JP3141163B2 - Porous composite - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous composite, and more particularly, to a porous composite that can be used in a wide range of fields such as foods, cosmetic puffs, sanitary articles, paper, and plant nurseries.

[0002]

2. Description of the Related Art Conventionally, as a porous complex using chitosan, a method for producing a porous chitin material, which comprises freeze-drying and acylating an acidic aqueous solution of a de-N-acetylation product of chitin (Japanese Patent Laid-Open Publication No. -261802), and a method for producing a sponge-like material in which a chitosan is formed into a sponge and then acylated (Japanese Patent Application Laid-Open No. 62-238209). 63-90507) is known. All of these are characterized by insolubilizing chitosan by converting it into N-acyl chitosan.

[0003] However, these techniques not only make it impossible to use them as foods because of the chemical treatment called acylation, but also perform dehydration or freeze-drying with a large amount of alcohol to promote the acylation or the reaction. It was necessary to perform a very complicated and inefficient process such as washing the porous body with a large amount of alcohol or water and drying it again.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to obtain a porous composite which can be insoluble by a simple process without acylation using chitosan and which can be applied to foods, papers, cosmetic puffs and the like. And

[0005]

The present invention is a porous composite obtained by subjecting a mixture containing solubilized chitosan to phosphoric acid treatment. According to the present invention, by performing a phosphoric acid treatment, the porous composite can be insolubilized without acylation. The mixture used in the present invention can contain plant fibers in addition to chitosan. As the plant fiber, any raw material containing cellulose, hemicellulose, xylan and the like can be used, but pulp is exemplified as a preferable one. In particular, when producing paper according to the present invention, pulp made from wood is preferably used. This plant fiber is dispersed in water and chitosan is added. The chitosan used in the present invention may be a commercially available one, but the degree of deacetylation is 40 to 40 in terms of solubility and the like.
100%, preferably 70-100% is desirable.

[0006] In the present invention, solubilized chitosan is used. Preferably, chitosan is used by dissolving it in an acid. Any kind of acid can be used as long as it can dissolve chitosan, but acetic acid, lactic acid, hydrochloric acid, citric acid and the like are preferred. The amount of the acid to be added is 10 to 500 parts, preferably 50 to 300 parts, per 100 parts of chitosan. These raw materials containing chitosan may be directly formed into a thin film and dried to form paper, or filled in an appropriate mold and freeze-dried to form a porous body. Also, without drying
The next step, phosphoric acid treatment, can also be performed.

[0007] The phosphoric acid treatment performed in the present invention is realized by bringing the above-mentioned porous material containing chitosan or paper into contact with a solution containing phosphoric acid. As phosphoric acid, polymeric phosphoric acid such as diphosphoric acid and tripolyphosphoric acid is preferable, and sodium salts and potassium salts thereof can also be used. The concentration of phosphoric acid is desirably 0.1 to 20%, preferably 2 to 10%. If the concentration exceeds 20%, the porous composite shrinks, which is not preferable. The amino group of phosphoric acid and chitosan has a very high reactivity and a complex of chitosan and phosphoric acid is formed only by treating for about 1 minute to 1 hour, and becomes insoluble in water and dilute acid. Further, the plant fiber is also immobilized in the composite, and becomes an insoluble porous composite as a whole.

Hereinafter, the present invention will be described in detail with reference to examples.

[0009]

【Example】

Example 1 3 g of pulp and 93 g of water were pulverized with a blender, and 1 g of chitosan (78% deacetylation degree) and 1 g of lactic acid were added to obtain a viscous pulp mixture. This mixed solution was applied on a glass plate and dried with a hot air drier. The obtained paper was immersed in a 5% sodium diphosphate solution, allowed to stand for 1 hour, washed with water, and dried again to obtain chitosan paper. This paper was extremely strong even when immersed in water for a long time, and did not tear off even when both ends were pulled.

As a control, the same treatment as described above was carried out except that the phosphoric acid treatment was not carried out, and the resulting product swelled immediately upon immersion in water, and almost dissolved after several minutes. Example 2 10 g of chitosan (deacetylation degree 78%), 10 g of acetic acid, and 10 g of dry pulp were mixed with 970 g of water, and the mixture was stirred with a blender for 5 minutes to obtain a chitosan-pulp mixed solution. This mixed solution was put in a square vat and freeze-dried. 5% of this dried product
It was immersed in a sodium polyphosphate solution and subjected to a phosphoric acid treatment for about 1 hour. This was washed with water and dried naturally to obtain a porous body. The porous body was molded into a prism having a size of 5 × 5 × 20 mm, and a tensile test was performed using a Leoner.

[0011] As a control, the same measurement was carried out for a sample not treated with phosphoric acid. The result is shown in FIG. In the figure, the horizontal axis indicates the amount of deformation per sample length, and the vertical axis indicates the stress per sample cross-sectional area. The solid line shows the sample prepared according to the present example, and the broken line shows the sample not treated with phosphoric acid as a control.

As is apparent from the figure, this example exhibited a tensile strength four times higher than that of the control. In addition, when immersed in water, in the present example, a sponge-like material was obtained, but the control was easily dissolved and could not maintain its shape.

[0013]

According to the present invention, a sponge-like porous composite can be obtained by a simple process by subjecting a solution containing chitosan to phosphoric acid treatment without performing a chemical treatment such as acylation. This composite can be applied to a wide range of industrial fields such as cosmetic puffs, sanitary articles, water-resistant paper, and plant nurseries.

[Brief description of the drawings]

FIG. 1 is a comparison of tensile strength. The solid line indicates that prepared according to Example 2, and the dashed line indicates the control. The horizontal axis indicates the amount of deformation per sample length, and the vertical axis indicates the stress per sample cross-sectional area.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI (C08L 1/02 5:08) (56) References JP-A-2-127596 (JP, A) JP-A-1-174699 ( JP, A) (58) Fields surveyed (Int. Cl. ⁷ , DB name) C08J 5/18 C08J 7/14 C08L 1/02 C08L 5/08

Claims (3)

(57) [Claims] 1. A mixture comprising a solubilized chitosan and a vegetable fiber is mixed with diphosphoric acid, tripolyphosphoric acid,
Selected from the group consisting of acids, polyphosphoric acids and their salts
A porous composite obtained by phosphoric acid treatment using one or two or more kinds . 2. The porous composite according to claim 1, wherein the plant fiber is pulp. 3. The porous composite according to claim 1, which is in the form of a sheet and can be used as paper.