JPH03131636A - New composite material and production thereof - Google Patents

Abstract

PURPOSE:To obtain a composite material useful as packaging film, agricultural and horticultural film, materials, molding tray, having excellent strength, decomposable with microorganisms in soil, by blending fine cellulosic fibers with an aqueous solution of protein and drying. CONSTITUTION:Fine cellulosic fibers (preferably fibers having <=1,000mu length and <=30mu diameter) are mixed with an aqueous solution of a protein (e.g. casein, gluten, soybean protein, gelatin) preferably at 50-160 deg.C and dried to give the composite material.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a novel composite material that has excellent strength and can be decomposed by microorganisms in soil, and is suitable for use in films and materials for packaging, agriculture and horticulture. , molded trays, etc.

[Prior Art] Many molded bodies made from natural products such as cellulose, starch, protein, and chitosan have been known. but,
These have lower strength than general plastics, and also have problems such as dissolving in water and extremely low strength in wet conditions.

In order to improve these problems, for example, in the case of a molded article using starch, a cross-linking agent such as formaldehyde is reacted, and in the case of a molded article using protein, a cross-linking agent such as isocyanate or dimethylol urea is reacted. In addition, in the case of a molded article using chitosan, complicated operations such as alkali fixation are performed.

On the other hand, plastic pollution has become a major problem in recent years, and there is a strong desire to develop plastics that can be incorporated into the natural decay cycle.

[Problems to be Solved by the Invention] The present invention solves, in a simple manner, the problem that molded bodies made of natural products cannot maintain their shape and strength in water or in wet conditions. The present invention provides a pollution-free molding material that can be formed into a film that quickly decomposes in the soil after use.

[Means for Solving the Problems] As a result of intensive studies on various combinations of natural products, the present inventors found that when fine cellulose fibers and proteins are dried alone, their shape and shape change in water or in a wet state. Despite not being able to maintain strength, the inventors have discovered that by mixing and drying them, they can be composited for the first time, and have excellent dry strength as well as sufficient strength even in water, leading to the present invention.

Furthermore, it was also found that these were decomposed by microorganisms in the soil.

Examples of cellulose fibers used in the present invention include cellulose, hemicellulose, lignocellulose, and pectocellulose obtained from plants such as wood, straw, cotton, hemp, bamboo, and bagasse, and bacterial cellulose produced by bacteria. 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 fiber, 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.

Moreover, there is no problem even if some fibers larger than those mentioned above are mixed in these.

The protein used in the present invention and L7 are casein,
Examples include those obtained by separating or concentrating from various animals, plants, and microorganisms, such as albumin, gluten, soybean protein, gelatin, and glue. These can be used alone or in combination of two or more.

In the present invention, a plasticizer is used for the purpose of imparting flexibility to the molding material. The plasticizer used is not particularly limited as long as it is water-soluble or hydrophilic, but examples include glycerin, sorbitol, trimethylolpropane, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, polyethylene glycol, and polypropylene glycol. Polyhydric alcohols such as the following are preferably used.

In the method for producing the composite material of the present invention, first, a protein is dissolved in water whose pH is adjusted to be suitable for dissolving the protein. The resulting aqueous protein solution is mixed with fine cellulose fibers,
Furthermore, if a plasticizer is used, the plasticizer is mixed therein.

Note that the mixing order is not limited to this. By evaporating water from this mixture and drying it, the novel composite material of the present invention in which fine cellulose and protein are combined can be obtained.

Although the details of the compounding mechanism are not clear,
It is presumed that the hydroxyl groups and carboxyl groups in cellulose and the amino groups and carboxyl groups in proteins form chemical bonds with each other during drying and form a complex.

The drying temperature is room temperature to 200°C, particularly preferably 5°C.
0-160°C is used.

On the other hand, when preparing the above mixture, it is also possible to add additives such as colorants, fillers, reinforcing agents, etc., if necessary.

[Function] When the fine cellulose fibers and protein used in the present invention are molded individually, they dissolve in water or in a wet state, and even if they keep their shape, they have only very weak strength. However, when they are mixed together, It forms a composite by drying, maintains its shape even in water, and exhibits sufficient wet strength. Also, since it uses natural raw materials, it is easily decomposed by microorganisms in the soil.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. In these examples, all parts refer to parts by weight.

Moreover, the tensile strength was measured according to ASTM D88281. Wet tensile strength was measured immediately after the sample was immersed in water at 23°C for 24 hours and then taken out. In the microbial decomposition test, the sample was buried in a plastic container containing soil, and the sample was heated at 23°C195~
After being left at 100% RH for 2 months, the sample was dug out and its state of decomposition was observed.

Example 1 Fine cellulose fiber 1 obtained by beating softwood bleached bulb
00 parts of an aqueous dispersion (concentration 4 wt%) are mixed with an aqueous solution of 10 parts gelatin (concentration 5-1%, pH 6). This was cast onto a glass plate and dried with air at 70° C. for 15 hours to obtain a translucent film with a thickness of 60 to 70 μm.

The resulting film has a dry tensile strength of 1102 kg/
ci and a wet tensile strength of 104 kg/crA, and in the microbial decomposition test, it was decomposed to such an extent that it did not retain its original shape.

Examples 2-6 Fine cellulose fibers 1 obtained by beating coniferous bleached bulbs
00 parts of an aqueous dispersion (concentration 4 wt%), a predetermined amount of gelatin aqueous solution (concentration 5 wt%, pH 6), and glycerin 5
0 parts and formed into a film in the same manner as in Example 1.

Table 1 shows the tensile strength 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 Example 1 Fine cellulose fiber 1 obtained by beating softwood bleached bulb
00 parts of an aqueous dispersion (concentration: 4 wt%) and 50 parts of glycerin were mixed and formed into a film in the same manner as in Example 1.

Table 1 shows the tensile strength of the obtained film.

Comparative Example 2 An aqueous solution of 100 parts of gelatin (concentration: 5 wt %, pH 6) and 50 parts of glycerin were mixed and formed into a film in the same manner as in Example 1.

Table 1 shows the tensile strength of the obtained film.

Example 7 Fine cellulose fiber 1 obtained by beating softwood bleached bulb
00 parts of the aqueous dispersion (concentration 4 wt%) was mixed with π-type casein IO.
of the aqueous solution (concentration: 3 wt %, pH 8) and 50 parts of glycerin, and formed into a film in the same manner as in Example 1.

The resulting film has a dry tensile strength of 1003 kg
/ cIIff, wet tensile strength 104kg/CT
A, and in the microbial decomposition test, it was decomposed to such an extent that it did not retain its original shape.

Comparative example 3 100 parts of pore casein dissolved in water M (concentration 3 wt%).

pH 8) and 50 parts of glycerin were mixed and formed into a film in the same manner as in Example 1.

The resulting film had a dry tensile strength of 167 kg;
However, the tensile strength when wet was so weak that it could not be measured.

Example 8 Fine cellulose fiber 1 obtained by beating softwood bleached bulb
00 parts of an aqueous dispersion (a degree 4 wt%) was mixed with 20 parts of dairy casein.
of an aqueous solution (concentration: 3 wt%, pH 8) and 50 parts of glycerin. This was cast onto a glass plate and 70°
C for 5 hours, and then dried with air at 60°C for 1 hour to obtain a translucent film with a thickness of 60 to 70 μm.

The obtained film has a dry tensile strength of 861 kg//
ci, and the wet tensile strength was 215 kg/cffl, and in the microbial decomposition test, it was decomposed to such an extent that it did not retain its original shape.

Example 9 Fine cellulose fiber 1 obtained by beating softwood bleached bulb
00 parts of an aqueous dispersion (concentration: 4 wt%) is mixed with an aqueous solution of 10 parts of soybean protein (concentration: 3 wt%, pH 8), and 100 parts of ethylene glycol. This was cast onto a glass plate and dried at 70°C for 5 hours and then at 130°C for 1 hour to obtain a translucent film with a thickness of 60 to 70μ.

The resulting film had a dry tensile strength of 952 kg/
cod, and the wet tensile strength was 219 kg/cffl, and in the microbial decomposition test, it was decomposed to such an extent that it did not retain its original shape.

[Effects of the Invention] The film-formable composite material obtained by the present invention has excellent dry strength and sufficient wet strength, and since it is made from natural materials, it does not produce harmful substances even after being decomposed. It has these characteristics and exhibits excellent effects as a non-polluting molding material in fields such as packaging films, agricultural films, molded trays, and seedling pots.

Claims (4)

[Claims] (1) A novel composite material characterized by consisting of fine cellulose fibers and protein. (2) A novel composite material consisting of fine cellulose fibers, proteins, and plasticizers. (3) A method for producing a novel composite material characterized by mixing fine cellulose fibers and an aqueous protein solution and drying the mixture. (4) A method for producing a novel composite material, which comprises mixing fine cellulose fibers, an aqueous protein solution, and a plasticizer, and drying the mixture.