Note: Descriptions are shown in the official language in which they were submitted.
1~ 9Z,~3
This invention relates to an antifoam
composition for lubricating oil compositions
and a process of dispersing said composition into
the lubricating oil compositions. ~ore particularly
it relates to compositions comprising certain poly
(dimethylsiloxanes) mixed with a minor portion of
certain perfluoroalkylpolyethers.
In many applications, lubricating oil com-
positions are employed as functional fluids or power
transmitting fluids. In such uses, the fluids are
pumped or circulated at high speeds which causes the
entrainment of air in the fluid with the resultant
! production of considerable amount of foam.
Foam in a functional fluid is highly de-
trimental to the operation of an automatic transmission
or an hytraulic device. The foaming tendency of oil
compositions is recognized as a serious problem and
industry-adopted specifications have been set on this
lubricating oil property.
The foaming tendency of a lubricating oil
composition is intensified by the presence of many
; additives conventionally employed in lubricating oils.
The problem is generally further aggravated where the
lubricating compositions contain poly(organosiloxanes)
as major constituents.
. . .
The use of perfluoroalkylpolyethers as
; antifoam agents in lubricating and hydraulic fluids
has been described in U.S. patent 3,77j,324 and in
U.S. Patent 4059534 issued November 22, 1977.
In industry, it is common practice to disperse anti-
; 30 foam agents such as perfluoroalkylpolyethers in foaming
fluids by first dissolving the said antifoam additives" i~-
~ . ~ . s ~
in solvents which are th~mselves soluble in the foaming
:~0~35~29
fluids (e.g. U.S. 3,775,324). A useful, very fine
dispersion of the antifoam is thus obtained. The only
known hydrocarbon oil soluble solvents for the per- -
fluoroalkylpolyethers of the invention are poly- or
per-halocarbons such as trichlorotrifluoroethane. However,
it has been shown by M.Z. Fainman ("Halogenated Solvents
and Corrosion in Dynamic Systems, Lubrication Engineering,
pp. 556-558, November 1974.) that a parts per million
concentration of such halocarbons can cause grave cor-
rosion problems in certain applications such as hydraulic
systems.
It has now been discovered that compositions
of matter can be prepared which contain minor amounts of
perfluoroalkylpolyethers as antifoam agents, and which
have excellent corrosion, and antifoaming properties.
It is therefore an object of this invention
to provide a novel antifoam composition which can be
used directly in lubricating oils which are compatible
with silicone oil.
It is another object of this invention to
provide a method of dispersing perfluoroalkylpolyethers
in lubricating oil compositions which are compatible
with poly(dimethylsiloxane).
These objects are obtained by means of an
antifoam composition comprisinga mixture of a major portion
of (A) poly(dimethylsiloxane) having the general formula:
lR
R-Si-0- ~ Si-0¦ -Si-R
R R / R
2.
1C)5~35`29
wherein R is a methyl group and n has a value such
that the average viscosity at 25C is between 5 cs
and 500 cs, and a minor amount finely dispersed therein
of (B) perfluoroalkylpolyether of the formula:
F- ~C~(CF3)CF20 ~ 2 5
; in which x has a value of from 10 to 41.
These objects are also obtained by means of
a method of dispersing perfluoroalkylpolyether in a
lubricating oil composition which is compatible with
poly(dimethylsiloxane) which method comprises:
mixing a major amount of (A) poly(dimethylsiloxane) of
the formula
R R ~ R
R-Si-0- Si-0 -Si-R
R R n R
wherein R is a methyl group and n has a value such
that the average viscosity at 25 C is between 5 cs
and 500 cs, and a minor amount finely dispersed therein
of (B) perfluoroalkylpolyether of the formula:
F- ~CF(CF3) CF20 ] C2F5
in which x has a value of from lO to 41, into said lub-
ricating oil composition to provide a concentration of
from 1 ppm to 500 ppm of said perfluoroalkylpolyether
in the total composition.
,
More specifically, one aspect of this invention
may be described as a foam inhibiting composition com-
prising a mixture of a major portion of (A) trimethyl
30 end-blocked poly(dimethylsiloxane) having viscosity at
25 C between 5 centistokes and 500 centistokes, and a
B minor amount finely dispersed therein of ~B) perfluoroalkyl-
3.
939Z~
polyether of the formula:
F- LCF(CF3)CF20 ] XC2F5
in which x has a value which provides an average molecular
weight for the perfluoroalkylpolyether ranging from about
2,000 to 7,000. -
The dimethylsiloxane oils employed in this in-
vention as well as methods for their preparation are well
known and consist essentially of siloxy units of the formula
R2SiO and end-blocking siloxy units of the formula R3SiO wherein
R is a methyl radical. As employed herein such siloxane oils
are essentially linear siloxane polymers having a viscosity in
the range of about 5 to about 500 centistokes at about 25C,
preferably about 10 to about 350 centistokes at about 25C,
and most preferably about 50 to about 200 centistokes at about
25 C. These siloxane oils are also conventionally represented
by the average formula:
R3Sio(R2SiO)xSiR3
wherein R is a methyl radical and x is an integer having a
value that corresponds to the viscosity of the particular
siloxane. FOr example, a trimethyl end-blocked dimethyl
siloxane oil having a viscosity of 100 centistokes at 25 C
can be represented as having the average formula:
Me3SiO(Me2SiO)48SiMe3
wherein Me is a methyl group.
It is to be understood, of course, that while the
dimethylsiloxane oils used in this invention can be discrete
chemical compounds, they are usually mixtures of various discrete
siloxane species, due at least in part to the fact the starting
materials used to produce the siloxane oils are themselves
usually mixtures. Thus, it is obvious that the dimethyl siloxane
oils employed herein need not be fractionated as by distillation
but may be sparged (i.e. stripped of lights~ or unsparged.
10~3~
The perfluoroalkylpolyethers of the invention
are also well known in the art, and have the general formula:
F- ¦CF(CF3)C~20 ~ X-C2F5
in which x has a value providing an average molecular weight
for the perfluoroalkylpolyether ranging from about 2,000 to
7,000. This molecular weight range will correspond to values
for x of about 10 to 41. The preferred perfluoroalkylpolyethers
are those in which the average molecular weight ranges from
about 2,000 to about 5,500 for which values of x correspond to
about ll to 32, respectively. Commercial products cor-
responding to this description are Krytox fluids manu-
factures by E. I. DuPont de Nemours & Company. Specific
examples of effective perfluoroalkylpolyethers are des-
cribed below.
The foam inhibiting compositions of matter of this
invention are prepared by mixing the two liquids in a high shear
mixer until a fine dispersion of a minor portion of perfluoro-
alkylpolyether is achieved. Such a state is typically evidenced
by the development of haziness in the mixture. The proportions
of poly(dimethylsiloxane) to perfluoroalkylpolyether should be
selected so as to provide a concentration of perfluoroalkylpolyether
of between 1 to 500 ppm in the final lubricating oil composition and
a concentration of dimethylsiloxane polymer in said lubricating
oil which is consistent with the intended application. Because
the poly(dimethyl siloxane) acts as a carrier for the perfluoro-
alkylpolyether, it is necessarily the major component of the
antifoam compositions. While not wishing to be bound by a pre-
cise range, the proportions of components (A~ to (B) typically
range from about 90 to 99.9 per cent by weight of (A) to about
10 to 0.1 per cent by weight of (B), and preferably from about
97 to 99.5 per cent by weight of (A) to about 3 to 0.5 per cent
by weight of (B).
*Trade Mark
5.
LB
z~
It is to be understood that the stability and
quality or the dispersion is greatly affected by the shear
rate of the mixer, and the viscosity and concentration of the
dimethylsiloxane polymer. It is therefore obvious that not
every possible proportionate range by weight employable herein
for every silicone oil and perfluoroalkylpolyether component
of this invention may give the same degree of results. However,
experience has shown that compositions of the invention which
are mixed llntil they appear to be homogeneous to an observer
unaided by optical instruments or other devices, and which are
used as foam inhibiting additives promptly, preferably within
24 hours, tend ~o give the most satisfactory and consistent
- results.
Those lubricating oil compositions with which the
antifoam compositions of matter of this invention may be used,
are well known in the art. While such lubricating oil com-
positions are most preferably limited in that they must be
compatible with the poly(dimethylsiloxane) oils of the anti-
foam compositions of the invention, they need not contain
silicone oils. Typically, however, the lubricating composi-
tions do contain silicone oils; for example, compositions as
described in U.S. Patent 3,974,080, and U.S. Patents 4059534
issued Nove~[ber 22, 1977 and U. S . 4097393 issued June 27, 1978.
The antifoam compositions of the invention can be
mixed with the desired lubricating oils in any conventional
~anner in proportions which provide the minute quantities of
perfluoroalkylpolyether required to inhibit foaming. Generally,
the two liquids need only be mixed together in the proportions
desired while stirring at room temperature.
The following examples illustrate the present
invention:
EXAMP~E No. 1
; 198 grams of poly(dimethylsiloxane) having a
viscosity of 50 cs at 25 C were agitated in a household type
blender while 2 grams of Krytox 143 AZ, a perfluoroalkylpolyether
as described above, were added dropwise. The resultant 1
emulsion was stable for more than 24 hours.
*Trade Mark
6.
..
'- iO'~3<3~
E~A*PLE No. 2
198 grams of poly(dimethylsiloxana) having a
viscosity of 50 cs at 25 C were agitated in a household type
blender while 2 grams of Krytox 143 AD* a perfluoroalkylpolyether
as described above, were added dropwise. The resultant 1%
emulsion was stable for more than 24 hours.
EXAMPLE No. 3
A~s described in Examples 1 and 2, ~rytox 143 AZ *
was dispersed in p~ly(dimethylsiloxane) having a viscosity of
100 cs at 25 C; the proportion by weight was 0.5% Krytox to
99.52 poly(dimethylsiloxane). When added with stirring to a
lubricating oil containing poly(dimethylsiloxane) of 100,000 cs
at 25C, a propylene oligomer, and various conventional lubri-
cating oil additives, a S0 ppm concentration by weight of the
a~tifoam composition markedly decreased the foaming tendency.
EXAMPLE Nos. _-6
- The antifoam composition of Example 1 was added
with stirring to the lubrica~t compositions shown in Table 1.
These flulds were tested for foaming characteristics before
and after the atdition of sufficient antifoam composition to
give the quantity of perfluoroalkylpolyether indicated.
As see~ by the test results presented in Table 1,
the method of dispersion is effective at various concentrations
in different lubricants consisting of hydrocarbon oil and
silicone oil.
E ~MPLE Nos. 7 and 8
These t~o examples demonstrate the effectiveness
of the antifoam of E~ample 1 in solutions containing silicone
oils other ~han poly(dimeebylsiloxane).
EXAMPLE Nos. 9 and 10
These two examples demonstrate the effectiveness
of the antifoam compositions of Example 2.
EXAMP~E No. 11
This exa~ple demonstrates the effectiveness of
the antifoam composition of Example 1 in a hydrocarbon lubri~
cating oil which is compatible with silicone oil.
EX~MELE No. 12
This e~ample uses a standard dispersion method
for comparison with the process of this invention. The per-
fluoroalkylpolyether was dissolved in UCOU 113 DCE, a trich-
lorotrifluoroethane/dichloroethane azeotrope, until an antifoam
concentration of 1.60% was obtained. Sufficient antifoam con-
centrate was added to the solution of Example 4 to arrive at
the quantity of perfluoropolyether indicated. This e~ample is
~rade Mark
7.
~0~;392~
included for comparison purposes and does not describe an
object of the present invention.
EXAMPLE Nos. 13 and 14
_ . _ . .
These two examples illustrate the superior per-
formance of antifoam compositions of this invention compared
to similar compositions without dimethylsiloxane polymer.
Example 13 is included for comparison purposes and does not
constitute an object of the present invention.
An additional advantage of compositions of the
present invention is the increased stabillty of these compo-
sitions. This is demonstrated in that after standin~ for 24
hours, the concentrate of Example 13 had clearly separated
into its constituents while the concentrate of Example 14
was still usable.
As can be seen from results of Table I, the
dispersion process of the invention is as efficient as the
previously known process while, at the same time, eliminating
the use of corrosive halocarbon solvents.
Various modifications and variations of this
invention will be obvious to a worker skilled in the art and
it is to be understood that such modifications and variations
are to be included within the purview of this application and
the spirit and scope of the appended claims.
.
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