Coating composition and dry lubricating film

Abstract

Provided are a coating composition that provides a dry lubricating film excellent in wear resistance, and the dry lubricating film thereof. A coating composition for forming a dry lubricating film, comprising a binder resin and a solid lubricant, the solid lubricant including graphite and molybdenum disulfide, the graphite including spherical graphite, and the content ratio (P / B) of the solid lubricant (P) to the binder resin (B) being 0.15 or more.

Description

Technical Field

[0001] The present invention relates to a paint composition for forming a dry lubricating film and a dry lubricating film.

Background Art

[0002] Conventionally, for the purpose of initial break-in countermeasures, improving baking properties, etc. of OA equipment, home appliances, automobiles, industrial machines, etc., a dry lubricating film in which a solid lubricant is dispersed and contained in a resin has been used. This dry lubricating film is formed by coating a composition containing a solid lubricant and a binder resin on the surface of a metal member or the surface of a rubber or resin member with an appropriate film thickness and drying or heat-curing it (for example, Patent Document 1).

[0003] In response to the recent demand for higher loads, it has been required to further improve the wear resistance of the dry lubricating film and extend the time (durability time) during which lubricity can be maintained.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been proposed in view of the above-described conventional circumstances, and an object thereof is to provide a paint composition that gives a dry lubricating film excellent in wear resistance and the dry lubricating film.

Means for Solving the Problems

[0006] The inventors of the present invention have intensively studied to solve the above-described problems. As a result, they have found that the above problems can be solved by using spherical graphite and molybdenum disulfide in combination as solid lubricants for the components constituting the dry lubricating film, and have thus completed the present invention. Specifically, the present invention is as follows.

[0007] (1) A paint composition for forming a dry lubricating film, comprising a binder resin and a solid lubricant, wherein the solid lubricant contains graphite and molybdenum disulfide, the graphite contains spherical graphite, and the content ratio (P / B) of the solid lubricant (P) to the binder resin (B) is 0.15 or more. Paint composition.

[0008] (2) The paint composition according to (1), wherein the graphite contains only spherical graphite.

[0009] (3) The paint composition according to (1) or (2), wherein the solid lubricant contains only spherical graphite and molybdenum disulfide.

[0010] (4) The paint composition according to any one of (1) to (3), wherein the content of the solid lubricant is 10 to 70% by mass based on the total solid content.

[0011] (5) The paint composition according to any one of (1) to (4), further comprising calcium carbonate.

[0012] (6) A dry lubricating film formed on the surface of a member and constituting a sliding layer, comprising a binder resin and a solid lubricant, wherein the solid lubricant contains graphite and molybdenum disulfide, the graphite contains spherical graphite, and the content ratio (P / B) of the solid lubricant (P) to the binder resin (B) is 0.15 or more. Dry lubricating film.

Advantages of the Invention

[0013] According to the present invention, it is possible to provide a paint composition that gives a dry lubricating film excellent in wear resistance, and the dry lubricating film thereof.

Modes for Carrying Out the Invention

[0014] Hereinafter, specific embodiments of the present invention (hereinafter referred to as "the present embodiment") will be described in detail. It should be noted that the present invention is not limited to the following embodiments, and various modifications can be made without departing from the gist of the present invention.

[0015] ≪1. Paint composition for forming dry lubricating film≫ The paint composition according to the present embodiment is a paint composition for forming a dry lubricating film. In particular, this paint composition is a paint composition for forming a dry lubricating film excellent in wear resistance.

[0016] Specifically, the paint composition according to the present embodiment contains a binder and a solid lubricant, the solid lubricant contains graphite and molybdenum disulfide, the graphite contains spherical graphite, and the content ratio (P / B) of the solid lubricant (P) to the binder (B) is 0.15 or more. It should be noted that the paint composition is composed of solid components (active ingredients) such as a binder resin and a solid lubricant dissolved or dispersed in a solvent that is a volatile component.

[0017] The reason why excellent wear resistance is obtained in the dry lubricating film formed by the paint composition according to the present embodiment is considered as follows.

[0018] As solid lubricants, for example, polytetrafluoroethylene (PTFE) has been used, where the discharged wear debris adheres to the mating material to form a good sliding surface. However, under high loads, wear is accelerated and the durability time may be shortened. On the other hand, by using molybdenum disulfide and graphite in combination, the film strength under high loads is increased and the wear resistance is improved. In particular, by using spherical graphite without orientation as graphite, a high load can be received at a constant surface pressure, so more stable wear resistance can be obtained.

[0019] <1-1. Regarding the constituent components> [Binder resin] The binder resin is not particularly limited. For example, polyamideimide resin, urethane resin, epoxy resin, phenol resin, acrylic resin, silicone resin, silicone polyester resin, melamine resin, polyimide resin, polyethersulfone resin, polyetheretherketone resin, etc. may be mentioned. Among these, polyamideimide resin is preferred in terms of wear resistance and adhesion to various metal substrates. These may be used alone or in combination of two or more.

[0020] The content of the binder resin is preferably 30% by mass or more, more preferably 40% by mass or more, still more preferably 50% by mass or more, and particularly preferably 60% by mass or more with respect to the total solid content contained in the coating composition. Also, 90% by mass or less is preferred, 85% by mass or less is more preferred, and 80% by mass or less is still more preferred. Within the above numerical range, good wear resistance is easily obtained.

[0021] [Solid lubricant] In this specification, the solid lubricant means a solid substance having self-lubricity. The solid lubricant includes graphite and molybdenum disulfide (MoS2). Examples of solid lubricants other than graphite and molybdenum disulfide include polytetrafluoroethylene (PTFE), tungsten disulfide (WS2), boron nitride (BN), graphene, etc. These may be used alone or in combination of two or more.

[0022] The graphite includes spherical graphite. Examples of graphite other than spherical graphite include flaky graphite. These may be used alone or in combination of two or more.

[0023] In this specification, spherical graphite means graphite having an aspect ratio (major axis / minor axis) of 1 to 2. The aspect ratio (major axis / minor axis) is obtained by measuring the major axis and minor axis of 50 arbitrarily selected graphite particles included in the captured image obtained when observing graphite at a magnification of 1000 times using a scanning electron microscope, and dividing the major axis by the minor axis for each particle to obtain the value of the aspect ratio (major axis / minor axis), and means the arithmetic mean value of the values of the aspect ratio (major axis / minor axis) obtained for 50 particles.

[0024] The average particle size of the solid lubricant may be, for example, 0.1 to 50 μm, or 1 to 20 μm.

[0025] From the viewpoint of wear resistance, the mass of spherical graphite in 100% by mass of graphite is preferably 70% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 100% by mass (graphite contains only spherical graphite).

[0026] From the viewpoint of wear resistance, the total mass of spherical graphite and molybdenum disulfide in 100% by mass of the solid lubricant is preferably 70% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 100% by mass (the solid lubricant contains only spherical graphite and molybdenum disulfide).

[0027] The content of spherical graphite is preferably 5% by mass or more, more preferably 7% by mass or more, and still more preferably 10% by mass or more, based on the total solid content contained in the coating composition. Also, it is preferably 35% by mass or less, more preferably 30% by mass or less, still more preferably 25% by mass or less, and particularly preferably 20% by mass or less. When within the above numerical range, good abrasion resistance is easily obtained.

[0028] The content of molybdenum disulfide is preferably 5% by mass or more, more preferably 7% by mass or more, and still more preferably 10% by mass or more, based on the total solid content contained in the coating composition. Also, it is preferably 35% by mass or less, more preferably 30% by mass or less, still more preferably 25% by mass or less, and particularly preferably 20% by mass or less. When within the above numerical range, good abrasion resistance is easily obtained.

[0029] The ratio of the mass of spherical graphite to the mass of molybdenum disulfide is preferably 10:90 to 90:10, more preferably 30:70 to 70:30, and still more preferably 40:60 to 60:40. When within the above numerical range, good abrasion resistance is easily obtained.

[0030] The content of the solid lubricant is preferably 10% by mass or more, more preferably 15% by mass or more, and still more preferably 20% by mass or more, based on the total solid content contained in the coating composition. Also, it is preferably 70% by mass or less, more preferably 60% by mass or less, still more preferably 50% by mass or less, and particularly preferably 40% by mass or less. When within the above numerical range, good abrasion resistance is easily obtained.

[0031] [Extender pigment] The coating composition preferably contains an extender pigment from the viewpoint of easily reinforcing the dry lubricating film and improving abrasion resistance. Examples of the extender pigment include calcium carbonate, barium sulfate, silica, etc. Among these, calcium carbonate is preferable from the viewpoint of abrasion resistance. These may be used alone or in combination of two or more.

[0032] The content of the extender pigment is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, based on the total solid content contained in the coating composition. Further, it is preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 6% by mass or less. When within the above numerical range, good abrasion resistance is easily obtained.

[0033] [Solvent] As described above, the coating composition is constituted by dissolving or dispersing a solid component containing the above-described binder resin, a solid lubricant, and, if necessary, an extender pigment in a solvent. When the coating composition is applied to the surface of an object to be coated (member) and subjected to a treatment such as baking, the solvent volatilizes and a dry lubricating film composed of the solid component is formed.

[0034] The solvent is not particularly limited, and it is preferably selected in consideration of the dissolving power for the binder resin to be used, drying properties, etc. Specifically, for example, when a polyamideimide resin is used as the binder resin, organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and cyclopentanone can be mentioned. These may be used alone or in combination of two or more.

[0035] [Other Additives] In the coating composition, various additive components can be contained as necessary. Specifically, for example, additives such as an anti-settling agent, a wetting and dispersing agent, an antifoaming agent, and a surface conditioner can be used.

[0036] The content ratio (P / B) (mass ratio) of the solid lubricant (P) to the binder resin (B) is 0.15 or more, preferably 0.2 or more, and more preferably 0.25 or more. Further, it is preferably 2.5 or less, more preferably 1.5 or less, even more preferably 1 or less, and particularly preferably 0.7 or less. When within the above numerical range, good abrasion resistance is easily obtained.

[0037] When the coating composition contains an extender pigment, the content ratio (P / E) (mass ratio) of the solid lubricant (P) to the extender pigment (E) is preferably 1 or more, more preferably 2.5 or more, and even more preferably 3 or more. Also, it is preferably 50 or less, more preferably 30 or less, and even more preferably 10 or less. When within the above numerical range, good abrasion resistance is easily obtained.

[0038] <1-2. Manufacturing Method of Coating Composition> The manufacturing method of the coating composition for forming a dry lubricating film according to this embodiment is not particularly limited and can be manufactured by a conventionally known method.

[0039] Specifically, it can be manufactured by blending and kneading a binder resin as a solid component, a solid lubricant, an extender pigment and other additives as required, and a solvent as a volatile component so that they have predetermined content ratios.

[0040] At this time, it is important that the solid lubricant is uniformly dispersed in the solution of the binder resin uniformly dissolved in the solvent. Therefore, for example, a solvent is put into a stirring container, and then a binder resin and a solid lubricant weighed so as to have a predetermined blending ratio are put in, and they are stirred by a stirrer such as a dissolver type stirrer or a ball mill until these materials are uniformly dissolved or dispersed. Further thereafter, it is preferable to perform a dispersion treatment for uniformly dispersing the solid lubricant in the solution of the binder resin using a disperser such as a sand mill type or a three-roll type according to the concentration of the active ingredient and the like.

[0041] Although an example in which the binder resin and the solid lubricant are put into the solvent and kneaded and dispersion-treated has been described, it is not limited thereto, and it may be diluted by adding the solvent after the dispersion treatment to obtain a composition.

[0042] ≪2. Formation of Dry Lubricating Film by Coating Composition≫ As described above, the paint composition according to this embodiment is for forming a dry lubricating film. By applying this paint composition to an object to be coated (member) and then performing a curing treatment, a dry lubricating film can be formed.

[0043] <2-1. Method for forming dry lubricating film> (Object to be coated) The object to be coated is not particularly limited. For example, metal members, rubber members, resin members, etc. can be mentioned, and a film can be formed by applying the paint composition to the surface of these members.

[0044] (Coating method) The method for applying the paint composition to the object to be coated is not particularly limited. Similar to general paints, for example, it can be carried out by methods such as air spray coating, dipping coating, brush painting, tumbling by spraying, screen printing, etc. The selection of these coating methods can be appropriately set according to the shape of the object to be coated and the processing quantity.

[0045] Note that prior to applying the paint composition to the object to be coated, degreasing treatment, surface treatment to enhance the adhesion of the film, or cleaning treatment, etc. can be performed on the object to be coated.

[0046] (Film thickness of dry lubricating film) The film thickness of the dry lubricating film to be formed is not particularly limited and can be appropriately determined according to the use of the object to be coated, etc. For example, it is preferably about 5 μm to 50 μm, and more preferably about 10 μm to 25 μm.

[0047] When applying the paint composition to the object to be coated, it is preferable to determine the coating amount so that the dry film obtained by curing the coating film (dry lubricating film composition) by means such as heating has the desired film thickness (dry film thickness), and then apply it.

[0048] (Curing treatment) The curing treatment of the coating film formed by applying the coating composition to the object to be coated is not particularly limited and can be carried out by ordinary coating film drying methods or baking methods.

[0049] <2-2. Dry Lubricating Coating> As described above, a dry lubricating coating can be formed by applying the coating composition to the surface of an object to be coated such as a resin member and curing it. Specifically, the dry lubricating coating formed by the coating composition according to the present embodiment contains a binder and a solid lubricant. The solid lubricant contains graphite and molybdenum disulfide, the graphite contains spherical graphite, and the content ratio (P / B) of the solid lubricant (P) to the binder (B) is 0.15 or more.

[0050] The dry lubricating coating formed on the surface of a member such as a resin member which is the object to be coated can constitute a sliding layer in that member.

Examples

[0051] Hereinafter, the examples and comparative examples of the present invention will be shown and described more specifically, but the present invention is not limited to these examples and comparative examples.

[0052] ≪Examples and Comparative Examples≫ A coating composition for forming a dry lubricating coating was produced, the obtained coating composition was applied to an object to be coated and cured to form a dry lubricating coating, and the following tests were carried out on the dry lubricating coating to evaluate its properties.

[0053] [Production of Coating Composition for Forming Dry Lubricating Coating] In Examples 1 to 6 and Comparative Examples 1 to 7, they were respectively weighed and mixed so as to have the mass compounding ratios shown in Table 1 below. Further, a solvent (N-methyl-2-pyrrolidone) was added, and kneading was carried out using a dispermat to prepare a coating composition. Furthermore, in order to uniformly disperse the solid lubricant in the coating composition, a dispersion treatment was performed using a sand mill. In addition, a dispersant was contained as an additive in each coating composition.

[0054] The details of the binder resin, solid lubricant, and extender pigment in Table 1 are as follows. PTFE: Amorphous, average particle size 0.5 μm Flaky graphite: Flaky, average particle size 5 μm Spherical graphite: Spherical, ratio of major axis to minor axis (major axis / minor axis) 1.8, average particle size 8 μm Molybdenum disulfide: Flaky, average particle size 5 μm Calcium carbonate: Amorphous, average particle size 0.5 μm

[0055] [Formation of dry lubricating film] Using carbon steel (S45C) as the base material (pretreatment: #180 polishing), the paint compositions prepared in each example and comparative example were sprayed and applied by air spraying. Then, the organic solvent contained in the paint composition was removed by drying, and fired at 250 °C for 30 minutes. As a result, a dry lubricating film with a film thickness of 25 μm was formed on the surface of the base material. In addition, evaluation was performed using a test piece of a sliding member having the dry lubricating film thus formed as a sliding layer.

[0056] ≪Evaluation test, evaluation results≫ Under the following test conditions, the limit durability and wear resistance of the dry lubricating films (sliding layers) prepared in each example and comparative example were evaluated. In the evaluation of the limit durability, the time until seizure occurred (maximum 360 minutes) was used as the test time, and the time until the end of the test (durability time) was measured. In addition, the friction coefficient immediately before seizure occurred (if seizure did not occur, immediately before the end of the test) was also measured. In the evaluation of wear resistance, for each example and comparative example where the durability time was 120 minutes or more, a test with a test time of 120 minutes was performed again, and the wear amount at the end of the test was measured. In addition, the friction coefficient immediately before the end of the test was also measured. These results are shown in Table 1.

[0057] (Test conditions) Test machine used: Ring on Disk test machine Disk (material): Coating treatment (#180 polished S45C) Disk (shape): φ55 × 5 mm Ring (material): Untreated (#2000 polished S45C) Ring (shape): Outer diameter 26 mm, inner diameter 20 mm, length 20 mm, hollow cylinder Oil: None Rotation speed: 500 rpm Load (surface pressure): 2000 N

[0058]

Table 1

[0059] As shown in Table 1, Examples 1 to 6, which contain spherical graphite and molybdenum disulfide as solid lubricants and have a P / B of 0.15 or more, had a longer endurance time and less wear amount than Comparative Examples 1 to 7.

Claims

1. A coating composition for forming a dry lubricating coating, comprising: The present invention includes a binder resin, a solid lubricant, and calcium carbonate, the solid lubricant includes graphite and molybdenum disulfide; The graphite comprises spherical graphite; a content ratio (P / B) of the solid lubricant (P) to the binder resin (B) is 0.15 or more; Paint composition.

2. 2. The coating composition of claim 1, wherein the graphite comprises only spherical graphite.

3. 3. The coating composition according to claim 1, wherein the solid lubricant comprises only spherical graphite and molybdenum disulfide.

4. 3. The coating composition according to claim 1, wherein the content of the solid lubricant is 10 to 70 mass % based on the total solid content.

5. A dry lubricating coating formed on a surface of a member to constitute a sliding layer, The present invention includes a binder resin, a solid lubricant, and calcium carbonate, the solid lubricant includes graphite and molybdenum disulfide; The graphite comprises spherical graphite; a content ratio (P / B) of the solid lubricant (P) to the binder resin (B) is 0.15 or more; Dry lubricating film.

Images