DESC:FIELD OF THE INVENTION:

The present invention relates to a calcium-lithium complex grease composition having properties such as a combination of higher dropping points, good mechanical stability and good yield or consistency with low soap content. More particularly, the present invention relates to a calcium-lithium complex grease composition and process for preparing the same.

BACKGROUND OF THE INVENTION:

Complex greases especially lithium complexes have been known for many decades and it has been manufactured for quite some time using different base oil stocks and complexing agents. These greases have specific characteristics including higher dropping point, better mechanical and/or shear stability, oxidation resistance, etc. All of these characteristics in combination play an important role in lubricating life of the greases in high temperature applications.

Lithium complex greases have been successfully used for the lubrication of traction motor bearings, automotive disc brake wheel bearings and the like, particularly for automobiles and locomotives. For wide applications, bearings are required to operate for a long period of time without maintenance at temperatures as high as 130°C.

Alkaline earth metal greases have been reported extensively and in particular calcium base greases have their reported in the prior arts i.e., US patents 2607735 and 2831811. Among alkaline earth metal greases, preparing calcium complex greases using acetic acid have also been described in literature i.e., US patents 2197263, 2607735, 2842495, 2861048, 30l8249, 3068175, 3088912, 3186944, 3202606, 3466245 and 3907692.

US patent 2417428 describes the complex greases of calcium, sodium, strontium, lithium and other metals are described using acetic acid as complexing agent.

Russian patent RU2529854 describes the calcium complex grease containing calcium stearate and calcium acetate is reported for heavily loaded rolling bearings.

PCT application WO2013079559 A1 describes the calcium complex greases having dropping points >260 °C and better heat resistance are reported using substituted or unsubstituted straight chain higher monocarboxylic fatty acid having 18 to 22 carbon atoms, an aromatic monocarboxylic fatty acid having a substituted or unsubstituted benzene ring and a straight chain saturated lower monocarboxylic fatty acid having 2 to 4 carbon atoms. In patents CN 101935573 and CN 101921651, calcium complex thickeners having low surface hardening are reported. In patent, JP 2009249419, calcium complex greases having dropping point =300 °C are reported using calcium salts of terephthalic acid and stearic acid. Despite having inherent extreme pressure properties, better shear stability and higher dropping points (>250 °C), calcium complex greases are not much in use due to certain drawbacks such as storage hardening, wide batch to batch variations, poor pumpability as described in prior arts [US patents 3907692 and 3466245].

Mixed soap grease compositions especially those of alkaline earth metal soaps existed in the art for many years. Among alkaline earth metal soaps, calcium soap is widely reported in prior art in combination with other alkali or alkaline metal soap.

US Patent US2929782A discloses that water sensitivity of the calcium 12-hydroxystearate grease was completely overcome by physically combining it with a minor amount of the lithium soap. US patent 3574111 describes aluminum complex greases having improved mechanical stability and extreme pressure properties by adding monohydrated alkaline earth metal salts. US Patent 2641577 contains a detailed description of the composition and preparation of lithium-calcium grease compositions in which mole ratios of the lithium soap to the calcium soap may vary between about 2:1 to 8:1, the preferred ratio being about 3:1 to 6:1. US patent 2908645, mixed lithium and calcium grease having lithium soap as dominant was made in-situ. Individual soaps were also made and then blended together by thorough mixing or by the use of a suitable homogenizer or grease mill. The resultant greases have excellent water emulsion stability and long lubrication service. US patents 3891564 and 5015403 lithium-calcium greases having lithium soap as dominant were made by in-situ process and these are reported to have better water resistance and shear stability.

US patent 2923782 describes physical combinations of lithium and calcium stearates and a dropping point of 149 °C was achieved with 20:80 ratio of lithium and calcium soaps. US patent 2719122, complex greases having better water and oxidation resistance were made by adding dry powdered alkaline earth metal salts of low molecular weight carboxylic acids to lithium soap of fatty acids. Complex grease having a dropping point of 221 °C was made by adding 4% of dry pre-formed calcium acrylate. US patent 4483776, lithium complex greases having calcium acetate in a certain weight ratio were reported and these greases were found suitable over a wide range of temperatures.

Recently, there is regenerated interest in non-lithium greases and their processing due to higher costs of lithium hydroxide as it is extensively used in lithium ion batteries, moreover pressurized reactors and high process temperatures (>220 °C) are required for manufacturing lithium complex greases. Patent application 2010/0048436 A1, patents US8603958, EP2154229A2, discusses calcium/lithium greases having a higher calcium fraction and complexing agents and its use in encapsulated constant velocity shafts.

Patent application, WO2014096258, discloses calcium complex thickeners having minor quantity of lithium soap. Mixtures of higher monocarboxylic fatty acid, lower monocarboxylic fatty acid and aromatic monocarboxylic acid were used for saponification and resultant greases were found to have high dropping points, better shear and thermal stability. The mass ratio of lithium metal content to calcium metal content is between 0.3 to 10.0 parts per 100. When the mass ratio of lithium metal content to calcium metal content is more than 10, softer greases with poor storage stability were obtained.

In present invention, calcium-lithium complex grease compositions and their manufacturing in which the mass ratio lithium metal content to calcium metal content can be varied, while still maintaining or achieving better performance in comparison to conventional calcium or lithium complex greases.

OBJECTIVES OF THE INVENTION:

It is the primary objective of the invention to provide calcium-lithium complex grease composition having superior properties such as a combination of higher dropping points, good mechanical stability and good yield or consistency with low soap content.

It is the further objective of the invention to provide calcium-lithium complex grease composition having tailor made dropping points which can be made in open kettle using low temperature energy efficient processes.

It is also another objective of the invention to provide the process in which two stage addition of complexing agents and hydrated lime which leads to complex greases having dropping points between 220 to 280 °C.

SUMMARY OF THE INVENTION:

The above discussed prior arts disclose in-situ production of calcium complex greases; however these greases are reported to have storage hardening and wide batch to batch variations. The present invention relates to a calcium-lithium complex grease composition having properties such as a combination of higher dropping points, good mechanical stability and good yield or consistency with low soap content. As per this invention, calcium-lithium complex grease composition having tailor made dropping points can be made in open kettle using low temperature energy efficient processes. Present invention discloses a process in which two stage addition of complexing agents and hydrated lime which leads to complex greases having dropping points between 220 to 263°C.

Accordingly, the present invention relates to a calcium-lithium complex grease composition comprising:
75.0 to 90.0 weight % base oil;
6.0 to 18.0 weight % saponifiable material;
0.5 to 2.5 weight % hydrated lime;
0.2 to 2.0 weight % lithium hydroxide monohydrate;
1.0 to 5.0 weight % one or more complexing agent;
0.05 to 0.5 weight % water; and
0.2 to 5.0 weight % acidic structure modifying agent,
wherein weight percentage being relative to the total weight of the composition.

According to the main embodiment, the present invention relates to a process for preparing calcium-lithium complex grease composition, the process comprising:
(i) adding and mixing a saponifiable material, a first portion of complexing agent, and water in a first portion of a base oil to obtain a first reaction mass;
(ii) adding and reacting a first portion of a hydrated lime to the first reaction mass with continuous mixing to obtain a second reaction mass;
(iii) mixing and heating the second reaction mass to a temperature in the range of 120 to 125 °C and adding remaining second portion of the complexing agent and followed by addition of a lithium hydroxide monohydrate and heating the mass to 135 to 145 °C and maintained at this temperature for a 1-1.5 hours to obtain a third reaction mass;
(iv) mixing and heating the third reaction mass and adding an acidic structure modifying agent to obtain a fourth reaction mass;
(v) adding and reacting remaining second portion of the hydrated lime to the fourth reaction mass to obtain a fifth reaction mass; and
(vi) optionally dehydrating the fifth reaction mass and adding the remaining second portion of the base oil then optionally adding an additive and mixing the mass to obtain the calcium-lithium complex grease composition.

In one of the embodiment of the present invention, the calcium-lithium complex grease composition having dropping points 220-263 °C.

In another embodiment of the present invention, the calcium-lithium complex grease composition has a higher faction of calcium metal with percentage lithium content varying from 0 to 87 or preferably 9 to 87 with respect to 100% calcium content.

In still another embodiment of the present invention, the saponifiable material is selected from fatty acid, hydroxy-substituted fatty acid and their esters, hydrogenated castor oil and mixture thereof; wherein:
(a) the fatty acid is stearic acid, and
(b) the hydroxy-substituted fatty acid is l2-hydroxystearic acid.

In still another embodiment of the present invention, the amount of saponifiable material is in the range of 6.0 to 18.0 weight % being relative to the total ingredient used in preparing the composition.

In yet another embodiment of the present invention, the saponifiable material is reacted with 0.5 to 2.5 weight % hydrated lime, and 0.2 to 2.0 weight % lithium hydroxide monohydrate to make the calcium-lithium complex grease composition and weight percentage being relative to the total weight of the ingredient used in preparing the composition.

In yet another embodiment of the present invention, the hydrated lime is white fine powder having 65.0-70.0% calcium oxide content.

In another embodiment of the present invention, the hydrated lime is added in two portions:
first portion of the hydrated lime is added just after mixing the saponifiable material, water and first portion of the complexing agent in the base oil; and
second portion of the hydrated lime is added just after mixing structure modifying agent.

In yet another embodiment of the present invention, the lithium hydroxide monohydrate is having 56.0-57.0% lithium hydroxide content and full quantity of lithium hydroxide monohydrate is added just after adding and mixing remaining second portion of the complexing agent.

In still another embodiment of the present invention, the calcium-lithium complex grease composition is produced by adding and reacting hydrated lime in two portions, wherein
50.0 to 70.0 weight % quantity as first portion of total hydrated lime as oil slurry added to mixture of full quantity of the saponifiable material, the first portion of complexing agent and water in the first portion of base oil and slowly heating to a temperature in the range of 95 to 100 °C and maintained at this temperature with continuous stirring till frothing subsided; and
second remaining portion of the hydrated lime is added after reacting lithium hydroxide monohydrate and just after adding and mixing acidic structure modifying agent at a temperature in the range of 155 to 165 °C.

In yet another embodiment of the present invention, the calcium-lithium complex grease composition is produced by adding and reacting the complexing agent in two portions, wherein:
(i) first portion of the complexing agent is used in the process is in the range of 20 to 35 weight % quantity of total complexing agent;
(ii) second remaining portion of the complexing agent is used in the process is in the range of 65 to 80 weight % quantity of total complexing agent.

In yet another embodiment of the present invention, the calcium-lithium complex grease composition is produced by adding and reacting the base oil in two portions, wherein:
(i) first portion of the base oil is used in the process is in the range of 25 to 40 weight % quantity of total base oil; and
(ii) second remaining portion of the base oil is used in the process is in the range of 60 to 75 weight % quantity of total base oil.

In still another embodiment of the present invention, the complexing agent is selected from a short chain monocarboxylic acid, hydroxybenzoic acid, polycarboxylic complexing acid, boric acid, phosphoric acid and mixture thereof, wherein:
(a) short chain monocarboxylic acid is selected from acetic acid, propanoic acid, and butanoic acid; and
(b) polycarboxylic complexing acid is selected from adipic acid, sebacic acid, and succinic acid.

In still another embodiment of the present invention, the total amount of complexing agents is in the range of 1.0 to 5.0 weight % being relative to the total ingredient used in preparing the composition.

In yet another embodiment of the present invention, calcium-lithium complex grease composition is produced by incorporating and mixing acidic structure modifying agent at 150-155 °C and these must be added after reacting lithium hydroxide monohydrate and prior to addition of second portion of the hydrated lime.

In yet another embodiment of the present invention, the acidic structure modifying agent is produced by acidic thermal polymerization of organic fatty acids and acid value of the fatty acid is in the range of 30 to 150.

In still one embodiment of the present invention, the amount of acidic structure modifying agent is in the range of 0.2 to 5.0 weight % being relative to the total ingredient used in preparing the composition.

In still another embodiment of the present invention, the base oil is selected from petroleum based naphthenic oil, petroleum based paraffinic oil, synthetic base oil and the synthetic base oil is selected from polyalphaolefins (PAO), polyalkyl gycol (PAG), and alkylated aromatic.

In still another embodiment of the present invention, the total amount of base oil is added in the range of 75.0 to 90.0 weight % being relative to the total ingredient used in preparing the composition

In yet another embodiment of the present invention, the additive is selected from rust inhibitor, corrosion inhibitor, metal deactivator, metal passivator, anti-oxidant, extreme pressure additive, friction modifier, ant-wear additive, polymer, tackifier, dye, chemical marker and fragrance imparter.

In yet another embodiment of the present invention, the saponifiable material, first portion of complexing agent and water in base oil are added at a temperature in the range of 50 to 75 °C

In one of the preferred embodiment of the present invention, the calcium-lithium complex grease composition comprises the following steps:
(i) adding and mixing the base oil, saponifiable material, first portion of complexing agents, water in a grease making kettle and slowly heating to 75 °C to obtain the first reaction mass;
(ii) slowly adding the first portion of hydrated lime as oil slurry to the first reaction mass with continuous mixing and slowly heating the mass to 100 °C and maintained at this temperature with continuous stirring till frothing subsided to obtain a second reaction mass;
(iii) mixing and heating the second reaction mass to 120 to 125 °C and adding the remaining second portion of the complexing agent followed by addition of full quantity of lithium hydroxide monohydrate, heating the mass to 135 to 145 °C and maintained at this temperature for a certain time to obtain a third reaction mass;
(iv) mixing and heating the third reaction mass to 155 to 165 °C and adding and mixing an acidic structure modifying agent to obtain the fourth reaction mass;
(v) adding and reacting remaining second portion of hydrated lime for a certain duration to obtain the fifth reaction mass; and
(vi) adding the remaining quantity of base oil as cut back to the fifth reaction mass and cooling the mass and optionally adding the additive below 90 °C and homogenizing or milling the mass to obtain the calcium-lithium complex grease composition.

DETAILED DESCRIPTION OF THE INVENTION:
While the invention is susceptible to various modifications and alternative forms, specific embodiment thereof will be described in detail below. It should be understood, however that it is not intended to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternative falling within the scope of the invention as defined by the appended claims.

The following description is of exemplary embodiments only and is not intended to limit the scope, applicability or configuration of the invention in any way. Rather, the following description provides a convenient illustration for implementing exemplary embodiments of the invention. Various changes to the described embodiments may be made in the function and arrangement of the elements described without departing from the scope of the invention.

The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that one or more processes or composition/s or methods proceeded by "comprises... a" does not, without more constraints, preclude the existence of other processes, sub-processes, composition, sub-compositions, minor or major compositions or other elements or other structures or additional processes or compositions or additional elements or additional features or additional characteristics or additional attributes.

According to one of the preferred embodiment of invention, the present invention describes that the calcium-lithium complex greases are obtained having following ingredients by weight;
75.0 to 90.0% base oils,
6.0 to 18.0% saponifiable materials,
0.5 to 2.5% hydrated lime,
0.2 to 2.0 % lithium hydroxide monohydrate,
1.0 to 5.0% one or more complexing agents,
0.05 to 0.5% water, and
0.2 to 5.0% structure modifying agent.

According to one embodiment of the present invention, calcium-lithium grease is produced by combining saponifiable materials, appropriate amount of complexing agents, and water in certain quantity of base oil, heating and reacting with appropriate amount of hydrated lime in reactor with continuous stirring till frothing subside. When frothing subsided, mass temperature was gradually raised to a certain temperature and maintained for a certain duration. After a certain duration, remaining quantities of complexing agents were added, mixed and followed by addition of full quantity of lithium hydroxide monohydrate. Finally, mass temperature was raised to final process temperature and at this temperature, structure modifying agent was added and mixed. To the above mixture, remaining quantities of hydrated lime was added and reacted for a certain duration. Finally the mass was completely dehydrated and remaining base oils were added as cut back. The Mass was cooled below 90 °C, additives added, mixed and finally homogenized to get a smooth homogenous grease.

According to another embodiment of the present invention, calcium-lithium greases having dropping points 220-263 °C were made with a process involving maximum processing temperatures of 160-165 °C thus saving time and expense associated with higher process temperatures reported in prior art methods of lithium complex greases.

When greases are produced according to the present invention described herein, they have a higher fraction of calcium metal with respect to lithium metal and the developed compositions have dropping points in range of 220 to 263 °C. Other properties such resistance to shear, oil bleed performance at higher temperature also improved in comparison to conventional lithium complex greases according to this invention. Softer or harder grades of greases may be produced by varying the thickener content.

In detailed embodiment of the present invention, saponifiable material refers to fatty acids, hydroxy-substituted fatty acids and their esters and their mixtures. Among saponifiable materials, l2-hydroxystearic acid, stearic acid, hydrogenated castor oil and their mixtures are most preferred. The amount of saponifiable material in embodiment of this invention can vary between 6.0% and 18.0%. Preferably, the amount of saponifiable material in (National Lubricating Grease Institute) NLGI grade 2 grease is between 7.0 to 12.0% and most preferably between 8.5 to 10.0%.

In detailed embodiment of the present invention, saponifiable material is reacted with 0.5 to 2.5% hydrated lime, and 0.2 to 2.0% lithium hydroxide monohydrate to make complex greases. Hydrated lime used in embodiments of this invention is commercially available white fine powder having minimum 65.0% calcium oxide content. As per invention, hydrated lime was added in two portions: one just after mixing saponifiable material, water and appropriate amount of complexing agents in base oil; second portion was added just after mixing acidic structure modifying agent. Lithium hydroxide monohydrate used in embodiments of present invention is having minimum 56.0% lithium hydroxide content and full quantity of lithium hydroxide monohydrate was added just after adding and mixing remaining quantities of complexing agents.

According to one embodiment of the present invention, calcium-lithium complex greases were produced by adding and reacting hydrated lime in two portions. 50.0 to 70.0% quantity of total hydrated lime as oil slurry added to mixture of full quantity of saponifiable material, a portion of complexing agents and water in base oil and slowly heated the mixture to 100 °C and maintained at this temperature with continuous stirring till frothing subsided. Second portion of hydrated lime was added at 155 to 165 °C after reacting lithium hydroxide monohydrate and just after adding and mixing acidic structure modifying agent.

According to the present invention, total amount of complexing agents is between 1.0 to 5.0%, preferably 2.0 to 4.5% and most preferably 2.5 to 3.5%. Short chain monocarboxylic acids are acetic acid, propanoic acid, hydroxybenzoic acids or their mixtures. Suitable polycarboxylic complexing acids are adipic acid, sebacic acid, boric acid, phosphoric acids and their mixtures.

According to one embodiment of the present invention, calcium-lithium complex greases are produced by incorporating and mixing acidic structure modifying agent at 150-155 °C and these must be added after reacting lithium hydroxide monohydrate and prior to addition of second portion of hydrated lime. Acidic structure modifying agent used in this invention can be produced by acidic thermal polymerization of organic fatty acids and acid value of these agents is between 30 to 150 and preferably 50 to 100 and most preferably 70 to 90. The amount of acidic structure modifying agent in embodiment of this invention can vary between 0.2 to 5.0% and preferably 0.5 to 2.0%.

Any commonly used oil, such as petroleum based naphthenic and paraffinic are well known in prior arts and can be used according to present invention. Synthetic base oils such as polyalphaolefins (PAO), polyalkyl gycol (PAG), alkylated aromatics may also be used for making greases. In some cases, base oils having less solvency can adversely affect the thickening efficiency leading to softer greases and this will be easily understood by those having ordinary skill of grease making. In some cases, some oils such diesters and polyol esters should be added after saponification to avoid interaction with alkaline/alkali hydroxides. Total amount of base oil added will be typically between 75.0 to 90.0% and most probably 85.0 to 90.0% for NLGI grade 2 grease.

Other performance additives described in prior arts may also be added to grease embodiments described in the invention. Such additives can include rust and corrosion inhibitors, metal deactivators, metal passivators, anti-oxidants, extreme pressure additives, friction modifiers, ant-wear additives, polymers, tackifiers, dyes, chemicals markers and fragrance imparters.

The compositions according to invention are preferably made as described herein. This process comprises the following steps: (1) adding and mixing an appropriate amount of base oil in a suitable grease making kettle, saponifiable material, first portion of complexing agents, water and slowly heating to 75 °C; (2) slow addition of first portion of hydrated lime as oil slurry with continuous mixing; (3) and continue to mix while slowly heating the mass to 100 °C and maintained at this temperature with continuous stirring till frothing subsided; (4) mixing and heating the mass to 120 to 125 °C and adding remaining quantities of complexing agents; (5) adding full quantity of lithium hydroxide monohydrate, heating the mass to 135 to 145 °C and maintained at this temperature for a certain time; (5) mixing and heating the mass to 155 to 165 °C and adding and mixing structure modifying agent; (6) adding and reacting remaining quantities of hydrated lime for a certain duration; (8) cut back with remaining quantity of base oil and cooling the mass; (9) adding the performance additives below 90 °C if desired (10) homogenization/milling the grease to obtain final grease.

Certain steps of the process are not critical for obtaining preferred grease composition. The temperature at which saponifiable material, first portion of complexing agents and water in base oil were added is not critical, but preferred that they may be added below 75 °C. Addition sequence of saponifiable material, first portion of complexing agents and water is also not critical with respect to each other.

Although the examples provided herein fall in NLGI grade 2, it should be further understood that the scope of this present invention includes all the NLGI consistency grades harder and softer than NLGI 2. As used herein, quantities of ingredients by parts by weight during manufacturing process, even though some ingredient such as water may not be present in final grease.
Those of ordinary skill in the art will appreciate upon reading this application, including examples contained herein, that modifications and alterations to composition and methodology for making composition may be within the scope of invention.

EXAMPLE-1

A NLGI grade 2 calcium-lithium complex grease was prepared according to invention as follows: 30 parts by weight of Group I paraffinic base oil (95 cSt at 40 °C) was charged to mixing vessel followed by 11.0 parts by weight of 12-hydroxystearic acid, 0.6 parts of weight of adipic acid (first portion) and 0.1 parts by weight of water and then heated to 75 °C with continuous stirring. 0.9 parts of hydrated lime (first portion) was added slowly to above mixture as oil slurry (50% in Group I, 95 cSt paraffinic base oil) and slowly heated the mixture to 100 °C and maintained at this temperature with continuous stirring till frothing subsided. When frothing subsided, mass temperature was raised to 125 oC, 1.4 parts of adipic acid (second portion) added and mixed for 15 minutes. Temperature of mass was raised to 140 oC, 0.9 parts of lithium hydroxide monohydrate added as oil slurry (50% in Group I, 95 cSt paraffinic base oil) and mass maintained at this temperature for one hour with continuous stirring. Mass heated to 165 oC, 1.5 parts of structure modifying agent (acid value 100) added and mixed for 15 minutes, followed by 0.45 parts of hydrated lime (second portion) as oil slurry (50% in Group 1, 95 cSt paraffinic base oil). After this, the mixture was maintained at 165 oC with continuous stirring for one hour under closed lid. After complete dehydration with vacuum suction, adjust mixture acidity between 0.2% as free oleic acid. Cut back the mass with 53.25 parts of Group I paraffinic base oil having viscosity of 95 cSt at 40 °C base oil. The heating was removed and cold oil was circulating to speed up cooling. When cooled to 90 oC, grease was passed through homogenizer and penetration was adjusted according to known methods to get a smooth homogenous product. Example-2 & 3 were made using same equipments, raw materials, and manufacturing process as the Example-1, except varying the thickener content while keeping hydrated lime/lithium hydroxide monohydrate ratio constant to get calcium-lithium greases of different NLGI grades. Test results of these batches are given in Table-1.

Table-1

Components Example no.
1 2 3
12-Hydroxystearic acid, parts by weight 11.00 8.50 13.00
Adipic acid, parts by weight 1.45 1.12 1.71
Hydrated lime, parts by weight 1.50 1.15 1.77
Lithium hydroxide monohydrate, parts by weight 0.90 0.69 1.06
Water, parts by weight 0.10 0.10 0.10
Structure modifying agent, parts by weight 1.50 1.50 1.50
Group I paraffinic base oil (95 cSt at 40 °C), parts by weight 83.55 86.94 80.86
Calcium metal content/Lithium metal content 0.70/0.15 0.53/0.11 0.82/0.17
% Lithium content with respect to 100% Calcium content 20.96 20.96 20.92
Test Test Method Units Results
Adipic acid,
Second portion/First Portion - Percent 70/30 70/30 70/30
Penetration worked ASTM
D-217 mm/10 267 315 238
Change in penetration after 105X double strokes +28 +23 +32
Dropping Point ASTM
D-566 °C 255 252 259
Heat Stability at 100 °C for 30 hrs, Oil Separation, ASTM
D-6184 %wt. 1.5 3.2 1.2
Roll stability, 16 hrs, 25 °C, Change in penetration ASTM
D-1831 % 7.8 6.0 11.0
Cu Corrosion at 100 °C, 24 hrs IP-112 Rating Pass Pass Pass

According to one embodiment of invention, calcium-lithium complex grease having dropping points between 220 to 280 °C can be produced by incorporating complexing agent in two portions while during process. First portion of complexing agent was added prior to addition of first portion of hydrated lime while second portion of complexing agent added prior to addition of full quantity of lithium hydroxide monohydrate. By varying the percent ratio between two portions of complexing agents, dropping points of greases can be modified accordingly. As per invention greases having dropping point more than 250 °C can be made by keeping the percent ratio between second and first portions of complexing acids in the range 80/20 to 60/40 and most preferably between 75/25 to 65/35. Example-4 & 5 grease batches were made using same equipments, raw materials, amounts and manufacturing process as the Example-1, except changing the percent ratio between second stage and first stage portions of adipic acid as 75/25 and 55/45 respectively. Dropping point of Example-5 grease was found to be less than Example-1 & 4 greases while all other Test data was found to similar to Example-1 grease. Example-6 grease was made similar to Example-1 grease, except that the full quantity of adipic acid was added in first portion prior to addition of first portion of hydrated lime. Example-7 grease was made similar to Example-1 grease; except that the full quantity of adipic acid was added after addition of first portion of hydrated lime and prior to addition of full quantity of lithium hydroxide monohydrate. Dropping points of Example-6 & 7 greases were observed to be lower in comparison to Example-1, 4 & 5 greases, indicating significance of two portion addition of complexing acids while other test data was found to be similar as shown in Table-2.

Table-2
Test Test Method Units Examples
1 4 5 6 7
Adipic acid, Second portion/First Portion - Percent 70/30 75/25 55/45 100/0 0/100
Penetration worked ASTM D-217
mm/10 267 270 269 268 269
Change in penetration after 105X double strokes +28 +23 +32 +25 +25
Dropping Point ASTM D-566 °C 255 251 245 210 225

To evaluate the role of lithium hydroxide monohydrate, Example-8 grease was made using same equipments, raw materials and manufacturing process as the Example-1, except that no lithium hydroxide monohydrate was used. The dropping point of the grease in Example-8 was found to be 180 °C confirming role of lithium hydroxide monohydrate in enhancing dropping point. Three grease batches of grease (Example-9, 10 & 11) were made similar to Example-1 grease except using different quantities of a lithium hydroxide monohydrate added just after addition of second portion of complexing agent and prior to structure modifying agent and test data of these batches are given in Table-3. Test results indicate that 0.9 or more parts of lithium hydroxide monohydrate along with suitable quantity of complexing agent are sufficient to achieve dropping points more than 250 °C in NLGI 2 grade greases. All other test data of Example-8, 9, 10 & 11 greases were found to be similar.

Table-3
Components Example no.
8 9 10 11
12-Hydroxystearic acid, parts by weight 11.00 11.00 11.00 11.00
Adipic acid, parts by weight 1.45 1.45 1.45 1.45
Hydrated lime, parts by weight 2.44 1.93 1.43 0.70
Lithium hydroxide monohydrate, parts by weight 0.00 0.50 1.00 1.75
Water , parts by weight 0.10 0.10 0.10 0.10
Structure modifying agent, parts by weight 1.50 1.50 1.50 1.50
Group I paraffinic base oil (95 cSt at 40 °C), parts by weight 83.51 83.52 83.52 83.50
Calcium metal content /Lithium metal content 1.13/0 0.90/0.08 0.66/0.16 0.33/0.28
% Lithium content with respect to 100% Calcium content 0.00 9.05 24.43 87.34
Test Test Method Units Results
Adipic acid,
Second portion/First Portion - Percent 70/30 70/30 70/30 70/30
Penetration worked ASTM
D-217
mm/10 270 275 280 283
Change in penetration after 105X double strokes +26 +32 +28 +27
Dropping Point ASTM
D-566 °C 185 225 245 260

To evaluate the role of addition sequence of lithium hydroxide monohydrate, Example-12 grease was made similar to Example-1, except that full quantity of lithium hydroxide monohydrate was added along with first portion of hydrated lime. Another batch of grease (Example-13) was made similar to Example-1, except that full quantity of lithium hydroxide monohydrate was reacted initially with 12-Hydroxystearic acid prior to addition of first portion of complexing agent and first portion of hydrated lime. Dropping points of Example-12 & 13 greases were found to be significantly lower than Example-1, while other test data was found to be similar as shown in Table-4.

Table-4
Test Test Method Units Results
1 12 13
Adipic acid, Second portion/First Portion - Percent 70/30 70/30 70/30
Penetration worked ASTM
D-217
mm/10 267 275 272
Change in penetration after 105X double strokes +28 +25 +24
Dropping Point ASTM
D-566 °C 255 220 210

To evaluate the role of different complexing agents, Example-14 & 15 grease batches were made using same equipments, raw materials, and manufacturing process as the Example-1, except using sebacic acid & azelaic acid respectively in same molar ratio. Example-14 & 15 greases were found to have dropping points more than 250 °C. All other test data of Example-14 & 15 greases was found be similar to Example-1 as shown in Table-5.

Table-5
Components Example no.
1 14 15
12-Hydroxystearic acid, parts by weight 11.00 11.00 11.00
Adipic acid, parts by weight 1.45 0.00 0.00
Sebacic acid, parts by weight 0.00 2.00 0.00
Azelaic acid, parts by weight 0.00 0.00 1.87
Hydrated lime, parts by weight 1.50 1.50 1.50
Lithium hydroxide monohydrate, parts by weight 0.90 0.90 0.90
Water , parts by weight 0.10 0.10 0.10
Structure modifying agent, parts by weight 1.50 1.50 1.50
Group I paraffinic base oil (95 cSt at 40 °C), parts by weight 83.55 83.00 83.13
Calcium metal content /Lithium metal content 0.70/0.15 0.70/0.15 0.70/0.15
% Lithium content with respect to 100% Calcium content 20.96 20.96 20.96
Test Test Method Units Results
Complexing agent,
Second portion/First Portion - Percent 70/30 70/30 70/30
Penetration worked ASTM
D-217
mm/10 267 275 288
Change in penetration after 105X double strokes +28 +25 +24
Dropping Point ASTM
D-566 °C 255 259 256
Heat Stability at 100 °C for 30 hrs, Oil Separation, ASTM
D-6184 %wt. 1.5 1.8 1.2
Roll stability, 16 hrs, 25 °C, Change in penetration ASTM
D-1831 % 7.8 7.0 11.0
Cu Corrosion at 100 °C, 24 hrs IP-112 Rating Pass Pass Pass

To evaluate the role of complexing agent content on grease performance, Example-16, 17, 18 & 19 grease batches were made using same equipments raw materials, and manufacturing process as the Example-14, except varying the sebacic acid content. Dropping point of Example-16 grease made without using sebacic acid was found to be 170 °C. No significant boost in dropping points was observed after 250 °C when sebacic acid content was increased gradually after 2.0 parts as shown in Table-6. All other test data of Example-16, 17, 18 &19 greases was found be similar as shown in Table-6.

Table-6
Components Example no.
14 16 17 18 19
12-Hydroxystearic acid, parts by weight 11.00 11.00 11.00 11.00 11.00
Sebacic acid, parts by weight 2.00 0.00 1.00 1.50 2.50
Hydrated lime, parts by weight 1.50 0.97 1.25 1.37 1.67
Lithium hydroxide monohydrate, parts by weight 0.90 0.58 0.75 0.82 1.00
Water , parts by weight 0.10 0.10 0.10 0.10 0.10
Structure modifying agent, parts by weight 1.50 1.50 1.50 1.50 1.50
Group I paraffinic base oil (95 cSt at 40 °C), parts by weight 83.00 85.85 84.40 83.71 82.23
Calcium metal content /Lithium metal content 0.70/0.15 0.45/0.09 0.58/0.12 0.64/0.13 0.78/0.16
% Lithium content with respect to 100% Calcium content 20.96 20.89 20.96 20.91 20.92
Test Test Method Units Results
Sebacic acid,
Second portion/First Portion - Percent 70/30 0/0 70/30 70/30 70/30
Penetration worked ASTM D-217
mm/10 267 270 275 278 279
Change in penetration after 105X double strokes +28 +25 +28 +24 +25
Dropping Point ASTM D-566 °C 259 170 240 255 263

To demonstrate the role of acidic structure modifying agent, Example-20 grease batch was made similar to Example-14 grease, except without using acidic structure modifying agent. Consistency of Example-20 grease was found to be on softer side with more oil bleed characteristics at higher temperatures. Three grease batches of grease (Example-21, 22 & 23) were made similar to Example-14 grease except using different quantities of a structure modifying agent having acid value (50 to 60) added just before second portion addition of hydrated lime. Results indicate that 1 to 2% of structure modifying agent is sufficient to make good quality greases as shown in Table-7. A grease batch (Example-24) similar to Example-14 grease except that structure modifying agent was added after full addition and reaction of hydrated lime and lithium hydroxide monohydrate. Example-24 grease was found to be of softer consistency having more oil bleed characteristics at high temperatures in comparison to Example-14 grease as shown in Table-7.
Table-7
Components Example no.
20 21 22 23 24
12-Hydroxystearic acid, parts by weight 11.00 11.00 11.00 11.00 11.00
Sebacic acid, parts by weight 2.00 2.00 2.00 2.00 2.00
Hydrated lime, parts by weight 1.50 1.50 1.50 1.50 1.50
Lithium hydroxide monohydrate, parts by weight 0.90 0.90 0.90 0.90 0.90
Water, parts by weight 0.10 0.10 0.10 0.10 0.10
Structure modifying agent, parts by weight 0.00 1.00 2.00 3.00 1.50
Group I paraffinic base oil (95 cSt at 40 °C), parts by weight 84.50 83.50 82.50 81.50 83.00
Calcium metal content /Lithium metal content 0.70/0.15 0.70/0.15 0.70/0.15 0.70/0.15 0.70/0.15
% Lithium content with respect to 100% Calcium content 20.96 20.96 20.96 20.96 20.96
Test Test Method Units Results
Sebacic acid,
Second stage/First stage - Percent 70/30 70/30 70/30 70/30 70/30
Penetration worked ASTM D-217
mm/10 290 267 273 270 305
Change in penetration after 105X double strokes +35 +25 +27 +22 +29
Dropping Point ASTM D-566 °C 252 255 250 251 249
Heat Stability at 100 °C for 30 hrs, Oil Separation, ASTM D-6184 % wt 4.5 1.1 1.0 0.8 4.8

To demonstrate the role of water, a grease batch (Example-25) was made similar to Example-14 grease, except without using water. There was no saponification even after keeping mass at 100 °C for three hours indicating the presence of water is must to start saponification. Water was added in amount 0.05 to 0.5%, most preferably between 0.1 to 0.25%, based on the final weight of grease. Four grease batches (Example-26, 27, 28 & 29) were made that were identical to Example-14 grease except different quantities of water added during charging. As can be seen from data shown in Table-8, best combination of thickener yield, dropping point and controlled frothing were obtained by using 0.1 to 0.3% water.

Table-8
Components/Characteristics Example no.
25 26 27 28 29
Water, parts by weight 0.00 0.10 0.25 0.70 1.00
Frothing at 100 °C No Frothing Controlled Controlled Uncontrolled Uncontrolled
Worked Penetration, mm/10, ASTM -217 No Grease formed 273 275 Not tested Not tested
Dropping Point, °C, ASTM D-566 No Grease formed 195 197 Not tested Not tested

To demonstrate the role of maximum process temperature and time, five grease batches (Example- 30, 31, 33, 33 & 34) were made using raw materials and amount similar to Example-14 except that different maximum temperatures and process times were applied just before addition of acidic structures agent. As can be seen form data of these batches in Table-9 and their comparison with Example-14 grease, the best combination of thickener yield and dropping point is obtained by keeping the maximum process temperature between 160 to 165 °C for 60 minutes. Maximum process temperature and time depends upon the complexing agent used and can be fine tuned.

Table-9
Components/Characteristics Example no.
30 31 32 33 34
Maximum process temperature (°C) 145 155 175 165 165
Time Grease maintained at maximum process temperature (minutes) 60 60 60 30 90
Worked Penetration, mm/10, ASTM -217 275 280 Fluid 270 278
Dropping Point, °C, ASTM D-566 240 245 Not tested 242 255

Example-35 grease was made to demonstrate that present invention can be used to prepare complex greases having extreme pressure properties useful for industrial applications. It was made using process similar to Example-1 and base oil viscosity was adjusted to VG 160 using mixtures of two Group I paraffinic base oils having viscosities of 400 cSt and 95 cSt at 40 °C. Composition of Example-35 grease is given in Table-10. 4 parts of commercially available grease package (LZ 5235 from M/s Lubrizol) was added, mixed properly and batch was homogenized to obtain smooth grain free grease. Several lab batches were made, tested and average results of those tests are compared with commercially available lithium complex grease as shown in Table-10.
Table-10
Composition and Test Data of Example-35
Component Composition (parts by weight)
12-Hydroxystearic acid 11.00
Adipic acid 1.45
Hydrated lime 1.50
Lithium hydroxide monohydrate 0.90
Water 0.10
Structure modifying agent (acid value 60) 1.50
LZ 5235 4.00
Group I paraffinic base oil (95 cSt at 40 °C) 46.20
Group I paraffinic base oil (400 cSt at 40 °C) 33.35
Test Test Method Result
Example-33 Commercially available Lithium Complex grease
Consistency, 1/10 mm
60 Strokes
105X Strokes ASTM D-217

279
304
285
310
Dropping Point, °C ASTM D-566 255 256
Roll stability, 25 °C, % Change in penetration
2 hrs,
16 hrs ASTM D-1831

5.6
9.2

7.0
11.0
Water wash out, % wt ASTM D-1264 1.3 1.2
Rust Preventive, rating ASTM D-1743 Pass Pass
Leakage tendency, gm. ASTM D-1263 1.1 1.3
Heat Stability at 100 °C for 30 hrs, Oil Separation, % wt ASTM D-6184 1.2 1.7
Oxidation Stability, Pressure Drop, kPa in 100 hrs ASTM D-942 21 25
EMCOR, rating IP 220 0, 0 0, 0
Copper Corrosion, rating ASTM D-4048 1 A 1 A
Weld load, Kg IP-239 250 225
Wear Scar Dia, mm ASTM D-2266 0.60 0.60

,CLAIMS:We claim:

1. A calcium-lithium complex grease composition comprising:
75.0 to 90.0 weight % base oil;
6.0 to 18.0 weight % saponifiable material;
0.5 to 2.5 weight % hydrated lime;
0.2 to 2.0 weight % lithium hydroxide monohydrate;
1.0 to 5.0 weight % one or more complexing agent;
0.05 to 0.5 weight % water; and
0.2 to 5.0 weight % acidic structure modifying agent,
wherein weight percentage being relative to the total weight of the composition.

2. A process for preparing calcium-lithium complex grease composition, the process comprising:
(i) adding and mixing a saponifiable material, a first portion of complexing agent, and water in a first portion of a base oil to obtain a first reaction mass;
(ii) adding and reacting a first portion of a hydrated lime to the first reaction mass with continuous mixing to obtain a second reaction mass;
(iii) mixing and heating the second reaction mass to a temperature in the range of 120 to 125 °C and adding remaining second portion of the complexing agent and followed by addition of a lithium hydroxide monohydrate and heating the mass to 135 to 145 °C and maintained at this temperature for a 1-1.5 hours to obtain a third reaction mass;
(iv) mixing and heating the third reaction mass and adding an acidic structure modifying agent to obtain a fourth reaction mass;
(v) adding and reacting remaining second portion of the hydrated lime to the fourth reaction mass to obtain a fifth reaction mass; and
(vi) optionally dehydrating the fifth reaction mass and adding the remaining second portion of the base oil then optionally adding an additive and mixing the mass to obtain the calcium-lithium complex grease composition.

3. The process as claimed in claim 2, wherein the calcium-lithium complex grease composition having dropping points 220-263 °C .

4. The process as claimed in claim 2, wherein the calcium-lithium complex grease composition has a higher faction of calcium metal with percentage lithium content varying from 9 to 87 with respect to 100% calcium content.

5. The process as claimed in claim 2, wherein the saponifiable material is selected from fatty acid, hydroxy-substituted fatty acid and their esters, hydrogenated castor oil and mixture thereof; wherein:
(a) the fatty acid is stearic acid, and
(b) the hydroxy-substituted fatty acid is l2-hydroxystearic acid.

6. The process as claimed in claim 2, wherein the amount of saponifiable material is in the range of 6.0 to 18.0 weight % being relative to the total ingredient used in preparing the composition.

7. The process as claimed in claim 2, wherein the saponifiable material is reacted with 0.5 to 2.5 weight % hydrated lime, and 0.2 to 2.0 weight % lithium hydroxide monohydrate to make the calcium-lithium complex grease composition and weight percentage being relative to the total weight of the ingredient used in preparing the composition.

8. The process as claimed in claim 2, wherein the hydrated lime is white fine powder having 65.0-70.0% calcium oxide content.

9. The process as claimed in claim 2, wherein the hydrated lime is added in two portions:
first portion of the hydrated lime is added just after mixing the saponifiable material, water and first portion of the complexing agent in the base oil; and
second portion of the hydrated lime is added just after mixing structure modifying agent.

10. The process as claimed in claim 2, wherein the lithium hydroxide monohydrate is having 56.0-57.0% lithium hydroxide content and full quantity of lithium hydroxide monohydrate is added just after adding and mixing remaining second portion of the complexing agent.

11. The process as claimed in claim 2, wherein the calcium-lithium complex grease composition is produced by adding and reacting hydrated lime in two portions, wherein
50.0 to 70.0 weight % quantity as first portion of total hydrated lime as oil slurry added to mixture of full quantity of the saponifiable material, the first portion of complexing agent and water in the first portion of base oil and slowly heating to a temperature in the range of 95 to 100 °C and maintained at this temperature with continuous stirring till frothing subsided; and
second remaining portion of the hydrated lime is added after reacting lithium hydroxide monohydrate and just after adding and mixing acidic structure modifying agent at a temperature in the range of 155 to 165 °C.

12. The process as claimed in claim 2, wherein the calcium-lithium complex grease composition is produced by adding and reacting the complexing agent in two portions, wherein:
(i) first portion of the complexing agent is used in the process is in the range of 20 to 35 weight % quantity of total complexing agent;
(ii) second remaining portion of the complexing agent is used in the process is in the range of 65 to 80 weight % quantity of total complexing agent.

13. The process as claimed in claim 2 wherein the calcium-lithium complex grease composition is produced by adding and reacting the base oil in two portions, wherein:
(i) first portion of the base oil is used in the process is in the range of 25 to 40 weight % quantity of total base oil; and
(ii) second remaining portion of the base oil is used in the process is in the range of 60 to 75 weight % quantity of total base oil.

14. The process as claimed in claim 2 wherein the complexing agent is selected from a short chain monocarboxylic acid, hydroxybenzoic acid, polycarboxylic complexing acid, boric acid, phosphoric acid and mixture thereof, wherein:
(a) short chain monocarboxylic acid is selected from acetic acid, propanoic acid, and butanoic acid; and
(b) polycarboxylic complexing acid is selected from adipic acid, sebacic acid, and succinic acid.

15. The process as claimed in claim 2, wherein the total amount of complexing agents is in the range of 1.0 to 5.0 weight % being relative to the total ingredient used in preparing the composition.

16. The process as claimed in claim 2, wherein calcium-lithium complex grease composition is produced by incorporating and mixing acidic structure modifying agent at 150-155 °C and these must be added after reacting lithium hydroxide monohydrate and prior to addition of second portion of the hydrated lime.

17. The process as claimed in claim 2, wherein the acidic structure modifying agent is produced by acidic thermal polymerization of organic fatty acids and acid value of the fatty acid is in the range of 30 to 150.

18. The process as claimed in claim 2, wherein the amount of acidic structure modifying agent is in the range of 0.2 to 5.0 weight % being relative to the total ingredient used in preparing the composition.

19. The process as claimed in claim 2, wherein the base oil is selected from petroleum based naphthenic oil, petroleum based paraffinic oil, synthetic base oil and the synthetic base oil is selected from polyalphaolefins (PAO), polyalkyl gycol (PAG), and alkylated aromatic.

20. The process as claimed in claim 2, wherein the total amount of base oil is added in the range of 75.0 to 90.0 weight % being relative to the total ingredient used in preparing the composition

21. The process as claimed in claim 2, wherein the additive is selected from rust inhibitor, corrosion inhibitor, metal deactivator, metal passivator, anti-oxidant, extreme pressure additive, friction modifier, ant-wear additive, polymer, tackifier, dye, chemical marker and fragrance imparter.

22. The process as claimed in claim 2, wherein the saponifiable material, first portion of complexing agent and water in base oil are added at a temperature in the range of 50 to 75 °C

23. The process as claimed in claim 2, wherein the calcium-lithium complex grease composition comprises the following steps:
(i) adding and mixing the base oil, saponifiable material, first portion of complexing agents, water in a grease making kettle and slowly heating to 75 °C to obtain the first reaction mass;
(ii) slowly adding the first portion of hydrated lime as oil slurry to the first reaction mass with continuous mixing and slowly heating the mass to 100 °C and maintained at this temperature with continuous stirring till frothing subsided to obtain a second reaction mass;
(iii) mixing and heating the second reaction mass to 120 to 125 °C and adding the remaining second portion of the complexing agent followed by addition of full quantity of lithium hydroxide monohydrate, heating the mass to 135 to 145 °C and maintained at this temperature for a certain time to obtain a third reaction mass;
(iv) mixing and heating the third reaction mass to 155 to 165 °C and adding and mixing an acidic structure modifying agent to obtain the fourth reaction mass;
(v) adding and reacting remaining second portion of hydrated lime for a certain duration to obtain the fifth reaction mass; and
(vi) adding the remaining quantity of base oil as cut back to the fifth reaction mass and cooling the mass and optionally adding the additive below 90 °C and homogenizing or milling the mass to obtain the calcium-lithium complex grease composition.