JP7448282B2 - Heat resistant grease composition - Google Patents

Description

The present invention relates to a grease composition having excellent heat resistance.

For example, a grease composition is a mixture of a base oil and a metal soap such as lithium soap as a thickener, and is generally widely used.

BACKGROUND ART In recent years, with advances in mechanical technology for industrial machinery, electrical equipment, automobiles, etc., various devices have become smaller, have higher output, and have improved durability such as heat resistance. On the other hand, measures against high temperatures during equipment operation are increasingly required, such as an increase in equipment temperature due to heat generation during operation, and equipment operation in high-temperature atmospheres. Along with this, the grease compositions used in these various types of equipment are required to be even more stable and have excellent heat resistance when used at high temperatures, as this is directly linked to extending the life of the equipment. ing.

When grease compositions are exposed to high-temperature environments, they undergo oxidation, and due to oil evaporation and thermal polymerization, they solidify in a short period of time, or soften, resulting in base oil leakage. It is known to stow away.

Japanese Patent Application Publication No. 2016-121336

The present invention has been made in view of these circumstances, and it maintains its grease-like properties and provides stable lubricity even under conditions of exposure to high temperatures exceeding 200°C. The purpose of the present invention is to provide a grease composition that can

The present inventor has made extensive studies to solve the above-mentioned problems. As a result, in a grease containing ether oil as a base oil and lithium complex soap as a thickener, by containing one or more selected from calcium salicylate, calcium phenate, and calcium sulfonate, the calcium salicylate The present inventors have demonstrated that lithium composite soap has the effect of protecting the three-dimensional fiber structure of lithium composite soap, thereby preventing grease from solidifying or softening and flowing out even in high-temperature environments, thereby completing the present invention.

(1) The first invention of the present invention contains ether oil as a base oil, lithium complex soap as a thickener, and one or more selected from calcium salicylate, calcium phenate, and calcium sulfonate. , a heat-resistant grease composition.

(2) A second aspect of the present invention is the heat-resistant grease composition according to the first aspect, wherein the ether oil includes an alkyldiphenyl ether oil.

(3) In a third aspect of the present invention, in the first or second aspect, the content of one or more selected from calcium salicylate, calcium phenate, and calcium sulfonate is contained in the entire grease composition. This is a heat-resistant grease composition in which the content is in the range of 0.5% by mass to 10% by mass based on 100% by mass.

(4) The fourth invention of the present invention is the method according to any one of the first to third inventions, further comprising one or more solid lubricants selected from the group consisting of organic molybdenum, melamine cyanurate, and calcium carbonate. A heat-resistant grease composition comprising:

According to the present invention, it is possible to provide a grease composition that can maintain grease-like properties and stably impart lubricity even under conditions of exposure to high temperatures.

FIG. 2 is a graph diagram showing the results of an SRV durability test for grease compositions of test samples A, B, and C. FIG. 2 is a graph diagram showing the results of a heat deterioration test on grease compositions of test samples A, B, and C. FIG. 3 is a graph showing the results of a heating test on grease compositions of test samples C and D. FIG. 2 is a graph showing the results of an SRV durability test for grease compositions of test samples C and D. FIG. 2 is a graph showing the results of an SRV durability test for grease compositions of test samples C and E.

Hereinafter, a specific embodiment of the present invention (hereinafter referred to as "this embodiment") will be described in detail. Note that the present invention can be modified in various ways without changing the gist thereof. Note that the present invention is not limited to the following embodiments, and can be modified as appropriate without changing the gist of the present invention. Furthermore, in this specification, the notation "x to y" (x, y are arbitrary numerical values) means "more than or equal to x and less than or equal to y" unless otherwise specified.

≪1. About grease composition≫
The grease composition according to the present embodiment contains ether oil as a base oil, lithium complex soap as a thickener, and one or more selected from calcium salicylate, calcium phenate, and calcium sulfonate. Moreover, this grease composition preferably further contains a thickener.

[Base oil]
The grease composition contains ether oil as a main component as a base oil. The term "main component" refers to a component contained in a proportion of 50% by mass or more in the total amount of base oil. Ether oils have excellent heat resistance, and by including such ether oils as a base oil, it is possible to create a grease composition with even better heat resistance, and it is possible to suppress solidification in high-temperature environments. . Moreover, the ether oil can disperse the thickener described later well, and can adjust the consistency to an appropriate degree.

The ether oil is not particularly limited, and examples thereof include polyphenyl ether oil, alkyl diphenyl ether oil, dialkyl diphenyl ether oil, alkyl triphenyl ether oil, alkyl tetraphenyl ether oil, dialkyl diphenyl ether oil, and the like. As the ether oil, these can be used alone or in combination of two or more.

Among these, it is preferable that the ether oil includes an alkyldiphenyl ether oil. By including the alkyldiphenyl ether oil, the heat resistance of the base oil can be further improved, and the solidification of the grease composition in a high-temperature environment can be prevented. Examples of the alkyl diphenyl ether oil include monoalkyldiphenyl ether oil, dialkyl diphenyl ether oil, and polyalkyldiphenyl ether.

The base oil content in the grease composition (when the total amount of the grease composition is 100% by mass) can be, for example, about 70% by mass to 90% by mass.

Further, the content of ether oil relative to the entire base oil is not particularly limited, but is preferably 60% by mass or more, and more preferably 80% by mass or more. Further, it is more preferable that the amount of the base oil be 100% by mass based on the entire base oil, that is, it is composed only of ether oil.

Note that when other base oils are contained in addition to ether oil, the type thereof is not particularly limited, but it is preferable to use mineral oil. Since mineral oil is a base oil that is relatively heat resistant and inexpensive, it is possible to produce grease at a lower cost. As the mineral oil, for example, liquid petroleum, paraffinic, naphthenic, or mixed paraffin/naphthenic oil treated with a solvent or acid can be used.

Here, FIG. 1 shows the results of the SRV durability test for the grease compositions of test samples A, B, and C. Table 1 below shows the respective grease compositions, which differ in terms of base oil, and the grease composition of test sample C was composed of a base oil consisting only of alkyl diphenyl ether oil. Table 2 below shows the SRV duration test conditions, and the test was carried out at a high temperature of 250°C.

Further, FIG. 2 shows the results of a heat deterioration test for the same test samples A, B, and C of the grease compositions. The thermal deterioration test was conducted by putting the grease in a glass beaker and placing it in a constant temperature bath at a temperature of 200° C. for a test period of 42 days.

Furthermore, a thin film evaporation test was conducted on the grease compositions of the same test samples A, B, and C at a temperature of 200° C., and the solidification time of the grease was measured. Table 3 below shows the results of the evaporation test.

As can be seen from the results of the SRV durability test shown in Figure 1, the grease composition of Test Sample C, which was composed of a base oil consisting only of alkyldiphenyl ether oil, had an extremely stable coefficient of friction even under the 3-h test condition in a high-temperature environment. and maintained high lubricity. On the other hand, with the test sample A grease composition made up of a base oil consisting only of mineral oil, and the test sample B grease composition made up of a mixed oil base oil of mineral oil and ether oil, the grease composition deteriorated over the course of the test. The coefficient of friction increased, resulting in inferior stable lubricity.

Moreover, as can be seen from the results of the heat deterioration test shown in FIG. 2, the change in consistency was small in the grease composition of test sample C. On the other hand, in the grease composition of test sample A, the consistency decreased and solidified. In addition, in the grease composition of test sample B, the consistency increased rapidly and softening occurred.

Further, from the results of the evaporation test shown in Table 3, it was found that the grease composition of Test Sample C, which was composed of a base oil consisting only of alkyldiphenyl ether oil, could effectively suppress solidification even in a high-temperature environment.

As can be seen from the above test results, by containing ether oil such as alkyldiphenyl ether oil, and in particular by composing a base oil consisting only of that ether oil, heat resistance is improved and it is effective even in high-temperature environments. Can suppress solidification.

[Thickener]
The grease composition contains lithium complex soap as a thickener. Lithium composite soap is a thickener that further improves the shear stability of lithium soap by reacting lithium soap with a fatty acid that is a material for soap. In this way, by using the lithium composite soap as a thickener, it is possible to adjust the consistency to an appropriate degree, and it is also possible to impart excellent shear stability.

As mentioned above, lithium composite soap is obtained by reacting fatty acids in a complex manner, and contains a metal salt of a second acid in addition to the lithium salt of the fatty acid. Specifically, lithium composite soaps include those containing lithium 12-hydroxystearate and lithium azelaate.

The content of the thickener in the grease composition (when the total amount of the grease composition is 100% by mass) is not particularly limited and may be set as appropriate depending on the desired consistency of the grease. It can be about % by mass to 20% by mass.

The structure of lithium composite soap grease is that a lithium salt of a fatty acid that functions as a thickener and a metal salt of a second acid are dispersed in the base oil in the form of strings and intertwined, forming a three-dimensional fiber structure. There is. In grease, the base oil and additives are retained in such a fibrous structure, thereby maintaining a semi-solid state with a desired consistency. On the other hand, it is known that when grease is exposed to high-temperature environments, it undergoes oxidation and solidifies in a short period of time due to oil evaporation and thermal polymerization. This is due to the inability of the thickener to maintain its three-dimensional fiber structure.

In particular, since lithium composite soap is an organic substance, it is more prone to deterioration than inorganic thickeners such as bentonite and silica, and it becomes difficult to maintain a three-dimensional fiber structure due to thermal deterioration as mentioned above, and the base The ability to retain oil and additives becomes weaker, resulting in a decrease in lubricity. Furthermore, the lubricity of the thickener itself is also reduced.

[Calcium salicylate]
The grease composition contains calcium (Ca) salicylate. Research conducted by the present inventor has shown that by containing calcium salicylate in grease containing lithium complex soap as a thickener, it is possible to prevent the grease from solidifying and maintain its properties even in high-temperature environments of 200°C or higher. It has been found that good lubricity can be stably imparted.

Although the detailed mechanism is not clear, it is presumed that by containing calcium salicylate in lithium composite soap grease, the calcium salicylate protects the three-dimensional fiber structure of the lithium composite soap, which is a thickener. . As a result, even in a high-temperature environment, it is thought that the protective action of the three-dimensional structure by calcium salicylate suppresses a decrease in the retention power of the base oil and prevents the grease from softening, flowing out, or solidifying.

Calcium salicylate has conventionally been used as a cleaning dispersant (metallic cleaning agent) that is an additive in grease compositions (see, for example, Patent Document 1). In general, detergent-dispersing agents act to disperse sludge generated by thermal load on grease into base oil, and are additives added for the purpose of suppressing deterioration of grease.

However, as mentioned above, as a result of studies by the present inventors, the inclusion of calcium salicylate in grease containing lithium complex soap as a thickener acts to moderately harden the grease, resulting in a change in the three-dimensional structure of the thickener. It was found that it protects the grease and prevents it from softening and flowing out. On the other hand, it has been found that solidification of grease can be effectively prevented.

Here, FIG. 3 shows the results of a heating test for the grease compositions of test samples C and D. The heating test was conducted by weighing approximately 10 g of grease into a tin plate prepared as a test container, at a temperature of 280° C., and for a test time of 16 hours. The consistency of the grease was measured every 4 hours to examine changes in consistency. The composition of each grease is shown in Table 4 below, and both differ only in the presence or absence of calcium salicylate.

Further, FIG. 4 shows the results of the SRV persistence test for the same test samples C and D grease compositions. Note that the conditions for the SRV persistence test were the same as those shown in Table 2 above.

As can be seen from the results of the heating test shown in FIG. 3, in the test sample D grease containing calcium salicylate, the penetration gradually decreased from the start of the test, and the grease hardened. On the other hand, in the test sample C grease that did not contain calcium salicylate, the consistency gradually increased and softened from the start of the test.

In addition, as can be seen from the results of the SRV sustainment test shown in Figure 4, the grease of test sample D containing calcium salicylate showed an extremely stable low friction coefficient even under the 3-hour test condition in a high-temperature environment, providing high lubrication. Maintained sexuality.

As can be seen from these test results, by including calcium salicylate in grease containing lithium composite soap as a thickener, the calcium salicylate accelerates the hardening of the grease, thereby increasing the thickening ability of lithium composite soap. In other words, it maintains the so-called retention ability for retaining base oil and the like, making it possible to stably impart high lubricity to the grease composition.

Calcium salicylates are not particularly limited, and include calcium salts of alkyl salicylic acids.

Further, the content of calcium salicylate in the grease composition (when the total amount of the grease composition is 100% by mass) is not particularly limited, but is preferably about 0.5% by mass to 10% by mass, for example, 1 It is more preferably about 2% to 7% by mass, and particularly preferably about 2% to 5% by mass.

[Calcium phenate]
Here, in the grease composition, calcium phenate can be blended in addition to calcium salicylate. Alternatively, calcium phenate can be added in place of calcium salicylate. Like calcium salicylate, the inclusion of calcium phenate acts to moderately harden the grease, protects the three-dimensional structure of the thickener, and prevents the grease from softening and flowing out. On the other hand, solidification of the grease can be effectively prevented.

The calcium phenate is not particularly limited, and examples thereof include alkylphenol, alkylphenol sulfide, and a calcium salt of methylenebisalkylphenol obtained by subjecting an alkylphenol to acetone through a condensation and dehydration reaction.

Note that the content of calcium phenate in the grease composition (when the total amount of the grease composition is 100% by mass) is also preferably about 0.5% by mass to 10% by mass, for example, similarly to calcium salicylate. The content is more preferably about 1% by mass to 7% by mass, and particularly preferably about 2% by mass to 5% by mass.

[Calcium sulfonate]
Furthermore, in the grease composition, calcium sulfonate can be blended in addition to calcium salicylate and calcium phenate. Alternatively, calcium sulfonate can be added in place of calcium salicylate or calcium phenate. That is, the grease composition according to the present embodiment contains one or more selected from the group consisting of calcium salicylate, calcium phenate, and calcium sulfonate.

Like calcium salicylate and calcium phenate, by including calcium sulfonate in the grease composition, it acts to moderately harden the grease, protects the three-dimensional structure of the thickener, and prevents the grease from softening and flowing out. Can be done. On the other hand, solidification of the grease can be effectively prevented.

The calcium sulfonate is not particularly limited, and examples thereof include calcium salts of alkylbenzenesulfonic acids such as dodecylbenzenesulfonic acid and octadecylbenzenesulfonic acid, calcium salts of petroleum sulfonic acids, and the like.

Note that the content of calcium phenate in the grease composition (when the total amount of the grease composition is 100% by mass) should be, for example, about 0.5% by mass to 10% by mass, similar to calcium salicylate and the like. It is preferably about 1% by mass to 7% by mass, more preferably about 2% by mass to 5% by mass.

[Thickener]
Although not an essential aspect, the grease composition may further contain a thickener. By increasing the viscosity of the base oil that constitutes the grease, the thickener can effectively suppress oil separation that accompanies deterioration in a high-temperature environment.

Examples of thickeners include olefin copolymers, high viscosity polyalphaolefins, polybutenes, polymethacrylates, and the like.

Further, the content of the thickener in the grease composition (when the total amount of the grease composition is 100% by mass) is not particularly limited, but is preferably about 1% by mass to 15% by mass, and 3% by mass. % to about 10% by mass.

Here, FIG. 5 shows the results of the SRV durability test for the grease compositions of test samples C and E. The respective grease compositions are shown in Table 5 below, and as the thickener contained in the grease composition of test sample E, a polybutene-based compound was used. Note that the conditions for the SRV persistence test were the same as those shown in Table 2 above.

Further, Table 6 below shows the results of measuring the oil separation degree (100° C., 24 hours) by a test based on JIS K 2220 (5.7):2013.

As can be seen from the results of the SRV duration test shown in Figure 5, the grease of test sample E containing calcium salicylate and a thickener exhibited an extremely stable low coefficient of friction even under test conditions in a high-temperature environment, resulting in high lubricity. Maintained sexuality. On the other hand, in the grease of test sample C, the coefficient of friction increased with the passage of time, and a decrease in lubricity was observed. Furthermore, based on the measurement results of the degree of oil separation shown in Table 6, it is considered that the grease of test sample E was able to reduce the degree of oil separation, thereby maintaining a stable high lubricity.

In this way, by including a thickener in a grease containing a lithium composite soap as a thickener, the degree of oil separation can also be effectively reduced. Coupled with the effect of protecting the three-dimensional structure of the thickener by containing calcium salicylate, heat resistance can be more effectively improved and high lubricity can be maintained.

[Solid lubricant]
The grease composition may contain a solid lubricant. By including the solid lubricant in this way, high lubricity can be imparted.

Solid lubricants include, but are not limited to, organic molybdenum, melamine cyanurate (MCA), calcium carbonate, polytetrafluoroethylene (PTFE), graphite, molybdenum disulfide, tungsten disulfide ( _WS2 ), and boron nitride (BN). ) etc. Among these, one or more selected from the group consisting of organic molybdenum, melamine cyanurate, and calcium carbonate is preferred. By using such a solid lubricant in a grease composition, it can be efficiently dispersed in ether oil and provide higher lubricity.

Incidentally, as the solid lubricant, one type can be used alone, or two or more types can be used in combination.

Further, the content of the solid lubricant in the grease composition (when the total amount of the grease composition is 100% by mass) is not particularly limited, but the total amount of one or more solid lubricants is, for example, 3% by mass. It is preferably about 20% by mass, more preferably about 5% by mass to 15% by mass.

[Other additives]
In addition to the above-mentioned components, the grease composition may contain various additives commonly used in grease, such as extreme pressure agents, antioxidants, rust preventives, anti-wear agents, etc., as necessary. can do. Note that such additives may be added as components constituting the base grease together with the base oil and the thickener.

Specifically, examples of the extreme pressure agent include sulfur-phosphorus extreme pressure agents and the like. The sulfur-phosphorus extreme pressure agent is a compound having a phosphorus atom and a sulfur atom, and examples thereof include thiophosphates and thiophosphites having both a phosphorus atom and a sulfur atom in the molecule. These antioxidants can be used alone or in combination of two or more.

Examples of the antioxidant include phenolic antioxidants, amine antioxidants, thioether antioxidants, and the like. These antioxidants can be used alone or in combination of two or more.

Further, examples of the rust preventive include neutral metal salts, amine salts, basic metal salts, and the like. Specifically, barium sulfonate and the like can be mentioned. These rust preventives can be used alone or in combination of two or more.

≪2. Method for manufacturing grease composition≫
As described above, the grease composition according to the present embodiment contains ether oil as a base oil, lithium complex soap as a thickener, and one or more selected from calcium salicylate, calcium phenate, and calcium sulfonate. It contains. Preferably, it further contains a thickener. Such a grease composition can be manufactured by a well-known method in the same manner as conventional grease compositions.

Specifically, for example, in a heat-resistant container such as a copper pot, add ether oil as a base oil and fatty acids and carboxylic acids that make up the lithium complex soap as a thickener, and heat the mixture to about 80°C to 100°C while stirring. After heating to a temperature of 100 mL, an aqueous lithium hydroxide solution is added and the mixture is allowed to react for about 1 to 2 hours. Subsequently, the reaction solution is heated to about 230° C., an additive containing one or more selected from calcium salicylate, calcium phenate, and calcium sulfonate is added, stirred, and then cooled. Thereby, a grease composition can be obtained.

Incidentally, the stirring and kneading treatment can be carried out using a well-known kneading treatment apparatus such as a three-roll mill, a universal stirrer, a homogenizer, and a colloid mill.

Claims (5)

an ether oil containing an alkyl diphenyl ether oil as a base oil;
With lithium complex soap as a thickener,
containing calcium salicylate ,
Heat-resistant grease composition. The ether oil consists only of alkyldiphenyl ether oil,
The heat-resistant grease composition according to claim 1. The content of the calcium salicylate is in the range of 0.5% by mass to 10% by mass, based on 100% by mass of the entire grease composition.
The heat-resistant grease composition according to claim 1 or 2. Furthermore, it contains one or more solid lubricants selected from the group consisting of organic molybdenum, melamine cyanurate, and calcium carbonate.
The heat-resistant grease composition according to any one of claims 1 to 3. Furthermore, it contains one or more selected from calcium phenate and calcium sulfonate,
The heat-resistant grease composition according to any one of claims 1 to 4.

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