CLIAMS:We Claim:

1. A compressor oil additive composition comprising:
(a) a polyisobutylene based polymer,
(b) a rust and oxidation inhibitor,
(c) a friction modifier, and
(d) a sulphur and phosphorus containing antiwear component.

2. The composition as claimed in claim 1, wherein the ratio of polyisobutylene based polymer : rust and oxidation inhibitor : friction modifier : sulphur and phosphorus containing antiwear is 2-40 : 4-24 : 1-22 : 2-30.

3. The composition as claimed in claim 1, wherein the rust and oxidation inhibitor is ashless rust & oxidation inhibitor additive system containing combination of additives of alkyl naphthylamine, mixture of triazoles of N,N-bis (2ethylhexyl)-4-methyl-1H-benzotrizole-1-methylamine and N,N-bis(2-ethylhexyl)-5-methyl-1H-benzotriazole-1methylamine, amine phosphate, acylsarkosinate, sterically hindered phenol, acid salt of 4-nonylphenoxy compounds, alkylated diphenylamines or mixture of aryl triazole, alkyl amines, aryl amine, alkyl alkyleneoxycarboxylic amine or mixtures of sterically hindered phenol, alkylated diphenyl amines, mixture of derivatives of triazoles / thiadiazoles.

4. The composition as claimed in claim 1, wherein the friction modifier is ashless surface active friction modifier additive, selected from array of boron containing, phosphorus containing, polymerised esters selected from amide borated ester or mixture of high molecular weight phenolic antioxidants or alkyl / aryl phosphates, phosphites, phosphonates or polymer based natural / synthetic fatty acids and polyols, or mixture thereof.

5. The composition as claimed in claim 1, wherein the sulphur and phosphorus containing antiwear component is selected from alkyl dithiophosphate or dialkyldithiophosphate, where alkyl group is from C1 to C14, the sulphur and phosphorus moieties are in the ratio of about 2:1. The phosphates are alkyl or aryl phosphates, where alkyl group is having carbon chain length of C1 to C18; ashless alkyl carbamates having sulphur and nitrogen content in the ratio of 5:1; ashless amine phosphate containing mixture of amine phosphates and having multifunctional performance with extreme pressure / antiwear and anti rust properties and phosphorus and nitrogen content in the ratio of about 2:1.

6. The composition as claimed in claim 1, wherein the composition further comprises a demulsifier and a defoamer.

7. The composition as claimed in claim 6, wherein 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.

8. An energy efficient compressor oil composition comprising:
(a) a polyisobutylene based polymer,
(b) a rust and oxidation inhibitor,
(c) a friction modifier,
(d) a sulphur and phosphorus containing antiwear component, and
(e) a mixture of severely hydrotreated / hydro-processed / iso-dewaxed base stocks and alkylated naphthalene, or mixture of synthetic bases and alkylated naphthalene or alkylated naphthalene bases or mixtures thereof.

9. The composition as claimed in claim 1, wherein the polyisobutylene based polymer is 0.10 to 2.0 percent by weight of the composition, the rust & oxidation inhibitor is 0.20 to 1.2 percent by weight of the composition, the friction modifier is 0.05 to 1.1 percent by weight of the composition, and the sulphur and phosphorus containing antiwear component is 0.10 to 1.50 percent by weight of the composition.

10. The composition as claimed in claim 8, wherein; the rust and oxidation inhibitor is ashless rust & oxidation inhibitor additive system containing combination of additives of alkyl naphthylamine, mixture of triazoles of N,N-bis (2ethylhexyl)-4-methyl-1H-benzotrizole-1-methylamine and N,N-bis(2-ethylhexyl)-5-methyl-1H-benzotriazole-1methylamine, amine phosphate, acylsarkosinate, sterically hindered phenol, acid salt of 4-nonylphenoxy compounds, alkylated diphenylamines or mixture of aryl triazole alkyl amines, aryl amine, alkyl alkyleneoxycarboxylic amine or mixtures of sterically hindered phenol, alkylated diphenyl amines, mixture of derivatives of triazoles / thiadiazoles; the friction modifier is ashless surface active friction modifier additive, selected from array of boron containing, phosphorus containing, polymerised esters selected from amide borated ester or mixture of high molecular weight phenolic antioxidants or alkyl / aryl phosphates, phosphites, phosphonates or polymer based natural / synthetic fatty acids and polyols, or mixture thereof; or succinic acid ester, succinic ester amide, mannich base, or mixtures thereof; and the sulphur and phosphorus containing antiwear component is selected from alkyl dithiophosphate or dialkyldithiophosphate, where alkyl group is from C1 to C14, the sulphur and phosphorus moieties are in the ratio of about 1:2, the phosphates are alkyl or aryl phosphates, where alkyl group is having carbon chain length of C1 to C18; ashless alkyl carbamates having sulphur and nitrogen content in the ratio of 5:1; ashless amine phosphate containing mixture of amine phosphates and having multifunctional performance with extreme pressure / antiwear and anti rust properties and phosphorus and nitrogen content in the ratio of about 2:1.

11. The composition as claimed in claim 8, wherein the mixture of severely hydrotreated / hydro-processed / iso-dewaxed base stocks and alkylated naphthalene, or mixture of synthetic bases and alkylated naphthalene or alkylated naphthalene bases 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.

12. The composition as claimed in claim 8, wherein the composition further comprises a demulsifier and a defoamer.

13. The composition as claimed in claim 12, wherein the demulsifier is selected from array of condensed polymeric alcohols, esters of fatty acids, fatty alcohols alkoxylated with alkylene oxides, or mixtures thereof and thedefoamer is selected from array of highly viscous organic polymer, like dimethyl polycyclohexane, polyacrylates.

14. The composition as claimed in claim 10, wherein said friction modifier is an organic friction modifier,preferably boron based ester, in an amountof 0.01 to 0.50 percent by weight of the composition.

15. The composition as clamed in claim 10, wherein said ashless antiwear component is alky (C4 – C14) dithiophosphate, in an amount of 0.05 to 1.0 percent by weight of the composition.

16. The composition as claimed in claim 10, wherein said polyisobutylene based polymer is in an amount of 0.50 to 1.0percent by weight of the composition.

17. The composition as claimed in claim 10, wherein said rust & oxidation inhibitor is in an amount of 0.20 to 1.0 percent by weight of the composition.

18. The composition as claimed in any of the preceding claims 8 to 17, wherein said composition is used for enhancing efficiency of a compressor.

19. The composition as claimed in any of the preceding claims 8 to 17, wherein the use of said composition in a rotary screw air compressor providesa power savings to the tune of 3.0 to 4.5 %.
,TagSPECI:Field of Invention:
This invention relates to the development of high performance composition of compressor oil, providing energy savings with excellent thermal & oxidation stability. More particularly, the present invention provides novel additive compositions for compressor oil, which can be added to a compressor oil and used as novel lubricant for compressors such as rotary screw air compressors.

Background Information & Prior Art:
One of the important tasks of the compressor is to compress the process gas / air for various industrial applications. In this regard, screw or centrifugal air compressors are being useddepending upon the pressure and flow rate requirements.

A screw rotary compressor contains a housing including bore, bearings, low pressure end as inlet and high pressure end with high pressure as outlet. An efficient screw compressor in general generates a pressure of about 5 to 30 bar. The compressor oil in a rotary screw compressor acts as coolant for absorbing compression / frictional heat, seal the rotors, lubricate the moving parts and protect the overall compressor system from rust & corrosion.

Energy conservation is the concept used for formulating superior products. As some energy of prime mover in compressor is being used for driving 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.

In the compression, compressor delivers high pressure gas / airthereby resulting to elevation in working temperature. During this process, compressor oil is oxidized as it comes in contact of the hot metal surfaces / hot air or gasin a running compressor. The main objective of the present invention is to develop a novel composition of compressor oil with superior energy efficiency and resistance to oxidation ensuring longer useful life in industrial equipments such as rotary screw air compressors.

US Pat. Appl Publ (2012) US 20120108479A A1 20120503 by Shah, Ravindra, titled Compressor oils having improved oxidation resistance.
A compressor lubricant composition, providing energy savings and exhibiting excellent oxidation stability is provided, as well as a process for preparation of the lubricant composition. The composition comprises: (i) from 68 to 99.999 wt % of an isomerized base oil or blend of isomerized base oils; (ii) 0.001 through 20 wt % of a blend of ashless additives, the ashless additives having a viscosity range at 40° C. of from 50 mm2/s to 60 mm2/s, a d. at 20° C. of from 0.95 through 1.05 g/cm3, a flash point of greater than 100° C. (COC), solublized in mineral oil of greater than 5 wt %, sulfur content of from 4.8 wt % through 6.0 wt %, and phosphorus content of from 2.9 through 3.6 wt %; (iii) less than 1.0 wt % of a dithiocarbamate, wherein the Conradson carbon residue is less than or equal to 3.00. The dithiocarbamate is added to the base oil blend as a top treatment.

US PatApplPubl (2009), US 20090181871 A1 20090716, by Shah Ravindra, Rosenbaum, John M.;Scholier, Thierry; De Keyser, Marianne; Bertrand Nancy J. of Chevron Corporation titled Compressor lubricant compositions and preparation thereof
A compressor lubricant composition providing energy savings and exhibiting excellent oxidation stability is provided. The composition comprises (i) 80 to 99.999 wt.% of an isomerized base oil; and (ii) 0.001-20 wt.% of at least an additive selected from an additive package, oxidation inhibitors, pour point depressants, metal deactivators, metal passivators, anti-foaming agents, friction modifiers, anti-wear agents, and mixtures thereof; wherein the isomerized base oil has consecutive nos. of carbon atoms, <0.05 wt.% aromatics, a ratio of mols. withmonocycloparaffinic functionality to mols. withmulticyloparaffinic functionality greater than 2. In one embodiment, compressors employing the lubricant composition with isomerized base oil consumes at least 1% less power than compressors employing the lubricant composition of the prior art.

US (1981), US 4302343 A 19811124, by Carswell, Robert; McGraw, Philip W. titled Rotary Screw Compressor lubricants
Rotary screw compressor lubricants were manufactured from blends of 22-35 wt.% esters of trimethylolpropane or pentaerythritol with C4-18 fatty acids and 65-78 wt.% polyether polyols with a no. av. mol. wt. 700-2500. Addn. of other commonly available components (up to 10 wt.% based on ester and polyol) completed the formulations, which had better oxidation stability than compressor lubricants. Thus, a composition containing polypropylene glycol [25322-69-4] (no. av. mol. wt. 1200) 175, Stauffer ester No. 825 (a pentaerythritoltetraester) [81181-26-2] 75, antioxidant 3.75, corrosion inhibitor 1.25, and metal deactivator 0.125 lbrequired 18 h 30 min to give a 25-lb pressure drop in a rotary bomb (ASTM D-2272 oxidn. test) compared with Anderol 495 (a com. lubricant based on a dialkyladipate) which required 9 h 50 min.

US (1979), US 4175045 A 19791120 by Timony, Peter E, titled Compressor lubrication
Lubricating oil composition suitable for the lubrication of compressors contains 80-90 wt.% of pentaerythritol ester and 10-20 wt.% of dipentaerythritol ester of C4-13-carboxylic acids. Thus, a formulated compressor lubricant containing 95.98 wt.% of a mixture of polyol (85 wt.% pentaerythritol and 15 wt.% dipentaerythritol) esters provided superior lubrication to a com. diester-based lubricant.

European Patent Application 09012058.5 number EP 2 305782 A1 in 2009 by Rinklieb, Ronny, Rettemeyer, Dirk, Scherer, Markustitled Lubricant compositions of Cognis IP Management GmbH
Machinery, such as compressors, hydraulic equipment or turbines, can be operated with increased energy efficiency, if it is running with a lubricant composition, containing an ester base oil together with an additive blend, the later one is in very low amounts, where by the additive blends comprises at least two different additives, selected (a) dithiophosphates, and (b) alkylated phosphorothionates.

Genesis for the development of energy efficient Air Compressor Oil:
It has been well established that 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
• By reducing the frictional losses in boundary or mixed lubrication regimes through the use of fiction reducer

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

Summary of the Invention:
The present invention provides a novel compressor oil additive composition. The additive composition comprises (a) a polyisobutylene based polymer, (b) a rust and oxidation inhibitor, (c) a friction modifier, and (d) a sulphur and phosphorus containing antiwear component.

In a preferred embodiment, in the additive composition, the ratio of polyisobutylene based polymer : rust and oxidation inhibitor : friction modifier : sulphur and phosphorus containing antiwear is 2-40 : 4-24 : 1-22 : 2-30.

In another aspect, the present invention provides an energy efficient compressor oil composition. The said compressor oil composition comprises (a) a polyisobutylene based polymer, (b) a rust and oxidation inhibitor, (c) a friction modifier, (d) a sulphur and phosphorus containing antiwear component, and (e) 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 alkylated naphthalene base or mixtures thereof.

In a preferred embodiment, in the compressor oil composition, the amount of polyisobutylene based polymer is 0.10 to 2.0 percent by weight of the composition, the rust & oxidation inhibitor is 0.20 to 1.2 percent by weight of the composition, the friction modifier is 0.05 to 1.1 percent by weight of the composition, and the sulphur and phosphorus containing antiwear componentis 0.10 to 1.50 percent by weight of the composition.

Detailed Description of the Invention:
The Innovation:
A novel energy efficient, cost effective air compressor oil composition has been developed after an exhaustive research work in the laboratory followed by field trial in a rotary screw air compressorunder the identical compressor test conditions. The composition of the energy efficient compressor oil includes ashless additive system in combination of premium quality severely hydrotreated / hydroprocessed / isodewaxed 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 novel compressor 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 - field evaluation was carried out on the energy efficient compressor oil to establish its performance in a rotary screw air compressor against genuine oil available from compressor OEM (original equipment manufacturer).

The additive composition for use in compressor oil composition comprises of (a) a polyisobutylene based polymer, (b) a rust and oxidation inhibitor, (c) a friction modifier, and (d) a sulphur and phosphorus containing antiwear component. The ratio of polyisobutylene based polymer : rust and oxidation inhibitor : friction modifier : sulphur and phosphorus containing antiwear is 2-40 : 4-24 : 1-22 : 2-30.

The compressor 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.

According to this invention, compressor oil composition comprises of:
(a) a polyisobutylene based polymer, (b) a rust and oxidation inhibitor, (c) a friction modifier, (d) a sulphur and phosphorus containing antiwear component, and (e) 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 alkylated naphthalene base or mixtures thereof.

The composition of the energy efficient compressor oil includes 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 interchangeability guidelines, or mixtures thereof. These base oils are commercially available in the market.

The ashless rust & oxidation inhibited additive system are packages commercially available in the market. The ashless rust & oxidation inhibited additive system contain combination of additives of alkyl naphthylamine, mixture of triazoles of N,N-bis (2ethylhexyl)-4-methyl-1H-benzotrizole-1-methylamine and N,N-bis(2-ethylhexyl)-5-methyl-1H-benzotriazole-1-methylamine, amine phosphate, acylsarkosinate, sterically hindered phenol, acid salt of 4-nonylphenoxy compounds, alkylated diphenylamines or mixture of aryl triazole alkyl amines, aryl amine, alkyl alkyleneoxycarboxylic amine or mixtures of sterically hindered phenol, alkylated diphenyl amines, mixture of derivatives of triazoles / thiadiazoles. The preferred range is from 0.20 to 1.2 percent by weight of the composition.

The ashless antiwear / extreme pressure component / additive are commercially available and can be from array of phosphates, carbamates, dithiophospates, amine phosphates, etc. The ashless antiwear / extreme pressure additive can be alkyl dithiophosphate or dialkyldithiophosphate, where alkyl group can be from C1 to C14. The sulphur and phosphorus moieties can be in the ratio of approximately of 2:1. The phosphates can be alkyl or aryl phosphates, where alkyl group can be having long chain length of C1 to C18. The ashless alkyl carbamates is ashless antiwear / extreme pressure additive and can have sulphur and nitrogen content in the ratio of 5:1. The ashless amine phosphate can be mixture of amine phosphates and having multifunctional performance with extreme pressure / antiwear and anti rust properties and phosphorus and nitrogen content can be approximately in the ratio of 2:1. The preferred range in the compressor oil composition is from 0.10 to 1.5 percent by weight.

The ashless surface active friction modifier additive is selected from array of boron containing, phosphorus containing, ester based, polymerised esters, etc. The friction modifier can be of amide borated ester or mixture of high molecular weight phenolic antioxidants or alkyl/aryl phosphates, phosphites, phosphonates or polymer based natural / synthetic fatty acids and polyols, or mixture thereof. The preferred range in the compressor oil composition is from 0.05 to 1.1percent by weight.

The polymer in the composition is polyisobutylene based polymer with average molecular weight from 1,000 to 5,00,000. The preferred range of average molecular weight of said polymer can be 1,500 to 3,50,000. The preferred range in the compressor oil composition is from 0.10 to 2.0 percent by weight. It would be within the scope of the present invention to use any other suitable polymer such as those selected from array of polyacrylates and polymetharcylates or ethylene propylene co-polymer of average molecular weight of 1,000 to 3,50,000.

The compressor oil composition optionally contains foam inhibitors, which are selected from array of highly viscous organic polymer and can be of dimethyl polycyclohexane, polyacrylates, etc. The preferred range in the compressor oil composition is from 0.005 to 0.10 percent by weight.

The compressor oil composition optionally contains demulsifier in sufficient amount to provide demulsification property. The demulsifieris 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 compressor oil composition is from 0.001 to 0.05 percent by weight.

The compressor 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 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 compressor 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, total acid number, conradson carbon residue (CCR), Rotating Pressure Vessel Oxidation Test (RPVOT), Pneurop Oxidation Test (POT) and tribological tests.

Examples:
The examples are listed in Table – 1A, Table – 1B & Table – 1C 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& additive package were selected in various combinations to achieve best performance. The ashless additives includes antiwear / extreme pressure additives, friction modifier, surface active dispersants, metal deactivator, rust & oxidation inhibitor additive system, corrosion inhibitor, demulsifier, defoament etc. The candidate blends were prepared and tested for various physico-chemical tests including performance properties such as kinematic viscosity, total acid number, conradson carbon residue (CCR), Rotating Pressure Vessel Oxidation Test (RPVOT), Pneurop Oxidation Test (POT) and tribological tests.

The referred formulae are suitable to use as compressor oil of different ISO viscosity grades. The viscosity grade can be of ISO VG 10 to ISO VG 1500 as recommended by the compressor manufacturer. The composition can be used in various compressor applications including reciprocating and screw air compressors. Various physico-chemical & performance tests were conducted to assess the performance in laboratory and thereafter trial of promising candidate was carried out in a rotary screw air compressor in actual operating conditions.

The components used in the examples are as follows:

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 polyisobutlyene based polymer of preferably having average molecular weight 2,500 to 2,50,000.

Additive-2 is commercially available rust & oxidation inhibitor additive package and can contain combination of aryl amine, alkyl amine, alkyl alkyleneoxycarboxylic amine, and mixtures of derivatives of aryl triazole.

Additive-3 is commercially available friction modifier, which is surface active boron containing mixture of amide ester.

Additive-4 is commercially available sulphur & phosphorus containing antiwear additive of ashless dithipohsphates of preferably alkyl chain length of C1 to C 14 and can be having sulphur & phosphorus content in the ratio of 2:1.

Additive-5 is commercially available demulsifier, which can be of alkoxylated fatty alcohols.

Additive-6 is commercially available ashless type defoamer, which can be organic polyacrylate polymer.

Additive-7 is commercially available rust & oxidation inhibited turbine oil package and can be combinations of alkylated diphenyl amines, alkyl naphthylamines, derivatives of triazoles, amine phosphates, sterically hindered phenol.

Additive-8 is commercially available ashless antiwear additive, which can be of aryl phosphates.

Additive-9 is commercially available polyalkyl methacrylate polymer, which can be preferably having average molecular weight of 1,000 to 2,50,000.

Additive-10 is commercially available friction modifying agent, which can be mixture of high molecular weight antioxidants.

Examples 1 to 6: Table – 1A
Components Example -1 Example-2 Example-3 Example-4 Example-5 Example-6
SN base 95.989 -- -- -- -- --
API Group II base -- 72.839 61.999 -- -- --
API Group IIIbase -- -- -- 42.849 -- --
API Group IV base -- -- -- -- 53.000 --
API Group V base -- 25.000 35.690 55.090 44.989 95.788
Additive 1 1.500 1.000 1.000 0.500 0.800 1.200
Additive 2 1.000 0.250 0.800 0.500 0.500 0.700
Additive 3 0.500 0.400 0.200 0.250 0.200 1.000
Additive 4 1.000 0.500 0.300 0.800 0.500 1.300
Additive 5 0.001 0.001 0.001 0.001 0.001 0.002
Additive 6 0.010 0.010 0.010 0.010 0.010 0.010
Total 100.000 100.000 100.000 100.000 100.000 100.000
Properties Example -1 Example-2 Example-3 Example-4 Example-5 Example-6
Appearance Clear Clear Clear Clear Clear Clear
Kinematic viscosity@40 0C 46.1 46.7 47.16 46.6 46.8 45.7
Total acid no., mg KOH/g 0.19 0.17 0.14 0.18 0.16 0.24
RPVOT, minutes 580 1160 1450 1170 1410 1350
POT, % weight 0.27 0.18 0.18 0.17 0.15 0.16
SRV, coefficient of friction 0.145 0.13 0.11 0.125 0.115 0.12
EHD film thickness, nm 140 139 140 139 140 139
Wear scar dia, mm 0.40 0.40 0.40 0.45 0.45 0.45
Remarks poor in RPVOT life&inferior in POT moderate RPVOT life superior RPVOT life moderate RPVOT life good RPVOT life & lower coefficient of friction good RPVOT life

Example 7 to 12: Table 1B
Components Example -7 Example-8 Example-9 Example-10 Example-11 Example-12
SN base 98.639 -- -- -- -- --
API Group II -- 58.339 -- -- 50.289 40.689
API Group III -- -- 67.588 -- -- --
API Group IV -- -- -- 38.339 -- --
API Group V -- 40.000 30.000 60.000 45.000 55.000
Additive 1 0.050 0.800 1.400 0.800 3.000 0.800
Additive 2 0.500 0.050 0.500 0.500 0.800 2.500
Additive 3 0.300 0.300 0.001 0.300 0.300 0.300
Additive 4 0.500 0.500 0.500 0.050 0.600 0.700
Additive 5 0.001 0.001 0.001 0.001 0.001 0.001
Additive 6 0.010 0.010 0.010 0.010 0.010 0.010
Total 100.000 100.000 100.000 100.000 100.000 100.000
Properties Example -7 Example-8 Example-9 Example-10 Example-11 Example-12
Appearance Clear Clear Clear Clear Clear Clear
Kinematic viscosity@40 0C 46.2 46.5 45.3 46.5 46.9 45.1
Total acid no., mg KOH/g 0.15 0.14 0.15 0.18 0.17 0.21
RPVOT, minutes 1280 540 1350 1450 1680 910
POT, % weight 0.28 0.20 0.21 0.19 0.23 0.18
SRV, coefficient of friction 0.135 0.12 0.14 0.12 0.115 0.12
EHD film thickness, nm 137 140 142 139 138 140
Wear scar dia (wsd), mm 0.45 0.40 0.40 1.60 0.40 0.40
Remarks inferior film thickness & coefficient of friction poor RPVOT life inferior coefficient of friction in SRV poor antiwear property in wsd superior RPVOT life but inferior in POT lower
RPVOT

Example 13 to 18: Table 1C
Components Example-13 Example-14 Example-15 Example-16 Example-17 Example-18
API Group II 50.389 58.289 -- -- 51.789 41.889
API Group III -- -- 62.879 -- -- --
API Group IV -- -- -- 37.939 -- --
API Group V 46.000 40.000 35.000 60.000 45.000 55.000
Additive 1 1.000 0.800 1.100 0.800 1.500 --
Additive 2 0.800 0.100 0.500 -- 0.800 --
Additive 3 1.200 0.300 0.010 0.300 -- 0.300
Additive 4 0.600 0.500 0.500 -- 0.600 1.200
Additive 5 0.001 0.001 0.001 0.001 0.001 0.001
Additive 6 0.010 0.010 0.010 0.010 0.010 0.010
Additive 7 -- -- -- 0.700 -- 0.800
Additive 8 -- -- -- 0.250 -- --
Additive 9 -- -- -- -- -- 0.800
Additive 10 -- -- -- -- 0.300 --
Total 100.000 100.000 100.000 100.000 100.000 100.000
Properties Example-13 Example-14 Example-15 Example-16 Example-17 Example-18
Appearance Clear Clear Clear Clear Clear Clear
Kinematic viscosity@40 0C 46.9 46.5 46.3 46.3 45.3 45.9
Total acid no., mg KOH/g 0.24 0.14 0.17 0.18 0.19 0.23
RPVOT, minutes 1720 840 1350 1710 1440 980
POT, % weight 0.26 0.20 0.21 0.18 0.20 0.26
SRV, coefficient of friction 0.11 0.12 0.12 0.115 0.115 0.12
EHD film thickness, nm 138 140 141 139 138 140
Wear scar dia, mm 0.40 0.40 0.40 0.40 0.40 0.60
Remarks superior RPVOT life but inferior in POT poor RPOVT life moderate RPVOT life superior RPVOT life moderate RPVOT life Lower RPVOT life & inferior in POT

Phase – 1: Laboratory Evaluation
The energy efficient air compressor oil (Composition of Example 3 of Table 1A) is evaluated against DIN 51506 VDL (VG 46) specifications. For comparison, genuine compressor oil (VG 46) available from one of the leading compressor manufacturer’s OEMs 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, high temperature oxidation tests such as Pneurop Oxidation Test (POT as per DIN 51352 Part 2), Rotating Pressure Vessel Oxidation test (RPVOT as per ASTM D 2272) and IP 280 oxidation tests were conducted on test oils.

Physico-chemical properties:
Table – 2 provides the physico-chemical data on energy efficient (EE) compressor oil (VG 46) vis-à-vis reference oil (VG 46). The kinematic viscosity as determined by ASTM D 445 in mm2/s is in accordance with viscosity grade 46 and viscosity index is of 106. The energy efficient lubricant composition has pour point as (-) 27°C which is indicative of its low temperature properties and its suitability for low temperature application. The composition according to the present invention also has low foaming and air release value in comparison to reference oil. The flash point as determined by ASTM D 92 is more than 200°C suggesting its suitability for higher discharge temperature application. The composition is having excellent demulsibility characteristics allowing better water separation characteristics. The proposed composition separates water in 15 minutes as measured according to ASTM D 1401. The poor demulsibility of the compressor oil causes sludge, corrosion / rust formation, clogging of the filter, reduced lubricant performances and shortening of oils’ life.

Performance of Test oils in High temperature Oxidation Tests:
Ageing characteristics in presence of iron (III) oxide as per Pneurop oxidation test (POT) is conducted at 200 ºC for 24 hours to assess the carbon forming tendency and viscosity percentage change of aged oils under the specified test conditions as per DIN 51352 Part 2. The aged oils after POT test showed carbon residue formation of 0.18 % wt and rise in kinematic viscosity @ 40 ºC of 1.30% over the reference oil having carbon residue formation of 1.79 % wt and rise in kinematic viscosity @40 ºC of 13.7 %, which is indicative of suitability of the energy efficient compressor oil in the extended running operation.

The compressor lubricant composition demonstrates excellent oxidation stability as measured according to ASTM D 2272 with a RPVOT life greater than the 1000 minutes indicating thereby superior oxidation life of the energy efficient compressor oil in comparison to the reference oil. As per IP 280 oxidation procedure the TOP value (total oxidation product, % by mass) of energy efficient compressor oil is 0.076 in comparison to the 0.23 for the reference oil.

Table 2: Test data of Reference oil (VG 46) genuine oil from leading compressor OEM &
Energy Efficient (EE) Compressor oil (VG 46)

No.
Property
Method
Unit Reference oil
(VG 46) EE
Compressor oil (VG 46)
Viscosity class ISO VG ISO 6743 -- 46 46
1 Density at 15 ºC ISO 3675 g/cm3 0.8803 0.8780
2 Viscosity at 40 ºC ASTM D445 mm2/s 46.45 47.16
3 Viscosity at 100 ºC ASTM D445 mm2/s 6.95 7.03
4 Pour point ASTM D 97 ºC (-) 27 (-) 27
5 Viscosity Index ASTMD2270 -- 106 106
6 Flash point, COC, ºC ASTM D 92 ºC 233 233
7 Total acid number, (TAN) ASTM D974 mg KOH/g 1.15 0.14
8 Demulsibility @ 54 ºC ASTMD1401 minutes 40-37-3 (15) 40-37-3 (15)
9 Rust test, Method `A’ ASTM D665 Pass/Fail Pass Pass
10 Rust test, Method `B’ ASTM D665 -- Pass Pass
11 Antioxidant test, Total Oxidation Product (TOP) IP 280 % 0.230
0.076
12 Pneurop Oxidation test (POT)
- CCR, % wt.
- % change in
KinematicViscosity
@ 40 ºC DIN 51352 Part 2
% weight
%

1.79
13.7

0.18
1.30

13 Four ball Weld load IP 239 Kgs. 180 180
14 Four ball Wear Scar Dia ASTM
D 4172 mm 0.40 0.40

Phase – 2: Evaluation in Tribological Tests:
In order to compare the anti-frictional performance of energy efficient compressor oil with that of reference compressor oil, weld load and wear scar dia (WSD) done as per IP 239 & ASTM D 4172 test methods (Table-1A, 1B, 1C). Energy efficiency of the energy efficient compressor 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 17 % approximately over the reference compressor oil.

The optical 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 30N with variable rolling speed of 0 to 4 meter per second with the increment of speed of 100 mm per second for test duration of one hour. The EHD film thickness of the energy efficient compressor oil was more or less similar, however traction coefficient was found comparatively lower than reference oil.

In order to validate the laboratory findings, energy efficientcompressor oil was evaluated in the Screw Air Compressor in comparison to reference oil for the duration of 1000 hours of operation in identical conditions.

Details of Single stage Rotary Screw Air Compressor:
Make : Atlas Copco
Model : GA 45
Full load current : 83 amps
Voltage : 415 volts
Frequency : 50 Hz
Motor rating : 45 kW
Refrigerated Air Dryer : For removal of water from air
Running hours : 1000 hours

Phase – 3: Field Evaluation:
In order to do a one to one comparison of the energy efficiency of two oils, a compressor of a standard make used in industry was run under constant duty cycle over a continuous 1000 hour period in a fixed loading cycle to unloading cycle ratio of 2:1. A loading cycle is when the compressor was compressing the air to the desired pressure, and the unloading cycle is when the compressor was rotating without any compression in progress. This was achieved by continuous forced venting of the air being compressed.

This test was done first over a 1000 Hours period with EE Compressor oil and subsequently with the reference oil. After a 1000 Hour comparison was completed between the two oils, the oils were repeated back to back again over a 1000 hour period to verify the comparison between the oils. The following parameters were logged during this period

1) Energy Consumption: using Electronic Energy meter - to measure
• Cumulative Energy Consumption
• Instantaneous values at specified intervals of time
2) Hour Meter: To measure running hours

The efficiencies in terms of the reduction in power consumed to compress the same quantity of air were taken the criteria. Hence,compressor was operated with fixed ratio of loading and unloading cycles and monitoring was done during the entire test period.

The back to back study conducted each of test oil for the period of 1000 hours in the rotary screw air compressor under identical conditions. The compressor was hooked with electronic energy meter to measure the energy consumption, hour meter to measure the total running hours. The Fluke make energy analysis equipment was used for instantaneous energy consumption and traces were taken over 10 minute intervals with high speed data acquisition. The compressor were run with fixed ratio of loading & unloading cyclesby using constant air venting to enable one to one energy consumption in the identical operating conditions. The ratio of loading & unloading cycles was kept in the ratio of 2:1. The sequence of evaluation was to run the EE compressor oil for 1000 hours and take the energy consumption, run the compressor with reference oil for 1000 hours and measure the energy consumption, run again the EE compressor oil for 1000 hours and take the energy consumption and run back to back with reference oil for 1000 hours and take the energy consumption. The average energy consumption was recorded for each of the oils. The instantaneous energy consumption at different point of time was also recorded.

The used oil samples were collected for checking the % change in kinematic viscosity, change in total acid number and generation of wear metals.

The summary of energy consumption of energy efficient compressor oils in comparison to the reference oil is provided in the Table – 3;

Table - 3: Power consumptions on reference oil &
Energy Efficient (EE) Compressor oil in the Screw Air Compressor

Average power consumption (KWh)
in First study Average power consumption (KWh)
in the back to back study
Description Reference
oil EE
Compressor
oil Description Reference
oil EE Compressor oil
Cumulative energy meter reading, KWh 46472.0 44767.8 Cumulative energy meter reading, KWh 42641.0 40874.0
Average power consumption in 1000 hours, KW 46.47 44.77 Average power consumption in 1000 hours, KW 42.64 40.87
Power savings, % -- 3.66 Power savings, % -- 4.15

The superior properties of the energy efficient compressor oil composition in terms of oxidation life is indicated with the lower rise in kinematic viscosity rise of used oil samples drawn after 1000 hours of operation with no abnormal change in total acid no and wear metals (Table – 4).

Table - 4: Used oil analysis results of reference oil &
Energy Efficient (EE) Compressor Oil collected from Rotary Screw Air Compressor

No.
Property
Method First study
(After 1000 hours) Back to back study
(After 1000 hours)
Reference oil EE
Compressor oil Reference oil EE Compressor oil
1. % increase in kin. viscosity @ 40 ºC, cSt D 445 (+) 13.49 (+) 1.20 12.51 (+) 3.51
2. Change in TAN, mg KOH/gm D 974 (-) 0.73 (+) 0.09 (-) 0.61 (+) 0.10
3. Wear metals (after 1000 hrs)
- Fe.
- Cr, Ni, Al, Cu, Si ICAP

1
<1

< 1
< 1

1
< 1

< 1
< 1

Benefits of the energy efficient compressor oil:
It has been concluded that by switching over with energy efficient compressor oil in a screw air compressor, an annual saving of INR 68,000/- approximately is expected taking into account the average power saving of 3.9% after considering the cost of the power @ INR 6.50 per KWh. (Table – 5)

Table - 5: Cost Benefit Analysis of Energy Efficient Compressor Oil
Description Screw Air Compressor
Average Power Consumption in Screw Air Compressor with Genuine oil, KW 44.6
Power consumption in one year (considering 20 hrs. operation in a day & 300 working days in a year), KWh 44.6 x 20 x 300 = 2,67,600
Power savings, % 3.9
Total power savings, KWh 10,436
Expected benefit @ INR 6.50 per KWh, in Rupees 67,834
Total benefit expected from one Compressor, in Rupees Rs. 67,834 or Rs.68,000/- Approx.

The important outcome of the trial on energy efficient compressor oil is as follows:
• The high performance compressor oil possess adequate viscometrics, superior viscosity index, antirust & anticorrosive properties with energy efficiency and load bearing capability
• Energy efficient compressor oil provided excellent lubrication to various moving parts of compressor with no abnormal functionalities observed
• Used oil samples collected at different intervals and evaluated for % change in Kinematic Viscosity @ 40 ºC, which showed no abnormal rise in viscosity, minimal change in TAN & with no abnormal build-up of wear metals
• The energy efficiency is to the tune of around 3.0 to 4.5 % in comparison to reference oil
• The energy efficient compressor oil composition would provide the enhancement in the life over reference oil as well as increased productivity and reduction in down time

An important benefit emerging out is the development of energy efficient high performance compressor oil, which is having extreme synergism between the chosen additive systems. The composition showed excellent performance with 3.0 to 4.5 percent energy efficiency over reference oil (genuine oil from leading compressor OEM) in Rotary Screw Air Compressor.

We Claim:

1. A compressor oil additive composition comprising:
(a) a polyisobutylene based polymer,
(b) a rust and oxidation inhibitor,
(c) a friction modifier, and
(d) a sulphur and phosphorus containing antiwear component.

2. The composition as claimed in claim 1, wherein the ratio of polyisobutylene based polymer : rust and oxidation inhibitor : friction modifier : sulphur and phosphorus containing antiwear is 2-40 : 4-24 : 1-22 : 2-30.

3. The composition as claimed in claim 1, wherein the rust and oxidation inhibitor is ashless rust & oxidation inhibitor additive system containing combination of additives of alkyl naphthylamine, mixture of triazoles of N,N-bis (2ethylhexyl)-4-methyl-1H-benzotrizole-1-methylamine and N,N-bis(2-ethylhexyl)-5-methyl-1H-benzotriazole-1methylamine, amine phosphate, acylsarkosinate, sterically hindered phenol, acid salt of 4-nonylphenoxy compounds, alkylated diphenylamines or mixture of aryl triazole, alkyl amines, aryl amine, alkyl alkyleneoxycarboxylic amine or mixtures of sterically hindered phenol, alkylated diphenyl amines, mixture of derivatives of triazoles / thiadiazoles.

4. The composition as claimed in claim 1, wherein the friction modifier is ashless surface active friction modifier additive, selected from array of boron containing, phosphorus containing, polymerised esters selected from amide borated ester or mixture of high molecular weight phenolic antioxidants or alkyl / aryl phosphates, phosphites, phosphonates or polymer based natural / synthetic fatty acids and polyols, or mixture thereof.

5. The composition as claimed in claim 1, wherein the sulphur and phosphorus containing antiwear component is selected from alkyl dithiophosphate or dialkyldithiophosphate, where alkyl group is from C1 to C14, the sulphur and phosphorus moieties are in the ratio of about 2:1. The phosphates are alkyl or aryl phosphates, where alkyl group is having carbon chain length of C1 to C18; ashless alkyl carbamates having sulphur and nitrogen content in the ratio of 5:1; ashless amine phosphate containing mixture of amine phosphates and having multifunctional performance with extreme pressure / antiwear and anti rust properties and phosphorus and nitrogen content in the ratio of about 2:1.

6. The composition as claimed in claim 1, wherein the composition further comprises a demulsifier and a defoamer.

7. The composition as claimed in claim 6, wherein 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.

8. An energy efficient compressor oil composition comprising:
(a) a polyisobutylene based polymer,
(b) a rust and oxidation inhibitor,
(c) a friction modifier,
(d) a sulphur and phosphorus containing antiwear component, and
(e) a mixture of severely hydrotreated / hydro-processed / iso-dewaxed base stocks and alkylated naphthalene, or mixture of synthetic bases and alkylated naphthalene or alkylated naphthalene bases or mixtures thereof.

9. The composition as claimed in claim 1, wherein the polyisobutylene based polymer is 0.10 to 2.0 percent by weight of the composition, the rust & oxidation inhibitor is 0.20 to 1.2 percent by weight of the composition, the friction modifier is 0.05 to 1.1 percent by weight of the composition, and the sulphur and phosphorus containing antiwear component is 0.10 to 1.50 percent by weight of the composition.

10. The composition as claimed in claim 8, wherein; the rust and oxidation inhibitor is ashless rust & oxidation inhibitor additive system containing combination of additives of alkyl naphthylamine, mixture of triazoles of N,N-bis (2ethylhexyl)-4-methyl-1H-benzotrizole-1-methylamine and N,N-bis(2-ethylhexyl)-5-methyl-1H-benzotriazole-1methylamine, amine phosphate, acylsarkosinate, sterically hindered phenol, acid salt of 4-nonylphenoxy compounds, alkylated diphenylamines or mixture of aryl triazole alkyl amines, aryl amine, alkyl alkyleneoxycarboxylic amine or mixtures of sterically hindered phenol, alkylated diphenyl amines, mixture of derivatives of triazoles / thiadiazoles; the friction modifier is ashless surface active friction modifier additive, selected from array of boron containing, phosphorus containing, polymerised esters selected from amide borated ester or mixture of high molecular weight phenolic antioxidants or alkyl / aryl phosphates, phosphites, phosphonates or polymer based natural / synthetic fatty acids and polyols, or mixture thereof; or succinic acid ester, succinic ester amide, mannich base, or mixtures thereof; and the sulphur and phosphorus containing antiwear component is selected from alkyl dithiophosphate or dialkyldithiophosphate, where alkyl group is from C1 to C14, the sulphur and phosphorus moieties are in the ratio of about 1:2, the phosphates are alkyl or aryl phosphates, where alkyl group is having carbon chain length of C1 to C18; ashless alkyl carbamates having sulphur and nitrogen content in the ratio of 5:1; ashless amine phosphate containing mixture of amine phosphates and having multifunctional performance with extreme pressure / antiwear and anti rust properties and phosphorus and nitrogen content in the ratio of about 2:1.

11. The composition as claimed in claim 8, wherein the mixture of severely hydrotreated / hydro-processed / iso-dewaxed base stocks and alkylated naphthalene, or mixture of synthetic bases and alkylated naphthalene or alkylated naphthalene bases 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.

12. The composition as claimed in claim 8, wherein the composition further comprises a demulsifier and a defoamer.

13. The composition as claimed in claim 12, wherein the demulsifier is selected from array of condensed polymeric alcohols, esters of fatty acids, fatty alcohols alkoxylated with alkylene oxides, or mixtures thereof and thedefoamer is selected from array of highly viscous organic polymer, like dimethyl polycyclohexane, polyacrylates.

14. The composition as claimed in claim 10, wherein said friction modifier is an organic friction modifier,preferably boron based ester, in an amountof 0.01 to 0.50 percent by weight of the composition.

15. The composition as clamed in claim 10, wherein said ashless antiwear component is alky (C4 – C14) dithiophosphate, in an amount of 0.05 to 1.0 percent by weight of the composition.

16. The composition as claimed in claim 10, wherein said polyisobutylene based polymer is in an amount of 0.50 to 1.0percent by weight of the composition.

17. The composition as claimed in claim 10, wherein said rust & oxidation inhibitor is in an amount of 0.20 to 1.0 percent by weight of the composition.

18. The composition as claimed in any of the preceding claims 8 to 17, wherein said composition is used for enhancing efficiency of a compressor.

19. The composition as claimed in any of the preceding claims 8 to 17, wherein the use of said composition in a rotary screw air compressor providesa power savings to the tune of 3.0 to 4.5 %.

Dated this the 9th day of October, 2013

NOVEL COMPOSITION OF ASHLESS ENERGY EFFICIENT COMPRESSOR OIL, AND COMPRESSOR OIL ADDITIVE COMPOSITION
Abstract Of The Invention
The present invention discloses a novel composition of ashless energy efficient compressor oil. The compressor oil composition of the present invention provides energy savings with excellent thermal and oxidation stability and reduced carbon deposits.