Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ 8SI-1450
This invention relates to sillcone-polyester copolymer
composition~, especially u~eful in coating applica~ions. Mbre
particularly, it relates to hea~-curable, fast-baking
~ilicone-polyester copolym~rs which are characterized by
excellent heat re~is~ance, as well a~ other desirable physical
characteristics, such as excellent adhe ion, excellent mar
resi~tance, and excellent gloss and color retention.
The use of silicones for heat re3isting coating
compositions is well known. Generally~ in addition to their
lO heat re~i~tant qualitie~, such compositions have a good gloss,
good impact strength and suitable light resistance. ~owever,
they leave much to be desired in the way of hardness, adhesion, ;~
and mar or abra~ion resistanca because of their relative
sotness. Additionally, they have a relatively long cure
cycle which is typically over 60 minutes at temperatures
of over 450 F.
In attempts to overcome the deficiencies o~ straight
silicone base coating materials, silicones have been combined
. ^ . , .
`~ mechanically or without chemical reaction with polyesters to ~`
20 obtain the heat resistance of the silicone along with the good
adhesion, hardness, quick cure and mar and abrasion resistance
of the polyesters. It was found, however, that in these
, compositions the silicone or organopolysiloxane and polyester
- were incompatible when used for coating purposes and did not
~ retain the heat resistance of the silicone alone. Moreover,
-
even when the silicone and polyester are heated together to ;~
] produce copolymerization, the resulting productR ar~ generally
~ deficient in heat resistance, which is required in high
`~ temperature insulation, as well as protective coating
`' 30 com~ositions for apparatu~ ~ubjected to heat, 9uch as heaters,
ovens, furnaces, incinerators, ranges, aircraft parts and other
industrial equipment.
~ ? ~ ~
.
. ......... . . . ... . - . . . .. . .
8SI-1450
3~t~ r ~
A relatively recent attempt to provide a ~uitable
heat resi~tant silicone-polyester copol~mer coating i~
disclosed in U S Patent 3,044~980 i~ued ~uly 17, 1962. While
this copolymer has been rela~ively successful, it has been
found nece~sary for most commercial applications to blend the
; copolymer with additional silicone in order to achieve a high
enough silicone content to provide sufficient heat resistance.
However, a~ a result of this blending with additional silicone,
the resulting product suffers from an undesirable relatively
luw average viscosity which, in turn, nece~sitates the use of
costly viscosity builders. Other problems as ociated with the
copolymers of U S Patent 3,044,980 include its cumber~ome and
costly method of prepara~ion, which primarily result~ from
the fact that these copol~mers are prepared from a process
which employs a high 501ics content.
Accordingly, it is one object of the present invention
to provide a novel silicone-poIyester copolymer, especially
suitable for use as a heat-resistant coating.
Another ~bject of this invention is to pro~ide a
- 20 silicone-polyester copolymer composition which, in ~ddition
to having excellent physical properties such as excellent
heat resistance, excellent cure time, excellent gloss and color
retention, excellent mar resistance and excellent hot hardness,
is further characterized by an improved higher viscosity in
~ compariso~ to other ~ilicone-polyester copolymer compositions
:~ provided heretofore and thus does not necessitate the use of
vi~c05ity builders.
:.
Still another object of this invention i9 to provide
an improved process for the preparation of the ~ilicone-
polye~ter copolymer composition of this invention~
A still further ~ject of this invention is to provide
a process for the preparation of the silicone polyester
- 2 -
. .
8SI-1450
1~5'7~7~
copolymers of this invention, whlch 1~ less tedious and less
costly than processes employed heretoore.
The~e and other object~ are accompli~hed herein by
providing a silicone-polyester copolymer composition prepared
by heating ~1) a sllane hydrolyzate and (2~ a hydroxyl rich
polye3ter, in the pre~ence of a gly~ol ether acylate of a
B carboxylic acid, such as cellosolve acetate (ethylene-glycol
monoethyl ether a~etate).
~ The silicones which are useful in conjunction with
- 10 the present invention are prepared by hydrolyzing an organo-
silane characterized by the Form~Ia:
~ ) (R)aSiX4-a
wherein R is a radical selected from the group consisting Of
a monovalent hydrocarbon, halogenated monovalent hydrocarbon
and mixtures thereof, X is a hydrolyzable radical selected ;
from the group consisting of halogen, alkoxy, amino, aryloxy
and acyloxy, and a is an integer from 1 to 3.
Radicals lncluded by R are, typically, alkyl and
haloalkyl, such as methyl, ethyl, propyl, octyl, chloromethyl,
chloroethyl, bromomethyl, and the like, aryl and haloaryl,
such as phenyl, methyl, tolyl, xylyl, chlorophenyl, bromophenyl,
dibromophenyl, dichlorophenyl, and the like. Of course, R is
:, ~
;~ intended to include mixtures of these alkyl, haloalkyl, aryl
and haloaxyl groups heretofore elucidated.
.. .~
`, Specific examples of organosilanes wi~hin the scope
1' of Formula I hereinabove include methyltrichlorosilane,
... .
dimethyldichlorosilane, methylphenyldichlorosilane, phenyltri--
chlorosilane, diphenyldichlorosilane and mixtures thereof.
It is well known that the ~ower alkyl groups and the
.,
phenyl group impart greater heat stability to silicone
materials and thus these groups and mixtures thereof are
preferred within the scope of R in Formula I~ However, up to
:: .
~ 3 ~
....
... . . . . . ...
.. . . :. .. . . .
,~ 8SI-1450
twenty~five percent of material containing other than methyl,
ethyl, and phenyl groups or derivatives thereof can be
tolerated withQut serious los.s of heat resistance, including
alkyl group~ containing from two to about eight carhon atoms.
While for best results and low cost the hydrolyzable
group X is preferably halogen, and most preferably chloro, the
other hydrolyzable groups elucidated hereinabove and mixtures
thereof are clearly encompas~ed within the scope o~ th~
invention.
Preferably, mixtures o~ the organosilanes of Formula
I are utilized herein. The precise proportions of each of the `~
organosilane~ which will constitute the mixture will depend upon ;
the particular properties desired in the final product. For
example, while both methyl and phenyl groups are superior in
heat resi~tance, an excessive amount of methyl groups tends
toward a brittle product, while an excessiv- amount of phenyl
groups results in too much thermoplasticity. Generally,
however, it is preferred to have ~rom about 40 to 60~o methyl
group~ with the remainder phenyl. Moreover, for purpo~es of
.. .. . . . .
thi~ invention, the ratio o~ organic groups, R, to silicone
atoms is generally ~rom about 1 to about 1.75, and preferably
; from about 1 to about 1.55.
A particularly preferrad organosilane mixture useful
in the practice of the pre~ent invention i9 comprlse:~ o~ a
blend of about 21~8 percent by weight of methyltrichlorosilane,
,;~ - - . . .
about 33.0 percent by weight of phenyltrichlorosilane, about
15.2 percent by weight dimethyldichlorsilane and about 3Q.0
'3. percent by weight of diphenyldichlorosilaneO
~3 The organosilane~ o~ Formula I can be hydrolyzed in
i 30 any of the usual manners. One description is ound in Rochow,
"Chemistry of the Silicones" (2d edition), John Wiley and Sons,
Inc., ~ew York, pages 90-94. Such procedures generally involve
.
- 4 - ~ ~
~ir~ S Sr 8SI-1450
the addition of water to the organo3ilane, or m~xtures thereof,
with aliphatic alcohol.
For tha purpose of this in~ention, particularly
excellent results are achieved when an organohalosilane
~, .
encompassed by Formula I hereinabove, or mlxtures thereof, is
hydralyzed in a two-phase system hydrolyYis medium comprising
a wat2r-immiscible organic s,olvent, water, and acetone.
'Th,i9 hydrolysis process i3 des,cribed in detail in a Canadian
}ication of D.F. Merrill, Serial No.~79~6~, ~ilod
~ec,~mhe~S~/q~~, assigned to the a~signee of the pre~ent
appli~ation. In brief, this preferred hydro}ysi~ process
comprises agitating tha organohalosilane of Formula I herain- ~
above or mixtures thereof in the presence of water, acetone ;
and a water-imm,iscible organic ~olvent, such as b,nzene,
toluene, xylene, etc. Th,e various components of the hydrolysis
medium can be added concomitantly or separately in any desired
order. Generally, the organohalosilane or mixtures thereof
,~
', is added to the mixture of water, acetone, and water-immiscible
i~, organic solvent. ~h~sn this hydrolysis medium is used, a
, ~! , .
j~! 20 proportion o~ from about 1.7 to about 10 parts by weight of
water, pre~erably from about 2 to about 6 parts by wei~ht of
water, about 0~2 to about 5 parts, by weight o acetoneS, `~
preferably rom about 0.3 to about 2 parts by weight of acetone
' and from about 0.3 to about 5 parts by weight of water-immiscible
;, organic solvent, preferably fxom about 0.6 to about 2 parts
;! of water-imm,iscible, organic solvent, per part of organohalo-
silane can be employed~ It is preferred that the organo-
halo~ilane be added to the hydrolysis medium rather than vice
'f,l ':
i versa, as this limits the concentration of acid, such as
.~ ,
30 hydrochloric acid, which is formed during the hydrolysis ; .
reaction. During the addition, the mixture is agitated to
_ 5 _
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; 8SI~1450
~3~ '7~ ~
pxovide a sufficient degree of hydrolysis of the organohalo-
silanes and formation of organosilanehydrolyzate, referred to
herein as the silane hydrolyzate. ~he temperature of the
hydrolysis mixture can be controllecl by the rate o~ addition
of the organohalosilanes or external heat, or cooling can be
employed if desired. During hydrolysis a temperature of
between 20C to 40 C is preferred. After the additLon has
been ~ompleted, the mLxture i~ generally stirred for an
additional period of time, such as 30 minutes or more, to allow
for complete hydrolysis. The m~x~ure i5 allowed to set~le and
the bottom acid layer is removed from the organic layer, and
the organic solvent i5 stripped from the organic layer leaving
the de~ired silane hydrolyæate re~idue. While this ~ilane
hydrolyzate may be copolymerized with the hydroxy rich
polyesters to be discussed in detail hereinafter, as such, it
is preerred that the acid content of the hydrolyzate be not
greater than about 5 part3 per million. To achieve ~his
, .,; .
preferred acid content, an acid reduction step can be used
wherein water is added to the silane hydrolyzate, after the
organic solvent has been stripped therefrom, and the mLxture
ref~uxed with the aqueous acid layer being trapped off~ The
- resulting silane hydrolyzate, which may also be referred to as
silanol-containing organopolysiloxane, will generally be
comprised of rom about 6% to about 12 % by weight of hydroxy
radicals attached to ~ilicon.
Ihe hydroxyl rich polyesters which are employed in
~ the formation of the ~ilicone-polyester copolymers of the
;` present invention are tho~e which are formed by the reaction of
l (a) an aromatic dicarboxylic acid selected from the ~roup
! 30 consisting of isophthalic acid, terephthalic acid ancl mixtures
thereo~ or a lower dialkyl estex o~ an aromatic di~arboxylic
-- 6
- . , ,
..
, .
8SI-1450
~L~S~7~
acid selected ~rom the group consisting of 130phthalic acid,
terephthalic acid and mixtures thereof; (b) ethylene glycol;
and (c~ a saturated aliphatic polyhydric alcohol having at
lea~t three hydroxyl groups. Whil~ the u~e of isophthalic ;~
acid, terephthalic acid or mixture3 thereof i5 preferred,
isophthalic acid being most preferred, among the lower alkyl
eqter~ of these acids which are also u~eful herein are those
in which the alkyl radicals have from 1 to 8, and preferably
1 to 4, carbon atoms, including, for example, the dimethyl
ester, the diethyl e~ter, the dipropyl ester, the dibutyl
ester, etc.
In maXing the hydroxyl rich polyesters o~ the present
invention, which are to be 3ubsequently copolymerized with the
hereinabove described silane hydroyl~ate of the pres2nt
l invention, the acid or ester i5 used in amounts ranging from
., , . :~.
about 25 to about 65% by weight, and preferably from about 25
to about 56% by weight, the ethylene glycol in amounts ranging
from about 10 to about 15% by weight, and the saturated
aliphatic polyhydric alcohol from about 20 to about 5~0 by
weight, and preferably from about 20 to about 3~% by weight.
m e term "saturated aliphatic polyhydric alcohol
- having at least three hydroxyl groups" include~ both polyhydric
alcohols in which the hydroxyl groups are connected by a
plurality of carbon to carbon linkages, as well as other
alcohols, having more than three hydroxy groups. Among the
saturated aliphatic polyhydric alcohols having at least three
sl hydroxyl groups which are useful herein are included, for
example, gylcerol, l,l,l-trimethylvl ethane, l,l,l-trimethylol
propane, pentaerythritol, sorbitolO mannitol, diglycerol,
dipentaerythritol and the like. Glycerol is most preferred.
The hydroxyl rich polyesters useful in this
invention may be prepared in conventional ways. Thus, using
:
;: . , . . ~
8SI~1450
8~5
the preferred reactants of this invention as exemplary,
isophthalic acid, ethylene glycol and glycerol are merely
added to any suitable reaction ve~sel. This reaction veYsel
may be formed of any suitable material, such as glas~,
stainless ~teel, etc. Suitable means ~hould be provided to
; vent or collect the water which is libarated. Of cour~e,
in the case of the use of the lower alkyl esters of the
aromatic dicarboxylic acids, which are aLso contemplated
herein, means should be provided to vent or collect the
appropriate alcohol, ~uch a~ methanol, which is given o~f.
Moreover, it has been found advantageous to provide the
reaction vessel with a cuitable moans, such as a packed column~
; to retain the ethylene glycol in the reaction vessel. Although
a ~olvent is not necessary, it al80 has been found advantageous
to prepare the polye~ter by a solvent reflux technique,
employing a suitable organic solvent such as xylene, toluene, ~;
benzene, cumene, etc., w~ich aids in the removal of water
azeotropically. Furthermore, while this esteri~ication or
alcoholysis reaction may be performed in the abse~e of a
catalyst, a suitable cataly~t may be used if desired. Among
such catalysts are included lead oxides, lead acetate, zinc
oxide, cadmium acetate, cuprous acetate, zinc acetate,
magnesium acetate, beryllium acetate, stearlc acetate, ferric
; acetate, nickel acetate, lithium carbonate, calcium oxide and
the like.
e preparation o~ the polyester can be carried out
at a temperature from about room temperature to about 250C. ~ ~;
It is preferred, however, for purpose~ of this invention, that
~` the reaction temperature does not exceed about 220 C0 The
reaction i~ continued until the polye~ter has attained a
me~sured aeid value o~ from about 3 to about 25, prefexably
:,
....
- 8 -
'- ~:;.'.
.... . . .. . .
85~ 50
11~57~ ;~S
about lO. At thl~ point, the resultant hydroxyl rich polyester
reaction mixture i9 cooled and ls ready for subsequent
copolymerization. However, since the ~ubsequent
copolymerization process of the present invention involving
the hydroxyl rich polyester and silane h~ydrolyzate i8 carried
out in the presence of a glycol ether acylate o a carboxylic
acid solvent, to be discussed in more detail hereinafter, it
is preferred that the appropriate glycol ether acylate be
added to the hydroxyl rich polyester a~ter the polyester
reaction mixture is cooled to from about 125C to about 180C,
most preferably about 165C. The mixture is then cool.ed to
room temperature. ~he amount of glycol ether acylate which is -
employed is generally that amount which is sufficient to adjust
the solids content of the polyester reaction mixture to from
about 50% to about 75% by welght, most preferably about 65%.
The glycol ether acylates o~ a carboxylic acid,
which are useful in the practice of the present invantion,
are derived from carboxylic acids of from about l to 5 carbon
atoms~ Thus, typical glycol ether acylates included in this
20 invention are, for example, ethyleneglycolmonoethyl ether
acetate (~elIosolve acetate), ethylene glycol monomethyl ether
acetate (methyl Cellosolve acetate3, ethylenegylcol monobutyl
ether acetate (butyl Cellosolve acetate), diethyleneglycol
ethyl ether acetate (Carbitol acetate), diethyleneglycol butyl
ether acetate (butyl Carbitol acetate) and ethylene glycol
monoethyl ether propionate (Ceilosolve propionate~, and mixtures -;
thereof.
merefore, in distinct contrast to, for example, the
process usèd in U.S. Patent 3,044,980, which utilizes the poly-
ester reactant in the copolymerization process at 100% solids
content, it has been found herein ~hat the adjustment of solids
:''''` "`
~.
8SI-1450
7~7'~
content, as described hereinabove, using the afore de~cribed
glycol ether acylate~, provides for an improved copolymerization
process, as well as an improved resultant: copolymerized
product.
Accordingly, the copolymerization of the hereinabove
described hydroxyl rich polyester and silane hydrolyzate
intermediates i9 carried out by charging, in desired proportions
(1) the silane hydroly~ate~ preferably acljusted to about a
60 - 75% solids con~ent with toluene or other suitable solvent,
10 such as benzene, ~ , cumene~ etc. and (2) the hydroxyl ~`
rich polyester adjusted to from about a 50% to about a 75%,
and preferably about a 65% 301ids content with the desired
glycol ether acylate of a carboxylic acid, preferably,
cellusolve acetate, to a ~uitabLe reaction ves~el equipped
with a thermometer, reflux condenser and receiver cold trap~
:,
The silane hydrdyzate and/or polyester may be added all at
once or incrementally to the reaction vessel. me reactants
are heated with agitation to reflux temperature, e.g., in the
range of from about 125C to about 175 C, preferably to about 165C
said re~lux temperature b~ing sufficient to remove the water
by-product azeotropically. qhe reaction is continued until a
sample of the copolymer product placed on a 200 C hot plate
has a gel time of about 10-30 seconds, preferably 10-15
- seconds. When the final end point has been reached, the
.
i reactio~ mixture is adjusted to a solids content of from about
50-70% solids, preferably from about 60 65% with the same
glycol ether acylate employed during the copolymerization
reaction, and cooled. Preferably, the copolymer is then
filtered, using, f~ example, a filter aid such as a diatomaceous
earth, like Celite 545, sold by ~ohns-Manville Company. If
necessary, readjustment of the solid~ content to from about
." ~0 -:
.
- 8SX-1450
50-65%, and preferably to about 55%, with the appropriate
glycol ether acylate, such a~ cello~olve acetate, i~
performed to obtain a preferred product. `~
A cataly~t, such as iron octoate, is preferably ~ ;
employed during the copolymerization reaction. Generally
the amount of cataly~t compound that is used is that which
is sufficient to provide from about 0.001% iron (a~ metal)
to about 0.010% ~ron (as metal).
The proportions of silane hydrolyzate and polyester
. :
constituents employed in the copolymerization ~ixture depend
upon the pæ ticular properties desired in the final product. ~;
Generally, however, ~or purposes o~ this inv~ntion, the
copolymer is comprised of from about 70 to about 95% silicone
constituent with the remainder polye~ter. For example, a
copolymer having about 85.5% silicone and 12.5% polyester with
a vi3cosity in the range o~ from about 100-300 centipoises at
25C is most preferred.
;, In order that those skilled in the art may better ~;~
-0 understand how the present invention is practic~d, the
~ 20 following examples are presented by way o illustration and ~ ~
'! not by way of limitation. ; ~; -
EXAMPhE
55.5% by weight of isophthalic acid, 31.5% by
weight glycerol, 13.0% by weight ethylene glycol and 3.0
i' parts by weight xylene are charged to a ~lask ~itted with a
~ thermometer, re1ux condenser and packed column (to retain
``;~ ethylene glycol) and capable of reaction by the solvent method,
The reaction mixture is heated under nitrogen purge with the
water by-product being azeotropically trapped out, until an
~ 30 acid ~alue o 10 is attained reaching a maximum ten~erature
-~ of about 220C. Reaction time is about 6 hoursO l~e reaction
.,~ .,
. .
'
. . .
, , :.
8SI-1450
7~ :
mixture is cooled to about 165C and is cut with Cello~olve
acetate to 65% solids and cooled to room temperature.
In a ~eparate ~la~k equipped for hydroly3is,
containing 600 part~ by weight of acetone and 2800 part3 by
weight of water, is added 218 parts by weight of me~hyl-
trichlorosilane, 330 parts by weight of phenyltrichlorosilane,
152 parts by weight o~ dimethyldichlorosilane, 300 parts by
weight of diphen~l dic~lorosilane and 900 part~ by welght of
toluene by controlling the feed rate for a 20-30 minute
`~10 addition. The mixture is allowed to warm to a maximum hydrolysis
`-temperature of about 60C and agitated for about 30 minutes
subse~uent to complete organohalosilane addition. The
resultant hydrolysis mixture is allowed to setkle for about
;15 minutes and the inorganic acid bot~m layer is separated
and discarded. The residual silane hydrolyzate is charged
to another vessel and the toluene ~olvent is atmospherically
stripped-off at about 130C. me remaining ~ilane hydroly-
zate is cooled to about 90C and 10% water, based on silane
hydrolyzate solid~, is added thereto. The mixture is heated
to re1ux and water is trapped off. The final silane
hydrolyzate has an acid content of less than 5 ppm. Sufficient
toluene i9 added to this silane hydrolyzate toa~ jU3t the solid~
content to about 10%.
11.31 parts by weight of the 65% ~olution o~ hydroxyl ;
rich polyester prepared above, 12.62 parts by weight of
Cello~olve acetate and 10.5 parts by weight of the 70%
solution of the silane hydrd~zate prepared above are added to
a reaction flask equipped with a thermometer and reflux
condenser. me temperature is rai~ed to 150C and is
;30 maintained until the 301utic)n in the flask i~ clearO The
clear solution is maintained at 150C for an addit$onal 20
.;! - 12
8SI-1450
78~75 ~:
minutes and the temperature i~ ralsed to refl~x (155C~ -
and water by-product i9 removed azeotropically for about 30
minutes. The reaction mixture is then he~d to remove
solvent to about 162 C, and maintained at this temperature for
about 2 hours. Another 62.94 parts by weigh~ of the 70%
solution of the silane hydrolyzate as pr~3pared above, 2.62
: .
parts by weight of Cellosolve acetate an~ 0.01 parts by
weight of 6% iron octoate ~.001 Fe~ are added to the reaction
, ~
mixture in two increments, 15 minutes apa~t, at which point
the temperature drops to 146 C, and is maintained thereat ~or
about 3 hours and then is raised to about 165C to remQve
... -
i the ~oluene solvent. Heating at this temperature is
? continued until the copolymer product has a 200C hot plate
cure of 20-25 seconds. When this is achieved, the copolymerized
reaction product 15 cut with su~icient Cellosolve acetate to
provide about 64% solids. The resultant silicone-polyester
.
composition is cooled to 70C and filtered u3ing a Celite
~' 545 ilter aid, avilable from Johns-Manville Company, and the
solids content is adjusted to about 55% with Cellosolve acetate.
The resultant copolymer is sparkling clear and has an average
-~ Brookfield viscosity of from about 100 to about 350 centipoise
~`J at 25C. Similar rasults are obtained without the incremental
.! addition of the ~ilane hydrolyzate and/or polyester.
;; A typical enamel is made from the above final
,~ :
copolymer material by mixing a 100 gallon miIlbase formed
~$ from, ~or example, 76g.0 pounds of silicone-~polyester
. i .
~'! copoly~er, 15900 pounds of titanium diox~de, 10.1 po~nds o
aluminum si}icate and cataLyst ~0.5% zinc metal~ and grinding j ;
the formulation t ~ ~egman value of 7. The enamel is sprayed
0 on a 880 Bonderite skeel panel. After curing this spray
applied coating ~1 Mil cured film thickne~s) ~or 60 minutes
- 13 - ;~
: 1
'' ' :
8SI-1450
'7~
at 400F. the enamel has a gloss of 96 as measured with a 60
Gardner Glos~ meter. After heat aged for ~40 hours at 500F,
the enamel ha~ a gloss of 86, as measurad with a 60 Gardner
Gloss meter, without film cracking and excellent color
; retention.
; Similar silicone polyester copolymer~ can be
prepared, also having excellent properties, in the same manner
, .
as in the example above ~ubstituting, for example,
terephthalic acid, l,l,l-trimethylolethane and methyl
Cellosolve acetate for the respective counterpart~.
It is to be understood that many variations of the
present invention are pos~ible in light of the above~detailed
description without departing from the spirit or scope thereof.
All aspect~ o~ the present invention are embraced within the
full intended scope of the appended claims.
.
,, ':
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- 14 -
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.. ` ' ~ , ...... ' ~ . ". ,,, , , "';"';''` , ,' ', ' ' ,, ,' , ' ' ` "
.. . . . . . . . . . . . . ... . . . .
