A dispersion on the basis of carbamate and a particle growth inhibiting agent and a method for treating beet culture

Abstract: The invention relates to a watery dispersion of a biologically active carbamate which contains a polyvinyl pyrrolidone or a copolymer thereof as particle growth inhibitor and to a herbicide concentrate comprising it. Preferably the polyvinyl pyrrolidone is a cross-linked homopolymer of N-vinyl-2 pyrrolidone, and the carbamate is propham, phenmedipham, or demedipham.

Description: The present invention relates to a watery dispersion of a biologically active carbamate and to a method for treating beet culture. Watery dispersions of carbamates that are biologically active, particularly in the form of herbicides, are used for controlling weeds in beet and bean cultivation. These watery dispersions cannot be stored in concentrated form for a longer period of time because during storage the dispersed particles grow and the crystals thereby formed acquire dimensions (> 40 µm) such that a solid precipitation results at the bottom which can no longer be absorbed into the dispersion by shaking. Moreover, during spreading of the diluted concentrates, the spreading devices, and spray devices in particular, become blocked. The biological activity also appears to diminish as a consequence of this crystal growth. WO 87/05778 discloses a herbicidal composition based on biscarbamate comprising further a vegetable oil, surface-active agents having emulsifying and dispersing properties and further water. Accordingly particle growth beyond 40 µm is avoided. DE-A-31 18 219 relates to the formation of a stable, watery suspension of carbendazim formed by reacting an aqueous solution of carbendazim with an alkali solution or with ammonia gas. Optionally a so called Schutzkolloide is added, examplified for instance polyvinyl pyrrolidone. The invention has for its object to provide a watery dispersion of a biologically active carbamate such that this dispersion can be stored in concentrated state for a longer period of time and up to temperatures of for instance 40°C (for example for 1-2 years at room temperature and 3-4 months at 40-50°C) without particles of a diameter greater than approximately 40 µm developing in this concentrate. The result of lengthy result is that such unwanted particle growth can be avoided with a watery dispersion of a biologically active carbamate selected from the group consisting of propham, phenmedipham and desmedipham, comprising polyvinyl, pyrrolidone or a copolymer thereof as particle growth inhibitor, obtained by separately adding the carbamate and the polyvinyl pyrrolidone to a volume of water and forming the watery dispersion, such that after three months at 40°C substantially no carbamate crystals occur in the watery dispersion having a particle size greater than 40 ppm. As polyvinyl pyrrolidone copolymers can be used copolymers with vinyl acetate, in ratios (PVP/VA) of 70:30 to 30:70. The E-, I- and S-PVP/VA copolymers of GAF in Schiedam, the Netherlands can for example be used. This polyvinyl pyrrolidone is preferably a cross-linked homopolymer of N-vinyl-2-pyrrolidone and in preference has a mean molecular weight of 40,000 Dalton (obtainable as PVP/K-30 from GAF Schiedam in the Netherlands). The concentration of the particle growth inhibitor normally lies between 0.05 and 20% by weight. Below 0.05% by weight the particle growth inhibiting effect is usually too small, while the upper limit of 20% by weight is determined substantially by commercial factors. In general the concentration lies between 2 and 10% by weight and more preferably between 5 and 10% by weight. It will further be apparent that the concentration of the particle growth inhibitor is dependent on the quantity of dispersed carbamate and the dispersing agents that may be used. The carbamate concentration lies normally between 50 and 600 g/l, preferably between 100 and 500 g/l and more preferably between 100 and 400 g/l. This carbamate concentration in the watery dispersion concentrate is to some extent dependent on the quantity of carbamate that is applied per hectare after dilution. The polyvinyl pyrrolidone or copolymer thereof has been found to inhibit in particular the particle growth of propham (isopropyl carbanilate) and the N-bis-carbamates phenmedipham (methyl-3-(3-methyl carbaniloyloxy)carbanilate) and desmedipham (ethyl-3′-phenyl carbamoyloxy carbanilate). The watery dispersions according to the invention can contain other active substances in addition to the biologically active carbamate, for instance the herbicides chloroidazon, phenuron and chloropropham. In addition the dispersions contain the usual dispersing agents such as polyoxypropylene-block polymer with polyoxyethylene, sodium lignosulphonate, calcium dodecyl benzene sulphonate and the like, anti-foam agents such as dimethyl polysiloxane, anti-freeze agent such as ethylene glycol, propylene glycol, a thickening agent such as a homopolysaccharide. Spreading agents, adhering agents and antioxidants can also be added particularly to enable an adequate application of the diluted herbicide. The invention relates further to a method for treating beet culture with a herbicide wherein the herbicide concentrate according to the invention is diluted with water and applied in a herbicidally active quantity to said beet culture. Following hereinafter are a number of examples of carbamate dispersions in water, the crystal growth of which has been examined after three months and after a year using a light microscope. Only those concentrated watery dispersions are satisfactory in which after one year substantially no crystals occur with a particle size greater than 40 µm. It is noted that the examples are only given by way of example and are not intended to restrict the invention thereto. Example I (in accordance with the invention) 400 g propham 30 g polyoxypropylene-block polymer with polyoxyethylene (tensiofix * 35600) 15 g sodium lignosulphonate (LX special *) 5 g dimethyl polysiloxane 80 g ethylene glycol 1.2 g homopolysaccharide (rhodopol *) 50 g polyvinyl pyrrolidone ad. 1000 ml water It was possible to prepare the dispersion easily in accordance with a conventional formulation method and after three months Storage at 40°C the dispersion had no crystals of a crystal size greater than 40 µm. Nor after a year in storage at room temperature did the dispersion contain any crystals of a dimension greater than 40 µm. Example II (not in accordance with the invention) 600 g propham 20 g polyoxypropylene-block polymer with polyoxyethylene (tensiofix * 35600) 10 g sodium lignosulphonate (LX special *) 50 g propylene glycol 5 g dimethyl polysiloxane 1.2 g homopolysaccharide (rhodopol *) ad. 1000 ml water It proved possible to prepare this dispersion reasonably easily as according to a conventional formulation method. After three months storage at 40° C however this dispersion contained crystals of a dimension greater than 40 µm, while after storage at room temperature for a one year period the dispersion likewise contained crystals larger than 40 µm. This dispersion does not therefore satisfy the criteria according to the invention. Example III (not in accordance with the invention) 400 g propham 20 g polyoxypropylene-block polymer with polyoxyethylene (tensiofix * 35600) 80 g propylene glycol 2.5 g homopolysaccharide (rhodopol *) 5 g dimethyl polysiloxane ad. 1000 ml water This dispersion was easy to prepare. The dispersion formed by pouring into water displayed a poor stability however. After three months storage at 40° C the dispersion contained crystals having dimensions greater than 40 µm. After storage at room temperature for a period of one year the dispersion did not contain any crystals of a size larger than 40 µm, so that the criteria according to the invention were only partially satisfied. Example IV (not in accordance with the invention) 250 g propham 25 g calcium dodecyl benzene sulphonate dissolved in isobutanol (soprophor 70 *) 10 g polyvinyl alcohol (airvol 540 *) 100 g ethylene glycol 2 g dimethyl polysiloxane ad. 1000 ml water It proved possible to prepare this dispersion easily as according to a conventional formulation method, but the dispersion possessed insufficient stability. After only three days storage at room temperature or at 40° C the dispersion contained crystals having a dimension greater than 40 µm.

Claims: Claims for the following Contracting States : BE, CH, FR, GB, IT, LI, NL Watery dispersion of a biologically active carbamate selected from the group consisting of propham, phenmedipham and desmedipham, comprising polyvinyl, pyrrolidone or a copolymer thereof as particle growth inhibitor, obtained by separately adding the carbamate and the polyvinyl pyrrolidone to a volume of water and forming the watery dispersion, such that after three months at 40°C substantially no carbamate crystals occur in the watery dispersion having a particle size greater than 40 ppm. Dispersion as claimed in claim 1, characterized in that the particle growth inhibitor is a cross-linked homo-polymer of N-vinyl-2 pyrrolidone. Dispersion as claimed in claim 1 or 2, characterized in that the mean molecular weight of the polyvinyl pyrrolidone or copolymer is approximately 40,000 Dalton. Dispersion as claimed in claims 1-3, characterized in that the concentration of the particle growth inhibitor is 0.05-20% by weight, is preferably 2-10% by weight and more preferably 5-10% by weight. Dispersion as claimed in claims 1-4, characterized in that the carbamate concentration is 50-600 g/l, is preferably 100-500 g/l and more preferably 100-400 g/l. Herbicide concentrate comprising a watery dispersion as claimed in claims 1-5. Method for treating beet culture with a herbicide wherein a herbicide concentrate as claimed in claim 6 is diluted with water and applied in a herbicidally active quantity to said beet culture. Claims for the following Contracting State : ES Method for preparing a Watery dispersion of a biologically active carbamate selected from the group consisting of propham, phenmedipham and desmedipham, comprising polyvinyl, pyrrolidone or a copolymer thereof as particle growth inhibitor, wherein the carbamate and the polyvinyl pyrrolidone are added separately to a volume of water and forming the watery dispersion, such that after three months at 40°C substantially no carbamate crystals occur in the watery dispersion having a particle size greater than 40 ppm. Method as claimed in claim 1, characterized in that the particle growth inhibitor is a cross-linked homo-polymer of N-vinyl-2 pyrrolidone. Method as claimed in claim 1 or 2, characterized in that the mean molecular weight of the polyvinyl pyrrolidone or copolymer is approximately 40,000 Dalton. Method as claimed in claims 1-3, characterized in that the concentration of the particle growth inhibitor is 0.05-20% by weight, is preferably 2-10% by weight and more preferably 5-10% by weight. Method as claimed in claims 1-4, characterized in that the carbamate concentration is 50-600 g/l, is preferably 100-500 g/l and more preferably 100-400 g/l. Method for producing a Herbicide concentrate comprising the addition of a watery dispersion prepared in claims 1-5. Method for treating beet culture with a herbicide wherein a herbicide concentrate as claimed in claim 6 is diluted with water and applied in a herbicidally active quantity to said beet culture.

Inventors: MUREAU-LENS MARIA CATHARINA, VAN DER WESTEN NICOLAAS JOHANN, MUREAU-LENS, MARIA CATHARINA, VAN DER WESTEN, NICOLAAS JOHANNES MARIA
Applicants: CHEMISCHE FABRIEK BRABANT J W, CHEMISCHE FABRIEK BRABANT J.W. VOORBRAAK B.V.
Application year: 1989
Main classification: A01N47
IPC codes: A01N47