Oil-soluble phosphorus- and nitrogen-containing additives

Abstract: An oil-soluble phosphorus- and nitrogen-containing composition having limited slip properties obtainable by (i) reacting an O,O-di-hydrocarbyl phosphorodithioic acid (a) wherein at least 50 mole % of the hydrocarbyl groups are secondary acyclic hydrocarbyl groups free of acetylenic unsaturation and the balance, if any, of the hydrocarbyl groups are primary acyclic hydrocarbyl groups free of acetylenic unsaturation with an epoxide (b) selected from a monoepoxide or mixture of monoepoxides each having 20 to 30 carbon atoms per molecule, epoxidized soybean oil, methyl epoxy soyate, butyl epoxy soyate, octyl epoxy soyate, epoxidized linseed oil, methyl epoxy linseedate, butyl epoxy linseedate or octyl epoxy linseedate to form a product, (ii) reacting the product with phosphorus pentoxide to produce an acid phosphate intermediate, and (iii) neutralizing at least a major proportion of the intermediate with at least one amine.

Description: TECHNICAL FIELD This invention relates to novel metal-free phosphorus- and nitrogen-containing compositions that are useful as multifunctional additives in oils of lubricating viscosity. BACKGROUND Although a substantial number of gear oils are available in the marketplace, there exists a need for further improvements in limited slip or enhanced positraction performance. It is known that the high pressures occurring in certain gears and bearings may cause a lubricant film to rupture so that opposing metal surfaces contact each other. This metal contact results in scuffing, seizure, excessive wear, loss of efficiency, and ultimately in the failure of the mechanism. In addition, these high pressures on the oil film effect a rise in internal heat which may be increased by any friction resulting from the metal contacts through breaks in the oil film. Consequently, mechanisms in which high mechanical pressures are likely to occur between interacting metal surfaces require lubricants that have both high lubricity and high film strength or extreme pressure properties. Unfortunately, these two requirements are frequently antipathetic to each other. That is, an additive which has high film strength does not necessarily have good lubricity or "oiliness' and may in fact increase friction and heating in the oil film. Conversely, an additive having good lubricity or "oiliness" does not necessarily have good extreme pressure properties, and may in fact mask or interfere with the action of a separate extreme pressure additive component. Limited slip axles or differentials are mechanisms which transmit the greater driving force to the vehicular wheel that has the better traction. Such mechanisms have a special lubrication problem peculiar unto themselves. The interplay of pressures and forces during turns under load often results in noise, often referred to as "chatter", and vibration or shudder of the vehicle. In order to function properly, limited slip axles or differentials require, among other things, lubricants that have both high lubricity and high film strength or extreme pressure properties, requirements which, as noted above, are frequently antipathetic to each other. Prior attempts to overcome this "chatter" problem generally involved research on and utilization of friction-reducing agents or oiliness agents which were added to the base lubricant. In that approach it was necessary to avoid upsetting the balance between extreme pressure, antiwear, and rust and corrosion protection as well as the oxidative stability afforded by the additive components utilized in such lubricants. A very desirable advance in the art would be the provision of additive compositions that have the capability of providing both limited slip properties and antiwear/ extreme pressure properties to a lubricating oil composition in which they are employed. Such an additive would enable the formulation of lubricants which avoid or at least minimize the "chatter" problem, contribute antiwear/extreme pressure properties, and at the same time make it possible to avoid the complications brought about by use of conventional friction-reducing additives in the lubricant. An additive possessing such multifunctionality is rarely, if ever, encountered in the art. U.S. Pat. Nos. 3,197,405 and 3,197,496 contain extensive descriptions of phosphorus- and nitrogen-containing products formed by reaction of a hydroxy-substituted triester of a phosphorothioic acid with particular inorganic phosphorus reagents, and neutralization of the product with an amine. These products are indicated to be useful as insecticides, corrosion inhibitors, rust inhibitors, antiwear agents, and are indicated to be especially effective as corrosion inhibiting and extreme pressure additives in lubricating compositions. According to these patents, the hydroxy-substituted phosphorothioate triester may be formed in various ways including reaction of an O,O-dihydrocarbyl phosphorodithioic acid with an epoxide or glycol. The preferred epoxides are aliphatic epoxides having less than about 8 carbon atoms and styrene oxides. Other acyclic aliphatic epoxides mentioned are 1,2-octene oxide, dodecene oxide and octadecene oxide. U.S. Pat. No. 4,435,338 describes products made by reaction of an O,O-dialkyl dithiophosphate with a difunctional, trifunctional or tetrafunctional epoxide compound. THE INVENTION Novel and eminently useful multifunctional additives having, inter alia, limited slip properties are provided by this invention. More particularly products having limited slip properties as well as antiwear/extreme pressure and corrosion inhibiting properties are produced by forming a hydroxy-substituted phosphorothioate by (i) reacting an O,O-dihydrocarbyl phosphorodithioic acid with a monoepoxide or mixture of monoepoxides having in the range of 20 to about 30 carbon atoms in the molecule or a vegetable oil epoxide selected from the group consisting of epoxidized soybean oil, methyl epoxy soyate, butyl epoxy soyate, octyl epoxy soyate, epoxidized linseed oil, methyl epoxy linseedate, butyl epoxy linseedate, and octyl epoxy linseedate, (ii) reacting this product with phosphorus pentoxide to produce an acid phosphate intermediate, and (iii) neutralizing at least a major proportion of the intermediate with at least one amine. At least 50 mole % of the hydrocarbyl groups of the O,O-dihydrocarbyl phosphorodithioic acid are secondary acyclic hydrocarbyl groups free of acetylenic unsaturation and the balance, if any, of such hydrocarbyl groups are primary acyclic hydrocarbyl groups free of acetylenic unsaturation. Preferably, essentially all of the hydrocarbyl groups (e.g., at least 98% of them) are secondary acyclic hydrocarbyl groups free of acetylenic unsaturation. In short, the lower the content of the primary hydrocarbyl groups, the better. Thus within reasonable limits of commercial practicality, O,O-dihydrocarbyl phosphorodithioic acids formed from substantially pure secondary alcohols should be used in the above first stage reaction. Preferred products of this invention when formed from a 1,2-epoxide are composed principally of an oil-soluble phosphorus-and nitrogen-containing composition of the formula: wherein R is at least one alkyl group, and preferably a mixture of alkyl groups having from 18 to about 28 carbon atoms, and preferably a mixture of alkyl groups having from 18 to about 22 carbon atoms; each R' is, independently, a secondary acyclic hydrocarbyl group free of acetylenic unsaturation and having 3 to 18 carbon atoms; Amine is, independently, a protonated primary or secondary amine; n is 1-2; m is 1-2; and the sum of n and m is no greater thank 3. Typically, the product will further comprise a minor proportion (i.e., less than 50 mole %) of an isomeric form of the composition of Formula (I) above, namely an isomeric form having the formula: wherein R, R', Amine, n and m are as defined above. It will be appreciated that there is some uncertainty of analysis that exists in determining whether the substitution by the dithioacid moiety occurs on the 1- or 2- carbon on the epoxide chain. Accordingly, preferred products of the invention will additionally comprise a composition of formula II as described above and a composition with a major proportion of the composition of formula II in combination with a minor proportion of formula I. These preferred compositions of this invention can be prepared by (i) reacting a dihydrocarbyl phosphorodithioic acid of the formula: wherein each R' is as defined above, with at least one 1,2-alkylene oxide having from 20 to about 30 carbon atoms in the molecule to form a dihydrocarbyl mono-(hydroxyalkyl) phosphorodithioate, (ii) reacting this triester with phosphorus pentoxide to form a substituted acid phosphate of the formula: wherein R, R', and n are as defined above, and (iii) neutralizing at least a substantial portion of this substituted acid phosphate with at least one primary or secondary amine. Typically, the acid phosphate (IV) will be accompanied by a minor proportion of an isomeric form of the acid phosphate, viz., an isomeric form having the formula: wherein R, R', and n are as defined above. Again, as discussed above, it will be appreciated that due to uncertainty of analysis that exists in determining whether the substitution by the dithioacid moiety occurs on the 1- or 2- carbon on the epoxide chain, the above described preparation may form a substituted acid phosphate of formula (V) that may be accompanied by a minor proportion of the substituted acid phosphate of formula (IV). The vegetable oil epoxides selected from the group consisting of epoxidized soybean oil, methyl epoxy soyate, butyl epoxy soyate, octyl epoxy soyate, epoxidized linseed oil, methyl epoxy linseedate, butyl epoxy linseedate, and octyl epoxy linseedate undergo a similar reaction with the phosphorodithioic acid which is further reacted with phosphorus pentoxide as illustrated above for the 1,2-epoxide. With multiple sites including di-, tri- and greater epoxides, it is not effective to represent these products with a simple structural formula. Preferred vegetable oil epoxides for the invention are epoxidized soybean oil and methyl epoxy soyate. Preparation of the dihydrocarbyl phosphorodithioic acid is usually accomplished by reacting phosphorus pentasulfide with the appropriate alcohol, namely a secondary acyclic monohydric alcohol free of acetylenic unsaturation and having 3 to 18 carbon atoms in the molecule. Examples of such alcohols include 2-propanol, 2-butanol, 2-pentanol, 3-pentanol, and the higher secondary alkanol homologs up to and including the octadecanols, and the analogous secondary olefinically unsaturated alcohols such as 3-butenol-2, 3-pentenol-2, 4-pentenol-2, and analogous secondary alkenols having up to about 18 carbon atoms per molecule. The olefinically unsaturated alcohols may contain from 1 to 3 olefinic double bonds. Mixtures of two or more alkanols can be employed. Likewise, mixtures of olefinically unsaturated alcohols can be used, as well as mixtures of at least one secondary alkanol and at least one secondary olefinically unsaturated alcohol. The reaction involves 4 moles of the alcohol per mole of the phosphorus pentasulfide. Reaction temperatures are normally in the range of 50 to 150°C. When mixtures of alcohols are used, as long as the mixture contains at least 50 mole % of secondary alcohol(s), there can be up to 50 mole % of primary alcohol(s) in the mixture. Preferably such mixtures contain no more than about 30 mole % primary and- at least about 70 mole % secondary alcohol, and more preferably the mixture contains no more than about 10 mole % primary and at least about 90 mole % secondary alcohol. Use of one or a mixture of substantially pure secondary alcohols is preferred. The most preferred type of secondary alcohols are branched-chain secondary alcohols, such as 4-methyl-2-pentanol, 4-methyl-2-hexanol, 5-methyl-2-hexanol, 6-methyl-3-heptanol, 5,7-dimethyl-3-octanol, and analogous secondary alkenols. Branched-chain secondary alcohols having from about 6 to about 12 carbon atoms are particularly preferred. Methyl branching is very desirable. Of the branched alcohols, 4-ethyl-2-pentanol is presently the most preferred of all. The reaction of the dihydrocarbyl phosphorodithioic acid with the monoepoxide to form the dihydrocarbyl mono-(hydroxyalkyl) phosphorodithioate is an exothermic reaction and thus is ordinarily initiated at, or somewhat below, room temperature and preferably is controlled so as not to exceed about 70°C. Most preferably the reaction is conducted at temperatures in the range of 25 to 50°C. It is also preferred to add the monoepoxide (an alkylene oxide, preferably a 1,2-alkylene oxide) in small portions to the dihydrocarbyl phosphorodithioic acid while continuously agitating the reaction mixture. After completing the reaction, the reaction mixture is typically maintained at about 50°C with mild agitation for about one hour. Formation of the substituted acid phosphate in the ensuing reaction between the dihydrocarbyl hydroxyalkyl triester and the phosphorus pentoxide also involves an exothermic reaction. Thus once again the reaction may be initiated at about room temperature and preferably is conducted at a temperature within the range of 20 to 60°C. Typically, the reactants are employed in proportions of 2 to 4 moles of the triester, and preferably about 3 moles, per mole of the P 2 O 5 . Preferably, the P 2 O 5 is added portion-wise to the triester while agitating the reactants to ensure intimate contact between them. Upon completion of the reaction, it is desirable to maintain the reaction mixture at 50 to 60°C for about one hour while mildly agitating the mixture. Neutralization of the substituted acid phosphate is readily accomplished simply by mixing the acid phosphate with one or more selected primary or secondary monoamines. Typically, this reaction is conducted at a temperature of 20 and 60°C. Once again, it is desirable to continue agitating the reaction mixture while holding the temperature in the range of 50 to 60°C for a period of one hour. Among suitable amines for use in the neutralization step are (a) monoalkyl amines in which the alkyl group is a primary alkyl group of 1 to 30 carbon atoms such as methyl amine, ethyl amine, 1-propyl amine, 1-butyl amine, 2-methyl-1-propyl amine, 1-pentyl amine, 2-methyl-1-butyl amine, 3-methyl-1-butyl amine, 2,2-dimethyl-1-propyl amine, 1-hexyl amine, 2-methyl-1-pentyl amine, 3-methyl-1-pentyl amine, 4-methyl-1-pentyl amine, 2,2-dimethyl-1-butyl amine, 2,3-dimethyl-1-butyl amine, 3,3-dimethyl-1-butyl amine, 2-ethyl-1-butyl amine, and similar higher straight chain and branched chain monoalkyl amine homologs in which the primary alkyl group contains from 7 to 30 carbon atoms; (b) monoalkyl amines in which the alkyl group is a secondary alkyl group of 3 to 30 carbon atoms such as 2-propyl amine, 2-butyl amine, 2-pentyl amine, 3-pentyl amine, 3-methyl-2-butyl amine, 2-hexyl amine, 3-hexyl amine, 3-methyl-2-pentyl amine, 4-methyl-2-pentyl amine, 2-methyl-3-pentyl amine, 3,3-dimethyl-2-butyl amine, and similar higher monoalkyl amine homologs in which the secondary alkyl group contains from 7 to 30 carbon atoms; (c) monoalkyl amines in which the alkyl group is a tertiary alkyl group of 4 to 30 carbon atoms such as 2-methyl-2-propyl amine, 2-methyl-2-butyl amine, 2-methyl-2-pentyl amine, 3-methyl-3-pentyl amine, 2,3-dimethyl-2-butyl amine, and similar higher monoalkyl amine homologs in which the tertiary alkyl group contains from 7 to 30 carbon atoms; (d) ethylenically unsaturated acyclic monohydrocarbyl primary, secondary and tertiary amines such as allyl amine, the butenyl amines, the pentenyl amines, the hexenyl amines, the heptenyl amines, the octenyl amines, and similar higher homologs and analogs in which the alkenyl group contains from 9 to 30 carbon atoms and from 1 to 3 ethylenic double bonds; (e) dialkyl amines in which the alkyl groups are primary, secondary and/or tertiary alkyl groups such as dimethyl amine, methyl ethyl amine, diethyl amine, dipropyl amine, dibutyl amine, diisobutyl amine, di-tert-butyl amine, dipentyl amine, dihexyl amine, diheptyl amine, dioctyl amine, and analogous compounds having straight and/or branched chain alkyl groups each having up to about 30 carbon atoms; (f) ethylenically unsaturated acyclic dihydrocarbyl primary, secondary and tertiary amines such as diallyl amine, butyl octenyl amine, ethyl oleyl amine, dioleyl amine, and analogous compounds having two ethylenically unsaturated groups each containing up to about 30 carbon atoms and from 1 to 3 ethylenic double bonds or one such ethylenically unsaturated group and one primary, secondary or tertiary alkyl group having up to about 30 carbon atoms. Mixtures of these various amines can be used. Commercially available amines such as stearyl amine, oleyl amine, mixtures of tertiary alkyl primary amines such as Primene® 81R amine and Primene® JM-T amine (Rohm & Haas Company) are preferred. The compositions of this invention and their synthesis are illustrated by the following examples. Example 1 O,O-bis(4-methyl-2-pentyl) phosphorodithioic acid (59.7g; 0.2 mole) is placed in a 300 Ml reaction flask equipped with a stirrer. With continuous stirring, 0.2 mole of a commercially available mixture of 1,2-alkylene oxides having 20 to 24 carbon atoms per molecule (VIKOLOX® 20-24) is added dropwise and when the temperature has reached 45°C, the mixture is cooled so as to maintain the temperature between 45 and 50°C. When the addition is complete, the reaction mixture is stirred for one hour. In the second stage reaction, phosphorus pentoxide (9.4g; 0.066 mole) is added in 6 equal portions at intervals of approximately 10 minutes each. During the addition, the reaction mixture is continuously stirred and cooled to maintain the mixture at 50 to 55°C. Upon completion of the addition, the reaction mixture is held at this temperature range for one hour with stirring. Neutralization, the third stage reaction, is effected by adding oleyl amine (Armeen® OL) (55.6g; 0.2 mole) dropwise to the product of the second stage reaction while holding the temperature at 50 to 55°C. The reaction mixture is stirred for one hour at 50 to 55°C upon completion of the amine. The resultant product is a composition of this invention. Example 2 The procedure of Example 1 is repeated with the exception that 0.2 mole of a C 12-15 tertiary alkyl primary amine mixture (Primene® 81R) is used in place of the oleyl amine. The resultant product is a composition of this invention. Example 3 A composition of this invention is formed by repeating the procedure of Example 1 with the exception that the amine used is an equimolar mixture of 1-octadecyl amine and 2-octadecyl amine. Example 4 Upon repetition of Example 1, but using octyl amine (0.2 mole) instead of the oleyl amine, yields another composition of this invention. Example 5 Examples 1-4 are each repeated substituting 0.2 mole of O,O-bis(2-hexyl) phosphorodithioic acid for the O,O-bis(4-methyl-2-pentyl) phosphorodithioic acid. The resultant final products constitute compositions of this invention. Example 6 Examples 1-4 are each repeated substituting 0.2 mole of O,O-bis(5-methyl-3-hexyl) O,O-bis(4-methyl-2-pentyl) phosphorodithioic acid for the phosphorodithioic acid. The resultant final products constitute compositions of this invention. Example 7 The procedure of Example 1 is repeated except that 75.7g (0.2 mole) of a commercially available mixture of 1,2-alkylene oxides having 24 to 28 carbon atoms per molecule (VIKOLOX® 24-28) is used as the epoxide in the first stage reaction. The resultant final products are compositions of this invention. A product formed in this manner was found to contain 5.14% phosphorus and 6.38% sulfur, and to have an average molecular weight of about 1365. Example 8 The procedure of Example 7 is repeated except that the O,O-dihydrocarbyl phosphorodithioic acid used in the first stage is a mixed di-secondary alkyl phosphorodithioic acid formed from an equimolar mixture of 4-methyl-2-pentanol and 2-propanol. Thus the charge in the first stage reaction is 57.7g (0.2 mole) of this mixed di-secondary alkyl phosphorodithioic acid and 75.7g of the VIKOLOX® 24-28 epoxide. A product formed in this manner was found to contain 5.19% phosphorus and 6.45% sulfur, and to have an average molecular weight of about 1350. Example 9 O,O-bis(4-methyl-2-pentyl) phosphorodithioic acid (119.4 g) is placed in a 500 Ml reaction flask equipped with a stirrer. With continuous stirring, 90.2 g of a commercially available methyl epoxy soyate (VIKOFLEX® 7010) is added dropwise and when the temperature has reached 45°C, the mixture is cooled so as to maintain the temperature between 45 and 50°C. When the addition is complete, the reaction mixture is stirred for one hour. In the second stage reaction, phosphorus pentoxide (18.8 g) is added in 6 equal portions at intervals of approximately 10 minutes each. During the addition, the reaction mixture is continuously stirred and cooled to maintain the mixture at 50 to 55°C. Upon completion of the addition, the reaction mixture is held at this temperature range for one hour with stirring. Neutralization, the third stage reaction, is effected by adding oleyl amine (Armeen® OL) (111.2 g) dropwise to the product of the second stage reaction while holding the temperature at 50 to 55°C. The reaction mixture is stirred for one hour at 50 to 55°C upon completion of the amine. The resultant product is a composition of this invention. Example 10 O,O-bis(4-methyl-2-pentyl) phosphorodithioic acid (119.4 g) is placed in a 500 Ml reaction flask equipped with a stirrer. With continuous stirring, 87.6 g of a commercially available epoxidized soybean oil (VIKOFLEX® 7070) is added dropwise and when the temperature has reached 45°C, the mixture is cooled so as to maintain the temperature between 45 and 50°C. When the addition is complete, the reaction mixture is stirred for one hour. In the second stage reaction, phosphorus pentoxide (18.8 g) is added in 6 equal portions at intervals of approximately 10 minutes each. During the addition, the reaction mixture is continuously stirred and cooled to maintain the mixture at 50 to 55°C. Upon completion of the addition, the reaction mixture is held at this temperature range for one hour with stirring. Neutralization, the third stage reaction, is effected by adding oleyl amine (Armeen® OL) (111.2 g) dropwise to the product of the second stage reaction while holding the temperature at 50 to 55°C. The reaction mixture is stirred for one hour at 50 to 55°C upon completion of the amine. The resultant product is a composition of this invention. The excellent limited slip characteristics of the compositions of this invention have been demonstrated both by bench tests and by use of the "Big Wheel-Little Wheel" test procedure of General Motors Corporation as performed by Southwest Research Institute. In particular, a lubricant formulation containing 1.91 percent by weight of a product formed as in Example 1 was run in the LVFA limited slip bench test at room temperature. For purposes of comparison, (1) Oil A, a lubricant containing a recommended dosage level of a commercially available automotive gear oil package, (2) Oil B, the Oil A lubricant composition to which had been added a recommended dosage level of a commercially available limited slip top treat additive, and (3) Oil C, a passing General Motors limited slip reference oil formulation were subjected to the same test bench test procedure under the same test conditions. The results of these tests are summarized in Table 1, wherein the average percentage improvement is the improvement as compared to the performance in the same test of a failing reference oil used by General Motors Corporation as a test standard for failure. Composition Average Improvement, % Standard Deviation Oil A 3.618 2.625 Oil B 3.662 2.813 Oil C 7.547 3.703 The Invention 16.33 1.414 It will be seen that the results in Table 1 are statistically significant results. Comparative tests were conducted in a vehicle using the Limited Slip Big Wheel-Little Wheel Test of General Motors Corporation. In these tests, Oil D, a base oil containing a premium commercial gear additive package at its recommended dosage level (7 wt%) was used as a control. Another control (Oil E) was another sample of the base oil formulated with a commercial gear additive package (6.5 wt%) treated with a commercially-available limited slip top treat (2 wt%) to provide limited slip properties. The lubricant of this invention was treated with 6.44 wt% of a package containing a product formed as in Example 1 as the limited slip component. The finished lubricant contained 1.91 percent by weight of this limited slip component. The results are summarized in Table 2. Composition Mileage Accumulated Results Oil D 4,056 Stopped due to chatter Oil E 8,569 Stopped due to chatter The Invention 8,000 No chatter Another remarkable feature of the products of this invention is the excellent performance exhibited under the "shock-bump" conditions of the L-42 test, under the rust/corrosion conditions of the L-33 test, and under the high temperature oxidation conditions of the L-37 test when formulated with sulfurized olefin as the sulfur source. Thus a formulated 80W90 gear oil containing by weight 1.338% of a product of this invention made as in Example 1 and 2% of sulfur as sulfurized isobutylene (HiTEC® 313 additive; Ethyl Petroleum Additives, Inc.) (Oil F), and another identical gear oil formulation (Oil G) wherein the level of the product of this invention was increased to 2.294%, gave the L-42 test results summarized in Table 3. Test Criteria Oil F Oil G Pinion Drive/Coast, % Score 0/8 0/11 Ring Drive/Coast, % Score 0/6 0/10 Sequence 3 Ring, Drive/Coast, % Score 0/0 0/0 Table 4 summarizes the results of four L-33 tests in which two formulated oils (Oils H and I) contained a commercially-available rust inhibitor (Vaporal®) and two formulated oils (Oils J and K) were devoid of conventional rust or corrosion inhibitor. Oils H, I and J contained 1.338 wt% of a product made as in Example 1, whereas Oil K contained 2.294 wt% of that product. The sulfur levels in Oils H and K was 2 wt%, and in oils I and J the sulfur level was 1.2 wt%. The sulfur-containing component in Oil J was di-tert-dodecyl disulfide whereas sulfurized isobutylene (HiTEC® 313 additive) was the sulfur-containing component in Oils H, I and K. Composition Rating Achieved Rating Needed for Pass Oil H 0 ≤2.5 Oil I 2.5 ≤2.5 Oil J 1.0 ≤2.5 Oil K 0.5 ≤2.5 It will be seen from Table 4 that the product of this invention not only possessed antirust properties, but was sufficiently effective in this regard that passing results were achieved with Oils J and K which contained no conventional antirust agent whatsoever. The high temperature L-37 results summarized in Table 5 again demonstrate the excellent performance of a product of this invention made as in Example 1, especially when formulated with a sulfurized olefin such as sulfurized isobutylene as a sulfur-containing component. The results in Table 5 also illustrate the significance and importance of chain length of the epoxide used in making the product. In particular, Oils M and O contained a product of this invention made as in Example 1 whereas Oils L and N contained a comparative product not of this invention made as in Example 1 except using propylene oxide as the epoxide. On a weight basis Oils L and M had a total phosphorus content of 700 ppm whereas in oils N and O the total phosphorus content was 1200 ppm. Except for the differences in epoxide and in proportions of the product of this invention and the comparative product to reach these total phosphorus levels, the four oils were identical in composition. Each oil contained 3.5 wt% of sulfurized isobutylene (HiTEC® 313 additive), and 1.0 wt% of the same phosphorus- and boron-containing dispersant. Therefore the tests focused upon the relative effectiveness of the respective products, namely the product of this invention and the comparative product made the same way with the same materials except for the epoxide. Oil L Oil M Oil N Oil O Phosphorus, ppm 700 700 1200 1200 Wear High Low Medium Trace Rippling Low Low Low Trace Ridging High Trace Medium Trace Pitting Low Low Low High Spalling None None None None Scoring None None None None Numerical Rating 216.5 6.11 111.0 10.22 The lower the numerical rating in Table 5, the better the result. The product of this invention (Oils M and O) gave passing results. The comparative product (Oils L and N) gave failing results. The clear superiority of the products of this invention as compared to the above comparative product was also demonstrated in LVFA tests. In these tests comparisons of low velocity friction properties were made among four compositions: 1) A standard commercially-used lubricant specifically formulated for limited slip axle usage where low velocity friction performance is desired (Oil P); 2) An 80W90 base oil devoid of an additive package (Oil Q); 3) The base oil of 2) containing 1000 ppm (wt) of phosphorus as the above comparative product in which propylene oxide was used in its synthesis (Oil R); and 4) The base oil of 2) containing 1000 ppm (wt) of phosphorus as a product made as in Example 1 (Oil S). The results of these tests are summarized in Table 6 wherein a negative improvement of course means that the test oil composition was less effective than the commercial formulation (Oil P) which was used as the basis for comparison. Composition % Improvement Over Performance of Oil P Oil Q -33.45 Oil R -2.30 Oil S +6.79 The high temperature L-37 results summarized in Table 7 below demonstrate the excellent performance of products of this invention made as in Examples 9 (Oil T) and 10 (Oil U), especially when formulated with a sulfurized olefin such as sulfurized isobutylene as a sulfur-containing component. On a weight basis Oils T and U had a total phosphorus content of 1000 ppm. Each oil T and U contained 3.5 wt% of sulfurized isobutylene (HiTEC® 313 additive), and 1.0 wt% of the same phosphorus- and boron-containing dispersant. Results are provided for Sequence 2- Pinion-gear drive side and ring-gear drive side conditions after complete test, gear tooth surface condition (pinion gear/ring gear). Oil T Oil U Phosphorus, ppm 1000 1000 Wear Trace/Trace Trace/Trace Rippling None/None None/None Ridging None/None None/None Scratching None/None None/None Pitting Light/None None/None Spalling None/None None/None Scoring None/None None/None Rating Excellent Pass Excellent Pass The products of the invention, oils T and U, demonstrated excellent passing results for the L-37 Sequence 2 testing. In accordance with this invention there are thus provided as additional embodiments thereof, lubricating oil compositions which comprise oil of lubricating viscosity and a phosphorus- and nitrogen-containing composition of the type described hereinabove. The proportions can range from a minor amount of lubricating oil whereby the resultant composition can be an additive concentrate, to a major amount of lubricating oil whereby the resultant composition can be a lubricant composition, such as a gear oil, a transmission fluid, a crankcase lubricant, a hydraulic fluid, a metal-working fluid, etc. The relative proportions can thus be varied within wide limits from as little as 0.05 wt% to as much as 99.95 wt% of the phosphorus- and nitrogen-containing products of this invention. Another embodiment of this invention is a method of inhibiting limited slip axle or differential noise in a vehicle equipped with a limited slip axle or differential, which comprises lubricating said axle with a lubricating oil composition which comprises a major amount of lubricating oil and a minor of phosphorus- and nitrogen-containing product of this invention. By providing such a lubricant composition for the operation of limited slip axle or differential, the positraction performance of the vehicle is improved. Amounts of the present additive in the finished fully-formulated lubricant for this usage will typically fall in the range sufficient to provide from 100 to 5000 ppm (by weight), preferably in the range of 500 to 1500 ppm, and most preferably in the range of 800 to 1200 ppm of phosphorus, and especially about 1000 ppm of phosphorus, in the lubricant. Still another embodiment of this invention is the provision of additive compositions and lubricating oil compositions which comprise a) an oil-soluble sulfur-containing antiwear/extreme pressure agent in which sulfur is bonded to carbon or to more sulfur, and b) a phosphorus- and nitrogen-containing product of this invention such as described hereinabove. These compositions are especially useful for operation of equipment or mechanisms in which extreme pressure and antiwear properties are needed, such as vehicular drivelines, gears, heavy duty engines, and the like. As indicated by test results shown above, these additive combinations -- especially when the sulfur component is a sulfurized olefin, notably a sulfurized branched chain olefin such as diisobutylene or triiisobutylene, and particularly, when the sulfur component is sulfurized isobutylene -- provide exceptionally good performance. The relative proportions of these two components may be varied to suit the particular application for which the finished lubricant is intended. Generally speaking however, they will typically be proportioned such that the weight ratio of sulfur as component a) to phosphorus as component b) falls in the range of 1:1 to 20:1, and more preferably in the range of 2:1 to 10:1. These combined additives are used in lubricating oil compositions. Again, depending on whether the lubricating oil composition is a concentrate for use in making finished lubricants or is itself a finished lubricant composition, the relative proportions between the oil and the combination of components a) and b) can be varied within wide limits from as little as 0.05 wt% to as much as 99.95 wt% of components a) plus b).

Claims: An oil-soluble phosphorus- and nitrogen-containing composition having limited slip properties obtainable by (i) reacting an O,O-di-hydrocarbyl phosphorodithioic acid (a) wherein at least 50 mole % of the hydrocarbyl groups are secondary acyclic hydrocarbyl groups free of acetylenic unsaturation and the balance, if any, of the hydrocarbyl groups are primary acyclic hydrocarbyl groups free of acetylenic unsaturation with an epoxide (b) selected from a monoepoxide or mixture of monoepoxides each having 20 to 30 carbon atoms per molecule, epoxidized soybean oil, methyl epoxy soyate, butyl epoxy soyate, octyl epoxy soyate, epoxidized linseed oil, methyl epoxy linseedate, butyl epoxy linseedate or octyl epoxy linseedate to form a product, (ii) reacting the product with phosphorus pentoxide to produce an acid phosphate intermediate, and (iii) neutralizing at least a major proportion of the intermediate with at least one amine. A composition according to claim 1 wherein all the hydrocarbyl groups of the O,O-di-hydrocarbyl phosphorodithioic acid are secondary acyclic hydrocarbyl groups free of acetylenic unsaturation. A composition according to claim 2 wherein the secondary acyclic hydrocarbyl groups contain 6 to 12 carbon atoms each. A composition according to claim 2 or claim 3 wherein the secondary acyclic hydrocarbyl groups are branched chain alkyl groups. A composition according to claim 1 wherein O,O-di-hydrocarbyl phosphorodithioic acid consists essentially of 4-methyl-2-pentyl phosphorodithioic acid. A composition according to claim 1 wherein the O,O-di-hydrocarbyl phosphorodithioic acid consists essentially of a mixed di-secondary alkyl phosphorodithioic acid obtainable from an equimolar mixture of 4-methyl-2-pentanol and 2-propanol. A composition according to any one of claims 1 to 6 wherein the epoxide (b) is epoxidized soybean oil or methyl epoxy soyate. An oil-soluble phosphorus- and nitrogen-containing material comprising a product of formula (I) wherein the groups R 1 are the same or different and each is alkyl having 18 to 28 carbon atoms, the groups R 2 are the same or different and each is a secondary acyclic hydrocarbyl group free of acetylenic unsaturation and having 3 to 18 carbon atoms, the groups X are the same or different and each is a primary or secondary amine, m is from 1 to 2, and the sum of m and n is no greater than 3. A material according to claim 8 further comprising a minor proportion of an isomeric form of the product of formula (I), the isomeric form having the formula (II) wherein R 1 , R 2 , X, m and n are as defined in respect of the product of formula (I). A material according to claim 8 or claim 9 wherein each group R 2 has 6 to 12 carbon atoms. A material according to any one of claims 8 to 10 wherein each group R 2 is a branched chain secondary alkyl group. A material according to any one of claims 8 to 11 comprising a mixture of products of formula (I) wherein all groups R 2 are 4-methyl-2-pentyl, and the groups R 1 are a mixture of alkyl groups of 18 to 22 carbon atoms. A material according to any one of claims 8 to 11 comprising a mixture of products of formula (I) wherein all groups R 2 are 4-methyl-2-pentyl, and the groups R 1 are a mixture of alkyl groups of 22 to 26 carbon atoms. A material according to any one of claims 8 to 13 wherein X is a primary alkyl amine, a primary alkenyl amine having 1 to 3 ethylenic double bonds, a tertiary alkyl primary amine or oleyl amine. A material according to any one of claims 8 to 13 wherein X is a tertiary alkyl primary amine having 12 to 15 carbon atoms per molecule. A material according to any one of claims 8 to 13 wherein X is an aliphatic primary amine having 6 to 24 carbon atoms per molecule. A material according to claim 16 wherein X is an aliphatic primary amine having 14 to 20 carbon atoms per molecule. A lubricating oil composition which comprises oil of lubricating viscosity and an oil-soluble phosphorus-and nitrogen-containing composition according to any one of claims 1 to 7 or an oil-soluble phosphorus- and nitrogen-containing material according to any one of claims 8 to 17. A composition which comprises an oil-soluble sulfur-containing antiwear/extreme pressure agent (A) wherein sulfur is bonded to carbon or to more sulfur, and a phosphorus- and nitrogen-containing composition according to any one of claims 1 to 7 or an oil-soluble phosphorus- and nitrogen-containing material according to any one of claims 8 to 17, (B) proportioned such that the weight ratio of sulfur in (A) to phosphorus in (B) is from 1:1 to 20:1. A composition according to claim 19 wherein the antiwear/extreme pressure agent (A) is sulfurized isobutylene. Use of a composition according to any one of claims 1 to 7 or an oil-soluble phosphorus- and nitrogen-containing material according to any one of claims 8 to 17 for inhibiting limited slip axle or differential noise in a vehicle equipped with a limited slip axle or differential.

Inventors: BALASUBRAMANIAM VASUDEVAN, HARTLEY ROLFE J, HUGHES JOE, BALASUBRAMANIAM, VASUDEVAN, HARTLEY, ROLFE J., HUGHES, JOE
Applicants: ETHYL CORP, ETHYL CORPORATION
Application year: 1996
Main classification: C10M159
IPC codes: C10M137, C07F9