EP0032281B1

EP0032281B1 - A process for making an extreme pressure lubricating oil additive

Info

Publication number: EP0032281B1
Application number: EP80300128A
Authority: EP
Inventors: Andrew George Papay; Joseph Peter O'brien
Original assignee: Edwin Cooper Inc
Current assignee: Edwin Cooper Inc
Priority date: 1980-01-15
Filing date: 1980-01-15
Publication date: 1984-04-04
Also published as: EP0032281A1; DE3067302D1

Description

Sulfurized olefins are well-known additives in lubricating oil, cutting oil and the like. U.S. Patent Specification No. 2,249,312, describes such a product. U.S. Patent Specification No. 2,708,199, describes a similar product in which a sulfur halide is reacted with an olefin using a lower alkanol promoter to obtain an intermediate which is reacted with an alkali or alkaline earth metal polysulfide. U.S. Patent Specification No. 3,471,404, describes a product in which sulfur monochloride is reacted with olefin to obtain an intermediate which is reacted with sulfur and alkali metal sulfide at a critical ratio of 1.8 to 2.2 gram moles of metal sulfide per gram mole of sulfur. This material is then typically refluxed for 1 to 24 hours with aqueous alkali metal hydroxide (in general terms, "reacted with an inorganic base").
GB-A-1308894 describes a method of sulfohalogenating olefins with a sulfurhalide in the presence of a catalytic quantity of a lower aliphatic alcohol to form a sulfohalogenated organic intermediate and thereafter sulfurising and dehalogenating the intermediate by treatment with an aqueous alkali metal monosulfide solution.
According to the present invention an improved sulfurized olefin additive for lubricating oil may be obtained by reacting sulfur monochloride with C_a-C₆ aliphatic monoolefin to form an adduct which is then reacted with sulfur and sodium sulfide, using from 0.1 to 0.4 gram atom sulfur per gram mole of sodium sulfide, and then recovered by conventional methods without the need for further treatment with aqueous inorganic base (caustic).
Thus, the invention provides a process for preparing a sulfurized lubricating oil additive for imparting extreme pressure properties to lubricating oil which process comprises (a) reacting sulfur monochloride with a C₃-C₆ aliphatic monoolefin to produce an adduct, (b) reacting the adduct produced in (a) with sulfur and sodium sulfide in an aqueous alkanol medium using from 0.1 to 0.4 gram atom of sulfur per gram mole of sodium sulfide, and (c) recovering the additive resulting from (b) without heating with aqueous caustic.
A preferred embodiment of this invention is the process consisting essentially of (a) reacting S_ZCI₂ with a C_a-6 aliphatic monoolefin at 30 to 100°C. to produce an adduct, (b) reacting said adduct with sulfur and Na_ZS in an aqueous alkanol medium at a temperature of from 50°C up to reflux using 0.1 to_'. 0.4 gram atom of sulfur per gram mole of Na₂S and then (c) recovering said additive without "treatment with an inorganic base".
Useful olefins are the monoethylenically unsaturated aliphatic hydrocarbons referred to as aliphatic monoolefins containing 3 to 6 carbon atoms. These include 1-butene, 2-butene, isobutene, 1-pentene, 2-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 2-methyl-2-butene, 1-hexene, 2-hexene, 3-hexene, 2-methyl-1-pentene, 2-methyl-2-pentene, 2-ethyl-2-butene and the like, including mixtures thereof.
Preferably the olefins are branched-chain olefins such as isobutene, 2-methyl-1-butene, 2-methyl-2-butene, 2-methyl-2-pentene and the like. More preferably the ethylenic double bond adjoins a tertiary carbon atom such as isobutylene, the most preferred olefin.
The first stage reaction is preferably conducted by adding the olefin to the sulfur monochloride. The olefin can be added as a gas or liquid. Preferably it is added beneath the surface of the sulfur monochloride as a liquid.
In practice the olefin is added until the reaction with the sulfur monochloride stops as indicated by loss of exotherm. An amount of from 0.75 to 2.0 gram moles of olefin for each 0.3 to 0.75 gram mole of sulfur monochloride usually suffices. A preferred amount is 1.8 to 2.2 gram moles of olefin per gram mole of sulfur monochloride.
In the reaction between sulfur monochloride and the olefin, the use of an alkanol promotor is preferred. In the present process use of such a promoter can give products having significantly better EP (extreme pressure) properties.
The lower alkanol promoter used in the first stage contains from 1 to 4 carbon atoms such as methanol, ethanol, n-propanol, isopropanol, isobutanol, tert-butanol and the like. The most preferred promoter is methanol.
The lower alkanol promoter can be added to the sulfur monochloride initially, added to the reaction mixture continuously or periodically during the course of the olefin addition or the alkanol can be mixed with the olefin and added together with the olefin. The preferred modes of addition are to either add the entire amount initially and then add the olefin or to concurrently add both alkanol and olefin.
The amount of alkanol promoter is preferably of from 0.001 to 0.3 gram moles for each 0.3 to 0.75 gram mole of sulfur monochloride.
The first stage reaction can be conducted at any temperature high enough to cause the reaction to proceed, but not so high as to cause decomposition of the reactants or products. A useful range is 30 to 100°C. A more preferred range is 40 to 75°C and a most preferred range is 50 to 60°C.
The first stage reaction should be conducted for a time sufficient to complete the reaction between sulfur monochloride and olefin. This is usually limited by heat removal. Olefin feed rate is preferably controlled to hold the temperature within the desired range. When the sulfur monochloride has been consumed the temperature will drop. External heat may be added to continue the reaction for a further time, but this does not appear to be necessary. The overall time required to complete the reaction depends upon the scale of the process and can vary from a few minutes up to 12 or more hours. The time is not critical.
During the first stage reaction, HCI gas is evolved so means should be provided to scrub the vent gas from the reactor to remove HCI prior to releasing it to the atmosphere.
In the second stage reaction, adduct from the first stage is reacted with sodium sulfide and sulfur in an aqueous alkanol reaction medium. The second stage is preferably carried out by charging aqueous sodium sulfide, water, alkanol and elemental sulfur flowers to a reactor and then adding the adduct to this at reaction temperature.
The sodium sulfide may be obtained from any of a number of sources. For example, it can be made by mixing approximately equal mole amounts of sodium hydrosulfide and sodium hydroxide. If hydrogen sulfide is available, it can be adsorbed in aqueous NaOH to form a solution of sodium sulfide and/or sodium hydrosulfide depending upon the amount of hydrogen sulfide adsorbed. Whatever the source, the resulting solution should be adjusted with either NaOH, NaSH or H₂S so that the resulting solution consists mainly of sodium sulfide with little or no free sodium hydroxide.
The amount of sodium sulfide can vary somewhat. For example, from 0.45 to 0.7 gram mole for each 0.3 to 0.75 gram mole of sulfur monochloride used in the first reaction stage. Preferably the amount of sodium sulfide is 0.7 to 2 gram mole per mole of sulfur monochloride and most preferably 0.8 to 1 gram mole per gram mole of sulfur monochloride. What is essential is that from 0.1 to 0.4 gram atom sulfur be used per gram mole of sodium sulfide.
The amount of water can vary widely without detrimental effect. Good results can be obtained using 10 to 20 gram moles of water per gram mole of sodium sulfide. This includes water added as such, water in aqueous reactants and water which might be formed by reaction of hydrogen sulfide or sodium hydrosulfide with sodium hydroxide in forming sodium sulfide solution.
Alcohol is required in the second stage reaction. Preferably, these are lower alkanols containing 1 to 4 carbon atoms such as methanol, ethanol, n-propanol, n-butanol, isobutanol, tert-butanol and the like, including mixtures thereof. The preferred alkanol is isopropanol either alone or mixed with other alkanols such as tert-butanol.
The amount of alkanol can likewise vary over a wide range. A useful range is 0.1 to 0.5 parts by weight per each part by weight of water. A more preferred range is 0.2 to 0.4 parts by weight alkanol per each part by weight water.
Preferred amounts of sulfur and sodium sulfide in the second reaction are 0.05 to 0.18 gram atom of sulfur and 0.45 to 0.7 gram mole of sodium sulfide. It is also preferred that 0.1 to 0.25 gram atom of sulfur be used per gram mole of sodium sulfide.
In a preferred mode of operation the mixture of sodium sulfide, sulfur and aqueous alkanol is stirred and heated to reaction temperature and then the adduct is added to it. However, the reaction can be carried out in other ways such as by adding the sodium sulfide, sulfur and aqueous alkanol mixture to the adduct or by mixing everything together and heating the mixture.
The preferred second stage reaction temperature is 50°C. up to reflux temperature. A more preferred reaction temperature is 60 to 80°C.
The preferred second stage reaction temperature is 50°C. up to reflux temperature. A more preferred reaction temperature is 60 to 80°C.
After the adduct has been added to the sodium sulfide/sulfur/aqueous alkanol mixture, which is usually completed in 1 to 8 hours, the mixture is preferably heated to reflux for 2 to 8 hours to assure completion of the reaction.
An essential feature of the new process is that an additive made according to the foregoing disclosure needs no further caustic treatment in order to obtain a useful EP additive. Accordingly, the present invention does not contemplate a process in which the product is subsequently heated with aqueous inorganic base (caustic) solution such as is disclosed in U.S. Patent Specification No. 3,471,404.
After reaction of the adduct with sodium sulfide and sulfur, the product may be recovered by conventional methods such as removing alkanol, water washing and filtering.
The following Example illustrates the invention.

Example

In a reaction vessel place 77.7 grams of sulfur monochloride and 0.31 grams of methanol. While stirring start adding liquid isobutylene below the surface to bring the temperature up to 55°C. Continue adding isobutylene at this temperature until the exothermic reaction stops. This requires 28 to 32 grams of isobutylene.
In a second reaction vessel mix 90 grams of 32.1 weight percent aqueous sodium hydrosulfide and 41.3 grams of 50 weight percent aqueous sodium hydroxide. To this add 44.4 grams of isopropanol and 2.9 grams of sulfur flowers. Stir for 5 minutes and then add 55.1 grams of water and heat the mixture to 75°C. Over a 2-hour period add the first stage adduct to this mixture while stirring at about 75°C. Following this, heat the mixture to reflux for 4 hours to complete the reaction.
Distill out isopropanol up to 90°C and then reduce pressure to complete removal of alcohol and most of the water. Wash the product with 68 grams of water to remove salt and separate off the aqueous layer. Wash the organic phase a second time with a mixture of 68 grams of water and 34 grams of hexane. While stirring, heat this mixture to reflux and then cool and allow to separate. Remove and discard the aqueous phase and distill hexane from the organic phase. Filter the resultant material to obtain a sulfurized olefin (48 weight percent sulfur) which is a very effective EP additive in lubricating oil.
The sulfurized olefin additive made by the present invention are especially useful in lubricating oil formulations used in gear applications. The base oil may be a mineral oil or a synthetic oil. Useful synthetic oils include olefine oligomers such as decene trimer, tetramer and pentamer made by oligomerizing 1-decene using a BF₃ catalyst. Useful olefin oligomers can be made using other catalysts such as the aluminum alkyl Ziegler catalyst. Likewise, other olefins can be used such as C,_-14 1-otefins.
Synthetic alkylbenzenes can also be used such as di-dodecylbenzene and the like.
Synthetic ester lubricating oil can also be employed such as the alkyl esters of dicarboxylic acid (e.g., di-2-ethyl-hexylsebacate), fatty acid esters of polyols (e.g., trimethylolpropane, tripelargonate) or complex esters of alkanols, alkane, polyols and carboxylic or polycarboxylic acid.
In this use the sulfurized olefin is added to an amount sufficient to improve the EP property of the lubricant. An amount of 0.1 to 10.0 weight percent is usually sufficient.
Fully formulated gear lubricants include other conventional additives which perform various functions. Examples of such other additives are corrosion inhibitors for ferrous and non-ferrous metals such as tetrapropenyl succinic acid and bis-(2,5-alkyldithia)-1,3,4-triadiazoles, and antiwear additives such as alkyl or aryl phosphonates, phosphite, thiophosphates, dithiophosphates, and phosphoric acids. Also zinc dialkyl or diaryl diethiophosphate, chlorinated hydrocarbons, sulfurized fatty esters and amines.
Tests have been conducted which demonstrate the EP effectiveness of the sulfurized olefin made by the invention. In thse tests an additive made essentially as in the example was compared to the product made according to Myers, US-A-3,471,404. The two products analyzed as follows:
The tests were conducted in SAE 90 mineral oil. The first was a 4-ball weld test (ASTM D2783) in which a steel ball is rotated in loaded contact with three fixed balls. The maximum load without weld is recorded as the pass load.
A second test conducted was the SAE Load Test in which 2 steel rings are rotated under loaded contact such that there is metal slide at the contact point. The maximum load prior to metal seizure is determined.
The results of these tests were as follows:
These results demonstrate the unusual effectiveness of the additive made by the present invention.

Claims

1. A process for preparing a sulfurized lubricating oil additive for imparting extreme pressure properties to lubricating oil which process comprises (a) reacting sulfur monochloride with a C_a-C₆ aliphatic monoolefin to produce an adduct, (b) reacting the adduct produced in (a) with sulfur and sodium sulfide in an aqueous alkanol medium using from 0.1 to 0.4 gram atom of sulfur per gram mole of sodium sulfide, and (c) recovering the additive resulting from (b) without heating with aqueous caustic.

2. A process as claimed in claim 1, wherein the monoolefin is reacted with sulfur monochloride at a temperature of from 30 to 100°C in (a), the reaction of (b) being effected at a temperature of from 50°C up to reflux temperature.

3. A process as claimed in claim 2, wherein the monoolefin is a branched chain monoolefin.

4. A process as claimed in claim 3, wherein the olefin is isobutene.

5. A process as claimed in any one of claims 2 to 4, wherein the ratio of sulfur to sodium sulfide in (b) is from 0.1 to 0.25 gram atom of sulfur per gram mole of sodium sulfide.

6. A process as claimed in any one of claims 2 to 5, wherein from 0.75 to 2 gram moles of the olefin are reacted with from 0.3 to 0.75 gram moles of sulfur monochloride in (a) and the resulting adduct is reacted with from o.45 to 0.7 gra moles of sodium sulfide and from 0.05 to 0.18 gram atom of sulfur in (b).