JP2008297447A - Lubricant and grease base oil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricant having a low clouding point, low viscosity and good low temperature-fluidity, excellent in evaporation properties and well-balanced in performances. <P>SOLUTION: The lubricant is represented by general formula (1), wherein, R<SP>1</SP>is an alkylene group of an odd carbon number selected from 3-11C; R<SP>2</SP>and R<SP>3</SP>are each a 1-15C alkyl group; A<SP>1</SP>and A<SP>2</SP>are each a 2-4C alkylene group; n and m are each a number of 1-2; one of R<SP>2</SP>and A<SP>1</SP>is a branched alkyl group or alkylene group; and one of R<SP>3</SP>and A<SP>2</SP>is a branched alkyl group or alkylene group. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a lubricating oil, in particular, a bearing lubricating oil or a grease base oil, and more particularly relates to a lubricating oil or a grease base oil having good low-temperature stability and excellent lubricity.

  In recent years, with the improvement in performance of precision instruments and the spread of portable use, there is a strong demand for high speed and miniaturization of small spindle motors and the like used in these rotating parts, and therefore, they are used in rotating support parts. There is always a demand for lower torque in bearings. Factors affecting the bearing torque include the bearing clearance and shaft diameter, and the lubricating oil and grease used for them are another major factor.

  These lubricants and grease base oils are required to have properties such as low viscosity for torque reduction and low temperature fluidity improvement for smooth operation at low temperatures. In order to draw out, the molecular weight of the lubricating oil must be reduced. However, when the molecular weight of the lubricating oil is reduced to lower the viscosity or improve the low temperature fluidity, the lubricating oil generally tends to evaporate, and therefore the lubricating oil tends to decrease due to evaporation. When the lubricating oil evaporates, an appropriate oil film pressure cannot be obtained, the rotational accuracy is significantly reduced, and the parts are damaged. In addition, such lubricants and base oils for grease are required to have other properties such as good low-temperature fluidity, high heat resistance, and good lubricity. It is extremely difficult to achieve these required various characteristics at the same time.

  In applications where the basic required characteristics are severe, synthetic lubricants such as synthetic hydrocarbons and organic acid esters capable of molecular design suitable for the purpose are mainly used. Among these synthetic lubricating oils, organic acid esters are widely used because of their good low temperature fluidity, evaporation characteristics, and heat resistance.

  Examples of the organic acid esters include monoesters obtained from the reaction of aliphatic monocarboxylic acids and monohydric alcohols, diesters obtained from the reaction of aliphatic dibasic acids and monohydric alcohols, polyhydric alcohols and aliphatic carboxylic acids, Various esters such as an ester obtained from the reaction of the above and a complex ester obtained from the reaction with a polyhydric alcohol, polybasic acid, or aliphatic monocarboxylic acid are disclosed (for example, see Patent Documents 1 to 5). ).

JP 2002-097482 A JP 2005-154726 A JP 2005-232434 A JP 2005-213377 A JP 2005-232470 A

However, these organic acid esters have poor evaporation characteristics if they have low viscosity or good low temperature fluidity, and poor low temperature fluidity if they have good evaporation characteristics, and if aromatics are used, heat resistance is improved. However, there are problems such as deterioration in low-temperature fluidity and lubricity, and the performance is unbalanced.
Accordingly, the problem to be solved by the present invention is to provide a lubricating oil having a low cloud point, a low viscosity, good low-temperature fluidity, and excellent vaporization characteristics and a well-balanced performance.

  Accordingly, the present inventors have intensively studied, and found an ester compound having excellent performance in a well-balanced manner, particularly as a lubricating oil for bearings or a base oil for grease, leading to the present invention. That is, the present invention provides the following general formula (1)

(R ¹ represents an alkylene group having an odd number of carbon atoms selected from 3 to 11 carbon atoms, R ² and R ³ each represent an alkyl group having 1 to 15 carbon atoms, and A ¹ and A ² represent carbon atoms, respectively. Represents an alkylene group having 2 to 4, n and m each represent a number of ^{1 to 2} , ^one of R ² and A ¹ is a branched alkyl group or alkylene group, and R ³ and A ² Any one of which is a branched alkyl group or an alkylene group).

  The effect of the present invention is to provide a lubricating oil that has a low cloud point, low viscosity, good low-temperature fluidity, and excellent vaporization characteristics and a good balance in performance.

  The lubricating oil of the present invention is a diester compound represented by the above general formula (1). The diester compound may be synthesized by any method as long as it is a known method, but in general, the dicarboxylic acid compound represented by the following general formula (2) and the following general formula (3) And a method of reacting the monoalcohol compound represented by (4).

(R ¹ , R ² , R ³ , A ¹ , A ² , n and m in the general formulas (2), (3) and (4) are the same as those represented by the general formula (1). .)

  Any reaction method may be used as long as it is a known method. For example, the catalyst is used in an amount of 0.1 to 1% by mass with respect to the total mass of the raw acid and alcohol, and the reaction temperature is 130 to 250 ° C. The dehydration reaction may be performed for about 2 to 30 hours. The reaction ratio of the raw material dicarboxylic acid compound to the monoalcohol compound should be such that the total amount of monoalcohol compound is 2 to 2.5 mol, preferably 2 to 2.3 mol, per 1 mol of the dicarboxylic acid compound. That's fine. Note that the compounds of the general formulas (3) and (4) may be the same or different, and the compounding ratio of the compounds of the general formulas (3) and (4) when they are different is not particularly specified.

  Examples of the catalyst include Lewis acids, alkali metals, alkaline earth metals, sulfonic acids and the like. Examples of Lewis acids include aluminum derivatives, tin derivatives, and titanium derivatives. Examples of alkali metals and alkaline earth metals include sodium hydroxide, potassium hydroxide, lithium hydroxide, barium hydroxide, and sodium. Examples of the sulfonic acids include p-toluenesulfonic acid, methanesulfonic acid, and sulfuric acid.

R ^{1 in the} general formula (1) is an alkylene group having an odd number of carbon atoms in the range of 3 to 11, and examples thereof include a pentylene group, a heptylene group, a nonylene group, an undecylene group, and a tridecylene group. It is done. R ¹ is a group derived from the compound of the general formula (2). Examples of the compound of the general formula (2) include glutaric acid (carbon number 3 of R ¹ ), pimelic acid (carbon number 5 of R ¹ ), Examples include azelaic acid (carbon number 7 of R ¹ ), undecanedioic acid (carbon number 9 of R ¹ ), and tridecanedioic acid (carbon number 11 of R ¹ ). Among these compounds, azelaic acid is preferable because a lubricating oil having a good balance can be obtained. When the carbon number of R ¹ is less than 3, the lubricating oil is likely to evaporate, and when the carbon number exceeds 11, the low-temperature fluidity is deteriorated.

Here, the necessity that the alkylene group represented by R ¹ is an odd number will be described. In general, a compound having an alkyl group or alkylene group having an even number of carbon atoms has higher crystallinity than those having an odd number of carbon atoms, and therefore tends to have a high cloud point and poor low-temperature fluidity. In addition, as the molecular weight increases, the cloud point also increases and the low-temperature fluidity deteriorates. The cloud point is a temperature at which a transparent solution becomes cloudy, and usually occurs when fine crystals are formed in the solution. As described in the background art, in order to avoid evaporation of the lubricating oil, it is necessary to increase the molecular weight as much as possible. By increasing the number of carbon atoms of the alkylene group represented by R ¹ , the molecular weight is increased. In addition, it is possible to realize a lubricating oil having a low cloud point and good low-temperature fluidity.

A ¹ and A ² in the above general formulas (1), (3), and (4) are alkylene groups having 2 to 4 carbon atoms. Examples of such alkylene groups include ethylene group, propylene group, and 1-methyl group. Examples thereof include an ethylene group, a 2-methylethylene group, a butylene group, and an isobutylene group. When the number of carbon atoms of A ¹ or A ² is 1 or less or 5 or more, the low temperature fluidity may be deteriorated or the cloud point may be high, and it is also difficult to produce industrially, which is not preferable. Moreover, although n and m are the numbers of 1-2, the number of 1 is more preferable. The n and m alkylene groups may all be the same or a mixture. When n or m is 3 or more, the heat resistance is deteriorated, which is not preferable. When n or m is 0, the low temperature fluidity is deteriorated, the cloud point is increased, or the evaporation characteristic is deteriorated. There is. The preferred forms of A ¹ and A ² vary depending on the forms of R ² and R ^{3 in} the general formulas (1), (3) and (4), and will be described in detail later.

R ² and R ³ in the general formulas (1), (3), and (4) are alkyl groups having 1 to 15 carbon atoms. Examples of such alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, and the like. Straight chain alkyl group: isopropyl group, isobutyl group, tertiary butyl group, isopentyl group, neopentyl group, tertiary pentyl group, 2-ethylhexyl group, isononyl group, isodecyl group, isoundecyl group, isododecyl group, isotridecyl group, isotetradecyl group Examples thereof include branched alkyl groups such as a decyl group and an isopentadecyl group. Among these, a C1-C10 alkyl group is preferable and a C1-C6 alkyl group is more preferable. When the carbon number exceeds 15, the low temperature fluidity may be deteriorated or the cloud point may be increased.

Next, preferred forms of A ¹ , A ² , R ² and R ³ will be described. First, the three physical properties of the lubricating oil, the viscosity, the low temperature fluidity and the cloud point, and the structure of the lubricating oil will be described. In the lubricating oil, these three physical property values are preferably low. If the viscosity is low, there is little loss due to resistance, which is effective in reducing torque, and if the low temperature fluidity is good and the cloud point is low, there are merits such that it can be used even in cold regions and low temperature places. The flowability and cloud point change in the same way depending on the structure of the lubricating oil, and the viscosity changes in the opposite manner. For example, if the alkyl group or alkylene group in the lubricating oil is branched, the low temperature fluidity will be good, and at the same time the cloud point will be low.
When this becomes a straight chain, the fluidity deteriorates and the cloud point also increases. On the other hand, the viscosity increases when the alkyl group or alkylene group in the lubricating oil is branched, and decreases when it is linear. However, even if the pour point is low, the cloud point becomes high if the carbon number of R ¹ is an even number. Thus, although its performance is greatly changed by the structure of each part, A ^{1, A 2,} for the case R ² and R ³ is a group of all linear not improved low temperature properties, either of R ² and A ¹ One of them is a branched alkyl group or an alkylene group, and one of R ³ and A ² needs to be a branched alkyl group or an alkylene group.

However, in order to obtain a better lubricating oil, it is preferable to further limit the structure of the lubricating oil. R ² and R ³ are alkyl groups, which may be straight chain alkyl groups and branched alkyl groups. When R ² and R ³ are linear alkyl groups, A ¹ and A ² are preferably branched alkylene groups such as 1-methylethylene group, 2-methylethylene group and isobutylene group, and have 3 carbon atoms. An alkylene group is more preferred. Also, in the case of ^{R 2} and ^{R 3} is a linear alkyl group, ^{A 1} and ^{A 2} is n or the m-containing polymers in ^(OA _{1) n} and ^(OA _{2) m,} from ^{A 1} and ^{A 2} The branched chain alkylene group is preferably more than 50%, more preferably 80% or more, and most preferably 100%.

Similarly, when R ² and R ³ are branched alkyl groups, A ¹ and A ² are preferably linear alkylene groups such as an ethylene group, a propylene group, and a butylene group, and more preferably an ethylene group. In the case where R ² and R ³ are branched alkyl groups, the polymer contains n or m A ¹ and A ² and (OA ¹ ) _n and (OA ² ) _m are composed of A ¹ and A ^2. The linear alkylene group is preferably more than 50%, more preferably 80% or more, and most preferably 100%.

In the case where R ² and R ³ are different and each is a linear or branched alkyl group, the corresponding preferred structures of A ¹ and A ² are the same as those described above, respectively, but since production is easy, R ² And R ³ preferably have the same structure. Moreover, since lubrication performance is favorable, it is more preferable that R ² and R ³ are linear alkyl groups having the same structure, and A ¹ and A ² are branched alkylene groups. When R ² and R ³ and A ¹ and A ² are both a linear alkyl group and a linear alkylene group, the low-temperature properties such as low-temperature fluidity and cloud point deteriorate, and both are branched alkyl and branched alkylene groups. May increase product viscosity or deteriorate lubricity.
A ¹ and A ² are groups derived from the compounds of the general formulas (3) and (4), and these are usually alcohols such as R ² —OH and R ³ —OH, ethylene oxide, propylene oxide, butylene oxide and the like. It can be obtained by adding an alkylene oxide. Such an addition method of alkylene oxide is, for example, 0.05 to 1.0% by mass of alcohol and alkylene oxide and a catalyst that can be used in the esterification reaction listed above in a closed container such as an autoclave. And may be reacted at a reaction temperature of 80 to 180 ° C. for 1 to 30 hours.

  In order to improve the performance of the lubricating oil of the present invention, the antioxidant, oily agent, antiwear agent, extreme pressure agent, metal deactivator, rust inhibitor, viscosity index improver, pour point depressant, One type or two or more types of additives such as foaming agents can be appropriately blended.

  Antioxidants include phenols such as 2,6-di-tert-butyl-p-cresol and 4,4′-methylenebis-2,6-di-tert-butylphenol, N-phenyl-α-naphthylamine, p , P′-dioctyldiphenylamine and the like, and sulfur compounds such as phenothiazine. These antioxidants are added in an amount of 0.01 to 5% by mass, preferably 0.05 to 3% by mass, based on the lubricating oil.

  Examples of oily agents include aliphatic saturated and unsaturated monocarboxylic acids such as stearic acid and oleic acid, polymerized fatty acids such as dimer acid and hydrogenated dimer acid, hydroxy fatty acids such as ricinoleic acid and 12-hydroxystearic acid, lauryl alcohol, Examples include aliphatic saturated and unsaturated monoalcohols such as oleyl alcohol, aliphatic saturated and unsaturated monoamines such as stearylamine and oleylamine, and aliphatic saturated and unsaturated monocarboxylic amides such as lauric acid amide and oleic acid amide. . These oil-based agents are usually added in an amount of 0.01% to 5% by weight, preferably 0.1% to 3% by weight, based on the lubricating oil.

  Antiwear or extreme pressure agents include tricresyl phosphate, cresyl diphenyl phosphate, alkylphenyl phosphates, phosphate esters such as tributyl phosphate, dibutyl phosphate, tributyl phosphate, dibutyl phosphate, triisopropyl phosphate, etc. Phosphorous esters of these and their amine salts such as phosphorus, sulfurized fats and oils, sulfurized fatty acids such as sulfurized oleic acid, sulfur such as dibenzyl disulfide, sulfurized olefin, dialkyl disulfide, Zn-dialkyldithiophosphate, Zn-dialkyl And organometallic compounds such as dithiocarbamate, Mo-dialkyldithiophosphate, and Mo-dialkyldithiocarbamate. These antiwear or extreme pressure agents are usually added in an amount of 0.01% to 10% by weight, preferably 0.1% to 5% by weight, based on the lubricating oil.

  Examples of the metal deactivator include benzotriazole-based, thiadiazole-based, and gallic acid ester-based compounds. These metal deactivators are usually added in an amount of 0.005 to 0.4 mass%, preferably 0.01 to 0.2 mass%, based on the lubricating oil.

  Examples of rust preventives include alkyl or alkenyl succinic acid derivatives such as dodecenyl succinic acid half ester, octadecenyl succinic anhydride, dodecenyl succinic acid amide, sorbitan monooleate, glycerin monooleate, pentaerythritol monooleate and many others. Monohydric alcohol partial ester, Ca-petroleum sulfonate, Ca-alkyl benzene sulfonate, Ba-alkyl benzene sulfonate, Mg-alkyl benzene sulfonate, Na-alkyl benzene sulfonate, Zn-alkyl benzene sulfonate, Ca-alkyl naphthalene sulfate Examples thereof include metal sulfonates such as phonates, amines such as rosin amine and N-oleyl sarcosine, and dialkyl phosphite amine salts. These rust inhibitors are usually added in an amount of 0.01 to 5% by mass, preferably 0.05 to 2% by mass, based on the lubricating oil.

  Examples of the viscosity index improver include olefin copolymers such as polyalkyl methacrylate, polyalkyl styrene, polybutene, ethylene-propylene copolymer, styrene-diene copolymer, and styrene-maleic anhydride ester copolymer. These viscosity index improvers are usually added in an amount of 0.1 to 15% by mass, preferably 0.5 to 7% by mass, based on the lubricating oil.

  Examples of the pour point depressant include condensates of chlorinated paraffin and alkylnaphthalene, condensates of chlorinated paraffin and phenol, polyalkyl methacrylate, polyalkylstyrene, polybutene and the like as the above viscosity index improvers. These pour point depressants are usually added in an amount of 0.01 to 5% by mass, preferably 0.1 to 3% by mass, based on the lubricating oil.

  A liquid silicone is mentioned as an antifoamer, and it is good to add 0.0005-0.01 mass% normally with respect to lubricating oil.

  The lubricating oil of the present invention is, for example, engine oil, gear oil, turbine oil, hydraulic oil, flame retardant hydraulic fluid, refrigeration oil, compressor oil, vacuum pump oil, bearing oil, insulating oil, sliding surface oil, rock drill It can be used for oil, metal working oil, plastic working oil, heat treated oil, grease base oil, etc., but it has good lubricity and low temperature fluidity, low cloud point, low viscosity and low volatility. Because it is a compound, it is preferably used for bearing oils and grease base oils that require stability, more preferably used for bearing oils and grease base oils for precision equipment, and it can be rotated in a small size such as a hard disk. It is most preferable to use as bearing oil or grease base oil that requires accuracy.

  Examples of thickeners that are essential components of grease include soap-based or complex soap-based thickeners, organic non-soap thickeners, and inorganic non-soap thickeners. Examples of soap thickeners include higher grades such as lauric acid, myristic acid, palmitic acid, stearic acid, 12-hydroxystearic acid, arachidic acid, behenic acid, zomarinic acid, oleic acid, linoleic acid, linolenic acid, and ricinoleic acid. Acetic acid, benzoic acid, sebacic acid, azelaic acid, phosphoric acid, boric acid, etc. are further reacted with soaps in which fatty acids are reacted with bases such as aluminum, barium, calcium, lithium, sodium, potassium, and the above fatty acids and bases. And complex soap thickeners.

  Examples of the organic non-soap thickener include terephthalate thickener, urea thickener, polytetrafluoroethylene, fluorinated ethylene-propylene copolymer, and other fluorine-based thickeners. A thickener is preferred. Examples of the urea thickener include a monourea compound obtained by reacting monoisocyanate and monoamine, a diurea compound obtained by reacting diisocyanate and monoamine, a urea urethane compound obtained by reacting diisocyanate, monoamine and monool, and diisocyanate and diamine. Examples include tetraurea compounds obtained by reacting monoisocyanate.

  Examples of the inorganic non-soap thickener include montmorillonite, bentonite, silica airgel, boron nitride and the like.

  Hereinafter, the present invention will be specifically described by way of examples. In the following examples and the like,% and ppm are based on mass unless otherwise specified.

Test oils (Examples 1 to 7, Comparative Examples 1 to 9) used for the tests were synthesized as follows.
<Example 1>
A 1000 ml flask equipped with a nitrogen inlet tube, a reflux tube, a stirrer and a thermometer was charged with 188 g (1 mol) of azelaic acid, 264 g (2 mol) of 1,2-propylene glycol mono-n-butyl ether and methanesulfonic acid 0 as a catalyst. After adding 4 g, the temperature was raised to 180 ° C., and the pressure was gradually reduced to 10 kPa while removing water produced by the reaction. After reaching 10 kPa, the reaction was carried out at the same temperature for 5 hours, and after confirming that the acid value was 0.1 mgKOH / g, the reaction was terminated. Thereafter, 4 g of KYOWARD 500 (manufactured by Kyowa Chemical Co., Ltd.) was added to the system to remove the catalyst, and the mixture was stirred at 100 ° C. for 1 hour, followed by filtration to obtain Example 1.

<Examples 2-7 and Comparative Examples 1-5>
In the same manner as in Example 1, 1 mol of dicarboxylic acid shown in Table 1 was reacted with 2 mol of monoalcohol. The composition of each example is shown in Table 2.

The following test was done about Examples 1-7 and Comparative Examples 1-5. The test results are shown in Table 3.
<Test method>
(1) Kinematic viscosity The test oil was put into a Canon Feske viscometer, allowed to stand in a constant temperature bath at 40 ° C for 30 minutes, and the viscosity at 40 ° C was measured.
(2) Pour point After heating the test oil to 45 ° C, the test oil was put into a test tube, and the test tube was gradually cooled without stirring. The test tube was tilted every 5 ° C. to confirm the fluidity of the test oil, and the lowest temperature at which the test oil flows was taken as the pour point.
(3) Cloud point By the same test method as the above pour point, the test tube was confirmed every 2.5 ° C., and the temperature at which the test oil at the bottom of the test tube became hazy or began to cloud was defined as the cloud point.
(4) Evaporation characteristics Test oil when the temperature is increased to 50 to 120 ° C. at a temperature increase rate of 1 ° C./min using a differential thermal analyzer (DTG-60A, manufactured by Shimadzu Corporation) and reaches 120 ° C. The evaporation loss was measured. The more evaporation loss, the worse the heat resistance.
(5) Lubricity The lubricity was evaluated using an SRV tester. The evaluation conditions are the point contact condition of the ball-on-plate, the upper cylinder (φ15 × 22 mm) is set on the plate (φ24 × 7.85 mm), reciprocally vibrated under the following conditions, and the friction coefficient after 3-15 minutes. The average was taken as the measured value. Both materials were SUJ-2.
Load: 200 N, temperature: 80 ° C., measurement time: 15 minutes, amplitude: 1 mm, cycle: 50 Hz

  From the above results, it can be seen that the present invention is a lubricating oil having a low cloud point, low viscosity, good low-temperature fluidity, and excellent vaporization characteristics and a well-balanced performance.

Claims (5)

The following general formula (1)

(R ¹ represents an alkylene group having an odd number of carbon atoms selected from 3 to 11 carbon atoms, R ² and R ³ each represent an alkyl group having 1 to 15 carbon atoms, and A ¹ and A ² represent carbon atoms, respectively. Represents an alkylene group having 2 to 4, n and m each represent a number of ^{1 to 2} , ^one of R ² and A ¹ is a branched alkyl group or alkylene group, and R ³ and A ² Any one of them is a branched alkyl group or an alkylene group.)
A lubricating oil characterized by the following: The lubricating oil according to claim 1, wherein R ² and R ³ are linear alkyl groups, and A ¹ and A ² are branched alkylene groups having 3 carbon atoms. The lubricating oil according to claim 1, wherein R ² and R ³ are branched alkyl groups, and A ¹ and A ² are linear alkylene groups having 2 carbon atoms.   The lubricating oil according to any one of claims 1 to 3, wherein the lubricating oil is a bearing lubricating oil.   The lubricating oil according to any one of claims 1 to 3, wherein the lubricating oil is a base oil for grease.