Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
This invention relates to a storage-s~able, herbicidally-active composi-
tion in the form of a concentrated aqueous emulsion of one or more
herbicidally ac~ive phenoxyalkanecarboxylic acid esters, and to a process for
the preparation thereoi.
Phenoxyalkanecarboxylic acids are amon~st the most commonly used
herbicides. They are employed in the form of their amine salts and mineral
salts, and also as esters? for example the isopropyl, butyl9 butylglycol or 2-
e~hylhexyl esters. The advantage of the esters is that they penetrate more
rapidly into the plant and accordingly their use is less dependent on the
weather. Their solubility in water is low, but they are soluble in oils, such asdiesel oil, kerosene9 petroleum ether9 xylenes, cyclohexanone, isophorone or
highly refined hydrocarbcns. Usually, the ester is dissolved in one of these
solvents, and an emulsifier is added to the solution, giving a concen-trated,
clear, ernulsifiable solution treferred to as an emulsion concentrate or EC),
which, for field use, is dilu~ed with water, thereby producing an oil-in-water
emulsion.
According to Austrian Patent Specification 307,802 it is also possible
to store pesticides by preparing a very viscous forrnulation of the oil-in-watertype, consisting of active ingredient9 mineral oil, water and formulation
auxiliaries~ which, for application, is inverted before use, by means of an
additive consistirlg of solvent and dispersant, ~ivin~ a mobile water-in-oil
dispersion referred to as an "inverse emulsion".
~oth types of formulation, namely the conventionally used emulsion
concentrate and the very viscous dispersion, however, have serious elisadvanta-
~es, the causes of` which rest wi~h the solvent used. All solvents conventionally
usecl for thls purpose are, like most or~anic solven~s, at least detrimental to
health, but in particular also flammable. Thus, highly purified,predominantly
aliphatic hydrocarbons have a flash point of 40 to 80C., isophorone has a
flash point of 93 C., cyclohexanone has a flash point of 44C. and the most
commonly used xylenes have a flash poin~ o only about 25C.
Accordin~ly, the emulsion concentra~e~ prepared with the aid of these
solvents are also flammable, and in the past there have been a number of fires
in stores of such concentrates, both on ~he manufac~urer's premises and also
on the user's premises.
In contrast to the prior art described above, it has now been found that
by using certain auxiliaries it is possible to produce a storage-stable, hi~hly
concentraeed emulsion of herbicide esters, which is water-based and is
therefore non-flammable and free from solvents detrimental to health. The
ability to use an aqueous medium to produce storage-stable emulsions of
phenoxy-esters is surprising since the esters are somewhat wa~er-soluble7
albeit only slightly, and can therefore undergo hydrolysis.
Accordingly9 the present invention provides a storage-stable herbicid-
ally-active composition comprising a concentrated aqueous emulsion of one or
more herbicidally active phenoxyalkanecarboxylic acid esters in which the
emulsion contains 091 to 5 par~s by wei~ht, referred to ~he completed
emulsion, of one or more oil-soluble emulsifiers which are soluble in the
esters, have an HLa value of 9 to 167 and are selected from fatty acid
polyethylene ~3ycol es~ers, polyethylene ~lycol ethers of fatty alcohols,
polyethylene ~Iycol ethers of glycerides, polyethylene glycol ethers of alkyl-
phenols, polyoxyethylene/polyoxypropylene block copolymers and mixtures of
the said polyetllylene glycol esters, polyethylene glycol ethers or polyethyleneglycol/polypropylene glycol block copolymers with alkylarylsulphonates; and
one or more water-soluble dispersant in an amount of 0,l to 3 parts by weight,
referred to the compieted emulsion selected from the group consisting of
alkali metal salts of single or multiple unsaturated fatty acid taurides or fatty
acid alkyltaurides, in which the amount of herbicidally actiYe ester is 30 to
75 ~6 by weight of the concentrated emulsion, the viscosity of the emulsion is
5d to 3,000 mPa.s9 the drople~ size is l to 5/um and the pH value is 6 to 9.
The concentrated aqueous emulsion of the invention optionally ma~ also
contain one or more conventional anti~reeze a~ents, conventional anti-foam
agents, thickeners or a rnixture thereof~
The highly concentra~ed emulsion according to the invention is prepared
by mixing the ;ndividual reactants or by mixing 2 solutions. Solution I containsthe phenoxyester or phenoxy~esters and an emulsifier soluble in the es~ers,
whilst solution 11 contains a dispersant, dissolved in wa~er, and optionally, anti-
free2e a~ents, thickeners, anti-foam agents or colorants.
Thus, the invention also provides a process for the preparation of a
storage-stable, herbicidally-active composi~ion in the form of a concen~rated
5 emulsion of herbicklally active phenoxyalkanecarboxylic acid esters contai-
ning 30 to 75 % by weight of active compound having a ~iscosity of 50 to 3,000
mPa.s, which comprises preparing a solution I from one or more phenoxyalka-
necarboxylic acid esters and at least one emulsifier which is soluble in the
ester and has an HLB value of 9 to 16, in which the amount of emulsifier is
0,15 ~o lO parts by weight per 100 parts by weight of the solution 1, and mixingsolution I with an aqueous solution Il, whlch contains one or more water-
soluble dispersants, selected from the group consisting of alkali metal salts ofsingle or rmultiple unsaturated fatty acid taurides or fatty acid alkyl tauridesin the amount of 0.2 to 10 parts by weight of dispersant per 100 parts of
aqueous solution 11, and subsequently homogenizing the mixture at a tempera-
ture within the range of 15 to 90C. until the droplet size is 1 to 5/um9 whilemaintaining the pH of the mixture at a value of from 6 to 9 and then dlluting
the homogenizate to the desired final volume.
The emulsifiers which are soluble in the phenoxyesters, i.e. fat-soluble
ernulsifiers, are responsible for the dispersion of the active substance in the
continuous phase. Such emulsifiers, havin~ an HLB ( hydrophilic-lipophilic
balance ) value of 9 to 1~ are fatty acid polyethylene glycol esters, the
polyethylene ~Iycol ethers of fatty alcohols, of monoglycerides or diglycerides
and of alkyl-phenols, and polyethylene glycol~polypropylene glycol block
polymers. The emulsifiers may be used individually, as a mix~ure with one
another or as a mixture with ammoniurn, calcium, magnesium, potassium,
sodiurn Dr zinc salts of alkyl (C~-C24)-benzenesulphonic acids. Fatty acid
polyethylene glycol esters or polyoxyethylene/polyoxypropylene block poly-
mers used to~ether wi~h alkylarylsu1phonates are particularly suitable.
Solution I contains the fat-soluble emulsifiers in a concentration of O.lS
to 10 per cent by weight, per 100 parts of solution I the range of 2 to 4 parts
by weight in solution 3 being particularly preferred. In the composition of ~he
invention, the emulsifier is present in an amount of 0.1 to 5 % by weight,
preferably 1 to 3 % by weight.
The water-soluble dispersant stabilizes the distribution of the disperse
phase, for example through elec~rostatic charging of the particles or through
-- 4 --
other forces which cause repulsion, for example steric hindrance.
llle dispersants used are the alkali metal salts, especial3y ~he sodium
salts, of fat~y acid taurides or fa~y acid alkyl-taurides. Examples s~f such
fatty acids, which are ~requently used in the form of mixtures, are straight-
5 chain or branched saturated or mono- or poly-unsaturated aliphatic carboxylic
acids having about 10 ~o 2Q carbon atoms, such as lauric acid, palmitic acid,
stearic acid, myristic acid and especially oleic acid. The alkyl radical in fat~y
acid alkyl-~aurides is a lower alkyl radical with up to 4 C atoms, especially the
methyl radical~
The dispersants can contain inorganic salts, but it is advantageous ~o
keep ~he salt ccntent low, or avoid any salt content at all.
Solution 11 contains ~he water-soluble dispersant in a concentration of
0~2 to 10 parts by weight, preferably 1 to 3 parts by weight, per 100 par~s of
solution 11. The dispersant concentration in the composition o~ the invention i5 0.1 to 3 % by weight, preferably 0.2 to I % by weight.
Usually, the storage-stable emulsion of the invention is prepared by
preparing an aqueous solution 11 of a dispersant, which soiution optionally
contains anti-freeze agents, anti-foam agents or ~hickeners, and stirring the
liquid phenoxy-ester or phenoxy-esters, containinX the emulsifier dissolved
20 therein, and constituting solution 1, into solution 1I so as to form a homogene-
ous mixture. This stirring-in is effected by means of apparatus which genera-
tes a shearing rate of between 1 o2 and 10 sec 1 in the emulsion. This
corresponds, at high viscosity (3,000 mPa.s~ to shearing stresses of 3.10 to
3.104Pa, for which an apparatus such as a Homorex or Ultra-Turrax or a
25 homo~enizer with a hornogenizing nozzle is suitable. At iow viscosity (50
mPa.s), the stated shearing rates correspond the shearing stresses of 5 to 500
Pa, for which an apparatus such as a vibrator, a low-speed mixer or a
centrifugal pump is suitable. Since the viscosity decreases with increasing
temperature, it is possible also to use a low-speed apparatus if an elevated
30 temperature, approximately from 50 to 90C., is employed. The mixing is
in~ended to produce homogeneous droplet dispersion, with droplet sizes of 1 to
S/um9 preferably of 2 to 3/um, but in addition to the size of the individual
droplets a very narrow size distribution and, at the same time, a low viscosity
of the emulsion are of impcrtance. It is also possible, to put both solutions into
35 a vessel with stirrer and mix subsequently, or to d~se both solutions simultane-
-- 5 --
ously via a suitable rnetering device in~o ~he vessel.
lhe viscosity of ~he concen~rated emulsion is an important factor in itsshelf life. The higher the viscosi~y, ~he better the shelf life. On the o~her
hand, ~oo high a viscosi~y adversely effects the ease of dilution wi~h water and5 the spontaneous dispersibility on use IJsing the concentrated emulsion prepa-
re i according to the inYention, it is possible ~o prepare stable, and at the same
time still easily dilutable, formulations havin~ a YisCosity within the range of50 to 3,000 mPa.s. The best results in respect of dilutability and spontaneous
dispersibility on the one hand, and stability, on the other hand, are achieved at
viscosities of from 500 to 1,500 mPa.s.
Another essential factor in preparing a stable ernulsion is the adjust-
ment of the pH value. For each combina~ion of active :ompound/emulsi-
fier/dispersant there is an optimum pH Yalue a~ which the emulsion is most
stable. This physical stability is bes~ in the alkaline range, but pH values of
about 9 should be avoided, since in this range, on prolonged storage and at
elevated temperature, partial hydrolysis of the ester may commerce. In an
acid medium, pH values of less than 6 are to be avoided, since in this range, onprolon~ed storage, coalescence may occur, i.e. the emulsion increasin~ly
becomes physically unstable. A pH range of 7 to 8 is especially preferred.
The cmposition according to the inven~ion may be prepared with any
herbicidally ac~i~e phenoxyalkanecarboxylic acid esters, used individually or asmixtures with one another9 expecially the esters with alcohols of chain length
C4-C8, for example the octyl esters of 2-(4-chloro-2-rnethylphenoxyl)-propio-
nic acid ~CMPP-acid), (2-methyl-4-chlorophenoxy~acetic acid ~MCPA-acid) or
2 5 2,4,5-trichlorophenoxyacetic acid (2,4,5-T-acid).
Since technical-grade phenoxyalkanecarboxylic acid esters, because of
their method of preparation, usually have a pH value of about 3 (measured in a
10 % strength aqueous dispersion~, the desired pH is obtained by use of a
conventional caustic alkali, for example sodium hyd~oxide or potassium
hydroxide. The pH may be adjusted to ~he desired value during or after
preparation of the emulsion, but it is also possible to use purified neutral
esters, which makes subsequent adjustment of the pH value u nnecessary.
To ensure adequate low temperature stabi~ity, conventional anti-freeze
agents, such as ethylene ~Iycol~ glycerol, urea, ~Iycol ethers or other alcoholsmay be added to the emulsions. Furthermore, it is possible to add known
- ~ -
inor~anic or organic ~hickeners, for examples xan~han gum, sodium polyacryla-
te, carboxymethylcellulose, colloidal silica or swelling clay minerals~ such as
ben~onite, in order to adjust the viscosity to a particular value. To reduce
foaming, anti-foam agents, such as long-chain alcohols, 2-ethylhexallol or
5 cetyl alcohol, high-polymer glycols and especially silicones may be added.
For field use, the concentreated emulsions prepared according to the
invention are diluted with wa~er in exac~ly the same way as the hitherto
customary flammable emulsion concentrates, and may be applied by means oE
the same spraying apparatus.
The Examples which follow describe the preparation, as well as the
chemical and physical stability, of the compositions according to the inven
tion. The technical-grade phenoxyalkanecarboxylic acid esters used conform to
the guideline recommended by the Worlds Health Or~anization The stability
was tested in a storage test, in which a 24-hour temperature cycle between
10C. and +50C. was followed. After storage for a period of 4 weeks, the
following were measured:
1. Change in pH value
2. Consumption of 0.01 N sodium hydroxide solution, in order to restore the
initial pl~.
3. Viscosity change (measured on a Brookfield LVT, viscometer, spindle 2, 6
rpm)
4. Change in the turbidity of a 0.01 % strength emuJsion, correlated with the
change in droplet size (measured by means of a Lange turbidimeter in 100
ml cells).
5. Supernatant liquid, in %
6. Coalescence ~formation of an oily phase)
7. Re-emulsifiability.
The results of the measurements relating to ~he Examples have been
summarized in a table. The resul~s of the measurement show that in none of
~he Examples in question was the change in 1., 2., 3., 4. and 5. more than 10 %
after a storage time of 4 weeks with a 24-hour ternperature cycle between
-10C. and ~50C. No coalescence occurred and any non-coalesced sediment
which might be present was completely re-ernulsifiable.
Example I
Solution 1: 64û ~ of 2,4,5-T-amyl ester, technical gr ~de
-- 7 --
g of fatty acid polye~hylene glycol ester
Solution 11: 5 ~ of Na oleyl-methyl-tauride 195 % stren~th3
~ of ethylene ~Iycol, technical grade
1.3 g of xanthane gum
443 ~ of distilled water.
SQlution 11 was ~aken and ~olu~ion I was stirred into it by means of
Homorex mixer.
After completion of addition, s~irring was continued for 10 minutes at
the highes~ speed, the pH value was then adjusted to 7.2S with half-normal
10 NaOH solution, and the mixture was again stirred briefly.
Example 2:
.. Solution 1: 350 ~ of MCPA-ethylhexyl ester, technical grade
g of fatty acid polye~hylene glycol ester
Solution ll: 2.5 g of the sodium salt of palm kernel fatty acicl
methyl-tauride (30% strength aqueous solution
containing 7% of NaCI)
g of ethylen~ glycol
126 g of distilled water
The method employed was as described in Example 1. The pH value
20 was adjusted to 7.55.
Example 3:
Solution 1: 350 g of 2,4-D-ethylhexyl ester
g of fa~ty acid polyethylene glycol es~er
Solu~ion 11: 2.5 ~ of the sodium salt of a fat~y acid me~hyl
tauride (30% strength a~ueous solution contai-
ning 7% of NaCI, fatty acid = palmitic/stearic
acid)
g of ethylene glycol
151 g of dis~illed water.
The method employed was as described in Example 1. The pH va3ue was
adjusted to 7.6.
Example 4:
Solution 1 350 ~ of MCPA-ethylhexyl ester, technical grade
g of faltty acid polyethylene ~Iyccl ester
~olution 11: 2.5 g of the sodium salt of a fat~y acid tauride
-- 8 -
kontaining inorganic and organk: salts, fatty
acid = lauriclmyristic acid)
g of ethylene glycol
125 8 Of distilled water
The me~hod employed was as described in Example lo The pH value was
adjusted to 7.5.
Example 5O
Solution 1: 350 ~ of CAlPP butylglycol ester
g of fatty acid polyethylene glycol ester
Solution 1l: 2.5 g of Na oleyl methyl tauride (25% strength
aqueous solution)
1~5 g of distllled water
The method employed was as described in Example 1. The pH value was
adjusted to 7.5.
Example 6:
Solution 1: 350 g of 2,4,5-T-amyl ester
g of a mixture of nonylphenyl-polyethylerle oxi-
de, polyoxyethylene/polyoxyp~opylene block
polymer (molecular weight 1,800 to 9,000) and
alkylarylsulfonate
Solution 11: 10 g of Na oleyl methyl tauride t25% strength
aqueous solution)
g of ethylene glycol
130 g of distilled water
I g of antifQam agent (silicone emulsion)
The method employed was as described in Exampie 1. The pH value was
adjus~ed to 3Ø
Example 7:
Solution 1: 350 g of 2,4-D-butyl ester
g of polyoxye~hylene triglyceride and alkylaryl-
sulfonate
Solution 11: iO g of Na oleyl methyl tauride (25% strength
aqueous solution3
g of ethylene glycol
16S g of distilled wa~er
119~76~
.. ~
The method employed was as clescribed in Example l. The pH value was
adjusted ~o 7Ø
Example 3:
Solution ~ 1,200 g ~of 2,4,5~T-ethylhexyl ester, technical grade
S 30 g of fatty acid polyglycol ester
Solution Il: g g sf Na oleyl methyl tauride ~25% strength
aqueous solution)
105 g of ethylene glycol
6 g of xanthan ~um
1,830 g of distilled water
2 g of antifoam ~silicone ernulsion)
1.68 g of NaOH
In a prelirninary experiment, it was established that 0.56 g/li~re of
NaOH are required ~o neutralize the formulation, after which the calculated
5 amoun~ of NaOH tl.68 g) was added to 5Olution 11. Thereupon, Solutions I and II
were fed by means of metering pumps to an apparatus which essentially
consisted of a centrifugal pump with bypass for product recycling and
pressure-maintaining valve at the exit. The optimum droplet distribution was
obtained at a me~ering pump:centrifugal pump feed ratio of l: 15 to 1: 25.
20 The pH value was 7~8.
Example 9:
Solution 1: 4290S g of MCPA-ethylhexyl ester, technical grade
226.6 g of 2,4,5-T-ethylhexyl ester, ~echnical grade
1.2 g of fatty alcohol polyglycol ether
Solution 11: 25 g of Na oleyl methyl rauride ~25% strength
aqueous solution)
~ of ethylene glycol
0.6 g of xanthan gum
321 g of distilled water
Solution 11 was taken, Soiution I was stirred in~o i~ by means of a
Homorex mixer, and the pH of the mixture was adjusted to 8.30 with half-
normal NaOH solution. For further homogenization, the emulsion was forced
through a homogenizing head under a pressure of 90 bar.
_ 10 -
Initial values after 4 weeks' s~orage at -10/~50C
ExamplepH-V21ue Yiscosity Turbidity pH-ValueViscosityTurbidity% of supernatant
in mPa.s in rnPa.s liquid
7,25 1 300 85 ~,~01 ~80 85
2 7,55 75G 84 7jOû 740 86
3 7,60 275 86 6,95 280 80
4 7~50 1 750 88 7,301 580 83 0
7,50 425 82 6,80 400 79 5
6 8,00 ~00 86 7,35 ~5~ 7~ 9
7 ~,00 350 81 ~,50 320 73
7,~0 1 2û0 79 7,00~ 175 71 0 ;~
9 ~.30 ~ 450 88 7,552 200 88 9
