Description:FIELD OF THE INVETNION:
The present invention relates to a barium complex grease composition and a method of preparing the same. More particularly, the present invention relates to a shear stable and shear reversible barium complex greases composition having inherent extreme pressure and anti-wear characteristics which can be produced by in situ formation of boron compounds by reacting boric acid with hydroxy fatty acids followed by neutralization with base. The present invention provides a method, which requires no added water and relatively low thickener content while still maintaining a desirable consistency.
BACKGROUND TO THE INVENTION:
Barium greases are known for their inherent properties of water resistance, adherence to metal surfaces and high dropping points (Institute Spokesman 12 (20-26), 1948). However, there use is limited due to higher soaps contents, special compositions and difficult manufacturing process which requires special cooling and milling/compounding operations to get desirable structure. Prior arts disclosed a number of inventions which deals with improvement in barium/barium complex greases through various compositions and manufacturing processes.
Barium complex greases are being used for high temperature application particularly in steel plants, cement plant, etc. Barium complex greases are also used in defense industry for very critical applications. MNCs grease producers are importing and marketing barium complex greases in the Indian market as niche and premium products.
The known prior arts disclose the shear stable barium complex made by reacting barium fatty acid soaps with boron esters which were again prepared separately reacting boric acid with hydroxy fatty acid esters.
US2450224 discloses that at particular transition temperature barium soap undergoes complete phase change after dehydration in which phase changes from homogeneous gel to dry mass which give inhomogeneous grease on milling. This can be avoided by keeping the soap content more than 40% and continuously stirring the mass. US2450224 also discloses improved barium grease manufacturing process with use of naphthenic oils during saponification and continued stirring while cooling below the critical transition temperature.
US2504717A discloses barium greases made with reaction of barium oxide & barium hydroxide with fatty acids between temperature 135 to 218 Deg C. US2504717A also disclose use of barium carbonate free barium oxide and hydroxide for smooth structured greases.
US2607735A discloses grease composition consisting of lubricating oil, barium complex soaps of substantially saturated hydroxy fatty acid (12 to 24 carbon atoms) & minor amount of acid (molecular weight below about 160) and 0 to 8% of a non-paraffinic wax of vegetable origin.
US2033148 discloses 0.3 to 0.5% of water is added to obtain glossy barium greases having dropping points more than 149 Deg C.
US2503749 discloses simplified barium grease manufacturing process with use of hydroxy fatty acids and mixtures with fatty acids/fats in place of only fatty acids/fats. In an example, 36% wt of barium soap of hydroxyl fatty acid is used to give a grease having 203 consistency and 157 Deg C. However, significant difference between worked and unworked consistency is also reported in this prior art.
US28927778 discloses barium greases made by reaction of N-octadecyl terephthalamates with barium hydroxide monohydrate in paraffin oils at 93deg C.
US2859178 discloses bright stock having viscosity of 170 SUS at 98.9 Deg C was treated with 17% wt P2S5 for 100 hrs at 204 Deg C. The reaction product was filtered, diluted with oil having 40 SUS at 98.9 Deg C and finally neutralized with 30% by wt barium hydroxide octahydrate, based on the wt of P2S5 treated hydrocarbon. Final grease composition had 24% barium salt and had a worked penetration of 260 and dropping point more than 260 Deg C.
US2628195 discloses barium greases were made by reacting mixtures of octoic acid with stearic acids. This prior art discloses that by incorporating small quantities of octoic acids leads to smooth buttery consistency with improved wear and adherence properties.
US2659695 discloses problem faced with Saponification of fatty acids with barium hydroxide and it require large quantity of water, prolonged dehydration periods. All these problems were removed when water-in-oil emulsion of barium hydroxide octahydrate was reacted with fatty acids.
US2595556 discloses fibrous barium complex greases made by reacting mixtures of tallow, tallow fatty acids and acetic acid with barium hydroxide octahydrate in naphthenic oil in presence of small quantities of urea or ammonium bicarbonate or ammonium carbamate.
US2564561 discloses candelilla wax, acetic acid and glycerine were used to make barium complex greases having better dropping point and oil bleed performance in companion to normal barium greases.
US2504717 discloses reversible, transparent, water resistant barium greases by reacting oleic acid and hydrogenated fish oils with barium hydroxide emulsion in water and oil.
GB1081008, discloses that reversibility of barium greases is dependent on amount of barium carbonate in barium oxide.
Prior art discloses a number of inventions of carbonated barium greases. US2535101 discloses barium sulfonate grease was made by reacting barium petroleum sulfonate, ethane sulfonic acid with barium hydroxide octahydrate in mineral oil and result grease had a penetration of 215 and a dropping point of 126.7 Deg C.
US2417428 & US2417430 disclose barium complex greases with the use of acetic acid as complexing agent with tallow and tallow fatty acids. Additionally, US2417428 also discloses use of carbon di oxide is bubbled to neutralize the excess barium hydroxide reaming after the saponification.
US3242079 and US3372115 disclose carbonated overbased barium complex greases made with bubbling of carbon dioxide in oil slurry of barium mahogany sulfonate, barium oxide and alcohol. In second step, other acids and remaining oils were added and followed by finishing of greases through homogenization.
US 3372114 discloses 6% wt of cobalt salt of naphthenic acid was added during carbonation process to make overbased barium sulfonate greases.
US3010897 discloses overbased barium sulfonate greases suitable for high temperature and high load application made with three components fatty acids, colloidal solution of barium and mineral oil. Overbased colloidal solution of barium was made by carbonation of clear solution of barium oxide in methyl alcohol followed by evaporation of methyl alcohol.
US2033148 and US2154383 disclose basic barium greases with use of excess of barium hydroxide.
GB610190 discloses hydroxystearic acid was autoclaved at 160°C with barium hydroxide octahydrate, dehydrated at this temperature and finally homogenized to obtain greases having dropping points upto 164°C.
GB651339, discloses stearic acid is reacted with hot aqueous slurry of barium hydroxide in naphthenic oil with maximum processing temperature of 157 Deg C.
US 2332247, discloses the water insoluble transparent and reversible greases with use of aluminum soaps. The ratio of barium soap to aluminum soap varies between the limits of 1:1 to 10:1. After melting of barium grease, the only mean of retaining the grease like structure is to work the grease while cooling.
Wunsch (NLGI Spokesman 58, 434-438, 1995) discloses barium greases made in polyalphaolefin oils for hybrid bearings operating at very high speed.
US2303256 discloses that barium greases made with reaction of barium hydroxide with saturated carboxylic acids and hydroxyl carboxylic acids which were produced by partial controlled oxidation of saturated hydrocarbons. These greases are reported to have deforming characteristics at low temperatures.
GB566886 discloses thermally and mechanical shear stable barium grease, and this grease is made by reaction of oleic acid with barium hydroxide-oil slurry.
US2375060 discloses Barium salts of phosphorus sesquisulfide treated fats such as wool grease are reported as EP additives for lubricants.
US4507214 discloses barium complex greases in which 3 wt% of cerium trifluoride was added to achieve a weld load of 200 Kg.
GB584850 also discloses barium complex grease having EP properties and this was made by reacting barium oxide and lauyl mercaptan.
GB1236140 discloses improved extreme pressure properties of barium greases by adding 10% of lead soap of tuna fish oil and 5% sulfonated sperm oil or 10% lead naphthenate and 5% sulfurized sperm oil.
US2943054 discloses Barium 12-hydroxy stearate greases having high dropping points and shear reversibility by incorporating a boron compound prepared by reacting orthoboric acid with an ester of the class consisting of glycol and polyglycol, mono and di-esters of hydroxy fatty acids and glycerol, mono, di and tri-esters of hydroxy fatty acids. Boron esters of hydroxy fatty acids are prepared between temperatures 101°C and about 218°C for a period of about 0.25 hour to about 2 hours.
Thus, it may be observed from the prior arts that there is a need to develop a new barium complex grease composition that has high dropping points and having shear stability, shear reversibility, inherent extreme pressure and anti-wear in required consistency with low soap content.

OBJECTIVE OF THE INVENTION:
One of the objectives of the present invention is to develop a high yield barium complex grease composition that has high dropping points and having excellent resistance to mechanical, or shear break down.
Another objective of the present invention is to provide a method of preparation of barium complex grease composition by reacting boric acid with hydroxy fatty acids followed by neutralization with base.
SUMMARY OF THE INVENTION:
The present invention provides a barium complex grease composition comprising: (a) 55.0% to 85.0% by weight of a base oil; (b) 8.0%-25.0% by weight a hydroxy fatty acid; (c) 0.5%-5.0% by weight of boric acid; and (d) 5.0%-20.0% by weight of hydrated barium hydroxide, wherein % by weight is based on the total weight of the composition.
The present invention also provides a method for preparing barium complex grease composition comprising the steps of: i) adding and mixing a first potion of base oil, a hydroxy fatty acid and boric acid to obtain a reaction mixture; ii) heating and maintaining the reaction mixture between 115 to 120°C for 30 to 45 minutes with continuous stirring; iii) adding base oil to bring the temperature of the reaction mixture of step (ii) to 80 to 90°C; iv) adding of hydrated barium hydroxide to the reaction mixture of step (iii) with continuous mixing; v) gradually heating the reaction mixture of step (iv) to 160-180°C and maintaining at this temperature for 60 to 90 minutes for complete dehydration; vi) gradually cooling the reaction mixture of step (v) to 135-150°C and adding second portion of base oil with continuous stirring to obtain a grease product; and vii) milling the grease product to obtain the barium complex grease composition.
The present invention concerns with the shear stable and shear resistant barium complex greases compositions having dropping points more than 180°C which is made in open kettle using time & energy saving processes.

DETAILED DESCRIPTION OF THE INVENTION:
Those skilled in the art will be aware that the present disclosure is subject to variations and modifications other than those specifically described herein. It is to be understood that the present disclosure includes all such variations and modifications. The disclosure also includes all such features of the invention, and steps of the process that are referred to or indicated in this specification, individually or collectively, and any and all combinations of any or more of such features or steps.
The articles “a”, “an” and “the” are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. The terms “comprise” and “comprising” are used in the inclusive, open sense, meaning that additional elements may be included. It is not intended to be construed as “consists of only”. Throughout this specification, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated element or step or group of elements or steps but not the exclusion of any other element or step or group of elements or steps.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the disclosure, the preferred methods, and materials are now described. All publications mentioned herein are incorporated herein by reference. The present disclosure is not to be limited in scope by the specific examples described herein, which are intended for the purposes of exemplification only. Functionally equivalent products and methods are clearly within the scope of the disclosure, as described herein.
All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein.
The description that follows, and the embodiments described therein, is provided by way of illustration of an example, or examples, of particular embodiments of the principles and aspects of the present disclosure. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the disclosure.
The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
Accordingly, the present invention provides a barium complex grease composition comprising:
(a) 55.0% to 85.0% by weight of a base oil;
(b) 8.0%-25.0% by weight a hydroxy fatty acid;
(c) 0.5%-5.0% by weight of boric acid; and
(d) 5.0%-20.0% by weight of hydrated barium hydroxide,
wherein % by weight is based on the total weight of the composition.

In one of the features of the present invention, the base oil is selected from Group I paraffinic oil, petroleum based naphthenic oil, polyalphaolefins (PAO), polyalkyl gycol (PAG), and alkylated aromatics oil.

In another feature of the present invention, the hydroxy fatty acid having 8 to 20 carbons or mixture thereof, and the hydroxy fatty acid is selected from l2-hydroxystearic acid (12-HSA), 9,10-dihydroxystearic, 12-hydroxy-9-cis-octadecenoic acid, and 2-hydroxyhexadecanoic acid.

In another feature of the present invention, the hydrated barium hydroxide is selected from barium hydroxide monohydrate, barium hydroxide pentahydrate and barium hydroxide octahydrate.

In yet another feature of the present invention, the barium complex grease composition optionally comprises 0.1 to 0.5% of water.

The present invention also provides a method for preparing of a barium complex grease composition comprising the steps of:
i) adding and mixing a first portion of base oil, a hydroxy fatty acid and boric acid to obtain a reaction mixture;
ii) heating and maintaining the reaction mixture between 115 to 120°C for 30 to 45 minutes with continuous stirring;
iii) adding base oil to bring the temperature of the reaction mixture of step (ii) to 80 to 90°C;
iv) adding of hydrated barium hydroxide to the reaction mixture of step (iii) with continuous mixing;
v) gradually heating the reaction mixture of step (iv) to 160-180°C and maintaining at this temperature for 60 to 90 minutes for complete dehydration;
vi) gradually cooling the reaction mixture of step (v) to 135-150° C and adding second portion of base oil with continuous stirring to obtain a grease product; and
vii) milling the grease product to obtain the barium complex grease composition.

In one of the features of the present invention, the first potion of base oil of step (i) is in the range of 5-15 parts of the total weight of the base oil and the second portion of base oil of step (vi) is in the range of 85-95 parts of the total weight of the base oil.

In another feature of the present invention, in step (i) 5-15 parts of total base oil is added to the open grease kettle at 60-80°C followed by addition of 8-25 parts of hydroxy fatty acid and 0.5-5.0 parts of boric acid with continuous mixing.

In yet another feature of the present invention, in step (iii) 5-15 parts of total base oil is added.

In yet another feature of the present invention, in step (iv) 5-20 parts of hydrated barium hydroxide is added.

In yet another feature of the present invention, in step (vi) 85-95 parts of total base oil as the second portion is added.

In yet another feature of the present invention, a performance additive is added at a temperature below 80°C to the reaction mixture of step (vi), results in higher dropping points in range of 200-230°C.

In yet another feature of the present invention, the performance additive is added in the range of 0.5 to 5.0 wt.% and the performance additive is selected from mono alkyl borate, dialkyl borate and trialkyl borate; wherein:
(a) the mono alkyl borate is selected from methyl borate, ethyl borate, propyl borate, butyl borate, amyl borate and hexyl borate,
(b) dialkyl borate is selected from dimethyl borate, diethyl borate, dipropyl borate, dibutyl borate, diamyl borate and dihexyl borate and
(c) the trialkyl borate is selected from trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, triamyl borate and trihexyl borate.

In yet another feature of the present invention, the barium complex grease composition is formed in situ.

The present invention in particular, relates to a barium complex grease composition with improved shear stability, inherent extreme pressure properties and anti-wear characteristics, said grease is made by incorporating and reacting boric acid with hydroxy fatty acids prior to saponification with hydrated barium hydroxide. Present invention discloses in-situ formation of boron compounds by reacting boric acid with hydroxy fatty acids followed by neutralization with base. The present invention provides, a barium complex grease composition comprises by weight; 55.0% to 85.0% base oils 8.0%-25.0% hydroxy fatty acids, 0.5%-5.0% boric acid, 5.0%-20.0% hydrated barium hydroxide base and 0.1 to 0.5% of water if desired. The present invention provides, a saponifiable material refers to hydroxy-substituted fatty acids having 8 to 20 carbons and their mixtures. Among saponifiable materials, l2-hydroxystearic acid (12-HSA) is most preferred. The amount of saponifiable material in the present invention can vary between 8.0% and 25.0%. Preferably, the amount of saponifiable material in NLGI grade 2 grease is between 10.0 to 17.0% and most preferably between 12.0 to 15.0%. Softer or harder grades of barium complex greases may be made as per the method of the invention by changing to concentrations of saponifiable materials and boric acid.
The present invention provides, saponifiable material is reacted with 5.0%-20.0% hydrated barium hydroxide to make complex greases. The hydrated barium hydroxide is selected from barium hydroxide monohydrate, barium hydroxide pentahydrate and barium hydroxide octahydrate. The preferred hydrated barium hydroxide is barium hydroxide octahydrate. Barium monohydrate, barium hydroxide pentahydrate and barium hydroxide octahydrate used in the present invention are commercially available white fine powders having minimum 98% assay. The present invention provides, a method of preparation of barium complex grease with the characteristics of higher dropping point, shear stability and shear reversibility. Said method comprising steps of: (i) adding and mixing in a suitable open grease kettle- first potion of base oil, hydroxy fatty acids and boric acid at a temperature that ranges between ambient temperature and about 80°C (ii) heating and maintaining the composition between 115 to 120°C for 30 to 45 minutes with continuous stirring (iii) addition of base oil to bring the temperature of composition to 80 to 90°C (iv) slow addition of hydrated barium hydroxide with continuous mixing (v) continue to mixing while gradually heating the mass to 160-180°C and maintained at this temperature for 60 to 90 minutes for complete dehydration (vi) gradual cooling the composition to 135-150°C and slow addition of second portion of base oil with continuous stirring (vii) adding the performance additives below 80°C, if desired; (viii) milling the final grease to obtain final product.
In one of the preferred aspect the temperature at which base oil, hydroxy fatty acid and boric acid are at below 80°C. The method as described in the present invention provides, removal of water from the grease after the saponification wherein grease is heated gradually and maintained at certain temperature to remove the water. Vacuum may be applied along with heating for quick removal of water. The grease should be heated to temperature sufficiently high to remove the water formed during the chemical reactions during the grease making. Generally, heating temperature will be between 150°C to 180°C, most preferably between 160°C to 170°C. No water is added in comparison to other processes where extra water is added for facilitating reaction of fatty and complexing acids with barium base. The method as described in the present invention provides, gradual cooling of mass to 135-150°C after the dehydration and prior to addition of second portion of oil in order to minimize the grains during addition of second portion of base oil.

The method of the present invention provides barium complex greases having dropping point more than 220° C and having improved extreme pressure and anti-wear properties by reacting alkyl borates after the addition of second portion of the base oils. The alkyl borates include the mono-, di- and trialkyl borates, such as the mono-, di- and trimethyl, triethyl, tripropyl, tributyl, triamyl and trihexyl borates. Preferably, the amount of alkyl borate is between 0.5 to 5.0% and most preferably between 1.5 to 3.0%.

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 55.0 to 85.0% and most probably 70.0 to 80.0% 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, antioxidants, extreme pressure additives, anti-wear additives, polymers, tackifiers, dyes, chemical markers and fragrance imparters.

EXAMPLES
The disclosure will now be illustrated with working examples, which is intended to illustrate the working of disclosure and not intended to take restrictively to imply any limitations on the scope of the present disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. The following examples are set forth below to illustrate the barium complex grease composition and method for preparation thereof of the present invention and results according to the disclosed subject matter. These examples are not intended to be inclusive of all aspects of the subject matter disclosed herein, but rather to illustrate representative product and results. These examples are not intended to exclude equivalents and variations of the present invention, which are apparent to one skilled in the art.
Example 1: Barium complex grease is prepared, as per the present invention it follows:10 parts by weight of total group I paraffinic base oil having viscosity of 95 cSt at 40°C was added to a mixing vessel followed by addition of 17 parts of 12-HSA and 1.7 parts of boric acid with continuous mixing. The mixture was heated under open condition until the temperature reached 120°C and maintained at this temperature for 30 minutes. The heating was removed, and mixture was allowed to cool to 85°C with constant mixing. Cold oil can also be circulated to speed up cooling. 5 parts by weight of total group I paraffinic base oil having viscosity of 95 cSt at 40°C was also added to mixture to assist cooling. When cooled to 85° C, 12.8 parts of barium hydroxide octahydrate added slowly with continuous stirring. Temperature of mixture raised gradually to 170°C in one hour with continuous mixing and maintained at this temperature for 60 minutes to ensure complete dehydration. The heating was removed and mixture was allowed to cool to 145°C with constant mixing. When cooled to 145°C, 85 parts by weight of total group 1 paraffinic base oil having viscosity of 95 cSt at 40°C was also added to mixture with continuous stirring. The heating was removed, and mixture was allowed to cool to 85°C with constant mixing. Cold oil can also be circulated in the outer jacket of the kettle to speed up cooling. Grease was milled to obtain smooth grain free grease. Test data of finished grease is given in Table-1.
Example-2, 3, 4, 5, 6 & 7: Greases are made using same equipments, raw materials, and manufacturing process as the Example-1, except varying the thickener content and different hydrates of barium oxide.

Example 8: To understand the role of addition sequence of hydrated barium hydroxide, Example-8 grease was made using same equipments, raw materials and manufacturing process as the Example-1, except that all components were added in one go at a temperature that ranges between ambient temperature and about 80°C and temperature raised gradually to 170°C. Working and rolling shear stability of Example-8 grease was found to be lower than Example-1, while other test data was found to be similar to Example-1 grease as shown in Table-1.
Table-1
Characteristics Test Method Example-1 Example-2 Example-3 Example-4 Example-5 Example-6 Example-7 Example-8
12-HSA, parts by weight - 17.00 13.60 9.35 13.60 13.60 17.00 17.00 17.00
Boric acid, parts by weight - 1.70 1.70 1.70 2.2 3.0 1.70 1.70 1.70
Barium hydroxide octahydrate, parts by weight - 12.80 10.40 7.20 13.00 17.10 0.00 0.00 12.80
Barium hydroxide pentahydrate, parts by weight - 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Barium hydroxide monohydrate, parts by weight - 0.00 0.00 0.00 0.00 0.00 8.50 10.10 0.00
Group I paraffinic base oil (95 cSt at 40 Deg C), parts by weight - 68.50
74.30
81.75
71.20
66.30
72.80
71.20
68.50

Characteristics - Example-1 Example-2 Example-3 Example-4 Example-5 Example-6 Example-7 Example-8
Thickener, % wt - 31.5 25.7 18.3 28.8 33.7 27.2 28.8 31.5
Worked penetration ASTM D217 235 275 325 288 295 245 243 233
Change in consistency after 100000 double strokes ASTM D217 +8 +6 +6 +8 +10 +10 +8 +25
Dropping point, Deg C ASTM D566 187 186 185 195 199 185 187 184
Change in consistency, 2 hours roll stability test at 25 Deg C ASTM D1831 +10 +8 +7 +12 +12 +8 +10 +20
Change in consistency, 16 hours roll stability test at 80 Deg C ASTM D1831 +8 +7 +7 +8 +9 +10 +8 +35
Weld Load, Kg IP 239 225 225 225 250 250 225 225 225
Wear Scar Dia, mm ASTM D2266 0.60 0.60 0.60 0.60 0.60 0.60 0.60 0.60

Example 9: To understand the role of boric acid, Example-9 grease was made using same equipments, raw materials and manufacturing process as the Example-1, except that no boric acid was used and barium hydroxide octahydrate was added slowly with continuous stirring and temperature raised gradually to 170°C. Working and rolling shear stability and dropping point of Example-9 grease was found to be significantly lower than Example-1 grease. Extreme pressure properties and anti-wear characteristics were also found to be inferior while other test data was found to be similar to Example-1 grease as shown in Table-2.

Table-2
Characteristics Test Method Example-1 Example-9
Thickener content, % wt - 31.5 31.5
Boric Acid, % wt - 1.70 0.00
Worked penetration ASTM D217 235 240
Change in consistency after 100000 double strokes ASTM D217 +8 +39
Dropping point, Deg C ASTM D566 187 172
Change in consistency, 2 hours roll stability test at 25 Deg C ASTM D1831 +10 +58
Change in consistency, 16 hours roll stability test at 80 Deg C ASTM D1831 +8 +88
Weld Load, Kg IP 239 225 160
Wear Scar Dia, mm ASTM D2266 0.60 0.75

Example-10&11: Example-8&9 batches were taken similar using same equipments, raw materials and manufacturing process as the Example-1, except that mixture of 12-HSA and boric acid was maintained at 100°C and 140°C respectively for 30 minutes prior to cooling to 85°C for addition of hydrated barium hydroxide. Working and rolling shear stability of Example-10 grease was found to be significantly lower than Example-1 grease while Example-11 grease data was found to similar to Example-1 grease as shown in Table-3.

Example-12&13: Example-12&13 batches were taken similar using same equipments, raw materials and manufacturing process as the Example-1, except that mixture of 12-HSA and boric acid was hold at 120°C for 60 minutes and 90 respectively prior to cooling to 85°C for addition of hydrated barium hydroxide base. Test data of Example-12&13 greases was found to similar to Example-1 grease as shown in Table-3.

Example-14: Example-14 batch was taken similar using same equipments, raw materials and manufacturing process as the Example-1, except that hydrated barium hydroxide was added to the mixture of 12-HSA and boric acid at 120°C after holding for 30 minutes. Excessive uncontrollable frothing was observed during addition of barium hydroxide octahydrate.
Table-3
Characteristics Test Method Example-1 Example-10 Example-11 Example-12 Example
-13
Hold temperature for mixing 12-HSA and boric acid, Deg C - 120 100 140 120 120
Hold time, minutes - 30 30 30 60 90
Worked penetration ASTM D217 235 240 +237 238 237
Change in consistency after 100000 double strokes ASTM D217 +8 +25 +5 +7 +5
Dropping point, Deg C ASTM D566 187 172 182 182 181
Change in consistency, 2 hours roll stability test at 25 Deg C ASTM D1831 +10 +58 +9 +11 +10
Change in consistency, 16 hours roll stability test at 80 Deg C ASTM D1831 +12 +55 +7 +7 +8
Weld Load, Kg IP 239 225 225 225 225 225
Wear Scar Dia, mm ASTM D2266 0.60 0.60 0.60 0.60 0.60

Example 15: To understand the role of temperature for addition of second portion of oil, Example-15 batch was taken similar using same equipments, raw materials and manufacturing process as the Example-1, except that second portion of oil was added at 170°C. Very grainy grease was obtained which required multiple pass milling for smooth grain free structure. Test data of Example-15 grease was found to similar to Example-1 grease.

Example-16&17: To understand the role of complexing acids other than boric acid, Example-16&17 batches was taken similar using same equipments, raw materials and manufacturing process as the Example-1, except that sebacic acid and azelaic acid were used respectively. Softer greases with poor shear stability were obtained. Composition and test data of Example-16 &17 are given in Table-4.

Example 18&19: To understand the role of alkyl borate, Example-18 &19 batches were taken similar using same equipments; raw materials and manufacturing process as the Example-1, except that 2.0% of commercially available tributyl borate and triamyl borate were added and mixed at 100 to 110°C after the addition of second portion of base oil but before milling. Both greases have dropping points of more than 220°C and improved extreme pressure & anti-wear properties as shown in Table-5.
Table-4
Characteristics - Example-1 Example-16 Example-17
Thickener, % wt - 31.5 31.5 31.5
Complexing acid & %wt - Boric acid (1.7%) Sebacic acid (1.7%) Azelaic acid (1.7%)
Worked penetration ASTM D217 235 310 315
Change in consistency after 100000 double strokes ASTM D217 +8 +35 +45
Dropping point, Deg C ASTM D566 187 172 185

Completion of the reaction is monitored by measuring the acidity/alkalinity of the soap as per IP37 test method before dehydration. No water is added for making barium grease as water produced during reaction of 12-HSA and hydrated barium hydroxide is sufficient for the completion of the reaction.

Example 20: To understand the role of added water, Example-20 batch was similar using same equipments; raw materials and manufacturing process as the Example-1, except that 1.0% water was added 15 minutes after the addition of hydrated barium hydroxide. Test data of Example-20 grease was found to be identical to Example-1 grease except shear stability. Shear stability of Example-20 was found to be inferior in comparison to Example-1 grease as shown in Table-5.
Table-5
Characteristics Test Method Example-1 Example-18 Example-19 Example-20
Thickener content, % wt - 31.5 31.5 31.5 31.5
Tributyl borate, % wt - 0.0 2.0 0.0 0.0
Trimayl borate, % wt - 0.0 0.0 2.0 0.0
Worked penetration ASTM D217 235 240 241 243
Change in consistency after 100000 double strokes ASTM D217 +8 +7 +5 +25
Dropping point, oC ASTM D566 187 225 223 186
Change in consistency, 2 hours roll stability test at 25oC ASTM D1831 +10 +6 +8 +32
Change in consistency, 16 hours roll stability test at 80oC ASTM D1831 +12 +10 +11 +35
Weld Load, Kg IP 239 225 315 315 225
Wear Scar Dia, mm ASTM D2266 0.60 0.45 0.45 0.60

Summarizing thus far, these examples taken together strongly demonstrate the following: (1) barium complex greases having high dropping points and having excellent resistance to mechanical, or shear break down can be prepared; (2) greases having inherently high weld loads and anti-wear characteristics can be prepared without addition of performance additives (3) Dropping points and welds loads can be further improved with addition of alkyl borates.

Example-21 grease demonstrates how the present invention can be applied to prepare barium complex grease composition useful for high temperature and high load applications. It was made as follows: 10 parts by weight of group I paraffinic base oil having viscosity of 460 cSt at 40°C was added to a mixing vessel followed by addition of 17 parts of 12-HSA and 1.7 parts of boric acid with continuous mixing. Mixing was done using the planetary paddle. The mix was heated under open condition until the temperature reached 120°C and maintained at this temperature for 30 minutes. The heating was removed, and mixture was allowed to cool to 85°C with constant mixing. Cold oil can also be circulated to speed up cooling in the outer jacket of the kettle. 5 parts by weight of group I paraffinic base oil having viscosity of 460 cSt at 40°C was also added to mixture to assist cooling. When cooled to 85° C, 12.8 parts of barium hydroxide octahydrate added slowly with continuous stirring. Temperature of mixture raised gradually to 170°C with continuous mixing and maintained at this temperature for 60 minutes to ensure complete dehydration. The heating was removed, and mixture was allowed to cool to 145°C with constant mixing. When cooled to 145° C, 85 parts by weight of group I paraffinic base oil having viscosity of 460 cSt at 40°C was also added to mixture with fast stirring. The heating was removed, and mixture was allowed to cool to 110°C. At 110° C, added 2 parts of commercially available borate ester package (LZ 5370C from M/s Lubrizol corporation) and mixed thoroughly with continuous cooling. At 85° C, 3 parts of commercially available grease package (LZ 5235 from M/s Lubrizol corporation) was added, mixed properly and milled through homogenizer to obtain smooth grain free grease. Cold oil can also be circulated to speed up cooling. Several lab batches were made according to the above procedure and tested. The average results of those tests are given in Table-6.
Table-6
Composition and test Data of Example-21 barium complex grease
Components Composition (parts by weight)
12-HSA 13.60
Boric acid 1.70
Barium hydroxide octahydrate 10.00
Group 1 paraffinic base oil (460 cSt at 40 Deg C) parts by weight 69.70
LZ 5370C 2.00
LZ 5235 3.00
Test Method Result
Consistency, 1/10 mm
Unworked
After 60 double strokes
After 100000 double strokes ASTM D-217
285
283
295
Dropping Point, Deg C ASTM D566 240
Oil separation, % wt ASTM D6184 1.0
Roll stability test, Change in consistency
2 hours, 30 Deg C
16 hours, 30 Deg C
16 hours, 80 Deg C ASTM D1831
+8
+12
+12
Rust Preventive, rating ASTM D1743 Pass
EMCOR, rating IP220 0, 0
Copper Corrosion, rating ASTM D4048 1a
Water washout, %wt ASTM D1264 1.5
Weld load, kg IP239 355
Wear Scar Dia, mm ASTM D2266 0.50

Barium complex greases developed as per present invention were found to have characteristics of shear reversibility. Grease samples worked in high temperature roll stability tests retained their original consistency when kept undisturbed at ambient temperature as shown in Table-7.
Table-7
Test Method Result
Worked consistency of Example-17 grease ASTM D1403 283
Worked consistency of Example-17 grease after high temperature roll stability test at 80 Deg C for 16 hours ASTM D1831/
ASTM D1403
297
Worked consistency of Example-17 grease after kept undisturbed for 24 hours at ambient temperature ASTM D1403 285

The examples of the present invention herein fall in the NLGI No. 2 or No. 3 grade, it should be further understood that the scope of this present invention includes all NLGI consistency grades harder and softer than a No. 2 grade. However, for such greases according to the present invention that are not NLGI No. 2 & 3 grade, their properties should be consistent with what would have been obtained if more or less base oil had been used so as to provide a No. 2 & 3 grade product, as will be understood by those of ordinary skill in the art.

As used herein, “thickener content” applies to the concentration of the hydroxy fatty acid (12-HSA), boric acid and hydrated barium hydroxide required to provide grease with a specific desired consistency as measured by the standard penetration tests ASTM D217. Similarly used herein the “dropping point” of grease shall refer to the value obtained by using the standard dropping point test ASTM D566 commonly used in lubricating grease manufacturing. As used herein, quantities of ingredients identified parts by weight during grease manufacturing.

Those of ordinary skill in the art will appreciate upon reading this specification, including the examples contained herein, that modifications and alterations to the composition and methodology for making the composition may be made within the scope of the invention and it is intended that the scope of the invention disclosed herein be limited only by the broadest interpretation of the appended claims to which the inventor is legally entitled.

Advantages:
Barium complex grease composition and method for preparation of same as per present invention described herein provides multiple advantages in general and over the methods known in the art and some of the important advantages are given herein.
i. barium complex greases having properties such shear stability, shear reversibility, inherent extreme pressure and anti-wear is prepared in required consistency with low soap content.
ii. Barium complex greases are used for high temperature application particularly in steel plants, cement plant, etc. Barium complex greases are also used in defense industry for very critical applications.
iii. The method as described herein is a simple, time and energy saving method in which no water is added for saponification.
iv. The method as described herein provides in situ formation of boron compounds by reacting boric acid with hydroxy fatty acids followed by neutralization with base, while still maintaining or achieving better performance in comparison to conventional barium complex greases.
, Claims:1. A barium complex grease composition comprising:
(a) 55.0% to 85.0% by weight of a base oil;
(b) 8.0%-25.0% by weight a hydroxy fatty acid;
(c) 0.5%-5.0% by weight of boric acid; and
(d) 5.0%-20.0% by weight of hydrated barium hydroxide,
wherein % by weight is based on the total weight of the composition.

2. The barium complex grease composition as claimed in claim 1, wherein the base oil is selected from Group I paraffinic oil, petroleum based naphthenic oil, polyalphaolefins (PAO), polyalkyl gycol (PAG), and alkylated aromatics oil.

3. The Barium complex grease composition as claimed in claim 1, wherein the hydroxy fatty acid having 8 to 20 carbons or mixture thereof, and the hydroxy fatty acid is selected from l2-hydroxystearic acid (12-HSA), 9,10-dihydroxystearic, 12-hydroxy-9-cis-octadecenoic acid, and 2-Hydroxyhexadecanoic acid.

4. The Barium complex grease composition as claimed in claim 1, wherein the hydrated barium hydroxide is selected from barium hydroxide monohydrate, barium hydroxide pentahydrate and barium hydroxide octahydrate.

5. The barium complex grease composition as claimed in claim 1, optionally comprises 0.1 to 0.5% of water.

6. A method for preparing of a barium complex grease composition comprising the steps of:
i) adding and mixing a first potion of base oil, a hydroxy fatty acid and boric acid to obtain a reaction mixture;
ii) heating and maintaining the reaction mixture between 115 to 120°C for 30 to 45 minutes with continuous stirring;
iii) adding base oil to bring the temperature of the reaction mixture of step (ii) to 80 to 90°C;
iv) adding of hydrated barium hydroxide to the reaction mixture of step (iii) with continuous mixing;
v) gradually heating the reaction mixture of step (iv) to 160-180°C and maintaining at this temperature for 60 to 90 minutes for complete dehydration;
vi) gradually cooling the reaction mixture of step (v) to 135-150° C and adding second portion of base oil with continuous stirring to obtain a grease product; and
vii) milling the grease product to obtain the barium complex grease composition.

7. The method as claimed in claim 6, wherein the first potion of base oil of step (i) is in the range of 5-15 parts of the total weight of base oil and the second portion of base oil of step (vi) is in the range of 85-95 parts of the total weight of the base oil.

8. The method as claimed in claim 6, wherein in step (i) 5-15 parts of total weight of base oil is added to the open grease kettle at 60-80°C followed by addition of 8-25 parts of the hydroxy fatty acid and 0.5-5.0 parts of boric acid with continuous mixing.

9. The method as claimed in claim 6, wherein in step (iii) 5-15 parts of total base oil is added.

10. The method as claimed in claim 6, wherein in step (iv) 5-20 parts of hydrated barium hydroxide is added.

11. The method as claimed in claim 6, wherein a performance additive is added at a temperature below 80°C to the reaction mixture of step (vi), results in higher dropping points in range of 200-230°C.

12. The method as claimed in claim 11, wherein the performance additive is added in the range of 0.5 to 5.0 wt.% and the performance additive is selected from mono alkyl borate, dialkyl borate and trialkyl borate; wherein:
(a) the mono alkyl borate is selected from methyl borate, ethyl borate, propyl borate, butyl borate, amyl borate and hexyl borate,
(b) dialkyl borate is selected from dimethyl borate, diethyl borate, dipropyl borate, dibutyl borate, diamyl borate and dihexyl borate and
(c) the trialkyl borate is selected from trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, triamyl borate and trihexyl borate.

13. The method as claimed in claim 6, wherein the barium complex grease composition is formed in situ.