JPH026689A - Novel composite sheet and production thereof - Google Patents

Abstract

PURPOSE:To obtain a composite sheet-like form capable of controlling biodegradability in soil, requiring no waste treatment after use thus useful for agricultural and food packaging use by bringing cellulose-based fiber into contact with an aqueous solution of chitosan salt. CONSTITUTION:Cellulose-based fiber is incorporated with >=1.0wt.% of a chitosan salt pref. with a deacetylation degree of 40-100% and molecular weight of 2000-500000 to obtain the objective composite sheet-like form. It is preferable that a 0.1-0.5% solution of >=12C higher fatty acid be attached to this composite form.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a composite sheet that is decomposed after a suitable period of time after use, and a method for producing the same.

More specifically, the present invention relates to a naturally easily degradable and controlled decomposition-timing sheet that is a composite of cellulose fibers, chitosan, and higher fatty acids as an alternative to current synthetic polymers, and a method for producing the same.

Note that the sheet of the present invention refers to the overall shape, and is not particularly limited in terms of thickness or the like. Furthermore, this does not preclude the mixing of plasticizers and the like into the sheet.

The present invention is used for food packaging, agricultural Sea 1-1 potted plants/leather bots, materials for water-based cultivation, and sheets or sheet-like structures that are discarded after a short period of use.

Conventional technology In addition to vinyl and polyethylene, there are also wood pulp coated with polyethylene, melamine resin, etc. to give it strength, but these synthetic resin parts are not biodegradable and must be treated after use. It is. There are also degradable polymers that contain photosensitizers in synthetic polymers to promote polymer breakdown by ultraviolet rays, but if used in large quantities, there is a risk of soil contamination due to decomposition products, and there is a risk that light will not reach. It is interesting to note that decomposition does not proceed in soils where there is no soil.

Among the materials used in the present invention, cellulose fibers are the most common polymeric substances in nature produced by plants and bacteria, and include cellulose, cellulose, pectocellulose, and bacterial cellulose. These cellulose fibers can be used as compost, and there is no need to worry about soil contamination.

Chitin is a nitrogen-containing polymeric substance that is contained in the epidermis of insects, shrimp shells, closed shells, fungi, etc., and is produced in large quantities in nature. When this is deacetylated, it becomes chitosan, but... Chitosan with various degrees of deacetylation is obtained depending on the degree of ￥゛Lf), :i. This chitin and chitosan are collectively called chitin. Since chitin has been produced in nature for a long time, there are a wide variety of microorganisms that decompose chitin. The present inventor collected field soil from all over Japan, from Hokkaido to Hokkaido, and confirmed that microorganisms that decompose even chitosan with a high degree of deacetylation are universally present.

Chitosan is used industrially as a flocculant for water treatment, and attempts are also being made to apply it to chitinous biocompatible materials. Furthermore, when applied to paper, the effect of increasing surface strength has been recognized. However, there is no example of preparing and applying a cellulose fiber-chitosan-based composite sheet material for the purpose of controlling degradability by soil microorganisms, nor is there any example of preparing a composite sheet material further treated with higher fatty acids.

Problems that the invention aims to solve Packaging materials and agricultural sheets are commonly used in human life and are used for a short period of time, but current products are difficult to dispose of after use. There is a strong demand for products.

The object of the present invention is to provide a novel composite sheet-like product that can satisfy this requirement and a method for manufacturing the same.

Means for Solving the Problems As a result of intensive research into decomposition-controlled polymer sheet materials, the present inventors discovered a cellulose fiber-chitosan composite sheet with appropriate microbial degradability and a method for manufacturing the same. The invention was completed.

Cellulose-based fiber sheets and chitosan salts do not maintain their strength and shape in moist soil when used alone. That is, the former quickly becomes a single fiber, and the latter dry sheet-like material quickly becomes a gel. The present invention combines various cellulosic fibers with chitosan salts of various molecular weights, and furthermore, by adding or not adding higher fatty acids, the present invention creates clear water-resistant or Water-absorbing composite sheet material Chitosan salt aqueous solution is composited to a concentration of 1% (chitosan weight %) or more based on cellulose fibers, and after drying, 0.1~
By contacting with 0.5% dilute higher fatty acid solution,
A cellulose fiber-chitosan-higher fatty acid composite sheet having different decomposition rates in soil can be obtained. The method for combining chitosan and cellulose fibers is as follows: 1. A cellulose fiber sheet is created and a chitosan aqueous solution is applied to it. 2. Cellulose fibers are treated with a chitosan aqueous solution and then dried to form a film sheet. 3. Chitosan is added to the process of forming cellulose fibers into sheets. These include, but are not limited to. Regarding higher fatty acid treatment, it is necessary to act as a dilute solution of 0.5% or less.

Any solvent may be used as long as it forms a dilute solution of higher fatty acids and does not react with chitosan, such as methanol, which is suitable for the process of the present invention, but is not limited thereto. Further, higher fatty acid treatment can also be omitted. In this case, these water-absorbing composite sheets not only have microbial degradability, but also the degradability can be appropriately controlled by changing the preparation conditions, ie, the molecular weight and composite amount of chitosan.

The chitin used had the highest degree of deacetylation of 40 to 100% in sheet forming ability. The higher fatty acid may be any non-salt type higher fatty acid having 12 or more carbon atoms and having low solubility in water, but stearic acid or palmitic acid was the most excellent in terms of the water clearing effect of the composite sheet.

When a cellulose fiber-chitosan-higher fatty acid composite sheet is first combined with chitosan salt, a chemical bond exists between the cellulose fiber surface and chitosan, resulting in a sheet that maintains its shape while being water permeable and is biodegradable. is obtained. Furthermore, by applying a dilute higher fatty acid solution to this sheet, a film is formed in which higher fatty acids are bonded to chitosan on the surface of the sheet, forming a composite sheet with low water absorption.

The composite sheet prepared by the method of the present invention can appropriately control microbial decomposition in soil, and does not produce harmful substances after being decomposed. This eliminates the need for disposal after use.
It can be used for various purposes such as food packaging materials, agricultural sheet-like structures, and base materials, and its effects can be expected to be great.

EXAMPLES Next, the composite sheet of the present invention and the method for manufacturing the same will be explained in more detail by examples, but the present invention is not limited thereto.

Example 1 Mechanical pulp paper made to have a basis weight of 50 g/m2 was impregnated with an acetic acid aqueous solution of chitosan (molecular weight: approximately 50,000, degree of deacetylation: 99%), and chitosan was 1 to 50% of the mechanical pulp paper. were combined and dried by heating at 105°C. 0 more
．． Stearic acid treatment was performed by impregnating the sample with a 1% stearic acid methanol solution and then drying. Table 1 shows the strength and soil biodegradation period of the obtained composite sheet. As for the decomposition period,
When the sheet is buried in field soil at 25°C, Q moisture, 2 to 8 cm from the ground surface, the wet tear length is 0.5.
The period during which the distance becomes less than km is shown in months.

Table 1 Amount of chitosan and sheet properties Example 2 Table 2 shows the decomposition period in soil of a composite sheet treated with stearic acid, in which 3% of chitosan with different molecular weight was composited with mechanical pulp in the same manner as in Example 1. .

Table 2 Chitosan molecular weight and composite sheet properties From Table 1, 1%
It was confirmed that the above composite with chitosan increases the sheet strength, which is sufficient to maintain the shape of the sheet-like product, and that the decomposition timing can be adjusted by adjusting the amount of chitosan added.

It is clear that the timing of decomposition of the composite sheet can be controlled by changing the molecular weight of the chitosan used. The decomposition period without stearic acid treatment was also investigated, but the presence or absence of treatment did not affect the decomposition period of the sheet.

1.

Example 3 An acetic acid aqueous solution of chitosan having a degree of deacetylation of 40 to 100% was added to an aqueous solution of finely beaten cellulose fiber dispersion so that the amount was 2% based on the cellulose, and then a sheet was prepared. The basis weight of this film-like sheet is approximately 50
g/m2.

This was further treated with stearic acid in the same manner as in Example 1. The relationship between the strength of the obtained composite sheet and the degree of deacetylation was investigated. The results are shown in Table 3.

Table 3 Relationship between the degree of deacetylation of chitosan and the wet strength of the composite sheet When the degree of deacetylation of chitosan is 40% or more, the strength of the composite becomes significant. It is clear that they match.

Example 4 The influence of the number of carbon atoms in higher fatty acids and methanol concentration was studied. Figure 1 shows the water absorbency of a composite sheet obtained by immersing the chitosan-cellulose sheet obtained by the method of Example 1 in a 0.5% methanol solution of higher fatty acids having different carbon numbers. Figure 1 shows that the greater the number of carbon atoms in a fatty acid, the lower its water absorbency, especially 12 carbon atoms.
It was found that above lauric acid, water absorption decreased rapidly and a remarkable water mixing effect was obtained.

In addition, methanol solutions of stearic acid with different concentrations (0
, 1 to 1.0%), the amount of stearic acid adhering to the sheet increases rapidly when the concentration of stearic acid exceeds 0.5%; There was no big difference.

This indicates that it is desirable to produce composite sheets by treatment with a stearic acid solution having a concentration of 0.5% or less.

[Brief explanation of the drawing]

In FIG. 1, the horizontal axis shows the number of carbon atoms in the higher fatty acids used in the composite treatment. The vertical axis shows the water absorption in percent when the composite sheet was immersed in water overnight. Patent Applicant: Director of the Agency of Industrial Science and Technology Kozo Iizuka Designated Agent: Director of the Shikoku Institute of Industrial Technology, Agency of Industrial Science and Technology Kinotane Takemori

Claims (5)

[Claims] (1) Cellulose fiber and 1 for cellulose fiber
A composite sheet-shaped object formed by combining more than % by weight of chitosan. (2) A composite sheet-shaped article comprising attaching a higher fatty acid to the composite sheet-shaped article set forth in claim 1. (3) A composite sheet-like structure according to claim 2, characterized in that the cellulose fibers are brought into contact with an aqueous chitosan salt solution, and then the material obtained by drying is brought into contact with a higher fatty acid solution. Production method. (4) The sheet according to claims 1 and 2, characterized in that a chitosan salt having a degree of deacetylation of 40 to 100% and a molecular weight of 2,000 to 500,000 is composited with cellulose fibers. A shaped object and its manufacturing method. (5) A dilute solution of higher fatty acids having 12 or more carbon atoms (0.
1 to 0.5%). 3. The method for manufacturing a composite sheet-shaped article according to claim 2.