Pesticide formulation for controlled release

Abstract: A pesticide formulation comprises pesticide compounded with biodegradable thermoplastic aliphatic polyester resin. The pesticide formulation provides provides pestcidal effect for controlled release by releasing active ingredient gradually and by degrading aliphatic polyester resin which can be disappeared by microbial attack in soil.

Description: BACKGROUND OF THE INVENTION The present invention relates to a pesticide formulation for controlled release, and in particular to such a formulation which will provide the controlled release of pesticidal active ingredient in effective amounts over a prolonged period of time by including pesticide into a biodegradable aliphatic polyester resin. Usually, in order to get a pesticidal effect such as prevention of breeding and extermination of main pest of nursery, it is required to use pesticide in excessive amounts at several times. But, distributed a large amount of pesticide causes problems such as a bad influence on the other plant, a damage of pesticide user/plant demander's health, a serious environmental pollution, complexity of work to distribute the pesticide and need for the excessive labor. Conventionally, many efforts have been made to solve these problems. For example, Japanese Patent Laying-Open Publication No. H6-116103 describes the manufacture of pesticide that biodegradable aliphatic polyester resin is extruded in the form of plate, following by including pesticide dissolved in solvent into the resin plate. Japanese Patent Laying-Open Publication No. H5-85902 describes a pesticide formulation produced by copolymerizing polyester together with raw pesticide and acid, dissolving the resulting polyester in chloroform. absorbing the polyester solution onto zeolite in needle form and evaporizing chloroform by heating it. But, it is pointed that method for producing such prior pesticide is complicate, its production environment is hazardous due to solvent or acid as used and its production cost is expensive. JP-A-08-092,006 discloses a biodegradable resin molded product containing a biologically active substance. The resin is produced by adding a biologically active agent such as a herbicide, an anti-fungal agent, an insecticide or a repellent to a biodegradable resin. The biologically active resin is preferably an aliphatic polyester resin produced by synthesizing a polyester prepolymer having relatively high molecular weight from a glycol and an aliphatic dibasic acid as main components and subsequently converting the prepolymer into a high polymer with a coupling agent. The molded product is capable of being easily wasted and has a property for slowly releasing physiologically active substances. The aliphatic polyester has a number average molecular weight of 5,000 to 10,000 or more and a melting point of at least 60°C . The coupling agent is selected from diisocyanate, oxazoline, a diepoxy compound or a carboxylic anhydride. The biologically active substances have a melting point of 70 to 80°C. US-A-3,850,862 discloses a blend comprising biodegradable thermoplastic dialkanoyl polymers which are prepared by esterification technique using predetermined amounts of an aliphatic diol and an alkanedioic acid. The aliphatic glycol contains desirably from 2 to 8 carbon atoms and the alkanedioic acid contains desirably from 2 to 12 carbon atoms. Additional ingredients which can be included in the blend are plant nutrients, fertilizer, insecticides, pesticides, herbicides, and the like. EP-A-0 542 081 discloses a container for active ingredients made of thermoplastic elastomers based on copolyesters wherein the active ingredients can be insecticides. Example C discloses a pesticide formulation with a mixing ratio of 92.5 weight% copolyester and 7.5 weight% pesticide (propoxur; an insecticide for flowers). SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a pesticide formulation which can be prepared by a simple and cheap production method and decrease damage due to abusing pesticide by being released in effective amounts and keeping pesticidal effect over a prolonged period of time by only one treatment. As the result of our research to accomplish the above object. we have eventually found that if a pesticide formulation, which is produced in the form of needle or plate by compounding a pesticide and biodegradable aliphatic polyester resin which can be completely degraded in natural environment, is treated to the plant, a controlled pesticidal effect at only one treatment has been kept by being released gradually in effective amounts, with biodegradable aliphatic polyester resin being degraded gradually. Therefore, the present invention provide a controlled release pesticide formulation characterized by being compounded with pesticide and biodegradable polyester resin. DESCRIPTION OF THE INVENTION It have been known that a specific aliphatic polyester is degraded completely in natural environment. Up to now, many researches for aliphatic polyester have made all over the world (see, Journal of Macromol. SCI-Chem., A23(3), 1986, 393-409). Preferred biodegradable aliphatic polyester used in this formulation is thermoplastic aliphatic polyester of the following general formula III having a number average molecular weight of 10,000 to 50,000, intrinsic viscosity of higher than 0.5 (measured at 30 °C using ortho-chlorophenol) and melting point of 60 °C to 120 °C, which is prepared by polymerization with more than one selected from the group consisting of dicarboxylic acid having the following formula I, C 1 - C 3 alkyl ester and anhydride of said dicarboxylic acid as an acidic monomer, and more than one of diol having the following formula II as a alcoholic monomer. wherein, R 1 is substituted or non-substituted alkylene group with carbon number in the range of 0 to 30. OH-R 2 -OH wherein R 2 is substituted or non-substituted alkylene group with carbon number in the range of 2 to 20, wherein n is a repeating unit. If intrinsic viscosity of said biodegradable aliphatic polyester is lower than 0.5, degradation speed is so fast that the preaparation can not have a controlled release effect of pesticide and the processibility of formulation can be bad. If the molecular weight is higher than 50,000, the degradation speed of polyester is unsuitable. Also, if the melting point is lower than 60 °C, it is difficult to store and working ability is bad. Therefore, the thermoplastic aliphatic polyester has a number average molecular weight of 10,000 to 50,000, intrinsic viscosity of higher than 0.5, melting point of 60 °C to 120 °C. Preferred acidic monomer I forming the biodegradable aliphatic polyester III include more than one selected from the group consisting of dicarboxylic acid such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid; alkyl ester of said dicarboxylic acid such as methylester, ethylester, propylester; and anhydride of said dicarboxylic acid. More prefered acidic monomer is more than one selected from the group consisting of succinic acid, adipic acid, methyl succinate, methyl adipate, succnic acid anhydride and adipic acid anhydride. Prefered alcoholic monomer II forming the biodegradable aliphatic polyester III include more than one selected from the group consisting of ethylene glycol, propanediol, pentanediol, hexanediol, heptanediol and octanediol with substituted or non-substituted group. More prefered alcoholic monomer II is ethylene glycol, 1,4-butanediol or the mixture thereof. In case of substituted diol, it is prefered that the substituted group is alkyl group with lower carbon number and/or hydroxyl group. According to the present invention, biodegradable aliphatic polyester may be also used one copolymerized with said monomers and a third ingredient such as polyethylene glycol having molecular weight of 100 to 9,000, isocyanate, multi-functional alcohol and/or multi-functional carboxylic acid. In order to obtain the desired effects of the present pesticide formulation, pesticide to be compounded with biodegradable aliphatic polyester should be considered physico-chemical properties of active ingredient as follows. As for physico-chemical characteristics, active ingredient should be in the powder form and as for chemical characteristics, melting point should be in the range of 50 to 150 °C. The pesticidal main ingredient should not degraded in the range of 100 to 200 °C. Also, in order to protect of loss of active ingredient by volatilization and safety of operator at preparation of product, vapor pressure should be lower than 1 mPa at 20 °C and solubility in water should be more than 50 mg/ℓ at 20 °C. The most important property is that the pesticidal main ingredient should be had a systemic compound. In order to be used at formulation of pesticide and biodegradable aliphatic polyester, the active ingredient should possess the said properties. Prefered pesticides have the above-mentioned characteristic are acephate, carbofuran and imidacloprid, for example. The following explanation is the illustrative of method for compounding pesticide and biodegradable aliphatic polyester. Firstly, biodegradable aliphatic polyester resin is selected with considering characteristics such as its physical properties and degradability and pesticide having said characteristics is selected. After selecting, it can be obtained in the form of pellet and plate by compounding them using single or twin screw extruder. Even if temperature of cylinder suitable for compounding depends on the melting point of the pesticide, prefered cylinder temperature is in the ranges of 60 to 250°C. Usually, cylinder temperature is higher than 70 °C because of the viscous heating by the friction coefficient of the screw. Therefore, to use pesticide having melting point lower than 70 °C should be avoided. If not, there are troublesome problems such as degradation and carbonation. The mixing ratio of aliphatic polyester resin to pesticide falls within the range of 50-99.9 : 50-0.1 by weight %, preferably 90-99 : 10-1 by weight %. If the mixing weight ratio of aliphatic polyester resin is less than 50 weight %, it makes compounding difficult and results in poor working performance. If the mixing weight ratio of the pesticide is less than 0.1 weight %, it decreases the effect of pesticide. The invention will be more clearly understood with reference to the following examples. In the following examples, the molecular weight of aliphatic polyester is measured by gelchromatography using chloroform as solvent and the melting point is measured by differential scanning calorimeter(DSC) with heating rate of 10 °C per minute, and the intrinsic viscosity of aliphatic polyester is measured at 30 °C using the ortho-chlorophenol. Example 1 98.6 g of aliphatic polyester having melting point of 113 °C, intrinsic viscosity of 1.2 and a number average molecular weight of 25,000 and 1.4 g of imidacloprid were mixed. The resulting mixture was passed through the twin screw-extruder at its cylinder temperature ranges of 120 to 150 °C. Sample in the form of stripe with 0.3 mm in thickness and 1.5 cm in width was prepared. Formulation efficiency are mentioned below. Example 2 The same procedure as described in Example 1, except that the shape of sample is in the form of rod with 1 mm in diameter. Formulation efficiency are mentioned below. Example 3 The same procedure as described in Example 1 was conducted except that aliphatic polyester resin has melting point of 91 °C, intrinsic viscosity of 1.5 and number average molecular weight of 31,000. Formulation efficiency are mentioned below. Example 4 The same procedure as described in Example 3 was conducted except that the shape of sample is in the form of rod with 1 mm in diameter. Formulation efficiency are mentioned below. Formulation efficiency of sample 1.5g of samples prepared by Example 1 to 4 were separately taken into 125 ml cap-stoppered Erlenmeyer flasks and 100 ml of acetonitrile : H 2 O (1:1, v/v, pH 6.5) including 1000 ppm, dimethyl phthalate(DMP) as internal standard was added to each flask. After heated to 100°C for 5 minutes, the extract was cooled to the room temperature and the sample was reextracted with ultrasonicator for 5 minutes. The extract obtained from the above procedure was analyzed with HPLC and formulation efficiency was determined on the basis of added value of active ingredient at the stage of formulation. The results are shown in the Table 1. Subject Added value (%) Analyzed value (%) Formulation efficiency (%) Example 1 1.52 1.37 90.1 Example 2 1.52 1.42 93.4 Example 3 1.52 1.38 90.8 Example 4 1.52 1.34 88.2 Stability of active ingredient in sample with the lapse of time of storage Samples prepared by Example 1 to 4 were taken into aluminum package and was sealed. And then the packages were stored at 50 °C. Degradation rate of active ingredient in sample were analyzed by the same method as the formulation efficiency with given days. The results are shown in Table 2. Subject Degradation rates (%) of active ingredient after given days 30 days after 60 days after 90 days after Example 1 0 0 0 Example 2 0 0 0 Example 3 0 0 0 Example 4 0 0 0 Biodegradation of aliphatic polyester resin in soil A fixed amount of field soil was taken into plastic container with 3 cm in diameter and a slice of sample prepared in Example 1 to 4 was treated in each container. And then small amount of the soil was covered on the sample. Soil moisture in each plastic container was adjusted to 60% of maximum water-holding capacity and the each plastic containers were kept at 50 °C for 7 months. Biodegradation rates were measured by weight differences of samples with the lapse of time. The results are shown in the Table 3. subject Biodegradation rates(%) of aliphatic polyester resin in soil after given months 1 month 3 months 5 months 7 months Example 1 2.2 10.1 16.7 21.4 Example 2 4.3 10.1 12.7 24.9 Example 3 2.6 8.1 40.5 67.4 Example 4 9.3 68 100 - Biodegradability of aliphatic polyester resin by microorganisms Sample prepared by Example 2 was buried in soil. After 150 days, a fixed amount of sample and soil was gathered in the field. Microorganisms were isolated from the soil adhered to sample. Isolates obtained from the soil such as bacteria and fungi were inoculated on water agar media. After 3 days, two slices of sample prepared by Example 2 were treated in the medium. The medium were kept at 28 °C. The samples treated with bacteria and fungi were taken 60 days and 45 days, respectively. Biodegradability of aliphatic polyester resin by microorganisms was determined by weight differences of resin. The results are shown in the Table 4. Reference was not inoculated with isolates. Subject Bacteria Fungi no. of bacteria degradation rate, (%) no. of isolates degradation rate, (%) Example 2 7 2.5 - 3.0 8 3.0 - 5.0 31 3.1 - 3.5 10 5.1 - 10.0 2 3.6 - 4.0 6 10.1 - 25.0 Reference - 3.06 - 2.96 Release rate of active ingredient from the sample into water 100 ml of distilled water was taken into 125 ml cap-stoppered test tube and the samples prepared by Example 1 to 4 were immersed in the water. Released amounts of active ingredient from the sample into water were analyzed with HPLC with the lapse of time. The results are shown in the Table 5. Subject Cumulative release rates (%) of active ingredient from the sample into water with lapse of day 1 day 4 days 9 days 16 days 25 days Example 1 16.3 27.6 43.0 49.4 50.9 Example 2 39.9 43.7 59.2 65.5 70.4 Example 3 53.2 76.7 90.5 94.9 98.3 Example 4 78.4 90.2 98.4 100 - Control effect of the sample on aphid The samples were treated by buring them in the soil furrow of rose and chrysanthemum. Target insect pests were rose aphid. Macrosiphum ibarae , in rose, Rosa hybrida . and cotton aphid, Myzus persicae , in chrysanthemum, Dendranthema grandiflorum , under greenhouse. After treatment, the control effects of the sample on the target insect pest were investigated with the lapse of time. The control effects of the sample on aphid are shown in the Table 6, 7 and 8. Materials and treatment conditions were as follows: [Rose] Variety : Rosa hybrida var. Sonia Insect : rose aphid ( Macrosiphum ibarae ) Pesticide application For cut-flower Samples prepared by Example 2 and 4 were buried in the soil around the roots at planting under greenhouse. Samples prepared by Example 1 and 3 were treated in furrow at planting under greenhouse. For pot-flower Samples prepared by Example 2 and 4 were buried in the pot around the roots at planting under greenhouse. Samples prepared by Example 1 and 3 were treated in seed furrow at planting under greenhouse. Investigation time For cut-flower : The number of survived insect on the plant was counted 35, 64, 91, 183, and 205 days after treatment. For pot-flower : The number of survived insect on the plant was counted 35, 64, 154, and 190 days after treatment. [Chrysanthemum] Variety : Dendranthema grandiflorum Insect : cotton aphid ( Myzus persicae ) Pesticide application same method as above was adopted. Investigation time : the number of the survived insect on the plant was counted 56, 70, 163, and 170 days after treatment. Control effects of sample on rose aphid, Macrosiphum ibarae, in Rosa hybrida var. Sonia for cut-flower under greenhouse Subject Mean percentage mortality of aphid on given days after treatment 35 days 64 days 91 days 183 days 190 days 205 days Example 1 86.1 98.8 91.4 98.6 97.0 80.9 Example 2 76.1 100.0 99.1 95.4 90.5 77.5 Example 3 84.7 98.8 98.5 95.5 84.5 77.9 Example 4 96.0 100.0 99.1 97.6 96.7 90.1 Reference (Acephate WP) 76.4 99.4 94.1 96.2 94.4 98.1 Untreated 93.3 571.7 413.0 96.0 93.8 209.0 Control effects of sample on rose aphid , Macrosiphum ibarae, in Rosa hybrida var. Sonia for pot-flower under greenhouse Subject Mean percentage mortality of aphid on given days after treatment 35 days 63 days 154 days 190 days Example 1 100.0 99.1 97.6 100.0 Example 2 98.6 95.5 100.0 100.0 Example 3 87.9 87.4 98.8 95.1 Example 4 99.7 97.3 100.0 98.6 Reference (Acephate WP) 99.0 94.6 100.0 100.0 Untreated 144.5 88.5 41.0 71.0 Control effects of sample on cotton apid, Myzus persicae, in Dendranthema grandiflorum under greenhouse Subject Mean percentage mortality of aphid on given days after treatment 56 days 70 days 163 days 170 days Example 1 87.4 99.2 82.6 96.9 Example 2 100.0 99.2 89.5 92.4 Example 3 77.7 93.8 84.2 83.4 Example 4 100.0 99.6 93.2 94.2 Reference (Acephate WP) - 76.2 77.4 89.7 Untreated 10.3 85.3 19.0 22.0 From the above test results, it can be seen the following facts. The amounts of active ingredient recovered from the formulations were over 90%. Degradation rates of active ingredient in stripe and rod type formulation after 90 days storage at 50 °C were not degraded. Biodegradability of aliphatic polyester resin in the sample by bacteria isolated from soil couldn't be observed, but six kinds of fungi among isolates were able to degrade 10.1-25.0% of sample. Therefore, biodegradability of aliphatic polyester resin by fungi is shown more excellent than bacteria. On the other hand, biodegradation rates of aliphatic polyester resin in the rod type in soli on 5 months after treatment is shown 100%. Efficacy of Example 1 to 4 on rose aphid and cotton aphid was maintained over 90% even 180 days after treatment under greenhouse. As described above, this pesticide formulation provides pesticidal effect for controlled release by releasing active ingredient gradually and by degrading aliphatic polyester resin. Conventional pesticide formulations have been suffered from the various shortcomings: a possible contamination of pesticides by excess application, intoxication by spraying of diluted pesticide solution, and complexity of pesticide application job. In order to approach the environmentally sound agriculture and minimize harmful side effects of pesticides, development of this formulation is able to be reduction of pesticide input and application frequencies. Furthermore, aliphatic polyester resin in this formulation can be induced to a complete degradation in soil after all.

Claims: A pesticide formulation for controlled release of active ingredient which pesticide is compounded with biodegradable thermoplastic aliphatic polyester, wherein (a) said polyester is thermoplastic aliphatic polyester having a number average molecular weight of 10,000 to 50,000, intrinsic viscosity of higher than 0.5 (measured at 30°C using ortho-chlorophenol) and melting point of 60°C to 120°C; (b) said pesticide satisfies all of the following properties: the pesticidal main ingredient having a systemic compound, vapour pressure being lower than 1mPa at 20°C, solubility in water being more than 50 mg/l at 20°C, melting point being 50 to 150°C, the pesticidal main ingredient being not degraded within temperature range of 100 to 200°C, and the active ingredient is in the powder form; and (c) the mixing ratio of said polyester resin to said pesticide falls within the range of 50-99.9 : 50-0.1 by weight %. A pesticide formulation according to claim 1, wherein said polyester is thermoplastic aliphatic polyester of the following general formular III having a number average molecular weight of 10,000 to 50,000, intrinsic viscosity of higher than 0.5 (measured at 30 °C using ortho-chlorophenol) and melting point of 60 °C to 120 °C. wherein n is repeated unit, the thermoplastic aliphatic polyester is prepared by polymerization with more than one selected from the group consisting of dicarboxylic acid having the following formular I, C 1 - C 3 alkyl ester and anhydride of the dicarboxylic acid as an acidic monomer, wherein, R 1 is substituted or non-substituted alkylene group with carbon number in the range of 0 to 30. and more than one of diol having the following formular II as a alcoholic monomer. OH-R 2 -OH wherein R 2 is substituted or non-substituted alkylene group with carbon number in the range of 2 to 20. A pesticide formulation according to claim 2, wherein said polyester is copolymer of said monomers and a third ingredient selected from a group consist of polyethylene glycol having molecular weight of 100 to 9,000, isocyanate, multi-functional alcohol, multi-functional carboxylic acid and the mixture thereof. A pesticide formulation according to claim 1, wherein said pesticide is an insecticide. A pesticide formulation according to claim 4, wherein said pesticide is an insecticide for flower. A pesticide formulation according to claim 1, wherein said pesticide has melting point of 50 to 150 °C and is not degraded within temperature range of 100 to 200 °C. A pesticide formulation according to claim 4, wherein said pesticide has melting point of 50 to 150 °C and is not degraded within temperature range of 100 to 200 °C. A pesticide formulation according to claim 5, wherein said pesticide has melting point of 50 to 150 °C and is not degraded within temperature range of 100 to 200 °C. A pesticide formulation according to claim 1, wherein said pesticide is acephate, carbofuran, diazinon, imidacloprid or propoxur. A pesticide formulation according to claim 1, wherein the mixing ratio of the aliphatic polyester resin to pesticide is 50-99.9 : 50-0.1 by weight %. A process for the production of the pesticide formulation of claim 1, which comprises compounding with biodegradable thermoplastic polyester resin and pesticide in an extruder at its cylinder temperature range of 60 - 250°C.

Inventors: BAEK SUNG-HO, KIM HYO-YEUL, KIM YOUNG-KOO, KU BON-CHEOL, OH BYUNG-YOUL, OH KYEONG-SEOK, PARK SEUNG-SOON, YOON KUN-SANG, BAEK, SUNG-HO, KIM, HYO-YEUL, KIM, YOUNG-KOO, KU, BON-CHEOL, OH, BYUNG-YOUL, OH, KYEONG-SEOK, PARK, SEUNG-SOON, YOON, KUN-SANG
Applicants: REPUBLIC OF KOREA REPRESENTED, SK CHEMICALS, REPUBLIC OF KOREA REPRESENTED BY RURAL DEVELOPMENT ADMINISTRATION
Application year: 1997
Main classification: A01N25
IPC codes: A01N43, A01N25, C08L67, C08K5, C08L101