KR20180070094A - Grease composition improved frictional resistance - Google Patents

Abstract

The present invention relates to a grease composition containing base oil, a thickener, and a polar additive, wherein the thickener added to the grease composition is polarized to improve the solubility of the polar additive, thereby improving the friction performance of grease. The grease composition of the present invention has a remarkable improvement effect on reducing the coefficient of friction and wear amount, and thus can be suitably used as grease for various friction portions including wheel bearings, joints, etc.

Description

Grease composition improved frictional resistance "

The present invention relates to a grease composition comprising a base oil, a thickener and a polar additive, wherein the thickener used is polarized to improve the solubility of the polar additive, thereby improving the friction performance of the grease.

Greases for automobile greases are generally made of metal soap as a thickener.

However, such metal soap has a problem in that the polarity property is not strong and the solubility of the polar additive is low, resulting in a grease having poor friction performance.

Korean Patent Laid-Open Publication No. 2009-39237 discloses a grease composition based on a base oil, which is obtained by reacting diphenylmethane-4,4-diisocyanate (MDI) and cyclohexylamine as a thickener in a grease composition comprising a thickener and an additive, Diurea, and a mixture of aliphatic diurea obtained by reacting toluene diisocyanate (TDI) with oleylamine, wherein the mixture contains molybdenum dithiocarbamate, zinc dithiophosphate and zinc dithiocarbamate Which is excellent in mechanical stability and water resistance, and which is excellent in friction resistance. However, the polar additive, molybdenum dithiocarbamate, still does not dissolve well, so that the friction performance is still limited.

It is necessary to provide a grease composition which improves the friction performance by improving the dissolution of the polar additive.

1. Korean Patent Publication No. 2009-39237

Thus, the present inventors have found that when lithium soap having a polar functional group introduced as a thickener is used, the solubility of the polar additive is improved to improve the friction performance of the grease, and thus the present invention has been accomplished.

It is therefore an object of the present invention to provide a grease composition with improved friction performance.

In order to solve the problems of the present invention as described above, (a) 70 to 90% by weight of at least one base oil selected from the group consisting of mineral oil, poly-a-olefin oil (PAO) and ester oil; (b) 8-25% by weight of a thickener comprising a lithium soap and a carboxylic acid salt having polarity; (c) 1 to 3% by weight of a polar additive which is molybdenum dithiocarbamate (MoDTC); And (d) 1 to 3% by weight of a polar additive which is molybdenum dithiocarbamate (MoDTP). The present invention also provides a grease composition having improved friction performance.

The grease composition according to the present invention greatly improves the friction coefficient and the wear reduction, and can be suitably used for various friction parts such as wheel bearings and joints.

1 is a view showing a grease according to the present invention.

Hereinafter, the present invention will be described in more detail as an embodiment.

(A) 70 to 90% by weight of at least one base oil selected from the group consisting of mineral oil, poly-a-olefin oil (PAO) and ester oil; (b) 8-25% by weight of a thickener comprising a lithium soap and a carboxylic acid salt having polarity; (c) 1 to 3% by weight of a polar additive which is molybdenum dithiocarbamate (MoDTC); And (d) 1 to 3 weight percent of a polar additive that is molybdenum dithiocarbamate (MoDTP).

As the base oil, at least one selected from the group consisting of mineral oil, poly-a-olefin oil (PAO) and ester oil can be used. At this time, the mineral oil preferably has a kinematic viscosity of 20 to 40 cSt at 40 占 폚. More preferably 30 cSt.

In addition, the base oil is preferably used in an amount of 70 to 90% by weight based on the total weight of the composition. When the base oil is less than 70% by weight, the base oil content is low and the lubricating ability is limited. When the base oil is more than 90% by weight, the effect of imparting polarity of the thickener is small and the solubility of the additive agent is reduced.

Next, the thickener used in the present invention is obtained by reacting generally used lithium soap, benzonic acid, and lithium hydroxide at a temperature of 90 to 100 ° C. Table 1 below shows the comparison between the conventional thickener and the thickener used in the present invention. The thickener according to the present invention comprises a lithium soap and a carboxylic acid salt having polarity. At this time, the carboxylic acid salt having the polarity is a lithium benzoate.

Conventional thickener The thickener of the present invention

Lithium soap (Li-soap)

Composite lithium soap (Li-comp)

As described above, the lithium soap has polarity due to the introduction of the above function into the lithium soap, and the friction performance can be further improved by improving the solubility of the polar additive used. At this time, the lithium soap preferably has 10 to 22 carbon atoms. If the number of carbon atoms is less than 10, the grease is not formed easily due to the low boiling property of the thickener, and if the carbon number exceeds 22, the shear characteristics of the thickener become poor and the load resistance becomes worse.

The thickener is preferably used in an amount of 8 to 25% by weight based on the total weight of the composition. When the amount of the thickener is less than 8% by weight, the effect of imparting the polarizer of the thickener is small, and thus the solubility of the additive decreases. When the amount of the thickener is less than 25% by weight, the content of the thickener is high. It is good.

In addition, molybdenum dithiocarbamate (MoDTC) and molybdenum dithiocarbamate (MoDTP) are used as the polar additive used in the present invention. Such a polar additive plays a role of reducing friction and abrasion. When the molybdenum dithiocarbamate (MoDTC) and molybdenum dithiocarbamate (MoDTP) are used in combination, The abrasion-reducing layer is uniformly distributed, and the effect of improving the friction and abrasion characteristics is more excellent.

The molybdenum dithiocarbamate (MoDTC) is preferably used in an amount of 1 to 3% by weight based on the total weight of the composition. When the content of the molybdenum dithiocarbamate (MoDTC) is less than 1% by weight, the distribution of the molybdenum dithiocarbamate (MoDTC) on the friction surface is smaller than that of the molybdenum dithiocarbamate (MoDTP) , And when the content is more than 3% by weight, the distribution of the molybdenum dithiocarbamate (MoDTC) on the friction surface is much larger than that of the molybdenum dithiocarbamate (MoDTP), and therefore, It is good.

The molybdenum dithiocarbamate (MoDTP) is preferably used in an amount of 1 to 3% by weight based on the total weight of the composition. When the content of molybdenum dithiocarbamate (MoDTP) is less than 1% by weight, the distribution of molybdenum dithiocarbamate (MoDTP) on the friction surface is smaller than that of molybdenum dithiocarbamate (MoDTC) , And when it is more than 3% by weight, the distribution of molybdenum dithiocarbamate (MoDTP) on the friction surface is too much larger than that of molybdenum dithiocarbamate (MoDTC) .

More preferably, molybdenum dithiocarbamate (MoDTC): molybdenum dithiocarbamate (MoDTP) is used in a weight ratio of 1: 3 to 3: 1. If the ratio is out of the range, the effect of improving the friction due to the addition of the polar additive is low.

 Accordingly, the grease composition according to the present invention has a great effect on the friction coefficient and the wear amount, and can be suitably used as a grease for various friction parts such as wheel bearings and joints.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples.

Manufacturing example  1: used in the present invention Thickener  Produce

Benzoic acid and lithium hydroxide were added at a mass ratio of 16: 3 after the formation of lithium soap, followed by reaction at about 95 ° C, followed by evaporation of water at 100 ° C. A thickener containing a lithium salt of benzoic acid having a polar functional group and a lithium soap was prepared. The lithium soap and benzoate are present in a ratio of 1: 1 in the thus prepared thickener.

Example  1 to 7

And the mixture was mixed at about 95 캜 in the composition and content shown in Table 2 below to prepare a grease.

division
(Unit: wt%) Example One 2 3 4 5 6 7 Base oil Mineral oil 1) 88 78 73 78 78 PAO2) 78 Ester oil 3) 78 Thickener Li-benz4) 8 18 23 18 18 18 18 Lithium soap Composite lithium soap additive MoDTC5) 2 2 2 2 2 One 3 MoDTP6) 2 2 2 2 2 3 One Total quantity 100 100 100 100 100 100 100 1) Kinematic viscosity: 30cSt, Product name: P96, Manufacturer: S-oil
2) Kinematic viscosity: 30cSt, Product name: Durasyn series, Manufacturer: Ineos
3) Kinematic viscosity: 30cSt, Product name: Hetcol series, Manufacturer: Chemtura
4) Fatty acid - Product name: 12-HSA, Manufacturer: Royal castor
Benzoic acid - Product name: Purox, Manufacturer: DSM
Lithium hydroxide - Product: Lithium hydroxide monohydrate Manufacturer: FMC
5) Product name: Molyvan A, Manufacturer: RTVanderbilt
6) Product name: Molyvan L, Manufacturer: RTVanderbilt

Comparative Example  1 to 12

The composition and content of the following Table 3 were mixed at about 95 캜 to prepare a grease.

division Comparative Example One 2 3 4 5 6 7 8 9 10 11 12 Base oil Mineral oil 78 78 91 68 78 78 78 78 PA0 91 68 Ester oil 91 68 Thickener Li-benz4) 5 28 5 28 5 28 18 18 18 18 Lithium soap 18 Composite lithium soap 18 additive MoDTC5) 2 2 2 2 2 2 2 2 0.5 3.5 4 MoDTP6) 2 2 2 2 2 2 2 2 3.5 0.5 4 Total quantity 100 100 100 100 100 100 100 100 100 100 100 100 1) Kinematic viscosity: 30cSt, Product name: P96, Manufacturer: S-oil
2) Kinematic viscosity: 30cSt, Product name: Durasyn series, Manufacturer: Ineos
3) Kinematic viscosity: 30cSt, Product name: Hetcol series, Manufacturer: Chemtura
4) Fatty acid - Product name: 12-HSA, Manufacturer: Royal castor
Benzoic acid - Product name: Purox, Manufacturer: DSM
Lithium hydroxide - Product: Lithium hydroxide monohydrate Manufacturer: FMC
5) Product name: Molyvan A, Manufacturer: RTVanderbilt
6) Product name: Molyvan L, Manufacturer: RTVanderbilt

Experimental Example : Coefficient of Friction and Measurement of Wear

A steel ball, D = 10 mm as the upper specimen, and Steel Disk, D = 24 mm and H = 7.9 mm as the lower specimen were prepared and tested in the Examples and Comparative Examples using a high frequency reciprocating friction tester (SRV) under conditions of 300 N × 1 mm × 80 ° C. × 50 Hz × 1 hour The friction coefficient and wear amount were measured and the results are shown in Tables 4 and 5 below.

(1) Coefficient of Friction Measurement: The average value of the friction coefficient inputted for one hour in a high frequency reciprocating friction tester (SRV).

(2) Measurement of abrasion amount: The abrasion amount of the upper specimen was measured and shown.

(1) Wear amount = (H + L) / 2

(Where H is the vertical direction diameter of the wear trace and L is the horizontal direction diameter of the wear trace).

division Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Coefficient of friction 0.080 0.055 0.060 0.061 0.058 0.061 0.069 Wear amount (μm) 581 472 494 488 490 516 557

division Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 Comparative Example 11 Comparative Example 12 Coefficient of friction 0.096 0.102 0.093 0.087 0.091 0.108 0.090 0.100 0.105 0.112 0.121 0.135 Wear amount (μm) 611 609 624 602 615 647 607 622 633 619 644 637

Table 4 and Table 5 show that the coefficient of friction and wear amount are influenced by the type of thickener, the amount of thickener, and the content of base oil.

When the lithium soap having the polar group prepared according to the present invention was used together with the polar additive of MoDTC and MoDPC, the friction performance of mineral oil, PAO, and ester oil was improved.

In particular, in Comparative Example 3 in which the thickener according to the present invention is less than 8% by weight, the polarity is weakened, the solubility of the polar additive is lowered and the effect of improving the friction coefficient is insignificant. In Comparative Example 4 in which the thickener is more than 25% by weight, there is a limit to increase the coefficient of friction by interfering with the lubricating action of the base oil.

In addition, in Comparative Example 11 and Comparative Example 12, when the MoDTC and MoDPC were used alone, the imbalance of the additive distribution on the friction surface was limited.

Also, it was confirmed from Comparative Example 9 and Comparative Example 10 using a mixture of MoDTC and MoDPC that the effect of improving the friction coefficient and the wear amount due to the addition of the polar additive is lowered when the additive ratio is more than 3/4 or less than 1/4 there was.

Accordingly, in the case of a grease composition including a polarizer-introduced thickener in a predetermined amount together with a polar additive, it can be suitably used as a grease for various friction parts such as a wheel bearing and a joint by improving the coefficient of friction and wear of the base oil Could know.

Claims (5)

(a) 70 to 90% by weight of at least one base oil selected from the group consisting of mineral oil, poly-a-olefin oil (PAO) and ester oil;
(b) 8-25% by weight of a thickener comprising a lithium soap and a carboxylic acid salt having polarity;
(c) 1 to 3% by weight of a polar additive which is molybdenum dithiocarbamate (MoDTC); And
(d) 1 to 3% by weight of a polar additive which is molybdenum dithiocarbamate (MoDTP);
The grease composition according to claim 1,
The grease composition according to claim 1, wherein the carboxylic acid salt having a polarity is a lithium salt of benzoic acid.
The grease composition according to claim 1, wherein the thickener is obtained by reacting lithium soap, benzonic acid, and lithium hydroxide at a temperature of 90 to 100 ° C.
The grease composition according to claim 1, wherein the lithium soap has 10 to 22 carbon atoms.
The friction stir welding method according to claim 1, wherein the molybdenum dithiocarbamate (MoDTC): molybdenum dithiocarbamate (MoDTP) is used in a weight ratio of 1: 3 to 3: 1 in the polar additive A grease composition with improved performance.

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