Coating composition

Abstract

To provide a coating composition capable of achieving both excellent jet blackness and appropriate glittering feeling.SOLUTION: There is provided a coating composition comprising carbon nanotubes, a glittering material, a coloring pigment other than the carbon nanotubes and a resin, wherein the coating composition comprises the carbon nanotubes in the range of 2.0 mass% or more and 13.0 mass% or less and the glittering material in the range of 3.0 mass% or more and 11.1 mass% or less in the total solid component.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a coating composition. [Background technology]

[0002] In fields requiring high design quality, such as automobile bodies, coating films using lustrous paints containing lustrous materials are required, and high-quality appearances, such as those with high flip-flop properties, are desired.

[0003] Metallic paint colors have become popular in industrial products such as automobiles. Among these, there is a demand for paint colors that are high in brightness in highlights (near specular reflection) and low in brightness in shades (oblique angles). To adjust the brightness and hue of metallic paint colors, black pigments and luster materials are typically used. For example, Patent Document 1 below discloses a resin composition comprising a pigment and a resin, wherein the pigment contains at least black pigment carbon nanotubes and a luster material, and the carbon nanotubes account for 0.001 to 0.5 mass% of the total pigment components. This composition is said to achieve high brightness in highlights and a low-brightness bluish hue in shades. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-94425 Summary of the Invention [Problem to be solved by the invention]

[0005] In black metallic paint, a design that is excellent in both jet blackness and brilliance is required. However, even when the technology of Patent Document 1 is adopted, it has been found that it is difficult to achieve both jet blackness and brilliance in black metallic paint. In other words, there is a trade-off between jet blackness and brilliance; increasing the amount of black pigment increases the jet blackness but decreases the brilliance, and increasing the amount of lustrous material to increase the brilliance results in a whitish appearance.

[0006] The present invention has been made in view of the above problems, and has as its object to provide a coating composition that can achieve both excellent jet blackness and a moderate sense of brilliance. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result have found that the above-mentioned problems can be solved by using carbon nanotubes as the black pigment in a coating composition containing a black pigment and a luster material, and by controlling the content of the carbon nanotubes and the luster material within a predetermined range, respectively, thereby completing the present invention.

[0008] That is, one aspect of the present invention is a paint composition comprising carbon nanotubes, a luster pigment, a color pigment other than the carbon nanotubes, and a resin, characterized in that the carbon nanotubes are contained in an amount of 2.0 mass% or more and 13.0 mass% or less of the total solids, and the luster pigment is contained in an amount of 3.0 mass% or more and 11.1 mass% or less of the total solids. [Effects of the Invention]

[0009] The coating composition of the present invention can achieve both excellent jet blackness and a moderate sense of brilliance. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view of a multilayer coating according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate explanations will be omitted. Furthermore, the dimensional proportions in the drawings are exaggerated for the convenience of explanation and may differ from the actual proportions.

[0012] (Paint composition) One aspect of the present invention is a coating composition comprising carbon nanotubes, a luster pigment, a color pigment other than the carbon nanotubes, and a resin, wherein the carbon nanotubes are contained in an amount of 2.0 mass% or more and 13.0 mass% or less of the total solids, and the luster pigment is contained in an amount of 3.0 mass% or more and 11.1 mass% or less of the total solids.

[0013] Vehicle paint is an important factor in determining the value of a vehicle, and high design quality is required. In particular, metallic and pearlescent paints require high brilliance in addition to excellent color saturation. To adjust the brightness and hue of metallic paints, a common method is to add carbon black, a black pigment, to a paint composition containing a lustrous material.

[0014] However, when carbon black is used in metallic paint, highlights appear white and out of focus. This is thought to be due to the fact that carbon black is a particulate material, and the unevenness of its surface causes light to be scattered, making the surface appear white.

[0015] Furthermore, in conventional black metallic paints, there is a trade-off between jet blackness and brilliance; increasing the amount of black pigment blended increases the jet blackness but reduces the brilliance, and increasing the amount of lustrous material blended to enhance the brilliance results in a whitish cast.

[0016] In contrast, the coating composition of this embodiment uses carbon nanotubes as the black pigment. Carbon nanotubes have a higher light absorption efficiency and less reflection than carbon black because light is repeatedly absorbed and attenuated inside the tubes (birdcage effect). Therefore, the use of carbon nanotubes suppresses the white blur caused by the luster pigment and enhances the jet-black color. Furthermore, because carbon nanotubes exhibit high coloring power even when added in small amounts, the jet-black color is less likely to be lost even when the amount of luster pigment is increased.

[0017] Furthermore, it was found that by controlling the carbon nanotube content and the luster material content within respective predetermined ranges, it is possible to achieve both jet blackness and luster at a higher level.

[0018] The coating composition of this embodiment contains carbon nanotubes in a range of 2.0% by mass to 13.0% by mass and luster pigments in a range of 3.0% by mass to 11.1% by mass of the total solid content. When two or more types of carbon nanotubes are used, the total amount thereof is within the above range. Similarly, when two or more types of luster pigments are used, the total amount thereof is within the above range.

[0019] If the carbon nanotube content in the coating composition is less than 2.0% by mass of the total solids, sufficient jet blackness cannot be achieved. Therefore, excellent jet blackness and a moderate brilliance cannot be achieved simultaneously. On the other hand, if the carbon nanotube content exceeds 13.0% by mass, the blackness increases but the brilliance tends to decrease, making it impossible to achieve both excellent jet blackness and a moderate brilliance. The carbon nanotube content is preferably 2.5% by mass or more, more preferably 6.0% by mass or more, even more preferably 6.5% by mass or more, even more preferably 7.5% by mass or more, even more preferably 8.5% by mass or more, and particularly preferably 10.0% by mass or more, based on the total solids of the coating composition. Furthermore, the carbon nanotube content is preferably 12.5% ​​by mass or less, more preferably 12.4% by mass or less, even more preferably 12.2% by mass or less, and even more preferably 12.0% by mass or less, based on the total solids of the coating composition. Within the above range, the effects of the present invention can be more significantly achieved.

[0020] Furthermore, if the content of the luster material in the coating composition is less than 3.0% by mass based on the total solids, the luster is insufficient. Therefore, it is not possible to achieve both excellent jet-black color and a moderate luster. On the other hand, if the content exceeds 11.1% by mass, the luster becomes too high, resulting in a whitish gray appearance, impairing the design. Preferably, the content of the luster material is 3.7% by mass or more, more preferably 4.0% by mass or more, even more preferably 4.5% by mass or more, even more preferably 5.0% by mass or more, even more preferably 5.2% by mass or more, and particularly preferably 5.4% by mass or more, based on the total solids of the coating composition. Furthermore, the content of the luster material is preferably 10.0% by mass or less, more preferably 9.0% by mass or less, even more preferably 8.5% by mass or less, even more preferably 8.0% by mass or less, and particularly preferably 7.4% by mass or less, based on the total solids of the coating composition. Within these ranges, the effects of the present invention can be more significantly achieved.

[0021] The composition of the coating composition of this embodiment will be described below.

[0022] (carbon nanotubes) Carbon nanotubes have a cylindrical shape with planar graphite rolled up. Carbon nanotubes can be single-walled carbon nanotubes (SWCNTs), which have a structure with one graphite layer rolled up, multi-walled carbon nanotubes (MWCNTs), which have two or more layers rolled up, or a mixture of these. Multi-walled carbon nanotubes (MWCNTs) are preferred in terms of cost and coloring effect. Furthermore, carbon nanotubes whose sidewalls have an amorphous structure rather than a graphite structure may also be used.

[0023] The shape of the carbon nanotube is not particularly limited, but examples include needles, cylindrical tubes, fishbone shapes (fishbone or cup stacked shapes), playing cards (platelets), and coil shapes. Examples of carbon nanotubes include graphite whiskers, filamentous carbon, graphite fibers, ultrafine carbon tubes, carbon tubes, carbon fibrils, carbon microtubes, and carbon nanofibers. Carbon nanotubes can be used in the form of one type or a combination of two or more types.

[0024] In the present invention, it is preferable to use carbon nanotubes other than those shaped like fishbone (fishbone, cup stacked type), playing card (platelet), or coil. It is particularly preferable to use carbon nanotubes in the shape of needles or cylindrical tubes. When carbon nanotubes other than those shaped like fishbone, playing card, or coil are used, the carbon nanotubes are less likely to break in the layer plane (xy plane) of the graphite sheet due to shear stress generated during the production of the coating composition or coating film. In other words, the three-dimensional structure of the carbon nanotubes is less likely to be destroyed during production. This allows the carbon nanotubes to form a sufficient network structure in the resin, resulting in a sufficient light trapping effect. As a result, the blackness and coloring effect can be improved.

[0025] The fiber diameter of the carbon nanotubes is not particularly limited, but from the viewpoint of ease of dispersion and color, it is preferably 1 to 500 nm, more preferably 5 to 100 nm.

[0026] The fiber length of the carbon nanotubes is not particularly limited, but from the viewpoint of ease of dispersion and color, it is preferably 0.1 to 150 μm, more preferably 1 to 100 μm.

[0027] The carbon purity of the carbon nanotubes is not particularly limited, but is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, based on 100% by mass of the carbon nanotubes.

[0028] Carbon nanotubes usually exist as secondary particles. The shape of these secondary particles may be, for example, a complex entanglement of carbon nanotubes, which are typical primary particles, or an aggregate of linear carbon nanotubes that are easy to disentangle. Secondary particles that are aggregates of linear carbon nanotubes are preferred because they have better dispersibility than entangled particles.

[0029] The carbon nanotubes may be surface-treated or may have functional groups such as carboxyl groups. Carbon nanotubes containing organic compounds, metal atoms, fullerenes, etc. may also be used. When surface-treated carbon nanotubes or carbon nanotubes containing functional groups are used, the carbon nanotube content is calculated based on the mass including the surface treatment agent and functional groups. When carbon nanotubes contain inclusions, the carbon nanotube content is calculated based on the mass including the mass of the inclusions.

[0030] The coating composition of this embodiment may further contain a black pigment other than carbon nanotubes. Examples of black pigments other than carbon nanotubes include organic black pigments such as aniline black, anthraquinone black, and perylene black; and inorganic black pigments such as carbon black, lamp black, graphite, magnetite, iron-titanium composite oxide, cobalt oxide, manganese dioxide, zinc sulfide, copper-chromium composite oxide, tin-antimony composite oxide, titanium-vanadium-antimony composite oxide, cobalt-nickel composite oxide, manganese-iron composite oxide, iron-cobalt-chromium composite oxide, copper-chromium composite oxide, iron-cobalt composite oxide, chromium-iron-nickel composite oxide, molybdenum disulfide, black titanium dioxide, titanium nitride, and chromium oxide.

[0031] However, in the paint composition of this embodiment, the carbon nanotubes as black pigment preferably account for 90% by mass or more of the total black pigment contained in the paint composition, more preferably 95% by mass or more, even more preferably 97% by mass or more, even more preferably 99% by mass or more, particularly preferably 99.5% by mass or more, and most preferably 100% by mass.

[0032] There are no particular limitations on the method for obtaining carbon nanotubes, and a commercially available carbon nanotube dispersion may be used.

[0033] (shining material) A lustrous pigment is a material with a pearlescent or metallic luster. Specifically, it is a pigment that looks different depending on the viewing angle due to variations in the light reflected from the surface of the lustrous pigment.

[0034] Examples of luster materials include aluminum flakes, metal oxide-coated alumina flakes, metal oxide-coated silica flakes, metal oxide-coated mica, titanium flakes, stainless steel flakes, plate-shaped iron oxide pigments, glass flakes, hologram pigments, pearl pigments, titanium dioxide, tin dioxide, aluminum oxide, and phthalocyanine flakes. Two or more types of luster materials may be used. It is preferable to use a flake-shaped luster material. Among these, it is preferable to use glass flakes because they are less likely to impair the jet black color. The glass flakes are not particularly limited, but metal oxide-coated glass flakes such as metal-plated glass flakes and titanium dioxide-coated glass flakes can be preferably used.

[0035] The average particle size of the flake-shaped luminous material is usually preferably about 5 to 50 μm, more preferably about 5 to 30 μm. The average thickness is usually preferably about 0.01 to 2 μm, more preferably about 0.05 to 1.5 μm. The ratio of the average particle size to the average thickness (average particle size / average thickness) is usually preferably about 5 to 500, more preferably about 20 to 300.

[0036] The luster material may be a pearl pigment having a coating layer formed by coating a base material such as natural mica with a metal oxide such as titanium dioxide, iron oxide, tin oxide, or aluminum oxide.

[0037] Furthermore, a paste containing a solvent or water may be used as the lustrous material, for example, Alpaste 76 series (7640NS, etc.), Alpaste 56 series, Alpaste 54 series (5422NS, etc.), Alpaste TCR series, Alpaste 63 series (6340NS, etc.), Alpaste 46 series, Alpaste WX series, Alpaste WL series, Alpaste manufactured by Toyo Aluminum K.K. Examples include the EMERAL series (EMR-B17640, EMR-D5422, EMR-D6340, etc.), and Asahi Kasei Corporation's MH-6601, MH8801, MH8802, MH-8805, MH-9901, BS-120, BS-240, BS-210, BS-400, O-2100, O-2130, GX-2140, GX-180A, GX-40A, GX-50A, GX-3108, GX-3109, GX-3100, GX4100, GX-3140, GX3160, GX3180, FD-5060, FD-4070, FD-408S, FD-508H, and FD-512H.

[0038] Alternatively, a commercially available paint containing a lustrous material may be used, and the lustrous material contained in the paint may be used as the lustrous material of the paint composition of this embodiment. Examples of such paints include the Pearl Base series and the Universal Base series, Crystal Flake and Crystal Base Fine, manufactured by Rock Paint Co., Ltd.

[0039] In a preferred embodiment of the present invention, the carbon nanotube content is 2.5% by mass or more and 12.4% by mass or less of the total solid content of the coating composition, and the metallic pigment content is 3.7% by mass or more and 11.1% by mass or less of the total solid content of the coating composition. Within these ranges, the effects of the present invention can be more significantly achieved.

[0040] In another preferred embodiment of the present invention, the carbon nanotube content is 6.5 to 13.0 mass%, particularly 7.5 to 12.4 mass%, of the total solid content of the coating composition, and the metallic pigment content is 4.5 to 8.0 mass%, particularly 5.0 to 7.4 mass%, of the total solid content of the coating composition. Within these ranges, the effects of the present invention can be obtained even more significantly.

[0041] In a preferred embodiment of the present invention, the carbon nanotube content is 8.5 to 13.0 mass %, particularly 10.0 to 12.4 mass %, of the total solid content of the coating composition, and the metallic pigment content is 4.5 to 8.0 mass %, particularly 5.0 to 7.4 mass %, of the total solid content of the coating composition. Within these ranges, the effects of the present invention can be obtained even more significantly.

[0042] In another preferred embodiment of the present invention, the carbon nanotube content is 8.5 to 13.0 mass%, preferably 8.5 to 12.2 mass%, and particularly 10.0 to 12.0 mass% of the total solids content of the coating composition, and the metallic pigment content is 5.2 to 8.0 mass%, and particularly 5.4 to 7.4 mass% of the total solids content of the coating composition. Within these ranges, the effects of the present invention can be obtained even more significantly.

[0043] In a particularly preferred embodiment of the present invention, the carbon nanotube content is 10.0 to 12.0 mass% of the total solid content of the coating composition, and the metallic pigment content is 6.0 to 7.4 mass% of the total solid content of the coating composition. Within these ranges, the effects of the present invention can be particularly pronounced.

[0044] (color pigments) The coating composition of this embodiment contains a color pigment other than carbon nanotubes. A color pigment refers to a pigment that imparts a desired color to a coating film and can generally be classified into achromatic pigments and chromatic pigments. Examples of achromatic pigments include white pigments and black pigments. Chromatic pigments include color pigments other than the achromatic pigments described above. The coating composition of this embodiment can use both the achromatic pigments and chromatic pigments described above except for carbon nanotubes as the color pigment. For example, the coating composition of this embodiment contains, as the color pigment, one or more pigments selected from the group consisting of chromatic pigments, white pigments, and black pigments other than carbon nanotubes. Preferably, the coating composition of this embodiment contains, as the color pigment, one or more pigments selected from the group consisting of chromatic pigments and white pigments. Here, unless otherwise specified, the color of a pigment refers to the color exhibited when the pigment is used alone as a colorant to form a coating composition. For example, a black pigment is a pigment that exhibits a black color when the pigment is used alone as a colorant to form a coating composition. In this specification, the term "color pigment" does not include luster pigments and matte pigments, which will be described later.

[0045] The color pigment can be arbitrarily selected from various conventionally known organic pigments and inorganic pigments, and is not particularly limited in terms of hue or structure, including, for example, phthalocyanine pigments, dioxazine violet pigments, indanthrene blue pigments, perylene pigments, quinacridone pigments, diketopyrrolopyrrole pigments, azo pigments, anthraquinone pigments, quinophthalone pigments, isoindoline pigments, quinoxaline pigments, and metal complex pigments.

[0046] Alternatively, a commercially available paint containing a coloring pigment may be used, and the coloring pigment contained in the paint may be used as the coloring pigment for the paint composition of this embodiment. Examples of such paints include the Pro Touch series manufactured by Rock Paint Co., Ltd. For example, Lake Blue and Magenta from the Pro Touch series manufactured by Rock Paint Co., Ltd. may be used.

[0047] The content of the color pigment in the coating composition is not particularly limited, but is, for example, 1.0 mass % or less, preferably 0.01 to 1.0 mass %, more preferably 0.05 to 1.0 mass %, and even more preferably 0.1 to 0.6 mass %, of the total solid content. If it is within the above range, the design properties will be better.

[0048] (Matte pigment) The coating composition of this embodiment preferably further contains a matte pigment to obtain a matte effect. The matte pigment refers to a pigment that reduces the amount of specular reflection on the coating surface and diffuses light, thereby giving a dull, subdued impression. A matte finish is also generally called a matte finish. The use of a matte pigment can adjust the gloss of the coating surface.

[0049] Examples of matte pigments include silicic acids such as silicic anhydride and hydrated silicic acid, silicic acid compounds such as aluminum silicate and magnesium silicate, inorganic pigments such as calcium carbonate, barium carbonate, titanium dioxide, gypsum, clay, talc, and aluminum white, organic fine particles such as poly(meth)acrylate, polystyrene, polyamide, polyurethane, and polyvinyl chloride, and cellulose resins such as acetyl cellulose, cellulose acetate butyrate, cellulose acetate propionate, and nitrocellulose.

[0050] Specific examples include Nipsil, SS-50, and E-200 manufactured by Tosoh Silica Corporation, and Sylysia 350 manufactured by Fuji Silysia Chemical Ltd.

[0051] If necessary, a matting agent in which a matte pigment is made into a paint can be used. Specific examples include Flat Base (manufactured by Rock Paint Co., Ltd.) and PG Eco (manufactured by Kansai Paint Co., Ltd.). In particular, Flat Base from the Pro Touch series manufactured by Rock Paint Co., Ltd. can be used.

[0052] The content of the matte pigment in the coating composition is not particularly limited and can be adjusted appropriately.

[0053] (resin) The coating composition of this embodiment further contains a resin. The resin is not particularly limited, but a thermosetting resin is preferably used. For example, a mixture containing one or more base resins selected from acrylic resins, polyester resins, alkyd resins, urethane resins, etc., having one or more crosslinkable functional groups selected from hydroxyl groups, carboxyl groups, silicon-containing groups, epoxy groups, and optionally blocked isocyanate groups, and one or more crosslinking agents reactive with these functional groups selected from melamine resins, urea resins, polyisocyanate compounds (including blocked compounds), carboxyl group-containing compounds, epoxy group-containing compounds, etc., can be used. These can be dissolved or dispersed in a solvent such as an organic solvent and / or water.

[0054] The ratio of base resin to crosslinker is not particularly limited, but is generally 90-50% by mass of base resin and 10-50% by mass of crosslinker, calculated as solids, and preferably 85-60% by mass of base resin and 15-40% by mass of crosslinker. A crosslinker content of 10% by mass or more (base resin of 90% by mass or less) is preferred because crosslinking in the coating film can proceed efficiently. On the other hand, a crosslinker content of 50% by mass or less (base resin of 50% by mass or more) is preferred because the coating composition has excellent storage stability and the curing rate is not too high, resulting in a good coating film appearance.

[0055] Examples of acrylic resins include copolymers of acrylic monomers and other ethylenically unsaturated monomers. Examples of acrylic monomers that can be used in the copolymerization include methyl, ethyl, propyl, n-butyl, i-butyl, t-butyl, 2-ethylhexyl, lauryl, phenyl, benzyl, 2-hydroxyethyl, and 2-hydroxypropyl esters of acrylic acid or methacrylic acid, ring-opening adducts of acrylic acid or 2-hydroxyethyl methacrylate with caprolactone, glycidyl acrylic acid or methacrylate, acrylamide, methacrylamide, and N-methylolacrylamide, and (meth)acrylic acid esters of polyhydric alcohols. Examples of other ethylenically unsaturated monomers that can be copolymerized with these include styrene, α-methylstyrene, itaconic acid, maleic acid, and vinyl acetate.

[0056] Commercially available acrylic resins can be used, including, for example, Acrydic 54-172-60, Acrydic A-332, A-405, Acrydic A-452, Acrydic 47-712, and A-801-P manufactured by DIC Corporation.

[0057] Examples of polyester resins include saturated polyester resins and unsaturated polyester resins, such as condensates obtained by thermally condensing a polybasic acid and a polyhydric alcohol. Examples of polybasic acids include saturated polybasic acids and unsaturated polybasic acids. Examples of saturated polybasic acids include phthalic anhydride, terephthalic acid, and succinic acid. Examples of unsaturated polybasic acids include maleic acid, maleic anhydride, and fumaric acid. Examples of polyhydric alcohols include dihydric alcohols and trihydric alcohols. Examples of dihydric alcohols include ethylene glycol and diethylene glycol, and examples of trihydric alcohols include glycerin and trimethylolpropane.

[0058] When the resin is a curable resin, the base resin is mixed with a crosslinking agent, and the curing reaction can proceed under heat or at room temperature. It is also possible to use a non-curable lacquer-type resin and a curable resin together as the resin.

[0059] In addition, resins such as acrylic resins, polyester resins, and specially modified polyester resins contained in commercially available paints may also be used as the resin of the paint composition of this embodiment. The content of the resin is not particularly limited, and conventionally known knowledge can be appropriately referred to.

[0060] The resin content in the coating composition is not particularly limited, but is, for example, 70 to 95 mass% of the total solid content, preferably 74 to 92 mass%, more preferably 78 to 85 mass%, and even more preferably 78 to 83 mass%. When two or more resins are used, the total amount is preferably within the above range. Within the above range, excellent design properties and durability of the coating film can be achieved.

[0061] (additives) The coating composition of the present embodiment may further contain additives such as surfactants, dispersants (preferably resin-type dispersants), wetting and penetrating agents, antiskinning agents, ultraviolet absorbers, antioxidants, crosslinking agents, preservatives, antifungal agents, viscosity adjusters, pH adjusters, leveling agents, and antifoaming agents, as required.

[0062] Surfactants are mainly classified into anionic, cationic, nonionic and amphoteric, and the type and amount of surfactants can be selected and used appropriately depending on the required properties.

[0063] Examples of anionic surfactants include fatty acid salts, polysulfonates, polycarboxylates, alkyl sulfate ester salts, alkylaryl sulfonates, alkylnaphthalenesulfonates, dialkylsulfonates, dialkylsulfosuccinates, alkyl phosphates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylaryl ether sulfates, naphthalenesulfonate formalin condensates, polyoxyethylene alkyl phosphate sulfonates, glycerol borate fatty acid esters, and polyoxyethylene glycerol fatty acid esters. Specific examples include sodium dodecylbenzenesulfonate, sodium laurate sulfate, polyoxyethylene lauryl ether sodium sulfate, polyoxyethylene nonylphenyl ether sulfate ester salts, and the sodium salt of a β-naphthalenesulfonate formalin condensate.

[0064] Cationic surfactants include alkylamine salts and quaternary ammonium salts, such as stearylamine acetate, trimethyl palmitate ammonium chloride, trimethyl tallow ammonium chloride, dimethyldioleylammonium chloride, methyl oleyldiethanol chloride, tetramethylammonium chloride, laurylpyridinium chloride, laurylpyridinium bromide, laurylpyridinium disulfate, cetylpyridinium bromide, 4-alkylmercaptopyridine, poly(vinylpyridine)-dodecyl bromide, and dodecylbenzyltriethylammonium chloride. Amphoteric surfactants include aminocarboxylic acid salts.

[0065] Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyalkylene derivatives, polyoxyethylene phenyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and alkyl allyl ethers, and specific examples include polyoxyethylene lauryl ethers, sorbitan fatty acid esters, and polyoxyethylene octylphenyl ether.

[0066] The surfactant is not limited to one type, and two or more surfactants may be used in combination, such as a combination of an anionic surfactant and a nonionic surfactant, or a combination of a cationic surfactant and a nonionic surfactant. Preferably, an anionic surfactant and a nonionic surfactant are used in combination. Polycarboxylates are preferred as anionic surfactants, and polyoxyethylene phenyl ethers are preferred as nonionic surfactants.

[0067] Resin-type dispersants include polyurethanes; polycarboxylic acid esters such as polyacrylates; unsaturated polyamides, polycarboxylic acids, polycarboxylic acid (partial) amine salts, polycarboxylic acid ammonium salts, polycarboxylic acid alkylamine salts, polysiloxanes, long-chain polyaminoamide phosphates, hydroxyl group-containing polycarboxylic acid esters, and their modified products; oil-based dispersants such as amides formed by the reaction of poly(lower alkylene imines) with polyesters having free carboxyl groups, and their salts; water-soluble resins and water-soluble polymers such as (meth)acrylic acid-styrene copolymers, (meth)acrylic acid-(meth)acrylic acid ester copolymers, styrene-maleic acid copolymers, polyvinyl alcohol, and polyvinylpyrrolidone; polyester-based resins, modified polyacrylate-based resins, ethylene oxide / propylene oxide adducts, and phosphate ester-based resins. Resin-type dispersants can be used alone or in combination. (Meth)acrylic acid refers to both acrylic acid and methacrylic acid.

[0068] These additives can be appropriately added within a range that does not impair the object of the present invention.

[0069] (solvent) The coating composition of this embodiment preferably further contains a solvent. The solvent is not particularly limited, and either water or an organic solvent can be used.

[0070] From the viewpoint of workability during application and drying properties before and after curing, organic solvents with a boiling point of 50 to 250°C are preferred. Specific examples of organic solvents include alcohol-based solvents such as methanol, ethanol, isopropyl alcohol, and 1-butanol; ketone-based solvents such as acetone, butyl diglycol acetate, and MEK; ester-based solvents such as ethyl acetate, butyl acetate, and ethyl 3-ethoxypropionate (EEP); ether-based solvents such as dibutyl ether, ethylene glycol, and monobutyl ether; aromatic solvents such as toluene and xylene; hydrocarbon-based solvents such as alicyclic hydrocarbons and isoparaffinic hydrocarbons; and aprotic polar solvents such as N-methyl-2-pyrrolidone. These solvents can be used alone or in combination.

[0071] In a preferred embodiment of the present invention, the coating composition does not contain carbon black. The carbon black content of the coating composition is, for example, less than 0.3 mass%, preferably 0.1 mass% or less, more preferably 0.05 mass% or less, and even more preferably 0.01 mass% or less, based on the total solid content of the coating composition.

[0072] (Method of producing coating composition) The method for producing the coating composition of this embodiment is not particularly limited. For example, a resin, carbon nanotubes, a luster pigment, and a coloring pigment are mixed together, as needed, with a matte pigment, additives, a solvent, etc. At this time, the amounts of each component may be adjusted so that the carbon nanotube and luster pigment contents in the resulting coating composition are each predetermined values. The resulting mixture is then subjected to a dispersion treatment using a disperser such as a paint shaker (manufactured by Red Devil), a colloid mill (PUC "PUC Colloid Mill", IKA "Colloid Mill MK"), a cone mill (IKA "Cone Mill MKO", etc.), a ball mill, a sand mill (Shinmaru Enterprises "Dyno Mill", etc.), an attritor, a pearl mill (Eirich "DCP Mill", etc.), a Coball mill, a basket mill, a homomixer, a homogenizer (M Technique "Clear Mix", etc.), a wet jet mill (M Technique "Genus PY", Sugino Machine "Starburst", Nanomizer "Nanomizer", etc.), M Technique "Clear SS-5", Nara Machine Co., Ltd. "MICROS", etc., a media-less disperser, a Huber Marler, a three-roll mill, an extruder (twin-screw extruder), a Henschel mixer, etc., to produce a coating composition.

[0073] A high-speed mixer can also be used to obtain the coating composition. Examples of high-speed mixers include Homo Disper (manufactured by PRIMIX), Filmix (manufactured by PRIMIX), Dissolver (manufactured by Inoue Seisakusho), and Hyper HS (manufactured by Ashizawa Finetech).

[0074] The coating composition of this embodiment can be prepared by various conventionally known methods. It can be produced by dispersing a mixture containing carbon nanotubes, a luster pigment, and other color pigments, a resin, a dispersion medium such as a solvent, and optional components as needed. Alternatively, the carbon nanotubes, the luster pigment, and other color pigments may be separately dispersed in dispersion media to form a carbon nanotube dispersion, a luster pigment dispersion, and other color pigment dispersion, and then used.

[0075] The order in which the carbon nanotubes, the luster pigment, the other color pigments, the dispersion medium, and the other optional components are mixed or dispersed is not particularly limited, and each may be added sequentially, or two or more of them may be added simultaneously.

[0076] In particular, carbon nanotubes are preferred because they are prepared as a carbon nanotube dispersion and then mixed together, allowing the carbon nanotubes and the luster pigment to be uniformly dispersed in the coating composition, thereby achieving both jet blackness and a lustrous finish in the coating film.

[0077] <Carbon nanotube dispersion> The carbon nanotube dispersion of this embodiment can be produced by dispersing carbon nanotubes in a dispersion medium such as a resin or a solvent, preferably using a surfactant, a dye derivative, or a dispersant. In this case, the surfactant or dispersant and the carbon nanotubes can be added simultaneously or sequentially and mixed, allowing the surfactant or dispersant to act on (adsorb) the carbon nanotubes while dispersing them. In particular, to more easily produce the carbon nanotube dispersion, it is preferable to dissolve, swell, or disperse the surfactant or dispersant in a solvent, and then add the carbon nanotubes to the liquid and mix to allow the surfactant or dispersant to act on (adsorb) the carbon nanotubes.

[0078] <Preparation of carbon nanotube dispersion> To obtain the carbon nanotube dispersion of this embodiment, a process is performed to disperse the carbon nanotubes in a dispersion medium. The dispersing device used for this process is not particularly limited, and a disperser or a high-speed stirrer can be used, as in the method for producing the coating composition described above.

[0079] The carbon nanotube content in the carbon nanotube dispersion of this embodiment is preferably 0.1 to 30 mass%, more preferably 0.5 to 25 mass%, still more preferably 1 to 10 mass%, and particularly preferably 1 to 5 mass%, relative to 100 mass% of the carbon nanotube dispersion.

[0080] <Coatings and multilayer coatings> The coating composition of this embodiment can be applied to a substrate to form a coating film. That is, according to the present invention, a coating film formed by the coating composition of this embodiment is provided. The coating film formed by the coating composition of this embodiment achieves both excellent jet blackness and a moderate sense of brilliance at a high level.

[0081] One preferred embodiment of the present invention is a multilayer coating film having a black layer formed on a substrate using a coating composition according to this embodiment. The multilayer coating film according to this embodiment combines excellent jet blackness and a moderate sense of brilliance at a high level. Figure 1 shows a schematic cross-sectional view of the multilayer coating film according to this embodiment. The multilayer coating film 10 of this embodiment has a black layer 12 on a substrate 11. The multilayer coating film 10 of this embodiment may further have a clear layer 13 on the black layer 12.

[0082] (base material) The substrate 11 used to form the multilayer coating film 10 in this embodiment is not particularly limited. Examples of materials for the substrate include, but are not limited to, metals such as iron, aluminum, and copper or alloys such as steel, stainless steel, chromium-molybdenum steel, brass, bronze, duralumin, and tinplate; inorganic materials such as glass, cement, and concrete; resins such as polyethylene resin, polypropylene resin, ethylene-vinyl acetate copolymer resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, and epoxy resin; plastic materials such as various fiber-reinforced plastics (FRP); wood; and natural or synthetic materials such as fibrous materials (including paper and cloth).

[0083] Among the above materials, metals such as iron, aluminum, copper, or steel, stainless steel, chromium-molybdenum steel, brass, bronze, duralumin, and tinplate are preferred. Furthermore, as coloring pigments, organic pigments, inorganic pigments, and resins containing luster materials that have been conventionally used in paints may also be used.

[0084] The shape of substrate can be plate-like, film-like, sheet-like or molded body-like.The method for producing molded body-like substrate is not particularly limited, but can use, for example, the injection molding method represented by insert injection molding, in-mold molding, overmolding, two-color injection molding, core-back injection molding and sandwich injection molding; the extrusion molding method represented by T-die lamination molding, multi-layer inflation molding, co-extrusion molding and extrusion coating; and other molding methods represented by multi-layer blow molding, multi-layer calendar molding, multi-layer press molding, slush molding and melt casting.

[0085] The black layer may be formed directly on the substrate, or a primer coating layer may be formed on the substrate in advance, and the black layer may be formed on the primer coating layer. The primer coating layer may be formed by, for example, chemical conversion treatment, electrodeposition coating, spray coating, powder coating, or the like. Furthermore, before forming the black layer, an intermediate coating layer may be further formed on the primer coating layer using a solvent-based paint, a water-based paint, a powder paint, or the like. It is also possible to form an intermediate coating layer on the substrate without forming a primer coating layer, and then form the black layer on top of that.

[0086] (black layer) The black layer is a coating layer formed using the coating composition of this embodiment.

[0087] To form a black layer on a substrate, an optimum technique may be selected from common techniques depending on the substrate, such as casting, spin coating, dip coating, bar coating, spraying, blade coating, slit die coating, gravure coating, reverse coating, screen printing, mold coating, print transfer, electrostatic coating, and wet coating methods including inkjet.

[0088] Preferably, the coating composition is applied by electrostatic coating, air spraying, airless spraying, or the like. After application, the coating film can be dried and cured by heating. For example, after application, the coating film can be dried at room temperature for 5 to 30 minutes, and then heated at a temperature of 50 to 160°C for 10 to 60 minutes to be cured.

[0089] Generally, after applying the coating composition as described above, the coating film is dried and heated to harden, but the clear layer coating composition described below may be further applied to the unhardened film.

[0090] Alternatively, a method can be used in which the coating composition is melt-kneaded using a two-roll mill, a three-roll mill, a pressure kneader, a Banbury mixer, a single-screw kneading extruder or a twin-screw kneading extruder, etc., and then molded and layered.

[0091] The thickness of the black layer 12 is not particularly limited, but it is preferable that the thickness of the cured coating film is 10 to 50 μm.

[0092] (clear layer) The multilayer coating film 10 of this embodiment may further include a clear layer 13 on the black layer 12. The clear layer has a transparency sufficient to allow the underlying black layer coating to be seen. Examples of the material for the clear layer include transparent materials such as transparent resin and glass. By providing such a clear layer, acid resistance and scratch resistance can be achieved. Furthermore, the surface can be made smooth.

[0093] Examples of transparent resins include, but are not limited to, polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyimides, polyphenylene sulfide, aramid, polypropylene, polyethylene, polylactic acid, polyvinyl chloride, polycarbonate, polymethyl methacrylate, alicyclic acrylic resins, cycloolefin resins, triacetyl cellulose, epoxy resins, phenolic resins, alkyd resins, petroleum resins, vinyl resins, olefin resins, synthetic rubber, polyamide resins, acrylic resins, styrene resins, melamine resins, urethane resins, amino resins, fluorine-based resins, vinylidene fluoride resins, vinyl chloride resins, ABS resins, silicone resins, nitrocellulose, rosin-modified phenolic resins, and rosin-modified polyamide resins. Ordinary soda glass can be used as the glass. A combination of these materials can also be used. Furthermore, a coloring pigment that allows the black coating layer to be visible may be included in the clear layer. The coloring pigment may be the same as that used in the coating composition.

[0094] The clear layer may contain a matte pigment in order to achieve a matte effect. The specific form of the matte pigment is the same as that used in the black layer.

[0095] The method for obtaining the clear layer coating composition when preparing the clear layer by the wet coating method is not particularly limited, and any method known to those skilled in the art can be used, such as kneading the components using a kneader or roll, or dispersing them using a sand grind mill or disperser. Commercially available clear paints may also be used as the clear layer coating composition. Preferred commercially available clear paints include automotive paints and automotive repair paints. For example, Rock Paint's Multitop Clear QR (standard type) 150-1150-01 / 02 can be used in combination with Multitop Q Curing Agent (standard type) 150-1120-02 / 03.

[0096] To form the clear layer 13 on the black layer 12, the optimum technique can be selected depending on the material to be formed. Such a technique can be selected from common methods, including dry methods such as vacuum deposition, EB deposition, and sputter deposition, as well as wet coating methods such as casting, spin coating, dip coating, bar coating, spray coating, blade coating, slit die coating, gravure coating, reverse coating, screen printing, mold coating, print transfer, and inkjet. The clear layer may also be a pre-formed film. As long as the clear layer is laminated on the black layer, these layers do not necessarily need to be in close contact with each other.

[0097] Preferably, the clear coat layer is prepared by applying the clear coat layer coating composition by electrostatic coating, air spraying, airless spraying, or the like. After application, the coating film can be dried and heated to cure. For example, after application, the coating film can be dried at room temperature for 5 to 30 minutes, and then heated at a temperature of 50 to 160°C for 10 to 60 minutes to cure.

[0098] The spectral transmittance of the clear layer over the entire wavelength range of visible light is not particularly limited, but is, for example, 70% or more, and preferably 90% or more.

[0099] The film thickness of the clear coat layer is not particularly limited, but the film thickness of the cured coating film is, for example, 5 to 150 μm, and preferably 20 to 50 μm.

[0100] The coating composition according to this embodiment, as well as the coating film and laminate obtained using the same, have high designability and excellent moldability, and are therefore suitable for use in housing and building materials, automobile bodies, automobile components, electrical and electronic parts, miscellaneous goods, films, etc. They are particularly suitable as exterior components that require high designability, and are suitable for use in vehicle components, home appliance components, furniture components, OA housing applications, film applications, etc.

[0101] The following embodiments are also included within the scope of the present invention: a coating composition according to claim 1 having the characteristics of claim 2; a coating composition according to claim 1 or 2 having the characteristics of claim 3; a coating composition according to any one of claims 1 to 3 having the characteristics of claim 4; a coating composition according to any one of claims 1 to 4 having the characteristics of claim 5; a multilayer coating film having a black layer formed on a substrate by the coating composition according to any one of claims 1 to 5; and a multilayer coating film according to claim 6 having the characteristics of claim 7. [Example]

[0102] The present invention will be described in more detail below with reference to examples. However, the technical scope of the present invention is not limited to the following examples. In these examples, "%" refers to "% by mass."

[0103] (Preparation of coating composition) A commercially available automotive paint and a carbon nanotube dispersion were mixed in amounts such that the carbon nanotube (CNT) content and the luster material content in the solids were as shown in Table 1 below, to obtain the paint compositions of each example and comparative example.

[0104] The raw materials used to prepare the coating compositions were as follows: Rock Paint Co., Ltd. Universal Base 051-4410 (Crystal Flake) and / or 051-4409 (Crystal Flake Fine) (contains 10% titanium dioxide glass flake and resin) 1.82 mass% dispersion of carbon nanotubes manufactured by Toyocolor Co., Ltd. (The fiber diameter of the carbon nanotubes is approximately 10 nm, and the fiber length is approximately 50 μm) Rock Paint Co., Ltd. Protouch 077-0072 (Lake Blue) (contains color pigments and resins) Rock Paint Protouch 077-0048 (Magenta) (contains color pigments and resins) Rock Paint Co., Ltd. Protouch 077-0204 (White) (Contains color pigments and resin) Rock Paint Protouch 077-0095 (Flat Base) (Contains Matte Pigments and Resin) Rock Paint Co., Ltd.'s Protouch 077-P150 (Nigori Clear) (contains clear pigment and resin).

[0105] In Comparative Example 9, instead of using a 1.82 mass % dispersion of carbon nanotubes, Protouch 077-0030 (Tinching Black) (containing 3 mass % carbon black (CB)) manufactured by Rock Paint Co., Ltd. was used.

[0106] (Preparation of coating samples) The coating compositions of the respective Examples and Comparative Examples obtained above were applied to a tin plate as a substrate using an air spray to form a black layer on the tin plate.

[0107] Next, commercially available clear paints, Multitop Clear QR (standard type) 150-1150-01 / 02 and Multitop Q hardener (standard type) 150-1120-02 / 03 manufactured by Rock Paint Co., Ltd., were mixed and sprayed onto the black layer using an air spray, left to stand at room temperature for 15 minutes, and then heated at 60°C for 30 minutes to create a clear layer. This resulted in a coating sample in which a black layer and a clear layer were laminated in that order on a tin plate.

[0108] [evaluation] <Combining jet black and brilliance> On a sunny day, the coating film samples prepared in each of the Examples and Comparative Examples were fixed facing west and evaluated (sensory evaluation) to see whether the design achieved both jet blackness and a lustrous feel. The evaluation was carried out visually by five designers. The results are shown in Table 1 below. If the sample was rated as ◎, ◯, or △ according to the following criteria, it could be used without any problems: ◎: The combination of jet blackness and brilliance was extremely excellent. ○: Jet blackness and brilliance were well combined. △: Jet blackness and brilliance were compatible to a practically acceptable extent. ×: Neither jet blackness nor brilliance was found to be compatible.

[0109] <Lightness: L 75 Value> The coating samples prepared in each example and comparative example were measured using a multi-angle colorimeter manufactured by BYK, BYK-mac i. * C * Lightness L in the h color system 75 The lower the L value, the darker the color. 75 indicates the L value measured when the measurement light is irradiated at an angle of 45° to the axis perpendicular to the surface of the object to be measured and received at an angle of 75° from the specular reflection angle to the direction of the measurement light. The results are shown in Table 1 below. If the product is rated as O or △ according to the following criteria, it can be used without any problems: ○: Less than 1.6, △: 1.6 or more and less than 2.1, ×: 2.1 or higher.

[0110] <Luminosity: Si 75 Value> The coating samples prepared in each example and comparative example were measured using a multi-angle colorimeter manufactured by BYK, BYK-mac i. 75 The higher the Si value, the greater the sense of brilliance. 75 The Si value is measured by irradiating the measurement light at an angle of 45° to the axis perpendicular to the measurement surface and receiving the light at an angle of 75° from the specular reflection angle in the direction of the measurement light. The results are shown in Table 1 below. If the result is rated as O or △ according to the following criteria, the product can be used without any problems: 〇: 55 or more and less than 100 (very good brightness), △: 30 or more but less than 55 or 100 or more but less than 130 (good brightness) ×: Less than 30 or more than 130 (insufficient or too strong brilliance).

[0111] <Saturation:C 75 Value> The coating samples prepared in each example and comparative example were measured using a multi-angle colorimeter manufactured by BYK, BYK-mac i. * C * Saturation C in the h color system 75 The higher the C value, the higher the saturation. 75is the saturation C measured when the measurement light is irradiated at an angle of 45° to the axis perpendicular to the measurement surface and received at an angle of 75° from the specular reflection angle to the direction of the measurement light. * The results are shown in Table 1 below. If the following criteria are met, the product can be used without any problems: 〇: 1.0 or less (achromatic), ×: More than 1.0.

[0112] [Table 1-1]

[0113] [Table 1-2]

[0114] [Table 1-3]

[0115] From the results in Table 1 above, it can be seen that the coating films prepared using the coating compositions of Examples 1 to 24, which contained carbon nanotubes in a range of 2.0% by mass to 13.0% by mass and luster pigments in a range of 3.0% by mass to 11.1% by mass of the total solid content, all had low brightness and saturation and excellent luster. Furthermore, in the sensory evaluation, they achieved both jet blackness and luster.

[0116] Among these, the coating films using the coating compositions of Examples 19 and 21 to 24, which contained carbon nanotubes in a range of 8.5% by mass to 13.0% by mass and luster pigments in a range of 4.5% by mass to 8.0% by mass based on the total solids content, achieved a higher level of both excellent jet-blackness and a moderate luster. In particular, the coating films using the coating compositions of Examples 21 to 24, which contained carbon nanotubes in a range of 8.5% by mass to 13.0% by mass and luster pigments in a range of 5.2% by mass to 8.0% by mass, achieved an even higher level of both excellent jet-blackness and a moderate luster.

[0117] On the other hand, in Comparative Example 9, in which carbon black was used as the black pigment, sufficient blackness was not obtained, and it was not possible to achieve both excellent jet-blackness and a moderate brilliance. Furthermore, in Comparative Examples 1 to 5, the carbon nanotube content was less than the specified amount, resulting in insufficient blackness. In Comparative Examples 6 to 8, the luster material content was less than the specified amount, resulting in insufficient luster. In Comparative Examples 11 and 12, the luster material content was greater than the specified amount, resulting in an excessively strong luster, making it impossible to achieve both excellent jet-blackness and a moderate brilliance. In Comparative Example 10, the amounts of carbon nanotubes and luster material added were too high, reaching the addition limit, and a coating film could not be formed. [Explanation of symbols]

[0118] 10 multilayer coatings, 11 base material, 12 black layer, 13 Clear layer.

Claims

1. The carbon nanotube coating composition includes a color pigment other than the carbon nanotube, a luster pigment, and a resin. A coating composition characterized in that the carbon nanotubes are contained in a range of 2.0 mass% or more and 13.0 mass% or less of the total solid content, and the lustrous material is contained in a range of 3.0 mass% or more and 11.1 mass% or less of the total solid content.

2. 2. The coating composition according to claim 1, wherein the content of the carbon nanotubes is 8.5% by mass or more and 13.0% by mass or less of the total solid content, and the content of the lustrous material is 4.5% by mass or more and 8.0% by mass or less of the total solid content.

3. 3. The coating composition according to claim 1, wherein the content of the carbon nanotubes is 8.5% by mass or more and 13.0% by mass or less of the total solid content, and the content of the lustrous material is 5.2% by mass or more and 8.0% by mass or less of the total solid content.

4. 3. The coating composition of claim 1, further comprising a matting pigment.

5. The coating composition according to claim 1 or 2, wherein the luster material comprises glass flakes.

6. A multilayer coating film having a black layer formed on a substrate using the coating composition according to claim 1 or 2.

7. The multilayer coating film according to claim 6, further comprising a clear layer containing a transparent resin or glass on the black layer.

Images