JP2020186361A - Coating film for metal member - Google Patents

Abstract

To provide a coating film that is smooth and can maintain wear resistance and low friction properties for a long time, the coating film being particularly suitable for a metal member.SOLUTION: A coating film for a metal member contains a resin (B) having an amide structure and an imide structure in a molecule skeleton, and graphite (SL1) and fluororesin (SL2).SELECTED DRAWING: Figure 1

Description

The present invention relates to a coating film formed on the surface of a metal member.

As an image formation recording method in an image formation recording device (hereinafter referred to as a copying machine) in which a copier and a facsimile are integrated, a mechanism for transferring toner onto a recording material using a photoconductor or the like is generally used. In such a copying machine, in order to fix the transferred toner 1 on the recording paper 2, a fixing mechanism including a fixing roller (belt) 3, a fixing pad 4, and a pressure roller 5 (hereinafter, referred to as a fixing unit). FIG. 1: A fixing unit mechanism) is provided, and the toner is fixed to the recording paper by pressurizing and heating when the recording paper passes between the pressure roller 5 and the fixing roller (belt) 3. A metal having excellent thermal conductivity is preferably used for the fixing pad 4 in the fixing unit in order to uniformly apply the heat of the halogen heater 5 to the toner 1 on the recording paper, but it slides on the inner peripheral surface of the fixing roller (belt) 3. Therefore, sliding resistance is generated. Since the sliding resistance hinders the operation of the fixing roller (belt) 3 and causes scratches and bleeding when the toner 1 is fixed to the recording paper, the fixing pad 4 comes into contact with the inner peripheral surface of the fixing roller (belt) 3. A low friction coating 6 is applied to the surface.

By the way, the polyimide resin coating film is a coating film having excellent wear resistance obtained by applying a polyamide-imide solution on a base material and then imidizing it by firing with heat, but generally at a high temperature of 300 ° C. or higher. Since it is necessary to perform firing, there is a restriction that a material that can withstand such a high temperature must be selected as the base material to be coated. On the other hand, if imidization is carried out at a relatively low temperature for a long time, only low molecular weight polyimide can be obtained, which causes a problem that the strength of the coating film is lowered.

Patent Document 1 is a polyimide composition used for coating a copying machine member, and is characterized by containing a polyimide solution obtained by mixing polyamide-imide, a dehydration cyclization reagent, a solvent, a fluororesin, and carbon black. Disclosed is a copying machine member characterized in that the polyimide composition to be used and a coating film formed by applying the polyimide composition to a base material and removing a solvent at a temperature of 250 ° C. or lower is provided on the surface. Has been done.

Japanese Unexamined Patent Publication No. 2013-6959

However, when the surface of such a copying machine member is continuously rubbed, the coating film obtained by simply adding carbon black, which has lubricity but does not have low frictional properties, to the polyimide solution is low. It is difficult to maintain frictional properties for a long period of time. Further, the polyimide solution in which the conductive carbon black particles having a large specific surface area are excessively blended has a significantly high viscosity. When such a high-viscosity solution is used as a coating film to form a film, a fine uneven surface (so-called yuzu skin) is formed, and the surface of the obtained coating film lacks smoothness and has poor wear resistance. Therefore, an object of the present invention is to provide a coating film which is smooth and can maintain wear resistance and low friction resistance for a long period of time, particularly a coating film suitable for a metal member.

The present invention includes the following.
[1] A coating film containing a resin (B) having an amide structure and an imide structure as a molecular skeleton, graphite (SL1), and a fluororesin (SL2).
[2] The weight ratio of the graphite (SL1) to the fluororesin (SL2) is more than 0.05: less than 1-3.3: 1, preferably 0.15: 1 to 2.5: 1. The coating film according to [1], which is present or is 0.37: 1 to 1: 1.
[3] The volume ratio of the solid lubricant (SL) composed of the graphite (SL1) and the fluororesin (SL2) to the resin (B) having the amide structure and the imide structure in the molecular skeleton is more than 0.1: [1] or [2], characterized in that it is less than 1-2: 1, preferably 0.2: 1-1.5: 1, or 0.5: 1-1.5: 1. ] The coating film described in.
[4] The coating film according to any one of [1] to [3], wherein the graphite (SL1) is an amorphous particle composed of graphite microcrystals.
[5] The item according to any one of [1] to [3], wherein the graphite (SL1) is at least one selected from the group consisting of scaly graphite, earth-like graphite and artificial graphite. Coating film.
[6] A metal member having the coating film according to any one of [1] to [5] on its surface.

Since graphite has a smaller specific surface area than carbon black, it does not increase the viscosity of the paint. Therefore, the surface of the coating film can be finished smoothly. Further, since graphite is excellent in low frictional property as compared with carbon black, it is possible to form a coating film having a low friction coefficient and maintain the friction coefficient low. As described above, by providing the coating film according to the present invention, it is possible to easily obtain a metal member that is smooth and can maintain wear resistance and a low coefficient of friction for a long period of time.

It is the schematic which showed the fixing unit mechanism.

Hereinafter, a method for producing a coating composition, a method for producing a coating film, and the like according to the present invention will be described in order.

[Manufacturing of coating composition]
[Polyamide-imide resin (A)]
A polyamide-imide resin (A) is blended in the coating composition according to the present invention. In the following description of the present specification, this may be referred to as a "binder having an amide structure and an imide structure in the molecular skeleton" or simply a "binder".
The polyamide-imide resin can be produced by reacting (a) a derivative of a trivalent carboxylic acid having an acid anhydride group, (b) a mixture of aromatic polyisocyanate and other optional components. Examples of the method include, but are not limited to, the following methods.
(1) A method of obtaining a polyamide-imide resin by mixing all the components (a), (b) and other optional components at once and reacting them.
(2) A method of deriving an amideimide oligomer having an isocyanate group at the terminal from the component (b) and reacting it with the component (a) to obtain a polyamide-imide resin.
(3) A method of deriving an amide-imide oligomer having an acid or acid anhydride group at the terminal from the component (a) and reacting it with the component (b) to obtain a polyamide-imide resin.

As the component (a), aromatic tricarboxylic acid anhydride is preferable. For example, the compound of the following formula can be preferably used.

(However, in both equations, R and R'indicate hydrogen, an alkyl group or a phenyl group having 1 to 10 carbon atoms, and Y indicates -CH _2- , -CO-, -SO _2- , or -O-. .)

The component (a) is used alone or in combination of two or more depending on the purpose.
Trimellitic anhydride is particularly preferable in consideration of heat resistance, cost, and the like.

In addition to the above compounds, if necessary, tetracarboxylic dianhydride (pyromellitic acid dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic dianhydride, 3,3', 4, 4'-biphenyltetracarboxylic acid dianhydride, 1,2,5,6-naphthalenetetracarboxylic acid dianhydride, 2,3,5,6-pyridinetetracarboxylic acid dianhydride, 1,4,5,8 -Naphthalenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 4,4'-sulfonyldiphthalic acid dianhydride, m-terphenyl-3,3', 4, 4'-tetracarboxylic dianhydride, 4,4'-oxydiphthalic acid dianhydride, 1,1,1,3,3,3-hexafluoro-2,2-bis (2,3- or 3,4) -Dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3- or 3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis [4- (2,3- or 3,3) 4-dicarboxyphenoxy) phenyl] propane dianhydride, 1,1,1,3,3,3-hexafluoro-2,2-bis [4- (2,3- or 3,4-dicarboxyphenoxy) Phenyl] Propane dianhydride, 1,3-bis (3,4-dicarboxyphenyl) -1,1,3,3-tetramethyldisiloxane dianhydride, butanetetracarboxylic dianhydride, bicyclo- [2 , 2,2] -Octo-7-ene-2: 3: 5: 6-tetracarboxylic dianhydride, etc.), aliphatic dicarboxylic acids (succinic acid, glutaric acid, adipic acid, azelaic acid, suberic acid, sebacine, etc.) Acid, decanedioic acid, dodecanedioic acid, dimeric acid, etc.), aromatic dicarboxylic acid (isophthalic acid, terephthalic acid, phthalic acid, naphthalenedicarboxylic acid, oxydibenzoic acid, etc.) are used together as part of the component (a). can do.

(B) Examples of the aromatic polyisocyanate include 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, 4,4'-diphenyl ether diisocyanate, and 4,4'-[2,2-bis (4-2-bis). Phenoxyphenyl) propane] diisocyanate, biphenyl-4,4'-diisocyanate, biphenyl-3,3'-diisocyanate, biphenyl-3,4'-diisocyanate, 3,3'-dimethylbiphenyl-4,4'-diisocyanate, 2 , 2'-dimethylbiphenyl-4,4'-diisocyanate, 3,3'-diethylbiphenyl-4,4'-diisocyanate, 2,2'-diethylbiphenyl-4,4'-diisocyanate, 3,3'-dimethoxy Biphenyl-4,4'-diisocyanate, 2,2'-dimethoxybiphenyl-4,4'-diisocyanate, naphthalene-1,5-diisocyanate, naphthalene-2,6-diisocyanate and the like can be used. These can be used alone or in combination. Hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, transcyclohexane-1,4-diisocyanate, hydrogenated m-xylylene diisocyanate as part of this, if necessary. Aliphatic, alicyclic isocyanates such as isocyanate and lysine diisocyanate and trifunctional or higher functional polyisocyanates can also be used.

4,4'-diphenylmethane diisocyanate is preferable from the viewpoint of balancing the heat resistance, solubility, mechanical properties, cost, etc. of the coating film.
Further, if the solvent resistance of the coating film is emphasized, toluene diisocyanate and 3,3'-dimethylbiphenyl-4,4'-diisocyanate are preferable.
In order to improve the weather resistance of the coating film, a blocking agent having stabilized isocyanate groups can also be used. Alcohol, phenol, oxime and the like are usually used as the blocking agent, but the blocking agent is not limited thereto.

The molar ratio of (b) aromatic polyisocyanate to (a) aromatic tricarboxylic acid anhydride to be subjected to the reaction is preferably 1.0: 0.9 to 1.0: 1.3, or 1.0: 0. It is 95 to 1.0: 1.2, or 1.0: 1.0 to 1.0: 1.1, or 1.0: 1.02 to 1.0: 1.05.

As an example of other optional components, for example, Nippon Soda Co., Ltd. Nisso-PB series, Ube Industries, Ltd. Hycar-RLP series (CTBN1300X9, etc.), Thiokol Co., Ltd. HC-polymer series, General Tire Co., Ltd. Telagen series, Phillips. Examples thereof include dicarboxylic acids such as the Butaretz series manufactured by Petroleum. These can be used alone or in combination of two or more.

The molar ratio of (a) aromatic tricarboxylic acid anhydride to the dicarboxylic acid to be subjected to the reaction is preferably 0.45: 0.55 to 0.8: 0.2, or 0.5: 0.5 to 0. It is 8: 0.2, or 0.55: 0.45-0.8: 0.2, or 0.6: 0.4 to 0.7: 0.3.

In order to reduce the elastic modulus of the coating film, a urethane bond can be further introduced by using a divalent or higher valent alcohol, carbonate diol or the like as a reaction raw material, and a more flexible resin can be obtained. Examples of the carbonate diol include CD220 and CD220PL manufactured by Daicel Chemical Industries, Ltd., and examples of the alcohol include ethylene glycol, but the alcohol is not limited thereto.

The reaction involves polar solvents such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide and γ-butyrolactone, aromatic hydrocarbon solvents such as xylene and toluene, methyl ethyl ketone, methyl isobutyl ketone and the like. It is carried out in a solvent such as ketones. The amount of the solvent used is not particularly limited, but is preferably 50 to 500 parts by weight with respect to 100 parts by weight of the total solid content. The reaction conditions can be appropriately determined by preliminary experiments. In order to reduce the influence of moisture in the air, it is generally carried out at a temperature of 80 to 150 ° C. in an inert atmosphere such as nitrogen.

The number average molecular weight of the polyamide-imide resin is usually 9,000 to 90,000. It is preferably 9,000 to 70,000, or 12,000 to 40,000, or 16,000 to 27,000.

The number average molecular weight of the polyamide-imide resin is determined by taking a sample from the product being synthesized at any time and determining the number average molecular weight by gel permeation chromatography (GPC) using a standard polystyrene calibration curve. It can be kept within the above range by continuing the synthesis until it becomes.

The polyamide-imide resin has, for example, a repeating unit of the following formula.

In the above formula, X indicates (a) a residue of the aromatic tricarboxylic acid anhydride excluding the acid anhydride group and the carboxyl group, and R indicates (b) a residue of the aromatic polyisocyanate excluding the isocyanate group.

Examples of the polyamide-imide resin include Toron (registered trademark) AI-10, Toron (registered trademark) AI-10 LM, Toron (registered trademark) AI-10 LS (all available from Solvay Specialty Polymers Japan Co., Ltd.), Component AI301 (manufactured by Arakawa Chemical Industry Co., Ltd.), Viromax (registered trademark) HR-11NN, HR-13NX, HR-16NN (all manufactured by Toyo Boseki Co., Ltd.), HPC-5010-30 (manufactured by Hitachi Kasei Co., Ltd.), etc. Is commercially available.

[Solid lubricant]
A solid lubricant is added to the coating composition according to the present invention. A solid lubricant is a solid substance used to reduce friction and wear on the surface of a material that moves relative to each other and to prevent damage. The solid lubricant to be blended in the coating composition according to the present invention contains graphite (SL1) and a fluororesin (SL2), and optionally contains other conventional solid lubricants such as carbon black. Preferably, the solid lubricant to be blended in the coating composition according to the present invention comprises graphite (SL1) and a fluororesin (SL2).

[Graphite (SL1)]
Graphite is an elemental mineral composed of carbon and is roughly classified into natural graphite and artificial graphite. Natural graphite includes earth-like graphite (amorphous graphite), scaly graphite (vein graphite), scaly graphite (flake graphite), spherical graphite (spherical graphite), expanded graphite (expandable graphite), and expanded graphite (expanded graphite). Can be mentioned. Examples of artificial graphite include artificial graphite (artificial graphite) and pyrolytic graphite (pyrolytic graphite). Of these, any one or two or more thereof can be appropriately selected and used in the present invention.

Of these, earthy graphite is generally characterized by a fixed carbon of 75-90%, an ash content of 8-21%, a volatile content of 2-4%, and an average particle size of 1.5-30 μm. On the other hand, graphites other than earth-like graphite usually have a fixed carbon content of 97% or more, often 98% or more, and a volatile content of 2% or less, often 1% or less.

Flaky graphite shows almost perfect crystals and is highly anisotropy. Compared to scaly graphite, scaly graphite has thicker scallops, and the average particle size is usually 35 μm or less. Spherical graphite is a spheroidized version of scaly graphite, and is characterized in that it has an ash content of 0.1% or less, a volatile content of 1% or less, and an average particle size of 40 μm or less. Expanded graphite and expanded graphite are graphite before and after expansion, respectively, and fixed carbon is approximately 92-95% for the former and 97-99% for the latter. The latter is obtained by cutting a graphite sheet and pulverizing it, and is characterized in that it has an ash content of about 1% and a volatile content of about 2%.

Artificial graphite is characterized by an ash content of about 1%. The pyrolytic graphite is obtained by heat-treating powdered coke to graphitize it, and is characterized in that it has an ash content of about 1% and an average particle size of about 40 μm or less.

Of the above, graphite in the form of amorphous particles composed of graphite microcrystals is preferable, and artificial graphite and earth-like graphite are particularly preferable.

Various types of graphite are commercially available. As earth-like graphite, CP2000M, MAC-5, 3000M (all Ito Graphite Industry Co., Ltd.), 1.5 μm, A-0, AG-30 (all Fuji Kokuen Industry Co., Ltd.), APR, K-5 (all) Also, earth-like graphite from Chuetsu Graphite Industry Co., Ltd.) is available. As artificial graphite, G-4AK (manufactured by Chuetsu Graphite Industry Co., Ltd.) is available.

[Fluorine resin (SL2)]

The fluorine-based resin refers to a polymer containing a structural unit derived from an olefin (fluoroolefin) containing a fluorine atom. Since the fluororesin can also impart releasability to the copying machine member, it can be expected to have an effect of preventing a developer such as toner from adhering to the copying machine member and facilitating transfer and fixing.

Examples of the fluoroolefin include vinylidene fluoride, hexafluoropropylene, tetrafluoroethylene and the like.
Specific examples of the fluororesin include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), ethylene tetrafluoroethylene-propylene hexafluoride resin (FEP), and tetrafluoroethylene. Tetrafluoroethylene copolymer (ETFE), ethylene trifluorochloride resin (PCTFE), ethylene trifluoroethylene-ethylene copolymer (ECTFE), perfluorocyclic polymer, vinyl fluoride resin (PVF) and the like are preferable. Can be mentioned. Of these, any one or two or more thereof can be appropriately selected and used in the present invention.

Fluorine-based resins are usually dispersed and blended in a coating composition in the form of particles, but in that case, the surface of the obtained coating film becomes rough and surface physical properties such as oil repellency are impaired. It is necessary to select fluororesin particles having an average particle size smaller than the thickness of the coating film so as not to prevent the particles. For example, the average particle size of the fluororesin particles is 25 μm or less, 10 μm or less, or 1 μm or less.

Fluorine-based resins include Fluorocarbon (registered trademark) PTFE Lubricant L172JE (manufactured by AGC), Lubron L-5, Lubron L-5F (all manufactured by Daikin Industries, Ltd.), Dynion TF9205, and Dynion TF9207Z (all manufactured by 3M Japan Ltd.). , TFW-500 (manufactured by Seishin Enterprise Co., Ltd.), Argoflon L206 (manufactured by Solvay Specialty Polymers Japan Ltd.) and the like are commercially available.

(Low friction over time and its suppression mechanism)
It is a common practice to use two or more types of solid lubricants in combination to improve low friction. Although it is not desired to be bound by the theory, it is presumed that when graphite and a fluororesin are used in combination, the fluororesin penetrates into the gaps in the layer structure of the graphite crystal to improve the low friction property. Therefore, scaly graphite having a large layer structure is preferably used as graphite. However, it cannot be denied that the fluororesin may be separated from the gaps in the layered structure of the scaly graphite due to long-term friction to worsen the low friction property. In this respect, since the particle shape of earth-like graphite is irregular, the fluororesin is held in the gaps between the particles. As a result, it is possible to suppress the desorption of the fluororesin in a long-term friction environment and suppress the change with time of low friction.

Carbon black may be blended in the coating composition according to the present invention. By containing carbon black, it is possible to impart antistatic properties to the copying machine member, prevent a developer such as toner from adhering to the copying machine member, and facilitate transfer and fixing. It is preferable that carbon black is blended in a uniformly dispersed state in the coating composition. However, it is not preferable to mix it in a high concentration because it has a great effect of increasing the viscosity of the coating composition. The upper limit of the concentration is, for example, 5% by weight, 3% by weight, or 1% by weight.

There are no particular restrictions on the type of carbon black, and available ones can be used. For example, pyrolysis of furnace black obtained by incomplete combustion of oil or gas in high temperature gas, channel black obtained by burning natural gas and collecting what is deposited on channel steel, and acetylene gas. Examples thereof include acetylene black obtained by, thermal black obtained by repeating combustion and decomposition of gas in a heat-storing furnace, carbon nanotubes, and the like. Only one type of carbon black may be used, or two or more types may be used.

[Other ingredients]
In the coating composition according to the present invention, various additives usually used, such as surfactants, dispersants, organic solvents, inorganic fillers, mold release agents, coupling agents, and flame retardants, are further added depending on the intended use. Etc. can be appropriately blended as long as the effects of the present invention are not impaired.

As the surfactant, Megafuck F444 (fluorine-based surfactant manufactured by DIC), Megafuck F555 (fluorine-based surfactant manufactured by DIC), Futergent 215M (fluorine-based surfactant manufactured by Neos Co., Ltd.), Surflon S420 ( Examples thereof include fluorine-based surfactants manufactured by AGC Seimi Chemical Co., Ltd.), FC4430 (fluorine-based surfactants manufactured by 3M Japan Co., Ltd.), and KP341 (silicone surfactants manufactured by Shin-Etsu Chemical Industry Co., Ltd.).

[solvent]
In addition to the above, a solvent can be added to the coating composition according to the present invention in consideration of the coatability of the composition. Such a solvent is not particularly limited as long as it dissolves the polyamide-imide resin. For example, N, N-dimethylacetamide, N, N-dimethylformamide, 4-formylmorpholine (4-morpholincarbaldehyde), N, N-acetylformamide, 3-methoxy-N, N-dimethylpropionamide, N, N. -Dimethylpropionamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, ethyl acetate, dimethylethanolamine, triethylamine, water and the like can be mentioned. These may be used alone or in combination of two or more. It is preferable to select a solvent that can be easily removed after film formation.

[Combining of each ingredient]
In the coating composition according to the present invention, the above-mentioned polyamide-imide resin (A), graphite (SL1), fluorinated resin (SL2), and other optional components are mixed with the above solvent by a conventional method. It can be prepared by stirring and dissolving.

The content of the polyamide-imide resin (A) in the coating composition according to the present invention can be appropriately selected as long as the amide structure to be produced and the resin (B) having the imide structure in the molecular skeleton do not precipitate. For example, it is preferably 35% by weight or less, more preferably 20% by weight or less, preferably 5% by weight or more, and more preferably 10% by weight or more, based on the entire coating composition.

The content of the solid lubricant in the coating composition according to the present invention can be appropriately selected within a range that satisfies the volume ratio to the resin (B) having the amide structure and the imide structure described later in the molecular skeleton. For example, it is preferably 35% by weight or less, more preferably 30% by weight or less, preferably 5% by weight or more, and more preferably 10% by weight or more, based on the entire coating composition.

The preferable weight ratio of the graphite (SL1) to the fluororesin (SL2) contained in the solid lubricant is more than 0.05: less than 1-3.3: 1 or 0.15: 1-2.5. 1 or 0.37: 1 to 1: 1.

The preferable volume ratio of the solid lubricant (SL) composed of the graphite (SL1) and the fluororesin (SL2) to the resin (B) having the amide structure and the imide structure in the molecular skeleton is more than 0.1: 1. Less than ~ 2: 1, or 0.2: 1 to 1.5: 1, or 0.5: 1 to 1.5: 1.

It is also possible to further add carbon black to the coating composition according to the present invention to impart antistatic properties to the obtained coating film. In such a case, the carbon black content is preferably kept at 5% or less. If the content of carbon black is too high, the viscosity of the coating composition may be too high to be applied.

The amount of the solvent in the coating composition according to the present invention is the residue of each of the above components, and is not particularly limited. Depending on the means for applying the composition to the substrate to obtain a coating film, a solvent may be used so as to have an appropriate viscosity. For example, the amount of the solvent is 80 to 200 parts by mass, or 100 parts by mass to 150 parts by mass with respect to 100 parts by mass of the polyamide-imide resin.

[Method for producing coating film]
As described above, a coating composition containing a polyamide-imide resin (A), graphite (SL1), a fluororesin (SL2), and a solvent is obtained. This coating composition is applied to the surface of various base materials (for example, a metal surface) to obtain a coating film, and the solvent in the obtained coating film is volatilized to prepare a coating film on the surface of the base material. To do.

[Base material]
The coating composition according to the present invention can be used for coating various base materials, and can be modified so that the surface of the base material is smooth, wear resistance and low coefficient of friction can be maintained for a long period of time. There are no particular restrictions on the use of the base material. Examples of the base material include a roll or belt having a metal surface, and a member such as a copying machine member having a metal surface (for example, a fixing roll, a transfer roll, a fixing belt, a transfer belt). As the metal, iron, carbon steel, special steel (for example, stainless steel) to which nickel, manganese, chromium and the like are added, aluminum and the like are suitable. In the coating composition according to the present invention, it is sufficient to volatilize the solvent under relatively mild conditions (for example, relatively low temperature), so that the base material body other than the metal surface is made of a general-purpose resin that can withstand the treatment temperature. It doesn't matter.

The means for obtaining the coating film by applying the coating composition according to the present invention to the substrate may be a conventional method and is not particularly limited. For example, it can be applied to the metal surface of a base material by ordinary means such as a spin coating method, a casting method, a roll coating method, a spray coating method, a bar coating method, a flexographic printing method, and a dip coating method. However, the dip coating method has the disadvantage that coating films are formed on the front and back surfaces of the substrate, and the normal coating method may cause uneven thickness. Therefore, the spray coating method is recommended. The spray coating method also has an advantage that a uniform coating film can be easily formed even on a substrate having a complicated shape.

The amount of the coating composition according to the present invention applied on the substrate is not particularly limited, but preferably the thickness of the coating film after drying is 0.5 μm or more, or 1 μm or more, 50 μm or less, or 30 μm or less. adjust.

The means for volatilizing the solvent in the coating film is not particularly limited. For example, (i) may be carried out by heating and firing, (ii) may be carried out by treating at a relatively low temperature of 300 ° C. or lower, preferably 250 ° C. or lower, more preferably 220 ° C. or lower, and (iii). It may be carried out by a method such as reducing the pressure at room temperature as needed. The time for volatilizing the solvent can be appropriately set by conducting a preliminary experiment.

[Confirmation of amide structure and imide structure in resin]
Confirmation that the amide structure and the imide structure are present in the polyamide-imide resin (A) and the resin (B) having the amide structure and the imide structure in the molecular skeleton can be confirmed by functional group analysis by FT-IR. The presence of the amide structure, from the vicinity of 1510 cm ^-1 derived from the vicinity of 1630 cm ^-1 derived from the C = O stretching vibration of an amide group absorption peak near 1750 cm ^-1, the N-H deformation vibration, and C-N stretching vibration it can be confirmed by observing the absorption peak around 1630 cm ^-1, presence of an imide structure is observed an absorption peak around 1780 cm ^-1 from the vicinity of 1720 cm ^-1 derived from the C = O stretching vibration of an imide group It can be confirmed by. The ATR method as a measurement method is widely known to those skilled in the art. Further, as the measuring device, for example, IRT-5000 manufactured by JASCO Corporation can be used. A collection of polymer papers, Vol. 44, No. 11, pp. 831-837 (1987) describes an example of actually examining the chemical structure of a sample.

The present invention will be described in more detail with reference to Examples and Comparative Examples below, but the present invention is not limited by the following Examples and Comparative Examples.

[Issue 1: Maintaining low friction for a long period of time]
Each component was mixed at the ratio shown in Table 1 to obtain coating agents of Examples 1 to 5 and Comparative Examples 1 to 3. The numerical values shown in Table 1 represent parts by weight.

<Example 1>
In NMP (N-methyl-2-pyrrolidone) and ethyl acetate, Megafuck F444 (manufactured by DIC) as a surfactant, earthy graphite K-5 (manufactured by Chuetsu Graphite Industry Co., Ltd.) as a surfactant, and Fluon (manufactured by Chuetsu Graphite Industry Co., Ltd.) PTFE (registered trademark) PTFE Lubricant L172JE (manufactured by AGC) was added so that the solid content was 30% by weight, and the mixture was pulverized and mixed in a ball mill for 12 hours to obtain a coating intermediate. The amount of the surfactant used was 6 parts by weight with respect to 100 parts by weight of the fluororesin. HPC-5010-30 (manufactured by Hitachi Kasei Co., Ltd.) was added to this intermediate as a binder having an amide structure and an imide structure in the molecular skeleton, and then NMP and ethyl acetate were further added so as to have a solid content of 20% by weight. A coating agent was obtained by pulverizing and mixing with a ball mill for 30 minutes. At this time, the addition amount was adjusted so that the weight ratio of the earth-like graphite to the fluororesin was 0.37: 1 and the volume ratio of the earth-like graphite and the fluororesin to the binder was 0.8: 1.

<Example 2>
The amount of addition was adjusted so that the weight ratio of earth-like graphite to fluororesin was 1: 1 and the volume ratio of earth-like graphite and fluororesin to binder was 0.8: 1 in the same procedure as in Example 1. , Obtained a coating agent.

<Example 3>
The addition amount was adjusted so that the weight ratio of earth-like graphite to fluororesin was 1: 1 and the volume ratio of earth-like graphite and fluororesin to binder was 0.5: 1 in the same procedure as in Example 1. , Obtained a coating agent.

<Example 4>
In the same procedure as in Example 1, the amount of addition was adjusted so that the weight ratio of earth-like graphite to fluororesin was 1: 1 and the volume ratio of earth-like graphite and fluororesin to binder was 1: 1 for coating. I got the agent.

<Example 5>
The addition amount was adjusted so that the weight ratio of earth-like graphite to fluorine-based resin was 1: 1 and the volume ratio of earth-like graphite and fluorine-based resin to binder was 1.5: 1 in the same procedure as in Example 1. , Obtained a coating agent.

<Example 6>
A coating agent was obtained in the same procedure as in Example 1 except that the earthy graphite was replaced with scaly graphite BF-3A (manufactured by Shin-Etsu Kasei Co., Ltd.) (weight ratio of scaly graphite to fluororesin 0.37). 1: Volume ratio of scaly graphite and fluororesin to binder 0.8: 1).

<Example 7>
A coating agent was obtained in the same procedure as in Example 1 except that the earth-like graphite was replaced with artificial graphite G-4AK (manufactured by Chuetsu Graphite Industry Co., Ltd.) (weight ratio of artificial graphite to fluororesin 1: 1). Volume ratio of artificial graphite and fluororesin to binder 0.2: 1).

<Example 8>
A coating agent was obtained in the same procedure as in Example 1 except that the earth-like graphite was replaced with artificial graphite G-4AK (manufactured by Chuetsu Graphite Industry Co., Ltd.) (weight ratio of artificial graphite to fluororesin 2.5: 1. Volume ratio of artificial graphite and fluororesin to binder 0.8: 1).

<Example 9>
In the same procedure as in Example 1, the addition amount was adjusted so that the weight ratio of earth-like graphite to fluororesin was 0.15: 1 and the volume ratio of earth-like graphite and fluororesin to binder was 0.8: 1. It was adjusted to obtain a coating agent.

<Comparative example 1>
In the same procedure as in Example 1, the amount of addition was adjusted so that the weight ratio of earth-like graphite to fluororesin was 3.3: 1 and the volume ratio of earth-like graphite and fluororesin to binder was 0.8: 1. It was adjusted to obtain a coating agent.

<Comparative example 2>
In the same procedure as in Example 1, the amount of addition was adjusted so that the weight ratio of earth-like graphite to fluorine-based resin was 0.05: 1 and the volume ratio of earth-like graphite and fluorine-based resin to binder was 0.1: 1. It was adjusted to obtain a coating agent.

<Comparative example 3>
In the same procedure as in Example 1, the amount of addition was adjusted so that the weight ratio of earth-like graphite to fluororesin was 1: 1 and the volume ratio of earth-like graphite and fluororesin to binder was 2: 1 for coating. I got the agent.

(Evaluation of low friction over time)
The coating agents of Examples 1 to 5 and Comparative Examples 1 to 4 shown in Table 1 were spray-coated on a SUS304 plate having a thickness of 3 mm so as to have a film thickness of 10 ± 3 μm, and sprayed at 100 ° C. for 10 minutes and at 150 ° C. for 30. A coating film was obtained by firing at 280 ° C. for 1 hour.
The coating film was evaluated by a ball-on wear test using a friction wear tester (manufactured by Takachiho Seiki). With a polyimide ball having a vertical load of 30 N, a rotation speed of 500 rpm, and a stylus outer diameter of 10 mm, the rate of change of the friction coefficient 60 seconds after the start of the test to the friction coefficient 3600 seconds after the start of the test was used as an evaluation index. From the results of Examples and Comparative Examples, it can be seen that the coefficient of friction of the coating films according to claims 1 to 4 does not easily change with time.

[Problem 2: Suppression of viscosity increase]
Each component was mixed at the ratio shown in Table 2 to obtain coating agents of Example 1 and Comparative Examples 4 to 5. The numerical values shown in Table 2 represent parts by weight.

<Comparative example 4>
The earthy graphite was replaced with carbon black (Ketjen Black EC600JD, manufactured by Lion Specialty Chemicals Co., Ltd.) in the same procedure as in Example 1, and the weight ratio of carbon black to fluororesin was 0.37: 1, carbon black. The addition amount was adjusted so that the volume ratio of the fluororesin to the binder was 0.8: 1 to obtain a coating agent.

<Comparative example 5>
The addition amount was adjusted so that the weight ratio of earth-like graphite to fluorine-based resin was 0: 1 and the volume ratio of earth-like graphite and fluorine-based resin to binder was 0.8: 1 in the same procedure as in Example 1. , Obtained a coating agent.

(Viscosity evaluation)
The viscosities were evaluated in Example 1 and Comparative Examples 4 to 5 shown in Table 2. For the evaluation, a rotary viscometer (manufactured by Malvern) was used at 25 ± 5 ° C. and 60 rpm, and the value 1 minute after the start of measurement was adopted. From the results in Table 2, it can be seen that the viscosity of the coating liquid is reduced by adding earth-like graphite.

According to the present invention, it is possible to easily obtain a metal member having a coating film that is smooth and can maintain wear resistance and a low coefficient of friction for a long period of time.

1 Toner 2 Recording paper 3 Fixing roller 4 Fixing pad 5 Halogen heater 6 Coating film

Claims (6)

A coating film comprising a resin (B) having an amide structure and an imide structure as a molecular skeleton, graphite (SL1) and a fluororesin (SL2). The weight ratio of the graphite (SL1) to the fluororesin (SL2) is more than 0.05: less than 1-3.3: 1, preferably 0.15: 1 to 2.5: 1, or The coating film according to claim 1, wherein the coating film is 0.37: 1 to 1: 1. The volume ratio of the solid lubricant (SL) composed of the graphite (SL1) and the fluororesin (SL2) to the resin (B) having the amide structure and the imide structure in the molecular skeleton is more than 0.1: 1-2. Less than 1 or 1, preferably 0.2: 1 to 1.5: 1, or 0.5: 1 to 1.5: 1, according to claim 1 or 2. Coating film. The coating film according to any one of claims 1 to 3, wherein the graphite (SL1) is an amorphous particle composed of graphite microcrystals. The coating film according to any one of claims 1 to 3, wherein the graphite (SL1) is at least one selected from the group consisting of scaly graphite, earth-like graphite and artificial graphite. A metal member having the coating film according to any one of claims 1 to 5 on its surface.