Note: Descriptions are shown in the official language in which they were submitted.
CA 02821204 2013-06-11
WO 2012/083497
PCT/CN2010/002123
1
METHODS OF REMOVING MICROBES FROM SURFACES
FIELD OF INVENTION
[0001] The field of the invention relates to methods for inhibiting microbial
biofilm on surfaces in contact with systems, including but not limited to
aqueous
systems. More particularly, the invention relates to the use of a modified
starch
biofilm control agent for inhibiting microbial biofilm.
BACKGROUND OF THE INVENTION
[0002] Industrial process- or operating-water systems, such as, open or closed
water-cycle systems, in particular cooling-water systems, offer suitable
conditions for
the growth of microorganisms, with the result that a slime known as biofilm is
formed
on the surfaces of water-bearing systems. In the case of cooling water systems
in
particular, these biofilm deposits can lead to reduced heat exchange
efficiency,
pipeline damage and corrosion within the systems. Adverse effects on process
control
are possible, which can ultimately reduce the efficiency of the industrial
process in
question and impair product quality. In addition to this, biofilm or slime
deposits
generally lead to higher energy consumption.
[0003] The deposition of the bacterial slimes can most effectively be
controlled
with biocides; the effect of these biocides being based on the fact that they
kill off the
microorganisms in the operating water and thus prevent slime production.
However,
biocide concentrations needed to control biofilm are much higher than that
needed to
control planktoriic bacteria. Thus, biocides to control biofilm increase
expenses, raise
doubts on ecological grounds, and, because of their toxicity, pose
considerable
dangers when handled. For this reason, alternative ways of eliminating biofilm
have
been sought in the past.
[0004] Industrial efforts to prevent colonization or to clean fouled surfaces
amount to costly expenditures in many industries. Often such expenditures are
made
for cleaning programs that include the use of surfactants. Surfactants are
regularly
applied in water treatment programs as agents believed to play a role in the
removal
CA 02821204 2013-06-11
WO 2012/083497
PCT/CN2010/002123
2
of organic masses from surfaces, in the enhancement of biocide efficacy or in
the
assistance in the water miscibility of various biocidal agents. The more non-
toxic
surfactants often require higher levels of concentrations to achieve their
purpose,
thereby making them uneconomical due to huge amount of water treated. These
surfactants are also prone to forming high level of unwanted foam, and are
toxic to
non-target aquatic organisms upon discharge to common receiving bodies of
water.
[0005] Beyond the higher levels of concentration, another issue of most non-
toxic surfactants is foaming which results in the need to feed antifoam
compositions to
the system. Foam, even with feeding antifoam compositions, is not preferred in
some
industrial applications like air separation processes. In fact, U.S. Patent
Nos.
6,054,054 and 5,128,100 refer to water soluble polymers, such as
polydiallyldimethylammonium chloride (PDADMAC) and ionene polymer, which
reputedly do not foam when fed to the system for microbial control functions.
SUMMARY OF THE INVENTION
[0006] In one exemplary embodiment of the invention, a method is provided
for inhibiting the growth of microbial biofilm on surfaces in contact with
aqueous
systems. The method comprises adding an effective amount of a modified,
naturally
occurring polymer to the aqueous system. In one embodiment, this modified
naturally
occurring polymer is a water soluble cationic quaternary ammonium starch. The
aqueous system may, for example, be a cooling water system.
[0007] In accordance with one aspect of the invention, the biofilm treatment
agent may be fed to the cooling water system in an amount of about 1 ppm to
about
400 ppm with an alternative range of from about 5 to about 200 ppm and a
further
embodiment of about 10-to about 100 ppm. It is noted that any range or ranges
disclosed in this specification are deemed to include and provide support for
sub-
ranges within the stated range or ranges. Any range or ranges disclosed in the
description are deemed to include and provide support for any point or points
within
that range or ranges.
[0008] The various features of novelty that characterize the invention are
pointed out with particularity in the claims annexed to and forming a part of
this
CA 02821204 2013-06-11
WO 2012/083497
PCT/CN2010/002123
3
disclosure. Changes to and substitutions of the components of the invention
can of
course be made. The invention resides as well in sub-combinations and sub-
systems
of the elements described, and in methods of using them.
DETAILED DESCRIPTION
[0009] Approximating language, as used herein throughout the specification
and claims, may be applied to modify any quantitative representation that
could
permissibly vary without resulting in a change in the basic function to which
it is
related. Accordingly, a value modified by a term or terms, such as "about",
are not
limited to the precise value specified. In at least some instances, the
approximating
language may correspond to the precision of an instrument for measuring the
value.
Range limitations may be combined and/or interchanged, and such ranges are
identified and include all the sub-ranges included herein unless context or
language
indicates otherwise. Other than in the operating examples or where otherwise
indicated, all numbers or expressions referring to quantities of ingredients,
reaction
conditions and the like, used in the specification and the claims, are to be
understood
as modified in all instances by the term "about".
[0010] As used herein, the terms "comprises," "comprising," "includes,"
"including," "has," "having" or any other variation thereof, are intended to
cover a
non-exclusive inclusion. For example, a process, method, article or apparatus
that
comprises a list of elements is not necessarily limited to only those
elements, but may
include other elements not expressly listed or inherent to such process,
method article
or apparatus. The phrase "modified naturally occurring polymer" means a
naturally
occurring polymer that has been chemically modified, preferably to contain
cationic
moieties, such as quaternary ammonium groups bonded to the polymer backbone.
[0011] In one embodiment of the present invention, the modified starch
biofilm control agent removes or reduces microbial slime from surfaces in
contact
with aqueous systems better than that caused by water alone. As used
throughout the
specification and claims, the words inhibit and/or inhibition are intended to
refer both
to the function of removing biofilm from structural surfaces in contact with
system
waters and to the retardation or growth diminishment of the biofilms.
CA 02821204 2013-06-11
WO 2012/083497
PCT/CN2010/002123
4
[0012] One embodiment of the present invention provides a method for
inhibiting the growth of microbial biofilm on surfaces in contact with
systems,
including, but not limited to aqueous systems such as cooling water systems
such as
open recirculating, closed recirculating and once through cooling systems,
pulping
and papermaking systems, water transport pipelines, reverse osmosis systems,
air
washer systems, shower water systems, hydrocarbon storage systems, hydrocarbon
transport pipelines, aqueous metal working systems and aqueous mineral
processing
systems.
[0013] In one aspect of the invention, the biofilm treatment agent in
accordance with the invention is a water soluble cationic quaternary ammonium
starch.
As to the cationic quaternary starches (CQS) that may be employed, these are
described in U.S. Patent 4,088,600 which disclosure is incorporated by
reference
herein in its entirety. Basically, as is set forth in U.S. Patent 4,088,600,
the CQS
consists mainly of two moieties, namely a starch group and a quaternary
ammonium
salt group. The starch group may be prepared from a host of starches and
starch
fractions including acid or enzyme modified corn or waxy starches. Exemplary
starches include those prepared from corn, potato, tapioca, sago, rice, wheat,
waxy
maize, grain sorghum, grain starches in raw or modified forms such as those
modified
with acids, oxidizing agents and the like; to amylose and amylpectin and to
the linear
and branched components respectively, of cornstarch and also to dextrins.
[0014] The quaternary ammonium compound used to form the CQS is
generally of the formula:
X
R,
+
_______________________ R2 (Formula I)
R3
in which X - is any monovalent anion, e.g., chloride, bromide, iodide, or
methyl
sulfate; Y is from the group consisting of 2,3-epoxy propyl, 3-halo-2-hydroxy
propyl,
CA 02821204 2013-06-11
WO 2012/083497 PCT/CN2010/002123
2 haloethyl, o, p, or m (a hydroxy ¨ phalo ethyl) benzyl; Ri, R2, and R3 are
from the
group consisting of hydrogen, hydroxyl, alkyl, substituted alkyl, aryl and
aralkyl; in
which two of the R's may be joined to form a hetercylic or homocyclic ring
compound; in which the total number of carbons in all three of Rõ R2, and R3
should
not exceed about 14 carbons. If all three of Rõ R2 and R3 are different, and
R3
contains more than 3 carbon atoms but not more than 12, then R, and R2 should
preferably be from the group consisting of methyl and ethyl; and if R, and R2
are
joined to form a ring compound, R3 should preferably not be greater than
ethyl.
[0015] The reaction to make the cationic starch involves the hydroxyl groups
on the starch molecule and the reactive Y group of the quaternary ammonium
reactant,
so that the resulting cationic starch product has the formula
X
R,
starch-O-Y' -N R2 __________________________________ (Formula II)
R3
in which Y' is the reaction residue of Y and X and the R¨>s are unaltered. Y'
would
thus be (typically) 2 hydroxyl propyl, ethyl, or o, p or m (a hydroxy-Phalo
ethyl)
benzyl.
[0016] In a typical case using N-(3-chloro-2-hydroxypropyl)
trimethylammonium chloride, the reaction may proceed simplistically as
Starch ¨OH + Cl CH2 ¨CH(OH) ¨CH2
1\1+(CH3)3C1 + NaOH¨
Starch ¨0 ¨CH2 --CH(OH) ¨
CH2N+(CH3)3C1 + NaCl + H20.
[0017] In one exemplary embodiment, a number of quaternary ammonium
cationic starches may be prepared by reacting modified cornstarch with varying
amounts of N- (3-chloro-2-hydroxy propyl) trimethylammonium chloride, with
sodium hydroxide as catalyst. The degree of substitution (D.S.) of these
products is
CA 02821204 2013-06-11
WO 2012/083497
PCT/CN2010/002123
6
calculated theoretically and is found to be in the range of 0.01 to about 0.75
and more
preferably from 0.1 to 0.45. The degree of substitution is defined as a number
of
moles of quaternary ammonium substituent, in this case
CH,
--(CH2--CH-GH2-N ___________________________ CH, Cl -)
OH
CH,
per anhydroglucose unit.
[0018] Exemplary quaternary ammonium cationic starches include those
wherein the degree of substitution can be within the range of about 0.01 to
0.75
quaternary units conforming to Formula II given above, per anhydroglucose unit
in
the starch group. Preferably, it is about 0.1-0.45. One preferred CQS is
prepared via
reaction of 3-chloro-2-hydroxpropyltrimethylammoniumchloride and "Melogel"
corn
starch. The corn starch is present in an amount of about 13.9% (by weight),
and the
polymer product contains about 31% actives (by weight). The quat component is
present in an amount of about 18.2 wt%. Another exemplary CQS is prepared via
reaction of 3-chloro-2-hydroxypropyltrimethyl ammonium chloride and a
hydrolyzed
starch. The acid hydrolyzed starch is present in an amount of about 16.6 wt%,
and
the product contains about 27% actives by weight. The "quat" is present in an
amount of about 5.4 wt%. Some commercially available CQS are sold commercially
by GE under the Klaraid PC2710 and Klaraid 2712 designations.
[0019] In one exemplary embodiment, from about 1 ppm to about 400 ppm (or
any range within this range) of the modified starch biofilm control agent is
added to
the aqueous system. The aqueous system may preferably have a pH from about 3.5
to
about 10.5 and, as stated above, varying amounts of the modified tannin may be
provided such as from about 5 ppm to about 200 ppm with an even more specific
CA 02821204 2013-06-11
WO 2012/083497
PCT/CN2010/002123
7
range of about 10-100 ppm. Preliminary investigation reveals that about 50 ppm
appears optimal.
[0020] The modified starch, in one aspect of the invention, does not foam at
working concentrations in aqueous systems. Therefore, in this aspect of the
invention,
substantially no antifoam is needed.
EXAMPLES
Example 1
[0021] In order to demonstrate the efficacy of the modified starch in
inhibiting
the growth of biofilms, microplate assay tests were undertaken on pseudomonas
aeruginosa bacteria. The pseudomonas aeruginosa biofilms were grown in 96 well
plates overnight and treated with the candidate treatments in 15 ppm (actives)
treatment amounts. Results are shown in Table 1Ø
Table 1.0
Pseudomonas Aeruginosa
Treatment Biofilm Removal %
(15 ppm active)
C-1 51%
C-2 85%
C-3 92%
C-4 76%
A-1 67%
C-5 76%
CA 02821204 2013-06-11
WO 2012/083497
PCT/CN2010/002123
8
C-1 = acrylamide/DADMAC copolymer - DADMAC is diallyldimethylammonium
chloride
C-2 = AETAC/tannin copolymer - AETAC is acryloxyethyltrimethyl ammonium
chloride - 57.5% cationic charge density
C-3 = AETAC/tannin copolymer; cationic charge density = 70%
C-4 = ethanolamine/formaldehyde/tannin Mannich reaction product
A-1 = modified starch; quaternary ammonium cationic starch; prepared via
reaction
of 3-chloro-2-hydroxypropyltrimethyl - ammonium chloride and "Melogel" corn
starch. The polymer product contains about 31% actives by weight. The quat is
present in an amount of about 18.2 wt%. The corn starch is present in an
amount of
about 13.9% (by wt.).
C-5 = polyethyleneimine.
[0022] While we have shown and described herein certain embodiments of the
invention, it is intended that these be covered as well any change or
modification
therein which may be made without departing from the spirit and scope of the
invention as defined in the appended claims.
[0023] What is claimed is:
