Grease composition for constant velocity joints and constant velocity joint charged with the grease composition

1. A grease composition for constant velocity joints, comprising;

(a) a base oil being mineral oil having a kinematic viscosity at 40° C. of 50 to 330 mm 2 /s,

(b) a diurea thickener,

(c) benzotriazole and/or a derivative thereof wherein the benzotriazole and/or a derivative thereof is the compound represented by formula (1)

wherein R 1 represents an alkyl group having 1 to 18 carbon atoms and R 3 represents CH 2 NR 5 R 6 in which R 5 and R 6 are each independently an alkyl group having 1 to 18 carbon atoms,

(d) a phosphate and/or an amine salt thereof, and

a castor oil in an amount of 0.25 to 1% by mass based on the total mass of the composition.

2. The grease composition for constant velocity joints of claim 1 , wherein the benzotriazole and/or the derivative thereof (c) is contained in an amount of 0.2 to 20 mass % based on the total mass of the composition.

3. The grease composition for constant velocity joints of claim 1 , wherein the phosphate and/or the amine salt thereof (d) is contained in an amount of 0.05 to 10 mass % based on the total mass of the composition.

4. A constant velocity joint charged with the grease composition for constant velocity joints of claim 1 .

5. The grease composition for constant velocity joints of claim 1 , wherein the diurea thickener (b) is contained in an amount of 1 to 25 mass % based on the total mass of the composition.

6. The grease composition for constant velocity joints of claim 1 , further comprising at least one selected from the group consisting of vegetable fats and oils other than castor oil, fatty acid amide waxes, and melamine cyanurate.

7. The grease composition for constant velocity joints of claim 6 , wherein said at least one selected from the group consisting of vegetable fats and oils other than castor oil, fatty acid amide waxes, and melamine cyanurate is contained in an amount of 0.1 to 10 mass % based on the total mass of the composition.

8. The grease composition for constant velocity joints of claim 1 , further comprising zinc dialkyldithiocarbamate.

9. The grease composition for constant velocity joints of claim 8 , wherein zinc dialkyldithiocarbamate is contained in an amount of 0.0001 to 10% by mass based on the total mass of the composition.

10. The grease composition for constant velocity joints of claim 1 , further comprising graphite.

11. The grease composition for constant velocity joints of claim 10 , wherein graphite is contained in an amount of 0.0001 to 10% by mass based on the total mass of the composition.

12. The grease composition for constant velocity joints of claim 1 , wherein the mineral oil is paraffin oil.

13. The grease composition for constant velocity joints of claim 1 , wherein phosphate and/or the amine salts thereof (d) is selected from the group consisting of the phosphates, phosphites, hypophosphites, amine salts of acid phosphates, amine salts of acid phosphites, and amine salts of acid hypophosphites.

14. A grease composition for constant velocity joints, consisting essentially of:

(a) a paraffin type mineral oil as a base oil;

(b) a diurea thickener represented by the formula (4):

R 13 —NH—CO—NH—C 6 H 4 - p -CH 2 —C 6 H 4 - p -NH—CO—NHR 14   (4)

wherein R 13 and R 14 both represent a straight-chain alkyl group having 8 carbon atoms;

(c) a benzotriazole derivative represented by the formula (1):

wherein R 1 is a halogen atom or an alkyl group having 1 to 4 carbon atoms, and R 3 is a halogen atom or CH 2 NR 5 R 6 in which R 5 and R 6 are each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms;

(d) an amine salt of an acid phosphate represented by the formula (5):

R 15 O A PO(OH) 3-A   (5)

wherein R 15 is an alkyl group having 1 to 4 carbon atoms, and A is 1 or 2

an olefin sulfide,

castor oil, and

a rust inhibitor,

wherein the grease composition has a worked penetration determined by the JIS K 2220 5.3 of 265 to 385.

15. The grease composition for constant velocity joints of claim 14 , wherein the content of the component (c) is 1 to 5 mass %, the content of the component (d) is 0.2 to 5 mass %, and the content of the sulfur-containing extreme-pressure agent is 0.1 to 5 mass %, the content of the castor oil is 0.25 to 1 mass %, and the content of the rust inhibitor is 0.05 to 1 mass %.