JPH05148387A - Flexible biodegradable film or sheet, and its preparation - Google Patents

Abstract

PURPOSE:To prepare the subject film or sheet which exhibits no degradation in flexibility and appearance due to aging and is excellent as a nonpolluting material for packaging and agricultural uses. CONSTITUTION:The objective film or sheet is prepd. by mixing a minute celulose fiber, a chitosan soln., and polyglycerol, forming the mixture into a film or sheet, and drying the film or sheet.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a biodegradable film or sheet which is rapidly decomposed by microorganisms.

[0002]

2. Description of the Related Art Plastics represented by polyethylene, polystyrene, polyvinyl chloride and the like are used for various purposes by taking advantage of their excellent characteristics. However, since these plastics are not decomposed in the natural environment, the problem of environmental pollution due to plastics has been highlighted in recent years. Against this background, biodegradable plastics such as polycaprolactone, polylactic acid, and polyhydroxybutyrate and its derivatives produced by microorganisms are used as plastic materials that are easily decomposed by microorganisms in soil and do not give a burden to the environment. Is proposed. In addition, many biodegradable materials using natural products such as starch, cellulose, chitosan, and pullulan have been proposed.

The inventors of the present invention previously prepared a novel biodegradable composite sheet [Japanese Patent Laid-Open No. 2-6689] obtained by compositing a natural material cellulose fiber and chitosan, and adding starch to the composite sheet to form a composite. Water-absorbent composite material
-281050], cellulosic fibers and chitosan,
And a water resistant film formed by combining glycerin [Patent Document 2]
-127486]. These have greatly improved the poor water resistance common to molding materials that use natural materials, and because they are composed mainly of natural materials, they have the excellent feature of being rapidly decomposed by microorganisms in the soil. Have

However, the composite sheet comprising the above-mentioned cellulose fiber and chitosan and the composite material obtained by adding starch to the composite sheet are expected to be utilized for various purposes by taking advantage of their excellent characteristics, but the obtained molded article is flexible. It is not suitable for applications requiring flexibility because it lacks in properties. Further, the sheet obtained by compositing cellulose fiber and chitosan, and glycerin, glycerin is added as a control agent of the biodegradation period, but in addition to this control effect, it also shows the effect as a plasticizer, so the obtained sheet Results in added flexibility. However, when the sheet containing glycerin is viewed from the viewpoint of the plasticizing effect, there is a problem that the glycerin volatilizes with time and the sheet becomes hard.

[0005]

DISCLOSURE OF THE INVENTION The present invention overcomes these drawbacks of the prior art, has flexibility that does not deteriorate over time, does not deteriorate the appearance, and is suitable for packaging and agriculture. It is an object of the present invention to provide an excellent biodegradable sheet free from environmental pollution in fields such as gardening.

[0006]

According to the present invention, there is provided a flexible biodegradable film or sheet comprising fine cellulose fibers, chitosan and polyglycerin, and fine cellulose fibers and Provided is a method for producing a flexible biodegradable film or sheet, which comprises mixing a chitosan solution and polyglycerin and drying the mixture.

Generally, the plasticizer not only gives the substrate sufficient flexibility, but also is sufficiently compatible with the substrate to prevent nonuniformity and stickiness, and does not separate or volatilize and escape over time. Is required. From these viewpoints, the present inventors have conducted various studies on plasticizers suitable for composite sheets composed of cellulose fibers and chitosan. Composite sheet consisting of cellulose fiber and chitosan is produced by mixing cellulose fiber and chitosan solution and drying, so it is used for general plastics, such as phthalate ester, aliphatic dibasic acid ester, trimellitic acid ester. Water-insoluble plasticizers such as the above were not suitable. Further, generally, for water-soluble plastics, polyhydric alcohols such as glycerin, ethylene glycol, polyethylene glycol and sorbitol are used as plasticizers. Therefore, in a composite sheet composed of cellulose fibers and chitosan, various polyhydric alcohols were examined as a plasticizer, and it was found that the condition as the plasticizer was satisfied only when polyglycerin was used, leading to the present invention. It was

The cellulose fibers used in the present invention include cellulose obtained from plants such as wood, straw, cotton, hemp, bamboo, and bacca, hemicellulose, lignocellulose, pectocellulose, and bacterial cellulose produced by fungi. The fibers are raised. These cellulose fibers can be made fine by various known methods, but finely beaten cellulose fibers are preferably used. Regarding the size of the fine cellulose fiber, the length is 2 mm or less,
A diameter of 10 μm or less, preferably a length of 1 mm or less,
The diameter is 5 μm or less, particularly preferably 0.5 mm or less and the diameter is 1 μm or less. If the size of the fine cellulose fibers exceeds the above range, the strength and transparency are deteriorated, which is not preferable.

The chitosan used in the present invention is deacetylated by subjecting chitin obtained from the shells of crustaceans such as crabs and shrimp, the shells of insects, mycelia, etc. to a chemical or biological treatment. Is. The molecular weight and degree of deacetylation of chitosan are not particularly limited, but those having a degree of deacetylation of 60% or more are preferable in terms of solubility. Since chitosan is not soluble in water as it is, it is used as a chitosan solution by dissolving it in an inorganic acid such as hydrochloric acid or a dilute aqueous acid solution of an organic acid such as formic acid, acetic acid, or lactic acid.

As the polyglycerin used in the present invention, those having a dimer or more and no more than 10 mer of glycerin are particularly preferably used. Also, a mixture of a small amount of glycerin may be used.

The blending ratio of the raw materials used is 2 to 100 parts by weight of chitosan and 10 to 200 parts by weight of polyglycerin per 100 parts by weight of fine cellulose fiber, particularly 5 to 80 parts by weight of chitosan and 50 to 150 parts of polyglycerin. Is preferred. If the content of chitosan is less than 2 parts by weight or exceeds 100 parts by weight, the wet strength becomes weak, which is not preferable.
Further, if the amount of polyglycerin is less than 10 parts by weight, flexibility is not imparted, and if it exceeds 200 parts by weight, the strength is lowered, which is not preferable. The flexible biodegradable sheet of the present invention may be one in which starch is added to impart water absorbability, or protein is added to accelerate biodegradability.

A method for producing a flexible biodegradable sheet of the present invention will be described. Fine cellulose fibers, a chitosan solution and polyglycerin are mixed to obtain a sheet and a composition for forming. A sheet having excellent strength and flexibility can be obtained by forming a sheet by a casting method or the like and drying it to form a composite. 30 as the drying temperature
C.-200.degree. C., especially 50.degree. C.-160.degree. C. are preferred. If the drying temperature exceeds 200 ° C., some decomposition starts and it is not preferable.

[0013]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. Tensile strength is ASTM D882-81
It was measured according to. Stiffness is 15 mm wide and 9 thick
The 0 μ film was measured using a film stiffener tester. The biodegradability test was conducted by filling the film in a plastic container containing soil and applying 3% at 23 ° C and 95 to 100% RH.
After leaving it for a month, it was dug out and the disassembled state was observed.

Example 1 Aqueous dispersion of finely beaten cellulose fibers [Daic Chemical Industry Co., Ltd. MFC-100 cellulose content 4% by weight]
100 parts by weight and chitosan [Katoyoshi Co., Ltd. Chitosan 10
B] 80 parts by weight of a solution prepared by dissolving 0.8 parts by weight in a 0.5% by weight acetic acid aqueous solution, 3 parts by weight of diglycerin [Unicel G2 manufactured by Daicel Chemical Industries Ltd.], and 300 parts by weight of water are sufficiently mixed. .. This was cast on a glass plate and dried at 70 ° C. for 6 hours to obtain a semitransparent film having flexibility. Immediately after preparation of the obtained film and at 23 ° C., 50% RH
Table 1 shows the appearance, stiffness, tensile strength, and weight change after standing for 6 months. In the biodegradability test, the film was decomposed to the extent that the original shape was not retained.

Example 2 A translucent film having flexibility was obtained in the same manner as in Example 1 except that a hexamer of glycerin [UNIGLY G6 manufactured by Daicel Chemical Industries, Ltd.] was used in place of diglycerin. .. Immediately after preparation of the obtained film and at 23 ° C., 50% RH
Table 1 shows the appearance, stiffness, tensile strength, and weight change after standing for 6 months. In the biodegradability test, the film was decomposed to the extent that the original shape was not retained.

[0016]

[Table 1]

Comparative Example 1 A semitransparent film was obtained in the same manner as in Example 1 except that the polyhydric alcohol shown in Table 2 was used instead of diglycerin. Immediately after preparation of the obtained film and at 23 ° C., 50%
Appearance, stiffness, tensile strength after being left for 6 months at RH,
And the change in weight is shown in Table 2. As is clear from Table 2, when glycerin or trimethylolpropane was used, weight loss due to volatilization was observed over time, and the flexibility of the film also decreased. When trimethylolethane or sorbitol was used, crystals began to precipitate on the film surface over time. Further, when mannitol or petaneerythritol was used, the film did not have flexibility.

[0018]

[Table 2]

Comparative Example 2 As a polyhydric alcohol instead of diglycerin, ethylene glycol, diethylene glycol, 1,4-butanediol, 1,6-hexanediol, polyethylene glycol # 200, # 400, # 600, polypropylene glycol # 400, A film was obtained in the same manner as in Example 1 except that neopentyl glycol was used.
However, the compatibility with the substrate was poor and all the films were whitened.

[0020]

Industrial Applicability The biodegradable film or sheet of the present invention has flexibility that does not deteriorate over time and does not deteriorate the appearance, and is suitable for packaging and agricultural / horticultural fields. As a pollution-free material, it has an excellent effect. Further, according to the present invention, the biodegradable film or sheet can be produced by an industrially advantageous method.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jun Hosokawa 2-3-3 Hananomiyamachi, Takamatsu City, Kagawa Prefecture, Shikoku Institute of Industrial Technology, Institute of Industrial Technology (72) Inventor, 1 year Yoshihara, Takamatsu City, Kagawa Prefecture 2-3-3 Miyanomachi, Shikoku Institute of Industrial Technology, Institute of Industrial Technology (72) Inventor Takamasa Kubo 2-3-3, Hananomiyacho, Takamatsu City, Kagawa Prefecture, Shikoku Institute of Industrial Technology (72) ) Inventor Satoshi Maruyama 1515 Nakatsu-cho, Marugame-shi, Kagawa Inside the Okura Industrial Co., Ltd. Research Institute (72) Kunio Kanaoka 1515 Nakatsu-cho, Marugame-shi, Kagawa Inside Okura Industrial Co., Ltd. (72) Inventor Akihiko Ueda Kagawa 1515 Nakatsu-machi, Marugame-shi, Japan Inside the Okura Industrial Co., Ltd. Research Institute (72) Inventor Kenji Tateishi 1515 Nakatsu-cho, Marugame-shi Kagawa Inside Okura Industrial Co., Ltd. (72) Inventor Kazuo Kondo 1515 Nakatsu-cho, Marugame-shi, Kagawa Okura Industrial Co., Ltd.

Claims (2)

[Claims] 1. A flexible biodegradable film or sheet comprising fine cellulose fibers, chitosan, and polyglycerin. 2. A method for producing a flexible biodegradable film or sheet, which comprises mixing fine cellulose fibers, a chitosan solution, and polyglycerin and drying the mixture.