KR100695041B1 - Grease composition for constant velocity joints - Google Patents

Abstract

A grease composition for constant velocity joints containing a base oil and a urea-based thickener, wherein the grease further comprises (A) molybdenum sulfide dialkyldithiocarbamate and (B) 5,5'-dithiobis A composition containing (1,3,4-thiadiazole-2-thiol); A constant velocity joint lubrication method comprising packing with the grease; Constant velocity joint packed with grease.

Description

Grease composition for constant velocity joints {GREASE COMPOSITION FOR CONSTANT VELOCITY JOINTS}

The present invention relates to a grease composition for constant velocity joints, a constant velocity joint lubrication method and a constant velocity joint packed with grease. In particular, the present invention relates to grease compositions that can be used in automobile drive shafts, propeller shafts and industrial mechanical joints.

Recent advances in machine technology have increased demands for reducing the size and weight of machines, enhancing machine precision, extending machine life, and the like.

Constant velocity joints are a special type of universal coupling that can transfer a drive from the final reduction gear to the road wheel axle at a constant rotational speed.

Since constant velocity joints used in automotive and industrial machines are used under high surface pressure conditions at high speeds, the grease used to lubricate these joints requires much better performance.

This situation will be described in more detail below in connection with a constant velocity joint for automobile (hereinafter abbreviated as CVJ).

With the spread of front wheel drive vehicles and four-wheel drive vehicles, there has been a significant increase in the use of CVJ in the automotive industry. Cars now have higher power, are smaller and lighter, which requires very high CVJ durability.

Greases used for CVJ lubrication also require better joint durability and life (damage resistance, eg flaking resistance and seizing resistance).

In response to this need, sulfur-phosphor-based extreme-pressure agents containing olefin sulfides in combination with sulfurated fat / oil and / or zinc dithiophosphate, and lead-based additives and Lithium grease containing molybdenum disulfide or the like has been mainly used commercially. In recent years, urea grease having excellent heat resistance is used more than lithium grease.

Examples of the prior art related to the use of molybdenum sulfide dialkyldithiocarbamate include Japanese Patent Application Laid-Open Nos. H4-34590 and JP H6-57283, H6-330072 and H10-273692. Included.

Japanese Patent Publication No. H4-34590 is incorporated into urea grease:-(A) molybdenum sulfide dialkyldithiocarbamate; And (B) at least one sulfur-phosphorus-based extreme pressure additive selected from the group consisting of sulfurized fat / oil, olefin sulfide, tricresyl phosphate, trialkylthiophosphate and zinc dialkyldithiophosphate. Doing. However, such systems are not always satisfactory under the current demanding CVJ operating conditions.

Japanese Laid-Open Patent Application H6-57283 discloses a system containing molybdenum sulfide dialkyldithiocarbamate, molybdenum disulfide and lead sulfide dialkyldithiocarbamate, mixed with urea grease. However, since the system contains lead-based additives, it is undesirable in view of the increasing importance of environmental protection.

Japanese Laid-open Patent Application H6-330072 discloses adding both (A) molybdenum sulfide dialkyldithiocarbamate and (C) triphenylphosphoronate to urea grease, but such a system is satisfactory. It does not exhibit damage resistance and abrasion resistance at the same time.

" Sekiyu Seihin Tenkazai " [Petroleum Output Additives] (p. 262 and later) by T. Sakurai introduces thiadiazole compounds as lubricant additives, and Table 3 on p.226 shows that the addition of thiadiazole-based compounds It has been suggested that it leads to excellent sulfur addition corrosion protection for silver. In addition, Japanese Laid-Open Patent Publication No. H4-32880 improves without corrosion or discoloration of the metal as a result of adding 5,5'-dithiobis (1,3,4-thiadiazole-2-thiol) to the lubricating grease. Although load resistance and extreme pressure properties are disclosed, there is no mention of a balance problem between damage resistance and abrasion resistance.

Japanese Laid-open Patent Application H11-131086 discloses the use of thiadiazole-based compounds as additives in lubricating greases obtained using calcium sulfonate complex-based thickeners, although thiadiazole-based compounds are described herein as metals. Used to deactivate.

Japanese Laid-Open Patent Application No. H10-273692 discloses a molybdenum disulfide, a free phosphorus sulfur-based extreme pressure additive and a sulfur-nitrogen-based extreme pressure additive with (A) molybdenum sulfide dialkyldithiocarbamate. A grease composition for constant velocity joints containing diurea as a thickener for use in combination is disclosed. However, it is not clear what specific compounds can be used as sulfur-nitrogen-based extreme pressure agents, and "Vanlube 601" (trade name) from RT Vanderbilt is disclosed only in the examples, and the trade name is "Vanlube 601". It merely confirms that it is a heterocyclic sulfur-nitrogen compound. In addition, according to the technique, the use of a combination of molybdenum disulfide and phosphorus-free sulfur-based extreme pressure additives is essential.
EP-A-0633 304 discloses a urea grease composition comprising urea grease and sulfided molybdenum dialkyldithiocarbamate represented by Formula A, and triphenylphosphorothionate B, incorporated as an additive. have:
[Formula A]
(R ₁ R ₂ N-CS-S) ₂ -Mo ₂ O _m S _n
[Wherein, R ₁ and R ₂ Each independently is an alkyl group having 1 to 24 carbon atoms, m + n = 4, m is 0 to 3 and n is 1 to 4;

There is a need in the field of lubricating grease compositions for constant velocity joints for both satisfactory damage resistance and satisfactory wear resistance. There are many greases that have good abrasion resistance but poor damage resistance. There is a great need for finding grease compositions for constant velocity joints in which all of these physical properties are improved.

It is now possible to formulate a grease for constant velocity joints containing 5,5'-dithiobis (1,3,4-thiadiazole-2-thiol) having advantageous properties in terms of damage resistance and abrasion resistance. Found.

The present invention provides a grease composition for constant velocity joints containing a base oil and a urea-based thickener, wherein the grease further comprises: (A) molybdenum sulfide dialkyldithiocarbamate; And (B) 5,5'-dithiobis (1,3,4-thiadiazole-2-thiol).

In a preferred embodiment, the grease composition of the present invention further contains (C) triphenylphosphoronate.

Molybdenum sulfide dialkyldithiocarbamate (A) may conveniently be a compound represented by the following general formula (I):

(R ¹ R ² N-CS-S) ₂ -Mo ₂ O _m S _n

[Wherein R ¹ and R ² are independently selected from the group consisting of alkyl groups of 1 to 24 carbon atoms, m + n = 4, m is 0 to 3 and n is 1 to 4].

Preferred alkyl groups are those having from 1 to 18 carbon atoms, more preferably from 1 to 12 carbon atoms, even more preferably from 1 to 6 carbon atoms, most preferably from 1 to 4 carbon atoms. The alkyl group can be linear or branched.

Specific examples of molybdenum sulfide dialkyldithiocarbamate (A) which may be conveniently used in the present invention include molybdenum sulfide diethyldithiocarbamate, molybdenum sulfide dibutyldithiocarbamate, molybdenum Sulfide diisobutyldithiocarbamate, molybdenum sulfide di (2-ethylhexyl) dithiocarbamate, molybdenum sulfide diamyldithiocarbamate, molybdenum sulfide diisoamyldithiocarbamate, molybdate Denium sulfide dilauryldithiocarbamate, molybdenum sulfide distearyldithiocarbamate, molybdenum sulfide n-butyl-2-ethylhexyldithiocarbamate and molybdenum sulfide 2-ethylhexylstearyldithio One or more of the carbamates are included.

5,5'-dithiobis (1,3,4-thiadiazole-2-thiol) (B) may be represented by the following formula (2):

Preferred compositions according to the invention have one or more of the following features with respect to the total weight of the grease composition:

(i) 0.5 to 10% by weight of A;

(ii) 0.5 to 5 weight percent A;

(iii) at least 2 weight percent A;

(iv) up to 3 weight percent of A;

(v) 0.1 to 10 weight percent B;

(vi) 0.1 to 5 weight percent B;

(vii) at least 0.5 weight percent B, and

(viii) 2 wt% or less of B.

Particularly preferred compositions according to the invention are those having the features (i) and (v); Having features (i) and (vi); Having features (i) and (vii); Having features (i) and (viii); Having features (i), (vii) and (viii); Having features (ii) and (v); Having features (ii) and (vi); Having features (ii) and (vii); Having features (ii) and (viii); Having features (ii), (vii) and (viii); Having features (iii) and (v); Having features (iii) and (vi); Having features (iii) and (vii); Having features (iii) and (viii); Having features (iii), (vii) and (viii); Having features (iv) and (v); Having features (iv) and (vi); Having features (iv) and (vii); Having features (iv) and (viii); Having features (iv), (vii) and (viii); Having features (iii), (iv) and (v); Having features (iii), (iv) and (vi); Having features (iii), (iv) and (vii); Having features (iii), (iv) and (viii); Having features (iii), (iv), (vii) and (viii).

If less than 0.5% by weight of A is used, the CVJ damage resistance effect is reduced, and using more than 10% by weight of A may limit the further improvement above this concentration, or cannot expect further improvement. There is no incentive.

If less than 0.1% by weight of B is used, the CVJ damage resistance effect is reduced, and using more than 10% by weight of B may limit the further improvement above or above, or no further improvement can be expected. There is no incentive.

Triphenylphosphorothionate (C) is a compound represented by the following general formula (3):

(C ₆ H ₅ -O) ₃ -P = S

When triphenylphosphorothionate (C) is added, preferably up to 10% by weight, for example 0.1 to 10% by weight, more preferably 0.1 to 5% by weight, relative to the total weight of the grease composition Incorporates at concentration.

If less than 0.1% by weight of C is added, the abrasion resistance effect is reduced, and using more than 10% by weight of B does not provide any incentive, as further improvement is limited or no improvement can be expected above this concentration. There is no.

 Any urea-based thickener may be used as the urea compound used in the thickener, and there is no specific limitation on its type. For example, diurea, triurea and / or tetraurea can be conveniently used. Mineral oils and / or synthetic oils are used as base oils. In a preferred embodiment of the invention, from 2 to 35% by weight of urea-based thickener is used relative to the total weight of the grease composition.

It is also possible to add various additives such as antioxidants, rust inhibitors and extreme pressure agents to the grease compositions of the present invention.

Preferred lubricating grease compositions for constant velocity joints according to the invention specifically described in the text significantly improve flaking resistance and ignition resistance (damage resistance), and also have excellent abrasion resistance and temperature-controlling properties.

The invention will now be described in the following examples which are not intended to limit the scope of the invention in any way.

Preparation of Grease Composition

Additives were added to the base grease according to the formulations shown in Tables 1-3 and the resulting system was treated using a 3-roller mill to obtain greases for the examples and comparative examples. It should be noted that purified mineral oil having a kinematic viscosity of 15 mm ² / s at 100 ° C. was used as the base oil.

I. Diurea Greece

1 mol of diphenylmethane-4,4'-diisocyanate and 2 mol of octylamine were reacted in the base oil, and the resulting urea compound was uniformly dispersed to give a base grease. Urea compound content was set to 10% by weight.

II. Tetraurea greece

2 mol of diphenylmethane-4,4'-diisocyanate, 2 mol of octylamine and 1 mol of ethylene diamine were reacted in the base oil, and the resulting urea compound was uniformly dispersed to give a base grease. Urea compound content was set to 15% by weight.

The thickness, abrasion resistance, joint damage and joint durability shown in the table below were evaluated according to the following test methods.

(1) The thickness was evaluated according to JIS K2220 5.3.

(2) Wear resistance was evaluated according to ASTM D2266.

(3) joint damage test

Each sample was introduced into a commercial CVJ and the system was operated under the following conditions, after which the presence or absence of minor damage, which is a signal of flaking inside the joint, was evaluated, and the maximum temperature of the joint during operation was also evaluated.

CVJ Type: Barfield Joint

rpm: 1500 rpm

Joint angle: 8。

Torque: 300 N.m

Time: 1 hour

Evaluation: (O) no damage; Damage; △ slightly damaged

(4) joint durability test

Each sample is introduced into a commercial CVJ and the system is operated under the following conditions, followed by flaking or seizure of the ball or inner race, outer race or cage in the joint. ) Presence or absence).

CVJ Type: Barfield Joint

rpm: 1500 rpm

Joint angle: 8。

Torque: 300 N.m

Time: 150 hours

Evaluation: (O) no damage; △ slightly damaged; × damage (no longer available)                 

Example 1 Example 2 Example 3 Base grease (% by weight) Diurea greece 95.0 95.0 - Tetraurea greece - - 95.0 Additive (wt%) A-1 * 1 3.0 2.0 - A-2 * 2 - - 2.0 B * 3 2.0 0.5 0.5 C * 4 - 1.0 1.0 Test result 60 W thick 320 316 318 Wear resistance (mm) 0.47 0.40 0.39 Joint damage test (O) (O) (O) Joint temperature (℃) 128 101 108 Joint durability test (O) (O) -

Comparative Example 1 Comparative Example 2 Comparative Example 3 Base grease (% by weight) Diurea greece 92.0 96.0 98.0 Tetraurea greece - - - Additive (wt%) A-1 * 1 3.0 3.0 - A-2 * 2 - - - B * 3 - - 2.0 C * 4 1.0 1.0 2,5-bis (tert-octyldithio) -1,3,4-thiadiazole  4.0  - - Zinc dialkyl dithiophosphate - - - Molybdenum disulfide - - - Test result 60 W thick 312 326 321 Wear resistance (mm) 0.45 0.39 0.55 Joint damage test △ × × Joint temperature (℃) 120 107 154 Joint durability test △ × -

Comparative Example 4 Comparative Example 5 Comparative Example 6 Base grease (% by weight) Diurea greece 96.0 96.0 92.0 Tetraurea greece - - - Additive (wt%) A-1 * 1 - 3.0 3.0 A-2 * 2 - - - B * 3 1.0 - - C * 4 1.0 - - 2,5-bis (tert-octyldithio) -1,3,4-thiadiazole  2.0  - - Zinc dialkyl dithiophosphate - 1.0 - Molybdenum disulfide - - 5.0 Test result 60 W thick 322 318 316 Wear resistance (mm) 0.48 0.41 0.65 Joint damage test × × × Joint temperature (℃) 106 108 118 Joint durability test - × -

* 1: A-1 is a molybdenum sulfide dialkyldithiocarbamate mixture wherein the alkyl group has four carbon atoms and n is 2 and 3.

* 2: A-2 is a molybdenum sulfide dialkyldithiocarbamate compound in which an alkyl group has four carbon atoms and n is 4.

* 3: B is a thiadiazole compound 5,5'-dithiobis (1,3,4-thiadiazole-2-thiol).

* 4: C is triphenylphosphorothionate.

Claims (10)

A grease composition for constant velocity joints containing a base oil and a urea-based thickener, wherein the grease is further selected from (A) molybdenum sulfide dialkyldithiocarbamate and (B) 5,5'-dithiobis A grease composition containing (1,3,4-thiadiazole-2-thiol). The method of claim 1, wherein 0.5 to 10% by weight of (A) molybdenum sulfide dialkyldithiocarbamate and 0.1 to 10% by weight of (B) 5,5'-dithiobis (to the total weight of the grease composition) 1,3,4-thiadiazole-2-thiol). 3. The grease according to claim 1 or 2, wherein the grease is 0.5 to 5% by weight (A) molybdenum sulfide dialkyldithiocarbamate and 0.1 to 5% by weight (B) 5 relative to the total weight of the grease composition. A grease composition containing, 5'-dithiobis (1,3,4-thiadiazole-2-thiol). The grease composition according to claim 1 or 2, wherein the grease contains 2 to 35% by weight of urea-based thickener based on the total weight of the grease composition. The molybdenum sulfide dialkyldithiocarbamate according to claim 1 or 2, wherein the molybdenum sulfide dialkyldithiocarbamate is molybdenum sulfide diethyldithiocarbamate, molybdenum sulfide dibutyldithiocarbamate, molybdenum sulfide Diisobutyldithiocarbamate, molybdenum sulfide di (2-ethylhexyl) dithiocarbamate, molybdenum sulfide diamyldithiocarbamate, molybdenium sulfide diisoamyldithiocarbamate, molybdenum Sulfide dilauryldithiocarbamate, molybdenum sulfide distearyldithiocarbamate, molybdenum sulfide n-butyl-2-ethylhexyldithiocarbamate and molybdenum sulfide 2-ethylhexylstearyldithiocarba At least one grease composition selected from mate. The grease composition according to claim 1 or 2, further comprising (C) triphenylphosphorothionate. The grease composition according to claim 6, which contains from 0.1 to 10% by weight of (C) triphenylphosphorothionate relative to the total weight of the grease composition. The grease composition according to claim 6, wherein the grease contains 0.1 to 5% by weight of (C) triphenylphosphorothionate relative to the total weight of the grease composition. A method of lubricating a constant velocity joint comprising packing with a grease according to claim 1. A constant velocity joint packed with grease according to claim 1.