KR100813289B1 - Method for Forming Paint Coating - Google Patents

Abstract

The present invention relates to a method for forming a paint coating having a dry film thickness of a target of 100 μm or more uniform on the surface of a workpiece, comprising an extender pigment having 0.01 to 3% by volume of a colored pigment and a whiteness of 85 or more relative to paint solids. A paint having a dry film thickness of the target, and (b) a paint coating having a dry film thickness of the target and (a dry film of the target). Thickness-50 or more color difference between paint coatings having a dry film thickness of less than 50 μm, and (c) paint coatings having a dry film thickness of the target and a dry film greater than (target dry film thickness + 50) μm. Adjusting the content of the colored pigment and the extender pigment in the film thickness-determination paint such that the color difference between paint coatings having a thickness satisfies less than one. It provides a method of forming an in coating.

Paint, coating, coloring pigment, sieving pigment, color difference, whiteness, dry film thickness

Description

Method for Forming Paint Coating

FIELD OF THE INVENTION The present invention relates to a method of forming a substantially uniform paint coating on a workpiece, more particularly easily and precisely at a desired dry film thickness on a workpiece, such as a vessel, which requires a different paint coating film thickness depending on the area. To a method of forming a paint coating without color difference in the dry film thickness of the above different targets.

Subjects such as ships, steel structures, etc., susceptible to severe corrosion require a single layer or multilayer paint coating of a predetermined film thickness, and the layer formed by a single coating step should have a thickness of 100 μm or more, which is rust and corrosion To have sufficient resistance to. In order to confirm the formation of paint coatings of such thicknesses, wet gauges, electromagnetic thickness meters and the like are currently used. However, because the workpieces such as ships, steel structures, etc. have a large area to be coated, and a part of the surface is not located in an area where easy coating is possible, it is necessary to measure the thickness of the paint coating film with a wet gauge during painting. It is practically difficult and it is also practically difficult to completely inspect the entire portion of the dried pate coating with an electromagnetic thickness meter or the like. Under these circumstances, various studies have been conducted on how to check whether a paint coating formed on a workpiece such as a ship, steel structure, etc. has reached the prescribed film thickness.

For example, Japanese Patent Laid-Open No. 10-216621 utilizes a paint having 0.01 to 3% by volume of colored pigment as the film thickness-determination paint to paint solids, so that a target dry film thickness of 100 μm or more is applied on the surface of the workpiece. A method of forming a substantially uniform paint coating is disclosed, wherein the colored pigment content of the film thickness-determination paint is adjusted to satisfy the following conditions:

(a) the color difference between the film thickness-determination paint and the workpiece is 20 or more,

(b) the color difference between the paint coating having a target dry film thickness and the paint coating having a dry film thickness of (target dry film thickness minus 50) μm or more, and 2

(c) The color difference between the paint coating having a dry film thickness of the target and the paint coating having a dry film thickness of (target dry film thickness + 50) µm or more is 1 or less.

However, the conventional film thickness-determination paint described above tends to provide a paint having a blackish color as the target dry film thickness increases.

For example, in the case of ships, the owners require paint coatings of different thicknesses depending on the area of the ship being painted. Thus, the film thickness-determination paint is prepared in advance for a plurality of target dry film thicknesses, such as 100 μm, 200 μm, 400 μm, and one of the paints is selected for each painting area. However, the conventional film thickness-determination paints described above tend to provide paint coatings having a blackish color as the target dry film thickness increases, which means that the paint coating has a slight color difference in the thick and thin portions. This results in a paint coating that is present and prevents a uniform color in any area of the paint coating. In particular, when the thick areas of the paint coating are adjacent to the thin areas, the color difference between them becomes remarkable, causing appearance problems.

In addition, in order to check whether the paint coating has reached the target dry film thickness, while the formed paint coating is still wet, the film thickness-determination of in situ is observed, since the color difference is visually observed. It is difficult to control the thickness of the paint coating when there is a slight difference in color depending on the target dry film thickness in the paint. Thus, a large difference in the thickness of the paint coating occurs according to the target dry film thickness, which leads to a deterioration in quality.

Accordingly, it is an object of the present invention to facilitate paint coating without color difference at the target dry film thickness precisely above the target dry film thickness on a workpiece such as a ship requiring a different paint coating film thickness depending on the area. It is to provide a method of forming.

As a result of diligent research efforts for the above aims, the inventors have found the following facts: (a) A paint comprising body pigments having a high whiteness and a relatively small amount of colored pigment is a film thickness-determination paint. When used as, the color difference between the film thickness-determination paint and the workpiece, the color difference between the paint coating having a target dry film thickness and the paint coating thinner than the target dry film thickness, the paint having a target dry film thickness By setting the color difference between the coating and the paint coating thicker than the target dry film thickness to a predetermined level, paint coating accurately at the target dry film thickness of each target on the surface of the workpiece having a target dry film thickness that differs from region to region. Can be obtained, and at the same time, it is possible to easily form a paint coating without color difference even at different thicknesses. High, and (b) the thickness of - the use of an extender pigment having a high degree of whiteness in the determination paint reduces the tendency of the coating than the paint of black blend even in the dry thickness of the thicker target. The present invention is based on the above findings.

Accordingly, according to one embodiment of the present invention, the present invention provides a method for forming a paint coating having a target film thickness of 100 μm or more substantially uniform on a surface of a workpiece, wherein the pigment is 0.01 to about pigment solids. A paint comprising a extender pigment having 3% by volume and a whiteness of 85 or more is used as the film thickness-determination paint, and the content of the colored pigment and the extender pigment in the film thickness-determination paint is adjusted so that the following conditions are satisfied. It provides a method of forming a paint coating, characterized in that:

(a) the color difference between the film thickness-determination paint and the workpiece is at least 20,

(b) the color difference between the paint coating having a target dry film thickness and the paint coating having a dry film thickness of (target dry film thickness minus 50) μm or more, and 2

(c) The color difference between the paint coating having a dry film thickness of the target and the paint coating having a dry film thickness of (target dry film thickness + 50) µm or more is 1 or less.

According to another embodiment of the present invention, the present invention provides a method of forming a paint coating having different target thickness areas on the surface of a workpiece using two or more film thickness-determination paints, wherein each target dry film thickness is At least 100 μm, each film thickness-determination paint comprises a sieving pigment having 0.01 to 3% by volume and a whiteness of 85 or more relative to the paint solids, wherein the color pigment and the sieving pigment in the film thickness-determination paint It provides a method of forming a paint coating, characterized in that to adjust the content of so that the following conditions are satisfied:

(a) the color difference between the film thickness-determination paint and the workpiece is at least 20,

(b) the color difference between the paint coating having a target dry film thickness and the paint coating having a dry film thickness of (target dry film thickness minus 50) μm or more, and 2

(c) The color difference between the paint coating having a dry film thickness of the target and the paint coating having a dry film thickness of (target dry film thickness + 50) µm or more is 1 or less.

The two or more film thickness-determination paints are preferably adjusted such that the color difference between the film thickness-determination paints at the target dry film thickness is 3 or less. In both embodiments of the invention described above, the paint coating preferably has a contrast of 0.90 to 0.98 at the target dry film thickness.

In the case where all of the colored pigments or colored pigments except titanium dioxide are removed from the film thickness-determination paint, the paint coating preferably has a brightness (L value) of 60 or more at the target dry film thickness.

Preferably, the colored pigment in the film thickness-determination paint comprises titanium dioxide and other colored pigments, and the total content of the titanium dioxide and other colored pigments is 0.1-3% by volume relative to paint solids.

The workpiece is preferably a steel plate coated with a shop primer and / or a film thickness-determination paint of different colors as an undercoat.

Preferably, the film thickness-determination paint is at least one binder resin selected from the group consisting of epoxy resins and epoxy resins modified with petroleum resins, and at least one selected from the group consisting of amine, polyamide and polyisocyanate compounds. It contains 1 type of hardening | curing agents.

In the present invention, by visually observing a change in the color difference in the wet state of the formed film thickness-determination paint coating, it is determined whether the film thickness-determination paint coating has reached a prescribed film thickness. .

[1] film thickness-determination paints

(A) pigment

Coloring components that affect the chromaticity and lightness of the film thickness-determination paint are mainly colored pigments. Although sieving pigments and anti-corrosive pigments also affect the chromaticity and lightness of the film thickness-determination paints, the whiteness of the sieving pigments is an important factor in accurately determining the whiteness of paint coatings having different colors. Anti-corrosive pigments are preferred because they can impart anti-corrosive effects to ships and the like.

(1) colored pigment

Color pigments that can be used in the present invention include carbon black, titanium dioxide, basic lead carbonate, graphite, zinc sulfide, zinc oxide, chromium oxide, yellow nickel titanium, yellow chrome titanium, yellow iron oxide, red iron oxide, black iron oxide Phthalocyanine blue, phthalocyanine green, ultramarine blue, quinacridone, red or yellow azo pigments. At least 1 type of colored pigment is mentioned above and titanium dioxide is preferable. Titanium dioxide is preferably used alone or in combination with other pigments, because titanium dioxide greatly affects the chromaticity, lightness and contrast ratio of the film thickness-determination paint and lightens the pate coating.

(2) sieving pigment

Sieving pigments that may be used in the present invention include talc, clay, mica, calcium carbonate, magnesium carbonate, barium sulfate, silicic acid, silicates, aluminum oxide hydrates, calcium sulfate and the like. Of these, talc is preferred.

The quality pigment should have a whiteness of at least 85, preferably at least 90. With the above whiteness, no color difference occurs due to the dry film thickness of the different target, which makes it possible to have a uniform color over the entire area of the paint coating. In addition, the paint coating can be provided at the correct thickness at each target dry film thickness. When the combined whiteness is 85 or more, two or more extender pigments having different whiteness may be used in combination. Whiteness is a variable measured according to JIS Z 8722 (1982) with powder whiteness meter C-100 (Filter Blue), available from Kett Electric Laboratory.

The extender pigment preferably has a refractive index of 1.8 or less, more preferably 1.6 or less. If the refractive index of the extender pigment is too high, the color adjustment of the paint coating is adversely affected.

(3) anti-corrosive pigments

Anti-corrosive pigments are preferably used for neutral coatings, and preferred examples of such anti-corrosive pigments include zinc phosphate, trilide tetraoxide, basic lead sulfate, lead suboxide, lead cyanamide, calcium zinc cyanide. Metal compounds such as namid, zinc molybdate, aluminum molybdate, basic lead chromate, zinc chromate, strontium chromium and barium chromium. In addition, the anti-corrosive pigments are preferably those having a white color.

(B) binder resin

The binder resin for the film thickness-determination paint is preferably an epoxy resin modified with (1) an epoxy resin and (2) a petroleum resin. Alkyd resins, acrylic resins, vinyl chloride resins, chlorinated olefin resins, chlorinated rubbers, vinyl acetate resins, and the like can also be used as binder resins.

(1) epoxy resin

Epoxy resins can be solid or liquid commonly used, examples of which include bisphenol-based epoxy resins, which contain condensation units of epihalohydrin and bisphenol compounds such as bisphenol A, F, B or their halogen derivatives. It is resin mainly made. Particularly preferred are diglycidyl ethers of bisphenol A, diglycidyl ethers of bisphenol F, phenol-novolak epoxy resins, adducts of bisphenol compounds and alkylene oxides, and the like. Further, epoxy resin modified with carboxylic acid disclosed in Japanese Patent Laid-Open No. 63-30569, epoxy resin modified with amine disclosed in Japanese Patent Laid-Open No. 63-30568, epoxy modified with phosphoric acid disclosed in Japanese Patent Laid-Open No. 61-91217 Resin can be used.

(2) modified epoxy resin

In place of or in conjunction with the above epoxy resins, epoxy resins modified with petroleum resins may also be used.

(a) petroleum resin                     

Petroleum resins are obtained by polymerizing diolefins or monoolefins which are produced as by-products in cracking of petroleum without separation. Petroleum resins are classified into C ₅ petroleum resins and C ₉ petroleum resins.

(b) deformation

Modification of the epoxy resin can be accomplished using a method of mixing the epoxy resin with a petroleum resin at room temperature or by reacting the two materials at 80-150 ° C. to open a portion of the epoxy group. The amount of petroleum resin in the modified epoxy resin is generally 10-500 parts by weight based on 100 parts by weight of the epoxy resin.

(c) curing agent

The curing agent for the above epoxy resin or the above modified epoxy resin is preferably an amine, polyamide or polyisocyanate compound, which may be used in combination.

(1) amine curing agent

Preferred examples of the amine curing agent include linear aliphatic polyamines such as diethylenetriamine, triethylenetetraamine, ethylaminopropylamine and the like; Alicyclic polyamines; Aliphatic polyamine additives; Ketamine; Modified aliphatic polyamines; Polyamide amines; Aromatic amines; Modified aromatic amines; Aromatic polyamines such as diaminodiphenylmethane and the like and modified aromatic polyamines and the like.

(2) polyamide curing agent

Preferred examples of the polyamide curing agent include aliphatic polyamides formed by polycondensation of polycarboxylic acids and polyamines; Aromatic polyamide formed by introducing an aromatic ring into the aliphatic polyamide described above; Aliphatic polyamide additives; Aromatic polyamide additives; And the like.

(3) polyisocyanate compound curing agent

Preferred examples of the polyisocyanate compound curing agent include aliphatic polyfunctional isocyanates such as hexamethylene diisocyanate (HMDI); Alicyclic polyfunctional isocyanates such as isophorone diisocyanate (IPDI); Polyisocyanate compounds such as diphenylmethane-4,4'-diisocyanate (MDI) and hydrogenated MDI, and the like; And blocked polyisocyanate compounds formed by partially or completely blocking the functional groups of the polyisocyanate compounds.

(D) content of component

(1) binder resin and curing agent

The amount of the curing agent is preferably 5-200 parts by weight in solid relative to 100 parts by weight of the binder resin. If the amount of curing agent is less than 5 parts by weight, the final paint coating has a low alternating-bond density, resulting in insufficient hardness, weather resistance, corrosion resistance, heat resistance, water resistance, and the like. On the other hand, when the amount of the curing agent exceeds 200 parts by weight, the final paint coating becomes brittle. The preferred weight ratio of curing agent to binder resin is 20 / 100-100 / 100.

(2) pigment

The total content of pigments is preferably in the range of 10-60% by volume with respect to paint solids. More preferred total content of pigment is 15-45% by volume. Since some binder resins have some color, the total content of the pigment is adjusted according to the kind of binder resin used.

(a) colored pigments

Since the film thickness-determination paint has a relatively small base hiding power, the film thickness-determination paint should include a small amount of colored pigment. Generally, the total content of colored pigments is from 0.01 to 3% by volume with respect to paint solids. When the total content of the colored pigment is less than 0.01% by volume, the film thickness-determination paint has too little hiding power for the coating or undercoat layer, so that substantially no color difference between the paint coating and the coating, even at a thickness of about 100 μm, It is impossible to determine the thickness of the final paint coating. On the other hand, when the total content of the colored pigment exceeds 3% by volume, the film thickness-determination paint shows too large hiding power, which results in the color difference disappearing before achieving the target dry film thickness. When titanium dioxide is used alone or in combination with other coloring pigments as the coloring pigment, the total content of the coloring pigment is preferably in the range of 0.1-3% by volume. When sieving pigments and / or anti-corrosive pigments are added, the content of the colored pigment is preferably 0.3-7% by volume relative to 100% by volume of the total pigment.

(b) sieving pigments

When the extender pigment is added, the amount thereof is preferably 60% by volume or less with respect to the paint solids. When the amount of the extender pigment exceeds 60% by volume, the film thickness-determination paint loses the film-forming property. The lowest limit of the amount of the extender pigment is preferably 10% by volume.

(c) anti-corrosive pigments

The amount of anti-corrosive pigment is preferably 0-10% by volume relative to paint solids. If the amount of anti-corrosive pigment exceeds 10% by volume, no further improvement of the anti-corrosive effect is achieved, which results in a decrease in the amount of the extender pigment, which in turn increases the paint price.

(E) other ingredients

The film thickness-determination paints of the present invention may include organic solvents, additives and the like in addition to binder resins, curing agents and pigments.

(1) organic solvent

Organic solvents widely used in paints or mixtures thereof can also be used in the present invention. Preferred examples of the organic solvent include aromatic hydrocarbons such as aromatic toluene xylene, and the like; Aliphatic hydrocarbons such as normal hexane, heptane, and the like; Petroleum fractions having various boiling points and containing aliphatic hydrocarbons as the main component and aromatic hydrocarbons as the minor component; Esters such as butyl acetate, acetylene glycol diacetate, 2-ethoxyethyl acetate; Ketones such as methyl isobutyl ketone and the like; Alcohols such as butyl alcohol and the like; Ethers such as ethylene glycol monobutyl ether and the like.

(2) additive

The film thickness-determination paint may additionally include ultraviolet absorbers, surface modifiers, viscosity modifiers, anti-sagging agents, leveling agents, pigment dispersants, plasticizers, antifoaming agents, and the like.

[2] chrominance

The film thickness-determination paint must satisfy the following conditions: (a) the color difference between the film thickness-determination paint and the workpiece is 20 or more; (b) the color difference between the paint coating having a target dry film thickness and the paint coating having a dry film thickness of (target dry film thickness minus 50) μm or more; And (c) the color difference between the paint coating having a target dry film thickness and the paint coating having a dry film thickness of (target dry film thickness + 50) μm or more is 1 or less.

The measurement of the color difference is carried out according to a commonly known method using a color difference meter such as an SM color computer (SM-7CH available from Suga Test Instruments).

(1) color difference with the object

The color difference between the film thickness-determination paint and the workpiece to be coated should be at least 20. When the above conditions are satisfied, it can be observed visually that the color difference with the workpiece changes as the thickness of the film-determination paint approaches the prescribed paint thickness (wet). Preferably, the color difference with the workpiece is 35 or more.

(2) Color difference with paint coating of dry film thickness of (target dry film thickness-50) or less

Since the paint coating having a dry film thickness of (target dry film thickness-50) or less is a paint coating immediately before completion, if at least a small color difference does not occur between the formed paint coating and the paint coating of the target dry film thickness, It is impossible to determine whether the paint coating has reached the target thickness. Therefore, the color difference between the paint coating having a target dry film thickness and the paint coating having a dry film thickness of (target dry film thickness-50) m or less needs to be 2 or more. Said color difference becomes like this. Preferably it is three or more. However, if the color difference is much greater than 3 just before reaching the target dry film thickness, it becomes too large between adjacent paint coatings of different thickness, resulting in distinct spots on the painted surface. Therefore, the maximum limit of the color difference is preferably 10, more preferably 5.

(3) color difference with paint coating having a dry film thickness of (target dry film thickness + 50) or more;

(Dry film thickness of target + 50) Since the paint coating having a dry film thickness of 50 mu m or more is a paint coating having a film thickness exceeding the target thickness, the color difference with the paint coating of the target dry film thickness should be as small as possible. Therefore, the color difference between the paint coating having a target dry film thickness and the paint coating having a dry film thickness of (target dry film thickness + 50) μm or more needs to be 1 or less. Said color difference becomes like this. Preferably it is 0.5 or less.

[3] contrast ratios

In the case of adjusting the contrast ratio as well as the color difference, the accuracy of determining whether the thickness of the paint coating is close to the target dry film thickness is greatly improved. The contrast ratio, which is a variable that shows how much a layer conceals the undercoat, is preferably adjusted from 0.90 to 0.98 in a paint coating having a desired thickness of at least 100 μm, which controls the amount of colored pigment in the film thickness-determination paint. Is done. Preferred contrast ratios are from 0.92 to 0.95. If the contrast ratio is low, the paint coating becomes thicker than desired, resulting in an increase in the amount of film thickness-determination paint used. On the other hand, when the contrast ratio is high, the paint coating does not reach the target thickness and eventually does not achieve the desired performance. The contrast ratio of the dry paint coating can be measured according to the method defined in "Measurement of 7.2 contrast ratio" of JIS K 5400.

[4] brightness (L value)

When all colored pigments or other colored pigments other than titanium dioxide are excluded from the film thickness-determination paint, the brightness of the paint coating is preferably at least 60, more preferably at least 70 at the target dry film thickness. Using the film thickness-determination paint that satisfies the above conditions, the thickness of the paint coating is easily determined. The above brightness values can be obtained by adjusting the amount of the colored pigment comprising titanium dioxide and the amount of the extender pigment having a whiteness of 85 or more. Brightness can be measured by the method according to JIS Z 8105.

[5] coating methods

The method of casting the film thickness-determination paint of the present invention is a method of (1) coating the film thickness-determination paint directly on the surface of the workpiece, or (2) a shop primer and / or a film thickness-determination paint of different colors of the coating material. Coating the surface and then coating a film thickness-determination paint having a desired color thereon. In both cases, the coating of the film thickness-determination paint is carried out until the final paint coating reaches the target thickness (wet), the formed paint coating and the coating or undercoat (shop primer layer or film thickness-determination of different colors). The color difference between the paint coating). More specifically, in order to confirm whether the final paint coating has reached the target thickness, a change in color difference between the paint coating and the coating or undercoat is observed as eyes while the formed paint coating is wet. Since the change in color difference does not depend on the state of the paint coating (wet or dry), the observation in the wet state can be applied to the thickness of the dried paint coating without deformation.

(1) direct coating

The workpieces usable in the present invention include various steels such as untreated steel, blasted steel, acid-treated steel, zinc-plated steel, stainless steel; Nonferrous metal materials such as aluminum or alloys thereof; Copper or alloys thereof; Etc. The steel or non-ferrous metal material may have a weld line.

(2) coating of shop primer and / or film thickness-determination paints of different colors

Shop primers that may be used in the present invention include:

(a) a primary anti-corrosive paint composition comprising an initial condensate of tetraalkoxy silicate, an acidic solvent dispersible colloidal silica, and zinc powder (Japanese Patent Laid-Open No. 60-235871);

(b) an anti-corrosive paint composition comprising a zinc alloy powder having a melting point higher than zinc and a potential lower than iron (Japanese Patent Laid-Open No. 60-235872);

(c) a binder and spherical zinc powder, wherein the average particle diameter of the zinc powder by the light transmission sedimentation method is in the range of 5-10 m, and the zinc powder of 2 m or more is 95 to the total amount of the zinc powder. Volume% or more, and the amount of zinc powder is 20 to 60 parts by volume with respect to 100 parts by volume of the final dry paint coating, the paint coating having a primary anti-corrosion paint composition having a heat resistance of 600 ° C. or higher. -141075); or

(d) An anti-corrosive paint composition having a composition similar to that of the anti-corrosive paint composition described above.

Application of film thickness-determination paints with different colors provides a multilayer paint coating. In this case, the term "color difference with the coating" is referred to as "color difference between the top coat and the undercoat" under conditions of a color difference satisfying the film thickness-determination paint of the topcoat. More specifically, the top coat should satisfy the following conditions: (a) the color difference between the top coat and the undercoat is at least 20, (b) a paint coating having a target dry film thickness and (the target dry film). Thickness-50 color difference between paint coatings having a dry film thickness of 50 μm or less, and (c) a paint coating having a target dry film thickness and a dry film thickness of (target dry film thickness + 50) μm or more. Color difference between paint coatings having 1 or less.

(3) coating of top coat

A top coat can additionally be formed on the film thickness-determination paint coating formed according to the invention. Useful top coats include epoxy resin paints, chlorinated rubber paints, vinyl chloride resin paints, alkyd resin paints, silicone alkyd resin paints, acrylic resin paints, urethane resin paints, fluorine resin paints, polyester resin paints, epoxy acrylic resin paints, and the like. have.

The invention is illustrated in more detail by the following examples, which are not intended to limit the scope of the invention.

Synthesis Example 1-14

Film Thickness-Preparation of Judgment Paint

A film thickness-determination paint (Paint 1-14) having the composition shown in Table 1 below was prepared. All the main ingredients other than the colored pigments except titanium dioxide were mixed together in glass beads and stainless steel containers, dispersed to the desired particle size using an auto homo-mixer and then mixed with the colored pigment paste. The amount of titanium dioxide and other colored pigments was adjusted to provide the desired contrast ratio at the target dry film thickness of the specification. Curing agents were prepared by uniformly mixing all the components using an auto mono-mixer.

Ingredients ⁽¹⁾ (% by volume) Paint 1 Paint 2 Paint 3 Paint 4 Paint 5 Paint 6 Paint 7 color yellow yellow yellow blue blue blue yellow Sieving pigment Talc A ⁽²⁾ 12.61 - - 13.06 - - - Talc B ⁽²⁾ - 12.71 - - 13.10 - 12.61 Talc C ⁽²⁾ - - 12.82 - - 13.14 - % Based on SPC ⁽³⁾ 21.32 21.50 21.67 22.08 22.15 22.22 21.32 Anti-corrosive Pigment ⁽⁴⁾ 4.14 4.14 4.14 4.14 4.14 4.14 4.14 Additives ⁽⁵⁾ 1.29 1.29 1.29 1.29 1.29 1.29 1.29 Coloring pigment Titanium Dioxide ⁽⁶⁾ 0.18 0.15 0.13 0.21 0.18 0.15 0.18 Yellow Iron Oxide ⁽⁶⁾ 0.53 0.46 0.37 - - - 0.53 Phthalocyanine Blue ⁽⁶⁾ - - - 0.05 0.04 0.03 - Percentage of colored pigment Based on SPC ⁽⁷⁾ 1.20 1.03 0.85 0.44 0.37 0.30 1.20 Base On All Pigments ⁽⁸⁾ 3.79 3.25 2.67 1.39 1.17 0.96 3.79 Anti-Sagging Agents ⁽⁹⁾ 4.87 4.87 4.87 4.87 4.87 4.87 4.87 Synthetic Petroleum Resin ⁽¹⁰⁾ 11.43 11.43 11.43 11.43 11.43 11.43 11.43 Epoxy Polyols ⁽¹¹⁾ 24.36 24.36 24.36 24.36 24.36 24.36 24.36 Mixed solvent 22.60 22.60 22.60 22.60 22.60 22.60 22.60 Isocyanate 17.99 17.99 17.99 17.99 17.99 17.99 17.99 Sum 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Note: (1) Volume% of each component based on total paint capacity (2) Whiteness of talc: Talc A: 98, Talc B: 80 and Talc C: 67 (3) Volume percent of extender pigment based on paint solids (4 ) Zinc molybdate (5) Powder-based sorbents and reaction accelerators (6) Capacities based on the total capacity of the film thickness-determination paint (7) Capacities of the colored pigments based on paint solids (8) Total capacity of pigments and additives Volume% of colored pigment based on (9) Disparlon A603-20X, available from Kusumoto Chemicals (solid content: 20 wt%, listed in the table as volume% containing solvent) (10) Necires EPX, available from Nevcin Polymers BV -L (solid content: 99 wt%, listed in the table by volume% containing solvent, weight ratio of synthetic petroleum resin / epoxy polyol: 77/100 based on solids) (11) aromatic epoxy polyol (solids: 60 wt. % Contains solvents (12) Aromatic hydrocarbon solvents and ketone solvents (weight ratio 1/1) (13) Aromatic polyisocyanates (solid content: 75% by weight, listed in the table by volume% including solvent) Weight ratio of aromatic polyisocyanate / epoxy polyol: 90/100 based on solids)

Ingredients ⁽¹⁾ (% by volume) Paint 8 Paint 9 Paint 10 Paint 11 Paint 12 Paint 13 Paint 14 color yellow yellow yellow yellow blue blue blue Sieving pigment Talc A ⁽²⁾ - 12.02 - - 12.85 - - Talc B ⁽²⁾ - - 12.20 - - 12.92 - Talc C ⁽²⁾ 12.61 - - 12.40 - - 13.00 % Based on SPC ⁽³⁾ 21.32 20.32 20.63 20.96 21.73 21.84 21.98 Anti-corrosive Pigment ⁽⁴⁾ 4.14 4.14 4.14 4.14 4.14 4.14 4.14 Additives ⁽⁵⁾ 1.29 1.29 1.29 1.29 1.29 1.29 1.29 Coloring pigment Titanium Dioxide ⁽⁶⁾ 0.18 0.33 0.28 0.24 0.38 0.33 0.27 Yellow Iron Oxide ⁽⁶⁾ 0.53 0.97 0.84 0.68 - - - Phthalocyanine Blue ⁽⁶⁾ - - - - 0.09 0.07 0.05 Percentage of colored pigment Based on SPC ⁽⁷⁾ 1.20 2.20 1.89 1.56 0.79 0.68 0.54 Base On All Pigments ⁽⁸⁾ 3.79 6.93 5.97 4.91 2.51 2.13 1.71 Anti-Sagging Agents ⁽⁹⁾ 4.87 4.87 4.87 4.87 4.87 4.87 4.87 Synthetic Petroleum Resin ⁽¹⁰⁾ 11.43 11.43 11.43 11.43 11.43 11.43 11.43 Epoxy Polyols ⁽¹¹⁾ 24.36 24.36 24.36 24.36 24.36 24.36 24.36 Mixed solvent 22.60 22.60 22.60 22.60 22.60 22.60 22.60 Isocyanate 17.99 17.99 17.99 17.99 17.99 17.99 17.99 Sum 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Note: same as (1)-(13) of table 1a

Examples 1 and 2, Comparative Examples 1-6

A plurality of 900 mm × 900 mm matt steel plates were coated with shop primer (“Nippe-Ceramo Gray” available from Nippon Paint Marine Coatings) at a thickness of 15 μm and dried at room temperature for at least 24 hours to prepare test plates. Each of the film thickness-determination paints (Paint 1-8) described in Table 1 was airless-spired to each of the test plates with a 400 μm wet thickness and a 250 μm target dry film thickness and then left at room temperature for 24 hours. For the final paint coating of each film thickness-determination paint, the color difference with the shop primer was measured by an SM color computer (SM-7CH, available from Suga Test Instruments). In addition, each of the paints 1-8 was coated on a white contrast ratio test paper with a target dry film thickness of 250 μm using a coater, and then the contrast ratio and the brightness L were measured. In addition, a target dry film thickness of 250 [mu] m was made to have ten testers coat each film thickness-determination paint on the test plate and then the thickness of the film thickness-determination paint coating at 30 points on each coated test plate. Was measured to determine the thickness non-flatness (minimum thickness, maximum thickness, average thickness and standard deviation δ) of the film thickness-determination paint coating on each test plate. The results are shown in Table 2.

division Example 1 Comparative Example 1 Comparative Example 2 Shop primer hue grey grey grey Munsel value ⁽¹⁾ 7.1GY 5.9 / 0.5 7.1GY 5.9 / 0.5 7.1GY 5.9 / 0.5 Film thickness-judgment paint Kinds Paint 1 Paint 2 Paint 3 Talc Whiteness ⁽²⁾ A B C hue yellow yellow yellow Munsel value ⁽¹⁾ 2.1Y 7.4 / 8.3 2.9Y 6.3 / 6.2 4.2Y 4.7 / 3.8 Dry film thickness of the target (μm) 250 250 250 Characteristics of paint coating Color difference ⁽³⁾ 42 32 19 Contrast Ratio ⁽⁴⁾ 0.94 0.94 0.94 Brightness (L value) ⁽⁵⁾ 77.96 68.29 51.66 Thickness of paint coating (μm) ⁽⁶⁾ Thickness 236 205 174 Max thickness 273 256 264 Average thickness 254 236 214 Standard deviation δ 11.9 21.9 44.7 Note: (1) Munsel notation (hue, lightness / saturation) (2) Whiteness measured with a whiteness meter (filter; blue, purchased from Kett Electric Laboratory) for Powder C-100 according to JIS Z 8722 (1982) A: 98, B: 80, C: 67) (3) Color difference between shop primer and dried film thickness-determination paint coating measured by SM color computer (SM-7CH available from Suga Test Instruments) (4) Measurement in accordance with JIS K 5400 7.2 (5) Brightness in the dry thickness of the target measured according to JIS Z 8105 on a film thickness-determination paint coating containing only titanium dioxide as the color pigment used in the white contrast ratio tester. Non-flatness of the thickness of the paint coating relative to the thickness of (10 testers apply each film thickness-determination paint to the test plate, and then 30 of each coated test plate Thicknesses were measured at dog points)

division Example 2 Comparative Example 3 Comparative Example 4 Shop primer hue grey grey grey Munsel value ⁽¹⁾ 7.1GY 5.9 / 0.5 7.1GY 5.9 / 0.5 7.1GY 5.9 / 0.5 Film thickness-judgment paint Kinds Paint 4 Paint 5 Paint 6 Talc Whiteness ⁽²⁾ A B C hue blue blue blue Munsel value ⁽¹⁾ 7.9B 6.3 / 8.7 6.4B 5.7 / 6.4 4.7B 3.7 / 4.3 Dry film thickness of the target (μm) 250 250 250 Characteristics of paint coating Color difference ⁽³⁾ 37 29 17 Contrast Ratio ⁽⁴⁾ 0.94 0.94 0.94 Brightness (L value) ⁽⁵⁾ 78.54 68.81 52.14 Thickness of paint coating (μm) ⁽⁶⁾ Thickness 232 199 126 Max thickness 276 259 259 Average thickness 252 218 194 Standard deviation δ 13.1 24.5 42.5 Note: Same as (1)-(6) in Table 2a

division Comparative Example 5 Comparative Example 6 Shop primer hue grey grey Munsel value ⁽¹⁾ 7.1GY 5.9 / 0.5 7.1GY 5.9 / 0.5 Film thickness-judgment paint Kinds Paint 7 Paint 8 Talc Whiteness ⁽²⁾ B C hue yellow yellow Munsel value ⁽¹⁾ 2.8Y 6.1 / 5.9 3.9Y 4.9 / 3.7 Dry film thickness of the target (μm) 250 250 Characteristics of paint coating Color difference ⁽³⁾ 35 26 Contrast Ratio ⁽⁴⁾ 1.00 1.00 Brightness (L value) ⁽⁵⁾ 70.31 54.93 Thickness of paint coating (μm) ⁽⁶⁾ Thickness 120 91 Max thickness 235 209 Average thickness 183 145 Standard deviation δ 43.2 57.6 Note: Same as (1)-(6) in Table 2a

Each of the film thickness-determination paints (paints 1-8) was then air-sprayed onto each test plate with the wet thicknesses and target dry film thicknesses listed in Table 3, followed by a paint coating of the desired dry film thickness and The color difference ΔE of was measured and the appearance of each paint coating was visually observed in the wet (wet) state and in the dry state. The results are shown in Table 3 below.

division Example 1 Comparative Example 1 Comparative Example 2 Thickness ⁽¹⁾ ΔE ⁽²⁾ Observation ⁽³⁾ ΔE ⁽²⁾ Observation ⁽³⁾ ΔE ⁽²⁾ Observation ⁽³⁾ 240/150 μm 8.9 X 7.9 △ 4.0 △ 280/175 μm 4.7 △ 4.2 □ 2.2 □ 320/200 μm 2.4 □ 2.1 O 1.2 ◎ 360/225 μm 1.1 O 0.9 ◎ 0.6 ◎ 400/250 μm 0.0 ◎ 0.0 ◎ 0.0 ◎ 440/275 μm 0.2 ◎ 0.2 ◎ 0.2 ◎ 480/300 ㎛ 0.4 ◎ 0.5 ◎ 0.4 ◎ Note: (1) Weather thickness / dry film thickness measured with electromagnetic thickness meter (COATING THICKNESS TESTER LE-900 available from Kett Electric Laboratory) (2) SM color computer (SM- available from Suga Test Instruments) (3) Criteria for observation by eye in wet and dry coatings X: Shop primer layer is entirely visible through the film thickness-determination paint coating Δ: The shop primer layer is significantly visible through the film thickness-determination paint coating □: The shop primer layer is somewhat visible through the film thickness-determination paint coating O: The film is except that the shop primer layer exhibits limited visibility. Substantially concealed by thickness-determination paint coating ◎: Shop plastic Murray layer thickness - being completely concealed by the determination paint coating

division Example 2 Comparative Example 3 Comparative Example 4 Thickness ⁽¹⁾ ΔE ⁽²⁾ Observation ⁽³⁾ ΔE ⁽²⁾ Observation ⁽³⁾ ΔE ⁽²⁾ Observation ⁽³⁾ 240/150 μm 8.2 X 7.7 △ 3.9 □ 280/175 μm 4.5 △ 0.4 □ 0.2 O 320/200 μm 2.2 □ 2.0 O 1.0 ◎ 360/225 μm 1.0 O 0.8 ◎ 0.5 ◎ 400/250 μm 0.0 ◎ 0.0 ◎ 0.0 ◎ 440/275 μm 0.3 ◎ 0.2 ◎ 0.3 ◎ 480/300 ㎛ 0.5 ◎ 0.5 ◎ 0.6 ◎ Note: Same as (1)-(3) in Table 3a

division Comparative Example 5 Comparative Example 6 Thickness ⁽¹⁾ ΔE ⁽²⁾ Observation ⁽³⁾ ΔE ⁽²⁾ Observation ⁽³⁾ 240/150 μm 2.6 O 2.3 ◎ 280/175 μm 2.1 ◎ 1.1 ◎ 320/200 μm 1.1 ◎ 0.8 ◎ 360/225 μm 0.6 ◎ 0.2 ◎ 400/250 μm 0.0 ◎ 0.0 ◎ 440/275 μm 0.2 ◎ 0.2 ◎ 480/300 ㎛ 0.5 ◎ 0.4 ◎ Note: Same as (1)-(3) in Table 3a

As can be clearly seen in Tables 2 and 3 above, it was possible to visually determine whether the paint coating had reached the prescribed film thickness in Examples 1 and 2 in the wet (wet) state. In addition, Examples 1 and 2 provided an average paint coating film thickness that was substantially equal to the desired thickness in the dry state with a very small standard deviation value compared to Comparative Examples 1-6.

Example 3, Comparative Examples 7 and 8

A paint coating was formed using the same film thickness-determination paint (Paint 9-11) as in Example 1, except that the target dry film thickness was 125 μm. For each of the final paint coatings, the color difference ΔE with the paint coating of the target dry film thickness and the color difference with the shop primer coating were measured using the above-described color difference meter. Each film thickness-determination paint was coated on a white contrast ratio test paper with the target dry film thickness, and then the contrast ratio and brightness L were measured. As can be seen in Table 4, the results of this experiment are presented in comparison with Example 1 and Comparative Examples 1 and 2.

division Example 3 Example 1 Shop primer hue grey grey Munsel value ⁽¹⁾ 7.1GY 5.9 / 0.5 7.1GY 5.9 / 0.5 Film thickness-judgment paint Kinds Paint 9 Paint 1 Talc Whiteness ⁽²⁾ A A hue yellow yellow Munsel value ⁽¹⁾ 1.8Y 6.6 / 8.9 2.1Y 7.4 / 8.3 Dry film thickness of the target (μm) 125 250 Characteristics of paint coating Color difference ⁽³⁾ 44 42 ΔE ⁽⁴⁾ 0 2 Contrast Ratio ⁽⁵⁾ 0.94 0.94 Brightness (L Value) ⁽⁶⁾ 79.21 77.96 Note: (1) Munsel notation (hue, lightness / saturation) (2) Whiteness measured with a whiteness meter (filter; blue, purchased from Kett Electric Laboratory) for Powder C-100 according to JIS Z 8722 (1982) A: 98, B: 80, C: 67) (3) Color difference between shop primer and dried film thickness-determination paint coating measured by SM color computer (SM-7CH available from Suga Test Instruments) (4) Color difference with 125 μm target dry film thickness paint coating measured by SM color computer (SM-7CH available from Suga Test Instruments) (5) Measured according to JIS K 5400 7.2 (6) Used in white contrast ratio tester Brightness at the target dry thickness measured according to JIS Z 8105 on a film thickness-determination paint coating containing only titanium dioxide as the colored pigment which had been used.

division Comparative Example 7 Comparative Example 1 Shop primer hue grey grey Munsel value ⁽¹⁾ 7.1GY 5.9 / 0.5 7.1GY 5.9 / 0.5 Film thickness-judgment paint Kinds Paint 10 Paint 2 Talc Whiteness ⁽²⁾ B B hue yellow yellow Munsel value ⁽¹⁾ 2.5Y 6.4 / 7.2 2.9Y 6.3 / 6.2 Dry film thickness of the target (μm) 125 250 Characteristics of paint coating Color difference ⁽³⁾ 36 32 ΔE ⁽⁴⁾ 0 4 Contrast Ratio ⁽⁵⁾ 0.94 0.94 Brightness (L Value) ⁽⁶⁾ 69.97 68.29 Note: Same as (1)-(6) in Table 4a.

division Comparative Example 8 Comparative Example 2 Shop primer hue grey grey Munsel value ⁽¹⁾ 7.1GY 5.9 / 0.5 7.1GY 5.9 / 0.5 Film thickness-judgment paint Kinds Paint 11 Paint 3 Talc Whiteness ⁽²⁾ C C hue yellow yellow Munsel value ⁽¹⁾ 3.4Y 5.2 / 4.5 4.2Y 4.7 / 3.8 Dry film thickness of the target (μm) 125 250 Characteristics of paint coating Color difference ⁽³⁾ 25 19 ΔE ⁽⁴⁾ 0 6 Contrast Ratio ⁽⁵⁾ 0.94 0.94 Brightness (L Value) ⁽⁶⁾ 53.27 51.66 Note: Same as (1)-(6) in Table 4a.

As apparent from Table 4 above, in the case of showing a difference between the desired dry film thicknesses, the color difference was much smaller between Examples 3 and 1 than between Comparative Examples 7 and 1 and between Comparative Examples 8 and 2. .

Example 4, Comparative Examples 9 and 10

By mixing film thickness-determination paints of different colors, a top coat having a target dry film thickness of 125 μm and a top coat having a target dry film thickness of 250 μm were formed on each test plate by an airless spray method, and then at room temperature for 24 hours. Politics for a while. About each top coat film, the color difference, contrast ratio, and brightness (DELTA) t with the undercoat film were measured. In addition, ten testers were coated with a film thickness-determination paint to form the undercoat and top coat, and then the total thickness was measured at 30 points on each coated test plate, The non-flatness in the total thickness (minimum thickness, maximum thickness, average thickness and standard deviation δ) of the film and the top coat was measured. The results are shown in Table 5.

division Example 4 Comparative Example 9 Comparative Example 10 Undercoat ⁽¹⁾ Kinds Paint 12 Paint 13 Paint 14 Whiteness of talc A B C hue blue blue blue Muncell value ⁾ 7.6B 5.9 / 9.0 6.1B 6.3 / 7.2 4.3B 4.8 / 5.6 Dry film thickness of the target (μm) 125 125 125 Contrast Ratio 0.94 0.94 0.94 Topcoat ⁽²⁾ Kinds Paint 1 Paint 2 Paint 3 Whiteness of talc A B C hue yellow yellow yellow Muncell value 2.1Y 7.4 / 8.3 2.9Y 6.3 / 6.2 4.2Y 4.7 / 3.8 Dry film thickness of the target (μm) 250 250 250 Color difference ⁽³⁾ 63 52 38 Contrast Ratio 0.94 0.94 0.94 Brightness (L value) 77.96 68.29 51.66 Total Thickness (μm) ⁽⁴⁾ Dry film thickness of the target 375 375 375 Thickness 354 311 245 Max thickness 409 431 399 Average thickness 379 340 302 Standard deviation δ 11.8 45.7 74.3 (Note): (1) Film thickness-determination paint having a target dry film thickness of 125 μm (2) Film thickness-determination paint having a target dry film thickness of 250 μm (3) SM color computer (from Suga Test Instruments) (4) Total thickness of the top coat and the bottom coat measured with an electromagnetic thickness tester (COATING THICKNESS TESTER LE-900 available from Kett Electric Laboratory) measured with commercially available SM-7CH)

Subsequently, film thickness-determination paints of different colors were mixed, so that the undercoat having a target dry film thickness of 125 μm, wet thickness / dry film thickness of 240/150 μm, 280/175 μm, 320/200 μm, 360/225 Top coats having μm, 400/250 μm, 440/275 μm and 480/300 μm were formed on each test plate by the airless spray method and then left at room temperature for 24 hours. For each top coat, the color difference ΔE with the paint coating of the target dry film thickness was measured and the appearance was visually observed. The results are shown in Table 6.

division Example 4 Comparative Example 9 Comparative Example 10 Undercoat ⁽¹⁾ Kinds Paint 12 Paint 13 Paint 14 Whiteness of talc A B C hue blue blue blue Muncell value ⁾ 7.6B 5.9 / 9.0 6.1B 6.3 / 7.2 4.3B 4.8 / 5.6 Dry film thickness of the target (μm) 125 125 125 Contrast Ratio 0.94 0.94 0.94 Topcoat ⁽²⁾ Kinds Paint 1 Paint 2 Paint 3 Whiteness of talc A B C hue yellow yellow yellow Muncell value 2.1Y 7.4 / 8.3 2.9Y 6.3 / 6.2 4.2Y 4.7 / 3.8 Thickness ⁽³ ΔE Observation ⁽⁴⁾ ΔE Observation ⁽⁴⁾ ΔE Observation ⁽⁴⁾ 240/150 μm 7.2 X 7.2 △ 4.2 □ 280/175 μm 3.1 △ 4.1 □ 2.3 O 320/200 μm 2.0 □ 2.2 O 1.1 ◎ 360/225 μm 1.2 O 0.9 ◎ 0.5 ◎ 400/250 μm 0.0 ◎ 0.0 ◎ 0.0 ◎ 440/275 μm 0.3 ◎ 0.3 ◎ 0.2 ◎ 480/300 ㎛ 0.6 ◎ 0.5 ◎ 0.4 ◎ Note: (1) Film thickness-determination paint having a target dry film thickness of 125 μm (2) Film thickness-determination paint having a target dry film thickness of 150-300 μm (3) Paint Borer available from Erichsen Wet thickness / dry film thickness measured at 518 (4) Same as Table 3a above

As is clear from Tables 5 and 6 above, whether or not the paint coating reached the prescribed film thickness could be visually determined in the wet state as in Example 4. In addition, Example 4 provided an average paint coating film thickness that was substantially equal to the target dry film thickness in the dry state, and showed a very small standard deviation compared to Comparative Examples 9 and 10.

As described above, the method of the present invention makes it possible to easily and accurately form paint coatings with respective target dry film thicknesses even in a coating requiring a different paint coating film thickness for each region, and paint coating without color difference even at different paint coating film thicknesses. To form. Therefore, the method of the present invention, which is a method of forming a paint coating, is very useful for painting a ship or the like.

Claims (10)

A method of forming a paint coating having a target dry film thickness of 100 to 400 μm uniform on the surface of a workpiece, comprising a sieving pigment having 0.01 to 3% by volume of a colored pigment and a whiteness of 85 to 98 relative to the paint solids Using paint to make film thickness-determination paint, (a) the color difference between the film thickness-determination paint and the workpiece is 20 to 44, (b) the color difference between the paint coating having a dry film thickness of the target and the paint coating having a dry film thickness of less than (target dry film thickness-50) μm is 2 to 10, and (c) the color difference in the film thickness-determination paint such that the color difference between the paint coating having the target dry film thickness and the paint coating having the dry film thickness greater than (target dry film thickness + 50) m satisfies 0.4 to 1. A method of forming a paint coating, characterized in that to adjust the content of the colored pigment and the extender pigment. In a method of forming a paint coating having different target film thickness regions on the surface of a workpiece using two or more film thickness-determination paints, each target dry film thickness is 100 to 400 mu m, and each film thickness- The judgment paint comprises a extender pigment having 0.01 to 3% by volume of the colored pigment and a whiteness of 85 to 98 relative to the paint solids, (a) the color difference between the film thickness-determination paint and the workpiece is 20 to 63, (b) the color difference between the paint coating having a dry film thickness of the target and the paint coating having a dry film thickness of (target dry film thickness-50) m or less is 2 to 10, and (c) the color difference-determination paint in the film thickness-determination paint such that the color difference between the paint coating having the target dry film thickness and the paint coating having the dry film thickness of (target dry film thickness + 50) or more satisfies 0.6 to 1. A method of forming a paint coating, characterized by adjusting the content of the colored pigment and the extender pigment. 3. The method of claim 2, wherein the two or more film thickness-determination paints are adjusted so that the color difference between the film thickness-determination paints at the target dry film thickness is 0 to 3. . 4. The method of any one of claims 1 to 3, wherein the paint coating has a contrast of 0.90 to 0.98 at the target dry film thickness. The composition according to any one of claims 1 to 3, wherein the colored pigment in the film thickness-determination paint is excluded from the colored pigment other than titanium dioxide, or the composition is free of the colored pigment in the film thickness-determination paint. And the brightness (L value) of the paint coating formed by the film is 60 to 85 in the target dry film thickness. 4. The method according to any one of claims 1 to 3, wherein the colored pigment in the film thickness-determination paint is made of titanium dioxide and other colored pigments, and the total amount of the titanium dioxide and the other colored pigments is based on paint solids. Method for forming a paint coating, characterized in that 0.1 to 3% by volume. 4. A method according to any one of claims 1 to 3, wherein a shop primer or a film thickness-determination paint of different colors is coated on the workpiece as a undercoat. 4. The method of any one of claims 1 to 3, wherein the workpiece is a steel plate. The film thickness-determination paint according to any one of claims 1 to 3, wherein the film thickness-determination paint is at least one binder resin selected from the group consisting of epoxy resins and epoxy resins modified with petroleum resins, and amines, polyamides and At least one curing agent selected from the group consisting of polyisocyanate compounds. The method according to any one of claims 1 to 3, wherein the film thickness-determination paint coating is visually observed for the change in the color difference in a wet state, so that the film thickness-determination paint coating has reached a prescribed film thickness. A method of forming a paint coating, characterized in that determining whether or not.