Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
D-589
FORMULATION OF STABLE WATER BASED SUSPENSIONS
OF MIXTURES OF TRIHALOALKYL SULFONE
This invention relates to the formulation of a stable,
water based suspension of trihaloalkyl su~fone. More particularly, the
invention relates to the formulation of a stable, water based
suspension of bis(trichloromethyl)sulfone (BTCMS) and methylene
bis(thiocyanate) (MBT).
Manufacturing as well as production processes use huge
quanti~ies of raw as well as potable water that must be treated with
biocides in order to assure product and production standards.
Typically, cooling towers, paper and pulp mills, canning industries,
animal hide processing plants, secondary oil reGovery using water
flooding, industrial water systems, to name a few, require the use
and recycling of the water used in these processes. These systems
become easily contaminated with microorganisms such as bac~eria,
algae, fungi, etc~, due to exposure to contaminants encountered in
the process of manufacturing and/or from the products being `
processed. These waters become a breeding media for microorganisms
which must be controlled and/or eliminated. Biocides have been
developed which conkrol such contaminants which if left unchecked,
will destroy equipment and/or reduce the quality of a manufactured
product.
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Two chemicals employed as biocides to control the
undesirable yrowth of microorganisms are bis trihaloalkyl sulfone
and MBT. Formulations containing mixture of these chemicals in
organic solvents are known to exhibit superior fungicidal and
bactericidal efficacy when compared to formulations containing
individual components. For example, U.S. Patent No. 3,426,134 to
Shema et al. discloses synergistic blends of these chemicals~ These
formulations involve the use of organic solvents. These mixtures
are used as slimicides in the production of paper and paperboard as
well as biocidal uses in other industries.
However there are growing objections to the use of costly
organic solvents in formulating biocides. Of extreme concern is the
ecological impact of these organic solvents. The organic solvents
typically used, for example dimethylformamide (DMF), are toxic by
themselves. In addition, these solvents can accelerate in the
ability of a biocide to penetrate human skin, so that in the case of
spills or accidental contact, the danger to human life is
increased. Other problems posed by utilizing organic solvents are
low flash point, hence a fire hazard, and excessive repulsive odors.
Economic problems are a concern when the biocides are
formulated using organic solvents. Organic solvents cost more and
they can present processing problems so that the effect is to
increase the cost of biocidal formulations containing organic
solvents.
Recent changes in Environmental Protection Agency (EPA)
regulations present additional difficulties by requiring the removal
of solvent based products from the marketplace. Action has already
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been taken by the EPA against DMF. It is anticipated that actionagainst other commonly used solvents for biocide formulations may be
taken.
Accordingly, there is a need for alternatives to organic
solvent based biocide formulations. It has now been discovered that
trihaloalkyl sulfone, specifically bis(trichloromethyl) sulfone and
mixtures of bis(trichloromethyl) sulfone and MBT can be formulated
as stable suspensions in water. The formulas of the present
invention have shown biocidal efficacy essentially equivalent to the
solvent based formulas~
These formulas avoid the disadvantages associated with the
use of organic solvents. The inventive formulas result in a reduced
risk to human life through accidental skin exposure. These novel
suspensions can be prepared so as to contain a variety of
concentrations of active ingredients. The technique involved
readily permits the introduction of other biocides into the product
suspension.
As shown by U.S. Patent No. 3,42~,124 to Shema et al~
combinations of trihaloalkyl sulfone, and more specifically
bis(tribromomethyl) sulfone (BTBMS) or bis(trichloromethyl) sulfone
(BTCMS), and methylene bis thiocyanate (MBT) are useful biocidal
compositions for controlling slime forming organisms in the water
employed in paper or pulp mills, cooling systems and other
industrial water systems.
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Water based formulations of biocidal compositions are also
known in the art~ U.S~ Patent 3,996,378 to Payton discloses a water
based composition comprising MBT in a xanthan gel and optionally an
auxiliary fast-acting biocide. The auxiliary biocide is selected
from an n-alkyl (C12 - Clg) dimethyl(benzyl~ ammonium chloride~
U~S. Patent 3,996,155 to Slovinsky et al~ discloses an oil
in water emulsion of BTS which can be made from dimethyl sulfide and
sodium hypochlorite or aqueous brine~ It is possible to add
additional biocides such as biocidal quaternary ammonium compounds9
MBT, and bis(tri-n-butyl tin)oxide to the BTCMS emulsion.
U~S. Patent 4,671,815 to Bellos et al~ discloses the use
of oxyalkylated amines which will render biocide actives such as a
BTCMS and MBT soluble in water for use as a biocidal composition~ -
Description of the Invention
In the present invention, it has been discovered that
blends comprising trihaloalkyl sulfone, a surfactant(s), a swellable
smectile clay, and a suitable thickener can be prepared to form
stable dispersions or suspensions in water~ Optionally, a suitable
auxiliary biocide such as a water-soluble biocide or methylene
bis(thiocyanate) (MBT) may be added to the dispersion or
suspension~ These mixtures have shown biocidal efficacy essentially
equivalent to the corresponding organic solvent containing formula~
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The trihaloalkyl sulfones utilized in the practice of the
invention are bis(trichloromethyl) sulfone (BTCMS) and
bis(tribromomethyl) sulfone (BTBMS), as disclosed by U.S. Patent
3,426,134. The preferred sulfone is BTCMS.
Surfactants which can be utilized in the practice of ~he
present invention include cationic, anionic, and nonionic
materials. These surfactants typically have HLB values of between 6
and 30. Examples of suitable anionic surfactants include, but are
not limited to, sulfates and sulfonates of the following
hydrophobes: alkyl, diphenyl, olefins, alcohols and ethoxylated
alcohols; ethoxylated alkyl phenols; fatty esters; oils and fatty
acids; alkylaryl, dodecyl and tridecylbenzenes; naphthalene and
alkyl naphthalenes; and petroleum derivatives. Examples of suitable
nonionic surfactants include, but are not limited to, block polymers
of poly(ethylene) and poly(propylene) oxides, ethoxylated alcohols,
ethoxylated alkyl phenols, ethoxylated fatty acids, ethoxylated
fatty acids and esters, fatty esters, glycerol and glycol esters,
and sorbitan esters.
Examples of suitable cationic surfactants include, but are
not limited to quaternary ammonium salts such as N,~-dialkyl (Cg to
C16) N,N,N-trimethyl-ammonium salts, and N-alkyl, N,N-dimethyl
N-benzyl-ammonium chloride.
Preferably, the surfactant is selected from the group
consisting of ethoxylated alcohols, ethoxylated alkyl phenols, block
polymers of poly(e~hylene) and poly(propylene) oxides, and N-alkyl
(40% C12, 50% C14, 10% C16) N,N-dimethyl N-benzyl-ammonium
chloride. Most preferrably, the surfactant is a nonylphenoxy
polyethoxy ethanol sold by Texaco Chemical Company under the name
"Surfonic N-95."
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The clay used in the present invention may be any suitable
synthetic or naturally occurring smectite clay which swells when
dispersed in water. Optionally, these clay materials may be
specially treated. Suitable clays may be generically described as
S magnesium aluminum silicates. Specific examples of suitable
naturally occurring smectite clays include, but are not limited to,
montmorillonite, bentonite, and hectorite. An example of a suitable
specially treated clay is available from R. T. Vanderbilt Co., Inc.
under the trademark "Veegum"~
Suitable thickeners used in the practice of the present
invention include both synthetic and naturally occurring materials.
Examples of suitable naturally occurring thickeners include, but are
not limited to, guar gum, locust bean gum, gum arabic, carrageenin,
xanthan, and cellulosics such as methyl cellulose, carboxymethyl
cellulose and hydroxypropyl methyl cellulose~ Preferrably the
thickener used is hydroxypropyl methyl cellulose.
The auxiliary biocide may be any compa~ible water soluble
or water slightly soluble biocide. Exemplary auxiliary biocides
include 5-chloro-2-methyl-4-isothiazoline-3 one and
2-methyl-4-isothiazoline-3-one, 2-(decylthio)ethanamine
hydrochloride9 3,5 D thiadiazinethione 2,2-dibromo-3-nitrilo
propionamide, and dodecylguanidine.
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One method used to make the formulation of the present
invention is as follows: -
1. In a suitable vessel, add the required water and begin
heating to about 85C.
2. Add the required quantity of swellable smectite clay
and agitate~
3. Continue heating to about 85C with constant agitation.
4~ Add the required quant;ty of thickener while
maintaining about 85C and constant agitation~
5~ Add the surfactant(s) while maintaining constant
temperature and mix for about 30 minutes~
6~ Optionally, add an auxilary biocide and mix~
7~ Add the sulfone and mix~
8~ Allow suspension to cool to about 23 to 33C while
constantly agitating the suspension.
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Another method of preparing the formulations of the
present invention is as follows:
1. Disperse about 1.0 parts (by weight~ of magnesium
aluminum silicate in about 78-80 parts (by weight) of water by
mixing at about 40 to 50 C for approximately 15 minutes.
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2. Adjust the pH of the above dispersion to 5.
3. Add about 10 parts (by weight) of BTCMS and mix for
about 10 to lS minutes at a temperature range of about 45 to 50 C.
4. Add about 10 parts (by weight) of MBT.
5. Homogenize for about 10 minutes at about 50C.
6. Remove heat and add about 0.20 parts (by weight) of
xanthan gum.
7~ Mix for about 20 to 30 minutes.
In accordance with the above procedure the following
compositions (A-J) were prepared~ These compositions were tested
for biocidal efficacy against Klebsiella pnemoniae at a 20 ppm
dosage. The make up of the compositions and the percent kill is
described in Table I below. Composition K is a commercially
available organic solvent based biocidal composition having MBT and
BTCMS as the active ingredients. The surfactant utilized is
Surfonic N-95 ~nonylphenoxy polyethoxy ethanol) a product of Texaco
Chemical Company. The thickener is hydroxypropyl methyl cellulose.
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TABLE I
Composition Surfactant Thickener MBT BTCMS Clay % Kill
20 ppm
S A 15.0% 0 0.0% 20.0% 0.5% 35
B 15.0% 0 0.0% 20.0% 1.5% 66
C 0.5% 0.5 0.0% 20.0% 0.5% 0
D 0.5% 0 0.0% 20.0% 1.5~O 11
E 0.5% 0.5 5.0% 0.0% 0.5% 10
F 0.5% 0 5.0% 0.0% 1.5% 38
G 0.5% 0 5.0% 20.0% 0.5% 16
H 0.5% 0.5 5.0% 20.0% 1.5% 71
I 5.0% 0.5 5.0% 17.5% 1.5% 56
J 5.5% 0.35 6.0% 11.0% 2.0% 99
K 5.0% - 5.0% 17.5% -- 60
Although not as efficacious as oil based formulations, the
BTCMS in conjunction with a surfactant, thickener, and clay still
represents an advancement in the art by eliminating the need for
troublesome organic solvents. ;
Alternatively, addition of about 5 to 10% (by weight) of
an organic solvent such as N,N-dimethylformamide (DMF) or a
paraffinic solvent to the formulation and mixing in Step 4 of the
procedure above will substantially reduce the particle size of the -
MBT crystals. Under these circumstances the process of homogenizing
of the MBT suspension (Step 5) can be avoided.
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Typical formulations for MBT and BTCMS which involve the
use of organic solvents are about 25% by weight active ingredients
and about 70-75% organic solvent. Even the reduction of the amount
of organic solvent utilized in the formulation ameliorates the
problems of utilizing organic solvent, namely high cost, low flash
point, high corrosion of storage and feeding equipment and excessive
repulsive odors.
Emulsification of the BTCMS readily occurs at temperatures
of about 40 to 50 C and no advantage is found in elevating the
temperature above 50C. In fact, higher temperatures are to be
avoided due to the possibility of hydrolysis of BTCMS.
While this invention has been described with respect to
particular embodi~ents 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 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.
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