JP4784092B2 - Lubricating grease composition - Google Patents

Description

  The present invention relates to a lubricating grease composition. More specifically, a lubricating grease composition suitably used for metal-resin sliding parts.

  Conventionally, grease has been used as a lubricant composition for sliding parts, but in recent years, automotive parts, home appliances, office automation equipment, etc. have resin parts on the sliding parts for the purpose of reducing weight and cost. Are increasingly being used. Grease used as a lubricant for such resin sliding parts is not satisfactory in terms of lowering the coefficient of friction and improving durability even if the grease used in conventional metal sliding parts is used as it is. .

Among the sliding parts, power transmission mechanism parts using resin parts are often used in power transmission mechanism parts, particularly in parts such as automobiles. For example, in a reduction mechanism, a metal worm gear and a resin worm wheel gear are used in combination. Of these power transmission mechanisms having sliding parts, grease for resin lubrication to which a fatty acid having a hydroxyl group or a polyhydric alcohol fatty acid ester is added as a grease composition used for lubrication of a metal member and a resin member A composition has been proposed, but when this grease composition is used under a high load, the friction coefficient is not reduced, and there is a problem in durability.
JP-A-8-209167

In addition, a grease composition for resin lubrication containing montan wax has been proposed for the purpose of reducing the coefficient of friction and improving durability at the sliding portion, and this grease composition has improved wear resistance. However, there is a problem in durability at high temperature use.
JP 2002-371290 A

In addition, the addition of polar wax has been proposed to improve the wettability of the resin and metal surfaces and improve the transmission efficiency (friction coefficient), but there is a concern that the durability of the wheel resin itself may be reduced by using polar substances. There is. In addition, since polar wax itself does not dissolve in base oil, it agglomerates by heating and cooling, and finally it is excluded from the lubrication part. Polar wax also swells in the rubber material part located in the periphery.・ There is a risk of adverse effects such as shrinkage.
JP 2004-301268 A

As a recent trend, greases using lithium-based composite soap, urea-based compounds or both as thickeners have been proposed. It aims to improve the characteristics at the same time.
Japanese Patent Laid-Open No. 2004-250481 JP 2004-314916 A

  However, the properties of greases using both lithium-based composite soaps and urea-based compounds as thickeners show only intermediate properties of greases to which these thickeners are added individually, which means that lithium-based composite soaps. It is considered that the grease containing the urea compound inhibits the low friction coefficient characteristics of the grease containing grease, while the grease containing the lithium composite soap inhibits the characteristics of the heat resistance and durability of the grease containing the urea compound.

  An object of the present invention is to provide a lubricating grease composition containing a lithium-based composite soap or a urea-based compound as a thickener and having improved properties such as lubricity, heat resistance and durability at the same time. It is in.

The object of the present invention is to provide synthetic hydrocarbon oil 42.5 to 49.8% by weight, ester synthetic oil 2 to 5% by weight, fluorinated oil 30 to 36% by weight, lithium complex soap or urea compound thickener 5.0 to 7.15. And a lubricating grease composition consisting of 9-12% by weight of polytetrafluoroethylene resin powder or 9-12% by weight of polytetrafluoroethylene resin powder or tetrafluoroethylene-hexafluoropropene copolymer powder .

In the lubricating grease composition containing lithium complex soap or urea compound as a thickener, the use of further mixing the fluorinated oil in the base oil consisting of synthetic hydrocarbon oils and synthetic ester oils, lubricity, Properties such as heat resistance and durability can be improved at the same time, and it is suitably used for gears, sliding bearings, sliding electrical contacts, etc. of metal-resin sliding parts. Furthermore, by including polytetrafluoroethylene resin powder or tetrafluoroethylene-hexafluoropropene copolymer powder , it is possible to further improve lubricity and durability.

Useful synthetic hydrocarbon oil used as the base oil, poly α- olefins include ethylene -α- olefin co-oligomer, polybutene or hydrides thereof, alkylbenzenes, alkyl naphthalenes and the like. Examples of synthetic ester oils, polyol esters, dibasic acid esters, aromatic polycarboxylic acid esters, phosphoric acid esters, phosphorous acid esters, carbonic esters, and the like, respectively.

These base oils generally have a kinematic viscosity at 40 ° C. (based on JIS K2283) of about ^{2 to} 1000 mm ² / sec, preferably about 10 to 500 mm ² / sec.

When the mixing ratio of the fluorinated oil is less than this, the lubricity and heat resistance are not improved. On the other hand, when the mixing ratio is higher than this, the stability of the grease is deteriorated.

As the fluorinated oil, one having a kinematic viscosity at 40 ° C. (based on JIS K2283) of about 10 to 1500 mm ² / sec, preferably about 20 to 500 mm ² / sec is generally used.
RfO (CF ₂ O) _x (C ₂ F ₄ O) _y (C ₃ F ₆ O) _z Rf
Is used. Specifically, for example, those represented by the following general formulas (1) to (3) are used, and those represented by the general formula (4) are also used. Rf is a perfluoro lower alkyl group having 1 to 5, preferably 1 to 3, carbon atoms such as a perfluoromethyl group, a perfluoroethyl group, and a perfluoropropyl group.
(1) RfO (CF ₂ CF ₂ O) _m (CF ₂ O) _n Rf
Here, m + n = 3 to 200, m: n = 10 to 90:90 to 10 and the CF ₂ CF ₂ O group and the CF ₂ O group are randomly bonded in the main chain. Yes, it can be obtained by completely fluorinating the precursor produced by photo-oxidative polymerization of tetrafluoroethylene.
(2) RfO [CF (CF ₃ ) CF ₂ O] _p (CF ₂ CF ₂ O) _q (CF ₂ O) _r Rf
Where p + q + r = 3 to 200 and q and r can be 0, (q + r) / p = 0 to 2 , and CF (CF ₃ ) CF ₂ O group, CF ₂ CF _{The 2} O group and the CF ₂ O group are randomly bonded in the main chain, and can be obtained by completely fluorinating a precursor produced by photo-oxidative polymerization of hexafluoropropene and tetrafluoroethylene.
(3) RfO [CF (CF ₃ ) CF ₂ O] _s (CF ₂ CF ₂ O) _t Rf
Here, s + t = 2 to 200, t can be 0, t / s = 0 to 2 , and CF (CF ₃ ) CF ₂ O group and CF ₂ CF ₂ O group are in the main chain Randomly bonded, by completely fluorinating the precursor produced by the photo-oxidative polymerization of hexafluoropropene and tetrafluoroethylene, or in the presence of a cesium fluoride catalyst, It is obtained by anionic polymerization of fluoroethylene oxide and treating the resulting acid fluoride compound having a terminal —CF (CF ₃ ) COF group with fluorine gas.
(4) F (CF ₂ CF ₂ CF ₂ O) _{2 to 100} C ₂ F ₅
This is because 2,2,3,3-tetrafluorooxetane is anionically polymerized in the presence of a cesium fluoride catalyst, and the resulting fluorinated polyether (CH ₂ CF ₂ CF ₂ O) _n is subjected to about UV irradiation. It is obtained by treating with fluorine gas at 160 to 300 ° C.

Thickeners include (a) an aliphatic monocarboxylic acid having 12 to 24 carbon atoms and / or an aliphatic monocarboxylic acid having 12 to 24 carbon atoms containing at least one hydroxyl group and (b) 2 carbon atoms. Lithium complex soap or diurea, triurea, tetraurea, urea compounds such as diurea, triurea, urea resin, etc. Is used. If a thickener other than the lithium complex soap or urea compound is used, the heat resistance and durability cannot be satisfied at the same time, and the object of the present invention cannot be achieved.

The lubricating grease composition additionally polytetrafluoroethylene (PTFE) resin powder or tetrafluoroethylene [TFE] - it is preferable to use the addition of hexafluoropropene [HFP] copolymer powder, thereby lubricity, Further improvement in durability and the like is achieved.

  Polytetrafluoroethylene 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, and physical grinding. The number average molecular weight Mn is about 1000 to 100000. Also, the copolymerization reaction of tetrafluoroethylene and hexafluoropropene and the molecular weight reduction treatment are performed in the same manner as in the case of polytetrafluoroethylene, and those having a number average molecular weight of about 1000 to 600000 are used. The molecular weight can also be controlled by using a chain transfer agent during the copolymerization reaction. The obtained powdery fluororesin generally has an average primary particle size of about 500 μm or less, preferably about 0.1 to 30 μm.

In the composition containing the above components as essential components, other additives such as antioxidants, rust inhibitors, corrosion inhibitors, extreme pressure agents, oiliness agents, viscosity index improvers, etc. that have been added to conventional lubricants These additives can be added as necessary. 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, 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 waxes, amide waxes, and the like. Examples of other solid lubricants include molybdenum disulfide, graphite, boron nitride, and silane nitride.

  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 thickener, a solid lubricant, and other necessary additives are added to the base oil and the fluorinated oil, and the mixture is sufficiently kneaded with a three-roll or high-pressure homogenizer.

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

Examples 1-24 (Examples 5, 8 and 11 are examples)
Using a pin-on-disk type tester, apply grease on the metal disk, press a resin pin on the coated surface, and rotate. Rotate the lower disk, calculate the friction coefficient at the beginning of the test and before the end of the test from the friction force generated between the resin pin and the disk, and wear the resin pin after the test to evaluate the durability The amount was measured.
(Pin-on-disk type testing machine)
Upper test piece: Polyamide pin (diameter 5mm, surface roughness Ra 2μm)
Lower test piece: S45C plate (surface roughness Ra 2μm)
Test load: 2kgf
Grease application amount: 0.05g
Sliding speed: 0.8m / sec Test temperature: 100 ℃
Test distance: 10000m

As a base grease, a Li composite occupying 13% by weight of the base grease as a thickener in a poly α-olefin oil (40 ° C kinematic viscosity 47 mm ² / sec) containing 2% amine-based antioxidant A blend of soap (base grease A) or 9% by weight of diurea (base grease B) was used.

A base grease, a fluorine oil, and a solid lubricant were added to and mixed with the base grease A or B to prepare a lubricating grease composition.
Base oil A: Pentaerythritol fatty acid ester polyol ester oil (40 ° C kinematic viscosity)
(33mm ² / sec)
Base oil B: alkyl diphenyl ether oil (40 ° C kinematic viscosity 100mm ² / sec)
Fluorine oil A: RfO [CF (CF ₃ ) CF ₂ O] _p Rf (40 ° C kinematic viscosity 100 mm ² / sec)
Fluorine oil B: F (CF ₂ CF ₂ CF ₂ O) _a C ₂ F ₅ (40 ° C kinematic viscosity 65 mm ² / sec)
Fluorine oil C: RfO (CF ₂ CF ₂ ) _m (CF ₂ O) _n Rf (40 ° C kinematic viscosity 85 mm ² / sec)
Solid lubricant A: PTFE resin powder (primary particle size 0.3μm)
Solid lubricant B: MoS ₂ powder (average particle size 0.4μm)
Solid lubricant C: Graphite powder (average particle size 4μm)

The measurement results for the composition (parts by weight) and the penetration of the lubricating grease composition (measured with a penetrometer according to JIS K2220) and the sliding test (the friction coefficient and the amount of wear) are shown in Tables 1 to 3 below. Indicated. Table 1 shows the results when fluorine oil A is used, Table 2 shows the results when fluorine oil B is used, and Table 3 shows the results when fluorine oil C is used. The amount of base grease (A or B) is the balance of 100 parts by weight of the entire composition.
Table 1
Example 1 2 3 4 5 6 7 8
〔composition〕
Base grease (type) A A A A A B B B
Base oil A 3 5 4
Base oil B 3 8
Fluorine oil A 7 5 6 10 30 8 11 31
Solid lubricant A 4 4 10 5 9
Solid lubricant B 3
Solid lubricant C 1 4
[Measurement]
Blending 298 270 276 264 288 271 271 290
Coefficient of friction Initial test 0.09 0.06 0.08 0.06 0.05 0.07 0.08 0.05
After the test 0.11 0.08 0.10 0.08 0.07 0.09 0.10 0.07
Amount of wear (mg) 7.8 5.3 6.6 5.4 4.0 5.3 6.3 4.1

Table 2
Example 9 10 11 12 13 14 15 16
〔composition〕
Base grease (type) A A A B B B B B
Base oil A 2 4
Base oil B 4 2 2
Fluorine oil B 8 8 36 8 12 9 7 24
Solid lubricant A 4 2 12 6 3 9
Solid lubricant B 2 3
Solid lubricant C 3
[Measurement]
Blending 286 285 284 289 287 290 262 278
Coefficient of friction Initial test 0.07 0.07 0.05 0.09 0.06 0.08 0.08 0.05
After the test 0.09 0.10 0.07 0.11 0.08 0.10 0.11 0.07
Amount of wear (mg) 5.6 6.0 4.1 7.9 5.4 6.6 6.4 4.5

Table 3
Example 17 18 19 20 21 22 23 24
〔composition〕
Base grease (type) A A A A B B B B
Base oil A 3 3
Base oil B 4 3
Fluorine oil C 7 8 10 21 13 8 7 27
Solid lubricant A 6 7 6 9
Solid lubricant B 7 3
Solid lubricant C 3
[Measurement]
Blend penetration 301 288 286 276 288 279 270 280
Coefficient of friction Initial test 0.09 0.07 0.08 0.05 0.06 0.08 0.08 0.05
After the test 0.11 0.09 0.10 0.07 0.08 0.10 0.10 0.07
Amount of wear (mg) 7.9 5.3 6.6 4.6 6.7 5.3 6.3 4.5

Comparative Example 1
A lubricating grease composition was prepared using the above-mentioned poly-α-olefin oil containing an amine-based antioxidant as a base oil and Li soap accounting for 9% by weight of the composition as a thickener. When the friction coefficient and the wear amount were measured in the same manner as in each of the above examples, the wear coefficient was 0.11 at the beginning of the test, 0.21 before the test was completed, and the wear amount was 17.7 mg.

Comparative Example 2
A lubricating grease composition was prepared using the poly-α-olefin oil containing the amine-based antioxidant as the base oil and diurea in an amount of 9% by weight in the composition as the thickener. When the friction coefficient and the amount of wear were measured in the same manner as in each of the above examples, the wear coefficient was 0.14 at the beginning of the test, 0.22 before the test was completed, and the amount of wear was 20.5 mg.

Claims (4)

Synthetic hydrocarbon oil 42.5-49.8 wt%, ester synthetic oil 2-5 wt%, fluorinated oil 30-36 wt%, lithium complex soap or urea compound thickener 5.0-7.15 wt% and polytetrafluoroethylene A lubricating grease composition comprising 9 to 12% by weight of resin powder or tetrafluoroethylene-hexafluoropropene copolymer powder . The lubricating grease composition according to claim 1, which is applied to a sliding portion. The lubricating grease composition according to claim 2, which is applied to a metal-resin sliding portion. 4. The lubricating grease composition according to claim 3, which is applied to a metal worm-resin wheel sliding portion of an electric power steering.