GB1592165A - Lubricating greases - Google Patents

Description

(54) LUBRICATING GREASES (71) We, EXXON RESEARCH AND ENGINEERING COMPANY, a Corporation duly organised and existing under the laws of the State of Delaware, United States of America, of Linden, New Jersey, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to lubricating greases. At the present time there are a large number of different types of greases available. They can be broadly classified, from the standpoint of cost, as expensive because of the soap-forming ingredients employed and/or because of requiring a high soap content.

There is need for a low cost grease which has a sufficient number of properties to enable the grease to be employed as a general purpose grease.

One object of the present invention is to provide a novel calcium complex general purpose, low cost, grease. Another object is the provision of a method for the preparation of such a grease.

In accordance with an aspect of the invention there is provided a calcium complex lubricating grease having the following combination of components and properties: (a) a major proportion by weight of a paraffinic or naphthenic mineral oil base or a synthetic oil, or a mixture of any two or all of those; (b) 7 to 17 wt.% of calcium complex soap derived from a calcium base, a C1 to C3 aliphatic carboxylic acid and one or more fatty acids or glycerides selected from tallow, tallow fatty acids, stearic acid or hydrogenated fish oil acids; the weight ratio of said fatty acid to said C1 to C3 acid being greater than 1:1; (c) one or more conventional oxidation inhibitors, the total amount of which does not exceed 5 wt.%; (d) a dropping point of at least 1700C; and (e) a dry-running temperature, as measured by Test Run B of the DIN 51806 standard, of at least 140"C.

Preferred such greases contain from 7 to 13 wt.% of component (b), with 8 to 12 wt.%.

being especially preferred.

A calcium complex lubricating grease according to the present invention can have its dropping point (d) at least 2000C, even above 300"C. In practice, although calcium complex greases are suitable for uses at high temperature they are somewhat prone to fail in the lubrication of anti-friction bearings because of "dry-running", a term which denotes a drying up of the anti-friction bearing due to more or less complete separation of the grease from sliding surfaces in the bearing. The SKF R2F ("SKF" is a registered Trade Mark) Anti-Friction-Bearing-Lubrication-Testing-Machine according to German Standard DIN 51 806, constitutes a recognized test machine for observation of dry-running. Test run B of DIN 51806 is carried out at 1500 r.p.m. and under additional heating conditions.

Preferably the lower carboxylic acid of the complex soap is acetic acid, but may be formic or propionic acid; and the acid per se is meant in quantities and other references herein.

Preferably the higher carboxylic acid of the complex soap is a mixture such as tallow fatty acids, employed as such or in glyceride form as tallow. Other acids may be employed, for example stearic acid or hydrogenated fish oil acids, which latter are essentially a mixture of C14 to C22 saturated acids and which correspond in practice to commercial stearic acid in degree of saturation and average molecular weight.

Desirably the wt. ratio of fatty acids to lower acid is greater than 1:1, and is preferably from 1.5:1 to 2.0:1. A mole ratio of acetic:fatty acids of about 3:1 is preferred.

Normally, from 0.5 to 2.5 wt.% of the oxidation inhibitor will be employed. Suitably the inhibitor is phenyl-alpha-naphthylamine, or is that sold under the name Vanlube RD (the word VANLUBE is a registered Trade Mark), being a polymerized trimethyldihydroquinoline compound. If necessary up to 5 wt.% of corrosion inhibitor(s) may be incorporated into the greases of this invention. From 0.25 wt.% to 2.5 wt.% is a suitable range, with 0.5 to 1.0 wt.% being preferred; including known sulphonates of calcium or barium. The product commercially available under the trade name Alox 2116A is one suitable product.

One or more other additives may, if desired, be present. Thus, for example, an extreme pressure agent such as dibenzyl disulphide or sulphurised sperm oil; a metal deactivator such as an ethylene diamine type complexing compound; an anti-wear agent such as zinc dialkyldithiophosphate; and a water-resistance additive such as the known high mol. wt.

isobutylene polymer type. Normally up to 2.5 wt.% based on the grease of any of these can be employed, with 0.25 to 1 wt.% being the usual amount.

Hence, greases in accordance with the invention usually consist of over 80 wt.% of the base oil. They do not contain any appreciable water content; less than 0.1 wt.% being normal.

The paraffinic base mineral oil will preferably have a viscosity in the range 105-115 cSt at 40"C, a minimum flash point of at least 245"C and a maximum pour point of -5"C, preferably -10"C or lower. It is an especial advantage of the invention that paraffinic base oils can be used.

The naphthenic base mineral oil will preferably be a phenol-or other extracted, hydrofined, oil. Preferably the oil will have a viscosity in the range 105-115 cSt at 400C; a flash point of at least 225"C and a pour point not higher than -5"C, preferably -10"C or lower.

The mineral base oil can be at least partly replaced by one or more other types, for example synthetic oils, provided that they are stable under the manufacturing conditions. If not stable, but are miscible with mineral oil (for example ester, diester oil bases), then the grease can be initially made with a content of mineral oil and then diluted with the synthetic or other base to the full base oil content of the required grease. As examples of synthetic oils reference is made to polyethylene glycol ethers and polypropylene glycol ethers.

A very preferred grease in accordance with the invention is derived from about 3 wt.% glacial acetic acid, about 5% tallow fatty acids, and about 3 wt.% of hydrated lime. The base oil is preferably the paraffinic type.

In accordance with another aspect, the invention provides a method of preparing a grease defined above, which method includes the steps of (i) heating the constituents in quantities required to form the defined calcium complex soap component (b) with at least part of the defined oil component (a), the heating being conducted so that the maximum temperature reached in the mixture during the heating lies in the range 240"C to 2500C; (ii) adding the defined component(s) (c) in the defined total quantity, and the remainder, if any, of the defined component (a) being added at the stage or stages conventional in grease manufacturing processes.

Hydrated lime is the preferred calcium base saponifying agent, but calcium oxide may be used. The base is preferably used in from 20 to 40 wt.%, suitably 25 to 35 wt.% of the total of acids plus calcium base. It is highly preferred that the amount of calcium base employed is such that there is an alkalinity (as defined in AM-S 160.40) in the finished grease of from 0.3 to 1.5 wt.%, preferably 0.3 to 0.6 wt.%.

The preferred range for the said maximum temperature is 242"C to 2480C, the most preferred range being 243"C to 247"C. Suitably, the maximum temperature is held for at least half an hour.

If required the manufacture can be conducted under an inert gas blanket, for example a nitrogen blanket. This may be desirable if the flash point of the mineral or other base oil being employed is close to the maximum manufacturing temperature employed. If during manufacture foaming occurs, the use of a small quantity of an alkali metal sulphonate, especially a petroleum sulphonate, may be found useful as an anti-foamant. In all cases the antioxidant and any corrosion inhibitor and/or other normal grease additives employed, is preferably added during cooling from the said maximum manufacturing temperature.

It has been surprisingly and unexpectedly found that the unworked and worked penetration (ASTM D217) of the grease products is a minimum and almost constant when the maximum manufacturing temperature is within the range 242"C to 2480C, particularly in the range 243"C to 247"C. This is illustrated hereinafter. Other properties of the grease products are also illustrated hereinafter. It is also found that the tendency to hardening (particularly at higher temperatures) is low, being comparable to lithium hydroxy-stearate greases.

Example I A calcium complex grease was made employing 5 wt.% of tallow fatty acids; 3 wt.% glacial acetic acid; 3 wt. 4b of hydrated lime; 0.5 wt.% of phenyl-alpha-naphthylamine. The remainder was a paraffinic mineral oil having the preferred characteristics hereinbefore referred to. About half the required mineral oil was present initially, its temperature being raised to about 100"C over a period, during which period the tallow fatty acids, hydrated lime and glacial acetic acid were added.

A further amount of the mineral oil was added, leaving about 10%. The mixture was then further heated until its temperature was within the range 243"C to 2470C and was held at that maximum for at least thirty minutes. Alkalinity was 0.6% (AM-S 160.40). Cooling was commenced, the amine compound and remaining mineral oil added, and the grease homogenised.

The product was a Grade 2 grease, of 10 wt. % to 12 wt. % soap content. The grease had a drop point of about 300"C, and passed the said DIN 51806 Test Run B at 140"C ("SKF" is a registered Trade Mark). The oil separation ASTM D 1742 was 2.3 wt. %; whilst on storage at 40"C for 168 hours (IP 121/DIN 51817) it was 3.0 wt.%. The grease passed the EMCOR Corrosion Test (DIN 51802).

It will be appreciated that by slightly raising or lowering the amount of the soap-making constituents a grease having a somewhat higher or lower soap content is obtainable. In all cases, however, to obtain the benefits of the invention, the maximum manufacturing temperature must be kept in the range 240"C to 250"C and very preferably in the range 243"C to 247"C.

Example 2 Following the procedure of Example 1, but altering only the maximum temperature in the range 239"C to 2510C a series of greases was made and tested for unworked and worked penetration (ASTM D 217). From the graph which was plotted, the following table was compiled. The influence of maximum manufacturing temperature (MMT) on penetrationis very clearly seen, together with a surprising constancy over the range 243 to 2470C.

MMT "C Penetration Unworked 60X 239 270 320 240 250 300 241 240 290 242 235 280 243 230 275 244 230 275 245 230 275 246 230 275 247 230 275 248 235 285 249 260 300 250 280 330 251 320 400 The greases of lowest penetration, i.e. the hardest, for the very low soap content (10 to 12 wt. %) and made from low cost materials, are those made in accordance with invention, that is to say in the maximum temperature range of 240"C to 2500C, especially 243"C to 2470C; and those greases have the properties (d) and (e) hereinbefore defined.

The difference in the above table of 45 tenths of a mm between the ASTM D 217 unworked and worked penetrations (over the preferred maximum manufacturing temperature range 243 to 2470C) has been found to represent the highest likely difference in practice. It is possible, for example, by slight adjustments of component quantities, to reduce that difference to less than 20 tenths of a mm.

WHAT WE CLAIM IS: 1. A calcium complex lubricating grease having the following combination of components and properties: (a a major proportion by weight of a paraffinic or naphthenic mineral oil base or a synthetic oil, or a mixture of any two or all of these; (b) 7 to 17 wt.% of calcium complex soap derived from a calcium base, a C1 to C3 aliphatic carboxylic acid and one or more fatty acids or glycerides selected from tallow, tallow fatty acids, stearic acid or hydrogenated fish oil acids; the weight ratio of said fatty acid to said C1 to C3 acid being greater than 1:1; (c) one or more conventional oxidation inhibitors, the total amount of which does not exceed 5 wt.%; (d) a dropping point of at least 1700C; and (e) a dry-running temperature, as measured by Test Run B of the DIN 51806 standard, of at least 140"C.

2. A lubricating grease as claimed in claim 1, in which component (a) is a paraffinic mineral oil.

3. A lubricating grease as claimed in claim 1 or claim 2, wherein the weight ratio of said fatty acid to said C1 to C3 acid is from 1.5:1 to 2.0:1.

4. A lubricating grease as claimed in any preceding claim, wherein the calcium complex soap is derived from tallow fatty acid and acetic acid.

5. A lubricating grease as claimed in any preceding claim, containing 7 to 13 wit. % of component (b).

6. A method of preparing the calcium complex lubricating grease claimed in any preceding claim, which method includes the steps of (i) heating the constituents in quantities required to form the defined calcium complex soap component (b) with at least part of the defined oil component (a), the heating being conducted so that the maximum temperature reached in the mixture during the heating will lie in the range 240"cato 250"C; (ii) adding the defined component(s) (c) in the defined total quantity, and the remainder, if any, of the defined component (a) at the stage or stages conventional in grease manufacturing processes.

7. A method as claimed in claim 6, wherein the calcium base is employed in an excess quantity sufficient to give the grease an alkalinity measurement (as defined in AM-S 160.40) of 0.3 to 1.5 wt.%, preferably 0.3 to 0.6 wt.%.

8. A method as claimed in claim 6 or claim 7, wherein the calcium base is hydrated lime.

9. A method as claimed in any one of claims 6 to 8, wherein the said maximum temperature lies in the range 243"C to 247"C.

10. A method as claimed in any one of claims 6 to 9 and substantially as herein described.

11. A method as claimed in claim 6 and substantially as herein described with reference to Example 1 or Example 2.

12. A calcium complex lubricating grease as claimed in claim 1 and substantially as herein described.

13. A calcium complex lubricating grease substantially as herein described with reference to Example 1.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (13)

**WARNING** start of CLMS field may overlap end of DESC **. and those greases have the properties (d) and (e) hereinbefore defined. The difference in the above table of 45 tenths of a mm between the ASTM D 217 unworked and worked penetrations (over the preferred maximum manufacturing temperature range 243 to 2470C) has been found to represent the highest likely difference in practice. It is possible, for example, by slight adjustments of component quantities, to reduce that difference to less than 20 tenths of a mm. WHAT WE CLAIM IS:

1. A calcium complex lubricating grease having the following combination of components and properties: (a a major proportion by weight of a paraffinic or naphthenic mineral oil base or a synthetic oil, or a mixture of any two or all of these; (b) 7 to 17 wt.% of calcium complex soap derived from a calcium base, a C1 to C3 aliphatic carboxylic acid and one or more fatty acids or glycerides selected from tallow, tallow fatty acids, stearic acid or hydrogenated fish oil acids; the weight ratio of said fatty acid to said C1 to C3 acid being greater than 1:1; (c) one or more conventional oxidation inhibitors, the total amount of which does not exceed 5 wt.%; (d) a dropping point of at least 1700C; and (e) a dry-running temperature, as measured by Test Run B of the DIN 51806 standard, of at least 140"C.

2. A lubricating grease as claimed in claim 1, in which component (a) is a paraffinic mineral oil.

3. A lubricating grease as claimed in claim 1 or claim 2, wherein the weight ratio of said fatty acid to said C1 to C3 acid is from 1.5:1 to 2.0:1.

4. A lubricating grease as claimed in any preceding claim, wherein the calcium complex soap is derived from tallow fatty acid and acetic acid.

5. A lubricating grease as claimed in any preceding claim, containing 7 to 13 wit. % of component (b).

6. A method of preparing the calcium complex lubricating grease claimed in any preceding claim, which method includes the steps of (i) heating the constituents in quantities required to form the defined calcium complex soap component (b) with at least part of the defined oil component (a), the heating being conducted so that the maximum temperature reached in the mixture during the heating will lie in the range 240"cato 250"C; (ii) adding the defined component(s) (c) in the defined total quantity, and the remainder, if any, of the defined component (a) at the stage or stages conventional in grease manufacturing processes.

7. A method as claimed in claim 6, wherein the calcium base is employed in an excess quantity sufficient to give the grease an alkalinity measurement (as defined in AM-S

160.40) of 0.3 to 1.5 wt.%, preferably 0.3 to 0.6 wt.%.

8. A method as claimed in claim 6 or claim 7, wherein the calcium base is hydrated lime.

9. A method as claimed in any one of claims 6 to 8, wherein the said maximum temperature lies in the range 243"C to 247"C.

10. A method as claimed in any one of claims 6 to 9 and substantially as herein described.

11. A method as claimed in claim 6 and substantially as herein described with reference to Example 1 or Example 2.

12. A calcium complex lubricating grease as claimed in claim 1 and substantially as herein described.

13. A calcium complex lubricating grease substantially as herein described with reference to Example 1.