US2368000A - Lubricating compositions - Google Patents

Description

Patented Jan. 23, 1945 L UBRICATING COMPOSITIONS Elmer W. Cook, New York, N. Y., and William D.- Thomas, Jr., Stamford, Qonrn, assignors to American- Cyanamid I Company, New

York,

N. Y., a corporation of Maine No Drawing. Application December 4, 1941,

Serial No. 421,650

This invention relates to the stabilization of lubricating oils of the type known as crankcase oils; 1. e. hydrocarbon oils of relatively low viscosity and pour point such as are used in the crankcases of internal combustion engines. More particularly, the invention relates to those classes of crankcase oils for truck, bus, aeroplane and marine gasoline and Diesel engines that are known as heavy duty" oils which contain added chemicals that increase their efiective service life under heavy operating conditions. A principal object of the invention resides in the provision of a crankcase lubricant of this type containing a class of compounds having both detergent and antioxidant properties, whereby the formation of hardsludge deposits is inhibited. A'further object resides in the provision of an inhibitor of this class which is of the metal salt type, but which has little or none of the undesirable oxidizing action on hydrocarbon oils that is a characteristic of many metal salt additives.

In our copending application, Serial No. 401,- 960, filed July 11, 1941, we havedemonstrated that the oil-soluble heavy metal salts of dithiophosphoric acid esters, when added to crankcase oils in concentrations of about 0.1% to 3%, are excellent detergents for the prevention of sludge deposits in the engine, and that these compounds also possess extremely important non-oxidizing or antioxidant properties when compared'with other metal salt detergents. Our present invention relates to the specific class of oil-soluble heavy metal salts of dithiophosphoric acid esters in which at least one ester-forming radical is a higher branched-chain alkyl radical containing at least 6 carbon atoms. I Q

We have found that the heavy" metal salts of esters of dithiophosphoric acid containing at least one and preferably two branched-chain higher alkyl radicals are important addition agents for the stabilization of lubricating oils of the class referred to above. These compounds, by reason 10 Claims. (01. 252-48) I s of the lubricating oil additives is thereby obtained. Thus, for example, numerous branchedchain higher aliphatic-alcohols and alcohol mixtures are obtainable as by-products in various chemical industries, and the use of dithiophosphates prepared from such by-product alcohols I and alcohol mixtures constitutes one of the most I important features of the invention.

Our invention in its broader aspects therefore consists in the addition to lubricating oils of the type of hydrocarbon crankcase oils of a heavy I metal salt of a dithiophosphoric acid ester conphatic alcohols may be used in preparing the reagents employed therein, either alone or in the taining at least one branched-chain higher alkyl radical, either alone or in admixture with other ingredients, in amounts suflicient to exert sludge dispersing properties under heavy duty service conditions but without substantial increase in J oxygen absorption and consequent sludge formation in the oil. The formation of sludge in crankcase oils is intimately related with the production of corrosive oxidation products of the type of organic acids, and accurate determination of these decomposition products is usually accomplished by measuring the naphtha-insoluble fraction of the oxidized oil. our invention can therefore be expressed by stating that'the heavy metal salts in question do not increase the naphtha-insoluble value of the oil,

and in fact these compounds usually bring about a marked reduction in this value.

It is an important advantage of our invention that a wide .variety of branched-chain higher aliform of higher-alcohol mixtures, or as mixtures of branched chain higher aliphatic alcohols with such as higher or lower straight-chain alcohols,

of the branched chain alkyl radicals which they phenols and the like. Typical branched-chain higher alcohols that may be used in this manner are pentamethyl ethyl alcohol, pinacolyl alcohol ((CI-Ia) 3C.CH(CH3)OH), 2-ethylhexyl alcohol, tetradecanol, undecanol, 5-ethylnonanol-2, and 3.9-diethyl tridecanol-G More important, however, are the mixtures of branched-chain alcohols obtained as by-p'roducts in the commercial hydrogenation of oxides of carbon and from other industrial sources such as the hydrogenation of higher aliphatic ketones in the .describedin our earlier application above referred to, and an importantreduction' in the cost presence of nickel catalysts. Thus, for example, the hydrogenation of carbon monoxide in the presence of promoted copper chromite catalysts produces methanol and ethanol as the principal products, but large quantities of byeproducts are obtained which consist of mixturesof numerous This feature of branched-chain alcohols and ketones. Such Fraction B-22Approximate boiling range 130- Fraction B-23- -Approximate boiling range 150- 160 C. Fraction B-24-Approximate boiling range 160- 200'C.. Fraction B--Approximate boiling range 200- The composition of these various fractions is given by this manufacturer as follows:

Fraction B-22 Boiling range "Approximately 130-150? C. Specific gravity at 15.6/15.6 C--- 03335-03375 Weight per U. S. gallon at 68 F 6.94 lbs. Saybolt viscosity at 100 F About 30 seconds Solubility in water at 20 C About 0.6% Solubility of water in 13-22 at 20 C -Less than 3 Solubility in H2504 Not less than 70% in 85% H2804 Approximate composition:

Primary alcohols (principally 2 methyl pentanol-l, B. P. 148 C.) 60-65% Secondary alcohols (principally di-isopropyl carbinol, B. P. 139" C.) 15-20% Ketones (principally 2,4-dimethyl hexanone-3) 18-20% Esters-unidentified 2% Fraction 8-23 pentanol-l, B. P. 159 C.) 43% Secondary-alcohols (principally 2,4-dimethyl hexano1-3, B. P. 158 C.) 48% Ketones-unidentified 9% Fraction 3-24 Boiling range Approximately 160-200 c.

Specific gravity at 15.6/15.8' C 0.8610-0.860 Weight per U. S. gallon at 68? F 7.17 lbs. Saybolt viscosity at 100 F.. About 32 seconds Solubility in water Less than 1.0% Solubility in HaSO4 Not less than 85% in 85% H2304 Approximate composition:

Primary alcohols;

about 4-methyl hexanol-l B. P.

165 C v 2,4-dimethyl hexanol-l B. P.

about 178 C 4-methy1 heptanol-l B. P.

4 .about185" 0-- Secondary alcohols-unidentified 34% Ketones-unidentified 18% Esters 3% Tentative identification; probably other alcohols alsopreaent.

Fraction 13-30 Boiling range 200-300 C. Specific gravity at 15.6/ 15.6? C 0.900-0.910 Weight per U. S. gallon at 68 F 7.5-7.6 lbs.

Approximate composition:

Alcohols-primary and secondary 68% Ketones-unidentified 12-17% Miscellaneous (phenol bases, unsaturated alcohols, etc.) 15-20% It is-a further specific object of the present invention to prepare dithiophosphates and their heavy metal salts from the above alcohol mixtures and mixtures of alcohols and ketones. These mixed dithiophosphates and theirheavy metal salts we regard as new compositions of matter, and we have found that they possess surprisingly good properties when used as additives for lubricating oils of the type specified above.

Another class of mixed higher branched-chain alcohols that we have found suitable for use in the preparation of dithiophosphate heavy metal salt additives for crankcase lubricants are those obtained by the reduction of the corresponding higher aliphatic ketones with hydrogen. Thus, for example, mixtures of beta, gamma-unsaturated ketones obtained by the rearrangement of alpha, beta-unsaturated ketones produced by the condensation of ketones of lower molecular weight may be employed. Typical alcohols that can be produced cheaply by'the method are 4-methyl hexanol-2, 5-methyl hexanol-3, 4-methy1 heptanol-2 and fi-methyl heptanol-3. We have found, however, that the higher aliphatic ketones of the type found in .the duPont alcohols are frequently advantageous in lubricating oils, for they appear to act as solubilizing agents for dithiophosphate heavy metal salts prepared from the corresponding alcohols and prevent the deposition of sludges at low temperatures, and the hydrogenation of the ketones present in these alcohol mixtures is not recommended.

The dithiophosphates of the above-described classes are preferably prepared by reacting the corresponding alcohols or alcohol mixtures with phosphorous pentasulfide, preferably in the ratio of about 4 moles of the alcohol for each mole of P285. The reaction is carried out by heating the reagents at -100 C. or higher with stirring, in the presence or absence of a solvent, until the evolution of hydrogen sulfide is practically complete. The heavy metal salts are then produced from the free dithiophosphoric acid esters so obtained by dissolving the acidesters in a low-boiling mixture of polar and non-polar solvents, such as a mixture of ethyl alcohol and benzene, toluol or other low-boiling hydrocarbon, introducing the theoretical quantity of a reactive heavy metal oxide such as barium oxide, calcium oxide and the like and agitating the mixture until a solution of the heavy metal salt is obtained. Alternatively, the alkali metal salts of the free dithiophosphoric acid esters may be formed by neutralizing with sodium carbonate or sodium hydroxide and these products may be converted to the correspending heavy metal dithiophosphates by double the present inventiombut any other heavy metal salt may be preparedin this manner and used such as the zinc, aluminum or tin salts.

Another important feature of the invention resides in the introduction of additional heat stabilizers or anti-sludging agents into crankcase lubricants containing heavy metal salts of branched chain alkyl dithiophosphates. We have found that such compounds as the heavy metal salts of diamyl phenol monosulfide described in our Patent No. 2,249,626 and oil-soluble organic sulfonates and their heavy metal salts such as calcium petroleum sulfonate or calcium didecyl sulfosuccinate described in, our copending application, Serial No. 419,016, filed November 13, 1941, will cooperate-effectively with the dithiophosphates referred to above to improve the heat stability of the oil. Thus, for example, two samples of conventionally refined Mid-Continent base lubricating oil of -W grade containing 1% by weight of barium dialkyl dithiophosphatea a small amount of sediment was found in the L cooled sample to which no calcium petroleum sulfo-nate was added.

The invention will be illustrated in greater de tail by the following specific examples, which describe the results obtained with representative embodiments thereof. It should be understood,

however, that although these examples may illustrate in detail som of the more specific features of the invention they are given primarily iorpurposes of illustration and the invention in its broader aspects is not limited thereto.

Example 1 400 parts by weight of 2-ethylhexanol-1 were mixed with 190 parts of powdered phosphorous pentasulfide and the mixture was heated with stirring at 80-90 C. for 2.5 to 3 hours until the evolution of hydrogen sulfide was substantially complete. The resulting dicctyl dithiophosphoric acid was a brownish yellow liquid. 300 parts by weight of the liquid were dissolved in a mixture of 120 parts of ethanol and 240 parts of benzene and an excess of powdered barium oxide was introduced. A total of 71 parts by weight of 92% IBaO was added, this being an excess or 8 parts over the amount theoretically necessary to form a neutral barium salt.

The mixture was heated with stirring to 40-50 C. and stirred at these temperatures for about 40 minutes, after which the solution of barium di- This ing in the crankcase or an engine weighed strips of copper-lead alloy are suspended in the oil samples. As metallic surfaces, particularly copper, greatly accelerate the rate of oxidation and decomposition of the oil in the absence of oxygen A Mid-Continent, solvent-refined lubricating oil containing 0.12% by weight of barium di- (ethylhexyl) dithiophosphate and 0.6% of barium diamylphenol monosulfide was tested in comparison with another sample of the same 011 containing no additive. The copper-lead bearing strip in the oil containing the dithiophosphate octyl dithiophosphate was filtered off. Upon evaporation of the solvent the salt was obtained as a yellow, low-melting solid, soluble in hot, 10-W grade lubricating oil to the extent of about 50%. By adding barium diamylphenol monosulfide it was possible to prevent separation of the dithiophosphate from a 50% solution at low temperatures. i

The emciency of the heavy metal salts of branched-chain dialkyl dithiophosphates described in this and subsequent examples as detergents. and antioxidants for crankcase 1ubrioil. In order to reproduce the conditions existvinsoluble. film.

Example 2 30 parts by weight of tetradecanol of the formula: I

olntcnrcim).olmcncuscmcnm were mixed with 21 parts of powdered P285 and tion of the barium di-tetradecyl dithiophosphate in lubricating oil.

A sample of the lubricating oil described in Example 1 containing 0.38% of this product showed zero bearing loss in the Catalytic Indiana test. The tube contalning the oil was relatively clean after a single rinse with solvent naphtha,

and the small amount of deposit was soft and easily removed with a brush.

Example 3 120 parts by weight of undecanol of the formula C4HaCH(C2H5).C2H|.CH.CH

and 39 parts of P2s5 were reacted as in Example 1.

50 parts by weight of the resulting di-undecyl dithiophosphoric acid were dissolved in a mixture of polar and nonpolar solvents as before, neutralized by the addition of 7.6 parts of BaO, and the solvents evaporated. The product, a yellow solid of low melting point, was easily soluble in lubricating oils.

0.3% of the barium di-undecyl dlthiophos-- phate was dissolved in a sample of theoihdescribed in Example 1,'which was then subjected to the Catalytic Indiana test. The bearing actually gained 14 milligrams in the test and the tube contained no naphtha-insoluble deposit.

Example 4 60 parts by weight of B-22" alcohol and 31 parts of finely ground phosphorous pentasulfide were mixed and heated with stirring at 85-95 C. for 2 hours, after which time the-evolution of hydrogen sulfide was. practically complete. The resulting crude dialkyl dithiophosphoric acid had a neutralization number corresponding .to a monobasic acid having a molecular weight of 377.

65 parts by weight of the product were dissolved in a mixture of 25 parts ethanol and 30 parts toluene and 15 parts by weight of powdered BaO were added. The mixture was stirred with gentle heating to dissolve the barium salt, filtered, and the solvent was evaporated. The product was' a light yellow crystalline solid meltin below 150 C., soluble in lubricating oils with diificulty but easily solubilized therein by the addition of smal1 quantities of barium diamylphenol monosulfide.

A lubricating oil of the type described in Example 1 containing 0.4% of the product formed almost no naphtha-insoluble deposit when subjected to the Catalytic Indiana test. The copperlead bearing strip showed a gain in the test of 30 milligrams.

Example 5 lubricating oil of 10-W grade but practically insoluble in water.

In producing heavy metal salts 01 mixed dithiophosphoric acid esters on a large scale it is preferable to blend the product with an equal quantity of lubricating oil during evaporation of the solvent so'that a 50% blend in lubricating oil is obtained. Such a blend is very convenient for handling and storing the product, and it can be readily mixed with any desired quantity of lubricating oil to produce a concentration of 0.1-3%

. of the heavy metal dithiophosphate in the oil.

60 parts by weight of 3-23 alcohol and 23 parts of phosphorous pentasulfide were reacted for 2 hours at 90- -95C. as in Example 1. The resulting crude dialkyl dithiophosphoric acid ester had a. neutralization number corresponding to a monobasic acid having a molecular weight of 391. 77 parts by weight of this product and 17 parts of 39.0 were stirred with gentle heating (-50 C.) in a mixture of 25 parts of ethanol and 50 parts toluene, the resulting solution was filtered and the solvent evaporated. The product was an amorphous yellow solid of low melting point that was soluble in lubricating oil of 10-W grade to the extent of about 50% by weight.

A sample of the lubricating oil of Example 1 containing 0.4% of this product showed excellent results when subjected to the Catalytic Indiana v 136 parts by weight of B24 alcohol was mixed with 72 parts of finely ground phosphorous pentasulfide and the mixture was stirred and heated at 90-105 C. for 2-3 hours until evolution of hydrogen sulfide was substantially complete. The unreacted P285 was allowed to settle and the supernatant liquid was decanted. The product consisted principally of mixed branched-chain dialkyl dithiophosphoric acids together with smaller quantities of thioketones and possibly, somethioesters.

' 100 parts by weight of the product were dis solveddn a mixture of parts of toluene and 25 parts 01. ethanol and 20 parts of powdered barium oxide were added with stirring. The agitation was continued at 40-50 C. for 0.5-1 hour, or until'all the free acid was neutralized. additional 50 parts of toluene were then added and the solution was filtered and the solvent evap- Grated, the last traces being taken off under reduced pressure; The res'iduewas a-yellowishbrown liquid, readily soluble'both in gasoline and 0.4% of the product .Were added to a solventextracted Pennsylvania oil of 10-W grade. which was then subjected to the Catalytic Indiana test in comparison with an-untreated sample of the same oil. The bearing metal immersed in the treated sample gained 10 milligrams while the metal in the untreated sample lost 215, and there was practically no naphtha-insoluble deposit on the walls of the tube containing the treated sample.

The 3-24 dithiophosphate barium salt was also tested in lubricating il by the Underwood test. {This test consists in heating 1500 cc. samples of the oil to 325 F. and continuously spraying a portion of the heated oil against a 2" x 10" freshly sanded copper strip and two freshly sanded bearings for five hours while permitting free circulation of air through the apparatus. 0.116% of iron naphthenate, equivalent to 0.01% of FezOa, was added to the oil before testing in order to reproduce the conditions present in an engine as a result of acid corrosion of the metal by acidic oxidation products imthe oil. The results are given in the following table.

What we claim is:

1. A lubricating composition comprising a hydrocarbon lubricating oil having dispersed therein a heavy metal'salt of the reaction product of phosphorous pentasulfide with a mixture of higher branched-chain aliphatic alcohols containing at least 6 carbon atoms.

2. A crankcase lubricant comprising a hydrocarbon lubricating oil having dispersed therein a composition operative to assist in preventing the deposition of hard deposits due to sludge forma- 'tion in the oil at elevated temperatures, 'said composition comprising as its essential ingredient the phosphorous pentasulfide reaction product of g a mixture consisting predominantly of higher branched-chain aliphatic alcoholsv of at least 6 carbon atoms, said reaction products being in the form of their heavy metal salts.

' 3. A crankcase lubricant comprising a hydrocarbon lubricating oil having dispersed therein a composition operative to assist in preventing the deposition of hard depositsidue to sludze formation in the oil at elevated temperatures, said composition comprising as its essential ingredient the phosphorous pentasulflde reaction product or a fraction of a byproduct obtained in the catalytic hydrogenation of oxides of carbon and consisting predominantly or branchedchain aliphatic alcohols within .the range of 6 to 8 carbon atoms, said phosphorous pentasulflde reaction products being in the form of their heavy metal salts.

4. A crankcase lubricant comprising a hydrocarbon lubricating oil having dispersed therein a composition operative to assist in preventing the deposition of hard deposits due to sludge formation in the oil. at elevated temperatures, said composition comprising as its essential ingredient a phosphorous pentasuliide reaction product of a fraction of a byproduct obtained in the catalytic hydrogenation of oxides of carbon, said fraction having ,an approximat boiling range of 160-200" C. and containing about 45% of a mixture of primary alcohols chiefly 4-methylhexanol-l, 2,4-dimethylhexanol-l, and 4-methylheptanol-l and about 34% of secondary alcohols and 18% of ketones boiling within the range specified above, said phosphorous pentasulilde reaction products being in the form of their heavy metal salts.

5. A method of preparing an improvement agent for lubricant oils which comprises the steps of heatin phosphorous pentasulfide with a mixture of branched-chain higher aliphatic alcohols until the evolution of hydrogen sulfide is substantially complete and neutralizing the reaction product with a reactive heavy metal oxide to form a heavy metal salt thereof.

6. A method of preparing an improvement agent for lubricant oils which comprises the steps of heating phosphorous pentasulfide with a fracproduct with a. reactive heavy metal-oxide to form a heavy metal salt thereof.

'7. A method of preparing an improvement agent for lubricant oils which comprises the steps of mixing phosphorous pentasulflde with a fraction of a byproduct obtained in the catalytic hydrogenation of oxides of carbon, said fraction having an approximate boiling range or 160-200 C. and containing about 45% of a mixture of primary alcohols chiefly 4-methylhexanol-1, 2,4- dimethylhexanol-l and 4-methylheptanol-1 and about 34% of secondaryalcohols and 18% of ketones boiling within the range specified above, heating the mixture until the evolution of hydroen sulfide is substantially complete and neutralizing the reaction product with a reactive heavy metal oxide to form a heavy metal salt thereof.

8. In the production of a heavy metal salt of an ester of dithiophosphoric acid suitable for use as an improvement agent for lubricant oils, the steps which consist in dissolving a diester of dithiophosphoric'acid in a low-boiling mixture of polar and non-polar'solvents, adding a heavy metal oxide and agitating the mixture until a solution oi. the heavy metal salt is obtained.

9. In the production of a heavy metal salt of an ester of dithiophosphoric acid suitable for use as an improvement agent for lubricant oils, the steps which consist in dissolving a dialkyl dithiophosphoric acid ester in a mixture of a low-boiling alcohol and a low-boiling hydrocarbon, adding a heavy metal oxide and agitating the mixture until a solution of the heavy metal salt is obtained.

10. The method of obtaining a solution of a heavy metal salt of 'a dialkyl ester of dithiophosphoric acid in lubricating oil which comprises the steps of dissolving a dialkyl dithiophosphoric is obtained, adding an excess of hydrocarbon lubricating oil, and heating to drive of! the lowboiling solvents.

ELMER W. COOK. WILLIAM D. THOMAS, JR.