Note: Descriptions are shown in the official language in which they were submitted.
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S P E C I F I C ~ T I O N
The present invention relates to an additive for water for
fire fighting containing a strongly swelling water-insoluble
high molecular weight polymer as gelatinizing agent. High
molecular weight polymer substances of the kind which are
added to the water for fire fighting as swelling agents are
descri.bed in EP-A-199 897. These substances are highly
absorptive and can absorb in a short time up to 500 fold of
their weight of water without, however, being dissolved in
water. These substances are then present in the form of gel
particles that are highly swollen due to hydration and are
dispersed in the water for fire fighting. If one adds to the
so-swollen gel particles an excess of water, the latter will
remain as pure aqueous phase. The viscosity of the water for
fire fighting after adding the gelatinizing agent is only
minorily higher than the viscosity of pure water. The
sufficiently low viscosity is important in order that the
water for fire fighting remains furtheron easy to handle, in
particular fully pumpable. The advantages of the water ror
fire fighting to which an additive of the kind is added are a
reduction of the amount of water necessary for fire fighting,
a reduction of the fire extinguishing time as well as the
reduction of the water for fire fighting which runs off from
the source of fire.
In spite of its excellent fire extinguishing effect, this
prior art additive for water for fire fighting exhibits
disadvantages which are a bar to its application on a large
scale. When the swelling high molecular weight polymeric
gelatinizing substance is added to the water for fire
fighting, lumps may be formed.
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In the Mediterrenean countries also seawater serves as
water for fighting forest fires. The sodium chloride
present therein leads, analogous to the hardness causing
salts, to a disturbance of the swelling procedure. Swelling
times of from one to several minutes are necessary to
swell the gelatinizing su~stance. It is true that when
water for fire fighting from a triple combination pumper
is used, in which the substances have enough time to swell,
the swelling times play only a subordlnate role, however,
o it is extremely difficult to disperse lumps once they are
formed.
Therefore, the object of the present invention is to
improve an additive for water for fire fighting of the
above-mentioned kind to the effect that the dlsadvantages
described above do no longer occur.
The solution of this problem is provided by the additive
for water for fire fighting according to the invention
wherein the particles of the gelatinizing agent are encased
by, or dispersed in, a water-soluble release agent of the
kind that does not cause the particles of the gelatinizing
agent to swell. The release agent protects the gPlatinizing
agent from becoming sticky upon the penetration of water
and thus from agglutinating. When using the release agent
according to the invention, the dispersing of the gelatlnizing
substance takes place without any problem.
It is important that the release agent has a good water
solubility and does not itself cause the particles of
the gelatinizing agent to swell.
According to the invention, the release agent functions
so to speak as a barriex between the particles of the
gelatinizing agent and, therefore, prevents agglutination.
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Since the prior art gelatinizlng substances require
a swelling time of from one to several minutes, the use
of water for fire fight~ng co~taining additives of the
kind would necessitate in the case of large-scale f~res
the storage of the water for fire fighting in intermediate
containers in order to achieve the necessary swelling time.
The use of intermediate container~ of the kind would become
superfluous if itwere possible to reduce the swelling time
to a few seconds. Such a reduction of the swelling time
can be basically achieved by reducing the partlcle size of
the particles of the gelatinizing agent. On the one hand,
one increases thereby the working surface of thc water durlng
the swelling procedure and, on the other hand, reduces
the diffusion path. However, uslng very ~lne partlcles of
the gelatinizlng agent increases the risk of agglutlnation.
It was, therefore, not possible to date to disper~e very
finely ground gelatinizing substances ln water without
the help of particular adjuvants. If, however, one encases
accordlng to the inventio~ the particles of the gelatinizing
20 agent by a water-soluble ~elease agent, also very finely
ground gelatinizing substances may-be used without any
agglutlnation of the partlcles. Hense, it is possible
by virtue thereof to directly spray the gelatinizing
substance into the hose plpe through a nozzle.
A preferred release agent according to the invention is
polyethylene glycol. In contrast to ethylene ylycol and
diethylene glycol, polyethylene glycol i8 not absorbed by
the gelatinizing substance. Therefore, a polyethylene glycol
30 layer protects the particles of the gelatinizing agent from
sticking to each other too quickly upon the penetration of
water and from agglutination. Moreover, polyethylene glycol
is absolutely non-toxic and is very ~uickly decomposed
and, therefore, can ~e considered an ecologically nonpolluting
35 substance.
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It has proved to be advantageous to wet the particles of
the gelatinizing agent with an amount of from 10 to 100
by weight polyethylene glycol 300 or 400, based on the
amount of gelatinizing substance.
Besides, diammonium biphosphate has proved to be a particularly
suitable release agent. In fire fighting in the mediterrenean
area, where the most disastrous forest fires occur, the
tanks are often filled with seawater. The sodium chloride
present in high concentration therein as well as the
hardness causing salts that are likewise contained therein
entail in a disadvantageous manner a strong reduction
of the swelling capacity of the gelatinizing substance.
This disadvantageous effect is considerably reduced when
diammonium blphosphate is used as release agent. The
phosphate ion blocks the hardness causing substances and
the ammonium ion compensates the negative effect of
the sodium ion on the swelling capacity. It is particularly
advantageous to use ~he diammonium biphosphate in amounts
of from 20 to 100% by weight, based on the gelatinizing
substance.
A particularly preferred method of preparing the additive
for water for fire fighting is to dry mix the gelatinizlng
substance with, for example, 50% by weight of diammonium
biphosphate in a high speed mixer. The diammonium biphosphate
crystals are crushed thereby. At the same time, from
10 to 30% by weight of water, based on the gelatinizing
substance, are sprayed. The particles of the gelatinizing
substance become sticky for a short time and the diammonium
biphosphate is permenantly fixed on the surface of the
particles of the gelatinizing agent.
Also sugars are suitable for use as release agent according
ts the invention, in partlcular mono- and disaccharides.
Good results were obtained, ~or example, with mannito~.
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Preferred gelatinizing agents are moderately cross-
linked water inso'uble acrylic or methacrylic acid
copolymers.
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