IE48157B1 - Storage stable quicly acting tablets for combatting vertebrates living predominantly in underground structures - Google Patents

Description

The present invention relates to a storage stable, quickly acting tablet for combatting vertebrates living predominantly in underground structures, for example moles, voles, hamsters and foxes.

Preparations of hydrophobized aluminium phosphide in the form of pressings are normally used for this purpose.

A major disadvantage, however, of these known agents is that they only develop phosphine slowly. This frequently leads to the result that the animals (forewarned by the odour) are able to leave their habitats before a lethal concentration is reached. Furthermore, these known agents are not storage stable once the package is opened and the remaining contents exposed to the atmospheric moisture. Moreover, the known agents do not completely hydrolise so that there is the possibility of endangering the users or even completely uninvolved people.

It is thus the purpose of the present invention to produce a storage stable, quickly acting tablet for combatting vertebrates living predominantly in underground structures, the tablet consisting essentially of a mixture of commercial magnesium phosphide and at least one pressing aid which tablet is individually placed in a cavity or recess depending on the size of the tablet, in a water vapour and air impermeable, tear- and break resistant film and covered with a water vapour and air impermeable, tearable and breakable film wherein the two films are tightly sealed -348157 together (e.g. welded) at their edges against water vapour and air. The tablets encased by the film are filled into cans from which they can be withdrawn individually.

Accordingly, the present invention relates to a packaged tablet comprising a storage stable, quickly acting tablet for combatting vertebrates living predominantly in underground structures, wherein the tablet comprises a mixture of magnesium phosphide and at least one pressing aid and is located in a cavity in a first film which is impermeable to water vapour and to air and which is tearand break-resistant, said cavity being covered by a second film which is impermeable to water vapour and to air and which is tearable and breakable, the two films being sealed together at their edges in such a way that they are impermeable to water vapour and to air. Because of the exclusion of air and water vapour, the tablets according to the present invention are practically of unlimited storage stability. If the tablet is broken, however, then the tearable and breakable covering film is broken as well and the magnesium phosphide is exposed to the influence of atmospheric moisture or earth moisture.

Accordingly, the packaged tablet according to the present invention is extremely easy and safe to use. The user need only break it and introduce the tablet together with the package into the openings of the structures to be gassed without having to come into contact with the -hmagnesium phosphide. Subsequently, the openings are covered for example with earth or with another suitable material.

The effect of atmospheric or earth moisture then causes phosphine to he released very quickly (in a marmot; structure, for example about 500 ppm of PH^ are released during one hour), The tablets consist essentially of from 40 to 90 cfl, preferably from 70 to 80 °/d of commercial magnesium phosphide and correspondingly from 10 to 60 ¢, preferably from 20 to 30 fo oi at least one pressing aid. Examples of suitable pressing aids are finely divided silica, brick dust, talcum, aluminium oxide and magnesium oxide.

Preferably, however, water soluble pressing aids are used such as polyethylene oxide and sodium chloride.

A particularly preferred pressing aid is urea.

In general, it is preferable for the pressing aids used to be non-toxic and neither to have a characteristic odour nor to form decomposition products having a characteristic odour.

The tablet is placed in a cavity or recess corresponding to its dimensions formed for example, by deep drawing of· a tear- and break-resistant, water vapour and air impermeable film and then covered with a tearable and breakable film which is also impermeable to water vapour and air. The two films are welded together at their edges -5in such a way that they are Impermeable to air and water vapours.

Deep drawable laminated films are particularly suitable as the tear resistant and break resistant films.

Such laminated films can consist of, for example, a layer of a thermoplastic synthetic resin such as polypropylene, polyethylene, polyamide, e.g., polycaprolactam or poly (hexamethylene adipamide) or polyester, e.g., polyethylene terephthalate and an aluminium layer overcoated with a heatsealing layer.

In one embodiment, the laminated film comprises a thermoplastic synthetic resin layer and an aluminium layer. In another embodiment, the laminated film comprises a thermoplastic synthetic resin and aluminium coated with a heat-sealing layer.

As the tearable and breakable coating films, aluminium films coating a heat-sealing layer are particularly suitable. In one embodiment, the tearable and breakable film comprises aluminium. In another embodiment, the tearable and breakable film comprises aluminium coated with a heat-sealing layer.

The tablets of the present invention can be produced in any desired size. Especially advantageous, however, are tablets having a weight of from 2 to 50 grams, particularly from 5 to 20 grams, a thickness of from 2 to 10 mm, preferably from 3 to 5 mm and a diameter of from 30 -6to 70 mm especially from 40 to 60 mm.

One embodiment of the packaged tablet according to the present invention is illustrated, in the accompanying Figure.

The Figure shows in schematic fashion and partially in section the tablet and container combination of the present invention.

Referring more specifically to the drawing, the magnesium phosphide pressing aid tablet 1 is located in a cup shaped cavity in the tear- and break-resistant film 2 and is covered with a tearable and breakable film 3, The two films are tightly sealed together at their edges 4 in such a way that they are impermeable to water vapour and air.

Unless otherwise indicated, all parts and percentages quoted are used on a weight basis! The product can comprise, consist essentially of or consist of the materials set forth.

The production and use of the pellets of the present invention is illustrated in the following examples.

EXAMPLE 1 (Production) parts by weight of powdery commercial magnesium phosphide, of particle size 3-600 microns having 39.5 % of inert constituents (essentially magnesium oxide) from its production were homogeneously mixed under the exclusion of atmospheric moisture by mechanical stirring with 20 parts by weight of urea (of particle size 3θ-4ΟΟ microns). The -7powder was subsequently pressed in a tablet press to form moulded articles having a diameter of 50 mm and a thickness of 3.8 mm.

The tablets were placed in the laminated film (polypropylene, aluminium, heat-sealing layer, total thickness 82 microns), the covering film (aluminium, heatsealing layer, total thickness 25 microns) was placed on top and the two films were sealed between two annular formed heat-sealing plates during which the lower plate had a temperature of 90°C and the upper plate a temperature of 150°C.

EXAMPLE 2 (Use) An operation was carried out in a field strongly infested with hamsters. For this purpose the packaged tablets according to the present invention were placed in 88 earth structures (1 tablet per structure opening).

After the introduetion of the packaged tablets straw and grass were stuffed into the holes and they were covered with earth. Each structure opening was marked and entered on a sketch. The success rate was then checked after 24 hours. Since it was not possible to dig up the about 0.5-1 metre deep structures, the effect was considered to be positive at structures which were still closed, and negative at structures which had meanwhile been opened.

In order to ascertain the time interval between introduction of the tablets and onset of the effect, the marked structures -848157 were slightly opened at intervals of 10 minutes and’a wire hook was inserted into the living .chamber. This was immediately approached hy the highly sensitive hamsterss as long as the gas had not acted sufficiently. The time interval between introduction of the tablets and the onset of the effect varied between 20 and 30 minutes.

Of the 88 structures treated with the tablets of the present invention only one structure had been opened again. Accordingly, the degree of effectiveness was about 99 °/°. The effect occurred even in relatively dry ground.

Claims (11)

1. A packaged tablet comprising a storage stable, quickly acting tablet for combatting vertebrates living predominantly in underground structures,whereh the tablet 5 comprises a mixture of magnesium phosphide and at least one pressing aid and is located in a cavity in a first film which is impermeable to water vapour and to air and which is tear- and break-resistant, said cavity being covered by a second film which is impermeable to water 10 vapour and to air and which is tearable and breakable, the two films being sealed together at their edges in such a way that they are impermeable to water vapour and to air.

2. A packaged tablet comprising a tablet as claimed 1- in claim 1 wherein the tablet comprises from AO to 90 % of magnesium phosphide and from 10 to 60 % of a pressing aid.

3. A packaged tablet as claimed in claim 1 or 2 wherein the pressing aid is water soluble. A. A packaged tablet as claimed in claim 3 wherein 20 the pressing aid is urea.

4. 5. A packaged tablet as claimed in any of claims 1 to A wherein the first film is laminated.

5. 6. A packaged tablet as claimed in claim 5 wherein the laminated film comprises a thermoplastic synthetic 25 resin layer and an aluminium layer.

6. 7. A packaged tablet as claimed in claim 5 °r 6 10 wherein the laminated film comprises a thermoplastic synthetic resin and aluminium coated with a heat-sealing layer.

7. 8. A packaged tablet as claimed in any of claims 1 to 7 5 wherein the second film comprises aluminium.

8. 9. A packaged tablet as olaimed in claim 8 wherein the second film comprises aluminium coated with a heat-sealing layer.

9. 10. A packaged tablet substantially as described with 10 particular reference to Example 1.

10.

11. A packaged tablet substantially as described with particular reference to the accompanying Figure.