JP2017186480A - Method for manufacturing steel plate with anticorrosive coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a steel plate with an anticorrosive coating film that has excellent curing dryness and easily suppresses whitening, which is useful for manufacture of a steel plate with an anticorrosive coating film under a particularly low temperature.SOLUTION: A method for manufacturing a steel plate with an anticorrosive coating film includes: applying an anticorrosive coating composition containing a siloxane binding agent (a) having a weight average molecular weight (Mw) of 5,000 or more and zinc powder and/or zinc alloy powder (b) onto a steel plate, on a temperature condition which is such a temperature that a temperature difference (steel plate temperature-dew point temperature) (°C) between a steel plate temperature and a dew point temperature is equal to or higher than any one lower temperature out of (-12 Ln (absolute humidity (g/m))+25)°C and 1°C; then curing the anticorrosive coating composition.SELECTED DRAWING: None

Description

  The present invention relates to a method of manufacturing a steel plate with a rust-proof coating film manufactured by a pretreatment of a steel plate performed in a steel plate processing step in a ship, an offshore structure, a plant, a bridge, an onshore tank or the like.

  Conventionally, a primary rust preventive paint is applied to the surface of a steel plate for the purpose of preventing rusting during construction of large steel structures such as ships, marine structures, plants, bridges, and land tanks. As such primary rust preventive paints, organic primary rust preventive paints such as wash primers, non-zinc epoxy primers, epoxy zinc rich primers, and inorganic zinc primary rust preventive paints containing siloxane binder and zinc powder are known. ing. Of these primary rust preventive paints, inorganic zinc primary rust preventive paints having excellent weldability are most widely used.

  For example, Patent Document 1 contains a siloxane-based binder (a) having a weight average molecular weight (Mw) of 1000 to 6000, and zinc powder (B) containing scaly zinc-based powder (b), and a pigment volume. A primary rust-preventive paint composition having a concentration (PVC) of 35 to 60% and a mass ratio of (B) to (A) ((B) / (A)) of 1.0 to 5.0. A method for painting a surface is disclosed.

International Publication No. 2014/014063

  A steel plate coated with an inorganic zinc primary rust-preventive coating composition containing a siloxane-based binder and zinc powder may be carried out outdoors within a short time (within about 20 minutes) after coating. When the coated steel sheet gets wet with water due to rain or the like, a phenomenon that the wet part turns white (hereinafter also referred to as “whitening”) may occur. For example, significant whitening occurs due to contact with water at an early stage after painting, and this whitening causes deterioration of the rust prevention and adhesion of the coating film. Since the coating film in which whitening has occurred requires surface treatment, there is a problem that the number of man-hours in the construction of steel structures increases and the construction period becomes longer.

  Also, in the low temperature period such as winter, since the film formed by applying paint is slow to cure and dry, until the coating film is resistant to damage (the property that plastic deformation or destruction due to external pressure hardly occurs) It took time to. Therefore, it is necessary to improve the curing and drying properties of the film formed by applying the paint, in other words, it is necessary to shorten the curing and drying time described later.

  The present invention is intended to solve such a problem in the prior art, and is a method for producing a steel sheet with an excellent rust-drying property and easy to suppress whitening, and in particular, An object of the present invention is to provide a useful method for producing a steel sheet with a rust-proof coating film at a low temperature.

  As a result of intensive research, the inventors of the present invention have found that when the absolute humidity is fixed and compared, the higher the steel plate temperature is higher than the dew point temperature, the better the rust-preventing coating film has a better curing drying property (that is, a shorter curing drying time). Although it can be produced, it has been found that the above-mentioned whitening is likely to occur, and even in such a case, if a siloxane-based binder having a relatively high molecular weight is used, whitening is easily suppressed, and the present invention has been completed. It was.

The gist of the present invention is as follows.
[1]
The temperature difference between the steel sheet temperature and the dew point temperature (steel sheet temperature-dew point temperature) (° C.) is (−12 Ln (absolute humidity (g / m ³ )) + 25) ° C. or 1 ° C., whichever is the lower temperature. An anticorrosive coating composition containing a siloxane-based binder (a) having a weight average molecular weight (Mw) of 5,000 or more and zinc powder and / or zinc alloy powder (b) on a steel sheet under temperature conditions The manufacturing method of the steel plate with a rust prevention coating film apply | coated and then hardened.

[2]
Manufacture of a steel sheet with a rust-preventing coating film according to [1] above, wherein the steel sheet with a rust-preventing coating film is a steel sheet with a rust-preventing coating film that is exposed outdoors within 20 minutes after application of the rust-preventing coating composition. Method.

[3]
The steel sheet with a rust-preventing coating film according to the above [1] or [2], wherein the rust-preventing coating film is a rust-preventing coating film that comes into contact with liquid water within 20 minutes after application of the rust-preventing coating composition. Production method.

[4]
The manufacturing method of the steel plate with a rust prevention coating film in any one of said [1]-[3] implemented under the temperature of 5 degrees C or less.

[5]
The rust prevention according to any one of [1] to [4], wherein the temperature difference is equal to or higher than (−12 Ln (absolute humidity (g / m ³ )) + 25) ° C. or 10 ° C., whichever is lower. Manufacturing method of steel plate with a coating film.

[6]
The manufacturing method of the steel plate with a rust preventive coating film in any one of said [1]-[5] whose weight average molecular weights (Mw) of the said siloxane type binder (a) are 5,000-10,000.

[7]
The rust preventive coating according to any one of the above [1] to [6], wherein the siloxane-based binder (a) is a condensate of at least one compound selected from the group consisting of alkyl silicates and methyltrialkoxysilanes. Manufacturing method of steel sheet with film.

[8]
The manufacturing method of the steel plate with an antirust coating film in any one of said [1]-[7] whose said antirust coating composition is a primary antirust coating composition.

  The production method of the present invention is capable of producing a steel sheet having a rust-proof coating film that has excellent curing and drying properties and is easy to suppress whitening, and has a rust-proof coating film under low-temperature conditions such as winter. This is particularly useful when manufacturing a steel sheet with a plate.

FIG. 1 shows the relationship between the absolute humidity and the temperature difference between the steel plate temperature and the dew point temperature and the curing and drying time of the coating film when producing a steel sheet with a rust-proof coating film.

Hereinafter, the manufacturing method of the steel plate with a rust prevention coating film which concerns on this invention is demonstrated in detail.
In the method for producing a steel plate with a rust-proof coating film according to the present invention, the temperature difference (° C.) between the steel plate temperature and the dew point temperature (that is, a value obtained by subtracting the dew point temperature (° C.) from the steel plate temperature (° C.)) is (− 12 Ln (absolute humidity (g / m ³ )) + 25) ° C. or 1 ° C., whichever is lower, preferably (−12 Ln (absolute humidity (g / m ³ )) + 25) ° C. or 10 ° C. The temperature is not lower than the lower temperature, more preferably (−12 Ln (absolute humidity (g / m ³ )) + 25) ° C. or 15 ° C., whichever is the lower temperature or higher. A rust preventive coating composition is applied and then cured to produce a steel sheet with a rust preventive coating.
In the present invention, the steel sheet temperature, the dew point temperature, the air temperature and the absolute humidity are temperatures or humidity when the rust preventive coating composition is applied to the steel sheet and then cured unless otherwise specified.

(Production conditions)
<Temperature difference conditions>
The temperature difference condition is derived from the following experiment.
A cold-rolled steel plate (JIS G3141, SPCC-SB, dimensions: 150 mm × 70 mm × 0.8 mm) set at a predetermined steel plate temperature in advance was manufactured in the examples described later under conditions of a predetermined temperature and humidity. The primary rust preventive paint composition (3) was applied so that the dry film thickness was 15 μm, and was allowed to stand while maintaining the conditions of each temperature and humidity immediately after the application to cure the paint film. A coated steel plate was produced. The manufacture of the steel sheet with a rust-proof coating was carried out for various conditions by changing the temperature and humidity conditions in the following ranges.
Temperature: 0-30 ° C
Humidity: 10-90RH%
Absolute humidity: 0.5-27.4 g / m ³
Dew point: -27.1 to 28.2 ° C
Steel plate temperature: 0-30 ° C
Steel plate temperature-dew point: 1.3-57.1 ° C.

  At that time, the curing and drying time was measured. This curing and drying time is the state of curing and drying from the end of coating, that is, the steel plate is placed horizontally so that the film faces upward, and the thumb and the arm are stretched in the direction of gravity with respect to the test piece. When the film is rotated 90 degrees while being pressed against the surface of the film, the time until the film reaches a state where no looseness, peeling, wrinkles or other signs of twist are observed. This measurement was performed every minute after the application was completed.

The curing and drying time was 4 to 20 minutes. FIG. 1 shows the relationship between absolute humidity (g / m ³ ) and steel plate temperature-dew point temperature (° C.).
FIG. 1 shows that when the absolute humidity is fixed, the curing and drying time is shorter, that is, the curing and drying properties are better as the temperature difference between the steel sheet temperature and the dew point temperature is larger (steel sheet temperature−dew point temperature). In addition, between the data of 11 minutes of curing and drying time,
Steel plate temperature−dew point temperature (° C.) = − 12 Ln (absolute humidity (g / m ³ )) + 25 (° C.)
The correlation represented by is recognized. Ln represents a natural logarithm. Therefore, in the present invention, in order to produce a rust-preventive coating film with good curing and drying properties, the temperature difference is (−12 Ln (absolute humidity (g / m ³ )) + 25) ° C. or more, The steel plate was coated with a rust-proof coating composition and then cured.
Even if the primary rust-preventive paint composition (3) is changed to another rust-preventive paint composition, substantially the same curing and drying properties as when the primary rust-preventive paint composition (3) is used are exhibited. The

Furthermore, in order to make it easy to produce a rust-preventive coating film with good curing and drying properties even under conditions where the absolute humidity is often low, such as in winter, when the temperature is low (for example, 5 ° C. or less), the temperature difference is set to (−12 Ln). (Absolute humidity (g / m ³ )) + 25) ° C. or 1 ° C. (preferably 10 ° C., more preferably 15 ° C.) or higher, whichever is the lower temperature or higher.

According to the method for producing a steel sheet with a rust-proof coating film of the present invention, which is carried out under the above temperature conditions, a steel sheet with a rust-proof coating film can be produced with excellent curing and drying properties. For example, when comparing the anti-corrosion paint composition and the absolute humidity when applying and curing the composition, it is superior to the case of producing a steel sheet with an anti-corrosion coating film without satisfying the above temperature condition. A steel sheet with a rust-proof coating film can be produced with a curing drying property.
The upper limit of the temperature difference is, for example, 40 ° C. from the viewpoint of film forming properties.

In another aspect of the present invention, the above-described method for producing a substrate with an anticorrosive coating film according to the present invention changes the temperature difference to 1 ° C or higher, preferably 10 ° C or higher, more preferably 15 ° C or higher. Implemented.
The temperature difference can be increased, for example, by heating a steel plate.

  The production method of the present invention is particularly useful when producing a steel sheet with an anticorrosive coating film with excellent curing and drying properties under conditions where the absolute humidity is often low and the temperature is particularly low (for example, 5 ° C. or less). . However, considering the actual coating environment, the lower limit of the temperature may be, for example, −10 ° C.

<Conditions other than temperature difference>
Examples of the steel plate include steel plates for large structures such as ships, offshore structures, plants, bridges, and land tanks. The steel plate is required to be protected from rust without hindering fusing, welding, etc. in the construction process of a large structure. Furthermore, whitening resistance is also required for a steel sheet provided with a rust-proof coating film. The steel sheet is usually subjected to blasting under conditions corresponding to a degree of rust removal Sa2 1/2 or higher in ISO 8501-1.

  From the viewpoint of ease of processing of the steel sheet with a rust-proof coating film, the rust-proof coating composition preferably has an average dry film thickness measured by an electromagnetic film thickness meter of preferably 30 μm or less, more preferably 5 to 25 μm. It is applied as follows.

There is no restriction | limiting in particular as a coating method of the said rust preventive coating composition, The conventionally well-known method using an air spray, an airless spray, etc. can be applied.
As a coating machine, generally, when painting at a shipyard, a steelworks, etc., an airless spray or a line coating machine is mainly used. The line coating machine manages the film thickness according to the coating speed, the coating pressure such as air spray and airless spray installed in the coating machine, and the spray tip size (caliber).

  The rust preventive coating composition is cured after being applied on a steel plate. There is no restriction | limiting in particular as a hardening method, A conventionally well-known hardening method is applicable. For example, when the rust preventive coating composition applied on a steel plate is left in the air (with heating as necessary), the solvent volatilizes, and the siloxane-based binder (a) is caused by moisture in the composition. It hardens | cures by hydrolytic condensation reaction.

(Anti-rust paint composition)
<Siloxane-based binder (a)>
In the present invention, when a rust-proof coating composition containing a siloxane-based binder and a zinc-based powder is applied to a steel sheet, the siloxane-based binder has a weight average molecular weight (Mw) of 5,000 or more. A siloxane-based binder (a) is used. When the siloxane-based binder (a) is used, whitening of the anticorrosive coating film can be easily suppressed.

On the other hand, the weight average molecular weight (Mw) of the siloxane-based binder (a) is preferably 10,000 or less because the rust preventive coating composition has a sufficient pot life.
In addition, a weight average molecular weight (Mw) is a value of standard polystyrene conversion measured by a gel permeation chromatography (GPC) method, and details of measurement conditions are described in the column of Examples described later.

  In a coating film formed from a siloxane-based binder (for example, a coating film consisting of a partial hydrolysis condensate of at least one compound selected from alkyl silicate and methyltrialkoxysilane), it remains due to moisture in the air. Hydrolytic condensation in the hydrolyzable group proceeds gradually. A coating film formed from a siloxane-based binder having a low Mw has a larger volume shrinkage due to a hydrolysis-condensation reaction than a coating film formed from a siloxane-based binder having a large Mw. If the hydrolytic condensation reaction proceeds rapidly due to wetness or the like, a shrinkage stress accompanying volume shrinkage is suddenly generated in the coating film, and a large number of fine cracks are generated in the coating film. It is estimated that whitening occurs.

  Examples of the siloxane-based binder (a) include condensates of at least one compound selected from alkyl silicates and methyltrialkoxysilanes, specifically, partial hydrolysis condensates of the compounds and the above Examples include partial hydrolysis condensates of compound condensates.

  Examples of the alkyl silicate include tetramethyl orthosilicate, tetraethyl orthosilicate, tetra-n-propyl orthosilicate, tetra-i-propyl orthosilicate, tetra-n-butyl orthosilicate, and tetra-sec-butyl orthosilicate. And compounds such as methyl polysilicate and ethyl polysilicate.

Examples of the methyltrialkoxysilane include compounds such as methyltrimethoxysilane and methyltriethoxysilane.
Among these, the siloxane-based binder (a) is preferably an alkyl silicate condensate, more preferably a tetraethyl orthosilicate condensate, and ethyl silicate 40 (trade name; Colcoat, which is an initial condensate of tetraethyl orthosilicate). A partially hydrolyzed condensate (manufactured by Co., Ltd.) is particularly preferred.

A siloxane type binder (a) may be used individually by 1 type, and may use 2 or more types together.
The siloxane-based binder (a) can be produced using a conventionally known method. For example, at least one compound selected from alkyl silicate and methyltrialkoxysilane is mixed with a suitable amount of water and catalyst. In the form of a first component (A) described later containing a siloxane-based binder (a) by carrying out a partial hydrolysis condensation reaction so that the weight average molecular weight (Mw) becomes a desired value in the presence of Can do.

  Examples of the catalyst include catalysts described later such as hydrochloric acid, and hydrochloric acid is preferred from the viewpoint that the remaining amount can be easily reduced by heating and the storage stability of the first component (A) can be improved.

The content of the siloxane-based binder (a) is obtained by converting the mass of the siloxane-based binder (a) into the mass of SiO ₂ (that is, the mass of the siloxane-based binder (a) is changed to the siloxane-based binder). (Converted to the mass of SiO ₂ having the same amount as the amount of Si atoms contained in (a)), and assuming that the solid content of the anticorrosive coating composition is 100% by mass, usually 2 to 90% by mass, Preferably it is 3-70 mass%, More preferably, it is 5-60 mass%. When the content of the siloxane-based binder (a) is in the above range, the resulting coating film is excellent in adhesion to a steel sheet substrate, top coat adhesion, rust prevention, and heat resistance. The solid content of the rust preventive coating composition is the residue when the composition containing a volatile component such as a solvent is dried in a hot air dryer at 105 ° C. for 3 hours to volatilize the solvent. It is.

<Other binders>
The rust preventive coating composition may contain a binder other than the siloxane-based binder (a) as long as the object and effect of the present invention are not impaired. Examples of other binders include polyvinyl butyral resin and acrylic resin. Examples of the polyvinyl butyral resin include ESREC BM-1 and ESREC BL-1 (trade name; manufactured by Sekisui Chemical Co., Ltd.). Examples of the acrylic resin include Dianal BR-106 (trade name; Mitsubishi Rayon Co., Ltd.). ))). The content of the other binder is preferably 0.05 to 4.0% by mass, more preferably 1.0 to 3.0% by mass, when the solid content of the rust preventive coating composition is 100% by mass. It is.

<Solvent>
The rust preventive coating composition preferably contains a solvent for the purpose of facilitating painting.
Examples of the solvent include organic solvents usually used in the paint field, such as alcohol solvents, aromatic solvents, and cellosolve solvents.

  Examples of the alcohol solvent include methanol, ethanol, isopropanol, and butanol. Examples of the aromatic solvent include benzene, xylene, and toluene. Examples of the cellosolve solvent include methyl cellosolve, ethyl cellosolve, and butyl cellosolve.

The content of the solvent is usually 10 to 90% by mass, preferably 20 to 80% by mass, when the amount of the anticorrosive coating composition is 100% by mass.
The solvent is preferably at least one solvent selected from the group consisting of ketone solvents, glycol ether solvents, and acetate solvents, for example, 1 to 80% by mass, preferably 3 to 50% by mass. More preferably, it contains in the ratio of 6-30 mass%. When these solvents are contained, pot life can be improved and workability of coating can be improved. This is because the siloxane-based binder (a) is stabilized by a hydrogen bond between a silanol group which the siloxane-based binder (a) may have and an oxygen atom such as the ketone solvent, and the condensation reaction is This is presumed to be suppressed.

The ketone solvent is preferably methyl ethyl ketone, the glycol ether solvent is preferably propylene glycol monomethyl ether, and the acetate solvent is preferably ethyl acetate. Among these, Ketone solvents are preferred, and methyl ethyl ketone is more preferred.
These solvents may be used alone or in combination of two or more.

<Water>
The rust preventive coating composition may contain water in order to cure the siloxane-based binder (a) by hydrolysis condensation reaction to form a coating film. The amount of water (including the amount of water in hydrochloric acid, which will be described later) may be appropriately set in consideration of the prior art. For example, the amount of water is about 0.1 with respect to 1 mol of silicon atom in the siloxane-based binder (a). 1 to 4.0 mol.

<Catalyst>
The rust preventive coating composition may contain a catalyst. Examples of the catalyst include hydrochloric acid, sulfuric acid, oxalic acid, ferric chloride, and zinc chloride.

  These catalysts are formed from the rust-preventive coating composition applied to the steel sheet as a reaction initiator that partially hydrolyzes the siloxane binder (a) to a desired weight average molecular weight in the presence of an appropriate amount of water. It also acts as a catalyst for further hydrolysis condensation of the siloxane binder in the antirust coating.

  When the catalyst is a catalyst containing chlorine such as hydrochloric acid, ferric chloride, zinc chloride, the content of the catalyst is such that the chloride ion content is 1 mol of silicon atoms contained in the siloxane-based binder (a). The amount is preferably 0.01 to 5.0 mmol, more preferably 0.2 to 4.5 mmol. When the content of the catalyst containing chlorine is in the above range, the further hydrolysis-condensation reaction of the siloxane binder in the rust-preventing coating film formed from the rust-preventing coating composition applied to the steel sheet can be sufficiently advanced. And the whitening resistance effect of the anticorrosive coating film described above can be further enhanced.

When used in combination with catalysts which do not contain chlorine, the content thereof, relative to 100 parts by weight of the siloxane-based binder in terms of the mass of SiO ₂ as described above (a), usually 0.03 to 0.3 mass Parts, preferably 0.07 to 0.2 parts by weight.
When the content of the catalyst is within the above range, the pot life of the rust preventive coating composition is long, and the coating film formed from this rust preventive coating composition is excellent in whitening resistance.

<Zinc powder and / or zinc alloy powder (b)>
The zinc powder and / or zinc alloy powder (b) (hereinafter also referred to as “zinc-based powder (b)”) acts as a rust preventive pigment for preventing rusting of the steel sheet.
Examples of the zinc alloy include an alloy of zinc and at least one selected from aluminum, magnesium and tin, and a zinc-aluminum alloy and a zinc-tin alloy are preferable.

Examples of the shape of the particles constituting the zinc-based powder (b) include various shapes such as a spherical shape and a scale shape.
Examples of commercially available zinc powder having a spherical particle shape include F-2000 (trade name; manufactured by Honjo Chemical Co., Ltd.).

  Examples of commercially available zinc powder having a scaly particle shape include STANDART Zinc flake GTT and STANDART Zinc flake G (trade name; manufactured by ECKART GmbH). Examples of commercially available zinc alloy powders having a scaly particle shape include STAPA 4 ZNAL7 (alloy of zinc and aluminum) and STAPA 4 ZNSN30 (alloy of zinc and tin) (trade name; manufactured by ECKART GmbH). Can be mentioned.

  As the zinc-based powder (b), one or both of zinc powder and zinc alloy powder can be used. Each of the zinc powder and zinc alloy powder can be used alone or in combination of two or more. Also good.

  The content of the zinc-based powder (b) is usually 10 to 98% by mass, preferably 30 to 97% by mass, more preferably 40 to 95% by mass, assuming that the solid content of the rust preventive coating composition is 100% by mass. It is. When the content of the zinc-based powder (b) is in the above range, the resulting coating film is excellent in rust prevention.

<Other pigments>
The rust preventive coating composition may contain other pigments other than the zinc-based powder (b) for the purpose of ensuring various coating properties. Other pigments may be used alone or in combination of two or more.

Examples of the other pigments include rust preventive pigments other than zinc powder and / or zinc alloy powder (b), which are used for the purpose of supplementing the rust preventive property of the coating film.
Examples of rust preventive pigments include zinc phosphate compounds, calcium phosphate compounds, aluminum phosphate compounds, magnesium phosphate compounds, zinc phosphite compounds, calcium phosphite compounds, aluminum phosphite compounds, Examples include strontium phosphate compounds, aluminum tripolyphosphate compounds, cyanamide zinc compounds, and borate compounds.

  Commercially available rust preventive pigments include, for example, LF Bousei CP-Z (trade name; manufactured by Kikuchi Color Co., Ltd.) as a zinc phosphate (aluminum) compound, and PROTEX YM- as a zinc phosphite (calcium) compound. 70 (trade name; manufactured by Taihei Chemical Sangyo Co., Ltd.), PROTEX YM-92NS (trade name; manufactured by Taihei Chemical Sangyo Co., Ltd.) as a zinc phosphite (strontium) compound, and K white # as an aluminum tripolyphosphate compound 84 (trade name; manufactured by Teika Co., Ltd.), and cyanamide zinc compounds include LF Bousei ZK-32 (manufactured by Kikuchi Color Co., Ltd.).

  Examples of the other pigments include metal powders (excluding molybdenum powders and molybdenum alloy powders), zinc compound powders (excluding zinc phosphate compounds, zinc phosphite compounds, and cyanamide zinc compounds). And at least one inorganic powder selected from mineral powders and inorganic compound powders that generate pyrolysis gas.

  The metal powder has conductivity and has an effect of facilitating the movement of iron ions and zinc ions to enhance the rust prevention effect of the coating film. Examples of the metal powder include Fe—Si powder, Fe—Mn powder, Fe—Cr powder, magnetic iron powder, and iron phosphide. Examples of commercially available metal powders include ferrosilicon (trade name), ferromanganese (trade name), ferrochrome (trade name), iron sand powder (manufactured by Kinsei Matec Co., Ltd.), and ferrophos 2132 (Occidental Chemical Corporation). Manufactured).

The zinc compound powder is considered to have an effect of adjusting the activity of the oxidation reaction, such as the degree of ionization (production of Zn ²⁺ ) of the zinc powder and / or the zinc alloy powder (b). When the rust preventive coating composition of the present invention contains a zinc compound powder, appropriate rust preventive properties are imparted to the composition.

  Examples of the zinc compound powder include powders of zinc oxide, zinc sulfide, zinc sulfate, and the like. Commercially available products of zinc compound powder include, for example, one type of zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd.), three types of zinc oxide (manufactured by Hakusui Tech Co., Ltd., Sakai Chemical Industry Co., Ltd.), Sachtorich HD (zinc sulfide) Trade name; manufactured by Sachleben Chemie GmbH).

  Examples of the mineral powder include titanium mineral powder, silica powder, soda feldspar, potash feldspar, zirconium silicate, wollastonite, and diatomaceous earth. Commercially available mineral powders include, for example, rutile flower S, ilmenite powder, A-PAX 45M, ceramic powder OF-T, Uplite (manufactured by Kinsei Matec Co., Ltd.), silica MC-O (Maruo Calcium Co., Ltd.) Product), Barite BA (manufactured by Sakai Chemical Co., Ltd.), Radiolite (Showa Chemical Industry Co., Ltd.), and Celite 545 (manufactured by John Mannville).

The inorganic compound powder that generates pyrolysis gas is a powder of an inorganic compound that generates gas, such as CO ₂ gas or F ₂ gas, by pyrolysis, for example, thermal decomposition at 500 to 1500 ° C. The inorganic compound powder is generated from a gas generated from an organic component contained in a binder or the like in a molten pool at the time of welding a steel plate having a coating film formed from a coating composition containing the inorganic compound powder. It has the effect | action which removes a bubble from the inside of a fusion pool with the gas derived from the said inorganic compound powder. Examples of the inorganic compound powder include calcium fluoride, calcium carbonate, magnesium carbonate, and strontium carbonate. Examples of commercially available inorganic compound powders include fluorite 400 mesh (manufactured by Kinsei Matec Co., Ltd.), NS # 400 (manufactured by Nitto Flour Chemical Co., Ltd.), magnesium carbonate (manufactured by Tomita Pharmaceutical Co., Ltd.), And strontium carbonate A (Honjo Chemical Co., Ltd.).
The content of other pigments is preferably 5 to 70% by mass, and more preferably 20 to 40% by mass, when the solid content of the rust preventive coating composition is 100% by mass.

<Molybdenum and molybdenum compounds>
The rust preventive coating composition may contain one or both of molybdenum (metal molybdenum) and a molybdenum compound. These act as an antioxidant for zinc (so-called white rust inhibitor).

  From the viewpoint that the occurrence of white rust can be reduced, the rust preventive coating composition of the present invention can be used as a zinc antioxidant (so-called white rust inhibitor), either molybdenum (metal molybdenum), molybdenum compound or Both may be contained.

  Examples of molybdenum compounds include molybdenum oxides such as molybdenum trioxide, molybdenum sulfide, molybdenum halides, molybdic acid, ammonium molybdate, phosphomolybdic acid, silicomolybdic acid, alkali metal salts of molybdic acid, and alkalis of phosphomolybdic acid. Of metal salt, alkali metal salt of silicomolybdic acid, alkaline earth metal salt of molybdic acid, alkaline earth metal salt of phosphomolybdic acid, alkaline earth metal salt of silicomolybdic acid, manganese salt of molybdic acid, phosphomolybdic acid Examples include manganese salts, manganese salts of silicomolybdic acid, basic nitrogen-containing compound salts of molybdic acid, basic nitrogen-containing compound salts of phosphomolybdic acid, and basic nitrogen-containing compound salts of silicomolybdic acid.

A molybdenum compound may be used individually by 1 type, and may use 2 or more types together.
The total content of molybdenum and the molybdenum compound is preferably 0.05 to 5.0 parts by mass, more preferably 0.1 to 3.0 parts by mass when the amount of the zinc-based powder (b) is 100 parts by mass. Part.

<Glass powder>
The rust preventive coating composition may contain glass powder. The glass powder acts as an antioxidant for zinc when the coating is heated at a high temperature, for example, 400 to 900 ° C., particularly when the glass powder has a softening point of 400 to 800 ° C.

Glass powder is generally SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , ZnO, BaO, MgO, CaO, SrO, Bi ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, PbO, A compound constituting a glass such as P ₂ O ₅ , In ₂ O ₃ , SnO, CuO, Ag ₂ O, V ₂ O ₅ , and TeO _{2 is} heated and melted at about 1000 to 1100 ° C. for a predetermined time, and after cooling, The powder is sized by a pulverizer. PbO can also be used as a compound constituting glass, but it is preferable not to use PbO because it may adversely affect the environment.

Examples of commercially available glass powders include NB122A (trade name, softening point 400 ° C.), AZ739 (trade name, softening point 605 ° C.), and PFL 20 (trade name, softening point 700 ° C.) (above, Central Glass Co., Ltd. ))). B ₂ O ₃ which is one of the components constituting glass is a glassy substance having a softening point of about 450 ° C. by itself, and can be used as glass powder. As a commercially available product of B ₂ O ₃ , for example, boron oxide (trade name; deer first grade reagent manufactured by Kanto Chemical Co., Inc.) can be mentioned.

A glass powder may be used individually by 1 type, and may use 2 or more types together.
The content of the glass powder is preferably 0.05 to 26% by mass, more preferably 0.15 to 20% by mass, and more preferably 0.5 when the solid content of the rust preventive coating composition is 100% by mass. ˜15 mass%.

<Coloring pigment>
The rust preventive coating composition may contain a color pigment for the purpose of obtaining a desired hue in the coating film. Examples of color pigments include titanium oxide, petals, carbon black, copper chrome black pigments, phthalocyanine green, and phthalocyanine blue. Examples of commercially available colored pigments include TITON R-5N (manufactured by Sakai Chemical Industry Co., Ltd.), Petal No. 404 (manufactured by Morishita Valve Industrial Co., Ltd.), Mitsubishi Carbon Black MA100 (manufactured by Mitsubishi Chemical Co., Ltd.), Dipiroxide Black # 9510 (manufactured by Dainichi Seika Kogyo Co., Ltd.), Heliogen Green L8690 (BASF Japan Co., Ltd.) And FASTOGEN Blue 5485 (manufactured by DIC Corporation).

A color pigment may be used individually by 1 type, and may use 2 or more types together.
The content of the color pigment is preferably 0.08 to 8.0% by mass, more preferably 0.15 to 7.0% by mass, when the solid content of the rust preventive coating composition is 100% by mass.

<Additives>
The rust preventive coating composition may contain an additive. Additives are materials used to improve or maintain the performance of paints and coatings. Examples of the additive include an antisettling agent, a curing accelerator, a drying agent, a fluidity adjusting agent, an antifoaming agent, a dispersant, a color separation preventing agent, an antiskinning agent, a plasticizer, and an ultraviolet absorber. It is done. An additive can be used individually by 1 type or in combination of 2 or more types.

Examples of the anti-settling agent include organic bentonite-based, polyethylene oxide-based, fumed silica-based, and amide-based agents. Commercially available anti-settling agents include, for example, TIXOGEL MPZ (trade name; manufactured by BYK Additives GmbH), BENTONE HD (trade name; manufactured by Elementis Specialties, Inc.), Dispalon 4200-20 (trade name), and Dispalon A630-20X. (Trade name) (supplied by Enomoto Kasei Co., Ltd.) and AEROSIL 200 (trade name; manufactured by Nippon Aerosil Co., Ltd.). One type of anti-settling agent may be used alone, or two or more types may be used in combination.
The content of the additive is preferably 0.1 to 3.0% by mass, more preferably 0.3 to 2.5% by mass, in the rust preventive coating composition.

<Anti-rust paint composition>
The rust preventive coating composition of the present invention is preferably a primary rust preventive paint composition.
The rust preventive coating composition is usually a first component (A) containing the siloxane-based binder (a) (also referred to as “main agent component”) and zinc-based, which are accommodated so as not to contact each other. A rust preventive paint having a second component (B) containing powder (b) (also referred to as “paste component”) (that is, a two-component rust preventive paint) is prepared, and the first component ( It is prepared by mixing A) and the second component (B).

  The ratio between the first component (A) and the second component (B) is the content of the siloxane-based binder (a) in the first component (A), the zinc component in the second component (B). Although it is not unconditionally determined depending on the content of the powder (b), etc., when the total of the first component (A) and the second component (B) is 100% by mass, the first component (A) is usually 10%. -80 mass%, Preferably it is 20-70 mass%, and the 2nd component (B) is 20-90 mass% normally, Preferably it is a ratio used as 30-80 mass%.

Details, such as a preferable aspect of each component contained in the said 1st component (A) and the said 2nd component (B), are as above-mentioned.
The amount of the siloxane-based binder (a) in the first component (A) is usually 5 to 20% by mass, preferably 10 to 20% by mass in terms of the mass of SiO ₂ as described above. If it is in the range, the storage stability of the first component (A) is excellent.

  The first component (A) usually contains the solvent described above. The first component (A) may contain at least one component selected from the other binders, water, catalysts, and additives described above.

  The said 1st component (A) can be prepared by mixing each component by a conventionally well-known method. Further, as described above, the first component (A) containing the siloxane-based binder (a) may be prepared from the raw material of the siloxane-based binder (a).

  The amount of the zinc-based powder (b) in the second component (B) (the amount of the second component (B) is 100% by mass, the same applies hereinafter) is usually 30 to 80% by mass, preferably Is 40-70 mass%.

  The second component (B) usually contains the solvent described above. The second component (B) may contain at least one component selected from the group consisting of the other pigments described above, molybdenum or a molybdenum compound, glass powder, a color pigment, and an additive.

Said 2nd component (B) can be prepared by mixing each component by a conventionally well-known method.
In addition to the first component (A) and the second component (B), the rust preventive coating composition of the present invention further includes a third component (C) in order to increase the degree of freedom of color matching at the painting site. You may have.

  The third component (C) contains the color pigment, and if necessary, one or more selected from other pigments, glass powder, molybdenum, molybdenum compounds, additives, solvents, and the like. May further be contained.

(Effects of manufacturing method of steel sheet with rust preventive coating)
As described above, the production method of the present invention is capable of producing a steel sheet having a rust-proof coating film that is easy to suppress the occurrence of whitening with excellent curing and drying properties, and has a low absolute humidity. It is particularly useful when producing a steel sheet with a rust-preventing coating film under many circumstances such as in winter when the temperature is low (for example, 5 ° C. or less).

  Conventionally, steel sheets coated with an inorganic zinc primary rust-preventive paint composition containing a siloxane-based binder and zinc powder are painted when transported to the outdoors within a short time (within approximately 20 minutes) after painting. When the applied steel sheet is wetted by rain or the like, whitening may occur. However, according to the manufacturing method of the present invention, the steel sheet with a rust-preventing coating film is outdoors within 20 minutes after application of the rust-preventive coating composition. With anti-corrosion coating that is easy to suppress whitening of the anti-corrosion coating even when it is exposed to liquid water within 20 minutes after application of the anti-corrosion coating composition Steel sheets can be manufactured.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.
The raw materials used in Examples and the like are as follows.
・ Alkyl silicate “ethyl silicate 40”: manufactured by Colcoat Co., Ltd. ・ spherical zinc powder “F-2000”: manufactured by Honjo Chemical Co., Ltd. ・ Anti-settling agent “TIXOGEL MPZ”: manufactured by BYK Additives GmbH, potash feldspar “ceramic powder OF” -T ": manufactured by Kinsei Matech Co., Ltd./Coloring pigment" Carbon Black MA-100 ": manufactured by Mitsubishi Chemical Corporation

[Preparation Example 1]-Preparation of main component-
13.20 parts by weight of ethyl silicate 40, 2.40 parts by weight of ethanol, 1.90 parts by weight of deionized water, 0.020 parts by weight of 35% hydrochloric acid, 0.020 parts by weight of 50% zinc chloride aqueous solution The mixture was placed in a container and the resulting raw material mixture was stirred at 65 ° C. for the time shown in Table 1, 16.46 parts by mass of isopropyl alcohol and 6.00 parts by mass of methyl ethyl ketone were added, and the siloxane binder (a) ( Main component (A-1) containing alkyl silicate condensate) was prepared.
Moreover, except having changed the stirring time of the mixture containing ethylsilicate 40 grade | etc., As shown in Table 1, operation similar to the above was performed and the main ingredient components (A-2)-(A-4) were prepared.

<Molecular weight of alkyl silicate condensate (Mw)>
The weight average molecular weight (Mw) of the siloxane binder (a) in the main component was measured by gel permeation chromatography (GPC).
The measurement conditions for GPC are as follows. A small amount of the main ingredient component was taken and diluted with tetrahydrofuran, and the resulting solution was filtered through a membrane filter to obtain a GPC measurement sample.
・ Apparatus: 2695 Separation Module manufactured by Japan Waters
(Aliance GPC multi-system)
Column: TSKgel Super H4000 manufactured by Tosoh Corporation
TSKgel Super H2000
・ Eluent: Tetrahydrofuran (THF)
・ Flow rate: 0.6 ml / min ・ Detector: Shodex RI-104
-Column temperature chamber: 40 ° C
Standard material: polystyrene Table 1 shows the measurement results.

[Preparation Example 2] -Preparation of paste components-
7.92 parts by weight of xylene as organic solvent, 3.96 parts by weight of butyl acetate and 3.96 parts by weight of isobutyl alcohol, 0.12 parts by weight of carbon black MA-100 as a coloring pigment, 15.56 parts by weight of pigment A portion of potash feldspar (ceramic powder OF-T) and 0.48 parts by mass of TIXOGEL MPZ as an anti-settling agent were charged in a polyethylene container, glass beads were added, and the mixture was shaken for 2 hours with a paint shaker. Next, 28 parts by mass of F-2000 was added as spherical zinc powder, and the mixture was further shaken for 5 minutes to disperse the pigment component. Thereafter, the glass beads were removed using an 80-mesh net to prepare a paste component.

[Preparation Example 3] -Preparation of primary rust preventive coating composition-
40 parts by mass of the main ingredient component (A-1) and 60 parts by mass of the paste component were charged in a polyethylene container and subjected to a dispersion treatment with a high-speed disper for 10 minutes to prepare a primary rust preventive coating composition (1). .
In addition, the main component (A-1) is changed to 40 parts by mass of each main component (A-2) to (A-4) and the same operation as described above is performed, and the primary rust preventive coating composition (2) to ( 4) were prepared respectively.

<Evaluation of pot life>
After the primary rust preventive paint composition prepared by the same method as in Preparation Example 3 was allowed to stand indoors (23 ° C.) for 3 days in an opening system, the state of skinning in the primary rust preventive paint composition was confirmed. The degree was evaluated in the following three stages.
3 points: Skinning is not recognized.
2 points: Slight skinning is observed.
1 point: Skinning is clearly recognized.

[Examples and Comparative Examples]
(A) Manufacture of steel plate with anticorrosive coating and evaluation of whitening resistance and antirust property Steel plate previously set to the steel plate temperature shown in Table 2 (sandblasted plate (JIS G3101, SS400, dimensions: 150 mm × 70 mm × 2 3 mm)) under the conditions of air temperature, humidity, absolute humidity and dew point shown in Table 2, each primary rust preventive coating composition was applied so that the dry film thickness was 15 μm. The coating film was cured until the above-described curing and drying time was reached while maintaining the conditions of humidity and humidity, and a steel plate with a rust-proof coating film was produced. The steel plate temperature was measured using a digital surface thermometer (manufactured by Anritsu Keiki Co., Ltd., product name HFT-40) immediately before the rust preventive coating composition was applied to the steel plate.
The whitening resistance and rust resistance of each steel sheet with a rust preventive coating film were evaluated as follows. The results are shown in Table 2.

(1) Whitening resistance After dropping several drops of tap water on the coating film surface of each steel sheet with anticorrosion coating immediately after production, and then allowing the steel sheet to stand for 12 hours, the appearance of the coating film where tap water was dropped Was visually evaluated, and the degree of whitening of the part was evaluated in the following five stages.
5 points: no whitening is observed 4 points: very slight whitening is observed 3 points: slight whitening is observed 2 points: whitening is observed 1 point: clear whitening is observed

(2) Rust prevention at the point where water contacted in the whitening resistance test The steel plate with a rust-proof coating film that was evaluated for the above-mentioned whitening resistance was installed horizontally at an outdoor exposure test site, and the coating film was covered for 3 months. During that time, tap water was constantly applied. On the surface of the test plate, the ratio of the area of the portion rusted in the area to which the tap water contacted in the above-described evaluation of whitening resistance (hereinafter referred to as “rusting area ratio”) (%) Was measured to evaluate the state of rusting. The evaluation criteria are as follows.
10 points: No rusting or rusting area ratio is 0.01% or less 9 points: Rusting area ratio exceeds 0.01% and 0.03% or less 8 points: Rusting area ratio is 0.03% Exceeding 0.1% or less 7 points: Rust area ratio exceeds 0.1% and 0.3% or less 6 points: Rust area ratio exceeds 0.3% and 1% or less 5 points: Rust area ratio 1% to 3% or less 4 points: Rust area ratio exceeds 3% to 10% or less 3 points: Rust area ratio exceeds 10% to 16% or less 2 points: Rust area ratio exceeds 16% to 33% % Or less 1 point: Rust area ratio exceeds 33% and 50% or less

(B) Manufacture of steel plate with rust preventive coating and evaluation of curing and drying properties Under the conditions of air temperature, humidity, absolute humidity and dew point temperature shown in Table 2, each primary rust preventive paint composition was cold rolled steel plate (JIS G3141, SPCC-SB, dimension: 150 mm × 70 mm × 0.8 mm) was applied so that the dry film thickness was 15 μm, and then the above-described curing and drying time was measured.
The shorter the curing and drying time, the better the curing and drying property. The results are shown in Table 2.

Claims (8)

The temperature difference between the steel sheet temperature and the dew point temperature (steel sheet temperature-dew point temperature) (° C.) is (−12 Ln (absolute humidity (g / m ³ )) + 25) ° C. or 1 ° C., whichever is the lower temperature. An anticorrosive coating composition containing a siloxane-based binder (a) having a weight average molecular weight (Mw) of 5,000 or more and zinc powder and / or zinc alloy powder (b) on a steel sheet under temperature conditions The manufacturing method of the steel plate with a rust prevention coating film apply | coated and then hardened.   The manufacturing method of the steel plate with a rust-proof coating film of Claim 1 which is a steel plate with a rust-proof coating film which the said steel plate with a rust-proof coating film is exposed outdoors within 20 minutes after application | coating of the said rust-proof coating composition. .   The manufacturing method of the steel plate with a rust prevention coating film of Claim 1 or 2 which is a rust prevention coating film which the said rust prevention coating film contacts with liquid water within 20 minutes after application | coating of the said rust prevention coating composition.   The manufacturing method of the steel plate with a rust prevention coating film as described in any one of Claims 1-3 implemented under the temperature of 5 degrees C or less. The temperature difference is (−12 Ln (absolute humidity (g / m ³ )) + 25) ° C. or 10 ° C., whichever is lower, the rust preventive coating according to claim 1. Manufacturing method of steel sheet with film.   The method for producing a steel sheet with a rust-proof coating film according to any one of claims 1 to 5, wherein the siloxane-based binder (a) has a weight average molecular weight (Mw) of 5,000 to 10,000.   The rust-proof coating film according to any one of claims 1 to 6, wherein the siloxane-based binder (a) is a condensate of at least one compound selected from the group consisting of alkyl silicates and methyltrialkoxysilanes. A manufacturing method of a steel sheet with a plate.   The manufacturing method of the steel plate with an antirust coating film as described in any one of Claims 1-7 whose said antirust coating composition is a primary antirust coating composition.

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