JPH04265260A - Synthetic ivory - Google Patents

Abstract

PURPOSE:To provide a synthetic ivory similar to natural ivory in color tone, feel and grindability. CONSTITUTION:This artificial ivory contains 4 components consisting of hydroxyapatite powder having 30-70% porosity measured by a mercury injection method, powder of an acrylate polymer and/or powder of a methacrylate polymer, powder of an acrylate monomer and/or powder of a methacrylate monomer and a polymn. catalyst.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to artificial ivory, which contains hydroxyapatite, which is the main component of natural ivory, and is suitable for use as a material for seals, crafts, and the like.

0002

[Prior Art] Natural ivory has a hardness suitable for careful processing, and has a soft translucent milky color tone and calm texture, giving the viewer an impression of elegance and nobility, and has been used since ancient times. It has been used as a material for seals and crafts. However, the amount of natural ivory produced is limited, and in light of international public opinion, it is difficult to collect live ivory.
Since it is legally prohibited, it is expected that it will become increasingly difficult to obtain in the future.

Under the above circumstances, in recent years, synthetic resins or synthetic resins with aggregates such as calcium carbonate, silica, alumina, and aluminum hydroxide have been devised as imitations of ivory. However, imitations made of synthetic resin not only feel far different from natural ivory when held in the hand, but also have a very soft feel when being ground, making them very different from natural ivory. On the other hand, synthetic resin imitations made by adding aggregate have a texture similar to natural ivory, but due to the hardness of the aggregate itself, it requires a lot of effort during grinding and is prone to chipping. Its properties are very different from natural ivory, such as its tendency to develop.

[0004] In order to solve the drawbacks of these imitation products, artificial ivory containing hydroxyapatite, which is the main inorganic component of ivory, has been proposed. Although this resin has improved color tone and feel compared to the synthetic resins mentioned above, the hardness of the cured product is still low, and it takes a long time to cure.
It has disadvantages such as easy disintegration in water.

[0005]

[Problems to be Solved by the Invention] The present inventors discovered that hydroxyapatite, the main inorganic component of natural ivory, has a unique color and hardness. discovered that it is possible to achieve properties that are extremely close to natural ivory, and have completed the present invention.The purpose of this invention is to provide artificial ivory that has color tone, feel, and grinding characteristics that are extremely similar to natural ivory. There is a particular thing.

[0006]

[Means for Solving the Problems] That is, the present invention provides the following (A)
This is an artificial ivory made by mixing the four components (D) and hardening the mixture in a mold. (A) Porosity measured by mercury intrusion method is 30-7
0% hydroxyapatite powder (B) acrylic ester polymer powder and/or methacrylic ester polymer powder (C) acrylic ester monomer powder and/or methacrylic ester monomer Powder (D) Polymerization Catalyst The invention will be explained in more detail below.

[0007] In the present invention, hydroxyapatite is
It is the component that plays the most important role in creating the color tone, hardness, and texture unique to natural ivory. Various types of hydroxyapatite are currently known. For example, there are synthetic hydroxyapatites produced from calcium salts and phosphorus salts, natural hydroxyapatites derived from the bones of mammals and fish, and calcined natural hydroxyapatites. A wide variety of products are manufactured, ranging from porous to porous.

[0008] In the present invention, hydroxyapatite powder having a porosity of 30 to 70% as measured by mercury porosimetry is used. If too dense powder with a porosity of 30% or less is used, the resulting artificial ivory will become too hard and the hydroxyapatite portion will cause chipping. I can't get the feeling of grinding. In addition, if a porous powder with a porosity of 70% or more is used, the (meth)acrylic acid ester monomer will not penetrate into the pores of hydroxyapatite, and in addition, it will be difficult to make it viscous enough to cast into the mold. Only a small amount of hydroxyapatite can be mixed.

As the hydroxyapatite, either the above-mentioned synthetic or natural hydroxyapatite may be used, but natural hydroxyapatite is preferred from the viewpoint of ease of adjustment of porosity and cost.

[0010] Furthermore, in natural hydroxyapatite, residual organic matter causes coloration and a decrease in stability during mixing, so it is particularly preferable that the residual organic matter is less than 1%.
For example, naturally occurring hydroxyapatite purified by enzyme treatment etc. can be used at an enzyme concentration of 5% or more (preferably 15%).
Examples include those fired at 350° C. or higher in the above atmosphere.

Incidentally, the porosity of natural hydroxyapatite can be freely controlled by heat treatment.

[0012] The amount of hydroxyapatite powder added is 1
0 to 60% by weight is preferred. If the amount added is less than 10% by weight, the resulting artificial ivory will be too soft. On the other hand, 60% by weight
If it exceeds this, the mixture becomes pasty and viscous, making subsequent polymerization difficult.

[0013] In addition to hydroxyapatite, other inorganic powders can be added to the artificial ivory of the present invention for the purpose of finely adjusting the color tone, hardness, texture, etc. Examples of such inorganic powders include silica, alumina, aluminum hydroxide, and various glasses.

[0014] When producing the artificial ivory of the present invention, the acrylic ester polymer powder and methacrylic ester polymer powder used in the present invention are mixed with hydroxyapatite and hydroxyapatite by adjusting the viscosity at the stage of liquid mixture. Prevents settling of other inorganic powders. Furthermore, it is mixed for the purpose of reducing shrinkage during polymerization and improving the dimensional stability of the product.

As the acrylic ester polymer and methacrylic ester polymer, homopolymers or copolymers of acrylic esters and methacrylic esters, or mixtures thereof can be used. Those that swell or dissolve when mixed with acid ester monomers or methacrylate monomers and are integrated after polymerization are preferred. Among these, methacrylic acid methyl ester polymer, methacrylic acid methyl ester-methacrylic acid ethyl ester copolymer, methacrylic acid methyl ester-propyl methacrylate ester copolymer, or methacrylic acid methyl ester-butyl methacrylate ester copolymer, etc. is preferred.

The amount of the above polymer powder added is preferably 10 to 30% by weight. If the amount added is less than 10% by weight, the resulting artificial ivory will become brittle and chipping will occur during grinding. If the amount added exceeds 30% by weight, the viscosity during mixing becomes high and molding becomes difficult.

[0017] The acrylic ester monomer and methacrylic ester monomer used in the present invention have the important property that they can be cured and molded by a polymerization reaction in the presence of a specific catalyst and at a specific temperature. It does a great job.

The acrylic ester monomer and methacrylic ester monomer may be monofunctional monomers or polyfunctional monomers, or a mixture of both may be used.

As the monofunctional monomer, for example, methacrylic acid methyl ester, methacrylic acid ethyl ester, methacrylic acid propyl ester, acrylic acid ethyl ester, etc. can be used.

Examples of the polyfunctional monomer include ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, tetramethylolmethane trimethacrylate, and tetramethylolmethanetetra. Methacrylate, dipentaerythritol hexaacrylate, 2,2-bis(4-methacryloxyethoxyphenyl)propane, etc. can be used.

The above monomers may be used alone or in a mixture of two or more types, but when mixed with the above-mentioned acrylic ester polymer powder or methacrylic ester polymer powder, In order to cause rapid swelling or dissolution, it is preferable to use methacrylic acid methyl ester as at least one component. In addition, when polyfunctional monomers are used together,
The hardness of the obtained artificial ivory can be changed as appropriate.

The amount of the (meth)acrylic acid ester monomer added is preferably 25 to 60% by weight. Addition amount is 2
If it is less than 5% by weight, the viscosity during mixing will be high and molding will be difficult, and the resulting artificial ivory will be too hard. Furthermore, if the amount added exceeds 60% by weight, a grinding feel similar to natural ivory cannot be obtained.

The polymerization catalyst used in the present invention may be any ordinary catalyst for vinyl polymerization. For example, benzoyl peroxide,
Polymerization catalysts such as benzoyl-amine peroxide, N,N-dimethyl para-toluidine, etc. can be used. The amount of polymerization catalyst added is 0.1 to 5% by weight.

In the present invention, pigments, various stabilizers, etc. can be added in addition to the above-mentioned components. for example,
Pigments include Bengara, Prussian blue, titanium oxide, zinc white,
Examples of stabilizers include ultraviolet absorbers, inorganic powder dispersants, and viscosity modifiers.

[0025] The above-mentioned components are then mixed and hardened by a polymerization reaction to form the artificial ivory of the present invention. The mixing may be carried out by a commonly used mixing method such as a mortar, a homodisper, or a ball mill. Thereafter, this mixture is injected into a desired mold, maintained at a temperature preferably in the range of 30 to 110°C, and polymerized, or after injection, the mixture is poured into a mold for 30 minutes.
Artificial ivory can be manufactured by using a method such as pressure polymerization at a temperature range of 0 to 50°C.

[0026]

[Effect of the invention] According to the present invention, the color tone similar to natural ivory,
It is possible to provide artificial ivory that has a tactile feel and a grinding feel.

[0027]

[Examples] Examples 1 to 4, Comparative Examples 1 to 3 Natural hydroxyapatite (porosity 60%), aluminum hydroxide powder (average particle size 0.5 μm), acrylic ester polymer powder, methacrylic ester A polymer powder, an acrylic ester monomer, a methacrylic ester monomer, and a polymerization catalyst were weighed to have the weight composition shown in Table 1, and mixed in a mortar.

Here, the methacrylic acid ester polymer powder is polymethacrylic acid methyl ester, and the methacrylic acid ester monomer is methacrylic acid methyl ester and trimethylolpropane trimethacrylate in a weight ratio of 95:5. A mixture of benzoyl peroxide and N. N-dimethyl para-toluidine was used.

Next, this mixture was poured into a silicone mold having a diameter of 15 mm and a depth of 80 mm, and after degassing by vibration, the mixture was placed in water at 40° C. and polymerized under a pressure of 100 kg/cm 2 .

The moldability, color tone, feel, and grindability of the obtained cured product were evaluated based on the criteria shown below.

Evaluation of moldability: ×: The obtained mixture becomes paste-like and difficult to mold. ○: The obtained mixture becomes a slurry or syrup and can be easily molded into a mold.

[0032] Evaluation of hue and feel ×: Does not resemble natural ivory. △: Comparable to ivory imitations currently on the market. ○: Very similar to natural ivory.

Evaluation of grindability Results of printing attempted with a printing grinder: ×: Grinding is difficult because it is too hard or too soft than natural ivory. Δ: Slightly harder or softer than natural ivory, and has slightly different grindability from natural ivory. ◯: Grinding properties were approximately the same as natural ivory.

[0034]

[Table 1]

Examples 5 to 7, Comparative Examples 4 and 5 Cured bodies were prepared and evaluated in accordance with Example 1, except that the porosity of natural hydroxyapatite was successively changed by heat treatment at 700 to 1200°C. , the methacrylic ester polymer, and the methacrylic ester monomer were mixed in a ratio of 40:20:40.

[0036]

[Table 2]

From the above results, if the porosity of the hydroxyapatite powder is less than 30%, the grindability is poor;
It can be seen that when it exceeds 0%, moldability is poor.

Claims (1)

[Claims] Claim 1: Artificial ivory (A) obtained by mixing the following four components (A) to (D) and hardening the mixture in a mold, and having a porosity of 30 to 7 as measured by mercury intrusion method.
0% hydroxyapatite powder (B) acrylic ester polymer powder and/or methacrylic ester polymer powder (C) acrylic ester monomer powder and/or methacrylic ester monomer Powder (D) Polymerization catalyst