Novel agriculturally acceptable formulations of the herbicide N-phosphonomethylglycine (glyphosate) comprising tertiary or quaternary etheramine or etheramine oxide surfactants are provided.
Glyphosate is well known as a highly effective and commercially important herbicide useful for combating the presence of a wide variety of unwanted vegetation, including a agricultural weeds. Glyphosate is conventionally applied as a formulated product dissolved in water to the foliage of annual and perennial grasses and broad leaf plants and the like, is taken up over a period of time into the leaves, and thereafter translocates throughout the plant.
Usually, glyphosate is formulated in commercial compositions in the form of a water-soluble salt. Salts in commercial use include the ammonium salt, alkylamine salts, such as the isopropylamine salt, alkali metal salts, such as the sodium salt, and the trimethylsulfonium salt. However, formulations of glyphosate in its acid form are also used. Typical glyphosate salt formulations include aqueous concentrates, requiring simple dilution and distributions in water for application by the end-user, and water-soluble or water-dispersible dry formulations, especially granules, requiring dissolution or dispersion in water prior to application.
Under most application conditions, the herbicidal efficacy of glyphosate can be significantly enhanced by including one or more surfactants in the composition to be applied. It is believed that such surfactants act partly by facilitating the penetration of glyphosate, a relatively hydrophilic compound, through the rather hydrophobic cuticle which normally covers the external above-ground surfaces of higher plants.
Wyrill and Burnside, Weed Science, Vol. 25 (1977), pp. 275-287, conducted a wide-ranging study of different classes of surfactants as agents for enhancing the herbicidal activity of glyphosate, applied as the isopropylamine salt. They demonstrated that the choice of surfactant has a pronounced effect on the herbicidal performance of a glyphosate formulation, but beyond showing a general tendency for surfactants having high values of hydrophile-lipophile balance (HLB) to be more efficacious than surfactants of the same class having low HLB values, they did not observe any predictive relationship between efficacy and surfactant chemical class. Some of the most effective surfactants identified in the Wyrill and Burnside study were ethoxylated tertiary and quaternary alkylamines.
Commercial formulations of glyphosate have frequently used ethoxylated tertiary alkylamine surfactants, for example an ethoxylated tallowamine having an average of about 15 moles of ethylene oxide (EO) per mole of tallowamine. Monsanto Company of St. Louis, Mo. has for many years sold, under the trademark Roundup(copyright) herbicide, glyphosate formulations containing various concentrations of such an ethoxylated tallowamine surfactant.
European Patent No. 0 290 416 to Forbes et al. discloses compositions of glyphosate salts comprising ethoxylated tertiary alkylamine surfactants having less than 15 moles of EO. For example a composition is disclosed comprising the isopropylamine salt of glyphosate and an ethoxylated cocoamine surfactant having an average of 5 moles of EO. It is taught by Forbes et al. that certain herbicidal efficacy advantages are obtainable with such compositions by comparison with compositions where the EO level in the surfactant is around 15 moles.
European Patent No. 0 274 369 to Sato et al. discloses glyphosate compositions comprising ethoxylated quaternary alkylamine surfactants. Several examples are shown wherein the surfactant is an ethoxylated N-methyl cocoammonium chloride surfactant having 2 moles of EO.
A drawback of ethoxylated tertiary alkylamine surfactants of prior art is that when included in concentrate formulations at levels consistent with good herbicidal performance, they tend to be irritant to eyes. In some, but not all, cases, eye irritancy can be reduced by converting the tertiary alkylamine to the corresponding quaternary (N-methyl) alkylamine. U.S. Pat. No. 5,317,003 to Kassebaum discloses that a glyphosate composition containing as the surfactant an ethoxylated N-methyl cocoammonium chloride surfactant having 15 moles of EO is less irritant to eyes than an otherwise identical composition wherein the surfactant is an ethoxylated tertiary cocoamine surfactant having 15 moles of EO.
An alternative solution to the eye irritancy problem is suggested in U.S. Pat. No. 5,118,444 to Nguyen, wherein ethoxylated tertiary alkylamine surfactants are converted to their N-oxides. Examples are shown of glyphosate compositions wherein the surfactant is an ethoxylated tallowamine oxide surfactant having 10, 15 or 20 moles of EO.
A further drawback of ethoxylated tertiary alkylamine surfactants of the prior art is that when water is added to them, they tend to form a stiff gel which adds to the complexity and expense of manufacturing formulations containing such surfactants, by making it difficult to clean vessels and pipes. In practice, this problem is ameliorated by adding an anti-gelling agent, such as polyethylene glycol, to the surfactant.
Never previously disclosed as components of concentrate glyphosate formulations are alkoxylated tertiary or quaternary etheramine or etheramine oxide surfactants. United Kingdom Patent No. 1,588,079 to Texaco Development Corporation discloses examples of ethoxylated alkyloxyisopropylamine and alkylpoly(isopropyl)amine surfactants and methods of preparing them, and suggests they are useful as detergents, dispersants, wetting agents and emulsifiers. Surfactants disclosed have the representative chemical structure 
wherein R1 is C8-C18 alkyl, m is a number from 1 to 5, and x and y are average numbers such that x+y is in the range from 2 to 20.
Tomah Products, Inc. of Milton, Wis. in a brochure titled xe2x80x9cEthoxylated Aminesxe2x80x9d, dated Aug. 22, 1994, disclose, together with a series of ethoxylated tertiary alkylamines, a number of ethoxylated tertiary etheramine surfactants having the representative chemical structure 
wherein R1 is C10-C26 alkyl and x and y are average numbers such that x+y is in the range from 2 to 15. Suggested uses of the Tomah ethoxylated amines include xe2x80x9cagricultural adjuvantsxe2x80x9d, a well-known application of the ethoxylated tertiary alkylamines listed. No suggestion is made that the ethoxylated tertiary etheramines included in the list would have advantages over the ethoxylated tertiary alkylamines as agricultural adjuvants, nor is there any teaching relevant to the making of concentrate glyphosate compositions with ethoxylated tertiary etheramines.
Another brochure from Tomah Products titled xe2x80x9cQuaternariesxe2x80x9d, dated Sep. 1, 1994, includes in a list of quaternary amine surfactants a number of ethoxylated quaternary etheramines having the representative chemical structure 
wherein R1 is an aliphatic group exemplified by isodecyl or isotridecyl and x+y is 2. The list of suggested uses for Tomah""s quaternaries does not include agricultural adjuvants.
Another brochure from Tomah Products titled xe2x80x9cAO-14-2xe2x80x9d, dated Aug. 24, 1994, discloses an ethoxylated etheramine oxide which can be deduced to have the representative chemical structure 
wherein R1 is an aliphatic group exemplified by isodecyl and x+y is 2. The list of suggested uses for AO-14-2 does not include agricultural adjuvants.
It is an object of the present invention to provide novel compositions of glyphosate herbicide containing an etheramine surfactant which imparts good herbicidal efficacy, yet having low irritancy to eyes.
It is a further object of the present invention to provide the commercial formulator of glyphosate with an alternative to ethoxylated alkylamine surfactants that (1) allows elimination or substantial reduction of the need for the use of an anti-gelling agent, (2) is soluble in aqueous formulations having higher glyphosate acid equivalent loadings than prior art formulations having comparable efficacy, and (3) provides herbicidal efficacy superior to that obtainable with comparable amounts of said ethoxylated alkylamine surfactants having similar degrees of ethoxylation.
It is a further object of the present invention to provide concentrate liquid and dry formulations of glyphosate with an etheramine surfactant having good storage stability.
These and other objectives are satisfied by the compositions disclosed herein. defined as an amine surfactant in which the hydrophobe is connected to the amine group via a series of up to about 10 oxyalkylene groups.
Specifically, the etheramine surfactant may be a tertiary amine having the representative chemical structure 
wherein R1 is a straight or branched chain C6 to about C22 alkyl, aryl or alkylaryl group, m is an average number from 1 to about 10. R2 in each of the m (Oxe2x80x94R2) groups are independently C1-C4 alkylene, and x and y are average numbers such that x+y is in the range from 2 to about 60.
Alternatively, the etheramine surfactant may be a quaternary amine having the representative chemical structure 
wherein R1 is a straight or branched chain C6 to about C22 alkyl, aryl or alkylaryl group, m is an average number from 1 to about 10, R2 in each of the m (Oxe2x80x94R2) groups is independently C1-C4 alkylene, R3 groups are independently C1-C4 alkylene, R4 is C1-C4 alkyl, x and y are average numbers such that x+y is in the range from 0 to about 60, and Axe2x88x92 is an agriculturally acceptable anion.
As a third possibility, the etheramine surfactant may be an amine oxide having the representative chemical structure 
wherein R1 is a straight or branched chain C6 to about C22 alkyl, aryl or alkylaryl group, m is an average number from 1 to about 10, R2 in each of the m (Oxe2x80x94R2) groups is independently C1-C4 alkylene, R3 groups are independently C1-C4 alkylene, and x and y are average numbers such that x+y is in the range from 2 to about 60.
Compositions of the invention may be prepared on site by the end-user shortly before application to the foliage of vegetation to be killed or controlled, by mixing in aqueous solution a glyphosate containing composition and a composition comprising a surfactant having a chemical structure encompassed by those represented immediately above. Such compositions of the invention are referred to herein as xe2x80x9ctank-mixxe2x80x9d compositions.
Alternatively, compositions of the invention may be provided to the end-user already formulated, either at the desired dilution for application (xe2x80x9cready to usexe2x80x9d compositions) or requiring dilution, dispersion or dissolution in water by the end-user (xe2x80x9cconcentratexe2x80x9d compositions). Such preformulated compositions of the invention are storage-stable and may be liquid or dry.
A method of use of compositions of the invention to kill or control weeds or other unwanted vegetation is also provided.
Compositions of the invention may contain glyphosate in its acid form. However, because of the relatively low solubility of glyphosate acid in water, more soluble salts of glyphosate are generally preferred. As in commercial compositions of prior art, an especially preferred salt for aqueous compositions of the invention is the isopropylamine salt of glyphosate, while an especially preferred salt for dry compositions of the invention is the ammonium salt. Many other salts may be used either in aqueous or in dry formulations, including but not restricted to alkylamine, such as dimethylamine and n-propylamine, alkanolamine, such as monoethanolamine, alkylsulfonium, such as trimethylsulfonium, and alkali metal, such as sodium and potassium, salts of glyphosate. Regardless of whether acid or a salt is used, it is generally preferred to refer to the amount of glyphosate applied or contained in a formulation in terms of glyphosate acid equivalent, conventionally abbreviated as xe2x80x9ca.e.xe2x80x9d.
Tank-mix and ready to use compositions of the invention are aqueous solutions comprising from about 1 to about 50 g glyphosate a.e./l, occasionally more. A preferred range for tank-mix and ready to use compositions is from about 5 to about 20 g a.e./l.
Concentrate compositions of the invention may be aqueous solutions comprising from about 50 to about 500 g glyphosate a.e./l or more, preferably from about 200 to about 500 g a.e./l and most preferably from about 350 to about 500 g a.e./l. An example of an especially preferred aqueous concentrate composition of the invention contains the isopropylamine salt of glyphosate at about 360 g a.e./l, the same level as is present in commercial compositions being sold as Roundup(copyright) herbicide by Monsanto Company.
A surprising advantage of aqueous compositions of the invention over prior art compositions is that the glyphosate concentration can be increased to very high levels, for example from about 450 to about 500 g a.e./l, yet the surfactant concentration is still adequate to give excellent herbicidal performance without the end-user requiring to add more surfactant in the spray tank. Many such highly concentrated compositions have remarkably good storage stability under a wide range of temperature conditions.
Alternatively, concentrate compositions of the invention may be dry formulations, presented for example in the form of powders, pellets, tablets or, preferably, granules, to be dispersed or dissolved in water prior to use. Typically no water-insoluble ingredients are present at substantial levels in such compositions and the formulations are therefore fully water-soluble. Dry water-soluble or water-dispersible compositions of the invention comprise from about 20% to about 80% weight/weight glyphosate a.e., preferably from about 50% to about 76%, and most preferably from about 60% to about 72%. An example of an especially preferred water-soluble granular composition of the invention contains the ammonium salt of glyphosate at about 72% weight/weight, the same level as is present in commercial compositions being sold as Scout(copyright) herbicide by Monsanto Company.
In dry compositions of the invention glyphosate may itself provide the support for other formulation ingredients, or there may additionally be present one or more inert ingredients providing such support. An example of an inert support that may be used is ammonium sulfate. The term xe2x80x9cdryxe2x80x9d as used herein does not imply that dry compositions are totally free of water; typically dry compositions of the invention comprise from about 0.5 to about 5 percent by weight, preferably less than about 1 percent by weight water.
Dry water-soluble or water-dispersible granular formulations of the invention can be made by any process known in the art, including but not restricted to spray drying, fluid-bed agglomeration, pan granulation, or extrusion. In dry formulations, glyphosate may be present as a salt, for example the sodium or ammonium salt, or as the acid. Formulations containing glyphosate acid may optionally contain an acid acceptor such as an ammonium or alkali metal carbonate or bicarbonate, ammonium dihydrogen phosphate or the like, so that upon dissolution or dispersion in water by the end user a water soluble salt of glyphosate is produced.
What distinguishes compositions of the invention from all previously described glyphosate compositions is the presence therein of an alkoxylated tertiary or an alkoxylated or non-alkoxylated quaternary etheramine or an alkoxylated etheramine oxide surfactant having the representative chemical structure (a) 
wherein R1 is a straight or branched chain C6 to about C22 alkyl, aryl or alkylaryl group, m is an average number from 1 to about 10, R2 in each of the m (Oxe2x80x94R2) groups is independently C1-C4 alkylene, R3 groups are independently C1-C4 alkylene, and x and y are average numbers such that x+y is in the range from 2 to about 60; or (b) 
wherein R1 is a straight or branched chain C6 to about C22 alkyl, aryl or alkylaryl group, m is an average number from 1 to about 10, R2 in each of the m (Oxe2x80x94R2) groups is independently C1-C4 alkylene, R3 groups are independently C1-C4 alkylene, R4 is C1-C4 alkyl, x and y are average numbers such that x+y is in the range from 0 to about 60, and Axe2x88x92 is an agriculturally acceptable anion; or (c) 
wherein R1 is a straight or branched chain C6 to about C22 alkyl, aryl or alkylaryl group, m is an average number from 1 to about 10, R2 in each of the m (Oxe2x80x94R2) groups is independently C1-C4 alkylene, R3 groups are independently C1-C4 alkylene, and x and y are average numbers such that x+y is in the range from 2 to about 60.
Alkylamine or alkylamine oxide surfactants in glyphosate compositions of prior art have no (Oxe2x80x94R2) groups, in other words m=0. We have found that surprisingly improved properties can be imparted to glyphosate compositions when from 1 to about 10 (Oxe2x80x94R2) groups are inserted in the surfactant structure between the R1 group and the nitrogen atom.
Aryl groups, if present in R1, have 5-7, preferably 6, carbon atoms and may or may not be substituted with moieties. The alkyl portion in any alkylaryl group comprising R1 has 1-16 carbon atoms. An example of such an alkylaryl group is alkylphenyl, for example nonylphenyl.
However, in preferred surfactants of the invention R1 is a straight or branched chain alkyl group having about 8 to about 18, for example about 10-15, carbon atoms, and are derived from the corresponding alcohol. For example, the alkyl group may be of natural derivation, such as from coconut or tallow, or may be derived from a synthetic alcohol such as isodecyl, isotridecyl, linear C12-C14 or octadecyl alcohols.
The R2 substituent closest to the nitrogen atom (the proximal R2 group) is in preferred examples a linear propylene (xe2x80x94CH2CH2CH2xe2x80x94), isopropylene (xe2x80x94CH2CH(CH3)xe2x80x94) or ethylene (xe2x80x94CH2CH2xe2x80x94) group. Preferred examples where the proximal R2 group is linear propylene have m=1. Where the proximal R2 group is isopropylene or ethylene, m is preferably in the range from 1 to 5, most preferably from 2 to 3, and all R2 groups are preferably the same.
R3 substituents in preferred examples are independently selected from isopropylene and ethylene. In especially preferred examples all R3 groups are ethylene. In tertiary etheramines and etheramine oxides of the invention it is preferred that x+y is in the range from 2 to about 20. In quaternary etheramines of the invention it is preferred that x+y is in the range from 0 to about 20. A particularly preferred range for x+y in tertiary and quaternary etheramines and etheramine oxides of the invention is from 2 to about 10, more particularly from 2 to about 5.
In quaternary etheramines of the invention R4 is preferably methyl and Axe2x88x92 is preferably a halide, for example chloride or bromide, a phosphate or a sulfate ion, or alternatively may be a glyphosate ion or may be contributed by an anionic surfactant included with the etheramine in the formulation. It will be recognized by those skilled in the art that a low pH, such as may well exist in a glyphosate formulation, tertiary etheramines will most likely be protonated at the nitrogen atom and may be associated with a counterion; in such cases the tertiary etheramine can be represented by the chemical structure shown above for a quaternary etheramine, except that R4 is hydrogen. The counterion Axe2x88x92 in a low pH glyphosate formulation comprising a tertiary etheramine is most likely glyphosate itself.
One especially preferred surfactant useful in compositions of the invention is a tertiary etheramine having R1=C12-C14 alkyl, R2=isopropylene, m=2, R3=ethylene and x+y=5.
Another especially preferred surfactant useful in compositions of the invention is a tertiary etheramine having R1=C12-C14 alkyl, R2=ethylene, m=3, R3=ethylene and x+y=5.
Two other especially preferred surfactants useful in compositions of the invention are tertiary etheramines having R1=isodecyl, R2=linear propylene, m=1, R3 ethylene and x+y=2 or 5 respectively..
Another series of especially preferred surfactants useful in compositions of the invention is a tertiary etheramine having R1=coco alkyl, R2=linear propylene, m=1, R3=ethylene and x+y=a number in the range from 2 to 10.
Two other especially preferred surfactants useful in compositions of the invention are tertiary etheramines having R1=isotridecyl, R2=linear propylene, m=1, R3=ethylene and x+y=2 or 5 respectively.
Two other especially preferred surfactants useful in compositions of the invention are quaternary etheramines having R1=isodecyl or isotridecyl respectively, R2=linear propylene, R3=ethylene, R4=methyl, m=1 and x+y=2.
Any convenient and effective herbicidal activity enhancing amount of the etheramine surfactant can be used in compositions of the invention. In tank-mix and ready to use formulations very high levels of surfactant are achievable. for example up to 5% weight/volume or even higher, but for reasons of economy it will be more normal to use a concentration in the range from about 0.125% to about 2% weight/volume. One of ordinary skill in the art will be able to determine from tests on different plant species an appropriate level of etheramine surfactant to include for any particular glyphosate application.
In concentrate liquid or dry compositions of the invention, the etheramine surfactant is preferably included at a weight/weight ratio to glyphosate a.e. in the range from about 1:20 to about 1:1, most preferably from about 1:10 to about 1:2, for example about 1:6.
Long-term storage stability is an important commercial attribute of concentrate formulations. In the case of aqueous concentrate formulations of glyphosate salts, it is particularly important that surfactants in the formulation do not separate concentrates made with surfactants of prior art show a tendency for phase separation at high temperatures. It is a feature of the etheramine surfactants herein disclosed that they show good compatibility with glyphosate salts, particularly the isopropylamine salt, as evidenced by relatively high cloud points even in aqueous solutions having high glyphosate concentrations. In general for most applications, a cloud point higher than about 50xc2x0 C. is desirable.
In addition to glyphosate or a salt thereof and the etheramine surfactant, any of a variety of further ingredients or adjuvants may be included in formulations of the present invention, as long as such added materials are not significantly antagonistic to the glyphosate herbicidal activity. Examples of such added materials illustratively include anti-gelling agents, antifreezes, thickeners, dyes, antimicrobial preservatives or additives to further enhance herbicidal activity, such as ammonium sulfate or fatty acids.
A second surfactant of a class other than etheramines, for example a primary or secondary alcohol ethoxylate, an alkyl ester of sucrose or sorbitan, or an alkyl polyglucoside, may also be included. When such a second surfactant is present, it is preferable that the weight/weight ratio of etheramine to the second surfactant is greater than about 1:1, most preferably greater than about 2:1, for example around 4:1.
Preferably when a second surfactant is included in a highly concentrated glyphosate formulation of the invention, for example one containing about 450 to about 500 g a.e./l, the etheramine surfactant comprises at least about 75% by weight of the total surfactant present.
Mixtures of glyphosate with other herbicides are also within the scope of the present invention if an etheramine surfactant is included in the formulation. Examples of such other herbicides include bialaphos, glufosinate, 2,4-D, MCPA, dicamba, diphenylethers, imidazolinones and sulfonylureas.
Methods of use of glyphosate formulations are well known to those of skill in the art. Aqueous concentrate formulations of the invention are diluted in an appropriate volume of water and applied, for example by spraying, to the weeds or other unwanted vegetation to be killed or controlled. Dry concentrate formulations of the invention are dissolved or dispersed in an appropriate volume of water and applied in the same way. For most purposes, compositions of the invention are applied at glyphosate a.e. rates in the range from about 0.1 to about 5 kg/ha, occasionally more. Typical glyphosate a.e. rates for control of annual and perennial grasses and broadleaves are in the range from about 0.3 to about 1.5 kg/ha. Compositions of the invention may be applied in any convenient volume of water, most typically in the range from about 50 to about 1000 l/ha.
The present invention is illustrated by but not limited to the following Examples.