Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
0050/47012 CA 022~78~4 1998-12-10
"PROCESS FOR THE PRODUCTION OF ALKALINE METAL SALTS AND EARTH ALKALI
METAL SALTS OF ARYLOXY-C -C -ALKALINE CARBOXYLIC"
5 The present invention relates to a process for preparing alkali
metal salts and alkaline earth metal salts of aryloxy-
Cl-C4-alkanecarboxylic acids by reacting the underlying aryloxy-
C1-C4-alkanecarboxylic acids with ~lk~l; metal bases or alkaline
earth metal bases as a melt.
The invention furthermore relates to the salts obt~;n~hle by this
process and the use of salts of this type, which as aryloxy-
Cl-C4-~lkAnecarboxylic acid contain a herbicidal crop protection
15 active compound, for controlling undesired plant growth.
The earlier German Patent Application P 44 46 387.1 discloses a
process for preparing solid, free-flowing, water-soluble salts of
aryloxy-Cl-C4-alkanecarboxylic acids, in which the underlying car-
20 boxylic acids are reacted with a salt-forming base as a melt.
EP-A 238 240 discloses a process in which the acidic form of crop
protection active compounds is continuously reacted with a
Bronsted base in an extruder to give salts of the active com-
25 pounds. Suitable bases are alkali metal hydroxides, alkalineearth metal hydroxides, ammonia and amines.
The products prepared by these known processes, however, show a
marked tendency to absorb moisture from the surrounding air and
as a result to form lumps and/or to deliquesce. In practice, this
leads in particular to the problem that the quality, in particu-
lar the fluidity of these products, continuously decreases in
opened cont~;ners.
35 It is therefore an object of the present invention to provide a
process for preparing alkali metal salts and alkaline earth metal
salts of aryloxy-Cl-C4-alkanecarboxylic acids, which leads to
products which do not have these disadvantageous properties.
40 We have found that this object is achieved by a process for pre-
paring alkali metal salts and alkaline earth metal salts of aryl-
oxy-cl-c4-~lk~necarboxylic acids by reacting the underling aryl-
oxy-Cl-C4-alkanecarboxylic acids with alkali metal bases or alka-
line earth metal bases as a melt, which comprises extruding a
45 mixture of the aryloxy-C1-C4-alkanecarboxylic acid and an at least
stoichiometric amount of an alkali metal base or of an alkaline
earth metal base, which are partially or completely converted to
volatile substances under the reaction conditions.
0050/47012 CA 022~78~4 1998-12-10
We have furthermore found the salts obt~;n~hle by this process
and the use of salts of this type, which as aryloxy-Cl-C4-alkane-
carboxylic acid contain a herbicidal crop protection active com-
5 pound, for controlling undesired plant growth.
Suitable aryloxy-Cl-C4-carboxylic acids are preferably those hav-
ing an action against undesired plant growth (the IUPAC name and
common name are given, cf. "The Pesticide Manual", The British
10 Crop Protection Council, 9th edition, London, 1991), for example:
(Rs)-2-(2~4-dichlorophenoxy)propionic acid (dichlorprop),
R-2-(2,4-dichlorophenoxy)propionic acid (dichlorprop-P,
D-2,4-DP), 2,4-dichlorophenoxyacetic acid (2,4-D), 4-(2,4-di-
chlorophenoxy)butyric acid (2,4-DB), 4-(4-chloro-o-tolyloxy)ace-
15 tic acid (MCPA), 4-(4-chloro-o-tolyloxy)butyric acid (MCPB) and
(R)-2-(4-chloro-o-tolyloxy)propionic acid (mecoprop-P, D-CMPP).
D-2,4-DP, MCPA and, in particular, D-CMPP can preferably be
reacted by the process according to the invention to give extru-
20 dates of their alkali metal or alkalkine earth metal salts.
Particularly advantageous h~n~ling properties are shown bygranules which have been prepared from hygroscopic aryloxy-
Cl-C4-~1kAnecarboxylic acids, e.g. mecoprop-P, by means of the
25 process according to the invention.
Mixtures of two or three aryloxy-Cl-C4-carboxylic acids can also
be employed, for example: dichlorprop-P and 2,4-D; dichlorprop-P
and MCPA; mecoprop-P and 2,4-D; mecoprop-P and MCPA; MCPA and
30 2,4-D; mecoprop-P, dichlorprop-P and MCPA.
Instead of the optically active aryloxy-Cl-C4-carboxylic acids,
their racemates can also be used.
35 It is furthermore possible to combine the aryloxy-Cl-C4-carboxylic
acids with other herbicides: bentazone and 2,4-D; bentazone and
dichlorprop-P; bentazone and mecoprop-P; bentazone and MCPA ben-
tazone and MCPB; bentazone, MCPB and MCPA; bentazone and 2,4-DB;
bentazone and MCPA.
Preferred alkali metal bases and alkaline earth metal bases which
are partially or completely converted to volatile substances un-
der the reaction conditions are acetates which during the reac-
tion yield acetic acid, and formates which yield formic acid, and
45 especially carbonates and hydrogen carbonates (formation of car-
bon dioxide) of alkaline earth metals and in particular of alkali
metals, such as sodium acetate, potassium acetate, sodium
0050/4701Z CA 022~78~4 1998-12-10
formate, potassium formate, preferably sodium carbonate, sodium
hydrogen carbonate and potassium hydrogen carbonate, very partic-
ularly preferably potassium carbonate.
5 Mixtures of the abovementioned alkali metal bases and alkaline
earth metal bases are furthermore also suitable.
The bases according to the invention are employed at least in a
stoichiometric amount, preferably in an excess, and especially in
lO an excess of from l to 40 and very particularly preferably from 2
to 30 mol% based on the aryloxy-Cl-C4-carboxylic acids.
While with an excess of the bases according to the invention oily
products of varying consistency generally result, when using
15 stoichiometric amounts of the bases according to the invention
and very particularly with an excess, products of granular struc-
ture having excellent pourability and storage stability with, at
the same time, good solubility and dissolution rate in water are
obtained.
Volatile substances contained in the starting substances and/or
formed in the reaction, such as water, carbon dioxide, acetic
acid, etc. generally escape from the product during the reaction
25 or, if the product leaves the extruder at a sufficiently high
temperature, additionally thereafter.
The reaction in the extruder can be carried out in the presence
of an entraining agent which assists the escape of the water on
30 evaporation.
Suitable entraining agents are cyclohexane, toluene and petroleum
ether. Low-molecular weight alcohols are preferred, in particular
Cl-C7-alkanols and Cl-C7-alkanediols. Primary, secondary and ter-
35 tiary alcohols are very particularly preferred, such as methanol,ethanol, propanol, isopropanol, n-butanol, isobutanol, tert-
butanol, pentanols, hexanols, heptanols and mixtures thereof.
In a preferred embodiment of the process according to the inven-
40 tion, the molten aryloxy-Cl-C4-AlkAnecarboxylic acid is reacted in
an extruder by intimate mixing with the solid base according to
the invention.
In a further preferred embodiment of the process according to the
45 invention, the solid aryl-Cl-C4-alkanecarboxylic acid is added to
the extruder, where it is melted and reacted with the solid base
according to the invention.
-
-
0050/47012 CA 022~78~4 1998-12-10
The bases according to the invention can also be employed dis-
solved or suspended in the entraining agent.
5 Solid starting substances can be fed to the extruder as such or
made into a paste or dissolved or suspended in a solvent. The
solvents are selected such that volatility thereof to the great-
est extent during the preparation of the extrudates according to
the invention is guaranteed. The solvents preferably used are one
10 or more of the abovementioned entraining agents.
Depending on their physical properties, all starting substances
can initially be premixed before the reaction. A premixture of
liquid and solid products, for example, has the advantage that
prewetting of the solid substances takes place. Favorable flow
properties in the case of the starting substances in general
result therefrom.
20 If flow problems occur during the pr~m;~ing, flow auxiliaries or
antiblocking agents, e.g. calcium carbonate, tricalcium phos-
phate, colloidal silica gel and talc, can be used.
Mechanical aids such as vibrators and stirrers can furthermore be
25 used in the h~n~l;ng of the premixture.
The nature of the extruder in the process according to the inven-
tion does not matter. Single-screw machines, contra- and corotat-
ing, meshing screw machines and multiple shaft extruders are
30 suitable. These appliances are familiar to the person skilled in
the art and therefore need no further explanation (cf., for
example, EP-A-238 240).
Preferred extruders in the process according to the invention are
35 corotating, meshing twin-screw machines.
In the case of hygroscopic or reactive starting substances and/or
products, the extruder is inertized before the reaction, expedi-
ently with nitrogen or carbon dioxide.
The reaction is often complete after less than 3 minutes resi-
dence time of the reaction mixture in the reaction zone of the
extruder.
45 The reaction in the extruder and the subsequent drying of the ex-
trudate can be carried out at normal pressure or at elevated or
reduced pressure and at from 0 to 250~C, in particular from 80 to
-
0050/47012 CA 022~78~4 1998-12-10
150~C.
Depending on the reaction temperature procedure, during the reac-
tion in the extruder the product is obtained in the form of par-
5 ticles or as a plastic mass which can be shaped in a m~nner knownper se.
A procedure is preferably used in which particles of from 0.1 to
5, preferably from 0.1 to 3, cm average diameter are obtained.
If still-volatile substances adhere to them, the extrudates ac-
cording to the invention can otherwise be freed from these by
conventional (drying) processes.
The extrudates prepared by the process according to the inven-
tion, which are based on a herbicidal crop protection active com-
pound of the aryloxy-C1-C4-carboxylic acid chemical class, are
used in the control of undesired plant growth.
For this purpose, they are normally dissolved in water or sus-
pended in water and applied in a manner known per se by allowing
the spray mixtures thus obtained to act on the crop plants, their
habitat and/or their seed. Otherwise, the preparation and the ap-
25 plication of spray mixtures of this type are known to the personskilled in the art tcf. the earlier German Patent Application
P 44 46 387.1), so that closer details thereof are unnecessary.
The process according to the invention is particularly suitable
30 for the preparation of comparatively large particles of aryloxy-
Cl-C4-alkanecarboxylic acids.
Preparation examples
35 In the following, "D + L" is the content of D- + L- isomers of
the particular compound in total. "D : L" designates the ratio of
these isomers.
For the preparation of the extrudates, a corotating, meshing
40 twin-screw machine (ZSK 30 from Werner & Pfleiderer, Stuttgart,
Germany) was used which consisted of 8 separately heatable or
coolable chamber-like zones. In the following, the zones are des-
ignated as "zone 1", Uzone 2", etc., where the starting sub-
stances are intended to enter at zone 1 and to emerge at zone 8.
45 Zone 1 was cooled with water (temperature of the water flowing
out: 38~C). Zone 2 was operated during the entire experimental pe-
riod at 80~C, zones 3 and 4 at 138~C. Zone 4 was furthermore open
0050/47012 CA 022S78~4 1998-12-10
at the top in order that it was possible for volatile substances
and steam formed in the reaction to escape in the form of gas.
Zones 5, 6, 7 and 8 were cooled with water, cooling water outflow
temperatures of 28 (zone 5), 21 (zone 6), 21 (zone 7) and 20~C
5 (zone ô) resulting.
The active compound contents of the products were independent,
inter alia, of the quality of the aryl-Cl-C4-alkanecarboxylic
acids employed, the amounts of base and the residual water con-
10 tent.
Example 1Preparation of the calcium salt of D-4-chloro-2-methylphenoxy-
15 propionic acid (D-CMPP, mecoprop-P)
532 parts (3.O55 mol) of potassium carbonate and 1380 parts-
(6.434 mol) of D-4-chloro-2-methylphenoxypropionic acid (D-CMPP,
mecoprop-P; D + L = 97.6% by weight, D : L = 94.7 : 5.3) were
20 introduced hourly into zone 1 of the extruder at a speed of rota-
tion of 36 rpm by means of belt wagons [sic] equipped with
screws. The extruder was operated for 40 hours, 69 kg of D-CMPP
potassium salt being obtained. D-CMPP was reacted completely in
this experiment to give the potassium salt. The product could be
25 characterized as follows:
Active compound content D + L = 75.3% by weight
Enantiomer ratio D : L = 94.8 : 5.2
30 Water content = 2.3% by weight
The extrudate of the potassium salt of D-CMPP, which cont~;ne~
71.3~ by weight of active compound, obtained in a corresponding
manner consisted of coarse-grained, readily water-soluble gran-
35 ules which could be furt~rmore characterized as follows:
The bulk weight after tamping (method CIPAC MT 169) was 614 g/l.The water content was 2.6% by weight. The grain size of the
water-soluble granules was from 0.25 cm to 2 cm. The product was
40 almost dust-free. On adding to water at 20~C, complete wetting oc-
curred immediately. The product dissolved completely in water
within 2 minutes with stirring to give a solution with 1% by
weight of active compound (method CIPAC MT 174).
45 The water-soluble granules were ground in a mortar to prepare a
comparison sample, and after screening the screened fraction of
<0.02 mm (powder) was used for testing.
0050/47012 CA 022~78~4 1998-12-10
10 g of product were weighed into a Petri dish of diameter 10 cm.
This sample and the comparison sample (powder) were exposed in a
chamber to air of 86 - 96% relative humidity. The measuring tem-
5 perature was 20~C. After 15 minutes in the chamber, the weight in-
crease in the samples and their flow behavior were tested.
Table: Behavior of the potassium salts of D-CMPP prepared accord-
lO ing to the invention in moist air compared to the powder
Water-soluble granules Powder
Grain size (cm) 0.25 - 2 <0.02
15 Weight increase (%) 0.306 0.564
Fluidity free-flowing caked together
Example 2
Preparation of the potassium salt of D-2,4-dichlorophenoxy-
20 propionic acid (D-2,4-DP)
6.1 kg (25.95 mol) of D-2,4-dichlorophenoxypropionic acid
(D + L = 98.8% by weight, D : L = 93.1 : 6.9) were reacted with
25 1.9 kg (13.768 mol) of potassium carbonate in the course of one
hour similarly to Example 1. After operation for a further 2
hours, a total of 22 kg of potassium salt of D-2,4-dichloro-
phenoxypropionic acid of the composition below were obtained:
30 Active compound content D + L = 75.0% by weight
Isomer ratio D : L = 93.1 : 6.9
Water content = 3.6% by weight.
35 Example 3
Preparation of the potassium salt of 2-methyl-4-chlorophenoxy-
acetic acid (MCPA)
S;m;l~rly to Example 1, by reaction of 3.67 kg (18.3 mol) of
40 2-methyl-4-chlorophenoxyacetic acid with 1.33 kg (9.64 mol) of
potassium carbonate, 27 kg of the potassium salt of 2-methyl-
4-chlorophenoxyacetic acid of the following composition were pre-
pared per hour in the course of 6 hours:
45 Active compound content = 74% by weight
Water content = 4.4% by weight.
