JP2000256087A - Slow releasing fertilizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slow releasing fertilizer excellent in the elution controllability of the fertilizer and free from leaving a coating film by the complete degradation after the elution of the fertilizer is finished. SOLUTION: A granular fertilizer is covered with the coating film and the coating film (I) is composed of a biodegradable coating film material consisting essentially of a lactic acid based polyester containing >=60 mol% lactic acid unit, (II) contains a swelling inorganic filler, which is at least one kind selected from hectorite, saponite, beidelite, nontronite, stevensite, montmorillonite, vermiculite, halloysite and synthetic mica.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sustained-release fertilizer in which fertilizer components are gradually eluted for a long period of time after fertilization, and the film is decomposed and disappears after the elution is completed.

[0002]

2. Description of the Related Art Conventionally, in order to control the dissolution rate of a fertilizer component, a sustained-release fertilizer obtained by coating a water-soluble fertilizer component with a film of a non-biodegradable resin, for example, an olefin resin, and forming it into granules has been used. Various proposals have been made and put to practical use.
However, these coated fertilizers have a problem that a film remains in the environment.

[0003] On the other hand, a sustained-release fertilizer using a so-called biodegradable resin for the film decomposes after the fertilizer component is eluted. In addition, the end of fertilization can be determined by disappearance, and there is little fear that the film remains in the environment.

[0004] As an example of a so-called completely degradable type coated fertilizer using an aliphatic polyester as a biodegradable resin, Japanese Patent Publication No. 23517/1990 uses a poly (3-hydroxyalkanoate copolymer) as a film. Granular fertilizer,
JP-A-7-33577 discloses a coated granular fertilizer using poly-L-lactic acid as a film, JP-A-7-309689 discloses a slow-release fertilizer coated or kneaded with a specific polylactic acid resin, and JP-A-8-157290. In the publication, there is a coated granular fertilizer using an aliphatic polyester polycondensed from an aliphatic dicarboxylic acid or a diol as a film.

[0005] These resins are decomposed by the action of microorganisms existing in the environment and have the above-mentioned advantages. However, in practice, these aliphatic polyester resins begin to decompose in a few months depending on the conditions in the environment,
It is difficult to control the elution rate of the fertilizer component due to the lack of a film such as a crack or a pinhole due to the crack.
Moreover, more importantly, it is known that the fertilizer coated with the aliphatic polyester resin causes a so-called burst phenomenon in which a large amount of the fertilizer component is released in the initial stage of fertilization. Therefore, there is a problem that these resins cannot be used as a coating material of a long-term dissolution type fertilizer which needs to control the dissolution rate over several months. This problem is considered to be due to the high moisture permeability of the aliphatic polyester resin itself.

[0006] In order to improve these drawbacks and mainly aim at the effect of delaying elution, a sustained release property using a blend composition of a biodegradable resin and a polyolefin resin or vinylidene chloride resin having low moisture permeability as a film. Fertilizers, that is, so-called collapse type coated fertilizers have been proposed. For example, JP-A-4-89
No. 384 discloses a coated fertilizer using a composition comprising polycaprolactone, polyolefin, and vinylidene chloride-based resin as a film, and Japanese Patent Application Laid-Open No. 9-263476 discloses a film comprising a composition comprising an aliphatic polyester and a specific polyolefin wax. Coated fertilizer used, JP-A-7-
No. 61884 proposes a coated fertilizer using a composition comprising polylactic acid, polyglycolic acid, an olefin, and a vinylidene chloride resin as a film.

In these proposals, since the film has a blend composition of a biodegradable resin and a hardly decomposable resin, even if the biodegradable resin part completely disappears, the hardly decomposable resin is finely disintegrated. However, it is easily expected that it will remain in the environment without decomposition. In addition, sufficient compatibility cannot be obtained due to the difference in polarity between the two resins, and there is also a problem that the film strength is reduced as compared with a film made of a single material, and as a result, due to external force received during recent machine fertilization. If the film is missing such as cracks, it becomes impossible to control the dissolution rate.

On the other hand, various additives such as an organic filler and an inorganic filler are added to a film made of a biodegradable resin in an amount of 1 to several tens.
% To control the elution of fertilizer components,
It is also known to accelerate the decomposition of the coating material. Among them, various inorganic fillers, that is, talc, calcium carbonate, kaolin, diatomaceous earth, silica, etc. are relatively large in amount because the filler itself is stable, mainly as a bulking agent and to prevent floating on the water surface after fertilization. However, in this case, it is known that as the amount of the filler increases, the fertilizer dissolves. On the other hand, the film strength tends to decrease, which may cause a problem.

[0009] From these facts, any of the completely decomposed or disintegrated coated fertilizers conventionally proposed have problems in terms of elution characteristics and environmental harmony, and have not been put to practical use at present. is there. Therefore, the appearance of a granular fertilizer capable of delaying elution of a fertilizer component has been demanded particularly in a coated fertilizer using a completely decomposed type film.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide good control of elution of fertilizer components, and that after the elution of fertilizer components is completed, the film is completely decomposed and remains in the environment. It is an object of the present invention to provide a novel sustained-release fertilizer using a completely decomposable material for a film without using the same.

[0011]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have made intensive studies and studies, and as a result, a special swellable inorganic filler different from the filler used in the conventional production of coated fertilizer. By using a composite material dispersed in lactic acid-based polyester for the film of a sustained-release fertilizer, surprisingly, the elution of the fertilizer can be suppressed, and as a result, the elution rate of the fertilizer can be easily controlled. And finally completed the present invention.

That is, the present invention provides the invention having the following constitutions (1) to (5).

(1) A sustained-release fertilizer comprising (a) a granular fertilizer and (b) a film covering the granular fertilizer, wherein the film comprises:
(i) a biodegradable coating material containing a lactic acid-based polyester containing at least 60 mol% of a lactic acid unit as an essential component; and (ii) a swellable inorganic filler containing a swellable inorganic filler. A sustained-release fertilizer wherein the filler is at least one selected from the group consisting of hectorite, saponite, beidellite, nontronite, stevensite, montmorillonite, vermiculite, halloysite, and synthetic mica.

(2) The film contains a swellable inorganic filler in an amount of 0.01 to 1 with respect to 100 parts by weight of the lactic acid-based polyester.
The sustained release fertilizer according to the above (1), wherein the fertilizer is contained in an amount of 00 parts by weight.

(3) The swellable inorganic filler is contained in the film,
The sustained-release according to the above (1) or (2), wherein the length is 30 nm or more, and 50% by weight or more is uniformly dispersed in a laminated state of 5 layers or less or in a form of delamination into a single layer. Fertilizer.

(4) The lactic acid-based polyester is polylactic acid, the ratio L / D of L-form to L-form of the lactic acid unit constituting the polylactic acid is 1 to 9, and the swellable inorganic filler is The sustained-release fertilizer according to any one of the above (1) to (3), which is montmorillonite and / or synthetic mica.

(5) In the presence of a swollen swellable inorganic filler, it is obtained by ring-opening polymerization of lactide or copolymerizing lactide with a comonomer that forms another biodegradable resin, and A method for producing a sustained-release fertilizer, comprising coating a granular fertilizer with a lactic acid-based polyester containing at least 60 mol% of a lactic acid unit.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. Lactic acid-based polyester As the lactic acid-based polyester used in the present invention, those conventionally known as bioabsorbable polymers or biodegradable polymers, for example, polylactic acid such as poly-DL-lactic acid and poly-L-lactic acid are used.

Lactic acid, which is a constituent unit of the lactic acid-based polyester used in the present invention, has an optically active site,
Both L-form and DL-form can be suitably used. The composition ratio is not particularly limited, but those having L / D representing the ratio of L-form of lactic acid unit to D-form in the range of 1 to 9 have high solubility in general-purpose solvents and are suitable for fertilizers. Preferred for production.

The above ratio L / D is determined at 20 ° C. of a chloroform solution of lactic acid-based polyester (concentration: 1 g / dl).
Can be determined from a calibration curve obtained in advance from the relationship between the specific rotation and the optical purity in.

These lactic acid-based polyesters can be used alone or in combination of two or more.

It is known that these lactic acid-based polyesters are generally produced by melt polycondensation of lactic acid, polycondensation in a high-boiling solvent, and ring-opening polymerization of a cyclic dimer of lactic acid called lactide. In the present invention, a lactic acid-based polyester produced by any of the methods can be suitably used.

If necessary, the lactic acid unit may contain 60 mol%
The other biodegradable components can be copolymerized within a range not less than the above. Copolymerization of other biodegradable components can be carried out by a conventionally known method such as polycondensation, random copolymerization by ring-opening polymerization, block copolymerization, graft copolymerization and the like.

Other biodegradable components (comonomer) for copolymerization include, for example, glycolide, caprolactone, polycaprolactone, poly-3-hydroxybutyrate and copolymers thereof (for example, poly (3-hydroxybutyric acid / Valeric acid), polyethylene succinate, polybutylene adipate, polybutylene succinate and aliphatic diols (for example, ethylene glycol, butanediol, etc.) and dicarboxylic acids (for example, succinic acid, adipic acid, etc.) , Polyethylene glycol, trimethylene carbonate and the like can be used. Further, a polyester containing an aromatic compound such as terephthalic acid or isophthalic acid as a part of the constituent component (for example, polyethylene terephthalate obtained by copolymerizing a large amount of a dicarboxylic acid such as adipic acid) as long as the biodegradability of the polyester is not impaired Etc.),
The other biodegradable component can be used for copolymerization with lactic acid.

These copolymer components may be appropriately selected according to the kind of the coating substance and the required elution pattern.
Any of them can be copolymerized with lactic acid according to a conventionally known method.

When the lactic acid unit content in the copolymer is less than 60 mol%, the following advantages exhibited when the lactic acid unit content is 60 mol% or more tend to be lost.

That is, when an aliphatic polyester component other than polylactic acid, such as polycaprolactone or polyhydroxyalkanoate, is used as a film material, microorganisms directly decompose the film surface in a normal soil or underwater environment, causing cracks or the like. In contrast to so-called polylactic acid, which degrades relatively slowly in a normal environment, the elution can be controlled over a long period of time, whereas the generation of pinholes makes it impossible to control elution. Furthermore, polylactic acid has a higher glass transition temperature than other biodegradable resins, and thus has an advantage that blocking can be suppressed during fertilizer production and storage. Therefore, the lactic acid-based polyester of the copolymer used in the present invention has a lactic acid unit of 60 mol% or more,
In particular, it is preferable to contain 90 mol% or more.

The polylactic acid used in the present invention and the lactic acid-based polyester of the copolymer having a lactic acid unit of 60 mol% or more are as follows:
GPC having a molecular weight in terms of polystyrene (weight average molecular weight) of about 5,000 to 300,000, particularly 2
Those having a molecular weight of from 000 to 200,000 are preferred.

It should be noted that in the present invention, the lactic acid-based polyester is used as a matrix of a composite material containing a swellable inorganic filler.

The swellable inorganic filler used in the present invention is a layered silicate, preferably hectorite, saponite, beidellite, nontronite, stevensite, montmorillonite, vermiculite, halloysite and synthetic. There is mica. These may be natural or synthetic. Among these, montmorillonite and synthetic mica (for example, Li-type fluorine teniolite, Na-type fluorine teniolite, Na
Type tetrasilicon fluorine mica, Li type tetrasilicon fluorine mica, etc.) are preferable from the viewpoint of easy dispersion.

These layered silicates may be used alone or in combination of two or more.

It is preferable that these fillers are pulverized using a mixer, a ball mill, a jet mill or the like to have a predetermined size in view of dispersibility and good appearance.
In general, it is preferable to use, as a raw material, a material that has been pulverized until the size (average particle size) of the desired inorganic filler becomes 50 μm or less.

The swellability in the present invention means that when these inorganic fillers come into contact with a swelling agent, for example, a quaternary organic onium ion or a low molecular compound, the inorganic filler absorbs the quaternary organic onium ion or the low molecular compound. , Swelling and cleaving properties.

As a specific example of the quaternary organic onium ion as the swelling agent, an ammonium ion and a phosphonium ion can be preferably used. Preferred ammonium ions include trimethyloctyl ammonium, trimethyl decyl ammonium, trimethyl dodecyl ammonium, trimethyl octadecyl ammonium, dimethyl dioctadecyl ammonium, ammonium having a polyethylene glycol chain, ammonium having a polypropylene glycol chain, aminocaproic acid, 12-
Ammonium aminododecanoate and the like. Specific examples of the phosphonium ion include trimethyloctylphosphonium, trimethyldecylphosphonium, trimethyldodecylphosphonium, trimethyloctadecylphosphonium, dimethyldioctadecylphosphonium, phosphonium having a polyethylene glycol chain, and phosphonium having a polypropylene glycol chain.

Specific examples of the low molecular weight compound as the swelling agent include water, alcohols such as ethanol, ethylene glycol and glycerin, amines such as alkylamine and piperidine, and amides such as urea, dimethylformamide and dimethylacetamide. , Aminocaproic acid, 12
-Amino acids such as aminododecanoic acid, acrylic compounds,
Lactams, lactones and the like can be mentioned.

Further, the layered silicate as the filler in the present invention may have a reactive functional group such as an epoxy group, an amino group or a carboxyl group added thereto. Examples of the addition method include a method of treating with a silane coupling agent without a solvent or in a solvent, but there is no particular limitation.
Conventionally known silane coupling agents are widely used. Specifically, 3-glycidyloxypropyldimethylchlorosilane, trichlorosilylpropionic acid, 3
-Aminopropyltriethoxysilane and the like.

The layer silicate as a filler in the present invention is preferably contained in an amount of 0.01 to 100 parts by weight based on 100 parts by weight of a lactic acid-based polyester as a matrix. When the amount is less than 0.01 part by weight, the object of the present invention cannot be satisfied because the amount of the layered silicate is too small. When the amount exceeds 100 parts by weight, the matrix component is small, so that the film of the sustained release fertilizer is used. Is difficult to form. Generally, the layered silicate as a filler in the present invention is a lactic acid-based polyester 10 as a matrix.
0.5 to 50 parts by weight, especially 1 to 20 parts by weight with respect to 0 parts by weight
More preferably, it is contained by weight.

These swellable phyllosilicates according to the present invention are uniformly dispersed in the coating in a state where they are exfoliated. Here, delamination means that the multilayer structure of the layered silicate is cleaved. Specifically, a swellable layered silicate having a length of 30 to the lactic acid-based polyester as a matrix is used.
It is recommended that the thickness is not less than 5 nm, preferably 30 to 200 nm, and 50% by weight or more of the layer is separated into layers of up to 5 layers or a single layer and uniformly dispersed. In particular, the swellable layered silicate has a length of 30 nm or more, preferably 30 to 200 nm, and 80% by weight or more of 5% or more.
It is more recommended that the layer is separated into layers having a thickness equal to or less than the layer or a single layer and is uniformly dispersed. Further, the swellable layered silicate has a length of 50 nm or more, preferably 50 to 200 nm.
It is most recommended that 90% by weight or more and 90% by weight or more of the layer be separated and uniformly dispersed in a laminated state of 5 layers or less or a single layer.

If the length of the layered silicate is less than 30 nm and / or the amount of delamination of less than 5 layers or a single layer is less than 50% by weight, the object of the present invention is reduced. I cannot be satisfied. For example, the filler contained in the coating material of the conventional coated fertilizer is not delaminated and has a large average particle size of about 1 to 50 μm. In such a case, such a filler is contained in the coating. , An effect completely opposite to the object of the present invention appears. That is, as compared with the case where no such filler is added, the elution of the fertilizer tends to be promoted, and it becomes difficult to delay the elution.

In the present invention, it can be confirmed from a TEM (transmission electron microscope) image of the lactic acid-based polyester composite that the layered silicate is uniformly dispersed in the above-mentioned predetermined state.

Coating Material For the coating material of the present invention, that is, a method for producing a lactic acid-based polyester composite material containing the lactic acid-based polyester and the swellable inorganic filler, a conventionally known method can be applied. Method of internal addition during polymerization,
Examples thereof include a method of dry blending using a blender or a mixer, and a method of melt-kneading using an extruder. Preferably, it is a method of adding internally during polymerization.

In the method of internal addition at the time of polymerization, ring-opening polymerization is used among polycondensation and ring-opening polymerization from the viewpoint of easy production of a composite material. Specific examples of the method of internal addition at the time of polymerization are as follows: a predetermined amount of a swellable layered silicate such as montmorillonite is quaternary onium-modified with 12-aminododecanoate ammonium such as hydrochloric acid or acetic acid; Swelled with the swelling agent such as trimethyloctadecyl ammonium, and in the presence of the thus obtained swollen layered silicate and a polymerization catalyst, lactic acid which is a lactic acid cyclic diester is heated to synthesize polylactic acid by ring-opening polymerization. Alternatively, there may be mentioned a method of synthesizing a lactic acid-based polyester as a copolymer by copolymerizing lactide and the above-mentioned comonomer which forms another biodegradable resin, preferably by ring-opening polymerization.

In the above method, the conditions for swelling the swellable phyllosilicate can be selected from a wide range. Generally, the swelling phyllosilicate is added to the aqueous dispersion of the swellable phyllosilicate with stirring. The aqueous solution of the agent may be dropped at a temperature of 60 to 120 ° C. and contacted with stirring for about 2 to 100 hours. The swollen layered silicate thus obtained is preferably separated by filtration or the like, dried and used.

The ring-opening polymerization for synthesizing the above-mentioned polylactic acid is carried out by heating lactide as a raw material in the presence of a layered silicate and a polymerization catalyst. In this polymerization, a solvent may be used, but it is preferable to perform the polymerization without a solvent.

In the above copolymerization with the comonomer, for example, a cyclic monomer such as glycolide or caprolactone can be subjected to ring-opening polymerization with lactide. Further, polymers or oligomers having a hydroxyl group at a terminal such as polycaprolactone and polyethylene succinate can be copolymerized by ring-opening polymerization of lactide using this as a macroinitiator. At this time, the number of terminal molecules may be appropriately selected from the range of 1 to the number that does not cause gelation. In addition, aliphatic and / or aromatic diols and aliphatic and / or aromatic dicarboxylic acids are appropriately polycondensed or copolycondensed with an excess of diol, and then lactide is subjected to ring-opening polymerization at the terminal hydroxyl group.

In the above copolymerization, the ratio of the lactide and the comonomer used as raw materials is selected so that the lactic acid units in the obtained copolymerization are 60 mol% or more. For example, when lactide and a comonomer for forming a copolymer are copolymerized, lactide is at least 43 mol%, preferably 82 mol%, based on the total amount of lactide and the comonomer.
It is desirable to use the above.

The raw material layered silicate and lactide (or the total amount of lactide and a comonomer for forming a copolymer)
In the lactic acid-based polyester composite material obtained by polymerization, the layered silicate as a filler is 0.01 to 100 parts by weight, preferably 0 to 100 parts by weight, based on the lactic acid-based polyester as a matrix. .5-5
The amount may be 0 parts by weight, particularly 1 to 20 parts by weight. In general, the layered silicate is used in an amount of 0.005 to 80 parts by weight, preferably 0.4 to 40 parts by weight, based on 100 parts by weight of the raw material lactide (or the total amount of lactide and a comonomer for forming a copolymer). Just use it.

As the polymerization catalyst, a conventionally known polymerization catalyst for a lactic acid-based polyester can be used. Specifically, tin, zinc, titanium, antimony, iron, aluminum,
Examples include compounds of rare earth metals such as lanthanum and cerium, but are not limited thereto.
Among them, compounds of tin and aluminum are particularly preferable, and tin octylate and aluminum acetylacetonate are particularly preferable. The amount of these catalysts used may be a commonly used amount, and generally, the raw material lactide (or the total amount of lactide and a comonomer for forming a copolymer) 10
The amount is preferably about 0.01 to 1 part by weight based on 0 part by weight.

The heating for the polymerization is preferably carried out by drying the raw material lactide (or lactide and a comonomer for forming a copolymer) or the like under reduced pressure, and then stirring the mixture in an inert gas atmosphere such as nitrogen gas under stirring for 120 to 120 hours. 200 ° C., preferably 150
The heat treatment may be performed at a temperature of about 180 ° C. for about 1 to 80 hours.

By performing ring-opening polymerization according to the above method, the layered silicate swells and cleaves, and is uniformly dispersed in the lactic acid-based polyester as a matrix to obtain a desired lactic acid-based polyester composite material. it can.

Further, after the polymerization of the lactic acid-based polyester is completed or after the polymerization is completed, devolatilization is performed under reduced pressure while the lactic acid-based polyester is in a molten state, and the remaining lactide is removed (demonomerization) to obtain a film obtained. It is preferable because the elution rate of the fertilizer when the coated fertilizer is made of the material can be controlled more precisely. That is, as the amount of residual monomer is reduced by the devolatilization, the elution rate of the fertilizer becomes slow. Therefore, the elution rate can be controlled by adjusting the amount of residual monomer.

In the present invention, the layered silicate as the filler and the molecular chain of the lactic acid-based polyester as the matrix are bonded at the molecular level (that is, the layered silicate is bonded to the swelling agent, The swelling agent bound in this way becomes an initiator of ring-opening polymerization and is incorporated into the polymer chain terminal), and they are uniformly finely dispersed and complexed. The filler used for the coating material of the conventional coated fertilizer is compounded at the time of fertilizer preparation, so there is only a weak interaction between the filler and the matrix molecular chain, and it is not bonded at the molecular level. In this case, the object of the present invention cannot be satisfied.

According to the present invention, when a lactic acid-based polyester inorganic composite material is used as a component of a coating material of a sustained-release fertilizer, elution of the fertilizer component is suppressed, and as a result, the elution rate can be easily controlled, so that it is suitable as a coating material. It is. Although the mechanism of suppressing the elution is not clear, it is considered that the moisture permeability of the lactic acid-based polyester-inorganic composite material is small.

It is essential that the coating material of the present invention contains the above-mentioned lactic acid-based polyester composite material. However, if necessary, different biodegradable components and a great influence on the control of the degree of decomposition and the elution rate are required. Various inorganic components and surfactants may be blended within a range that does not affect the above.

Specifically, the biodegradable components include:
3-hydroxyalkanoate copolymers, especially copolymers of 3-hydroxybutyric acid and 3-hydroxyvaleric acid, polyesters polymerized from caprolactone, aliphatic dicarboxylic acids (eg, succinic acid, adipic acid, sebacic acid, etc.) ) And a diol (eg, ethylene glycol, butanediol, etc.), an aliphatic polyester polycondensed,
Examples include natural vegetable oil, rosin, paraffin wax, beeswax, and wood wax. Further, as the inorganic component,
Examples thereof include commonly used talc, calcium carbonate, silica, clay, and sulfur powder. As the surfactant, any of cationic, anionic, amphoteric and nonionic surfactants can be used.

Sustained- release fertilizer The sustained-release fertilizer of the present invention is produced by a method generally used as a method for producing a sustained-release fertilizer.

For example, the lactic acid-based polyester composite material obtained above is dissolved in an organic solvent (eg, trichloroethane, toluene, xylene, etc.), and a fertilizer is immersed in the organic solvent solution, or the organic solvent solution is dissolved. Is sprayed on a fertilizer and then dried to form a resin film on the outer periphery of the granular fertilizer.

In order to make the thickness uniform, it is preferable to carry out the coating while the fertilizer particles are being rotated and floated. A well-known jet coating device such as a layer, a rotating drum type, and a pan type coating device may be used, but of course, other devices may be used.

In addition, the lactic acid-based polyester composite material of the present invention is heated and melted, sprayed and cooled to form a film, and the lactic acid-based polyester composite material of the present invention is formed into a capsule or tube. Examples of the method include a method in which a fertilizer is added and bonded and melted, and a method in which a fertilizer is contained in microspheres of a lactic acid-based polyester composite material. However, the method is not limited to these methods.

The thickness of the coating is preferably 0.01 to 0.5.
4 mm, especially 0.01-0.1 mm. 0.01m
If it is thinner than 30 m, defects such as pinholes are likely to occur in the film, making it difficult to control the dissolution rate.
If it exceeds mm, the elution will be unnecessarily delayed, and it will be difficult to control the elution rate.

The size of the fertilizer particles after coating is about 10 to 1 mm, especially about 2 to 6 mm from the elution period and ease of use, and the shape is not particularly limited, but is preferably spherical, oval spherical, or cylindrical. , Disk-shaped.

The fertilizer used in the present invention includes
Generally, any fertilizer used in the whole field of each crop in the art can be applied. Specifically, urea, ammonium sulfate, salt salt, ammonium nitrate, sodium nitrate, isobutyraldehyde condensed urea, potassium phosphate, phosphate lime, calcined phosphorus fertilizer,
Examples include potassium chloride, potassium sulfate, potassium bicarbonate, potassium phosphate, potassium nitrate and the like. These 2
Chemical fertilizers composed of more than one component are also used. In addition, natural fertilizers are also covered. In addition, when used for a poorly water-soluble fertilizer such as IBDU (isobutylidene diurea), it becomes easy to control the elution rate of the fertilizer. In addition, compounds such as iron, boron, manganese, zinc, molybdenum, and copper may be contained as magnesium, calcium, sulfur, and micronutrients. Further, one or more fertilizer components can be used, and a plurality of types can be used in combination.

It is also possible to coat several layers of a fertilizer and a film made of the lactic acid-based polyester composite material of the present invention.

The sustained-release fertilizer of the present invention may optionally contain
Pesticides can be added within a range that does not adversely affect the growth of the target crop. Specific examples include fungicides, insecticides, herbicides, and the like.

The sustained-release fertilizer of the present invention thus obtained is
Fertilization can be carried out in the same manner as conventionally known coated fertilizers, and can also be applied by mechanical fertilization. In addition, when used in combination with other coated fertilizers having different dissolution patterns, as well as ordinary chemical fertilizers and natural fertilizers, it is possible to bring about a fertilizing effect according to the intended crop.

[0066]

EXAMPLES Next, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples. Parts in the examples represent parts by weight. In addition, the characteristic value in an Example was measured by the following method.

(1) Dissolution rate measurement 10 g of fertilizer particles were immersed in 200 ml of water and sealed.
Leave at 5 ° C. After a predetermined time, the sample is separated from water and the amount of the fertilizer component eluted in the water (the amount of nitrogen) is measured, and the ratio of the amount of the eluted nitrogen to the total amount of nitrogen in the test sample is determined as the elution rate.

(2) Measurement of molecular weight The composite material is obtained by dissociating the layered silicate bonded with lithium chloride and regenerating the matrix polymer.
The molecular weight in terms of polystyrene was determined by C (gel filtration permeation chromatography). (Solvent chloroform) (3) Dispersibility Long thin sections (thickness 10
0 nm), and a TEM (transmission electron microscope) image was taken and evaluated as follows: ：: the layered silicate is 30 nm or more in length, and
50% by weight or more of the layered silicate is delaminated to a layered state of 5 layers or less or a single layer and uniformly finely dispersed. Δ: The layered silicate delaminated to a layered state of 5 layers or less or a single layer is layered. Less than 50% by weight of the entire silicate ×: The layer is not exfoliated, and a dispersed phase on the order of μm is observed.

Reference Example 1 75 parts of montmorillonite (trade name "Kunipia F", manufactured by Kunimine Industries Co., Ltd.) was suspended in 2,000 parts of ion-exchanged water, and heated and stirred at 85.degree.
To this, a salt aqueous solution (temperature: 85 ° C.) prepared from 39 parts of 12-aminododecanoic acid (manufactured by Tokyo Chemical Industry) and 37 parts of concentrated hydrochloric acid was added dropwise over 30 minutes, and 4000 parts of ion-exchanged water was further added for 24 hours. Stirred.

The obtained white suspension was subjected to suction filtration with a Nutsche filter, and the powder on the filter paper was washed with 1000 parts of hot water at 85 to 89 ° C. by 5 parts.
After washing twice, it was dried at 100 to 120 ° C. under a reduced pressure of 0.6 mmHg for 24 hours to obtain a slightly off-white powder.

(Production Example 1) Synthesis of lactic acid-based polyester composite material Using 5 parts of the white powder obtained in Reference Example 1 and 100 parts of DL-lactide (manufactured by Tokyo Kasei) as raw materials, a stirrer, a nitrogen introducing pipe, Pour into a polymerization can with a lower outlet,
It dried under reduced pressure for 2 hours. Thereafter, the pressure was returned to normal pressure with nitrogen, and the mixture was heated and stirred at 140 ° C. in a nitrogen atmosphere to give a gray melt. When this was further heated, the melt viscosity gradually increased. When the temperature was further raised to 160 ° C. and stirring was continued, a slightly yellowish gray viscous body was finally obtained in 52 hours. This was extracted from the lower part of the can in the form of a pellet.

(Production Example 2) A lactic acid-based polyester composite material was synthesized in the same manner as in Production Example 1 except that 10 parts of the white powder obtained in Reference Example 1 was used.

(Production Example 3) Talc (manufactured by Shiraishi Industry Co., Ltd.) 80
Parts, 20 parts of sodium silicofluoride, 5 parts of synthetic fluorine mica calcined in a porcelain crucible, 0.5 part of 12-aminododecanoic acid, and 100 parts of DL-lactide (manufactured by Tokyo Chemical Industry) as raw materials. A lactic acid-based polyester composite material was synthesized in the same manner as in Production Example 1.

(Production Example 4) A lactic acid-based polyester composite material was synthesized in the same manner as in Production Example 1, except that 100 parts of L-lactide (manufactured by Purac) was used as a raw material.

(Production Example 5) A lactic acid-based polyester composite material was synthesized in the same manner as in Production Example 1, except that 75 parts of L-lactide (manufactured by Purac) and 25 parts of glycolide (manufactured by Taki Kagaku) were used as raw materials. .

(Production Example 6) Production of Comparative Coating Material 100 parts of DL-lactide (manufactured by Tokyo Kasei), 4 parts of lauryl alcohol (used as a molecular weight regulator) and 0.2 part of aluminum acetylacetonate were mixed with a stirrer and nitrogen. It was charged into a polymerization vessel equipped with an inlet tube and a lower outlet, and dried under reduced pressure for 2 hours. Thereafter, the pressure was returned to normal pressure with nitrogen, and the mixture was heated and stirred at 140 ° C. under a nitrogen atmosphere to obtain a colorless and transparent melt. When this was further heated, the melt viscosity gradually increased. When the temperature was further raised to 165 ° C. and stirring was continued, a slightly yellowish transparent lactic acid-based polyester was finally obtained in 4 hours. This was extracted from the lower part of the can in the form of a pellet.

Example 1 50 parts of the lactic acid-based polyester composite material obtained in Production Example 1 was replaced with trichloroethane 1000
The solution dissolved in the portion was sprayed onto a nitrogen-based granular fertilizer (urea particles) having an average particle diameter of 4 mm using a jet coating device, and dried to prepare a coated granular fertilizer.

Example 2 A coated granular fertilizer was prepared in the same manner as in Example 1 except that the lactic acid-based polyester composite material obtained in Production Example 2 was used.

Example 3 A coated granular fertilizer was prepared in the same manner as in Example 1 except that the lactic acid-based polyester composite material obtained in Production Example 3 was used.

Example 4 A coated granular fertilizer was prepared in the same manner as in Example 1 except that the lactic acid-based polyester composite material obtained in Production Example 4 was used.

Example 5 A coated granular fertilizer was prepared in the same manner as in Example 1 except that the lactic acid-based polyester composite material obtained in Production Example 5 was used.

Comparative Example 1 A coated granular fertilizer was prepared in the same manner as in Example 1 except that the lactic acid-based polyester obtained in Production Example 6 was used.

(Comparative Examples 2 and 3) Coating was performed in the same manner as in Example 1 except that the lactic acid-based polyester obtained in Production Example 6 and talc (average particle size: 12 μm) in the amount shown in Table 1 were used. A granular fertilizer was made.

Comparative Example 4 Coated granular fertilizer was prepared in the same manner as in Example 1 except that 25 parts of the lactic acid-based polyester obtained in Production Example 6 and 25 parts of polyethylene (low-density polyethylene having a melt index of 20) were used. Created.

Table 1 shows the type of matrix, the type and amount of filler used, and the molecular weight of the lactic acid-based polyester used as the matrix in Examples 1 to 5 and Comparative Examples 1 to 4.

Further, the above Examples 1 to 5 and Comparative Examples 1 to 4
Table 2 shows the dissolution rate of the coated fertilizer and the dispersibility of the filler in the film obtained in the above.

In Table 1, the abbreviations of the matrix have the following meanings: PDLLA: poly DL-lactic acid PLLA: poly L-lactic acid PGLA: copolymer of L-lactic acid and glycolide PE: polyethylene.

[0088]

[Table 1]

[0089]

[Table 2]

[0090]

As is clear from the above Examples 1 to 5 and Comparative Examples 1 to 4, the sustained-release fertilizer using the lactic acid-based polyester composite material of the present invention as a film material is a conventional biodegradable fertilizer. Compared to a coated fertilizer using a resin, the elution rate of the fertilizer component can be delayed, and the elution rate can be easily controlled.

Further, since only the biodegradable resin is used, the non-degradable resin does not remain in the environment as in the prior art.

Thus, the sustained-release fertilizer of the present invention greatly contributes to the development of industry and to the resolution of environmental problems.

Claims (5)

[Claims] 1. A sustained-release fertilizer comprising (a) a granular fertilizer and (b) a coating covering the granular fertilizer, wherein the coating comprises: It is composed of a biodegradable film material containing polyester as an essential component, and (ii) contains a swellable inorganic filler, wherein the swellable inorganic filler is hectorite, saponite, beidellite,
A sustained-release fertilizer of at least one selected from the group consisting of nontronite, stevensite, montmorillonite, vermiculite, halloysite, and synthetic mica. 2. The film according to claim 1, wherein the swellable inorganic filler is 0.01 to 100 parts by weight based on 100 parts by weight of the lactic acid-based polyester.
2. The controlled release fertilizer according to claim 1, wherein the fertilizer is contained in an amount of part by weight. 3. The swellable inorganic filler is uniformly dispersed in the film in a form of a layer having a length of 30 nm or more, and 50% by weight or more of the swellable inorganic filler having a thickness of 5 layers or less or a single layer. The sustained-release fertilizer according to claim 1 or 2, wherein 4. The lactic acid-based polyester is polylactic acid, wherein the ratio L / D of L-form to L-form of lactic acid units constituting the polylactic acid is 1 to 9, and the swellable inorganic filler is montmorillonite. The sustained release fertilizer according to any one of claims 1 to 3, which is a synthetic mica. 5. A lactic acid unit obtained by ring-opening polymerization of lactide in the presence of a swollen swellable inorganic filler or copolymerizing lactide with a comonomer that forms another biodegradable resin. A method for producing a sustained-release fertilizer, comprising coating a granular fertilizer with a lactic acid-based polyester containing at least 60 mol% of a lactic acid-based polyester.