US3702823A - Fluorosilicone lubricants containing 2-nitromesitylene - Google Patents

Abstract

MINOR AMOUNTS OF 2-NITROMESITYLENE ARE ADDED TO FLUOROSILICONE LUBRICANTS TO IMPROVE THE STEEL ON BRASS AND STEEL ON ALUMINUM ANTI-WEAR CHARACTERISTCS.

Description

United States Patent US. Cl. 252-496 6 Claims ABSTRACT OF THE DISCLOSURE Minor amounts of 2-nitromesitylene are added to fluorosilicone lubricants to improve the steel on brass and steel on aluminum anti-wear characteristics.

This invention relates to improved fiuoroalkylpolysiloxanes which contain minor amounts of Z-nitromesitylene. In one aspect the invention relates to fluorosilicone fluids exhibiting enhanced antiwear characteristics and superior thermal stability.

Organopolysiloxane fluids are known lubricants. Dimethylpolysiloxanes are general lubricants but have poor antiwear characteristics whenused to lubricate steel on steel sliding surfaces. Fluorosilicones, such as trifluoropropylmethylpolysiloxanes are much better lubricants for steel on steel but exhibit poor lubrication for steel on brass and steel on aluminum. Thus, the fluorosilicone fluids find only limited use in environments requiring lubrication of metal surfaces other than steel on steel.

By the practice of the present invention, the antiwear characteristics of fluorosilicones on steel on brass and steel on aluminum are greatly enhanced and the thermal stability is increased, thus rendering them suitable for high temperature lubrication of various metals.

In accordance with the invention, there are provided improved organosilicon compositions comprising of (a) 98 to 99.8 weight percent of an organopolysilxane fluid containing at least 30 mol percent units in which R; is a perfluoroalkylethyl radical of from 3 to 12 carbon atoms, and R is selected from the group consisting of lower alkyl radicals and the phenyl radical; any remaining units being of the formula R' SiO or in which R' is selected from the group consisting of monovalent hydrocarbon radicals and monovalent halohydrocarbon radicals; and (b) 0.2 to 2 weight percent 2- nitromesitylene.

As described above, R can be any perfluoroalkylethyl radical of no more than 12 carbon atoms, such as and the like.

R can be any lower alkyl radical containing from 1 to 6 inclusive carbon atoms, such as methyl, propyl, isopropyl, butyl and hexyl. R can also be a phenyl radical.

R can be any monovalent hydrocarbon radicals, such as alkyl radicals such as methyl, ethyl, propyl, isopropyl, butyl, pentyl, isopentyl, neopentyl, hexyl, octyl, dodecyl, octadecyl, 3 methylheptyl, 6 butyloctadecyl, tertiary butyl, myricyl and 2,2-diethylpentyl; alkenyl radicals such as, vinyl, allyl, hexenyl, butenyl, 3-octeny1, 4,9- octadecadienyl and 4-nonenyl; alkynyl radicals such as propynyl, heptynyl, butynyl, decynyl; alkenynyl radicals such as 1-penten-3-ynyl, 2-ethyl-l-buten-3-ynyl; cycloaliphatic radicals such as, cyclobutyl, cyclopentyl, cyclo- 3,702,823 Patented Nov. 14, 1972 hexyl, cycloheptyl, propylcyclohexyl, 2,4 dimethylcyclopentyl, cyclohexenyl, bicyclo-[3.1.0]hexyl, tricyclo- [3.2.1.1- ]-5-nonenyl, spiro[4.5]decyl, dispiro[4.1.4.2]- l-tridecenyl, decahydronaphthyl, 2,3-dihydroindyl and 1,2,3,4-tetrahydronaphthyl; aryl radicals such as phenyl, tolyl, xylyl, 3-ethylphenyl, xenyl, naphthyl, anthracyl, pentacenyl, 3,4-methylethylphenyl, 9,9'-bifluoryl and 4-mterphenyl; and aralkyl radicals such as 2-phenyl-octyl, S-methyl 2 (4-isopropylphenyl)heptyl, benzyl, Z-ethyltolyl, 2 ethyl p cymyl, diphenylrnethyl, 4,5 diphenylpentyl, Z-phenylethyl and 2-phenylpropyl.

Also included within the scope of R' are monovalent halohydrocarbon radicals, such as 'aliphatic groups such as chloromethyl, 3-chloropropyl, 3,3,3-trichloropropyl, perfiuorovinyl, chlorooctadecyl or radicals of the formula R CH CH where R, can be any perfluoroalkyl group such as trifluoromethyl, perfluoroethyl, perfluoroisobutyl, perfluoroheptyl or perfluorooctadecyl; aromatic groups such as dichlorophenyl, tetrabromoxenyl, tetrachlorophenyl, alpha,alpha,alpha-trifluorotolyl or iodonaphthy]; cycloaliphatic groups such as chlorocyclohexyl, bromocyclopentyl or chlorocyclohexenyl and aralkyl groups such as chlorobenzyl, beta-(ch1orophenyl)ethyl or beta- (iodophenyl)ethyl or beta- (bromophenyl)propyl.

The preferred monovalent hydrocarbon and halohydrocarbon radicals are those having no more than 18 carbon atoms. Especially preferred as R groups are lower alkyl radicals, the phenyl radical and Z-phenylpropyl radicals.

The above-described fiuoroalkylpolysiloxanes are fluids, generally having viscosity in the range of 20 to 20,000 cs. and include copolymers such as and the like.

Particularly preferred fluids are the triorganosilyl endblocked 3,3,3 trifluoropropylmethylpolysiloxanes having a viscosity in the range of about 20 to 1000 cs. when measured at 77 F.

7 The 2-nitromesitylene additive is a known compound and is commercially available from a number of sources. The compound can be depicted as CH; CH:

Only minor amounts of the additive, from 0.2 to 2 weight percent, preferably from 0.5 to 1.5 weight percent, are necessary to obtain the desired degree of lubricity. The optimum amount will depend upon the nature of the fluorosilicone and its application. Amounts greater than two weight percent can be used, but are generally uneconomical. W

Other additives can be utilized in the above compositions without departing from scope of the invention. Thus, the lubricating compositions of the invention may optionally contain corrosion inhibitors, extreme pressure agents, anti-oxidants, dyes and the like. The invention also contemplates the use of thickening agents in combination with the compositions to formulate improved greases. Thickening agents suitable for use in such a grease formulation include fatty acid soaps, carbon blacks, silica, clay, polytetrafluoroethylene and the like. The thickener should not be one that is reactive with the 2- nitromesitylene additive. The thickening agent will generally be present in an amount from about 10 to 60 weight percent of the grease compositions.

In addition to enhancing the antiwear properties of fluorosilicones, the 2-nitromestitylene increases the ther mal stability of the fluid. The weight loss at elevated temperatures of additive-containing fluids is significantly decreased. Because of this thermal stability, the compositions of the invention have utility as base stocks in fluorosilicone rubber formulations.

The following examples are illustrative and not intended to be limiting of the present invention which is delineated in the claims. In the examples, the lubricity characteristics were determined by means of the 4-Ball test. The 4-Ball tests were conducted on a Roxanna wear testing machine wherein a /2 inch diameter steel ball is rotated against three lubricated stationary /2 inch metal balls under various conditions and loads. After testing, the length and width of the scar on each stationary ball is measured and the average of the six measurements is taken as the wear scar diameter. The smaller the wear scar, of course, the better the lubricant.

EXAMPLE 1 Suflicient 2-nitromesityle'ne was mixed with trimethylsilyl endblocked 3,3,3 trifiuoropropylmethylpolysiloxane (300 cs.) to form a fluorosilicone composition containing 1.5 weight percent of the additive. The antiwear properties and thermal stability of this composition were compared to the properties of the pure polymer. Results are given below:

These data demonstrate the eifect of the additive on the steel on brass and steel on aluminum lubrication properties of fiuorosilicones. The additive also reduces the weight loss of fluorosilicones at elevated temperature. These effects are quite unexpected since they were not observed in other silicone lubricants, such as polydimethylsiloxane.

EXAMPLE 2 A fluorosilicone composition similar to that of Example 1 except that it contained only 0.5 weight nitromesitylene was tested as a lubricant for steel on alumi num. The wear scar after A: hour at 167 F., 1200 r.p.m. and 10 kg. load was 0.50 mm., showing that the additive is eifective at low concentrations.

EXAMPLE 3 Sufiicient Z-nitromesitylene was mixed with trimethylsilyl-endblocked fluorosilicone copolymer (60 mole percent CH SiO units and 40 mol percent CF CH CH (CH SiO units) having a viscosity of 288 cs. to form a composition containing 1.5 weight percent of the additive. The wear scar for steel on aluminum under the conditions of Example 2 was 2.1 mm., demonstrating that the additive is effective with copolymeric fluorosilicones.

That which is claimed is:

1. A composition consisting essentially of 98 to 99.8 weight percent of an organopolysiloxane fluid containing at least 30 mol percent units in which R, is a perfluoroalkylethyl radical of from 3 to 12 inclusive carbon atoms, and R is selected from the group consisting of alkyl radicals of no more than 6 carbon atoms and the phenyl radical; any remaining units being of the formula R' SiO or RESPO- in which R is selected from the group consisting of monovalent hydrocarbon radicals and monovalent halohydrocarbon radicals; and 0.2 to 2 weight percent of 2- nitromesitylene.

2. The composition of claim 1 wherein the organopolysiloxane is triorganosilyl-endblocked 3,3,3-trifiuoropropylmethylpolysiloxane having a viscosity of from 20 to 1000 centistokes at 77 F.

3. The composition of claim 1 where the organopolysiloxane is trimethylsilyl-endblocked 3,3,3-trifluoropropylmethylpolysiloxane.

4. The composition of claim 3 wherein the 2-nitromesitylene is present in an amount in the range of from 0.5 to 1.5 weight percent.

5. A lubricant comprising the composition of claim 1 containing sufficient thickening agent to form a grease.

6. The lubricant of claim 5 wherein the thickening agent is present in an amount in the range of from 10 to 60 weight percent, based on the total weight of lubricant.

References Cited UNITED STATES PATENTS 3,629,106 12/1971 Quaal et al. 25249.6 X

DANIEL E. WYMAN, Primary Examiner W. I. SHINE, Assistant Examiner U.S. Cl. X.R. 252-515 R, 403