JP2008222536A - Coating composition for fertilizer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating composition for fertilizer which uses raw materials having biodegradability and can be well adjusted in the elution accuracy of fertilizer components by the use of a simple method. <P>SOLUTION: The coating composition for fertilizer is prepared by reacting an alkyd resin, which is modified with a sorbitan fatty acid ester, and polyisocyanate. The use of the coating composition for fertilizer improves the biodegradability of the coating composition and produces a coated fertilizer which is adjusted the elution of fertilizer components with well accuracy, and thereby the technology is extremely useful in industrial utilization. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fertilizer coating composition. More specifically, the present invention relates to a fertilizer coating composition that can adjust the elution accuracy of fertilizer components satisfactorily by a simple method using a biodegradable raw material.

In recent years, many coated granular fertilizers due to environmental problems such as eutrophication in closed waters such as lakes and marshes and groundwater contamination by nitrate nitrogen, demand for labor-saving fertilizers due to a decrease in the agricultural population and the aging of workers, etc. Has been developed and commercialized. However, problems such as an increased load on the environment have arisen due to the non-disintegrating nature of these fertilizer coatings.
Therefore, as a coating material having a low environmental load, the use of castor oil or castor oil derivative having an ester bond as a raw material of the resin can be expected to provide biodegradability of the resin. A method of using a polyurethane resin reacted with polyisocyanate as a coating has been proposed (see, for example, Patent Documents 1 to 3).
However, such a resin coating composition is not yet sufficiently effective in terms of biodegradability.

The present inventors have developed a coated granular fertilizer using an oil-modified alkyd resin and a polyisocyanate as a fertilizer coating material as a coating composition with good elution accuracy of fertilizer in adjusting fertilization effect, and filed an application earlier. (For example, see Patent Documents 4 and 5).
However, although the elution performance of these fertilizers is excellent, the effect of the biodegradability of the resin component is not sufficient.
In other words, the elution control of fertilizer components and the biodegradability of the resin require a contradictory effect, and those with easy elution control are poor in biodegradability. As a result, elution control becomes difficult.
Accordingly, the present situation is that there is a strong demand for the appearance of a fertilizer coating composition that has both the elution characteristics of the fertilizer component and the biodegradability of the resin component.

Patent Registration No. 3161997 Japanese Patent Laid-Open No. 2001-213865 JP 2005-1957 A JP 2001-163691 A JP 2003-277178 A

  In order to develop a coating composition for a fertilizer that has both the elution characteristics of the fertilizer component and the biodegradability of the resin component as described above, the present inventors use a raw material having biodegradability, We have intensively studied to develop a fertilizer coating composition with excellent elution accuracy of fertilizer components that can be manufactured by this method.

  As a result, the polyurethane resin obtained by reacting this with a polyisocyanate component using an alkyd resin modified with sorbitan fatty acid ester as a polyol component becomes an excellent fertilizer coating composition that solves the aforementioned problems. And the present invention was completed based on such findings.

That is, the present invention relates to a fertilizer coating composition obtained by reacting an alkyd resin modified with a sorbitan fatty acid ester and a polyisocyanate.
The coated fertilizer coated with a polyurethane resin obtained by reacting these raw materials has excellent characteristics that the elution of the fertilizer components can be controlled with high accuracy and the biodegradability of the coating is promoted.

  The use of the coating material in the present invention can promote the biodegradability of the coating composition and can produce a coated fertilizer in which the elution of fertilizer components is accurately adjusted. Therefore, the technology of the present invention is utilized industrially. Very useful above.

Hereinafter, the present invention will be described in more detail.
The fertilizer coating composition used for coating in the present invention is a polyurethane-based resin, and is a thermosetting resin formed by a reaction between an alkyd resin and a polyisocyanate.
The alkyd resin used in the present invention is characterized in that sorbitan fatty acid ester is used as a modifier.

As a method for synthesizing an alkyd resin by modifying the alkyd resin with a sorbitan fatty acid ester, any of a commonly used direct method, an alcoholysis method, and an acidolysis method may be used. The direct method is a method in which sorbitan fatty acid ester, polybasic acid, polyhydric alcohol and the like are simultaneously charged and heated to polyester to synthesize an alkyd resin. In the alcoholysis method, first, an alcoholysis reaction is carried out with a sorbitan fatty acid ester and a polyhydric alcohol to form a fatty acid partial ester of the polyhydric alcohol, and then a polyesterification reaction is carried out with the hydroxyl group and a polybasic acid. This is a method of synthesizing an alkyd resin by a two-stage method.
In addition, in the acidolysis method, in the first stage, a part of the fatty acid group of the sorbitan fatty acid ester is esterified with the polybasic acid group by an acidolysis reaction between the sorbitan fatty acid ester and the polybasic acid. Thereafter, in the second stage reaction, polyhydric alcohol or the like is added to proceed with the polyesterification reaction to synthesize an alkyd resin. Of these, a direct method with few reaction steps, or a method in which the reaction is carried out by an alcoholysis method that can easily control the reaction rate and stabilize the quality is industrially advantageous.

  The sorbitan fatty acid ester is a sorbitan obtained by intramolecular dehydration of sorbit and a fatty acid ester-bonded, and there are 1,5-sorbitan fatty acid ester, 1,4 or 3,6-sorbitan fatty acid ester. For example, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan sesquistearate, sorbitan tristearate, sorbitan monooleate, sorbitan sesquioleate, sorbitan trioleate, sorbitan monoisostearate, sorbitan sesquiisostearate Etc. Mixtures of these can also be used. Of these, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, and sorbitan trioleate are preferably used.

When the alkyd resin using sorbitan fatty acid ester as a modifier is urethanized and used as a coating material, the sorbitan fatty acid ester content in the alkyd resin is usually 5 from the viewpoint of both biodegradability and elution controllability of the film. -70 mass%, Preferably, it is 10-50 mass%. If it is less than 5% by mass, the biodegradability of the film is insufficient, and if it exceeds 70% by mass, the biodegradability is too early to make it possible to adjust elution, and the strength of the coating film is lowered and defects are likely to occur.
In the present invention, as the alkyd resin, an oil-modified alkyd resin modified with vegetable oil such as linseed oil or castor oil or a fatty acid thereof may be used.

Except for using the sorbitan fatty acid ester as a modifier, the raw materials used for the alkyd resin are not particularly limited in addition to the above oil-modified raw materials, and polybasic substances such as phthalic acid, maleic acid, adipic acid, and sebacic acid Acid and glycerin, ethylene glycol, hexanediol, pentaerythritol, trimethylolpropane, sorbitol, mannitol and other polyhydric alcohols, or oxyacids and cyclic esters such as lactic acid, glycolic acid, caprolactone, hydroxystearic acid and ricinoleic acid can do.
From the viewpoint of film strength when urethane is used as a resin, it is more preferable to use phthalic acid or adipic acid as the polybasic acid, and glycerin, trimethylolpropane or hexanediol as the polyhydric alcohol. .

The alkyd resin obtained by heat condensation of the above raw materials is preferably urethane having a hydroxyl value of 50 to 400 for urethanization and use as a coating material. Outside this range, the elution of fertilizer components should be accurately adjusted. Becomes difficult. That is, when the hydroxyl value exceeds 400, the coating becomes brittle, and when it is less than 50, the coating becomes soft. In any case, the coating tends to be deficient. As for the acid value, if the acid value is high, the urethanization reaction is inhibited and the curability of the film is deteriorated, and it is difficult to form a uniform film. Therefore, the acid value is 15 or less, more preferably 10 or less. .
By the way, regarding the polyisocyanate used for urethanization, monomeric diisocyanate and liquid polyisocyanate can be used. Preferable examples include tolylene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, xylene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate and the like. Mixtures of these can also be used. However, among these, the use of polymethylene polyphenyl polyisocyanate is most preferable from the viewpoint of the present invention and the film-forming property.

  The reaction ratio between the alkyd resin and the polyisocyanate is preferably in the range of 0.5 to 2.0 as the molar ratio of isocyanate group to hydroxyl group (NCO / OH). When this molar ratio is less than 0.5 and polyurethane crosslinking decreases, the water resistance of the coating decreases. In addition, when the molar ratio exceeds 2.0 and the polyurethane crosslinking increases, the biodegradability becomes insufficient.

  In the reaction between the alkyd resin and the polyisocyanate, a catalyst can be added and used to accelerate the reaction. For example, an organic salt such as potassium octoate or an amine compound such as triethylenediamine can be used as the catalyst. However, it is preferable to use potassium aliphatic monocarboxylate because the reaction rate can be easily adjusted and a uniform film can be easily formed. It is also useful to use organic salts such as manganese naphthenate and cobalt octoate as a crosslinking catalyst for the purpose of crosslinking between alkyd resin molecules to form a tougher film.

  The fertilizer that can be used in the present invention is not particularly limited as long as it is granular. For example, urea, ammonium sulfate, ammonium chloride, ammonium phosphate, ammonium nitrate, potassium sulfate, potassium chloride, magnesium phosphate, ammonium phosphate, ammonium sulfate sulfate. Typical examples thereof include granular products such as potassium phosphate, potassium phosphate and lime superphosphate. Moreover, there is no restriction | limiting in particular regarding the particle size of a granular fertilizer, The use of about 1 mm-5 mm is preferable.

Next, with respect to the method for coating the granular fertilizer of the present invention, each coating material, that is, the alkyd resin and the polyisocyanate are caused to adhere to and react with the granular fertilizer in a fluidized or rolled state. A film is formed on the surface of the granular fertilizer by heating with, for example.
As a method of flowing and rolling the granular fertilizer in this way, for example, a fluidizing device or a jet fluidizing device can be used for fluidization, and a device such as a rotating pan or a rotating drum can be used for rolling.
Each coating material is preferably liquefied and adjusted to have a viscosity of 300 mPa · s or less. For example, in the case of an alkyd resin, the resin temperature may be heated to 80 to 120 ° C. and used.
As the polyisocyanate, those having a viscosity of 300 mPa · s or less at room temperature can be used as they are, and those having a solid state can be heated to a melting point or higher to be liquefied. In this case, if the viscosity of the coating material exceeds 300 mPa · s, the workability is deteriorated, and further, it becomes difficult to form a uniform film, and the elution control of the fertilizer becomes difficult.

The method of attaching the coating material to the fertilizer particles is not particularly limited as long as the coating material can be uniformly applied to the fertilizer particles, and can be performed without being limited to spraying or dropping.
Moreover, each coating | coated material may be sprayed on a granular fertilizer from the same location, or may be sprayed from a separate location. However, from the viewpoint of workability, it is preferable that the catalyst is used by being mixed with the alkyd resin in advance, and the alkyd resin and the polyisocyanate are sprayed from different places.
In order to harden the coating formed by the adhesion and reaction of the coating material to the fertilizer, it is only necessary to heat in the range of room temperature to 90 ° C, but if the curing temperature is too low, the viscosity of the sprayed solution will increase, and the fertilizer A uniform film is not formed on the particle surface. On the other hand, when the curing temperature is too high, the speed of the urethanization reaction is increased, so that it is difficult to adjust the curing speed, and it is difficult to form a uniform film. Therefore, the heating temperature is more preferably in the range of 50 ° C to 80 ° C.

By the way, it is desirable to form the coating on the fertilizer particles by repeating the adhesion of the coating material and heating and drying, that is, a dense coating can be formed by multilayering the coating by repetition. In this case, the amount of the coating material used for forming a single coating varies depending on conditions such as the spraying or dripping speed of the coating material, the curing speed, etc., and cannot be generally mentioned. Preferably it is 0.3-1.5 mass%. Below this lower limit, the number of coatings increases, which is not only industrially disadvantageous, but also tends to cause coating unevenness. On the other hand, if the upper limit is exceeded, a large number of coating material lumps are formed on the granular fertilizer particles, and these lumps are detached from the fertilizer particles during rolling or flow, and defects in the coating are liable to occur.
It is preferable that the coating material is repeatedly adhered and dried to the fertilizer particles at least three times, that is, the coating is multilayered into three or more layers. With regard to the upper limit of the multi-layering, it is preferable that the number of coatings is 30 times or less, that is, the film is 30 layers or less. The number of repeated steps of attaching and drying the coating material to the fertilizer particles is out of the above range, and when the number is small, the initial elution rate of the fertilizer increases due to the influence of pinholes existing in the coating. Moreover, when the number of times increases, productivity decreases, which is industrially disadvantageous.

Further, the coating is within an allowable range in the elution performance of the fertilizer, and as an auxiliary means for improving workability and adjusting the fertilization effect, the coating material is an aliphatic ester, wax, rosin or a derivative thereof, a surfactant, talc, Various additives such as calcium carbonate may be added.
Also, when a more tough coating is required, such as when coated fertilizer is sprayed with a granular fertilizer spreader, it is also useful to form a protective film, for example, as a protective film forming material, polyethylene resin, Vinyl acetate resin, ethylene-vinyl acetate resin, polyvinyl alcohol resin, acrylic resin, alkyd resin, urethane resin and the like can be used. The use ratio of these additives and protective film forming agent is required to be 30% by mass or less of the total coating amount, and if it exceeds this, it may be difficult to achieve the object of the present invention. is there.
The fertilizer coated with the fertilizer coating composition of the present invention thus obtained has a coating that is biodegradable, the fertilizer components are accurately dissolved and adjusted, and industrially advantageous such as production efficiency. Become a granular fertilizer.

  The following examples further illustrate the present invention, but the present invention is not limited thereto. In Examples, “%” means “% by mass” unless otherwise specified.

<Synthesis of modified alkyd resin>
An alkyd resin modified with sorbitan fatty acid ester was obtained by the following method.

(Synthesis of resin A)
A 1L four-necked flask equipped with a stirrer, a condenser with a water separator, a thermometer, and a nitrogen gas inlet tube was mixed with castor oil 117g, oleic acid 42g, adipic acid 84g, trimethylolpropane (TMP) 123g, tristearic acid 157 g of sorbitan and 15 g of xylene were charged, the temperature was raised, and the reaction was carried out at 230 ° C. for 5 hours under reflux of xylene. Next, xylene was recovered under reduced pressure to obtain 500 g of a sorbitan fatty acid ester-modified alkyd resin. The composition ratio of this resin is shown in Table 1.

(Synthesis of resin B)
Into a 1L four-necked flask equipped with a stirrer, condenser with water separator, thermometer and nitrogen gas inlet tube, 139g castor oil, 49g oleic acid, 87g succinic acid, 95g glycerin, 159g sorbitan tristearate, and xylene 15 g was charged and the temperature was raised, and the reaction was carried out at 230 ° C. under reflux of xylene for 5 hours. Next, xylene was recovered under reduced pressure to obtain 500 g of a sorbitan fatty acid ester-modified alkyd resin. The composition ratio of this resin is shown in Table 2.

(Synthesis of Resin C)
A 1L four-necked flask equipped with a stirrer, condenser with water separator, thermometer and nitrogen gas inlet tube was charged with 14g castor oil, 24g adipic acid, 62g glycerin, 405g sorbitan tristearate, and 15g xylene. The reaction was carried out at 230 ° C. under reflux of xylene for 5 hours. Next, xylene was recovered under reduced pressure to obtain 500 g of a sorbitan fatty acid ester-modified alkyd resin. The composition ratio of this resin is shown in Table 3.

(Synthesis of Resin D)
A 1 L four-necked flask equipped with a stirrer, condenser with water separator, thermometer and nitrogen gas inlet tube was charged with 296 g of castor oil, 48 g of oleic acid, 95 g of adipic acid, 87 g of glycerin and 15 g of xylene, and the temperature was raised. The reaction was carried out at 230 ° C. under reflux of xylene for 5 hours. Next, xylene was recovered under reduced pressure to obtain 500 g of an alkyd resin not modified with sorbitan fatty acid ester. The composition ratio of this resin is shown in Table 4.

(Synthesis of resins E, F and G)
A 1 L four-necked flask equipped with a stirrer, a cooler with a water separator, a thermometer, and a nitrogen gas introduction tube is reacted in the same manner as in the synthesis method of resins A, B, C, and D. 500 g of sorbitan fatty acid ester-modified alkyd resin of G was obtained. The composition ratios of these resins are shown in Table 5.

In using the fertilizer coating composition of the present invention, the raw materials used were as follows.
Modified and unmodified alkyd resins: 1% aliphatic monocarboxylate solution (concentration 70%) as a catalyst is mixed with the modified and unmodified alkyd resins shown in Tables 1 to 5 and heated to 100 ° C for coating. Used as raw material.
Polyisocyanate component: Polymeric diphenylmethane diisocyanate (manufactured by Sumika Bayer Urethane, trade name Sumijour 44V10)

[Production method of coated granular fertilizer]
1 kg of granular urea (average particle diameter: 3 mm) was charged into a centrifugal rolling granulation coating apparatus (rotating disk diameter: 230 mm) equipped with a hot air generator. The rotating disk of the apparatus was rotated at 200 rpm to bring the granular fertilizer into a rolling state, and hot air was fed from the lower part and maintained at 70 ° C.
Spray the heated and rolling granular urea with 4.0g modified alkyd resin or unmodified alkyd resin and 2.0g polyisocyanate component separately from two places with two fluid nozzles and roll for 2 minutes to cure. I let you. In this case, the reaction ratio between the modified alkyd resin or unmodified alkyd resin and the polyisocyanate component is 1.0 as the molar ratio of isocyanate group to hydroxyl group (NCO / OH).
This spraying and curing process was repeated 19 times to produce a coated granular fertilizer. The coverage in this case is about 10%. The coverage of the coating composition was determined by the following formula.
Covering rate (%) = (film mass / mass of coated granular fertilizer) × 100
As the performance evaluation of the fertilizer coating composition obtained by the coating test, the biodegradability evaluation of the coating composition and the measurement of the fertilizer elution rate were performed. The measuring method is as follows.

[Measurement of biodegradability of coating composition for fertilizer]
The biodegradation degree of the coating composition was measured according to "JIS K 6950 Plastic-Determination of aerobic ultimate biodegradation degree in aqueous medium-Method by measurement of oxygen consumption using a closed respirometer". .
Device: Closed system oxygen consumption measuring device / coulometer (Okura Electric Co., Ltd. model OM-3001A)
Preparation of planting source: Activated sludge was collected from a wastewater treatment facility of A supermarket located in Kakogawa City, Hyogo Prefecture, and this was cultured and used.
Sample preparation: A 30 ml polypropylene beaker was charged with 4.0 g of a modified alkyd resin or unmodified alkyd resin and 2.0 g of a polyisocyanate component, and the mixture was stirred at room temperature for 1 minute. Next, this was coated on a Teflon (registered trademark) sheet, and heated and cured at 70 ° C. for 10 minutes to form a film.
This film was pulverized and used as a test sample.
Test method: 300 mL of a standard test culture solution (pH 7.0) was placed in a culture bottle, and a test sample was added thereto so that the microorganism addition concentration was 200 mg-dry SS / L and the sample addition concentration was 100 mg / L. This culture bottle was set in a closed system oxygen consumption measuring device and cultured for 28 days at 25 ° C. in the dark and under stirring.
After culturing, the biological oxygen demand was measured, and the degree of biodegradation was determined from the following equation.
Biodegradability (%) = (Biological oxygen demand of sample) / (Theoretical oxygen demand of sample) × 100

[Measurement of fertilizer elution rate of coated granular fertilizer]
12.5 g of coated granular fertilizer was added to 250 ml of water, and the container was sealed and placed in a thermostatic bath at 25 ° C. This was taken out after a lapse of a predetermined period, the fertilizer and the solution were separated (Note 1), the nitrogen component eluted in the solution was quantified, and the dissolution rate was calculated by the following formula.
Dissolution rate (%) = (nitrogen content in solution / nitrogen content in coated granular fertilizer) x 100 (Note 2)
(Note 1) Every time the nitrogen component was measured, 250 ml of water was added to the fertilizer separated each time.
(Note 2) The dissolution rate after the lapse of each specified period is shown as a cumulative value.

[Examples 1 to 3]
Using the alkyd resin modified with sorbitan tristearate, which is the resin shown in Table 1, Table 2 and Table 3, the degree of biodegradation of the fertilizer coating composition was measured, and a coated granular fertilizer was produced. Table 6 shows the degree of biodegradation of this composition and the dissolution rate of the coated granular fertilizer.

[Examples 4 to 6]
Using various modified alkyd resins shown in Table 5, the biodegradability of the fertilizer coating composition was measured, and a coated granular fertilizer was produced. Table 6 shows the degree of biodegradation of this composition and the dissolution rate of the coated granular fertilizer.

[Comparative Example 1]
Using the resin D shown in Table 4, the biodegradation degree of the fertilizer coating composition using an alkyd resin not modified with sorbitan fatty acid ester was measured, and a coated granular fertilizer was produced. Table 6 shows the degree of biodegradation of this composition and the dissolution rate of the coated granular fertilizer.

  As is clear from the results in Table 6, the alkyd resin using sorbitan fatty acid ester as the modifier applied to the fertilizer coating has a high degree of biodegradation, and the elution rate is adjusted with high accuracy. I understand that.

Claims (5)

A fertilizer coating composition obtained by reacting an alkyd resin modified with sorbitan fatty acid ester and polyisocyanate. 2. The fertilizer coating composition according to claim 1, wherein the alkyd resin is an alkyd resin modified with castor oil. The fertilizer coating composition according to claim 1 or 2, wherein the sorbitan fatty acid ester content in the alkyd resin is 5 to 70 mass% with respect to the total amount with the alkyd resin. 4. The fertilizer coating composition according to claim 1, 2 or 3, wherein the polyisocyanate is polymethylene polyphenyl polyisocyanate. The reaction ratio between the alkyd resin modified with sorbitan fatty acid ester and the polyisocyanate is in the range of 0.5 to 2.0 as the molar ratio of isocyanate group to hydroxyl group (NCO / OH). The coating composition for fertilizers according to 1.