JPH08157290A - Aliphatic polyester coated granular fertilizer - Google Patents

Abstract

PURPOSE: To obtain an aliphatic polyester coated granular fertilizer controlled in the elution of fertilizer and capable of decomposing and eliminating the coating film by the biodegradation after the elution of fertilizer. CONSTITUTION: This aliphatic polyester coated granular fertilizer has the coated layer containing an aliphatic polyester expressed by a formula, -(OR<1> OCOR<2> CO)n - ((n) represents the degree of polymerization necessary for the polyester resin having the number average molecular weight of >15,000 to <=1,000,000, R<1> represents a >=2C to <=20C alkylene group and R<2> represents a >=2C to <=22C alkylene group).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to improved coated granular fertilizers. In particular, it relates to a coated granular fertilizer whose coating material has biodegradability.

[0002]

2. Description of the Related Art Coated granular fertilizer has shown a steady increase in the amount of use in recent years as a product form that realizes labor saving in agricultural work and effective use of fertilizer. Conventionally, in coated granular fertilizers, high performance has been attempted by using polymer compounds as coating materials. However, as the amount of utilization increases, there is concern about the effect of the coating material left by the used coated granular fertilizer on the natural environment. As one of the countermeasures, attempts have been made so far to utilize a degradable material as a coating material. As such attempts, use of a drying oil-modified phthalic acid resin varnish (Japanese Patent Publication No. 59-30679), use of polycaprolactone (Japanese Patent Laid-Open No. 3-146492), poly-3-hydroxy-3-alkylpropionic acid. Is proposed (Japanese Patent Publication No. 2-23517). However, there are problems such as insufficient degradability, insufficient control of fertilizer elution, and difficulty in manufacturing and obtaining degradable materials.

[0003]

In view of the above-mentioned problems relating to the conventional degradable coated granular fertilizer, the present invention uses a specific aliphatic polyester having biodegradability as a coating material, so that the The present invention provides a new coated granular fertilizer with improved degradability and control of fertilizer elution.

[0004]

The present invention has been realized by using a specific aliphatic polyester as a coating material. The aliphatic polyester is a polyester having a structure in which alkylene diol and alkylene dicarboxylic acid are polycondensed. As the polyester, an aliphatic polyester (Japanese Patent Application No. 6-186952), which has been proposed by the present inventors and can be easily molded as a thermoplastic resin, particularly a fat having a flexible and strong structure and high molecular weight even in a thin film Group polyester (Japanese Patent Application No. 6-185880) is used. The present invention has been completed based on the invention of such an aliphatic polyester, finding that the above problems can be solved by coating granular fertilizer with a coating material containing the aliphatic polyester.

That is, the present invention is as follows. 1. A coated granular fertilizer having a coat layer containing an aliphatic polyester represented by the following general formula (I). ^{- (OR 1 OCOR 2 CO)} n - (I) (n is a larger than the number average molecular weight Mn of 15,000 polyester represented by the general formula (I), 1,000,
The degree of polymerization required to be 000 or less. However, R ¹ is an alkylene group having 2 to 20 carbon atoms, and R ² is an alkylene group having 2 to 22 carbon atoms. ) 2. The coated granular fertilizer according to 1 above, wherein at least one of R ¹ and R ^{2 is} an alkylene group having 10 or more carbon atoms. 3. The number average molecular weight Mn of the aliphatic polyester is 70,
The coated granular fertilizer according to 1 above, which is greater than 000 and 1,000,000 or less.

The present invention will be described in more detail below. The aliphatic polyester used in the coating material of the present invention is represented by the following formula (I). ^{- (OR 1 OCOR 2 CO)} n - (I) (n is a larger than the number average molecular weight Mn of 15,000 polyester represented by the general formula (I), 1,000,
The degree of polymerization required to be 000 or less. However, R ¹ is an alkylene group having 2 to 20 carbon atoms, and R ² is an alkylene group having 2 to 22 carbon atoms. ) The Mn value of the polyester of formula (I) is greater than 15,000, preferably greater than 25,000, more preferably greater than 70,000. When the value of Mn is 15,000 or less, it is difficult to form a coating when used as a coating material, or even when it is formed, the mechanical strength is insufficient and the coating is likely to crack or fall off. On the other hand, the value of Mn is 70,000
When it is larger, the mechanical strength is high even when used in a thin film, which is particularly advantageous in practical use. The higher the Mn value, the better from the viewpoint of the strength of the coating film, but in order to optimize the viscosity of the coating material when coating the granular fertilizer with the coating material, it is 200,000.
The following are preferred.

R ¹ is an alkylene group having 2 to 20 carbon atoms, and R ² is an alkylene group having 2 to 22 carbon atoms. R ¹ may include an alicyclic structure. R ² may contain less than 50 mol% of alkenylene groups as a copolymerization unit. In this case, the alkenylene group also has 2 or more and 22 or less carbon atoms. R ¹ and R ² may each have a structure containing two or more alkylene groups. Further, when at least one of R ¹ and R ² has a carbon number of more than 10, it is suitable for the production of a long-term fertilizing type coated granular fertilizer in which the fertilizer elution property of the coating is particularly low and the control of fertilizer elution is more difficult Is preferred.

The aliphatic polyester as a component of the coating material of the present invention is produced by the method disclosed in Japanese Patent Application No. 6-196773. The aliphatic polyester is produced from an alkylene diol (hereinafter, simply referred to as diol) and an alkylene dicarboxylic acid (hereinafter, simply referred to as dicarboxylic acid) by polycondensation. Examples of the diol include ethylene glycol, propylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1 , 8-Octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,1
2-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, 1,18-octadecanediol,
1,20-eicosane diol, neopentyl glycol, 1,4-cyclohexane dimethanol and the like can be mentioned.

The dicarboxylic acid is selected from dicarboxylic acid itself, dicarboxylic acid ester and dicarboxylic acid anhydride. The dicarboxylic acid ester is preferably methyl ester or ethyl ester. Examples of dicarboxylic acids include succinic acid, glutaric acid, adipic acid, pimelic acid,
Suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid, eicosanedioic acid, heneicosanoic acid, docosanedioic acid, tetracosane Diacid, dimethyl succinate, dimethyl glutarate, dimethyl adipate, dimethyl azelate, diethyl sebacate, dimethyl dodecanedioate, diethyl tetradecanedioate, dimethyl eicosanedioate, succinic anhydride, glutaric anhydride, maleic acid, fumar An acid, dimethyl maleate, dimethyl fumarate, etc. can be used.

It is also possible to react two or more kinds of diols and dicarboxylic acids in order to control the melting point and film-forming property of the aliphatic polyester to be produced. The charging ratio of the raw material diol and dicarboxylic acid is not particularly limited, but is preferably 0.5 or more and 2.0 or less, more preferably 0.8 or more and 1.2 or less, and further preferably 0.9.
The above range is 1.1 or less.

As a method for producing an aliphatic polyester,
It is important to increase the evaporation surface area with respect to the charged amount by making the heated melt of the raw material mixture into a thin film.
That is, when the volume of the reaction melt is V (cm ³ ) and the surface area thereof is A (cm ² ), the larger A / V is, the better for the production of high molecular weight aliphatic polyester. Considering economic efficiency, A / V is 1 or more and 500 or less, preferably 4
It is 50 or more and 50 or less, and more preferably 6 or more and 50 or less. When the A / V changes during the production, it suffices that the A / V at the time when the molecular weight becomes the highest, that is, at the end of the polymerization is usually the value.

The lower the pressure during production, the higher the molecular weight of the aliphatic polyester tends to be. However, the desired number average molecular weight Mn can be obtained within the range of more than 0.1 mmHg and 1 mmHg or less. When the pressure fluctuates during manufacturing, the final ultimate pressure should fall within the above range. The production temperature is 120 ° C. or higher and 350 ° C. or lower, preferably 160
℃ or more and 300 ℃ or less, more preferably 160 ℃ or more 2
It is performed at 50 ° C or lower.

The reactor is not limited as long as it can realize the above conditions. A surface renewal type twin-screw kneader, a surface renewal type thin film reactor, a circulation type device having a free fall zone as a polymerization accelerating region as disclosed in Japanese Patent Application No. 6-169149, a rotary tube oven and the like are suitable for production. is there. For example, a rotary tube oven has a large evaporation surface area because 1) the reaction solution rotates in a thin film along a cylindrical surface heater, and 2) a sufficient distance between the reaction solution heating surface and the distillate condensation surface. Since they are close to each other, it is easy to distill components that are difficult to distill in a normal flask reaction. for that reason,
The components evaporated from the heating surface can reach the distillate condensing surface without condensing in the reaction tube. As a result, the elimination of alcohol or water can be efficiently promoted in the esterification step, and the elimination of diol, diester or dicarboxylic acid can be efficiently promoted in the subsequent polycondensation step.

A diol and a dicarboxylic acid are charged into the above apparatus, and esterification is carried out in an atmosphere of an inert gas such as nitrogen. The esterification temperature is preferably lower than the boiling points of both the raw material diol and dicarboxylic acid.
Continue the reaction to make sure that alcohol or water is completely distilled. Since the polycondensation reaction requires a small amount of catalyst, the temperature is once returned to room temperature and the catalyst is added. However, the catalyst may be added in advance when the raw material diol or dicarboxylic acid is charged. The catalyst used is a compound containing a metal ion such as titanium, zinc, germanium or iron, and for example, zinc acetate, zinc stearate, zinc octanoate or the like can be used. The amount of catalyst added is 0.0001 mol, based on the total amount of monomers charged.
% Or more and 0.1 mol% or less, preferably 0.0005 mo
It is preferably about 1% or more and 0.01 mol% or less. The polycondensation reaction after addition of the catalyst is carried out at a temperature equal to or higher than the esterification reaction and under reduced pressure. It is preferable to gradually reach the predetermined pressure and temperature. The produced polyester can be used as it is for producing a coating material.

Next, a method for producing coated granular fertilizer will be described. The above-mentioned aliphatic polyester is contained in the coating material. The aliphatic polyester may be used as a mixture of two or more kinds. The content of the aliphatic polyester in the coating material is 20 to 100
%, Preferably 30-100% by weight. If it is less than 20% by weight, decomposition of the coating film after elution of the fertilizer is insufficient, so that the shape of the coated capsule tends to remain as it is for a long period of time, which does not meet the object of the present invention.

In order to control the properties of the coating such as mechanical properties, fertilizer elution and degradability, the coating material may contain other components together with the aliphatic polyester. The components that form the coated substrate together with the aliphatic polyester include polyethylene, polypropylene, polybutene, ethylene
Vinyl acetate copolymer, styrene-butadiene copolymer,
Polymer compounds such as polyoxymethylene, vinylidene chloride copolymers, and diene rubbers can be used. When the polymer compound is used in combination, a compatibilizer may be appropriately used.
Examples of the compatibilizer include maleic anhydride-grafted polypropylene, acid-modified polypropylene, acid-modified polyethylene, and styrene thermoplastic elastomer (SEBS).
And the like. Other combined ingredients include talc,
Insoluble fillers such as calcium carbonate, diatomaceous earth and metal oxides, surfactants as elution regulators, waxes as hydrophobic substances, rosins and petroleum resins can also be used.

The thickness of the coat layer is preferably 0.01 to 1.
mm, and more preferably 0.02 to 0.4 mm.
If the thickness is less than 0.01 mm, defects such as pinholes are likely to occur in the film, making it difficult to control the elution of fertilizer. In addition, 1m
If it exceeds m, elution of fertilizer will be delayed more than necessary, and an excessive burden on the coating process, for example, a large use of the coating material and a large amount of energy consumption will be caused.

There are various types of fertilizer to be coated, and there is no particular limitation. For example, ammonium sulfate, ammonium salt, ammonium nitrate, urea, sodium nitrate, potassium chloride, potassium sulfate, potassium nitrate, ammonium phosphate, potassium phosphate, lime phosphate and the like can be mentioned. Also,
Chemical fertilizers composed of two or more of these components are also used.
The maximum size of fertilizer particles is 2 depending on the elution period and usability.
-10 mm and minimum diameter 1-10 mm. The shape of the fertilizer particles is not particularly limited, but is preferably spherical, elliptic spherical, cylindrical, disk-shaped or the like.

As a method of coating the coating material with fertilizer,
It can be roughly divided into the solvent method and the solventless method. In the solvent method, a fertilizer is sprayed with a coating material dissolved or dispersed in a suitable solvent, or the fertilizer is dipped in a coating material solution or dispersion, and then the solvent is removed and dried. Drying with warm air or hot air is particularly efficient for drying. When coating,
In order to make the coating thickness uniform, the fertilizer particles are preferably rolled or floated. The solvent used for the coating material solution or dispersion varies depending on the composition of each aliphatic polyester or coating material, but is chloroform, methylene chloride, o-dichlorobenzene, trichloroethylene, tetrachloroethylene, o-chlorophenol, N-methylpyrrolidone. Many others can be used as a representative example. The drying temperature is determined in consideration of the solubility, the evaporation rate, and the boiling point of the solvent, but it is usually 0 to 12
It is 0 ° C, preferably 10 to 100 ° C.

In the solventless method, a melt or melt dispersion of the coating material is used instead of the coating material solution or dispersion in the solvent method. In that case, the melting temperature is 80 to 250 ° C., preferably 130 to 23 from the viewpoint of adjusting the viscosity and preventing thermal decomposition.
Although it is 0 ° C., the appropriate temperature is determined according to the individual aliphatic polyester and the components used in combination, particularly the polymer component. A jet tower, a rotary pan, a rotary drum, or the like can be used as the coating device.

The fertilizer releasing property of the produced coated granular fertilizer can be examined by a fertilizer dissolution test in water. This method is effective not only for simulating fertilizer release in rice fields and hydroponics, but also for predicting fertilizer release in soil of fields. The disappearance of the coating can be examined by a long-term soil burying test of coated granular fertilizer or a short-term accelerated test in activated sludge.

[0022]

Embodiments of the present invention will be described below. Production of Aliphatic Polyester: Poly 1,4-butylene succinate was produced by the following procedure. 6.8 g of 1,4-butanediol, 10.0 g of dimethyl succinate, and 0.041 g of zinc acetate dihydrate were added to a reaction vessel of a glass tube oven [diameter 44.4 mm, length 96.4 mm (inner diameter 13. It was connected to the cooling part with a joint part having a length of 4 mm and a length of 10 mm. 160 while rotating the reaction vessel at 12 rpm under nitrogen stream
The temperature was raised to ℃ and heated for 4 hours. Subsequently, the temperature was raised to 180 ° C. for 1 hr, and the temperature was raised to 200 ° C. for 1 hr, and esterification was carried out at each temperature until distillation stopped. Then, the pressure was slowly reduced with a vacuum pump while maintaining the temperature at 200 ° C. in a nitrogen stream, and a deglycol reaction was performed at 0.44 mmHg. After 1.5 hours, the temperature was further raised to 220 ° C. and the deglycolation reaction was continued for 3 hours. Final reached pressure is 0.42mm
It was Hg. The A / V at this time was calculated to be 9.8. After the completion, the mixture was allowed to cool to room temperature and slowly returned to atmospheric pressure, whereby a film-like polymer was produced.

The number average molecular weight Mn and the weight average molecular weight Mw of the obtained polyester were measured by GPC. GPC: Model used ... Tosoh GPC HCL-8020 type solvent ... CHCl ₃ / MeOH = 98/2 (vo
l ratio) Sample concentration: 1 mg / ml Column temperature: 40 ° C. Molecular weight standard: Polystyrene molecular weight: Number average molecular weight Mn = 120,000, Mw / Mn
= 7.5 Other polyesters were produced by substantially the same operation.
The required amount of coating material was secured by repeating the production.

[0024]

Example 1 A jet tower (tower diameter 200 mm, height 1800 mm, air jet diameter 42) was used to produce the coated granular fertilizer of the present invention.
mm) was used. Fertilizer (potassium phosphorus nitrate) of 5-9 mesh (standard sieve manufactured by Tyler) used for coating
5 kg was charged into the tower, and hot air of 50 ° C. was introduced from below to form a jet stream. As the coating material, poly-1,4-butylene succinate (abbreviated as C4-C4, Mn = 120,000) produced as described above was used. A coating liquid prepared by adding C4-C4 as a coating material in a liquid tank and chloroform as a solvent and stirring the mixture near the boiling point of the solvent (coating material 3
% By weight) was sent to the jet tower at 0.5 kg / min by a pump, and hot air of 4 m ³ / min was also supplied from below the tower to obtain a coated granular fertilizer. A coated granular fertilizer having a coating time of 27 min and a coating rate (against fertilizer) of 8% by weight was obtained. The nitrogen elution amount of the obtained coated granular fertilizer in water at 25 ° C. was analyzed by an analytical instrument. The results are shown in Table 1.

[0025]

Examples 2 to 5 The coating materials shown in Table 1 were coated in the same manner as in Example 1 except that the coating material was changed to produce coated phosphorous ammonium nitrate potassium. The nitrogen elution amount of the obtained coated granular fertilizer in water at 25 ° C. was analyzed by an analytical instrument. The results are shown in Table 1. The abbreviations in Table 1 are as follows. C4-C4: poly 1,4-butylene succinate (Mn
= 120,000) C4-C6: poly 1,4-butylene adipate (Mn =
100,000) C10-C12: poly 1,10-decamethylene dodecanedioate (Mn = 120,000) C2-C13: polyethylene tridecanedioate (M
n = 39,000) C2-C14: polyethylene tetradecanedioate (Mn = 80,000)

[0026]

[Example 6] Coated granular fertilizer 1 produced in the same manner as in Example 1
Make pinholes for each grain with a needle, let stand in water and completely elute the fertilizer inside, and then make a dried hollow capsule. 50 capsules were weighed one by one and placed in a polyethylene dish having a diameter of 15 mm and a depth of 10 mm (a hole having a diameter of 1 mm was formed in the center) containing soil. Further, this dish was embedded in a soil depth of 5 cm placed in a planter having a length of 29.5 cm, a width of 9 cm and a height of 9 cm. This planter was placed in a thermo-hygrostat having a humidity of 80% and a temperature of 30 ° C.
After a certain period of time, the dish was taken out from the soil, the soil was removed, and the dish was put into water to collect the capsules. After drying, the weight was measured. The weight after 3 months is 80% of the weight before putting it in the soil,
The weight after 6 months was 63%.

[0027]

[Table 1]

[0028]

The coated granular fertilizer of the present invention enables control of fertilizer elution without causing cracks or fractures in the coating.
After the fertilizer is eluted, the coating can be decomposed and dissipated by the biodegradability of the aliphatic polyester.

Claims (3)

[Claims] 1. A coated granular fertilizer having a coat layer containing an aliphatic polyester represented by the following general formula (I). ^{- (OR 1 OCOR 2 CO)} n - (I) (n is a larger than the number average molecular weight Mn of 15,000 polyester represented by the general formula (I), 1,000,
The degree of polymerization required to be 000 or less. However, R ¹ is an alkylene group having 2 to 20 carbon atoms, and R ² is an alkylene group having 2 to 22 carbon atoms. ) 2. The coated granular fertilizer according to claim 1, wherein at least one of R ¹ and R ^{2 is} an alkylene group having 10 or more carbon atoms. 3. The number average molecular weight Mn of the aliphatic polyester
Is more than 70,000 and not more than 1,000,000, the coated granular fertilizer according to claim 1.