US2790772A - Cutting oil composition - Google Patents

Description

, operations.

CUTTING OIL COMPOSITION Everett c. Hughes, Shaker Heights, and Harrison M. Stine, Lyndhurst, Ohio, assignors to The Standard Oil Company, Cleveland, Ohio, a corporation of Ohio No Drawing. Application May 19, 1954, Serial No. 430,972

2 Claims. (Cl. 252-45) The present invention relates to a cutting oil concentrate, cutting oils containing such a concentrate and characterized by a unique combination of superior cutting ability and absence of the formation of disagreeable odors when in use, and to a method of making the concentrate.

Oils containing sulfur or sulfur compounds dissolved therein have been suggested heretofore as cutting oils. Such oils also frequently contain chlorine and a.fatsuch as lard oil. It is believed that the sulfur, to be effective in improving the cutting ability of a cutting oil, must be 11 an active form, i. e., not bound to a carbon atom, which can react with metal being machined under the condition existing at the point of contact between the tool and the machined metal. Heretofore, the amount of active sulfur which could be incorporated into an oil has been dependent largely upon the solubility of free sulfur in the oil and upon the amount of sulfur which can be chemically combined but not bound to a carbon atom.

A great many suggestions have been made heretofore for increasing the active sulfur content of cutting oils. In some instances, these suggestions have resulted in oils having excellent cutting ability but poor odor characteristics and/or stability. In other instances, they have resulted in oils of acceptable odor but of poor cutting ability. Generally it has been found that some compromise must be made among odor, stability, and cutting ability factors, the cutting ability being improved with an increase in sulfur content at the expense, however, of odor and stability.

The odor characteristics of a cutting oil are not necessarily apparent upon an examination of the oil as produc'ed or supplied to a user. In many instances, odors are developed only when the oil is used in machining This is apparently due to the formation of odoriferous compounds under the conditions prevailing at the cutting tool. If the cutting oil develops an unpleasant or obnoxious odor during use, it makes no difference how good the oil is from the standpoint of cutting ability, i. e., the number of pieces that can be machined with a given tool, the wear on the tool and the surface finish of the metal being machined because machinists will refuse to work with it.

Hydrocarbon polysulfides containing one or more alkyl unpleasant door that is characteristic of the polysulfide itself rather than of a mercaptan impurity, since it cannot be altered by caustic washing, and diallyl tetrasulfide nited States PatentO 2 I which, because of its light yellow color, ready miscibility with mineral oil and very high sulfur content appeared very promising, was found to have a nauseating garlic odor. The few polysulfides in this group that do not possess such odors initially, almost without exception develop odors, upon use, that are or soon become so obnoxious as to cause machinists to walk off the job. in some instances the odors developed during use do not seem too unpleasant at first but for some reason become intolerable upon continued use due to a subtle accumulation of odors in high speed, automatic, multispindie machines, because of the large volumes of oil they require and the heat, violet agitation and splashing to which the oil is subjected.

lroposals to utilize aryl sulfides in cutting oils relate generally to those aryl sulfides in which a sulfur atom or a chain of sulfur atoms is substituted directly on the aromatic nucleus. Thus, for example, proposals have been made to utilize aryl sulfides, such as phenyl-, tolyl-, xylyl-, naphthyland anthracene sulfides in cutting oils without suggesting that there are any material differences among the many aryl sulfides that would make some of them less suitable than others.

It has also been proposed in the art to utilize in cutting oils aryl sulfides in which the sulfur atoms or chains of sulfur atoms are connected to the aromatic nuclei by methene or ethene groups. These proposals are limited, however,- to aryl sulfides in which one methyl group and, in one unsupported, purely prophetic proposal, two methyl groups, are substituted on the aromatic nuclei and in which the number of sulfur atoms is limited to two despite generalizations as to polysulfides. It appears to be generally believed in the art that in this more limited class or aryl sulfides, the monosulfides and disulfides are to be preferred over sulfides containing more than two sulfur atoms and the unsubstituted aryl sulfides are to be preferred over substituted aryl sulfides. This preference is apparently based on conclusions by some investigators that the lengthening of the sulfur chain and the substitution of alkyl groups on the aryl nuclei would both contribute to reducing the oilsolubility of such compounds and to making them solid rather than liquid at ordinary temperatures.

The surprising and unexpected discovery has now beenmade that it is feasible to prepare alkyl-substituted benzyl polysulfides, a term intended herein to include the various isomeric forms of trimethylbenzyl, methylethylbenzyl,

propylbenzyl and isopropylbenzyl polysulfides, as well as.

mixtures thereof, which contain ten carbon atoms in each alkyl-substituted benzyl group and are characterized by appreciably higher total and active sulfur content and molecular weight than has hitherto been considered possible. These compounds have the empirical formula CzoI-lzeS: and are characterized by the general formula R1SX-R2 in which R1 and R2 are alkyl-substituted benzyl radicals each having a total of ten carbon atoms and x is between about 4 and 5. R1 and R2 may be the same or different so long as each is a trimethylbenzyl, methylethylbenzyl, propylbenzyl or isopropylbenzyl radical. The compounds are liquid at room temperature,

readily soluble in cutting oil bases, substantially odorless, and have low volatility and excellent adherence to cutting surfaces at high temperature, all properties that are highly desirable in cutting oils and cutting oil concentrates.

ethyl-, proplyand isopropylbenzyl halides, with an excess of alkali-metal polysulfide and elemental sulfur at an elevated temperature. The reactants may all be mixed together and reacted in a single step. It is preferred, however, first to react one or more of the alkyl-substituted benzyl chlorides with. alkali-metal tetrasulfide to form alkyl-substituted benzyl polysulfides containing an average of at least about three and preferably about four sulfur-atoms per molecule. These polysulfides are highly useful, as cutting oil concentrates but are then preferably reacted with elemental sulfur to form alkyl-substituted benzyl, polysulfides containing an average of between about four and five, and preferably close to five, sulfur atoms per molecule.

'In accordance with one embodiment of the method of the invention, preferred because of the ready availability of the starting material, a catalytic reformate containing a mixture primarily of the various isomers of trimethylbenzene and methylethylbenzene is chloromethylated by .anysuitable means such as, for example, by reaction with formaldehyde, or a formaldehyde engendering material, and HCl in, the form of hydrochloric acid, hydrogen chloride gas, or both, for from about two to about seven hours at temperatures of the order of about l50 F. This reaction is advantageously carried out while stirring the reactants under a reflux and, after thereaction is completed to the extent desired, cooling the reaction mixture-to room temperature, separating the two'immisciblephases, washing theupper oily layer with water and separating the aqueous phase, washing the upper layer with sodium carbonate solution until the products are neutral, separating the layers, washing the products aglain with water and separating the layers, andfinally drying the'products with anhydrous calcium chloride. The organic reaction .product so obtained after removal of anyxylylene dichlorides formed, is a mixture, which may if desired be diluted with unreacted benzenes, of aromatic moriochlorides. These monochlorides are primarily the isomers of trimethylbenzyl chlorides having the formula (CHshCsHzCHzCl. Methylethylbenzyl chlorides having the formula CH3(C2H5)C6H3CH2C1, and propyland .isopropylb'enzyl chlorides having the formula (C3H7)CsH4CHaC1,may also be included.

, The mixture of aromatic monochlorides obtained in thisfr'nauner, or any oneor combination of alkyl-substituted beniyl halides containing ten carbon atoms from aiiyother source, is reacted at an elevated temperature of the order, of about 200 F., for several hours with an excess 'of'sodiurnltetrasul fide in the form of an aqueous solution, preferably with agitation under an inert atmosphere such asnitrogen. Upon cooling and settling, the reaction mixture forms an upper organic phase and a lower aqueous phase. The lower aqueous phase is separated and the remainder, i. e., the upper organic phase, is washed with an alkali-metalhydroxide solution. Upon separation of the alkali-metal hydroxide solution, high yields of alkyl-substituted benzyl polysulfides having ten carbon atoms in each benzyl radical and containing an average of at least about three and generally about four sulfur atoms per molecule are obtained. For convenitime, these are referred to herein as alkylbenzyl tetrasulfides. I

The reaction between the halides and alkalimetal tetrasulfide is preferably carried out in the presence of a diluent having a low viscosity and a highflash point. Hydrocarbon fractions having boiling points ranging from the kerosene to the fuel oil boiling ranges, generally designated as gas oil, are particularly suitable for this purpose. 'I'he'addition of a gas oil orfuel oil, which doesnot react with 'either the reactants, the alkyl-sub stituted benzyl tetrasulfides or the ultimately desired alkyl-substituted benzyl'pentasulfides, hasthe highly desirable and purely physical functions of imparting to the mixtures thereof lower viscosities than either the tetrasulfides or the pentasulfides per se, facilitating the handling of the reactants and the products, and aiding in the separation of any aqueous phase after the .:reaction, :Alkylsubstituted benzenes, having boiling points *above about 300 F.,=such as any 'thatfiniay be unreacted "in the Fchloromethylation "described,:are "also *e'ruinently suitable as diluents. The

diluent remains with the organic phase and serves as such isthe succeeding reaction step with elemental sulfur.

The alkylbenzyl tetrasulfides obtained by reaction between the benzyl chlorides and sodium tetrasulfide are then reacted, preferably while remaining in the presence of the diluent, with an excess, preferably 5%, of elemental sulfur for two to three hours at a temperature between about 200 F. and about 300 F., preferably about 240 F., to form the corresponding alkyl-substituted benzyl polysulfides having ten carbon atoms in each benzyl radical and containing an average of between about four and five and preferably close to five sulfur atoms per molecule. For convenience, these are referred to herein as the alkylbenzylpentasulfides.

In another emb diment of the method of the invention, which involves a higher consumption of sulfur, the alkylbenzyl pentasulfides are prepared directly by admixing alkylbenzyl chlorides simultaneously with an excess of sodium polysulfide and an excess of elemental sulfur and reacting at a temperature below the boiling point of the lowest boiling component in the reaction mixture, e. g., between about 150 F. and about 250 F. The temperature and time of reaction preferred, to avoid settling out of sulfur from thezproduct upon prolonged standing, are about 200 F. and about 2 hours.

It:is tob'eunderstood, of course, that it is within the scope of the invention toprepare any one or a selected combination of the possible isomers of the trimethyl' benzyl, methylethylbenzyl, propylbenzyl and isopropylbenzyl'polysulfides by appropriate isolation of the correspondiug isomeror isomers of the starting material.

Both the alkylbenzyl tetraand pentasulfides, diluted or not =with"a suitable hydrocarbon diluent such as gas oil, may be blended to formstable and clear solutions with any mineral cutting oil base, e. g., a hydrocarbon oil, such "as an acid-treated oil, "having a viscosity between about 75 and 300 SSU at 100 F., and said cutting oil a base mayitself contain free sulfur dissolved therein. The

lower limit :of viscosity specified is imposed largely by sulfur solubility. (Dils having viscosities higher than 300 SSUat 100 'F.are not preferred because of difficulties of handling and flowing. Cutting oil blends containing as little-as 0.5% or less by weight of alkylbenzyl tetrasulfide or pentasulfide have excellent cutting ability. Concentrates containing as much as about to 70% or more of alkylbenzyl 'polysulfide in gas oil or other hydrocarbon diluent, without being blended with a cutting oil base,

' have superior cutting ability and excellent odor characteristics. The concentrates of the invention, apparently because of their higher molecular weight and surprisingly high content of active sulfur, combine this unusually excellcnticutting abilitylwith low volatility, ability to stay on the tooland the work at the cutting point, absence of objectionable'o'd'oreither upon standing or in severe use and ability to form stable blends with mineral cutting oil Ebases. For cutting operations on ductile steels, sulfurized oil blends containing between about 0.5% and about 5% "by weight of the concentrate are highly satisfactory.

Perhapsthe'most surprising characteristic of the alkylbenzyl tetrasulfide and pentasulfide cutting oil concentrates of the invention is that they make it possible to incorporate into a cutting oil blend more active sulfur than isrequired'oridesired forsome types of cutting operations. .The present invention, therefore, provides an excellent;rneans of controlling accurately the amount of active sulfur inarcutting oil so that it will be the optimum amount. for anypa'rticul'ar metal cutting operation. It is alsopossible to add small amounts of other ingredients, e..g.', 1%. by volumelardoil, that mask the effect of excess active sulfur. git is-to be-"und'ei stood thatwhile the products of this 1nv'ention 'eoiisist essentially of one ora combination of alhyl sub" polysulfides containing ten carbon atomsdn each benzyl groupy'preferably diluted with unsulfurized gas oil or blended with a mineral cutting oil base or both, conventional additives such as lard oil, graphite and oil-soluble chlorinated compounds such as chlorinated wax and chlorinated aromatics typical of which is chlorinated biphenyl and the like may be added inamounts that do not materially alter the character of the products. It is also within the scope of the invention to add minor proportions, i. e., of the order of 1% or less, of antioxidants.

The blending of the cutting oil of the invention with lard oil in an appreciable amount, i. e., above about 1%, and preferably from about 2 to 10% by volume, is particularly desirable and advantageous for reducing tool wear when cutting operations are carried out on abrasive steels and has the further advantage of providing a cutting oil that is most universally useful on both abrasive steels and ductile steels. ferred cutting oil is a blend of a mineral cutting oil base with about 4% by volume lard oil and about 1% by weight of a 60/40 mixture of alkylbenzyl polysulfide and gas oil. It is to be understood, therefore, that it is within the scope of the invention to add amounts of lard oil which do alter somewhat the character of the alkylbenzyl polysulfide-containing cutting oils of the invention in so far as the machining of abrasive steels is concerned.

The advantages and utility of the cutting oil concentrate, cutting oil and method of this invention will become more apparent from the following example illustrating the invention.

EXAMPLE Part A 120 parts by weight of Solvesso 100, a catalytic reformate comprising a mixture of 4% aliphatic hydrocarbons and 96% aromatic hydrocarbons containing approximately 39% by weight trimethylbenzene isomers (7% 1,3,5-trimethylbenzene, 27% 1,2,4-trimethylbenzene and 1,2,3-trimethylbenzene), 36% by weight methylethylbenzene isomers (20% l-methyl-3-ethylbenzene, 8% 1-methyl-4-ethylbenzene and 8% 1-methyl-2-ethylbenzene), 3% isopropylbenzene and minor amounts of m-xylene (3%), o-xylene (6%), p-xylene (trace) and (13%) unidentified monoalkylbenzenes probably including n-propylbenzene isomers, were refluxed at 140 to 158 F. for seven hours under a water condenser while stirring the reactants with 525 parts by weight of 36% aqueous hydrochloric acid and 42.8 parts by weight of 91% paraformaldehyde in the form of flakes. During the reaction a slow stream of HCl gas was fed to the reaction mixture and care was taken to provide good ventilation. After seven hours, the reaction mixture was cooled to room temperature and allowed to settle into two immiscible layers, the lower aqueous layer was separated, the upper oily layer was washed with water, then washed with a 5% aqueous sodium carbonate solution until neutral and then washed again and finally dried with anhydrous calcium chloride.

55% of the final oily phase was found to be a mixture of alkyl-substituted benzyl chlorides having the empirical formula C1oH13Cl, 19% was found to be a mixture of alkyl-substituted xylylene dichlorides and the remaining 26% was found to be substantially unreacted. The products were then subjected to vacuum distillation to separate the alkylbenzyl chlorides and unreacted alkylbenzenes from the alkylxylylene dichlorides.

Part B 168.5 parts by weight of the alkylbenzyl chlorides of Part A were admixed with 368 parts by weight of a 40% aqueous solution of sodium tetrasulfide (approximately a 30% excess of the tetrasulfide to insure complete reaction of the chloride) and with 132 parts by weight of a gas oil having a viscosity of 42 SSU at 100 F. and a flash point at 275 F. The mixture was heated to 200 F. and maintained at that temperature for from 3 to 5 One example of such a pre- I hours while stirring well. The reaction products were then cooled and allowed to settle, the lower aqueous phase was separated and the remaining organic phase was hydroxide solution per 5 parts by volume of organic v phase, and the mixture was stirred for thirty minutes, the

caustic then being separated. Thereupon, 3% Super Filtrol, a mineral adsorbent, was added and the mixture stirred for about ten minutes. The mixture was then filtered to yield 94 to 99% of the theoretical yield of alkylbenzyl polysulfides in the gas oil.

The product was a 60/40 mixture of alkyl-substituted benzyl tetrasulfides, having the empirical formula CZOHZSSx, and gas oil having a total sulfur content of 18.5% (95% of the theoretical 19.4% total sulfur content, or containing an average of about four sulfur atoms per molecule of polysulfide) and an active sulfurcontent of 8.7% (90% of the 9.7% theoretical active sulfur content). 1

Part C 329 parts by weight of the 60/40 mixture of alkylbenzyl tetrasulfide and gas oil prepared in accordance with part B of the example were admixed with 16 parts by weight of elemental sulfur and sufficient additional gas oil, about 10 parts by weight, to maintain the ratio of polysulfide to gas oil at about 60/40. The mixture was then. stirred for 2 hours under nitrogen atmosphere at a temperature of 240 F.

The total sulfur content of the alkyl-substituted benzyl pentasulfides, likewise having the empirical formula C20H26Sx, analyzed 22.9% (98% of the theoretical 23.5%, or containing an average of about five sulfur atoms per molecule) and the active sulfur content analyzed 15.1% (105% of the theoretical active sulfur con tent of 14.3%). The amount of sulfur introduced was about equal to the theoretical amount considering the precision of the available analytical methods.

Part D A cutting oil base was prepared by adding, to Diamond Paraiiin oil, an acid treated lubricating oil stock having a viscosity of SSU at 100 F., 0.8% by weight elemental sulfur, i. e., the maximum amount of sulfur soluble in the oil at 0 C. The mixture was heated and stirred at 240 F. until all of the sulfur was dissolved. This took approximately one to two hours.

Blends of the cutting oil base with 0.5 to 5% by weight of the 60/40 alkylbenzyl tetrasulfides-gas oil concentrate prepared in Part B of the example and with 0.5 to 5% by weight of the 60/40 alkylbenzyl pentasulfides-gas oil concentrate prepared in Part C of the example form excellent cutting oils characterized by remarkable cutting ability, low volatility and absence of odor, and ability to remain on the work and the tool at the point of cut. A blend of cutting oil base with 1% by volume of the 60/40 alkylbenzyl pentasulfide-gas oil concentrate, 4% lard oil and 0.5% Aroclor 1254, a chlorinated biphenyl available as a yellow-tinted, viscous oil having a chlorine content of 54%, a specific gravity between 1.538 and 1.548 and a distillation range of 365-390" (3., was found to be particularly effective.

it is obvious that in the foregoing example bromine or iodine can be substituted for chlorine and that likewise potassium tetrasulfide can be used in place of sodium tetrasulfide. Chlorine, alkyl-substituted benzyl chlorides, and sodium tetrasulfide are preferred because they are relatively inexpensive and most readily available.

It is to be understood that these and other modifications of the method and products described herein will readily occur to those skilled in the art. All such modifications are intended to be included within the scope of the invention as defined in the accompanying claims.

We claim:

1. A cutting oil concentrate comprising from about 50 to about 70% by weight of a mixture of organic polytreated with one part by volume of a 3% aqueous sodium 1 5 18 t e mul wherein R1 and R2 are selected from the group consisting of three methyl radicals, one methyl and one ethyl radical, and one propyl radical, and x averages between about 4 and 5, said mixture having been derived from a mixture of aromatic hydrocarbons containing approximately 9% xylenes, 3% isopropyl benzene, 36% methyl ethylbenzenes 39% trimethylbenzenes, and 13% mixed monoalkylbenzenes, by chloromethylation and reaction with sodium tetrasulfide, and with sulfur when x is in excess of 4,,and from about 50 to about 30% by weight of a hydrocarbon diluent.

2. A cutting oil comprising a mineral oil and from about 0.5 to about by weight of a mixture of organic polysulfi des having the formula where R1 and R2 are selected from the group consisting of three methyl radicals, one methyl and One ethyl radical, and one propyl radical, and x averages between about 4 and 5, said mixture having been derived from a mixture of aromatic hydrocarbons containing approximately 9% xylenes, 3% isopropyl benzene, 36% methyl ethylbenzenes, 39% tn'methylbenzenes, and 13% mixed monoalkylbenzenes, by chloromethylation and reaction with sodium tetrasulfide, and with sulfur when x is in excess of 4.

References Cited in the file, of this patent UNITED STATES PATENTS 2,113,092 Moran et a1 Apr. 5, 1.938 2,185,008 Wojcik Dec, 26, I939 2,273,471 Kimball Feb. 17, 1942 2,538,941 McCallum Ian. 23, 676,987 Lewis et a]. Apr. 27, 1954

Claims (1)

1. 2. A CUTTING OIL COMPRISING A MINERAL OIL AND FROM ABOUT 0.5 TO ABOUT 5% BY WEIGHT OF A MIXTURE OF ORGANIC POLYSULFIDES HAVING THE FORMULA