MIST LUBRICATION WITH OIL CONTAINING A POLYMERIC ADDITIVE

In the attached drawing, FIG. 1 illustrates the relationship between the two major desired properties of a mist lubricant, expressed, in FIG. 1, as a function of the molecular weight of the polymeric additive and, in FIG. 2, as a function of the volume percent of the polymer dispersion. It can be seen that, at a given concentration of the methacrylic polymer, only a very narrow molecular weight range will produce a mist oil having the requisite stray fog and reclassification properties. In FIG. 1 it can be seen that a viscosity average molecular weight of about 300,000 was necessary in order to produce a satisfactory mist lubricant. In general, with acrylic polymers, particularly polymethacrylates, the viscosity average molecular weight (VAMW) is preferably in the range of 200,000 to 400,000; however, with the dispersant type terpolymer (e.g "Acryloid 966S") a VAMW as high as two million can be effective at concentrations no greater than 0.5 weight percent polymer.

In FIG. 2, the polymer additive was a commercially available polyisobutylene, "Paratone N." The product contained about 20% solids; therefore the weight percent concentration of polymer on a solids basis in the lubricant is about one-fifth of the indicated volume percent. As can be seen in FIG. 2, only a very narrow concentration of the polyisobutylene additive produced 3, 7 the requisite combination of stray fog and reclassification properties. Note, however, that for some uses the requisites can be a stray fog of 8 grams per hour or less and/or reclassification of 0.6 ounces per hour, or greater, per bearing inches, thus, permitting the use of a lower molecular weight polymer and/or a wider concentration range.

In the studies of FIGS. 1 and 2 the test conditions were: an oil temperature of F an air temperature of 100" F. in Norgren test apparatus. The study was 1C conducted in a blend of solvent refined paraffmic base oils, the blend having a viscosity at F. of 1500 SUS and a viscosity at 210F. of 111 SUS (97 V.I.). The polybutene had a viscosity average molecular weight (VAMW) of about 150,00. The acrylic polymers were If of the terpolymer, nondispersant type (the "Acryloid 700" series) and were tested at the 1% volume level (the solids content of the polymer dispersions varied between about and 60%; however, with these polymers the concentration variation within this range does 2C not appreciably change the conclusion, shown in FIG. 1, that a terpolymer methacrylate polymer in the 200,000 to 400,000 molecular weight range will produce a mist oil with the desired properties. The tested terpolymer contained at least two different alkyl groups n the Ci0-C22 range.

In the following examples all percentages are by weight unless otherwise specified.

EXAMPLE 1 A mist lubricant having a viscosity at F. of SUS was formulated as follows (all percentages are volume percent): 22% of a solvent refined paraffinic lube " containing 15.5 weight percent gel aromatics and havng an SUS viscosity of 508 at F. and 64.3 at F.; 75.78% of a paraffinic bright stock containing 24% gel aromatics and having an SUS viscosity at F. 2700 and at 210F.; 1.72% of "Vanlube 71" (a 4C lead diamyl dithio carbamate); 0.02% of "Acryloid 162" (an acrylic polymer, generally used as a pour depressant); 0.5% of "Acryioid 966S" (a jjolymethylmethacrylate terpolymer of the dispersant type and having an average molecular weight of about one million and being about 26 weight % polymer solids. The mist lubricant, upon use testing, had superior reclassification properties and the test indicated that the acrylic dispersant polymer was beneficial as an additive in a mist oil.

Similar results can be obtained when the "Vanlube 71" is replaced by zinc dialkyl dithiophosphate or a chlorine-phosphorous additive, such as "Lubrizol 757," or other E.P. additive.

In general such lubricants can be similarly formulated to have any desired viscosity in the range of about to 3000 SUS at F by suitable choice of the base oil. One good base oil combination is to blend SAE and motor oils.

EXAMPLE II A mist oil was formulated from 78.0% Sunvis 21" (a solvent refined paraffinic lube containing 13%gel aromatics and having an SUS viscosity at F. of 208 ,- and 47.4 at 210F.); 19.6 "Sunvis 51" (a solvent refined paraffinic lube containing 15.5% gel aromatics and having an SUS viscosity at F. of 508 and 64.3 ,135 at F.); 2.0% "Paratac" (a polyisobutylene dispersion containing about percent polymer solids); and 0.4% "Lubrizol 1360 (a conventional additive package of the zinc dithiophosphate type). The formulated mist oil had an SUS viscosity at F. of and 54. at F. and as ASTM pour point of +5 F.

EXAMPLE III A mist oil was formulated containing 31.8% "Sunvis ) 11" (a solvent refined paraffinic lube containing 12%

gel aromatics and having an SUS viscosity at F. of 110 and 46.3 at F.); 59.8% of "Sunvis 21," 8.0%

Paratone N" (a polyisobutylene dispersion containing about 20% polymer) and 0.4% "Lubrizol 1360." The > formulated mist oil had an SUS viscosity at F. of 513 and 59.2 at F. and an ASTM pour point of 0 EXAMPLE IV

A mist oil was formulated containing 72.48% "Sunvis 11," 25.95% "Sunvis 51," 0.1 % of "Acryloid 162" (an acrylic polymer, generally used as a pour point depressant), 0.3% zinc dithiophosphate, 1.0% "Lubrizol 1734" (a motor oil additive package); 0.15% "Vanderbilt BSN," a neutral barium petroleum sulfonate rust nhibitor and 0.02% Dow Corning defoamer. This mist oil gave satisfactory service when tested for use in Norgren Microfog Lubricators.

A mist oil was formulated containing 22% of "Sunvis 21," 73% of the bright stock of Example 1, 1% of a polymethacrylate terpolymer solution of the "nondispersant" type, containing 47.5% polymer and having a viscosity average molecular weight of 290,000 (number average molecular weight 80,000); 0.5% of "Santalube 680" (a mixed phenolic phosphate-sulfonate) 0.1% of "Ortholeum 535" (a mixture of alkyl ammonium mixed acid phosphates); 2.75% of a cosulfurized blend of lard oil and Cllt a-olefins, 0.5% "Ortholeum 162" (a fatty acid phosphate E.P. additive); and 0.02% of a 1% solution of Dow Corning Silicone Defoamer (60,000 cs, at F.).

This mist lubricant was tested for bearings in cold rolling machinery in a steel mill. It exhibited expecially good lubrication properties and satisfactory misting and reclassification properties. Similar lubricants can be formulated having SUS viscosities in the range of ( to 3000 by suitable choice of the base oil.

The mist oil of this example can be improved (e.g as in oxidation stability) by substitution, in part or whole, of a hydrocracked paraffinic oil (preferably stabilized) of about the same viscosity for the mixture of ; "Sunvis 21" and bright stock. Hydrorefined paraffinic oils (e.g the "Sunvis H" Series) can also be substituted in whole or part for the solvent refined paraffinic oils of this and other examples.

EXAMPLE VI i A conventional way lubricant (useful, for example, in lubrication of lathes for metal working) was made by blending the following Parts by Volume Naphthenic distillate (100 SUS at 100T.) 36.9 3,855, -Continued Parts by Volume Napntnemc distillate (2400 SUS at 100F.) 55.0 Tallow fatty acid 8.0 The way lubricant was unsatifactory in a mist lubrication system because of excess stray fog.

EXAMPLE VII 0.1 parts by volume of a commercially available (Paraton N from Enjay Co.) polyisobutylene disperion (about vo. % polymer in SUS at 100F. in mineral oil) was added to the way lubricant of Example VI. 1 The paraton N had a Staudinger molecular weight of about 20,000. The resulting lubricant performed satisfactorily in the same mist lubrication system in which the Example VI oil was unsatisfactory. That is, the polymeric additives reduced the stray fog to a satisfactory level.

The resulting mist lubricant had the following properties: Such way lubricants, for use as mist oils, can comprise a mineral oil, a stick-slip additive in amount effective to produce a stick-slip ratio of 0.85 or less and a polymeric mist suppressant additive in an amount sufficient to suppress stray fog.

The preferred stick-slip additives include tallow fatty acids, sulfurized sperm oil, and synthetic sperm substitutes (e.g Caravan 6106 of Cincinnati Milacron Chemicals, Inc.), a cosulfurized blend of lard oil and olefin, neutralized acid phosphates and acid phosphates (Ortholeum 162 or 535).

Especially useful stick-slip additives are the chemical reaction products which can be produced by the action of sulfur or sulfur monochloride on lard oil and olefms (or polyolefin oils). Such cosulfurized compositions are generally useful as a replacement for sulfurized sperm oil and can be obtained by sulfurizing a blend of to parts by weight of lard oil and to parts of an aliphatic olefin containing 6 to 128 carbon atoms (preferably 12-60 carbon atoms). The sulfurization is carried out using elemental sufur. Sulfur monochloride can be used for both sulfurizing and chlorinating simultaneously. The sulfurization can involve cooking at from to 445F. for minutes to hours followed by blowing with a gas (preferably, at from to 340F. for minutes to hours) to remove hydrogen sulfide. With sulfur monochloride, the preferred cooking temperature iss in the range of 150250 (under pressure if desired). The sulfurized oils can contain from 5 to weight percent sulfur as based on the blend of olefin and lard oil (i.e 5 to parts by weight of sulfur per parts by weight of olefin-lard oil blend).

For example, effective slip-stick ratio reduction, can be achieved by adding to a mineral oil from 0.1-10 wt. % of a composition consisting esentially of a sulfurcontaining chemical reaction product of a blend of lard oil and polyisobutylene containing in the range of 12-60 carbon atoms.

One such cosulfurized blend is made as follows:

Twenty-two hundred and sixty ml. of winter strained lard oil were blended with ml. of tetraisobutylene n a 5 L kettle equipped with a vibromixer. The mixture was heated to 250F. and the vibromixer operated at maximum speed. Sulfur (239 g) was added and the temperature of the mixture was raised to 375F. for hours. The mixture was then cooled to 200F. and air was bubbled through the mixture by means of a glass tube at a moderate rate 9below that at which splashing and agitation take place) for 1 hour. The resulting sulfurized oil was analyzed and found to contain 8.23% sulfur. A gram portion of the sulfurized oil was dissolved in g. of a commercially available solvent refined paraffinic lube having a viscosity at 210F. of 40.45 SUS, an ASTM viscosity index of 104 and containing 12% aromatics (by ASTM D2007). The oil solution remained clear with no separation after being tested at 36F. overnight and for 1 week at room temperature.

In mist lubricants any mineral oil or blend of mineral oils having a viscosity in the range of 100-3000 SUS at 100F. can be used; however, the preferred mineral oils comprise solvent refined paraffinic distillate or bright stock, hydrorefined paraffinic distillate or bright stock, hydrocracked paraffinic distillate (which can be stabilized by solvent extraction or by hydrorefming), napthenic distillates (preferably of low napthenic acid content), solvent and/or acid refined naphthenic distillate, and hydrorefined naphthenic distillate and mixtures of two or more of these oils. Especially preferred where there is a possibility of inhalation or ingestion are hydorefined napthenic distillate, stabilized hydrocracked paraffinic distillate and hydrorefined paraffinic distillate (which can be solvent refined before or after the hydrorefming).

The term "hydrocracked paraffinic oil" as used herein is defined as a lube oil viscosity range product of hydrocracking a petroleum charge stock (which can be either paraffinic or napthenic by VGC classification), said hydrocracked product having a VGC below 0.820. That is, hydrocracking (like heavy solvent extraction) can produce oils having a lower VGC (therefore, which are more "paraffinic") than the VGC of the charge. For example, a charge to a hydrocracker can be a distillate fraction of a Lagomedio crude having a viscosity at 100F. of 191 SUS, API gravity 27.5 and VGC of 0.837 (which would, thus, be classified as "relatively napthenic"). The hydrocracked oil can boil within about the same range as the charge and have a viscosity at 100F. of 93.5 SUS, API gravity 36.5, and VGC of 0.791 (or "paraffinic" by class). After dewaxng the ASTM-VI of the product can be 120. Such a hydrocracked oil, having a "paraffinic" VGC is included within the term "hydrocracked paraffinic oil." TEST PROCEDURE

The "Norgren" test apparatus, as referred to herein, s illustrated schematically in the accompanying FIG. 3.

3, 11 It comprises a gas regulater 1, gas filter 2, air control valve (including a flow gauge) 3, timer 4, air heater 5, primary pressure gauge 5, thermometers 7, and 8, the C. A. Norgren mist generator (9), oil heater 10, sump 11, manifold pressure gauge 12, manifold assembly 13, reclassifier nozzles 14 and reclassifier collection cup 15.

The accompanying FIG. 4 illustrates the three main types of nozzle (mist, spray and condensing). In all of the work reported herein, the "mist" nozzle was used. C

The following is the test procedure used with the Norgren test apparatus.

1. Weigh all oil-containing or collecting components (9, 11, 13, 14, 15).

2. Fill sump with test oil.

3. Weigh sump again to calculate oil weight.

4. Assemble sump and turn-on air to 23.0 p.s.i.g. (gauge 6). Flow rate should be approx. 5.35 SCFM air.

5. Run for about 1 hour, bringing oil and air to desired temperature.

6. Disassemble and weigh all components.

7. Repeat steps 3-6 as desired to obtain test dats (the first hour run results are usually discounted). -8. Calculations A. Output is oil weight taken from generator divided by total SCFM of air through, generally reported as (gm/SCF.hr).

B Manifold losses are weight of oil collected in sump and manifold (generally expressed as % of total output).

C. Rectification is weight of oil collected in cup 15, expressed as % of total output (or, by calculation, as oz/hr/100 B.I. or as drops per CF per minute (where a drop is 0.071 gram).

D. Stray fog is the oil taken from the generator minus manifold losses and reclassification, generally reported as % stray fog 9100-B-C) or as grams/hour.

In this test procedure the important parameters are time, air pressure and flow rate, manifold pressure, air and oil temperatures, and type and number of reclassifiers (each) nozzle being called a reclassifier). In the testing referred to herein, mist nozzles were used.

The two key characteristics of a mist lubricant are the amount of product getting to the bearing to satisfy the lubrication requirements, and the amount of stray fog going to the atmosphere. In general, no visible stray fog should be produced by the oil during use. In general, the performance of a misting lubricant can involve four factors (the first two being the more important in the Norgren tester):

1. Stray Fog is a portion of mist output which does not reclassify at lubrication point 2. Reclassification - is the percent of oil output which recombines to become usable lubricant 3. Mist Output - is the amount of mist taken from reservoir per cubic foot of air (this is principally a function of oil viscosity and temperature)

4. Manifold Loss - is the percent of mist output that s lost in the system s plumbing. In the testing referred to herein, this loss should be less than 60%; however, in commercial operations this loss is less , than 10%.

Since vicosity has an effect on misting, the following table compares properties of three viscosity grades of ,135 the mist lubricant of Example V (the differing viscosities being due to differing base oils).

Oil A Oil B Oil C

The oil of Example V is especially useful as a mist lubricant since it possesses a good combination of misting characteristics and lubrication properties. The misting properties include low stray fog, high constant oiloutput (low change with temperature) and low manifold loss, the lubrication properties include good oxidation stability, foam resistance, good demulsibility, rust and corrosion resistance, good load carrying ability and, for waxy lubrication, low static coefficient of friction. Oxidation stability and foam resistance are of prime importance during the process of mist lubrication. Regarding oxidation resistance, the following test results show the excellent oxidation stability of the Example V oil in comparison with a commercially available mist oil. The test was a modified (no water) D oxidation test run for 1000 hours with copper and iron catalysts, and air at 203F.

Foam resistance and demulsibility are also important f the charge oil becomes contaminated with water. The Example V oil has excellent foam resistance and demulsibility both of which are quite poor for the commercial mist oil B, as shown by the following data:

Commercial Mist Oil Example V Oil Once the oil has reclassified at the point of lubrication, it must be a good lubricant and rust preventive. The ability of the Example V oil to lubricate and protect against rust in conventional tests is illustrated by the ASTM D665 B test, which the Example V oil passes and by the ASTM D130 corrosion test ( hours/212F.) in which the Example V oil rates "No. 1." 3,855, 13 The lubricity of the Example V type oil under high unit loads for short time periods (E.P.) can be tested by the Timken Tester, and under normal loads for a long time (antiwear) by the 4-Ball Wear Tester.

The data for Example V oil are shown below in com- 5 parison with a commercial antiwear E.P. Mist oil. Both provided excellent performance.

The suitability of the Example V oil for feeding slide ways is shown by measurements using the Cincinnati Milling Machine Test procedure which has tentative approval by ASTM D2877. A comparison of the Example Voil coefficient of friction with the commercial mist oil follows (both performed well).

Note that static friction is reduced below kinetic (moving) friction which eliminates stick-slip and provides smooth machine start up.

In mist lubrication systems, the oil output from the mist generator is transported in an air stream as mist to the lubrication point where it is reclassified or liquified.

Optimum mist droplets vary in particle size from 0. to 2.0 microns. These small droplets are required at low air velocities of approximately feet per second or less to maintain stable non-condensing mists. Any particles above 2.0 microns are knocked out by a baffle and are returned to the reservoir. Extremely small particles (below 0.5 micron) can be stable at high air velocities but condensation is difficult, and an objectionable fog can fill the atmosphere around the equipment.

Reclassified oil percent is the amount of oil output which recombines to become usable lubricant. Oil out- , put is the grams of oil taken from the reservoir per cubic foot of air. The amount of mist generated and reclassified can be affected by pressure and temperature. The mist output increases with feed air pressure. However, a critical balance must be maintained because too high a feed air pressure to the generator can pick up too much oil and cause increased dropout (wet out) in the manifold line. Oil sump and air heaters can be used to facilitate misting of viscous products. The viscosity grade is usually determined by the lubrication require- 6Q ments. If the grade is too heavy for optimum misting, temperature should be adjusted to thin it to the proper misting viscosity. Heating is recommended when an oil SUS at 100F. or above is used, because it has been determined that to obtain satisfactory lubrication of one fluid ounce per hour for bearing inches, the viscosity should preferably be below seconds at application temperature.

When the customer uses mist oils of the Example V type (e.g high VI, paraffinic base oil) he should follow the table below:

Generator Oil The portion of the oil output that is not reclassified at the lubrication points or lost as stray fog represents "Wet out" in the mist delivery plumbing and is called manifold loss. Stray fog is the portion of the oil output which does not reclassify at the lubrication point. It usually vents at the lubrication point into the room housing the machinery. The polymer level should be adjusted so there is no visible stray fog (e.g less than g/hr in Norgrentest).

Reclassifier nozzles are designed to provide turbulence which promotes reclassification. Three different types of reclassifying nozzles are shown in FIG. 4. They are:

a. Mist nozzle - for operations such as high-speed ball and roller bearings where the nozzle simply directs the oil/air mixture to the bearing which is moving fast enough to reclassify the oil.

b. Spray nozzle - has a more restricted orifice flow area and a longer passageway which results in a semi-wet spray. This nozzle is used when lubricatng moderate-speed gears, chains, and antifriction bearings.

c. Condensing nozzle - tiny droplets are formed when the mist hits a baffle in the nozzle and drop into or onto the mechanism to be lubricated. This nozzle s used for low-speed bearings, ways, and slides.

Various combinations of these nozzles can be used with a single mist system. It should be understood that none of them is 100% efficient and some quantity of oil escapes to the atmosphere as "stray fog." Mist lubricators are very sensitive and require precise adjustment. Based on the type of system involved, some or all of the following adjustments may have to be considered for optimum operation:

1. Feed-air pressure - increasing the air pressure increases the amount of oil mist generated.

2. Feed-air temperature - increasing this also will increase the amount of oil mist generated.

3. Oil-sump temperature - can be used to control the oil viscosity to optimize misting.

4. Oil suction tube control - the amount of oil atomzed at a given temperature, pressure, and oil viscosity is controlled by the size of the suction tube.

These controls affect the mist output in a predictable fashion and should be set to minimize manifold wet-out and stray fog. Selection of oil viscosity should be based on the lubrication requirement, and adjusted for optimum misting by changing temperatures and, if necessary, pressure.

Bearing Inch:

Is a unit of measurement used for selecting the appropriate capacity misting unit. The shaft diameter meas3, urement in inches represents "bearing inch" rating for a single row antifriction bearing.

CFM (SCFM):

Cubic feet per minute of air or mist.

Fluid Ounce (Fl. oz.):

One fluid ounce (Fl. oz.); 1.805 cu. in.

Manifold:

Mist distribution piping.

Manifold Pressure:

Gauge pressure of mist in manifold.

Mist:

Oil-mist is an aerosol dispersion of air and oil particles ranging in size from one-half micron diameter to approximately 8 micron diameter.

Mist Fitting:

An application fitting that meters oil-mist with minimum coversion to oil spray or droplets, Mist Velocity:

Feet per second (FPS); maximum recommended mist velocity is 24 FPS. Prelubrication Since oil-mist is a system which continuously supplies make-up oil, all machine elements must be pre-oiled before initial machine operation Regulated Air Pressure:

Controlled gauge pressure applied to the oil-mist generating nozzle. Pressure drop across the nozzle equals regulated air pressure minus the manifold pressure in psi.

Following is a table showing the typical properties of mist lubricants of the Example V type (the polymer can either be acrylic or a mixture of acrylic polyolefin).

TYPICAL PROPERTIES (

1) ?niF, 1000 hrs 3 liters oxygen/hr, ml oil, As in Example V, but with base oils of dlffe The invention