JPH0559215A - Chitosan-vegetable fiber composite and preparation thereof - Google Patents

Abstract

PURPOSE:To efficiently obtain a chitosan-vegetable fiber composite useful as, e.g. a material for use in biotechnology by mixing a chitosan powder with vegetable fibers, dispersing the mixture in a dilute acid, and then drying the dispersion. CONSTITUTION:A chitosan powder is mixed with vegetable fibers (e.g. a pulp powder). The mixture may be pulverized by applying a shear force. This mixture is added to a dilute acid and completely dispersed therein to give a paste. The paste is dried and, according to need, is then acetylated and/or neutralized, thereby to obtain a chitosan-vegetable fiber composite. Various properties including strength and solubility can be controlled by changing the proportion of chitosan to vegetable fibers. The properties can be changed in wider ranges by a post-treatment such as neutralization with an alkali or acetylation with acetic anhydride.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite containing chitosan and vegetable fibers as main raw materials and a method for preparing the same. The complex can be widely used in the fields of biotechnology-related materials, pharmaceutical materials, agricultural materials, packaging materials, etc. as a functional structure that can be prepared very easily.

[0002]

2. Description of the Related Art Chitosan is a crustacean such as crab and shrimp,
It is a polymeric substance derived by deacetylating chitin contained in insects such as beetles. Chitin is produced in large quantities next to cellulose in the biological world, and chitosan derived from this is a substance expected to be applied to various fields, like chitin. For example, a separation membrane (Japanese Patent Laid-Open No.
-135134), food wrapping paper (JP-A-62-8).
3875), medical materials (Japanese Patent Laid-Open No. 62-12702).
54). In addition, a combination of chitosan and vegetable fiber is utilized for an agricultural sheet (Japanese Patent Laid-Open No. 2-2303) and a versatile paper-making product (Japanese Laid-Open Patent Publication No. 2-200894) by taking advantage of biodegradability. Is being developed. The agricultural sheet has improved strength and the like under wet conditions while maintaining degradability in soil by applying chitosan to a natural pulp sheet at a specific ratio, and a versatile papermaking product. , An alkali solution was added to a cellulosic pulp suspension containing a chitosan salt while stirring to precipitate chitosan, and then papermaking was performed.

All of these conventional techniques were developed on the premise of the solubility of chitosan, and it was necessary to utilize the dissolved state of chitosan in order to exert the functions of a binder, a reinforcing agent, a coating agent and the like. .. Therefore, for the production of a complex of chitosan and plant fiber, a method is mainly used in which chitosan is prepared in a solution form and mixed with plant fiber, or a method in which plant fiber is dispersed in a solution and mixed with chitosan. Then, after this, operations of drying and heat compression are performed. However, in these manufacturing methods, since the raw materials are used as a solution, it takes a lot of time to prepare the solution. Further, since the water content is high, the drying efficiency is very poor and the drying time is long. For this reason, the sample is likely to be deformed or metamorphosed during drying, which may deteriorate the product.

[0004]

DISCLOSURE OF THE INVENTION In view of the problems of the above-mentioned prior art, the present invention simply and efficiently produces a novel composite containing chitosan and plant fiber as a main raw material and a composite of chitosan and plant fiber. It provides a way to do it.

[0005]

The present invention is a chitosan-vegetable fiber composite obtained by subjecting a mixture of chitosan and vegetable fiber powders dispersed in a dilute acid solution in a paste form to a drying treatment. Further, as a method for preparing the complex, chitosan and vegetable fibers in a granular form are mixed, and a dilute acid solution is added to completely disperse each, or alternatively, a dilute acid solution is added to a mixture of chitosan and plant fibers. Chitosan, which comprises a step of adding, adding a shearing force to each to atomize each, and then drying and optionally performing an acetylation treatment and / or a neutralization treatment.
It is a method for preparing a plant fiber complex.

[0006] According to the present invention, a chitosan-vegetable fiber composite can be obtained without a dissolution treatment of chitosan, so that not only can it be prepared very simply, but the obtained composite can be biodegradable and have antibacterial activity. It has excellent utility because it can be widely used in various fields. Heretofore, it has not been known that a structure can be formed using a dispersed phase.

The present invention will be described in detail below. A feature of the chitosan-vegetable fiber composite of the present invention is that it is prepared from a dispersed phase using chitosan, vegetable fibers as a dispersoid and a dilute acid solution as a dispersion medium. Therefore, the surface and the internal structure of the obtained composite have a concrete-like property in which chitosan and plant fiber particles are combined in a mosaic pattern.

The fact that the powdery particles of chitosan and vegetable fibers are dispersed in a paste in a dilute acid solution means that the dilute acid solution exists as a continuous phase between the particles of chitosan and plant fibers. .. However, it does not mean that chitosan and vegetable fibers are not dissolved at all, and some are dissolved in a dilute acid solution,
Further, it is not necessary that all particles have a granular shape. or,
The particle size and shape of chitosan and plant fiber do not have to be the same. As described above, the paste-like dispersed phase in which the solution is impregnated in the spaces between the particles (hereinafter referred to as the dispersed phase) is a means capable of realizing uniform dispersion regardless of the preparation method.
The material that has been granulated in advance may be dispersed, or the granulation treatment may be performed after the dispersion.

The term "obtained by drying the disperse phase" means not only immediately drying the disperse phase to obtain a composite, but also further kneading the disperse phase and subjecting it to sufficient swelling, partial dissolution and the like. Then, it is dried to obtain a composite. The preparation method will be described later.

The mixing ratio of chitosan and vegetable fiber in the composite is not particularly limited, but usually chitosan / vegetable fiber =
The ratio is preferably 10/1 to 1/10 (weight ratio). The properties of the composite can be adjusted by changing the mixing ratio. That is, when the proportion of chitosan is increased, it becomes hard and tenacious, and when the proportion of plant fiber is increased, it becomes soft and brittle. Further, when the composite is immersed in water, the higher the proportion of chitosan, the more easily it swells. On the contrary, the higher the proportion of plant fibers, the looser the fibers and the easier they break. Based on this property, it is possible to prepare a composite having desired mechanical properties, water resistance and the like according to the intended use.

Next, a method for preparing the complex of the present invention will be described. There are two methods of preparation, but the principle of using the dispersed phase is the same. In the first method, a dilute acid solution is added to and dispersed in chitosan and vegetable fiber which have been granulated in advance.

First, chitosan which can be used in the present invention is a deacetylated product of chitin and can be used regardless of the production method. The degree of polymerization and deacetylation of chitosan affect the solubility, stability, etc. of chitosan. The lower the degree of polymerization, the better the solubility and stability, but the tendency for the strength of the structure to decrease. In addition, the lower the degree of deacetylation, the lower the reactivity and the poorer the solubility. Considering these properties, the degree of polymerization of chitosan is preferably 100 or more and the degree of deacetylation is preferably 60% or more.

Next, the plant fiber used in the present invention is not particularly limited, but it has a water-insoluble polymer such as cellulose powder, pulp fiber for papermaking, pulp fiber such as dissolving pulp, or a negative charge if it is water-soluble. Preferred are those that form a polyion complex with chitosan to form an aggregate.
For example, carboxymethyl cellulose, starches, soybean press residue (okara), and the like. However, even when water-soluble plant fibers are used, it does not mean that these fibers are immediately dissolved in the dispersed phase or subjected to a dissolution treatment to be dissolved. After all, in the disperse phase, the plant fiber is dispersed as a dispersoid together with the degree of chitosan.

Chitosan and vegetable fibers are in the form of granules. The granular material does not necessarily have to be spherical or the like, and includes fibrous materials that can be uniformly mixed. Since both are powdery particles, they can be combined with each other to be compact and form a concrete-like strong structure. In addition, since the dispersion medium is a dilute acid solution and part of chitosan is dissolved, the entire solution can be thickened, the dispersion system can be homogenized, and the affinity with plant fibers and the fixability can be improved. Allows body formation. Therefore,
Chitosan not only acts as a binder, but also functions to form the skeleton of the structure with plant fibers. The particle size of chitosan and plant fiber as raw materials capable of exhibiting the above functions is preferably in the range of several microns to several thousands of microns, and the particle size distribution is in this range. The average particle size is about 100 to 500 microns. When the particle size distribution is smaller, the strength of the structure is improved and the viscoelasticity is increased. On the other hand, if the distribution is large, the structure becomes fragile, and if it is too large, the structure cannot be formed.

After mixing chitosan and vegetable fibers, a dilute acid solution is added. As the dilute acid solution, any solution having a chitosan-dissolving ability may be used, and an acetic acid aqueous solution is the most common, but lactic acid, citric acid, hydrochloric acid, etc. may also be used. In the present invention, the amount of dilute acid solution used is generally much smaller than that of the prior art. This is because the dilute acid solution is not intended to completely dissolve chitosan, but it is sufficient if the dilute acid solution has a sufficient amount to uniformly disperse the chitosan and partially dissolve the chitosan and the plant fiber. Since the amount used is small, the subsequent treatment, such as drying, can be made extremely efficient. However, the acid concentration of the solution is relatively high because a small amount forms a uniform dispersion system to produce a composite.

From the above viewpoint, the dilute acid solution has a pH of
About 2 to 6.2, and the amount used may be 10 times or less the weight of chitosan. The viscosity of the dispersed phase is generally 1-10 cp
It becomes a degree. The amount of acid added is based on whether chitosan and plant fibers are evenly dispersed, but various properties of the structure differ depending on the amount added, so it may be adjusted depending on the purpose. If the addition amount of the acid is small, the formation of the complex is not sufficient because the chitosan is not dissolved, and if the addition amount of the acid is large, the complex formation becomes easy but the pH is too low, and the subsequent handling and use may be limited. is there.

After adding the dilute acid solution, stirring and kneading are continued until chitosan and vegetable fibers are completely dispersed. However, it is not necessary to completely dissolve it.

Next, the dispersed phase is optionally shaped and dried. Drying can be adopted regardless of the means. For example, hot-air drying, freeze-drying, etc., but it is preferable that the drying temperature can be carried out at a relatively low temperature of 50 ° C. to 80 ° C. or lower in order to prevent deformation due to drying. The degree of drying is appropriately adjusted depending on the intended use of the composite. Generally, a water content of 5-10
% Is enough.

Although the acid used for dispersing chitosan remains in the obtained complex, it can be removed by neutralizing it by immersing it in an alkaline solution. Further, by acetylating with acetic anhydride or the like to insolubilize chitosan, water resistance can be imparted to the composite and strength can be increased at the same time. Acetylation is, for example,
It can be carried out by dipping in a solution of an organic acid anhydride such as acetic anhydride or by exposing the solution to a gasified atmosphere. The higher the degree of acetylation, the lower the solubility and the higher the stability. Normally, about 68% can be acetylated in gas in 1 hour. Even if the treatment is continued overnight thereafter, it is about 70%.

In the above-mentioned preparation method, another mode can be adopted for preparing the dispersed phase. That is, it is a mode in which chitosan and vegetable fiber are added to a dilute acid solution and shearing force is applied to atomize each. According to this, it is not necessary to adjust the particle size of the initial chitosan and vegetable fiber. As a means for applying a shearing force, for example, a stone-mill type crusher, a pin mill, a roller, a twin-screw extruder or the like can be adopted. As a result, the respective particle sizes may be adjusted so as to fall within the above-mentioned particle size range. According to this aspect,
Since atomization and dispersed phase formation can be performed at the same time, it is possible to further improve efficiency.

[0021]

EXAMPLES The present invention will be specifically described below based on examples.

Example 1. 50 g of pulp powder (manufactured by Toyo Roshi Co., Ltd.) having a particle size of 50 to 200 μm (average particle size 100 μm) and chitosan powder (polymerization degree of about 2000, deacetylation degree of 8)
50% (0%) was mixed, and 500 g of 10% acetic acid aqueous solution (pH 4) was added with stirring. The mixture was sufficiently kneaded for about 10 minutes until the chitosan and the pulp were completely dispersed, then molded into a flat plate and dried at 60 ° C. for 5 hours with a hot air dryer to obtain a composite (water content 5%). The resulting composite was a solid structure. When this product was immersed in water, disintegration of the surface structure was observed after 1 hour.

Example 2. The composite obtained in Example 1 was
The glass layer containing acetic anhydride was sealed so as not to come into contact with acetic acid, and acetylated with acetic acid gas (room temperature, saturated vapor) (24 hours). The degree of acetylation was about 70%. Next, it was immersed in 1% sodium hydroxide for neutralization. When this was thoroughly washed with water and dried, a water resistant composite was obtained that did not break even when immersed in water.

[0024]

INDUSTRIAL APPLICABILITY As described above, the composite prepared by utilizing the dispersed phase not only brings the advantage that the preparation method can be greatly simplified, but the composite according to the present invention has the following features. Have. (1) Various properties such as strength and solubility can be controlled by changing the ratio of vegetable fiber and chitosan. (2) The properties can be further changed by post-treatment such as neutralization with alkali or acetylation with acetic anhydride. (3) The antibacterial property of chitosan is exhibited. (4) It can be used as a biodegradable material. Therefore, the composite according to the present invention is not particularly limited in shape and can be applied in various fields. For example, a biomaterial, biodegradability and antibacterial property utilizing properties such as biocompatibility and antibacterial property. It can be applied to a nursery bed for hydroponic cultivation using the above, a cell immobilization carrier utilizing biocompatibility, a heat insulating material and a building material utilizing strength and biodegradability. As described above, according to the present invention, it is possible to prepare a complex of plant fiber and chitosan, and by utilizing its properties, application to biotechnology-related materials, pharmaceutical materials, agricultural materials, building materials, packaging materials, etc. Is possible, which is extremely beneficial to industry.

Claims (4)

[Claims] 1. A chitosan-vegetable fiber composite obtained by subjecting a mixture of chitosan and plant fiber powders dispersed in a dilute acid solution in a paste form to a drying treatment. 2. Chitosan in the form of granules and vegetable fibers are mixed, a dilute acid solution is added to completely disperse each, and then
A method for preparing a chitosan-vegetable fiber complex, which comprises the steps of drying and optionally performing an acetylation treatment and / or a neutralization treatment. 3. A step of adding a dilute acid solution to a mixture of chitosan and plant fibers, applying a shearing force to atomize each, and then drying and, if necessary, performing an acetylation treatment and / or a neutralization treatment. Method for preparing chitosan-vegetable fiber complex. 4. The preparation method according to claim 2, wherein the particle size of chitosan and vegetable fiber is several microns to several thousands microns.