JP2017043745A - Grease composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grease composition having heat resistance and low temperature property almost equivalent to those using a synthetic oil even though using a mineral oil as a base oil.SOLUTION: There is provided a grease composition containing a mineral oil having a saturated component of 90 mass% or more, a sulfur component of 0.03 mass% or less, viscosity index of less than 120 and 40°C kinetic viscosity of 75 to 400 mm/s as a base oil and a thickener.SELECTED DRAWING: None

Description

  The present invention relates to a grease composition.

Grease is used in various machine parts such as automotive bearings such as constant velocity joints and electrical equipment bearings, industrial machinery such as machine tool spindle bearings and sliding parts of construction machines.
In recent years, with the reduction in size and weight of mechanical devices and higher performance of equipment, the environment in which grease is used has become increasingly hot and severe. Therefore, the grease used for these machine parts is required to have a longer lubrication life at a high temperature.

  Further, from the viewpoint of energy saving, the grease is also required to have performance that contributes to power saving and fuel saving, that is, low torque. In particular, smooth startability, that is, excellent low temperature torque performance is desired in an environment where the machine is used at a low temperature such as a cold region in winter.

As a technical method for improving the heat resistance of the grease, that is, the long life of lubrication, there is a method of improving the heat resistance of the base oil which is a constituent component of the grease. Specifically, synthetic oils such as polyalphaolefins, ester oils and ether oils are used in place of mineral oils (see, for example, Patent Document 1).
Further, as a conventional means for reducing the torque of the grease, it is possible to reduce the viscosity of the base oil component (see, for example, Patent Document 2).

JP 2014-088527 A JP 2000-198993 A

Many synthetic oils have a low pour point compared to mineral oil and are excellent in low-temperature properties when grease is obtained, but synthetic oil is more expensive than mineral oil, and it is more economical to use mineral oil. It is advantageous.
In addition, a low-viscosity base oil tends to evaporate more than a high-viscosity base oil, and the lubrication life tends to be short at high temperatures.
Therefore, it is a requirement from the entire market that grease having excellent heat resistance and low temperature characteristics can be obtained at low cost.

  An object of the present invention is to provide a grease composition having heat resistance and low-temperature characteristics close to those obtained when a synthetic oil is used, although a mineral oil is used as a base oil.

  As a result of diligent studies to achieve the above object, the present inventor uses highly refined mineral oil having a specific physical property value as a base oil, so that the heat resistance and low temperature are at a level close to that when synthetic oil is used. It has been found that a grease composition having excellent characteristics can be obtained at a lower cost. The present invention has been completed based on these findings. That is, the following invention is provided.

<1> The base oil has a saturated content of 90% by mass or more, a sulfur content of 0.03% by mass or less, a viscosity index of less than 120, and a 40 ° C. kinematic viscosity of 75 to 400 mm ² / s. A grease composition comprising a mineral oil and a thickener.

  According to the present invention, although a mineral oil is used as a base oil, a grease composition having heat resistance and low temperature characteristics close to those obtained when a synthetic oil is used is provided.

  Hereinafter, the grease composition of the present invention (hereinafter sometimes simply referred to as “grease”) will be described in detail. In addition, in this specification, "-" showing a numerical range represents the range containing the numerical value each described as the upper limit and the minimum. In addition, when only the upper limit value is described in the numerical range represented by “to”, it means that the lower limit value is also the same unit.

The grease composition of the present invention has, as a base oil, a saturated content of 90% by mass or more, a sulfur content of 0.03% by mass or less, a viscosity index of less than 120, and a 40 ° C. kinematic viscosity of 75 to 400 mm. ² / s mineral oil and a thickener, and if necessary, additives suitable for the application are contained.

(1) Base oil The grease composition of the present invention has, as a base oil, a saturated content of 90% by mass or more, a sulfur content of 0.03% by mass or less, a viscosity index of less than 120, and a 40 ° C. Contains highly refined mineral oil with a viscosity of 75-400 mm ² / s.
Hereinafter, the physical properties of the base oil (mineral oil) used in the grease composition of the present invention will be described.

(I) Saturated component The saturated component (paraffin + naphthene) of the base oil (mineral oil) used in the grease composition of the present invention is 90% by mass or more. Here, the saturated content of the base oil is a value measured based on the ASTM D 3238-85 ndM method.
Oxidation stability can be improved because the saturated part of a base oil is 90 mass% or more.

(Ii) Sulfur content The sulfur content of the base oil (mineral oil) used in the grease composition of the present invention is 0.03% by mass or less. Here, the sulfur content of the base oil is a value measured based on the JIS K2541-7: 2003 fluorescent X-ray method sulfur content test.
When the sulfur content of the base oil is 0.03% by mass or less, both heat resistance and low temperature characteristics can be improved.

(Iii) Viscosity index The viscosity index of the base oil (mineral oil) used in the grease composition of the present invention is less than 120. Here, the viscosity index of the base oil is a value measured based on a JIS K 2283: 2000 kinematic viscosity test method.
When the viscosity index of the base oil is less than 120, the additive can be appropriately dissolved. In addition, it is preferable that the viscosity index of a base oil is 80 or more from a heat resistant viewpoint of a base oil.

(Iv) 40 ° C. Kinematic Viscosity The base oil used in the grease composition of the present invention has a 40 ° C. kinematic viscosity of 75 to 400 mm ² / s, preferably 90 to 300 mm ² / s.
In the case of mineral oil, if the 40 ° C. kinematic viscosity is less than 75 mm ² / s, the evaporation loss of the base oil increases, that is, the lubrication life tends to be shortened. Further, when the 40 ° C. kinematic viscosity is 400 mm ² / s or more, the stirring resistance increases, that is, the torque performance tends to be inferior. Here, the viscosity index of the base oil is a value measured based on a JIS K 2283: 2000 kinematic viscosity test method.

(V) Pour point The pour point of the base oil (mineral oil) used in the grease composition of the present invention is preferably −20 ° C. or less, more preferably −30 ° C. or less, and particularly preferably −35 ° C. or less. It is. If the pour point of the base oil is −20 ° C. or lower, a predetermined low-temperature torque performance is easily obtained. Here, the pour point of the base oil is a value measured based on the JIS K 2269: 1987 pour point test method.

  The grease composition of the present invention may contain a plurality of mineral oil components. When a plurality of mineral oil components are used as the base oil in the present invention, the physical property values of (i) to (iv) after mixing the mineral oil components may be within the above range. It is more preferable that the physical property values of (i) to (iv) above satisfy the above range.

In addition, the grease composition of the present invention preferably contains only mineral oil as a base oil from the viewpoint of providing a particularly inexpensive grease composition, but may contain synthetic oil as long as the effects of the present invention are not significantly impaired. Good. However, when synthetic oil is also blended as the base oil, it is preferable to satisfy the above physical properties (i) to (iv) as the base oil after mixing with the mineral oil.
In addition, when the grease composition of the present invention is blended with synthetic oil as a base oil, the blending amount of the synthetic oil may be 25% by mass or less of the entire base oil from the viewpoint of providing an inexpensive grease composition. preferable.

(2) Thickener The thickener used in the grease composition of the present invention is not limited. It can be selected as appropriate in consideration of the grease usage environment and temperature, such as grease penetration and dropping point.
Examples of the thickener include lithium soap, lithium complex soap, calcium soap, calcium complex soap, urea series, sodium terephthalate, and the like.

  Further, the blending amount of the thickener in the grease composition of the present invention may be appropriately set in consideration of the grease usage environment and temperature such as the penetration of the grease and the dropping point. When the amount of the thickener is too large, the grease becomes hard, and when it is too small, the grease becomes soft. More preferred.

(3) Additive The grease composition of the present invention is obtained by blending a base oil (mineral oil) and a thickener that satisfy the above physical property values (i) to (iv), and an additive is added as necessary. It can mix | blend suitably.
Additives include various antiwear agents such as zinc, phosphorus, sulfur, amine and ester; alkylphenols such as 2,6-di-tert-butyl-p-cresol, 4,4′-methylenebis -Bisphenols such as (2,6-di-t-butylphenol), phenolic compounds such as n-octadecyl-3- (4'-hydroxy-3 ', 5'-di-t-butylphenol) propionate, naphthylamines Antioxidants such as aromatic amine compounds such as olefins and dialkyldiphenylamines; extreme pressure agents such as sulfurized olefins and sulfurized fats and oils; various corrosion inhibitors such as benzotriazole and benzimidazole; metal salts of sulfonic acids, sorbitan compounds, etc. Various rust preventives are mentioned.
An additive can be used individually by 1 type or in combination of 2 or more types, What is necessary is just to select the addition amount suitably. For example, if it is antioxidant, the addition amount is 0.5-5 mass% with respect to the grease composition whole quantity, and 1-4 mass% is especially preferable.

(4) Consistency of penetration The grease composition of the present invention preferably has a penetration of 130-340, more preferably 220-310. The blending penetration is preferably 340 or less because the oil separation prevention property can be further improved, and as a result, the lubrication long life can be improved. Further, it is preferable that the penetration degree is 130 or more because low temperature torque performance can be improved.
In addition, this blending penetration is a value measured based on the JIS K 2220: 2013 penetration testing method.

  Next, the present invention will be specifically described with reference to examples. In addition, this invention is not limited at all by these Examples.

[Example 1, Comparative Examples 1-2]
In Examples and Comparative Examples, grease compositions containing the components * 1 to * 5 shown below in the proportions (mass) shown in Table 1 were prepared.

* 1: Refined mineral oil A
(Saturated content: 99% by mass or more, sulfur content: less than 0.01% by mass, viscosity index: 106, 40 ° C. kinematic viscosity: 100 mm ² / s, pour point: −37.5 ° C.)
* 2: Refined mineral oil B
(Saturated content: 92% by mass, sulfur content: 0.1% by mass, viscosity index: 97, 40 ° C. kinematic viscosity: 99 mm ² / s, pour point: −12.5 ° C.)
* 3: Refined mineral oil C
(Saturated content: 99% by mass or more, sulfur content: less than 0.01% by mass, viscosity index: 111, 40 ° C. kinematic viscosity: 32 mm ² / s, pour point: −15.0 ° C.)
* 4: Lithium soap * 5: Amine-based antioxidant

  In addition, the thickener (lithium soap) of * 4 is mixed with the base oil used in the grease composition of the example or the comparative example in the base oil as described below. By reacting these raw materials, a thickener was synthesized, and as a result, a grease composition containing a predetermined amount of each of * 1 to * 5 was prepared. The grease composition was prepared to contain a predetermined amount of each component, and then milled to uniformly disperse the thickener in the grease to obtain a final composition.

<Manufacturing procedure>
Each base oil and fatty acid shown in Table 1 are put into a heat-resistant container, and after heating and stirring to about 90 ° C., an aqueous lithium hydroxide solution is added and reacted for about 60 minutes. Thereafter, the mixture was heated to 200 ° C. with stirring to dissolve the fatty acid lithium salt, and then cooled to 60 ° C.

The saturated content, sulfur content, 40 ° C. kinematic viscosity, viscosity index, and pour point of the base oil were determined by the following measuring methods.
In addition, the obtained grease compositions were evaluated for their respective penetration, low temperature torque test, that is, low temperature torque performance, bearing life test, that is, lubrication long life, and evaporation loss.

(Measuring method)
(1) Saturation of base oil Measured based on ASTM D 3238-85 ndM method.
(2) Sulfur content of base oil JIS K2541-7: 2003 Measured based on a fluorescent X-ray method sulfur content test.
(4) 40 ° C. kinematic viscosity and viscosity index of base oil Measured and calculated based on JIS K 2283: 2000 kinematic viscosity test method.
(5) Pour point of base oil Measured based on JIS K 2269: 1987 pour point test method.

(6) Mixing penetration Measured based on JIS K 2220: 2013 penetration testing method.
(7) Low temperature torque performance JIS K 2220: 2013 Based on the low temperature torque test method, the test temperature was set to -20 ° C and measured.
(8) Long lubricating life In order to evaluate the lubricating life of the grease, a test was conducted under the following conditions based on ASTM D1741. A bearing (JIS nominal number 6308) filled with 6.0 g of grease was intermittently rotated (started for 20 hours, suspended for 4 hours) at a bearing temperature of 140 ° C. and a rotational speed of 3500 rpm. The lubrication life is the time until bearing seizure occurs and the outer ring temperature rises to 150 ° C. or higher, and it is preferable that this time be longer.
(9) Loss on evaporation Based on ASTM D 972, the test temperature was set to 125 ° C. and measured.
Table 1 shows the compositions and evaluation results of the greases prepared in each example.

As shown in Table 1, (i) the saturation content is 90% by mass or more, (ii) the sulfur content is 0.03% by mass or less, (iii) the viscosity index is less than 120, and (iv) the 40 ° C. kinematic viscosity is 75 to 75%. In Example 1 using the mineral oil A satisfying all of 400 mm ² / s, the low-temperature torque performance, the bearing life and the evaporation loss are at a level close to that in the case of using the synthetic oil (polyalphaolefin), and the heat resistance In addition, a grease composition having good low-temperature heat resistance and low-temperature characteristics and an economical advantage was obtained.

  The grease composition of the present invention can be suitably used for grease lubrication parts of home appliances such as information equipment and air conditioners, various industrial machines and automobiles, for example.

Claims (1)

As a base oil, a mineral oil having a saturated content of 90% by mass or more, a sulfur content of 0.03% by mass or less, a viscosity index of less than 120, and a 40 ° C. kinematic viscosity of 75 to 400 mm ² / s;
A thickener,
A grease composition comprising: