JP2549531B2 - Method for producing hydroxyapatite or tricalcium phosphate made from rice bran - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing hydroxyapatite or tricalcium phosphate using rice bran as a raw material.

Conventional technology and its problems The main component of minerals such as bones and teeth of vertebrates is a calcium phosphate-based inorganic substance, which is considered to be hydroxyapatite (hereinafter referred to as HAp). Therefore, in the fields of dentistry and medicine, research on HAp powders, granules, and sintered bodies as bone fillers, bone replacement materials, implant materials, etc. is being actively conducted, and those already in practical use. There is also. HAp is also used as a catalyst, temperature sensor, and packing material for high-performance chromatography.

As a method for producing HAp, a dry method, a wet method and a hydrothermal method are known, and the outline and problems of each are as follows.

(1) Dry method: In this method, phosphates such as CaHPO ₄ , Ca ₂ P ₂ O ₇ and CaC are used.
Combined with calcium salts such as O ₃ and Ca (OH) ₂ , 10
Solid-phase reaction is performed in air or steam atmosphere at a high temperature of 00 ° C or higher. According to this method, HAp of stoichiometric composition
However, since it is based on a solid-phase reaction, the reaction time is long and it is not practical.

(2) Wet method: In this method, an aqueous solution containing phosphoric acid ions (phosphoric acid, water-soluble ammonium phosphate salt, sodium salt, etc.) is dropped into an alkaline solution containing calcium ions (pH about 7 to 11) and reacted. . An example of the reaction is as follows (however, the coefficient is omitted).

Ca (NO ₃ ) ₂ + (NH ₄ ) ₂ HPO ₄ → Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ This method is suitable for mass production, but the product is fine particles (about 200 Å) , The product is difficult to filter.

(3) Hydrothermal method: In this method, the calcium phosphate salt is hydrolyzed with hot water in a high-pressure vessel. To give an example of that reaction,
It is as follows (however, the coefficient is omitted).

In this case, relatively large crystals are obtained. However, this method is not suitable for mass production and uses a high-pressure container, so that the production cost is high.

Therefore, at present, the wet method is mainly used in spite of the problem that filtration is difficult.

In any of the above methods (1) to (3), phosphoric acid or calcium phosphate derived from imported phosphate rock is used as the phosphorus raw material. In recent years, phosphate rock is
It is being depleted gradually, and its quality deterioration and quantitative shortage are problems. Therefore, the development of new phosphorus resources has been earnestly desired.

Means for Solving the Problems The present inventor has been thinking in view of the state of the art as described above. In the process, we focused on defatted rice bran, which currently produces about 500,000 tons per year in Japan. That is, rice bran contains about 9.5% to 14.5% phytin, and phytin contains about 19.5% phosphorus atoms. However, most of the rice bran is used as livestock feed, and part of it is only used as a raw material for phytin, phytic acid and its derivatives, which are useful as pharmaceuticals and chemicals. Therefore, if this defatted rice bran is effectively used, it should become a new phosphorus resource. As a result of further research based on such a new idea, the present inventors have finally completed the present invention. That is, the present invention provides the following method: "(a) a step of treating defatted rice bran with a dilute solution of an inorganic acid, filtering and washing to obtain a phytic acid solution, (b) The phytic acid solution is passed through a cation exchange resin to remove cations for purification. (C) A calcium salt is added to the purified phytic acid solution for reaction, and the purified precipitate is filtered, washed and dried. And (d) baking the obtained dried product at 900 to 1200 ° C., a method for producing hydroxyapatite or tricalcium phosphate made from rice bran. ”Starting in the present invention The defatted rice bran used as a raw material is
The rice bran is defatted according to a conventional method and obtained as a residue obtained by collecting edible oil and the like. Therefore, for degreasing,
Although not described in detail, it is usually obtained by adding an organic solvent such as hexane, benzene, toluene, xylene, and acetone to rice bran and stirring to extract oil. In this case, for example, when the rice bran is pulverized by a grinder or the like, not only the oil content but also the phytic acid described below is satisfactorily extracted.

Defatted rice bran is treated with a dilute solution of inorganic acid. As the inorganic acid, hydrochloric acid, nitric acid, sulfuric acid or the like is used, and the solution concentration thereof is usually about 0.01 to 0.05% by weight. The processing temperature is
Although not particularly limited, it is preferably about 15 to 80 ° C. Then, the treatment liquid is filtered and the filtrate is washed to obtain a phytin solution.

The phytin solution thus obtained contains Fe ³⁺ , Mg ²⁺ , N
Since cations such as a ⁺ and K ⁺ are contained as impurities, these cations are removed by passing through a cation exchanger.

Then, a solid or pasty calcium salt is added to the purified phytic acid solution and reacted at 15 to 100 ° C.
As the calcium salt, CaO, CaCO ₃ and Ca (OH) ₂ can be used alone or in combination. PH during reaction
Is 6.5 or more in the case of adding CaCO ₃ , CaO and / or C
In the case of a (OH) ₂ is 11.5 or more, when using a mixture of CaCO ₃ and Ca (OH) ₂ is preferably set to 7.0 or more. This reaction produces a white precipitate,
This is left as it is or left to stand for a while to be aged, then filtered, washed and dried. The drying temperature is not particularly limited, but it is advantageous to carry out in a heating state of usually about 40 to 80 ° C. When Ca (CH ₃ · COO) ₂ is used as the calcium salt, HAp is not formed in the subsequent steps. Also, when CaCl ₂ is used, a mixture of HAp and tricalcium phosphate (TCP) is formed.

Next, the obtained dried product is fired in the air at a temperature of about 900 to 1200 ° C. to obtain the desired HAp or TCP. Got
HAp or TCP varies depending on reaction conditions etc., but is usually 0.2-
The particles are spherical or approximately spherical in shape of about 0.5 μm.

When the obtained HAp contains excess CaO, it is treated with NH ₄ Cl solution to remove CaO, and the stoichiometric composition
You can get HAp. For example, during the production of HAp obtained when HAp containing excess CaO obtained by using a mixture of CaCO ₃ and Ca (OH) ₂ as a calcium salt was treated with a 1% NH ₄ Cl solution. Table 1 below shows the relationship between pH and Ca / P.

As is clear from the results shown in Table 1, HAp produced at a pH of about 5 to less than 7 has a theoretical Ca / P ratio of 1.67.
In the case of pH 7 or higher, a stoichiometric HAp is obtained, whereas the pH is less than calcium-deficient type. Further, under the condition of pH less than about 5, that is, when the ratio of Ca / P is remarkably low, the one mainly containing tricalcium phosphate is obtained.

In one embodiment of the invention, about 10% of the weight of rice bran is
HAp was obtained, and it was revealed that the phosphorus component in rice bran was completely utilized as the HAp component.

Furthermore, according to X-ray diffraction, the dried product before firing was composed of calcium phytate and β-Ca ₂ P ₂ O _7, but during the firing process, calcium phytate was decomposed and CaO and H ₂ O were decomposed.
, And these react with β-Ca ₂ P ₂ O ₇ to form TCP, and at 900 ° C or higher, TCP reacts with excess CaO and HAp
Was found.

According to the present invention, without using imported phosphate rock,
Phosphorus-containing materials such as HAp and TCP are obtained from defatted rice bran produced in large quantities in Japan. The recovery rate of phosphorus in rice bran is close to 100%.

Examples The following examples will be given to further clarify the features of the present invention.

Example 1 (1) Rice bran was crushed for 1 hour by a sand mill and then extracted with hexane. 0.01N HCl 30 was added to 10 g of the defatted rice bran obtained.
After adding 0 ml and treating at 60 ° C. for 1 hour under stirring to extract phytic acid, the mixture was cooled, filtered, and thoroughly washed with water.

(2) Then, the obtained aqueous phytic acid solution (ml) was dissolved in an ion exchange resin ("Amberlite IR-120B", USA,
Rohm and Haas) to remove cationic impurities.

(3) Heat the purified phytic acid aqueous solution to about 300 ml.
Concentrate until it becomes, and add CaCO ₃ 0.7g and Ca (OH) ₂ 0.3g to it.
And the mixture was stirred at 60 ° C. for 1 hour. The pH of the solution after stirring was 8.30. The precipitate formed was filtered, washed and then dried in a dryer at 60 ° C. for 12 hours.

(4) Next, the obtained dried product was calcined in an electric furnace at 1000 ° C. for 1 hour, and the calcined product was treated in 100 ml of 1% NH ₄ Cl at 60 ° C. for 1 hour to remove excess CaO, and then filtered. Then wash and wash 100 more
It was dried at ℃ for 3 hours to obtain 1.0 g of HAp.

The obtained HAp was a particle having a particle size of about 0.25 μm and having a substantially spherical shape.

Example 2 After the steps (1) and (2) were carried out in the same manner as in Example 1, the purified phytic acid aqueous solution was heated to about 300 m.
The mixture was concentrated to 1 l, 0.25 g of CaCO ₃ was added, and the mixture was stirred at 60 ° C for 1 hour. The pH of the solution after stirring was 4.0.
The precipitate formed is filtered, washed and dried in a dryer at 60 ° C for 12 hours.
Dried for hours.

Next, the obtained dried product was baked in an electric furnace at 900 ° C. for 1 hour to obtain 0.73 g of TCP.

Claims (1)

(57) [Claims] 1. A step of: (a) treating defatted rice bran with a dilute solution of an inorganic acid, filtering and washing to obtain a phytic acid solution; (b) passing the obtained phytic acid solution through a cation exchange resin. A step of purifying by removing cations, (c) a step of adding a calcium salt to a purified phytic acid solution to cause a reaction, filtering the formed precipitate, washing, and drying, (d) obtaining the dried product. A method for producing hydroxyapatite or tricalcium phosphate made from rice bran, which comprises a step of firing at 900 to 1200 ° C.