JP7389511B2 - Coating composition for pre-coated metal plate, pre-coated metal plate and manufacturing method thereof - Google Patents

Description

The present disclosure relates to a coating composition for a precoated metal plate, a precoated metal plate having a coating film formed from the coating composition, and a method for manufacturing the same.

Painted metal sheets, which are coated on metal base materials such as cold-rolled steel sheets and plated steel sheets, are also called pre-coated metal sheets (PCM), and are used in construction materials such as shutters, shutters, doors, roofs and siding, and outdoor coolers. It is used for various parts such as exterior materials and interior materials for electrical equipment such as machines. Usually, pre-coated metal plates are processed into various products after coating the surface of the metal plate to form a coating film. For this reason, the coating film formed on the pre-coated metal plate is required to have flexibility and high workability, such as not cracking or peeling during processing, for example when the pre-coated metal plate is bent.

As part of these studies, Patent Document 1 discloses that a matte base coat layer formed on the main body of a synthetic resin molded product is made of a base coat resin and 12 to 90 parts by mass of base coat resin, based on 100 parts by mass of the base coat resin. It has been proposed to form a base coat paint containing crosslinked acrylic particles and 0.1 to 12.0 parts by mass of an amide needle filler.

Patent Document 2 includes a polyvinylidene fluoride resin, an acrylic resin, polytetrafluoroethylene particles, a wax, an aggregate, and a solvent, the acrylic resin includes a thermosetting acrylic resin, and the solvent includes: A coating composition for precoated metal plates has been proposed that includes a solvent having a ketone structure and has a boiling point of 180°C.

Patent Document 3 proposes a coating film formed by coating a polyester resin paint containing a light stabilizer and a matting agent.

Patent Document 4 contains 1 to 40% by mass of ceramic inorganic aggregate, 1 to 30% by mass of polyacrylonitrile beads, and 0.5 to 10% by mass of fluororesin powder, and the inorganic aggregate particle size and film thickness. A top coat film has been proposed in which the ratio of polyacrylonitrile beads is 0.04 to 1.0 and the ratio of the particle size of polyacrylonitrile beads to the film thickness is 1.0 to 3.0.

Japanese Patent Application Publication No. 2012-30431 JP2020-100740A JP2007-283718A Japanese Patent Application Publication No. 11-156999

In recent years, in the field of pre-coated metal sheets for building materials and utensil processing, there has been a demand for coated metal sheets with superior cosmetic properties, and a large amount of topcoat paints containing organic resin particles with large particle sizes and inorganic particles are being used. Matte-coated metal sheets and other products are now on the market, coated with a topcoat containing an amine compound and a topcoat that creates a uniform matte appearance by taking advantage of the difference in curing speed between the surface of the coating and the inside of the coating. ing.

In addition, as consumers have recently become more sophisticated, there has been a demand for a calm, low-gloss (matte) paint appearance, and fluororesins such as polyvinylidene fluoride (PVDF), which can provide coatings with high durability, are being used. Similar requirements exist for paint compositions, and various paint compositions and coating methods are being studied.

To adjust the glossiness, for example, as described in Patent Documents 1 to 4, various coating compositions containing matting agents such as inorganic fine particles such as silica or organic resin fine particles have been investigated. ing. However, in order to obtain a coating film with the required low gloss (matte), it has been necessary to incorporate a large amount of the matting agent into the coating composition. Furthermore, since the coating film obtained from the fluororesin coating composition has the property of easily forming a crystalline structure, there is a problem that cracks are likely to occur during processing and molding. Cracks are also a factor that deteriorates the aesthetic appearance of paint films.

Therefore, the appearance of a fluororesin-based coating composition that is less prone to cracking, has good workability, and provides a low-gloss (matte) coating has been eagerly awaited.

The present disclosure aims to provide a coating composition for a precoated metal plate that has good processability and durability and is capable of forming a low gloss (matte) coating film. Further, another object of the present disclosure relates to a precoated metal plate using such a coating composition for precoated metal plates and a method for manufacturing the same.

The present disclosure includes the following aspects.
[1] Polyvinylidene fluoride resin (A),
Acrylic resin (B),
including matting agent particles (C),
A coating composition for a precoated metal plate, wherein the value of the distance (Ra) of the Hansen solubility parameter (HSP) between the polyvinylidene fluoride resin (A) and the matting agent particles (C) is 3.5 or less. .
[2] In [1], the value of the Hansen solubility parameter (HSP) distance (Ra) between the polyvinylidene fluoride resin (A) and the matting agent particles (C) is 3.0 or less. The coating composition for pre-coated metal plates as described above.
[3] The precoated metal according to [1] or [2], wherein the difference between the refractive index of the polyvinylidene fluoride resin (A) and the refractive index of the matting agent particles (C) is 0.10 or more. Paint composition for boards.
[4] Any of [1] to [3], wherein the matting agent particles (C) include at least one selected from the group consisting of acrylic resin particles, polyester resin particles, urea resin particles, and polyurethane resin particles. The coating composition for precoated metal plates according to item 1.
[5] The precoated metal according to any one of [1] to [4], wherein the matting agent particles (C) contain at least one selected from the group consisting of urea resin particles and polyurethane resin particles. Paint composition for boards.
[6] The content of the matting agent particles (C) is 1 part by mass or more based on a total of 100 parts by mass of the solid content of the polyvinylidene fluoride resin (A) and the solid content of the acrylic resin (B). The coating composition for a precoated metal plate according to any one of [1] to [5], which contains 6 parts by mass or less.
[7] The content of the polyvinylidene fluoride resin (A) is 50 parts by mass or more and 80 parts by mass out of the total of 100 parts by mass of the solid content of the polyvinylidene fluoride resin (A) and the solid content of the acrylic resin (B). The coating composition for a pre-coated metal plate according to any one of [1] to [6], wherein the coating composition is less than or equal to
[8] The coating composition for a precoated metal plate according to any one of [1] to [7], wherein the acrylic resin (B) contains a thermosetting acrylic resin.
[9] The coating composition for a precoated metal plate according to any one of [1] to [8], wherein the average particle diameter of the matting agent particles (C) is 1 μm or more and 10 μm or less.
[10] A metal plate, and a coating film disposed on at least one surface of the metal plate and formed from the coating composition for precoated metal plates according to any one of [1] to [9]. , pre-painted metal sheet.
[11] The precoated metal plate according to [10], wherein the coating film has a 60 degree specular gloss of 3 or more and 30 or less.
[12] Further comprising an undercoat film disposed between the metal plate and the paint film,
The thickness of the undercoat film is 3 μm or more and 10 μm or less,
The precoated metal plate according to [10] or [11], wherein the coating film has a thickness of 10 μm or more and 25 μm or less.
[13] The precoated metal plate according to [12], wherein the undercoat film contains a polyester resin.
[14] The coating composition for a pre-coated metal plate according to any one of [1] to [9] is applied on at least one surface of the metal plate so that the thickness after curing is 10 μm or more and 25 μm or less. obtaining a coating film, and applying the coating film under conditions in which the temperature reached by the metal plate is 230°C or more and 270°C or less, and the drying and curing time is 20 seconds or more and 120 seconds or less, A method for producing a pre-coated metal sheet, comprising drying and curing to obtain a coating film.

The coating composition for pre-coated metal plates of the present disclosure has good processability and durability, and can form a low gloss (matte) coating film. Another object of the present disclosure is to provide a precoated metal plate using such a coating composition for a precoated metal plate and a method for manufacturing the same.

The coating composition for pre-coated metal plates of the present disclosure (hereinafter also simply referred to as "coating composition") includes polyvinylidene fluoride resin (A), acrylic resin (B), and matting agent particles (C). , the value of the distance (Ra) of the Hansen solubility parameter (HSP) representing the compatibility between the polyvinylidene fluoride resin (A) and the matting agent particles (C) is 3.5 or less. According to the coating composition for pre-coated metal plates of the present disclosure, processability and durability are good, and a low gloss (matte) coating film can be formed. Without being bound by a particular theory, in a composition containing polyvinylidene fluoride resin, acrylic resin, and matting agent particles, it is the matting agent particles and polyfluoride that contribute to suppressing cracking and peeling of the resulting coating film. The inventors of the present invention discovered through studies that this is due to the affinity of the vinylidene resin interface. Furthermore, we focused on the Hansen solubility parameter (HSP) as an index of compatibility between the polyvinylidene fluoride resin and the matting agent particles, and determined the distance (Ra) of the Hansen solubility parameter between the polyvinylidene fluoride resin and the matting agent particles. The inventors have discovered that by setting the amount below this value, cracking of the resulting coating film can be effectively suppressed while exhibiting the low gloss effect of the matting agent particles, and the present invention has been completed.

The coating composition of the present disclosure includes a polyvinylidene fluoride resin (A) and an acrylic resin (B) as coating film-forming resins.

[(A) Polyvinylidene fluoride resin]
The polyvinylidene fluoride resin (A) may be a homopolymer of vinylidene fluoride or a copolymer of vinylidene fluoride, which is the main component, and other monomers. By including the polyvinylidene fluoride resin (A), weather resistance and durability can be imparted to the resulting coating film.

Polyvinylidene fluoride resin (A) is obtained by polymerizing a mixture of monomers containing vinylidene fluoride. Such polymerization may be carried out using, for example, a radical polymerization initiator at high temperature and high pressure. The other monomer is not particularly limited as long as it is a monomer having an ethylenic carbon-carbon double bond. The other monomer may be a monomer having a fluorine atom, and examples of such a monomer having a fluorine atom include hexafluoropropylene, tetrafluoroethylene, and the like. When the other monomer contains a fluorine atom, the weather resistance of the copolymer can be further improved.

The polyvinylidene fluoride resin (A) may have a functional group such as a carboxyl group or a sulfonic acid group.

The polyvinylidene fluoride resin (A) contains a vinylidene fluoride homopolymer. When the polyvinylidene fluoride resin (A) contains a homopolymer of vinylidene fluoride, it can have good weather resistance and stability of the coating composition (for example, storage stability) in a well-balanced manner. The content of the vinylidene fluoride homopolymer in the polyvinylidene fluoride resin (A) may be, for example, 90% by mass or more and 100% by mass or less, preferably 95% by mass or more and 100% by mass or less.

The weight average molecular weight of the polyvinylidene fluoride resin (A) is from 100,000 to 700,000, for example from 150,000 to 500,000, and from 150,000 to 400,000.
Note that in the present disclosure, the weight average molecular weight is a value obtained by converting a value measured by gel permeation chromatography (GPC) method using a polystyrene standard.

The melting point of the polyvinylidene fluoride resin (A) is 140°C or more and 190°C or less, preferably 150°C or more and 180°C or less.

As the polyvinylidene fluoride resin (A), commercially available ones may be used. Examples include HYLAR5000 (manufactured by Solvay) and Kynar500 (manufactured by Arkema).

In one embodiment, the solid content of the polyvinylidene fluoride resin (A) is, for example, 50 parts by mass or more and 80 parts by mass out of 100 parts by mass of the total solid content of the polyvinylidene fluoride resin (A) and the acrylic resin (B). parts, preferably more than 55 parts by weight and less than 80 parts by weight.
The coating composition of the present disclosure can sufficiently ensure weather resistance and durability by containing the polyvinylidene fluoride resin (A) in the above range.
Hereinafter, in the description of content, "resin content" means "resin solid content". For example, "content of polyvinylidene fluoride resin" means "solid content of polyvinylidene fluoride resin (A)", and "content of acrylic resin (B)" means "content of acrylic resin (B)". solids content. The same applies to thermosetting acrylic resins and thermoplastic acrylic resins.

[(B) Acrylic resin]
By containing the acrylic resin (B) as a coating film-forming resin, the coating composition of the present disclosure has the effect of improving adhesion with the undercoat film, film formability, and pigment dispersibility.

Furthermore, the acrylic resin (B) contains at least one type of thermosetting acrylic resin. In the present disclosure, thermosetting acrylic resin means a resin containing a copolymer of acrylic monomers that can undergo a polymerization/curing reaction by applying heat (for example, 140° C. or higher). In some embodiments, the thermosetting acrylic resin can be cured by a polymerization/curing reaction by applying heat at a temperature of 160° C. or higher, for example, 200° C. or higher. When the acrylic resin (B) contains a thermosetting acrylic resin, weather resistance, water resistance, chemical resistance, etc. can be imparted while maintaining excellent workability. Further, it is possible to suppress deterioration in workability due to aging and deterioration in workability due to heat generated during processing.

For example, when the acrylic resin (B) according to the present disclosure includes a thermosetting acrylic resin, the content of the thermosetting acrylic resin is 100 parts by mass in total of the polyvinylidene fluoride resin (A) and the acrylic resin (B). For example, it is 20 parts by mass or more and 46 parts by mass or less, preferably 25 parts by mass or more and 39.9 parts by mass or less, and more preferably 28 parts by mass or more and 39.9 parts by mass or less.

In some embodiments, the acrylic resin (B) may contain two or more types of thermosetting acrylic resins. In a certain embodiment, in an embodiment in which the acrylic resin (B) contains two or more kinds of acrylic resins, at least one kind may be a thermosetting acrylic resin, and the others may be thermoplastic acrylic resins. In the present disclosure, thermoplastic acrylic resin means acrylic resins other than thermosetting acrylic resins. Typically, thermoplastic acrylic resins soften when they reach their glass transition temperature or melting point.

When the acrylic resin (B) contains a thermosetting acrylic resin and a thermoplastic acrylic resin, the content of the thermoplastic acrylic resin is the sum of the solid content of the thermosetting acrylic resin and the solid content of the thermoplastic acrylic resin. For example, the amount may be 20 parts by mass or more and 99 parts by mass or less, preferably 30 parts by mass or more and 99 parts by mass or less, based on 100 parts by mass. When the ratio of thermosetting acrylic resin and thermoplastic acrylic resin is within the above range, weather resistance, water resistance, chemical resistance, etc. can be imparted to the obtained coating film, and the processability of the obtained coating film can be further improved. It has the effect of improving

In one embodiment, when the acrylic resin (B) contains two or more types of acrylic resins, it may contain at least one type of thermosetting acrylic resin and at least one type of thermoplastic acrylic resin. By containing a thermosetting acrylic resin and a thermoplastic acrylic resin, weather resistance, water resistance, chemical resistance, etc. can be imparted to the obtained coating film, and the processability of the obtained coating film is further improved. be. Furthermore, the adhesion between the coating composition and the undercoat film can be improved. As a result, even in an embodiment where the pre-coated metal plate has a known undercoat film, the coating composition of the present disclosure can have good adhesion.

The coating composition of the present disclosure may contain a crosslinking agent depending on the structure of the coating film-forming resin. Further, the thermosetting acrylic resin also includes a resin that gels by itself at the above temperature or higher.

In one embodiment, the thermosetting acrylic resin may be a self-crosslinking acrylic resin copolymerized with monomer components such as N-hydroxyacrylamide, N-alkoxyacrylamide, N-alkylolacrylamide, and diacetone acrylamide. The acrylic resin may be a hardening agent type acrylic resin that is crosslinked by using an acrylic monomer having a substituent such as a hydroxyl group and a crosslinking agent such as melamine.

For example, the acrylic resin (B) can be prepared by copolymerizing a hydroxyl group-containing monomer (b-1) and another monomer (b-2) in addition to the above monomers.

Examples of the hydroxyl group-containing monomer (b-1) include 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 2,3-dihydroxybutyl (meth)acrylate, and 4-hydroxy(meth)acrylate. Examples include butyl, reaction products of these hydroxyl group-containing (meth)acrylic esters and ε-caprolactone, and esters of polyhydric alcohols such as polyethylene glycol mono(meth)acrylate and (meth)acrylic acid. Furthermore, a reaction product obtained by ring-opening polymerization of ε-caprolactone to a monoester of the polyhydric alcohol and (meth)acrylic acid can also be used. These hydroxyl group-containing monomers (b-1) may be used alone or in combination of two or more.
Note that in the present disclosure, (meth)acrylic acid means acrylic acid or methacrylic acid.

Examples of other monomers (b-2) include carboxyl group-containing monomers such as (meth)acrylic acid, crotonic acid, maleic acid, itaconic acid, and fumaric acid; and ethyl maleate, butyl maleate, ethyl itaconate, and itacon. Dicarboxylic acid monoester monomers such as butyl acrylate; methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n, i or t-butyl (meth)acrylate, (meth)acrylic acid 2 - (meth)acrylic acid alkyl ester monomers such as ethylhexyl and lauryl (meth)acrylate; cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, tricyclodecanyl (meth)acrylate , alicyclic group-containing monomers such as adamantyl (meth)acrylate; (meth)acrylic acid aminoalkyl esters such as aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, butylaminoethyl (meth)acrylate, etc. Monomer: Aminoalkyl (meth)acrylamide monomers such as aminoethyl (meth)acrylamide, dimethylaminomethyl (meth)acrylamide, methylaminopropyl (meth)acrylamide; Other N-substituted (meth)acrylamide series such as acrylamide and methacrylamide Monomers: Vinyl cyanide monomers such as (meth)acrylonitrile and α-chloroacrylonitrile; Saturated aliphatic carboxylic acid vinyl ester monomers such as vinyl acetate and vinyl propionate; Styrene monomers such as styrene, α-methylstyrene, and vinyltoluene Bifunctional monomers such as divinylbenzene and ethylene glycol (meth)acrylate can be mentioned. These other monomers (b-2) may be used alone or in combination of two or more.
Among the other monomers (b-2), (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, (meth)acrylate, ) Cyclohexyl acrylate and the like are preferably used.

As a method for polymerizing the hydroxyl group-containing monomer (b-1) and the other monomer (b-2), methods commonly used by those skilled in the art can be used. As the polymerization method, for example, a bulk polymerization method using a radical polymerization initiator, a solution polymerization method, a two-stage bulk-suspension polymerization method in which suspension polymerization is performed after bulk polymerization, etc. can be used. Among these, solution polymerization method can be particularly preferably used. Examples of the solution polymerization method include a method in which the monomer mixture is heated with stirring at a temperature of 80 to 200° C. in the presence of a radical polymerization initiator.

The number average molecular weight of the acrylic resin (B) may be 3,000 to 150,000, in some embodiments 3,000 to 50,000, for example 3,500 to 30,000, and in other embodiments In the embodiment, it is 3,500 to 20,000. When the number average molecular weight of the acrylic resin (B) is within the above range, it is possible to achieve both good coating film hardness and processability, and furthermore, it is possible to form a coating film with excellent weather resistance. Furthermore, when the number average molecular weight of the acrylic resin (B) is within the above range, the coating composition has good drying properties.
In the present disclosure, the number average molecular weight is a value measured by GPC (gel permeation chromatography) in terms of polystyrene.
Moreover, when the acrylic resin (B) contains multiple types of acrylic resins, the number average molecular weight of the acrylic resin (B) indicates the number average molecular weight of a mixture thereof.

The hydroxyl value of the acrylic resin (B) is, for example, 0 mgKOH/g or more and 250 mgKOH/g or less, preferably 0 mgKOH/g or more and 100 mgKOH/g or less, and more preferably 0 mgKOH/g or more and 70 mgKOH/g or less.
When the hydroxyl value is within the above range, it is possible to ensure good reactivity as a thermosetting acrylic resin, good dispersibility of color pigments, and good adhesion to the undercoat film.
In addition, in this disclosure, the hydroxyl value of the resin indicates a solid content equivalent value, and is a value measured by a method based on JIS K 0070.
Moreover, when the acrylic resin (B) contains multiple types of acrylic resins, it is preferable that the hydroxyl value of the acrylic resin (B) as a whole falls within the above range. In another embodiment, the weighted average value of the hydroxyl values of each acrylic resin contained in the acrylic resin (B) may be included in the above range.

The glass transition temperature (Tg _B ) of the acrylic resin (B) is, for example, 10°C or more and 120°C or less, preferably 20°C or more and 80°C or less. When the glass transition temperature of the acrylic resin (B) is within such a range, excellent workability can be imparted while ensuring the hardness, scratch resistance, water resistance, chemical resistance, and corrosion resistance of the coating film. Moreover, the coating film can be dried well.
Note that in the present disclosure, the glass transition temperature is a value measured by a differential scanning calorimeter, and can be measured, for example, by a differential scanning calorimeter DSC-6100 (manufactured by Seiko Instruments Inc.).

A commercially available acrylic resin may be used as the acrylic resin (B). Specific examples of such acrylic resins include Acrydic series (manufactured by DIC), Dianal series (manufactured by Mitsubishi Chemical), Hytaloid series (manufactured by Hitachi Chemical), PARALOID series (manufactured by Dow Chemical), etc. can be mentioned. These may be used alone or two or more types may be mixed.

In the coating film forming resin, the total content of polyvinylidene fluoride resin (A) and acrylic resin (B) is preferably 90% by mass or more and 100% by mass or less, more preferably 95% by mass or more and 100% by mass or less. .

[Other coating film-forming resins]
In addition to polyvinylidene fluoride resin (A) and acrylic resin (B), the coating composition of the present disclosure may contain other resins as coating film-forming resins to the extent that they do not affect the performance of the coating composition or the resulting coating film. may contain. Examples of such other resins include urethane resins, polyester resins, polyether resins, polystyrene resins, melamine resins, polyamide resins, and polyimide resins.

[(C) Matting agent particles]
The coating composition of the present disclosure includes matting agent particles (C). By containing the matting agent particles (C), the coating composition can form a matte coating film with excellent processability.

The matting agent particles (C) preferably have a Hansen solubility parameter (HSP) distance (Ra) value of 3.5 or less between the polyvinylidene fluoride resin (A) and the matting agent particles (C). is a particle with a value of 3.0 or less. When the Ra value is within this range, there is an advantage that the processability of the resulting coating film is improved.

Further, it is preferable that the difference in refractive index between the polyvinylidene fluoride resin (A) and the matting agent particles (C) is 0.1 or more. When the refractive index difference is within such a range, there is an advantage that a coating film with good gloss adjustment effect and processability can be obtained.

The matting agent particles (C) are not particularly limited as long as they satisfy the Hansen solubility parameter (HSP) distance (Ra) value and refractive index difference, but include resin particles. Such resin particles include, for example, at least one selected from the group consisting of polyurethane resin particles, urea resin particles, polyester resin particles, vinyl butyral resin particles, styrene resin particles, and acrylic resin particles, and preferably polyurethane resin particles. The particles include at least one selected from the group consisting of urea resin particles, polyester resin particles, and acrylic resin particles, and more preferably at least one selected from the group consisting of polyurethane resin particles and urea resin particles. When the matting agent particles (C) contain such particles, there is an advantage that a coating film with good gloss adjustment effect and processability can be obtained.

The average particle diameter of the matting agent particles (C) is 1 μm or more and 10 μm or less, and 2 μm or more and 8 μm or less. When the average particle size is within the above range, the storage stability and coating workability of the resulting coating composition are compatible, and the resulting coating film has good physical properties such as appearance and processability. There are advantages.
In the present disclosure, the average particle diameter of particles is the median diameter (D50) of a volume-based particle size distribution measured by a laser diffraction scattering method using a Microtrac particle size distribution analyzer (trade name "MT3300", manufactured by Nikkiso Co., Ltd.). is the value of

The solid content of the matting agent particles (C) is, for example, 0.1 parts by mass or more and 10.0 parts by mass based on a total of 100 parts by mass of the polyvinylidene fluoride resin (A) and the acrylic resin (B). The content is preferably 0.5 parts by mass or more and 8 parts by mass or less. When the content of the matting agent particles (C) is within the above range, there is an advantage that a coating film with low gloss and good processability can be obtained.

(Urea resin particles)
The urea resin particles include a urea resin, and such urea resin can be a reaction product of urea and an aldehyde. The urea resin particles may be in powder form and may be produced by pulverizing the urea resin. The average particle diameter of the urea resin particles is, for example, 1 to 10 μm, preferably 2 to 8 μm.

As the aldehyde component, formaldehyde, acetaldehyde, crotonaldehyde, benzaldehyde, etc. can be used. Among these, the use of formaldehyde is advantageous because the condensation reaction can proceed easily. Commercially available products of urea resin particles include Pergopack M3, Pergopack M4, Pergopack M5 (manufactured by Lonza Japan), SOOFINE JJ POWDER (manufactured by Hangzhou Seisai Chemical Co., Ltd.), and the like.

(Urethane resin particles)
The urethane resin particles include a urethane resin, and the urethane resin may be a reaction product of a polyol, a polyisocyanate, and a chain extender and/or terminal capper used as necessary.

Examples of the polyol include polymer polyols such as polyether polyol, polyester polyol, polycarbonate polyol, and glycerin polycaprolactone triol; and low molecular weight polyols. The number average molecular weight of such polymer polyols may be, for example, from 300 to 5,000, or even from 500 to 3,000. Further, the number of hydroxyl groups contained in the polymer polyol may be 2 to 3.

Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc.; examples of the polyester polyol include polybutylene adipate, polyhexamethylene adipate, polyneopentyl adipate, etc., and examples of the polycarbonate polyol include Examples include polycaprolactone diol, poly-3-methylvalerolactone diol, polyhexamethylene carbonate, and the like.

The low molecular weight polyols include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butanediol, pentanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, cyclohexanediol, hexanediol, dicyclohexanediol, Aliphatic polyols such as dicyclohexanedimethanol, hydrogenated bisphenol A, and cyclohexanetriol; bisphenol compounds such as bisphenol A, bisphenol F, and bisphenol AD, and aromatic polyols such as ethylene oxide or propylene oxide adducts of such bisphenol compounds. Triols such as trimethylolpropane and trimethylolethane; Polyols having a carboxyl group such as dimethylolacetic acid, dimethylolpropionic acid and dimethylolbutyric acid.

Examples of the chain extender include the low molecular weight polyols; ethylenediamine, propanediamine, butanediamine, hexamethylenediamine, cyclohexanediamine, isophoronediamine, dicyclohexylmethanediamine, bis(aminomethyl)cyclohexane, hydrazine, tolylenediamine, diethylenetriamine, and triamine. Examples include polyamine compounds such as ethylenetetramine and tetraethylenepentamine.

Examples of the terminal capping agent include methanol, ethanol, propanol, butanol, ammonia, dibutylamine, and aminosilane.

(Polyester resin particles)
The polyester resin particles include a polyester resin, and examples of the polyester resin include a reaction product of a polyol and a polycarboxylic acid. Examples of the polyol include the compounds exemplified as the low molecular weight polyol. Examples of the polycarboxylic acids include succinic acid (anhydride), phthalic acid (anhydride), isophthalic acid, terephthalic acid, adipic acid, sebacic acid, hexahydrophthalic acid (anhydride), trimellitic acid (anhydride), and pyrolytic acid (anhydride). Examples include mellitic acid. The acid value of the polyester resin particles may be 100 mgKOH/g or less.

(Polyvinyl butyral resin particles)
The vinyl butyral resin particles include a polyvinyl butyral resin, and examples of the polyvinyl butyral resin include a reaction product of polyvinyl alcohol and butyraldehyde. The reaction between polyvinyl alcohol and butyraldehyde may be carried out under acidic conditions.

(Styrene resin particles and/or acrylic resin particles)
The styrene resin particles and/or acrylic resin particles include a styrene resin and/or an acrylic resin, and the styrene resin and/or acrylic resin may be a polymer of ethylenically unsaturated monomers. Examples of the ethylenically unsaturated monomer include the monomer exemplified as the hydroxyl group-containing monomer (b-1); and the monomer exemplified as the other monomer (b-2).

As the ethylenically unsaturated monomer, a monomer having two or more ethylenically unsaturated bonds in one molecule may be used. The monomer having two or more ethylenically unsaturated bonds in one molecule is not particularly limited, and examples include ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, and tetraethylene glycol di(meth)acrylate. ) acrylate, 1,3-butylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexane Diol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, glycerol di(meth)acrylate, glycerol di(meth)acrylate, glycerol allyloxy di( meth)acrylate, 1,1,1-trishydroxymethylethane di(meth)acrylate, 1,1,1-trishydroxymethylethane tri(meth)acrylate, 1,1-trishydroxymethylpropane di(meth)acrylate, Unsaturated monocarboxylic acid esters of polyhydric alcohols such as 1,1,1-trishydroxymethylpropane tri(meth)acrylate; triallyl cyanurate, triallyl isocyanurate, triallyl trimellitate, diallyl terephthalate, diallyl phthalate, etc. unsaturated alcohol esters of polybasic acids; aromatic monomers substituted with two or more vinyl groups such as divinylbenzene; and the like.

In the present disclosure, resin particles obtained using a styrene monomer are referred to as styrene resin particles, and resin particles obtained without using a styrenic monomer are referred to as acrylic resin particles.

The total content of resin particles in the matting agent particles (C) is preferably 90% by mass or more and 100% by mass or less, more preferably 95% by mass or more and 100% by mass or less.

In the present disclosure, the Hansen solubility parameter (HSP) distance (Ra) between the polyvinylidene fluoride resin (A) and the matting agent particles (C) is 3.5 or less, preferably 0 or more and 3.0. or less, and may be 0.5 or more and 3.0 or less. When the Hansen solubility parameter between the polyvinylidene fluoride resin (A) and the matting agent particles (C) is within the above range, the processability of the resulting coating film is improved.
In the present disclosure, the unit of Hansen solubility parameter (HSP) and distance (Ra) is (MPa) ^0.5 .

The Hansen solubility parameter (HSP) is an index representing the degree of affinity (compatibility) of a certain substance (Y) with a certain substance (X). In detail, the Hansen solubility parameter (HSP) is a solubility parameter introduced by Hildebrand, which Hansen divides into three components: a dispersion term δd, a polarity term δp, and a hydrogen bond term δh. It is expressed numerically using vectors in dimensional space. The dispersion term δd represents the effect of dispersion force, the polar term δp represents the effect of dipole-dipole force, and the hydrogen bond term δh represents the effect of hydrogen bond force. The closer the distance (HSP distance (Ra)) between the coordinates of the vector of one substance (X) and the vector of another substance (Y) in three-dimensional space, the easier it is to dissolve each other (higher compatibility). .
HSP distance (Ra) is defined by the following formula.
Ra = [4( ^δd _X - δd _{Y )} ² + (δp _X - δp _Y ) ² + ₍ ^δh
δd _i : Dispersion force term of substance i δp _i : Polar term of substance i δh _i : Hydrogen bond term of substance i

For the definition and calculation of the Hansen solubility parameter, see Charles M. Hansen, "Hansen Solubility Parameters: A Users Handbook (CRC Press, 2007)".

In the present disclosure, the Hansen solubility parameters of the polyvinylidene fluoride resin (A) and the matting agent particles (C) can be calculated using computer software (Hansen Solubility Parameters in Practice (HSPiP) version 5.3.05).
Specifically, 20 mL of the various organic solvents listed in Table 1 are added to 0.2 g of polyvinylidene fluoride resin (A) or matting agent particles (C). After standing for 30 minutes, those that were dispersed or dissolved were determined to be good solvents, and those that precipitated or were insoluble were determined to be poor solvents. Based on the affinity evaluation results, Hansen solubility spheres were created using the HSPiP (version 5.3.05), and Hansen solubility parameters were calculated.

In the present disclosure, the difference between the refractive index of the polyvinylidene fluoride resin (A) and the refractive index of the matting agent particles (C) is preferably 0.1 or more, and further 0.1 or more and 0.3 or less. It's fine. By being within the above range, a high matting effect can be obtained with the addition of a small amount of (C), and the processability of the resulting coating film will be good.

The refractive index of the polyvinylidene fluoride resin (A) and the matting agent particles (C) was determined according to method B (immersion method using a microscope (Becke line method)) of JIS K 7142 "Method for measuring refractive index of plastics". It was measured.
That is, polyvinylidene fluoride resin or matting agent particles are placed on a slide glass, and a refractive liquid (manufactured by CARGILLE, prepared in plurality with a refractive index difference of 0.01) is dropped. After mixing the matting agent particles and the refractive liquid, polyvinylidene fluoride resin or matting was examined using an optical microscope from above while irradiating light from a high-pressure sodium lamp NX35 (manufactured by Iwasaki Electric Co., Ltd., center wavelength: 589 nm) from below. The outline of the agent particles was observed. If the outline is not visible, it is determined that the refractive index of the refractive liquid and the polyvinylidene fluoride resin or the matting agent particles are equal, and the refractive index of the refractive liquid is set to the refractive index of the polyvinylidene fluoride resin or the matting agent particles. did. The measurement temperature was 25°C.

The matting agent particles (C) may contain inorganic particles such as silica particles within a range that does not impede the processability of the resulting coating film.

(Other ingredients)
In the coating composition of the present disclosure, the solid content may be, for example, 20% by mass or more and 80% by mass or less, further 25% by mass or more and 75% by mass or less, particularly 30% by mass or more and 70% by mass or less. In the present disclosure, solid content means the total of components other than the solvent in the coating composition.

[solvent]
The coating composition of the present disclosure may contain a solvent. Examples of the solvent include water; ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monobutyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, Glycol-based organic solvents such as dipropylene glycol monoethyl ether and propylene glycol monomethyl ether acetate; Alcohol-based organic solvents such as methanol, ethanol, isopropyl alcohol, isobutanol, and benzyl alcohol; Ether-based organic solvents such as dioxane and tetrahydrofuran; 3- Ester organic solvents such as methoxybutyl acetate, ethyl acetate, isopropyl acetate, butyl acetate; Ketone organic solvents such as methyl ethyl ketone, acetone, methyl isobutyl ketone, cyclohexanone, isophorone; N-methyl-2-pyrrolidone, toluene, pentane, iso Examples include -pentane, hexane, iso-hexane, cyclohexane, solvent naphtha, mineral spirit, T-SOL 100, and T-SOL 150 (all aromatic hydrocarbon solvents, manufactured by ENEOS). Among these, ketone organic solvents such as cyclohexanone and isophorone. These solvents may be used alone or in combination of two or more.

[Other ingredients]
In addition to components (A) to (C), the coating composition of the present disclosure may contain coloring pigments, extender pigments, other additives, etc., as necessary, depending on the purpose and use. However, other additives can be added in a manner that does not impair the physical properties of the coating composition of the present disclosure.

Other additives include, for example, curing catalysts such as p-toluenesulfonic acid, tin octoate, dibutyltin dilaurate, lead 2-ethylhexoate, calcium carbonate, kaolin, clay, titanium oxide, talc, barium sulfate, Pigments such as mica, Bengara, manganese blue, carbon black, aluminum powder, pearl mica, etc., waxes, antifoaming agents, leveling agents, thickeners, plasticizers, antioxidants, ultraviolet absorbers, anti-cissing agents, Examples include anti-skinning agents.

The 60 degree specular gloss of the coating film formed from the coating composition of the present disclosure is, for example, 3 or more and 30 or less, and may further be 5 or more and 20 or less.
In the present disclosure, 60 degree specular gloss can be measured in accordance with JIS K 5600-4-7.

(Method for preparing paint composition)
The method for preparing the coating composition according to the present disclosure is not particularly limited. For example, it can be prepared by mixing each component using a selected mixer, disperser, kneader, etc. such as a sand grind mill, ball mill, blender, paint shaker, or disper.

(subject to be coated)
The objects to be coated with the coating composition for pre-coated metal sheets of the present disclosure include, for example, galvanized steel sheets manufactured by a melting method or an electrolytic method, zinc-aluminum alloy-plated steel sheets, aluminum alloy-plated steel sheets, melt-dipped steel sheets, etc. Examples include zinc-aluminum-magnesium alloy plated steel sheets, stainless steel sheets, and cold-rolled steel sheets. In addition to these steel plates or plated steel plates, metal plates such as aluminum plates (including aluminum alloy plates) can also be coated.

The metal plate according to the present disclosure is preferably surface-treated. Specifically, the metal plate of the present disclosure is preferably subjected to pretreatment such as alkaline degreasing, hot water washing, and water washing, and then to chemical conversion treatment. The chemical conversion treatment may be performed by a known method, and examples thereof include chromate treatment, non-chromate treatment such as zinc phosphate treatment, and the like.

In one embodiment, a precoated metal plate includes a metal plate and a coating film disposed on at least one surface of the metal plate and formed from the coating composition for precoated metal plates according to the present disclosure.

In one embodiment, the thickness of the coating film formed from the coating composition for precoated metal plates may be, for example, 10 μm or more and 25 μm or less, and further 15 μm or more and 23 μm or less. When the thickness of the coating film formed from the coating composition for pre-coated metal plates is within such a range, the workability of the pre-coated metal plates becomes even better.

The 60 degree specular gloss of the coating film is, for example, 3 or more and 30 or less, and may further be 5 or more and 20 or less.

When the pre-coated metal plate has a coating film formed from the coating composition for pre-coated metal plates according to the present disclosure on one surface, the other surface may have a coating film formed from a known coating composition. good.

For example, the other side may have a coating formed from a known coating composition, such as a coating composition containing an epoxy resin and/or a polyester resin.

The precoated metal sheet may further include an undercoat film disposed between the metal sheet and the paint film formed from the coating composition of the present disclosure. By having the undercoat film, it is possible to improve the adhesion and corrosion resistance of the paint film formed from the coating composition of the present disclosure. Furthermore, since the properties of the coating film formed from the coating composition of the present disclosure can be more strongly supplemented, the durability of the pre-coated metal plate can be increased.

In one embodiment, the undercoat film preferably contains a polyester resin or a urethane resin. Further, in one embodiment, the thickness of the undercoat film is 3 μm or more and 15 μm or less, for example, 5 μm or more and 10 μm or less.

(Coating film formation method)
When applying the coating composition of the present disclosure, it is preferable to apply a chemical conversion treatment such as phosphate treatment or chromate treatment to the surface of a metal plate or the like to be coated as a coating base treatment, and then apply the coating composition thereon. By coating the coating composition of the present disclosure on the metal plate surface that has been subjected to chemical conversion treatment in this way, the adhesion of the coating film to the metal plate surface is improved, and the corrosion resistance is also improved. It is also possible to form an undercoat film (primer film) on the surface of a metal plate that has been subjected to a chemical conversion treatment, and then paint over it.

The method of applying the coating composition to the surface of the metal plate is not particularly limited, but conventionally known methods such as a roll coater, airless spray, electrostatic spray, curtain flow coater, etc. can be employed, and preferably a roll coater or curtain flow coater. It is best to paint with a coater. After coating, the coating film is baked by heating means such as hot air heating, infrared heating, induction heating, etc. to crosslink the resin and obtain a cured coating film.

The method for producing a precoated metal plate of the present disclosure includes coating the precoated metal plate coating composition of the present disclosure on at least one surface of the metal plate so that the thickness after curing is 10 μm or more and 25 μm or less. to obtain a coating film, and drying and curing the coating film under conditions where the temperature reached by the metal plate is 230°C or more and 270°C or less, and the drying and curing time is 20 seconds or more and 120 seconds or less. to obtain a coating film.

Here, "on the surface" refers not to an absolute direction such as vertical information defined by the direction of gravity, but to a direction toward the outside between the outside and inside of the substrate with the main surface as a boundary. Therefore, "on the main surface" is a relative direction determined by the inorganic material on the main surface. In addition, "above" an element includes not only the position directly above the element (on), but also the position or distance above the element, that is, above the element through other objects. It also includes positions above the space.

In one embodiment, after coating the coating composition, the coating film can be dried and cured (baked) under conditions such that the maximum temperature reached by the material is 230° C. or higher and 260° C. or lower.

After the baking treatment, a precoated metal plate can be obtained by cooling to room temperature. For cooling after the baking treatment, it is preferable to rapidly cool the board to room temperature using water.

The thickness of the cured coating film of the precoated metal plate thus formed is, for example, 10 μm or more and 25 μm or less, and in one embodiment, the film thickness is 12 μm or more and 23 μm or less.
A pre-coated metal plate having a coating film formed from a coating composition for a pre-coated metal plate and having a coating film having superior workability, aesthetic appearance, and weather resistance by having a film thickness within the above range. can be obtained.

The coating composition for pre-coated metal plates of the present disclosure is particularly preferably used as a top coat in a 2-coat/2-bake system or a 3-coat/3-bake system. When used in a 3-coat/3-bake method, a conventional 3-coat/3-bake method is used between the coating film made of the coating composition for pre-coated metal plates of the present disclosure and the primer coating film (undercoat coating film). Provide an intermediate coating film.

The present disclosure will be explained in more detail with reference to the following examples, but the present disclosure is not limited thereto.

Each component used to prepare the coating composition is as follows. Moreover, regarding the acrylic resin (B), the manufacturing method thereof will be explained.

(1) Material used polyvinylidene fluoride resin (A)
(A-1) Kynar500 (manufactured by Arkema); Hansen solubility parameters: δd = 17.7, δp = 13.0, δh = 9.3, refractive index: 1.42; solid content concentration: 100% by mass

(Manufacturing example B-1)
Synthesis of acrylic resin (B-1) (thermosetting acrylic resin) 667.5 parts by mass of isophorone was charged into a reaction vessel equipped with a reflux condenser, a dropping funnel, a stirrer, a thermometer, a condenser, and a nitrogen gas inlet. The temperature was raised to 90° C. under a nitrogen atmosphere. To this, 7.65 parts by mass of methacrylic acid, 310.8 parts by mass of methyl methacrylate, 168.9 parts by mass of n-butyl acrylate, 1.0 parts by mass of ethylene glycol dimethacrylate, and 11.6 parts by mass of N-methoxymethylacrylamide. Parts by mass of a mixed solution, and a mixed solution of 1.5 parts by mass of 2,2'-azobisisobutyronitrile and 47.5 parts by mass of isophorone as initiators were added dropwise at the same time through a dropping funnel over a period of 3 hours. did. After the dropwise addition was completed, stirring was continued for 30 minutes while maintaining the temperature at 90°C, and then the temperature of the reaction vessel was raised to 120°C. Next, a mixed solution of 5 parts by mass of 2,2'-azobisisobutyronitrile and 35 parts by mass of isophorone was added dropwise at a constant rate over 30 minutes. After the dropwise addition, the temperature was maintained at 120°C and stirred for 2 hours to prepare acrylic resin (B-1) (solid content concentration: 40% by mass, solid content acid value: 10 mgKOH/g, solid content hydroxyl value: 0 mgKOH/g, glass A transition temperature of 30° C. and a number average molecular weight of 120,000 were obtained.

(Manufacturing example B-2)
Synthesis of acrylic resin (B-2) (thermoplastic acrylic resin) 667.5 parts by mass of isophorone was charged into a reaction vessel equipped with a reflux condenser, a dropping funnel, a stirrer, a thermometer, a condenser, and a nitrogen gas inlet. The temperature was raised to 90°C under a nitrogen atmosphere. To this, 7.65 parts by mass of methacrylic acid, 310.8 parts by mass of methyl methacrylate, 168.9 parts by mass of n-butyl acrylate, 1.0 parts by mass of ethylene glycol dimethacrylate, and 11 parts by mass of 2-hydroxyethyl methacrylate. A mixed solution of 6 parts by mass, and a mixed solution of 1.5 parts by mass of 2,2'-azobisisobutyronitrile and 47.5 parts by mass of isophorone as initiators were simultaneously added through a dropping funnel at a uniform rate for 3 hours. dripped. After the dropwise addition was completed, stirring was continued for 30 minutes while maintaining the temperature at 90°C, and then the temperature of the reaction vessel was raised to 120°C. Next, a mixed solution of 5 parts by mass of 2,2'-azobisisobutyronitrile and 35 parts by mass of isophorone was added dropwise at a constant rate over 30 minutes. After the dropwise addition was completed, the temperature was maintained at 120°C and stirred for 2 hours to form an acrylic resin (B-2) with a solid content acid value of 10 mgKOH/g, a solid content hydroxyl value of 0 mgKOH/g, and a Tg of 30°C (solid content concentration: 40% by mass, Solid content acid value: 10 mgKOH/g, solid content hydroxyl value: 0 mgKOH/g, glass transition temperature: 30°C, number average molecular weight: 10,000).

Matting agent particles (C)
(C-1) Urea resin particles 1; Eposter M30 (manufactured by Nippon Shokubai Co., Ltd.) average particle diameter: 3 μm, Hansen solubility parameters: δd = 18.5, δp = 12.8, δh = 11.5, refractive index: 1 .66, solid content concentration: 100% by mass
(C-2) Urea resin particles 2; Eposter M05 (manufactured by Nippon Shokubai Co., Ltd.) average particle diameter 5 μm, Hansen solubility parameters: δd = 18.5, δp = 12.8, δh = 11.5, refractive index: 1. 66, solid content concentration: 100% by mass
(C-3) Urethane resin particles 1; Granpearl GU-0700P (manufactured by Aica Kogyo Co., Ltd.) Average particle diameter: 7 μm, Hansen solubility parameters: δd = 17.9, δp = 13.3, δh = 10.7, refraction Rate: 1.66, solid content concentration: 100% by mass
(C-4) Urethane resin particles 2; Art Pearl U-600T (manufactured by Aica Kogyo Co., Ltd.) Average particle diameter: 7 μm, Hansen solubility parameters: δd = 17.9, δp = 13.3, δh = 10.7, refraction Rate: 1.66, solid content concentration: 100% by mass
(C-5) Urethane resin particles 3; Granpearl GU-2000P (manufactured by Aica Kogyo Co., Ltd.) Average particle diameter: 20 μm, Hansen solubility parameters: δd = 17.9, δp = 13.3, δh = 10.7, refraction Rate: 1.66, solid content concentration: 100% by mass
(C-6) Polyester resin particles; Granpearl GU-2000P (manufactured by Aica Kogyo Co., Ltd.) Average particle diameter: 20 μm, Hansen solubility parameters: δd = 17.7, δp = 10.6, δh = 11.6, refractive index : 1.66, solid content concentration: 100% by mass
(C-7) Styrene resin particles; MA2003 (manufactured by Nippon Shokubai Co., Ltd.) Average particle diameter: 3 μm, Hansen solubility parameters: δd = 18.9, δp = 10.9, δh = 10.7, refractive index: 1.56 , solid content concentration: 100% by mass
(c-1) Acrylic resin particles; Ganzpearl GM-0801 (manufactured by Aica Kogyo Co., Ltd.) Average particle diameter: 8 μm, Hansen solubility parameters: δd = 19.7, δp = 11.2, δh = 8.7, refractive index : 1.49, solid content concentration: 100% by mass
(c-2) Silica particles; Cycilia 435 (manufactured by Fuji Syria) average particle diameter: 6 μm, Hansen solubility parameters: δd = 18.6, δp = 12.2, δh = 18.2, refractive index: 1.54 , solid content concentration: 100% by mass

(2) Method for adjusting paint and coating film (test plate) (Example 1)
Preparation of coating composition 1
Kynar500 (solid content concentration: 100 mass %) 19 parts by mass, acrylic resin (B-1, solid content concentration: 40 mass %) 16 parts by mass, acrylic resin (B-2, solid content concentration: 40 mass %) 16 parts by mass 1 part by mass, 28 parts by mass of isophorone, 3 parts by mass of cyclohexanone, 11 parts by mass of xylene, and 11 parts by mass of pigment were mixed, and mixed using a sand mill (dispersion medium: glass beads) until the maximum particle size of coarse pigment particles became 10 μm or less. Dispersion composition 1 was prepared. To the obtained dispersion composition 1, 4 parts by mass of Hi-Disper 1250 and 0.3 parts by mass of matting agent particles (C-1) were added and mixed uniformly with a disper to prepare coating composition 1.

Preparation of test plate : Superlac R-90 (Nippon Paint・After applying epoxy resin paint (manufactured by Industrial Coatings) with a bar coater to a dry film thickness of 5 μm, baking at the maximum material temperature of 210°C for 60 seconds, immediately submerging in water and cooling. A back coating film was formed.

On the other hand, the surface was coated with Fine Tough G Primer (manufactured by Nippon Paint Industrial Coatings Co., Ltd., epoxy resin primer: paint composition 40) as an undercoat to a dry film thickness of 5 μm using a bar coater. Baking was performed for 60 seconds at a maximum temperature of 210° C. to form an undercoat film. Next, coating composition 1 prepared in Production Example 1 was coated with a bar coater so that the dry film thickness was 15 μm, and then baked at the maximum material temperature of 250°C for 60 seconds, and then immediately submerged in water and cooled. , a topcoat film was formed.

(Examples 2 to 14, Comparative Examples 1 to 3)
Coating compositions 2 to 16 were prepared in the same manner as in Example 1, except that the polyvinylidene fluoride resin (A), acrylic resin (B), and matting agent particles (C) were changed as shown in Table 1. A top coat film was formed in the same manner as in Example 1, except that coating compositions 2 to 17 were used instead of coating composition 1.

(3) Evaluation item 1) Paint film appearance (gloss)
The 60° gloss of the coating films obtained in Examples and Comparative Examples was measured using a gloss meter VG 7000 (manufactured by Nippon Denshoku Kogyo Co., Ltd.) in accordance with JIS K 5600-4-7 (specular gloss). did.

2) Processability (initial and over time)

The test plates obtained in each Example and Comparative Example were cut into 50 mm width pieces, and a workability test was conducted in a room at 23°C.
Specifically, several coated plates with the same thickness (0.35 mm) as the test piece to be processed were sandwiched inside the test piece to be processed (with the coating surface facing outward) and bent 180 degrees tightly. . The processed portion was observed and evaluated using a 10x magnifying glass.
The case where there were three coated plates to be sandwiched was defined as "3T", and the minimum value at which no cracks were observed in the processed portion was defined as the processability evaluation result. For example, an evaluation of "4T" indicates that no cracks are observed in the processed portion at 4T, but cracks are observed in the processed portion at 3T.
The above test was conducted immediately after the coated board was manufactured (initial stage) and after being left at room temperature for one month (aging stage). In the initial stage, 4T or less was considered to be a pass, and after aging, 6T or less was considered to be a pass.

Examples 1 to 14 are examples of the present invention, and the gloss was adjusted to a low gloss range, and the initial processability and aging processability were good.
Comparative Example 1 is an example in which the Hansen solubility parameter distance (Ra) between the polyvinylidene fluoride resin and the matting agent particles exceeds 3.5, and the processability decreases over time and the durability is insufficient. It wasn't satisfying. Further, the difference in refractive index between the polyvinylidene fluoride resin and the matting agent particles is less than 0.1, and it is necessary to use a large amount of the matting agent particles.
Comparative Example 2 is an example in which the Hansen solubility parameter distance (Ra) between the polyvinylidene fluoride resin and the matting agent particles exceeds 3.5, and the initial processability is not fully satisfactory. However, the workability deteriorated over time, and the durability was not fully satisfactory.
Comparative Example 3 is an example that does not contain an acrylic resin, and a coating composition could not be produced.

Claims (14)

Polyvinylidene fluoride resin (A),
Acrylic resin (B),
including matting agent particles (C),
A coating composition for a precoated metal plate, wherein the value of the distance (Ra) of the Hansen solubility parameter (HSP) between the polyvinylidene fluoride resin (A) and the matting agent particles (C) is 3.5 or less. . The precoat according to claim 1, wherein the value of the Hansen solubility parameter (HSP) distance (Ra) between the polyvinylidene fluoride resin (A) and the matting agent particles (C) is 3.0 or less. Coating composition for metal plates. The coating composition for a precoated metal plate according to claim 1 or 2, wherein the difference between the refractive index of the polyvinylidene fluoride resin (A) and the refractive index of the matting agent particles (C) is 0.10 or more. . 4. The matting agent particles (C) include at least one selected from the group consisting of acrylic resin particles, polyester resin particles, urea resin particles, and polyurethane resin particles, according to any one of claims 1 to 3. A coating composition for pre-coated metal plates. The coating composition for a precoated metal plate according to any one of claims 1 to 4, wherein the matting agent particles (C) contain at least one selected from the group consisting of urea resin particles and polyurethane resin particles. . The content of the matting agent particles (C) is 1 part by mass or more and 6 parts by mass based on a total of 100 parts by mass of the solid content of the polyvinylidene fluoride resin (A) and the solid content of the acrylic resin (B). The coating composition for precoated metal plates according to any one of claims 1 to 5, which is as follows. The content of the polyvinylidene fluoride resin (A) is 50 parts by mass or more and 80 parts by mass or less out of a total of 100 parts by mass of the solid content of the polyvinylidene fluoride resin (A) and the solid content of the acrylic resin (B). The coating composition for a precoated metal plate according to any one of claims 1 to 6. The coating composition for a precoated metal plate according to any one of claims 1 to 7, wherein the acrylic resin (B) contains a thermosetting acrylic resin. The coating composition for a precoated metal plate according to any one of claims 1 to 8, wherein the average particle diameter of the matting agent particles (C) is 1 μm or more and 10 μm or less. A precoated metal plate comprising a metal plate and a coating film formed from the coating composition for a precoated metal plate according to any one of claims 1 to 9, which is disposed on at least one surface of the metal plate. The precoated metal plate according to claim 10, wherein the coating film has a 60 degree specular gloss of 3 or more and 30 or less. further comprising an undercoat film disposed between the metal plate and the paint film,
The thickness of the undercoat film is 3 μm or more and 10 μm or less,
The precoated metal plate according to claim 10 or 11, wherein the coating film has a thickness of 10 μm or more and 25 μm or less. The precoated metal plate according to claim 12, wherein the undercoat film contains a polyester resin. Coating the precoated metal plate coating composition according to any one of claims 1 to 9 on at least one surface of the metal plate so that the thickness after curing is 10 μm or more and 25 μm or less, obtaining a coating film, and drying and curing the coating film under conditions where the temperature reached by the metal plate is 230°C or more and 270°C or less, and the drying and curing time is 20 seconds or more and 120 seconds or less. , a method for producing a pre-coated metal sheet, comprising obtaining a coating film.