WO1990011129A1

WO1990011129A1 - Method for producing ecologic capsule of natural origin for products with controlled release of the active ingredient

Info

Publication number: WO1990011129A1
Application number: PCT/HU1990/000021
Authority: WO
Inventors: Albert Bagi; Jeno^' FARAGÓ; László MEISZEL; Magdolna Hasznos; József PERNYESZI; György MOGYORÓSY; Károly SÁGI; László Szabó; Dezso^' MIKLÓS; Katalin Simon; László BAGI; Judit Gesztelyi Nagy
Original assignee: Nehézvegyipari Kutató Intézet; Magyar Viszkózagyár
Priority date: 1989-03-24
Filing date: 1990-03-23
Publication date: 1990-10-04
Also published as: HUT53258A; GR1000998B; NL9020411A; GR900100217A; HU208220B; YU57490A; PL284427A1; ES2038940A6

Abstract

The invention relates to a process for producing capsule or microcapsule containing cellulose and/or starch. The process according to the invention can be characterized in that 0-50 % by weight of polymers are added to the capsule material of natural origin at a temperature of 10 to 50°C, the suspension is vigorously stirred, thereafter 0 to 50 % by weight of urea-formaldehyde resin pre-condensate are admixed, the colloidal solution thus obtained is applied onto the acid mixture - preferably with 10 % by weight of sulphur acid - containing 0.1 to 5 % by weight of cross-linking catalyst, expediently ammonium sulfate, furtheron 0.01 to 5 % by weight of ethoxylated amine surface-active material, the capsules thus obtained are washed and dried at 40 to 100°C, thereafter different active ingredients respectively the solutions thereof are contacted with the capsule, at last the blotted capsule is to be powdered.

Description

METHOD FOR PRODUCING ECOLOGIC CAPSULE OF NATURAL ORIGIN FOR PRODUCTS WITH CONTROLLED RELEASE OF THE ACTIVE

INGREDIENT

The invention relates to a method for producing ecologic capsules of natural origin decomposing in the environment which can preferably be used for selective plant protecting agents with timed release of the active ingredient.

In recent decades all over the world research activ¬ ity with considerable effort has been performed in order to produce such capsules for applying plant protecting compositions which assure maximal efficiency even in minimal doses, simultaneously prevent leakage of the plant protecting agent from the zone of utilization or unwanted premature decomposition thereof, e.g. upon UV-radiation.

In case, if rooting zone is considered as the zone of utilization, it is of utmost importance that the plant pro- tecting agent should meet here expediently all the harmful organisms, such as fungi and other pathogenic bacteria, weeds or other parasites living in the soil.

The application of the plant protecting agents does not always coincide with the appearance of pathogenic and parasite beings. A further problem lies in the matter of shelf-life of the active ingredients, guaranteed time.

Application of natural polymers or the derivatives thereof orming a complex,with the given plant protecting agent belong to successful solutions. The use of e.g. starch or starch derivatives for encapsulating EPTC has also been known, and it has been tried to bind on urea- -formaldehyde resin, resulting in the accessory advantage that the carrier serves also as artificial fertilizer. A further method has been elaborated, by which - starting from emulsion - a solid crust was formed on the surface of drops of colloidal size by means of condensation on phase boundary. This crust assures that the active ingredient gets onto the aimed surface when decomposing or as a semi-permeable film.

Experts are also dealing with the combination of various natural polymers, such as starch, latex and artifi¬ cial resins. So e.g. shelf-life could successfully be improved, release of the active ingredient could be controlled, when assurance of proper particle size is problematic.

In the Japanese Patent Specifications 0072-806, 2033- -103, 2003-795, 0072-804, 1129-138, 8021-602, 0104-095 various cyclodextrin derivatives are used for the formula¬ tion of the active ingredients of plant -protecting agents. According to Japanese Patent Specification 8021-605 some porous carriers (e.g. a sponge, paper, a cloth etc.) are impregnated with the volatile plant protecting composi- tions.

According to the WP Patent Specification 8300-796 for encapsulating of plant protecting agents hollow rods on cellulose basis are used, optionally the outer surface is treated with paraffin. As it becomes obvious from the WIP0 Patent Specifica¬ tion 8303-61 a double capsule system is formed, in which the capsule of larger dimension contains a plurality of micro- capsules. For the shaping of the capsule cellulose acetate is used. According to Japanese Patent Specification No. 8121- -212 a gel-type product, i.e. a plant protecting agent is produced from polyacrylate and epoxy-resin for the controlled release of the active ingredient.

In accordance with EP 205 978 carriers containing polyviπyl alcohol and starch are used as capsules for different pesticides (parathion, trifluraline), feromones and regulators.

In accordance with the EP 121 712 biocides and medicines can be encapsulated by using organophil cellulose ethers.

DE-PS 1567 066 suggests to encapsulate plant growth regulators and herbicides by using carriers made of thermoplastic synthetic resin and resin soluble in a solvent. In accordance with the Japanese Patent Specification No. 9142 264 polysulfone, polycarbonate, cellulose and vinyl- acetate copolymers are applied as carriers for insecticides.

According to US-PS 4451 635 a carrier is described using water-soluble polymethane-quaternary ammonium salts and ion-exchanging resin.

J 5 7185-344 describes the production of a carrier with timely prolonged release of the active ingredient for attractants, disinfectants and plant protecting agents. As carrier poly-caprolactame is used, which can be combined with other synthetic materials, so e.g. nitro¬ cellulose, butylcaoutchouc etc. containing also filler, such as silicagel, calcium carbonate or aluminium oxide.

In accordance with the J5 8010- -503 polymer with a high water-absorbing capacity, e.g. inoculated copolymer of starch and polyacrylonitrile is applied for the preparation of agrochemicals, which can optionally be cross-linked.

According to EP - 214 396 A water- soluble polymers are used (e.g. poly-vinyl-alcohol, hydroxy- -ethyl-, hydroxypropyl-, methyl-cellulose).

Additionally condensation on the phase boundary is performed by using urea-resin.

EP 158-449 specifies a pro- cess for producing capsules for liquids inmsicible with water, in the course of which a porous crust is formed from the pre-polymerisate of urea-formaldehyde in an organic solvent, to encapsulate plant protecting agents and artificial fertilizers. According to J6 2201-156 a carrier is made with a slow release of the active ingredient by using binding materials and film-forming materials, as e.g. poly- vinyl-alcohol, polyvinyl-acetate, polyethylene and silicon resin. The US-PS 4 615 883 describes the production of a macrocapsule with a grain size of 0,4 - 5,0 mm, made of hydro- gel, which can be produced from sodium-alginate, gelatine and acacia gum.

According to Australian Patent A 8 767-199 a polymer is used, which tends to biological decomposition, in such a manner microorganisms are encapsulated, wherein the number of germs may amount to 10 -10 unit/g and the size of pearls can be controlled in the range between 0,5 and 40 mm. As material we may use gelatine, alginate, polyacryla ide and cellulose ether.

According to J5 9050-086 a granulate is prepared which is made of some hydrophobic materials, such as paraffin, resin and waxes. Paraffin- shell serves as a coating of grains of artificial fertilizers. J5 9048-402 offers a solution for preparing capsules for volatile insecticides. Evaporation of the active ingredient is achieved by a controllable calorific process. Calorification is started respectively controlled by diffusing oxygen. According to the solution, suggested in US-PS

4400391 alginate pearls are used for fixing insecticides. As gel-forming agents Cu, Zn, Al, Pb- salts can be applied.

According to research activities in the USA, the results of which were published in 1975 and 1976, starch - - xanthogeπate is well suitable for encapsulating plant protecting agents, as a matrix assuring slow release of the active ingredient. When using xanthogenate cross-linking may be performed by using epychlorohydrine or hydrogen peroxide. In this case water-soluble and insoluble plant protecting agents are encapsulated.

Plant protecting agents having been encapsulated with starch-xanthate are stable, they can be stored without problems. Upon water the active ingredient will be released.

EPTC (S-ethyl-dipropyl-thiocarbamate) and DBPC (1,2- -dibromo-3-chloropropane) give a stable capsule, from which volatility of the active ingredient is satisfactory, simultaneously it is well-resistent to sunlight.

Said researchers tested the applicability of latex in respect to the aforementioned active ingredients, while prior to xanthogenation small quantities of latex were added to the starch and cross-linked with sodium-nitrite. In course of some tests zinc sulfate was also used for cross-linking.

In laboratory experiments encapsulation of N- -(phosphorous methyl)-glyciπe and ammonium sulfate could be performed with the best results.

The effect of SBR 1502 (Styrene-butadiene latex) additive on encapsulating DBCP has been tested, at a determined mixing ratio an excellent shelf-time could be achieved. (Northern Regional Research Laboratory Agricultural Research Service, U.S. Department of Agriculture, Preoria, Illinois 61604) received March 12, 1976).

The aim of our invention:

The capsules as elaborated by us are ecologic, they consist of quickly decomposing and cheap material, the decomposition thereof in the soil takes places without harm¬ ful residues. Novelty of the method according to the invention lies in that the aggregate of microcapsule(s) is (are) stiffened in a solid matrix - optionally in colloidal distribution-, in respect to bond strength and releasing ability it (they) act(s), as if it (they) were individual particles.

We have also recognized another method that is the microcapsule is arranged in the centre of the solid matrix as a result of the process according to the invention and communication with the outer world is realized through the channels and cavities of the matrix.

Another construction is based on the recognition, in so far as the spherical matrix is woven through radially by the polymer threads and funnels of the active carrier, and the microsize appears in one dimension only, while the other size falls into the mezo-range.

The matrix according to the invention can be character¬ ized in that it is insoluble in water but is decomposed in the soil without harmful residues, the active filler does not dissolve in water either and it is ecologic.

A novelty of the method of the invention, lies in that the plant protecting agent intended to be encapsulated are prepared expediently for fixing in the carrier, in the capsule.

E.g. from the well-known active ingredient beno yl a stable suspension is prepared in carbon disulfide, or the heptane solution thereof is used.

Similarly to benomyl, the fuπgicidally active carbendazim with systemic effect, can be encapsulated. When formulating captan fungicide we started from ethyl alcoholic or acetone solutions.

In accordance with the process according to the invention, when producing microcapsule or capsule we started with natural polymers. E.G. aqueous solution of cellolose, aqueous starch suspension and/or aqueous solution of starch, latex solution, urea-formaldehyde resin of low condensation grade or starting components are used, when condensation is carried out in course of capsulation, in the presence of a coagulation catalyst. In the initial phase of capsule production optionally active carbon of well-defined grain size can be added to the polymer compound being present. In the course of the capsule- -forming process, taking place in the mixture of mineral and organic acids, surfactants are used, as e.g. BEROL products and as a cross-linking agent copper complexes are used. In certain cases as filler polyacryloπitrile in a pulverized form is used of a grain size of 1 to 10 micron.

The formulation of the capsules may be carried out by methods known per se, however different methods of drying can also be used.

The active ingredient (solution, suspension, emulsion) is absorbed by the finished capsule by methods known per se. In certain cases, by using the method according to the invention, condensation on the phase frontier may be carried out too.

The details of the invention are illustrated in the following examples.

Example 1

A carrier (capsule) for encapsulating selective herbicides can be prepared, as follows:

100 dm cellulose solution is weighed into a tank of 0.25 m equipped with an agitator (related to the cellulose a 5% solution), 50 dm starch suspension are admixed thereto (suspension may be prepared from corn starch in a 5% NaOH solution, while the suspension content of the solution amounts to 10%), 1 dm ammonia latex solution with an active ingredient content of 60% is added too. After vigorous stirring 10 dm urea-formaldehyde-resin precondensate are admixed, while the required catalyst is added to the acidic solution to precipitate.

As a cross-linking agent we add 1 dm of 1% copper - tetramiπe hydroxyde. The polymer mixture thus produced is put into the acidic bath in the shaping equipment known per se, which is preferably an aqueous mixture of 10% sulfuric acid and 5% acetic acid. The bath contains in a concentration of 1-2 g/dm³ a surfactant (BEROL SPINN 62).

The capsule thus obtained is washed and dried. We obtain a granular carrier of a diameter of 1-2 mm, there¬ after the prepared plant protecting agent is adsorbed thereon.

The application of the product into the soil is carried out by methods known per se in the period of sowing of cultivated plants. Upon the effect of soil moisture caused by rainwater the active ingredient will be released gradually.

Example 2

A cellulose solution - of a concentration of 4,8 - - 5,3% related to cellulose - is added into a 0,25 m enamelled tank equipped with an agitator. The cellulose solution contains 80% cellulose xanthogeπate, 15% carboxy-

-methyl cellulose, as well as 5% starch-xaπthogeπate.

6 kg finely-divided active charcoal are added to the

2 aforementioned solution with an active surface of 1000 m /g, furtheron finely-ground bran in an amount of 20 kg.

Finally 2 kg of urea-formaldehyde pre-condensate are added, thereafter the mixture is stirred for two hours with an

Anker-agitator. The solution thus obtained is allowed to pass through a sieve cloth of 100 Ai mesh.

The filtered polymer concentrate is converted into drops. Upon contacting them with acid fume drops are coagulated, the coagulated substance is washed and dried. We thus obtain a carrier of a grain-size of 0.5 - 1.0 mm, by the aid of which herbicide with a selective effect (e.g. EPTC) is encapsulated by a method known per se.

The used polymer components bind the plant protecting agents with different strength, thus the combined carrier guarantees timely programmed release of the active ingredient. The release of the active ingredient is completed with the complete decomposition of the carrier in the soil.

Example 3 Using the equipment as described in example 2, we admix 10 kg of pulverized acrylonitrile - styrene sulfonate copolymer to 200 dm cellulose solution, (grain size in the range between 1 and 10 micron). Due to the ion-exchanging groups of said additive the binding of the plant protecting agent and the controlled release of the active ingredient can be achieved.

Claims

C l a i m s

1. A process for producing capsule or microcapsule containing cellulose and/or starch, characterized in that 0-50 % by weight of polymers are added to the capsule material of natural origin at a temperature of 10 to 50 C , the suspension is vigorously stirred, thereafter 0 to 50 % by weight of urea-formaldehyde resin pre-condensate are admixed, the colloidal solution thus obtained is applied onto the acid solution mixture - preferably 10 % by weight of sulphuric acid - containing 0,1 to 5 % by weight of cross-linking catalyst, preferably ammonium sulfate, furtheron 0,01 to 5 % by weight of ethoxylated amine surfactant, the capsules thus obtained are washed and dried at 40 to 100 C°, thereafter various active ingredients respectively the solutions thereof are contacted with the capsule, and the absorbed capsule is powdered.

2. A process as claimed in claim 1, characterized in that in order to produce capsules as gel-forming additives ammonium sulfate, ammonium carbonate, zinc tetramiπe hydroxyde or copper tetra ine hydroxyde are added.

3. A process as claimed in claim 1, characterized in that in addition to the micro- capsule structure fixed in the matrix, by using the so-called powdering method, by the additional application of a mixture made of the fine grist of one or more components onto the grain surface a loosely bond crust is produced resulting in a double shell-structure, while adhesion is achieved by a natural polymer solution or the powder thereof, preferably pulverized potassium humate or solution, or pulverized carboxy-methyl cellulose or solution.

4. A process as claimed in claim 1 and 3, characterized in that when preparing the active ingredient, particularly a plant protecting agent to be encapsulated, a stable suspension or emulsion is prepared of a solvent being efficient and unharmful from the point of view of ecology, as well as of additives (e.g. carbon disulfide) promoting adsorption in the capsule and improving chemical bond, while in the soil proper desorption is assured upon the effect of moisture.