JP2003171787A - Corrosion prevention method for weather resistant steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a corrosion prevention method for maintaining the rust preventability and weather resistance of weather resistant steel over a long period, and optionally coloring the steel. <P>SOLUTION: A corrosion prevention coating film with a film thickness of 30 to 80 μm containing the grains of metal selected from aluminum, zinc and their alloys is formed on the surface of weather resistant steel. After that, a colored organic-inorganic composite top coat containing the following components is applied thereto so as to control a dry film thickness in 20 to 40 μm: (1) mercapto-containing polyorganosiloxane obtained by subjecting an organic silicon compound having a mercapto group capable of reacting with an epoxy group, and a hydrolyzable group directly bonded to a silicon atom, and organosilane shown by general formula (1): R<SP>1</SP><SB>n</SB>Si(OR<SP>2</SP>)<SB>4-n</SB>[wherein, R<SP>1</SP>is a 1 to 8C organic groups; R<SP>2</SP>is a 1 to 5C alkyl group; and n is 1 or 2], or the partially hydrolyzed condensate of the organosilane to hydrolytic condensation reaction; (2) an epoxy resin hardening agent having two or more epoxy groups in a molecule; and (3) a coloring agent. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel anticorrosion method for weather-resistant steel, and more specifically, it prevents flow rust (red rust) of weather-resistant steel and makes it possible to impart various colors in harmony with the environment. Further, the present invention relates to a method for preventing corrosion of weather-resistant steel, which imparts long-term weather resistance and rust-prevention properties in a further process-saving manner.

[0002]

2. Description of the Related Art Generally, carbon steel is often used for steel structures because of its low cost. However, in carbon steel, moisture in the air (rainfall, humidity, etc.) and oxygen come into contact with the surface of the steel material, and red rust occurs in a short period of time. As a method for preventing the generation of red rust, a method of applying a paint is generally used. In this method, it is common to apply a coating having good durability in order to reduce repainting as much as possible. For example, inorganic zinc rich paint coating → epoxy resin paint mist coat → epoxy resin paint base coat (2
→ Epoxy resin paint intermediate coating → Polyurethane resin paint Top coating is a typical steel coating system that has a durability of 15 years or more. This coating system has the advantage that it can maintain the aesthetic appearance with colors that are in harmony with the environment and maintain long-term rust prevention, but on the other hand, this coating system has a thick film thickness and requires 6 additional coatings, so Takes time and costs. Therefore, in recent years, cases of using weather resistant steel having good corrosion resistance for steel structures have been increasing. The weathering steel is generally a low alloy steel to which elements such as P, Cu, Cr and Ni are added. This steel material forms a rust that protects against corrosion in the open air for more than a dozen years (hereinafter referred to as "protective rust"), and eliminates the need for rust preventive processing thereafter, so-called maintenance-free characteristics. have. The protective action against this corrosion is to control rust with so-called rust, and mainly amorphous iron oxyhydroxide containing a large amount of crystal water contributes to the formation of protective rust that is dense and has good adhesion. It is thought to do.

[0003]

However, when the weather-resistant steel material is used without treatment, floating rust such as red rust or yellow rust or flow rust occurs during the period until protective rust is formed. However, there is a problem in that not only is it unfavorable in appearance, but it also causes pollution of the surrounding environment. Further, 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 film itself It causes problems such as whitening, blistering, and peeling. Further, in order to make the generated rust inconspicuous, the color tone is unified to rust color, and no consideration has been given to imparting various colors in harmony with the environment like painting on carbon steel. Existing weather-resistant steel in which the occurrence of red rust or yellow rust has become noticeable is left as it is, or if it is left to stand until protective rust is formed, or when repairing it, usually after removing rust completely, organic zinc rich It is common to apply the paint → epoxy resin paint undercoating → epoxy resin paint intermediate coating → topcoating 4 to 5 times, and there are problems in that the number of coating steps is large and time and cost are required.

[0004]

Means for Solving the Problems The inventors of the present invention have made diligent studies to solve the above-mentioned problems, and as a result, by forming an anticorrosion coating film containing aluminum particles, zinc particles or the like on the surface of weather resistant steel. The rustproof property is maintained for a long time, and further, the weather resistance is maintained for a long time by applying an overcoat paint containing an organic-inorganic composite resin having good weather resistance and a colorant, and further, any coloring can be performed. This is the completed anticorrosion method for weatherproof steel in the process.

That is, according to the present invention, a film having a thickness of 30 to 80 μm containing particles of a metal selected from the group consisting of aluminum, zinc and alloys thereof (hereinafter simply referred to as “metal particles”) on the surface of weather resistant steel. To form an anticorrosion coating of
Furthermore, the following components, (1) an organosilicon compound (component A) having a mercapto group capable of reacting with an epoxy group and a hydrolyzable group directly bonded to a silicon atom, and a general formula (1), R ¹ _n Si (OR ² ) _4-n [wherein R ¹ is an organic group having 1 to 8 carbon atoms, and R ² is
It is an alkyl group having 1 to 5 carbon atoms, and n is 1 or 2. ] Or a partially hydrolyzed condensate of organosilane (component B) represented by the formula [1], a mercapto group-containing polyorganosiloxane (component 1), (2) 2 per molecule. A coating film containing an epoxy resin curing agent having at least one epoxy group (component 2) and (3) a colorant, and having a gloss retention rate of 85% or more after 300 hours of accelerated weather resistance test sunshine weather meter irradiation. The present invention relates to a corrosion-resistant method for weather-resistant steel, which comprises coating a colored organic-inorganic composite top coating composition to form a film having a dry film thickness of 20 to 40 μm.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The weather resistant steel used in the present invention includes SPA material and SMA.
It is called a material and is defined in JIS G3141, and it may be blasted or pickled, or weather-resistant steel in which only the floating rust is removed and the rust remains. Next, the anticorrosion paint used for forming the anticorrosion coating film in the present invention will be described. The anticorrosive paint is composed of a binder resin, metal particles, a solvent to be blended if necessary, and further various additives such as a dispersant, an antibacterial agent, an anti-cissing agent, and a silane coupling agent. The form of the paint may be solvent-based, water-based, or solvent-free. As the binder resin constituting the anticorrosion paint, it is necessary to use a resin that has good adhesion and is less likely to permeate water and oxygen that cause corrosion. Specific examples of such a resin include, for example, an epoxy resin, a modified epoxy resin, a moisture curing type urethane resin,
Preferable examples include acrylic resins, polyester resins, acrylic silicone resins, inorganic resins, epoxy silicone resins and the like, and combinations of these resins with a curing agent.

The metal particles used in the anticorrosion paint are made of aluminum, zinc, or an alloy thereof, and have a so-called sacrificial anticorrosion action, in which when water or oxygen, which causes corrosion, permeates, it corrodes instead of the steel material. In addition, the corrosion product forms a dense film and has the effect of preventing water and oxygen from penetrating and contacting the surface of the steel material. It is suitable that the metal particles have, for example, an average particle diameter of 2 to 25 μm, preferably 5 to 15 μm. The metal particles are resin (and, if necessary, its curing agent) 1
5 to 800 parts by mass with respect to 00 parts by mass, preferably 8 to 200 parts by mass in the case of aluminum or alloy particles containing aluminum as a main component, and 100 to 600 in the case of zinc or alloy particles containing zinc as a main component. Mass parts are suitable. If the amount added is less than the above range, the anticorrosive property is insufficient, while if the amount is excessive, the storage stability of the anticorrosion paint and the physical properties of various coatings tend to deteriorate. The anticorrosion coating film has a dry film thickness of 30 to 80 μm, preferably 3
5-60 μm is suitable. If it is less than 30 μm, the rust-preventive property is insufficient. On the other hand, if it exceeds 80 μm, when the paint is applied to a vertical surface, the paint is liable to sag, and the drying tends to be delayed.

Next, the colored organic-inorganic composite top coating composition used in the present invention will be described. The colored organic-inorganic composite top coating is a mercapto group-containing polyorganosiloxane (component 1), an epoxy resin curing agent (component 2), a colorant (component 3),
And a solvent that is blended as necessary, a pollution-free rust preventive pigment,
It is composed of a silane coupling agent, and various additives such as a dispersant, an ultraviolet absorber, an antibacterial agent, and a cissing inhibitor. The form of the paint may be solvent-based, water-based, or solvent-free. Polyorganosiloxane (component 1) and epoxy resin curing agent (component 2) that compose a colored organic-inorganic composite top coating composition
It is necessary to use a resin having good weather resistance.
That is, a resin that forms a coating film having a gloss retention rate of 85% or more, preferably 90% or more (however, the upper limit will be 100%, for example) after 300 hours of irradiation in the accelerated weather resistance test sunshine weather meter. is there. Gloss retention rate is 85
If it is less than%, whitening, blistering, peeling, etc. occur in the coating film, which is not preferable. Accelerated weather resistance test The sunshine weather meter is a sunshine carbon arc lamp-type accelerated weather resistance tester that correlates with actual outdoor exposure specified by JIS K5400. The gloss retention rate is specified by JIS K5400. Degree The degree of gloss remaining calculated from the specular gloss according to the following formula. Gloss retention = (Sunshine weather meter irradiation 30
0 hour gloss) x 100 / initial gloss (%)

Next, each component used in the colored organic-inorganic composite top coating composition will be described. Regarding Organosilicon Compound (Component A) Component A is a hydrolytic condensation-reactive alkoxysilane having a mercapto group in the molecule and capable of causing a ring-opening addition reaction with an epoxy group at room temperature. Component A is specifically represented by the general formula (1), HS (R ⁴ ) _n (R ⁵ ) _m Si (OR ³ ) _4-nm (wherein R ³ is an alkyl group having 1 to 5 carbon atoms). And R ⁴
Is an alkylene group having 1 to 5 carbon atoms, R ⁵ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms or an aryl group having 6 to 8 carbon atoms, n
Is 1 or 2 and m is 0 or 1. ) And a mercapto group-containing alkoxysilane represented by R ³ may be linear or branched. Examples of such an alkyl group include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, an s-butyl group, a t-butyl group and a pentyl group. The alkyl group of is preferable. A preferred alkyl group has, for example, 1 to 2 carbon atoms.
The alkylene group as R ⁴ may be linear or branched. Examples of such an alkylene group include a methylene group, an ethylene group, a propylene group and the like. The preferred alkylene group has usually 1 to 3 carbon atoms. The alkyl group having 1 to 5 carbon atoms as R ^{5 is the same} as the above R ³ . Moreover, examples of the cycloalkyl group as R ⁵ include a cyclohexyl group, a cycloheptyl group, and the like. Moreover, examples of the aryl group as R ⁵ include a phenyl group and a naphthyl group. Examples of the mercapto group-containing alkoxysilane represented by the above formula (1) include γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropylmethyldimethoxysilane, and γ-mercaptopropylmethyldiethoxy. Typical examples include silane.

Organosilane or part of the organosilane
Regarding the partial hydrolysis-condensation product (component B) Component B is represented by the general formula (2), R ¹ _n Si (OR ² ) _4-n [wherein R ¹ is an organic group having 1 to 8 carbon atoms, R ² is
It is an alkyl group having 1 to 5 carbon atoms, and n is 1 or 2. ] The organosilane or its partial hydrolysis-condensation product shown by these. In the above formula (2), examples of the organic group as R ¹ include an alkyl group, a cycloalkyl group, an aryl group, a vinyl group and the like. Here, the alkyl group may be linear or branched. Examples of the alkyl group include a methyl group, an ethyl group, and n-
Examples thereof include alkyl groups such as propyl group, i-propyl group, n-butyl group, i-butyl group, s-butyl group, t-butyl group, pentyl group, hexyl group, heptyl group and octyl group. Preferred alkyl groups have 1 to 4 carbon atoms.

Preferable examples of the cycloalkyl group include a cyclohexyl group, a cycloheptyl group, a cyclooctyl group and the like. As the aryl group, for example,
Examples thereof include a phenyl group and a naphthyl group. Each of the above 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 and the like), a (meth) acryloyl group, an alicyclic group and the like. A preferable functional group is a phenyl group which has excellent compatibility with an epoxy resin. The alkyl group as R ² may be linear or branched. Examples of such an alkyl group include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, and an n-group.
-Butyl group, i-butyl group, s-butyl group, t-butyl group, pentyl group and the like, and preferable alkyl group is
It has 1 to 2 carbon atoms. R ¹ in the general formula (2) is 10 of the total organosilane monomer of the organosilane or the partial hydrolysis-condensation product of the organosilane.
% Or more, and preferably 20% or more is a phenyl group. When the amount of the phenyl group is 10% or more, the compatibility with the epoxy resin becomes excellent. In addition, the maximum amount of phenyl groups is appropriate, for example, about 90%.

Specific examples of the organosilane represented by the above formula (2) include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, and n-propyltrimethoxysilane. -Propyltriethoxysilane, i-
Propyltrimethoxysilane, i-propyltriethoxysilane, γ-chloropropyltrimethoxysilane, γ
-Chloropropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3,3,3-
Trifluoropropyltrimethoxysilane, 3,3,3
-Trifluoropropyltriethoxysilane, cyclohexyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, phenyltrimethoxy Silane, phenyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, methylphenyldimethoxysilane, dimethyldipropoxysilane, and the like, preferably , Methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, dimethyldimethoxysilane, etc. .

The partially hydrolyzed condensate of organosilane is
It is a partially hydrolyzed condensate of one kind of organosilane or a mixture of two or more kinds. The polystyrene equivalent weight average molecular weight of the condensate is, for example, 300 to 5,000, preferably 500 to 4,200. By using such a condensate, good storage stability,
A coating film with good adhesion can be obtained. Specific examples of such condensates include SR2402 manufactured by Toray Dow Corning Co., Ltd., DC3037, and DC3074; KR-211 manufactured by Shin-Etsu Chemical Co., Ltd., KR-212, and KR- as commercially available products.
213, KR-214, KR-216, KR-218;
TSR-145 and TSR-16 manufactured by Toshiba Silicone Co., Ltd.
0, TSR-165, YR-3187 and the like.

Polyorganosiloxane containing mercapto group
Regarding (Component 1) Next, a method for producing the mercapto group-containing polyorganosiloxane (Component 1) will be described. The organosilicon compound (component A) is mixed with an organosilane or a partially hydrolyzed condensate of the organosilane (component B), and hydrolysis and hydrolysis are carried out in the presence of water and, if necessary, a catalyst. Allow condensation reaction. The mixing ratio of the component A and the component B is such that the active hydrogen equivalent (solid content) is, for example, 250 to 1500, preferably 300 to 800. The amount of water used in the hydrolysis and condensation reaction is, for example, 45 to 100%, preferably 50 to 90% of the hydrolyzable groups initially present in the mixture of component A and component B. The amount is sufficient for the hydrolysis and condensation reaction, specifically, 0.4 to 1.0 times the total number of hydrolyzable groups in the mixture of component A and component B, preferably 0.5. An amount that provides a mole number of up to 0.9 times is suitable.

The hydrolysis-condensation reaction is, for example, 40-80.
C., preferably 45 to 65.degree. C., for example, for 2 to 10 hours with stirring, but is not limited to this method. Examples of the reaction catalyst used in the hydrolytic condensation reaction include trimethoxyborane, trialkoxyborane such as triethoxyborane, and tri-n-
Butoxyethyl acetoacetate zirconium, di-n
Zirconium chelate compounds such as butoxydi (ethylacetoacetate) zirconium and tetrakis (ethylacetoacetate) zirconium, titanium chelate compounds such as diisopropoxybis (acetylacetate) titanium, diisopropoxybis (ethylacetoacetate) titanium, monoacetyl Examples thereof include organometallic compounds such as aluminum chelates such as bis (ethylacetoacetate) aluminum acetate and diisopropoxyethylacetoacetate aluminum. In addition, a polyorganosiloxane resin solution having a mercapto group in a solution state is synthesized by a hydrolysis-condensation reaction, an alcohol content generated in the reaction, or the alcohol content and an organic solvent described later that is added as necessary. can do.

Epoxy resin curing agent (component 2) The epoxy resin curing agent has two or more in one molecule.
The epoxy resin curing agent has an epoxy equivalent of, for example, 15
It is preferably in the range of 0 to 5,000, preferably 180 to 1,000, from the viewpoint of the corrosion resistance and weather resistance of the coating film. Examples of the epoxy resin curing agent include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, alkyl ether type epoxy resin, and hydrogenated bisphenol A.
It can be suitably selected from epoxy resin and the like.
The epoxy resin curing agent can be used alone or as a mixture of two or more thereof.

As the colorant to be blended in the colored organic-inorganic composite top coating composition used in the present invention, those used for coloring in the field of coating composition are not particularly limited and may be appropriately used. it can. Specific examples of such colorants include titanium dioxide, white pigments such as zinc oxide, carbon black, black pigments such as graphite, molybdate orange, permanent carmine, red pigments such as quinacridone red, and quinophthalene yellow. Representative examples include yellow pigments such as permanent yellow, green pigments such as phthalocyanine green and phthalocyanine blue, and pigments of each color such as blue pigment. Further, an extender pigment may be used in combination. Although the color pigment differs depending on the type, for example, 0.1 to 70 parts by mass with respect to 100 parts by mass of the total amount of the mercapto group-containing polyorganosiloxane (component 1) and the epoxy resin curing agent (component 2). , Preferably 1-5
It is suitable to add it in an amount of 0 parts by mass.

If desired, the colored organic-inorganic composite top coat used in the present invention may contain a pollution-free rust preventive pigment. 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, phosphoric acid. Examples thereof include rust preventive pigments such as zinc aluminum, zinc molybdate, zinc phosphomolybdate, aluminum phosphomolybdate, calcium molybdate, and hydrocalumite, and one or a mixture of two or more thereof is used. However, chromium type and lead type are not preferable from the viewpoint of toxicity.

The pollution-free rust preventive pigment is added in order to adjust the elution rate of the metal particles in the anticorrosive coating film constituting the lower layer, and thereby improve the long-term rust preventive property for the weather resistant steel. The pollution-free rust preventive pigment is, for example, 1 to 80 parts by weight based on 100 parts by weight of the total amount of the mercapto group-containing polyorganosiloxane (component 1) and the epoxy resin curing agent (component 2).
It is suitable to add it in an amount of parts by mass, preferably 5 to 60 parts by mass. If the amount of the pollution-free rust-preventive pigment is less than 1 part by mass, the rust preventive property tends to be insufficient, while if it exceeds 80 parts by mass, the stability of the coating tends to be poor.

A silane coupling agent may be added to the colored organic-inorganic composite top coating composition used in the present invention. Examples of the silane coupling agent include γ-chloropropyltrimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, and the like.
β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane,
γ-aminopropyltriethoxysilane, N-β- (aminoethyl) γ-aminopropyltrimethoxysilane,
Typical examples include γ-ureidopropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyldimethylmethoxysilane, and γ-glycidoxypropyldimethylethoxysilane.

The silane coupling agent is compounded in order to form a composite with the metal particles in the anticorrosion coating forming the lower layer and improve the adhesion between the anticorrosion coating and the colored organic-inorganic composite topcoat coating. . The silane coupling agent is, for example, 0 to 20 parts by mass, preferably 1 to 5 parts by mass with respect to 100 parts by mass of the total amount of the mercapto group-containing polyorganosiloxane (component 1) and the epoxy resin curing agent (component 2). It is expedient to add in parts. If the amount of the silane coupling agent exceeds 20 parts by mass, the stability of the coating tends to decrease.

The film thickness of the colored organic-inorganic composite top coating composition is 20 to 40 μm, preferably 25 to 35 μm as a dry film thickness.
Is suitable. When the film thickness is less than 20 μm, the hiding property and weather resistance are insufficient. On the other hand, the film thickness is 4
When it exceeds 0 μm, foaming and curing failure are likely to occur, and when applied on a vertical surface, problems such as sagging of the paint may occur. Next, the coating method of weather resistant steel will be described. If floating rust is generated on the surface of the weather resistant steel used, remove only the floating rust with a wire brush. Although rust such as red rust adhered to weather resistant steel and yellow rust is not a problem, floating rust easily causes the coating film to peel off together with the floating rust, and it is desirable to remove it as a pretreatment for that. Next, the anticorrosive paint is applied to the weather resistant steel by means of brush, spray, roller or the like so as to have a dry film thickness of 30 to 80 μm, for example, natural drying or at a temperature of 100 ° C. or lower. Force dry. Next, the organic-inorganic composite top coating composition is applied by the same means so that the dry film thickness is 20 to 40 μm, and dried in the same manner.

[0023]

EXAMPLES The present invention will be described in more detail below with reference to examples. In the examples, "parts" and "%" are based on mass unless otherwise specified.

Polyorganosiloxane containing mercapto group
Preparation of Synthetic Example 1 A reactor equipped with a reflux condenser and a stirrer was charged with 15 parts of propylene glycol mono-n-propyl ether and 10 parts of xylene, and stirred at room temperature with 50 parts of γ-mercaptopropyltrimethoxysilane and phenyl. After adding and mixing 20 parts of partially hydrolyzed cocondensate of trimethoxysilane (DC3074 manufactured by Toray Dow Corning Co., Ltd., solid content 100%) and 30 parts of methyltrimethoxysilane, and mixing.
Ion-exchanged water (9 parts) and isopropyl alcohol (5 parts) were added, and the mixture was reacted at 60 ° C. for 3 hours. Next, 0.5 parts of triethoxyborane was added, and stirring was continued at 60 ° C. for 3 hours to obtain a mercapto group-containing polyorganosiloxane 1 having a solid content of 60% and an active hydrogen equivalent of 510 (varnish value).

Synthesis Example 2 A reactor equipped with a reflux condenser and a stirrer was charged with 20 parts of propylene glycol mono-n-propyl ether and 10 parts of xylene and 40 parts of γ-mercaptopropyltrimethoxysilane under stirring at room temperature. Partially hydrolyzed cocondensate of phenyltrimethoxysilane (DC3074 manufactured by Toray Dow Corning Co., Ltd., solid content 100%) 20 parts, partially hydrolyzed cocondensate of phenyltrimethoxysilane (Toray Dow Corning Co., Ltd.) Made DC3037, solid content 1
(00%) and 30 parts of methyltrimethoxysilane were added and mixed, and then 7.2 parts of ion-exchanged water and 5 parts of isopropyl alcohol were added and reacted at 60 ° C. for 3 hours. Next, 0.5 parts of triethoxyborane was added, and stirring was continued at 60 ° C. for 3 hours to obtain a mercapto group-containing polyorganosiloxane 2 having a solid content of 60% and an active hydrogen equivalent of 680 (varnish value).

Of a resin solution for a pigmented organic-inorganic composite topcoat
Preparative Examples 1-5 and Comparative Example 1 In the table below, polyorganosiloxane component I and
II was mixed in the ratio shown in Table 1 and heated and stirred at 60 ° C. for 3 hours to prepare a uniformly dissolved polyorganosiloxane solution, and then III and IV components were added at 20 ° C. or lower until a uniform solution was obtained. Stirring was continued to prepare a resin solution.

<Table 1> Coloring organic-inorganic composite top coating resin
Composition of fat solution (unit: part) Note 1) Epoxy resin Epicoat 1004 (the number of epoxy groups in one molecule is 2, epoxy equivalent 900) manufactured by Yuka Shell Epoxy Co., Ltd. was diluted with xylene to a solid content of 50%. Note 2) Epoxy resin (1) manufactured by Yuka Shell Epoxy Co., Ltd.
The number of epoxy groups in the molecule is 2, solid content 70% xylene diluted product, epoxy equivalent 320 / varnish) Sunmide D-1100 is a curing agent.

Example 1 Average surface roughness 30 μm after alumina blast treatment
And having a size of 3 × 100 × 300 (mm), JIS
On the surface of weather resistant steel (SMA400) specified in G3141,
The following epoxy resin anticorrosive paint was applied once to a dry film thickness of 50 μm and naturally dried for 1 day. Then, apply the following colored organic-inorganic composite top coat on it to give a dry film thickness of 35μ.
It was coated once so as to be m, then the back and side surfaces were sealed with an epoxy resin paint, and naturally dried for 7 days. The resulting coated steel was evaluated for weather resistance and corrosion resistance, and the results are shown in Table 2.

[Anticorrosion paint] <Main component> Epoxy resin solution ^{Note 3)} 200.0 parts Zinc particles (average particle size 5 μm) 800.0 parts Xylene 75.0 parts Note 3) Bisphenol A type epoxy resin with an epoxy equivalent of 450 , Solid content 70% <Curing component> Polyamidoamine resin solution ^{Note 4)} 101.6 parts Xylene 172.4 parts Note 4) Amine value 75 mg KOH / g, solid content 65%

[0030]   [Colored organic-inorganic composite top coating]        Resin solution 1 120.0 parts shown in Table 1        Aluminum tripolyphosphate 18.0 parts        γ-glycidoxypropyltrimethoxysilane 6.4 parts        Dibutyltin dilaurate 4.0 parts        Quinacridone Red 32.3 parts

Example 2 The same weathering steel (SMA40 as used in Example 1)
0) The following moisture-curable urethane resin-based anticorrosive paint was applied on the surface once to a dry film thickness of 50 μm, and naturally dried for 1 day. Then, a colored organic-inorganic composite top coating composition having the following composition is coated thereon once to give a dry film thickness of 35 μm,
Then, seal the back and side with epoxy resin paint,
It was naturally dried for 7 days. The resulting coated steel was evaluated for weather resistance and corrosion resistance, and the results are shown in Table 2. [Anticorrosion paint] Xylene resin ^{Note 5)} 39.0 parts Aromatic polyisocyanate ^{Note 6)} 91.0 parts Zinc particles (average particle size 8 μm) 770.0 parts Dehydrating agent ^{Note 7)} 16.0 parts Xylene 680.0 parts Note 5) Mitsubishi Gas Chemical Industry Co., Ltd. product name “Nicanol 3L” (xylene / formaldehyde resin) Note 6) Sumitomo Bayer Urethane Co., Ltd. product name “Sumijour E21-1” Note 7) Sumitomo Bayer Urethane Co., Ltd. product name "Additive TI" (tosyl isocyanate)

[0032]   [Colored organic-inorganic composite top coating]       120.0 parts of resin solution 2 shown in Table 1       Cyanamide zinc 18.0 parts       γ-glycidoxypropyltrimethoxysilane 6.4 parts       3.4 parts of dibutyltin dilaurate       Quinacridone Red 28.5 copies

Example 3 The same weathering steel as used in Example 1 (SMA40
0) The following epoxy resin-based anticorrosive paint on the surface to dry film thickness 5
It was applied once to 0 μm and naturally dried for 1 day.
Then, a colored organic-inorganic composite top coating composition having the following composition was applied thereon once to give a dry film thickness of 35 μm, the back and side surfaces were sealed with an epoxy resin coating, and naturally dried for 7 days. The resulting coated steel was evaluated for weather resistance and corrosion resistance, and the results are shown in Table 2.

[Anticorrosion paint] <Main component> Epoxy resin solution ^{Note 8)} 200.0 parts Aluminum paste ^{Note 9)} 35.6 parts Mineral spirits 200.0 parts Note 8) Bisphenol A type epoxy resin with epoxy equivalent of 210, solid 100% Note 9) Average particle size of aluminum particles 12 μm, solid content 75% <Curing agent component> Polyamide amine resin solution ^{Note 10)} 102.8 parts Xylene 69.6 parts Note 10) Amine value 255 mg KOH / g, solid content 76%

[0035]   [Colored organic-inorganic composite top coating]        Resin solution 3 shown in Table 1 120.0 parts        Zinc phosphite 8.0 parts        γ-glycidoxypropyltrimethoxysilane 10.5 parts        Quinophthalene yellow 32.0 parts        3.8 parts of dibutyltin dilaurate

Example 4 3 × 100 exposed to the outdoors for 5 years without treatment and having floating rust
The surface of the weather resistant steel (SMA400) specified in JIS G3141 of × 300 (mm) was lightly removed by floating rust with a wire brush, and then the above epoxy resin anticorrosive paint was dried to a film thickness of 50 μm in the same manner as in Example 3. Paint once so that 1
Air-dry for one day, and then apply the same colored organic-inorganic composite top-coat paint as in Example 3 once to a dry film thickness of 35 μm, seal the back and side with epoxy resin paint, and air-dry for 7 days. Let The resulting coated steel was evaluated for weather resistance and corrosion resistance, and the results are shown in Table 2.

Example 5 3 × 100 having floating rust after being exposed outdoors for 5 years
The surface of the weather resistant steel (SMA400) specified in JIS G 3141 of × 300 (mm) was lightly floated with a wire brush to remove rust. Then, in the same manner as in Example 1, an epoxy resin-based anticorrosive paint was applied once to the surface of this weather resistant steel so as to have a dry film thickness of 50 μm, naturally dried for 1 day, and then the same coloring as in Example 1 was applied. The organic-inorganic composite top-coat paint was applied once to a dry film thickness of 35 μm, the back and side surfaces were sealed with an epoxy resin paint, and naturally dried for 7 days. The resulting coated steel was evaluated for weather resistance and corrosion resistance, and the results are shown in Table 2.

Comparative Example 1 The same weathering steel as used in Example 1 (SMA4
00) The same anticorrosive coating film as in Example 1 is formed on the surface, and a colored organic-inorganic composite topcoat material having the following composition is applied once on the surface so that the dry film thickness is 35 μm, and the back surface and the side surface are coated with epoxy. It was sealed with a resin paint and naturally dried for 7 days. The resulting coated steel was evaluated for weather resistance and corrosion resistance, and the results are shown in Table 2. [Colored coating composition] Resin solution 4 shown in Table 1 140.0 parts Quinacridone red 32.3 parts

Comparative Example 2 Example 1 was repeated, except that no coating was applied.
For the obtained coated steel, evaluate the weather resistance and corrosion resistance,
The results are shown in Table 2.

Comparative Example 3 Example 4 was repeated, except that no coating was applied.
For the obtained coated steel, evaluate the weather resistance and corrosion resistance,
The results are shown in Table 2.

<Table 2> Weather resistance and corrosion resistance evaluation results and color
Taste, gloss retention * 11) Gloss retention (%) after 300 hours of sunshine weather meter * 12) Outdoor exposure for 1 year * 13) Salt spray test for 1000 hours

As is clear from Table 2, in the examples of the present invention, the weather resistant steel could be colored in any color, and the weather resistant steel could be provided with excellent weather resistance and corrosion resistance. . On the other hand, red rust was generated in Comparative Example 1 in which the top coating composition did not use the mercapto group-containing polyorganosiloxane and Comparative Examples 2 and 3 in which no coating was applied.

[0043]

Industrial Applicability According to the present invention, there is provided a process-saving, corrosion-resistant method for weather-resistant steel, which is capable of retaining rust resistance and weather resistance for a long period of time and further enabling arbitrary coloring.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Toru Taki, the inventor             7-1414 Shimonagata, Nishinasuno Town, Nasu District, Tochigi Prefecture             34 (72) Inventor Hiroharu Sasaki             7-1414 Shimonagata, Nishinasuno Town, Nasu District, Tochigi Prefecture             46 (72) Inventor Hiroyuki Tanabe             8-15 Asahi-cho, Nishinasuno-cho, Nasu-gun, Tochigi Prefecture F-term (reference) 4D075 AE03 AE27 CA13 CA32 CA33                       CB04 DA06 DB02 DC05 EA07                       EB22 EB33 EB34 EB35 EB38                       EB43 EB45 EB47 EC10 EC11                       EC15 EC45                 4F100 AB03A AB10B AB10H AB18B                       AB18H AB31B AB31H AK52C                       AK52K AK53C BA03 BA07                       BA10A BA10C CA02C CA13C                       CC00C DE01B DE01H JB02C                       JL09A YY00B                 4K062 AA01 BA08 BA10 BB21 BB30                       CA04

Claims (4)

[Claims] 1. An anticorrosion coating having a film thickness of 30 to 80 μm containing particles of a metal selected from the group consisting of aluminum, zinc and alloys thereof is formed on the surface of weather resistant steel, and then, thereon. The following components, (1) an organosilicon compound having a mercapto group capable of reacting with an epoxy group and a hydrolyzable group directly bonded to a silicon atom (component A), the general formula (1), R ¹ _n Si (OR ² ) _4-n [wherein, R ¹ is an organic group having 1 to 8 carbon atoms, and R ² is
It is an alkyl group having 1 to 5 carbon atoms, and n is 1 or 2. ] The mercapto group-containing polyorganosiloxane (component 1) or (2) obtained by hydrolytic condensation reaction of the organosilane represented by the above or a partial hydrolysis condensate of the organosilane (component B) Epoxy resin curing agent having two or more epoxy groups (component 2), and (3)
A colored organic-inorganic composite top coating composition containing a colorant (component 3) and forming a coating film having a gloss retention rate of 85% or more after 300 hours of accelerated sunshine weather meter irradiation is dried to a thickness of 20 to 40 μm. Anticorrosion method for weather-resistant steel, which is characterized by coating so that 2. The anticorrosion method according to claim 1, wherein the colored organic-inorganic composite top coating composition further contains a silane coupling agent. 3. The anticorrosion method according to claim 1, wherein the colored organic-inorganic composite topcoat further contains a pollution-free rust preventive pigment. 4. The anticorrosion method according to claim 1, wherein the weather resistant steel is a weather resistant steel in which only floating rust is removed and rust remains.