Note: Descriptions are shown in the official language in which they were submitted.
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FLOWABLE 2-CHLORO-N-ISOPROPYLACETANILIDE
This invention relates to a flowable aqueous ~-
suspension concentrate of the herbicide 2-chloro-N-
-isopropylacetanilide (propachlor) or a herbicidal
mixture of 2-chloro-N-isopropylacetanilide and a triazine
herbicide such as 2-chloro-4-(ethylamino)-6-(isopropyl-
amino)-s-triazine, having not only desirable storage
properties but also being readily dispersible as a tank
mix in the field. The invention further relates to a
flowable aqueous suspension concentrate of the herbicide
2-chloro-N-isopropylacetanilide containing at least 30
percent by weight of 2-chloro-N-isopropylacetanilide and
at least one or more active herbicide ingredient useful
in controlling broadleaf weeds, particularly those which
are sparingly soluble in water or the aqueous suspension
vehicle and even more particularly wherein problems are
encountered with the propachlor in the mixture.
The preparation of suitable aqueous suspension
concentrates of sparingly soluble pesticides has been an
important objective of formulators. While wettable
20 powders have been in use for some time, such compositions ;
are frequently undesirable, particularly in the case
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where the active ingredient is difficult to handle
because of such properties as skin sensitivity. Thls is
particularly true in the case of the herbicide propachlor.
A description of desired properties of sus-
pension concentrates and means for obtaining such proper-
ties are described in the chapter by H. Schaller and
H. Niessen, entitled "Properties of Suspension
Concentrates", in the text, Pesticide Chemistry, Volume
V, Gordon and Breach Science Publishers, New York, NY,
1972, p. 441.
French Patent No. 2,247,976 describes aqueous
suspensions of pesticides made up of a salt solution
as a suspension medium. The French patent describes
the preparation of aqueous suspensions of pesticides
having a melting point above 50C and a solubility
in the suspension medium of less than 500 parts per
million (ppm) at 25C and employs in such compo-
sitions a major proportion of a soluble salt such as
sodium sulfate, ammonium sulfate or sodium biphosphate;
sodium lignosulfate; an anionic surfactant such as
sodium alkyl benzene sulfonate, sodium alkyl naphtha-
lene sulfonate, or sodium dioctylsulfosuccinate; and,
in some mixtures, a combination of kaolinite clay and
synthetic silica; the pesticide employed; and the
balance water. Such compositions are taught to contain
from about 8 to about 40 percent by weight of the
pesticide, from 40 to about 91.9 percent by weight of
the soluble inorganic salt, from 0.1 to 10 percent by
weight of lignosulfate salt, up to 3 percent of a
wetting agent, a corrosion inhibitor, if desired, in
minor amount and the balance substantially water.
Such compositions contain no xanthan gum and no non-
ionic surfactant.
18,246A-F 2-
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Of particular interest is U.S. Patent 3,948,636
and its British counterpart 1,421,092 as w~ll as its
South African counterpart identified as Patent Appli-
cation No. 74/2789. These patents describe and claim
flowable aqueous suspension concentrates of relatively
insoluble pesticides such as propachlor, i.e., 2-chloro-
-N-isopropylacetanilide, containing from 10 to 60 per-
cent by weight of the pesticide, from 1 to 10 percent
of a nonionic surfactant, from 0.02 to 1 percent o~ a
heteropolysaccharide gum, up to 10 percent of an
anticaking agent, up to 5 percent of an antifoaming
agent and up to 10 percent of a freeæing point depres-
sant, and the balance water.
Such a concentrate composition suffers from
the disadvantage that crystal growth, sometimes called
Ostwald-ripening, appears to take place, and in any
event the suspension settles out on accelerated storage
(at about 50C) of more than 7 weeks and resùspension
thereafter becomes increasingly difficult. Moreover,
the patented composition suffers from the further
disadvantage that it does not disperse as well as
would be desired on preparation of a tank mix. This
is particularly noted if the water employed in making
up the tank mix is hard water such as might be drawn
from a well in the field. The xanthan gum of the
composition is of little utility when dilution is
made to the tank mix and no dispersant is provided
in the patented formulation.
Propachlor is particularly difficult to work
with since it has a solubility in water at 25C of
approximately 580 ppm by weight while at 40C the
solubility rises to about 1000 ppm by weight. At this
level of solubility, crystal growth can occur leading
18,246A-F ~3-
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to particle size enlargement and sedimentation or
gelation of suspended particles in a pesticide formu-
lation under normal storage conditions which can range
from ambient winter temperatures to about 50C. If the
settled particles are not readily resuspended and/or are
not readily dispersible on dilution with water, the
formulation is commercially unacceptable to most users.
The problem is made more difficult by the fact propachlor
tends to crystallize as thin enlongated crystals.
The triazine herbicides of commercial interest
are sparingly soluble in water, less soluble than pro-
pachlor, and are not difficult to formulate. The
problems with propachlor must still be met in a pro-
pachlor-triazine mixture to be suspended in a flowable
suspension concentrate. Likewise, the problems with
propachlor must still be met in making a suitable
flowable suspension concentrate of a mixture of pro-
pachlor and one or more other active herbicides useful
for the control of broadleaf weeds wherein at leasi 30
percent by weight propachlor is contained in the
concentrate.
In accordance with this invention a flowable
a~ueous suspension concentrate of propachlor or a
propachlor-triazine mixture or a mixture of propachlor
and at least one additional active herbicide useful for
the control of broadleaf weeds wherein the concentrate
contains at least 30 percent by weight propachlor having
improved storage properties and further improved dis-
persibility on preparation of tank mixes in the field
consists essentially of, by weight:
from 30 to 60 percent of particulate propachlor
or propachlor-triazine mixture or mixture of propachlor
1~,246A-F -~-
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and at least one other said herbicide having a particle
size mainly in the range of 1 to 10 microns;
from 1 to 10 percent of an anionic surfactant
or a nonionic surfactant, or a mixture of an anionic
S surfactant and a nonionic surfactant;
up to 1.0 percent of a heteropolysaccharide
gum;
from 1 to 10 percent of an anticaking agent
selected from ball clays of the kaolinite group such as
Bandy Tan, Gleason, ~tratton, or Barden clay; diatomites
such as Celite~ 209 diatomaceous earth, Celatom~ MM-309
diatomaceous earth; a finely divided precipitated hydrated
silica; and a mixture of any such ciays or diatomite with
such hydrated silica;
- 15 from 0.1 to 6 percent of a dispersing agent,
with the proviso that when the surfactant is a nonionic
surfactant or a mixture containing more than 4 parts
nonionic surfactant per part of anionic surfactant the
proportion O$ dispersing agent is at least 1.0 percent;
up to 1.0 percent of an antifoaming agent;
and the baIance substantially water;
the composition essentially having a viscosity
at 25C of 200 to 3500 centipoises and preferably 700 to
2000 centipoises as determined by a Brookfield Viscometer
Model RVT (No. 3 spindle - 10 rpm).
`,:
Generally it is desirable to include in the
composition from 2 to 15 percent of a freezing point
depressant. Also it is essential when the composition is
not to be used immediately to add an effective amount of
a preservative to prevent or inhibit microbial growth,
generally 0.1 to 0.25 percent by weight being sufficient,
based on the total formulation.
18,246A-F -S-
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The composition of the invention is a flow-
able aqueous suspension concentxate of propachlor,
or propachlor-triazine herbicide mixture or mixture
of propachlor with at least one additional herbicide
S useful in controlling broadleaf weeds wherein the
concentrate contains at least 30 percent by weight
propachlor exhibiting substantially improved storage
stability and water dispersibil:ity over the compo-
sitions described in U.S. Patent 3,948,636. Like
the compositions there described, the present compo-
sition is capable of incorporat:ing high solids in
concentration, e.g., up to and including 6 pounds
of propachlor or total herbicide solids per gallon.
On careful selection of ingredients here set forth,
up to the theoretical maximum concentration somewhat
above 6 pounds of propachlor or herbicide mixture
per gallon may be properly suspended.
In general, the propachlor content of the
flowable compositions of this invention may vary
from 30 to 60 percent by weight. In those compositions,
containing high solids content of commercial interest,
the propachlor content typically varies from 40 to
60 percent by weight. In practice, the propachlor
and any other sparingly soluble herbicide actively
present are employed in a finely divided form having
an average particle size ranging preferably between
1 to 10 microns. It is desirable that the propachlor
and other insolubles have an average particle size
within the stated range so that the greatest particle
surface per unit of weight will be provided, thereby
allowing the solids to be most homogenously suspended.
In preparing the flowable aqueous suspension concen-
trate of the invention, it is necessary, in order to
1~,246A-F -6-
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bring the propachlor and any other solids to the desired
average particle size, to subject the particulate
material to air milling, or preferably sand milling
or ball milling after initial hammer milling or other
eonventional comminuting treatment known in the art.
It is to be noted, moreover that it i6 also
possible to prepare suitable compositions which incor-
porate, in addition to the propachlor, one or more
solid, water-soluble pesticide components. Water
soluble components have a solubility greater than
2000 ppm. In such composition, the soluble pesticide
will of course be in solution in water as the con-
tinuous phase. Other suitable active herbicides
inelude dieamba, i.e., 2,5-diehloro-6-methoxy benzoie
aeid and amine salts thereof as well as sparingly
soluble esters; 2,4-dichlorophenoxyacetic acid and
; amine salts thereof as well as the sparingly soluble
butoxyethanol ester; bifenox and linuron as well as i
the aforementioned herbicidal triazines. Sparingly
soluble compounds are those having a solubility below
1500 ppm and preferably below 200 ppm.
The three-way eombination o~ heteropolysae-
eharide gum, the surfactant or surfactants and the
dispersant employed in combination comprise an important
dispersing-suspending system in an important embodiment
of the flowable pesticide composition of this inven-
tion. It is critical to employ these components in
eertain prescribed ratios both in relation to each
other and to the concentration of pesticide component~
in order to obtain compositions with the desired storage
stability and water dispersibility.
18,246A-F -7-
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In another preferred embodiment, the gum is
substantially or entirely omitted, while the relative
proportion of surfactant is increased in preparing
higher propachlor solids compositions containing 5 or
more pounds propachlor per gallon. In such embodiment
in which the propachlor or propachlor-triazine com-
ponent or other solids mixture is relatively high and
the gum is largely or entirely omitted, the surfactant
and dispersant serve as the dispersing suspending
system.
The terms "heteropolysaccharide" and "hetero-
polysaccharide gum" as used-herein are meant to include
the use of the polysaccharide in the form of the colloid
and its salts, e.g. amine derivatives prepared by the
method disclosed for example in U.S. Patent 3,244,595.
The heteropolysaccharde which is commonly designated
in the art as the xanthan gum is a high molecular
weight linear cellular material prepared by the action
o~ bacteria of the genus Xanthomonas on carbohydrates.
It has a molecular weight in excess of 200,000, pre-
ferably over one million. A variety of carbohydrates
can be fermented with various species of this genus
Xanthomonas to produce the heteropolysaccharide.
Examples of suitable bacterium species of the genus
Xanthomonas include X. campestris, X. carothee,
X. inconue, X. begoniae, X. malvacerum, X. vesicatoria,
_ translucens, and X. vaculorum, among others.
Suitable carbohydrates include, glucose, sucrose,
fructose, maltose, lactose, galactose, soluble starch,
corn starch, potato starch, and the like. Preparation
of heteropolysaccharides suitably used herein is
described in greater detail but not solely in U.S.
18,246A-F o8_
Patent 3,020,~06. It is to be understood that neither
the heteropolysaccharides per se nor their preparation
consitute a part of the present invention.
The surfactant system employed in the sus-
pending-dispersing system of the flowable composition
of this invention is either a b:Lend of anionic and
nonionic surfactants or composed entirely of either
a nonionic surfactant or an anionic surfactant. A
blend consisting of up to 4 parts nonionic per part
anionic surfactant is treated or used in the same
manner as anionic surfactant, while a blend consis-
ting of more than 4 parts nonionic per part o~
anionic surfactant is treated or used in the same
manner as nonionic surfactant used as sole dispersant.
Specific suitable anionic surfactants are selected
from the following classes or types of materials:
ethoxylated monohydric sulfated alcohol salts of
sodium, potassium, alkaline earth metals, ammonium,
alkyl amines, alkanolamines or blends thereof (also
20 designated in the art as alkyl polyether alcohol ;
sulfates); ethoxylated sulfated alkylphenol salts
of sodium, potassium, alkaline earth me-tals, ammonium,
alkyl amines, or alkanolamines or blends thereof
(also designated in the art as alkylaryl polyether
alcohol sulfates); and the sodium, potassium, alkaline
earth metal, or ammonium salts of alkyl phenoxybenzene
disulfonates.
Specific suitable nonionic surfactants are
selected from the following classes or types of non-
ionic surfactant materials: ethoxylated alkyl phenols(also designated in the art as alkylaryl polyether
alcohols); ethoxylated aliphatic alcohols (or alkyl
~polyether alcohols); ethoxylated fatty acids (or
.
18,246A-F 9- ~i
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polyoxyethylene fatty acid esters); ethoxylated
anhydrosorbitol esters (or polyethylene sorbitan
fatty acid esters); ethoxylated polyoxypropylene
glycols (polyalkylene oxide block copolymers);
ethoxylated polyoxypropylene monohydric alcohols
(polyalkylene oxide block copolymers of monohydric
alcohols); and ethoxylated polyoxypropylene alkyl
phenols (polyalkylene oxide block copolymers of
alkyl phenols).
. Of these the preferred surfactants are a
blend of:
(a) (1) ethoxylated monohydric alcohol, i.e.,
alkyl polyether alcohol sulfates of the general formula:
+
C10 to C15 linear or branched
chain alkyl group, y is an integer of from 2 to 19 and
M is a cation selected from ammonium, calcium, magnesium,
potassium, sodium and zinc;
(2) ethoxylated, sulfated alkyl phenols,
i.e., alkylaryl polyether alcohol sulfates of the
. general formula:
R ~ o-(cH2cH2o)y-cE2cH2oso3 M
wherein R is a C8 to C12 linear or branched
chain alkyl, y is an integer of 3 to 13 and M is a
25 - cation selected from ammonium,- calcium, magnesium,
potassium, sodium and zinc; alone or in admixture with
one or more of the following nonionic surfactants:
18,246A-F ~10-
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(b) (1) ethoxylated polyoxypropylene
glycols, i.e., polyalkylene oxide block copolymers
of the general formu]a:
HOCH2 C~I2 O- ( CH2 CH20 ) X- ( C3H6 ) y
wherein x is an integer of from 5 to 95 and
y is an integer from 5 to 150 and the average molecular
weight of the copolymer is in the range of 1800 to 9000;
(2) ethoxylated polyoxypropylene monohydric
alcohols, i.e., polyalkylene oxide block copolymer
of mononydric alcohols of the general formula:
R-ocH2cH2o-(cH2cH2o)x (c3H6o)y
wherein R is a Cl to C8 linear or branched
- chain alkyl group, x is an integer of from 5 to-70
y is an integer of from 5 to 55 and the average
molecular weight of the copolymer is in the range of
2400 to 3500; and
(3~ ethoxylated polyoxypropylene alkyl
phenol, i.e., polyalkylene oxide block copolymer of
alkyl phenol of the general formula:
- R ~ (CH2CH2O)X-(C3H6O)y
wherein R is a C8 to C12 linear or branched
chain alkyl group, x is an integer of 30 to 60, y is
an integer of 5 to 35, and the average molecular weight
of the copolymer is about 3000.
.
Utilizing these surfactant systems, formula-
tions are obtained with optimum water dispersibility
and adequate storage stability. Within this class, `
especially preferred combinations of surfactants are
18,246A-F -11-
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any of (a) alkyl polyether alcohol sulfate wherein R is a
C12 alkyl, y is an integer selected from 3 and 4 and M is
sodium or ammonium; or alkylaryl polyether alcohol sul-
fate wherein R is a C9 alkyl, y averages 3 and M is
sodium or ammonium; with one or more of (b) polyalkylene
oxide block copolymer wherein the weight percent of the
polyoxyethylene units in the mo:Lecule range from 30 to 60
percent of the average molecular weight of the polymer;
polyalkylene oxide block copolymer of monohydric alcohol
wherein R is a C4 alkyl; and polyalkylene oxide block
copolymer of alkyl phenol wherein R is a Cg alkyl, the
surfactants being otherwise as described in the general
categories above.
In compositions containing a higher propachlor
solids content, such as 40 to 60 percent by weight, the
xanthan gum generally is employed in an amount ranging
from 0.1 to 0.5 percent by weight; the surfactant in an
amount ranging generally from 2 to 7 percent by weight;
and the dispersant in an amount ranging from 0.5 to 4
percent by weight, and most preferably in an amount
ranging from 0.5 to 2 percent by weight. If each of
these components were employed separately as the sole
suspending or wetting agent in otherwise similar for-
mulations, the troublesome solid pesticide component,
i.e., propachlor, would soon settle out of the continuous
water phase. ~epending upon the length of time allowed
to stand after the settling of the solid, it would become
increasingly difficult to resuspend the solids, even with
vigorous and prolonged agitation.
In the pesticide composition of this inven-
tion, it is necessary to employ each of the hetero-
polysaccharide and surface active agent (or wetting
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agent) and dispersant components within the ranges
stated above in order to obtain the desired compo-
sition properties. Formulations containing amounts
of these components outside the stated ranges will
either be too low or too high in viscosity and non-
flowable, exhibiting inferior water dispersibility
and unsatisfactory storage stability of the sus-
pension concentrate.
In the pesticide composition of this inven-
tion containing the heteropolysaccharide gum as well
as dispersant and one of (a) an anionic surfactant,
(b) a nonionic surfactant, or (c) both an anionic and
a nonionic surfactant, it is necessary to employ each
within the ranges stated hereinabove in order to
assuredly obtain the desired composition properties.
- Formulations containing amounts of these components
outside the stated ranges will either be too low in
viscosity with a tendency to settle out solids or too
high in viscosity and nonflowable, exhibiting inferior
water dispersibility on dilution and unsatisfactory
storage stability.
.
In concentrate compositions containing 5
pounds or more propachlor per gallon of concentrate,
the composition tends to be thicker, i.e., more vis-
cous, because of the higher solids content. This ispreferably overcome by reducing and/or altogether
omitting the amount of heteropolysaccharide gum other-
wise employed, while employing the surfactant at a
concentration of at least 6 percent by weight, and
18,246A-F i13-
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preferably also increasing the dispersant to aneffective amount above 1 percent by weight, gen-
erally to 2 percent by weight.
Compositions having viscosities ranying from
300 to 4500 centipoises (cps), and more preferably
700 to 3500 (cps), as measured with a Brookfield
Viscometer, Model RVT (No. 3 Spindle - 10 rpm) gen-
erally will exhibit the desired flowability char-
acteristics. As preYiously mentioned, the hetero-
polysaccharide gum and the described surfactantsand the dispersant, in combination, comprise one of
the dispersing-suspending systems of the flowable
propachlor compositions of this invention. In
compositions containing higher propachlor content,
such as, at least 50 percent by weight of propachlor,
a desirable dispersing-suspending system contains
more surfactant, more dispersant and little or no
gum. These components must be ratioed properly to
each other and to the propachlor concentration in
order to obtain compositions with desirable storage
stability and water dispersibility.
Thus, the ratio, by weight, of propachlor
to the anticaking agent, or flow-aid, should be in
the range of from 5.5 to 1 to 26 to 1. Nonionic
surfactant may be omitted altogether but preferably
is employed in a ratio of, by weight, 1 to 2 with
respect to the amount of anionic surfactant in the
composition. The dispersant should be used in an
effective amount within the range herein recited as
needed to obtain ready dispersibility of the solids
on dilution in making a tank mix and as an inhibitor
of crystal growth.
.
18,246A-F 14-
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Also critical to the storage stability of
these compositions is both the type and concentration
of the inert carriers used in these formulations
functioning as flow-aids or anticaking aids.
Numerous pesticidal dust diluents and car-
riers are known to the art. The "Handbook of Insec-
ticide Dust Diluents and Carriers" by T. C. Watkins
and L. B. Norton, Dorland Books, Caldwell, New Jersey
(1955) lists many of those commonly used in the trade
for those purposes. We have found that many of those
are also commonly used in the art for flowable pes-
ticidal compositions that will not serve to maintain,
in combination with the present suspending-dispersing
system, the desired storage stability of the composition. 15 under extreme storage conditions. The suitable inert
carriers are selected from the ball (China) clays such
as Bandy Tan, Gleason, Stratton and Barden clays; the
diatomites sold as, Celite~ 209 and Celatom~ MN-39;
and a finely divided synthetic precipitated hydrated
silicon dioxide (silica) such as the silica sold under
the trademarks or tradenames Cab-0-Sil~ and Hi-Sil~,
e.g., Hi-Sil~ 233. Any of these are used alone or
in combination. For optimum performance character-
istics, a blend of a silica and a ball clay of the
kaolinite group is preferred. In such a blend, the
silica content can range from 5 to 95 percent by
- weight of the combination with the preferred com-
bination containing 25 to 75 weight percent silica
and the balance the ball clay. The total composition,
as indicated above, contains from 1 to 10 percent by
weight of the anticaking or flow-aid. Preferably
the total flowable composition contains from 3 to
8 percent by weight of the anticaking aid.
18,246A-F 15-
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The novel and highly essential component
of the present suspension concentrate is a dis-
persant which facilitates the dispersion or dilution
of the suspension concentrate with water in the pre-
paration of the final mix in the field, generally
referred to as a tank mix. It should be noted that
it may be possible to prepare an entirely satisfactory
looking and performing suspension concentrate so far
as can be ascertained in the concentrate form which
is not at all satisfactory upon dilution as the solids
tend to settle rapidly, and/or to agglomerate,
especially when the tank mix is made up using hard
water. It is therefore essential to include in the
composition an adequate dispersant.
Even more importantly the dispersant is
critical to concentrate stability under various
storage conditions such as during freeze-thaw cycles
which lead or tend to lead to crystal growth.
.. . ..
For purposes of the present description
and the appended claims a disp~rsant is defined as
a polar organic material with dispersant properties
which does not lower the surface tension of water more
than 30 percent from the normal 72 dynes per square
centimeter in contrast to surfactants which lower
surface tension of water 50 percent or more-.
'` ..:
Suitable dispersants are selected from the
sodium, potassium, ammonium, calcium, magnesium or
zinc salts of the commonly available lignosulfonic
acids, the sodium salt being preferred, or, the poly-
merized alkyl or alkylaryl sulfonic acid salts, suchas, the potassium, sodiurn, calcium or an~lonium salts,
with the sodiurn salt bein~ preferred. A specific
18,246A-F 16-
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example of a suitable sodium salt of polymerized
alkyl, alkylaryl or aralkyl sulfonic acid is:
Daxad~ 27, sodium salt of benzoid alkyl sulfonic
acid.
The amount of dispersant used should be
in the range of from 0.1 to 6 weight percent, with
the preferred amount being in the range of 0.5 to
4 percent and the most preferred amount being 0.5 to
2 percent by weight. Functionally, the dispersant
retards or preven-ts settling of the suspended solids
and is believed to aid in the prevention or inhibition
of crystal growth of the propachlor solids in the
aqueous concentrate, as during freeze-thaw cycles.
Should the propachlor or other active
herbicide employed in making the suspension concen~
trate of the invention contain acidic manufacturing
contaminants causing a 10 weight percent water dis-
persion thereof to e~hibit a p~ below 4, then compo-
sitions to meet the objectives of this invention must
contain somewhat more dispersant than stated above
as may readily be determined by trial and error.
Below pH 1 the use of additional dispersant does not
compensate adequately for the increased acidity.
Minor quantities of one or more additional
compone~ts are preferably included in the composition
to provide a highly useful and convenient, practical
pesticide composition concentrate. A freezing point
depressant is preferably incorporated into the compo-
sition to ensure good formulation properties are
maintined under adverse storage conditions such as
low temperature conditions. A number of freezing
point depressants known to the art may be used,
18,246A-F
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however, the best performance is obtained using from
2 to 10 percent by weight of a lower alkylene glycol,
such as ethylene glycol or propylene glycol.
In order to facilitate preparation of a
tank mix in the field without the formation of undue
foam because of the presence of a surfactant and
dispersant components hereof, it is highly useful to
employ an antifoaming agent. The various commercially
available silicone materials or emulsions such as
Dow Corning Antifoam A~ are examples of suitable
antifoaming agents which may be incorporated in the
flowable concentrate in an amount ranging generally
from ~.05 to 1 percent by weight of the total compo-
sition. A specific example of an antifoaming agent
is dimethylpolysiloxane.
It is also generally preferred to employ a
preservative to prevent the growth of bacteria and/or
fungi in the concentrate during storage. Any of a
number of bactericides and fungicides may be employed
that are compatible with the present system. A highly
satisfactory preservative useable in the present
invention is sodium ortho phenyl phenate sold under
the trademark Dowicide~ A. Other suitable preservatives
are formaldehyde and sodium pentachlorophenate.
Water is employed in sufficient amount ~o
serve as the continuous phase for the dispersed pro-
pachlor and to achieve reasonahle viscosity charac-
teristics compatible with the need for supplying a
concentrate with sufficient active solids content.
18,246A-F -18-
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In preferred compositions, i.e., those which incor-
porate high concentrations of propachlor, from 20
to 40 percent by weight of water will generally be
employed.
The order of addition of the ingredients
is not especially critical to the preparation of the
composition, although it is preferred to mix the
heteropolysaccharide gum (if employed), the surfac-
tant, the antifoam agent, the freezing point aid,
any preservative employed, any soluble herbicide and
the dispersant with the continuous water phase before
adding the solid propachlor and other sparingly
- soluble pesticide and the anticaking aid. The pre-
paration is carried out at ambient -temperature with
mild agitation, no heat or undue pressure being
required to obtain a homogenous suspension. How-
ever, in order to ensure that the pesticide ingredient
will have the desired average particle size, it is
necessary beforehand to subject the propachlor by
itself or in combination with any of the above men-
tioned ingredients to air milling, hammer milling,
ball milling or other conventional comminuting
treatment known to the art.
.
In combinations of propachlor and most any
of the triazine herbicides previously employed as
wettable powders, e.g., weight ratios of 2 to 3 parts
propachlor per part of triazine have been generally
suitable considering the relative dosage rate of each
to be applied in the control of undesired vegetation.
The same ratios are desirably employed in preparing
a flowable aqueous suspension concentrate of a pro-
pachlor-triazine herbicide mixture according to the
invention.
1~,246A-F -19-
.
:
-
'
-
~ J~ ~
-20-
The criteria set forth above for the pre-
paration of flowable concentrates containing propachlor
only are generally applicable to the preparation of
flowable concentrates of the mixtures. The solids
- 5 should be comminuted during some stage of preparation
of the flowable concentrate to bring the insoluble
solid herbicide to a fineness in the range o~ l to
10 microns average particle size in order that the
solids are rather readily suspended initially.
The problems of propachlor remain because
its solubility is just sufficiently high to create
crystal growth possibilities on storage with atten-
dant settling out and caking and finally dispersibility
problems in the field when tank mixes are prepared.
The triazines of commercial interest are
rather sparingly soluble in water. The principal
triazines of interest include the s-triazine herbicides
atrazine, i.e., 2-chloro-4-(ethylamino)-6-(isopropyl-
amino)-s-triazine, having a reported solubility in
water at 27C of 33 parts per million by weight (ppmw);
cyanazine, i.e., 2-[[4-chloro-6-(ethylamino)-s-triazin-
-2-yl]amino]-2-methylpropionitrile, having a reported
solubility in water at 23C of 160 ppmw and at 25C
of 171 ppmw; propazine, i.e., 2-chloro-4,6-bis(iso-
propylamino)-s-triazine, having a reported solubility
in water at 20C of 8.6 ppmw; cyprazine, i.e., 2-chloro-
-4-(cyclopropylamino)-6-(isopropylamino)-2-triazine,
having a reported solubility in water at 25C of
6.9 ppmw and at 40C of about 195 ppmw; and simazine,
i.e., 2-chloro-4,6-bis(ethylamino)~s-triazine, having
a reported solubility in water at 20C of 5 ppmw and
at 85C of 84 ppmw;`and the as-triazine metribuzin,
. .
18,246A-F -20-
.
,. . . , ~. , ~.. ; . ,, ~ .
..
-21-
i.e., 4-amino-6-tert-butyl~3-(methylthio)-as-triazin-
-5(4H)one ha~ing a water solubility at 20C of
1220 ppmw.
Any of the triazine herbicidal compounds
of commercial utility, such as the foregoing, and
other sparingly soluble broadleaf herbicides may be
combined with propachlor in the weight ratios indicated
and in the preparation of an aqueous flowable sus-
pension concentrate according to the invention and
substantially in the manner described above for
flowable concentrates containing propachlor only,
achieving the advantages of stability, i.e., rela-
tive freedom from serious adverse settling and caking
on extended storage, and good dispersibility charac-
teristics on preparing tank mixes, even with hard oralkaline waters.
In preparing a flowable concentrate of
propachlor and triazine mixture, the total amount - - -
of herbicidal solids suspended is in the range of
propachlor solids suspended as described hereinabove.
Thus, a 4 pound gallon of the combination of propachlor
and a triazine suitably contains, by way of illustration
2.88 pounds of propachlor and 1.12 pounds of triazine,
such as atrazine, in one embodiment and 3 pounds of
propachlor and 1 pound of triazine in another embodiment.
Similarly, a 5 pound gallon of the combination
of propachlor and a triazine such as propazine suitably
contains, by way of illustration, 3.6 pounds of pro-
pachlor and 1.4 pounds of propazine.
In preparing a flowable concentrate of pro-
pachlor and at least one other broadleaf herbicide
18,246A-F 21-
.:
' ! ' .
"
;. '' ' ~' ~:
~' ' ~ ' ' . ' ' .
; ; ~ ', !
,.'' ' ,"
', ~ " '' : ' ',
, ~ ` '
.~ . ' . '; '
6b~
--22--
wherein a triazine is not included unless there is
more than one additional broadleaf herbicide, the
composition contains at least 30 percent by weight
propachlor and is one in which problems of storage
stability and final dispersibility as a tank mix are
encountered unless prepared according to this invention.
~.
The following examples serve to illustrate
the invention and not to limit the claims thereof.
Example l
A flowable aqueous suspension concentrate
of propachlor is prepared having the following
composition:
~eight
Ingredients Percent
15 Propachlor-tech. grade (95% active) 43.95
Hi-Sil~ 233 hydrated precipitated silica 1.80
Bandy Tan clay 3.59
p-Nonylphenoxy ethoxylated ethanol
sulfate, ammonium salt 2.00
20 Ethoxyiated polyoxypropylene butanol 4.00
Antifoam A~ (dimethylpolysiloxane) 0.25
Kelzan heteropolysaccharide gum
(Galaxy XB~ is equivalent) 0.12
Ethylene glycol 5.00 -
25 Polyfon H~ lignosulfonate salt 1.00
Water Balance
.
18,246A-F -22-
.' ' : ' . " ' ' ', '" ' ` , ` ' ~ ' '
"'`~ . ~ '' i '`, ''. '
-23-
In general, it is preferred to add the pre-
scribed amounts of surfactant and ethylene glycol,
such as those set forth above, to the water. This is
followed by the lignosulfonate salt and the antifoam
ingredient. The heteropolysaccharide gum is normally
added as a 2 percent by weight aqueous solution pre-
viously prepared or premixed. The foregoing ingre-
dients are all added while mixing of the composition
continues and with continued agitation, the clay,
silica and propachlor are incorporated into the
solution. This homogenous composition or suspension
is then subjected to one of the conventional com-
minuting treatments known in the art, preferably
sand milling, to assure that the propachlor solid
will have the desired average particle size pre-
ferably between 1 and 10 microns average diameter.
The so-prepared composition appears grayish
opaque in color. It has a Brookfield viscosity at
23C of 1100 to 1200 cps as determined at 10 rpm. The
pH is in the range of 5.5 to 6.5. The specific gravity
is 1.15 grams per cc. The concentration of the pesti-
cide is 4 pounds active ingredient per gallon.
The formulation is of quite thin consistency
and pours easily. When poured into water it exhibits
excellent bloom spreading out uniformly into the water
and good dispersibility, i.e., no settling of solids.
The medium particle size of the propachlor is 4 to 8
microns with 98~2 percent being less than 20 microns
average diameter. Upon dilution of 1 part formulation
concentrate per 99 parts water (alkaline 300 ppm
water and 100 ppm, 500 ppm and 1000 ppm calcium hard-
ness, respectively) there is less than 0.1 milliliter
of sediment after one hour in each of the ~ilutions
18,246A-F -23-
.
. . , :'- :: ;: - '
.
-24-
so prepared. Redispersibility of sediment after 24
hours was good. The formulation shows good physical
and chemical stability under accelerated tempera~ure
storage at 50C. After more than three months storage
at 50C, the formulation shows no significant loss
in the active assay, only little liquid separation
which readily redisperses to a homogenous suspension
on shaking, no gelling, sediment or tendency to
agglomerate or become thixotropic. The formulation
has passed 10 freeze-thaw cycles (two per week) with
no lumps, agglomeration or sediment visible, very
little liquid separation which easily redisperses
on shaking to a free-flowing homogenous suspension.
Example 2
15 A flowable aqueous suspension concentrate
of propachlor was prepared having the ~ollowing
composition:
Weight
Inaredients Percent
-
20 Propachlor-tech. grade (about 95% active)57.9
Hi-Sil~ 233 precipitated silica 2.23
Bandy Tan Clay 2.23
p-Nonylphenoxy ethoxylated ethanol
sulfate, ammonium salt 2.0
25 Ethoxylated polyoxypropylene butanol 4.0
Antifoam A~ 0.2
Polyfon H~ sodium lignosulfonate 1.5
Ethylene glycol 3.0
Water Balance
18,246A-F -2~-
.
~, .
~25-
On preparation of the foregoing composition
in a manner similar to that described for Example l,
the following physical properties were noted:
The so-prepared composition appears grayish
opaque in color. It has a Brookfield viscosity at
23C of 3100 cps as determined at 10 rpm. The pH
is in the range of 5.5 to 6.5. The specific gravity
is 1.114 grams per cc. The concentration of the
pesticide concentration is 5.22 pounds active ingre-
dient per gallon.
The formulation pours easily and when pouredinto water exhibits excellent bloom. ~he median par-
ticle size of the propachlor is well within the range
of 1 to 10 microns. Upon dilution of l part formula-
tion concentrate per 99 parts water in several testsusing water of 100 to lQ00 ppm calcium hardness, there
is less than 0.1 milliliter of sediment after one
hour in each of the dilutions prepared.
The formulation on accelerated temperature ;
20 storage at 50C for more than three months showed no ,
significant loss in the active assay, only little
liquid separation which readily redispersed to a
homogenous suspension on shaking, no gelling, sedi-
ment or tendency to agglomerate or become thixotropic.
The formulation has passed 10 freeze-thaw cycles
(two per week) with no lumps, agglomerate or sediment
- visible, very littie liquid separation which easily
redispersed on shaking to a free-flowing homogenous
-suspension.
18,246~-F -25-
.
; "~ ::~.. ': ' '' ~. '
.. . . : , :~ :: :- . .
: ., , : ~ - , . :: ....
-26-
Examples 3 and 4
Flowable aqueous suspension concentrates of
propachlor were prepared according to the invention
from a purified grade propachlor using substantially
the procedure of Example 1 wherein comminution is
carried out using a ceramic kall mill with ceramic
balls for 24 hours. Each concentrate contained by
weight 0.12 percent Galaxy XB~ heteropolysaccharide
gum with an average molecular weight greater than
200,000; 0.2 percent Polyfon H~ sodium lignosulfonate;
0.45 percent Dow-Corning Antifoam B~, an alkylpoly
siloxane; 2 percent of Steol~ 4N sodium lauryl ether
sulfate and 2 percent of Terric~ 200 polyalkylene
oxide (ethylene oxide-propylene oxide) copolymer of
nonylphenyl, 41.8 percent by weight propachlor, 5 per-
cent by weight ethylene glycol; in addition to anti-
caking agent and the balance water. The antical~ing ,
agent used in the proportions thereo~ are set forth
in Table 1, along with "initial viscosity" values.
"I~itial viscosity" values are determined
when the concentrate is freshly prepared. If the
initial viscosity does not fall within the range of
about 20 to about 3500 as determined at about 25C
with a Brookfield Viscometer, Model RVT (No. 3
spindle - 10 rpm), the composition, especially if
somewhat more viscous, may be stable and redispersible
but is sufficently hard to handle to be of little or
no commerical interest and is therefore outside the
scope of this invention.
Test portions of each of the compositions
of Examples 3 and 4 remained satisfactory after being
subjected to 10 freeze-thaw cycles in one test and
18,246A-F -26-
.: . - -
-, . .
a.3
27-
to at least three months accelerated storage at 50C,
showing little or no settling and exhibiting ready
dispersability in water to a dilution of 1 to 99 by
volume.
18,246~-F -27-
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- . ~ : : ; :~ ; . ~
--28--
m ^
~ o o
,1 o o
:~ o ,
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,, _
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o
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rl ,
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18, 246A-F -2 8-
.
` . ,. : '........ , ' . , . `, . , ., :`.. :: ~ ' :
-29-
Similar ~ine results like those achieved
in Examples 3 and 4 are obtained using Hi-Sil~ 233
alone in place of Bandy Tan clay in the amounts there
employed.
Examples 5-8
Flowable aqueous suspension concentrates of
propachlor were prepared according to the invention
from a purified grade propachlor using substantially
the procedure of Example l and wherein the comminution
to 1-10 microns was carried out using a ceramic ball
mill with ceramic balls and milling for 24 hours to
reduce the propachlor particle size to an average
value in the range of 1 to lO microns. Each concen-
trate contained, by weight, 41.8 percent propachlor,
3.53 percent Bandy Tan clay, 1.77 percent Hi-Sil~ 233
precipitated hydrated silica, 0.45 percent Dow-Corning
Antifoam C~, 0.20 percent Polyfon H~, 0.12 percent
Galaxy XB~ xanthan gum, 5 percent ethylene glycol,
a trace of preservative, 4 to 6 percent of surfactant,
and the balance water. A comparison composition
containing only nonionic surfactant was similarly
prepared.
` ~ach composition was tested~for dispersibility
by diluting one part concentrate in 99 parts water,
stirring rapidly ~1700 rpm~ for one minute and allowing
to stand undisturbed in a 100 ml graduated tube. The
amount of sedimentation was read in milliliters (ml)
after one hour. In respective tests of each concen-
trate, the 99 parts water contained: 300 ppm caustic,
expressed as ppm Na; lO0 ppm, 500 ppm and lO00 ppm,
respectively Ca++.
18,246A-F -29-
.
, , , , ~ : : . :,. :
, :~ ~ . . : ~ .; .
-30-
The surfactants and the amounts thereof
employed, initial viscosities and pH readings as
well as sedimentation test results are tabulated in
Table 2. A large amount of sedimentation is noted
in the comparison concentrate in which no anionic
surfactant was employed.
Each concentrate was also subjected to
freeze-thaw cycles and accelerated storage at 50C.
Each concentrate appeared satisfactory after 10
freeze-thaw cycles except Example 8 which showed
agglomeration after six cycles. All of the concen-
trates appeared stable after three months accelerated
storage. The concentrate of Example 6 exhibited
slight agglomeration which did not appear to inter-
fere with ready dispersion.
18,246A-F -30-
:
-:. : . : . . " : ;
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--31--
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o o ~ ,1 o o
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o
o o o ' o o
V
V~ N O
oo O ~1 0 0 0
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rl
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O ~ ~ o o o o o
N U O C~1 U) Ll~ Lt) lSl U~
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X O X O ~C X O
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h ~ o d o ~ ~ O
V~ o o o o o o o
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3 3 3-3 3 33
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p~ O S~
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~Z o
18, 246A-F -31-
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: ~: : .: :
:. :. ' :: :~. :
~32--
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U d1
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,~ o
o ~ ~ ~ ,~
" ,, ~ o ~ ~ ,
o ~ o a~
s~ o .c ~ 4
U X ~ ~ o
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U ~ 3
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o I o r~
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v
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o-,, ~ ~ ~ ~ ~
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1~ N 1--l W
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x I o
~ O ~ ~ X U ~ ~,
0 ~1 X
N ~ ~ U~
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fll N t'~ V U~
N O ~
U~ V ~ ~
X -- ~ O
~C O (~ O I 11') 0 0 O
U) O ~ OLl'~
~5 W ~ ~ rl U~
a) U~ ~I N (~S O O U~ O
a) ~ ~ v ~ ~
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3 3 ~ K
~ 18, 246A-F O --32-
... . ........ . ~ . . , ~,. . .. , , . :
. . : ~, .
--. ~ . . . . . :
Example 9
When the comparison run described in Table 2
is repeated using 1.2 percent Polyfon H~ instead of
0.2 percent by weight the suspension concentrate is
stable on storage with freeze-thaw cycles during at
least 12 weeks and the concentrate is readily dis-
persible in hard water at any time during the storage
test.
Examples 10 and 11
Flowable aqueous suspension concentrates of
propachlor were prepared substantially as in Examples
5-3 except that comminution was with an Attritor
operated for 90 minutes at 270-370 rpm using 1/8 inch
diameter 440 C stainless steel balls. Dow-Corning
Antifoam A~ in a proportion of 0.25 percent by weight
was used instead of Antifoam C~, and the amount of
Polyfon H~ in each case was 1.0 percent by weight.
In the case of Example 10, the surfactant
was 2 percent by weight Witcolate~ 1075X plus 4 weight
percent Witconol NS~ 500K, 0.25 percent by weight of
Dow-Corning Antifoam A~ was used in place of iAntifoam
C~, and the initial viscosity at 23C was 1200 cps
and the pH was 6.2.
In Example 11, the same surfactant blend
was used as in Example 10, the initial viscosity was
1100 and the pH was 5.4.
On subjecting both concentrates to the
sedimentation test used in the testing of Examples
5-8, very little sedimentation, 0.01-0.07 ml, was
observed. Samples of both concentrates showed no
.
18,246A-F ~33- -
.
`: :
t ..
7'-~j
-34-
agglomeration or other instability after 10 freeze-
-thaw cycles and were stable and readily dispersible
after three months accelerated storage at 50C.
Example 12
~ flowable aqueous suspension concentrate
of propachlor was prepared as i.n Example 10 except
that the dispersant used was Daxad~ 27 brand sodium
salt of benzoid alkyl sulfonic acid. The initial
viscosity at 23C was 1400 cps and the pH was 5.5.
On subjecting the concentrate to the sedi-
mentation test used in the testing of Examples 5-8,
sedimentation was not mroe then 0.04 ml except in
the case of the 1000 ppm Ca water, in which case
O.25 ml was observed, indicating overall quite good
dispersibility in hard waters.
The concentrate showed good stability after
10 freeze-thaw cycles and also after three months
accelerated storage at 50C.
Similar fine results to the foregoing
examples are obtained using anionic surfactants of
each of the classes set forth hereinabove alone or
in combination with any of the classes of nonionic
surfactants set forth or nonionic surfactants in the
proportions described above with sufficient dispersant
employed.
In each of the examples described above,
the xanthan gum used contained about 1.7 percent
Dowicide A~ preservative to provide about 1000 ppm
preservative in the finished concentrate.
18,246A-F -34-
~ : . . : . . ~ :
35-
Exam~le 13
As an example of flowable aqueous suspension
concentrate of a mixture of propachlor and atrazine,
a composition having the following listed components
was prepared substantially according to Example 1
except that the herbicidal ingredients propachlor
and atrazine were added simultaneously.
ComponentWeight Percent
Propachlor 30.40
10 Hi-Sil~ 233 1.80
Bandy Tan Clay 3.59
Atrazine 11.36
Witconol NS~ 500 K (Witco) 6.00
Antifoam A~ 0.10
15 2% Galaxy XB~-23* 5.89
Daxad~ 27 1.00
Propylene Glycol 4.00
Water + Inerts 35.86
100.00
-*Contains 1000 ppm Dowicide A~ on total
formulatio~ basis. There is 1.7 perce~t
Dowicide A in the 2 percent Galaxy XB~-23.
The resulting composition had initial
viscosities as follows:
4 rpm 2250 cps
10 rpm 1200 cps
20 rpm 775 cps
18,246A-F ~35-
,: c
!
-36-
The specific gravity of the composition was
1.153, thus providing a 4 pound gallon containing
2.9 pounds propachlor and 1.1 pounds atrazine.
The composition is stable on long storage
and is readily dispersible in water, including hard
waters.
Example 14
As an example of a flowable aqueous suspen-
sion concentrate of a mixture of propachlor and atra-
zine, a composition having the following listed com-
ponents was prepared substantially according to
Examples 1 and 13.
ComponentWeight Percent
Propachlor 30.40 .
~i-Sil~ 233 1.80
Bandy Tan Clay 3.59
Atrazine 11.36
Pluraflo E~ ~Wyandotte) 6.00
2% Galaxy XB~-23* 0.10
Daxad~ 27 5.89
Antifoam A~ 1.00
Ethylene Glycol 4.00
Water + Inerts 35.86
100 . 00
*Contains 1000 ppm Dowicide A~ on total for-
mulation b~sis. There is 1.7 percent
Dowicide A in the 2 percent Galaxy XB~-23.
18,246A-F ~36-
~: ;
.
:
: .: - : .; : .,.
, ~ - . ~ .
.
~. ~3 7~S
The resulting composition had initial
viscosities as follows:
4 rpm 1875 cps
10 rpm 950 cps
520 rpm 625 cps
The specific gravity of the composition
was 1.154, providing a 9.60 pound gallon containing
2.9 pounds propachlor and 1.1 pounds atrazine.
The composition is stable on long storage
with substantially no settling and very little bleed
and is readily dispersible in water, including hard
waters.
Similarly excellent results compared to
those in Examples 13 and 14 are obtained in sub-
stituting any of cyanazine, i.e., 2-[[4-chloro-6-
-(ethylamino)-s-triazin-2-yl]amino]-2-methylpro-
pionitrile; propazine, i.e., 2-chloro-4~6-bis(isopro-
pylamino)-s-triazine; simazine, i.e., 2-chloro-4,6-
-bis(ethylamino)-s-triazine; cyprazine; or metribuzin
for the atrazine in said examples.
Also similarly excellent results compared
to those in Examples 13 and 14 are obtained on sub-
stituting mixtures of propachlor with any of dicamba,
bifenox, linuron or butoxyethanol ester of 2,4-D with
at least 30 percent by weight propachlor in the con-
centrate for the propachlor-atrazine mixtures as set
forth in the above examples.
.
The composition of this invention, even if
containing a high concentration of propachlor pro-
30 . vides to the routineer an easily flowable formulation
18,246A-F 37-
-38-
which utilizes water as the sole inexpensive dispersion
medium. The present composition has excellent bloom
characteristics, i.e., it is totally dispersible when
added to water, even hard water. It can be diluted
with water in all proportions to provide agglomerate-
free, sprayable pesticide compositions of any desired
toxicant concentration. The propachor particles in
the suspension concentrate substantially do not undergo
crystal growth during accelerated storage for a minimum
of 12 weeks at 50C, so that on undergoing freeze-thaw
cycles for a minimum of 12 weeks the composition sub-
stantially does not settle out. Such a composition is
expected to have a normal shelf life of 18 to 24 months
or more. Preparation of the spray formulation may be
easily accomplished at the application site by simply
pouring an appropriate amount of the concentrated com-
position into water within the spray tank or other
convenient container. It is also possible to apply
the composition in undiluted form, utilizing newer,
specialized spray techniques.
The sprayable, agglomerate-free pesticide
compositions formulated from the present composition
may be applied from all types of presently used spray
e~uipment with no plugging of the spray nozzles or
other malfunction of the spray e~uipment.
18,246A-F -38-
~ , i
-
' - ' ,:'' .'.` ~ :
:"' :', - : -. ~:
.
