Sealing device and rubber composition

Abstract

The present invention provides a novel sealing device capable of suppressing friction even in boundary lubrication or mixed lubrication.　A sealing device (1) comprises a seal member (6). The seal member (6) contains a rubber composition. The rubber composition contains a compound having a functional group at a terminal and having an aliphatic hydrocarbon group having 4 or more carbon atoms.

Description

Sealing device and rubber composition

[0001] The present invention relates to a sealing device and a rubber composition.

[0002] In the fields of vehicles, general-purpose machinery, industrial machinery, etc., various sealing devices are used to seal gaps between rotating and stationary members, gaps between reciprocating and stationary members, etc. A typical sealing device includes a sealing member made of a rubber composition, and the sealing member slides on the surface of an opposing member.

[0003] To suppress friction in the sliding parts of sealing members, it is desirable to use fluid lubrication. To achieve this, methods to ensure fluid lubrication have been adopted, such as increasing the operating speed of the device or using a highly viscous lubricating liquid. Meanwhile, in recent years, the viscosity of lubricating liquids has tended to decrease due to demands for energy conservation. Therefore, it is necessary to consider methods to suppress friction in boundary lubrication or mixed lubrication, where it is difficult to form an oil film in the sliding parts.

[0004] Known methods for suppressing friction in boundary lubrication include coating the surface of a sealing member or designing the surface shape to improve lubricity. Furthermore, instead of using a lubricating oil, self-lubricating rubber compositions are known that suppress friction by blending a solid lubricant or a specific compound into rubber and allowing it to bloom or bleed onto the rubber surface (e.g., Patent Documents 1 to 4). Meanwhile, for sealing devices that require the presence of a lubricating oil, there remains a need for sealing members that can be manufactured without complex processes, have a high degree of freedom in surface shape, a high degree of freedom in the rubber components used, and allow for easy friction control.

[0005] Japanese Patent Laid-Open No. 6-166774 Japanese Patent Laid-Open No. 8-012733 Japanese Patent Laid-Open No. 2008-285562 Japanese Patent Laid-Open No. 2011-046812

[0006] The present invention provides a novel sealing device that can suppress friction even under boundary or mixed lubrication.

[0007] The gist of the present invention is as follows, for example. [1] A sealing device comprising a seal member, the seal member containing a rubber composition, the rubber composition containing a compound having a functional group at an end and having an aliphatic hydrocarbon group having 4 or more carbon atoms. [2] The sealing device of [1], wherein the rubber composition contains an inorganic filler. [3] The sealing device of [2], wherein the inorganic filler is at least one selected from the group consisting of carbon black, metal oxides, metal hydroxides, and silicate minerals. [4] The sealing device of [2] or [3], wherein the compound modifies the surface of the inorganic filler. [5] The sealing device of any of [1] to [3], wherein the functional group is a phosphate group, a hydroxy group, a carboxy group, a carboxylic acid ester group, an amide group, or an amino group. [6] A rubber composition containing a compound having a functional group at an end and having an aliphatic hydrocarbon group having 4 or more carbon atoms. [7] A method for improving lubricant retention on a sliding surface of a sealing device, wherein the rubber composition of [6] is used for a sealing member. [8] A sealing device comprising a seal member, the seal member including a rubber composition, and the rubber composition including an ashless friction modifier.

[0008] According to the present invention, a novel sealing device can be provided that can suppress friction even under boundary lubrication or mixed lubrication.

[0009] 1 is a plot showing the results of a reciprocating friction test on fluororubber (FKM), acrylonitrile-butadiene rubber (NBR), and acrylic rubber (ACM). The horizontal axis represents G (viscosity, speed, contact width / straining force), and the vertical axis represents the coefficient of friction. This is a plot showing the results of a reciprocating friction test conducted using a cold-rolled steel plate (SPCC) to evaluate the influence of terminal functional groups. The horizontal axis represents the sliding speed (mm / s), and the vertical axis represents the coefficient of friction. This is a plot showing the results of a reciprocating friction test conducted using a rubber composition molded product to evaluate the influence of terminal functional groups. The horizontal axis represents the sliding speed (mm / s), and the vertical axis represents the coefficient of friction. This is a plot showing the results of a reciprocating friction test conducted using a cold-rolled steel plate (SPCC) to evaluate the influence of the chain length of the aliphatic hydrocarbon group. The horizontal axis represents the sliding speed (mm / s), and the vertical axis represents the coefficient of friction. 1 is a plot showing the results of a reciprocating friction test conducted using cold-rolled steel plate (SPCC) to evaluate the effect of the structure (linear or branched) of the aliphatic hydrocarbon group. The horizontal axis represents the sliding speed (mm / s), and the vertical axis represents the friction coefficient. 2 is a cross-sectional view of a sealing device according to an example of the present invention.

[0010] [Lubricating Oil] The sealing device of the present invention includes a sealing member. The sealing member may be used together with a lubricating oil. In this specification, the term "lubricating oil" does not refer to a component that blooms or bleeds from the rubber composition that constitutes the sealing member, but refers to a lubricating fluid that is prepared and used independently of the sealing member. When the object to be sealed is oil, the oil may act as the lubricating oil. Furthermore, "used together with a lubricating oil" typically indicates that at least a portion of the sealing member comes into contact with the lubricating oil when the sealing device is in use.

[0011] The type of lubricating oil used with the sealing device of the present invention is not particularly limited. The lubricating oil may be one that uses a synthetic oil or a mineral oil as a base oil. Examples of the synthetic oil include synthetic hydrocarbon oil, ester oil, ether oil, and glycol oil. The synthetic oil and the mineral oil may be used alone or in combination.

[0012] Examples of the synthetic hydrocarbon oils include poly-α-olefins, ethylene-α-olefin copolymers, polybutene (polyisobutylene), alkylbenzenes, and alkylnaphthalenes. Examples of the ester oils include diesters (esters of dicarboxylic acids and monoalcohols), polyol esters, and aromatic esters. Examples of the ether oils include alkyl diphenyl ethers. Examples of the glycol oils include polyalkylene glycols. These may be used alone or in combination of two or more.

[0013] The lubricating oil may contain other components as needed in addition to the base oil. Examples of the other components include, but are not limited to, thickeners, extreme pressure agents, antioxidants, rust inhibitors, oiliness agents, viscosity index improvers, etc. The lubricating oil may be one that uses only the base oil.

[0014] [Rubber Composition] In the sealing device of the present invention, the seal member includes a rubber composition containing a compound having a functional group at its terminal and an aliphatic hydrocarbon group having 4 or more carbon atoms (hereinafter, for convenience, also referred to as "compound A"). The rubber composition will be described in detail below.

[0015] (Rubber Component) The rubber composition contains a rubber component. The type of the rubber component is not particularly limited. Examples of the rubber component include natural rubber, styrene-butadiene rubber, butadiene rubber, chloroprene rubber, acrylonitrile-butadiene rubber (nitrile rubber, NBR), hydrogenated nitrile rubber, isoprene rubber, butyl rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber (EPDM), acrylic rubber (ACM), fluororubber (FKM), and silicone rubber. Among these, a rubber component selected from the group consisting of fluororubber (FKM), acrylonitrile-butadiene rubber (nitrile rubber, NBR), silicone rubber, and acrylic rubber (ACM) is preferred.

[0016] (Compound A) Compound A can typically be known as an ashless friction modifier. Compound A has a functional group at its terminal. The type of functional group is not particularly limited, but is preferably one that can modify the surface of the inorganic filler described below. The surface modification may be either physical adsorption or chemical adsorption, but chemical adsorption, i.e., adsorption by a chemical bond formed by a chemical reaction with the functional group on the surface of the inorganic filler, is preferred. When compound A has a functional group at its terminal, the functional group functions as an anchor, suppressing the elution of compound A into the lubricating oil and making it easier to maintain the friction suppression effect for a long period of time.

[0017] Examples of the functional group include a phosphate group (H ２ P.O. ４ -), a hydroxy group (-OH), a carboxy group or a carboxylic acid ester group (-COOR １ ), carboxylic acid halide group (-COX), amide group (-CONR ２ R ３ ), or an amino group (—NR ４ R ５ ) can be mentioned. １ ~R ５ The group represented by R is not particularly limited. １ ~R ５ The groups represented by may each independently be, for example, a hydrogen atom, a hydrocarbon group having 1 to 12 carbon atoms, or a hydrocarbon group having 1 to 12 carbon atoms substituted with one or more hydroxy groups. X represents a halogen atom. X is preferably, for example, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom, and more preferably a chlorine atom. Compound A may have two or more of the functional groups, but preferably has only one of the functional groups.

[0018] The hydrocarbon group having 1 to 12 carbon atoms is not particularly limited as long as it is a hydrocarbon group consisting of carbon atoms and hydrogen atoms and has 1 to 12 carbon atoms, and examples thereof include chain hydrocarbon groups, aromatic hydrocarbon groups, and alicyclic hydrocarbon groups. The chain hydrocarbon group is not particularly limited as long as it has a total of 1 to 12 carbon atoms, and may be a straight-chain hydrocarbon group or a branched-chain hydrocarbon group. The aromatic hydrocarbon group is not particularly limited as long as it has a total of 6 to 12 carbon atoms, and may be a substituted or unsubstituted aromatic hydrocarbon group. The aromatic hydrocarbon group may also have a fused polycyclic structure. The alicyclic hydrocarbon group is not particularly limited as long as it has a total of 3 to 12 carbon atoms, and may be a substituted or unsubstituted alicyclic hydrocarbon group. The alicyclic hydrocarbon group may also have a bridged ring structure.

[0019] Examples of the chain hydrocarbon group include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl groups; alkenyl groups such as ethenyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, and dodecenyl groups; and alkynyl groups such as ethynyl, propynyl, butynyl, pentynyl, hexynyl, heptynyl, octynyl, nonynyl, decynyl, undecynyl, and dodecynyl groups.

[0020] Examples of the aromatic hydrocarbon group include a phenyl group, a benzyl group, a tolyl group, a naphthyl group, etc. The tolyl group may be any of an o-tolyl group, an m-tolyl group, and a p-tolyl group.

[0021] The alicyclic hydrocarbon group includes saturated or unsaturated cyclic hydrocarbon groups, such as cyclopropyl, cyclobutyl, cyclohexyl, cyclopentyl, adamantyl, and norbornyl.

[0022] Examples of the hydrocarbon group having 1 to 12 carbon atoms substituted with one or more hydroxy groups include hydroxyalkyl groups such as a hydroxymethyl group, a 1-hydroxyethyl group, a 2-hydroxyethyl group, a 1-hydroxypropyl group, a 2-hydroxypropyl group, a 3-hydroxypropyl group, and a 2,3-dihydroxypropyl group (glycerol group).

[0023] R １ is preferably a hydrogen atom, an alkyl group, or a hydroxyalkyl group, more preferably a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a hydroxymethyl group, a 1-hydroxyethyl group, a 2-hydroxyethyl group, a 1-hydroxypropyl group, a 2-hydroxypropyl group, a 3-hydroxypropyl group, or a 2,3-dihydroxypropyl group (glycerol group), and even more preferably a hydrogen atom or a 2,3-dihydroxypropyl group (glycerol group).

[0024] R ２ ~R ５ is preferably a hydrogen atom, an alkyl group, or a hydroxyalkyl group, more preferably a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a hydroxymethyl group, a 1-hydroxyethyl group, a 2-hydroxyethyl group, a 1-hydroxypropyl group, a 2-hydroxypropyl group, or a 3-hydroxypropyl group, still more preferably a hydrogen atom, a methyl group, or a 2-hydroxyethyl group, and most preferably a hydrogen atom.

[0025] From the viewpoint of easily obtaining a friction reducing effect, the functional group is preferably a phosphate group (H ２ P.O. ４ -), a carboxy group or a carboxylic acid ester group (-COOR １ ), amide group (-CONR ２ R ３ ), or an amino group (—NR ４ R ５ ) is preferred, and a phosphate group (H ２ P.O. ４ -) or a carboxy group is more preferred, and a phosphate group (H ２ P.O. ４The phosphate group, carboxy group, and amino group may be in the form of a salt.

[0026] In addition to the functional group, compound A has an aliphatic hydrocarbon group having 4 or more carbon atoms. Compound A may have one, two, three, or four or more aliphatic hydrocarbon groups having 4 or more carbon atoms. Compound A preferably has only one aliphatic hydrocarbon group having 4 or more carbon atoms. When compound A has an aliphatic hydrocarbon group having 4 or more carbon atoms, its affinity with lubricating oil is improved, making it easier to retain the lubricating oil on the sliding surface even in a boundary lubrication state, and effectively suppressing friction. In other words, by using a rubber composition containing compound A for a seal member, the lubricating oil retention ability of the sliding surface in a sealing device is improved.

[0027] The aliphatic hydrocarbon group having 4 or more carbon atoms is not particularly limited as long as it is an aliphatic hydrocarbon group having 4 or more carbon atoms and consisting of carbon atoms and hydrogen atoms, and examples thereof include linear or branched chain aliphatic hydrocarbon groups, and alicyclic hydrocarbon groups. The alicyclic hydrocarbon group may have a bridged ring structure.

[0028] Examples of the chain aliphatic hydrocarbon group include an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, a 16-methylheptadecyl group (isostearyl group), an octadecyl group, a nonadecyl group, an icosyl group, a henicosyl group, a docosyl group, a tricosyl group, a tetracosyl group, a pentacosyl group, a hexacosyl group, a heptacosyl group, an octacosyl group, a nonacosyl group, a triaconitic group, and alkyl groups having 4 to 40 carbon atoms, such as a 4 to 40 alkyl group, hentriacontyl group, dotriacontyl group, tritriacontyl group, tetratriacontyl group, pentatriacontyl group, hexatriacontyl group, heptatriacontyl group, octatriacontyl group, nonatriacontyl group, and tetracontyl group; alkenyl groups in which one or two or more carbon-carbon single bonds in the alkyl group having 4 to 40 carbon atoms are replaced with carbon-carbon double bonds; and alkynyl groups in which one or two or more carbon-carbon single bonds in the alkyl group having 4 to 40 carbon atoms are replaced with carbon-carbon triple bonds.

[0029] When the aliphatic hydrocarbon group having 4 or more carbon atoms is an alkenyl group, the number of double bonds is preferably 6 or less, more preferably 5 or less, even more preferably 3 or less, still more preferably 2 or less, and most preferably 1. In this case, the double bond is preferably located between the third carbon-carbon bond and the ninth carbon-carbon bond counting from the end (methyl group side).

[0030] The alicyclic hydrocarbon group includes saturated or unsaturated cyclic hydrocarbon groups, such as cyclobutyl, cyclohexyl, cyclopentyl, adamantyl, and norbornyl.

[0031] From the viewpoint of easily obtaining a friction-reducing effect, the aliphatic hydrocarbon group having 4 or more carbon atoms is preferably a chain aliphatic hydrocarbon group, more preferably a straight-chain aliphatic hydrocarbon group, even more preferably a straight-chain alkyl group or straight-chain alkenyl group, and most preferably a straight-chain alkyl group.

[0032] Furthermore, from the viewpoints of friction-reducing effect and availability, the number of carbon atoms in the aliphatic hydrocarbon group having 4 or more carbon atoms is preferably 4 to 40, more preferably 8 to 35, even more preferably 10 to 30, still more preferably 12 to 25, and most preferably 15 to 20. Typically, the larger the carbon number of the aliphatic hydrocarbon group, the more hydrophobic it becomes, improving its affinity with lubricating oil and making it easier to achieve a friction-reducing effect. Also, typically, the smaller the carbon number of the aliphatic hydrocarbon group, the easier it is to keep costs down.

[0033] The functional group and the aliphatic hydrocarbon group having 4 or more carbon atoms may be bonded directly or via a group having a valence of 2 or more. The group having a valence of 2 or more may be, for example, one represented by the following general formula:

[0034]

[0035] Here, n and m each independently represent an integer of 1 or greater. n is preferably an integer of 1 to 4, more preferably 2 or 3, and even more preferably 2. m is preferably an integer of 1 to 10, more preferably an integer of 1 to 5, and most preferably an integer of 1 to 4. The group represented by the above general formula is particularly preferably an ethylene oxide unit.

[0036] Specific examples of compound A are listed below. Examples when the terminal functional group is a phosphate group: dodecyl phosphate (lauryl phosphate), tetradecyl phosphate (myristyl phosphate), hexadecyl phosphate (cetyl phosphate), octadecyl phosphate (stearyl phosphate), 9-octadecenyl phosphate (oleyl phosphate), laureth-2phosphate, laureth-3phosphate, laureth-4phosphate, steareth-2phosphate, steareth-3phosphate, steareth-4phosphate, oleth-2phosphate, oleth-3phosphate, oleth-4phosphate, tris(2-ethylhexyl) phosphate, or alkali metal salts, alkaline earth metal salts, or amine salts thereof. However, these may be in the form of diesters, or may be a mixture of monoesters and diesters.

[0037] Examples of when the terminal functional group is a hydroxy group: 1-dodecanol (lauryl alcohol), 1-tetradecanol (myristyl alcohol), 1-hexadecanol (cetyl alcohol), 1-octadecanol (stearyl alcohol), 9-octadecen-1-ol (oleyl alcohol), etc.

[0038] Examples when the terminal functional group is a carboxy group, a carboxylic acid ester group, or a carboxylic acid halide group: saturated fatty acids such as pentanoic acid (valeric acid), hexanoic acid (caproic acid), heptanoic acid (enanthic acid), octanoic acid (caprylic acid), nonanoic acid (pelargonic acid), decanoic acid (capric acid), undecanoic acid (undecylic acid), dodecanoic acid (lauric acid), tetradecanoic acid (myristic acid), hexadecanoic acid (palmitic acid), octadecanoic acid (stearic acid), eicosanoic acid (arachidic acid), triacontanoic acid (melissic acid); ω-3 fatty acids such as α-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid; ω-6 fatty acids such as linoleic acid, γ-linolenic acid; ω-9 fatty acids such as oleic acid; dimer acids (C36 dicarboxylic acids); methyl esters or 2,3-dihydroxypropyl esters thereof (for example, glycerol monooleate, etc.); alkali metal salts, alkaline earth metal salts, or amine salts thereof; or acid halides (particularly acid chlorides) of these.

[0039] Examples of compounds in which the terminal functional group is an amide group: dodecaneamide (lauric acid amide, lauramide), hexadecanamide (palmitic acid amide, palmitamide), octadecanamide (stearic acid amide, stearamide), 9-octadeceneamide (oleic acid amide, oleamide), isostearyl polyamide, etc.

[0040] Examples of compounds in which the terminal functional group is an amino group: dodecylamine (laurylamine), tetradecylamine (myristylamine), hexadecylamine (cetylamine), octadecylamine (stearylamine), 9-octadecenylamine (oleylamine), lauryldiethanolamine, myristyldiethanolamine, cetyldiethanolamine, stearyldiethanolamine, oleyldiethanolamine, etc.

[0041] There are no particular limitations on the content of compound A in the rubber composition. The content of compound A in the rubber composition is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 15 parts by mass, and even more preferably 1 to 10 parts by mass, per 100 parts by mass of the rubber composition.

[0042] (Inorganic Filler) The rubber composition may contain an inorganic filler. When the rubber composition contains an inorganic filler, Compound A is adsorbed to the inorganic filler, and elution of Compound A into the lubricating oil is suppressed, making it easier to maintain the friction suppression effect for a long period of time.

[0043] The type of inorganic filler is not particularly limited, but for example, at least one selected from the group consisting of carbon black, metal oxides, metal hydroxides, and silicate minerals can be used. Examples of the metal oxide include iron (III) oxide (Fe ２ O ３ ), chromium (III) oxide (Cr ２ O ３ ), titanium dioxide (TiO ２ ), aluminum oxide (Al ２ O ３Examples of the metal hydroxides include magnesium hydroxide and aluminum hydroxide. Examples of the silicate minerals include silica, wollastonite, talc, and mica.

[0044] Among inorganic fillers, from the viewpoints of availability and adsorption to compound A, metal oxides, metal hydroxides, and silicate minerals are preferred, iron (III) oxide, chromium (III) oxide, titanium dioxide, aluminum hydroxide, silica, wollastonite, and talc are preferred, iron (III) oxide, chromium (III) oxide, titanium dioxide, aluminum hydroxide, and wollastonite are more preferred, and iron (III) oxide, chromium (III) oxide, titanium dioxide, and aluminum hydroxide are even more preferred.

[0045] The content of the inorganic filler in the rubber composition is not particularly limited, and is preferably 10 to 300 parts by mass, more preferably 20 to 250 parts by mass, still more preferably 30 to 200 parts by mass, and most preferably 50 to 150 parts by mass, per 100 parts by mass of the rubber composition.

[0046] (Other Components) In addition to the above components, the rubber composition may contain, as necessary, various additives commonly used in the field of rubber compositions, such as an antioxidant, a plasticizer, a crosslinking agent, a crosslinking accelerator, an acid acceptor, and a processing aid.

[0047] (Method for producing rubber composition and sealing member) The rubber composition is obtained by kneading the above-mentioned components using a kneader, an open roll, or the like. The sealing member is obtained by forming the obtained rubber composition into a ribbon-shaped or pellet-shaped preform using an extruder or the like as needed, and then appropriately molding and vulcanizing it. When an inorganic filler is used, compound A and the inorganic filler may be added separately to the rubber component, or the inorganic filler may be treated in advance to adsorb compound A onto its surface, and the treated inorganic filler may then be added to the rubber component.

[0048] [Sealing Device] The sealing device of the present invention may be any sealing device for sealing a gap between a rotating member and a stationary member, a gap between a reciprocating member and a stationary member, etc. in vehicles, general-purpose machines, industrial machines, etc. Examples of such sealing devices include, but are not limited to, engine seals, steering dust seals, bonded piston seals, transmission seals, differential side seals, universal joint seals, shock absorber seals, hub seals, valve stem seals, etc.

[0049] FIG. 6 shows a cross-sectional view of a sealing device 1 (oil seal) as an example of the present invention. The sealing device 1 is an approximately annular device disposed between a shaft 2 and a housing 3. The sealing device 1 is fixed by fitting into a hole formed in the housing 3. The sealing device 1 includes a seal member 6 including a dust lip 4 and a seal lip 5, a metal ring 7, and a spring 8. The seal member 6 is formed from the rubber composition described above. The seal lip 5 is in sliding contact with the surface of the shaft 2 and prevents leakage of the sealed object from the sealed side 10 to the atmosphere side 9. The spring 8 biases the seal lip 5 toward the shaft 2, increasing the pressing force of the seal lip 5. The dust lip 4 prevents dust from entering from the atmosphere side 9.

[0050] 6 is merely one example of the sealing device of the present invention. As described above, the sealing device of the present invention may be any other sealing device for sealing a gap between a rotating member and a stationary member, a gap between a reciprocating member and a stationary member, etc. in a vehicle, a general-purpose machine, an industrial machine, etc.

[0051] The sealing device of the present invention can be manufactured without complicated processes, compared to techniques that apply a coating to the surface of a sealing member. Furthermore, since the rubber composition itself has a friction-reducing effect, the effect is likely to be maintained even in a worn state. Furthermore, since the sealing device of the present invention is not limited to the surface shape of the sealing member, various conventional sealing device structures can be applied as is. Furthermore, compared to techniques that use a self-lubricating rubber composition, the sealing member of the sealing device of the present invention can reduce friction even in the presence of a lubricant, suppresses the elution of components into the lubricant, and is not limited to the type of rubber component. The friction-reducing effect of the sealing member of the sealing device of the present invention does not depend on the bloom or bleed rate, making it easy to control friction.

[0052] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, but includes all aspects encompassed by the concept of the present invention and the scope of the claims, and can be modified in various ways within the scope of the present invention.

[0053] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0054] [Test Conditions] (Dynamic Friction Test Using Rubber Composition Molded Product) The rubber component, Compound A, and inorganic filler were kneaded using a kneader and an open roll, and molded at 180° C. for 6 minutes to obtain a semispherical rubber test piece with a diameter of 5 mm. A dynamic friction test was performed using a reciprocating dynamic friction tester (manufactured in-house) under the following conditions.

[0055] Lubricant: mineral oil Load: 3N Temperature: 60°C Speed: 0.01 to 10 mm / s (except for Test Example 2), 0.01 mm / s (Test Example 2)

[0056] (Dynamic friction test using cold-rolled steel plate (SPCC)) The surface of a cold-rolled steel plate measuring 30 mm x 50 mm x 2 mm was coated with compound A. A dynamic friction test was carried out using a reciprocating friction tester (manufactured in-house) under the following conditions.

[0057] Lubricating oil: Mineral oil Load: 3N Temperature: 60℃ Speed: 0.01~10mm / s

[0058] (Test Example 1 - Effect of Rubber Component) Rubber composition molded bodies were produced using FKM (fluororubber, Technoflon (registered trademark) P757 manufactured by Solvay), NBR (acrylonitrile-butadiene rubber, N220S manufactured by JSR Corporation), and ACM (acrylic rubber, commercially available) as the rubber component, and dynamic friction tests were performed. For FKM, a test specimen was used which was obtained by using 5 parts by mass of Compound A1 described below as Compound A and 75 parts by mass of iron (III) oxide as an inorganic filler per 100 parts by mass of FKM. For NBR, a test specimen was used which was obtained by using 9 parts by mass of Compound A1 as Compound A and 140 parts by mass of iron (III) oxide as an inorganic filler per 100 parts by mass of NBR. For ACM, a test specimen was used which was obtained by using a predetermined amount of Compound A and a predetermined amount of inorganic filler with respect to ACM. In addition, for each rubber composition, a test specimen to which Compound A was not added was produced and used as a control. Figure 1 shows a plot of the coefficient of friction (dynamic coefficient of friction) against G (viscosity, speed, contact width / tension force). Note that when there are multiple plots for the same G, it means that multiple tests were conducted at the same G.

[0059] As shown in Figure 1, regardless of whether FKM, NBR, or ACM was used as the rubber component, the composition containing Compound A exhibited a significantly reduced friction coefficient compared to the control not containing Compound A. The effect of reducing the friction coefficient was particularly notable in the low-speed (low G) region where boundary lubrication or mixed lubrication occurs.

[0060] (Test Example 2 - Effect of inorganic filler) A dynamic friction test was performed on various rubber composition molded articles obtained by using 5 parts by mass of various compounds A and 75 parts by mass of various inorganic fillers with 100 parts by mass of FKM (fluororubber, Tecnoflon (registered trademark) P757 manufactured by Solvay). In addition, for each rubber composition, a test piece without compound A was produced and used as a control. The sliding speed was fixed at 0.01 mm / s, and the coefficient of friction was evaluated as a when it was less than 0.1, b when it was 0.1 or more but less than 0.5, and c when it was 0.5 or more.

[0061] The ashless friction modifiers used as Compound A were Compounds A1 to A5 below. Compound A1: Glycerin monooleate Compound A2: Oleyl diethanolamine Compound A3: Isostearyl polyamide Compound A4: Mono-dioleyl acid phosphate amine salt (oleyl phosphate (mono- and diester mixture)) Compound A5: Steareth-3 phosphate

[0062] The inorganic fillers used were as follows: Iron (III) oxide: Brown #601 manufactured by Resino Color Kogyo Co., Ltd. Chromium (III) oxide: STV-T-3466 manufactured by Resino Color Kogyo Co., Ltd. Titanium dioxide: Type A100 manufactured by Ishihara Sangyo Kaisha, Ltd. Aluminum hydroxide: BF013 manufactured by Nippon Light Metal Co., Ltd. Wollastonite A: Wollastnite 1250 manufactured by IMERYS Wollastnite B: Wollastnite 400 manufactured by IMERYS Wollastonite C: NYGLOS4W manufactured by NYCO Minerals Carbon black A: Acetylene black (Denka Black manufactured by Denka Co., Ltd.) Carbon black B: Carbon black N330 (Show Black N330 manufactured by Showa Cabot Corporation) Carbon black C: Carbon black N990 (Thermax manufactured by Cancarb) Silica A : Nipsil E74P Silica B manufactured by Tosoh Silica Corporation : Reoloseal CP-102 manufactured by Tokuyama Corporation

[0063] The results are shown in Table 1.

[0064]

[0065] As shown in Table 1, when a wide range of inorganic fillers were used in combination with Compound A, the coefficient of friction in the low speed range (corresponding to boundary lubrication or mixed lubrication) was significantly suppressed.

[0066] (Test Example 3 - Effect of Functional Group A) The surface of a cold-rolled steel plate (SPCC) was treated with stearylamine, oleamide, stearic acid, or steareth-2 phosphoric acid as Compound A, and a dynamic friction test was carried out. A cold-rolled steel plate (SPCC) not treated with Compound A served as a control. Figure 2 shows a plot of the friction coefficient (dynamic friction coefficient) against the sliding speed (mm / s).

[0067] As shown in Figure 2, when Compound A having any terminal functional group was used, a suppression effect on the friction coefficient was observed in the low speed range (at least one of 0.01 mm / s and 0.1 mm / s). Furthermore, a particularly remarkable effect was observed when the terminal functional group was a phosphate group.

[0068] (Test Example 4 - Effect of Functional Group B) Dynamic friction tests were performed on various rubber composition molded articles obtained by using 100 parts by mass of FKM (fluororubber, Tecnoflon (registered trademark) P757 manufactured by Solvay), 5 parts by mass of stearylamine, oleamide, stearic acid, or steareth-2phosphate as Compound A, and 75 parts by mass of iron (III) oxide. Test pieces to which no Compound A was added were also prepared as controls. Figure 3 shows a plot of the friction coefficient (dynamic friction coefficient) versus the sliding speed (mm / s).

[0069] As shown in Figure 3, in the test using the rubber composition molded article, when Compound A having any terminal functional group was used, the effect of suppressing the friction coefficient in the low speed range (at least one of 0.01 mm / s and 0.1 mm / s) was observed. Furthermore, the type of functional group that was particularly effective showed a tendency similar to that in Test Example 3 using cold-rolled steel plate (SPCC).

[0070] From the results of Test Examples 3 and 4, it was found that tests using cold-rolled steel plates (SPCC) gave results that correlated to a certain extent with tests using rubber composition molded bodies. Therefore, various investigations were carried out using tests using cold-rolled steel plates (SPCC) as follows.

[0071] (Test Example 5 - Effect of Carbon Number) The surface of a cold-rolled steel plate (SPCC) was treated with valeric acid, stearic acid, or melissic acid as compound A, and a dynamic friction test was carried out. A cold-rolled steel plate (SPCC) not treated with compound A served as a control. Figure 4 shows a plot of the friction coefficient (dynamic friction coefficient) against the sliding speed (mm / s).

[0072] As shown in FIG. 4, when Compound A having an aliphatic hydrocarbon group with a large number of carbon atoms is used, the effect of suppressing the friction coefficient in the low speed region (corresponding to boundary lubrication or mixed lubrication) is more pronounced.

[0073] (Test Example 6 - Effect of Structure) The surface of a cold-rolled steel plate (SPCC) was treated with Compound A having a branched structure (tris(2-ethylhexyl)phosphate) or a linear structure (steareth-diphosphate), and a dynamic friction test was carried out. A cold-rolled steel plate (SPCC) not treated with Compound A served as a control. Figure 5 shows a plot of the friction coefficient (dynamic friction coefficient) against the sliding speed (mm / s).

[0074] As shown in FIG. 5, it was found that when Compound A having a linear structure was used, the effect of suppressing the friction coefficient in the low speed range (corresponding to boundary lubrication or mixed lubrication) was more pronounced.

[0075] The sealing device and rubber composition of the present invention can be suitably used in fields such as vehicles, general-purpose machinery, and industrial machinery to seal gaps between rotating members and stationary members, gaps between reciprocating members and stationary members, and the like.

[0076] REFERENCE SIGNS LIST 1... sealing device, 2... shaft, 3... housing, 4... dust lip, 5... seal lip, 6... seal member, 7... metal ring, 8... spring, 9... atmosphere side, 10... sealed object side

Claims

1. A sealing device comprising a seal member, the seal member containing a rubber composition, the rubber composition containing a compound having a functional group at an end and having an aliphatic hydrocarbon group having 4 or more carbon atoms.

2. The sealing device according to claim 1, wherein the rubber composition contains an inorganic filler.

3. The sealing device according to claim 2, wherein the inorganic filler is at least one selected from the group consisting of carbon black, metal oxides, metal hydroxides, and silicate minerals.

4. The sealing device according to claim 2 or 3, wherein the compound modifies the surface of the inorganic filler.

5. The sealing device according to any one of claims 1 to 3, wherein the functional group is a phosphate group, a hydroxy group, a carboxy group, a carboxylate group, an amide group, or an amino group.

6. A rubber composition containing a compound having a functional group at its terminal and an aliphatic hydrocarbon group having 4 or more carbon atoms.

7. A method for improving the lubricant retention of the sliding surface of a sealing device, comprising using the rubber composition according to claim 6 as a seal member.

8. A sealing device comprising a seal member, the seal member including a rubber composition, the rubber composition including an ashless friction modifier.