Chemistry: fertilizers – Processes and products – Forms or conditioning
Patent
1994-11-29
1997-07-08
Lander, Ferris
Chemistry: fertilizers
Processes and products
Forms or conditioning
71 6411, 71 6413, C05G 300, C05G 500
Patent
active
056456247
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a granular fertilizer with a multilayer coating for agriculture and gardening. The fertilizer is coated with coating materials having different degrading rates in a multilayer structure in order to control the dissolving-out rate and dissolving-out profile of the fertilizer nutrients. The coating materials do not remain in soil or water since they are degraded by microorganisms or light after all the nutrients are dissolved out.
BACKGROUND ART
It has been proposed to coat fertilizers with various polymers and inorganic materials. For example, Japanese Patent Publication Nos. 28927/1965 and 13681/1967 disclose various coating materials, but they have difficulties in controlling the dissolving-out rate of fertilizer nutrients.
U.S. Pat. No. 4,369,055 and Japanese Patent Application Laid-Open No. 167197/1980 have tried to facilitate degradation of coating materials while maintaining the function for controlling the dissolving-out rate by dispersing inorganic powders such as sulfur and talc in a low molecular olefin polymer. However, the disclosed coating materials are not completely degraded and they remain in soil.
Further, U.S. Pat. Nos. 5,176,734 and 5,206,341 and Japanese Patent Application Laid-Open No. 146492/1991 propose to coat a fertilizer with a biodegradable polymer. They only disclose to coat the fertilizer with a biodegradable coating material in a single layer. The single layer coating has a difficulty in controlling both the dissolving-out rate of fertilizer nutrients and the biodegradability at the same time.
Japanese Patent Application Laid-Open No. 97561/1993 discloses a three layer coating prepared by using one type of biodegradable film and a water-soluble resin. It also has a difficulty in controlling both the dissolving-out rate and the biodegradability at the same time. The application discloses that a thickness of the coating material is 500 to 2,000 .mu.m. This invites high cost so that the coating material is not suitable for practical use.
The problem addressed by the present invention is to provide a granular fertilizer with a multilayer coating for agriculture and gardening, in which the dissolving-out rate and dissolving-out pattern of fertilizer nutrients are controllable and also the coating material does not remain in soil or water after the fertilizer nutrients are dissolved out.
DISCLOSURE OF THE INVENTION
The present inventors have made intensive and extensive studies to find that the above problem can be solved by coating a fertilizer with at least two types of coating materials having different dissolving-out rates and moisture permeability in a multilayer structure.
Namely, the present invention provides a granular fertilizer with a multilayer coating comprising a first layer containing at least one rapidly biodegradable polymer selected from the group consisting of a rapidly biodegradable aliphatic polyester and a rapidly biodegradable polyurethane compound, and a water-insoluble second layer containing at least one slowly biodegradable polymer selected from the group consisting of a slowly biodegradable cellulose derivative, low molecular weight polyethylene, low molecular weight wax and low molecular weight paraffin or light-degradable resins.
The first layer contains at least one rapidly biodegradable polymer selected from the group consisting of a rapidly biodegradable aliphatic polyester and a rapidly biodegradable polyurethane compound.
As criterion for biodegradability of plastics, colony growth rating of fungus is well known, which is disclosed in Biodegradable Plastics, Iwao Yamashita, CTI Processing Technology Researching Group, pp. 39-41 and The Encyclopedia of Chemical Technology, Supplemental Volume, 3rd Edition, J. E. Potts, John wiley & Sons, 1982, p. 626. The colony growth rating is measured according to ASTM G21-70 by taking the following steps.
Specimens are placed in or on a solid agar growth medium containing necessary components (excluding carbon) for the colony growth, and a suspension of fung
REFERENCES:
patent: 3264089 (1966-08-01), Hansen
patent: 4369055 (1983-01-01), Fujita et al.
patent: 5176734 (1993-01-01), Fujita et al.
patent: 5206341 (1993-04-01), Ibay et al.
patent: 5300135 (1994-04-01), Hudson et al.
Naka Hiroshi
Takase Shunsuke
Asahi Kasei Kogyo Kabushiki Kaisha
Lander Ferris
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