FORM - 2
THE PATENTS ACT, 1970
COMPLETE
SPECIFICATION
SECTION 10
TITLE : A PROCESS FOR THE PREPARATION OF A LUBRICATING GREASE
COMPOSITION
APPLICANT (S): INDIAN OIL CORPORATION LIMITED, AN INDIAN COMPANY
OF G-9, ALI YAVAR JUNG MARG, BANDRA (EAST), MUMBAI-400 051, MAHARASHTRA, INDIA
The following Specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed:-

2
Field of Invention:
The present invention relates to a process for the preparation of a lubricating grease composition and more particularly a new process for the preparation of Aluminium soap base grease. In this process during phase transition period chiller has been added resulting into improved, smooth grease in less processing time compared to conventional approaches. The primary role of chiller in this invention is to catalyze the de-gelling process to give improved grease primarily recommended for railroad applications and other applications. Additionally 'in situ' added chiller, unlike other processes, does not remain in the system and escapes from grease avoiding any adverse effect of chiller on the properties of the grease.
BACKGROUND OF THE INVENTION:
Aluminium soap base grease are conventionally well known in the art and are widely used for lubrication purpose on account of their water proof characteristics, tackiness and attractive appearance. However, this class of grease possesses some distinct disadvantages like tendency to attain gel like structure / rubbery texture upon heating above the phase transition temperature, tendency towards syneresis or bleeding out oil on storage & use. The biggest challenge lies in manufacturing of this class of grease in conventional manufacturing plants.
These greases have been reported to be prepared by variety of processes and the characteristics of end product significantly influenced by control of processing parameters. Polishuk (A brief history of Lubricating Grease, L&M Inc, 1998) indicated detailed history as well as reference sited for the manufacture of this class of greases. In general Al-soap base greases could either be prepared by 'in situ' formation of Al-soap in oil (British Patent: 582502, 1943) or by dispersing preformed soap in desired oil. The later process is simple and is being commonly followed to manufacture Al-soap base greases. For preformed soap type of grease preparation, preformed soap is gradually dispersed in desired oil, heated to the range 140-190°C followed by cooling and adding additives & mixing. Manufacturing process though appears simple however heating, cooling & mixing of this class of greases is quite complex. It has been generally observed that >50°C this grease attains jelly like structure due to which further heating & mixing the ingredient become quite difficult and therefore product can not be milled or homogenized to get a grease. The temperature generally required to have proper dispersion could be as high as
2

3
150 - 180 °C. In such case cooling of grease particularly large batches 5-10 ton in conventional grease kettle becomes very difficult and cumbersome due to jelly nature of the product. This is also particularly important due to the fact that the quality, consistency, structural properties of grease is highly depending on agitation & rate of cooling. Al-soap base greases are known to have poor shear stability and cooling in a conventional plant cannot be attained without shearing. It is therefore imperative to provide an optimum shearing to the product so that desired consistency grease could be achieved. Additionally at phase transition temperature, if product is exclusively sheared, the resulting grease ends up into soft grease.
In manufacturing of Al-soap grease, cooling is particularly important because jelly type of mass converts into grease structure only at < 50 deg. C and therefore cooling of jelled mass to such a low temperature is practically very difficult compared to other type of greases due to poor heat transfer. F J Licata (Ind. Eng. Chem, 30,5,pp550-553, 1938) showed that controlling the viscosity of type of oil, rate of cooling, time of compounding and moisture content could modify the properties of Al-grease. F J Licata (US Patent 2448721) however indicated the disadvantage of Al-grease upon heating and their tendency towards oil separation on storage & use.
The normal practice to cool these greases are heating the grease up to desired temperature and pouring the same in open pan followed by leaving the same for over night cooling followed by proper mixing either by milling / homogenizing. Polishuk (A brief history of Lubricating Grease, L&M Inc, 1998) indicated that the process of grease as batch wise by heating Al-soap & oil to about 150 °C and pouring the charge into pan to cool, this enables gel structure to break. The cooling rate takes > 12 hrs. The problem stated in this is the non-uniform cooling and unhomogenious grease. Grease around the edges of the pan cooled rapidly; while at center cool slowly leading to the formation of a soft gel and grainy appearance. If Al greases are agitated during transition phase the gel tends to break down to a stringy, semi-liquid product. This type of cooling processes however poses great difficulty in manufacturing this class of grease in conventional plants where Li-base greases are normally made. Oil heated kettles have serious problem of cooling. Even steam heated kettles, the cold-water circulation kettle jacket does not yield desired quality grease and yield is normally poor. This also takes lot of time in cooling leading to softening of grease. As the product formed is in jelly nature even at low temperature < 60 °C, cooling near the transition temperature is very slow.
3

4
FJ Licata (US patent 2448721) recommended the addition of small quantity of certain heavy metal non-soaps to Al-soap base grease in order to reduce the gelling tendency of grease and also to control bleeding of grease. Zimmer etal disclosed (US patent No 2394567 and 2449580) processes for rapid production method by making Al-soap greases, by adding crystallization modifiers such as alkylated mononuclear phenol or related material. According to one of the example in patents, about 0.75% by weight of tert. Octyl phenol is added to Al-soap grease and such grease may then be prepared by mixing lubricating oil and Aluminum soap at a temperature of about 280 to 300 °F (138 to 150 °C) and running the hot mixture through a rapid chiller. Gurd, G.W., (US Patent 2480647) envisaged by way of example that cooling by adding solid C02 (0.5-3.0%) reduced the temperature of 5000 pound grease batch in water cooled kettle from 120°F to 100°F (49 °C to 38 °C) and thus facilitating the cooling process.
The present invention is based upon the innovation that is readily possible, by studying the gellation and phase transition temperature and controlling the process by sophisticated techniques like PDSC & FT-IR to envisage a novel manufacturing process by way of de-gelling the highly tedious plastic gel like material at gellation temperature (70-80 deg C) and converting the gelled mass in to a grease structure at comparatively high temperature (70-80 deg C), thereby avoiding the step of cooling the product below 50 deg C to reach phase transition temperature. In other words, by this novel method transition temperature (40' - 50 deg C) is shifted closure to gellation temperature (70 - 80 deg C). This product is therefore de-gelled by carefully adding & controlling in-situ chillers like solid C02 & liquid N2 to get grease with improved properties in terms of improved structure, harder grease, better yield as well as substantial reduction in processing time & temperature. The grease prepared by this process is suitable for intended application.
Object of the Invention:
The primary object of this invention is to propose a lubricating grease-manufacturing process capable of use for making Al-base greases for intended application.
Another object of this invention is to propose a novel lubricating manufacturing process with improved properties of said lubricating grease.
4

5
Still further object of this invention is to de-gel the grease by addition of chiller at high temperature (70-80 deg. C) to get desired improved properties of the grease and thus avoiding cumbersome cooling < 60 deg. C.
Further object of this invention is to reduce the processing time with improved properties.
Still another object of this invention is to propose novel lubricating grease manufacturing process reducing the processing time at commercial level by way of studying gellation & phase transition temperature and effect of chiller by sophisticated techniques like PDSC & FT-IR.
Yet another object of this invention is to propose a novel lubricating grease manufacturing process by adding suitable ingredient which primarily act as de-geller /chiller propagating the chain reaction of chilling process and escapes from the product with out posing any side effects.
Yet another object of this invention is to propose a novel lubricating grease process improving the yield of desired consistency grease.
Still another object of this invention is to propose a novel lubricating grease-manufacturing process reducing the processing temperature.
SUMMARY OF THE INVENTION:
To achieve the aforementioned objects the present invention provides a process for preparing a lubricating grease composition comprising-
(i) heating a substantial portion of the total amount of base oil to about 60-100°C,
(ii) adding slowly about 5-20% by weight of preformed soap with mixing;
(iii) further raising the temperature of the mixture to about 90 to 180 °C slowly in 1 hrs to 5 hrs
(iv) adding the remaining portion of the base oil and cooling the mixture to about 70-80 °C,
(v) adding about 1- 5 % by weight of de-geller to obtain the lubricating grease composition and adding a 0- 20 % by weight of additive
5

6
The mixture is heated in step (iii) up to 100-120 °C. The amount of base oil used in the composition is 40-94 % by weight of the composition. The substantial portion of base oil is about 50- 90 % by weight of the total amount of the base oil. The degeller is solid carbon dioxide or liquid nitrogen. The base oil is mineral base stocks or neutral oils The additives used are crystallization modifier, oil thickening agents, corrosion inhibitors, solid lubricants or a combination thereof. The crystallization modifier is selected from glycerol or resorcinol. The oil thickening agent is polyisobutylene. The solid lubricants is graphite or MoS2 The final grease composition is further homogenized or milled in a colloid mill.
Detailed Description of the Invention:
In accordance with this invention the basic lubricating grease composition comprises of 5L30% wt of Al-stearate, 0-20% of additive, 1-5% chiller and 40 - 94.0% wt of mineral base oil.
Further according to this invention the progress of the reaction is monitored through various, sophisticated techniques viz., FT-IR, PDSC etc. to understand the nature of reaction, gellation and phase transition temperature so that the effect of mechanical shearing during cooling process can be established. PDSC result of Al-soap given in Fig 1, showed the gellation (around 80 °C) and phase transition temperature (below 50 °C)
Further according to this invention, there is provided a process for the preparation of a lubricating grease composition which comprises the heating of base oil first up to 50-90 °C in required proportion, stirring and adding Al-stearate in required proportion and mixing it thoroughly by agitation. The mixture so formed is then heated around 90 to 170 °C in 1 to 5 hrs followed by cooling the said product, adding in third stage de-geller followed by addition of balance base oil & additives, and subjecting the mixture to the step of shearing if desired to obtain the required grease.
In accordance with this invention, a vessel equipped with a stirrer of rpm 0-150 (2-6 kg / 60-80 kg capacity) in the first stage is charged with 40-70%, of mineral bas2stocks, neutral oils or their mixture based on the total weight of the final grease composition. This is stirred and heat is provided through heating mantle / jacketed hot oil to reach the temperature 50-100°C. At the end of this stage 5-30% weight of Al-stearate is added slowly by continuous agitation based on the total weight of the final grease composition. The charge is continuously mixed and held at 50-90°C for 15 — 120 mins, the temperature
6

7
being raised slowly to 90-170 °C; duration of maintaining at this temperature is 1-5 hrs. During this period the product assumes a thick gel type of structure and converts into a thickened mass. The balance quantity of base oil as taken initially is added very slowly by continuous agitation. The duration of the same is 30 min to 3 hrs.
The product is then cooled with continuous stirring from 120 to 70°C at the end of the second stage, chiller / combination of chillers 1-5 % added insitu at this stage by continuous / stopping agitation intermittently. The total time duration of addition of chiller is 15 min - 3 hrs. This mixture is added with 0-20% of additives. The mass is mixed carefully and stirred if required to get resultant grease in NLGI 0 to 3 consistencies.
It is however possible to propose a alternate process by changing the sequence of addition. In alternate process for the preparation of a lubricating grease composition which comprises in preparing first and second stage as envisaged above. However while cooling the mixture, after addition of balance quantity of base oil, the required quantity of additives 0-20% is added while continuing stirring and cooling process. At 50-100 °C, chiller / combination of chillers is added by intermittent agitation. The duration of addition of chiller is 15 min - 3 hrs. The mixture is then added with addition of additives followed by mixing the product by either stirring or milling through colloid mill / homogeniser to get grease of NLGI 0-3 consistency.
The primary role of chiller in this invention is to catalyze the de-gelling process to give improved grease primarily recommended for railroad applications and other applications. Additionally cin situ' added chiller, unlike other processes, does not remain in the system and escapes from grease avoiding any adverse effect of chiller on the properties of the grease.
Preformed Al-soap used in present invention is preferably Al-stearate having Al-content minimum of 10 % by weight as A1203 and used in amount 5 - 30% by weight of the total lubricating grease composition. The base oil used in the composition of present invention is mineral base stocks, neutral oils includes light, inter & heavy neutral or blends thereof.
Additives used in present invention are glycerol or resorcinol as a crystallization modifier, PIB as an oil thickening agent & corrosion inhibitors and solid lubricants. Solid lubricant used in present invention could be either graphite/ MoS2 and is present in concentration varying 0.0 - 20.0%.
7

8
In order to describe more fully the nature of the present invention, specific examples will be here in after be described. It should be understood, however that this is done solely by way of example and is intended neither to delineate nor limit the ambit of the appended claims.
Example 1
The lubricating grease composition has been proposed consisting the ingredients with proportion indicated in the Table 1.
TABLE - 1

S No. Component %
1. Al-Stearate 5-30
2. Base oil 40-94
3 Chiller 1-5
4 Additives 0-20
This example delineates the process whereas in 90% base oil is taken initially. Here initially heat is applied slowly to raise temperature around 60-80 °C, therein Al-stearate is added slowly in 15min to 2 hrs by continuous agitation. Temperature is further raised to 140-180 °C. This is followed by cooling to 80-60 °C and therein adding solid C02 / dry ice in 1-5% slowly by intermittent agitation. The addition of Solid C02 has initiated de-gelling of the structure and converting the whole product in to grease form. Addition of C02 not only initiated de gelling but also propagating a chain reaction facilitating the conversion of rubbery mass in to well defined grease structure through gel formation. This is followed by cooling further adding graphite as an additive in 0.5 - 10%. This is further followed by milling / homogenization. The comparative properties are envisaged in the Table -2.
TABLE - 2
Results

S. No. Characteristics Composition A Composition B
1. Al-stearate 12% 15%
2. 3. 4. Max Temperature Initial Oil Solid C02 140 -180 °C90%1 - 3 % 140-180 °C 90% NIL
8

9
5. Process time ' 12-14hrs 20-25hrs
6. Penetration, Worked (60x) (D-217) 330 + 400
7. Drop point (D-566) 119°C 98°C
8. Copper corrosion (IP-112) - ive - ive
9. Oil Separation (IP-121) 2.0% 3.5%
The effectiveness of the lubricating grease composition described as above demonstrate comparatively harder penetration of this novel process compared to conventional process (composition B) thus reduces processing time, giving better yield, better structure, improved oil separation and higher drop point which fulfils the objectives stated earlier. FT-IR spectra of greases obtained from composition A & B are given in Fig 2a & 2b and both IR spectra were found to be same, which indicated that chiller did not have any chemical interaction with the thickener system.
Example - 2
A lubricating composition was prepared consisting the ingredient with properties indicated in Table-1. The example consisted the change as compared to Example 1 that only 50 - 60% oil is taken initially rest parameters remain the same. The balance oil is added as cut back before starting the cooling process.
The lubricating grease composition of Example-2 and prepared as per method described for grease composition of Table 1 showed the physico chemical characteristics as listed in Table - 3.
TABLE-3

S. No. Characteristics Results
1. Al- stearate 12.0 %
2. Max-temperature 140-180 °C
3. Initial oil 50 - 60 %
4. Solid C02 1 - 3 %
5. Process Time 10 -12 hrs
6. Penetration, Worked (60x)(D- •217) 335
7. Drop point (D-566) 121 °C
8. Copper corrosion (IP-112) - ive
9

10
The effectiveness of the lubricating grease composition described as above demonstrate harder grease / better yield, reduced processing time and smooth structure of grease compared to composition B of Table 2.
Example - 3
The lubricating grease composition was prepared consisting the ingredient indicated in table - 1. The progress of reaction was monitored by PDSC for finding out the phase transition temperature (Solid to fluid, while heating and fluid to gel, while cooling the mass). Based on PSDC results the maximum process temperature was reduced to 100 - 110 °C, other parameter of processing remains same as indicated in Example 2
The composition prepared as above as per Example 3 has the following properties.
TABLE - 4

S.No. Characteristics Results
1. Al- stearate 12.0 %
2. 3. Max-temperature Initial oil 100-110 °C 50 - 60 %
4. Solid C02 1 - 3 %
5. Process Time 8 - 9 hrs
6. Penetration, Worked (60x)(D-217) 290
7. 8. 9. Drop point (D-566) Copper corrosion (IP-112) Oil separation (IP-121) 120 °C -ive 1.6%
The effectiveness of the lubricating grease composition described above demonstrates its smooth structure, less processing time retaining the improved properties of the grease compared to conventional process as described in composition B of Table-2.
Example 4
The lubricating grease composition prepared consisting the ingredients with proportions indicated in Table 1. Processing parameter is kept as indicated in
10

11
example 3 with a change in addition sequence. Herein this examples additives / solid lubricants are added prior to the addition of solid C02.
The lubricating grease composition of Example 4 and prepared as method described for Table 1 showed the physico-chemical characteristics as listed in Table -5.
TABLE - 5

S. No. Characteristics Results
1. Al- stearate 12.0 %
2. Max-temperature 100-110 °C
3. Initial oil 50 - 60 %
4. Solid C02 1 - 3 %
5. Process Time 7 - 9 hrs
6. Penetration, Worked (60x) (D-217) 288
7. Drop point (D-566) 123 °C
8. Copper corrosion (IP -112) -ive
Thus less processing time, an alternate manufacturing procedures with smooth grease structure, reduced process time retaining other properties has been demonstrated by example 4 as well.
Example 5
A lubricating grease composition was prepared consisting the ingredients Table 1. This example consists the process as indicated in example 2. However the chiller used in this example is liquid N2 in 1 - 5 % concentration and added slowly. Like solid C02 liquid nitrogen also initiated the process of de gelling and propagating the chain reaction.
The lubricating grease composition of example 6 and prepared as per method described for table 1 showed the physico chemical properties as listed in Table
-7.
Table - 7
S. No. Characteristics Results
1. Al-stearate 15%
11

12

2. 3. Max-temperature Initial oil 190 °C 90%
4. 5. Liquid N2 Process Time 1 - 5 % 10-15hrs
6. Penetration, Worked (60x)(D-217) 336
7. 8. Drop point (D-566) Copper corrosion (IP-112) 108 °C - ive
The effectiveness of lubricating grease composition prepared in example 5 demonstrates as smooth grease, possible used of liquid N2 as de-geller while retaining the properties of grease
Example 6
A lubricating grease composition was prepared consisting the ingredients indicated in Table 1. The process of preparing grease composition remains practically same as in example 5. This example has variation compared to example five that the maximum process temperature is 100-120 °C.
The lubricating grease composition of example of prepared as per method for grease composition of Table 1 showed physico-chemical characteristics as indicated in Table 8.
TABLE - 7

S. No. Characteristics Results
1. Al- stearate 15%
2. 3. Max-temperature Initial oil 100 - 120 °C 50 - 60 %
4. 5. Liquid N2 Process Time 1 - 5 % 8-10hrs
6. Penetration, Worked (60x)(D-217) 332
7. 8. Drop point (D-566) Copper Corrosion (IP -112) 110°C -ive
This example indicates preparation of smooth grease less process time compared to composition B of Table 2 and possible use of liquid N2 as de-geller.
While the present invention has been particularly shown and described
12

13
with reference to the preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be effected therein without departing from the spirit and scope of the invention as defined by the appended claims.
13

We Claim:
1. A process for preparing a lubricating grease composition comprising:
(i) heating a substantial portion of the total amount of base oil to 60-100°C,
(ii) adding slowly 5-20% by weight of preformed soap with mixing;
(iii) further raising the temperature of the mixture to 90 to 180°C slowly in 1 hrs to 5 hrs
(iv) adding the remaining portion of the base oil and cooling the mixture to 70-80 °C,
(v) adding 1- 5 % by weight of de-geller to obtain the lubricating grease composition and adding a 0- 20 % by weight of additive to obtain said lubricating grease composition.
2. A process as claimed in claim 1, wherein the mixture is heated in step (iii) up to 100-120 °C
3. A process as claimed in claim 1, wherein the amount of base oil used in the composition is 40-94 % by weight of the composition.
4. A process as claimed in claim 1, wherein the substantial portion of base oil is 50- 90 % by weight of the total amount of the base oil.
5. A process as claimed in claim 1, wherein the degeller is solid carbon dioxide or liquid nitrogen
6. A process as claimed in claim 1, wherein the base oil is mineral base stocks or neutral oils
7. A process as claimed in claim 1, wherein the additives used are crystallization modifier, oil thickening agents, corrosion inhibitors, solid lubricants or a combination thereof.
8. A process as claimed in claim 7, wherein the crystallization modifier is selected from glycerol or resorcinol.
9. A process as claimed in claim 7, wherein the oil thickening agent is polyisobutylene.
14

10. A process as claimed in claim 7, wherein the solid lubricants is graphite or MoS2.
11. A process as claimed in claim 1, wherein base, oil is taken only 40 - 60 % and balance is added at the maximum temperature as cut back.
12. A process as claimed in 1 wherein the lubricating grease composition is homogenized or milled in a colloid mill.
13. A process for preparing a lubricating grease composition substantially as herein described with reference to the foregoing examples.
Dated this 3rd day of February 2003

16
ABSTRACT
The present invention provides a a process for the preparation of a lubricating grease composition which comprises the healing of base oil first up to 50-90 °C in required proportion, stirring and adding preformed soap in required proportion and mixing it thoroughly by agitation. The mixture so formed is then heated around 90 to 170 °C in 1 to 5 hrs followed by cooling the said product, adding in third stage de-geller followed by addition of balance base oil & additives, and subjecting the mixture to the step of shearing-if desired to obtain the required grease.

16