Liquid composition

2,175,877

Oct. 10, 1939.

F. M. CLARK LIQUID COMPOSITION Filed Sept. 30, 1936 n^.z.

V7SC0S/TY

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Inventor:

by

Frank M. Clark, His/Attorney.

Patented Oct. 10, 193d

2,175,877

UNITED STATES PATENT OFFICE

2,175,877

LIQUID COMPOSITION

Frank M. Clark, Pittsfield, Mass., assignor to General Electric Company, a corporation of New York

Application September 30,1936, Serial No. 103,313

Claims. (Cl. 87—9)

The present application comprises liquid compositions of neutral oily consistency characterized by low viscosity at low temperature and more uniform viscosity-temperature relation than is normally associated with ordinary mineral oil or vegetable oil compositions, such as are used for lubricating, electrical insulating and other industrial purposes.

It is one of the objects of my invention to provide oily liquids suitable for cooling and dielectric purposes in electric devices, such as transformers.

Another object of my invention is to provide low viscosity liquids of superior characteristics for use in electric cables of the liquid-filled type,

It is a further object of my invention to provide an improved liquid dielectric impregnant for capacitors whereby the electric capacity is materially increased and the electrical operation at low temperature improved.

Still another object is to provide an improved liquid dielectric for arc interrupting devices. Many arc interruption devices operate efficiently only when they are provided with liquids of low viscosity. This is especially true for those arc interrupting devices which are constructed to open an electric circuit within a definite number of alternations of voltage on alternating current circuits. Even the lowest viscosity niineral oil having a required resistance to ignition within a prescribed limit of temperature has such increased viscosity at temperatures below room temperature, especially at temperatures as low as —30° C. and lower, that it constitutes a serious obstacle in the operation of such devices.

It is also an object of my invention to provide compositions of superior lubrication characteristics. My improved liquid compositions not only have minimum viscosity change with temperature but also have as well superior extreme pressure lubrication characteristics as will hereinafter be shown. As a consequence of my invention I have provided lubricant and dielectric compositions of low pour point.

Other and important objects and applications of my invention will appear hereinafter.

The essential ingredients of my novel compositions are oily liquid materials of mineral or vegetable or synthetic origin in combination with one or more alkyl phosphates, this term being used to designate such phosphates in their ordinary, unsubstituted form. Such compositions normally should contain by weight about 5 to 25 per cent of the alkyl phosphate, but such ingredient is not necessarily restricted to such limits.

Examples of oily materials constituting an essential ingredient of the compositions of this invention are mineral oils of the type in general use in electric transformers, cables, capacitors, ars interrupting devices and the like; mineral oils in 6 general lubrication Use for automotive and other mechanical devices; vegetable oils such as castor and linseed oils, synthetic oily liquids of the ester type (for example, butyl stearate, or tartrate or phthalate), or other oily ester derivatives of the 10 alkyl or phenyl hydrocarbon nuclei!, or chlorinated oil liquids such as the chlorodiphenyl, chlorodiphenyl oxides and others hereinafter designated..

As illustrative of the second ingredient used 15 in combination with the foregoing materials, are alkyl phosphate esters, such as the ethyl, propyl or butyl esters, or combinations thereof. Such esters may be designated, generally, by the empirical formula RPO«, wherein R comprises an 20 alkyl radical containing not exceeding four (4) carbon atoms. For some purposes tributyl phosphate is preferred.

In the accompanying drawing Fig. 1 is a graph showing the viscosity characteristics of mineral 25 oil compositions embodying my invention over a range of temperatures; and Fig. 2 is a graph showing the viscosity variation of a composition embodying my invention with changes of proportion of the ingredients. 30

In the graph of Fig. 1 temperature values are plotted as abscissae over a range from about 50° C. down to the lowest temperatures encountered climatically. The curve A shows the viscosities over a range of about 100° of a mixture by weight 35 of 25 per cent of tributyl phosphate and 75 per cent of a mineral oil. The data given for a composition containing a light mineral oil such as commercially designated as “10-C Oil”. The viscosity of the mixture changes but little as the 40 temperature falls from 50° C. to about 20° C. and then as the temperature continues to fall to about —40° C. the viscosity rises only to 600 seconds Saybolt. The mineral oil unassociated with modifying ingredients on the other hand begins 45 to rapidly increase in viscosity at about 0° C. Its viscosity-temperature characteristic is shown by curve B as rising to about 10,000 seconds Saybolt at —40° C.

As shown by curve C a mixture of equal parts 50 by weight of tributyl phosphate and mineral oil has an even lower viscosity at very low temperatures. At —45° C. the viscosity of this mixture is still below 400 seconds Saybolt. .

A particular composition adapted for use in 55

Saybolt

590 seconds Universal seconds Universal 35 seconds Universal

Saybolt

Saybolt

Clear

2,175,877 transformers, electric cables and arc interrupting devices consists of 75 per cent mineral oil of the type normally used in electric transformers and 25 per cent by weight of the _g phate. Such a composition has the xollowm* properties:

Viscosity at —40° C----Viscosity at 4-37.8° C— ¹⁰

Viscosity at 100° C-----Gravity at 15.5/15.5° CCondition-------------IS Plash noint____________

Burn point-------------r⁶⁸° ^c· -θθ _c

Pour point_____________^^{er C}

Dielectric strength------ 33 kv.

eA Because of its improved viscosity-temperature ²⁰ characteristics coupled with the point than that normally associated with the Zal transformer oil, such a been found particularly well adapted for __ insulating use in electric devices. One of my ²⁸ improved compositions when used in. an arc interrupting device in which speed ^oi ' zuntion is oi major importance resuhui m a speed of operation at temperatures m the range „_lt _40 to —50° C., approximately 66 per ⁸⁰ tent over the normal speed obtained with the low viscosity mineral oil which had been used..

Compositions comprising mixtures “ nil and tributyl phosphate further illustrate toe SeSSUXnL The reUtivgy hg Pog point of castor oil (about -10 C.) tonits use as a lubricant and as a liquid dielwtnc m •.--rial in electrical devices. Sy toe adaitiox oi tributyl phosphate, or equivalent ester phosphate* to castor oil the viscosity at low remperatures’is materially decreased. In the. following table are compared viscosities at various temp-vnture' end also nour point οι λιο such mix tures‘with castor‘oil such as ordinarily obtained, that is, unmixed with any mooA. (designs,tsd ss product 3).

Castor oil

Percent

100

<td colspan="2"> Trib- 1 _m</td><td colspan="5"> Viscosity</td>

<td> uvyi phosphate</td><td> point</td><td> 100°·</td><td> 37.8°</td><td> 25°</td><td> -17°</td><td> -25°</td>

<td> Percent 25 50 0</td><td> -35 -00 -10</td><td> °C. 64 47 120</td><td> °C. 378 128 1,350</td><td> °C. 660 196 C)</td><td> °C. 52,000 (²) (³)</td><td> °C. (¹) 36,000 (³)</td>

duct

Viscous. ² Not measured. ³ Semisolid.

Tn Place of a mineral or vegetable oil other liouicToily materials having a viscosity characterointab’e for use for lubricating or dielectric

PiZoses may be used in compositions ing my invention. For example, a may employ as the oily constituent or base liquid chim mated diphenyl or liquid chlorinated diphenyl onoe, Xr with or without mineral oil In my prior «<5 Patent 2,037,686 patented April f ^jSo> /· Ε'ί ^e described compositions of mineral oil and cnlorirated dinhenyl. 1 prefer to employ uquid chlorinated dinhenyl compound containing about 54 uer cent chlorine (corresponding suhsbamially τη in composition to pentachlor diphenyl), although some chlorinated compounds or lower and chlorine content may be present. As described 2,041,594, patented May 19, such as are ordinarily obhet consist of s mixture of in my pric1936, comr tainable or various isomers of pentachlor diphenyl. Such SSct iemoln IWUld at a « than a composition consisting of but a single isomer. Pentachlor diphenyl as ordinal ily prepared, is a viscous liquid having a ^cosity of about 43 to 50 seconds Saybolt at -00 k,. a about 11,000 seconds SayboL· at 25 C. _ne yju.. noint of this product is approximately 10 C.

When this material is compounded with even as little as 5 to 10 per cent by weight of tributyl phosphate, then the low temperature characteiistics are remarkably cnanged. The viscosity is lowered materially by the presence of even a few per cent of alkyl phosphate, as shown m U·/, which shows a graph D of the relation of viscosity at 25° C. of pentachlor diphenyl containing various proportions of tributyl phosphate.

Decreased, viscosity of these compositions is accompanied by lowered pour points as shown in the following tabulation showing the pour points of three mixed products compared with chlorinated diphenyl (product 4) unassociated with phosphate ester:

Tributyl

Product

Chlor ----- .

diphenyl phosphate

5.

6.

7.

Percent

IGO 85

Percent 0 15 25 50

Pour point +10

Such mixtures are of particular utility as impregnants in capacitors. A given capacitor containing kraft paper when impregnated with , pentachlor diphenyl as described m my prioi Patent 2,041,594 (product 4) has a capacity oi 5 microfarads. When product 6 (25 per cent of tributyl phosphate) is introduced in ios place in such capacitor, the capacity is found to be 8 microfarads. When product 7 is employed the capacity is still further increased to approximately 11 microfarads. At temperatures below about 0° C. the capacity of capacitors impregnated with chlorinated diphenyl falls, due to solidification, to about 75 per cent of theii original values. The drop in capacity of capacitors impregnated with mixtures containing tiibutyl phosphate is eliminated down to temperatures as low as the pour point of the mixtures.

compounds may be used as the oily base. For example, I may use chlorinated diphenyl ketone (described in U. S. Patent 2,012,301 of August 27, 1935) or chlorinated polyphenyl methane (described in U. S. Patent 2,012,302) or chlorinated d’benzvl (described in U. S. Patent 2,033,612, patented March 10, 1936) or chlorinated diphenyl oxide (described in my pending application Serial No. 73,595 filed April 9, 1936). All of these chlorinated compounds may be considered for the purpose of this invention as being chlorinated derivatives of diphenyl.

Illustrative of the lubricant use of my improved compositions are mixtures made up in part of a lubricant mineral oil having a viscosity of 100 seconds Saybolt Universal at 100° C. and of approximately 1200 to 1400 seconds at 37.8° C. Such a composition when including 25 per cent tr’butyl phosphate by weight has a viscosity of 26*1 seconds at 37.8° C., a reduction of about 82 percent. When containing 50 per cent tributyl phosphate, the viscosity is reduced at 37.8° C. ' to less than 6 per cent of the normal oil vis' cosity. Such admixtures containing tnoutyl

3!

4¹

In place of chlorinated diphenyl other similar 8,175,877 phosphate exhibit improved extreme pressure lubrication. With the selected lubricant oil the maximum load-carrying capacity was determined as 325 pounds for given conditions in a 5 Timken lubricant tester. With only 5 per cent by weight tributyl phosphate present the loadcarrying capacity was increased to greater than 1,000 pounds. Similar increased load-carrying capacity was observed for mixtures containing jo triethyl phosphate.

As a further illustration of the increase in the lubrication characteristics produced by compositions embodying my invention, the coefficient of friction and unit pressure values obtained at the j ₅ time of seizure of such compositions tested in the Timken tester are given in the following table from which the improved characteristics of my new compositions are evident:

<td> Product</td><td> Coefficient of friction</td><td> Unit pressure at seizure</td>

<td> Lubricant oil________________ Lubricant oil plus 5 percent tributyl phosphate. Lubricant oil plus 5 percent triethyl phosphate.</td><td> ,0.102_____________ Less than .076* ... Less than ,051*....</td><td> 2,355 Ibs./sq. in. Greater than 19,600.* Greater than 20,000.*</td>

‘Limit of test machine. Actual lubricant breakdown and seizure of rubbing surfaces did not occur.