JP4697225B2 - lubricant - Google Patents

Description

The present invention relates to a lubricant. More specifically, the present invention relates to a lubricant made of lubricating oil or grease, which is used for an application in contact with a sliding member using an aluminum material .

The number of automobile bearings that use sintered oil-impregnated bearings, which are less expensive than rolling bearings, is increasing, and high-temperature durability and low-temperature characteristics are particularly important for lubricants used in such sintered oil-impregnated bearings. It will be placed in a more severe environment for lubricants to be seen. Lubricating oil compositions based on perfluoropolyether oil are used for this type of purpose, but such base oils also come into contact with several metals and solid lubricants that have a very large surface area. As a result, some perfluoropolyether oils are unable to maintain stable high-temperature characteristics due to their structure.
Japanese Patent No. 2,595,583

Aluminum has a large specific strength for light weight, and it can be made into an alloy or processed to give further strength, and it has corrosion resistance, so it has sliding parts, automobile parts, aircraft and ship parts, It is used in various applications ranging from home appliances and power tools. These contribute to reducing the weight of various machines, improving the working efficiency of high-speed rotating parts and sliding parts, and improving fuel efficiency. Also in the sliding member using these aluminum materials, it is required that the lubricant used for them can stably maintain excellent performance.

The present inventors have found that the high temperature characteristics of perfluoropolyether oil are not only due to the structure thereof, but also due to contact with the aluminum material sliding member , the high temperature characteristics rapidly decrease.

An object of the present invention is to provide a lubricant that does not significantly impair high-temperature characteristics (high-temperature durability) even when it is used for an application that uses an aluminum material as a sliding member .

The purpose of the present invention is that the kinematic viscosity at 40 ° C. is 50 to 1500 mm ² / sec, preferably 50 to 250 mm ² / sec, particularly preferably 65 to ²⁰⁰ mm ² / sec, and (CF ₂ O ) It is achieved by a lubricant that is used in applications in which perfluoropolyether oil containing no _n group is used as a base oil and comes into contact with an aluminum sliding member . The lubricant may be in any form of lubricating oil or grease. Here, as the perfluoropolyether base oil, a perfluoropolyether oil represented by the following general formula is used.
F (CF ₂ CF ₂ CF ₂ O) _m C ₂ F ₅
RfO [CF (CF ₃ ) CF ₂ O] _p (CF ₂ CF ₂ O) _q Rf ′

High temperature properties of Pafuru Oro polyether oil (high temperature durability), when used in applications that use aluminum material as a sliding member also has reducing its properties rapidly, used in such applications Even in this case, the high temperature characteristics of the lubricant of the present invention are not significantly impaired. That is, in the presence of aluminum sliding members , even if the lubricant of the present invention is used under high temperature conditions exceeding 150 ° C. or 200 ° C., the volatility and stability are maintained over a long period of time, and lubricity in various types of sliding By exhibiting, it is possible to achieve a long service life of the parts used.

The lubricant, rolling bearings, sliding bearings, sintered bearings, gears, valves, cocks, oil seals, rolls, are also used to lubricate the sliding portion between individuals contacting portions such as electrical contacts.

The base oil has a kinematic viscosity at 40 ° C. (conforms to JIS K2283; conforms to ASTM D445) of 50 to 1500 mm ² / sec, preferably 50 to 250 mm ² / sec, particularly preferably 65 to ²⁰⁰ mm ² / sec. A repeating unit that does not contain a (CF ₂ O) _n group is used. As shown in the results of Examples below, in the presence of an aluminum material, the weight loss amount of the lubricant according to the present invention at a high temperature of 250 ° C. is within an allowable range, and also in the kinematic viscosity at −40 ° C. That's true.

Examples of perfluoropolyether oil (base oil) that does not contain (CF ₂ O) _n group as a repeating unit of the polymer include the following.
(A) F (CF ₂ CF ₂ CF ₂ O) _m C ₂ F ₅
(B) RfO [CF (CF ₃ ) CF ₂ O] _p (CF ₂ CF ₂ O) _q Rf ′
Rf, Rf ′: the same or different C 1-5 perfluoroalkyl groups

Perfluoropolyether oil (A): Anionic polymerization of 2,2,3,3-tetrafluorooxetane in the presence of a cesium fluoride catalyst, and the resulting fluorinated polyether (CH ₂ CF ₂ CF ₂ O) _n It can be obtained by treating with fluorine gas under ultraviolet irradiation at 160 to 300 ° C. For this, a kinematic viscosity at 40 ° C. in the range of 5 to 2000 mm ² / sec can be used, and such is a general formula of perfluoropolyether oil (A), m = 2 to 100 Satisfy the conditions.

Perfluoropolyether oil (B): hexafluoropropylene oxide or hexafluoropropylene oxide obtained by completely fluorinating a precursor produced by photo-oxidative polymerization of hexafluoropropylene or tetrafluoroethylene, or in the presence of a cesium fluoride catalyst This is obtained by anionic polymerization of tetrafluoroethylene oxide and treating the resulting acid fluoride compound having a terminal CF (CF ₃ ) COF group with fluorine gas. For this, one having a kinematic viscosity at 40 ° C. in the range of 5 to 2000 mm ² / sec can be used, and such is the general formula of perfluoropolyether oil (B), p + q = 2 to 200, q / p = 0-2 is satisfied.

However, when the kinematic viscosity is 50 or less, the evaporation loss rate (weight reduction rate) increases, and the oil film strength decreases, which may cause a decrease in life, wear and seizure. Those with kinematic viscosity not only have a very high pour point and cannot obtain sufficient low-temperature characteristics, but also cause problems such as increased power consumption and torque due to increased viscous resistance. As long as the kinematic viscosity at 40 ° C is 50-1500mm ² / sec, it can exhibit sufficient heat stability, and good low temperature characteristics are required especially under low temperature conditions such as -40 ° C. In some cases, it is limited to perfluoropolyether oils of 50 to 250 mm ² / sec, preferably 65 to ²⁰⁰ mm ² / sec. The perfluoropolyether oil having such a kinematic viscosity not only satisfies sufficient evaporation loss characteristics and low temperature characteristics, but also enables stable use under high temperature conditions exceeding 200 ° C. However, two or more kinds of perfluoropolyether oils can be mixed and used. In that case, the kinematic viscosity at 40 ° C. of the mixed base oil should be within such a range.

  Such a base oil is used with a thickener added, and preferably a fluororesin is used. As the fluororesin, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropene copolymer, perfluoroalkylene resin and the like conventionally used as a lubricant are used. Polytetrafluoroethylene produces polytetrafluoroethylene with a number average molecular weight Mn of about 1000 to 100000 by methods such as emulsion polymerization, suspension polymerization, and solution polymerization of tetrafluoroethylene. A material having a number average molecular weight Mn of about 1000 to 500,000, which is processed by a method such as beam irradiation decomposition or physical pulverization, is used. Further, the copolymerization reaction of tetrafluoroethylene and hexafluoropropene and the molecular weight reduction treatment are also performed in the same manner as in the case of polytetrafluoroethylene, and the number average molecular weight Mn is about 1000 to 600,000. . The molecular weight can be controlled 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. The addition of a powdery fluororesin imparts oil film forming ability, anti-scattering / leakage, and rust prevention, and can further improve lubricity and durability.

  In addition, as a thickener other than fluororesin, metal soap such as Li soap, urea resin, minerals such as bentonite, organic pigments, polyethylene, polypropylene, polyamide, etc. can be used, but considering heat resistance and lubricity Aliphatic dicarboxylic acid metal salts, monoamide monocarboxylic acid metal salts, monoester carboxylic acid metal salts, diurea, triurea, tetraurea and the like are used.

  These thickeners such as fluororesin powder are added and mixed at a ratio of 0.1 to 40% by weight, preferably 0.5 to 30% by weight of the total composition obtained by adding the thickener to the perfluoropolyether oil base oil. . If the addition ratio is higher than this, the composition becomes too hard to be sealed in a bearing or the like. On the other hand, if the addition ratio is less than this, the thickening ability of the fluororesin is not exhibited, the apparent viscosity is reduced, the base oil The oil dispersibility deteriorates, and the oil film forming ability, anti-scattering / leakage resistance, and rust prevention are not sufficiently expected. A grease is formed when the addition ratio of the thickener is less than about 10% by weight in the total amount with the base oil. In Examples and Comparative Examples described below, when the ratio of the thickener is 5% by weight or less, “ Since it exhibits fluidity in the category of “liquid grease”, the evaluation of the low temperature property is shown as the low temperature viscosity of the base oil mixture. On the other hand, in the example in which the proportion of the thickener is 30% by weight, it becomes a semi-solid in the category of grease, so the evaluation of the low temperature characteristics is shown as the evaluation result of the low temperature torque.

  Further, within the range where the object of the present invention is not impaired, a conventionally known fluorine-based additive such as perfluoropolyether oil is terminated with alcohol, carboxylic acid or ester thereof, amine, amide, phosphoric acid or ester thereof. A compound substituted with phosphonic acid or an ester thereof, a reaction product of isocyanate and alcohol or amine, and the like can be blended and used as required.

  In addition, a fluororesin is added to the lubricant base oil, so that various non-fluorine additives, viscosity index improvers, pour point depressants, ashless, which were not compatible with perfluoropolyether oils in the past. Additions added to conventional lubricants such as system dispersants, metal detergents, antioxidants, rust inhibitors, corrosion inhibitors, antifoaming agents, extreme pressure agents, oiliness agents, friction modifiers, solid lubricants, etc. Agents can be added as needed.

  Examples of the antioxidant include phenol-based antioxidants such as 2,6-di-tert-butyl-4-methylphenol and 4,4′-methylenebis (2,6-di-tert-butylphenol), 4 to 20 carbon atoms. And amine-based antioxidants such as alkyldiphenylamine, triphenylamine, phenyl-α-naphthylamine, phenothiazine, alkylated-α-naphthylamine, and alkylated phenothiazine having an alkyl group.

  Examples of rust preventives include fatty acids, fatty acid amines, alkyl sulfonic acid metal salts, alkyl sulfonic acid amine salts, oxidized paraffins, polyoxyethylene alkyl ethers, etc., and corrosion inhibitors include, for example, benzotriazole, benzimidazole, And thiadiazole.

  Examples of extreme pressure agents include phosphorus 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. Is mentioned.

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

  Examples of the solid lubricant include graphite, molybdenum disulfide, nitrogen boron, nitrogen silane, and the like. Even when graphite or molybdenum disulfide is used as the solid lubricant, the perfluoropolyether base oil is resistant to heat. A decrease in change can be effectively prevented.

Preparation of the composition formed by adding a thickener to a perfluoropolyether base oil is performed, for example, as follows.
(a) A method in which a predetermined amount of a thickener is blended in a perfluoropolyether base oil and kneaded sufficiently with a three-roll or high-pressure homogenizer, and (b) a perfluoropolyether oil in a reaction kettle capable of heating and stirring. And an aliphatic carboxylic acid are added and melted by heating, and a predetermined amount of metal hydroxide (and amide compound or alcohol compound) is added thereto, followed by metal chloride reaction (and amidation reaction or esterification reaction) and cooling. After that, a method of sufficiently kneading with a three-roll or high-pressure homogenizer, or (c) a reaction kettle capable of heating and stirring, adding perfluoropolyether oil and isocyanate and heating, and adding a predetermined amount of amine thereto After the reaction and cooling, it is carried out by a method of sufficiently kneading with a three-roll or high-pressure homogenizer.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Example 10% by weight of aluminum powder (Wako Pure Chemicals; purity 99.5%, particle size 53 to 150 μm) in the following perfluoropolyether base oil (A) or (B) having various kinematic viscosities at 40 ° C. After mixing 0.6 g of this test sample in a 37 mm diameter glass petri dish and uniformly coating it in a thin film, it was left in a constant temperature bath at 250 ° C. and after 100 hours had passed. The weight of the whole glass petri dish was measured, and the weight reduction rate of the oil was calculated.
Perfluoropolyether oil (A): F (CF ₂ CF ₂ CF ₂ O) _m C ₂ F ₅
Kinematic viscosity at 40 ℃ (A-1) 65mm ² / sec
(A-2) 100mm ² / sec
(A-3) 200mm ² / sec
(A-4) 23 mm ² / sec Perfluoropolyether oil (B): RfO [CF (CF ₃ ) CF ₂ O] _p Rf ′
Kinematic viscosity at 40 ° C (B-1) 180mm ² / sec
(B-2) 400mm ² / sec
(B-3) 25mm ² / sec
(B-4) 1200mm ² / sec Perfluoropolyether oil (C): RfO (CF ₂ CF ₂ O) _m (CF ₂ O) _n Rf ′
Kinematic viscosity at 40 ° C 140mm ² / sec

  As the fluororesin powder, emulsion polymerization polytetrafluoroethylene powder (Mn: about 50,000 to 100,000, average primary particle size: 0.2 μm) was used.

The results obtained are based on the type and amount of base oil (parts by weight) and the amount of fluororesin (parts by weight) as well as the kinematic viscosity and pour point of the base oil or base oil-fluororesin mixture (according to JIS K2269; ASTM D97), oil (base oil) weight loss rate and low temperature viscosity (based on JIS K2283, kinematic viscosity at -40 ° C .; corresponding to ASTM D445) are shown in Table 1 below. In addition, No. 1-12 is an Example and No. 13-15 is a comparative example.

From the above results, it can be seen that the weight loss rate at 250 ° C. increases remarkably when the one having a 40 ° C. kinematic viscosity of less than 50 mm ² / sec is used (No. 13, 14). In addition, when the polymer repeat unit containing (CF ₂ O) _n group was used (No. 15), the weight loss rate after 100 hours at 250 ° C. was large, and most of the sample disappeared. I understand that. On the other hand, when the 40 ° C. kinematic viscosity is in the range of 50 to 1500 mm ² / sec, the weight loss at a high temperature of 250 ° C. is within the allowable range, and the 40 ° C. kinematic viscosity is 50 to 250 mm ^2. The same is true for the kinematic viscosity at -40 ° C. in the range of / sec (No. 1 to 10).

Furthermore, A-1 70 parts by weight-fluororesin 30 parts by weight (No. 21), A-2 70 parts by weight-fluororesin 30 parts by weight (No. 22), B-2 70 parts by weight-fluororesin 30 parts by weight (No. 23) and B-3 70 parts by weight-Fluorine resin 30 parts by weight (No. 24) grease, in addition to the above items, low temperature torque test (compliant with JIS K2220.5.14, starting at -40 ° C) Time and steady-state values were measured (according to ASTM D1478). The results obtained are shown in Table 2 below. No. 24 is a comparative example.

Claims (10)

For applications where the kinematic viscosity at 40 ° C is 50 to 1500 mm ² / sec and the polymer repeat unit is based on perfluoropolyether oil that does not contain (CF ₂ O) _n groups, and comes in contact with aluminum sliding members Lubricant used. The lubricant according to claim 1, wherein a perfluoropolyether oil having a kinematic viscosity at 40 ° C of 50 to 250 mm ² / sec is used as a base oil. Perfluoropolyether base oil has the general formula
F (CF ₂ CF ₂ CF ₂ O) _m C ₂ F ₅
(Where m is an integer from 2 to 100) and the perfluoropolyether oil (A) and the general formula
RfO [CF (CF ₃ ) CF ₂ O] _p (CF ₂ CF ₂ O) _q Rf ′
(Wherein Rf and Rf ′ are the same or different perfluoroalkyl groups having 1 to 5 carbon atoms, p + q = 2 to 200, q / p = 0 to 2 and q can be 0, CF The lubrication according to claim 1, which is at least one kind of perfluoropolyether oil (B) represented by (CF ₃ ) CF ₂ O group and CF ₂ CF ₂ O group are randomly bonded in the main chain). Agent. Perfluoropolyether base oil has the general formula
F (CF ₂ CF ₂ CF ₂ O) _m C ₂ F ₅
(Where m is an integer from 2 to 100) and the perfluoropolyether oil (A) and the general formula
RfO [CF (CF ₃ ) CF ₂ O] _p (CF ₂ CF ₂ O) _q Rf ′
(Wherein Rf and Rf ′ are the same or different perfluoroalkyl groups having 1 to 5 carbon atoms, p + q = 2 to 200, q / p = 0 to 2 and q can be 0, CF (CF ₃₎ CF ₂ O group and CF ₂ CF ₂ O group lubricant according to claim 2, wherein the at least one perfluoropolyether oil represented by is coupled randomly) in the main chain (B) Agent.   The lubricant according to claim 1, which is a lubricating oil.   The lubricant according to claim 2, which is a lubricating oil.   The lubricant according to claim 1, wherein a thickener is further mixed and used as a grease.   The lubricant according to claim 7, wherein the thickener is a fluororesin powder.   The lubricant according to claim 2, wherein a thickener is further mixed and used as a grease.   The lubricant according to claim 9, wherein the thickener is a fluororesin powder.