JPS6040224A - Manufacture of formed article of chitosan - Google Patents

Abstract

PURPOSE:To prepare efficiently formed articles of chitosan being excellent in the strength and elasticity modulus without using an intricate solidifying medium, by extruding an aqueous chitosan solution concentrated high than a specified value, under pressure. CONSTITUTION:An aqueous solution of high concentration, which is prepared by dissolving chitosan of 10wt% or more in a dilute-acid water solution of acetic acid, hydrochloric acid, sulfamine acid or the like, is extruded to be formed under pressure through a spinning nozzle or any other forming nozzle. The forming pressure applied on the occasion is about 10-500kg/cm<2>. By extruding the aqueous chitosan solution of high concentration under said pressure, chitosan molecules are orientated in a high degree in the extrusion, and as the result, formed articles having remarkable strength, such as threads, for instance, are formed without using any solidifying medium and even just after the forming. In addition, the strength and the elasticity modulus of the extruded threads can be improved sharply by stretching the threads to be about 2-10 times longer just after the extrusion or thereafter.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for efficiently producing threads, films and other molded articles with excellent physical properties from chitosan.

Conventionally, much research has been conducted on the effective use of chitosan, which is a hydrolysis product of chitin, and several methods for obtaining chitosan molded products such as chitosan threads and chitosan films are known.

For example, for chitosan thread, the method is to prepare an aqueous solution of chitosan and then spin it.However, in the conventional spinning method, chitosan is a low-molecular-weight product and exhibits high viscosity even at low concentrations, so its use limit concentration is is about 8 weight φ, and it is impossible to obtain chitosan thread using a chitosan aqueous solution with a higher concentration than this, and chitosan with a high molecule J) has an even higher viscosity. The limit concentration for use has been lowered.Therefore, since conventional chitosan yarns are usually spun using a spinning stock solution with a low concentration of 3 to 8% by weight, most of the yarns immediately after coming out of the spinning nozzle are It lacked strength, and the shape of the yarn could not be maintained unless it was immediately introduced into a coagulation bath and coagulated.Furthermore, even with wet spinning in this way, the spinning efficiency was low due to the low concentration of the spinning stock solution. Another problem was that it was not possible to obtain a yarn with practical strength and Young's modulus.

The inventor of the present invention has conducted extensive research to solve the problems of the prior art as described above, and has found a 10-fold solution! By using an aqueous solution of chitosan with a concentration of at least 10% as a spinning stock solution and extruding it from a molding nozzle under pressure, the drawbacks of the conventional technology described above can be fully solved, and chitosan threads or chitosan molded products with excellent physical properties can be obtained. The present invention was completed based on the knowledge that

That is, the present invention is a method for producing a chitosan molded article, which is characterized by preparing an aqueous chitosan solution containing 10% by weight or more of chitosan, and extruding the aqueous solution under pressure.

To explain the present invention in detail, the chitosan used in the present invention is obtained by alkaline hydrolysis of chitin, a natural polymer present in the outer shells of shrimp, crabs, insects, and other crustaceans. It is a basic polysaccharide whose constituent position is 2-amino-2-deoxy-D-glucose.
, such chitosan itself has already been produced industrially and is available on the market. Such chitosan can be dissolved in, for example, dilute acetic acid, but even if it is a low molecular weight chitosan, if the concentration exceeds about 80%, the solution becomes extremely viscous, making it difficult to use conventional chitosan spinning. Highly concentrated solutions of more than about 8% by weight have never been used in the art. In the present invention, a highly concentrated solution is prepared by dissolving such chitosan in an aqueous solution of acetic acid, hydrochloric acid, sulfamic acid, or other dilute acid to a concentration of 10% by weight to 801% by weight, preferably about 15% by weight to 40% by weight. One special feature is the use of . In the present invention, when preparing such an aqueous chitosan solution, a volatile organic solvent that is compatible with water, such as methanol, ethanol, impropatol, acetone, etc., is added to the dilute acid aqueous solution per 100 parts by weight of water. It can be added in a proportion of 0 to 100 parts by weight to simultaneously accelerate drying during subsequent molding. In addition, various additives such as enzymes, yeast, other useful beef extracts, various medicines, coloring agents, fragrances, etc. can also be added to the chitosan aqueous solution depending on the heart wall.

The method for producing a molded article of the present invention also involves extruding the above-described high-concentration chitosan aqueous solution under pressure through a spinning nozzle or other molding nozzle. The molding pressure at this time is 10 to 500 to 9/' crA, preferably 20 to 50 Kt/crl. According to the inventor's detailed research, by extruding a highly concentrated chitosan aqueous solution under such pressure, chitosan molecules become highly oriented during extrusion, and as a result, even without using a coagulation bath, It has also been found that a molded product, such as a thread, having a certain strength can be formed even immediately after molding.

Therefore, in the method of the present invention, there is no need to use a coagulation bath with a complicated composition or strong chemicals as in the prior art. The desired molded product can be obtained by simply neutralizing the small amount of acid present. In addition, the strength and elastic modulus of the obtained yarn can be dramatically improved by stretching the extruded yarn by about 2 to 10 times immediately after or after extrusion. Of course, it is also possible to extrude into other atmospheres, such as inert gas or ammonia gas, and extrusion into an alkaline neutralization bath is also a preferred method. That is, in the method of the present invention, the use of a coagulation bath as in the prior art is substantially unnecessary due to the above-mentioned technical configuration.

According to the present invention as described above, when molding chitosan,
By extrusion molding under pressure using a highly concentrated chitran aqueous solution or a high molecular weight chitosan aqueous solution unimaginable with conventional techniques, a high degree of molecular orientation of chitosan is observed during molding, resulting in a high degree of molecular orientation compared to conventional methods. A complicated coagulation bath is substantially unnecessary, and chitosan molded articles with excellent strength and elastic modulus can be efficiently provided.

Although the method of the present invention has been explained above mainly for forming threads, the method of the present invention can be similarly applied to the production of molded products other than threads, such as rondos, films, sheets, and other shapes. It is something.

Next, the present invention will be specifically explained with reference to Examples.

Note that the text in the middle of the sentence or ``chi'' is based on weight.

Example 1 Chitin isolated from shrimp shells was treated in a 42 wt. caustic soda aqueous solution at 100'C for 2 hours to obtain chitosan. The viscosity of the chitosan was 20 centivoise at 20° C. at a concentration of 0.5%.

20 parts of the chitosan was added to a 20% aqueous acetic acid solution and left to stand for 3 days to obtain a highly viscous chitosan solution with a concentration of 20%. The solution was degassed and passed through a spinning nozzle with a pore size of 0.4 at 15K.
00 mm/n+1n at a spinning pressure of g/-.

The mixture was extruded into air at a discharge rate of , and then exposed to ammonia gas and washed with water to obtain a chitosan system. This chitosan yarn had a dry strength of 2 t/a, an elongation of 11 inches, and a Young's modulus of 100 y/d. In addition, the wet strength is 0.8 t/a, and the elongation is 3
It was 2 plasters.

Example 2 Chitosan in Example 1 was replaced with 20 at a concentration of 0.5%.
Chitosan 1 with a viscosity of 200 centiboise at °C
0 part was dissolved in an aqueous solution of 5-thiacetic acid to obtain a 10% aqueous solution of Ki].san. Using this aqueous solution, chitosan threads were obtained under the same conditions as in Example 1. The dry strength of this chitosan type is 3.5r/
a, its elongation is 12 inches, and its Young's modulus is 100
It was t/a.

The wet strength was 1.1 f/d and the elongation was 40.

Claims (3)

[Claims] (1) A method for producing a chitosan molded article, which comprises preparing an aqueous solution containing chitosan of 10 weight φ or more, and extruding the aqueous solution under pressure. (2) Chitosan aqueous solution in nitrogen atmosphere, inert gas or l
(i) The manufacturing method according to claim (1), which involves extrusion molding in an ammonia gas atmosphere. (3) The manufacturing method according to claim 1, wherein the chitosan concentration is 151 q6 to 40 wt.