JP3194721B2 - Composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a composition having excellent biodegradability .

[0002]

2. Description of the Related Art Conventionally, in the field of agriculture, the insulation of soil,
Multi-films are used in large quantities for the purpose of preventing germination of weed seeds, preventing stains on fruits such as strawberries, and the like.
Most of these multi-films are mainly composed of polyethylene and are usually used for one or two years.

[0003]

The multi-film is usually collected and incinerated after use. However, since the recovery requires a great deal of labor, it is difficult to collect the multi-film. It is left in the field in anticipation of intentional decomposition by light or the like, causing various problems. Polyethylene is not so biodegradable as to be exaggerated,
It is well known that it exists semipermanently in the soil.

In recent years, blending of biodegradable starch, for example, to impart biodegradability to this polyethylene has been studied around the world, and various attempts have been made to improve the dispersion state of starch. ing. Further, a device for imparting photodegradability to polyethylene and approaching biodegradability, or blending of polyethylene with photodegradability and starch has been studied.

[0005] In the method of blending starch, it is recognized that the starch portion is decomposed by bacteria in the soil, so that the mechanical strength of the film is extremely reduced depending on the starch content, and eventually becomes fragmented. Can be However, it is not surprising that the polyethylene itself does not undergo biodegradation at that time, but is merely cut relatively finely, and is not essentially a solution. In addition, polyethylene to which photodegradation has been imparted merely causes a decrease in the degree of polymerization due to light, and is far from imparting biodegradability.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies with the aim of developing a composition imparted with a true biodegradability, and as a result, have found that ethylene-vinyl alcohol copolymer (EVOH) ) A composition consisting of 10 to 90% by weight and 90 to 10% by weight of raw starch has been found to be suitable.

In the present invention, it is surprising that by blending EVOH and raw starch, the biodegradability of EVOH is remarkably improved, and in particular, excellent characteristics can be imparted as an agricultural multi-film. It is. Furthermore, the film obtained by blending the EVOH and the raw starch in the present invention not only has excellent weather resistance, but also has excellent strength and water resistance. As described above, when used as an agricultural multi-film, the protective performance of the plant is sufficient, and when used and discarded in soil or water, it shows excellent microbial degradability, so the film of the present invention is used as a pollution-free multi-film. Very useful in industry.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, EVOH is a saponified ethylene-vinyl acetate copolymer having an ethylene content of 5 to 60 mol%, preferably 20 to 60 mol%, and a saponification degree of a vinyl acetate component. Is 90% or more, preferably 95%
The above can be used. EVOH can also contain other small amounts of copolymerized units in addition to ethylene units, vinyl alcohol units, and vinyl acetate units, and examples thereof include acrylic acid, methacrylic acid, crotonic acid, maleic acid, and the like. Unsaturated acids such as itaconic acid and maleic anhydride, salts thereof and alkyl esters, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, alkyl vinyl ether, N,
N-dimethylacrylamide, N-vinylpyrrolidone,
Examples thereof include vinyl chloride, vinylidene chloride, 2-acrylamidopropanesulfonic acid and salts thereof. However, it is not necessarily limited to these.

Further, the melt index of EVOH (M
I) (at 190 ° C. under a load of 2160 g): 0.1 to 50 g
/ 10 min, preferably 0.5 to 20 g / 10 min. The MI in the present invention is JIS K7210.
Measure according to However, in the present invention, EVOH
If the melting point exceeds 190 ° C. and the measurement of MI at 190 ° C. is difficult, it is measured at a plurality of temperatures exceeding 190 ° C. under a load of 2160 g, and the value extrapolated to the value of 190 ° C. I do.

[0010] EVOH is used in combination with raw starch.
In order to obtain a film having excellent strength and water resistance, it is preferably water-insoluble. When imparting water insolubility, the ethylene content is preferably selected from the range of 20 to 60 mol%. A composition excellent in biodegradability by blending such EVOH and raw starch,
It is clear from the examples described below that the film can be obtained and that the film has excellent properties when used as an agricultural multi-film.

In the present invention, raw starch refers to raw starch such as corn starch and potato starch, and processed starch (dextrin, oxidized starch, etherified starch, etc.) obtained by subjecting these to physical or chemical treatment.
Esterified starch, cationized starch, etc.) are not included.

In the present invention, the mixing ratio of EVOH and raw starch is 10 to 90% by weight for the former and 90 to 10% by weight for the latter.
% By weight. If the compounding ratio of EVOH is less than 10% by weight, a film having excellent strength, water resistance and weather resistance during use cannot be obtained, and if it exceeds 90% by weight, a film having excellent biodegradability cannot be obtained. The more preferable compounding ratio of EVOH is 25 to 80% by weight.

In the present invention, other additives, for example, plasticizers such as water and glycerin can be freely added for the purpose of enhancing the processability of raw starch and increasing the flexibility of the blend film. Further, other additives may be freely added as long as the object of the present invention is not hindered.

The film of the present invention comprising EVOH and raw starch can be obtained by melt-kneading the above-mentioned mixture of EVOH and raw starch, or a mixture of this mixture with other additives, and extruding the mixture. Can be At the time of melt-kneading and / or extrusion film formation, water is preferably present in less than 10% by weight, preferably 8% by weight or less, more preferably 6% by weight or less, based on the raw starch, and 0.3% by weight or less. It is preferable that these are present. After extrusion film formation, heat treatment or stretching (uniaxial or biaxial stretching) to impart excellent water resistance or physical strength can be appropriately performed depending on the purpose.

The obtained multi-film is often used as a single-layer film, but may also be used as a multi-layer film. It is also free to provide a layer made of another material (for example, a cellulosic paper, a nonwoven fabric, a woven fabric, a net, or another biodegradable film) as long as the object of the present invention is not hindered.

Further, a split yarn obtained by stretching a film and obtained by weaving or knitting is also one embodiment of the agricultural multi-film of the present invention.

[0017]

The present invention will be further described with reference to the following examples. Example 1 Fully saponified ethylene-vinyl alcohol copolymer having an ethylene content of 47 mol% {melt index: 15 g / 1
0 minutes (at 190 ° C. under a load of 2160 g)}, 40 parts by weight, 8 parts by weight of glycerin, and 52 parts by weight of corn starch adjusted to a water content of 1.5% by weight were kneaded, and pellets were prepared. After humidifying the pellets, a 100 μm thick film was formed at 165 ° C. using an extruder.

The film prepared in Example 1 was buried in soil collected from a farmer's field, kept at a temperature of 35 ° C. and under sufficient humidity for 6 months, taken out of the soil and observed. Table 1 shows the results.

[0019]

[Table 1]

From Table 1, it can be seen that the EVOH used has undergone microbial degradation. The film obtained in Example 1 had excellent weather resistance, mechanical strength, and water resistance, and had good properties when used as a multi-film.

[0021]

Industrial Applicability The composition of the present invention has excellent biodegradability, and the agricultural multi-film obtained thereby has the following features:
Has excellent weather resistance, mechanical strength and water resistance.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C08L 29/04 C08L 3/02

Claims (4)

(57) [Claims] 1. An ethylene content of 5 to 60 mol%, a saponification degree of 90% or more, and a melt index (190 ° C., 2160
(under g load) A composition comprising 10 to 90% by weight of an ethylene-vinyl alcohol copolymer having a weight of 0.1 to 50g / 10min and 90 to 10% by weight of raw starch. 2. The composition according to claim 1, wherein the water content of the raw starch is less than 10% by weight. 3. The composition according to claim 1, wherein the water content of the raw starch is 0.3% by weight or more. 4. A pellet comprising the composition according to claim 1.