NZ203359A - A storage stable concentrated aqueous emulsion including herbicidally-active phenoxyalkanecarboxylic acid esters,and alkali metal salts of fatty acid taurides/alkyltaurides - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £03359 r\ 203 [Priority Datofs): ... F, Specification FiSod: QXgm: Ms , <?P.&?Z/AL...

Dat<55 , . *8.? ... [p. O. Jtetjfr.-ci Wo: 1 rVTl....

N! iff 23^'il NEW ZEALAND PATENTS ACT, J953 No . Patent of Addition to 198,156 Date: 25 August 1981 it? 22FEB1983, COMPLETE SPECIFICATION STORAGE-STABLE CONCENTRATED EMULSICN OF HERBIdDALLY-ACTIVE PHENOXY-ALKANECAFBOXYLIC ACID ESTERS AND THE PREPARATION THEREOF" */ We, CHEMIE LINZ AKTIENGESELLSCHAFT, an Austrian Body Corporate, of St-Peter-Strasse 25, 4 020 Linz, Austria, hereby declare the invention for which i / we pray that a patent may be granted to jsxe/us, arid the method by which it is to be performed, to be particularly described in and by the following statement:- (followed by page la) ^ ^ ^ *v>.' 1Vv \c\- The present invention relates to a storage-stable, herbicidally-active composition in the form of a concentrated aqueous emulsion of one or more herbicidally active phenoxyalkanecarboxylic acid esters, and to a process for the preparation thereof, which invention is a modification of that described and claimed in Patent Application No. 198,156.

Patent Application No. 198,156 describes and claims a storage-stable herbicidally-active composition, which comprises a concentrated aqueous emulsion of one or more herbicidally active phenoxyalkanecarboxylic acid esters, the emulsion containing 1.01 to 11,1 parts by weight per 100 parts of ester one or more oil-soluble emulsifiers, being soluble in the esters, having an HLB-value of 9 to 16, being selected from fatty acid polyethyleneglycol esters, polyethyleneglycol ethers of fatty alcohols, polyethyleneglycol ethers of glycerides, polyethyleneglycol ethers of alkylphenols, polyoxyethylene/poly-oxypropylene block copolymers and mixtures of the said polyethyleneglycol esters, polyethyleneglycol ethers or polyethyleneglycol block copolymers with alkylarylsulphonates; and one or more ionic or non-ionic water-soluble disper-sants being selected from phosphated alkylarylpolyethylene oxides and ethylene oxide condensates of fatty amines, the herbicidally active ester being present in an amount of 30 to 75 % by weight of the concentrated emulsion, the viscosity of the emulsion being 50 to 3000 mPa.s, the droplet size being 1 to 5^um and the pH value being 4 to 10.

Patent Application No. 198,1 56 also describes and claims a process for the preparation of said storage stable herbicidally active composition, comprising preparing a solution I from one or more phenoxyalkanecarboxylic acid esters and at least one emulsifier being soluble in the ester and having an HLB value of 9 to 16, the amount of emulsifier being I to 10 parts by weight per 100 parts by weight of the solution I, and mixing solution I with an aqueous solution II, containing an ionic or nonionic water-soluble dispersant, in the amount of 0.5 to 5 parts by weight of dispersant per 100 parts of aqueous 2 033 5 solution II, and subsequently homogenizing the mixture at a temperature within the range of 15° to 90°C. until the droplet size is 1 to 5^um, while maintaining the pH of the mixture at a value of from 4 to 10, and then diluting the homogenizate to the desired final volume.

Surprisingly it has now been found, that a comparable or even better storage-stable herbicidally-active composition can be prepared, if water-soluble dispersants, the alkali metal salts of single or multiple unsaturated fatty acid taurides or fatty acid alkyltaurides are used.

Accordingly, the present invention provides a storage-stable herbicid-1 0 ally-active composition comprising a concentrated aqueous emulsion of one or more herbicidally active phenoxyalkanecarboxylic acid esters in which the emulsion contains 0,1 to 5 parts by weight, referred to the completed emulsion, of one or more oil-soluble emulsifiers which are soluble in the esters, have an HLB value of 9 to 16, and are selected from fatty acid 1 5 polyethylene glycol esters, polyethylene glycol ethers of fatty alcohols, polyethylene glycol ethers of glycerides, polyethylene glycol ethers of alkyl-phenols, polyoxyethylene/polyoxypropylene block copolymers and mixtures of the said polyethylene glycol esters, polyethylene glycol ethers or polyethylene glycol/polypropylene glycol block copolymers with alkylarylsulphonates; and 2 0 one or more water-soluble dispersant in an amount of 0,1 to 3 parts by weight, referred to the completed emulsion selected from the group consisting of alkali metal salts of single or multiple unsaturated fatty acid taurides or fatty acid alkyltaurides, in which the amount of herbicidally active ester is 30 to 75 % by weight of the concentrated emulsion, the viscosity of the emulsion is 2 5 50 to 3,000 mPa.s, the droplet size is 1 to 5^um and the pH value is 6 to 9.

The concentrated aqueous emulsion of the invention optionally may also contain one or more conventional antifreeze agents, conventional anti-foam agents, thickeners or a mixture thereof.

The highly concentrated emulsion according to the invention is prepared 20 by mixing the individual reactants or by mixing 2 solutions. Solution I contains the phenoxyester or phenoxy-esters and an emulsifier soluble in the esters, whilst solution II contains a dispersant, dissolved in water, and optionally, antifreeze agents, thickeners, anti-foam agents or colorants.

Thus, the invention also provides a process for the preparation of a 2: storage-stable, herbicidally-active composition in the form of a concentrated 203359 emulsion of herbicidally active phenoxyalkanecarboxylic acid esters containing 30 to 75 % by weight of active compound having a viscosity of 50 to 3,000 rnPa.s, which comprises preparing a solution I from one or more phenoxyalkanecarboxylic acid esters and at least one emulsifier which is soluble in the ester and has an HLB value of 9 to 16, in which the amount of emulsifier is 0,15 to 10 parts by weight per 100 parts by weight of the solution I, and mixing solution I with an aqueous solution II, which contains one or more water-soluble dispersants, selected from the group consisting of alkali metal salts of single or multiple unsaturated fatty acid taurides or fatty acid alkyl taurides in the amount of 0.2 to 10 parts by weight of dispersant per 100 parts of aqueous solution II, and subsequently homogenizing the mixture at a temperature within the range of 15° to 90°C. until the droplet size is I to 5^um, while maintaining the pH of the mixture at a value of from 6 to 9 and then diluting the homogenizate to the desired final volume.

The emulsifiers which are soluble in the phenoxyesters, i.e. fat-soluble emulsifiers, are responsible for the dispersion of the active substance in the continuous phase. Such emulsifiers, having an HLB ("hydrophilic-Iipophilic balance") value of 9 to 16 are fatty acid polyethylene glycol esters, the polyethylene glycol ethers of fatty alcohols, of monoglycerides or diglycerides and of alkyl-phenols, and polyethylene glycol/polypropylene glycol block polymers. The emulsifiers may be used individually, as a mixture with one another or as a mixture with ammonium, calcium, magnesium, potassium, sodium or zinc salts of alkyl (Cg-C2^)-benzenesulphonic acids. Fatty acid polyethylene glycol esters or polyoxyethylene/polyoxypropylene block polymers used together with alkylarylsulphonates are particularly suitable.

Solution I contains the fat-soluble emulsifiers in a concentration of 0.15 to 10 per cent by weight, per 100 parts of solution I the range of 2 to 4 parts by weight in solution I being particularly preferred. In the composition of the invention, the emulsifier is present in an amount of 0.1 to 5 % by weight, preferably 1 to 3 % by weight.

The water-soluble dispersant stabilizes the distribution of the disperse phase, for example through electrostatic charging of the particles or through other forces which cause repulsion, for example steric hindrance.

The dispersants used are the alkali metal salts, especially the sodium salts, of fatty acid taurides or fatty acid alkyl-taurides. Taurides are derived from taurine or 2-aminoethanesulfonic acid of the formula H2NCH2-CH2SO2OH. Fatty acid taurides have fatty acids bound to the nitrogen atom of taurine. Examples of such 203359 fatty acids, which are frequently used in the form of mixtures, are straight-chain or branched saturated or mono- or poly—unsaturated aliphatic car-boxylic acids having about 10 to 20 carbon atoms, such as lauric acid, palmitic acid, stearic acid, myristic acid and especially oleic acid. For example, the sodium salt of palmitic acid tauride has the formula CH3(CH2>i4-C0NHCH2CH2S020Na. Fatty acid alkyltaurides have in addition a lower alkyl radical with up to 4 C atoms, preferably a methyl or ethyl radical. For example, the sodium salt of palmitic acid methyl tauride has the formula CH3(CH2)14CON(CH3)-CH2-CH2-S020Na.

The dispersants can contain inorganic salts, but it is advantageous to keep the salt content low, or avoid any salt content at all.

Solution II contains the water-soluble dispersant in a concentration of 10 0.2 to 10 parts by weight, preferably 1 to 3 parts by weight, per 100 parts of solution II. The dispersant concentration in the composition of the invention is 0.1 to 3 % by weight, preferably 0.2 to 1 % by weight.

Usually, the storage-stable emulsion of the invention is prepared by preparing an aqueous solution II of a dispersant, which solution optionally 1 5 contains anti-freeze agents, anti-foam agents or thickeners, and stirring the liquid phenoxy-ester or phenoxy-esters, containing the emulsifier dissolved therein, and constituting solution I, into solution II so as to form a homogeneous mixture. This stirring-in is effected by means of apparatus which genera- 2 tf. _i tes a shearing rate of between 10 and 10 sec in the emulsion. This 2 corresponds, at high viscosity (3,000 mPa.s) to shearing stresses of 3.10 to if 3.10 Pa, for which an apparatus such as a Homorex or Ultra-Turrax or a homogenizer with a homogenizing nozzle is suitable. At low viscosity (50 mPa.s), the stated shearing rates correspond the shearing stresses of 5 to 500 Pa, for which an apparatus such as a vibrator, a low-speed mixer or a 25 centrifugal pump is suitable. Since the viscosity decreases with increasing temperature, it is possible also to use a low-speed apparatus if an elevated temperature, approximately from 50° to 90°C., is employed. The mixing is intended to produce homogeneous droplet dispersion, with droplet sizes of 1 to 5^um, preferably of 2 to 3^um, but in addition to the size of the individual 30 droplets a very narrow size distribution and, at the same time, a low viscosity of the emulsion are of importance. It is also possible, to put both solutions into a vessel with stirrer and mix subsequently, or to dose both solutions simultaneously via a suitable metering device into the vessel.

The viscosity of the concentrated emulsion is an important factor in its 25 shelf life. The higher the viscosity, the better the shelf life. On the other 2033 5 hand, too high a viscosity adversely effects the ease of dilution with water and the spontaneous dispersibility on use. Using the concentrated emulsion prepared according to the invention, it is possible to prepare stable, and at the same time still easily dilutable, formulations having a viscosity within the range of 50 to 3,000 mPa.s. The best results in respect of dilutability and spontaneous dispersibility on the one hand, and stability, on the other hand, are achieved at viscosities of from 500 to 1,500 mPa.s.

Another essential factor in preparing a stable emulsion is the adjustment of the pH value. For each combination of active compound/emulsi-fier/dispersant there is an optimum pH value at which the emulsion is most stable. This physical stability is best in the alkaline range, but pH values of about 9 should be avoided, since in this range, on prolonged storage and at elevated temperature, partial hydrolysis of the ester may commerce. In an acid medium, pH values of less than 6 are to be avoided, since in this range, on prolonged storage, coalescence may occur, i.e. the emulsion increasingly becomes physically unstable. A pH range of 7 to 8 is especially preferred.

The cmposition according to the invention may be prepared with any herbicidally active phenoxyalkanecarboxylic acid esters, used individually or as mixtures with one another, expecially the esters with alcohols of chain length C^-Cg, for example the octyl esters of 2-(4-chloro-2-methylphenoxyI)-propio-nic acid (CMPP-acid), (2-methyl-4-chlorophenoxy)acetic acid (MCPA-acid) or 2,4,5-trichlorophenoxyacetic acid (2,4,5-T-acid).

Since technical-grade phenoxyalkanecarboxylic acid esters, because of their method of preparation, usually have a pH value of about 3 (measured in a 10 % strength aqueous dispersion), the desired pH is obtained by use of a conventional caustic alkali, for example sodium hydroxide or potassium hydroxide. The pH may be adjusted to the desired value during or after preparation of the emulsion, but it is also possible to use purified "neutral" esters, which makes subsequent adjustment of the pH value unnecessary.

To ensure adequate low temperature stability, conventional anti-freeze agents, such as ethylene glycol, glycerol, urea, glycol ethers or other alcohols may be added to the emulsions. Furthermore, it is possible to add known inorganic or organic thickeners, for examples xanthan gum, sodium polyacryla-te, carboxymethylcellulose, colloidal silica or swelling clay minerals, such as bentonite, in order to adjust the viscosity to a particular value. To reduce 2 033 5 foaming, anti-foam agents, such as long-chain alcohols, 2-ethylhexanoI or cetyl alcohol, high-polymer glycols and especially silicones may be added.

For field use, the concentreated emulsions prepared according to the invention are diluted with water in exactly the same way as the hitherto customary flammable emulsion concentrates, and may be applied by means of the same spraying apparatus.

The Examples which follow describe the preparation, as well as the chemical and physical stability, of the compositions according to the invention. The technical-grade phenoxyalkanecarboxylic acid esters used conform to the guideline recommended by the Worlds Health Organization The stability was tested in a storage test, in which a 24-hour temperature cycle between -10°C. and +50°C. was followed. After storage for a period of 4 weeks, the following were measured: 1. Change in pH value 2. Consumption of 0.01 N sodium hydroxide solution, in order to restore the initial pH. 3. Viscosity change (measured on a Brookfield LVT, viscometer, spindle 2, 6 rpm) 4. Change in the turbidity of a 0.01 % strength emulsion, correlated with the change in droplet size (measured by means of a Lange turbidimeter in 100 ml cells).

. Supernatant liquid, in % 6. Coalescence (formation of an oily phase) 7. Re-emulsifiability.

The results of the measurements relating to the Examples have been summarized in a table. The results of the measurement show that in none of the Examples in question was the change in 1., 2., 3., 4. and 5. more than 10 % after a storage time of 4 weeks with a 24-hour temperature cycle between -10°C. and + 50°C. No coalescence occurred and any non-coalesced sediment which might be present was completely re-emulsifiable.

Solution I: Solution II: 640 Example 1 g of 2,4,5-T-amyI ester, technical grade g of fatty acid polyethylene glycol ester g of Na oleyl-methy 1-tauride (95 % strength) g of ethylene glycol, technical grade < vV' *.-> «!»•* :0 Solution I: Solution II: 350 10 2.5 126 1.3 g of xanthane gum 443 g of distilled water.

Solution II was taken and Solution I was stirred into it by means of a Homorex mixer.

After completion of addition, stirring was continued for 10 minutes at the highest speed, the pH value was then adjusted to 7.25 with half-normal NaOH solution, and the mixture was again stirred briefly.

Example 2: g of MCPA-ethylhexyl ester, technical grade g of fatty acid polyethylene glycol ester g of the sodium salt of palm kernel fatty acid methyl-tauride (30% strength aqueous solution containing 7% of NaCl) g of ethylene glycol g of distilled water The method employed was as described in Example 1. The pH value was adjusted to 7.55.

Example 3: g of 2,4-D-ethylhexyI ester g of fatty acid polyethylene glycol ester g of the sodium salt of a fatty acid methyl tauride (30% strength aqueous solution containing 7% of NaCI, fatty acid = palmitic/stearic acid) g of ethylene glycol g of distilled water.

The method employed was as described in Example 1. The pH value was adjusted to 7.6.

Example 4: of MCPA-ethylhexyl ester, technical grade of fatty acid polyethylene glycol ester of the sodium salt of a fatty acid tauride (containing inorganic and organic salts, fatty acid = lauric/myristic acid) of ethylene glycol of distilled water Solution I: Solution II: 350 10 2.5 151 Solution I: Solution II: 350 10 2.5 g g g 125 g g - 8 1 5 :0 2 5 Solution I: Solution 11: The method employed was as described in Example 1. The pH value was adjusted to 7.5.

Example 5: 350 g of CWPP-butylglycol ester g of fatty acid polyethylene glycol ester 2.5 g of Na oleyl methyl tauride (25% strength aqueous solution) 145 g of distilled water The method employed was as described in Example 1. The pH value was adjusted to 7.5.

Example 6: Solution I: 350 g of 2,4,5-T-amyl ester g of a mixture of nonylphenyl-polyethylene oxi de, polyoxyethylene/polyoxypropylene block polymer (molecular weight 1,800 to 9,000) and alkylarylsulfonate Solution 11: 10 g of Na oleyl methyl tauride (25% strength aqueous solution) g of ethylene glycol 150 g of distilled water 1 g of antifoam agent (silicone emulsion) The method employed was as described in Example 1. The pH value was adjusted to 8.0.

Example 7: 350 g of 2,4-D-butyl ester g of polyoxyethylene triglyceride and alkylaryl sulfonate g of Na oleyl methyl tauride (25% strength aqueous solution) g of ethylene glycol 165 g of distilled water The method employed was as described in Example 1. The pH value was adjusted to 7.0.

Example 8: Solution I: 1,200 g of 2,4,5-T-ethyIhexyl ester, technical grade Solution I: Solution II: 2033 105 6 1,830 2 1.68 g g g of fatty acid polyglycol ester Solution II: 9 g of Na oleyl methyl tauride (25% strength aqueous solution) g of ethylene glycol of xanthan gum of distilled water g of antifoam (silicone emulsion) g of NaOH In a preliminary experiment, it was established that 0.56 g/litre of NaOH are required to neutralize the formulation, after which the calculated amount of NaOH (1.68 g) was added to Solution II. Thereupon, Solutions I and II were fed by means of metering pumps to an apparatus which essentially consisted of a centrifugal pump with bypass for product recycling and pressure-maintaining valve at the exit. The optimum droplet distribution was obtained at a metering pump:centrifugal pump feed ratio of 1:15 to 1 : 25. The pH value was 7.8.

Example 9: g of MCPA-ethylhexyl ester, technical grade g of 2,4,5-T-ethylhexyl ester, technical grade g of fatty alcohol polyglycol ether g of Na oleyl methyl rauride (25% strength aqueous solution) g of ethylene glycol g of xanthan gum g of distilled water Solution II was taken, Solution I was stirred into it by means of a Homorex mixer, and the pH of the mixture was adjusted to 8.30 with half-normal NaOH solution. For further homogenization, the emulsion was forced through a homogenizing head under a pressure of 90 bar.

Solution I: Solution II: 429.5 226.6 1.2 0.6 321

Claims (12)

Initial values Example pH-Value Viscosity Turbidity in mPa.s 1 7,25 1 300 85 2 7,55 750 84 3 7,60 275 86 4 7,50 I 750 88 5 7,50 425 82 6 8,00 600 86 7 7,00 350 81 8 7,80 1 200 79 9 8.30 2 450 88 after 4 weeks' storage at -l0/-t-50°C pH-Value Viscosity Turbidity % of supernatant in mPa.s liquid 7,20 1 280 85 1 7,00 740 86 0 6,95 280 80 2 7,30 1 580 83 0 6,80 400 79 5 7,35 550 78 9 6,50 320 73 8 7,00 1 175 71 0 7,55 2 200 88 9 N) O 04 UJ Ul vQ — I I — 203359 WHAT ME CLAIM IS:

1. A storage-stable herbidically-active composition comprising a concentrated aqueous emulsion of one or more herbicidally active phenoxyalkanecarboxylic acid esters in which the emulsion contains 0.1 to 5 parts by weight, referred to the completed emulsion, of one or more oil-soluble emulsifiers which are soluble in the esters, have an HLB value of 9 to 16, and are selected from fatty acid polyethylene glycol esters, polyethylene glycol ethers of fatty alcohols, polyethylene glycol ethers of glycerides, polyethylene glycol ethers of alkyiphenols, polyoxyethylene/polyoxypropylene block copolymers and mixtures of the said polyethylene glycol esters, polyethylene glycol ethers or polyethylene glycol/polypropylene glycol block copolymers with alkylarylsul-phonates; and one or more water-soluble dispersants in an amount of 0.1 to 3 parts by weight, referred to the completed emulsion, selected from the group consisting of alkali metal salts of single or multiple unsaturated fatty acid taurides or fatty acid alkyltaurides, in which the amount of herbicidally active ester is 30 to 75 % by weight of the concentrated emulsion, the viscosity of the emulsion is 50 to 3,000 mPa.s, the droplet size is 1 to 5^um and the pH value is 6 to 9.

2. A composition according to claim 1, which additionally contains one or more conventional anti-freeze agents, conventional anti-foam agents, thickeners or a mixture thereof.

3. A composition according to claim 1 or 2, in which the ester soluble emulsifiers are one or more fatty acid polyethylene glycol esters.

4. A composition according to any one of claims 1 to 3, in which the watersoluble dispersant is Sodium-oleyl-methyltauride.

5. A composition according to any one of claims 1 to 4, in which the herbicidally-active phenoxyalkanecarboxylic acid esters are the octyl esters.

6. A composition according to any one of claims 1 to 5, in which the amount of emulsifier is 1 to 3% by weight.

7. A composition according to any one of claims 1 to 6, in which the amount of dispersant is 0.2 to 1% by weight.

• 8. A composition according to any one of claims 1 to^^j^ijal which the viscosity is 500 to 1,500 mPa.s. fry r^N>\ I 2 disss'"' — 12- 203359

9. A composition according to any one of claims 1 to 8 in which the pH-value is 7 to 8.

10. A process for the preparation of a storage-stable herbicidally-active composition in the form of a concentrated emulsion of one or more phenoxyalkanecarboxylic acid esters containing 30 to 75% by weight of active compound having a viscosity of 50 to 3,000 mPa.s., which comprises preparing a solution I from one or more phenoxyalkanecarboxylic acid esters and at least one emulsifier which is soluble in the ester and has an HLB value of 9 to 16, in which the amount of emulsifier is 0.15 to 10 parts by weight per 100 parts by weight of the solution I, and mixing solution I with an aqueous solution II, which contains one or more water-soluble dispersants, selected from the group consisting of alkali metal salts of single or multiple unsaturated fatty acid taurides or fatty acid, alkyl tauiides in the amount of 0.2 to 10 parts by weight of dispersant per 100 parts of aqueous solution II, and subsequently homogenizing the mixture at a temperature within the range of 15° to 90°C. until the droplet size is 1 to 5^um, while maintaining the pH of the mixture at a value of from 6 to 9 and then diluting the homogenizate to the desired final volume.

11. A storage-stable herbicidally-active composition according to claim 1, and substantially as hereinbefore described with reference to the Examples.

12. A process for the preparation of a storage-stable herbicidally-active composition according to claim 10, and substantially as hereinbefore described with reference to the Examples. By y^/their authorised Agents., A. J. PARK &S<