Microencapsulated pyrethroidal cockroach-controlling composition is provided, which has an excellent residual effect. The composition comprises phenylxylylethane and a pyrethroidal compound and is encapsulated in microcapsules formed of a polyurethane wall which have an average particle diameter of not more than 80 .mu.m, a wall thickness of not more than 0.3 .mu.m, and a value of the average particle diameter/wall thickness of 100-400.

BACKGROUND OF THE INVENTION 
The present invention relates to a microencapsulated cockroach-controlling 
composition wherein an insecticide having a 3-phenoxybenzyl group and 
phenylxylylethane are encapsulated in microcapsules having polyurethane 
wall which have an average particle diameter of not more than 80 .mu.m, a 
wall thickness of not more than 0.3 .mu.m and a value of the average 
particle diameter/wall thickness of 100-400. 
Controlling cockroach has been mainly carried out by a residual spray 
method. 
At present, formulations such as emulsifiable concentrate, solubilized 
emulsion concentrate and oil solution which contain, for example, an 
organophosphorus insecticide or pyrethroidal insecticide as an active 
ingredient are used for the residual spray. 
Especially residual efficacy and safety are desired factors to formulations 
used for the residual spray. If the residual efficacy is to be enhanced 
with the conventional formulations such as emulsifiable concentrate, 
solubilized emulsion concentrate and oil solution, a high application 
dosage is required, which may bring about problem in safety. Thus, 
formulations being safer and having greater in efficacy are increasingly 
demanded. 
Under the circumstances, research and development of so-called 
microencapsulation technique that an active ingredient is enclosed in a 
wall material have become intensive. As microencapsulated insecticides, 
those which contain organophosphorus insecticide as an active ingredient 
are disclosed in Japanese Patent Kokai No. 62-161706 and those which 
contain pyrethroidal insecticide as an active ingredient are disclosed in 
Japanese Patent Kokoku No. 55-38325. 
In some cases, microencapsulation of insecticides might be effective for 
improving residual efficacy. 
However, residual efficacy of microencapsulated insecticides varies 
depending upon a particle diameter of microcapsule and a wall thickness. 
Optimum particle diameter and wall thickness should be chosen in order to 
maintain residual efficacy for a prolonged period of time. The optimum 
range naturally varies depending on varieties of insect pests to be 
controlled and of insecticides. 
In general, microencapsulation of insecticides having a polyurethane wall 
is performed by interfacial polymerization using a polyfunctional 
isocyanate. 
The interfacial polymerization method essentially requires a step of 
homogeneously mixing an active ingredient to be enclosed in capsules with 
polyfunctional isocyanate. 
In the case when the active ingredient is a pyrethroidal insecticide, an 
organic solvent may be added as so-called cosolvent when the insecticide 
is mixed with a polyfunctional isocyanate which is sometimes high in 
viscosity, since this insecticide is generally high in viscosity and 
sometimes is in the form of crystal. Japanese Patent Kokoku No. 55-38325 
mentions "For example, as usual organic solvents, there may be selected 
from hydrocarbons such as xylene, toluene, hexane and heptane, chlorinated 
hydrocarbons such as carbon tetrachloride and chloroform, ketones such as 
methylisobutyl ketone, methyl ethyl ketone and cyclohexanone and esters 
such as diethyl phthalate and n-butyl acetate." 
However, these known techniques are not necessarily satisfactory when some 
pyrethroidal insecticides are used as an active ingredient for 
cockroach-controlling. 
The inventors have made intensive study on optimum ranges of particle 
diameter and wall thickness of microcapsules and on selection of optimum 
organic solvents when an insecticide having a 3-phenoxybenzyl group is 
encapsulated as a core material in a polyurethane wall and then this is 
used for cockroach-controlling. 
As a result, it has been found that some insecticides having a 
3-phenoxybenzyl group microencapsulated as a core material in polyurethane 
wall using phenylxylylethane as a cosolvent have residual efficacy for a 
prolonged period of time for cockroach-controlling. 
SUMMARY OF THE INVENTION 
The present invention provides a microencapsulated cockroach-controlling 
composition which is referred to as "the present composition" hereinafter, 
wherein phenylxylylethane and at least one active ingredient defined below 
are encapsulated in a microcapsule having a polyurethane wall which has an 
average particle diameter of not more than 80 .mu.m, a wall thickness of 
not more than 0.3 .mu.m and a value of the average particle diameter/wall 
thickness of 100-400. The active ingredients mentioned above are those 
represented by the formula: 
##STR1## 
wherein R.sup.1 represents a hydrogen atom or a fluorine atom, X 
represents a hydrogen atom or a cyano group, and Y represents a group 
represented by the formula: 
##STR2## 
wherein R.sup.2 represents a hydrogen atom or a methyl group; when R.sup.2 
is a hydrogen atom, R.sup.3 represents a group of the formula 
##STR3## 
in which R.sup.4 represents a methyl group, a chlorine atom, a bromine 
atom or a fluorine atom, R.sup.5 represents a methyl group, a 
trifluoromethyl group, a chlorine atom, a bromine atom or a fluorine atom 
and R.sup.6, R.sup.7, R.sup.8 and R.sup.9 are the same or different and 
each represents a chlorine atom, a bromine atom or a fluorine atom, and 
when R.sup.2 is a methyl group, R.sup.3 represents a methyl group, a group 
represented by the formula: 
##STR4## 
wherein R.sup.10 represents a chlorine atom, a bromine atom, a fluorine 
atom, a trifluoromethoxy group, a difluoromethoxy group or a 
3,4-methylenedioxy group, or a group represented by the formula: 
##STR5## 
wherein Z represents an oxygen atom or a --CH.sub.22 -- group, R.sup.11 
represents a lower alkoxyl group (e.g. C.sub.1 -C.sub.5 alkoxyl group), a 
chlorine atom, a bromine atom or a fluorine atom, R.sup.12 represents a 
hydrogen atom or a lower alkyl group (e.g. C.sub.1 -C.sub.2 alkyl group) 
and R.sup.13 represents a lower alkyl group (e.g. C.sub.1 -C.sub.2 alkyl 
group) or a trifluoromethyl group. 
DESCRIPTION OF THE INVENTION 
Cockroaches to which the present composition is applied include, for 
example, American cockroach (Periplaneta americana), brown cockroach 
(Periplaneta brunnea), smokybrown cockroach (Periplaneta fuliginosa), 
Nauphaeta cinerea and German cockroach (Blattella germanica). 
Phenylxylylethane, one of the essential elements of the present invention, 
is found among cosolvents for preparing homogeneous solution of active 
ingredient (I) and polyfunctional isocyanate when a polyurethane wall is 
prepared by an interfacial polymerization method. 
As cosolvents, there may be used various organic solvents as disclosed in 
Japanese Patent Kokoku No. 55-38325, but those which are high in flash 
point and less in irritating smell are preferred from a viewpoint of 
safety and prevention of disaster. 
Table 1 shows flash point and degree of smell of various organic solvents 
disclosed in Japanese Patent Kokoku No. 55-38325 and phenylxylylethane 
used in the present invention. Clearly, phenylxylylethane is so high in 
flash point and so weak in smell that it is especially suitable for use as 
a cosolvent. Furthermore, when phenylxylylethane is compared with diethyl 
phthalate, the former is preferred to the latter in cost and safety. 
TABLE 1 
______________________________________ 
Flash point 
Name of organic solvent 
(.degree.C.) 
Degree of smell 
______________________________________ 
Xylene 25 Strong 
Toluene 4 " 
Hexane -26 " 
Heptane -4 " 
Carbon tetrachloride 
-- " 
Chloroform -- " 
Methylisobutyl ketone 
23 " 
Methyl ethyl ketone 
-1 " 
Diethyl phthalate 
152 Weak 
n-Butyl acetate 22 Middle 
Phenylxylylethane 
152 Weak 
______________________________________ 
Surprisingly, the microencapsulated composition of the active ingredient 
(I) prepared using the phenylxylylethane as a cosolvent has residual 
efficacy for cockroach-controlling superior to that of the 
microencapsulated composition of the active ingredient (I) prepared using 
other organic solvents such as methyl isobutyl ketone and cyclohexanone or 
without using any organic solvent. 
When the microencapsulated composition of the active ingredient (I) having 
polyurethane wall is used for cockroach-control, residual efficacy against 
cockroach is able to be retained for a prolonged period of time only by 
microencapsulating the active ingredient (I) and phenylxylylethane in a 
microcapsule having a polyurethane wall which has an average particle 
diameter of not more than 80 .mu.m, a wall thickness of not more than 0.3 
.mu.m and a value of the average particle diameter/wall thickness of 
100-400. 
The microencapsulation is performed, for example, by the method that a 
hydrophobic solution containing a polyfunctional isocyanate, active 
ingredient (I) and phenylxylylethane is dispersed in an aqueous solution 
containing a water-soluble polymer as a dispersing agent in the form of 
droplets and then polymerization reaction with a polyhydric alcohol having 
at least two hydroxy groups is allowed to run. After the encapsulation 
reaction is over, the resulting capsule suspension as such is diluted with 
water so as to obtain a desired concentration and, if necessary, a 
suspension stabilizer is added to obtain a stable slurry formulation. 
As the polyhydric alcohols having at least two OH groups, mention may be 
made of, for example, ethylene glycol, propylene glycol, butylene glycol, 
hexanediol, heptanediol, dipropylene glycol, triethylene glycol, glycerin, 
resorcin and hydroquinone. As the polyfunctional isocyanate, mention may 
be made of, for example, toluene diisocyanate, hexamethylene diisocyanate, 
adducts of toluene diisocyanate and trimethylolpropane, self-condensates 
of hexamethylenediisocyanate, SUMIDUR L.RTM. (made by Sumitomo-Bayer 
Urethane Co., Ltd.) and SUMIDUR N.RTM. (made by Sumitomo-Bayer Urethane 
Co., Ltd.). 
The dispersing agents used for dispersing a hydrophobic solution containing 
active ingredient (I), phenylxylylethane and polyfunctional isocyanate 
include, for example, natural polysaccharides such as gum arabic, 
semi-synthetic polysaccharides such as carboxymethyl cellulose and methyl 
cellulose, synthetic polymers such as polyvinyl alcohol and fine mineral 
powders such as magnesium aluminum silicate. They may be used alone or in 
combination of two or more. When dispersibility is weak, this may be 
improved by adding a known surfactant such as given in H. Horiguchi, 
"Synthetic Surface Active Agent". 
As suspension stabilizers for capsule slurry, the water-soluble polymers 
enumerated above as dispersing agents may be used as such, but, if 
necessary, there may be used, as thickening agents, one or more of natural 
polysaccharides such as xanthane gum and locust bean gum, semi-synthetic 
polysaccharides such as carboxymethyl cellulose, synthetic polymers such 
as sodium polyacrylate and fine mineral powders such as magnesium aluminum 
silicate. 
The active ingredient (I) used in the present invention includes 
geometrical isomers and further includes optical isomers resulting from 
the presence of asymmetric carbon and further includes mixtures thereof. 
Typical examples of the active ingredients (I) are as follows. 
(RS)-.alpha.-cyano-3-phenoxybenzyl (RS)-2-(4-chlorophenyl)-3-methylbutyrate 
(fenvalerate), 
(S)-.alpha.-cyano-3-phenoxybenzyl (S)-2-(4-chlorophenyl)-3-methylbutyrate 
(esfenvalerate), 
(RS)-.alpha.-cyano-3-phenoxybenzyl 
2,2,3,3-tetramethylcyclopropanecarboxylate (fenpropathrin), 
3-Phenoxybenzyl (lR)-cis, trans-chrysanthemate (dphenothrin), 
(RS)-.alpha.-cyano-3-phenoxybenzyl (lR)-cis,transchrysanthemate 
(cyphenothrin), 
3-Phenoxybenzyl 
(lRS)-cis,trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate 
(permethrin), 
.alpha.-Cyano-3-phenoxybenzyl 
(lR)-cis,trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate 
(cypermethrin), 
.alpha.-Cyano-3-phenoxybenzyl 
(lR)-cis,trans-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropanecarboxylate 
(deltamethrin), 
2-(4-Ethoxyphenyl)-2-methylpropyl 3-phenoxybenzyl ether (ethofenprox), and 
(S)-.alpha.-cyano-3-phenoxybenzyl 
(lR)-cis-2,2-dimethyl-3-(1,2,2,2-tetrabromoethyl) cyclopropanecarboxylate 
(tralomethrin). 
If necessary, synergists such as piperonyl butoxide and stabilizers such as 
BHT (2,6-di-t-butyl-4-methylphenol) may also be optionally added. 
When addition amount of phenylxylylethane is too small, development of 
efficacy is insufficient and when too much, concentration of active 
ingredient decreases. Therefore, addition amount of phenylxylylethane is 
usually 0.2-5 parts by weight per part by weight of active ingredient (I). 
The average particle diameter of microcapsules is determined depending on 
varieties and concentration of dispersing agent used for dispersion and on 
the degree of mechanical agitation during dispersion. For measurement of 
average particle diameter, the Coulter counter Model TA-II (available from 
Nikkaki) may be used, for example. 
Wall thickness of microcapsule varies depending on volume ratio of a core 
material to a wall material and is obtained from the following approximate 
equation. 
##EQU1## 
wherein d: Average particle diameter of microcapsules 
wc: Weight of core material 
Ww: Weight of wall material 
.rho.w: Density of wall material 
.rho.c: Density of core material 
The wall thickness in the present invention is calculated using the above 
equation. 
The present composition, before being applied to, is usually diluted 
several times-several hundreds times with water, although it depends on 
the nominal content of the active ingredient, and then the diluted 
composition is applied to by a conventional sprayer. Dosage which varies 
depending on varieties of the active ingredient is usually 10-1000 
mg/m.sup.2 in terms of the active ingredient.

The present invention will be explained in more detail by the following 
Examples, Comparative Examples and Test Examples. 
EXAMPLE 1 
Ten gram of "SUMIDUR" L.RTM. (as indicated herebefore) and 100 g of "HISOL" 
SAS-296.RTM. (1-phenyl-1-xylylethane made by Nippon Petrochemicals Co.) 
were added to 100 g of cyphenothrin and stirred until uniform solution was 
obtained. This solution was added to 350 g of aqueous solution containing 
5% by weight of gum arabic as a dispersing agent and stirring was carried 
out for several minutes by means of "T.K. autohomomixer" (commercial name, 
Tokushukika Kogyo Co.) at room temperature until microdrops were formed. 
The revolution rate was 8000 rpm. Then, to the dispersed solution was 
added 10 g of ethylene glycol and the reaction was allowed to proceed with 
gently stirring in a constant temperature bath at 60.degree. C. for 24 
hours to obtain suspension of a microencapsulated composition. 
Water was added to the suspension to make total weight of 1000 g to obtain 
slurry of microcapsules wherein 10% by weight of cyphenothrin is 
encapsulated (Present composition (1)). 
The resulting microcapsule had an average particle diameter of 20 .mu.m, a 
wall thickness of 0.11 .mu.m and a ratio of average particle diameter/wall 
thickness of 182. 
EXAMPLE 2 
Example 1 was repeated except that amount of "SUMIDUR" L.RTM. (as indicated 
herebefore) was changed to 6 g, thereby obtaining slurry of microcapsules 
wherein 10% by weight of cyphenothrin is encapsulated (present composition 
(2)). 
The resulting microcapsules had an average particle size of 19 .mu.m, a 
wall thickness of 0.06 .mu.m and a ratio of average particle diameter/wall 
thickness of 317. 
EXAMPLE 3 
Example 1 was repeated except that amount of "SUMIDUR" L.RTM. (as indicated 
before) was changed to 8 g and the revolution rate of T.K. autohomomixer 
(as indicated above) was 6500 rpm, thereby to obtain slurry of 
microcapsules wherein 10% by weight of cyphenothrin is encapsulated 
(present composition (3)). 
The resulting microcapsules had an average particle diameter of 30 .mu.m, a 
wall thickness of 0.14 .mu.m and a ratio of average particle diameter/wall 
thickness of 214. 
EXAMPLE 4 
Example 1 was repeated except that amount of "SUMIDUR" L.RTM. (as indicated 
before) was changed to 5 g and the revolution rate of T.K. homomixer (as 
indicated before) was changed to 4700 rpm, thereby to obtain slurry of 
microcapsules wherein 10% by weight of cyphenothrin is encapsulated 
(present composition (4)). 
The resulting microcapsules had an average particle diameter of 50 .mu.m, a 
wall thickness of 0.14 .mu.m and a ratio of average particle diameter/wall 
thickness of 357. 
EXAMPLE 5 
Example 4 was repeated except that the revolution rate of T.K. homomixer 
(indicated above) was changed to 4000 rpm, thereby to obtain slurry of 
microcapsules wherein 10% by weight of cyphenothrin is encapsulated 
(present composition (5)). 
The resulting microcapsules had an average particle diameter of 70 .mu.m, a 
wall thickness of 0.20 .mu.m and a ratio of average particle diameter/wall 
thickness of 350. 
EXAMPLE 6 
Eight gram of "SUMIDUR" L.RTM. (as indicated before) and 100 g of "HISOL" 
SAS-296.RTM. (as indicated before) were added to 100 g of fenvalerate and 
stirred until uniform solution was obtained. This solution was added to 
350 g of aqueous solution containing 5% by weight of gum arabic as a 
dispersing agent, followed by stirring for several minutes by T.K. 
homomixer (as indicated before) at a revolution rate of 4700 rpm at room 
temperature until microdrops were formed. Then, to the dispersed solution 
was added 10 g of ethylene glycol and the reaction was allowed to proceed 
with gentle stirring in a constant temperature bath of 60.degree. C. for 
24 hours to obtain suspension of microencapsulated composition. 
Water was added to the suspension to make total weight of 1000 g to obtain 
slurry of microcapsules wherein 10% by weight of fenvalerate is 
encapsulated (present composition (6)). 
The resulting microcapsules had an average particle diameter of 50 .mu.m, a 
wall thickness of 0.22 .mu.m and a ratio of average particle diameter/wall 
thickness of 227. 
EXAMPLE 7 
Seven gram of "SUMIDUR" L.RTM. (as indicated before) and 20 g of "HISOL" 
SAS-296.RTM. (as indicated before) were added to 100 g of d-phenothrin and 
stirred until uniform solution was obtained. This solution was added to 
200 g of aqueous solution containing 5% by weight of gum arabic as a 
dispersing agent, followed by stirring for several minutes by T.K. 
homomixer (as indicated before) at 6400 rpm at room temperature until 
microdrops were formed. Then, to the dispersed solution was added 12 g of 
ethylene glycol and the reaction was allowed to proceed with gentle 
stirring in a constant temperature bath of 70.degree. C. for 18 hours to 
obtain suspension of microencapsulated composition. 
To the suspension was added aqueous solution containing 0.6% by weight of 
xanthane gum to make total weight of 500 g to obtain slurry of 
microcapsules wherein 20% by weight of d-phenothrin is encapsulated 
(present composition (7)). 
The resulting microcapsules had an average particle diameter of 30 .mu.m, a 
wall thickness of 0.2 .mu.m and a ratio of average particle diameter/wall 
thickness of 150. 
EXAMPLE 8 
Twelve gram of "SUMIDUR" L.RTM. (as indicated before) and 50 g of "HISOL" 
SAS-296.RTM. (as indicated before) were added to 100 g of cyphenothrin and 
stirred until uniform solution was obtained. This solution was added to 
300 g of aqueous solution containing 5% by weight of gum arabic as a 
dispersing agent, followed by stirring for several minutes by T.K. 
homomixer (as indicated before) at 8500 rpm at room temperature until 
microdrops were formed. Then, to the dispersed solution was added 15 g of 
ethylene glycol and the reaction was allowed to proceed with gentle 
stirring in a constant temperature bath of 50.degree. C. for 40 hours to 
obtain suspension of microencapsulated composition. 
To the suspension was added aqueous solution containing 20% by weight of 
neutralized "AGRISOL" FL-100F.RTM. (Kao Soap Co., Ltd.) to make total 
weight of 1000 g to obtain slurry of microcapsules wherein 10% by weight 
of cyphenothrin is encapsulated (present composition (8)). 
The resulting microcapsules had an average particle diameter of 20 .mu.m, a 
wall thickness of 0.18 .mu.m and a ratio of average particle diameter/wall 
thickness of 111. 
EXAMPLE 9 
Eight gram of "SUMIDUR" L.RTM. (as indicated before) and 150 g of "HISOL" 
SAS-296.RTM. (as indicated before) were added to 50 g of fenvalerate and 
stirred until uniform solution was obtained. This solution was added to 
350 g of aqueous solution containing 5% by weight of gum arabic as a 
dispersing agent, followed by stirring for several minutes by T.K. 
homomixer (as indicated before) at 6500 rpm at room temperature until 
microdrops were formed. Then, to the dispersed solution was added 20 g of 
propylene glycol and the reaction was allowed to proceed with gentle 
stirring in a constant temperature bath of 60.degree. C. for 24 hours to 
obtain suspension of microencapsulated composition. 
To the suspension was added aqueous solution containing 0.4% by weight of 
xanthane gum and 0.8% by weight of magnesium aluminum silicate to make 
total weight of 1000 g to obtain slurry of microcapsules wherein 5% by 
weight of fenvalerate is encapsulated (present composition (9)). 
The resulting microcapsules had an average particle diameter of 30 .mu.m, a 
wall thickness of 0.13 .mu.m and a ratio of average particle diameter/wall 
thickness of 231. 
EXAMPLE 10 
Example 8 was repeated except that 7 g of "SUMIDUR" N.RTM. (as indicated 
before) was used in place of 12 g of "SUMIDUR" L.RTM. (as indicated 
before) and the revolution rate was changed to 4700 rpm, thereby to obtain 
slurry of microcapsules wherein 10% by weight of cyphenothrin is 
encapsulated(present composition (10)). 
The resulting microcapsules had an average particle diameter of 50 .mu.m, a 
wall thickness of 0.28 .mu.m and a ratio of average particle diameter/wall 
thickness of 179. 
EXAMPLE 11 
Example 8 was repeated except that 4 g of "SUMIDUR" L.RTM. (as indicated 
before) and 4 g of "SUMIDUR" T-80.RTM. (toluene diisocyanate made by 
Sumitomo-Bayer Urethane Co., ltd.) were used in place of 12 g of the 
"SUMIDUR" L.RTM. (as indicated before), thereby to obtain slurry of 
microcapsules wherein 10% by weight of cyphenothrin is encapsulated 
(present composition (11)). 
The resulting microcapsules had an average particle diameter of 21 .mu.m, a 
wall thickness of 0.16 .mu.m and a ratio of average particle diameter/wall 
thickness of 131. 
EXAMPLE 12 
Ten gram of "SUMIDUR" L.RTM. (as indicated before) and 150 g of "HISOL" 
SAS-296.RTM. (as indicated before) were added to 100 g of permethrin and 
stirred until uniform solution was obtained. This solution was added to 
400 g of aqueous solution containing 5% by weight of gum arabic and 3% by 
weight of ethylene glycol, followed by stirring for several minutes by 
T.K. homomixer (as indicated before) at 4700 rpm at room temperature until 
microdrops were formed. Then, the reaction was allowed to proceed with 
gentle stirring in a constant temperature bath of 70.degree. C. for 18 
hours to obtain suspension of microencapsulated composition. 
To the suspension was added water to make total weight of 1000 g and this 
suspension was diluted twice with aqueous solution containing 0.4% by 
weight of xanthane gum and 1.0% by weight of magnesium aluminum silicate 
to obtain slurry of microcapsules wherein 5% by weight of permethrin is 
encapsulated (present composition (12)). 
The resulting microcapsules had an average particle diameter of 50 .mu.m, a 
wall thickness of 0.23 .mu.m and a ratio of average particle diameter/wall 
thickness of 217. 
EXAMPLE 13 
Six gram of "SUMIDUR" L.RTM. (as indicated before) and 80 g of "HISOL" 
SAS-296.RTM. (as indicated before) were added to 100 g of cypermethrin to 
obtain uniform solution. This solution was added to 400 g of aqueous 
solution containing 10% by weight of polyvinyl alcohol as a dispersing 
agent, followed by stirring for several minutes by T.K. homomixer (as 
indicated before) at 2700 rpm until microdrops were formed. Then, to the 
dispersed solution was added 8 g of ethylene glycol and the reaction was 
allowed to proceed with gentle stirring in a constant temperature bath of 
60.degree. C. for 24 hours to obtain suspension of microencapsulated 
composition. 
Water was added thereto to make total weight of 1000 g to obtain slurry of 
microcapsules wherein 10% by weight of cypermethrin is encapsulated 
(present composition (13)). 
The resulting microcapsules had an average particle diameter of 16 .mu.m, a 
wall thickness of 0.07 .mu.m and a ratio of average particle diameter/wall 
thickness of 229. 
COMATIVE EXAMPLE 1 
Twentytwo gram of "SUMIDUR" L.RTM. (as indicated before) and 100 g of 
"HISOL" SAS-296.RTM. (as indicated before) were added to 100 g of 
cyfenothrin to make uniform solution. This solution was added to 400 g of 
aqueous solution containing 10% by weight of polyvinyl alcohol as a 
dispersing agent, followed by stirring for several minutes by T.K. 
homomixer (as indicated before) at 3500 rpm until microdrops were formed. 
Then, to the dispersed solution was added 20 g of ethylene glycol and the 
reaction was allowed to proceed with gentle stirring in a constant 
temperature bath of 60.degree. C. for 24 hours to obtain suspension of 
microencapsulated composition. 
Water was added thereto to make total weight of 1000 g to obtain slurry of 
microcapsules wherein 10% by weight of cyphenothrin is encapsulated 
(comparative composition (1)). 
The resulting microcapsules had an average particle diameter of 10 .mu.m, a 
wall thickness of 0.12 .mu.m and a ratio of average particle diameter/wall 
thickness of 83. 
COMATIVE EXAMPLE 2 
Example 1 was repeated except that amount of "SUMUDUR" L.RTM. (as indicated 
before) was changed to 3.5 g and the revolution rate of T.K. homomixer was 
changed to 4700 rpm, thereby to obtain slurry of microcapsules wherein 10% 
by weight of cyphenothrin is encapsulated (comparative composition (2)). 
The resulting microcapsules had an average particle diameter of 50 .mu.m, a 
wall thickness of 0.1 .mu.m and a ratio of average particle diameter/wall 
thickness of 500. 
COMATIVE EXAMPLE 3 
Six gram of "SUMIDUR" L.RTM. (as indicated before) was added to 100 g of 
cyphenothrin to make uniform solution. This solution was added to 400 g of 
aqueous solution containing 10% by weight of polyvinyl alcohol as a 
dispersing agent, followed by stirring for several minutes by T.K. 
homomixer (as indicated before) at 2700 rpm until microdrops were formed. 
Then, to the dispersed solution was added 6 g of ethylene glycol and 
reaction was allowed to proceed with gentle stirring in a constant 
temperature bath of 60.degree. C. for 24 hours to obtain suspension of 
microencapsulated composition. 
Water was added to the suspension to make total weight of 1000 g to obtain 
slurry of microcapsules wherein 10% by weight of cyphenothrin is 
encapsulated (comparative composition (3)). 
The resulting microcapsules had an average particle diameter of 15 .mu.m, a 
wall thickness of 0.11 .mu.m and a ratio of average particle diameter/wall 
thickness of 136. 
COMATIVE EXAMPLE 4 
Example 6 was repeated except that methyl isobutyl ketone was used in place 
of the "HISOL" SAS-296.RTM. (as indicated before), thereby to obtain 
slurry of microcapsules wherein 10% by weight of fenvalerate is 
encapsulated (comparative composition (4)). 
The resulting microcapsules had an average particle diameter of 50 .mu.m, a 
wall thickness of 0.21 .mu.m and a ratio of average particle diameter/wall 
thickness of 238. 
COMATIVE EXAMPLE 5 
Example 6 was repeated except that acetophenone was used in place of the 
"HISOL" SAS-296.RTM. (as indicated before), thereby to obtain slurry of 
microcapsules wherein 10% by weight of fenvalerate is encapsulated 
(comparative composition (5)). 
The resulting microcapsules had an average particle diameter of 50 .mu.m, a 
wall thickness of 0.23 .mu.m and a ratio of average particle diameter/wall 
thickness of 217. 
COMATIVE EXAMPLE 6 
Example 6 was repeated except that cyclohexanone was used in place of the 
"HISOL" SAS-296.RTM. (as indicated before), thereby to obtain slurry of 
microcapsules wherein 10% by weight of fenvalerate is encapsulated 
(comparative composition (6)). 
The resulting microcapsules had an average particle diameter of 50 .mu.m, a 
wall thickness of 0.22 .mu.m and a ratio of average particle diameter/wall 
thickness of 227. 
COMATIVE EXAMPLE 7 
Four gram of "SUMIDUR" L.RTM. (as indicated before) was added to 100 g of 
heated fenvalerate to make uniform solution. Immediately, this solution 
was added to 350 g of heated aqueous solution containing 5% by weight of 
gum arabic as a dispersing agent, followed by stirring for several minutes 
by T.K. homomixer (as indicated before) at 4800 rpm until microdrops were 
formed. Then, to the dispersed solution was added 6 g of ethylene glycol 
and the reaction was allowed to proceed with gentle stirring in a constant 
temperature bath of 60.degree. C. for 24 hours to obtain suspension of 
microencapsulated composition. 
Water was added to the suspension to make total weight of 1000 g to obtain 
slurry of microcapsules wherein 10% by weight of fenvalerate is 
encapsulated (comparative composition (7)). 
The resulting microcapsules had an average particle diameter of 50 .mu.m, a 
wall thickness of 0.23 .mu.m and a ratio of average particle diameter/wall 
thickness of 217. 
TEST EXAMPLE 1 
Each of the present composition (6) and comparative compositions (4)-(6) 
was put in a 100 cc beaker and olfactory test was conducted on whether or 
not the compositions have smell of a solvent. Ten subjects were employed, 
to whom no information was given as to the name of solvents used in the 
preparation of microcapsules. The results are shown in Table 2. 
TABLE 2 
______________________________________ 
(Test on smell of a solvent) 
Number of persons (subjects) 
Test composition 
who sensed smell of a solvent 
______________________________________ 
Present composition (6) 
1 
Comparative composition (4) 
10 
Comparative composition (5) 
10 
Comparative composition (6) 
10 
______________________________________ 
That is, all persons sensed smell of the solvent for comparative 
compositions in which methyl isobutyl ketone, acetophenone or 
cyclohexanone was used as a solvent while only one person sensed smell of 
the solvent for the present composition (6) in which phenylxylylethane was 
used. 
TEST EXAMPLE 2 
Each of the test compositions enumerated in Table 3 was diluted twenty 
times with water and each of the diluted composition was uniformly sprayed 
on a plywood panel of 15 cm.times.15 cm at a rate of 50 ml/m.sup.2. After 
the treated plywood panel was dried for 2 hours, a plastic ring of 13 cm 
in diameter and 5 cm in height (for prevention of escape; inner surface 
was coated with butter) was placed on the treated panel and a group of ten 
German cockroaches were confined to contact with the treated panel for 2 
hours. The cockroaches were transferred to a plastic cup with water and 
diet, and mortality was observed after 3 days. 
Furthermore, mortality after lapse of 2, 4 and 8 weeks was obtained using 
the same sprayed surfaces. 
TABLE 3 
__________________________________________________________________________ 
Mortality of German cockroach (Repeated 3 times) 
Average 
Time (week) for treatment 
Average particle 
with the test composition 
particle 
Wall diameter/ 
and mortality (%) after 
Test diameter 
thickness 
wall 72 hours 
composition 
(.mu.m) 
(.mu.m) 
thickness 
0 2 4 8 
__________________________________________________________________________ 
The present 
20 0.11 182 100 
100 100 
100 
composition (1) 
The present 
19 0.06 317 100 
100 100 
90 
composition (2) 
The present 
30 0.14 214 100 
100 100 
94 
composition (3) 
The present 
50 0.14 357 100 
100 100 
83 
composition (4) 
The present 
70 0.20 350 100 
100 100 
80 
composition (5) 
Comparative 
10 0.12 83 100 
100 70 
50 
composition (1) 
Comparative 
50 0.10 500 100 
67 47 
47 
composition (2) 
Comparative 
15 0.11 136 100 
87 69 
52 
composition (3)* 
__________________________________________________________________________ 
*No phenylxylylethane was used. 
TEST EXAMPLE 3 
Each of the test compositions enumerated in Table 4 was diluted forty times 
with water and each dilution was applied onto a plywood panel of 15 
cm.times.15 cm at a rate of 50 ml/m.sup.2 After the treated panel was 
dried for 2 hours, a plastic ring of 13 cm in diameter and 5 cm in height 
(for prevention of escape; inner surface was coated with butter) was 
placed on the panel and a group of ten German cockroaches were confined to 
contact with the treated panel for 2 hours. The cockroaches were 
transferred into a plastic cup with water and diet, and mortality was 
observed after 3 days. 
Furthermore, mortality after treatment for 2, 4 and 8 weeks was obtained 
using the same applied surfaces. 
TABLE 4 
__________________________________________________________________________ 
Mortality of German cockroach (repeated 3 times) 
Average Time (week) for treatment 
Average particle with composition and 
particle 
Wall diameter/ mortality (%) after 72 
diameter 
thickness 
wall hours 
Test composition 
(.mu.m) 
(.mu.m) 
thickness 
Solvent used 
0 2 4 8 
__________________________________________________________________________ 
The present 
50 0.22 227 Phenylxylyl- 
100 
100 100 
80 
composition (6) ethane 
Comparative 
50 0.21 238 Methyl iso- 
100 
90 67 53 
composition (4) butyl ketone 
Comparative 
50 0.23 217 Acetophenone 
100 
93 83 53 
composition (5) 
Comparative 
50 0.22 227 Cyclohexanone 
100 
100 70 67 
composition (6) 
Comparative 
50 0.23 217 -- 100 
67 50 43 
composition (7) 
__________________________________________________________________________