Coating formation method

Abstract

To provide a film formation method which is excellent in adhesion between a metal base material and a top coating material.SOLUTION: A film formation method applies an undercoat material to a metal base material and then applies a top coating material thereto, wherein the undercoat material is composed of a main agent containing an epoxy resin (A) and a pigment (B) and a curing agent containing a polyamine compound (C), and the polyamine compound (C) contains a polyamine compound (c1) having an active hydrogen equivalent per solid content of 30 g / eq or more and 240 g / eq or less, and a polyamine compound (c2) having an active hydrogen equivalent per solid content of more than 240 g / eq or more and 800 g / eq or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a novel coating forming method. [Background Art]

[0002] Metal base materials used for wall materials, roofing materials, beams, columns, handrails, air conditioner outdoor units and the like are subjected to various types of coating for the purpose of improving corrosion resistance, aesthetic appearance and other properties. In such coating, an undercoating material and a topcoating material are often used, and among these, epoxy resin coating materials, which are excellent in adhesion to metal base materials and corrosion resistance, are widely employed as the undercoating material.

[0003] However, for epoxy resin coating materials, the coating interval before applying the topcoating material is specified, and it is known that when the upper limit of the interval is exceeded, the adhesion to the topcoating material is significantly reduced. To address such problems, for example, Patent Document 1 describes that an epoxy ester resin obtained by reacting dimer acid with a bisphenol-type epoxy resin is used as a binder resin. [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. H8-048914 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] However, simply blending a specific epoxy resin as in Patent Document 1 may make it difficult to ensure sufficient adhesion depending on the coating conditions of the topcoating material, etc., and there was room for improvement.

[0006] The present invention has been made in view of the above problems, and an object of the present invention is to provide a coating forming method excellent in adhesion to a topcoating material. [Means for Solving the Problem]

[0007] To solve these problems, the present inventors, after diligent research, conceived a method for forming a coating using a primer comprising an epoxy resin and a curing agent containing two polyamine compounds having a specific amount of active hydrogen equivalent, and thus completed the present invention.

[0008] In other words, the present invention has the following features. 1. A method for forming a coating on a metal substrate, comprising applying a primer and then a topcoat, The above-mentioned primer consists of a main component containing epoxy resin (A) and pigment (B), and a curing agent containing a polyamine compound (C). The aforementioned polyamine compound (C) The amount of active hydrogen per unit of solid content 190 g / eq or higher 230 Polyamine compounds (c1) with a g / eq or less, and The amount of active hydrogen per unit of solid content 280 g / eq or higher 400 A method for forming a coating, characterized by containing a polyamine compound (C2) with a concentration of g / eq or less. 2. The above polyamine compound (C) is The method for forming a film according to claim 1, characterized in that it contains the polyamine compound (c1) and the polyamine compound (c2) in a solid weight ratio of 5:95 to 50:50. [Effects of the Invention]

[0009] According to the coating formation method of the present invention, excellent performance in terms of adhesion can be achieved. [Modes for carrying out the invention]

[0010] The following describes embodiments for carrying out the present invention.

[0011] [Metal base material] Examples of objects to be coated with the present invention include wall materials, roofing materials, beams, columns, handrails, air conditioner outdoor units, doors, fences, frames, guardrails, bridges, and steel towers. The present invention can be applied to the metal substrates that constitute these objects. Examples of metal substrates include iron, cold-rolled steel, aluminum steel, stainless steel, copper steel, hot-dip galvanized steel, hot-dip zinc-aluminum alloy plated steel, electro-galvanized steel, electro-alloy plated steel, alloy plated steel, copper plated steel, tin-plated steel, and other metal substrates, or metal substrates that have been subjected to surface treatments such as phosphate-based or chromate-based coatings. Furthermore, these metal substrates may have various existing coatings such as alkyd resin-based, chlorinated rubber-based, acrylic resin-based, urethane resin-based, acrylic silicone resin-based, and fluororesin-based coatings.

[0012] [Undercoat material] In this invention, a primer is first applied to the metal substrate. That is, the primer is a material for the metal substrate. The primer of this invention consists of a main component containing epoxy resin (A) and pigment (B), and an amine curing agent (C).

[0013] The main component of the primer of the present invention comprises an epoxy resin (A) and a pigment (B). As epoxy resin (A), any epoxy resin having two or more epoxy groups in one molecule can be used. Examples include bisphenol type epoxy resins such as bisphenol A type epoxy resin and bisphenol F type epoxy resin, phenol novolac type epoxy resins such as phenol novolac type bisphenol A epoxy resin and phenol novolac type bisphenol F epoxy resin, novolac type epoxy resins such as cresol novolac type epoxy resin and bisphenol A novolac type epoxy resin, copolymer epoxy resins of bisphenol A type epoxy resin and phenol novolac resin, diglycidyl ether of dihydroxynaphthalene, polyglycidyl ether of mono(di)hydroxynaphthalene novolac, polyglycidyl ether of phenol-divinylbenzene crosslinked phenol resin, polyglycidyl ether of bisphenol A-divinylbenzene crosslinked phenol resin, polyglycidyl ether of mono(di)hydroxynaphthalene-divinylbenzene crosslinked phenol resin, or modified versions thereof. These can be used individually or in combination of two or more.

[0014] The epoxy equivalent (per solid content) of the epoxy resin is preferably 300 to 2000 g / eq, more preferably 350 to 1800 g / eq. Note that epoxy equivalent is the value obtained by dividing the molecular weight of the epoxy resin by the number of epoxy groups.

[0015] As the pigment (B), for example, coloring pigments, extender pigments, rust-preventive pigments and the like can be used. Among these, examples of coloring pigments include titanium oxide, zinc oxide, carbon black, graphite, black iron oxide, copper chromium black, cobalt black, copper manganese iron black, red iron oxide, molybdate orange, permanent red, permanent carmine, anthraquinone red, perylene red, quinacridone red, yellow iron oxide, titanium yellow, fast yellow, benzimidazolone yellow, chromium green, cobalt green, phthalocyanine green, ultramarine blue, Prussian blue, cobalt blue, phthalocyanine blue, quinacridone violet, dioxazine violet, and the like. The color tone of the coating film can be adjusted by appropriately using one or two or more of these coloring pigments.

[0016] Examples of extender pigments include heavy calcium carbonate, light calcium carbonate, kaolin, clay, pottery clay, China clay, diatomaceous earth, hydrated fine powder silicic acid, talc, baryta powder, barium sulfate, precipitated barium sulfate, barium carbonate, magnesium carbonate, silica powder, aluminum hydroxide, and the like, and one or two or more of these can be used.

[0017] Examples of rust-preventive pigments include phosphoric acid compounds such as zinc phosphate, iron phosphate, aluminum phosphate, calcium phosphate, and magnesium phosphate; phosphorous acid compounds such as zinc phosphite, iron phosphite, aluminum phosphite, calcium phosphite, and magnesium phosphite; polyphosphoric acid compounds such as zinc polyphosphate, iron polyphosphate, and aluminum polyphosphate; molybdic acid compounds such as zinc molybdate, aluminum molybdate, calcium molybdate, barium molybdate, and aluminum phosphomolybdate; vanadium compounds such as vanadium oxide; boric acid compounds such as barium borate, barium metaborate, and calcium borate; cyanamide compounds such as zinc cyanamide and calcium zinc cyanamide; and one or two or more of these can be used.

[0018] The proportion of such pigment (B) is 100 to 500 parts by weight, preferably 130 to 400 parts by weight, more preferably 150 to 300 parts by weight, relative to 100 parts by weight of the solid content of the epoxy resin. In such a case, adhesion to the metal substrate and the top coating material can be enhanced, and excellent performance in terms of corrosion resistance and the like can be obtained.

[0019] In addition to the above components, various other components can also be mixed into the main agent to an extent that does not affect the effects of the present invention. Examples of such components include solvents, plasticizers, preservatives, antifungal agents, antialgal agents, rust inhibitors, defoamers, leveling agents, pigment dispersants, anti-sedimentation agents, anti-sagging agents, anti-skinning agents, dehydrating agents, matting agents, ultraviolet absorbers, light stabilizers, antioxidants, catalysts, silane coupling agents, and the like. The main agent can be produced by uniformly stirring and mixing each of the above components according to a conventional method.

[0020] The curing agent in the undercoat material of the present invention contains a polyamine compound (C). The polyamine compound (C) is a component that forms a crosslinked coating film by reacting with the epoxy resin (A). The present invention is characterized in that the polyamine compound (C) includes a polyamine (c1) having an active hydrogen equivalent per solid content of 30 g / eq or more and 240 g / eq or less, and a polyamine (c2) having an active hydrogen equivalent per solid content of more than 240 g / eq and 800 g / eq or less. By including two types of polyamines having active hydrogen equivalents within such specific ranges in combination, adhesion to the top coating material can be improved.

[0021] Specifically, the polyamine (c1) has an active hydrogen equivalent per solid content of 30 g / eq or more and 240 g / eq or less, preferably 40 g / eq or more and 235 g / eq or less, more preferably 50 g / eq or more and 230 g / eq or less, and particularly preferably 110 g / eq or more and 220 g / eq or less. By including a polyamine having an active hydrogen equivalent within such a range, the crosslinking density of the formed coating film is increased, and the durability and corrosion resistance of the formed coating film can be enhanced. On the other hand, the polyamine (c2) described above has an active hydrogen equivalent per solid content of more than 240 g / eq and 8000 g / eq or less, preferably 245 g / eq to 700 g / eq, more preferably 250 g / eq to 600 g / eq, and particularly preferably 300 g / eq to 490 g / eq. By including a polyamine having an active hydrogen equivalent within this range, sufficient adhesion to the metal substrate can be ensured, and corrosion protection can be fully demonstrated. Active hydrogen equivalent is the value obtained by dividing the molecular weight of a polyamine compound by the number of hydrogen atoms in the amino group.

[0022] In the present invention, the above polyamine compound (c1) and the above polyamine compound (c2) are preferably contained in a solid content weight ratio of 5:95 to 50:50, more preferably 8:92 to 45:55, and even more preferably 10:90 to 40:60. In this case, even if there is a painting interval before applying the topcoat, the adhesion to the topcoat can be further improved.

[0023] Examples of the polyamine compound (C) mentioned above include polyamines, polyamidoamines (also called polyaminoamides or polyamide resins), and the like.

[0024] Examples of polyamines include aliphatic polyamines, aromatic polyamines, alicyclic polyamines, and modified polyamines thereof. Examples of aliphatic polyamines include ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, diethylenetriamine, dipropylenetriamine, triethylenetetramine, and pentaethylenehexamine. Examples of aromatic polyamines include tolylenediamine, xylylenediamine, phenylenediamine, and diaminodiphenylmethane. Examples of alicyclic polyamines include diaminocyclohexylmethane, piperazine, 2,5-dimethylpiperazine, and isophoronediamine.

[0025] Examples of modified polyamines include epoxy adduct modified products, which are reaction products of the above polyamines with epoxy compounds; Michael modified products, which are reaction products of the above polyamines with acrylic compounds; Mannich modified products, which are reaction products of amines with phenol compounds and aldehydes; ketimines (ketoimines), which are reaction products of amines with ketones; and reaction products of amines with urea or thiourea.

[0026] Examples of polyamidoamines include reaction products of the above-mentioned polyamines with dimer acids (polymers of unsaturated fatty acids) or other polycarboxylic acids, and modified polyamidoamines (e.g., epoxy adduct modified products, Michael modified products, Mannich modified products), etc.

[0027] The present invention preferably contains polyamidoamines, and more preferably contains modified polyamidoamines. This can further improve adhesion to the topcoat material. In particular, the above effect can be enhanced even when there is a painting interval before applying the topcoat material.

[0028] In addition to the components mentioned above, the curing agent may also contain various other components to the extent that they do not affect the effects of the present invention. Examples of such components include solvents, plasticizers, preservatives, fungicides, anti-algal agents, rust inhibitors, defoamers, leveling agents, pigment dispersants, anti-settling agents, anti-sagging agents, anti-skinning agents, dehydrating agents, matting agents, UV absorbers, light stabilizers, antioxidants, catalysts, and silane coupling agents. The curing agent can be manufactured by uniformly stirring and mixing each of the above components using conventional methods.

[0029] The primer of the present invention is distributed in a two-component form consisting of the main component and the hardener described above, and these are mixed and used during painting. The mixing ratio of the main component and the hardener is not particularly limited, but it should be set within a range in which the equivalent ratio [(equivalent of active hydrogen) / (equivalent of epoxy)] is preferably 0.1 to 2, more preferably 0.2 to 1, and even more preferably 0.3 to 0.9. In this range, the effects of the present invention can be further enhanced. The equivalent ratio [(equivalent of active hydrogen) / (equivalent of epoxy)] in the present invention is a value obtained by {[(amount of polyamine compound (c1) / equivalent of active hydrogen of polyamine compound (c1)) + (amount of polyamine compound (c2) / equivalent of active hydrogen of polyamine compound (c2)] / (amount of epoxy resin / equivalent of epoxy resin)}.

[0030] Various methods can be used to apply the primer, such as brush painting, roller painting, spray painting, roll coater, and flow coater. The application amount is preferably 30 to 500 g / m². 2 Comfortable 50-300g / m 2 Furthermore, the dry film thickness is preferably 10 to 100 μm, more preferably 20 to 80 μm. The number of coats of the primer can be set appropriately depending on the surface condition of the metal substrate, but is preferably 1 to 2 times.

[0031] The drying time for the primer is preferably 1 hour or more, more preferably 2 to 400 hours. However, even if the painting interval between the application of the primer and the application of the topcoat is 30 days, sufficient adhesion can still be ensured. The drying temperature is preferably -10 to 50°C, more preferably -5 to 40°C. In this invention, excellent performance can be achieved even at relatively low drying temperatures (for example, -10 to 15°C).

[0032] [Top coat material] The present invention is characterized by applying a topcoat after applying and drying a primer. Examples of topcoats include those containing resin components and coloring pigments. Such topcoats are suitable in terms of improving corrosion resistance, weather resistance, and providing aesthetic appeal through various colors.

[0033] Various resins can be used as the resin component in the topcoat material. Examples of resin types include vinyl acetate resin, polyester resin, alkyd resin, vinyl chloride resin, epoxy resin, acrylic resin, urethane resin, acrylic silicone resin, fluororesin, etc., or composite resins thereof. Among these, one or more types selected from acrylic resin, urethane resin, acrylic silicone resin, fluororesin, etc. are preferred. Furthermore, examples of such resin components include water-soluble resins, water-dispersible resins (resin emulsions), solvent-soluble resins, solvent-free resins, non-aqueous-dispersible resins, powder resins, etc. Among these, one or more types selected from water-soluble resins, water-dispersible resins, solvent-soluble resins, and non-aqueous-dispersible resins are preferred. Of these, weak solvent-type resins containing aliphatic hydrocarbon solvents are preferred as solvent-soluble resins and / or non-aqueous-dispersible resins. In addition, these resin components may have crosslinking reactivity. When resin components with crosslinking reactivity are used, the durability, water resistance, weather resistance, chemical resistance, adhesion, etc. of the coating can be improved.

[0034] As the coloring pigment, known coloring pigments can be used, such as those exemplified in the above-mentioned undercoat material. By using one or more of these coloring pigments as appropriate, the undercoat material can be set to a desired hue. The mixing ratio of the coloring pigment in the topcoat material is preferably 1 to 500 parts by weight, more preferably 5 to 200 parts by weight, and even more preferably 10 to 100 parts by weight, per 100 parts by weight of the solid content of the above-mentioned resin component.

[0035] Such topcoat materials may contain various components other than those listed above, as long as the effects of the present invention are not significantly impaired. Examples of such components include thickeners, film-forming aids, leveling agents, wetting agents, plasticizers, antifreeze agents, pH adjusters, extender pigments, preservatives, antifungal agents, antialgal agents, antibacterial agents, dispersants, defoaming agents, adsorbents, fibers, crosslinking agents, ultraviolet absorbers, antioxidants, destaining agents, water repellents, catalysts, solvents, and water. The second film-forming material of the present invention can be manufactured by uniformly mixing the above resin components, coloring pigments, and the various components listed above as needed, using conventional methods.

[0036] For applying the topcoat, known painting tools can be used. Examples of painting tools include sprayers, rollers, and brushes. The amount of the second film-forming material applied is preferably 50 to 500 g / m². 2 More preferably 80-400 g / m² 2 The paint can be diluted as needed during application. The topcoat is preferably applied 1 to 2 times. [Examples]

[0037] Examples and comparative examples are shown below to further clarify the features of the present invention.

[0038] ○Undercoat material (A) Epoxy resin • Epoxy resin 1: Bisphenol A type solid epoxy resin solution, solid content 70% by weight, epoxy equivalent (solid content) 470 g / eq (B) Pigments Pigment 1: Titanium dioxide Pigment 2: Precipitated barium sulfate Pigment 3: Talc (C) Polyamine compound • Polyamine 1: Mannich-modified polyamine, solids content 100% by weight, active hydrogen equivalent (solids content) 130 g / eq • Polyamine 2: Adduct-modified polyamidoamine, solids content 70% by weight, active hydrogen equivalent (solids content) 190 g / eq • Polyamine 3: Adduct-modified polyamidoamine, solids content 60% by weight, active hydrogen equivalent (solids) 230 g / eq • Polyamine 4: Adduct-modified polyamidoamine, solids content 60% by weight, active hydrogen equivalent (solids) 280 g / eq • Polyamine 5: Polyamidoamine (dimer acid modified polyamine), solids content 60% by weight, active hydrogen equivalent (solids content) 400g / eq • Polyamine 6: Polyetheramine, 100% by weight of solids, active hydrogen equivalent (solids) 1000 g / eq (others) • Additives: Thickeners, dispersants, defoamers, etc. • Solvents: xylene, isobutyl alcohol, etc.

[0039] (Examples 1-7, Comparative Examples 1-4) Following the formulations shown in Table 1, the main component and hardener were prepared, and then these were mixed to create primers 1 to 11.

[0040] <Adhesion> Test specimens were prepared by spraying a primer onto a steel plate (150mm x 70mm x 3.2mm) to a dry film thickness of 60μm, (I) drying for 24 hours, (II) drying for 7 days, and (III) drying for 30 days, then spraying a topcoat (acrylic resin paint, containing titanium dioxide) to a dry film thickness of 30μm and drying for 96 hours. Painting and drying were carried out under standard conditions (temperature 23°C, relative humidity 50%). The obtained test specimens were subjected to adhesion tests (cross-cut method) in accordance with JIS K 5600-5-6:1992, and their adhesion was evaluated. The evaluation criteria were set on a four-level scale (a>b>c>d), with "a" indicating no peeling and "d" indicating peeling across the entire surface.

[0041] <Corrosion Resistance> A primer was spray-applied to a steel plate (150mm x 70mm x 3.2mm) to a dry film thickness of 60μm. Test specimens were dried for 7 days and then subjected to a cyclic corrosion test in accordance with JIS K5551:2018 to check for the occurrence of abnormalities (rust, blistering, cracking, and peeling). The evaluation criteria were set on a four-level scale (a>b>c>d), with "a" indicating no abnormalities and "d" indicating clearly abnormalities.

[0042] [Table 1]

[0043] [Table 2]

Claims

1. A method for forming a coating on a metal substrate, comprising applying a primer and then a topcoat, The above-mentioned primer consists of a main component containing epoxy resin (A) and pigment (B), and a curing agent containing a polyamine compound (C). The polyamine compound (C) is A polyamine compound (c1) having an active hydrogen equivalent per solid content of 190 g / eq or more and 230 g / eq or less, and A method for forming a coating, characterized by containing a polyamine compound (C2) having an active hydrogen equivalent per solid content of 280 g / eq or more and 400 g / eq or less.

2. The above polyamine compound (C) The method for forming a coating according to claim 1, characterized in that the polyamine compound (c1) and the polyamine compound (c2) are contained in a solid content weight ratio of 5:95 to 50:50.

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