JPH0912967A - Fluorine-based coating composition and coated stainless steel plate using the same - Google Patents

Abstract

(57) [Summary] [Structure] Epoxy resin is 5% of the total amount of resin components.
-20% by weight, crosslinking agent 1-10% by weight, acrylic resin 20-80% by weight and fluororesin 20-80% by weight
And a coated stainless steel sheet coated with the coating composition. When a crosslinking reaction catalyst and / or a silane coupling agent is added to the coating composition, the coating film adhesion is improved. [Effect] The coated stainless steel sheet of the present invention has excellent weather resistance and is extremely suitable for building materials. This steel plate can be used for one pass (undercoating + 1
It is possible to manufacture at low cost with a coat.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluororesin coating composition for forming a coating film having excellent weather resistance, and a coated stainless steel sheet obtained by coating a stainless steel sheet with the coating composition.

[0002]

2. Description of the Related Art Conventionally, a coated hot-dip galvanized steel sheet has been mainly used as a steel sheet for building materials used outdoors such as roofs and outer walls.

As a highly durable product based on hot-dip galvanizing and having excellent weather resistance, a 20-year warranty or 30
Steel sheets coated with fluorine resin, such as a yearly warranty, are already on the market. In addition, laminated steel plates using vinyl fluoride or vinylidene fluoride as a main resin are mainly applied to decorative walls for soundproof walls of expressways. Regarding such technology, Japanese Patent Publication No. 60-51423 or Kosho 60-5
No. 1424. Regarding the method of laminating a fluorine-based film, see JP-A-63-168.
No. 333, and Japanese Patent Application Laid-Open No. 5-186757, US Pat. No. 4,314,004 (US Patent) describes a technique relating to a coating composition for a fluororesin-coated metal plate.

On the other hand, in recent years, the demand for maintenance-free properties has increased with the rise in personnel costs, and the use of coated stainless steel sheets for outdoor building materials is gradually increasing. A resin-based resin having excellent weather resistance is used as a coating film-constituting resin.

However, when manufacturing such a coated stainless steel sheet, the zinc phosphate base treatment cannot be applied, and the chromate base treatment (roll coat pretreatment) must be performed by the roll coating method. Therefore, in order to manufacture a coated stainless steel plate in a coating line equipped with a normal two roll coater, a two-pass process (primer coat, primer coat and top coat) is required, and an increase in manufacturing cost cannot be avoided.

[0006]

The present invention has been made in view of such a situation, and an object thereof is to provide a fluororesin coating composition capable of forming a coating film having excellent weather resistance (hereinafter, referred to as "Fluorine-based coating composition"), and coated stainless steel sheet coated with this coating composition, which has excellent durability and is inexpensive (specifically, coating of fluorine-based resin coating 1 coat type) Stainless steel plate).

[0007]

The gist of the present invention lies in the following fluorine-containing coating compositions and the following coated stainless steel sheets.

The epoxy resin is 5 to 20% by weight, the crosslinking agent is 1 to 10% by weight, the acrylic resin is 20 to 80% by weight, and the fluororesin is 20 to 8 with respect to the total amount of the resin components.
A fluorine-based coating composition characterized by being contained in an amount of 0% by weight.

The total amount of the resin component of the crosslinking reaction catalyst is 10
0.05 to 5 parts by weight based on 0 parts by weight is contained, and the above-mentioned fluorine-based coating composition is characterized.

The fluorine-containing coating composition as described above or above, wherein the silane coupling agent is contained in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the total amount of the resin components.

A coated stainless steel sheet, characterized in that the coating composition according to any one of the above or any one of (1) to (4) above is applied onto an undertreated stainless steel sheet.

The above-mentioned resin component means here an epoxy resin, a crosslinking agent, an acrylic resin and a fluororesin,
Cross-linking reaction catalyst and silane coupling agent are not included. Further, the coating composition refers to a film constituent component excluding a solvent (thinner) used when the composition is applied to an object to be coated, that is, a solid content in the coating composition.

[0013]

The function and effect of the present invention will be described in detail below.

The above-mentioned inventions are a fluorine-based coating composition capable of forming a coating film having excellent durability on a stainless steel plate. As a thinner used for coating the coating composition, a general-purpose general thinner can be used as described later.

The coating composition of 5 contains an epoxy resin in an amount of 5 to 2
0% by weight, 1-10% by weight of crosslinking agent, 2% of acrylic resin
It is a fluorine-based coating composition containing 0 to 80% by weight and 20 to 80% by weight of a fluororesin (each is a weight percentage with respect to the total amount of resin components). The coating composition (1) further comprises a crosslinking reaction catalyst, and the coating composition (1) further comprises a silane coupling agent in these or other coating compositions.

Epoxy resin is a resin which is effective for securing the adhesion between the undercoating layer and the coating film applied to the stainless steel sheet before coating, which will be described later. The epoxy resin is hardened by using the crosslinking agent described below together. By doing so, primary adhesion (adhesion immediately after adhesion) and secondary adhesion (water resistance adhesion) are improved. If the content of the epoxy resin is less than 5% by weight, good adhesion cannot be obtained, and if it is added in excess of 20% by weight,
The workability of the coating film is impaired.

Examples of the epoxy resin include epoxy compounds composed of bisphenols such as bisphenol A, bisphenol F and bisphenol AD and epihalohydrin or β-methylepihalohydrin, or copolymers thereof. Further, monocarboxylic acid or dicarboxylic acid modified products, mono-, di- or polyalcohol modified products, mono- or diamine-modified products, mono-, di- or polyphenol-modified products of these epoxy compounds can also be used as the epoxy resin.

Examples of the crosslinking agent (curing agent) include polyisocyanate resin and amino resin. Only one of these crosslinking agents may be used, or a mixture of two or more may be used.

The cross-linking agent is used within the range of 1 to 10% by weight based on 5 to 20% by weight of the epoxy resin. If the amount is less than 1% by weight, the crosslinking reaction does not easily occur, and sufficient adhesion between the undercoat layer and the coating film cannot be obtained. If the amount exceeds 10% by weight, the processability of the coating film, which is considered to be due to self-condensation of the crosslinking agent, occurs. .

As the above polyisocyanate resin,
Aromatic diisocyanates such as xylylene diisocyanate, tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate, Further, polyisocyanate compounds such as multimers of these diisocyanates, or adducts with polyhydric alcohols,
And reacting these polyisocyanate compounds with blocking agents (for example, phenol-based, lactam-based, alcohol-based, active methylene-based, mercaptan-based, imine-based, amine-based, imidazole-based, oxime-based, or sulfite-based blocking agents) And a blocked polyisocyanate resin in which the isocyanate group is blocked. When such a blocked isocyanate resin is used, a conventional one such as an organotin compound such as dibutyltin dilaurate can be used as the dissociation catalyst.

The above-mentioned amino resin is, for example, a condensate of formaldehyde or paraformaldehyde alkylated with an alcohol having 1 to 4 carbon atoms with urea, N, N'-ethyleneurea, dicyandiamide, aminotriazine or the like. Specifically, methoxylated methylol urea, methoxylated methylol-N,
Examples thereof include N′-ethylene urea, methoxylated methylol dicyandiamide, methoxylated methylol melamine, methoxylated methylol benzoguanamine, butoxylated methylol melamine, butoxylated methylol benzoguanamine.

In addition to the above-mentioned cross-linking agent, a catalyst or a silane coupling agent for promoting the reaction between the epoxy resin and the cross-linking agent may be added in order to further improve the adhesion of the coating film to the undercoat layer. It is valid. When a crosslinking reaction catalyst is added (the above-mentioned invention), its content is the total amount of resin components of 1
0.05 to 5 parts by weight with respect to 00 parts by weight. 0.0
If it is less than 5% by weight, the action of accelerating the reaction of the crosslinking agent is not sufficiently exhibited, and if it exceeds 5% by weight, the workability of the coating film is remarkably lowered due to the excessive crosslinking reaction.

When the silane coupling agent is added (the above invention), its content is 0.01 to 5 parts by weight based on 100 parts by weight of the total amount of the resin components.
If it is less than 0.01% by weight, the effect is not sufficiently exhibited, while if it exceeds 5% by weight, the effect is not seen and it is economically disadvantageous.

Examples of the crosslinking reaction catalyst include acid catalysts, titanium chelating agents and titanate coupling agents.

Among them, the acid catalyst includes phosphoric acid, butyl phosphate, paratoluenesulfonic acid, dinonylnaphthalenesulfonic acid, cyclohexylsulfamic acid and the like, and the titanium chelating agent includes titanium acetylacetate, tetranormal butyl titanate and the like. Can be used. Examples of titanate coupling agents include isopropyltriisostearoyl titanate, isopropyltridodecylbenzenesulfonyl titanate, isopropyl tris (dioctylbairophosphate) titanate, tetraisopropylbis (dioctylphosphite) titanate, tetraoctylbis (ditridecylphosphite). ) Titanate, tetra (2,2-diallyloxymethyl-1-butyl) bis (di-tridecyl) phosphite titanate, bis (dioctylpyrophosphate) oxyacetate titanate, bis (dioctylpyrophosphate) ethylene titanate, isopropyltrioctanoyl Titanate, isopropyl dimethacryl isostearoyl titanate, isopropyl isostearoyl diacryl Taneto, isopropyl tri (dioctyl phosphate) titanate, isopropyl tricumyl phenylalanine titanate, isopropyl tri (N- aminoethyl - aminoethyl) titanate, dicumyl phenyloxy acetate titanate, diisostearoyl ethylene titanate.

On the other hand, as the silane coupling agent, vinyltrichlorosilane, vinyltriethoxysilane, γ
-Chloropropyltrimethoxysilane, γ-chloropropylmethyldichlorosilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropylmethyldiethoxysilane, γ-aminopropyltriethoxysilane, N
-(Β-aminoethyl) -γ-aminopropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane , Γ-glycidoxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, vinyltris (β-methoxy-ethoxy) silane, β- (3,4-epoxycyclohexyl)- Examples thereof include ethyltrimethoxysilane.

The fluororesin is a resin necessary for imparting excellent weather resistance to the coating film, and its content is 20 to 80% by weight. If it is less than 20% by weight, the weather resistance is insufficient,
If the content is more than 80% by weight, the amount of other resins is too small and the adhesion with the steel sheet cannot be maintained.

As the fluororesin, homopolymerization of fluorine-containing monomers such as tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, trifluoroethylene, vinyl fluoride, and vinylidene fluoride,
Alternatively, all the fluoropolymers obtained by copolymerization with other monomers are included. Examples thereof include polyvinyl fluoride and polyvinylidene fluoride. Specifically, as the thermoplastic fluororesin, for example, Kynar 5
00 (polyvinylidene fluoride manufactured by Atochem North America), and the thermosetting fluororesin includes, for example, Lumiflon 200 (manufactured by Asahi Glass).

When a thermosetting fluororesin is used,
As a cross-linking agent, one or more kinds of melamine resin, isocyanate resin and urea resin are contained in an amount of 5 to 30 parts by weight based on 100 parts by weight of the fluororesin.

The acrylic resin is compatible with the fluororesin, and as will be described later, in the coated stainless steel sheet of the present invention coated with the fluorine-based coating composition, the epoxy resin thickened on the lower layer side of the coating film and the upper layer side It is added in order to secure the adhesiveness with the fluororesin which is thickened. However, if the content is less than 20% by weight, the effect of adhering the fluororesin to the epoxy resin is small, while if it exceeds 80% by weight, the amount of other resins is small. If it is too small, the adhesion will be poor. Therefore,
The content of the acrylic resin is within the range of 20 to 80% by weight.

As the acrylic resin, those having a high compatibility with the fluororesin to be used are preferable. For example, when vinylidene fluoride resin is used as the fluororesin, a preferable example is a polymer of methyl methacrylate.

The other acrylic resin which can be used in combination with the fluororesin may be either thermoplastic or thermosetting. Examples of the thermoplastic acrylic resin include polymers of acrylic acid esters and methacrylic acid esters or copolymers thereof. In this case, examples of the ester group include methyl, ethyl, propyl, butyl, isobutyl, n-hexyl, lauryl, stearyl and the like. The copolymer may contain two or more kinds of these ester groups instead of one kind.

The thermosetting acrylic resin is a monomer having a functional group (carboxyl group, hydroxyl group, amino group, methylol group, epoxy group, etc.) that forms a crosslinked structure in the molecule, such as acrylic acid or methacrylic acid. , Acrylamide, methacrylamide, N-methylol acrylamide, allyl glycidyl ether, glycidyl methacrylate and two or more kinds of monomers selected from two groups of styrene, acrylic acid ester, and methacrylic acid ester. The resulting polymers include, but are not limited to.

Known pigments may be added to the fluorine-based coating composition of the present invention. Examples of such pigments include titanium white, silica, iron oxide, talc, clay, calcium carbonate and the like.

The amount of the pigment added is preferably about 20 to 200 parts by weight with respect to 100 parts by weight of the resin component, the crosslinking reaction catalyst and the silane coupling agent (total amount of the resin component etc.). If it is contained in excess of this range, the workability of the coating film will be significantly reduced.

The above invention is a coated stainless steel plate which is coated with the above-mentioned fluorine-based coating composition on a stainless steel plate which has been pretreated.

Since the zinc phosphate-based treatment used in the production of ordinary hot-dip galvanized steel sheets and the like cannot be applied to the stainless steel sheet as the base treatment, it is assumed that the coating type chromate treatment is applied by the roll coating method. By this pretreatment (rollcoat pretreatment), the secondary adhesiveness (waterproof adhesiveness) is significantly improved. The coating type chromate treatment is exemplified by a chromium-based treatment containing an extender pigment such as silica and phosphoric acid and having a chromium fixing rate of 30 to 70%, in which a resin such as an acrylic resin is partially added. May be.

The thinner used in coating the above fluorine-based coating composition is an epoxy resin, an acrylic resin,
Any general-purpose thinner can be used as long as it can dissolve the melamine resin. Specifically, it is a hydrocarbon solvent such as toluene and xylene, a ketone solvent such as methyl ethyl ketone, cyclohexanone, and isophorone.

The fluorine-based coating composition of the present invention is excellent in weather resistance, and therefore the coated stainless steel sheet of the present invention coated with this coating composition has good weather resistance.

In the above-mentioned coated stainless steel sheet of the present invention, the chromium-based rust preventive pigment required for enhancing the end face corrosion resistance in the coated steel sheet based on the conventional galvanized steel sheet or the laminated steel sheet. There is no need to apply a primer coating containing a large amount of.

Further, in the coated stainless steel sheet of the present invention, the epoxy resin is concentrated on the stainless steel sheet side (lower layer side) of the coating film, and the fluororesin is concentrated on the surface (upper layer side). Since it is performed with one coat, the manufacturing cost can be significantly reduced.

That is, as described above, the roll coat pretreatment must be carried out in the production of the coated stainless steel sheet, and in a usual coating line equipped with two roll coaters, the treatment is performed in two passes (primer treatment, primer,
Since a top coat is required and an increase in manufacturing cost is inevitable, the coated stainless steel sheet of the present invention can be coated with one coat, and therefore a normal coating line can be used for one pass (base coat). It can be manufactured by processing + 1 coat).

[0043]

[Example] As a base metal plate, an austenitic stainless steel plate (SUS304, plate thickness: 0.5 m) that has been subjected to a chromate-based surface treatment (chromium adhesion amount: 50 mg / m ² ).
m) is used, and each resin is collected on the surface so as to have the composition (solid content parts by weight) shown in Table 1, mixed and dispersed with a paint conditioner to apply the prepared coating material to obtain a coated stainless steel sheet. It was made.

The resin used is an epoxy resin (trade name:
Epicron 7050, manufactured by Dainippon Ink and Chemicals, Inc., amino resin as a cross-linking agent (Super Beckamine J-82)
0, manufactured by Dainippon Ink and Chemicals, Inc., acrylic resin (Hi-Pet HPS, manufactured by Mitsubishi Rayon Co., Ltd.) and fluororesin (Kainer 500 (Fuccavinylidene resin), manufactured by Amchem North America). P-toluenesulfonic acid manufactured by Wako Pure Chemical Industries, Ltd., and TSL8303 (vinyltrichlorosilane) manufactured by Toshiba Silicone was used as a coupling agent.

As the pigment, TYPAKE R820 (titanium oxide) manufactured by Ishihara Sangyo Co., Ltd. was used and adjusted to a white paint.

The coating material was applied by a bar coater so that the amount of adhesion was 30 g / m ² , dried in a conveyor type hot air oven for about 1 minute, and then cooled with water.

With respect to the coated stainless steel sheet produced as described above, after putting a grid of 1 mm width on the surface of the test piece,
Erichsen overhang of 5 mm was performed and the adhesiveness (primary adhesiveness) of the coating film was investigated. Further, the test piece was immersed in boiling water for 2 hours or 24 hours, and then the same overhanging was performed to examine the secondary adhesion. The evaluation criteria were good (indicated by a circle) when no peeling of the cross (100 pieces) was observed, and bad (indicated by a mark x) when even one piece of the cross was peeled.

The workability was evaluated by a T-bending test (23 ° C.). That is, a stainless steel plate having the same plate thickness as that of the test piece was sandwiched between the plates, and the result was indicated by the minimum number of plate sandwiches that did not cause cracks on the coated surface when it was bent. .

The pencil hardness is indicated by the hardness of the hardest pencil with no scratches in accordance with the method defined in JIS K5400, and H is considered good.

The weather resistance of the coating film was evaluated by measuring the gloss retention and the color change (ΔE) before and after the test with a sunshine weather meter. Gloss retention rate is 10
The "post-test gloss / initial gloss" after the 00-hour test, and 90% or more was considered good. Also, ΔE
Was 1.5 or less was considered good.

The test results are shown in Table 2. As is clear from these results, in the present invention examples, good results were obtained with respect to the primary adhesion of the coating film, the secondary adhesion after dipping in boiling water for 2 hours, workability, and weather resistance. The coating composition No. 5-14 and coating composition No. From the comparison with 3 and 4, it is understood that when the lubricating treatment film contains the crosslinking reaction catalyst and / or the silane coupling agent, the secondary adhesion after immersion in boiling water for 24 hours becomes good.

On the other hand, in Comparative Examples in which the epoxy resin and the cross-linking agent were not contained in the film, the adhesion was poor, and a coated stainless steel sheet that could be put to practical use could not be obtained.

[0053]

[Table 1]

[0054]

[Table 2]

[0055]

The coated stainless steel sheet of the present invention coated with the fluorine-based coating composition of the present invention has excellent coating film adhesion and excellent weather resistance and is extremely suitable for building materials.

Since this coated stainless steel sheet can be coated with one coat at the time of manufacture, one pass (undercoating + one coat) can be performed using a normal coating line.
Can be manufactured at low cost.

Claims (4)

[Claims] 1. An epoxy resin in an amount of 5 to 20% by weight, a crosslinking agent in an amount of 1 to 10% by weight, an acrylic resin in an amount of 20 to 80% by weight, and a fluororesin in an amount of 20 to 80% by weight, based on the total amount of resin components. A fluorine-based coating composition characterized by being contained within the range. 2. The fluorine-based coating composition according to claim 1, wherein the crosslinking reaction catalyst is contained in an amount of 0.05 to 5 parts by weight based on 100 parts by weight of the total amount of the resin components. 3. The fluorinated coating composition according to claim 1, wherein the silane coupling agent is contained in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the total amount of the resin components. . 4. A coated stainless steel sheet, characterized in that the coating with the coating composition according to any one of claims 1, 2 or 3 is applied on a stainless steel sheet subjected to a base treatment.