TW202302673A - Aqueous coating composition, coating film, and method for producing coating film - Google Patents

Abstract

The present invention addresses the problem of providing an aqueous coating composition which, although of a one-pack type, has excellent storage stability and which can form coating films satisfactory in terms of processability including bendability and of crack resistance and scratch resistance during processing. This aqueous coating composition comprises a film-forming resin (A), a crosslinking agent (B), a sulfonic acid compound (C), and an amine compound (D), wherein the film-forming resin (A) includes an acrylic resin (A1), the film-forming resin (A) has a hydroxyl value of 5-35 mgKOH/g, the crosslinking agent (B) includes a fully alkylated melamine resin (B1), and the degree of neutralization of the acid groups of the sulfonic acid compound (C) with the amine compound (D) is 100-1,300% by mole.

Description

Water-based paint composition, coating film and method for producing coating film

The disclosure relates to a water-based coating composition, a coating film and a method for manufacturing the coating film.

Background technique Coated steel sheets that are formed after coating metal substrates such as cold-rolled steel sheets and plated steel sheets are also called pre-coated steel sheets (hereinafter also referred to as "PCM"), and are used for the following purposes: iron rolling doors, Building components such as shutters, doors, roofs, and exterior wall panels; exterior materials for electrical appliances such as air-conditioning outdoor units; and interior materials, etc. The above-mentioned pre-coated steel sheet is usually manufactured by coating the surface of the above-mentioned metal substrate with a coating composition and heating (baking) at 200-270° C. for 30-60 seconds to form a coating film, and then subjected to forming processing. Therefore, the coating film of the precoated steel sheet is required to have processability to the extent that no cracks or peeling occurs during processing, and hardness to the extent that no scratches or dents occur.

There are the following two types of paint compositions, namely: a one-component paint composition in which a main agent containing a coating film-forming resin and a hardener containing a crosslinking agent coexist in the same system; and, a main agent and a hardener are kept separately , A two-component coating composition that is only mixed when used. Among them, the two-component paint composition has higher storage stability than the one-component paint composition because the main agent and the hardener are not mixed until use. However, since the two-component paint composition needs to be mixed with the main agent and the hardener in a predetermined ratio and stirred uniformly, and the usable time is limited, there are sometimes problems with its handling and painting workability. , thus requiring a one-component coating composition.

In addition, awareness of reducing environmental burdens has increased in recent years, and it is necessary to switch to products that consider the environment. Even in the field of coatings, there are requirements such as reducing the amount of volatile organic compounds (VOCs), and such requirements can be met by using water-based coating compositions. That is, in the market, the demand for one-component water-based paint compositions has become extremely high.

There have been various proposals for such a one-component water-based paint composition. For example, a water-based paint composition has been proposed, which is composed of an acrylic copolymer containing a hydroxyl group and a carboxyl group, a water-based amine-based resin, an amine compound, and a hydrophilic organic compound. In this water-based paint composition, an amine compound is used to neutralize the carboxyl group contained in the acrylic copolymer containing a hydroxyl group and a carboxyl group (Patent Document 1). In addition, it is also proposed: an acrylic water-soluble paint composition, which includes: hydroxyl-containing (meth)acrylates, carboxyl-containing vinyl monomers, long-chain alkyl-containing (meth)acrylates and vinyl monomer copolymers; water-soluble amine-based resins; and aqueous media; in the acrylic water-soluble paint composition, use amine compounds to neutralize the carboxyl groups in the acrylic copolymers containing hydroxyl and carboxyl groups (patent Document 2). It is further proposed: a metal-coated water-based coating composition, which includes an acrylic resin with a glass transition point in the range of -10°C to 80°C and containing hydroxyl and carboxyl groups, a glass transition point in the range of -50°C to 20°C and containing Hydroxyl and carboxyl acrylic resin, water-based amino resin, basic compound and water-based medium; in the metal-coated water-based coating composition, the basic compound is used to neutralize the carboxyl group in the hydroxyl and carboxyl-containing acrylic resin (patent document 3). In addition, Patent Document 4 proposes a water-based coating composition comprising water-based resin, melamine resin, and a phosphate catalyst used as a weak acid catalyst, and proposes to use a basic compound to neutralize the water-based resin (Patent Document 4). Prior art literature patent documents

[Patent Document 1] Japanese Unexamined Patent Publication No. 2001-323207 [Patent Document 2] Japanese Patent Laid-Open No. 2001-240624 [Patent Document 3] Japanese Patent Laid-Open No. 2000-17225 [Patent Document 4] Japanese Patent Laid-Open No. 2015-174958

Summary of the invention The problem to be solved by the invention However, the processability (adhesion, crack resistance) and scratch resistance of the obtained precoated steel sheet are not fully satisfactory for the coating film formed by the coating compositions disclosed in the aforementioned Patent Documents 1 to 4.

Furthermore, in the one-component paint composition, since the main agent and the hardener coexist in the same system, if the reactivity of the main agent and the hardener is improved for the purpose of improving the physical properties of the coating film, the storage of the paint composition will Stability is lowered. On the other hand, if the reactivity is lowered for the purpose of improving the storage stability of the coating composition, the physical properties of the coating film will be lowered, and there is a trade-off relationship. Therefore, it is extremely difficult to balance the storage stability and the physical properties of the coating film with respect to the one-component coating composition.

In order to solve the above problems, the inventors of the present case found after repeated careful research that by using all-alkyl melamine resin as a cross-linking agent and further using sulfonic acid compounds and amine compounds to satisfy a specific neutralization rate, even The one-component composition can still achieve high storage stability, and even in the case of further coating under the high temperature and short time conditions unique to pre-coated steel sheets, it can still exhibit good coating film properties (especially processing properties (adhesion, crack resistance), scratch resistance), and then completed the manufacturing method of the disclosed water-based paint composition and coating film.

The object of the present disclosure is to provide a water-based paint composition which has excellent storage stability even in a one-component form, and which can form a coating film with good processability such as bending, crack resistance and scratch resistance during processing. means to solve problems

This disclosure provides the following aspects. [1] A water-based paint composition comprising a coating film forming resin (A), a crosslinking agent (B), a sulfonic acid compound (C) and an amine compound (D); The aforementioned coating film-forming resin (A) comprises an acrylic resin (A1) having a hydroxyl group; The hydroxyl value of the coating film-forming resin (A) is not less than 5 mgKOH/g and not more than 35 mgKOH/g; The aforementioned crosslinking agent (B) comprises a full alkyl type melamine resin (B1); And the neutralization rate of the acid group of the said sulfonic acid compound (C) by the said amine compound (D) is 100 % or more and 1,300 % or less in mole conversion. [2] The water-based coating composition according to [1], wherein the coating film-forming resin (A) has a weight average molecular weight of 100,000 or more. [3] The water-based paint composition as described in [1] or [2], whose shear viscosity measured at a temperature of 23°C at a shear rate of 0.01 s-1 is below 30,000 mPa·s, and at a shear rate of 10 s-1 1 The measured shear viscosity is below 800mPa·s, and the shear viscosity measured at a shear rate of 1,000s-1 is above 150mPa·s. [4] The water-based paint composition according to any one of [1] to [3], which further contains an organic solvent (E1). [5] The water-based paint composition according to any one of [1] to [4], which is used for coil coating. [6] A method of manufacturing a coating film, comprising the following steps: Applying the water-based coating composition according to any one of [1] to [5] on the object to be coated to form a coating film; and The coating film is formed by drying and/or curing the above-mentioned coating film under the condition that the maximum attained temperature is 180° C. or higher and the drying and/or curing time is 120 seconds or less. Invention effect

According to the present disclosure, it is possible to provide a water-based coating composition which has excellent storage stability even in a one-component type, and which can form a coating film with good processability such as bending, crack resistance and scratch resistance during processing.

form for carrying out the invention The water-based coating composition disclosed herein includes a coating film forming resin (A), a crosslinking agent (B), a sulfonic acid compound (C) and an amine compound (D).

＜Coating film forming resin (A)＞ The said coating film forming resin (A) contains an acrylic resin (A1). The aforementioned acrylic resin (A1) represents a polymer having a unit derived from a monomer having a (meth)acryl group, and can be prepared by polymerizing a monomer mixture of a monomer having an ethylenically unsaturated bond. In addition, in this specification, (meth)acrylic acid means acrylic acid or methacrylic acid.

The aforementioned monomers with ethylenically unsaturated bonds can be cited as: unsaturated carboxylic acids such as (meth)acrylic acid, crotonic acid, isocrotonic acid, 2-acrylic acid, ethyl acrylic acid, propyl acrylic acid, and isopropyl acrylic acid; Unsaturated polycarboxylic acids such as butenedioic acid, fumaric acid and itaconic acid (including their anhydrides); ethyl maleate, butyl maleate, fumaric acid Monoalkyl esters of unsaturated polycarboxylic acids such as ethyl ester, butyl fumarate, ethyl itaconate, and butyl itaconate; methyl (meth)acrylate, ethyl (meth)acrylate, Propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tertiary butyl (meth)acrylate, n-pentyl (meth)acrylate, (meth)acrylic acid Neopentyl, Isopentyl (meth)acrylate, Secondary pentyl (meth)acrylate, 3-pentyl (meth)acrylate, Hexyl (meth)acrylate, Heptyl (meth)acrylate, ( n-octyl methacrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, (meth)acrylate ) Alkyl (meth)acrylate such as lauryl acrylate, stearyl (meth)acrylate; cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, iso(meth)acrylate (meth)acrylates with alicyclic hydrocarbon groups such as camphor, tricyclodecanyl (meth)acrylate, adamantyl (meth)acrylate; 2-hydroxyethyl (meth)acrylate, (meth)acrylate ) Hydroxyalkyl (meth)acrylates such as 2-hydroxypropyl acrylate, 4-hydroxybutyl (meth)acrylate, etc.; these lactone adducts (such as ε-valerolactone, etc.) ) and other (meth)acrylates with hydroxyl groups; γ-(meth)acryloxypropyltrimethoxysilane, γ-(meth)acryloxypropylmethyldimethoxysilane, γ -(Meth)acryloxypropyltriethoxysilane, γ-(meth)acryloxypropylmethyldiethoxysilane, vinyltrimethoxysilane, vinylmethyldimethylsilane Oxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane and other monomers with organosilicon groups; α-vinylbenzenesulfonic acid, p-(meth)acrylamide propanesulfonic acid, three Monomers with sulfonic acid groups such as butyl (meth)acrylamide sulfonic acid; monomers with phosphoric acid groups such as phosphoric acid monoesters of (meth)acrylates with hydroxyl groups; (meth)acrylamide , N-methylol (meth)acrylamide, methoxybutyl (meth)acrylamide, diacetone (meth)acrylamide and other (meth)acrylamide monomers; amino ethyl (meth)acrylamide, dimethylaminoethyl (meth)acrylamide, methylaminopropyl (meth)acrylamide, etc. Glycidyl (meth)acrylate and other (meth)acrylates with epoxy groups (oxylanyl); (meth)acrylonitrile, α-chloro(meth)acrylonitrile (meth)acrylonitrile monomer; vinyl acetate, vinyl propionate and other carboxylate vinyl esters; styrene, α-methylstyrene, α-methylstyrene dimer, vinyl toluene, divinyl Styrenic monomers such as benzene; carbonyl monomers; and cross-linking monomers such as polyfunctional vinyl monomers other than those mentioned above. The said monomer which has an ethylenically unsaturated bond may use only 1 type, and may use 2 or more types together.

The said acrylic resin (A1) has a hydroxyl group. The said acrylic resin (A1) can harden a coating film by having a hydroxyl group and crosslinking reaction between this hydroxyl group and the reactive group of a crosslinking agent. In order to obtain a hydroxyl group for the acrylic resin (A1), what is necessary is to use a (meth)acrylate having a hydroxyl group as the monomer having an ethylenically unsaturated bond when forming a polymer.

The hydroxyl value of the aforementioned acrylic resin (A1) having hydroxyl groups is preferably not less than 5 mgKOH/g, more preferably not less than 7 mgKOH/g, more preferably not less than 10 mgKOH/g, and preferably not more than 50 mgKOH/g, more preferably not more than 35 mgKOH/g , more preferably less than 30 mgKOH/g, more preferably less than 25 mgKOH/g. There is an advantage that a coating film with good workability (adhesion, crack resistance) can be obtained by falling within the above-mentioned range.

Among the above-mentioned (meth)acrylates having a hydroxyl group, the carbon number of the group to which the (meth)acryl group is bonded is particularly preferably 1-3, more preferably 2. There is an advantage that a coating film excellent in scratch resistance can be obtained by including a (meth)acrylate having a hydroxyl group and having a carbon number of 1 to 3 bonded to the (meth)acryl group. In the (meth)acrylate having a hydroxyl group, the content of the (meth)acrylate having a hydroxyl group and having 1 to 3 carbon atoms in a group bonded to a (meth)acryl group is preferably 70% by mass or more. , more preferably more than 80% by mass, and the upper limit is 100% by mass.

The weight average molecular weight of the acrylic resin (A1) is, for example, not less than 50,000, preferably not less than 100,000, more preferably not less than 150,000, and for example, not more than 10,000,000, and preferably not more than 2,000,000. The larger the weight average molecular weight of the acrylic resin (A1), the better the scratch resistance and the advantage of being able to obtain a coating film with excellent processability.

In addition, in this specification, weight average molecular weight is the value obtained by polystyrene conversion using gel permeation chromatography (GPC).

The aforementioned acrylic resin (A1) preferably has an acid group. The dispersibility to the aqueous medium (E) mentioned later can be imparted by making the said acrylic resin (A1) have an acid group. In order to obtain acid groups for the aforementioned acrylic resin (A1), it is only necessary to use unsaturated monocarboxylic acids, unsaturated polycarboxylic acids, monoalkyl esters of unsaturated polycarboxylic acids, and monoalkyl esters with sulfonic acid groups when making polymers. A monomer having an acid group such as a monomer having a phosphoric acid group or a monomer having a phosphoric acid group may be used as the monomer having the aforementioned ethylenically unsaturated bond.

The aforementioned monomers with acid groups are preferably monoalkyl esters of unsaturated monocarboxylic acids, unsaturated polycarboxylic acids, and unsaturated polycarboxylic acids, and are preferably unsaturated monocarboxylic acids and unsaturated polycarboxylic acids. Saturated monocarboxylic acids are more preferred, and (meth)acrylic acids are especially preferred.

The acid value of the aforementioned acrylic resin (A1) is preferably not less than 5 mgKOH/g, more preferably not more than 50 mgKOH/g, more preferably not more than 30 mgKOH/g. There is an advantage that an acrylic resin (A1) can be stably dispersed in an aqueous medium (E) by falling within the said range.

In addition, in this specification, the acid value and the hydroxyl value of an acrylic resin (A1) represent a solid content acid value and a solid content hydroxyl value, respectively, and can measure it based on JISK0070:1999.

The glass transition temperature (Tg) of the aforementioned acrylic resin (A1) is preferably not less than -70°C, more preferably not less than 0°C, more preferably not less than 10°C, more preferably not less than 15°C, and preferably not more than 95°C , preferably below 90°C, more preferably below 85°C, and more preferably below 80°C. By being within the above range, there is an advantage that a coating film excellent in coating film processability and scratch resistance can be obtained.

The aforementioned glass transition temperature can be calculated as follows: divide the mass fraction of each monomer constituting the acrylic resin (A1) by the Tg (K: absolute temperature) value of the homopolymer (homopolymer) derived from each monomer, and then After summing up the obtained quotients, it is calculated as the reciprocal. More specifically, in this specification, the aforementioned glass transition temperature (Tg) can be calculated using Fox's formula (T. G. Fox; Bull. Am. Phys. Soc., 1(3), 123(1956)). For example, when the resin is a polymer of many monomers (monomer A, monomer B, ... monomer N), the Tg shown in the following general formula can be the Tg of the resin. 1/Tg=wa/Tga＋wb/Tgb＋・・・＋wn/Tgn Here, Tga means the glass transition temperature (K) of the homopolymer of monomer A, wa means the mass fraction of monomer A, Tgb means the glass transition temperature (K) of the homopolymer of monomer B, wb means the mass fraction of monomer B, Tgn means the glass transition temperature (K) of the homopolymer of monomer N, wn means the mass fraction of monomer N, and wa+wb+・・・+wn=1 .

Among the monomers forming the aforementioned acrylic resin (A1), the monomer having an ethylenically unsaturated bond preferably includes an alkyl (meth)acrylate, and more preferably includes an alkyl group having 1 to 6 carbon atoms (preferably 1 to 4) Alkyl (meth)acrylate. There is an advantage that the scratch resistance of the obtained coating film is excellent by using the monomer in the said range. Among the aforementioned alkyl (meth)acrylates, the content of alkyl (meth)acrylates having an alkyl group having 1 to 6 carbon atoms is preferably at least 20% by mass, more preferably at least 30% by mass, more preferably at least 30% by mass. 40% by mass or more, and preferably 95% by mass or less, more preferably 85% by mass or less, more preferably 80% by mass or less.

Among the monomers contained in the acrylic resin (A1), the content of the styrene-based monomer is preferably 10% by mass or less, more preferably 5% by mass or less, more preferably 3% by mass from the viewpoint of weather resistance. Below, the lower limit is 0% by mass.

When the aforementioned acrylic resin (A1) has an acidic group, the aforementioned aqueous coating composition may contain a basic compound. The aforementioned water-based paint composition can impart good water dispersibility to the acrylic resin by including a basic compound to neutralize a part or all of the acid groups. As the basic compound, for example, ammonia, an amine compound, an alkali metal, or the like can be used. Moreover, a part of the amine compound (D) mentioned later can also be used as the said basic compound. In addition, known anionic and/or nonionic surfactants can also be used to impart water dispersibility to the acrylic resin.

The content of the acrylic resin (A1) in the coating film-forming resin (A) is preferably at least 5% by mass, more preferably at least 10% by mass, more preferably at least 15% by mass, and the upper limit is 100% by mass.

The above-mentioned acrylic resin (A1) is preferably a water-based resin, and can be a water-soluble resin soluble in the water-based medium (E), or can be dispersible in water-based resins such as colloid dispersion type and emulsion type (emulsion polymerization type, forced emulsification type). Water-dispersible resin of medium (E). The aforementioned acrylic resin (A1) is preferably a water-dispersible resin, more preferably an emulsion-type water-dispersible resin, especially an emulsion-type water-dispersible resin utilizing emulsion polymerization. The aforementioned acrylic resin (A1) can be made into a water-based resin by having an acid group and/or a hydroxyl group, and/or coexisting with an emulsifier.

When the aforementioned acrylic resin (A1) is an emulsion-type water-dispersible resin, the average particle diameter of the emulsion particles is preferably not more than 500 nm, more preferably not more than 300 nm, more preferably not more than 200 nm, for example, it may be not less than 10 nm, not less than 30 nm , 50nm or more. When it falls within the above-mentioned range, there is an advantage that the storage stability of the emulsion particles and the paint composition containing the above-mentioned emulsion particles is good. In addition, in this specification, an average particle diameter is the average particle diameter determined by the dynamic light scattering method, Specifically, it can measure using electrophoretic light scattering photometer ELSZ series (made by Otsuka Electronics Co., Ltd.) etc.

The minimum film forming temperature (MFT) of the aforementioned acrylic resin (A1) is preferably 50°C or higher, more preferably 60°C, more preferably 70°C or higher, for example, it may be below 200°C, below 150°C, or at 120 below ℃. By being within the above-mentioned range, there are advantages in that the scratch resistance of the obtained coating film is improved and the situation of mutual adhesion (blocking) of the coating films is suppressed. In addition, in this specification, the minimum film-forming temperature means the minimum temperature at which a uniform film without cracks can be formed when the emulsion-type water-dispersible resin is dried, and it can be measured in accordance with JIS K 6828-2:2003.

When the aforementioned acrylic resin (A1) is an emulsion-type water-dispersible resin, the emulsion may be an emulsion in which multilayered particles are dispersed, and the multilayered particles are composed of an inner core and an outer shell.

For example, the aforementioned multilayered structure particles can be prepared by the method described in JP-A-2002-12816 or the like.

The aforementioned acrylic resin (A1) can be produced by polymerizing the aforementioned monomer having an ethylenically unsaturated bond. For example, the aforementioned monomer having an ethylenically unsaturated bond can be made The body is heated under stirring, whereby the aforementioned polymerization reaction is carried out. The aforementioned polymerization reaction is preferably an emulsion polymerization reaction. During the above-mentioned polymerization reaction, it is preferable to make a polymerization initiator coexist, and it is preferable to make an emulsifier coexist as needed. The reaction temperature is, for example, preferably 30 to 100° C., and the reaction time is, for example, preferably 1 to 10 hours.

The aforementioned polymerization initiator is preferably a radical polymerization initiator. As the water-soluble radical polymerization initiator, persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate can be used. In addition, a redox system in which an oxidizing agent such as potassium persulfate, sodium persulfate, ammonium persulfate, and hydrogen peroxide is combined with a reducing agent such as sodium bisulfite, sodium thiosulfate, Rongalite, or ascorbic acid can be used. Initiator. These radical polymerization initiators can also be used in the form of an aqueous solution after dissolving part or all of the aqueous medium (E).

As for the aforementioned emulsifier, an anionic or nonionic emulsifier can be used, which is a hydrophobic moiety such as a hydrocarbon group with a carbon number of 6 or more and a carboxylate, sulfonate or sulfate partial ester (partial ester) and other hydrophilic parts. The aforementioned anionic emulsifiers can be, for example: alkali metal salts or ammonium salts of sulfuric acid half esters (half ester) of alkylphenols or higher alcohols; alkali metal salts or ammonium salts of alkyl or allyl sulfonates; Alkali metal or ammonium salts of sulfate half-esters of polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl ethers or polyoxyethylene allyl ethers; and, with acrylic, methacrylic, acrylic, Allyl-based, allyl ether-based, maleic acid-based and various anionic reactive emulsifiers with ethylenically unsaturated bonds, etc. Furthermore, nonionic emulsifiers can be, for example: polyoxyalkylene ethers such as polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether or polyoxyethylene allyl ether; Non-ionic reactive emulsifiers based on acrylic, acrylic, allyl, allyl ether, maleic acid and other groups and ethylenically unsaturated bonds.

In addition, when polymerizing (emulsification polymerization is preferred), it is preferable to use thiol-based compounds and Lower alcohols and other auxiliary agents (chain transfer agents) used to adjust the molecular weight are often used, and it can be done appropriately depending on the situation.

When implementing emulsion polymerization, any one of the following emulsion polymerization methods can be used: general single-stage continuous monomer uniform titration method, core-shell polymerization method belonging to multi-stage monomer feeding method, and feeding-in monomer during polymerization Power-fed polymerization method with continuously changing composition, etc.

The aforementioned acrylic resin (A1) can be prepared in advance into an aqueous solution or aqueous dispersion comprising the acrylic resin (A1) and a part of the aqueous medium (E) described later, and then used to prepare an aqueous coating composition. The aqueous solution or dispersion may further contain the aforementioned emulsifier.

A commercial item can be used for the said acrylic resin (A1). Moreover, only 1 type may be used, and 2 or more types may be used together.

The said coating film forming resin (A) may contain other resin (A2) other than the said acrylic resin (A1).

The aforementioned other resins (A2) can be exemplified as non-hydroxyl-containing acrylic resins, urethane resins, vinyl acetate resins, fluororesins, and vinyl chloride resins, and are preferably water-based resins, and more preferably water-dispersible resins. More preferably, it is an emulsion-type water-dispersible resin. The other resin (A2) can also be prepared in advance as an aqueous solution or dispersion comprising a part of the other resin (A2) and the aqueous medium (E), and then used to prepare an aqueous coating composition. The aqueous solutions or dispersions may also contain emulsifiers.

The aforementioned acrylic resin not containing a hydroxyl group means a polymer having a unit derived from a monomer having a (meth)acryl group, which can be obtained by polymerizing a mixture of the aforementioned monomers having an ethylenically unsaturated bond that does not have a hydroxyl group. modulation.

The weight average molecular weight of the acrylic resin not containing hydroxyl groups is preferably 50,000 or more, more preferably 100,000 or more, more preferably 150,000 or more, and preferably 10,000,000 or less, more preferably 2,000,000 or less, more preferably 500,000 or less. When it falls within the said range, there exists an advantage that the processability of the obtained coating film becomes favorable.

The glass transition temperature of the acrylic resin without hydroxyl group is preferably below 80°C, more preferably below 60°C, more preferably below 50°C, and preferably above 20°C, preferably above 30°C, more preferably above 40°C ℃ or more. Being within the above range, there is an advantage of good scratch resistance.

The minimum film forming temperature (MFT) of the acrylic resin is preferably above 50°C, more preferably above 60°C, more preferably above 70°C, for example, below 200°C, below 150°C, below 120°C. When it falls within the above-mentioned range, there are advantages in that the scratch resistance of the obtained coating film is improved and the adhesion of the coating films is suppressed.

The above-mentioned acrylic resin not containing a hydroxyl group preferably has an acid group. The acid value of the acrylic resin without hydroxyl group is preferably above 5 mgKOH/g, more preferably below 50 mgKOH/g, more preferably below 30 mgKOH/g.

When the acrylic resin not containing a hydroxyl group is contained, the content is preferably at least 20% by mass, more preferably at least 30% by mass, based on the total of the acrylic resin (A1) and the acrylic resin not containing a hydroxyl group, and is preferably 90 mass % or less, more preferably 85 mass % or less.

The hydroxyl value of the aforementioned coating film-forming resin (A) is 5 mgKOH/g or more, preferably 7 mgKOH/g or more, more preferably 10 mgKOH/g or more, and 35 mgKOH/g or less, preferably 30 mgKOH/g or less, more preferably Below 25mgKOH/g. There is an advantage that a coating film having good workability and scratch resistance can be obtained by falling within the above-mentioned range.

The acid value of the coating film-forming resin (A) is preferably not less than 5 mgKOH/g and not more than 50 mgKOH/g, more preferably not more than 30 mgKOH/g. There is an advantage that the aforementioned coating film-forming resin (A) can be stably dispersed in the aqueous medium (E) by being within the aforementioned range.

The weight average molecular weight of the coating film forming resin (A) is, for example, 50,000 or more, preferably 100,000 or more, more preferably 150,000 or more, and, for example, 10,000,000 or less, preferably 2,000,000 or less. There is an advantage that a coating film with good workability can be obtained by falling within the above-mentioned range.

The glass transition temperature (Tg) of the aforementioned coating film-forming resin (A) is preferably -70°C or higher, more preferably 20°C or higher, more preferably 25°C or higher, more preferably 30°C or higher, and preferably 95°C It is more preferably below 70°C, more preferably below 60°C, and more preferably below 50°C. When it falls within the said range, there exists an advantage that the coating film excellent in coating film processability and scratch resistance can be obtained.

The said coating film forming resin (A) may use only 1 type, and may use 2 or more types together. When two or more kinds of the above-mentioned coating film-forming resins (A) are contained, each parameter of the above-mentioned coating film-forming resin (A) can be calculated as a weighted average based on the parameters and content of each resin in addition to the glass transition temperature. In addition, the glass transition temperature can also be calculated by adding up the values obtained by dividing the mass-based content of each coating film-forming resin by the glass transition temperature (K: absolute temperature value), and calculating the inverse number.

In 100 parts by mass of the solid content of the water-based paint composition, the content of the coating film-forming resin (A) is preferably at least 50 parts by mass, more preferably at least 70 parts by mass, more preferably at least 80 parts by mass, and is preferably 100 parts by mass or less, preferably 95 parts by mass or less, more preferably 90 parts by mass or less. In addition, in this specification, let content of coating-film forming resin (A) show only content of solid content.

In this specification, let the solid content of the water-based paint composition represent the portion after subtracting the water-based medium (E) from the entire water-based paint composition.

＜Crosslinking agent (B)＞ The aforementioned crosslinking agent (B) is a compound having two or more groups in one molecule capable of reacting with the hydroxyl groups contained in the aforementioned coating film forming resin (A), and is capable of crosslinking with the aforementioned coating film forming resin (A) react to form a film. The aforementioned crosslinking agent (B) includes an amine-based resin, and the aforementioned amine-based resin may, for example, be melamine resin, urea resin, or benzoguanamine. From the standpoint of storage stability of the obtained coating composition and various physical properties (processability, scratch resistance) of the obtained coating film, the amino resin preferably includes a melamine resin.

The melamine resin is a thermosetting resin synthesized from melamine and formaldehyde, and is preferably a compound or polycondensate having three reactive functional groups represented by the following formula in one molecule of the trimeric nucleus. -NX ₁ X ₂ [X ₁ and X ₂ each independently represent a hydrogen atom, a hydroxymethyl group or -CH ₂ -OR ¹ . R ¹ represents an alkyl group having 1 to 8 carbon atoms, and preferably represents a linear or branched chain alkyl group having 1 to 8 carbon atoms. When a plurality of -CH ₂ -OR ^1s are included in the same molecule, the plurality of R ^1s may be the same or different].

The melamine resin can be exemplified as the following four types: the peralkyl type containing only -N(CH ₂ OR ¹ ) ₂ as a reactive functional group; the type containing -N(CH ₂ OR ¹ )(CH ₂ OH) as a reactive functional group The hydroxymethyl type; the imino type containing -N(CH ₂ OR ¹ )(H) as a reactive functional group; the type containing -N(CH ₂ OR ¹ )(CH ₂ OH) and -N(CH ₂ OR ¹ ) (H) or methylol/imino type containing -N(CH ₂ OH)(H) as reactive functional group. R ¹ is preferably an alkyl group having 1 to 4 carbon atoms, and is preferably methyl, n-butyl or isobutyl.

In the present disclosure, among the above-mentioned melamine resins, it is particularly preferable to include all-alkyl melamine resins (B1) in which X ¹ and X ² are both -CH ₂ -OR ¹ compounds or polycondensates thereof. Such resins include Such as methylated melamine resin, butylated melamine resin, isobutylated melamine resin, etc. By containing the peralkyl-type melamine resin, there are advantages in that the storage stability of the obtained coating composition is good and the reactivity with the acrylic resin (A1) is good under high temperature and in the presence of a catalyst.

The polymerization degree of the above-mentioned all-alkyl type melamine resin (B1) is 1 or more, preferably 1.2 or more, more preferably 1.5 or more, and preferably 10 or less, more preferably 5 or less, more preferably 3 or less.

The number average molecular weight of the aforementioned all-alkyl type melamine resin (B1) is preferably not less than 300 and not more than 2,000, more preferably not more than 1,300, more preferably not more than 1,000, especially preferably not more than 800. In addition, in this specification, the number average molecular weight is the value converted into polystyrene using the gel permeation chromatography (GPC).

The above-mentioned all-alkyl type melamine resin (B1) can also use commercially available products, such as CYMEL 303, CYMEL 325, CYMEL 350, CYMEL 370, MYCOAT 715 (all are methylated melamine resins, manufactured by Allnex Japan), CYMEL 202, CYMEL 235, CYMEL 254, CYMEL 1123, CYMEL 1128, CYMEL 1170, MYCOAT 212 (all are methyl-butylated mixed melamine resin, manufactured by Allnex Japan), SUMIMAL M-40S (methylated melamine resin, manufactured by Sumitomo Chemical Co., Ltd.), AMIDIR J-820-60, AMIDIR L-127-60 (all are butylated melamine resins, manufactured by DIC Corporation), etc. These may use only 1 type, and may use 2 or more types together.

In the aforementioned crosslinking agent (B), the content of the aforementioned all-alkyl type melamine resin (B1) is preferably at least 80% by mass, more preferably at least 90% by mass, more preferably at least 95% by mass, and the upper limit is 100% by mass. quality%.

The said crosslinking agent (B) may contain other crosslinking agents (B2) other than the said peralkyl type melamine resin (B1). Examples of the other crosslinking agent (B2) include amino resins such as melamine resins, urea resins, and benzoguanamine resins other than the aforementioned peralkyl-type melamine resins (B1). The above-mentioned amino resin has high reactivity with the above-mentioned coating film-forming resin (A), and the appearance and moisture resistance of the obtained coating film are good.

The said crosslinking agent (B) may use only 1 type, and may use 2 or more types together.

The content ratio ((B)/(A)) of the aforementioned crosslinking agent (B) relative to the content of the aforementioned coating film-forming resin (A) is preferably 5/95 on a mass basis, more preferably 10/90 or more, More preferably below 30/70, especially preferably below 20/80. When it falls within the said range, there exists an advantage that the workability and scratch resistance of the obtained coating film are favorable.

＜Sulfonic acid compound (C)＞ The said sulfonic acid compound (C) functions as a catalyst which accelerates reaction of the said coating-film forming resin (A) and a crosslinking agent (B). Therefore, there is an advantage that high reactivity can be imparted to the resulting coating composition.

The aforementioned sulfonic acid compound (C) may be a monosulfonic acid compound or a polysulfonic acid compound. The aforementioned sulfonic acid compounds include, for example: aliphatic sulfonic acids such as methanesulfonic acid; Sulfonic acid etc. The said sulfonic acid compound (C) may use only 1 type, and may use 2 or more types together.

The content of the sulfonic acid compound (C) is preferably at least 0.1 parts by mass, more preferably at least 0.5 parts by mass, and preferably at most 5 parts by mass, more preferably at most 5 parts by mass, based on 100 parts by mass of the coating film-forming resin (A). 3 parts by mass or less. By making the content of the sulfonic acid compound (C) fall within the above range, a coating film having good workability (adhesion, crack resistance) and scratch resistance of a precoated steel sheet can be formed.

＜Amine compound (D)＞ The above-mentioned amine compound (D) has the effect of neutralizing the sulfonic acid compound (C), and by making it coexist with the sulfonic acid compound (C) and showing a specific neutralization rate, it has the effect of taking into account the storage of the water-based coating composition (for example, 15 ~50℃) stability and high reactivity when heat drying/hardening after coating. A part of the aforementioned amine compound (D) may form a salt with a sulfonic acid compound (C).

The aforementioned amine compound (D) is a compound having one or more amine groups, and is preferably a second or third amine compound.

In addition, the substituent of the nitrogen atom of the aforementioned amine compound is preferably a saturated or unsaturated aliphatic hydrocarbon group, and the hydrogen atoms contained in the saturated or unsaturated aliphatic hydrocarbon group can be independently replaced by -COOH, -OH, etc. Or the -CH ₂ - contained in the unsaturated aliphatic hydrocarbon group can also be substituted with -O-. In addition, the substituents of the nitrogen atom of the aforementioned amine compound may also be bonded to each other to form a ring containing the nitrogen atom.

The aforementioned amine compound (D) can be exemplified for example: diethylamine, di-n-propylamine, diisopropylamine, diisobutylamine, di-n-butylamine, di(secondary butyl)amine, dipentylamine, N-ethyl- 1,2-dimethylpropylamine, N-methylhexylamine, di-n-octylamine, diallylamine and other secondary aliphatic amine compounds; triethylamine, tributylamine, triallylamine, N,N -Dimethylethanolamine, N-methyldiallylamine, N,N-dimethylallylamine and other third-level aliphatic amine compounds; piperidine, 2-methylpiperidine, 3-methylpiperidine, 4-methylpiperidine Secondary cyclic amine compounds such as piperidine, 2,4-dimethylpiperidine, 2,6-dimethylpiperidine, 3,5-dimethylpiperidine, 3-piperidinemethanol; N-methylpiperidine tertiary cyclic amine compounds such as basepiperidine, N-methylpiperidine, N-methylpiperidine, etc.; amine compounds belonging to aromatic compounds such as pyridine and 4-ethylpyridine, etc.

The boiling point of the aforementioned amine compound (D) is preferably 50°C or higher, more preferably 70°C or higher, more preferably 100°C or higher, and preferably 250°C or lower, more preferably 220°C or lower. By falling within the aforementioned range, there is an advantage that the storage stability of the aforementioned water-based paint composition can be further improved.

The content of the aforementioned amine compound (D) is as follows: The neutralization rate of the aforementioned sulfonic acid compound (C) by the aforementioned amine compound (D), that is, the neutralization rate in molar conversion calculated from the following formula is 100% or more and 1,300 The range below %. Neutralization rate (%)=[(base number of amine compound (D) x molar number of amine compound (D))/(acid number of sulfonic acid compound (C) x mole of sulfonic acid compound (C) Number of ears)]×100

The aforementioned neutralization rate is preferably 200% or more, more preferably 300% or more. For example, the aforementioned neutralization rate can be 1,300% or less, 1,100% or less, 1,000% or less, or 900% or less, 800% or less . Although it should not be limited to a specific theory to explain, it is conceivable that by falling within the aforementioned range, the aforementioned amine compound (D) will convert the sulfonic acid group of the aforementioned sulfonic acid compound (C) during storage (for example, 15 to 30° C.) Blocking inhibits catalyst action and improves storage stability, and when heat drying/hardening (for example, above 180°C) after coating, the blocking will be released, and the sulfonic acid compound (C) can function as a catalyst.

It is known that the aforementioned peralkyl-type melamine resin (B1) has lower reactivity than melamine resins generally used as crosslinking agents such as imino-type melamine resins and methylol-type melamine resins. However, the inventors of the present case found that the low reactivity of the above-mentioned all-alkyl melamine resin (B1) was due to low temperature reaction (such as 60-80°C), and if the all-alkyl melamine resin (B1) ) and the above-mentioned sulfonic acid compound (C) and the above-mentioned amine compound (D) are used in such a manner that the above-mentioned neutralization ratio is satisfied, the reactivity at high temperature will increase. By combining the above-mentioned all-alkyl type melamine resin (B1), the above-mentioned sulfonic acid compound (D), the above-mentioned amine compound (D) and the above-mentioned neutralization rate, it can be obtained that the storage stability is good and it is especially suitable for high temperature and short time. Furthermore, the water-based paint composition for painting has the advantage of being able to obtain a paint film with excellent film processability (adhesion, crack resistance) due to the increased crosslink density.

The above-mentioned sulfonic acid compound (C) and the above-mentioned amine compound (D) can be directly used to prepare a water-based paint composition, or they can be mixed in advance to form a mixture and then used to prepare a water-based paint composition. At this time, in the aforementioned mixture, the aforementioned sulfonic acid compound (C) can form a salt with a part or all of the aforementioned amine compound (D) (for example, the amine group contained in the amine compound (D) makes the sulfonic acid compound (C) contain The sulfonic acid group is blocked), and the sulfonic acid compound (C) can also be blended into the coating composition after forming a salt with a part or all of the amine compound (D). Examples of salts of the aforementioned sulfonic acid compound (C) and a part or all of the amine compound (D) include aliphatic sulfonic acids such as methanesulfonic acid and aromatic sulfonic acids such as dinonylnaphthalene disulfonic acid and dinonylnaphthalenesulfonic acid. Acid-terminated amines. Commercially available salts of the above-mentioned sulfonic acid compound (C) and some or all of the amine compounds (D) can also be used.

In one embodiment, the content of the sulfonic acid compound (C) is preferably not less than 1 part by mass and not more than 5 parts by mass with respect to 100 parts by mass of the coating film forming resin (A), and the neutralization rate is preferably not less than 100%. and not more than 1,300%; the content of the sulfonic acid compound (C) is preferably not less than 0.1 parts by mass and not more than 5 parts by mass with respect to 100 parts by mass of the coating film-forming resin (A), and the neutralization rate is preferably not less than 200% 1,000% or less; the content of the sulfonic acid compound (C) is preferably not less than 2 parts by mass and not more than 9 parts by mass relative to 100 parts by mass of the coating film-forming resin (A), and the neutralization rate is more preferably not less than 300% and Below 900%. The coating composition has high storage stability at low temperature (storage temperature, such as 15~30°C) and the reaction at high temperature Higher toughness, better processability (adhesion, crack resistance) and scratch resistance of the obtained coating film.

In the solid content of the aforementioned water-based paint composition, the total content of the coating film-forming resin (A), crosslinking agent (B), sulfonic acid compound (C) and amine compound (D) is preferably, for example, 50% by mass or more. , more preferably 70% by mass or more, more preferably 80% by mass or more, and the upper limit is 100% by mass or less.

＜Aqueous medium (E)＞ The aforementioned aqueous paint composition contains an aqueous medium (E). The aforementioned aqueous medium (E) is preferably water, an organic solvent (E1) or a mixture of water and an organic solvent (E1).

The aforementioned organic solvent (E1) is preferably a hydrophilic organic solvent, for example, an organic solvent with a water solubility of 0.1 g/100 gH ₂ O or higher at 25°C. This kind of organic solvent can for example: glycol series solvents such as ethylene glycol, propylene glycol, butanediol, pentanediol, diethylene glycol, dipropylene glycol, triethylene glycol; Lu Su), diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, Glycol ether solvents such as dipropylene glycol monoethyl ether and propylene glycol monomethyl ether acetate; alcohol solvents such as methanol, ethanol, isopropanol, and benzyl alcohol; cyclic ether solvents such as dioxane and tetrahydrofuran;2,2 , alcohol ester solvents such as 4-trimethylpentane-1,3-diol monoisobutyrate; ketone solvents such as acetone; and N-methyl-2-pyrrolidone and the like. By using such an organic solvent, there is an advantage that the wettability of the obtained coating composition and the substrate is good.

In one embodiment, the boiling point of the aforementioned organic solvent (E1) is preferably above 150°C, more preferably above 180°C, more preferably below 300°C, and preferably below 250°C. Examples of such organic solvents include glycol-based solvents such as propylene glycol (1,2-propanediol), 1,4-butanediol, 1,5-pentanediol, diethylene glycol, and dipropylene glycol, and diethylene glycol Excellent. These may use only 1 type, and may use 2 or more types.

The water solubility of the aforementioned organic solvent (E1) at 25°C is preferably at least 0.1g/100gH ₂ O, more preferably at least 1g/100gH ₂ O, more preferably at least 5g/100gH ₂ O. The aforementioned organic solvent (E1) may also be arbitrarily mixed with water.

The content of the organic solvent (E1) in the aforementioned aqueous medium (E) is 3% by mass or more, preferably 4% by mass or more, more preferably 5% by mass or more, and preferably 30% by mass or less, more preferably 20 mass % or less, more preferably 10 mass % or less. By falling within the above-mentioned range, the environmental burden can be reduced. In addition, the storage stability of the above-mentioned coating composition, the wettability to the substrate, and furthermore, the appearance of the obtained coating film is good.

The content of the aforementioned aqueous medium (E) is preferably at least 40% by mass, more preferably at least 50% by mass, more preferably at least 55% by mass, and preferably not more than 90% by mass, more preferably not more than 80% by mass, and more preferably not more than 80% by mass. It is preferably 85% by mass or less.

The said aqueous paint composition may contain the organic solvent other than the said aqueous medium (E) as needed. Examples of organic solvents other than the aforementioned (E) include diethylene glycol dibutyl ether, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (Texanol), and the like. The boiling point of the organic solvent other than (E) above is preferably 150°C or higher, more preferably 180°C or higher, and preferably 300°C or lower, more preferably 250°C or lower.

＜Other＞ The aforementioned water-based paint composition may further contain other additives as needed. Examples of other additives mentioned above include: extender pigments; coloring agents such as coloring pigments and dyes; heat-shielding pigments; bright pigments; aggregates (resin particles, silica particles, etc.); (benzophenone-based UV absorbers, etc.); antioxidants (phenol-based, sulfide-based, hindered amine-based antioxidants, etc.); plasticizers; coupling agents (silane-based, titanium-based, zirconium-based coupling agents, etc.); Anti-sagging agent; Viscosity regulator; Pigment dispersant; Pigment wetting agent; Surface regulator (polysiloxane series, organic polymer system, etc.); ; Defoamer; Surfactant; Antifreeze agent; Emulsifier; Antirust agent; Preservative; Antifungal agent; These additives may be used alone or in combination of two or more.

The aforementioned viscosity modifier (F) can be, for example: an associative viscosity modifier utilizing the bonding force (interaction) of a hydrophilic group (part) or a hydrophobic group (part); Viscosity-increasing viscosity regulator. The above-mentioned associative viscosity modifiers can be, for example, hydrogen bonds formed between the viscosity modifiers, or between the viscosity modifiers and the matrix resin, and the hydrophilic associative viscosity modifiers that utilize the bonding force (interaction) agent; and, a hydrophobic associative viscosity modifier utilizing the interaction between hydrophobic groups (parts) in the molecule; the aforementioned associative viscosity modifier can be, for example, polymer solubilization/increasing by alkali Alkali viscosity-increasing viscosity modifier.

The aforementioned hydrophilic associative viscosity modifiers can be, for example, polyamide-type viscosity modifiers. Commercially available products can be used for the above-mentioned polyamide-type viscosity modifier, and examples thereof (hereinafter all are trade names) BYK-430, BYK-431 (manufactured by BYK Corporation), DISPARLON AQ-580, DISPARLON AQ-600, DISPARLON AQ -607 (manufactured by Kusumoto Chemical Co., Ltd.), THIXOL W-300, THIXOL W-400LP (manufactured by Kyoeisha Chemical Co., Ltd.), etc.

The aforementioned hydrophobic association type viscosity modifiers can be commercially available, such as ADEKA NOL UH-420, ADEKA NOL UH-462, ADEKA NOL UH-472, ADEKA NOL UH-526, UH-540, ADEKA NOL UH-472, ADEKA NOL UH-540, ADEKA NOL UH- 814N (manufactured by ADEKA), PRIMAL RH-1020, PRIMAL RM-2020 (manufactured by Dow Chemical Company), SN-THICKENER 612, SN-THICKENER 621, Nopall 700N (manufactured by SAN NOPCO LIMITED), etc.

The above-mentioned alkali viscosity-increasing viscosity modifiers include, for example, viscose, methylcellulose, ethylcellulose, hydroxyethylcellulose, sodium polyacrylate, polyvinyl alcohol, carboxymethylcellulose, and the like. In addition, commercially available products can also be used, such as cellulose-based viscosity modifiers such as Tylose MH and Tylose H (manufactured by Merck); PRIMAL ASE-60, PRIMAL TT-615, PRIMAL RM-5 (Dow Chemical Corporation), UCAR polyphobe (manufactured by Union Carbide Corporation), etc. These may use only 1 type, and may use 2 or more types together.

The aforementioned viscosity modifier (F) is preferably an associative viscosity modifier. By including the associative viscosity modifier, there is an advantage that the coating workability of the roll coater (roll coater applicability) is good. Specifically, the viscosity of the paint composition can be made Newtonian at a high shear rate. In addition, it is more preferable to use it together with a hydrophobic association type viscosity modifier, thereby having the advantage of improving physical properties such as water resistance of the obtained coating film.

The content of the viscosity modifier (F) contained in the water-based paint composition disclosed herein is preferably 0.01-20 parts by mass relative to 100 parts by mass of the total solid content of the coating film-forming resin (A) and the crosslinking agent (B). More preferably, it is 0.1-10 mass parts. When the amount of the viscosity modifier (F) falls within the above-mentioned range, there are advantages in that the coating workability of a roll coater (roll coater applicability) and the appearance and water resistance of the obtained coating film are good.

Examples of the aforementioned extender pigments include calcium carbonate, barium sulfate, clay, talc, mica, and glass fiber. These may use only 1 type, and may use 2 or more types together.

In one embodiment, the amount of the extender pigment is preferably not less than 1 part by mass and not more than 40 parts by mass, more preferably 10 parts by mass, based on 100 parts by mass of the total solid content of the coating film-forming resin (A) and hardener (B). More than 30 parts by mass and less than or equal to 30 parts by mass. By making the amount of the extender fall within the above-mentioned range, the scratch resistance of the coating film is easily improved.

The aforementioned colored pigments can be, for example: colored inorganic pigments such as titanium dioxide, carbon black, graphite, iron oxide, coal powder, etc.; , azo orange, yellow ketone yellow, isoindoline yellow, azo yellow, indanthrene blue, dibromoanthrene red, perylene red, azo red, anthraquinone red and other colored organic pigments; aluminum Powder, alumina powder, bronze powder, copper powder, tin powder, zinc powder, iron phosphide, micronized titanium, etc. These may use only 1 type, and may use 2 or more types together.

The aforementioned heat-shielding pigment refers to a pigment that does not absorb light in the near-infrared wavelength region (wavelength: 780nm~2,500nm), or has a very small absorption rate of light in the near-infrared wavelength region (wavelength: 780nm~2,500nm). The aforementioned heat shielding pigments are not particularly limited, and the following inorganic heat shielding pigments and organic heat shielding pigments can be used.

Inorganic thermal insulation pigments include titanium oxide, magnesium oxide, barium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, indium oxide, sodium titanate, silicon oxide, nickel oxide, manganese oxide, chromium oxide, iron oxide , copper oxide, cerium oxide, aluminum oxide and other metal oxide pigments; iron oxide-manganese oxide, iron oxide-chromium oxide (such as DAIPYROXIDE Color Black #9595 manufactured by Dainichi Seika Co., Ltd., Black6350 manufactured by ASAHI Chemical Industry Co., Ltd.), Iron oxide-cobalt oxide-chromium oxide (such as DAIPYROXIDE Color Brown #9290, DAIPYROXIDE Color Black #9590 manufactured by Dainichi Seika Co., Ltd.), copper oxide-magnesium oxide (such as DAIPYROXIDE Color Black #9598 manufactured by Dainichi Seika Co., Ltd.), oxide Composite oxide pigments such as manganese-bismuth oxide (such as Black 6301 produced by ASAHI Chemical Industry Co., Ltd.), manganese oxide-yttrium oxide (such as Black 6303 produced by ASAHI Chemical Industry Co., Ltd.); silicon, aluminum, iron, magnesium, manganese, nickel, Metal-based pigments such as titanium, chromium, and calcium; further examples include alloy-based pigments such as iron-chromium, bismuth-manganese, iron-manganese, and manganese-yttrium. These may use only 1 type, and may use 2 or more types together.

Organic heat-shielding pigments include, for example, azo pigments, methine azo pigments, lake (lake) pigments, thioindigo pigments, anthraquinone pigments (anthraquinone pigments, diaminoanthraquinone base pigments, indanthrene pigments, flavanthone pigments, anthracene pigments, etc.), perylene-based pigments, perinone-based pigments, diketopyrrolopyrrole-based pigments, diketopyrrole-based pigments, phthalocyanine-based pigments , quinophthalone pigments, quinacridone pigments, isoindoline pigments, isoindolinone pigments, etc. These may use only 1 type, and may use 2 or more types together.

Examples of the bright pigment include foil pigments such as aluminum foil, copper foil, tin foil, gold foil, silver foil, titanium metal foil, stainless steel foil, nickel/copper alloy foil, and foil-like phthalocyanine blue. These may use only 1 type, and may use 2 or more types together.

Waxes known in the industry for coatings can be used, such as microcrystalline wax, polyethylene, polypropylene, paraffin wax, carnauba wax, and modified products thereof. These may use only 1 type, and may use 2 or more types together.

The shear viscosity of the aforementioned water-based paint composition is preferably 30,000mPa·s or less, more preferably 20,000mPa·s or less, more preferably 10,000mPa·s or less when measured at a temperature of 23°C and a shear rate of 0.01s ^-1 , and preferably at least 3,000 mPa·s, more preferably at least 4,000 mPa·s, more preferably at least 5,000 mPa·s. When measured at a shear rate of 10s ^-1 , it should be less than 800mPa·s, more preferably less than 700mPa·s, more preferably less than 600mPa·s, and preferably more than 300mPa·s, more preferably more than 400mPa·s, more preferably It is above 500mPa・s. When measured at a shear rate of 1,000 s ^-1 , it is preferably not more than 1,000 mPa·s, more preferably not less than 150 mPa·s, and more preferably not more than 500 mPa·s. By falling within the above-mentioned range, it will become the viscosity suitable for the paint pick-up property at the time of roller coater coating. The aforementioned shear viscosity can be, for example, a value measured immediately after preparation of the paint composition. The aforementioned shear viscosity can be measured using a rotary viscometer, for example, it can be measured using a stress control type rheometer MCR301 (manufactured by Anton Paar Co., Ltd.).

＜Preparation method of water-based paint composition＞ The preparation method of the water-based paint composition disclosed in the present disclosure is not particularly limited, and can be prepared by mixing various components. For example, a mixer disperser such as a roll mill, a ball mill, a bead mill, a pebble mill, a sand mill, a pot mill, a paint shaker or a disperser, a kneader, and the like can be used.

The coating film formed by the aforementioned water-based paint composition and the manufacturing method of the coating film are also included in the technical scope of the present disclosure.

＜To be coated＞ The object to be coated (substrate) of the water-based paint composition disclosed herein can be, for example, a galvanized steel sheet, a zinc-aluminum alloy coated steel sheet, an aluminum alloy coated steel sheet, a molten Zinc-aluminum-magnesium alloy plated steel sheet, stainless steel sheet, cold-rolled steel sheet, etc. In addition, other than these steel sheets or plated steel sheets, metal sheets such as aluminum sheets (including aluminum alloy sheets) can also be used as objects of coating.

The aforementioned object to be coated should be surface treated. Specifically, the coated object should be subjected to chemical conversion treatment after pretreatment such as alkali degreasing treatment, hot water washing treatment, and water washing treatment. The aforementioned chemical conversion treatment can be performed by known methods, for example, including non-chromate treatments such as chromate treatment and zinc phosphate treatment. The above-mentioned surface treatment can be properly selected according to the steel plate used, but the treatment without heavy metal is preferred. By coating the coating composition of the present disclosure on the coated object that has been subjected to chemical conversion treatment as described above, the adhesion to the metal plate surface of the coating film is improved, and the corrosion resistance is also improved. In addition, it is also possible to form a primer coating film (primer coating film) on the surface of the metal plate that has been subjected to chemical conversion treatment, and then paint on it. The film thickness of the primer coating film is preferably 3 μm or more, more preferably 5 μm or more, and preferably 15 μm or less, more preferably 10 μm or less.

＜Manufacturing method of coating film＞ The manufacturing method of the coating film of the present disclosure includes the following steps: coating the object to be coated with the water-based coating composition of the disclosure to form a coating film; Under the condition of less than 2 seconds, the above-mentioned coating film is dried and/or hardened to form a coating film.

The method of applying the aforementioned water-based coating composition of the present disclosure to the object to be coated is not particularly limited, and commonly known methods such as roller coating, airless spraying, electrostatic spraying, and curtain coating can be used. And suitable examples are roll coating method and curtain coating method, more preferably roll coating method.

The above-mentioned maximum attained temperature is preferably not less than 200 seconds, for example, not more than 280 seconds, not more than 270 seconds, or not more than 250 seconds. The drying and/or hardening time is 120 seconds or less, may be 60 seconds or less, 30 seconds or less, 10 seconds or less, 6 seconds or less, and preferably 1 second or more.

The method of drying and/or hardening the aforementioned coating film is not particularly limited, and heating methods such as hot air heating, infrared heating, and induction heating can be used.

The coating film thickness (dry film thickness) after drying and/or hardening is preferably 1 μm or more, more preferably 5 μm or more, and preferably 30 μm or less, more preferably 25 μm or less.

A laminate having the aforementioned object to be coated and the aforementioned coating film formed on the object to be coated is also included in the technical scope of the present disclosure.

When the aforementioned object to be coated further has the aforementioned coating film on one side, the other side may have a coating film formed of a known coating composition such as a coating composition containing an epoxy resin.

The water-based coating composition disclosed in this disclosure is even under higher temperature and shorter time conditions than those used in general metal substrate coating conditions (such as drying/hardening temperature 60~80°C, drying/hardening time 30 minutes~1 hour) When coating, the curability is still high, and a coating film with good coating film properties (adhesion, processability such as crack resistance, and scratch resistance) can be obtained.

The water-based paint composition disclosed in the present invention has high storage stability, and the obtained coating film is not easy to peel off from the coated object during bending and other processing, and has good adhesion. In addition, the occurrence of cracks is also suppressed, and the crack resistance is good, and , excellent scratch resistance. Therefore, the water-based coating composition disclosed in the present disclosure is suitable for coating on metals, especially for pre-coating. Example

The present disclosure is illustrated more specifically through the following examples, but the present disclosure is not limited thereto. In the examples, "parts" and "%" are based on mass unless otherwise stated.

<Production example of coating film forming resin (A-1)> 0.6 parts by mass of PELEX SS-H (surfactant, manufactured by Kao Corporation) was dissolved in 60 parts by mass of ion-exchanged water. To this was added a monomer mixture consisting of 53.0 parts by mass of methyl methacrylate, 39.2 parts by mass of n-butyl acrylate, 5.8 parts by mass of 2-hydroxyethyl methacrylate and 2.0 parts by mass of methacrylic acid, and stirred to prepare a single Body pre-emulsion 150.5 parts by mass. Moreover, 1.0 mass parts of ammonium persulfates were used as an initiator, and it was made to dissolve in 20 mass parts of ion exchanged water, and the initiator aqueous solution was prepared.

40 parts by mass of ion-exchanged water and 0.4 parts by mass of PELEX SS-H were fed into a reaction vessel equipped with a thermometer, a capacitor, and a stirrer, and heated to 80° C. under a nitrogen atmosphere. Here, the initiator aqueous solution was titrated over 180 minutes while maintaining 80° C., and 10 minutes after the titration started, the monomer pre-emulsion was titrated over 150 minutes from the other opening of the reaction vessel to perform emulsion polymerization. After the titration of the aforementioned initiator aqueous solution was completed, it was further heated and stirred at 80°C for 60 minutes, then cooled to room temperature, and 2.10 parts by mass of dimethylethanolamine was added thereto to prepare a coating film-forming resin (A-1) dispersed in an aqueous Acrylic emulsion in medium (solid content concentration: 45% by mass).

Coating film-forming resins (A-2) to (A-11) were prepared in the same manner as above except that the type, amount, and initiator amount of the monomers were changed as shown in Table 1. Table 1 shows the characteristic values such as the hydroxyl value of each coating film forming resin.

The details of each component shown in the following table|surface used for an Example and a comparative example are as follows. Coating film forming resin (A) (A-12) Vylonal MD2000 (manufactured by Toyobo Co., Ltd., polyester resin emulsion); hydroxyl value: 6 mgKOH/g, acid value: 2 mgKOH/g, weight average molecular weight: 30,000, glass transition temperature: 67°C, minimum film-forming temperature: 48°C, average particle diameter: 125nm, solid content concentration: 40% by mass Cross-linking agent (B) (B-1) CYMEL 303 (manufactured by Allnex Japan, peralkyl-type methylated melamine resin); solid content concentration: 100 mass % number average molecular weight: 455 (B-2) CYMEL 300 (manufactured by Allnex Japan, peralkyl-type methylated melamine resin); solid content concentration: 100 mass % number average molecular weight: 390 Other crosslinkers (b-1) CYMEL 327 (manufactured by Allnex Japan, imino-type methylated melamine resin); solid content concentration: 90 mass % number average molecular weight: 470 (b-2) MYCOAT 508 (manufactured by Allnex Japan, imino-type butylated melamine resin): solid content concentration: 80% by mass, number average molecular weight: 1,500 Sulfonic acid compound (C) (C-1) AC400S (manufactured by TAYCA CORPORATION, dodecylbenzenesulfonic acid); solid content concentration: 25% by mass (C-2) AC700 (manufactured by TAYCA CORPORATION, p-toluenesulfonic acid); solid content concentration: 25% by mass (C-3) Nacure-1051 (manufactured by Kusumoto Chemicals Co., Ltd., dinonylnaphthalenesulfonic acid); solid content concentration: 51% by mass other acid compounds (c-1) Cycat296 (manufactured by Allnex Japan, phosphoric acid compound); solid content concentration: 50% by mass Amine compound (D) (D-1) DMEA (dimethylethanolamine, manufactured by Mitsubishi Gas Chemical Co.); boiling point: 134° C. (D-2) AMP (2-amino-2-methyl-1-propanol, manufactured by Kokusai Chemical Co., Ltd.); boiling point: 165°C (D-3) TEA (triethylamine, manufactured by Mitsubishi Gas Chemical Co.); boiling point: 90° C. Aqueous medium (E) (E1-1) Diethylene glycol (manufactured by Nippon Shokubai Co.); boiling point: 244°C, solubility in water: infinite (mixed with water arbitrarily) (E1-2) Propylene glycol (manufactured by Sankyo Chemical Co., Ltd.); boiling point: 187°C, solubility in water: infinite (optionally mixed with water) (E1-3) Dipropylene glycol (manufactured by Showa Chemical Co., Ltd.); boiling point: 232°C, solubility in water: infinite (mix with water arbitrarily) (E1-4) 1,4-butanediol (manufactured by Sankyo Chemical Co., Ltd.); boiling point: 228°C, solubility in water: infinite (mix with water arbitrarily) (E1-5) 1,5-pentanediol (manufactured by Ube Industries); boiling point: 242°C, solubility in water: infinite (mix with water freely) Viscosity modifier (F) (F-1) SN-THICKENER 612 (polyether urethane-based hydrophobic association type viscosity modifier, manufactured by SAN NOPCO LIMITED); solid content concentration: 40% by mass (F-2) SN-THICKENER 621 (polyether urethane-based hydrophobic association type viscosity modifier, manufactured by SAN NOPCO LIMITED); solid content concentration: 30% by mass (F-3) ADEKA NOL UH-526 (polyether urethane hydrophobic association type viscosity modifier, manufactured by ADEKA Corporation); solid content concentration: 30% by mass (F-4) PRIMAL RM-2020NPR (polyether urethane hydrophobic association type viscosity modifier, manufactured by The Dow Chemical Company); solid content concentration: 20% by mass (F-5) PRIMAL ASE-60 (polyacrylate emulsion alkali swelling type thickener, manufactured by Dow Chemical Company); solid content concentration: 28% by mass

＜Manufacturing example of pigment dispersion paste＞ 1.63 parts by mass of Disperbyk 190 (manufactured by BKY Corporation) used as a dispersant, 0.25 parts by mass of dimethylethanolamine, 0.05 parts by mass of SN-477T (manufactured by SAN NOPCO LIMITED) used as a defoamer, 32.9 parts by mass of ion-exchanged water, and 65.2 parts by mass of titanium dioxide used as a pigment (Ti-Pure R-706, manufactured by DuPont Co.) was prepared and mixed, and dispersed at 1,600 rpm using an SG mill (dispersion medium: glass beads) until the maximum particle size of the pigment coarse particles was 5 μm So far, a pigment dispersion paste is obtained.

<Manufacturing example of water-based paint composition 1> 55.1 parts by mass of the pigment dispersion paste obtained in the aforementioned manufacturing example, 80.0 parts by mass of the coating film-forming resin (A-1) obtained in the aforementioned manufacturing example, 20.0 parts by mass of the coating film-forming resin (A-8) and used as a crosslinking agent (B -1) After mixing 17.6 parts by mass of CYMEL 303, 5.4 parts by mass of diethylene glycol (E1-1) and 5.4 parts by mass of propylene glycol (E1-2) used as an aqueous medium were mixed and stirred. Next, stir 1.2 parts by mass of dodecylbenzenesulfonic acid used as the sulfonic acid compound (C-1) and 1.9 parts by mass of dimethylethanolamine used as the amine compound (D-1) with a disperser, and further use 0.2 parts by mass of SN-THICKENER 612 used as a viscosity modifier (F-1) was mixed to obtain a coating composition 1.

(Paint composition 2~45, comparative example 1~10) A paint composition was prepared in the same manner as paint composition 1, except that the type and amount of each component were changed as shown in Tables 2 to 7.

＜Manufacturing example of coated steel sheet＞ After alkali degreasing the hot-dip galvanized steel sheet with a thickness of 0.4mm, apply phosphoric acid treatment agent SURFCOAT EC2310 (manufactured by Nippon Paint Surf Chemicals Co., Ltd.) on the surface and back of the steel sheet, thereby performing non-chromium chemical conversion treatment and drying . Next, using a bar coater, the coating composition 1 obtained in the production example was coated on the surface of the steel plate in such a way that the dry coating film was 18 μm, and baked for 30 seconds under the condition of the highest material reaching temperature of 230° C. to form a surface coating film. Obtain painted steel panels.

1) Shear Viscosity Measurement The shear viscosity of the coating compositions obtained in Examples and Comparative Examples was measured using a stress-controlled rheometer MCR301 (manufactured by Anton Paar, fixture: 50 mm parallel plate, gap: 0.5 mm), and the shear rate was measured at 0.1 Shear viscosity at s ^-1 , 10s ^-1 and 1,000s ^-1 . Let measurement temperature be 23 degreeC.

2) Storage stability Evaluation was performed using Ford Cup No. 4 (manufactured by Uejima Seisakusho) in accordance with the method prescribed in JIS K 5600 2-2 (flow cup method). Ion-exchanged water was added to the coating compositions obtained in Examples and Comparative Examples to adjust the viscosity to 60±10 seconds (initial viscosity (seconds)). In detail, let the initial viscosity be as follows: the viscosity measured immediately after diluting with the aforementioned ion-exchanged water and stirring at 1,000 rpm for 3 minutes using a disperser. Let the coating temperature be 25°C.

Fill 1/5 of the can with the paint composition adjusted to the aforementioned initial viscosity (60±10 seconds (25°C)) to 8-9 minutes full, seal it and place it in a constant temperature room at 40°C. Thereafter, it was taken out 14 days (two weeks) later, and the viscosity (elapsed viscosity (second)) was measured in the same manner as above. Calculate the change rate of the elapsed viscosity relative to the initial viscosity according to the following formula, and evaluate the storage stability according to the following criteria. ○Above is qualified. Viscosity change rate (%) = elapsed viscosity (seconds) / initial viscosity (seconds) × 100 ◎: The viscosity change rate is 0% or more and less than 30%. ◯: The viscosity change rate is 30% or more and less than 50%. Δ: The viscosity change rate is 50% or more and less than 100%. ×: The viscosity change rate is 100% or more.

5) Coating workability (roll coater applicability) For the coating compositions obtained in Examples and Comparative Examples, a small test coater (NK Tech Co. system), apply on the object to be coated under the following conditions, and evaluate the applicability of the roll coater according to the following criteria. ○Above is qualified. In addition, the test conditions were a room temperature of 23°C and a humidity of 60RH%.・Object to be coated: 300mm×2,000mm×0.35mm GL steel plate (manufactured by Nippon Steel Steel Co., Ltd.) ・Coating conditions: ・Linear speed: 50m/min Speed ratio 130%), pick-up roller: 20m/min (ratio to line speed 40%) ・Backup roller pressure: 60kgf ・Basic coating amount: The quality of the dry coating film is 28g/m ² The material reaches the maximum temperature of 230°C for 30 seconds ◎: The entire surface can be evenly coated according to the standard coating amount ○: Although it can be evenly coated on the entire surface, the coating amount is 20~28g/m ² △: Although it can be coated Full surface, but the coating amount is less than 20g/m ² , and the film thickness is uneven ×: Uncoated parts occur, and the entire surface cannot be painted

In addition, in the roller coater, the paint will be rolled up by the pick-up roller, transferred to the application roller, and then transferred to the back-up roller to be coated on the object to be coated. The paint is properly rolled up by the pick-up roller, and the paint is properly transferred to the backup roller by using the applicator roller and the back-up roller. The paint is evenly coated on the object to be coated, but only a small amount of paint is rolled up by the pick-up roller. , There will be deviations during the transfer between the rollers, and it will not be evenly applied to the coated object.

4) Processability (adhesion) Each of the coated steel sheets obtained in Examples and Comparative Examples was cut into 5 cm x 3 cm, and pre-bent so that the coated film surface would become the front side using a sheet metal folding machine (manufactured by Uejima Seisakusho Co., Ltd.). Two steel plates of the same thickness (0.4 mm) were sandwiched between the test pieces, and were bent by a press (manufactured by Kyoritsu Kogyo Co., Ltd.). Cellophane tape (registered trademark) (LP-24, manufactured by Nichiban Co., Ltd.) was adhered to the processed part of the coated steel plate, and then peeled off at a stretch to evaluate the adhesion of the coating film on the processed part. The appearance of the portion peeled off by the tape was evaluated according to the following criteria. A score of 4 or higher is considered acceptable. 5: The metal substrate was not observed in the tape-peeled portion. 4: The metal substrate portion was observed in less than 20% of the area (more than 0%) of the tape peeled portion. 3: The metal substrate part is observed in 20% or more and less than 50% of the area of the tape peeled part. 2: The base portion of the metal is observed in 50% or more and less than 80% of the area of the tape-peeled portion. 1: The metal substrate portion was observed in 80% or more of the area of the tape-peeled portion.

5) Processability (crack resistance) Each of the coated steel sheets obtained in Examples and Comparative Examples was cut into 5 cm x 3 cm, and pre-bent so that the coated film surface would become the front side using a sheet metal folding machine (manufactured by Uejima Seisakusho Co., Ltd.). Five steel plates of the same thickness (0.4 mm) were sandwiched between the test pieces, and bent with a press (manufactured by Kyoritsu Kogyo Co., Ltd.). Observe the coating state (cracks) of the processed part with a 15 times magnifying glass, and evaluate the processability according to the following criteria. A score of 4 or higher is considered acceptable. In addition, the test conditions were a temperature of 23°C and a humidity of 60RH%. 5: No cracks were observed in the processed portion. 4: Cracks were observed in less than 20% of the processed portion area (greater than 0%). 3: Cracks are observed in more than 20% and less than 50% of the processed part area. 2: Cracks were observed in 50% or more and less than 80% of the processed portion area. 1: Cracks were observed in 80% or more of the processed portion area.

6) Scar resistance Using a continuous weighted scratch strength tester TYPE: 18/18L (manufactured by Shinto Scientific Co., Ltd.), a diamond needle that has been subjected to R processing to become R0.4mm (conical scratch needle with R processing applied, diameter 0.4 mm) against the coated film surface of each coated steel sheet obtained in the examples and comparative examples, and scraped once with a load of 300 mm/min and a moving width of 10 cm. Evaluate the coating surface damage and the load weight when the base material is exposed according to the following criteria. ○Above is qualified. In addition, a load of 500gf is applied one by one, and the test conditions are a temperature of 23°C and a humidity of 60RH%. ◎: The substrate is not exposed when the load is greater than 3,000g ○: The load is greater than 2,000 and less than 3,000g △: The load is greater than 1,000g and less than 2,000g ×: Load 1,000g or less

[Table 1]

[Table 2]

[table 3]

[Table 4]

[table 5]

[Table 6]

[Table 7]

Examples 1-45 are examples of the present disclosure, and they have high storage stability, excellent processability and good scratch resistance.

Comparative examples 1 and 2 are examples in which the hydroxyl value of the acrylic resin (A1) is less than 5 mgKOH/g, and the scratch resistance is not good. Comparative examples 3 and 4 are examples in which the hydroxyl value of the acrylic resin (A1) is greater than 35 mgKOH/g, and the storage stability and processability are not good. Comparative Examples 5 and 6 are examples in which the neutralization rate of the sulfonic acid compound (C) caused by the amine compound (D) is less than 100%, and the storage stability is not good. Comparative Example 7 is an example in which the neutralization rate of the sulfonic acid compound (D) caused by the amine compound (D) is greater than 1,300%, and the storage stability is not good. Comparative Examples 8 and 9 are examples in which the crosslinking agent (B) does not contain the peralkyl-type melamine resin (B1), and the processability is not good. Comparative example 10 is an example which does not contain a sulfonic acid compound (C), but uses a phosphoric acid compound, and storage stability and scratch resistance are unfavorable.

(none)

Claims (6)

A water-based paint composition, comprising a coating film forming resin (A), a crosslinking agent (B), a sulfonic acid compound (C) and an amine compound (D); The aforementioned coating film-forming resin (A) comprises an acrylic resin (A1) having a hydroxyl group; The hydroxyl value of the coating film-forming resin (A) is not less than 5 mgKOH/g and not more than 35 mgKOH/g; The aforementioned crosslinking agent (B) comprises a full alkyl type melamine resin (B1); And the neutralization rate of the acid group of the said sulfonic acid compound (C) by the said amine compound (D) is 100 % or more and 1,300 % or less in mole conversion. The water-based coating composition according to claim 1, wherein the weight average molecular weight of the coating film-forming resin (A1) is 100,000 or more. For the water-based coating composition of claim 1 or 2, the shear viscosity measured at a shear rate of 0.01s ^-1 at a temperature of 23°C is below 30,000mPa·s, and the shear viscosity measured at a shear rate of 10s ^-1 The shear viscosity is below 800mPa·s, and the shear viscosity measured at a shear rate of 1,000s ^-1 is above 150mPa·s. The water-based paint composition according to claim 1 or 2, which further comprises an organic solvent (E1). Such as the water-based coating composition of claim 1 or 2, which is used for coil coating. A method of manufacturing a coating film, comprising the following steps: Coating the water-based coating composition according to any one of claims 1 to 5 on the object to be coated to form a coating film; and The coating film is formed by drying and/or curing the above-mentioned coating film under the condition that the maximum attained temperature is 180° C. or higher and the drying and/or curing time is 120 seconds or less.