DESC:FIELD OF THE INVENTION
The present invention relates to the development of high performance energy efficient composition of industrial gear oil, providing energy savings with excellent thermal & oxidation stability and tribological properties. More particularly, the present invention discloses an energy efficient industrial gear oil composition comprising: (a) a sulphur, phosphorus and nitrogen (S-P-N) based antiwear and extreme pressure additive system, (b) an oxidation inhibitor, (c) a metal passivator cum corrosion inhibitor, (d) a friction modifier, (e) a viscosity modifier, and (f) a mixture of severely refined base stocks, or hydrotreated / hydro-processed / iso-dewaxed base stocks and alkylated naphthalene, or mixture of synthetic bases and ester or mixture of synthetic bases and alkylated naphthalene or alkylated naphthalene bases or mixtures thereof. The present gear oil composition meets industrial gear oil specifications and suitable for use in enclosed gear systems & other industrial machineries.

BACKGROUND OF THE INVENTION
One of the important tasks of the enclosed gear systems, which is encased in a housing that transmits mechanical energy from prime mover to an output device, also known as gear box. Energy losses occur in gear systems used in the industries. In order to improve the working efficiency of the industrial machines, especially gear systems are required to be able to operate in a stable manner even in harsh conditions such as high speed and high load conditions. With an increase in the required performance of gears, demands for high performance gear oils are also increasing.

There are industrial gear oils available in market with energy saving claims of industrial machineries. There is still room for improving performances such as energy efficiency, improved thermal / oxidation stability & tribological performance.

Energy conservation is the concept used for formulating superior products. As some energy loss in gear transmission is being observed for the moving parts against friction, the use of superior lubricant with comparatively lower coefficient of friction may help in energy conservation. Based on this concept, the present work was undertaken in the authors’ laboratory.

CN 103074144 A relates to the industrial gear oil which comprises thiodipropionic acid diester, p-phenylenediamine, dibenzyl disulfide, chlorinated paraffin, dimethicone, benzotriazole, and synthetic base oils wt. parts. The industrial gear oil has excellent antiwear and load resistance, and good rust-proof and anti-corrosion performance, and is suitable for high load industrial equipment.

CN 102888262 A relates to an industrial gear oil composition which comprises low-basic value detergent 0.1-2.0, sulfur-contg. extreme pressure antiwear agent (sulfurized isobutylene, sulfurized whale oil, dibenzyl disulfide and/or alkyl polysulfides) 0.1-3.0, antioxidant (amine-, phenol-, thiocarbamate-, or ZDDP-type antioxidant) 0.1-2, metal deactivator (triazole derivatives, thiazole derivatives, thiadiazole derivs. and/or anthraquinone derivatives) 0.01-0.5, antirusting agent (sulfonate, imidazoles, imidazoline alkenyl succinate, alkenyl succinic acid and/or alkenyl succinic acid ester) 0.01-0.5 wt.%, and the balance as lubricating.

WO 2012152060 A1 relates to an industrial gear lubricating oil with micro-pitting resistance comprises: (1) one or more deeply refined hydrocarbon oil or synthetic oil, (2) one or more anti-micro-pitting additive, (3) one or more antiwear additive, (4) one or more metallic passivator, and (5) one or more antioxidant. The lubricating oil composition has excellent high and low temperature performances to meet the viscosity grade requirements of industrial (68, 100, 150, 220, 320, 460 and 680) gear oils, has excellent micro-pitting resistance performance, anti-wear performance and anti-oxidation performance.

CN 102766504 A relates to anti-micro-pitting industrial gear lubricating oil composition contains (A) at least one deep refining mineral oil, or synthetic oil, or random composition of above component 88.00-98.79 wt.%; (B) at least one anti-micro-pitting additive that is dialkyl dithiophosphate, or alkyl phosphate amine salt, or m-diphosphonate, or mixture thereof 0.2-5.0 wt.%; (C) at least one anti-wear additive that is trialkyl phosphate, or triaryl phosphate, or trialkyl thiophosphate, or triaryl thiophosphate, or mixture thereof 0.5-3.0 wt.%; (D) at least one metal passivation additive.

WO 2011070141 A2 relates to a lubricating oil composition comprising a succinic acid derivative and an epoxy compound as additives, and a base oil selected from a mineral oil, a synthetic oil, and mixtures thereof, wherein the base oil has a sulfur content of not more than 0.3% by mass. The lubricating oil composition of the present invention has good rust-preventing properties, low sludge and also excellent energy saving characteristics through having a low friction coefficient, and can be used as an industrial lubricating oil, in particular for machine oils, hydraulic oils, turbine oils, compressor oils, gear oils and bearing oils.

WO 2011070140 A2 relates to a lubricating oil composition characterized in that it comprises a succinic acid derivative and an amide compound as additives, and a base oil selected from a mineral oil, and a synthetic oil or their mixt. The succinic acid derivative has the general formula of X1O2CCH2CH(X3)CO2X2 (X1, X2 = H, alkyl, alkenyl or C3-6 hydroxyalkyl; X3 = C1-30 alkyl, alkenyl, alkyl contg. ether bonds, hydroxyalkyl ). The lubricating oil composition of the present invention has good rust-preventing properties, a reduced friction coefficient and good energy-saving characteristics.

CN 102031185 A relates to a micropitting-resistant industrial gear oil contains (by wt.%): pour-point depressant (hydrogenated poly-a-olefin) 0.2-3.0, extreme-pressure antiwear agent (mixt. of S-P-N compd. and borate) 0.5-3.0, antioxidant (octylbutyldiphenylamine, 2,6-di-tert-butyl-4-methylphenol, and/or Irganox phenol-type antioxidant) 0.5-3.0, polyester (polyol fatty acid ester) 5.0-10.0, and mineral base oil. The gear oil is prepd. by mixing the base oil with ester and pour-point depressant, heating to 60-70°C, mixing for 0.5-1 h, adding the remaining ingredients, and mixing at 50-60°C for 2-4 h.

CN 101298574 A relates to an additive composition comprises (by wt.%): at least one S-contg. ultra-pressure antiwear additive 82-96, at least one P-contg. multifunctional antiwear additive 1-10, and at least one anticorrosive additive 1-10. The S-contg. ultra-pressure antiwear additive is selected from sulfurized isobutylene, alkyl polysulfide, and their mixtures. The P-contg. multifunctional antiwear additive is ammonium salt of sulfurized phosphite. The anticorrosive additive is selected from benzotriazole and its derivatives. The composition has low dosage, simple composition, high generality, and good properties.

IN 186184 A1 relates to an energy efficient industrial (EEG) gear oil composition comprises solvent extracted, dewaxed and hydrofinished mineral base stock 93-98, an antiwear agent selected from C2-8 alkyl phosphites 0.2-1.0, EP additives selected from ashless sulfur compds. such as diaryl disulfide or sulfurized, poly hydrocarbon alkyl xanthate 0.5-20, a friction modifier selected from sol. molybdenum compds., long chain fatty amines/amides, fatty esters, or borated compds. 0.5-2, an antioxidant selected from a mixt. of C6-10 alkylated arom. diamine 0.1-0.5, a corrosion inhibitor 0.05-0.2, rust inhibitor and overbased dispersion.

CN 1403549 A to a composition comprises =1 S-contg. extreme-pressure antiwear agent (isobutene sulfide) 10-90, = antioxidation corrosion inhibitor (Zn dialkyldithiophosphate or its derivs.) 1-30, =1 P-contg. antiwear agent 10-40, =1 metal passivating agent (thiadiazole or benzotriazole derivs.) 1-20, =1 detergents (org. sulfonate Ca) 1-15, and =1 anti-rust agent (alkenylbutanedioic acid, Ba nonylnaphthalenesulfonate, fatty acid amide, benzotriazole, and their derivs.) 2-30%. The composition is superior in stability and durability for gear oil with middle or high viscosity index.

EP 1148114 A2 relates to a lubricating oil composition for use in industrial oils such as hydraulic oils, bearing oils, industrial gear oils and sliding surface lubricating oils.

CN 1057477 A relates to a medium load-carrying extreme-pressure gear oil composition contains (1) S-P-N-type extreme-pressure antiwear agent 0.1-1.0 (preferably 0.3-0.5), (2) S-contg. extreme-pressure additive 0.4-2.0 (0.5-1.5), (3) benzotriazole amine salt multifunctional additives 0.05-0.5 (0.1-0.3), (4) antioxidants 0.1-0.8 (0.1-0.5), (5) compounded demulsifying agent 0.01-0.3 wt.% (0.03-0.15 wt.%), and the balance base oil.

IN 148995 A1 relates to an industrial gear oil with good corrosion oxidation and wear properties comprises a solvent-refined dewaxed hydrofinished stock contg. a S-P additive 3.5, octylated diphenylamine 0.5, and metal deactivator 0.02 wt.%, and 10 ppm silicone antifoam.

WO 2011085969 A1relates to a lubricant composition useful esp. for the lubrification of gears, having a boundary loss coefficient XLG of 0.6 to 0.8 measured at temps. of 40 to 120 °C with a modified method according to DIN 51354, whereby the lubricant composition contains of a base oil a optional additives, whereby the base oil is selected from complex ester, said, said complex ester having a kinematic viscosity at 40°C of greater than 400 and up to 50 000 mm2/s.

WO 2011070141 A2 relates to a lubricating oil composition comprising a succinic acid derivative and an epoxy compound as additives, and a base oil selected from a mineral oil, a synthetic oil, and mixtures thereof, wherein the base oil has a sulfur content of not more than 0.3% by mass. The lubricating oil composition of the present invention has good rust-preventing properties, low sludge and also excellent energy saving characteristics through having a low friction coefficient, and can be used as an industrial lubricating oil, in particular for machine oils, hydraulic oils, turbine oils, compressor oils, gear oils and bearing oils.

GB 2413560 A is directed to a method of operating a worm gear drive at high energy efficiency comprising filling an oil reservoir with a worm gear lubricant comprising an isomerized Fischer-Tropsch derived distillate fraction having a low traction coefficient and operating the worm gear drive with the filled oil reservoir at an equilibrium temperature between 20°C and 225°C. This invention is also directed to a process for reducing the traction coefficient of a higher-traction coefficient lubricating base oil by blending it with an isomerized Fischer-Tropsch derived distillate fraction.

JP 2011126976 A relates to a compositions containing (A) base oils contg. refined mineral oils selected from American Petroleum Institute (API) group I base oils, group II base oils, and group III base oils, and/or poly(a-olefins) group IV base oils, and optionally API group 5 base oils, and (B) org. sulfur compounds., and the compositions show kinematic viscosity at 100°C 2-30 mm2/s, viscosity index 95-200, initial seizure load (ISL) =1260 N in four-ball shell extreme-pressure test (ASTM D 2783). The compositions show excellent friction-reducing effects, high load- and wear resistance, and low viscosity.

WO 2011070141 A2 relates to a lubricating oil composition comprising a succinic acid derivative and an epoxy compound as additives, and a base oil selected from a mineral oil, a synthetic oil, and mixtures thereof, wherein the base oil has a sulfur content of not more than 0.3% by mass. The lubricating oil composition of the present invention has good rust-preventing properties, low sludge and also excellent energy saving characteristics through having a low friction coefficient, and can be used as an industrial lubricating oil, in particular for machine oils, hydraulic oils, turbine oils, compressor oils, gear oils and bearing oils.

WO 2010012598 A2 provides a lubricating composition comprising a base oil and one or more additives, wherein the base oil comprises a Fischer-Tropsch derived base oil and wherein the composition has a kinematic viscosity at 40°C (according to ASTM D445) of above 150 mm2/s, preferably above 180 mm2/s. The lubricating composition according to the present invention can be used in order to improve one or more of oxidation resistance, sludge generation, gear wear and friction reduction properties.

JP 2000328084 A discloses that composition is prepd. by blending a base oil (kinematic viscosity 2-80 mm2/s at 100°C) with (A) =1 dialkyl sulfides of formula: R1S-S-SR1 (R1 = hydrocarbyl) 0.1 - 10; (B) =1 dithiophosphate esters of formula: (R2O)2P(:S)SR3 (R2-3 = hydrocarbyl) 0.1-5; (C) =1 acidic phosphate esters, phosphite esters or their alkylamine salts of formula: (R4O)nP(:O)(OH)3-n (R4 = hydrocarbyl; n = an integer of 1-3) 0.1-5, and (D) optionally alkenyl succinimide or its derivs. 0.1-5 wt.%. The gear oil composition is superior in oxidation stability at =150°C, corrosion resistance and extreme-pressure characteristics.

JP 2000063866 A discloses ashless lubricating oil compositions with improved thermal oxidation stability, antiwear, extreme-pressure, frictional characteristics, corrosion inhibition properties against various machines, and without the plugging of filter when lubricating oils contg. alkaline earth metal salts, contain combination of specific antiwear agents and specific corrosion inhibitors.

Reference Friction behavior of lubricants containing organomolybdenum compound. I. Application to sulfur-phosphorus-type gear lubricants by Kubo, Kouichi; Moriki, Keiichi; Kibukawa, Minoru from Junkatsu (1988), 33(4), 309-15 discloses friction characteristics of gear oils contg. org Mo (I), S, and P compounds as friction reducers were studied. The worn surfaces were examd. by electron probe microanal. The anal. of the worn surfaces indicated that excellent friction redn. was assocd. with a modification in the P-rich surface film due to the interaction of I with the S-P type oils additives; the load-carrying characteristics some S-P-type oils were decreased by incorporating I. The effects of additives on the friction and load-carrying properties of the oils were also discussed.

Reference Lubrication of gears with synthetic lubricants by Laukotka, E. M. from Journal of Synthetic Lubrication (1985), 2(1), 39-62 discloses the suitability of synthetic lubricating oils, esp. polyglycols and esters, for worm gears and friction-wheel gears and lubrication in such gears.

Reference Formation and behavior of an extreme-pressure [lubricant] film by Borsoff, V. N.; Wagner, C. D. from Lubrication Engineering (1957), 13, 91-9 discloses films formed on steel surfaces by reaction with solutions of dibenzyl disulfide contg. radioactive S35 in mineral oil were studied (1) by immersing steel strips in the oil solns. at temperatures. from 25°C to 190°C and detg. the extent of reaction by autoradiograph and (2) by detg. the amts. of S35 remaining on loaded spur gears lubricated with the same solutions. The steel-strip expts. showed that the reaction was autocatalytic and highly temp. dependent. The expts. with gears showed the formation of a steady-state thickness of film contg. S35 on the working surfaces.
US 2755250 discloses that an acidic polyester is added to a poly(ethylene oxide-propylene oxide) base fluid to improve its extreme-pressure properties. For example, 15 parts by wt. of propylene glycol and 85 parts of tartaric acid were heated to 150°C until 6.8% wt. of water was lost; the product solidifies on cooling.

SUMMARY OF THE INVENTION:

The energy saving through the use of the lubricants can be achieved through the following two approaches:
• By reducing the viscous drag through choosing optimum viscosity of the lubricants at the operating temperatures with superior visco-elastic behavior.
• By reducing the frictional losses in boundary or mixed lubrication regimes through the use of fiction reducer.

Review on energy efficient industrial gear oils revealed that use of mineral or synthetic bases with high performance additives has been practiced to achieve energy efficiency with improved fluid performance.

Accordingly, the present invention provides a novel industrial gear oil additive composition. The additive composition comprises (a) a sulphur, phosphorus and nitrogen (S-P-N) containing antiwear / extreme pressure additive system, (b) an oxidation inhibitor, (c) a metal passivator (d) a friction modifier, and (e) viscosity modifier component.

In a preferred embodiment, in the industrial gear oil composition, the amount of sulphur, phosphorus and nitrogen based additive is 1.0 to 3.5 percent by weight of the composition, the oxidation inhibitor is 0.01 to 0.50 percent by weight of the composition, the metal passivator is 0.01 to 0.10 percent by weight of the composition, the friction modifier is 0.20 to 2.5 percent by weight of the composition, and the viscosity modifier is 1 to 90 percent by weight of the composition.

In another aspect, the present invention provides a novel energy efficient industrial gear oil composition. The said energy efficient industrial gear oil composition comprises (a) a sulphur, phosphorus and nitrogen (S-P-N) based antiwear and extreme pressure additive system, (b) an oxidation inhibitor, (c) a metal passivator cum corrosion inhibitor, (d) friction modifier, (e) viscosity modifier, and (f) a mixture of severely refined base stocks, or hydrotreated /hydro-processed /iso-dewaxed base stocks and alkylated naphthalene, or mixture of synthetic bases and ester or mixture of synthetic bases and alkylated naphthalene or alkylated naphthalene bases or mixtures thereof.

In one embodiment of the present invention, the sulphur, phosphorus and nitrogen (S-P-N) based additive system is antiwear and extreme pressure additive system containing combination of additives of olefin sulfide, alkyl phosphonate, alkyl phosphate, long chain alkyl amine having alkyl chain length of C10 to C20, long chain alkenyl amine having alkyl chain length of C10 to C30, alkyl amine or combination of long chain alkyl amine C10 to C20, alkyl phosphate, alkyl phosphonate, alkyl dithio thiadiazole, alkoxylated long chain alkanol borate having alkyl chain length of C9 to C18, alkenyl amine, alkyl amine.
In one embodiment of the present invention, the sulphur, phosphorus and nitrogen (S-P-N) based antiwear and extreme pressure additive system is in the range from 1.0 to 3.5 percent by weight of the composition.

In yet another embodiment of the present invention, the oxidation inhibitor is alkylated diamines, having alkyl chain length of C2 to C10. In one of the preferred embodiment the alkyl chain length can be of the range of C4 to C8.

In still an embodiment of the present invention, the oxidation inhibitor is present in an amount of 0.05 to 0.50 percent by weight of the composition.

In one embodiment of the present invention, nitrogen content of the oxidation inhibitor is in the range of 3.0 to 7.0 percent by weight in antioxidant. In one of the preferred embodiment nitrogen content of the oxidation inhibitor is in the range of 4 to 6 percent by weight in antioxidant.

In one embodiment of the present invention, the metal passivator cum corrosion inhibitor is selected from the group comprising of N, N-bis (2 ethylhexyl)-ar-methyl-1H-benzotriazole-1-methanamine and alkyl thiadiazole.

In yet another embodiment of the present invention, the metal passivator cum corrosion inhibitor is present in the range from 0.01 to 0.10 percent by total weight of the composition.

In still an embodiment of the present invention, the friction modifier is selected from the group comprising of soluble molybdenum compounds, long chain fatty amines/amides having alkyl chain length of C6 to C14 or their compounds.
In still an embodiment of the present invention, the friction modifier additive is present in an amount of 0.2 to 2.5 percent by weight of the composition.
In yet another embodiment of the present invention, the molybdenum content is in the range of 3 to 12 percent by weight in oil soluble friction modifier.

In one embodiment of the present invention, the viscosity modifier is selected from group comprising of:
hydrocarbon based polymer which is ethylene and propylene co-oligomer and kinematic viscosity @ 100 °C is in the range of from 10 cSt to 4,000 cSt, and average molecular weight can be from 1,000 to 2,00,000, or
polyalkyl methacrylates or co-polymer of alkylmethacrylate and alphaolefines, and kinematic viscosity @ 100 °C is in the range of from 100 cSt to 700 cSt., and the average molecular weight can be from 1,000 to 50,000, or
poly alkylmethacrylate polymer having kinematic viscosity @ 100 °C is in the range of from 100 cSt to 500 cSt., and with average molecular weight of 10,000 to 2,00,000 or mixtures thereof.
In yet another embodiment of the present invention, the viscosity modifier is present in an amount of 1.0 to 90.0 percent by weight of the composition.
In yet another embodiment of the present invention, the composition further comprises a pour point depressant, demulsifier and a defoamer wherein:

the pour point depressant is selected from a group comprising of poly methacrylates or its derivatives, polyacrylamides, and olefin copolymer,

the demulsifier is selected from array of condensed polymeric alcohols, esters of fatty acids, fatty alcohols alkoxylated with alkylene oxides, or mixtures thereof and

the defoamer is selected from array of highly viscous organic polymer, like dimethyl polycyclohexane, polyacrylates or silicone based defoamer or mixture thereof.

In one embodiment of the present invention, the mixture of severely refined base stocks, or hydrotreated / hydro-processed / iso-dewaxed base stocks and alkylated naphthalene, or mixture of synthetic bases and ester or mixture of synthetic bases and alkylated naphthalene or alkylated naphthalene bases or mixtures thereof are selected from combination of premium quality base oils of API Group II, Group III and base oils of Group IV, Group V class, as defined in the API inter-changeability guidelines.

In one embodiment of the present invention, the energy efficient industrial gear oil composition is used for enhancing efficiency of a gear system.

In yet another embodiment of the present invention, the use of the energy efficient industrial gear oil composition in a FZG gear rig provides a power savings to the tune of 6.0 to 9.0 % over conventional commercially available industrial gear oil.

BRIEF DESCRIPTION OF DRAWING
Figure 1 : Schematic of the FZG test set up.

DETAILED DESCRIPTION OF THE INVENTION:
A novel energy efficient, industrial gear oil composition has been developed after an exhaustive research work in the laboratory for physico-chemical and tribological performance. The energy efficiency has been demonstrated in the field simulated tribological performance tests. The composition of the energy efficient gear oil includes high performance additive system in combination of premium quality severely hydrotreated / hydroprocessed / iso-dewaxed base oils of API Group II, Group III and base oils of Group IV, Group V class or mixtures thereof. It would be within the scope of this invention to use any other suitable base oil, like severely hydrotreated base oils of API Group I, with appropriate modifications. The industrial gear lubricant should have right boundary additives along with correct viscosity to form elasto-hydrodynamic film and energy efficiency can be achieved through viscosity optimization and friction modification with appropriate additive systems.

The novel industrial gear oil composition has been finalized in three phases, in the phase I - laboratory evaluation of candidate blends for physico-chemical properties; in the phase II - tribological studies conducted and finally in the phase III – assessment of energy efficiency on the novel energy efficient gear oil to establish its performance in a FZG gear machine against commercially available conventional industrial gear oils available in the market.

The additive composition for use in industrial gear oil composition comprises of (a) a sulphur, phosphorus and nitrogen (S-P-N) containing antiwear / extreme pressure additive system, (b) an oxidation inhibitor, (c) a metal passivator (d) a friction modifier, and (e) viscosity modifier component is in percentage by weight as above mentioned composition.

The industrial gear oil additive composition has been prepared by mixing the appropriate amount of chosen additives or additive systems in a beaker / container.

According to this invention, industrial gear oil composition comprises of:
The additive composition for use in industrial gear oil composition comprises of (a) a sulphur, phosphorus and nitrogen (S-P-N) containing antiwear / extreme pressure additive system, (b) an oxidation inhibitor, (c) a metal passivator cum corrosion inhibitor (d) a friction modifier, and (e) viscosity modifier (f) a mixture of severely refined base stocks, or mixture of severely hydro-processed iso-dewaxed base stock and alkylated naphthalene, or mixture of synthetic base and alkylated naphthalene or synthetic base and ester, alkylated naphthalene base or mixtures thereof.

The antiwear and extreme pressure additives used in this invention is sulphur and phosphorus containing additive system. The preferred range in this invention is from 1.0 to 3.0 percent by weight.

The antioxidant/ oxidation inhibitor used in this invention is a mixture of alkylated aromatic diamine having C2 to C10 alkyl chain length. The nitrogen content of the antioxidant is in the range of 3.0 to 7.0 percent by weight, more preferably 4 to 6 percent by weight of antioxidant. The preferred range of antioxidant is from 0.01 to 0.50 percent by weight of the composition. More preferably the oxidation inhibitor is present in an amount of 0.05 to 0.50 percent by weight of the composition.

The metal passivator cum corrosion inhibitor is commercially available and can be from array of derivative of benzotriazole or derivative of thiadiazole. The preferred range in the industrial gear oil composition is from 0.01 to 0.10 percent by weight of the composition.

The friction modifier additive is selected from array of soluble molybedenum compounds containing, long chain fatty amine / amides, fatty esters, or borated compounds, etc. The preferred compound may be soluble molybdenum compounds and molybdenum content in the range of 3 to 12 percent by weight. The preferred range in the industrial gear oil composition is from 0.10 to 2.5 by weight.

The viscosity modifier in the present composition is low molecular weight polyalkyl- methacrylates or copolymers of alkylmethacrylate and alphaolefines. The viscosity modifier has average molecular weight from 1,000 to 50,000. The preferred range of average molecular weight of said polymer can be 1,500 to 25,000. It would be within the scope of the present invention to use any other suitable viscosity modifier such as those selected from array of ethylene and propylene co-oligomer of average molecular weight of 1,000 to 50,000. Further, it would be within the scope of invention that polymethacrylates can be selected with molecular weight range of 10,000 to 2,00,000. The preferred range in the industrial gear oil composition is from 1 to 90 percent by weight.

The industrial gear oil composition optionally comprises a sufficient amount of pour point depressant to provide desired pour point depression. The pour point depressant is selected from array of poly methacrylates, polyacrylamides, olefin copolymer, etc. The preferred molecular weight can be in the range of 2,500 to 3,50,000. The preferred range in the compressor composition is from 0.01 to 1.0 percent by weight.

The industrial gear oil composition optionally contains foam inhibitors/ defoamer, which are selected from array of highly viscous organic polymer and can be of dimethyl polycyclohexane, polyacrylates or array of silicone based defoamer, or mixture thereof, etc. The preferred range in the industrial gear oil composition is from 0.01 to 0.10 percent by weight.

The industrial gear oil composition optionally contains demulsifier in sufficient amount to provide demulsification property. The demulsifiers selected from array of condensed polymeric alcohols, esters of fatty acids, fatty alcohols alkoxylated with alkylene oxides, or mixtures thereof. The preferred range in the industrial gear oil composition is from 0.01 to 0.05 percent by weight.

The composition of novel energy efficient industrial gear oil includes combination of premium quality base oils of American Petroleum Institute API Group II, Group III and base oils of Group IV, Group V class, as defined in the API interchangeability guidelines, or mixtures thereof. These base oils are commercially available in the market.

An aspect of the present invention also provides for a process for preparing the industrial gear oil composition. In an embodiment of the present invention, the industrial gear oil additive composition has been prepared by mixing the appropriate amount of chosen additives or additive systems in a beaker / container. The additives combinations are further optimised in combination of selected hydrocarbon base oils to achieve desired performance in the laboratory tests. The chosen additives are mixed in selected base oils at an appropriate temperature such as an average blending temperature of 60 ºC to 65 ºC, so that mixture gets bright, clear and homogeneous.

A high performance energy efficient industrial gear oil composition according to the preferred embodiment is herein described in the following examples:

Several candidate blends of aforesaid additives and base stocks were prepared and evaluated in laboratory for critical properties like kinematic viscosity, gear oil oxidation test (GOOT) and tribological tests.

Examples:
The examples are listed in Table – 1A & Table – 1B and these examples were prepared by mixing the components in percentage by weight. The base oils used in the examples are of API Group I, Group II, Group III, Group IV & Group V types. These base oils are commercially available in the market. The array of commercially available additives and additive systems were selected in various combinations to achieve best performance. The additives includes antiwear / extreme pressure additive system, antioxidant, metal deactivator, friction modifier, pour point depressant, demulsifier, defoament, etc. The candidate blends were prepared and tested for various physico-chemical tests including performance properties such as kinematic viscosity, copper strip corrosion, rust test, demulsibility as per ASTM D 1401 and ASTM D 2711, gear oil oxidation test (GOOT) as per ASTM D 2893 and tribological tests as per industry accepted industrial gear standard US Steel (AIST) 224.

The referred formulae are suitable to use as industrial gear & bearing oil of different ISO viscosity grades. The viscosity grade can be of ISO VG 10 to ISO VG 1500 as recommended by the gear manufacturer. The composition can be used in various gear applications including enclosed type gear systems. Various physico-chemical & performance tests were conducted to assess the performance in laboratory and thereafter energy efficiency assessed on promising candidate in a "Forschungsstelle fur Zahnrader und Getriebebau" FZG gear machine.

The components used in the examples are as follows;

Solvent Neutral (SN) base oils are solvent neutral or solvent refined base oils (API Group I) and are commercially available.

Group II are commercially available API Group II base oils.

Group III are commercially available API Group III base oils.

Group IV are commercially available API Group IV base oils.

Group V are commercially available API Group V base oils.

Additive-1 is commercially available antiwear & extreme pressure additive package and can contain combination of olefin sulpfide, long chain alkyl phosphonate, alkyl phosphate, long chain alkyl amine, long chain alkenyl amine, alkyl amine or combination of long chain alkyl amine, alkyl phosphate, alkyl phosphonate, alkyl dithio thiadiazole, alkoxylated long chain alkanol borate, long chain alkenyl amine, alkyl amine.

Additive-2 is commercially available antioxidant selected from a mixture of alkylated diamines, which can have alkyl chain length of C2 to C10.

Additive-3 is commercially available metal passivator cum corrosion inhibitor selected from N, N-bis (2 ethylhexyl)-ar-methyl-1H-benzotriazole-1-methanamine or alkyl thiadiazole.

Additive-4 is commercially available friction modifier selected from soluble molybdenum compounds, long chain fatty amines / amides, or borated compounds, which is commercially available friction modifier.

Additive-5 is commercially available hydrocarbon based polymer which is ethylene and propylene co-oligomer and kinematic viscosity @ 100 0C can vary from 10 cSt to 4,000 cSt or polyalkyl methacrylates or co-polymer of alkylmethacrylate and alphaolefines, and kinematic viscosity @ 100 0C can vary from 100 cSt to 700 cSt. or poly alkylmethacrylate polymer, kinematic viscosity @ 100 0C can vary from 100 cSt to 500 cSt.

Additive-6 is commercially available pour point depressant which can be polymethacrylate or their compounds

Additive-7 is commercially available demulsifier, which can be of alkoxylated fatty alcohols.

Additive-8 is commercially available ashless type defoamer, which can be organic polyacrylate polymer.

Additive-9 is commercially available ash containing defoamer, which can be silicon based defoamer.

Examples 1 to 8: Table – 1A
Components Example-1 Example-2 Example-3 Example-4 Example-5 Example-6 Example-7 Example-8
API Group I base 14.00 35.00 -- 35.00 35.00 -- -- --
API Group II base 44.47 -- 56.66 53.06 51.86 57.66 58.46 58.16
API Group III base -- 44.62 -- -- -- -- -- --
API Group IV base 20.00 -- 20.00 -- -- -- -- --
API Group V base 10.00 10.00 10.00 -- -- -- -- --
Additive 1 1.10 1.50 2.00 3.50 2.75 1.00 1.70 2.20
Additive 2 0.01 0.05 0.10 0.25 0.20 -- -- --
Additive 3 -- -- -- 0.05 0.05 -- -- --
Additive 4 0.40 0.80 1.20 0.10 2.00 1.00 0.30 0.10
Additive 5 10.00 8.00 10.00 8.00 8.00 39.50 39.50 39.50
Additive 6 -- -- -- 0.01 0.10 0.80 -- --
Additive 7 0.01 0.01 0.02 -- -- -- -- --
Additive 8 -- -- -- 0.01 0.02 0.02 0.02 0.02
Additive 9 0.01 0.02 0.02 0.02 0.02 0.02 0.02 0.02
Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00
Properties Example-1 Example-2 Example-3 Example-4 Example-5 Example-
6 Example-
7 Example-
8
Appearance Clear Clear Clear Clear Clear Clear Clear Clear
Kinematic viscosity @ 100 0C 28.4 28.1 28.3 28.2 28.4 28.2 28.4 28.2
GOOT, % rise in Kin. Viscosity @ 100 0C 8.2 7.1 6.0 5.2 5.1

7.2 6.2
6.0
SRV, coefficient of friction 0.09 0.10 0.07 0.12 0.07 0.10 0.12 0.13
Remarks Poor Fair Good Fair Good Poor Fair Poor

Example 9 to 15: Table 1B
Components
Example-9 Example-10 Example-11 Example-12 Example-13 Example-14 Example-15
API Group I base -- -- -- -- -- 63.95 --
API Group II base 50.96 45.84 44.25 57.99 50.81 -- --
API Group III base -- -- -- -- -- -- 56.56
API Group IV base -- -- -- -- -- 20.00 --
API Group V base -- 10.00 10.00 -- -- 5.00 --
Additive 1 3.00 2.50 2.50 1.10 2.80 2.55 2.65
Additive 2 -- 0.01 0.50 0.25 0.10 0.10 0.10
Additive 3 -- 0.01 0.10 0.03 0.05 0.05 0.05
Additive 4 1.00 1.50 2.50 1.00 1.10 0.20 1.00
Additive 5 45.00 40.00 40.00 39.50 45.00 8.00 39.50
Additive 6 -- 0.10 0.10 0.10 0.10 0.10 0.10
Additive 7 -- -- 0.01 0.01 -- 0.01 --
Additive 8 0.02 0.02 0.02 0.01 0.02 0.02 0.02
Additive 9 0.02 0.02 0.02 0.01 0.02 0.02 0.02
Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00
Properties Example-9 Example-10 Example-11 Example-12 Example-13 Example-14 Example-15
Appearance Clear Clear Clear Clear Clear Clear Clear
Kinematic viscosity @ 1000C 29.5 28.2 28.6 28.1 29.5 28.4 28.9
GOOT, % rise in Kin. Viscosity @ 100 0C 5.7 6.4 6.8 7.9 4.8 5.5 4.9
SRV, coefficient of friction 0.07 0.07 0.07 0.10 0.07 0.12 0.07
Remarks Good Fair Fair Poor V. Good Poor V. Good

Phase – 1: Laboratory Evaluation
The energy efficient industrial gear oil (Composition of Examples 13 & 15 of Table 1B) is evaluated against US Steel (AIST) 224 specifications.

Physico-chemical properties:
Table – 2 provides the physico-chemical data on energy efficient (EE) industrial gear oil vis-à-vis reference oil. The energy efficient lubricant composition has pour point as (-) 21 °C which is indicative of its low temperature properties and its suitability for low temperature application. The flash point as determined by ASTM D 92 is more than 200°C suggesting its suitability for gear systems working at elevated temperatures in actual operation. The composition is having excellent demulsibility characteristics allowing better water separation characteristics. The poor demulsibility of the industrial gear oil causes sludge, corrosion / rust formation, clogging of the strainer / filter, reduced lubricant performances and shortening of oils’ life.

Performance of Test oils in High temperature Oxidation Tests:
For comparison, conventional industrial oil (Kinematic Viscosity @ 100 0C : 23.4 cSt) available commercially in the market has been chosen as reference oil for generating base line data. In order to confirm the oxidation inhibiting properties of the selected novel additive system, gear oil oxidation test (GOOT) as per ASTM D 2893 were conducted on test oils.

Phase – 2: Evaluation in Tribological Tests:
In order to compare the anti-frictional performance of energy efficient industrial gear oil with that of reference industrial gear oil, weld load and wear scar dia (WSD) done as per IP 239 & ASTM D 2266 test methods. FZG test was conducted to assess the load bearing behaviour in comparison to reference oil (table 3). The newly developed candidate meets the industrial gear oil requirements as per industry accepted US Steel (AIST) 224 international standard.

Phase – 3 : Assessment of Energy Efficiency of Industrial Gear oils :
In general, gear contacts work under the boundary and EHD lubrication regimes, it is therefore, important to assess the gear lubricants to predict the overall effect under these regimes on the gear efficiency. So, it was decided to use a gear box properly instrumented to precisely control the parameters. The popular FZG gear test machine used for gear oil testing as per DIN 51354 test was selected since it was best suited for this purpose and named as modified FZG test. Two laboratory bench test viz SRV friction and wear test to assess frictional characteristics and EHD ultra thin measurement system for the mapping of the oil film thickness over a wide speed range from 20 mm / sec to 5 meters / sec by optical interferometry were used for assessing the factors responsible for energy efficiency.

Table 2: Test data of Energy Efficient Oils vs. Reference oil
No. Property Method Conventional oil EE commercial Synthetic
commercial Synthetic
commercial EE
candidate oil EE
candidate oil
Base type -- Mineral Mineral PAG PAG Semi-synthetic Semi-synthetic
Candidate oil -- Reference Candidate 1 Candidate 2 Candidate 3 Candidate 4 Candidate 5
1. Appearance Visual C&B C&B C&B C&B C&B C&B
2. ASTM color D 1500 3.5 <4.5 <1.0 <1.0 <2.0 < 2.0
3. K.Vis @ 100°C, cSt D 445 23.4 23.4 34.4 36.6 29.5 28.9
4. Pour point, COC, °C D 92 (-) 9 (-) 9 (-) 36 (-) 36 (-) 21 (-) 21
5. Flash Point, °C D 97 238 238 298 282 251 252
6. Density @ 25 °C, gm/cm3 D 1298 0.9004 0.9010 1.074 1.071 0.8947 0.8942
7. Cu Corrosion test @100 0C for 3 hours D 130 1 1 1 1 1 1
8. Rust test, D 665, B Pass Pass Fail Fail Pass Pass
9. Foaming, tendency/stability
Seq I ,
Seq II,
Seq III D 892
Nil/Nil
10/Nil
Nil/Nil
Nil/Nil
10/Nil
Nil/Nil
Nil/Nil
30/Nil
Nil/Nil
Nil/Nil
30/Nil
Nil/Nil
Nil/Nil
30/Nil
Nil/Nil
Nil/Nil
30/Nil
Nil/Nil
10. Demulsibility @82°C, time in minutes D 1401 40-40-0 (15) 40-37-3 (20) 10-10-60 (30) 10-10-60 (30) 40-37-3 (10) 40-37-3 (10)
11.

i.
ii. Gear Oil Oxidation Test @ 121.1 0C for 312 hours
- % change in K.V@ 100°C
- Precipitation number D 2893

5.5
Nil

5.4
Nil

3.5
Nil

3.3
Nil

4.8
Nil

4.9
Nil
12.
i.
ii.
iii. Demulsibility @ 82 °C
- Free water, ml
- Emulsion, ml
- Water in oil, % D 2711
81.5
0.1
0.2
82.0
0.1
0.2 ND
ND

84.4
0.1
0.1
85.3
0.1
0.1
C&B=Clear & Bright, ND=Not done

Table 3 : Tribological data of candidate oils vs reference oil
No.
Property Method Conventional oil EE commercial Synthetic
commercial Synthetic
commercial EE
candidate oil EE
candidate oil
Base type
-- Mineral Mineral PAG PAG Semi-synthetic Semi-synthetic
Candidate oil
-- Reference Candidate 1 Candidate 2 Candidate 3 Candidate 4 Candidate 5
1. Weld Load, Kgs
IP 239 250 280 180 180 250 250
2.
i.

ii. Wear Scar Dia,
@ 20 kg, 1800 rpm, 54 0C & 1 hour, mm
@ 40 kg, 1800 rpm, 54°C & 1 hour, mm D 2266
0.35

0.40
0.35

0.40
0.30

0.40
0.30

0.40
0.35

0.40
0.35

0.40
3. FZG pass load stage DIN 51354 11 12 >12 >12 >12 >12
PAG=Polyalkylene Glycol

Energy efficiency of the energy efficient industrial gear oil was assessed in the laboratory in SRV test rig. This machine is used to measure the coefficient of friction between oscillating ball on a flat disc in a sliding contact geometry. Reduction in coefficient of friction during the test run was taken as criteria for energy saving potential. The higher is the reduction in the coefficient of friction, better will be the energy efficiency in the oil. In this screening test @ 200N, 50°C, 50 Hz, 1 mm for 1 hour, energy efficient oil provided reduction in coefficient of friction to the extent of 4 to 39 percent approximately over the reference industrial gear oil (table 4).

Table 4 : Frictional study of candidate oils in SRV test:
Candidates Coefficient of friction % reduction in coefficient of friction
Reference oil 0.115 --
Candidate 1 0.10 – 0.11 4.3 – 13.0
Candidate 2 0.10 – 0.105 8.6 – 13.0
Candidate 3 0.10 – 0.105 8.6 – 13.0
Candidate 4 0.07 – 0.10 13.0 – 39.0
Candidate 5 0.07 – 0.105 8.6 – 39.0

The optical Elastohydrodynamic EHD apparatus was used to measure EHD film thickness by steel ball on glass disc and friction (traction) coefficient was measured under EHD regime by steel ball on steel disc. The contact of steel ball on glass disc is coated with silica spacer layer. The load was kept 20N with variable rolling speed of 0 to 5 meter per second and bulk oil temperature of 60 0C for test duration of one hour. The EHD film thickness of the energy efficient gear oil was less than reference oil. The reference oil and candidate 1 possess similar film thickness in the range of 800 – 1000 nm, candidate 2 and candidate 3 possess film thickness in the range of 400 to 550 nm, however candidate 4 and candidate 5 possess film thickness in the range of 600 to 800 nm with the rolling speed of 2 to 5 meter per second.

The principle of power circulation of FZG test rig is favourable for the measurement of frictional losses, since by construction, the electric motors overcome the losses. The power consumed by the motor is the sum of (i) the internal losses of the motor and the frictional losses in the couplings etc., which was reasonably taken as constant during the test and (ii) the frictional losses between gear teeth and the bearing of the machine, which affected by test oil taken during the test. Thus the frictional losses were evaluated by the measurement of electric motor. It avoids more delicate and cumbersome task of measuring torques of rotating shafts. This can precisely distinguish the narrow differences in energy consumed with two oils.

The principle of the test is to measure the electric power consumption using a precise microprocessor controlled energy meter at three standard FZG test load i.e. 4, 6 & 8 load stage at speed of 1500 rpm maintaining the oil at a constant oil temperature of 80 0C by using heating coil and cooling water for running period of 1 hour at each load stage (table 5). This test condition enabled to assess the effect of both friction modifier, working under boundary regime and effect of viscometrics working under hydrodynamic regimes (Figure 1).

Table 5 : Details of FZG test conditions:
Parameter Details of test conditions & type of gear
Gear Spur Gear (100 MnCr5)
Pinion speed, rpm 1500
Load stage 4, 6 & 8
Temperature 80 0C
Time duration 1 hour
Parameter taken Energy consumed in kW

Table 6 : Reduction in Energy consumed (kW) in FZG Gear Rig Test
Candidate oils
4th stage 6th stage 8th stage Cumulative
kW % kW % kW % kW %
Reference oil 1.56
-- 1.96 -- 2.52 -- 2.01 --
Candidate 1 1.60
(+)2.56 1.90 (-)3.06 2.40 (-)4.76 1.96 (-)1.75
Candidate 2 1.60 (+)2.56 1.80 (-)8.16
2.20 (-)12.6 1.86 (-)6.10
Candidate 3 1.50 (-)3.84 1.90 (-)3.06
2.20 (-)12.6 1.86 (-)6.54
Candidate 4 1.50 (-)3.84 1.80 (-)8.16
2.30 (-)8.73 1.86 (-)6.91
Candidate 5 1.40 (-)10.2 1.80 (-)8.16
2.30 (-)8.73 1.83 (-)9.05

Candidate 1 yield energy efficiency by friction modification, candidate 2 and candidate 3 provided energy efficiency due to their lower viscous drag from lower film thickness however candidate 4 & candidate 5 provided energy efficiency owing to low viscous drag and friction modification (table 6).

The important outcome of the energy efficiency test on novel energy efficient industrial gear oil is as follows:
• The novel performance industrial gear oil as per the invention possess superior oxidation stability, antirust & anticorrosive properties with energy efficiency and load bearing capability
• The energy efficiency of novel energy efficient industrial gear oil as per the invention is to the tune of around 6.0 to 9.0 % in comparison to reference oil assessed in modified FZG gear test
• The energy efficient industrial gear oil composition would provide the enhancement in the life over reference oil as well as increased productivity and reduction in down time.

The field evaluation of energy efficient industrial gear oil composition compared the conventional oil (reference oil) carried in coal mill gear boxes of the thermal power plant provided following benefits;
a) Improved average power savings to the order of 5 to 7 percent

b) Significant reduction in lube oil temperature upto 5 0C observed with the use of candidate oil -

c) Significantly enhanced wear protection with the use of candidate oil resulting in insignificant wear metals build-up in candidate oil leading to enhanced life of the oil

d) Retention of lower coefficient of friction characteristics by the candidate oil even after prolonged use as compared to the conventional oil indicating enhanced durability of the energy efficient industrial gear oil composition when tested in a reciprocating rig exhibiting excellent frictional efficiency characteristics of the candidate oil.
,CLAIMS:We Claim:

1. An energy efficient industrial gear oil composition comprising:
(a) a sulphur, phosphorus and nitrogen (S-P-N) based antiwear and extreme
pressure additive system,
(b) an oxidation inhibitor,
(c) a metal passivator cum corrosion inhibitor,
(d) a friction modifier,
(e) a viscosity modifier, and
(f) a mixture of severely refined base stocks, or hydrotreated / hydro-processed / iso-dewaxed base stocks and alkylated naphthalene, or mixture of synthetic bases and ester or mixture of synthetic bases and alkylated naphthalene or alkylated naphthalene base or mixtures thereof.

2. The composition as claimed in claim 1, wherein the sulphur, phosphorus and nitrogen (S-P-N) based additive system is antiwear and extreme pressure additive system containing combination of additives of olefin sulfide, alkyl phosphonate, alkyl phosphate, long chain alkyl amine having alkyl chain length of C10 to C20, long chain alkenyl amine having alkyl chain length of C10 to C30, alkyl amine or combination of long chain alkyl amine having alkyl chain length of 10 to C20, alkyl phosphate, alkyl phosphonate, alkyl dithio thiadiazole, alkoxylated long chain alkanol borate having alkyl chain length of C9 to C18, alkenyl amine, alkyl amine.

3. The composition as claimed in claim 1, wherein the sulphur, phosphorus and nitrogen (S-P-N) based antiwear and extreme pressure additive system is in the range from 1.0 to 3.5 percent by weight of the composition.

4. The composition as claimed in claim 1, wherein the oxidation inhibitor is alkylated diamines, having alkyl chain length of C2 to C10.

5. The composition as claimed in claim 1, wherein the oxidation inhibitor is present preferably in an amount of 0.05 to 0.50 percent by weight of the composition.

6. The composition as claimed in claim 1, wherein nitrogen content of the oxidation inhibitor is in the range of 4.0 to 6.0 percent by weight in antioxidant.

7. The composition as claimed in claim 1, wherein the metal passivator cum corrosion inhibitor is selected from the group comprising of N, N-bis (2 ethylhexyl)-ar-methyl-1H-benzotriazole-1-methanamine and alkyl thiadiazole.

8. The composition as claimed in claim 1, wherein the metal passivator cum corrosion inhibitor is present in the range from 0.01 to 0.10 percent by total weight of the composition.

9. The composition as claimed in claim 1, wherein the friction modifier is selected from the group comprising of soluble molybdenum compounds, long chain fatty amines/amides having alkyl chain length of C6 to C14 or their compounds.
10. The composition as claimed in claim 1, wherein friction modifier additive is present in an amount of 0.2 to 2.5 percent by weight of the composition.
11. The composition as claimed in claim 1, wherein the molybdenum content is in the range of 3 to 12 percent by weight of oil soluble friction modifier.
12. The composition as claimed in claim 1, wherein the viscosity modifier is selected from group comprising of:
hydrocarbon based polymer which is ethylene and propylene co-oligomer and kinematic viscosity @ 100 °C is in the range of from 10 cSt to 4,000 cSt, and average molecular weight can be from 1,000 to 2,00,000, or
polyalkyl methacrylates or co-polymer of alkylmethacrylate and alphaolefines, and kinematic viscosity @ 100 °C is in the range of from 100 cSt to 700 cSt., and the average molecular weight can be from 1000 to 50,000, or
poly alkylmethacrylate polymer having kinematic viscosity @ 100 °C is in the range of from 100 cSt to 500 cSt, and with average molecular weight of 10,000 to 2,00,000 or mixtures thereof.

13. The composition as claimed in claim 1, wherein the viscosity modifier is present in an amount of 1.0 to 90.0 percent by weight of the composition.
14. The composition as claimed in claim 1, wherein the composition further comprises a pour point depressant, demulsifier and a defoamer wherein:

the pour point depressant is selected from a group comprising of poly methacrylates or its derivatives, polyacrylamides, and olefin copolymer,

the demulsifier is selected from array of condensed polymeric alcohols, esters of fatty acids, fatty alcohols alkoxylated with alkylene oxides, or mixtures thereof and

the defoamer is selected from array of highly viscous organic polymer, like dimethyl polycyclohexane, polyacrylates or silicone based defoamer or mixture thereof.

15. The composition as claimed in claim 1, wherein the mixture of severely refined base stocks, or hydrotreated / hydro-processed / iso-dewaxed base stocks and alkylated naphthalene, or mixture of synthetic bases and ester or mixture of synthetic bases and alkylated naphthalene or alkylated naphthalene bases or mixtures thereof are selected from combination of premium quality base oils of API Group II, Group III and base oils of Group IV, Group V class.

16. The composition as claimed in any of the preceding claims 1 to 15, wherein said composition is used for enhancing efficiency of a gear system.

17. The composition as claimed in any of the preceding claims 1 to 16, wherein the use of said composition in a FZG gear rig provides a power savings to the tune of 6.0 to 9.0 %.