WO2000008925A1 - Method for preparing a solid phytosanitary composition - Google Patents

Abstract

The invention concerns a method for preparing phytosanitary compositions in solid form, which consists in grinding a suspension containing at least an active phytosanitary substance, at least a surfactant and at least an anti-foaming agent, followed by spray-drying to obtain a phytosanitary composition in solid form. The method consists in grinding a suspension comprising at least an anti-foaming agent selected among silicone substances having a viscosity not less than 8 Pa's. The anti-foaming agent used in the invention has the advantage of preserving its properties, not only during the preparation of the phytosanitary composition but also when the latter is used (dilution/dispersion).

Description

 PREPARATION OF A SOLID PHYTOSANITARY COMPOSITION

The present invention relates to a process for the preparation of phytosanitary compositions in solid form, obtained by grinding and then drying a suspension comprising the active material.

More particularly, the subject of the invention is a process using a particular anti-foaming agent, which can be introduced at the time of the preparation of the phytosanitary composition and which is capable of retaining its activity when the latter is used .

The phytosanitary compositions, in addition to the active materials and fillers, contain surfactants, which have, inter alia, the roles of improving the wetting and the dispersion of the compositions during their use. However, very often, these surfactants are the cause of difficulties associated with the production of foam; difficulties encountered, not only during the preparation of these compositions, but also, and above all, during their use.

This is why it is known to add during the manufacture of the phytosanitary composition, then during the use (dilution / dispersion) of the latter, an anti-foaming agent. It is indeed necessary to proceed in two stages, because most of the anti-foaming agents lose their properties during the manufacture of the phytosanitary composition when they are subjected to high degrees of shearing. This is particularly the case for the preparation of water dispersible granules, which are obtained by grinding a suspension comprising the active material and the surfactants, followed by spray drying of the resulting suspension.

The disadvantages associated with this two-part solution are, on the one hand, that the user must use the anti-foaming agent in a tank-mix, and on the other hand that it is not always easy to dose the formulation and the anti-foaming agent correctly. Another solution would be to add the second anti-foaming agent, no longer at the time of the dilution of the phytosanitary composition but during the process for preparing the composition, either before drying, or once the latter is dried. However, such a solution requires the use of appropriate mixing devices and the implementation of an additional operation which can cause deterioration of the granules obtained. One of the objectives of the present invention is to provide a composition which does not have the aforementioned drawbacks.

These and other objects are achieved by the present invention which therefore relates to a process for the preparation of phytosanitary compositions in solid form, in which is carried out grinding a suspension comprising at least one phytosanitary active material, at least one surfactant and at least one anti-foaming agent, followed by drying to obtain the phytosanitary composition in solid form. The method according to the invention is characterized in that the grinding is carried out with a suspension comprising at least one anti-foaming agent chosen from silicone substances having a Brookfield viscosity measured at 25 ° C, greater than or equal to 8 Pa.s.

The choice of this particular type of silicone anti-foaming agent makes it possible to have an acceptable level of foam during the grinding operation, and a conservation of these properties at the time of the dilution (dispersion) of the composition by the user. . Such a result being obtained without having to add an anti-foaming agent, either when the composition is used, or after it has dried. In addition, completely unexpectedly, this result could be obtained without having to add anti-foaming agent after the suspension of active material has undergone a significant shearing operation (grinding).

However, other advantages and characteristics will appear more clearly on reading the description and the examples which follow.

The anti-foaming agent used in the process according to the invention is therefore chosen from silicone substances, further having a Brookfield viscosity measured at 25 ° C., greater than or equal to 8 Pa.s.

According to a particular embodiment of the invention, at least one anti-foaming agent having a Brookfield viscosity measured at 25 ° C., greater than or equal to 10 Pa.s, preferably greater than or equal to 20 Pa, is used. .s.

The silicone substance (or silicone) is more particularly chosen from polyorganosiloxanes in which at least 50% of the organic substituents are methyl radicals.

The other radicals of the silicone substance may be hydrogen atoms, hydroxyls, linear or branched C 1 -C 10 alkyl radicals, linear or branched C2-C 10 alkenyl radicals, aryl or alkylaryl radicals in C5-C10.

More particularly, the silicone substances used correspond to the following formula:

[(R1) ₃ SiO] - [R2R4SiO] _x - [(R3) ₂ SiO] y - [(Ri) ₃ SiO] in which: - the radicals R ¹ , identical or different, substituted or not, represent a linear alkyl or branched, in CIC-IO; a C2-C10 linear or branched alkenyl radical; an aryl, alkyl-aryl, aryl-alkyl, aryl-alkenyl, alkenyl-aryl radical, C5-C10 for the aryl part and C1-C4 for the alkyl or alkenyl part, or hydroxyie; - the radicals R2, R3, 4 ₎ substituted or not, identical or different, represent a linear or branched, C1-C6 alkyl; a C2-C10 linear or branched alkenyl radical; an aryl, alkyl-aryl, aryl-alkyl, aryl-alkenyl, alkenyl-aryl radical, C5-C10 for the aryl part and C1-C4 for the alkyl or alkenyl part; - x and y represent average numbers of patterns, chosen to ensure the Brookfield viscosity greater than or equal to 8 Pa.s, more particularly 10 Pa.s, preferably 20 Pa.s.

More particularly, silicone oils are used for which the radicals R, which are identical or different, represent methyl, ethyl, vinyl, phenyl or hydroxyl radicals. Preferably, the preferred radicals R ¹ are methyl, hydroxyl radicals. More particularly, silicones comprising only terminal methyl radicals are suitable, or else silicones having, at each of the ends, a hydroxyl radical and two methyl radicals.

As regards the radicals R ² , R3, R4, the methyl, ethyl, vinyl and phenyl radicals are preferred. It should be noted that according to a particular embodiment, at least 80% of said radicals are methyls. As preferred examples, there may be mentioned: (CH ₃ ) ₃ Si-O - [(CH ₃ ) ₂ -SiO] _z -Si (CH ₃ ) ₃ or [(CH ₃ ) ₂ (OH)] Si- O - [(CH3) ₂ Si-O] _z -Si [(CH3) 2 (OH)] with z representing a number of values sufficient to ensure a Brookfield viscosity greater than or equal to 8 Pa.s, more particularly 10 Pa. s, preferably 20 Pa.s.

Obviously, it would not be departing from the scope of the present invention to use a mixture of these two compounds. The silicone substance used can be in the form of an oil, or even a compound.

It should be noted that the term compound is a conventional term in the field of silicones, and which designates a silicone substance associated with at least one mineral filler. Compounds are used whose Brookfield viscosity is greater than or equal to 8 Pa.s, more particularly 10 Pa.s, preferably 20 Pa.s.

Generally, the mineral fillers used to obtain the compounds have a specific surface, measured according to BET methods, of at least

50 m ² / g, in particular between 50 and 400 m ² / g, preferably greater than 70 rτv7g. They also have an average particle size of less than

0.1 μm and an apparent density less than 200 g / l.

More particularly, the mineral filler is chosen from silica, ground quartz, calcined clays, or even diatomaceous earths, oxides, hydroxides or sulfates of elements from columns MA, IIIB of the periodic table, mica, gypsum, alone or in mixtures.

Preferably, the mineral filler associated with the silicone substance is silica. This can be in precipitated or calcined form.

It may possibly have undergone a surface treatment aimed at hydrophobing it. It should be noted that this treatment can be carried out beforehand or in situ.

Conventionally, the hydrophobation treatment consists in contacting the silica with one or more organosilicon compounds. Among these compounds, mention may be made of methylpolysiloxanes such as hexamethyldisiloxane, octamethylcyclotetrasiloxane; methylpolysilazanes such as hexamethyldisilazane, hexamethylcyclot silazane; chlorosilanes such as dimethyldichlorosilane, trimethylchlorosilane, methylvinyldichlorosilane, dimethylvinylchlorosilane; alkoxysilanes such as dimethylmethoxysilane, MQ resins.

During this treatment, the silicas can increase their starting weight up to a rate of 20%.

According to a particularly advantageous embodiment of the invention, a compound is used whose mineral filler is precipitated silica. Preferably, the silica used in the composition of the compound is hydrophobic.

It has been found that the higher the viscosity of the silicone substance, the less critical the hydrophobicity of the filler, and more particularly of the silica, is. However, a particularly advantageous embodiment of the invention consists in using a silicone substance of high viscosity with a filler, and more particularly silica, made very hydrophobic.

Conventionally, in a compound, the proportion of silicone with respect to the mineral filler, and more particularly with respect to silica, varies between 2 and 15 and preferably between 2 and 10.

The compounds are prepared in the usual manner by mixing the two components, then heating the mixture obtained between 60 and 200 ° C, in particular around 150 ° C, preferably under reduced pressure.

If an in situ hydrophobation treatment is used, the silica undergoes a heat treatment at a temperature above 100 - 150 ° C., in the absence of the aforementioned silicic compounds. The anti-foaming agent used in the invention may be in the form of an oil, of a compound. but also an emulsion. Such an embodiment is advantageous in the sense that the anti-foaming agent becomes easier to use, since the viscosity of the emulsion is very low, while retaining its advantageous properties because the viscosity of the anti-foaming agent, as such, always remains greater than or equal to 8 Pa.s, preferably greater than or equal to 10 Pa.s, more particularly greater than or equal to 20 Pa.s .

When the silicone substance is used in the form of an emulsion, the continuous medium can be chosen from water or any other compound which does not or substantially does not dissolve the silicone substance.

Among the silicone compounds, in the form of an oil, an emulsion or a compound, commercially available and capable of entering into the composition according to the invention, there may be mentioned, for example, the compound Rhodorsil® 471, sold by the Rhodia company.

It should be noted that the composition according to the invention may comprise one or more silicone substances, as such or combined with one or more mineral fillers.

The total amount of anti-foaming agent in the phytosanitary composition represents 0.1 to 2% by weight relative to the total weight of the phytosanitary composition in solid form.

The process according to the invention is suitable for the preparation of phytosanitary compositions in solid form, and more particularly in the form of dispersible granules. The term “phytosanitary composition” means any composition intended for applications in the field of agriculture, comprising at least one biologically active material, as are in particular pesticides. By pesticides, we mean among others, herbicides, fungicides, acaricides, insecticides, nematicides. It should be noted that if the method according to the invention can be used for any type of phytosanitary active ingredient, it is nevertheless particularly suitable for solid active ingredients, insoluble or poorly soluble in water.

By way of nonlimiting example of suitable active ingredients, there may be mentioned, among others, Ametryne, Diuron, Linuron, Chlortoluron, Isoproturon, Nicosulfuron, Metamitron, Diazinon, Glyphosate, Aclonifen, Atrazine, Chlorothalonil,

Bromoxynil, Bromoxynil heptanoate, Bromoxynil octanoate, Glufosinate,

Mancozeb, Maneb, Zineb, Phenmedipham, Propanyl, phenoxyphenoxy series, heteroaryloxyphenoxy series, CMPP, MCPA, 2,4-D,

Simazine, the active products of the imidazolinone series, the organophosphate family, with in particular Azinphos-ethyl, Azinphos-methyl, Alachlore,

Chlorpyriphos, Diclofop-methyl, Fenoxaprop-p-ethyl, Methoxychlor,

Cypermethrin, Fenoxycarb. The amount of active material in the solid phytosanitary composition represents more particularly 50 to 95% by weight relative to the total weight of the solid phytosanitary composition.

As indicated previously, the phytosanitary composition comprises at least one surfactant.

Among the suitable surfactants, mention may be made of surfactants having mainly a role of wetting agent.

Among the suitable wetting agents, there may be mentioned without intending to be limited thereto, N-methyl-N-oleoyl taurates; alkylarylsulfonate salts, such as alkylbenzene sulfonate salts, alkyl diphenyl ether sulfonate salts, alkylnaphthalene sulfonate salts; mono-alkyl sulfosuccinates, di-alkyl sulfosuccinates; ethoxylated alkylphenois. These wetting agents can be used alone or as a mixture.

Mention may for example be made, as wetting surfactants, of Geropon® SDS, Geropon® T / 77, Supragil® NC / 85, Rhodacal® DS / 10, te Supragil® WP, sold by the company Rhodia Chimie.

The amount of wetting agent may be between 0.5 and 10% by weight, relative to the total weight of the solid phytosanitary composition, preferably between 1 and 5% by weight, relative to the same reference. The solid phytosanitary compositions according to the present invention can also comprise at least one surfactant having mainly a role of dispersing agent.

Among the dispersants suitable in the context of the present invention, there may be mentioned, inter alia, the alkali metal or ammonium salts of alkylnaphthalene sulfonates condensed with formalin; the alkali metal or ammonium salts of 4,4'-dihydroxybiphenyisulfonate condensed with formalin; alkali or ammonium salts of alkylarylphosphates or alkylarylsulfates, such as polyoxyethylenated and / or polyoxypropylenated, phosphated or sulphated, neutralized or not, mono-, di- or tri-styrylphenols; alkali, alkaline earth metal or ammonium lignosulfonates; and their mixtures. It should be noted that ammonium has the same following meaning: N (R3) ₄ ⁺ , with R ³ , identical or different, representing hydrogen atoms, or C1-C4 hydrocarbon radicals.

The ethylene oxide / propylene oxide copolymers are also compounds which can be used as dispersing agents. Particularly suitable are compounds having a molecular mass of between 3000 and 25000 g / mol.

Also suitable are the alkali metal or ammonium salts of polymers comprising at least one monomer chosen from acids, diacids or unsaturated C3-C5 anhydrides, optionally combined with at least one monomer chosen from hydrocarbon radicals, unsaturated, linear or branched in C4-C8.

More particularly, it is possible to use polymers comprising, as monomers, maleic acid, maleic anhydride, acrylic acid, methacrylic acid, alone or in mixtures. Said polymers can likewise comprise at least one monomer chosen from pisobutylene or diisobutylene.

This polymer may be in an acid form or else in the form of an alkali metal or ammonium salt of type N (R3) ⁺ , with R3, identical or different, representing hydrogen atoms, or hydrocarbon radicals in C1-C4. Preferably, the copolymer is in the form of sodium salts.

Preferably, a polymer comprising maleic acid and / or maleic anhydride combined (s) with pisobutylene and / or diisobutylene is used.

It is likewise possible to use advantageously the combination of an alkylbenzene sulfonate salt (such as more particularly, alkylbenzene sulfonate, and preferably dodecylbenzene sulfonate, of sodium) with the abovementioned polymer, saying the polymer comprising maleic acid, and / or maleic anhydride combined with isobutylene and / or diisobutylene, preferably in the form of a sodium salt. The weight ratio of salt to polymer being more particularly 10/90. By way of nonlimiting illustration, the dispersing agents can be chosen from the following products: Geropon® T / 36, Geropon® TA / 72, Geropon® SC / 213, Supragil® MNS / 90, Supragil® GN, Soprophor® FL, Soprophor® FLK, Soprophor® 4D384.

The amount of dispersing agent in the solid phytosanitary composition is generally between 2 and 20% by weight, relative to the total weight of the composition, preferably between 2 and 15% by weight, relative to the same reference.

It is advantageously between 2 and 10% by weight, relative to the total weight of the solid phytosanitary composition.

The composition can likewise comprise additives common in the field, such as in particular disintegrating agents, anti-caking agents, binding agents, inert fillers.

Examples of such compounds that may be mentioned include starch, crosslinked polyvinylpyrrolidones, microcrystalline cellulose, crosslinked sodium carboxymethylcellulose, ammonium or sodium phosphates, sodium carbonate or bicarbonate, sodium acetate, sodium metasilicate, magnesium sulfates, zinc or calcium, magnesium hydroxide, calcium chloride, molecular sieves. Generally, the total amount of additives of this type, if they are present, varies between 0.5 and 40% by weight relative to the total weight of the solid phytosanitary composition, preferably between 1 and 30% by weight relative to the same reference.

As inert fillers which may be used in the phytosanitary compositions according to the invention, mention may be made, without being limited thereto, of soluble or partially soluble starch; bentonite; kaolin; diatomaceous earth; attapulgite; zeolites; carbonate, silicates, of alkaline earth metal (calcium, magnesium in particular); talc; mica; silicon dioxide; silico-aluminates, sulfates of alkali metal, alkaline earth metal or ammonium; the oxides, hydroxides or sulfates of elements in columns MA, IIIB of the periodic table of the elements; carbon black, alone or in mixtures.

The method according to the invention will now be described.

In a first step, a suspension is prepared comprising at least one active material, at least one surfactant and at least one antifoaming agent as defined above.

Advantageously, the suspension is an aqueous suspension.

The amount of water added is more particularly between 20 and 60% by weight relative to the weight of said suspension.

The preparation of the suspension is done in a conventional manner in the field. Thus, one can put in contact all the products simultaneously.

The preparation of the suspension is generally carried out at a temperature close to room temperature.

The second step of the process for preparing the solid phytosanitary composition according to the invention consists in grinding the suspension, so as to obtain an appropriate particle size distribution of the particles forming the suspension.

Conventionally, the grinding is carried out until an average particle size of the order of 1 to 10 μm is obtained, preferably close to 1 to 4 μm.

The grinding operation takes place in any suitable type of equipment, such as in ball mills. It should be noted, and this represents a very important advantage of the present invention, that it is no longer necessary to add an anti-foaming agent once the grinding has been carried out.

The suspension obtained is then dried.

Drying takes place using conventional means. However, preferably, said drying takes place by atomization, that is to say by spraying the suspension in a hot atmosphere (spray-drying). This warm atmosphere is advantageously on par. The atomization can be carried out by means of any sprayer known per se, for example by a spray nozzle of the sprinkler apple type or the like.

One can also use so-called turbine atomizers.

This drying can take place co-current, against the current. On the various spraying techniques likely to be used in the present process, reference may be made in particular to the basic work by MASTERS entitled "SPRAY-DRYING" (second edition, 1976, Editions George Godwin - London).

It will be noted that it is also possible to carry out the spray-drying operation by means of a "flash" reactor, for example of the type described in particular in French patent applications No. 2 257 326, 2 419 754 and 2,431,321.

By way of illustration, the gas inlet temperature during drying (whatever the method used) is between 130 and 250 ° C.

Obviously, the temperature to which the active material is subjected during drying remains below the degradation temperature of said active material.

At the end of this drying operation, the solid phytosanitary composition according to the invention is obtained. It conventionally has an average particle size of the order of 400 μm.

The solid phytosanitary composition obtained according to the process according to the invention, more particularly in the form of a dispersible granule, has low foaming properties, when it is diluted or dispersed at the time of its use.

In addition, it retains such properties after storage.

A concrete but nonlimiting example of the invention will now be presented.

EXAMPLE

The following compositions are prepared:

1 / preparation of the suspension.

In a beaker, with stirring with a deflocculating blade of 65 mm in diameter), all the constituents are added in the order indicated above. then homogenized for 2 minutes at 6000 rpm, with Ultra-Turrax.

The mixture demixes quickly (brown liquid, beige solid).

2 / Grinding of the suspension

Minimotormill grinding is then carried out (grinder comprising 190 ml of glass beads (diameter 0.8-1.2 mm)).

One grinding is carried out at 1500 rpm and three grindings at 2000 rpm.

3 / Atomization / Drying of the suspension Atomization conditions:

Atomizer inlet temperature: 145 ° C

Atomizer outlet temperature: 135 ° C

Nozzle air flow: 900 l / h

Nozzle air pressure: 0.2 bar

Drying takes place in an Aeromatic fluid bed for 30 minutes at 60 ° C.

A composition is obtained in the form of granules.

4 / Foam persistence test before and after aging

Part of the powder obtained previously was treated for 15 days at 54 ° C (simulation of storage conditions).

The foam persistence test was carried out as follows, with water

CIPAC 500 ppm:

Pour 100 ml of water into a test tube and introduce 2 g of product to be tested, before closing the test tube.

Perform 30 complete reversals, letting the air bubble rise at the top at each reversal. Uncork the test tube and start the stopwatch. Measure volumes of mosses at 0, 1, 5, 10, 20 and 30 mns.

The results are collated in the following tables:

1 / without storage

/ after 15 days storage at 54 ° C

It is found that the composition has a significant defoaming activity, compared to the comparative compositions.

In addition, the composition is stable after aging and the defoaming effect is retained.

Claims

1. Process for the preparation of phytosanitary compositions in solid form, in which a suspension is crushed comprising at least one phytosanitary active material, at least one surfactant and at least one anti-foaming agent, followed by drying to obtain the phytosanitary composition in solid form, characterized in that grinding is carried out with a suspension comprising at least one anti-foaming agent, chosen from silicone substances, having a Brookfield viscosity measured at 25 ° C., greater than or equal at 8 Pa.s 2. Method according to the preceding claim, characterized in that at least one anti-foaming agent is used whose Brookfield viscosity is greater than or equal to 10 Pa.s and preferably greater than or equal to 20 Pa.s. 3. Method according to any one of the preceding claims, characterized in that at least one anti-foaming agent chosen from silicone substances of the following formula is used: [(R1) ₃ SiO] - [R2R4SiO] _x - [(R3) ₂ SiO] _y - [(Rl) ₃ SIO] in which: - the radicals R ¹ , identical or different, substituted or not, represent a linear or branched C1-C10 alkyl; a C2-C10 linear or branched alkenyl radical; an aryl, alkyl-aryl, aryl-alkyl, aryl-alkenyl, alkenyl-aryl radical, C5-C10 for the aryl part and C1-C4 for the alkyl or alkenyl part, or a hydroxyl; - the radicals R2, R3, R4_ substituted or not, identical or different, represent a linear or branched C1-C10 alkyl; a C2-C10 linear or branched alkenyl radical; an aryl, alkyl-aryl, aryl-alkyl, aryl-alkenyl, alkenyl-aryl radical, C5-C10 for the aryl part and C-1-C4 for the alkyl or alkenyl part; - x and y represent average numbers of patterns chosen to ensure a Brookfield viscosity greater than or equal to 8 Pa.s, more particularly greater than or equal to 10 Pa.s, preferably greater than or equal to 20 Pa.s. 4. Method according to the preceding claim, characterized in that at least one anti-foaming agent is used, the radicals R ^{1 of which} , which are identical or different, represent methyl, ethyl, vinyl, phenyl or hydroxyl radicals; the radicals R, R3, R4, identical or different, represent methyl, ethyl, vinyl, phenyl radicals. 5. Method according to any one of the preceding claims, characterized in that a total quantity of anti-foaming agent is used representing 0.1 to 2% by weight relative to the total weight of the phytosanitary composition in the form solid. 6. Method according to any one of the preceding claims, characterized in that at least one anti-foaming agent is used in the form of a compound. 7. Method according to the preceding claim, characterized in that the compound comprises at least one mineral filler chosen from precipitated silica, calcined silica, having possibly undergone a surface treatment aimed at hydrophobing it, quartz, calcined clays, or also the diatomaceous earths, oxides, hydroxides or sulfates of elements of columns IIA, IIIB of the periodic table of the elements, mica, gypsum, alone or in mixtures. 8. Method according to any one of the preceding claims, characterized in that at least one anti-foaming agent is used in the form of an emulsion. 9. Method according to any one of the preceding claims, characterized in that an amount of active material corresponding to 50 to 95% by weight relative to the total weight of the solid phytosanitary composition is used. 10. Method according to any one of the preceding claims, characterized in that the above suspension is an aqueous suspension. 11. Method according to the preceding claim, characterized in that the water content of the suspension represents 20 to 60% by weight relative to the total weight of the suspension. 12. Method according to any one of the preceding claims, characterized in that a spray drying is carried out.