阅读说明：本技术 树脂润滑用润滑脂组合物和树脂滑动部件 (Grease composition for resin lubrication and resin sliding member ) 是由 浅井佑介 山本大贵 北岛啄也 纲基次郎 于 2019-06-12 设计创作，主要内容包括：本发明提供对树脂滑动面的附着性和润滑特性优异的润滑脂组合物、以及使用该润滑脂组合物而抑制了摩擦·磨损、实现长寿命化的树脂滑动部件。一种树脂润滑用润滑脂组合物(G)以及具有使用了该润滑脂组合物(G)的树脂制的滑动面的树脂滑动部件(滑动开关101),该树脂润滑用润滑脂组合物(G)含有作为基础油的氟系基础油和合成烃油、作为增稠剂的氟系增稠剂和锂皂增稠剂或锂复合皂增稠剂、作为添加剂的极压添加剂。(The invention provides a grease composition having excellent adhesion to a resin sliding surface and excellent lubricating properties, and a resin sliding member using the grease composition, wherein friction and wear are suppressed, and a long life is achieved. A grease composition (G) for resin lubrication, which contains a fluorine-based base oil and a synthetic hydrocarbon oil as base oils, a fluorine-based thickener and a lithium soap thickener or a lithium complex soap thickener as thickeners, and an extreme pressure additive as additives, and a resin sliding member (sliding switch 101) having a resin sliding surface using the grease composition (G).)

1. A grease composition for resin lubrication, which is used for a resin sliding surface, comprising:

a fluorine-based base oil and a synthetic hydrocarbon oil,

Fluorine-based thickener and lithium soap thickener or lithium complex soap thickener, and

an extreme-pressure additive, which is a mixture of an extreme-pressure additive,

and the kinematic viscosity of the synthetic hydrocarbon oil at 40 ℃ is 30-220 mm ²/s。

2. The grease composition for resin lubrication according to claim 1, wherein the extreme pressure additive is at least one selected from a phosphorus-based additive and a polyester-based additive.

3. The grease composition for resin lubrication according to claim 1 or 2, wherein the working penetration of the grease composition for resin lubrication is 265 to 340.

4. A resin sliding member having a sliding surface made of a resin using the grease composition for resin lubrication according to any one of claims 1 to 3.

5. The resin slide member according to claim 4, wherein the resin slide member is a slide switch.

6. The resin slide member according to claim 4, wherein the resin slide member is a gear device.

Technical Field

The present invention relates to a grease composition for resin lubrication and a resin sliding member.

Background

Patent document 1 proposes a slide switch (resin slide member) in which water resistance is improved.

Disclosure of Invention

In an environment where contact with water is easy, if a sliding member having a sliding surface made of resin (hereinafter referred to as a resin sliding surface) is used, the grease composition applied to the sliding surface tends to be easily removed from the sliding surface.

Removal of the grease composition from the resin sliding surface may cause a rapid increase in frictional force on the sliding surface, an increase in the amount of wear, and a reduction in the life of a product having the resin sliding surface.

Therefore, there is a need for a grease that can prevent friction and wear from being removed from a sliding surface even when a resin sliding member is used in an environment in which the grease is likely to come into contact with water, for example, in an environment in water.

The present invention has been made in view of such circumstances, and an object thereof is to provide a grease composition which is excellent in adhesion to a resin sliding surface particularly in an environment where the grease is likely to contact water and which is excellent in lubricity of the grease itself, and to provide a resin sliding member which can suppress friction and wear and which can achieve a long life of the product by using the grease composition.

The present inventors have conducted intensive studies to achieve the above object and as a result, have found that a grease composition having excellent adhesion and excellent lubricating properties can be obtained by blending a fluorine-based base oil and a synthetic hydrocarbon oil as base oils, a fluorine-based thickener and a lithium soap thickener or a lithium complex soap thickener as thickeners, and further blending an extreme pressure additive, and have completed the present invention.

That is, one embodiment of the present invention relates to a grease composition for resin lubrication, which contains a fluorine-based base oil as a base oil and a synthetic hydrocarbon oil, and a fluorine-based thickenerThickener, lithium soap thickener or lithium complex soap thickener, and extreme pressure additive as additive, wherein the synthetic hydrocarbon oil has a kinematic viscosity at 40 deg.C of 30-220 mm ²/s。

In a preferred embodiment of the present invention, the extreme pressure additive is preferably at least one selected from the group consisting of phosphorus additives and polyester additives.

The working penetration of the grease composition for resin lubrication is preferably 265 to 340.

The present invention also relates to a resin sliding member having a resin sliding surface using the grease composition for resin lubrication.

Among them, as a preferable embodiment of the present invention, the resin sliding member is a slide switch or a gear device.

According to the present invention, the grease composition for resin lubrication having the above-described configuration has improved adhesion to the use site (sliding surface) thereof, and is provided with excellent lubricating properties. Therefore, when the grease composition for resin lubrication of the present invention is used for a resin sliding member, removal of grease from the sliding surface of the resin sliding member can be suppressed, excellent lubrication characteristics of the grease itself can be maintained, friction and wear of the sliding surface can be suppressed, and the life of the resin sliding member can be extended.

Drawings

Fig. 1 is a schematic diagram illustrating a configuration of one embodiment of a slide member (slide switch) according to the present invention, in which fig. 1 (a) shows a sectional view of the slide switch when viewed from the front (switch off), and fig. 1 (b) shows a sectional view of the slide switch when viewed from the front (switch on).

Fig. 2 is a schematic diagram illustrating a configuration of one embodiment (multistage gear device) of the sliding member according to the present invention, in which fig. 2 (a) shows a front view of the multistage gear device, and fig. 2 (b) shows a side view (including a partial cross section) of the multistage gear device.

FIG. 3 is a schematic view of an apparatus used in the frictional wear test conducted in the examples.

FIG. 4 is a schematic representation of the rheometer apparatus used in the viscometry tests performed in the examples.

FIG. 5 shows the behavior of the displacement of the friction coefficient observed in the frictional wear test for the grease compositions of example 2 and comparative example 3 (example 2: FIG. 5 (a), comparative example 3: FIG. 5 (b)).

FIG. 6 shows the viscosity values (Pa · s) of the grease compositions measured with respect to the kinematic viscosity value at 40 ℃ of the synthetic hydrocarbon oil (poly α olefin) used in the grease compositions of examples 1 to 4 and comparative examples 8 and 9.

FIG. 7 shows the friction coefficient values of the grease compositions measured with respect to the kinematic viscosity value at 40 ℃ of the synthetic hydrocarbon oil (poly α olefin) used in the grease compositions of examples 1 to 4 and comparative examples 8 and 9.

FIG. 8 shows the friction coefficient values against the measured viscosity values (Pa · s) in the grease compositions of examples 1 to 8 and comparative examples 1 to 11.

Description of the symbols

101 … slide switch, 102 … case, 103 … cover, 104 … first waterproof film, 105 … second waterproof film, 106 … first fixed contact, 107 … second fixed contact, 108 … third fixed contact, 109 … movable contact, 110 … slider, 110a … convex portion, 113 … contact operating portion, 114 … ratchet spring, 114a … convex portion 201 … multistage resin gear device, 202 … first stage gear, 203 … second stage gear, shaft of 204 … second stage gear, 204a … bearing portion (grease coating portion), 205 … third stage gear, shaft of 206 … third stage gear, 206a … bearing portion (grease coating portion), engaging portion of X … first stage gear and second stage gear, engaging portion of Y … second stage gear and third stage gear, 36211 motor output shaft, 212 a … actuator output shaft, 36211 motor output shaft

Detailed Description

As described above, there is a problem that the grease is likely to peel off from the coated surface in an environment in which the grease is in contact with water, for example, an environment in which condensation is likely to occur in water (hereinafter, collectively referred to as a water contact environment). For example, in view of the possibility that the slide switch disclosed in patent document 1 is used in a water-contact environment, a waterproof sheet made of resin is provided to improve the waterproof property, and the slide switch is opened and closed via the waterproof sheet as described below. In this case, grease is used to improve the lubricity between the waterproof sheet and the slider or the lubricity between the slider and another contact surface. However, if the adhesion of the grease is insufficient, the grease is removed during the use of the switch (the execution of opening and closing), which may increase the frictional force between the slider and the waterproof sheet, cause abrasion and damage of the waterproof sheet, and consequently shorten the life of the slide switch.

Even if the sliding member other than the above-described slide switch is used in a water contact environment, the grease is peeled off from the sliding surface, and the friction force on the sliding surface is increased, which may cause an increase in the amount of wear and damage to the sliding member.

In order to solve such problems, the present inventors have studied a grease composition having excellent adhesion to a sliding surface made of a resin, and as a result, have found that by blending a grease containing a fluorine-based base oil and a synthetic hydrocarbon oil as base oils, a fluorine-based thickener and a lithium soap thickener or a lithium complex soap thickener as thickeners, and an extreme pressure additive, the adhesion of the grease particularly in an environment in which water contacts can be improved, and the grease composition has excellent lubricating properties.

The grease composition for resin lubrication according to the present invention is characterized by being compounded by combining a specific base oil, a specific thickener and an extreme pressure additive as described below. The following description will be specifically made.

[ resin sliding parts ]

The resin sliding member to which the grease composition for resin lubrication according to the present invention can be applied is not particularly limited, and examples thereof include a slide switch, a gear device, and a bearing.

The resin sliding member to be the object of the present invention is not particularly limited as long as it is a sliding member at least a part of which has a sliding surface made of resin. Therefore, the present invention is also intended to include various sliding members in addition to the slide switch, the gear device, and the bearing described above.

The resin sliding member of the present invention has a resin sliding surface using a grease composition for resin lubrication (described later) (a resin sliding surface at least partially covered with the grease composition for resin lubrication by being coated or sealed in contact with the grease composition).

Preferred embodiments of the resin sliding member will be described below in detail with reference to the drawings, but the present invention is not limited to the embodiments below.

[ slide switch ]

A slide switch 101 of a preferred embodiment of the present invention is shown in a cross section viewed from the front in fig. 1.

In one example shown in fig. 1, a slide switch 101 is provided with: the electronic device includes a case 102, a cover 103, a first waterproof film 104, a second waterproof film 105, a first fixed contact 106, a second fixed contact 107, a third fixed contact 108, a movable contact 109, a slider 110, a contact operating portion 113, and a click spring (click spring) 114.

As shown in fig. 1, the case 102 and the cover 103 are combined to constitute an outer case. The case 102 is made of an insulating material, and the cover 103 is made of a metal such as stainless steel. The cover 103 may be made of an insulating material.

As described below, the first waterproof film 104 and the second waterproof film 105 are provided to improve the waterproof property of the slide switch 101, and as shown in fig. 1, the first waterproof film 104 is attached to the outer surface of the housing 102, and the second waterproof film 205 is attached to the inside of the housing 102.

The first fixed contact 106, the second fixed contact 107, and the third fixed contact 108 are fixed to the housing 102 between the first waterproof film 104 and the second waterproof film 105. The first fixed contact 106, the second fixed contact 107, and the third fixed contact 108 are electrically insulated from each other by being separated from each other through the housing 102, and are formed of an electrically conductive material. Although not shown, the end of the first fixed contact 106, the end of the second fixed contact 107, and the end of the third fixed contact 108 are exposed at the bottom of the housing 102, and are used as connection terminals for connecting to an external circuit.

Movable contact 109 is made of a conductive material. As shown in fig. 1, the movable contact 109 is displaceable between a separated position (on position, fig. 1 (a)) where it is separated from the first fixed contact 106 and the second fixed contact 107, and a contact position (off position, fig. 1 (b)) where it is in contact with the first fixed contact 106 and the second fixed contact 107. The movable contact 109 is formed of an elastic member configured to be at a separated position in a no-load state (fig. 1 (a)).

The slider 110 is formed of an insulating resin material. As shown in fig. 1 (a), the slider 110 is supported inside the housing 102. The slider 110 is movable in the longitudinal direction of the housing 102 between the off position and the on position (in fig. 1 (a), the range indicated by two arrows is the movable range of the slider 110).

The cover 103 includes a slide groove 103a extending in the longitudinal direction of the housing 102, and the slide groove 103a is configured to guide the movement of the slider 110 between the off position and the on position.

Further, the slider 110 is provided with a contact operating portion 113. The contact operating unit 113 is configured to displace the movable contact 109 from the separated position to the contact position via the second waterproof film 105 by moving the slider 110 from the off position to the on position.

Fig. 1 (b) shows a state in which the slider 110 is moved from the state shown in fig. 1 (a) to the on position along the slide groove 103 a. As the slider 110 moves, the contact operating portion 113 provided in the slider 110 displaces the movable contact 109 via the second waterproof film 105. When the movable contact 109 is in contact with the first fixed contact 106 and the second fixed contact 107, the first fixed contact 106 and the second fixed contact 107 are electrically connected via the movable contact 109.

When the conductive state between the first fixed contact 106 and the second fixed contact 107 is released, the above-described operation may be reversed. That is, the slider 110 is moved toward the off position along the slide groove 103a, and the movable contact 109 is released from being pressed by the contact operating portion 113. Movable contact 109 returns to the separated position by its own elastic restoring force. That is, the contact state of the movable contact 109, the first fixed contact 106, and the second fixed contact 107 is released.

According to the above configuration, the first fixed contact 106, the second fixed contact 107, and the movable contact 109 are disposed between the first waterproof film 104 and the second waterproof film 105, and contact or separation between the first waterproof film 104 and the second waterproof film 105 is performed through the second waterproof film 105 by the contact operating portion 113 provided in the slider 110. Moisture can enter the housing 102 from the outside through the opening of the slide groove 103 a.

The slide switch 101 includes a pair of ratchet springs 114 (elastic members). Each ratchet spring 114 includes a convex portion 114 a. On the other hand, the slider 110 includes a pair of convex portions 110 a.

As described above, when the slider 110 moves between the off position and the on position, the convex portions 110a of the slider 110 elastically deform the opposed ratchet springs 114 and displace the convex portions 114a of the ratchet springs 114 in the short side direction (the direction perpendicular to the paper surface of fig. 1) of the housing 102. When the respective convex portions 110a of the slider 110 pass through the convex portions 114a of the ratchet spring 114 facing each other, the elastic restoring force of the ratchet spring 114 assists the slider 110 in moving to the on position or the off position, and gives a switch click feeling.

In the slide switch 101, the second waterproof film is formed of, for example, a polyamide resin such as nylon or a polyphthalamide (PPA) resin material. The slider 110 may be made of an insulating resin material such as Polyamide (PA), polyphenylene sulfide (PPS), or polyphthalamide (PPA).

In the slide switch 101 of the present embodiment, the grease composition G for resin lubrication according to the present invention is applied to each of the contact point operation portion 113 of the slider 110 at the contact position where it contacts the second waterproof film 105 (the lower portion of the slider 110 is a resin sliding surface) and each of the convex portions 110a (resin sliding surfaces) of the slider 110. That is, the grease composition G for resin lubrication is applied to the resin sliding surface of the slide switch 101. The slide switch 101 uses the grease composition G which is excellent in adhesion to a resin sliding surface described later and also excellent in lubricity of the grease itself even in an environment where water enters the housing 102 from the sliding groove 103 a. Therefore, the slide switch 101 can suppress friction and wear, and can have a long life.

[ Gear device ]

As an example of the gear device according to the preferred embodiment of the present invention, a multistage gear device provided in an actuator will be described.

The "multistage gear device" using the grease composition for resin lubrication according to the present invention is a multistage gear device including at least one gear that is made of resin, and in the multistage gear device, the resin gear may be used in combination with a gear made of a material other than resin, such as a metal gear, or may be constituted only by the resin gear.

The grease composition for resin lubrication described later is applied to the bearing portion of the resin gear and the meshing portion between the resin gear and the gear made of resin or made of a material other than resin, respectively.

Fig. 2 is a schematic diagram of a multistage gear device 201 provided in an actuator, where fig. 2 (a) is a front view of the multistage gear device 201, and fig. 2 (b) is a side view (including a partial cross section) of the multistage gear device 201. Note that, in fig. 2 (b), the motor 211, its output shaft 211a, and the actuator output shaft 212 are also shown in addition to the multi-stage gear device 201.

The multistage gear device 201 shown in fig. 2 includes: a first stage gear 202 integrally rotatably mounted to an output shaft 211a of the motor 211, a second stage gear 203 meshed with the first stage gear 202, and a third stage gear 205 meshed with the second stage gear 203. Fig. 2 shows a shaft 204 of the second-stage gear 203, a shaft 206 of the third-stage gear 205, and an output shaft 212 of the actuator.

In the present embodiment, a grease composition for resin lubrication, which will be described later, is applied to the meshing portion X between the first-stage gear 202 and the second-stage gear 203, the meshing portion Y between the second-stage gear 203 and the third-stage gear 205, the bearing portion 204a of the second-stage gear 203, and the bearing portion 206a of the third-stage gear 205 in fig. 2.

In the above-described multistage gear device 201, the shafts constituting the device, that is, the shafts (204, 206) of the multistage gear device, the output shaft 202a of the motor, and the output shaft 212 of the actuator may be made of any of metal or resin, but may have the following configuration, for example.

For example, the output shaft 211a of the motor 211 is a metal rotary shaft. Since the output shaft 211a and the first stage gear 202 are fixed and the first stage gear 202 rotates together with the output shaft 211a, there is no bearing portion for relative rotation between the first stage gear 202 and the output shaft 211 a.

On the other hand, the shaft 204 of the second-stage gear 203 and the shaft 206 of the third-stage gear 205 are both made of resin and are fixed shafts. The second stage gear 203 and the third stage gear 205 rotate while sliding on the respective fixed shafts. Therefore, a grease composition for resin lubrication, which will be described later, is applied to the bearing portion 204a between the second-stage gear 203 and the shaft 204 (fixed shaft) of the second-stage gear, and the bearing portion 206a between the third-stage gear 205 and the shaft 206 (fixed shaft) of the third-stage gear, and the meshing portion X, Y between the gears is also applied

Further, examples of the resin that can be used as the resin component constituting the gear device (gear, shaft of gear) and the actuator (output shaft of motor, base member, exterior member (housing), output shaft of actuator, etc.) provided with the gear device include Polyethylene (PE), polypropylene (PP), ABS resin (ABS), Polyoxymethylene (POM), Polyamide (PA), Polycarbonate (PC), phenol resin (PF), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), Polyphenylene Sulfide (PPs), Polyether Sulfone (PEs), Polyimide (PI), polyether ether ketone (PEEK), and the like.

The gear device of the present embodiment is applicable to an actuator used in an in-vehicle air conditioning system or the like. In an air conditioning system for a vehicle, the air conditioning system is used in a wide range of-40 to 100 ℃, and when the air conditioning system is used in the above temperature cycle, dew condensation may occur inside the actuator, and water droplets may adhere to the tooth surface and the grease.

The gear device of the present embodiment is also applicable to an actuator used in, for example, automatic opening/closing devices for toilet seats and toilet covers. In an automatic opening/closing device such as a toilet seat, the actuator may be immersed in water during cleaning or the like.

Even in a gear device which is used in such an environment where it is likely to come into contact with water, friction and wear can be suppressed and the life of the product can be prolonged by using the grease composition for resin lubrication of the present invention.

[ grease composition for resin lubrication ]

The grease composition for resin lubrication of the present invention will be explained.

< base oil >

In the grease composition for resin lubrication according to the present embodiment, a fluorine-based base oil and a synthetic hydrocarbon oil are used as the base oil.

Examples of the fluorine-based base oil include a fluorine-based base oil containing perfluoropolyether (PFPE) as a main component. It should be noted that PFPE is of the general formula: RfO (CF) ₂O) _p(C ₂F ₄O) _q(C ₃F ₆O) _rAnd Rf (Rf: perfluoro lower alkyl, p, q, r: integer).

Perfluoropolyethers are roughly classified into linear type and side chain type, and the linear type has smaller temperature dependence of kinematic viscosity than the side chain type. This means that the linear type has a lower viscosity than the side chain type in a low temperature environment and a higher viscosity than the side chain type in a high temperature environment. For example, when the grease is used in a high-temperature environment, it is preferable that the viscosity in the high-temperature environment is high, that is, it is preferable to use a linear perfluoropolyether, from the viewpoint of suppressing the grease from flowing out from the use site and the grease from being depleted.

As the synthetic hydrocarbon oil, for example, poly α olefins (PAO) such as n-paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, and a co-oligomer of 1-decene and ethylene are preferable.

Further, the present inventors have studied the constitution for satisfying the optimum viscosity of the grease composition as an index of adhesion and the optimum friction coefficient value as an index of lubrication characteristics, and as a result, have found that the kinematic viscosity value of the synthetic hydrocarbon oil is an important factor in addition to the composition of the grease composition.

As an example, in a grease composition containing a specific base oil, a thickener and an extreme pressure additive, the kinematic viscosity value of a synthetic hydrocarbon oil (poly α olefin) at 40 ℃ is variously changed (18 to 300 mm) ²In/s), the results of the viscosity measurement test of the grease composition are shown in fig. 6, and the results of the friction wear test are shown in fig. 7.

As shown in fig. 6, it was confirmed that the following behavior was exhibited: the synthetic hydrocarbon oil in the grease composition has a kinematic viscosity at 40 ℃ of less than 50mm ²At s, the viscosity of the grease composition itself begins to drop sharply, below 30mm ²The viscosity at/s is less than 4 pas. In addition, as shown in fig. 7, it was confirmed that the following behavior was exhibited: the kinematic viscosity of the synthetic hydrocarbon oil at 40 ℃ is more than 100mm ²At s, the friction coefficient of the grease composition begins to rise sharply, exceeding 220mm ²The coefficient of friction at/s is greater than 0.1.

As shown by the results of FIGS. 6 and 7, it was confirmed that in the grease composition for resin lubrication containing a fluorine-based base oil and a synthetic hydrocarbon oil, a fluorine-based thickener, a lithium soap thickener, and an extreme pressure additive, the synthetic hydrocarbon oil was allowed to have a kinematic viscosity at 40 ℃ of 30 to 220mm ²At/s, both the viscometric test (adhesion) and the frictional wear test (lubrication characteristics) are excellent. In fig. 6 and 7, the range indicated by an arrow parallel to the horizontal axis (kinematic viscosity) indicates the range of kinematic viscosity at 40 ℃ of the synthetic hydrocarbon oil in which good characteristics were obtained in both the viscosity measurement test and the frictional wear test.

Fig. 8 shows that, among the grease compositions prepared in examples and comparative examples described later, the grease compositions located in the optimum region (viscosity of 4.0Pa · s or more and friction coefficient of 0.1 or less) in fig. 8 are grease compositions having good properties in both the viscosity measurement test and the frictional wear test, with respect to the friction coefficient value with respect to the measured viscosity value (Pa · s).

As shown by the above results, in the grease composition for resin lubrication of the present invention, the kinematic viscosity of the synthetic hydrocarbon oil at 40 ℃ is preferably 30 to 220mm ²(ii) a range of/s. Wherein the kinematic viscosity at 40 ℃ is preferably 50-200mm ²The most preferable range is 50 to 100mm ²Synthetic hydrocarbon oils in the s range.

The blending ratio of the fluorine-based base oil and the synthetic hydrocarbon oil is not particularly limited, and for example, the ratio of the fluorine-based base oil to the synthetic hydrocarbon oil is, relative to 100 mass% of the total amount of the base oils: 95-5 mass% of synthetic hydrocarbon oil: 5 to 95% by mass, for example, a fluorine-based base oil: the synthetic hydrocarbon oil accounts for 90-10 mass%: 10 to 90% by mass, preferably a fluorine-based base oil: 80-20 mass% of synthetic hydrocarbon oil: 20 to 80% by mass, particularly preferably a fluorine-based base oil: 75-22% by mass of a synthetic hydrocarbon oil: 78 to 25 mass% and the like.

The total amount of the base oil including the fluorine-based base oil and the synthetic hydrocarbon oil may be 70 to 90% by mass, for example, 75 to 95% by mass or 80 to 85% by mass, based on the total amount of the grease composition of the present invention.

< thickening agent >

In the grease composition of the present invention, a fluorine-based thickener and a lithium soap thickener or a lithium complex soap thickener are added as thickeners.

Among these, the fluorine-based thickener is preferably contained in an amount of 1 to 20% by mass, for example, 5 to 15% by mass, and the lithium soap thickener or lithium complex soap thickener is preferably contained in an amount of 1 to 15% by mass, for example, 3 to 9% by mass, based on the total amount of the grease composition.

The total amount of the fluorine-based thickener and the lithium soap thickener or lithium complex soap thickener (total amount of thickeners) is preferably 2 to 35% by mass, for example, 5 to 30% by mass, preferably 10 to 30% by mass, and particularly preferably 10 to 20% by mass, based on the total amount of the grease composition for resin lubrication.

< fluorine-based thickener >

As the fluorine-based thickener, fluororesin particles are preferable, and particles of Polytetrafluoroethylene (PTFE), for example, are preferably used. PTFE is a polymer of tetrafluoroethylene and is represented by the general formula: [ C ] ₂F ₄] _n(n: degree of polymerization).

Examples of the fluorine-based thickener that can be used include perfluoroethylene propylene copolymer (FEP), ethylene tetrafluoroethylene copolymer (ETFE), and tetrafluoroethylene perfluoroalkylvinyl ether copolymer (PFA).

The size of the PTFE particles is not particularly limited, and for example, polytetrafluoroethylene having an average particle diameter of 0.1 to 100 μm can be used. The shape of the PTFE particles is not particularly limited, and may be spherical, polyhedral, needle-like, or the like.

The fluorine-based thickener is used in an amount of 1 to 20% by mass, preferably 5 to 15% by mass, based on the total amount of the grease composition.

< lithium soap thickener lithium complex soap thickener >

In the present invention, a lithium soap thickener is used in addition to the fluorine-based thickener.

As the lithium soap thickener, a lithium salt of an aliphatic monocarboxylic acid can be used.

The aliphatic carboxylic acid may be any of straight chain, branched chain, saturated and unsaturated, and generally, a fatty acid having about 2 to 30 carbon atoms, for example, 12 to 24 carbon atoms can be used.

Specific examples thereof include saturated fatty acids such as butyric acid, caproic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, and the like; unsaturated fatty acids such as oleic acid, linoleic acid, linolenic acid, and ricinoleic acid (ricinoleic acid).

Among them, as the lithium soap thickener, a lithium salt of stearic acid, lauric acid, ricinoleic acid, or a lithium salt of a compound in which the acid is substituted with a hydroxyl group is given as a representative example.

In the present invention, a lithium complex soap thickener may be used instead of the lithium soap thickener.

The lithium complex soap thickener is improved in heat resistance to be higher than that of the lithium soap thickener by combining a higher fatty acid with a dibasic acid, an inorganic acid (boric acid, etc.), or the like.

The lithium complex soap thickener can be obtained, for example, by reacting lithium hydroxide with an aliphatic monocarboxylic acid having about 12 to 24 carbon atoms and an aliphatic dicarboxylic acid having about 2 to 12 carbon atoms, each of which contains at least one hydroxyl group.

Examples of the aliphatic monocarboxylic acid having 12 to 24 carbon atoms and containing at least one hydroxyl group include hydroxylauric acid, hydroxypalmitic acid, hydroxystearic acid, hydroxyoleic acid, hydroxyarachidic acid, hydroxybehenic acid, and hydroxytetracosanoic acid.

Examples of the aliphatic dicarboxylic acid having 2 to 12 carbon atoms include oxalic acid, malonic acid, succinic acid, methylsuccinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, nonamethylenedicarboxylic acid, decamethylenedicarboxylic acid, and the like.

These monocarboxylic acids and dicarboxylic acids may be used alone or in combination of 2 or more.

Among these, as a typical example of the lithium complex soap thickener, a thickener obtained by reacting lithium hydroxide with hydroxystearic acid and azelaic acid in combination is given.

The lithium soap thickener or lithium complex soap thickener is used in an amount of 1 to 15 mass%, preferably 3 to 9 mass%, based on the total amount of the grease composition.

Extreme pressure additive

The grease for resin lubrication of the present invention contains an extreme pressure additive (extreme pressure agent).

It is known that an extreme pressure additive reacts with a metal surface to form a lubricating film, thereby having functions of reducing friction and wear of the metal surface and preventing ablation. Therefore, even when the grease for resin lubrication containing an extreme pressure additive is used for the resin sliding surface, it is considered that the grease does not exert any effect on the resin sliding surface. However, in the present invention, it has been found that when an extreme pressure additive is blended into a grease composition used for a resin sliding surface, the friction coefficient is also lowered when the grease composition is applied to the resin sliding surface, and therefore the extreme pressure additive is blended.

Examples of the extreme pressure additive include phosphorus compounds, sulfur compounds, chlorine compounds, metal salts of sulfur compounds, and polymer esters.

In the present invention, at least one of a phosphorus compound (phosphorus-based additive) and a high molecular ester (high molecular ester-based additive) is preferably used as the extreme pressure additive, and these may be used in combination.

Examples of the phosphorus-based additive include phosphoric acid esters, phosphorous acid esters, amine salts of phosphoric acid esters, and thiophosphoric acid esters.

Preferable examples of the phosphorus-based additive include phosphoric acid triesters such as tricresyl phosphate (TCP), triphenyl phosphate, tributyl phosphate, trioctyl phosphate, triolein phosphate, and thiophosphoric acid triesters such as triphenoxy phosphine sulfide (TPPS), which are commercially available.

Examples of the polymer ester include esters of aliphatic 1-and 2-membered carboxylic acids and polyhydric alcohols. Specific examples of the polymer ester include, but are not limited to, PERFAD (registered trademark) series and PRIOLUBE (registered trademark) series manufactured by Croda Japan.

The extreme pressure additive is used in an amount of 0.1 to 10% by mass, preferably 0.1 to 5% by mass, for example, 0.5 to 3% by mass, based on the total amount of the grease composition.

< other additives >

In addition, the grease composition for resin lubrication may contain, in addition to the above-mentioned essential components, additives generally used in grease compositions as needed within a range not to impair the effects of the present invention.

Examples of such additives include antioxidants, metal deactivators, rust inhibitors, oil improvers, viscosity index improvers, and tackifiers.

When these other additives are contained, the amount (total amount) thereof added is usually 0.1 to 10% by mass based on the total amount of the grease composition.

Examples of the antioxidant include hindered phenol antioxidants such as octadecyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate, pentaerythrityl tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], 2, 4-bis- (N-octylthio) -6- (4-hydroxy-3, 5-di-tert-butylanilino) -1,3, 5-triazine, 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene, triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate ], 1, 6-hexanediol-bis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], 2-thio-diethylene bis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], N' -hexamethylene bis (3, 5-di-tert-butyl-4-hydroxy-hydrocinnamide), 2, 6-di-tert-butyl-4-hydroxyphenyl) propionate, 2, 6-di-tert-butyl-4-hydroxy-hydrocinnamamide, 2, 3, 6-di-butyl-4-hydroxyphenyl) phenothiazine, 2-naphthylamine, and the like.

Examples of the metal deactivator include benzotriazole and sodium nitrite.

The grease composition for resin lubrication of the present invention can be obtained by mixing the above-mentioned various base oils, various thickeners, and extreme pressure additives in a predetermined ratio, and adding other additives as needed.

Further, a grease composition for resin lubrication can also be obtained by blending 2 types of base greases, i.e., a fluorine-based grease composed of a fluorine-based base oil and a fluorine-based thickener, a lithium soap grease (or a lithium complex soap grease) composed of a synthetic hydrocarbon oil and a lithium soap thickener (or a lithium complex soap thickener), with an extreme pressure additive and, if necessary, other additives. Alternatively, a grease composition for resin lubrication may be prepared by blending 1 of the above base greases with the remaining base oil, thickener, extreme pressure additive, and other additives as necessary.

The content of the thickener in the base grease is usually about 10 to 30% by mass, and for example, in the above 2 base greases, the content of each thickener in each base grease may be a fluorine-based thickener: 15 to 30 mass%, a lithium soap or lithium complex soap-based thickener: 10 to 20 mass%.

The grease composition for resin lubrication of the present invention is a relatively soft grease for use in a resin sliding surface, and the working penetration is preferably in the range of 265 to 340.

The present invention is not limited to the embodiments and specific examples described in the present specification, and various changes and modifications can be made within the scope of the technical idea described in the claims.