JPH0517882B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field The present invention has excellent efficacy as a nematocidal ingredient, but
On the other hand, it is difficult to use ethoprophos as a nematocide due to its strong toxicity, but the present invention relates to a capsule containing ethoprophos, which is made easier to use as a nematocide by reducing its toxicity. Prior Art Since ethoprophos originally has high activity as a nematicidal component, it has been put to practical use as a nematicide in foreign countries such as South Korea and the United States. However, ethoprofos is highly toxic;
In addition, due to its strong irritant properties, it has not yet been used as a nematocide in Japan, and attempts have been made to make ethoprophos into granules in order to reduce its toxicity and odor. However, it has not reached a level where it can be put to practical use. On the other hand, we have also proposed an attempt to micro-encapsulate active ingredients as pesticides to achieve sustained efficacy by slow release, and to prevent adverse effects on organisms other than the pests targeted for control. (For example, Japanese Patent Application Laid-Open No. 1983-
No. 124705). However, even if the method of encapsulating the active ingredient as a core material as disclosed in JP-A-58-124705 is applied to ethoprofos, it is practically impossible to encapsulate it. It is possible. Problems to be Solved by the Invention In view of the above-mentioned circumstances, the present invention was achieved as a result of studying the encapsulation of ethoprofos to reduce the toxicity of ethoprofos, which has high nematicidal activity but is highly toxic. First, ethoprophos in the form of a solution dissolved in vegetable oil is microencapsulated using a core material and aminoplast as a membrane material, and then the resulting capsule membrane is aged under specific conditions to be used as a nematocide. The purpose of the present invention is to provide ethoprofos capsules with reduced toxicity to the extent that they can be put to practical use. The present invention will be explained in detail below. Structure of the Invention The present invention is characterized in that it consists of microcapsules whose core material is a mixture of ethoprophos and vegetable oil and whose membrane material is a polycondensate of urea formaldehyde prepolymer and/or melamine formaldehyde prepolymer, and which is equivalent to 30 mg of ethoprofos. The capsule has an ethoprophos dissolution rate of 10% or less after the microcapsule is shaken in 70 ml of water for 1 hour. Means for Solving the Problems The encapsulation of ethoprofos in the present invention is
Droplets of a solution of ethoprophos as a core material mixed and dissolved in vegetable oil are made into urea formaldehyde prepolymer (hereinafter abbreviated as "UF prepolymer").
and/or by dispersing melamine formaldehyde prepolymer (hereinafter abbreviated as "MF prepolymer") in an aqueous liquid and polycondensing the UF prepolymer and/or MF prepolymer at the interface of the droplets. Examples of vegetable oils used in the capsule core include soybean oil, cottonseed oil, linseed oil, olive oil, rapeseed oil, and corn oil. The mixing ratio of such vegetable oil and ethoprophos is 7:3 to 3 by weight.
The ratio is 2:8, preferably 5:5 to 3:7. Incidentally, ethoprophos is an oily liquid and has poor emulsifying properties and film-forming properties at the interface.
Although it was impossible to encapsulate it as it is like with ordinary oily substances, as mentioned above, by mixing and dissolving ethoprophos in vegetable oil, it was possible to suppress its odor, improve emulsifying properties, and improve film formation. The properties are improved and encapsulation becomes possible. Next, encapsulation in the present invention will be specifically explained. Add the solution of ethoprophos mixed and dissolved in vegetable oil as described above to an aqueous mixture containing an aqueous cationic urea resin and an anionic surfactant, adjust the pH to 4 to 5, and use a suitable device such as a homogenizer, stirrer, or ultrasonic device. Emulsification and dispersion is performed using appropriate means to form droplets of an appropriate size, for example, 1 to 6 μm. On the other hand, the resin prepolymer as the membrane material is preferably used in an amount of 9:1 to 1:1 by weight to the mixture of ethoprophos and vegetable oil as the core material.
It may be added in advance to the mixture before emulsification and dispersion to emulsify it, or it may be added once or in several portions during or after emulsification. The emulsification at this time is
It is carried out at a pH of 4 to 5 and a temperature of 20 to 60°C, preferably 30 to 50°C. After adding the resin polymer as described above, the emulsion was allowed to react (polycondensate) for 15 to 25 hours while being gently stirred, and then the pH was adjusted to 2.5 to 3.0 and heated to 30 to 60°C.
Encapsulation is completed by further reacting at a temperature of 40 to 50 hours. Note that the resin prepolymer used here is
UF prepolymer means methylolated urea ranging from monomethylolurea to tetramethylolurea, a mixture of these methylolureas with different degrees of methylolation, or a mixture of the methylolurea, urea, and formaldehyde, and furthermore, a mixture of methylolurea, urea, and formaldehyde. It may also be an oligomer that has undergone further reaction, that is, a transparent colloidal solution having a hydrophilic group with a degree of polymerization of 2 to 5. Furthermore, MF prepolymer means methylolmelamine ranging from monomethylolmelamine to hexamethylolmelamine, a mixture of these methylolmelamines with different degrees of methylolation, or a mixture of the above-mentioned methylolmelamine, melamine, and formaldehyde, and furthermore, melamine and formaldehyde. It may also be a transparent colloidal aqueous solution obtained by further proceeding with the above reaction, that is, by treating methylolmelamine with a degree of polymerization of 2 to 10 with hydrochloric acid. This MF prepolymer can be easily produced by heating a mixture of melamine and formalin in alkaline conditions, and this aqueous reaction solution can be directly used for encapsulation. In addition, the water-soluble cationic urea resin used in the above encapsulation is a urea formaldehyde resin with a cationic modifier introduced therein, such as tetraethylenepentamine, diaminoethanol, dicyandiamide, diethylaminoethanol as a modifier in the urea formaldehyde prepolymer. , guanylurea or similar substances are added thereto and polycondensed by a known method. The weight ratio of the water-soluble cationic urea resin to the resin prepolymer is preferably in the range of 1:0.01 to 2.0. Further, examples of the anionic surfactant include fatty acid salts, higher alcohol sulfates, alkylaryl sulfonates, etc., but sodium dodecylbenzenesulfonate is preferred. In the microcapsules of the present invention, the pH of the capsules is set to 3.5 in order to control the release of the active ingredient, ethoprophos, in the capsules (in the form of a slurry) obtained as described above.
Adjust to ~7 and add 0.5 to 2% by weight of dispersant, and add 40
The capsule membrane is aged by standing at a temperature of ~60 degrees for 60 to 80 hours. The aging time may be determined by taking into account the type of resin prepolymer used and the water dissolution rate of ethoprophos in the capsule. The aging of the capsule membrane can also be gradually progressed by allowing the slurry to stand after encapsulation, but this is not practical as it takes several months before it can be used. As the dispersant used for ripening the capsules, alkylallylsulfonates such as alkylbenzenesulfonates and alkylnaphthalenesulfonates, and formaldehyde condensates thereof are preferably used. The water dissolution rate of ethoprophos in capsules is the amount of ethoprophos dissolved in water after shaking an amount of capsules equivalent to 30 mg of ethoprophos in 700 ml of water for 1 hour, expressed as a percentage. means something that has been done. In other words, the above water elution rate indicates the degree of release of ethoprophos from the microcapsules, and although the water elution rate of ethoprophos varies depending on the capsule film thickness, the degree of aging of the film, etc., it mainly depends on the resin prepolymer used. influenced by. That is,
Although UF prepolymers are useful for forming dense films, they have a slow film formation rate and are prone to agglomeration, making it difficult to form capsules, but the water dissolution rate of ethoprophos from the resulting capsules is extremely low. On the other hand, the MF prepolymer has a fast film formation rate and is easy to encapsulate, but its film density is poor and therefore the water dissolution rate of ethoprophos is high. For this reason, in the capsule of the present invention, MF prepolymer and UF prepolymer are added to the resin prepolymer as a membrane material at a weight ratio of 1:1.
It is preferable to use them together at a ratio of ~1:4. Furthermore, if the water dissolution rate of ethoprofos from the capsule exceeds 10%, the toxicity and odor of ethoprofos will not be sufficiently reduced;
If it is lower than %, the membrane becomes too dense and the nematicidal efficacy becomes poor. Regarding this point, when MF prepolymer and UF prepolymer are used together as membrane materials in the ratio within the above range, the dermal toxicity of ethoprofos is almost eliminated,
Moreover, capsules whose nematicidal effect is maintained for several months can be obtained. The microcapsules according to the present invention can be used as a water-sealing slurry after the slurry has been aged to a desired degree as described above, and the ethoprophos concentration is adjusted without filtering the slurry. In this case, it is preferable to add a dispersant to the slurry and adjust the amount of water to achieve the desired concentration before aging the film as described above. Note that even if ethoprofos is at the same concentration, the capsule slurry concentration will differ depending on the ethoprofos content in the capsule, but the slurry concentration is usually 20 to 50.
Preferably, it is in the range of % by weight. Furthermore, after aging of the capsule membrane, the ethoprophos capsules can be separated from the slurry to form a powder, which can be used in the form of preparations such as powders and wettable powders. When formulating such a formulation, it is best to use commonly used auxiliaries such as granulation aids, fillers, surfactants, etc. In particular, in the case of granules, ethoprofos capsules contain 5 to 30% by weight. It is preferable to granulate it so that it is contained. EXAMPLES The present invention and its effects will be explained in more detail with reference to Examples below. Example 1 This example shows a method for preparing microcapsules according to the present invention. Preparation of resin prepolymer as membrane material: 35% by weight adjusted to pH 9.0 with 2% NaOH aqueous solution
Add and mix 63 g (0.5 mol) of melamine to 171.5 g (2.0 mol) of formaldehyde aqueous solution, react at 70°C, and immediately add 234.5 g of water once the melamine is dissolved.
was added and stirred for 3 minutes to prepare an aqueous MF prepolymer solution. Separately, prepare 386 g (4.5 wt.%) of a 35 wt.
Add and mix 150g (2.5mol) of urea to 70
A UF prepolymer aqueous solution was prepared by reacting at ℃ for 1 hour. Microencapsulation: Euramin, a water-soluble cationic urea resin
P1500 (manufactured by Mitsui Toatsu Chemical Co., Ltd.) 120g, water 900g, 10
% triethanolamine aqueous solution and 450 g of the MF prepolymer aqueous solution previously prepared as above.
450 g of UF prepolymer aqueous solution was mixed, the pH of this mixture was adjusted to 4.2 with 25% citric acid aqueous solution, and 13.5 g of 10% Neopelex (sodium alkylbenzene sulfonate [manufactured by Kao Corporation] aqueous solution) was added. , Ethoprophos drug substance (96% purity) 630
Add 900g of a mixed solution of 270g of soybean oil and 270g of soybean oil, emulsify with a homogenizer so that the droplet diameter is 1.5 to 4μ, and then raise the temperature to 50℃ with gentle stirring.
After 10 minutes and 3 hours of stirring, add one portion of 50°C warm water, and after 24 hours, 25%
The pH was adjusted to 2.8 using an aqueous citric acid solution, and microencapsulation was completed 48 hours later. Aging of microcapsule membrane: Adjust the capsule slurry obtained by completing microencapsulation to PH5.0 with 28% ammonia water, remove part of the water so that the drug component is 15% by weight, and make a slurry amount of 4000g. Adjusted to. Add 40 g of the dispersant Demol N (alkylaryl sulfonic acid-formalin condensate [manufactured by Kao Corporation]) to this slurry,
The mixture was slowly stirred while maintaining the temperature at 50°C, and the curing process was completed after 72 hours. This slurry was filtered to obtain capsules in powder form. The average particle size of the capsules was 2.48μ, and the ethoprophos content was 46.87% by weight. Example 2 MF as the resin prepolymer in Example 1
Encapsulation of ethoprofos was carried out as described in Example 1 except that 1350 g of prepolymer was used alone. The average particle size of the capsules obtained is
2.84μ, and the ethoprophos content was 46.14% by weight. Example 3 In Example 1, UF was used as the resin prepolymer.
Encapsulation of ethoprofos was carried out as described in Example 1 except that 675 g of prepolymer was used alone. The average particle size of the capsules obtained is
2.13μ, and the ethoprophos content was 46.19% by weight. Example 4 In Example 1, a mixed solution of 630 g of ethoprophos and 270 g of olive oil was used for microencapsulation.
Ethoprofos was microencapsulated in the same manner as described in Example 1, except that 900 g was used. The average particle size of the obtained capsules was 2.94μ, and the ethoprophos content was 46.70% by weight. Example 5 In Example 1, a mixed solution of 630 g of ethoprophos and 270 g of cottonseed oil was used for microencapsulation.
Microencapsulation of ethoprofos was carried out in the same manner as described in Example 1, except that g was used. The average particle size of the obtained capsules was 2.42μ, and the ethoprophos content was 46.91%. Examples 6 to 8 shown below are examples of formulation of microcapsules. Example 6 The slurry in which the capsules had been hardened in Example 1 was directly used as a slurry agent without separating the capsules. The capsule concentration in the slurry is
The ethoprophos concentration was 15.25% by weight. Example 5 Solid content (ethoprophos content
26% by weight, water content 40% by weight) 120g, 8%
The resulting suspension was mixed with 250 g of an aqueous polyvinyl alcohol solution, and the resulting suspension was spray-dried onto the surface of 900 g of fine pumice particles with an average diameter of 0.7 mm to obtain 690 g of a preparation as granules. The ethoprophos content in the granules was 3.12%. Example 6 700g of the slurry after the capsule hardening process in Example 1 was dried into powder using a spray dryer.
A hydrated powder containing about 3% of the dispersant Demol N was prepared.
The ethoprophos content in the hydrated powder was 44.50%. Example 9 A slurry agent was obtained in the same manner as described in Example 6 using the slurry after the capsule hardening treatment in Example 4. The capsule concentration in the slurry was 32.62% by weight, and the ethoprophos concentration was 15.17%. Example 10 A slurry agent was obtained in the same manner as described in Example 6 using the slurry after the capsule hardening treatment in Example 2. The capsule concentration in the slurry was 32.52% by weight.
Ethoprophos concentration was 15.27% by weight. Comparative Example 1 Example 1 except that 900 g of ethoprophos drug substance was added to the microencapsulation in Example 1.
Ethoprophos was microencapsulated in the same manner as described in 1. However, a large amount of ethoprophos that was not incorporated into the microcapsules floated up as free oil, making microencapsulation impossible and the reaction was stopped. Comparative Example 2 Ethoprophos was microencapsulated in the same manner as described in Example 1, except that 900 g of a mixed solution of 630 g of ethoprophos raw material and 270 g of diisopropylnaphthalene with a water solubility of 1 ppm or less was used for microencapsulation. I went there. The average particle size of the obtained capsules was 2.52μ, and the ethoprophos content was 46.76% by weight. Comparative Example 3 Ethoprophos was microencapsulated in the same manner as described in Example 1, except that 900 g of a mixed solution of 630 g of ethoprophos raw material and 270 g of diethyl phthalate with a water solubility of 900 ppm was used for microencapsulation. I went there. The average particle size of the obtained capsules was 3.42μ, and the ethoprophos content was 47.01% by weight. Comparative Example 4 The slurry after the capsule hardening treatment in Comparative Example 2 was made into an ethoprofos capsule slurry in the same manner as described in Example 6. The capsule concentration in the obtained slurry was 32.11% by weight, and the ethoprophos concentration was 14.93% by weight. Comparative Example 5 The slurry in which the capsules had been hardened in Comparative Example 3 was made into an ethoprofos capsule slurry in the same manner as described in Example 6. The capsule concentration in the obtained slurry was 32.14% by weight, and the ethoprophos concentration was 15.03% by weight. Comparative Example 6 35g of ethoprophos raw material (purity 96%) with average particle size
After impregnating the surface of 900 g of 0.7 mm pumice fine granules by spraying, 250 g of a polyvinyl alcohol aqueous solution was sprayed onto the surface to obtain 925 g of granules. The ethoprophos content in the granules was 3.3%. Next, the results of testing the effects of the capsules of the present invention are shown as Test Examples 1 to 5. Test Example 1 Regarding the water dissolution rate of ethoprofos in capsules, an amount equivalent to 30 mg of ethoprofos from each of the ethoprofos capsules obtained in Examples 1 to 5 and Comparative Examples 2 to 3 was separately placed in one round-bottomed flask. Then, 700 ml of water was added to this, and the water was shaken at a temperature of 20°C using an up-and-down shaker. 50 ml of the water portion was collected at predetermined time intervals, and the ethoprophos concentration therein was measured to determine the water elution rate ( %) was calculated. The results are shown in Table 1.

[Table] Test Example 2 The water dissolution rate (%) of ethoprofos was measured in the same manner as Test Example 1 from capsules formulated according to the procedures described in Examples 6 to 10 and Comparative Examples 4 to 6. . The results are shown in Table 2.

【table】

[Table] Test Example 3 For each of the preparations obtained in Examples 6 to 8 and Comparative Example 6, put an amount equivalent to 8 mg of ethoprophos into a 50 ml test bottle, add 40 ml of water to each, and shake 5 times. After mixing, the mixture was left in an incubator at 40°C, taken out at regular intervals, shaken 5 times, filtered, and the ethoprophos concentration in the filtrate was measured to calculate the water elution rate. The results are shown in Table 3. In addition, this example shows the water elution rate of ethoprofos from capsules by the standing method instead of the shaking method.

[Table] Test Example 4 This example shows the microcapsules obtained in Example 1, capsules obtained by formulating from Examples 6 to 10 and Comparative Examples 4 to 5, and Comparative Example 6 (granules using bulk material). agent)
The following shows the results of the acute dermal toxicity test for the following. Test method: ICR male mice (7 weeks old) were used as test animals, and each group of 5 mice was tested in accordance with the Ministry of Agriculture, Forestry and Fisheries' Pesticide Toxicity Test Guidelines (No. 4200). Then, the _LD50 value was determined. The results are shown in Table 4.

[Table] Test Example 5 In this example, nematode control was conducted using ethoprophos capsules and Comparative Example (granules using active substance) obtained by formulating from Examples 6 to 10 and Comparative Examples 4 to 5. This shows the results of tests and growth tests. Test method: Each of the above test agents was mixed into the contaminated soil of sweet potato knotweed in an amount of 250g/10a, 500g/10a, and 1000g/10a in terms of ethoprophos, the active ingredient. Soil was loaded into three 1/10000a plastic pots at 200 g per pot. Next, 7 days after the above mixing treatment, 15 tomato seeds were sown in each pot, and 20 g of soil was collected from each pot at the time of sowing and 36 days after seedling raising.
The centipedes were separated using the Bellman method and the number of survivors was determined. The contaminated soil used here was a small amount of soil contaminated with Nekokub nematodes added to the normal soil for seedling raising tests, and sweet potatoes were grown and Nekkub nematodes were multiplied. The soil itself was used. In addition, 36 days after the chemical treatment, the root knot index of all the seedlings in each pot was determined according to the following calculation criteria, and the plant height and fresh weight of stems and leaves were measured for 10 seedlings in each pot. Root Cobb index = Σ (class value × number of plants in the same class)
/ Total number of surveyed plants x 4 x 100 Class value 0... No galls observed 1... Few galls 2... Normal galls 3... Many galls 4... Extremely galls Table 5 summarizes the results of the above survey and measurements.

[Table] As shown in Table 5, all of the capsules of the present invention are equivalent to or better than the comparative formulations (non-capsule granules) in terms of centipede control effect and crop growth, especially the slurry formulations. is 250
A remarkable effect was achieved at an application amount of g/10a, and no chemical damage was observed. Effects of the Invention As described above, the ethoprofos capsules according to the present invention exhibit a nematicidal effect similar to or greater than that of ethoprofos raw material made into granules without encapsulation, and, on the other hand, As for the toxicity in question, the dermal toxicity in mice of ethoprophos drug substance is LD ₅₀ of 45 mg/Kg, whereas the microcapsule itself in the present invention has an ethoprophos drug equivalent of 2600 mg/Kg, and the slurry form of capsules has a LD 50 of 45 mg/Kg. 3200mg/Kg, which significantly reduces toxicity. In particular, the slurry-form capsules of the present invention do not require separating the capsules from the slurry obtained by microcapsulating ethoprofos, and can be applied directly as a slurry formulation after diluting it 5 to 50 times. There are practical advantages. In addition, a granulating agent can be added to the slurry to form granules, or capsules can be separated from the slurry to form a powder and then formulated into a desired form. Furthermore, in the capsules of the present invention, the strong odor peculiar to ethoprofos is hardly felt, so that in addition to the above-mentioned reduction in transdermal toxicity, there are no problems in handling.

Claims (1)

[Claims] 1. A mixture of ethoprophos and vegetable oil is used as a core agent,
It consists of microcapsules whose film material is a polycondensate of urea formaldehyde prepolymer and/or melamine formaldehyde prepolymer.
A capsule of ethoprofos, characterized in that the dissolution rate of ethoprofos after shaking in 700 ml for 1 hour is 10% or less. 2. The ethoprofos capsule according to claim 1, wherein the mixing ratio of ethoprophos and vegetable oil is 7:3 to 2:8 by weight. 3. The ethoprofos capsule according to claim 1 or 2, wherein the weight ratio of the core material to the membrane material is 9:1 to 1:1. 4. The ethoprophos capsule according to any one of claims 1 to 3, wherein the membrane material is a polycondensate of 1 part by weight of melamine formaldehyde prepolymer and 1 to 4 parts by weight of urea formaldehyde prepolymer. 5 The microcapsule contains 20 to 50% by weight of the microcapsule and 0.5 to 2% by weight of the dispersant, and has a pH of 3.5 to 7.
The capsule of ethoprofos according to claim 1, which is in the form of an aqueous slurry adjusted to 6. The ethoprofos capsule according to claim 1, wherein the microcapsule is in powder form containing 80 to 97% by weight of the microcapsule and 20 to 3% by weight of a surfactant. 7. The ethoprofos capsule according to claim 1, wherein the microcapsule is in a granular form containing 5 to 30% by weight.