Granular fertilizer containing guanylurea using biodegradable resin emulsion

Abstract

To obtain a guanylurea granular fertilizer with a high product yield while preventing guanylurea from dissolving in the granulation process.SOLUTION: A granular fertilizer containing 80 wt.% or more of guanylurea sulfate or guanylurea phosphate includes a biodegradable resin formed of an aqueous emulsion of a biodegradable resin having a minimum film-forming temperature of 80°C or lower in a state being dispersed inside the granular fertilizer. A manufacturing method for the granular fertilizer includes granulating a raw material including the guanylurea sulfate or guanylurea phosphate using the aqueous emulsion of biodegradable resin having the minimum film-forming temperature of 80°C or lower.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a granular fertilizer containing guanylurea as a main component, which utilizes an emulsion of a biodegradable resin. [Background technology]

[0002] Since their development in the 1970s, coated fertilizers have been used to reduce the labor required for fertilization, particularly in paddy fields where fertilization is heavy labor, and have been positioned as environmentally friendly agricultural materials because they reduce fertilizer resources by limiting the amount of fertilizer applied, as well as prevent water pollution caused by runoff of fertilizer components and reduce the generation of nitrous oxide gas, a greenhouse gas. However, since 2000, environmental pollution caused by microplastics has come to light, and coated fertilizer husks remain and run off as microplastics, so there is a demand for controlled-release fertilizers to replace the conventional non-degradable coated fertilizers.

[0003] As for controlled-effect fertilizers that can replace non-degradable coated fertilizers, Patent Documents 1 to 3 disclose technologies for coating granulated fertilizers with biodegradable resins, and Patent Document 4 discloses a technology for coating grains containing liquid fertilizer components with polylactic acid and using the coated grains for fertilizer granulation. Thus, there have been many technical proposals and publications regarding fertilizer coating using biodegradable resins.

[0004] Furthermore, as controlled-release fertilizers, many slow-release nitrogen fertilizers have been publicly known from Non-Patent Document 1, and among these, isobutyraldehyde condensed urea, acetaldehyde condensed urea, methylol urea polymer fertilizer, guanylurea sulfate, and oxamide are particularly widely used.

[0005] In particular, Patent Documents 5 and 6 show that the fertilizer efficacy of guanylurea can be adjusted according to the situation of use by adding a decomposition inhibitor, making it a highly effective slow-release nitrogen fertilizer that can replace non-decomposable coated fertilizers. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2019-534837 [Patent Document 2] JP 2003-55079 A [Patent Document 3] Patent No. 4050052 [Patent Document 4] Patent No. 6491380 [Patent Document 5] Patent No. 6125446 [Patent Document 6] Patent No. 6364394 [Non-patent literature]

[0007] [Non-Patent Document 1] Pocket Fertilizer Handbook 2019 / 2020 p88, by Agriculture and Forestry Statistics Association [Non-Patent Document 2] Pocket Fertilizer Handbook 2019 / 2020 p377-379, published by the Agriculture and Forestry Statistics Association Summary of the Invention [Problem to be solved by the invention]

[0008] Among the widely used slow-release nitrogen fertilizers, guanylurea sulfate and guanylurea phosphate are highly soluble in water, and when they are granulated by the commonly used wet tumbling granulation, the guanylurea dissolves in the granulation water, resulting in a significant drop in yield. Therefore, no fertilizer containing a large amount of guanylurea and granulated by tumbling granulation has been produced. As a similar fertilizer, Patent Document 5 and Patent Document 6 show guanylurea granules granulated by compression molding, but the guanylurea content of the examples granulated by tumbling granulation is 20% by weight or less, and no examples of granular fertilizers containing more than 80% by weight of guanylurea according to the present invention have been produced by tumbling granulation.

[0009] In granulating fertilizers, the additives described in Non-Patent Document 2 are used as granulation promoters to improve granulation properties and quality. However, in order to improve the yield reduction associated with guanylurea granulation, the raw material ratio of guanylurea must be significantly reduced, resulting in a decrease in the amount of nitrogen content and making it impossible to obtain the effectiveness of a slow-release nitrogenous granular fertilizer. [Means for solving the problem]

[0010] The inventors have investigated methods for granulating guanylurea and have found that a high product yield can be obtained by using an emulsion of a biodegradable resin as the granulation water and granulation promoter, thereby completing the present invention.

[0011] That is, the gist of the present invention is as follows. (1) A granular fertilizer containing 80% by weight or more of guanylurea sulfate or guanylurea phosphate, and having a biodegradable resin formed from an aqueous emulsion of a biodegradable resin having a minimum film-forming temperature of 80°C or less dispersed within the granular fertilizer. (2) A granular fertilizer according to (1) above, wherein the biodegradable resin contains polylactic acid. (3) A granular fertilizer according to (1) or (2) above, which does not contain 1-amidino-2-thiourea and sulfathiazole. (4) A method for producing a granular fertilizer according to any one of (1) to (3) above, comprising granulating a raw material containing guanylurea sulfate or guanylurea phosphate using an aqueous emulsion of a biodegradable resin having a minimum film-forming temperature of 80°C or lower. (5) The method according to (4) above, wherein the aqueous emulsion contains 1 to 50% by weight of a biodegradable resin. (6) The method according to (4) or (5) above, wherein the aqueous emulsion is sprayed or dropped and granulated by tumbling. (7) The method according to any one of (4) to (6), wherein the granulation is carried out using a pan granulator, a drum granulator or an agitator granulator. Effect of the Invention

[0012] According to the present invention, dissolution of guanylurea during granulation is suppressed and the raw material powders are bound together, thereby making it possible to obtain a high product yield with only two steps, granulation and drying. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The method for granulating guanylurea sulfate or guanylurea phosphate according to the present invention is not particularly limited as long as it is a granulation method classified as tumbling granulation, and examples thereof include the following methods.

[0014] That is, powdered fertilizer raw material with a particle size of less than 1.00 mm is thoroughly mixed. A known method can be used for mixing, and for example, mixing may be performed using a powder mixer, a crusher, a V-type mixer, or a sugar coating machine.

[0015] The granulator used for granulation can be any known granulator classified as a tumbling granulator, but it is particularly preferable to use a pan granulator, drum granulator or agitator granulator.

[0016] When the viscosity of the biodegradable resin emulsion is high, the viscosity can be reduced by mixing the biodegradable resin emulsion with water. The mixing can be performed by a known liquid mixing method and liquid mixing device. The viscosity of the biodegradable resin emulsion can be appropriately changed and adjusted within the range in which the biodegradable resin emulsion can be added, according to the performance of the sprayer and discharge nozzle attached to the tumbling granulator.

[0017] The viscosity of the biodegradable resin emulsion is not limited as it depends on the performance of the granulator, but it can usually be used within the range of 1 to 1,100 mPa s, and it is preferable to use it in the range of 1 to 50 mPa s especially when spraying.

[0018] The fertilizer raw material powder prepared by the above method is put into a tumbling granulator, and tumbling granulation is carried out while the viscosity-adjusted biodegradable resin emulsion is sprayed or dropped from a spray nozzle. At this time, the biodegradable resin emulsion is added to the position where the fertilizer raw material powder, which has been stirred up by the tumbling, falls and flows most rapidly inside the granulator, thereby making it possible to mix the biodegradable resin emulsion and the fertilizer raw material powder uniformly. The biodegradable resin emulsion also serves as granulation water that binds the particles of the fertilizer raw material powder, and it is possible to granulate by adding only the biodegradable resin emulsion, but if the formation of particles is insufficient with the addition of only the biodegradable resin emulsion, additional granulation water can be added.

[0019] The composition ratio of guanylurea sulfate or guanylurea phosphate must be 80% by weight or more, preferably 85% by weight or more, and more preferably 85 to 95% by weight, in order to maximize the nitrogen content.

[0020] The biodegradable resin in the biodegradable resin emulsion can be selected from polyvinyl alcohol, polybutylene adipate terephthalate, polybutylene succinate, polybutylene succinate adipate, polyethylene terephthalate succinate, polyethylene terephthalate copolymer, polytetramethylene adipate-co-terephthalate, aliphatic aromatic polyester, polybutylene adipate / terephthalate, butanediol / long-chain dicarboxylic acid copolymer, polylactic acid, polylactic acid / polyether copolymer, polylactic acid / polycaprolactone copolymer, polyglycolic acid, cellulose acetate, and starch polyester, but it is preferable to use polylactic acid, which can form a film at a relatively low temperature. In addition, multiple biodegradable resins can be mixed in any ratio to adjust the minimum film formation temperature. The minimum film formation temperature can also be lowered by using polylactic acid in this case.

[0021] In the present invention, a biodegradable resin emulsion is used whose minimum film-forming temperature is adjusted to 80°C or less, preferably 60°C or less. If the minimum film-forming temperature of the biodegradable resin emulsion exceeds 80°C, the biodegradable resin does not function as a granulation promoter that binds guanylurea in the rolling granulation process, and instead the adhesion of the fertilizer raw material to the inside of the granulator occurs due to the viscosity derived from the biodegradable resin emulsion, and the production of large particles or lumps exceeding the product size or the recovery amount of powdered material increases, resulting in a significant decrease in product yield. This occurs in the same way whether the guanylurea to be granulated is guanylurea sulfate or guanylurea phosphate. In order to avoid the influence of the raw material dissolution that occurs during granulation, it is necessary that the minimum film-forming temperature of the biodegradable resin emulsion is 80°C or less.

[0022] In the present invention, the minimum film-forming temperature refers to the minimum temperature at which a coating film made of an aqueous emulsion of a biodegradable resin changes from white to transparent.

[0023] The minimum film-forming temperature can be measured, for example, by coating a sample on black paper with a doctor blade (coating thickness: 50 μm) to prepare a test piece, then heating and drying the test piece in a hot air dryer at a specified temperature for 5 minutes, and determining the minimum temperature at which the coating changes from white to transparent.

[0024] As an example of an aqueous emulsion of a biodegradable resin having a minimum film-forming temperature of 80° C. or less, a polylactic acid emulsion is commercially available, and such a commercially available product can be used.

[0025] The content of the biodegradable resin in the granular fertilizer of the present invention is usually 0.5 to 10.0% by weight, and preferably 1.0 to 5.0% by weight.

[0026] If necessary, the granular fertilizer of the present invention may contain a granulation promoter (e.g., attapulgite, CMC (carboxymethylcellulose), lignin sulfonic acid, sodium polyphosphate, polyethylene glycol, polyvinyl alcohol, attapulgite, starch, gum arabic, molasses), peat moss, humic acid material, bentonite, zeolite, vermiculite, perlite, pulverized coal incineration ash, gypsum, or the like.

[0027] The proportions of these fertilizer components used can be appropriately varied within a range that does not impair the effects of the present invention. EXAMPLES

[0028] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these. In the following, all parts are by weight.

[0029] In the following, the minimum film-forming temperature of the biodegradable resin emulsion was measured as follows.

[0030] (Method for measuring the minimum film-forming temperature of biodegradable resin emulsion) A test piece (15cm x 7.5cm) made of black paper was fixed to a smooth plastic board, and 0.5g of biodegradable resin emulsion was dropped onto the center of the test piece and applied to the test piece using a doctor blade film applicator (Allgood Co., Ltd., coating width 5cm, coating thickness 50μm). The test piece coated with the biodegradable resin emulsion in a uniform thickness was heated and dried for 5 minutes in a ventilated dryer set to a predetermined temperature, and the transparency of the coating was visually confirmed. The lowest temperature at which the coating became transparent enough to confirm the black color of the test piece was recorded as the minimum film formation temperature.

[0031] (Example 1) 95.0 parts of guanylurea sulfate, sprayed with 20°C film-forming resin emulsion 95.0 parts of guanylurea sulfate, the particle size of which had been adjusted to less than 1.00 mm by sieving, was put into a pan granulator (pan diameter 80 cm, rotation speed 22 rpm, inclination angle 52.5°; the same applies below). A 10.0% by weight polylactic acid emulsion (commercial product A, minimum film formation temperature 20°C) was sprayed onto the mixture until the amount of polylactic acid added reached 5.0 parts, and granular fertilizer was obtained. The granular fertilizer was dried for 5 hours in a ventilated dryer set at 80°C.

[0032] (Example 2) 87.0 parts of guanylurea sulfate, dropwise addition of film-forming resin emulsion at 20°C 87.0 parts of guanylurea sulfate, the particle size of which was adjusted to less than 1.00 mm by sieving, 3.0 parts of attapulgite, a known granulation promoter, and 5.0 parts of gypsum dihydrate were charged into a stirring granulator (Nihon Eirich Co., Ltd., Intensive Mixer R02 type), and a polylactic acid emulsion adjusted to 40.0% by weight (commercial product A, minimum film formation temperature 20°C) was added dropwise until the amount of polylactic acid added reached 5.0 parts, and tumbling granulation was performed to obtain a granular fertilizer. The produced granular fertilizer was dried for 5 hours in a ventilated dryer set at 80°C.

[0033] (Example 3) 87.0 parts of guanylurea sulfate, sprayed with 80°C film-forming resin emulsion 87.0 parts of guanylurea sulfate, the particle size of which was adjusted to less than 1.00 mm by sieving, 3.0 parts of attapulgite, a known granulation promoter, and 5.0 parts of gypsum dihydrate were mixed by rolling in a sugar coating machine and then charged into a pan granulator. A 10.0% by weight polylactic acid emulsion (commercial product B, minimum film formation temperature 80°C) was sprayed on the mixture until the amount of polylactic acid added reached 5.0 parts, and a granular fertilizer was obtained. The granular fertilizer was dried for 5 hours in a ventilated dryer set at 80°C.

[0034] (Comparative Example 1) 87.0 parts of guanylurea sulfate, 180°C film-forming resin emulsion dripped 87.0 parts of guanylurea sulfate, the particle size of which was adjusted to less than 1.00 mm by sieving, 3.0 parts of attapulgite, a known granulation promoter, and 5.0 parts of gypsum dihydrate were charged into a stirring granulator (Nihon Eirich Co., Ltd., Intensive Mixer R02 type), and a polylactic acid emulsion adjusted to 40.0% by weight (commercial product C, minimum film formation temperature 180°C) was added dropwise until the amount of polylactic acid added reached 5.0 parts, and tumbling granulation was performed to obtain a granular fertilizer. The produced granular fertilizer was dried for 5 hours in a ventilated dryer set at 80°C.

[0035] (Comparative Example 2) 100.0 parts of guanylurea sulfate, no granulation promoter used 100.0 parts of guanylurea sulfate, which had been sieved to a particle size of less than 1.00 mm, was placed in a pan granulator. Granular fertilizer was obtained by rolling granulation while spraying tap water. The granular fertilizer was dried for 5 hours in a ventilated dryer set at 80°C.

[0036] (Comparative Example 3) 90.0 parts of guanylurea sulfate, 10.0 parts of a known granulation promoter 90.0 parts of guanylurea sulfate, which had been sieved to a particle size of less than 1.00 mm, 5.0 parts of attapulgite, a known granulation promoter, and 5.0 parts of bentonite were mixed by rolling in a sugar coating machine and then put into a pan granulator. Granulated fertilizer was obtained by rolling while spraying tap water. The granulated fertilizer was dried for 5 hours in a ventilated dryer set at 80°C.

[0037] (Comparative Example 4) 75.0 parts of guanylurea sulfate, 25.0 parts of a known granulation promoter 75.0 parts of guanylurea sulfate, which had been sieved to a particle size of less than 1.00 mm, 18.7 parts of superphosphate, and 6.3 parts of attapulgite, a known granulation promoter, were mixed by rolling in a sugar-coating machine and then put into a pan granulator. Granulated fertilizer was obtained by rolling while spraying tap water. The granulated fertilizer was dried for 5 hours in a ventilated dryer set at 80°C.

[0038] (Comparative Example 5) 71.2 parts of guanylurea sulfate, 5.8 parts of a known granulation promoter 71.2 parts of guanylurea sulfate, which had been sieved to a particle size of less than 1.00 mm, 23.0 parts of superphosphate, 1.1 parts of attapulgite, a known granulation promoter, and 4.7 parts of diatomaceous earth were mixed by rolling in a sugar coating machine and then charged into a pan granulator. Granulated fertilizer was obtained by rolling while spraying tap water. The granular fertilizer was dried for 5 hours in a ventilated dryer set at 80°C.

[0039] (Test Example 1) Product Yield and Particle Size Distribution Evaluation The total amount of fertilizer raw materials in the Examples and Comparative Examples shown in Table 1 was set as 100, and the yield was calculated from the weight of the granular fertilizer obtained after the drying step. Furthermore, the granular fertilizer was sieved through 4.00 mm and 2.00 mm sieves, which are the general particle size standards for commercially available chemical fertilizers, and the product yield was calculated from the weight of the granular fertilizer with a particle size of less than 4.00 mm and not less than 2.00 mm, and evaluated as shown in Table 2. In addition, the weight lost from the tumbling granulation step through the drying step, and the weight of the granular fertilizer with a particle size of not less than 4.00 mm or not less than 2.00 mm after sieving were totaled to calculate the loss rate in the granular fertilizer manufacturing step and evaluate it together with the product yield. In addition, product specifications with particle sizes between 4.00 mm and 2.00 mm were further sieved, and the weight of the granular fertilizer sieved into large particle sizes of 4.00 mm to 3.35 mm, medium particle sizes of 3.35 mm to 2.83 mm, and small particle sizes of 2.83 mm to 2.00 mm was measured and the particle size distribution was calculated and evaluated as shown in Table 3.

[0040] [Table 1]

[0041] [Table 2]

[0042] [Table 3]

[0043] In Examples 1 to 3, in which the minimum film-forming temperature of the biodegradable resin emulsion is 80°C or lower, the added biodegradable resin prevents excessive particle enlargement due to the dissolution of guanylurea sulfate, and the product yield is mainly obtained in the small particle size range of 2.83 mm to 2.00 mm, while preventing an increase in the loss rate due to particle sizes exceeding 4.00 mm.

[0044] In Comparative Example 2, in which neither a biodegradable resin nor a granulation promoter was used, the loss due to the particle size being 4.00 mm or more exceeded 60% by weight. Even in the case of a particle size of less than 4.00 mm, the yield was high for larger particle sizes, and the dissolution of guanylurea sulfate could not be prevented, leading to a state in which the particles were prone to enlargement.

[0045] In Comparative Example 1, in which the minimum film-forming temperature of the biodegradable resin was 180°C, and Comparative Examples 3 to 5, in which granulation was performed using only a known granulation promoter without using a biodegradable resin, the loss rate due to the particle size being 4.00 mm or more was about 50% by weight. Even within the product specifications, many of the particles had larger particle sizes, and the fertilizer granules were in a state where they were prone to becoming enlarged.

Claims

1. A granular fertilizer containing 80% by weight or more of guanylurea sulfate or guanylurea phosphate, and having a biodegradable resin formed from an aqueous emulsion of a biodegradable resin having a minimum film-forming temperature of 80°C or less dispersed within the granular fertilizer.

2. 2. The granular fertilizer according to claim 1, wherein the biodegradable resin comprises polylactic acid.

3. 2. The granular fertilizer according to claim 1, which is free of 1-amidino-2-thiourea and sulfathiazole.

4. A method for producing the granular fertilizer according to any one of claims 1 to 3, comprising granulating a raw material containing guanylurea sulfate or guanylurea phosphate with an aqueous emulsion of a biodegradable resin having a minimum film-forming temperature of 80°C or less.

5. 5. The method according to claim 4, wherein the aqueous emulsion contains 1 to 50% by weight of a biodegradable resin.

6. 5. The method according to claim 4, wherein the aqueous emulsion is sprayed or dropped and then tumbling granulated.

7. 5. The method according to claim 4, wherein the granulation is carried out using a pan granulator, a drum granulator or an agitator granulator.

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