JP2009001467A - 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 well adjust the elution accuracy of fertilizer components by the use of a simple method. <P>SOLUTION: The coating composition for fertilizer is prepared by reacting a polyester polyol obtained by reacting lactic acid, ≥6C oxycarboxylic acid and a polyhydric alcohol with each other with polyisocyanate. The use of the coating composition for fertilizer improves the biodegradability of the coating composition and produces a coated fertilizer in which the elution of fertilizer components is adjusted with well accuracy, and thereby the technology is extremely useful in industrial utilization. <P>COPYRIGHT: (C)2009,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 of fertilizer components with high accuracy by a simple method using a biodegradable raw material without using an organic solvent or the like.

In recent years, many coated granular fertilizers have been developed in response to environmental problems such as eutrophication of closed water areas such as lakes and marshes and groundwater contamination by nitrate nitrogen, labor-saving fertilizers due to a decrease in the agricultural population and the aging of workers. It is commercially available and commercialized. However, problems such as an increased environmental load due to the non-disintegrating nature of the coating have also occurred.
Therefore, as a coating material having a small environmental load, it is possible to expect the biodegradability of the resin by using castor oil or castor oil derivative having an ester bond as a raw material. It has been proposed to use a polyurethane resin obtained by reacting as a coating (see, for example, Patent Documents 1 to 3). However, the biodegradability of such a resin coating composition is low, and the present condition is that it remains in the environment for a long time even after the fertilizer components are eluted.

  In addition, it has been proposed to coat granular fertilizer with a biodegradable resin having an ester bond in the main chain, represented by polylactic acid and polycaprolactone (see, for example, Patent Documents 4 to 7). Although the biodegradability of such a resin is high, since the resin is dissolved and coated in an organic solvent at the time of production, there is a problem that a part of the solvent used is diffused into the atmosphere. Also, the elution performance tends to be inferior compared to the conventional coated granular fertilizer using non-degradable resin.

  Furthermore, it is also proposed to coat a fertilizer with a polyester polyol composed of a lactic acid component, a dicarboxylic acid component, and a diol component (see, for example, Patent Documents 8 to 9). In this case, there is a method in which the resin melted by heating is coated, or there is a method of coating by dissolving in an organic solvent, but the former tends to have poor elution performance, and the latter has a problem of diffusing organic solvent. It is left.

  In this way, the resin coating composition for fertilizer is not yet sufficient in terms of resin biodegradability, elution performance of fertilizer, etc., and when environmentally hazardous substances such as organic solvents are released into the atmosphere during production There is a current situation.

Patent Registration No. 3161997 Japanese Patent Laid-Open No. 2001-213865 JP 2005-1957 A JP 7-33577 A JP-A-9-263476 JP-A-10-67591 JP 2002-284594 A Japanese Patent Laid-Open No. 7-309688 Japanese Patent Laid-Open No. 9-249477

  The present invention provides a fertilizer coating composition capable of accurately adjusting the elution of fertilizer components by a simple method using raw materials considering biodegradability and not using an organic solvent in consideration of the environment. The task is to do.

  As a result of intensive studies on coated fertilizers, the present inventors have reacted a polyester polyol component obtained mainly by reacting lactic acid, an oxycarboxylic acid having 6 or more carbon atoms and a polyhydric alcohol with a polyisocyanate component. The present inventors have found that a polyurethane resin can solve the above problems and have completed the present invention based on such knowledge.

  That is, the present invention relates to a fertilizer coating composition obtained by reacting a polyisocyanate with a polyester polyol component obtained by reacting lactic acid, an oxycarboxylic acid having 6 or more carbon atoms and a polyhydric alcohol.

  Since the polyester polyol used in the present invention is a paste at room temperature, it can be coated on a fertilizer without using an organic solvent or the like, and further, this is reacted with polyisocyanate for the fertilizer of the present invention. The resin composition is characterized in that the elution of the fertilizer component of the coated fertilizer is adjusted with high accuracy and the biodegradability is promoted mainly by the ester group in the coating.

Hereinafter, the coating composition for fertilizer of the present invention will be described in more detail.
In the present invention, the fertilizer coating composition used for coating fertilizer grains is a polyurethane resin, and is a paste-like polyester polyol formed by reacting lactic acid, an oxycarboxylic acid having 6 or more carbon atoms and a polyhydric alcohol. And a thermosetting resin obtained by reacting polyisocyanate.

Speaking of the method for synthesizing the polyester polyol, it may be carried out by either a direct method, which is a method for synthesizing a general alkyd resin, or an alcoholysis method in which a transesterification reaction is performed.
Speaking of lactic acid used for the synthesis of the polyester polyol, there is no problem even if any of L-lactic acid, DL-lactic acid and D-lactic acid is used, but it is preferable because the use of L-lactic acid is widely used. As for oxycarboxylic acid, it is necessary to use an oxycarboxylic acid having 6 or more carbon atoms, such as a castor oil fatty acid mainly composed of ricinoleic acid or a hydrolyzate of ε-caprolactone. If it becomes several 5 or less, since the hydrophilic property of the obtained polyurethane resin will become high, the elution control of a fertilizer component will become difficult. In addition, since the polyester polyol referred to in the present invention is coated on fertilizer grains without using an organic solvent, it is important that the polyester polyol is in a paste form at room temperature. For this reason, the lactic acid composition in the polyester polyol is 20-80. The amount of oxycarboxylic acid used is preferably 10 to 70% by mass.

  Next, with regard to polyhydric alcohol, it can be used if the number of hydroxyl groups is 2 or more, and glycerin, pentaerythritol, trimethylolpropane, mannitol, sorbitol and the like having 3 or more hydroxyl groups are preferably used. It is not limited to.

The polyester polyol obtained by heat condensation of the above raw materials is preferably urethanized and used as a coating material, so that the hydroxyl value is preferably 50 to 400, and outside this range, the coated fertilizer components should be adjusted accurately. It becomes difficult. In terms of the acid value, if the acid value is high, the urethanization reaction is inhibited and the coating film is hardened and it becomes difficult to form a uniform film. Therefore, the acid value is 15 or less, more preferably 10 or less.
Further, the polyester polyol can be mixed with a polyether polyol or various castor oils having a hydroxyl group derived from a natural product, if necessary, within a range that does not significantly reduce biodegradability.

  The polyisocyanate used for urethanization includes monomeric diisocyanate and liquid polyisocyanate. Preferred examples include tolylene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, xylene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, Examples include isophorone diisocyanate and dicyclohexylmethane diisocyanate. Mixtures of these can also be used. However, among these, the use of polymethylene polyphenyl polyisocyanate is most preferable from the viewpoints of the object of the present invention and the film-forming property.

  The reaction ratio between the polyester polyol 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, polyurethane crosslinking is reduced and the water resistance of the coating is lowered. Further, if the molar ratio exceeds 2.0 and the urethane crosslinking increases, the biodegradability decreases, which is not preferable.

In the urethanization accompanying such a reaction, it is useful to add a catalyst in order to accelerate the reaction. As such a catalyst, a known catalyst can be used. For example, organic salts such as potassium octoate and amine compounds such as triethylenediamine can be used.
However, it is preferable to use an aliphatic monocarboxylic acid potassium from the viewpoint of easy adjustment of the reaction rate and easy formation of a uniform film. In addition, when ricinoleic acid or castor oil fatty acid is used as one component of the polyester polyol, an organic salt such as manganese naphthenate or cobalt octoate is used as a crosslinking catalyst for the purpose of forming a tougher film. Is also useful.

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

  Next, with respect to the method of coating the granular fertilizer with the resin composition for fertilizer of the present invention, each coating material, that is, polyester polyol and polyisocyanate is adhered to and reacted with the granular fertilizer in a flowing or rolling state. By heating with hot air or the like, it is dried on the surface of the granular fertilizer to form a film. In order to flow and roll the granular fertilizer, a known method can be used. For example, a fluidizing device or jetting device can be used for fluidization, and a rotating pan or a rotating drum device can be used for rolling.

Moreover, it is preferable to use each coating material adjusted so that the viscosity is 300 mPa · s or less. For example, when the polyester polyol is heated to 60 to 120 ° C., the viscosity is drastically decreased to 300 mPa · s or less.
Polyisocyanates having a viscosity of 300 mPa · s or less at room temperature are used as they are, and solid isocyanates are heated to a melting point or higher to be liquefied before use. In this case, when the viscosity of each coating material exceeds 300 mPa · s, workability is deteriorated, and further, a uniform film is not formed, and it is difficult to control fertilizer elution.

The method of attaching the coating material to the fertilizer particles is not particularly limited as long as it can be uniformly applied to the fertilizer particles, and can be carried out without being limited to spraying and dropping. Moreover, each coating | coated material may be sprayed on granular fertilizer from the same location, or may be sprayed from a different location.
Further, from the viewpoint of workability, there is no particular limitation whether the catalyst is mixed with polyester polyol in advance and the polyester polyol and polyisocyanate are sprayed from different places or mixed immediately before spraying.

  Furthermore, in order to cure the coating formed by the adhesion and reaction of the fertilizer coating composition, heating is performed in the range of room temperature to 90 ° C. If the curing temperature is too low, the viscosity of the sprayed solution increases, and the fertilizer A uniform film is not formed on the grain surface. On the other hand, if the curing temperature is too high, the speed of the urethanization reaction is increased, it is difficult to adjust the curing speed, and it is difficult to form a uniform film. Therefore, the heating temperature is preferably in the range of about 50 ° C to 80 ° C.

By the way, it is desirable to form the coating film on the fertilizer grain surface by repeatedly applying and drying the coating composition. That is, a dense coating can be formed by multilayering the coating by repetition. The amount of the coating composition used for forming a single coating varies depending on the spraying or dropping rate of the coating composition, the curing rate, etc., and cannot be generally mentioned, but is preferably 0.3 for the granular fertilizer to be coated. It is -1.5 mass%. In this case, if the lower limit is not reached, 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 particle lumps are formed on the granular fertilizer particles, and these lumps are detached from the fertilizer particles during rolling or flow, causing defects in the coating. It is preferable that the coating composition is repeatedly adhered and dried to the fertilizer grains at least three times, that is, the coating is multilayered by 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 composition to the fertilizer grains 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.

In addition, the coating is within the allowable range in performance, and as an auxiliary means for improving workability and adjusting fertilization effect, the coating composition includes aliphatic esters, wax, rosin or derivatives thereof, surfactants, talc, calcium carbonate, etc. Various additives can be added.
In addition, when a tougher coating is required, such as when sprayed with a granular fertilizer spreader, formation of a protective film is also useful. For example, as a protective film forming material, polyethylene resin, vinyl acetate resin, ethylene-acetic acid Vinyl resin, polyvinyl alcohol resin, acrylic resin, alkyd resin, urethane resin, or the like can be used. The use ratio of these additives and protective film forming agent is 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.
The fertilizer coated with the fertilizer coating composition of the present invention thus obtained has a coating biodegradability, the dissolution of fertilizer components is accurately adjusted, and is also an industrially advantageous coated granular fertilizer It becomes.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these. Unless otherwise specified, all percentages are by mass.

<Synthesis of polyester polyol>
The polyester polyol resin used in the present invention was obtained by the following method.

(Synthesis of Resin A)
In a 1L four-necked flask equipped with a stirrer, thermometer, nitrogen gas inlet pipe and exhaust gas pipe, 88g L-lactic acid (PURAC, for food additives) 200g, ε-caprolactone (manufactured by Daicel Chemical Industries) 223g, 40 g of D-mannitol (reagent) was charged, and the reaction was carried out at 200 ° C. for 7 hours while flowing nitrogen gas at 300 ml / min with stirring to obtain 385 g of the resin shown in Table 1. This resin A was in the form of a paste of 7,600 (mPa · s) / 25 ° C.

(Synthesis of Resin B)
A 1L four-necked flask equipped with a stirrer, thermometer, nitrogen gas inlet tube and exhaust gas tube was charged with 280g of 88% L-lactic acid, 134g of ε-caprolactone, and 53g of pentaerythritol (reagent). While flowing at 300 ml / min, the reaction was carried out at 200 ° C. for 8 hours to obtain 372 g of the resin shown in Table 2. This resin B was a paste of 3,200 (mPa · s) / 25 ° C.

(Synthesis of Resin C)
A 1L four-necked flask equipped with a stirrer, thermometer, nitrogen gas inlet tube and exhaust gas tube was charged with 340g of 88% L-lactic acid, 84g of ε-caprolactone and 36g of trimethylolpropane (reagent), and nitrogen gas was stirred. Was allowed to flow at 300 ml / min for 6 hours at 200 ° C. to obtain 346 g of the resin shown in Table 3. The resin C was in the form of a paste at 8,700 (mPa · s) / 25 ° C.

(Synthesis of Resin D)
A 1L four-necked flask equipped with a stirrer, thermometer, nitrogen gas inlet tube and exhaust gas tube was charged with 265g of 88% L-lactic acid, 180g of castor oil fatty acid (manufactured by Ito Oil), and 36g of glycerin (reagent). The reaction was carried out at 200 ° C. for 8 hours while flowing nitrogen gas at 300 ml / min to obtain 381 g of the resin shown in Table 4. The resin D was in the form of a paste at 9,800 (mPa · s) / 25 ° C.

(Synthesis of Resin E)
A 1L four-necked flask equipped with a stirrer, thermometer, nitrogen gas inlet tube and exhaust gas tube was charged with 225g of 88% L-lactic acid, 215g of castor oil fatty acid and 56g of pentaerythritol, and nitrogen gas was stirred at 300ml / min. Then, the reaction was carried out at 200 ° C. for 8 hours to obtain 420 g of the resin shown in Table 5. The resin E was a paste of 6,900 (mPa · s) / 25 ° C.

(Synthesis of resin F)
Resin A was synthesized under the same conditions except that 100 g of water was used instead of 88% L-lactic acid to obtain 256 g of resin shown in Table 6. The resin E was a waxy solid at room temperature.

(Synthesis of Resin G)
A 1L four-necked flask equipped with a stirrer, thermometer, nitrogen gas inlet tube and exhaust gas tube was charged with 310% of 88% L-lactic acid, 150g of α-oxybutyric acid (reagent) and 48g of pentaerythritol, and nitrogen gas was stirred. Was allowed to flow at 300 ml / min for 8 hours at 200 ° C. to obtain 385 g of the resin shown in Table 7. This resin E was semi-solid at room temperature.

Moreover, when the viscosity at 100 degrees C of resin A-G was measured, it confirmed that it was 300 mPa * s or less except resin G.

In using the fertilizer coating composition of the present invention, the raw materials used were as follows.
Polyester polyol resin: 2% of an aliphatic monocarboxylic acid potassium solution (concentration: 70%) was mixed as a catalyst with the polyester polyol shown in Tables 1 to 7, and heated to 100 ° C. to obtain a coating raw material.
Polyisocyanate resin: 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 size: 3 mm) was charged into a centrifugal rolling granulation coating apparatus (rotating disc diameter: 230 mm) equipped with a hot air generator. The rotating disk was rotated at 200 rpm to turn the granular fertilizer into a rolling state, and hot air was fed from the lower part and maintained at 70 ° C.
Polyester polyol resin (4.0 g) and polyisocyanate resin (2.0 g) were sprayed separately from two locations with a two-fluid nozzle onto granular urea that was heated and in a rolling state, and rolled and cured for 3 minutes. In this case, the reaction ratio between the polyester polyol and the polyisocyanate is shown in Table 8 as the molar ratio of isocyanate group to hydroxyl group (NCO / OH)).

Next, Example 6 is a coated fertilizer manufactured under the same conditions as Example 5 except that 2.6 g of the resin E and 3.4 g of the polyisocyanate resin are used. Similarly, Example 7 is a coated fertilizer produced under the same conditions as in Example 5 except that 5.0 g of resin E and 1.0 g of polyisocyanate resin are used. Table 8 also shows the reaction ratio between the polyester polyol and the polyisocyanate in these examples.

This spraying and curing process was repeated 18 times to produce a coated granular fertilizer. In this case, the coverage was 9.7%. The coverage of the coating composition was determined by the following formula.
Covering rate (%) = (film mass / mass of coated granular fertilizer) × 100
As performance evaluation of the coating composition for fertilizer obtained by the coating test, biodegradability evaluation of the coating composition and measurement of the elution rate of the fertilizer were performed. The measuring method is as follows.

[Measurement of biodegradability of coating composition for fertilizer]
The biodegradability was evaluated in accordance with “JIS K 6950 Plastic—How to determine the aerobic ultimate biodegradability in an aqueous culture medium—Method of measuring oxygen consumption using a closed respirometer”.
Measuring device: Closed system oxygen consumption measuring device / Coulometer (Okura Electric Co., Ltd., OM-3001A type)
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 polyol resin and a polyisocyanate resin having the same weight as those described in Examples 1 to 7 and Comparative Examples 1 and 2 were placed in a 30 ml polypropylene beaker and stirred at room temperature for 1 minute. Next, it 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 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 a dark place with stirring. The biological oxygen demand was measured and the biodegradability was calculated 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 predetermined period of time, and the fertilizer and the solution were separated (Note 1), the nitrogen component eluted in the solution was quantified, and the fertilizer elution rate was calculated by the following formula.
Fertilizer elution rate (%) = (nitrogen content in solution / nitrogen content in coated granular fertilizer) x 100 (Note 2)
(Note 1) Every time nitrogen component measurement, 250 ml of water was newly added to the fertilizer separated each time.
(Note 2) The dissolution rate after the elapse of each predetermined period is a cumulative value.

[Examples 1-7]
The coated granular fertilizer was produced by the reaction of the polyester polyol resins A to E and the polyisocyanate resin shown in Tables 1 to 5, and the biodegradability of the fertilizer coating composition obtained by the reaction was measured. The biodegradability of this composition and the dissolution rate of the coated granular fertilizer are shown in Table 9.

[Comparative Examples 1 and 2]
Polyester polyol resins F and G shown in Tables 6 and 7 were used to measure the biodegradability of the fertilizer coating composition and to produce coated granular fertilizers. The biodegradability of this composition and the dissolution rate of the coated granular fertilizer are shown in Table 9.

From Table 9, the polyester polyol resin of the present invention and the polyisocyanate resin are reacted, and the obtained fertilizer coating composition applied to the coating material of granular fertilizer has a high degree of biodegradation and the elution of fertilizer is accurate. It turns out that it is well adjusted. On the other hand, those using the resin obtained in Comparative Example 1 clearly have low biodegradability, and those using the resin obtained in Comparative Example 2 have a high degree of biodegradation, Obviously, the elution performance of fertilizer is inferior.

Claims (5)

A fertilizer coating composition obtained by reacting a polyester polyol obtained by reacting lactic acid, an oxycarboxylic acid having 6 or more carbon atoms and a polyhydric alcohol with a polyisocyanate. The fertilizer coating composition according to claim 1, wherein the oxycarboxylic acid is a castor oil fatty acid or ε-caprolactone hydrolyzate containing ricinoleic acid as a main component. The fertilizer coating composition according to claim 1 or 2, wherein the polyhydric alcohol is glycerin, pentaerythritol, trimethylolpropane, sorbitol, or mannitol. The fertilizer coating composition according to claim 1, 2 or 3, wherein the polyisocyanate is polymethylene polyphenyl polyisocyanate. The fertilizer according to any one of claims 1 to 4, wherein a reaction ratio between the polyester polyol and the polyisocyanate is in a range of 0.5 to 2.0 as a molar ratio of isocyanate group to hydroxyl group (NCO / OH). Coating composition.