JP2005105080A - Grease composition and rolling apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a grease composition having excellent heat resistance and lubricating properties and to provide a rolling apparatus having a long life even at a high temperature. <P>SOLUTION: The grease composition comprises a first thickening agent and a second thickening agent in base oil in which the first thickening agent is a diurea compound represented by formula (I) (R<SB>2</SB>is a 6-15C aromatic hydrocarbon group; R<SB>1</SB>and R<SB>3</SB>are each a 6-20C straight-chain or branched-chain, preferably straight-chain aliphatic hydrocarbon group), the second thickening agent is a fluororesin and the base oil contains an ester-based synthetic oil and a perfluoropolyether oil in the ratio of preferably 30-80 wt.% of the diurea compound and 70-20 wt.% of the fluororesin based on the total of the thickening agents and in the ratio of 30-80 wt.% of the ester-based synthetic oil and 70-20 wt.% of the perfluoropolyether oil in the total of the base oil. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a grease composition and a rolling device to which the grease composition is applied, and more particularly to a grease composition having excellent heat resistance and a rolling device to which the grease composition is applied.

  In recent years, automobile engine room spaces tend to be smaller due to demands for smaller and lighter automobiles and larger living spaces. Accordingly, electrical components and engine accessories installed in the engine room are further reduced in size and weight. However, with the progress of such miniaturization, there is a problem that the engine room becomes hot. In addition to this, since the engine room is being sealed due to a demand for improving the quietness of the engine room, the temperature of the engine room tends to be further increased. Therefore, the heat resistance of the parts installed in the engine room is becoming more and more important. For example, an electric fan motor bearing has been conventionally used at a bearing temperature of 130 to 150 ° C. However, in recent years, a bearing that can withstand a high temperature of 180 to 200 ° C. is required. Therefore, the grease used for the bearing is also required to have high heat resistance.

Conventionally, in a bearing used at a temperature of 150 ° C. or higher, for example, as disclosed in Patent Document 1 (Patent No. 2,977,624), Li-based soap is used as a synthetic lubricant. In addition, grease containing a urea-based compound was enclosed. However, since this grease is baked early at a high temperature of 160 ° C. or higher, development of a grease with higher heat resistance has been desired.
Japanese Patent No. 2,977,624 Japanese Patent Laid-Open No. 11-181465

  Under such circumstances, various greases with improved heat resistance have been developed.

  For example, a fluorine-based grease in which polytetrafluoroethylene (PTFE) is blended with a thickener and a perfluoropolyether oil is used as a base oil is one example. When such a fluorine-based grease is used for a bearing, It is known that it can be used in an environment of 160 ° C. or higher.

  However, it is difficult to add an additive blended with a general grease, and the fluorine-based grease tends to be inferior in terms of lubricity, rust prevention, and metal corrosion performance.

  Patent Document 2 (Japanese Patent Application Laid-Open No. 11-181465) discloses a grease composition in which heat resistance is improved by adding a fluorine oil to a urea-based grease. However, since this grease composition lacks a thickener component that is compatible with fluorine oil, there is a problem that oil separation and leakage are large, and the life is short when used for a high-temperature bearing. It was.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-described problems, to provide a grease composition having excellent heat resistance and lubricity, and to provide a rolling device having a long life even at high temperatures. It is said.

  As a result of diligent research to solve the above problems, the present inventors have achieved excellent heat resistance when a predetermined compound is used as a first thickener and a second thickener in a predetermined base oil. The present invention has been found by having the properties and lubricity.

  That is, the grease composition of the present invention contains a first thickener and a second thickener in the base oil, and the first thickener has the following formula (I):

The second thickener is a fluororesin, and the base oil contains an ester synthetic oil and a perfluoropolyether oil.

  In this invention, since a fluororesin is included as a 2nd thickener component, the outstanding heat resistance is shown by mixing with the base oil containing perfluoro ether oil. Therefore, according to such a grease composition, it is possible to provide a rolling device having a long life even at a high temperature. Moreover, since the said base oil also contains ester synthetic oil, it becomes possible to add various additives. Therefore, since a wide range of additives can be used, it is possible to provide a grease composition excellent in lubricity, rust prevention, and corrosion resistance by adding an appropriate additive. Furthermore, since the diurea compound is contained as the first thickener and the ester-based synthetic oil is contained as the base oil, an inexpensive grease composition can be provided as compared with a normal fluorine-based grease.

  It is preferable that the diurea compound is contained in an amount of 30 to 80% by weight and the fluororesin is contained in a range of 70 to 20% by weight with respect to the total amount of the thickener. It is preferable to contain in the range of -40weight%. When the diurea compound and the fluororesin are in the above range, a grease composition having excellent heat resistance and low cost can be provided.

  The base oil preferably contains 30 to 80% by weight of ester synthetic oil and 70 to 20% by weight of perfluoropolyether oil based on the total amount of base oil. When the amount of the ester synthetic oil and the perfluoropolyether oil is in the above range, a grease composition having excellent heat resistance and low cost can be provided.

  It is preferable that the total amount of said 1st thickener and said 2nd thickener is 5 to 40 weight% of the whole said grease composition. If it is less than 5% by weight, it will be difficult to maintain the grease state, and if it exceeds 40% by weight, the grease composition will be hardened and it will be difficult to exhibit sufficient lubricity. However, from the viewpoint of the penetration of the grease composition and the application to the rolling device, the content of the thickener is preferably 10 to 30% by weight of the entire grease composition.

The ester-based synthetic oil has a kinematic viscosity at 40 ° C. (based on JIS K2283) of 20 to 500 mm ² / s, and the perfluoropolyether oil has a kinematic viscosity at 40 ° C. (based on JIS K2283) of 20 to 500 mm ^2. / S is preferable. If the kinematic viscosity at 40 ° C. of both exceeds 500 mm ² / s, the torque of the rolling device tends to increase too much. Further, the fluidity at low temperatures becomes insufficient, and there is a possibility that abnormal noise is generated when the rolling device is started at a low temperature. Further, if the kinematic viscosity is less than 20 mm ² / s, it is not appropriate from the viewpoint of evaporation loss and lubricity. That is, if the viscosity of the base oil is too low, it becomes difficult to form a lubricating oil film sufficient to avoid metal contact between the raceway surface and the rolling element at high temperatures, for example, during rotation of the bearing. Therefore, it is preferable that the kinematic viscosity at 40 ° C. of both base oils is 30 to 400 mm ² / s from the viewpoint of the balance of torque of the rolling device, fluidity at low temperature, evaporation loss and lubricity.

  Moreover, it is preferable that the penetration degree of the grease composition of this invention is 220-385. If the penetration is less than 220, the grease composition is too hard and the torque performance of the rolling device tends to be reduced. Moreover, if it exceeds 385, the amount of leakage from the rolling device will increase.

  The rolling device of the present invention is characterized in that the above grease composition is enclosed.

  According to the present invention, a grease composition having excellent heat resistance and lubricity can be provided. In addition, a rolling device having a long life even at high temperatures can be provided.

  The grease composition of the present invention contains a first thickener and a second thickener in the base oil. The base oil includes ester synthetic oil and perfluoropolyether oil.

Hereinafter, the grease composition of the present invention will be described in detail.
<First thickener (diurea compound)>
In the present invention, the diurea compound used as the first thickener is represented by the following general formula (I).

In the above formula (I), R ₂ is an aromatic hydrocarbon group having 6 to 15 carbon atoms, and R ₁ and R ₃ are linear or branched, preferably straight, having 6 to 20 carbon atoms. It is a chained aliphatic hydrocarbon group. When the carbon number of these hydrocarbon groups is smaller than the lower limit, the thickener is difficult to disperse in the base oil and the thickener and the base oil tend to be separated. On the other hand, when the carbon number of the hydrocarbon group is larger than the upper limit, it tends to be difficult to produce industrially. R ₁ and R ₃ may be the same or different.

The diurea compound represented by the general formula (I) can be produced by a known method. For example, in the base oil, R ₁ and 1 mol of diisocyanate containing R ₂ in the skeleton thereof can be produced. It can be obtained by reacting monoamines containing R ₃ in the skeleton in a ratio of about 2 mol in total. Such diurea compounds are also commercially available.

As the diisocyanate containing R ₂ in the skeleton, for example, diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, biphenylene diisocyanate, dimethyldiphenylene diisocyanate, or an alkyl-substituted product thereof is preferably used.

Examples of monoamines containing R ₁ or R ₃ in the skeleton include hexylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, hepta Aliphatic amines such as decylamine, octadecylamine, nonadecylamine, and eicosylamine can be used.
<Second thickener (fluororesin)>
The type of fluororesin used as the second thickener is not particularly limited. For example, polytetrafluoroethylene (PTFE), or other tetrafluoroethylene and all or a part thereof are fluorinated. A copolymer with an ethylenically unsaturated hydrocarbon monomer (hereinafter referred to as “tetrafluoroethylene copolymer”) is preferred.

Examples of the tetrafluoroethylene copolymer include the following (1) to (4).
(1) Vinylidene fluoride; hexafluoroisobutene; chlorotrifluoroethylene; one or more comonomers of perfluoroalkylethylenes such as perfluoropropene are 0.01 to 3 mol%, preferably 0.05 to Modified polytetrafluoroethylene copolymerized by 0.5 mol%.
(2) TFE heat obtained by copolymerizing at least one perfluoroalkyl vinyl ether (perfluoroalkyl group having 1 to 6 carbon atoms) with tetrafluoroethylene (TFE) in an amount of 0.5 to 8 mol%. Plastic copolymer.

Specific examples include a copolymer of perfluoropropyl vinyl ether and TFE, a copolymer of perfluoromethyl vinyl ether and TFE, a copolymer of perfluoroethyl vinyl ether and TFE, and the like.
(3) A TFE thermoplastic copolymer obtained by copolymerizing 2 to 20 mol% of a perfluoroolefin having 3 to 8 carbon atoms.

The copolymer may be copolymerized with another comonomer having a perfluorovinyl ether structure as long as it is less than 5 mol%.
(4) TFE obtained by copolymerizing 0.5 to 13 mol% of perfluoromethyl vinyl ether and one or more (0.05 to 5 mol%) of fluorinated monomers of the following formulas (II) to (IV) Thermoplastic copolymer.

However, in formula (II) and formula (III), RF is at least one of the following (i) to (iii).
(I) a perfluoroalkyl group containing 2 to 12 carbon atoms (ii) a group having a chemical structure represented by the following formula (V). However, in Formula (V), r is an integer of 1-4 and r 'is an integer of 0-3.

(Iii) A group having a chemical structure represented by the following formula (VI). However, in the formula (VI), the structural units (OCFX) and (OCF ₂ -CFY) are statistically distributed along the chain. T is a perfluoroalkyl group containing 1 to 3 carbon atoms, and optionally has one H or Cl. X and Y are F groups or CF ₃ groups. Z is — (CFX) — or — (CF ₂ CFY) —, and q and q ′ may be integers of 0 to 10 and may be the same or different from each other.

  Here, the number average molecular weight of the fluorine compound monomer represented by the formula (II) and the formula (III) is 200 to 2000.

In the formula (IV), R ₄ is a perfluoroalkyl group having 1 to 5 carbons, and CF ₃ is preferable. X ₁ and X ₂ are each independently a perfluoroalkyl group or F group having 1 to 3 carbons, and among these, a CF ₃ group is preferred.

In addition, in (1) to (4), suitable numerical ranges for the numerical value in the molecular formula, copolymerization, and average molecular weight are limited, but when these numerical values are less than the lower limit of the above range, The tetrafluoroethylene copolymer is not imparted with sufficient thickening properties to form a grease. When the upper limit of the above range is exceeded, it is difficult for the grease composition to harden and exhibit sufficient lubricity.
<Other thickeners>
The present invention includes, as a thickener component, a diurea compound as a first thickener and a fluororesin as a second thickener, but other thickeners are used as long as the effects of the present invention are not hindered. It may be included in the grease composition. A conventionally well-known thing is used as such a thickener.
<Base oil>
As the base oil used in the present invention, a base oil containing an ester-based synthetic oil and / or a perfluoropolyether oil is preferably used.

  Although it does not specifically limit as ester system synthetic oil, For example, Diesters, such as di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate; Trimethylol propane caprylate, pentaerythritol-2-ethyl Examples include polyol esters such as hexanoate; aromatic ester oils such as trimellitic acid ester, trioctyl trimellitate, tridecyl trimellitate, and tetraoctyl pyromellitate. Among these, aromatic ester oil is preferable from the viewpoint of thermal oxidation stability.

The kinematic viscosity of the ester synthetic oil is 20 to 500 mm ² / s at 40 ° C., preferably 30 to 400 mm ² / s. When the base oil kinematic viscosity is in the above range, it tends to be excellent in lubrication characteristics, evaporation characteristics and low temperature fluidity.

  Although it does not specifically limit as perfluoropolyether oil, For example, it is preferable that it is comprised including the at least 1 sort (s) of fluorooxyalkylene structural unit selected from the group as shown below, for example.

Group of fluorooxyalkylene structural units: (CF ₂ CF ₂ O), (CF ₂ O), (CF ₂ CF (CF ₃ ) O), (CF (CF ₃ ) O), (CF ₂ CF ₂ CF ₂ O ), (CF ₂ CF (OX ₃ ) O) and (CF (OX ₃ ) O)
In the above formula, X ₃ is — (CF ₂ ) _n F ₃ , where n is an integer of 0 to 4.

When the perfluoropolyether oil is composed of two or more of the fluorooxyalkylene structural units shown in the above group, each structural unit is statistically distributed along the chain. Further, the terminal _{group, -CF 3, -C 2 F 5} , -C 3 F 7, ClCF 2 CF (CF 3) -, CF 3 CFClCF 2 -, ClCF 2 CF 2 -, ClCF 3 -, - CF A fluoroalkyl group optionally having one H and / or Cl, such as ₂ H, —CF (CF ₃ ) H, and the like.

From the viewpoint of avoiding abnormal noise at low temperature startup due to low temperature fluidity and seizure that occurs because an oil film is not easily formed at high temperature, the kinematic viscosity at 40 ° C. of perfluoropolyether oil is 20 to 500 mm ² / s, preferably 30 to 400 mm ² / s.

As long as the object of the present invention can be achieved, as the base oil of the present invention, in addition to the ester synthetic oil and perfluoropolyether oil, for example, mineral oil, highly refined mineral oil, synthetic hydrocarbon oil, phenyl ether synthetic Conventional base oils such as oil and silicone-based synthetic oil may be included. Such other base oil is not particularly limited, but is preferably 30% by weight or less of the total base oil from the viewpoint of thermal oxidation stability.
<Additives>
The grease composition of the present invention may be mixed with various additives as desired in order to further improve various performances.

  As such an additive, an additive usually added to a grease composition can be used, and is not particularly limited. For example, an antioxidant, a rust inhibitor, an extreme pressure agent, an oil agent, a metal Examples thereof include an inactivating agent.

  As the antioxidant, a commonly used antioxidant can be used, for example, an amine-based antioxidant such as phenyl-1-naphthylamine, or a phenol-based antioxidant such as 2,6-di-tert-dibutylphenol. Other antioxidants such as oxidants, sulfur-based antioxidants and zinc dithiophosphate can be used.

  Examples of the rust preventive include organic sulfonates such as alkali metals and alkaline earth metals, alkyl succinic acid derivatives such as alkyl succinic acid esters, alkenyl succinic acid derivatives such as alkenyl succinic acid esters, and sorbitan monooleate. A partial ester of a polyhydric alcohol can be used.

  As the extreme pressure agent, for example, a phosphorus-based extreme pressure agent, zinc dithiophosphate, organic molybdenum and the like can be used.

  As the oily agent, for example, oily improvers such as fatty acids and animal and vegetable oils can be used.

  As the metal deactivator, for example, benzotriazole can be used.

Such additives may be used alone or in admixture of two or more. Moreover, the addition amount of these additives will not be specifically limited if it is a grade which does not impair the objective of this invention.
<Method for producing grease composition>
The method for producing the grease composition of the present invention is not particularly limited. For example, a diurea grease containing an ester synthetic oil as a base oil and a urea compound as a thickener, and a perfluoropolyether oil as a base oil. And a fluorine grease containing a fluororesin as a thickener may be separately manufactured and mixed.

  Or you may manufacture by adding a diurea compound and a fluororesin as a thickener to the base oil which mixed ester synthetic oil and perfluoropolyether oil.

Although the grease composition of the present invention is not limited by its use, it has excellent heat resistance and lubricity, so it can be used at high temperature and high speed for automobile electrical parts such as alternators and electromagnetic clutches, automobiles such as idler pulleys, etc. It can be suitably used for rotating parts and sliding parts of equipment used under conditions. Specifically, it is suitably used for, for example, a rolling bearing, particularly a rolling bearing of an embodiment described later.
<Rolling device>
Next, the rolling device of the present invention will be described in detail.

  The rolling device of the present invention is one in which the above-described grease composition is enclosed. Since the rolling device of the present invention has such a configuration, it has a long life even at high temperatures. Although it does not restrict | limit especially as a sealing location of the said grease composition in the rolling device of this invention, It is predetermined locations, such as a lubrication location, such as a rotation part or a sliding part used under high temperature high speed conditions.

  As the rolling device of the present invention, a ball bearing shown in FIG. As shown in FIG. 1, the ball bearing 1 of the present embodiment includes a plurality of balls 13 that are rotatably disposed between an inner ring 10 and an outer ring 11, a cage 12 that holds the plurality of balls, And a contact-type seal 14 attached to the outer ring 11. A bearing space surrounded by the inner ring 10, the outer ring 11, and the seals 14 and 14 is filled with the grease composition G and sealed in the ball bearing 1 by the seals 14 and 14. The grease composition G lubricates the contact surfaces between the raceway surfaces of the wheels 10 and 11 and the balls 13.

  In this example, a deep groove ball bearing is used as the rolling device. However, the rolling device is not limited to this and may be another rolling bearing. Examples of such rolling bearings include radial ball bearings, self-aligning ball bearings, cylindrical roller bearings, tapered roller bearings, needle roller bearings, self-aligning roller bearings, and the like, and thrust ball bearings. And thrust type rolling bearings such as thrust roller bearings.

The rolling device of the present invention is not limited to a rolling bearing, and may be other types of rolling devices such as a ball screw, a linear guide device, and a linear motion bearing.
[Example]
EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples at all.

The main compositions of the grease compositions used in Examples 1 to 10 and Comparative Examples 1 to 5 are as shown in Tables 1 to 3, and the grease compositions of Examples 1 to 10 are diurea compounds (aliphatic diureas). ) And a fluororesin (PTFE or copolymer) and a base oil (B) consisting of an ester synthetic oil and a perfluoropolyether oil (PFPE oil). As other additives, 1.0% by weight of an amine-based antioxidant (trade name: VANLUBE 81, manufactured by Ciba Special Chemicals Co., Ltd.), 0.5% by weight of Ca sulfonate, 0% of the entire grease composition, 0.05 wt% of a benzotriazole metal deactivator (trade name: benzotriazole, manufactured by Johoku Chemical Co., Ltd.).
[Examples 1 to 10 and Comparative Examples 1 to 5]
The grease compositions shown in Tables 1 to 3 were subjected to a rust prevention test and a seizure test according to the following test methods.

The mixing penetration was measured according to JIS K2220.
<Rust prevention test>
The grease compositions of Examples 1 to 10 and Comparative Examples 1 to 5 account for 50% of the bearing space volume in a deep groove ball bearing with contact rubber seal (see FIG. 1) having an inner diameter of 17 mm, an outer diameter of 47 mm, and a width of 14 mm. Filled.

After running-in (rotating) for 30 seconds at a rotational speed of 1800 min-1, 0.5 ml of 0.5 wt% salt water was injected into the bearing, and running-in was performed again for 30 seconds at a rotational speed of 1800 min-1. Next, the ball bearing was left for 48 hours in a constant temperature and humidity chamber adjusted to 80 ° C. and 100% RH, and then the ball bearing was disassembled and the rust generated on the raceway surface was observed with the naked eye. The results were evaluated as follows.
Criteria for evaluating rust prevention # 7: No rust generation # 6: There is fine spot-like rust # 5: There is spot-like rust with a diameter of 0.3 mm or less # 4: With rust with a diameter of 1.0 mm or less # 3: Rust with a diameter of 5.0 mm or less # 2: Rust with a diameter of 10.0 mm or less # 1: Rust is generated on almost the entire raceway surface Note that # 7 to # 5 have good antirust properties, and # 4 to # 1 The rust resistance is poor.

The results are shown in Tables 1-3. The grease compositions of Examples 1 to 10 showed good rust prevention properties. Therefore, the grease compositions of Examples 1 to 10 can be suitably used for bearings that are used in harsh environments that easily come into contact with rainwater or the like and easily generate rust. On the other hand, as shown in Comparative Example 1, the conventional fluorine grease (grease composition) had poor rust prevention properties.
<Seizure test>
Filled with an iron shield deep groove ball bearing (see FIG. 1) having an inner diameter of 8 mm, an outer diameter of 22 mm, and a width of 7 mm with the grease compositions of Examples 1 to 10 and Comparative Examples 1 to 5 so as to occupy 50% of the bearing space. did. This ball bearing was mounted on a testing machine similar to the ASTM D1741 bearing life testing machine as shown in FIG.

  It was rotated at a rotational speed of 3000 min −1 under conditions of a bearing temperature of 180 ° C. and an axial load of 59 N, and the time until seizure occurred and the temperature of the outer ring rose to 190 ° C. or higher was defined as the lifetime. And even if it rotated for 3000 hours, when it did not raise to 190 degreeC or more, the test was stopped. Other conditions conformed to ASTM D1741.

  This rotation test was performed four times for one type of bearing, and the average value was used as a test result. Relative comparison was made with the baking time when the grease composition of Comparative Example 3 was used as the reference (1.0).

  The results are shown in Tables 1-3. The grease compositions of Examples 1 to 10 showed good baking life, whereas Comparative Examples 1 and 2 did not have the first thickener component as the first thickener component. The seizure property at high temperature was inferior. Moreover, since the comparative example 3 does not contain the 1st base oil component, since the comparative example 4 does not contain the 2nd base oil component, the seizure property in high temperature was inadequate.

FIG. 1 is a longitudinal sectional view showing a structure of a ball bearing which is an embodiment of a rolling device according to the present invention. FIG. 2 is a cross-sectional view showing the configuration of a bearing life tester for evaluating the lubrication life of the grease composition.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Ball bearing, 10 ... Inner ring, 11 ... Outer ring, 12 ... Cage, 13 ... Ball, 14 ... Seal, G ... Grease composition

Claims (6)

The base oil contains a first thickener and a second thickener,
The first thickener is represented by the following formula (I):
A grease composition, wherein the second thickener is a fluororesin, and the base oil comprises an ester synthetic oil and a perfluoropolyether oil.   2. The grease composition according to claim 1, comprising 30 to 80% by weight of the diurea compound and 70 to 20% by weight of the fluororesin with respect to the total amount of the thickener.   The base oil contains 30 to 80% by weight of ester synthetic oil and 70 to 20% by weight of perfluoropolyether oil based on the total amount of base oil. Grease composition.   The total amount of said 1st thickener and said 2nd thickener is 5 to 40 weight% of the said whole grease composition, The grease composition in any one of Claims 1-3 characterized by the above-mentioned. . The kinematic viscosity at 40 ° C of the ester synthetic oil is 20 to 500 mm ² / s, and the kinematic viscosity at 40 ° C of the perfluoropolyether oil is 20 to 500 mm ² / s. The grease composition in any one of -4. A rolling device in which the grease composition according to any one of claims 1 to 5 is enclosed.