KR20230075379A - paint composition - Google Patents

Abstract

A coating composition that has good storage stability and can be cured in a short time is provided. A hydroxyl group-containing resin (A), an amino resin (B), a covalently bonded block type acid catalyst (C), and a phosphoric acid-modified epoxy resin (D), the resin solid content of the hydroxyl group-containing resin (A) and the amino 60 to 90 parts by mass of the hydroxyl group-containing resin (A), 10 to 40 parts by mass of the amino resin (B), and the covalently bonded block acid A coating composition comprising 1 to 10 parts by mass of the acid catalyst portion of the catalyst (C) and 1 to 10 parts by mass of the solid content of the phosphoric acid-modified epoxy resin (D).

Description

paint composition

The present invention relates to a coating composition.

In a wide range of industrial products such as home appliances, electronic devices, ornaments, furniture, building materials, etc., it is common to apply a coating composition to the surface or the like to form a coating film for the purpose of protection or decoration of the products or parts. all.

There are two-component paint compositions composed of a main agent and a crosslinking agent, and one-component types in which the main agent and a crosslinking agent are mixed in advance in a stable state. In the two-component type, it is easy to achieve both the storage stability of the coating composition and the physical properties of the resulting coating film. However, the two-component type has problems in its handling and painting workability, such as the need for the user to accurately mix the main agent and the crosslinking agent in a predetermined ratio at the painting site and sufficiently stirring, and there is a limit to the time available for use. Therefore, a one-component coating composition is required.

By the way, in recent years, the shortening of a coating process is calculated|required from the viewpoint of energy saving and carbon dioxide emission reduction.

For example, in Japanese Unexamined Patent Publication No. 2020-100740 (Patent Document 1), an invention related to a precoated steel sheet (also referred to as "PCM"), which is a coated steel sheet coated with a cold-rolled steel sheet or a coated steel sheet as a base material, is described. there is.

Usually, the precoated steel sheet is coated on the surface of the steel sheet, and, for example, a heating step of 30 to 60 seconds at 200 to 270 ° C. After forming a coating film through a baking process), it is processed into a required product. In this case, as a baking furnace used for baking, a hot air type furnace using gas or the like is generally used as a heating method.

However, in this case, it is necessary to maintain the ambient temperature of 300° C. or higher at all times, and reduction of energy cost is required.

Japanese Unexamined Patent Publication No. 2020-100740

Instead of the above hot air type furnace, an induction heating type induction heater (also referred to as "IH") type furnace has been developed, and various companies are beginning to introduce it. As a result, the length of the furnace was shortened, reducing the production space was possible, and the temperature of the PMT could be raised to 220°C in a short time.

On the other hand, since the furnace length is shortened in the above IH type furnace, the curing time of the coating composition is also required to be shortened. In a one-component paint composition, in order to shorten the curing time, it is necessary to increase the curing reaction rate by using a large amount of acid catalyst. However, when the coating composition contains a large amount of acid catalyst, there is a problem in the storage stability of the coating composition.

In this way, it has been difficult to obtain a coating composition that has good storage stability and can be cured in a short time.

An object of the present invention is to provide a coating composition that has good storage stability and can be cured in a short time.

Moreover, an object of this invention is to provide the method of manufacturing a coating film by heating for a short time using the said coating composition.

Another object of the present invention is to provide a method for producing a precoated metal sheet by heating in a short time using the coating composition.

The present invention provides the following aspects [1] to [13].

[1] a hydroxyl group-containing resin (A), an amino resin (B), a covalently bonded block type acid catalyst (C), and a phosphoric acid-modified epoxy resin (D),

With respect to a total of 100 parts by mass of the resin solid content of the hydroxyl group-containing resin (A) and the resin solid content of the amino resin (B),

60 to 90 parts by mass of the hydroxyl group-containing resin (A);

10 to 40 parts by mass of the amino resin (B),

1 to 10 parts by mass of the acid catalyst portion of the covalently bonded block type acid catalyst (C), and

A coating composition containing 1 to 10 parts by mass of the solid content of the phosphoric acid-modified epoxy resin (D).

[2] The coating composition according to [1], wherein the phosphoric acid-modified epoxy resin (D) has a number average molecular weight in the range of 460 to 4,000.

[3] The coating composition according to [1] or [2], wherein the covalently bonded blocked acid catalyst (C) is a catalyst obtained by blocking an aromatic sulfonic acid with a compound having a glycidyl group.

[4] In the covalently bonded block type acid catalyst (C), the compound having a glycidyl group is an epoxy resin having two or more glycidyl groups in its molecule, or a glycidyl group having one glycidyl group in its molecule. The coating composition according to [3], which is an ether compound.

[5] The coating composition according to [4], wherein the number average molecular weight of the epoxy resin having two or more glycidyl groups in the covalently bonded block acid catalyst (C) is in the range of 2,000 to 7,000.

[6] The coating composition according to [5], wherein the molecular weight of the glycidyl ether compound having one glycidyl group in the molecule in the covalently bonded block acid catalyst (C) is in the range of 140 to 200.

[7] The hydroxyl group-containing resin (A) is a polyester resin, the number average molecular weight of the hydroxyl group-containing resin (A) is within the range of 1,500 to 5,000, and the hydroxyl value is within the range of 40 to 100 mgKOH / g, [ The coating composition according to any one of 1] to [6].

[8] The coating composition according to any one of [1] to [7], wherein the amino resin (B) contains a melamine resin.

[9] The coating composition according to any one of [1] to [8], further comprising an alkanolamine (E).

[10] The coating composition according to [9], wherein the alkanolamine (E) contains two or more alkanol groups in a molecule.

[11] The content of the alkanolamine (E) is 1.0 to 4.0 parts by mass based on 100 parts by mass of the total of the resin solid content of the hydroxyl group-containing resin (A) and the resin solid content of the amino resin (B), [9 ] or the coating composition described in [10].

[12] a step of forming a coating film by coating the coating composition according to any one of [1] to [11] on an object to be coated; and

A method for producing a coating film, comprising a step of drying and/or curing the coating film under the condition that the reach temperature of the object to be coated is 180°C to 270°C and the drying and/or curing time is 1 to 10 seconds.

[13] A step of forming a coating film by coating the coating composition according to any one of [1] to [11] on at least one surface of the metal plate so that the film thickness after curing is 5 to 25 μm, and

A method for producing a precoated metal sheet, comprising a step of drying and/or curing the coated film under the condition that the metal sheet has an ultimate temperature of 180°C to 270°C and a drying and/or curing time of 1 to 10 seconds.

The coating composition of the present invention has good storage stability, and the curing reaction can sufficiently proceed even by heating for a short time.

Moreover, with the method for producing a coating film of the present invention, a coating film can be produced by heating in a short time.

Moreover, according to the manufacturing method of the precoated metal sheet of this invention, a precoated metal sheet can be manufactured by heating in a short time.

[Paint Composition]

The coating composition of the present disclosure will be described.

The coating composition of the present disclosure includes a hydroxyl group-containing resin (A), an amino resin (B), a covalently bonded block type acid catalyst (C), and a phosphoric acid-modified epoxy resin (D),

With respect to a total of 100 parts by mass of the resin solid content of the hydroxyl group-containing resin (A) and the resin solid content of the amino resin (B),

60 to 90 parts by mass of the hydroxyl group-containing resin (A);

10 to 40 parts by mass of the amino resin (B),

1 to 10 parts by mass of the acid catalyst portion of the covalently bonded block type acid catalyst (C), and

The solid content of the phosphoric acid-modified epoxy resin (D) is contained in an amount of 1 to 10 parts by mass.

<Hydroxyl group-containing resin (A)>

The hydroxyl group-containing resin (A) is a resin having a hydroxyl group in its molecular structure. The hydroxyl group-containing resin (A) reacts with the amino resin (B) as a curing agent to form a coating film.

Examples of the hydroxyl group-containing resin (A) include polyester resins, epoxy resins, acrylic resins, and the like, and polyester resins are preferable.

(Polyester Resin)

The polyester resin is not particularly limited as long as it is a polyester resin generally used for coating materials. On the other hand, in the present disclosure, unless otherwise specified, when simply described as a polyester resin, it means including at least one selected from the group consisting of polyester resins and modified materials of polyester resins.

It is preferable that it is 40-100 mgKOH/g, and, as for the hydroxyl value of polyester resin, it is more preferable that it is 60-100 mgKOH/g. When the hydroxyl value of the polyester resin is within the above range, the reaction with the amino resin (B) as a curing agent proceeds favorably. When the coating composition contains such a polyester resin, the resulting coating film has advantages such as high solvent resistance, bending workability, processing adhesion, and chemical resistance.

On the other hand, in the present disclosure, the hydroxyl value represents the solid content hydroxyl value and is a value measured by the method described in JIS K 0070.

The number average molecular weight of the polyester resin is preferably 1,500 to 5,000, more preferably 2,000 to 4,500, and particularly preferably 2,000 to 4,000. When the number average molecular weight of the polyester resin is within the above range, the curing reaction with the amino resin (B) sufficiently proceeds, and a coating film having high solvent resistance and chemical resistance can be formed. In addition, excessive increase in crosslinking density of the coating film can be suppressed, and a coating film having sufficient elongation can be formed, for example, a coating film having sufficient bending workability and processing adhesion can be formed. In addition, the coating composition of the present disclosure has an appropriate viscosity and has good handling properties.

On the other hand, in the present disclosure, the number average molecular weight is a value obtained in terms of polystyrene by gel permeation chromatography (GPC).

The glass transition temperature (Tg) of the polyester resin is preferably -35°C or more and 110°C or less, for example, -30°C or more and 80°C or less, and may be -30°C or more and 60°C or less. When the glass transition temperature (Tg) of the polyester resin is within the above range, the moisture resistance and chemical resistance of the coating film become sufficient without excessively increasing the moisture permeability of the coating film.

On the other hand, in the present disclosure, the glass transition temperature (Tg) can be measured using, for example, a thermal analyzer (TMA7100 (manufactured by Hitachi High-Tech Science Co., Ltd.) or the like).

The acid value of the polyester resin is, for example, 0.1 mgKOH/g or more and 30 mgKOH/g or less, 0.2 mgKOH/g or more and 30 mgKOH/g or less, and may be 0.3 mgKOH/g or more and 30 mgKOH/g or less. When the acid value of the polyester resin is within the above range, for example, hydrolysis resistance can be improved, and a coating film having moisture resistance and chemical resistance can be formed.

On the other hand, in the present disclosure, the acid value represents the solid content acid value and is a value measured by the method described in JIS K 0070.

A polyester resin can be obtained by polycondensation of a polyhydric alcohol and a polybasic acid. Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, neopentyl glycol, 1,2 -Butanediol, 1,3-butanediol, 2,3-butanediol or 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol , hydrogenated bisphenol A, hydroxyalkylated bisphenol A, 1,4-cyclohexanedimethanol, 2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate (BASHPN ), N,N-bis-(2-hydroxyethyl)dimethylhydantoin, polycaprolactone polyol, glycerin, sorbitol, mannitol, trimethylolethane, trimethylolpropane, trimethylolbutane, hexane Lyol, pentaerythritol, dipentaerythritol, tris (2-hydroxyethyl) isocyanurate, etc. are mentioned. A polyhydric alcohol may use only 1 type, and may use 2 or more types together.

Examples of the polybasic acid include phthalic acid, phthalic anhydride, tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, methyl tetraphthalic acid, methyl tetrahydrophthalic anhydride, hymic acid anhydride, trimellitic acid, and tri anhydride. Mellitic acid, pyromellitic acid, pyromellitic anhydride, isophthalic acid, terephthalic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, adipic acid, azelaic acid, sebacic acid, succinic acid, succinic anhydride, lactic acid, dodecenyl Succinic acid, dodecenyl succinic anhydride, cyclohexane-1,4-dicarboxylic acid, endo acid anhydride, etc. are mentioned. A polybasic acid may use only 1 type, and may use 2 or more types together.

Examples of the modified polyester resin include modified polyester resins such as urethane-modified polyester resins, epoxy-modified polyester resins, acrylic-modified polyester resins, and silicone-modified polyester resins. For example, a urethane-modified polyester resin is a resin which has polyester as a main chain, denatures the terminal with isocyanate, and urethane-denatures. For example, a silicone-modified polyester resin is a polyester resin and an organic silicone (for example, an organic silicone having a number average molecular weight of about 300 to 1,000 having a -Si-OCH ₃ group and/or a Si-OH group as a functional group). It can be prepared by making it react. The amount of organic silicon used is usually about 5 to 50 parts by mass with respect to 100 parts by mass of the polyester resin. Further, for example, a urethane-modified polyester resin can be prepared by reacting the polyester resin and a polyisocyanate compound.

As the polyester resin, a commercial item can also be used, for example, DYNAPOL LH820, DYNAPOL LH826, DYNAPOL LH727 (all manufactured by Evonik), ETERKYD 5084-R-60-6E, ETERKYD 3103-X-70, ETERKYD 50528-R- 70, ETERKYD, 5055R-65-3 (all manufactured by Eternal Materials), Bekcolite M-6902-50 (manufactured by DIC), SYNOLAC 9605 (manufactured by ARKEMA), and the like.

(epoxy resin)

The epoxy resin is not particularly limited as long as it is an epoxy resin generally used for paint. On the other hand, in the present disclosure, unless otherwise specified, when simply described as an epoxy resin, it means including at least one selected from the group consisting of epoxy resins and modified products of epoxy resins.

It is preferable that it is 40-200 mgKOH/g, and, as for the hydroxyl value of an epoxy resin, it is more preferable that it is 60-180 mgKOH/g. When the hydroxyl value of the epoxy resin is within the above range, the reaction with the amino resin (B) as a curing agent proceeds favorably. When the coating composition contains such an epoxy resin, the obtained coating film has advantages such as high solvent resistance, sufficient bending workability, processing adhesion, and chemical resistance.

It is preferable that it is 1,500-5,000, and, as for the number average molecular weight of an epoxy resin, it is more preferable that it is 2,000-4,000. When the number average molecular weight of the epoxy resin is within the above range, the curing reaction with the amino resin (B) described later proceeds sufficiently, and a coating film having a good coating appearance can be formed. In addition, excessive increase in crosslinking density of the coating film can be suppressed, and a coating film having sufficient elongation can be formed, for example, a coating film having sufficient bending workability and processing adhesion can be formed. In addition, the coating composition of the present disclosure has an appropriate viscosity and has good handling properties.

The glass transition temperature (Tg) of the epoxy resin may be 120°C or less, or 115°C or less. For example, the glass transition temperature (Tg) of the epoxy resin may be 110°C or less. In one embodiment, the glass transition temperature (Tg) of the epoxy resin is 50°C or higher, and may be 55°C or higher. For example, the glass transition temperature (Tg) of the epoxy resin may be in the range of 50°C or higher and 120°C or lower. When the glass transition temperature (Tg) of the epoxy resin is within the above range, the moisture resistance and chemical resistance of the coating film become sufficient without excessively increasing the moisture permeability of the coating film.

The epoxy resin may be a hydroxyl group-containing epoxy resin (including a hydroxyl group-containing epoxy resin modified product). As an epoxy resin, resin formed by condensing epichlorohydrin and bisphenol to a high molecular weight in catalyst presence, such as an alkali catalyst, as needed; bisphenol type epoxy resins such as bisphenol A type and bisphenol F type; and novolak-type epoxy resins.

As a modified substance of an epoxy resin, modified epoxy resins, such as an acryl-modified epoxy resin, a urethane-modified epoxy resin, and an amine-modified epoxy resin, are mentioned, for example. For example, the acrylic-modified epoxy resin can be prepared by reacting the bisphenol-type epoxy resin or the novolac-type epoxy resin with a polymerizable unsaturated monomer component containing acrylic acid or methacrylic acid. Further, for example, the urethane-modified epoxy resin can be prepared by reacting a polyisocyanate compound with the bisphenol-type epoxy resin or the novolak-type epoxy resin.

In one embodiment, the modified epoxy resin is a resin other than phosphoric acid-modified epoxy resin and sulfonic acid-modified epoxy resin.

Commercially available products can also be used as the epoxy resin, for example, jER825, jER828, jER835, jER1004, jER1007, jER1010, jER1255HX30, jERYX8100BH30 (all bisphenol A type, manufactured by Mitsubishi Chemical Corporation), jER1009F (bisphenol F type, manufactured by Mitsubishi Chemical Corporation), etc. can be heard

(acrylic resin)

The acrylic resin is not particularly limited as long as it is an acrylic resin generally used for paint. On the other hand, in the present disclosure, unless otherwise specified, when simply described as an acrylic resin, it means including at least one selected from the group consisting of acrylic resins and modified products of acrylic resins.

It is preferable that it is 40-100 mgKOH/g, and, as for the hydroxyl value of an acrylic resin, it is more preferable that it is 60-100 mgKOH/g. When the hydroxyl value of the acrylic resin is within the above range, the reaction with the amino resin (B) as a curing agent proceeds favorably. When the coating composition contains such an acrylic resin, the resulting coating film has advantages such as high solvent resistance, chemical resistance, sufficient bending workability, and processing adhesion.

It is preferable that it is 1,500-5,000, and, as for the number average molecular weight of an acrylic resin, it is more preferable that it is 2,000-4,000. When the number average molecular weight of the acrylic resin is within the above range, the curing reaction with the amino resin (B) proceeds sufficiently, and a coating film having a good coating appearance can be formed. In addition, excessive increase in crosslinking density of the coating film can be suppressed, and a coating film having sufficient elongation can be formed, for example, a coating film having sufficient bending workability can be formed. In addition, the coating composition of the present disclosure has an appropriate viscosity and has good handling properties.

The glass transition temperature (Tg) of the acrylic resin is preferably -35°C or more and 110°C or less, for example, -30°C or more and 80°C or less, and may be -30°C or more and 60°C or less. When the glass transition temperature (Tg) of the acrylic resin is within the above range, the moisture resistance and chemical resistance of the coating film are improved without excessively increasing the moisture permeability of the coating film.

The acid value of the acrylic resin (including modified substances thereof) may be, for example, 0.1 mgKOH/g or more and 30 mgKOH/g or less, 0.2 mgKOH/g or more and 30 mgKOH/g or less, and 0.3 mgKOH/g or more and 30 mgKOH/g or less. do. When the acid value of the acrylic resin is in such a range, for example, hydrolysis resistance can be improved, and a coating film having moisture resistance and chemical resistance can be formed.

Examples of the acrylic resin include hydroxymethyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and hydroxyl such as N-methylolacrylamide. group-containing (meth)acrylic monomers and lactone adducts thereof; (meth)acrylic acid; (meth)acrylic acid esters such as alkyl (meth)acrylates; (meth)acrylonitrile, etc., and an acrylic resin composed of one or two or more monomers selected from the group consisting of. In addition to the constituent units derived from the above monomers, the acrylic resin is formed from other monomers (e.g., carboxy group-containing ethylenic monomers such as crotonic acid, itaconic acid, fumaric acid, and maleic acid, and vinyl monomers such as styrene). You may contain the structural unit derived. As a modified substance of an acrylic resin, modified acrylic resins, such as silicone modified acrylic resin, are mentioned, for example. For example, a silicone-modified acrylic resin can be prepared by making an acrylic resin and organic silicone as described above react. The amount of organic silicon used is usually about 5 to 50 parts by mass with respect to 100 parts by mass of the acrylic resin. Meanwhile, in the present disclosure, (meth)acrylic acid represents acrylic acid or methacrylic acid.

A commercial item can also be used as an acrylic resin, and, for example, Acridic A-608, Acridic A-452, Acridic A-830 (both made by DIC Corporation), etc. are mentioned.

As for hydroxyl-containing resin (A), only 1 type may be used, and 2 or more types may be used together.

<Amino resin (B)>

The amino resin (B) reacts with the hydroxyl group-containing resin (A) and the phosphoric acid-modified epoxy resin (D) to form a cured coating film.

The amino resin (B) is excellent in curing reactivity with the hydroxyl group-containing resin (A) and the like, and a coating film having good appearance and moisture resistance can be obtained.

Examples of the amino resin include melamine resin, urea resin, and benzoguanamine, and melamine resin and urea resin are preferable. In particular, from a weather resistance viewpoint, it is preferable that an amino resin contains a melamine resin, and it is more preferable that it is a melamine resin.

"Melamine resin" generally means a thermosetting resin synthesized from melamine and aldehyde, and has three reactive functional groups -NX ¹ X ² in one molecule of tria eukaryotic.

As the melamine resin, a complete alkyl type containing -N(CH ₂ OR) ₂ [R represents an alkyl group having 1 to 8 carbon atoms, the same hereinafter] as a reactive functional group; a methylol group containing -N(CH ₂ OR)(CH ₂ OH) as a reactive functional group; an imino group containing -N(CH ₂ OR)(H) as a reactive functional group; Methylol/imino containing -N(CH ₂ OR)(CH ₂ OH) and -N(CH ₂ OR)(H) as reactive functional groups, or -N(CH ₂ OH)(H) Four types of malformations can be exemplified.

In the present invention, it is preferable to use a completely alkylated melamine resin among the above melamine resins, and methylated melamine resin, butylated melamine resin, isobutylated melamine resin, etc. are mentioned as such a resin.

Commercially available products can also be used as the melamine resin, for example, Cymel 303, Cymel 325, Cymel 350, Cymel 370, Mycoat 715 (all methylated melamine resins, Allnex Japan Co., Ltd.), Cymel 202, Cymel 202 Mel 235, Cymel 254, Cymel 1123, Cymel 1128, Cymel 1170, Mycoat 212 (all methyl-butylated mixed melamine resins, manufactured by Allnex Japan), Sumimal M-40S (methylated melamine resin, Sumitomo Chemical manufactured by Amidia), Amidia J-820-60, Amidia L-127-60 (both butylated melamine resins, manufactured by DIC), and the like.

An amino resin (B) may use only 1 type, and may use 2 or more types together.

In one embodiment, a polyester resin is used as the hydroxyl group-containing resin (A) and a melamine resin is used as the amino resin (B).

In the coating composition of the present disclosure, 60 to 90 parts by mass of the hydroxyl group-containing resin (A) and the amino resin ( 10 to 40 parts by mass of B), preferably 70 to 80 parts by mass of hydroxyl group-containing resin (A) and 20 to 30 parts by mass of amino resin (B). By containing the hydroxyl group-containing resin (A) and the amino resin (B) within the above ranges, the curing reaction between the hydroxyl group-containing resin (A) and the amino resin (B) proceeds favorably. Moreover, by including it in the above range, the appearance of the obtained coating film can be improved. In addition, the solvent resistance, bending workability, processing adhesion, and chemical resistance of the coating film obtained from the coating composition of the present disclosure are improved.

<Covalent bond block type acid catalyst (C)>

The covalently bonded blocked acid catalyst (C) protects the acid catalyst by covalently binding the blocking agent to a structure in which the acid catalyst is blocked by a blocking agent, for example, an acid catalyst (particularly, an acid group of the acid catalyst). have one structure. By protecting the acid catalyst, the action as a curing catalyst is suppressed during storage, and the storage stability of the coating composition is improved. In addition, when the blocking agent is dissociated by heating or the like, the acid catalyst acts as a curing catalyst and promotes the reaction of the hydroxyl group-containing resin (A), the amino resin (B) and the phosphoric acid-modified epoxy resin (D).

In the coating composition of the present disclosure, the acid catalyst part of the covalently bonded block type acid catalyst (C) is added in an amount of 1 to 100 parts by mass in total of the resin solid content of the hydroxyl group-containing resin (A) and the resin solid content of the amino resin (B). 10 parts by mass, preferably 1 to 7 parts by mass, more preferably 1 to 5 parts by mass. By containing the covalently-bonded block-type acid catalyst (C) within the above range, the storage stability of the obtained coating composition is improved, and it has high solvent resistance, sufficient bending workability, processing adhesion, and chemical resistance by curing. A coating is formed.

On the other hand, the acid catalyst moiety refers to a sulfonic acid when the covalently bonded block type acid catalyst (C) has a structure in which a blocking agent is covalently bonded to sulfonic acid, for example.

Usually, the coating composition often contains an acid catalyst in order to increase the curing rate. However, when the content of the acid catalyst is increased, the storage stability of the paint composition tends to deteriorate. Further, as the acid catalyst, when an acid catalyst not protected by a blocking agent is used, or when an acid catalyst neutralized with an amine (i.e., an amine block type acid catalyst) is used, the storage stability of the coating composition obtained However, there are cases where the physical properties of the formed coating film are deteriorated.

In contrast, in the coating composition of the present disclosure, the inclusion of the covalently-bonded blocked acid catalyst (C) accelerates the curing reaction and further improves the storage stability.

The covalently bonded block type acid catalyst (C) preferably contains sulfonic acid as the acid catalyst, and more preferably the acid catalyst is sulfonic acid. The number of sulfonic acid groups in the sulfonic acid is 1 or more per molecule, for example, 2 or less may be sufficient, and it is 1 in particular.

In one embodiment, the covalently bonded block type acid catalyst (C) excludes a phosphoric acid compound.

In the covalently bonded block type acid catalyst (C), it is preferable that the blocking agent is covalently bonded to all of the sulfonic acid groups of the acid catalyst, sulfonic acid.

Examples of the sulfonic acid include aliphatic sulfonic acids such as methanesulfonic acid, aromatic sulfonic acids such as p-toluenesulfonic acid, dinonylnaphthalenesulfonic acid, dinonylnaphthalenedisulfonic acid, and dodecylbenzenesulfonic acid. . These may use only 1 type, and may use 2 or more types together. On the other hand, in the present disclosure, aromatic sulfonic acid refers to one having a structure in which one or more sulfonic acid groups (for example, 1 or 2, specifically 1 sulfonic acid group) are directly bonded to an aromatic ring.

In aromatic sulfonic acid, as an aromatic ring, a benzene ring, a naphthalene ring, etc. are mentioned, for example.

In the aromatic sulfonic acid, one or more alkyl groups having 1 to 15 carbon atoms may be bonded to the carbon atoms constituting the aromatic ring, more specifically, one or two may be bonded, for example, one bond There may be.

Preferably, the covalently bonded blocked acid catalyst (C) has a blocked structure by covalently bonding a compound having a glycidyl group as a blocking agent to sulfonic acid as an acid catalyst. In other words, it has a structure in which sulfonic acid (specifically, the sulfonic acid group of sulfonic acid) is blocked by a compound having a glycidyl group (specifically, the glycidyl group of a compound having a glycidyl group).

Further, the covalently bonded blocked acid catalyst (C) preferably has a structure in which an aromatic sulfonic acid is blocked by a compound having a glycidyl group. In other words, it is preferable that the sulfonic acid group of aromatic sulfonic acid is blocked with the glycidyl group of a compound having a glycidyl group. By including such a covalently bonded block type acid catalyst (C), the stability of the coating composition during storage can be further improved, and the glycidyl group is dissociated by heating or the like, so that the curing reaction can be further accelerated. there is.

Examples of aromatic sulfonic acids blocked with glycidyl groups include those obtained by blocking aromatic sulfonic acids such as dinonylnaphthalenesulfonic acid, dinonylnaphthalenedisulfonic acid, p-toluenesulfonic acid, and dodecylbenzenesulfonic acid with glycidyl groups. . Among these, a catalyst obtained by blocking dinonylnaphthalenesulfonic acid with a glycidyl group is particularly preferred. As an aromatic sulfonic acid blocked with a glycidyl group, a commercial item may be used, and examples thereof include Nacure 1419 (manufactured by King Industries, brand name) and the like.

In the covalently bonded block type acid catalyst (C), as the compound having a glycidyl group used for the block of sulfonic acid, an epoxy resin having two or more glycidyl groups in a molecule or a compound having one glycidyl group in a molecule Lycidyl ether compounds are preferred. By using such a compound, while the stability at the time of storage of the coating composition obtained can be further improved, the glycidyl group is dissociated by heating or the like, and the curing reaction can be further accelerated.

Hereinafter, as a blocking agent, a covalently bonded blocked acid catalyst using an epoxy resin having two or more glycidyl groups in the molecule is sometimes referred to as a covalently bonded blocked acid catalyst (C1). A covalent-bond block type acid catalyst using a glycidyl ether compound having one lysidyl group is sometimes referred to as a covalent-bond block type acid catalyst (C2).

The number of glycidyl groups in the compound having the glycidyl group is 1 or more per molecule, and may be, for example, 5 or less, or 3 or less.

Moreover, it is preferable that it is 100-10,000, and, as for the number average molecular weight of the compound which has the said glycidyl group, it is more preferable that it is 140-7,000.

In one embodiment, the compound having a glycidyl group used for the block of sulfonic acid is preferably an epoxy resin having two or more glycidyl groups in a molecule.

The epoxy resin used for the block of sulfonic acid is not particularly limited as long as it is an epoxy resin having two or more glycidyl groups in the molecule.

The epoxy resin may be a hydroxyl group-containing epoxy resin (including a hydroxyl group-containing epoxy resin modified product).

As said epoxy resin, resin formed by condensing epichlorohydrin and bisphenol to a high molecular weight in the presence of catalysts, such as an alkali catalyst, as needed; bisphenol type epoxy resins such as bisphenol A type and bisphenol F type; and novolak-type epoxy resins. Among these, bisphenol-type epoxy resins are preferred, and bisphenol A-type epoxy resins are more preferred.

As a modified substance of an epoxy resin, modified epoxy resins, such as an acryl-modified epoxy resin, a urethane-modified epoxy resin, and an amine-modified epoxy resin, are mentioned, for example. For example, taking an acrylic-modified epoxy resin as an example, it can be prepared by reacting the above bisphenol type epoxy resin or the above novolak type epoxy resin with a polymerizable unsaturated monomer component containing acrylic acid or methacrylic acid. Further, taking a urethane-modified epoxy resin as an example, it can be prepared by reacting a polyisocyanate compound with the bisphenol-type epoxy resin or the novolak-type epoxy resin.

In one embodiment, the modified epoxy resin is excluding phosphoric acid-modified epoxy resin.

As said epoxy resin, you may use a commercial item, for example, jER825, jER828, jER834, jER1004, jER1007, jER1009, jER1010, jER1255HX30 (all bisphenol A type, Mitsubishi Chemical Corporation make), jER1009F (bisphenol F type, Mitsubishi Chemical Corporation make) These etc. are mentioned, and jER1007, jER1009, and jER1010 are preferable.

It is preferable that the number average molecular weight of the said epoxy resin is 2,000-7,000. When the number average molecular weight of the epoxy resin is within the above range, the curing reaction with the hydroxyl group-containing resin (A), amino resin (B), and phosphoric acid-modified epoxy resin (D) sufficiently proceeds, resulting in high solvent resistance, sufficient bending workability, and processing adhesion. , it is possible to form a coating film having chemical resistance.

In one embodiment, the compound having a glycidyl group used for the block of sulfonic acid is preferably a glycidyl ether compound having one glycidyl group in the molecule.

The glycidyl ether compound used for the block of sulfonic acid is not particularly limited as long as it is a glycidyl ether compound having one glycidyl group in the molecule.

Examples of the glycidyl ether compound include aromatic glycidyl ether compounds, aliphatic glycidyl ether compounds, and alicyclic glycidyl ether compounds. Among these, aromatic glycidyl ether compounds are preferred. and phenyl glycidyl ether is more preferred.

Commercially available products may be used as the glycidyl ether compound, for example, phenyl glycidyl ether, o-cresyl glycidyl ether (both aromatic glycidyl ether compounds, manufactured by Yokkaichi Synthetic Industries Co., Ltd.), DY-BP , Epogose 2EH, Epogose LA (D), Epogose AN (all are aliphatic glycidyl ether compounds, manufactured by Yokkaichi Seisei Co., Ltd.), etc., and phenyl glycidyl ether is preferable.

It is preferable that the molecular weight of the said glycidyl ether compound is 140-200. When the molecular weight of the glycidyl ether compound is within the above range, the curing reaction with the hydroxyl group-containing resin (A), amino resin (B), and phosphoric acid-modified epoxy resin (D) proceeds sufficiently, resulting in high solvent resistance, sufficient bending workability, and processing A coating film having adhesion and chemical resistance can be formed. Meanwhile, in the present disclosure, the molecular weight of the glycidyl ether compound is a value calculated from a molecular formula.

The covalently bonded block type acid catalyst (C) is, for example, a compound having a sulfonic acid group of sulfonic acid and a glycidyl group (specifically, an epoxy resin having two or more glycidyl groups or one glycidyl group). It can be formed by blocking with a glycidyl group of a glycidyl ether compound having (hereinafter, the same in this paragraph). Specifically, after weighing a compound having a sulfonic acid and a glycidyl group, the sulfonic acid group of the sulfonic acid and the glycidyl group of the compound having a glycidyl group have a molar ratio in the range of 1: 1 to 1: 2, By adding to a container and stirring at 90° C. for 120 minutes, for example, a sulfonic acid group is blocked with a glycidyl group, and a covalently bonded blocked acid catalyst (C) can be formed.

A coating composition can be formed by mixing the formed covalently bonded block type acid catalyst (C), a hydroxyl group-containing resin (A), an amino resin (B), a phosphoric acid-modified epoxy resin (D), and other components as necessary. there is.

<Phosphoric Acid Modified Epoxy Resin (D)>

The phosphoric acid-modified epoxy resin (D) contains a phosphoric acid group [-OPO(OH)(OR ¹ )] (where R ¹ is a hydrogen atom, a phenyl group or an alkyl group having 1 to 20 carbon atoms, and a hydrogen atom is particularly preferable). . As the phosphoric acid-modified epoxy resin (D), one compatible with the hydroxyl group-containing resin (A) and the amino resin (B) is used.

In the coating composition of the present disclosure, 1 to 10 parts by mass of the solid content of the phosphoric acid-modified epoxy resin (D) is included with respect to 100 parts by mass in total of the resin solid content of the hydroxyl group-containing resin (A) and the resin solid content of the amino resin (B) and preferably 1 to 5 parts by mass. By containing the phosphoric acid-modified epoxy resin (D) within the above range, a coating film having high solvent resistance, sufficient bending workability, processing adhesion, and chemical resistance can be formed. In particular, even when the curing time is short, curing sufficiently proceeds, and a coating film having good physical properties can be formed.

It is preferable that it is 400-6,000, and, as for the number average molecular weight of a phosphoric acid-modified epoxy resin (D), it is more preferable that it is 460-4,000. When the phosphoric acid-modified epoxy resin (D) has such a number average molecular weight, it can further contribute to formation of a coating film having high solvent resistance, sufficient bending workability, processing adhesion, and chemical resistance.

The phosphoric acid-modified epoxy resin (D) can be obtained, for example, by adding a phosphoric acid-based compound to an epoxy resin. Specifically, an epoxy resin and a phosphoric acid compound are mixed in a mass such that the glycidyl group of the epoxy resin and the phosphoric acid group of the phosphoric acid compound have a molar ratio of 1:1 to 1:2, for example, at 80°C for 120 minutes. It can be obtained by reacting.

In one embodiment, the epoxy resin has glycidyl groups only at both ends.

In one embodiment, the phosphoric acid-modified epoxy resin (D) excludes phosphoric acid-modified epoxy resins reacted with sulfonic acid.

In the phosphoric acid-modified epoxy resin (D), examples of the epoxy resin include bisphenol-type epoxy resins, novolak-type epoxy resins, and modified epoxy resins obtained by reacting various modifiers with glycidyl groups or hydroxyl groups in these epoxy resins. Among these, it is preferable to use a bisphenol type epoxy resin, and it is more preferable to use a bisphenol A type epoxy resin.

Commercially available products may be used as the epoxy resin, for example, jER825, jER828, jER834, jER1004, jER1007, jER1009, jER1010, jER1255HX30 (all bisphenol A type, manufactured by Mitsubishi Chemical Corporation), jER1009F (bisphenol F type, manufactured by Mitsubishi Chemical Corporation), etc. are mentioned, and jER828, jER834, jER1004, jER1007, and jER1009 are preferable.

The number average molecular weight of the epoxy resin is preferably 370 to 3,800, for example, when the phosphoric acid compound to be modified is phosphoric acid.

As the epoxy resin, an acrylic-modified epoxy resin, a polyester-modified epoxy resin, or the like may be used.

In one embodiment, in the phosphoric acid-modified epoxy resin (D), the molecular weight of the phosphoric acid-based compound is 98 to 1,200.

In the phosphoric acid-modified epoxy resin (D), the phosphoric acid-based compound is not particularly limited as long as it can introduce a phosphoric acid group into the epoxy resin, and examples thereof include orthophosphoric acid and acidic phosphoric acid esters.

An acidic phosphoric acid ester refers to a structure in which one or two hydrogens among the three hydrogens of phosphoric acid (O=P(OH) ₃ ) are substituted with an organic group. Here, the organic group is an alkyl group (eg, 1 to 24 carbon atoms), an alkyl ether group (eg, R ³ -OR ⁴ O-, R ³ is an alkyl group having 1 to 5 carbon atoms, R ⁴ is methylene group, an ethylene group, a propylene group, preferably an ethylene group or a propylene group), and an aromatic group. Examples of acidic phosphoric acid esters include methyl acid phosphate, butyl acid phosphate, 2-ethylhexyl acid phosphate, isodecyl acid phosphate, lauryl acid phosphate, isotridecyl acid phosphate, oleyl acid phosphate, tetracosyl acid phosphate and phenyl acid phosphate. etc. can be mentioned.

In the coating composition of the present disclosure, as described above, together with the hydroxyl group-containing resin (A) and the amino resin (B), the covalently bonded block type acid catalyst (C) and the phosphoric acid-modified epoxy resin (D) are included. By containing both the covalent-bond block type acid catalyst (C) and the phosphoric acid-modified epoxy resin (D), the storage stability of the coating composition, specifically, the increase in viscosity during storage can be suppressed, and a short time (For example, 1 to 10 seconds, specifically, 1 to 6 seconds) the curing reaction sufficiently advances even by heating, and a coating film can be formed. For example, in an IH type furnace, temperature can be raised in a short time, and specifically, PMT can be heated to 220°C in about 6 seconds. In the coating composition of the present disclosure, even when such an IH type furnace is used, the curing reaction sufficiently proceeds, and a coating film having good physical properties can be formed.

In addition, by heating the coating composition of the present disclosure at, for example, 170°C to 280°C, the curing reaction sufficiently proceeds, and a coating film can be formed. In particular, in the coating composition of the present disclosure, the curing reaction sufficiently proceeds even when heated at a relatively low temperature (for example, 170 ° C to 220 ° C, specifically 180 ° C to 220 ° C), and the coating film appearance, solvent resistance, bending A coating film having good physical properties such as processability, processability, alkali resistance, and acid resistance can be obtained. A coating film obtained by heating at a relatively low temperature has the same physical properties as a coating film obtained at a commonly used temperature such as 270°C or 280°C, for example.

In addition, when the coating composition of the present disclosure is used, even when a coating film is formed by heating for a short time, a coating film having good physical properties such as coating appearance, solvent resistance, bending workability, processing adhesion, and chemical resistance can be obtained. The physical properties of the coating film formed by this short-time heating are equivalent to those of the coating film formed by normal heating time (for example, 25 seconds, 30 seconds, etc.).

<Other resin>

The coating composition may include other resins used in the field of coating compositions within a range that does not impair the effects exhibited by the present disclosure. Examples of other resins include polyester resins other than those described above and modified products thereof (such as urethane-modified polyester resins, epoxy-modified polyester resins, and silicone-modified polyester resins); urethane resins and modified products thereof (ester-based urethane resins, ether-based urethane resins, carbonate-based urethane resins, epoxy-based urethane resins, etc.); phenol resins and modified products thereof (acrylic-modified phenol resins, epoxy-modified phenol resins, etc.); phenoxy resin; alkyd resins and modified products thereof (urethane-modified alkyd resins, acrylic-modified alkyd resins, etc.); Resins, such as a fluororesin, are mentioned. These resins may use only 1 type, and may use 2 or more types together.

<Alkanolamine (E)>

The coating composition of the present disclosure may further include an alkanolamine (E). The alkanolamine (E) is a compound having one or more alkanol groups, and is particularly an amine having one or more alkanol groups. Meanwhile, in the present disclosure, an alkanol group represents a group represented by -R ² -OH (where R ² is an alkylene group having 1 or more carbon atoms).

By including the alkanolamine (E), there is an advantage of further improving the storage stability of the coating composition.

The alkanolamine (E) preferably has one or more amino groups and two or more alkanol groups per molecule, more preferably has one or more amino groups and two or three alkanol groups, and still more preferably has one or more amino groups and two or more alkanol groups. It has one amino group and two or three alkanol groups.

In one embodiment, the molecular weight of the alkanolamine (E) is in the range of 60 to 200.

The alkanol group of the alkanolamine (E) has preferably 1 to 3 carbon atoms, more preferably 2 to 3 carbon atoms.

In one embodiment, the alkanolamine (E) is represented by NR ²² _3-n (-R ² -OH) _n . n is an integer of 1 to 3, preferably 2 or 3, R ²² is each independently, for example, a hydrogen atom or an alkyl group having 1 to 5 carbon atoms (specifically, 1 to 3 carbon atoms), and R ² is , are each independently an alkylene group having 1 to 3 carbon atoms (preferably 2 to 3 carbon atoms).

Although it does not specifically limit as an alkanolamine (E), For example, amine which has one alkanol group, such as ethanolamine and dimethylaminoethanol; amines having two alkanol groups such as diisopropanolamine and diethanolamine; and amines having three alkanol groups such as triisopropanolamine and triethanolamine. Among these, diisopropanolamine, triisopropanolamine, diethanolamine, and triethanolamine are preferable. Diisopropanolamine, Triisopropanolamine is more preferred. Alkanolamine (E) may use only 1 type, and may use 2 or more types together.

The content of the alkanolamine (E) is preferably 1.0 to 10.0 parts by mass, preferably 1.0 to 4.0 parts by mass, based on 100 parts by mass in total of the resin solid content of the hydroxyl group-containing resin (A) and the resin solid content of the amino resin (B). It is more preferable, and it is more preferable that it is 1.0-3.5 mass parts, and 1.0-3.0 mass parts may be sufficient. By including the alkanolamine (E) in the above range, there is an advantage of further improving the storage stability of the coating composition.

<Other additives>

The coating composition of the present disclosure may contain additives other than those described above, if necessary.

Examples of other additives include extender pigments; coloring agents such as colored pigments and dyes; bright pigments; Aggregates (resin particles, silica particles, etc.); wax; solvent; ultraviolet absorbers (such as benzophenone-based ultraviolet absorbers); antioxidants (phenol-based, sulfide-based, hindered amine-based antioxidants, etc.); plasticizer; coupling agents (silane-based, titanium-based, zirconium-based coupling agents, etc.); anti-sagging agent; thickening agent; pigment dispersants; pigment wetting agents; surface conditioners (silicone-based, organic polymer-based, etc.); leveling agent; color separation inhibitor; anti-settling agents; antifoam; cryoprotectants; emulsifier; antiseptic; antifouling agent; antibacterial agent; stabilizers, etc. These additives may use only 1 type, and may use 2 or more types together.

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

In one embodiment, the amount of the extender pigment is 1 part by mass or more and 40 parts by mass or less relative to 100 parts by mass in total of the resin solid content of the hydroxyl group-containing resin (A) and the resin solid content of the amino resin (B), for example, It is 10 mass parts or more and 30 mass parts or less. When the amount of the extender pigment is within this range, there are advantageous effects such as improving the scratch resistance of the coating film.

Examples of the colored pigment include colored inorganic pigments such as titanium dioxide, carbon black, graphite, iron oxide, and cold dust; Phthalocyanine Blue, Phthalocyanine Green, Quinacridone, Perylene, Anthrapyrimidine, Carbazole Violet, Anthrapyridine, Azo Orange, Flavanthron Yellow, Isoindoline Yellow, Azo Yellow, Indanthrone Blue, colored organic pigments such as dibromoandanthrone red, perylene red, azo red, and anthraquinone red; Aluminum powder, alumina powder, bronze powder, copper powder, tin powder, zinc powder, iron phosphide, micronized titanium, etc. are mentioned. These may use only 1 type, and may use 2 or more types together.

In one embodiment, the coating composition may also contain a heat-shielding pigment. It does not specifically limit as a heat-shielding pigment used, For example, the following heat-shielding pigments etc. are mentioned. On the other hand, in the present disclosure, the heat-shielding pigment is a pigment that does not absorb light in the near-infrared wavelength range (wavelength: 780 nm to 2,500 nm) or has a low absorption rate of light in the near-infrared wavelength range (wavelength: 780 nm to 2,500 nm). point

The thermal barrier pigments include inorganic thermal barrier pigments and organic thermal barrier pigments.

Examples of the inorganic heat-shielding pigment 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, metal oxide pigments such as iron oxide, copper oxide, cerium oxide, and aluminum oxide; Iron oxide-manganese oxide, iron oxide-chromium oxide (e.g., dipyroxide color black #9595 manufactured by Dainichi Seika Co., Ltd., Black6350 manufactured by Asahi Kasei Industrial Co., Ltd.), iron oxide-cobalt oxide-chromium oxide (e.g., , Dipyroxide Color Brown #9290 by Dainichi Seika, Dipyroxide Color Black #9590), copper oxide-magnesium oxide (e.g., Dipyroxide Color Black #9598 by Dainichi Seika), manganese oxide - complex oxide pigments such as bismuth oxide (eg Black 6301 manufactured by Asahi Kasei Industrial Co., Ltd.), manganese oxide-yttrium oxide (eg Black 6303 manufactured by Asahi Kasei Industrial Co., Ltd.); metal pigments such as silicon, aluminum, iron, magnesium, manganese, nickel, titanium, chromium, and calcium; In addition, alloy-based pigments such as iron-chromium, bismuth-manganese, iron-manganese, and manganese-yttrium are exemplified. These may use only 1 type, and may use 2 or more types together.

Examples of organic heat-shielding pigments include azo pigments, azomethine pigments, lake pigments, thioindigo pigments, and anthraquinone pigments (anthanthrone pigments, diaminoanthraquinonyl pigments, indanthrone pigments, plastic Vantron pigments, anthrapyrimidine pigments, etc.), perylene pigments, perinone pigments, diketopyrrolopyrrole pigments, dioxazine pigments, phthalocyanine pigments, quinophthalone pigments, quinacridone pigments, eye Soindoline-based pigments, isoindolinone-based pigments, and the like are exemplified. These can be used individually or in combination of 2 or more types.

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

As the wax, waxes known to those skilled in the art for paints can be used, and examples thereof include microcrystalline, polyethylene, polypropylene, paraffin, carnauba, and modified products thereof. These may use only 1 type, and may use 2 or more types together.

As a solvent, it is water, for example; Ethylene Glycol Monobutyl Ether (Butyl Cellosolve), Diethylene Glycol Monobutyl Ether, Triethylene Glycol Monoethyl Ether, Propylene Glycol Monomethyl Ether, Propylene Glycol Monoethyl Ether, Propylene Glycol glycol-based organic solvents such as col monopropyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, and propylene glycol monomethyl ether acetate; alcohol-based organic solvents such as methanol, ethanol, and isopropyl alcohol; ether-based organic solvents such as dioxane and tetrahydrofuran; ester organic solvents such as 3-methoxybutyl acetate, ethyl acetate, isopropyl acetate, and butyl acetate; ketone organic solvents such as methyl ethyl ketone, acetone, methyl isobutyl ketone, cyclohexanone, and isophorone; and nitrogen-containing organic solvents such as N-methyl-2-pyrrolidone; Toluene, pentane, isopentane, hexane, isohexane, cyclohexane, solvent naphtha, mineral spirits, T-SOL 100, T-SOL 150 (all aromatic hydrocarbon solvents, manufactured by JXTG Energy Co., Ltd.), etc. there is. These may use only 1 type, and may use 2 or more types together.

The coating composition of the present invention may be a water-based coating material or an organic solvent-based coating material.

[Preparation method of coating composition]

A method for preparing the coating composition according to the present disclosure is not particularly limited. For example, by selecting and using a mixer, disperser, kneader, etc. such as a roller mill, ball mill, bead mill, pebble mill, sand grind mill, pot mill, paint shaker or disper, and mixing each component , can be prepared.

[Method of producing coating film]

The method for producing the coating film of the present disclosure,

A step of forming a coating film by coating the coating composition of the present disclosure on an object to be coated such as a steel plate, and

A step of heating the object to be coated and drying and/or curing the coating film

includes

Examples of the coated material include galvanized steel sheets, zinc-aluminum alloy coated steel sheets, aluminum alloy coated steel sheets, hot-dip zinc-aluminum-magnesium alloy coated steel sheets, stainless steel sheets, and cold-rolled steel sheets manufactured by a melting method or an electrolytic method. can In addition to these steel sheets or plated steel sheets, metal sheets such as aluminum sheets (including aluminum alloy sheets) can also be coated.

The object to be coated is preferably subjected to surface treatment. Specifically, it is preferable that chemical conversion treatment is performed on the object to be coated after pretreatment such as alkali degreasing treatment, hot water washing treatment, and water washing treatment is performed.

Chemical conversion treatment may be performed by a known method, and non-chromate treatment, such as a chromate treatment and a zinc phosphate treatment, etc. are included, for example. As the surface treatment, it can be appropriately selected according to the steel sheet to be used, but a treatment that does not contain heavy metals is preferable. By coating the coating composition of the present disclosure on the coated object subjected to the chemical conversion treatment in this way, while the adhesion of the coating film to the metal plate surface is improved, the corrosion resistance is also improved. Alternatively, an undercoating film (primer coating film) may be formed on the surface of the metal sheet subjected to chemical conversion treatment, and painting may be applied thereon.

The method of coating the coating composition is not particularly limited, but a conventionally known method such as a roll coater, airless spray, electrostatic spray, curtain flow coater, etc. can be employed, and it is preferable to apply with a roll coater or curtain flow coater. good night.

The temperature at which the coating film formed by coating of the coating composition is dried and/or cured, that is, the temperature reached (the highest temperature reached by an object such as a steel plate) is, for example, 170°C to 280°C, specifically 180°C to 180°C. It is 270 degreeC, and 200 degreeC - 250 degreeC may be sufficient. The drying and/or curing time can be as short as, for example, 1 to 10 seconds, specifically 1 to 6 seconds.

The method of drying and/or curing the coating film is not particularly limited, but a heating means such as hot air heating, infrared heating, or induction heating can be used.

That is, the manufacturing method of the coating film of this disclosure,

A step of forming a coating film by coating the coating composition of the present disclosure on an object to be coated; and

A step of drying and/or curing the coating film under the condition that the temperature of the coated material is 180° C. to 270° C. and the drying and/or curing time is 1 to 10 seconds.

may contain

The film thickness (dry film thickness) of the coating film obtained by baking the coating film and curing the resin is usually 1 to 30 µm, and, for example, in the case of an undercoating film, preferably 5 to 30 µm. For example, the dry film thickness may be 5 μm to 25 μm.

Meanwhile, in the present disclosure, drying and/or curing refers to performing at least one of drying and curing, and preferably refers to performing drying and curing.

[Pre-coated metal plate]

The precoated metal sheet of the present disclosure has a coating film formed from the coating composition according to the present disclosure on at least one side of the metal sheet.

For example, the film thickness of the coating film formed from the coating composition according to the present disclosure is 5 μm or more and 30 μm or less, and in some embodiments, the film thickness is 10 μm or more and 25 μm or less.

As the metal plate, those described above as the coated material can be used.

When the precoated metal sheet has a coating film formed from the coating composition according to the present disclosure on one surface of the metal sheet, the other surface may be a coating film formed from a known coating composition. For example, the other surface may have a coating film formed from a known coating composition such as a coating composition containing an epoxy resin.

The precoated metal sheet may have an undercoating film between the metal sheet and the coating film formed from the coating composition of the present disclosure.

The undercoating material may be a conventionally known one, and examples thereof include conventionally known non-chromium-based anticorrosive coatings. By having an undercoating film, the adhesiveness and corrosion resistance of the coating film formed from the coating composition of this indication can be improved.

In any aspect, the film thickness of the undercoating film is 3 μm or more and 15 μm or less, for example, 5 μm or more and 10 μm or less.

In aspect 1, the precoated metal sheet of the present disclosure,

A step of coating at least one surface of a metal plate with the coating composition of the present disclosure so that the film thickness after curing is 5 to 25 μm to form a coating film; and

A step of drying and/or curing the coating film under the condition that the temperature reached by the metal plate is 180° C. to 270° C. and the drying and/or curing time is 1 to 10 seconds.

It can be prepared by a method including.

Formation of a coating film and drying and/or curing of the coating film in the method for producing a precoated metal sheet can be performed in the same manner as in the above-described method for producing a coating film.

Example

The present invention is explained more specifically by the following examples, but the present invention is not limited thereto. In Examples, “parts” and “%” are based on mass unless otherwise specified.

Details of the hydroxyl-containing resins (A1) to (A13) used in Examples, Comparative Examples, and Reference Examples are shown in Tables 1A to 1C.

[Table 1A]

[Table 1B]

[Table 1C]

On the other hand, hydroxyl group-containing resin (A12) (epoxy resin 1) was obtained by dissolving 90 parts by mass of jER1007 (manufactured by Mitsubishi Chemical Corporation; solid content concentration: 100 mass%) in 210 parts by mass of cyclohexanone and adjusting the solid content concentration to 30 mass%. used that

<Amino resin (B)>

Details of the amino resins (B1) to (B6) are as shown in Tables 2A and 2B. In addition, the details of the isocyanate compound used in the comparative example are also shown collectively in Table 2B.

[Table 2A]

[Table 2B]

<Example of production of covalently bonded block type acid catalyst (C11)>

37 parts by mass of Nacure 1051 (manufactured by KING INDUSTRIES) was put into a reaction vessel equipped with a thermometer, condenser, dropping funnel and stirrer, and the temperature was raised to 90°C in a nitrogen atmosphere. To this, a mixed solution in which 220 parts by mass of jER 1010 (bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation) was dissolved in advance as an epoxy resin in 220 parts by mass of methyl propylene glycol (manufactured by Nippon Yumo Co., Ltd.) was added to the mixture through a dropping funnel for 60 minutes. It was loaded at constant speed. Thereafter, the reactant temperature was maintained at 90°C for 60 minutes to prepare a covalently bonded block type acid catalyst (C11). On the other hand, after the synthesis, it was confirmed that the solid acid value of the covalently bonded blocked acid catalyst (C11) had become 0, thereby confirming that the blocking agent was covalently bonded to all of the sulfonic acid groups.

<Production examples of covalently bonded block type acid catalysts (C12) to (C28)>

Covalent-bond block type acid catalysts (C12) to (C28) were prepared in the same manner as in the production example of (C11), except that the type and amount of each component was changed as shown in the table. In addition, as in the case of (C11), it was confirmed that the solid acid value of each covalently bonded block type acid catalyst became zero after synthesis.

Tables 3A to 3D show various specific values of each component and the prepared covalently bonded block type acid catalysts (C11) to (C28).

<Acid catalyst (c31), (c32)>

<Production Example of Acid Catalyst (c31)>

185 parts by mass of Nacure 1051 (manufactured by KING INDUSTRIES) was charged into a reaction vessel equipped with a thermometer, condenser, dropping funnel and stirrer, and the temperature was raised to 40°C in a nitrogen atmosphere. To this, a mixed solution in which 20 parts by mass of triethylamine (manufactured by Tokyo Kasei Kogyo Co., Ltd.) was previously dissolved in 20 parts by mass of methyl propylene glycol (manufactured by Nippon Yumo Co., Ltd.) was added dropwise at constant speed in 60 minutes through a dropping funnel. Thereafter, the temperature of the reactant was maintained at 40°C for 60 minutes to prepare an acid catalyst (c31). On the other hand, after the synthesis, it was confirmed that the solid content acid value of the acid catalyst (c31) had become 0, thereby confirming that the blocking agent was covalently bonded to all of the sulfonic acid groups.

Table 3B shows various specific values of the prepared acid catalysts (c31) and (c32).

[Table 3A]

[Table 3B]

[Table 3C]

[Table 3D]

On the other hand, the compounds described in Tables 3A to 3D are as follows.

[sulfonic acid]

Nacure 1051: dinonylnaphthalenesulfonic acid (manufactured by KING INDUSTRIES) active ingredient concentration: 50% by mass

・ Teikacure AC400S: Dodecylbenzenesulfonic acid (manufactured by Teika Co., Ltd.) Active ingredient concentration: 40% by mass

Teikacure AC700: p-toluenesulfonic acid (manufactured by Teika Co., Ltd.) active ingredient concentration: 25% by mass

[Epoxy Resin]

· jER 1004: bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation) number average molecular weight: 1,700, solid content concentration: 100% by mass

· jER 1007: bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation) number average molecular weight: 2,900, solid content concentration: 100% by mass

· jER 1009: bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation) number average molecular weight: 3,800, solid content concentration: 100% by mass

· jER 1010: bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation) number average molecular weight: 5,500, solid content concentration: 100% by mass

- jER1255HX30: bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation) number average molecular weight: 10,000, solid content concentration: 100% by mass

· jER 1009F: bisphenol F type epoxy resin (manufactured by Mitsubishi Chemical Corporation) number average molecular weight: 2,900, solid content concentration: 100% by mass

[Glycidyl ether compound]

Phenyl glycidyl ether: aromatic glycidyl ether compound (manufactured by Yokkaichi Synthetic Co., Ltd.) molecular weight: 150, active ingredient concentration: 100% by mass

o-creyl glycidyl ether: aromatic glycidyl ether compound (manufactured by Yokkaichi Synthetic Co., Ltd.) molecular weight: 164, active ingredient concentration: 100% by mass

DY-BP: aliphatic glycidyl ether compound (manufactured by Yokkaichi Synthetic Industries Co., Ltd., butyl glycidyl ether) molecular weight: 130, active ingredient concentration: 100% by mass

Epogose 2EH: aliphatic glycidyl ether compound (2-ethylhexyl glycidyl ether, manufactured by Yokkaichi Synthetic Co., Ltd.) molecular weight: 186, active ingredient concentration: 100% by mass

Epogose LA (D): aliphatic glycidyl ether compound (lauryl glycidyl ether, manufactured by Yokkaichi Synthetic Co., Ltd.) molecular weight: 242, active ingredient concentration: 100% by mass

・Epogose AN: aliphatic glycidyl ether compound (manufactured by Yokkaichi Synthetic Co., Ltd., C (carbon number) 12-13 mixed alcohol glycidyl ether) molecular weight: 251, active ingredient concentration: 100% by mass

[etc]

· amine compounds; Triethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.), active ingredient concentration: 100% by mass

· Solvent; Methyl propylene glycol: Propylene glycol monomethyl ether (manufactured by Nippon Yuyu Co., Ltd.)

<Manufacture example of phosphoric acid modified epoxy resin (D1)>

43 parts by mass of 85% aqueous phosphoric acid solution and 22 parts by mass of propylene glycol monomethyl ether were charged into a reaction vessel equipped with a thermometer, condenser, dropping funnel and stirrer, and the temperature was raised to 80°C in a nitrogen atmosphere. To this, a mixed solution in which 179 parts by mass of jER 834 (bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation) was dissolved in advance as an epoxy resin in 32 parts by mass of propylene glycol monomethyl ether was added dropwise at constant speed over 60 minutes through a dropping funnel. . After that, the temperature of the reactant was maintained at 80°C for 60 minutes to prepare a phosphoric acid-modified epoxy resin (D1).

<Production examples of phosphoric acid-modified epoxy resins (D2) to (D7)>

Phosphoric acid-modified epoxy resins (D2) to (D7) were prepared in the same manner as in the production example of (D1), except that the type and amount of each component was changed as described in the table. Table 4A and Table 4B show various special values of each component and prepared phosphoric acid-modified epoxy resins (D1) to (D7).

[Table 4A]

[Table 4B]

On the other hand, the compounds described in Table 4A and Table 4B are as follows.

[Phosphoric acid]

85% phosphoric acid: manufactured by Kishida Chemical Co., Ltd.

[Epoxy Resin]

· jER 825: bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation) number average molecular weight: 340, solid content concentration: 100% by mass

· jER 828: bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation) number average molecular weight: 370, solid content concentration: 100% by mass

· jER 834: bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation) number average molecular weight: 470, solid content concentration: 100% by mass

· jER 1009: bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation) number average molecular weight: 3,800, solid content concentration: 100% by mass

- jER 1010: bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation; number average molecular weight) 5,500, solid content concentration: 100% by mass

· jER 1009F: bisphenol F type epoxy resin (manufactured by Mitsubishi Chemical Corporation) number average molecular weight: 2,900, solid content concentration: 100% by mass

[etc]

· Solvent; Methyl propylene glycol: Propylene glycol monomethyl ether (manufactured by Nippon Yuyu Co., Ltd.)

<Alkanolamine (E)>

Details of the alkanolamine (E) are as shown in Table 5A and Table 5B.

[Table 5A]

[Table 5B]

<Production example of coating composition 1>

107.7 parts by mass of hydroxyl group-containing resin (A1), 2.4 parts by mass of T-SOL 100 (manufactured by JXTG Energy Co., Ltd.) as a solvent, 2.4 parts by mass of ethylene glycol monobutyl ether (manufactured by Dow Chemical Co., Ltd.), TIPAQUE CR-97 (oxidized) as a pigment Titanium, manufactured by Ishihara Sangyo) 67.0 parts by mass were stirred and mixed with a disper to obtain a mixture.

Next, the entire amount of the obtained mixture and glass beads (the same amount as the total mass part of the mixture) were put into a tabletop SG mill 1500W type disperser (manufactured by Taihei Systems Co., Ltd.), and the particle size of TIPAQUE CR-97 was 10 μm or less. Pigment dispersion was performed to prepare a pigment dispersion paint.

Further, with respect to 179.5 parts by mass of the pigment dispersion paint, 30.0 parts by mass of an amino resin (B1), 38.5 parts by mass of a covalently bonded block type acid catalyst (C11), and 3.9 parts by mass of a phosphoric acid-modified epoxy resin (D1) were stirred with a disper , and mixed to obtain a coating composition.

The obtained coating composition was mixed with Ford Cup No. It was diluted using a mixed solution of T-SOL 100/ethylene glycol monobutyl ether = 1/1 (mass ratio) so as to be 100 seconds (25°C) at 4, and coating composition 1 was obtained.

<Production examples of coating compositions 2 to 69>

Coating compositions 2 to 69 were prepared in the same manner as in the production example of coating composition 1, except that the type and amount of each component was changed as described in Tables 6A to 6P.

[Table 6A]

[Table 6B]

[Table 6C]

[Table 6D]

[Table 6E]

[Table 6F]

[Table 6G]

[Table 6H]

[Table 6I]

[Table 6J]

[Table 6K]

[Table 6L]

[Table 6M]

[Table 6N]

[Table 6O]

[Table 6P]

(Examples 1 to 64, Comparative Examples 1 to 12 and Reference Example 1)

As Examples 1 to 64, Comparative Examples 1 to 12, and Reference Example 1, evaluation was performed using the coating compositions shown in Tables 6A to 6P, respectively. The evaluation results are shown in Tables 7A to 7P.

On the other hand, Comparative Example 11 used a coating composition in which 0.5 parts by mass of TVS#Tin Lau (dibutyltin dilaurate, manufactured by Nitto Kasei Co., Ltd.; active ingredient concentration: 100% by mass) was further added as a catalyst. In Comparative Example 11 of Table 7N, the value of "parts by mass (solid content) of (B) relative to 100 parts by mass solid content of (A) and (B)" is "(A) and polyisocyanate" Mass parts (solid content) of polyisocyanate compound 1 with respect to 100 mass parts of solid content of compound 1".

In addition, the coated steel sheet of Example 1 was manufactured as shown in the following manufacturing examples.

<Manufacture example of coated steel sheet of Example 1>

After alkaline degreasing of a hot-dip galvanized steel sheet with a thickness of 0.4 mm, a non-chromium chemical conversion treatment was performed by applying a phosphoric acid treatment agent Surfcoat EC2310 (manufactured by Nippon Paint Surf Chemicals Co., Ltd.) to the front and back surfaces of the steel sheet, and dried. .

Next, the coating composition 1 is coated on the surface of the steel sheet using a bar coater so that the dry film is 10 μm, and an induction heating type induction/heater type furnace is used to achieve a temperature (PMT) of the steel sheet of 220° C. Baking (heating) was performed for 6 seconds under the conditions to form a surface coating film, and a coated steel sheet was obtained.

<Production examples of coated steel sheets of Examples 2 to 64, Comparative Examples 1 to 12, and Reference Example 1>

For the coated steel sheets of Examples 2 to 64, Comparative Examples 1 to 12, and Reference Example 1, in the production example of the coated steel sheet of Example 1, the coating film composition, baking temperature, and baking time were changed to the conditions described in Tables 7A to 7P. it was manufactured by On the other hand, "with respect to 100 parts by mass of solid content of (A) and (B)" in Tables 7A to 7P is "a total of 100 mass parts of the resin solid content of the hydroxyl group-containing resin (A) and the resin solid content of the amino resin (B)" It means “about wealth”.

[Table 7A]

[Table 7B]

[Table 7C]

[Table 7D]

[Table 7E]

[Table 7F]

[Table 7G]

[Table 7H]

[Table 7I]

[Table 7J]

[Table 7K]

[Table 7L]

[Table 7M]

[Table 7N]

[Table 7O]

[Table 7P]

<Evaluation items>

1) Storage stability

Based on the method stipulated in JIS K 5600-2-2 (Flow cup method), Ford Cup No. 4 (manufactured by Ueshima Seisakusho Co., Ltd.) was used for evaluation.

The coating compositions obtained in Examples, Comparative Examples, and Reference Examples were stirred at 1,000 rpm for 3 minutes using a disper. Immediately after stirring, the paint was filled to the full in a cup so that air bubbles did not enter the paint. At this time, the outlet was pressed so that the paint would not leak from the lower outlet (orifice). After that, release the press, start measuring the time with a stopwatch as soon as the paint flows down, stop the stopwatch when the flow from the lower outlet (orifice) is no longer a continuous flow, read the number of seconds at that time , time was recorded (initial viscosity). On the other hand, the temperature of the coating composition was 25°C.

Further, 8 to 90% of the coating compositions of Examples, Comparative Examples and Reference Examples whose initial viscosity was measured were put into 1/5 L cans, sealed, and then allowed to stand in a constant temperature room at 50°C. After that, it was taken out after 28 days and the viscosity was measured in the same manner as above (viscosity over time).

The ratio of the viscosity over time to the initial viscosity (viscosity ratio) was calculated by the following formula to evaluate the storage stability. The viscosity ratio judged less than 150% as having good storage stability.

Viscosity ratio (%) = viscosity over time / initial viscosity × 100

2) Appearance of coating film

The appearance of the coating films obtained in Examples, Comparative Examples, and Reference Examples was visually observed, and the degree of pitting was evaluated according to the following criteria.

(circle): Pitting did not generate|occur|produce in the coating film.

x: Pitting has arisen in the coating film.

3) Solvent resistance

The coated steel sheets obtained in Examples, Comparative Examples, and Reference Examples were affixed with adhesive tape to an evaluation table of an abrasion resistance tester IMC-155F (manufactured by Imoto Seisakusho), and a rubbing test was conducted. The measurement conditions were a load of 2 kgf, a reciprocating speed of 30 times/minute, a reciprocating distance of 70 mm, and a reciprocating frequency of 200 times using a absorbent containing methyl ethyl ketone wrapped in 4 pieces of gauze as an abrasive. The number of rubbing reciprocations until the substrate of the base steel sheet was exposed was measured and evaluated according to the following criteria. 3 or more points|pieces were set as pass, and 5 points|pieces were made favorable. On the other hand, test conditions were made into the temperature of 23 degreeC, and the humidity of 60RH%.

5 points: 200+

4 points: 100 or more but less than 200

3 points: 50 or more but less than 100

2 points: 10 or more but less than 50

1 point: less than 10 times

4) Machinability (bending test)

The coated steel sheets obtained in Examples, Comparative Examples, and Reference Examples were cut into 5 cm x 3 cm, and pre-bent was performed so that the coated film surface was on the front side using a sheet metal folding machine (manufactured by Ueshima Seisakusho Co., Ltd.). Five steel plates of the same thickness (0.4 mm) were sandwiched on the test piece, and bent using a press machine (manufactured by Kyoritsu Kogyo). The state (crack) of the coating film of the processed portion was observed with a 15-fold loupe, and workability was evaluated according to the following criteria. A score of 4 or more was regarded as a pass. On the other hand, test conditions were made into the temperature of 23 degreeC, and the humidity of 60RH%.

5: Cracks are not confirmed in the processed part.

4: Cracks are observed in less than 20% (more than 0%) of the area of the processed portion.

3: Cracks are confirmed in 20% or more and less than 50% of the area of the processed portion.

2: Cracks are confirmed in 50% or more and less than 80% of the area of the processed portion.

1: Cracks are confirmed in 80% or more of the area of the processed part.

5) Processability (Adhesion)

The coated steel sheets obtained in Examples, Comparative Examples, and Reference Examples were cut into 5 cm x 3 cm, and pre-bent was performed so that the coated film surface was on the front side using a sheet metal folding machine (manufactured by Ueshima Seisakusho Co., Ltd.). Two steel plates of the same thickness (0.4 mm) were sandwiched on the test piece, and bent using a press machine (manufactured by Kyoritsu Kogyo). Cellophane tape (trademark) (LP-24, manufactured by Nichiban Co., Ltd.) was adhered to the processing portion of the coated steel sheet, peeled off at once, and the appearance of the portion peeled off with the tape was observed with a loupe 15 times, and the processing adhesion was determined according to the following criteria. Evaluated. A score of 4 or more was regarded as a pass. On the other hand, test conditions were made into the temperature of 23 degreeC, and the humidity of 60RH%.

5: Metal material is not recognized in the tape peeling part.

4: Substance of metal is confirmed in less than 20% (more than 0%) of the area of the tape peeling part.

3: Substance of metal is confirmed in 20% or more and less than 50% of the area of the tape peeling part.

2: Substance of metal is confirmed in 50% or more and less than 80% of the area of the tape peeling part.

1: Substance of metal is confirmed in 80% or more of the area of the tape peeling part.

6) Alkali resistance test

The coated steel sheets obtained in Examples, Comparative Examples, and Reference Examples were cut into 5 cm × 10 cm, and each test piece was immersed in 5% sodium hydroxide aqueous solution at 23 ° C. for 48 hours, then taken out, washed with water, and then at 20 ° C. dried for 2 hours. About this coated steel sheet test piece, blistering evaluation of the flat part was performed according to ASTM D714-56. Here, ASTM D714-56 evaluates the size (average diameter) and density of each blister against a standard judgment photograph, and indicates a rating symbol. Regarding the size, 8 (approx. 1 mm in diameter), 6 (approx. 2 mm in diameter), 4 (approx. 3 mm in diameter), 2 (approx. 5 mm in diameter) in order of 4 steps. Regarding the density, F, FM, M, MD from the smallest one , It was graded into 5 stages of D, and if there were no blisters, it was set as 10. A score of 8FM or higher was regarded as passing.

7) Acid resistance test

The coated steel sheets obtained in Examples, Comparative Examples, and Reference Examples were cut into 5 cm × 10 cm, and each test piece was immersed in 5% sulfuric acid aqueous solution at 23 ° C. for 48 hours, then taken out, washed with water, and then 2 at 20 ° C. time to dry About this coated steel sheet test piece, the blisters of the flat part were visually observed according to ASTM D714-56, and acid resistance was evaluated. A score of 8FM or higher was regarded as passing.

As shown in the table above, in Examples 1 to 64, the storage stability of the coating composition was good.

Among the Examples, in Examples 1 to 57, a coating film was formed with the baking temperature set to 220°C and the baking time set to 6 seconds. In these Examples, a coating film having good physical properties in all of coating appearance, solvent resistance, bending workability, processing adhesion, alkali resistance, and acid resistance was obtained.

Examples 62, 1, 63, and 64 are examples in which the baking temperature was 220°C and the baking time was 1 second, 6 seconds, 10 seconds, and 25 seconds, respectively. In Example 62, despite setting the baking time to 1 second, a coating film having good physical properties was obtained, and it was confirmed that it was sufficiently cured even in a short time of 1 second. In Example 63, the baking time was 10 seconds, and in Example 64, the baking time was 25 seconds. Also in these Examples, coating films having good physical properties were obtained. That is, when the coating composition of the present invention is used, it is sufficiently cured even in a short time, and the coating film obtained by baking in a short time (for example, Examples 62, 1, and 63) is a coating film obtained by baking for a relatively long time (Examples 64) was found to have good physical properties.

Examples 58, 59, 1, 60 and 61 are examples in which the baking time was 6 seconds and the baking temperature was 180°C, 170°C, 220°C, 270°C and 280°C, respectively. For example, in Examples 58 and 59, despite the formation of a coating film at a low baking temperature, a coating film having good physical properties was obtained, and it was confirmed that the coating composition of the present invention was sufficiently cured even when baking at a low temperature. . Further, in Examples 60 and 61, it was confirmed that a coating film having good physical properties was obtained in the coating composition of the present invention by forming a coating film at a relatively high baking temperature.

In Comparative Examples 1 to 12, it is shown that the storage stability of the coating composition and curing in a short time are not compatible. Hereinafter, each comparative example is described in detail.

The coating composition of Comparative Example 1 contains 95 parts by mass of hydroxyl group-containing resin (A1) and 5 parts by mass of amino resin (B1) based on 100 parts by mass of the total of hydroxyl group-containing resin (A1) and amino resin (B1). . The results of solvent resistance, alkali resistance and acid resistance of the coating film formed in Comparative Example 1 were not good. That is, in Comparative Example 1, it was found that the curing reaction did not sufficiently proceed with heating at 220°C for 6 seconds, and thus a coating film having good physical properties could not be obtained.

The coating composition of Comparative Example 2 contains 50 parts by mass of the hydroxyl group-containing resin (A1) and 50 parts by mass of the amino resin (B1) based on 100 parts by mass of the hydroxyl group-containing resin (A1) and the amino resin (B1) in total. . The results of the coating film appearance, bending workability, and processing adhesion of the coating film formed in Comparative Example 2 were not good. That is, in Comparative Example 2, it was found that the curing reaction did not proceed properly with heating at 220°C for 6 seconds, and thus a coating film having good physical properties could not be obtained.

In the coating composition of Comparative Example 3, the content of the covalently-bonded blocked acid catalyst (C11) was small, and in the coating composition of Comparative Example 5, the content of the covalently-bonded blocked acid catalyst (C11) was high. In the coating film formed in Comparative Example 3, the results of solvent resistance, alkali resistance, and acid resistance were not good, and in the coating film formed in Comparative Example 5, the coating appearance, bending workability, and processing adhesion were not good. That is, in Comparative Examples 3 and 5, it can be seen that an appropriate curing reaction did not proceed with heating at 220°C for 6 seconds, and a coating film having good physical properties could not be obtained.

The coating composition of Comparative Example 4 did not contain the covalently bonded block type acid catalyst (C). The coating film formed in Comparative Example 4 did not have good solvent resistance, processing adhesion, alkali resistance and acid resistance. That is, in Comparative Example 4, it was found that the curing reaction did not sufficiently proceed with heating at 220°C for 6 seconds, and a coating film having good physical properties was not obtained.

In the coating composition of Comparative Example 6, the content of the phosphoric acid-modified epoxy resin (D1) is small, and in the coating composition of Comparative Example 8, the content of the phosphoric acid-modified epoxy resin (D1) is high. In the coating film formed in Comparative Example 6, the results of solvent resistance, alkali resistance and acid resistance were not good, and in the coating film formed in Comparative Example 8, the results of the coating film appearance, bending workability and processing adhesion were not good. That is, in Comparative Examples 6 and 8, it can be seen that a proper curing reaction did not proceed with heating at 220°C for 6 seconds, and a coating film having good physical properties could not be obtained.

The coating composition of Comparative Example 7 did not contain the phosphoric acid-modified epoxy resin (D). The coating film formed in Comparative Example 7 had poor solvent resistance, processing adhesion, alkali resistance and acid resistance. That is, in Comparative Example 7, it was found that the curing reaction did not sufficiently proceed with heating at 220°C for 6 seconds, and a coating film having good physical properties was not obtained.

The coating composition of Comparative Example 9 includes an amine block type acid catalyst (acid catalyst 1 (c31)) as an acid catalyst, and the coating composition of Comparative Example 10 contains a sulfonic acid that is not blocked (acid catalyst 2 (acid catalyst 2 ( c32)). In these comparative examples, the viscosity of the coating composition increased, and the formed coating film had poor appearance, solvent resistance, processing adhesion, alkali resistance, and acid resistance. That is, in Comparative Examples 9 and 10, the storage stability of the coating composition was significantly reduced, and in forming a coating film, the curing reaction did not proceed properly with heating at 220 ° C. for 6 seconds, and a coating film having good physical properties was not obtained. In Comparative Example 10, it is considered that the sulfonic acid acts as a curing catalyst during storage, and as a result, the viscosity of the coating composition increased. In Comparative Example 9, it is considered that the amine compound blocking sulfonic acid was dissociated from sulfonic acid during storage, and this sulfonic acid acted as a curing catalyst. In general, in the curing process of a coating film, solvent evaporation occurs from the coated film, and then curing of the coating film begins. In Comparative Examples 9 and 10, in the curing process of the coating film, since the catalyst acts before the evaporation of the solvent is completed to accelerate curing, it is thought that pinhole-shaped holes called pitting occurred in the appearance of the coating film after curing. It is thought that this fitting caused the exposure of the substrate in the solvent resistance test and peeling of the coating film in the processing adhesion test.

The coating composition of Comparative Example 11 contains a polyisocyanate compound as a curing agent, not an amino resin. The coating film formed in Comparative Example 11 did not have good solvent resistance, process adhesion, alkali resistance and acid resistance. That is, in Comparative Example 11, it was found that the curing reaction did not sufficiently proceed with heating at 220°C for 6 seconds, and a coating film having good physical properties was not obtained. In the case of using an amino resin as in the examples, in addition to the curing reaction with the hydroxyl group-containing resin or phosphoric acid-modified epoxy resin in the presence of an acid catalyst, self-condensation occurs and it is considered that the curing reaction sufficiently proceeds. However, in the case of using an isocyanate compound as in Comparative Example 11, a curing reaction with a hydroxyl group-containing resin and a phosphoric acid-modified epoxy resin occurs, but no self-condensation reaction occurs, and it is considered that the curing reaction did not sufficiently proceed. In addition, since the polyisocyanate compound is blocked with a blocking agent, in order for the curing reaction to proceed, the blocking agent needs to be dissociated before the isocyanate reaction, but the blocking agent can be sufficiently dissociated in a short time of 6 seconds. No, it is considered that the curing reaction did not proceed.

In Reference Example 1, a general coating composition for precoated steel sheets was used. This coating composition does not contain a covalently bonded block type acid catalyst (C) and a phosphoric acid-modified epoxy resin (D). The coating composition of Reference Example 1 was evaluated for storage stability, and a coating film having good physical properties was obtained by heating at a baking temperature of 200°C for 25 seconds. Comparative Example 12 was obtained using the coating composition of Reference Example 1 and heating at a baking temperature of 220°C for 6 seconds. The coating film formed in Comparative Example 12 did not have good coating film appearance, solvent resistance, bending workability, processing adhesion, alkali resistance, and acid resistance. That is, in Comparative Example 12, it can be seen that the curing reaction did not sufficiently proceed with heating at a baking temperature of 220° C. for 6 seconds, and a coating film having good physical properties was not obtained.

The coating composition of the present disclosure has good storage stability, and a curing reaction proceeds by baking in a short time, and a coating film having good physical properties can be formed even by baking in a short time. In the coating composition of the present disclosure, even in a furnace having a shortened furnace length, such as an IH type furnace, the curing reaction proceeds favorably, and a coating film having good physical properties can be formed.

Claims (13)

A hydroxyl group-containing resin (A);
an amino resin (B);
A covalently bonded block type acid catalyst (C);
A phosphoric acid-modified epoxy resin (D) is included;
With respect to a total of 100 parts by mass of the resin solid content of the hydroxyl group-containing resin (A) and the resin solid content of the amino resin (B),
60 to 90 parts by mass of the hydroxyl group-containing resin (A);
10 to 40 parts by mass of the amino resin (B),
1 to 10 parts by mass of the acid catalyst portion of the covalently bonded block type acid catalyst (C), and
Containing 1 to 10 parts by mass of the solid content of the phosphoric acid-modified epoxy resin (D),
paint composition. According to claim 1,
The coating composition in which the number average molecular weight of the phosphoric acid-modified epoxy resin (D) is in the range of 460 to 4,000. According to claim 1 or 2,
The coating composition wherein the covalently bonded blocked acid catalyst (C) is a catalyst obtained by blocking an aromatic sulfonic acid with a compound having a glycidyl group. According to claim 3,
In the covalently bonded block type acid catalyst (C), the compound having a glycidyl group is an epoxy resin having two or more glycidyl groups in a molecule or a glycidyl ether compound having one glycidyl group in a molecule. , paint composition. According to claim 4,
In the covalently bonded block-type acid catalyst (C), the number average molecular weight of the epoxy resin having two or more glycidyl groups in the molecule is within the range of 2,000 to 7,000. According to claim 4,
The coating composition in which the molecular weight of the glycidyl ether compound having one glycidyl group in the molecule in the covalently bonded block-type acid catalyst (C) is in the range of 140 to 200. According to any one of claims 1 to 6,
The hydroxyl group-containing resin (A) is a polyester resin,
The number average molecular weight of the hydroxyl group-containing resin (A) is within the range of 1,500 to 5,000, and the hydroxyl value is within the range of 40 to 100 mgKOH / g,
paint composition. According to any one of claims 1 to 7,
The amino resin (B) is a coating composition containing a melamine resin. According to any one of claims 1 to 8,
Further, a coating composition comprising an alkanolamine (E). According to claim 9,
The alkanolamine (E) contains two or more alkanol groups in a molecule, the coating composition. According to claim 9 or 10,
The content of the alkanolamine (E) is 1.0 to 4.0 parts by mass based on 100 parts by mass in total of the resin solid content of the hydroxyl group-containing resin (A) and the resin solid content of the amino resin (B). A step of coating an object with the coating composition according to any one of claims 1 to 11 to form a coated film; and
A step of drying and/or curing the coating film under the condition that the temperature of the coated material is 180° C. to 270° C. and the drying and/or curing time is 1 to 10 seconds.
Including, a method for producing a coating film. A step of coating at least one surface of a metal sheet with the coating composition according to any one of claims 1 to 11 so that the film thickness after curing is 5 to 25 μm to form a coating film; and
A step of drying and/or curing the coating film under the condition that the temperature reached by the metal plate is 180° C. to 270° C. and the drying and/or curing time is 1 to 10 seconds.
Including, the manufacturing method of the pre-coated metal plate.