US3361667A - Lubricating compositions - Google Patents

Description

United States Patent 3,361,667 LUBRICATING COMPOSITIONS Ronald Francis Alfred Eatly Wenhorne and David Michael Soul, London, England, assignors to Castro] Limited, London, England, a British company No Drawing. Filed Aug. 30, 1965, Ser. No. 483,833 Claims priority, application Great Britain, Aug. 31, 1964, 35,583/64 14 Claims. (Cl. 25232.7)

ABSTRACT OF THE DISCLOSURE A lubricating composition, particularly suitable for the lubrication of hypoid gears, which composition comprises a mineral lubricating oil and dissolved therein an additive combination which confers extreme pressure properties on the composition and which consists of (a) a chlorine-containing hydrocarbon having a boiling point or decomposition temperature of not less than 160 C.,

(b) an oil-soluble polyvalent metal salt of a dithiophosphoric acid, and

(c) a dialky phosphite,

the proportion of (a) being such as to provide from 0.42% to 6.0% by Weight of chlorine in the composition, the proportion of (b) being such as to provide from 0.048% to 1.0% by weight of sulphur in the composition, and the proportion of (0) being such as to provide from 0.036% to 0.3% by weight of phosphorus in the composition.

This invention is for improvements in or relating to lubricating compositions and is particularly concerned with lubricating compositions having extreme pressure properties especially suitable for the lubrication of hypoid gears, which compositions will operate under conditions of low speed and high torque as well as under conditions of high speed and high load. The lubricating compositions of this invention may (however, be used for lubricating all kinds of industrial gears.

It is well known that under certain conditions, e.g. for the lubrication of hypoid gears, it is necessary to employ lubricants containing chemical compounds capable of reacting with metals at high temperatures and under high pressures to form films (e.g. of iron sulphide, iron chloride or iron oxide) which prevent seizure and welding of the metal surfaces. A variety of organic compounds have been suggested for this purpose, including sulphur compounds of various types and containing sulphur in varying degrees of activity. It has generally been found advantageous to use these sulphur compounds in conjunction with lead soaps or organic halogen compounds, or both. It is now recognised that many such libricants, which behave perfectly satisfactorily under normal operating conditions and even under high loads at high speed, are not satisfactory under conditions of high torque and low speed, e. g. for lubricating rear axles of vehicles operating in mountainous terrain. Under these conditions, certain lubricants, e.g. those containing lead soaps or sulphur in active form, tend to cause high rates of wear or, in some cases, rippling or ridging of the gear teeth, and

to promote the rusting of ferrous metal parts in the presence of condensed moisture.

On the other hand lubricants which perform well under conditions of high torque and low speed do not necessarily possess adequate load-carrying capacity under high-speed conditions and particularly under conditions of shock loading. In fact the two requirements have been for some time regarded as being conflicting and British Gear Oil Specification No. CS,3000A and the now obsolete U.S. Army Specification M1LL2l02, to which most commonly used hypoid rear axle oils have conformed for some time, represent a compromise.

The practice among motor manufacturers for sometime past has been to use lubricants having better E.P. properties under high-speed conditions than the conventional MlL L2l05 oils for factory fills for passenger cars. After running-in the gears for a certain period on these oils, which generally contain active sulphur and sometimes also lead soaps, the rear-axle may be drained and filled with MILL-2105 oil. Some of these oils, particularly those containing lead soaps, while providing adequate protection of the gears against scufiing, have been found to give rise to an undesirable amount of wear in anti-friction bearings resulting in loss of pre-load with consequent deterioration of the gear and development of noise and other troubles. Furthermore, it is an obvious disadvantage to have different rear axle Oils for factory fills for passenger cars and trucks, since confusion may occure and breakdown of heavily-loaded truck axles might take place under low-speed high-torque conditions if lubricated with an oil of the wrong type.

It is clearly desirable that hypoid gear Oils used for factory fills should be compatible with hypoid gear oils used subsequently after the running-in process has been completed. It is, therefore, advantageous if the same additives are present in the oil used for factory fills as in the oil subsequently purchased from a garage and used either for topping-up or defilling the axle housing after draining. The additive combination of the present invention has the advantage that it may be used both for factory fill purposes and at a lower dosage level for general use in which case no problems due to incompatibiity will be encountered.

Recent improvements in engine designs have led to increased power output and this, combined With the tendency to increase the hypoid pinion offset, has brought about a very considerable increase in the severity of the operating conditions of the gears of passenger cars. The loading on truck axles has also increased and the high speeds at which many vehicles, particularly military vehices, operate combined with the heavy loads carried have exposed the limitations of MILL-2105 oils both under high-speed conditions of operation and under lowspeed high torque conditions.

In addition to having adequate extreme pressure properties, a universal hypoid axle lubricant must be relatively non-corrosive to cuprous metals at high operating temperatures and must provide adequate resistance to the corrosion of ferrous metals in the presence of water.

To obtain a satisfactory oil for first fill purposes, it is highly desirable that axle tests should be passed both under high speed/high load conditions and under low speed high torque conditions. It has generally been considered b that a compound containing a fair quantity of fairly active sulphur is necessary together with chlorine to pass the former type of test, Whilst phosphorus compounds are required to pass the latter type of test.

A surprising feature of the present invention is that both requirements can be satisfied by using relatively small amounts of two readily available and inexpensive phosphorus compounds in conjunction with a chorine compound. Furthermore, these compounds are freely oil soluble and without corrosive attack on copper at temperatures up to 135 C.

According to the present invention there is provided a lubricating composition comprising a mineral lubricating oil and dissolved therein an additive combination which confers extreme pressure properties on the composition and which consists of (a) a chlorine-containing hydrocarbon having a boiling point or decomposition temperature of not less than 160 C.,

(b) an oil-soluble polyvalent metal salt of a dithiophosphoric acid, and

(c) a dialkyl phosphite.

Where the lubricating compositions are for use specifically as hypoid gear lubricants, it is preferred that the total chlorine content is from 2.5% to 6.0% by Weight, the proportion of (b) is such as to provide from 0.2% to 1.0% 'by weight of sulphur in the composition, and the proportion of (c) is such as to provide from 0.1% to 0.3% by Weight of phosphorus in the composition. The proportion of (b) is preferably such as to provide from 0.3% to 0.7% by Weight of sulphur in the composition.

Examples of additive (a) are:

Chlorinated parafiin wax,

Chlorinated kerosine,

Hexachlorethane,

Benzene hexachloride,

Chlorinated indenes, Dichlordiphenyltrichlorethane (DDT) and Chlorinated diphenyls.

Examples of additive (b) are:

Zinc di-n-pentyl dithiophosphate Zinc di(l,3 dimethyl butyl)dithiophosphate Zinc isopropyl/ 1,3 dimethyl butyl dithiophosphate Zinc isobutyl/a-myl dithiophosphate Zinc diamyl dithiophosphate derived from mixed amyl alcohols Zinc dialkyl dithiophosphate derived from mixed straight chain -0 alcohols Zinc dialkyl dithiophosphate derived from mixed C -C alcohols Nickel di(2-ethyl hexyl)dithiophosphate Barium di lauryl dithiophosphate Chromium di(p-octylphenyl) dithiophosphate Examples of additive (c) are:

Diethyl phosphite,

Di-isopropylphosphite Di-n-butylphosphite,

Dioctyl phosphite,

Dilauryl phosphite.

These phosphites have the formula:

where R and R are the same or different alkyl groups. Preferably R and R together have a total of from 3 to 12 carbon atoms.

Additive (a) is preferably a parafiin wax containing from 40 to 70% of chlorine, additive (b) is preferably a zinc dialkyl-di thiophosphate wherein each alkyl group contains from 3 to 12 carbon atoms and additive (c) is preferably di-isopropyl phosphite.

It is to be understood that the composition may contain conventional lubricating oil additives, for example, antioxidants or corrosion inhibitors, dispersants, detergents, pour point depressants and V1. Improvers.

A corrosion inhibitor which is particularly useful in the compositions of the present invention is on oil-soluble basic alkaline earth metal sulphonate which may or may not be neutralized with a Weak acid, e.g. carbon dioxide and is preferably employed in an amount of at least 0.05% and more preferably in an amount from 0.1 to 0.5% by weight of the total composition.

Examples of these additives are:

Basic barium petroleum sulphonate,

Basic calcium petroleum sulphonate,

Basic strontium petroleum sulphonate,

Basic barium dinonyl naphthalene sulphonate, and, Basic barium didodecyl or octadecyl benzene sulphonate.

Any of these compounds may be neutralized wholly or in part with CO to give the corresponding carbonate complex.

Another additive which is particularly usefulin this invention is the additive prepared by reacting a phosphosulphurised polyisobutylene with barium hydroxide in the presence of an alkyl phenol, carbonating and further reacting with a basic alkaline earth metal sulphonate.

The invention also includes an additive combination for conferring extreme pressure properties to a mineral oil lubricant, which combination comprises from 67% to 74% of a chlorinated paraffin wax containing from 40% to 70% by weight of chlorine, from 15% to 20% of a zinc dialkyl dithiophosphate having from 3 to 12 carbon atoms in each alkyl group, and from 4.8% to 5.5% of a dialkyl phosphite having a total of from 3 to 12 carbon atoms per molecule, the percentages being by weight on the total weight of addition. The dialkyl phosphite is preferably diisopropyl phosphite.

The combination may also with advantage contain from 6% to 8% of a phosphosulphurised polyisobutylene reacted with a barium alkyl phenate and over-based with a basic barium petroleum sulphonate as a detergent, and from 0.6% to 0.8% of a co-polymer of mixed fatty acid methacrylates as a pour point depressant. Reference is made to US. Patent No. 2,969,324 for further description of the phosphosulphurized detergents.

These additive combinations may be supplied either near or as oil concentrates for dilution to the extent required for the particular lubricating job for which they are to be used.

A representative lubricating composition of the invention consists essentially of a mineral lubricating oil having dissolved therein from 5% to 15% of a chlorinated paraifin wax containing from 40% to 70% by weight of chlorine, from 1.5% to 3.5% of a zinc dialkyl dithiophosphate having from 3 to 12 carbon atoms in each alkyl group, from 0.5 to 1.0% of a dialkyl phosphite having from 1 to 6 carbon atoms in each alkyl group, from 0.5% to 2% of a phosphosulphurized polyisobutylene reacted with a barium alkyl phenate and over-based with a basic barium petroleum sulphonate and from 0.05% to 0.2% of a co-polymer of mixed fatty acid methacrylates, all percentages being by weight on the Weight of the composition.

Following is a description by way of example of typical compositions of the present invention.

EXAMPLE I Percent Mineral oil A 44.0

Mineral oil B 41.65

Percent Chlorinated parafiin wax containing about 42% chlorine 10.0 Zinc isopropyl/ 1,3 dimethyl butyl dithiophosphate 2.5 Detergent D 1.0 Di-isopropyl phosphite 0.75 Pour Point Depressant A 0.1

Mineral oil A was a high viscosity, Western bright stock, having a viscosity of about 800 seconds Redwood I bright stock at 140 F.

Mineral oil B was a solvent refined mineral oil of viscosity about 150 seconds Redwood I at 140 F.

The zinc dithiophosphate was in the form of an approximately 80% concentrate in oil, the phosphorous content of the concentrate being approximately 8%. The detergent D was a phosphosulpliurized polyisobutylene reacted with a barium alkyl phenate and overbased with a basic barium petroleum sulphonate. The pour point depressant A was a copolymer of mixed fatty acid methacrylates.

This composition possessed the following viscosity characteristics:

The composition gave good results when subjected to a relatively severe road test in the hypoid rear axle of a motor vehicle.

EXAMPLE II Percent Mineral oil A 39.5

Mineral oil B 46.15 Chlorinated parafiin wax containing 42% chlorine 10.0 Zinc isobutyl/amyl dithiophasphate 2.5 Di-isopropyl phosphite 0.75 Detergent D 1.0 Pour pont depressant 0.1

The zinc dithiophosphate wa in the form of an approximately 80% concentrate in oil, the phosphorus content of the concentrate being about 8.0%.

In order to test the properties of these compositions that of Example I was run in the rear axle of a high performance 2 litre saloon car under high speed conditions, together with braking tests, these tests being carried out in the Alps over a total distance of approximately 5000 miles. Identical tests were carried out on an identical vehicle using a well-known prior art hypoid gear oil (Blend A) containing 5.5% of an Extreme pressure additive containing about 16% sulphur, 3% Zn, 3% P and 16.5% C1, and 0.05% pour point depressant. This particular type of vehicle was chosen since the cooling air flow normally experienced by the rear axle had been greately reduced due to the design of the axle unit, which was partly housed in a well in order to accommodate the suspension unit. Consequently the rear axle tended to run at higher temperatures than normal, these temperatures being greatly increased under heavy braking conditions by conduction from the disc brakes along the drive shafts to the axle casing.

The extreme pressure properties of both the prior art oil and the composition of the present invention (Example I) were examined before and after test by testing on the well-known Four-ball Machine, similar to that described by Boerlage in Engineering July 13, 1933, volume 136, page 46. This apparatus comprised four steel balls arranged in the form of a pyramid. The top ball was held in a chuck attached to a spindle rotating at approximately 1500 rev./min. and pressed against the three bottom balls clamped in a stationary ball-holder. The balls were immersed in the oil to be tested. Tests were normally run for one minute at a series of diflFerent loads. The results of these tests are given in Table I.

The surprising effect was that the composition of the present invention was more efiicient after test than before particularly with regard to the load at incipient seizure.

Although the above test showed that a typical composition of the present invention was efiioient under rigorous conditions involving high speed operation with braking, it was felt that more controlled conditions could be obtained by carrying out tests on a tesbtrack.

Accordingly another model of the same vehicle was fitted with a rear axle which had been previously run-in. Thermocouples were attached to the drain plug in order to measure the bulk oil temperature, to the bearing assembly in order to measure the temperature of the shaft and the gear in general, and to the inspection cover in order to measure the temperature of the oil jet leaving the teeth of the gear. The thermocouples were connected via a switch mechanism to a recording head fitted in the car. The cold junction was also located in the car and consequently all temperature readings had to be adjusted to the temperature ambient in the car. In order to prevent loss of heat from the forward end of the axle a fibreglass/ asbestos lagging was wrapped around the housing at the nose end. The car towed a dynamometer by means of a draw bar. The load imposed was continuously adjustable from within the car by means of an electronic control, so enabling absolute control over the load to be maintained.

Four test sequences were devised in order to obtain a bulk oil temperature of about 150 C. These are given in Table II.

TABLE II.TESI SEQUENCES FOR DYNAMOMEIER Sequence Load (1135.) on Car Gear Car Speed,

Draw Bar m.p.h.

Tests were carried out in the following order:

(1) Fresh Blend A, sequence 1, 3 and 4. Allowed to cool to ambient (approximately 1 hours), then run at normal road speed for 10 minutes.

(2) Used Blend A, sequence 1, 3 and 4.

(3) Fresh composition of Example II, sequence 1 and 2.

(4) Used composition of Example II, sequence 1 and 2.

The results of these tests are given in Table III.

The results obtained on the two oils are given below.

All runs were conducted in similar climatic conditions of dry, Warm weather with light winds.

These results-showed clearly that the composition of the present invention allowed the rear-axle to run at a much lower temperature than the prior art hypoid gear oil. Furthermore, the load which had to be applied to cause the oil to reach a temperature of about 150 C., was very much higher than in the case of the prior art gear oil. This is shown by the fact that sequence 2 was much more severe than either sequence 3 or sequence 4, in fact so severe that undue strain was placed on the dynarnometer, the engine of the car and on components not connected with the axle..

Four-ball tests were again carried 'out on Blend A before and after test and the composition of Example 11 as used in the above dynamometer tests and here again the improved extreme pressure properties of the composition according to the present invention after use were demonstrated, the results of these tests being given in Table IV.

Example Blend B Spec.

II Required 21. 49 17. 29 28. 61 30. 19 33. 1 74. 6 100% max. Acid No. of oil after test. 3.06 7. 2 None. Pentane insolubles, percent".-. 3. 39 6.09 3% max. Benzene insolubles, percent 2. 07 2. 72 2% max. Catalyst weight loss (g.) 0. 44 2. 21 Report. Gear back lash (inches) 0.0005 0.002 Do. Bearing clearance (inches) 0.0005 0.0005 Do.

The results indicated that the performance of Example 11 was a significant improvement over that of Blend B, a typical MIL-L-2105 lubricant.

We claim:

1. A lubricating composition consisting essentially of a mineral lubricating oil having dissolved therein an additive combination which confers extreme pressure prop- TABLE IV Load kg. at Weld Scar diameter (mm) at load in kg. of

incipient pt.

seizure (kg) Blend A:

Before test 120/130 400 1. 20 1.56 1. 61 2. 17

After test 120/135 310 l. 34 1. 64 1. 71 1. 78 2.13 Composition of Example II:

Before test 160/165 350 0.58 1. 73 1. 98 2. 2

After test 195/200 400 0. 89 1. 02 1. 62 2. 0

In order to evaluate the oxidation stability of a typical composition in accordance with the invention, Example II was compared with a blend (Blend B) containing the same additive package as Blend A but in a higher concentration (9.5%). The test chosen was that laid down in US. Military Specification MI-L-2105B. In this test a small gear box is run for hours at a controlled temperature, the gears being lubricated by the oil under test. At the end of the alloted time the oil is examined for viscosity increase and insolubles content.

The test is fully described in Federal Test Method Std-191, method 2504T, the conditions of test being as follows:

Temperature 325 F.i1 F. (l57.2 C.i0.6 C.).

Load on gears provided by driving an electric generator to give an output of 128 watts.

Air flow through lubricant 1.11 litres per hour.

As well as the steel gears a copper catalyst was included in the system to determine the copper activity of the lubricant.

erties on the composition and which consists of (a) a chlorine-containing aliphatic hydrocarbon having a boiling point or decomposition temperature of not less than C. selected from the group onsisting of chlorinated paraffin wax, chlorinated kerosine, hexachlorethane, benzene hexachloride, chlorinated indenes, clichlordiphenyltrichlorenthane and chlorinated diphenyls;

(b) an oil-soluble polyvalent metal salt of a dialkyl dithiophosphoric acid wherein each alkyl group contains from 3 to 12 carbon atoms; and

(c) a dialkyl phosphite having a total of from 2 to 12 carbon atoms in the alkyl group, the proportion of (a) being such as to provide from about 2.5% to 6.0% by weight of chlorine in the composition, the proportion of (b) being such as to provide from about 0.2% to 1.0% by weight of sulphur in the composition, and the proportion of (c) being such as to provide from about 0.1% to 0.3% by weight of phosphorus in the composition.

2. A lubricating composition as claimed in claim 1 wherein the proportion of (b) is such as to provide from 0.3% to 0.7% by weight of sulphur in the composition.

3. A lubricating composition as claimed in claim 1 wherein (a) is a parafiin wax containing from 40% to 70% by Weight of chlorine.

4. A lubricating composition as claimed in claim 1 wherein the polyvalent metal of (b) is zinc.

5. A lubricating composition as claimed in claim 1 wherein (c) is di-isopropyl phosphite.

6. A lubricating composition as claimed in claim 1 wherein there is also present at least 0.05% by Weight of an oil-soluble basic alkaline earth metal sulphonate.

7. A lubricating composition as claimed in claim 6 wherein there is present fr rn 0.1% to 0.5% by Weight of the oil-soluble basic alkaline earth metal sulphonate.

8. A lubricating composition as claimed in claim 6 wherein the oil-soluble basic alkaline earth metal sulphonate is wholly or partially neutralised with carbon dioxide to give the corresponding carbonate complex.

9. A lubricating composition consisting essentially of a mineral lubricating oil having dissolved therein from to of a chlorinated parafiin Wax containing from 40% to 70% by weight of chlorine, from 1.5% to 3.5% of a zinc dialkyl dithiophosphate having from 3 to 12 carbon atoms in each alkyl group, from 0.5% to 1.0% of a dialkyl phosphite having from 1 to 6 carbon atoms in each alkyl group, from 0.5% to 2% of a phosphosulphurised polyisobutylene reacted with a barium alkyl phenate and over-based with a basic barium petroleum sulphonate and from 0.05% to 0.2% of a co-polymer of mixed fatty acid methacrylates, all percentages being by Weight on the Weight of the composition.

10. An additive combination for conferring extreme pressure properties to a mineral oil lubricant, which combination consists essentially of from 67% to 74% of a chlorinated parafiin wax containing from to by weight of chlorine from 15% to 20% of a zinc dialkyl dithiophosphate having from 3 to 12 carbon atoms in each alkyl group, and

from 4.8% to 5.5% of a dialkyl phosphite having a total of from 3 to 12 carbon atoms per molecule, the percentages being by weight on the total Weight of the combination.

11. An additive combination as claimed in claim 10 wherein the dialkyl phosphite is di-isopropyl phosphite.

12. An additive combination as claimed in claim 10 containing from 6% to 8% of a phosphosulphurised polyisobutylene reacted with a barium allcyl phenate and over-based with a basic barium petroleum sulphonate as a detergent.

13. An additive combination as claimed in claim 10 containing from 0.6% to 0.8% of a co-polymer of mixed fatty acid methacrylates as a pour point depressant.

14. An additive combination as claimed in claim 10 in solution in a mineral lubricating oil.

References (Iited UNITED STATES PATENTS 2,285,855 6/1942 Downing et al. 25249.8 3,001,939 9/1961 OHalloran 25232.7 3,013,971 12/1961 Mastin 25232.7 3,029,268 4/1962 Goldsmith 252-327 X 3,053,766 9/1962 Munsell et al. 252-32] DANIEL E. WY MAN, Primary Examiner. PATRICK P. GARVIN, Examiner.