JPH09208714A - Production of biodegradable composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the above material having excellent strength and degredable property by microorganisms, easy for forming and processing, not producing a harmful substance even after degradation thereof, and useful as a packing material, etc., by mixing a fine cellulose fiber with a protein and a plasticizer and hot press forming. SOLUTION: This biodegradable composite material is obtained by mixing (A) a fine cellulose fiber with (B) a protein and (C) a plasticizer, and performing a hot press forming preferably at 50-250 deg.C and under 10-200kgf/m<2> pressure. Further, e.g. as the components (A), (B) and (C), a cellulose, etc., having <=3000μm length and <=50μm diameter, a casein, and glycerin, etc., are used respectively. Based on 100 pts.wt. component (A), it is preferable to blend in the ratio of 20-100 pts.wt. component (B) and 20-100 pts.wt. component (C).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a biodegradable composite material, and more specifically, a packaging material, a film for agricultural and horticultural use, a nursery pot, a material for civil engineering and building materials, a molding tray and other molded articles. The present invention relates to a method for producing a biodegradable composite material which is used for, for example, excellent strength and can be decomposed by microorganisms in soil.

[0002]

2. Description of the Related Art There are many known molded products made of natural products such as cellulose, starch, and protein. However, these molded products have weaker strength than general-purpose plastics and can be used in a wet state. Due to moisture absorption, there are problems that the strength is further reduced, and that it dissolves in water.

In order to improve these problems, for example,
Operations such as reacting a cross-linking agent such as formaldehyde with starch and a cross-linking agent such as isocyanate and dimethylolurea with a molding using protein are performed.

For example, as described in JP-A-3-131636, for the purpose of improving the strength in water or in a wet state, an aqueous protein solution is mixed with fine cellulose fibers and / or a plasticizer and then dried to form a composite. It has been found that a molded product can be obtained, which retains its shape even in water and exhibits sufficient wet strength.

Further, as described in JP-A-2-6689, a simple method of compounding fine cellulose fibers which is a natural material and chitosan has a strength equal to or higher than that of a general-purpose plastic, and is underwater. New composite materials have been found that have sufficient strength even in wet and wet conditions.

Further, as described in JP-A-4-59830 and JP-B-6-25260, in order to accelerate the microbial decomposition rate of the composite material, a protein is further added in addition to the fine cellulose fiber and chitosan. It has been found that the microbial decomposition rate can be controlled by changing the amount of the microbial compound added, or by changing the addition amount.

[0007]

The above-mentioned composite material comprising protein and fine cellulose fiber and / or plasticizer, and composite material comprising fine cellulose fiber and chitosan and / or protein are water-dispersible or aqueous solutions thereof. Since the biodegradable composite material is obtained by drying, complicated operations such as molding and drying are required. Further, there is a problem that shrinkage occurs in the drying process and the dimensional accuracy deteriorates.

In view of the above, the present invention is easy to mold and has the same strength as general-purpose plastics.
It is intended to clarify a method for producing a biodegradable composite material which is easily decomposed by microorganisms in the soil.

[0009]

The method for producing a biodegradable composite material according to the present invention is characterized in that fine cellulose fibers are mixed with a protein and a plasticizer and subjected to hot press molding.

That is, according to the present invention, as a result of diligent study of a processing method capable of easily maintaining the strength of a biodegradable composite material composed of fine cellulose fibers, proteins and a plasticizer, and further, easily forming the fine cellulose fibers, proteins and By mixing the plasticizer and hot pressing, it has been found that a biodegradable composite material which does not have a decrease in strength of the composite material, has a fast biodegradability, and is easy to mold and process has been completed. is there.

[0011]

When a fine cellulose fiber, a protein and a plasticizer are dissolved or dispersed in an aqueous solution and then dried to form a composite, the production method, particularly the drying step is complicated,
In addition, shrinkage of the molding material occurs during drying, resulting in poor dimensional accuracy.

By thoroughly mixing the fine cellulose fibers according to the present invention with the protein and the plasticizer and then compounding them by hot press molding, the same strength as general-purpose plastics can be maintained,
Moreover, the molding process is easy and a biodegradable composite material can be obtained. In addition, because it uses biodegradable raw materials, it is easily decomposed by microorganisms in the soil.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Cellulose fibers used in the composite material according to the method of the present invention include, for example, cellulose obtained from plants such as paper powder, wood, cotton, hemp, straw, bamboo, chaff and bagasse, Hemicellulose, lignocellulose,
Examples of the fiber include vector cellulose and bacterial cellulose produced by bacteria.

As these cellulose fibers, those finely divided by various known methods are used. It is preferable that the fine cellulose has a length of 3000 μm or less and a diameter of 50 μm or less, but fibers of a larger size may be partially mixed in these fine celluloses.

The protein used in the composite material according to the method of the present invention is obtained, for example, by separating or concentrating from various animal and plant bodies or microorganisms such as casein, albumin, gluten, soybean protein, corn protein, gelatin and glue. Some of them are listed. These may be used alone or in combination of two or more. These are used by being dissolved in water adjusted to a pH suitable for dissolving each protein.

In the present invention, a plasticizer is used for the purpose of imparting plasticity to the molding material, and examples of the plasticizer used include hydrophilic ones. For example, glycerin,
Polyhydric alcohols such as diglycerin, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, trimethylolpropane and polyethylene glycol are preferably used. These may be used alone or in combination of two or more, but are not limited thereto.

The mixing ratio of the raw materials used is 2 to 200 parts by weight of protein per 100 parts by weight of fine cellulose fiber,
Particularly, 20 to 100 parts by weight, plasticizer 2 to 200 parts by weight, and particularly 20 to 100 parts by weight are preferable.

The method for producing the biodegradable composite material of the present invention will be described. First, fine cellulose fibers, protein and plasticizer are sufficiently mixed. As a device for mixing, a Henschel mixer, a mixer such as a ribbon blender, a roll mill, a crusher or the like is used. The biodegradable composite material of the present invention is obtained by hot pressing this mixture.

The hot press molding temperature is in the range of 50 to 250 ° C, particularly preferably in the range of 120 to 180 ° C. The hot press molding pressure is in the range of 10 to 200 Kgf / cm ² . Press molding time is 5 seconds to 20 minutes, preferably 1 minute to
10 minutes.

When preparing the mixture, additives such as a colorant, a filler, a reinforcing agent and a cross-linking agent can be added if necessary. Especially for applications requiring water resistance, the water resistance is improved by adding polyethylene wax, paraffin wax, oils and fats, silicon compounds, fluorine compounds and the like. Water resistance can also be imparted by applying these water resistance improvers to a molded article.

Although the mechanism of complexation by hot press molding is not clear, the hydroxyl group or carbonyl group in cellulose and the hydroxyl group of the plasticizer and the amino group or carboxyl group of the protein chemically react with each other during hot press molding. It is presumed that they are bound and complexed.

Various molded articles and sheets are molded by hot pressing. Further, the obtained sheet can be formed into a desired tray or various containers by secondary forming such as vacuum forming and pressure forming.

[0023]

EXAMPLES The present invention will now be described in more detail with reference to Examples. In these examples, all parts are parts by weight.

The tensile strength was measured according to JIS K7113, and the bending strength was measured according to JIS K7203. The microbial degradability test was carried out by burying the sample in soil, excavating it every week, and observing the state of degradation.

Examples 1 to 6 Fine cellulosic fibers (beaten softwood bleached pulp, the same applies hereinafter), soybean protein and glycerin were mixed at the ratios shown in Table 1, and the hot press temperature was 160 ° C. and the pressure was 1
20 kgf / cm ² , press time 2 minutes, thickness 2 mm
And 5 mm sheets were obtained. Table 1 shows the tensile strength (using a 2 mm sheet), the bending strength (using a 5 mm sheet) and the number of days (weeks) of microbial decomposition of the obtained sheet.

Comparative Examples 1-2 A mixture of an aqueous dispersion of fine cellulose fibers (concentration 3%), an aqueous soybean protein solution (concentration 3%, pH 8) and glycerin in the ratios shown in Table 1 was cast on a glass plate. 6 at 70 ° C
Air-dried for an hour to obtain sheets with thicknesses of 2 mm and 5 mm. Table 1 shows the tensile strength (using a 2 mm sheet), the bending strength (using a 5 mm sheet) and the number of days (weeks) of microbial decomposition of the obtained sheet.

[0027]

[Table 1] Examples 7 to 10 Fine cellulose fibers were mixed with gluten and ethylene glycol in the ratios shown in Table 2, and then the hot press temperature was 140.
A sheet having a thickness of 2 mm and a sheet having a thickness of 5 mm was obtained at a temperature of 120 ° C., a pressure of 120 kgf / cm ² , and a pressing time of 2 minutes. Table 2 shows the tensile strength (using a 2 mm sheet), the bending strength (using a 5 mm sheet) and the number of days (weeks) of microbial decomposition of the obtained sheet.

Comparative Examples 3 to 4 Fine cellulose fibers were mixed with gluten and ethylene glycol at the ratios shown in Table 2, and then hot-pressed under the same conditions as in Examples 7 to 10 to give a thickness of 2 mm and 5 mm. Got the sheet. Tensile strength of the obtained sheet (2 mm
Table 2 shows the bending strength (using a sheet of 5 mm) and the number of days of microbial decomposition.

[0029]

[Table 2]

[0030]

Industrial Applicability The biodegradable composite material obtained by the method of the present invention has excellent strength and microbial degradability, is easy to mold, and is decomposed because it uses a natural product as a raw material. It also has the characteristic that it does not produce harmful substances even after it has been used. It is a general-purpose plastic molded product in the fields of packaging materials, films for agricultural and horticultural use, nursery pots, materials for civil engineering and construction materials, molding trays and other molded products. It exhibits excellent effects as a substitute material for paper products, pulp molded products, etc.

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Claims (2)

[Claims] 1. A method for producing a biodegradable composite material, which comprises mixing fine cellulose fibers with a protein and a plasticizer, followed by hot press molding. 2. The method for producing a biodegradable composite material according to claim 1, wherein the hot press molding temperature is 50 to 250 ° C. and the hot press molding pressure is 10 to 200 Kgf / m ² .