Classifications

• • A—HUMAN NECESSITIES
  • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
  • A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
  • A01N25/00—Biocides, pest repellants or attractants, or plant growth regulators, characterised by their forms, or by their non-active ingredients or by their methods of application, e.g. seed treatment or sequential application; Substances for reducing the noxious effect of the active ingredients to organisms other than pests
  • A01N25/12—Powders or granules

Definitions

• Insecticides such as the phosphorodithioic acid derivatives have a pronounced tendency to decompose, with the formation of thiol groups.
• the formulations acquire an offensive smell and suffer a considerable loss of activity due to substantial reductions in the content of the active constituent.
• Various methods have previously been proposed for deodorising insecticides of this type, but these methods have usually relied on the removal of the offensive thiol compounds formed on decomposition, and have done nothing to maintain the activity of insecticidal compositions by inhibiting the decomposition itself.
• the present invention provides an insecticidal powder in which the content of the active ingredient remains substantially constant over a long period, and is characterised by a particulate carrier composed of substantially iron-free kieselguhr, or diatomaceous earth, impregnated with a phosphorodithioate insecticide in the presence of a solvent oil of low volatility.
• an inert wetting and/or dispersing or suspending agent may be incorporated in the product.
• the kieselguhr should be of high absorptivity. It has been observed that kieselguhrs containing considerable amounts of iron and of low absorptivity do not provide carriers on which the insecticide is stable. It is found that the kieselguhr should preferably be of white or nearly White grade. A brick red color indicates a high iron content, high density and low absorptivity and such material is unsuitable for the purposes of the invention. A buff color indicates a lower iron content, a lower density and a higher absorptivity, and a material more suitable for use according to the invention. It is also preferable for the kieselguhr to have a low moisture content, and to be uncalcined.
• the iron content of an initially iron-rich kieselguhr can be reduced by washing it with acid and/ or a chelating agent such as oxine or S-hydroxyguinoline, the resulting material is for the purposes of the invention 3,390,048 Patented June 25, 1968 markedly inferior to a kieselguhr which in its original condition has a very low iron content.
• kieselguhrs which are substantially iron-free, and have the other preferred properties indicated above, nevertheless differ somewhat in the extent to which they stabilise these insecticides. Accordingly, when a stabilised powder is to be prepared, it is desirable that several grades of suitable kieselguhr should be tested in order that the most effective available grade should be employed.
• insecticide is not stable, even on the preferred carrier, in the absence of the solvent oil of low volatility, which exerts a protective action.
• Aromatic or predominantly aromatic oils are preferred, for example those sold under the trademarks Shellsol E and Shellsol R.
• long-chain alcohols can be employed but are dear and less stable, while chlorinated hydrocarbons are often too volatile.
• Kieselguhr is a relatively expensive material, and it is economically undesirable that it should form the bulk of a dilute powder. This is particularly important in the case of dusting powders. Accordingly, a preferred modification of the invention is a powder which comprises an insecticidal powder as hereinbefore defined, in admixture with an inert, solid particulate extender.
• a number of solids available at low cost are not suitable for use as extenders in that they increase the rate of decomposition of the insecticide, not being completely inert.
• the preferred extender is pumice powder, which is relatively cheap and does not affect the stability of the insecticide on the carrier. It should be noted that the insecticide must be applied to the carrier first, and the extender added later. The desired stabilisation will not be achieved if powdered pumice is added to the kieselguhr before the insecticide is applied.
• the preferred method for the production of wettable and dispersable powders which should always be followed if the maximum stability is to be achieved, requires that the wetting and/or suspending agents should only be added after the application of the insecticide to the carrier and the drying of the resulting powder. Heavy milling of these powders is undesirable, although light milling is not harmful.
• the shelf life of powders prepared in this way is not quite as good as that of the dusting or other powder formulated without wetting or suspending agents, but is adequate for normal purposes.
• Example 1 Deodorised Malathion, 75 parts by volume, was mixed with 25 parts Shellsol E (an 84% aromatic solvent of low volatility) and applied to a powdered, substantially iron-free California kieselguhr of low moisture content and high absorptivity, to give a powder of nominal 25% content of Malathion.
• Shellsol E an 84% aromatic solvent of low volatility
• the resulting dry powder was subjected to accelerated storage tests by being maintained for long periods at elevated temperatures in sealed containers. It was found that at temperatures of up to C. the odor did not return in a period of 6 /2. months. This observation was confirmed by analysis, which showed that the content of 3 Malathion, originally 25.1%, was still 25.0i0.1% after the same time at 55 C.
• Example 2 The 25% concentrate prepared as in Example 1 was mixed with dry Italian pumice dust to yield powders of various Malathion contents below 25%. All the low dilution powders so prepared had excellent stability when stored at elevated temperatures. The content of a powder initially 3.7% remain unchanged after 8 months hot storage.
• Example 3 Deodorised Malathion (Kypfos 93D), 75 parts, is added to 25 parts of Shellsol E and thoroughly mixed. The solution is then sprayed onto a powdered, substantially iron-free kieselguhr of high absorptivity (Johns Manville Celite), while being mixed in a trough mixer,
• the quantity of insecticide applied being suflicient to achieve a final active content of 25% Malathion.
• the result is a dry powder with a faintly perafiinic odor, which stores well, remaining substantially free from offensive odors for at least 4 /2 months in a sealed container at 55 C.
• a powdered wetting agent for example Arylan A840
• a powdered suspending agent for example Dispersol AT
• the invention provides powders which are more stable than conventional formulations of the insecticides concerned. Moreover, if an insecticide is employed which has previously been deodorised, for example an oxidative process, and preferably by the process of US. 3,275,499, a powder is obtained which will remain inoifensive in odor for long periods. Dusting powders according to the invention are eminently suitable for the protection of stored grain without contamination thereof.
• a stabilized insectical powder comprising: a phosphorodithioate insecticide; a solvent oil of low volatility; and a particulate carrier composed of substantially ironfree kieselguhr; said insecticide being in admixture with said oil and supported on and stabilized by said carrier.
• a dilute insecticidal powder comprising: a phosphorodithioate insecticide; an aromatic solvent oil of low volatility; a particulate carrier composed of a substantially iron-free kieselguhr; and an inert solid particulate extender; said carrier being impregnated with said insecticide and said oil in admixture whereby said insecticide is stabilized against decomposition, and said impregnated kiselghur being admixed with said extender.
• An insecticidal dusting powder comprising 0,0-dimethyl S-(1,2-dicarbethoxyethyl) phosphorodithioate; an aromatic solvent oil of low volatility in admixture with said insecticide; and a particulate carrier consisting of pulverulent substantially iron-free kieselguhr impregnated with said insecticide and oil and stabilizing said insecticide.
• a wettable insecticidal powder comprising a phosphorodithioate insecticide; an aromatic solvent oil of low volatility in admixture with said insecticide; a particulate carrier composed of substantially iron-free kieselguhr impregnated with said insecticide and oil and stabilizing said insecticide; and a powder wetting agent or dispersing agent in admixture with said impregnated carrier.
• a method of preparing a stabilised insecticidal powder comprising the steps of: admixing a phosphor-odithioate insecticide with a solvent oil of low volatility; impregnating pulverulent substantially iron-free kieselguhr with said insecticide and oil mixture; and agitating said impregnated kieselguhr until said mixture is fully absorbed.

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• Life Sciences & Earth Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Health & Medical Sciences (AREA)
• Toxicology (AREA)
• Pest Control & Pesticides (AREA)
• Plant Pathology (AREA)
• Agronomy & Crop Science (AREA)
• Engineering & Computer Science (AREA)
• Dentistry (AREA)
• Wood Science & Technology (AREA)
• Zoology (AREA)
• Environmental Sciences (AREA)
• Agricultural Chemicals And Associated Chemicals (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=26250690

Family Applications (1)

Country Status (7)

Citations (8)

• 1964
  • 1964-10-12 GB GB41619/64A patent/GB1124296A/en not_active Expired
• 1965
  • 1965-10-06 BR BR173774/65A patent/BR6573774D0/pt unknown
  • 1965-10-11 DE DE19651542966 patent/DE1542966A1/de active Pending
  • 1965-10-11 CH CH1397565A patent/CH462534A/de unknown
  • 1965-10-11 US US494896A patent/US3390048A/en not_active Expired - Lifetime
  • 1965-10-12 DK DK522365AA patent/DK118111B/da unknown
  • 1965-10-12 NL NL6513179A patent/NL6513179A/xx unknown

Patent Citations (8)

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