US3704277A - Polyphenyl ether lubricating compositions - Google Patents

Abstract

COMPOSITION COMPRISING POLYPHENYL ETHERS OR MIXTURES THEREOF AND PERFLUORO ALIPHATIC DIBASIC ACIDS EXHIBIT IMPROVED LUBRICATING PROPERTIES OVER WIDE TEMPERATURE RANGES.

Description

United States Patent US. Cl. 25254.6 5 Claims ABSTRACT OF THE DISCLOSURE Composition comprising polyphenyl ethers or mixtures thereof and perfluoro aliphatic dibasic acids exhibit improved lubricating properties over wide temperature ranges.

This invention relates to improved lubricating compositions comprising polyphenyl ethers and mixtures thereof containing from 3 to 8 aromatic groups and a perfiuoro aliphatic dibasic acid as a lubricating additive.

Polyphenyl ethers have found wide application as functional fluids in view of their excellent thermal stability and lubricity. For example they have been found to be valuable as hydraulic fluids and as lubricants in motor operation, particularly in jet engines.

Development of synthetic base stocks such as the polyphenyl ether has provided lubricant fluids which are useful at elevated temperature such as 400 to 500 F. It is known that one of the aspects in which the polyphenyl ether base stocks are considered deficient is in their lubricating characteristics. These lubricating characteristics include the load-carrying abilities and wear properties, especially under conditions of high pressures and temperatures reached in the advance design aircraft engines. Thus there is a demand for polyphenyl ethers having improved lubricity properties.

An object of the present invention is to provide base stock compositions employing polyphenyl ethers or mixtures thereof that exhibit improved lubricating properties.

These and other objects will become evident upon consideration of the following specification and example.

It has now been found that compositions comprising a major amount of a polyphenyl ether base stock and a lubricating additive amount of a perfluorinated aliphatic dibasic acid, have unusual ability to lubricate under high load at high temperatures.

Any of the well known polyphenyl ether base stocks can be used in accordance with this invention. However, the polyphenylether base stocks represented by a member selected from the following formulae are preferred.

where m is 2, 3, or 4 such as ice 2 Q such as 3,3'-bisphenoxy biphenyl o o H MM 23 such as 1,3,4-triphenoxybenzene and mixtures thereof.

Mixtures of polyphenyl ethers in which the nonterminal phenylene rings are linked through oxygen atoms in the meta and/or parapositions, have been found to be particularly suitable. An example of such polyphenyl ether compositions are those containing, in percent by weight, from about 0 to 6% of o-bis(m-phenoxyphenoxy)benzene (1), about 40 to 85% of m-bis(m-phenoxyphenoxy)- benzene (2), about 0 to 40% of m-[(m-phenoxyphenoxy) (p-phenoxyphenoxy)]benzene (3), about 0 to 12% of p-bis(m-phenoxyphenoxy)benzene (4), about 0 to 10% of p-[ (p-phenoxyphenoxy) (m-phenoxyphenoxy) ]benzene (5), and about 0 to 6% of m-bis(p-phenoxyphenoxy) benzene (6). Typical compositions of such mixtures are listed below. The number in parentheses refers to the compound mentioned above having the same number thereafter.

Mixtures percent by weight of components A B C D Component:

wherein n is an integer of from 1 to 6. It is particularly preferred to employ perfluorinated dibasic acids of Formula V wherein n is an integer of from 2 to 4.

Illustrative of the perfluorinated dibasic acids represented by Formula V are, for example, perfluoro malonic acid, perfluoro succinic acid, perfluoroglutaric acid, perfiuoro adipic acid,-perfluoropimelic acid, and perfluoro suberic acid.

The improvement in lubricity characteristics achieved by the addition of the perfluoro aliphatic dibasic acid to the polyphenyl ether base fluid is unusualaud surprising. The compositions are particularly useful for steel on steel lubrication.

The compositions of this invention contain a major amount of the polyphenyl ether base stock, i.e., at least 50% by weight of the total composition comprises a polyphenyl ether. It is preferred that at least 60% by weight of the composition be a polyphenyl ether base stock and even more preferred that at least 85% by weight of the total composition comprise a polyphenyl ether.

The compositions of this invention can also contain from 0.01 to by weight of the total composition of a dialkyl hydrogen phosphite extreme pressure additive. The dialkyl hydrogen phosphites useful are those wherein the alkyl groups contain from 1 to 12 carbon atoms. These alkyl groups are, for example, methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, t-butyl, hexyl, decyl, isodecyl, dodecyl and the like.

The following example serves to further illustrate the invention. All parts are parts by weight unless otherwise expressly set forth.

EXAMPLE After stirring at 40 C. to dissolve the acid, the mixture is cooled to room temperature and filtered.

The lubrication of the composition is shown with a slow speed four ball machine. A slow speed four ball machine measures the boundary lubricity action of additives. This test is a variation of the well known Shell Four Ball Test in which a ball is rotated against three stationary balls. Wear scars and/or seizure loads measure additive lubricity. In the slow speed instrument the three stationary balls are replaced with circular discs. Standard operating conditions are:

3 kg. load 1 r.p.m. Room temperature to 700 The speed of rotation is very low, namely one r.p.m. This equals 0.88 inch/minute. This is done for two reasons. It insures boundary conditions, i.e., metal to metal contact. It also eliminates metal skin temperature flashes which can occur at high speeds. Thus the bulk oil temperature is equivalent to the metal surface temperature. Under these conditions wear is negligible and friction is used to follow lubrication. After covering the ball and disc with the test oil, the initial friction is recorded. The test sample is thenheated at 700 F. with continuous recording of the friction. This gives a boundary frictiontemperature profile for the experimental fluid over this temperature range.

The polyphenyl ether composition of this example is tested by this procedure on 316 stainless steel. The measured coefficient of friction remained below about 0.4 from room temperature to 700 F.

When the base fluid was tested under the same conditions the coefficient of friction showed a steep increase as the temperature was increased and exceeded 2.0 at 450 F. and remained between 1.0 and 2.0 through 700 F.

The embodiments in which an exclusive property or privilege is claimed are defined as follows:

1. Composition comprising a major amount of a polyphenyl ether and from about 0.01 to about 0.2% by weight of a perfluorodibasic aliphatic acid of the formula wherein n is an integer of from 1 to 6.

2. Composition of claim 1 wherein said perfluoro dibasic aliphtaic acid is present in amounts of from about 0.05 to about 0.1% by weight.

3. Composition of claim 1 wherein said per'fluoro dibasic aliphatic acid is perfluoroglutaric acid.

4. Composition of claim 2 wherein said perfluoro dibasic aliphatic acid is perfluoroglutaric acid.

5. A composition of claim 1 where n is from 1 to 3.

References Cited UNITED STATES PATENTS 3,409,677 ll/l968 Duncker et al. 25252 R 3,476,815 11/1969 Williams et al. 25252 R 3,490,738 11/1970 Stemnisk 25252 R 3,541,015 11/1970 Schultz et al 25252 R 3,567,783 3/1971 Brown 25252 R 3,677,944 7/1972 Clark 25254.6

DANIEL E. WY-MAN, Primary Examiner Y. H. SMITH, Assistant Examiner US. Cl. X.R. 25252 R