JP2008255271A - Lubricating oil composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricating oil composition having excellent load-bearing properties. <P>SOLUTION: A lubricating oil composition is prepared by formulating a solid lubricant in a proportion of 0.1-5 wt.%, based on the composition, with a base oil comprising a synthetic oil, preferably at least one kind of a synthetic hydrocarbon oil, an ester-based synthetic oil and a glycol oil. The lubricating oil composition exhibits excellent load-bearing properties by the incorporation of PTFE or the like conventionally used as a solid lubricant in a lubricant such as grease to a lubricating oil. The resultant lubricating oil composition can effectively be used for various kinds of devices requiring the load-bearing properties such as a bearing, a bushing, a chain and a gear. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a lubricating oil composition. More specifically, the present invention relates to a lubricating oil composition having excellent load resistance.

  Conventionally, lubricating oils used for sliding parts have been required to have good friction and wear characteristics. In general, oil-based agents, antiwear agents, and extreme pressure agents are used alone to meet these requirements. Alternatively, a plurality of blends are performed. These lubricating oil compositions are used for sliding parts between metal-metal, metal-resin, and resin-resin, and can smoothly run without problems such as seizure and torque increase during sliding such as rotation, reciprocation, and swing. On the other hand, there are many adverse effects such as metal corrosion, sludge generation, resin cracking and cracking on sliding members such as metal and resin. There's a problem.

  On the other hand, in lubricants such as grease, it is possible to use, for example, polytetrafluoroethylene resin (PTFE) as a solid lubricant that is chemically relatively stable and exhibits friction characteristics and extreme pressure performance due to a layered structure. Has been done. This PTFE has the characteristic that there is no worry of attacking metals or resins.

On the other hand, with regard to bearings, bushes, chains, and gears, with the recent increase in output and efficiency of machinery, load resistance is increasingly required. For example, automatic transmissions, shock absorbers, etc. In drive system equipment that requires load resistance such as power steering, a lubricating oil containing a sulfur-based additive has been proposed to facilitate its operation.
JP 2006-045335 A

  However, such a lubricating oil composition requires an additive mainly composed of a specific disulfide compound and lacks versatility.

  An object of the present invention is to provide a lubricating oil composition having excellent load resistance.

  The object of the present invention is to blend a solid lubricant in a composition at a ratio of 0.1 to 5% by weight in a synthetic oil, preferably a base oil consisting of at least one of a synthetic hydrocarbon oil, an ester-based synthetic oil and a glycol oil. This is achieved by a lubricating oil composition.

  The present inventors have found that a lubricating oil composition in which PTFE or the like used as a solid lubricant in the lubricating composition is added to the lubricating oil has excellent load resistance, and has led to the present invention. .

  The lubricating oil composition of the present invention exhibits excellent load resistance by adding PTFE or the like, which has been conventionally used as a solid lubricant to a lubricant such as grease, to the lubricating oil. Therefore, it is effectively used for various devices that require load resistance such as bearings, bushes, chains, or gears.

  As the synthetic oil, at least one of a synthetic hydrocarbon oil, an ester synthetic oil and a glycol oil is used, and a mixed oil of these is preferably used. Synthetic hydrocarbon oils include poly α-olefins, ethylene-α-olefin co-oligomers, polybutenes or their hydrides, alkylbenzenes, alkyl naphthalenes, etc., and ester-based synthetic oils include polyol esters, dibasic fatty acid esters, Aromatic polyvalent carboxylic acid ester, phosphoric acid ester, phosphorous acid ester, carbonic acid ester, etc., and examples of glycol oil are polyoxypropylene glycol monoether, poly (oxyethylene-oxypropylene) glycol monoether, etc. Is done. When two or more kinds of base oils are used in combination, the ester synthetic oil is preferably used in a proportion of about 60 to 95% by weight.

These base oils generally have a kinematic viscosity at 40 ° C. (based on JIS K2283) of about 20 to 800 mm ² / sec. Of these, for bearings and bushes, those of about 20 to 250 mm ² / sec, preferably about 20 to 100 mm ² / sec are used, and chain oil, gear oil, etc. do not require low temperature properties, In applications in which heat resistance is important, a material having a temperature of about 100 to 800 mm ² / second, preferably about 100 to 400 mm ² / second is used. Here, if a base oil with a kinematic viscosity higher than this is used for bearings and bushes, the low temperature fluidity deteriorates and the torque increases in the low temperature range, while a base oil with a kinematic viscosity lower than this is used. If used, it is not sufficient in terms of volatility, and a sufficient oil film cannot be maintained under high temperature conditions. Also, for chains and gears that do not require very low temperature and use heat resistance, using a base oil with a kinematic viscosity higher than this is satisfactory in terms of heat resistance, but a wide range From the standpoint of obtaining good sliding characteristics within the operating temperature range, if a base oil having a kinematic viscosity lower than this is used, heat resistance cannot be sufficiently satisfied.

  Polytetrafluoroethylene resin (PTFE), graphite, molybdenum disulfide, melamine cyanurate (MCA), preferably PTFE is added to the base oil. These solid lubricants are used in such a proportion that they occupy 0.1 to 5% by weight, preferably 0.3 to 3% by weight in the composition. When the solid lubricant is used at a ratio below this, the load bearing effect due to the solid lubricant is not sufficiently exhibited, whereas when used at a ratio above this, the viscosity of the lubricating oil composition becomes too high, Liquidity will be lost.

  PTFE produces polytetrafluoroethylene by methods such as emulsion polymerization, suspension polymerization, and solution polymerization of tetrafluoroethylene, and it is processed by methods such as thermal decomposition, electron beam irradiation decomposition, physical grinding, and the number average. A molecular weight Mn of about 1000 to 100000, preferably about 100000 to 200,000 is used. The molecular weight can also be controlled by using a chain transfer agent during the copolymerization reaction. The powdery fluororesin used generally has an average primary particle size of about 500 μm or less, preferably about 0.1 to 30 μm.

  In the composition, other additives such as antioxidants, rust inhibitors, corrosion inhibitors, extreme pressure agents, oiliness agents, viscosity index improvers, etc., which have been added to the lubricating oil in advance, are added to the lubricating oil in the past. These additives can be added as necessary to form a lubricant.

  Examples of the antioxidant include phenolic antioxidants such as 2,6-ditertiarybutyl-4-methylphenol and 4,4′-methylenebis (2,6-ditertiarybutylphenol), alkyldiphenylamine, Examples include amine-based antioxidants such as phenylamine, phenyl-α-naphthylamine, phenothiazine, alkylated phenyl-α-naphthylamine, phenothiazine, and alkylated phenothiazine, and phosphoric acid-based antioxidants and sulfur-based antioxidants. It is done.

  Examples of the rust preventive agent include fatty acids, fatty acid amines, alkyl sulfonic acid metal salts, alkyl sulfonic acid amine salts, oxidized paraffins, polyoxyethylene alkyl ethers, and the like, and corrosion inhibitors include, for example, benzotriazole and benzimidazole. , Thiadiazole and the like.

  Examples of extreme pressure agents include phosphorous compounds such as phosphate esters, phosphite esters, and phosphate ester amine salts, sulfur compounds such as sulfides and disulfides, dialkyldithiophosphate metal salts, and dialkyldithiocarbamic acid metal salts. And sulfur-based compound metal salts, chlorinated paraffin, chlorinated diphenyl and other chlorinated compounds.

  Examples of the oily agent include fatty acids or esters thereof, higher alcohols, polyhydric alcohols or esters thereof, aliphatic amines, fatty acid monoglycerides, montan wax, amide waxes, and the like.

  Examples of the viscosity index improver include polymethacrylate, ethylene-propylene copolymer, polyisobutylene, polyalkylstyrene, styrene-isoprene copolymer hydride, and the like.

  The composition is prepared by a method in which a predetermined amount of a solid lubricant and other necessary additives are added to the base oil, and the mixture is sufficiently kneaded with a homomixer, three rolls or a high-pressure homogenizer.

  Next, the present invention will be described with reference to examples.

Example 1
Pentaerythritol C ₆ -C ₉ carboxylic acid ester 87.1% by weight
(Cognis product, 40 ° C kinematic viscosity; 23 mm ² / sec)
Synthetic hydrocarbon oil (Inobean product PAO 6, kinematic viscosity at 40 ℃; 31mm ² / sec) 10.3% by weight
Synthetic hydrocarbon oil (PAO 40, 40 ° C kinematic viscosity; 390mm ² / sec) 2.6% by weight
PMA-based viscosity index improver (Mw = 250,000) synthesized in 97.9 parts by weight of a mixed base oil in pentaerythritol C ₆ -C ₉ carboxylic acid ester, amine antioxidant (Ciba Specialty Chemicals) Lubricant A was prepared by blending 1.0 part by weight of Irganox L57) and 0.1 part by weight of a benzotriazole metal deactivator with a homomixer. The lubricating oil A had a kinematic viscosity at 40 ° C. of 25.3 mm ² / sec and an evaporation loss of 150 ° C. and 100 hours was 18.1% by weight.

  A lubricating oil composition was prepared by mixing 1 part by weight of PTFE (emulsion polymerization method polytetrafluoroethylene; average primary particle size 0.2 μm; Mn about 100,000 to 200,000) with 99 parts by weight of the lubricating oil A. In the following Examples and Comparative Examples, the same viscosity index improver, antioxidant, metal deactivator and PTFE were used.

Example 2
In Example 1, a mixture of 97 parts by weight of lubricant A and 3 parts by weight of PTFE was used as the lubricant composition.

Example 3
In Example 1, a mixture of 95 parts by weight of lubricant A and 5 parts by weight of PTFE was used as the lubricant composition.

Example 4
Trimethylolpropane C ₈ -C ₁₂ carboxylic acid ester 72.9% by weight
(Cognis product, 40 ° C kinematic viscosity; 18 mm ² / sec)
Synthetic hydrocarbon oil (PAO 6, 40 ° C kinematic viscosity; 31mm ² / sec) 20.8% by weight
Synthetic hydrocarbon oil (PAO 40, 40 ° C kinematic viscosity; 390 mm ² / sec) 6.3 wt%
Lubricant B was prepared by blending 8.0 parts by weight of PMA viscosity index improver, 1.0 parts by weight of amine antioxidant and 0.1 parts by weight of benzotriazole metal deactivator with 90.9 parts by weight of mixed base oil. . The lubricating oil B had a kinematic viscosity at 40 ° C. of 60.3 mm ² / sec and an evaporation loss of 100 ° C. for 100 hours was 21.5% by weight. Next, 97 parts by weight of this lubricating oil B was mixed with 3 parts by weight of PTFE to prepare a lubricating oil composition.

Example 5
Synthetic hydrocarbon oil (Inobean product PAO 10, 40 ° C kinematic viscosity; 68 mm ² / sec) 98.9 parts by weight, 1.0 parts by weight of amine antioxidant and 0.1% by weight of benzotriazole metal deactivator, Lubricant C was prepared. The lubricating oil C had a kinematic viscosity at 40 ° C. of 69.1 mm ² / sec and an evaporation loss of 100 ° C. for 100 hours was 34.5% by weight. Next, 99.5 parts by weight of this lubricant C was mixed with 0.5 parts by weight of PTFE to prepare a lubricant composition.

Example 6
Trimethylolpropane C ₈ -C ₁₂ carboxylic acid ester 65.0 wt%
(Cognis product, 40 ° C kinematic viscosity; 18 mm ² / sec)
Polybutene 30.0% by weight
Amine antioxidant 2.5% by weight
C ₁₂ zinc dithiophosphate 2.5% by weight
Was added to prepare Lubricant D. The lubricating oil D had a kinematic viscosity at 40 ° C. of 105 mm ² / sec and an evaporation loss of 100 ° C. for 100 hours was 10.5% by weight. Next, 97 parts by weight of this lubricant D was mixed with 3 parts by weight of PTFE to prepare a lubricant composition.

Example 7
Poly (oxyethylene oxypropylene) glycol monoether 50.0% by weight
(Sanyo Chemical product, 40 ° C kinematic viscosity; 135mm ² / sec)
Poly (oxyethylene oxypropylene) glycol monoether 46.5% by weight
(Sanyo Chemical product, 40 ° C kinematic viscosity; 380 mm ² / sec)
Triphenyl phosphorothioate 0.5% by weight
(Ciba Specialty Chemicals product; Phosphorous wear inhibitor)
Amine antioxidant 2.5% by weight
Benzotriazole metal deactivator 0.5% by weight
Was added to prepare lubricating oil E. The lubricating oil E had a kinematic viscosity at 40 ° C. of 215 mm ² / sec and an evaporation loss of 100 ° C. for 100 hours was 40.5% by weight. Next, 99 parts by weight of the lubricant E was mixed with 1 part by weight of PTFE to prepare a lubricant composition.

Comparative Example 1
In the lubricating oil composition of Example 1, PTFE was not used, and only 100 parts by weight of the lubricating oil A was used.

Comparative Example 2
In the lubricating oil composition of Example 4, PTFE was not used, and only 100 parts by weight of lubricating oil B was used.

Comparative Example 3
In the lubricating oil composition of Example 5, PTFE was not used, and only 100 parts by weight of lubricating oil C was used.

Comparative Example 4
In the lubricating oil composition of Example 6, PTFE was not used, and only 100 parts by weight of lubricating oil D was used.

Comparative Example 5
In Example 1, a mixture of 90 parts by weight of the lubricant A and 10 parts by weight of PTFE was used as the lubricant composition.

Comparative Example 6
Neopentyl glycol C ₉ carboxylic acid ester 98.9% by weight
(Cognis product, 40 ° C kinematic viscosity; 8.5 mm ² / sec)
Amine antioxidant 1.0% by weight
Benzotriazole metal deactivator 0.1% by weight
Was added to prepare Lubricant F. The lubricating oil C had a kinematic viscosity at 40 ° C. of 9.7 mm ² / sec and an evaporation loss of 100 ° C. for 100 hours was 80.3% by weight. Next, 97 parts by weight of this lubricating oil F was mixed with 3 parts by weight of PTFE to prepare a lubricating oil composition.

Example 8
In Example 1, the same amount of graphite (Japanese graphite product J-CPB, average particle size: 5 μm) was used instead of PTFE.

Example 9
In Example 1, the same amount of molybdenum disulfide (Daito Lubricated Product LM13-SM powder, average particle size: 0.4 μm) was used instead of PTFE.

Example 10
In Example 1, MCA (Nissan Chemical Product MCA-6000, average particle size: 1 to 5 μm) was used in the same amount instead of PTFE.

Example 11
In Example 4, the same amount of graphite (J-CPB, average particle size; 5 μm) was used instead of PTFE.

Example 12
In Example 4, the same amount of molybdenum disulfide (LM13-SM powder, average particle size; 0.4 μm) was used instead of PTFE.

Example 13
In Example 5, a mixture of 99 parts by weight of lubricating oil C and 1 part by weight of MCA (MCA-6000, average particle size: 1 to 5 μm) was used as the lubricating oil composition.

Comparative Example 7
In Comparative Example 5, the same amount of graphite (J-CPB, average particle size; 5 μm) was used instead of PTFE.

Comparative Example 8
In Comparative Example 5, the same amount of molybdenum disulfide (LM13-SM powder, average particle size; 0.4 μm) was used instead of PTFE.

Comparative Example 9
In Comparative Example 5, the same amount of MCA (MCA-6000, average particle size; 1 to 5 μm) was used instead of PTFE.

Comparative Example 10
In Example 5, as a lubricating oil composition, 90 parts by weight of lubricant C was mixed with 10 parts by weight of MCA (MCA-6000, average particle size: 1 to 5 μm).

The fluidity and dispersion stability of the lubricating oil compositions obtained in the above Examples and Comparative Examples were examined.
Flowability: Viscosity measured at 25 ° C and 300 / sec using a cone-plate rheometer, and 5,000 mPa · sec or less evaluated as good fluidity Dispersibility: Settling tube with 10 ml scale In the synthetic oil, 10 ml of the lubricating oil composition obtained in each of the examples and comparative examples was placed and allowed to stand for one week after stirring. By visually confirming the sedimentation state of the dispersed solid lubricant particles, the particles were A product obtained with a uniform dispersion without aggregation and sedimentation was evaluated as having good dispersibility.

  As a result, the lubricating oil compositions obtained in Examples and Comparative Examples 1 to 4 and 6 had good fluidity and dispersion stability, but were obtained in Comparative Examples 5 and 7 to 10. In the lubricating oil composition, although the fluidity was good, the dispersion stability was insufficient.

  In addition, a sliding property test (evaluation of load resistance and measurement of friction coefficient) was performed using each lubricating oil composition. Using a SRV friction tester, the load resistance was measured using a SUJ2 disk for the lower test piece and a SUJ2 ball of 10 mm diameter for the upper test piece, which were point-contacted, with a frequency of 50 Hz, an amplitude of 1 mm, and a temperature of 100 ° C. Under the conditions, the load was increased by 50N every minute, this was continuously performed until it reached 500N, the maximum load at which seizure did not occur was evaluated, and the friction coefficient was measured for each load. The reason for setting the test temperature to 100 ° C. is to make it difficult to hold the oil film.

The results obtained are shown in the following table. In Comparative Examples 1 to 4, the load resistance was inferior, and with the load of Comparative Example 6 of 200 to 300 N, the measured value of the friction coefficient was not stable.
table
Load (N) / Contact surface pressure (N / mm ² )
Withstand load 50/100/150/200/250/300/350/400/450/500 /
Example (N) 105 149 183 211 236 258 279 298 316 333
Example 1 400 0.155 0.126 0.111 0.107 0.106 0.099 0.104 0.103--
〃 2> 500 0.131 0.129 0.113 0.105 0.103 0.099 0.099 0.100 0.101 0.102
３ 3> 500 0.127 0.119 0.110 0.103 0.101 0.100 0.097 0.098 0.096 0.097
〃 4> 500 0.130 0.127 0.112 0.102 0.103 0.098 0.097 0.097 0.098 0.098
450 5 450 0.232 0.202 0.185 0.170 0.151 0.152 0.150 0.148 0.145-
６ 6> 500 0.129 0.110 0.104 0.103 0.101 0.100 0.100 0.099 0.098 0.099
〃 7> 500 0.126 0.105 0.096 0.095 0.094 0.095 0.093 0.093 0.093 0.092
Comparative Example 1 300 0.155 0.141 0.147 0.141 0.143 0.150----
〃 2 350 0.156 0.141 0.145 0.139 0.138 0.150 0.155---
〃 3 300 0.297 0.230 0.198 0.188 0.177 0.166----
４ 4 400 0.128 0.117 0.109 0.104 0.102 0.103 0.102---
〃 6 300 0.167 0.147 0.147-------
Example 8 450 0.144 0.120 0.105 0.103 0.101 0.099 0.098 0.097 0.098-
〃 9> 500 0.131 0.127 0.125 0.120 0.117 0.113 0.110 0.105 0.101 0.101
〃 10 400 0.147 0.115 0.109 0.107 0.105 0.102 0.101 0.099--
〃 11 450 0.133 0.120 0.112 0.108 0.105 0.102 0.101 0.099 0.099-
〃 12> 500 0.132 0.127 0.123 0.117 0.111 0.105 0.103 0.099 0.098 0.098
〃 13 400 0.225 0.211 0.197 0.183 0.177 0.170 0.163 0.155--

  The lubricating oil composition of the present invention is effectively used as a lubricating oil applied to bearings, bushes, chains or gears.

Claims (5)

  A lubricating oil composition comprising polytetrafluoroethylene resin, graphite, molybdenum disulfide or melamine cyanurate blended at a ratio of 0.1 to 5% by weight in a composition with a base oil composed of synthetic oil.   The lubricating oil composition according to claim 1, wherein the synthetic oil is at least one of a synthetic hydrocarbon oil, an ester-based synthetic oil and a glycol oil. The lubricating oil composition according to claim 1, wherein a base oil having a kinematic viscosity at 40 ° C of 20 to 800 mm ² / sec is used. 4. The lubricating oil composition according to claim 3, wherein a base oil having a kinematic viscosity at 40 [deg.] C. of 20 to 250 mm < ² > / sec is used for bearings and bushes. The lubricating oil composition according to claim 3, wherein a base oil having a kinematic viscosity at 40 ° C of 100 to 800 mm ² / sec is used for chain oil or gear oil applications.