Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
s~
PESTICIDALLY-ACT[~E C(~NCENTR~I'ED OIL-IN-~TER
EM[ILSIONS
m e present invention relates to a pesticidally-active con-
centrated oil-in-water emulsion and to a process for its prepara-tion.
Because pesticide form~lations are stored over long periods of time
under changing temperature conditions or extremes of weather, it is
necessary that their formulations have a stability over the broad
range of storage temperatures, including an ability to retain their
integrity after being frozen.
While preformed emulsions of lipophilic substances in
aqueous media are kno~n, mainly in the cosmetic, food and pharmaceu-
tical industries, these emwlsions are incapable of undergoing re-
peated freeze/thaw conditions without breaking. It was desirable,
therefore, to devise new emulsions, capable of undergoing extremes
of temperature.
m e present invention provides a pesticidally-active con-
centrated emulsion comprising:-
3.5-6.5 or 10-35 parts by weight of a lipophilic pesticide,
3.5-6.5 or 10-35 parts by weight of a hydrocarbon solvent,
0.1-10 parts by weight of an alkanol,
0.5-32 parts by weight of at least one nonionic surfactant
to stabilise the emLlsion, and
water to bring the total of all oomponents of the emulsion
to 100 parts by weight.
In contrast to ordinary emulsions, which are simple mix-
tures, i.e., dispersions of one immiscible liquid into another made
relatively stable by an emulsifying agent, the subject of this inven-
tion is stoichiometrically well-defined within the boundaries de-
picted in a three phase diagram. Further, the unusual stability of
these emulsions, at temperatures in the range -18 to 120C, appears
to be associated with a definite structure which i5 made evident by
the birefringent property of the em~lsions observed in a microoe ll
with a polarizing microscope. Birefrigence is the numerical differ-
ence between the ma~imum and minimum refractive indices in a sub-
stance which is capable of having more than one refraction index.
me birefringenoe disappears when the emulsion is broken at 120&
and boiling occurs. Practical emulsions of this type were generally
discussed by Stig Friberg and Inza Wirton in American Perfumes and
Cosmetics 85 (12)27 (1970). me emulsions are believed to have this
unusual stability due to the formation of a structure not unlike
liquid crystals.
The lipophilic pesticide may be selected from a variety of
broad spectrum or selective pesticides including insecticides,
acaricides, fungicides and herbicides.
Any pes-ticide which has lipophilic properties and low water
solubility, for example, a water solubility of 100 ppm or lower, is
suitable for formulation into the concentrated oil-in-water emulsions
of this invention. Such pesticides include lipophilic organophos-
phates including organo~hosphorus oompounds such as diethyl (2-iso-
propyl-4-methyl-6-pyrimidinyl)phosphorothioate or ~imethyl S-[(4-oxo-
1,2,3-benzotriaz.in-3(4H)-yl)methyl]phosphorodithioate, par~icularly
including lipophilic vinylorganophosphates such as dimethyl 1-(2,4/5-
trichlorophenyl)-2-chlorovinyl p~osphate, natural products and deriva-
tives thereof including pyrethrins, rotenones, tobacco extracts,
pine oil, resin, tar or gum and the like, liphophilic al~line deriva-
tives such as ~ -trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine
and N-butyl-N-ethyl-2,6-dinitro-4-trifluoromethylaniline or chlorin-
ated hydrocarbons such as chlordane and numerous other lipophilic
pesticides.
A p æticularly suitable class of pesticides are those
termed "synthetic pyrethroids". Preferably, the pesticidally-active
pyrethroid has the formula I
0~
A -- C - O -- CH~_~
s~
wherein A is an optionally-substitu~ed aralkyl, alkyl or cycloalkyl
group and R is hydrogen, cyano or ethynyl. Generally speaking, the
alkyl, cycloalkyl, or aralkyl groups preferably co.ntain up to 10
carbon atoms.
When A represents an optionally-substituted cycloalkyl
group in formula I, the preferred co~lpounds are those containing a
cyclopropyl group of formwla II
R ~ R
a ~ b
~ II
c / - \ - H
Rd
wherein Ra and Rb each represent an alkyl group containing 1 to 6
carbon atoms, especially methyl, or a halos-en atom having an atomic
number of 9 to 35, inclusive, especially chlorine atom; or when Ra
represents a hydrogen atom then Rb represents an alkenyl group con-
taining 2 to 6 carbon atoms optionally-substituted by 1 to 3
chlorine or bromine atoms, especially isobutenyl or a m~no- or
dichlorovinyl group; Rc and Rd each represent an alkyl group contain-
ing 1 to 6 carbon atoms, or when Rc is hydrogen then Rd is an alkenyl
group containing 2 to 6 carbon atoms optionally-substitu-ted by 1 to 3
chlorine or brc~une atoms, especially a mono- or dichlorovinyl group;
or at least one of Ra and Rb together or Rc and Rd together each
represent an alkylene group containing 2 to 6, especially 3 carbon
atoms.
~.~
S~
Preferred because of their inseeticidal properties are
those pyrethroids wherein in the eyelopropyl group of formula II Ra
and ~ eaeh is methyl, Rc and Rd eaeh is methyl or when Rc is a
hydrogen atom then Rd is isobutenyl, 2,2-diehlorovinyl, or 2,2-
dibromovinyl.
When A represents an aralkyl group in formula I, preferred
eompounds are those containing a substituted benzyl group of formNla
III H
7 Q III
wherein Z represents a halogen atcm having an atomie numker of 9 b~
35, inclusive, or an alkyl or alkoxy group of 1 to 4 carbon atoms,
e.g. methyl or methoxy, and Q represents cm alkyl group of 1 to 6
earbon atoms, espeeially a branehed ehain group sueh as an isopropyl
group.
m e most preferred pyrethroids for use in the pestieidal
em~lsion aceording to the invention have the formula I wherein A is
alpha-isopropyl-4-chlorokenzyl, 2,2,3,3-tetramethylcyelopropyl,
2-(2,2-dichlorovinyl)-3,3-dimethylcyclopropyl, or 2-(2,2-dibromovinyl)-
3,3~dimethyleyelopropyl; R is hydrogen, ethynyl or cyano.
,~ ~
.
It should ke noted that optical isomers, cis-trans isomers
and other kinds of geometric isomers of the compounds according to
formula I are within the scope of the present invention as well and
mixtures of one or more of iscmers of the pesticidally active com-
pounds according to formula I. The various isomers of the compounds
according to formula I may have different pesticidal toxicities and/
or knock-down potency. m us, one may prefer to resolve mLxtures of
isQmers to recover a more pesticidally-active isomer or diastereo-
isomer pair or to prepare the more active forms directly for use in
the em~lsions of the invention.
As stated hereinbefore, the lipophilic pesticide is pre-
sent in amounts of 10-35 parts by weight. Preferably, emulsions are
formulated in which the pesticide is present in amounts of 28-32
parts by weight. In the case of the synthetic pyrethroids descriked
herein the amounts of about 30-31 parts by weight have been found
especially suitable for the formation of stable emulsions.
The hydrocarbon solvent used may include any numker of
alkane, cycloalkane, alkene, aromatic and alkyl-aromatic hydro-
OE kons. Generally speaking, the alkanes, including cycloalkanes,
and alkenes contain from 1 12 carbon atoms, for example, p~ntane,
hexane,
,
.
85~
heptane, hexene, and cyclohexane, while the aromatic and alkyl-
aromatics contain 6-20 carbon atoms and 1-2 hydrocarbyl rings, for
example benzene, naphthalene, toluene, ethylbenzene, xylene, tri-
methylbenzene, p-ethyltoluene; mixtures of any of the above hydro-
carbons may be used. Particularly useful are mixtures of alkyl-
benzenes. One such mixture is sold under the trademark Tenneco
500-100 by Tenneco Oil Company and contains predominantly p-ethyl-
toluene and 1,2,4-trimethylbenzene with minor amounts of ~rtho-
xylene, other alkylbenzenes, C10 and heavier aromatics and non-
aromatics and is especially desirable because of its high flashpoint. Naphthas, petroluem distillates and certain lubricating
fractions can also be used. In general, mixtures of aromatic hydro-
carbons having a flash point by Tag Closed Cup Tester of over 100F
are preferred.
The hydrocarbon solvent is present in an amount sufficient
to make the density of the solvent-pesticide phase equal to that
of the water-alkanol phase of 10-35 parts by weightOPreferably,
emulsions are formulated in which the solvent is present in amounts
of 28-32 parts by weight, or more suitably in amount of about 30-31
parts by weight. In the case of formulations in which the above-
described synthetic pyrethroids are used as the lipophilic
'
pesticide, the solvent is preferably Tenneco 500-100. The solvent
is preferably used in about the same amount (parts by weight) as the
pyrethroid.
Exa~ples of the alkanol ccmponent include monohydroxy
alcohols containing 1 to 4 carbon atoms and dihydro~y alcohols con-
taining from 2 to 4 carbon atoms, for example methanol, ethanol, iso-
propanol, ethylene glycol, propylene glycol, 1,3-propandiol, and
1,2-butandiol. Preferably, an alkandiol containing from 2 to 3
carbon atcms is used, especially ethylene glycol or propylene glycol.
A trihydroxy alcohol such as glycerol may also be used.
m e alkanol co~ponent of the emulsion is present in
amounts of 0.1-10 parts by weight. Preferably, the aIkanol is pre-
s~nt in amounts of 2-6 parts by weight, suitably 3-5 parts by weight.
Suitable nonionic surfactants (surface-active agents) can
bP broadly defined as the emulsifying co~pounds required to give a
stable em~lsion with the particular hydrophile/lipophile balanoe of
the oil phase containing the pesticidally-active ingredient as deter-
mined by the method descri~ed by A. Beerbower and M.W. Hill in
M~Cutcheon's Detergents and Emulsifiers, page 223 (1971) and are
usually compounds, aliphatic or aIkylaromatic in nature, which do
not ionize in water solution. For example, a
35~
well-known class of nonionic agents is available under the trade-
mark "Pluronic". These compounds are Eormed by condensing ethylene
oxide with a hydrophobic base formed by the condensation of propy-
lene oxide with propylene glycol. The hydrophobic portion of the
molecule which, of course, exhibits water insolubility has a mole-
cular weight of from about 1,500 to 1,800. The addition of poly-
oxyethylene radicals to this hydrophobic portion tends to increase
the water solubility of the molecule as a whole and the liquid
character of the product is retained up to the point where polyoxy-
ethylene content is about 50~ of the total weight of the condensa-
tion product.
Other suitable nonionic surfactants include:
(1~ The polyethylene oxide or propylene oxide condensates
of alkyl phenols, e.g., the condensation products of alkyl phenols
having an alkyl group containing about 6 to 12 carbon atoms in
either a straight chain or branched chain configuration, with ethy-
lene oxide, the said ethylene oxide being present in amounts equal
to 10 to 25 moles of ethylene oxide per mole of alkyl phenol. The
alkyl substituent in such compounds is derived, for example, from
polymerized propylene, di-isobutylene, octene, or nonene;
(2) The condensates derived from ethylene oxide
~L2~
and the product resulting rom the reaction of propylene oxide and
ethylenediamine. For example, compounds containing about 40% to
about 80% polyoxyethylene by weight and having a molecular weight of
about 5,000 to about 11,000 resulting from the reaction of ethylene
o~ide groups with a hydrophobic base constituted of -the reaction pro-
duct of ethylene diamine and excess propylene oxide, said hydro-
phobic bases having a molecular weight o the order of 2,500 to
3,000, are satisactory;
(3) The condensation product of fatty acids, hydrogenated
fatty acids (including hydrogenated castor oil) or aliphatic
alcohols having 8 to 18 carbon atcms, in ei-ther straight chain~or
branched chain conflguration, with propylene oxide or ethylene oxide,
e.g. a coco~ut alcohol-ethylene oxide condensate having 10 to 30
moles of ethylene oxide per mole of coconut alcohol, the coconut
alcohol fraction having 10 to 14 carbon atoms;
(4) Long chain tertiary amine oxides corresponding to the
following general formula, ~ ~ ~N -~ O, wherein ~ is alkyl of about
8 to 18 carbon atcms, and R2 and ~ are each methyl or ethyl
radicals. Examples of amine oxides suitable for use in this inven-
tion include dimethyldodecylamine oxide, dimethyloctylami~e o~ide,
dimethyldecylamine oxide,
--10--
~l
~L~42856~
dimethyltetradecylamine oxide, dimethylhexadecylamine oxide;
(5) Long chain tertiary phosphine oxides corresponding
to the following formula RR'R"P O, wherein R is an alkyl, alkenyl
or monohydroxyalkyl radical ranging from 10 to 18 carbon atoms in
chain length and R' and R" are each alkyl or monohydroxyalkyl
groups containing 1 to 3 carbon atoms.
(6) Dialkyl sulphoxides corresponding to the following
formula, RR'S ~O, wherein R is an alkyl, alkenyl, beta- or gamma-
monohydroxyalkyl radical or an alkyl or beta- or gamma-monohydroxy-
alkyl radical containing one or two other oxygen atoms in the chain,
the R groups ranging from 10 to 18 carbon atoms in chain length,
and wherein R' is methyl or ethyl;
(7) The ammonia, monoethanol and diethanol amides of
fatty acids having an acyl moiety of about 8 to about 18 carbon
atoms;
(8) Mono-, poly- and di-glycerides of fat forming acids;
(9) A sorbitan monoester with one or more long chain
fatty acids of 8 to 20 carbon atoms or resin acids which include
those sold under the trademarks l~Atlox"and "Atpet", including
those modified by reaction with ethylene oxide or propylene oxide;
(10) ~n alkylbenzene containing a straight-chain alkyl
group. Suitable alkylbenzenes contain an aIkyl group of 8 to 20
carbon atoms; or
(11) Condensates of ethylene oxide or propylene oxide with
fatty acids.
The use of mixtures of nonionic surfactants is also within
the scope of the present invention.
me concentration of the surfactant must be higher than
the critical micelle concentration (CMC). The surfactant(s) can be
present in a total amount of 0.5 to 32 parts by weight, usually be-
t~7een 1-16 parts by weight but preferably 1-2 parts by weight and
especially about 1.5 parts by weight of the concentrated em~lsion
according to the invention.
Preferred surfactants are one or more of polyethylene
oxide condensates of alkyl phenols, C8-C18 alkanols or fatty acids,
sorbitan esters of fatty acids, polyethylene oxide sorbitan esters
of mixed fatty and resin acids and polyglycerides of fatty acids,
for example, NEODOL~Detergent alcohols, T~eens and Igepals.
A preferred concentrated emulsion according to the inven-
tion oomprises
28-32 parts by weight of lipophilic pesticide,
28-32 parts by weight of hydroc æbon solvent,
-12-
- ~l
2-6 parts by weight of an aIkanol,
1-16 parts by weight oE at least one nonionic surfactant
to stabilise the emulsion, and water -to bring the total of all com-
ponents of the e~ulsion to 100 parts by weight.
In the concentrated ~mulsions of the invention water
usually camprises about 48.9-17 parts by weight of the emulsion.
When the emulsions are formulated with the preferred amounts of
ingredients previously specified above, then water is present in
amounts of about 41-28 parts by weight or more suitably 36-21 parts
by weight. The emulsion forms very readily when the ratio of oil
phase (oil plus pesticide) to water phase (water plus emulsifier and
alkanol) is about 1.6 to 1.
A separately-prepared stable, con oe ntrated emulsion within
the scope of the present invention cc~,prises components of the same
chemical co~positions as described in relation to preferred emul-
sions but in different proportions. Broadly these proportions are:
3.5 to 6.5 parts by weight of at least one lipophilic
pesticide,
3.5 to 6.5 parts by weight of a hydrocarbon solvent,
7 to 9.5 parts by weight of an alkanol
-13-
6 to 14 parts by weight of at least one nonionic surfact-
ant to stabilise the emulsion and water to bring the total of all
components of the emulsion to 100 parts by ~eightO
m e preferences expressed with regard to each particular
component of the first concentrated emulsion also hold true for the
second, only the proportions are different. ~he preferred formula-
tions of the second ooncentrated emulsion of the invention are:
4.5 to 5.5 parts by weight of lipophilic pesticide,
4.5 to 5.5 parts by weight of hydrocarbon solven-t,
8 to 9 parts by weight of an alkanol,
9 to 11 parts by weight of at least one nonionic surfact-
ant to stabilise the emulsion and water to bring the total of all
ccmponents of the emulsion to 100 parts by weight.
m e above oil-in-water concentrated emulsions may be pre-
pared by any convenient technique but are preferably prepared by the
combination of the nonionic surfactant with a mlxture of the hydro-
carbon solvent and lipophilic pesticide and subsequently the combina-
tion of the resulting three-component mixture with the alkanol and
water, the latter step being accompanied by agitation to form the
emLlsion. A poorer quality emulsion results when the nonionic sur-
-14-
~4~8~1
factant (emulsifler) is added to the water phase in the emulsifica-
tion step.
me concentrated emulsions of-the present invention are
superior in camparison with conventional concentrate formulations
previously known in the art. In particular, the formulations of the
invention are stable over a broad range of temperatures, e.g., from
-18C to 120C. Furthermore, the emulsions of the invention are
unusual in that freezing doe s not cause separation of the oil and
water phase and on thawing the emulsion remains unchanged. me high
thermal stability and optical (birefringent) properties of the con-
centrated emwlsions of ~he invention are indicative of a specific
three-dimensional structure having specific stoichicmetry. A phase
diagram, Figure 1 of the accompanying drawings, supports this view.
me three variables used to plot this diayram are:
(1) me oil phase camprising a 50% by weight solution of
lipophilic pesticide in a hydrocarbon solven~, e.g.,
50~ ~-cyano-3-phenoxybenzyl ~-isopropyl-p-chloro
phenylacetate in Tenneco 500-100.
(2) The aqueous phase comprising a 10~ by weight solution
of alkanol in water, e.g., ethylene glycol in deion-
ized water.
~ i
(3) The nonionic surfactant, e.g., Atlox 8916-F. In the phase
diagram there are two widely separated areas, "A" and "B",
in which birefringent, stable emulsions are obtained. The
products obtained in between these two areas are emulsions
in which an aqueous layer forms below the emulsion in less
than 24 hours. While the stable emulsions are formed in
areas "A" and "B", the rheological properties of the two
are different and it is likely that the products differ in
spatial arrangements; i.e~, the~ have different crystalline
structures.
An added advantage of the emulsions of the invention is
quantity of character of solvent. Because part of the organic
solvent normally used is replaced by water, the formulations of the
invention are less eye irritating, the quantity of solvent evapor
ated to the environment is reduced, and the formulations are less
expensive. Addit~onally, the use of high flash point solvents such
as Tenneco 500 ~ 100 results in safer formulations because of
their lower fire hazard characteristics. The present emulsions
requlre a~out less than hal~ the amount of solvent as conventional
emuls~on concentrates.
The stable, concentrated oll-in-water emulsions of this
invention are effective for use as pesticide formulations. In
particular use will, of course, depend on the pesticide used,
e.g., ~nsecticide,
16 -
herbicide, or fungicide. For example, when the pesticide is an
insecticide the formulations of the invention can be effective
for (1) control of ectoparasites in warm-blooded animals, (2)
control of insects on agricultural crops and in gardens, (3)
control of insects in public places as fumigant or space spray,
(4) control of insects attacking trees, and (5) use to control
insects in and around the home. The stability, reduced eye
irritation and lower fire hazard characteristics can be particularly
advantageous for these uses. IJnder normal use, the concentrated
emulsions are diluted with water prior to application.
It should ~e noted that the pyrethroids of formula I
are well-known for their pesticidal properties as insecticides
for control of flies, mosquitoes, cockroaches, acarids, and
ticks. Accordingly, the concentrated emulsions of the invention
formulated using the p~rethroids of formula I are~useful for
the above-noted pest~cidal applications.
The invent~on further illustrated by the follo~ing
Examples:-
Example 1
A typical concentrated o~l-in-water emulsion was formed
havin~ the following ingredients in the indicated proportions:
- 17 -
5~
Percent Weight
~-cyano-3-phenoxybenzyl ~- 30.3
-isopropyl-p-chlorophenylacetate
Tenneco 500 - 100 30.3
Atloxo~ 8916TF Emulsifiers 1.5
(Polyoxyethylene (20~ sorbitan monooleate
mixed esters)
Water 27.9
Ethylene glycol 10.0
100. 0
The first three ingredients were combined to form a
clear yellow solution which was then swlrled into a water
solution of ethylene glycol to obtain an opaque white oil-in-
water emulsion. The emulsion was stable when held at -18C.
Examples 2 to`7
Further concentrated oil-in-water emulsions of
this invention ware formed, the`details of which are shown in
Table 1 below:-
- 18 -
.,
I o
l~ o o ~ o ~ o
~ ~ ~ o
~ ol o
~ o o ~ ~ u~o
~ ~ ~ o
u~ n o o ~ ~ ~ o
H .;: tv~ ~ ~ ~1
Cl~ t~
.~
~ ~ ~ . O
a ~ ~: O O ~ O
~ ~ ~ ~ ~ O
~ ~ ~ ~ .
~Z X ~ ~ O I O
o ~ O O ~, ~ ~ O
~ ~ ~ ~ ~0
E~
Z ~ O
H (N O O ~1 ~ O O : i
~:1 ~ ~1 .
H
H
E~
U~
a
~3
_l
N ~ ~rl
~1 ~ ~ ~1
O ~1
~ R ~ u~
E~ ~ O o ,~
O ~ ~1 ~ ~1
O
~2, 1 o E~ --i
~ o ~9
O O O a~
O ~ O
1 9 -
Sa~
Similar emulsions were formulated by substitution of
~-cyano-3-phenoxybenzyl 2,2,3,3-tetramethylcyclopropanecarboxylate,
3-phenoxybenzyl 2,2-dimethyl-3-(2,2-dichlorovinyl)cyclopropanecar-
boxylate, ~-cyano-3-phenoxybenzyl 2,2-dimethyl-3-(2,2-dichloro-
vinyl)cyclopropanecarboxylate, or ~-cyano-3-phenoxybenzyl 2,2-di-
methyl-3-(2,2-dibromovinyl)cyclopropanecarboxylate for the ~-cyano-
3-phenoxybenzyl ~-isopropyl-p-chlorophenylacetate.
Exa_ple 8
A further concentrated emulsion was prepared having the
following ingredients:
Percent Weight
Oil phase 62
(31% ~-cyano-3-pheno~ybenyl ~-
isopropyl-p-chlorophenylacetate and
31% Tenneco 500-100)
Surfactant Tween* 40 1,5
(polyoxyethylene(20)sorbitan mono~
palmitate)
Water phase (10% solution of 36.5
propylene glycol in deionized water)
The required amount of the sur~actant was weighed and
dissolved in the oil phase. The required amount of water phase was
then added and the mixture shaken vigorously for 30 seconds to form
a stable oil-in-water concentrated emulsion.
* Trade Mark
- 20 -
.~
~;~3
Examples 9 to 14
Following procedures similar to those of Example
8 above, stable oil-in-water concentrated emulsions were
prepared using the surfactants shown in Table 2 below:
- 21 -
~g !
.
~Z8S~
o
~o ~ o
~i ~A
Q~ I u~
O O~1
$-~ OO O S~
Q, U~ O S l a~
O ~ O ~ .5::
Ul Or--l S-lrC ~ a) ~
tl~.,1 ~) ~ ~1) ~) ~ ~1) ~I
Z I a) ~
HO ~ ~ ~ ~ ~ ~ ~ O
U~ ~1 ~) O ~ ~ tJ~
~:1 ~ ,~ 1 o o O
D N ~ ~ ~ ~ h ~)
~: 0~ ~ ~ a~1 ~ A
~ ~1 O ~ td
Q ~)h ~to ~ ~ ~) O
E~ ~ ~ o o o o n o
E~ O ~ ~ ~ ~ ~ ~ ~ ~r
O _ _ _ _ _ _
P~ O a~
Z Ql ~~0
~ I tdr~
C~
Z 1 ~3
O O t)r-l~ ~ ~) ~ ~)
~1) 0 ~1 Aa~ a~ O a)
t~Q a) o ~ ~ ~>1
C X ~&
~ O ~o~o ~ O O O O O O
E~ I a)o 3 o~O
, ~~0 rO O O O
rAO O a) r-l P IP I P~ Pl 14 ~1
Z r-l ~1 0\ N
H ~) O11') r l
~r-l ~
1:1 ~: ~ O
H o\ V~-~1
O ~ I O
U~
~ tn
H
~ ~ U~
H ~ h
E~ a
U~ ~ ~ U~
1:~ ,~ ~ ~ 1:4
P~ o
*;C ~
~ C~CO *
t~l C~In 1~ J *
~C O
4~ r7r~ O ~ a
:l ~ r lr~ O
~1 ~
, s u~ ~ m ~
r-l
k q)
tl~ cn O r-lt~ r~
X ~I r-l~I r-l r-l td
~'1 E~
*
-- 22 --
L
