JP4971261B2 - Corrosion protection for weathering steel - Google Patents

Description

  The present invention relates to a novel coating method for weathering steel, and more specifically, prevents flow rust (red rust) of weathering steel, enables various colorings in harmony with the environment, and provides long-term weather resistance with reduced processes. The present invention relates to an anticorrosion method for weathering steel that imparts rust resistance and rust resistance.

In general, carbon steel is often used for steel structures because of its low cost.
However, carbon steel generates red rust in a short period of time when moisture in the air (rainfall, moisture, etc.) and oxygen come into contact with the steel material surface. As a method for preventing the occurrence of red rust, a method of applying a paint is common. In this method, in order to reduce the repainting as much as possible, it is common to apply a paint having good durability. For example, inorganic zinc rich paint painting → epoxy resin paint mist coat → epoxy resin paint undercoat (twice) → epoxy resin paint intermediate coat → polyurethane resin paint topcoat is a typical steel coating system with a durability of 15 years or more. It is.

  This coating system has the advantage of maintaining the beauty and long-term rust prevention with colors that are in harmony with the environment, but on the other hand, this coating system is thick and requires six more coats, so it can be completed. Takes time and money. Therefore, recently, the use of weathering steel having good corrosion resistance for steel structures has been increasing.

The weather resistant steel is generally a low alloy steel to which elements such as P, Cu, Cr, and Ni are added. This steel material forms rust that protects against corrosion (hereinafter referred to as “protective rust”) in over a decade in the outdoors, so that it does not require rust-proofing work and becomes so-called maintenance-free. have.
This protective action against corrosion is to suppress rust with so-called rust, and this protective rust is mainly amorphous iron oxyhydroxide containing a large amount of crystal water, and this is a protective rust that is dense and has good adhesion. It is thought to contribute to formation. When it is time to repaint the existing steel structure, a lot of red rust is usually generated on the surface of the steel material. It cannot be protected from rust.

However, if the steel material of the weather resistant steel is used without any treatment, floating rust such as red rust and yellow rust and flow rust are generated during the period until protective rust is formed, which is not preferable in appearance. In addition to the problem of causing pollution of the surrounding environment.
In addition, in the conventional example, there is a surface treatment method by painting to obtain protective rust on the surface of weather resistant steel, but it still takes a long period of several years until protective rust is formed, during which the coating itself Causes problems such as whitening, blistering and peeling. In addition, the color tone is unified to rust to make the generated rust inconspicuous, and no consideration has been given to providing various colors in harmony with the environment, such as painting on carbon steel.

As a result of intensive studies to solve the above problems, the present inventors have applied a colored top coating containing a resin and a colorant having good weather resistance to the rust-proof steel surface for a long period of time. As a result, a corrosion-resistant method for weather-resistant steel with a reduced process, which can maintain the weather resistance for a long period of time and can be arbitrarily colored, has been completed.
That is, the present invention provides an adhesion-imparting coating containing (a) a moisture-curable resin, (b) a rust-preventing pigment, (c) a corrosive ion fixing agent, and (d) a coupling agent on the surface of the weathering steel. Film (A) is formed in a dry coating amount of 0.03 to 2.00 Kg / m ² , and then a coating film having a gloss retention of 85% or more after 300 hours of irradiation of the accelerated weather resistance test sunshine weather meter is formed. The present invention relates to an anticorrosion method for weathering steel, wherein the colored top coat film (B) to be formed is formed with a dry film thickness of 50 to 90 μm.

Hereinafter, the present invention will be described in detail.
The weather-resistant steel used in the present invention is said to be SPA material or SMA material, and is stipulated in JIS. When rust or the like is attached, the steel is subjected to blasting or pickling as pretreatment. preferable.
Next, the adhesion imparting coating film of the present invention will be described.
(A) About ingredients
The component (a) reacts and hardens with moisture on the steel surface and moisture in the air, strengthens the adhesion to the steel, and adds a rust preventive pigment, a corrosive ion fixing agent, a coupling agent, etc. described later. It is a binder for fixing. If it has such a function, various moisture curable resins conventionally used for paints can be used. Specifically, for example, a urethane resin (polyisocyanate polymer) system or an epoxy resin can be used. -Ketimine curing system, alkyl silicate resin system, alkyl alkoxysilane resin system and the like are representative examples. In particular, a moisture curable urethane resin excellent in water resistance is preferable.

  As the moisture curable urethane resin, for example, a urethane polymer having a free isocyanate group obtained by reacting a polyol and a polyisocyanate can be suitably used. As the polyol, for example, polyether polyol, polyolefin polyol and the like can be used. The polyether polyol includes ethylene glycol, propylene glycol, butanediol diethylene glycol, glycerin, hexanediol hexanetriol, trimethylolpropane, pentaerythritol and the like having 2 or more, preferably 2 to 6 carbon atoms having 2 to 8 carbon atoms. 2 to 4 in a molecule obtained by addition polymerization of an alkylene oxide such as ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, etc., preferably 2 to 8 carbon atoms in the presence of an alkali catalyst, etc. It is appropriate to use a polyalkylene polyol having a single hydroxyl group.

The polyolefin polyol is, for example, 2 to 4 in the molecular weight obtained by addition polymerization of an alkylene oxide such as ethylene oxide, propylene oxide, butylene oxide, or tetrahydrofuran to a diene compound such as butadiene or isoprene. It is suitable to use a polydiene polyol having a hydroxyl group.
As the polyisocyanate, a compound having 2 or more, preferably 2 to 3 isocyanate groups in one molecule is suitable. Specifically, for example, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,4-phenylmethane diphenyl diisocyanate, carbodiimide-modified diphenyl diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, metaxylene diisocyanate, 1,5 -Naphthalene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated toluylene diisocyanate, hydrogenated xylylene diisocyanate , isophorone diisocyanate and other isocyanate compounds, burette polyisocyanate compounds, polyisocyanate compounds having an isocyanate ring, adduct polyisocyanate compounds . These polyisocyanates can be used alone or as a mixture of two or more.

The method for producing the moisture curable urethane resin is not particularly limited, and various conventionally known methods can be used. Specifically, for example, it is produced by polymerizing polyol and excess polyisocyanate. Excess polyisocyanate means that the isocyanate equivalent is more than the hydroxyl equivalent of the polyol, and the equivalent relationship can be expressed as NCO / OH. In particular, in order to form a liquid, low-viscosity moisture-curing urethane resin, while considering the type of polyol, the number of functional groups, the molecular weight, and the like, NCO / OH is, for example, 2 to 10, preferably 5 to It is preferable to adjust to 10. The polymerization temperature and polymerization time are not particularly limited, but it is usually appropriate to react at 50 to 100 ° C. for 3 to 8 hours after mixing the polyol and isocyanate under a nitrogen stream in order to avoid the influence of moisture. It is.
An appropriate amount of an organometallic salt-based urethane polymerization catalyst, a stabilizer, a dehydrating agent, a polymerization regulator, or the like may be added at any time before the reaction, during the reaction, or after the reaction.

(B) About ingredients
The component (b) is a rust preventive pigment for preventing corrosion of the steel material. As the anti-corrosion pigment, those conventionally used for anti-corrosion paints can be used without particular limitation, but typically, for example, aluminum phosphate, condensed aluminum phosphate, zinc phosphate, aluminum phosphite (Phosphite) such as zinc phosphite and calcium phosphite, molybdate such as zinc molybdate, calcium molybdate, manganese molybdate, other stearic acid, tannic acid, citric acid, itaconic acid, boric acid, tungsten Examples thereof include metal salts of various acids such as acids and polyaniline.

(C) About ingredients
Component (c) collects corrosive ionic substances such as Cl ^- and SO ₄ ^2- that permeate into the coating and reacts chemically to form a water-insoluble double salt, immobilizing corrosive ions, It is a corrosive ion fixing agent for inactivation. Examples of such immobilizing agents typically include hydrocalumite and hydrotalcite.
Hydrocalumite has the formula
3CaO ・ Al ₂ O ₃・ CaX _{2 / m}・ nH ₂ O
(Wherein X represents a monovalent or divalent anion, m represents the valence of the anion, and n represents 20 or less), and is a hydrous crystalline powder having a layered structure. Representative examples of the anion (X) include NO ₃ ⁻ , NO ₂ ⁻ , OH ⁻ , CH ₃ COO ⁻ , CO ₃ ^{2− and the} like. These anions, and chlorine ions when contacted with sulfuric acid ion, etc., anion exchange, NO ₃ is a X ^- and NO ₂ ^- as well as free etc., immobilized corrosive ionic material in hydrocalumite, inert Turn into.

In addition, the liberated anion forms a passive film on the surface of the weathering steel material, and has the effect of further improving the corrosion resistance.
Hydrotalcite is a formula,
Mg _4.5 Al ₂ (OH) ₁₃ CO ₃・ nH ₂ O
(In the formula, n is 4 or less, preferably 3.5.)
A water-containing crystalline powder having a layered structure represented by These anions, and chlorine ions when contacted with sulfuric acid ion, etc., anion exchange, NO ₃ is a X ^- and NO ₂ ^- as well as free etc., immobilized corrosive ionic material in hydrotalcite, inert Turn into.

(D) Coupling agent The component (d) is for improving the adhesion to a steel material and for improving the adhesion to a colored top coating to be coated thereon. Specific examples of coupling agents include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, vinyltriethoxy. Silane coupling agents such as silane, γ-methacryloxytrimethoxysilane, γ-mercaptopropyltrimethoxysilane, isopropyltriisostearoyl titanate, tetraoctylbis (didodecyl) phosphite titanate, isopropyltrioctanoyl titanate, isopropyltridodecyl Typical examples include titanium coupling agents such as benzenesulfonyl titanate, other aluminum coupling agents, and zirconium coupling agents.

The adhesion-imparting coating film of the present invention is formed from an adhesion-imparting composition containing the components (a) to (d) described above as essential components. Adhesiveness-imparting composition contains various additives such as hydrocarbon solvents that do not contain active hydrogen, organic solvents for paints such as esters and ketones, antifoaming agents, dispersants, and dehydrating agents as necessary. Consists of blends.
In the adhesion-imparting composition, the blending ratio of each component is 100 parts by mass of the moisture curable resin (a), and the rust preventive pigment (b) is, for example, 1 to 95 parts by mass, Preferably, the corrosive ion immobilizing agent which is 10 to 50 parts by mass and component (c) is, for example, 1 to 95 parts by mass, preferably 10 to 50 parts by mass and the coupling agent which is component (d) is For example, 0.1 to 10 parts by mass, preferably 1 to 5 parts by mass, and the total of component (b) and component (c) is, for example, 5 to 100 parts by mass, preferably 15 to 70 parts by mass. Part.

The amount of the organic solvent used is suitably such that the solid content of the adhesion-imparting composition is, for example, 20 to 80% by mass, preferably 30 to 70% by mass. Moreover, various additives are mix | blended, for example in 0.1-10 mass% in solid content of an adhesive provision composition, Preferably, 1-5 mass% is suitable.
If the amount of the component (b) is less than the above range, sufficient rust-preventing power cannot be exhibited. Conversely, if the amount is too large, the amount of the component (a) is relatively small and the cohesive strength of the coating film is poor. It tends to be enough. Further, when the amount of the component (c) is less than the above range, the collection and immobilization of the corrosive ionic substance becomes insufficient. Conversely, when the amount is too large, the amount of the component (a) is relatively reduced, The strengthening of the coating film tends to be insufficient. Further, when the amount of the component (d) is less than the above range, the adhesion to the steel material surface and the adhesion with the colored top coating material to be coated thereon become insufficient, and conversely, even if it is too much, the above-mentioned effect is improved. Is not allowed and is economically disadvantageous.

In the present invention, the adhesion-imparting composition is applied to the surface of the weathering steel by means of, for example, a brush, a roller, or a spray, in an amount of coating (in terms of solid content) 0.03 to 2.00 Kg / m ² Preferably, about 0.05 to 1.50 Kg / m ^{2 is} applied and dried.
Drying may be natural drying or forced drying. The surface of the weather resistant steel may be blasted in advance. When a colored top coating is applied to the weather resistant steel surface on which an adhesion-imparting coating film has been formed, a coating film that is difficult to swell and peel for a long period of time is obtained, and therefore the weather resistant steel has excellent long-term corrosion resistance.

Next, the colored top coat will be described.
The colored top coating contains various additives such as a resin, a colorant, a rust preventive pigment, a silane coupling agent, a solvent, a dispersant, an ultraviolet absorber, and an antibacterial agent, which are blended as necessary. The form of the colored top coating may be solvent-based, water-based, or solvent-free.
It is necessary to use a resin having good weather resistance as a resin to be blended in the colored top coating. That is, the resin to be blended is a resin that forms a coating film having a gloss retention of 85% or more, preferably 90% or more after 300 hours of irradiation with an accelerated weather resistance test and sunshine weather meter. A gloss retention of less than 85% is not preferable because whitening, blistering, peeling, and the like occur in the colored top coat film.

Preferred examples of such a weather-resistant resin having a gloss retention rate include organic resins, organic-inorganic composite resins, and inorganic resins.
Specific examples of the organic resin include, for example, a chlorinated rubber resin, an acrylic resin, a polyester resin, a urethane resin, a fluororesin, and a combination of these resins with a curing agent, and more preferably a moisture curable urethane resin, It is a fluororesin.

Examples of the organic-inorganic composite resin include, for example, an organic resin having a hydrolyzable silyl group, a general formula,
R ¹ _n Si (OR ² ) _4-n
[Wherein, R ¹ is an organic group having 1 to 8 carbon atoms, R ² is an alkyl group having 1 to 5 carbon atoms, and n is 1 or 2. ] Containing the organosilane shown by these, or its partial hydrolyzate.
As an example of the organic resin which has a hydrolyzable silyl group used for organic inorganic composite resin, a fluororesin, an epoxy resin, an acrylic resin etc. are mentioned suitably, for example.

Examples of organosilanes that introduce hydrolyzable silyl groups into fluororesins, epoxy resins, acrylic resins, etc.
R ¹ _n Si (OR ² ) _4-n
[Wherein, R ¹ is an organic group having 1 to 8 carbon atoms, R ² is an alkyl group having 1 to 5 carbon atoms, and n is 1 or 2. ]
Preferable examples are organosilanes represented by:
In the above formula, examples of the organic group as R ¹ include an alkyl group, a cycloalkyl group, an aryl group, and a vinyl group.

Here, the alkyl group may be linear or branched. Examples of the alkyl group include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, s-butyl group, t-butyl group, pentyl group, hexyl group, Examples thereof include alkyl groups such as heptyl group and octyl group. Preferred alkyl groups are those having 1 to 4 carbon atoms.
Preferred examples of the cycloalkyl group include a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and the like.

Examples of the aryl group include a phenyl group.
Each of the functional groups may optionally have a substituent. Examples of such a substituent include a halogen atom (for example, a chlorine atom, a bromine atom, and a fluorine atom), a (meth) acryloyl group, a mercapto group, and an alicyclic group.
The alkyl group as R ² may be linear or branched. Examples of such an alkyl group include a methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, s-butyl group, t-butyl group, and pentyl group. And preferred alkyl groups are those having 1 to 2 carbon atoms.

  Specific examples of the organosilane represented by the above formula include, for example, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, i-propyltrimethoxysilane, i-propyltriethoxysilane, γ-chloropropyltrimethoxysilane, γ-chloropropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3,3,3-trifluoropropyltri Methoxysilane, 3,3,3-trifluoropropyltriethoxysilane, cyclohexyltrimethoxysilane,

γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethyldimethoxysilane, dimethyldi Examples include ethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, methylphenyldimethoxysilane, dimethyldipropoxysilane, and the like. Preferred are methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, and dimethyldimethoxysilane.

In the organic-inorganic composite resin used for the colored top coating composition of the present invention, a fluororesin having a hydrolyzable silyl group, an epoxy resin, and an acrylic resin are used.
R ¹ _n Si (OR ² ) _4-n
[Wherein, R ¹ is an organic group having 1 to 8 carbon atoms, R ² is an alkyl group having 1 to 5 carbon atoms, and n is 1 or 2. ]
Preferable examples include organosilanes represented by the above and / or partial hydrolysis condensates thereof.
Organosilanes may be used alone or in a mixture of two or more. The partially hydrolyzed condensate of organosilane has a polystyrene equivalent weight average molecular weight (Mn) of, for example, 300 to 5000, preferably 500 to 4200. By using such a partially hydrolyzed condensate, a coating film having good storage stability and good adhesion can be obtained.

Specific examples of such partially hydrolyzed condensates include commercially available SR2402 manufactured by Toray Dow Corning, DC3037, DC3074; KR-211 manufactured by Shin-Etsu Chemical Co., Ltd., KR-212, KR-213, KR-214, KR-216, KR-218; Toshiba Silicone TSR-145, TSR-160, TSR-165, YR-3187, etc. are mentioned.
The hydrolysis-condensation reaction in the organic-inorganic composite resin is carried out by stirring the mixture of the above components in the presence of a catalyst at 40 to 80 ° C., preferably 45 to 65 ° C., for example, for 2 to 10 hours. However, the reaction is not limited to this method.

  Examples of the reaction catalyst used in the hydrolysis condensation reaction include trialkoxyboranes such as trimethoxyborane and triethoxyborane; tri-n-butoxyethyl acetoacetate zirconium, di-n-butoxydi (ethylacetoacetate) zirconium. , Zirconium chelate compounds such as tetrakis (ethyl acetoacetate) zirconium, titanium chelate compounds such as diisopropoxy bis (acetyl acetate) titanium, diisopropoxy bis (ethyl acetoacetate) titanium, monoacetyl acetate bis (ethyl acetoacetate) aluminum And organometallic compounds such as aluminum chelate compounds such as diisopropoxyethyl acetoacetate aluminum.

The hydrolysis-condensation reaction product synthesizes a polyorganosiloxane resin solution having a mercapto group in a solution state depending on the alcohol content generated by the reaction or the alcohol content and an organic solvent described later. be able to.
As an inorganic resin used in the colored top coating composition of the present invention, a general formula,
R ¹ _n Si (OR ² ) _4-n
[Wherein, R ¹ is an organic group having 1 to 8 carbon atoms, R ² is an alkyl group having 1 to 5 carbon atoms, and n is 1 or 2. An alkyl silicate hydrolysis condensate represented by

Examples of the organic group as R ¹ in the general formula include an alkyl group, a cycloalkyl group, an aryl group, and a vinyl group.
Here, the alkyl group may be linear or branched. Examples of the alkyl group include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, s-butyl group, t-butyl group, pentyl group, hexyl group, Examples thereof include alkyl groups such as heptyl group and octyl group. Preferred alkyl groups are those having 1 to 4 carbon atoms.

Preferred examples of the cycloalkyl group include a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and the like.
Examples of the aryl group include a phenyl group.
Each of the functional groups may optionally have a substituent. Examples of such a substituent include a halogen atom (for example, a chlorine atom, a bromine atom, a fluorine atom, etc.), an amino group, a (meth) acryloyl group, a mercapto group, a glycidyl group, an alicyclic group, and the like. It is done.

R ² in the general formula is an alkyl group having 1 to 5 carbon atoms, for example, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, s-butyl group, t-butyl. Group, i-butyl group, n-pentyl group and the like.
N is 0 or 1.
Specific examples of such alkyl silicates include, for example, alkyl silicates where n is 0, such as tetramethyl silicate, tetraethyl silicate, tetra-n-propyl silicate, tetra-i-propyl silicate, tetra-n-butyl silicate and the like. Methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, i-propyltrimethoxysilane, i-propyltriethoxysilane, γ -Glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-mercaptopropi Rutrimethoxysilane,

n such as γ-mercaptopropyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, γ-aminopropyltrimethoxysilane, 3,4-epoxycyclohexylethyltrimethoxysilane, 3,4-epoxycyclohexylethyltriethoxysilane And alkyl silicates in the case where is 1. Further, these alkyl silicate partial hydrolysis condensates preferably have a condensation degree of, for example, 30 or less, preferably 10 or less, from the viewpoint of coating workability and the like.

  Specific examples of the curing catalyst used for promoting the hydrolysis of organosilane and curing with a siloxane bond include, for example, dibutyltin dilaurate, dibutyltin dimaleate, dioctyltin dilaurate, dioctyltin dimaleate, dioctyltin. Organotin compounds such as maleate and tin octylate; phosphoric acid, monomethyl phosphate, monoethyl phosphate, monobutyl phosphate, monooctyl phosphate, monodecyl phosphate, dimethyl phosphate, diethyl phosphate, dibutyl phosphate, dioctyl phosphate, didecyl phosphate, etc. Phosphoric acid or phosphoric acid ester; diisopropoxybis (acetylacetate) titanium, diisopropoxybis (ethylacetoacetate) titanium Which organic titanate compounds; organoaluminum compounds such as tris (ethylacetoacetate) aluminum, tris (acetylacetonato) aluminum; tetrabutylzirconate, tetrakis (acetylacetonato) zirconium, tetraisobutylzirconate, butoxytris (acetylacetonate) ) Organic zirconium compounds such as zirconium are typical examples.

Accelerated weathering test Sunshine weather meter is a sunshine carbon arc lamp type accelerating weathering tester that is correlated with actual outdoor exposure specified in JIS K5400, and gloss retention is specified in JIS K5400. The degree of remaining gloss calculated from the 60-degree specular gloss by the following formula.
Gloss retention rate = (gloss after 300 hours of sunshine weather meter irradiation) × 100 / initial gloss (%)
Moreover, as a rust preventive pigment mix | blended with a colored top coat, a pollution-free rust preventive pigment is used suitably. Examples of such pollution-free rust preventive pigments include aluminum phosphate, aluminum tripolyphosphate, zinc phosphate, zinc phosphite, potassium phosphite, calcium phosphite, aluminum phosphite, zinc calcium phosphate, phosphorus Examples thereof include rust preventive pigments such as zinc aluminum oxide, zinc molybdate, zinc phosphomolybdate, aluminum phosphomolybdate, calcium molybdate, and hydrocalumite. The rust preventive pigment may be used alone or as a mixture of two or more. However, chromium and lead are not preferable from the viewpoint of toxicity.

  Specific examples of coloring pigments to be used in the colored top coating include white pigments such as titanium dioxide and zinc oxide, black pigments such as carbon black and graphite, red pigments such as molybdate orange, permanent carmine, and quinacridone red. Typical examples include pigments of various colors usually used for paints, such as yellow pigments such as quinophthalene yellow and permanent yellow, and green and blue pigments such as phthalocyanine green and phthalocyanine blue. Further, extender pigments may be used in combination. Although a color pigment changes also with the kinds, 0.1-70 mass parts is added with respect to 100 mass parts of resin, Preferably, 0.8-50 mass parts is added suitably.

  Moreover, as a silane coupling agent mix | blended with a colored top coat, for example, γ-chloropropyltrimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris (β-methoxyethoxy) silane, γ- (methacryloxypropyl) trimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxy Silane, N-β- (aminoethyl) γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyldimethylsilane, γ-glycidoxyp Pills dimethylethoxysilane like can be mentioned as a typical example.

The silane coupling agent is blended in order to improve the adhesion between the colored top coating film and the adhesion-imparting coating film, and the blending amount is, for example, 0 to 20 with respect to 100 parts by mass of the resin. It is desirable to add 1 part by mass, preferably 1 to 5 parts by mass.
In addition, when a compounding quantity exceeds 20 mass parts, it exists in the tendency for coating-material stability to fall.
The colored top coating is suitably applied so as to have a dry film thickness of 50 to 90 μm, preferably 60 to 80 μm. If it is less than 50 μm, the concealability and weather resistance will be insufficient. On the other hand, when the thickness exceeds 90 μm, foaming and poor curing are likely to occur, and when applied to a vertical surface, problems such as paint dripping occur.
The colored top coating is applied on the adhesion-imparting coating film by means of, for example, brushing, spraying, or roller, so that the dry film thickness is 50 to 90 μm, preferably 55 to 80 μm, and is naturally dried or Force drying at a temperature of 100 ° C. or lower.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples.
In the examples, “parts” and “%” are based on mass.

Preparation of Adhesiveness-Providing Composition Components shown in Table 1 below were mixed and dispersed to prepare an adhesiveness-imparting composition and stored in a sealed container.

Note 1) Aromatic polyisocyanate prepolymer;
"Sumijour E21-1" (trade name, manufactured by Sumitomo Bayer Urethane Co., Ltd.)
Note 2) Aluminum phosphate anticorrosive pigment;
"K White # 94" (trade name, manufactured by Teika)
Note 3) In Examples 1 to 3 and Comparative Example 3, hydrotalcite; “DHT-4A” (trade name, manufactured by Kyowa Chemical Co., Ltd.)
In Examples 4 to 6, nitrite type hydrocalumite; “Solkat” (trade name, manufactured by Nippon Chemical Industry Co., Ltd.)
Note 4) “KBM403” (trade name, manufactured by Shin-Etsu Silicon) (γ-glycidoxypropyltrimethoxysilane)
Note 5) “Additive TI” (trade name, manufactured by Sumitomo Bayer Urethane Co., Ltd.)
Note 6) “BYK354” (trade name, manufactured by BYK Chemie)

(B) Synthesis of organic-inorganic composite resin
Synthesis example 1
A reactor equipped with a reflux condenser and a stirrer was charged with 190 g of a fluororesin (trade name Zeffle GK550, solid content 60%, manufactured by Daikin Industries, Ltd.). 05 g was added and stirred at 40 ° C. for 4 hours to synthesize a fluororesin (v) having a hydrolyzable silyl group having a solid content of 67%.

Synthesis example 2
To a reactor equipped with a reflux condenser and a stirrer, 55 parts of xylene and 40 parts of isobutanol were added, mixed, and then heated to 85 ° C. with stirring. Next, a mixed solution of 50 parts of isobutyl methacrylate, 35 parts of 2-ethylhexyl methacrylate, 15 parts of γ- (methacryloxypropyl) trimethoxysilane and 1.5 parts of azobisisovaleronitrile was dropped at 85 ° C. over 3 hours, Thereafter, the temperature was raised to 90 ° C. and maintained for 2 hours to complete the reaction. An acrylic resin (vi) having a hydrolyzable silyl group with a solid content of 50% was synthesized.

(C) Examples of inorganic resin synthesis
Synthesis example 3
The following silicone intermediate is added to a reactor equipped with a reflux condenser and a stirrer, and stirred at 60 ° C. for 3 hours to obtain an alkoxysilicate hydrolyzate (vii) (polystyrene-converted mass average molecular weight (Mn) 1500). It was.
Shinetsu Silicon KBM13 45.0 parts Shinetsu Silicon KBM103 25.0 parts Toshiba Dow Corning SH6018 25.0 parts

Synthesis example 4
The following silicone intermediate was added to a reactor equipped with a reflux condenser and a stirrer, and stirred at 60 ° C. for 3 hours to obtain an alkoxysilicate hydrolyzate (viii) (Mn1800).
KBM14 13.5 parts made by Shin-Etsu Silicon Co., Ltd. KBM103 11.5 parts made by Shin-Etsu Silicon Co. SR2402 75.0 parts made by Toshiba Dow Corning

Example 1
The adhesion imparting composition (i) shown in Table 1 is dried on the surface of weather resistant steel (SMA400) specified in JIS G3141 of 3 × 100 × 300 (mm) that has been subjected to alumina blast treatment with an average surface roughness of 30 μm. The coating amount is 0.1 kg / m ² and dried to form an adhesion-imparting coating film. On top of that, the following fluororesin overcoating is applied once so that the dry film thickness is 60 μm. After drying, the back and side surfaces were sealed with an epoxy resin paint and allowed to air dry for 7 days. The results of evaluating the weather resistance and corrosion resistance of the coated steel are shown in Table 2 below.

(Main ingredient)
Fluorine resin solution ^{Note 7)} 154.0 parts Aluminum tripolyphosphate 18.0 parts γ-glycidoxypropyltrimethoxysilane 6.4 parts Titanium dioxide 55.4 parts Xylene 61.6 parts Note 7) Resin hydroxyl value 45 mgKOH / g, number average molecular weight 7000, solid content 65%

[Curing agent component]
Hexamethylene diisocyanate 17.6 parts Butyl acetate 53.6 parts

Example 2
The adhesion imparting composition (i) shown in Table 1 is dried on the surface of weather resistant steel (SMA400) specified in JIS G3141 of 3 × 100 × 300 (mm) that has been subjected to alumina blast treatment with an average surface roughness of 30 μm. The coating amount is 0.1 kg / m ² and dried to form an adhesion-imparting coating film. On top of this, the following urethane resin top coating is applied once to a dry film thickness of 60 μm. After drying, the back and side surfaces were sealed with an epoxy resin paint and allowed to air dry for 7 days. Table 2 shows the results of evaluating the weather resistance and corrosion resistance of the coated steel.

(Main ingredient)
Acrylic resin solution ^{Note 8)} 154.0 parts Zinc molybdate 9.9 parts γ-glycidoxypropyltrimethoxysilane 4.9 parts Quinacridone red 30.8 parts Xylene 43.1 parts Note 8) Hydroxyl value of resin 80 mgKOH / g, number average molecular weight 12000, solid content 65%

[Curing agent component]
Hexamethylene diisocyanate 27.7 parts Butyl acetate 75.8 parts

Example 3
The adhesion imparting composition (ii) shown in Table 1 is dried on the surface of weather resistant steel (SMA400) specified in JIS G3141 of 3 × 100 × 300 (mm) that has been subjected to alumina blast treatment with an average surface roughness of 30 μm. A coating amount of 0.1 kg / m ² is applied and dried to form an adhesion-imparting coating film. On top of that, a fluororesin (v) having a hydrolyzable silyl group prepared in Synthesis Example 1 and The colored top coating composition containing the alkoxysilicate hydrolyzate (vii) prepared in Synthesis Example 3 and having the following composition was applied once so that the dry film thickness was 60 μm, dried, and then the back surface and side surfaces were epoxy resin Sealed with paint and allowed to air dry for 7 days. The results of evaluating the weather resistance and corrosion resistance of the coated steel are shown in Table 2 below.

Fluororesin having hydrolyzable silyl group (v) 130.0 parts Alkoxysilicate hydrolyzate (vii) 40.0 parts γ-glycidoxypropyltrimethoxysilane 2.5 parts Aluminum tripolyphosphate 18.0 parts Quinacridone red 32.3 parts

Example 4
The adhesion imparting composition (ii) shown in Table 1 is dried on the surface of weather resistant steel (SMA400) specified in JIS G3141 of 3 × 100 × 300 (mm) that has been subjected to alumina blast treatment with an average surface roughness of 30 μm. A coating amount of 0.1 kg / m ² is applied and dried to form an adhesion-imparting coating film, on which an acrylic resin (vi) having a hydrolyzable silyl group prepared in Synthesis Example 2 and The colored top coating composition containing the alkoxysilicate hydrolyzate (vii) prepared in Synthesis Example 3 and having the following composition was applied once so that the dry film thickness was 60 μm, dried, and then the back surface and side surfaces were epoxy resin Sealed with paint and allowed to air dry for 7 days. The results of evaluating the weather resistance and corrosion resistance of the coated steel are shown in Table 2 below.

Acrylic resin having a hydrolyzable silyl group (vi) 125.0 parts Alkoxysilicate hydrolyzate (vii) 30.0 parts γ-glycidoxypropyltrimethoxysilane 1.8 parts cyanamide zinc 21.5 parts Quinacridone red 32 .3 parts

Example 5
The adhesion imparting composition (iii) shown in Table 1 is dried on the surface of weather resistant steel (SMA400) specified in JIS G3141 of 3 × 100 × 300 (mm) which has been subjected to alumina blast treatment with an average surface roughness of 30 μm. The coating amount is 0.1 kg / m ² , dried to form an adhesion-imparting coating film, on which the alkoxysilicate hydrolyzate (vii) prepared in Synthesis Example 3 is contained, and The colored top coat having the composition was applied once so that the dry film thickness was 60 μm and dried, and then the back and side surfaces were sealed with an epoxy resin paint and allowed to dry naturally for 7 days. The results of evaluating the weather resistance and corrosion resistance of the coated steel are shown in Table 2 below.

Alkoxysilicate hydrolyzate (vii) 125.0 parts Zinc phosphite 8.0 parts γ-glycidoxypropyltrimethoxysilane 10.5 parts Quinophthalene yellow 32.0 parts

Example 6
The adhesion imparting composition (iii) shown in Table 1 is dried on the surface of weather resistant steel (SMA400) specified in JIS G3141 of 3 × 100 × 300 (mm) which has been subjected to alumina blast treatment with an average surface roughness of 30 μm. The coating amount was 0.1 kg / m ² , dried to form an adhesion-imparting coating film, which contained the alkoxysilicate hydrolyzate (viii) prepared in Synthesis Example 4 and The colored top coat having the composition was applied once so as to have a dry film thickness of 60 μm and dried, and then the back and side surfaces were sealed with an epoxy resin paint and allowed to dry naturally for 7 days. The results of evaluating the weather resistance and corrosion resistance of the coated steel are shown in Table 2 below.

Alkoxysilicate hydrolyzate (viii) 125.0 parts Aluminum tripolyphosphate 18.4 parts γ-glycidoxypropyltrimethoxysilane 10.5 parts Titanium dioxide 32.0 parts

Comparative Example 1
Table 2 below shows the results of evaluating the weather resistance and corrosion resistance of the same blast-treated weathering steel as in Example 1 without painting.

Comparative Example 2
Table 2 below shows the results of applying a colored fluororesin-based top coating without applying the adhesion-imparting composition in Example 1 and evaluating the weather resistance and corrosion resistance of the coated steel.

Comparative Example 3
The adhesion imparting composition (iv) shown in Table 1 is dried on the surface of weather resistant steel (SMA400) specified in JIS G3141 of 3 × 100 × 300 (mm) that has been subjected to alumina blast treatment with an average surface roughness of 30 μm. Apply to an application amount of 0.1 kg / m ² , dry to form an adhesion-imparting coating film, and seal the back and sides with an epoxy resin paint without coating a colored top coating on it. Air dried for 7 days. The results of evaluating the weather resistance and corrosion resistance of the coated steel are shown in Table 2 below.

Note 9) Gloss retention after 300 hours of sunshine weather meter (%)
Note 10) Outdoor exposure 2 years Note 11) Combined cycle test 900C
Note 12) 2mm cross-cut test after combined cycle test 900C

  As is clear from Table 2, in the examples of the present invention, the coated steel can be colored in any color, and can be imparted with excellent weather resistance and corrosion resistance. On the other hand, in Comparative Example 1 without coating, Comparative Example 2 in which no adhesion imparting coating film was formed, and Comparative Example 3 in which only an adhesion imparting coating film was formed, red rust occurred.

  According to the method of the present invention, there is provided a corrosion-resistant method for weather-resistant steel having a reduced number of steps, which can maintain rust resistance and weather resistance for a long period of time and further enables arbitrary coloring.

Claims (5)

Dry the adhesion-imparting coating film (A) containing (a) moisture-curing resin, (b) rust preventive pigment, (c) corrosive ion fixing agent, and (d) coupling agent on the weather-resistant steel surface. Formed in the range of 0.03-2.00 Kg / m ² , then accelerated weatherability test Gloss retention after 300 hours of irradiation with sunshine weathermeter is 85% or more, alkoxysilicate hydrolyzate, silane coupling agent And an anticorrosive method for weathering steel, comprising forming a colored top coating film (B) containing an antirust pigment with a dry film thickness of 50 to 90 μm.   1 to 95 parts by weight of component (b), 1 to 95 parts by weight of component (c), 0.1 to 10 parts by weight of component (d) with respect to 100 parts by weight of component (a), and The anticorrosion method according to claim 1, wherein the sum of the component (b) and the component (c) is 5 to 100 parts by mass.   The anticorrosion method according to claim 1, wherein the component (a) is a moisture curable urethane resin.   The anticorrosion method according to claim 1 or 2, wherein the component (c) is hydrocalumite and / or hydrotalcite.   The anticorrosion method according to any one of claims 1 to 4, wherein the colored top coat film (B) further contains a fluororesin.