Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Aqueous, Herbicidal Means
This invention relates to water-based herbicidal preparations
containing at least one agrochemical agent from the group consisting of
bromoxynil and its derivatives and certain alkoxylated fatty acid esters, to
the use of such fatty acid esters for increasing the penetration of
bromoxynil and its derivatives into plant leaves and to a process for
controlling unwanted plant growth.
It is known that weeds can be controlled with a variety of herbicides
which often have little or no solubility in water. One important
representative is bromoxynil (3,5-dibromo-4-hydroxybenzonitrile) and its
derivatives. Where herbicidal agents such as these are applied,
penetration into the plant is minimal on account of their poor solubility in
water, resulting in an inadequate herbicidal effect. Accordingly,
agrochemical agents of the type in question are formulated as aqueous
dispersions or emulsions so that they can be applied without difficulty, for
example by spraying onto the plants, the emulsifier also acting as a wetting
agent to improve uptake of the agent into the plant. The greater the
penetration of the herbicide, the more effectively and efficiently it can be
used. Accordingly, there is a general need for formulations which provide
for substantially complete penetration of the herbicidal agent into the plant.
DE-OS 29 24 403, for example, describes water-based preparations
containing bromoxynil salts and - as formulation aids - alkali metal salts of
alkyl p olyglycol a ther p hosphate p artial esters. E P 0 485 207 describes
aqueous emulsions containing bromoxynil octanoate and heptanoate and,
as emulsifiers, polyalkylene oxide-modified silanes or ethoxylated tall oil
amides.
It has surprisingly been found that water-based preparations
containing bromoxynil or derivatives thereof and, as emulsifiers, certain
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alkoxylated alcohols provide for very high penetration of the herbicide into
the plant.
Accordingly, the present invention relates to water-based
preparations containing bromoxynil or derivatives thereof and one or more
compounds corresponding to general formula (I):
RO-(C2H40)n(C3H60)m-R' (.l )
in which RO is an alcohol selected from the group of branched or linear,
saturated or unsaturated monohydric alcohols containing 1 to 6 carbon
atoms or polyols containing 2 to 12 carbon atoms and 2 to 6 hydroxyl
groups and R' is hydrogen andlor a group -CO-R", where R" is a branched
or linear, saturated or unsaturated alkyl g roup c ontaining 5 t o 2 9 c arbon
atoms, n is a number of 1 to 50 and m is 0 or a number of 1 to 10.
The preparations according to the invention contain bromoxynil
andlor derivatives thereof, preferably bromoxynil alkyl esters or sodium
andlor p otassium s alts of bromoxynil o r s ulfates a nd c arbonates t
hereof.
Preparations containing bromoxynil octanoate or heptanoate are
particularly preferred.
The alkoxylated compounds corresponding to formula (I) are known
substances which are described, for example, in US 2,678,935, US
3,539,518, US 4,022,808 or GB 1 ,050,497 of which the disclosures are
also part of the present invention.
The compounds corresponding to formula (I) may by prepared by
any methods known to the expert, for example by esterification of fatty
acids with alkoxylated methanol, as described in US 3,539,518.
Unfortunately, this process has certain disadvantages. It is a two-stage
process, the esterification reaction is very time-consuming and the products
are colored by the high reaction temperatures. In addition, fatty acid
methylester ethoxylates produced by this process have relatively high OH
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values after the esterification step which can be problematical for certain
applications. Another possibility is the direct reaction of fatty acid esters
with alkylene oxides in the presence of transition metal catalysts, as
described in US 4,022,808. However, the fatty acid alkyl ester alkoxylates
are preferably produced by the heterogeneously catalyzed direct
alkoxylation of fatty acid alkyl esters with ethylene oxide and/or propylene
oxide on calcined or hydrophobicized hydrotalcites. These synthesis
processes are d escribed i n d etail i n W O 90113533 a nd W O 91!15441 of
which t he d isclosure i s a Iso part of t he present i nvention. T he p
roducts
formed are distinguished by a low OH value, the reaction is carried out in a
single stage and light-colored products are obtained. The fatty acid alkyl
esters used as starting materials may be obtained from natural oils and fats
or may be synthetically produced.
The alkoxylated fatty acid esters contain at least 1 mol ethylene
oxide groups per mol ester. Compounds of formula (I) containing between
1 and 30 mol ethylene oxide per mol ester are preferred. In addition to the
ethylene oxide units, between 1 and 10 propylene oxide groups are also
present in the molecule. Other preferred compounds corresponding to
formula (I) are those which contain between 1 and 30 mol ethylene oxide
per mol ester and 1 to 10 mol propylene oxide groups. For these mixed
ethylene oxidelpropylene oxide adducts, it is possible to use both
compounds reacted with a mixture of ethylene oxide and propylene oxide
and compounds reacted with ethylene oxide and p ropylene oxide in two
separate steps. The alkoxides are statistically distributed between the OH
groups present, depending on the production process.
If compounds corresponding to formula (I) containing polyols as the
alcohol component RO are used, the quantitative data for the ethylene or
propylene oxide units (indices n and m) are always based on the molecule
as a whole. However, the exact distribution of the ethylene or propylene
oxide units between the various hydroxyl groups of the polyols is known to
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comply with a distribution dependent on the synthesis process.
The f atty acid esters -CO-R" contain alkyl groups R" with 5 to 29
carbon atoms. Suitable fatty acid components are natural or synthetic fatty
acids, more particularly straight-chain, saturated or unsaturated C~3o fatty
acids, including technical mixtures thereof obtainable by lipolysis from
animal and vegetable fats and oils, for example from coconut oil, palm
kernel oil, soybean oil, sunflower oil, rapeseed oil, cottonseed oil, fish
oil,
bovine tallow and lard; special examples are caprylic, capric, lauric,
lauroleic, myristic, m yristoleic, p almitic, p almitoleic, oleic, elaidic,
arachic,
gadoleic, behenic and erucic acid.
Suitable alcohol components RO are linear or branched, saturated
or unsaturated monohydric alcohols containing 1 to 6 carbon atoms, for
example methanol, ethanol, n- and i-propanol, n- and i-butanol, pentanol,
hexanol, 2-ethylhexanol and cyclohexanol. Suitable C2_6 polyols are, for
example, ethylene glycol, 1,2-propylene glycol, 1,2-butylene glycol, glycerol
or trimethylol propane and pentaerythritol.
Basically, all the hydroxyl groups of the alcohols are substituted by
the alkoxides although not all terminal alkoxide groups are capped by ester
groups. Accordingly, if polyols, such as glycerol or ethylene glycol, are
used as the alcohol component RO, the preparations may contain
compounds corresponding to formula (I) obtained by reaction both of the
full esters and of the partial esters with alkoxides. However, preferred
compounds of formula (I) are those in which all the hydroxyl groups of the
alcohols a re alkoxylated and all terminal alkoxide groups are capped by
ester groups with the formula -CO-R". Accordingly, in these preferred
compounds, R" in formula (I) stands exclusively for a branched or linear,
saturated or unsaturated alkyl group containing 5 to 29 carbon atoms.
In addition, alkoxylated fatty acid esters corresponding to formula (I)
of which the fatty acid component is selected from linear, unbranched C~~a
fatty acids and of which the alcohol component is methanol, the esters (I)
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preferably containing between 1 and 3 mol propylene oxide and between 1
and 6 mol ethylene oxide per mol ester, are preferably used in the
preparations according to the invention. Compounds such as these can be
obtained, for example, by the above-described reactions of palmitic,
5 stearic, oleic, linoleic or linolenic acid, lauric acid and myristic acid or
esters
thereof with alkoxides.
Also suitable are alkoxylated compounds where the alcohol
component is glycerol and the fatty acid component is selected from
saturated or unsaturated, branched or unbranched fatty acids containing 18
to 22 carbon atoms and the esters contain between 1 and 3 mol ethylene
oxide per mol ester. Compounds of formula (I) in which n is 5, 10 or 30 and
m is 0 are particularly preferred. Compounds such as these can be
obtained, for example, by reacting glycerol esters of natural fatty acids,
such as, for example, palm oil, rapeseed oil, soybean oil or preferably
castor oil, with ethylene oxide.
The compounds of formula (I) present in the preparations according
to the invention are nonionic compounds which may also be characterized
by their HLB value (hydrophilicllipophilic balance according to Griffin's
definition; see Rompp, Lexikon Chemie, 10th Edition 1997, page 1764).
Preferred preparations contain compounds of formula (I) with HLB values
of 4 to 10 and preferably 5 to 9.
The preparations contain at least bromoxynil or derivatives thereof
as herbicides although mixtures with various other herbicides may also be
used. The preparations according to the invention may contain the
herbicide in enriched form, in which case they are formulated as
concentrates containing more than 50% by weight to at most 90% by
weight of herbicidal agent. However, they may also be present i n d flute
form. Preferred preparations contain between 0.01 and 5% by weight of
bromoxynil or derivatives thereof, based on the weight of the preparation.
If the preparations contain other agrochemical agents, they are present in
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quantities of 0.01 to 10% by weight. The percentage water content of the
preparations according to the invention is preferably between 10 and
99.9% by weight. The quantity ratio between the compounds of formula (I)
and the herbicidal agents is preferably between 1:1 and 1:100. Particularly
preferred preparations are those in which the ratio by weight between the
compounds of formula ( I) a nd t he herbicidal a gents is in the range f rom
1:10 to 1:80 and more particularly in the range from 1:2 to 1:5.
Besides bromoxynil and its derivatives and the compounds of
formula ( I), t he water-based p reparations a ccording to t he i nvention may
contain other typical ingredients and additives. These include solvents,
such as ethylene or propylene glycols and C~_6 alcohols, solid carriers,
such a s I ignin, I ignin d erivatives o r c lays a nd o they k nown a
mulsifiers or
dispersants. However, preparations containing only emulsifiers
corresponding to formula (I) and no other emulsifiers or dispersants are
particularly preferred. Most particularly preferred preparations are those
which are free from colloids, such as titanium dioxide, andlor free from
solvents, more particularly mineral-oil-based solvents.
The preparations a ccording to the invention are stable in storage,
even at temperatures above 30°C, and can be produced without intensive
shearing, for example by manual stirring. The preparations according to
the invention are formed without intensive shearing, for example by simple
manual stirring. To this end, the compounds of formula (I) may be initially
introduced into a mixing vessel, for example in liquid form. The herbicidal
agent is then added and the resulting mixture is dispersed in water. If
compounds of formula (I) with melting points above room temperature are
used, they may be used in molten form. However, compounds
corresponding to formula (I) with a melting point below 25°C are
preferably
used. Alternatively, a mixture of the agrochemical agent in water may also
be prepared in a first step and the mixture thus prepared may be
subsequently emulsified or dispersed by addition of compounds
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corresponding to formula (I).
The present invention also relates to a process for controlling
unwanted plants in which a water-based bromoxynil-containing preparation
as described in the foregoing is applied to the leaves of the plants by any
method known to the expert in such quantities that the plants die off.
The present invention also relates to the use of compounds
corresponding to formula (I) for increasing the penetration of bromoxynil or
its derivatives into plant leaves.
Examples
Six aqueous bromoxynil Na salt emulsions were prepared. They
were either free from emulsifiers or contained known emulsifiers and were
compared with a preparation according to the invention containing as
additive a compound corresponding to formula (I) in which RO = glycerol,
R' = COR" with R" = C~s_~8, m = 0, n = 30.
The emulsifiers were present in quantities of 0.5% by weight, based
on the preparation as a whole. The concentration of the sodium salt of the
bromoxynil was 4.1 mM. Quantities of 0.1 p1 of the water-based
preparations were applied to the first leaves of deadly nightshade.
Penetration into the leaves was measured after 24 hours. The results are
set out in Table 2.
Table 1:
Test Emulsifier
(1 ) -
(2) C$_~o Alkyl (oligo)glucoside
(3) C6_~o Fatty acid methyl ester
+ 3 EO
(4) C6_~o Fatty acid methyl ester
+ 6 EO
(5) Nonylphenol + 10 EO
(6) Triglyceride according to the
invention
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Table 2:
Test Penetration after 24
h in
(1 ) 0
(2) 2
(3) 22
(4) 56
(5) 42
(6) 82
The results show the increase in the penetration of bromoxynil
achieved by adding the preparations according to the invention.
