JPH1175607A - Core for cultured pearl, and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a core for a cultured pearl, excellent in biocompatibility with a mother shell such as Pinctada martensii, capable of reducing mortality rate of the pearl mother shell, capable of providing a high quality pearl in good yield, having a specific gravity nearly same as that of a natural core, and capable of allowing an easy drilling processing by a high-speed steel or cemented carbide drill. SOLUTION: The objective ceramic solidified substance has 2.65-2.85 specific gravity and a porous ceramic sintered body before impregnating and solidifying a resin, preferably of calcium phosphate-based porous sintered body has 2.5-2.7 specific gravity. The ceramic solidified substance is obtained by compacting a ceramic raw material powder, preferably the raw material powder consisting essentially of calcium phosphate-based compound into a spherical compact, firing the compact to provide the porous ceramic sintered body, which is a calcined body, impregnating the calcined body with a liquid synthetic resin and hardening the calcined body impregnated with the resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cultured pearl nucleus made of a solidified ceramic material impregnated with a resin and a method for producing the same.

[0002]

2. Description of the Related Art Cultured pearls are produced by inserting a nucleus into a mother oyster such as a pearl oyster and then raising the mother mussel for a certain period of time to form a nacre on the surface of the nucleus. As nuclei for cultured pearls, cut and polished thick shells such as sea shells are used to make small spheres with a diameter of several mm to several tens of mm, and are generally called natural nuclei. I have. The natural nucleus is composed of calcium carbonate (aragonite crystals), and is white and semi-translucent. However, the price of natural nuclei has risen due to an increase in the use of natural nuclei and a decrease in mussels due to overfishing, which is putting pressure on the business conditions of cultured pearl companies. In addition, overfishing of mussels and the like causes destruction of natural ecosystems and a kind of global environmental destruction.

[0003] The characteristics required for the pearl nucleus are as follows. (1) It has excellent histocompatibility with pearl oysters, such as pearl oysters, which affect the yield such as mortality, enucleation, and yield of non-pearl mussels. (2) The surface is smooth and It must be white and translucent (this is not the case when the culture period is lengthened and a thick nacre is formed on the nucleus surface. However, when the culture period is short and the nacre is thin, the pearl nucleus is white. The degree and translucency greatly affect the quality of the pearl, such as the luster.), (3) The ability to be easily drilled with high-speed steel or carbide drills (an essential property for producing pearl necklaces). (4) Specific gravity is between about 2.65 and 2.85 (the specific gravity of natural nuclei is in this range, and pearl brokerage is conducted by weight.)

[0004] Against this background, various artificial pearl nuclei have been proposed. An artificial nucleus made of calcium carbonate is conceivable in terms of the same material as the natural nucleus, but it is extremely difficult to sinter calcium carbonate (calcite crystal) at normal pressure, and sinter under high pressure using a hot press or the like. And there is a problem in terms of cost. For sintering under normal pressure, it is possible to form a sintered body at a temperature lower than the decomposition temperature of calcium carbonate by uniformly dispersing lithium fluoride as a sintering aid. However, during pearl culture, lithium remaining in the calcium carbonate grain boundaries dissolves, and thus has a problem in histocompatibility with the mother mussel. Also, an artificial nucleus composed of a synthetic resin with calcium carbonate (calcite crystal) has been proposed. However, the specific gravity of calcium carbonate (calcite crystal) is 2.71, and the specific gravity of the synthetic resin is about 1. Therefore, there is a problem in the specific gravity of the manufactured artificial nucleus depending on the mixing ratio. A solidified body composed of aragonite crystals of the same material as natural pearl nuclei can be produced by a hydrothermal hot pressing method, but since the equipment is expensive and the reaction time is long, artificial nuclei can be produced at low cost. It cannot be manufactured.

On the other hand, artificial nuclei for cultured pearls have been proposed which use calcium phosphate compounds such as hydroxyapatite (HAP) and β-type tribasic calcium phosphate (β-TCP), which have attracted attention as biocompatible materials, as main raw materials. ,
It has been reported that these artificial nuclei have excellent affinity with pearl oysters and the like. However, although artificial nuclei containing calcium phosphate compounds as the main component are dense sintered compacts, there is no problem in terms of the specific gravity of the artificial nuclei, but in terms of hardness and brittleness, conventional high-speed steel or superhard drills are used. Drilling is not possible, as is the case with nuclei. The artificial nucleus made of a mixture with a synthetic resin has no problem in drilling, but has a smaller specific gravity than a natural nucleus. That is, it is because the Vol% of the synthetic resin in the mixture is 40 or more, and therefore, zirconia (specific gravity 6.06) is used for specific gravity adjustment.
Is added in a large amount, so that the mixing amount of the calcium phosphate compound is reduced. As described above, various artificial nuclei for cultured pearls have been proposed so far, but their properties are advantageous and disadvantageous, and none are actually used by pearl farmers.

[0006]

The present invention has excellent biocompatibility with mother mussels such as pearl oysters, has a low mortality of mother pearls, can produce high quality pearls with good yield, and has the same specific gravity as natural nuclei. It is an object of the present invention to provide a cultured pearl nucleus having a high-speed or superhard drill that can be easily drilled.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a cultured pearl comprising a ceramic sintered body obtained by impregnating and solidifying a porous ceramic sintered body, preferably a calcium phosphate based porous sintered body with a resin. The nucleus is a gist.
In the present invention, the porous ceramic sintered body before the resin is impregnated and solidified, preferably a calcium phosphate based porous sintered body has a specific gravity of 2.5 to 2.7, and the target ceramic based solidified body is It has a specific gravity of 2.65 to 2.85. The present invention provides a culture comprising a calcium phosphate-based solidified material having a specific gravity of 2.65 to 2.85 obtained by impregnating and solidifying a resin into a calcium phosphate-based porous sintered body having a specific gravity of 2.5 to 2.7. The gist is a pearl core.

The present invention provides an invention of the above-mentioned method for producing cultured pearl nuclei, that is, a ceramic raw material powder, preferably a raw material powder containing a calcium phosphate compound as a main component, is formed into a spherical molded body, which is calcined and temporarily molded. The gist of the present invention is a method for producing a cultured pearl nucleus, which comprises preparing a sintered ceramic sintered body, impregnating the calcined body with a liquid synthetic resin, and curing the sintered body to obtain a ceramic-based solidified body. .
It is formed into a spherical molded body having a diameter that is 1 to 3 mm larger than the diameter of the final product. It is fired at a temperature lower than the firing temperature at which a dense sintered body is obtained, and a calcined body having a theoretical density of 70 to 90% is produced. A ceramic solidified material having a specific gravity of 2.65 to 2.85 is used. More specifically, the present invention uses a raw material powder containing a calcium phosphate-based compound as a main component and forms a spherical molded body having a diameter that is 1 to 3 mm larger than the diameter of the final product to obtain a dense sintered body. The calcination is performed at a temperature lower than the calcination temperature to produce a calcined body having a theoretical density of 70 to 90%. In the present invention, the porous ceramic sintered body, preferably a calcium phosphate porous sintered body, which is a calcined body before impregnating and solidifying the resin, has a specific gravity of 2.5 to 2.7. The solidified material has a specific gravity of 2.6.
5 to 2.85.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A porous ceramic sintered body is made of synthesized hydroxyapatite [Ca ₁₀ (PO ₄ ) ₆ (O
H) ₂ , hereinafter also referred to as “HAP”. ] Or β-type tricalcium phosphate [Ca ₃ (PO ₄ ) ₂ ,
Hereinafter, it may be described as “β-TCP”. And the like, and a raw material powder mainly composed of a calcium phosphate-based compound is formed into a spherical molded body, and a porous ceramic sintered body having a specific gravity of 2.5 to 2.7, that is, a temporary sintered body is produced. Zirconia or the like having a large specific gravity is added to the raw material powder for the purpose of adjusting the specific gravity.

Various resins such as ABS resin, epoxy resin, polypropylene and melanin resin can be used as the synthetic resin impregnated in the porous ceramic sintered body. Used as a liquid synthetic resin. In the artificial nucleus to make,
In order to add more excellent translucency, a synthetic resin having a refractive index similar to that of the calcium phosphate compound used is desirable. This is because, in the case of a composite material such as the artificial nucleus according to the present invention, if the refractive index between the constituent materials is different, the light that has entered the boundary between the materials is scattered and does not pass, but if the refractive index is similar. By transmitting light.

The impregnated solidified ceramic material is manufactured so as to have a specific gravity of about 2.65 to 2.85 which is the same as the specific gravity of the natural core. The ceramic raw material powder is formed into a spherical molded body, which is fired to produce a temporary sintered body,
This temporary sintered body was impregnated with a liquid synthetic resin and hardened to form a ceramic solidified body, which could not be obtained with a conventionally proposed mixture of a powder mainly composed of a calcium phosphate compound and a synthetic resin. An artificial nucleus having a specific gravity can be manufactured.

Press molding, injection molding or extrusion / granulation molding is used as means for molding into a spherical molded body. As a molding raw material, a raw material powder containing the above-mentioned calcium phosphate compound as a main component, and a material to which an organic binder for molding is added as necessary are used. It is formed into a spherical molded body having a diameter that is 1 to 3 mm larger than the diameter of the final product.

The sintering of the spherical molded body is performed at a temperature lower than the sintering temperature at which a dense sintered body is obtained, and the theoretical density is 70 to 9
This is performed so that a 0% temporary sintered body is obtained. This pre-sintered body is impregnated with a liquid synthetic resin and cured to obtain a ceramic solidified body having a specific gravity of 2.65 to 2.85. Depressurized during the impregnation process depending on the type of resin. It is necessary to heat in addition to the pressurizing operation. After solidifying the resin, the surface is smoothed by polishing.

An outline of the method for producing a cultured pearl nucleus of the present invention will be described. Raw material powder containing a calcium phosphate compound such as hydroxyapatite (HAP) or β-TCP as a main component is subjected to press molding, injection molding or extrusion / granulation molding to reduce the diameter of the raw material by 1 to 3 times.
A spherical molded body having a diameter larger by mm is formed. This is fired at a temperature lower than the firing temperature at which a dense sintered body is obtained, and has a theoretical density of 70 to 90%, that is, a specific gravity of 2.5 to 2.
A porous sintered body of No. 7, ie, a temporary sintered body, is produced. After the liquid synthetic resin is impregnated under reduced pressure and pressure up to the center of the pores of the porous sintered body, the resin is cured to obtain a resin-impregnated calcium phosphate-based solid having a specific gravity of 2.65 to 2.85. Make it. However, the pressure is reduced during the impregnation process depending on the type of resin. It is necessary to heat in addition to the pressurizing operation. Next, the surface is smoothed by the polishing process, thereby forming an artificial nucleus of a pearl.

[0015]

According to the present invention, a porous sintered body is impregnated with a resin by an artificial nucleus having a specific gravity which cannot be obtained by a conventionally proposed mixture of a powder mainly composed of a calcium phosphate compound and a synthetic resin. Manufacturable. Also,
Even if zirconia or the like having a large specific gravity is added for the purpose of adjusting the specific gravity, the amount of the zirconia added is small and an artificial nucleus excellent in biocompatibility and having a high content of a calcium phosphate compound is obtained.

Further, the artificial nucleus according to the present invention can be easily drilled with a high-speed steel or a carbide drill. This is due to the fact that the hardness of the solidified body is reduced by the porosity, and the pores are filled by impregnation with the resin, thereby facilitating the discharge of chips in the drilling process. When drilling is performed with the porous sintered body, drilling is possible for the time being.However, since chips are clogged in the pores, and the drill is burned, it is necessary to drill for a long time with a single drill. Is impossible.

By using a synthetic resin having a refractive index similar to that of a calcium phosphate compound used as a synthetic resin to be impregnated into a porous sintered body, it is possible to produce an artificial nucleus with a more excellent light transmittance. it can.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to embodiments. The present invention is not limited by these examples.

Example 1 Calcium carbonate and dibasic calcium phosphate were weighed so that the Ca / P ratio was 1.66.
After adding water so as to have a mass of 45 mass%, the mixture was subjected to a ball mill for 24 hours to synthesize amorphous hydroxyapatite (HAP) by a mechanochemical reaction. This is dried, calcined at 800 ° C., and ground to obtain a HAP.
Powder. After adding 2 mass% of polyvinyl alcohol as a binder to the HAP powder to obtain granules having an average granule diameter of 70 μm, a substantially spherical compact having a diameter of about 9 mm was formed by a press molding method. This is heated in air at a firing temperature of 1050.
C. to obtain a porous HAP sintered body having a bulk specific gravity of 2.65. Next, an epoxy resin and a melanin resin are impregnated into almost all pores of the porous HAP sintered body by a reduced pressure and a pressure method, and then the resin is solidified and polished to have a diameter of 6.5.
The artificial nucleus had a spherical shape of mm. The specific gravity of the artificial nucleus impregnated with epoxy resin is 2.78, and the specific gravity of the artificial nucleus impregnated with melanin resin is 2.76, and any artificial nucleus can be easily drilled with a high-speed drill. Met.

Example 2 Calcium carbonate and dibasic calcium hydrogen phosphate were weighed so that the Ca / P ratio was 1.5, and the mixture was 35 to 4%.
After water was added so as to be 5 mass%, the mixture was applied to a ball mill for 24 hours to synthesize β-type tricalcium phosphate (β-TCP) by a mechanochemical reaction. This is dried, calcined at 800 ° C., and ground to obtain β-T
CP powder was obtained. 2 mass% of polyvinyl alcohol was added as a binder to 90 mass% of β-TCP powder and 10 mass% of zirconia powder, and the average granule diameter was 70 μm.
And then formed into a substantially spherical compact having a diameter of 9 mm by a press molding method. This is fired in air at 1150 ° C.
After impregnating almost all pores of a porous β-TCP sintered body having a bulk specific gravity of 2.65, the resin was solidified and polished to obtain a spherical artificial nucleus having a diameter of 6.5 mm. The specific gravity of the prototype artificial nucleus was 2.75, and it was possible to easily perform drilling with a high-speed drill.

Example 3 Pearl culture tests were carried out on three types of artificial nuclei produced in Examples 1 and 2 using pearl oysters as mother mussels. The number of artificial nuclei subjected to the test was 100, and two artificial nuclei were inserted into one mother mussel, so that the number of mother mussels was 50. The culture period from inoculation to testing is 226 days.
Table 1 shows the results. All of the artificial nuclei had good affinity with the mother mussel, and the growth of nacre at least as high as that of the natural nucleus was confirmed. In addition, the color tone varies depending on the type of calcium phosphate as a main raw material, and this is presumed to be mainly due to the difference in the color tone of the artificial nucleus.

[0022]

[Table 1]

[0023]

The present invention is excellent in tissue compatibility of pearl oysters, etc., has a smooth surface, exhibits a white color, has translucency, and can be easily drilled with a high-speed or superhard drill. A cultured pearl nucleus having a specific gravity in the same range can be produced at low cost without requiring special equipment.

Claims (9)

[Claims] 1. A cultured pearl nucleus comprising a ceramic solidified body obtained by impregnating and solidifying a resin into a porous ceramic sintered body. 2. A porous ceramic sintered body having a specific gravity of 2.5
2. The cultured pearl nucleus according to claim 1, wherein the nucleus is a pearl. 3. The cultured pearl nucleus according to claim 1 or 2, which is a ceramic solidified material having a specific gravity of 2.65 to 2.85. 4. The cultured pearl nucleus according to claim 1, wherein the porous ceramics sintered body is a calcium phosphate based porous sintered body. 5. A ceramic raw material powder is formed into a spherical compact, which is fired to produce a calcined porous ceramic sintered body, which is impregnated with a liquid synthetic resin and cured. A method for producing a cultured pearl nucleus, wherein the pearl is a ceramic-based solidified body. 6. The method for producing a cultured pearl nucleus according to claim 5, wherein the pearl is molded into a spherical molded body having a diameter 1 to 3 mm larger than the diameter of the final product. 7. A porous ceramic sintered body which is a calcined body having a theoretical density of 70 to 90% by firing at a temperature lower than a firing temperature at which a dense sintered body is obtained.
For producing cultured pearl nuclei. 8. The method for producing a cultured pearl nucleus according to claim 5, 6 or 7, which is a ceramic solidified body having a specific gravity of 2.65 to 2.85. 9. The method for producing cultured pearl nuclei according to claim 5, wherein a raw material powder containing a calcium phosphate compound as a main component is used as the ceramic raw material powder.