Lubricating grease composition

Abstract

A lubricating grease composition, and more specifically, to a lubricating grease composition which, when used with an article clamping device, such as a chuck, produces excellent lubricating properties whilst remaining strongly adhered to metal parts in the clamping mechanism of the device and showing enhanced chemical and physical resistance to fluids such as cutting fluids with which they come into contact.

Claims

1. A lubricating grease composition comprising: a) from 20.69 to 50.8% by weight of one or more solid lubricants powders comprising hydrated tricalcium phosphate and calcium carbonate treated with stearic acid; b) from 14.3 to 36.5% by weight of or one more base oils comprising mineral oil; c) from 7.5 to 9.9% by weight of one or more adhesion improver comprising polyisobutylene; d) from 3 to 4.8% by weight of one or more waxes comprising beeswax and synthetic hydrocarbon wax; e) from 19 to 40.6% by weight of one or more thickeners comprising lithium-12-hydroxystearate and zinc stearate; and an optional corrosion inhibitor present in an amount of from 0 to 1% by weight.

2. A lubricating grease composition in accordance with claim 1 wherein the adhesion improver (c) further comprises other polymers dissolved in oil chosen from Poly(methyl methacrylate) and thermoplastic elastomer block-copolymers from the groups TPE-A, thermoplastic copolyesters (TPE-E), thermoplastic olefins (TPE-O), thermoplastic styrene block copolymers (TPE-S), thermoplastic polyurethanes (TPE-U) and/or elastomeric alloys (TPE-V).

3. A lubricating grease composition in accordance with claim 1 wherein the wax (d) further comprises one or more natural waxes, synthetic hydrocarbon waxes, polymer waxes, or mixtures thereof.

4. A lubricating grease composition in accordance with claim 1 which additionally comprises up to 10% by weight of one or more additives.

5. A lubricating grease composition in accordance with claim 4 wherein the additives are selected from one or more friction modifiers, anti-wear additives, extreme pressure additives, seal swelling agents, pour point depressants, anti-oxidants, free-radical scavengers, hydroperoxide decomposers, metal passivators, surface active agents chosen from detergents, emulsifiers, demulsifiers, defoamants, dispersants, deposit control additives, film forming additives, tackifiers, antimicrobials, additives for biodegradable lubricants, haze inhibitors, chromophores, and limited slip additives and mixtures thereof.

6. A lubricating grease composition in accordance with claim 1 further comprising a metallic single or complex soap of lithium, aluminium, zinc, magnesium, sodium, barium and calcium, polyurea, PTFE, silica and/or bentonite, and/or mixtures thereof.

7. An article clamping device lubricating grease in accordance with claim 1.

8. An article clamping device lubricating grease in accordance with claim 7 wherein the device is a keyed chuck device, a keyless chuck, a collet and fastening devices or mechanisms for attaching grinding discs, saw blades, and the like to drive spindles.

9. A method of making a lubricating grease in accordance with claim 1 comprising the steps of: adding adhesion promoter c), waxes d) and thickeners e) into the base oil(s) b), stirring and optionally heating until homogeneously mixed; (ii) adding component a) the solid lubricant(s) to the composition of (i) and mixing until homogeneous; (iii) cooling to room temperature with continuous stirring; (iv) optionally adding optional additives, during step (iii); and (v) optionally finishing using a suitable finishing device.

10. An article clamping device comprising a lubricating grease composition in accordance with claim 1.

11. An article clamping device in accordance with claim 10 wherein the device is a keyed chuck device, a keyless chuck, a collet and fastening devices or mechanisms for attaching grinding discs, saw blades, and the like to drive spindles.

12. The lubricating grease of claim 1 wherein the one or more solid lubricants powders is present in an amount of 50.8% by weight.

13. The lubricating grease of claim 1 wherein the one or more solid lubricants powders is present in an amount of 20.69% by weight.

14. The lubricating grease of claim 1 wherein the one or more solid lubricants powders is present in an amount of 30.7% by weight.

15. The lubricating grease of claim 1 wherein the mineral oil is present in an amount of 14.3% by weight.

16. The lubricating grease of claim 1 wherein the mineral oil is present in an amount of 17.1% by weight.

17. The lubricating grease of claim 1 wherein the mineral oil is present in an amount of 24.75% by weight.

18. The lubricating grease of claim 1 wherein the mineral oil is present in an amount of 36.5% by weight.

19. The lubricating grease of claim 1 wherein the one or more thickeners is present in an amount of 19 to 21.7% by weight.

20. The lubricating grease of claim 1 wherein the one or more thickeners is present in an amount of 40.6% by weight.

Description

EXAMPLES

(1) The invention will be further described with reference to practical examples and comparative examples. It is understood, however, that the invention is not limited by the aforementioned practical examples.

(2) Compositions of greases as hereinbefore described were prepared in accordance with the formulations in Table 1.

(3) TABLE-US-00001 TABLE 1 Example Example Example Example Ingredient A B C D Calcium Carbonate 41.50% 41.50% 16.83% 25.00% Polyisobutylene  9.00%  9.00%   9.9%  7.50% Tricalcium Phosphate  9.30%  9.30%  3.86%  5.70% Mineral White Oil 17.10% 14.30% 24.75% 36.50% Mineral Oil Li-12- 18.00% 20.70% 40.60% 14.50% Hydroxystearate Grease Beeswax  1.55%   1.6%  1.53%  2.40% Synthetic Hydrocarbon  1.55%   1.6%  1.53%  2.40% Wax Zinc Stearate  1.00%  1.00% —  6.00% Corrosion Inhibitor  1.00%  1.00%  1.00% — Total   100%   100%   100%   100%

(4) It can be seen from the composition content that the lubricant grease as described herein does not contain any toxic, environmental toxic or harmful substances.

(5) The samples were then compared with two commercial products to determine the clamping force drop. A Schunk Rota S plus 2.0 manual lathe chuck was lubricated with the sample/comparative being tested and the static clamping force of the chuck was measured. The clamping mechanism of the chuck was moved by using a screw supplied on the side of the chuck. The screw was fitted to an in-house designed adapter which was programmed to tighten the screw (and consequently the chuck) at a speed of 10 revolutions per minute (rpm or sometimes written as 10 l/min) until a torque of 80 Nm was achieved. Once the 80 Nm torque threshold was reached the screw was maintained at that torque for a period of five seconds and then the tightening step was reversed to loosen the chuck at the same speed (10 rpm) to complete a cycle. This process was repeated 100 times, Results with respect to each lubricating grease used following this process were provided in Table 2 below.

(6) TABLE-US-00002 TABLE 2 Cycle Cycle Clamping 1 100 Max. Min. Average Force Drop Example [kN] [kN] [kN] [kN] [kN] (%) A 108.9 105.0 110.4 105.0 106.6 3.6 B 109.8 95.4 110.4 95.1 99.7 13.1 C 111.0 105.9 111.0 105.6 107.5 4.6 D 114.0 113.1 114.9 112.5 113.5 0.8 Comp. 1 114.6 90.3 114.6 90.3 97.3 21.2 Comp. 2 88.8 62.7 88.8 62.7 72.7 29.4

(7) It will be seen from Table 2 that the examples as hereinbefore described all provide significantly smaller clamping force drop than the currently available commercial products used as comparatives. It would appear that this is because the lubricating greases as hereinbefore described provide a significantly better internal lubrication which is retained in/on the metal parts of the chuck and which results in a longer maintenance of clamping forces compared to the commercially available products and as such enable the user to use the chuck for a longer continuous period before the need to re-lubricate the parts.

(8) The invented composition demonstrates relatively constant clamping forces at a high level compared to reference products.

(9) Physical properties of the greases prepared from the ingredients listed in Table 1 and having the properties indicated in Table 2 have been further assessed in respect of several standard properties of importance for greases and the results are provided in Table 3 below.

(10) Unworked and worked penetration were assessed to determine grease penetration. The optimum grease penetration range for this application is from 265 mm/10 to 340 mm/10 as it has been identified as having the best consistency for the application. This is because the resulting composition is suitable to be used with grease guns whilst also being sufficiently “pasty” to stick on lubricated metal parts. Values outside this range may also be suitable for use as and when appropriate and based on the specific application. The value 60× in the Table indicates that the grease was worked 60 times before measurement. Flow pressure is measured because to determine whether a grease will have sufficient pumpability at temperatures below e.g. −20° C. In this instance a flow pressure of less than 1400 mbar is generally interpreted to mean that there should be an appropriate level of pumpability at such lower temperatures.

(11) Dropping point can be used as an indication of the thermal stability of the lubricating grease composition as described herein. This value needs to be significantly above the working temperature of the clamping device. It is anticipated that clamping devices such as chucks and collets will function up to about 60° C., not least because of the cutting fluid acting as coolant.

(12) Water resistance is an important feature for greases for these applications because the cutting fluids are often water based emulsions. In this application instead of the normal period of three hours used under DIN 51807 pt. 1 it was decided samples were tested for water resistance for a full 24 hours. Cutting fluid resistance was assessed based on DIN 51807 pt. 1 excepting that the tests were undertaken over a 7 day period at room temperature. Three commercially available, water miscible cutting fluids were used in this test. They were used in different concentrations of between 5% and 12% by weight in water but in each case as will be seen below the same results were found.

(13) TABLE-US-00003 TABLE 3 Ex. A Ex. B Ex. C Ex. D Unworked Penetration, ISO 287 267 329 289 2137: 2007 (en) (mm/10) Worked Penetration, ISO 2137 307 290 334 327 2007 (en) 60× (mm/10) Density @20° C., DIN 1.31 1.32 1.02 1.09 51757: 2011-01 (g/ml) Flow Pressure @ −20° C., DIN 900 1075 550 550 51805-2: 2016-09 (mbar) Dropping Point, Energy Institute 174.5 202 190 232 IP 396/02, 10K/min (° C.) Water Resistance, 24 h/90° C., 0-90 0-90 0-90 0-90 DIN 51807 pt.1 Cutting fluid resistance, tested 0-25 0-25 0-25 0-25 for a 7 day period at room temperature with 3 different commercial cutting fluids, on basis of DIN 51807 pt. 1 Corrosion Protection DIN51802, 0 0 0 0-1  using an EMCOR Test rig after a 1 week period in distilled water

(14) The results in Table 3 above show that the penetration results are within the accepted range. The flow pressure results can be seen to be below the 1400 mbar value required. The dropping point for all examples can be seen to be significantly above the anticipated approximate working temperature for the clamping devices of about 60° C. The water resistance results show that no change was visually noticeable to the observer after the samples were retaining in water at 90° C. Finally a similar result was determined in the presence of the different cutting fluids after 7 days at room temperature. Hence, there was no significant changes in adhesion and appearance after storage in various commercial cutting fluids at room temperature over 1 week. (cutting fluid resistance test, see examples) Excellent water-resistance (Water Resistance, 24 h/90° C., DIN 51807 pt. 1: 0-90, see examples). Hence, it would appear the lubricating grease compositions as hereinbefore described provide both an appropriate level of clamping forces to clamp articles and Table 3 shows they also have good water and cutting fluid resistance which combination has been a potential issue with current commercially available materials. Corrosion testing was undertaken in accordance with DIN 51802, using an EMCOR Test Rig after a 1 week period in distilled water. Results are Rated between 0 (least corrosion to 5 most corrosion).