US 3751235 A
Gasoline compositions containing an additive for reducing the amount of deposits formed in engine intake manifolds and on the intake valve tulips. The compositions contain the base gasoline and as an additive, a heavy distillate naphthenic oil, and, preferably, also a gasoline-soluble nickel, cobalt, chromium or zinc organophosphate.
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Description (OCR text may contain errors)
United States Patent 1 Schoen 1 GASOLINE COMPOSITION  Inventor: Walter F. Schoen, South Holland, 111.
 Assignee: Atlantic Richfield Company, New
\ York, NY.
 Filed: May 21, 1970  Appl. No.: 39,564
Related U.S. Application Data  Continuation-impart of Ser. No. 753,832, July 31, 1968, abandoned, which is a continuation of Ser. No. 528,777, Feb. 21, 1966, abandoned, which is a continuation-in-part of Ser. No. 413,303, Nov. 23, 1964, abandoned.
 U.S. Cl 44/58, 44/68, 44/69, 44/D1G.  Int. Cl. ..Cl0l1/18, C101 1/26, C101 1/30  Field of Search 44/58, 68, 69, 76;
 References Cited UNITED STATES PATENTS 3,293,181 12/1966 Stuart 44/68 X 3,396,183 8/1968 Brasch 3,445,206 5/1969 Revukas 44/68 X Aug. 7, 1973 Primary Examiner-Daniel E. Wyman Assistant Examiner-W. U. Shine Att0rney.l0hn W. Behringer, Eugene L. Bernard, Mark J. Brown, James N. Dresser, John T. Roberts, Malcolm L. Sutherland, W. Brown, Morton & Thomas and J Clough  ABSTRACT Gasoline compositions containing an additive for reducing the amount of deposits formed in engine intake manifolds and on the intake valve tulips. The compositions contain the base gasoline and as an additive, a heavy distillate naphthenic oil, and, preferably, also a gasoline-soluble nickel, cobalt, chromium or zinc organophosphate.
11 Claims, N0 Drawings This application is a continuation-in-part of copending application, Ser. No. 753,832, filed July 31, 1968, now abandoned, which application was a continuation of application, Ser. No. 528,777, filed Feb. 21, 1966, now abandoned, which application was a continuationin-part of application, Ser. No. 413,303, filed Nov. 23, 1964, now abandoned.
This invention relates to gasolines exhibiting reduced tendencies towards the formation of deposits in sparkignition internal combustion engine intake manifolds and/or intake valve tulips. More specifically, this invention relates to an upper cylinder lubricant formulation containing a heavy distillate naphthenic oil and, optionally, and preferably, a nickel, cobalt, chromium or zinc organophosphate, and to gasolines containing such oils and, if desired, the organophosphate salt.
One problem associated with gasoline engines is that deposits collect in the intake manifold and on the intake valve tulips. This deposit accumulation is particularly prevalent in engines used in mild duty operations, industrial engines, engines run at constant speeds and- /or loads, engines run on rich air-fuel mixtures, and engines using triple graded motor oils. The intake system deposit build-up can seriously affect engine performance by blocking the intake passages and thereby limiting the air intake, by causing sticking of the intake valves, and by having pieces of this deposit break off and damage engine parts.
One known method of minimizing the formation of deposits in intake manifolds and on intakevalve tulips is to add a light distillate naphthenic oil to the gasoline as an upper cylinder lubricant. Thus, commercial upper cylinder lubricant formulations generally are based on light distillate naphthenic oils having a gravity between 225 and 25.5? API, and a Saybolt viscostiy at l F. of 55 to 60 seconds.
This invention provides unique gasoline compositions that are more effective than gasolines containing presently available commercial upper cylinder lubricant formulations in reducing intake system deposits, and in its preferred form the composition does not increase the engine octane requirement to any significant extent, if at all, over and above that normally experienced from use of the base gasoline. The composition of the present invention in its broader form is a hydrocarbon gasoline, having added thereto a minor amount sufficient to reduce deposits in the intake systems of spark-ignition internal combustion engines using the gasoline, of a heavy distillate naphthenic mineral oil. Since this heavy oil additive may have a tendency to increase deposits in the combustion chambers of such engines usingv the gasoline or adversely afiect engine performance, for instance, in terms of octane requirement increase or rumble, the fuel preferably also contains a minor amount sufficient to decrease the amount of these deposits or to reduce rumble or octane requirement increase based on the heavy distillate naphthenic oil-containing gasoline, of one or more nickel, cobalt, chromium or zinc organophosphate. The combination of the heavy distillate oil and organophosphate can also be made or preblended as an additive composition for the gasoline. Thus, the new additive composition consists essentially of the heavy distillate naphthenic mineral oil and one or more, nickel, cobalt, chromium or zinc organophosphate. To facilitate 2 ease of handling, the additive composition or gasolines may contain a hydrocarbon solvent boiling in the gasoline range, e.g., primarily in the range of about to I 450F., as well as antioxidants, antiwear agents or other additive agents.
The heavy naphthenic oils used in thecompositions of this invention can be obtained by distillation of naphthenic crude mineral oils. The heavy naphthenic mineral oils of this invention are composed of at least about 25 percent by volume naphthene hydrocarbons, often at least about35 percent. The naphthenic oil may also contain up to about 55 volume percent parafiin hydrocarbons and up to about 20 volume percent aromatic hydrocarbons. The preferred heavy naphthenic oils contain at least about 40 percent naphthenes, about 30 to 50 percent paraffins and about 8 to 18 percent aromatics. The naphthenic oils are of lubricating viscosity and thus usually have a viscosity of about 1,600 to 6,000 SUS at 100F., preferably about 1,800 to'2,300 or 3,000 SUS at 100F. The oils can have an API gravity (60F.) of about 18 to 24, advantageously about l8.5 to 21.5". I v
The heavy distillate naphthenic oil should be added to the gasoline in a minor amount at least sufficient to be effective in reducing or minimizing the formation of deposits in intake systems of spark ignition engines using the gasoline, e.g.in manifolds and on intake valve tulips. The amount of heavy naphthenic oil will usually vary from about 0.002 to 3 volume percent based on the gasoline, with the preferred concentration being from about 0.1 to 1.0 volume percent.
The organophosphates .which are preferably used in this invention are nickel, cobalt, chromium or zinc salts of compounds represented by the following formula:
wherein R is a hydrocarbon radical of up to about 30 ormore carbon atoms on the average, often at least about tive and preferably eight to 18 carbon atoms, R is hydrogen or R, and X is chalcogen having an atomic number of eight or 16, i.e. oxygen or sulfur. R can be an aliphatic, aromatic or mixed aliphatic aromatic radical and is preferably non-olefinic and non-acetylenic, i.e. having adjacent carbon atoms no closer than 1.40 A. The total carbon atoms in a molecule of the phosphorous compound is preferably up to about 40 or even up to about 30 and the nickel, cobalt, chromium or zinc salt of the phosphorous compound is soluble in gasoline at least to the extent employed.
The phosphoruscompounds from which the metal salts used in the invention are made can be obtained by methods known to the art as, for instance, by reacting aliphatic alcohols, including cycloaliphatic alcohols or aromatic hydroxy compounds with P 0 or P,S,. The preferred alcohols are alkanols which can be straight or branch chained and alkyl-substituted phenols whose alkyl substituents contain a total of up to 18 carbon atoms, and preferably are lower alkyl, especially methyl. The aromatic hydroxy compounds and aliphatic alcohols may. be substituted with nondeleterious groups. Illustrative of suitable alcohols are pentanol, butanol, octanol, isooctanol, 2-
ethylheptanol, dodecanol, oleyl alcohol, octadecyl alcohol, tetradecyl alcohol alcohols prepared by the Oxo process, phenol and alkylated phenols such as cresol, xylenol, propyl phenol, butyl phenol, dibutyl phenol, monoamylphenol, diamyl phenol,'decyl phenol, dodecyl phenol, tetradecyl phenol, hexadecyl phenol and octadecyl phenol.
The reaction of the alcohol and P or P 8 to prepare the partial esters or thioesterscan be conducted by heating the reactants at temperatures of from about 75F. to about 125C. for a period of time sufficient to effect substantially complete reaction, usually about 1 to hours. An inert solvent such as toluene, xylene or the like may be used to facilitate the reaction. A suitable molar ration of alcohol w o, or P 8 may be about 3:1.
The ester products thus produced can be, for instance, dialkyl or diaryl esters of dithiophosphoric acid or monoalkyl, dialkyl, monoaryl or diaryl esters of phosphoric acid, or any combination thereof. The mixed esters of phosphoric acid are often present, for instance, in a mole ratio of at least about 25 percent of each, say about 60 to 40 percent monoester; 40 to 60 percent diester. The metal salts of the esters can be prepared by directly reacting the esters with a cobalt, nickel, chromium or zinc carbonate or acetate. Either the metal or the acidic component of the salts may be used in excess and either the monoor dipartial ester salts may be employed but they are conveniently prepared and made available as the mixed ester salts. Mixed organophosphates of two or more of the cobalt, nickel, chromium and zinc salts may also be used.
The phosphorus metal salt component used in the invention can be incorporated in the gasoline in minor amounts sufficient to reduce the formation of deposits in the combustion chamber of a spark-ignition engine employing the gasoline. The phosphorus metal salt may be present in amounts to give about 50 to 1,000 grams of metal per thousand barrels of gasoline. The preferred amount of metal salt provides about 150 to 500 grams of metal per thousand barrels of gasoline. The amount of metal salt is often about 1 to 15 weight percent, preferably about 3 to 10 percent, based on the heavy distillate naphthenic oil, whether these components be separately added to the gasoline or first combined and then added to the fuel. Thus, the invention also provides a new additive composition consisting essentially of the naphthenic oil and the metal organophosphate. As stated, the additive combination may contain other ingredients such as a light hydrocarbon solvent to facilitate handling. Suitable aromatic solvents include benzene, toluene, xylene, etc. Where used, the solvent is often about 25 to 75 volume percent of the combined solvent and heavy distillate naphthenic oil.
The gasolines to which the additives of the present invention are added are hydrocarbons boiling primarily in the gasoline range, usually about 100 to 425F. which may have added thereto a small amount, generally between about 1 to 6 cc. per gallon, preferably about 2 to 4 cc. per gallon, of a tetra-lower-alkyl lead compound as an antiknock agent. The gasolines are usually composed of a major amount of a blend of hydrocarbon mineral oil fraction boiling primarily in the aforementioned rangeand may contain varying proportions of paraffins, olefins, naphthenes and aromatics derived by distillation, cracking and other refining and chemical conversion processes practiced upon crude oil fractions. Straight run gasolines, gasolines derived from cracking gas oil, gasolines or reformate from reforming straight run naphtha over a platinum-alumina catalyst in the presence of hydrogen, etc., are components frequently used in making up a gasoline composi tion. A typical premium gasoline, besides containing a small amount of a tetra-lower-alkyl lead compound as an antiknock agent may also contain small amounts of other non-hydrocarbon constituents used to impart various properties to the gasoline in its use in internal combustion engines, e.g. halohydrocarbon scavengers, oxidation inhibitors, etc. Such gasolines frequently have a Research Method octane number of about 90 to 105, and a Motor Method octane number of about to 98.
In order to provide leaded gasolines of further enhanced characteristics, for instance, as to preignition, spark plug fouling and even, in at least some cases, rumble, there can be included in the gasoline composition of the invention a gasolinesoluble' phosphorus compound having the formul wherein R has. the value described above with respect to the phosphorus compounds from which the cobalt, nickel, chromium or zinc salts of the invention are made; R is hydrogen or R and n is an integer of 0 to l. R is preferably an aromatic e.g., phenyl, hydrocarbon or radical of six to 12 carbon atoms and can be substituted as, for instance, with lower alkyl groups say of one to four carbon atoms. Thus, the phosphorus compound can be a mono-, di-, triester, or a mixture of such and is preferably a triester. lt is also preferred to employ a phenyl, alkyl phenyl or a mixed phenyl-alkyl phenyl ester of phosphorus. Thus, one or more of the ester groups is preferably an alkyl phenyl radical, often of about seven to 15 carbon atoms. See US. Pat. No. 2,889,212 for a further list of the useful phosphates and phosphites.
These auxiliary phosphate and phosphite additives can be prepared by reacting the appropriate alcohol or phenol with phosphoric acid to make the phosphate or with phosphorus trichloride to form the phosphite. Illustrative of suitable alcohols and phenols are those mentioned above in the description of the phosphorus esters used to fonn the metal salts of the invention. Examples of suitable alkyl phenols are ortho, meta and para cresol; 2,4- and 2,5-xylenol; 2,4-dimethyl-6- tertiary butylphenol; octyl and monyl phenols, etc.
When used, about 0.05 to 0.6 theory, preferably about 0.15 to 0.5 theory, of the auxiliary phosphate or phosphite additive, based on the lead content of the gasoline, is generally employed. The term theory as applied to the amount of the second phosphorus additive means the amount required to react stoichiometrically with the lead to that all of the lead atoms and all of the phosphorus atoms form Pb,(PO,),.
The effectiveness of the unique upper cylinder lubricant of this invention to reduce intake system deposits without increasing engine octane requirements, is demonstrated in the following examples.
EXAMPLE I A clean 1963 Oldsmobile engine was run with a controlled cycline procedure for 216 hours on a typical commercial gasoline. This gasoline had a boiling range of 98 to 370F. and consisted of 25 percent straight run gasoline, 25 percent isobutane-butene alkylate, 25 percent catalytically cracked gasoline, and 25 percent catalytically reformed gasoline. This blend contained 3.0 cc. TEL/gal. and other gasoline additives, e.g. 0.2 theory of cresyl diphenyl phosphate and a mixed ethylene dichloride-ethylene dibromide scavenger. The engine was lubrciated with a premium quality SAE 20 grade oil. The octane requirement of this engine increased four (4) octanes during the test run. The deposits accumulated in the intake manifold weighed 13.47 grams and 9.77 grams of material deposited on the intake valve tulips.
EXAMPLE II An additive combination was made by adding 6 weight percent of a nickel salt of a mixed, approximately 50% monoand 50% di-, C -Oxo alcohol esters of phosphoric acid, analyzing about 10 percent nickel, to a naphthenic lube oil having an API gravity of about 20 and a viscosity of 2,000 SUS at 100F. and containing 40 percent naphthenes, 45 percent paraffin and the engine was again four (4) octane numbers, but the intake manifold was completely free of deposits and the intake valve tulips accumulated only 1.44 grams of deposit. Similar results'are obtained with the corresponding cobalt organic phosphate salt, analyzing about 4.5 percent cobalt.
EXAMPLE Ill The advantage in adding the nickel and cobalt organophosphates to the naphthenic oil was demonstrated by the following run. The same 1963 Oldsmobile engine used in Examples I and II was cleaned and run on the same fuel as in Example I, but which was added the naphthenic oil of Example 11 but without the nickel phosphate salt. In this run the volume of naphthenic oil was the same as the volume of naphthenic oil plus the nickel phosphate compound added in Example 11. After the 216 hour test, the intake manifold accumulated 5.77 grams of deposit, and the intake valve tulips accumulated 2.16 grams of deposit. However, the octane requirement increase for this run was five (5) octanes; a percent increase over Example I.
EXAMPLES IV & V
Results similar to those in Example II are obtained by replacing the nickel salt with the nickel salts of approximately 50% monoand 50% di-,.cresyl ester of phosphoric acid (2.8 percent nickel), or approximately 50% monoand approximately 50% di-, C alkyl phosphoric acid ester (3.5 percent nickel).
EXAMPLES Vl & Vll
\ One mole of mixed, approximately 50% monoand approximately 50% di-, C -oxo alcohol esters of phosphoric acid was reacted with slightly more than one mole of chromium acetate in a hexane solvent. The reaction was carried out at C. for one hour, and the product was then filtered. The hydrocarbon solubles were water-washed several times, refiltered and the resulting chromium salt of mixed monoand di- C -oxo esters of phosphoric acid was dried to constant weight, analyzing 1.82 percent chromium and 6.8 percent phosphorus.
The corresponding zinc salt can be made in a similar manner using zinc acetate.
Results similar to those of Example 11 can be obtained by replacing the nickel salt with the thusprepared chromium salt or zinc salt.
EXAMPLE Vlll A clean 1963 Oldsmobile engine was run using a typical commercial gasoline. This gasoline had a boiling range of 83 to 404F. and consisted of 25 percent straight-run gasoline, 25 percent isobutane-butene alkylate, 25 percent catalytically cracked gasoline and 25 percent catalytically reformed gasoline. The blend contained 3 g. of tetramethyl lead/gal. added with halogencontaining scavengers, 0.2 theory of cresyl diphenyl phosphate and minor amounts of alkyl monoamine salts of monoand di-phosphates, metal deactivator (disalicylal propylene diamine) and oxidation inhibitor (dibutyl-para-cresol) (Blend A"). The deposits accumulated in the valve tulip weighed 9.8 grams and 13.5 grams of material deposited in the port. The octane requirement of this engine increased four (4) octanes during the test run. Rumble was measured as 30 and 62.7 grams of material were: deposited in the combustion chamber.
The same test was run on the same engine with the same gasoline blend to which was added 0.1 volume percent of a distillate naphthenic lubricating oil having an AP] gravity of about 20.4, a viscosity of about 2,000 SUS at 100F. and containing about 48 percent naphthenes, 38 percent paraffins and 14 percent aromatics (Blend B). The deposits accumulated in the valve tulip weighed 2.2 grams and 5.8 grams of material deposited in the port. The octane requirement of this engine increased five (5) octanes during this run. Rumble was measured at and 62.5 grams of material were deposited in the combustion chamber.
The same test was run again on the same engine with the same base gasoline blend to which was added 0.1 volume percent of the oil of Blend B and a minor amount sufiicient to yield 300 gms. of nickel/ 1000 barrels of gasoline of a nickel salt of a mixed, approximately 50% monoand 50% di-, C -Oxo alcohol esters of phosphoric acid, analyzing about 10% nickel (Blend C"). The deposits accumulated in the valve tulips weighed 1.4 grams and no measurable deposits of material were found in the part. The octane requirement of this engine increased four (4) octanes during the test run. Rumble was measured at 60 and combustion chamber deposits measured 58.8 grams.
EXAMPLE 1X Gasoline-additive combinations were made by adding various amounts of distillate naphthenic lubricating 7 8 oils of varying viscosities to a typical commercial gasooil of lubricating viscosity containing at least about 25 line. The gasoline had a boiling range of 83 to 404C. percent naphthene hydrocarbons, up to about 55% par and consisted of 25 percent straight-run gasoline, 25 affin hydrocarbons and up to percent aromatic hypercent isobutane-butene alkylate, percent catalytidrocarbons, said oil having a viscosity of about 1,600
cally cracked gasoline and 25 percent catalytically re- 5 to 6,000 SUS at 100F. and an API gravity of about 18 formed gasoline. The blend contained 3 g. tetramethyl to 24, and from about 50 to 1,000 gms. of metal per lead/gal. added with halogen-containing scavengers, thousand barrels of gasoline of a metal member se- 300 g. of nickel/ 1,000 barrels of a nickel salt of a lected from the group consisting of the gasoline-soluble mixed, approximately 50% monoand 50% di-, C nickel, cobalt, chromium or zinc salts of a phosphorus Oxo alcohol esters of phosphoric acid, analyzing about 10 compound having the formula: 10 percent nickel, 0.05 theories of cresyl diphenyl phosphate, one pound/1,000 barrels of disalicylal pro- R0 XH pylene diamine, two pounds/1,000 barrels of alkyl monoamine salt of monoand di-alkyl phosphates and three pounds/ 1,000 barrels of dibutyl-paracresol antil5 oxidant. The blends were tested on a clean 1966 Oldsmobile engine. The compositions tested and the test results are shown below in Table I.
wherein R is a hydrocarbor iradical of up to about carbon atoms on the average, R is selected from the 'T ABLE I Intake system deposits, Performance t iscosgrams C RC checks Combus- Conccntraity, intake Appearance of tion Oil tion, vol. SUS, Valve 1 valve intake Rumchamber Test N 0. additive percent 100 F. tulip Port Total rating 4 valve deposits 0R1 ble deposits 32 Nonc 16. 0 10. 7 36. 6 6. 2 Hard and brittle. 3 78.9 0. 1 2, 000 16. 9 1. 4 18. 3 7. 5 Dry and crumbly. 3 30 01. 3 0. 1 1, 200 26. 3 11. 9 38. 2 6. 1 Hard and brittle. 3 40 41. 6 8' 8g 1,600 28. 2 7.0 35. 2 5.8 Dry and crumbly. a 40 47. s g: 1, 400 31.8 s. 0 39. s 5.6 Hard and brittle a 30 43. o 0.1 3, 000 27. 4 8. 8 36. 2 7. 7 Dry and crumbly. 3 51. 1
1 ()il lwas a rciincd distillate lubricating oil having a viscosity of approximately 2,000 SUS at 100 F. derived from a naphthenic petroleum oil and having an API gravity of about 201 and containing about 48% naphthenc hydrocarbons, about 38% paraffin hydrocarbons and about 14% aromatic hydrocarbons.
2 Oil 2 was a rclincd distillate lubricating oil having a viscosity of approximately 1,200 SUS at 100 F. derived from a naphthcnic petroleum oil and having an AIl gravity of about 103 and containing about 46% naphthene hydrocarbons, about 40% paraffin liydrocarlons and about 14% aromatic hydrocarbons.
Oil 3 was a refined distillate lubricating oil having a viscosity of approximately 3,000 SUS at 100 F. derived from a naphthcnic pclrolcum oil and having an Ali gravity of about 10.1 and containing about 41% naphthenc hydrocarbons, about 43% paraliin hydrocarbons and about 16% aromatic hydrocarbons.
1 Rating scale from 1 to 10, whcrc 10 is a clean valve.
EXAMPLE X group consisting of hydrogeh and R and X is a chalco- A clean 1968 Oldsmobile engine was run using gen having an atomic numb of eight or blends of the same gasoline blend as in Example IX to 40 2. A gasoline composition of claim 1 wherein the which were added varying amounts of naphthenic luvnaphthenic mineral oil has aviscosity of 1,800 to 3,000 bricating oils of varying viscosities. The compositions SUS at 100F. and an API gravity of about 18.5 to tested and the test results are shown below in Table 11. 2l.5.
7 'TABLE 11 Oil addi- Intake system tive visdeposits, grams CRC Concentracositg, intake Oil tion, vol. SU Volvo valve Appearance of intake valve 'lcst No. udditwo percent 100 F. tulip Port Total rating deposits 12.5 4.3 10.x 11.4 llurd 111171 1mm".
0.1 300 14.7 2.7 17.4 as Do.
1,000 12.2 3.0 15.2 0.4 -l)ry and crumbly. 8: 1, 57.5 15.0 2.4 18.3 0.1 Hard and brittle.
0. 2 2,000 15. 2 1.1 16.3 7. 7 Oily with isolated deposits.
l Oil 4 was a refined distillate lubricating oil having a viscosity of approximately 300 SUS at 100 F. derived from a naphthcnic petroleum oil and having an API gravity of about 21.0 and containing about 45% naphthone hydrocarbons, about 311% paraflin hydrocarbons and about 16% aromatic hydrocarbons.
2 Oil 1 was a refined distillate lubricating oil having a viscosity of approximately 2,000 SUS at 100 F. derived from a naphthcnic petroleum oil and having an A PI gravity of about 20.4 and containing about 48% naphtheno hydrocarbons, about 38% paratlin hydrocarbons and about 14% aromatic hydrocarbons.
3 Oil 2 was a refined distillate lubricating oil having a viscosity of approximately 1,200 SUS at 100 F. derived from a naphthcnic petroleum oil and having an API gravity of about 19.4" and containing about 46% naphthcne hydrocarbons, about 40% parailln hydrocarbons and about 14% aromatic hydrocarbons.
it is claimed: 3. A composition of claim 1 wherein at least one R 1. A gasoline composition comprising a major is an alkyl radical of eight to 18 carbon atoms and X is amount of a hydrocarbon gasoline and an amount suffioxygen.
cient to reduce the formation of deposits in the intake system of a spark-ignition engine using said gasoline, of 6 from about 0.002 to 3 volume percent based on the hydrocarbon gasoline of a distillate naphthenic mineral, 5. A composition of claim 2 wherein at least one R 5 4. A composition of claim 3 wherein the metal of said selected phosphorus compound is zinc.
9. A composition of claim 6 wherein there is also included about 0.05 to 0.6 theory of a gasoline-soluble phosphorus compound having the formula:
wherein R is a hydrocarBon radical of up :6 about 30 carbon atoms on the average, R is selected from the group consisting of hydrogen and R, and n is an integer having a value of 0 to l.
10. A composition of claim 9 wherein at least one R is an alkyl phenyl radical of seven to 15 carbon atoms.
11. A composition of claim 10 wherein at least one R is an alkyl radical of eight to 18 carbon atoms and X is oxygen.
l I II! l