Grease composition and methods for manufacturing the grease composition
The present invention relates to a non-hydroxide grease composition comprising a base oil and a thickener which comprises amorphous hydrophilic silicon oxide particles and one or more metal salts of different organic acids, wherein the silicon oxide particles have a BET specific surface area of at least 50 m 2 /g and wherein the amount of the metal salt(s) is 4-25% by weight, based on the total weight of the grease composition. The present invention further relates to a method for manufacturing said grease composition and the use of said grease composition for lubricating a bearing and in couplings and gearings.
1. A non-hydroxide grease composition comprising:
a base oil,
1-5% by weight, based on the total weight of the grease composition, amorphous hydrophilic silicon oxide particles, and
one or more metal salts of different organic acids in a non-saponified state, the metal salt(s) being selected from the group consisting of calcium stearate and calcium 12-hydroxystearate, wherein:
the silicon oxide particles have a BET specific surface area of at least 50 m 2 /g and at least 80% of the silicon oxide particles have a mean particle size of 5-50 nm,
the amount of the metal salt(s) is 4-20% by weight, based on the total weight of the grease composition, with the proviso that the total amount of the amorphous hydrophilic fumed silicon oxide particles and the one or more metal salts of different organic acids is 8-25% by weight, based on the total weight of the grease composition,
the base oil is mineral oil and/or poly-α-olefin,
the base oil is present in the grease composition in an amount of 70-90 wt % by weight based upon the total weight of the grease composition, and
the grease composition has a dropping point higher than 220° C. and contains less than 0.2 wt % of free hydroxide ions and/or metal hydroxide.
2. The grease composition according to claim 1 , wherein the one or more metal salts are substantially pure metal salts.
3. The grease composition according to claim 1 , wherein the silicon oxide particles are amorphous hydrophilic fumed silicon oxide particles.
4. The grease composition according to claim 1 , comprising only one type of metal salt of an organic acid.
5. The grease composition according to claim 4 , wherein the metal salt is only calcium stearate.
6. The grease composition according to claim 1 , wherein the grease composition comprises:
calcium stearate, and
calcium 12-hydroxystearate.
7. The grease composition according to claim 1 , wherein the grease composition contains less than 0.1% by weight of free hydroxide ions and/or metal hydroxide, based on the total weight of the grease composition.
8. The grease composition according to claim 4 , wherein the metal salt is only calcium-12-hydroxystearate.
9. The grease composition according to claim 1 , wherein the amount of the metal salt(s) is 5-20% by weight, based on the total weight of the grease composition.
10. The grease composition according to claim 9 , wherein the grease composition contains less than 0.1% by weight of free organic acids, based on the total weight of the grease composition.
11. The grease composition according to claim 1 , wherein the base oil is only poly-α-olefin.
12. A grease prepared by mixing, in weight percent based upon the total weight of the grease:
70-90 wt % mineral oil and/or poly-α-olefin,
1-5 wt % amorphous hydrophilic fumed silicon oxide particles having a BET specific surface area of at least 50 m 2 /g and, at least 80% of the silicon oxide particles having a mean particle size of 5-50 nm, and
5-20 wt % at least substantially pure calcium stearate and/or calcium 12-hydroxystearate, with the proviso that the total amount of the amorphous hydrophilic fumed silicon oxide particles and the calcium stearate and/or calcium 12-hydroxystearate is 8-20 wt %,
wherein the grease composition has a dropping point higher than 220° C. and contains less than 0.2 wt % of free hydroxide ions and/or metal hydroxide.