US2313248A - Sulphur containing lubricant - Google Patents

Description

Patented Mar. 9, 1943 UNi'I'E SULPHUR CONTAINING LUBRICANT Delaware No Drawing. Application January 12, 1940, Serial No. 313,604

Claims.

Our invention relates to sulphur containing lubricants and more particularly to a lubricant containing a sulphur bearing addition agent, substantially noncorrosive to the newer types of. bearing metals now used in present day automotive vehicles.

, This application is a continuation in part of our copending application Serial No. 205,531, filed May 2, 1938, now Patent 2,218,132, dated October 15, 1940.

Automotive engineers are using bearings containing cadmium and copper-lead mixtures as well as high lead content compositions. These new bearing compositions, while possessing certain mechanical advantages over the old tin-babbitt bearings, are more susceptible to corrosion. Oxidation and decomposition products of the lubricant react with these bearings and often cause failure through corrosion.

One object of our invention is to provide a lubricant containing a new type of sulphur compound which will impart increased film strength to the lubricant while being substantially noncorrosive to the new type bearing metals.

Another object of our invention is to provide a sulphur containing addition agent which is at once a film strength improver and a corrosion inhibitor.

Another object of our invention is to provide a lubricating oil containing a sulphur bearing addition agent which will reduce oxidation, with the resultant sludge and acid formation.

Another object of our invention is to provide a lubricant having-increased oiliness characteristics and color stability.

Other and further objects of our invention will appear from the following description:

In general, our invention comprises the addition of small quantities of sulphurized olefins of high molecular weight to hydrocarbon oils. By sulphurize, we mean the process of combining the olefins described below with sulphur or various sulphur compounds such as sulphur chlorides, phosphorus pentasulphide, phosphorus trisulphide, and similar compounds. As little as 0.01 of one per cent of these new sulphurized compounds, added to a lubricant, appreciably increaseits resistance to oxidation and corrosiveness. As much as per cent of these sulphurized compounds may be added to a lubricant with beneficial results with respect to its film strength and oiliness properties, although it is seldom that more than two per cent need be used for-.a crankcase lubricant. A lubricant containing from two to twenty per cent makes an admirable cutting oil or an extreme pressure lubricant.

To obtain our sulphurized olefins of high molecular weight, we start with a substantially oilfree paraflin wax. By way of example but not by way of limitation, we shall describe the method of obtaining our addition agent from a low melting point wax of from 18 to 24 carbon atoms. The wax is halogenated to a halogen content of 8 to 12 per cent. The crude halogenation mixture will comprise some unchlorinated wax, mostly monochlor wax and some dichlor or more highly chlorinated waxes. Chlorination of wax lowers its melting point stepwise inversely as the degree of chlorination. A monochlor wax will melt lower than the like unchlorinated wax. A dichlorinated wax will have a .lower melting point than the monochloro wax. The unchlorinated wax may be separated readily from the crude chlorination mixture by melting point differences, using sweating or selective solvent extraction at various temperatures.

A solution of the crude chlorination mixture may be formed with acetone. At about F., the chlorinated waxes will be in solution, while the unchlorinated wax will not dissolve and may be separated by settling, centrifuging, or filtering. The solution may be chilled to precipitate the monochloro wax; thus the monochloro wax may be separated from the polychloro wax employing the same methods as those outlined for separating unchlorinated wax from the chlorinated wax mixture.

The monochlor wax thus obtained is substantially free of unchlorinated waxes or more highly chlorinated waxes and may be converted to the corresponding olefin by removing the chlorine as hydrogen chloride, thus producing a double bond or an olefin. To prepare the olefin, the monochlor wax may be heated for a period of one minute or less to five hours, with one tenth of its weight or more of lime or other dehalogenating agent, at temperatures between 200 F. and 550 F. The olefin may be formed by removing the hydrogen chloride by heating alone or by other methods, although the color of the resulting olefin may be darker than when lime is used. After dehalogenation, the lime or other dehalogenating agent is removed from the resulting olefin by the usual means, such as by filtering.

The theoretical iodine value for an olefinic hydrocarbon having the formula CzsHso is 72.6. The iodine value of the olefin prepared as described is about 72.

It should be pointed out that olefin as made as described is a definite type of compound having the structure When prepared from a paraffln wax, R1 is an aliphatic group containing 1 to about 20 or more carbon atoms. The sum of the two Rs" should be between and 60 carbon atoms. When the olefin is prepared from a wax, a high boiling mineral oil, or mixture of wax and mineral oil, a specific type of structure is always obtained and may include carbocyclic groups on large aliphatic radicals. In sulphurizingthis type of compound, the sulphur adds on to the double bond; and none is substituted for hydrogen, as is proved by the fact that in the sulphurization practically no His is formed. This fact makes it possible to prepare a. definite type of sulphur compound in contrast to the heterogeneous mixture which is obtained when a cracked petroleum derivative containing many types of unsatunates is sulphurzed. The advantages of the former because of its relative purity are obvious.

The process substantially as described above may be practiced using aliphatic hydrocarbons whose monochloro derivatives melt lower than the hydrocarbons themselves. Many naturally occurring waxes are amenable to the same process including carnauba wax, candelilla wax, beeswax, and the like.

In the dehalogenation process as described, it is sometimes desirable to remove only part of the chlorine so that the residual product after sulphurizing will contain residual chlorine from this source. It may even be desirable in some cases to use a less highly prified high molecular weight olefin such as obtained by partially or completely dehalogenating the mixtures of chlor waxes obtained by simply dewaxing the chlorination mixture. This will remove the unhalogenated wax from the mixed chlor waxes, which are then dehalogenated and sulphurized; furthermore, chlorine may 'be introduced into the material after sulphurizing if desired.

One hundred parts of the olefin are chemically combined with 10 to parts of sulphur chloride (or phosphorus pentasulphide, phosphorus trisulphide, or the like). This is accomplished by heating and stirring at temperatures up to 300 to 360 F. Amounts of sulphur compounds and temperatures outside the given ranges may be used with less satisfactory results. The heating is continued until all of the sulphur has chemically combined. A copper strip test on aone per cent blend in gasoline or mineral oil, for example, giving a good color will indicate when the reaction has been completed. Improved results are obtained by first mixing the olefin with about an equal volume of refined mineral oil before sulphurizing. The sulphurized olefin thus prepared is now ready for use in a variety of lubricants such as gear lubricants, extreme pressure lubricants, and cutting oils. It is merely blended with a suitable base oil in proportions of 0.05 to per cent or more, depending on the amount of sulphur required in the lubricant. These blends yield superior lubricants compared with the corresponding blends made from the well-known sulphurized fatty oils, in that they contain no glycerine either free or in combination. Glycerine compounds in a lubricant are prone to cause gumming of mechanical parts and are less stable than the sulphurized olefin lubricants. A further important superiority of the latter is the relativeiy low viscosity of the blends at low temperatures compared with the viscous blends that result when sulphurized fatty oils or glycerides are used. We are aware of .prior art which describes lubricants containing sulphurized unsaturated hydrocarbons irom the cracking of mineral oil. In said art, a conglomerate mixture of compounds containing some unsaturates is sulphurized. It is unlikely that any high boiling olefins are present in this mixture, since it consists of a cracked product; and most, if not all, of the unsaturates would thereiorebe cyclics. On sulphurizing these, some sulphur will enter into chemical combination by hydrogen substitution, which is objectionable. The unsaturated, double bonds in a cracked product are not of equal chemical activity; therefore there, cannot be an even distribution of sulphur throughout its mass, which is very highly undesirable. In our invention, -we sulphurize a relatively pure olefin and obtain a relatively pure compound having constant, definite, and predictable properties. Our product readily lends itself to refining. It does not contain any objectionable components after refining.

When the sulphurized olefin is to be used as an inhibitor in a crankcase lubricant for protection of the new type bearings, it may be first refined. The sulphurized olefin should be treated to remove the usual traces of H28 present. This may be done by blowing with an inert gas or other suitable means. (Unremoved H2S is oxidized in the subsequent acid treat to free sulphur and gives a product which will darken a copper strip.) The olefin (or blend of olefin in mineral oil) is contacted with .5 to 3 .per cent by weight of per cent sulphuric acid for 5 to 30 minutes at to F. The sludge is allowed to settle thoroughly, and the treated product is transferred to a clean container and neutralized with fuller's earth or the equivalent, such as activated carbon, bauxite, lime, or caustic at temperatures between 200 and 275 F. for 5 to 10 minutes. The mixture is filtered to remove the neutralizing agent. The finished product has a color of about 3 A. S. T. M., is odorless, and when blended with a lubricating oil does not afiect the color or Lille emulsion test as do the sulphurized glycer- The sulphurized olefin does not affect the A. S. T. M. copper strip test of blends in lubricants even when run for 30 minutes at 210 F. The addition of .05 per cent to two per cent of this sulphur compound to a lubricating oil gives a lubricant which is practically free of any tendency to corrode the new type bearings, as determined by the Underwood corrosion test.

The manner in which this inhibitor stops corrosion is not known, but the following theory gives a fairly satisfactory explanation. It is a fact that some metallic oxides and soaps have a. strong catalytic efiect on the oxidation of mineral oil, which in turn gives rise to the formation of corrosive organic compounds; furthermore, it is known that the metallic sulphides are insoluble in mineral oil. It is assumed, therefore, that as soon as any metals, such as iron from the engine and copper, lead, or other metals from the bearings, start to corrode, they form the relatively inert sulphides instead of the active oxides and soaps, thus slowing down the rate of oxidationof the lubricant. It is obvious then that a sulphur compound to be a good inhibitor must not be too stable or itemnot give up sulphur at a rate equal to the lubricants tendency to form oxidation products and soaps; furthermore, it must not be too unstable or it will give up too much sulphur and cause corrosion from the action of free sulphur, which would first manifest itself in the darkening of copper parts. The sulphurized olefin of our invention has just the correct degree of stability, since it inhibits corrosion but does not darken the copper-lead bearings.

The sulphurized olefin does not only stop corrosion of the new type bearings, but it also reduces the amount of oxidation of the oil.

In. practicing this invention, the relatively pure mono-olefin which is obtained from the relatively pure mono-chlor wax is sulphurized as was stated previously; however the olefins, diolefins, and polyolefins resulting from the dehalogenation of dichlor and polychlor wax or mixtures thereof with each other and unchlorinated wax may be used with some degree of success in preparing a sulphur base for use in a cutting oil, gear lubricant, extreme pressure lubricant, etc.; but they are not so satisfactory for crankcase lubricants because of the difficulty of refining them.

Our olefins are characterized by the fact that considerably more sulphur (a total of 20 per cent or more) can be made to combine with them by using temperatures up to 450 F. than is obtained by saturating them at 300 to 360 F. with sulphur. This holds true for the mono-olefins as well as for the polyolefins. Prepared this way, they are able to hold in solution additional percentages of elemental sulphur. A sulphur base of this type is well suited for use in cutting oils, .etc. The olefins may be treated with varying quantities of the different sulphurizing agents until the olefin contains per cent of sulphur by weight or a little less. Usually from 8 to 18' per cent of sulphur is found very satisfactory.

The sulphurized olefins described in this invention may be blended with any mineral, synthetic, animal, or vegetable oil to improve resistance to oxidation, with its attendant increase in sludge formation and tendency to corrode metals.

By oil of lubricating viscosity in the appended claims, we mean to include any of these types of oils or mixtures thereof.

It is to be understood that the examples hereinabove given are by way of illustration only and not by way of limitation and that the theories advanced with regard to the action of our sulphurized olefins are our conception of what takes place. We do not wish to be bound by the theories but base our claims upon the improved results which are obtained.

It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of our claims. It is further obvious that various changes may be made in details within the scope of our claims without departing from the spirit of our invention. It is therefore to be understood that our invention is not to be limited to the specific details shown and described.

Having thus described our invention, we claim:

1. -A lubricant comprising a major proportion of an oil of lubricating viscosity and a minor proportion of a chlorine bearing relatively pure, sulphurized olefin having a sulphur content between 5 per cent and 18 per cent.

2. A lubricant comprising an oil of lubricating viscosity and 0.05 to 2 per cent of chlorine-bearing sulphurized relatively pure olefin having a sulphur contact between 5 per cent and 18 per cent.

3. A lubricant comprising an oil of lubricating viscosity and from 2 to 20 per cent of a chlorinebearing relatively pure, sulphurized olefin having a sulphur content between 5 per cent and 18 per cent.

4. A lubricant comprising a major proportion of an oil of lubricating viscosity and a minor proportion of a chlorine-bearing sulphurized olefin, said olefin having the structure R o=c n 1 1 n in which R represents an aliphatic group containing between 1 and 20 carbon atoms, said sulphurized olefin having a sulphur content between 5 per cent and 18 per cent.

5. A lubricant comprising a major proportion of an oil of lubricating viscosity and a minor proportion of a chlorine-bearing relatively pure, sulphurized olefin having a sulphur content between 5 per cent and 18 per cent, said olefin being prepared by dehalogenating a monochloro petroleum derivative of 10 to carbon atoms by means of heating said monochloro derivative with a basic compound to temperatures of 200 F. to 550 F.

BERT H. LINCOLN. WALDO L. STEINER. GORDON D. BYRKIT.