GB2127431A - Lubricating oil composition - Google Patents

Abstract

A lubricating oil composition having improved friction reducing properties comprises a major amount of weight of lubricating base oil and from 0.01 to 5.0% by weight of at least one oil-soluble hydroxyl terminated polymer of butadiene and/or styrene- butadiene. Preferably the number average molecular weight of the polymer(s) in from 100 to 10,000, more especially 1,000 to 6,000. Preferred polymers are those having the structures <IMAGE> where n is from 2 to 100.0

Description

SPECIFICATION Lubricating oil composition This invention relates to a lubricating oil composition having improved friction reducing properties and to a method for reducing friction in internal combustion engines.

There has been considerable effort in recent years to develop lubricating oil compositions which will reduce friction in engines, and particularly, automotive engines. This effort is based on the need to improve the fuel economy of such engines which operate on petroleum fuel, a product having a declining source of supply and escalating price. It is knownthathigh enginefriction causes significant energy loss and,thus, onewayto improvefuel economy is to reduce such friction.

Known ways to solve the problems of energy losses due to high friction, e.g., in crankcase motor oils, include the use of synthetic ester base oils which are expensive and the use of insoluble molybdenum sulfides, which have the disadvantage of giving the oil composition a black or hazy appearance.

Various friction reducing additives have been disclosed in the art as well as many other additives known for providing antioxidant, antiwear, corrosion inhibiting and other useful properties. While such known additives may in fact satisfy one or more of these properties, it is also known that many additives act in a different physical or chemical manner and often complete with one another, e.g., they may compete forthe surface of moving metal parts which are subjected to lubrication and often times are incompatible with one another. Accordingly, extreme care must be exercised in the selection of these additives to insure compatibility and effectiveness.

Among the friction reducing additives which have been used are a number of molybdenum compounds including insoluble molybdenum sulfides, and organo molybdenum complexes e.g. molybdenum amine complexes disclosed in U.S. Patent 4,164,473, molybdenum thio - bis - phenol complexes disclosed in U.S.

Patents 4,192,757,4,201,683 and 4,248,720, molybdenum oxazoline complexes disclosed in U.S. Patent 4,176,074 and molybdenum lactone oxazoline complexes disclosed in U.S. Patent 4,176,073.

Another group offriction reducing additives which have been used in lubricating oils are the carboxylic acid esters. These compounds include the esters of fatty acid dimers and glycols as disclosed in U.S.

Patent 4,105,571, the esters of monocarboxylic acids and glycerol as disclosed in U.S. 4,304,678, the ester of dimer acids and monohydric alcohol disclosed in U.S. 4,167,486, the esters of glycerol and monocar boxylicfatty acids as disclosed in U.K. 2,038,355 and 2,038,356, and esters of monocarboxylicfatty acids and polyhydric alcohols disclosed in U.S. 3,933,659.

While the different approaches and additives all generally provide some reduced engine friction and consequently improved fuel economy, there is still the need for additional additives and compositions which besides providing the necessary and desired friction reduction, are also economical, readily available, and most important, are compatible with commonly used lubricating base oils and the many conventional additives used in lubricating oil compositions.

Now it has been found that lubricating oil compositions containing hydroxyl terminated polymers of butadiene or styrene - butadiene as an additive, have significantly improved friction reducing properties.

More particularly, this invention is directed to a lubricating oil composition having improved friction reducing properties comprising a major amount of lubricating base oil and from about 0.01 to about 5.0 parts by weight of oil soluble hydroxyl terminated polymer(s) butadiene and/or styrene - butadiene.

Another embodiment of this invention relates to a method of reducing friction in an internal combustion engine by lubricating said engine using a lubricating oil composition containing an effective friction reducing amount of an additive which is an oil soluble hydroxyl terminated polymer of butadiene or styrene - butadiene.

This invention is directed to a lubricating oil composition containing a selected polymer additive to provide improved friction reducing properties and to a method of reducing friction in an internal combustion engine by using a lubricating oil composition which contains said polymer additive.

Thisfriction reducing additive which is used in this invention is 3/oil soluble, hydroxyl terminated polymer(s) of butadiene andiorstyrene- butadiene.

Such polymer additives typically have strictures such as:

where n is an integer which will vary depending on the particular molecular weight desired, as discussed below, and generally will vary between about 2 to about 100. In the above butadiene polymer, the configuration can vary with differing amounts of e.g.

the trans, cis and vinyl butadieneform present and in the styrene - butadiene polymer, varying amounts of the styrene and butadiene components can be present.

Generally, the polymer additives ofthis invention will be liquid, oil suluble and have an average number molecule weight of from about 100 to about 10,000, preferablyfrom about 1,000 to about 6,000 and more preferably from about 2,000 to about4,000. Compounds ofthistype are commercially available and can be prepared in accordance with known methods of preparation. Discussions involving polymers of this general type and the preparation thereof may be found in Kirk-Othmer Encyclopedia of Chemical Technology, 2nd edition, 1968, Vol. 16, pp.219 to 252 and Vol. 17, pp.657 to 660 as well as Textbook of Polymer Science by F. W. Billmeyer, Jn, 2nd edition, 1970, pp.255-376.

The hydroxyl terminated polymer additives ofthis invention will generally be used at a concentration of from about 0.01 to about 5.0 parts by weight, preferably from about 0.01 to about 2.0 and more preferably from about 0.1 to about 1.0 parts by weight per 100 parts of lubricating oil composition.

The lubricating base oil will generally comprise a major amount of the lubricating composition, i.e., at least 50% by weight thereof, and will include liquid hydrocarbons such as the mineral lubricating oils and the synthetic lubricating oils and mixtures thereof.

The synthetic oils which can be used include diester oils such as di (2 - ethylhexyi) sebacate, azelate and adipate; complex ester oils such as those formed from dicarboxylic acids, glycols and either monobasic acids or monohydric alcohols; silicone oils, sulfide esters, organic carbonates; and other synthetic oils known to the art.

Other additives, known in the art, may be added to the oil composition of the present invention to form a finished oil. Such additives include dispersants, antiwear agents, antioxidants, corrosion inhibitors, detergents, pour point depressants, extreme pressure additives, viscosity index improvers, etc. These additives are typically disclosed for example in "Lubricant Additives" by C. V. Smalheer and R.

Kennedy Smith, 1967, pp. 1-1 1 and in the U.S. Patent 4,105,571.

The following examples are further illustrative of this invention and are not intended to be construed as limitations thereof.

EXAMPLE 1 A 1 OW40SE quality automotive engine oil was prepared containing 0.1 wt.% based on total lubricating oil of an hydroxyl terminated butadiene polymer having a number average molecularweightofabout 3,000. The oil also contained conventional additives, namely, a zinc dialkyl dithiophosphate antioxidanti antiwearagent; a rust inhibitor, i.e. overbased magnesium sulfonate; a detergent, being a basic sulfurised metal phenate; a V.l. improver, i.e. an ethylene - propylene copolymer; and a polyiso butenylsuccinic anhydrideipolyamine dispersant.

The prepared composition was tested for relative friction using a ball on cylindertest described in the "Journal of the Aermican Society of Lubrication Engineers" (ASLETransaction),Vol.4, pages 1-11, 1961. In essence, the apparatus consists basically of a fixed metal ball loaded against a rotating cylinder.

The weight on the ball and the rotation of the cylinder can be varied during any given test or from testto test. Also, thetime of any given test can be varied.

Generally, however, steel on steel is used at a constant load, constant rpm and a fixed time and in each ofthetests ofthese examples, a 4 kg load, 0.26 rpm and 70 minutes was used. The apparatus and method used is more fully described in U.S. Patent 3,129,580.

The sample formulation containing the hydroxyl terminated butadiene polymer additive gave a rela tive friction of 0.19 while the same formulation withoutthe additive had a relative friction of 0.29.

For comparison purposes, a similarformulation containing 0.5 and 1.0 wt.% ofthe butadiene polymer additive had respective relative frictions of 0.09 and 0.07.

EXAMPLE2 Another automotive engine oil, being as described in Example 1 but having a PlBSNpentaerythritoli polyamine dispersant, was tested for relative friction in the same manner as described in Example 1.

The fresh test oil containing 1.0wt.% of a hydroxyl terminated butadiene polymer having an average number molecularweight of about 3,000 had a relative friction of 0.08 as compared to a relative friction of 0.28 forthe same oil without the butadiene additive. The same oils were also tested for relative friction after being oxidized for 3 hours so as to simulate engine service. The results were a relative friction of 0.07 for the oil containing the butadiene additive as compared to a relativefric#ion of 0.29 for the same oil withoutthe butadiene additive.

EXAMPLE 3 Another automotive engine oil having similar quality to the one described in Example 1 and having a different V.l. additive, i.e. an esterified am ine treated styreneimaleic anhydride copolymer, was tested for relative friction in the same manner as described in Example 1. The fresh test oil containing 0.3 wt.% of an hydroxyterminated butadiene polymer having an average number molecularweight about3,000 had a relative friction of 0.12 as compared to a relative friction of 0.22 for the same oil withoutthe butadiene additive. The same oils were also tested for relative friction after being oxidized for3 hours so asto simulate engine service. The results were relative friction of0.O9fortheoil containing the butadiene additive as compared to a relative friction of 0.29 for the same oil without the butadiene additive.

Claims (10)

CLAIMS:

1. A lubricating oil composition having improved friction reducing properties comprising a major amount by weight of lubricating base oil and a total of from 0.01 to 5.0% by weight of at least one oil-soluble hydroxyl terminated polymer of butadiene and/or styrene - butadiene.

2. A composition as claimed in claim 1, wherein a total offrom 0.01 to 2.0% by weight of said polymer(s) is used.

3. A composition as claimed in claim 2, wherein a total of from 0A to 1.a% byweight of said polymer(# is used.

4. A composition as claimed in any preceding claim, wherein the average number molecularweight of said polymers} is 100 to 10,000.

5. A composition as claimed in claim 4,wherein the average numbermolecularweightofsaid polym er(s) is 1,000 to 6,000.

6. Acomposition as claimed in any preceding claim, wherein said polymer is an oil-soluble hydroxyl terminated polymer of butadiene.

7. A composition as claimed in claim 6, wherein said polymer has an average number molecular weightof 2,000to4,000.

8. Acompositionasclaimedinclaim 1 and substantially as herein described.

9, Acompositionasclaimedinclaim 1 and substantially as herein described with reference to any one ofthe Examples 1 to 3.

10. A method of reducing friction in an internal combustion engine comprising lubricating said engine using a lubricating oil composition defined in any one of the preceding claims.