SK288066B6 - Granulated fertilizer with controlled release of nutrients - Google Patents

Abstract

Granulated fertilizer with controlled release of nutrients is producible by coating of fertilizer granules with the mixture of epoxy resin with low molar weight 100 to 400 in amount of 50 to 85 % by weight, imidazole derivative in amount of 1 to 20 % by weight and modified vegetable oil in amount of 10 to 30 % by weight. The epoxy resin with low molar weight 100 to 400 is optionally bisphenol A diglycidyl ether with epoxy equivalent 182 - 192 g/mol, the imidazole derivative is 2-ethyl-4-methylimidazole and the modified vegetable oil is methyl ester of rape-seed oil. The coating mixture optimally contains 77.3 % by weight of the epoxy resin, 3.4 % by weight of imidazole derivative and 19.3 % by weight of methyl ester of rape-seed oil. The fertilizer is coated by successive deposition of 3 to 20 doses of the coating mixture, wherein the deposition is carried out in a rotating drum or in a fluid device at the temperature 60 to 120 øC, advantageously 105 to 115 øC. Layer of the coating mixture constitutes 6 to 25 % of the total weight of a coated granule.

Description

Technical field

The invention relates to a controlled release nutrient obtainable by coating the fertilizer granules with a mixture of epoxy resin, an imidazole derivative as a hardener and a modified vegetable oil. The release rate of the nutrients is controlled by the amount of epoxy resin.

BACKGROUND OF THE INVENTION

Plant nutrition depends on the availability of mineral nitrogen, phosphorus and potassium in the soil. A wide range of mineral fertilizers is produced in the world, which differ only in the ratio of the three components, or in the presence of other elements (Mg, S, Ca) or trace elements. A common disadvantage of all these mineral fertilizers is their high water solubility. A key solution to this problem is the development of new types of fertilizers that slow down the release of nutrients into the soil so that they are gradually used. Fertilizers with slow release of nutrients are divided into two groups:

1. Slow-Release Fertilizer (SRF),

2. Controlled Release Fertilizer (CRF).

CRFs can be represented by traditional soluble fertilizers with readily available nutrients in which, after granules, adherence or crystallization, a protective coating is applied to control the penetration of water, affecting the solubility ratio and the release rate of the nutrients. A typical core composition is urea or N-P-K in various combinations, with or without the addition of microelements.

Three groups of polymer-coated fertilizers (PCF) are distinguished according to the type of polymer applied or the method of preparation:

- a thermosetting copolymer is applied to the fertilizer surface,

- a thermoplastic polymer or copolymer is applied to the fertilizer surface,

- two monomers are applied to the surface of the fertilizer, which are polymerized on the surface.

According to US Pat. 6,187,074 (2001) fertilizer granules can be coated with a carboxyethylene copolymer [75-95% ethylene and 10-25% unsaturated carboxylic acids (acrylic, methacrylic, maleic, crotonic, fumaric)]. The Tg of the polymer is from -20 ° C to + 20 ° C. Acrylamide, methacrylamide, N-methylolacrylamide, N-butoxymethacrylamide, glycidyl methacrylate and hydroxyethyl acrylate are also recommended as a comonomer to ethylene. The melting point of the polymer above 110 ° C is preferred. The deposit (layer) of the copolymer is from 2% to 10% by weight of the granule. Lignin, starch or cellulose (0.1 to 3%) is added to control nutrient secretion. The copolymer coating is at a temperature of 30 ° C to 70 ° C. To prevent granules sticking, SiO ₂ or TiO ₂ is added after the polymer layer has been applied.

Hygroscopic polymer (sodium polyacrylate, acrylic-vinyl alcohol copolymer, starch grafted polymers, carboxymethylcellulose) can be applied first to the fertilizer granules, followed by polyurethane resin (US 6,358,295; 2002). The polyurethane resin is formed by the reaction of an isocyanate (e.g., toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexymethylene diisocyanate) and a polyol (propylene glycol, trimethylolpropane, polytetetramethylene ether glycol). The ratio of the - NCO / -OH groups in the isocyanate to polyol used is usually 0.9: 1.2. Addition of NaOH, urea or triethylenediamine may be used as the hardener of the polyurethane resin. The amount of hygroscopic polymer ranges from 1 h.d. do 20 h.d. per 100 h.d. urethane resin. The urea is heated to 70 ° C, a hygroscopic polymer is added, followed by dispersion and addition of isocyanate, polyol and hardener.

The polymeric coating component may also be a dispersed polysaccharide: cellulose, starch or sugars: glucose, fructose, xylose, arabinose (US 102829; 1993). Also applicable are oxidized starch, alkyl or hydroxyalkyl ether starch, phosphoric, nitric, succinic, starch modified, carboxymethyl starch, hydroxyalkyl starch, cationic starch and cellulose derivatives: carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose and carboxymethylethylcellulose. In particular, carboxymethylcellulose is recommended. As the resin, vinylidene chloride polymer, vinylidene chloride copolymer with ethylene, propylene, butene, ethylene vinyl ketone, vinyl chloride or vinylidene acrylate copolymer can be used. The addition of powdered polysaccharide or sugar is from 0.5% to 20% by weight of the resin. A water-insoluble or sparingly soluble filler, e.g. talc, CaCO ₃ , SiO ₂ , sulfur, zeolite. The filler addition is 20% to 70% by weight of the resin. The polymer component of the coating is dissolved in an organic solvent and sprayed onto the granulated fertilizer. After coating the particles, the solvent is evaporated under the influence of hot air and the coating solidifies. Controlled dissolution of the fertilizer takes 26 to 315 days.

Slowly soluble nitrogen fertilizer can also be prepared by copolymerization of acrylic acid and maleic anhydride (dihydro-2,5-dioxofuran) using Ν, Ν-methylenebisacrylamide as a crosslinker in aqueous medium in the presence of urea, ammonium persulphate and sodium sulfite as initiator (Liu M., Liang R., Zhan F., Liu Z., Niu A., 2006: Synthesis of Slow Release and Superabsorbent Nitrogen Fertilizer and its Properties, Research Article, Department of Chemistry, Lanzhou University, China). The product was surface crosslinked with trihydroxymethylpropane glycidol ether to improve slow dissolution and water retention. The nitrogen content of the synthesized fertilizer was 28.5% and the water absorption was about 900 g / g in distilled water and 180 g / g in tap water. From the results of testing the nitrogen dissolution rate and water absorption, it was found that the surface crosslinked product not only provides a slow dissolution of the nitrogen fertilizer, but also a high soil moisture retention capacity. Fertilizer could find application in drier areas.

Fertilizer granules can be coated first with a layer of wax, then with an alkyd resin-based material and a swellable substance (JP 08151286; 1994). Urea (3.3 mm diameter) is heated to 70 ° C and paraffin wax (60 ° C) is sprayed at this temperature. The wax layer constitutes 6.2% by weight of the coated granule. A second layer consisting of a soybean oil, tung oil alkyd resin and absorbent sodium polyacrylate resin (Aqua Keep 10 SH) in a ratio of 95: 5 is then injected. This constitutes 8.1% by weight of the coated granule. The surface-treated urea releases 8% of nitrogen in water at 25 ° C in 30 days and 75% in 120 days.

The fertilizer granules can also be coated with a thermoplastic resin, and then with a substance selected from the group consisting of other thermoplastic resins, thermosetting resins, or inorganic substances (JP 07315975; 1994). The urea granules with a diameter of 3.3 mm were coated with a wax and then with a mixture of alkyd resin, tung oil, pentaerythritol linollan and metal soap.

JP 07033575 (1993) discloses granules coated with an oil-modified alkyd resin (soybean based) blend, unsaturated conjugated double bonded oil (palm oil, tung oil, tall oil), pentaerythritol (maleic or phthalic anhydride), metallic soap and amino resin (melamine resin, benzoguanamine resin, glycoluryl resin). No organic solvents were used in the surface treatment. The rate of release of nutrients from the coated granules was controlled by the type and amount of amino resin used. Amino resin was tested either as the topsheet of the bilayer package or in admixture with the alkyd resin in the single-layer package.

In JP Pat. 06056567 (1992) the coating composition comprises an oil-modified alkyd resin, an unsaturated oil with conjugated double bonds and a wax as a major component. Urea granules of 3.3 mm diameter were coated with a mixture of soybean modified alkyd resin (30 wt%), tung oil (50 wt%), pentaerythritol linoleic ester (15 wt%), metal soap (3 wt%). ) and conditioner (2 wt%).

The fertilizer granules in EP 520456 BI (1991) are also coated with a mixture containing an oil-modified alkyd resin and unsaturated oil with conjugated double bonds. Metal soap may also be present. The coating composition comprises an alkyd resin based on soybean oil (30 wt%), tung oil (49 wt%), pentaerythritol linoleic ester (15 wt%), zirconium octylate (1.2 wt%), cobalt octylate (1.2 wt.%), Manganese naphthenate (0.6 wt.%), And an antifoam agent (2 wt.%). After heating, the mixture was injected onto fluidized urea.

In JP Pat. No. 02111686 (1988), the coating composition comprises a thermosetting carboxyl-terminating resin and a filler, e.g. talc. The filler concentration in the mixture is from 5 to 25 wt. %. Fertilizer granules containing 20% N and 10% K ₂ O were coated with a mixture of alkyd resin based on soybean oil and talc (5.9 and 1.5 wt%). The time to release 80% of the nutrients was 96 days.

Sustained release fertilizer was prepared by coating the fertilizer granules with a mixture of an oil-modified phthalic acid resin and a miscible petroleum resin (JP 63095189; 1986). Soybean oil-modified phthalic acid resin (250 hd) and aromatic petroleum resin (25 hd) were mixed to obtain a coating mixture. The fertilizer granules (1 kg) containing N 18% and K ₂ O 16% were poured into a rotating drum and the fertilizer mixture was sprayed over the nozzles at 60 to 100 ° C through the nozzles. The percentage of ammonia nitrogen released from the fertilizer in water on days 10, 30, 50, 80 and 100 was 13%, 34%, 52%, 71% and 79%, respectively. In the case of fertilizer granules coated only with petroleum resin, 100% N was released after 10 days.

A polymer for coating the surface of fertilizer granules can also be obtained by reacting a polyisocyanate and an alkyd resin modified with a sorbitol fatty acid ester (JP 2008222536; 2007). An alkyd resin mixture containing 22% castor oil, 8% oleic acid, 16% adipic acid, 24% trimethylolpropane and 30% sorbitol tristearate was mixed with the catalyst and heated. The urea granules (1 kg) in a centrifugal rotary granulation machine were heated to 70 ° C, then sprayed onto an alkyd resin (4 g) and as a Sumidur 44V10 polyisocyanate component (2 g), separated by two nozzles. After curing of the resin, the alkyd and polyisocyanate spraying process was repeated until the coating layer constituted 10% by weight of the coated urea. The polymer coating showed 12.5% biodegradability and 88.3% nitrogen was released after 130 days. Similar granules coated with an alkyd resin composition without sorbitol tristearate had 2.5% biodegradability and 93.6% nitrogen was released after 40 days.

According to patent CN101289349 (2008), CRF is composed of a core (fertilizer) and a coating containing sulfur on the surface of the granule and on the sulfur surface of a polymer film based on a water-soluble alkyd resin. The content of sulfur and polymer film is from 5 to 30%, respectively. from 0.5 to 10% by weight of the coated fertilizer. Water soluble

The alkyd reagent comprises an alkyd prepolymer having an acid number of 10-150 mg KOH / g resin. The alkyd prepolymer is obtained by polycondensation of an unsaturated conjugated vegetable oil or vegetable acid fatty acid with a synthetic fatty acid or anhydride thereof. The coating may also contain an inorganic layer (montmorillonite, chalk, kaolin, talc).

In the production of polymer-coated fertilizer according to US 569 8002 (1997), the base coat comprises an epoxide reaction product with at least two epoxy groups / mol and at least one amino hardener with at least two N-H groups / mol. Of the commercial epoxy resins, the structure of diglycidyl ether of bifenol A (DER 330 and 331 from Dow CHC) is preferred. Of the polyalkyl polyamide curing agents triethylenetetramine is recommended. 2-Aminoethylpiperazine is added to accelerate curing. The most preferred ratio between the epoxy equivalents of the epoxy resin and the hydrogen atoms bound to the amino nitrogen of the amino hardener is 1. The amount of the base coat is in the range of 1 to 20% by weight of the granules. Subsequently, at least one layer of polymer, consisting of either other epoxy polymers, in-situ reaction polymers (urethanes as a product of the reaction of polyols with isocyanates), thermoplastic polymers (polyalkylacrylates, styrene-butadienes), or waxy (paraffins), is applied to the base coat. oils). The addition of wax varies from 1 to 6% by weight of the granules. Samples of polymer-coated urea were prepared using DER 330, a long chain amine (C 14 to C 18), and a C30 alpha olefin. During 7 days of testing in water at 25 ° C, from 7 to 100% nitrogen was released in each sample.

In CN Pat. 101037368 (2007) is a coated fertilizer prepared by uniformly spraying a water-soluble polymer. The ratio of fertilizer granules to polymer is (0.3-0.4): (9.6-9.7). The water-soluble polymer is prepared from cellulose (22-35 wt%), oxidized starch (1-2 wt%), polyvinyl alcohol (4-8 wt%), polyurethane prepolymer (5-8 wt%), epoxy resin E 44 (6-18 wt.%), Epoxy resin curing agents T593 (2-3 wt.%), N-hydroxymethyl acrylamide as crosslinker (1-2 wt.%), Potassium persulfate initiator (0.001 - 0.002 wt.%) ) and deionized water (35-51 wt.%). The fertilizer thus prepared has good properties in terms of nutrient release rate control, high nitrogen utilization by plants, low consumption and low pollution.

According to US 3264088 (1966), a resin is prepared by reacting epoxy compounds such as epichlorohydrin with dihydric phenols (bisphenol A) to form glycidyl ethers. Aliphatic or aromatic amines, dibasic acid anhydrides can be used as hardeners. The coating composition consists of a mixture of epoxy resin and its hardener in the presence of acetone. The coating layer varies from 3 to 15% by weight of the granules, depending on the smoothness of the surface. The granules are preferably heated to 56-160 ° C. Each layer of the deposited mixture is dried until the start of the gel formation. The mixing of the granules in the drum during drying improves the coating range, the film uniformity and reduces the formation of adhesives. The wrapping was carried out in a 76.2 cm long drum with a diameter of 40.6 cm, placed horizontally using an air flow apparatus heated to 78-139 ° C, in the direction of the axis through the drum. There were compartments in the drum and the peripheral rotation speed was 330-360 cm / minute. The urea adhered was coated with 12.5 wt. % resin containing 80 parts of Epon 815 (liquid bisphenol-epichlorohydrin resin having epoxy end groups and epoxy equivalents < 500) and 20 parts of the oleonitrile-triethylenetetraamine epoxidation reaction product. The urea was preheated to 89 ° C and the coated mixture was gradually applied in 9 portions. The first application rate was 2% by weight of the granules, the other four each at 1.5% and the last four each at 1%. When 20 g of the product was mixed with 100 ml of water, 19% of the nutrient was dissolved after 72 hours of standing.

Fertilizer granules (adhered urea, ammonium nitrate) according to US 3259482 (1966) were coated with multiple layers of epoxy resins. The fertilizer was poured into a rotary drum and heated to 139 ° C. The resin was then sprayed successively onto the heated granules. At the same time, air heated to 145 ° C was passed through the drum. Resin A (copolymer of dichloropentadiene with modified vegetable oil, dissolved in an organic solvent) was added in 5 portions. The first was 3% by weight of the granules, the remaining four by 1.5%. This was followed by the addition of resin B in three portions of 1.5% by weight of the granules. Resin B was a mixture of epoxidized soybean and linseed oil with oxirane (above 7%) in an organic solvent, a hardener having an acid number of 160-70, preformed from phthalic anhydride, chlorenedic acid and pentaerythritol where the initial ratio of CO ₂ H groups to OH groups before esterification was 1.8: 1. A mixture of dimethylphenol and cellosolve acetate was used as solvent. After the last spraying, the granules were dried until they became sticky. After 72 hours, the nutrient leaching rate was only 0.7%.

The regulation of nutrient release depends on the packaging used. For alkyd resins, release is achieved by varying the composition of the coating or its thickness. In polyurethane resin coatings, but also in many other types of resins and thermoplastic polymers, the release is mainly influenced by temperature, with the moisture content in the soil, pH, weather and / or temperature. microbiological activity has a low release effect. In polyethylene containers, a portion of the low permeability polyethylene is replaced by a high permeability polymer, e.g. ethylene-vinyl acetate.

A major disadvantage of using resins for coating is their considerable tackiness in their original state. As a result, the individual fertilizer granules stick together during the coating process. After the resin has hardened, the coated granules can be separated from each other, but the package is damaged. To prevent ill4

For example, the coating of granules during coating is recommended, e.g. addition of native vegetable oil (palm, rapeseed, castor, linseed). However, if the oil is not part of the polymer chain, it can be degraded during storage under certain conditions and thus deteriorate the quality of the package. Another problem with the direct use of resins for coating is their high viscosity. The patents mostly recommend diluting them in an organic solvent, which, however, presents environmental problems due to the volatility of the solvent.

It is an object of the present invention to provide a granular fertilizer that will substantially minimize the described disadvantages.

SUMMARY OF THE INVENTION

The aforementioned drawbacks are largely overcome by the controlled-controlled, controlled-release nutrient granular fertilizer of the present invention. The granular surface film fertilizer of the present invention is obtainable from a basic granular fertilizer and a polymeric coating, wherein the polymeric coating (film, layer) is based on a low molecular weight epoxy resin of 100 to 400. Epoxy resins are produced by alkaline condensation of diane (2,2- bis (4-hydroxy-phenyl) -propane) with epichlorohydrin to form bituminous products containing reactive epoxy groups. Epoxy resins cure hot or cold when hardeners are used. The curing reaction of the epoxy resins takes place at very small volume changes and does not produce any volatile fumes; the hardener is chemically bound to the resin.

An organic solvent-free epoxy resin was used to coat the granular fertilizer. The amount of epoxy resin in the coating composition ranged from 50 to 85 wt. %. Preferably, the diglycidyl ether of bisphenol A with an epoxy equivalent of 182-192 g / mol can be used as the epoxy resin.

The epoxy resins contain in their structure reactive epoxy groups capable of reacting with the hydrogens of the primary and secondary amino groups. For this reason, amine derivatives having at least two N-H groups (ethylenediamine, polypropylene glycololdiamine, glycoltriamines, triethylene glycol triamine, triethylenetetraamine), piperazine and imidazole derivatives may be used as suitable epoxy resin curing agents.

An imidazole derivative was used as a suitable hardener of the epoxy resin. The hardener concentration in the mixture with the epoxy resin was in the range of 1 to 20 wt. %.

Due to the high viscosity of the epoxy resin, it is necessary to use a suitable substance to dilute it. Finding a substance which, in addition to diluting the resin and preventing granules sticking during the surface film formation process, to be nonvolatile under the given conditions, has led the authors to add a liquid prepared by re-esterification of the crude vegetable oil with methanol. Its amount was in the range of 10 to 30 wt. %. The advantage of using a modified vegetable oil to prevent the granules from sticking over the natural oil in admixture with the epoxy resin is a significantly slower release of nutrients through the coating formed on the granule surface (see examples).

The coating composition can be prepared in a container with a stirrer at room temperature. After the epoxy resin has been weighed, the hardener is gradually added. After thorough mixing, the modified vegetable oil is added. After homogenization, the mixture is ready for coating.

Coating under laboratory conditions was carried out in an Aeromatic AG dryer with spray coating of the coating mixture using compressed air. The granules were entrained and dried with a stream of warm air flowing from the bottom, narrower part of the column. The coating mixture was dispensed into the air stream by means of a syringe. The coating mixture was injected in 3 to 20 uniform doses. The drying was carried out at a temperature of 70 to 120 ° C. Each subsequent batch of the mixture was injected only after the mixture had cured from the previous batch on the surface of the granules at intervals of 5 to 15 minutes. The resulting film has the character of a crosslinked polymer, similar to thermosets, which reduces the temperature sensitivity of the water through the film.

DETAILED DESCRIPTION OF THE INVENTION

The rate of release of nutrients from the coated fertilizer was tested in a duplicator container with fertilizer granules incorporated into the sand layer. After the container was closed, distilled water was poured into the duplicator, which was passed through a layer of granular sand and wetted. The water intended for the analysis of the concentration of released nutrients was collected in a glass flask after passing through a sand layer with a granular fertilizer sample. The water wetting cycle was repeated at appropriate time intervals.

Urea granules from SKW Piesteritz (Germany) and Piagran 46 (nitrogen content 46%) were used for coating. The diameter of the granules was 2 to 5 mm. The granules were coated with the alkyd resin compositions of Examples 1 to 7.

Methodology of evaluation of controlled nutrient fertilizers by water test

Prepared samples of granular fertilizer with controlled release of nutrients (40 g) were tested in a duplicator tank incorporated into the sand layer. Fine, washed and dried sand was used; j. inert material in the absence of organic matter. The vessel was closed, the thermostat water pump turned on for the jacket tempering circulating circuit. The circulating water temperature was set at a constant temperature of 23 ° C. Thermostate water and distilled water intended to extract nutrients from coated samples were also heated to the same temperature. The water dosing time (500 ml) through the fertilizer sample was optimized for about 120 minutes. The water dosing rate was set to max. 14 ml / min. After a level on the sand surface was formed in the vessel, this level was maintained at a dosage rate range of 3.5-4 ml / min.

The water intended to analyze the concentration of released nutrients was collected in a glass flask after passing through the sand layer with the fertilizer sample.

Examples 1-7

Piagran 46 urea granules (1 kg) were used to prepare the granular fertilizer of the present invention. Coating compositions were prepared for coating granules in the following composition:

1. 63.3% epoxy resin (CHS Epoxy 520), 11.4% imidazole derivative (IMICURE EMI-24), 25.3% modified rapeseed oil (MERO),

2. 67.4% epoxy resin (CHS Epoxy 520), 10.1% imidazole derivative (IMICURE EMI-24), 22.5% modified rapeseed oil (MERO),

3. 73.3% epoxy resin (CHS Epoxy 520), 8.3% imidazole derivative (IMICURE EMI-24), 18.4% modified rapeseed oil (MERO),

4. 77.5% epoxy resin (CHS Epoxy 520), 7.0% imidazole derivative (IMICURE EMI-24), 15.5% modified rapeseed oil (MERO),

5. 80.5% epoxy resin (CHS Epoxy 520), 6.0% imidazole derivative (IMICURE EMI-24), 13.5% modified rapeseed oil (MERO),

6. 82.8% epoxy resin (CHS Epoxy 520), 5.3% imidazole derivative (IMICURE EMI-24), 11.9% modified rapeseed oil (MERO),

7. 77,3% epoxy resin (CHS Epoxy 520), 3,4% imidazole derivative (IMICURE EMI-24), 19,3% modified rapeseed oil (MERO),

8. 70.7% epoxy resin (CHS Epoxy 520), 7.6% imidazole derivative (IMICURE EMI-24), 10.9% linseed oil, 10.8% castor oil,

9. 70.7% epoxy resin (CHS Epoxy 520), 7.6% imidazole derivative (IMICURE EMI-24), 21.7% linseed oil.

The urea granules were heated to 110 ° C with a stream of warm air. The coating composition was dosed sequentially. After coating the fertilizer granules, the samples were subjected to the described water test. The time course of nitrogen release from individual granular fertilizer samples is shown in Tables 1 and 2.

Table 1: Water test of granular fertilizer samples according to Examples 1-7

measurement day Concentration of N released [%] GH so mixture no. 1 GH so mixture no. 2 GH so mixture no. 3 GH so mixture no. 4 GH so mixture no. 5 GH so mixture no. 6 GH so mixture no. 7 1 First 1.7 1.8 2.2 0.8 0.9 0.5 0 2 Second 13.5 5.2 3.5 2.0 1.7 1.2 0 3 4th 11.4 4.3 2.0 2.6 1.8 0.9 2.9 4 7th 10.7 6.4 2.1 3.3 2.6 1.0 6.6 5 17th 21.8 8.8 3.2 12.5 11.2 4.4 20.1 6 28th 8.4 18.4 12.5 6.3 5.8 4.5 10.3 7 56th 2.4 4.9 6.2 2.7 2.7 3.2 8.2 8 84th 1.5 1.6 1.7 1.9 3.0 3.1 2.1 PRETTY 71.4 51.5 33.4 32.1 29.7 18.8 50.2 % wt. container 5.8 6.0 8.2 9.5 10.4 14.0 9.8

SK 288066 Β6

Table 2: Water test of granular fertilizer samples according to Examples 8-7

measurement day Concentration of N released [%] GH with mixture no. 8 GH with mixture no. 9 1 1 3.0 5.2 2 2 14.3 11.8 3 4 12.1 14.7 4 7 11.7 9.9 5 17 35.8 45.2 6 28 22.6 12.5 PRETTY 99.5 99.3 % wt. container 8.1 8.4

A comparison of the results in Table 2 shows that 99.5% of the nitrogen was released after 28 days of testing with natural oils, whereas in Table 1 it was less than 71.5% after 84 days.

Industrial usability

The present invention can be used in the manufacture of granular controlled release fertilizer (PCF) fertilizers.

Claims (7)

PATENT CLAIMS A controlled-release granular fertilizer obtainable by coating the fertilizer granules with a low molecular weight epoxy resin mixture of 100 to 400 in an amount of 50 to 85 wt. %, imidazole derivative in an amount of from 1 to 20 wt. % and modified vegetable oil in an amount of from 10 to 30 wt. %. Granular fertilizer according to claim 1, characterized in that the low molecular weight epoxy resin of 100 to 400 is a diglycidyl ether of bisphenol A with an epoxy equivalent of 182-192 g / mol. Granular fertilizer according to claim 1 and 2, characterized in that the imidazole derivative is 2-ethyl-4-methylimidazole. Granular fertilizer according to any one of claims 1 to 3, characterized in that the modified vegetable oil is rapeseed oil methyl ester. Granular fertilizer according to any one of claims 1 to 4, characterized in that the coating composition contains optimally 77.3 wt. % epoxy resin, 3.4 wt. % imidazole derivative and 19.3 wt. % of rapeseed oil methyl ester. Granular fertilizer according to any one of claims 1 to 5, characterized in that the fertilizer is coated by sequential application of 3 to 20 doses of coating mixture, the application being carried out in a rotating roller or fluidized bed at a temperature of 60 to 120 ° C, preferably 105-115 ° C. Granular fertilizer according to claim 6, characterized in that the coating layer comprises 6 to 25% of the total weight of the coated granule, preferably 8 to 12 wt. %. End of document