Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
This invention relates to water-tolerant
organic lubricants for use in the lubrication of
close-fitting moving parts, such as in gear boxes.
Petroleum-based lubricants are well known.
Similarly, water-soluble posy (alkaline oxide)
polymers are known for use as thickeners in
aqueous hydraulic fluids. See, for example, US.
Pat. Nos. 2,602,780 and 2,768,141. While such
aqueous hydraulic fluids have certain desirable
properties, such as non-flammability, good
temperature stability and relatively low cost, their
lubrication characteristics are often inferior to
those of petroleum-based products. Efforts have
often been made to improve the lubrication
properties of water-soluble organic materials by the
use of various additives. See, for example,
Canadian patent No. 1,161,829. Water insoluble
~oly(alkylene oxide) polymers have also been
known for some years as gear box lubricants but,
like petroleum-based lubricants, they do not
perform satisfactorily when contaminated
with water.
any uses for lubricants involve
requirements for the lubricity of petroleum
products, but yet require a high level of tolerance
for water as an impurity since the uses unavoidably
expose the lubricant to contamination by water.
Unfortunately, even a small amount of water, e.g.,
I or less, by weight, and even as little as about
900 Pam in some high-pressure uses, causes severe
detrimental effects, such as visc06ity change and
substantial lows of loacl-carrying ability of
petroleum lubricant. An effective lubricant
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capable of dissolving a substantial amount of water
without sacrificing significant levels of important
properties would clearly be very desirable.
SUMMARY OF THE INVENTION
It has now been discovered that certain
polyoxyalkylene glycols which are water-soluble make
excellent lubricants for close-fitting moving
parts. Because of their water-solubility, they are
able to take up substantial amounts of ambient water
without significant loss of their lubricity and
load-bearing properties.
The polyoxyalkylene glycols useful in this
invention are the water-soluble reaction products of
an alkanol having up to 4 carbon atoms with ethylene
oxide or mixtures of ethylene oxide and higher
alkaline oxide. The concentration of the ethylene
oxide moiety can be as much as 100% of the total
alkaline oxide content. The lower limit of ethylene
oxide is that concentration which renders the
polyoxyalkylene glycol soluble in water, usually
about 20% by weight.
Accordingly, this invention provides a
lubricant for close-fitting, moving parts which
comprises a water-soluble polyoxyalkylene glycol
capable of dissolving 20% or more, by weight of the
solution, of ambient water without losing more than
about 40% of its water-free viscosity and without
significant loss of its load-carrying ability, as
measured by the folks" test, ASTM D-3704. In
addition, this invention provides a method for
lubrication of close-fitting, moving parts exposed
to ambient moisture comprising using as the
lubricant for such moving parts the polyoxyalkylene
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glycols disclosed herein. The lubricants of this
invention are particularly suitable for moving parts
subject to close tolerances, high shear and high
pressure, such as occur in gear boxes.
DETAILED DESCRIPTION OF THE INVENTION
Poly(alkylene oxide) polymers useful in
this invention are those which are water-soluble and
thus are capable of themselves dissolving a
substantial quantity of water. In general, these
polymers will contain oxyethylene groups or both
oxyethylene groups and higher oxyalkylene groups,
such as oxypropylene and oxybutylene groups, either
in random or block distribution in their molecules,
and will have average molecular weights from about
400 to about 40,000, or even higher. Preferably,
the average molecular weight ranges from about 400
to about 4,000. The amount of oxyethylene groups in
the molecule is such that the poly(alkylene oxide)
polymers are soluble in water at ordinary
temperatures, and the amount of oxypropylene or
higher oxyalkylene groups is such that the
poly(alkylene oxide) remains liquid at ordinary
temperatures up to an average molecular weight of
40,000 and higher. The oxypropylene/oxyethylene
ratio may vary from zero to about unity.
Preferably, the ethylene oxide content will be at
least about 20~ by weight of the polymer. These
poly~alkylene oxide) polymers may be made by
processes well known in the art by reacting ethylene
oxide or mixtures of ethylene oxide and propylene
oxide or higher alkaline oxide with a compound,
known as a "starter, n having at least one active
hydrogen atom up to as many as six such active
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hydrogen atoms including, for example, water,
monohydroxylic alcohols such as ethanol and
propanol, dihydroxylic alcohols such as ethylene
glycol, trihydroxylic alcohols such as glycerine and
trimethylolpropane, tetrahydroxylic alcohols such as
pentaerythritol, hexahydroxylic alcohols such as
sorbitol, and moo- or polyp functional amine such
as butylamine and ethylene Damon. The
poly(alkylene oxide) products of such reaction will
have linear or branched oxyethylene or
oxyethylene-higher oxyalkylene chains and such
chains will terminate with hydroxyl groups. Some or
all of these hydroxyl groups may be etherified by
reaction with a dialkyl sulfate such as deathly
sulfate.
Mixtures of alkaline oxide homopolymers and
copolymers can also be used, provided that such
mixtures are water-soluble.
The preferred polymers are copolymers of
ethylene oxide and propylene oxide. In order to be
rendered water-soluble, such copolymers will
ordinarily contain at least about 20% by weight
ethylene oxide. The most preferred copolymers are
those containing about 50% ethylene oxide and about
50% propylene oxide and having viscosities ranging
from about 100 SUP to about 5,000 SUP at 100F.
Useful copolymers meeting these criteria include
those sold by Union Carbide Corporation under the
trademark UPON fluids, as the series 50 HUB.
It will be appreciated by those skilled in
the art that one of the primary criteria for
specifying lubricants, especially gear lubricants,
for which this invention is particularly suited, is
viscosity. Typically, the viscosity requirements
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are stated, at a given temperature, in terms of a
test known in the industry as ASTM D-2270. For
convenience in the industry, viscosity is often
expressed in SWISS units, stated at 100F. It has
been found that the viscosity specifications for any
given use can be met either by selecting a
polyalkylene glycol inherently having the required
viscosity, or by mixing two or more polyalkylene
glycols having different viscosities. Useful
polyalkylene glycols will have SUP viscosities at
100F ranging from about 100 to about 90,000, and
preferably from about 150 and about 5,000 SUP units.
It will also be understood that the
lubricants of this invention can be formulated,
within the skill of the art, to include corrosion
inhibitors, antioxidant, viscosity control agents,
extreme pressure additives, anti-wear additives,
freezing point depressants, pi conditioners,
anti-foaming agents, and the like.
The invention is demonstrated in the
following examples which are offered for
illustration only and are not intended to impose any
necessary limitations on the invention.
EXAMPLES
Example 1
A polyalkylene glycol lubricant mixture was
prepared containing the following, in parts by
weight:
68.6 parts glycol I
30.3 parts glycol II
0.5 part antioxidant
0.2 part solvent
0.4 part corrosion inhibitors
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Glycols I and II are buttonhole - started, random
copolymers containing about 50% by weight ethylene
oxide and about 50% by weight propylene oxide and
having nominal viscosities of 2000 and 170,
respectively, as determined by ASTM D-2270. This
mixture was divided into a control and six samples
to which were added various amounts of deionized
water. SUP viscosity was measured at luff, with
the following results:
TABLE I - Viscosity
Water Content,
Sample % by WeightSUS Viscosity
A (control) 0 1022
B 1.0 1035
C 3.0 1036
D 5.0 1028
E 8.0 994
F 10.0 957
G 20.0 718
H 50.0 159
Although the viscosity did decrease upon addition of
large amounts of water, it will be seen that the
viscosity with as much as 20% water is still quite
serviceable.
Example 2
The compositions of Example 1 were
subjected to a procedure known as a "Flex" test
(ASTM D-3233) to measure their load-carrying
capacity. The results were as follows:
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Table II - Torque, Pound - Inches at Stated Pressure
Sample: A B C D E F G
Pressure, psi Torque
300 6 6 6 6 6 6 6
500 10 10 10 11 11 11 11
750 12 13 14 15 15 16 15
1000 15 I 16 18 17 18 19
1250 18 18 19 21 19 20 22
1500 21 20 21 24 21 22 24
1750 * 22 23 25 23 24 26
2000 24 24 27 24 26 28
2250 26 27 29 26 28 31
2500 * 30 31 28 31 35
2750 33 35 31 34 *
3000 * * 34 38
3250 * *
*Pin Broke
It will be seen from Table II that load-bearing
ability, as evidenced by psi load to break, is
retained throughout a broad range of pressure, even
for materials containing as much as 20~ water
(Sample G).
Example 3.
A polyalkylene glycol lubricant mixture was
prepared containing the following, in parts by
weight:
97.65 parts glycol III
2.0 parts antioxidant
0.35 part corrosion inhibitors
Glycol III is buttonhole - started, random copolymer
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containing about 50% by weight ethylene oxide and
about 50% by weight propylene oxide and having a
nominal viscosity of 660 SUP as determined by ASTM
D-2270.
This mixture was found to have a SUP
viscosity of 664 at 100F. Its performance, without
water, in the Flex test was as follows:
TABLE III
Pressure, psi Torque
300 6
500 11
750 14
1000 35
1250 Pin Broke
This lubricant was not evaluated with water
contaminant in the Flex test: however, its
performance leads to the expectation that the
addition of substantial amounts of water would not
significantly degrade performance.
Example 4.
The lubricant mixture of Example 3 was used
to replace the normal petroleum lubricant in the
gear box of a Lightning n mixer which tends to
absorb a substantial quantity of ambient moisture
through "breathers. n Typical petroleum oil service
life in this gear box is three months or less, at
which time the lubricant is changed because its
performance has been substantially degraded by water
contamination. In contrast, the lubricant of
Example 3 showed no digression after four months of
service even though water content had risen to 2-3
by weight. After eight months of service,
performance remained normal.
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Example 5.
The lubricant mixture of Example 3 was used
to replace the petroleum lubricant in a gear box in
a can drawing system subject to extensive contamina-
lion by water. The lubricant of this invention
operated well for several weeks, thereby
substantially out-performing petroleum-based
lubricants. When it did fail, it was found to have
a water content of more than 30%. It was also
observed that the operating temperature of this gear
box dropped to 105F from 150F, thus evidencing the
excellent lubricating qualities of this composition.
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