JP7282405B2 - lubricating grease composition - Google Patents

Description

The present invention relates, for example, to grease compositions for movable joints.

Conventionally, grease using, for example, mineral oil or synthetic hydrocarbon oil has been used for movable joints such as automobile suspensions and lower arms (see Patent Document 1).

In order to maintain the lubricity of the movable joints, these greases use relatively high-viscosity base oil or improve the thickener to increase the viscosity of the base oil and improve the adhesion of the grease. ing.

Japanese Patent Application Laid-Open No. 2000-230188

However, conventional grease has a high viscosity in order to maintain lubricity, and this has the problem of increasing the operating torque of the movable joint. In addition, at low temperatures, the viscosity of the grease becomes extremely high, and there is a concern that malfunction may occur.

Therefore, the present invention has been made in view of such problems, and provides a grease composition capable of reducing operating torque and improving low-temperature resistance as compared with conventional grease compositions, and a movable joint using the same. intended to provide

The lubricating grease composition of the present invention comprises a dimethyl silicone oil as a base oil and an additive, the additive comprising a carboxylic acid-modified silicone, and the dimethyl silicone oil occupying the grease composition, 57 parts by mass or more and 82 parts by mass or less, the carboxylic acid-modified silicone occupying the grease composition is 0.01 parts by mass or more and 10 parts by mass or less, and the consistency is 225 or more and 465 or less. Characterized by

Moreover, in the lubricating grease composition of the present invention, the additive is preferably a modified silicone represented by the following general formula (1), (2) or (3).

Moreover, in the grease composition of the present invention, the kinematic viscosity of the additive is preferably 15000 mm ² /s or less at 25°C.

Further, in the grease composition of the present invention, the viscosity of the grease composition is preferably 5500 Pa·s or less at −40° C. and a shear modulus of 1.0 S ⁻¹ .

Moreover, in the grease composition of the present invention, the kinematic viscosity of the base oil is preferably 100000 mm ² /s or less at 25°C.

The present invention also provides a movable joint having a spherical portion, a receiving member for receiving the spherical portion, and a surface layer covering the surface of the spherical portion, wherein at least one of the spherical portion and the surface layer is made of resin. and the grease composition described above is filled between the spherical portion and the surface layer.

According to the grease composition of the present invention, the operating torque can be reduced and the low-temperature resistance can be improved as compared with conventional grease compositions.

Therefore, the grease composition of the present invention can be suitably used as a lubricant for movable joints.

4 is a graph showing the relationship between temperature and operating torque measured using a plurality of grease compositions with different compositions for movable joints.

An embodiment of the present invention (hereinafter abbreviated as "embodiment") will be described in detail below. It should be noted that the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.

The present inventors have made earnest research on a grease composition used for lubricating the inside of a movable joint having a spherical portion and a receiving member for receiving the spherical portion. By using , the operability at low temperatures has been improved.

(Grease composition)
The grease composition in the present embodiment contains a dimethyl silicone oil as a base oil, and preferably contains the additives described below.

In addition, what is conventionally included in a grease composition, such as a thickener, is appropriately added.

In the present embodiment, the kinematic viscosity of the base oil is preferably 100000 mm ² /s or less at 25°C. As will be shown in experiments to be described later, in the present embodiment, the kinematic viscosity of the base oil can be defined within the above range. In addition, the kinematic viscosity of the base oil at 25° C. is more preferably 10000 mm ² /s or less, still more preferably 5000 mm ² /s or less, and even more preferably 2000 mm ² /s or less. Although the lower limit is not particularly limited, for example, the kinematic viscosity of the base oil can be lowered to about 5 mm ² /s at 25°C.

In the present embodiment, two or more different types of base oils may be mixed and used, and dimethyl silicone oil may be used as one of the base oils. However, when two or more types of base oils are combined, it is preferable that half or more (50 parts by mass or more) of the base oils in the grease composition is composed of dimethylsilicone oil.

The additive contained in the grease composition preferably contains at least one of carboxylic acid-modified silicone and amino-modified silicone.

ここで、数値を限定するものではないが、ｍは、数十以上であり、具体的には５０以上であり、後述する実施例では、８０～７５０程度である。また、ｎは、１００程度以下であり、具体的には２０以下であり、後述する実施例では、１～１０程度である。

Specifically, the additive is preferably a modified silicone represented by the following general formula (1), (2) or (3).

Here, although the numerical value is not limited, m is several tens or more, specifically 50 or more, and about 80 to 750 in the examples described later. Also, n is about 100 or less, specifically 20 or less, and about 1 to 10 in the examples described later.

Thus, in the present embodiment, it is preferable to include carboxylic acid-modified silicone and/or amino-modified silicone as additives. is preferably included.

In this embodiment, it is preferable to adjust the content of the additive within a predetermined range. If the content of the additive is too large, oil separation tends to occur, so specifically, the content of the additive is preferably 15 parts by mass or less. Here, 100 parts by mass is the total amount of the grease composition, and therefore "parts by mass" means the percentage relative to the total amount of the grease composition. The same shall apply hereinafter.

Moreover, in the present embodiment, the amount of the additive added is preferably 0.01 parts by mass or more. If this level of additive is included, the operating torque can be reduced compared to the conventional art.

In the present embodiment, the additive amount is more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less. Moreover, the amount of the additive added is more preferably 0.2 parts by mass or more. The amount of additive added is most preferably about 0.02 parts by mass to 1 part by mass.

Further, in the present embodiment, the dynamic viscosity of the additive is preferably 15000 mm ² /s or less at 25°C. This kinematic viscosity can be adjusted by the number of repetitions of the chemical formula described in the general formula above.

The thickener contained in the grease composition of the present embodiment is not particularly limited, but examples include lithium soap, calcium soap, sodium soap, aluminum soap, lithium complex soap, calcium complex soap, and aluminum complex soap. , a urea compound, organized bentonite, polytetrafluoroethylene, silica gel, and sodium terephthalamate. Lithium soap is a saponification reaction product of fatty acid or its derivative and lithium hydroxide. The fatty acid used is at least one selected from the group consisting of saturated or unsaturated fatty acids having 2 to 22 carbon atoms and derivatives thereof. In addition, "soap" obtained by reacting the fatty acid or its derivative with lithium hydroxide is commercially available, and this can also be used.

Moreover, antioxidants, rust inhibitors, metal corrosion inhibitors, oiliness agents, antiwear agents, extreme pressure agents, solid lubricants, and the like can be added as necessary. The content of these additives is within the range of about 0.01 to 20 parts by weight. Antioxidants can be selected from hindered phenols, alkylated diphenylamines, phenyl-α-naphthylamines, and the like. The rust inhibitor can be selected from carboxylic acids such as stearic acid, dicarboxylic acids, metal soaps, amine salts of carboxylic acids, metal salts of heavy sulfonic acids, carboxylic acid partial esters of polyhydric alcohols, and the like. The metal corrosion inhibitor can be selected from benzotriazole, benzimidazole, and the like. The oiliness agent can be selected from amines such as laurylamine, higher alcohols such as myristyl alcohol, higher fatty acids such as palmitic acid, fatty acid esters such as methyl stearate, and amides such as oleylamide. can. The antiwear agent can be selected from zinc-based, sulfur-based, phosphorus-based, amine-based, ester-based, and the like. The extreme pressure agent should be selected from zinc dialkyldithiophosphate, molybdenum dialkyldithiophosphate, sulfurized olefin, sulfurized oil, methyltrichlorostearate, chlorinated naphthalene, benzyl iodide, fluoroalkylpolysiloxane, lead naphthenate, and the like. can be done. The solid lubricant can be selected from graphite, graphite fluoride, polytetrafluoroethylene, melamine cyanurate, molybdenum disulfide, antimony sulfide, and the like.

The viscosity of the grease composition in the present embodiment is preferably 5500 Pa·s or less at −40° C. and a shear rate of 1.0 S ⁻¹ . In addition, since the viscosity of the grease composition changes depending on the shear rate, the shear rate is specified. Further, in the present embodiment, the difference in viscosity between normal temperature (25° C.) and −40° C. can be approximately 4000 Pa·s or less at a shear rate of 1.0 S ⁻¹ .

Also, the consistency of the grease composition can be about 200 to 500. A method for measuring the consistency will be described in the section of Examples described later.

(movable joint)
A movable joint using the grease composition of the present embodiment can be used, for example, in movable parts such as automobile suspensions, lower arms, and tie rod ends.

The movable joint includes a spherical portion, a receiving member for receiving the spherical portion, and a surface layer covering the surface of the spherical portion. The surface layer is held by the receiving member.

Then, the grease composition of the present embodiment is filled between the spherical portion and the surface layer. By the way, the spherical portion is made of metal, for example, and the receiving member and surface layer are made of resin, for example. Although the material is not limited, examples of the resin include polyacetal resin, polyester resin, and the like.

Thus, in the present embodiment, a grease composition containing dimethylsilicone oil having a high viscosity index as a base oil is filled between the metal and the resin. That is, for example, a grease composition containing dimethyl silicone oil as a base oil can effectively exhibit desired lubricating performance between a metal and a resin, compared to the case where both are metals. In particular, with the miniaturization of movable joints, the change in grease viscosity at low temperatures cannot be ignored with the conventionally used mineral oil and synthetic hydrocarbon oil, but in the present embodiment, it can be avoided. It is possible to overcome this problem, suppress the increase in viscosity of the grease composition at low temperatures, and appropriately maintain the fluidity of the grease composition.

In addition, the carboxylic acid portion of the carboxylic acid-modified silicone used as an additive easily adsorbs to metal materials, which improves the lubricity of movable joints, reduces operating torque, and suppresses stick-slip. becomes possible. Therefore, by using the movable joint of the present embodiment, it is possible to improve the steering performance of the automobile, and in particular, it is possible to suppress malfunction at low temperatures.

Further, the movable joint of the present embodiment has a spherical portion, a receiving member for receiving the spherical portion, and a surface layer covering the surface of the spherical portion, and at least one of the spherical portion and the surface layer is made of resin. A grease composition having a viscosity of 5500 Pa·s or less at −40° C. and a shear rate of 1.0 S ⁻¹ may be filled between the spherical portion and the surface layer.

In the above-described embodiments, a movable joint for automobiles was given as an example of a movable joint, but it can also be applied to transportation equipment and industrial equipment other than automobiles as long as it has a high load and a movable part.

EXAMPLES The present invention will now be described in detail with reference to examples carried out to clarify the effects of the present invention. In addition, the present invention is not limited at all by the following examples.

In the experiment, the base oil viscosity, consistency, and grease viscosity of the grease compositions shown in Tables 1 and 2 were measured, and each grease composition was filled between the spherical portion and the surface layer of the movable joint, The operating torque at room temperature (25°C), the operating torque at -40°C, and the presence or absence of stick-slip were measured.

In addition, "carboxyl-modified-1", "carboxyl-modified-2", "carboxyl-modified-3", "amino-modified-1", "amino-modified-2", and "amino-modified-3" shown in Tables 1 and 2 are shown in Table 3 below.

The viscosities of the base oils shown in Tables 1 and 2 are measured values at 25°C. For the grease compositions with a base oil viscosity of 1800 cSt (=mm ² /s) shown in Tables 1 and 2, the 100 cSt product and the 10000 cSt product were mixed to adjust the viscosity. On the other hand, for the grease composition with a base oil viscosity of 5 cSt and the grease composition with a base oil viscosity of 100000 cSt, commercially available dimethyl silicone oil was used as it was.

The consistency was measured by the consistency test method specified in JIS K2220.

The operating torque at room temperature was measured using a commercially available tie-rod end with an application amount of the grease composition of 0.5 g at a rotation speed of 0.2 rpm and a rotation angle of 45 degrees (reciprocating motion). . The operating torque at −40° C. was measured in the same manner as the operating torque at room temperature after leaving the movable joint coated with the grease composition in a constant temperature bath at −40° C. for 4 hours.

Also, the viscosity of the grease composition at -40°C was measured with a rheometer owned by Nippeco Corporation. In the measurement, the viscosity was measured at a shear rate of 1 s ^-1 .

Based on the examples shown in Tables 1 and 2, the content of the carboxylic acid-modified silicone or amino-modified silicone additive is set to 15 parts by mass or less, preferably 10 parts by mass or less, more preferably , 5 parts by mass or less, and more preferably 3 parts by mass or less.

If the content of the additive is too high, the structure of the thickener constituting the grease composition is likely to be deformed or destroyed, and softening leakage and oil separation of the grease composition are likely to occur. The smaller the amount, the better.

On the other hand, it was found that even with the addition of 0.01% by mass of Example-2 shown in Table 1, which is the lower limit of the content of the additive, the operating torque can be reduced compared to the conventional case. Therefore, the lower limit of the content of the additive was set to 0.01 parts by mass. However, if the content of the additive is increased a little more, for example, as can be seen from Example-3, it is possible to further reduce the operating torque. It was found that the operating torque can also be stably kept at a low value.

Also, according to Example-10 shown in Table 1, the kinematic viscosity of the base oil was set to 100000 mm ² /s or less at 25°C. If the kinematic viscosity of the base oil becomes higher than this, there is a concern that workability will deteriorate in practical use.

Also, according to Example-9 shown in Table 1, the kinematic viscosity of the base oil was set to 5 mm ² /s or more at 25°C. If the kinematic viscosity of the base oil is made lower than this, it is considered that the lubricating ability is likely to be lowered and the base oil is likely to be dried.

Further, the hardness (consistency) of the grease composition is preferably about 225 (consistency: No. 3) from Example-11. If it is harder than this, there is a concern that workability will deteriorate in actual use.

In addition, the softness (consistency) of the grease composition is preferably about 465 (consistency: No. 000) from Implementation-12. If it is softer than this, there is concern that the lubricity will deteriorate and the grease composition will leak.

Based on the above experimental results, it was determined that the consistency of the grease composition is preferably about 200 to 500.

Further, in this embodiment, the viscosity of the grease composition at -40°C can be 5500 Pa·s or less at a shear rate of 1.0 S ^-1 . On the other hand, in the comparative example, the viscosity of the grease composition was approximately 40000 Pa·s or more at a shear rate of 1.0 S ⁻¹ or could not be measured.

Using Example-3 shown in Table 1 and Comparative Examples-3 and Comparative Examples-4 shown in Table 2, the operating torque of the movable joint was measured at each temperature. The measurement conditions are as listed above.

The experimental results are shown in Table 4 below and FIG.

As shown in Table 4 and FIG. 1, in Comparative Examples-3 and Comparative Examples-4, when the temperature fell below 0.degree. C., the operating torque increased sharply. On the other hand, in Example-3, it was found that the operating torque could be suppressed to about 2000 mN·m or less in the temperature range of about -40°C to 100°C. In addition, in Comparative Examples-3 and 4, the operating torque at -40°C increased by about 5000 mNm compared to the operating torque at 25°C, whereas in Example-3, It was found that the operating torque at −40° C. and the operating torque at 25° C. hardly changed (approximately 300 nN·m or less).

The grease composition of the present invention using dimethyl silicone oil with a high viscosity index as the base oil can suppress the increase in viscosity at low temperatures and maintain good fluidity. By using the grease composition of the present invention as a lubricant for a movable joint in which at least one of the spherical portion and the surface layer covering the spherical portion is formed of resin, the operating torque can be reduced (especially at low temperatures). reduction) and suppression of stick strips. As the movable joint to which the grease composition of the present invention is applied, it can be suitably used for movable joints of automobiles, but it can also be effectively used for transportation equipment and industrial equipment other than automobiles.

Claims (5)

Containing dimethyl silicone oil as a base oil and an additive,
The additive comprises a carboxylic acid-modified silicone,
The dimethyl silicone oil occupying the grease composition is 57 parts by mass or more and 82 parts by mass or less,
The carboxylic acid-modified silicone accounts for 0.01 parts by mass or more and 10 parts by mass or less in the grease composition,
The consistency is 225 or more and 465 or less,
A lubricating grease composition characterized by: 2. The lubricating grease composition according to claim 1 , wherein the additive is a modified silicone represented by the following general formula (1), (2) or (3).

3. The lubricating grease composition according to claim 1 , wherein the additive has a kinematic viscosity of 15000 mm ^<2> /s or less at 25[deg.]C. The lubricating grease according to any one of claims 1 to 3 , wherein the viscosity of the grease composition is 5500 Pa s or less at -40 ° C. and a shear rate of 1.0 S ^-1 . Composition. The lubricating grease composition according to any one of claims 1 to 4, wherein the kinematic viscosity of the base oil is 100000 ^mm2 /s or less at 25°C.

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