JP2003053262A - Method for coating polyamide resin-coated steel material and steel material coated by the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a means for making it possible to easily form a coating film having a good adhesiveness on a highly hydrophobic film when the surface of the film of a polyamide resin-coated steel material is over-coated for the purpose of repair coating of a damaged area, coloring and the like. SOLUTION: The surface of the film of the polyamide resin-coated steel material is directly coated with a composition containing as essential components (A) an epoxy resin or polyol resin, (B) an amine based compound or polyisocyanate based compound, and (C) an aromatic oligomer as a surface modifying agent for reducing surface tension, or this composition is applied as a primer, and the surface thereof is top-coated with a coloring coating, an antifouling coating, an algae-resistant coating or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to chemically bond a defective surface of a polyamide resin coating of a pipe or a member coated with a polyamide resin, that is, a portion where peeling of a partial coating or a pinhole occurs. The present invention relates to a coating method for repairing a polyamide resin-coated steel material capable of maintaining the anticorrosion property, the scenic property, etc. originally possessed by the polyamide resin coating by forming the coating film.

Further, according to the present invention, when the surface of a polyamide resin film having poor wettability and poor coatability is overcoated for the purpose of coloring, antifouling, algae prevention, etc., it is chemically bonded to the surface of the polyamide resin. The present invention relates to a method for coating a polyamide resin-coated steel material capable of easily forming an overcoat coating film having good adhesion and a uniform film thickness by interposing a primer layer, and a polyamide resin-coated steel material coated by this method.

[0003]

2. Description of the Related Art Repair of polyamide resin coated steel pipes applied to plant pipes, water pipe bridges, etc. is done by a soldering iron method for small pinholes, and if large pinholes or damaged parts occur, they must be repainted. I was in a situation where I couldn't. Therefore, there is a difficulty in repairing on-site construction, and for a long time, development of a repairing method for the coated steel material has been desired.

On the other hand, regarding the coloring of the polyamide resin-coated steel material, a variety of shades are required due to the needs of the landscape, etc. In view of the coating method, it is necessary to economically form coatings of various shades. There is a problem that it is difficult.

That is, coating of a polyamide resin on the surface of a steel material is often carried out by a fluidized-bed coating method of powder coating, but the number of fluidized-bed tanks on the manufacturing side is limited, and powder coating replacement is not possible. Directly forming coatings of various shades by the fluid immersion coating method because it greatly affects the manufacturing cost and it is not economical to prepare colored powder coatings of polyamide resins of various shades in small lots. It is difficult to do so, and an easy method of coloring a polyamide resin-coated steel material has been desired.

In the environment where the coated pipe is actually used, there is also a place where the pipe is installed in a humid place, and moss or mold may grow on the lower surface during long-term exposure of the coated pipe. In some cases, the landscape may be significantly impaired. Therefore, it has been necessary to apply an overcoat for the purpose of antifouling, algae prevention, or the like, or to reapply the surface of the coated steel material used for a certain period of time.

However, considering that the polyamide resin originally used for the anticorrosion coating has a low melting point and a low water absorption, the so-called nylon 11 and nylon are very large in the ratio of the hydrophobic portion (chain hydrocarbon portion). 12 is frequently used. Since the molecular weight of these polyamide resins is very large, from tens of thousands to hundreds of thousands, and the hydrophobic portion in the molecule is very large, the surface of the coating film may have amino groups or carboxyl groups at the ends of the polyamide resin. Regardless, it expresses strong hydrophobicity.

Therefore, it is difficult to form a new coating film on the surface of the polyamide resin-coated steel material, and the urethane-based or epoxy-based coatings that are commercially available in the past are
Since there was not sufficient wettability, the coatability was extremely poor. Therefore, in the past, the surface of the coating was roughened and covered with pseudo-adhesion, but this method also has a problem in workability, and it is possible to develop an adhesive force with long-term durability in the top coating film. There wasn't.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to repair a pinhole or damaged part of a polyamide resin-coated steel material coating film by using a repairing paint that is sufficiently wet to the highly hydrophobic coating film. The object is to provide a means capable of ensuring the adhesion of the repair coating film for a long period of time.

Another object of the present invention is to provide a primer layer having good wettability with a polyamide resin when applying a top coat on the surface of a polyamide resin-coated steel material for the purpose of coloring, antifouling, antialgae, etc. An object of the present invention is to provide a means capable of easily forming an overcoat film having good adhesion and a uniform film thickness by interposing it.

[0011]

The first method of coating a polyamide resin-coated steel material according to the present invention to solve the above-mentioned problems is to (A) epoxy resin or polyol as an essential component on the coating surface of the polyamide resin-coated steel material. A method for coating a polyamide resin-coated steel material, which comprises applying a composition containing a resin, (B) an amine compound or an isocyanate compound, and (C) an aromatic oligomer as a surface modifier for lowering the surface tension. Is.

A second method of coating a polyamide resin-coated steel material according to the present invention comprises: (A) an epoxy resin or a polyol resin, (B) an amine compound or an isocyanate compound and ( C) Applying a composition containing an aromatic oligomer as a main component as a surface modifier for lowering the surface tension as a primer, and further applying a coloring paint, antifouling paint or algae preventive paint on the surface thereof. A coating method for a polyamide resin-coated steel material, characterized in that

In the above first and second coating methods,
The aromatic oligomer is a low-viscosity xylene resin, a liquid coumarone resin, a low molecular weight petroleum resin, a liquid low-polymerization product of isopropenyltoluene, a copolymerization product of isopropenyltoluene and α-methylstyrene, and styrene, coumarone, indene, One or more selected from the group consisting of phenols, formaldehyde, or oligomers modified with phenol and formaldehyde from isopropenyltoluene, α-methylstyrenes or low molecular weight polymers or copolymers thereof, The content is (A) component 10
It is preferably 10 to 200 parts by weight with respect to 0 parts by weight.

The first of the polyamide resin-coated steel materials of the present invention is (A) epoxy resin or polyol resin, (B) amine compound or isocyanate compound, and (C) surface tension on the surface of the polyamide resin-coated steel material. A polyamide resin-coated steel material having a colored coating film containing an aromatic oligomer as a surface modifier to be reduced and (D) a coloring pigment as main components.

The second aspect of the polyamide resin-coated steel material of the present invention is that (A) epoxy resin or polyol resin, (B) amine compound or isocyanate compound and (C) surface on the coating surface of the polyamide resin coated steel material. An intermediate coating film composed mainly of an aromatic oligomer as a surface modifier for reducing tension is formed, and a surface coating film for coloring paint, antifouling paint or algae paint is formed on the surface of the intermediate coating film. Is a polyamide resin-coated steel material.

The polyamide resin-coated steel material which is the object of the present invention includes all steel materials coated with a resin (nylon resin) having an acid amide bond (-CONH-) as a repeating unit in the molecule. In particular, from the viewpoint of anticorrosion property, a steel material having a powdery coating of nylon 11 or nylon 12 having a low melting point and a low water absorption is often used, and the effect of the present invention is particularly large in these resin coatings.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram for explaining an embodiment of a coating method of the present invention, and FIGS. 1 (a) and 1 (b) are examples of an embodiment of the first coating method. 1 (c) shows an embodiment of the second coating method. In FIG. 1 (a), in the film damage portion 3 of the polyamide resin film 2 formed on the surface of the steel material 1,
(A) resin component, (B) curing agent component and (C) as essential components
It is characterized in that a composition containing an aromatic oligomer as a surface modifier for reducing the surface tension (hereinafter referred to as “polyamide resin coating material”) is applied to form a repair coating film 4.

In FIG. 1 (b), a polyamide resin coating material containing a color pigment component is applied to the entire surface of the polyamide resin coating film 2 to form a colored coating film 5. Further, in FIG. 1 (c), (A) resin component, (B) curing agent component and
(C) A composition containing an aromatic oligomer as a main component (hereinafter referred to as a “primer for polyamide resin”) is applied as a surface modifier for reducing the surface tension to form an intermediate coating film 6,
Further, the surface coating film 7 is formed on the surface thereof with a coloring paint, an antifouling paint or an algae preventing paint.

The constituents of the above coating material will be described below, but the following description is common to coating materials and primers for polyamide resins. First, the aromatic oligomer as the component (C) refers to an aromatic low-polymerization product having a number average molecular weight in the range of about 300 to 600 or a modified product thereof. Among them, a low-viscosity xylene resin, a liquid coumarone resin ,
Low molecular weight petroleum resin, liquid low-polymerization product of isopropenyltoluene, copolymerization product of isopropenyltoluene and α-methylstyrene, and styrene, coumarone, indene, isopropenyltoluene or α-methylstyrene alone or a low content thereof. It is preferable to use one or more of a phenol, formaldehyde, or an oligomer obtained by modifying the molecular weight polymer or copolymer with phenol and formaldehyde.

The amount of the surface modifier added is
It is preferably 10 to 200 parts by weight with respect to 100 parts by weight of the resin component (A). This is because if the amount is less than 10 parts by weight, sufficient adhesiveness with the polyamide resin-coated steel material cannot be obtained, and if it exceeds 200 parts by weight, the coating film strength is remarkably reduced. The more preferable amount of the (C) aromatic oligomer added is 40 to 80 parts by weight with respect to 100 parts by weight of the component (A).

As the resin component (A) which is the base component of the paint, a known polyol resin or epoxy resin is used. The polyol resin may be liquid or solid as long as it has two or more hydroxyl groups in one molecule and can react with an isocyanate compound to form a cross-linked coating film with a hydroxyl equivalent of about 100 to 2000. Can be used without. Examples of such a polyol resin include one kind or two or more kinds of epoxy modified polyol, polyester polyol, polyether polyol, acrylic polyol, chelate modified polyol, castor oil modified polyol, and the like.

Of these polyol resins, epoxy-modified polyols are preferable from the viewpoint of corrosion resistance, and specifically, bisphenol type epoxy resins and phenol novolac type epoxy resins having an epoxy equivalent of about 180 to 2200 and diethanolamine, diisopropanolamine and the like are used. Examples thereof include epoxy-modified polyols obtained by addition reaction of alkanolamines.

The epoxy resin has an epoxy equivalent of 180 which has two or more epoxy groups in one molecule and can react with an amine compound to form a crosslinked coating film.
As long as it is an epoxy resin of about 2200, liquid resin or solid resin can be used. Examples of such epoxy resins include epoxy resins such as bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, bisphenol AD-type epoxy resin and the like, special epoxy resins such as poropylene oxide-modified epoxy resin and sulfide-containing epoxy resin. Or two or more species. In addition, in order to reduce the viscosity, various reactive diluents such as monoglycidyl ether and diglycidyl ether may be used in combination.

Next, as the curing agent component (B), it is preferable to use an isocyanate compound when the paint base resin is a polyol resin and an amine compound when the paint base resin is an epoxy resin.

The isocyanate compound (hardener) is
A compound having two or more isocyanate groups in one molecule may be used, and a general-purpose type, a yellowing type (discoloring property under UV exposure), a non-yellowing type (discoloring property under UV exposure), etc. may be used. it can. First, as a general-purpose type, tolylene diisocyanate (abbreviated as TDI), isocyanurate, which is a trimer of TDI, and 4.4′-diphenylmethane diisocyanate (abbreviated as MDI), and the like can be mentioned.

Further, as the non-yellowing type, hexamethylene diisocyanate (abbreviated as HDI), isophorone diisocyanate, hydrogenated xylylene diisocyanate (X
DI) and hydrogenated MDI. Further, the above isocyanates are trimethylolpropane (T).
Adducts modified with polyhydric alcohols such as MP) or polyhydric phenols can also be used.

The amount of the isocyanate curing agent used is preferably 0.3 to 1.5 in terms of the molar ratio of isocyanate group / hydroxyl group of polyol resin,
More preferably, this molar ratio is 0.5 to 1.0.

Examples of amine compounds (curing agents) include polyamide curing agents, aliphatic or aromatic amines,
Alternatively, one or more amines such as Mannich-modified and adduct-modified, and ketimine-based curing agents may be used. The amount of amine-based curing agent used is preferably 0.5 to 1.5 in terms of amine / epoxy equivalent, and more preferably 0.5 to 1.0.

Incidentally, when an amine-based curing agent is used, the curing rate tends to be slightly lowered. In order to accelerate the curing, various curing accelerators (catalysts) or equipment such as far infrared heating equipment are used. You may adopt.

Further, in the case of a polyamide resin coating material, in addition to the above-mentioned essential components, for example, a pigment may be optionally blended with a scaly pigment, an extender pigment and a coloring pigment. Various additives such as a foaming agent, a leveling agent, and a thixotropic agent (anti-sagging agent) can be optionally blended. However, it is preferable that the amount of the essential components (A) + (B) + (C) is 30 parts by weight or more based on 100 parts by weight of all the paint components excluding the solvent.

In the case of a polyamide resin primer, in addition to the above-mentioned essential components, some pigment components and various additives such as dispersants, defoaming agents, leveling agents and thixotropic agents (anti-sagging agents) are added. Although a small amount of the agent may be blended, the content of the essential components is preferably 50 parts by weight or more based on 100 parts by weight of all the coating components excluding the solvent.

In any of the paints and primers for polyamide resins, the solvent may be, for example, an aromatic solvent such as toluene or xylene, a ketone solvent such as methyl ethyl ketone or methyl isobutyl ketone, or a fat such as ethyl acetate or butyl acetate. A group ester solvent, a mixed solvent thereof or the like can be appropriately used.

When the above-mentioned primer for polyamide resin is used, the colored coating as the top coat is not particularly limited as long as it has weather resistance. For example, generally commercially available acrylic urethane resin-based colored coating, A fluororesin-based color paint or the like can be used. Similarly,
As the top coat antifouling paint and algae preventive paint, commercially available products can be used without any problem.

The coating method of the present invention is not limited to the case where the base material of the polyamide resin coating is steel, but a polyamide resin coating is formed on the surface of metal materials other than steel, plastics, ceramics, wood materials, etc. The same can be applied to the case.

[0035]

Example 1 <Repair coating of polyamide resin coated steel> A polyamide resin powder coating (nylon 11) coating (film thickness: 300 μm) steel pipe was used on the surface of a 300A flanged steel pipe. An artificial coating film damaged portion (100 mm × 100 mm area was peeled off by a belt sander) was produced in the central portion, and then repair coating of the coating film damaged portion was performed.

With respect to the repair method, the coating material containing the components (A) to (C) (aromatic oligomer), which was essential in the present invention, was used to repair the test material of the present invention with a film thickness of 300 μm. As a comparative example, a comparative material which was repaired using a paint lacking the component (C) was prepared.

Both the material of the present invention and the comparative material were subjected to an adhesion test (immersion in warm water at 60 ° C. for 500 hours, evaluation method / pull-off test,
Measurement location / polyamide resin film-repair coating film interface and steel material-repair coating film interface). In this repair, the surface of the polyamide resin coating was not roughened with sandpaper or the like, but was tested on a smooth coating surface.

In both the material of the present invention and the comparative material, as the component (A) (hereinafter referred to as the main agent), an epoxy modified polyol was mainly used, and a bisphenol A type epoxy resin was used in part.
The component (B) (hereinafter referred to as the curing agent) is mainly MDI.
And a part of TDI, XDI, HDI, polyamide, aliphatic amine, and aromatic amine was used. Component (C) (hereinafter,
As the surface modifier), liquid coumarone resin was mainly used, and low viscosity xylene resin, low molecular weight petroleum resin, liquid low polymerization product of isopropenyltoluene, styrene oligomer and the like were mainly used.

The material of the present invention is a coating composition in which 50 parts by weight (partly 10 and 200 parts by weight) of the surface modifier is added to 100 parts by weight of the main component, and the comparative material is a surface modifier-free (partly). 5,
And 250 parts by weight) were used. Table 1 shows the test results of the composition and adhesion of the repair paint for 16 kinds of the invention materials and 10 kinds of the comparative materials in which the paint components are variously changed.

From the results shown in Table 1, in the materials of the present invention, good adhesion (⊚) was obtained both in the interface between the repair coating film, the polyamide resin coating and the steel material, both in the initial stage and after 500 hours. I know it was there. On the other hand, in the comparative material, at the interface between the repair coating film and the polyamide resin coating film, the initial adhesion was somewhat poor (△) in both cases,
The adhesion after 500 hours was poor (x).

Example 2 <Color coating of polyamide resin-coated steel material> A polyamide resin powder coating (nylon 11: white) coating (film thickness: 300 μm) steel pipe was used on the surface of a 300A flanged steel pipe, and the outer surface of this coated steel pipe was colored. It was painted. As a method of coloring coating, (A) to
A coating containing the component (C) as an essential component was applied as a primer for a colored coating with a film thickness of 30 μm, and a colored coating (acrylic urethane resin coating, fluororesin coating) was laminated with a film thickness of 50 μm.

As a comparative example, a paint containing no component (C) was applied to the above-mentioned colored polyamide resin-coated steel pipe as a primer for the colored paint with a film thickness of 30 μm, and then the colored paint (acrylic urethane resin paint) was applied in the same manner as above. ) Was laminated with a film thickness of 50 μm to obtain a colored polyamide resin-coated steel pipe.

Both the inventive material and the comparative material were tested for adhesion in the same manner as in Example 1 (immersion in warm water at 60 ° C. for 500 hours,
Evaluation method / pull-off test, measurement point / adhesion between polyamide resin coating and colored coating). During the surface treatment of the primer for colored coating this time, the surface of the polyamide resin coating was not roughened with sandpaper or the like, and a smooth coating surface was used.

The main component of the primer of the present invention material and the comparative material,
The kinds of the curing agent and the surface modifier and the amount of the surface modifier added were almost the same as in Example 1. In the material of the present invention, 16 kinds each of the acrylic urethane resin paint and the fluororesin paint were used as the coloring paint, A total of 32 types of test materials were prepared, and as a comparative material, 10 types of test materials using acrylic urethane resin paint as a coloring paint were created. Table 2 shows the test results of the primer composition, the type of the colored coating material and the adhesive force for 32 kinds of the materials of the present invention, and Table 3 shows these data for the 10 kinds of the comparative materials.

From the results shown in Table 2, in the material of the present invention, the adhesion between the colored coating film and the polyamide resin coating film was good at the initial stage and after the elapse of 500 hours regardless of whether the colored coating material was an acrylic urethane resin or a fluororesin. It is known that it was (◎). On the other hand, as shown in Table 3, in the comparative material using the primer which does not contain the component (C), the adhesive force between the colored coating film and the polyamide resin coating is somewhat poor in the initial stage (Δ), After the elapse of 500 hours, it was defective (x).

[0046]

EFFECTS OF THE INVENTION According to the present invention, it is possible to easily repair a pinhole and a film peeling portion of a polyamide resin-coated steel material,
The original long-term corrosion resistance of the polyamide resin-coated steel material can be maintained. Further, according to the present invention, it becomes possible to provide polyamide resin-coated steel materials having various colors to meet the needs of harmony with the scenery at low cost even in a small lot. Furthermore, it has become possible to easily impart new functions such as antifouling and algae to the surface of the polyamide resin-coated steel material.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view for explaining an embodiment of a coating method of the present invention, in which (a) is a case where a damaged portion of a polyamide resin coating is repaired, and (b) is a colored coating directly applied to the surface of the polyamide resin coating. In this case, (c) shows a case where the surface of the polyamide resin coating is overcoated via a primer layer.

[Explanation of symbols]

1 steel 2 Polyamide resin coating 3 coating damage 4 Repair coating film 5 Colored coating film 6 Intermediate coating 7 Surface coating

[Table 1]

[Table 2]

[Table 3]

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shoichi Kawasaki             2-11-9 Iwamotocho, Chiyoda-ku, Tokyo Sun             Iron Corrosion Protection Co., Ltd. (72) Inventor Takayuki Ashino             2-11-9 Iwamotocho, Chiyoda-ku, Tokyo Sun             Iron Corrosion Protection Co., Ltd. F-term (reference) 4D075 AE03 CA12 CA13 CA32 CA33                       CA34 CA45 CA48 DA06 DA10                       DA15 DA20 DA27 DB01 DB14                       DB21 DB53 DC05 EA07 EA41                       EB08 EB14 EB16 EB22 EB24                       EB32 EB33 EB34 EB37 EB38                       EB56 EC07 EC11 EC33 EC54                 4F100 AB03A AH03C AK02C AK46B                       AK48B AK53C AK54C AL06C                       BA04 BA07 BA10D CA13D                       CC10D GB07 JL00 JL00D                       JL01 JL06D

Claims (5)

[Claims] 1. A coating surface of a polyamide resin-coated steel material,
(A) epoxy resin or polyol resin as an essential component,
(B) amine-based compound or isocyanate-based compound and
(C) A method for coating a polyamide resin-coated steel material, which comprises applying a composition containing an aromatic oligomer as a surface modifier for reducing the surface tension. 2. A coating surface of a polyamide resin-coated steel material,
A composition containing (A) an epoxy resin or a polyol resin, (B) an amine-based compound or an isocyanate-based compound, and (C) an aromatic oligomer as a surface modifier for reducing the surface tension as a main component is applied as a primer, Further, a method for coating a polyamide resin-coated steel material, which comprises applying a coloring paint, an antifouling paint or an algae preventive paint on the surface thereof. 3. The aromatic oligomer is a low viscosity xylene resin, a liquid coumarone resin, a low molecular weight petroleum resin, a liquid low polymer of isopropenyltoluene, a copolymer of isopropenyltoluene and α-methylstyrene, and styrene. , Coumarone, indene, isopropenyltoluene, α
-One or more selected from the group consisting of phenols, formaldehyde, or oligomers obtained by modifying phenols with formaldehyde of low molecular weight polymers or copolymers of methylstyrenes or their low molecular weight polymers, and the content thereof is ( The method for coating a polyamide resin-coated steel material according to claim 1 or 2, wherein the amount is 10 to 200 parts by weight with respect to 100 parts by weight of the component (A). 4. A coating surface of a polyamide resin-coated steel material,
(A) Epoxy resin or polyol resin, (B) Amine-based compound or isocyanate-based compound, (C) Aromatic oligomer as a surface modifier for reducing surface tension, and (D) Colored coating containing a coloring pigment as a main component. A polyamide resin-coated steel material having a film formed thereon. 5. A coating surface of a polyamide resin-coated steel material,
An intermediate coating film containing (A) an epoxy resin or a polyol resin, (B) an amine compound or an isocyanate compound, and (C) an aromatic oligomer as a surface modifier for reducing the surface tension is formed. A polyamide resin-coated steel material having a surface coating film of a coloring paint, antifouling paint or algae protection paint formed on its surface.