US3267032A

US3267032A - Metal antioxidants for fluid bis (phenoxyphenoxy) benzene

Info

Publication number: US3267032A
Application number: US291216A
Authority: US
Inventors: Ravner Harold
Original assignee: Individual
Current assignee: Individual
Priority date: 1963-06-27
Filing date: 1963-06-27
Publication date: 1966-08-16
Anticipated expiration: 1983-08-16

Description

P 3,267,032 lc Patented August 16, 1966 the Navy N Drawing. Filed June 27, 1963, Ser. No. 291,216 2 Claims. (Cl. 252-26) The invention described herein may be manufactured by or for the Government of the United States of America for governmental purposes without the paymentof any royalties thereon or therefor.

This invention relates to improvement in the oxidation stability at high temperatures of a fluid polyphenyl ether which is the meta isomer of his (phenoxyphenoxy) benzene.

Developments in jet engine aircraft have presented an increasing demand for lubricants which can meet severe operational requirements. Among such requirements is oxidation stability at high temperatures.

The meta isomer of his (phenoxyphenoxy) benzene has heretofore received considerable attention as a candidate for use as a high temperature lubricant. It is a liquid having a pour point of 40 F and good resistance to oxidation, pyrolysis and radiation. The oxidation resistance does not, however, extend to temperatures in the range of 600 to 650 F.

It is an object of the present invention to improve the oxidation resistance of the meta isomer of bis (phenoxyphenoxy) benzene at temperatures in the range of 600 to 650 F. whereby to extend the high temperature range over which this compound may be used as a lubricant and as a hydraulic fluid.

I have found the metals, copper, barium and strontium, to be antioxidants for the meta isomer of bis (phenoxyphenoxy) benzene at temperatures in the range of from about 600 to 650 F. These metals are effective even in small concentrations, on the order of as low as from about 0.050.5% :by weight of the weight of the meta isomer, to impart a high degree of oxidation stability to the meta isomer at temperatures in the aforesaid range.

The metals which are antioxidants in accordance with my invention may be present in the meta isomer as such or as a constituent of alloys. In either case, the meta isomer will take contact with the metal to receive the antioxidant protection afforded by the metal. The metals may be brought into contact with the meta isomer in particle form or in the form of plates or other larger shapes or configurations as found suitable. The surface of parts of engines or of other mechanisms with which the meta isomer comes into contact, such as oil lines, may consist of the antioxidant metal or a by-pass system may contain the antioxidant metal in the form of a wire mesh or as a confined mass of granules through which the meta isomer flows in contact before returning to areas of lubrication.

The mechanism whereby the metals function as antioxidants in the meta isomer is not known but is believed to involve formation of metal ions in the meta isomer.

The oxidation stability imparted to the meta isomer will vary with the particular metal and will be higher at the lower temperatures in the aforesaid range since the oxidative stress is less at the lower temperatures.

The antioxidant activity of the metals for the met-a isomer may be evaluated in terms of increase in the viscosity of the meta isomer, the smaller this increase the greater the oxidation stability imparted to the meta isomer at a given temperature in the aforesaid range. Acid may be developed in the meta isomer on heating, but, characteristically, only in small amounts. The neutralization number for this acid may be determined but it is of minor and may be of no significance as a determining factor of the efiicacy of the metals as antioxidants for the meta isomer.

Increase in the viscosity of the meta isomer and the amount of acid developed therein on heating and meta isomer to temperature in the aforesaid range in the presence of the metal antioxidants may be determined by use of the dynamic oxidation test procedure and apparatus described in Ind. Eng. Chem., 39, 491 (1947). In this test, equal volume samples of the meta isomer, with and without a specimen of the metal antioxidant immersed therein, are contained in cyclindrical cells made of borosilicate glass. The metal specimens, which may be in the form of strips, are used in a clean, degreased condition. The sample of the meta isomer without a metal specimen therein is the control. Each of the cells is equipped with a water-cooled condenser fitted to the top thereof and has a rubber tube connected from the condenser to a separate water trap. Sealed to the upper wall of each of the cells is means for delivering bubbled air into the bottom of the meta isomer samples in the cells. The cells containing the samples of the meta isomer, with and without the metal specimens, are placed in snugly fitting holes in an electrically heated Duralumen block which is thermostatically controlled to hold at the test temperature i 0.5" F. Clean dry air, free from CO is bubbled through the heated meta isomer samples in the cells at a predetermined volume and rate. The viscosity in centistokes at F. and the neutralization number of the meta isomer are determined before and after the test. The neutralization number is the number of milligrams of potassium hydroxide required to neutralize the meta isomer.

Indicative of the oxidation stability which can be imparted to the meta isomer by the metal antioxidants of the invention are results obtained with commercial meta isomer of bis (phenoxyphenoxy) benzene which contained small amounts of adjacently homologous meta polyphenyl ethers. The tests were conducted at temperatures of 600 F. and 650 F. for a period of 48 hours, using 20 ml. samples of the commercial meta isomer and metal antioxidant specimens which generally had surface areas of 10 square centimeters. The air was bubbled into the meta isomer samples in the cells at the rate of 1 cc./ gram sample/minute. Test results with the several metals as antioxidants are set forth in the following table.

DYNAMIC OXIDATION TEST Viscosity Neutraliza- Under the conditions of the test, the meta isomer which had not been provided with a metal antioxidant, lost all fluidity at 600 F., being oxidized to a gel. With copper as the antioxidant, the meta isomer was still fluid at 600 F., although not at 650 F. Barium and stron- 3 tium as antioxidants provided a greater degree of protection such that the meta isomer was still fluid at 650 F.

Since the invention herein described may be variously embodied without departing from the spirit or scope thereof, it is intended that the specific embodiments appearing in the above description shall be taken by way of illustration and not in limitation except as may be defined in the appended claims.

What is claimed is:

1. A system comprising the meta isomer of bis (phenoxyphenoxy) benzene in contact with an amount of a metal of the group consisting of copper, barium and strontium which is sufiicient to improve the oxidation stability of said meta isomer at a temperature in the range of from about 600 to 650 F.

2. A system as defined in claim 1, wherein the metal is strontium.

References Cited by the Examiner UNITED STATES PATENTS 1,992,292 2/1935 Cox et al. 260611.5 3,151,082 9/1964 Wesley et al. 2606ll.5

FOREIGN PATENTS 851,651 10/ 1960 Great Britain.

OTHER REFERENCES Ravner et al., Antioxidant Action of Metals and Organometal Compounds in Fluoresters and Polyphenyl Ethers, NRL Report 5794 (Dec. 5, 1962); page 8, most pertinent.

15 DANIEL E. WYMAN, Primary Examiner.

J. R. MCBRIDE, P. P. GARVIN, Assistant Examiners.

Claims

1. A SYSTEM COMPRISING THE META ISOMER OF BIS (PHENOXYPHENOXY) BENZENE IN CONTACT WITH AN AMOUNT OF A METAL OF THE GROUP CONSISTING OF COPPER, BARIUM AND STRONTIUM WHICH IS SUFFICIENT TO IMPROVE THE OXIDATION STABILITY OF SAID META ISOMER AT A TEMPERATURE IN THE RANGE OF FROM ABOUT 600 TO 650*F.