US2121611A - Naphthenyl esters of phosphorous acids - Google Patents

Description

Patented 1...... 21, 1938 NAiHTHENYL ESTERS OF PHOSPHOROUS ACIDS Paul Lawrence Salzberg, Carrcroit, Del., assignor to E. I. du Pont de Nemours & Company. Wilmington, Del., a corporation of Delaware NoDrawing. Application June 29, 1937,

Serial No. 150,958

11 Claims.

This invention relatesto naphthenyl esters of acids of phosphorus, some of which are new chemical compounds, the methods of preparing the same, and particularly to the use of such esters in lubricating oils to provide lubricants having improved properties.

Aliphatic and aromatic esters of ortho-phosphoric acids are known. Such esters have been employed as plasticizers in molding and coating compositions, particularly in those containing cellulose ethers and esters. They have also been proposed for use as textile lubricants and as assistants for extreme pressure lubricants and for many other purposes. Such prior known phosphates, particularly the higher aliphatic phosphates, have the disadvantage that, under certain conditions, they tend to exude from the compositions containing them.

The advantages of a high pressure lubricant become apparent when the present trend in design of automotive and other machine parts, and the increased strength of metal parts, due to the use of alloy steels, is considered. The pressures ordinarily found in well lubricated journal bearings do not exceed 2,000 lbs/sq. in. and for conditions such as this, a film of heavy oil can be expected to remain between the rubbing surfaces. When gears are considered, where the contact between surfaces is of very small width, the bearing pressures often reach values as high as 25,000 lbsllsq. in. Under such extreme pressure, it is unlikely that any oil or grease can be obtained which will be viscous enough to prevent metallic contact. The result of the lack of a lubricating film between the rubbing surfaces results in scoring and scufling of the gears.

Failure to maintain lubricant films on idle bearing surfaces is now well recognized as the cause of 70 to 80% of the wear occurring on cylinder walls of automotive and other internal combustion engines. When an engine is stopped,

the oil film on the vertical surfaces soon drains' off and, when the machine is again started, an appreciable time elapses before the circulation provides oil .for the formation of new lubricant An assistant which, when added to the motor oil, will prevent'the separation of the oil film from the metal should prevent a large part of the wear now occurring.

Recently new bearing metals have been pro- .vance the art.

posed for use in automobiles such as those composed of cadmium-silver alloys, cadmium-nickel alloys and copper-lead alloys supported upon steel backings. These new alloys have many advantages over the older type, but are in general subject to destructive agencies of a corrosive nature. The more highly refined oils, particularly those obtained by solvent refining, appear to be particularly corrosive toward such new alloys.

Various agents have been added to oils to improve their properties. Among such agents which have been used are sulfur, sulfur-containing compounds, metal soaps, halogen compounds and the like. Some of these agents, such as the sulfur and halogen compounds, greatly improve the lubricating properties of the oils, whereas others, such as the metal soaps, have been of little value for this purpose. Some of such agents are corrosive or give rise to corrosive products, and are therefore objectionable. Many of such agents tend to increase or accelerate sludge formation in the oils to an objectionable extent, and are objectionable for this reason.

It is an object of the present invention to provide new materials for addition to lubricating oils for improving their properties. A further object is to provide improved lubricating oils. A still further object is to provide a method for preparing improved lubricants. Other objects are to provide new compositions of matter and to ad- Still other objects will appear hereinafter.

The above objects may be accomplished in accordance with my invention, which comprises incorporating in lubricating oils, particularly petroleum lubricating oils, naphthenyl esters of the acids of phosphorus and mixtures of such esters, some of which esters are new chemical compounds. I preferably employ the naphthenyl esters of phosphorous acids;'in other words, the naphthenyl phosphites and naphthenyl thiophosphites. These esters may, in general, be prepared by any of the methods well known to the art.

By the term naphthenyl alcohols" as employed herein and in the claims, I mean the alcohols which are obtainable by the carboxylic reduction of naphthenic acids and their esters. These alcohols contain at least six carbon atoms and may contain as many as twenty or more carbon atoms. These naphthenyl alcohols contain the hydroxy group in a side chain as distinguished from the cycloallphatic alcohols in which the hydroxyl group is attached to a carbon of the cyclic nucleus. A naphthenyl radical as employed hereinafter and in the claims will be understood to mean a radical derivable from such naphthenyl alcohols. The naphthenyl esters of my invention are those obtainable by esterifying such naphthenyl alcohols.

By an acid of phosphorus as employed herein and in the claims, I intend to include the various phosphoric and phosphorous acids such as the ortho, meta, pyro and hypo acids together with the corresponding thio acids in which one or more of the oxygens are replaced by sulphur atoms. Among the esterifying derivatives of acids of phosphorus, the following are the most common:

Phosphorus oxychloride, POCl3 Phosphorus pentoxide, P205 Phosphorus pentachloride, PO Phosphorus trichloride, PCla Phosphorus pentasulfide, P285 Phosphorus sulphochloride, PSCla Phosphorus trisulphide, P486 and Phosphorus trisulpho tetrabromide, PzsaBn.

The process of making naphthenyl esters of ortho-phosphoric acid may be carried out by placing one or more of the naphthenyl alcohols alone or dissolved in a suitable solvent, such as benzene, toluene, chloroform and the like, in a vessel connected with a reflux condenser. The material in the vessel is warmed to the desired temperature, preferably 30 to 100 C., under reduced pressure and phosphorus oxychloride is then gradually admitted in liquid or vapor form. The reaction is carried to completion under reduced pressure in the heated vessel and the hydrogen chloride formed is continuously removed. The resulting phosphates may be purlfied by distillation under reduced pressure. The resulting product comprises the mono-, di-, or tri-naphthenyl phosphate, depending upon the proportion of alcohol employed. When more than one molecular proportion of the alcohol is employed and the alcohol comprises a mixture of naphthenyl alcohols, the resulting product is a mixture of phosphates which apparently contains a substantial proportion of mixed phosphates each of which contains two or more different naphthenyl radicals.

The esters of orthophosphoric acid may also be obtained by heating the naphthenyl alcohol on a water bath and then adding phosphorus pentachloride thereto, slowly. The product may be washed with water and dried in vacuo.

The esters of ortho phosphoric acid may also 7 be obtained by dissolving a'mixture of the alcohols in ether or other suitable solvent, such as pyridine or other'tertiary base, and then heating with phosphorus pentoxide under a reflux condenser. When ether is used as the solvent, the

ester separates on cooling. When pyridine and like compounds are used, the solvent is removed by distillation, the product washed with water and dried by heating under reduced pressure.

The esters may also be prepared by first reacting the alcohols with sodium to obtain the corresponding alkoxides and then reacting the alkoxides with phosphorus oxychloride or the like.

An alternative procedure comprises first preparing the naphthenyl iodides or other halides and then reacting the halide with the silver salt of pyrophosphoric, metaphosphoric, orthophosphoric or other acid of phosphorus to obtain the neutral or acid esters, depending upon the proportions employed.

If it is desired to obtain pure mixed esters of ortho phosphoric, acid, it will be desirable to react one molecular proportion of phosphorus oxy- I chloride with one or two molecular proportions ,of the naphthenyl alcohol. The resulting prodthis method, the pure mixed neutral or acid esters are obtained.

Catalysts such as copper powder or a. metallic chloride maybe added to the reaction liquid in order to facilitate the splitting ofi of the hydrogen chloride. Also, the degree of reduced pressure employed may vary within wide limits depending upon the desire of the operator and the materials being treated.

The esters of the other acids of phosphorus may be prepared in similar manner to the methods disclosed above by substituting the proper esterifying derivative for the phosphorus oxychloride and the like, disclosed above. For example, when phosphorus trichloride is employed, the phosphites will be produced. When phosphorus sulphochloride is employed, the resulting products will be the monothio ortho-phosphates. When phosphorus pentasulfide is employed, the dithio ortho-phosphates result. When phosphorus trisulpho tetra bromide is employed, the corresponding trithio pyro-phosphates will be produced. The meta-phosphates may be obtained by treating the neutral ortho-phosphates with concentrated sulphuric acid.

Esters of thio acids of phosphorus may be produced by treating the naphthenyl thio alcohols with an esterifying derivative of phosphorus. The resulting compounds will generally have the naphthenyl radical attached to the phosphorus through a sulphur atom. These esters may be called thio esters of the acids of phosphorus to distinguish them from the esters of the thio-acids in which the naphthenyl radical is attached to the phosphorus through an oxygen atom.

When the neutral esters are treated with alkali, the alkali metal salt of the dinaphthenyl ester is obtained. These salts may be prepared byboiling one part by weight of the neutral phosphate with 8 parts by weight of sodium hydroxide dissolved in 192 parts by weight of water for two hours. water. The sodium salts of the mixed dinaphthenyl phosphates can be employed to emulsii'y a mineral oil in a large amount of water to obtain an emulsion which can be diluted indefinitely with water.

The neutral naphthenyl esters can also be hydrolyzed by cooking with an acid such as hydrochloric acid to yield mixtures of the mononaphthenyl and dinaphthenyl phosphates.

While the sodium salts of the acid esters of my invention are soluble in water, the salts obtained with organic bases, such as triethanolamine or methyl glucamine, are even more soluble. These various salts also form a part of my invention.

In order more clearly to illustrate my invention and the preferred modes of preparing my new compounds, the following examples are given:

These salts are soluble or dispersible in Example 1 A mixture of naphthenyl alcohols boiling between 101 and 141 C. at 19 mm. was obtained-by hydrogenation of a mixture of ethyl naphthenates. This mixture of naphthenyl alcohols had an average molecular weight of 160 as calculated from analytical determinations 'of the saponiflcation number of the ethyl naphthenates from which they were obtained. 25 parts by weight of this mixture was mixed with 100 parts of benzene. 8 parts by weight of phosphorous oxychloride was then added slowly. The mixture was placed in a glass vessel attachedto a reflux condenser and heated at the reflux temperature under a slight vacuum for 20 hours. The slight vacuum served to assist inthe removal of the hydrogen chloride which was formed. The benzene solution was then washed with warm water until neutral and the benzene evaporated. The mixture was then steam distilled until no more oily liquids came over. The solution in the steam distillation flask was then extracted with benzene and the layers separated. The benzene layer was then evaporated on a steam bath leaving dinaphthenyl phosphate. The last traces of benzene were removed by heating under reduced pressure. The product was a light yellow viscous liquid, soluble in aromatic hydrocarbons and insoluble in water. Determination-of the phosphorus content indicated that the product was the expected dinaphthenyl phosphates.

Example 2 A mixture of naphthenyl alcohols, having boiling point between 101 and 141 C. at 19 mm., having an indicated molecular weight of 169, as calculated from analytical determinations of hydroxyl number, was obtained. ,weight of this mixture was mixed with 200 parts of benzene and 32 parts of phosphorus oxychloride was then added slowly. The mixture was placed in a glass vessel attached to a reflux condenser and allowed to stand at room temperature for 3 hours under a slight vacuum. The mixture was then heated in a steam bath over night under a slight vacuum. The reaction mixture was then poured into an excess of dilute sodium carbonate solution and the mixture steam distilled until there was no further detectable dis- 0 tillation of oily materials. The residue in the steam distillation flask was then extracted with benzene and thoroughly washed with water. The benzene solution was dried by distillation of the benzene, the last traces of the benzene being reproduct was a light yellow viscous liquid, soluble in aromatic hydrocarbons and insoluble in water. Determination of the phosphorus content indicated the product to be dinaphthenyl phosphates.

Example 3 A mixture of the ethyl esters of naphthenic acids was prepared and such esters were reduced by sodium reduction. This produced a mixture of naphthenyl alcohols boiling between 130 and glass vessel attached to a reflux condenser and heated gently on a steam bath under slight vacuum to remove liberated hydrogen chloride.

100 parts by benzene solution washed thoroughly with dilute sodium carbonate solution. Very stable emulsions were formed, which were broken with difficulty by heating with sodium chloride solution.

The emulsions formed again when water was added. Dilute hydrochloric acid was then added to decompose the sodium salt and the solution washed thoroughly with water. The benzene layer was separated and the benzene was removed under vacuum on the steam bath. The product was a light yellow colored very viscous liquid, soluble in aromatic hydrocarbons and insoluble in water. Determination of the phosphorus content indicated the product to be dinaphthenyl ortho-phosphates. This material was added to an oil in 2% concentration and the resulting lubricant witthstood a load of about 28,000 lbs,/sq. in., when tested on the Almen machine.

While the phosphates will to some extent reduce the tendency of lubricating oils to corrode alloy bearing metals such as cadmium-silver, copper-lead and caymium-nickel alloys, I have found that the naphthenyl phosphites and naphthenyl thiophosphites are particularly effective for retarding corrosion of such bearing alloys by lubricating oils. The following additional examples illustrate this desirable property:

Example 4 A solution of 41 gms. naphthenyl alcohols, having an average molecular weight of 274, and 12 gms. pyridine was prepared in 250 cc. benzene. To this was added, slowly and with vigorous agitation, a solution of 6.9 gms. phosphorus trichloride in 50 cc. benzene. The reaction mixture was agitated 1 hour at 25 C. and subsequently heated 1 hour on a steam bath. After chilling, the solution was filtered to remove the solid pyridine hydrochloride. shaken for 30 minutes'with 20 gms. sodium carbonate monohydrate to complete the removal of chlorine-containing compounds, filtered, and the solvent removed under reduced pressure. A clear liquid residue was obtained, weighing 40 gms., which upon analysis yielded the following data: phosphorus (found), 3.45%; phosphorus (calculated), 3.65%; N35, 1.4965.

The effect of this material on the film strength of an SAE 30 oil was determined on the Almen machine with the following results:

Load supported Oil alone 3,000 lbs./sq. in. Oil+1% naphthenyl phosphite- 24,000 lbs/sq. in.

The effect of this material on inhibiting the corrosion of a copper-lead alloy bearing and a cadmium-silver alloy bearing was determined on an SAE 30 oil as follows:

Fifty grams of oil containing 0.5% by weight of the naphthenyl phosphite were placed in 125 cc. Erlenmeyer flasks each equipped with a 1 mm. capillary inlet tube through which moist air was passing at the rate of 2 to 3 bubbles per second. Strips cut from the bearings were suspended in the flasks i a position such that half of the surface of eac strip was immersed in the oil and half exposed to the vapors. The flasks and contents were placed in an oil bath at 170 C. for 50 hours. A control test was run simultaneously.

Benzene was added to the reaction mixture and the At the end of the test, the bearing strips were removed, washed with chloroform and acetone, and weighed. The data obtained are as follows:

A solution of 23 gms. naphthenyl mercaptans, having an average molecular weight of 180, and 10 gms. pyridine was prepared in 100 cc. benzene. To this was added, slowly and with vigorous agitation, a solution of 5.5 gms. phosphorus trichloride in 50 cc. benzene. The reaction mixture was agitated 1 hour at 25 C. and subsequently heated 1 hour on a steam bath. After chilling, the solution was filtered to remove the solid pyridine hydrochloride, shaken for 30 minutes with sodium bicarbonateto complete the removal of chlorinecontaining compounds, filtered, and the solvent removed under reduced pressure. residue was obtained weighing 21 grns. Upon analysis this yielded the following data: phosphorus (found), 5.28%; phosphorus (calculated), 5.45%; sulfur (found), 15.49%; sulfur (calculated), 16.9%; N, 1,5269.

The effect of this material on the film strength of an SAE 30 oil was determined on the Almen machine with the following results:

Load supported Oil alone. 3,000 lbs/sq. in. Oil+1% naphthenyl trithiophosphite 24,000 lbs/sq. in.

The effect of this material on inhibiting the corrosion of bearings lined with a silver-cadmium alloy and with a cooper-lead alloy was determined on an SAE 30 oil as follows:

Fifty grams of oil containing.0.5% by weight of the naphthenyl trithiophosphite were placed in 125 cc. Erlenmeyer flasks each equipped with a 1 mm. capillary inlet tube through which moist air was passing at the rate of 2 to 3 bubbles per second. Strips cut from a silver-cadmium alloy bearing and a copper-lead alloy bearing were suspended in the flasks in such a fashion that half the surface of each strip was immersed in the oil and half exposed to the vapors. The flasks and contents were placed in an oil bath at 170 C. for 50 hours. A control test was run simultaneously. At the end of the test, the bearing strips were removed, washed with chloroform and I have found that the naphthenyl phosphites and the naphthenyl thiophosphites have a further advantage over the prior art compounds in that they have greatly improved sludging char- A clear liquid Concen- Mg. sludge tration Length Tempera- Gmnpound percent of test of test by wt.

' Hra. C. N aphthenyl phosphite. 0. 5 50 170 17. 5 N aghthenyl trithiop osphite 0. b 50 170 4. 6 'lriphenyl phosphite (commercial grade). 0. 6 '50 170 23. i

The sludge values were determined by diluting 10 ms. of the oil to a volume of 100 cc. with a highly refined petroleum naphtha, allowing the solution to stand at 0 C. for one hour, filtering the solution on a weighed Gooch crucible, and weighing the collected sludge.

From the above tests, it will be apparent that.

the oil containing the phosphites and thiophosphites of my invention had much less tendency toward the formation of sludge than triphenyl phosphite, which is a representative of similar types of compounds which have been proposed for addition to lubricating oils.

The preferred esters of the acids of phosphorus of my invention are derived from naphthenyl alcohols obtained by hydrogenation or sodium reduction of derivatives of naphthenic acids from petroleum, and particularly the esters of the phosphorous acids. However, I intend to include within the scope of my invention the mixed esters such as dinaphthenyl ethyl ortho-phosphate, dinaphthenyl cresyl ortho-phosphate, dinaphthenyl 9, IO-octadecenyl ortho-phosphate, dinaphthenyl dodecyl ortho-phosphate, acid naphthenyl dodecyi ortho-phosphate, acid naphthenyl ethyl ortho-phosphate, acid naphthenyl cresyl orthophosphate, acid naphthenyl tetradecyl orthophosphate, acid naphthenyl 9, IO-octadecenyl ortho-phosphate, acid naphthenyl phenyl orthophosphate and similar compounds. These mixed phosphates may be obtained by esterifying a mixture comprising at least one molecular proportion of the naphthenyl alcohols and one molecular proportion of a different alcohol or a phenol. They may also be obtained by first esterifying the naphthenyl alcohols and then reacting with the other alcohol or phenol. Alternatively the other alcohol or phenol may be first esterified and then reacted with the naphthenyl alcohols.

The neutral esters of my invention may be employed as plasticizers in molding and coating compositions, particularly those comprising cellulose ethers, such as the benzyl ethers, and cellulose esters, such as the nitrate and acetate. The acid phosphates and their alkali metal salts such as sodium and potassium and the ammonium and amine salts are useful as wetting agents. detergents, textile lubricants and the like. The acid phosphates are also useful as lubricant assistants for extreme pressure lubricants. For example, when 2% of dinaphthenyl phosphate, such as that obtained in accordance with Example 3, is added to a medium viscosity mineral oil, SAE-30, and dissolved therein by heating, the

oil was able to maintain a lubricant film under The method of testing my compounds was that devised by J. 0. Almen (Oil and Gas Journal, 30,109, 1931). This method consists of running a A" diameterdrill rod between two halves of a split bushing which is maintained stationaryn added to the loading lever increases the pressure on the bushing by about 125 lbs. The machine provides for beam loadings up to 20 weights which corresponds to a pressure of 20,000 lbs/sq. in. on the full projected area of the drill rod. The bearing surface of the bushing is cut to a diameter 0.007 inch larger than the drill rod so that, before any wear occurs, the actual bearing surface is a line. As wear occurs, the bearing surface widens but seldom covers the bushing. After a test, the width of the bearing scar can be measured and an approximate value for the actual bearing pressure obtained. The values given in the preceding examples represent the calculated actual bearing pressures which were reached in the tests without failure of the film. These values represent film strength or film resistance.

when subjected to the above test, a good grade of paraflln oil will withstand a pressure of only 3 to 5,000 lbs/sq. in. When an oil containing sulfur is tested by the same method, such oil will show a film strength of about 20,000 lbs./sq. in. and will give a torque reading of over 4.0 lbs. it. at this load.

This application is in part a continuation of my copending application Serial No. 11,809, filed cation. 1 have disclosed that these compounds are useful additions to lubricating oils for producing extreme pressure lubricants. The present application includes a description 01' the preparation of the phosphites and thiophosphites and the results of tests of lubricating oils containing such compounds.

While I have disclosed the preferred embodiments of my invention and the preferred modes of carrying the same into efiect, it will be readily apparent to those skilled in the art that many modifications may be made therein without departing from the spirit of my invention. Accordingly, the scope of my invention is to be limited solely by the appended claims construed as broadly as is permissible in view of the prior art.

I claim:

1. A naphthenyl ester of a phosphorous acid.

2. A naphthenyl ester of a thiophosphorous acid.

3. A trinaphthenyl phosphite.

4. A trinaphthenyl thiophosphite.

5. A trinaphthenyl trithiophosphite.

6. A mixture of naphthenyl esters of a phosphorous acid obtained by reacting an esterifying derivative of a phosphorous acid with at least one molecular proportionof a mixture of naphthenyl alcohols.

'7. A mixture of naphthenyl esters of a phosphorous acid obtainable by reacting an esterifyterifying derivative of a phosphorous acid with three molecular proportions of a mixture of naphthenyl mercaptans.

10. A mixture of trinaphthenyl phosphites. 11. A mixture of trinaphthenyl trithiophosphites.

. PAUL LAWRENCE SALZBERG.