JP2004143423A - Undercoating composition and coating method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an undercoating composition having high sealability to rusty surfaces and expressing excellent overcoatability and provide a method for coating using the base coating composition. <P>SOLUTION: The undercoating composition contains (A) an OH-containing nonaqueous dispersion resin, (B) an OH-containing solvent-soluble resin and (C) an isocyanate compound. The ingredient (B) has chelate-forming ability. A solvent comprises ≥50 wt.% aliphatic hydrocarbon. Various problems, e.g., sealability is solely acquired by many times of coatings as the coating is absorbed into the rusty surface when a conventional coating is applied to a remarkably rusty metal surface, overcoatability, adhesiveness and the like of the overcoat are reduced when the sealability is insufficient, and so forth are improved. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to an undercoat material composition that can be preferably applied to a metal surface having rust, and a coating method using the same.

Rust generated on metal members used for buildings, civil engineering structures, and the like not only impairs aesthetics but also may cause a reduction in strength of the metal members. For this reason, some kind of rust prevention treatment is required for the member in which rust has occurred.
As such a rust preventive treatment, a method is generally used in which after removing rust to some extent with kerosene or the like, a rust preventive undercoating material is applied, and then an overcoating material is applied.
Japanese Patent Application Laid-Open No. 2000-140746 discloses a coating method for a metal surface having rust, and as a rust-preventive undercoat material, a rust conversion type rust prevention containing a phosphoric acid compound and an organic chelating agent based on an epoxy resin. Undercoat material is described.

JP-A-2000-140746 (claims)

However, when the undercoat material described in the publication is applied to a metal surface on which rust is remarkably generated, the paint is sucked into the rust layer, so that sealability cannot be ensured unless it is applied many times. There's a problem. If the sealability is insufficient, the finish, adhesion and the like of the topcoat material may be reduced.
The present invention has been made in view of the above points, and has a high sealing property to a rust surface, and an undercoat material composition capable of exhibiting excellent overcoat compatibility, and coating using the undercoat material composition It is intended to provide a method.

In order to solve such a problem, the present inventors have conducted intensive studies, and as a result, a hydroxyl group-containing non-aqueous dispersion type resin, a hydroxyl group-containing solvent-soluble resin having chelate forming ability, and an isocyanate compound as essential components Have been conceived. That is, if this undercoat material composition is used, an undercoat film having high sealing properties can be formed with a small number of coatings on a metal surface having rust, and further, if an overcoat material is formed on this undercoat film, the finish is obtained. The inventors have found that a coating film having excellent properties and adhesion can be obtained, and have completed the present invention.

The present invention has the following features.
1. (A) a hydroxyl group-containing non-aqueous dispersion resin, (B) a hydroxyl group-containing solvent-soluble resin, (C) an isocyanate compound,
Wherein the component (B) has chelating ability;
An undercoat material composition characterized in that at least 50% by weight of all solvents are aliphatic hydrocarbons.
2. For rusted metal surfaces: A coating method, characterized by applying a topcoat material after applying the undercoat material composition described in the above.

According to the present invention, it is possible to obtain an undercoat material composition which has a high sealing property to a rust surface and can exhibit excellent overcoat compatibility.

Hereinafter, the present invention will be described in detail based on its embodiments.
The undercoat material composition of the present invention comprises (A) a hydroxyl group-containing non-aqueous dispersion type resin and (B) a hydroxyl group-containing solvent-soluble resin having chelate-forming ability as a binder, and (C) an isocyanate compound as a curing agent. It contains.

[(A) Hydroxyl group-containing non-aqueous dispersion type resin]
The component (A) in the present invention is a hydroxyl group-containing non-aqueous dispersion type resin (hereinafter, referred to as “component (A)”). The component (A) has both a resin portion soluble in a non-aqueous solvent and a resin portion not soluble in a non-aqueous solvent, and is dispersed in the non-aqueous solvent. The component (A) can be usually obtained by polymerizing various radically polymerizable unsaturated monomers by a conventional method in the presence of a resin soluble in a non-aqueous solvent.
The composition of the present invention can exhibit excellent sealing properties by including the component (A) as an essential component.

The component (A) can be obtained by copolymerizing a hydroxyl group-containing monomer with another copolymerizable monomer. Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 3-hydroxybutyl. (Meth) acrylate, 4-hydroxybutyl (meth) acrylate, di-2-hydroxyethyl fumarate, mono-2-hydroxyethyl-monobutyl fumarate, ethylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate Propylene glycol mono (meth) acrylate, or an adduct thereof with a lactone such as ε-caprolactone, γ-valerolactone, and the like. One or more selected from these are copolymerized. Can be obtained.
Examples of monomers copolymerizable with the hydroxyl group-containing monomer include (meth) acrylic acid alkyl ester, (meth) acrylamide and derivatives thereof, styrene derivative, vinyl chloride, vinyl acetate, maleic acid dialkyl ester, fluoroolefin, and reactive silyl. Group-containing vinyl compounds. In addition, compounds having chelating ability can also be used.

As the component (A), those having a weight average molecular weight of 10,000 to 300,000, preferably 50,000 to 150,000 can be used. If the weight average molecular weight is less than 10,000, it becomes difficult to form a coating film having good sealing properties with a small number of coatings. In addition, physical properties of the coating film such as water resistance may be reduced. When the weight average molecular weight is larger than 300,000, sufficient film forming performance may not be obtained.
The hydroxyl value of the component (A) is usually from 10 to 100 KOH mg / g, preferably from 15 to 80 KOH mg / g. When the hydroxyl value is less than 10 KOHmg / g, sufficient crosslink density cannot be obtained, and the properties of various coating films are inferior. When the hydroxyl value is more than 100 KOHmg / g, the pot life becomes short or the adhesion decreases. It becomes a tendency.
The glass transition point of the component (A) is usually from -50 to 100C, preferably from -30 to 80C.

[(B) Hydroxyl group-containing solvent-soluble resin]
In the present invention, (B) a hydroxyl group-containing solvent-soluble resin (hereinafter, referred to as “component (B)”) is used as the binder in addition to the above-mentioned component (A). The component (B) penetrates into the rust layer and plays a role of enhancing the binding to rust by its chelating ability. Examples of the functional group capable of forming a chelate in the component (B) include a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, a hydroxyl group, a thiol group, and a carbonyl group.
As the component (B), a solvent-soluble resin having such a chelate-forming ability and containing a hydroxyl group capable of reacting with the isocyanate compound (C) described later can be used. The hydroxyl value of the component (B) is usually from 10 to 300 KOH mg / g, preferably from 20 to 200 KOH mg / g.

As the component (B) in the present invention, a hydroxyl group-containing solvent-soluble modified epoxy resin (hereinafter, referred to as “component (B-1)”) is particularly preferable. The component (B-1) is a component in which a hydroxyl group is generated by ring-opening an epoxy group of an epoxy resin. Examples of the component (B-1) include a reaction product of an epoxy resin and an amine compound, and a reaction product of an epoxy resin and a fatty acid. Of these, a reaction product of an epoxy resin and an amine compound is particularly preferred in the present invention.
As the epoxy resin, for example, bisphenol A type epoxy resin, bisphenol type epoxy resin such as bisphenol F type epoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxy resin, novolak type epoxy resin such as bisphenol A novolak type epoxy resin, Copolymer type epoxy resin of bisphenol A type epoxy resin and phenol novolak resin, diglycidyl ether of dihydroxynaphthalene, polyglycidyl ether of mono (di) hydroxynaphthalene novolak, polyglycidyl ether of phenol-divinylbenzene crosslinked phenol resin, bisphenol A-Divinylbenzene crosslinked phenolic resin polyglycidyl ether, mono (di) hydroxynaphthalene-divinylbenzene frame Polyglycidyl ethers of type phenol resin. The epoxy equivalent of the epoxy resin is usually about 100 to 10,000.
As the amine compound, a secondary amino group-containing compound is preferable, and examples thereof include dialkylamines such as diethylamine, dipropylamine and dibutylamine, N-methylethanolamine, N-butylethanolamine, diethanolamine and dipropanolamine. And the like. Of these, alkanolamines are preferred as the amine compound.
As a method of reacting the epoxy resin with the amine compound, a known method can be employed. The reaction ratio between the epoxy resin and the amine compound is usually about 0.5 to 2.0 for the amino group per 1 equivalent of the epoxy group.

In the present invention, the solid content weight ratio of component (A) / component (B) is preferably from 95/5 to 5/95, more preferably from 85/15 to 15/85, and even more preferably from 65/35. 35/65. This makes it possible to form a coating film having an excellent balance between permeability to the rust layer, sealing properties, and top coat compatibility. When the weight ratio of the component (A) is small, the sealing property may be insufficient. Further, when a glossy paint is applied as an overcoat material, the glossiness tends to decrease. When the weight ratio of the component (B) is small, the effect of stabilizing rust may be insufficient.

[(C) isocyanate compound]
In the present invention, (C) an isocyanate compound is mixed as a curing agent for the components (A) and (B). Examples of such a curing agent include Burnock DN-990, DN-991, and DN-992 (both manufactured by Dainippon Ink and Chemicals, Inc.), Duranate TSA (manufactured by Asahi Chemical Industry Co., Ltd.), and Takenate D-177N. (Manufactured by Mitsui Takeda Chemical Co., Ltd.). These curing agents can be suitably used because they are dissolved in a solvent having a low dissolving power.

In addition, toluene diisocyanate (TDI), 4,4-diphenylmethane diisocyanate (pure-MDI), polymeric MDI, xylylene diisocyanate (XDI), hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), hydrogenated XDI, hydrogenated MDI Isocyanate monomers such as allophanate, biuret, dimerization (uretdione), trimerization (isocyanurate), adduct, carbodiimide reaction and the like, and a mixture thereof are dissolved in a solvent having strong dissolving power. It is also possible to use.
As the component (C) in the present invention, a polyisocyanate compound having two or more isocyanate groups in one molecule is usually used.

The component (C) has an NCO / OH equivalent ratio of 0.1 to 2.0 (preferably 0.2 to 1.0, more preferably 0.2 to 2.0) based on the total amount of the components (A) and (B). ~ 0.95). At this time, if the NCO / OH equivalent ratio is larger than such a value, there is a possibility that the adhesion to the overcoating material is reduced. When the NCO / OH equivalent ratio is small, the degree of crosslinking of the coating film is low, and the curability and durability tend to be poor.

[solvent]
The undercoat material composition of the present invention uses a non-aqueous solvent as a solvent, and is a so-called weak solvent type paint composition in which 50% by weight or more of all solvents are aliphatic hydrocarbons. Such an aliphatic hydrocarbon-based solvent is characterized in that it has lower toxicity, higher operational safety, and less influence on air pollution than an aromatic hydrocarbon-based solvent. It also contributes to the prevention of lifting when the surface including the existing coating film is painted. Furthermore, since the aliphatic hydrocarbon-based solvent has an appropriate evaporation rate, it also advantageously acts on the penetration of the undercoat material composition of the present invention into the rust layer.

Examples of the aliphatic hydrocarbon-based solvent include, for example, n-hexane, n-pentane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, terpin oil, mineral spirit, and the like. . In addition, a solvent containing a high ratio of an aliphatic hydrocarbon-based solvent such as “HAWS” and “LAWS” (product of Shell Chemical Co., Ltd.) can also be used.
In addition to such aliphatic hydrocarbon solvents, it is also possible to use non-aqueous solvents that are commonly used in coatings, but the proportion is less than 50% by weight (preferably less than 40% by weight, more preferably less than 40% by weight). Less than 30% by weight). Examples of such non-aqueous solvents include aromatic hydrocarbon solvents such as toluene, xylene, and solvent naphtha, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and the like.

で は In the present invention, one or a combination of two or more of such non-aqueous solvents is used so that 50% by weight or more of the non-aqueous solvent is an aliphatic hydrocarbon. In particular, those which do not contain toluene and xylene and correspond to the second petroleum having a flash point of 21 ° C. or higher are preferable in terms of safety and health. When the amount of the aliphatic hydrocarbon is less than 50% by weight, the odor may be increased and the work safety may be reduced, or lifting may occur when the surface including the existing coating film is applied. Furthermore, there is a possibility that the permeability to the rust layer may be insufficient.

[Dehydrating agent]
In the undercoat material composition of the present invention, a dehydrating agent can be mixed. By mixing the dehydrating agent, excellent adhesion can be exhibited even when the rust surface contains moisture.

Examples of the dehydrating agent include trialkyl orthoformate, trialkyl orthoacetate, trialkyl orthoborate, and monoisocyanate compounds. Among them, the trialkyl orthoformate includes trimethyl orthoformate, triethyl orthoformate, tributyl orthoformate and the like. Examples of the trialkyl orthoacetate include trimethyl orthoacetate, triethyl orthoacetate, and tributyl orthoacetate. Examples of the trialkyl orthoborate include trimethyl orthoborate, triethyl orthoborate, and tributyl orthoborate. Examples of the monoisocyanate compound include phenyl isocyanate, p-chlorophenyl isocyanate, benzenesulfonyl isocyanate, p-toluenesulfonyl isocyanate, isocyanate ethyl methacrylate and the like.

As the dehydrating agent in the composition of the present invention, one or more selected from trimethyl orthoformate, triethyl orthoformate, tributyl orthoformate, trimethyl orthoacetate, triethyl orthoacetate, and tributyl orthoacetate are particularly suitable. Such a compound produces an ester and an alcohol by a chemical reaction with moisture remaining on the surface to be coated. For example, in the case of trimethyl orthoacetate, methyl acetate and methanol are produced.
When the above-mentioned compound is used as a dehydrating agent, the compound itself has volatility, and the reaction product (ester and alcohol) with the remaining water also has volatility and easily volatilizes in the atmosphere. Therefore, it is preferable because it does not adversely affect the physical properties of the formed coating film.

The content of the dehydrating agent in the composition of the present invention is usually 0.5 to 50 parts by weight, preferably 5 to 50 parts by weight, based on 100 parts by weight of the solid content of the resin (the total solid content of the components (A) and (B)). It is 40 parts by weight, more preferably 10 to 30 parts by weight. With such a content, the adhesion to the water-containing substrate can be sufficiently increased.

[Other ingredients]
In the composition of the present invention, in addition to the above-mentioned components, a rust preventive pigment, a coloring pigment, an extender pigment, a curing accelerator, a stable rust forming auxiliary, and the like can be mixed.

As the rust preventive pigment, for example, zinc powder, iron hydroxide, copper sulfate, nickel sulfate, zinc chromate, strontium chromate, iron oxide, aluminum tripolyphosphate, zinc phosphate, calcium phosphate, zinc molybdate, zinc calcium molybdate , Calcium molybdate, zinc phosphomolybdate, calcium phosphomolybdate, aluminum zinc phosphomolybdate and the like.
Examples of color pigments include, for example, inorganic pigments such as titanium oxide, zinc oxide, carbon black, iron oxide, ultramarine, and cobalt green, azo-based, naphthol-based, pyrazolone-based, anthraquinone-based, perylene-based, quinacridone-based, and disazo-based pigments. Organic pigments such as benzimidazole type and phthalocyanine type are exemplified.
Examples of the extender include heavy calcium carbonate, clay, kaolin, talc, precipitated barium sulfate, barium carbonate, white carbon, diatomaceous earth, and the like.
Examples of the curing accelerator include organic tin compounds such as dibutyltin dilaurate, dibutyltin dimaleate, dioctyltin dilaurate, dioctyltin dimaleate, dibutyltin acetate, and tin octylate; aluminum tris (acetylacetonate), and titanium bis (acetylacetonate). ), Zirconium bis (butoxy) bis (acetylacetonate) and other metal chelate compounds.
Examples of the stable rust forming aid include copper oxide, nickel oxide, manganese oxide, chromium nitrate, chromium phosphate and the like.

の 下 In addition to the above-mentioned components, various additives that can be generally added to a coating material can be added to the undercoat material composition of the present invention to such an extent that the effects of the present invention are not affected. Examples of such additives include a plasticizer, a preservative, a fungicide, an antialgal agent, an antifoaming agent, a leveling agent, a pigment dispersant, an anti-settling agent, an anti-sagging agent, and an antioxidant.

The solid content of the undercoat material composition of the present invention is usually 5 to 60% by weight, preferably 10 to 50% by weight. When the solid content is set in such a range, the balance between the permeability to the rust layer and the sealing property is improved, and the coating workability can be further improved.

[Applicable surface / painting method]
The composition of the present invention is used as a primer for metal surfaces in buildings, civil engineering structures, and the like. Specifically, it can be applied to, for example, a building steel frame, an iron door, a handrail, a fence, a gate, a gantry, a lightweight steel frame, a guardrail, a bridge, a steel tower, and the like. Even if these metal surfaces have already been coated with various coatings such as alkyd resin paints, chloride rubber paints, acrylic resin paints, urethane resin paints, acrylic silicone resin paints, fluororesin paints, etc. Good.

As a pretreatment for coating the undercoat material, it is desirable to perform keren with a disc sander, a wire foil, a scraper, a wire brush, sandpaper, or the like. In addition, a treatment with a thinner, an acid, or the like can be performed.
Further, the rust surface can be cleaned as a pretreatment. That is, the undercoat material may be applied after cleaning the rust surface. In particular, if an undercoating material containing a dehydrating agent is used, even if moisture is left by such a washing step, a decrease in adhesion of the undercoating material can be sufficiently suppressed. Therefore, the coating process can be started without waiting for the rust surface after the cleaning to be completely dried, which is advantageous in terms of shortening the construction period.
In the cleaning step, a method capable of removing deposits and the like on the rust surface may be appropriately adopted. Examples of the washing method include high-pressure washing with water and the like.

The undercoat material in the present invention can be applied by using, for example, various methods such as brush coating, roller coating, and spray coating. The coating amount at the time of coating is usually 50 to 500 g / m ² , preferably 100 to 300 g / m ² .
The number of times of application of the undercoat material may be appropriately set depending on the surface condition of the surface to be coated, and is usually 1 to 2 times. With the undercoat material of the present invention, even with such a small number of coatings, a coating film having both permeability to the rust layer and sealing properties can be formed.
The drying time of the undercoat material may usually be 3 hours or more.

After drying the undercoat, various overcoats can be applied.
The topcoat material is not particularly limited as long as it has cosmetic properties, and various materials can be used. Specifically, for example, an alkyd resin paint, an acrylic resin paint, a urethane resin paint, an acrylic silicone resin paint, a fluororesin paint, and the like can be given. These overcoating materials are desirably weak solvent type paints or water-based paints.
The overcoat material may be finished in one layer, or may be finished by laminating two or more layers.

実 施 Examples and comparative examples are shown below to further clarify the features of the present invention.

(Undercoat material production)
Undercoat materials 1 to 10 were manufactured with the formulations shown in Table 1, and the following tests were performed. The following materials were used as raw materials for producing the undercoat material.

-Resin 1: hydroxyl group-containing non-aqueous dispersion type resin (monomer composition: MMA, EA, St, 2-EHA, i-BMA, 2-HEMA, solid content: 50% by weight, hydroxyl value: 20 KOHmg / g, weight average molecular weight) : 80000, glass transition temperature: 35 ° C, solvent: mineral spirit)
・ Resin 2: Hydroxyl group-containing solvent-soluble resin (monomer composition: St, 2-EHA, i-BMA, 2-HEMA, solid content: 50% by weight, hydroxyl value: 20 KOH mg / g, weight average molecular weight: 20,000, glass) (Transition temperature: 35 ° C, solvent: mineral spirit)
・ Resin 3: Hydroxyl-containing solvent-soluble resin (monomer composition: MMA, St, n-BA, 2-HEMA, solid content: 50% by weight, hydroxyl value: 20 KOHmg / g, weight average molecular weight: 40000, glass transition temperature) : 50 ° C, solvent: xylene, butyl acetate)
・ Resin 4: Phosphoric acid group / hydroxyl group-containing solvent-soluble modified epoxy resin (dialkanolamine adduct of phosphoric acid modified phenol novolak type epoxy resin, solid content: 50% by weight, hydroxyl value: 110 KOHmg / g, solvent: HAWS (Product of Shell Chemical Co., Ltd.))
Curing agent: isocyanate compound (solid content: 80% by weight, NCO content: 15% by weight)
-Dehydrating agent: trimethyl orthoacetate MMA: methyl methacrylate, EA: ethyl acrylate, St: styrene, 2-EHA: 2-ethylhexyl acrylate, n-BA: n-butyl acrylate, i-BMA: i-butyl methacrylate, 2-HEMA: 2-hydroxyethyl methacrylate

(Test method)
(1) Penetration test An undercoat material is applied to a steel sheet that has been rusted by exposing the steel sheet SPCC-SB specified in JIS G3141 "Cold rolled steel sheet and steel strip" outdoors for three months. After brush-coating at 150 g / m ² and curing for 7 days in a standard condition (temperature of 23 ° C., humidity of 50%), the permeability to the rust layer was evaluated by a grid tape method (4 × 4 mm × 25 squares). Evaluation,
：: No peeling ：: Break in rust layer is less than 2/25 △: Break in rust layer is 2/25 or more and less than 5/25 x: Break in rust layer is 5/25 or more.
In addition, the surface of the exposed steel sheet was sufficiently washed with water, left standing for 2 hours in a standard state, and then subjected to a similar test on a test piece obtained by brush-coating a primer material at a coating amount of 150 g / m ^2. Was.

(2) Topcoat compatibility test A basecoat material is applied to a steel sheet that has been rusted by exposing the steel sheet SPCC-SB specified in JIS G3141 "Cold rolled steel sheet and steel strip" outdoors for three months. Brushing was carried out in an amount of 150 g / m ² . After curing for 3 hours in a standard state, a top coat material (trade name “Clean Mild Urethane”; manufactured by SK Chemical Co., Ltd.) was brush-coated at a coating amount of 200 g / m ² .
After curing for 7 days under the standard condition, the top coat compatibility was evaluated by measuring the specular glossiness (measurement angle: 60 degrees) of the coating film surface. Evaluation,
：: Specular gloss 70 or more 以上: Specular gloss 65 or more and less than 70 △: Specular gloss 60 or more and less than 65 ×: Specular gloss less than 60

(3) Lifting resistance test A two-component weak solvent soluble acrylic urethane resin paint (trade name "Clean Mild Urethane"; manufactured by SK Chemicals Co., Ltd.) was spray-coated on a tin plate and used as a test substrate. did. A cut (X cut) of 5 × 4 cm was made on the test substrate using a cutter, and the presence or absence of lifting when the test paint was brushed on the X cut portion was visually checked. Evaluation,
：: Lifting did not occur. ：: Lifting occurred slightly in the X-cut portion. △: Lifting occurred in the X-cut portion. X: Lifting occurred in a plane portion other than the X-cut portion.

(Test results)
As shown in the test results in Table 2, in Examples 1 to 6, good results could be obtained in any of the tests.
In contrast, Comparative Examples 1 and 3 resulted in poor topcoat compatibility. Comparative Example 2 resulted in poor permeability to the rust layer. In Comparative Example 4, the results were inferior in overcoat suitability and lifting resistance.

Claims (2)

(A) a hydroxyl group-containing non-aqueous dispersion resin, (B) a hydroxyl group-containing solvent-soluble resin, (C) an isocyanate compound,
Wherein the component (B) has chelating ability;
An undercoat material composition characterized in that at least 50% by weight of all solvents are aliphatic hydrocarbons. (4) A coating method comprising applying the undercoat material composition according to claim 1 to a metal surface having rust, and then applying an overcoat material.