RATICIDE ET METHODE DE PRODUCTION CONNEXE

PESTICIDE AND PROCESS FOR ITS PRODUCTION

Abrégé anglais

ABSTRACT OF THE DISCLOSURE
"Pesticide and process for its production"
The present invention relates to a pesticide comprising
a moulded body made of a water-insoluble organic solid substance
in which at least one finely divided metal phosphide is embedded,
the moulded body being coated on at least one side with fibrous
substance which is permeable to water vapour and whose fibres
at least partially extend as far as the embedded phosphide
particles and to a process for producing such a pesticide.

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Revendications

The embodiments of the invention in which an
exclusive property or privilege is claimed are defined as
follows:-

1. A pesticide comprising a moulded body made of
60 to 120 parts by weight of a water-insoluble organic solid
substance in which at least 100 parts by weight of at least
one finely divided metal phosphide are embedded, the moulded
body being coated on at least one side with a fibrous
substance which is permeable to water vapour and whose
fibres at least partially extend as far as the embedded
phosphide particles.
2. A pesticide as claimed in claim 1, in which
the water-insoluble organic solid substance is a thermo-
plastic substance.
3. A pesticide as claimed in claim 2, in which
the thermoplastic substance is selected from the group
consisting of polyethylene, polypropylene, polyvinyl chlo-
ride, polyvinyl acetate and hard paraffin.
4. A pesticide as claimed in claim 1, in which
the at least one finely divided metal phosphide is selected
from the group consisting of aluminum phosphide and magnesium
phosphide.
5. A pesticide as claimed in claim 4, in which
the aluminum phosphide and magnesium phosphide have particle
diameters up to 300 u.


6. A pesticide as claimed in claim 1, in which the
water-insoluble organic solid substance is present in an amount
of 60 to 120 parts by weight per 100 parts by weight of the
metal phosphide.
7. A pesticide as claimed in claim 1, in which the
fibrous substance is selected from the group consisting of a
fabric, a felt and a non-woven fabric.
8. A pesticide as claimed in claim 1, in which the
fibrous substance comprises at least partially cellulose fibres.
9. A pesticide as claimed in claim 8, in which the
fibrous substance comprises wholly cellulose fibres.
10. A pesticide as claimed in claim 1, which is in
a form selected from a plate, a band and a strip.
11. A pesticide as claimed in claim 10, in which the
form is 3 to 9 mm. thick.
12. A process for producing a pesticide as claimed
in claim 1, in which process a layer comprising a mixture
of the at least one finely divided metal phosphide and the
water-insoluble organic solid substance is applied to a layer of
the fibrous substance, and the whole is then heated to a
sufficiently high temperature and for a sufficient length of
time so that a moulded body is produced from the water-insoluble
organic substance and the at least one phosphide and this
moulded body becomes joined to the layer of the fibrous substance.

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13. A process as claimed in claim 12, in which the
said whole is heated to a temperature of from approximately
140 to 160°C.
14. A process as claimed in claim 12, in which the
said whole is heated for a period of from approximately 3 to 8
minutes.
15. A process as claimed in claim 12, in wich a
second layer of a fibrous substance is rolled onto the moulded
body when it is warm.
16. A process as claimed in claim 12, in which the
water-insoluble organic solid substance is a thermoplastic
substance.
17. A process as claimed in claim 16, in which the
thermoplastic substance is selected from the group consisting
of polyethylene, polypropylene, polyvinyl chloride, polyvinyl
acetate and hard paraffin.
18. A process as claimed in claim 12, in which the
at least one finely divided metal phosphide is selected from
the group consisting of aluminium phosphide and magnesium
phosphide.
19. A process as claimed in claim 18, in which the
aluminium phosphide and magnesium phosphide have particle
diameters up to 300µ.

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20. A process as claimed in claim 12, in which
the fibrous substance is selected from the group consisting
of a felt, a fabric and a non-woven fabric.
21. A process as claimed in claim 12, in which
the fibrous substance comprises at least partially cellulose
fibres.
22. A process as claimed in claim 21, in which
the fibrous substance comprises wholly cellulose fibres.
23. A process as claimed in claim 12, in which
the pesticide is in a form selected from a plate, a band and
a strip.
24. A process as claimed in claim 23, in which
the form is 3 to 9 mm thick.

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Description

~04Z788
The present invention relates to pesticides.
More particularly, the present invention relates
to a pesticide comprising a moulded body made of a water-insoluble
organic solid substance in which one or more finely divided metal
phosphides, preferably aluminium phosphide and/or magnesium
phosphide, are embedded and to a process for producing such a
pesticide.
French Patent Specification No. 1,531,677 describes
moulded bodies, e.g. tablets or pellets, which are used as
insecticides. These comprise finely divided metal phosphides,
preferably the phosphides of aluminium and magnesium, especially
~` with particle diameters of 10 to 1000 microns, which are embedded
in a polyester resin, polyurethane resin, polyvinyl resin or
polystyrene resin. These moulded bodies may contain 30 to 60%
by weight of the metal phosphide/phosphides.
The disadvantage of these insecticides is that they
give off gas slowly. When brought -into an atmosphere having 60%
` relative humidity at room temperature~ compositions having 60
or 50% by weight of aluminium phosphide and magnesium phosphide
and having 40 or 50% by weight of polyester resin~ to some extend,
only release the full amount of gas after approximately 20 days.

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104~:788
It is obvious, therefore, that a long time is needed before the
residues do not contain any considerable quantities of phosphides
and can therefore be removed and eliminated safely, and that the
concentration of hydrogen phosphide in the gas-filled room is only
very low because of the slow release of gas with a given quantity
of the composition.
The present invention seeks to provide pesticides
of the type mentioned such that they release gas more quickly
and can be removed easily and completely from the gas-filled
room after the release of gas.
According to the present invention, this aim may be
achieved in that the moulded body ~s coated on one or more sides
with a fibrous substance which is permeable to water vapour
and whose fibres at least partially extend as far as the embedded
phosphide particles.
These fibres which extend to the inside of the moulded
bodies act as "wicks", by means of which the atmospheric moisture
reaches at least some of the phosphide particles. These particles
of the metal phosphides thus decompose with the development of
gaseous hydrogen phosphide and with the increase in volume.
Consequently, the water-insoluble organic solid substance around
`~ the remaining phosphide particles is shattered and a regulated and
quick release of gas takes place.

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~0~ 8~
The pesticides o~ the present invention preferably
contain as the water-insoluble or~anicic solid substance
a thermoplastic substance, such as polyethylene, polypropylene,
hard paraffin, polyvinyl chloride or polyvinyl acetate.
Finely divided aluminium phosphide and/or magnesium
phosphide having particle diameters up to 300 ~ have proved
to be particularly suitable.
Good results are obtained with pesticides which
contain 60 to 120 parts by weight of the water-insoluble
organic solid substance per 100 parts by weight of the metal
phosphide. The release of gas is too slow when the content of
water~insoluble organic solid substance is increased, and it
takes place too quickly and even during the coating process
with a smaller content.
The fibrous substance which coats the moulded body on
one or more sides may, for example, be a fabric, a felt or a non-
woven fabric. Fibrous substances made of cellulose, such as
cotton fibres, wood pulp, regenerated cellulose or the like are
particularly suitable. These substances conduct the atmospheric
moisture into the interior of the moulded bodies particularly
well.
:

~042788
The pesticide according to the present inventlon is
preferably in the shapc of a pl~te, a band or a strip. It is
therefore easily possible to bring the respective desirable
quantities of the composition into the room which is to be filled
with gas, e.g. by cutting off the desired lengths from a band.
The plate, the band or the strip is preferably 3 to 9 mm.
thick.
A particular embodiment of the present invention relates
to a process for the production of such a pesticide. The process
is characterised in that a layer comprising a mixture of the at
least one finely divided metal phosphide and the water-insoluble
organic solid substance is applied to a layer of the fibrous
substance, the whole being then heated to such a high temperature
and for so long that a moulded body is produced from the water-
insoluble organic substance and the at least one phosphide and
this moulded body becomes joined to~the layer of the fibrous
substance.
Thus, the whole may, for example, be heated at a
~ temperature of from approximately 140 to 160C and for a time
- 20 of from approximately 3 to 8 minutes.
If it is desirable to produce a layered body which is
coated with a fibrous substance on two sides, then a second layer
of a fibrous substance is rolled onto the moulded body when it
is warm.



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~04Z78(~
The process may bc carried out continuously or
discontinuously.
The pesticides of the present invention may be used to
fill, with gas, rooms where there may even be, for example,
cereals, tobacco, foodstuffs or luxury foodstuffs. The hydrogen

phosphide which has been developed destroys all pests such as
insects or rodents.
The present invention will now be further described
with reference to the following Example:-


EXAMPLE
A layer, approximately 7 mm thick, of aluminiumphosphide having particle diameters of 10 to 300~ and granulated
polyvinyl acetate in the weight ratio of 80 parts of polyvinyl
acetate~ containing plasticizers, to 100 parts of aluminium
phosphide is applied to a layer, 0.2 mm thick, of non-woven
fabric comprising cellulose fibres. The whole is heated to
160 C for approximately 5 minutes by means of an infra-red
radiator.
A second layer of the non-woven fabric, which serves
as the underneath layer~ is rolled onto the surface of the
moulded body thus produced, when it is hot, by means of a
roller heated to approximately 150C and for a period of
approximately 1 minute. A plate which is 4 mm. thick is produced.
. ~ .

~Q4Z7~1
l~en this moulded body i9 brought into an atmosphere
of 65% relative humidity st a room temperature of 20 C., gas
is released from the phosphide contained in the composition
at the rate of 1.2% after 2 hours, 9.5% after 5 hours and 21%
after 10 hours, the greatest possible release of gas being
achieved after 72 hours.
~ he present invention will now be further illustrated
by way of the accompanying drawing which shows, on an enlarged
scale, a section through a pesticide according to the present
invention.
Particles 2 of aluminium phosphide are embedded in a
plate 1 comprising polyvinyl acetate. On the surface there is
a non-woven fabric 3 comprising cellulose fibres whose fibres
extend to a portion of the embedded phosphide particles.




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