JP2019081128A - Multicolor finish coating method and manufacturing method of coating material - Google Patents

Abstract

To provide a multicolor finish coating method capable of reducing a work process including a dry process, capable of shortening time, and very excellent in a finish property, when executing multicolor separately-painting coating on coated matter of the large area such as a railway vehicle.SOLUTION: In a multicolor finish coating method including (1) a process S1 of forming a base coating film by coating a base coating composition on coated matter of the large area, (2) a process S2 of forming a top coat coating film by partially coating at least one time of the top coat coating composition of a different color on the base coating film and (3) a process S3 of forming a clear coating film by drying by superposably coating a top clear coating composition on the whole surface in the next place, both the base coating composition and the top coat coating composition include (a) a cellulose derivative, (b) a hydroxy group-including resin and (c) pigment, and the content of the cellulose derivative falls within a range ot 5-75 pts. mass to the total 100 pts. mass of the solid content of the component (a) and component (b).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a multicolor finish coating method and a coated material more than two-tone coating which is most suitable for coating particularly on relatively large substrates such as railway cars, buses, trucks, construction machines or industrial equipment.

  A thermosetting composition containing a hydroxyl group-containing resin such as a hydroxyl group-containing acrylic resin, a crosslinking agent such as a melamine resin and / or a polyisocyanate compound, and a pigment as a paint composition conventionally used for painting automobile bodies such as passenger cars Coating compositions are widely used. However, when a melamine resin is used as a crosslinking agent in the coating process, a heating and drying temperature of about 140 ° C. is required, and a heating and drying temperature of about 80 ° C. is required even when a polyisocyanate compound is used as a crosslinking agent ( Patent Document 1 and Patent Document 2).

  Large-sized car bodies or parts such as railway cars, trucks, buses, construction machines or industrial equipment have a large coated area as the coated object compared to car bodies such as passenger cars, which inevitably results in a large drying furnace and a huge amount of In addition to the need for equipment investment, there may be a case where a sufficient and uniform heating and drying temperature can not be secured for the entire object to be coated. In addition, since the object to be coated is large, it takes a long time to cool when placed in a drying furnace. At present, when applying multi-tone coating of two or more tones, a drying process is required for about one day for each color to ensure sufficient finish, and a large number of man-hours are required for the drying process. In particular, when painting multi-color coatings on large-area coated objects such as railway cars, without drying after each color coating, tape marks on the coating film of masking tape, adhesive residue, mixed layers of colors, etc. are generated and finished Sex is not good. Therefore, not only the man-hours are required as described above, but there are dissatisfaction with the finishing property and the stain resistance due to the difference in level of the color boundary portion and the film thickness.

  In recent years, also in the painting process of such a large vehicle, although productivity improvement by reduction of man-hours is desired, a drying process of each color is indispensable to improve finish.

Unexamined-Japanese-Patent No. 1-203085 JP-A-8-332448

  The present invention has been made in view of the above circumstances, and in the case of multi-color coating on a large-area object such as a railway vehicle, it is possible to reduce the work process including the drying process and shorten the time. Also, it is an object of the present invention to provide a multicolor finish coating method and a method of producing a coated article which are very excellent in finish.

  Under these circumstances, as a result of intensive studies, the present inventors apply the base paint composition and the top coat composition containing a specific amount of cellulose derivative, and then coat the top clear paint composition and dry the entire surface. We found that we could solve the above problems.

The present invention provides the methods set forth in the following section:
(Aspect 1) On a large-area object to be coated
(1) a step of applying a base paint composition to form a base coating,
(2) A step of partially coating at least once a different color top coat composition on the base coat to form a top coat,
(3) applying a top clear coating composition to the entire surface and drying it to form a clear coating film;
The base coating composition and the top coating composition each contain a cellulose derivative (a), a hydroxyl group-containing resin (b) and a pigment (c), and the content of the cellulose derivative (a) is a component It is in the range of 5-75 mass parts with respect to a total of 100 mass parts of solid content of (a) and a component (b), The multicolor finish coating method characterized by the above-mentioned.

  (Aspect 2) The multicolor finish coating method according to aspect 1, wherein the top clear coating composition is a urethane curable coating composition.

  (Aspect 3) The multicolor finish coating method according to aspect 1 or 2, wherein the base paint composition and the topcoat paint composition are one-pack type paint compositions containing no crosslinking agent.

  (Aspect 4) In the step (1), the base coating composition is applied so that the dry film thickness of the base coating film is 5 to 30 μm, and in the step (2), the dried film of the top coating film The multicolor finish-coating method of any one of the aspect 1-3 which coats a topcoat coating composition so that thickness may be set to 5-30 micrometers.

  (Aspect 5) The multicolor finish coating method according to any one of Aspects 1 to 4, wherein the object to be coated is a railway vehicle.

  (Aspect 6) A method of producing a coated article having a coating which is separately applied in two or more colors by using the multicolor finish coating method according to any one of Aspects 1 to 5.

  According to the multicolor finish coating method of the present invention (hereinafter sometimes referred to as "the present method"), even in the case of a relatively large-area object to be coated, shortening of the process including the drying time in the coating process It is possible to obtain a coated film which is possible and excellent in finish and adhesion and a coated article having the coated film. According to the present invention, multi-color coating can be performed separately and finishability is excellent without making heating and drying essential in all steps.

  Since the drying process which has conventionally taken many color man-hours can be shortened or reduced, it becomes possible to paint for any number of colors per day, and the work process until completion can be significantly reduced, and the productivity is improved. In addition, despite the fact that the working process can be shortened, finish defects due to film thickness differences and contamination resistance (less likely to cause dirt accumulation due to film thickness differences) are improved, coating film defects are less likely to occur, and total film thickness is also small. Therefore, it is expected to be effective in reducing carbon dioxide emissions and cost, and reducing weight and safety.

FIGS. 1-5 is a flowchart for demonstrating the flow of the coating method which concerns on one Embodiment of invention.
It is a flowchart for demonstrating the flow of the coating method which concerns on one Embodiment of this invention. It is a flowchart for demonstrating the flow of the coating method which concerns on one Embodiment of this invention. It is a flowchart for demonstrating the flow of the coating method which concerns on one Embodiment of this invention. It is a flowchart for demonstrating the flow of the coating method which concerns on one Embodiment of the past. It is a flowchart for demonstrating the flow of the coating method which concerns on one Embodiment of the past.

<Multicolor finish painting method>
The multicolor finish coating method of the present invention is
On a large area of object,
(1) a step of applying a base paint composition to form a base coating,
(2) A step of partially coating at least once a different color top coat composition on the base coat to form a top coat,
(3) a multicolor finish coating method comprising the steps of: applying a top clear paint composition over the entire surface and drying it to form a clear paint film, wherein the cellulose derivative in the base paint composition and the top paint composition ( It is characterized by using what has a content of a) in a specific range.

<Coated object>
The object to which this method is applied is a material having a large coated area, and the shape and the like are not particularly limited. However, the object does not enter an industrial drying oven or the like, or is placed in a drying oven and dried. Even if it is, it is a to-be-painted thing of the coated area used as the raw material attainment temperature becomes less than 60 degreeC (for example, set temperature 80 degreeC).

For example, construction machines / large vehicles, industrial equipment, blades for wind power generators, aircraft, etc. may be mentioned, and more specifically, car bodies of railway cars, buses, trucks, parts thereof etc. may be mentioned.
Rail vehicles are particularly preferred. Moreover, the to-be-coated-article may have an old coating film.

  As a specific example of the material of the above-mentioned to-be-coated-article, a steel plate, zinc plating, stainless steel, aluminum etc. are mentioned as a metal material, for example, Moreover, as a plastic material, a polyethylene resin, a polypropylene resin, acrylonitrile butadiene styrene (ABS) Resins such as resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, epoxy resin and the like, plastic materials such as various FRP, and the like. Moreover, the thing etc. which compounded these metal raw materials and plastic raw materials can be mentioned as a to-be-coated-article. Depending on these materials, the substrate may be subjected to polishing treatment, degreasing treatment, surface treatment, paint of a putty composition, primer surfacer, and the like to adjust the substrate.

<Step (1) Step of Forming a Base Coating>
Base Coating Composition The base coating composition used in the present method is formed to impart weather resistance, corrosion resistance, corrosion resistance, chipping resistance and the like to a substrate, and is coated with the base coating composition. Can be obtained by forming a base coating film.

  The base paint composition used in this method contains a cellulose derivative (a), a hydroxyl group-containing resin (b) and a pigment (c), and the content of the cellulose derivative (a) is the component (a) and It is characterized by containing 5-75 mass parts with respect to a total of 100 mass parts of solid content of a component (b).

(A) Cellulose Derivative The cellulose derivative (a) is a compound containing cellulose as a constituent unit, for example, an esterified product of cellulose obtained by esterifying a hydroxyl group of cellulose with an acid such as a fatty acid or nitric acid, an esterified product of the cellulose. The cellulose modified copolymer etc. which are formed by reacting the polymerizable unsaturated group containing cellulose ester compound obtained by introduce | transducing a polymerizable unsaturated group with other polymerizable unsaturated monomers can be mentioned.

  Examples of the esterified product of cellulose include nitrocellulose, cellulose acetate butyrate, cellulose acetate, cellulose acetate propionate and the like. Among these, cellulose acetate butyrate can be suitably used.

  Cellulose acetate butyrate (hereinafter sometimes abbreviated as CAB) is obtained by further butyl esterifying a partially acetylated product of cellulose, and specifically, for example, specifically, for example, “CAB-381- 0.5 "," CAB-381-0.1 "," CAB-381-2.0 "," CAB-381-20 "," CAB-551-0.2 "," CAB-551-0. 01 "," CAB-553-0.4 "," CAB-531-1 "," CAB-500-5 "," CAB-321-0.1 "," Solus 2100 "," Solus 2300 "(all in the US) Examples thereof include commercially available products such as Eastman Chemical Co., Ltd., trade names), which may be used alone or in combination of two or more.

  The number average molecular weight of the cellulose acetate butyrate is preferably in the range of 1,000 to 100,000, particularly 3,000 or more and less than 50,000, from the viewpoint of drying property, finishing property and polishing property.

  Content of a cellulose derivative (a) is in the range of 5-75 mass parts with respect to a total of 100 mass parts of solid content of the said cellulose derivative (a) and the hydroxyl-containing resin (b) mentioned later, and surface drying From the viewpoint of the balance between the properties and the finish, the range of 15 to 70 parts by mass is preferable, and the range of 20 to 60 parts by mass is more preferable.

(B) Hydroxyl Group-Containing Resin The hydroxyl group-containing resin (b) is not particularly limited as long as it contains a hydroxyl group, and examples thereof include alkyd resin, polyester resin, acrylic resin and the like. It is preferable to contain a hydroxyl group-containing polyester resin (b-1) from the viewpoints of penetration of the crosslinking component from the clear coat, adhesion and finish, and further from the viewpoint of the weather resistance and scratch resistance of the coating film It is preferable to contain a hydroxyl group-containing acrylic resin (b-2).

(B-1) Hydroxyl group-containing polyester resin The hydroxyl group-containing polyester resin (b-1) can be obtained by reacting a conventionally known polybasic acid with a polyhydric alcohol. Examples of polybasic acids include adipic acid, succinic acid, isophthalic acid, terephthalic acid, phthalic acid anhydride, maleic acid anhydride, trimellitic acid, hexahydrophthalic acid anhydride, sodium 5-sulfoisophthalic acid, etc., and polyhydric alcohols Examples thereof include ethylene glycol, propylene glycol, glycerin, trimethylolpropane, neopentyl glycol, 1,6-hexanediol, pentaerythritol, sorbitol and the like. Furthermore, if necessary, fatty acids such as dehydrated castor oil fatty acid, linseed oil fatty acid, soybean oil fatty acid, tall oil fatty acid, monobasic acids such as benzoic acid, and oils and fats can be used as copolymerization components.

  The glass transition temperature (Tg) of the hydroxyl group-containing polyester resin (b-1) is from -70 to 0 from the viewpoint of improving the drying property, the penetration property of the crosslinking component from the top clear coat described later, adhesion and finish. C., preferably in the range of -65 to -10.degree.

  The weight average molecular weight of the hydroxyl group-containing polyester resin (b-1) is from 1,000 to 30,000, preferably from 3000 to 25,000, from the viewpoints of the physical properties of the coating film and the improvement of the solid content in coating and the finish. It is in the range.

  The hydroxyl value of the hydroxyl group-containing polyester resin (b-1) can be appropriately set in the range of 20 to 200 mg KOH / g, preferably 30 to 170 mg KOH / g, from the viewpoint of the curability and finish of the coating film.

  When the hydroxyl group-containing polyester resin (b-1) is contained in the hydroxyl group-containing resin (b) to be compounded, the content thereof is a hydroxyl group-containing polyester resin (b) from the viewpoint of achieving both surface drying and finish. -1) / Other hydroxyl group-containing resin = 5/95 to 95/5, preferably 15/85 to 60/40, which can be appropriately set.

(B-2) Hydroxyl Group-Containing Acrylic Resin The hydroxyl group-containing acrylic resin (b-2) is, for example, a hydroxyl group-containing polymerizable unsaturated monomer and another polymerizable unsaturated monomer copolymerizable with the hydroxyl group-containing polymerizable unsaturated monomer. Can be produced by copolymerization.

  Examples of the hydroxyl group-containing polymerizable unsaturated monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate. Etc. of monoesters of (meth) acrylic acid and dihydric alcohols having 2 to 8 carbon atoms; ε-caprolactone modified products of these monoesters; N-hydroxymethyl (meth) acrylamide; allyl alcohol; The (meth) acrylate etc. which have the polyoxyethylene chain which is a hydroxyl group are mentioned, These can be used individually or in combination of 2 or more types, respectively.

  Examples of other polymerizable unsaturated monomers copolymerizable with the above-mentioned hydroxyl group-containing polymerizable unsaturated monomer include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate Alkyl esters of acrylic acid or methacrylic acid such as lauryl (meth) acrylate, isobornyl (meth) acrylate; (meth) acrylic acid, styrene, vinyl toluene, vinyl acetate, (meth) acrylonitrile, (meth) acrylamide, glycidyl (meth) ) Acrylate, dimethylaminoethyl (meth) acrylate, (meth) acryloyloxyethyl ammonium chloride, t-butyl acrylamide sulfonic acid, Na salt of sulfoethyl methacrylate, K salt and ammonium salt, Na salt of sulfone acids, such as K salts and ammonium salts.

  The weight average molecular weight of the hydroxyl group-containing acrylic resin (b-2) is 1,000 to 100,000, preferably 3,000 to 80, from the viewpoints of the physical properties of the coating film and the improvement of the solid content at the time of coating and the finish. It is in the range of 000.

  The hydroxyl value of the hydroxyl group-containing acrylic resin (b-2) is in the range of 20 to 200 mg KOH / g, preferably 30 to 170 mg KOH / g, from the viewpoint of the curability and finish of the coating film.

  The glass transition temperature (Tg) of the hydroxyl group-containing acrylic resin (b-2) is preferably 0 to 90 ° C., preferably 20, from the viewpoint of the physical properties (particularly scratch resistance) of the resulting coating and the adhesion to the substrate. It is in the range of ° C to 80 ° C.

  In the present specification, the measurement of weight average molecular weight (Mw) and number average molecular weight (Mn) is measured by gel permeation chromatography (gel permeation chromatograph: GPC) using a calibration curve of standard polystyrene. It is.

  As gel permeation chromatograph, "HLC-8120GPC" (trade name, manufactured by Tosoh Corp.) is used, "TSKgel G4000HXL" is one, "TSKgel G3000HXL" is two, and "TSKgel G2000HXL" is one. A total of four (brand name, all manufactured by Tosoh Corporation) are used, a differential refractometer is used as a detector, mobile phase: tetrahydrofuran, measurement temperature: 40 ° C., flow rate: 1 mL / min. It can be measured by

  The "glass transition temperature" is a static glass transition temperature, for example, a sample is placed in a measuring cup using a differential scanning calorimeter "DSC-50Q type" (manufactured by Shimadzu Corporation), and vacuum suction is performed. And after removing the solvent completely, measure the heat change in the range of -100 ° C to + 100 ° C at a heating rate of 3 ° C / min, and change the first baseline change point on the low temperature side to the static glass transition temperature And

  When the hydroxyl group-containing acrylic resin (b-2) is contained in the hydroxyl group-containing resin (b) to be compounded, the content thereof is a hydroxyl group-containing acrylic resin (b) from the viewpoint of achieving both surface drying and finish. -2) / Other hydroxyl group-containing resin = 5/95 to 95/5, preferably 15/85 to 60/40, can be suitably set.

  Content of a hydroxyl-containing resin (b) is 25-95 mass parts with respect to a total of 100 mass parts of solid content of a component (a) and the below-mentioned component (b), and is within the range of 30-85 mass parts Is preferable, and the range of 40 to 80 parts by mass is more preferable.

(C) Pigment As a pigment (c) used for the base paint composition applied to this method, a luster pigment, a color pigment, an extender pigment etc. which are well-known in the paint field | area can be mentioned. The pigments can be used alone or in combination of two or more.

  As the bright pigment, metal flake powder or paste such as aluminum, pearl powder, graphite, bright pigment such as MIO, etc. may be mentioned as a typical example. Examples of the metal flake powder include aluminum flakes, nickel flakes, copper flakes, stainless steel flakes, brass flakes and chromium flakes, and examples of pearl powder include pearl mica, colored pearl mica and the like.

  As a color pigment, for example, titanium oxide, zinc flower, carbon black, graphite, iron oxide, molybdenum red, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment, quinacridone pigment, isoindoline pigment, graphene pigment, Perylene pigments, dioxazine pigments, diketopyrrolopyrrole pigments and the like can be mentioned.

  Further, examples of the extender pigment include clay, kaolin, barium sulfate, barium carbonate, calcium carbonate, talc, silica, alumina white and the like.

  These pigment components may be added directly to the coating composition, or may be mixed with a dispersing agent and a dispersing resin, dispersed and pasted, and then incorporated into the coating. The dispersant, the dispersing resin and the dispersing method may be known ones.

  The solid content of the pigment (c) can be appropriately adjusted according to the type of the pigment, and for example, relative to 100 parts by mass of the total solid of the cellulose derivative (a) and the hydroxyl group-containing resin (b) The range of 1 to 250 parts by mass is preferable, and the range of 15 to 200 parts by mass is more preferable.

  When the pigment (c) contains a color pigment, it may be a color base paint composition.

  In the present invention, the color base coating composition can be coated to adjust the brightness and hue of the substrate to form a color base coating.

  In this method, by using a color base coating film, the difference in color tone or texture decreases even if the film thickness changes when the upper coating composition described later is applied, or the coating surface becomes noticeable when scratched. It may be difficult to do so, which is preferable.

  The color base coating composition in the present method can incorporate a white pigment as a color pigment. The white pigment includes titanium oxide, and titanium oxide pigment is widely used as a white pigment because of its high refractive index. There are rutile type and anatase type depending on the crystal form, and any of them may be used in the present invention, but rutile type can be used from the point of weather resistance. Moreover, you may use what processed the surface with inorganic compounds, such as a silica, a zirconium, aluminum, in order to improve a dispersibility and a weather resistance. From the viewpoint of the hiding power of the coating film, it is preferable to use one having an average particle diameter in the range of 100 to 400 nm, and more preferably in the range of 200 to 300 nm. This average particle system is an average particle size measured by observation with an electron microscope.

  The content of the white pigment is 70 to 100 parts by mass of the total solids of the cellulose derivative (a) and the hydroxyl group-containing resin (b) from the viewpoint of the balance between the hiding property of the coating film and the finishing property and drying property. 200 parts by weight, preferably 100 to 195 parts by weight, in particular 135 to 185 parts by weight are preferred.

  In the present invention, when a color base paint composition is blended with a color pigment other than a titanium oxide pigment, its content is 100 parts by mass of the hydroxyl group-containing resin solid content contained in the paint composition from the viewpoint of the lightness of the multilayer coating film. The amount is preferably in the range of 0.01 to 30 parts by mass, and more preferably in the range of 0.05 to 25 parts by mass.

  The solid content of the base coating composition can be suitably adjusted in the range of 3 to 70% by mass, particularly 4 to 60% by mass, from the viewpoint of spray coating suitability and finish.

  In particular, when the bright paint and / or the white pigment is contained in the base paint composition, the solid content at the time of coating is 3 to 30% by mass, up to 4 to 20% by mass, and the organic solvent In some cases, the paintability (especially the looseness) of the formed coating film may be improved by dilution and coating. The organic solvent used for dilution is not particularly limited, and a common organic solvent for paint can be used.

  Here, in the present specification, the solid content of the coating composition means that about 2.0 g of a sample is collected in an aluminum foil cup having a diameter of about 5 cm, and the remaining content (g) after heating for 3 hours at 105 ° C. It is the value calculated by

In the case of containing a titanium oxide pigment as the pigment (c) in the base coating composition applied to the present method, when the pigment concentration is relatively high and the solid content ratio at the time of coating is low, the excellent film-screening property is excellent. And, it is particularly preferable because of a good balance between finish and drying properties.
Other Components The base coating composition to be applied to the present invention may further contain, if necessary, organic polymer fine particles, UV absorbers, light stabilizers, antioxidants, surface conditioners, pigment dispersants, curing catalysts, etc. A film forming resin other than the paint additive, the component (a) and the component (b) can be blended.

  As film-forming resins other than the component (b), first, crosslinking agents such as polyisocyanate compounds may be mentioned, but it is not necessary to contain a crosslinking agent in view of drying property and finish. Thereby, it can be set as one-pack type paint composition.

  In addition, it is preferable to include a phosphate group-containing copolymer in the base paint composition, since it may promote penetration of the crosslinker component from the top clear paint composition described later. When it contains the copolymer containing a phosphoric acid group, 0.2-10 mass parts is preferable with respect to a total of 100 mass parts of all the film formation resin in a coating composition. Here, the total film-forming resin in the coating composition includes the cellulose derivative (a), the hydroxyl group-containing resin (b), and a copolymer containing a crosslinking agent and a phosphate group when it contains a crosslinking agent. It is.

Coating method As a coating method at the time of coating the said base coating composition, it can coat by well-known means, such as spray coating, roller coating, brush coating, flow coating, for example. The number of times of coating is not particularly limited, and may be applied one or more times.

  When the coating is repeated several times, the base coating composition may be coated with a non-dried coating, but specifically, it is preferable to apply the coating in a state of being dry in touch or more. In the present specification, the dry-to-touch state refers to the dry state defined in JIS K 5600-1-1, which is the extent to which the finger does not touch the paint with light touch.

  As a solid content rate of the coating film obtained at this time, 50 mass% or more and 70 mass% or more, especially 80 mass% or more are preferable. The solid content of the obtained coating film can be calculated by weighing the mass change before and after drying.

  In the present specification, a cured coating or a dried coating is a cured and dried state defined in JIS K 5600-1-1, that is, the center of the coated surface is strongly sandwiched between the thumb and the index finger, It is a coating film in which no dents are formed by fingerprints, no movement of the coating film is felt, and the center of the coating surface is rubbed rapidly and repeatedly with a finger to leave no marks on the coating surface. On the other hand, the undried coating film is a state in which the coating film has not reached the above-mentioned cured and dried state, and also includes a touch-dried state and a semi-cured dried state defined in JIS K 5600-1-1.

Dry film thickness The dry film thickness of the base coating film varies depending on the condition of the coated object and the type of color pigment, but is preferably in the range of 5 to 30 μm per color, from the viewpoint of the balance between drying property and finishing property The range of 8 to 25 μm is more preferable, and the range of 10 to 25 μm is particularly preferable.

  After coating the base coating composition, drying is not essential, but for example, it may be left standing at ordinary temperature, and air blowing (wind drying) may be performed if necessary. Drying at normal temperature, for example, allows a film to be formed by gradually volatilizing volatile components in the coating film by standing under an environment of normal temperature (5 to 45 ° C.), whereby a dried coating film can be obtained.

  The relative humidity (hereinafter sometimes abbreviated as RH) at the time of coating is preferably 70% or less, particularly 60% or less. As a drying time of normal temperature drying, although it changes with dry film thickness, it can be carried out within 24 hours.

  When wind drying is used in combination, for example, it can be carried out by spraying air heated to a normal temperature or a temperature of about 25 ° C. to about 80 ° C. for about 30 seconds to about 15 minutes on the coated surface of the substrate. In addition, a circulator or the like may be installed in a normal temperature environment, and ventilation may be performed for 5 to 120 minutes, preferably 10 to 100 minutes.

  There is no particular problem even if it is dried by heating or forced drying depending on the coating environment and the like, but normal temperature drying is preferable from the viewpoint of shortening of the drying process and finish. As a heat source assumed, sunlight may be used. The painting environment may be indoors or outdoors.

<Step (2) Step of Forming a Coated Film>
Topcoat composition The topcoat composition used in the present method is formed to impart design properties and chipping resistance to a substrate, and is formed on the base coating film formed in the step (1). A topcoat composition of a color different from that of the base coat can be obtained at least once by coating at least once to form a topcoat.

  The place to be coated on the substrate is not particularly limited, and may include, for example, a two-tone pattern, a line color pattern of two or more colors, a stripe pattern, and a pattern having a complicated shape such as writing. The two-tone or more of the method may include, for example, those which are divided into two or more colors so as to form these patterns. When the part is separately painted by painting, you may use masking.

  The above-mentioned masking material is not particularly limited, and conventionally known ones can be used. As a masking material, a commercially available tape etc. can be used, for example. By coating using a masking tape, a color boundary with an unpainted part can be formed, and the design is excellent.

  The time to the masking application applied to the present method varies depending on the applied amount of the base coating composition, etc., but the dry film thickness is in the range of 5 to 30 μm and relative to the balance of finishability. When the humidity is 70% or less, 24 hours or less is possible, and specifically, it is possible to attach the masking tape in 30 minutes to 120 minutes. This method is very excellent in design without impairing the finish due to tape marks and the like if the coating film is touch-dried even if masked in the undried state.

  The topcoating composition used in this method contains a cellulose derivative (a), a hydroxyl group-containing resin (b) and a pigment (c), and the content of the cellulose derivative (a) is the component (a) and It is characterized by containing 5-75 mass parts with respect to a total of 100 mass parts of solid content of a component (b).

  As the cellulose derivative (a), the hydroxyl group-containing resin (b) and the pigment (c), those mentioned in the section of the base coating composition can be used. In particular, from the viewpoint of designability, it is preferable that the topcoating composition is a colored coating composition containing a coloring pigment as a pigment. The color pigment is not particularly limited, and can be appropriately selected from the viewpoint of visibility and design.

  As specific color pigments, those mentioned in the item of the pigment (c) can be used.

  The solid content of the pigment component can be appropriately adjusted according to the type of pigment, and for example, it is 10 with respect to 100 parts by mass of the total solid content of the cellulose derivative (a) and the hydroxyl group-containing resin (b). The range of -250 mass parts is preferable, and the range of 15-200 mass parts is more preferable.

  The solid content of the topcoating composition is preferably in the range of 3 to 50% by mass and 4 to 45% by mass in terms of spray coating suitability and finish.

  In particular, when the bright paint and / or the white pigment is contained in the top coat composition, the solid content is 3 to 30% by mass, and diluted with an organic solvent to 4 to 20% by mass. In some cases, the design of the formed coating film may be improved by coating. The organic solvent used for dilution is not particularly limited, and a common organic solvent for paint can be used.

Other Components The top coating composition to be applied to the present invention further comprises, if necessary, organic polymer fine particles, an ultraviolet light absorber, a light stabilizer, an antioxidant, a surface conditioner, a pigment dispersant, a curing catalyst, etc. A film forming resin other than the paint additive, the component (a) and the component (b) can be blended.

  As film-forming resins other than the component (b), first, crosslinking agents such as polyisocyanate compounds may be mentioned, but it is not necessary to contain a crosslinking agent in view of drying property and finish. Thereby, it can be set as one-pack type paint composition.

  In addition, it is preferable to include a phosphate group-containing copolymer in the topcoating composition, since it may promote penetration of the crosslinker component from the top clear coating composition described later. When it contains the copolymer containing a phosphoric acid group, 0.2-10 mass parts is preferable with respect to a total of 100 mass parts of all the film formation resin in a coating composition. Here, the total film-forming resin in the top coating composition includes the cellulose derivative (a), the hydroxyl group-containing resin (b), and the crosslinking agent and the copolymer containing a phosphoric acid group when the crosslinking agent is contained. It is.

Coating method As a coating method at the time of coating the said top-coat coating composition, it can coat by well-known means, such as spray coating, roller coating, brush coating, flow coating, for example. The number of times of coating is not particularly limited, and may be applied one or more times. That is, this step (2) may be repeated multiple times. At the time of over-coating, it may be over the base coating, over-coating on the over-coating, or both.

  The top coating composition may be coated with a wet film, and specifically, it is preferable to apply a dry coating or more. The dry-to-touch state refers to the dry state defined in JIS K 5600-1-1, which is the extent to which the paint can not be applied to the finger by lightly touching it with the finger. The solid content of the coating film obtained at this time is preferably 50% by mass or more, 70% by mass or more, particularly about 80% by mass or more. The solid content of the obtained coating film can be calculated by weighing the mass change before and after drying.

Dry film thickness The dry film thickness of the top coating film varies depending on the state of the coated object and the type of color pigment, but is preferably in the range of 5 to 30 μm per color, from the viewpoint of the balance between drying properties and finishing properties. The range of 8 to 25 μm is more preferable, and the range of 10 to 25 μm is particularly preferable.

  After the topcoat composition is applied, drying is not essential, but for example, it may be left standing at ordinary temperature, and air blowing (wind drying) may be performed if necessary. Drying at normal temperature, for example, allows a film to be formed by gradually volatilizing volatile components in the coating film by standing under an environment of normal temperature (5 to 45 ° C.), whereby a dried coating film can be obtained.

  The relative humidity (hereinafter sometimes abbreviated as RH) at the time of coating is preferably 70% or less, particularly 60% or less. As a drying time of normal temperature drying, although it changes with dry film thickness, it can be carried out within 24 hours.

  When wind drying is used in combination, for example, it can be carried out by spraying air heated to a normal temperature or a temperature of about 25 ° C. to about 80 ° C. for about 30 seconds to about 15 minutes on the coated surface of the substrate. In addition, a circulator or the like may be installed in a normal temperature environment, and ventilation may be performed for 5 to 120 minutes, preferably 10 to 100 minutes.

  There is no particular problem even if it is dried by heating or forced drying depending on the coating environment and the like, but normal temperature drying is preferable from the viewpoint of shortening of the drying process and finish. As a heat source assumed, sunlight may be used. The painting environment may be indoors or outdoors.

<Step (3) Step of Forming a Top Clear Coating>
In this method, after a coating film is sequentially formed by the above-described steps (1) and (2), a top clear coating composition is then applied on the front surface to form a clear coating film.

Top clear paint composition The top clear paint composition used in the method of the present invention is a top clear used as the top layer (top coat), for example, acrylic resin or fluorine resin having a crosslinkable functional group such as hydroxyl group (block A curable coating composition mainly composed of a crosslinking agent such as polyisocyanate or melamine resin, or a lacquer coating composition mainly composed of a cellulose acetate butyrate-modified acrylic resin can be suitably used. By using the top coat in the present method, the design, finish and stain resistance are improved. In particular, when a urethane-curable coating composition is used as the top clear coating composition, the isocyanate component partially penetrates into the top coating film and the base coating film from the clear coating film, and the cellulose derivative used in the base coating (a) And it reacts with the hydroxyl group of the hydroxyl group-containing resin (b) to form an adhesive and tough film without using a crosslinking agent component in the base coat paint or the top coat, which is preferable.

  In addition, the top clear coating composition can be blended, if necessary, with additives for coating such as polymer fine particles, a curing catalyst, an ultraviolet absorber, an antioxidant, a surface conditioner, and an antifoamer. The coating film of the top clear coating composition preferably has a dry film thickness in the range of 10 to 100 μm.

  As a coating method of top clear paint composition, it can paint by publicly known means, such as spray application, roller application, brush application, flow application, etc., for example. The number of times of coating is not particularly limited, and may be applied one or more times.

  As a drying method, either heating drying or normal temperature drying may be used, and setting and / or air blowing (wind drying) may be performed as necessary. As a drying method, it is more preferable to carry out heat drying or forced drying since curing can be promoted and drying time can be shortened.

  In the case of heat drying, a coated film can be obtained, for example, by drying for 5 to 120 minutes, preferably 10 to 100 minutes in an environment of 30 to 80 ° C., preferably 35 to 70 ° C., particularly 40 to 60 ° C. it can. The heat source may be sunlight.

  The contents of a coating method according to an embodiment of the present invention will be described based on the drawings. In the present embodiment, the contents will be described below, taking line color coating on the outer surface of a body such as a railway as an example.

  FIG. 1 is a flowchart for explaining the flow of a coating method according to an embodiment of the present invention.

As shown in the figure, this coating method is carried out on a substrate which has been subjected to substrate adjustment as required.
(S1) a step of applying a base paint composition to form a base coating,
(S2) a step of partially coating at least once a different color top coat composition on the base coat to form a top coat;
(S3) coating the top clear paint composition over the entire surface, and drying it,
As needed, after forming a base coating film, you may provide the process of masking the one part on a base coating layer with a masking sheet (S12), and the process of removing a masking (S23).

  As the number of work items, if painting process, drying process, masking work (pasting), masking work (removal), drying process (drying), drying process (cooling after heating and drying) are counted as one work item respectively, In the case of 1, the number of work items is 9 excluding the substrate adjustment.

  As described above, it is possible to obtain a coated article having a coating which is separately applied in two-tone or more by this method. The obtained coating film is a multilayer coating film, and the total dry film thickness varies depending on the number of coating colors, but, for example, three layers in which all of the base coating film, the top coating film and the clear coating film of FIG. The maximum total film thickness of the dry film thickness in the case of the above can be in the range of 15 to 160 μm, preferably in the range of 28 to 150 μm. The multilayer coating obtained by the present method is a coating of the base coating and the top coating at least once or a plurality of times, and finally a clear coating is formed, but at least three or more layers and partially colored It becomes a multilayer coating film which was painted separately.

  Hereinafter, the present invention will be further described by way of examples. Here, "part" and "%" mean "mass part" and "mass%", respectively.

Production Example 1 Coating Composition No. 1 B-1
Cellulose derivative No. 1 (note 1) 45 parts, 50% hydroxyl group-containing acrylic resin (A-1) (note 3) 50 parts (solid content 25 parts by mass), 70% hydroxyl group-containing polyester resin (E-1) 42 A mixed solvent consisting of 9 parts (solid content: 30 parts by weight) and 167 parts of TIPAK CR-93 (Note 5) as pigment P-1 and xylene / butyl acetate = 50/50 is added, and the mixture is stirred for about 20 minutes with a disper Coating composition No. 1 for base B-1 (White) was produced. The same mixed solvent was used as a dilution solvent at the time of coating to adjust to a solid content of 15% by mass, and the drying property of the obtained coating composition and the adhesion after drying were evaluated and are shown in Table 1.

(Production Examples 2 to 6 and Production Examples 7 to 11)
In Production Example 1, base coating composition No. 1 was prepared in the same manner as in Production Example 1 except that the ingredients of the respective components were blended as shown in Table 1. B-2 to B-6 and topcoat composition No. 1 T-1 to T-5 were manufactured. The obtained coating compositions were diluted and adjusted so as to have a solid content at the time of coating shown in Table 1, and the drying property and the adhesion after drying were evaluated and shown in Table 1. In addition, the composition of Table 1 is a solid content display.

  The notes in the table indicate the following.

(Note 1) Cellulose derivative No. 1 1: "CAB-381-0.5", trade name, manufactured by Eastman Chemical Products, cellulose acetate butyrate, number average molecular weight 30,000,
(Note 2) Cellulose derivative No. 2: Solid content of 30% by mass, cellulose modified copolymer (Method for producing cellulose derivative No. 2: Production example: The following components are charged in a reactor equipped with a thermometer, a stirrer, a reflux condenser and a dropping funnel, nitrogen gas It was heated under an atmosphere and heated to 110 ° C. for about 4 hours.
600 parts of butyl acetate,
200 parts of "CAB-381-0.5" (note 1),
After raising temperature, after confirming that "CAB-381-0.5" (note 1) had dissolved completely, heating was stopped and 133 parts of butyl acetates were distilled off under reduced pressure. The temperature in the reactor was 87 ° C. 11.1 parts of a 90% butyl acetate solution of equimolar addition product of isophorone diisocyanate and 2-hydroxyethyl acrylate while maintaining this temperature, 0.02 parts of p-t-butylcatechol as a polymerization inhibitor, and urethane As a conversion catalyst, 0.02 part of dibutyltin dilaurate was charged into the reactor, and aged under dry air at 87 ° C. for 7 hours to obtain an unsaturated group-containing cellulose acetate butyrate solution. Next, the reaction temperature was raised to 115 ° C., and a mixed solution of the following polymerizable unsaturated monomer and a polymerization initiator was added dropwise over 2 hours under a nitrogen atmosphere. 130 parts of butyl acetate 58.2 parts of methyl methacrylate 2 parts of t-butylperoxy-2-ethylhexanoate after the dropwise addition, 0.5 parts of t-butylperoxy-2-ethylhexanoate, 20 parts of butyl acetate The mixed solution was added dropwise over 1 hour and aged under nitrogen atmosphere at 115.degree. C. for 1 hour. A cellulose modified copolymer solution having a solid content of 30% was obtained.

  (Note 3) Hydroxyl group-containing acrylic resin (A-1): solid content 50% by mass, hydroxyl value 92 mg KOH / g, acid value less than 1 mg KOH / g, glass transition temperature 42 ° C., weight average molecular weight 50,000.

  (Note 4) Hydroxyl group-containing polyester resin (E-1): solid content 70% by mass, hydroxyl value 55 mg KOH / g, weight average molecular weight 20,000, glass transition temperature -60 ° C., DBR (dibasic acid ratio) 0.95.

(Note 5) Pigment P-1: Typek CR-93, trade name, manufactured by Ishihara Sangyo Co., Ltd., white pigment, titanium white, average particle diameter 280 nm,
(Note 6) Pigment P-2: Aluminum paste CR-9800RM, trade name, manufactured by Asahi Kasei Metals, metallic pigment, aluminum paste, average particle diameter 7 μm, specific gravity 1.1, mixed solvent of solvent mineral spirit and solvent naphtha, solid Minute content rate 42%,
(Note 7) Pigment P-3: Black pigment, carbon black, average particle size 0.01 μm
(Note 8) Pigment P-4: red pigment, perylene red pigment,
(Note 9) Pigment P-5: Blue pigment, phthalocyanine pigment.

  (Note 10) Polyisocyanate compound: SUMIDUR N 3300, trade name, manufactured by Sumika Korobetrourethane, isocyanurate of hexamethylene diisocyanate, solid content 100%.

Test item 1: Drying property A commercially available lacquer primer surfacer was coated with a thickness of 40 μm on a commercially available tin plate of 300 × 150 × 2.0 mm, dried at room temperature for 30 minutes, and polished with # 400 water-resistant abrasive paper. The paint compositions of Production Examples 1 to 11 were coated on this coated plate to a dry film thickness of 20 ± 5 μm, and left at room temperature (23 ± 5 ° C., humidity 50 ± 10% RH) for 10 minutes. Thereafter, a masking tape was attached to the surface of the coating, and after standing for 1 hour at room temperature, the tape was peeled off, and the surface of the coating was visually observed. After that, clear coating is applied by spray so that the dry film thickness is 15 ± 5 μm, and heat drying is performed for 30 minutes in a drying oven (maximum reaching temperature of 45 ° C.) set at 50 ° C. assuming a large drying oven. I did. The remaining tape mark of the test coating was visually evaluated. Evaluation criteria were as follows.
:: At the time of tape peeling, almost no trace of the tape can be seen after formation of the clear coating film,
:: The tape mark remains when the tape is peeled, but the tape mark is not seen after the clear film formation,
:: The tape marks of all the attached parts remain, but the tape marks become slightly inconspicuous after clear film formation,
X: The tape mark of all the pasted parts remains strongly.

Test item 2: Adhesion (after drying test)
The coated film on the test plate after the drying test is cross-cut to reach the substrate, and the coated surface is adhered with a cellophane, and the interface when the coating is peeled off is the base coated film or the coated film / It was between the objects to be coated.
○: no peeling,
:: Slight peeling,
X: Remarkable peeling.

Example 1
A commercially available tin plate of 300 × 150 × 2.0 mm in size was coated with 40 μm of a commercially available lacquer primer surfacer as a substrate preparation, dried for 30 minutes at room temperature and then polished with # 400 water-resistant abrasive paper. The base paint composition described in Table 2 was spray-coated on the entire surface of the coated plate to a dry film thickness of 15 μm, and left for 30 minutes at room temperature (air temperature 23 ° C., humidity 50% RH). Thereafter, masking is performed with a masking tape so as to form a line pattern, and the top coating composition described in Table 2 is spray coated so that the unmasked portion has a dry film thickness of 15 μm, room temperature (air temperature 23 ° C., humidity 50 It was left for 30 minutes under the conditions of% RH). After standing, the masking was removed, and the top clear paint composition No. 1 was removed. As “1”, “Retan PG2K clear” (urethane curable coating composition manufactured by Kansai Paint Co., Ltd.) was spray-coated to a dry film thickness of 15 μm. Thereafter, the coated plate was placed in a drying oven at 50 ° C. (material achieving temperature 45 ° C.) assuming a large drying oven for 30 minutes, and dried by heating to obtain a test plate.

  A schematic diagram of the work procedure of the present embodiment is shown in FIG. The maximum total film thickness of the dry film thickness of the test plate, the total number of steps, the number of coating colors, and the time from painting to completion are shown in Table 2. The time required for cooling after drying by heating was 2 hours. The number of work items in this case is nine.

(Example 2)
A commercially available tin plate of 300 × 150 × 2.0 mm in size was coated with 40 μm of a commercially available lacquer primer surfacer as a substrate preparation, dried for 30 minutes at room temperature and then polished with # 400 water-resistant abrasive paper. On this coated plate, the base paint composition (B-2) described in Table 2 is spray coated on the entire surface to a dry film thickness of 15 μm, and under conditions of room temperature (air temperature 23 ° C., humidity 50% RH) 30 I left for a minute. Thereafter, masking is performed with a masking tape so as to form a line pattern, and a non-masked portion is spray coated as a top coat composition 1 described in Table 2 (T-1: gray) to a dry film thickness of 15 μm. And 30 minutes at room temperature (temperature 23 ° C., humidity 50% RH). Thereafter, masking is further performed with a masking tape so as to form another line pattern on the top coat 1, and the unmasked portion is partially covered on the base coat and the top coat 1, The top coat composition 2 was spray-coated with (T-3: blue) to a dry film thickness of 15 μm, and left for 15 minutes at room temperature (air temperature 23 ° C., humidity 50% RH). After leaving, the masking was removed, and clear paint composition No. 1 was obtained. As “1”, “Retan PG2K clear” (urethane curable coating composition manufactured by Kansai Paint Co., Ltd.) was spray-coated to a dry film thickness of 15 μm. Thereafter, the coated plate was placed in a drying oven at 50 ° C. (material achieving temperature 45 ° C.) assuming a large drying oven for 30 minutes, and dried by heating to obtain a test plate.

  A schematic diagram of the work procedure of this embodiment is shown in FIG. The maximum total film thickness of the dry film thickness of the test plate, the total number of steps, the number of coating colors, and the time from painting to completion are shown in Table 2. The time required for cooling after drying by heating was 2 hours. In this case, the number of work items is 12.

(Example 3)
A commercially available tin plate of 300 × 150 × 2.0 mm in size was coated with 40 μm of a commercially available lacquer primer surfacer as a substrate preparation, dried for 30 minutes at room temperature and then polished with # 400 water-resistant abrasive paper. On this coated plate, the base paint composition (B-1) described in Table 2 is spray coated on the entire surface to a dry film thickness of 15 μm, and 30 at room temperature (air temperature 23 ° C., humidity 50% RH) I left for a minute. Thereafter, masking is performed with a masking tape, and the unmasked portion is spray-coated as the top coat composition 1 described in Table 2 (T-1: gray) to a dry film thickness of 15 μm, and room temperature (air temperature 23) It was left for 30 minutes under the conditions of ° C., humidity 50% RH). Thereafter, the film is further masked with a masking tape, and the unmasked portion is partially coated on the base coating and the top coating 1 as a top coating composition 2 (T-2: red) as a dried film. It spray-painted so that it might become 15 micrometers in thickness, and it left for 15 minutes on condition of room temperature (air temperature 23 ° C, humidity 50% RH). Thereafter, a masking tape is further masked, and a non-masked portion is partially coated on the multilayer coating in which the base coating, the top coating 1 and the top coating 2 are sequentially laminated. As composition 3, (T-3: blue) was spray-coated to a dry film thickness of 15 μm, and left for 15 minutes under the conditions of room temperature (air temperature 23 ° C., humidity 50% RH). Thereafter, the masking was removed, and clear paint composition No. 1 was obtained. As “1”, “Retan PG2K clear” (urethane curable coating composition manufactured by Kansai Paint Co., Ltd.) was spray-coated to a dry film thickness of 15 μm. Thereafter, the coated plate was placed in a drying oven at 50 ° C. (material achieving temperature 45 ° C.) assuming a large drying oven for 30 minutes, and dried by heating to obtain a test plate.

  A schematic drawing of the work procedure of this embodiment is shown in FIG. The maximum total film thickness of the dry film thickness of the test plate, the total number of steps, the number of coating colors, and the time from painting to completion are shown in Table 2. The time required for cooling after drying by heating was 2 hours. In this case, the number of work items is 15.

(Examples 4-5, comparative examples 1-3)
A test plate was produced in the same manner as in Example 1 except that the base paint composition, the upper paint composition, the coating film thickness, the drying temperature and the time were as shown in Table 2 in Example 1. The working procedures of Examples 4 to 5 and Comparative Examples 1 to 3 and Comparative Examples 5 to 6 are the same as those shown in FIG. The number of work items in this case is nine.

(Comparative example 4)
A commercially available tin plate of 300 × 150 × 2.0 mm in size was coated with 40 μm of a commercially available lacquer primer surfacer as a substrate preparation, dried for 30 minutes at room temperature and then polished with # 400 water-resistant abrasive paper. On this coated plate, the base coating composition (B-5) described in Table 2 is spray coated on the entire surface to a dry film thickness of 15 μm, and 50 ° C. (material reach temperature 45 ° C.) assuming a large drying oven. The mixture was placed in a drying oven for 60 minutes and dried by heating. After that, when it is cooled to room temperature, the coated plate is masked with a masking tape, and the unmasked portion is described as a top coating composition 1 described in Table 2 (T-1: gray) with a dry film thickness of 15 μm. It spray-coated so that it might become, and it was made to heat-dry for 60 minutes in the drying oven of 50 degreeC (material complete temperature 45 degreeC) supposing a large-sized drying oven. After that, when cooled to room temperature, the coated plate is further masked with a masking tape, and the unmasked portion is partially formed on the base coating film and the top coating film 1 as a top coating composition 2 (T-3: blue) was spray-coated to a dry film thickness of 15 μm, and placed in a drying oven at 50 ° C. (material achieving temperature 45 ° C.) assuming a large drying oven, for 60 minutes, and dried by heating. After cooling to room temperature, the masking was removed, and clear paint composition No. 1 was removed. As “1”, “Retan PG2K clear” (urethane curable coating composition manufactured by Kansai Paint Co., Ltd.) was spray-coated to a dry film thickness of 15 μm. Thereafter, the coated plate was put into a drying oven at 50 ° C. (material reaching temperature 45 ° C.) for 30 minutes, assuming a large drying oven, and dried by heating to obtain a test plate.

  A schematic diagram of the work procedure of this embodiment is shown in FIG. The maximum total film thickness of the dry film thickness of the test plate, the total number of steps, the number of coating colors, and the time from painting to completion are shown in Table 2. The time required for cooling after drying was 2 hours. In this case, the number of work items is 15.

(Comparative Examples 5 and 6)
A test plate was produced in the same manner as in Example 1 except that the base paint composition, the upper paint composition, the coating film thickness, the drying temperature and the time were as shown in Table 2 in Example 1. The operation procedures of Comparative Examples 5 and 6 are the same as those shown in FIG. The number of work items in this case is nine.

(Comparative example 7)
A test plate was prepared in the same manner as in Example 1 except that the base paint composition, the top paint composition, the coating film thickness, the drying temperature and time are as shown in Table 2 and the working procedure is as shown in FIG. Was produced. As shown in FIG. 5 of the working procedure, clear paint composition No. 1 was applied between the base and the top coat. I have painted one. A schematic drawing of the work procedure is shown in FIG. The number of work items in this case is 21. Maximum total film thickness of dried film thickness of test plate, total number of processes (painting, masking sticking operation, masking removing operation, drying and drying (cooling) are counted as one operation item), number of colors and coating to completion The time is shown together in Table 2.

Test item 3. Coating appearance:
The coating film appearance (glossy, softness, designability) of each test plate was visually observed and evaluated according to the following criteria.

Coating film appearance (Glossy)
○: good (uniform glossiness observed)
:: slightly poor (very slight unevenness in gloss is observed)
X Poor (gloss unevenness is observed).

Coating film appearance (Hada):
The coating film appearance (body) of each test plate was visually evaluated according to the following criteria.
○: good (uniform and smooth)
:: Slightly poor (Slightly wrinkled skin is observed)
X Poor (remarkable wrinkled skin is observed).

Coating film appearance (design property)
The color boundary of each test plate was visually observed and evaluated according to the following criteria.
○: good (color border is clear),
:: slightly defective (slightly blurred color border)
X: Defective (color boundary is not clearly clear).

Test item 4: Contamination resistance: carbon adhesion test
A 10% by mass aqueous dispersion of carbon pigment (FW-200, trade name, manufactured by Orion Engineer Carbons Co., Ltd.) is used as a model contaminated water, and 2 g of the contaminated water is spot-dropped on the coating film surface of each test plate. After baking at 30 ° C. for 30 minutes, after water-washing with a sponge lightly, carbon remaining on the flat portion and the color boundary portion on each test plate was confirmed.
○: Good with almost no difference in residual carbon ratio between flat area and color boundary area
X: Carbon remains at the color boundary and defective.

S0: Substrate-adjusted coated object S1: Step of forming base coating film S2: Step of forming top coating film on base coating film S3: Top clear coating composition coated and dried to form clear coating film Step S1 'of forming: a step of forming a base coating for comparison S2': a step of forming a top coating on a base coating for comparison S3 ': clear coating composition which is not the top is overcoated and dried, clear coating Step S11 of forming a film: Coating step S1 in the step S12: Drying step S1 in the step S13: Masking operation after the coating film formation S1: Coating step S2 in the step S22: Drying step S2 in the step S2: S2: Coating process in S2: Coating process in S3: Drying process in S3: S3: Cooling process in S3: S3 (S2) Cooling process in S3: 1st (first color) forming top coat The Step S2 (2): Second step (second color) of forming a top coated film Step S2 (3): third step (third color) of forming a top coated film S2 (1) 1: 1 time (first color) Coating step S2 (1) in the S2 step) drying step S2 (1) in the 2nd (first color) S2 step S2 (1) 3: 1 masking operation S2 after the S2 coat formation (first color) (2) Coating step S2 (2) in the S2 step of the 1: 2nd (second color) 2: drying step S2 (2) in the S2 step of the second (second color) 3: 2nd (second color) Masking operation S2 (3) after the coating film formation of S2: Coating step S2 (3) during the S2 step of the third (third color) S2 (3) Drying step S2 during the S2 step of the third (third color) S2 (3) ) 3: Masking work after the third (third color) S2 coating formation

Claims (6)

On a large area of object,
(1) a step of applying a base paint composition to form a base coating,
(2) A step of partially coating at least once a different color top coat composition on the base coat to form a top coat,
(3) applying a top clear coating composition to the entire surface and drying it to form a clear coating film;
The base coating composition and the top coating composition each contain a cellulose derivative (a), a hydroxyl group-containing resin (b) and a pigment (c), and the content of the cellulose derivative (a) is a component It is in the range of 5-75 mass parts with respect to a total of 100 mass parts of solid content of (a) and a component (b), The multicolor finish coating method characterized by the above-mentioned. The multicolor finish coating method according to claim 1, wherein the top clear coating composition is a urethane curable coating composition. The multicolor finish coating method according to claim 1 or 2, wherein the base paint composition and the topcoat paint composition are one-pack type paint compositions containing no crosslinking agent. The base coating composition is applied so that the dry film thickness of the base coating film is 5 to 30 μm in the step (1), and the dry film thickness of the top coating film is 5 to 30 μm in the step (2). The multicolor finish coating method according to any one of claims 1 to 3, wherein the topcoat composition is applied to achieve The multicolor finish coating method according to any one of claims 1 to 4, wherein the object to be coated is a railway vehicle. The manufacturing method of the coated article which has the coating film color-divided by two or more colors using the multicolor finish-coating method of any one of Claims 1-5.

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