JP7636866B2 - Coating Method - Google Patents

Description

The present invention relates to a novel method for forming a coating.

Traditionally, buildings, civil engineering structures, and the like have been finished by laminating various coating materials (undercoat materials, topcoat materials, etc.) to form a coating film for the purpose of imparting functionality to the base material and improving its protection and aesthetics. In recent years, in the field of such coating materials, there has been a growing movement to reduce the use of aromatic hydrocarbon-containing solvents such as toluene and xylene, taking into consideration safety during painting, work hygiene, and the impact on air pollution. In response to this trend, various environmentally friendly coating materials that use aliphatic hydrocarbon-containing solvents have been proposed.

Furthermore, as such environmentally friendly coating materials, coating materials that use oxidatively cured resins are known (Patent Document 1, etc.). Patent Document 1 describes a one-component cross-linking (curing) coating material that causes a cross-linking reaction by oxidation between reactive double bonds contained in unsaturated fatty acids. Coating materials that contain such oxidatively cured resins are often used as topcoat materials because they have excellent gloss and workability.

JP 2001-262055 A

However, when such environmentally friendly coating materials are used as topcoats, depending on the type of undercoat, the adhesion of the topcoat may be insufficient, causing lifting and other problems. There are also cases where the gloss is poor.

The present invention was developed in consideration of these points, and aims to improve adhesion, lifting resistance, etc., in a coating formation method in which a base coat is applied to a substrate, and then a top coat containing an oxidatively curable resin is applied.

In order to solve these problems, the inventors conducted extensive research and came up with the idea of a coating method in which a base coat is applied to a substrate, and then a top coat is applied, the essential component of which is a specific oxidatively curable resin, thus completing the present invention.

That is, the present invention has the following features.
1. A coating method for applying a base coat material to a substrate and then applying a top coat material to the substrate.
The topcoat material comprises an oxidatively curable resin (A), a metal dryer (B), and an aliphatic hydrocarbon-containing solvent;
The oxidation-curing resin (A) is a mineral spirit solution of an oxidation-curing resin,
The oxidatively curable resin (A) has an amine value of 0.1 mgKOH/g or more relative to the solid content of the oxidatively curable resin (A) , and the content of the alkyd resin in the solid content of the oxidatively curable resin (A) is 10% by weight or more and 22% by weight or less in terms of solid content,
The aliphatic hydrocarbon-containing solvent is selected from the group consisting of n-hexane, n-pentane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, terpine oil, and mineral spirits, and is characterized in that the coating forming method contains mineral spirits.
2. The method for forming a coating film according to 1., wherein the oxidatively curable resin (A) is a mineral spirit solution of an alkyd resin-modified acrylic resin.
3. The method for forming a coating according to 1. or 2., wherein the undercoat material contains an epoxy resin.

The coating formation method of the present invention makes it possible to form a coating that has excellent adhesion to the undercoat material, resistance to lifting, etc. Furthermore, it is possible to obtain advantageous effects in terms of finish properties such as gloss, etc.

The following describes how to implement the present invention.

The present invention relates to a coating method in which a base material is coated with an undercoat and then coated with a topcoat, and can be used primarily to protect the framework and improve the aesthetics of buildings and civil engineering structures. In particular, the present invention is characterized by the application of a topcoat that contains a specific oxidatively cured resin as an essential component.

<Substrate>
The present invention is mainly used for protecting the framework of buildings, civil engineering structures, etc., and can be used for surface finishing of various substrates such as concrete, mortar, porcelain tiles, siding boards, extrusion molding plates, color steel plates, copper plates, aluminum plates, titanium plates, stainless steel plates, galvanized steel plates, metals, glass, plastics, wood, plywood, etc. These substrates may have an old coating film on their surfaces.
In the coating formation method of the present invention, the undercoat material can be applied directly to the substrate, but it is also possible to previously apply some kind of surface treatment to the substrate (such as a primer treatment using a sealer, primer, surfacer, filler, putty, or other undercoat material).

<Undercoat material>
As the undercoat material of the present invention, various known or commercially available undercoat materials can be used.Specific undercoat materials include, for example, acrylic resin undercoat materials, epoxy resin undercoat materials, urethane resin undercoat materials, chlorinated rubber undercoat materials, etc.Such undercoat materials may be either clear type or colored type.In addition, they may contain rust-preventive pigments such as phosphate-based, molybdate-based, and zinc-based.

In the present invention, a remarkable effect can be obtained when an epoxy resin undercoat is used. Normally, when a topcoat containing an oxidatively cured resin and a metal dryer is applied on an epoxy resin undercoat, the reactivity of the topcoat may decrease due to the interaction between the undercoat and the metal dryer. Therefore, when the topcoat is applied two or more times, the lower topcoat coating film is likely to dissolve or lift (lifting). In contrast, the present invention uses a specific topcoat, which can suppress the occurrence of such defects, and can provide excellent adhesion and lifting resistance, and improve the finish.

The epoxy resin undercoat material may contain one or more epoxy resins as a binder component. Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, alkyl ether type epoxy resin, hydrogenated bisphenol A type epoxy resin, and the like, or modified products thereof.
The epoxy resin undercoat material may be in the form of either a one-component type or a two-component type. In the case of the two-component type, a hardener containing an amine compound or the like can be used.

The undercoat material requires the binder component as an essential component, and various other components can be blended in as long as they do not affect the effects of the present invention. Examples of such components include color pigments, extender pigments, rust inhibitors, thickeners, film-forming aids, leveling agents, plasticizers, antifreeze agents, pH adjusters, diluents, preservatives, antifungal agents, anti-algae agents, antibacterial agents, dispersants, defoamers, UV absorbers, antioxidants, light stabilizers, fibers, catalysts, crosslinking agents, etc.

Such undercoat materials can be applied using various methods, for example, brush coating, roller coating, spray coating, roll coater, flow coater, etc. The amount of application varies depending on the form of the undercoat material, but is preferably 0.05 to 3 kg/m ² (more preferably 0.05 to 2 kg/m ² ).

<Topcoat material>
The topcoat material of the present invention contains an oxidatively curable resin (A), a metal drier (B), and an aliphatic hydrocarbon-containing solvent, and is a so-called weak solvent type coating material.

The oxidatively curable resin (A) of the present invention (hereinafter also referred to as "component (A)") is oxidized in air by the double bond (oxidatively polymerizable group) that can be oxidized and polymerized, and is cured and dried. There are no particular limitations on the type of resin (A) as long as it has an oxidatively polymerizable group, and examples of the resin include acrylic resin, polyester resin, polyurethane resin, and epoxy resin.

In the present invention, it is preferable to contain an oxidatively curable acrylic resin as component (A). In the present invention, it is preferable to contain an alkyd resin-modified acrylic resin as the oxidatively curable acrylic resin, and specifically, the following resins can be used.
1) A resin obtained by polymerizing an alkyd resin with a vinyl monomer capable of being copolymerized and/or graft polymerized with the alkyd resin.
2) Resins obtained by reacting an alkyd resin with an acrylic resin having a group reactive with the alkyd resin (such as a carboxyl group, a hydroxyl group, or an epoxy group).

The alkyd resin in 1) and 2) above can be a resin obtained by a condensation reaction of a polyhydric alcohol, a polybasic acid, and an unsaturated fatty acid and/or an oil.

Examples of polyhydric alcohols include dihydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, and hexanediol; trihydric alcohols such as glycerin and trimethylolpropane; tetrahydric alcohols such as pentaerythritol; and hexahydric alcohols such as dipentaerythritol, mannitol, and D-sorbitol. These can be used alone or in combination of two or more.

Examples of polybasic acids include phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, succinic anhydride, maleic acid, maleic anhydride, adipic acid, sebacic acid, and tetrahydrophthalic anhydride. These can be used alone or in combination of two or more.

The unsaturated fatty acid is not particularly limited as long as it has at least one oxidatively polymerizable group (unsaturated carbon bond) in the molecule, and examples of the unsaturated fatty acid include known unsaturated fatty acids. Examples of unsaturated fatty acids include drying oil fatty acids and semi-drying oil fatty acids. In the present invention, a drying oil fatty acid refers to a fatty acid with a solid iodine value of 130 or more, and a semi-drying oil fatty acid refers to a fatty acid with a solid iodine value of 100 or more and less than 130.

Examples of drying oil fatty acids and semi-drying oil fatty acids include fish oil fatty acids, dehydrated castor oil fatty acids, safflower oil fatty acids, linseed oil (linseed oil) fatty acids, tung oil fatty acids, soybean oil fatty acids, sesame oil fatty acids, poppy oil fatty acids, perilla oil fatty acids, hemp seed oil fatty acids, grape kernel oil fatty acids, corn oil fatty acids, tall oil fatty acids, sunflower oil fatty acids, cottonseed oil fatty acids, walnut oil fatty acids, rubber seed oil fatty acids, hydinoic acid fatty acids, oleic acid, linoleic acid, linolenic acid, etc. These can be used alone or in combination of two or more.

If necessary, drying oil fatty acids and/or semi-drying oil fatty acids can be used in combination with non-drying oil fatty acids. In the present invention, non-drying oil fatty acids refer to fatty acids with a solid iodine value of less than 100. Examples of non-drying oil fatty acids include coconut oil fatty acids, hydrogenated coconut oil fatty acids, palm oil fatty acids, caproic acid, capric acid, lauric acid, myristic acid, palmitic acid, and stearic acid. These can be used alone or in combination of two or more.

The oils and fats include oils and fats having unsaturated carbon bonds, such as drying oils or semi-drying oils such as fish oil, dehydrated castor oil, castor oil, safflower oil, linseed oil, tung oil, soybean oil, sesame oil, poppy seed oil, perilla oil, hemp seed oil, grape kernel oil, corn oil, tall oil, sunflower oil, cottonseed oil, walnut oil, and rubber seed oil. These can be used alone or in combination of two or more.

As the alkyd resin in 1) and 2) above, an alkyd resin having an oxidative polymerizable group in which an unsaturated carbon bond derived from an unsaturated fatty acid and/or fat is introduced can also be used.

The component (A) of the present invention is characterized in that the content of the alkyd resin is 5% by weight or more and 50% by weight or less (preferably 10% by weight or more and 40% by weight or less) as solids in the solid content of the component (A). In such a case, it is possible to exhibit excellent adhesion, lifting resistance, etc.

The vinyl monomer in 1) above, or the vinyl monomer constituting the acrylic resin in 2) above, is, for example, one that contains an alkyl (meth)acrylate ester as an essential component, and preferably also contains an aromatic monomer and other vinyl monomers, etc.

Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-amyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, octadecyl (meth)acrylate, cyclohexyl (meth)acrylate, and the like. These can be used alone or in combination of two or more.

Aromatic monomers include, for example, styrene, 2-methylstyrene, vinyltoluene, t-butylstyrene, chlorostyrene, vinylanisole, vinylnaphthalene, divinylbenzene, etc. These can be used alone or in combination of two or more.

The (A) component of the present invention is characterized by an amine value of 0.1 mgKOH/g or more (preferably 0.3 to 10 mgKOH/g, more preferably 0.5 to 8 mgKOH/g). Such an amine value of the (A) component can be significantly effective in improving adhesion to various undercoats and lifting resistance, particularly when the undercoat contains an epoxy resin as a resin component. The amine value is a value expressed by the number of mg of potassium hydroxide equivalent to the moles of acid groups contained in 1 g of solids of the (A) component.

To set the amine value of component (A) within the above range, for example, it is preferable to use an amino group-containing vinyl monomer as the vinyl monomer during polymerization of component (A). This can improve adhesion and lifting resistance. Examples of amino group-containing vinyl monomers include N-methylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminoethyl vinyl ether, N-(2-dimethylaminoethyl)acrylamide, and N-(2-dimethylaminoethyl)methacrylamide. These can be used alone or in combination of two or more.

In the present invention, other vinyl monomers such as hydroxyl group-containing vinyl monomers, carboxyl group-containing vinyl monomers, and epoxy group-containing vinyl monomers can also be used.
Examples of hydroxyl group-containing vinyl monomers include 2-hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate;
Examples of the carboxyl group-containing vinyl monomer include acrylic acid, methacrylic acid, crotonic acid, maleic acid or its monoalkyl ester, itaconic acid or its monoalkyl ester, fumaric acid or its monoalkyl ester, etc.;
Examples of epoxy group-containing vinyl monomers include glycidyl (meth)acrylate, diglycidyl (meth)acrylate, allyl glycidyl ether, diglycidyl fumarate, 3,4-epoxycyclohexyl (meth)acrylate, 3,4-epoxyvinylcyclohexane, ε-caprolactone-modified glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, and the like;
These can be used alone or in combination of two or more.

In addition to the alkyd resin, oxidatively polymerizable groups can also be introduced into the (A) component of the present invention. In this case, for example, when polymerizing the (A) component, it is possible to use a vinyl monomer having an oxidatively polymerizable group, or a vinyl monomer in which an unsaturated fatty acid is added to an epoxy group-containing vinyl monomer. It is also possible to add an unsaturated fatty acid to an epoxy group-containing resin obtained by copolymerizing an epoxy group-containing vinyl monomer with another vinyl monomer that is copolymerizable with this monomer.

As vinyl monomers having an oxidative polymerizable group, for example, vinyl monomers containing a dicyclopentadieneoxyalkyl group such as dicyclopentadieneoxyalkyl (meth)acrylate, and vinyl monomers containing an allyl group such as allyl (meth)acrylate can be used. These can be used alone or in combination of two or more.

A vinyl monomer in which an unsaturated fatty acid is added to an epoxy group-containing vinyl monomer is obtained by the reaction of an epoxy group with a carboxyl group in an unsaturated fatty acid. Examples of the epoxy group-containing vinyl monomer include those similar to those mentioned above. Examples of the unsaturated fatty acid include those similar to those mentioned above.

The (A) component of the present invention may have an acid value. The acid value is preferably 0.1 to 30 mgKOH/g (more preferably 0.5 to 10 mgKOH/g, more preferably 1 to 8 mgKOH/g). Such an acid value of the (A) component can improve the curing property and enhance the suitability for overcoating. The acid value is a value expressed by the number of mg of potassium hydroxide equivalent to the moles of acid groups contained in 1 g of resin solids. To set the acid value in the (A) component within the above range, for example, an alkyd resin having an acid value may be used as the alkyd resin, or the above carboxyl group-containing vinyl monomer may be used as the vinyl monomer.

The metal drier (B) in the coating material of the present invention is a component that acts as a curing catalyst for the above-mentioned component (A). As the component (B), for example, known organometallic compounds such as cobalt-based, manganese-based, zirconium-based, tin-based, lead-based, zinc-based, copper-based, iron-based, calcium-based, and barium-based compounds can be used. Specific examples include cobalt octylate, cobalt naphthenate, manganese octylate, manganese naphthenate, zirconium octylate, zirconium naphthenate, tin octylate, lead naphthenate, zinc naphthenate, copper naphthenate, iron naphthenate, calcium octylate, calcium naphthenate, barium octylate, and barium naphthenate. These can be used alone or in combination of two or more.

The mixing ratio of component (B) is preferably 0.001 to 10 parts by weight (more preferably 0.01 to 5 parts by weight) of metal content per 100 parts by weight of the solid content of component (A).

The aliphatic hydrocarbon-containing solvent of the present invention is a non-aqueous solvent that is less toxic than aromatic hydrocarbon-containing solvents, has high operational safety, and has little impact on air pollution. Examples of aliphatic hydrocarbons include n-hexane, n-pentane, n-octane, n-nonane, n-decane, n-undecane, and n-dodecane. In addition, terpine oil, mineral spirits, and the like can also be used as the aliphatic hydrocarbon-containing solvent in the present invention.

In addition to the above-mentioned components, the topcoat material of the present invention can also contain various other components to the extent that they do not affect the effects of the present invention. Examples of such components include color pigments, extender pigments, thickeners, film-forming agents, leveling agents, plasticizers, antifreeze agents, pH adjusters, diluents, preservatives, antifungal agents, anti-algae agents, antibacterial agents, dispersants, defoamers, UV absorbers, antioxidants, light stabilizers, fibers, catalysts, crosslinking agents, etc.

The topcoat material of the present invention can be manufactured by uniformly stirring and mixing the above-mentioned components by conventional methods. The topcoat material of the present invention can be used in the form of a one-component type.

The topcoat material of the present invention can be applied to the substrate via the undercoat material coating film. In this case, the composition of the present invention can also be appropriately diluted with an aliphatic hydrocarbon solvent. As a coating method, for example, various methods such as brush coating, roller coating, spray coating, roll coater, flow coater, etc. can be used. The coating amount is preferably about 0.1 to 0.5 kg/m ^2. In addition, the topcoat material may be finished with one layer, or it can be finished by laminating two or more layers.

The following examples will clarify the features of the present invention.

(Topcoat materials 1 to 5)
The raw materials shown below were mixed in the usual manner according to the composition shown in Table 1 to produce topcoat materials 1 to 5.

The following materials were used for each topcoat:
・Oxidation curing resin 1
Alkyd resin modified acrylic resin [mineral spirit solution of copolymer of alkyd resin, styrene, isobutyl methacrylate, 2-ethylhexyl acrylate, and dimethylaminoethyl methacrylate, amine value: 0.4 mg KOH/g, acid value: 3 mg KOH/g, solid content: 50% by weight (alkyd resin content in solid content: 22% by weight)]
Oxidation curing resin 2
Alkyd resin modified acrylic resin [mineral spirit solution of copolymer of alkyd resin, styrene, isobutyl methacrylate, 2-ethylhexyl acrylate, and dimethylaminoethyl methacrylate, amine value: 2 mg KOH/g, acid value: 3 mg KOH/g, solid content: 50% by weight (alkyd resin content in solid content: 18% by weight)]
Oxidation curing resin 3
Alkyd resin modified acrylic resin [mineral spirit solution of copolymer of alkyd resin, styrene, isobutyl methacrylate, 2-ethylhexyl acrylate, and dimethylaminoethyl methacrylate, amine value: 0.4 mg KOH/g, acid value: 3 mg KOH/g, solid content: 50% by weight (alkyd resin content in solid content: 8% by weight)]
Oxidation curing resin 4
Alkyd resin modified acrylic resin [mineral spirit solution of copolymer of alkyd resin, styrene, isobutyl methacrylate, and 2-ethylhexyl acrylate, amine value: 0 mg KOH/g, acid value: 3 mg KOH/g, solid content: 50% by weight (alkyd resin content in solid content: 3% by weight)]
Oxidation curing resin 5
Alkyd resin modified acrylic resin [mineral spirit solution of copolymer of alkyd resin, styrene, isobutyl methacrylate, and 2-ethylhexyl acrylate, amine value: 0 mg KOH/g, acid value: 3 mg KOH/g, solid content: 50% by weight (alkyd resin content in solid content: 8% by weight)]
Metal dryer: Mixture of cobalt naphthenate and zirconium naphthenate (mineral spirit solution, Co content 0.3 wt%, Zr content 3 wt%)
Color pigment: titanium oxide Additives: antifoaming agent, dispersant, light stabilizer, etc. Solvent: non-aqueous solvent containing aliphatic hydrocarbons (mixture of mineral spirits and petroleum solvent containing aromatic hydrocarbons, aliphatic hydrocarbon content: 65% by weight)

(Examples 1 to 3, Comparative Examples 1 and 2)
A two-component reactive curing epoxy resin undercoat material [main component: phenol novolac type epoxy resin with an epoxy equivalent of 1350 g/eq, hardener component: polyamide amine with an active hydrogen equivalent of 360 g/eq] was brushed onto a 200 x 150 mm tinplate at an application rate of 0.1 kg/ ^m2 , and the plate was dried and cured under standard conditions for 24 hours.
Next, the topcoat material obtained by the above method was brushed at a coating amount of 0.12 kg/ ^m2 , and after drying and curing for a predetermined time (24 hours, 48 hours), the same topcoat material was brushed at a coating amount of 0.12 kg/ ^m2 to prepare a test specimen, which was then evaluated as follows. The results are shown in Table 1.

(Lifting resistance evaluation)
The surface condition of the test specimens prepared by the above method was observed and evaluated according to the following four-level scale.
- Those where no abnormality was found are rated "A".
- Items with almost no abnormalities (some shrinkage) are rated as "B".
- If lifting is observed (shrinkage on the entire surface), the product is rated as "C".
- If dissolution was observed, it is marked as "D".

(Adhesion)
The coating of the test specimen prepared by the above method was cross-cut with a cutter knife, and tape was applied to the cross-cut area and peeled off to evaluate adhesion. The evaluation was performed on a four-level scale (A>B>C>D: poor), with "A" being the one where no abnormality was observed and "D" being the one where peeling was observed.

(Finishability)
The finished appearance (color tone, gloss, etc.) of the test specimens prepared by the above method was visually confirmed. The evaluation was performed on a four-level scale (A>B>C>D: poor), with "A" representing excellent finish and "D" representing poor finish.

Claims (3)

A coating method for applying a base coat material to a substrate and then applying a top coat material to the substrate,
The topcoat material comprises an oxidatively curable resin (A), a metal dryer (B), and an aliphatic hydrocarbon-containing solvent;
The oxidation-curing resin (A) is a mineral spirit solution of an oxidation-curing resin,
The oxidatively curable resin (A) has an amine value of 0.1 mgKOH/g or more relative to the solid content of the oxidatively curable resin (A), and the content of the alkyd resin in the solid content of the oxidatively curable resin (A) is 10% by weight or more and 22% by weight or less in terms of solid content,
The aliphatic hydrocarbon-containing solvent is selected from the group consisting of n-hexane, n-pentane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, terpine oil, and mineral spirits, and is characterized in that the coating forming method contains mineral spirits. The coating method according to claim 1, characterized in that the oxidatively curable resin (A) is a mineral spirit solution of an alkyd resin-modified acrylic resin. 3. The method for forming a coating film according to claim 1, wherein the undercoat material contains an epoxy resin.