AU617893B2 - Solid herbicidal preparations - Google Patents

Description

u r I- S F Ref: 106336 FORM COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION 617 8

(ORIGINAL)

FOR OFFICE USE: Class Int Class Complete Specification Lodged: Accepted: Published: 0 I l Priority: Related Art: C. C CCC C C Name and Address of Applicant: Address for Service: Ciba-Geigy AG Klybeckstrasse 141 4002 Basle

SWITZERLAND

Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia

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Complete Specification for the invention entitled: Solid Herbicidal Preparations The following statement is a full description of this invention, including the best method of performing it known to me/us 5845/5 -I 5-17297/1+2/+/MA 1947 Solid Herbicidal Preparations Abstract of the Disclosure The present invention provides a composition comprising ionoxynil and/or bromoxynil in their phenolic form, together with an alkali metal salt of a weak acid.

o o o ooo 0000 0 00 o 0 0 o 0 00 00 0 o oa 6 0 0 o Co6 i 1A- 5-17297/1+2/+/MA 1947 Solid Herbicidal Preparations The present invention relates to Cranular herbicidal compositions of hydroxy benzonitriles (HBN's) namely Ioxynil and Bromoxynil.

00 S These two active ingredients are normally prepared as esters oo a a S° for Emulsifiable Concentrates (EC's) and as alkali metal o" salts for other liquid formulations. The liquid formula- 00 o tions, especially EC's containing esters, are toxic onskin o0 0 contact.

0.00 The HBN salts are soluble in water and this facilitates dispersion of the formulation in aqueous systems. However, 00 a these HBN salts, when processed as a dry powder are extremely o°o"o irritating to eye, nose and throat. Bearing this in mind, the products are difficult to handle and also have theundesirable property of being very difficult to dry andthereooo fore cannot be formulated easily with other water sensitive 0 0 active ingredients.

00 0 o oo S 0 The HBN's in their phenol form do not have the same irritancy or drying problems associated with their salt counterparts.

Unfortunately, they are insoluble in water andcannoteasily be formulated as soluble powders or granules.

The present invention overcomes this problem by formulating the phenolic form of the HBN's with an alkali metal salt which, on addition to water, causes an in situ neutralisation to occur, forming the soluble salts of the HBN's.

°y n i _II I~ 3--C41 2 Accordingly, the present invention provides a composition comprising ioxynil and/or bromoxynil in their phenolic form, together with an amount of an alkali metal salt of a weak acidwhich is preferably that which is stoichiometrically requiredto react with the ioxynil and/or bromoxynil phenol, in orderto form a water-soluble salt thereof.

By weak acid is meant an organic or an inorganic acid with dissociation contant Ka between 10 8 and 10 3 S..i Sodium and potassium ions are preferred as alkali metal o kat:ions.

00 a Suitable salts of weak acids are, for example, acetates, 4400 carbonates, hydrogencarbonates, hydrogenphosphites, dihydrogenphosphates, hydrogenphosphates, nitrites, hydrogensulphites and polycarboxylates such as malonates.

o° o Preferred alkali metal salts of weak acids are sodiumo carbonate, potassiumcarbonate, sodium acetate, sodium malonate and sodium hydrogenphosphite. A very particularly Spreferred alkali metal salt of a weak acid is sodium carbonate.

0 o0 Simple phenolic formulations can be prepared which contain sodium or potassium salts of weak acids. These active ingredients when added to the spray tank will dissolve, leaving solutions of spray liquor. The benefits of using these types of solid formulations are: The less irritant and less moisture sensitive HBN phenols can be used in the preparation.

The formulations in their solid form are very simple in their composition and can be prepared with or without the use of ~----4islil

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or, 0 0 00 0 no o 0 0 00 0 0 00 0 0 0 0 000 0 0 0 00 0 3 wetting or dispersing aids. The formulations can contain water-soluble carriers or fillers.

Compositions according to the present invention also may contain minor amounts of anionic surfactants. Suitable anionic surfactants are polymer- or copolymer-molecules containing hydrophilic groups which are capable of forminganions, for example, polymer- or copolymer-molecules containing carboxyl groups, sulfuric acid ester groups, sulphonic acid groups or phosphoric acid ester groups. Preferred polymer-molecules are polyacrylates, alkali metal salts ofdiisobutylene maleicacid copolymers, ligninsulphonates andcondensed alkyl arylsulphonates. A particularly preferred anionic surfactant is the sodium salt of diisobutylene maleicacid copolymer.

Suitable groups of water-soluble carriers or fillers may be organic andinorganic salts, ureas and sugars. Preferred water-soluble carriers or fillers are ureas and inorganic salts. Particularly preferred water soluble carriers or fillers are inorganic salts, for example sodium sulphate, potassium sulphate, sodium chloride, potassium chloride, sodium nitrate, potassium nitrate and calcium nitrate but in particular sodium sulphate.

The fact that the active ingredients and in many cases the formulation dissolves in the spray tank gives rise to a non sedimenting spray liquor which can be successfully sprayed over an extended period of time.

Because of the solubility of the formulations, fine grinding of active ingredients is unnecessary.

Another method of exploiting these formulations is that they can be granulated to reduce the level of dust which is generally considered as an undesirable property.

I 7 I 1 I 074 4 Granulation of these formulations can be effected using techniques such as compaction, extrusion, agglomeration or spray drying. Compaction granulation involves compressing dry powder components to form solid sheets which are subsequently broken down into granules, using a suitable crusher. Extrusion granulation comprises pressing a paste or wetted powder of the formulation through a screen; the material extruded is then dried and broken down to granules of a convenient size. Agglomeration granulation comprises spraying a liquid, which is usually aqueous, into a fluidized powder. The powder agglomerates, form larger particles which are subsequently dried.

Spray drying granulation involves preparing a solution or suspension of the formulation, and spraying the solution or suspension down a hot column of air. The droplets are thereby dried to form spherical granules. In the case of spray drying, reaction will occur between the HBN phenol andthe oo salt of the weak acid during the preparation of the solution o0 "o or slurry. Consequently, HBN salt will be formed, therefore, during this granulation technique. Salt formationmay also occur, to some extent, during extrusion or agglomeration granulation procedures, when quantities of aqueous medium are 0 0 added prior to, and during granulation respectively. No og detrimental effect is observed on the quality of the formulation.

Another aspect of the formulation of the present invention is the fact that the HBN components can be mixed with other soluble active ingredients such as soluble salts ofchlorophenoxyalkanoic acids i.e. Mecoprop or sulphonylureas e.g.

Triasulfuron. In the case of Triasulfuron, which is a potent herbicide, the solubility increases with increasing pH. It is insoluble at pH 2.5 but has a solubility of 1.5g/l at pH7. However, in view of the hydrolysis of Triasulfuron at low pH-values, pH 5-6 represents an optimum.

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The granules produced in these cases still have the same property of being fully dispersible and soluble once stirred into the spray liquor.

The following Examples further illustrate the present invention.

Examples 1 to 3: Compositions comprising ioxynil and bromoxynil in their phenol form as well as a salt of a weak acid are formulated and have the compositions as set out in Table I.

Table I Component w/w w/w w/w 0 00 0 0 0 00 0 o 0 o 0 0o 0 0 0 0 0 Ioxynil as phenol 30 Bromoxynil as phenol 30 Sodium Carbonate 15 Sodium Sulphate to 100 Sodium salt of maleic acid diisobutylen copulymer 0 2 30 30 20 to 100 0 2 to 100% 0 2 The powdered components are homogenised and then granulated by one of the previously mentioned techniques. The result is water soluble granules that eventually dissolve in the spray liquor.

Example 4: A formulation similar to that of Examples 1 to 3, but containing Mecoprop in salt form, is made up and has the composition set out in Table II.

i 6 Table II Component w/w Ioxynil as phenol Bromoxynil as phenol Mecoprop asTriethanolamine salt Sodium salt of maleic acid diisobutylene copolymer Sodium Carbonate Sodium Sulphate 46.5 to 100 S I 0 oc 00 c 04 r 0000 00I0 0J The powdered components may be homogenised in a suitable blender then granulated by first compacting then sieving to a desirable particle size.

Example 5: The formulation defined in Table III is made up: Table III oa.

o o 000 a o 00) 0 03 Component w/w Triasulfuron Ioxynil as phenol 1 Bromoxynil as phenol Mecoprop as magnesium salt or Triethanolamine salt J Sodium salt of maleic acid diisobutylene copolymer Sodium Carbonate Sodium Sulphate 0.25 46.75 to 100 The formulation is granulated using the technique described in Example 4.

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Claims (4)

1. A herbicidal composition comprising -ionoeynil and/or bromoxynil intheir phenolic form, together with an alkali metal salt of a weak acid.

2. A herbicidal composition according to claim 1 wherein the salt of theweak acid is present in an amount which is at C0 least the stoichiometric amount required to react with the 0 0 ioxynil and/or bromoxynil phenol to form a water-soluble salt o a thereof. 0

3. A herbicidal composition according to claim 1 or 2 wherein 0 00 oo, the alkali metal salt of the weak acid is a sodium or potassium salt of carbonic acid: a polycarboxylic acid or phosphoric acid. qoo 4. A herbicidal composition according to claim 1 substantial- 0 Sly as described with reference to any of the Examples. oo Spray liquor comprising a composition according to any of the preceding claims, dissolved in water.

6. A method of controlling undesired plant.growth at a locus which method comprises applying to said locus an effective amount of a composition according to any one of claims 1 to 4 or of a liquor accordin 7 to claim DATED this NINTH day of OCTOBER 1989 Ciba-Geigy AG Patent Attorneys for the Applicant SPRUSON FERGUSON