CA1225082A

CA1225082A - Hydrogenated polyisoprene lubricating composition

Info

Publication number: CA1225082A
Application number: CA000449136A
Authority: CA
Inventors: Frederick C. Loveless; Walter Nudenberg; Raymond F. Watts
Original assignee: Uniroyal Chemical Co Inc
Current assignee: Uniroyal Chemical Co Inc
Priority date: 1983-03-09
Filing date: 1984-03-08
Publication date: 1987-08-04
Also published as: EP0119792A3; EP0119792A2

Abstract

ABSTRACT
A lubricating composition is provided containing: a liquid hydrogenated polyisoprene having a viscosity of 1000-3500 genii-stokes at 100°C; a low viscosity synthetic hydrocarbon and/or a low viscosity ester; and optionally an additive package to impart desire able performance properties to the composition.

Description

kiwi HYDROGENATED POLYISOPRENE LUBRICATING COMPOSITION

This invention relates Jo compositions useful as lubricating oils having high viscosity index, improved resistance to oxidative dog-radiation and resistance to viscosity losses caused by permanent or temporary shear.
According to the instant invention a lubricating composition is provided comprising (1) an hydrogenated polyisoprene having a viscosity of 1000 to 3500 centistokes at 100C; (2) a low viscosity synthetic hydrocarbon, such as alkyd Bunsen so low viscosity polyalphaolefin and/or a low viscosity ester, such as monstrous, divesters, polyesters, and optionally (3) an additive package.
A further object of the invention is to provide a lubricating composition with properties not obtainable with conventional polyp metric thickeners A further object of the invention is to provide lubricating lo compositions exhibiting improved shear stability, oxidative stability and excellent temperature-viscosity properties.
The viscosity-temperature relationship of a lubricating oil is one of the critical criteria which must be considered when selecting a lubricant for a particular application. The mineral oils colr~nonly used as a base for single and multi graded lubricants exhibit a relatively large change in viscosity with a change in temperature.
Fluids exhibiting such a relatively large change in viscosity with temperature are said to have a low viscosity index. The viscosity index of a common paraffinic mineral oil is usually given a value of about 100. Viscosity index (VI) is determined according to ASTM
Method D 2770-74 wherein the VI is related to kinematic viscosities measured at 40~C and 1û0C.
Lubricating oils composed mainly of mineral oil are said to be single graded. SUE grading requires that oils have a certain ~`~

minimum viscosity at high temperatures and, to be multi graded, a certain maximum viscosity at low temperatures. For instance, an oil having a viscosity of 10 cyst. at 100C (hereinafter all viscosities are at 100C unless otherwise noted) would be an SUE 30 and if 5 that oil had a viscosity of 3400 cup. at -OKAY, the oil would be graded WOW. An unmodified mineral oil of 10 cyst. can no-t meet the low temperature requirements for a 10~-30 multi grade rating, since its viscosity index dictates that it would Howe a viscosity considerably greater than 3500 cup. at -20C, which Is the maximum 10 allowed viscosity for a WOW rating.
The viscosity requirements for qualification as multi grade engine oils are described by the SUE Engine Oil Viscosity Classify-cation - SUE J300 ~EP80, which became effective April 1, 1982.
The low temperature (W) viscosity requirements are determined by 15 ASTM D 2602, Method of Test for Apparent Viscosity of Motor Oils at Low Temperature Using the Cold Cranking Simulator, and the results are reported in centipoise (cup). The higher temperature (100C) viscosity is measured according to ASTM D445, Method of Test for Kinematic Viscosity of Transparent and Opaque Liquids, 20 and the results are reported in centistokes (cyst. ). The following table outlines the high and low temperature requirements for the recognized SUE grades for engine oils.

SUE Viscosity (cup) at Viscosity (cyst.) Viscosity Temperature (C) at 100C
25 Grade _ Max. _ Min. Max.
OW 3250 at -30 3.8 OW 3500 at -25 3.8 low 3500 at -20 4.1 WOW 3500 at -15 5.6 WOW 4500 a -10 5.6 WOW 6D0~ at -5 9.3 5.6 Less than 9.3 9.3 Less than 12.5 12.5 Less than 16.3 16.3 Less than 21.9 In a similar manner, SUE J306c describes the viscometric qualifications for axle and manual transmission lubricants. High temperature (100C) viscosity measurements are performed according to ASTM D445. The low temperature viscosity values are deter-5 mined according to ASTM D2983, Method of Test for Apparent Viscosity at Low Temperature Using the Brook field Viscometer and these results are reported in centipoise (cup), where (cup) and (cyst) are related as follows:

cyst = cup Density, k~7dm3 The following table summarizes the high and low -temperature requirements for qualification of axle and manual transmission tub-recants .

SUE Maximum Temperature Viscosity at 15 Viscosity for Viscosity 100C, cyst.
Grade of 150,000 cup, cMinimum Maximum WOW -40 4.1 WOW -26 7.0 WOW ~12 11.0 -- 13.5 24.0 140 -- 24.0 41.0 It is obvious from these tables that the viscosity index of a 25 broadly multi graded oil such as WOW or WOW will require fluids having considerably higher viscosity index than narrowly multi-graded lubricants such as WOW. The viscosity index require-mints for different multi grade fluids can be approximated by the use of ASTM Standard Viscosity-Tempearture Charts for Liquid Petroleum Products (D 341).
If one assumes that extrapolation of the high temperature (40C and 100C) viscosities to -40C or below is linear on chart D 341, then a line connecting a 100C viscosity of, for example, 12.5 cyst. and a low temperature viscosity of 3500 cup at -25C would I

give the correct 40C viscosity and permit an approximation of the minimum viscosity index required for that particular grade of oil (Lowe) .
The 40C viscosity estimated by linearly connecting the 100C
5 and -25~C viscosities would be about: 70 cyst. The viscosity index of an oil having K.V.1oo = 12.5 cyst. end K.V.40 = 70 cyst. would be about 180 (ASTM D 2270-74). Unless the -25C viscosity of a fluid is lower than the linear relationship illustrated, then an oil must have a viscosity index of at least 180 to even potentially 10 qualify as a WOW oil.
In actual fact, many V. I . improved oils have viscosities at -25C which are considerably greater than predicted by linear extrapolation of the K.V.1oo and K.V.40 values. Therefore, even having a V. I . of 180 does not guarantee the blend would be a 15 WOW oil .
Using this technique minimum viscosity index requirements for various grades of crankcase or gear oils can be estimated. A few typical estimations are shown in the following table:

Estimated Required crankcase K-V-100C V 40C Viscosity Oil Grade cyst. cyst. Index . _ .
Lowe 9.3 60 135 WOW 12.5 70 180 WOW 9.3 53 159 250~-50 16.3 75.5 232 Gear Oil Grade guy 24 ~70 112 WOW 41 31~ 184 It can thus be seen that preparation of very broadly graded lubricants, such as SW-40 or WOW requires thickeners which produce very high viscosity indices in the final blends.

I

It has been the practice to improve the viscosity index of mineral oils or low viscosity synthetic oils by adding a polymeric thickener to relatively non-viscous base fluids. Polymeric thick-enters are commonly used in the production of multi grade lubricants.
Typical polymers used as thickeners include hydrogenated styrenes isoprene block copolymers, rubbers based on ethylene and propel-one (COP), polymers produced by polymerizing high molecular weight esters of the cruelty series, polyisobutylene and the like.
These polymeric thickeners are added to bring the viscosity of a base fluid up to that required for a certain SUE grade and to increase the viscosity index of the fluid, allowing the production of multi graded oils. Polymeric VI improvers are traditionally high molecular weight tubbers whose molecular weights may vary from 10,000 to 1,000,000. Since the thickening power and VI increase are related to the molecular weight of the VI improver, most of these polymers normally have a molecular weight of at least 100,000.
The use of these high molecular weight VI improvers, in the production of multi graded lubricants has some serious drawbacks:
1. They are very sensitive Jo oxidation, which results in a loss of VI and thickening power and frequently in the formation of unwanted deposits.
I. They are sensitive to large viscosity losses from mechanical shear when exposed to the high shear rates and stresses encountered in crankcases or gears.
3. They are susceptible to a high degree of temporary shear .
Temporary shear is the result of the non-Newtonian viscometrics associated with solutions of high molecular weight polymers. It is caused by an alignment of the polymer chains with the shear field under high shear rates with a resultant decrease in viscosity. The decreased viscosity reduces the wear protection associated with viscous oils. Newtonian fluids maintain their viscosity regardless of shear rate.
We have found that certain combinations of fluids and additives can be used to prepare multi graded lubricants which outperform prior art formulations and have none or a greatly decreased amount of the above listed deficiencies found in polymerically thickened oils .

I

Certain specific blends of high viscosity hydrogenated polyp isoprene, low viscosity synthetic hydrocarbons and/or low viscosity esters form base fluids from which superior crankcase or gear oils can be produced by the addition ox the proper additive "packages".
5 The finished oils thus prepared exhibit very high stability to per-Mennonite shear and, because of their nearly Newtonian nature, very little, if any, temporary shear and so maintain the viscosity no-squired for proper wear protection. The oils of this invention have remarkably better stability toward oxidative degradation than those 10 of the prior art. The unexpectedly high viscosity indices produced from our base fluid blends permit the preparation of broadly multi-graded crankcase fluids, such as WOW and gear oils such as WOW. Up to now it has been difficult if not impossible, to prepare such lubricants without the use of frequently harmful 15 amounts of polymeric V.I. improvers.
The oligomeric polyisoprenes of this invention may be prepared by Ziegler or, preferably, anionic polymerization. Such polymeric ration techniques are described in United States Patent 4,060,492.
For the purposes of this invention, the preferred method of preparation for the liquid hydrogenated polyisoprenes is by the anionic alkyd lithium catalyzed polymerization of isoprene. Many references are available to those familiar with this art which desk crime the use of such catalysts and procedures. The use of alkyd lithium catalysts such as secondary bottle lithium results in a polyp 25 isoprene oligomer having a very high (usually greater than continuity, which results in backbone unsaturation.
When alkyd lithium catalysts are modified by the addition of ethers or amine, a controlled amount of 1,2- and 3,4- addition can take place in the polymerization.

I

SHEA SHEA
CH2=C-CH=CH2 Eli { CH2-C=CH-CH2~-1,4-addition _ Eli SHEA
ROW
SCHICK-- ~CH2-CH~
OH C-CH
lo " " 3 SHEA SHEA

1,2-addition 3,4-addition Hydrogenation of these structures gives rise to the saturated species represented below:

SHEA SHEA
-CH2-C=CH-CH2- Ho -CH2-C-CH2-CH
H

1,4-addition (A) SHEA SHEA
-OH -C- -I J- -SCHICK-OH SHEA

SHEA SHEA
1,2-addition (B)

2 SHEA OH -OH-lc,-c~3 H-C-CH3 SHEA SHEA

3,4-addition I

I

Structure (A) is the preferred structure because of its low Tug and because it has a lower percent of its mass in the pendant groups (SHEA-). Structure (B) is deficient in that the tetrasu~sti-tuned carbons produced serve as points of thermal instability.
5 Structure (C) has 60% of its mass in a pendant (isopropyl) group which, if repeated decreases the thickening power of the oligomer for a given molecular weight and also raises the Tug of the resultant polymer. This latter property has been shown to correlate with viscosity index. Optimization of structure (A) is desired for the 10 best combination of thickening power, stability and V. I . improve-mint properties.
Another feature of alkyd lithium polymers is the ease with which molecular weight and molecular weight distribution can be controlled. The molecular weight is a direct function of the moo-15 men to catalyst ratio and, taking the proper precautions to exclude impurities, can be controlled very accurately thus assuring good quality control in the production of such polymer. The alkyd lithe I'm catalysts produce very narrow molecular weight distributions such that Mom ratios of 1.1 are easily gained . For V . I . imp 20 provers a narrow molecular weight distribution is highly desirable since, at the given molecular weight, thickening power is maximized while oxidative and shear instability are minimized. If desired, broad or even polymodal MOW. distributions are easily produced by a variety of techniques well known in the art. Star-shaped or 25 branched polymers can also be readily prepared by the inclusion of multi functional monomers such as divinely Bunsen or by termination of the "lovingly chains with a polyfunctional coupling agent such as dim ethyl terephthalate .
It is well known that highly unsaturated polymers are concede-30 drably less stable than saturated polymers toward oxidation. It isimportan~, therefore, that the ~rno~lnt of unsaturation present in the polyisoprenes be draslicall~7 reduced. This is accomplished easily by anyone skilled in the art using, for instance, a Pi, Pod or No catalyst in a pressurized hydrogen atmosphere at elevated temper-35 azure.
Regardless of the mode of preparation, isoprene oligomersrequire hydrogenation to reduce the high level of unsaturation I

present after polymerization. For optimum oxidation stability, 90%, and preferably 99% or more of the olefinic linkages should be saturated .
The low viscosity synthetic hydrocarbons of the present invent 5 lion, having viscosities of from l to 10 cyst., consist primarily ofoligomers of alphaolefins and alkylated benzenes.
Low molecular weight oligomers of alphaolefins from C8 (octane) to C12 (dodecene) or mixtures of the olefins can be utilized. Low viscosity a]phaolefin oligomers can be produced by Ziegler catalysis, 10 thermal polymerization, free radically catalyzed polymerization and, preferably, By catalyzed polymerization. A host of similar pro-cusses involving BF3 in conjunction with a cocatalyst is Nina in the patent literature. A typical polymerization technique is desk cried in United States Patent No. 4,045,50~.
The alkylbenzenes may be used in the present invention alone or in conjunction with low viscosity polyalphaolefins in blends with high viscosity synthetic hydrocarbons and low viscosity esters.
The alkylbenzenes, prepared by Friedel-Crafts alkylation of Bunsen with offense are usually predominantly dialkylbenzenes wherein the 20 alkyd chain may be 6 to 14 carbon atoms long. The alkylating olefins used in the preparation of alkylbenzenes can be straight or branched chain olefins or combinations. These materials may be prepared as shown in US 3,909,432.
The low viscosity esters of this invention, having viscosities of 25 from 1 to 10 cyst. can be selected from classes of esters readily available commercially, e . g ., monstrous prepared from monobasic acids such as pelargonic acid and alcohols; divesters prepared from dibasic acids and alcohols or from dills and monobasic acids or mixtures of acids; and polyol esters prepared from dills, trios 30 (especially trimethylol propane), tutorials (such as pentaerythritol), hexaols (such as dipentaerythritol) and the like reacted with moo-basic acids or mixtures of acids.
Examples of such esters include tridecyl pelargonate, Dow-ethylhexyl adipate, Dow ethylhexyl assault, trimethylolpropane 35 triheptanoate and pentaerythritol tetraheptanoate.
An alternative to the synthetically produced esters described above are those esters and mixtures of esters derived from natural q38~

sources, plant or animal. Examples of these materials are the fluids produced from jujube nuts, tallows, safflowers and sperm whales.
The esters used in our blends ought to be carefully selected to insure compatibility of all components in finished lubricants of 5 this invention. If esters having a high degree of polarity (roughly indicated by oxygen content) are blended with certain combinations of high viscosity synthetic hydrocarbons and low viscosity synthetic hydrocarbons, phase separation can occur at low temperatures with a resultant increase in apparent viscosity. Such phase separation 10 is, of course, incompatible with long term storage of lubricants under a variety of temperature conditions.
The additive "packages" mixed with the recommended base oil blend for the production of multi graded crankcase fluids or gear oils are usually combination of various types of chemical add lives 15 so chosen to operate best under the use conditions which the par-titular formulated fluid may encounter.
Additives can be classified as materials which either impart or enhance a desirable property of the base lubricant blend into which they are incorporated. While the general nature of the additives 20 might be the same for various types or blends of the base Libra-cants, the specific additives chosen will depend on the particular type of service in which the lubricant is employed and the kirk-teristics of the base lubricants.
The main types of current day additives are:
1. Dispersals 2. Oxidation and Corrosion Inhibitors, 3. Anti-Wear Agents,

4. Viscosity Improvers,

5. Pour Point Depressants,

6. Anti-Rust Compounds, and

7. roam Inhibitors.
Normally a finished lubricant will contain several and possibly most or all of the above types of additives in what is commonly called an "additive package The development of a balanced add-35 live package involves considerably more work than the casual use officio of the additive types. Quite often functional difficulties arising from combinations of these materials show up under actual operating conditions. On the other hand, certain unpredictable synergistic effects of a desirable nature may also become evident.
The only methods currently available for obtaining such data are from extensive full scale testing both in the laboratory and in the 5 field. Such testing is costly and time-consuming.
Dispersants have been described in the literature as "deter-gents". wince their function appears to be one of effecting a dispersion of particulate matter, rather than one of "cleaning up"
any existing dirt and debris, it is more appropriate to categorize 10 them as dispersants. Materials of this type are generally molecules having a large hydrocarbon "tail" and a polar group head. The tail section, an oleophilic group, serves as a solubilizer in the base fluid while the polar group serves as the element which is attracted to particulate contaminants in the lubricant.
The dispersants include metallic and cashless types. The metallic dispersants include sulfonates (products of the neutralize-lion of a sulfonic acid with a metallic base), thiophosphonates (acidic components derived from the reaction between polybutene and phosphorus pentasulfide) and founts and phenol sulfide salts 20 the broad class of metal founts includes the salts of alkylphen-owls, alkylphenol sulfides, and alkyd phenol alluded products).
The cashless type dispersants may be categorized into two broad types: high molecular weight polymeric dispersants for the formula-lion of multi grade oils and lower molecular weight additives for use 25 where viscosity improvement is not necessary. The compounds useful for this purpose are again characterized by a "polar" group attached to a relatively high molecular weight hydrocarbon chain.
The "polar" group generally contains one or more of the eye-ments--nitrogen, oxygen, and phosphorus. The solubilizing chains 30 are generally higher in molecular weight than those employed in the metallic types; however, in some instances they may be quite similar. Rome examples are N-substituted long chain alkenyl sue-cinimides, high molecular weight esters, such as products formed by the esterificatio~ of moo or polyhydric aliphatic alcohols with 35 olefin substituted succinic acid, and Mannish bases from high mole-cuter weight alkylated phenols.

I

The high molecular weight polymeric cashless dispersants have the general formula:

R R R R R
.
C-cH2-c-cH2~c-cH~-c-cH2-c-cH2 o o P o o where O = Oleophilic Group P = Polar Group R = Hydrogen or Alkyd Group The function of an oxidation inhibitor is the prevention of a deterioration associated with oxygen attack on the lubricant base fluid. These inhibitors function either to destroy free radicals (chain breaking) or to interact with peroxides which are involved in the oxidation mechanism. Among the widely used anti-oxidants are the finlike types (chain-breaking) e.g., 2,6-di-tert.-butyl pane crossly and 9,4' methylenebis(2,6-di-tert.-butylphenol), and the zinc dithiophosphates (peroxide-destroying).
Wear is loss of metal with subsequent change in clearance between surfaces moving relative to each other. If continued, it will result in engine or gear malfunction. Among the principal factors causing wear are rnetal-to-metal contact, presence of Abram size particulate matter, and attack of corrosive acids.
Metal-to-metal contact can be prevented by the addition of film-forming compounds which protect the surface either by physical absorption or by chemical reaction. The zinc dithiophosphates are widely used for this purpose. These compounds were described under anti-oxidant and anti-bearing corrosion additives. Other effective additives contain phosphorus, sulfur or combinations of these elements.
Abrasive wear can be prevented by effective removal of par-ticulate matter by filtration while corrosive wear from acidic mater-tats can be controlled by the use of alkaline additives such as basic founts and sulfonates.
Although conventional viscosity improvers are of ten used in "additive packages" their use should not be necessary for the ~2~5~

practice of this invention since our particular blends of high and low molecular weight base lubricants produce the same effect.
However, we do not want to exclude the possibility of adding some amounts of conventional viscosity improvers. These materials are 5 usually oil-soluble organic polymers with molecular weights ranging from approximately 10, 000 to 1, 000, 000 . The polymer molecule in solution is swollen by the lubricant. The volume of this swollen entity determines the degree to which the polymer increases its viscosity .
Pour point depressants prevent the congelation of the oil at low temperatures. This phenomenon is associated with the crystal-ligation of waxes from the lubricants. Chemical structures of rep-resentative commercial pour point depressants are:
COO OH
__~ _ . paraffin paraffin paraffin SHEA C _ ¦ 1 _ n _ SHEA paraffin paraffin n Alkylated Wax Naphthal~ne PolymethacrylaLe Alkylated Wax Phenol Chemicals employed as rust inhibitors include sulfonates, alkenyl succinic acids, substituted imidazolines, amine, and amine phosphates .
The anti-foam agents include the silicones and miscellaneous 25 organic copolymers.
Additive packages known to perform adequately for their recommended purpose are prepared and supplied by several major manufacturers. The percentage and type of additive to be used in each application is recommended by the suppliers. Typically avail-30 able packages are:
1. HAYAKAWA [Trademark E-320 for use in automotive gear oils, 2. L~brizol trademark] 5002 for use in industrial gear oils, 3. Laboriously 4856 supplied by the Laboriously Corp. for use in gasoline crankcase oil, and 4. OLGA trademark] 8717 for use in diesel crankcase oils.
A typical additive package for an automotive gear lubricant would normally contain antioxidant, corrosion inhibitor, anti-wear ~2~18~

agents, anti-rust agents, extreme pressure agent and foam inn-biter .
A typical additive package for a crankcase lubricarlt would normally be comprised of a dispers~nt, antioxidant, corrosion inn-biter, anti-wear agent, anti-rust agent and foam inhibitor.
An additive package useful for formulating a compressor fluid would typically contain an antioxidant anti-wear agent, an anti-rust agent and foam inhibitor.
This invention uses blends of HI having a viscosity range of 1000 to 3500 cyst. with one or more synthetic hydrocarbon fluids having viscosities in the range of 1 to 10 cyst. and/or one or more comma title ester fluids having a viscosity range of 1 to 10 cyst .
Such blends, viny treated with a properly chosen additive "package", can be formulated in broad range multi graded crankcase or gear oils having improved shear stability, improved oxidative stability, and nearly Newtonian viscometric properties. The blends of this invention also find uses in certain applications where no additive need be employed.
In discussing the constitution of the base oil blend, i-t is convenient to normalize the percentages of HI, low viscosity synthetic hydrocarbons, and low viscosity esters in the final Libra-cant so that they total 100%. The actual percentages used in the final formulation would then be decreased depending on the amount of additive packages utilized.
Each of the ingredients, HI, low viscosity synthetic hydra-carbons, and low viscosity esters are essential parts of this invent lion . The HI provides thickening and V . I . improvement to the base oil blend . The V. I . improvement produced by HI in blends with low viscosity synthetic hydrocarbons or low viscosity esters is shown in the examples.
The low viscosity synthetic hydrocarbon fluid is frequently the main ingredient in the base oil blend, particularly in finished Libra-cants having an SUE viscosity grade of 30 or 40. While certain low viscosity esters are insoluble in (high viscosity) HI, the presence of low viscosity synthetic hydrocarbon, being a better solvent for low viscosity esters, permits greater variations in the type of esters used in base oil blends of high viscosity synthetic hydrocar-buns, low viscosity synthetic hydrocarbons, and low viscose try esters .
Crankcase and gear oils consisting solely of hydrogenated polyisoprene oligomers and low viscosity synthetic hydrocarbons 5 with the proper additives produce synthetic fluids having excellent oxidative and hydroly tic stability . Such fluids are exemplified in Example 3.
The third optional component, low viscosity esters can be used in combination with hydrogenated polyisoprene oligomers and low 10 viscosity hydrocarbons or alone with hydrogenated polyisoprene oligomers. In the three component blend the proper choice Or ester and hydrogenated polyisoprene oligomers can produce crankcase and gear oil formulations having outstanding viscosity indices and low temperature properties. Such three component blends are thus-treated in Examples 1 and 2.
Two component blends of hydrogenated polyisoprene oligomersand esters can be used to prepare multi graded lubricants having outstanding viscometric properties, detergency, and oxidative stability. While some applications present environments having high moisture levels, which would be deleterious to certain esters, there are other applications such as automotive gear oils where the high ester contents found in the hydrogenated polyisoprene oligomers-en ton blends can be used to advantage . Example 4 illustrates the formulation of multi grade lubricants with such two component blends.
When it is deemed advantageous to use a low viscosity ester as part of the blend, the low viscosity hydrocarbons act as a common solvent for the HI and the added ester. Depending on the polarity of the ester, the latter two are frequently somewhat in-compatible. Excellent multi graded lubricants can be formulated with or without ester.
The third component, low viscosity esters, can be added to produce the superior lubricants of this invention. HI and low viscosity synthetic hydrocarbons can be used alone to produce multi graded lubricants. The addition ox low levels of low viscosity esters, usually 1-25% results in a base oil blend superior to blends of high viscosity s,vnLhetic hydrocarbons and low viscosity synthetic hydrocarbons alone in low -temperature fluidity.

., ~2;~:~Q~3~

Low viscosity esters usually constitute 10-25% of the synthetic base oil blend, more or less can be used in specific formulations.
When the final application involves exposure to moisture elimination or limitation of toe amount of ester in blends may be advantageous.
The components of the finished lubricants of this invention can be admixed in any convenient manner or sequence.
An important aspect of the present invention is in the use of the properly constituted base oft blend in combination with the proper compatible additive package to produce finished broad range multi grade lubricants having:
1. Improved temporary shear stability.
2. Excellent oxidation stability.
3. High viscosity index.
The range of percentages for each of the components, i . e ., HI, low viscosity synthetic hydrocarbons, low viscosity esters, and additive packages, will vary widely depending on the end use for the formulated lubricant, but the benefits of the compositions of this invention accrue when the base oil blend contains (normalized):
From 1 to 99% HI from 1 to 9g% low viscosity synthetic hydrocarbons esters or mixtures thereof. It is preferred to blend from 3 to 80% HI with correspondingly 90 to 20% of at least one low viscosity ester base fluid or hydrocarbon base fluid. The additive package can be used in from 0 to 25% of the total formulation, all by weight.
The lubricants of -this invention approach viscometrics of Newtonian fluids . The t is, their viscosities are changed little over a wide range of shear rates. While the HI of the invention may, in themselves, display non-Newtonian characteristics, particularly at low temperatures, the final lubricant products utilizing low viscosity oils as delineates are nearly Newtonian.
The non-Newtonian character of currently used V.I. improvers is well documented. An excellent discussion can be found in an SUE: publication entitled, "The Relationship Between Engine Oil Viscosity and Engine Performance Part III. " The papers in this publication were preset ted at a 1978 SUE Congress and Exposition in Detroit on February 27 to March 3, 1978.

The reference of interest is Paper 78037~:
"Temporary Viscosity Loss and its Relationship to Journal Bearing Performance, " M . L . MacMillan and C . K .
Murphy, General Motors Research Labs.
this reference, and many others familiar to researchers in the field, illustrates hotly commercial polymeric VI improvers of molecular weights from 30,000 and up all show a temporary viscosity loss when subjected to shear rates of 105 to 106 sea 1 The temporary shear loss is greater for any shear rate with higher molecular White polymers. for instance, oils thickened to the same viscosity with polymethacrylates of 32,000; 157,000; and 275,000 molecular weight show percentage losses in viscosity at a 5 x 105 sea 1 shear rate of 10, 22 and 32%, respectively.
The His of this invention have molecular weights below 5000, Andy shear tunneling of their solutions is minimal.
The shear rates developed in pistons and gears (equal to or greater than 106 sea 1) is such -that, depending on the polymeric thickener used, -the apparent viscosity of the oils approaches that of -the unthickened base fluids resulting in loss of hydrodynamics films. Since wear protection of moving parts has been correlated with oil viscosity, it is apparent that the wear characteristics of a lubricant can be downgraded as a result of temporary shear. The nearly Newtonian fluids of this invention maintain their viscosity under these use conditions and therefore afford more protection to Andy longer lifetime for the machinery being lubricated.
The currently used polymeric thickeners which show temporary (recoverable) shear are also subject to permanent shear. Extended use of polymeric thickeners leads to their mechanical breakdown with resultant loss in thickening power and decrease in VI. This is illustrated in Example 5. Paper 780372 (op. aft), "Polymer Stability in Engines" by W. Wunderlich and H. Just discusses the relation-ship between polymer type and permanent shear. The multi grade lubricants of -this invention are not as susceptible to mechanical shear .
thus same paper also recognizes an often overlooked feature of high molecular weight polymeric VI improvers, i.e., their instability toward oxidation. Just as these polymers lose viscosity by shear Lo they are also readily degraded by oxygen with the resultant break down of the polymer and decrease in viscosity index. The Libra-acting fluids of this invention suffer much less change in viscosity index upon oxidation.
As mentioned earlier, the smelt amount of temporary shear exhibited by the lubricants of -this invention guarantees optimum viscosity for the protection of moving parts where high shear rates are encountered. The importance of this feature is widely recog-sized . In the past, SUE grading (e . g . SUE 30) relied only on a measurement of the viscosity of a fluid at 100C under low shear conditions, despite the fact that in machinery such as a crankcase high temperatures and very high shear rates are encoun toned .
This disparity has led to the adoption in Europe of a new grading system wherein viscosities for a certain grade are those measured at 150C and 106 sea 1 shear rate. This more realistic approach is currently being considered in the United States . The ad van taxes a Newtonian fluid brings to such a grading system are obvious to anyone skilled in the art. The viscosity of a Newtonian fluid can be directly extrapolated to 150C under high shear conditions. A
polymer thickened fluid, however, will invariably have a viscosity lower than the extrapolated value, frequently close to the base fluid itself. In order to attain a certain grade under high shear condo-lions, polymer thickened oils will require a more viscous base fluid.
The use of thicker base fluids will produce higher viscosities at low temperature making it more difficult to meet the low temperature (OW for crankcase of WOW for gear oil) requirements for broadly multi graded oils.
Stated another way, current high molecular weight VI impure-Yens "artificially" improve the viscosity index, since realistic high temperature high shear measurements are not utilized in determining VI. Viscosity index is determined by low shear viscosity measure-mints at 40C and 100C. The n~rly Newtonian lubricants of this invention not only produce high viscosity index multi graded fluids which stay "in grade", but the VI and multi grade rating are real-fistic since they are not very sensitive to shear.
While the specific compositions exemplified in this patent are fairly precise, i-i: should be obvious to anyone skilled in -the art to -lug-produce even further combinations within the scope of this invent lion which will be valuable lubricants.
The following examples illustrate some of the blends encom-passed my our invention:

This example illustrates the preparation of crankcase lubricants using hydrogenated polyisoprene (HI) of the viscosities shown:

INGREDIENT wry %
( 100 1310) 12 POW (1) 50 Di-2-Ethylhexyl assault 20 Laboriously 3940 (2) 18 B. HI (KVloo = 3360) 9 Di-2-Ethylhexyl assault 20 Laboriously 3940 18 The lubricants had the properties shown:
KV100'CSt KV40CS~ VI CCS, cup SUE Grade A. 13.5 81.3 170 3010@-20C Lowe B. 13.3 76.5 177 2215@-20C Lowe (1) 4 cyst Polyalphaolefin (2) Additive package made by Laboriously Corporation This example illustrates the preparation of automotive gear 25 lubricants using His of the kinematic viscosities shown:

I

INGREDIENT WIT %

Di-2-Ethylhe~yl assault 20 Anglamol 6043 (1) 10 B- HI (KVlOO = 3360) 20 Di-2-Ethylhexyl assault 20 Anglamol 6043 10 The lubricants had the properties shown:
-100' KV40Cst VI Vis@-40C,cP SUE Grade A. 15.1 87.4 183 27,320 WOW
B. 25.4 166.0 188 72,410 WOW
(1) Additive package made by Laboriously Corporation This example illustrates the preparation of lubricants with His of the kinematic viscosities shown in blends with only sync Thetis hydrocarboIl and additive package:

INGREDIENT WIT %
- Crankcase -(I.) HI (KV1oo = 1310) 11 Dialkyl Bunsen (DN-600) 20 Laboriously 3940 18 25 (B.) HI (KV1oo = 3360) 10 Laboriously 3940 12 I

Automotive Gear O_ (C.) HI (VOW = 3360) 19 Anglaolol 6043 10 The lubricants had the properties shown:
- 100'-- - 40 VI Skip SUE Grade (Aye 83.8 161 KIWI
(B.)13.4 79.0 174 KIWI
(C.)25.0 162.0 189 83,420~-40C WOW

This example illustrates the preparation of lubricants with Hops of the kinematic viscosities shown in blends with only esters and additive package:

INGREDIENT WIT %
- Crankcase -(A.) HI (KV1oo = 1310) 13 Deciduously Adipate 75 Laboriously 3940 12 (B.) HI (KVloo = 3360) 10 Deciduously Adipate 78 Laboriously 4856 12 Automotive Gear Oil (C.) HI (KVloo = 1310) 25 Deciduously Adipate 65 Anglamol 6043 10 (D.) HI (KV1oo = 3360) 20 Deciduously Adipate 70 Anglamol 6043 10 The lubricants had the properties shown:
-100' - _ 40, Sty VI Vis,cP -SUE Grade (~.)13.9 74.9 192 KIWI
(B.)13.4 71.2 277 KIWI
(C.)27.1 171.g 1g5 77,470@-40C WOW
(D-)29.0 177.9 204 78,630@-40C WOW

Claims

We claim:

1. A lubricating composition comprising:
(A) a hydrogenated polyisoprene oligomer having a viscosity of from 1000-3500 centistokes at 100°C, and (B ) a synthetic hydrocarbon, an ester or mixtures thereof having a viscosity of from 1-10 centistokes at 100°C.

2. The lubricating composition of claim 1 further comprising an additive package comprising at least one additive selected from the group consisting of dispersants, oxidation inhibitors, corrosion inhibitors, anti-wear agents, pour point depressants, anti-rust agents, foam inhibitors and extreme pressure agents.