JPWO2017159430A1 - Resin-coated steel material and method for producing the same - Google Patents

Abstract

  The resin-coated steel material includes a steel material, a primer layer on the surface of the steel material, a urethane resin layer on the surface of the primer layer, and a topcoat layer on the surface of the urethane resin layer. The urethane resin layer contains a castor oil derivative having 2.7 or more hydroxyl groups per molecule, an organic composition having 2.0 hydroxyl groups per molecule, and a urethane resin obtained by polymerizing isocyanate. The top coat layer includes an acrylic urethane resin.

Description

The present invention relates to a steel material (resin-coated steel material) coated with urethane resin and a method for producing the same.
This application claims priority on March 16, 2016 based on Japanese Patent Application No. 2006-052696 for which it applied to Japan, and uses the content for it here.

  A heavy anticorrosion coating using a thick urethane resin coating of 2 mm or more is applied to steel pipe piles, steel pipe sheet piles, and steel sheet piles used in severe marine corrosive environments from the viewpoint of reliability of corrosion resistance. Urethane resin coating is generally a non-solvent spray coating of a two-component polyurethane resin composition prepared by mixing a main agent containing various polyols and a curing agent mainly composed of an aromatic isocyanate. Formed with. Since this urethane elastomer composition has a high viscosity and a high curing speed, a thick coating of 2 mm or more can be achieved by a single coating. Therefore, the urethane resin composition can be applied not only to steel pipe piles but also to steel materials having complicated shapes, such as steel pipe sheet piles and steel sheet piles. A highly reliable anticorrosion layer is required to prevent the wrinkles from reaching the steel material even when wrinkles occur in the anticorrosion layer. The highly reliable anticorrosion layer has a thick urethane resin coating excellent in impact resistance. A heavy anticorrosion coating method using this urethane resin coating is a standard anticorrosion method in Japan. Urethane resin-coated steel materials are mainly produced in factories because they require surface treatment, painting equipment, and painting technology.

  Urethane resin is generally not a resin with good weather resistance. For this reason, it is difficult to color the urethane resin other than black in a corrosive environment. If carbon black is added to the urethane resin, a black urethane resin is obtained, and the deterioration of the urethane resin due to ultraviolet rays is suppressed by the carbon black. Therefore, even if the urethane resin is deteriorated by ultraviolet rays and the urethane resin coating is worn out, the ratio of the depth of wear to the total thickness of the urethane resin film is sufficiently small. Therefore, conventionally, it has been considered that if a black urethane resin coating is applied to the surface of a steel material, the steel material can be sufficiently prevented by the urethane resin coating. However, it has also been found that the amount of wear may be greater in the tidal and splash zones of structures in the actual marine environment than estimated by conventional laboratory tests. In addition, there is a growing need for offshore structures in environments where it is estimated that resin degradation is severe, such as in tropical environments. Therefore, a new measure for preventing the deterioration of the resin has become necessary.

  Generally, in order to improve the weather resistance of a urethane resin, an ultraviolet absorber or an antioxidant is added to the urethane resin. However, since the urethane resin is a thermosetting resin, it is difficult for the additive to move inside the resin. Therefore, the effect that an additive prevents deterioration of urethane resin is small.

  In the field of general coating, a coating on a steel material is used not only to protect the steel material from corrosion but also to impart a predetermined design (appearance) to the steel material. In order to give a design, a top coat colored in a color different from that of the lower layer is easily used. In order to maintain the design for a long period of time, the top coat is required not to be discolored by ultraviolet rays. For this reason, a fluorine-based or silicon-based topcoat is recognized as an excellent topcoat with little discoloration because bonds between molecules are not easily broken by ultraviolet rays.

  As another top coat, Patent Document 1 discloses a method of coating a colored acrylic urethane resin having the same color as the colored urethane resin on the surface of the colored urethane resin in order to maintain the design for a long period of time. In the method of Patent Document 1, both resins are colored in a color other than black, and weather resistance (fading resistance) is emphasized. Therefore, the polyurethane elastomer coating layer contains an aliphatic isocyanate which is inferior in corrosion resistance but has high weather resistance.

  Patent Document 2 discloses a method of forming an acrylic urethane resin layer on an anticorrosion layer containing a urethane resin in order to prevent discoloration of the resin. In Patent Document 2, the weather resistance of acrylic urethane resin coating is confirmed by an accelerated weather resistance test using a sunshine weather meter. In addition, a polymer polyol such as a hydroxyl-terminated polybutadiene is used as an essential component of the polyurethane resin.

  Patent Document 3 discloses a method of applying a colored coating film other than black on the black urethane elastomer layer at a position higher than the tidal zone. In the method of Patent Document 3, an excellent aesthetic appearance can be maintained for a long time by the colored coating film.

  However, in the top coats disclosed in Patent Documents 1 to 3 above, when the resin-coated steel material is used as a material for an offshore structure, the resin coating cannot protect the steel material for a long period of time.

Japanese Unexamined Patent Publication No. 63-183838 Japanese National Publication No. 63-13826 Japanese Unexamined Patent Publication No. 8-27826

  The purpose of the present invention is to prevent deterioration and wear of the urethane resin coating even when it is used as a material for a structure for a long period of time in the ocean, and the urethane resin coating that allows the urethane resin to continue to prevent corrosion of steel. It is to provide steel. Another object of the present invention is to provide a method for producing such a heavy anticorrosion urethane resin-coated steel material.

  The gist of the present invention is as follows.

  (1) A resin-coated steel material according to an aspect of the present invention includes a steel material, a primer layer on the surface of the steel material, a urethane resin layer on the surface of the primer layer, and a top coat on the surface of the urethane resin layer. The urethane resin layer includes an inorganic pigment containing carbon black, and a urethane resin having a urethane bond composed of a constituent atom of a hydroxyl group of a polyol and an isocyanate group of an isocyanate, and the topcoat layer is made of carbon black. And an acrylic urethane resin, and the polyol contains a castor oil derivative having 2.7 or more hydroxyl groups per molecule and an organic composition having 2.0 hydroxyl groups per molecule, , Diphenylmethane diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate The carbon black contains at least one selected from the group consisting of a derivative and a toluene diisocyanate derivative. In the urethane resin layer, the mass obtained by subtracting the mass of the isocyanate from the mass of the urethane resin layer is defined as the mass of the main agent. The mass of the main agent is 0.2 to 5.0% of the mass of the main pigment, the mass of the inorganic pigment subtracted from the mass of the carbon black is 10 to 60% of the mass of the main agent, and the castor oil derivative. Is 10 to 70% of the mass of the main agent, and in the top coat layer, the mass of the carbon black is 0.2 to 5.0% of the mass of the top coat layer.

  (2) A method for producing a resin-coated steel material according to an aspect of the present invention includes: applying a primer on a surface of a steel material to form a primer layer; and a liquid mixture comprising a main agent and a curing agent on the surface of the primer layer. The liquid mixture is cured to form a urethane resin layer, an acrylic urethane resin paint containing carbon black is applied to the surface of the urethane resin layer, and the acrylic urethane resin paint is cured to form a topcoat layer. The main component includes an inorganic pigment containing carbon black and a polyol, and the curing agent is composed of diphenylmethane diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate derivative, and toluene diisocyanate derivative. Including at least one selected from the group, Riol includes a castor oil derivative having 2.7 or more hydroxyl groups per molecule and an organic composition having 2.0 hydroxyl groups per molecule, wherein the mass of carbon black is the mass of the main agent. 0.2% to 5.0%, the mass obtained by subtracting the mass of the carbon black from the mass of the inorganic pigment is 10% to 60% of the mass of the main agent, and the mass of the castor oil derivative is the mass of the main agent. In the acrylic urethane resin paint, the mass of the carbon black is 0.2 to 5.0% of the mass of the acrylic urethane resin paint.

  According to the above aspect of the present invention, since the top coat layer protects the urethane resin layer from the ultraviolet ray and water even in an environment exposed to ultraviolet rays and water such as the ocean, the urethane resin layer prevents the steel material from corrosion over a long period of time. Can do. Therefore, according to the above aspect of the present invention, it has high durability even under conditions exposed to water, such as the ocean, particularly in the region from the tidal zone to the mid-sea that is affected by both ultraviolet rays and moisture. A resin coating can be provided. Therefore, according to the said aspect of this invention, the low-cost structure which has high durability on the conditions exposed to water, such as the ocean, can be comprised.

It is the schematic of the partial cross section of the resin-coated steel material which concerns on one Embodiment of this invention. It is a figure which shows the relationship between the ratio with respect to the mass of the main ingredient of the mass of the castor oil derivative (1st polyol) which has a 2.7 or more hydroxyl group per molecule, and a composite cycle test result.

  The present inventor has studied a method for preventing wear of the urethane resin due to ultraviolet rays, water, etc., and maintaining the durability of the heavy anticorrosion coating over a long period of time. First, the inventor formed a thin film protective layer for improving the weather resistance on the surface of the urethane resin layer as the means. As the thin film protective layer, the present inventor used an acrylic urethane resin that is considered to have high adhesion to the urethane resin layer. Since the curing speed of the urethane resin layer was fast, the top coat (thin film protective layer) was applied after the urethane resin layer was cured. However, the urethane resin-coated steel material obtained by this method cannot prevent the resin from corrosion over a long period of time. As a result of studying the reason by the present inventors, it has been found that it is difficult to stably obtain sufficient adhesion to the urethane resin layer of the top coat layer of the urethane-coated steel material.

  Moreover, since the purpose of the conventional top coat was to impart a design to the steel as described above, little study was made on the adhesion of the top coat to the urethane resin. In particular, the relationship between multiple factors (eg, UV and water) and adhesion in an actual environment has not been recognized. For example, a fluorine-based or silicon-based modified resin has lower adhesion to a urethane resin than a general acrylic urethane resin. However, since the adhesiveness of these modified resins in the short period in the air is sufficient for ordinary applications, the adhesiveness has hardly been discussed.

  The inventor examined the reason why the adhesion of the topcoat layer to the urethane resin layer is not sufficient even if the topcoat layer contains an acrylic urethane resin. The acrylic urethane resin is bonded to the lower layer mainly by hydrogen bonding due to molecular polarity and a throwing effect due to surface irregularities. Therefore, the number of chemical bonds is relatively small between the acrylic urethane resin and the lower layer. In this case, moisture easily enters between the acrylic urethane resin and the lower layer. Therefore, even if the acrylic urethane resin has sufficient adhesion to the lower layer in the atmosphere, the adhesion of the acrylic urethane resin to the lower layer easily decreases in water. Therefore, the present inventor has studied a method in which the surface of the urethane resin layer can form a chemical bond with the acrylic urethane resin even after the urethane resin layer is cured with respect to the chemical component of the urethane resin.

  The urethane bond is formed by the hydroxyl group (—OH) of the polyol in the main agent and the isocyanate group (—NCO) of the curing agent. Therefore, the present inventor has studied a method of leaving these functional groups, which are considered to be able to adhere the acrylic urethane resin to the urethane resin layer by urethane bonds, on the surface of the urethane resin layer. Since the isocyanate group easily reacts with water in the air, it is difficult to remain on the surface of the urethane resin layer. The hydroxyl group (—OH) is usually small on the surface of the urethane resin after curing of the urethane resin, but does not react with water in the air. Therefore, the present inventor has studied a method of leaving the hydroxyl group of the polyol in the main agent on the surface of the urethane resin layer, particularly from the viewpoint of chemical components. As a result, the present inventors can sufficiently secure the adhesion of the acrylic urethane resin to the urethane resin layer when using a urethane resin containing an appropriate amount of castor oil-based polyol having 2.7 or more hydroxyl groups per molecule. I found out that I can do it. By this method, the adhesion of the topcoat layer containing the acrylic urethane resin to the urethane resin layer was sufficient, and the present inventors further conducted a method in which ultraviolet rays hardly reach the interface between the topcoat layer and the urethane resin layer. investigated.

  Hereinafter, a resin-coated steel material according to an embodiment of the present invention will be described in detail.

  FIG. 1 is a schematic view of a partial cross section (one side) of a resin-coated steel material according to the present embodiment. As shown in FIG. 1, the resin-coated steel material 5 includes a steel material 1, a primer layer 2 on the surface of the steel material 1, a urethane resin layer 3 on the surface of the primer layer 2, and a surface of the urethane resin layer 3. A top coat layer 4. The resin layer 6 including the primer layer 2, the urethane resin layer 3, and the top coat layer 4 is formed on at least one surface of the steel material 1. That is, the resin layer 6 may be formed on both surfaces of the steel material 1. Further, the resin layer 6 may be formed on the entire surface of the steel material 1.

(Steel 1)
The steel type (chemical composition), shape, dimensions, and product category of the steel material 1 are not particularly limited. As will be described later, since the resin layer 6 has particularly excellent durability in a severe corrosive environment such as the ocean, the steel material 1 is preferably a product that needs to be protected against corrosion for a long period of time. For example, the steel material 1 is preferably a large steel product such as a steel pipe, a steel pipe pile, a steel pipe sheet pile, or a steel sheet pile. For example, the thickness of the steel material 1 may be 5 mm to 50 mm. The steel type of the steel material 1 may be plain steel or high alloy steel. The resin layer 6 can be applied to the steel material 1 of any steel type. For example, the surface layer of the steel material 1 may be ordinary steel, high alloy steel, or a non-ferrous metal such as a plating metal.

(Primer layer 2)
In order to firmly bond the resin layer 6 to the steel material 1, the resin-coated steel material 5 includes the primer layer 2. Therefore, the chemical composition and thickness of the primer layer 2 are not particularly limited as long as the primer layer 2 has affinity for both the steel material 1 and the urethane resin layer 3. For example, the primer layer 2 may include at least one selected from the group consisting of a urethane resin and an epoxy resin. For example, the primer layer 2 may have a thickness of 10 to 200 μm.

(Urethane resin layer 3)
In order to prevent the steel material 1 from corrosion, the resin-coated steel material 5 includes a urethane resin layer 3. The urethane resin layer 3 includes an inorganic pigment containing carbon black and a urethane resin. The urethane resin is a component atom (that is, urethane) of a hydroxyl group (—OH) of a polyol (eg, HO—R ₁ —OH) and an isocyanate group (—NCO) of an isocyanate [diisocyanate] (eg, OCN—R ₂ —NCO). Each bond has a urethane bond (—NHCOO—) composed of one nitrogen atom, one carbon atom, one hydrogen atom, and two oxygen atoms. This urethane bond, a urethane resin, a polyol having a molecular skeleton (R ₁₎ with an isocyanate of the molecular skeleton (R ₂₎ and are coupled. In this embodiment, in order to clarify the standard of the mass in the urethane resin layer 3, the mass obtained by subtracting the mass of the isocyanate (total mass of atoms supplied from the isocyanate) from the mass of the urethane resin layer 3 is the main agent (main resin). ) Mass.

(Carbon black in urethane resin 3)
The urethane resin layer 3 contains carbon black (CB) as one of inorganic pigments. Since carbon black absorbs ultraviolet rays well, it protects the urethane resin layer 3 from ultraviolet rays and enhances the weather resistance of the urethane resin layer 3. In order to sufficiently protect the urethane resin layer 3 from ultraviolet rays while uniformly dispersing the carbon black in the urethane resin layer 3, the mass of the carbon black is 0.2 to 5.0% of the mass of the main agent. is necessary. When the mass of the carbon black is less than 0.2% of the mass of the main agent, the weather resistance of the urethane resin layer 3 is not sufficient. Further, when the mass of the carbon black is more than 5.0% of the mass of the main agent, the carbon black aggregates in the urethane resin layer 3.

(Inorganic pigment in the urethane resin layer 3 (excluding carbon black))
Except for carbon black, the material of the inorganic pigment is not particularly limited. An inorganic pigment is selected according to the characteristics required for the urethane resin layer 3. For example, when an inorganic pigment is selected as an extender, the inorganic pigment includes an oxide mineral such as clay, pearlite, kaolin, kaolin clay, montmorillonite, talc, alumina ore. Clay and pearlite contain silicon oxide (silica), kaolin, kaolin clay and montmorillonite contain aluminum silicate, and talc contains magnesium silicate. Therefore, for example, the inorganic pigment contains an oxide, and the oxide may be silicon oxide (silica) or silicate (silicate). When the inorganic pigment contains an oxide mineral, the strength of the urethane resin layer 3 increases, and the anticorrosion performance of the urethane resin layer 3 increases, while the adhesion of the urethane resin layer 3 to the topcoat layer 4 decreases. Therefore, the mass of the inorganic pigment excluding carbon black (the mass obtained by subtracting the mass of carbon black from the mass of the inorganic pigment) needs to be 10 to 60% of the mass of the main agent. This mass is preferably 15 to 50% of the mass of the main agent. When the mass of the inorganic pigment excluding carbon black is less than 10% of the mass of the main agent, the strength of the urethane resin layer 3 is not sufficient. Further, when the mass of the inorganic pigment excluding carbon black is more than 60% of the mass of the main agent, the adhesion of the urethane resin layer 3 to the top coat layer 4 is not sufficient. For example, when the inorganic pigment mainly contains silica, the specific gravity of the inorganic pigment is often 2.6 to 2.7. Further, the shape of the inorganic pigment is not particularly limited. For example, the inorganic mineral may be a ground oxide mineral.

(Urethane resin in urethane resin layer 3)
The urethane resin includes a molecular skeleton (R ₁ ) of polyol, a molecular skeleton (R ₂ ) of isocyanate, and a urethane bond (—NHCOO—). The urethane resin is a group consisting of an unreacted hydroxyl group (—OH), an unreacted isocyanate group (—NCO), a functional group derived from a hydroxyl group other than a urethane bond, and a functional group derived from an isocyanate group other than a urethane bond. It may optionally include at least one selected from The molecular skeleton of the polyol is a partial structure (skeleton) obtained by removing a hydroxyl group from the polyol. The molecular skeleton of isocyanate is a partial structure (skeleton part) obtained by removing isocyanate groups from isocyanate. These partial structures vary depending on the types of polyol and isocyanate.

  When three or more hydroxyl groups bonded to one polyol molecule are used for urethane bonding, a three-dimensional network structure is formed around the molecular skeleton of the polyol molecule. Therefore, a polyol molecule having three or more hydroxyl groups can easily supply hydroxyl groups to the surface of the urethane resin layer 3. As a result, the greater the number of polyol molecules having three or more hydroxyl groups, the greater the number of hydroxyl groups at the interface between the urethane resin layer 3 and the topcoat layer 4 (hereinafter referred to as the upper interface). On the other hand, the three-dimensional network structure makes the urethane resin layer 3 brittle. Therefore, embrittlement caused by an increase in the number of bonds is offset by the flexibility (flexibility) of the molecular structure (molecular skeleton). The castor oil derivative having 2.7 or more hydroxyl groups (functional groups) per molecule contains a sufficient amount of polyol molecules having a flexible molecular structure to supply sufficient hydroxyl groups to the surface of the urethane resin layer 3. Therefore, the polyol according to this embodiment needs to contain a castor oil derivative (hereinafter referred to as the first polyol) having 2.7 or more hydroxyl groups (functional groups) per molecule. When the mass of the first polyol is less than 10% of the mass of the main agent, a sufficient amount of hydroxyl groups cannot be supplied to the upper interface. If the mass of the first polyol is more than 70% of the mass of the main agent, the urethane resin layer 3 is brittle because there are too many hydroxyl groups. Therefore, as shown in FIG. 2, the mass of the first polyol is 10 to 70% of the mass of the main agent. The mass of the first polyol is particularly preferably 30 to 60% of the mass of the main agent. Moreover, it is preferable that a polyol consists only of a 1st polyol and the 2nd polyol mentioned later.

  The first polyol is classified as a castor oil-based polyol. The castor oil-based polyol includes a castor oil, a transesterification product of castor oil and a polyol, an ester compound of castor oil and a polyol, and an addition compound of these with an alkylene oxide. . That is, castor oil-based polyol is a polyol that can be produced using castor oil (including castor oil-based fatty acid) as a main raw material.

  A commercially available castor oil-based polyol can be used for the first polyol. For example, URIC H series manufactured by Ito Oil Co., Ltd. is commercially available. As URIC H series corresponding to the first polyol, URIC H-30 (hydroxyl value 155 to 165 mgKOH / g, functional group number 2.7), URIC H-52 (hydroxyl value 195 to 205 mgKOH / g, functional group number 3) , URIC H-57 (hydroxyl value 85-115 mgKOH / g, functional group number 3), URIC H-73X (hydroxyl value 260-280 mgKOH / g, functional group number 3), URIC H-81 (hydroxyl value 330-350 mgKOH / g, Functional group number 3), URIC H-102 (hydroxyl value 300-340 mgKOH / g, functional group number 5), URIC H-420 (hydroxyl value 300-340 mgKOH / g, functional group number 3), URIC H-854 (hydroxyl value 205-205). 225 mg KOH / g, functional group number 3), URIC H-870 (hydroxyl value 2) 4 to 276 mgKOH / g, functional group number 3), POLYCASTOR # 10 (hydroxyl value 155 to 165 mgKOH / g, functional group number 5 to 6), POLYCASTOR # 30 (hydroxyl value 150 to 160 mgKOH / g, functional group number 5 to 6) . These castor oil-based polyols have 2.7 or more functional groups (hydroxyl groups), a flexible molecular structure, and excellent mechanical strength. Further, the upper limit of the number of functional groups in the URIC H series is about 6. Thus, since the castor oil-based polyol having a functional group of 6.0 or less is easily available, the upper limit of the number of functional groups may be 6.0. The number of functional groups (number of hydroxyl groups) of the polyol means the number of hydroxyl groups defined in JIS K 1557 and ISO 14900 and 15063.

  Castor oil-based polyols contain chemical components or derivatives derived from castor oil in the molecular skeleton of individual molecules. The main component of castor oil is fatty acid glycerides. In this glyceride, a fatty acid is bonded to the hydroxyl group of glycerol by an ester bond. Most of the fatty acids are ricinoleic acid (ricinoleic acid), and the remaining fatty acids are, for example, oleic acid, linoleic acid, linolenic acid, palmitic acid, stearic acid, and dihydroxy acid. Since the castor oil-based polyol has a chemical component derived from such castor oil, the molecular skeleton of the castor oil-based polyol imparts flexibility to the resin.

  When only two hydroxyl groups bonded to one polyol molecule are used for urethane bonding, a chain structure is formed around the molecular skeleton of the polyol molecule. Therefore, the polyol molecule having two hydroxyl groups is not restrained by the other molecules so much and increases the elongation of the urethane resin layer 3. Therefore, the polyol according to the present embodiment needs to include an organic composition (hereinafter, second polyol) having 2.0 hydroxyl groups (functional groups) per molecule. A 2nd polyol contains the polyol product described as the number of hydroxyl groups (functional group number) being 2, and a diol compound. The amount of the second polyol is not particularly limited. In order to increase the elongation of the urethane resin layer 3, the mass of the second polyol is preferably 10 to 80% of the mass of the main agent, and more preferably 20 to 60%. A 2nd polyol can be suitably selected according to the characteristic provided to the urethane resin layer 3 additionally. For example, such characteristics include flexibility and heat resistance. The specific mass of the second polyol can be determined according to this additional property. For example, at least one selected from the following groups (a) to (d) can be used as the second polyol.

  (A) A castor oil-based polyol can be used as the second polyol. Castor oil-based polyols corresponding to the second polyol include, for example, URIC H-62, URIC Y-202, URIC Y-403, URIC Y-406, and URIC Y-332. These products are manufactured by Ito Oil Co., Ltd. and have two functional groups (hydroxyl groups).

  (B) An amine polyol can be used as the second polyol. As an amine polyol corresponding to the second polyol, for example, there is a polyol obtained by adding an alkylene oxide having 2 to 4 carbon atoms to amines. Amines are classified into aromatic amines and aliphatic amines. Examples of the aromatic amine include aniline, toluenediamine, diethyltoluenediamine, and 4,4'-diamino-3,3'-diethyldiphenylmethane. The aromatic amine may be an aromatic monoamine or an aromatic polyamine. Aliphatic amines include ethylenediamine, hexamethylenediamine, and diethylenetriamine. The aliphatic amine may be an aliphatic polyamine. Examples of the alkylene oxide having 2 to 4 carbon atoms include ethylene oxide and propylene oxide. An example of a compound of an amine and an alkylene oxide having 2 to 4 carbon atoms is N, N-bis (2-hydroxypropyl) aniline.

(C) Polybutadiene polyol can be used as the second polyol. Examples of the polybutadiene polyol corresponding to the second polyol include Poly bd ^™ R-45HT and Poly bd ^™ R-15HT. These products are manufactured by Idemitsu Kosan Co., Ltd. and have two functional groups (hydroxyl groups).

  (D) An alkylene diol can be used as the second polyol. The alkylene diol corresponding to the second polyol may have, for example, a branched saturated hydrocarbon or a linear saturated hydrocarbon. Specific alkylene diols having a branched saturated hydrocarbon include, for example, 2-methyl-1,3-propanediol (freezing point: −91 ° C.), 2-methyl-1,4-butanediol (freezing point: −30). ° C or lower), 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, and the like. Moreover, as a specific alkylene diol having a linear saturated hydrocarbon, for example, 1,3-propanediol can be mentioned.

  The second polyol according to this embodiment may be at least one selected from the group consisting of (a) castor oil-based polyol, (b) amine polyol, (c) polybutadiene polyol, and (d) alkylene diol. . That is, a single compound, a single product, and a mixture can be used for the second polyol according to this embodiment.

  The isocyanate according to this embodiment may be at least one selected from the group consisting of diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), diphenylmethane diisocyanate derivative (MDI derivative), and toluene diisocyanate derivative (TDI derivative). . MDI and TDI are aromatic diisocyanates and have two isocyanate groups. The MDI derivative and the TDI derivative include an MDI oligomer and a TDI oligomer. For example, the isocyanate according to the present embodiment includes monomeric MDI, polymeric MDI, modified isocyanate, pure TDI isomer, isomer mixture of TDI, and blended isocyanate. In addition, as products manufactured by Tosoh Corporation, Millionate MT series (monomeric MDI product), Millionate MR series (polymeric MDI product), Coronate series (polyol-modified isocyanate product), Millionate MTL series (MDI carbodiimide-modified product), Coronate T-80 / T-65 / T-100 (TDI product) and their blended isocyanates (mixed products of MDI and TDI). Further, as products manufactured by BASF INOAC Polyurethane Co., Ltd., Luplanate MS and MI (monomeric MDI products), Luplanate M20S, M11S, M5S (polymeric MDI products), MM-103, MP-102, MB-301 (modified MDI products) ), Lupranate T-80 (TDI product). For the isocyanate according to this embodiment, a mixture of the above products may be used.

  The ratio of the amount of isocyanate according to this embodiment to the amount of polyol according to this embodiment is defined by the number (total number) of isocyanate groups that the isocyanate has relative to the number (total number) of hydroxyl groups that the polyol has. The ratio of the number of isocyanate groups (—NCO) to the number of hydroxyl groups (—OH) (—NCO / —OH) is preferably in the range of 0.9 to 1.2. If this ratio is 0.9 or more, the urethane resin layer 3 has sufficient hardness. When the ratio (-NCO / -OH) is 1.2 or less, the urethane resin layer 3 has good quality in density. A preferred range of the ratio (—NCO / —OH) is 1.0 to 1.1.

(Other chemical components in urethane resin layer 3)
The urethane resin layer 3 may include a chemical component derived from at least one selected from the group consisting of a reaction accelerator, a water absorbent (humidifier), a thixotropic agent, a flame retardant, and a plasticizer as other chemical components. Good.

  As the reaction accelerator, for example, an amine compound or a metal catalyst can be used. Examples of the amine compound include triethylenediamine, bis (2-dimethylaminoethyl) ether, and N, N, N ′, N′-tetramethylhexamethylenediamine. Examples of the metal catalyst include dioctyltin dilaurate and stannous octoate.

  A zeolite compound is preferably used as the water absorbing agent. For example, there are Zeolum A-3, A-4, and F-9 manufactured by Tosoh Corporation as powdery zeolite compounds.

  As the thixotropic agent, for example, Aerosil which is dry silica manufactured by Nippon Aerosil Co., Ltd. can be used.

  As the flame retardant, antimony trioxide, aluminum hydroxide, tetrabromophenyl ether, tris (chloropropyl) phosphate (TCPP), or the like can be used.

  As the plasticizer, carboxylic acid esters such as phthalic acid esters, adipic acid esters, and sebacic acid esters can be used. Such carboxylic acid esters include, for example, dibutyl phthalate (DBP), dioctyl phthalate (DOP), diisodecyl phthalate (DIDP), dioctyl adipate (DOA), trioctyl trimetate (TOTM), tricresyl phosphate ( TCP). In particular, the plasticizer is preferably diisononyl adipate (DINA) or diisononyl phthalate (DINP).

(Thickness of urethane resin layer 3)
The thickness of the urethane resin layer 3 is not particularly limited. When the thickness of the urethane resin layer 3 is 2 mm or more, the urethane resin layer 3 has sufficient weather resistance and corrosion resistance. Moreover, the internal stress in the urethane resin layer 3 can be reduced as the thickness of the urethane resin layer 3 is 5 mm or less, and the peeling resistance in low temperature can be provided to the urethane resin layer 3. Therefore, the thickness of the urethane resin layer 3 is preferably 2 to 5 mm.

(Essential structure related to chemical components of urethane resin layer 3)
Therefore, the urethane resin layer 3 according to the present embodiment includes an inorganic pigment containing carbon black (CB) and a urethane resin having a urethane bond composed of a constituent atom of a hydroxyl group of a polyol and an isocyanate group of an isocyanate. In the present embodiment, the polyol is a castor oil derivative (first polyol) having 2.7 or more hydroxyl groups (functional groups) per molecule and an organic compound having 2.0 hydroxyl groups (functional groups) per molecule. And a composition (second polyol). In the present embodiment, the isocyanate includes at least one selected from the group consisting of diphenylmethane diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate derivatives, and toluene diisocyanate derivatives. Furthermore, in the urethane resin layer 3 according to the present embodiment, when the mass obtained by subtracting the mass of isocyanate from the mass of the urethane resin layer 3 is defined as the mass of the main agent, the mass of carbon black is 0.2-5. The mass obtained by subtracting the mass of carbon black from the mass of the inorganic pigment is 10 to 60% of the mass of the main agent, and the mass of the castor oil derivative is 10 to 70% of the mass of the main agent.

(Topcoat layer 4)
In order to protect the urethane resin layer 3 from ultraviolet rays and water, the resin-coated steel material 5 includes a top coat layer 4. The top coat layer 4 includes carbon black and an acrylic urethane resin. The acrylic urethane resin is a urethane bond composed of a hydroxyl group (—OH) of an acrylic polyol (eg, HO—R ₃ —OH) and an isocyanate group (—NCO) of an isocyanate (eg, OCN—R ₄ —NCO). (-NHCOO-). By this urethane bond, in the urethane resin, the molecular skeleton (R ₃ ) of polyol and the molecular skeleton (R ₄ ) of isocyanate are bonded.

(Carbon black in the top coat layer 4)
The top coat layer 4 contains carbon black. Since carbon black absorbs ultraviolet rays well, it protects the urethane resin layer 3 and the topcoat layer 4 from ultraviolet rays and enhances the weather resistance of the urethane resin layer 3 and the topcoat layer 4. In order to sufficiently protect the urethane resin layer 3 from ultraviolet rays, the mass of the carbon black needs to be 0.2 to 5.0% of the mass of the top coat layer 4. When the mass of the carbon black is less than 0.2% of the mass of the top coat layer 4, the ultraviolet rays pass through the top coat layer 4 and reach the upper interface. Therefore, deterioration of the urethane resin layer 3 in the vicinity of the upper interface cannot be suppressed. Further, when the mass of the carbon black is more than 5.0% of the mass of the top coat layer 4, the carbon black aggregates in the top coat layer 4. In this case, even if the mass of the carbon black is further increased, the intensity of the ultraviolet rays transmitted through the top coat layer 4 is hardly changed. Moreover, since the topcoat layer 4 contains carbon black, the surface of the resin-coated steel material 5 is black.

(Acrylic urethane resin in top coat layer 4)
The acrylic urethane resin includes an acrylic polyol molecular skeleton (R ₃ ), an isocyanate molecular skeleton (R ₄ ), and a urethane bond (—NHCOO—). The acrylic urethane resin is composed of an unreacted hydroxyl group (—OH), an unreacted isocyanate group (—NCO), a functional group derived from a hydroxyl group other than a urethane bond, and a functional group derived from an isocyanate group other than a urethane bond. At least one selected from the group may optionally be included. The molecular skeleton of acrylic polyol is a partial structure (skeleton) obtained by removing hydroxyl groups from acrylic polyol. The molecular skeleton of isocyanate is a partial structure (skeleton part) obtained by removing isocyanate groups from isocyanate. These partial structures change according to the kind of acrylic polyol and isocyanate.

  The molecular skeleton of the acrylic polyol imparts weather resistance to the topcoat layer 4. For the acrylic polyol of the present embodiment, a copolymer of a methacrylate monomer or an acrylate ester and an unsaturated monomer (ethylenically unsaturated monomer) having a hydroxyl group and a double bond can be used. Examples of the methacrylate monomer include methyl methacrylate and ethyl methacrylate. Examples of the acrylate ester include methyl acrylate and ethyl acrylate. Examples of the unsaturated monomer having a hydroxyl group and a double bond include hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, and hydroxypropyl acrylate. The copolymerization method may be a known method.

  A commercially available acrylic polyol can be used for said acrylic polyol. For example, there are Takelac UA-702, Takelac UA-902, Takelac UA-905, etc., as acrylic polyols manufactured by Takeda Pharmaceutical Company Limited.

  The isocyanate group of the isocyanate is chemically bonded to the hydroxyl group of the urethane resin layer 3 at the upper interface. This chemical bond (urethane bond) increases the adhesion between the urethane resin layer 3 and the topcoat layer 4. The isocyanate according to this embodiment may be a prepolymer produced from an aliphatic isocyanate. Examples of the aliphatic isocyanate include xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), and hexamethylene diisocyanate (HDI). Further, for example, the prepolymer may include a compound obtained by adding an aliphatic isocyanate to a polyether polyol. Further, for example, a polyether polyol is a polyalkylene polyol having 2 to 3 active hydrogen groups (hydroxyl groups) in one molecule obtained by polymerizing an alkylene oxide to the polyol in the presence of an alkali catalyst or the like. May be. Examples of the polyol used for this polymerization include propylene glycol, butanediol, neopentyl glycol, hexanediol, glycerin, and trimethylolpropane. Moreover, as an alkylene oxide used for superposition | polymerization, a propylene oxide, ethylene oxide, a butylene oxide, etc. are mentioned. By adding an aliphatic isocyanate to the polyalkylene polyol, a urethane prepolymer having an aliphatic isocyanate at the terminal can be produced. In this embodiment, such a urethane prepolymer can be used. In this embodiment, 1,6-hexamethylene diisocyanate homopolymer that can be produced from HDI can be used. When the topcoat layer 4 includes a molecular skeleton of such an aliphatic isocyanate-derived compound (aliphatic isocyanate derivative), the color of the topcoat layer 4 is not easily changed to yellow by ultraviolet rays. Therefore, in the topcoat layer 4, it is preferable that the molecular skeleton of the aliphatic isocyanate is larger than the molecular skeleton of the aromatic isocyanate. Examples of the aromatic isocyanate include diphenylmethane diisocyanate (MDI) and toluene diisocyanate (TDI).

  In order to further improve the weather resistance, the top coat layer 4 may contain an ultraviolet absorber or a light stabilizer. For example, a hindered amine light stabilizer can be used as the light stabilizer. As this hindered amine light stabilizer, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, 8-benzyl -7,7,9,9-tetramethyl-3-octyl 1,3,8-triazaspiro [4,5] undecane-2,4-dione.

  As a product containing bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, Sanol LS-292 and Sanol LS-765 manufactured by Sankyo Co., Ltd. can be used. Sankyo LS-770 manufactured by Sankyo Co., Ltd. can be used as a product containing bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate. Furthermore, as a product containing 8-benzyl-7,7,9,9-tetramethyl-3-octyl-1,3,8-triazaspiro [4,5] undecane-2,4-dione, Sanol LS manufactured by Sankyo Co., Ltd. -1114 is available.

(Thickness of top coat layer 4)
The thickness of the top coat layer 4 is not particularly limited. When the thickness of the top coat layer 4 is 30 μm or more, the strength of the top coat layer 4 is sufficient, and the weather resistance of the resin-coated steel material 5 can be more reliably improved. In order to reduce the cost, the thickness of the topcoat layer 4 may be 100 μm or less. Therefore, the thickness of the top coat layer 4 is preferably 30 to 100 μm.

(Essential configuration related to chemical components of topcoat layer 4)
Therefore, the topcoat layer 4 according to this embodiment includes carbon black and an acrylic urethane resin. In the top coat layer according to this embodiment, the mass of carbon black is 0.2 to 5.0% of the mass of the top coat layer 4.

(Effect of the resin-coated steel material 5 according to this embodiment)
In the resin-coated steel material 5 according to the present embodiment, since the number of chemical bonding points (the number of strong bonds) at the interface between the urethane resin layer 3 and the topcoat layer 4 is large, water enters the interface. The adhesion between the urethane resin layer 3 and the top coat layer 4 can be maintained even under conditions of exposure to water such as the ocean. Further, since the top coat layer 4 protects the urethane resin layer 3 from ultraviolet rays and water, the urethane resin layer 3 can prevent the steel material 1 from corrosion over a long period of time. Therefore, it is not necessary to form the urethane resin layer 3 extremely thick. As a result, the resin-coated steel material 5 according to the present embodiment can provide a low-cost structure having high durability under conditions exposed to water such as the ocean.

  Moreover, when actually constructing a steel pipe pile, the depth at which the pile is driven is changed for each normal construction. At a position higher than the splash band, the adhesion between the resins is easily maintained for a long time, but at a position lower than the tidal band, the adhesion between the resins decreases in a short period of time. In the resin-coated steel material 5 according to the present embodiment, the adhesion between the urethane resin layer 3 and the topcoat layer 4 can be maintained even at a position lower than the tidal zone. Therefore, in the resin-coated steel material 5 according to the present embodiment, it is not necessary to consider the area to which the resin layer 6 or the topcoat layer 4 is applied. Therefore, the resin-coated steel material 5 according to the present embodiment is suitably used for steel pipe piles. can do.

  Below, the manufacturing method of the resin-coated steel material which concerns on one Embodiment of this invention is demonstrated in detail.

(Primer application)
First, a primer layer is formed by applying a primer on the surface of a steel material (primary treatment). For example, a two-component mixed type urethane resin or epoxy resin can be used for the primer. The lower the viscosity of the primer, the easier it is to adapt to the irregularities on the steel surface. Therefore, the primer is preferably a solvent-type primer having a low viscosity. The application method may be spray coating. Further, it is preferable that the primer is applied on the surface of the steel material so that the thickness of the primer layer is 10 to 200 μm. In order to enhance the adhesion between the primer layer and the urethane resin layer as much as possible, blasting using sand, alumina, grid, or shot may be performed before applying the primer to the surface of the steel material. By this blasting process, scales and contaminants on the surface of the steel material can be removed. Moreover, the steel materials described in the embodiments according to the resin-coated steel materials can be used as the steel materials according to the present embodiment.

(Application of main agent and curing agent)
Next, a liquid mixture comprising a main agent and a curing agent is applied on the surface of the primer layer, and the liquid mixture is cured to form a urethane resin layer. For example, the liquid mixture may be prepared by premixing the main agent and the curing agent, and this liquid mixture may be applied onto the surface of the primer layer by spraying. Moreover, it is preferable to apply the liquid mixture on the surface of the primer layer so that the thickness of the urethane resin layer is 2 to 5 mm. In this case, the thickness of the liquid mixture is a few mm. The liquid mixture is a two-component solventless paint.

  The liquid mixture according to this embodiment is a two-component polyurethane resin composition composed of a main agent and a curing agent, and urethane polymerization is started by mixing the two components. The main agent contains an inorganic pigment containing carbon black (CB) and a polyol. The polyol is a castor oil derivative having a hydroxyl group (functional group) of 2.7 or more per molecule (hereinafter referred to as a first polyol) and an organic composition having 2.0 hydroxyl groups per molecule (hereinafter referred to as a second polymer). Polyol). The first polyol is a polyol that can be derived from castor oil as a raw material. The mass of the first polyol is 10 to 70% of the mass (total mass) of the main agent. The mass of the inorganic pigment excluding carbon black is 10 to 60% of the mass of the main agent. The mass of carbon black is 0.2 to 5.0% of the main agent. The polyol is preferably composed of only the first polyol and the second polyol. The curing agent includes at least one selected from the group consisting of diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), diphenylmethane diisocyanate derivative (MDI derivative), and toluene diisocyanate derivative (TDI derivative).

  In this embodiment, the inorganic pigment described in the embodiment according to the resin-coated steel material can be used as the inorganic pigment. Also in this embodiment, the mass of the inorganic pigment excluding carbon black is 10 to 60% of the mass of the main agent. When the mass of the inorganic pigment is reduced, the viscosity of the main agent can be reduced, and thus the coating efficiency can be increased. Moreover, when the mass of the inorganic pigment is increased, the strength of the urethane resin layer can be increased. Therefore, the mass of the inorganic pigment excluding carbon black may be 15 to 50% of the mass of the main agent.

  In this embodiment, the 1st polyol described in embodiment which concerns on said resin-coated steel materials can be used as a 1st polyol. Also in this embodiment, the mass of the first polyol is 10 to 70% of the mass of the main agent. The mass of the first polyol is particularly preferably 30 to 60% of the mass of the main agent. The upper limit of the number of hydroxyl groups in the first polyol may be 6.0. The number of functional groups (number of hydroxyl groups) of the polyol means the number of hydroxyl groups defined in JIS K 1557 and ISO 14900 and 15063.

  In this embodiment, the 2nd polyol described in embodiment which concerns on said resin-coated steel materials can be used as a 2nd polyol. Also in this embodiment, the mass of the second polyol is preferably 10 to 80% of the mass of the main agent, and more preferably 20 to 60% of the mass of the main agent.

  In this embodiment, the isocyanate in the urethane resin layer 3 described in embodiment concerning said resin-coated steel material can be used as isocyanate. Also in this embodiment, the ratio of the number of isocyanate groups (—NCO) derived from isocyanate to the number of hydroxyl groups (—OH) derived from polyol (—NCO / —OH) is in the range of 0.9 to 1.2. It is preferable to mix the main agent and the curing agent (that is, isocyanate) so as to be. As the amount of curing agent increases, the amount of foaming in the liquid mixture increases. On the other hand, when the amount of the curing agent decreases, there is a possibility that the curing amount is insufficient when the isocyanate reacts with moisture in the air. Therefore, the ratio (-NCO / -OH) may be 1.0 to 1.1 in order to further increase productivity or yield.

  In the present embodiment, as other chemical components in the main agent, other chemical components described in the embodiment relating to the resin-coated steel material can be used. That is, the main agent may contain a chemical component derived from at least one selected from the group consisting of a reaction accelerator, a water absorbing agent, a thixotropic agent, a flame retardant, and a plasticizer.

(Application of acrylic urethane resin paint)
Finally, an acrylic urethane resin paint containing carbon black (CB) is applied on the surface of the urethane resin layer, and the acrylic urethane resin is cured to form a topcoat layer. For example, a solvent-type acrylic polyol containing carbon black (main component of acrylic urethane resin paint) and isocyanate (curing agent of acrylic urethane resin paint) are mixed in advance to prepare an acrylic urethane resin paint, and this acrylic urethane resin paint May be applied onto the surface of the urethane resin layer by spraying. Moreover, it is preferable to apply an acrylic urethane resin paint on the surface of the urethane resin layer so that the thickness of the topcoat layer is 30 to 100 μm. In this acrylic urethane resin paint, the mass of carbon black is 0.2 to 5.0% of the mass of the acrylic urethane resin paint. In addition, the dispersibility in the acrylic urethane resin coating material of carbon black is so high that the quantity of carbon black is small.

  The acrylic resin paint contains acrylic polyol and isocyanate in addition to carbon black. In the present embodiment, the acrylic polyol described in the embodiment relating to the resin-coated steel material can be used as the acrylic polyol. Moreover, the isocyanate in the topcoat layer 4 described in embodiment which concerns on said resin-coated steel material can be used as isocyanate. The acrylic resin paint may contain an ultraviolet absorber or a light stabilizer as an optional chemical component. In this embodiment, the light stabilizer described in the embodiment according to the resin-coated steel material can be used as the light stabilizer.

  In addition, since a by-product is not produced in urethane polymerization, the mass of the main agent in the present embodiment is equivalent to the mass of the main agent in the embodiment according to the resin-coated steel material. Moreover, the mass of the acrylic urethane resin paint in this embodiment is equivalent to the mass of the topcoat layer 4 of the embodiment according to the above resin-coated steel material. Thus, in both embodiments, it can be considered that the weight of each chemical component is not changed by urethane polymerization.

  In the method for producing a resin-coated steel material according to the present embodiment, it is possible to provide a resin-coated steel material capable of preventing the steel material from being corroded for a long time by the urethane resin layer even under conditions exposed to water such as the ocean.

1) Preparation procedure and evaluation method of test plate 1 to 22 test plates were prepared and evaluated according to the following procedures.
Grit blasting was performed on the surface of a 6 × 100 × 150 mm steel plate, and rust was removed until the degree of rust removal was Sa2 · 1/2 or more. For the base treatment, PG331 urethane primer manufactured by Daiichi Kogyo Seiyaku was used as a commercially available primer of urethane resin composition. This urethane primer was applied to the surface of the steel plate using a spray, and a primer layer having a thickness of 30 μm was formed on the surface of the steel plate. Three hours later, a urethane resin coating was applied on the surface of the primer layer using a high-pressure spray coating machine to form a urethane resin layer having a thickness of 2 to 5 mm. The high-pressure spray coating machine is prepared by mixing the main agent and curing agent (curing agent / main agent) with a mixer so that the ratio of -NCO number to -OH number (-NCO / -OH) is 1.1. Supplied urethane resin paint. On the next day, a top coat paint was applied with a cup gun (spray) to form a top coat layer having a thickness of 30 to 100 μm. This top coat paint was prepared by previously mixing the main agent and the curing agent with a stirrer.

  The obtained test plate was cured for one week and then cut to a size of 75 × 150 mm. The back and side surfaces of the cut test plate were sealed with an epoxy resin. A seawater immersion test at 40 ° C. specified in ISO 20340 and a combined cycle test for 175 days were performed on the test piece after sealing. In the combined cycle test, a combination (cycle) of a wet weathering test for 3 days by QUV, a cooling to −20 ° C. for 1 day, and a salt spray for 3 days is repeated. For each test piece after the test (initial adhesion), after the seawater immersion test, and after the combined cycle test, the adhesion of the topcoat layer to the urethane resin layer was measured using a dolly having a diameter of 20 mm (test cylinder). Evaluation was performed with a pull-off tester. With respect to this evaluation result, a test piece having an adhesion strength of 5 MPa or more was judged to be good, and a test piece having an adhesion strength of less than 5 MPa was judged to be defective.

2) Main component of urethane resin paint In Nos. 1 to 17, a castor oil-based polyol (hereinafter referred to as the first polyol) having 2.7 or more hydroxyl groups per molecule was used as one of the main components of the urethane resin layer (urethane resin paint). No. In Nos. 1 to 14, URIC H-30 (hydroxyl value: 155 to 165 mgKOH / g, functional group number: 2.7) manufactured by Ito Oil Co., Ltd. was used as the first polyol. No. In 15-17, URIC H-57 (hydroxyl value 85-115 mgKOH / g, functional group number 3) made from Ito Oil Co., Ltd. was used as a 1st polyol. No. In 1-17, the mass of the 1st polyol was 5 to 80% of the mass of the main ingredient.

No. In Nos. 1 to 18, a polyol having 2.0 hydroxyl groups per molecule (hereinafter referred to as a second polyol) was used as one of the main components of the urethane resin layer. No. In Nos. 1 to 5 and 18, URIC Y-403 (hydroxyl value 150 to 170 mgKOH / g, functional group number 2) manufactured by Ito Oil Co., Ltd., which is a representative example of castor oil-based polyol, was used as the second polyol. No. In 7 to 11, 3-methyl-1,5-pentanediol, which is a representative example of a diol-based polyol, was used as the second polyol. No. In Nos. 12 to 14, N, N-bis (2-hydroxypropyl) aniline, which is a typical example of an aromatic amine-based polyol, was used as the second polyol. No. In 15 to 18, Poly bd ^™ R-15HT manufactured by Idemitsu Kosan Co., Ltd., which is a representative example of a polybutadiene-based polyol, was used as the second polyol. No. In 1-5 and 7-18, the mass of the 2nd polyol was 11-81% of the mass of the main ingredient. No. 18 uses two types of second polyols.

Furthermore, no. In Nos. 1 to 18, an inorganic pigment was used as one of the main components of the urethane resin layer. No. In 1 to 11 and 13 to 18, carbon black (CB) was used as one of inorganic pigments (ultraviolet resistant color pigments). The mass of this carbon black was 0.5 to 5.0% of the mass of the main agent. No. In 1-6 and 8-18, clay was used as one of the inorganic pigments (inorganic extender pigments). The mass of this clay was 10 to 60% of the mass of the main agent. No. In Nos. 1 to 18, Zeorum A-4 (Zeolite) manufactured by Tosoh Corporation was used as a hygroscopic agent, hexabromobenzene was used as a flame retardant, and diisononyl phthalate was used as a plasticizer. Further, as other chemical components, a curing catalyst (dioctyltin dilaurate) and a thixotropic agent (Aerosil # 200 manufactured by Nippon Aerosil Co., Ltd.) were used.
The main agent was prepared by mixing the above main agent components.

3) Urethane resin paint curing agent In 1-14 and 18, Millionate MR-200 manufactured by Tosoh Corporation was used as the polymeric MDI (Cr-MDI) (curing agent). No. In 15-17, CORONATE T-100 made by Tosoh Corporation was used as TDI (curing agent).

6) Top coat paint In Nos. 1 to 6, nax mighty rack G-2 (acrylic urethane (1)) manufactured by Nippon Paint Co., Ltd. was used as the top coat layer (top coat paint). No. In 7-15 and 18, Hardtop XP (acrylic urethane (2)) manufactured by Jotun was used as the topcoat layer. These two types of paints are general acrylic urethane resin paints, in which an acrylic polyol (main agent), 1,6-hexamethylene diisocyanate homopolymer (HDI isocyanate curing agent), a colored paint and a light stabilizer are mixed. ing. No. In 1 to 15 and 18, carbon black was used as the colored paint, and the mass of the carbon black was 0.5% of the top coat paint. No. In No. 16, Hardtop XP (acrylic urethane (3)) manufactured by Jotun was used as the topcoat layer. This No. In No. 16, a blue paint was used as the colored paint. No. In No. 17, Duflon 100 (fluorine-based paint) manufactured by Nippon Paint Co., Ltd. was used.

7) No. 19-22
No. 19 is a reproduction test corresponding to the invention example (second line of Table 1) disclosed in Patent Document 1. No. 20 is a reproduction test corresponding to Example 1 disclosed in Patent Document 2. No. 21 is a test in which carbon black was added to the acrylic urethane paint of Example 1 disclosed in Patent Document 2. No. 22 is a reproduction test corresponding to the example disclosed in Patent Document 3.

No. In 19-22, the following polyol was used as a main ingredient component. No. In No. 19, NIPPOLLAN 141 (hydroxyl value: 102 to 108 KOHmg / g) manufactured by Tosoh Corporation was used as the polyester polyol. No. In 20 to 22, Poly bd ^™ R-45HT manufactured by Idemitsu Kosan was used as the polybutadiene polyol. No. In 20 and 21, N, N bis (2-hydroxypropyl) aniline was used as the aromatic amine-based polyol.
No. In 19-22, the following MDI was used as a hardening | curing agent. No. In 19 and 22, Millionate MT manufactured by Tosoh Corporation was used as MDI. No. In 20 and 21, Millionate MR-100 manufactured by Tosoh Corporation was used as crude MDI (Cr-MDI).
Furthermore, no. In 19-22, Zeolum A-4 manufactured by Tosoh Corporation was used as the zeolite, and dioctyl phthalate was used as the plasticizer.
For top coat paint, In 19-21, Nippon Paint's Hypon 50 topcoat was used as an acrylic urethane paint (acrylic urethane). No. In No. 22, Duflon 100 was used as the fluorine-based paint (fluorine). As described above, No. 21, carbon black is added to the Hypon 50 overcoat.

No. Tables 1 to 3 show the experimental conditions and evaluation results of 1 to 18. An underlined number or letter in the columns of Tables 1 and 3 indicates that the conditions according to the present invention are not satisfied.
No. In 2-5, 8-10, and 13-15, in order to satisfy | fill the conditions which concern on this invention, the test plate was excellent in the adhesiveness with respect to the urethane resin layer of a topcoat layer also in a water environment. Therefore, these test plates were excellent in initial adhesion, and maintained sufficient adhesion even after both tests in a water environment and a combined environment of ultraviolet light and water. On the other hand, no. In No. 7, the test plate did not have sufficient initial adhesion. No. In 1, 11, 17, and 18, the test plate could not maintain sufficient adhesion after the immersion test and the combined cycle test. No. In 6, 12, and 16, the test plate could not maintain sufficient adhesion after the combined cycle test. No. In No. 7, it is considered that the physical properties of the urethane resin were lowered during curing. No. In 1, 11, 17, and 18, it is considered that water entered the interface between the top coat layer and the urethane resin layer, and the bond at the interface between the urethane resin layer and the top coat layer was broken. No. In Nos. 6, 12 and 16, it is considered that ultraviolet rays were transmitted through the top coat layer and the interface between the top coat layer and the urethane resin layer was significantly deteriorated.

  No. Tables 4 and 5 show the experimental conditions and evaluation results of 19-22. No. In Nos. 19 to 22, the urethane resin layer did not contain a chemical component derived from a castor oil-based polyol having 2.7 or more hydroxyl groups per molecule, so that the test plate had sufficient adhesion after the immersion test and the combined cycle test. Could not be maintained. In particular, no. In No. 20, since neither a color pigment nor carbon black was added to the top coat layer, the surface of the urethane resin layer was greatly deteriorated, and the top coat layer was easily peeled off from the urethane resin layer.

  Disclosed is a resin-coated steel material and a method for producing the same, in which the resin coating can protect the steel material over a long period of time even under severe corrosive environments such as the ocean.

DESCRIPTION OF SYMBOLS 1 Steel material 2 Primer layer 3 Urethane resin layer 4 Topcoat layer 5 Resin coated steel material 6 Resin layer

Claims (2)

Steel,
A primer layer on the surface of the steel material;
A urethane resin layer on the surface of the primer layer;
A topcoat layer on the surface of the urethane resin layer;
With
The urethane resin layer includes an inorganic pigment containing carbon black, and a urethane resin having a urethane bond composed of a constituent atom of a hydroxyl group of a polyol and an isocyanate group of an isocyanate,
The top coat layer includes carbon black and an acrylic urethane resin,
The polyol includes a castor oil derivative having 2.7 or more hydroxyl groups per molecule and an organic composition having 2.0 hydroxyl groups per molecule,
The isocyanate includes at least one selected from the group consisting of diphenylmethane diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate derivative, toluene diisocyanate derivative,
In the urethane resin layer, when the mass obtained by subtracting the mass of the isocyanate from the mass of the urethane resin layer is defined as the mass of the main agent, the mass of the carbon black is 0.2 to 5.0% of the mass of the main agent. The mass obtained by subtracting the mass of the carbon black from the mass of the inorganic pigment is 10 to 60% of the mass of the main agent, and the mass of the castor oil derivative is 10 to 70% of the mass of the main agent.
In the top coat layer, the mass of the carbon black is 0.2 to 5.0% of the mass of the top coat layer. Apply a primer on the surface of the steel material to form a primer layer,
Applying a liquid mixture composed of a main agent and a curing agent on the surface of the primer layer, curing the liquid mixture to form a urethane resin layer,
Applying an acrylic urethane resin paint containing carbon black on the surface of the urethane resin layer, curing the acrylic urethane resin paint to form a topcoat layer,
The main agent contains an inorganic pigment containing carbon black and a polyol,
The curing agent includes at least one selected from the group consisting of diphenylmethane diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate derivative, toluene diisocyanate derivative,
The polyol includes a castor oil derivative having 2.7 or more hydroxyl groups per molecule and an organic composition having 2.0 hydroxyl groups per molecule,
In the main agent, the mass of carbon black is 0.2 to 5.0% of the mass of the main agent, and the mass obtained by subtracting the mass of the carbon black from the mass of the inorganic pigment is 10 to 60% of the mass of the main agent. And the mass of the castor oil derivative is 10 to 70% of the mass of the main agent,
In the said acrylic urethane resin coating material, the mass of the said carbon black is 0.2 to 5.0% of the mass of the said acrylic urethane resin coating material, The manufacturing method of the resin-coated steel material characterized by the above-mentioned.

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