GREASE COMPOSITIONS AND METHOD FOR MAKING THE SAME

Abstract

A grease composition comprising a lubricating base oil and a thickener, which thickener comprises an ester-terminated oligomer and a polymer. The polymer is a polyolefin. The ester-terminated oligomer has the general formula: R1O[COR2CONHR3NHCOR2CO].sub.nOR1. R1 each independently represent a hydrocarbon group containing 4-22 carbon atoms. R2 represents a hydrocarbon group containing 4-42 carbon atoms. R3 represents a hydrocarbon group containing 2-9 carbon atoms. n represents an integer in the range of 1-20. A method for preparing the present grease composition. The present grease composition can be used for (a) lubricating a mechanical component having a metal surface and (b) protecting a mechanical component having a metal surface against corrosion, wear and/or fretting.

Claims

1. A grease composition comprising: a lubricating base oil and a thickener comprising an ester-terminated oligomer and a polymer, wherein the polymer is a polyolefin, wherein the ester-terminated oligomer has the general formula of:
R1O[COR2CONHR3NHCOR2CO].sub.nOR1, wherein R1 each independently represents a hydrocarbon group containing 4-22 carbon atoms; wherein R2 represents a hydrocarbon group containing 4-42 carbon atoms; wherein R3 represents a hydrocarbon group containing 2-9 carbon atoms; wherein n represents an integer in the range of 1-20.

2. The grease composition according to claims 1 comprising: (a) 75 to 90 wt. % of the lubricating base oil; (b) 1 to 19 wt. % of the ester terminated oligomer; and (c) 1 to 19 wt. % of the polymer which is a polyolefin, all weights based on the total weight of the grease composition.

3. The grease composition according to claims 1 comprising: (a) 76 -84 wt. % of the lubricating base oil; (b) 11-15 wt. % of the ester terminated oligomer; and (c) 5-9 wt. % of the polymer which is a polyolefin, wherein all weights are based on the total weight of the grease composition.

4. The grease composition according to claim 1, wherein n is an integer in the range of from 2-14.

5. The grease composition according to claim 1, wherein the polymer comprises one of: polyethylene, polypropylene, polyisoprene or polybutadiene.

6. The grease composition according claim 1, wherein the polymer comprises a mixture of: (1) a (co- or homo-) polymer of polyolefin with a weight average molecular weight of more than 200,000; and (2) a (co- or homo-) polymer of polyolefin with a weight average molecular weight of less than 100,000.

7. The grease composition according to claim 6, wherein the (co- or homo-) polymer of propylene with a weight average molecular weight of less than 100,000 is a polypropylene homopolymer.

8. The grease composition according to claim 6, wherein the (co- or homo-) polymer of propylene with a weight average molecular weight of more than 200,000 is one of: a polypropylene homopolymer or a propylene/ethylene-copolymer.

9. The grease composition according to claim 1, further comprising at least one of the following: anti-wear additives, anti-corrosion additives, and anti-fretting additives.

10. A method for preparing a grease composition, the method comprising the steps: (a) obtaining a lubricating base oil; (b) obtaining a thickener comprising an ester-terminated oligomer and a polymer, wherein the polymer is a polyolefin, wherein the ester-terminated oligomer has the general formula of:
R1O[COR2CONHR3NHCOR2CO].sub.nOR1, wherein R1 each independently represents a hydrocarbon group containing 4-22 carbon atoms; wherein R2 represents a hydrocarbon group containing 4-42 carbon atoms; wherein R3 represents a hydrocarbon group containing 2-9 carbon atoms; wherein n represents an integer in the range of 1-20; (c) mixing the oligomer, the polymer, and the lubricating base oil in any possible order at a temperature above the melting points of the oligomer and the polymer; and (d) cooling the mixture as obtained in step (a) to a temperature in the range of from 0-120 C. in less than 3 minutes.

11. The method of using a grease composition according to claim 10, wherein the method further comprising a step of lubricating the mechanical component.

12. The method of using a grease composition according to claim 10, wherein the method further comprising a step of protecting the mechanical component against at least one of: corrosion, wear, and fretting.

13. The method of using a grease composition according to claim 10, wherein the mechanical component comprises at least one of: a bearing, a bearing component, or a gear box component.

Description

EXAMPLES

Example 1

(According to the Invention)

[0076] An ester-terminated polyamide was prepared by reacting 61 gram of a dimer and 7.4 gram of azealic acid with 5.9 gram of ethylene diamine The acids were mixed under heating at a temperature of 95 C. until the mixture was homogeneous. Ethylene diamine was added slowly to the mixture dropwise with constant stirring under dry nitrogen supply. 25.7 gram of stearyl alcohol was added to the reaction vessel. After the completion of monoalcohol addition, the temperature of reaction mixture was raised to 180 C. and maintained for 3 hours. The temperature of the reaction mixture was raised to 205 C. and kept under constant dry nitrogen supply and constant stirring for 30 minutes. The mixture was discharged onto a metal plate and cooled to room temperature. In a reaction vessel, 13 gram of the ester-terminated oligomer polyamide was heated to its melting point of around 160 C. in the presence of dry nitrogen and under continuous stirring. 80 gram of a lubricating ester base oil Priolube 1426 (available from Croda) was added slowly and the temperature was not allowed to cool down to below 145 C. The temperature was raised to 160 C., after which 6.65 gram of a low molecular weight homo-polymer of polypropylene was added, and 0.35 gram of a high molecular weight co-polymer of a polypropylene were added. The low molecular weight homo-polymer of polypropylene was Borflow HL508 FB, obtained from Borealis. The high molecular weight co-polymer of polypropylene was Moplen EP300K, a poly(ethylene-co-propylene) block co-polymer, obtained from Lyondell Basell. The temperature of the mixture was then raised to 180 C. and kept under dry nitrogen and continuous stirring for 60 minutes. The temperature was then further raised to 205 C. and kept under dry nitrogen, whilst the mixture was continuously stirred for 30 minutes. The mixture so obtained was then cooled to room temperature within 10 seconds by means of quenching, executed by discharging the mixture in a thin layer onto a solid metal plate at room temperature. The properties of the grease obtained are listed in Table 1.

Example 2

(According to the Invention)

[0077] In accordance with the procedure described in Example 1, a grease composition was prepared wherein the lubricating base oil was a mineral base oil (Cirkan C68, available from Total Lubricants). The properties of the grease obtained are listed in Table 1.

Solubility in Oil: Completely Soluble (Visual Appearance)

Example 3

[0078] In accordance with the procedure in Example 2, a homogeneous, heated mixture of ester-terminated polyamide and lubricating mineral oil was prepared, and kept under stirring and nitrogen at 205 C. In the final step, the mixture was removed from the heating source and allowed to cool to room temperature without any quenching and any time limit, in more than 30 minutes.

[0079] A grease structure was not formed. At the early stage there was little formation of gel structure and at later stage gel was separated into oil and oligomer. This example shows that cooling by quenching during the preparation of a grease composition in step (b) of the method of the present invention is of essential importance.

Example 4

[0080] In a reaction vessel, 20 gram of the ester-terminated polyamide used in Example 1 was heated to its melting point of around 160 C. in the presence of dry nitrogen and under continuous stirring. 80 gram of lubricating ester base oil Priolube 1851 (available from Croda) was added slowly and the temperature was not allowed to cool down to below 145 C. The temperature of the reaction mixture was then raised to 180 C. and kept under dry nitrogen and continuous stirring for 60 minutes. The temperature was then further raised to 205 C. and kept under dry nitrogen, whilst the mixture was continuously stirred for 30 minutes. The mixture so obtained was then cooled to room temperature within 10 seconds by means of quenching, executed by discharging the mixture in a thin layer onto a solid metal plate at room temperature. The properties of the grease obtained are listed in Table 1.

Solubility in Oil: Completely Soluble (Visual Appearance)

Example 5

[0081] In a reaction vessel, 435 gram of a lubricating mineral oil (Cirkan C68 from Total Lubricants) was mixed with 61.75 gram of the low molecular weight homo-polymer of polypropylene as used in Example 1, and 3.25 gram of the high molecular weight co-polymer of propylene as used in Example 1. The temperature of the mixture was then raised to 180 C. and kept under dry nitrogen and continuous stirring for 60 minutes. The temperature was then further raised to 205 C. and kept under dry nitrogen, whilst the mixture was continuously stirred for 30 minutes. The mixture so obtained was then cooled to room temperature within 10 seconds by means of quenching, executed by discharging the mixture in a thin layer onto a solid metal plate at room temperature. The properties of the grease obtained are listed in Table 1.

TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Oligomer content 13 13 13 20 0 (wt. %) Polymer content 7 7 7 0 13 (wt. %) Lubricating base Ester Mineral Mineral Mineral Mineral oil type Base oil viscosity 65 68 (cSt at 40 C.) Cooling method Quenching Quenching Slow Quenching Quenching cooling Physical Clear Clear Turbid Clear Opaque appearance Semi-solid Semi-solid Semi-liquid Semi-solid Semi-solid homogeneous homogeneous Separated Homogeneous Homogeneous Penetration 207 215 N.A. 283 270 (mm/10) Consistency 3-4 3-4 N.A. 2 2 (NLGI grade) Oil separation 1.6 1.1 N.A. 11.5 7.5 (%) Dropping point 179 145 N.A. 128 145 ( C.)

[0082] Examples 1 and 2 represent greases in accordance with the present invention, wherein the thickener comprises an ester-terminated oligomer and a polymer (polypropylene in the given examples). Example 4 represents a grease wherein the thickener comprises only an ester-terminated oligomer; Example 5 is a polypropylene-thickened grease containing no ester-terminated oligomer. Example 3 failed to produce a grease structure, due to the slow cooling rate during preparation, and tests could not be performed.

[0083] The remaining examples were subjected to an oil separation test according to DIN 51817, to determine oil bleeding. Consistency was measured using a standard cone penetration method (DIN 51804) and the dropping point of the grease was measured according to DIN 51801.

[0084] The results of the oil separation test are particularly interesting. The polypropylene-thickened grease of Example 5 has better oil-bleeding characteristics than the oligomer-thickened grease of Example 4, and it might have been expected that a grease having a hybrid thickener comprising both components would exhibit an oil bleeding rate of between 7.5% and 11.5%. Surprisingly, the greases of Examples 1 and 2 exhibit considerably lower oil bleeding, having lost only 1.6% and 1.1% by weight of oil after conclusion of the test. The advantageous oil bleeding characteristics of the hybrid greases according to the invention are thus clear.