AU704560B2

AU704560B2 - Coated fertilizer

Info

Publication number: AU704560B2
Application number: AU12569/97A
Authority: AU
Inventors: Hiroshi Nakamura
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 1996-02-08
Filing date: 1997-02-06
Publication date: 1999-04-29
Anticipated expiration: 2017-02-06
Also published as: KR100453751B1; ID15896A; TW349082B; KR970065478A; AU1256997A; MY112695A

Description

1 Coated Fertiliser Background of the Invention Field of the Invention The present invention relates to a controlled-release (slow-release) granular fertiliser. More specifically, the present invention pertains to a controlled-release fertiliser coated with a thermosetting resin, such as an urethane resin.

Related Art of the Invention There have been many known controlled-release granular fertilisers manufactured by coating or encapsulating a granular fertiliser with or in a resin, wax or sulfur to regulate the releasing pattern of the fertiliser. A variety of coating materials and coating processes are disclosed in, for example, Japanese Patent .Publication Gazette No. S-40-28927, No. S-44-28457, No S-37-15382, and No. 42-13681. As for the coating techniques with a thermosetting resin, an urethane resin coating material including a reaction product of a polyisocyanate compound S 15 and a polyol compound is disclosed in US 3 264 089, whereas an epoxy resin coating material is disclosed in US 3,264 088.

As for the controlled release of a coated fertiliser, a technique of adding inorganic powder or a surface active agent to a polyolefin: resin to control the release of a fertiliser component is disclosed in, for example, Japanese Patent S 20 Publication Gazette No. S-60-3040 and No, S-60-37074. Another technique of combining a polyolefin with sulfur is disclosed in Japanese Patent Publication Gazette No. H-139995 and No. H-1-3996. Still another technique disclosed in Japanese Patent Publication Gazette No. H-2-28559 combines a polyolefin with either oxidised wax or oxidised petrolatum. A double-coating technique disclosed in Japanese Patent Publication Gazette No. H-4-202079 uses a high water absorbing, swelling substance as a first layer and an olefin resin as a second layer.

The conventional techniques are mainly divided into two groups, the release pattern of the fertiliser component is controlled by artificially introducing defects (such as pinholes) to the water-resistant coat or through the thickness of the waterpermeable resin coat. Both methods may, however, result in insufficient control of the release pattern or have disadvantages in industrial production, thereby being unsatisfactory.

Summary of the Invention The object of the present invention is thus to provide a controlled-release coated fertiliser having an accurately controlled releasing behaviour of the fertiliser component.

The inventors have intensively studied to solve the above problem and found that the releasing pattern of the fertiliser component from a granular fertiliser coated with a thermosetting resin can be controlled easily and with a high accuracy by using a combination of two or more thermosetting resins having different hydrophilic properties and thereby regulating the hydrophilic properties of the thermosetting resin, or by using a thermosetting resin containing dispersed powder that is insoluble or sparingly soluble in water.

The present invention is directed to the following: A granular fertiliser coated with a thermosetting resin that is thermally set, wherein said coating resin comprises two or more thermosetting resins having different hydrophilic properties, and at least one of the thermosetting resins is obtained by reaction of a polyisocyanate compound with a polyether polyol or a polyester polyol.

A coated fertiliser in accordance with wherein the coating resin comprises two or more thermosetting resins having different crosslinking densities.

A coated fertiliser in accordance with either one of and wherein the thermosetting resin is an urethane resin.

A coated fertiliser comprising a granular fertiliser having a surface coated with a thermosetting resin film containing dispersed powder that is insoluble or sparingly soluble in water, wherein said thermosetting resin comprises an epoxy resin or a urethane resin.

A coated fertiliser in accordance with wherein said thermosetting resin comprises a urethane resin.

.n g Detailed Description of the Invention *For coating a granular fertiliser with a resin, any known or conventional method is applicable. For example, while the granular fertiliser is kept in a fluid state by a fluidiser f or a jet fluidiser or kept in a rolling state with a rotating pan or a rotating drum, a coating material including an uncured resin is added dropwise or sprayed to coat the granular fertiliser. The resin included in the coating material is then cured to complete production of the coated fertiliser.

The granular fertiliser of interest may be any known fertiliser having granular structure. Concrete examples are granular fertilisers which are obtained by granulating 30 the followings by the known processes: nitrogen fertilisers, such as urea, ammonium sulfate, ammonium chloride, ammonium phosphate, ammonium nitrate, lime nitrogen, sodium nitrate, and acetaldehyde-condensate urea; phosphate fertilisers, such as a calcined phosphate fertiliser, a processed phosphate fertiliser, triple superphosphate of lime, and a mixed phosphate fertilisers potassium fertilisers, such as potassium chloride, potassium sulfate-magnesium oxide, potassium hydrogen carbonate, and a potassium silicate fertilisers synthetic fertilisers, such as a potassium phosphate fertiliser and a potassium nitrate fertiliser; organic fertilisers; and mixtures thereof. Although the mean particle diameter of the granular fertiliser is not limited, the range of 1 to 5mm is preferable in manufacture.

[n:\libz]00994:SAK For the thermosetting resin of the present invention, known thermosetting resins, such as an urethane resin, an epoxy resin, an unsaturated polyester resin, a phenol resin, an alkyd resin, a xylene resin, a melamine resin, a furan resin, and a silicone resin, maybe applied. Mixtures of two or more selected among the above thermosetting resins may be used according to the requirements. In case that two or more resins are mixed, it is preferable that these resins are compatible with each other. Among these available examples, the epoxy resin and the urethane resin are preferable in the aspects of workability and performance thereof. The urethane resin is especially preferable.

The urethane resin is described further in detail. The urethane resin is a generic name of three-dimensional crosslinked resins obtained by a reaction of a polyisocyanate compound with a polyol compound. The uncured urethane resin in the present invention is a mixture of the polyisocyanate compound and the polyol compound that is not allowed to react with each other at all or has been made to 15 react partly in advance to the extent that causes no three-dimensional structure.

Addition of a catalyst to accelerate the reaction is a useful technique. The uncured resin may have any form like a non-solvent form, a solution form, or an aqueous emulsion form, but it is especially preferable that the uncured resin has the nonsolvent form and is liquid at a working temperature.

The polyisocyanate compound used herein is not specifically limited, but available examples include toluene diisocyanate (may be referred to as TDI), diphenylmethane diisocyanate (may be referred to as MDI), naphthalene diisocyanate, tolidine isocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and xylylene diisocyanate. Mixtures of these available examples may 25 be used according to the requirements. Especially preferable are MDI, TDI, and oligomers derived from MDI or TDI.

The polyol compound used herein is not specifically limited, but available examples include: polyether polyols, such as polyether polyol obtained by polyaddition of ethylene oxide or propylene oxide with a polyol, an amino alcohol, or an amine as an initiator and polytetramethylene ether glycol obtained by polymerisation of tetrahydrofuran, and polyester polyols obtained by reaction of a polyol, polyether polyol, and a carboxylate. By taking advantage of the biodegradability, OH group-containing natural substances and their modified substances are also applicable.

A catalyst may be added to the resin component according to the requirements. Any known or conventional catalysts may be applied, but amine catalysts, such as triethylenediamine, N-methyl-morpholine, N,N-dimethylmorpholine, diazabicycloundecene, and 2,4,6-tris(dimethylaminomethyl)phenol, are preferably used.

The present invention regulates the hydrophilic properties (may also be referred to as "water permeability") of the resin coat, which is obtained by curing the above thermosetting resin to coat the granular fertiliser, by its crosslinking density and/or chemical structure, so as to control the releasing behaviour of the fertiliser component. The crosslinking density is generally defined as the number of crosslinking points per unit volume (or weight). In other words, the crosslinking density represents an amount that is inversely proportional to the length of the molecule between the crosslinking points in a network structure generated by the curing reaction, and can be defined as an indication of the mesh of the network structure. The resin having the higher crosslinking density or having the smaller mesh in the three-dimensional network structure results in the lower water :oV permeability and thereby the slower release of the fertiliser component. The resin having the lower crosslinking density or having the larger mesh, on the other hand, results in the faster release of the fertiliser component Namely the desired S 15 releasing rate of the fertiliser component can be attained by regulating the crosslinking density. The desired crosslinking density is obtained readily by adequately selecting the resin and the curing agent among the commercially available ones. By way of example, while the polyisocyanate component is fixed, the crosslinking density is varied with a variation in density of the functional group of the polyol component, that is, with a variation in equivalent of the hydroxyl group.

:Another method favourably applicable to the present invention combines the resins having different crosslinking densities with each other in a compatible state. In case that the resins with different crosslinking densities are incompatible with each other, a troublesome problem., such as control of the separated double-phase structure, 0 25 may arise. The known fact that the crosslinking density is varied with a variation in stoichiometric ratio of the resin to the curing agent is also practically applicable to the present invention.

The crosslinking density is generally calculated from the storage elastic modulus of the rubber-like flat area in measurement of the viscoelasticity or from the solvent swell of the cured substance. The simplified method to determine the crosslinking density is the one based on the variation in glass transition temperature. As another method, the molecular weight between the crosslinking points can be calculated from the functional group-equivalents of the resin and the curing agent.

It is known that the hydrophilic properties of the resin are affected by the crosslinking density as well as the contribution of the hydrophilic groups attributable to the chemical structure of the molecule. The greater number of hydrophilic groups results in the higher hydrophilic properties. The hydrophilic properties may be indicated as the diffusion coefficient of water, the amount of water absorption when the resin is soaked in water for a fixed time period, or the amount of saturated water absorption at a fixed temperature. The desired hydrophilic properties of the cured substance are obtained readily by adequately selecting the resin and the curing agent among the commercially available ones. Another method favourably applicable to the present invention combines the resins having different hydrophilic properties with each other in a compatible state. In case that the resins with different hydrophilic properties are incompatible with each other, a troublesome problem, such as the controlling of the phase separation, may arise. The known fact that the hydrophilic properties are varied with a variation in stoichiometric ratio of the resin to the curing agent is also practically applicable to the present invention.

The water-insoluble or sparingly-soluble powder used in the present invention preferably has the mean particle diameter of not greater than 50pm. The powder used herein is not specifically limited, but preferable examples include metal or inorganic powders, such as metals, metal oxides, talc, mica, and silica, and plastic 15 powders obtained by grinding polyethylene, polypropylene, and polyamide. In the case of using the powder, the thermosetting resin may be used alone or in combination of two or more.

The method applied in the present invention for coating the fertiliser particles mixes or disperses a predetermined amount of the powder in advance to a uncured coating resin, and subsequently coats the fertiliser particles with the resin containing the mixed or dispersed powder. Another applicable method coats the fertiliser with a uncured resin, and adds the powder to the uncured resin prior to completion of the curing process of the uncured resin, so as to make the powder contained and dispersed in the coating resin.

o 25 Pigments and dyes for colour development and inorganic or organic powders like talc, mica, silica, carbon black, and resin powder as fillers may further be added to the coating resin according to the requirements.

Examples The present invention is described concretely based on some examples, which are! however, only illustrative and not restrictive in any sense.

Referential Example 1 A uncured liquid resin was prepared by homogeneously mixing 135 parts by weight of a polymeric MDI (manufactured by Sumitomo Bayer Urethane Co., Ltd., trade name: Sumijule 44V-10, equivalent of isocyanate: 135g) as the polyisocyanate compound, 148 parts by weight of a branched polyetherpolyol (manufactured by Sumitomo Bayer Urethane Co., Ltd., trade name: Sumifen TM, equivalent of OH: 148g) as the polyol compound, and 2.8 parts by weight of 2,4,6tris(dimethylaminomethyl)phenol (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumicure D) as the catalyst. The resin composition was cured at 70 0

C

for 30 minutes. Tg of the cured resin substance was read from a peak of the loss elastic modulus obtained in measurement of viscoelasticity and is shown in Table 1. Table 1 also shows the amount of water absorption that was measured after the cured resin substance was kept in boiled water for 24 hours.

Referential Example 2 A uncured liquid resin was prepared by homogeneously mixing 135 parts by weight of the polymeric MDI used in Referential Example I as the polyisocyanate compound, 486 parts by weight of a straight-chain polyether polyol (manufactured by Sumitomo Bayer Urethane Co., Ltd., trade name; Desmofen 1600U, equivalent of OH: 486g) as the polyol compound, and 12 parts by weight of the 2,4,6tris(dimethylaminomethyl)phenol as the catalyst. The resin composition was cured at 70°C for 30 minutes. Tg of the cured resin substance was read from a peak of obtained in measurement of viscoelasticity and is shown in Table 1.

Table 1 OH-equivalent Tg Water absorption ratio .Referential Example 1 148 73 2.17 Referential Example 2 486 -24 6.19 1 5 The values of the OH-equivalent and Tg show that the resin of Referential Example 1 has a high crosslinking density, whereas the value of water absorption ratio proves that the resin of Referential Example 2 has high hydrophilic properties.

Referential Example 3 In a temperature adjustable, inclined pan-type rolling granulator (diameter of the pan: 520mm) having a hot air generator, 2kg of urea particles (mean particle diameter: 2.9mm) were rotated at 20 to 30rpm to a rolling state. The urea particles loaded in the granulator, which was heated, were kept at the temperature of at to 750C and under the rolling condition. The resin composition prepared in the same manner as Referential Example 1 was added quickly to the heated urea particles in the rolling state, so that the urea particles were coated with the urethane resin. The amount of the resin used for coating was 896 by weight relative to the fertilizer.

The releasing behaviour of the resin-coated granular fertilizer obtained by the above process was evaluated at 25°C. The coated urea released 80% of its fertilizer component in approximately 130 days. The evaluation of the release of the Rertilizer component followed a method proposed by Research Institute of Environmental Technology, the Hinistry of Agriculture, Forestry, and Fisheries (for example, 'Detailed Method of Fertilizer Analyses' edited by Masayoshi KOSHINO, 1988).

Referential Example 4 The coated fertiliser was prepared by coating 2kg of urea particles (mean particle diameter: 2.9mm) with the urethane resin in the same manner as Example 1, except that the resin of Reference 2 was used as the coating resin. The amount of the resin used for coating was 8% by weight relative to the fertilizer.

The releasing behaviour of the fertiliser component from the coated fertilizer was evaluated in the same manner as Exalnple 1. It was proved that the coated urea released more than 80% of its fertilizer component in one week.

Examples 4, 5, 6, 7 Urethane resins were prepared as shown in Table 2 by combining the polyol components of Referential Examples 1 and 2 and using the other constituents as described in Table 2. Coated fertilizers were then manufactured in the same manner as Referential Example 3.

The releasing behaviour of the coated fertilizers thus obtained were evaluated 15 in the same manner as Referential Example 3. Table 2 also shows the results of measurement for Tg and water absorption ratio of the resin compositions in the same manner as Referential Example 3.

Table 2 Table 2 I 0* 0 *0 Resin Composition Examples 3 4 5 6 Sumijule 44V-10 45.2 35.8 40.9 42.5 Sumifen TM 18.3 31.1 39. 4 43.1 Desmofen 1600U 36.6 31.1 19.7 14.3 Sumicure D 2.0 1.5 1.5 Weight ratio of polyols (Desmofen 1600U/Sumifen TM 2/1 1/1 1/2 1/3 Polyol-equivalent(g) 279 230 196 182 Properties Water absorption 3.64 3.32 2.97 2.50 Tg(oC) 11 37 56 Time for 80% release (days) 15 28 57 72 These Examples show that the controlled-release fertiliser having the accurately controlled release rate of the fertiliser component can be manufactured by coating the granular fertiliser with the thermosetting resin that consists of the resins having different crosslinking densities or those having different hydrophilic properties.

Referential Example In a temperature adjustable, inclined pan-type rolling granulator (diameter of the pan: 520mm) having a hot air generator, 2kg of urea particles (mean particle diameter: 2.9mm) were rotated at 20 to 30rpm to a rolling state. The urea particles loaded in the granulator, which was heated, were kept at the temperature of at to 75°C and under the rolling condition. After 135 parts by weight of a polyisocyanate compound (polymeric MDI, manufactured by Sumitomo Bayer Urethane Co., Ltd., tradename: Sumijule 44V10, equivalent of isocyanate: 135g) and 148 parts by weight of a polyol compound (branched polyether polyol, manufactured by Sumitomo Bayer Urethane Co., Ltd., trade name: Sumifen TM, equivalent of OH: 148g) as the coating resins and 2.8 parts by weight of a tertiary amine (2,4,6-tris(dimethylaminomethyl)phenol, manufactured by Sumitomo Chemical Co., Ltd. trade name: Sumicure D) as the catalyst were mixed homogeneously, the resin composition was added quickly to the heated urea particles in the rolling state, so that the urea particles were coated with the urethane resin. The amount of the resin used for coating was 10% by weight relative to the fertiliser.

The releasing behaviour of the resin-coated granular fertiliser obtained by the above process was evaluated at 35°C The coated urea released 80% of its fertiliser component in approximately 70 days, which proved the controlled-release property. The results of evaluation are shown in Table 1.

Examples 5, 6, 7, 8 15 The coated fertilisers were prepared in the same manner as Referential Example 5, except that a water-sparingly soluble inorganic powder, clay (Special Snow Cut Clay manufactured by Showa Kogyo Co., Ltd., Ratio of passing through the 46pm mesh: not less than 99.5%) was contained and dispersed in the coating Surethane resin. The amount of coat as the resin component was 10% by weight relative to the fertiliser. The composition of the coating materials is shown in Table 3. The releasing behaviour of the fertiliser component from the coated fertilisers thus manufactured was evaluated in the same manner as Referential Example 3.

The results of evaluation are shown in Table 1.

:.Table 33 Table 33 Referential example Example 5 6 7 8 Resin composition Sumijule 44V-10 47 47 47 47 41 Sumifen TM 53 53 53 53 53 Sumicure D 1 1 1 1 1 Crau 0 10 30 50 100 Time tor 80% release (days) 70 65 55 50 Unit of Composition of Coating Material: Parts by weight The coated fertiliser of the present intention has the controlled release rate of the fertiliser component.

The claims defining the invention are as follows: 1. A granular fertiliser coated with a thermosetting resin that is thermally set, wherein said coating resin comprises two or more thermosetting resins having different hydrophilic properties, and at least one of the thermosetting resins is obtained by reaction of a polyisocyanate compound with a polyether polyol or a polyester polyol.

2. A coated fertiliser in accordance with claim 1, wherein said coating resin comprises two or more thermosetting resins having different crosslinking densities.

3. A coated fertiliser in accordance with claim 1 or claim 2, wherein said thermosetting resin is a non-solvent-type urethane resin.

4. A coated fertiliser comprising a granular fertiliser having a surface coated with a thermosetting resin film containing dispersed powder that is insoluble or sparingly soluble in water, wherein said thermosetting resin comprises an epoxy resin or a urethane resin.

A coated fertiliser in accordance with claim 4, wherein said thermosetting resin comprises a urethane resin.

6. A granular fertiliser, substantially as hereinbefore described with reference to any one of the examples but excluding the comparative examples.

Dated 23 November, 1998 Sumitomo Chemical Company, Limited 20 Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON *e *5 oo *o•

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