JPS6274970A - Coating composition for steel plate and plate coated therewith - Google Patents

Abstract

PURPOSE:To obtain the titled coated steel plate having a surface with elegant undulation and matt finish, by forming a thin film prepared from a film-forming organic binder, a specified fine organic powder, and a specified film-surface modifier on the surface of a steel plate on which a film has been formed. CONSTITUTION:A phosphate conversion coating or a chromate conversion coating is formed on the surface of a steel plate such as a cold-rolled steel plate and, if necessary, a primer is applied on this film, thus giving an objective steel plate. 100pts.wt. (solid) film-forming organic binder (A), such as a polyester resin, is mixed with 1-150pts.wt. fine organic powder (B), such as a powder of nylon 11, which has an average particle diameter of 15-80mum and will not completely melt and/or mix with component A at its film-forming temperature, and 0.5-70pts.wt. inorganic film-surface modifier (C), such as SiO2, which has an average particle diameter of 1/3 that of component B or smaller and an oil absorption of 80 or more, giving a coating composition. This composition is applied on the aforementioned steel plate and is heated at 180-270 deg.C for 15-60sec to cure.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel coating composition for steel plates and a precoated A-plate coated with the coating composition.

After forming a coating film, the pre-painted steel sheet is cut and used for various purposes.So-called pre-painted steel sheets began to be used as building materials in the 1950s, and in recent years have been further expanded to include home appliances and other uses. It's coming. In addition to this situation, various improvements have been made to paint compositions and coating methods due to consumers' preference for luxury products and diversification of preferences.
board is proposed. However, pre-coated steel sheets are painted at high speeds, and in the market where they are actually used, painted sheets with different lofts (LoL) are used mixed (so-called bonding), so the color tone and appearance between the painted lofts are different. The reality is that even if new pre-coated steel sheets are proposed, they are rarely put on the market.

As a coating composition for pre-coated steel sheets that satisfies the consumer's desire for luxury and preferences, for example, it is possible to apply a high-molecular-weight, inert, non-elastic,
A compound containing organic fine particles with high abrasion resistance has been proposed, and it has been shown that this compound gives the paint an uneven appearance and improves hardness, abrasion resistance, etc.
(See Publication No. 67).

However, when such a paint composition is used, it is not possible to obtain the matte, calm, and heavy gloss appearance that is desired by consumers in recent years. If you try to do so, the durability of the paint film will be significantly reduced.

Furthermore, when ordinary pre-coating is carried out using such a coating composition, the dispersion state of the organic fine powder in the coating film not only changes significantly due to subtle differences in conditions such as coating speed and coating film thickness, but also In some cases, uneven distribution occurs, and as a result, unevenness of the uneven parts of the coating film and non-uniformity of the depth of the waves occur, so that the pre-coated steel sheet has no commercial value at all.

Therefore, the present inventors have conducted intensive research to obtain a coating composition for pre-coated steel plates and a pre-coated steel plate that eliminates the above-mentioned drawbacks, and as a result, they have completed the present invention.

Thus, according to the present invention, (^) a film-forming organic binder, (B) organic fine particles with an average particle diameter of 15 to 80 μ that do not completely melt and/or miscible with the above (^) at the film-forming temperature, and (C) The average particle diameter is 1/3 or less of the above (B) and 80
A coating composition for a steel plate, characterized in that it contains an inorganic coating film surface conditioner having an oil absorption amount of the above amount as an essential component, and the coating composition is applied to the surface of a steel plate subjected to a chemical conversion coating treatment, if necessary, via a primer. A coated and hardened pre-coated steel sheet is provided.

As the film-forming organic binder (A) used in the present invention, any paint binder that is normally used for colored steel sheets can be used, but polyester resins, silicone polyester resins, and acrylic resins are particularly suitable. A paint binder containing a resin as a main component is suitable.

The organic fine particles (B) used in the present invention are (A
) Any material that is not completely melted and/or miscible with the component can be used in the present invention. Here, "not completely melted and/or miscible" means that the organic fine particles are neither completely melted nor mixed with component (A), but also partially melted and the surrounding surface of each fine particle is partially means covered with molten material. Specific examples of the organic fine particles include:
Nylon 6, nylon 11. Examples include polyamide resins such as nylon 12, polyimide resins, polyvinylidene fluoride resins, polyacrylonitrile resins, etc.
These resins can be used alone or in combination. Among these resins, nylon 11. Nylon 1
No. 2 is a preferred resin in the present invention because it can provide an elegant coating appearance.

The average particle diameter of the organic fine particles (B) described above is 15 to 80
μ, preferably 30 to 50 μ. Average particle size is 15μ
In the following cases, depending on the thickness of the coating film, the coating film becomes too smooth and an elegant uneven feel cannot be obtained. On the other hand, if it is 80μ or more, a uniform coating film cannot be obtained, especially in roll coating, which is unsuitable. However, organic fine particles with a size of 15 μm or less or 80 μm or more may be used as a small amount component for appearance adjustment.

In addition, in the present invention, an inorganic coating film surface conditioner (C
) is used as an essential ingredient. The coating film surface conditioner (C
) ensures uniform dispersion of the organic fine particles (B) in the applied coating film when pre-coating the obtained coating composition onto a copper plate using a normal coating method, even if the coating speed and coating film thickness change. At the same time, since this product itself has a matte effect, it is possible to easily form a paint film with a calm, deep glossy appearance without sacrificing durability. It has a preparation function.

The coating surface conditioner (C) needs to have an average particle diameter of ⅓ or less of the organic fine particles (B) and an oil absorption of 80 or more, preferably 90 to 350. The regulator (C) includes silicon dioxide-based, clay-based (aluminum silicate), talc-based (magnesium silicate), calcium carbonate-based, mica-based (AlzO+ .K2O.S
iO□) A regulator that satisfies the above average particle diameter and oil absorption is selected from among the regulators and the like. Among these, silicon dioxide is preferred. Other than silicon dioxide, the oil absorption is generally 80
However, by using these in combination with silicon dioxide, if the oil absorption of the mixture is 80 or more, it can be used as the preparation agent (C) in the present invention.

The average particle diameter of the coating film surface conditioner (C) is that of the organic fine particles (B).
), the coating surface conditioner causes roughness of the coating surface, which not only significantly damages the appearance of the coating film but also impairs the durability of the coating film. Further, if the oil absorption is less than 80, the surface conditioning function of the coating film is insufficient, and a large amount must be used to compensate for this insufficiency.

In this case, the durability of the coating film is impaired.

In the present invention, organic fine particles (B) and an inorganic surface conditioner (
The amount of C) is not particularly limited in order to obtain the desired appearance, but in order to particularly exhibit the effects of the present invention, the organic fine particles (B) should be added to the film-forming binder (A).
1 to 150 parts by weight, preferably 5 to 100 parts by weight, inorganic surface conditioner (C) per 100 parts by weight (solid content)
is 0.5 to 70 parts by weight, preferably 3 to 50 parts by weight. If the amount of organic fine particles (B) added is less than 1 part by weight, the appearance of the coating film will not be sufficiently modified by the organic fine particles (B), whereas if it exceeds 100 parts by weight, the organic fine particles ( The fixing effect of B) is not sufficient. Further, if the amount of the inorganic surface conditioner (C) added is less than 0.5 parts by weight, the coating film appearance adjustment function during coating will not be sufficient, while if it exceeds 70 parts by weight, the durability of the coating film will be impaired.

In the coating composition of the present invention, the above-mentioned (A) is used.

In addition to components (B) and (C), known materials conventionally used in coatings for steel plates, such as coloring pigments, additives, and solvents, can also be used.

Examples of steel plates to be coated with the coating composition of the present invention include cold-rolled steel plates, hot-dip galvanized steel plates, electrogalvanized steel plates, alloy-plated steel plates, aluminum plates, stainless steel plates, copper plates, copper-plated steel plates, and tin-plated steel plates. It can be applied to anything, and the coating form may be a long coil or a short sheet-shaped cut plate as long as curtain coating or roll coating is possible. Furthermore, when painting, if the surface of the material to be painted is not contaminated with oil or other contaminants, it may be painted as is, but in order to improve the adhesion and corrosion resistance between the paint film and the paint film, metal surface treatment using known techniques can be applied. It is desirable to apply These known surface treatment methods include phosphate-based surface treatment, chromate-based surface treatment, and coating treatment with a chromic acid-based coating agent. In addition, when it is necessary to improve the quality of the coating film, it is preferable to apply the primer coating after the metal surface treatment and then apply the coating composition of the present invention. Applicable primers include the known primers currently used for colored steel plates, and are selected appropriately depending on the type of steel material to be painted and the type of metal surface treatment, but in particular, epoxy-based and/or polyester-based primers and their modified Primers are preferred, and if processability is particularly required, polyester primers are preferred.

When coating with the coating composition of the present invention, there are no restrictions on the coating method, but curtain coating and roll coating are recommended from the economic efficiency of precoated steel sheet coating. In particular, in the case of a paint containing large organic fine particles, the curtain coating method is suitable. When applying a roll coating method, a top feed method using three rolls is recommended in order to achieve the best uniformity of the coated surface, but for practical purposes, a bottom feed method using ordinary two rolls may also be used.

The coating composition applied to the steel plate is then cured, but
The heat curing temperature (coating film forming temperature) is the heat curing temperature of the film forming binder, and is usually 180 to 270'C.
It takes 15 to 60 seconds.

The pre-coated steel sheet obtained by applying the coating composition of the present invention exhibits an elegant uneven surface and a calm, deep matte luster. Furthermore, the coating composition of the present invention can easily form a uniform coating film (a coating film without uneven distribution of Ia-containing fine particles) without being affected by changes in coating speed or coating film thickness during normal pre-coat coating. .

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Examples 1 to 9 and Comparative Examples 1 to 5 Coating compositions corresponding to the present invention and comparative examples were prepared by dispersing raw materials in the formulations shown in Table 1 below using a pebble mill.

In addition, the blending amount is shown in parts by weight.

The raw materials (1) to (15) used in Table 1 are as follows.

(1) Phthalkid 813-70A: Polyester resin manufactured by Hitachi Chemical Co., Ltd. (2) Almatex XV-KT-58”i3: Acrylic resin manufactured by Mitsui Toatsu Co., Ltd. (3) XR-6-0059: Silicone manufactured by Toshi Silicone Co., Ltd. Polyester resin (4) Super Beckamine J-820-607 Melamine resin manufactured by Dainippon Ink Co., Ltd. (5) Nylon 12: Manufactured by Atochem (France) Part name "Orgasol 2002" (6) Nylon 11: Atochem (France) Product name 1 Orgasol 1002″ (7) Nylon 6: Manufactured by Atochem (France) Part name “Rilsan” (8) Thyroid 308: Silicon dioxide manufactured by Fuji Davison (9) Micromica C-1000: The Engl
ish MicaCo, Mica (10) Talc MS: Nippon Talc Co., Ltd. Talc (11) Barium sulfate 400: Sakai Chemical Co., Ltd. (12) Titanium white: Teikoku Kako Co., Ltd. Product name JR701 (13) 700 Cyanine Blue XF: Toyo Ink Manufactured by (14) Tsurpets 100
: Petroleum-based aromatic solvent, manufactured by Maruzen Oil Co., Ltd. Galvanized steel sheet treated with zinc phosphate using the coating composition obtained in the above examples and comparative examples (manufactured by Nisshin Steel Co., Ltd., product name: “
Pentite B”, thickness 0.35mm) with KP color 84
10 Primer (epoxy resin primer, trade name, manufactured by Kansai Paint Co., Ltd.) was coated with 5 μm of paint and baked at 200°C for 30 seconds, using a roll coater to give a dry film thickness of 15 μm.
I did the painting. The baking drying was carried out at 230° C. for 45 seconds for polyester and acrylic coating compositions, and at 250° C. for 45 seconds for silicone polyester coating compositions. Comparative tests were conducted on the finished appearance of the thus obtained painted steel sheets, and the results are shown in Table 1.

*1 Height of uneven parts of painted surface (5c+nx5cm) (depth of waves)
The uniformity was visually observed.

◎ The depth of the waves is large and the wavelength (pitch) is short and constant ○ The depth of the waves is large and the wavelength is slightly irregular Δ The depth of the waves is large but the wavelength is extremely irregular × Unevenness No difference in height *2 Uniformity of unevenness The painted surface (30 cm x 30 cm) was observed with the naked eye and evaluated according to the following criteria.

◎ There is no bias in unevenness and the reflected light is uniform. ○ There are 1 to 4 places where the reflected light differs from the surroundings. △ Same as above with 5 to 10 locations × Same as above, with 10 or more locations - Smooth coating film with no unevenness

Claims (1)

[Scope of Claims] 1. (A) a film-forming organic binder; (B) organic fine particles having an average particle diameter of 15 to 80 μm that do not completely melt and/or miscible with the above (A) at the film-forming temperature; (C) The average particle diameter is 1/3 or less of the above (B) and 80
A coating composition for a steel plate, characterized in that it contains as an essential component an inorganic coating film surface conditioner having an oil absorption amount of the above amount. 2. The coating composition for steel plates according to claim 1, wherein the film-forming organic binder (A) is a polyester resin, a silicone polyester resin, or an acrylic resin. 3. Organic fine particles (B) are nylon 11 or nylon 12
The coating composition for steel plates according to claim 1. 4. The coating composition for steel plates according to claim 1, wherein the coating film surface conditioner (C) is silicon dioxide. 5. A phosphate-based chemical conversion film or a chromate-based chemical conversion film is formed on the surface of the steel sheet, and if necessary, a primer is applied to the chemical conversion film to form (A) a film-forming organic binder; (B) ) Organic fine particles with an average particle size of 15 to 80 μ that do not completely melt and/or miscible with the above (A) at the coating film forming temperature, and (C) an average particle size of 1/3 or less of the previous stage (B) and 80 μ
A pre-coated steel sheet coated with a thin film formed from a coating composition containing as an essential component an inorganic coating film surface conditioner having the above oil absorption amount.