Note: Descriptions are shown in the official language in which they were submitted.
1~730~ 13,069
This invention is directed to a process for
~apidly obtaining a stable freeze polnt depressed
aqueous solution comprising a dialdehyde and an
aliphatic alcohol and~or polyol by adding thereto a
catalytic amount of a strong acid. Also, included
herein is a method for liberating the dialdehyde
in the aqueous solution by dilution with water and the
addition of a catalytic amou~t of a strong acid.
Aqueou~ ~olutions of glutaraldehyde are
well known commercially available materi~ls uEeful
for killing or inhibiting the growth of microorgan~sms.
These squeous solutions of glutaraldehyde have been
used to control the growth of bacteria in a number
of different environment~. For example, glutaraldehyde
~olutions have been used to disinfect medical and
surgical supplies and household ob~ects. Further,
a~ described in U.S. Patent 2,801,216 glutaraldehyde
601utions have been u6ed to control bacteria in water
flooding operations for the 6econdary recovery of oil
and used to prevent corrosion and plugging of iron
equipment due to the action of bacterin in ~torage
vessel6 and as60c~ated plumbing and equipment. Thus,
it can be ~een that there are occa610ns when glutaral-
dehyde ~olutions are ~tored out of door~ and may be
sub~ected to freezing condition6. ~he freezing
point of a 25 percent aqueou6 solution of glutsraldehyde
i~ ~bout 22Y~ Therefore, ~t would ~e desirsble under
these conditiong to further depre~s the freezing point
of the aqueou~ solution of glutaraldehyde. H~wever,
~ny additive to the ~queous glutaraldehyde ~olut~on
wh~ch coula depre6~ the freeælng point of the solution
2.
7 3~ 5 8 13,069
~ust not decrease ~he chemlcal or biological activity
of the solution at time o~ use and must be one which
~aintains the freezing point at the desired tempera-
ture, That is, the additive should be one which is
able to main~ain the desired temperature o~er extended
periods of time. For example, both alcohols and
glycols, such as methanol and ethylene glyco~ are
known to react with glutaraldehyde so that even though
addition of methanol or ethylene glycol to an aqueous
solution of glutaraldehyde initially depresses the
freezing point, upon storage, the freezing point rises
as ~he alcohol and glycol react with the glutaraldehyde
to form a mixture containing acetal linkages. There-
fore, it is dçsirable to have a stable ~ixed freezing
point.
DESCRIPTION OF THE INVENTION
It has been found that the addition of a
catalytic amount of a strong acid to an aqueous solu-
tion comprising a dialdehyde and an aliphatic alcohol
and/or polyol freeze point depressant rapidly catalyzes
the formation of an equilibrium mixture of the dial-
dehyde, acetal, and freeze point depressant, which
equilibrium mi~ture has a stable and fixed freezing
point.
It has also been found that in order to
rapidly and efficiently liberate the dialdehyde for
active chemical or biologi~al reactions, dilution
of the equilibrium mixture with water and the further
addition of a catalytic amount ~f a strong acid is
necessary.
13,069
~1~73(~51~
The allphatic alcohol~ which may be used
as ~reeze point depressants herein contain from 1 to
4 carbon ato~s, such as methanol, ethanol and the like,
and mixtures there~f.;~The preferred alcohol iB
methanol.
The aliphatic polyols which may be employed
in this invention as freezing point depressants contain
from 2 to 6 carbon atoms, and include ethylene glycol,
propylene glycol, glycerol ant the like, and mixtures
thereof. The preferred polyol is ethylene glycol.
It is understood that one or more aliphatic
alcohols may be mixed with one sr more aliphatic
polyols.
The acids which are ~uitable for use in this
invention are acids capable of achieving an aqueous
pH below abou~ 3.0, preferably below about 2.0, and include
phosphoric acid, hydrochloric acid, sulfuric acid,
trifluoromethylsulfonic acid,para-toluenesulfonic acid,
as well as ~upported acid catalysts, such as Amberlyst~
which i8 a supported arylsulfonic acid (sold by Rohm
& Haas Company) and Nafio~ which is a supported fluoro-
sulfonic acid (sold by E. I. duPont de Nemours Co.).
In order to achieve 8 stable freeze point
depresset product, the aqueous solution generally
contains from about 0.1 to about 50 percent by welght
o~ the di~ldehyde; from about 5 to about ~0 percent
by weight of the alcohol andtor glycol.with the
remainder of ehe 801ution being water such that the
total solution is 100 percent by weight. A preferred
~olution contains 25 percene by weight o~ dialdehyde,
_ . _ _ " .. _ . .. __ _ , ._ _ _ . , .. _ . . .. ..
1~73~5~ 13,069
30 percent by weight o~ alcohol and/or glycol and 45
percent by weight of water.
In order to rapid~y and efficiently liberate
the dialdehyde for active chemical or biological reac-
tions, the aqueous solution should contain from about
0.01 to about 10 percent of the dialdehyde and a cataly-
tic amount of an acid, and may conta~n up to about 40
percent by weight of the alcohol and/or polyol, with
the remainder of the solution being water such that
the total solution is 100 percent by weight.
The solutions may contain other additives
such as colorants, surfactants, chelating agents,
pH buffers,and the li~e.
EXAMPLE_
The following examples serve to give specific
illustrations of the practice of this invention but
they are not intended in any way to limit the scope
of this invention.
CONTROL A
The freezing point of a mixture of 25 percent
by weight of glutaraldehyde and 75 percent by weight
of water is 22~F (as determined by the procedure as
,
set forth in ASTM D-1177-65).
CONTR~L B
;
The following lngredients were mixed:
25 percent by weight of glutaraldehyde,
25 percent by weight of methanol, and
50 percent by weight of water.
- The freezing point OI the mixture was -20.5~ -
and the pH was about 4Ø After storage for 55 days
.,
5.
.,
~173~5~ 13,069
at a~out 25C, the f~eezing point of the mixture was
measured and found to be -9.5F.
`CONTROL C
. The following ingredients were mixed:
25 percent by weight of glutaraldehyde,
25 percent by weight of ethylene glycol, and
50 percent by weight of water.
The freezing point of the mixture was -14.0F
and the pH was about 4Ø After storage for 55 days
at about 25C, the freezing point of the mixture was
measured and found to be -7.5F.
EXAMPLE 1
The following ingredients were mixed:
25 percent by weight of glutaraldehyde,
25 percent by weight of methanol, and
50 percent by weight of water.
A one percent solution of phosphoric acid
' was added to the solution until a pH of 1 to 2 was
, achieved.
The freezing point of the equilibrium mixture
was -9.0F.
EXAMPLE 2
The following ingredients were mixed:
25 percent by weight of glutaraldehyde,
25 percent by weight of ethylene glycol, and
50 percent by weight of water.
A one pe~cent solution of phosphoric acid was
added to the solution until a pH o~ 1 to 2 was achieved.
The ~reezing point of the mixture was 3F.
The aqueous equilibri~m mixtures in Examples 1
6.
~ ;30SI~
and 2 were formed in less than about 3 hours. These
equilibrium mixtures are a~le to maintain the stated
~reezing point over long periods of time, even after
6 months of storage.
In contradistinction, the freezing points of
the mixtures of Controls A and B varied significantly ,
after only 55 days and up to three months may be
required for the solution to achieve equilibrium.
EXAMPLES 3 TQ 7
In these examples, the following ingredients
were mlxed:
25 percent by weight of glutaraldehyde,
30 percent by weight of methanol, and
45 percent by we'ight of water.
This mixture was stored for about 6 months.
The final equilibrium of the mixture had been reached
at this point in time. This mixture was diluted to
0.1% of theoretical glutaraldehyde. To separate por-
tions of the mixture was added a one percent solution
of phosphoric acid until the desired pH was achieved.
The percent of glutaraldehyde recovered from the mixture
at various times and pH values is shown in Table I.
The glutaraldehyde levels were determined by gas
chromatography.
TABLE I
Time H
'Examp'le' th'rs~ 2 3 4 5 -
3 1.0 90% 77Z 58% - -
4 3.0 93~/O 78lo
5.0 93% 81~/~ 58% - -
6 24.0 97V/o 93% 69% 37% 44%
7 48.0 94% 93% 73% 37% 44%
~73058 13,069
EXAMPLES 8 T0 13
. .
In these Examples, the following ingredients
were mixed:
25 percent by weight of glutaraldehyde,
30 percent by weight of ethylene glycol, and
45 percent by weight of water.
This mixture was stored for 6 months. The
final equilibrium of the mixture had been reached.
This mixture was diluted to 0.1% of theoretical glu-
taraldehyde. To separate portions of the mixtùre was
added a one percent solution of phosphoric acid until
the desired pH was achieved. The percent of glutar-
aldehyde recovered from the mixture at variQus times
and pH values is shown in Table II. The glutaraldehyde
levels were determined by gas chromatography.
TABLE II
Time pH
Exam~
8 1~0 - - 50%
9 1.67 77% 54%
2.17 81% 66% - - -
11 3.0 - - - 59% 57%
12 24.0 99% 76% 54%
13 72.0 - - - 61% 52%
