JP2563006B2 - Coating composition for galvanized steel wire and galvanized steel wire for cable applied with the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition for galvanized steel wires and a galvanized steel wire for bridge cables 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 (called primary rust prevention treatment) is performed to prevent zinc corrosion. Is going. Chromate treatment has been performed for a long time, but since chromate coating layers were eluted due to rainfall and there is concern about the impact on the environment, non-chromate treatment has been applied since the 1980s.

The non-chromate treatment is (a) Japanese Patent Publication No. 6
No. 2-40473, (B) Japanese Patent Publication No. 63-11383.
The processes described in Japanese Patent Publications and the like are known.
These anticorrosion coatings do not always 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 in the bridge construction site such as peeling and the corrosion resistance is deteriorated.

[0004]

By the way, the properties required for a cable steel wire are: corrosion resistance that can withstand long-term outdoor exposure, and coating layer that resists friction and bending when drawing the steel wire during cable construction. Adhesion and a moderate friction coefficient for easy construction. The coefficient of friction is preferably small when the cable strand is drawn out, and is preferably large when the cable band for supporting the bridge plate is installed. Since most of the conventional cable construction equipment is intended for galvanized steel wire without surface treatment, it is desirable that the difference from the friction coefficient of galvanized steel wire is small.

The required performance of the coating layer for the primary anticorrosion treatment is that it has corrosion resistance, adhesion, and a moderate friction coefficient. However, sufficient corrosion resistance could not be obtained by the conventional non-chromate type primary rust preventive treatment.

[0006]

From such a viewpoint, the present inventors have made a coating composition consisting of an epoxy resin having good adhesion to a galvanized steel wire surface a base resin and a curing agent and silica uniformly. It was found that a coating layer having excellent corrosion resistance, workability, and adhesion, and having an appropriate friction coefficient can be formed by coating with a uniform thickness and heating and drying, and for the galvanized steel wire of the present invention. The present invention has led to the development of a coating composition and a galvanized steel wire for cables coated therewith. The coating composition according to the invention thus comprises (A)
A phenoxy resin (i) having a number average molecular weight of 8,000 to 20,000, or a fatty acid-modified or unmodified epoxy resin having an epoxy equivalent of 300 or more (ii), (B) a urea resin, a melamine resin and a polyisocyanate compound. At least one curing agent, (C) silica, is contained as an essential component, and {(A) + (B)} / (C)
Is in the range of 95/5 to 50/50 by weight.

The phenoxy resin (i) used as the component (A) in the present invention is a number average molecular weight of about 8,000 synthesized from bisphenol A type and epichlorohydrin.
.About.20,000 polyhydroxypolyether 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 have been 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. Further, the silica used as the component (C) in the present invention includes colloidal silica, hydrophilic silica called fumed silica and hydrophobic silica. Any of them can be used, but fumed silica is preferred from the viewpoint of corrosion resistance. preferable. The particle size of silica is suitably 1 to 500 mμ, and particularly 10 to 100
mμ is preferred.

In the present invention, the above-mentioned (A) to (C)
The weight ratio of the components is {(A) + (B)} / (C) is 95 /
It is necessary to blend in the range of 5 to 50/50, preferably 90/10 to 70/30. There is a problem that the corrosion resistance of the coating layer is inferior when the content of the resin component is higher than that of silica except the above-mentioned mixing ratio, and the adhesion is inferior when the content of silica is higher than the resin component.

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 terminal 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.

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 an 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 one or more selected from benzoguanamine with formaldehyde, and a monohydric alcohol having 1 to 5 carbon atoms However, when a coating layer is formed 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 primarily 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. These are reacted at room temperature with a polyisocyanate compound. A polyisocyanate compound stably protected with is obtained. Such a blocked polyisocyanate compound is blended 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).

The corrosion resistance of the coating layer formed from the coating composition of the present invention is sufficient if the thickness of the coating layer is 4 μm or more, and even if the thickness is increased, the effect of improving the corrosion resistance is relatively small. Further, if the thickness of the coating layer exceeds 30 μm, the adhesion of the coating layer due to the bending process deteriorates. Further, the friction coefficient of the coated steel wire varies depending on the thickness of the coating layer, but is 3 to 30 μm.
In the range of m, the value is closer to that of the untreated galvanized steel wire as compared with the coated steel wires of the above-mentioned conventional techniques (a) and (b). Therefore, from the viewpoint of performance in use, it is possible to achieve the purpose of obtaining an appropriate friction coefficient by coating the coating layer containing the epoxy resin as the base resin to a thickness of 3 to 30 μm.

In order to coat a steel wire with a coating composition having an epoxy resin as a base resin to a thickness within the above-mentioned range, the solid content concentration in the coating composition is set to 15 to 28% by weight, and other components are used. It is necessary to prepare a coating liquid using as an organic solvent and adjust the viscosity of the coating liquid within the range of 20 to 170 centipoise. When the steel wire is continuously coated while traveling in the horizontal direction, a difference naturally occurs in the thickness of the coating layer between the upper surface and the lower surface of the steel wire. If the viscosity of the coating liquid is less than 20 centipoise, the thickness of the coating layer on the upper surface cannot be maintained at 3 μm or more, and if it exceeds 170 centipoise, the thickness of the coating layer on the lower surface exceeds 30 μm. .

Meanwhile, when the solid concentration of the coating solution to less than 15 wt%, even by adjusting the viscosity within the above range, flaws in it to hold the thickness of the coating layer on the upper surface of the steel wire above 3μm ,
On the other hand, if it exceeds 28% 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 can be directly applied to galvanized steel wire,
Alternatively, it may be applied after being subjected to phosphate treatment, chromate treatment, or the like. As a coating method, dip coating is usually used. The coating composition is dried by natural drying or heat drying at room temperature to 250 ° C.

[0018]

EXAMPLES The present invention will be described in detail 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 Examples 4 and 5 show the solid content concentration ( (% By weight) and the viscosity of the coating liquid show the grounds for limiting the 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 time, 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 the 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 Co., number average molecular weight 12,000) 200 g of cyclohexanone solution 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 uniformly dissolved, and then 88 parts of a cellosolve acetate solution of 50% trimethylolpropane was added thereto. 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 1 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 was added, and the obtained product was used as a curing agent A. The active ingredient of the curing agent was 60%.

Example 1 A coating solution having a solid content of 20% was prepared by using a solvent having a composition of butyl cellosolve / xylene = 1/1 as a diluting solvent. The composition of the coating liquid is shown in Table 1.

[0023]

[Table 1]

This coating solution (viscosity 20 ° C., 80 centipoise) was applied to a hot-dip galvanized steel sheet (plate thickness 0.8 mm, coating weight 90 g / m ² ) with a bar coater while changing the thickness of the coating layer. The steel plate was heat-cured at 220 ° C. for 60 seconds. Table 4 shows the results obtained by subjecting these steel plates 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 2 Cyclohexanone was used as a diluting solvent to prepare a coating liquid having a solid content of 15%. The composition of this coating liquid is shown in Table 2.

[0026]

[Table 2]

This coating solution (viscosity 20 ° C., 95 centipoise) was applied to a hot-dip galvanized steel sheet (plate thickness 0.8 mm, coating amount 90 g / m ² ) with a bar coater while changing the thickness of the coating layer, and then the final coating. The steel plate was heat-cured at 220 ° C. for 60 seconds. Table 4 shows the results obtained by subjecting these steel plates 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) Butyl cellosolve / xylene = 1/1 was used as a diluting solvent to prepare a coating liquid having a solid content of 25%. The composition of this coating liquid is shown in Table 3.

[0029]

[Table 3]

This coating solution (viscosity 20 ° C., 45 centipoise) was applied to a hot-dip galvanized steel sheet (plate thickness 0.8 mm, coating amount 90 g / m ² ) with a bar coater while changing the thickness of the coating layer. The steel plate was heat-cured at 220 ° C. for 60 seconds. Table 4 shows the results obtained by subjecting these steel plates 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.

(Comparative Example) No. 6 described in Japanese Patent Publication No. 63-11383. The water-dispersed coating composition of No. 1 was used. The performance comparison is shown in Table 4.

[0032]

[Table 4]

Example 4 A coating composition shown in Table 5 was prepared by varying the solid content of the coating composition having the same composition as in Example 1 to 10 to 30% by weight and changing the ratio of butyl cellosolve and xylene as the organic solvent. Created.

[0034]

[Table 5]

At this time, the viscosity of the coating liquid at 20 ° C. is shown in Table 5.
It was 9 to 240 centipoise as shown in FIG. A galvanized steel wire having a diameter of 5.2 mm and a length of 250 mm was dipped in these coating liquids and kept vertically so that the final steel wire temperature was 220.
When heat curing was carried out under the conditions of ° C and a time of 60 seconds, the coating layer thicknesses shown in Table 5 were obtained. The coated steel wires were bent to have a diameter of 500 mm, and a peel test was performed on the apex portion of the outer diameter using an adhesive tape. The results shown in FIG. 1 were obtained. From this result, it is understood that the thickness of the coating layer must be 30 μm or less.

Table 5 also shows the coefficient of friction of the coated steel wire, which is 0.13 to 0.1 for untreated galvanized steel wire.
5, the composition using the composition described in JP-B-63-11383 is 0.24 to 0.48, and the composition using the coating composition of the present invention has a conventional thickness of 3 to 30 μm. It can be seen that it is closer to untreated galvanized steel wire than the product.
The friction coefficient was measured by HEIDON-14 manufactured by HEIDON (measurement condition load 1 kg, pulling speed 10 c).
m / min).

(Example 5) For the coating composition of Example 1 above, butyl cellosolve was used as a diluting solvent,
The solid content of the coating liquid was changed to 5 to 28%, and a hot dip galvanized steel wire having a diameter of 5.2 mm was run horizontally in the coating liquid tank at a speed of 10 m / min and passed through the coating liquid tank. Then, it was heat-cured in a heating furnace adjusted so that the final steel wire temperature was 220 ° C. At that time, there is a difference in the thickness of the coating layer between the upper surface and the lower surface of the steel wire, and the relationship between the solid content (% by weight) of the coating liquid and the thickness of the coating layer is plotted in FIG. Fig. 3 is a plot of the relationship between viscosity and coating layer thickness.
Is. 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 28% by weight, the thickness of the coating layer on the lower surface of the steel wire exceeds 30 μm. From FIG. 3, when the viscosity of the coating liquid is less than 20 centipoise, the thickness of the coating layer on the upper surface of the steel wire is less than 3 μm,
It can be seen that when it exceeds 0 centipoise, the thickness of the coating layer on the lower surface of the steel wire exceeds 30 μm.

[0038]

The coating composition of the present invention is used to apply a coating solution whose solid content and viscosity are adjusted to the surface of a steel wire, and by heating and curing it, it is excellent in corrosion resistance and adhesion and suitable for on-site construction. A galvanized steel wire for a cable having a coefficient of friction can be provided. Further, it becomes possible to prevent corrosion of the galvanized steel wire even after long-term outdoor exposure after the cable is installed.

[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 for degree of peeling (○: No peeling, △: Partial peeling,
×: Complete peeling)

FIG. 2 is a diagram showing the thickness of the coating layer with respect to the solid content of the 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 front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C09D 163/00 PKJ C09D 163/00 PKJ 171/10 PLQ 171/10 PLQ 175/04 PHP 175/04 PHP PHW PHW (72) Inventor Kazuo Yoshii 4-17-1, Higashi-Hachiman, Hiratsuka City, Kanagawa Prefecture Kansai Paint Co., Ltd. 56) References JP-A-61-55281 (JP, A)

Claims (3)

(57) [Claims] 1. A number average molecular weight of 8,000 to 20,
000 phenoxy resin (i), or a fatty acid-modified or non-modified 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) ) Silica is contained as an essential component, and {(A)
The ratio of + (B)} / (C) is 95/5 to 50 / by weight.
A coating composition for galvanized steel wire in the range of 50. 2. The 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
Zinc plating for cables, containing 5 to 28% by weight, and applying a coating liquid mixed with an organic solvent so that the viscosity is 20 to 170 centipoise, and baking and curing the resin coating layer after curing to have a thickness of 3 to 30 μm. Steel wire.