US2323360A - Transmission oil - Google Patents

Description

mission gears.

Patented July 6, 1943 TRAN SDHSSION OIL Joseph S. Wallace, Whiting, Ind., assignor to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Application July 1, 1941, Serial No. 400,657

3 Claims.

The present invention relates to gear lubricants, and more particularly to transmission oils.

In the past various kinds of oils and oil containing compositions have been used for trans- However, with the advent of automatic transmission gears it has been necessary to improve the properties of the gear lubricants to a considerable extent. Whereas previously, the extreme pressure properties of the oil were of the utmost importance it is now essential to provide an oil having a high viscosity index and a low pour point as well. To obtain these addi tional qualities gear lubricants are at present prepared by admixing a heavy mineral oil having a viscosity index approaching that desired in the gear lubricant, an extreme pressure agent and a pour depressant to obtain the low pour point. Such lubricating compositions-have a viscosity index of from about 70 to about 100 and a pour point from l5 F. to F. Usually, however, it is difficult to obtain a low pour point when using an oil of desired viscosity having a high viscosity index. These lubricating compositions present various difficulties which seriously interfere with the proper lubrication of gears. The heavy oils used are susceptible to oxidation and give products which have little or no lubricating value.

It is an object of the present invention to pro-' vide a lubricant which avoids the above-mentioned difficulties. A further object is to prepare a gear lubricant which is not easily oxidized and therefore retains its lubricating properties.

Still another object of the present invention is to provide a lubricant which meets rigid specifications as to pour point, flash point, fire point, viscosity, extreme pressur properties, color and the like which, at the same time, is highly resistant to oxidation and carbon formation and has a high viscosity index.

According to th present invention the gear lubricant contains a comparatively light petroleum oil, an extreme pressure agent and a high molecular weight hydrocarbon oil. The latter component, because of its high molecular weight, appearance and physical characteristics is sometimes referred to as a resin or a resinous oil" even though its chemical characteristics are far different from those materials more commonly and more properly known as resins. In order to distinguish the high molecular weight oil more clearly from the comparatively light petroleum oil in the following description, the former will be referred to hereinafter as a resin-like oil.

While light petroleum oils of differing characteristics may be used, depending on the nature and properties desired in the final product, it has been found that from about to about of an oil having a viscosity of from about 70. seconds Saybolt Universal at F. to about seconds Saybolt Universal at 100 F. and a viscosity index of less than 50 is suitable. Various types of extreme pressure agents, such as sulfurized sperm oil, sulfurlzed fatty oils, sulfurized fat, sulfurized isobutylene polymers, and other sulfur-containing extreme pressure agents may be usedin quantities ranging from about 1% to about 15% of the total composition.

The resin-like oil has a molecular weight of from about 1000 to about 2000 and may be added in quantities ranging from about 10% to about 30% but preferably from about 17% to about 20% of the composition. This resin-like oil may be obtained preferably from a Pennsylvania cyl-' inder stock which has been dewaxed at about -40 F. The dewaxed stock is then treated with four to ten volumes of propane at a temperature from about F. to about F. to produce two phases, a lighter propane-soluble phase and aheavy propane-insoluble phase containing the resin-like oils. The heavy fraction is then treated with additional propane at from 135 F. to 155 F., usually about 145 F., the ratio of propane to heavy oil being from about 5 to l to about 10 to l, and usually about '7 to 1. By this treatment about 3% to about fil /2% of the resin-like oil based on the original amount of dewaxed oil precipitates out from the propane-soluble constituents of the heavy oil. Although propane has been referred to as the refining agent it will be understood that the propane may contain or be replaced by other normally gaseous hydrocarbons, particularly ethane, isobutane, butane, propylene, butylene, etc. This resin-like oil is a substantiall wax-free and asphalt-free product having a Saybolt Universal viscosity at 210 F. of from about 1000 to about 4000 or more seconds, a viscosity index of about 90 or more and a relatively high pour point. The characteristics of a specific example are as follows: I

Gravity=A. P. I. 16.7 Flash point=615 F. Fire point=720 F.

Viscosity at 210 Ff=2910 seconds Saybolt Universal Viscosity index=95 Pour point (natural) =60 F.

mixed base oil such as Mid-Continent. Obviously in this case it would be necessary to deasphalt as well as dewax theoil before precipitation of the resin-like oil. When a Mid-Continent oil is used the asphalt maybe removed by treatment with propane at temperatures of from 105 F. to 115 F.. the oil-propane ratio being about 1 to 2.

A more detailed description of the process for obtaining the'resin-like oil will be found in U. 8. Patents 2,143,872 and 2,143,882.

An example of a transmission oil according to the present invention contains:

Oil (viscosity of 85 seconds at 100 F., V. 1.

less than 50 and 300 F. min. flash) '73 Resin-like 17 Sulfurized sperm oil A lubricant having the foregoing composition has the following properties and characteristics:

Almen failure (extreme pressure) Passes maximum 30 lb. load Copper strip (3 hrs. at 200 F.) No corrosion Heating test (125 hrs. at 200 F.)

Evaporation loss per cent 0.9 Residue ppt, None vis. incr. at 210 F 31% decrease Vis. incr. at 130 F .5% decrease It will be noted that this lubricant has an exceedingly high viscosity index, excellent extreme pressure properties and low pour point. In Table I below, the characteristics of three transmission oils without'the resin-like oil are compared with a lubricant according to the present invention.

Per cent:

Saponifiable oil -per cent 7.6 Added sulfur do 1.1 Total sulfur M 2.2 Flash point F 320 Fire poi 9 IL- 370 Pour point (shock chilling) 1 25 S. U. vis. at 210 F 58 8. U. vis. at 130 F 176 S. U. vis. at 100 F 365 Viscosity index 108 Ash --per cent 0.015 Moisture do Trace The characteristicso'f base oils Nos. 1 to 4 inclusive are given in the following Table II:

Tana: II-

' Characteristics of base oils on Viscosi Visoosit Viscosity Pour at 100 at 210 index point F. 31: 48 Below to o 314 so on +15 ass as. a 92.4 0 as as. 0 Below to 25 The pour depressant referred to in the above Table I is of the type obtained by the condensation of a halogenated long chain aliphatic hydrocarbon such as chlorinated parafiln wax, with an aromatic hydrocarbon such as naphthalene in the presence of a Friedel-Crafts catalyst such as aluminum chloride. It is' clearly evident from Table I that whenever an eifort was made to improve the viscosity index of the lubricant, the pour point rose above the minimum requirement. However,

the lubricant containing the resin-like oil and without a pour depressant not only gives an excellent viscosity index but also meets the maximum pour point requirements.

With reference to the present invention attention is called tothe application of Claron N. White and Frederick H. MacLaren filed June 30, 1941, Serial No. 400,460, entitled Lubricants.

Although the present invention has been described with reference to specific examples, these are not to be construed as limitations. The scope of the present invention is defined by the appended claims.

V I claim: Y 1. An extreme pressure lubricant suitable for use as a transmission lubricant containing from about 55% to about of a mineral lubricating oil having a relatively low viscosity index anda viscosity of from about 70 to about 150 seconds Saybolt Universal at F., from about 1% to about 15% of a sulfur-containing extreme pressure agent and from about 10% to about 30% of a resin-like oil obtained by treating a substantially asphalt-free, wax-free lubricating oil stock with a liquefied normally gaseous hydrocarbon to effect a phase separation of a light fraction soluble in said liquefied hydrocarbon and a heavy fraction containing the resin-like oil insoluble in said liquefied hydrocarbon, and precipitating the resin-like oil from said heavy fraction by treating said heavy fractionwith further amounts of the liquefied normally gaseous hydrocarbon.

2. An extreme pressure lubricant suitable for use as a transmission lubricant as claimed in claim 1 wherein the percentage range of resinlike oil is from about 17% to about 20%.

3. An extreme pressure lubricant suitable for use as a transmission lubricant as claimed in claim 1 consisting of 73% of the mineral lubricating oil, 10% of sulfurized' sperm oil and 17% of the resin-like oil.

JOSEPH B. WALLACE.