JPH02127486A - Formation of water-resistant coating film - Google Patents

Abstract

PURPOSE:To form a water-resistant coating film capable of being naturally readily decomposed and of controlling the time of the decomposition by coating or impregnating an article with the solution of a mixture of cellulose fibers, chitosan and glycerol and subsequently drying the coated or impregnated solution. CONSTITUTION:An article to be treated is coated or impregnated with the solution of a mixture of (A) cellulose fibers preferably beaten into fine micro- fibrils, (B) chitosan (preferably a solution thereof using an organic acid such as acetic acid or formic acid and an aqueous solution of a mineral acid) in an amount of >=5wt.% based on the component A and (C) <=150wt.% of glycerol, followed by drying the coated or impregnated solution to form a water-resistant coating film.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for forming water-resistant coatings that are decomposed by microorganisms.

More specifically, the present invention relates to a method for forming a water-resistant member that is naturally easily degradable and whose decomposition timing can be controlled by kneading cellulose fibers and chitosan.

The present invention can be used to form a covering for objects where it is desired that the skin will decompose in the soil for a certain period of time and the contents will be exposed, such as special sheets, pots for plants and paintings, materials for slow-release drugs, etc. be done.

Conventional technology There are 11 types of film-forming paints, and the film is generally formed by dissolving synthetic resin in a solvent, but these synthetic resin parts are not biodegradable by microorganisms. Research is being conducted to produce plastic, but
However, it has not yet been put into practical use.

By the way, chitosan is a substance obtained by deacetylating chitin, a nitrogen-containing N group contained in shrimp, crab shells, etc. Microorganisms that break down chitin are widely present in the soil. Regarding chitosan, the present inventor collected field soil from all over Japan, from Hokkaido to general use, and found that microorganisms that decompose even highly deacetylated chitosan are universally present, and that this application and increase in paper surface strength are possible. Only attempts have been made to use it. To date, there have been no examples of applying chitosan as a composite film in combination with cellulose fibers.

Problems to be Solved by the Invention There are many products that are used in soil and require that the coating decomposes after a certain period of time to expose the inner layer. Such products are
It is strongly required that the film not only decompose naturally in the soil for a certain period of time, but also be harmless to the soil ecosystem.

The object of the present invention is to provide a novel method for forming a film that can satisfy this requirement.

Means for Solving the Problems The present inventors have conducted intensive research on decomposer film materials, and have found that cellulose fibers with excellent microbial degradability have been developed.
We discovered a method for forming a chitosan-based film and completed the present invention. The dried product of the latter becomes gel-like.

The present invention mixes various cellulose fibers and chitosan salt in the presence of glycerol, coats or impregnates the object with the mixture, and then dries to form a composite, which improves strength and water resistance in soil and water. This method produces a film that is decomposed by microorganisms in one barley for a certain period of time.

These composite films are not only microbially degradable, but can also be modified by changing the preparation conditions, i.e., the amount of chitosan combined and the amount of glycerol mixed. 2. Degradability can be appropriately controlled by changing the temperature. The chitosan used in the present invention had the highest film-forming ability with a degree of deacetylation of 40 to 100%.

Due to the bond between the cellulose fiber surface and chitosan, this film is water permeable, has strong strength in wet conditions, and is biodegradable by microorganisms. Furthermore, by treating this film with a dilute higher fatty acid solution, it is possible to obtain a film with low water absorption.

Effects of the Invention The film formed by the method of the present invention can control microbial decomposition in the soil, and does not produce harmful substances in the decomposed gravel.
Therefore, by encapsulating the drug or forming a surface film, it is possible to give the drug a sustained release effect. Furthermore, it can be used for various purposes as a coating on a substrate that needs to be exposed and acted upon after a certain period of time, and its effects can be expected to be great.

EXAMPLES Next, the method for forming a composite film of the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 Chitosan (molecular agreement three-way,
An acetic acid aqueous solution with a degree of deacetylation (99%) was mixed so that the amount of chitosan added was 0 to 60% based on the cellulose fibers. In addition, glycerol is 93% of the pulp.
Mixed. 0.5mg of this mixture is cellulose fiber type.
/cm” on a glass plate, and heated to 70°C for 15 min.
Dry-smoked for hours.

After the film on the glass plate was reduced in volume by placing it in a solution of acid and water having a pH of 6, bacteria collected from field soil were inoculated, cultured by shaking, and the decomposition of the film was observed with the naked eye.

Table 1 Amount of chitosan and decomposition period of film From Table 1, 0% chitosan does not maintain its shape, but when combined with 5% or more chitosan, it is sufficient to maintain the shape of a film, and the decomposition time also increases. It was confirmed that this can be controlled by the amount of chitosan added. Example 2 In Table 2, chitosan was mixed at 25% with respect to cellulose fiber,
The decomposition period of a composite film formed by adding and mixing glycerol from 0% to 200% is shown.

The formation method and decomposition method are the same as in Example 1.

Table 2 Amount of glycerol and composite film The flexibility of the composite film gradually increases until the amount of glycerol mixed in is 150%. It turns out that it is possible to control.

Example 3 In Table 3, 25% chitosan was mixed with cellulose fiber,
After adding and mixing 93% glycerol, the drying degree was 70, which indicates the decomposition period of the composite film formed on the valve paper sheet.
~180''C1 drying time was 1 hour. The method of forming the pond and the method of decomposition were the same as in Example 1.

Table 3: Effect of Formation Temperature The higher the formation temperature, the longer the decomposition time of the film, which indicates that the degree of complexation increases, and it is clear that the decomposition time can be controlled by this.

however, The film turns brown at temperatures above 5°C. Ta.

Claims (2)

[Claims] (1) Cellulose fiber and 5% for cellulose fiber
A method for forming a water-resistant film, which comprises applying or impregnating a treated object with a mixed solution of chitosan in an amount of at least 150% by weight and glycerol, and then drying. (2) As the chitosan solution, an aqueous solution of an organic acid such as acetic acid or formic acid and a mineral acid is used, and as the cellulose fiber, finely beaten and microfifurylated fiber is used. Film forming method described in section.