US3336227A - Polyalkylene glycol-diorthosilicic acid ester lubricants and power transmitting fluids - Google Patents

Description

United States Patent No Drawing. Filed July 8, 1965, Ser. No. 470,629 Claims priority, application Germany, July 10, 1964,

20 Claims. of. 25249.6)

This invention relates to new and useful synthetic liquid compositions or oils. More particularly, the invention is concerned with fluid or. oily compositions comprising a diorthosilicic acid ester or a mixture containing a diorthosilicic acid ester.

The fluid compositions of this invention may be used alone or admixed with other liquid materialse.g., fluid bodies such as polyoxyalkyleneglycol-diortho-silicic acidhexaalkyl esters disclosed in US. Patent No. 2,776,307 as electrically insulating fluids, hydraulic fluids, damping fluids, lubricants, etc.

Synthetic lubricants, power transmission fluids, etc., must possess a number of properties in order to be capable of heavy duty service under varying operating conditions. Such fluids must be characterized by small changes in viscosity with temperature, remain fluid at low temperatures, be non-volatile at high temperatures, have high thermal and oxidative stability, and the lubricating films formed therefrom must have adequate load carrying capacities.

Silicic acid esters are known which more or less meet the above requirements, as, for instance, polyoxyalkyleneglycol-diorthosilicic acid-heXa-alkyl esters disclosed in U.S Patent No. 2,776,307. However, the viscosity indices of these esters' decrease in those instances where the esters have alkyl groups which contain more than 8 carbon atoms. The esters having low viscosity indices are not satisfactory for application as jet propulsion engine oils.

-An object of the present invention is to provide silicic acid esters having high boiling ranges, 10w volatilities, high viscosity indices, low viscos-ities at low temperatures and as well capable of forming lubricating films having satisfactory load carrying capacities.

Another object of this invention is to provide fluidcompositions suitable for use as electrically insulating fluids,

been found that liquid material comprising diorthosilicic acid esters of the formula I i)z( )s n( R')n wherein A represents a polyoxyalkylene radical having 1 3,335,227 Patented Aug. 15, 1967 "ice to 6 and preferably 2 to 4 ether-oxygen atoms, R represents a polyoxyalkylene glycol ether radical having 2 to 8 ether-oxygen atoms, R represents an alkyl group having 9 to 20 carbon atoms, n is of the class consisting of from 1 to 4 and 0 and wherein R and R may be the same or different, provides liquid or fluid compositions which are suitable for use as lubricants, brake fluids, hydraulic fluids, etc.

A preferred group of diorthosilicic acid esters for the purposes of the invention has the following formulae:

are shown in the following table wherein a comparison of certain of the esters of the invention with certain known silicic acid esters having similar molecular sizes has been set out. The known esters employed in comparison include diand tri-oxyalkyleneglycol-diorthosilicic acidheXa-isodecyl-ester (I, III) as well as tri-oxyalkyleneglycol-diorthosilicic acid-hexa-iso-tridecyl-ester (VIII) corresponding to the formula:

The esters of the invention used in the comparison are the following:

(II) diethyleneglycol-di-o'rthosilicic acid-hexa-(diethyleneglycol-n-butyl-ether) -este r (VI) diethyleneglycol-di-orthosilicic acid-tri-(diethyleneglycol-ethyl-ether) -tridiethyleneglycol-n=butyl-ether)-ester (IV) triethyleneglycol-di-orthosilicic acid-heXa-(diethyleneglycol-n-butyl-ether) -ester (V) triethyleneglycol-di-orthosilicic acid-tri-(diethyleneglycol-ethyl-ether) -'tri- (diethyleneglycol-n-butyl-ether) ester (VII) triethyleneglycol-di-orthosilicic acid-tri-(diethyleneglycol-n-butyl-ether) -tri- (iso-decyl -ester (IX) triethylenegly-coldi-orthosilicic acid-tri-(diethyleneglycol-n-butyl-ether) -tri-(isotridecyl) -ester The expressions Oxo C H andOXoC H as used in the table designate radicals of alcohols obtained from trimeror tetramer-propylene by hydroformylation (oxo synthesis) followed by hydrogenation of the hydroformylation product.

The load carrying capacity of the lubricating film of each of the esters was determined using the four-ball testing apparatus as described by Boerlage (Lexikon der Schmiertechnik, G. Voegtle, Franckh'sche Verlangshandlun-g Stuttgart 1964).

In the table, two numbers are set out under the column Welding Value. The first number represents the highest possible load in kg. which the lubricating film withstands for one minute, without alteration, while the second number designates the load at which the balls are welded, i.e.,

4. inertness to broad temperatures changes is desirable or required.

frozen together. When the viscosity of an oil changes only slightly as TABLE I Di-orthosilicic acid esters Molec- Viscosity (st.) in C. Vls- Welding No. 71. ular cosity Pour value wt. index point, load, kg. A R R 93.9 37.3 -40 54 o.

I omomocmom OX0-C1oH21.- 0 1,102 5.19 22.0 3,030 20,200 107 -09 100/170 II CHCH 0CHzCHz p rr og og 1 4165 0 1,120 3.9 13.5 1,273 7,490 203 -71 170/130 2 2 2 2 VI-- CH2CH2OCH2OH2 0 1,042 4.05 10.2 1,950 17,050 200 70 130/190 111---- (CHZCH)2CHQCHL- 0 1,140 7.3 34.0 0,530 49,000 103 -03 100/170 IV (CHzCHzO)2CHzCH2 (CHzCH20):-l1-C4H9 0 1,170 7.0 20.1 2,915 13,050 130 -70 130/190 CH.CH.O .CH.CH..-.{ggggggggggggggg 0 1,030 0.31 24.25 3.005 24,050 135 -09 130/190 VII (CHzCHaO)5CH9CHz (0H,o112o)rn-olH5 Oxo-C10Hz1 3 1,153 0.9 27.5 3,540 29,350 175 -05 170/130 vrn (CHzCHzOhCHzCHn.-. OXO'CnHfl" 0 1,393 9.2 50.0 30,400 133 -52 100/170 IX (CHgCHgO)zCHaCHz- (CHzCHzO) -n-C4H0 OXO-Cl3H27- 3 1,234 3.93 41.3 11,400 100 -00 170/130 As can be seen from the table, the viscosities of silicic acid esters having approximately equal molecular weights I and II, III and IV, I and V, I and VI, III and VII, and VIII and IX differ greatly. The viscosity indices of the esters II and IV (according to the invention) lie above 200, which is significantly higher than the viscosity index of the hexa-isodecyl-ester I. The viscosity indices of the triethyleneglycol-diorthosilicic acid esters IV and V differ considerably from those of esters I and III, respectively, of comparable molecular size and, namely, by 17 or 18 units, respectively.

While the viscosity indices of hexa-alkyl esters decrease with increasing size of carbon chains of the radicals R (III, VIII) high viscosity indices, i.e., above 180, for the silicic acid esters according to the invention are retained. If three of the six alkyl radicals in the said silicic acid ester molecular are substituted by diethyleneglycol-n-butyl-ether radicals (VII, IX), the viscosity index is considerably improved.

The silicic acid esters according to the invention possess satisfactory low temperature viscosities at, for example, -40 and at 54 C. Because of this favorable viscositytemperature relationship, the esters of the invention are particularly well suited for use as lubricants, additives to lubricants, as well as power transmission fluids, where extremely low temperatures must be encountered.

Although the esters IV and V, containing oxyalkyleneglycol ether residues, are more viscous at 37.8 and 98.9 C. than the known hexa-isodecyl-ester 1, they are much more fluid in the cold than the commercially available lubricating oils of different chemical composition used at present for gas turbine airplanes. The known bis-(2-ethylhexyl)-sebacic acid ester, for instance, which has at 37.8 C. the same viscosity as ester H, has a cold viscosity of 10,150 cst.

Ester VII, although highly viscous at 37.8 and 989 C., has substantially the same viscosity as ester I at extremely low temperatures. Thus, the di-orthosilicic acid esters containing oxyalkyleneglycol-ether radicals in their molecule according to the invention exhibit an unexpectedly great improvement in their viscosity-temperature relationship, their low temperature behavior, as well as an increased load carrying capacity of their lubricating films as compared with the di-orthosilicic acid esters known in the art.

Because of the high load carrying capacity of lubricating film, the esters according to the invention have proved especially useful under the application of high loads of the resulting mixed friction.

Polyoxyalkyleneglycol-diorthosilicic acid-hexaoxyalkylene-ether esters according to the invention have molecular weights below 900 and are especially suitable for use as hydraulic fluids due to their high viscosity indices, their low viscosities at low temperatures and adequate viscosities at high temperatures, i.e., under conditions wherein a function of the temperature, it likewise exhibits but an extremely small pressure responsivity. This property is of considerable importance for hydraulic fluids. For instance, diethyleneglycol -diorthosilicic acid-hexa-(ethyleneglycol-n-butyl-ether)-ester (molecular weight 862) has a viscosity index of 218. Its viscosity at -40 and 54 C. amounts to 780 and 3460 cst., respectively, which constitute very low values. Its viscosity at 988 C. amounts to 4.1 cst., which is considerably higher than that of the dibasic carboxylic acid esters known in the art.

The esters of this invention can be used alone or in admixture with other liquid materials known in the art as lubricants or power transmission fluids, e.g., mineral lubricants, dicarboxylic acid esters, phosphoric acid esters, organo-silicium compounds of different structure, as well as with conventional oxidation inhibitors and other like conventional additives. For instance, they may be admixed with (1) a liquid dicarboxylic acid ester or with (2) a liquid organo-silicium compound, as, for example, a methyl polysiloxane, or (3) with both a phosphoric acid ester and an oxidation inhibitor. The ester of the invention is present in any admixture in an amount equal to at least 5%, preferably at least 50%, of the resulting admixture.

An especially well suited oxidation inhibitor is phenothiazine. It can be added in amounts from 0.1 up to 1.5% by weight, dependant upon the quantity of the lubricant.

Conventional additives for improving the oiliness of the lubricants consisting of or containing the esters of the invention, as for instance tricresylphosphate may be added in amounts from 0.1 up to 3% by weight dependant upon the quantity of the lubricant. It is not however necessary to employ these additives, since the esters according to the invention per se exhibit outstanding lubricating action.

The diorthosilicic acid esters can be prepared, for instance, by reacting stoichiometric mixtures of suitable alcohols and ether alcohols with gaseous SiCl according to the disclosure of German Patent No. 1,142,855 or as disclosed in German patent application R 32,696 IVb/ 120, Deutsche Auslegeschrift 1,180,359.

The following examples are intended to illustrate the invention and are not to be interpreted as limiting the same.

Example I A reaction vessel (a so-called bubble-column reactor) consisting of a vertical glass tube with an internal diameter of 69 mm. and a height of 550 mm. provided with a glass frit (Jena apparatus glass, grain coarseness 2) in its bottom was charged with 121 g. diethyleneglycol and 1122 g. diethyleneglycol-n-butylether, which had previously been dried to a water content below 0.1%. Silicium tetrachloride was applied dropwise from a dosing vessel 5 into an evaporator coil heated at C., which was gastight connected with the said reaction vessel, by a conduit joining the said reaction vessel below the said glass hit. The silicium tetrachloride vapors evolved in the evaporator coil were sucked through the frit under a vacuum of of theinvention to the conventional ester lubricant are shown in the following Table 2, wherein the properties of the two single esters are shown in comparison with those of the ester mixture, hereinafter designated admixture 180 torr. The ascending SiCl vapors together with the 5 50/50 percent by vol.

TABLE 2 Viscosity in est. at 0. Welding Viscosity Flame value load d4 index point, C. in kg.

Bis-3,5,5-trimethy1hexyl adipate 0. 916 3.15 11.86 15,720 147 222 150/160 Diethyleneglycol-diorthosilicic acid-tri- (diethyleneglycol-n-butylether)-tri- (isodecyD-ester 0- 969 3- 9 14. 43 10, 100 188 264 170/180 Admixture, 50/50 percent by vol 0. 944 3. 52 13.01 12, 700 169 238 170/180 hydrogen chloride evolved during the reaction formed a Example 3 bubble-column of 420 mm.'height with the liquid in the reactor. The liquid mixture of said alcohol and ether,

70 parts by volume bis-3,5,5-(trimethylhexyl)-adipate were admixed with parts by volume diethyleneglycoldiorthosilicic acid hexa-(diethyleneglycol-n-butylether)- ester (ester II as hereinbefore mentioned). The properties of the two single esters are shown in comparison with those of the ester mixture, designated admixture 70/ 30% by course of the reaction. 357 g. SiCl, were introduced and 25 vol. in Table 3.

TABLE 3 Viscosity in cst. at C. Weldin Viscosity Flame value load (14 index point, C. in kg.

Bis-3,5,5-(trimethylhexyD-adipate. 0.916 3. 15 11. 86 15, 720 147 222 150/160 Ester II 035 3.9 13.5 7, 490 204 251 170/1s0 Admixture, 70/30 percent by vol 0. 952 3. 4 12. 69 11, 150 163 230 170/180 converted during 100 minutes. After termination of the reaction, the reaction vessel was heated at 110 C. for 2 hours whereby dissolved hydrogen chloride was removed from the reaction mixture under introduction of nitrogen at a vacuum of 20 torr. (After the said treatment the Beilstein-reaction was negative.) Thereafter the non-reacted excess amounts of the reactants (125 g.) were distilled off from the reaction product under a vacuum of 0.01 torr up to a temperature of 196? C. As distillation residue 1150 g. of diethyleneglycol-diorthosilicic acid hexa (diethyleneglycol n butylether)ester (density d =1.038, index of refraction n =l.4452) were obtained. The silicium content of the product ester was determined to 5.02% (calculated 4.98%); the viscosity of the ester at 989 C. was 3.9 cst., at 37.8 C. 13.5 cst., at 40C. 1273 cst., at 54 C. 7490 est; its viscosity index amounted to 203, its flow point (or setting point) was 71 C.

In analogous manner other esters according to the invention can be prepared.

Due to the admixture of the ester of the invention the following propertiesof dibasic esters, serving as lubricants for turbo-jets are generally improved:

The viscosity in the temperature range above 50 C. is increased, in the temperature range below 37.8 C. decreased. The viscosity index is increased, the flame point and the load carrying capacity are also increased.

Example 4 75 parts by volume of a mineral lubricating oil (free of any additive) were admixed with 25 parts by volume of 1 diethyleneglycol-diorthosilicic"acid-hexa-(diethyleneglycoln-butylether)-ester (ester II of the invention). A comparison of the lubricant so obtained (hereinafter called admixture 75/25 percent by vol.'M) with the said mineral oil and ester II has been set out in Table 4.

Example 5 TAB LE 4 Viscosity in cst. at C.

. v Viscosity Flame Setting d4 index point, C. point, O.

Mineral lubricating oil 0.990 11. 5 130 25, 79 238 19 Ester II 1. 035 3. 9 13. 5 132 204 251 72 Admixture, 75/25 percent by vol. M 1. 002 9.01 67. 6 4, 030 241 -21 Diethyleneglycol-diorthosilicic acid-tri- (diethyleneglycol-n-butylether)-tri- (isodecyl)-ester 0. 969 3. 9 14. 43 152 188 252 71 Admixture, 50/50 percent by vol. M 0. 979 6. 4 34. 7 2, 136 244 23 The admixture according to Examples 4 and 5 represent motor oils, which meet the demands for several classes according to the SAE-classification (Society of Automotive Engineers).

Due to the addition of the esters of the invention to mineral lubricating oils, essential properties of these oils are improved. The viscosity index is increased (as for instance for 36 units at an addition of 25% of the ester of the invention). The viscosity, especially at low temperatures is diminished. The flame points are raised and the setting points are lowered. Further on, the lubricating action is improved.

We claim:

1. A lubricant and power transmission fluid comprising at least 5% by weight of a diorthosilicic acid ester of the formula:

wherein A represents a polyoxyalkylene radical having 1 to 6 ether oxygen atoms, R represents a polyoxyalkylene-glycol-ether radical having 2 to 8 ether-oxygen atoms, R' represents alkyl having 9 to 20 carbons atoms, and n is of the class consisting of integers of from 1 to 4 and 0 admixed with another liquid lubricant.

2. A lubricant and power transmission fluid according to claim 1 additionally containing an anti-oxidant.

3. A lubricant and power transmission fluid according to claim 1 wherein said diorthosilicic acid ester is RO liOAOSlOR wherein R is as defined in claim 1, and A is a polyoxyalkylene radical having 1 to 6 ether oxygen atoms.

4. A lubricant and power transmission fluid according to claim 1, wherein said diorthosilicic acid ester has the formula:

wherein A, R, and R are as defined in claim 1.

5. A lubricant and power transmission fluid according to claim 1, wherein said diorthosilicic acid ester is diethylenegylcol diorthosilicic acid hexa-(diethyleneglycol-nbutyl-ether)-ester.

6. A lubricant and power transmission fluid according to claim 1, wherein said diorthosilicic acid ester is diethyleneglycol diorthosilicic acid tri-(diethyleneglycolethyl-ether)-tri-(diethyleneglycol-n-butyl-ether) ester.

7. A lubricant and power transmission fluid according to claim 1, wherein said diorthosilicic acid ester is triethyleneglycol-diorthosilicic acid-hexa-(diethyleneglycoln-butyl-ether) -ester.

8. A lubricant and power transmission fluid according to claim 1, wherein said diorthosilicic acid ester is triethyleneglycol diorthosilicic acid tri-(diethyleneglycolethyl-ether) -tri- (diethyleneglycol-n-butyl-ether) -ester.

9. A lubricant and power transmission fluid according to claim 1, wherein said diorthosilicic acid ester is triethyleneglycol diorthosilicic acid-tri-,(diethyleneglycol-n butyl-ether) -tri- (iso-decyl) -ester.

10. A lubricant and power transmission fluid according to claim 1, wherein said diorthosilicic acid ester is triethyleneglycol-diorthosilicic acid-tri-(diethyleneglycoln-butyl-ether) -tri- (iso-tridecyl -ester.

11. A lubricant and power transmission fluid comprising at least 5.0% by weight of a diorthosilicic acid ester of the formula:

R R 6 6 ROQlOAOS lOR wherein A and R are as defined in claim 11.

14. A lubricant and power transmission fluid according to claim 11, wherein said diorthosilicic acid ester has the formula:

wherein A, R and R are as defined in claim 11.

15. A lubricant and power transmission fluid according to claim 11, wherein said diorthosilicic acid ester is diethyleneglycol diorthosilicic acid hexa-(diethyleneglycol-n-butyl-ether) -ester.

16. A lubricant and power transmission fluid according to claim 11, wherein said diorthosilicic acid ester is diethyleneglycol diorthosilicic acid tri (diethyleneglycol ethyl-ether)-tri-(diethyleneglycol-n-butyl-ether)- ester.

17. A lubricant and power transmission fluid according to claim 11, wherein said diorthosilicic acid ester is triethyleneglycol diorthosilicic acid hexa (diethyleneglycol-n-butyl-ether -ester.

18. A lubricant and power transmission fluid according to claim 11, wherein said diorthosilicic acid ester is triethyleneglycol diorthosilicic acid tri (diethyleneglycol ethyl-ether)-tri-(diethyleneglycol-n-butyl-ether)- ester.

19. A lubricant and power transmission fluid according to claim 11, wherein said diorthosilicic acid ester is triethyleneglycol diorthosilicic acid tri (diethyleneglycol-n-butyl-ether)-t1i-(iso-decyl)-ester.

20. A lubricant and power transmission fluid according to claim 11, wherein said diorthosilicic acid ester is triethyleneglycol diorthosilicic acid tri (diethyleneglycol-n-butyLether)-tri-(iso-tridecyl)-ester.

References Cited UNITED STATES PATENTS 2,724,698 11/ 1955 Kittleson 25249.6 2,947,772 8/1960 Eynon 25249.6 X 3,029,269 4/1962 Abbott 25249.6 X 3,118,841 1/1964 Moreton 25249.6 X 3,133,111 5/1964 Wheeler 25249.6 X

DANIEL E. WYMAN, Primary Examiner.

W. H. CANNON, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,336 ,227 August 15 1967 Herbert G'othel et a1. It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Columns 5 and 6 TABLE 2 third column, line 3 thereof, for "d 52" read 3 53 column 8 line 27 for "((501) (OR) (OR) "read A(OSi) (OR) (OR Signed and sealed this 15th day of October 1968 (SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, Jr. Attesting Officer Commissioner of Patents

Claims (1)

1. A LUBRICANT AND POWER TRANSMISSION FLUID COMPRISING AT LEAST 5% BY WEIGHT OF A DIORTHOSILICIC ACID ESTER OF THE FORMULA: