NZ235955A - Insecticidal composition comprising diazinon and a pyrethroid. - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £35955 235955 / Dste(s): . =. ■ £ I' Complete Cpscificuticn f-i!ec!: .bitfit.

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NO srjao® Patents Form No. 5 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION After Provisional No. 235955 Dated 2 November 1990 "PESTICIDAL FORMULATIONS" WE, CIBA-GEIGY NEW ZEALAND LIMITED, a New Zealand company of 47-51 Pataki Road, Avondale, Auckland, New Zealand, hereby declare the invention, for which We pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: H.2. PATENT -4 NOV 1931 I RECEIV'T 235955 This invention relates to a pesticidal formulation.

Diazinon is a known insecticide which has been used for many years to control certain insect and other pests. In some situations, it is desirable to boost the insecticidal action of diazinon by using one of the more highly active synthetic pyrethroids which have been more recently introduced. When applying two or more pesticides, it is always more beneficial to have one formulation containing two or more of the active ingredients. One highly effective synthetic pyrethroid is permethrin. Both diazinon and permethrin are normally available as wettable powders, but when these are mixed together to form a formulation in a desired ratio, it is difficult to obtain a homogeneous mix of the two active substances and what tends to happen is a layering effect of the active ingredients. When using such a mixture, different results will be obtained depending upon the particular "layer" of active material utilised at any particular time.

This invention has as its object a formulation and method of producing such a formulation which enables a mixture of diazinon and one or more synthetic pyrethroids to be provided.

In accordance with this invention there is provided a premix of diazinon and a synthetic pyrethroid, wherein the pyrethroid is dissolved in the diazinon and wherein additional adjuvants if required are provided to maintain the formulation in a stable state.

Further in accordance with the invention there is provided a wettable powder containing diazinon and a synthetic pyrethroid comprising the premix as defined above together with a suitable inert powder base to provide a wettable powder formulation.

In accordance with the invention there is further provided a process for making a premix containing a synthetic pyrethroid and diazinon, comprising mixing diazinon and the pyrethroid together with the required adjuvants under conditions so that the pyrethroid is added as a liquid to the diazinon. 235SL>5 h % \-6Sfcri5W In accordance with the invention, the solvent properties or* ,, s / diazinon are used to dissolve the synthetic pyrethroid. In the'^f '" process of the invention, since pyrethroids are normally obtained as low melting point solids, to convert them into liquid-form,. warming of the pyrethroid is required. With permethrin for example, the melting point is just above normal ambient temperature and hence this material can be warmed to about 60°C to achieve a liquid state.

The synthetic pyrethroid can be any suitable pyrethroid which is compatible with diazinon. Permethrin is a good example and is one of the pyrethroids of the invention. Permethrin and other pyrethroids in general will have different wetting characteristics than diazinon. Therefore, to formulate them as a wettable powder in the most effective manner, a different surfactant is required. Surfactants are generally used in the formulations of the invention to provide wettability characteristics and hence enable the formation of a wettable powder and these are generally of the non-ionic type. Non-ionic surfactants are provided having various wettability characteristics generally defined by their hydrophilic/lipophilic balance (h/1 balance). A number of surfactants known under the trade mark Teric are provide with varous h/1 balances. A good surfactant for use with diazinon is Teric GN9 (a condensation product of nonyl phenol with 9 moles of ethylene oxide) while a good surfactant to use with permethrin is Teric GN 15 (a condensation product of nonyl phenol with 15 moles of ethylene oxide). In the process of the invention, the surfactant matched with diazinon is added to the diazinon and mixed therewith prior to addition of the permethrin which is premixed with the surfactant most suitable therefor.

Diazinon is moisture sensitive so that moisture needs to be excluded from the mixing process and the mixture. It is desirable when the premix or other formulation is to be stored to include a stabiliser which generally acts to scavenge any moisture which be present or be included during the mixing process. The technical grade of diazinon is normally supplied with such a stabilizer, but it is in accordance with the invention desirable to add another stabiliser to the premix. A suitable stabiliser is an epoxidised soya oil, such as that sold under the trade mark Reoplast 39. 235955 The process of the invention comprises taking diazinon which is a liquid at room temperature generally in the technical form which contains 91.4% of diazinon, mixing that with the surfactant such as Teric GN9 and the stabliliser Reoplast 39 in a mixer designed for mixing low to moderate viscosity liquids, such as a paddle mixer. The permethrin technical grade which usually consists of 94.5% of active ingredient is mixed with Teric GN15 or else these two can be separately added with each being warmed to around 60 aC to melt the permethrin. Mixing of the ingredients will then take place in about 2 hours. If solid permethrin was added, the dissolution thereof into the diazinon would take a much greater period of time.

The permethrin is incorporated into the premix at a low ratio to that of the diazinon. Diazinon is present in a major amount generally at least 10:1 or more desirably 20:1 in comparison to the amount of permethrin.

The premix can be stored or can be made into the wettable powder which can then be stored.

The wettable powder is formed by mixing the premix with an inert powder base. The inert powder base can comprise suitable inert inorganic substances such as calcium aluminium silicates which are produced with a high surface area adapted to adsorb liquids, such as Microcel E or Sipemat. Also present is preferably a dispersing agent such as a lignosulphonate, e.g. that sold under the trade mark Totanin QX or Polyton 0 and finally an inert filler of lower surface area adapted to modify the concentration of the technical ingredients or other ingredients. This will generally have a lower surface area than the adsorbent powder. A suitable material is clay marketed under the name "Clay GM40".

The following example illustrates one formulation of a premix and of a wettable powder and the method of forming the materials.