Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
10S9980
BACKGROUND OF THE INVENTION
This invention relates to metal working lubricant
compositions having low air mist forming properties. In
particular, this invention is directed to metal working
lubricant compositions used as cutting oils in metal machining
and grinding operations. This invehtion is directed more
particularly to cutting oil additives which will surpress
the mist generation in these industrial metal working
lubricants.
~he economy of industrial nations is closely
associated with metal products and the design, construction
and use of machines to fashion these metals into useful tools
and products. Metal working lubricants play a significant
role in increasing the efficiency of metal working machines
used in forging, drawing quenching, cutting and grind ing
processes. Approximately half of the total quantity of metal
working lubricants used in the metal working industry are
consumed in metal cutting and grind ing .
Cutting and grinding are metal working processes
~ ~ wherein the shape of the final object is obtained by
progressive removal of metal in the form of chips rather than
by plastic reforming of the metal as in other metal working
processes, such as forging and drawing.
~ Cutting and grinding lubricants are generally
; ~ termed cutting fluids and perform two basic functions: (1)
; as a coolant (to cool the tool and reduce wear and loss of
hardness and to cool the work to prevent distortion and
~; dimensional inaccuracies), and (2~ as a lubricant (to
lubricate the chip-tool interface and reduce frictional heat,
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tool wear and power consumption and improve surface finish;
also to prevent welding of metal to the tool point and
subsequent rough surfaces). In addition, the cutting fluids
should flush chips away from the work area, protect the
finished work surfaces, the tools and the machines from rust
and discolorization and resist smoking and fogging in use.
Cutting fluids can be broadly classified as mineral
oil base cutting oils, soluble oil and chemical coolants.
This invention is concerned with the mineral oil base cutting
oils. These cutting oils include several general types:
straight mineral oils, mineral-fatty oil blends, mild EP oils,
dark heavy duty oils and multi-purpose oils. Straight mineral
oil cutting oils are used in mild cutting operations. Where
additional lubricity is needed, fatty oils or fatty acids
may be added. Paraffinic or mixed base mineral oils are
preferred since in severe service they generally form less
smoke than naphthenic oils. In most metal cutting operations,
an additive-containing oil having extreme pressure (EP)
characteristics is required. Useful additives include fatty
oils and acids, sulfurized oils and fatty oils, chlorinated
oils, organic phosphorous materials and waxes. The dark
colored, highly sulfurized oils possess excellent performance
characteristics and are the workhorse of the industry.
Their dark color and pungent odor are not acceptable in some
operations, leading to th~ development and increasing use of
transparent cutting oils. The principal advantage of these
oils is that easier inspection of parts is possible, resulting
in increased production and reduction of rejects. The
quality of transparent oils has been improving rapidly and
they have been receiving more wide spread acceptance and
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use. They are formulated with various combinations of
sulfur, chlorine and phosphorous additives, depending on
service requirements. Some cutting oils are prepared to serve
as a multipurpose oil, particularly in automatic screw
machines. They can be used as a cutting oil, a general machine
lubricant and/or a hydraulic fluid in hydralically-powered
machines. In addition to reducing oil inventories and
eliminating cross-contamination when filling oil reservoirs,
; these dual and tri-purpose oils avoid the problems attendant
from leakage from one oil system to the other. Dilu~ion of
the cutting oil by ordinary machine tool lubricant or hydraulic
fluid will reduce its EP level and eventually its performance.
On the other hand, contamination of the machine tool lubricant
or the hydraulic fluid by one of the usual cutting oils,
particularly one of the corrosive ones, has serious consequences.
This~is avoided with a multipurpose cutting oil.
During cutting and grinding processes (generally
referred~to hereinaftor as a machining process), an oil mist
or fog is oten generated from the cutting oil, particularly
20~ during high opeed metal cutting operations. This oil mist
or fog can create an occupational health hazard to machine
operators. In fact, the Federal Occupational Safety and
Health Act (OSHA) recognizes this danger by establishing
maximum levels of oil spray or mist content in the air of
machine shop work areas during the presence of machine
operators and other personnel. To comply with these federal
standards~, polymers havs been found to be successful in
~; surpressing the mist generation in cutting oils. However,
.
- many of the cutting oils containing these polymers do not
retain their mist surpression qualities after continued use
under ihdustrial conditions.
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It is therefore an object of this invention to provide
a cutting oil composition which will not only have a low air
misting quality when manufactured but will maintain this
property over prolonged use in industrial applications.
SUMMARY OF THE INVENTION
We have found that additions of an amorphous ethylene-
propylene copolymer to a cutting oil will not only surpress
the mist generation of the cutting oil but will maintain the
air misting at significantly low levels during prolonged use
of the cutting oil. The ethylene-propylene copolymer found
useful for these purposes has an amorphous structure, a
number average molecular weight between about 10,000 and
100,000,preferably between about 30,000 and 80,000, a
propylene content of 20 to 70, preferably 30 to 55,mole
percent and a MW/Mn of less than about 5. Minor quantities
of this copolymer, between about 0.01 and 1.0, preferably
between about 0.04 and 0.35, weight percent of the cutting
oil composition are found to be effective in reducing the
~20 air misting of the cutting oils to below the standards
established by the OSHA. Concentrations of the copolymer
higher than 1.0 weight percent may be used but there is no
apparent further improvëment in product quality or mist
resistance.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
:~ Broadly, we have found that the mist generation of a
cutting oil can be significantly reduced by incorporating
therein small quantities of an amorphous ethylene-propylene
copolymer. Further, this particular copolymer maintains
the air misting at acceptable low levels for prolonged
periods of time despite the continuous s~bjection of the
cutting oil to high shearing forces during the machining
operation. -4-
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More specifically, our invention relates to a process
for reducing the air misting of a cutting oil during metal
machining operations which comprises supplying to a metal
machining tool, for use as a lubricant,a cutting oil
composition comprising a major portion of a mineral oil base
cutting oil and a minor portion, sufficient to reduce the
air misting qualities of said cutting oil composition, of an
ethylene-propylene copolymer having an amorphous structure, a
number average molecular weight of between about 10,000 and
100,000, a propylene content of 20 to 70 mole percent of a
MW/Mn of less than about 5.
As discussed above, our invention is directed to
cutting oil compositions comprising a major portion of a
mineral oil base cutting oil and a minor portion,sufficient
to reduce the air misting qualities of said cutting oil
composition when used as a metal machining lubricant during
metal machining operations, of an ethylene-propylene copolymer
- having an amorphous structure, a number average molecular weight
of between about 10,000 and 100,000, a propylene content of
:~ 20 2~0 to 70 mole percent and a MW/Mn of less than about 5.
The cutting oils whose misting qualities can be
successfully suppressed by admixing therewith the amorphous
ethylene-propylene copolymers disclosed herein include a
wide variety of mineral oil base cutting oils. In fact,
where misting of a cutting oil is a problem, the addition
of a quantity of an amorphous ethylene-propylene copolymer will
. control the misting. Examples of these cutting oils include
the dual and tri-purpose cutting oils, transparent cutting
oils, EP cutting oils, cutting oils compounded with sulfur,
chlorine and/or phorphous compounds, as well as a wide
variety of cutting oils compounded for special purposes
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such as for the machining of magnesium, aluminum and other
metals and alloys having special machining characteristics.
In general, cutting oils have viscosities coverlng a
broaa spectrum, viz, 30-500 SUSeDI00 F.
The ethylene propylene copolymers we utilize are
amorphous by infra red analysis and have a narrow molecular
- weight distribution. These copolymers may be prepared as
described in U.S. 3,522,180. This patent discloses that
amorphpus ethylene-propylene copolymers may be prepared in
a hydrogen moderated reaction at moderate temperatures and
pressures in the presence of a solvent soluble Ziegler-Natta
catalyst. In U.S. 3,522,180, amorphous ethylene copolymers
having a number average molecular weight of 10,000 and 4~,000,
a propylene content of 20 to 70 mole percent and a MW/Mn of
less than 5 are disclosed as viscosity index improvement
additives for lubricating oils. We have found that these
same copolymers are useful as mist suppressing additives
for cutting oils. In fact,we have found that the number
average molecular weight of the amorphous ethylene
copolymers we employ may be 10,000 to 100,000 although we
prefer to use those whose number average molecular is
30,000 to 80,000.
The concentration of the amorphous ethylene-
propylene copolymers necessary to suppress the misting of
cutting oils should be between about 0.01 and 1.0,
preferably between about 0.04 and 0.35,weight percent
of the final cutting oil blend. Those skilled in the art
will realize that some experimentation may be necessary to
arrive at the minimum concentration required by both
economic and service requirements. In general, the more
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severe the shearing experienced by the cutting oil the
higher the concentration of a given amorphous ethylene-
propylene copolymer necessary for satis~actory service.
EXAMPLE I
This example shows the mist surpression properties
of a number of materials when added to a cutting oil. In a
series of tests a small quantity of each material was added
to a cutting oil composition and the misting properties of
the resultant blend evaluated by visually observing the
quantity of mist formed above a small quantity of the oil while
a stream of air was passing through the oil. Then the oil
was subjected to severe shearing conditions and its misting
propensities were then re-evaluated. The cutting oil used
was a tri-purpose oil compounded from paraffin base oils
and containing rust and oxidation inhibitors and an extreme
pressure additive. The cutting oil used in this series of
tests had the following properties:
Gravity, API 28.1
Flash,COC, F. 390
Viscosity, SUS 157
~p 100F
SUS~p210F 43.1
Pour, ASTM,F +10
Chlorine, % 1.39
Antioxidant~% 0.29
The misting characteristics were determined
visually in an apparatus consisting of a vertical glass
cylinder, 2 inch I.D., 12" long, attached to a stainless
steel plate. After cleaning the cylinder with a light
solvent and blowing it dry,180 ml. of the oil under test were
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introduced into the cylinder filling it to a height of
approximately 3 l/4 inches. Air was introduced into the
cylinder through a 0.018 inch orifice in the stainless
steel plate at a regulated pressure of 35 psig while the
cylinder was maintained in an upright position. After
allowing one minute for the formation of an oil mist to
stabilize, an observer made a visual evaluation of the
quantity of mist or fog which had formed in the vicinity
of the top of the tube and assigned a qualitative rating as
follows:
Very Good - No mist or fog to barely perceptible
mist or fog
Good - Very slight mist or fog
Fiar - Slight mist or fog
Poor - Much mist or fog
The oil under test was then subjected to high shearing
by pumping the oil for either 10 or 20 passes through a
Bosch fuel injection nozzle. This equipment is utilized in
Fuel Injector Shear Stability Test (FISST) as described in
Paper No~ 57A, entitled "Simplified Shear Stability Testing"
~ by R. Rawson, presented at the June 1958 meeting of the
Society of Automotive Engineers. Following the shearing,
the oil was re-evaluated in the misting test. The screening
test results are shown in Table I below:
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These series of tests show that initially many
materials tested had very poor mist suppression properties,
others were moderately successful in this area while still
others did a very good job in suppressing mist. After
subjecting the cutting oils containing these additives to
severe shearing, most of the tested materials were unsatis-
factory. Only the ethylene-propylene copolymers, particularly
those of the amorphous type (Runs 18-27),showed an ability to
suppress misting of the cutting oil after being subjected
to severe shearing forces. Subsequent testing in a machine
shop of those ~lends which passed these screening tests
confirmed their suitability in actual service.
These tests also show that although as little as
0.008 wt.% of a particular ethylene-propylene copolymer
provided good mist control (Run 27), 0.04 wt.~ of this
copo~ymer was required to retain these anti-misting properties
after severe shearing (Run 25).
ExAMæLE II
This example demonstrates that amorphous ethylene-
propylene copolymers similar to those employed in Runs 22-27
of Example I are effective in controlling the misting of other
types of cutting oils.
The testing procedures were the same as those used
in ExampIe I. In all instances a copolymer concentration of
0.16 wt.~ was used. A description of the cutting oils tested
and the results are shown in Table II below:
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This series of runs demonstrates the superiority of
amorphous ethylene-propylene copolymers in suppressing the
misting properties of a wide variety of cutting oils
subjected to severe shearing forces.
