Note: Descriptions are shown in the official language in which they were submitted.
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The invention concerns an H202-containing germicidal agent
for aqueous systems and to the use thereof.
Water, which up to recently has been an inexpensive
substance abundantly available in nature, is increasingly
becoming a valuable and expensive resource material, espe-
cially for industry, and it is not always available in the
quantity desired. For some time, therefore, effor~s have
been made in communities and in .industry to limit the con-
sumption of fresh water, and for that purpose to purify and
reuse waste water--in other words to recycle it by means of
one or more regenerating treatments. Typical of these
efforts are cooling water recycling systems in various in-
~ustries and recirculating systems in swimming pool in-
stallations.
. . .
For instance, in closed circulating systems used in paper
factories, water is separated from waste streams mechanically,
e.g., by filtration, and is reused. The waste water that is
recycled generally contains high concentrations of impurities
which constitute nutrients for microorganisms of all kinds.
Precisely in the case of papermills, the cellulose present in
25 the filtered water is a very good nutrient medium for algae,
fungi and other microbes whose access can hardly be prevented
even in closed waste-water systems. This micro~ial flora is
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manifested by slime which can cause considerable trouble at
various points in the circulation system.
It is known to prevent the occurrence of microorganisms
in waters of all kinds by the addition of a suitable germi-
cidal agent. It is also known to use for this purpose
germicides which act without leaving afterproducts, or at
least without leaving in the water substances having unde-
sirable or even toxic or corrosion-promoting properties.
Such a known germicide, which is completely consumed
without the formation of any residues, is hydrogen peroxide,
which breaks down into oxygen and water. ~ydrogen peroxide
not only has bactericidal, deodorizing, oxidi~ing and anti-
phlogistic actions, but also fungistatic and fungicidal ac-
tions (cf., for example, Dermatologische Wochenschrift, 152,
p. 1105 [1966]).
~ydrogen peroxide, however, i8 not universally usable
as a germicidal agent, and especially it is not suitable for
the continuous treatment of certain waste waters, because
there are a number of microorganisms which are capable of
forming resistant strains within a relatively short time,
which are no longer attacked by hydrogen peroxide.
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German Offenlegungsschrift 2,228,011 has disclosed a
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biological clarification method in which hydrogen peroxide
is added to the waste water, and provides the oxygen re-
quired for the entire aerobic bacterial clarification, while
at the same time preventing the development of filamentous
bacteria. In this case, therefore, use is made of the
selective effectiveness of hydrogen peroxide, on the basis
of which specific microorganisms are completely destroyed,
but at the same time the growth conditions for other micro-
organisms are optimized.
To render aqueous systems completely germ-free, it
has therefore also been proposed to use hydrogen peroxide
together with organic compounds as a germicidal agent. For
example, German Offenlegungsschrift 2,221,047 describes a
method of preparing a purification and sterilization solu-
tion for soft contact lenses, in which hydrogen peroxide or -
water-soluble, nontoxic peroxides are used together with
phenyl mercury~II) salts, especially with sodium ethyl mer-
cury thioæalicilate, in the form of an a~ueous, isotonic
solution. This known agent is not universally usable, either,
especially on account of the toxicity of the mercury, which
forbids the use of such an agent, not just in bathing estab-
lishments and the like, for example, but also in industry,
such as the paper industry, for example, when the paper is
intended for use in the packaging of foods, or in the phar-
maceutical industry or in other areas where, in the event
of a rupture in the circulation system, materials intended
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for use by man might come in contact with toxic substances.
There is a need, therefore, for another germicidal
agent which will have a broader spectrum of action than
hydrogen peroxide alone.
The invention is addressed to the problem of satisfy-
ing this need and of creating a germicidal agent for aqueous
; systems on a basis of hydrogen peroxide, which is univer-
sally usable, effectively destroys germs of all kinds, does
not leave undesirable or corrosion-producing afterproducts,
and neither is toxic in itself nor yields any toxic degrada-
tion products.
This problem i8 solved in accordance with the invention
by a germicidal agent of the initially mentioned kind hav-
ing a content of p-hydroxybenzoic acid or of one of its
salts or alkyl esters of l to 4 carbon atoms and/or at least
one nitrogen-heterocyclic, aromatic compound which does not
react with hydrogen peroxide with degradation, and which
contains at least one hydroxyl group and/or at least one
carboxyl group, or salts or alkyl esters thereof of 1 to 4
carbon atoms, and/or an aminosulfonic acid of the general
formula R2NS03H, wherein R represent~ hydrogen or an alkyl
group of l to 6 carbon atoms, or a salt thereof, as a syn-
ergetic active substance or mixture of active substances,
as the case may be, and a corrosion inhibitor if desired.
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It has been found surprisingly that the germicidal
agent of the invention has a synergetic effect, i.e., that
the action of the two components, hydrogen peroxide and
aromatic compound and/or aminosulfonic acid, combined is
substantially greater than the mere additive effectiveness
of the components of the same composition. One advantage
of the agent of the invention for its practical use con-
sists in the fact that the stability of the hydrogen per-
oxide is not impaired by the germicidally active additive
or germicidally active additives, as the case may be, and
thus the shelf life of the germicide and hence the econom-
icalness of its use are not impaired. Another important
advantage of the agent of the invention consists in the
fact that the substances remaining after water treatment,
which are not completely used up by chemical reaction like
the hydrogen peroxide itself, have virtually no properties
physiologically objectionable for the human organism. This
is especially important in the use of the agent of the in-
vention, say, for the disinfection of swimming pool water
or, in the industrial area, for use in paper mills in which
wrapping material for foods is manufactured.
The p-hydroxybenzoic acid ethyl and propyl esters
which can be used as synergetic active substances in addi-
tion to hydrogen peroxide are, for example, physiologicallyentirely unobjectionable and therefore approved under the
name, "PHB esters," as food preservatives.
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In a preferred embodiment of the agent of the invention
the agent contains the synergetic active substance or sub-
stances in the form of aqueous and, in some cases, mineral
acid solutions. The addition of a small amount of a min-
eral acid has the advantage that any active substance ofcomparatively low solubility in water that may be contained
in the agent can be easily dissolved therein.
Additional advantageous developments of the agent of
the invention consist in incorporating the synergetic active
substance or substances in amounts between 0.1 and 5~ by
weight, in using as an aromatic nitrogen-heterocyclic com-
pound one having only one nitrogen ring atom, and in using
as an aromatic nitrogen-heterocyclic compound a hydroxy-
15 quinoline and/or a pyridine dicarboxylic acid.
Preferred are those germicidal agents which contain8-hydroxyquinoline and/or dipicolinic acid as aromatic nitro-
gen-containing compound.
The germicides of the invention contain hydrogen per-
oxide preferably in the form of a commercial aqueous, stabil-
ized or unstabilized solution. The common hydrogen peroxide
stabilizing agents, such as sodium pyrophosphate for example,
25 impair neither the synergetic effect ~or the properties of
the individual components contained in the agent of the in-
vention.
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The problem described in the beginning is furthermore
solved by the use of the germicidal agent of the invention
in a concentration corresponding to O.Ol to 2 ml of a 35~
a~ueous hydrogen peroxide solution per liter of the medium
being treated.
A corrosion inhibitor, such as ammonium nitrate for
example, can be added, if desired, to the germicidal agent
if parts sensitive or liable to corrosion are present in the
system, such as fittings, pumps and couplings of any kind,
without thereby impairing the synergetic effect between the
hydrogen peroxide and the organic compound.
The addition of the agent of the invention to the aque-
15 ous medium to be disinfected is performed by means of con- -
ventional apparatus, such as continuously or periodically
operating proportioning apparatus made of a material com-
patible with hydrogen peroxide.
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EXAMPLES
The invention will be further explained with the aid
of the examples and of a description of an experiment.
The Examples 1 to 7 that follow represent effective
germicidal agents in accordance with the invention. They
are prepared by mixing 35 wt.-~ aqueous hydrogen peroxide
solution with the stated synergetic active substances in
the ratio given in each case, and they can be stored in this
form unobjectionably, and without losing any of their ef-
fectiveness, and they can be used at any time after their
preparation.
15 Example 1:
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35 wt.-% H22
2 wt.-% ammonium aminosulfonate ;
Balance, water
Example 2:
H22
1.5 g/l p-hydroxybenzoic acid ethyl ester
Balance, water
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Example 3: -
35 wt.-% H22
0.5 wt.-~ dipicolinic acid
Balance, water
Example 4:
35 wt.-~ H2O2
2 wt.-% ammonium aminosulfonate
0.5 g/l sodium pyrophosphate
Balance, water
Example 5:
35 wt.-% H22
2 wt.-~ ammonium aminosulfonate -
0.25 wt.-% dipicolinic acid
Balance, water
Example 6:
5 wt. % H22
2 wt.-% 8-hydroxy~uinoline
0.25 wt.-% dipicolinic acid
plus sulfuric acid until the hydroxyquinoline
is completely dissolved
Balance, water
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Example 7:
35 wt.-~ H O
2 wt.-% 8-hydroxy~uinoline
1.5 g/l p-hydroxybenzoic acid ethyl ester
plus sulfuric acid until the hydroxyquinoline
is completely dissolved
Balance, water.
The germicidal effectiveness of the agents of the in-
vention in accordance with Examples l to 7 was determined
by means of the following experiment.
For the concentration of cellulose decomposing agents,
5 g of cellulose powder, O.l g of yeast extract and 5 g of
humus earth are added to a Dubo's salt solution, consisting
of 0.5 g of NaN03, l kg of K2HP04, 0.5 g of MgS04 ~ 7H2O,
0.5 g of KCl, O.Ol g of FeS04 ~ 7H20 and one liter of
distilled water, and the mixture is aired for several weeks.
Experimental batches were then prepared which contained
Dubo's salt solution and ~0% of the concentrated cellulose
decomposing agent substrate. 0.25 ml/l and 0.05 ml/l of the
germicidal agents of Examples l to 7 were added to these
experimental batches; the mixtures were incubated at 15~C
and slightly aired. At the beginning of the experiments,
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as well as one day, seven days, fourteen days and twenty
days afterward, the total germ count was determined on PC
agar (10 days of incubation at 22C. In addition, blind
tests were peformed, i.e., tests without the addition of a
germicidal agent, in order to determine the total germ
count originally contained in the experimental mixtures.
For the comparison and illustration of the synergetic ef-
fect achieved with the agents of the invention, the same
experimental mixtures were tested under the same conditions
without hydrogen peroxide, i.e., with only the organic com-
ponents of Examples 1 to 7 (including Na2H2P207 and H2SO4),
and finally, again for purposes or comparison, the germic-
idal effect of 35 wt.-% hydrogen peroxide solution in com-
mercial form was tested alone, i.e., without the addition
of other active substances.
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The results are recorded in the following Tables 1 and -
2. Given in each case is the number of living germs con-
. . .
tained in one milliliter of the experimental mixtures ~the
expression, ~101, means that no living germs could be found
in 0.1 ml of mixture). In the case of Examples 1' to 7',
the germicidal agents are the agents which contained no hyd-
rogen peroxide, but otherwise are the same as the agents of
Examples 1 to 7.
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~able 1
(Germicidal agent concentration: 0.25 ml/l of test mixture)
Germicidal Live Germ Count
agent
Initial 1 Day 7 Days 14 Days
__ 7 x 104 6 x 105 5 x 106 2 x 106
Example 1 2 x 104 < 1Ol < lol < lol
Example 1' 2 x 105 4 x 105 3 x 107 5 x 105
Example 2 2 x 104 < lol < lol < lol
Example 2' 2 x 105 2 x 106 3 x 106 1o6
Example 3 2 x 105 < lol < lol < lol
Example 3' 2 x 105 2 x 106 5 x 105 105
Example 4 5 x 105 < lol < lol < lol
Example 4' 2 x 106 . 3 x 105 4 x 105 5 x 105
35% ~ O
~ 5 (compar~son) 5 x 104 2 x 102 5 x 101 5 x 10
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Table 2
(Germicidal agent concentration: 0.05 ml/l of test mixture)
GermicidalLive Germ Count
agent
Initial 1 Day7 Days 14 Days
- 3 x 108 3 x 108 8 x 106 107
Example 5 3 x 108 2 x 103 < lol c lol
Example 5' 3 x 108 1 x 108 8 x 106. 3 x 106 . .
Example 6 3 x 108 6 x 102 ~ lol < 10
Example 6' 3 x 10 1 x 108 106 1o6
Example 7 3 x 108 3 x 1o2 < lol < 101 ~ ::
Example 7~ 3 x 108 1 x 1o8 3 x 107 2 x 106
35% H202 3 x 108 1o6 1o3 2 x 104
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The results given in Tables 1 and 2 show that, when the
germicidal agents of the invention are used in a concentra-
tion of 0.25 ml/l, no live germs were to be found after one
day in 0.1 ml of the test solutions, whereas with 35 weight-
percent solutions of ~2O2, 2 x 102 were found after one day,and after fourteen days as much as 5 x 102 were found, and,
with the additive organic active substances alone, i~e.,
without the addition of H2O2, 3 x 105 to 2 x 106 were found
after one day and, after 14 days, 105 to 106 live germs were
found. From this it appears that the effectiveness of the
agents of the invention is not, as might have been expected,
the mere sum of the effectivenesses of H2O2 and the ad-
ditionally used active agent, but that a genuinely syner-
getic effect is produced by the agents of the invention.
The results furthermore show that neither the presence of a
conventional stabilizer for hydrogen peroxide ~Example 4)
nor the presence of small amounts of a mineral acid (Examples
6 and 7) are able to impair the synergetic effect and the
effectiveness of the agents of the invention.
The agents of the invention are thus outstandingly
suited quite generally for the sterilization and/or disin-
fection of aqueous systems, not only for waste waters re-
circulated in industry, but also in other fields, as for
example the treatment of swimming pool water.
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It will be. understood.that the speciication and
examples are illustrative but not limitative of the present
invention and that other embodiments within the spirit and
scope of the invention will suggest themselves to those skilled
in the art. ~
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