JP5693240B2 - Lubricating oil composition - Google Patents

Description

  The present invention relates to a lubricating oil composition, in particular, a lubricating oil composition used as a lubricating oil for internal combustion engines, a drive system lubricating oil or a working oil.

In recent years, various fields have been required to cope with environmental load reduction. In particular, the reduction of carbon dioxide is an urgent issue, and energy saving has been achieved in various domestic industrial fields, transportation fields including automobiles, and general consumer life.
For example, in automobiles, in order to improve fuel efficiency and suppress CO ₂ emissions, the engine engine efficiency is improved by adopting lean burn and direct injection technologies in gasoline engines. In order to reduce this, use of a low-friction material for sliding parts, fuel-saving internal combustion engine lubricants, and drive system lubricants are being adopted. By the way, the engine is equipped with a three-way catalyst for purifying the exhaust gas, and this three-way catalyst is poisoned by phosphorus, and the purification rate of exhaust gas decreases with use. There has been a demand for reduction of phosphorus content. However, since the decrease in the phosphorus content in the lubricating oil has a problem of causing a decrease in wear resistance and seizure, the present applicant has a lubricating oil for internal combustion engines in which dimer acid diamide and molybdenum dithiocarbamate (MoDTC) are blended. (Patent Document 1).

Also, in industrial equipment machines, the pressure energy of hydraulic pumps is converted into kinetic energy (work energy) for systems that require large work energy such as injection molding machines, machine tools, press machines, and forging press machines. The hydraulic system that can be used is widely used. Even in this hydraulic system, energy saving needs are increasing, and energy saving measures are also required for hydraulic fluid that is the pressure medium of the hydraulic system, and low viscosity and high viscosity index are being achieved. As a result of lowering the viscosity, there has been a problem of reduced wear resistance and seizure of the sliding portion.
In recent years, a load on a sliding portion has increased due to downsizing, speeding up, and fuel and energy savings of a mechanical system, and a lubricating oil that is more excellent in lubricity such as wear resistance has been demanded.

The ideal characteristic of the lubricating oil is that there is little friction loss at high speeds and low speeds, and there is little wear such as fretting wear. That is, the lubricating oil is required to reduce friction loss and reduce wear. Therefore, it is desired that the friction loss is small and the wear is small even when the contact surface speed is high, such as when rotating at high speed, or when high torque is applied at low speed.
To reduce the friction loss at high speed, it is necessary to reduce the viscosity of the lubricating base oil itself. However, when the viscosity of the base oil is lowered, it becomes weak against wear such as fretting, that is, contact between base materials such as sliding metals may occur and wear or seizure may occur.

JP 2008-37894 A

The inventors of the present invention have made extensive studies in order to achieve such problems, and as a result, 3,4,5-trihydroxybenzoic acid ester is
(1) having a function of reducing friction coefficient and suppressing wear;
(2) Because hematite, which is iron red rust, is reduced to hard and strong black rust (magnetite), it has a high anti-rust effect.
(3) The 3,4,5-trihydroxybenzoic acid compound itself has low solubility in mineral-based lubricating base oils, so it does not exhibit the above effect as it is, but it can exhibit its effect when used with a cleaning dispersant. ,
As a result, they have come up with the present invention.
The present invention solves various problems in the sliding part that is more severe by the above-mentioned miniaturization, high speed, fuel saving and energy saving, and the problem to be solved by the present invention is to greatly reduce wear. And providing a lubricating oil composition having a low friction coefficient and having high rust prevention properties in lubrication of iron-based sliding parts.

That is, the present invention is as follows.
(1) 3,4,5-trihydroxybenzoic acid ester in the lubricating base oil, 0.01 to 10% by mass on the basis of the total amount of the lubricating oil composition, and the detergent dispersant on the basis of the total amount of the lubricating oil composition A lubricating oil composition characterized by adding 0.1 to 20% by mass.
(2) 3,4,5-trihydroxy synthesized from 3,4,5-trihydroxybenzoic acid ester with 3,4,5-trihydroxybenzoic acid and a linear or branched alcohol having 3 to 12 carbon atoms The lubricating oil composition according to the above (1), which is an alkyl benzoate.
(3) The lubricant composition according to the above (1) or (2), wherein the lubricating base oil has a kinematic viscosity at 40 ° C. of 5 to 1000 mm ² / s.
(4) A lubricating oil for an internal combustion engine, a drive system lubricating oil or a hydraulic oil comprising the lubricating oil composition according to the above (1) to (3).

  The lubricating oil composition of the present invention includes a lubricant base oil containing an ester of 3,4,5-trihydroxybenzoic acid and a detergent / dispersant, thereby significantly reducing wear and having a low coefficient of friction and stability. In addition, the iron-based sliding portion has a high antirust effect. Therefore, the lubricating oil composition of the present invention is suitable for long-term use and has a remarkable effect on energy saving due to the low and stable characteristic of the friction coefficient.

  The lubricating oil composition of the present invention comprises a lubricating base oil containing 0.01 to 10% by mass of 3,4,5-trihydroxybenzoic acid ester and 0.1 to 20% by mass of a detergent dispersant. is there. Since 3,4,5-trihydroxybenzoic acid ester has low solubility in hydrocarbon base oils other than mineral base oils and base oils having polar groups such as esters and ethers, it itself has lubricating properties. Although it cannot be added to such a concentration that the improvement can be exerted, it can be used at a concentration at which the lubricity is improved by using it together with a cleaning dispersant.

[Lubricant base oil]
In the present invention, as the lubricating base oil, a lubricating base oil such as mineral oil, synthetic oil, animal or vegetable oil can be used. Further, two or more of these lubricating base oils can be mixed and used.
The physical properties of the lubricating base oil used in the present invention are not particularly limited, but those having a kinematic viscosity of 5 to 1000 mm ² / s at 40 ° C. are preferable, and energy saving can be achieved by lowering the viscosity. ˜500 mm ² / s, more preferably 5 to 100 mm ² / s. However, it is preferable to use a high viscosity base oil for high load applications.
The viscosity index is preferably 90 or more, more preferably 100 to 250. Moreover, the pour point which is a low temperature characteristic is preferably −10 ° C. or lower, more preferably −15 ° C. or lower. Furthermore, from the viewpoint of safety, the flash point is preferably 70 ° C. or higher, and more preferably 150 ° C. or higher.
In addition, it is preferable to mix | blend 70-99 mass% of this lubricating base oil based on the total amount of the lubricating oil composition, and more preferably 80-98 mass%.

  Mineral oil-based lubricating base oils include hydrocracking, solvent extraction, hydrorefining, and solvent removal of lubricating oil fractions obtained by atmospheric distillation of crude oil or vacuum distillation of atmospheric distillation residues. A refined lubricating base oil obtained by appropriately combining lubricating oil refining means such as wax, hydrodewaxing, and clay treatment can be suitably used. Mineral-based lubricating base oils made from such a relatively high boiling fraction of petroleum are generally inexpensive and are widely used in various lubricating oils and greases. Therefore, in this invention, it is economical and preferable to use this mineral oil base oil alone.

  Synthetic oil-based lubricating base oils include poly-α-olefin (PAO), alkylbenzene, alkylnaphthalene, ester, ether, glycol, silicone oil, fluorinated oil, and the like. Of these, PAO and esters are preferably used. PAO is chemically inert, has excellent viscosity characteristics, and is commercially available with a wide range of viscosities.

  Esters are also commercially available as compounds having various molecular structures, each having unique characteristics and having a high flash point as compared with hydrocarbon base oils having the same viscosity. The ester can be obtained by a dehydration condensation polymerization reaction between an alcohol and a fatty acid. In the present invention, however, in terms of chemical stability, a diester of a dibasic acid and a monohydric alcohol, or a polyol of a polyol and a monohydric fatty acid. Esters are suitable as lubricating base oils.

  Animal and vegetable oil-based lubricating base oils include milk fat, beef tallow, lard (pig tallow), sheep fat, beef leg oil, whale oil coconut oil, bonito oil, herring oil, coconut oil, and soybean oil, rapeseed oil, Sunflower oil, safflower oil, peanut oil, corn oil, cottonseed oil, rice bran oil, kapok oil, sesame oil, olive oil, linseed oil, castor oil, cacao butter, sha fat, palm oil, palm kernel oil, coconut oil, hemp seed oil, Rice oil and tea seed oil are preferred, but not limited thereto.

Usually, these base oils such as mineral oils, synthetic oils and animal and vegetable oils can be appropriately combined and blended at an appropriate ratio so as to satisfy various performances required for each application. At this time, a plurality of lubricating base oils of mineral oil type, synthetic oil type and animal and vegetable oil type may be used.
In addition, since 3,4,5-trihydroxybenzoic acid ester has high solubility in lubricating base oils having polar groups such as synthetic esters, ethers, or animal and plant systems, when these base oils are used, The amount of the cleaning dispersant added can be reduced. However, the lubricating base oils having these polar groups generally have low hydrolysis resistance, and from the economical aspect, the lubricating base oils having polar groups with respect to 100 parts by weight of the mineral-based lubricating base oil The mixing ratio of is preferably 50 parts by mass or less, more preferably 5 to 30 parts by mass, based on the lubricating base oil.

[3,4,5-trihydroxybenzoic acid ester]
In the present invention, 3,4,5-trihydroxybenzoic acid ester is added, and the ester is synthesized with 3,4,5-trihydroxybenzoic acid and a linear or branched alcohol having 3 to 12 carbon atoms. The 3,4,5-trihydroxybenzoic acid alkyl esters are preferred. Among the alkyl esters of 3,4,5-trihydroxybenzoic acid, propyl ester, butyl ester, hexyl ester, octyl ester, decyl ester and dodecyl ester are preferable, and propyl ester of 3,4,5-trihydroxybenzoic acid is particularly preferable. 3,4,5-Trihydroxybenzoic acid octyl ester is preferred from the standpoint of the balance between solubility in base oil and improvement in lubricity. The alkyl group may be linear or branched.
The 3,4,5-trihydroxybenzoic acid ester is added in an amount of 0.01 to 10% by mass, preferably 0.1 to 5% by mass based on the total amount of the lubricating oil composition. If the amount is less than 0.01% by mass, the reduction in wear, the reduction in the friction coefficient, and the rust prevention effect cannot be sufficiently achieved. Can not be expected, it is not economical.

[Cleaning dispersant]
Examples of the detergent dispersant include metal detergents such as alkaline earth metal sulfonates, alkaline earth metal phenates, and alkaline earth metal salicylates, or polyalkenyl succinimides, polyalkenyl succinates and their respective boric acid modifications. And phosphonate types, or ashless dispersants such as benzylamines, boron-containing benzylamines, monovalent or divalent carboxylic acid amides represented by fatty acids or succinic acid are suitable.
Alkaline earth metal sulfonate is an alkaline earth metal salt of a product obtained by sulfonating an alkyl aromatic compound using fuming sulfuric acid or sulfuric acid, alkaline earth metal phenate is an alkylphenol sulfide or alkylphenol sulfide and formaldehyde. The alkaline earth metal salt of the Mannich reaction product of alkylphenol obtained by the reaction, and the alkaline earth metal salicylate are alkaline earth metal salts of alkylsalicylic acid. Examples of the alkaline earth metal that forms a salt include calcium, barium, and magnesium, with calcium being particularly preferred. In addition, there is not only a neutral salt but also an overbased metal salt to which an alkaline earth metal salt is further added, either of which may be used.
As the polyalkenyl succinimide, an ashless detergent obtained by reaction of polybutenyl succinate polyamine by maleating a polybutene having a molecular weight of 1,000 to several thousand is particularly suitable.

Although it is difficult to accurately consider the action of the detergent and dispersant, in the case of the present invention, 3,4,5-trihydroxybenzoic acid ester having low solubility in hydrocarbon oil is dissolved in the base oil. , Presumed to play a role of dispersion.
The detergent-dispersant is added in an amount of 0.1 to 20% by mass based on the total amount of the lubricating oil composition, and particularly preferably 1 to 10% by mass. If the amount is less than 0.1% by mass, the effect cannot be sufficiently exerted, and even if it is added in excess of 20% by mass, the effect cannot be expected for an increase in the amount added, and this is not economical.

[Other additives]
In the lubricating oil composition of the present invention, friction modifiers, antiwear agents, extreme pressure agents, antioxidants, which are conventionally used in lubricating oils and greases, etc., as long as the object of the present invention is not impaired. Additives such as rust inhibitors, metal deactivators, and antifoaming agents can be added to further improve performance.
As friction modifiers, molybdenum dithiocarbamate and molybdenum dithiophosphate, which are organic molybdenum compounds, aliphatic amines, aliphatic amides, aliphatic imides and alcohols, nitrogen compounds, esters, phosphate ester amine salts, phosphite amines Deactivate metals, such as salts, phosphate esters and zinc dialkyldithiophosphates as antiwear agents, sulfurized olefins and sulfurized fats and oils as extreme pressure agents, amine and phenolic antioxidants as antioxidants Examples of the agent include benzotriazole, examples of the rust inhibitor include alkenyl succinic acid ester and partial ester, and examples of the antifoaming agent include a silicone compound and an ester-based antifoaming agent.
As the use of the lubricating oil composition of the present invention, a lubricating oil for an internal combustion engine, a drive system lubricating oil, and a working oil are suitable.

    EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example and a comparative example, this invention is not limited to this example.

(Preparation of lubricating oil composition)
Using the following 3,4,5-trihydroxybenzoate ester, lubricating base oil, detergent dispersant, and other additives, the blending ratio shown in Table 1 (addition amount is mass% based on the total amount of the composition) The lubricating oil compositions of Examples and Comparative Examples were prepared. The properties of the base oil and the lubricating oils of Examples and Comparative Examples were measured by the methods specified in JIS K2283, the pour point was JIS K2269, and the flash point was JIS K2265-4.

(A) 3,4,5-trihydroxybenzoic acid ester (A1) 3,4,5-trihydroxybenzoic acid propyl (n-propyl) ester [manufactured by Iwate Chemical Co., Ltd.]
(A2) 3,4,5-Trihydroxybenzoic acid octyl (n-octyl) ester [Wako Pure Chemical Industries, Ltd.]

(B) Lubricating base oil (B1) Paraffinic mineral oil (40 ° C. kinematic viscosity: 32 mm ² / s, viscosity index: 106, pour point: −15 ° C., flash point: 230 ° C.)
(B2) Polyol ester oil (40 ° C. kinematic viscosity: 10 mm ² / s, viscosity index: 95, pour point: −50 ° C., flash point: 190 ° C.)
(B3) Polyalphaolefin (PAO, 40 ° C. kinematic viscosity: 400 mm ² / s, viscosity index: 150, pour point: −35 ° C., flash point: 280 ° C.)

(C) detergent dispersant (C1) neutral calcium sulfonate (C2) polybutenyl succinimide (D) other additives (D1) antioxidant: di-t.-butyl-p.-cresol ( DBPC)
(D2) Antiwear agent: tricresyl phosphate (TCP)
(D3) Friction modifier: Molybdenum dithiocarbamate (MoDTC)

Thus, about the obtained lubricant composition of Examples 1-7 and Comparative Examples 1-4, the external appearance and lubrication performance (friction coefficient, wear depth) as a general lubricant composition were evaluated.
[Measurement and evaluation method]
The measurement and evaluation were performed by the following method.
〔appearance〕
After blending at the blending ratio shown in Table 1 and cooling to room temperature, the finished composition was visually observed. The case where a precipitate or a precipitate was generated was rejected, and the case where a uniform liquid was obtained was determined as acceptable.
[Abrasion resistance test]
The wear resistance of the lubricating oil compositions of Examples 1 to 7 and Comparative Examples 1 to 4 was measured using a ball / disk type reciprocating friction tester.
The test conditions were such that the oil film was not easily formed and the sliding speed was low (1 cm / s), high load (2200 gf), the amplitude was 20 mm, and the test was started at room temperature, so that the strict lubrication conditions were achieved. Friction was performed. Ball and disk test pieces were made of bearing carbon steel (SUJ-2). The friction coefficient after 2 hours and the disc wear depth after the test were measured with a stylus type surface roughness meter.

Next, the characteristics as a lubricating oil for internal combustion engines, a drive system lubricating oil, and a working oil were evaluated using the lubricating oil compositions of Examples 1 to 7, and compared with Comparative Examples 1 to 4.
[Evaluation as lubricating oil for internal combustion engines]
For evaluation as a lubricating oil for an internal combustion engine, a cylinder / disk type SRV friction tester was used, the temperature was set at a high temperature of 100 ° C., and the disk wear scar diameter and the friction coefficient were measured.
The conditions were load: 200 N, frequency: 300 Hz, amplitude: 1.0 mm, test time: 1 hour, the disc was subjected to reciprocating friction with the cylinder, and the wear scar diameter generated on the disc was measured with a microscope. The coefficient of friction was measured with a strain gauge provided in advance in the friction tester.

[Evaluation as driveline lubricant]
Evaluation as a drive system lubricant was performed by the FZG pitching test. The test was conducted in accordance with DIN 51354, using a TYPE PT-C gear, with a load of 9 stages, an oil temperature of 120 ° C., and a rotational speed of 1440 times / minute. The fatigue life determination method was performed by stopping the test apparatus, periodically observing the tooth surface, and setting the time (hr) when 1 mm ² pitching occurred. The observation interval was every 8 hours for the first 24 hours and every 2 to 4 hours thereafter.

[Evaluation as hydraulic oil]
The hydraulic oil was evaluated by a high pressure vane pump test. The test conforms to ASTM D2882 and circulates 56.8 liters of oil in the pump tester, pressure: 140 kg / cm ² , pump speed: 1200 rpm, inlet oil temperature: 65.5 ° C., after 100 hours of test time The total weight loss of vanes and cam rings was measured and used as the amount of wear.
The obtained measurement and evaluation results are summarized in Table 1.

The lubricating oil compositions of Examples 1 to 7 all became uniform liquids. The friction coefficient in the friction test of these examples is 0.05 to 0.07, and is low and stable. Further, the disc wear depth after the friction test is 0.04 to 0.06 μm, which is a level with almost no wear.
In contrast, in Comparative Example 1 in which propyl 3,4,5-trihydroxybenzoate was added, but no detergent dispersant was blended, the composition was turbid and propyl 3,4,5-trihydroxybenzoate was It can be seen that they are not uniformly dissolved or dispersed. For this reason, the friction coefficient is high and the disk wear depth is also large. In Comparative Examples 2 to 4, in which 3,4,5-trihydroxybenzoic acid ester is not added, the friction coefficient is high and the wear depth is much larger than in the examples.
Thus, the lubricity of the lubricating oil composition can be significantly improved by blending the lubricating base oil with 3,4,5-trihydroxybenzoic acid ester and a detergent dispersant.
Moreover, it turns out that the lubricating oil composition of Examples 1-7 is excellent in the characteristic as a lubricating oil for internal combustion engines, a drive system lubricating oil, and a working oil.

  The lubricating oil composition of the present invention has a characteristic that the wear is remarkably reduced and the coefficient of friction is low and stable, and has a high antirust effect in the iron-based sliding part, so that sliding of various machines and devices is possible. It is useful as a lubricating oil for some parts, particularly as a lubricating oil for internal combustion engines, a drive system lubricating oil or a working oil.

Claims (6)

Made of mineral oil or poly-α-olefin , 3,4,5-trihydroxybenzoic acid ester is added to 80 to 98% by mass of lubricating base oil based on the total amount of lubricating oil composition, based on the total amount of lubricating oil composition 0.1 to 5 % by weight , and at least one metal-based detergent selected from the group of alkaline earth metal sulfonates, alkaline earth metal phenates, and alkaline earth metal salicylates, or polyalkenyl succinimides and polyalkenyl succinic acids 1 to 10 % by mass of a detergent dispersant comprising at least one ashless dispersant selected from the group of esters and respective boric acid modified products based on the total amount of the lubricant composition, Composition. The lubricating oil composition according to claim 1, wherein the detergent dispersant is a metal detergent composed of alkaline earth metal sulfonate or an ashless dispersant composed of polyalkenyl succinimide. 3,4,5-Trihydroxybenzoic acid ester is synthesized with 3,4,5-trihydroxybenzoic acid and C3-C12 linear or branched alcohol alkyl 3,4,5-trihydroxybenzoic acid the lubricating oil composition according to claim 1 or 2 is an ester. The lubricant composition according to any one of claims 1 to 3, wherein the lubricating base oil has a kinematic viscosity at 40 ° C of 5 to 1000 mm ² / s. A lubricating oil for an internal combustion engine, a drive system lubricating oil or a hydraulic oil comprising the lubricating oil composition according to any one of claims 1 to 4 . The lubrication method of the iron-type sliding part using the lubricating oil composition of any one of Claims 1-5.