JP2905092B2 - Method for producing chitosan fine particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing fine chitosan.

[0002]

2. Description of the Related Art Chitosan obtained by deacetylating chitin has been attempted to be applied to various fields by utilizing its unique properties. For example, attempts have been made to use it as a wound dressing in the medical field, as a powder property improver in the cosmetic field, and as a thickener, dispersant or film-forming agent in the coating field. Particularly in the field of cosmetics, there is a strong demand for fine chitosan as a powder property improving agent for powder cosmetics and the like.

It is well known that chitosan dissolves in a dilute aqueous acid solution at room temperature. In addition, it is sparingly soluble in aqueous solutions of salicylic acid and phosphoric acid, etc.
It is also well known that chitosan does not precipitate and remains as a stable aqueous solution even when cooled. In order to isolate solid particulate chitosan from these aqueous solutions, expensive methods such as freeze-drying and spray drying are required, and it is not easy to obtain inexpensive particulate chitosan.

Further, Japanese Patent Application Laid-Open Nos. 58-57401, 60-215003, and 61-4033 are disclosed.
No. 7, JP-A-62-62827 and JP-A-Hei.
No. 140961 also disclose methods for producing chitosan microspheres, but these methods require expensive reagents or require complicated operations, and these methods also produce chitosan microparticles at low cost. Not suitable as a method.

[0005]

SUMMARY OF THE INVENTION The present inventors have studied variously to develop an inexpensive and simple method which can easily precipitate and isolate fine chitosan particles from a solution, which is different from the above-mentioned prior art which is expensive. As a result, the present inventors have found that chitosan dissolves in dilute sulfuric acid, which is one of the few dilute acids that do not dissolve chitosan under specific conditions, and that chitosan fine particles can be easily precipitated and isolated from this solution, and completed the present invention. I came to.

[0006]

According to the present invention, there is provided a method for producing chitosan fine particles, which comprises heating and dissolving chitosan in dilute sulfuric acid and cooling the resulting diluted aqueous sulfuric acid solution of chitosan to precipitate chitosan. Is provided.

[0007]

[Function] Chitosan is dissolved in diluted sulfuric acid by heating, and the resulting diluted aqueous sulfuric acid solution of heated chitosan is cooled to precipitate fine chitosan.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. The chitosan used in the present invention is a deacetylated product of chitin, which is a kind of natural polymer contained in crustaceans, shrimps, insects and other shells or mushrooms, and is 2-amino-2-deoxy-D-.
It is a basic polysaccharide having glucose as a constituent unit. Such a deacetylated chitin, chitosan, has already been industrially produced and various grades are available. Usually, the degree of deacetylation is about 70 to 80%. In the present invention, the degree of deacetylation is not particularly limited. The molecular weight of chitosan is not particularly limited. The optimum degree of deacetylation and molecular weight may be appropriately selected so as to satisfy the characteristics required for chitosan fine particles according to the application.

The dilute sulfuric acid used in the present invention has a concentration of 0.5 to 30 to dissolve chitosan without deteriorating chitosan.
In the range of weight%, the amount of sulfuric acid used is preferably 0.2 to 10 moles per mole of the amino group of chitosan. 0.2
If the molar ratio is less than twice, the chitosan is difficult to dissolve. If the molar ratio exceeds 10 times, the molecular weight is undesirably reduced by hydrolysis. Preferably it is 0.8 to 4 times mol.

In the present invention, in order to dissolve chitosan in dilute sulfuric acid, it is preferable to use dilute sulfuric acid at least at 50 ° C. Below 50 ° C., chitosan is difficult to dissolve. 90
If the temperature is higher than 0 ° C., it becomes undesirably colored brown.
Preferably it is 60-80 degreeC. In order to dissolve chitosan in diluted sulfuric acid, chitosan and diluted sulfuric acid heated to 50 ° C. or higher may be mixed, or chitosan and diluted sulfuric acid may be mixed, and then the mixture may be heated to 50 ° C. or higher. The concentration of chitosan is not particularly limited.
% By weight.

Thus, a dilute sulfuric acid aqueous solution of chitosan is obtained. By cooling this solution below 50 ° C.,
Fine particulate chitosan precipitates. Chitosan microparticles can be easily isolated by using a known separation method such as filtration and centrifugation. In the method of the present invention, chitosan dissolved in dilute sulfuric acid precipitates as chitosan or a sulfate salt of chitosan or a mixture thereof depending on the amount (concentration) of sulfuric acid used. Therefore, when it is inconvenient to use the chitosan fine particles in the form of a sulfate, the isolated fine particles can be neutralized with an aqueous solution of an alkali such as sodium hydroxide or ammonia to obtain the original chitosan.

[0012]

The present invention will be described in more detail with reference to the following examples. Unless otherwise specified, the percentages in the examples are on a weight basis. Example 1 A 5-liter separable flask was charged with chitosan (0.5
% Concentration, viscosity 1500 cps, degree of deacetylation 75%)
240 g and 3600 g of ion-exchanged water were added, and 290 g of 95% concentrated sulfuric acid was added with stirring. After completion of the addition, the contents of the flask were heated to 80 ° C., and the chitosan was dissolved, and a dilute sulfuric acid aqueous solution of chitosan was obtained. After holding for 1 hour as it was, the solution was filtered while hot with a glass filter to remove insoluble components, and when the filtrate was cooled to room temperature, chitosan was precipitated in fine particles.

After filtration, the filtration residue was peptized in 2.5 liters of ion-exchanged water and neutralized to pH 7 to 8 with 2% sodium hydroxide. Filtration and washing were repeated to wash and remove salts. The filtration residue was peptized with 5 liters of isopropyl alcohol to replace the alcohol, filtered, and dried at 50 ° C. for 10 hours. Fine particles of chitosan having an average particle diameter of 2 μm were obtained. When this product was roughly crushed and placed on the skin and stretched with a finger, the product spread very smoothly on the skin, and a good feel was obtained, which proved to be effective as a powder cosmetic.

Example 2 240 g of chitosan (1% concentration, viscosity 10 cps, degree of deacetylation 98%) was placed in a 5-liter separable flask.
And 3600 g of ion-exchanged water, and 150 g of 95% concentrated sulfuric acid was added with stirring. After the addition, heat the contents to 80
When the temperature was raised to ° C., chitosan was dissolved, and a dilute sulfuric acid aqueous solution of chitosan was obtained. After holding for 30 minutes as it was, the solution was filtered while hot with a glass filter to remove insoluble components, and the filtrate was cooled to room temperature, whereby chitosan was precipitated in fine particles. After neutralization in the same manner as in Example 1, washing with water and filtration were repeated to obtain 450 g of wet chitosan fine particles having an average particle size of 1 μm. This product was taken in the palm of the hand, thoroughly rubbed with both hands, and then rinsed with running water. As a result, not only the stains on the hands were removed but also the moist feeling on the hands was maintained.

[0015]

By carrying out the method of the present invention, fine particles of chitosan can be obtained by an inexpensive and extremely simple operation.
The chitosan fine particles obtained by the method of the present invention are useful as a powder improving agent for extending powder cosmetics on the skin and improving adhesion to the skin, and as a scrub component of scrub cosmetics. Furthermore, it is also useful as a food additive material that does not give a feeling of discomfort during chewing. In addition to these uses, it can be used for various uses such as agricultural water retention gels.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinya Tsuchida 1-7-6 Nihombashi Bakurocho, Chuo-ku, Tokyo Inside Dainichi Seika Kogyo Co., Ltd. (72) Inventor Takanori Yamanan 1-7 Nihonbashi Bakurocho, Chuo-ku, Tokyo No. 6 Inside Dainichi Seika Kogyo Co., Ltd. (72) Inventor Shojiro Horiguchi 1-7-6 Bakurocho, Nihonbashi, Chuo-ku, Tokyo Inside Dainichi Seika Kogyo Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) ) C08B 37/08

Claims (4)

(57) [Claims] 1. A method for producing chitosan fine particles, comprising dissolving chitosan in diluted sulfuric acid by heating and cooling the diluted aqueous solution of heated chitosan to precipitate chitosan. 2. The method for producing chitosan fine particles according to claim 1, wherein the chitosan is dissolved in dilute sulfuric acid at least at 50 ° C. 3. The method for producing chitosan fine particles according to claim 1, wherein the concentration of the dilute sulfuric acid is 0.5 to 30% by weight. 4. The amount of sulfuric acid is 0.1% of the amount of amino group of chitosan.
The method for producing fine chitosan particles according to claim 1, wherein the molar amount is 2 to 10 times.