Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Bead polymer formulations
The present invention relates to new bead polymer formulations of agrochemical
active compounds, to a process for producing these preparations, and to their
use for
applying agrochemical active compounds.
EP-A 0 201 214 has already disclosed microparticles which can be prepared from
ethylenically unsaturated monomers and which comprise pesticidal active
compounds and have a particle diameter of between approximately 0.01 and 250
pm.
However, the disadvantage of these preparations is that the active components
are not
always released at the rate which is required for the biological effect.
Furthermore, there have already been described formulations comprising readily
teachable agrochemical active compounds in microencapsulated form in
unsaturated
polyester resins (cf. EP-A 0 517 669). Again, the release kinetics of the
microencapsulated active compounds do not always meet the practical
requirements
in this case. Hydrophobic active compounds are only released at a very slow
rate
from these formulations.
Furthermore, it can be seen from EP-A 0 281 918 that macroporous, crosslinked
polystyrene bead polymers are suitable as Garners for agrochemicals and can be
applied in crop protection. When employing these products, again, the rate at
which
the agrochemicals are released and their quantity frequently leaves something
to be
desired.
Finally, it can be seen from US-A 4 269 959 that weakly crosslinked
polystyrene
bead polymers are capable of absorbing liquid active compounds, such as
agrochemicals, and the products thus loaded can be employed as slow-release
formulations. However, the duration of action of such preparations is not
always
sufficient.
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New bead polymer formulations have now been found which are composed of
I) a particulate solid phase comprising
A) copolymer of
a) 40 to 95% by weight of water-insoluble monomer
b) 5 to 35% by weight of water-soluble monomer
c) 0 to 25% by weight of crosslinker,
and
B) at least one agrochemical active compound
and,
C) if appropriate, additives,
the agrochemical active compound content being between 5 and 75% by
weight and the solid phase having a mean particle size of between 1 and
100 pm,
and,
II) if appropriate, a liquid phase.
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Furthermore, it has been found that bead polymer formulations according to the
invention can be produced by finely dividing, at temperatures between
0°C and 60°C
and with stirring,
A) an organic phase of
- 25 to 95% by weight of a monomer mixture of
a) 40 to 95% by weight of water-insoluble monomer,
b) 5 to 35% by weight of water-soluble monomer
c) 0 to 25% by weight of crosslinker,
S to 75% by weight of at least one agrochemical active compound,
- at least one initiator,
- if appropriate, additives
and,
- if appropriate, an organic solvent which is sparingly miscible with
water,
B) in an aqueous phase of
- water,
- at least one dispersant and,
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- if appropriate, a buffer reagent,
C) then polymerizing the stirred mixture while increasing the temperature,
D) and, if appropriate, thereupon either
a) isolating, washing and drying the resulting bead polymer
or
(3) removing any volatile organic substances which may be present and
thus retaining the bead polymer in aqueous suspension.
Finally, it has been found that the bead polymer formulations according to the
invention are very suited for applying agrochemical active compounds.
The bead polymer formulations according to the invention are distinguished by
a
series of advantages. Thus, they are capable of releasing a uniform quantity
of the
active components over a substantial period. What is especially expedient is
that the
release rate of the active compound can be controlled within wide limits by
the
content of water-soluble monomer.
The copolymers present in the bead polymer formulations according to the
invention
are characterized by the components listed under (a) to (c).
The term water-insoluble monomers (a) is to be understood as meaning
monoethylenically unsaturated compounds of which less than 5% dissolve in
water at
20°C. Preferred water-insoluble monomers (a) are the alkyl esters of
acrylic acid and
methacrylic acid, styrene, styrene derivatives and mixtures of styrene and
acrylonitrile, or else vinyl derivatives. Examples which may be mentioned are:
styrene, alpha-methylstyrene, vinyl chloride, vinylidene chloride, vinyl
acetate, vinyl
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propionate, vinyl laurate, vinyl adipate, methyl methacrylate, methyl
acrylate, ethyl
acrylate, isopropyl methacrylate, n-propyl methacrylate, n-butyl acrylate, n-
butyl
methacrylate, isobutyl acrylate, isobutyl methacrylate, n-hexyl acrylate, n-
hexyl
methacrylate, ethylhexyl acrylate, ethylhexyl methacrylate, n-octyl acrylate,
n-octyl
methacrylate, decyl acrylate, decyl methacrylate, dodecyl acrylate, dodecvl
methacrylate, stearyl acrylate, stearyl methacrylate, cyclohexyl acrylate, and
cyclohexyl methacrylate. Another possibility is acrylonitrile, which is
slightly more
readily soluble in water, as part of a mixture with other monomers (a),
preferably a
mixture with styrene.
Water-soluble monomers (b) for the purposes of the invention are
monoethylenically
unsaturated compounds of which more than 5% by weight dissolve in water at
20°C.
Examples which may be mentioned are: acrylic acid and its alkali metal and
ammonium salts, methacrylic acid and its alkali metal and ammonium salts,
hydroxyethyl methacrylate, hydroxyethyl acrylate, diethylene glycol
monoacrylate,
diethylene glycol monomethacrylate, triethylene glycol monoacrylate,
triethylene
glycol monomethacrylate, tetraethylene glycol monoacrylate, tetraethylene
glycol
monomethacrylate, glycerol monoacrylate, aminoethyl methacrylate,
dimethylaminoethyl methacrylate, acrylamide, methacrylamide, vinylpyrrolidone
and
vinylimidazole. Hydroxyethyl methacrylate is preferred.
The amount of water-soluble monomer (b) is essential for the release of the
active
compound. The release rate of the agrochemical active compound can be
controlled
within wide limits via the amount of (b). The greater the amount of (b), the
higher the
release rate of the active compound. For most practical applications, the
amount of
(b) is in the range of 5 to 35% by weight. In many cases, an amount of (b) in
the
range of 7.5 to 20% by weight results in particularly good effects.
Suitable crosslinkers (c) are compounds with at least two ethylenically
unsaturated
groups in the molecule. Examples which may be mentioned are: allyl
methacrylate,
ethylene glycol dimethacrylate, ethylene glycol diacrylate, butanediol
diacrylate,
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butanediol dimethacrylate, hexane diol dimethacrylate, triethylene glycol
dimethacrylate, tetraethylene glycol dimethacrylate, trimethylolpropane
triacrylate,
pentaerythritol tetramethacrylate and divinylbenzene. Ethylene glycol
dimethacrylate
and divinylbenzene are preferred.
S
The amount of crosslinker (c) in the copolymer can be varied within a certain
range.
In general, the amount of crosslinker (c) is between 0 and 25% by weight,
preferably
between 0.1 and 15% by weight, especially preferably between 0.5 and 10% by
weight.
Agrochemical active compounds are to be understood as meaning in the present
context all substances which are customary in the treatment of plants.
Substances
which may preferably be mentioned are fungicides, bactericides, insecticides,
acaricides, nematicides, herbicides, plant growth regulators, plant nutrients
and
repellents.
Examples of fungicides which may be mentioned are:
2-aminobutane; 2-anilino-4-methyl-6-cyclopropylpyrimidine; 2',6'-dibromo-
2-methyl-4'-trifluoromethoxy-4'-trifluoromethyl-1,3-thiazole-5-carboxanilide;
2,6-dichloro-N-(4-trifluoromethylbenzyl)benzamide; (E)-2-methoximino-N-methyl-
2-(2-phenoxyphenyl)acetamide; 8-hydroxyquinoline sulphate;
methyl (E)-2-{2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy]phenyl}-3-methoxy
acrylate; methyl (E)-methoximino[alpha-(o-tolyloxy)-o-tolyl]acetate; 2-
phenylphenol
(OPP),
aldimorph, ampropylfos, anilazin, azaconazole,
benalaxyl, benodanil, benomyl, binapacryl, bion, biphenyl, bitertanol,
blasticidin-S,
bromuconazole, bupirimate, buthiobate,
calcium polysulphide, captafol, captan, carbendazim, carboxin, quinomethionate
chloroneb, chloropicrin, chlorothalonil, chlozolinate, cufraneb, cymoxanil,
cyproconazole, cyprofuram,
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dichlorophene, diclobutrazole, dichlofluanide, diclomezin, dicloran,
diethofencarb,
difenoconazole, dimethirimol, dimethomorph, diniconazole, dinocap,
diphenylamine,
dipyrithion, ditalimfos, dithianon, dodine, drazoxolon,
edifenphos, epoxyconazole, ethirimol, etridiazole,
fenarimol, fenbuconazole, fenfuram, fenitropan, fenpiclonil, fenpropidin,
fenpropimorph, fentin acetate, fentin hydroxide, ferbam, ferimzone, fluazinam,
fludioxonil, fluoromide, fluquinconazole, flusilazole, flusulphamide,
flutolanil,
flutriafol, folpet, fosetyl-aluminium, fthalide, fuberidazole, furalaxyl,
furmecyclox,
guazatine,
hexachlorobenzene, hexaconazole, hymexazol,
imazalil, imibenconazole, iminoctadin, iprobenfos (IBP), iprodion,
isoprothiolan,
kasugamycin, mancozeb, maneb, mepanipyrim, mepronil, metalaxyl, metconazole,
methasulphocarb, methfuroxam, metiram, metsulphovax, myclobutanil,
nickel dimethyldithiocarbamate, nitrothalisopropyl, nuarimol,
ofurace, oxadixyl, oxamocarb, oxycarboxin,
pefurazoate, penconazole, pencycuron, phosdiphen, pimaricin, piperalin,
polyoxin,
probenazole, prochloraz, procymidone, propamocarb, propiconazole, propineb,
pyrazophos, pyrifenox, pyrimethanil, pyroquilon,
quintozene (PCNB),
tebuconazole, tecloftalam, techazen, tetraconazole, thiabendazole, thicyufen,
thiophanate-methyl, thiram, tolclophos-methyl, tolylfluanid, triadimefon,
triadimenol, triazoxide, trichlamid, tricyclazole, tridemorph, triflumizole,
triforine,
triticonazole,
validamycin A, vinclozolin,
Zineb, Ziram,
8-tert-butyl-2-(N-ethyl-N-n-propyl-amino)-methyl-1,4-dioxa-spiro-[4,5 ]
decane,
N-(R)-[ 1-(4-chlorophenyl)-ethyl]-2,2-dichloro-I -ethyl-3t-methyl-1 r-
cyclopropanecarboxamide (diastereomer mixture or individual isomers),
1-methylethyl [2-methyl-I-[[[1-(4-methylphenyl)-ethyl]-amino]-carbonyl]-
propyl]-
carbamate,
(2,3-dichloro-4-hydroxy)-1-methyl-cyclohexane- I -carboxanilide,
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2-[2-( 1-chloro-cyclopropyl)-3-(2-chlorophenyl)-2-hydroxypropyl]-2,4-dihydro-
[1,2,4]-triazole-3-thione and
1-(3,5-dimethyl-isoxazo le-4-sulphonyl)-2-chloro-6,6-difluoro-[ 1,3 ]-dioxolo-
[4, 5-f]-
benzimidazole.
Examples of bactericides which may be mentioned are:
bronopol, dichlorophen, nitrapyrin, nickel dimethyldithiocarbamate,
kasugamycin,
octhilinone, furane carboxylic acid, oxytetracyclin, probenazole,
streptomycin,
tecloftalam, copper sulphate and other copper preparations.
Examples of insecticides, acaricides and nematicides which may be mentioned
are:
abamectin, acephate, acrinathrin, alanycarb, aldicarb, alphamethrin, amitraz,
avermectin, AZ 60541, azadirachtin, azinphos A, azinphos M, azocyclotin,
Bacillus thuringiensis, 4-bromo-2-(4-chlorophenyl)-1-(ethoxymethyl)
5-(trifluoromethyl)-1H-pyrrole-3-carbonitrile, bendiocarb, benfuracarb,
bensultap,
betacyfluthrin, bifenthrin, BPMC, brofenprox, bromophos A, bufencarb,
buprofezin,
butocarboxin, butylpyridaben,
cadusafos, carbaryl, carbofuran, carbophenothion, carbosulphan, cartap,
chloethocarb, chloretoxyfos, chlorfenvinphos, chlorfluazuron, chlormephos, N-
[(6
chloro-3-pyridinyl)-methyl]-N'-cyano-N-methyl-ethanimidamide, chlorpyrifos,
chlorpyrifos M, cis-resmethrin, clocythrin, clofentezine, cyanophos,
cycloprothrin,
cyfluthrin, cyhalothrin, cyhexatin, cypermethrin, cyromazine,
deltamethrin, demeton-M, demeton-S, demeton-S-methyl, diafenthiuron, diazinon,
dichlofenthion, dichlorvos, dicliphos, dicrotophos, diethion, diflubenzuron,
dimethoate,
dimethylvinphos, dioxathion, disulphoton,
edifenphos, emamectin, esfenvalerate, ethiofencarb, ethion, ethofenprox,
ethoprophos, etrimphos,
fenamiphos, fenazaquin, fenbutatin oxide, fenitrothion, fenobucarb,
fenothiocarb,
fenoxycarb, fenpropathrin, fenpyrad, fenpyroximate, fenthion, fenvalerate,
fipronil,
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fluazinam, fluazuron, flucycloxuron, flucythrinate, flufenoxuron, flufenprox,
fluvalinate, fonophos, formothion, fosthiazate, fubfenprox, furathiocarb,
HCH, heptenophos, hexaflumuron, hexythiazox,
imidacloprid, iprobenfos, isazophos, isofenphos, isoprocarb, isoxathion,
ivermectin,
lambda-cyhalothrin, lufenuron,
malathion, mecarbam, mevinphos, mesulphenphos, metaldehyde, methacrifos,
methamidophos, methidathion, methiocarb, methomyl, metolcarb, milbemectin,
monocrotophos, moxidectin,
naled, NC 184, nitenpyram,
omethoat, oxamyl, oxydemethon M, oxydeprofos,
parathion A, parathion M, permethrin, phenthoate, phorate, phosalone, phosmet,
phosphamidon, phoxim, pirimicarb, pirimiphos M, pirimiphos A, profenophos,
promecarb, propaphos, propoxur, prothiophos, prothoate, pymetrozin,
pyrachlophos,
pyridaphenthion, pyresmethrin, pyrethrum, pyridaben, pyrimidifen,
pyriproxifen,
quinalphos,
salithion, sebufos, silafluofen, sulphotep, sulprofos,
tebufenozide, tebufenpyrad, tebupirimiphos, teflubenzuron, tefluthrin,
temephos,
terbam, terbufos, tetrachlorvinphos, thiafenox, thiodicarb, thiofanox,
thiomethon,
thionazin, thuringiensin, tralomethrin, transfluthrin, triarathene,
triazophos, triazuron,
trichlorfon, triflumuron, trimethacarb,
vamidothion, XMC, xylylcarb, zetamethrin.
Examples of herbicides which may be mentioned are:
anilides such as, for example, diflufenican and propanil; aryl carboxylic
acids such
as, for example, dichloropicolinic acid, dicamba and picloram; aryloxyalkanoic
acids
such as, for example, 2,4-D, 2,4-DB, 2,4-DP, fluroxypyr, MCPA, MCPP and
triclopyr; aryloxy-phenoxy-alkanoates such as, for example, diclofop-methyl,
fenoxaprop-ethyl, fluazifop-butyl, haloxyfop-methyl and quizalofop-ethyl;
azinones
such as, for example, chloridazon and norflurazon; carbamates such as, for
example,
chlorpropham, desmedipham, phenmedipham and propham; Chloroacetanilides such
as, for example, alachlor, acetochlor, butachlor, metazachlor, metolachlor,
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pretilachlor and propachlor; dinitroanilines such as, for example, oryzalin,
pendimethalin and trifluralin; Biphenyl ethers such as, for example,
acifluorfen,
bifenox, fluoroglycofen, fomesafen, halosafen, lactofen and oxyfluorfen; ureas
such
as, for example, chlortoluron, diuron, fluometuron, isoproturon, linuron and
methabenzthiazuron; hydroxylamines such as, for example, alloxydim, clethodim,
cycloxydim, sethoxydim and tralkoxydim; imidazolinones such as, for example,
imazethapyr, imazamethabenz, imazapyr and imazaquin; nitriles such as, for
example, bromoxynil, dichlobenil and ioxynil; oxyacetamides such as, for
example,
mefenacet; sulphonylureas such as, for example, amidosulphuron, bensulphuron-
methyl, chlorimuron-ethyl, chlorsulphuron, cinosulphuron, metsulphuron-methyl,
nicosulphuron, primisulphuron, pyrazosulphuron-ethyl, thifensulphuron-methyl,
triasulphuron and tribenuron-methyl; thiolcarbamates such as, for example,
butylate,
cycloate, di-allate, EPTC, esprocarb, molinate, prosulphocarb, thiobencarb and
tri-
allate; triazines such as, for example, atrazine, cyanazine, simazine,
simetryn,
terbutryn and terbutylazine; triazinones such as, for example, hexazinon,
metamitron
and metribuzin; others such as, for example, aminotriazole, 4-amino-N-(1,1-
dimethylethyl)-4,5-dihydro-3-( 1-methylethyl)-5-oxo-1 H-1,2,4-triazole-1-
carboxamide, benfuresate, bentazone, cinmethylin, clomazone, clopyralid,
difenzoquat, dithiopyr, ethofumesate, fluorochloridone, glufosinate,
glyphosate,
isoxaben, pyridate, quinchlorac, quinmerac, sulphosate and tridiphane.
Examples of plant growth regulators which may be mentioned are chlorocholine
chloride and ethephon.
Examples of plant nutrients which may be mentioned are customary inorganic or
organic fertilizers for providing plants with macro- and/or micronutrients.
Examples of repellents which may be mentioned are diethyltolylamide,
ethylhexanediol and butopyronoxyl.
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Suitable additives which may be present in the solid phase in the bead polymer
formulations according to the invention are all those substances which can
conventionally be employed as additives in plant treatment products. These
include,
for example, plasticizers, colours, antioxidants, antifreeze agents and
fillers.
Plasticizers which are suitable in the present case are liquid or solid
indifferent
materials with a low vapour pressure and a molecular weight of between 150 and
1000 which interact with highly-polymeric materials without chemical reaction,
preferably by virtue of their dissolving power or swelling capacity, thus
forming a
homogeneous physical system with the former.
Suitable colours are soluble or sparingly soluble colour pigments such as, for
example, titanium dioxide, colour black or zinc oxide.
Suitable antioxidants are all substances which can conventionally be employed
for
this purpose in plant treatment compositions. Sterically hindered phenols and
alkyl-
substituted hydroxyanisoles and hydroxytoluenes are preferred.
Suitable antifreeze agents are all materials which can conventionally be
employed for
this purpose in plant treatment compositions. Urea, glycerol or propylene
glycol are
preferably suitable.
Fillers which are mainly suitable are inorganic particles such as, for
example,
carbonates, silicates and oxides with a mean particle size of 0.005 to 5 pm,
preferably
0.02 to 2 pm. Especially well suited are silicon dioxide, so-called highly-
disperse
silica, silica gels, and natural and synthetic silicates and alumosilicates.
The amount of the individual components in the bead polymer formulations
according to the invention can be varied within a substantial range. In the
solid phase,
the concentrations
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- of copolymer (A) are thus generally between 25 and 95% by weight,
preferably between 40 and 90% by weight,
- of agrochemical active compounds (B) are generally between 5 and 75% by
weight, preferably between 10 and 60% by weight, and
- of additives (C) are generally between 0 and 30% by weight, preferably
between 0 and 15% by weight.
The particle size of the solid particles in the bead polymer formulations
according to
the invention can be varied within a certain range. It is generally between 1
and
100 ~tm, preferably between 5 and 50 pm.
The bead polymer formulations according to the invention can either be present
as
particulate solid phase or as a dispersion of solid particles in a liquid
phase.
If a liquid phase is present, it consists essentially of water. In addition,
components
may be present which are employed in the preparation of the bead polymer
formulations according to the invention and which remain in the liquid phase.
Substances which are suitable as such components are organic solvents which
are
sparingly miscible with water, dispersants (protective colloids) and buffer
reagents.
Suitable organic solvents in this context are all those customary organic
solvents
which, on the one hand, are sparingly miscible with water but, on the other
hand,
effectively dissolve the agrochemical active compounds employed. Examples of
such
solvents which may be mentioned are aromatic hydrocarbons such as toluene and
xylene, furthermore halogenated hydrocarbons such as tetrachloromethane,
chloroform, methylene chloride and dichloroethane, and furthermore also esters
such
as ethyl acetate.
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Substances which are suitable as dispersants are all those conventionally
employed
for this purpose. The following may be mentioned as being preferred: natural
and
synthetic water-soluble polymers such as gelatin, starch, and cellulose
derivatives, in
particular cellulose esters and cellulose ethers, furthermore polyvinyl
alcohol,
polyvinylpyrrolidone, polyacrylic acid, polymethacrylic acid and copolymers of
(meth)acrylic acid and (meth)acrylates, and also copolymers of methacrylic
acid and
methacrylate which have been neutralized with alkali metal hydroxide.
Substances which are suitable as buffer reagents are all those conventionally
employed for this purpose. Phosphate and borate salts may be mentioned as
being
preferred.
The amounts of the additional substances in the aqueous phase which have been
mentioned can be varied within a substantial range. The concentration depends
on the
amounts in which these substances are employed during the preparation of the
bead
polymer formulations according to the invention and on the type of work-up
after
polymerization.
The bead polymer formulations according to the invention are prepared by the
suspension polymerization method.
The term suspension polymerization is to be understood as meaning a process in
which a monomer or a monomer-comprising mixture comprising an initiator which
is
soluble in the monomers) is distributed in the form of droplets, if
appropriate in a
mixture with small, solid particles, in a phase comprising a dispersant and
essentially
not miscible with the monomer(s), and the mixture is cured, with stirring, by
increasing the temperature. More details on suspension polymerization are
described,
for example, in the publication "Polyner Processes", edited by C.E.
Schildknecht,
published 1956 by Interscience Publishers lnc., New York, in the chapter
"Polymerization in Suspension" on pages 69 to 109.
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The monomer mixtures required as starting materials for carrying out the
process
according to the invention are characterized by the components listed under
(a) to (c).
Preferably suitable components are those which have already been mentioned in
connection with the description of the copolymers.
Agrochemical active compounds which can be employed in carrying out the
process
according to the invention are all those substances which can be used for
treating
plants and which have already been mentioned as agrochemical active compounds
in
connection with the description of the bead polymer formulations according to
the
invention.
Initiators which can be employed in carrying out the process according to the
invention are all substances which can conventionally be used for initiating
polymerizations. Initiators which are soluble in oil are preferably suitable.
Examples
which may be mentioned are peroxy compounds such as dibenzoyl peroxide,
dilauryl
peroxide, bis(p-chlorobenzoyl peroxide), dicyclohexyl peroxydicarbonate, tert-
butyl
peroctoate, 2,5-bis-(2-ethylhexanoylperoxy)-2,5-dimethylhexane and
tert-amylperoxy-2-ethylhexane, and furthermore azo compounds such as
2,2'-azobis(isobutyronitrile) and 2,2'-azobis(2-methylisobutyronitrile).
Additives which can be employed in carrying out the process according to the
invention are all those substances which have already been mentioned as
additives in
connection with the description of the bead polymer formulations according to
the
W vention.
When carrying out the process according to the invention, organic solvents
which are
sparingly miscible with water can be employed as cosolvents. Suitable
cosolvents are
all those organic diluents which have already been mentioned in connection
with the
description of the aqueous phase of the bead polymer formulations according to
the
invention.
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The substances which are suitable as dispersants or buffer reagents for
carrying out
the process according to the invention, too, have already been mentioned in
connection with the description of the aqueous phase of the bead polymer
formulations according to the invention.
When carrying out the process according to the invention, a procedure is
generally
followed in which a homogeneous mixture of monomer mixture (a - c), one or
more
agrochemical active compounds and, if appropriate, additives is prepared
first. This
homogeneous mixture may be a solution or else a fine dispersion.
If an agrochemical active compound is not, or is insufficiently, soluble in
the
monomer mixture, it can exist in finely disperse form. The term fine in the
present
context is to be understood as meaning that the active compound particles, or
active
compound droplets, have a mean particle size of less than 2 pm, preferably
less than
I pm. A fine dispersion can be prepared with the aid of high-performance
stirrers
(preferred in the case of liquid active compounds) or bead mills/ball mills
(preferred
in the case of solid active compounds).
In a preferred variant, the process according to the invention can be carried
out in
such a manner that the mixture of monomer mixture, agrochemical active
compound
and, if appropriate, additives is employed in the form of a solution, a
cosolvent being
employed to improve the solubility of the agrochemical active compound.
Suitable
cosolvents are organic solvents which, while being sparingly miscible with
water,
dissolve the respective agrochemical active compound well. Materials which can
preferably be used are the organic diluents which have already been mentioned.
In a further preferred variant, the process according to the invention can be
carried
out in such a manner that a buffer reagent is added to the aqueous phase (B)
so that
the pH of the aqueous phase has a value of between 12 and ~, preferably
between 10
and 6, at the beginning of the polymerization.
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When carrying out the process according to the invention, the quantitative
ratios of
the components employed can be varied within a substantial range.
In general, the amounts of monomer mixture and agrochemical active compound
are
chosen in such a way that between 25 and 95% by weight of monomer mixture and
between 5 and 75% by weight of agrochemical active compound, preferably
between
40 and 90% by weight of monomer mixture and between 10 and 60% by weight of
agrochemical compound, are present in the homogeneous mixture employed.
Initiators are generally employed in amounts of between 0.05 and 2.5% by
weight,
preferably between 0.2 and 1.5% by weight, based on the monomer mixture.
The cosolvent generally amounts to between 30 and 300% by weight, based on the
total of monomer mixture and agrochemical active compound.
The aqueous phase generally amounts to between 75 and 1200% by weight,
preferably between 100 and 500% by weight, based on the total of monomer
mixture
and agrochemical active compound.
The dispersant generally amounts to between 0.05 and 2% by weight, preferably
between 0.1 and 1 % by weight, based on the aqueous phase.
In the first step of the process according to the invention, the organic phase
is added
to the stirred aqueous phase. During this process, the temperature can be
varied
within a certain range. In general, the process is carried out at temperatures
between
0°C and 60°C, preferably between 10°C and 50°C.
Polymerization is effected during the second step of the process according to
the
invention. The stirring rate is important for establishing the particle size.
Thus, the
mean particle size of the bead polymers decreases with increasing stirring
speed. The
exact stirring speed for establishing a particular, predetermined bead size
depends
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greatly in each individual case on the reactor size, the reactor geometry and
the stirrer
geometry. It has proved expedient to determine the required stirring speed by
experimentation. If copolymers of (meth)acrylic acid and (meth)acrylates as
dispersants are used, bead sizes of between 6 and 30 pm are generally achieved
at
speeds between 300 and 500 revolutions per minute in the case of laboratory
reactors
which have a reaction volume of 3 litres and are equipped with blade stirrers.
The polymerization temperature can be varied within a substantial range. It
depends
on the disintegration temperature of the initiator employed. In general, the
process is
earned out at temperatures between 50°C and 150°C, preferably
between 55°C and
100°C.
The polymerization time depends on the reactivity of the compounds employed.
In
general, polymerization takes between 30 minutes and several hours. It has
proved
expedient to use a temperature programme in which polymerization starts at low
temperature, for example 70°C, and the reaction time is increased as
polymerization
progresses.
Work-up during the last step of the process according to the invention is
carried out
by customary methods. If it is desired to remove the finely divided solid
phase, the
bead polymer can be isolated, for example by filtration or decanting, and then
dried,
if appropriate after washing. If it is desired to produce a suspension of bead
polymer
in the aqueous phase, further work-up can be dispensed with in most cases. Any
remaining cosolvent can be removed from the resulting mixture by distillation,
if
appropriate together with some of the water.
The bead polymer formulations according to the invention are outstandingly
suited
for applying agrochemical active compounds to plants and/or their environment.
They allow in each case the desired amount of active components to be released
over
a prolonged period.
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The bead polymer formulations according to the invention as such can be
employed
in practice either in solid form or as suspensions, if appropriate after
previous
dilution with water. They are applied by customary methods, for example,
watering,
spraying, atomizing or spreading.
The application rate of the bead polymer formulations according to the
invention can
be varied within a substantial range. It depends on the respective
agrochemical active
compounds and their content in the bead polymers.
The invention is illustrated by the examples which follow.
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Preparation examples
Example 1
Bead polymers, comprising 4-amino-N-(l,l-dimethylethyl)-4,5-dihydro-3-(1-
methyl-
ethyl)-5-oxo-1H-1,2,4-triazole-1-carboxamide, of the formula
~N
~N~N~NH~
HZN
O
Three different bead polymers with different copolymer compositions are
prepared.
In each case x g of methyl methacrylate, y g of hydroxyethyl methacrylate, z g
of
ethylene glycol dimethyl acrylate and 97 g of 4-amino-N-(1,1-dimethylethyl)-
4,5-di-
hydro-3-(1-methylethyl)-5-oxo-1H-1,2,4-triazole-1-carboxamide are mixed for 2
hours in a ball mill, and 3.9 g of dibenzoyl peroxide are subsequently added
to the
stirred mixture at room temperature. The mixture is transferred into a stirred
reactor
which had previously been charged with 1.5 litres of a 1 % by weight aqueous-
alkaline solution of a copolymer of 50% by weight of methacrylate and 50% by
weight of methyl methacrylate, which solution had been brought to pH 8 with
sodium
hydroxide solution. The stirnng rate is set at 700 revolutions per minute and
the
temperature is held for 3 hours at 60°C, then for 10 hours at
78°C and then for 2
hours at 85°C. Then, the mixture is cooled to room temperature in the
course of 2
hours. This gives dispersions of active-compound-containing bead polymers.
Example x y z Hydroxyethyl Mean particle
No. (in g) (in g) (in g) methacrylate diameter
content of the bead
in the co of polymer
mer articles
I A232.8 29.1 29.1 10 % 7.9 m
1 B 203.7 58.2 29. l 20 % 7.6 m
1 C 174.6 87.3 29.1 30 % 6.5 m
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Example 2
Bead polymers, comprising imidacloprid, of the formula
N~N02
N~NH
o~ ~,
CI N
Three different bead polymers with different copolymer compositions are
prepared.
In each case x g of methyl methacrylate, y g of hydroxyethyl methacrylate, z g
of
ethylene glycol dimethyl acrylate and 100 g of imidacloprid and 30 g of finely
divided silicon dioxide (HDK H2000, from Wacker) are mixed for 2 hours in a
ball
mill, and 3 g of dibenzoyl peroxide are subsequently added to the stirred
mixture at
room temperature. The mixture is transferred into a stirred reactor which had
previously been charged with 1.5 litres of a 1 % by weight aqueous-alkaline
solution
of a copolymer of 50% by weight of methacrylate and 50% by weight of methyl
methacrylate, which solution had been brought to pH 8 with sodium hydroxide
solution. The stirring rate is set at 500 revolutions per minute and the
temperature is
held for 8 hours at 78°C and then for 2 hours at 85°C. Then, the
mixture is cooled to
room temperature in the course of 2 hours. The bead polymer is isolated by
allowing
it to settle and decanting off, is washed with cold water and dried in the
drying oven
at 50°C.
Example x y z Hydroxyethyl Mean particle
No. (in g) (in g) (in g) methacrylate diameter of
content the bead
in the co of mer articles
of mer
2A 255 _ 10 % 42 m
30 15
2B 225 60 15 20 % 50 ~tm
2C 195 90 15 30 ,% 45 m
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Release test A
To check the release rate of the active compound, homogeneous samples of in
each
case 4 ml of the dispersions of Examples 1 A - C were diluted with 950 ml of
water.
The mixture was stored for 35 days with shaking. After the times shown in
Table 1,
the active compound content in the aqueous phase was determined by means of
HPLC. The numerical value in the table which follows indicates the percentage
of the
active compound which has been released into the water, based on the amount of
active compound which has been added.
Table 1
Bead polymerAmount
of of active
compound
released
afrer
Exam le 1 da 3 ~da s 14 da 21 da s 35 da
No. s s i
1 A 35 % 48 % 55 % 60 % 68 % II
1B 46% 58% 66% 71% 80% 'I
IC 76 % 81 % 87 % 92 % 97
The experimental series demonstrates clearly that the release rate of the
active
compound is governed by the hydroxyethyl methacrylate content in the
copolymer.
Release test B
To check the release rate of the active compound, in each case 1 g of the bead
polymers of Examples 2 A - C were dispersed in 1 litre of water. The
dispersion was
stored for 240 hours, with shaking. After the times indicated in Table 2, the
active
compound content in the aqueous phase was determined. The numerical value
indicates the percentage of the active compound released into the water, based
on the
amount of active compound which has been added.
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Table 2
Bead polymerAmount
of of
active
compound
released
after
Example 4 h 24 h 48 h 96 h 192 h
No.
2A 2% 5% 7% 10% 18%
2B 8% il% 13% 17% 32%
2C 20 % 38 % 50 % 62 % 74
Again, the experimental series demonstrates clearly that the release rate of
the active
compound is governed by the hydroxyethyl methacrylate content in the
copolymer.
