JP4599134B2 - Grease base oil - Google Patents

Description

  The present invention relates to a grease base oil and a lubricating oil containing it.

Patent Document 1 discloses a grease base oil that exhibits excellent lubricity over a long period of time in a wide use temperature range from low temperature to high temperature. However, when the lubricating oil containing the grease base oil is used for a long time, the lubricity may be insufficient.
Japanese Patent Laid-Open No. 11-80766

  An object of the present invention is to provide a grease base oil and a lubricating oil containing the same that exhibit further superior properties over a wide temperature range and exhibit a sufficient and stable lubricity even after long-term use. To do.

  As a result of studying the case where the lubricity decreases when used for a long period of time, the present inventors have found that in an open system that can come into contact with moisture, for example, in an environment where external water or water generated by condensation can be mixed into the lubricant. The inventors have found that such a problem is remarkable and have completed the present invention. That is, the present invention is a grease base oil containing an ester of pentaerythritol and carboxylic acid, wherein the carboxylic acid has a total content of 2-ethylhexanoic acid, n-heptanoic acid and n-octanoic acid. And 90% by mass or more of a grease base oil, and a lubricating oil containing the grease base oil.

  The lubricating oil containing the grease base oil of the present invention exhibits excellent lubricity in a wide temperature range from low temperature to high temperature and has an open system that can come into contact with moisture, for example, external water or water generated by condensation. It can be used stably for a long time in an environment where it can be mixed with the lubricant.

  The grease base oil of the present invention contains an ester of pentaerythritol and carboxylic acid, and the carboxylic acid has a total content of 2-ethylhexanoic acid, n-heptanoic acid and n-octanoic acid. One major feature is that it is contained in an amount of 90% by mass or more.

  Since the grease base oil of the present invention has such a configuration, it has excellent lubricity in a wide temperature range, and an open system that can come into contact with moisture, for example, external water or water generated by condensation is a lubricant. It can be used stably for a long time in an environment where it can be mixed in.

  The total content of 2-ethylhexanoic acid, n-heptanoic acid and n-octanoic acid in the carboxylic acid, which is the raw material of the ester, is excellent under the condition that the grease base oil exhibits excellent lubricity and is rich in moisture. Even from the viewpoint of enabling stable use over a long period of time, it is 90% by mass or more, preferably 95% by mass or more, more preferably 99% by mass or more.

  Similarly to the above, the grease base oil has excellent lubricity in a wide temperature range, and an open system that can come into contact with moisture, for example, external water or an environment where water generated by condensation can be mixed in the lubricant. Mass ratio of the content of 2-ethylhexanoic acid to the total content of n-heptanoic acid and n-octanoic acid in the carboxylic acid [2-ethylhexane Acid / (n-heptanoic acid + n-octanoic acid)] is preferably 65/35 to 35/65, more preferably 60/40 to 40/60, and still more preferably 58/42 to 45 / 55. Further, the content of 2-ethylhexanoic acid in the carboxylic acid is preferably 35 to 65% by mass, more preferably 40 to 60% by mass, still more preferably 45 to 58% by mass, n − The heptanoic acid content is preferably 15 to 40% by mass, more preferably 15 to 35% by mass, still more preferably 15 to 30% by mass, and the n-octanoic acid content is preferably Is 15-40 mass%, More preferably, it is 15-35 mass%, More preferably, it is 15-30 mass%.

  The carboxylic acid may optionally contain other carboxylic acids other than 2-ethylhexanoic acid, n-heptanoic acid, and n-octanoic acid as long as the desired effects of the present invention are not inhibited. . Examples of other carboxylic acids include n-pentanoic acid, n-hexanoic acid, n-nonanoic acid, n-decanoic acid, and other branched chain fatty acids having 6 to 10 carbon atoms having an alkyl group at the α-position. .

  Esters of pentaerythritol and a carboxylic acid containing a predetermined amount of 2-ethylhexanoic acid, n-heptanoic acid and n-octanoic acid can be produced between both components according to a known method (for example, see JP-A-11-80766). Can be prepared by carrying out an esterification reaction.

  In the reaction of pentaerythritol and carboxylic acid, the equivalent ratio of the two is not particularly limited, but is usually adjusted so that the carboxyl group of carboxylic acid is 1 to 1.3 equivalent to 1 equivalent of hydroxyl group of pentaerythritol. It is preferable to do. In addition, when the ratio of the carboxyl group of carboxylic acid is made high, the reactivity of pentaerythritol and carboxylic acid becomes good, but it is necessary to remove excess carboxylic acid after completion of the reaction. When a large amount of carboxylic acid is used, excess carboxylic acid may be removed by methods such as distillation under reduced pressure, steaming, adsorption using an adsorbent, and removal.

  The grease base oil of the present invention is not particularly limited, but preferably contains 80 to 100% by mass, more preferably 90 to 100% by mass of the ester. When 100% by mass is contained, the grease base oil consists of the ester of the present invention itself. Examples of esters other than the esters used in the present invention include diester oils such as di-2-ethylhexyl sebacate, polyol ester oils produced from trimethylolpropane, neopentyl glycol and the like and carboxylic acids, pyromellitic acid, Aromatic ester oil produced from trimellitic acid and alcohol can be used. Examples of components other than esters in the grease base oil include hydrocarbon oils and ethers.

  The volatilization amount of the grease base oil of the present invention is preferably 30% by mass or less, more preferably from the viewpoint of heat resistance capable of maintaining excellent lubricity even when the grease base oil is used at a high temperature for a long period of time. Is 25% by mass or less. The volatilization amount can be obtained by a method described later.

  In addition, the pour point of the grease base oil of the present invention is preferably −45 ° C. or less, more preferably −50 ° C. or less, from the viewpoint of having a low temperature fluidity with even better lubricity at low temperatures. It is preferably −52.5 ° C. or less. The pour point is measured according to JIS K2269. Grease base oil containing an ester having such a pour point, when used in, for example, air-conditioner fan motor bearings, automotive bearings, acoustic equipment bearings, computer bearings, spindle motor bearings, etc., provides low temperature starting torque. It can be drastically reduced.

  Furthermore, the viscosity index of the grease base oil of the present invention is preferably 110 or more, and more preferably 112 or more, from the viewpoint of having high temperature lubricity such that the decrease in viscosity at high temperature is small. The viscosity index is determined according to JISK2283.

  Therefore, as the grease base oil of the present invention, those having a pour point of −45 ° C. or less, a volatilization amount of 30% by mass or less, and a viscosity index of 110 or more are particularly preferable.

As the kinematic viscosity at 40 ° C. Grease oil of the present invention, in order to ensure the lubricity of the starting or the like of the motor, preferably 20 to 40 mm ² / sec, more preferably at 24~36mm ² / sec is there. The kinematic viscosity at 40 ° C. is measured according to JIS K2283.

  The acid value of the grease base oil of the present invention is preferably 0.5 mgKOH / g or less, more preferably from the viewpoint of good flash point, oxidation stability, thermal stability, hydrolysis resistance, metal corrosion resistance, etc. It is 0.1 mgKOH / g or less. Further, the hydroxyl value of the grease base oil of the present invention is preferably 4 mgKOH / g or less, more preferably 3 mgKOH / g or less, because of its good flash point, low temperature fluidity, thermal stability, hydrolysis resistance and the like. It is.

  Furthermore, the acid value of the grease base oil of the present invention after the hydrolysis standard test described later is preferably 10 mgKOH / g or less, more preferably 5 mgKOH / g or less, from the viewpoint of preventing corrosion to the metal member, The hydroxyl value after the test is preferably 10 mgKOH / g or less, more preferably 6 mgKOH / g or less, because if the hydroxyl value becomes large, moisture tends to be contained and there is a risk of corrosion of the metal.

  Hydrolysis standard test is the resistance to hydrolysis when the grease base oil of the present invention is used in an open system that can come into contact with moisture, such as external water or water in which condensation has occurred. The degree of increase in acid value and hydroxyl value of the grease base oil is preferably 5 mgKOH / g or less, more preferably 3 mgKOH / g, compared to the grease base oil before being subjected to the test. It can be said that it has the outstanding hydrolysis resistance as it is the following.

  The grease base oil of the present invention can be used as a lubricating oil as it is. The physical properties of the grease base oil and the lubricating oil of the present invention reflect the physical properties of the ester of the present invention, and these physical properties are common to each other. In addition, the lubricating oil of the present invention includes antioxidants, extreme pressure agents, rust preventives, antifoaming agents, demulsifiers, and the like that are usually used as lubricating oil additives within the range in which the object of the present invention is not hindered. If desired, it may be prepared by mixing with the ester as desired. The content of the grease base oil of the present invention in the lubricating oil of the present invention is preferably 80 to 100% by mass, more preferably 90 to 100% by mass.

  Examples of the antioxidant include phenols such as 2,6-di-t-butyl-4-methylphenol and 4,4′-methylenebis (2,6-di-t-butyl-4-methylphenol). Antioxidant; p, p′-dioctylphenylamine, monooctyldiphenylamine, phenothiazine, 3,7-dioctylphenothiazine, phenyl-1-naphthylamine, phenyl-2-naphthylamine, alkylphenyl-1-naphthylamine, alkylphenyl-2- Examples thereof include amine-based antioxidants such as naphthylamine; sulfur-based antioxidants such as alkyl disulfide, thiodipropionic acid ester and benzothiazole; zinc dialkyldithiophosphate and zinc diallyldithiophosphate. These antioxidants can be used alone or in admixture of two or more.

  Examples of the extreme pressure agent include zinc dialkyldithiophosphate, zinc diaryldithiophosphate, dialkylpolysulfide, triarylphosphate, and trialkylphosphate. These extreme pressure agents can be used alone or in admixture of two or more.

  Examples of the rust preventive include alkenyl succinic acid, alkenyl succinic acid derivative, sorbitan monooleate, pentaerythritol monooleate, glycerin monooleate, and amine phosphate. These rust inhibitors can be used alone or in admixture of two or more.

  Examples of the antifoaming agent include silicone oils such as dimethylpolysiloxane and organosilicates such as diethyl silicate. These antifoaming agents can be used alone or in admixture of two or more.

  Examples of the demulsifier include polyoxyalkylene glycol, polyoxyalkylene alkyl ether, polyoxyalkylene alkylamide, polyoxyalkylene fatty acid ester, and the like, but are not limited to such examples. These demulsifiers can be used alone or in admixture of two or more.

  When preparing grease using the grease base oil of the present invention, additives such as thickeners, antioxidants, rust inhibitors, extreme pressure agents, oil agents, solid lubricants, etc., are mixed as necessary. do it. Examples of the thickener include soaps such as calcium soap, sodium soap, and lithium soap; complex soaps such as calcium complex soap, aluminum complex soap, and lithium complex soap; terephthalamidate, urea, silica airgel, and the like. It is done.

  Since the grease base oil of the present invention and the lubricating oil containing it have excellent hydrolysis resistance, it can be used for air conditioner fan motor bearings, automobile bearings, acoustic equipment bearings, computer bearings, spindle motor bearings, etc. Even when it is used for an open system that can be contacted, for example, an external water or a component that is used in an environment where water generated by condensation can be mixed in the lubricant, it can be used stably for a long period of time.

Examples 1-3, Comparative Examples 1-4 (However, Examples 2 and 3 are reference examples.)
Esters were synthesized as follows to obtain grease base oils composed of the esters.

  A 2 liter four-necked flask was equipped with a stirrer, thermometer, nitrogen gas blowing tube and cooling tube. Into this flask, 290 g of n-heptanoic acid, 360 g of n-octanoic acid, and 800 g of 2-ethylhexanoic acid were added, and 280 g of pentaerythritol was added thereto. Set to be 1.25 equivalent).

  Next, the reaction was carried out at 230 ° C. for 14 hours while blowing nitrogen gas into the flask, and the distilled water was removed. After completion of the reaction, excess carboxylic acid was removed under reduced pressure of 0.13 kPa, and steaming was performed for 1 hour under reduced pressure of 0.67 kPa. Adsorbent (Kyowa Chemical Industry Co., Ltd., trade name: KYOWARD 500SH) The remaining carboxylic acid was adsorbed in (3), followed by filtration to obtain an ester (Example 1).

  Table 1 shows the carboxylic acid composition in Example 1. The esters of Examples 2 and 3 and Comparative Examples 1 to 4 were prepared in the same manner as the ester of Example 1 using carboxylic acids having the compositions shown in Table 1. In Table 1, iC9 acid represents 3,5,5-trimethylhexanoic acid. Note that Comparative Examples 1 and 2 in Table 1 are equivalent to Production Examples 2 and 3 of JP-A-11-80766.

Next, the volatilization amount, pour point, kinematic viscosity at 40 ° C., viscosity index, acid value, and hydroxyl value of the obtained grease base oil were measured according to the following methods. The results are shown in Table 2.
(1) Volatilization amount: About 20 g of the obtained grease base oil as a sample oil is weighed in a 100 cc glass beaker having a diameter of about 55 mm, heated in a thermostat having an atmospheric temperature of 180 ° C. for 500 hours, and then weighed again. Then, the volatilization amount is obtained from the following formula.

(2) Pour point: The pour point is determined according to JIS K2269.
(3) Kinematic viscosity at 40 ° C .: The kinematic viscosity at 40 ° C. is determined according to JIS K2283.
In addition, the kinematic viscosity at 100 ° C. is also measured.
(4) Viscosity index: after determining the viscosity at 100 ° C. according to JIS K2283,
The viscosity index is determined by K2283.
(5) Acid value: The acid value is determined according to JIS K0070 3.1.
(6) Hydroxyl value: The hydroxyl value is determined according to JIS K0070 7.2.

  The grease base oils of Examples 1 to 3 have excellent volatility of 30% by mass or less, pour point of −45 ° C. or less, and a viscosity index of 110 or more. Therefore, it can be said that it is more suitable than the grease base oils of Comparative Examples 1 to 4 for use in a wide temperature range from low temperature to high temperature.

Test example (hydrolysis standard test)
A hydrolysis standard test was performed on the grease base oils of Examples 1 to 3 and Comparative Examples 1 to 4 as follows. That is, 23 g of grease base oil and 7 g of ion-exchanged water are sealed in a glass tube having an inner diameter of 30 mm and a length of 150 mm, and the previous glass tube is rotated (5 rpm) in a constant temperature bath at 93 ° C. by ASTM D2619 and stirred. However, it was left for 720 hours.

  After the hydrolysis standard test, the acid value and hydroxyl value of the grease base oil in the glass tube were measured, and the changes were examined. The test results are shown in Table 3. The acid value and hydroxyl value were measured according to the above methods.

  The hydrolysis standard test was conducted under severe conditions in which the grease base oil was left in contact with water at 93 ° C. for 720 hours. However, hydrolysis of the grease base oils of Examples 1 to 3 hardly progressed.

  The grease base oils of Examples 1 to 3 can exhibit stable lubricity even when used for a long period of time in a low temperature and / or high temperature open system as a lubricating oil.

  The present invention can be used in a wide temperature range from a low temperature to a high temperature, and in an open system that can come into contact with moisture, for example, external water or an environment in which water generated by condensation can be mixed in a lubricant for a long period of time. Provided are a grease base oil and a lubricating oil containing the grease that exhibit sufficient lubricity even when used.

Claims (5)

A grease base oil containing an ester of pentaerythritol and carboxylic acid, wherein the carboxylic acid contains 2-ethylhexanoic acid, n-heptanoic acid and n-octanoic acid in a total content of 90% by mass or more and, in the carboxylic acid, 2-content of ethylhexanoic acid Ri 55 to 65% by mass, and 15 to 30 mass% content of n- heptanoic acid, and the content of n- octanoic acid Ru 15-30% by mass, the grease base oil. In the carboxylic acid, the content of 2-ethylhexanoic acid is 55% by mass, the content of n-heptanoic acid is 20 % by mass, and the content of n-octanoic acid is 25 % by mass. The grease base oil according to 1.   The grease base oil according to claim 1 or 2, having a pour point of -45 ° C or lower, a volatilization amount of 30% by mass or lower, and a viscosity index of 110 or higher.   The grease base oil according to any one of claims 1 to 3, wherein an acid value and a hydroxyl value after hydrolysis standard test are 10 mgKOH / g or less.   A lubricating oil comprising the grease base oil according to any one of claims 1 to 4.