AU2018259149A1 - Herbicidal formulation - Google Patents

Abstract

The invention provides an herbicidal formulation which includes hexazinone and imazapic, the latter in the form of the urea or ammonium salt or a combination thereof. The formulation is a soluble concentrate (SL) and also includes a solvent. The formulation is substantially free of alkylene carbonate and methanol.

Description

Technical Field

The invention described herein relates to an herbicidal formulation. In particular, the invention is directed to a formulation for an herbicide which includes as active ingredients imazapic (5-methyl-2-(4-methyl-5-oxo-4-propan-2-yl-lH-imidazol-2-yl) pyridine-3-carboxylic acid) and hexazinone (3-cyclohexyl-6-(dimethylamino)-l-methyl 1,3,5-triazine-2,4-dione).

Background Art

Agricultural chemical products such as herbicides can undergo chemical and physical changes during storage. The rate at which these changes occur may depend on the nature of the components, the formulation type, the packaging and, notably, the storage conditions, including temperature, light and humidity.

The product may remain fit for use as long as these changes have no adverse effects on application, biological performance, and the safety of operators, consumers and environment. However, in some cases degradation of the active ingredient may occur, reducing efficacy and/or shelf life.

Some soluble concentrate (SL) formulations for herbicides available on the market include propylene carbonate and water, which react to produce small amounts of carbon dioxide on storage, or may contain flammable solvents such as methanol. The emission of CO2 results in the need to use a vented cap to prevent swelling of the storage containers and possible leakage of contents. It has also been found that, with the emission of CO2, crystals may form in the soluble concentrate. For SL formulations based on methanol, the flammability creates greater risk for production, transport, storage and application of the herbicide.

It is an aim of the invention to provide a formulation which overcomes or ameliorates one or more of the disadvantages or problems described above, or which at least provides a useful choice.

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Summary of the Invention

According to one aspect of the invention, there is provided an herbicidal formulation in the form of a soluble concentrate (SL), the formulation including:

an effective amount of imazapic in the form of the urea or ammonium salt, or a combination thereof, an effective amount of hexazinone, and a solvent, wherein the formulation is substantially free of alkylene carbonate and methanol.

In one embodiment, the formulation of the invention may include about 2% to 3% of 10 imazapic. Accordingly, the effective amount of imazapic may be about 22.5 to 27.5 g/L, and preferably about 25 g/L. The formulation may include 12% to 13% hexazinone. Accordingly, the effective amount of hexazinone may be about 118 - 132 g/L and preferably about 125 g/L.

Preferably, the formulation of the invention contains imazapic: hexazinone in the ratio 15 range of 1: 4 to 1: 5. Other ratio ranges may also be applicable, particularly if the formulation of the invention contains one or more further active ingredients. For example, the formulation may have a ratio of 1:2 in those circumstances.

The solvent may be any suitable solvent but is preferably an N-alklyenepyrrolidine solvent. It may include an effective amount of l-methylpyrrolidin-2-one. The solvent 20 may include an effective amount of l-butylpyrrolidin-2-one. The solvent may include a combination of l-methylpyrrolidin-2-one and l-butylpyrrolidin-2-one. In particular, the formulation may include 10% to 11% l-methylpyrrolidin-2-one, and 19% to 20% 1butylpyrrolidin-2-one.

The herbicidal formulation of the invention is in the form of a soluble concentrate (SL). 25 This form lends itself to convenient handling and use and avoids issues associated with dry herbicide products. Herbicides in the form of powder or granules require handling before mixing with water until the solids dissolve before use. As herbicides can often contain toxic substances, the manual handling of herbicides in these circumstances can present a health and safety hazard, and lead to spillage and contamination. In contrast, 30 SL formulations typically only require dilution before use, and can be safer to use.

Typically, the formulation of the invention has a pH balance of less than 7.

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The formulation of the invention may include one or more buffering agents. A buffering agent may be potassium dihydrogen phosphate. A buffering agent may be acetic acid. In one embodiment, the formulation may include 1% to 2% of potassium dihydrogen phosphate. The formulation may further include 1 to 2% of acetic acid.

The formulation may further include water, such as 50% to 60% deionised water.

According to another aspect of the invention, there is provided a method for controlling unwanted vegetation, which method comprises applying an effective amount of a formulation as described above to the unwanted vegetation, to parts of the unwanted vegetation, to seeds of the unwanted vegetation or to the area on which the unwanted vegetation grows. Preferably, the method of the invention is used to control unwanted vegetation in sugarcane and other crops. The method may also be used to manage unwanted vegetation, especially weeds, in other situations. An example is weed management in industrial settings, such as wastelands, around buildings, along fence lines and along railway lines.

Reference throughout this specification to 'one embodiment' or 'an embodiment' means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases 'in one embodiment' or 'in an embodiment' in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristic described herein may be combined in any suitable manner in one or more combinations.

Detailed Description of Preferred Embodiment

In one embodiment, a detailed breakdown of content of the formulation is provided in Table 1 below.

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Table 1: Imazapic - Hexazinone co-formulation

Content g/L	Component	IUPAC Name	Purpose in Formulation	Supplier
25.43	Imazapic Technical 98.3 %	5-methyl-2-(4-methyl5-oxo-4-propan-2-yllH-imidazol-2yl)pyridine-3carboxylic acid	active ingredient	Shandong Cynda Chemical Co., Ltd
126.51	Hexazinone Technical 98.8 %	3-cyclohexyl-6(dimethyl amino)-1methyl-1,3,5 -triazine2,4-dione	active ingredient	Nutrichem Co., Ltd
101.30	NMP	1 -methylpyrrolidin-2one	co-solvent	Marchem Australasia Pty Ltd
198.00	Genagen NBP	1 -butylpyrrolidin-2-one	co-solvent	Clariant Australia Pty Ltd
5.45	Urea	urea	Reactant	Redox Pty Ltd
1.09	Monopotassiu m Phosphate	Potassium dihydrogen phosphate	buffering agent	Redox Pty Ltd
9.76	Ammonia Solution 28%	ammonium hydroxide	reactant	Redox Pty Ltd
1.86	Acetic Acid Glacial	acetic acid	buffering agent	Redox Pty Ltd
558.40	Deionised water	Water	solvent	Recochem Inc.

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Manufacturing procedure for Imazapic - Hexazinone formulation

In one embodiment, the formulation can be manufactured in two parts (Part I and Part II).

In Part I, an imazapic ammonium salt solution is prepared. The constituents of the imazapic ammonium salt solution are provided in Table 2 below.

Table 2: Imazapic Ammonium Salt Solution

Content g/L	Component	Purpose in Formulation
200.00	Deionised water (Paid A)	solvent
5.45	Urea	reactant
1.09	Monopotassium Phosphate	buffering agent
25.43	Imazapic Technical 98.3 %	active ingredient
As required	Ammonia Solution 28 %	reactant
As required	Citric Acid Glacial	buffering agent

The imazapic ammonium salt solution is prepared using a suitable vessel equipped with a stirrer, by first adding Part A of the water and then whilst stirring adding the urea. Whilst continuing to stir, monopotassium phosphate is added, followed by imazapic technical.

The ammonia solution is then charged and stirring is continued until all of the imazapic has completely reacted and dissolved. Whilst the ammonia solution is nominally 28%, the concentration can vary from 10 - 35%. The quantity required for a complete reaction (dissolution) of the imazapic technical is adjusted. Excess ammonia solution, as indicated by neat pH at this point which must not exceed 9.0, should be avoided.

Citric acid is then carefully added until the neat pH is brought into the range 7.0 - 7.5. The imazapic ammonium salt solution (Part I) is put aside and ready for subsequent addition to the hexazinone solution (Part II), prepared as set out below.

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In Part II, a hexazinone solution is prepared and subsequently combined with the imazapic ammonium salt solution prepared in Part I above. The constituents of the hexazinone solution are provided in Table 3 below.

Table 3: Hexazinone solution

Content g/L	Component	Purpose in Formulation
358.40	Deionised water (Part B)	solvent
101.30	NMP	co-solvent
198.00	Genagen NBP	co-solvent
126.51	Hexazinone Technical 98.8 %	active ingredient

The hexazinone solution is prepared in a suitable vessel equipped with a stirrer, by first adding Part B of the water. Whilst stirring, NMP is added, followed by GenagenNBP. As stirring continues, hexazinone technical is added. Stirring is continued for a further 30 minutes until hexazinone technical is completely dissolved.

Whilst, continuing to stir, the previously prepared imazapic ammonium salt solution (Part I) is charged and combined with the hexazinone solution (Part II). Stirring is continued for a further 10 minutes. The content of the active ingredients is tested and can be adjusted as required. The formulation is a clear pale yellow liquid having a pH balance of less than 7. The pH balance of a tested formulation sample (1% v/v dilution) was 6.73.

Preferably, the content of the imazapic ranges between 22.5 to 27.5g/L, and the content of Hexazinone ranges between 118-132 g/L. Testing revealed the content of the active ingredients for the formulation produced using the above method was 26.5 g/L for imazapic, and 127 g/L for hexazinone.

The formulation according to the present invention can be stored in a standard high density polyethylene (HDPE) capped bottle, without the need for venting.

Storage Stability Testing

Studies were undertaken to obtain information on the shelf life of the formulation produced according to the preferred embodiment described above. The APVMA

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Guidelines Generation of Storage Stability Data for Agricultural Chemical Products (Version 2, 22 July 2015) were followed. (APVMA is an abbreviation for Australian Pesticides and Veterinary Medicine Authority, the Australian national registration authority for agricultural and veterinary chemicals.)

In particular, a study was undertaken to examine the effect of accelerated storage on the stability of the product in commercial packaging material.

During the study, a 1000 mL sample of the formulation having nominal 25 g/L of imazapic in the form of an ammonium salt (actual was 26.5 g/L imazapic) and nominal 125 g/L of hexazinone (actual was 127 g/L hexazinone) packaged in a 1000 mL HDPE screw cap bottle (no packaging ventilation) was first analysed, with the results shown in Table 4.

The sample was then placed into a thermostatically controlled oven (VWR Mini Incubator: SNR 0811V1169, sourced from VWR, now Avantor of Radford, PA, USA) and heated to 54 ± 2 °C for a period of 14 days. At the end of this period, the sample was removed from the oven and placed into a desiccation chamber to allow cooling to ambience. The results of the study are set out in Table 5 below.

Imazapic and hexazinone were determined by reversed phase, high performance liquid chromatography (HPLC), using UV detection and external standardisation.

Table 4: Results Summary Table Time Zero (Ambient) Sample

Determination	Method	Acceptable Limits	Analysis	Result
Appearance, Physical State & Colour	Visual	Clear pale yellow liquid	Clear pale yellow liquid	PASS
Odour	Olfactory	Characteristic	Characteristic	PASS
pH l%v/v dilution	CIPAC MT 75.3	6.50-7.50	6.73	PASS
Density @ 20 °C	CIPAC MT 3.2	1.025- 1.045 g/mL	1.036 g/mL @20 °C	PASS

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Determination	Method	Acceptable Limits	Analysis	Result
Solution Stability Standard Water C @ 20 °C	CIPAC MT 41 5.0 mL/100 mL	trace sediment after 30 mins	nil sediment after 18 hrs	PASS
Persistent Foam Standard Water C	CIPAC MT 47.2 10.0mL/200 mL	max 60 mL foam after 1 min	Initial 27 mL After 10 sec 0 mL After 1 min 0 mL After 3 min 0 mL After 12 min 0 mL	PASS
Content Imazapic	QCM-114.03	22.5 - 27.5 g/L	26.5 g/L	PASS
Content Hexazinone	118- 132 g/L	127 g/L	PASS

Table 5: Results Summary Table Accelerated Stability Sample

Determination	Method	Acceptable Limits	Analysis	Result
Appearance, Physical State & Colour	Visual	Clear pale yellow liquid	Clear pale yellow liquid	PASS
Odour	Olfactory	Characteristic	Characteristic	PASS
pH 1% v/v dilution	CIPAC MT 75.3,	6.50-7.50	6.89	PASS
Density @ 20 °C	CIPAC MT 3.2	1.025- 1.045 g/mL	1.040 g/mL @20 °C	PASS
Solution Stability Standard Water C @ 20 °C	CIPAC MT 41 5.0 mL/100 mL	trace sediment after 30 mins	nil sediment after 18 hrs	PASS

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Determination	Method	Acceptable Limits	Analysis	Result
Persistent Foam Standard Water C	CIPAC MT 47.2 10.0mL/200 mL	max 60 mL foam after 1 min	Initial 23 mL After 10 sec 0 mL After 1 min 0 mL After 3 min 0 mL After 12 min 0 mL	PASS
Content Imazapic	QCM-114.03	22.5-27.5 g/L	25.6 g/L	PASS
Content Hexazinone	118 —132 g/L	123 g/L	PASS

No observable degradation, deformation, discolouration or etching of the container or lid was evident after accelerated storage. No odour was detectable emanating from the seal.

The pre-storage weight of the sample formulation was 1103.5 g and the post-storage weight of the sample was 1103.4 g, resulting in a negligible 0.1 g weight difference. It was therefore determined that there was no appreciable weight difference over the 14 day period for the 54 °C storage conditions.

Advantageously, the formulation described above can be stored in a standard HDPE bottle without any ventilation. Test results show that the formulation will remain stable for extended periods of storage without CO2 emission.

The foregoing embodiments are illustrative only of the principles of the invention, and various modifications and changes will readily occur to those skilled in the art. The invention is capable of being practiced and carried out in various ways and in other embodiments. It is also to be understood that the terminology employed herein is for the purpose of description and should not be regarded as limiting.

The term “comprise” and variants of that term such as “comprises” or “comprising” are used herein to denote the inclusion of a stated integer or integers but not to exclude any other integer or any other integers, unless in the context or usage an exclusive interpretation of the term is required.

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Reference to prior art disclosures in this specification is not an admission that the disclosures constitute common general knowledge.

Industrial Applicability

The herbicide formulation of the invention provides a combination of imazapic and hexazinone which exhibits stability and which can be stored in standard packaging without the need for packaging ventilation.

Claims (11)

1. Claims

   1. An herbicidal formulation in the form of a soluble concentrate (SL), the formulation including:

   an effective amount of imazapic in the form of the urea or ammonium salt, or a combination thereof;

   an effective amount of hexazinone; and a solvent, wherein the formulation is substantially free of alkylene carbonate and methanol.
2. 2. The formulation of claim 1, which contains imazapic: hexazinone in the ratio range of 1: 4 to 1: 5.
3. 3. The formulation of claim 1, which contains imazapic: hexazinone in the ratio range of 1:2 together with one or more other active ingredients.
4. 4. The formulation of any one of claims 1 to 3, wherein the solvent is chosen from l-methylpyrrolidin-2-one, l-butylpyrrolidin-2-one and mixtures of 1methylpyrrolidin-2-one and l-butylpyrrolidin-2-one.
5. 5. The formulation any one of claims 1 to 4, which includes one or more buffering agents.
6. 6. The formulation of claim 5, wherein the buffering agent is chosen from potassium dihydrogen phosphate, acetic acid, citric acid and mixtures thereof.
7. 7. The formulation of claim 1 which includes:

   about 25 g/L of imazapic in the form of the urea or ammonium salt, or a combination thereof;

   about 125 g/1 of hexazinone; and

   1 -methylpyrrolidin-2-one and l-butylpyrrolidin-2-one;

   wherein the formulation is free of alkylene carbonate and methanol.

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8. 8. A method for controlling unwanted vegetation, which method comprises applying an effective amount of a formulation as claimed in any one of claims 1 to 7 to the unwanted vegetation, to parts of the unwanted vegetation, to seeds of the unwanted vegetation or to an area on which the unwanted vegetation grows.
9. 9. The method of claim 8, when used to control unwanted vegetation in one or more crops.
10. 10. The method of claim 8, when used to control unwanted vegetation in sugarcane crop.
11. 11. The method of claim 8, when used to control weeds in wastelands, around buildings, along fence lines or along railway lines.