JP2005068278A - High corrosion-proof coating composition containing zinc dust - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating material containing zinc dust, which is good in coating workability and exhibits high corrosion prevention. <P>SOLUTION: The composition contains (A) 100 mass pts. binder resin, (B) 200-800 mass pts. zinc dust, (C) 5-50 mass pts. conductive high molecular compound and/or carbon nanofiber and/or carbon nanotube, and (D) 200-1,000 mass pts. solvent to disperse the above ingredients. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a highly anticorrosive zinc powder-containing coating composition. More specifically, the present invention relates to a coating composition that is useful as a primary rust-preventing paint or undercoat paint for large steel structures, has good workability, and has higher corrosion resistance than conventional zinc dust-containing paints.

Zinc dust-containing paints in which a relatively large amount of zinc dust is blended in a binder resin are widely used for the purpose of anticorrosion of ships, bridges, tanks, plants, marine structures and the like. Zinc powder-containing paints are roughly classified into organic zinc powder-containing paints and inorganic zinc powder-containing paints depending on the type of binder resin used.
Organic zinc dust-containing paints are generally made by adding a large amount of zinc dust to a binder resin such as an epoxy resin or an acrylic resin, and are easy to prepare and paint, and are applicable to top coats. Have the characteristics that are good. On the other hand, since the anticorrosion function and the cohesive force of the coating film are somewhat insufficient, it is not often used when long-term anticorrosion is important.

In contrast, inorganic zinc dust-containing paints generally use alkyl silicate resins as binders and have excellent anti-corrosion function and durability of the coating film. However, it is not easy to adjust the base material and workability of painting, and it is necessary to carefully adjust the base material such as polishing and blasting.
In paints containing a large amount of zinc dust, attempts have been made mainly to improve the paint workability. However, in any zinc powder-containing paint, since the main method is to add other components, the corrosion resistance tends to be lowered. For example, by previously coating zinc powder with a flow preventive agent, the coating operation is improved while maintaining the corrosion resistance of the coating powder containing zinc powder, and a method for preventing the occurrence of sagging and cracking even when thickly applied is disclosed. (For example, refer to Patent Document 1).

  However, the occurrence of cracks cannot be sufficiently suppressed only by coating the zinc powder with a flow preventive agent. Further, it contains a rust-proof coating composition containing needle-like or long columnar calcium metasilicate to prevent cracking or peeling of the coating film (for example, see Patent Document 2), and contains needle-like and / or fibrous substances. The thixotropic coating composition contains fibrous viscous minerals such as acicular calcium silicate (wollastonite), sepiolite, serpentinite lizarite, or potassium titanate, gypsum fiber, slag fiber, rock wool, glass fiber, etc. In addition, a composition (see, for example, Patent Document 3) with improved thick coating properties and scattering prevention properties is disclosed. However, these needle-like or fibrous materials have poor permeability when meshed for use in filtration, so the yield when adjusting the powder component in the pre-process of paint production is poor, resulting in blend blurring, There was a problem that the spray of the coating machine was clogged during painting.

JP-A 63-17976 JP-A-62-181370 Japanese Patent Laid-Open No. 2-75675

  In view of such circumstances, an object of the present invention is to provide a zinc powder-containing paint that improves coating workability and further exhibits a higher anticorrosive property than conventional zinc powder-containing paints.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-described problems can be achieved by the following configurations, and have reached the present invention.
That is, the present invention provides (A) 100 parts by mass of a binder resin, (B) 200 to 800 parts by mass of zinc powder, (C) a conductive polymer selected from the group consisting of conductive polymer compounds, carbon nanofibers, and carbon nanotubes. The present invention relates to a highly anticorrosive zinc dust-containing coating composition containing 5 to 50 parts by mass of component and (D) 200 to 1000 parts by mass of a solvent for dispersing these components.

  The highly anticorrosive zinc powder-containing coating composition of the present invention has good coating workability and exhibits high anticorrosion properties.

The present invention will be described in detail below.
The binder resin (A) used in the present invention may be organic or inorganic, and may be aqueous or solvent-based. As the organic binder resin, for example, a resin such as an epoxy resin, a modified epoxy resin, an acrylic resin, or a urethane resin can be suitably used. In particular, an epoxy resin and an acrylic resin that have good anticorrosion properties and adhesion to the substrate are preferable.
As the water-based organic binder resin, those obtained by introducing a hydrophilic functional group such as —OH, —NH ₂ , or —COOH into the above resin or the like and dispersing in water are used.

  Examples of the inorganic binder resin used in the present invention include a partially hydrolyzed polyalkyl silicate and a modified product thereof. Specifically, for example, tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, tetrapentyl orthosilicate, tetrahexyl orthosilicate, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxy Hydrolysis initial condensate of alkyl silicate using silane, ethyltrimethoxysilane, ethyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, amyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane as raw materials In this case, the hydrolysis rate is preferably 50 to 98%, for example. These hydrolysates may be derivatives obtained by reacting with other organic polymer compounds. These may be used alone or in combination of two or more, or may be used by mixing organic or inorganic binder resins. Specific examples of the inorganic binder resin include, for example, ethyl silicate 40 (manufactured by Colcoat Co., Ltd.), ethyl silicate 40 (manufactured by Tama Chemical Industry Co., Ltd.), Silbond 40 (manufactured by Stauffer Chemical Co.), Ethyl Silicate 40 ( Union Carbide Co.).

As the water-based inorganic binder resin, a general formula R ₂ O · nSiO ₂ (I)
(In the formula, R represents an alkali metal atom, and n represents a positive number of 1.0 to 5.0) selected from the group consisting of a water-soluble silicate or colloidal silica aqueous dispersion. Preferably, at least one binder is used.
In the general formula (I), examples of the alkali metal atom represented by R include lithium, sodium, and potassium.
As the water-soluble silicate represented by the general formula (I), conventionally known water-soluble silicates can be widely used. In the present invention, these can be used alone or in combination of two or more. Moreover, it is used also by organic and inorganic binder resin mixing, and the reaction material of organic and inorganic binder resin can also be used.
You may mix | blend a hardening | curing agent with these binder resin as needed. For example, for an epoxy resin, a curing agent such as polyamidoamine, polyisocyanate, acid anhydride, or melamine resin can be used.

As the zinc powder (B) used in the present invention, a conventionally known one can be used as long as zinc is eluted and has a sacrificial anodic action. In addition, the particle size of zinc powder is usually in the range of 1 to 100 μm, but the particle size in the range of 3 to 7 μm is preferable. When zinc powder particles having a suitable particle size range are used, workability during coating is further improved, and a coating film having a more uniform appearance can be obtained.
The amount of zinc powder to be blended in the paint of the present invention is 200 to 800 parts by weight, preferably 250 to 700 parts by weight, based on 100 parts by weight of the solid content of the binder resin. . When the blending amount of the zinc powder is less than 200 parts by mass, the anticorrosion property tends to be insufficient. When the blending amount exceeds 800 parts by mass, the coating properties and coating properties of the resulting highly anticorrosive zinc dust-containing coating composition are obtained. The film appearance tends to be poor, the binder resin cannot be sufficiently bonded to the substrate surface, and the adhesion of the coating film tends to be poor.

Next, the conductive polymer compound, carbon nanofiber, and carbon nanotube as the conductive component (C) used in the present invention will be described.
The conductive polymer compound used in the present invention is preferably polyaniline, polypyrrole, polythiophene, polythiophene vinylene, polyisothianaphthene, polyacetylene, polyalkylpyrrole, polyalkylthiophene, poly-p-phenylene, polyphenylene vinylene. , Polymethoxyphenylene, polyphenylene sulfide, polyphenylene oxide, polyanthracene, polynaphthalene, polypyrene, polyazulene, or polymers of these derivatives and carbon fibers.
In addition, these electroconductive components (C) may be used independently and may be used as a 2 or more types of mixture.

These conductive polymer compounds are preferably doped, and the conductivity is improved by this doping. Examples of the dopant include donor-type dopants such as alkali metals such as Li, Na and K, alkaline earth metals such as Ca, halogens such as Cl ₂ , Br ₂ and I ₂ , PF ₃ and AsF _5. Lewis such as BF ₃ , protonic acids such as HF, HCl, HNO ₃ , H ₂ SO ₄ , HClO ₄ , transition metal compounds such as FeCl ₃ , FeOCl ₂ , TiCl ₄ , WCl ₃ , Cl ⁻ , Br ⁻ , Acceptor-type dopants of electrolyte anions such as I ⁻ , ClO ₄ ⁻ , PF ₃ ⁻ , BF ₃ ⁻ and AsF ₃ ⁻ are used.
Carbon nanofibers and carbon nanotubes are extremely small structures made of carbon, and have a volume resistivity of 1 to 2 digits lower than that of ordinary graphite and carbon black. Carbon black has a volume characteristic of the order of 10 ^-1 Ω · cm. In contrast to resistance, carbon nanofibers and carbon nanotubes have a volume resistivity of the order of 10 ⁻³ Ω · cm. The diameter of the carbon nanotube and the carbon nanofiber is, for example, 200 nm or less (for example, the lower limit is 1 nm), and the length is, for example, preferably 30 μm or less (for example, the lower limit is 20 nm), more preferably. The carbon nanotubes and carbon nanofibers preferably have a diameter of 1 to 180 nm and a length of 1 to 25 μm.

If the diameters of the carbon nanotubes and carbon nanofibers are larger than 200 nm, the viscosity of the paint tends to increase, and the coating workability tends to decrease. Moreover, it is limited to the quantity with few amounts which can be mix | blended. On the other hand, when the length is larger than 30 μm, the viscosity of the paint is also increased and the coating workability tends to be lowered. Moreover, it is limited to the quantity with few amounts which can be mix | blended.
Typical commercially available carbon nanofibers are carbon nanofibers having a diameter of 50 to 200 nm and a length of about 20 μm, such as VGCF, VGCFII, and VGNF manufactured by Showa Denko KK. Typical commercially available carbon nanotubes generally have a diameter of 0.6 to 20 nm and a length of 1 to 20 μm, and include those manufactured by Honjo Chemical Co., Ltd. and Toray Industries.

Carbon nanofibers and carbon nanotubes having various structures can be used as long as the carbon nanofibers and carbon nanotubes have diameters and lengths in the above ranges. Carbon nanotubes can be used regardless of whether the structure is single-walled or multi-walled. Moreover, even if carbon nanotubes contain elements other than carbon atoms, such as metal atoms, as long as they have electrical conductivity, they can be used.
The compounding quantity of an electroconductive component (C) is 5-50 mass parts with respect to 100 mass parts of binder resin, Preferably, it is suitable that it is 8-45 mass parts. Preferably, when the blending amount is less than 5 parts by mass, the conductivity of the coating film surface becomes insufficient, and it becomes difficult to exhibit high anticorrosion properties. On the other hand, when the compounding amount of this component exceeds 50 parts by mass, the coating viscosity of the obtained zinc dust-containing coating composition increases, and the coating workability tends to decrease.
By the way, when zinc powder-containing coating composition is applied to a steel material, since zinc is more easily eluted than iron, zinc powder exhibits the sacrificial anticorrosive action of iron. However, after the paint containing zinc dust is applied, the red rust occurs on the steel material not after the zinc is completely eluted and the zinc is consumed, but the zinc elution progresses locally and the zinc is It is consumed and iron elution occurs at that part, resulting in red rust. On the other hand, when the conductive component (C) is blended in the zinc dust-containing paint, the potential of the coating surface of the coating becomes uniform, and local elution of zinc is prevented. The anti-corrosion property of is maintained for a long time.

In general, as the conductive component (C), metal powder, metal oxide, graphite, carbon black, and the like can be considered in addition to the conductive polymer compound, carbon nanofiber, and carbon nanotube. However, when metal powder or metal oxide is blended, the conductivity of the coating film surface is improved, but the specific gravity is large, and it settles in the paint, so that the storage stability is not good. Further, when graphite or carbon black is used, the conductivity is insufficient as described above, and if it is blended in a large amount, the viscosity is extremely increased and the coating workability is lowered. It is practically difficult to blend 20 parts by mass or more with respect to the amount.

  The solvent (D) used in the present invention may be either an organic solvent or water as long as it can dissolve or disperse the components (A) to (C). Examples of the organic solvent include aromatic solvents such as toluene and xylene, alcohol solvents such as ethanol, methanol and butanol, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, propylene glycol monomethyl ether, and ethylene glycol. Preferable examples include ether solvents such as monomethyl ether and ester solvents such as butyl acetate and ethyl acetate. When the paint form is aqueous, water is used as the solvent. In that case, a water-soluble organic solvent may be further added. Examples of the water-soluble organic solvent include methanol, ethanol, 1-propanol, 2-propanol, t-butyl alcohol, ethylene glycol, propylene glycol, 1,2-propanediol, 1,3-propanediol, glycerin, Preferable examples include acetone, methyl cellosolve, ethyl cellosolve, butyl cellosolve, methyl carbitol, ethyl carbitol, propyl carbitol, butyl carbitol, diacetone alcohol and the like.

The compounding quantity of a solvent (D) is 200-1000 mass parts normally with respect to 100 mass parts of binder resin, Preferably, it is 200-600 mass parts.
When the blending amount of the solvent (D) is less than 200 parts by mass, the coating viscosity of the obtained zinc dust-containing coating composition becomes high, and the coating stability and the coating workability tend to be inferior. On the other hand, when the blending amount exceeds 1000 parts by mass, the coating viscosity of the obtained zinc dust-containing coating composition becomes too low, and for example, it becomes difficult to attach a prescribed film thickness (50 μm or more).
In the coating composition of the present invention, if necessary, a dispersing agent is used in combination to uniformly disperse the zinc dust (B) and the conductive component (C) in the zinc dust-containing coating composition. Also good.
Examples of such a dispersant include a cationic system such as a quaternary ammonium salt, an anionic system such as a carboxylate, a sulfonate, a sulfate ester salt, and a phosphate ester salt, an ether type, an ether ester type, and an ester. Nonionic types such as molds and nitrogen-containing types are preferred.

In addition, as an additive that is optionally used, a sagging inhibitor, a pigment, and the like can be blended. As the anti-sagging agent, various sagging-inhibiting agents can be used as long as they are usually blended in a coating material to exhibit structural viscosity and impart thixotropic properties to the coating material. Suitable examples of such an anti-sagging agent include amorphous silica, colloidal calcium carbonate, organic bentonite, hydrogenated castor oil, aliphatic amides, higher fatty acids, microgel particles, and the like. These anti-sagging agents may be used alone or in combination of two or more. In particular, an organic bentonite-based sagging inhibitor is preferable because it exhibits a large structural viscosity when added in a small amount.
As the pigment, extender pigments used in ordinary rust-proof paints, rust-proof pigments, colored pigments, and the like can be appropriately used. Specific examples of such pigments include talc, mica, barium sulfate, clay, calcium carbonate, zinc oxide, titanium dioxide, bengara, zinc phosphate, aluminum phosphate, barium metaborate, aluminum molybdate, and phosphorus. Examples include iron oxides. These pigments may be used alone or in combination of two or more.

The zinc dust-containing coating composition of the present invention can be prepared in accordance with a conventional method, and the coating is generally performed by mixing each component immediately before use. For the dispersion of the liquid component and the powder component, a roll mill, a sand grind mill, a media mill such as a ball, a disper disperser, etc., which are usually used for dispersion of paints are used. The zinc powder-containing paint thus formed is applied to a steel structure or the like by means of, for example, air spray, airless spray, roll coater, or brush, but is generally applied by spray. is there.
The coated zinc powder-containing coating composition of the present invention is dried at room temperature, for example, for 18 to 48 hours, or forcedly dried at a temperature of about 80 ° C. for 30 minutes or more to volatilize the solvent, and the coating film Can be formed.
FIG. 1 is a diagram schematically showing the structure of a coating film formed on a material. In the cross section of the coating film formed on the material, the binder resin 1 is in close contact with the surface of the material 4, and the zinc powder 3 and the conductive component 2 dispersed in the binder resin 1 are networked in the coating film. In order to impart conductivity to the coating film and maintain the potential of the coating film surface uniformly, it is considered to exhibit high anticorrosion properties.

  Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. However, these examples and comparative examples do not limit the scope of the present invention. In Examples, “parts” and “%” represent “parts by mass” and “% by mass” unless otherwise specified.

[Example 1]
400 parts of ethyl silicate solution A (manufactured by Colcoat, ethyl silicate 40, solid content 25%, solvent: xylene), 500 parts of zinc dust A (manufactured by Honjo Chemical Co., Ltd., average particle size 5 μm), polyaniline solution as a conductive polymer compound (Toyobo Co., Ltd., A-100, solid content 25%) 60 parts, carbon nanofiber (Showa Denko Co., Ltd., VGCFII, average diameter 120 nm, average length 20 μm) 30 parts in a container, and further xylene 20 Part was added and stirred until uniform to prepare a paint.
Next, the paint was applied to a sandblasted steel plate having a thickness of 3.0 mm and a size of 70 × 150 mm by air spray so that the film thickness after 48 hours at room temperature was 50 μm.
Using the produced test piece, performance evaluation was performed as follows, and the results are shown in Table 2.

[Examples 2 to 6 and Comparative Examples 1 to 3]
Similarly to Example 1, paints of Examples 2 to 6 and Comparative Examples 1 to 3 were prepared according to the formulation shown in Table 1, and test pieces for evaluation were prepared in the same manner as in Example 1.
Furthermore, performance evaluation was performed as follows, and Table 2 shows the results.

<Performance evaluation>
The anticorrosion property and coating workability of the coating film were performed as follows.
Salt water spray test Using the test piece prepared as described above, in accordance with JIS K 5400, 9.1 salt water spray resistance test method, the appearance of the cross-cut coating film after spraying with salt water for 5000 hours is as follows. Visual judgment was made on the basis of
(Evaluation)
◎: No abnormality on the coating film surface ○: Some red rust is generated at the crosscut part △: Red rust with a diameter of 1 to 2 mm is generated around the crosscut part ×: Red rust with a diameter of 3 mm or more around the crosscut part Occurs

Salt water immersion test Using the test piece prepared as described above, in accordance with JIS K 5400, 8.23 salt water resistance test method, the appearance of the coating film after immersion in salt water for 8000 hours at room temperature is as follows. Visual judgment was made.
(Evaluation)
◎: There is no abnormality on the coating film surface. ○: About 1 to 2 points of red rust is generated on the coating film surface. △: About 10% red rust is generated on the coating film surface. 50% or more of red rust occurs

Natural potential After the specimen prepared as described above was immersed in 3% saline for 12000 hours, it was a fully automatic polarization measuring device HZ-3000 manufactured by Hokuto Denko Co., Ltd., and the reference electrode was Ag / AgCl. The potential was measured and judged according to the following criteria.
(Evaluation)
A: -900 mV or less B: -899 to -750 mV
Δ: −749 to −650 mV
×: −649 mV or more

Combined cycle test Using the test piece prepared as described above, in accordance with the test method of JIS K 5621, 5.11 combined cycle anti-corrosion resistance, the appearance of the cross-cut portion after 1200 cycles was visually observed according to the following criteria. Judged.
(Evaluation)
◎: No abnormality on the coating film surface ○: Some red rust is generated around the crosscut portion △: Red rust with a diameter of 1 to 2 mm is generated around the crosscut portion ×: The diameter is 3 mm or more around the crosscut portion Red rust occurs

Coating workability The atomization state of the paint sprayed during air spray coating was visually judged according to the following criteria.
(Evaluation)
◎: Fine atomization and smooth coating surface ○: Addition of diluting solvent causes agglomeration and flickering on coating surface △: Spray particles are intermittently ejected ×: Fine atomization is poor and cannot be ejected

※バインダー樹脂中の溶媒は含まない。














Table 1 Paint formulation
(Blending unit: parts)

* Does not include the solvent in the binder resin.

※バインダー樹脂中の溶媒は含まない。






















Table 1 Paint formulation (continued)
(Blending unit: parts)

* Does not include the solvent in the binder resin.

Table 2 Performance evaluation results

Table 2 Performance evaluation results (continued)

1) Ethyl silicate solution A: “Ethyl silicate 40” manufactured by Colcoat
(Solid content 25%)
2) Epoxy resin solution B: “Epicoat 1001” manufactured by Yuka Shell
(Solid content 70%)
3) Lithium silicate aqueous solution C: “Lithium silicate aqueous solution” manufactured by Nippon Chemical Industry Co., Ltd.
(Solid content 40%)
4) Urethane resin aqueous dispersion D: “Adekabon titer 290H” manufactured by Asahi Denka Co., Ltd.
(Solid content 40%)
5) Polysilicon aqueous solution E: “KBM403” manufactured by Shin-Etsu Silicone
(Solid content 80%)
6) Zinc Powder A: “Zinc Powder F-1000” manufactured by Honjo Chemical Co., Ltd.
(Average particle size 5μm)
7) Zinc Powder B: “Zinc Powder # 3-13L” manufactured by Sakai Chemical Co., Ltd.
(Average particle size 4μm)
8) Polyaniline solution (conductive polymer compound): “A-100” manufactured by Toyobo Co., Ltd.
(Solid content 25%)

9) Carbon nanofiber: “VGCFII” manufactured by Showa Denko
(Average diameter 120nm, average length 20μm)
10) Carbon nanotube: manufactured by Toray Industries, Inc. (diameter 5 nm, length 120 nm)
11) Carbon black: “MA-100” manufactured by Mitsubishi Chemical Corporation
12) Polyamidoamine solution A: “Tomide TXK-659A” manufactured by Fuji Kasei Co., Ltd.
(Solid content 60%, amine value 120)

  As is clear from the results in Table 2, a paint in which a specific conductive component selected from the group consisting of a conductive polymer compound, carbon nanofibers, and carbon nanotubes is blended with a zinc powder-containing paint is compared with a comparative paint. Corrosion resistance was good and painting workability was also good. On the other hand, in the comparative example 1 which mix | blended carbon black, the obtained zinc dust containing coating composition was inadequate in corrosion resistance, and the coating state was inferior and the coating workability | operativity was bad. In the comparative example 2 which mix | blended 1 part of carbon nanofibers with respect to 100 parts of binder resins, and the comparative example 3 which does not mix | blend an electroconductive component, all the obtained zinc dust containing coating compositions were inferior in corrosion resistance.

  The highly anticorrosive zinc dust-containing coating composition of the present invention is useful as a primary rust-preventing coating or base coating for large steel structures.

FIG. 1 is a diagram schematically showing a coating film structure formed on a material of a coating film formed from the highly anticorrosive zinc dust-containing coating composition of the present invention.

Explanation of symbols

1 Binder resin 2 Conductive component 3 Zinc powder

Claims (2)

  (A) 100 mass parts of binder resin, (B) 200-800 mass parts of zinc powder, (C) 5-50 mass parts of conductive component selected from the group consisting of conductive polymer compound, carbon nanofiber and carbon nanotube. And (D) A highly anticorrosive zinc dust-containing coating composition comprising 200 to 1000 parts by mass of a solvent for dispersing each of the above components.   (C) The highly anticorrosive zinc dust-containing coating composition according to claim 1, wherein the carbon nanofiber or the carbon nanotube has a diameter of 200 nm or less and a length of 30 μm or less.

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