GB2081301A - Composition for mechanical power transmission and operating traction drives - Google Patents

Abstract

A composition for use in mechanical power transmission devices comprises a C19-30 hydrocarbon oil, and three six-membered carbocyclic rings and consists of a mixture of compounds having the following formula: <IMAGE> wherein R<1> is a divalent straight or branched chain radical CyH2y where y is 1 to 3; R<2> is a straight chain radical CzH2z where z is 1 to 3; R<3,> R<4> and R<5> are the C1-4 alkyl groups; l, m, and n are 0 to 3; and x is 0 or 1; the rings A and B are hydrogenated benzene rings and ring C is a hydrogenated benzene ring when x is 1 and a hydrogenated benzene ring or a cyclohexane ring when x is 0, the hydrogenated benzene rings being saturated with hydrogen to the extent of at least 80% but less than 100% of the theoretical. The composition can additionally contain one or more of an antioxidant, a rustproofing agent, a viscosity index improver, and an antifoaming agent.

Description

SPECIFICATION Composition for mechanical power transmission and process for operating traction drives This invention relates to a composition suitable for use in mechanical power transmission units, for example, compositions adapted for use with traction drives, and to a process for operating traction drives.

In the past, gears and hydraulic devices have been used for power transmission or speed control, and drive systems, called traction drives (rolling friction drive devices), which resort to point contact or line contact between rolling solid bodies have developed. These traction drives are particularly useful in industrial machines because they provide high power transmission efficiency without the vibration characteristics of devices using gears and other similar positive forms of engagement.

The fluid which is to act as lubricant between the contact parts of these traction drives, must be suitable from the functional point of view. Specifically, the fluid between the contact parts must be capable of undergoing reversible glass transition, increasing its viscosity, and enhancing the efficiency of power transmission between rolling contact surfaces under high pressure and, on departure from the contact surfaces, it must immediately return to its original fluid state. It must also be capable of avoidin direct contact between metal bodies, preventing metal bodies from seizure, wear and fatigue damage and as with other lubricants it must prevent the occurrence of rust and undesirable elevations in temperature.

Friction of traction drive devices for transmission of mechanical power have been disclosed in a number of reports in prior technical literature. They are dealt with in full detail in US Patents 3,394,603 and 3,411,369; the Journal of Chemical and Engineering Data, Vol. 5, No. 4, p.p. 499-507 (1960), and Hewko et al., in Proceedings of the Symposium on Rolling Contact Phenomena, p.p. 1 57-185 (1962), Elsevier, Amsterdam, Netherlands, for example.

As compositions for use in traction drives, many substances have been suggested, including mineral oils (Japanese Patent Publication 24,635/1964), mixtures of dialkyl aromatic hydrocarbons with diarylalkanes (Japanese Patent Publication 40, 525/1 972), polymethylmethacrylate (Japanese Patent Publication 31,828/1973), adamantanes (Japanese Patent Publications 42,067/1973 and 42,068/1973). polyolefins (Japanese Patents KOKAI 4,766/1971 and 2,229/1972) and alkylnaphthalenes (US Patent 2,549,377), for example. Japanese Patent KOKAI 40,726/1980 has proposed fluids which are obtained by hydrogenating bis-(a-methylbenzyltoluene) and/or bis-(anethylbenzyl)-xylene.

In addition there have been proposals to use naphthenic oils having naphthenic rings. These naphthenic oils include di-cyclohexylethane (US Patent 3,577,361), dicyclohexylpropane (Japanese Patent Publication 36,105/1978), hydrogenated condensation ring compounds (US Patent 3,411,369) naphthenes containing at least one saturated carbon-containing cyclic ring (US Patent 3,440,894), naphthenes containing at least two saturated carbon-containing cyclic rings (US Patent 3,925,21 7), and mixtures of naphthenes and paraffins (US Patents 3,595,796 and 3,595,797) and an oil which is obtained by hydrogenating the product of alkylation of xylene and/or toluene with styrene (Japanese Patent KOKAI 43,108/1980), for example.

US Patents 3,440,894 and 3,925,217 mentioned above embrace a wide range of naphthenic compounds and cite a large number of naphthenes by way of example. Most of them are compounds which possess one or two hydrogenated rings. Among the compounds disclosed therein, those which possess three or more hydrogenated rings are limited to a small number, including tercyclohexyls 1,2,3 tricyclohexylpropane and tricyclohexylmethane, for example. Although they have a high traction factor, they are poor in practice because of high viscosity or high crystal-precipitating temperature. It is noted from the prior technical literature that naphthenic oils containing hydrogenated rings generally have good properties as lubricants, particularly those to be used in traction drives.

An object of this invention, therefore, is to provide improved compositions suitable for use in mechanical power transmission devices which do not suffer the disadvantages of the prior art. Thus it ie an object of the invention to provide such compositions having better traction properties and other properties such as resistance to oxidation and resistance to corrosion and which are easily synthesized from inexpensive raw materials on a commercial scale. Still another object is to provide an improved process for operating traction drives.

According to the present invention there is provided a composition for use in mechanical power transmission units, consisting of a minor amount of an antioxidant in admixture with a hydrocarbon oil which has from 1 9 to 30 carbon atoms and three six-membered carbocyclic rings and consists of a mixture of compounds having the following formula:

wherein R1 is a divalent straight or branched chain radical C,H2y where y is an integer from 1 to 3:R2 is a straight chain radical CzH22 wherein z is an integer from 1 to 3; R3, Rq and d5 are the same or different alkyl groups having from 1 to 4 carbon atoms; I, m, and n each is an integer from 0 to 3; and x is O or 1; and wherein rings A and B are hydrogenated benzene rings and ring C is a hydrogenated benzene ring when X is 1 and a hydrogenated benzene ring or a cyclohexane ring when x is 0 the said hydrogenated benzene rings being saturated with hydrogen to the extent of at least 80% but less than 100% of the theoretical, the hydrocarbon oil being otherwise unsaturated. Preferably, the rings are saturated to at least 95%.

In one form of the invention it is preferred that X in the formula is 1; in another, that it is 0.

Preferred compounds in such cases include hydrogenated 1-(benzylphenyl)-1-phenylethane having from 0 to 2, inclusive, methyl substituents and from 0 to 2, inclusive, ethyl substituents; hydrogenated dibenzylbenzene having from 0 to 2, inclusive, ethyl substituents; hydrogenated benzylbiphenyl having from 0 to 2, inclusive, methyl substituents and from 0 to 2, inclusive, ethyl substituents; and, hydrogenated 1 -biphenyl-1 -phenylethane having from 0 to 2, inclusive, methyl substituents and from 0 to 2, inclusive, ethyl substituents.

Advantageously, the composition contains additionally up to 100 parts, preferably 10 to 60 parts, of an alkylcyclohexane in which the alkyl group contains from 0 to 20 carbon atoms for each 100 parts of the hydrocarbon.

The invention also relates to a process for operating traction drives which have an area of point or line contact between rolling solid bodies in which the area of contact is oiled with the above composition.

Thus, it has been found that a mixture of hydrocarbons having a backbone in which three hydrogenated benzene rings are linearly linked via two chains, CyH2y and CzH2y. or two hydrogenated benzene rings are linearly linked directly by a CvH2v group and a hydrogenated benzene or cyclohexane ring is linked to one of them without any intervening chain, because of its peculiarly molecular structure, is particularly effective in fulfilling the objects of the present invention.

Thus, the principal component of the hydrocarbon oil of this invention for use in mechanical power transmission devices is a naphthenic-type hydrocarbon compound having 19 to 30 carbon atoms, inclusive, and three hydrocarbon benzene rings and is represented by the aforementioned general formula I, wherein y and z in R1 and R2 severally are 1,2, or 3, preferably y is 1 or 2 and z is 1, R3 R4, and R5 severally are alkyl groups having 1 to 4 carbon atoms, inclusive, preferably 1 or 2 carbon atoms, l, and n severally are 0, 1, 2. 3, or desirably, 0. 1, 2. or 3 and preferably, 0, 1 or 2, and X is either 0 or 1.

Where X is 1, therefore, the compound of the general formula I can be expressed by the general formula II. Where X is 0, therefore, this compound can be expressed by the general formula ill.

wherein Ri, R2, R3, R4, R5, I, m and n have the same meanings as defined above and ring C in formula Ill is a hydrogenated benzene or a cyclohexane ring.

Where X is 1, the compounds represented by the general formula I include hydrogenated dibenzylbenzenes, hydrogenated (methylbenzyl)-benzylbenzenes, hydrogenated (dimethylbenzyl)benzylbenzenes, hydrogenated di-(methylbenzyl)-benzenes, hydrogenated (ethylbenzyl)benzylbenzenes, hydrogenated di-(ethyl benzyl)-benzenes, hydrogenated (diethylbenzyl)benzylbenzenes, hydrogenated dibenzyltoluenes, hydrogenated dibenzyl-dimethylbenzenes, hydrogenated dibenzyl-ethylbenzenes, hydrogenated (methylbenzyl)-benzyltoluenes, hydrogenated (dimethylbenzyl)-benzyltoluenes, hydrogenated (ethylbenzyl)-benzyltoluenes, hydrogenated di (methylbenzyl)toluenes, hydrogenated di-(ethylbenzyl)toluenes, hydrogenated di-(methylbenzyl)xylenes, hydrogenated 1.1 -(benzylphenyl)-phenylethanes, hydrogenated 1,1 [(methylbenzyl)-phenyl] phenylethanes, hydrogenated 1,1 -(benzylphenyl)(methylphenyl)-ethanes, hydrogenated 1 ,1 - (benzylmethylphenyl)-phenylethanes, hydrogenated 1,1 (benzylphenyl)(ethylphenyl)ethanes, hydrogenated 1,1 -(benzylethylphenyl)-phenylethanes, hydrogenated phenethyl-benzylbenzenes, hydrogenated phenethyl-benzyltoluenes, hydrogenated diphenethylbenzenes, and hydrogenated diphenethyltoluenes, for example.

Among the compounds represented by the general formula 11 mentioned above, hydrogenated dibenzylbenzenes and hydrogenated (benzylphenyl)-phenylethanes or the derivatives thereof incorporating one or two methyl or ethyl substituents, particularly hydrogenated dibenzyltoluenes, are especially suitable for the objects of the present invention.

Where X is 0, the compounds represented by the general formula I mentioned above include hydrogenated benzyl-biphenyls, hydrogenated benzyi-momomethyl-biphenyls, hydrogenated benzyldimethyl-biphenyls, hydrogenated benzyl-trimethyl-biphenyls, hydrogenated benzylmonoethylbiphenyls, hydrogenated benzyi-diethyl-biphenyls, hydrogenated benzyl-triethyl-biphenyls, hydrogenated biphenylyltolyl-methanes, hydrogenated (methyl-bi-phenylyl) tolylmethanes, hydrogenated (dimethylbiphenylyl) tolyl-methanes, hydrogenated (trimethylbiphenylyl)tolyl-methanes, (ethylbiphenylyl)tolyl-methanes, hydrogenated (diethylbiphenylyl)tolyl-methanes, hydrogenated (biphenylyl) (ethylphenyl)-ethanes, hydrogenated (methylbiphenylyl) (ethylphenyl)-methanes, hydrogenated (dimethyl-biphenylyl) (ethylphenyl)-methanes, hydrogenated (trimethylbiphenylyl) (ethylphenyl)-methanes, hydrogenated (ethylbiphenylyl) (ethylphenyl)-methanes, hydrogenated (diethylbiphenylyl) (ethylphenyl)-methanes, hydrogenated 1 -bi-phenylyl- 1 -phenyl-ethanes, hydrogenated 1 -(methylbiphenylyl)- 1 -phenylethanes, hydrogenated 1 -(dimethylbiphenylyl)-1 -phenylethanes, hydrogenated (1 -ethylbiphenylyl)- 1 -phenylethanes, hydrogenated 1 -(diethylbiphenylyl) 1 - phenylethanes, hydrogenated 1-biphenylyl-1- (methylphenyl)ethanes, hydrogenated 1 (ethylbiphenylyl)- 1 -(methylphenyl)ethanes, hydrogenated 1 -(methylbiphenylyl)-1 (methylphenyl)ethanes, hydrogenated 1 -biphenylyl-1 -(ethylphenyl)ethanes, hydrogenated 1 (methylbiphenylyl)-1 -(ethylphenyl)ethanes, hydrogenated 1 -(dimethylbiphenylyl)-1 (ethylphenyl)ethanes, hydrogenated 1 -(ethylbiphenylyl)-1 -(ethylphenyl)ethanes, hydrogenated phenethylbiphenyls, hydrogenated phenethyl-methylbiphenyls, hydrogenated phenethyldimethylbiphenyls, hydrogenated phenethyl-ethylbiphenyls, hydrogenated phenethyl-diethylbiphenyls, hydrogenated (methylphenethyl) biphenyls, hydrogenated (methylphenethyl)-methylbiphenyls, hydrogenated (methylphenethyl)-ethylbiphenyls, and hydrogenated (ethylphenethyl)biphenyls, for example.

Among the compounds which are represented by the general formula Ill mentioned above, hydrogenated benzylbiphenyls or derivatives thereof incorporating one or two methyl or ethyl substituents are particularly suitable for the objects of this invention.

The compound of the general formula II such as, for example, hydrogenated dibenzylbenzenes may be obtained by hydrogenating dibenzylbenzene resulting from the reaction of benzyl halides and benzene in the presence of a Friedel-Crafts catalyst. Among other benzyl halides, benzyl chloride is preferred. Advantageously, the benzyl halides are used in an amount of not more than 1 mol. preferably in the range of from 0.1 to 0.5 mol per mol of benzene. Among other compounds useable as Friedel Crafts catalysts, sulphuric acid, boron trifluoride and aluminum chloride prove particularly suitable, with aluminum chloride as the most preferable. The amount of aluminum chloride to be used is desired to fall in the range of from 0.0001 to 0.1 mol, per mol of benzyl chloride.Although the reaction temperature can be selected in the range of from 200 to 1 500C, it is preferably chosen from the range of from 400 to 800 C. Although the reaction pressure has only to exceed the minimum level required for maintaining the contents of the reactor in a liquid phase, a pressure in the range of from 0 to 10 kg/cm2G proves advantageous for the sake of the reaction. This reaction affords as its product dibenzylbenzene which is a mixture of ortho, meta and para isomers. These isomers may be subjected to hydrogenation in their mixed form or in their separated form.Preparatory to the hydrogenation, the Friedel-Crafts catalyst may be removed from the reaction mixture by washing with water and the unreacted portions of reactants and possibly by-products of reaction expelled from the reaction mixture by distillation to isolate dibenzylbenzene. Then, the isolated reaction product can be treated in the presence of a hydrogenation catalyst to undergo hydrogenation.

Suitable hydrogenation catalysts are platinum, rhodium, ruthenium or nickel. The nickel catalyst may be used in an amount within the range of from 0.1 to 20 weight percent. The hydrogen pressure is suitable in the range of from 10 to 200 kg/cm2G. The hydrogen for the hydrogenation may be used in an amount of 9 mols or more per mol of dibenzylbenzene, preferably 1.1 times the mol ratio mentioned above. The reaction temperature of hydrogenation may be in the range of from 1000 to 2000 C, preferably from 1400 to 1700 C. When the hydrogenation has proceeded to a predetermined ratio of hydrogenation, the reaction is stopped and followed by insolation of hydrogenated dibenzylbenzene.

This isolation of the reaction product may be obtained by simply removing the used catalyst. It may be effected by separation through filtration or optionally by any known method for treatment of lubricants such as, for example, treatment with activated clay. When necessary, distillation may be adopted for this purpose. Little advantage, however, is usually derived from the distillation unless the reaction has produced low boiling compounds as by-products because, by distillation, separation of fully hydrogenated dibenzylbenzene and partially hydrogenated dibenzylbenzene or separation of isomers is obtained only with great difficulty.

Production of an alkyl-substituted hydrogenated dibenzylbenzene may be accomplished by substituting benzene or benzyl halides or both respectively with an alkyl-substituted benzene or alkylsubstituted benzyl halides or both as the raw materials and using these raw materials in suitable combinations. Suitable alkyl-substituted benzenes for this purpose are toluene, ethylbenzene, propylbenzene, xylene, cumene, diethylbenzene, and methylethylbenzene. Suitable alkyl-substituted benzyl halides for the purpose include derivatives of benzyl halides incorporating monomethyl or monoethyl substituents. When such alkyl-substituted raw materials are adopted, the reaction can be carried out under similar conditions as described above and the hydrogenation can be performed similarly.

When a compound represented by the general formula:

(wherein, R3 and I have the same meanings as defined above and X stands for a halogen) is used in place of the aforementioned benzyl halides or an alkyl-substituted derivative thereof, there can be obtained hydrogenated diphenethyl benzene or an alkyl-substituted derivative thereof.

In a preferred embodiment of the method for the manufacture of the compounds of this invention, a hydrogenated (benzylphenyl)-phenyl alkane-type compound is obtained by reacting a diphenyl alkane with benzyl halides in the presence of a Friedel-Crafts catalyst to afford a (benzylphenyl)-phenyl alkane and subsequently hydrogenating this reaction product. In this case, when a 1 ,1 -diphenyl alkane is used as the diphenyl alkane, there is produced a hydrogenated 1 -(benzylphenyl)-1 -phenyl alkane-type compound. Use of an alkyl-substituted 1,1 -diphenyl alkane or an alkyl-substituted benzyl halide or both results in production of a hydrogenated alkyl-substituted 1 -(benzylphenyl)-1 -phenyl alkane-type compound.When a 1 ,3diphenyl alkane is used as the diphenyl alkane, there is obtained a hydrogenated 1-(benzylphenyl)-3-phenyl alkane-type compound and when a 1 ,2-diphenyl alkane is used, there is obtained a 1-benzylphenyl-2-phenyl alkane or a 2-benzylphenyl-1-phenyl alkane. In all these cases, the kind of the Friedel-Crafts catalyst, the conditions of the Friedel-Crafts reaction of alkyl halides, the conditions of the hydrogenation, etc., are similar to those described above. The aforementioned 1,1 diphenyl alkanes can be obtained by the reaction of ethylbenzene or styrene and benzene in the presence of the Friedel-Crafts catalyst.

The compounds of the general formula Ill such as, for example, hydrogenated benzylbiphenyl are obtained, similarly to those of the general formula II, by hydrogenating benzylbiphenyls resulting from the reaction of benzyl halides with biphenyls in the presence of the Friedel-Crafts catalyst. In this case, the amount of aluminum chloride to be used is desired to fall in the range of from 0.0001 to 0.05 mol per mol of benzyl chloride. Although the reaction temperature can be selected in the range from a level exceeding the melting point of the biphenyls involved to 1800 C, it is preferably selected in the range of from 700 to 1000C. Although the reaction pressure has only to exceed the minimum level required for maintaining the contents of the reactor in a liquid phase, it is preferred to fall in the range of from 0 to 50 kg/cm2G.This reaction affords as its product benzylbiphenyl, which is a mixture of ortho, meta and para isomers. These isomers may be subjected to hydrogenation either in their mixed form or in their separated form. Preparatory to the hydrogenation, the reaction mixture may be washed with water and distilled to effect removal of the unreacted reactants and the used Friedel-Crafts catalyst and isolation ol benzylbiphenyl. The isolated benzylbiphenyl is then hydrogenated by introduction of hydrogen in the presence of a hydrogenation catalyst. In this case, the conditions for the hydrogenation are the same as those adopted in the hydrogenation for the production of the compounds of general formula II.

Production of a hydrogenated alkyl-substituted benzylbiphenyl is accomplished by substituting a bipheny or a benzyl halide or both respectively with an alkyl-substituted biphenyl or an alkyl-substituted benzyl halide or both as the raw materials by using these raw materials in suitable combinations.

Suitable alkyl-substituted biphenyls are monomethylbiphenyl, monoethylbiphenyl, monopropylbiphenyl, dimethylbiphenyl, diethylbiphenyl, and methylethylbiphenyl. Suitable alkylsubstituted benzyl halides are derivatives of benzyl halides incorporating monomethyl, monoethyl and other similar substituents. When these alkyl-substituted derivatives are used, the reaction can be carried out under similar conditions, as described above. The hydrogenation can also be performed similarly.

When a compound represented by the general formula:

(wherein, R3 and I have the same meanings as defined above and X stands for a halogen) is used in place of the aforementioned benzyl halides or an alkyl-substituted derivative thereof, there can be obtained hydrogenated phenethylbiphenyl or an alkyl-substituted derivative thereof.

Another preferred embodiment of the method for the manufacture of the compound of this invention comprises the steps of reacting cyclohexylbenzene or a biphenyl with styrene in the presence of the Friedel-Craft catalyst and hydrogenating the resultant reaction product. Suitable Friedel-Crafts catalysts for this reaction are boron trifluoride, aluminum chloride and sulphuric acid. When sulphuric acid is adopted as the catalyst, the amount of this catalyst is desired to fall in the range of from 5 to 50 weight percent based on the amount of the biphenyl involved. The cyclohexylbenzene or biphenyl and styrene are preferably used in equal or nearly equal molar proportions in order to preclude the otherwise possible polymerization of styrene in the reaction. The reaction temperature is desired to be low, falling on the order of from 0 to 300C.When the reaction is terminated, the reaction mixture is washed with water to effect removal of the used catalyst and then distilled to effect isolation of 1 -(biphenylyl)-1 phenylethane or 1 -(cyclohexylphenyl)-1 -phenylethane as the reaction product.

The compound, when subjected to hydrogenation by the same method as described above, produces hydrogenated 1 -(biphenylyl)-1 -phenylethane.

When a similar procedure is repeated by using an alkyl-substituted cyclohexylbenzene or an alkylsubstituted biphenyl or an alkyl-substituted styrene respectively in the place of cyclohexylbenzene or biphenyl or styrene, there is obtained an alkyl-substituted hydrogenated 1 ,-(biphenylyl)-1 -phenylethane.

Alkyl-substituted cyclohexyl benzenes suitably usable for the purpose are cyclohexylmethylbenzenes, cyclohexylethylbenzenes, cyclohexyl-propylbenzenes, cyclohexyl-dimethylbenzenes, cyclohexyldiethylbenzenes, (methylcyclohexyl)benzenes, (dimethylcyclohexyl)benzenes, (ethylcyclohexyl)benzenes, (diethyl-cyclohexyl)benzenes, and mixtures thereof. Suitable alkyl substituted biphenyls may be the same as those mentioned above. Suitable alkyl-substituted styrenes include those compounds represented by the general formula:

(wherein R3 and I have the same meanings).

A typical example of these compounds is vinyl toluene. Also, a-methylstyrene can be used similarly with advantage. When these alkyl-substituted derivatives are utilized, the reaction can be carried out under similar conditions as described above.

The composition of the present invention for use in mechanical power transmission devices can be used in its independent form. When it is mixed with an alkyl (C9-C20) cyclohexane added in an amount of at most 100 parts by weight, preferably in the range of from 10 to 60 parts by weight, based on 100 parts by weight of the compound of the invention, a composition may be obtained which possesses a varying degree of viscosity useful in mechanical power transmission devices without substantially degrading the properties which the oil is expected to possess to fulfill its functions. Alkyl cyclohexanes suitable for this purpose may be obtained by hydrogenating alkylbenzenes derived by the reaction of trimer through pentamer of propylene with benzene.

The reaction compositions of the invention can contain, in addition to essential ingredients, a minor amount of an antioxidant and a hydrocarbon oil as described above, can also contain other additives or by-products as long as they do not detract from its suitability for use in mechanical power transmission. Thus, in addition to antioxidants, the compositions can contain such additives as rustproofing agents, antifoam agents, and the like. They also can include a small amount of the by products which occur in the course of the production of the hydrocarbon oils represented by the general formula I. However, a large quantity of aromatic hydrocarbons or compounds possessing a double bond are preferably avoided.In the production of a compound represented by the general formula I by the hydrogenation of a corresponding aromatic hydrocarbon, therefore, the hydrogeneation is desired to be performed until the hydrogenation reaches at least 80% completion, desirably 95% and preferably more than 95%. Substantially complete hydrogenation, e.g., removal to less than 1% is practically impossible.

Such complete removal of unsaturation, however, is not called for, because the objects of this invention are not obstructed by the presence of unsaturated compounds in small amounts. Thus, the hydrocarbon 'oils which constitute the essential components of the compositions of the invention may be mixtures of components in different stages of hydrogenation or isomers or both and can be used as such or in combination with suitable additives, as mentioned above.

The reference to hydrogenated compounds, accordingly, is to be understood to include such compounds which have been hydrogenated to at least 80% and preferably to at least 95%, of the theoretical.

The traction coefficient of a given oil is generally measured by use of a traction drive device. In the present invention, the measurement has been made by use of a Soda's four roller machine friction tester. (T. Kimura and M. Muraki "TRIBOLOGY", 1979 (12), p. 255). In this tester, traction (rolling friction) occurs at the three areas of contact formed between an inner centrally located roller and three outer rollers tangentially located around the inner central roller. These rollers are arranged so that equal perpendicular loads are caused to bear on the three areas of contact. The surface pressure of contact as expressed by the average Hertzian pressure falls in the range of from 0.575 to 1.157 GPa. The other conditions for the determination of traction by this tester are as shown in Table 1 below.

Table 1. Conditions for determination of traction Speed of rotation 1.05 to 4.1 9 m/sec Speed of sliding 0 to 0.22 m/sec Test rollers Material bearing steel, SUJ-2 Hardness (Hv) 760 to 800 Dimensions 40 mm x 9 mm (outer rollers) (diam x width) 40 mm x 5 mm (central roller) Method of lubrication-Dripping about 10 ml/min in flow volume Feed temperature 280 C.

The procedure of the test comprised first setting the central and outer rollers rotating at a fixed speed, applying a load to bear upon these rollers and thereafter accelerating the rotational speeds of the outer rollers while keeping that of the central roller constant thereby inducing slide/roll ratios to permit continuous measurement of the change in the friction torque or the traction coefficient. The friction torque was determined by directly measuring the torsional moment of the centerlessly-supported shaft of the central roller with a resistance-wire strain meter.

The traction coefficient determined under the conditions mentioned above tends first to rise in a straight line with the increasing slide/roll ratios, then reach a peak and start falling. Of the curve thus drawn, the important zone from the standpoint of the practical use of oil falls in the first portion of straight line in which the magnitude of heat generated by the shearing of the oil film is not large. Thus, the traction coefficient specifically within this zone will be considered exclusively below.

Under the test conditions of 1.157 GPa of average Hertzian pressure and 4.19 m/s of rotational speed, for example, the following traction coefficients were obtained.

viscosityrcst) traction at 40 OC coefficient Naphthenic mineral oil 8.0 0.050 Hydrogenated Polyisobutylene 10.0 0.060 Dicyclohexane 2.9 0.065 Ethyl Dicyclohexane 4.0 0.060 Methylcyclohexyl Cyclohexylmethane 4.2 0.065 Viscosity(cst) traction at 40 0C co-efficient Dicyclohexylethane 4.0 0.070 sec-Dodecylcyclohexane 5.4 0.050 Tercyclohexyls(o-and m- mixture)* 30 0.090 Hydrogenated (r-Methylstyrene 22 0.090 linear dimer *crystals were precipitated at room temperature.

In contrast, the traction coefficient of the compound obtained by the present invention reached as high as 0.095, a value definitely higher than the values found for the aforementioned hydrocarbons. It has been found consequently that the product of this invention may even be superior to hydrogenated a-methylstyrene linear dimer, which is now thought of as perhaps the best synthetic traction fluid.

In addition to a good traction coefficient and oxidation stability, the composition for mechanical power transmission preferably has a pour point or freezing point of at most -1 00C preferably a viscosity of 7-1 50 cst at 4000 under atmospheric pressure.

Viscosityrcts pour point at 40 OC or freezing point lOCI o-tercyclohexyl 45 m-tercyclohexyl 63 p-tercyclohexyl 162 m-, p-tercyclohexyls mixture 30 crystals precipitated at room temperature Tricyclohexylmethane 59 1,1,3-tricyclohexyl propane about 2500 As being clear from above, the above-mentioned compounds are not appropriate as a base oil for the composition for mechanical power transmission.

Further, in order to ensure stable operation of a traction device for a long time, the composition for mechanical power transmission should have good sealing properties. The following table shows the sealing properties of a composition for mechanical power transmission using base oils having appropriate viscosity and relatively good traction properties. The tests were carried out at 1 200C for 70 hours about nitrile rubber (Buna N) and acrylic rubber based on method JIS K6301.

An oil Hydrogenateda-Methyl- of Example 1 styrene dimer oil (below) for traction drives Nitrile Nitrile rubber Acrylic rubber Acrylic Property (Buna N) rubber (Buna N) rubber Increase of weight (%) 3.45 1.48 7.30 3.86 Increase of volume ( /0) 6.58 3.42 13.6 7.67 Tensile strength (Kgf/ cm2) 195 81 168 85 Elongation (%) 260 140 150 110 Variation of hardness (%) 6 0 6 -1 Aniline point 8500 700C Similar results to those in the above table for Example 1 may be obtained using other oils in accordance The oil in accordance with the present invention can be used by itself, but the addition of various additives may be preferable.

In addition to the traction characteristics described above, the oil for use in traction drives preferably possesses properties usually expected of ordinary lubricants such as, for example, oxidation stability, resistance to wear, rust inhibiting properties, rubber swelling property, and an ability to prevent foaming. Thus, depending on the nature of use, suitable additives, for example 2,6-di-tertiary-butyl paracresol and other similar alkyl phenols, zinc dialkyldithiophosphate and other similar sulphurphosphorous compounds can be incorporated as antioxidants; amines, esters and metal salts as rustproofing agents; polymethacrylates as viscosity index improvers; and silicone type polymers as antifoaming agents, can be included.

The invention will now be described more specifically with reference to the following examples to which the invention is not limited. Wherever "parts" or "percentages" are mentioned in the following examples, and elsewhere, they are by weight unless otherwise specified.

In the following examples, a composition suitable for use in traction drives was prepared by adding to hydrogenated dibenzyltoluene, or a similar oil 2,6-di-tertiary-butyl-parac'esol and zinc dialkyldithiophosphate as antioxidants, each in an amount of 0.5 weight percent. The traction coefficient of this oil was tested under the aforementioned conditions and then subjected to an oxidation test by the procedure described in Paragraph 3.2 (Testing Method for Oxidation Stability of Interned Combustion Engine Oil of Japanese Industrial Standard (JIS) K-251 4-1980 (Testing Method for Oxidation Stability of Lubricating Oils).

EXAMPLE 1 To 3 parts of toluene was added 0.002 to 0.01 part of aluminum chloride. The mixture was heated to 700C and then allowed to react with 1 part of benzyl chloride for two hours. The reaction mixture was washed with water to remove the used catalyst and then distilled to remove the unreacted portion of reactants. The dibenzyltoluene (mixture of isomers) thus obtained was supplied to an autoclave and, in the presence of a nickel catalyst, subjected to hydrogenation for four hours under the conditions of 40 kg/cm2G of initial hydrogen pressure and 2000C of temperature, to afford hydrogenated dibenzyltoluene (mixture of isomers). The general properties of this hydrogenated dibenzyltoluene are shown in Table 2.

The results of the oxidation test are shown in Table 3. For the purpose of comparison, a commercially available hydrogenated -methylstyrene linear dimer-type oil for traction drives and an oil prepared from a naphthenic mineral oil were subjected to the same tests.

The oxidation test was carried out under the following conditions.

Amount of test specimen 300 ml Temperature 1 65.50C Time 72 hours Oxidation catalyst Copper and iron EXAMPLE 2 To 4 mols of 1,1 diphenylethane was added 0.001 to 0.005 mol of aluminum chloride. The mixture was heated to 600C and allowed to react with 1 mol of benzyl chloride for 20 minutes. Then, the reaction mixture was washed with water to remove the used catalyst and subsequently distilled to remove the unreacted portions of the reactants. The isolated 1-(benzylphenyl)-1-phenylethane (mixture of isomers) was supplied to an autoclave and, in the presence of a nickel catalyst, subjected to hydrogenation under the conditions of 100 kg/cm2G of initial hydrogen pressure, 140 to 1 700C of temperature for five hours, to afford hydrogenated 1-(benzylphenyl)-1-phenylethane (mixture of isomers). The general properties of this reaction product are shown in Table 2.

This product, was tested to determine its traction coefficient and subjected to the oxidation test, specified in Paragraph 3.2 of JIS K-2514-1 980. The results are shown in Table 3.

EXAMPLE 3 A hydrogenated monoethyl-substituted 1 -(benzylphenyl)-1 -phenylethane, a mixture of compounds of the formulae

and

was obtained by following the procedure of Example 2, except that 4 mols of monoethyl-substituted 1,1 -diphenylethane was used in the place of 1,1 < iiphenylethane. The general properties of this reaction product are shown in Table 2. This product was tested to determine its traction coefficient and subjected to the oxidation test specified in Paragraph 3.2 of JIS K-251 4-1980. The results are shown in Table 3.

TABLE 2 General Properties Hydrogenated Hydrogenated monoethyl-substituted Hydrogenated 1-(benzylphenyl)-1- 1-(benzylphenyl)-1 Property dibenzyl toluene phenylethane phenylethane Specific gravity (15/4 C) 0.90 0.90 0.89 Appearance colourless, clear colourless, clear colourless, clear Viscosity (cat) (40 C) 66 106.5 618.5 Viscosity (cat) (100 C) 5.8 7.6 14.5 Pour point ( C) -20 -20 max. -20 max.

Flash point ( C) 152 - Hydrogenation ratio (%) 99 98 98 TABLE 3 Traction Coeficient and Result of Oxidation Test Hydrogenated &alpha;-methyl-styrene linear dimer oil for Naphthenic Item of test Example 1 Example 2 Example 3 traction drives oil Traction coeficient 0.094 0.09 0.09 0.09 0.06 Oxidation Test : Viscosity ratio * 1.08 1.10 1.06 1.20 8.24 Increase of total acid number 0.06 0.10 0.08 0.40 3.7 (mg KOH/g) Heptane insolubles after 0.12 0.15 0.18 0.28 5.72 oxidation test (weigth %) * Viscosity after oxidation test/initial viscosity.

EXAMPLE 4 To 5 parts of biphenyl was added 0.001 to 0.005 part of aluminum chloride. The mixture was heated to 700C and then allowed to react with 1 part of benzyl chloride for 20 minutes. The reaction mixture was washed with water to remove the used catalyst and then distilled to remove the unreacted fractions of the reactants. The benzylbiphenyl (a mixture of isomers) produced was supplied to an autoclave having an inner volume of 1 litre and, in the presence of a nickel catalyst, subjected to hydrogenation under the conditions of 100 kg/cm2G of initial hydrogen pressure and 1400 to 1 700C temperature for two hours, to afford hydrogenated benzylbiphenyl (a mixture of isomers). The general properties of this hydrogenated benzylbiphenyl are as shown in Table 4.

This product, compounded as described above with 0.5 weight percent each of 2,6-di-tertiarybutyl-para-cresol and zinc dialkyl-dithiophosphate as antioxidants, was tested to determine its traction coefficient and subjected to the oxidation test specified in Paragraph 3.2 of JIS K-251 4-1980. The results are shown in Table 5.

EXAMPLE 5 A hydrogenated benzyl-monoethylbiphenyl, a mixture of compounds of the formulae and

was obtained by following the procedure of Example 4, except 5 parts of monoethylbiphenyl and 0.03 part of aluminum chloride were used. The general properties of this reaction product are shown in Table 4. This product, was tested to determine its traction coefficient and subjected to the oxidation test specified in Paragraph 3.2 of JIS K-2514-1 980. The results are shown in Table 5.

EXAMPLE 6 One litre of cyclohexylbenzene and 200 ml of concentrated sulphuric acid were introduced into a reactor and the resultant mixture was kept at 1 5 C. Then, 800 ml of a 1:1 mixture of cyclohexylbenzene and styrene was added dropwise to the resultant mixture over a period of two hours, while the temperature of the mixture was kept in the range of from 1 50 to 200C. At the end of the dropwise addition of the mixture, 200 ml of concentrated sulphuric acid was added and the reaction continued for a further 30 minutes. Then, the reaction mixture was washed repeatedly with water to remove residual sulphuric acid and then distilled to isolate 1 -(cyclohexylphenyl)-1 -phenylethane (a mixture of structural isomers).Then, 1 litre of 1 -(cyclohexylphenyl)-1 -phenylethane was introduced to an autoclave and, in the presence of a nickel catalyst, subjected to hydrogenation under the conditions of 100 kg/cm2G of initial hydrogen pressure and 1 400 to 1 700 temperature for two hours, to afford hydrogenated 1 (biphenylyl)-1 -phenylethane (a mixture of structural isomers). The general properties of this hydrogenation product are shown in Table 4.

A compos:tion suitable for traction drives prepared by incorporating into this hydrogenation product the same additives as given above, was tested to determine its traction coefficient and subjected to the oxidation test specified in Paragraph 3.2 of JIS K-25 14-1 980. The results are shown in Table 5.

EXAMPLE 7 Hydrogenated 1 -(ethylbiphenylyl)-1 -phenylethane, a mixture of compounds of the formulae and

was obtained by following the procedure of Example 6, except 1 litre of monoethylbiphenyl was used in the place of cyclohexylbenzene and 800 ml of 1:1 mixture of monoethylbiphenyl and styrene was used in place of the mixture of cyclohexylbenzene and styrene. The general properties of this product are shown in Table 4.This product was tested to determine its traction coefficient and then subjected to the oxidation test specified in Paragraph 3.2 of JIS K-25 1 41 980. The results are shown in Table 5. TABLE 4 General Properties Hydrogenated Hydrogenated monoethyl-substituted Hydrogenated Hydrogenated benzyl-monoethyl 1-(biphenylyl)-1- 1-(ethylbiphenylyl)-1 Property benzylbiphenyl phenylethane phenylethane phenylethane Specific gravity (15/4 C) 0.95 0.93 0.93 0.93 Appearance Colourless, clear Colourless, clear Colourless, clear Colourless, clear Viscosity (cst) (40 C) 41.2 68.9 80.2 201 Viscosity (cst) (100 C) 4.9 6.5 7.0 10.5 Pour point ( C) -15 -20 max. -20 max. -17.5 max.

Hydrogenation ratio (%) 98 98 98 98 TABLE 5 Traction Coeficient and Result of Oxidation Test Hydrogenated &alpha;-methyl-styrene linear dimer oil for Naphthenic Item of test Example 4 Example 5 Example 6 Example 6 traction drives oil Traction coeficient 0.095 0.09 0.09 0.09 0.09 0.05 Oxidation Test :: Viscosity ratio * 1.06 1.10 1.08 1.08 1.20 8.24 Increase of total acid number 0.06 0.08 0.08 0.08 0.40 3.7 (mg KOH/g) Heptane insolubles after 0.15 0.20 0.18 0.15 0.28 5.72 oxidation test (weigth %) EXAMPLE 8 Dodecylbenzene obtained by the reaction of propylene tetramer with benzene was introduced into an autoclave and, in the presence of a nickel catalyst, subjected to hydrogenation under the conditions of 50 kg/cm2G of initial hydrogen pressure and 1 500C of temperature for 4 hours, to afford alkylcyclohexane. An oil for traction drives was prepared by mixing 50 parts by volume of this alkylcyclohexane with 50 parts by volume of the hydrogenated dibenzyltoluene obtained in Example 1 and incorporating into this mixture 0.5 weight percent, based on the amount of the mixture, each of 2,6-ditertiary butyl-paracresol and zinc dialkyldithiophosphate. This fluid was tested to determine its traction coefficient and subjected to the oxidation test specified in Paragraph 3.2 of JIS K 251 1 980. The results of the tests are shown together with the general properties in Table 6.

EXAMPLE 9.

By following the procedure of Example 8, an oil for traction drives was prepared from 50 parts by volume of alkylcyclohexane obtained in Example 8 and 50 parts by volume of hydrogenated benzylbiphenyl obtained in Example 4. Then, the fluid was subjected to the same tests as described in Example 8. The results are shown in Table 6.

TABLE 6 General Properties Property Example 8 Example 9 Specific gravity (15/4'C) 0.88 0.87 Appearance Colourless, clear Colourless, clear Viscosity (cst) (40eC) 20.2 17.5 Viscosity (cst) (1000C) 3.4 3.1 Pour point ('C) -37.5 -35 Flash point ("C) 150 150 Hydrogenation ratio (%) 98 98 Traction Coefficient and Result of Oxidation Test Item of Test Example 8 Example 9 Traction coefficient 0.086 0.088 Oxidation Test: : Viscosity ratio 1.08 1.07 Increase of total acid number 0.07 0.05 (mg KOH /g) Heptane insolubles after oxidation 0.15 0.13 test (weight %) As shown by the Examples, the addition of dodecyclcyclohexane gave compositions having substantially lower viscosities and substantially lower pour points without substantial loss in traction coefficient or stability to oxidation.

Claims (13)

CLAIMS:

1. A composition for use in mechanical power transmission units, consisting of a minor amount of an antioxidant in admixture with a hydrocarbon oil which has from 19 to 30 carbon atoms and three six membered carbocyclic rings and consists of a mixture of compounds having the following formula

wherein Rt is a divalent straight or branched chain radical CyH2y where y is an integer from 1 to 3; R2 is a straight chain radical CzH 2z wherein z is an integer from 1 to 3; R3, R4, and Rs are the same or different alkyl groups having from 1 to 4 carbon atoms;I, m, and n each is an integer from 0 to 3; and x is O or 1; and wherein rings A and B are hydrogenated benzene rings and ring C is a hydrogenated benzene ring when x is 1 and a hydrogenated benzene ring or a cyclohexane ring when x is 0 the said hydrogenated benzene rings being saturated with hydrogen to the extent of at least 80% but less than 100% of the theoretical, the hydrocarbon oil being otherwise unsaturated.

2. A composition as claimed in Claim 1, in which the benzene rings are saturated to at least 95%.

3. A composition as claimed in Claim 1 or Claim 2 in which the hydrocarbon oil is stabilized by an antioxidant.

4. A composition as claimed in any preceding claim in which the hydrocarbon comprises hydrogenated (benzylphenyl)-phenylethane having from zero to two, inclusive, methyl substituents and from zero to two, inclusive, ethyl substituents.

5. A composition as claimed in Claim 4 in which the hydrocarbon comprises hydrogenated 1 (benzylphenyí)-1 -phenylethane.

6. A composition as claimed in any of Claims 1 to 3 in which the hydrocarbon comprises hydrogenated dibenzylbenzene having from zero to two, inclusive, methyl substituents and from zero to two, inclusive, ethyl substituents.

7. A composition as claimed in any of Claims 1 to 3 in which the hydrocarbon comprises hydrogenated benzylbiphenyl having from zero to two, inclusive, methyl substituents and from zero to two, inclusive, ethyl substituents.

8. A composition as claimed in any of Claims 1 to 3 in which the hydrocarbon comprises hydrogenated biphenyl-phenylethane having from zero to two, inclusive, methyl substituents and from zero to two, inclusive, ethyl substituents.

9. A composition as claimed in Claim 8 in which the hydrocarbon comprises hydrogenated 1 biphenyl-l-phenylethane.

10. A composition as claimed in any preceding claim which contains additionally up to 100 parts of an alkylcyclohexane in which the alkyl group contains from 9 to 20 carbon atoms for each 100 parts of the hydrocarbons.

11. A composition as claimed in Claim 10, which contains from 10 to 60 parts of the alkylcyclohexane.

12. A composition for use in mechanical power transmission units substantially as herein specifically described in any one of the accompanying Examples.

13. A process for operating traction drives which have an area of point or line contact between rolling solid bodies which comprises oiling the area of contact with a hydrocarbon oil as claimed in any preceding claim.