EP0612837A1 - Polyphenylene ether lubricant containing hydrocarbyl bis(dihydrocarbylphosphate) compound - Google Patents

Abstract

Polyphenylene ether-based lubricant compositions can be improved in regard to anti-wear properties by inclusion of a hydrocarbyl bis(dihydrocarbylphosphate) compound, for example, at up to about 10% by weight. The preferred compounds contain a hydrocarbyl group derived from a monoaromatic diol such as resorcinol or hydroquinone and are diphenylphosphate species.

Description

BACKGROUND OF THE INVENTION
• Polyphenylene ether lubricants represent very stable organic structures which meet the needs of jet engines, high temperature hydraulic systems, nuclear power plants, and as the fluid component of high temperature greases. Although this class of lubricant is thermally and oxidatively stable, they can cause significant wear of high-alloy steels that are typically used in supersonic and hypersonic aircraft jet engines.
  Polyphenylene ether lubricants have been proposed which contain various additives for a variety of purposes. A representative, non-limiting listing of additives which have been proposed is as follows:
• chelates of a heavy metal of Groups I-IV and VI-VIII of the Periodic Table of the Elements for wear and oxidation resistance and non-sludging behavior (U.S. Patent No. 3,360,467);
• organolead compounds for increased resistance to oxidation, improved viscosity stability, and increased color stability (U.S. Patent No. 3,423,469);
• perfluorinated aliphatic dibasic acids for enhanced lubrication under high load at high temperatures (U.S. Patent No. 3,704,277);
• phenoxyphenylphosphinic acid for enhanced lubrication under high load at high temperature (U.S. Patent No. 3,706,668).
SUMMARY OF THE INVENTION
• The present invention relates to a polyphenylene ether lubricant comprising an effective amount of a hydrocarbyl bis(dihydrocarbylphosphate) compound as an anti-wear additive. These additives have been unexpectedly found not to significantly affect the excellent thermal stability of the polyphenylene ether lubricant. Hydrocarbyl bis(dihydro-carbylphosphate) compounds have been used as additives in fuels for internal combustion engines (U.S. Patent No. 3,254,973), as extreme pressure and anti-wear additives in oleaginous or petroleum based lubricants (U.S. Patent No. 3,492,373; also see U.S. Patent No. 3,360,467 at Col. 1, line 58 to Col. 2, line 2, for the non-predictable behavior of such additives when in a polyphenylene either fluid), and as a low flammability hydraulic oil, in general (U.S. Patent No. 4,212,832).
DESCRIPTION OF PREFERRED EMBODIMENTS
• The polyphenylene ether lubricant of the present invention comprises, as the base stock, a polyphenylene ether of the formula
  
  
  
          Ar-O-[Ar-O]_n-Ar
  
  
  
  where Ar stands for a phenyl ring, n is a whole number of generally from 2 to 5. This class of lubricant is well known to persons of ordinary skill in the art with the following patents, which are incorporated herein by reference, providing further disclosure: U.S. Patent Nos. 3,360,467; 3,423,469; 3,476,815; 3,704,277; and 3,706,668. Generally speaking, the polyphenylene ether base stock will comprise from about 90% to about 99.5%, by weight, of the entire lubricant composition.
  The hydrocarbyl (bisdihydrocarbylphosphate) compounds which are used as an anti-wear additive with the previously described polyphenylene ether base stock are of the formula

  

  
  where R is either unsubstituted or substituted hydrocarbyl such as alkyl or aryl and A is a bridging group containing alkylene, haloalkylene, arylene, two arylene groups joined by a bridging group (e.g., -C(CH₃), -SO₂ or -CO), or a bridging group containing biarylene. Such compounds are a known class of flame retardant in polymers and, as indicated above, have had some degree of use in certain fuel and lubricant compositions. Preferred R groups are phenyl with A also being phenylene, such as derived from a monoaromatic diol, such as either resorcinol or hydroquinone. Generally, such diphosphate additive is present in a relatively low amount such as about 0.1% to about 10%, by weight of the composition. The polyphenylene ether lubricants of the present invention can contain other additives, particularly those recognized for use in fluids of that type. Inclusive of such additives are pour point depressants, viscosity index improvers, dyes, rust inhibitors, other anti-wear additives, and the like.
• The present invention is further illustrated by the Examples which follow.
EXAMPLE 1
• This Example sets forth the wear data at various temperatures and loads (Four-Ball Wear scar at 600 rpm for two hours, two runs) for a control polyphenylene ether fluid and similar fluids containing certain bisphosphate additives:

  

  
• All three of the bisphosphate additives tested showed good performance in the Four-Ball wear test.

  
• The above data illustrate the poorer performance for the neopentyl glycol bis(diphenyl phosphate) additive ("NGBDP") as compared to either the bisphenol A or resorcinol derived bisphosphates ("BABDP" and "RBDP", respectively).
• The foregoing Examples should not be construed in a limiting sense since they merely serve to illustrate certain embodiments of the invention. The scope of protection sought is set forth in the claims which follow.

Claims (6)

1. A polyphenylene ether lubricant which comprises a polyphenylene ether base stock and an effective anti-wear amount of a hydrocarbyl bis(dihydrocarbylphosphate) compound.
2. A lubricant as claimed in Claim 1 wherein the compound is a bis(diphenylphosphate).
3. A lubricant as claimed in any one of Claims 1-2 wherein the hydrocarbyl group is derived from a monoaromatic diol.
4. A lubricant as claimed in any one of Claims 1-3 wherein the amount of the compound is from about 0.1% to about 10%, by weight of the lubricant.
5. A lubricant as claimed in Claim 1 comprising from about 0.1% to about 10%, by weight, of resorcinol bis(diphenylphosphate).
6. A lubricant as claimed in Claim 1 comprising from about 0.1% to about 10%, by weight, of hydroquinone bis(diphenylphosphate).