Note: Descriptions are shown in the official language in which they were submitted.
12~34091
LUBRICANT COMPOSITIONS
Technical Field
The present invention relates to lubricant
compositions, and, in particular, to lubricant
compositions for use in lubricating traction motor
gears of the type found in Diesel locomotives.
Back~round of the Prior Art
Heretofore, lubricants for use in
lubricating traction motor gears of the type
employed in Diesel locomotives have comprised
asphalt-oil blends, or petroleum resin-oil blends,
which have been thickened with a metallic soap such
as a sodium or lithium soap. These lubricants often
contain extreme pressure additives, as well as
corrosion and oxidation inhibitors, and antifoaming
agents. An important disadvantage of soap thickened
asphalt-oil, and petroleum resin-oil, based traction
motor gear lubricants centers on their
incompatibility with the oils used to lubricate the
bearings of the traction motor. More specifically
in this connection, if, due to poor gear box
integrity resulting from a defective or worn seal,
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leakage of the thickened lubricant occurs, and, as a
result, the lubricant migrates along the traction
motor armature and into contact with the motor
bearing, failure of the bearing is inevitable.
Replacement of the bearing is a time consuming and
costly operation. A further noteworthy disadvantage
of such soap thickened traction motor gear
lubricants is their inability to provide proper
lubrication at low temperatures. Thus, at freezing,
or below freezing, temperatures the soap thickened
lubricants have a gelled, or solid, consistency. In
this state, they are ineffective as a gear
lubricant. It is only after the gear box has heated
up that the lubricants begin to perform their
intended function. Yet another disadvantage
encountered in the use of soap thickened traction
motor gear lubricants, especially the asphalt-oil
based types, is their tendency to oxidize. Oxidation
acts to solidify the lubricant, rendering it useless
as a lubricant, and requiring its immediate
replacement. A still further disadvantage of soap
thickened traction motor gear lubricants is the need
for packaging them in containers, usually plastic
bags, which are placed into the gear box. The
action of the gears, coupled with the heat generated
in the gear box, causes the bags to disintegrate
thereby releasing the lubricant. The need for bags
adds significantly to the manufact~lring costs of the
lubricants.
Brief SummarY of the Inven io
The present invention provides lubricant
compositions which are uniquely adapted for use in
lubricating traction motor gears. Not only are the
lubricant compositions of this invention capable of
35 providing excellent lubrication over a wide
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temperature range, but, also, they have extreme
pressu~e properties which enable them to remain
stable even after prolonged use at the high
pressures and temperatures encountered in Diesel
locomotive gears. Their extreme pressure
capabilities are complimented by their resistance to
oxidation, and other chemical attack, both in use,
and during periods of non-use. In addition, they do
not require packaging in bags as is the case with
soap thickened lubricants. The elimination of soap
thickeners and heavy fluids significantly improves
the low temperature lubrication properties of the
compositions. The elimination of bags, of course,
represents an important reduction in material and
labor costs in the manufacture of the lubricant
compositions of this invention.
The lubricant compositions of the present
invention, in brief, comprise a major proportion of
a base oil, preferably a mineral oil, and a minor
proportion of an oil soluble polymer, the polymer
being present in an amount sufficient to impart
improved temperature tolerance and anti-leak
properties to the compositions. In the preferred
embodiments of the invention, minor proportions of
additives in the form of oxidation inhibitors, load
carrying substances, pour depressants, and
antifoaming agents are incorporated into the
compositions. In those cases in which the
compositions are intended for use under less severe
operating conditions, and where product life is not
a factor, a portion of the base oil may be
substituted by thickening agents such as petroleum
resins, or even asphalt.
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Detailed Description of the Invention
The base oils employed in the preparation
of the lubricant compositions ad~antageously are
petroleum derived lubricating oi~s. Especially
5 preferred are mineral oils of the bright stock type
having viscosities of about 140 SUS to about 225 S~S
at 210F. Higher viscosity grades of lubricating
oils of the so called neutral and na~hthenic types
can also be used. The base oil, as indicated,
10 comprises the major proportion, usually about 80~ to
about 96%, by weight, of the compositions.
The oil soluble polymers used in preparing
the lubricant compositions can be selected from a
wide group. Exemplary of polymers having utility in
15 the practice of the present invention are
polyiso~utylenes, ethylene-propylene copolymers,
hydrogenated styrene-isoprene copolymers, styrene-
butadiene copolymers, hydrogenated styrene-butadiene
copolymers, polymethyl methacrylate, polyethyl
20 methacrylate, and styrene-methyl methacrylate
copolymers, to mention a few. While the molecular
weight oE the polymer is not a critical
consideration , it is preferred to use polymers of
relatively low molecular weight for improved shear
25 stability. As used herein, the term "low molecular
weight" means a molecular weight of about 5000 to
about 20000 (Staudinger). of the foregoing
polymers, a particularly preferred polymer is the
; polyisobutylene available under the trade mark
~ 30 "Vistanex LM-MS" tExxon). This product is sold in
s the form of a viscous semi-solid having a molecular
weight of the order of 8700 to 10000 (Staudinger).
Polvmers sold under the "~Tistanex" trade mark as well as
other trade marks such as, for exam~le, "Ortholeum" (Du
35 Pont) having molecular weights ranging from 2S,000
~,.
12;~4(~91
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to 140,000 (Staudinger) can also be used, but axe
less preferred due to possible degradation of the
polymer under the shear forces encountered in
traction motor gears. Mixtures of low, and high,
molecular weight polymers can be used in achieving
the objectives of this invention.
As stated, the oil soluble polymer
comprises a minor proportion of the lubricant
compositions of this invention. The generally
optimum objectives of the invention are achieved
with polymer proportions of the order of about 2~ to
about 40%, preferably about 5% to about 20%, by
weight, of the compositions.
The performance characteristics, as well
as the stability of the lubricant compositions can
be enhanced and augmented by the inclusion of minor
amounts of various additives into the compositions.
Thus, the extreme pressure or load carrying
capabilities of the lubricant compositions, along
with the resistance of the compositions to
deterioration or aging due to oxidation, can be
improved by adding a metal substituted dialkyl- or
diaryl- dithiophosphate to the compositions.
Products which can be used are sold commercially
under the trade marks "Lubrizol 1395", "Lubrizol
677A" (Lubrizol), "~`itec E-682" (Edwin Cooper), and
"Vanlube 71" (R. T. Vanderbilt). Other compounds
such as lead diamyl-dithiocarbamate, zinc diamyl-
dithiocarbamate and antimony diamyl-dithiocarbamate
may also be used. Also useful as load carrying
additives are sulfur-phosphorus gear oil additives
based on sulfurized fats and polymers such as
polyolefins and phosphate esters. Oxidiation
inhibitors, other than the dithiophosphates and
dithiocarbamates named above, which can be employed
include hindered phenols such as 2,6 di- tertiary
, ~
1~3~(~91
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butyl paracresol, and phosphite esters such as
triphenyl phosphite. Also useful for this purpose
are various aromatic amines such as diphenyl amine,
alkylated diphenylamine, phenyl-alpha-naphthylamine
and phenyl-beta naphthylamine, aminophenols,
phenols, and polymerized quinolines.
The proportion of the load carrying
additive used can range from about 1% to about 10~,
usually about 2% to about 5%, by weight, of the
composition. In those instances where an oxidation
inhibitor other than a dithiophosphate or
dithiocarbamate is added to the compositions, the
proportion of the inhibitor will range from about 1%
to about 10~, desirably about 2% to 8%, by weight,
of the composition.
Other additives which can be incorporated
into the compositions to improve their properties
are pour depressants and antifoam agents. Pour
depressants significantly extend the lower operating
temperature range of the compositions. Exemplary of
pour depressants which can be used are the
polymethacrylates sold under the trade mark
"Acryloid" (Rohm & Haas). Also useful is the
alkylated styrene sold under thetrade mark OA-100
(Pearsall division of Witco). Other pour
depressants are available under the trade ~arks
"Hitec E-672" (Edwin Cooper), and "Paraflow 149R
(Exxon).
Antifoaming agents having utility for the
purposes of this invention include silicone types
s~ch as dimethyl silicone, and the organosilicones
available commercially under the trade marks "Union
Carbide L-7500", "Dow Corning 200" and "General
Electric SF96n.
The proportion of pour depressant employed
in the compositions can range from about 0.1% to
lZ3'~0~
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about 2~, preferably about 1% to about 1.5%, by
weight, of the composition. The quantity of
antifoaming agent used can vary between about 0.001%
to about 1~, usually about 0.05~ to about 0.5%, by
weight, of the composition.
As indicated above, in those instances in
which the compositions of the present invention are
intended for ultimate use under less severe
operating conditions than those encountered in the
lubrication of traction motor gears, and where
product life is not a factor, a portion of the base
oil may be substituted by a thickening agent such as
a petroleum resin or asphalt. In such cases,
upwards of about 30~ to about 75%, by weight, of the
composition may comprise such a thickening agent.
Illustrative formulations, representing
the best embodiments of the invention, are shown in
the following examples and feature the foregoing
materials and compounds in which the ingredients are
set forth in the following percentages by weight: -
EXAMPLE 1:
In redient Percentaqe
q
Mineral oil (140 SUS @ 210F,
Bright Stock) 89.19
Polyisobutylene (VISTA~EX LM-MS) 7.50
Dimethyl silicone (antifoaming agent) 0.01
* trade mark
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Zinc dialkyl ~ithiophosphate
(HITEC E-682) Z.80
Pour depressant (HITEC E-672) 0.50
Approximately two thirds of the mineral
oil is blended with the polyisobutylene at 160F for
30 minutes. The heat is removed and the remaining
mineral oil and additives are blended into the oil-
polymer solution over a period of 30 minutes. The
viscosity is checked, and adjusted with oil or
polymer as needed to provide a composition having a
viscosity of approximately 500 SUS at 210F.
EXAMPLE 2:
Inqredient Percenta~e
Mineral Oil (140 SUS @ 210F,
Bright Stock) 93.0
Ethylene-propylene copolymer
(Ortholeum 2035*) 2.5
Lead diamyl dithiophosphate
(Vanlube 7~) 2.0
Organosilicone (Union Carbide L-7500) 0.5
Diphenylamine (oxidation inhibitor) 2.0
The ingredients were processed as in
Example 1.
Given the above teachings and illustrative
examples thereof, it will be apparent to those
skilled in the art that various lubricant
compositions can be prepared in light of the guiding
* trade mark
lZ3~391
g
principles and teachings provided herein without
departing from the spirit and scope of the present
invention.
