JPH05179587A - Color coating composition for galvanized steel wire and colored galvanized steel wire for cable coated with the composition - Google Patents

Abstract

PURPOSE:To provide a color coating composition for galvanized steel wire and provide a colored galvanized steel wire for cable coated with the composition, easily applicable in site and having excellent corrosion resistance. CONSTITUTION:The objective color-coating composition for galvanized steel wire is produced by using (A) a phenoxy resin having a number-average molecular weight of 8,000-20,000 and/or a fatty acid-modified or unmodified epoxy resin having an epoxy equivalent of >=300, (B) at least one kind of curing agent selected from urea resin, melamine resin and polyisocyanate compounds and (C) a color pigment as essential components in a weight ratio {(A)+(B)}/(C) of 95/5 to 50/50. The colored galvanized steel wire for cable has a coating layer produced by applying a coating liquid containing the coating composition to a steel wire and curing the composition by baking.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a colored coating composition for galvanized steel wire and a colored galvanized steel wire for bridge cable which is easy to be installed locally and has excellent corrosion resistance.

[0002]

2. Description of the Related Art A bridge cable is exposed outdoors after the cable is erected until the bridge is completed, and corrosion protection is performed after the bridge is completed. Therefore, as cable anticorrosion measures from cable production and storage to the completion of the bridge, the cable strands are galvanized, and surface treatment (known as primary anticorrosion treatment) is performed to prevent zinc corrosion. Is going.

Chromate treatment has been performed for a long time as the primary rust preventive treatment, but since the chromate coating layer elutes due to rainfall and there is a concern that it may affect the environment, non-chromate treatment will be performed after the 1980s. It became so. As the non-chromate treatment, the treatments described in (B) JP-B-62-40473 and (B) JP-B-63-11383 are known. These anticorrosion coatings do not necessarily have sufficient corrosion resistance as compared with the above chromate treatment. In particular, since the workability and adhesion of the coating layer are not sufficient, the coating layer is damaged during the cable construction at the bridge construction site, such as peeling, and the corrosion resistance is impaired.

The bridge cable is erected for each parallel wire cable strand consisting of 127 cable strands, but a colored marked steel wire is required to prevent twisting during erection.

[0005]

By the way, the required properties of the colored steel wire for cables are corrosion resistance capable of withstanding long-term outdoor exposure, friction during drawing of the steel wire during cable construction,
The adhesiveness of the coating layer endures bending and the like, and further, it is easy to color and has a labeling property. Regarding the corrosion resistance, as the bridge lengthened, the period from the production of the steel wire for cable to the corrosion protection of the entire cable became longer, and sufficient corrosion resistance could not be obtained by the conventional non-chromate type primary rustproofing treatment.

In the coloring step, conventionally, a method of applying a coloring paint to the steel wire after the primary anticorrosion treatment has been carried out, and the treatment cannot be carried out in one step. Regarding the adhesion of the colored coating film,
The colored coating film was easily peeled off, and there was a problem as a marking steel wire.

[0007]

From the above viewpoints, the present inventors have proposed a coating composition comprising an epoxy resin having good adhesion to the surface of a galvanized steel wire as a base resin and a curing agent and a coloring pigment. By coating to a uniform thickness, by heating and drying, it was found that it is possible to form a colored coating layer excellent in corrosion resistance, workability, and adhesion, and the colored coating composition for galvanized steel wire of the present invention and We have developed a colored galvanized steel wire for cables that covers this.

The coating composition according to the invention thus comprises
(A) Phenoxy resin (i) having a number average molecular weight of 8,000 to 20,000, or epoxy resin (ii) having a fatty acid modified or unmodified epoxy equivalent of 300 or more, (B)
It contains at least one curing agent selected from a urea resin, a melamine resin and a polyisocyanate compound, (C) a color pigment, and {(A) + (B)}.
The ratio of / (C) is in the range of 95/5 to 50/50 by weight.

[0009]

The phenoxy resin (i) used as the component (A) in the present invention is a number average molecular weight of about 8,000 to 2 synthesized from bisphenol A type and epichlorohydrin.
It is 10,000 polyhydroxy polyether resin.
Such a phenoxy resin has been conventionally known, and is commercially available from Union Carbide (USA) under the brand names PKHH and the like.

As the epoxy resin (ii), bisphenol A type, bisphenol F type, novolac type,
Glycidyl ether type epoxy resin, and epoxy ester resin obtained by reacting the epoxy group and hydroxyl group in the epoxy resin with the carboxyl group in the drying oil fatty acid,
Examples include modified epoxy resins such as urethane-modified epoxy resins reacted with isocyanates, basic epoxy resins in which at least one basic nitrogen atom and at least two primary hydroxyl groups are added to the ends of the epoxy resin. You can

The curing agent used as the component (B) in the present invention is a urea resin, a melamine resin, and a polyisocyanate compound, and these can be used alone or in combination. The color pigment used as the component (C) in the present invention is most preferably a red pigment from the viewpoint of the labeling function, and other than this, yellow, blue and green color tones can be mentioned. Examples of red pigments include monoazo pigments, organic pigments such as quinalidone pigments,
Inorganic pigments such as lead molybdate / lead chromate / lead sulfate mixed crystals are used.

As the yellow pigment, a monoazo pigment, a benzimidazolone pigment, an azomethyleneazo pigment, and a lead chromate inorganic pigment are used. Copper phthalocyanine organic pigments are mainly used as blue pigments and green pigments. Further, pigments such as titanium oxide, iron oxide and carbon black are appropriately used for adjusting the lightness and saturation of the color tone.

In the present invention, the above (A) to
The weight ratio of the component (C) is {(A) + (B)} / (C),
95/5 to 50/50, preferably 80/20 to 60/4
It is necessary to blend in the range of 0. Except for the above-mentioned blending ratio, that is, when the resin component is more than the color pigment, not only the covering layer hiding power decreases but also the corrosion resistance deteriorates. On the other hand, when the amount of the color pigment is larger than that of the resin component, there is a problem that not only the gloss and smoothness of the coating film are inferior but also the adhesiveness is inferior.

In the present invention, the coating composition comprising the above-mentioned components (A) to (C) sufficiently solves the conventional problems, but when higher corrosion resistance is required, as the component (A), It is preferable to use a basic epoxy resin obtained by adding at least one basic nitrogen atom and at least two primary hydroxyl groups to the end of the epoxy resin. To introduce a basic nitrogen atom and a primary hydroxyl group into the epoxy resin, for example, a method of adding an alkanolamine to the oxirane group of the epoxy resin can be used. Examples of these alkanolamines include monoethanolamine, diethanolamine, dimethylaminoethanol, monopropanolamine, dipropanol and dibutanolamine, and these amines can be used alone or in combination.

If further corrosion resistance is required, (C)
This is accomplished by replacing some of the component color pigments with silica. The content of silica is 50% by weight of the component (C).
Hereafter, it is preferably in the range of 30% by weight or less. There are hydrophilic silica called colloidal silica and fumed silica and hydrophobic silica, and any of them can be used.

When a coating layer is formed using the coating composition of the present invention, the composition using the phenoxy resin (i) does not necessarily require a curing agent because it is a polymer itself, but the epoxy resin When using (ii), it is necessary to use a curing agent. As a curing agent, melamine, urea,
Use of a conventionally known alkyl etherified amino resin obtained by reacting a part or all of a methylol compound obtained by reacting formaldehyde with at least one selected from benzoguanamine and a monohydric alcohol having 1 to 5 carbon atoms However, when forming a coating layer using the coating composition of the present invention, it is preferable to use a polyisocyanate compound to form a urethane bond with the hydroxyl group in the base resin.

In order to stably store the coating composition of the present invention, it is necessary to temporarily protect the isocyanate group in the polyisocyanate compound used as a curing agent. As a method of protecting the isocyanate group, a protecting method in which the protecting group (blocking agent) is released during heating and the isocyanate group is regenerated can be adopted. The polyisocyanate compound is an aliphatic, decyclic (including heterocyclic) or aromatic isocyanate compound having at least two isocyanate groups in one molecule, or a compound obtained by partially reacting these compounds with a polyhydric alcohol. is there.

Examples of the blocking agent include aliphatic monoalcohols, aromatic alcohols such as phenol and cresols, oximes such as acetoxime and methyl ethyl ketone oxime, and the like. A polyisocyanate compound stably protected with is obtained. Such a blocked polyisocyanate compound is compounded as a curing agent in a ratio of 5 to 40 parts, preferably 10 to 30 parts, relative to 100 parts of the base resin (solid content).

As for the corrosion resistance of the colored coating layer formed from the colored coating composition of the present invention, it is sufficient that the thickness of the coating layer is 3 μm or more, and the effect of improving the corrosion resistance is relatively small even if the thickness is increased. Further, when the thickness of the coating layer exceeds 30 μm, the adhesion of the coating layer due to the bending process deteriorates. To coat a steel wire with a coating composition having an epoxy resin as a base resin to a thickness within the above range, the solid content in the coating composition is 15
It is necessary to prepare a coating liquid having an amount of ˜45% by weight and other components as an organic solvent, and adjust the viscosity of the coating liquid with Ford cup # 4 within a range of 15 to 80 seconds.

When the steel wire is continuously coated while traveling horizontally, a difference in the thickness of the coating layer naturally occurs between the upper surface and the lower surface of the steel wire. If the viscosity of the coating liquid is less than 15 seconds with Ford Cup # 4, the thickness of the coating layer on the upper surface cannot be kept above 3 μm, and if it exceeds 80 seconds, the thickness of the coating layer on the lower surface is 30 μm. It becomes super.

On the other hand, when the solid content concentration of the coating liquid is less than 15% by weight, it is difficult to keep the thickness of the coating layer on the upper surface of the steel wire at 3 μm or more even if the viscosity is adjusted within the above range. is there. On the other hand, if it exceeds 45% by weight, the thickness of the coating layer on the lower surface of the steel wire exceeds 30 μm even if the viscosity of the coating liquid is adjusted to the above range due to the characteristics such as the dissolving power of the organic solvent and the boiling point. The coating composition obtained by the present invention may be applied directly to a galvanized steel wire, or may be applied after being subjected to a phosphate treatment, a chromate treatment or the like. As a coating method, dip coating is usually used. The coating composition is dried at room temperature to 250 ° C.
It is performed by natural drying or heat drying at the temperature of.

[0022]

EXAMPLES The present invention will be specifically described below with reference to examples. Examples 1, 2 and 3 show the corrosion resistance with respect to the thickness of the coating layer containing a basic epoxy resin, a phenoxy resin and a fatty acid modified epoxy resin as a base resin, respectively, and Example 4 shows the solid content concentration (% by weight) of the coating liquid. ) And the viscosity of the coating liquid show the grounds for limiting numerical values.

Preparation of Resin Solution (1) Preparation of Basic Epoxy Resin Solution 1,880 g (0.5) of Epicoat 1009 (epoxy resin manufactured by Shell Chemical Co., molecular weight of about 3,750) was placed in a reactor.
Mol) and butyl cellosolve / methyl isobutyl ketone =
After adding 1,950 g of a mixed solvent of 78/22 (weight ratio), the mixture was stirred and heated to uniformly dissolve. Then, it was cooled to 70 ° C., and di (n-propanol) was collected in a liquid dropping device.
70 g of amine was added dropwise over 30 minutes. During this period, the reaction temperature was maintained at 70 ° C. After the completion of dropping, the temperature was maintained at 120 ° C. for 2 hours, and after cooling, 950 g of a mixed solvent of butyl cellosolve / methyl isobutyl ketone = 78/22 was added to terminate the reaction. The obtained reaction product is used as a basic epoxy resin solution. The active ingredient of the resin is 50%.

(2) Preparation of phenoxy resin (polyhydroxypolyether resin) solution Polyhydroxypolyether resin (phenoxy resin, trade name PKHH manufactured by Union Carbide, number average molecular weight 12,000) 200 g of cyclohexanone solvent 1
After adding 000 g, the mixture was heated to 60 ° C. and uniformly dissolved to obtain a resin solution containing 20% of active ingredient.

(3) Preparation of curing agent 222 parts of isophorone diisocyanate was placed in a reaction vessel, 100 parts of cellosolve acetate was added thereto, and the mixture was uniformly dissolved. Then 88 parts of 50% trimethylolpropane cellosolve acetate solution was added to the above-mentioned mixture. 7 from the dropping funnel
The solution was added dropwise to the stirred isocyanate solution kept at 0 ° C. over 1 hour. After that, the temperature was held at 70 ° C. for another hour and then at 90 ° C. for 1 hour. Then, 90 parts of methyl ethyl ketone oxime was added and reacted at 90 ° C. for 3 hours to obtain a blocked polyisocyanate. After cooling, 70 parts of cellosolve acetate is added, and this is designated as curing agent A. The active ingredient of the curing agent was 60%.

(Example 1) A diluting solvent having a composition of butyl cellosolve / xylene = 1/1 was used to prepare a coating liquid having a solid content of 41%. The composition of the coating liquid is shown in Table 1.

[0027]

[Table 1]

This coating solution (viscosity at 20 ° C .: 50 seconds / Ford cup # 4, heating residue: 41%) was applied to a hot-dip galvanized steel sheet (plate thickness 0.8 mm, coating weight 90 g / m ² ) with a bar. After coating the coating layer while changing the thickness of the coating layer, heat curing was performed under the conditions of a final steel plate temperature of 220 ° C. and a time of 60 seconds. These steel sheets were subjected to a salt spray test (JIS Z 237).
Table 6 shows the results of examining the ratio of white rust generation area to the total surface area after 72 hours in 1). The thickness of the coating layer is 3μ
It can be seen that it is at least m, preferably at least 4 μm. From this result, it is clear that the coating composition of the present invention has excellent corrosion resistance.

Example 2 Cyclohexanone was used as the phenoxy resin solution and the diluting solvent, and the solid content was 23%.
Was prepared. The composition of this coating liquid is shown in Table 2.

[0030]

[Table 2]

This coating solution (viscosity at 20 ° C .: 20 seconds / Ford cup # 4) was applied to a hot-dip galvanized steel sheet (0.8 m thick).
m, coating amount 90 g / m ² ) with a bar coater while changing the thickness of the coating layer, followed by heat curing under the conditions of the final steel plate temperature of 220 ° C. and time of 60 seconds. Table 6 shows the results obtained by subjecting these steel sheets to a salt spray test (JIS Z 2371) and examining the ratio of white rust generation area to the total surface area after 72 hours. It can be seen that the thickness of the coating layer is 3 μm or more, preferably 4 μm or more. From this result, it is clear that the coating composition of the present invention has excellent corrosion resistance.

Example 3 A coating solution having a solid content of 43.8% was prepared by using an epoxy ester resin solution and butyl cellosolve / xylene = 1/1 as a diluting solvent. The composition of this coating liquid is shown in Table 3.

[0033]

[Table 3]

This coating solution (viscosity at 20 ° C .: 60 seconds / Ford cup # 4) was applied to a hot-dip galvanized steel sheet (0.8 m thick).
m, coating amount 90 g / m ² ) with a bar coater while changing the thickness of the coating layer, followed by heat curing under the conditions of the final steel plate temperature of 220 ° C. and time of 60 seconds. Table 6 shows the results obtained by subjecting these steel sheets to a salt spray test (JIS Z 2371) and examining the ratio of white rust generation area to the total surface area after 72 hours. It can be seen that the thickness of the coating layer is 3 μm or more, preferably 4 μm or more.

(Example 4) Butyl cellosolve / xylene = 1/1 was used as the organic solvent, and the solid content of the coating composition having the same composition as in Example 1 was varied to 10 to 50% by weight and shown in Table 4. A coating liquid was prepared.

[0036]

[Table 4]

At this time, the viscosity of the coating liquid at 20 ° C. is shown in Table 4.
13 to 160 seconds with Ford Cup # 4 as shown in FIG. In a coating liquid tank containing the coating liquid having the composition shown in Table 4,
A hot dip galvanized steel wire with a diameter of 5.2 mm was run horizontally at a speed of 10 m / min, passed through a paint tank, and then heated in a heating furnace adjusted to a final steel wire temperature of 220 ° C. Cured. At that time, there was a difference in the thickness of the coating layer between the upper surface and the lower surface of the steel wire (Table 4).

For these coated steel wires a diameter of 100
When a peeling test was performed using an adhesive tape on the apex portion of the outer diameter after performing bending processing of mm, the result of FIG. 1 was obtained. From this result, it is understood that the thickness of the coating layer must be 30 μm or less. The relationship between the solid content (% by weight) of the coating liquid and the thickness of the coating layer is plotted in FIG. 2, and the relationship between the viscosity of the coating liquid and the thickness of the coating layer is plotted in FIG. From FIG. 2, when the solid content of the coating liquid is less than 15% by weight, the thickness of the coating layer on the upper surface of the steel wire is less than 3 μm, and when it exceeds 45% by weight, the thickness of the coating layer on the lower surface of the steel wire exceeds 30 μm. From Figure 3, the viscosity of the coating solution is 15 for Ford Cup # 4.
If it is less than seconds, the thickness of the coating layer on the upper surface of the steel wire will be less than 3 μm, and if it exceeds 80 seconds, the thickness of the coating layer on the lower surface of the steel wire will be 30 μm.
It can be seen that it exceeds μm.

Comparative Example 1 A hot-dip galvanized steel sheet (sheet thickness 0.8 mm, coating weight 90 g / m ² ) was coated with the water-dispersed coating composition described in Japanese Patent Publication No. 63-11383 to prepare a colored coating composition. Table 6 shows a comparison of performance regarding corrosion resistance between the case where a nitrocellulose-modified acrylic resin having the compounding ratio shown in Table 5 of a room-temperature dry type is applied and the above Examples 1 to 3.
Shown in.

(The coating condition is that the water-dispersed coating composition has a film thickness of 2
~ 20 μm, drying conditions: 6 at wire rod maximum ultimate temperature of 150 ° C
0 seconds, the thickness of the colored paint was 5 μm, and the drying condition was a maximum reaching temperature of the wire material of 100 ° C. for 60 seconds. )

[0041]

[Table 5]

[0042]

[Table 6]

Comparative Example 2 A coating composition having the composition of Example 1 was applied to a hot-dip galvanized steel sheet (sheet thickness 0.8 mm, coating amount 90 g / m ² ) and Japanese Patent Publication No. 63-
The water-dispersed coating composition described in 11383 is hot-dip galvanized steel sheet (plate thickness 0.8 mm, coating weight 90 g /
Table 7 shows a performance comparison concerning adhesion when a nitrocellulose-modified acrylic resin having a compounding ratio shown in Table 5 which is a room-temperature-dried type is applied as a colored paint after coating on m ² ).

(Coating conditions: coating composition of Example 1 having a film thickness of 3 to 30 μm, drying conditions: maximum attainable temperature of wire 220 ° C.
For 60 seconds, the water-dispersed coating composition has a film thickness of 5 μm, the drying condition: the wire material reaches the maximum temperature of 150 ° C. for 60 seconds, the color coating has a film thickness of 3 to 30 μm, the drying condition: the wire material reaches the maximum temperature of 100.
It was 60 ° C. for 60 seconds. )

[0045]

[Table 7]

[0046]

EFFECTS OF THE INVENTION A colored galvanized steel for cables which is excellent in corrosion resistance and adhesion is obtained by applying a coating solution of which the solid content and viscosity are adjusted using the coating composition of the present invention to the surface of a steel wire and curing it by heating. Lines can be provided. Further, it becomes possible to prevent corrosion of zinc even after long-term outdoor exposure after cable installation, and the marking property is secured as a twist detection steel wire.

[Brief description of drawings]

FIG. 1 is a diagram showing the degree of peeling with respect to the thickness of a coating layer. * Evaluation criteria of degree of peeling (○: No peeling, △: 1/3 peeling, ×: 1/2 or more peeling)

FIG. 2 is a diagram showing a thickness of a coating layer with respect to a solid content of a coating liquid. ○: Thickness of lower surface, ●: Thickness of upper surface.

FIG. 3 is a diagram showing the thickness of a coating layer with respect to the viscosity of a coating liquid. ○: Thickness of lower surface, ●: Thickness of upper surface.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location D07B 1/16 (72) Inventor Kazuo Yoshii 4-17-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Kansai Paint Within the corporation

Claims (3)

[Claims] 1. A number average molecular weight of 8,000 to 20,
Phenoxy resin (i), or a fatty acid-modified or unmodified epoxy resin having an epoxy equivalent of 300 or more (ii), (B) at least one curing agent selected from urea resins, melamine resins and polyisocyanate compounds, (C) ) A color pigment is contained as an essential component, and {(A) + (B)} /
The colored coating composition for galvanized steel wire, wherein the proportion of (C) is in the range of 95/5 to 50/50 by weight. 2. The colored coating composition for galvanized steel wire according to claim 1, wherein the epoxy resin has at least one basic nitrogen atom and at least two primary hydroxyl groups at the terminal. 3. A coating composition according to claim 1 or 2.
A coating liquid containing 5 to 45% by weight of which is mixed with an organic solvent so that the viscosity of the Ford cup # 4 is 15 to 80 seconds, is baked and cured, and the thickness of the resin coating layer after curing is 3 to 30.
Colored galvanized steel wire for cable with μm.