US3780145A

US3780145A - Triphenyl phosphates

Info

Publication number: US3780145A
Application number: US00117095A
Authority: US
Inventors: R Malec
Original assignee: Ethyl Corp
Current assignee: Ethyl Corp
Priority date: 1971-02-19
Filing date: 1971-02-19
Publication date: 1973-12-18
Anticipated expiration: 1990-12-18

Abstract

TRIPHENYL PHOSPHATES IN WHICH AN AVERAGE OF AT LEAST ONE PHENYL GROUP PER MOLECULE IS SUBSTITUTED WITH AT LEAST ONE ALKYL GROUP CONTAINING FROM L-30 CARBON ATOMS HAVE BEEN FOUND TO BE EXCELLENT LUBRICANTS AND FUNCTIONAL FLUIDS HAVING MUCH LOWER POUR POINTS AND HIGHER VISCOSITY INDICES THAN CONVENTIONAL PHOSPHATE ESTERS.

Description

United States Patent 3,780,145 TRIPHENYL PHOSPHATES Robert E. Malec, Birmingham, Mich., assignor to Ethyl Corporation, Richmond, Va. No Drawing. Filed Feb. 19, 1971, Ser. No. 117,095

Int. Cl. C071? 9/12; C10m 1/46 US. Cl. 260-966 2 Claims ABSTRACT OF THE DISCLOSURE Triphenyl phosphates in which an average of at least one phenyl group per molecule is substituted with at least one alkyl group containing from 6-30 carbon atoms have been found to be excellent lubricants and functional fluids having much lower pour points and higher viscosity indices than conventional phosphate esters.

BACKGROUND Triaryl phosphates have been used both as lubricants and as hydraulic fluids. They are most useful in stationary turbine installations and in mining equipment where a nonflammable fluid is required. In the past, fluids such as tricresyl phosphate have predominated in such use. One deficiency of such fluids is their relatively high pour point and low viscosity index. An object of this invention is to provide a class of phosphate esters which has a low pour point and a high viscosity index.

SUMMARY The objects of the present invention are accomplished by providing a triphenyl phosphate ester in which an average of at least one phenyl group per molecule is substituted with a C alkyl group which preferably contains a linear alkyl chain of at least 5 carbon atoms.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention is a triphenyl phosphate ester in which an average of at least one phenyl group per molecule is substituted with at least one alkyl group containing from 6-30 carbon atoms.

In stating that an average of at least one phenyl group per molecule is substituted with at least one alkyl group containing 6-30 carbon atoms, it is meant that the number of C alkyl-substituted phenyl groups present in the phosphate ester divided by the number of molecules of phospshate ester is at least one. From this, it is apparent that the ester need not be a single compound but can be, and as a practical matter generally is, a mixture of triphenyl phosphate esters containing varying amounts of C alkyl substituents on the phenyl ester groups in an amount such that an average of at least one phenyl group is C alkyl substituted per molecule of phosphate ester in the mixture.

The preferred phosphate esters contain an average of from 1-6 C alkyl substituents per molecule of phosphate ester. As above, this is an average value determined by dividing the total moles of C alkyl substituents by the total moles of phosphate ester.

Although good results are obtained with all alkyl groups containing 6-30 carbon atoms, an especially useful product is obtained when the alkyl group has a substantially linear structure. By this, is it meant that the preferred alkyl substituents contain linear carbon chains of at least 5 carbon atoms. Preferably this linear chain is unbranched. This is not to say that the alkyl groups need to be normal alkyl groups. For example, l-methyl-npentyl is a 6 carbon alkyl containing a 5 carbon linear alkyl chain. Likewise, l-ethyl-n-hexyl is a 8 carbon alkyl containing a 6 carbon linear chain. Similarly, l-n-butyl-npentyl is a 9 carbon alkyl group containing two 5 carbon linear chains. Some further examples of alkyl radicals containing from 6-30 carbon atoms and one or more linear alkyl chains of at least 5 carbon atoms are: 1- methyl-n-eicosyl, l-n-pentyl-n-hexyl, 1,1-dimethyl-n-heptyl, n-pentyl, n-hexyl, n-octyl, n-decyl, n-dodecyl, l-methyl-n-nonosyl, l-n-octyl-n-tiidecyl, l-n-heptyl-n-tricosyl, 1- n-butyl-n-undecyl, 1-methyl-n-heptyl, and the like.

Although alkyl groups containing from 6-30 carbon atoms are useful in providing the low pour point and high viscosity index properties of the present phosphate esters, it has been found that alkyls containing 6-18 carbon atoms are a more preferred group. As above, these preferred alkyls have a structure such that they are substantially linearthat is, they contain linear alkyl chains of at least 5 carbon atoms. Some especially useful esters within this class are those in which the alkyl groups contain about 6-8 carbon atoms. In other words these are: n-hexyl, n-heptyl, n-octyl, l-methyl-n-pentyl, l-methyl-nhexyl, 1-ethyl-n-pentyl, l-methyl-n-heptyl, l-ethyl-n-hexyl, 1,1-dimethyl-n-hexyl, and the like.

Another highly preferred embodiment is a triphenyl phosphate in which an average of at least one phenyl group per molecule is substituted with an alkyl group containing 10-12 carbon atoms and having a linear alkyl chain of at least 5 carbon atoms such that the ester contains an average of from 1-6 alkyl groups per molecule.

As stated above, the preferred esters contain an average of from 1-6 alkyl groups per molecule. However, a more preferred embodiment is a triphenyl phosphate ester containing an average of about 5-6 alkyl groups per molecule of phosphate ester wherein the alkyl groups contain about 12 carbon atoms and have a structure such that they contain a linear alkyl chain of at least 5 ca"- bon atoms.

The phenyl phosphate esters of this invention are an ester or mixture of esters having the formula:

( )m I M:

wherein R represents an alkyl group containing from 6- 30 carbon atoms, and m, n and p are integers selected from 0, 1, 2 and 3. When the ester is a single compound the sum of m, n and p is from 1-9, and when the ester is a mixture of different phosphate esters the sum of the average value of values of m, n and p is from 1-6. The alkyl groups represented by R preferably have a linear alkyl chain of at least 5 carbon atoms in their structure. The more preferred R groups contain from 6-18 carbon atoms.

The phosphate esters are made by conventional methods. For example, phenol can be alkylated with a C olefin using a Friedel-Crafts catalyst to give a mixture of alkylphenols containing the required average of at least one alkyl for each 3 molecules of phenol, and preferably from 1-6 alkyls for each 3 molecules of phenol. The alkylated phenol mixture containing the Friedel-Crafts catalyst can then be reacted directly with phosphorous oxychloride to form the phosphate ester of this invention or it can be first converted to its alkali metal salt by reaction with an alkali metal hydroxide or alkoxide and the salt then reacted with phosphorus oxychloride. These methods of alkylating phenols and forming aryl phosphate esters are well known. The following examples will serve to illustrate how the synthesis can be carried out. All parts are by weight.

Example 1 Viscosity (cs.)

210 F. 5.84 100 F. 42.91 F. 4,650 Viscosity index 81 Pour point, F

Example 2 One mole part of phenol was alkylated with 1.83 mole parts of dodecene-l using a BF -ether catalyst to provide a mixture of l-methyl-n-undecylphenols having an average of about 1.83 alkyl groups per mole of phenol. This was reacted with 0.33 mole of phosphorus oxychloride and 2 grams of aluminum chloride, giving a triphenyl phosphate ester having an average of 5.5 l-methyl-nundecyl alkyl groups per molecule of phosphate ester. This ester mixture had the following physical properties:

Viscosity (cs.):

210 F 11 100 F. 96.4 0 F. 6,990 Viscosity index 108 Pour point, F -35 Example 3 In a reaction vessel was placed 1.33 mole parts of phenol, a small amount of BF 'ether catalyst and 1.6 mole parts of a mixture of olefins containing from about 12- 30 carbon atoms. The olefin composition used was 81.4% olefin and 18.6% paraflin. Excluding the paraffin, the olefiHS WCI'C 2.46% C6 10, 23.8% C12, C14, C15, 10.9% C18, C20, 8.1% C22, C24: C26, 2.9% C and 1.1% C olefins. The olefins were a mixture of alpha-olefins, branched olefins and internal olefins in the ratio of about 12222. The mixture was stirred at about -90 C. for an hour. The resultant alkylphenol mixture was reacted with 1.3 moles of phosphorus oxychloride at 90 C. for an hour to form a phosphate ester. A small amount of unreacted phosphorus oxychloride was then distilled out and then 3.5 mole parts of phenol added. The esterification was completed by stirring an additional 12 hours at 100200 C. Unreacted phenol was then washed out. Parafiin and other volatiles were distilled out. The product was a triphenyl phosphate having an average of about 1.5 alkyl groups per molecule in which the alkyl group contained from about 12-30 carbon atoms. The physical properties of the ester were as follows:

Viscosity (cs.):

210 F. 11.07 100 F. 107.2 Viscosity index 96 Pour point, F.

used in spark ignition internal combustion engines. In this use they function to extend spark plug life. Amounts of from about 0.1 to 0.5 theories are used (one theory being the amount required to convert the lead to lead phosphate). They can be used as anti-wear agents in other lubricant formulations. For example, they are customarily added to synthetic ester lubricants used in turbojet aircraft engines. In this use, amounts of from about 1-5 percent are blended with the ester lubricant together with the other additives normally required such as an an antioxidant (e.g., phenyl-B-naphthyl amine, phenyl-u-naphthyl amine, dioctyl phenylenediamine, etc.), metal deactivators, silicone antifoam agents, and the like.

The present esters have a further quite unexpected property when used as antiwear agents in synthetic ester lubriants. In synthetic ester lubricants, viscosity properties are quite important and, in fact, both the Air Force and Navy set stringent specifications on viscosity. For example, the most recent Air Force specification (MIL-L 27502) requires a 40 F. viscosity of 15,000 max. It has been found that the present phosphate esters when compared to the generally used tricresyl phosphate have very little etfect on viscosity at higher temperatures while at the same time decreasing the 40 F. viscosity. Thus, use of the present esters in place of the art-revered tricresyl phosphate additive can be very beneficial in helping an ester meet the -40 F. viscosity specification. This is illustrated by the following data in which the synthetic ester is a trimethylolpropane ester of a mixture of adipic and C aliphatic monocarboxylic acids.

From the above data, it can be seen that the ester of this invention (Example 1) when compared with use of tricresyl phosphate has very little effect at 210 F. or F. In fact, if any, the esters of this invention give a slightly higher viscosty at these higher temperatures which in itself is beneficial. A highly unexpected property of the present phosphate esters is their effect on viscosity at 40 F. Here it can be seen that the ester containing 2 percent tricresylphosphate has a -40 F. viscosity of 13,- 450 cs. whereas the same synthetic ester lubricant containing the same amount of the phosphate ester of Example 1 exhibits a 40 F. viscosity of 13,160 cs. This reduction in viscosity at 40 F. is quite significant and can mean the dilference between meeting the specification and not meeting the specification because other additives routinely used in synthetic esters such as the phenyl-anaphthyl amine and phenylenediamine type antioxidants are known to increase the viscosity of the lubricant.

I claim:

1. A triphenyl phosphate ester in which one phenyl group per molecule is substituted with 13 alkyl groups containing from about 10-12 carbon atoms and having a linear alkyl chain of at least 5 carbon atoms.

2. A triphenyl phosphate ester of claim 1 wherein said alkyl group contains 10 carbon atoms and has a linear alkyl chain of 9 carbon atoms, namely, diphenyl(1-methyl-n-nonylphenyl) -phosphate.

References Cited UNITED STATES PATENTS 2,193,252 3/1940 Kyrides 260966 2,237,632 4/1941 Ries 260966 X 3,012,057 12/1961 Fierce et al 260966 3,553,155 1/1971 Garrett 260966 R ANTON H. SUTTO, Primary Examiner US. Cl. X.R. 25249.8