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Патент USA US2255208

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Sept. 9, 1941. .
,
H, R. FIFE ..
HYDRAULIC
"
BRAKE FLUID
'
_
2,255,208
'
Filed April 15, 1939
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INVENTOR
HARVEY R. FIFE
BY
/
ATN
2,255,208
Patented Sept. 9, 1.941.’
UNITED STATES PATENT 'OFFlClE‘."
HYDRAULIC BRAKE FLUID
Harvey R. Fife, Mount Lebanon, Pa., assiznor to
Carbide and Carbon Chemicals Corporation, a
corporation of New York
’
Application April 15, 1939, Serial No. 268,100
7 Claims.
This invention 'is concerned with improve
(Cl, 252-79)
tendency which is also accentuated at'low tem
peratures. In such case‘ the separated castor oil
ments in hydraulic brake ?uids and it is par
ticularly directed to making improved substances
_
phase may congeal.
~
to use as the lubricating elements of these ?uids.
This application is a continuation-in-part of my
The object of the present invention is to cor
rect such disadvantageous features accompany
copending application Serial No. 111,682, ?led
November 19, 1936, now Patent No. 2,200,494, is
ing the use of castor oil in brake ?uids as are
sued May 14, 1940.
_
.
.
It is essential that a brake ?uid contain a
v lubricating element to insure proper operation 10
of the moving parts of the system. However, all
known hydraulic brake systems contain rubber
parts as essential parts of the system, and the
vast majority of both mineral and vegetable
outlined above and yet retain all the present de
sirable characteristics of castor oil, such as its
lubricity and its low swelling action for rubber.
It has been found that this object can be suc
cessfully achieved by appropriate chemical modi
?cation of castor oil. This chemical modi?cation
comprises reacting castor oil, by heating it in the
presence of a substantially non-volatile alkaline
lubricating oils are characterized by excessive 15 catalyst, with a substantial excess of polypropyl
ene glycol above that stoichiometrically required
to form the monoricinoleate ester of the poly
erty makes them entirely unsuited for use in
glycol by complete radical interchange with the
brake ?uids. 0f the lubricating oils, castor oil
glyceryl triricinoleate constituent of the castor
is practically the only oil which is su?iciently
inert toward rubber to permit its use in brake 20 oil. It is an important feature of this invention
that unreacted polypropylene glycol resulting
?uids. Unfortunately, castor oil alone cannot be
from the use of such excess, which must also be
used as a hydraulic brake ?uid because it pos
su?icient to make up for polypropylene glycol sesses a relatively high freezing point and con
swelling or solvent action on rubber. This prop
consumed in any incidental side reaction, is re
25 tained as a miscible constituent of the reaction products._ It has been found that such a mixture
Consequently, it is necessary to add diluents to
geals at temperatures normally encountered in
the operation of the brake system.
'
‘
is particularly desirable as the lubricating'ele
ment of hydraulic ‘brake ?uid. The polypropyl
ene glycol used in this invention" may be pre
requisites for such diluents are that the diluent
is sumciently non-volatile; that it does not va- ,_30 pared by the reaction of propylene oxide with
propylene glycol and may consist of substantially
porize unduly at the highest temperatures en
95% dipropylene glycol, the ‘remainder being
countered in the operation of the brake system;
higher homologs of dipropylene glycol. The term
that it be non-corrosive to aluminum and other
“polypropylene glycol,” as used
the speci?ca
metals used in constructing the brake system;
and that it does not exert an excessive swelling 35 tion andv claims, is intended to include such mix
the castor oil in order to reduce its viscosity to
working limits at low temperatures. Among the
action on rubber.
However, many diluents are
known which ful?ll these requirements, and yet
> they fail to meet the primary requisite for such
7 tures.
‘
It is acknowledged that the use of ricinoleate
esters of glycerine and glycols in brake ?uids has
diluents namely, miscibility with castor oil, par 40 previously been suggested. The distinguishing
attribute of this invention is that“ a‘ homogeneous
ticularly at low temperatures. Thus, a disad
vantageous characteristic of castor oil in brake - mixture of the reacted and modi?ed castor oil
with the excess polypropylene glycol is employed
?uids is ‘its relative lack of miscibility with
as the lubricating element of the brake fluid. It
diluents, especially at low temperatures. Such
has
been found that when castor oil is modi?ed
low temperature separation of the components 45
by heating with an excess of such substances as
of brake ?uids is very undesirable because a free
ethylene glycol, glycerine or diethylene glycol,
castor oil phase is formed and the castor oil may '
the
resulting reaction products, are not miscible,
congeal at temperatures usually encountered in
especially
at low temperatures. This effect, in
the operation of a brake system.
_
Another disadvantage of the present brake 50 contrast to that obtained in the present inven
tion, may be illustrated, in part, by the following
?uids containing castor oil is that, upon absorp
example :
tion of small amounts of water, either acciden
Example I
‘ tally or promoted by any hygroscopicity oi the
A
sample
of
castor
oil was reacted in the pres
diluent, the ?uids have a tendency to separate
into a castor oil phase and a diluent phase, a 55 ence of 0.2% by weight of a 50% ‘solution of
Q
2,255,208
caustic soda at a temperature of 200° C. with
Table B
equal proportions by weight of (1) glycerine,
(2) ethylene glycol, and (3) polypropylene glycol.
In each case, the polyhydroxy substance was
Added diluent,
1-.
present in excess of that stoichiometrlcally re
cent of total ?ulrfgy
quired to form its monoricinoleate ester. The
resulting reaction products were compounded in
equal proportions by weight with each of three
diluents, as shown. Water, in amounts shown
below, was then added and the separation tem
perature of the different ?uids determined. The
separation temperature is obtained by cooling the
?uid from a temperature at which the ?uid is
homogeneous to the point at which the com
volume
,
o excess polypro
Excess polypropylw? Npylene
glycol
glycol used, 1 part
3 parts castor oil
by volume '
Ethylene glygol
Immlsciblc.
9%....
Mlsclble.
immiscible.
Do.
Gl cerine: W ______ __
ponents begin to separate. This point is detected
.
o.
immiscible.
Do.
water, be below minimum operating tempera
tures normally encountered, this test is determi 20
native of one of the most vital characteristics
of the ?uids. The separation temperature of the
,
Example II
The value of the present invention in increas
ing the tolerance of brake ?uids for water with
out separation of the components may be better
understood by reference to the attached draw~
ing. The composition of the original ?uid by
25 volume was castor oil, 15 parts; propylene gly
col 15 parts; polypropylene glycol, ‘ 15 parts;
Table A
Separation temperature, ° 0.,
diluent-diacetone alcohol,
Castor oil reacted with excess
propylene glycol.
by vo ume
by the appearance of cloudiness in the ?uid.
Since it is requisite in a brake ?uid that its sep
aration temperature, even in the presence of
di?erent ?uids was as follows:
used, 1 part poly- '
polypropylene sly
col, 1 art castor oil
added water’ percent’
0 l l
l
Glycerlne ____________________ _-
+153
2
3
Ethylene glycol _____________ -.
Polypropylene glycol ________ ..
—l3
-35
2
3
butanol, 55 parts. Its water tolerance was 23.8
expressed in volumes of water absorbed without
separation of the components per 100 volumes
30 of ?uid tested. Since both propylene and poly
propylene glycol are quite hygroscopic, the ?uid
4
has a tendency to~absorb water, which may cause
separation and it is therefore essential that the
?uid have high water tolerance.
____________________ _.
—l2
~—35
—l2
-—33
—l1
—33
—9
—3()
35
The polypropylene glycol and the castor oil, in
the same amounts as above, were then reacted
together but separate from the other ingredients
Separation temperature, ° 0.,
diluent-ethylene glycol
Castor oil reacted with excess
monoethyl ether, added wa
tor, percent
0
1
Glycerine _____________ -_,.___'...
+108
2
3
Ethylene glycol _____________ __
Polypropylene glycol ........ __
—l6
—30
1
2
3 ‘ 4
at about 200° C. for the times shown in the draw
ing and both with and without the presence of
40 caustic soda as a catalyst. The reaction products
were then diluted with the same amounts of
butanol and propylene glycol as above and the
separation temperature determined. The results
as set forth graphically in the drawing, show the
pronounced increase in water tolerance obtained
in both instances. However, the time required
_____________________ __
~14
—30
—12
-—30
—12
-—28
~10
—28
for reaction is excessive when a catalyst,‘ such as
caustic soda, is not used.
The reaction products, when caustic soda was
Cnstor oil reacted with excess
Separation temperature, “ 0.,
diluent-butanol, added wa 50 employed, were believed principally to consist of
tel" percent
- polypropylene glycol mono-ricinoleate, unreacted
0 I 1
2 l 3
polypropylene glycol, and small amounts of
sodium ricinoleate and free glycerine. In this
4
instance the amount of polypropylene glycol
l
Glycerinc ____________________ _. +73.5
2
3
Ethylene glycol _____________ .. —l8.5
Polypropylene glycol ________ _. —45
present was about two times as much as that
_____________________ ..
—l8
—45
—l8
---42
—l6
—-42
—l6
—40
stoichiometrically required to form its mono
ricinoleate ester.
The reaction product of the castor oil with the
excess polypropylene glycol is also character
In each of the cases marked 1 and 2 above,
high separation temperatures are obtained ap 60 ized by greatly increased miscibility with dilu
ents as compared with castor oil itself. ‘This in
parently because the ricinoleate ester formed is
I ‘only partially miscible with the unreacted glycer
. creased miscibility with a variety of diluents is
. ine or ethylene glycol.
' Further experiments have also shown the de
a very important improvement, especially from
a practical viewpoint, because a number of di?
erent brake ?uids are available and are very '
sirability of using an excess polypropylene glycol
to react with the castor oil. The results of these“
experiments are presented in tabulated form
below; The reaction mixtures were prepared by
likely to become intermixed during re?lling of
following the procedure speci?ed precedingly.
would occur on such intermixing.
By using an excess of the polypropylene glycol,
the objects of this invention are more satisfac
torily achieved, as is illustrated by the improved .
miscibility of the lubricating element with dilu
ents when an excess polypropylene glycol is used. 75
a given hydraulic brake system. The increased
miscibility of the new ?uid lessens the danger
that separation of the components of the ?uids
The following table shows the improved'mis
clbility at ordinary'temperatures and at low tem
peratures of the new lubricating element with di
luents as compared to unreacted
mixtures of
castor oil and polypropylene glycol. The reacted
2,255,209 g
_
3
'
mixture was prepared by following the procedure
parts byweight otbutanol in order to. form a‘
speci?ed in ExampleI.
?uid'suitable for use in hydraulic brake ?uids.
The new ?uid possessed a water tolerance. or 38.
volumes of water per 100 volumes of ?uid, where
as ,a‘?uid oi the same empirical composition
which had not received the heat treatment de
scribed had a water tolerance of only 11- in the
. "
Table 0
React'ed
mum _
Added diluent, per-
. A
cent of total ?uid
by volume
C
same units. In other respects, the new?uid
showed operating features decidedly superior to
>
,
1 part poly- 1 part poiy1 part poly
ropy en
propylene gly- propylene gly
gycolandl col andlpart col and Sifmrts
oil by volume
Ethylene glycol:
B
,
castor
Glyoerine: 9% .... ._
Unreacted mixtures
Miscible_ ___
9%"; _____________ __do ____ __
castor oil by
by volume
Immlscible_-__
Miscible______
Immiscible___-_
the unreacted ?uid oi the‘ same empirical compo
sition andtov many ?uids now in use.
by volume
example, may, of course, be varied.
Do. -
Do.
D0.
____ _do ______ __
Do.
For in- f
stance, other substantially non-volatile alkaline.
catalysts, such as potassium'hydroxide and tri
ethanolamine, may be used. Also, as shown in
the drawing, the catalyst may be omitted al-'
though longer reaction times are then required.
When a catalyst is used, the temperature may be
Immiscible.
____ -do ______ _.
,
The‘vexact ‘conditions speci?ed in the above
castor o by
widely varied from about 70° C. to about 300° C.
depending largely on the time of heating.
Incarrying out the reaction between castor
oil and the excess polypropylene glycol,‘ it is
desirable .to observe certain precautions. For
25 instance, the caustic should be addedslowly and
uniformly with vigorous agitation. Otherwise,
up.
Methyl ether of diethylene glycol:
50% __________ __
the caustic solution separates to the bottom of
the reaction vessel and solid sodium ricinoleate
.
_
Miscible at
tempera-
immiscible at
tempera-
.
_
immiscible at
tempera
t u r e s
tures below
tures
above
—-23°G.
—4°C.
below
>
30
—38° C.
is deposited. This is undesirable and promotes
discoloration and high alkalinity in the reaction
products. The pH of the reaction products pro
duced under these conditions 'may be as high as'
9 and this is sometimes su?‘icient to cause severe
A wide range of diluents may thus be employed
alkaline corrosion of the aluminum pistons in
with the new lubricating element. As examples 35 the brake system. In contrast, by using vigorous
may be mentioned butanol, secondary butyl al
> agitation and slow addition of the caustic, a pH ‘
cohol, tertiary butyl alcohol, the methyl, ethyl
as low as 7.4 to 7.8'may beobtained and the
and butyl monoethers of ethylene glycol and of
propylene glycol.
possibility of alkaline corrosion by the ?uid thus
avoided.
'
Another outstanding advantage of the newl - 40
In addition, it is desirable to use several times
bricating element is its lower viscosity at reduced
the amount of caustic required for neutralization
temperatures as compared to castor oil alone or
of the free fatty acid contained in the castor oil.
simple mixtures of castor oil and polypropylene
The excess caustib serves as a catalyst and also
glycol. The lubricating element of this invention
produces an equivalent amount of sodium ricino
is also characterized by improved chemical sta 45 leate which acts as a .bu?er salt in maintaining
bility in service. For instance, castor oil is un
the proper alkalinity to avoid corrosion. Conse
stable in , service in the presence of sodium
quently, the use of a corrosion inhibitor with the
ricinoleate, since it tends to decompose and form
new ?uid is not essential. It is also desirable to
carbon dioxide, whereas the new ?uid is extreme
carry out the reaction in the absence of air and
ly stable in the presence of this salt and it is not
in a closed system.
necessary to remove it from the reaction prod 59
Example IV
ucts before use. Finally, the lubricating element
of this invention is substantially as inert toward
Following these precautions, a large scale ex
rubber as is castor oil and it does not promote
periment was conducted in which ~15 parts by
corrosion of the metallic parts of the system nor
volume of castor oil and 15 parts by volume of
does it separate from diluents at temperatures
polypropylene glycol were reacted'by pumping
above zero Fahrenheit in any case.
.the reactants through a heating coil. Uniform
Further examples to illustrate the manner of
heating was carried out at a temperature within,
making the improved lubricating element will
now be given.
Example III
A mixture consisting. of 31% by weight of
castor oil, 67% by weight of a mixture of poly
the range of 160°- to 215° C. and for a period of
60
about 45 minutes.
‘.
,
-
On cooling, the reaction products were mixed
with 55 parts of butanol and‘ 15 parts of pro
; pylene glycol, all by volume. This fluid was not
discolored; it had a pH range of 7.4 to 8.2; and
propylene glycols consisting of dipropylene glycol
a water tolerance of 38 to 44 volumes per 100
and a small amount of its higher homologs, and 65 volumes of ?uid. The separation temperature of
0.2% by weight of a 36% aqueous solution of
the-?uid was far below zero Fahrenheit, the
sodium hydroxide was heated for about 2 hours
actual test value being 4-60“ F. After a year's
at a\ temperature of about 200° C. In this case
service, this ?uid had caused no corrosion, did
the polypropylene glycols present were about ?ve 70 not gum, maintained a pH range of 7.4 to 8.2,
times the amount stoichiometrically required to
form the mono-ricinoleate ester of the respective
polyglycols.
and retained its high water tolerance; and the
original separation temperature remained un
changed.
_
‘
After cooling, 66 parts by weight of the modi
Other modi?cations of the invention other
lied and homogeneous oil were mixed with 34 75 than those disclosedtwill be readily apparent to
4
2,2553%
5.- A hydraulic brake ?uid comprising a lubri
»' those skilled in the art and are intended to be
included within the invention as de?ned by the
appended claims.
eating element, which comprises a homogeneous
mixture of polypropylene glycol mono-rlcinoleate
and-polypropylene glycol, combined with a dilu
ent of the group of aliphatic alcohols and mono
alkyl ethers of alkylene and polyalkylene glycols.
lubricating element comprising polypropylene
6. A hydraulic brake ?uid comprising a homo
glycol mono-ricinoleate and polypropylene glycol;
geneous mixture of polypropylene glycol mono
2. In a hydraulic brake fluid, ‘a homogeneous
ricinoleate and polypropylene glycol, as a lubri
lubricating element comprising polypropylene
glycol and the polypropylene glycol mono-esters '10 cating element, combined with an organic liquid
diluent; said polypropylene glycol in each in
of the fatty acids derived from castor oil.
stance being substantially identical with that
3. A hydraulic brake fluid comprising a homo
resulting from the reaction of propylene glycol
geneous mixture of polypropylene glycol mono
with propylene oxide.
ricinoleate and polypropylene glycol, as a lubri
I claim:
1. In a hydraulic brake ?uid, a homogeneous
eating element, combined with an organic liquid
diluent.
'
4. A’ hydraulic brake ?uid comprising a lubri
cating element and an organic liquid diluent, said
lubricating element being a homogeneous mix
U.
'7. A hydraulic “brake ?uid’ comprising, by vol
ume, about six parts of a homogeneous mixture
of polypropylene glycol with the polypropylene
glycol mono-esters of the fatty acids derived from
castor oil, about three parts of monopropylene
ture of polypropylene glycol and an ester ex '20 glycol, and about eleven parts of butanol.
change product of castor oil and polypropylene
glycol containing polypropylene glycol mono
riclnoleate.
'
HARVEY lit’. FIFE.
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