Herbicidal compositions

Details Herbicidal compositions Herbicidal compositions

1999-07-19

2001-06-19

Clardy, S. Mark (Department: 1616)

Plant protecting and regulating compositions

Plant growth regulating compositions

Organic active compound containing

Reexamination Certificate

active

06248695

ABSTRACT:

This invention relates to herbicide formulations, in particular to herbicide compositions comprising N-phosphonomethylglycine (glyphosate) herbicides and alkyldiamine tetraalkoxylate surfactants. The invention also relates to a surfactant composition comprising an alkyldiamine tetraalkoxylate surfactant and an alkyl glycoside or alkylpolyglycoside surfactant and its use with glyphosate herbicides, and to water soluble or water dispersible granules comprising a non-hygroscopic salt of glyphosate and a solid alkyldiamine tetraalkoxylate surfactant.
N-phosphonomethylglycine, commonly known as “Glyphosate”, and its salts are well known non-selective systemic herbicides, first developed in the early 1970s by Monsanto Company. After absorption through the foliage it is rapidly translocated to regions of metabolic activity, including the roots and shoots. It has been found that formulation of glyphosate with some surfactant adjuvants can lead to enhancement of herbicidal activity.
Wyrill and Burnside, Weed Science Vol. 25 (1977), 275-287, conducted a study of the effects of different surfactants on the herbicidal action of glyphosate. Some classes of surfactant were more effective than others in enhancing the herbicidal effect of glyphosate (in particular as a solution of the isopropylamine salt).
Despite this study and subsequent attempts to correlate glyphosate activity enhancement with surfactant structure, the effectiveness of surfactants with glyphosate is variable and difficult to predict.
The most commonly used surfactant adjuvants in glyphosate formulations are the tallow amine ethoxylates. While these surfactants are very effective in enhancing the activity of glyphosate, they have recently been shown to have significant aquatic toxicity. Accordingly in many regions the use of glyphosate compositions comprising tallow amine ethoxylates in proximity to waterways and catchment areas has been severely regulated. In particular it has been shown that about 3 ppm of a standard ethoxylated tallow amine/glyphosate formulation has an acute toxic effect on
Daphnia carinata
according to a standard 48 hour EC
50
test.
It has now been surprisingly found that the use of alkyldiamine tetraalkoxylate as a surfactant in a glyphosate compositions provides glyphosate formulations with activity comparable to the known glyphosate/ethoxylated tallow amine compositions, and which exhibit low aquatic toxicity.
According to a first aspect of the present invention there is provided a herbicide composition comprising N-phosphonomethylglycine and/or a salt thereof and an alkyldiamine tetraalkoxylate surfactant.
As used herein, “glyphosate composition” means N-phosphonomethylglycine as well as any composition or formulation containing a glyphosate herbicide. “Glyphosate herbicide” means any form of glyphosate which in aqueous solution provides glyphosate anions along with suitable cations or glyphosate acid. Glyphosate herbicide includes the isopropylamine salts of glyphosate and other agriculturally acceptable salts of glyphosate such as those disclosed in U.S. Pat. No. 3,799,758.
Examples of such suitable cations are alkali metal cations, for instance sodium and potassium, and ammonium and substituted ammonium cations. The latter include cations derived from primary or secondary amines such as isopropylamine or dimethylamine, and from diamines such as ethylenediamine.
Further, examples of agriculturally acceptable salts of glyphosate are trimethyl-sulfonium salt (“sulfosate”) or aminoguanidine salts as disclosed in EP-A-0 088 180. Because glyphosate has more than one replaceable hydrogen atom, mono- and di-salts are possible, as well as mixtures of such salts. Typical glyphosate salts are the sodium, ammonium and trimethylsulphonium salts as well as the mixed alkylsulfonium salts and trialkyl salts.
It has been found that the surfactant adjuvants of the present invention have an efficacy which is comparable to the standard tallow amine ethoxylates currently in use. This is surprising since the hydrophobe in tallow amine is a mixture of fatty monoamines with a carbon chain link of 16 to 18 units. In contrast the base hydrophobe of the surfactants of the present invention is a diamine of a short C1-C
6
alkyl chain. In addition the hydrophilic portions of the tallow amine contain only ethoxylate whereas the surfactant of the present invention may contain some higher alkoxylate groups.
In addition it would not be expected that the surfactants of the present invention would have a low toxicity profile from their structure. It is also unexpected that the surfactants of the present invention would perform as well as tallow amine as an adjuvant for glyphosate. All that the two hydrophobes have in common is an amine functionality, this amine functionality not having been previously identified as important for suitability for use with glyphosate. It has generally been considered that it is the alkyl chain function which is more important. It was therefore not expected that a short chain diamine would function as well as a long chain monoamine.
On the basis of their structure alkyldiamine tetraalkoxylate surfactants would not be expected to be compatible with the high salt and low pH environment of an aqueous glyphosate composition, and accordingly it is surprising that they are useful adjuvants for glyphosate herbicides.
The term “low aquatic toxicity” is used herein in connection with the surfactants or herbicide compositions of the present invention to refer to an acute aquatic toxicity less than the toxicity of an equivalent composition comprising an ethoxylated tallow amine as the surfactant component. The term also indicates that the toxicity of the surfactant or composition is sufficiently low to satisfy local, regional or national regulations governing the toxicity of surfactants or herbicide compositions in the locality, region or country in which the surfactant or composition is used. The herbicide compositions according to the present invention preferably meet a standard EC
50
or LC
50
test in respect of a suitable indictor organism, for example Daphnia species such as
Daphnia carinata,
at a concentration of 100 ppm, more preferably 300 ppm, and most preferably 1000 ppm.
In addition to the advantages of low aquatic toxicity and efficacy of alkyldiamine tetraalkoxylates as surfactants with glyphosate formulations, they also possess advantages over other surfactants which have been used with glyphosate formulations, such as ease of handling, and a lower foaming profile than some other surfactants currently used.
In a preferred embodiment the alkyldiamine tetraalkoxylate surfactant comprises a compound of formula (I):
wherein Q is a linear or branched C
1
-C
6
alkylene, and each R is independently selected from oxyalkylene polymer or block copolymer chains.
Q is preferably —(CH
2
)
n
— where in n is 2 to 6 or a branched alkylene group having 3 to 6 carbon atoms such as
Most preferably Q is ethylene.
R may be a polymer of an oxyalkylene group such as oxyethylene, oxypropylene or oxybutylene. R may be a block copolymer of two or more different oxyalkylene groups such as oxyethylene, oxypropylene or oxybutylene. It is preferred that R is a block copolymer of oxyethylene and oxypropylene.
The blocks may alternative in the chain. For example compounds of formula (I) may be made by starting with a compound of formula (II):
wherein A is an alkylene group. The compound of formula (II) may then be condensed with an alkylene oxide wherein the alkyl group may be the same or different to A. The resulting compound may be further condensed with a different alkylene oxide and so on to give the final compound.
In a further preferred embodiment, the surfactants of the present invention have the following formula (III):
wherein A and B are different C
2
-C
4
alkylene groups,
R is H or C
1
-C
6
alkyl, and
X and Y are integers from 0 to 150, provided X and Y are not both zero.
Preferably A is propylene and B is ethylene, or A is ethylene and B is propylene.
Where A is propylene and B is ethylene, X is prefer

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