JPH0678438B2 - Method of manufacturing composite material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a composite material which has excellent strength and flexibility and can be decomposed by microorganisms in soil. It is useful in the fields of film and materials for use, molding trays, etc.

[Conventional technology]

Conventionally, many molded products made of natural products such as cellulose, starch, and chitosan are known.

However, all of them have problems that they are weak in strength as compared with general-purpose plastics, they dissolve in water, and their strength is extremely weak in a wet state.

In order to improve these problems, for example, complicated operations such as reacting a cross-linking agent such as formaldehyde in the case of a molded article using starch and fixing an alkali in the case of a molded article using chitosan are performed. It is being appreciated.

By the simple method of compounding cellulose and chitosan, which are natural materials of the present inventors, a novel composite that has strength equal to or higher than that of general-purpose plastic and retains sufficient strength even in water or in a wet state. He found that he could obtain the material and applied for a patent. (Japanese Patent Laid-Open No. 2-6689) This composite material is also rapidly decomposed by microorganisms in soil, and plastic pollution has become a problem in recent years.
It was also found to be useful as a pollution-free molding material.

[Problems to be Solved by the Invention] The composite material composed of cellulose and chitosan is used for packaging, agricultural and horticultural, and various other applications by utilizing its excellent strength. Since the molded product obtained is a little hard, it is necessary to impart flexibility depending on the intended use. Therefore, for the purpose of imparting flexibility, known water-soluble plasticizers such as glycerin, sorbitol, ethylene glycol, and polyethylene glycol are added, but when the molded body thus obtained is immersed in water, it is plasticized. There is a problem in that a large amount of the drug escapes and the product dried again loses its flexibility.

[Means for solving problems]

The present inventor has conducted a diligent study to solve the above problems when imparting flexibility to a novel composite material composed of cellulose and chitosan by using a known plasticizer, and as a result, it is fibrillated by beating. By mixing and drying the finely divided cellulose fibers, an aqueous chitosan salt solution, and a polyurethane aqueous dispersion, a composite material having excellent strength and flexibility and not losing its flexibility even when immersed in water is obtained. The inventors have found that they can be obtained and have reached the present invention.

Furthermore, they have also been found to be degraded by microorganisms in the soil.

The fine cellulose used in the present invention is obtained by beating the cellulose fibers by beating by various known methods.

For the size of such fine cellulosic fibers, length 30
00μ or less, diameter 50μ or less, especially length 1000μ or less,
The diameter is preferably 30 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.

Cellulose fibers used in the present invention include wood, straw, cotton, hemp, bamboo, cellulose obtained from plants such as bacas, hemicellulose, lignocellulose, fibers made of pectocellulose and bacterial cellulose produced by fungi. .

The chitosan used in the present invention is deacetylated by subjecting chitin obtained from shells of crustaceans such as crab and shrimp, outer coat of insects, mycelium and the like to a chemical or biological treatment.

The molecular weight and the deacetylation degree of chitosan are not particularly limited, but those having a deacetylation degree of 60% or more are preferable in terms of solubility.

Since chitosan does not dissolve in water as it is, it is used as a chitosan salt in water with an inorganic acid such as hydrochloric acid or an organic acid such as formic acid, acetic acid or lactic acid.

The polyurethane aqueous dispersion used in the present invention means polyurethane dispersed in water with or without an emulsifier.

As the polyurethane, any conventionally known unmodified or modified polyurethane can be used. Examples of these polyurethane aqueous dispersions include Superflex and Superflex E manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. and Iodozole manufactured by Kanebo UNC Co., Ltd.

The method for producing the composite material of the present invention shows that an aqueous solution of fine cellulose fibers and an aqueous chitosan salt is mixed, and a polyurethane aqueous dispersion is mixed, and the composite is completed, which has excellent strength and flexibility. A composite material is obtained.

Although the mechanism of conjugation is not clear, it is presumed that a chemical bond is formed between the carbonyl group in cellulose and the amino group in chitosan during the drying process.

The blending ratio of the raw materials used is 100% fine cellulose fibers.
2 to 100 parts by weight of chitosan, 10 to 600 parts by weight of the polymer content of the polyurethane water dispersion, particularly 5 to 80 parts by weight of chitosan, and 20 to 400 parts by weight of the polymer content of the water dispersion of polyurethane are preferable. If the amount of chitosan exceeds 2 parts by weight or exceeds 100 parts by weight, the wet strength becomes weak, which is not preferable. Further, if the polymer content of the polyurethane aqueous dispersion is less than 10 parts by weight, flexibility is not imparted, and if it exceeds 600 parts by weight, microbial degradability is deteriorated, which is not preferable.

The drying temperature is room temperature to 200 ° C, especially 50 ° C to 160 ° C.
Is preferred. If the drying temperature exceeds 200 ° C, some decomposition starts and it is not preferable.

When manufacturing the composite material of the present invention, it is possible to add organic or inorganic fillers such as starch and silica, and additives such as colorants, if necessary.

[Action]

The composite material obtained according to the production method of the present invention exhibits excellent dry strength and sufficient wet strength due to the composite of cellulose and chitosan in the drying process, and is imparted with flexibility by polyurethane. The polyurethane in the composite is
Since it does not elute in a large amount in water like ordinary water-soluble plasticizers, the composite material of the present invention does not lose its flexibility even after immersion in water.

In addition, since natural polysaccharides such as cellulose and chitosan are used as the main raw material, they are decomposed by microorganisms in the soil.

〔Example〕

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. Parts in these examples represent all parts by weight.

The tensile strength was measured according to ASTM 882-81, and the wet strength was measured immediately after the sample was immersed in water at 23 ° C for 24 hours and then taken out.

The stiffness was measured by using a film stiffener tester with a filter having a width of 15 mm and a thickness of 90 μm.

Regarding the weight reduction by immersion in water, the sample was immersed in water at 23 ° C. for 24 hours, taken out and dried, and the weight reduction rate was obtained.

The microbial degradability test was carried out by burying the sample in a plastic container containing soil, leaving it at 23 ° C. and 95 to 100% RH for 3 months, and then digging out the sample and observing the state of decomposition.

Examples 1 to 3 An aqueous dispersion of fine cellulose fibers obtained by beating softwood bleached pulp (concentration 1 wt%), an aqueous solution of chitosan acetate salt (concentration 1 wt%), and an aqueous polyurethane dispersion shown in Table 1,
Mix 100 parts of fine cellulose fibers with 20 parts of chitosan and 75 parts of polyurethane component in the polyurethane aqueous dispersion. This was cast on a glass plate and blow-dried at 70 ° C. for 6 hours to obtain a translucent film.

Table 1 shows the tensile strength, stiffness, and weight change of the obtained film due to immersion in water.

Further, in the microbial degradability test, all the films were decomposed to the extent that the original shape was not retained.

Comparative Examples 1 to 4 An aqueous dispersion of fine cellulose fibers (concentration 1 wt%) obtained by beating softwood bleached pulp, an aqueous solution of chitosan acetate (concentration 1 wt%), and a plasticizer shown in Table 2 were used. 20 parts by weight of chitosan and 75 parts by weight of a plasticizer were mixed, and a film was formed in the same manner as in Examples 1 to 5.

Table 2 shows the tensile strength, stiffness, and weight change of the obtained film due to immersion in water.

From Table 1 and Table 2, the film obtained by the production method of the present invention has a tensile strength and flexibility that are almost the same as those of a film using a normal plasticizer, but it is observed when a normal plasticizer is used. It is clear that large amounts of such plasticizers do not elute in water.

Examples 4 to 12 An aqueous dispersion of fine cellulose fibers obtained by beating softwood bleached pulp (concentration 1 wt%), an aqueous solution of chitosan acetate (concentration 1 wt%), and an aqueous polyurethane dispersion were prepared as shown in Table 3. The resulting mixture was mixed and formed into a film in the same manner as in Examples 1 to 3.

Table 3 shows the tensile strength, stiffness, and weight change due to water immersion of the obtained film.

Further, in the microbial degradability test, all the films were decomposed to the extent that the original shape was not retained.

Comparative Examples 5 to 7 An aqueous dispersion of fine cellulose fibers (concentration 1 wt%) obtained by beating softwood bleached pulp and an aqueous solution of chitosan acetate (concentration 1 wt%) were mixed so as to have the composition shown in Table 3, A film was obtained by forming a film in the same manner as in Examples 1 to 3.

Table 3 shows the tensile strength, stiffness, and weight change of the obtained film due to immersion in water.

From Table 3, it is clear that the use of the aqueous polyurethane dispersion gives the film flexibility and less elution into water.

[Advantages of the Invention] The composite material obtained by the present invention has excellent dry strength and sufficient wet strength, and also has flexibility that is not lost even after being immersed in water. Particularly effective as a molded product requiring flexibility such as the film and sheet.

Further, since it has the property of being decomposed by microorganisms, it is biodegraded in the soil after a certain period of time after disposal, and exhibits an excellent effect as a pollution-free molding material that does not adversely affect the environment.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location C08L 75:04 (72) Inventor Yoshihara One year 2-3-3 Hananomiyacho, Takamatsu City, Kagawa Prefecture No. Shikoku Institute of Industrial Technology, Institute of Industrial Technology (72) Takamasa Kubo, 2-3-3 Hananomiyamachi, Takamatsu City, Kagawa Prefecture Inside Shikoku Institute of Industrial Technology, Institute of Industrial Technology (72) Kunio Kanaoka Marugame, Kagawa Prefecture 1515 Nakatsucho, Nakatsu, Okura Industrial Co., Ltd. Research Institute (72) Inventor Kazuo Kondo 1515 Nakatsucho, Marugame, Kagawa Pref. Inside Research Institute, Okura Industrial Co., Ltd. Industrial Co., Ltd. Research Institute (72) Inventor Kenji Tateishi 1515 Nakatsu-cho, Marugame, Kagawa Okura Industrial Co., Ltd. Research Institute (72) Inventor Akihiko Ueda, Marugame, Kagawa 1515 Tsumachi, Okura Kogyo Co., Ltd. Researcher, Researcher, Masami Kobayashi (56) Reference: JP-A-3-143901 (JP, A)

Claims (1)

[Claims] 1. A method for producing a composite material, which comprises mixing fine cellulose fibers fibrillated by beating, an aqueous chitosan salt solution, and an aqueous polyurethane dispersion, and drying the mixture.