US2096390A - Compounded lubricants - Google Patents

Description

Patented Oct. 19, 1937 UNITED; ST E PATENT OFFICE,

Kempe, l Hackensack, N. 1.,

aslignors to Alox Corporation, a corporation of York No Drawing. Application December 27,.1934, Sl'hl N0. 759,432

v v I Claims. This invention relates to the production of lubricating compositions consisting essentially of eral origin, in the liquidphase, at a temperature 1 of from about 100 to about 175 c. and at a superatmospheric pressure not greater than about 320 pounds per square inch, in the presence 20 of an exciter of oxidation, until V the point of incipient formation of compounds which are insoluble in petroleum and in the reaction mixture, which mixture comprises saponiflable and unsaponifiable components, separating the sawmillseparated portion containing said saponiflable components with. steam until substantially no he resulting residue.

In the carrying out of the described oxidation process there are produced in admixture both sapofiifiable and unsaponiflable oxidation prod-' 45 the xor ism acids: and alcoholic. compounds .formedby; the oxidation,- respectively. The unsaponitlable portion of the oxidation reaction rn ii' z turev consists largely of oxygen-compounds or; alcoholic, ketonic," and keto alcoholic 50 constitutionfiandproperties, with or without some maize-imme ses I It has now'beenro that the afo e d acidic constituents be: averted into neutral esters hereof, and thejesulting neutral esters able components from at least the major portion of the unsaponiflable components, treating the more volatilematerial passes over, and drying above the boiling point of water, e. g., at a temagent, such as dilute aqueous alkali (i. e., a soluhave yielded to esterification.

rior degree, the same properties with respect to reduction in surface tension and improvement of the lubricity of lubricating oils as those possessed 'by the aforesaid free acids or mixtures comprising free acids.

According to the present invention the free acids content of the oxidation reactionmixture is esterifled by one or another of the optional methods following: g

a .(a) Addition of non-volatile alcohols to the 10 acids, and heating at above 100 C.

(b) Treating the acids with volatile alcohols, in the presence of condensing agents, and thereafter washing with alkali. I

(0) Heating, alone, at above 100 C.

Among operable esterifying agents we may use methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, isopropyl alcohol, secondary butyl alcohol, glycerine, glycol, ethylene glycol, and, in general, any commercially known, normally liquld, alcohol.

The tree acids content of the oxidation reaction mixture may be esterified by heating the acids with an esterifying agent; e. g., a non-volatile alcohol, at a temperature above the boiling point of water. In carrying this conception into practice the acid is admixed with a non-volatile alcohol, such -for instance as glycerine, and the mixture thus made is heated at a temperature perature of, say, 150 C., for several hours. There is practically no volatilization by this procedure (beyond separation of water), it being found that lower molecular weight acids which may be present readily combine with the high boiling alcohol perature, at which the alcohol boils.

The resulting esterified product may, in any case, finally be treated with an acid-binding tlon ofnot to exceed 1%. caustic soda, in water, or an aqueous-solution of sodium carbonate of like strength),and then washed with water, to remove any traces of free'acid which, might not Discussing the last mentioned method of cats!- iflcation, it has been found that if the whole oxidation reaction mixture, containing contents of free acids and alcohols produced by the oxidaare produced mixtures of wholly neutral oxygenv petroleum-type waxes, and the like.

compounds of the original hydrocarbons in which neutral mixture the compounds of acidic constitution are present in ester form. This procedure, however, is open to the objection that under the conditions of operation lower molecular weight acids tend to be lost by evaporation, from which acids desirable esters could have been formed. Moreover, the degree of neutralization realized by this procedure may, in particular instances, be found to be insufiicient.

As has been indicated hereinbefore, the acids fromwhich the neutral ester mixtures of the present invention are prepared are produced by the -liquid-phase, controlled oxidation of mixtures of relatively high molecular weight aliphatic hydrocarbons of mineral origin, such, for instance, as petroleum distillates consisting chiefly of relatively high molecular weight hydrocarbons, amorphous wax such as Sharples wax, other The said oxidationmay be practiced under employment oi such conditions of temperature, pressure, time, etc., as to yield a reaction product in which little or no unoxidized hydrocarbon remains: oxidation in the presence of a. suitable accelerator of oxidation at a temperature of about C. and under a superatmospheric pressure of say 200 pounds per square inch for a period of about 10 hours normally will result in a reaction mixture containing no unoxidized (i. e., "original) hydrocarbons. This condition may be ascertained by recourse to a sulphonation test according to which 1 part by weight of reaction mixture is heated with 3 parts by weight of sulphuric acid for about 30 minutes at a temperature of about C. The absencefof unoxidized hydrocarbons in the so-sulphonated mixture is determined by measuring the solubility of the latter in water:

if all of the original hydrocarbons have been oxidized the total sulphonation mass will be found to be soluble in water.

In a reaction mixture showing by the sulphonation test no unoxidized hydrocarbons there have been found by analysis the following types of compounds: free acids, lactones; alcohols-frequently, poly-alcohols containing from 1 to 3 hydroxyl groups to the molecule; alcohol ketones, in which one of the hydroxyl groups has been further oxidized to the carbonyl group; carbonyl compounds containing no hydroxyl groups and which may contain a plurality of carbonyl radicals; and diflicultly s'aponifiable esterswhich we shall, in this description, identify as selfformed esters. I

This invention is predicated upon what is believed to be a new conception of lubrication, namely, that the normally given characteristics of a particular so-called lubricating oil (e. g.,

specific gravity, fire, flash, viscosity, color, etc.)

do not necessarily foretell whether or not that particular oil is operable in a given relation, and that in most instances an oil must be constructed in the light of the requirements of the intended particular application thereof. -While the above-mentioned characteristics are important to the refiner (in order that he may be able to 9,096,390 i p a reproduce a given refined oil) they have little if any bearing on the actual lubricating properties of the oil. Thus, it has been found that the viscosity of an oil is not, in general, an index of its relative resistance to film rupture. Resistance to film rupture is more dependent'upon the individual oiliness" of the oil than upon its viscosity: oils of the highest viscosity at high temperature may show easy film rupture at low pressure and at low temperature. On the other hand, it is possible to construct oily lubricating 'compositions of low relative viscosity which compositions show high resistance to film rupture under the most exacting conditions of pressure and temperature. 7

' A probable explanation is that the film which constitutes the actual lubricating material between the', surfaces to be lubricated is not closely related tothe oil as a whole: it is-related only to the mixture of bodies which are segregated at the surfaces and which form the actual lubri- 1 eating film. Ifthere are present in the oily composition bodies which will be segregated at the surfaces and which are capable of resistingfilm rupture to a determined high point of pressure and temperature, then that oily composition will,

regardless of its actual Saybolt viscosity,'function' properly within the ranges specified and at all temperatures, and pressures, below those shown as the final ones at which the film shows rupture.

Exhaustive tests of oily lubricating composi-' tions, over wide ranges of pressures and of temperatures, have demonstrated the unforeseeable fact that the addition to straight petroleum lubricating oils of one or more non-acidic oxidized petroleum hydrocarbons materially improves the oiliness of the oils, enabling films thereof to withstand rupture at higher pressures and/ortemperatures than afilm of the "straight oil could withstand, while-generally simultaneously reducing the drag, or internal friction, of the oil film at all pressures. These tests were made in several ways: in one way the oil was maintained at, say, 212 F. and tested at all pressures from zero to 1500 or 2000 pounds. In a. second mode of examination, the pressure was held at, say, 1500, or 2000, pounds, and the oil was tested at all temperatures between, say, 140 F. and 400 F. (this latter range covering all temperatures normally encountered in the crank-- compositions having almost any predetermined desired film strength and/or desired low coefficient of friction by proper incorporation into the straight oil of relatively small but effective amounts of the hereinbefore discussed nonacidic oxidized petroleum hydrocarbons.

The invention will be described in further de-' tall by reference to the following illustrative specific examples:

1.-Into a. still or other closed vessel equipped with means for heating the contents thereof were charged 1 pound of acids derived from the oxidation of amorphous wax i. e., Sharples wax), derived from petroleum oil, and .06 pound of glycerine. The mixture of acids and glycerine was brought up to a temperature of 110. C. within twenty minutes and maintained at about that temperature for eighty-six hours. The acids and glvcerine reacted. to form the glycerolesters of the acids, water being evolved and distilled 011'. During the treatment a stream of an inert gas was passed through the reaction mixture, to agi-- late the latteriand to carry off water vapor as formed. The resulting. esterifled product was approximately neutral, only 1.4 cc. of. normal alkali solution' being required to neutralize the free acid content of a 10 gram sample of said product. The original acidity for 10 grams was 16.2 cc. 4

KOH.

One 'pm of the so-produced esteriiled productwas admixed with 199 parts of a motor lubricating oil. The resulting composition was found to have a muc lower coemcient of friction, and

.lowertangent riction drag, at bearing loads of from 500to 1000 pounds perv square inch, than 'did the same oil without the ester addition.

- 2.--A portion of the esterifled product of Example 1 was washed with a 1% aqueous solution of caustic soda until by test it showed no free acid.

The washed esterified product was blended with motor lubricating oil in the proportion of 0.75 part of the esterifled material to 99.25 parts of the oil. The resulting composition was found to have an improved lubricity" over that of the 'oil per se, as evidenced in lowered coemcient of I friction 'and in lowered tangent friction drag.

3.--150 pounds "of sulphuric acid, oil vitriol,

. were added slowly to 400 pounds of methanol,

under agitation, and the mixture was cooled.

- 100 pounds of methanol were added to, 400 pounds of the acidic saponiflable material derived from the oxidation of amorphous wax (i..e., Sharples wax), and this mixture was heated, under agitation and reflux, to 60 to 65 C. While this temperature was maintained the cooled mixture of methanol and sulphuric acid was added to the heated mixture slowly (over a period of from 1 vto .2 hours time), and the reaction mixture was heated and agitated, under reflux, at Bil-65 C.

until by test it was determined that a maximum of esterlflcationl had been reached. The reaction mixture was then admixed with water,

whereby to dissolve the catalyst (i. e., the sulphuric acid), the ester mixture was separated from the aqueous solution of sulphuri acid, and the separated ester niixture was washed with water and then with dilute aqueous sodium carbonate solution (1%) to remove any unesterifled acids.

The resulting methyl estermixturewas found to improvethe lubricity of a lubricating oil. In.

thisnconnection it may be mentioned that the smaller the molecule of the alcohol used in esterifying the acid the more pronounced appears to be its lubricity-improving properties.

remarked that there appears to be a. direct ratio between the amount'of oxygen (relative) in the compound and the degree of lubricity-improving effect producedby that compound. 7 The procedure of Example 3' has been carried out using another relatively low molecular weight alcohol in place of the methanol: thus, ethanol, propanol and other similar alcohols have been found to bepoperable in the production of neutral esters of the aforesaid acids, which esters were. found to have desirable lubricity-increasing properties. a e n I I other catalytic assistants of esteriflcation may be used i'n. place of'the sulphuric acid of Example 3, e..g'., another inorganic acid. Zinc chloride,

aooaaao It may be d and calcium chloride, have been found to be operable assistants also.

The ester mixtures so formed have, in general, physical'properties similar to those of the nonesterified products: they differ therefrom in having lower melting points, a more pleasant odor, and greater solubillties in petroleum hydrocarbons.

We have discovered, also,- that the hereinbefore described esterification of the free acids contents of oxidation reaction mixtures prepared as above described may be effected without having recourse to separation of the acids from other, co-existent,

oxidation products. Thus, we have found that the acids content of the hereinbefore described saponiflable" portion of the crude oxidation reactioxf mixture may be converted into neutral esters by practicing the above described esteriflcation procedure upon the saponiflables separated from said crude oxidation reaction mixture, and that the resulting neutral mixtures have lubricity-improying properties similar to those of I the isolated synthesized esters. In carrying out this embodiment of the invention we determine the content'of. free acids in the saponiflable.

portion and react the said portion with alcohol (in accordance with the procedure of Examples 1, 2 and 3 above) in that amount which is calculated to be necessary for maximum esteriflcation of that free acids content. When maximum esteriflcation has been eifected the catalyst (if any catalyst has been used) is removed, and any residual free acid, if there be any, may be separated out by cautious treatment of the product. with a dilute aqueous solution of soda ash or caustic soda and washing with water. The resulting mixture, consisting essentially of esterized acids,

oil, whereby to produce the maximum amount of lactones and self-formed esters in said mixture, any residual free acid therein thereaftei'v being either (1) neutralized and removed or (2) esterlfled by means of alcohol (preferably, a low molecular-weight alcohol such as methanol or ethanol). The resulting neutral or substantially neutral mixtures are of high value as lubrication addition materials. J

Lastly, the whole (i.-e., crude) oxidation re-- action mixture, containing a content of free acids, may be treated by ascertaining the amount of free acids contained therein and esterifying those Y free acids with added alcohol (either with ahigh molecular-weight alcohol, at a temperature above 100 C., or with a' low molecular-weight alcohol with the aid of a condensing'agent, at a temperature below 100 C.), any residual (i. e., unesteriiled) acid then being. removed, yielding a mixture of wholly neutral compounds which mixture has lubricity-improvingproperties. It isto be noted that this last-mentioned mixture diners from that produced by 1) prolonged heating of the crude oxidation reaction mixture followed by (2) esteriflcation of residual free acid in that the latter I product contains a. relatively larger proportion of lactones the former, in that 7 the reason that it makes possible the retention and use of these less readily soluble acids in lubricating compositions. It is probably for this reason, also, that the esterized acids are more valuable as lubricity-increa i e' agents than are the acids not so esterized. Higher film strengths and lower coeificients of friction are attained-by use of the esterized acids than are attained by the use of the corresponding free acids.

*troleum, which saponifiable portion upon analy- .4.-1 pound of the saponifiable portion of a crude oxidation reaction mixture obtained, by the oxidation procedure hereinbefore described, "from a 36-40 distillate of Pennsylvania pesis showed a free acidscontent of 30% by weight, were admixed with 0.1 pound of glycerine, this being a large excess of glyceriue, and the mixture was heated in a still to about 150 C., while agitating the mixture and removing evolved water therefrom by blowing a stream of a non-reactive gas vtherethrough. The heating was continued at about 150 C. for thirty-one hours. The resulting product was found-to contain a residual acid .(free acid) content equivalent to 1.3. cc. of normal alkali per 10 gram sample of the esteriaed product, which free acid content was too immaterial to warrant removal as by treatment with very dilute alkali solution.

. We have found that while the amount of the neutral esters, or of the esteriaed saponifiables portion of the oxidation reaction mixture, to be added to the lubricating oil may be varied, and ,while the determination of the'amount to be added depends upon a number of factors including especially the intended use of the resulting lubri eating composition, the characteristics of the oil used, etc., it maybe stated that the amount to be added to a lubricating oil intended for use in the crankcase of an automotive engine will range from 0.25% by weight up to, say, 0.75%.

In the caseof cylinder oils, we may use from 1 to 2% of the esterized material. The use of larger proportions of the esterized material, e. g., up to about 4 to 6%, with lubricating oils afiords very tough films (of lubricant) under wide ranges of pressure. The addition of these esterized materials tothe constituents of greaseshas proved valuable for two reasons: 1) they, greatly reduce the high drag of the grease and (2) they make possible the easy solution in the grease of highly chlorinated aromatic hydrocarbons '(e. g., high chlorinated naphthalenes) widely used in high pressure greases. .Thus, for example, we have found that a pressure grease having very desirable properties may be prepared from ,a 750 fire test cylinder stock of Pennsylvania origin, having a viscosity of about 400-450 at 210 F., plus 8% filed November 27, 1933.

oxidation.

of highly chlorinated naphthalene plus 4-6% of esterized product derived from the oxidation products of amorphous wax and parafiin in about equal proportions.

While in theforegolng the invention has been described with reference to synthetic esters produced by reacting aliphatic alcohols with free saturated aliphatic hydroxy carboxylic acids of high molecular weight, said acids being obtained, in association with other saponifiable bodies and with unsaponifiable oxygenated bodies, by the controlled, liquid-phase, partial oxidation of hydroc-arbon mixtures of mineral origin at a temperature between about C. and about C.

This application'contains subject matter .in

common with our application Serial No, 700,018,

We claim: 1. A lubricating composition consisting of a major amount of lubricating oil of mineral origin and dissolved-therein-a minor amount of neutral aliphatic alcohol esters of the free saturated aliphatic hydroxy carboxylic acids content of an trolled liquid-phase oxidation of hydrocarbons of mineral origin at a temperature between about 100 C. and about 175 C. and at a superatmospheric pressure not above about 320 pounds per square inch, in the presence of an exciter -of oxidation, the alcohols being members of the group consisting of relatively low molecular weight, normally liquid, aliphatic alcohols including glycerin andfglycol, and the alcohols derived from the aforesaid mineral hydrocarbons in the production of the aforesaid acids.

2. A lubricating composition as defined in claim 1, in which the alcohol is methyl alcohol.

3. A lubricating composition as defined in claim 1, in which the alcohol is glycerin.

4. A lubricating composition as defined in claim 1, in which the alcohol is one derived from said mineral hydrocarbons in the production of said acids.

'5. A lubricating composition consisting ofa major amount of lubricating oil of mineral origin and dissolved therein a minor amount of neutral low molecular weight aliphatic alcohol esters of the free saturated aliphatic hydroxy phase oxidation of a hydrocarbon mixture of mineral originat a temperature between about 100 C. and about 1'75" 6., and at a superatmospheric pressure not above about 320 pounds per square inch, in the presence of an exciter of ARTHUR w. nuawmn ADOLF KnmPn