CA2078273C

CA2078273C - Granular fertilizer encapsuled with a decomposable coating

Info

Publication number: CA2078273C
Application number: CA002078273A
Authority: CA
Inventors: Shigeo Okuda; Hiroki Kai
Original assignee: Asahi Kasei Kogyo KK
Current assignee: Chisso Asahi Fertilizer Co Ltd
Priority date: 1991-09-19
Filing date: 1992-09-15
Publication date: 1996-12-10
Anticipated expiration: 2012-09-15
Also published as: GB2259698B; TW210995B; FR2681593A1; DE4231153C2; GB9218765D0; DE4231153A1; KR930005943A; GB2259698A; KR950007161B1; FR2681593B1; CA2078273A1; GB9219445D0

Abstract

A novel granular fertilizer encapsuled with a decomposable coating, the coating comprising a vinyl resin containing at least one type of metal complex. The dissolving period of the fertilizer of the present invention does not change drasti-cally in any cultures, and after the components of the fer-tilizer dissolves, the coating degrades and decomposes under natural environmental conditions.

Description

Backqround of the Invention 1. Field of the Invention The present invention relates to granular fertilizers whose granules are encapsuled with polymeric coatings decom-posable by the action of light, enzymes and/or microorganisms.

2. Description of Related Art Various types of fertilizers have been developed to work effectively in accordance with the growth of crops.
Particularly, many granular fertilizers, the surface of which is encapsuled with a coating material, have been developed and sold in the market. For example, various coating materials have been proposed in U.S. Patent No. 3,295,950, Japanese Patent Publication Nos. 28927/1965 and 28457/1969, British Patent No. 815,829 and Japanese Patent Publication Nos.
15832/1962 and 13681/1967. However, these materials are not sufficient to adjust the dissolving rate of the fertilizer components.
On the other hand, Japanese Patent Publicatioin No. 21952/
1985 and U.S. Patent No. 4,369,055 disclose coating methods, wherein the granular fertilizer is sprayed with the solution of the coating material and is simultaneously dried with hot air when the granular fertilizer is encapsuled with the coating material comprising a polyolefin as the main com-ponent. They also disclose, as a characteristic of this tech-nology, that the dissolving rate can be adjusted.
U.S. Patent No. 4,369,055 and Japanese Patent Application Laid-Open No. 167197/1980 disclose that, by dispersing inorga-nic powder such as talc and the like or sulphur into the ..
coating comprising a polyolefin resin or the like, control of the dissolution function is maintained and also the degrada-tion and decomposition of the resudal coating are promoted, after the fertilizer components dissolve.
However, the coatings of conventionally coated granular fertilizer degrade and decompose very slowly after the com-ponents of the fertilizers dissolve. Therefore, the coating remains in and on the surface of the soil for a long period.
It may cause poor growth of crops and environmental pollution in the soil, and in nearly irrigation canals, rivers and the like.
Further, for the purpose of improving the degradation and decomposition of the coating, European Patent Unexamined Publication No. 255,160 suggests a method wherein a copolymer of ethylene-carbon monoxide is added. Also, European Patent UnPx~ined Publication No. 252,553 discloses a method wherein a terpolymer of ethylene-vinyl acetate-carbon monoxide is employed as an effective component.
Though the degradation rate of these fertilizers is acce-lerated under sunlight, however, it is not satisfactory when crops are grown in greenhouses such as those made of glass which easily absorbs W radiation. Further, when these fer-tilizers are applied to the surface of the soil, their degra-dation rate is too high, so that the dissolving control function is destroyed and excess fertilizers are dissolved while crops are growing, which causes problems due to the high fertilizer concentration.
Therefore, an object of the present invention is to pro-vide fertilizer compositions capable of being applied tovarious kinds of plants without undue disruption of the natural environment. The fertilizer has a coating with degra-dation and decomposition properties, permitting said coating to be degraded and decomposed by sunlight even in the greenhouse and having a lag time in the initiation period of the degradation and decomposition processes.
SummarY of the Invention The present inventors have made extensive and intensive studies about the coating material in order to solve the above problems. Then, they have completed the present invention.
That is, the present invention provides a novel granular fertilizer encapsuled with a decomposable coating, the coating comprising a vinyl resin containing at least one type of the metal complexes, which posseses the above-mentioned proper-ties.
Brief descriPtion of the Drawinqs Fig. 1 shows one of the preferable coating apparatus in the present invention.
Numerals and symbols are as follows:
1: Spouting column 2: Fertilizer-feeding port 3: Exhaust gas-discharging port 4: Nozzle for a fluid 5: Pump 6: Valve 7: Discharging port 8: Heat exchanger 9: Orifice meter 2 0 7 8 Z 7 ~

10: Blower 11: Tank for liquid Tl, T2 and T3: Thermometers SL: Steam Fig. 2 shows the changes of the ring strength arranged in the glass greenhouse for the degradation and decomposition tests in Examples and Comparative Examples of the present invention.
Fig.3 shows the changes of the ring strength arranged out-side for the degradation and decomposition tests in Examples and Comparative Examples of the present invention.
Detailed DescriPtion of the Invention In one aspect of the present invention, there is provided a granular fertilizer encapsuled with a decomposable coating, the coating comprising a vinyl resin containing at least one metal complex selected from the following group:
(1) the first complex, wherein the complexing agent is bonded to a metal through oxygen and the metal is a transition metal; and (2) the second complex, wherein the complexing agent is bonded to a metal through sulphur and the metal is a transition metal or a metal of group II or IV of the periodic table of the elements.
In another aspect of the present invention, there is also provided a method for fertilizing plants, comprising applying an effective fertilizing amount of the above-mentioned gran-nular fertilizer.

As the metal complex of the present invention, represen-tative examples of the first complex include an iron acetonyl-acetonate, an iron acetylacetonate, cobalt acetonylacetonate, cobalt acetyl-acetonate and the like. Representative examples of the second complex include an iron, nickel, zinc or tin dialkyldithiocarbamate wherein alkyl preferably has 1 to 20 carbon atoms; an iron, nickel, zinc or tin dithiophosphate; an iron, nickel, zinc or tin xanthate; an iron, nickel, zinc or tin benzthiazole; and the like. An iron or cobalt acetonyl-acetonate, an iron or cobalt acetylacetonate and an iron, nickel,-zinc or tin dialkylditiocarbamate are preferred.
A concentration of these complexes in the coating is optionally selected according to the period and the rate of the degradation and decomposition and the like. When the con-centration of the complexes is too low, the degradation and decomposition of the coating are not sufficient. When the concentration of the complexes is too high, the complexing agents are believed to cause bad effect on crops. Therefore, the concentration is ordinarily preferably in the range of 0.02 x 10-4 to 20.0 x 10-4 mol, more preferably 0.1 x 10-4 to 5.0 x 10-4 mol per 100 g of the decomposable coating.
In the present invention, inert pigments, dyes, other con-ventional additives and carbon black can be added besides two types of the complexes.
Further, an antioxidant and other compounding ingredients (e.g., blowing agents, stabilizers, lubrificants, antistatic agents and antiblocking agents) can be used in ordinary amounts.

- In the present invention, the vinyl resin is a polyolefin such as polyethylene, polypropylene, polybutene and the like, polystyrene, polyvinylacetate, polyvinylchloride, polyvinyli-dene chloride, a polyacrylate, polymethyl methacrylate, polyacrylonitrile, a polyvinyl ether, a polyvinyl ketone, a dien polymer, copolymers containing the corresponding mono-mers, and mixtures of these polymers.
Representative examples of diene polymers include a buta-diene polymer, an isoprene polymer, a chloroprene polymer, a butadiene-styrene copolymer, an ethylene-propylene-diene polymer, a styrene-isoprene copolymer, and the like.
Representative examples of copolymers containing olefin include an ethylene-propylene copolymer, a butene-ethylene copolymer, a butene-propylene copolymer, an ethylene-vinylacetate copolymer, an ethylene-acrylic acid copolymer, an ethylene-acrylic ester copolymer, an ethylene-methacrylic acid copolymer, an ethylene-methacrylic ester copolymer, an ethylene-carbon monoxide copolymer, an ethylene-vinylacetate-carbon monoxide copolymer, and the like.
Representative examples of copolymers containing vinyl chloride are a vinyl chloride-vinyl acetate copolymer, and a vinylidene chloride-vinyl chloride copolymer.
In addition to the above vinyl resins, one or more types of the coating materials selected from the group consisting of polycaprolactone, waxes, natural resin, fats and oils, and modified materials thereof can be used as coating materials in order to obtain the appropriate dissolving rate of the fer-tilizer components corresponding to the growth rate of crops ._ by adjusting the degradation and decomposition period of the coating.
Representative examples of waxes include bees wax, Japan wax, paraffin and the like. Representative examples of natural resins include natural rubber, rosin and the like.
Representative examples of fats and oils and these modified materials include hardened oil, solid fatty acids, metallic salts thereof and the like.
A type of the fertilizer to be used in the present inven-tion is not particularly limited. Known chemical fertilizers including ammonium sulfate, ammonium chloride, ammonium nitrate, urea, potassium chloride, potassium sulfate, potassium nitrate, sodium nitrate, ammonium phosphate, potassium phosphate, lime phosphate, salts containing microelements and fertilizers compounded from a plurality of these fertilizers can be used.
In the present invention, the percentage of the coating material to the coated granular fertilizer, i.e., coating ratio, is preferably 2 to 20% by weight, based on the coated granular fertilizer. The vinyl resin constitutes 1 to 100~ by weight based on the coating material, and the other coating components constitute 0 to 99~ by weight based on the coating material. The coating ratio and the compounding ratio of the vinyl resin containing the metal complexes to other coating elements can be selected, according to the types of crops and the degradation period desired.
For obtaining the appropriate dissolving rate of the fer-tilizer corresponding to the growth of crops by adjusting the ~_ 2078273 degradation and decomposition period of the coating, inorganic particles such as talc, calcium carbonate, clay, bentonite, silica, diatomaceous earth, metallic oxides, sulphur or the like, or organic particles such as starch or the like can be used as a low water-soluble or water-insoluble filler, which is capable of mixlng in the range of O to 90% by weight based on the coating material. Those mixtures with the filler and the coating material have to be dispersed uniformly on the fertilizer. When the mixture is not dispersed uniformly, a continuous layer of the coating composition will be broken by agglomerations of fine particles, and the effect of the coating will be impaired.
Further, a surface-active agent can be added to adjust the dissolving rate, if necessary.
To obtain the granular fertilizer of the present inven-tion, a solution, in which the coating material is dissolved or dispersed in organic solvent, is kept at high temperature.
Then, the solution is sprayed onto the granular fertilizer.
At the same time, the sprayed fertilizer is instantly dryed with a high stream of hot air. As a result, the coated granu-lar fertilizer of the present invention is obtained.
Any organic solvent may be suitable for use in the present invention, if it is capable of dissolving or dispersing in the coating material.
In the present invention, an effective fertilizing amount of the fertilizer would be apparent to those skilled in the art having the benefit of the present disclosure before them.
Description of Preferred Embodiments ~"_ The present invention will be illustrated in more detail with reference to the following non-limiting Examples and Comparative Examples.
[Example 1]
(1) Apparatus and producing method:
Figure 1 shows an example of a preferred appratus comprising a spouting column 1 having a column diameter of 200 mm, height of 1,800 mm, and air-spouting diameter of 42 mm, a fertilizer-feeding port 2 and an exhaust gas-discharging port 3. Air is sent from the blower 10 via the orifice flowmeter 9 and the heat-exchanger 8 to the spouting column 1. The flow rate and the air temperature are controlled by the flowmeter and the heat-exchanger, respectively, and the exhaust gas is discharged from column 1 through the discharging port 3. The granular fertilizer subjected to the coating treatment is fed through the fertilizer-feeding port 2 with a certain amount of hot air to form the spout.
The coating treatment is conducted by blowing the coating liquid through the fluid-nozzle 4 towards the spout in the spray form when the temperature of the coating particle reaches a certain degree. The coating liquid is prepared by feeding certain amounts of the coating material and the solvent in the tank 11 with stirring at about the boiling point of the solvent. The coating liquid is fed to the nozzle 4 by the pump S. This system should be well-warmed in advance to maintain the temperature. After a certain amount of the coating liquid is fed, the pump 5 and blower 10 are stopped.
The resultant coated fertilizer is taken out from the _ g ~ 2078273 discharging port 7. The coating of the granular fertilizer is conducted under the following basic condition~ in all Examples.
Fluid-nozzle: opening 0.8 mm, full cone type Amount of hot air: 4 m3/min.
Temperature of hot air: 100 C
Type of the fertilizer: granular potassium nitro-phosphate of 5 to 7 meshes Amount of the fertilizer at its feeding port: 5 kg Concentration of the coating solution: solids content 5 wt. %
Amount of the coating solution fed: O.5 kg/min.
Solvent: perchloroethylene Coating time: 10 minutes Percentage coating (relative to fertilizer): 5.5 wt. %
According to the above-mentioned apparatus and procedure, 5% by weight of polyethylene cont~i ni ng iron di-isononyldithiocarbamate (2.5 x 10-4 mol/lOOg) (Coating Material 1), 25% by weight of polyethylene and 20% by weight of ethylene-vinyl acetate copolymer (Coating Material 2), and 20% by weight of talc (Coating Material 3) are added to per-chloroethylene and warmed. The resulting coating liquid is blowed in the spout and dried to obtain granular fertilizers having coating percentage of 5.5%.
(2) Coating degradation and decomposition test:
Each of 60 granules (particle size: 2.8-4.0 mm) obtained in Example 1(1) is subjected to a two-surface-cutoff, followed by allowing the resulting granules to stand still in water, whereby the inside fertilizer of the granules is removed to prepare ring coatings (width: 2.5-3.0 mm, thicknes~: approx.
40 ~) Fertilized diluvial soil (obtained in Fu~i City) is placed in the box to prepare the bed, followed by arranging the ring coatings on the bed and placing the resulting box in the glass greenhouse and outside. Water is sometimes poured into the bed to prevent from drying up. Samples are collected every three months to observe the state of the ring coating and measure its strength. The ring strength of the coating is measured as follows. The breaking load is measured by means of SUN RHEO METER (Model CR-150) manufactured and sold by Sun Scientific Co., Ltd. The measured load (g) represents the ring strength. The observation results are shown in Tables 5 and 6. The changes of the ring strength arranged in the glass greenhouse are shown in Fig. 2. The changes of the ring strength arranged outside are shown in Fig. 3.
[Examples 2 to 21]
By means of the same apparatus and procedures as in Example 1(1), the coated potassium nitro-phosphate fertilizers are produced, which comprise various types of the coating materials as shown in Tables 1, 2, 3 and 4.
According to the same procedure as in Example 1(2), the resulting granules are tested for their degradation and decom-position properties. The observed results of the resulting rings are shown in Tables 5 and 6. As for the results of Examples 2 to 4, the changes of the ring strength arranged in the glass greenhouse are shown in Fig. 2 and the changes of the ring strength arranged outside are shown in Fig. 3.

* trade-mark ~ [Comparative Examples 1 and 2] 2 0 7 8 2 7 3 By means of the same apparatus and procedures as in Example 1(1), the coated potassium nitro-phosphate fertilizers are produced by using the coating materials as shown in Table 1.
According to the same procedures as in Example 1(2), the resulting granules are tested for their degradation and decom-position properties. The observed results of the resulting rings are shown in Tables 5 and 6, and the changes of the ring strength are shown in Figs. 2 and 3.
As is apparent from the above results, the coated granular fertilizer of the present invention has the following desired effects:
1. the dissolving period of the fertilizer does not change drastically in any cultures, e.g., in the open air culture or in the greenhouse such as the glass greenhouse which easily absorbs W radiation;
2. after the components of the fertilizer are dissolved, the coating degrades and decomposes under natural environmen-tal condition;
3. after crop growth has ceased, the coating degrades and decomposes and the residual components disappear so that it becomes easier to control the growth of crops by feeding fertilizers; and, 4. since the coating of the present fertilizer has a lag time in the initiation period of the degradation and decom-position, it is possible to prevent crops from being closed with too much fertilizer at the beginning of the culture and from being stres~ed by excessively high fer-tilizer concentrations.

~078273 Tabl~~1 Component of coating material (~) Example Coating material 1 Coating material 2 material 3 Polyethylene 30.0 C 1 Ethylene-vinyl 20 0 Talc SO.O
o acetate copolymer M

P.
Ethylene-carbon 30 0 E monoxide copolymer X. 2 Ethylene-vinyl n 50.0 acetate carbon 20.0 monoxide terpolymer Polyethylene containing Polyethylene 25.0 1 iron di-isononyldithio- 5 0 n 50.0 E carbamate Ethylene-vinyl 20 0 (2.5 x 10-4 molllOOg) acetate copolymer X

Polyethylene 10.0 2 n 20.0 Ethylene-vinyl 20.0 n 50 . O
A acetate copolymer M Polyethylene containing iron di-isononyldithio- Polyethylene 45.0 carbamate P 3 (2.5 x 10-4 molllOOg) and 5.0 Ethylene-vinyl 10 o n 40.0 nickel di-isononyldithio- acetate copolymer carbamate L (5 x 10-4 mol/lOOg) E Polyethylene 15.0 4 n 15.0 Ethylene-vinyl 20 0 n 50 . O
acetate copolymer Tabl~~2 Component of coating material (Z) Example Coating material 1 Coating material 2 material 3 . . Polyethylene 25.0 Calucium Poiyethylene contaln1ng carbonate 5 iron acetonylacetonate 5.0 Ethylene-vinyl (7 X 10-4 mol/lOOg) acetate copolymer 20-0 50,0 E

Polyethylene containing iron acetylacetonate X 6 (5 x 10- 4 mol/lOOg) and 50.0 Talc 50.0 zinc diethyldithiocarbamate (1.5 x 10-4 mol/lOOg) A

Polyethylene 50.0 7 r 5.0 Ethylene-vinyl 45 0 acetate copolymer M

Polyethylene 10.0 8 n 20.0 Ethylene-vinyl 20 0Talc 50.0 P acetate copolymer Polycaprolactone 10.0 L 9 r 10 . 0 Ethylene-vinyl 20 0 60.0 acetate copolymer E Polypropylene containing Polyethylene 20.0 iron acetylacetonate (5 x 10-4 mol/lOOg) and 10.0 Ethylene-vinyl 20 0 " 50-0 nickel dimethyldithiocarbamate acetate copolymer (1.5 x 10-4 mol/lOOg) - 20~8273 Table 3 Component of coating material (Z) Example Coating material 1 Coating material 2 Coating Polyethylene containing Ethylene-carbon 20.0 iron acetylacetonate monoxide copolymer 11 (5 x 10-4 mol/lOOg) and 10.0 Talc 50.0 zinc diethyldithiocarbamate Ethylene-vinyl 20.0 E (1.5 x 10-4 mol/lOOg) acetate copolymer X Polyethylene 15.0 12 n 15.0 Polybutadiene 20 0 n 50.0 rubber A
Polyethylene 20.0 M 13 n 30 . O n 20 . O
Petroleum resin 30 . 0 p Polyethylene 25.0 14 n 20 . 0 n 45.0 L Japan wax 10.0 20.0 Polyvinylidene 30 0 n 50 0 chloride Polyethylene 30.0 16 n 15.0 n 40.0 Rosin 15.0 20782~3 .
Table 4 .

Component of coating material (~) Example Coating material 1 Coating material 2 Coating polyethylene containing copolymer Polyethylene containing iron acetylacetonate of methyl vinyl ZO.O
E17 (5 x 10-4 mol!lOOg) and lO.o ketn and methyl- Talc 50.0 zinc diethyldlthiocarbamate ( 1 . 5 X 10- 4 mol/lOOg) Ethylene-vinyl 20 0 X acetate copolymer A Polyethylene containing Polyethylene 20.0 18 iron acetylacetonate 10.0 . n 50 . 0 (5 x 10- 4 mol/lOOg) Ethylene-vlnyl 20.0 M acetate copolymer P Polyethylene containing Polyethylene 18.0 .19 iron acetonylacetonate 12.0 . , 50 . 0 (7 x 10-4 mol/lOOg) Ethylene-vlnyl 20.0 L acetate copolymer Polyethylene contai n i ng Polyethylene 20 . 0 tin di-isononyldithio- 15 . 0 . n 40 . 0 carbamate (4 x 10-4 mol/lOOg) Ethylene-vlnyl 25.0 acetate copolymer le 5 2078273 xample State of the coating arranged on the surface of the soil in the glass greenhouse 1 After 12 months, no change is observed.

p After 6 months, a part hardening is observed. - 2 After 9 months, hardening is observed all over the coating.
X After 12 months, the coating is degraded by the external pressure.

After 3 months, hardening is observed all over the coating.
l After 6 months, the coating got crumbly and is degraded easily by the weak external pressure.
E After 3 months, the coating gets crumbly and is degraded by the 2 external pressure.
After 6 months, the coating gets crumbly and is degraded easily by the weak external pressure.
X 3 After 6 months, a part hardening is observed.
After 9 months, the coating is degraded by the external pressure.
4 After 3 months, a part hardening is observed.
After 6 months, the coating is degraded by the external pressure.
5 Same as in Example 1.
6 Same as in Example 2.
M 7 Same as in Example 4.
8 Same as in Example 2.
9 Same as in Example 1.
lO Same as in Example 1.
11 Same as in Example 2.
L 12 Same as in Example 2.

13 Same as in Example 4.

14 Same as in Example 1.
lS Same as in Example 2.
16 Same as in Example 1.
17 Same as in Example 2.
18 Same as in Example 2.
l9 Same as in Example 2.

Same as in Example 4.

~e 6 State of the coating arranged on the ~urface Example of the 90il outside C 1 After 12 months, no change is observed.
M

P. After 3 months, the coating gets crumbly and degraded by the external pressure.

X. After 6 months, the coating gets crumbly and does not remain in the shape of the ring.

E to The coating is in the almost same state as one arranged in theX. 20 glass greenhouse.

Claims

1. A granular fertilizer encapsuled with a decomposable coating, the coating comprising a vinyl resin containing at least one metal complex selected from the following group:
(1) the first complex, wherein the complexing agent is bonded to a metal through oxygen and the metal is a transition metal; and (2) the second complex, wherein the complexing agent is bonded to a metal through sulphur and the metal is a transition metal or a metal of group II
or IV of the periodic table of the elements;
wherein a concentration of the metal complexes is in the range of 0.02 X 10-4 to 20.0 X 10-4 mol per 100 g of the decomposable coating; and wherein a coating ratio of the decomposable coating is in the range of 2 to 20% by weight based on the granular fertilizer.

2. The granular fertilizer according to claim 1, wherein the metal of the first complex is an iron or cobalt.

3. The granular fertilizer according to claim 1, wherein the metal of the second complex is an iron, nickel, zinc or tin.

4. The granular fertilizer according to claim 1, wherein the complexing agent of the first complex is acetonylacetonate or acetylacetonate.

5. The granular fertilizer according to claim 1, wherein the complexing agent of the second complex is dialkyldithiocarbamate.

6. The granular fertilizer according to claim 1, wherein a water-difficult soluble or water-insoluble filler is mixed in the decomposable coating.

7. The granular fertilizer according to claim 6, wherein the filler is selected from the group consisting of talc, calcium carbonate, clay, bentonite, silica, diatomaceous earth, metal oxides, sulphur and starch.

8. A method for fertilizing plants, comprising applying an effective fertilizing amount of a granular fertilizer encapsuled with a decomposable coating, the coating comprising a vinyl resin containing at least one metal complex selected from the following group:

(1) the first complex, wherein the complexing agent is bonded top a metal through oxygen and the metal is a transition metal; and (2) the second complex, wherein the complexing agent is bonded to a metal through sulphur and the metal is a transition metal or a metal of group II
or IV of the periodic table of the elements;
wherein a concentration of the metal complexes is in the range of 0.02 X 10-4 to 20.0 X 10-4 mol per 100 g of the decomposable coating; and wherein a coating ratio of the decomposable coating is in the range of 2 to 20% by weight based on the granular fertilizer.