Lubricant and lubricant application method

Abstract

An aspect of the present invention relates to a lubricant including a base oil, a cellulose microparticle, and at least one selected from the group consisting of a class I petroleum and a class II petroleum, wherein the cellulose microparticle content is in a range of 1 to 4.5 wt%.

Description

Field of the Invention

[0001] The present invention relates to a lubricant and a lubricant application method.Background Art

[0002] In a machine including parts (sliding parts) that slide against each other involving a friction, a lubricant is conventionally used to reduce the wear and friction between the sliding surfaces.

[0003] As a lubricant, Japanese Unexamined Patent Publication No. 2012-246499 discloses a lubricating oil composition that is a mixture of: a base oil including at least one of synthetic hydrocarbon oil and ester-based synthetic oil; a solid lubricant including graphite, molybdenum disulfide, or melamine cyanurate; and a lithium-based soap, a lithium-based complex soap, or a urea-based compound. It is mentioned that the lubricating oil composition can keep a good dispersion state of the solid lubricant dispersed in the base oil for a long period of time without impairing the fluidity, load bearing capacity, and wear characteristics for lubricant.

[0004] International Unexamined Patent Publication No. 2020 / 129587 discloses a lubricating grease composition comprising: a base oil having a kinematic viscosity of 10 mm 2< / s or more and 60 mm 2< / s or less at 40° C; a thickener containing at least one soap selected from the group consisting of a metal soap and a metal complex soap; and a solid lubricant containing porous polyamide particles. It is mentioned that the lubricating grease composition can increase the static friction coefficient between sliding members and has excellent starting performance, durability, and low-temperature performance.

[0005] However, the technologies of Japanese Unexamined Patent Publication No. 2012-246499 and International Unexamined Patent Publication No. 2020 / 129587 impart an insufficient wear resistance to a sliding surface. Thus, a further improvement in the wear resistance has been demanded.Summary of the Invention

[0006] The present invention has been worked out in view of the circumstances described above, and an object thereof is to provide a lubricant that can impart an excellent wear resistance to a sliding surface.

[0007] A lubricant according to an aspect of the present invention contains a base oil, a cellulose microparticle, and at least one selected from the group consisting of a class I petroleum and a class II petroleum, wherein the cellulose microparticle content is in a range of 0.1 to 4.5 wt%.Brief Description of the Drawings

[0008] Fig. 1 is a cross-sectional view of a chain to be applied with a lubricant in Examples 1 to 3 and Comparative Examples 1 to 3. Fig. 2 is a graph showing a result of a wear resistance test on a lubricant of Examples 1 to 2 and Comparative Examples 1 to 2. Fig. 3 is a graph showing a result of a wear resistance test on a lubricant of Example 3 and Comparative Example 3. Description of Embodiments

[0009] Hereinafter, an embodiment of the present invention will be described. However, the present invention is not limited thereto.Lubricant

[0010] A lubricant in the present embodiment includes a base oil, a cellulose microparticle, and at least one selected from the group consisting of a class I petroleum and a class II petroleum, wherein the cellulose microparticle content is in a range of 0.1 to 4.5 wt%. This composition can provide a lubricant that imparts an excellent wear resistance to a sliding surface.

[0011] The lubricant which contains cellulose microparticles, and at least one selected from the group consisting of a class I petroleum or a class II petroleum can keep a proper viscosity. The lubricant thus has an excellent permeability to a sliding surface. Consequently, the sliding surface can have an excellent wear resistance. The lubricant may contain both the class I petroleum and the class II petroleum, or either the class I petroleum or the class II petroleum (i.e., at least one selected from the group consisting of the class I petroleum and the class II petroleum).

[0012] The cellulose microparticle content is 0.1 wt% or more in 100 wt% of the lubricant. This facilitates a uniform dispersion of the cellulose microparticles in the lubricant. Consequently, the sliding surface can have an excellent wear resistance. The cellulose microparticle content is 4.5 wt% or less in 100 wt% of the lubricant. This keeps a proper viscosity of the lubricant. The lubricant thus has an excellent permeability to a sliding surface. Consequently, the sliding surface can have an excellent wear resistance.

[0013] Hereinafter, each component contained in the lubricant of the present embodiment will be specifically described.Cellulose Microparticles

[0014] A median diameter in a particle size distribution of the cellulose microparticles in the present embodiment is preferably in a range of 1 to 100 µm. The median diameter which is within the above range enables the lubricant to keep a proper viscosity, ensuring thus an excellent permeability of the lubricant to a sliding surface. Consequently, the sliding surface can more reliably have an excellent wear resistance.

[0015] The median diameter is more preferably in a range of 1 to 50 µm, and still more preferably in a range of 1.5 to 30 µm.

[0016] The median diameter (a particle diameter at which a volume-based cumulative frequency is 50%) is obtained by way of a laser diffraction-scattering particle size distribution measurer (manufactured by HORIBA, Ltd., device name: LA960). Specifically, cellulose microparticles are prepared to have a final concentration of 0.5 mass% with ion-exchanged water, placed under a process of 3400 rpm for five minutes by a Waring Blender (manufactured by WARING, device name: 7012S), and subjected to an ultrasonic dispersion for one minute, thereafter a particle size distribution measurement is conducted. A half width is a width of a half maximum frequency of a peak of a particle size distribution obtained by the measurement. The particle size measurement is in a range of 0.1 to 500 µm.

[0017] In the present embodiment, a method for preparing cellulose microparticles is not limited to a particular one, but cellulose microparticles may be prepared from cellulose material by various preparation methods.

[0018] For example, pulps, such as wood pulp made from wood and cotton linter pulp obtained from cotton, and papers may be used as cellulose material.

[0019] As exemplary methods for preparing cellulose microparticles, there is a method of preparing desired cellulose by mechanical defibration. Specifically, desired cellulose microparticles may be obtained by making the cellulose material have a certain length using a beater or a refiner and fibrillating it or reducing it in size (mechanically grinding) using a highpressure homogenizer, a grinder, an impact mill, and a bead mill. Alternatively, desired cellulose microparticles may be obtained by treating the cellulose material by a chemical for easy downsizing, and thereafter miniaturizing it by mechanical defibration.

[0020] The cellulose microparticles in the present embodiment are preferably prepared by mechanical defibration. The cellulose microparticles prepared by mechanical defibration have an advantage of being chemically and thermally stable owing to absence of compound liable to affect the microparticles because of employing only aqueous medium as medium without chemical modification in the miniaturization.Class I Petroleum

[0021] The class I petroleum in the present embodiment is a liquid having a flash point lower than 21 °C at 1 atmospheric pressure. The class I petroleum preferably includes at least one selected from the group consisting of isohexane, n-hexane, toluene, ethyl acetate, and n-heptane from the viewpoint of improvement in wear resistance. One kind of the class I petroleum may be used singly, or two or more kinds thereof may be used.Class II Petroleum

[0022] The class II petroleum in the present embodiment is a liquid having a flash point of 21 °C or higher but lower than 70 °C at 1 atmospheric pressure. The class II petroleum preferably includes at least one selected from the group consisting of xylene, mineral spirit, and chlorobenzene from the viewpoint of improvement in the wear resistance. One kind of the class II petroleum may be used singly, or two or more kinds thereof may be used.Base Oil

[0023] The base oil in the present embodiment is not limited to a particular one, but a mineral base oil (mineral oil) and / or a synthetic base oil, which are generally usable as a base oil, may be used, for example. The base oil preferably includes at least one selected from the group consisting of a mineral oil and a synthetic base oil. This composition has an advantage of more reliably imparting an excellent wear resistance to a sliding surface.

[0024] The mineral oil is not limited to a particular one, but a mineral oil which is refined by suitably combining: distillation under reduced pressure; solvent deasphalting; solvent extraction; hydrocracking, solvent dewaxing, cleaning with sulfuric acid, refining with white clay, and refining by hydrogenation may be used, for example. As the mineral oil, a paraffinic mineral oil, an intermediate mineral oil, a naphthenic mineral oil, and the like are preferably used. One kind of the mineral oil may be used singly, or two or more kinds thereof may be used.

[0025] The synthetic base oil is not limited to a particular one, but preferably includes a hydrocarbon base oil (hydrocarbon oil), an aromatic base oil, an ester base oil, an ether base oil, and a fatty acid ester base oil, for example. One kind of the synthetic base oil may be used singly, or two or more kinds thereof may be used.

[0026] The hydrocarbon base oil is not limited to a particular one, but preferably includes normal paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, polyalphaolefin (PAO), for example. One kind of the hydrocarbon base oil may be used singly, or two or more kinds thereof may be used.

[0027] The base oil preferably contains at least one selected from the group consisting of a mineral oil and a hydrocarbon oil. This composition has an advantage of more reliably imparting an excellent wear resistance to a sliding surface. Additionally, this composition can attain an improved permeability.Others

[0028] In the present embodiment, the lubricant may contain, in addition to the components described above, various additives which are generally blended in lubricant insofar as the additives do not impair the advantageous effects of the present invention. The lubricant may contain, for example, a propellant, a thickener, or the like.Content

[0029] In the present embodiment, the cellulose microparticle content is in a range of 0.1 to 4.5 wt% in 100 wt% of the lubricant. The cellulose microparticle content is preferably in a range of 0.5 to 4.0 wt%, and more preferably in a range of 1.0 to 3.0 wt% in 100 wt% of the lubricant.

[0030] In a case where the lubricant contains a class I petroleum, the class I petroleum content is preferably in a range of 10 to 60 wt% in 100 wt% of the lubricant. This composition can more reliably impart an excellent wear resistance to a sliding surface. The class I petroleum content is more preferably in a range of 10 to 50 wt%, and still more preferably in a range of 15 to 40 wt% in 100 wt% of the lubricant.

[0031] In a case where the lubricant contains a class II petroleum, the class II petroleum content is preferably in a range of 10 to 50 wt% in 100 wt% of the lubricant. This composition can more reliably impart an excellent wear resistance to a sliding surface. The class II petroleum content is more preferably in a range of 15 to 40 wt% in 100 wt% of the lubricant.

[0032] The base oil content is preferably in a range of 10 to 60 wt% in 100 wt% of the lubricant. This composition can more reliably impart an excellent wear resistance to a sliding surface. The base oil content is more preferably in a range of 15 to 50 wt%, and still more preferably in a range of 20 to 40 wt% in 100 wt% of the lubricant.

[0033] In the present embodiment, a ratio of a total weight of the class I petroleum and the class II petroleum to a weight of the base oil (i.e., the total weight of the class I petroleum and the class II petroleum / the weight of the base oil) is preferably in a range of 0.1 to 6.0.

[0034] In a case where the lubricant contains a propellant, the base oil content is preferably in a range of 20 to 80 wt% in 100 wt% of the lubricant, and the propellant content is preferably in a range of 30 to 70 wt% in 100 wt% of the lubricant. In a case where the lubricant contains no propellant, the base oil content is preferably in a range of 35 to 60 wt% in 100 wt% of the lubricant.

[0035] In a case where the lubricant in the present embodiment contains a propellant, a ratio of a weight of the propellant to a total weight of the cellulose microparticles, the class I petroleum, the class II petroleum, and the base oil (i.e., the weight of the propellant / the total weight of the cellulose microparticles, the class I petroleum, the class II petroleum, and the base oil) is preferably in a range of 0.4 to 2.5.Producing Method of Lubricant

[0036] The lubricant in the present embodiment may be produced by uniformly mixing a base oil, a cellulose microparticle, at least one selected from the group consisting of a class I petroleum and a class II petroleum, and another component if necessary. For example, a publicly known or commercially available apparatus such as a mixer and a kneader may be used for mixing.Use of Lubricant

[0037] The lubricant in the present embodiment may be used for application to a desired target such as a sliding part in various mechanical components included, for example, in an automobile, a motorcycle, a machine, and an electric or electronic device.

[0038] The lubricant is suitably used for application to a roller chain, and further suitably used for application to a motorcycle drive chain and a bicycle chain. Specifically, a chain such as a roller chain, a motorcycle drive chain, and a bicycle chain is liable to elongate mainly due to wear between a pin and a bush in the chain. When the elongation is at or over a certain limit, the chain no longer meshes with a sprocket smoothly. The lubricant in the present embodiment imparts excellent wear resistance to a sliding surface. Accordingly, the lubricant is applied to a sliding part of a roller chain, a motorcycle drive chain, and a bicycle chain, for example, so that the wear between the pin and the bush in the chain can be suppressed.Lubricant Application Method

[0039] In the present embodiment, the applying method of the lubricant to a desired target (sliding part) is not limited to a particular one, but a publicly known method such as an application in spray and an application with a brush may be used. The lubricant is suitable for the application in spray because it ensures an easy uniform application.

[0040] In the present embodiment, hereinafter, the lubricant applying method in spray will be specifically described.

[0041] In a case where the lubricant is applied in spray in the present embodiment, the lubricant preferably further contains a propellant in addition to the cellulose microparticle, the base oil and at least one selected from the group consisting of the class I petroleum and the class II petroleum. Further, it may be appreciated that the lubricant containing the components is contained in a desired spray container such as a general aerosol spray and applied in spray to a desired target (sliding part).

[0042] The propellant is not limited to a particular one as long as it can be used in spray together with the cellulose microparticle, the base oil and at least one selected from the group consisting of the class I petroleum and the class II petroleum. The state of the propellant may be either gaseous or liquid. As the propellant, for example, there are liquefied petroleum gas (LPG) which contains propane, butane, isobutane, or the like as a main component, dimethyl ether (DME), isopentane, nitrogen gas, and carbon dioxide. One kind of the propellant may be used singly, or two or more kinds of the propellant may be used.

[0043] Among them, LPG is preferably used as the propellant from the viewpoint of costs.

[0044] The lubricant containing no propellant may be contained in another type of spray container such as a so-called "atomizer".

[0045] The present specification discloses the technology having various features as described above. Among them, significant features are summarized hereinbelow.

[0046] A lubricant according to a first aspect includes a base oil, a cellulose microparticle, and at least one selected from the group consisting of a class I petroleum and a class II petroleum, wherein the cellulose microparticle content is in a range of 1 to 4.5 wt%.

[0047] A lubricant according to a second aspect is the lubricant according to the first aspect, in which a median diameter of the cellulose microparticle is in a range of 1 to 100 µm.

[0048] A lubricant according to a third aspect is the lubricant according to the first or second aspect, in which the class I petroleum includes at least one selected from the group consisting of isohexane, n-hexane, toluene, ethyl acetate, and n-heptane.

[0049] A lubricant according to a fourth aspect is the lubricant according to any one of the first to third aspects, in which the class II petroleum includes at least one selected from the group consisting of xylene, mineral spirit, and chlorobenzene.

[0050] A lubricant according to a fifth aspect is the lubricant according to any one of the first to fourth aspects, in which the base oil includes at least one selected from the group consisting of a mineral oil and a synthetic base oil.

[0051] A lubricant according to a sixth aspect is the lubricant according to any one of the first to fifth aspects, which is used for a roller chain.

[0052] A lubricant application method according to a seventh aspect includes applying the lubricant according to any one of the first to sixth aspect in spray.

[0053] Hereinafter, the present invention will be further specifically described by way of Examples. However, the present invention is not limited to the Examples.ExamplesExample 1

[0054] Lubricant containing cellulose microfiber (product number "F25", produced by Sugino Machine Limited, median diameter of 7 µm) (cellulose microparticle), isohexane (class I petroleum), a paraffinic mineral oil (base oil) as a mineral oil, and LPG (propellant) was prepared. Specifically, 1 wt% cellulose microfiber was contained in 100 wt% of the lubricant. Further, 24 wt% isohexane was contained in 100 wt% of the lubricant. Then, 25 wt% paraffinic mineral oil was contained in 100 wt% of the lubricant. Further, LPG was contained such that a ratio of a weight of LPG to a total weight of the cellulose microfiber, isohexane and the paraffinic mineral oil (LPG / cellulose microfiber, isohexane, and paraffinic mineral oil) is 1. The lubricant of Example 1 was thus obtained.Example 2

[0055] Lubricant of Example 2 was obtained in the same manner as Example 1 except that the cellulose micro fiber content was 3 wt% in 100 wt% of the lubricant and 22 wt% isohexane was contained in 100 wt% of the lubricant.Example 3

[0056] Lubricant of Example 3 was obtained in the same manner as Example 1 except that 24 wt% mineral spirit (class II petroleum) was contained in place of isohexane in 100 wt% of the lubricant.Comparative Example 1

[0057] Lubricant of Comparative Example 1 was obtained in the same manner as Example 1 except that no cellulose microfiber was contained, and 25 wt% isohexane was contained in 100 wt% of the lubricant.Comparative Example 2

[0058] Lubricant of Comparative Example 2 was obtained in the same manner as Example 1 except that the cellulose micro fiber content was 5 wt% in 100 wt% of the lubricant and 20 wt% isohexane was contained in 100 wt% of the lubricant.Comparative Example 3

[0059] Lubricant of Comparative Example 3 was obtained in the same manner as Example 1 except that no cellulose microfiber was contained, 25 wt% mineral spirit (class II petroleum) was contained in place of isohexane in 100 wt% of the lubricant, and 25 wt% polybutene was contained in place of the mineral oil as a hydrocarbon oil in 100 wt% of the lubricant.

[0060] Blending ratios of cellulose microparticles, class II petroleum, class I petroleum, base oil, and propellant in the lubricants of Examples 1 to 3 and Comparative Examples 1 to 3 described above are shown in Table 1. In Table 1, a content of each component in a composition is expressed in terms of "a percentage by weight". [Table 1]Example 1Example 2Example 3Comparative Example 1Comparative Example 2Comparative Example 3Cellulose microparticles131050Class I petroleumIsohexane2422025200Class II petroleumMineral spirit00240025Base oilPolybutene0000025Paraffinic mineral oil25252525250PropellantLPG505050505050 Wear Resistance Test

[0061] A wear resistance of the lubricants of Examples 1 to 3 and Comparative Examples 1 to 3, which were respectively obtained as described above, was evaluated according to a method described below.

[0062] First, a chain used for the wear resistance test was degreased. Specifically, a chain (product number "DID50", manufactured by Daido Kogyo Co., Ltd.) was immersed in cleaning liquid and degreased by an ultrasonic cleaning machine for 10 minutes. Subsequently, the chain was placed upside down and degreased for 10 minutes. Thereafter, unnecessary cleaning liquid was eliminated by an air blow. Lastly, the chain was dried in a thermostatic chamber at 40 °C for 12 to 15 hours and thereafter cleaned with acetone.

[0063] Next, a spray container (aerosol can) was filled with lubricant, and the lubricant was applied to the chain. As a specific application method, first, the aerosol can containing the lubricant (chain lube) was shaken substantially 100 times and thereafter the lubricant was applied to the chain while keeping a distal end of a nozzle of the aerosol can about 2 or 3 millimeters away from the chain. A more specific application method will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view of a chain 1 including a roller 2, a bush 3, a pin 4, an inner plate 5, and an outer plate 6. The chain 1 was placed on a workbench to expose the roller 2 upwardly. The lubricant was applied between the pin 4 and the bush 3 from both sides and was applied between the bush 3 and the roller 2. The chain 1 was placed upside down. The lubricant was applied between the pin 4 and the bush 3 from both sides and lastly was applied between the bush 3 and the roller 2. After the application, the chain was dried by keeping it in midair at a position parallel to a floor at a room temperature for an hour.

[0064] A length of the chain applied with the lubricant was measured. Thereafter, the chain was formed into an annular shape. The same pin and outer plates as those of the chain were used as a connecting component.

[0065] The chain having the annular shape was attached to two sprockets (number of teeth: Dr 15T × Dn 43T). In the attachment, a load of 1.5 kN (3 kN in total for both directions) was applied in a direction from a center of one sprocket to the other sprocket and in a direction opposite thereto (constantly tensioned on one side). The chain had a slack of substantially 30 mm. In this state, the sprockets were rotated at a rotational speed of 2000 rpm, and the elongation rate of the chain was measured every 7 hours or 15 hours. No lubrication was done during the measurement. An initial length of the chain before the test was measured, and a length of the chain every predetermined period was thereafter measured. The elongation rate represents in a percentage a proportional amount of an elongation of the chain against the initial length of the chain before the test.

[0066] Results of the wear resistance test are shown in Fig. 2 and Fig. 3. In Fig. 2 and Fig. 3, a vertical axis indicates an elongation rate (%), and a horizontal axis indicates time (hr).Discussion

[0067] Fig. 2 shows that, in the case that the lubricants of Examples 1 and 2 with proper cellulose microparticle contents were used, the elongation of the chain was suppressed, and a sliding surface had an excellent wear resistance. In contrast, in the case that the lubricant of Comparative Example 1 containing no cellulose microparticle was used, the elongation rate of the chain was higher, and the sliding surface had a poor wear resistance than Examples 1 and 3. The lubricant of Comparative Example 2, which contains the cellulose microparticles but the cellulose microparticle content is more than 4.5 wt%, imparted a poor wear resistance to the sliding surface than Examples 1 and 2.

[0068] Fig. 3 shows that the lubricant of Example 3 with a proper cellulose microparticle content imparted an excellent wear resistance. In contrast, the lubricant of Comparative Example 3 containing no cellulose microparticle imparted a poor wear resistance to a sliding surface than Example 3.

[0069] While the present invention has been fully and appropriately described in the above with reference to drawings and by way of embodiment in order to express the present invention, it is to be recognized that those skilled in the art can readily change and / or modify the embodiment described above. Therefore, it is to be construed that the changes or modifications made by those skilled in the art are encompassed within the scope of the claims unless those changes or modifications are at a level that departs from the scope of the claims described in the claims section of the present application.Industrial Applicability

[0070] The present invention can provide a lubricant that imparts an excellent wear resistance to a sliding surface.

Claims

1. A lubricant comprising a base oil, a cellulose microparticle, and at least one selected from the group consisting of a class I petroleum and a class II petroleum, wherein the cellulose microparticle content is in a range of 0.1 to 4.5 wt%.

2. The lubricant according to claim 1, wherein a median diameter of the cellulose microparticle is in a range of 1 to 100 µm.

3. The lubricant according to claim 1 or 2, wherein the class I petroleum includes at least one selected from the group consisting of isohexane, n-hexane, toluene, ethyl acetate, and n-heptane.

4. The lubricant according to any one of claims 1 to 3, wherein the class II petroleum includes at least one selected from the group consisting of xylene, mineral spirit, and chlorobenzene.

5. The lubricant according to any one of claims 1 to 4, wherein the base oil includes at least one selected from the group consisting of a mineral oil and a synthetic base oil.

6. The lubricant according to any one of claims 1 to 5, which is used for a roller chain.

7. A lubricant application method comprising applying the lubricant according to any one of claims 1 to 6 in spray.

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