method.

The artificial pearl nucleus obtained by the production method of the present invention has all of the properties required for a cultured pearl nucleus, and is exhaled from a shellfish or a pearl of good quality without killing the shellfish. Can be produced with good yield.

The pearl obtained by using the artificial pearl nucleus of the present invention has a uniform nacre, and has high commercial value with beautiful brightness and color tone.

Claims (1)

(57) [Claims] 1. An oxide-based weight ratio of SiO ₂ of 40 to 50%,
Al ₂ O ₃ is 10 to 20%, MgO is 10~20%, K ₂ O is 5~15%, B ₂ O
₃ is 0 to 15% and F is 5 to 15%.
The raw material powder mixture containing the compounds of i, Al, Mg, K, B and F is subjected to heat treatment at a maximum temperature of 1000 to 1100 ° C. to precipitate crystals of fluorophlogopite, and the obtained heat-treated product is averaged. After pulverizing so that the particle diameter becomes 5 μm or less, the one molded into a desired shape is sintered at 1100 to 1300 ° C., and the obtained sintered body is HIPed and then polished to obtain an artificial pearl nucleus. A method for producing an artificial pearl nucleus.