JP2555545B2 - Method for producing cellulose / chitosan-based molded product - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a cellulose-chitosan-based molded article having improved mechanical strength and having biodegradability.

[0002]

2. Description of the Related Art Conventionally, a film, sheet or foam-molded article made of a thermoplastic resin such as polyolefin resin, polyvinyl chloride resin, polystyrene resin, etc.
Utilizing its characteristics, it is used for various purposes such as packaging materials, agricultural materials, and industrial materials.

However, since molded articles made of these thermoplastic resins are chemically stable, it takes a very long time to decompose once left in the natural environment. Therefore, the problem of their disposal has become a kind of social problem in recent years.

In view of such circumstances, various degradable plastics have been developed in recent years. For example, one obtained by adding a starch material such as corn starch to microbial degradability to polyolefin, one made of PHB (polyhydroxybutyrate) produced by a microorganism and its derivative, and one made of a composition composed of modified starch and modified PVA. Alternatively, photodegradable plastics in which a carbonyl group is introduced into the polymer main chain have been reported.

On the other hand, the inventors of the present invention have previously proposed a cellulose-chitosan-based microbial-degradable molded article composed of cellulose and chitosan (JP-A-2-6689 and JP-A-2-127486). In addition, a method for producing the molded product was also proposed (Japanese Patent Laid-Open No. 2-135730). This cellulose-chitosan-based microbial-degradable molded article has a fast microbial-degrading rate because it is a natural material, and has no adverse effect on the natural world after degradation. However, in terms of mechanical strength, both dry and wet conditions are almost good, but there is a problem that it is difficult to apply it in applications where particularly high mechanical strength is required. As a means for solving this problem, there is a method in which a cellulose-chitosan-based microbial-degradable molded article is molded and then kept at a temperature of around 100 ° C. for a certain period of time. According to this method, although the mechanical strength is certainly improved, there is a problem that the molded product is discolored brown with the improvement of the strength and the commercial price is lowered.

On the other hand, the corona discharge treatment is a method generally used for improving the printing characteristics of plastics such as polyethylene. However, there has not been reported yet that the strength of the plastic is improved by the corona discharge treatment. In addition, although there is a research example of subjecting cellulose to corona discharge treatment, no improvement in strength has been reported.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to machine a cellulose-chitosan-based molded article having a biodegradability of cellulose and chitosan by a simpler means without impairing the appearance of the molded article. It is to provide a method of improving the physical strength.

[0008]

According to the present invention, a cellulose-chitosan-based molding characterized by subjecting a molded product mainly composed of celluloses and chitosans to corona discharge treatment in an atmosphere in which oxygen is present. Further provided is a method for producing a product, wherein the molded product is a sheet or film obtained by casting an aqueous suspension containing celluloses and chitosans, wherein the cellulose-chitosan system is provided. A method of manufacturing a molded article is provided.

That is, the mechanical strength of a molded product of celluloses and chitosans is greatly improved by subjecting it to corona discharge treatment in an atmosphere containing oxygen, and in particular, a molded product of celluloses and chitosans. The present invention has been completed by finding that the effect is more remarkable when the sheet or film is obtained by casting an aqueous suspension containing celluloses and chitosans.

Hereinafter, the present invention will be described in detail. Cellulose used in the present invention, wood, straw,
Cellulose obtained from plants such as cotton, hemp, bamboo and bagasse,
Examples thereof include hemicellulose, lignocellulose, pectocellulose, and bacterial acetylcellulose produced by fungi. Among these, fibrous ones are preferable, and finely beaten fibers are particularly preferable.

On the other hand, the chitosans used in the present invention are deacetylated chitins obtained from shells of crustaceans such as crabs and shrimps, mycelium, etc., but the molecular weight and the degree of deacetylation of chitosans. Is not particularly limited. Since chitosans are insoluble in water as they are, they are usually used as an aqueous solution by forming a chitosan salt with an inorganic acid such as hydrochloric acid or an organic acid such as formic acid, acetic acid or lactic acid.

In the present invention, the molded product is composed of 20 to 99.5% by weight of celluloses and 0.5 to 40% by weight of chitosans.
It is preferable that the content is 30 to 70% by weight of celluloses and 10 to 20% by weight of chitosans. If the content of celluloses or chitosans is too small, the effect of corona discharge treatment cannot be fully exerted.

Further, in the present invention, known additives such as a plasticizer, a biodegradation aid such as protein and starch, a filler, a coloring agent, a foaming agent and the like may be used in combination if necessary.

The molded article of the present invention includes a film, a sheet, and a molded article having a certain three-dimensional shape,
It is a foam or the like.

The molded article containing cellulose and chitosan as main components of the present invention is, for example, prepared by mixing an aqueous dispersion of cellulose and an aqueous solution of chitosan salt to prepare an aqueous suspension containing cellulose and chitosan. Examples thereof include a method of casting this to produce a sheet or film, a method of applying an aqueous solution of chitosan salt to a cellulosic material such as paper, or a method of producing by dipping in the aqueous solution and then drying.
In particular, in the present invention, a molded product produced by casting the above-mentioned water suspension in a sheet shape or a film shape can be preferably used.

In the present invention, the molded product containing cellulose and chitosan as main components thus obtained is subjected to corona discharge treatment in an atmosphere in which oxygen is present. It is not particularly limited. For example, a sheet or film obtained by casting an aqueous suspension of celluloses and chitosans may be subjected to corona discharge treatment, or may be subjected to corona discharge treatment in the process of casting the aqueous suspension. Good. The treatment strength of the corona discharge treatment is not particularly limited, and it can be performed in a wide treatment strength range from a low treatment strength to a high treatment strength.

As described above, by subjecting a molded article containing celluloses and chitosans as main components to corona discharge treatment in an atmosphere in which oxygen is present, the strength of the resulting cellulose / chitosan molded article is improved. Although the mechanical mechanism is not clear, a carbonyl group is generated in a part of the cellulose component in the molded product by subjecting the molded product mainly composed of celluloses and chitosans to corona discharge treatment in an atmosphere containing oxygen. It is believed that a Schiff base cross-linking structure is formed between the carbonyl group and the amino group in the chitosan molecule, resulting in improvement in mechanical strength. Such an effect is higher when the thickness of the molded product made of cellulose and chitosan is smaller. Therefore, the shape of the molded product is preferably sheet-like or film-like, and the thickness thereof is particularly preferably 100 μm or less.

[0018]

EXAMPLES The present invention will now be specifically described with reference to examples, but the present invention is not limited thereto. still,
The tensile strength and the elongation in the examples were measured by using an autograph AG-5000 manufactured by Shimadzu Corporation, and ASTM D-88 was used.
It measured based on 2. Also, in this embodiment, as a corona discharge treatment device, ε-TREATER manufactured by Betahorn Co., Ltd.
(Corona discharge treatment width: 1.3 m) was used.

Production Example An aqueous dispersion of fine cellulose fibers (concentration 4 wt%) obtained by beating hardwood pulp, an aqueous chitosan acetate solution, diglycerin as a plasticizer, and an aqueous gelatin solution as a biodegradation aid, Cellulose: chitosan: diglycerin: gelatin are mixed so that the weight ratio is 100: 30: 75: 2, and the solid content concentration in the mixed solution is 4%. A suspension was obtained. This water suspension was cast on an endless belt through a die slit, dried at a temperature of 140 ° C., and then peeled off from the endless belt to obtain a sheet-shaped molded product made of cellulose and chitosan. . The thickness of this molded product was 50 μm.

Examples 1 to 4 and Comparative Example Both sides of the sheet-like molded article composed of cellulose and chitosan obtained in the Production Example were treated in air at a treatment speed of 15 m / mi.
n, corona discharge treatment was performed with a predetermined corona discharge treatment power to obtain a cellulose-chitosan-based molded product of the present invention. This molded product showed no change in appearance and showed excellent biodegradability.
The tensile strength and elongation are shown in Table 1. In addition, for comparison, Table 1 also shows the tensile strength and elongation of the molded product not subjected to the corona discharge treatment.

[0021]

[Table 1]

[0022]

EFFECTS OF THE INVENTION According to the method of the present invention, the strength of a cellulose / chitosan-based molded article containing cellulose and chitosan as main components can be improved without impairing the appearance, and particularly strong mechanical strength is required. It can be applied to the intended use.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location C08L 5/00 LAW C08L 5/00 LAW // B29K 1:00 (72) Inventor Kunio Kanaoka Kagawa Prefecture 1515 Nakatsu-cho, Marugame City Okura Industry Co., Ltd. (72) Kenji Tateishi 1515 Nakatsu-cho, Marugame City Kagawa Prefecture Okura Industry Co., Ltd. (72) Inventor Akihiko Ueda 1515 Nakatsu-cho Marugame City Kagawa Prefecture Okura Industry Co., Ltd. Internal Examiner Ryuichi Ide (56) References Japanese Patent Publication Sho 45-6433 (JP, B1)

Claims (2)

(57) [Claims] 1. A method for producing a cellulose-chitosan-based molded article, which comprises subjecting a molded article containing cellulose and chitosan as main components to corona discharge treatment in an atmosphere in which oxygen is present. 2. The cellulose-chitosan-based molding according to claim 1, wherein the molded product is a sheet or film obtained by casting an aqueous suspension containing celluloses and chitosans. Method of manufacturing goods.