Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-09-04
2003-07-22
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
Reexamination Certificate
active
06596788
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a composition useful as a biodegradable material.
In recent years, an interest in “biodegradable plastic” is very high. The biodegradable plastic referred to so in the invention means “a plastic that can be used similarly to ordinary plastics during use, becomes low-molecular compounds through the participation of microbes or moisture in the natural world after use, and finally decomposes into water and carbon dioxide”, and is expected particularly to be applied in the fields of agriculture and forestry. For example, when applying to multifilm, if the film is unnecessary to be collected after harvest and it can be degraded only by plowing back, the labor saving will be possible. However, traditional biodegradable plastics have such problems that the biodegradation rate is not necessarily enough, and the like.
With respect to the biodegradable material capable of converting to film, moldings, etc., the purpose of the invention is to provide a biodegradable composition that allows drastic labor saving particularly in the fields of agriculture and forestry, because of easy biodegradation and additional fertilizer effect etc. as well, and a method of producing the same.
As a result of diligent investigations, the inventors have found that a composition obtainable by formulating yeast and biodegradable plastic at a particular proportion can solve the subject as described above, leading to the completion of the invention.
SUMMARY OF THE INVENTION
The invention relates to a biodegradable composition comprising yeast (A) and biodegradable plastic (B) at a particular proportion. The purpose is to provide a biodegradable composition having very good biodegradability and additional fertilizer effect, making good use of the characteristics of yeast.
DETAILED DESCRIPTION OF THE INVENTION
The yeast (A) to be used in the invention is not particularly restricted, and baker's yeast, alcohol yeast, sake yeast, further brewer's yeast produced in large quantities, and the like can be used.
As the examples of such yeasts,
Saccharomyces cerevisiae
(IFO 1954, IFO 0309, IAM 4274),
Candida utilis
(IFO 0619, ATCC 15239),
Torulopsis nodaensis
(IFO 1942),
Torulopsis stellata
(IFO 1953),
Hansenula anomala
(IFO 1150), etc. are mentioned.
Moreover, yeasts after treatment of extraction etc. such as yeast after extracted nucleic acid (denucleated yeast) are also useful.
The yeast can be used as a lump of yeast, but it is preferable for yeast to be in the shape of passing through a screen with mesh opening of 53 &mgr;m by pulverization etc. In the case of yeast in the shape of not passing through a screen with mesh opening of 53 &mgr;m, the flexibility of film becomes poor when converting to film. More preferable is a yeast in the shape of passing through a screen with mesh opening of 38 &mgr;m.
The yeast contains nitrogen, phosphoric acid and potassium being three big components of fertilizer in abundance and is an organic fertilizer with very high composting effect. Moreover, amino acid In the yeast is taken into the plant body and has also an action of increasing flavor.
Furthermore, the cell wall of yeast consisting of polysaccharides such as glucan and mannan is subject to decomposition in the soil, and the decomposed products are conducive to useful microbes in soil as sugar sources to take part in the propagation thereof, thus bringing about a thickening effect on fruits.
For the biodegradable plastic (B) to be used in the invention, the thermoplastic biodegradable resins known currently as biodegradable plastics are usable, and, for example, resins produced by microbes such as polyhydroxybutyrate, chemically synthesized resins such as polycaprolactone, poly(butylene succinate), poly(butylene succinate·adipate), poly(ethylene succinate), poly(glycolic acid), poly(lactic acid) and poly(vinyl alcohol), and further resins obtained by modifying natural products such as cellulose acetate and thermally plasticized starch are usable. In particular, biodegradable polyester is preferable from the aspect of physical properties. As the biodegradable polyesters, polycaprolactone, poly(butylene succinate), poly(butylene succinate·adipate), poly(ethylene succinate), poly(glycolic acid), poly(lactic acid), etc. as described above are mentioned. These can be used also by combining two or more kinds.
It is required that the formulating proportion of yeast (A) to biodegradable plastic (B) is within a range of following general formula 1. Besides, in the invention, these indicate dry weights.
A: 90~10 parts by weight B: 10~90 parts by weight
A+B=
100 parts by weight General formula 1
If the proportion of yeast (A) exceeds 90 parts by weight, then the flexibility cannot be obtained at all when converting to moldings, and, in particular, when converting to film etc., the use becomes difficult. Also, if the proportion of yeast (A) is under 10 parts by weight, then the promotion of biodegradation rate becomes insufficient. More preferable is a range of general formula 2.
A: 50~10 parts by weight B: 50~90 parts by weight
A+B=
100 parts by weight General formula 2
The inventive composition allows to adjust the biodegradation rate depending on the uses. For example, when the biodegradation rate is too fast depending on the use, it is possible to make the biodegradation rate slower, by additionally formulating lignin with low hydrophilicity, than that before formulation. The formulation level of lignin is preferable to be within a range of not exceeding 40 parts by weight based on 100 parts by weight of yeast used. If exceeding 40 parts by weight, then the inhibitory effect of the biodegradation becomes significant. Moreover, since lignin is used for the purpose of inhibiting the biodegradation, lignin with lower hydrophilicity is advantageous. Lignin with higher hydrophilicity will be dissolved out with rainwater to inversely promote the biodegradation of moldings. Concretely, the content of organic sulfur in lignin is preferable to be 3% by weight or less. The content of organic sulfur indicates the extent of hydrophilicity of lignin and becomes an index of solubility into water.
The inventive composition can be used in combination with natural high-molecular polysaccharides and their derivatives produced industrially in large quantities such as cellulose, starch and chitin-chitosan, within a range of not deviating from the gist of the invention. As the celluloses, wood pulp fibers manufactured through sulfite process and kraft process, regenerated cellulose, cotton, raw cotton, etc. can be mentioned and wood pulp fibers produced in large quantities are preferable. Moreover, mechanical pulp, wood flour, bamboo flour, etc. containing relatively more lignin are also usable. Furthermore, in the invention, plasticizer, blowing agent, dye and pigment, agricultural chemicals, etc. used commonly can also be added, if need be, for use. Fertilizer component may be added additionally. The addition levels thereof are determined appropriately depending on the purposes, but it is preferable to be within a range of not exceeding 80 parts by weight based on 100 parts by weight of the inventive biodegradable composition.
The inventive biodegradable composition is ordinarily converted to moldings, after yeast and biodegradable plastic are formulated at a fixed proportion and kneaded. The kneading equipment and molding equipment used are not particularly restricted and equipments known hitherto can be used.
For example, as the kneading equipments, roll mill, intensive mixer, single-screw extruder, double-screw extruder, etc. are mentioned. It is required to set the kneading temperature over the melting point of biodegradable plastic for melting and kneading, but it can be altered appropriately depending on the characteristics of raw material, formulation ratio, kneading situation, etc.
Moreover, if the yeast and biodegradable plastic are molten and kneaded in the presence of 3 to 20% by weight of moisture based on y
Arai Makoto
Kawamura Masanobu
Nishijima Eiji
Tabata Masahiko
Nippon Paper Industries Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Sanders Kriellion A.
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