JP4162872B2 - Corrosion protection for weathering steel - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel coating method for weathering steel in which rust remains, and more specifically, prevents flow rust (red rust) of weathering steel, enables various colorings in harmony with the environment, and saves further. The present invention relates to an anticorrosion method for weathering steel, which provides long-term weather resistance and rust prevention in a process.
[0002]
[Prior art]
In general, carbon steel is often used for steel structures because of its low cost. However, in carbon steel, red rust is generated in a short period of time when moisture (rainfall, moisture, etc.) and oxygen in the air contact the surface of the steel material. 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.
[0003]
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 in the outdoors for more than 10 years (hereinafter referred to as “protective rust”). It has characteristics.
This protective action against corrosion is to control rust with so-called rust, mainly consisting of amorphous iron oxyhydroxide containing a large amount of crystal water, which contributes to the formation of dense and well-adhered protective rust It is believed that.
However, if the weather-resistant steel is used without treatment, floating rust and flow rust such as red rust and yellow rust are generated during the period until protective rust is formed, which is not preferable in appearance. In addition, there was a problem that it could cause pollution of the surrounding environment.
[0004]
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.
[0005]
[Problems to be solved by the invention]
The existing weather-resistant steel, in which the occurrence of red rust and yellow rust has become noticeable, is left as it is until protective rust is formed, or when repairing, usually after completely removing the rust, organic zinc rich paint → In general, the coating is performed 4 to 5 times, such as epoxy resin coating undercoating → epoxy resin coating intermediate coating → topcoating coating, but it has many problems in that it involves many coating processes and takes time and cost.
[0006]
[Means for Solving the Problems]
As a result of diligent studies to solve the above problems, the present inventors have removed the existing weathering steel having the floating rust, and after removing only the floating rust, other rust such as red rust and yellow rust is adhered and remains. By forming a corrosion-resistant coating film containing aluminum particles, zinc particles, etc. on the weather-resistant steel surface, it is possible to maintain rust prevention for a long period of time, and furthermore, an overcoating containing an organopolysiloxane with good weather resistance and a colorant By applying the paint, the weather resistance is maintained for a long period of time, the flow rust is prevented, and further, it is possible to achieve any coloration, and a corrosion-resistant method for weather-resistant steel with a reduced process has been completed.
[0007]
That is, the present invention forms an anticorrosion coating film having a thickness of 30 to 80 μm containing metal particles selected from the group consisting of aluminum, zinc and alloys thereof on the weatherproof steel surface where rust other than floating rust remains. And then on it, the 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 6 carbon atoms, and n is an integer of 0 to 2. ]
A coating film containing a partially hydrolyzed condensate of organosilane (A) and a curing catalyst (B) represented by the above formula and having a gloss retention of 80% or more after 400 hours of irradiation with an accelerated weather resistance test sunshine weather meter is formed. The present invention relates to an anticorrosion method for weathering steel, characterized in that a colored organopolysiloxane-based top coating is applied to a dry film thickness of 20 to 40 μm and dried.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
Examples of the weathering steel used in the present invention include, for example, SPA materials and SMA materials, and those specified in JIS. The present invention has been exposed to several years after being exposed to floating rust. Applies to weathering steels that have
[0009]
Next, the anticorrosion coating used in the present invention will be described.
The anticorrosive coating film contains a binder and anticorrosive metal particles. The anticorrosion paint used to form this anticorrosion coating film is a resin, at least one or more metal particles selected from aluminum, zinc and alloys thereof, a solvent blended as necessary, and And various additives such as dispersants, antibacterial agents, anti-repellent agents, and silane coupling agents. The form of the paint may be solvent-based, water-based, or solvent-free.
Resin is used as the binder used in the anticorrosion paint to form the anticorrosion coating, and the resin should have good adhesion and resin that does not easily penetrate water and oxygen that cause corrosion. is required. Specific examples of such resins include, for example, epoxy resins, modified epoxy resins, moisture-curing urethane resins, acrylic resins, polyester resins, acrylic silicone resins, organopolysiloxanes, epoxy silicone resins, and these resins. Accordingly, there may be mentioned those in which various curing agents conventionally used in combination with these resins are used in combination.
[0010]
Aluminum particles, zinc particles, or alloy particles thereof used in anticorrosion paints have a so-called sacrificial anticorrosive action that corrodes instead of steel when water or oxygen that causes corrosion is permeated. The corrosion product forms a dense film and has the effect of preventing water and oxygen from penetrating and contacting the steel surface.
The average particle diameter of the metal particles is, for example, 2 to 25 μm, preferably 5 to 15 μm.
The compounding amount of these metal particles is, for example, 5 to 800 parts by mass with respect to 100 parts by mass of the resin (and its curing agent), preferably 8 to 200 parts by mass in the case of aluminum or alloy particles mainly containing aluminum. In the case of zinc or alloy particles containing zinc as a main component, 100 to 600 parts by mass is appropriate. If the addition amount is within this range, sufficient antirust properties, good storage stability of the anticorrosive paint and various physical properties of the coating film can be obtained.
The anticorrosion coating film has a thickness of 30 to 80 μm, preferably 35 to 60 μm. If it is less than 30 μm, the rust prevention property tends to be insufficient. On the other hand, if it exceeds 80 μm, when the anticorrosion paint is applied to the vertical surface, the paint tends to dripping and drying tends to be slow, which is preferable. Absent.
[0011]
Next, the organopolysiloxane top coat used in the present invention will be described.
The organopolysiloxane-based top coating composition contains a partially hydrolyzed condensate of organosilane (A), a curing catalyst (B), and a colorant (C), and optionally, a pollution-free rust preventive pigment, solvent, silane cup Contains various additives such as ring agents, dispersants, UV absorbers, antibacterial agents, repellency inhibitors. The form of the paint may be solvent-based, water-based or solvent-free.
[0012]
The organosilane used in the partial hydrolysis condensate of organosilane has the 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 6 carbon atoms, and n is an integer of 0 to 2. ]
Indicated by
In the above general formula, R ¹ is an organic group having 1 to 8 carbon atoms, and includes, for example, an alkyl group, a cycloalkyl group, an aryl group, a vinyl group, and the like.
[0013]
The alkyl group may be branched. Specifically, 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, and a t-butyl group. And alkyl groups such as a group, a pentyl group, a hexyl group, a heptyl group, and an 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.
[0014]
Examples of the aryl group include a phenyl group.
Each of these functional groups may optionally have a substituent. Examples of such substituents include halogen atoms (eg, chlorine atoms, bromine atoms, fluorine atoms, etc.), epoxy groups, glycidoxy groups, amino groups, (meth) acryloyl groups, mercapto groups, alicyclic groups. Groups and the like.
The alkyl group as R ² may be linear or branched.
[0015]
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 and the like. Preferred alkyl groups are those having 1 to 2 carbon atoms.
The alkyl group may have a branch. Examples of such an alkyl group include alkyl groups such as methyl group, ethyl group, n-propyl group, i-propyl group, γ-glycidoxypropyl group, γ-methacryloxypropyl group, and γ-mercapto. Examples include propyl group, phenyl group, 3,4-epoxycyclohexylethyl group, and γ-aminopropyl group.
[0016]
In said formula, R < ² > is a C1-C6 alkyl group and may have a branch. Examples of such an alkyl group include a methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, s-butyl group, t-butyl group, i-butyl group, and n-pentyl. Group, n-hexyl group and the like.
[0017]
Specific examples of such organosilanes include organosilanes where n is 0, such as tetramethyl silicate, tetraethyl silicate, tetra-n-propyl silicate, tetra-i-propyl silicate, tetra-n-butyl silicate; Methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, i-propyltrimethoxysilane, i-propyltriethoxysilane, γ -Glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane,
[0018]
γ-methacryloxypropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, γ-aminopropyltrimethoxysilane, 3,4-epoxycyclohexylethyl Organosilane when n is 1, such as trimethoxysilane, 3,4-epoxycyclohexylethyltriethoxysilane; n such as dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane A typical example is an organosilane in the case where is 2. These partially hydrolyzed condensates of organosilane have a condensation degree of, for example, 30 or less, preferably 10 or less, from the viewpoint of coating workability and the like.
[0019]
In addition, it is necessary to selectively use a partially hydrolyzed condensate (A) of organosilane that forms a coating film with good weather resistance when condensed with a curing agent (B). That is, it is necessary to use a partially hydrolyzed condensate of organosilane that forms a coating film having a gloss retention of 80% or more, preferably 90% or more after 400 hours of irradiation of the accelerated weathering test sunshine weather meter. Therefore, one or a combination of two or more of the aforementioned organosilanes is selected and used to form a coating film having the gloss retention characteristics. A gloss retention of less than 80% is not preferable because whitening, blistering, peeling, and the like occur in the coating film. The accelerated weathering test sunshine weather meter referred to here is a sunshine carbon arc lamp type accelerating weathering tester correlated with actual outdoor exposure specified in JIS K5400. The degree of remaining gloss calculated from the 60 degree specular gloss specified by JIS K5400 by the following formula.
[0020]
Gloss retention rate = (Gloss after 400 hours of sunshine weather meter irradiation)
× 100 / initial gloss (%)
The curing catalyst (B) used in the organopolysiloxane-based top coating is a catalyst that causes a condensation reaction of the organosilane partial hydrolysis condensate (A) to cure the coating film. As the curing catalyst (B), those conventionally used in general can be used without particular limitation. Specific examples of the curing catalyst (B) include organic tin compounds such as dibutyltin dilaurate, dibutyltin dimaleate, dioctyltin dilaurate, dioctyltin dimaleate, dioctyltin maleate, and tin octylate. Phosphoric acid or phosphate esters such as phosphoric acid, monomethyl phosphate, monoethyl phosphate, monobutyl phosphate, monooctyl phosphate, monodecyl phosphate, dimethyl phosphate, diethyl phosphate, dibutyl phosphate, dioctyl phosphate, didecyl phosphate;
[0021]
Organic titanate compounds such as diisopropoxybis (acetylacetate) titanium and diisopropoxybis (ethylacetoacetate) titanium; Organoaluminum compounds such as tris (ethylacetoacetate) aluminum and tris (acetylacetonato) aluminum; Tetrabutylzirco Typical examples include organic zirconium compounds such as nitrate, tetrakis (acetylacetonato) zirconium, tetraisobutylzirconate, butoxytris (acetylacetonato) zirconium.
[0022]
The amount of the curing catalyst is, for example, 0.1 to 10 parts by mass, preferably 0.5 to 6 parts per 100 parts by mass of the organosilane partial hydrolysis condensate (A). Within this range, good curability is obtained and good paint stability is obtained.
Examples of pollution-free rust preventive pigments that are optionally blended in organopolysiloxane-based top coats include aluminum phosphate, aluminum tripolyphosphate, zinc phosphate, zinc phosphite, potassium phosphite, calcium phosphite, phosphorus phosphite Examples include rust preventive pigments such as aluminum phosphate, zinc calcium phosphate, zinc aluminum phosphate, zinc molybdate, zinc phosphomolybdate, aluminum phosphomolybdate, calcium molybdate, hydrocalumite, and these are one or more. A mixture of However, chromium and lead are not preferable from the viewpoint of toxicity.
[0023]
These pollution-free rust preventive pigments are blended to adjust the elution rate of particles in the anticorrosive coating film and thereby improve long-term rust prevention properties, and the blending amount thereof is partial hydrolysis of organosilane. For example, 1 to 80 parts by mass, preferably 5 to 60 parts by mass is added to 100 parts by mass of the condensate (A). Within this range, good rust prevention and good storage stability of the paint can be obtained.
[0024]
Specific examples of coloring pigments used for coloring organopolysiloxane-based top coatings include titanium dioxide, white pigments such as zinc oxide, black pigments such as carbon black and graphite, molybdate orange, and permanent carmine. Typical examples are pigments of various colors usually used for paints such as red pigments such as quinacridone red, yellow pigments such as quinophthalene yellow and permanent yellow, green and blue pigments such as phthalocyanine green and phthalocyanine blue. Can be mentioned. Further, extender pigments may be used in combination. Although a color pigment changes also with the kind, it is 0.1-70 mass parts with respect to 100 mass parts of partial hydrolysis-condensation products (A) of organosilane, Preferably, it is 0.5-60 mass parts. It is appropriate to add.
[0025]
Examples of the silane coupling agent appropriately mixed in the organopolysiloxane-based top coating composition include γ-chloropyrtrimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyl tris (β-methoxy). Ethoxy) silane, γ-methacryloxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyl Triethoxysilane, N-β- (aminoethyl) aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyldimethyl, γ-glycidoxy B pills dimethylethoxysilane like can be mentioned as a typical example.
[0026]
The silane coupling agent is compounded with the metal particles in the anticorrosion coating to improve the adhesion between the anticorrosion coating and the coating formed by the colored organopolysiloxane top coating. The compounding amount is, for example, 0 to 20 parts by mass, and preferably 1 to 15 parts by mass with respect to 100 parts by mass of the partially hydrolyzed condensate (A) of organosilane. By blending within this range, good storage stability of the paint can be obtained.
[0027]
The organopolysiloxane-based top coating is suitably applied with a dry film thickness of 20 to 40 μm, preferably 25 to 35 μm. If it is less than 20 μm, the concealability and weather resistance will be insufficient. On the other hand, if it exceeds 40 μm, foaming and poor curing are likely to occur, and when applied to a vertical surface, problems such as dripping of the paint tend to occur.
[0028]
Next, the weathering steel coating method will be described.
Remove weathered steel with floating rust on the surface with a wire brush. Although there is no problem with red rust or yellow rust fixed to the weathering steel, the floating rust is easy to peel off together with the floating rust, and it is necessary to remove it as a pretreatment for that purpose. Next, the anticorrosive paint forming the anticorrosive coating is applied by means of brush, spray, roller or the like so that the dry film thickness is 30 to 80 μm, and is naturally dried or forcedly dried at a temperature of 100 ° C. or less. . Next, an organopolysiloxane-based top coating material is applied on the anticorrosion coating film by the same means so that the dry film thickness becomes 20 to 40 μm and dried.
[0029]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. In the examples, “parts” and “%” are based on mass.
[0030]
Example 1
The surface of weather resistant steel (SMA400) defined in JIS G3141 of 3 × 100 × 300 (mm) having floating rust was exposed to the outside without treatment for 5 years, and the surface was lightly lifted to remove rust. Next, an epoxy resin-based anticorrosive paint having the following composition was applied once on the surface of the weather resistant steel so as to have a dry film thickness of 50 μm, followed by natural drying for one day. Next, an organopolysiloxane-based top coating material having the following composition was coated thereon once so as to have a dry film thickness of 35 μm, the back surface and side surfaces were sealed with an epoxy resin coating material, and air-dried for 7 days. The weather resistance and corrosion resistance of the obtained coated steel were evaluated, and the results are shown in Table 1 below.
[0031]
[Anti-corrosion paint]
<Main ingredient>
Epoxy resin solution ^{Note 1)} 200.0 parts Zinc particles (average particle size 5 μm) 800.0 parts Xylene 75.0 parts Note 1) Bisphenol A type epoxy resin having an epoxy equivalent of 450,
70% solids
[0032]
<Curing agent component>
172.4 parts of a polyamide amine resin solution ^{* 2)} 101.6 parts of xylene Note 2) amine value 75 mgKOH / g, solid content of 65%
[0033]
[Top coat]
Partially hydrolyzed condensate of organosilane (I) ^{Note 3)} 100.0 parts (solid content conversion)
Aluminum tripolyphosphate 18.0 parts γ-glycidoxypropyltrimethoxysilane 6.4 parts dibutyltin dilaurate 4.0 parts quinacridone red 32.3 parts Note 3) Methyltrimethoxysilane (trade name, manufactured by Shin-Etsu Silicone; KBM13) ) 45.0 parts, phenyltrimethoxysilane (trade name, manufactured by Shin-Etsu Silicon; KBM103) 25.0 parts, partially hydrolyzed condensate of phenyltripropoxysilane (trade name, manufactured by Toshiba Dow Corning; SH6018) 25.0 parts And a condensate solution obtained by stirring and reacting 4.6 parts of an aluminum chelating agent (trade name, manufactured by Kawaken Fine Chemical Co., Ltd .; aluminum chelate D) at 60 ° C. for 3 hours. (90% solid content)
[0034]
Example 2
After the surface of the weather-resistant steel similar to that of Example 1 was lifted with a wire brush and the rust was lightly removed, a moisture-curing urethane resin anticorrosive paint having the following composition was applied once so as to have a dry film thickness of 50 μm. Dried. Next, the same organopolysiloxane top coating as in Example 1 was applied once so as to have a dry film thickness of 35 μm, and the back and side surfaces were sealed with an epoxy resin coating and allowed to air dry for 7 days. Table 1 shows the results of evaluating the weather resistance and corrosion resistance of the obtained coated steel.
[0035]
[Anti-corrosion paint]
Xylene resin ^{Note 4)} 39.0 parts Aromatic polyisocyanate ^{Note 5)} 91.0 parts Zinc particles (average particle size 8 μm) 770.0 parts Dehydrating agent ^{Note 6)} 16.0 parts Xylene 680.0 parts Note 4) Mitsubishi Product name manufactured by Gas Chemical Industry Co., Ltd .; Nikanol 3L (xylene / formaldehyde resin)
Note 5) Sumitomo Bayer Urethane Co., Ltd. product name; Sumijour E21-1
Note 6) Product name manufactured by Sumitomo Bayer Urethane Co., Ltd .; Additive T1 (tosyl isocyanate)
[0039]
Comparative Example 1
Table 1 shows the results of evaluating the weather resistance and corrosion resistance of the same weather resistant steel as in Example 1 by removing floating rust with a wire brush and not painting at all.
Comparative Example 2
In Example 1, using an anticorrosion paint that does not contain zinc powder or aluminum powder, and using a top coat that does not contain a rust preventive pigment and a silane coupling agent, it was applied in the same manner as in Example 1, The results of evaluating the weather resistance and corrosion resistance of the coated steel are shown in Table 1.
[0040]
[Table 1]
Table 1
Color Gloss retention ^{* 11)} Weather resistance ^{Note 12)} Anticorrosion ^{Note 13)}
Example 1 Red 94 Good Good Example 2 Red 93 Good Good Comparative Example 1-Full red rust after 48H
Whole surface red rust comparison example 2 Red 93 Red spot rust after 320H
Red spot rust
[0041]
Note 11) Gloss retention after 400 hours of sunshine weather meter (%)
Note 12) Outdoor exposure 1 year Note 13) Salt spray test 1000 hours [0042]
As is clear from Table 1, according to the present invention, a coated steel that can be colored in any color and has excellent weather resistance and corrosion resistance can be obtained. On the other hand, in the uncoated Comparative Example 1 and the Comparative Example 2 containing no rust preventive agent, red rust was generated.
[0043]
【The invention's effect】
According to the method of the present invention, it is possible to prevent corrosion of a weather-resistant steel with a reduced process, which maintains rust resistance and weather resistance for a long period of time, prevents flow rust, and enables arbitrary coloring.

Claims (3)

An anticorrosion coating film having a film thickness of 30 to 80 μm containing metal particles selected from the group consisting of aluminum, zinc and alloys thereof is formed on the weatherproof steel surface where rust other than floating rust remains, and then In 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 6 carbon atoms, n is an integer of 0-2. ] A coating film containing a partially hydrolyzed condensate of organosilane (A) and a curing catalyst (B) represented by the following formula and having a gloss retention of 80% or more after 400 hours of accelerated weathering test sunshine weather meter irradiation: A colored organopolysiloxane-based top coating is applied so as to have a dry film thickness of 20 to 40 μm, and dried to prevent corrosion of weathering steel,
The partially hydrolyzed condensate (A) of organosilane is 45.0 parts of methyltrimethoxysilane, 25.0 parts of phenyltrimethoxysilane, and 25.0 parts of partially hydrolyzed condensate of phenyltripropoxysilane. An anticorrosion method for weathering steel, characterized by being a decomposition condensate .   The anticorrosion method according to claim 1, wherein the top coating contains a silane coupling agent.   The anticorrosion method according to claim 1, wherein the top coating contains a pollution-free rust preventive pigment.