Note: Descriptions are shown in the official language in which they were submitted.
~ 2~26 48 ~
CH-1725 TITLE
TERNARY AZEOTROPIC COMPOSITIONS OF
1,1-DICHLORO-1,2-DI~ W OROETHANE AND
TRANS-1,2-DICHLOROETHYLENE WITH
S NET~ANOL, ETHANOL OR ~SOPROPANOL
INVENTIO~ BACXGROUND
As modern electronic circuit boards evolve
toward increased circuit and component densities,
thorough ~oard cleaning after soldering becomes a more
important criterion. Current industr~al processes for
soldering electronic components to circuit boards
involve coating the entire circuit side of the board
with flux and thereafter passing the flux-coated board
over preheaters and through molten solder. The flux
c~eans the conductive metal parts and promotes solder
fusion. Co~monly used solder fluxes generally consist
of rosin, either used alone or with activating
additives, such as amine hydrochlorides or oxalic acid
derivatives.
After soldering, which thermally degrades
part of the rosin, the flux-residues are often removed
from th-~ci~cuit boards with an organic solvent. The
re~ulrements for such~solvents are very stringent.
Defluxing~solvents should have the following
chara~teristics: a low ~oiling point, be nonflammable,
have low toxicity and have high solvency power, so
th~t~lùx~and~ flux-residues can be removed without
damaging the~substrate being cleaned.
While boiling point, flammability and
30~ solvent power characteristics can often be adjusted by
preparlng solvent~mixtures, these mixtures ~re often
unsatisfactory because they fractionate to an
undesirable degree during use. Such solvent mixtures
` also fractionate dur~ng solvent d~stillation, wh~ch
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~akes it virtually impossible to recover a solvent
mixture with the original composition.
On the other hand, azeotropic ~xtures, with
their constant boiling points and const~nt
compositions, have been found to be very use~ul for
these applications. Azeotropic mixtures exhibit
either a maximum or minimum boiling point and they do
not fractionate on boiling. These characteristics are
also important when using solvent compocitions to --
remove solder ~lux-s and flux-residues from printed
circuit boards. Preferential evaporation of the more
volatile solvent mixture components would occur, i~
the mixtures were not azeotropic and would result in
mixtures with changed compositions, and with -
less-desirable solvency properties, such as lower
rosin flux solvency and lower inertness toward the
electrical components being cleaned. The azeotropic
character is also desirable in vapor degreasing
operations, where redistilled solvent is generally
20 employed for final rinse cleaning. -~
In summary, vapor defluxing and degreasing
systems act as~a still. Unless the solvent
composition~exhibLts a constant-boiling point, i.e.,
is~a~ingle -aterial, or Ls~an azeotrope,
25~ fractionation will occur and undesirable solvent
distributions will result, which could detrimentally
affect the~-afety and~efficacy of the cleaning
operation.
; A number of halocar~on based azeotropic
;30 ~composLtio~ns hav- b~-en disoovered and in some cases
' used as solvents for ~older~flux and flux-residue
; removal ~rom printed c~rcuit boards and àlso for
` m~scellaneous~d-greasing~applications. For example:
U.S. Patent No. 3,903,009 discloses the ternary
azeotrope of 1,1,2-trichloro-1,2,2-trifluoroethane
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2~2~487
with ethanol and nitromethane; U.S. Patent No.
2,999,815 discloses the binary azeotrope of
1,1,2-trichloro-1,2,2-trifluoroethane and acetone.
U.S. Patent No. 2,999,816 discloses the binary
azeotrope of 1,1,2-trichloro-1,2,2-tri~luoroethane and
methyl alcohol. U.S. Patent No. 4,767,561 discloses
the ternary azeotrope of
1,1,2-trtchloro-1,2,2-trifluoroethane, methanol and
1,2-dichloroethylene.
Some o~ the ¢hIorofluorocarbons which are
currently used for cleaning and other applications
have been theoretically linked to depletion of the
earth,s ozone layer. As early as the mid-1970,s, it
was known that introduction of hydro~en into the
chemical structure of pr-viously ~ully-halogenated
chlorofluorocarbons reduced the chemical stability of
these compounds. Hence, these now destabilized
compounds would be expected to degrade in the lower
atmosphere and not reach the tratospheric ozone layer
in-tact. What is also needed, t~erefore, are
,
substitute chlorofluorocarbons which have low
theoretical ozone depletion potentials.
Unfortunately, as recognized in the art, it
s~not poss~ible~to predict the formation of
25~ az-otropes. This~fact obviously complicates the
8 rch for new a~zeotropic compositions, which have
application;~in the~field.~ Nevertheless, there is a
constant effort in the art to discover new azeotropic
compositions, which~have desirable solvency
~characteristics~and particularly greater versatilities
ln~solvency power.
StlMMARY OF T~?E INVENTION
According to the presént invention,
azeotropic compositions have been discovered
;; ~ 35 compri-ing admiYtures of effective amounts o~
:
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1,1-dichloro-1,2-difluoroethane with
tranc-1,2-dichloroethylene plus an alcohol from the
group consisting of methanol, ethanol and ~sopropanol.
More specifically, the azeotropic mixtures -
are: an admixture of about 51-61 weight percent
1,1-dichloro-1,2-difluoroethane and about 31-41 weight
percent trans-1,2-dichloroethylene and about 4-10
weight percent methanol: an admixture of about 65-75
weight percent 1,1-dichloro-1,2-difluoroethane and
about 19-29 weight percent trans-1,2-dichloroethylene
and about 3-7 weight percent ethanol; an admixture of -~
about 61-71 weight percent
1,1-dichloro-1,2-difluoroethane and about 27-37 weight
percent trans-1,2-dichloroethylene and about 0.7-1.7 ~-
15 weight percent isopropanol. - -~
The present invention provides nonflammable
azeotropic compositions which are well suited for
so~vent clea~ning applications.
DETAIL~D~DESCRIP$~ON
20 ~ The ¢ompos1tions of the instant invention
comprise~admixtures of effective amounts of
dichloro-1,2-difluoroeth~ne ~CFCI2CH2F, boiling
point ~ 48~-4-C) with~trans~ 2-dichloroethylene
(bo~l~ing point ~ 48-~C)~and an alcohol selected~rom ;
5~ the group~consistlng ot~methanol (CH30H~,~boiling point
6~4-6-C)~or~ethanol ~CH3 ~ 0H, boi}ing point~ 8'C)
or lsopropanol~(CH3CHOHCH3,;boiling point~-~82-C) to
form azeotropic~ompositions~ The~ha~ogenated
' materials~are known as HCFC-132c and T-HCC-1130,
30~ #Sp-ctiV~ly~ :~n th- nomenclature convèntional to the
halocarbon~ield;,~
By~az-otrople composition is meant, a -~
constant boiling liquid admixture of three or more
substances, whose~admlxture behaves as a single
35 ~ subs~tanc-, ln that~th- vapor, produc-d by partial
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2~26~87
e~aporation or distillation of the liquid has
substantially the same composition as the liquid,
i.e., the admixture distills without substantial
compositional change. Constant boiling compositions,
which are characterized as azeotropic, exhibit either
a maximum or minimum bo~ling point, as compared with
that of the nonazeotropic m~xtures o~ the same
substance~.
For purposes o~ this invention, effective
amount is defined as the amount of each component of
the instant invention admixture which, when combined,
~ results in the formation of the azeotropic
- compositions of the instant invention. This
definition includes the amounts of each component,
which amounts may ~ary depending upon the pressure
applied to the composition so long as the azeotropic
compositions continue to exist at the different
pressures, but with poæsible different boiling points.
Therefore, effective amount includes each components,
weight percentaqe for each composition of the instant
invention,~ which form azeotropic compositions at
pressures othes than atmospheric pressure.`
The language ~an azeotropic composition
¢onslsting essentially of.,.~ is not intended to
5~;eYclud-~the~lnclusion of minor amounts of other
;ma~terials~wh~ch do not iignificantly alter the
azeotroplc ch~aracter o~ the composition.
It is~-possibIe to characterize, in effect, a
constant boiling adm~xture, which may appear under
30~ many~guises, dep-nd~ng upon the conditions chosen, by
any of several criteria: ~
* The composition can ~e defined as an
azeotrope of~A, B, and C sinc- th- very ~-
te~rm~azeotrope~ is at once both
definitive and limitative, and requires
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`"` 2026:~g7
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that effective amounts of A, B and C form
this unique composition of matter, which
is a constant boiling admixture
~ It is well known by those skilled in the
art that at dif~erent pressures, the
composition of ~ given azeotrope will
vary - at least to some degree - and
changes in pressuro will also change - at ~ -
least to some degree - the bo~l$ng point
temperature Thus ~n azeotrope of A, B
and C represents a unique type o~
relationsh~p but with a variable
composition which depends on temperature
and/or pressure Therefore compositional
ranges, rather than ~ixed compositions,
ar- oten used to de~ine~azeotropes
* $he composition can be def~ned~as a
particular~weight percent relationShip or
mole percont relationship of A,~B and~C,
9;~ ~ =whi~le recognizing that such sp-cific
; valueg~point~out only one particulàr such ;~
relati~onship~and that in~actuality,~a~
serles~o~such~relationsh~ps,~ r~-presented
by~A~ B~and~C~actually exi~t~for a~g~ven
e, varied by~the 1nfluence of~
*~Az-trope~A,~B~and C;oan~be characterlzed
by;~defining the compositlon as an
azeotrope~characterized ~y a boil$ng
30 ~ point~at~a~given pressure, thus~giving
ident~fyIng~characteristics w~thout
undùly~ ~1t1ng the -cop- of~the ~ -
invent~on~by a~speci~¢~;~numer~cal~
composition,~which is limited~by and is~
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202~487
only as accurate as the analytical
equipment available.
Ternary mixtures o~ about 51-61 weight
percent l,l-dichloro-1,2-difluoroethane and about
31-41 weight percent trans-1,2-dichloroethylene and
about 4-10 weight percent ~ethanol are characterized
as azeotropic, in that mixtures within th$s range
exhibit a substantially constant boiling po~nt at
constant pressure. Being substantially constant
boiling, the ~ixtures do not tend to rractionate to
any great extent upon evaporation. A~ter evaporation,
~; ~ only a small difference exists between the co~position
of the vapor and the composition of th~ inltial liquid
phase. This difference is such that the co~positions
lS o~ the vapor and liguid phases are considered
substantial}y identical. Accordingly, any mixture
within this range exhibits properties which are
characteristic of a true ternary azeotrope. Tbe
ternary composition consisting of about 56.5 weight
percent 1,1-dichloro-1,2-difluoroethane, a~out 36.~5
wei~ht~percent trans-1,2-dichloroethylene and abo~ut
7.0~weight percent ~ethanol has b-en established,
within;the~accuracy~of~the fractional distillat~'on
method,~s a true ternary azeotrope, boiling at about
2~5~ ~41.~0-~C-, at substantially atmospherio pressure.
Al~o,~according~to the~instant~im ention,
ternary~;mi ~ es of~about~;65-~5 weight~percent
dichloro-1~,2-di~luoroethane, about 19-29 weight
' percent'trans-1,2-d~chloroethylene and about 3-7
30 ~weight~percent ethanol;~are characterized as
azeotropic,~in~that~mixtur-s within this~r~nge exhib~t '~
ubs*antially'constant ~oiling point~at constant
pre~ure~ ~e~ng~substantially constant boil~ng~ thQ
m~xtures do not tend to fractionate to any great
35 extent upon e~aporat~on. After evaporation, only a ;~
..
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2026487
- 8 -
small difference exists between the composition of the
vapor and the composition of the initial liquid phase.
This difference is such that the compositions o~ the
vapor and liquid phases are considered substantially
S identical. Accordingly, any mixture within this range
exhibits properties which are characteristic of a true
ternary azeotrope. The ternary composition consisting
of about 70.0 weight percent
1,1-dichloro-1,2-difluoroethane, about 24.6 weight
percent trans-1,2-dichloroethylene and about 5.4
weight percent ethanol has been established, within
the accuracy o~ the fractional distillation method, as
a true ternary azeotrope, boiling at about 44.S-C, at
substantially atmospheric pressure.
lS Also, accordinq to the instant invention,
ternary mixtures of about 61-71 weight percent ;-~
1,1-dichloro-1,2-difluoroethane, about 27-37 weight
percent trans-1,2-dichloroethylene and about 0.7-1.7
weight percent isopropanol are characterized as
azeotropic, in that mixtures within this range exhibit
a substant~ally constant boiling point at constant
pr-ssure. Being substantially constant boiling, the
mixtures do not tend to ~ractionate to any great
ext~nt upon evaporation. After evaporation, only a
~small difference exists between the composition of the
vapor and the composition of the initial liquid phase.
This differenc- is such that the compositions of the
vapor and liquid phases are considered substantia}ly
identical. Accordingly, any mixture within this range
exhibits properties which are characteristic of a~true
ternary azeotrope. Tbe ternary compositioh consisting
of about 66.3 weight percent
dichloro-1,2-difluoroethane, about 32.5 weight
percent trans-1,2-dichloroethylene and about 1.2
weight percent isopropanol has been established,
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2~2G487
within the accuracy of the fractional distillation
method, as a true ternary azeotrope, boiling at about
46.5-C, at substantially atmospheric pressure.
The a~orestated azeotropes have low
S ozone-depletion potentials and are expected to
decompose almost completely, prior to reaching the
stratosphere.
The azeotropic compositions of the present
invention permiit easy recovery and reuse o~ the
solvent ~rom vapor defluxing and degreasing operations
because o~ tbeir azeotropic nature. As an example,
the azeotropic mixtures of this invention can be used
in cleaning processes such as described in U.S. Patent
No. 3,881,949, which is incorporated herein by
lS referenCe-
The azeotropic compositions of the instantinvention can be prepared by any convenient method
including mixing or combining the desired component
amounts. A preferred method is to weigh the desired
component amounts and thereafter combine them in an
appropriate container.
EXAMPL~S
a~ple 1
A;solution which contained 61.7 weight
5~ percent 1,~1-dichloro-1,2-dif~uoroethane, 31.8 weight ' ' "
percent tran~-~,2-dichloroethylene and 6.S weight
pérc-nt metbanol~was~ prepared in a 'suitab~le contalner
and mlxed thoroughly. -~
' ; The solution was distilled in a Perkin-Elmer
~odel 251~autoannular spinning band still (200 plate ' "~
3~ fractionatlng capability)~ u ing about a 10:1 reflux '' ~ -
to ta~e-o~f ratio. Head temperatures were read~
directly to O.l-C~. All temperatures were adjusted to
760 mm pressure. Distillate compositions were ~ ~P'~
; 3S
.
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-- 10 --
determined by gas chromatography. Results obtained
are summarized in Table 1.
TABLE 1
DISTILLATION OF:
~61.7 + 31.8 + 6.5)
51,1-D}CHLORO-1,2-DIFLUOROETHANE (DCDFE),
T~ANS-1,2-DICHLOROETHYLENE (T-9CE) AND METHANOL (MEOH)
WT.%
DISTILLED
TEMPE~ATURE,C OR
CUTS POT RECOVERED-- DCDFE T-DCE MEOH
1 41.1 2.6 57.1 35.7 7.2
2 41.0 10.3 56.1 36.9 7.0
3 41.1 15.0 56.1 36.8 7.1 -
4 41.1 20.0 56.5 36.5 7.0
S 41.1 22.0 56.6 36.4 7.0
6 41.1 25.0 56.8 36.3 6.9
7 41.1 30.0 S6.9 36.2 6.9
HEEL -- 79.8 63.4 29.5 7.1
~ nalysis of the above data indicates ~ery
small differences among head temperatures and
distillate compositlons, as the distillation
progressed. A statistical analysis of the data
~ndicates that the true ternary azeotrope
o~ dichloro-1,2-difluoroethane,
trans-1,2-dichloroethylene and methanol has the
following~characteristic- at atmospheric pressure (99
p-rcent~confidence limits):
Dichloro-1,2-d~fluoroethane = 56.5 * I.3 wt.~
trans-1,2-Dichloroethylene - 36.5 1 1.1 wt.%
Methanol ~ 7.0 ~ 0.3 wt.%
Boiling point, C ~ 41.0 1 0.1
Example 2
A solution which contained 76.3 weight
percent 1,~1-dichloro-1,2-difluoroethane, 16.~ weight
perc-nt trans-1,2-d~chloroethylene 6.9 weight percent
~ ethanol was prepared in a suitable container and ~ixed
;;~ thoroughly.
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2026 ~7
The solution was distilled in a Perkin-Elmer
Model 251 autoannular spinning band still (200 plate
~ractionating capa~ility), using about a 10:1 reflux
to take-off ratio. Head temperatures were read
directly to O.l-C. All temperatures were adjusted to
760 mm pressure. Distillate compositions were
determined by gas chromatography. Results obtained
are summarized in Table 2.
TA8LE 2
DISTILLATION OF:
~76.3 + 16.8 + 6.9)
1,1-DICH~ORO-1,2-DIFLUOROETHANE (DCDFE),
TRANS-1,2-DICHLOROETHYLENE (T-DCE) AND ETHANOL (ETOH)
WT.%
D~STILLED
TEMPE~ATURE,C OR
CUTSHEADRECOVERED DCDFE T-DCE ETOH
1 44.5 5.0 70.0 24.6 5.4
2 44.5 9.8 69.6 25.0 5.4 -
3 44.5 14.6 69.8 24.9 5.3 ~ ;~
4. 44.5 20.0 69.7 24.8 5.5
44.5 24.4 70.2 24.5 5.3
6 44.5 28.6 70.8 23.8 5.4
7 50.0 32.9 72.4 22.4 5.2
HEEL -- 93.5 86.2 S.6 8.2
Analysis of the a~ove data indicates very -
small differences among head temperatures and
distillat- compos~itions, as the distillation
progressed. A statistical analysis of the data
-indicates that the true ternary azeotrope of
dlchloro-1,2-dirluoroethane,
trans-1,2-dichloroethylene and ethanol has the
following characterlstics at atmospheric pressure (99
percen~ donfidence limits)~
Dichloro~ 2-difluoroethane ~ 70.0 + 1.9 wt.%
trans-1,2-Dichloroethylene - 24.6 1 1.9 wt.~
Ethanol - 5.4 + 0.3 wt.%
Boiling point, C ~ ~ 44.5 ~ 0.1
, ~ :' ~ :-
20264~7
ExamDle 3
A solution which contained 64.6 weightpercent l,l-dichloro-1,2-difluoroethane, 30.0 weight
percent trans-1,2-dichloroethylene and 5.4 weight
percent isopropanol was prepared in a suitable
container and mixed thoroughly.
Tbe solution was distilled in a Perkin-Elmer
Model 251 autoannular spinning band still (200 plate
~ractionating capabi~ity), using a~out a 10:1 re~lux
to take-off ratio. Head temperatures were read
directly to O.l-C. All temperatures were ad~usted to
760 mm pressure. D~stillate compositions were
determined by gas chromatography. Results o~tained
are su~arized in Table 3.
TABLE 3
DISTILLATION OF: `
(64.6 ~ 30.0 ~ 5.4)
DICH~ORO-1,2-DIFLUOROETHANE (DCDFE),
TRANS-1,2~DICHLOROETHYLENE (T-DCE) AND
ISOPROPANOL(IPROH)
,~;,
` ~ WT.%
DISTILLED
TEMPERATURE,-C OR
CUTSHEADRECOVERED DCPFP T-DCE IPROH
1 45.g ~4.7 64.6 34.4 1.0
2 46.4 29.8 65.8 32.9 1.3
3 46.4 41.6 65.9 32~9 1.2
4 46.3 65.2 ~66.8 31.9 1.3
5 46.7 72.8 66.5 32.4 1.1
6~46.~9 87.6 69.3 29.3 1.4
EE~ ~ 100.0 63.8 12.423.8
Analysis of the above data indicates very
small~di~er-nces among head temperatures and
distillate~ compositions, as the distillation
progressed. A statisticàl analysis o~ the data
--~ lnd~cates~t~at the true ternary azeotrope Or
diohloro-1,2-difluoroethane,
trans-1,2-d$chloroethylene and isopropanol has the
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2026487
- 13 -
following characterlstics at atmospheric pressure (99
percent conridence limits):
l,l-Dichloro-1,~-difluoroethane - 66.3 1 2.2 wt.%
trans-1,2-Dichloroethylene ~ 32.5 + 2.2 wt.
Isopropanol ~ 1.2 + 0.3 wt.%
Boiling point, C ~ 46.5 + 0.8
ExamDle 4
Several single sided circuit boards were
coated with activated rosin flux and soldered by
passing the board over a preheater to obtain a top
side board temperature of approximately 200-F (93-C)
and then through 500-F (260'C) molten solder. The
s~ldered boards were defluxed separately with the -
three azeotropic mixtures cited in Examples 1, 2 and 3
abo~e, ~y suspending a circuit board, first, for three
minutes in the boiling sump, which contained the
azeotropic m~xture, then, for one minute in the rinse
sump, which contained the same azeotrop1o mixture, a~nd
finally, ~or one minute in the solvent vapor above the -;~
boiling sump. The boards cleaned in each azeotropic
mixture had no visible resldue remaining thereon. ` ;
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