Bis(trimethylolpropane diallyl ether) dilinoleate and its phosphonates and lubricant compositions

United States Patent Office

3,536,738

Patented Oct. 27, 1970

3,536,738

BIS(TRIMETHYLOLPROI’ANE DIALLYL ETHER) DILINOLEATE AND ITS PHOSPHONATES AND LUBRICANT COMPOSITIONS

Winfred E. Parker, Philadelphia, and Ronald Έ. Koos, Lansdale, Pa., assignors to the United States of Amer· ica as represented by the Secretary of Agriculture

No Drawing. Original application Aug. 18,1966, Ser. No. 573,428, now Patent No. 3,423,319, dated Jan. 21, 1969. Divided and this application Jan. 29, 1968, Ser. No. 719,813

Int. Cl. C07f 9/28; C08h 9/00

U.S. Cl. 260—403 5 Claims

ABSTRACT OF THE DISCLOSURE

This invention provides diallyl ether esters of dimerized linoleic acid useful as lubricant compositions.

This application is a division of Ser. No. 573,428, filed Aug. 18, 1966, now Pat. No. 3,423,319.

A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the U.S. Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to esters of dimer acids and their phosphonates and more particularly to the diallyl ether esters of dimer acids and their phosphonates.

An object of the invention is to prepare thermally stable fluids for use as extreme pressure and base oil lubricants, lubricant additives, hydraulic fluids and the liquid phase of gas-liquid chromatographic columns.

Another object of the invention is to formulate thermally stable compositions for use as extreme pressure, anti-wear lubricants.

Other objects and a fuller understanding of the invention may be had by referring to the following description and claims.

Effective lubricants for any type of machinery should be capable of performing their function over long periods of time without appreciable changes in their physical and chemical characteristics. Mineral hydrocarbon lubricating oils are not suitable for many lubrication problems of modern industry. Consequently, synthetic lubricants, such as bis (2 ethylhexyl) sebacate and dibenzyl sebacate, employed as controls for evaluating the compounds of the present invention, have been prepared and used as specialty products. There is, however, continued need for better and more effective lubricants and lubricant additives capable of sustained performance under more demanding operating conditions.

The compounds of the present invention are represented by the formula:

C₂H₅ CH2OCH2—R'^-

V _—OCH2 CH2OCH2—R/_ 2 wherein R is the diacyl radical derived from dimerized linoleic acid or the hydrogenated product thereof, R' represents —CH=CH₂ or

-(CHjJi-l-COR), and R is any straight or branched chain aliphatic alkyl radical containing 1 to 8 carbon atoms. These compounds and the lubricant compositions formulated with these compounds as additives are thermally stable and represent a marked improvement in performance characteristics as evaluated by wear test and extreme pressure tests.

Anti-wear properties were determined using the Shell Four Ball Wear Tester as described by Peale et al., American Society of Lubrication Engineers Transactions 3, 48 (I960). Approximately 10 ml. of the test oil were placed in the test cup so that the three bottom stationary balls ⁵ were covered to about a 2 mm. depth. After positioning the cup on its stand in contact with the fourth ball, the oil was heated to 120° C., a 50 kg. load was placed on the weight tray, and the upper ball was allowed to rotate at 600 r.p.m. for 1 hour. The diameters of the circular scars worn on the three stationary balls were measured by means of a low power microscope. The results are shown in Table I.

The 5% by weight of the compounds of the present in_lg vention (lubricants 1, 2 and 3 in Table I) used as additives in the formulation of lubricant mixtures is arbitrary and is not intended to limit the use of the compounds to that amount. Although the amount would usually be about 5% or less, it is obvious to anyone skilled in the art that other 2q amounts would produce desirable results.

In the wear tests, the smaller value denotes the oil with the better lubricating property. The compounds of the present invention (Nos. 1, 2 and 3 in Table I) and the lubricant compositions (Nos. 10, 11, 13, 15, 17 and 19 in _2g Table I) formulated by the addition of the fully phosphonated ester (No. 3 in Table I) to the reference lubricants (Nos. 4, 5, 12, 14, 16 and 18 in Table I) show a very marked improvement in anti-wear lubricant properties over the reference compounds. For example, when ₃θ bis (2-ethylhexyl) sebacate (No. 4, Table I) was used without additive the diameter of the wear scar measured 0.830 mm. However by adding 5% by weight of the fully phosphonated ester (No. 3, Table I) to the bis (2-ethylhexyl) sebacate, the diameter of the wear scar was reduced almost 50% to 0.442 mm. (No. 10, Table I). Another example is the paraffin oil (No. 5, Table I). Without additive, the wear scar measured 0.803 mm. in diameter. With the fully phosphonated ester (No. 3, Table I) added to it, the wear scar was only 0.460 mm. in di₄₀ ameter (No. 11, Table I). Other examples showing similar improvement in lubricating properties can be found in Table I.

TABLE I—LUBRICATION AS MEASURED BY WEAR SCAR

Lubricant Additive Wear scar,

No. Name (5% by weight) dia. mm;

1_____Dilinoleate ester_________None 0.760 '2_____53% phosphonated _____do ........... '0.483 dilinoleate ester.

.. 3_____100%phosphonateddi- _____do ... 0.410 w linoleate ester.

4_Bis(2-ethylhexyl)- _____do 0.830 sebacate.

5_100 paraffin oil______₃.........do 0.803

6_Bis (2-ethylhexyl)- Dilinoeete ester.........0.778 sebacate.

7.100 paraffin oil...............do 0.597

8_____Bis(2-ethylhexyl) 53% phosphonated di-0.455 sebacate. linoleate ester.

9_100 paraffin oil_______________do 0.460

10_.___Bis(2-ethylhexyl) 100% phosphonated di-0.442 sebacate. linoleate ester.

.... 100paraffin oil.______________do .. 0.460

12_Bis(benzyl)dilinoleate.. None __ 0.653 do _______________100% phosphonated di-0.470 ou linoleate ester.

.... Hydrogenated bis (ben- None.. .. 0.748 zyl)-dilinoleate.

_____do _______________100% phosphonated di-0.447 linoleate ester.

Bis-(p-isopropylbenzyl)-None 0.843

-----do _______________100% phosphonated di-0.587 linoleate ester.

18____Dibenzyl sebacate______None 0.950

19---------do _______________100% phosphonated di- 0.620 linoleate ester.

γθ The extreme pressure properties were determined with a Shell Four Ball Extreme Pressure Tester also described by Peale et al. This is similar to the Wear Tester except

3,536,738 that it is more rigidly built and made to accommodate higher loads.

This instrument was used to determine loads at incipient seizure and at welding. Incipient seizure is defined as the load at which a sudden sizeable increase in wear scar diameter occurs, and welding is the load at which motion of the upper rotating ball in relation to the other three is no longer possible. The samples were run at room temperature under available loads for a one minute period. A fresh sample was used for each load. Rotation of the upper ball was 1700 r.p.m. The results, Tables II and III, show that the fully phosphonated bis (trimethylolpropane diallyl ether) dilinoleate can perform its lubricating function under much greater pressures than can the reference lubricants (Nos. 1, 2, 3, 4, Table II). For example, the extreme seizure load for a commercial built lubrication oil (No. 3, Table II) was 110 kg. while that of the fully phosphonated ester (No. 5, Table II) was 300 kg. Also, the pressure weld load for the same commercial oil (No. 3, Table II) was 190 kg. while that of the fully phosphonated ester of this invention (No. 5, Table II) was 350 kg.

Thermal stability was determined by the thermogravimetry, heating the compound in a specially designed sample holder suspended from a weighing mechanism. This procedure has been described by Parker, et al., I. Am. Oil Chem. Soc. 42, 792, (1965). The “Onset of De- cant additives. The kinematic viscosity, viscosity index, and the ASTM slope were determined according to ASTM D445-60 and ASTM D567-53 using CannonManning semi-micro viscometers.

_g The compounds of the present invention have several other desirable features: (1) they are relatively high molecular weight compounds, yet they are monomers, not polymers; (2) their molecular weights can be varied in the range between about 953 and 2179 depending on jq the extent of phosphonation, thus allowing the production of tailor-made compounds with predetermined physical and chemical properties; (3) they could be expected to have the lubricating properties of an ether, an alkane or alkene and a dibasic ester and when phosphonated, those 15 of an alkyl phosphonate; (4) they should be compatible or soluble in base oils that contain any of the above named functional groups; (5) that portion of the molecule represented by R' in the unphosphonated compound has four reactive sites which may be reacted with any compound that usually adds across a double bond.

In a typical procedure for the preparation of the esters about a 2 to 1 molar ratio of alcohol to dimer acid and a small amount of an acid catalyst were dissolved in an inert organic solvent such as benzene and refluxed until 25 the reaction was complete, as indicated by the amount of water collected. The benzene solution was washed until free of acid, dried over calcium sulfate, the benzene reTABLE IV.—VISCOSITY CHARACTERISTICS OF BIS(METHYLOLPROPANE DIALLYL ETHER) DILINOLEATE AND ITS PHOSPHONATED ESTER WHEN USED AS BASE OIL AND AS ADDITIVE

Kinematic viscosity centistokes at⁰ C.

•---------------------------Viscosity A.S.T.M.

<td> Sample</td><td> 37.8</td><td> 54.3</td><td> 98.8</td><td> index</td><td> slope</td>

<td> Dllinoleate ester (D.E.)...............</td><td> 257.8</td><td> 115.58</td><td> 24.6</td><td> 118.1</td><td> 0.602</td>

<td> 100% phosphonated dilinoleate ester (PDE)_____________________________</td><td> 752.4</td><td> 255.8</td><td> 40.3</td><td> 105.5</td><td> 0.638</td>

<td> Bis(2-ettiylhexyl sebacate) (D.O.S.)...</td><td> 12.7</td><td> 8.08</td><td> 3.34</td><td> 154</td><td> 0.710</td>

<td> 100 paraffin oil ______________________</td><td> 51.3</td><td> 24.7</td><td> 6.80</td><td> 94.0</td><td> 0.742</td>

<td> D.O.S.4-5% DE (asadditive)_________</td><td> 14.8</td><td> 9.12</td><td> 3.76</td><td> 175</td><td> 0.729</td>

<td> 100 paraffin oil+5% DE (as additive).</td><td> 50.4</td><td> 24.2</td><td> 6.40</td><td> 78.8</td><td> 0.778</td>

<td> D.O.S.4-5% P.D.E.(as additive)______</td><td> 17.8</td><td> 10.9</td><td> 4.28</td><td> 170</td><td> 0.672</td>

<td> 100 paraffin oil+5% P.D.E. (as additive)------------------------------</td><td> 73.8</td><td> 33.8</td><td> 8.70</td><td> 97.9</td><td> 0.733</td>

<td> D.O.S.+5% P.D.E.-531 (as additive)</td><td> 14.6</td><td> 9.10</td><td> 3.66</td><td> 158.8</td><td> 0.688</td>

<td> 100 paraffin oil+5% P.D.E.—53 ^{1 * 3} (as additive)___________________________</td><td> 50.7</td><td> 23.8</td><td> 6.36</td><td> 75.6</td><td> 0.783</td>

¹ 53% phosphonated dilinoleate ester.

composition” for these compounds is in the range 410- 45 490° F. Phosphonated compounds decompose in the lower temperature range to the original dilinoleate ester. Bis(trimethylolpropane diallyl ether) dilinoleate starts to decompose at 490°.

TABLE II.—COMPARATIVE FOUR BALL EXTREME PRESSURE TEST DATA &gt;

<td></td><td> Lubricant</td><td> Extreme</td><td> Pressure</td>

<td> No. Name</td><td></td><td> load, kg.</td><td> load, kg.</td>

<td> 1...</td><td> __ 100 paraffin oil__________________________</td><td> 60</td><td> 100</td>

<td> 2...</td><td> __ Bis (2-ethylhexyl) sebacate_____________</td><td> 70</td><td> 110</td>

<td></td><td> Commercial built lubrication oil________</td><td> 110</td><td> 190</td>

<td> 4__.</td><td> __ S.A.E. 90 gear lube______________________</td><td> 160</td><td> 280</td>

<td> 5...</td><td> .. 100% phosphonated bis(trimethylolpropane diallyl ether) dilinoleate______</td><td> 300</td><td> 350</td>

* Tests conducted at room temperature for one minute.

TABLE III—FOUR BALL EXTREME PRESSURE TEST DATA ON PHOSPONATED BIS(METHYLOLPROPANE DIALLYL ETHER) DILINOLEATE (PDE) I

P.D.E. 100% Load, kg. Scar dia., mm.

P.D.E. 100%_______________________________ 1500.596

P.D.E. 100%_______________________________ 2000.693

P.D.E. 100%....__________ 2500.710

P.D.E. 100%_______________________________ 300(2)

P.D.E. 100%_______________________________ 350(3) ¹ Tests run at room temperature for one minute. vq s Incipient seizure.

Weld—10 sec.

The compounds have a wide range of viscosity characteristics as shown in Table IV. The viscosity of the fully phosphonated ester is similar to that of commercial lubri- ‘⁵ moved, and the crude product purified by molecular distillation.

In the preparation of the phosphonated esters, about one mole of the above ester was reacted with about nine moles of a dialkyl phosphonate (dialkyl hydrogen phosphite) in the presence of a peroxide catalyst. The catalyst was added in one-quarter portions at four hour intervals. The excess phosphonate was distilled off under reduced pressure, and the phosphonated ester was purified by molecular distillation. The extent of reaction was determined by infrared spectra, iodine number and percent phosphorus.

The alkyl radical of the dialkyl phosphonate can be any straight or branched chain aliphatic alkyl radical containing 1 to 8 carbon atoms such as methyl, ethyl, propyl, butyl, amyl, hexyl, heptyl, octyl and any of their isomers. The di-2-ethylhexyl phosphonate derivatives are used to exemplify this invention.

The dimer acid employed in the preparation of the esters contained 95% dilinoleic acid, 4% trimer acid, and 1% monobasic acid and had the following characteristics: Acid number, 191.2; neutralization equivalent, 293.4; and molecular weight, 565. The dialkyl phosphonate (dialkyl hydrogen phosphite) was redistilled before use. Best results were obtained with use of naphthalene-2-sulfonic acid as the esterification catalyst. Naphthalene-l-sulfonic acid, methane sulfonic acid, and sulfuric acid can also be used in the catalyst, but give poorer results than naphthalene-2-sulfonic acid. The catalyst used for the dialkyl phosphonate addition was t-butyl perbenzoate.

Preparation of the esters is illustrated by the following

3,536,738 . ⁵ examples which are not intended to he in limitation of the scope of the present invention:

EXAMPLE 1

Dimer acid, 141 g.; trimethylolpropane diallyl ether, 107 g.; and 2.8 g. naphthalene-2-sulfonic acid were dissolved in 450 ml. benzene in a two-liter 3-neck flask. The flask was equipped with a magnetic stirrer, thermometer, and a Dean and Stark tube with a water-cooled condenser. The mixture was heated at 90° C. reflux temperature until 7.5 ml. of water was taken off in 7 hours reaction time. Since the amount of water collected indicated that the reaction had not gone to completion, an additional 1.4 g. catalyst was added to the reaction mixture, and the rejuvenated reaction gave off an additional 1.5 ml. water in 2 hours. Total reaction time: 9 hours; total weight of catalyst, 4.2 g. After cooling, the reaction mixture was washed with water until acid-free. The benzene solution was dried over calcium sulfate, filtered, and the benzene evaporated under vacuum. The crude product, a dark amber fluid, weighed 233.5 g., percent yield, 96.6; acid number, 5.5; np²⁵&gt; 1.4776.

The crude product was purified by molecular distillation, the main fraction being collected above 225° C. at 7 micron pressure. This fraction weighed 101 g. The purified product, his (trimethylolpropane diallyl ether) dilinoleate, a medium amber liquid had the following characteristics: «d²⁵&gt; 1.4782; iodine number 135.1; saponification number 121.1, calc’d., 117.7; saponification equivalent 465.5, calcd., 476.8; percent carbon 75.78, calcd., 75.88; percent hydrogen, 11.08 calcd. 10.99; molecular weight, 931, calcd., 953.

EXAMPLE 2

Bis(trimethylolpropane diallyl ether) dilinoleate, 50 g.; di-2-ethylhexyl phosphonate, 144 g., and one-quarter of the total amount (4.6 g.) of t-butyl perbenzoate were mixed in a 500 ml. 3-neck flask. The flask was equipped with a magnetic stirrer, water condenser, thermometer, and gas inlet tube. The reaction mixture was blanketed with nitrogen until the reaction was completed. While the reaction mixture was heated at 110° C. for 16 hours, one-quarter portions of the catalysts were added at four hour intervals. After each catalyst addition, except the last, the reaction temperature rose 5-6 degrees. The last addition resulted in only a two-degree rise. The reaction mixture was degassed in a molecular still at room temperature under a partial pressure. The excess phosphonate was distilled off at 120-150° C. at 15 microns pressure. The main fraction, a viscous amber liquid, was collected above 200° C. at 7 microns. The purified product weighed 64.0 g.; percent carbon, 71.42, calcd., 68.34; percent hydrogen, 11.15, calcd., 11.29; percent phosphorus, 3.03, calcd., 5.68; iodine number, 75.7. The infrared spectra, iodine number, and the percent phosphorus indicated that the compound had attained 53% of the maximum amount of dialkyl phosphonate addition.

EXAMPLE 3

The procedure of Example 2 was repeated except that the reaction time was increased to 32 hours and 1.1 g. Catalyst was added at 4 hour intervals (total amount, 9g.). Molecular distillation, above 240° C. at 7 microns pressure, yielded a very pale amber viscous liquid. The purified product weighed 60.0 g.; percent yield, 52.6; iodine number 20.7; «d²⁵, 1.4755; percent carbon, 67.82, calcd., 68.34; percent hydrogen, 10.99, calcd., 11.29; percent phosphorus, 5.64, calcd., 5.68; molecular weight (calcd.), 2179. The iodine number and percent phosphorus indicated that the ester had been phosphonated 100%.

Since both the 53% and the 100% phosphonated derivatives are markedly improved lubricants over the unphosphonated compound and over the reference lubricants (Table I), it is considered that any products in the range of about from 50% to 100% phosphonated compounds are operative in the present invention.