by agrochemical active compound it is meant a compound having an effect on a plant growth , whether by killing undesired organisms or avoiding development thereof , or by directly having an effect on the plant . examples of organic water - insoluble agrochemical active ingredient include : insecticides , for example selected from the group consisting of carbamates , such as methomyl , carbaryl , carbofuran , or aldicarb ; organo thiophosphates such as epn , isofenphos , isoxathion , chlorpyrifos , or chlormephos ; organo phosphates such as terbufos , monocrotophos , or terachlorvinphos ; perchlorinated organics such as methoxychlor ; synthetic pyrethroids such as fenvalerate herbicides , for example selected from the group consisting of triazines such as metribuzin , hexaxinone , or atrazine ; sulfonylureas such as 2 - chloro - n -[( 4 - methoxy - 6 - methyl - 1 , 3 , 5 - triazin - 2 - yl ) aminocarbonyl ]- benzenesulfonamide ; uracils ( pyrimidines ) such as lenacil , bromacil , or terbacil ; ureas such as linuron , diuron , siduron , or neburon ; acetanilides such as alachlor , or metolachlor ; thiocarbamates such as benthiocarb ( saturn ), triallate ; oxadiazol - ones such as oxadiazon ; phenoxyacetic acids such as 2 , 4 - d ; diphenyl ethers such as fluazifop - butyl , acifluorfen , bifenox , or oxyfluorfen ; dinitro anilines such as trifluralin ; glycine phosphonates such as glyphosate salts and esters ; dihalobenzonitriles such as bromoxynil , or ioxynil fungicides , for example selected from the group consisting of nitrilo oximes such as cymoxanil ( curzate ); imidazoles such as benomyl , carbendazim , or thiophanate - methyl ; triazoles such as triadimefon ; sulfenamidessuch as captan ; dithiocarbamates such as maneb , mancozeb , or thiram ; chloronated aromatics such as chloroneb ; dichloro anilines such as iprodione aphicides , for example selected in the group consisting of carbamates , such as pirimicarb , miticides , for example selected in the group consisting of propynyl sulfites such as propargite ; triazapentadienes such as amitraz ; chlorinated aromatics such as chlorobenzilate , or tetradifan ; dinitrophenols such as binapacryl . the organic water - insoluble agrochemical active ingredients may be comprised in the particles as a mixture of several ingredients . especially preferred organic water - insoluble agrochemical active ingredients are atrazine , cymoxanil , chlorothalanil , cyproconazole , and tebuconazole . the amphiphilic compound comprises at least one hydrophilic moiety and at least one hydrophobic moiety . the hydrophilic moiety is preferably a hydrophilic polymeric block . hydrophilic blocks are homopolymer blocks or copolymer blocks comprising hydrophilic units ( deriving from hydrophilic monomers or from units that are reacted to bercome hydrophilic ). hydrophilic blocks optionally comprise some hydrophobic units , but most of the units are hydrophilic . the hydrophobic moiety may be a polymeric or a non - polymeric moiety . the weight - average molecular weight of the hydrophilic block is preferably of greater than 1000 g / mol . examples of non polymeric hydrophobic moieties include alpha -{ 2 , 4 , 6 - tris [ 1 -( phenyl ) ethyl ] phenyl }- omega - hydroxy group . such a moiety is particularly preferred in combination with organic active ingredient comprising at least an aromatic ring , such as atrazine . preferred amphiphilic compounds comprising alpha -{ 2 , 4 , 6 - tris [ 1 -( phenyl ) ethyl ] phenyl }- omega - hydroxy group hydrophobic moiety comprise , as a hydrophilic polymeric block , poly ( oxyethelene ), poly ( oxypropylene ), or a poly ( oxyethelene )- poly ( oxypropylene ) copolymer . an especially preferred amphiphilic compound is alpha -{ 2 , 4 , 6 - tris [ 1 -( phenyl ) ethyl ] phenyl }- omega - hydroxy poly ( oxyethelene )- poly ( oxypropylene ) copolymer comprising from 2 to 8 moles of poly ( oxypropylene ) units and 16 - 30 units of poly ( oxyeythylene ) units . such an amphiphilic compound is for example soprophor 796 / p , marketed by rhodia . amphiphilic compounds comprising a polymeric hydrophobic moiety and a polymeric hydrophilic moiety are block copolymers . di - block copolymers are preferred . hydrophilic polymeric blocks are homopolymer blocks or copolymer blocks comprising hydrophilic units ( deriving from hydrophilic monomers or from units that are reacted to become hydrophilic ). hydrophobic polymeric blocks are homopolymer blocks or copolymer blocks comprising hydrophobic units ( obtained with hydrophobic monomers ). hydrophobic blocks optionally comprise some hydrophilic units , but most of the units are hydrophobic . examples of hydrophilic blocks include blocks comprising units deriving from monomers being : monoalkyl esters of unsaturated ethylenic dicarboxylic acids or n - substituted derivatives of monoalkyl esters of unsaturated ethylenic dicarboxylic , ethylenic monomers comprising a sulphonic acid group , their alkali metal , their ammonium salts , examples of preferred hydrophilic blocks include blocks comprising units deriving from monomers being : acrylic acid ( aa ), methacrylic acid , itaconic acid , maleic acid , fumaric acid , 2 - hydroxyethyl acrylate , 2 - hydroxyethyl acrylate methacrylate , acrylamide ( am ), methacrylamide , vinylsulphonic acid , vinylbenzenesulphonic acid , alpha - acrylamidomethylpropanesulphonic acid , 2 - sulphoethyl methacrylate , 2 - acrylamido - 2 - methylpropanesulphonic acid ( amps ), or styrenesulphonate ( ss ). examples of hydrophobic blocks include blocks comprising units deriving from monomers being : esters of acrylic acid and of methacrylic acid with hydrogenated or fluorinated c 1 - c 12 alcohols , unsaturated ethylenic monomers comprising a secondary , tertiary or quaternary amino group , or unsaturated ethylenic monomers comprising a heterocyclic group comprising nitrogen , or examples of preferred hydrophobic blocks include blocks comprising units deriving from monomers being : methyl acrylate , ethyl acrylate , propyl acrylate , n - butyl acrylate , isobutyl acrylate , 2 - ethylhexyl acrylate , t - butyl acrylate , methyl methacrylate , ethyl methacrylate , n - butyl methacrylate , isobutyl methacrylate , acrylonitrile , methacrylonitrile , vinyl acetate , vinyl versatate , vinyl propionate vinylformamide , vinylacetamide , vinylpyridines , vinylimidazole , aminoalkyl ( meth ) acrylates , aminoalkyl ( meth ) acrylamides , dimethylaminoethyl acrylate , dimethylaminoethyl methacrylate , di - tert - butylaminoethyl acrylate , di - tert - butylaminoethyl methacrylate , dimethylaminomethylacrylamide or dimethylaminomethylacrylamide methacrylamide . in a particular embodiment , the block copolymer has a weight - average molecular weight comprised between 1000 and 50000 g / mol , with a glass transition temperature of the hydrophilic block ( s ) being lower than 30 ° c . polymers according to this particular embodiment have particularly good and suitable surfactant properties , to obtain nanoparticles . preferred block copolymers are di - block copolymers , that is block copolymers comprising one hydrophilic block , one hydrophobic block and , optionally chain transfer units or specific chain - end units at the ends of blocks . the presence of chain transfer units or specific end - chain units is usually a consequence of the process used for making the di - block copolymer . especially preferred di - block copolymers comprise two blocks comprising units deriving from mono - α - ethylenically unsaturated monomers . examples of processes for making di - block , or poly - blocks , copolymers are “ living ” or “ controlled ” radical polymerization processes . such processes involve using a transfer agent that is specific for this purpose . generally , the preceding block copolymers can be obtained by any “ living ” or “ controlled ” polymerization process , such as , for example : radical polymerization controlled by xanthates according to the teaching of application wo 98 / 58974 , radical polymerization controlled by dithioesters according to the teaching of application wo 97 / 01478 , polymerization using nitroxide precursors according to the teaching of application wo 99 / 03894 , radical polymerization controlled by dithiocarbamates according to the teaching of application wo 99 / 31144 , atom transfer radical polymerization ( atrp ) according to the teaching of application wo 96 / 30421 , radical polymerization controlled by iniferters according to the teaching of otu et al ., makromol . chem . rapid . commun ., 3 , 127 ( 1982 ), radical polymerization controlled by degenerative transfer of iodine according to the teaching of tatemoto et al ., jap . 50 , 127 , 991 ( 1975 ), daikin kogyo co ltd japan , and matyjaszewski et al ., macromolecules , 28 , 2093 ( 1995 ), group transfer polymerization according to the teaching of webster o . w ., “ group transfer polymerization ”, p . 580 - 588 , in the “ encyclopedia of polymer science and engineering ”, vol . 7 , edited by h . f . mark , n . m . bikales , c . g . overberger and g . menges , wiley interscience , new york , 1987 , radical polymerization controlled by tetraphenylethane derivatives ( d . braun et al ., macromol . symp ., 111 , 63 ( 1996 )), radical polymerization controlled by organocobalt complexes ( wayland et al ., j . am . chem . soc ., 116 , 7973 ( 1994 )). preferred transfer agents for implementing a controlled polymerization process are agents comprising a dithioester group , a thioether - thione group , a dithiocarbamate group , or a xanthate group . a “ living ” or “ controlled ” radical polymerization process used to make block copolymers comprises for example the steps of : a ) reacting an ethylenically unsaturated , preferably mono - α - ethylenically unsaturated , hydrophobic or hydrophilic monomer , at least a free radicals source compound , and a transfer agent , to obtain a first block , the transfer agent being linked to said first block , b1 ) reacting the first block , an ethylenically unsaturated , preferably mono - α - ethylenically unsaturated , hydrophobic or hydrophilic monomer , and , optionally , at least a radical source compound , to obtain a di - block copolymer , b2 ) optionally , repeating n times ( n being equal to or greater than 0 ) step b1 ) to obtain a ( n - 2 )- block copolymer , and then c ) optionally , reacting the transfer agent with means to render it inactive , or to remove it . for example , a “ living ” or “ controlled ” radical polymerization process used to make the di - block copolymers comprises the steps of : a ) reacting an ethylenically unsaturated , preferably mono - α - ethylenically unsaturated , hydrophobic or hydrophilic monomer , at least a free radicals source compound , and a transfer agent , to obtain a first block , the transfer agent being bounded to said first block , b ) reacting the first block , an ethylenically unsaturated , preferably mono - α - ethylenically unsaturated , hydrophobic or hydrophilic monomer , and , optionally , at least a radical source compound , to obtain a di - block copolymer , and then c ) optionally , reacting the transfer agent with means to render it inactive , or to remove it . during step a ), a first block of the polymer is synthesized with a hydrophilic or hydrophobic nature , according to the nature and the amount of the monomers used . during step b ), b1 ), or b2 ), another block of the polymer is synthesized . r represents an r 2 o —, r 2 r ′ 2 n — or r 3 — group , r 2 and r ′ 2 , which are identical or different , representing ( i ) an alkyl , acyl , aryl , alkene or alkyne group or ( ii ) an optionally aromatic , saturated or unsaturated carbonaceous ring or ( iii ) a saturated or unsaturated heterocycle , it being possible for these groups and rings ( i ), ( ii ) and ( iii ) to be substituted , r 3 representing h , cl , an alkyl , aryl , alkene or alkyne group , an optionally substituted , saturated or unsaturated ( hetero ) cycle , an alkylthio , alkoxycarbonyl , aryloxycarbonyl , carboxyl , acyloxy , carbamoyl , cyano , dialkyl - or diarylphosphonato , or dialkyl - or diarylphosphinato group , or a polymer chain , r1 represents ( i ) an optionally substituted alkyl , acyl , aryl , alkene or alkyne group or ( ii ) a carbonaceous ring which is saturated or unsaturated and which is optionally subsituted or aromatic or ( iii ) an optionally substituted , saturated or unsaturated heterocycle or a polymer chain , and the r1 , r 2 , r ′ 2 and r 3 groups can be substituted by substituted phenyl or alkyl groups , substituted aromatic groups or the following groups : oxo , alkoxycarbonyl or aryloxycarbonyl (— coor ), carboxyl (— cooh ), acyloxy (— o 2 cr ), carbamoyl (— conr 2 ), cyano (— cn ), alkylcarbonyl , alkylarylcarbonyl , arylcarbonyl , arylalkylcarbonyl , isocyanato , phthalimido , maleimido , succinimido , amidino , guanidino , hydroxyl (— oh ), amino (— nr 2 ), halogen , allyl , epoxy , alkoxy (— or ), s - alkyl , s - aryl or silyl , groups exhibiting a hydrophilic or ionic nature , such as alkaline salts of carboxylic acids or alkaline salts of sulphonic acid , poly ( alkylene oxide ) ( peo , ppo ) chains , or cationic substituents ( quaternary ammonium salts ), r representing an alkyl or aryl group . preferably , the transfer agent of formula ( i ) is a dithiocarbonate chosen from the compounds of following formulae ( ia ), ( ib ) and ( ic ): r 2 and r 2 ′ represent ( i ) an alkyl , acyl , aryl , alkene or alkyne group or ( ii ) an optionally aromatic , saturated or unsaturated carbonaceous ring or ( iii ) a saturated or unsaturated heterocycle , it being possible for these groups and rings ( i ), ( ii ) and ( iii ) to be substituted , r 1 and r 1 ′ represent ( i ) an optionally substituted alkyl , acyl , aryl , alkene or alkyne group or ( ii ) a carbonaceous ring which is saturated or unsaturated and which is optionally substituted or aromatic or ( iii ) an optionally substituted , saturated or unsaturated heterocycle or a polymer chain , and according to the above described process , if all the successive polymerizations are carried out in the same reactor , it is generally preferable for all the monomers used during one stage to have been consumed before the polymerization of the following stage begins , therefore before the new monomers are introduced . however , it may happen that the hydrophobic or hydrophilic monomers of the preceding stage are still present in the reactor during the polymerization of the following block . in this case , these monomers generally do not represent more than 5 mol % of all the monomers and they participate in the following polymerization by contributing to the introduction of the hydrophobic or hydrophilic units into the following block . the block copolymers prepared according to this polymerization process can be simply di - blocks , with a hydrophobic block and a hydrophilic block , or even triblocks , with either a hydrophilic block framed by two hydrophobic blocks or a hydrophobic block framed by two hydrophilic blocks . the polymerization can be carried out in an aqueous and / or organic solvent medium , such as tetrahydrofuran or a linear , cyclic or branched c 1 - c 8 aliphatic alcohol , such as methanol , ethanol or cyclohexanol , or a diol , such as ethylene glycol . an alcoholic solvent is more particularly recommended in the case where the hydrophilic monomers are acrylic acid ( aa ), acrylamide ( am ), 2 - acrylamido - 2 - methylpropanesulphonic acid ( amps ) and styrenesulphonate ( ss ) and the hydrophobic monomers are n - butyl acrylate , isobutyl acrylate , 2 - ethylhexyl acrylate or t - butyl acrylate . the polymerization can also be also be carried out in a neat form , or according to a latex type process . in a preferred embodiment , the hydrophobic block is a polybutylacrylate block , and the hydrophilic block is a polyacrylic acid block . in this embodiment , the ratio between the weight - average molecular weight of the hydrophilic block and the weight - average molecular weight of the hydrophobic block is preferably from 1 to 5 . in this embodiment , the weight - average molecular weight of the hydrophobic block is comprised between 1000 g / mol and 10000 g / mol , and the weight - average molecular weight of the hydrophilic block is preferably comprised between 1000 g / mol and 50000 g / mol . a process to obtain the aqueous suspension of nanoparticles comprises the step of mixing water , the organic the water - insoluble agrochemical active ingredient dissolved in a water - miscible solvent , and the amphiphilic compound . the amphiphilic compound may be added to water or to the solution comprising the organic water - insoluble agrochemical active ingredient , prior to mixing them . mixing may be performed by any means , such as a conventional mixing device . when mixing water and the organic water - insoluble agrochemical active ingredient , said water - insoluble organic agrochemical active ingredient precipitates to form solid nanoparticles , usually in a crystal form . it is believed that the amphiphilic compound has an effect at the interface of the active ingredient and water , which allows to obtain particles with the desired size and / or with a desired stability . the above described process is particularly simple and economical . it avoids performing milling , emulsification ( using a homogenizer ), atomizing steps , or other high - energy steps . in a preferred embodiment , a premix comprising a solvent of a water - insoluble organic agrochemical active ingredient , the active ingredient and the amphiphilic compound , dissolved in the solvent is prepared , and then mixed with water . dissolution may be eased by heating . mixing with water is for example carried out by pouring the premix into water . in another embodiment , a premix comprising a solvent of a water - insoluble - organic active ingredient , and the active ingredient , dissolved in the solvent is prepared , and then mixed with a premix of water and the amphiphilic compound . usually , the amphiphilic compound is comprised in a mixture wherein it is soluble , either a water - based mixture , or a mixture comprising an organic water - insoluble agrochemical ingredient . as the water is added , the amphiphilic compound ( at least the hydrophobic moiety thereof ) and the organic water - insoluble agrochemical active ingredient precipitate to form nanoparticles comprising the organic water - insoluble agrochemical active ingredient . said nanoparticles are in suspension in water . the mixing ratio between the solvent , or premix , and water is preferably comprised between 0 . 5 and 2 . in a particular embodiment , the obtained suspension of nanoparticles is re - diluted in water . this dilution improves the stability of the suspension . it may also lead to the concentration suitable for the use of the organic agrochemical active ingredient . in a further embodiment , the solvent may be removed , for example by distillation . aqueous suspensions may be used as such . they may be for example applied on a field , by spraying . in a particular embodiment of the invention , the water comprised in the aqueous suspension is removed , for example by freeze - drying or evaporating , to obtain dry solid nanoparticles . said dry solid nanoparticles may be in an agglomerate form . the dried solid nanoparticles , in an agglomerate form or not , are then rehydrated with water to obtain an aqueous suspension of the nanoparticles . drying the suspension may allow easier handling and cost - effective transportation . some illustrative but non - limitating examples are provided hereunder for the better understanding of the invention . amphiphilic compound a is alpha -{ 2 , 4 , 6 - tris [ 1 -( phenyl ) ethyl ] phenyl }- omega - hydroxy poly ( oxyethelene )- poly ( oxypropylene ) copolymer comprising from 2 to 8 moles of poly ( oxypropylene ) units and 16 - 30 units of poly ( oxyeythylene ) units , soprophor 796 / p , marketed by rhodia amphiphilic compound b is a di - block polybutylacrylate - polyacrylic acid ( pba - b - paa ) copolymer comprising a xanthate end - chain . the weight - average molecular weight of the pba block is 3000 g / mol , the weight - average molecular weight of the paa block is 12000 g / mol . this block copolymer is prepared by using a living polymerization process with a xanthate transfer agent . 0 . 5 weight % of amphiphilic compound b , 1 weight % of atrazine and methanol are mixed in a first beaker , to obtain 60 g of a solvent solution . 40 g of distilled water is poured into a second beaker . the two beakers are placed on separate heating plates with magnetic stirrers to ensure moderate agitation during heating . the solution and the water are heated to 35 ° c . temperature is monitored with temperature probes . atrazine and amphiphilic compound b are perfectly soluble at this temperature . the solvent solution is then poured into the water and the resultant mixture . a suspension of nanopaticles in water is obtained . it is then further diluted ten times ( 1 : 10 ). a particle size analysis is made , using a malvern mastersizer s version 2 . 18 device , and a size analysis performed assuming a polydisperse model and the standard - wet ( 3ohd ) presentation that assumes the particle is suspended in water . the mass median diameter of the nanoparticles is 520 nm , 90 % of the particles having a diameter of lower than 6 . 17 μm . more than 75 % of the particles have a diameter of lower than 1060 nm . the procedure of example 1 is carried out , using 0 . 1 weight % of amphiphilic compound b , and 0 . 1 weight % of atrazine , dissolved in 19 . 45 g of methanol , and using 30 g water . the mass median diameter is 350 nm , 90 % of the particles having a diameter lower than 1 . 53 μm . more than 75 % of the particles have a diameter of lower than 1060 nm . in a first beaker 0 . 5 g of atrazine ( 1 weight %) is dissolved in 24 . 5 g of methanol , at 35 ° c . in a second beaker 0 . 5 g of amphiphilic compound a ( 1 weight %) is dissolved in 24 . 5 g of distilled water . the two beakers are placed on separate heating plates with magnetic stirrers to ensure moderate agitation during heating . the solution and the water are heated to 35 ° c . temperature is monitored with temperature probes . the solvent solution is then poured into the water and the resultant mixture . a suspension of nanoparticles in water is obtained . it is then further diluted ten times ( 1 : 10 ). the mass median diameter of the nanoparticles is 300 nm , 90 % of the particles having a diameter lower than 6 . 37 μm . more than 75 % of the particles have a diameter of lower than 1060 nm .
the invention relates to an aqueous suspension of particles , said particles comprising an organic active ingredient . a controlled release of the ingredient occurs . the invention is especially suitable for the controlled release of organic agrochemical active ingredients useful in crop sciences , such as pesticides .