US2737492A - Lubricating oil compositions - Google Patents

Description

United States P ten LUBRICATING OIL COMPOSITIONS Lindley Clair Beeg'le, Stamford, Charles Funk, In, Cos Cob, and Edwin Oscar Hook, New Canaan, Conn, assignors to American Cyanamid Company, New York, N. Y., a corporation of Maine 7 No "Drawing. Application March 26, 1952, Serial No. 278,758

11 Claims. (Cl. 252-325) The present invention relates to lubricating oil composition to lubricatin oil additives to be incorporated therein, and imeluuzles methods of incorporating these edditives in the lubricating oils and methods of producin such additives. More particularly, these lubricating oil compositi ns are those of the type .known as crankcase oil for internal combustion engines and incl ding heavysiuty oils for truck, bus, airplane and marine gasoline and diesel engines. More specifically, the present invention is concerned with irrrproving' agents .or chemical additives for lubricating oils to increase the effective service life of engines using such .oils :under all :types of operating conditions. 1

These .additivesare nil soluble and are .ciiective :to re- :duce .or retard the oxidation or deterioration of the lubriranting oil and to inhibit .or mitigate the normal corrosive action of such oils or the decomposition products thereof on metallic-parts. Additionally, these additives .act as dispersa-nts :or antiesludge agents .to prevent the formation ,of hard sludge deposits .due to sludge formation in the .oil particularly at elevated temperatures to thereby maintain engine cleanliness. Although these compositions have particular applicability to mineral lubricating oils such as crankcase oils, it is to be appreciated that they find use in other oils such as animaland vegetable oils, including cutting oils, slush'ing oils, turbine oils, transformer oils, and the like oils, having tendencies to undergo oxidational changes.

When soils, such as conventional lubricating oils, are subjected to extended periods of use, especially at high operating temperatures, as in heavy duty service, they tend to decompose and for complex and objectionable oxidation and decomposition products including peroxides and organic acids. Ilhese substances possess corrosive and other deleterious properties and, unless neutralized or counteracted, will attack and damage engine metallic parts such as, for example, the hard bearing alloy metals as copper-lead and cadmium-silver. These acids, furthermore, may go through a chemical process whereby'the molecules combine or polymerize into large aggregates to form lacquer-like deposits on or between the moving parts of thecngine, causing excessive wearing or even sticking of operating parts. Even'larger quantities of polymerize tion productsremain dispersed inthepartially oxidized oil and are readily precipitated to form a -mayonnaise=like sludge when the engine cools or when 'fresh oil'is added ,2 stantially retard the oxidation of the oil and to inhibit or mitigate the corrosive action of any oxidation or decompositin products which may be formed in the oil.

It is a further principal object of the present invention to provide a lubricating oil composition possessing sufiito-the engine. These precipitated sludges become caked sages of .smalL-diameter through which the luhricatingpil J normally .flows to the bearings, whereby hearing iaflures are caused. Y

. The prin ip l obje ts of the present .inventionare there- .fore :to ,provide a lubricating oil composition capable of heavy .duty service .under varying operating conditions,

which compositions shall be efiective to reduce or to subcient reserve alkalinity to neutralize the acid oxidation and decomposition products as they are developed during use of the oil.

It is another principal object of the present inventipn 0 provide an anti-oxidant and corrosion-inhibiting-lubrieating .oil composition having detergent or anti-slpdge properties.

T es obj s an the s wh h may ppea he einaits re a comp she by p ov g omp s t on su tabl -fo use as impr m n age s for yd on ub i at oils and capable of retarding the deterioration of such oils y oxida ion a o n tr l zin t e a i ox d i n and decomposition products which are liberated or foprned in the oil during use. :In this way, the corrosive and .o er deleterious efiects normally resulting from such ac dic products are immediately neutralized andzcounteracted and conditions detrimental to metallic engine elements arcavoided.

is .ofise ting o t ef e o the ac matofie edeel p u i g the use f h o is accompli h d y p oviding an improvement agent having suificient latent efiective alkalinity or falkaline reserve properties capable of acting upon the acid material as it is developed and nepitralizing .or counteracting the same. This falkaline reserve th s rep se s lat n heutr l zihs a nt Whish comes into effective operation to neutralize acidic mateials when they are liberated.

These improvement agents ,may :be derived from the chemical combination of metallic salts of 0,0.-di esters .pf dithiophosphoric acid and ammonia or amines and have the iollowing general structural formula:

wherein each of R1 and R2 is an ester-forming member of ithe gr up on s ng of kyl r-l, ky and cycloal kyl radi al Me i a m a c p b o fo m n coo dinat on comp e es th amm z is th y oh o Me; each orA, B and :C is a em e of the storm co t o hydro e e kyl and lhy di ls;andxi aoiutese om t th or na on-n m o of efit i l ph tic 'dithiop o p r acid meson .cluding the dicycloalkyl .dithiophosphoric acid esters, r .anysQD'diaryldithiophosphodc acid diester or any migred O Ordiester .ofqdithiophosphoric acid may the- 118 .6 in pr duc ng the novel d c o th pre en nv ntion- Whon a dit comp u s ha in o ela v y h gh pe coina i-. e phosp oru an l u a des red, as in the -plzoduction of lubricating oil anti-oxidantshaving a high activity at relatively lop/temperatures, it prefer able to employ .an Q,O-dialkyl dithisophosphoric acid ,diester tin which-the alkyl'groups are of relatively Joyv mole u a w h u h a h ethyl, to opy o ihuty radicals. When o p n hav n a rela e y rea e so ubil ty in lub t n o s a e desi ed, i i rretetahl to employ n QG-dia y it oph p o i ac sl ster in :whic th alky g oup ar o r a i e y hi h mo ecula weight such as those having up to 20 carbon atoms. Such alkyl radicals as lauryl, octadecyl, tetradecyl, etc., may be adva ta eous y use v uc .a cas s n e the o ger a ky g oup tend t n rease he s luhi vo th di h on o pha o Ii hydro rbon lu r c t n :oi Ihe QO-die y dit i phosphori ac d may fr quent y e used toadvantage as in th producti n oluh o ns oi .sl tives also having a high degree of heat stability wherein 3 the 0,0-diphenyl, 0,0-dialkylphenyl, and 0,0-dinaphthyl dithiophosphoric acids may be employed. It will be understood that mixed 0,0-dithiophosphoric acid diesters may also be employed such as various mixed alkyl-phenyl dithiophosphoric acid diesters.

Any metal may be used in accordance with the principles of the present invention provided it is capable of (1) forming a salt with a dithiophosphoric acid diester, and (2) forming a coordination complex with ammonia or amines. Such metals would include, for example, zinc, copper, chromium, cobalt, nickel and the like. As used herein, therefore, the term complex-forming metals will refer to and include such metals. In order to further describe the present invention, the preferred complexforming metal, zinc, will be used hereinafter primarily for purposes of illustration but it is to be pointed out that such is not to be construed as limitative of the invention and that the other above-mentioned metals may be used.

Ammonia or any suitably reactive amine may be used to form the coordination complex with the zinc, and the term amine" is understood to include ammonia unless the contrary is indicated. Examples of amines would include ethylamine, propylamine, isopropylamine, ethanolamine, diethanolamine, triethanolamine, cyclohexylamine, cyclopentylamine, di-isopropylamine, diethylamine, guanidine tripropylamine, triethylamine, and the like. The use of an amine containing a long chain hydrocarbon radical is particularly desirable where a greater oil solubility is desired, such as in the use of a lower alkyl diester of dithiophosphoric acid.

With regard to the character x as an integer from 1 to the coordination number of the metal used to form the complex salt, it is to be pointed out that its value will depend upon the number of ammonia or amine molecules linked to the zinc salt of the dithiophosphoric acid diester. The maximum value of x will therefore be normally twice the valence of the metal and, in the case of zinc, would be 4.

One general method of preparation of the novel products of the present invention comprises the initial formation of the zinc complex with ammonia or an amine, followed by its reaction with the sodium salt of the selected dithiophosphoric diester. For example, a complex-forming metallic salt, such as zinc sulfate (or zinc chloride) may be reacted with aqueous ammonium hydroxide to form zinc ammonium sulfate (Zn(NI-I3)4SO4.HzO). This complex salt may then be reacted with the sodium salt of the selected dithiophosphoric acid di-ester to form the zinc ammonium salt of the dithiophosphoric acid di-ester.

Another general method of preparation comprises the initial, separate formation of the zinc salt of the selected dithiophosphoric diester and the direct reaction therewith of the selected amine or ammonia. Such a reaction is exothermic and may be carried out very simply by mixing the reactants together at room temperatures, or at a higher temperature if an accelerated reaction is desired, in the required proportions and permitting the desired reaction to take place. Should it be desired to increase or decrease the temperature of the exothermic reaction mixture, such may be done by appropriate cooling or heating control means, as is well known in the industry.

The invention will be further illustrated in greater detail by the following specific examples. It should be understood, however, that although these examples may describe in particular detail some of the more specific features of the present invention, they are given primarily for the purpose of illustration and the invention in its broader aspects is not to be construed as limited thereto.

Example I To a solution of 40 grams of sodium hydroxide in 800 ml. of water was added 320 grams dihexyldithiophosphoric acid (prepared from methyl isobutyl carbinol). An exothermic reaction started immediately and the temperature of the reaction mixture was held between 25? I and 35- The pH of the final solution was adjusted to 10.3 by further addition of sodium hydroxide. 3 grams of Darco were added to this solution and, after stirring for 5 minutes, the solution was filtered through a Hyflo pre-coated filter to give a clear yellow filtrate. To this filtrate was added a solution of zinc ammonium sulfate prepared by dissolving 143 grams of zinc sulfate and 211 cc. of ammonium hydroxide in about 300 cc. of water. An oily product separated out which was drawn off and stripped under vacuum on a steam bath and filtered through a steam-heated, Hyflo, pre-coated filter. The final product was a viscous yellow liquid which was soluble in lubricating oil and had the following analysis:

Per cent Nitrogen 1.86 Phosphorus 9.12 Sulfur 18.40 Zinc 9.56

Example 2 A solution of sodium dihexyldithiophosphate was prepared by adding grams of dihexyldithiophosphoric acid (prepared from methyl isobutyl carbinol) to 32 grams of sodium carbonate in 300 m1. of water. The solution had a pH of approximately 8.7 and, after filtering, was treated with a solution prepared by dissolving 72 grams of zinc sulfate heptahydrate and 107 grams ethanolamine in 250 ml. of water. An oily material which separated out was washed with 250 ml. of water and stripped under vacuum on a steam bath to give a viscous liquid material, which was soluble in oil. The product had properties similar to those possessed by the product of Example 1.

Example 3 on a steam bath and filtered to give a viscous, oil-soluble product having detergent and alkaline reserve" properties and capable of reducing or retarding the undesirable effects of the oxidation products developed or liberated during use of a lubricating oil.

Example 4 To 66 grams of zinc dihexyldithiophosphate was added 1.7 grams of anhydrous ammonia. An exothermic reactiontook place immediately and the temperature of the reaction mixture was held to between 25 and 30 C. The material became quite viscous. After standing several days, the concentrated oil-soluble material crystallized and appeared to be in every way similar to the product resulting from Example 1.

Example 5 To 33 grams of zinc dihexyldithiophosphate was added 10 grams of di-isopropylamine. An exothermic reaction took place immediately and a light yellow viscous oil soluble reaction product resulted. This product was oilsoluble and showed no tendency to crystallize out at any concentration over a period of several weeks and was found to be an excellent lubricating oil additive;

oils and the like.

1 Example 7 To 33 grams of zinc dihexyldithiophosphate was added grams of cyclohexylamine. A vigorous exothermic reaction took place immediately resulting in a light yellow viscous, oil-soluble reaction product having the desired detergent, anti-oxidant and corrosion inhibiting properties.

The novel products of the present invention are preferably used in hydrocarbon lubricating mineral oils in relatively small stabilizing amounts which may vary from about 0.1% up to about 4.5% by weight or greater depending on the nature of the particular oil and on the degree of protection desired therein. In automobile engine lubricating oils, stabilizing quantities on the order of from about 0.30% up to about 2.0% by weight are usually incorporated into the oil. Our novel alkaline reserve additives, having excellent detergents, anti-oxidant and corrosion inhibiting properties, are compatible with all of the commonly used detergents, stabilizers, sludge inhibitors and other ingredients of compounded oils and may be used in conjunction therewith in smaller or larger quantities, as desired.

If desired, our novel products may be mixed with lubricating oils to form various concentrates, such as for example, a 50% concentrate, and used in such a form rather than in 100% concentrations. Such will facilitate the use thereof and will aid in preventing the crystallization of the product which occurs occasionally with higher concentrations of the ammonia complexes, as noted in Examples 1 and 4.

A representative sample of the product produced as described in Example 1 was tested for efficiency in a Chevrolet L-4 test. This test consists of operating the engine continuously at a speed of 3150 R. P. M. for 36 hours at 30 H. P. loading with a crankcase oil temperature of 280 F. and a water jacket outlet temperature of 200 F. The engine is then disassembled and the parts are inspected and rated. The amount of varnish on the pistons is reported on a scale ranging from 1-10 and 10' means a perfectly clean piston and I means a piston which is very dirty with stuck piston rings. The overall rating is reported on a scale ranging from 1-100 in which 100 means a clean engine with no sludge deposits and clean pistons.

The average weight loss per whole bearing may be determined by individually weighing each one of a pair of whole bearings before and after the test with the average of the resulting differences being equal to the average weight loss per whole bearing.

The neutralization number means the alkali equivalent in milligrams of potassium hydroxide which is required to neutralize a gram of the oil.

An S. A. E. 30 Mid-Continent solvent-refined base oil having a viscosity index of 85-95 and with no additive was used as a control and showed the following results:

Piston rating 9.2 Overall rating 93.3 Wt. loss per whole bearing mgms 2677 Neutralization number (new) 0.1 Neutralization number (used) 2.7 Percent viscosity increase percent 34 0.35% by weight of a zinc ammonium dihexyldithiophosphate was incorporated in a Mid-Continent solventenemas refined base oils rjto the aboveused oil. The results were as follows:

L-l caterpillar diesel engine 'test was run on "(1') a Mid-Continent solvent refined base oil containing 0.91% by weight of a detergent commonly used in the industry and 0.79% by weight of a corrosion inhibitor and antioxidant also commonly used in the industry and (2) a Mid-Continent solvent-refined base oil wherein a zinc ammonium dihexyldithiophosphate replaced the corrosion inhibitor and anti-oxidant. At the conclusion of the tests, a comparison of the carbon filling in the top ring groove showed an improvement of 30% for the composition containing the ammonium zinc dihexyldithiophosphate.

Although we have described but a few specific examples of our invention, we consider the inventive concept not to be limited thereby nor to the specific substances mentioned therein, but to include various other equivalent compounds of similar constitution as set forth in the claims appended hereto. It is understood that any suitable changes or variations may be made without departing from the spirit or scope of the inventive concept.

We claim:

1. A lubricating oil composition comprising a major portion of hydrocarbon mineral oil subject to oxidation and from about 0.1% to about 5% by Weight of a compound having the general formula wherein each of R1 and R2 is a member of the group consisting of alkyl, aryl, aralkyl, alkaryl and cycloalkyl radicals; Me is a metal from the group consisting of zinc, copper, chromium, cobalt and nickel capable of forming coordination complexes with ammonia; z is the valence of Me; each of A, B and C is a member of the group consisting of hydrogen, alkyl and alkylol radicals; and x is an integer from 1 to the coordination number of Me.

2. The invention as defined in claim 1 wherein said compound is present in amounts from about 0.30 percent by weight to about 2.0 percent by weight.

3. A lubricating oil composition comprising a major portion of a hydrocarbon mineral oil subject to oxidation and from about 0.1% to about 5% by weight of a compound having the general formula wherein each of R1 and R2 is a member of the group consisting of alkyl, aryl, aralkyl, alkaryl and cycloalkyl radicals; each of A, B and C is a member of the group consisting of hydrogen, alkyl and alkylol radicals; and x is an integer from 1 to 4, inclusive.

4. A lubricating oil composition comprising a major portion of a hydrocarbon mineral oil subject to oxidation and from about 0.1% to about 5% by weight of a compound having the general formula wherein each of R1 and R2 is a member of the group consisting of alkyl, aryl, aralkyl, alkaryl and cycloalkyl radicals; and x is an integer from 1 to 4, inclusive.

5. The invention as defined in claim 4 wherein said compound is present in amounts from about 0.30 percent by weight to about 2.0 percent by weight.

a 6. A lubricating oil composition as defined in claim 1 wherein R1 and R2 are alkyl radicals; Me is zinc; z is 2;

wherein R1 and R2 are alkyl radicals; Me is zinc; x is 2; and x is an integer from 1 to 4, inclusive. A, B and C are hydrogen; and x is an integer from 1 to 11. A lubricating oil composition as defined in claim 1 4, inclusive. wherein R1 and R2 are alkyl radicals having six carbon 7. A lubricating oil composition as defined in claim 1 5 atoms; Me is zine; z is 2; and x is an integer from 1 to 4, wherein R1 and R2 are alkyl radicals having six carbon inclusive. atoms; Me is zinc; z is 2; A, B and C are hydrogen; and x is an integer from 1 to 4, inclusive. References Cited in the file of this patent 8. A lubricating oil composition as defined in claim 3 UNITED STATES PATENTS wherein R1 and R2 are hydrocarbon aliphatic radicals. l0 9. A lubricating oil composition as defined in claim 4 g i i2 wherein R1 and R2 are hydrocarbon aliphatic radicals. 00 e 10. A lubricating oil composition as defined in claim 1

Claims (1)

1. A LUBRICATING OIL COMPOSITION COMPRISING A MAJOR PORTION OF HYDROCARBON MINERAL OIL SUBJECT TO OXIDATION AND FROM ABOUT 0.1% TO ABOUT 5% BY WEIGHT OF A COMPOUND HAVING THE GENERAL FORMULA