JPH10204375A - Paint composition and coated metal plate using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating material which has good hardness and workability, has excellent slipperiness on a coating film surface, has no coating film defects, and can form a coating film having no problem in recoat adhesion. . SOLUTION: (A) Hydroxyl group-containing polyester resin 60
To 95 parts by weight and 5 to 40 parts by weight of at least one crosslinking agent selected from the group consisting of a melamine resin and a blocked polyisocyanate compound, and 100 parts by weight of the total solid content of the film-forming resin component. (C) 0.01 to 1 part by weight of a modified silicone oil and at least one selected from paraffin wax and fatty acid ester wax
A lubricant component consisting of 0.5 to 10 parts by weight of a seed wax, and a coating composition, and directly on a metal plate,
Alternatively, a coated metal plate on which a coating film of the coating composition is formed via a primer coating film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a coating composition which can form a coating film having good slipperiness and excellent scratch resistance, and which has good recoating properties and coating properties. The present invention relates to a painted metal plate obtained by painting.

[0002]

2. Description of the Related Art
As a topcoat paint for steel plate processing and building materials prepainted by continuous coating such as coil coating, a polyester resin is used as a base resin, and a methyl etherified methylolmelamine resin or a polyisocyanate compound is combined as a crosslinking agent. Resin-based paints are widely used. In recent years, these pre-coated steel sheets have been required to have not only hardness and workability but also slipperiness of the coating film surface from the viewpoint of preventing scratches during press working and improving the scratch resistance of the coating film.

[0003] As a method of improving the slipperiness of the coating film surface, a method of blending a lubricant into a coating material has conventionally been used.

[0004] However, when silicone oil is blended as a lubricant in a polyester resin paint for precoated steel sheets, the effect of lowering the coefficient of kinetic friction on the coating film surface and improving the slipperiness on the coating film surface is great. There was a problem that repelling was easily generated in the coating film. Also, when polyethylene wax is blended as a lubricant until the desired slip property is obtained on the coating film surface, the recoating film has poor adhesion when recoated on the coating film obtained from this coating, that is, recoat adhesion There was a problem that was bad.

The present invention relates to a polyester resin paint for a precoated steel sheet, which has good hardness and workability and can form a coating film having excellent slipperiness on the coating film surface. An object of the present invention is to obtain a paint which does not occur and has no problem in recoat adhesion.

As a result of intensive studies, the present inventors have achieved the above object by blending a silicone oil and a paraffin wax and / or a fatty acid ester wax in a specific amount as a lubricant in a polyester resin paint. It has been found that the present invention can be achieved, and the present invention has been completed.

[0007]

That is, the present invention provides:
(A) 60 to 95 parts by weight of a hydroxyl group-containing polyester resin and (B) at least one kind of crosslinking agent 5 to 40 selected from a melamine resin and a blocked polyisocyanate compound.
1 part by weight of the total solid content of the film-forming resin component
(C) modified silicone oil to 0.1 part by weight.
A coating composition characterized by containing a lubricant component consisting of 01 to 1 part by weight and 0.5 to 10 parts by weight of at least one kind of wax selected from paraffin wax and fatty acid ester wax. Things.

Further, the present invention is characterized in that a top-coat cured coating film of the above-mentioned coating composition is formed directly on a metal plate or via a polyester-based primer coating film or an epoxy-based primer coating film. And a coated metal plate.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the coating composition of the present invention will be described in more detail.

Polyester Resin (A) The polyester resin as the component (A) in the composition of the present invention is a polyester resin containing a hydroxyl group, and is an oil-free polyester resin, an oil-modified alkyd resin, or a modified product of these resins. Examples thereof include urethane-modified polyester resins, urethane-modified alkyd resins, and epoxy-modified polyester resins.

The above oil-free polyester resin comprises an esterified product of a polybasic acid component and a polyhydric alcohol component. Examples of the polybasic acid component include one or more selected from phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, succinic acid, fumaric acid, adipic acid, sebacic acid, maleic anhydride, and the like. Dibasic acids and lower alkyl esterified products of these acids are mainly used, and if necessary, monobasic acids such as benzoic acid, crotonic acid, pt-butylbenzoic acid, trimellitic anhydride, methylcyclohexenetricarboxylic acid And tribasic or higher polybasic acids such as pyromellitic anhydride. Examples of the polyhydric alcohol component include ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol,
Dihydric alcohols such as neopentyl glycol, 3-methylpentanediol, 1,4-hexanediol and 1,6-hexanediol are mainly used, and if necessary, glycerin, trimethylolethane, trimethylolpropane, pentane A trihydric or higher polyhydric alcohol such as erythritol can be used in combination. These polyhydric alcohols can be used alone or in combination of two or more. The esterification or transesterification of both components can be carried out by a method known per se. As the acid component, isophthalic acid, terephthalic acid,
And lower alkyl esters of these acids are particularly preferred.

The alkyd resin is obtained by reacting an oil fatty acid by a method known per se in addition to the acid component and the alcohol component of the above-mentioned oil-free polyester resin. Soybean oil fatty acids, linseed oil fatty acids, safflower oil fatty acids, tall oil fatty acids, dehydrated castor oil fatty acids, kiri oil fatty acids and the like can be mentioned. The oil length of the alkyd resin is preferably 30% or less, particularly preferably about 5 to 20%.

The urethane-modified polyester resin includes:
The oil-free polyester resin, or a low-molecular-weight oil-free polyester resin obtained by reacting an acid component and an alcohol component used in the production of the oil-free polyester resin, reacts with a polyisocyanate compound by a method known per se. Examples include: Further, the urethane-modified alkyd resin, the alkyd resin, or a low molecular weight alkyd resin obtained by reacting each component used in the production of the alkyd resin was reacted with a polyisocyanate compound by a method known per se. Things are included. Examples of polyisocyanate compounds that can be used when producing urethane-modified polyester resin and urethane-modified alkyd resin include hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate,
4,4'-methylenebis (cyclohexyl isocyanate), 2,4,6-triisocyanatotoluene, and the like. In general, as the urethane-modified resin, those having a modification degree in which the amount of the polyisocyanate compound forming the urethane-modified resin is 30% by weight or less based on the urethane-modified resin can be suitably used.

As the epoxy-modified polyester resin,
Using a polyester resin produced from each component used in the production of the above polyester resin, a reaction product of a carboxyl group of this resin and an epoxy group-containing resin, and a hydroxyl group in the polyester resin and a hydroxyl group in the epoxy resin are polyisocyanate. Reaction products such as addition, condensation, and grafting of a polyester resin and an epoxy resin, such as a product bonded via a compound, can be given.
In general, the degree of modification in such an epoxy-modified polyester resin is preferably such that the amount of the epoxy resin is 0.1 to 30% by weight based on the epoxy-modified polyester resin.

Among the polyester resins described above, an oil-free polyester resin is particularly preferable.

The polyester resin (A) preferably has a number average molecular weight of 1,000 to 35,000, more preferably 7,000, from the viewpoint of the balance between processability and hardness of the obtained coating film. To 30,000, and the glass transition temperature (Tg point) is preferably from -10 ° C to 80 ° C, more preferably from -5 ° C to 30 ° C.
The hydroxyl value is preferably from 3 to 160 mgKOH / g, more preferably from 5 to 30 mgKOH / g.
/ G of a polyester resin is preferred.

In the present invention, the glass transition temperature (Tg)
Is measured by differential thermal analysis (DTA), and the number average molecular weight is measured by gel permeation chromatography (GPC) using a standard polystyrene calibration curve.

Crosslinking Agent (B) The crosslinking agent as the component (B) is capable of reacting with the polyester resin (A) to cure the resin (A). Representative examples thereof include amino resins and block resins. Polyisocyanate compound.

Examples of the amino resin include methylolated amino resins obtained by reacting an aldehyde with an amino component such as melamine, urea, benzoguanamine, acetoguanamine, steloguanamine, spiroguanamine and dicyandiamide. Examples of the aldehyde used in the above reaction include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde and the like. Further, those obtained by etherifying the above methylolated amino resin with a suitable alcohol can also be used as the amino resin. Examples of the alcohol used for the etherification include methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, 2-ethylbutanol, 2-ethylhexanol and the like.

The blocked polyisocyanate compound is a compound obtained by blocking free isocyanate groups of a polyisocyanate compound with a blocking agent.

Examples of the polyisocyanate compound before blocking include aliphatic diisocyanates such as hexamethylene diisocyanate or trimethylhexamethylene diisocyanate; cycloaliphatic diisocyanates such as hydrogenated xylylene diisocyanate or isophorone diisocyanate; tolylene diisocyanate Or an organic diisocyanate itself such as an aromatic diisocyanate such as 4,4'-diphenylmethane diisocyanate, or an adduct of each of these organic diisocyanates with a polyhydric alcohol, a low molecular weight polyester resin or water; Cyclic polymers among diisocyanates, and isocyanate / biuret compounds are also included.

Examples of the blocking agent for blocking the isocyanate group include phenols such as phenol, cresol and xylenol; ε-caprolactam;
Lactams such as valerolactam, γ-butyrolactam, β-propiolactam; methanol, ethanol, n-
Or i-propyl alcohol, n-, i- or t-butyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether,
Alcohols such as benzyl alcohol; oximes such as formamidoxime, acetoaldoxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime; dimethyl malonate, diethyl malonate, ethyl acetoacetate, ethyl acetoacetate, methyl acetoacetate, acetylacetone A blocking agent such as an active methylene type can be suitably used.

The free isocyanate groups of the polyisocyanate compound can be easily blocked by mixing the polyisocyanate compound with the blocking agent.

The crosslinking agent (B) may be composed of one kind of crosslinking agent, or may be a mixture of two or more kinds of crosslinking agents.

In the composition of the present invention, the compounding amount of the hydroxyl group-containing resin (A) and the crosslinking agent (B) in 100 parts by weight of the resin component must be within the following range.

Hydroxyl-containing resin (A): 60 to 95 parts by weight, preferably 65 to 85 parts by weight, crosslinking agent (B)
: 5 to 40 parts by weight, preferably 15 to 35 parts by weight.

Lubricant (C) The lubricant (C) is a mixture of a modified silicone oil and at least one wax selected from paraffin wax and fatty acid ester wax.

The above modified silicone oil has a structure in which an organic group is introduced into a side chain and / or a terminal of the silicone oil. Depending on the type of the organic group, the modified silicone oil may be polyether-modified [-R- (C ₂ H). ₄ O) _a- (C ₃ H ₆ O) _b-
R ′], methylstyryl-modified [—CH ₂ —CH (C
H ₃₎ -Ph], alkyl-modified _{[-C a H 2a + 1]} , a higher fatty acid ester modified [-OCOR'], higher alkoxy-modified [-OR'], a fluorine atom-containing hydrocarbon group modified [-
CH ₂ CH ₂ CF ₃ ], amino-modified [—R—NH ₂ ],
Epoxy-modified [-R-Glycidil or -R-
(3,4-epoxycyclohexyl)], carboxyl-modified [-R-COOH], carbinol-modified [-RO]
H], methacryl-modified [-RC (CH ₃ ) = C
H _2], mercapto-modified [-R-SH], mention may be made of modified silicone oils, phenol-modified [-R-Ph-OH]. (In each of the above formulas, R represents a divalent organic group such as an alkylene group or a direct bond, R ′ represents a monovalent organic group such as an alkyl group, Ph represents a phenyl group or a phenylene group, and a and b represents an integer of 0 or more.) Of these, the polyether-modified silicone oil is
It is preferable from the viewpoint of the balance between slipperiness and recoatability.

Commercially available polyether-modified silicone oils include, for example, "DK Q8-8195", "Paintad 57", and "Paintad M" (all manufactured by Dow Corning Asia).

Typical examples of the paraffin wax include microcrystalline wax, and microcrystalline wax is suitable from the viewpoint of a balance between slipperiness and recoatability. Commercial products of microcrystalline wax include High Disper X-
3322, X-7909 (all manufactured by Gifu Shellac Manufacturing Co., Ltd.), Multi Wax 180M (Witoco Chmie
(Manufactured by Witco Chemie) and Topco S923 (manufactured by Toyo Petrolite).

Representative examples of the fatty acid ester wax include montan wax, lanolin wax, carnauba wax, beeswax, and spermaceti. Of these, montan wax and lanolin wax are preferred from the viewpoint of the balance between slipperiness and recoatability. A commercially available product of montan wax is CR-112.
(Manufactured by Koyo Chemical Co., Ltd.). Examples of the mixed wax of montan wax and microcrystalline wax include Microflat TK-17B (manufactured by Koyo Chemical Co., Ltd.). Commercial products of lanolin wax include Kurodaran SWL (manufactured by Croda Japan), Lanocerin (manufactured by Croda Japan),
Purified lanolin (manufactured by Chukyo Yushi Co., Ltd.) and the like can be mentioned.

In the composition of the present invention, the lubricant (C) comprises:
The modified silicone oil is used in an amount of 0.01 to 1 part by weight, preferably 0.02 part by weight, based on 100 parts by weight of the total solid content of the film-forming resin component comprising the polyester resin (A) and the crosslinking agent (B). 0.5 to 0.5 parts by weight, more preferably 0.03 to 0.3 parts by weight, and at least one wax selected from paraffin wax and fatty acid ester wax is 0.5 to 10 parts by weight, preferably 0.5 to 10 parts by weight. It is in the range of 1 to 5 parts by weight, more preferably 1.5 to 4 parts by weight.

When the amount of the modified silicone oil is 0.0
When the amount is less than 1 part by weight, the smoothness of the coating film surface becomes insufficient. On the other hand, when the amount is more than 1 part by weight, poor appearance of the coating film such as repelling is likely to occur on the coated surface. If the amount of at least one wax selected from the paraffin wax and the fatty acid ester wax is less than 0.5 part by weight, the coating film surface will not have sufficient slipperiness and the coating surface will have poor appearance such as repelling. Can not be suppressed. On the other hand, when the amount exceeds 10 parts by weight, the recoating adhesion of the obtained coated surface deteriorates.

In the composition of the present invention, when only the modified silicone oil is used as the lubricant (C), there is a problem that the appearance of the coating film such as repelling is easily generated on the coated surface, and the modified silicone oil is not used. However, when only paraffin wax and / or fatty acid ester wax is used, there is a problem that the recoat adhesion is deteriorated. By using both of the modified silicone oil and the waxes in a predetermined amount, the kinetic friction coefficient of the coating film surface can be reduced without causing poor coating film appearance such as repelling, and without deteriorating recoat adhesion. Reduction, that is, slipperiness can be improved.

The coating composition of the present invention can substantially consist of a polyester resin (A), a crosslinking agent (B), and a lubricant component (C), and if necessary, a curing catalyst; an organic solvent; Color pigments; glitter pigments such as aluminum powder, copper powder, nickel powder, mica powder coated with titanium oxide, mica powder coated with iron oxide, and glitter graphite; extender pigments such as talc, clay, silica, mica, and alumina; It may contain additives known per se, such as an antifoaming agent and a coating surface adjusting agent.

The curing catalyst is a polyester resin (A)
It is added as needed to promote the curing reaction between the crosslinking agent and the crosslinking agent (B), and can be appropriately selected and used according to the type of the crosslinking agent (B).

When the crosslinking agent (B) is a melamine resin, particularly a low-molecular-weight melamine resin of methyl etherification or a mixed etherification of methyl ether and butyl ether, a sulfonic acid compound or an amine of a sulfonic acid compound is used as a curing catalyst. A neutralized product is preferably used. Representative examples of the sulfonic acid compound include p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, and dinonylnaphthalenedisulfonic acid. The amine in the amine-neutralized sulfonic acid compound may be any of a primary amine, a secondary amine and a tertiary amine. Of these, paint stability,
From the viewpoint of the reaction promoting effect and the physical properties of the obtained coating film, p-
Amine neutralized products of toluenesulfonic acid and / or amine neutralized products of dodecylbenzenesulfonic acid are preferred.

When the crosslinking agent (B) is a blocked polyisocyanate compound, a curing catalyst which promotes the dissociation of the blocking agent of the blocked polyisocyanate compound as the crosslinking agent is suitable. For example, tin octylate, dibutyltin di (2-ethylhexanoate), dioctyltin di (2-ethylhexanoate), dibutyltin dilaurate, dibutyltin oxide, dioctyltin oxide, lead 2-ethylhexanoate, etc. Organic metal catalysts.

The organic solvent is added as necessary to improve the coatability of the composition of the present invention, and is used for the polyester resin (A), the crosslinking agent (B) and the lubricant component (C). Those which can dissolve or disperse each component can be used.Specifically, for example, hydrocarbon solvents such as toluene, xylene and high-boiling petroleum hydrocarbons, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and isophorone Ethyl acetate, butyl acetate, ester solvents such as ethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether acetate, alcohol solvents such as methanol, ethanol, butanol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol Etc. can be mentioned ether alcohol solvents such as mono-butyl ether,
These can be used alone or in combination of two or more.

The coloring pigments which can be used if necessary include those usually used in the field of coatings, for example, white pigments such as titanium white and zinc white; cyanine blue, cyanine green, azo-based and quinacridone-based pigments. Organic red pigments, organic yellow pigments such as benzimidazolone-based, isoindolinone-based, isoindoline-based, and quinophthalone-based; and inorganic coloring pigments such as titanium yellow, red iron black, carbon black, graphite and various calcined pigments.

The composition of the present invention can be applied to various objects to be coated such as a metal plate, plastics, a glass plate and the like. Use Examples of the metal plate used as an object to be coated include a cold-rolled steel plate, a zinc-plated steel plate, and an aluminum plate. Among them, a zinc-plated steel plate can be preferably used. Galvanized steel sheet, hot-dip galvanized steel sheet, electro-galvanized steel sheet, iron
Zinc alloy plated steel sheet, nickel-zinc alloy plated steel sheet,
Aluminum-zinc alloy plated steel sheets (for example, “galvalume”, “galvan” plated steel sheets) and the like, and zinc-treated zinc-coated steel sheets,
A chemical conversion-treated zinc-based plated steel sheet subjected to a chemical conversion treatment such as a chromate treatment can be given. In addition, a primer-coated metal plate provided with a primer coating film on a metal plate for the purpose of improving corrosion resistance and coating adhesion can also be used as an object to be coated. As the primer coating film, a coating film obtained from a polyester-based primer or an epoxy-based primer is preferable, and usually 2 to 10
It has a thickness of μm.

The coating of the coating composition of the present invention is not particularly limited. For example, roll coating, curtain flow coating, dip coating, spray coating and the like can be used. Usually has a dry film thickness of 5 to 5.
A range of 30 μm, especially 10 to 25 μm is suitable.
In addition, the curing conditions of the coating composition can be appropriately selected from among the baking conditions under which the coating is cured, but a long metal plate or a primer-coated metal plate that moves continuously is roll-coated or the like. In the case of coil coating that is applied continuously, the maximum material temperature (PMT) is usually 1
60-260 ° C. for 15-90 seconds, especially PMT1
Conditions within the range of 90 to 230 ° C and 20 to 60 seconds are suitable.

[0043]

The present invention will be described more specifically with reference to the following examples. Hereinafter, “parts” and “%” are based on weight.

Examples 1 to 8 and Comparative Examples 1 to 5 Coatings were prepared according to the composition shown in Table 1 below to obtain respective top coatings. On a 0.5 mm thick electrogalvanized steel sheet subjected to chromate treatment, KP Color 8620 primer (polyester primer for pre-coated steel sheet) manufactured by Kansai Paint Co., Ltd. is applied to a dry film thickness of about 4 μm. Then, it was baked for 30 seconds so that the maximum temperature of the material reached 220 ° C. to obtain a primer-coated steel sheet. On the primer-coated steel sheet, each of the overcoats obtained as described above is applied by a bar coater so as to have a dry film thickness of about 18 μm, and baked for 45 seconds so that the maximum temperature of the material reaches 220 ° C. A coated steel plate was obtained. Various tests were performed on the obtained coated steel sheet.

Table 3 shows the test results. In Table 1, the amounts of the polyester resin, melamine resin and blocked polyisocyanate compound are indicated by the weight of the solid content, and the amount of the curing catalyst is the sulfonic acid obtained by removing the respective neutralizing agents for the neutralized sulfonic acid compounds. And the weight was expressed in terms of the amount of the tin compound. In addition, at the time of making the top coats of Examples and Comparative Examples into a paint, titanium white as a white pigment was dispersed. Also,
A mixed solvent of cyclohexanone / swazol 1500 (manufactured by Cosmo Oil Co., Ltd., aromatic petroleum-based high-boiling solvent) = 60/40 (weight ratio) was used for adjusting the viscosity of the paint. At the time of painting, the viscosity of the paint was adjusted to about 90 seconds (25 ° C.) using a Ford cup # 4.

Example 9 The same procedure as in Example 1 was carried out except that the chromate-treated thickness 0.5
The procedure was performed in the same manner as in Example 1 except that the coating composition having the composition described in the column of Example 9 in Table 1 below was directly applied to this steel sheet without coating the primer on the electrogalvanized steel sheet having a thickness of 1 mm. Thus, a coated steel sheet having an overcoat film formed on the plated steel sheet without the intervention of a primer coating film was obtained. Various tests were performed on the obtained coated steel sheet. Table 3 shows the results.

[0047]

[Table 1]

(Note) in Table 1 has the following meanings, respectively.

The polyester resins indicated by (* 1) to (* 5) in Table 1 are all polyester resins manufactured by Toyobo Co., Ltd. and have the property values shown in Table 2 below.

[0050]

[Table 2]

(* 6) Cymel 303: manufactured by Mitsui Cytec Co., Ltd., having a low molecular weight methyl etherified melamine resin and a content of hexakis (methoxymethyl) melamine of 60% by weight or more. (* 7) Super Beckamine J-820-60: n-butyl etherified melamine resin manufactured by Dainippon Ink and Chemicals, Inc. (* 8) Desmodur BL-3175: a blocked polyisocyanate compound manufactured by Sumitomo Bayer Urethane Co., Ltd.

(* 9) Nailure 5225: A solution of an amine neutralized dodecylbenzenesulfonic acid, manufactured by King Industries, USA. (* 10) Formate TK-1: An organotin-based curing catalyst manufactured by Takeda Pharmaceutical Co., Ltd.

(* 11) DK Q8-8195: a polyether-modified silicone oil manufactured by Dow Corning Asia. (* 12) Paintad 57: Polyether-modified silicone oil, manufactured by Dow Corning Asia. (* 13) Kurodaran SWL: manufactured by Croda Japan
Lanolin wax. (* 14) High Disper X-3322: Microcrystalline wax manufactured by Gifu Shellac Works. (* 15) Microflat TK-17B: Koyo Chemical Co., Ltd.
A mixed wax of montan wax and microcrystalline wax.

[0054]

[Table 3]

The tests in Table 3 were performed according to the following test methods.

Test Method Appearance of Painted Surface: The appearance of the painted surface (30 cm × 30 cm) of the coated steel plate was visually observed and expressed based on a chipping standard.

：: No irregularities in the coated surface such as cissing, dents, and fogging were observed on the coated surface. Δ: Any of repelling, dents, and fogging were recognized on the coated surface. X: Remarkable cissing on the coated surface. Either dents or fogging are observed.

Pencil hardness: For coating film of painted steel sheet,
SK-5400 A pencil scratch test specified in 8.4.2 (1990) was performed, and an evaluation based on scratches was performed.

Impact resistance: JIS K-5400
According to 3.2 (1990) Dupont impact resistance test,
The impact of the painted surface of the coated steel plate was given under the conditions of a falling weight of 500 g, a tip diameter of the hammer of 1/2 inch, and a falling weight height of 50 cm. Then, a cellophane adhesive tape was adhered to the portion where the impact was applied, and the degree of peeling of the coating film when the tape was instantaneously peeled was evaluated according to the following criteria.

：: No peeling was observed on the coated surface. Δ: Slight peeling was observed on the coated surface. X: Significant peeling was observed on the coated surface.

Bending workability: In a room at 20 ° C. and 0 ° C., the coated steel sheet was bent 180 ° with the coated surface outside, and the T number at which no crack was generated in the bent portion was visually evaluated and indicated. . The T number is defined as 0T when 180 ° bending is performed without putting anything inside the bent portion, and 1 when bending a plate having the same thickness as the test plate.
T, 2 sheets are 2T,... (The same applies hereinafter), and 6 sheets are 6T.

Dynamic friction coefficient: Surface property measuring instrument "HEIDON"
Using -14D (manufactured by Shinto Kagaku Co., Ltd.), the dynamic friction coefficient of the coating film surface of the coated steel plate was measured at 20 ° C. under the condition of a load of 1 kg of the ball indenter.

Recoat adhesion: coated on a coated steel sheet with Magiclon No. 1000 White (a white paint of acrylic-melamine resin, manufactured by Kansai Paint Co., Ltd.) so that the dry film thickness becomes 20 μm. Bake at 160 ° C. for 20 minutes. JIS K-5400 8.5.2.
(1990) According to the crosscut-tape method, 11 parallel vertical and horizontal straight lines are drawn at 1 mm intervals so as to reach the substrate with a cutter knife, and 100 squares of 1 mm × 1 mm are drawn. Created. Cellophane adhesive tape on the surface
The tape was brought into close contact with each other, and the degree of peeling of the squares when the tape was rapidly peeled was observed and evaluated according to the following criteria.

：: No peeling of the coating film is observed at all. Δ: The number of remaining squares of the recoated coating film is 30 to 99. ×: Interlayer between the recoated coating film and the coating film surface of the coated steel sheet. The number of remaining squares in the peeled and recoated coating film was less than 30.

[0065]

The coating composition of the present invention is obtained by using a modified silicone oil in combination with at least one wax selected from paraffin wax and fatty acid ester wax in a predetermined amount to give a coating film appearance such as cissing. It was possible to reduce the dynamic friction coefficient of the coating film surface, that is, to improve the slipperiness, without causing defects and without deteriorating the recoat adhesion. ADVANTAGE OF THE INVENTION The coating composition of this invention has favorable hardness and workability, is excellent in the smoothness of a coating film surface, has no coating defect, and can form a coating film with no problem in recoat adhesion.

Accordingly, the coated steel sheet on which the coating film of the coating composition of the present invention is formed can be suitably used as a pre-coated steel sheet for processing objects and building materials.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09D 161: 20)

Claims (4)

[Claims] (A) a hydroxyl group-containing polyester resin 60
-95 parts by weight and (B) 5-40 parts by weight of at least one crosslinking agent selected from a melamine resin and a blocked polyisocyanate compound;
A lubricant component comprising (C) 0.01 to 1 part by weight of a modified silicone oil and 0.5 to 10 parts by weight of at least one kind of wax selected from paraffin wax and fatty acid ester wax with respect to 0 part by weight. And a coating composition comprising: 2. The polyester resin (A) has a number average molecular weight of 1,000 to 35,000 and a glass transition temperature of −10 ° C.
The coating composition according to claim 1, which is a polyester resin having a hydroxyl value of 3 to 160 mgKOH / g at -80 ° C. 3. The lubricant component (C), wherein the silicone oil is a polyether-modified silicone oil, and the wax is at least one wax selected from microcrystalline wax, montan wax and lanolin wax. The coating composition according to any one of the preceding claims. 4. A cured top coat of the coating composition according to claim 1, which is formed directly on the metal plate or through a polyester primer coat or an epoxy primer coat. And painted metal plate.