JP2700048B2 - Manufacturing method of pre-primed galvanized steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a pre-primed galvanized steel sheet which is capable of forming a coating film having good coating workability and excellent adhesion, workability, corrosion resistance, top coat adhesion and the like. More particularly, the present invention relates to a method for producing a pre-primed galvanized steel sheet suitable for use as a fire door.

[0002]

2. Description of the Related Art Conventionally, a coated metal product such as a fire door is assembled into a product shape by cutting, bending, welding or the like a galvanized steel plate as a substrate, and then subjected to a pretreatment such as a degreasing process. Then, the paint was applied by spraying or the like, dried naturally, and finished.

[0003]

However, according to the conventional method as described above, the coating work environment is degraded due to the occurrence of paint mist and the like, and the continuous coating is difficult. There was a problem that the sex was poor. Further, in the conventional method as described above, since calcium lead rust preventive paint specified in JIS K 5629 is used as a paint, a drying time of several tens minutes or more is required. It requires a large space to be left until it dries, and if it gets wet before it dries, it tends to cause problems such as peeling off of the paint film. There are problems such as severe restrictions on the handling of paints because they fall under the category.

[0004] The present invention overcomes the above-mentioned problems of the conventional coating method for fire doors and the like, has good coating workability, and the obtained coating film is a JIS equivalent product satisfying the provisions of JIS K 5629. It is another object of the present invention to provide a method for producing a pre-primed galvanized steel sheet capable of forming a coating film having excellent adhesion, workability, corrosion resistance and the like.

[0005]

The present inventors have conducted various studies to achieve such an object. As a result, the present inventors have applied a coating means such as a roll coater to the surface of a galvanized steel sheet as a substrate before forming. By applying a specific paint in a continuous coating-baking line, and baking for a short time, the coating workability is good, a large space for drying is unnecessary, and troubles when wet with rain are also eliminated, In addition, the inventors have found that a coating film excellent in adhesion, workability, corrosion resistance, and the like, which is JIS equivalent, can be obtained, thereby completing the present invention.

That is, in the method for producing a pre-primed galvanized steel sheet of the present invention, (A) the number average molecular weight (hereinafter referred to as “Mn”) of 2,500 to 25,000
0, hydroxyl value 5 to 70, glass transition temperature (hereinafter “Tg”)
100 parts by weight of a polyester resin at 5 to 80 ° C,
Epoxy resin 5-2 having an epoxy equivalent of 180 to 1,000
A binder component comprising 0 parts by weight and 5 to 30 parts by weight of a melamine resin, and (B) a pigment component, wherein the weight ratio of the binder component to the pigment component is A: B = 1: 0.8. ~ 1:
A solvent-based paint in which 3.5% of the pigment component is occupied by 20 to 40% by weight of calcium lead oxide on the surface of the galvanized steel sheet by a continuous coating-baking line, and baking. I do.

Hereinafter, the present invention will be described in detail: A zinc-plated steel sheet used as a substrate for a fire door and the like used in the present invention may be a zinc phosphate-based treatment which has conventionally been generally performed.
Typical examples include a hot-dip galvanized steel sheet, a galvannealed steel sheet, a Zn-Al-based hot-dip galvanized steel sheet, and an electro-galvanized steel sheet that have been subjected to a surface treatment such as a coating type chromate treatment.

The coating material used in the present invention comprises, as essential components, a film-forming component comprising a binder component (A) comprising a polyester resin, an epoxy resin and a melamine resin and a pigment component (B), and an organic solvent. If necessary, various additives such as a pigment dispersant, an antisettling agent, an antifoaming agent, a leveling agent, a curing catalyst, and components such as a modified resin are additionally blended.

The polyester resin constituting the binder component (A) is produced by condensation polymerization of a polybasic acid and a polyhydric alcohol by a conventional method. In the production, benzoic acid or the like is used as a terminal blocking agent. May be used to adjust the molecular weight. Examples of the polybasic acid include aromatic polybasic acids such as phthalic acid, terephthalic acid, isophthalic acid, and trimellitic acid; aliphatic polybasic acids such as oxalic acid, malonic acid, succinic acid, adipic acid, and sebacic acid; Typical examples thereof include pentanedicarboxylic acid, hexahydrophthalic acid, hexahydrotrimellitic acid and the like and acid anhydrides thereof. Further, as the polyhydric alcohol, ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol, butylene glycol,
Hexanediol, pentanediol, hexanediol, trimethylolethane, trimethylolpropane,
Glycerin, pentaerythritol, sorbitol and the like are typical examples.

The polyester resin used in the present invention has an Mn of 2,500 to 25,000, preferably 3,000 to 10,000 obtained by appropriately combining and reacting these polybasic acids and polyhydric alcohols. A hydroxyl value of 5 to 70,
The resin is preferably 20 to 65; Tg is 5 to 80C, preferably 10 to 30C. If Mn is larger than the above range, it is difficult to dissolve in an organic solvent, the smoothness is poor, and the coating film hardness is reduced. Conversely, if the Mn is small, workability such as cutting and bending is unfavorably deteriorated. On the other hand, if the hydroxyl value is larger than the above range, the workability such as cutting and bending decreases, and if it is smaller, the hardness of the coating film decreases, which is not preferable. Also Tg
If it is higher than the above range, workability such as cutting and bending decreases, while if it is smaller, the adhesiveness, hardness, etc. decrease, which is not preferable. The acid value of the polyester resin used in the present invention is not particularly limited, but is generally 0 to 10,
Preferably it is 2-9.

The epoxy resin constituting the binder component (A) is blended in order to improve the adhesion of the coating film, and has an epoxy equivalent of 180 to 1,000, preferably 30.
A range of 0 to 900 is suitable. When the epoxy equivalent is larger than the above range, the compatibility with the polyester resin is deteriorated, and when the epoxy equivalent is smaller, the hardness of the coating film is decreased, which is not preferable. As the epoxy resin, it is possible to use bisphenol A epoxy resin, bisphenol F epoxy resin, phenol novolak type epoxy resin, orthocresol novolak type epoxy resin and other commonly used epoxy resins.

The melamine resin constituting the binder component (A) is a resin obtained by etherifying a product obtained by condensing melamine and formaldehyde with alcohols such as methanol, ethanol and butanol.

The binder component (A) is composed of the above-described polyester resin, epoxy resin and melamine resin. The compounding ratio is 5 to 20 parts by weight of epoxy resin, 100 parts by weight of polyester resin, and 5 parts by weight of melamine resin. 5
Suitably, it is 30 parts by weight. If the amount of the epoxy resin is more than the above range, the processability is reduced, and if the amount is too small, the adhesion is deteriorated, which is not preferable. On the other hand, if the amount of the melamine resin is more than the above range, the strength of the coating film is reduced.

The pigment component (B) is used for improving the corrosion resistance and for forming a coating film equivalent to JIS, such as calcium lead oxide, other coloring pigments such as titanium oxide, iron oxide and phthalocyanine blue, and talc. , Calcium carbonate, barium sulfate, kaolin and the like, but in the present invention, it is necessary that the calcium plumbate accounts for 20 to 40% by weight of the pigment component (B). If the calcium plumbate is less than the above range, the corrosion resistance is reduced, and if it is too large, the effect is not improved,
It is not preferable because the cost increases. In the present invention, it is particularly desirable that talc accounts for 2 to 20% by weight of the pigment component (B) in order to improve scratch resistance and adhesion to the top coat.

Examples of the organic solvent include aromatic hydrocarbons such as toluene and xylene, alcohols such as butanol, propanol, ethylene glycol monoethyl ether and ethylene glycol monobutyl ether; esters such as butyl acetate, methoxyethyl acetate and ethoxyethyl acetate. Kinds: Various solvents commonly used for coating materials such as methyl ethyl ketone, methyl isobutyl ketone, and isophorone can be used.

The paint used in the present invention comprises the components described above, and comprises a binder component (A) and a pigment component (B).
A: B = 1: 0.8 to 1: 3.5, preferably 1: 1.5 to 1: 3.2. When the pigment component (B) is more than the above range, various physical and chemical properties of the obtained coating film are deteriorated. On the contrary, when the pigment component (B) is less, the adhesion to the overcoating material and the scratch resistance are deteriorated. . The organic solvent is suitably blended so that the viscosity of the coating material is 40 to 200 seconds (Ford Cup No. 4 / room temperature) according to the coating workability.

The coating material used in the present invention is suitably prepared by kneading and dispersing such constituents so that the degree of pigment dispersion is 50 μm or less by a grind gauge A method.

Next, a method for producing the pre-primed galvanized steel sheet of the present invention will be described. The above-mentioned paint is applied to a sheet-shaped or coil-shaped galvanized steel sheet by a continuous coating-baking line adopted in a usual method of manufacturing a pre-primed steel sheet, and baked. That is, the above-mentioned paint is dried by a continuous coating means such as a reverse type or natural type roll coater or a flow coater to a dry film thickness of about 15 to
50 μm, preferably 20 to 40 μm, is applied once or divided into a plurality of times, and the maximum sheet temperature (hereinafter referred to as “PM
(T) is baked at a temperature of about 180 to 250 ° C. for a short time of 30 to 120 seconds to form a cured coating film and produce a pre-primed steel sheet. Line speed is 10-10
About 0 m / min is appropriate.

The pre-primed galvanized steel sheet manufactured in this manner is assembled into a product shape such as a door shape by forming such as cutting, bending, welding, etc., and then, if necessary, a phthalic acid resin paint or the like. Apply top coat and finish.

The pre-primed galvanized steel sheet of the present invention is suitable for fire doors as described above, but can also be applied to various other metal products such as shutters, cabinets and home appliances.

[0021]

The present invention will be described in more detail with reference to the following examples. In the examples, “parts” and “%” are shown on a weight basis. Examples 1 to 4 and Comparative Examples 1 to 4 Polyester resin solutions having the characteristic values shown in Table 1 [solid content: 50%; 1: 1 mixed solvent of cyclohexanone and Solvesso 150 (trade name of Shell Co.)], epoxy resin Solution [Epicoat 1001 × 70 (trade name, manufactured by Yuka Shell Epoxy Co.); solid content 70%; epoxy equivalent about 470; xylol solvent]; melamine resin solution [Cymel 370]
(Trade name, manufactured by Mitsui Cyanamid Co.); solid content: 88%; 1: 1 mixed solvent of isobutanol and isopropanol]
And the pigment were kneaded and dispersed in the amounts shown in Table 1 and then a solvent [solvent 100 (trade name, manufactured by Shell Co., Ltd.), a mixed solvent of propylene glycol monomethyl ether acetate and cyclohexanone, 2: 1: 1) was added, and the pigment was added. Paints having a degree of dispersion of 40 μm by a grind gauge A method were prepared, and paints A, B, C, D, E, F, G and H were obtained.

The coatings A, B, C, D, E, F, G or H are applied to a galvannealed steel sheet (sheet thickness 1.6 mm) subjected to a chromate conversion treatment by a coil coating line to a dry film thickness of 15 μm. Reverse roll painting to become PMT2
It was baked and dried in a hot air drying oven for 60 seconds so as to reach 00 ° C. Next, the same coating material was reverse-roll coated so as to have a dry film thickness of 20 μm, and baked and dried in a hot air drying oven at a PMT of 230 ° C. for 90 seconds to produce a pre-primed galvanized steel sheet.

The coated plates obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were tested for workability, pencil hardness, adhesion, corrosion resistance and topcoat adhesion. The evaluation of each test was as follows: Workability: The coated plate was bent to R1 mm within 90 °, a tape test was performed, and the degree of peeling was observed: ○: no abnormality, Δ: coating film peeled slightly, × Pencil hardness: Tested in accordance with the method of JIS K 5400: ○: 2H or more, Δ: F to H, ×: HB or less Adhesiveness: Cut off at 1 mm intervals according to the method of JIS K 5400, Then use the Erichsen tester,
Extruded 5 mm and performed a tape test of the convex part to observe the degree of peeling: ○: no abnormality, Δ: little peeling of the coating, ×: peeling of many coatings Corrosion resistance: Conducted a salt water resistance test according to the method of JIS K 5629 , Blisters, rust, etc. were observed.

：: no abnormality, Δ: slight occurrence of blisters, rust, etc. ×: significant occurrence of blisters, rust, etc. Top coat adhesion: phthalic acid resin-based paint [“Hymel” (trade name of Dainippon Paint Co., Ltd.) ] Was applied to a dry film thickness of 25 μm and dried, and the degree of peeling was observed according to the cut tape method of JIS K 5400: ○: no abnormality, Δ: little peeling of the coating, ×: many peeling of the coating The results are also shown in Table 1. As is clear from Table 1, the coated plate obtained by the method of the present invention had excellent performance. On the other hand, in the case of Comparative Example 1 in which a polyester resin having a high hydroxyl value was used, workability and adhesion were poor.
In the case of Comparative Example 2 in which no epoxy resin was blended, the adhesion was poor. Conversely, Comparative Example 3 with an excess of epoxy resin
In the case of, workability was poor. In the case of Comparative Example 4 containing less calcium plumbate, the corrosion resistance was poor.

[0025]

[Table 1]

[0026]

According to the method for producing a pre-primed galvanized steel sheet of the present invention, continuous coating is possible, and therefore, the coating work time is short, the coating work environment is good, and when it is wet by rain, etc. And the resulting coating film is a JIS equivalent product satisfying the requirements of JIS K 5629, and has features such as excellent adhesion, workability, and corrosion resistance.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication B05D 7/14 B05D 7/14 A (72) Inventor Saburo Ito 5-25 Highland, Yokosuka City, Kanagawa Prefecture -3 (72) Inventor Susumu Ogawa 3-3359-37 Mihara, Otawara-shi, Tochigi Prefecture (72) Inventor Osamu 3-1172 Shimo-Nagata, Nishinasuno-cho, Nasu-gun, Tochigi Prefecture -4 A-105 (56) References JP-A Sho JP-A-5-138120 (JP, A) JP-A-5-301071 (JP, A) JP-A-5-138122 (JP, A) JP-A-58-68175 (JP, A) A)

Claims (2)

(57) [Claims] 1. As the solid content of the coating composition, (A) 100 parts by weight of a polyester resin having a number average molecular weight of 2,500 to 25,000, a hydroxyl value of 5 to 70, and a glass transition temperature of 5 to 80 ° C.
Epoxy resin 5-2 having an epoxy equivalent of 180 to 1,000
A binder component comprising 0 parts by weight and 5 to 30 parts by weight of a melamine resin, and (B) a pigment component, wherein the weight ratio of the binder component to the pigment component is A: B = 1: 0.8. ~ 1:
A method of applying a continuous paint-bake line to the surface of a galvanized steel sheet with a solvent-type paint in which 3.5% of the pigment component is occupied by 20 to 40% by weight of calcium lead oxide, and baking. To manufacture pre-primed galvanized steel sheet. 2. The pre-primed galvanized steel sheet for a fire door according to claim 1.
The manufacturing method as described.