Polymer thickened grease compositions with improved low friction properties

Patent metadata

Field	Value
Publication number	US-9487727-B2
Application number	US-201113992429-A
Country	US
Kind code	B2
Filing date	Dec 8, 2011
Priority date	Dec 9, 2010
Publication date	Nov 8, 2016
Grant date	Nov 8, 2016

Abstract

The invention provides a grease composition comprising:
(a) a lubricating base oil; (b) a polymeric thickener comprising a mixture of (1) a (co- or homo)polymer of propylene with a weight average molecular weight of more than 200.000 and (2) a (co- or homo)polymer of propylene with a weight average molecular weight of less than 200.000; and (c) a polar wax.

The invention further provides a mechanical component having a metal surface onto which a layer of the grease composition according to the invention has been applied. The invention also relates to the use of a polar wax in the preparation of a grease composition for bearing applications, and the use of a polar wax in a grease composition for bearing applications. In addition, the present invention relates to the use of the grease composition for reducing friction in a bearing, between bearing components or within a bearing application system. The invention also relates to a method for preparing the present grease composition.

First claim

The invention claimed is:

1. A grease composition comprising:
(a) 74-79 wt % of a poly alpha olefin lubricating base oil;
(b) 6-11 wt % of a polymeric thickener comprising a mixture of (1) a (co- or homo)polymer of propylene with a weight average molecular weight of more than 200,000 and (2) a (co- or homo)polymer of propylene with a weight average molecular weight of less than 200,000; and
(c) 5-10 wt % of a polar polypropylene wax,
wherein all weight percentages are based on the total weight of the grease composition.

2. The grease composition according to claim 1 , wherein the weight ratio between the high molecular weight component and the low molecular weight component is 1:40-1:5.

3. The grease composition according to claim 2 , wherein the low molecular weight component is a polypropylene homopolymer.

4. The grease composition according to claim 3 , wherein the low molecular weight component has an average molecular weight between 20,000 and 200,000 and a melt flow rate of 500-1500 dg/min.

5. The grease composition according to claim 4 , wherein the high molecular weight component is a polypropylene homopolymer or a propylene/ethylene-copolymer.

6. The grease composition according to claim 5 , wherein the high molecular weight component has an average molecular weight of 200,000-350,000 and a melt flow rate of 1.5-15 dg/min.

7. The grease composition according to claim 1 , further comprising a metal salt which is selected from the group consisting of stearates, hydroxystearates and any mixture thereof.

8. The grease composition according to claim 7 , wherein the metal of the metal salt is bismuth.

9. The grease composition according to claim 8 , which further comprising:
at least one additive component which is selected from the group consisting of antioxidants, corrosion inhibitors, anti-wear agents and pressure tolerance-increasing additives, and wherein
the total content of the additive component(s) is in the range between 0.2 and 15% by weight, based on the total weight of the grease composition.

10. A method for preparing a grease composition comprising:
(a) 74-79 wt % of a poly alpha olefin lubricating base oil;
(b) 6-11 wt % of a polymeric thickener comprising a mixture of (1) a (co- or homo)polymer of propylene with a weight avenge molecular weight of more than 200,000 and (2) a (co- or homo)polymer of propylene with a weight average molecular weight of less than 200,000; and
(c) 5-10 wt % of a polar polypropylene wax,
wherein all weight percentages are based on the total weight of the grease composition, the method comprising the following steps:
a) providing the poly alpha olefin lubricating base oil; polymeric thickener, and the polar wax;
b) mixing the polymeric thickener with the poly alpha olefin lubricating oil at a temperature higher than the melting point of the polymers used;
c) adding the polar polypropylene wax to the mixture obtained in step (b).

11. The method according to claim 10 comprising additionally mixing during step (b) one or more anti-wear additives, anti-corrosion additives, anti-oxidants and/or other additives.

12. The method according to 11 , wherein a final mixing in step (b) is carried out using a three-roll mill or ball-mill.

13. The method according to claim 11 , further comprising using a polar wax in the preparation of the grease composition for reducing friction in a bearing, between bearing components or within a bearing application system.

14. The grease composition according to claim 1 , wherein the weight ratio between the high molecular weight component and the low molecular weight component is 1:25-1:15.

15. The grease composition according to claim 1 , wherein the weight ratio between the high molecular weight component and the low molecular weight component is 1:18-1:20.

16. The grease composition according to claim 3 , wherein the low molecular weight component has an average molecular weight between 20,000 and 200,000 and a melt flow rate of 750-1250 dg/min.

17. The grease composition according to claim 5 , wherein the high molecular weight component has an average molecular weight of 200,000-350,000 and a melt flow rate of 1.5-7.

18. The grease composition according to claim 9 , wherein the total content of at least one additive component is in the range of between 1 and 8% by weight based on the total weight of the grease composition.

19. The grease composition according to claim 1 , wherein the grease composition has a coefficient of friction of between 0.015 and 0.058 as measured using a reciprocating sliding test at 60° C. with a stroke length of 4 mm at a frequency of 0.5 Hz and a normal load of 3.4 N.

Assignees

• Meijer Dick
• Pasaribu Rihard
• Skf Ab

Inventors

• Meijer Dick
• Pasaribu Rihard

Classifications

• C10M2205/0213

  used as thickening agents · CPC title

• C10M2205/12

  Oxidised hydrocarbons, i.e. oxidised subsequent to macromolecular formation · CPC title

• C10N2040/02

  Bearings · CPC title

• C10M169/06 Primary

  Mixtures of thickeners and additives · CPC title

• C10M119/02 Primary

  Hydrocarbon polymers; Hydrocarbon polymers modified by oxidation · CPC title