CA1154607A - Processes for manufacturing herbicidal formulations - Google Patents

Abstract

Abstract of the Disclosure The invention provides a method of formulating a herbicidal 2,6-dinitroaniline on an agriculturally-acceptable carrier for use in controlling the growth of undesired vegetation. In this method, a 2,6-dinitro-aniline herbicide having a melting point of less than 200°C but more than 25°C is melted. The herbicide is then sprayed on a granular agriculturally-acceptable carrier, such as limestone, having particles which lie in the range from about 8 to about 70 mesh U. S. sieve. The granules are agitated during the spraying step and sufficient of the herbicide is applied to form a granular composition containing from about 1 to about 10 percent of the herbicide by weight.

Description

j ~1S~60 X-5678 -l-'. , ~
'~ ~
4 IM~ROVEMENTS IN OR RELATING TO
s PROCESSES FOR MANUFACTURING
HERBICIDAL FORMULATIONS
7 ~
Dinitroaniline herbicides are well known to those familiar with agricultural chemistry. It is also well known that in order to use these compounds most effectively they must 11 be formulated to ensure ease of handling and uniformity of application. Research has been ongoing in an effort to discover more efficient and less expensive procedures and 14 materidls in which these active agents may be formulated.
A procedure currently being used to formulate these active agents involves dissolving the active agent in a 17 suitable organic solvent and sprayinc1 the solution onto an 18 absorptive carrier. Clay has been the carrier of choice for 19 this procedure.
The present invention relates to a method of 21 formulating a herbicidal 2,6-dinitroaniline on a granular

2' agriculturally-acceptable carrier whereby the 23 2,6-dinitroaniline, for example trifluralin, is melted and 24 sprayed onto the carrier, preferably limestone. The mol~en 25 trifluralin is therefore adsorbed onto the surface of the '6 1 imestone. There are several advantages to this novel 27 invention over prior methods. First, limestone is a less -28 expensive and generally a more readily available carrier than 29 its clay counterpart. Second, since solvent is not necessary 30 to practice the present invention, a substantial monetary 31 savings is realized. There is also the unavoidable fire risk

3~

~ , ,, 6~

associated with the storage of organic solvents. Third, :~ the use of limestone as a carrier creates a more dense granule which permits greater control of the formulation in some application techniques, for example in an aerial application.
According to the invention there is provided a method of formulating a herbicidal 2,6-dinitroanaline having a melting point less than 200C. but more than 25C. on a granular agriculturally-acceptable carrier comprising the ~ ~
: 10 step of spraying the herbicidal 2,6-dinitroanaline in a ;
molten state onto the carrier the particles of which lie in the range from about 8 to about 70 mesh U.S. sieve in a state of agitation to obtain a granular composition containing from about 1 to about 10 percent of the `~ dinitroaniline by weight.
A related invention is claimed in our co-pending Canadian patent application Serial No. 385,707 filed ;`
on September 11, 1981~ ; :
The term "herbicidal 2,6-dinitroaniline" designates any herbicide comprising the 2,6-dinitroaniline structure, typically, such herbicides include substitution on the .
aniline nitrogen and additional substituents on the phenyl : ring. Exemplary herbicidal 2,6-dinitroanilines include the following:
benefin ~N-butyl-N-ethyl-2,6 dinitro-4-trifluoro-s: methylaniline) butralin chlornidine . dinitramine "
,. .. : , ., .

, s~

-2a-ethalfluralin fluchloralin nitralin oryzalin prodiamine profluralin prosulfalin ~.
trifluralin (2,6-dinitro-N,N-dipropyl-4-trifluoro-methylaniline) and the like. ~ ~;
The process of the present invention may be used not only for a ,11 6~7 ~ I
t 2,6-dinitroaniline derivative alone, but also for two or more 3 2,6-dinitroanilines in combination and for a 2,6-dinitroaniline

4 in combination with other solid herbicides. The active agents

5 employed in the present invention are solids at atmospheric pressure and temperature and characteristically possess a 7 melting point which is less than 200C but more than 25C.
x They should be capable of being melted and should remain 9 relatively stable while in molten form.
1o The carriers used in the present process can be adsorptive or absorptive and should be agriculturally-acceptable; examples of adsorptive carriers include limestone, 3 sand, gypsum, cement and the like. Examples of absorptive 4 carriers include clay, fertilizer and the like. Limestone is the carrier of choice. The carrier îs preferably sieved

6 through wire meshed screens before being used in the present ' 17 process in order to ensure proper particle size. It has been `! 18 found that such sized particles are rnore uniformly coated with 19 the molten herbicidal 2,6-dinitroaniline and also contribute to the assurance of acceptably sized particles of the formulated 21 product. Suitably sized particles of unformulated carrier may 22 be in the range of from about 8 mesh to about 70 mesh U. S.
23 sieve. Preferred sieve size is 30/60 mesh.
,~ The exact percentage of the herbicidal ' 25 2,6-dinitroaniline present in the composition prepared ~6 according to the present invention will vary somewhat with the 27 identity of the carrier and identity and quantity of the anti-caking agent. Generally, the composition should contain 29 from about l to about lO percent of the 2,6-ainitroaniline by 30 weight. When the 2,6-dinitroaniline is trifluralin, the 3~ especial1 prefer ed c~ncentration rf the ac i e ag~n in t~-6~7 , composition should be from about 2 to about 8 percent by weight. Typica11y~ as the amount of anti-caking agent added to 1 the admixture is increased, the higher the concentration of the 5 active ingredient which can be supported on the surface of the 6 granule. Also, it has been found that the more porous the

7 surface of the carrier, the higher the concentration of the ~ `
active that can be adsorbed onto it.
The process of the present invention used to formulate n a herbicidal 2,6-dinitroaniline is described below.
ll The 2,6-dinitroanilines employed in the present l~ invention are liquified by apparatuses well known to the art.
13 The active agents which have melting points below 100C. are 14 preferably melted by steam in a melt tank. Melt tanks are s typically stainless steel and come in assorted sizes. Nearly 16 any vessel that is capable of being pressurized may be used in 17 this process. After the active has reached a liquid state, the 18 tank is pressurized, typically by forcing air into it.
19 Suitable pressures for spraying may range from 5 to 50 pounds ~o oer square inch with preferred pressures ranging from 10 to 30 ~l pounds per square inch depending on the type and temperature of the molten active.
23 The molten herbicidal 2,6-dinitroaniline is preferably ~4 sprayed onto the carrier in a state of agitation, which is 25 readily practiced by known methods and apparatuses. Suitable -;~
~6 types of mixers include a Munson*mixer (Munson Mill Machinery 27 Co.; Utica, New York)~ coating pan mixer, cement mixer, ~8 mini-tumbler~ ribbon blender, or the like. Preferably, the ~9 mixing is done in a Munson*mixer. Within this type of mixer is generally contained a spray bar onto which from 1 to 20 spray 3l nozzles may be attached depending on the size of the mixer.
3~
* Tradelrark g~
Il s67a , The height of the spray bar above the stationary bed of 3 carrier, the number and type of spray nozzles, and pressure of 4 the molten spray are all important factors in assuring the s uniformity of active agent on the carrier.
6 The height of the spray bar suspended above the 7 stationary bed of carrier and the number and type of nozzles should be adjusted in an effort to minimize the amount of 9 oversize produced by this process. The term "oversize", as 1o used herein, refers to the amount of commercially less 11 acceptable formulated product which is obtained after the final 1~ product is sieved following processing. Generally, this ;-13 material will not pass through a U. S. sieve size 8 mesh, and 14 characteristically possesses the 2,6^dinitroaniline on its 15 surface at concentrations of l5% to 20% active or greater. In 16 practicing this invention it is preferable to minimize the 17 production of oversize.
18 It has been found that oversize is minimized when the 19 distance from the spray nozzle to the bed of carrier is from ~o about 4 to about 40 inches in height. The spray nozzles used z1 are well known in the art and include those series designated as 6500 and 8000, for example, as manufactured by Spraying 3 Systems Co., Wheaton, Illinois. These designations represent a ~1 65 or 80 angle, respectively, created by the molten 25 2,6-dinitroaniline as it exits the spray orifice. The nozzle ~6 of choice has been found to be those designated as 8000, ~1 particularly 8003 and 8004. The number of nozzles varies ~8 ~epending on the quantity of carrier to be formulated and size 29 of mixer used to perform this novel process. For example, it 30 has been discovered that using a 4.25 cubic meter Munson*mixer 31 ¦ containing a level bed of limestone weighing about 2725 kg., 3~ l .
¦ * Trademark t~ 11 Il .
- :-, " ~ :

I
, the preferred process conditions for formulating the 3 2,6-dinitroaniline benefin are that the spray pressure should 4 be 20 pounds per square inch. There should be six spray s nozzles of the type designated 8003 located about 9 inches apart on two separate spray arms, one arm being 18 inches above 7 the bed of limestone with the other arm placed 15 inches above the bed, said latter arm being suspended 40 inches from the top of the .~unson*mixer. Following spraying the admixture is usually agitated for an additional period of from about 2 to 1l about 7 minutes.
~, Anti-caking agents are preferably used in the process 13 of the present invention to prevent agglomeration of the formulated product, thereby improving its flowability.
Agriculturally-acceptable anti-caking agents found useful in 16 this novel process include the various attapulgites, 17 diatomites, fullers earths, montmorillonites, vermiculites, 18 bentonites, kaolinites, pyrophyllites, talcs, synthetics and 19 the like. Of these, the diatomites are the anti-caking agents of choice, with the Celatom~ (Eagle-Picher, Cincinnati~ Ohio) 21 being preferred. Another preferred anti-caking agent is the 1 -22 synthetic Micro-Cel (Johns-Manville Products Corp., New York, New York). However, as noted below in Experiment 3, it is not ,~ always necessary to add an anti-caking agen' to the 2s formuiation. When used, the anti-caking agent may be present ~6 in from about 0.1 to about 10 percent by weight of the ,7 admixture, preferably from about 1 to about 5 percent by ~ -28 weight. The anti-caking agent may be added to the mixer before 2g or after spraying the molten active agent onto the carrier.

30 Generally, the anti-caking agent is added to the mixer 31 containing the formulated admixture and agitated until 3~ l ¦¦ * Trademark ~ 11 Il . , - - .

- 1 ~1~46 I .
uniformly dispersed throughout. The preferred mixing time 3 usually ranges from about 1 to about 5 minutes in length.
4 An additional step may be employed following the novel s process disclosed in the present invention which in~olves 6 sieving the formulated herbicide to ensure proper particle 7 size. Typically, the oversize is removed with 8 to 14 mesh

8 wire screens; however, slightly larger or smaller screens may `

9 be used depending on the herbicidal 2,6-dinitroaniline. It is `
lo also desired to remove the smaller particles as well, and this l~ is typically done using a wire meshed screen containing 1, approximately 60 squares per inch. Again, slightly larger or 3 smaller screens may be used. This preferred range of particle l4 sizes has been discovered to give the most uniform distribut~on Is when applied to the area for which weed control is aesired.
16 The fol10wing experiments further illustrate this 1 7 invention.
l8 Experiment 1 19 A 4.25 cubic meter Munson mixer was charged with ~o 3328.97 kg. of 20/60 mesh limestone. To a melt tank was added Zl 190.97 kg, of 95% pure technical trifluralin, which was heated 7 to a temperature of about 82C. With the mixer rotating, the molten trifluralin was sprayed onto the limestone using 8 spray t4 nozzles of the type designated 8003 E (Spraying Systems Co., 2s Wheaton, Illinois). The nozzles were placed 13 inches above ~6 the bed of limestone. The spray pressure was 24 pounds per 7;~ square inch and the spray time was approximately 29 minutes.
28 The material was allowed to mix for 3 additional minutes after 29 spraying, and 108~86 kg. of Celato~ MN-41 (Eagle-Picher, Cincinnati, Ohio) was added in about 40 kg. portions. Six 31 rotations of the mixer occurred while all of the anti-caking 3~
j * Trad~rk I
.

5~6 ,, I
, agent was added. The product was post blended for an ~;
3 additional 5 minwtes and passed over a 10 mesh screen to yield 4 1.59 kg. of oversized material t0.04%). The acceptably sized 5 particles, as determined by assay, contained 4.79% trifluralin 6 by weight.
7 Experiment 2 A 0.85 cubic meter Munson*mixer was charged with 9 464.05 kg. of 30/60 mesh ammonium sulfate fertilizer. To a lo steam heated spray tank was added 23.15 kg. of 98% pure technical trifluralin which was heated to a temperature of l~ about 75C. With the mixer rotating~ the molten trifluralin 13 was sprayed onto the carrier for 10 minutes. The material was allowed to mix for 3 additional minutes and 10.00 kg. of ls Celatom*MN-39 was added. The m;xer was rotated for 3 minutes 16 and the product was sieved to give acceptably sized particles 17 containing trifluralin, as determined by assay, at a 18 concentration of 5.92% by weight.
Experiment 3 A coating pan mixer was charged with 69.0 kg. of 20/60 21 mesh limestone. To a spray tank immersed in a hot water bath ?~ was added 1.91 kg. of 93% pure technical benefin which was ~3 melted to a temperature of about 85C. With the mixer .4 rotat~ng, the molten benefin was sprayed onto the limestone 25 using a hand-held spray line and an 8003 spray nozzle at a '6 pressure of 25 pounds per square inch for 2 minutes. The ~7 material was allowed to mix for about 5 minutes after the ~8 spraying was completed. Finally, the granular product was ~9 sieved through an 8 mesh wire screen to give acceptably sized 30 particles containing benefin, as determined by assay, at a 31 concentration of 2.22% by weight.
3~
* l~ademark 1 ~ 6~

I .
, Experiment 4 3 A 0.85 cubic meter Munson*mixer was charged with 4 450.86 kg. of 30/60 mesh limestone. To a spray tank s approximately 70% immersed in a hot water bath was added 24.34 6 kg. of 98.6% pure technical ethalfluralin, and the active agent was melted ta approximately 65C. With the mixer rotating, the molten ethalfluralin was sprayed onto the limestone using 4 9 spray nozzles, all of the type designated 8004 E, at a pressure of 30 pounds per square inch for 7 minutes. The material was allowed to mix for 3 additional minutes, and 4.80 kg. Celatom*
MN-51 was added. The mixture was post blended for 3 minutes l3 and sieved to give acceptably sized particles containing 14 ethalfluralin, as determined by assay, at a concentration of .22% by weight.
l6 Experiment 5 17 A coating pan mixer was charged with 127.055 kg. of I8 20/60 mesh limestone. To a small spray melt tank immersed in a 19 hot water bath was added 3.66 kg. of 98% pure technical 0 trifluralin and 3.74 kg. of 95% pure technical ethalfluralin.
21 The mixture was melted to a uniform temperature. With the 2~ mixer in operation, the molten combination was sprayed onto the ~3 limestone using a hand-held spray line and an 8003 spray ?4 nozzle. The pressure was about 25 pounds per square inch.
~s Following addition of the molten, the mixture was allowed to ~6 mix for about S minutes. Finally 2.045 kg. of Celatom*MN-41 ~7 was added and mixed for two additional minutes. The final ~8 product was sieved using a 14 mesh wire screen giving ?9 acceptably sized particles containing ethalfluralin, as 30 determined by assay, at a concentration of 2.58~ by weight and 3l trifluralin, at a concentration of 2.56% by weight.

* Trad~3nark ;;

I

Claims (7)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of formulating a herbicidal 2,6-dinitro-analine having a melting point less than 200°C. but more than 25°C. on a granular agriculturally-acceptable carrier comprising the step of spraying the herbicidal 2,6-dinitro-analine in a molten state onto the carrier the particles of which lie in the range from about 8 to about 70 mesh U.S. sieve in a state of agitation to obtain a granular composition containing from about 1 to about 10 percent of the dinitroaniline by weight.

2. The method of Claim 1 wherein the carrier is uniformly sized by having been passed over 10 and 60 mesh screens.

3. The method of Claim 2 comprising the additional step of passing the granular composition over 8 and 60 mesh screens to obtain a uniformly sized granular formulation.

4. The method of Claim 3 wherein the agriculturally-acceptable carrier is an adsorptive carrier.

5. The method of Claim 4 wherein the agriculturally-acceptable carrier is limestone.

6. The method of Claim 4 wherein the herbicidal 2,6-dinitroaniline is 2,6-dinitro-N,N-dipropyl-4-trifluoromethylaniline (trifluralin).

7. The method of Claim 4 wherein the herbicidal 2,6-dinitroaniline is N-butyl-N-ethyl-2,6-dinitro-4-trifluoromethylaniline (benefin).