Insecticide compositions made from polymers

Details Insecticide compositions made from polymers Insecticide compositions made from polymers

1998-08-07

2001-10-02

Kulkosky, Peter F. (Department: 1615)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Biocides; animal or insect repellents or attractants

C424S411000

Reexamination Certificate

active

06296865

ABSTRACT:

The invention relates to insecticidal compositions based on polymers, processes for their preparation and their use for controlling insects which occur in interior rooms. These new compositions are characterized in that they contain at least one type of insecticide which is incorporated into a suitable polymer. The compositions are further characterized in that they are able to release the insecticide in a controlled manner at room temperature or optionally at a certain temperature, without the shape and macroscopic appearance being changed.
It is an object of the present invention to formulate insecticidal active compounds in such a way that they are not only stable on storage but can also be vaporized in a controlled manner at room temperature or optionally by warming. In this way, a very high activity and duration of action are achieved with low energy consumption. The use of these new insecticidal compositions should be carried out without using a customary container, by standing up the polymeric shaped body containing the active compound without warming, or heating it directly in a suitable vaporization apparatus.
In the case of killing, for example, mosquitoes using an electrical heating apparatus, known as a platelet vaporizer, it is known that suitable materials such as cellulose or cotton board, asbestos or ceramic are impregnated with pyrethroid insecticides to give insecticide plates. The insecticides are volatilized by the action of a heating apparatus which generates a temperature of 120-190° C. A similar principle forms the basis of a gel vaporizer, where insecticides are incorporated into a gel formulation.
Another method of controlling, for example, mosquitoes is the use of liquid vaporizers in which an insecticidal liquid formulation is continuously vaporize by warming via a wick system.
Considerable disadvantages of these platelet, gel or liquid vaporizers result from the fact that vaporization accelerators and other formulation auxiliaries have to be incorporated into the insecticidal composition to prevent thermal decomposition of the active compounds, and also the necessity of using organic solvents in the manufacture.
A further considerable disadvantage of all these known vaporization principles is the fact that the user can come into contact with the active compound or the active compound formulation, for example if the liquid formulation leaks out in the case of liquid vaporizers or the paper platelet is swallowed in the case of platelet vaporizers.
A further disadvantage of the known vaporizer systems mentioned is the nonuniform active compound release characteristics.
In addition, in the case of platelet vaporizers the duration of action is limited to at most 12 hours.
The present invention provides new insecticidal compositions based on polymers which do not have the abovementioned disadvantages and, in addition, are simple to use, for example in known vaporizer apparatuses as are employed for gel vaporizers (EP 0 693 254 A1 (U.S. Pat. No. 5,645,845)). A continuous release rate of the active compound for up to 60 days, preferably up to 45 days, is ensured without warming or optionally at a low working temperature from 60 to 150° C., preferably 80-120° C.
The insecticidal compositions of the invention comprise mixtures containing at least one type of a pyrethroid insecticide and at least one polymer having a crystallite melting range between 100 and 300° C., preferably between 150 and 250° C., particularly preferably between 150 and 200° C. The softening range is determined by the glass transition temperature in the case of amorphous thermoplastic polymers and by the melting point in the case of partially crystalline polymers. In addition, organic or inorganic auxiliaries such as stabilizers, dyes or fragrances can be incorporated as further additives into the mixtures.
The insecticidal compositions of the invention are prepared by introducing a thermoplastic polymer as granules or powder into a suitable extruder at a suitable temperature and plasticizing it. Under the typical plasticizing conditions and temperatures for the polymer selected, the active compound is introduced directly into the polymer melt by means of a suitable metering-in device and is uniformly distributed in the polymer melt.
The polymer compositions are plasticized by kneading in variable shearing roller extruders, in kneaders (Banbury or Werner und Pfleiderer) in single-screw and twin-screw extruders or special kneaders. The shearing roller extruder is used mainly for batch production, while the incorporation of the additives is carried out continuously using single-screw or twin-screw extruders or Buss-KO kneaders. Suitable extruders or kneaders for incorporating the additives are based on the principle of friction; the heat of friction is achieved by the horizontal back and forth motion of the screws. The screws differ in thread depths, thread widths, pitch in the direction of rotation, depending on polymer/additive mixture. The quality of the homogenization can be adjusted by the kneading time and the ratio of length to diameter of the extruder screws. Good homogenization and plasticization is a prerequisite for the further processing of the active compound-containing polymer compositions.
To obtain homogeneous plasticizable products for thermoplastic processing to give molding compositions, the materials have to be added in a particular form. The thermoplastic is added in granule or powder form. The active compound is added as a solid or liquid depending on the accuracy required by means of volumetric or gravimetric metering devices. Volumetric metering devices are screw, compartmented wheel, rotating disk or vibrating channel feeders. Gravimetric metering devices are feed belt balances or differential feed balances. For free-flowing polymer granules (particle size >50 &mgr;m), metering devices used are vibrating channels, spiral or leaf screws and belts. The active compounds having powder sizes between 10 and 50 &mgr;m are treated like liquids and preferably metered in using “chamber systems” such as compartmented wheels or double screws. The active compounds can be fed into the filling zone of the extruder or further downstream in one or more stages. They are metered into the molten thermoplastics to avoid the formation of secondary agglomerates.
Liquid active compounds are treated differently when added to thermoplastics. Liquid active compounds are added in the premix (heating/cooling mixers). Wax-like active compounds are first melted at 60-80° C. and stored in a heated reservoir before they are fed to the extruder. Liquid active compounds are metered in using gear pumps, screw spindle pumps or single-piston or multipiston pumps. They are fed to the extruder at a point where the melt is under pressure. The pressure in the melt has to be above the vapor pressure of the active compound at the respective temperature of the melt, since otherwise vapor and foam are produced. At the injection point, the pressure should drop in the direction of the point of the screw, i.e. the pressure gradient should be negative, so that the active compound fed in is not squeezed out upstream. In the case of larger amounts of active compounds and large viscosity differences between thermoplastic melt and liquid active compound, it is advantageous to inject the liquid simultaneously at a plurality of points. In the case of thermally sensitive active compounds, the distribution of the active compound in the melt can be achieved more rapidly in this way. It is important that the liquid active compounds are embedded as directly as possible into the melt and are not only injected at the edge of the internal wall of the barrel. Film formation of low-viscosity liquids at the barrel wall has to be avoided by reducing the rate of addition, since otherwise the conveyance of material in the extruder is impaired or can even break down in the case of single-screw extruders. This has to be taken into account particularly for high active compound contents. In this case, use should be made of injection v

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