JPH107484A - Slow-release fertilizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the desired dissolution rate and storage stability of a fertilizer by using a polylactate-type resin satisfying specific formulas containing a hydrolysis rate constant as a variable. SOLUTION: This slow-release fertilizer contains a polylactate-type resin composition satisfying the formula I and the formula II [A is the molar number of the ester bond in the original polymer; (b) is the molar number of water reacted with 1mol of the polymer; (t) is immersion period (hr); Tg is the glass transition temperature ( deg.C) of the polymer; (k) is the hydrolysis rate constant (hr)] when immersed in a phosphate buffer solution of pH7.0 at a temperature between Tg and 90 deg.C. The polylactate-type resin can be produced by the ring- opening polymerization of a lactide (a cyclic diester) and a corresponding lactone. For example, it can be produced by heating a toluene solution of 100 pts.wt. of an L-lactide, 0.3 pt.wt. of steary alcohol and 0.1 pt.wt. of aluminum acetylacetonate in N2 at 190 deg.C to effect the ring-opening polymerization of the lactide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slow-release fertilizer having a sustained release property, particularly excellent in biodegradability, and capable of controlling fertilizer release.

[0002]

2. Description of the Related Art Although chemical fertilizers are fast-acting, they are inherently water-soluble, so that loss due to runoff or denitrification is large, and it is difficult to maintain the fertilizing effect for a long period of time. On the other hand, if a large amount of chemical fertilizer is applied at one time, there is a risk that the concentration of the fertilizer will be impaired, and that the leaching of the fertilizer will cause pollution of rivers and the like. As a means for improving the above points, various methods for coating or mixing various resins on a fertilizer and imparting a slow effect to the fertilizer by using a sustained release effect of the fertilizer have been conventionally proposed. According to page 335 of the Handbook of New Polymer Materials (edited by the Society of Polymer Science, published by Maruzen Co., Ltd., September 20, 1989), phenolic resin and talc, sulfur or paraffin are currently used as fertilizer coating materials. Wax and diatomaceous earth or talc, olefin resin, or olefin resin and surfactant or talc,
Pinaya, paraffin wax, polypropylene, polyethylene, talc, soybean oil and cyclopentadiene
There are types. In addition to the above, according to Japanese Patent Publication No. 60-21952, a mixture of a polyolefin and an ethylene-vinyl acetate copolymer is disclosed, and in JP-A-62-21698, a mixture of a polyolefin and a diene-based polymer is disclosed. JP-17286 discloses a mixture of a polyolefin resin, an ethylene / vinyl acetate / carbon monoxide copolymer and a poorly water-soluble inorganic powder.
No. 30690 discloses vinyl chloride / ethylene copolymer,
JP-A-4-16584 discloses a polymer latex containing styrene and butadiene as main components having a glass transition temperature in the range of -5 ° C to 50 ° C, and JP-A-3-16984 discloses polyimide and styrene block copolymer. Alternatively, a proposal has been made to use a water-insoluble polymer such as n-polybutyl methacrylate as a fertilizer coating material. However, since these slow-release fertilizers have a mechanism in which water enters from relatively incomplete coatings in relatively hard coatings, pinholes, and cracks and fertilizer components gradually elute, these fertilizers are used in the manufacturing process. It is difficult to control the mechanism. Therefore, for example, there is a defect that the fertilizer component is rapidly eluted immediately after the fertilizer is sprayed, or conversely, the expected elution behavior cannot be obtained with good reproducibility with a small amount of elution. Furthermore, due to the nature of the polymer material for the coating used, even after the fertilization effect is over, these coating polymers remain in the soil and have the disadvantage that the life of the fertilizer cannot be determined from the appearance because the shape is retained, It will also pollute the soil and lead to environmental destruction.

[0003] In order to solve the above-mentioned drawbacks in the fertilizer coating material using a water-insoluble polymer, a fertilizer molded article for underwater plants using a water-soluble polymer such as polyvinyl alcohol and polyethylene glycol has been proposed. It has a very short time to disappearance and is not of a satisfactory quality as a slow release fertilizer.

In Japanese Patent Publication No. 2-23517,
There is a description of a fertilizer composition using poly (3-hydroxyalkanoate) as a covering material. This resin is water-insoluble and is decomposed by microorganisms in the soil, which solves the above-mentioned problem. However, since the resin has poor fluidity in a molten and molded state, it has poor moldability and free fertilizer. Difficult to form. Furthermore, the solubility in a solvent is poor, and it is difficult to form such a form by spraying a solvent solution on fertilizer granules in the production of a slow-release fertilizer. In JP-A-7-309689, a lactic acid-based resin composition is used as a covering material for fertilizers, but lactic acid-based resins generally have insufficient stability in water or under humidity,
When used as a coating material for a slow-acting fertilizer, fertilizer particles may adhere to each other during storage or fertilizer components may elute. In addition, an aromatic compound such as terephthalic acid is used as the lactic acid resin used in the examples, and the aromatic compound remains in the soil in an invisible form.

[0005]

SUMMARY OF THE INVENTION The present invention is intended to improve the disadvantages of these conventional fertilizer coating materials. The present invention controls the elution rate and elution pattern of the fertilizer components and, after the elution is completed, removes the fertilizer. It is an object of the present invention to provide a fertilizer coating material having so-called biodegradability, in which the coating material disappears without remaining in the soil, and which can be easily molded as a slow-release fertilizer, and which has good storage stability. And

[0006]

In view of the above-mentioned problems, the present researchers have developed a method of completely biodegradable, capable of controlling the dissolution of fertilizer components, and having good storage stability. As a result of intensive studies to obtain a fertilizer material, they have found that a polymer that achieves the above object can be obtained by satisfying a specific relational expression represented by a hydrolysis reaction rate constant of a lactic acid-based polymer and a glass transition temperature, Finally, the present invention has been completed.

That is, the present invention is characterized by satisfying the following formulas (I) and (II) when immersed in a phosphate buffer having a pH of 7.0 in a temperature range of Tg or more and 90 ° C. or less. It is a slow-release fertilizer containing a polylactic acid-based resin composition.

(3.28-lnk) × (3Tg + 168) ≧ 4500 (I) kt = log (A / (A−b)) (II) A: mol number of ester bond in 1 mol of initial polymer b: polymer The number of mols of water reacted with 1 mol t: immersion time [hr] Tg: glass transition temperature of polymer [° C] k: hydrolysis reaction rate constant [hr ^-1 ]

In the present invention, one of the methods for improving the storage stability of the polylactic acid-based resin is to reduce the amount of low-molecular-weight compounds such as unreacted monomers and impurities, chain-like and cyclic oligomers generated by side reactions in the polymer. Method. Usually, polylactic acid-based resins are produced by ring-opening polymerization of lactide, which is a cyclic diester, and corresponding lactones. In this case, the ring-opening polymerization reaction and the thermal ring-closing (depolymerization) reaction are in an equilibrium relationship, and a low molecular weight compound such as lactide, lactones, lactic acid or oligomer remains in the polymer. These low molecular weight compounds have a very strong hydrophilicity, and the hydrolyzate itself or its hydrolyzate shows strong acidity, and significantly promotes the hydrolysis of the polymer. Therefore, these low molecular weight compounds are used as a slow-release fertilizer composition. If it is included, the fertilizer component elutes in large quantities immediately after fertilization (burst phenomenon) or storage stability decreases.

The polymerization reaction can be carried out by a method other than the lactide method, for example, a direct dehydration condensation method of lactic acid, a polycondensation method of formalin and carbon dioxide gas, and the polymers obtained by these methods can be similarly treated with low molecular weight compounds. Is one of the main causes of hydrolysis and degrades its properties as a slow-release fertilizer. Therefore, it is necessary to reduce low molecular weight compounds in the polymer.

As a method for reducing a low molecular weight compound in a polymer, the following method generally used can be used. For example, a polymer is dissolved in a solvent and the polymer is deposited in a poor solvent with respect to the polymer to precipitate the polymer. Examples thereof include a reprecipitation method and a method of extracting with a solvent in which only low molecular weight compounds and residual monomers are dissolved. In addition, a low molecular weight compound can be efficiently removed by a method of reducing the pressure in the molten state of the polymer at the latter stage of polymerization of the polymer or after completion of the polymerization. For example, in the case of polylactic acid, the melting point of the polymer is +5
Decompression treatment may be performed at 0 ° C. or in the range from the glass transition point to the glass transition point + 200 degrees. Furthermore, low molecular weight compounds can be reduced by solid phase heat treatment of the polymer.
For example, in the case of polylactic acid, heat treatment may be performed at a temperature not lower than the glass transition temperature of the polymer and not higher than 150 ° C. in a completely dry state. In this case, there is no problem under any flow of an inert gas or the like, under reduced pressure, or under increased pressure. When both the melt pressure reduction treatment and the solid state heat treatment of the polymer are used, the low molecular weight compound can be more effectively removed. Examples of the method for reducing the low molecular weight compound include the above methods, but are not limited thereto.

The hydrolyzability of an α-oxy acid ester polyester such as polylactic acid has a correlation with the number of terminal carboxyl groups in the molecular chain, and the hydrolysis resistance tends to decrease as the number of carboxyl groups in the polymer increases. It is in. Therefore, as a method of improving the hydrolysis resistance of the polylactic acid-based resin, a method of blocking the carboxyl group at the terminal of the polymer molecular chain can be mentioned.

As a method for blocking the carboxyl group at the terminal of the polymer molecular chain, when a polylactic acid-based resin is produced by a lactide method, a ring-opening polymerization reaction may be carried out in the coexistence of lactide and other lactones with an aliphatic alcohol. .

The aliphatic alcohol used may be a mono-, di-, or polyhydric alcohol, and may be saturated or unsaturated. Specifically, methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, nonanol, decanol, lauryl alcohol, myristyl alcohol,
Cetyl alcohol, monoalcohols such as stearyl alcohol, ethylene glycol, butanediol, hexanediol, nonanediol, dialcohols such as tetramethylene glycol, dialcohols, glycerol, sorbitol,
Polyhydric alcohols such as xylitol, ribitol, and erythritol, and methyl lactate and ethyl lactate can be used, but are not limited thereto. Particularly preferably, long-chain aliphatic alcohols such as decanol, lauryl alcohol, myristyl alcohol, cetyl alcohol and stearyl alcohol are used. One or more of these alcohols can be used in combination. When the boiling point of the alcohol used is lower than the polymerization temperature, it is necessary to carry out the reaction under pressure.

The amount of alcohol depends on the purpose,
If the amount is too large, the molecular weight hardly increases, and the amount of the low molecular weight compound increases, which is not preferable. 0.01 to the total amount of monomer
It is used in a proportion of 1 mol%.

Further, a resin having a hydroxyl group in the molecular chain can be used instead of the aliphatic alcohol. The resin referred to here includes, for example, poly- (β-butyrolactone), poly- (γ-butyrolactone), poly- (ε
-Caprolactone), polypropiolactone, poly-
(Δ-valerolactone), poly- (4-valerolactone), poly- (β-methyl-δ-valerolactone), polyglycolic acid and a type obtained by polycondensing an aliphatic carboxylic acid with an aliphatic alcohol And aliphatic polyesters such as polyester.

When these are added to lactide, they may be used as they are (liquid or solid) or may be dissolved in an appropriate solvent. However, when a solvent is used, it is desirable that the solvent can be easily distilled off before or during the reaction.

Further, a plasticizer can be added in order to improve the storage stability of the polylactic acid resin. The plasticizer used is, for example, di-n-octyl phthalate, di-
Phthalic acid derivatives such as 2-ethylhexyl phthalate and dibenzyl phthalate; isophthalic acid derivatives such as diisooctyl phthalate; adipic acid derivatives such as di-n-butyl adipate and dioctyl adipate; sebacic acid derivatives such as dioctyl sebacate; maleic acid derivatives such as n-butyl maleate; citric acid derivatives such as tri-n-butyl citrate; oleic acid derivatives such as butyl oleate; itaconic acid derivatives such as monobutyl itaconate; glycerin monolithiate; Examples thereof include phosphate plasticizers such as ricinoleic acid derivatives, tricresyl phosphate, and trixylenyl phosphate. These plasticizers may be used alone or in combination of two or more. By adding the plasticizer to the lactic acid-based resin, the hydrophobicity of the polymer is increased and the storage stability is improved, and at the same time, the lactic acid-based resin is effectively plasticized, and the obtained resin composition has flexibility and moldability. Becomes better.

The polylactic acid-based resin having excellent storage stability according to the present invention is realized by using a plurality of the above-mentioned methods for reducing the amount of low molecular weight compounds and other methods. When each of these methods is used alone, a great effect cannot be obtained.

A catalyst is generally used for the polymerization of the polylactic acid resin, and a known catalyst is used for these.
When manufactured by the lactide method, specific examples include tin, antimony, zinc, titanium, iron, and aluminum compounds, but are not limited thereto. Of these, tin catalysts and aluminum catalysts are particularly preferred, and tin octylate and aluminum acetylacetonate are particularly preferred.

In the present invention, the hydroxyl group at the terminal of the molecular chain may be blocked with an aliphatic carboxylic acid. The aliphatic carboxylic acid having 2 to 51 carbon atoms to be used may be any of mono-, di- and polycarboxylic acids, and may be saturated or unsaturated. Specifically, acetic acid, propionic acid,
Butyric, valeric, caproic, caprylic, pelargonic, lauric, myristic, palmitic, stearic, arachidic, behenic, linoleic, oleic, succinic, adipic, suberic, azelaic, Sebacic acid, undecandioic acid, dodecandioic acid, dimer acid, fumaric acid and the like can be used. Further, it does not matter even if these acid anhydrides are added. One or more of these carboxylic acids may be used in combination. However, when an acid having a boiling point lower than the polymerization temperature is used, it is necessary to carry out the reaction under pressure. In particular, stearic acid, palmitic acid, myristic acid, linoleic acid, and oleic acid are flavoring agents, emulsifiers, vitamin enhancers, and fumaric acid, succinic acid, and adipic acid are seasonings, sour amounts, or food additives as their raw materials. It is a preferred carboxylic acid because its safety has been confirmed. Still more preferably, stearic acid, which is a raw material of calcium stearyl lactate used as an auxiliary for baking, is exemplified. By blocking the hydroxyl group terminal in this manner, the hydrophilicity of the polymer is reduced, and the hydrolysis resistance is improved, and at the same time, the melt stability of the polymer is improved.

The lactide used in the present invention is L
-Lactide, D-lactide, DL-lactide, meso-lactide may be used. It is desirable to use those which are sufficiently purified by ordinary purification operations, that is, recrystallization, rectification, sublimation and the like. The reaction may be performed in an inert atmosphere such as nitrogen or argon, or under reduced pressure or increased pressure. At that time, a catalyst, a carboxylic acid, an alcohol, or the like may be sequentially added.

In the present invention, the polylactic acid-based resin may be mixed and / or copolymerized with a second component in order to variously change the dissolution behavior and degradability of the fertilizer, and among others, it has biodegradability. The components are preferred. Examples of the mixed component include an aliphatic polyester such as an oxyacid ester polymer comprising an alkylene group having 1 to 20 carbon atoms. Specifically, poly- (β-butyrolactone), poly- (γ-butyrolactone), poly- (ε-caprolactone), poly- (propiolactone), poly- (δ-valerolactone), poly- (4- Valerolactone), poly-lactones such as poly- (β-methyl-δ-valerolactone), polyglycolic acid, and polyesters of the type obtained by polycondensing an aliphatic carboxylic acid and an aliphatic alcohol; Poly- (3-hydroxybutyrate), poly- (hydroxyvalerate), poly- (3-hydroxybutyrate) -co- (3-hydroxyvalerate), poly- (3-hydroxybutyrate) -co Poly-hydroxyalkanoates such as-(4-hydroxybutyrate), polyethylene glycol,
Examples thereof include, but are not limited to, polyethers such as polypropylene glycol, polyvinyl alcohol, polyamino acids, proteins, sugars, celluloses, and starch. Mixing non-degradable components and / or
Alternatively, in the case of copolymerization, those which are chemically stable without contaminating or modifying soil or water quality when left in the environment are preferred. As a mixed component, for example, polyethylene,
Examples include polypropylene and polystyrene.

The polylactic acid-based resin thus obtained has an arbitrary molecular weight according to the use. If necessary, an additive such as a pigment, an antioxidant, a deterioration inhibitor, a plasticizer, an ultraviolet absorber, or a lubricant may be added.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The slow-release fertilizer of the present invention is produced by a generally used method. For example, a method of dissolving a lactic acid-based resin in an organic solvent, immersing the fertilizer in the organic solvent solution or spraying the fertilizer, drying and forming a resin film on the outer periphery of the granular fertilizer, melting the resin, and melting the resin. A method in which a granular fertilizer is mixed and a resin film is formed on the outer periphery of the granular fertilizer or a mixture is crushed to form a mass, a method in which the granular fertilizer is coated with an aqueous emulsion of a lactic acid-based resin, and a capsule in which the lactic acid-based resin is encapsulated. Alternatively, fertilizer is put into a tube-shaped material, and the method of adhering and fusing, a method of including a fertilizer component in microspheres of a lactic acid-based resin, and further kneading the fertilizer in a polylactic acid-based resin, forming a sheet, a pellet. Shape,
Examples include a method of forming a rod, but the method is not limited to these methods.

In order to prevent blocking of fertilizer particles due to plasticization by heat or a solvent in producing the slow-release fertilizer of the present invention, inorganic particles, organic particles, oil, etc. are adhered or mixed to the surface or inside of the fertilizer. be able to. Examples of the inorganic particles used include colloidal silica, titanium oxide, talc, clay, calcium carbonate, magnesium carbonate, and silicon carbide. Organic particles include polyethylene latex, polystyrene latex, starch and the like, and oils include animal oils, vegetable oils, mineral oils and the like. By adding these, it is possible not only to prevent fusion of the fertilizer particles but also to control the elution rate of the fertilizer.

The fertilizer component of the slow-release fertilizer in the present invention is not particularly limited. In addition, natural fertilizers as well as chemical fertilizers are also covered. One or more types of fertilizer components are used, and a plurality of types can be used in combination. Furthermore, by covering several layers of the fertilizer and the polymer, the required fertilizer component can be eluted into the soil at the required time, so that the number of times of fertilization is reduced and the labor can be reduced. Pesticides can be added to the slow-release fertilizer of the present invention as needed, as long as they do not adversely affect the growth of the target plant. The kind of pesticide is not particularly limited, but specific examples include a fungicide, an insecticide, a herbicide, a plant growth regulator, and a soil conditioner for promoting the growth of a target plant.

The slow-release fertilizer of the present invention achieves the generally required fertilizer elution rate and storage stability by using a polylactic acid-based resin falling within the range defined by the hydrolysis rate constant. It is an essential condition to use a resin falling within this range.

[0029]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. The characteristic values in the examples were measured by the following methods.

(1) Evaluation of Hydrolysis Property A sheet having a size of 35 mm × 17.5 mm and a thickness of 0.5 mm was prepared at a pH of 7.
0 was immersed in a phosphate buffer for 24 hours, and X in the following formula was determined.

X = (3.28-lnk) × (3Tg + 168) (I) kt = log (A / (A−b)) (II) A: mol number of ester bond in initial polymer b: 1 mol of polymer T: immersion time [hr] Tg: glass transition temperature of polymer [° C] k: hydrolysis reaction rate constant [hr ^-1 ]

(2) Measurement of dissolution rate 10 g of fertilizer particles were immersed in 200 ml of water and sealed.
Leave at 0 ° C. After a predetermined time, the sample and water are separated, and the amount (nitrogen amount) of the fertilizer component eluted into the water is determined by quantitative analysis, and the total nitrogen amount and the percentage of the eluted nitrogen amount in the test sample are determined as the elution rate.

(Equation 1)

(3) Blocking test A fertilizer particle was left standing in a thermo-hygrostat at 30 ° C. and 90% RH for 1 month to visually determine the presence or absence of blocking.

Preparation Example 1 100 parts by weight of L-lactide, stearyl alcohol 0.1 part
A toluene solution of 3 parts by weight and 0.1 part by weight of aluminum acetylacetonate was charged into a polymerization tube equipped with a stirrer and a nitrogen introduction tube, and dried under vacuum for 2 hours and then replaced with nitrogen.
The mixture was heated to 190 ° C. in a nitrogen atmosphere, and a ring-opening polymerization reaction was performed for 2 hours to obtain a polymer. 0.1 m
After treating at 100 ° C. for 12 hours under a reduced pressure of mHg, the solid was treated at 120 ° C. for 24 hours under a nitrogen stream. A, b, T when the hydrolyzability of the obtained polymer was evaluated at 90 ° C.
Table 1 shows the values of g, k, and X.

Production Example 2 A toluene solution of 100 parts by weight of L-lactide, 0.2 parts by weight of laurylyl alcohol, 0.3 parts by weight of stearic acid, and 0.03 parts by weight of stannous octylate was stirred with a stirrer and a nitrogen inlet tube. , And dried under vacuum for 2 hours and purged with nitrogen, and then heated to 190 ° C. under a nitrogen atmosphere.
The ring-opening polymerization reaction was performed for 2 hours. After the reaction was completed, the resulting polymer was dissolved in chloroform (60 ml), poured into methanol (400 ml) and reprecipitated. The obtained white powder was sequentially washed with methanol and ether, and then dried at 60 ° C. in vacuo. The obtained polymer was evaluated for hydrolysis at 90 ° C.
Table 1 shows each value of A, b, Tg, k, and X when the test was performed.

Production Example 3 50 parts by weight of L-lactide, 50 parts by weight of DL lactide,
A toluene solution of 0.5 part by weight of stearyl alcohol and 0.1 part by weight of aluminum acetylacetonate was charged into a polymerization tube equipped with a stirrer and a nitrogen inlet tube, dried under vacuum for 2 hours, and replaced with nitrogen. The mixture was heated to 190 ° C. in an atmosphere, and a ring-opening polymerization reaction was performed for 2 hours. After the reaction was completed, the resulting polymer was dissolved in chloroform (60 ml), poured into methanol (400 ml) and reprecipitated. The obtained white powder was washed sequentially with methanol and ether, and then washed at 60 ° C.
And vacuum dried. Table 1 shows the values of A, b, Tg, k, and X when the obtained polymer was evaluated for hydrolysis at 75 ° C.

Production Example 4 A polymerization reaction was carried out in the same manner as in Production Example 1 except that 100 parts by weight of DL-lactide was used instead of L-lactide, and then a vacuum pump was maintained while maintaining the temperature in the reaction system. The pressure in the reactor was reduced to 5 mmHg, and after continuing for 1 hour, the inside of the reactor was replaced with nitrogen to take out a polymer. A, b, when the hydrolytic property evaluation of the obtained polymer was performed at 60 ° C.
Table 1 shows the Tg, k, and X values.

Production Example 5 Polymerization and melt pressure reduction were carried out in the same manner as in Production Example 4, except that 10 parts by weight of polycaprolactone (PLACCEL220, manufactured by Daicel Chemical) was used instead of stearyl alcohol. Evaluation of the hydrolyzability of the obtained polymer was 6
Table 1 shows the values of A, b, Tg, k, and X at 0 ° C.

Production Example 6 A polymerization reaction was carried out in the same manner as in Production Example 1, and the reaction was completed in 2 hours. The evaluation of the hydrolyzability of the obtained polymer was 90.
Table 1 shows the values of A, b, Tg, k, and X when the measurement was performed at ° C.

Production Example 7 A toluene solution of 100 parts by weight of L-lactide and 0.1 part by weight of aluminum acetylacetonate was charged into a polymerization tube equipped with a stirrer and a nitrogen inlet tube, and dried under vacuum for 2 hours and replaced with nitrogen. After that, the mixture was heated to 190 ° C. in a nitrogen atmosphere, and a ring-opening polymerization reaction was performed for 2 hours. While maintaining the temperature in the reaction system, degassing was performed with a vacuum pump to reduce the pressure to 5 mmHg. After continuing for 1 hour, the inside of the reactor was replaced with nitrogen and a polymer was taken out. The obtained polymer was evaluated for hydrolysis by 9
Table 1 shows the values of A, b, Tg, k, and X at 0 ° C.

Production Example 8 A polymerization reaction was carried out in the same manner as in Production Example 3, and the reaction was completed in 2 hours. The evaluation of the hydrolyzability of the obtained polymer was 75.
Table 1 shows the values of A, b, Tg, k, and X when the measurement was performed at ° C.

Production Example 9 A toluene solution containing 100 parts by weight of DL-lactide, 0.3 part by weight of stearic acid and 0.03 part by weight of stannous octylate was charged into a polymerization tube equipped with a stirrer and a nitrogen inlet tube. After vacuum drying for 2 hours and purging with nitrogen, 19
The mixture was heated to 0 ° C. and a ring-opening polymerization reaction was performed for 2 hours. Degas with a vacuum pump while maintaining the temperature inside the reaction system, 5m
After reducing the pressure to mHg and continuing for 1 hour, the inside of the reactor was replaced with nitrogen and the polymer was taken out. A, b, Tg, k, X when the hydrolyzability of the obtained polymer was evaluated at 60 ° C.
Each value is shown in Table 1.

Production Example 10 100 parts by weight of DL-lactide, polycaprolactone (P
LACCEL220, manufactured by Daicel Chemical Industries) 10 parts by weight,
A toluene solution containing 0.1 parts by weight of aluminum acetylacetonate was charged into a polymerization tube equipped with a stirrer and a nitrogen introduction tube, vacuum-dried for 2 hours and replaced with nitrogen, and then heated to 190 ° C. under a nitrogen atmosphere. A ring opening polymerization reaction was performed for 3 hours.
Table 1 shows the values of A, b, Tg, k, and X when the obtained polymer was evaluated for hydrolysis at 60 ° C.

Example 1 A solution obtained by dissolving 5 parts by weight of the polymer obtained in Production Example 1 in 100 parts by weight of trichloroethane was sprayed onto a nitrogen-based granular fertilizer having an average particle size of about 4 mm using a spray coating apparatus, and dried. To produce a coated granular fertilizer. The dissolution rate of the fertilizer is shown in FIG. 1, and the results of the blocking test are shown in Table 2.

Example 2 7 parts by weight of the polymer obtained in Production Example 1 was mixed with chloroform 1
In a solution dissolved in 00 parts by weight, 2 parts by weight of corn starch having an average particle size of about 3 μm were dispersed. The obtained liquid was used in Example 1.
Was coated with a nitrogen-based granular fertilizer in the same manner as described above, and dried to prepare a coated granular fertilizer. The dissolution rate of the fertilizer is shown in FIG. 1, and the results of the blocking test are shown in Table 2.

Example 3 60 parts by weight of the polymer obtained in Production Example 2 was crushed into flakes, blended with 40 parts by weight of a nitrogen-based fertilizer and 5 parts by weight of coconut oil, and kneaded at 190 ° C. by a kneader. The removed strand is crushed by a crusher and the particle size is about 4mm
Flake fertilizer was obtained. The dissolution rate of the fertilizer is shown in FIG. 1, and the results of the blocking test are shown in Table 2.

Example 4 5 parts by weight of the polymer obtained in Production Example 3 was dissolved in 100 parts by weight of trichloroethane. When the polymer solution is sprayed in the same manner as in Example 1, the colloidal silica 10
A part by weight was sprayed and dried to produce a coated granular fertilizer. The dissolution rate of the fertilizer is shown in FIG. 1, and the results of the blocking test are shown in Table 2.

Example 5 30 parts by weight of the polymer obtained in Production Example 4 was dissolved in 100 parts by weight of methyl ethyl ketone, and coated with a nitrogen-based granular fertilizer having a diameter of about 3 mm using a vertical jet type fluidized bed. Produced. The fertilizer dissolution rate is shown in FIG. 2 and the results of the blocking test are shown in Table 2.

Example 6 60 parts by weight of the polymer obtained in Production Example 4 and nitrogenous fertilizer 4
0 parts by weight and 5 parts by weight of talc were kneaded and crushed in the same manner as in Example 3 to obtain a flake-shaped fertilizer having a particle size of about 4 mm. The elution rate of the fertilizer is shown in FIG. 2, and the results of the blocking test are shown in Table 2.

Example 7 A coated granular fertilizer was prepared in the same manner as in Example 1 except that the polymer obtained in Production Example 5 was used. The elution rate of the fertilizer is shown in FIG. 2, and the results of the blocking test are shown in Table 2.

Comparative Example 1 A coated granular fertilizer was prepared in the same manner as in Example 1 except that the polymer obtained in Production Example 6 was used. The dissolution rate of the fertilizer is shown in FIG. 3, and the result of the blocking test is shown in Table 2.

Comparative Example 2 A flake fertilizer was obtained in the same manner as in Example 3 except that the polymer obtained in Production Example 7 was used. The dissolution rate of the fertilizer is shown in FIG. 3, and the result of the blocking test is shown in Table 2.

Comparative Example 3 A coated granular fertilizer was obtained in the same manner as in Example 4 except that the polymer obtained in Production Example 8 was used. Fig. 3 Fertilizer elution rate
The results of the blocking test are shown in Table 2.

Comparative Example 4 A coated granular fertilizer was obtained in the same manner as in Example 5 except that the polymer obtained in Production Example 9 was used. Fig. 4 Fertilizer elution rate
The results of the blocking test are shown in Table 2.

Comparative Example 5 Example 1 was repeated except that the polymer obtained in Production Example 10 was used.
A coated granular fertilizer was prepared in the same manner as described above. The fertilizer dissolution rate is shown in FIG. 4, and the results of the blocking test are shown in Table 2.

[0056]

[Table 1]

[0057]

[Table 2]

[0058]

As is clear from the above examples, the slow-release fertilizer using the polylactic acid resin in the present invention can control the elution rate of the fertilizer component as compared with the conventional fertilizer, Moreover, it has excellent storage stability. Further, since the slow-release fertilizer of the present invention is essentially completely degradable, environmental safety, which has been a problem in the past, has been significantly improved. Therefore, the slow-release fertilizer using the polylactic acid-based resin of the present invention greatly contributes to solving the industry or environmental problems.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the immersion time of a coated granular fertilizer in water at 25 ° C. and the dissolution rate in Examples of the present invention (Examples 1-4).

FIG. 2 is a graph showing the relationship between the immersion time in water at 25 ° C. and the dissolution rate of coated granular fertilizers of the present invention (Examples 5 to 7).

FIG. 3 shows 2 of coated granular fertilizers of Comparative Examples (Comparative Examples 1 to 3).
It is a figure which shows the relationship between the immersion time in 5 degreeC water, and an elution rate.

FIG. 4 shows 2 of the coated granular fertilizers of Comparative Examples (Comparative Examples 4 to 5).
It is a figure which shows the relationship between the immersion time in 5 degreeC water, and an elution rate.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Keiichi Uno 2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo Co., Ltd. Research Laboratory

Claims (1)

[Claims] 1. A polysaccharide which satisfies the following formulas (I) and (II) when immersed in a phosphate buffer having a pH of 7.0 in a temperature range of not lower than Tg and not higher than 90 ° C. A slow-release fertilizer containing a lactic acid-based resin composition. (3.28-lnk) × (3Tg + 168) ≧ 4500 (I) kt = log (A / (A−b)) (II) A: mol number of ester bond in initial polymer b: reacted with 1 mol of polymer Mol number of water t: immersion time [hr] Tg: glass transition temperature of polymer [° C] k: hydrolysis reaction rate constant [hr ^-1 ]