JPH0459829A - Production of composite material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for producing a composite material that has excellent strength and flexibility and is degradable by microorganisms in soil, and is suitable for packaging, agriculture, and horticulture. It is useful in fields such as films and materials for use in plastics, molded trays, etc.

[Conventional technology]

Conventionally, many molded bodies made from natural products such as cellulose, starch, and chitosan have been known.

However, all of these have problems such as having lower strength than general-purpose plastics, dissolving in water, and having extremely low strength in wet conditions.

In order to improve these problems, complicated operations such as reacting with a cross-linking agent such as formaldehyde in the case of molded objects using starch, or fixing with alkali in the case of molded objects using chitosan are carried out. It is being said.

The present inventors have developed a new composite material that has strength equal to or greater than that of general-purpose plastics, and that maintains sufficient strength even in water and in wet conditions, by a simple method of combining the natural materials cellulose and chitosan. He discovered that the material could be obtained and applied for a patent. (Japanese Unexamined Patent Publication No. 2-6689) This composite material is also quickly decomposed by microorganisms in the soil, and as plastic pollution has become a problem in recent years,
It has also been found that it is useful as a non-polluting molding material.

[Problem that the invention seeks to solve]

The above-mentioned composite material made of cellulose and chitosan can be used for packaging, agriculture, horticulture, and various other uses due to its excellent strength. According to the law, it is necessary to provide flexibility. Therefore, for the purpose of imparting flexibility, known water-soluble plasticizers such as glycerin, sorbitol, ethylene glycol, and polyethylene glycol are added. The problem is that a large amount of the agent is drawn out and the product loses its flexibility when dried again.

[Means to solve the problem]

The present inventors conducted intensive studies to solve the above-mentioned problems when adding flexibility to a novel composite material consisting of cellulose and chitosan using a known plasticizer, and found that fine cellulose fibers and chitosan The authors discovered that by mixing and drying an aqueous salt solution and a water-soluble synthetic polymer, a composite material with excellent strength and flexibility that does not lose its flexibility even when immersed in water can be obtained. This led to the invention.

Furthermore, it has been found that they are also degraded by microorganisms in the soil.

Examples of cellulose fibers used in the present invention include fibers made of cellulose, hemicellulose, lignocellulose, and pectocellulose obtained from plants such as wood, straw, cotton, hemp, bamboo, and Jacas, and bacterial cellulose produced by bacteria. It will be done.

Although these cellulose fibers can be made fine by various known methods, finely beaten cellulose fibers are particularly preferably used.

Regarding the size of fine cellulose fibers, the length is 3000
μ or less, the diameter is 50 μ or less, and particularly preferably the length is 1000 μ or less and the diameter is 30 μ or less.

When the size of fine cellulose fibers exceeds the above range,
This is undesirable because strength and transparency decrease.

The chitosan used in the present invention is deacetylated chitin obtained from the shells of crustaceans such as crabs and shrimps, the rinds of insects, mycelium, etc. through chemical or biological treatment. be.

There are no particular restrictions on the molecular weight or degree of deacetylation of chitosan, but from the viewpoint of solubility, the degree of deacetylation is preferably 60% or more.

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

The water-soluble synthetic polymer used in the present invention includes an aqueous solution of a water-soluble polymer such as polyvinyl alcohol,
or substantially water-insoluble polymers such as polyurethane, polyacrylic esters or copolymers thereof, polyvinyl acetate or copolymers thereof, polyesters, polyamides, polyethylene oxides, etc., dispersed in water with or without emulsifiers. The following can be mentioned. These are commercially available, for example, under trade names such as Superflex and Superflex E from Dai-Kota Pharmaceutical Co., Ltd. and Natalilik, Yodozol, and Resin from Kanebo NSC Co., Ltd.

Among the above water-soluble synthetic polymers, water-soluble polyurethane is
It is particularly preferably used in terms of flexibility and microbial degradability.

The method for manufacturing the composite material of the present invention is as follows. By mixing fine cellulose fibers, an aqueous solution of chitosan salt, and an aqueous polymer, and drying the mixture, the composite is completed and the composite material has excellent strength and flexibility. is obtained.

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

The blending ratio of the raw materials used is: 10 fine cellulose fibers
0 parts by weight, 2 to 100 parts by weight of chitosan, 10 to 600 parts by weight as the polymer content of the water-soluble synthetic polymer, especially 5 to 80 parts by weight of chitosan, and 20 to 400 parts by weight as the polymer content of the water-soluble synthetic polymer. preferable. If the amount of chitosan exceeds 2 parts by weight or 100 parts by weight, the wet strength will become weak, which is not preferable. Further, if the polymer content of the water-soluble synthetic polymer is less than 10 parts by weight, flexibility will not be imparted, and if it exceeds 600 parts by weight, microbial decomposition will deteriorate, which is not preferable.

Also, the drying temperature is room/! The range of i to 200'C1, particularly 50°C to 160°C, is preferred. Drying temperature is 2
If the temperature exceeds 00°C, partial decomposition will begin, which is not preferable.

In addition, when producing the composite material of the present invention, it is also possible to add additives such as starch, organic fillers such as silica, inorganic fillers, colorants, etc., if necessary.

[Effect]

The composite material obtained according to the production method of the present invention exhibits excellent dry strength and sufficient wet strength due to the combination of cellulose and chitosan during the drying process, and is also provided with flexibility by the polymer component in the aqueous polymer. Since the polymer component in the composite material does not dissolve in large amounts in water like ordinary water-soluble plasticizers, the composite material of the present invention does not lose flexibility even after being immersed in water.

Additionally, because it uses natural polysaccharides such as cellulose and chitosan as the main raw materials, it is decomposed by microorganisms in the soil.

[Example: Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. All parts in these examples represent parts by weight.

Tensile strength was measured according to ASTM 08B2-all, and wet strength was measured after immersing the sample in water at 23°C for 24 hours.
I took it out and immediately measured it.

Stiffness was measured using a film stiffness tester on a film with a width of 15++ m and a thickness of 90 μm.

Weight loss due to water immersion was determined by immersing the sample in 23°C water for 24 hours, taking it out and drying it, and then determining the weight loss rate.

The microbial decomposition test was carried out by burying a sample in a plastic container filled with soil, leaving it at 23° C. and 95-100% RH for 3 months, digging out the sample, and observing its decomposition state.

Examples 1 to 5 An aqueous dispersion of fine cellulose fibers (concentration IWT%) obtained by beating softwood bleached pulp and an aqueous solution of chitosan acetate (
i degree IWT%) and the aqueous polymer shown in Table 1 are mixed in such a manner that the amount of chitosan is 20 parts and the polymer component in the aqueous polymer is 75 parts per 100 parts of fine cellulose fiber.

This was temporarily cast into glass and dried with air at 70°C for 6 hours to obtain a translucent film.

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

Furthermore, in the microbial decomposition test, the Φ film was eventually decomposed to such an extent that it did not retain its original shape.

Comparative Examples 1 to 4 An aqueous dispersion of fine cellulose fibers (concentration 1″7%) obtained by beating softwood bleach bulbs and an aqueous solution of chitosan acetate (
Concentration l''T%) and the plasticizer shown in Table 2 were mixed so that 20 parts of chitosan and 75 parts of plasticizer were mixed with 100 parts of fine cellulose fibers, and a film was formed in the same manner as in Examples 1 to 5. I got the film.

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

Table 1 Table 2 Tables 1 and 2 show that the film obtained by the production method of the present invention has almost the same tensile strength and flexibility as a film using a normal plasticizer, but It is clear that there is no large amount of plasticizer leaching into the water as seen in the case.

Examples 6 to 15 An aqueous dispersion of fine cellulose fibers obtained by beating softwood bleached pulp (1.7% per degree) and an aqueous solution of chitosan acetate (
(Concentration: 11+H%) and aqueous polymer were mixed to have the composition shown in Table 3, and films were formed in the same manner as in Examples 1 to 5.

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

Furthermore, in the microbial decomposition test, all films were decomposed to such an extent that their original shapes were not retained.

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

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

From Table 3, it is clear that the use of the aqueous polymer imparts flexibility to the film and that it is less leached into water.

〔Effect of the invention〕

The composite material obtained by the present invention has excellent dry strength and sufficient wet strength, and has flexibility that does not lose even after being immersed in water, and can be used as a film or sheet for packaging or for AM meetings. It is particularly effective for molded objects that require flexibility.

In addition, since it has the property of being decomposed by microorganisms, it biodegrades in the soil after a certain period of time after being disposed of, making it an excellent non-polluting molding material that does not have a negative impact on the environment.

Claims (2)

[Claims] (1) A method for producing a composite material, which comprises mixing fine cellulose fibers, an aqueous chitosan salt solution, and an aqueous polymer, and drying the mixture. (2) A method for producing a composite material, which comprises mixing fine cellulose fibers, an aqueous chitosan salt solution, and water-soluble polyurethane, and drying the mixture.