SK500222010A3 - Granulated fertilizer with controlled release of nutrients - Google Patents

Abstract

Granular fertilizer with controlled release of nutrients can be prepared by coating the fertilizer with a mixture consisting of the alkyd resin containing cross-linkable functional groups with mean molecular weight between 500 and 2000 in the amount 30 to 80 % w/w, amino resin in the amount of 1 to 30 % and vegetable oil in the amount of1 to 30 % w/w. The coating mixture contains 66.6 % w/w of alkyd resin, 16.8 % w/w of amino resin, 8.3 % w/w of castor oil and 8.3 % w/w of butylalcohol, and the fertilizer is coated by gradual spraying of 3 to 20 doses of the coating mixture, wherein the coating is performed in the rotary cylindrical container or fluid apparatus at the temperature of 60 to 120 °C. The layer of coating mixture makes 6 to 25 % w/w of the overall weight of the coated granule.

Description

Technical field

The invention relates to a controlled-release granular fertilizer obtainable by coating the fertilizer granules with a mixture of alkyd resin, amino resin and vegetable oil. The rate of release of nutrients is regulated by the amount and ratio of alkyd and amino resins.

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 which, after granulation, adherence or crystallization, are applied with a protective coating to control water penetration, affecting the solubility ratio and the rate of nutrient release. 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,

- 2 - Two monomers are applied to the fertilizer surface, which are polymerised on the surface.

According to US Pat. 6,187,074 (2001), fertilizer granules can be coated with a carboxylethylene 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 for 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) may be applied first to the fertilizer granules and then to a 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 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 polymer component of the coating may also be a dispersed polysaccharide in the resin: 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,

-3-ethylene vinyl ketone, vinyl chloride or vinylidene acrylate copolymer. 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 polymeric coating component 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, methy-methylenebisacrylamide as a crosslinker in aqueous medium in the presence of urea, ammonium persulfate 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. Then a second layer consisting of a 95: 5 mixture of soybean oil, tung oil and absorbent sodium polyacrylate resin (Aqua Keep 10 SH) is 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 may also be coated with a thermoplastic resin and then a substance selected from the group consisting of other thermoplastic resins, resins

-4-hardeners or inorganic substances (JP 07315975; 1994). The urea granules with a diameter of 3.3 mm were coated with a wax and then a mixture of alkyd resin, tung oil, pentaerythritol linolan and metal soap.

JP 07033575 (1993) discloses granules coated with an oil-modified alkyd resin (soybean based) blend, unsaturated conjugated double bond oil (palm oil, tung oil, tall oil), pentaerythritol (maleic or phthalic anhydride), metal 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%).

Fertilizer granules in EP 520456 B1 (1991) are also coated with a composition comprising 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 nutrient 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 Sumidur44V10 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 after 130 days 88.3% nitrogen was released. 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 CN 101289349 (2008), the 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 polymeric 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. The water-soluble alkyd reagent comprises an alkyd prepolymer with 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).

-6Checking the release of nutrients 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, whereby the moisture content of the soil, pH, weather, respectively. microbiological activity has a low effect on release. In polyethylene containers, a portion of the low permeability polyethylene is replaced by a high permeability polymer, e.g. ethylene vinyl acetate.

A major problem with the use of an alkyd resin for coating granules is its low glass transition temperature (Tg) and the resulting lower water resistance of the film. At the same time, the low Tg also causes its significant tackiness in its 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. All this results in insufficient nutrient utilization by plants and, as a result, significant nutrient losses. In order to prevent the granules from sticking during the coating, e.g. addition of native vegetable oil (palm, rapeseed, castor, linseed).

However, if the oil does not become part of the polymer chain, it may be degraded during storage under certain conditions and thus deteriorate in packaging quality.

These and other disadvantages of the described processes are overcome by the application of the present invention.

SUMMARY OF THE INVENTION

A substantial part of the above drawbacks is overcome by the controlled nutrient granular fertilizer of the present invention, which is obtainable by coating the fertilizer granules with a mixture consisting of alkyd resin containing crosslinkable functional groups having a mean molar mass of 500 to 2000. Alkyds are classified as polyesters and prepared from acid anhydrides (phthalic, maleic, linoleic anhydride) and polyols (glycerol, pentaerythritol) in the presence of

-Ί unsaturated fatty acids (castor, soybean, linseed oil) that help the film dry in the air. Oils, due to the presence of double bonds in acids, react with air oxygen and crosslink the individual components of the coating. Calcium, zirconium or cobalt salts of octylic or naphthenic acid, metal soaps, etc. are added to accelerate the drying of the coating.

Amino resin addition (urea, melamine, benzoguanamine resin) may be used to increase the water resistance of the alkyd resin film (JP 07033575 (1993)). Amino resins have a significantly higher Tg value than the alkyd resin and therefore increase film hardness after setting. According to the present invention, it is preferred to use the alkyd resin either as an inner shell of the granule to which the amino resin film is then applied or to use the amino resin to coat the granules in admixture with the alkyd resin. In both cases, however, the amino resin does not directly react with the tung oil alkyd resin but is self-condensing. In the absence of cross-linking of alkyd and amino resins, the quality of the coating may deteriorate during prolonged storage of the coated granules.

The quality problems of the alkyd resin-based fertilizer coating can be avoided by creating conditions such that the alkyd and amino resin crosslinks during granular coating. This process not only significantly shortens the drying process of the mixture on the surface of the granules (from 60 minutes to 10 minutes) but also significantly reduces the necessary proportion of the coating to the weight of the coated granules (see examples).

In order to achieve crosslinking, the alkyd resin must contain crosslinking functional groups (hydroxy, amino, epoxy group). Since the esterification process in the production of a standard alkyd resin is led to a high degree of conversion, there is only a minimum of free hydroxy groups in the structure of the resin molecule.

The functional group can be incorporated into the alkyd resin structure by, for example, seeding with a functional monomer (2-hydroxyethyl methacrylate, N-methylolacrylamide, ethylene glycol dimethacrylate, etc.). This variant of treating the alkyd resin allows the oil present in the resin to contain acids (e.g., oleic, linoleic) having one or two acids, respectively. two double bonds and these are capable

-8polymerizácie. An organic peroxide (tert-butyl hydroperoxide, tert-butyl perbenzoate) can be used as initiator. The inoculation is carried out at a temperature of 120 to 180 ° C.

A second variant is the use of a castor oil alkyd resin. Castor oil consists largely of ricinoleic acid triglycerides. It contains in its molecule a reactive -OH group suitable for crosslinking with the methylol groups of the amino resin.

Since the inoculation process requires an extra technological step, it appears economically more advantageous to apply an alkyd resin of preferably pentaerythritic polyester of the orthophthalic type modified with castor oil fatty acids available on the market without further treatment for coating. The amount of alkyd resin in the coating composition ranged from 30 to 80 wt. %.

A suitable resin of the castor oil alkyd resin was an amino resin containing reactive methylol groups (-CH ₂ -OH). The concentration of the amino resin in the mixture with the alkyd resin ranged from 1 to 30 wt. %.

As an alkyd resin hardener, urea-formaldehyde resin or melamine-formaldehyde resin, preferably methylated, e.g. with higher reactivity. In order to prolong the pot life of the alkyd / amino resin mixture, it has been found appropriate to dissolve the amino resin in butyl alcohol, preferably butyl acetate, before adding it to the alkyd resin.

An additional addition of vegetable oil (palm, rapeseed, castor, linseed) has proven to be suitable to prevent the granules from sticking during the coating. Sufficient addition of vegetable oil to the alkyd resin and amino resin mixture ranges from 1 to 40 wt. %. It has been found advantageous to use castor oil in the presence of an amino resin to prevent sticking. This reacts with the amino resin and thus prevents oil degradation during storage of the coated fertilizer.

The coating composition can be prepared in a container with a stirrer at room temperature. After weighing the alkyd resin, the amino resin dissolved in butyl alcohol is gradually added. After thorough mixing, vegetable oil is added. After homogenization, the coating composition is ready for coating, which is effected by spraying 3 to 20 batches of coating composition in a rotating cylinder or fluidized bed at a temperature of 60 to 120 ° C, preferably 80 to 100 ° C. Is a

Desirably, the resulting granule comprises a coating composition based on the coating composition in an amount of 6 to 25 wt. % of the total weight of the coated granule, preferably 9 to 15 wt. %.

Coating under laboratory conditions was carried out in an Aeromatic AG dryer with the coating mixture being applied by means of compressed air. The granules were entrained and dried with a stream of warm air flowing from the bottom, narrower portion of the column. The coating mixture was dosed into the air stream by means of a syringe. The coating mixture was injected in 4 to 10 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 from the previous batch had cured 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.

Granules from Agrofert Duslo a.s. The range is Duslofert Extra NPK 14-10-20 (+ 7S) and ammonium nitrate granulate with finely ground dolomite (Ammonium Leak, 27% N). The diameter of the granules was 2 to 5 mm. The granules were coated with the alkyd resin compositions of Examples 1 to 6.

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.

A fine, washed and dried sand was used, i. 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 1-5

Nitrogen fertilizer granules (ammonium nitrate with finely ground dolomite) were used to prepare the coated fertilizer of the present invention. For coating 1 kg of granules, the following coating compositions were prepared:

1. 63.6% alkyd resin (R 45/65 BC), 18.2% amino resin (Luwipal), 9.1% castor oil and 9.1% butyl alcohol

2. 69.2% alkyd resin (R 45/65 BC), 15.4% amino resin (Luwipal), 7.7% castor oil and 7.7% butyl alcohol

3. 73.3% alkyd resin (R 45/65 BC), 13.3% amino resin (Luwipal), 6.7% castor oil and 6.7% butyl alcohol

4. 76.5% alkyd resin (R 45/65 BC), 11.7% amino resin (Luwipal), 5.9% castor oil and 5.9% butyl alcohol

5. 78.9% alkyd resin (R 45/65 BC), 10.5% amino resin (Luwipal), 5.3% castor oil and 5.3% butyl alcohol

The ammonium nitrate granules were heated to 100 ° C with a stream of warm air. The coating mixture was sprayed gradually. After coating the fertilizer granules, the samples were subjected to a water test. The time course of nitrogen release from individual samples of granular fertilizer is shown in Table 1.

Table 1: Water test of granular fertilizer samples prepared according to Examples 1-5

measurement day Concentration of N released [%] GH so mixture no. 1 GH so mixture no. 2 GHso mixture no. 3 GHso mixture no. 4 GH so mixture no. 5 1 First 1.8 0.9 0.4 0.5 0.5 2 Second 4.8 3.4 0.9 1.5 2.0 3 4th 6.7 4.4 1.2 1.9 3.0 4 7th 8.2 4.9 1.7 2.2 3.5 5 17th 48.1 39.5 27.6 16.9 6.0 6 28th 95.3 91.0 74.7 63.6 35.9 7 56th - - 99.9 92.4 69.7 8 84th - - - - 85.6 9 112th - - - - 96.5 % wt. container 7.2 8.5 9.8 11.1 12.4

Example 6

For coating, the Duslofert Extra NPK 14-10-20 (+ 7S) fertilizer pellets were used according to the present invention. A coating composition consisting of 66.6% alkyd resin (R 45/65 BC), 16.8% amino resin (Luwipal), 8.3% castor oil, and 8.3% butyl alcohol was prepared. The dry weight of the mixture was 67%. The following batches of the mixture were tested for granulating:

1. 150 g / 1 kg granules

2. 140 g / 1 kg granules

3. 130 g / 1 kg granules

4. 120 g / 1 kg granules

5. 110 g / 1 kg granules

The granules were heated to 100 ° C with a stream of warm air. The coating composition was dosed sequentially. After coating the fertilizer granules, the samples were subjected to a water test. The measured values of nitrogen evolution over time are shown in Table 2.

- 12Table 2: Water test of granular fertilizer samples prepared according to Example 6

measurement day Concentration of N released [%] GH with dose no. 1 GH with dose 2 GH with dose 3 GH with dose 4 GH with dose 5 1 First 0.9 1.0 0.4 2.1 1.4 2 Second 2.3 4.0 4.6 11.3 14.2 3 4th 2.8 11.4 15.2 27.0 34.2 4 7th 3.8 17.9 24.6 45.5 74.4 5 17th 17.5 39.7 48.3 76.3 97.8 6 28th 56.1 62.4 71.8 98.1 - 7 56th 75.6 85.2 98.1 - - 8 84th 89.1 96.9 - - - 9 112th 94.2 - - - - % wt. container 8.5 7.8 6.9 6.1 5.4

Tables 1 and 2 show the results of an aqueous test of coated nitrogen and granular fertilizer granules with a mixture of alkyd resin based on conjugated esters of orthophthalic acid and pentaerythritol containing castor oil and melamine formaldehyde resin. The results show that by crosslinking an alkyd resin with an amino resin, as opposed to physical drying of the alkyd resin (see Examples 7 to 11) on the granule surface, it is possible to achieve a sustained release of nutrient from the fertilizer at a lower coating ratio. ).

Example 7

Duslofert Extra NPK 14-10-20 (+ 7S) fertilizer pellets were used for coating. A coating composition of 69.4% alkyd resin (CHS Alkyd 870), 19.8% amino resin (Cymel 303), 10.3% rapeseed methyl ester, 0.3% p-toluenesulfonic acid and 0.2% was prepared. cobalt octylate.

13 The dry mixture was 97%. The following batches of the mixture were tested for granulating:

1. 180 g / 1 kg granules

2. 150 g / 1 kg granules

3. 100 g / 1 kg granules

The granules were heated to 100 ° C with a stream of warm air. The coating composition was dosed sequentially. After coating the fertilizer granules, the samples were subjected to a water test. The measured values of nitrogen evolution over time are shown in Table 3.

Table 3: Water test of granular fertilizer samples prepared according to Example 7

measurement day Concentration of N released [%] GH with dose no. 1 GH with dose 2 GH with dose 3 1 First 1.3 3.0 5.4 2 Second 3.7 5.9 12.6 3 4th 8.1 12.4 18.2 4 7th 16.8 21.9 29.8 5 17th 37.1 49.7 58.3 6 28th 66.8 75.4 97.4 7 56th 85.4 97.5 - 8 84th 99.1 - - % wt. container 17.1 14.5 9.3

Table 3 shows the results of an aqueous test of coated fertilizer granules (Duslofert Extra NPK 14-10-20 (+ 7S)) with a mixture of alkyd resin based on conjugated isophthalic acid esters and pentaerythritol containing tall oil and melamine formaldehyde resin with a high degree of alkylation. In the granular coating process, crosslinking does not occur because the alkyd resin used does not contain crosslinkable functional groups but the physical process of drying the alkyd resin under the catalytic action of the metal soap and the melamine resin self-condenses by the acid catalyst.

- 14Example 8

Table 4: Water test of granulated fertilizer samples with a mixture of alkyd resin containing tung oil and cobalt octylate [US 5310785 (1994)]

measurement % weight. container Concentration of released nitrogen (wt%) Third day 10th day 30th day 50th day 70th day 1 17.6 0.7 7.5 45.0 66.0 78.1 2 18.7 0.7 5.2 46.5 67.4 77.0

Table 4 shows the results of an aqueous test of coated nitrogen fertilizer (urea) granules with an alkyd resin mixture based on conjugated linoleic acid and pentaerythritol esters containing tung oil and cobalt octylate according to US 5310785 (1994). In the process of coating the granules, there is no cross-linking but a physical process of drying the alkyd resin under the catalytic action of the metal soap.

Example 9

Table 5: Water test of granular fertilizer samples with alkyd resin mixture containing soybean and tung oil and metal soap [JP 6056567A (1994)]

measurement % weight. container Concentration of released nitrogen (wt%) 10 day 20 day 30 day 50 day 70 day 90 day 1 15.0 6.1 33.2 50.9 66.4 75.2 - 2 20.0 0.6 11.2 27.9 50.5 63.9 73.9

Table 5 shows the results of an aqueous test of coated nitrogen fertilizer (urea) granules with an alkyd resin mixture based on conjugated linoleic acid and pentaerythritol esters containing soybean and tung oil and metal soap according to JP 6056567A (1994). In the process of coating the granules, there is no cross-linking but a physical process of drying the alkyd resin under the catalytic action of the metal soap.

- 15Example 10

Table 6: Water test of granular fertilizer samples with alkyd resin mixture containing soy and tung oil, metal soap and wax [JP 8151286A (1996)]

measurement % weight. container Concentration of released nitrogen (wt%) Day 30 5O.deň 7O.deň 9O.deň 1 13.6 33.0 61.0 80.0 94.0 2 14.1 40.0 75.0 90.0 -

Table 6 shows the results of an aqueous test of coated nitrogen fertilizer (urea) granules with a mixture of alkyd resin based on conjugated maleic acid and pentaerythritol esters containing soybean and tung oil, metal soap and wax according to JP 8151286A (1996). In the process of coating the granules, there is no cross-linking but a physical process of drying the alkyd resin under the catalytic action of the metal soap.

Example 11

Table 7: Water test of granular fertilizer samples with alkyd resin mixture containing soybean and tung oil metal soap [JP 7315975A (1995)]

measurement % weight. container Concentration of released nitrogen (wt%) 10 day 20 day 30 day 50 day 70 day 90 day 1 17.3 8 19 38 63 77 94 2 17.0 6 15 27 57 79 98 3 12.0 22 51 89 98 - -

Table 7 shows the results of an aqueous test of coated nitrogen fertilizer (urea) granules with an alkyd resin mixture based on conjugated linoleic acid and pentaerythritol esters containing soybean and tung oil and metal soap according to JP 7315975A (1995). In the process of coating granules

- 16 there is no crosslinking but a physical process of drying the alkyd resin under the catalytic action of the metal soap.

The process of physical drying of the alkyd resin is time consuming. At the same time, cross-linking is sufficient to achieve the desired level of nitrogen release rate by lowering the percentage of packaging (8% - 12%), thus making the coating process more economical.

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 with a mixture consisting of an alkyd resin containing cross-linking functional groups having an average molar mass of 500 to 2000 in an amount of 30 to 80 wt. % amino resins in an amount of 1 to 30 wt. % and vegetable oil in an amount of 1 to 30 wt. %. Granular fertilizer according to claim 1, characterized in that the amino resin is dissolved in butyl alcohol, preferably butyl acetate. Granular fertilizer according to claim 1 or 2, characterized in that the amino resin is a methylated melamine-formaldehyde resin. Granular fertilizer according to any one of claims 1 to 3, characterized in that the vegetable oil is castor oil. Granular fertilizer according to any one of claims 1 to 4, characterized in that the coating composition comprises 66.6 wt. % alkyd resin, 16.8 wt. % amino resin, 8.3 wt. % castor oil and 8.3 wt. % butylalcohol. Granular fertilizer according to any one of claims 1 to 5, characterized in that the fertilizer is coated by sequentially spraying 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, with preferably 80 to 100 ° C. A granular fertilizer according to claim 6, characterized in that the coating mixture layer comprises 6 to 25 masses. % of the total weight of the coated granule, preferably 9 to 15 wt. %.