JPH064808B2 - Water resistant film formation method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for forming a water resistant film which is decomposed by microorganisms.

More specifically, the present invention relates to a method for forming a water-resistant film which is composed of cellulosic fibers and chitosan and is easily decomposable naturally and whose decomposition time can be controlled.

INDUSTRIAL APPLICABILITY The present invention is used for forming a film of an object whose contents are desired to be exposed by decomposing the film in soil after a certain period of time, such as a special sheet, a pot for planting / seedling, a sustained-release chemical material and the like.

2. Description of the Related Art There are various types of film-forming paints, and it is common to dissolve a synthetic resin with a solvent to form a film, but these synthetic resin parts are not biodegradable. Currently, research is being conducted to make microorganisms produce plastic, but it has not yet been put to practical use.

By the way, chitosan is a substance obtained by deacetylating a chitin substance which is a nitrogen-containing polysaccharide contained in shrimp, crab shell and the like. Microorganisms that decompose this chitin are widely present in soil. With respect to chitosan, the present inventor also collected field soils from various parts of Japan from Hokkaido to Kyushu, and confirmed that a microorganism that decomposes chitosan having a high degree of deacetylation is universally present.

Chitosan is industrially used as a flocculant for water treatment, and is only attempted to be applied to a biocompatible material of chitin and to increase the surface strength of paper. Until now, there has been no application of chitosan as a composite film in which cellulosic fibers are combined.

Problems to be Solved by the Invention Many products are required to be used in soil and require that the coating film be decomposed and the contents exposed after a certain period of time. Such products are
It is strongly required that the film decomposes naturally in the soil after a certain period of time and that it is harmless to the soil ecosystem.

The present invention is to provide a novel method for forming a film capable of satisfying this requirement.

Means for Solving the Problems As a result of intensive studies on the decomposition control coating material, the present inventors have found that a cellulosic fiber having an appropriate biodegradability-
A method for forming a chitosan-based film has been found, and the present invention has been completed. The sheet-like material containing only cellulosic fibers or the chitosan salt alone does not maintain its strength and shape in soil with high water content. That is, the former becomes a monofilament promptly, and the dried product of the latter becomes a gel.

The present invention mixes various cellulosic fibers and chitosan salt in the presence of glycerol, coats or impregnates this with an object, and then dries to form a composite, which gives strength and water resistance in soil or water. And obtains a film that is microbially decomposed after a certain period of time.

These composite films are not only biodegradable, but their degradability can be properly controlled by changing the preparation conditions, that is, the combined amount of chitosan and the mixed amount of glycerol, and by changing the preparation temperature. The chitosan used in the present invention had the best film-forming ability with a deacetylation degree of 40 to 100%.

By having a bond between the surface of the cellulose fiber and chitosan, this film has a strong strength in a wet state while having water permeability, and becomes a biodegradable film. Further, a diluted higher fatty acid solution is allowed to act on this film to form a film having low water absorption.

Effects of the Invention The film formed by the method of the present invention can control microbial degradability in soil and does not produce harmful substances after being decomposed.
Therefore, the drug or the like can have a sustained release effect by encapsulation or surface coating of the drug or the like. Further, it can be used in various applications as a film of a base material that needs to be exposed and acted after a certain period of time, and its effect can be expected greatly.

Example Next, the method for forming the composite film of the present invention will be described in more detail with reference to examples, but the invention is not limited thereto.

Example 1 Finely beaten bleached pulp and chitosan (molecular weight about 50,000,
An acetic acid aqueous solution having a deacetylation degree of about 99%) was mixed so that the amount of chitosan added was 0 to 60% based on the cellulose fiber. In addition, glycerol is 93% to pulp
Mixed. This mixture has a cellulose fiber content of 0.5 mg / cm ²
It was cast on a glass plate so as to have the above temperature and dried by heating at 70 ° C. for 15 hours.

The film on the glass plate was put into a phosphoric acid aqueous solution of pH 6 to sterilize it, and then the bacteria collected from upland soil were inoculated and shaken and cultured, and the decomposition of the film was visually observed.

From Table 1, it can be seen that the shape is not maintained at 0%, but when combined with 5% or more of chitosan, it is sufficient to maintain the shape as a film-like substance, and the decomposition time can be controlled by the amount of chitosan added. Admitted. A film with 0% cellulose fibers was also formed, but the film was not suitable as a film due to the phenomenon of swelling and dissolution in water.

Example 2 In Table 2, chitosan was mixed with cellulose fiber in an amount of 25%,
The decomposition period of the composite film formed by adding and mixing glycerol from 0% to 200% is shown. The forming method and the disassembling method are the same as those in the first embodiment.

It was found that the film gradually increased in flexibility until the amount of glycerol mixed was 150%, and had properties suitable as a film. When it became 200%, the film strength decreased and it was not suitable as a film. Furthermore, it was found that the decomposition time of the composite film can be controlled by changing the mixing amount of glycerol.

Example 3 In Table 3, chitosan was mixed at 25% with respect to the cellulose fiber,
The decomposition period of the composite film formed on the pulp paper sheet after adding and mixing 93% of glycerol is shown. Drying temperature is 70
The drying time was 1 hour at ˜180 ° C. Other forming methods and disassembling methods are the same as those in the first embodiment.

The higher the formation temperature, the longer the decomposition time of the film, so it is clear that the degree of complexation increases, and it is clear that the decomposition time can be controlled by this. However, 1
The film at 45 ° C or higher turned brown.

Claims (2)

[Claims] 1. A water resistant material, characterized in that a treated solution is coated with or impregnated with a mixed solution of cellulosic fibers, 5% by weight or more of chitosan and 150% at maximum of glycerol, and then dried. Method of forming a protective film. 2. A chitosan solution is an aqueous solution of an organic acid such as acetic acid and formic acid and a mineral acid, and finely beaten microfibrillated fibers are used as the cellulosic fibers. The film forming method according to item 1.