Note: Descriptions are shown in the official language in which they were submitted.
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METHOD FOR ENHANCING BIOCIDAL ACTIVITY
BACKGROUND OF THE INVENTION
Bacterial attachments to surfaces in virtually any non-sterile aquatic
environment is a well-established phenomenon. Industrial efforts to prevent
colonization or to clean fouled surfaces amount to costly expenditures in a
number of
industrial sectors. Surfactants are regularly employed in water treatment
programs as
agents believed to play a role in the prevention of organic masses from
adhering to
surfaces, in the enhancement of biocide efficacy or in the assistance in the
water
miscibility of various biocidal agents. Surfactants are also regularly used in
the
agrichemical business, particularly to enhance the action of herbicides. This
is
accomplished by using the surfactants to alter the surface behavior of the
applied
droplets, maximizing their interaction with the leaf surface.
There are numerous examples of surfactants which are able to inhibit the
colonization of surfaces by inhibiting the overall growth of the organisms in
the target
environment. Many surfactants, regardless of class, show some inhibition of
bacterial
growth when used at concentrations high enough to impede surface colonization.
In
the water treatment industry, the most well known class of surfactants which
impart a
measure of colonization resistance to submerged surfaces are the cationic
quaternary
amine surfactants, which also function as biocides. However, even relatively
mild
nonionic and anionic surfactants can function in an analogous fashion. The
concentration of nonionic or anionic surfactants necessary to mediate toxicity
is
substantially higher than for cationic surfactants, however.
Surfactants have historically been added to biocide packages because they (1)
help to maintain some actives in aqueous solution which may otherwise separate
(formulation aids) and (2) help relatively hydrophobic biocides to be more
miscible in
an aqueous environment. Surfactants have also been considered as enhancers of
the
efficacy of biocides against biofilm-associated organisms by increasing the
accessibility of the biocide to its cellular target.
As previously noted, bacteria attach to surfaces, metabolize and grow,
resulting
in biofilms or microbial slime. This can result in problems in cooling water
systems,
such as reduced heat exchanger efficiency, blockage of pipes, corrosion of
equipment,
and harboring of potentially harmful bacteria. Control of slime, including the
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2
prevention of formation of slime and/or removal of slime, is important in
alleviating
these problems.
The present invention refers to a method for enhancing the activity of
biocides
to control the growth of microbes in an aqueous system. The materials of the
present
invention have been previously used in areas such as spray, soak tank, in-
place
pipeline cleaners, and floor scrubbing formulations.
SUMMARY OF THE INVENTION
The present invention relates to methods for enhancing a treatment containing
biocidal component to control growth of microbes in an aqueous system. the
method
comprising adding low foaming, ethoxylated anionic surfactant to the aqueous
system,
the low foaming, ethoxylated anionic surfactant comprising (a) at least one of
alkyl
substituted carboxylated acid and alkyl substituted carboxylated acid salt,
and (b)
polyoxyethylene-polyoxypropylene block copolymer.
The (a) at least one of alkyl substituted carboxylated acid and alkyl
substituted
carboxylated acid salt, and (b) polyoxyethylene-polyoxypropylene block
copolymer
can be added in amounts effective to control growth of microbes in the aqueous
system at lower levels of biocidal component in the aqueous system than in the
absence of the (a) at least one of alkyl substituted carboxylated acid and
alkyl
substituted carboxylated acid salt, and (b) polyoxyethylene-polyoxypropylene
block
copolymer.
The (a) at least one of alkyl substituted carboxylated acid and alkyl
substituted
carboxylated acid salt, and (b) polyoxyethylene-polyoxypropylene block
copolymer
can be added in amounts effective to obtain at least the same, if not better,
control of
growth of microbes in the aqueous system as compared to same and/or higher
concentrations of biocidal component in the aqueous system in the absence of
the (a)
at least one of alkyl substituted carboxylated acid and alkyl substituted
carboxylated
acid salt, and (b) polyoxyethylene-polyoxypropylene block copolymer.
The (a) at least one of alkyl substituted carboxylated acid and alkyl
substituted
carboxylated acid salt, and (b) polyoxyethylene-polyoxypropylene block
copolymer
can be added in amounts effective to obtain greater control of growth of
microbes in
the aqueous system as compared to higher concentrations of biocidal component
in
the aqueous system in the absence of the (a) at least one of alkyl substituted
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carboxylated acid and alkyl substituted carboxylated acid salt, and (b)
polyoxyethylene-polyoxypropylene block copolymer.
The alkyl substituted carboxylated acid or salt can contain from 6 to 18
carbon
atoms, preferably 6 to 12 carbon atoms, and even more preferably 6 to 9 carbon
atoms.
The alkyl groups can contain from 1 to 6 carbon atoms, preferably 1 to 3
carbon
atoms, and even more preferably 1 carbon atom. Preferably, the alkyl
substitution is
on 3 and 5 carbon atoms of the carboxylic acid. Preferably, the alkyl
substituted
carboxylated acid or salt comprises at least one of 3,5,5 trimethyl hexanoic
acid and
salts thereof, 3,5,5 trimethyl octanoic acid and salts thereof, 3,7,7
trimethyl octanoic
acid and salts thereof, 3,5,5 trimethyl decanoic acid and salts thereof, and
3,9,9
trimethyl decanoic acid and salts thereof.
Preferably, the alkyl substituted carboxylated acid or salt comprises alkyl
substituted carboxylated acid salt, preferably a potassium or sodium salt.
The polyoxyethylene-polyoxypropylene block copolymer preferably has a
mole ratio of about 1 to 1.6 moles of polyoxyethylene to 1 mole of
polyoxypropylene,
more preferably about 1.3 moles of polyoxyethylene to 1 mole of
polyoxypropylene.
The polyoxyethylene-polyoxypropylene block copolymer preferably has a
molecular
weight of about 3,000 to 6,600, more preferably about 4,000 to 5,000, and even
more
preferably about 4,500.
The low foaming, ethoxylated anionic surfactant preferably comprises about
35 to 60 wt% water, based upon total weight of the surfactant, preferably
about 25 to
45 wt% of the at least one of alkyl substituted carboxylated acid and alkyl
substituted
carboxylated acid salt, and more preferably about 28 to 32 wt% of the at least
one of
alkyl substituted carboxylated acid and alkyl substituted carboxylated acid
salt, and
about 5 to 25 wt% of the polyoxyethylene-polyoxypropylene block copolymer,
more
preferably about 11 to 18 wt% of the polyoxyethylene-polyoxypropylene block
copolymer.
The biocidal component can comprise at least one of non-oxidizing and
oxidizing biocidal compounds. The at least one non-oxidizing biocidal compound
can
comprise at least of at least one isothiazolone compound and at least one
bromonitropropanediol compound. The at least one isothiazolone compound can
comprise at least one of 5-chloro-2-methyl-4-isothiazolin-3-one and 2- methyl-
4-
isothiazolin-3-one, as well as a mixture of 5-chloro-2-methyl-4-isothiazolin-3-
one, 2-
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methyl-4-isothiazolin-3-one, and 2-bromo-2-nitropropane-1,3-diol. The at least
one
oxidizing biocidal compound can comprise at least one of hypochlorites, sodium
bromide; hydantoins; peracetic acid; chlorine dioxide; ozone; hydrogen
peroxide; and
halogenated isocyanurates, preferably sodium hypochlorite.
The surfactant can include additional components such as at least one
sequestrant, which preferably comprises at least one of polyepoxysuccinic acid
and
hydroxyethylidene diphosphonic acid.
At least about 5 ppm of the surfactant, more preferably at least about 10 ppm
of the surfactant, can be added to the aqueous system, with preferred ranges
being
about 5 to 200 ppm, more preferably 10 to 50 ppm of the surfactant added to
the
aqueous system.
The microbes can comprise bacteria, fungi, algae and/or protozoa, including
protozoan cysts.
The aqueous system can comprise at least one of cooling water systems
(preferably recirculating and/or closed water systems), reverse osmosis
systems,
pulping and papermaking systems, air washer systems, pasteurizer systems, fire
water
safety systems, shower water systems, metalworking fluid systems, hydrocarbon
storage systems, and aqueous mineral processing systems.
Preferably, the at least one of alkyl substituted carboxylated acid and alkyl
substituted carboxylated acid salt comprises potassium or sodium salt of an
alkyl
substituted carboxylated acid having 6 to 12 carbon atoms and alkyl groups of
1
carbon atom, and the polyoxypropylene-polyoxyethylene block copolymer has a
molecular weight of about 4,000 to 5,000 and a mole ratio of about 1 to 1.6
moles of
polyoxyethylene to 1 mole of polyoxypropylene. More preferably, the potassium
or
sodium salt of an alkyl substituted carboxylated acid comprises a potassium or
sodium
salt of 3,5,5 trimethyl hexanoic acid.
DETAILED DESCRIPTION OF THE INVENTION
The particulars shown herein are by way of example and for purposes of
illustrative discussion of embodiments of the present invention only and are
presented
in the cause of providing what is believed to be the most useful and readily
understood
description of the principles and conceptual aspects of the present invention.
In this
regard, no attempt is made to show structural details of the present invention
in more
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detail than is necessary for the fundamental understanding of the present
invention, the
description making apparent to those skilled in the art how varying forms of
the
present invention may be embodied in practice.
Unless otherwise stated, all percentages, parts, ratios, etc., are by weight.
Also, all percent measurements in this application, unless otherwise stated,
are
measured by weight based upon 100% of a given sample weight. Thus, for
example,
30% represents 30 weight parts out of every 100 weight parts of the sample.
Unless otherwise stated, a reference to a compound or component includes the
compound or component by itself, as well as in combination with other
compounds or
components, such as mixtures of compounds.
Further, when an amount, concentration, or other value or parameter, is given
as a list of upper preferable values and lower preferable values, this is to
be
understood as specifically disclosing all ranges formed from any pair of an
upper
preferred value and a lower preferred value, regardless whether ranges are
separately
disclosed.
The dispersant of the present invention enhances biocidal activity as compared
to the use of biocides alone. The dispersant according to the present
invention
includes a combination of an alkyl substituted carboxylated acid salt and a
block
copolymer that when agitated, such as in cooling towers, will not form
excessive
amounts of foam, which would be unacceptable for use in various aqueous
systems.
The method of the present invention allows for a decrease in the amount of
biocidal
compound added to the system, while maintaining the efficacy of the treatment.
Thus,
a more environmentally acceptable outcome is achieved, in that less biocidal
material
may be used while still preferably achieving at least the same level of
biofilm kill
efficacy. Thus, the dispersant of the present invention is particularly useful
in
combination with biocides to kill organisms. In addition, it is very effective
at
removing pre-existing biofilms in aqueous systems. Thus, the dispersant of the
present invention is particularly useful in the control of microbes, including
the
prevention of formation and/or the removal of slime in aqueous systems.
The present invention relates to methods and compositions for enhancing
activity of a treatment including a biocidal compound to control growth of
microbes,
including the prevention of formation and/or the removal of slime, in aqueous
systems, which comprises adding to the aqueous system an effective amount of
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dispersant comprising low foaming, ethoxylated anionic surfactant which is
composed
of alkyl substituted carboxylated acid and/or salt thereof and ethylene
oxide/propylene
oxide block copolymer.
The alkyl substituted carboxylated acid or salt thereof can include, but is
not
limited to, acids and/or salts containing from about 6 to 18 carbon atoms,
more
preferably from about 6 to 12 carbon atoms, and most preferably from about 6
to 9
carbon atoms. Moreover, the alkyl groups can comprise alkyl groups having from
about 1 to 6 carbon atoms, more preferably from about 1 to 3 carbon atoms, and
most
preferably 1 carbon atom. Preferably, the alkyl substituted carboxylated acid
or salt
comprises up to about 7 alkyl groups, and preferably contains 3 alkyl groups.
Preferably, the acid comprises hexanoic, octanoic and/or decanoic acid, with
from 1 to
3 alkyl groups on the various carbons of the acid, which are preferably methyl
groups.
Moreover, preferably the alkyl substitution is on the 3 and 5 carbons,
preferably of
hexanoic acid. Particularly preferred alkyl substituted carboxylated acid or
salt
thereof comprises hexanoic acid, with the alkyl substitution being on the 3
and 5
carbons, preferably one alkyl group on the 3 carbon and two alkyl groups of
the 5
carbon, and preferably each of the three alkyl groups are methyl. Thus, a
particularly
preferred alkyl substituted carboxylated acid or salt thereof comprises 3, 5,
5 hexanoic
acid or salt thereof.
Preferably, the alkyl substituted carboxylated acid and/or salt thereof
comprises the salt. The salt form can include any canon that helps dissolve
the
carboxylic acid into solution, and preferably comprises potassium or sodium as
the
cation. For example, the acid can be formed into the salt by reaction with
potassium
hydroxide or sodium hydroxide.
Examples of alkyl substituted carboxylated acid and salts according to the
present invention include, but are not limited to, 3,5,5 trimethyl hexanoic
acid and
salts thereof, preferably sodium or potassium salts thereof, 3,5,5 trimethyl
octanoic
acid and salts thereof, 3,7,7 trimethyl octanoic acid and salts thereof, 3,5,5
trimethyl
decanoic acid and salts thereof, and 3,9,9 trimethyl decanoic acid and salts
thereof.
The block copolymer comprises polyoxyethylene (E0) - polyoxypropylene
(PO), which for the sake of convenience will also be referred to herein as
EO/PO
block coplymer. The EO/PO block copolymer can comprise any EO/PO block
coploymer that maintains low foaming and/or reduces foaming of the alkyl
substituted
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carboxylated acid or salt. The EO/PO mole ratio preferably ranges from about 1
to 1.6
moles EO to 1 mole PO, with a particularly preferred mole ratio being about
1.3 moles
EO to 1 mole PO.
The molecular weight range of the EO/PO block copolymer is preferably about
3,000 to 6,600, most preferably about 4,000 to 5,000, with a particularly
preferred
value being about 4,500. Thus, a particularly preferred EO/PO block copolymer
comprises EO/PO having 1.3 moles EO to 1 mole PO, and a molecular weight of
about 4,500.
Examples of EO/PO block copolymers according to the present invention
include, but are not limited to, the Plutonic P series available from BASF
(Mount
Olive, New Jersey), and examples thereof include P65, P68, P84, P85, P104 and
P105.
An especially useful material for forming the dispersant of the present
invention is Mona NF 10, available from Uniqema, Paterson, NJ (formerly Mona
Industries, Inc.), which includes therein alkyl substituted carboxylated acid
salt and
EO/PO block copolymer according to the present invention.
Still further, a particularly preferred low foaming, ethoxylated anionic
surfactant according to the present invention is composed of the potassium
salt of
3,5,5 trimethyl hexanoic acid and EO/PO block copolymer having a molecular
weight
of about 4,500, such as P85 available from BASF.
The dispersant preferably comprises about 35 to 70 wt% water, based on the
total weight of the dispersant. The amount of the alkyl substituted
carboxylated acid
or salt in the dispersant is preferably from about 25 to 45 wt%, more
preferably from
about 28 to 32 wt%, based on the total weight of the dispersant. Moreover, the
amount of the EO/PO block copolymer in the dispersant is preferably from about
5 to
25 wt%, more preferably from about 11 to 18 wt%, based on the total weight of
the
dispersant.
The dispersant according to the present invention can include one or more
biocides therein, or biocides can be separately added to the aqueous system.
In this
regard, the biocide can be added to the aqueous system at the same time as the
dispersant, prior to the addition of the dispersant, and/or after the addition
of the
dispersant. It is preferred that the dispersant be added to the aqueous system
prior to
addition of the biocide.
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As noted above, the present invention allows a decrease in the amount of
biocide fed to a system, without decreasing the efficacy of a particular
treatment
protocol.
Biocides utilizable with the present invention are not limited to any
particular
biocide or mixture of biocides. Therefore, the following discussion of
biocides is not
intended to limit the present invention, but is provided to indicate preferred
biocides
according to the present invention.
Preferably, the biocides according to the present invention include "non-
oxidizing" biocides and/or "oxidizing" biocides, and mixtures thereof. For
example,
non-oxidizing biocides include, but are not limited to, isothiazolones
including 5-
chloro-2-methyl-4-isothiazolin-3-one, 2- methyl-4-isothiazolin-3-one, and a
mixture
of 5-chloro-2-methyl-4-isothiazolin-3-one and 2- methyl-4-isothiazolin-3-one
sold as
Kathon~ 886F, available from Rohm and Haas Co.; and 2-bromo-2-nitropropane-1,3-
diol (BNPD), available from Angus Chemical Co.
A particularly preferred non-oxidizing biocide comprises a mixture of 5-
chloro-2-methyl-4-isothiazolin-3-one, 2- methyl-4-isothiazolin-3-one and 2-
bromo-2-
nitropropane-1,3-diol, such as disclosed in U.S. Patent No. 4,732,905, which
is
incorporated by reference herein in its entirety. Preferably, the weight ratio
of a
combination of the 5-chloro-2-methyl-4-isothiazolin-3-one and 2- methyl-4-
isothiazolin-3-one to the 2-bromo-2-nitropropane-1,3-diol is about 1:2.
Oxidizing biocides include, but are not limited to hypochlorites, such as
sodium hypochlorite (bleach), potassium hypochlorite and calcium hypochlorite;
sodium bromide; hydantoins; peracetic acid; chlorine dioxide; ozone; hydrogen
peroxide; and halogenated isocyanurates, preferably sodium hypochlorite.
The organism that is treatable with the dispersant of the present invention
can
include diverse organisms, including bacteria, fungi, algae and protozoa,
including
protozoan cysts. In the examples herein Pseudomonas aeruginosa, a bacterial
species,
was utilized in studying the present invention. However, with the guidelines
herein,
the invention can be utilized to treat various organisms, and is not limited
to the
specifically disclosed examples.
Materials in addition to the alkyl substituted carboxylated acid salt, the
EO/PO
block copolymer, and optionally one or more biocides can be included in the
dispersant according to the present invention. For example, additives such as
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sequestrants such as polyepoxysuccinic acid, hydroxyethylidene diphosphonic
acid,
citric acid and/or ethylenediamine tetraacetic acid (EDTA) can be included in
the
dispersant according to the present invention.
The dispersant, by itself, or including sequestrants such as polyepoxysuccinic
acid or hydroxyethylidene diphosphonic acid, is able to control microbial
slime on
surfaces. The means of control is by increasing the effectiveness of biocides
to kill
cells within the slime.
The dispersant according to the present invention is preferably included in
the
aqueous system at a concentration of at least about 5 parts per million (ppm),
more
preferably about 10 ppm, with preferred ranges being about 5 to 200 ppm, more
preferably about 5 to 50 ppm, more preferably about 10 to 50 ppm.
The concentration of biocide in an aqueous system can be reduced by about
25%, and even more preferably by about 50%, and still maintain at least the
same
level of effectiveness of biocidal activity by incorporating the effective
amounts of
dispersion of the present invention in the aqueous system.
The dispersant according to the present invention can be utilized in a variety
of
aqueous systems, e.g., open recirculating cooling water systems, closed
cooling
systems, reverse osmosis systems, pulping or papermaking systems, air washer
systems, pasteurizer systems, once-through cooling reverse osmosis systems,
fire
water safety systems, shower water systems, metalworking fluid systems,
hydrocarbon
storage systems, and aqueous mineral processing systems.
The invention will now be described with respect to certain examples which
are merely representative of the invention and should not be construed as
limiting
thereof.
EXAMPLES
The invention is illustrated in the following non-limiting examples, which are
provided for the purpose of representation, and are not to be construed as
limiting the
scope of the invention. All parts and percentages in the examples are by
weight unless
indicated otherwise.
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Examples 1-8
Bacteria in slime (biofilm) was simulated by incorporating bacteria (P.
aeruginosa) into alginate, which was then layered onto metal coupons. Layers
were
exposed to biocide with surfactant and with and without sequestrants. At the
end of
the treatment (about 24 hours), the alginate was dissolved, releasing bacteria
that were
monitored by determining viable numbers of bacteria and microbial ATP.
As noted in Table I below, the alkyl carboxylic acid/block copolymer
dispersants,
examples are the commercial product, Mona NF-10 (available from Uniqema,
formerly Mona Industries, Inc.) with and without sequestrant
(polyepoxysuccinic acid,
available from BetzDearborn Inc., Trevose, PA) enhanced biocide performance.
This
was detected by plate counting and ATP measurement. Biocide NX1100
(isothiazolinone/bronopol, available from BetzDearborn Inc., Trevose, PA) with
10 or
50 ppm Mona NF-10 killed 0.4 and 0.6 log more bacteria, respectively, than
biocide
(NXl 100) alone. In other experiments, biocide (NX1100) with 20 ppm Mona NF-10
and sequestrant killed 0.9 log more bacteria and decreased ATP levels 81 %
greater
than with biocide alone. At 100 ppm Mona-NF-10 with sequestrant, biocide
efficacy
measured as CFU/ml increased 1.2 logs, and as ATP decreased 96% (Table 1).
Still
further, Dispersant A is prepared by mixing 38 wt% 3,5,5 trimethyl hexanoic
acid
(obtained from BetzDearborn Inc., Trevose, PA) and 12 wt% P85 (obtained from
BASF (Mount Olive, New Jersey) with sufficient KOH to get the 3,5,5 trimethyl
hexanoic acid into solution. Increased performance is most likely due to these
types of
dispersants increasing biocide penetration into the biofilm.
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Table
1
ExampleTreatment: productCFU/ml D log, DecreasemATP Decrease
No. (ppm) (log) decrease (%) (RLU)
from
biocide
1 Biocide (25 6.5E -----
ppm) (3.8)
2 Mona NF-10/Biocide2.5E3 0.4 62
(3.4)
(10 ppm/25 ppm)
3 Mona NF-10/biocide1.5E3 0.6 77
(3.2)
(50 ppm/25 ppm)
4 Biocide (25 1E5(5) ----- ----- 2238 -----
ppm)
MonaNFlO/Sequestranb1.3E4 0.9 85 427 81
(4.1)
Biocide
(20 ppm/40 ppm/25
ppm)
6 Mona NF10 5.8E3 1.2 94 93 96
(3.8)
/SequestrantlBiocide
( 100 ppm/40
ppm/25
ppm)
7 Biocide (25 9.5E4 ----- ----- ----- -----
ppm)
(4.98)
8 Dispersant A 1.8E4 0.72 81 ----- -----
/biocide
(50 ppm/25 ppm)(4.26)
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12
Examples 9-18
Bacteria were suspended in phosphate/saline water to which was added
NXl 100, obtained from BetzDearborn Inc., Trevose, PA, ( representative of non-
oxidizer biocide) or sodium hypochlorite, obtained from BetzDearborn Inc.,
Trevose,
PA (representative of oxidizer biocide), and Mona NF-10, obtained from
Uniqema.
Paterson, NJ (representative of alkyl carboxylic acid/block copolymer
dispersant
material), with and without sequestrant (polyepoxysuccinic acid, obtained from
BetzDearborn Inc., Trevose, PA). Initial concentration of bacteria was about
107 - 10g
CFU/ml. Treatment was for 3 hours at 24 ~ 2°C. Samples were removed and
plated,
with results shown in Table 2, below. The dispersant increases the efficacy of
the non-
oxidizer and oxidizer biocide above the biocide alone. As found in Table 2,
the
biocide efficacy increase for the non-oxidizer was 98%, and for the oxidizer
was 78%.
Table
2
Example Treatment: % Decrease % Decrease
No. product (ppm) From Biocide From Control
9 A ( 10) ---- 51
A/B (10/10) 98.1 99.1
11 A/B (10/20) 98.6 99.3
12 A/B (10/50) 99.3 99.7
13 A/B/C (10/10/40)98.3 99.1
14 A/B/C (10/50/40)99.5 99.8
D (0.75) ----- 34.5
16 D/B/C (0.75/10/40)78 85.5
17 D/B/C (0.75/50/40)90 93.3
18 DB/C (0.75/100/40)99 99.1
A = NX1100 (IsothiazolinoneBronopol)
B = Mona NF-10 (alkyl carboxylic acid/block copolymer)
C = Polyepoxysuccinic Acid
D = I4ypochlorite
While this invention has been described with respect to particular
embodiments thereof, it is apparent that numerous other forms and
modifications of
this invention will be obvious to those skilled in the art. The appended
claims and this
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13
invention generally should be construed to cover all such obvious forms and
modifications which are within the true spirit and scope of the present
invention.
