GB2050170A - Liquid compositions of phosphoric and thiophosphoric pesticides stabilized to low and high temperatures - Google Patents

Abstract

Pesticidal compositions which are stable to both high and low temperatures and comprise a mixture of 0.5 to 90% phosphoric and/or thiophosphoric pesticide and 99.5 to 10% one or more organic acids, the mixture being diluted with one or more of the following solvents: (1) an aromatic solvent or an aromatic-aliphatic solvent, (2) dimethylformamide, dimethylsulphoxide, an alcohol having from 1 to 6 carbon atoms, or a glycol having 2 to 20 carbon atoms, (3) cyclohexanone, ethylamylketone or acetophenone, (4) amyl acetate or methylbenzoate, (5) a surfactant.

Description

SPECIFICATION Liquid compositions of phosphoric and thiophosphoric pesticides stabilised to low and high temperatures The present invention relates to liquid compositions containing phosphoric and/or thiophosphoric pesticides. In particular the invention relates to such compositions which are stable with time and at both high and low temperatures.

Phdsphoric and thiophosphoric pesticides are known and include: O, O-dimethyl-S-(N-methylcarbamoyl methyl)-phosphod ith ioate commercially available from Montedison S.p.A. under the trade mark Rogor, O,O-dimethyl-S-(a-ethoxywarbonylbenzyl)-phosphorodithioate commercially available from Soc.

Montedison under the trade mark Cidial, 0, 0-diethyl-S-(N-isopropylcarbamoylmethyl)-phosphorodithioate commercially available from Montedison S.p.A. under the trade mark FAC, S-[1,2-di-(ethoxycarbonyl)ethyl]phosphorothiolthionate commercially available from American Cyanamid Co. Under the trade mark Malathion, and O,O-dimethyl-O-nitrophenyl-phosphorothioate commercially available from American Cyanamid Co. under the trade mark Parathion.

Parathion, Malathion and many other phosphoric and thiophosphoric pesticides are liquids and Rogor and FAC are solids.

The liquid solutions of these pesticides are more convenient for handling and for the preparation of emulsifyable formulations and of concentrates since they are used at very low volume. However, such liquid solutions are difficult to prepare and store due to the physical instability at low and high temperatures and with regard to the chemical stability which, if not respected, leads to a dropping of the biological activity.

The phosphate and thiophosphate pesticides exhibit either a low solubility in the most common organic solvents, particularly at low temperatures, or a chemical stability that is insufficient to ensure the activity. For example phosphoric or thiophosphoric pesticides are often difficult to dissolve in' many of the organic solvents, e.g. xylene, Shellsol A and Shellsol AB (a mixture of aromatic and aliphatic hydrocarbons of the Shell Company), while in solvents such as alcohols, glycols, ketones, dimethylformamide, dimethylsulphoxide, a decomposition of the active principle often occurs.

In order to obviate these drawbacks various solutions have been suggested. For example, United States Patent Specification No. 3 444 273 proposes mixing the thiophosphoric esters with dialkylphenols and diluting the resulting mixture with aromatic hydrocarbons. The composition obtained has sufficient chemical stability and a good resistance or fastness to low temperatures. However, the alkylphenols are rather expensive and difficult to handle and sometimes impart a certain phytotoxicity to the formulations in which they are used.

It is an object of this invention to provide liquid compositions of phosphoric and/or thiophosphoric pesticides which are stable both at low and high temperatures.

The composition of the invention comprises a mixture of: 0.5 to 90% by weight of phosphoric and/or thiophosphoric pesticides, 99.5 to 10% by weight of one or more organic acids, the mixture being diluted with one or more of: (1) an aromatic solvent, e.g. toluene or xylene, or an aromatic-aliphatic solvent, e.g.Shellsol A, AB (mixtures of dimethyl, ethyl, tetramethylbenzene) or like Solvesso 100-150, 200 (mixtures of dimethyl, ethyl, tetramethylbenzene, a trade mark of the Esso Company), (2) dimethylformamide, dimethylsulphoxide, an alcohol having 1 to 6 carbon atoms or a glycol having 2 to 20 carbon atoms, (3) cyclohexanone, ethylamylketone or acetophenone, (4) amyl acetate or methylbenzoate, (5) a surfactant, e.g. of the Setrolene O type (registered trade mark of the ROL-ME Company, consisting of polyoxyethylate sorbitan oleate), Emulsion 1 0B (registered trade mark of the ROL Company and consisting of alkylphenolpolyoxyethylate), Emulsion 255 (registered trade mark of the ROL-ME Company, and consisting of alkylbenzenesulphonate).

Suitable phosphoric and thiophosphoric pesticides for use in the invention include, Rogor, Methyl-parathion (O, O-dimethyl-O-nitrophenyl-phosphorothioate), Monocrotophos (1-methyl 3(methylamino)-3-oxo-1-propenyl phosphate), M8174 Idinphos (a Montedison trade mark for O,O-diethyl-O-[l -methyl-3(P,P-dichlorovinyl)-l ,2,4-triazol-5-yllthiophosphate), FAC and Azinphos-methyl (0, O-dimethyl-S-[(4-oxo 1,2, 3-benzotriazin-3(4H)-yl)-methyl]phosphorodithioate).

Suitable organic acids for use in the invention include acetic acid, propionic acid, butyric acid, caprylic acid, oleic acid, phenylacetic acid, formic acid, capronic acid, stearic acid and in general all the organic acids miscible with the diluents of the pesticide phosphorus-organic acid mixture.

In the compositions of the invention the stability at high and/or at low temperatures and/or the solubility of the phosphoric and thiophosphoric pesticides increases considerably compared to many prior art formulations. The solubility of Rogor in various organic solvents often is not very high particularly at low temperatures as will be evidenced by the figures reported in Table 1.

Table 1 Percentage solubility of Rogor [O,O-dimethyl-S-(N-methylcarbamoylmethyl)-phosphorodithioate] at 20"C and 0 C.

Temperature Solvent 20"C 0 C Xylene 12% 3% Shellsol AB 8% 2% Butyl alcohol 50% 10% Amyl acetate 30% 8% Dimethylformamide 75% 50% Diethyloxalate 60% 35% Cyclohexanone 60% 50% In those cases where the solubility appears to be good (dimethylformamide, cyclohexanone) the chemical stability of the pesticide solutions is unsatisfactory, particularly at high temperature (i.e. at above 50"C).

Table 2 reports the stability of solutions of Rogor and it will be seen that the drop (calculated as a decreasing of active substance in percentage) is high in solvents in which Rogor is more soluble.

Table 2 Stability of Rogor in a number of solvents after 5 days at 60"C

Drop in Mixture percentage Rogor 40 Dimethylformamide 60 90 Rogor 40 60 Dimethylsulphoxide 60 Rogor 40 Butyl alcohol 60 30 Rogor 40 Propylene-glycol 60 70 Rogor 40 Methylcellosolve 60 Rogor 40 6.3 Cyclohexanone 60 From Tables 1 and 2 it will be seen that as a general rule Rogor is stable in those solvents, e.g. aromatic solvents in which it is sparingly soluble, while it is unstable in those solvents in which it is more soluble. Cyclohexanone is an exception but this solvent is very expensive.

Utilizing mixtures of this invention it is possible both to avoid the problems of instability as well as increasing the solubility of the pesticide in solvents in which the pesticide is normally sparingly soluble.

The invention will now be illustrated by the following Examples.

Example 1 A solution of 0.5 g of Rogor, 0.1 g of acetic acid and 99.4 g of xylene was prepared byw mixing together, at room temperature, the pesticide with the acetic acid and then with xylene.

50 g of this solution, maintained at 0 C for 48 hours, or for 5 days at 60"C, did not show any alteration, while the liquid gas chromatographic analysis showed that no appreciable decomposition had taken place.

Example 2 A solution was prepared by mixing together at room temperature and under stirring, 72 g of Rogor, 1 8 g of acetic acid, 10 g of Shellsol AB (trade mark of the Shell Company for a mixture of aromatic and aliphatic solvents, consisting of dimethyl-, ethyl-, tetramethylbenzene).

50 g of the mixture, maintained at 0 C for 48 hours or at 60"C for 5 days, did not show any alteration and the liquid-gas chromatographic analysis showed that no appreciable decomposition occured.

Example 3 A solution of 40 g of Rogor, 10 g of acetic acid, 50 9 of xylene was prepared at room temperature. This solution displayed the same stability as that described in the preceding Examples.

Examples 4 to 8 Similar results to the preceding Examples were obtained with the following mixtures: Example 4: Rogor 40 g, acetic acid 5 g, dimethylformamide 5 g and xylene.

Example 5: Rogor 40 g, acetic acid 5 g, cyclohexanone 25 g and xylene 30 g.

Example 6: Rogor 72 g, acetic acid 18 9 and Setrolene (registered trade mark of ROL-ME Company for the polyoxyethylate sorbitan oleate surfactant) 10 g, Example 7: Rogor 40 g, acetic acid 10 g, xylene 40 g and a mixture of nonylphenylpolyoxyethylate and dodecylbenzenesulphonate 10 g, Example 8: Rogor 40 g, acetic acid 5 g, dimethylformamide 5 g, xylene 40 g and Setrolene 10 9.

The mixtures of Examples 3 to 8 did not show any phytotoxicity at doses of 0.05% and 0.1% with regard to cucumber, beets, vine, apples, cabbage, cotton.

Example 9 A formulation was prepared by mixing together, under stirring, 40 g of technical Rogor, 1 5 g of propionic acid, 35 g of xylol and 10 g of Setrolene O (trade mark of ROL-ME Company for polyoxyethylate sorbitan oleate).

50 g of this mixture were then allowed to rest for 48 hours at 0 C and 50 g at 60"C for 5 days. After both tests, the liquid-gas chromatographic analysis showed that no appreciable decomposition had occured.

Example 10 A formulation was prepared by mixing together, under stirring, 40 g of technical Rogor, 20 g of phenylacetic acid, 25 g of xylol and 10 9 of Setrolene O.

50 g of this mixture were maintained at 0 C for 48 hours while 50 g were maintained at 60"C for 5 days. After both tests the liquid-gas chromatographic analysis did not detect any significant degrading Example 11 40 g of technical M 8174 were admixed at room temperature to 10 g of acetic acid, 40 g of xylene and 10 g of Emulson 1 or. 50 g of such a mixture were maintained at 0 C for 48 hours and 50 g were maintained at 60"C for 5 days. After the tests no separation could be observed while the liquid-gas chromatographic analysis showed that no significant degrading had occured Example 12 40 g of technical Methyl-parathion were admixed at room temperature with 10 g of acetic acid, 40 9 of xylene and 10 g of Emulson 1 OB.

50 g of this mixture were maintained for 48 hours at 0 C while 50 g were maintained at 60"C for 5 days. After these tests no separation could be observed while the liquid-gas chromatographic analysis showed that no significant degrading had taken place.

Example 13 40 g of technical Monocrotophos were admixed to 10 g of acetic acid and 50 g of xylene.

50 g of this mixture were maintained at 0 C for 48 hours and 50 g were maintained at 60"C for 5 days. After these tests no separation could be observed while the liquid-gas chromatographic analysis showed that no appreciable degrading had taken place.

The following Tables 3 to 6 illustrate the stability of compositions of the invention in comparison to prior art formulations Table 3 Stability of Rogor in admixture with various organic acids after dilution with xylol and surfactants, after 5 days at 60 C.

Component Composition (parts by weight) Technical Rogor 95% 40 40 40 40 40 40 40 40 40 40 40 Formic acid 10 Acetic acid 10 10 Propionic acid 15 15 Butyric acid 15 15 Oleic acid 25 Phenylacetic acid 20 Caprylic acid 25 Linoleic acid 25 Xylene 50 50 40 45 35 25 30 25 25 Setrolene O 10 10 10 10 10 10 10 Drop in percentage 3.4% 2.0% 2.1% 0.0% 1.0% 0.5% 3.0% 0.8% 2.0% Table 4 Stability of Rogor with various acids and solvents compared to Prior Art formulations

Drop Composition 5 days at 60 C (1) Technical Rogor 95% Acetic acid 24% 4.6% Shellsol AB 11 %.

(2) Technical Rogor 95% 65% Propionic acid 30% 4.1% Shellsol AB 5% (3) Comparative formulation: Technical Rogor 95% 65% Phenol 30% 12.6% Shellsol AB 5% Table 5 Stability tests at various temperatures of Rogor formulations with acetic acid (1, 2) in comparison with prior art Rogor formulations (3, 4).

Drop in percentage after: Composition 5 days 14 days 1 month 1 month (parts by weight) at 60 C at 54 C at 50 C at 40"C (1) Tech. Rogor 40 Acetic acid 40 2.0% 2.8% 4.7% 0.5% Xylene 50 (2) Tech. Rogor 40 Acetic acid 10 Xyiene 40 2.1% 3.9% 6.8% 1.0% Setrolene 0 7 Emulsion 255 3 (3) (Prior Art) Tech. Rogor 40 Xylol 10 3.9% 6.6% 7.6% 3.1% Cyclohexanone 50 (4) (Prior Art) Tech. Rogor 40 Xylol 42 4.5% 6.3% 7.1% 2.9% Phenol 18 'Emulson 255 = ROL-ME trade mark for alkylbenzene sulphonate.

Table 6 Stability of some pesticide compounds in formulations based'own acetic acid and xylene, after 5 days at 60"C.

Composition (parts by weight) Drop in percentage Technical M 8174 40 Acetic acid 10 2.3% Xylol 50 Tech. Methyl-parathion 40 Acetic acid 10 0.8% Xylol 50 Monocrotophos 40 Acetic acid 10 3.0% Xylol 50

Claims (10)

1. A liquid pesticidal composition comprising a mixture of: 0.5 to 90% phosphoric and/or thiophosphoric pesticide,

99.5 to 10% one or more organic acids, the mixture being diluted with one or more of the following solvents: (1) an aromatic solvent or an aromatic-aliphatic solvent, (2) dimethylformamide, dimethylsulphoxide, an alcohol having from 1 to 6 carbon atoms, or a glycol having 2 to 20 carbon atoms, (3) cyclohexanone, ethylamylketone or acetophenone, (4) amyl acetate or methylbenzoate, (5) a surfactant.

2. A composition as claimed in Claim 1 in which the organic acid is acetic, propionic, butyric, capronic, caprylic, oleic, ricinoleic, stearic, formic or phenylacetic acid.

3. A composition as claimed in Claim 1 or Claim 2 in which the pesticide of O,O-dimethyl-S (N-methylcarbamoylmethyl)-phosphodithionate.

4. A composition as claimed in Claim 1 or Claim 2 in which the pesticide is O,O-diethyl-O [1 -methyl-3(fi,fl-d ichlorovinyl)-2, 2,4-triazol-5-ylth iophosphate.

5. A composition as claimed in Claim 1 or Claim 2 in which the pesticide is O,O-dimethyl-O pnitrophenylphosphorothioate.

6. A composition as claimed in Claim 1 or Claim 2 in which the pesticide is O,O-diethyl-S (N-isopropylcarbamoylmethyl)phosphorodithioate.

7. A composition as claimed in Claim 1 or Claim 2 in which the pesticide is 1 (-methyl3(methyla mino-3-oxo- 1 -propenyl phosphate).

8. A composition as claimed in any preceding claim which includes xylene.

9. A composition as claimed in any preceding claim which includes a surfactant.

10. A liquid pesticidal composition of phosphoric and/or thiophosphoric pesticides as claimed in Claim 1 substantially as herein described with reference to any one of the Examples.