JP2016145292A - Grease - Google Patents

Abstract

The present invention provides a grease having excellent acoustic characteristics. The present invention relates to a grease containing a base oil and a thickener, and the volume-based arithmetic average particle diameter of the particles contained in the grease determined by a laser diffraction / scattering method is A (unit: μm). ), The following expression (1) is satisfied. A ≦ 3 (1) [Selection figure] None

Description

  The present invention relates to grease.

Grease, particularly diurea-based grease, generally contains non-uniform particles called lumps. The lumps include those that are thought to be derived from the reaction product of isocyanate and amine, and impurities that are mixed in during the manufacturing process and storage. Also in this specification, the term “dama” includes both those derived from the reactants and impurities.
In a general method for producing urea grease, an isocyanate is mixed with a base oil and heated to about 60 ° C., and a solution of about 60 ° C. mixed with an amine is added to the base oil and stirred for a while. After being heated to room temperature, it is allowed to cool to room temperature. However, such a method requires time for production (synthesis reaction) and easily produces lumps. In addition, it is known that large lumps deteriorate the acoustic characteristics when grease is applied to sliding devices such as bearings. Furthermore, since the non-uniform structure consisting of large lumps contributes little to the original performance of the grease, the efficiency as a thickener is reduced. In other words, many thickeners are required to achieve a certain hardness.

  In view of this, there has been proposed a grease manufacturing method that suppresses generation of large lumps and improves acoustic characteristics (see Patent Documents 1 and 2). The production method of Patent Document 1 is a method in which an amine solution (isocyanate solution) is made into droplets having a diameter of 300 μm or less with a spray nozzle and charged into the isocyanate solution (amine solution), and a method in which both solutions are sprayed and reacted. The manufacturing method of Patent Document 2 is a method in which an amine solution and an isocyanate solution are pressurized to a predetermined pressure using a pressurizing apparatus, and both solutions are collided and reacted. With this manufacturing method, the size of the dama is controlled to about several hundreds to several tens of μm. A method for controlling the particle size during the production of grease by high-pressure jet mixing has also been proposed (see Patent Document 3).

JP 2000-248290 A Japanese Patent Laid-Open No. 3-190996 JP 2014-208551 A

  However, in the production methods described in Patent Documents 1 and 2, environmental pollution and phytotoxicity due to scattering of amines and isocyanates are a concern, and the refinement of lumps is not always sufficient. Therefore, when the obtained grease is applied to a sliding device such as a bearing, a great improvement in acoustic characteristics cannot be expected. Moreover, the manufacturing method described in Patent Document 3 has a problem in the design of equipment to withstand high pressure, and the obtained grease cannot be expected to greatly improve acoustic characteristics.

  The present invention provides a grease with very good acoustic properties.

In order to solve the above-mentioned problems, the present invention provides the following grease.
The present invention is a grease containing a base oil and a thickener, and the volume-based arithmetic average particle diameter of the particles contained in the grease determined by the laser diffraction / scattering method is A (unit: μm). The following formula (1) is satisfied.
A ≦ 3 (1)

  According to the present invention, it is possible to provide a grease having excellent acoustic characteristics.

FIG. 3 is a schematic cross-sectional view showing a grease manufacturing method (manufacturing apparatus) in the embodiment of the present invention. The schematic sectional drawing which shows the manufacturing method (manufacturing apparatus) of grease in other embodiment of this invention. The figure which shows both the outline of a side, and the outline of an upper surface about the manufacturing apparatus of FIG. 1 and FIG. The schematic sectional drawing which shows the manufacturing method (manufacturing apparatus) of grease in other embodiment of this invention. Schematic which shows the manufacturing method of the conventional urea grease.

The present inventor examined the volume-based arithmetic average particle size of the fine particles dispersed in the grease, and found that this was related to the acoustic characteristics of the grease. The present invention has been completed based on this finding.
The grease according to an embodiment of the present invention (hereinafter, also simply referred to as “the present grease”) includes a base oil and a thickener, and is based on the volume basis of particles contained in the grease obtained by a laser diffraction / scattering method. When the arithmetic average particle diameter is A (unit: μm), the following formula (1) is satisfied.
A ≦ 3 (1)
Hereinafter, the grease will be described in detail.

[Raw material for grease production]
(Base oil)
There is no restriction | limiting in particular as base oil used for manufacture of this grease, The mineral base oil and synthetic base oil used for normal grease manufacture are mentioned. These can be used alone or as a mixture. In addition, you may add water and an organic acid as needed.
As the mineral oil base oil, those refined by appropriately combining vacuum distillation, solvent deburring, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, clay refining, hydrogenation refining and the like can be used. Synthetic base oils include polyalphaolefin (PAO) base oils, other hydrocarbon base oils, ester base oils, alkyl diphenyl ether base oils, polyalkylene glycol base oils (PAG), and alkylbenzene bases. Examples include base oils. 40 ° C. The kinematic viscosity of the base oil is, 10 mm ² / preferably s or 600mm is ² / s or less, more preferably at most 20 mm ² / s or more 300 mm ² / s, 30 mm ² / s or more 100 mm ² / More preferably, it is s or less.

(Thickener)
As the thickener, any of urea, a thickener for single soap grease, and a thickener for complex grease may be used.
Examples of the thickener for the single soap grease or the thickener for the complex grease include calcium soap, lithium soap, sodium soap, calcium complex soap, lithium complex soap, and calcium sulfonate complex soap.

Thickeners used for urea greases include monoamines and isocyanates (diisocyanates) as thickener precursors. The monoamine may be either a single amine compound or a mixture containing a plurality of types of amine compounds.
Examples of monoamines include aniline, p-toluidine, and naphthylamine for aromatic monoamines, and hexylamine, cyclohexylamine, octylamine, dodecylamine, hexadecylamine, and eicosylamine for aliphatic monoamines. .
Examples of the isocyanate include diphenylmethane-4,4′-diisocyanate (MDI), tolylene diisocyanate, and naphthylene-1,5-diisocyanate.
The polyurea compound can be obtained, for example, by reacting diisocyanate with a monoamine or diamine. Examples of the diisocyanate and monoamine include those similar to those used for the production of the diurea compound. Examples of the diamine include ethylenediamine, propanediamine, butanediamine, hexanediamine, octanediamine, phenylenediamine, tolylenediamine, xylenediamine, and And diaminodiphenylmethane.
Each of the above-described amines may be used alone, or a plurality of amines may be mixed and used. In addition, each of the above-described isocyanates may be used alone, or a plurality of isocyanates may be mixed and used.

[Grease production method]
This grease can be obtained by carrying out a grease formation reaction while giving a high shear rate to a thickener or its precursor in the base oil.
As a grease manufacturing apparatus capable of generating such a high shear rate, for example, a manufacturing apparatus having a structure as shown in FIGS. FIG. 3 shows both the outline of the side surface and the outline of the upper surface of the manufacturing apparatus of FIGS. 1 and 2. 1 is suitable for the production of soap-based grease, and the production apparatus of FIG. 2 is suitable for the production of urea grease.
The manufacturing apparatus shown in FIGS. 1 and 2 has a structure capable of imparting high-speed shear uniformly in a very short time. High-speed shearing is applied to the mixed solution by a gap (gap a, b) between the high-speed rotating part and the inner wall of the apparatus. The high-speed rotating part may have a constant diameter in the direction of the rotation axis (a = b) or a structure with a different gap. Such a gap is adjusted by changing the diameter of the high-speed rotating part in the direction of the rotation axis, or by making the high-speed rotating part a truncated cone and moving the high-speed rotating part up and down with respect to the inner wall of the reaction vessel provided with a taper. May be.
Furthermore, you may give extrusion capability by making the part with a large gap into the screw or spiral shape which inclined continuously.

When the production apparatus shown in FIG. 1 is used, a grease formation reaction can be carried out by applying a predetermined high shear rate to a mixed base oil containing a thickener or a precursor thereof. When the manufacturing apparatus of FIG. 2 is used, the base oil 1 containing the thickener precursor 1 and the base oil 2 containing the thickener precursor 2 are mixed to form a mixed solution, and a predetermined amount is added to the mixed solution. A grease formation reaction can be performed by applying a high shear rate. For example, in the case of urea grease, the thickener precursor 1 is an amine, and the thickener precursor 2 is an isocyanate (diisocyanate).
In order to produce this grease, it is preferable to give a shear rate of 10 ² s ⁻¹ or more to the above-mentioned mixed solution, and a more preferable shear rate is 10 ³ s ⁻¹ or more, more preferably 10 ⁴ s ^−1. That's it. A higher shear rate improves the dispersion state of the thickener and its precursor, resulting in a more uniform grease structure.
However, the shear rate applied to the above-mentioned mixed solution is preferably 10 ⁷ s ⁻¹ or less from the viewpoints of the safety of the apparatus, heat generation due to shearing, etc. and removal of the heat.
As can be seen from FIGS. 1 and 2, such a shear rate can be imparted by introducing the mixed solution into a manufacturing apparatus that generates shear by the relative motion between the opposing wall surfaces. In addition, the above-mentioned minimum shear rate is synonymous with the minimum shear rate mentioned later, and means the lower limit of the shear rate in the site | part which provides shear to a liquid mixture in reaction container.

  FIG. 4 shows a grease manufacturing apparatus in a mode different from that in FIGS. 1 and 2, but the portions (c, d) having different gaps are arranged in the rotation direction. In the case of this manufacturing apparatus, it is possible to provide an extrusion ability like a screw by inclining a portion having a large gap with respect to the rotation axis.

In the above manufacturing apparatus, the ratio (Max / Min) of the maximum shear rate (Max) and the minimum shear rate (Min) in the shear applied to the mixed solution is preferably 100 or less, and more preferably 50 or less. More preferably, it is 10 or less. When the shear rate with respect to the mixed solution is as uniform as possible, the thickener and its precursor are well dispersed, and a uniform grease structure is obtained.
Here, the maximum shear rate (Max) is the highest shear rate applied to the mixed solution, and the minimum shear rate (Min) is the lowest shear rate applied to the mixed solution. Taking the reaction vessel shown in FIGS. 1 and 2 as an example, the reaction vessel is defined as follows.
Max = (Linear velocity of the surface of the high-speed rotating part in the portion where the gap between the surface of the high-speed rotating part and the inner wall surface of the container is minimized / the gap)
Min = (Linear velocity of the surface of the high-speed rotating part at the portion where the gap between the surface of the high-speed rotating part and the inner wall surface of the container is maximized / the gap)
In FIG. 1 and FIG. 2, the gap in the calculation of Max is a, and the gap in the calculation of Min is b.
As described above, since Max / Min is preferably smaller, a = b ideally. That is, in the case of the manufacturing apparatus of the type shown in FIGS. 1 and 2, it is most preferable that the high-speed rotating part has a cylindrical shape having a uniform diameter in the vertical direction.

  The production method of this embodiment can be applied to all the production of greases using a mixed solution containing a base oil and a thickener or a precursor thereof. The temperature conditions in the production apparatus vary depending on the thickener used and its precursor, but when producing a diurea grease, it is preferably about 40 ° C. or more and 200 ° C. or less. When this temperature is 200 ° C. or lower, the base oil is hardly deteriorated, and the reaction is not so fast that it is difficult to control. Moreover, when this temperature is 40 ° C. or higher, isocyanates and amines (for example, stearylamine) that are precursors of thickeners are difficult to precipitate from the base oil, which is preferable in terms of dispersibility and reaction rate.

[Post-process in grease manufacturing method]
This grease may be further kneaded with the grease obtained by the production method described above. For this kneading, a roll mill generally used in grease production can be used. The above grease may be passed through a roll mill two or more times.
In addition, the grease may be further heated to a temperature of 80 ° C. or higher and 200 ° C. or lower with respect to the grease obtained by the manufacturing method described above. Furthermore, in order to heat uniformly, you may knead | mix and stir. Note that a heating furnace or the like may be used for heating.

This grease has the same raw material (base oil, thickener, thickener) because the volume-based arithmetic average particle diameter (A) of the particles dispersed in the grease satisfies the relationship (3 μm or less) of the above formula (1). Compared to grease manufactured by the conventional method, the acoustic properties are very good. From the viewpoint of the effect of the present invention, the preferable volume-based arithmetic average particle diameter (A) is 2.6 μm or less, more preferably 2 μm or less, further preferably 1.6 μm or less, and most preferably 1 μm. It is as follows. In order to satisfy the parameter of the formula (1), it can be achieved by increasing the minimum shear rate applied to the mixed base oil in the grease production apparatus.
Here, the volume-based arithmetic average particle size of the particles dispersed in the grease can be easily obtained by a commercially available laser diffraction / scattering particle size distribution measuring device. For example, the measurement can be preferably performed using Partica LA-950V2 manufactured by Horiba Seisakusho using both wavelengths of 405 nm and 650 nm.

Since this grease is extremely excellent in acoustic characteristics, it is suitable for sliding devices such as bearings.
Examples of the acoustic characteristics include Peak High 32-64s and Level High 32-64s by FAG method. The evaluation of acoustic characteristics by the FAG method will be described in detail in Examples.

〔Additive〕
Various additives can be blended with the grease obtained by the present production method as long as the effects of the invention are not impaired. Such additives include antioxidants, extreme pressure agents, rust inhibitors and the like.
Examples of the antioxidant include amine-based antioxidants such as alkylated diphenylamine, phenyl-α-naphthylamine, and alkylated-α-naphthylamine, 2,6-di-t-butyl-4-methylphenol, and 4, And phenolic antioxidants such as 4-methylenebis (2,6-di-t-butylphenol). A preferable blending amount of these antioxidants is about 0.05% by mass or more and 5% by mass or less based on the total amount of grease.

  Extreme pressure agents include zinc dialkyldithiophosphates, molybdenum dialkyldithiophosphates, ashless dithiocarbamates, zinc dithiocarbamates, molybdenum dithiocarbamates, sulfur compounds (sulfurized oils, sulfurized olefins, polysulfides, sulfide mineral oils, thiophosphorus Acid, thioterpene, dialkylthiodipyropionate, etc.), phosphate ester, phosphite ester (tricresyl phosphate, triphenyl phosphite, etc.) and the like. A preferable blending amount of the extreme pressure agent is about 0.1% by mass or more and 5% by mass or less based on the total amount of grease.

  Examples of rust inhibitors include benzotriazole, zinc stearate, succinate, succinic acid derivatives, thiadiazole, benzotriazole, benzotriazole derivatives, sodium nitrite, petroleum sulfonate, sorbitan monooleate, fatty acid soap, and amine compounds. Can be mentioned. A preferable blending amount of the rust inhibitor is about 0.01% by mass or more and 10% by mass or less based on the total amount of grease.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these descriptions. Specifically, grease was produced under various conditions shown below, and the properties of the obtained grease were evaluated.

[Example 1]
Grease was manufactured with the grease manufacturing apparatus shown in FIG. A specific manufacturing method is as follows.
500N mineral oil heated to 70 ° C. (40 ° C. kinematic viscosity 90 mm ² / s, containing 11.0% by mass of MDI) and 500 N mineral oil similarly heated to 70 ° C. (40 ° C. kinematic viscosity 90 mm ² / s, octylamine 11.1 Mass% and cyclohexylamine 2.13% by mass contained) at a flow rate of 258 mL / min and 214 mL / min, respectively, and continuously introduced into the production apparatus. A minimum shear rate of ^-1 was applied. The ratio (Max / Min) between the maximum shear rate (Max) and the minimum shear rate (Min) was 1.03. Further, the time from mixing the above two solutions to applying the maximum shear rate to the mixed solution was about 3 seconds.
The grease discharged from the production apparatus was placed in a container preheated to 60 ° C., immediately heated to 120 ° C. with stirring at 250 rpm, held for 30 minutes, then heated to 160 ° C. and held for 1 hour. Thereafter, the mixture was allowed to cool while maintaining stirring. After the obtained grease was kneaded twice with a roll mill, various properties were evaluated by the methods described later. The results are shown in Table 1.

[Comparative Example 1]
Grease was produced by a conventional method. Specifically, as shown in FIG. 5, 500 N at 60 ° C. with respect to 500 N mineral oil (40 ° C. kinematic viscosity 90 mm ² / s, containing MDI 11.2% by mass) stirred at a stirring blade and kept at 60 ° C. Mineral oil (40 ° C. kinematic viscosity 90 mm ² / s, octylamine 10.9 mass%, cyclohexylamine 2.11 mass% contained) was added dropwise. After dropwise addition of the amine solution, the temperature was raised to 160 ° C. with stirring and held for 1 hour. Thereafter, the mixture was allowed to cool with stirring, and the obtained grease was kneaded twice with a roll mill. The obtained grease was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Example 2]
In Example 1, a PAO base oil heated to 70 ° C. (40 ° C. kinematic viscosity 63 mm ² / s, containing MDI 6.09% by mass) and a PAO base oil heated to 70 ° C. (40 ° C. kinematic viscosity 63 mm) ² / s, 4.78% by mass of stearylamine, and 7.03% by mass of cyclohexylamine) were introduced into the production apparatus continuously at a flow rate of 880 mL / min and 474 mL / min, respectively, as in Example 1. Thus, a grease was manufactured. The minimum shear rate (Min) was 10,200 s ⁻¹ and the ratio (Max / Min) of the maximum shear rate (Max) to the minimum shear rate (Min) was 1.03. The obtained grease was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Comparative Example 2]
In Comparative Example 1, PAO was kept at 60 ° C. Keimotoyu to (40 ° C. kinematic viscosity 63mm ² / s, MDI 6.57 wt% content), 60 ° C. of PAO Keimotoyu (40 ° C. kinematic viscosity 63 mm ² / S, cyclohexylamine 6.19% by mass, stearylamine 4.21% by mass) was added in the same manner as in Comparative Example 1 to produce a grease. The obtained grease was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 3
In Example 1, 500N mineral oil heated to 70 ° C. (40 ° C. kinematic viscosity 90 mm ² / s, MDI 6.76% by mass) and 500 N mineral oil similarly heated to 70 ° C. (40 ° C. kinematic viscosity 90 mm ² / s, cyclohexylamine 10.3 wt% containing) and the respective flow rate 325 mL / min, was introduced into the continuous production apparatus 175 mL / min, immediately the high-speed rotation portion of 210,000S ^-1 when the gap passes to mixture A grease was produced in the same manner as in Example 1 except that the lowest shear rate was applied. The ratio (Max / Min) between the maximum shear rate (Max) and the minimum shear rate (Min) was 1.03. The obtained grease was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Comparative Example 3]
In Comparative Example 1, a 500N mineral oil (40 ° C. kinematic viscosity 90 mm ² / s, containing 7.35% by mass of MDI) maintained at 60 ° C., a 500 N mineral oil (40 ° C. kinematic viscosity 90 mm ² / s, cyclohexyl) A grease was produced in the same manner as in Comparative Example 1, except that amine (containing 0.06% by mass of amine) was added dropwise. The obtained grease was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 4
In Example 1, PAO base oil heated to 70 ° C. (40 ° C. kinematic viscosity 63 mm ² / s, MDI 6.98% by mass) and PAO base oil heated to 70 ° C. (40 ° C. kinematic viscosity 63 mm) ² / s, containing 18.4% by mass of octylamine) at a flow rate of 325 mL / min and 120 mL / min. A grease was produced in the same manner as in Example 1 except that a minimum shear rate of 000 s ^-1 was applied. The ratio (Max / Min) between the maximum shear rate (Max) and the minimum shear rate (Min) was 1.03. The obtained grease was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Comparative Example 4]
In Comparative Example 1, PAO was kept at 60 ° C. Keimotoyu to (40 ° C. kinematic viscosity 63mm ² / s, MDI 9.09 wt% content), 60 ° C. of PAO Keimotoyu (40 ° C. kinematic viscosity 63 mm ² / S, containing 12.4% by mass of octylamine) was added in the same manner as in Comparative Example 1 to produce a grease. The obtained grease was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 5
In Example 1, 500N mineral oil heated to 70 ° C. (40 ° C. kinematic viscosity 90 mm ² / s, containing 7.49% by mass of MDI) and 500 N mineral oil similarly heated to 70 ° C. (40 ° C. kinematic viscosity 90 mm ² / s, Octylamine (containing 14.7% by mass)) at a flow rate of 300 mL / min and 204 mL / min continuously into the production apparatus, respectively, except that a minimum shear rate of 20,400 s ⁻¹ was given. A grease was produced in the same manner. The ratio (Max / Min) between the maximum shear rate (Max) and the minimum shear rate (Min) was 1.03. The obtained grease was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Comparative Example 5]
In Comparative Example 1, 500N mineral oil (40 ° C. kinematic viscosity 90 mm ² / s, 40 ° C. kinematic viscosity 90 mm ² / s, octyl) with respect to 500N mineral oil maintained at 60 ° C. (40 ° C. kinematic viscosity 90 mm ² / s, containing MDI 9.09% by mass). A grease was produced in the same manner as in Comparative Example 1 except that 12.4% by mass of amine was added dropwise. The obtained grease was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 6
In Example 1, a PAO base oil heated to 70 ° C. (40 ° C. kinematic viscosity 63 mm ² / s, containing 8.96% by mass of MDI) and a PAO base oil similarly heated to 70 ° C. (40 ° C. kinematic viscosity 63 mm ² / s, containing 23.8% by mass of cyclohexylamine) at a flow rate of 325 mL / min and 92 mL / min, respectively, and immediately introduced into the production apparatus by a high-speed rotating part when the gap is passed through the gap. A grease was produced in the same manner as in Example 1 except that a minimum shear rate of 000 s ^-1 was applied and the roll discharged on the grease discharged from the production apparatus was applied twice. The ratio (Max / Min) between the maximum shear rate (Max) and the minimum shear rate (Min) was 1.03. The obtained grease was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Comparative Example 6]
In Comparative Example 1, to PAO was kept at 60 ° C. Keimotoyu (40 ° C. kinematic viscosity 63mm ² / s, MDI 13.3 mass% content), 60 ° C. of PAO Keimotoyu (40 ° C. kinematic viscosity 63 mm ² / S, containing 10.2 mass% of cyclohexylamine) was added in the same manner as in Comparative Example 1 to produce a grease. The obtained grease was evaluated in the same manner as in Example 1, and the results are shown in Table 1. In the measurement by the laser diffraction / scattering method, the arithmetic mean particle diameter based on volume could not be obtained accurately due to the influence of multiple scattering. However, it is clear that the arithmetic average particle diameter based on volume exceeds 3 μm.

Example 7
In Example 1, a PAO base oil heated to 70 ° C. (40 ° C. kinematic viscosity 63 mm ² / s, MDI 6.03 mass% contained) and a PAO base oil similarly heated to 70 ° C. (40 ° C. kinematic viscosity 63 mm ² / s, 3.35% by mass of cyclohexylamine, and 13.7% by mass of stearylamine) were continuously introduced into the production apparatus at flow rates of 303 mL / min and 170 mL / min, respectively, and immediately mixed by a high-speed rotating part. A grease was produced in the same manner as in Example 1 except that a minimum shear rate of 210,000 s ⁻¹ was given to the liquid when passing through the gap. The ratio (Max / Min) between the maximum shear rate (Max) and the minimum shear rate (Min) was 1.03. The obtained grease was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Comparative Example 7]
In Comparative Example 1, to PAO was kept at 60 ° C. Keimotoyu (40 ° C. kinematic viscosity 63mm ² /s,MDI7.25 wt% content), 60 ° C. of PAO Keimotoyu (40 ° C. kinematic viscosity 63 mm ² / s, cyclohexylamine 2.59 mass%, stearylamine 10.5 mass% contained) was added dropwise, and a grease was produced in the same manner as Comparative Example 1. The obtained grease was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Grease evaluation method]
(1) Thickener amount The grease is filtered through a membrane filter (HAWP04700 manufactured by Millipore) to separate it into base oil and thickener, and by measuring each mass, the amount of thickener in the grease (mass) %) Was calculated.
(2) Mixing penetration Measured according to JIS K 22205.3.

(3) Centrifugal oil separation Using a centrifuge, put a 20 g sample (grease) into a centrifuge tube and obtain the centrifugal oil separation when the acceleration of 16,000 G is applied for 3 hours at 20 ° C using the following formula. It was.
Centrifugal oil separation (mass%) = (mass of oil removed / mass of prepared grease) × 100

(4) Arithmetic average particle size Laser diffraction / scattering particle size distribution measuring device (Partica LA-950V2 manufactured by Horiba, corresponding particle size: 10 nm to 1 μm (wavelength 405 nm), 100 nm to 3 mm (wavelength 650 nm)) in grease The volume-based arithmetic average particle diameter of the particles dispersed in was measured. Specifically, in order to remove the influence of air bubbles, paste cell is made of grease defoamed with a planetary agitation deaerator (manufactured by Kurashiki Spinning Association Company (Kurabo), MAZERUSTAR model KK-V300SS-I). It was applied to and sandwiched between (LY-9504 manufactured by Horiba Seisakusho) and used for measurement. After adjusting the grease thickness (sample thickness) in the paste cell so that the arithmetic average particle size based on volume is within the range of 70% to 90% where the transmittance is an appropriate value, the laser diffraction / scattering described above It calculated | required using wavelength 405nm and 650nm with a type | formula particle size distribution measuring apparatus.
In the measurement of the arithmetic average particle diameter, multiple scattering was evaluated when the transmittance was less than 70% even when the sample thickness was reduced.

(5) Acoustic characteristics Peak High 32-64s and Level High 32-64s were measured using an acoustic measuring instrument dedicated to grease (Green Test Rig Be Quiet +) manufactured by SKF. Specifically, a dedicated grease measurement bearing without grease was set in this acoustic measurement device, and acoustic data from 32 seconds to 64 seconds after the start of rotation was obtained while rotating at a predetermined speed. In addition, a predetermined amount of sample (grease) is sealed in these bearings, and while rotating at a predetermined speed, acoustic data is obtained 32 seconds to 64 seconds after the start of rotation, and these are stored in a program built into the acoustic measurement device. By analyzing, the values of Peak High and Level High were obtained.

〔Evaluation results〕
The greases of Examples 1 to 7 have the same raw materials (base oil, thickener, thickener amount)) as the corresponding greases of Comparative Examples 1 to 7. Since the greases of Examples 1 to 7 all satisfy the configuration of the present invention, the greases of Comparative Examples 1 to 7 that are greases of the same raw material (base oil, thickener, thickener amount) are used. It can be understood that each of them has very excellent acoustic characteristics.

Claims (6)

A grease containing a base oil and a thickener,
A grease characterized by satisfying the following formula (1), where A (unit: μm) is the volume-based arithmetic average particle size of the particles contained in the grease determined by a laser diffraction / scattering method.
A ≦ 3 (1) The grease according to claim 1,
The grease is characterized in that the thickener is urea, a thickener for single soap grease, or a thickener for complex grease. The grease according to claim 2,
The grease is characterized in that the thickener is any one of calcium soap, lithium soap, sodium soap, calcium complex soap, lithium complex soap, and calcium sulfonate complex soap. The grease according to claim 2,
The thickener is urea;
The urea is obtained by reacting a monoamine and diisocyanate,
The grease, wherein the monoamine is a single amine compound or a mixture containing a plurality of types of amine compounds. In the grease according to any one of claims 1 to 4,
The grease is
A base oil is mixed with a thickener or its precursor to make a mixed solution,
A grease obtained by giving a minimum shear rate of 10 ² s ⁻¹ or more to the mixed solution. In the grease according to any one of claims 1 to 4,
The grease is
It is obtained by giving a minimum shear rate of 10 ² s ⁻¹ or more to a mixed solution obtained by mixing a base oil 1 containing a thickener precursor 1 and a base oil 2 containing a thickener precursor 2. Grease characterized by that.

Images