Coating composition

Abstract

This disclosure aims to provide a paint composition using biomass raw materials that has an appropriate viscosity and good hardness and processability of the coating film in PCM applications. [Solution] The solution comprises a coating-forming resin (A) and a crosslinking agent (B), The aforementioned coating-forming resin (A) includes a polyester resin (A1), The polyester resin (A1) comprises a reaction product of a polycarboxylic acid (a1), a polyol (a2), and hydroxycarboxylic acids (a3). The polyol (a2) is a paint composition containing isosorbide.

Description

Technical Field

[0001] The present disclosure relates to a paint composition.

Background Art

[0002] A painted metal plate obtained by applying paint to a metal substrate such as a cold-rolled steel sheet or a plated steel sheet is also called a pre-coated metal plate (also referred to as "PCM"), and is used as various members such as building members such as shutters, rain doors, doors, roofs, and siding, exterior materials for electric appliances such as outdoor coolers, and interior materials. Usually, the pre-coated metal plate is processed into various products after being coated with a paint composition on the surface of the metal plate to form a paint film.

[0003] Although various types of resins are used as the paint film-forming resin for such applications, polyester resins are widely used because they are relatively inexpensive and have excellent physical properties such as adhesion, flexibility, and hardness.

[0004] Most of the plastics (synthetic resins, polymers) currently in circulation are manufactured from petroleum-derived raw materials, and ultimately, greenhouse gas (GHG) is大量に排出される。これらは地球温暖化の主原因の一つであるため、近年、その対策として、GHG排出量の削減の方法が種々検討されている。塗料分野においても、主な構成要素である塗膜形成樹脂はプラスチック(合成樹脂、ポリマー)から成るため、それを再生可能な原材料を用いて製造する方法が種々検討されている。前記再生可能な原材料としては、バイオマス(特に植物)由来の原材料が注目されている。

[0005] <用いて製造する方法が種々検討されている。前記再生可能な原材料としては、バイオマス(特に植物)由来の原材料が注目されている。 It should be noted that there are some unclear parts in the original text (such as "大量に排出される。これらは地球温暖化の主原因の一つであるため、近年、その対策として、GHG排出量の削減の方法が種々検討されている。塗料分野においても、主な構成要素である塗膜形成樹脂はプラスチック(合成樹脂、ポリマー)から成るため、それを再生可能な原材料を用いて製造する方法が種々検討されている。前記再生可能な原材料としては、バイオマス(特に植物)由来の原材料が注目されている。"), and the translation is done as accurately as possible based on the available content. If there are any further clarifications or corrections needed for this part, it would be better to have the complete and correct text.

[0006] Patent Document 2 describes a polyester resin containing 0.05 to 0.5 moles of isosorbide-derived constituent units and 0.015 to 0.4 moles of trivalent or higher alcohol-derived constituent units per mole of polycarboxylic acid-derived constituent units.

[0007] Patent Document 3 describes a polyester resin binder for coatings characterized by having a structure in which a divalent acid component; a diol component containing 1 to 60 moles of isosorbide relative to the total diol component; and 1 to 50% by weight of lactic acid or a compound derived therefrom relative to the total resin polymerization reaction product are copolymerized, and a divalent acid portion derived from the divalent acid component, a diol portion derived from the diol component, and a hydroxy monoacid portion derived from lactic acid or a compound derived therefrom are repeated.

[0008] Patent Document 4 describes a polyester resin comprising repeating units obtained by copolymerizing (a) a divalent acid component and (b) a diol component including isosorbide and an alicyclic diol, wherein the polyester resin has a glass transition temperature of 80°C or higher. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2010-95696 [Patent Document 2] International Publication No. 2015 / 163400 [Patent Document 3] Special Publication No. 2014-515053 [Patent Document 4] Special Publication No. 2019-510093 [Overview of the project] [Problems that the invention aims to solve]

[0010] Isosorbide is a biomass-derived raw material for polyester resins. Isosorbide can be easily obtained from sugars derived from starch, which is a starch derived from corn. Furthermore, due to its structure, compounds and resins containing it are expected to have good mechanical and thermal properties, and are therefore attracting attention as a glycol component that can replace aromatic glycols.

[0011] However, conventional polyester resins using biomass-derived raw materials did not provide sufficient viscosity for paint compositions, nor did they offer satisfactory hardness or processability for PCM applications.

[0012] Furthermore, in the field of paints, it is required that the paint film obtained from the paint composition exhibits the desired performance with an appropriate film thickness, and also has a good appearance. To achieve this, it is necessary to have appropriate viscosity behavior at an appropriate solid content concentration, that is, good paintability.

[0013] However, when isosorbide is used as a raw material, problems such as increased viscosity and crystallization can occur in the manufacture of polyester resin or paint composition. As mentioned above, various physical properties are required for PCM coating films, and a paint composition that satisfies all of these requirements has not yet been obtained.

[0014] This disclosure aims to provide a paint composition using biomass raw materials that has an appropriate viscosity and good hardness and processability of the coating film in PCM applications. [Means for solving the problem]

[0015] This disclosure provides the following aspects: [1] It contains a coating-forming resin (A) and a crosslinking agent (B), The aforementioned coating-forming resin (A) includes a polyester resin (A1), The polyester resin (A1) contains a reaction product of a polycarboxylic acid (a1), a polyol (a2), and hydroxycarboxylic acids (a3). The polyol (a2) contains isosorbide, and it is a coating composition. [2] The polycarboxylic acid (a1) contains an aliphatic dicarboxylic acid having 4 to 10 carbon atoms, and it is the coating composition according to [1]. [3] The amount of the polycarboxylic acid (a1) is 30 mol% or more and 50 mol% or less in 100 mol% of the total amount of the polycarboxylic acid (a1), the polyol (a2), and the hydroxycarboxylic acids (a3), and it is the coating composition according to [1] or [2]. [4] The polyol (a2) further contains a divalent polyol other than isosorbide and a polyol having 3 or more valences, and it is the coating composition according to any one of [1] to [3]. [5] The amount of the isosorbide is 3 mol% or more and 90 mol% or less in 100 mol% of the total amount of the polyol (a2), and it is the coating composition according to any one of [1] to [4]. [6] The amount of the divalent polyol other than isosorbide is 3 mol% or more and 80 mol% or less in 100 mol% of the total amount of the polyol (a2), and it is the coating composition according to any one of [1] to [5]. [7] The amount of the trivalent polyol is 0 mol% or more and 20 mol% or less in 100 mol% of the total amount of the polyol (a2), and it is the coating composition according to any one of [1] to [6]. [8] The hydroxycarboxylic acids (a3) contain hydroxycarboxylic acids having 3 to 7 carbon atoms, and it is the coating composition according to any one of [1] to [7]. [9] The amount of the hydroxycarboxylic acids (a3) is more than 0 mol% and 45 mol% or less in 100 mol% of the total amount of the polycarboxylic acid (a1), the polyol (a2), and the hydroxycarboxylic acids (a3), and it is the coating composition according to any one of [1] to [8].

[10] The hydroxyl value of the polyester resin (A1) is 5 mgKOH / g or more and 200 mgKOH / g or less, and the coating composition according to any one of [1] to [9].

[11] The acid value of the polyester resin (A1) is 1 mgKOH / g or more and 50 mgKOH / g or less, and the coating composition according to any one of [1] to

[10] .

[12] The crystallization temperature of the polyester resin (A1) is -70°C or more and 5°C or less, and the coating composition according to any one of [1] to

[11] .

[13] The weight average molecular weight of the polyester resin (A1) is 3,000 or more and 35,000 or less, and the coating composition according to any one of [1] to

[12] .

[14] The crosslinking agent (B) contains one or more selected from the group consisting of amino resins and blocked isocyanate compounds, and the coating composition according to any one of [1] to

[13] .

[15] The content of the crosslinking agent (B) is 1 part by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the film-forming resin (A), and the coating composition according to any one of [1] to

[15] .

[16] A coating step of coating an object to be coated with the coating composition according to any one of [1] to

[15] to obtain a coating film, and A curing step of curing the coating film at a temperature of 150°C or more and 270°C or less to obtain a coating film, and a method for producing a coating film.

Effect of the Invention

[0016] According to the present disclosure, there is provided a coating composition using a biomass raw material, which has an appropriate viscosity and provides a coating composition having good hardness and processability of the coating film in PCM applications.

Mode for Carrying Out the Invention

[0017] The coating composition of this disclosure comprises a film-forming resin (A) and a crosslinking agent (B), wherein the film-forming resin (A) comprises a polyester resin (A1), the polyester resin (A1) comprises a reaction product of a polycarboxylic acid (a1), a polyol (a2), and hydroxycarboxylic acids (a3), and the polyol (a2) comprises isosorbide.

[0018] The coating composition disclosed herein uses biomass raw materials, has an appropriate viscosity, and exhibits good hardness and processability of the coating film in PCM applications. Although this disclosure should not be interpreted as being limited to any particular theory, the reasons why the coating composition disclosed herein may achieve such effects are thought to be as follows.

[0019] In other words, in this disclosure, by including isosorbide as a polyol, which is a raw material for polyester resin, the hardness and durability of the resulting coating film can be improved. Furthermore, by using isosorbide and hydroxycarboxylic acids as raw materials for polyester resin, the highly reactive carboxyl groups of the hydroxycarboxylic acids, or those generated by their ring-opening, can react with the less reactive secondary hydroxyl groups of isosorbide. This allows the isosorbide to be incorporated into the resin backbone of the polyester resin, improving the flexibility of the resin and bringing the viscosity of the resin composition within an appropriate range.

[0020] (A) Film-forming resin The coating-forming resin (A) is a resin that reacts with the crosslinking agent (B), described later, to form a coating film, and includes polyester resin (A1).

[0021] The polyester resin (A1) contains reaction products of polycarboxylic acid (a1), polyol (a2), and hydroxycarboxylic acids (a3).

[0022] Polycarboxylic acid (a1) refers to a compound having two or more carboxyl groups in one molecule, and also includes compounds in which these two or more carboxyl groups undergo dehydration condensation to form an acid anhydride structure (-CO-O-CO-).

[0023] The polycarboxylic acid (a1) is not particularly limited and includes, for example, aromatic dicarboxylic acids or trifunctional or more aromatic polycarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 3-methylphthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, trimellitic acid, pyromellitic acid, and their anhydrides; aliphatic dicarboxylic acids such as maleic acid, fumaric acid, succinic acid, methylsuccinic acid, dodecenylsuccinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, and itaconic acid; alicyclic dicarboxylic acids such as endoic acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, cyclohexane-1,2-dicarboxylic acid, cyclohexane-1,4-dicarboxylic acid, and hymicic acid, and their anhydrides; and aromatic oxymonocarboxylic acids such as p-oxyethoxybenzoic acid. One polycarboxylic acid may be used alone, or two or more may be used in combination.

[0024] The polycarboxylic acid (a1) preferably contains aliphatic dicarboxylic acids having 4 to 10 carbon atoms, such as maleic acid, fumaric acid, succinic acid, methylsuccinic acid, dodecenylsuccinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, and itaconic acid, and more preferably contains alkylenedicarboxylic acids having 4 to 10 carbon atoms. By including aliphatic dicarboxylic acids having 4 to 10 carbon atoms (preferably alkylenedicarboxylic acids having 4 to 10 carbon atoms), it is easy to achieve both hardness and processability in the resulting coating film.

[0025] The structure of the aliphatic dicarboxylic acid having 4 to 10 carbon atoms may be either a linear or branched structure. The aliphatic dicarboxylic acid having 4 to 10 carbon atoms preferably includes a linear or branched aliphatic dicarboxylic acid having 4 to 9 carbon atoms, and more preferably includes a linear or branched aliphatic dicarboxylic acid having 4 to 6 carbon atoms.

[0026] The amount of aliphatic dicarboxylic acid having 4 to 10 carbon atoms is preferably 80 mol% to 100 mol%, more preferably 90 mol% to 100 mol%, and even more preferably 95 mol% to 100 mol%, of the total amount of polycarboxylic acid (a1) (100 mol%).

[0027] The amount of polycarboxylic acid (a1) is preferably 20 mol% to 60 mol%, more preferably 25 mol% to 55 mol%, and even more preferably 30 mol% to 50 mol%, of the total amount of polycarboxylic acid (a1), polyol (a2), and hydroxycarboxylic acids (a3) ​​in 100 mol%. Being within this range allows for an appropriate viscosity of the resulting polyester resin and coating composition, and can result in good hardness of the resulting coating film.

[0028] Polyol (a2) refers to a compound having two or more hydroxyl groups in one molecule.

[0029] The polyol (a2) contains at least isosorbide. The isosorbide may be 1,4-dianhydro-D-sorbitol, 3,6-dianhydro-D-sorbitol, or mixtures thereof. Isosorbide can be readily obtained from renewable resources, such as sugars and starches, and can be produced, for example, by hydrogenating and dehydrating D-glucose.

[0030] The amount of isosorbide is preferably 3 mol% to 90 mol%, more preferably 5 mol% to 88 mol%, and even more preferably 10 mol% to 80 mol%, out of 100 mol% of the total amount of polyol (a2). Being within this range allows the viscosity of the resulting polyester resin to be appropriate, and the hardness and processability of the resulting coating film to be good.

[0031] The polyol (a2) preferably includes polyols other than isosorbide. Examples of polyols other than isosorbide include divalent and trivalent polyols other than isosorbide. Including polyols other than isosorbide may make it easier to control the properties of the resulting coating film. It is preferable that the polyols other than isosorbide include divalent and trivalent polyols other than isosorbide.

[0032] A divalent polyol refers to a compound that has two or more hydroxyl groups in one molecule. Examples of divalent polyols other than isosorbide include linear or branched alkylenediols such as ethylene glycol, diethylene glycol, polyethylene glycol, 1,2-propylene glycol, 1,3-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, 1,2-hexanediol, and 1,2-octanediol; alicyclic diols such as 1,4-cyclohexanedimethanol; aromatic diols such as hydrogenated bisphenol A and hydroxyalkylated bisphenol A; heterocyclic diols such as N,N-bis-(2-hydroxyethyl)dimethylhydantoin; high molecular weight diols such as polycaprolactone polyols; and neopentyl glycol mono(hydroxypivalate). These may be used individually or in combination of two or more.

[0033] The polyol (a2) preferably contains one or more divalent polyols other than isosorbide, selected from linear and branched alkylenediols. It is believed that including one or more linear and branched alkylenediols can reduce the crystallinity of the resin and improve the processability of the coating film. From the viewpoint of processability of the coating film, branched alkylenediols are preferred.

[0034] In one embodiment, the polyol (a2) preferably includes a linear alkylenediol as a divalent polyol other than isosorbide, and in another embodiment, the polyol (a2) preferably includes a branched alkylenediol as a divalent polyol other than isosorbide. The number of carbon atoms in the linear or branched alkylene glycol is preferably 2 to 10, more preferably 2 to 8, and even more preferably 2 to 6.

[0035] The molecular weight of the linear or branched alkylenediol is preferably 50 to 800, more preferably 50 to 200.

[0036] The content of linear or branched alkylenediol in polyol (a2) is preferably 2 mol% to 88 mol%, more preferably 8 mol% to 85 mol%, and even more preferably 10 mol% to 80 mol%, of 100 mol% of the total amount of polyol (a2). Being within this range allows for appropriate viscosity of the resulting polyester resin and paint composition, and good hardness of the resulting coating film.

[0037] The content of divalent polyols other than isosorbide is preferably 2 mol% to 95 mol%, more preferably 3 mol% to 85 mol%, and even more preferably 3 mol% to 80 mol%, out of 100 mol% of the total amount of polyol (a2).

[0038] A trivalent polyol is a compound that has three hydroxyl groups in one molecule. Examples of trivalent polyols include glycerin, trimethylolethane, trimethylolpropane, trimethylolbutane, and hexanetriol. These may be used individually or in combination of two or more.

[0039] The content of trivalent polyol is preferably 0 mol% to 30 mol%, more preferably 0 mol% to 25 mol%, and even more preferably 0 mol% to 20 mol%, out of 100 mol% of the total amount of polyol (a2). Having the trivalent polyol content within this range results in good processability, hardness, and solvent resistance of the resulting coating film.

[0040] The content of trivalent polyol is preferably 0 moles to 45 moles, more preferably 0 moles to 35 moles, and even more preferably 0 moles to 25 moles, relative to 100 moles of divalent polyol. Being within this range allows the viscosity of the resulting polyester resin and coating composition to be appropriate, and the hardness, processability, and durability of the resulting coating film to be good.

[0041] The total content of divalent and trivalent polyols may be preferably 80 mol% to 100 mol%, more preferably 85 mol% to 100 mol%, and even more preferably 90 mol% to 100 mol%, out of 100 mol% of the total amount of polyol (a2).

[0042] Polyol (a2) may contain other polyols in addition to the divalent and trivalent polyols mentioned above. Examples of such other polyols include tetravalent or higher polyols such as pentaerythritol, dipentaerythritol, tris-(hydroxyethyl) isocyanate, xylitol, sorbitol, and mannitol. These may be used individually or in combination of two or more.

[0043] The total content of polyols with tetravalent or higher valency may be preferably 0 mol% to 20 mol%, more preferably 0 mol% to 15 mol%, and even more preferably 0 mol% to 10 mol%, out of 100 mol% of the total amount of polyol (a2).

[0044] The content of trivalent or higher polyols is preferably 5 mol% to 30 mol%, more preferably 5 mol% to 25 mol%, and even more preferably 5 mol% to 20 mol%, of the total amount of polyol (a2) in 100 mol%. Having a trivalent or higher polyol content within this range results in good processability, hardness, and solvent resistance of the resulting coating film.

[0045] Hydroxycarboxylic acids (a3) ​​are compounds that possess both a hydroxyl group and a carboxyl group within a single molecule. Examples include aliphatic hydroxycarboxylic acids such as glycolic acid, lactic acid, 3-hydroxypropionic acid, glyceric acid, 2-hydroxyisobutyric acid, 2-hydroxy-2-methylbutyric acid, 2-hydroxy-2,2-dialkylacetic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxyvaleric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, 3-hydroxyhexanoic acid, 4-hydroxybutanoic acid, 6-hydroxycaproic acid, 2-hydroxyisocaproic acid, 10-hydroxystearic acid, 1,2-hydroxystearic acid, malic acid, citric acid, and tartaric acid; aromatic hydroxycarboxylic acids such as salicylic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, vanillic acid, protocatechuic acid, and ferulic acid; and derivatives thereof. Examples of the aforementioned derivatives include cyclic ester compounds obtained by dehydration condensation of a hydroxyl group and a carboxyl group within a single molecule.

[0046] Examples of the aforementioned cyclic ester compounds include cyclic ester compounds having 3 to 7 carbon atoms, such as β-propiolactone, β-butyrolactone, γ-butyrolactone, δ-valerolactone, ε-caprolactone, and γ-valerolactone. The number of carbon atoms in the hydroxycarboxylic acids (a3) ​​(especially the cyclic ester compounds) is preferably 3 to 7, more preferably 4 to 7. Although it should not be interpreted as being limited to a specific theory, it is believed that by including a cyclic ester compound, the highly reactive carboxyl group generated by ring opening can react with the less reactive secondary hydroxyl group of isosorbide, incorporating isosorbide into the resin backbone of the polyester resin, improving flexibility, and bringing the viscosity of the resin composition into an appropriate range.

[0047] As for hydroxycarboxylic acids (a3), ε-caprolactone, γ-butyrolactone, and γ-valerolactone are preferred from the viewpoint of achieving both hardness and processability of the resulting coating film.

[0048] The amount of hydroxycarboxylic acids (a3) ​​is preferably more than 0 mol% and 45 mol% or less, more preferably 3 mol% to 40 mol%, and even more preferably 5 mol% to 35 mol%, out of 100 mol% of the total amount of polycarboxylic acid (a1), polyol (a2), and hydroxycarboxylic acids (a3). Being within this range allows the viscosity of the resulting polyester resin to be appropriate and the processability of the resulting coating film to be good.

[0049] In 100 mol% of the raw material for polyester resin (A1), the total proportion of polycarboxylic acid (a1), polyol (a2), and hydroxycarboxylic acids (a3) ​​is preferably 80 mol% or more and 100 mol% or less, more preferably 90 mol% or more and 100 mol% or less, and even more preferably 95 mol% or more and 100 mol% or less.

[0050] In the preparation of the polyester resin (A1) described above, other reaction components may be used in addition to polycarboxylic acids and polyols. Examples of other reaction components include monocarboxylic acids; drying oils, semi-drying oils and their fatty acids. More specifically, examples include monoepoxide compounds such as oxirane and Cardura E (manufactured by Shell Chemical).

[0051] The polyester resin (A1) may be modified. Examples of modified polyester resins include urethane-modified polyester resin, epoxy-modified polyester resin, acrylic-modified polyester resin, and silicone-modified polyester resin. For example, urethane-modified polyester resin is a resin having polyester as the main chain, with its ends modified with isocyanate, and then urethane-modified. For example, silicone-modified polyester resin can be prepared by reacting a polyester resin with an organosilicone (for example, an organosilicone with a number average molecular weight of about 300 to 1,000 having -SiOCH3 groups and / or SiOH groups as functional groups). The amount of organosilicone used for modification is usually about 5 to 50 parts by mass per 100 parts by mass of polyester resin. Furthermore, urethane-modified polyester resin can be prepared by reacting the polyester resin with a polyisocyanate compound.

[0052] The polyester resin (A1) can be produced by conventional methods of condensation polymerization using polycarboxylic acid (a1), polyol (a2), and hydroxycarboxylic acids (a3) ​​as raw materials. In one embodiment, such a production method may involve charging the polycarboxylic acid (a1), polyol (a2), and hydroxycarboxylic acids (a3) ​​together, then raising the temperature while stirring and mixing to carry out a dehydration polycondensation reaction. A catalyst may be used to accelerate the reaction during condensation polymerization. Known catalysts include tin compounds, titanium compounds, zirconium compounds, etc.

[0053] The crystallization temperature of the polyester resin (A1) is preferably between -75°C and 10°C, more preferably between -70°C and 5°C, and even more preferably between -65°C and 0°C. Being within this range allows the viscosity of the resulting polyester resin to be appropriate, and the stability and paintability of the resulting coating composition can be improved.

[0054] In this disclosure, the crystallization temperature can be measured by a differential scanning calorimeter, for example, by a differential scanning calorimeter DSC-6100 (manufactured by Seiko Instruments Corporation).

[0055] The hydroxyl value of the polyester resin (A1) is preferably 5 mg KOH / g or more and 200 mg KOH / g or less, more preferably 40 mg KOH / g or more and 150 mg KOH / g or less, and even more preferably 60 mg KOH / g or more and 130 mg KOH / g or less. Being within this range can result in good hardness, processability, etc. of the resulting coating film.

[0056] The acid value of the polyester resin (A1) is preferably 1 mg KOH / g or more and 50 mg KOH / g or less, more preferably 3 mg KOH / g or more and 40 mg KOH / g or less, and even more preferably 5 mg KOH / g or more and 35 mg KOH / g or less. Being within this range allows for expected functions as a pigment dispersant and acid catalyst, and the resulting coating film may have good processability, solvent resistance, and durability such as boiling water resistance.

[0057] In this disclosure, the acid value and hydroxyl value are both expressed as solid content equivalents and are values ​​measured according to the method in accordance with JIS K 0070.

[0058] The weight-average molecular weight of the polyester resin (A1) is preferably 2,500 to 50,000, more preferably 3,000 to 40,000, even more preferably 5,000 to 35,000, and even more preferably 6,000 to 32,000. Being within this range can result in good stability and paintability of the resulting coating composition, as well as good processability of the resulting coating film.

[0059] In this disclosure, the weight-average molecular weight is a polystyrene-equivalent value measured by gel permeation chromatography.

[0060] In the coating resin (A), the solid content of the polyester resin (A1) is preferably 80% to 100% by mass, more preferably 90% to 100% by mass, and even more preferably 95% to 100% by mass, out of 100% by mass of the total solid content of the coating resin (A). In this disclosure, the amount of solids of a component means the residue after heating at 110°C for 3 hours.

[0061] The biomass content of the coating-forming resin (A) is preferably 10% or more, more preferably 30% or more, and even more preferably 50% or more, with an upper limit of 100%, and may be 80% or less. In this disclosure, biomass content refers to the ratio of the solid content mass of plant-derived raw materials, i.e., various glycols and carboxylic acids produced from plant-derived raw materials, to the total solid content mass of all raw materials used to constitute the paint composition, and is calculated in accordance with ISO 16620.

[0062] The coating-forming resin (A) may contain other resins in addition to the polyester resin (A1) as needed. Examples of other resins include thermosetting resins and thermoplastic resins, such as polyester resins that do not contain isosorbide, acrylic resins, urethane resins, epoxy resins, chlorinated polyethylene, chlorinated polypropylene and other chlorinated olefin resins; homopolymers or copolymers with vinyl chloride, vinyl acetate, vinylidene chloride, etc. as monomer components; cellulose resins; acetal resins; alkyd resins; chlorinated rubber resins; modified polypropylene resins (acid anhydride modified polypropylene resins, etc.); fluororesins (for example, vinylidene fluoride resin, vinyl fluoride resin, copolymers of fluorinated olefins and vinyl ethers, copolymers of fluorinated olefins and vinyl esters), xylene resins, and other resins known in the paint field. The other resins may be used individually or in combination of two or more. Furthermore, by using thermoplastic resins in combination, better coating film properties, such as coating film strength and elongation, can be obtained.

[0063] The solid content of the coating resin (A) is preferably 10% to 95% by mass, more preferably 15% to 30% by mass, and even more preferably 22% to 80% by mass, out of 100% by mass of the total solid content of the coating composition of this disclosure.

[0064] In this disclosure, the solid content of a component means the heating residue as defined in JIS K 5601-1-2:2008, and the solid content percentage is calculated by measuring the percentage of the mass of the residue after heating at 105°C for 60 minutes relative to the original mass.

[0065] The content of the thermoplastic resin may be preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass, and even more preferably 3 to 10 parts by mass, based on 100 parts by mass of the total amount of the coating resin (A).

[0066] (B) Crosslinking agent: The crosslinking agent (B) reacts with the film-forming resin (A) to form a cured coating film, and is typically a compound having two or more groups in one molecule that can react with the film-forming resin (A).

[0067] Examples of the crosslinking agent (B) include polyisocyanate compounds; blocked polyisocyanate compounds obtained by blocking the isocyanate groups of polyisocyanate compounds with an active hydrogen-containing compound; amino resins; phenolic resins, etc. It is preferable to include one or more selected from blocked polyisocyanate compounds and amino resins. By including the crosslinking agent (B), it is possible to exhibit excellent rust prevention over a long period of time, and furthermore, to form a coating film that exhibits excellent moisture resistance and durability.

[0068] The polyisocyanate compound and the polyisocyanate compound constituting the said block polyisocyanate compound are not particularly limited, and conventionally known compounds can be used. Specific examples include, for example, 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,7-heptamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, dimer acid diisocyanate, lysine diisocyanate, cyclohexane-1,3- or 1,4-diisocyanate, 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethylcyclohexane (also known as isophorone diisocyanate; IPDI), dicyclohexylmethane-4,4'-diisocyanate (also known as hydrogenated MDI), 2- or 4-isocyanate Examples include sodium cyclohexyl-2'-isocyanatocyclohexylmethane, 1,3- or 1,4-bis-(isocyanatomethyl)-cyclohexane, bis-(4-isocyanato-3-methylcyclohexyl)methane, 1,3- or 1,4-α,α,α'α'-tetramethylxylylene diisocyanate, 2,4- or 2,6-diisocyanatotoluene, 2,2'-, 2,4'- or 4,4'-diisocyanatodiphenylmethane (MDI), 1,5-naphthalene diisocyanate, p- or m-phenylene diisocyanate, xylene diisocyanate, diphenyl-4,4'-diisocyanate, etc. Furthermore, as polyisocyanate compounds, cyclized polymers of each diisocyanate (isocyanurate type), as well as isocyanate biuret derivatives (biuret type) and adduct types may be used.

[0069] Polyisocyanate compounds may be used individually or in combination of two or more. Isocyanurate-type polyisocyanate compounds are one of the compounds that are preferably used in the present invention.

[0070] In the polyisocyanate compound constituting the block polyisocyanate compound, the isocyanate group content, measured in accordance with JIS K 7301-1995, is typically 3-20%, preferably 5-15%, of the solid content of the polyisocyanate compound. Having the isocyanate group content within this range further improves the curability of the coating film. Furthermore, it can suppress excessively high crosslinking density in the resulting coating film, potentially leading to improved corrosion resistance and chemical resistance.

[0071] The active hydrogen-containing compound (blocking agent) used in the blocked polyisocyanate compound is not particularly limited and can include compounds having an -OH group (alcohols, phenols, etc.), an =N-OH group (oximes, etc.), an =NH group (amines, amides, imides, lactams, etc.), a -CH2- group (active methylene group), and azoles. Specific examples include phenol, cresol, xylenol, ε-caprolactam, σ-valerolactam, γ-butyrolactam, methanol, ethanol, n-, i-, or t-butyl alcohol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, benzyl alcohol, formamide oxime, acetaldehyde oxime, acetoxime, methyl ethyl kedoxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime, dimethyl malonate, ethyl acetoacetate, acetylacetone, pyrazole, and the like. The active hydrogen-containing compound may be used alone or in combination of two or more types.

[0072] The thermal dissociation temperature of a blocked polyisocyanate compound depends on the type of polyisocyanate compound and active hydrogen-containing compound that constitute it, as well as the presence and amount of catalyst. In this disclosure, a blocked polyisocyanate compound having a thermal dissociation temperature (without catalyst) of 120 to 180°C is preferably used. By using a blocked polyisocyanate compound exhibiting a dissociation temperature within this range, the stability of the paint can be improved, and because of its excellent crosslinking reactivity with the film-forming resin (A), a paint film with good moisture resistance can be obtained. Examples of blocked polyisocyanate compounds with a dissociation temperature of 120 to 180°C include Desmodule BL3175 and BL3575 manufactured by Sumika Covestro Urethane Co., Ltd., and Coronate 2554 manufactured by Tosoh Corporation.

[0073] In this disclosure, blocked polyisocyanate compounds may be denoted as (BI).

[0074] Examples of amino resins include melamine resin and urea resin, with melamine resin being preferred.

[0075] Melamine resin generally refers to a thermosetting resin synthesized from melamine and an aldehyde, and has three reactive functional groups -NX1X2 in one triazine molecule. Examples of melamine resins include the fully alkyl type containing -N-(CH2OR)2 (where R is an alkyl group, the same applies below) as a reactive functional group; the methylol type containing -N-(CH2OR)(CH2OH) as a reactive functional group; the imino type containing -N-(CH2OR)(H) as a reactive functional group; and the methylol / imino type containing both -N-(CH2OR)(CH2OH) and -N-(CH2OR)(H), or -N-(CH2OH)(H) as reactive functional groups.

[0076] Among the melamine resins mentioned above, it is preferable to use a fully alkylated melamine resin. Examples of such resins include methylated melamine resin, butylated melamine resin, methyl-butyl mixed melamine resin, and isobutylated melamine resin. Of these, methylated melamine resin, butylated melamine resin, and methyl-butyl mixed melamine resin are preferred.

[0077] Commercially available melamine resins may be used. Examples of commercially available products include Cymel 303, Cymel 254, Cymel 1170, Cymel 235, Cymel 238, Cymel 1123, Mycoat 715 (manufactured by Daicel Ornex), Sumimaru M-40S (manufactured by Sumitomo Chemical Co., Ltd.), Super Beccamine J-820-60, Super Beccamine L-121-60 (manufactured by DIC Corporation), Yuban 20SE-60, Yuban 312, Yuban 703 (manufactured by Mitsui Chemicals, Inc.).

[0078] The melamine resin may be used alone or in combination of two or more types. In some embodiments, the melamine resin may be used in combination with a polyisocyanate compound. Furthermore, a metal catalyst such as a tin compound or a titanium compound may be used as needed.

[0079] The amount of crosslinking agent (B) is preferably 1 to 150 parts by mass, for example, 2 to 150 parts by mass, per 100 parts by mass of solids of the coating resin (A). By including the crosslinking agent (B) under these conditions, it is possible to form a coating film that exhibits excellent rust prevention over a long period of time and also exhibits excellent moisture resistance.

[0080] When melamine resin is used as the crosslinking agent (B), the coating composition of this disclosure may further contain a curing catalyst. Examples of curing catalysts include sulfonic acid compounds, such as aliphatic sulfonic acids like methanesulfonic acid; aromatic sulfonic acids like p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, and dinonylnaphthalenedisulfonic acid; and so on. Only one type of curing catalyst may be used, or two or more types may be used in combination.

[0081] When a blocked polyisocyanate compound and / or a polyisocyanate compound is used as the crosslinking agent (B), the coating composition of this disclosure may further contain a curing catalyst. Examples of curing catalysts include tin catalysts, bismuth catalysts, titanium catalysts, lead catalysts, amine catalysts, etc., with organotin compounds being particularly preferred. Examples of organotin compounds include dibutyltin dilaurate (DBTL), dibutyltin oxide, tetra-n-butyl-1,3-diacetoxystanoxane, etc. Only one type of curing catalyst may be used, or two or more types may be used in combination.

[0082] The amount of the curing catalyst is, for example, 0.1 parts by mass or more and 10 parts by mass or less, per 100 parts by mass of the total solid content of the film-forming resin (A) and the crosslinking agent (B), and may be 0.1 parts by mass or more and 1.5 parts by mass or less. Being within this range improves the reactivity of the paint composition during film formation, and the resulting paint film may have good solvent resistance, corrosion resistance, etc.

[0083] [Other ingredients] The paint compositions of this disclosure may, if necessary, contain other components not mentioned above. Other components include, for example, extender pigments; colorants such as pigments and dyes; rust-preventive pigments and luminous pigments; solvents; ultraviolet absorbers (such as benzophenone-based ultraviolet absorbers); antioxidants (such as phenol-based, sulfoid-based, and hindered amine-based antioxidants); plasticizers; surface modifiers (such as silicones and organic polymers); anti-sagging agents; thickeners; lubricants such as waxes; pigment dispersants; pigment wetting agents; leveling agents; color separation inhibitors; sedimentation inhibitors; defoaming agents; preservatives; antifreeze agents; emulsifiers; fungicides; antibacterial agents; stabilizers; coupling agents; curing catalysts, etc. These additives may be used individually or in combination of two or more.

[0084] Examples of solvents include water; glycol-based organic solvents such as 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, dipropylene glycol monoethyl ether, propylene glycol monomethyl ether acetate, and isoamyl acetate; methanol, ethanol, isopropyl alcohol, and isoamyl alcohol. Examples include alcohol-based organic solvents such as kohl; ether-based organic solvents such as dioxane and tetrahydrofuran; ester-based organic solvents such as 3-methoxybutyl acetate, ethyl acetate, isopropyl acetate, and butyl acetate; ketone-based organic solvents such as methyl ethyl ketone, acetone, methyl isobutyl ketone, cyclohexanone, and isophorone; and N-methyl-2-pyrrolidone, toluene, pentane, iso-pentane, hexane, iso-hexane, cyclohexane, solvent naphtha, mineral spirits, high-boiling point aromatic solvent S100, and high-boiling point aromatic solvent S150 (manufactured by ENEOS Corporation). These may be used individually or in combination of two or more.

[0085] The paint composition of this disclosure may be a water-based paint or an organic solvent-based paint.

[0086] The paint composition disclosed herein may be used as an undercoat paint, also known as a primer. It may also be used as a topcoat paint applied over an undercoat paint. In another embodiment, the coating composition of this disclosure may be used as a coating composition for forming a single coating film rather than for forming a multi-layer coating film.

[0087] The paint composition disclosed herein can exhibit excellent corrosion resistance and moisture resistance regardless of which part of a multi-layer coating it is used on. The primer, topcoat, and intermediate coat other than the paint composition disclosed herein may be conventionally known. For example, the primer may be a conventionally known non-chromium rust-preventive paint, and the topcoat may be an alkyd resin-based paint, an acrylic resin-based paint, a fluororesin-based paint, etc.

[0088] The paint composition of this disclosure is preferably used as a primer. When the paint composition of this disclosure is used as a primer, it exhibits particularly good adhesion at the contact surface between the primer and the coating film formed by the topcoat that is in direct contact with it.

[0089] The biomass content of the coating composition of this disclosure is preferably 1% or more, more preferably 3% or more, even more preferably 5% or more, and may be 80% or less, or 60% or less.

[0090] [Method for preparing paint composition] The method for preparing the paint composition according to this disclosure is not particularly limited. The paint composition according to this disclosure can be prepared, for example, by mixing a film-forming resin (A) and a crosslinking agent (B), as well as optionally used rust-preventive pigments and thermoplastic resins, extender pigments, coupling agents, curing catalysts, and other additives, using a mixer such as a roller mill, ball mill, bead mill, pebble mill, sand grind mill, pot mill, paint shaker, or disper. In another embodiment, the coating composition of the present disclosure may be a two-component coating comprising a main component containing a film-forming resin (A) and an optional rust-preventive pigment, and a crosslinking agent component containing a crosslinking agent (B).

[0091] [Object to be coated] The substrate on which a coating film of the rust-preventive paint composition of this disclosure is formed is not particularly limited as long as corrosion resistance is required. For example, a steel sheet that serves as a base material, such as a pre-coated metal (painted steel sheet), can be used.

[0092] Examples of steel sheets include galvanized steel sheets, cold-rolled steel sheets, stainless steel sheets, and aluminum sheets.

[0093] Examples of galvanized steel sheets include zinc-containing plated steel sheets that utilize zinc sacrificial corrosion protection, specifically hot-dip galvanized steel sheets, electro-galvanized steel sheets, alloyed hot-dip galvanized steel sheets, aluminum-zinc plated steel sheets, nickel-zinc plated steel sheets, magnesium-aluminum-zinc plated steel sheets, magnesium-aluminum-silica-zinc plated steel sheets, and so on.

[0094] It is preferable that the steel sheet be surface-treated with a chemical conversion agent before painting. The surface treatment may be carried out by known methods, including chromate treatment, zinc phosphate treatment, and other non-chromate treatments. The surface treatment can be appropriately selected depending on the steel sheet used, but treatments that do not contain heavy metals are preferred.

[0095] [Method for manufacturing coating film] In one embodiment, the present disclosure provides a method for manufacturing a rust-preventive coating, comprising a painting step of applying the coating composition of the present disclosure to an object to be coated, and a step of curing the coating composition at a temperature of 150°C to 270°C.

[0096] Conventional known methods such as roll coaters and curtain flow coaters can be used as methods for applying the coating composition of this disclosure to an object to be coated.

[0097] The coating film of the present invention can be formed by applying the paint composition to a workpiece such as a steel plate, and then performing a baking treatment by heating the workpiece. The baking temperature (the highest temperature reached by the workpiece such as a steel plate) is, for example, 180°C to 270°C. By curing the paint composition of this disclosure at such a temperature, a coating film with sufficient strength can be formed. By forming a coating film with sufficient strength, it is possible to further demonstrate excellent rust prevention over a long period of time and to form a coating film that exhibits excellent moisture resistance.

[0098] The curing time is, for example, 10 to 200 seconds. For example, when forming a multi-layer coating consisting of two layers, a primer coating and a topcoat coating, the primer coating composition may be applied and then cured, followed by the application of the topcoat coating composition and subsequent curing of the topcoat coating. Alternatively, the primer coating composition may be applied, and then the topcoat coating composition may be applied wet-on-wet without curing, and both coats may be cured simultaneously.

[0099] The film thickness (dry film thickness) of the coating film of the present invention is typically 1 to 30 μm, and for example, in the case of a topcoat coating film, it is preferably 5 to 25 μm.

[0100] The paint composition disclosed herein is a paint composition using biomass raw materials, has an appropriate viscosity, and the resulting coating film has good hardness and processability in PCM applications. For this reason, the paint composition disclosed herein is preferably used in PCM applications, for example, for coating metal substrates such as cold-rolled steel sheets and plated steel sheets, in particular for building components such as steel furniture, shutters, storm shutters, doors, roofs and siding, exterior materials for electrical equipment such as air conditioner outdoor units, and interior materials. [Examples]

[0101] The present invention will be further described in detail by the following examples, but the present invention is not limited thereto.

[0102] (Preparation example A-1) [Coating film-forming resin (A1) (Preparation of polyester resin (A1-1))] In a reaction vessel equipped with a thermometer, condenser, and stirrer, 309.2 parts by mass of isosorbide, 400.6 parts by mass of 1,4-butanediol, 76.6 parts by mass of glycerin, 175.5 parts by mass of ε-caprolactone, and 801.6 parts by mass of succinic acid were mixed. The mixture was heated under a nitrogen stream to 215°C over 2.5 hours, and the esterification reaction was carried out for approximately 5 hours while distilling off the generated water until the acid value reached 16 mg KOH / g (amount of dewatered: 264.4 parts by mass). After that, the temperature of the reaction vessel was lowered to 50°C, and 807.0 parts by mass of cyclohexanone was mixed to obtain polyester resin (A1-1) (solid content concentration: 65% by mass).

[0103] (Preparation Example A-2)~(Preparation Example A-22), (Preparation Example z-1)~(Preparation Example z-4) Polyester resins (A1-2) to (A1-22) and (z-1) to (z-4) were prepared in the same manner as in (Preparation Example A-1), except that the types and amounts of each component were as shown in Tables 1 to 3. The composition and various characteristic values ​​are shown in Tables 1 to 3.

[0104] [Table 1]

[0105] [Table 2]

[0106] [Table 3]

[0107] (Example 1) A dispersion composition was prepared by mixing 135 parts by mass of polyester resin (A1-1) as a coating film-forming resin, 150 parts by mass of TITANIX JR-603 as a pigment, 6 parts by mass of Florene G-700 as a pigment dispersion resin, and 65 parts by mass of cyclohexanone and 65 parts by mass of Ipsol 150 as solvents. The mixture was then dispersed using a sand mill (dispersion medium: glass beads) until the maximum particle size of the coarse pigment particles was 10 μm or less. To the obtained dispersion composition, 40 parts by mass of Yuban 312 as a crosslinking agent (B1), 80 parts by mass of Desmodule BL3575 as a crosslinking agent (B2), 1 part by mass of Disparon OX-811 as a surface modifier, and 1 part by mass of dodecylbenzenesulfonic acid and 2 parts by mass of dibutyltin oxide as curing catalysts were added and uniformly mixed in a disperser to prepare paint composition 1.

[0108] (Examples 2-30, Comparative Examples 1-4) The paint composition was prepared in the same manner as the preparation method for paint composition 1, except that the types and amounts of each component were as shown in Tables 4 to 7. The amounts in the tables represent the amounts in their natural state (including both solid and liquid components).

[0109] The components used in the preparation of the paint composition are as follows: Crosslinking agent (B) Crosslinking agent (B1): Yuban 312 (manufactured by Mitsui Chemicals, amino resin), butylated melamine resin; solid content concentration: 70% by mass Crosslinking agent (B2): Super Beccamine L-109-65 (manufactured by DIC Corporation, amino resin), butylated melamine resin; solid content concentration: 65% by mass Crosslinking agent (B3): Desmodule BL3575 (manufactured by Sumika Covestro Urethane Co., Ltd., block polyisocyanate), hexamethylene diisocyanate (HDI) isocyanurate type block; solid content concentration: 75% by mass Crosslinking agent (B4): Desmodule BL3175 (manufactured by Sumika Covestro Urethane Co., Ltd., block polyisocyanate), hexamethylene diisocyanate (HDI) isocyanurate type block; solid content concentration: 75% by mass

[0110] Details of other ingredients are as follows: Pigment dispersion resin; • Floren G-700 (manufactured by Kyoeisha Chemical Co., Ltd.), carboxyl group-containing polymer modified product; solid content concentration: 100% by mass Surface modifier; • Disparon OX-811 (manufactured by Kusumoto Kasei Co., Ltd.), acrylic surface modifier; solid content concentration: 30% by mass Pigment; • TITANIX JR-603 (manufactured by Teika Co., Ltd.), Titanium Dioxide curing catalyst; • Curing catalyst 1: Dodecylbenzenesulfonic acid (manufactured by Kao Corporation), acidic catalyst; active ingredient concentration: 99% by mass • Curing catalyst 2: Dibutyltin oxide (manufactured by Nitto Chemical Co., Ltd.), metal catalyst; solid content concentration: 100% by mass solvent; Solvent 1: Cyclohexanone (manufactured by Shoei Chemical Co., Ltd.), ketone-based solvent • Solvent 2: Ipsol 150 (manufactured by Idemitsu Kosan Co., Ltd.), aromatic hydrocarbon solvent

[0111] Preparation of test plates After alkaline degreasing of an aluminum-zinc plated steel sheet (210 x 300 x 0.35 mm), Surfcoat EC2310 (phosphate-based surface treatment agent: manufactured by Nippon Paint Surf Chemicals Co., Ltd.) was applied to both the front and back surfaces of the steel sheet as a surface treatment agent, and then dried.

[0112] The paint composition obtained above was applied to the surface of the treated steel plate using a roll coater so that the dry coating film was 5 μm thick, and the coating film was baked at a maximum temperature of 230°C for 50 seconds to form a coating film and obtain a test plate.

[0113] Evaluation items 1) Paint viscosity Each paint composition obtained in the examples and comparative examples was diluted with a mixed solvent prepared by mixing solvent 1 and solvent 2 in a 1:1 mass ratio to achieve a solid content concentration of 60% by mass. The solid content was then measured at 25°C using a Ford cup No. 4 (manufactured by Ueshima Seisakusho Co., Ltd.) in accordance with the method specified in JIS K 5600 2-2 (flow cup method). The evaluation criteria were as follows: A score of △ or higher was considered acceptable. The time is 150 seconds or less. △: The paint composition does not stop flowing out even after 150 seconds. ×: The paint composition can be poured into the cup, but it does not flow out of the orifice, or the paint composition has no fluidity at all.

[0114] 2) Pencil hardness The pencil hardness of the coating film was measured for each test plate obtained in the examples and comparative examples in accordance with JIS K 5600-5-4. A hardness of H or higher was considered acceptable.

[0115] 3) Solvent resistance (xylene rubbing resistance) The test plates obtained in the examples and comparative examples were attached to the evaluation stand of the IMC-155F abrasion resistance testing machine (manufactured by Imoto Seisakusho Co., Ltd.) using adhesive tape, and a rubbing test was performed. The measurement conditions were as follows: gauze impregnated with xylene as the abrasive material, load of 1 kg, reciprocating speed of 30 times / min, and reciprocating distance of 70 mm. The number of rubbing reciprocations until the base material of the underlying steel plate was exposed was measured and evaluated according to the following criteria. ○ or higher was considered a pass. ◎: The base material does not become exposed even after more than 100 round trips. ○: The base material is exposed after 80 to less than 100 round trips. △: The base material is exposed after 30 to less than 80 round trips. ×: The base material is exposed if the number of round trips is less than 30.

[0116] 4) Alkali resistance Each test plate obtained in the examples and comparative examples was cut into 5cm x 10cm sections, immersed in a 5% sodium hydroxide aqueous solution at 23°C for 48 hours, then removed, washed with water, and dried at room temperature. The appearance of the coating on these test plates was evaluated for blistering on the flat surface according to ASTM D714-56. Here, ASTM D714-56 evaluates the size (average diameter) and density of each blister by comparing them with standard judgment photographs and indicates a grade symbol. The size is graded in four stages in the order of 8 (approximately 1mm in diameter), 6 (approximately 2mm in diameter), 4 (approximately 3mm in diameter), and 2 (approximately 5mm in diameter), and the density is graded in five stages from smallest to largest: F, M, MD, and D. A grade of 10 was used for no blistering observed at all, and a grade of 8 or higher was considered acceptable.

[0117] 5) Boiling water resistance Each test plate obtained in the examples and comparative examples was cut into 5cm x 10cm pieces, immersed in boiling water at approximately 100°C for 5 hours, and then removed. The appearance of the coating on the test plate was evaluated in the same manner as in the alkali resistance test. A score of 8 or higher was considered acceptable.

[0118] 6) Processability (adhesion) Each test plate obtained in the examples and comparative examples was cut to 5cm x 3cm and pre-bent using a seam-folding machine (manufactured by Ueshima Seisakusho Co., Ltd.) so that the coated surface was facing outwards. Two steel plates of the same thickness (0.35mm) were placed between the test plates and folded using a press machine (manufactured by Kyōritsu Kogyo Co., Ltd.). Next, cellophane tape (registered trademark) (LP-24, manufactured by Nichiban Co., Ltd.) was applied tightly to the processed area of ​​the painted steel plate and peeled off in one swift motion. The condition of the coating on the peeled area was visually observed, and the adhesion of the coating on the processed area was evaluated according to the following criteria. A score of 4 or higher was considered a pass. 5: No metal surface was found in the area where the tape was peeled off. 4: The metal substrate is visible in less than 20% of the area where the tape has been peeled off (more than 0%). 3: Metal surface material is visible in 20% to less than 50% of the area where the tape has been peeled off. 2: Metal surface material is visible in 50% to less than 80% of the area where the tape has been removed. 1: More than 80% of the area where the tape has been removed shows the bare metal surface.

[0119] 7) Processability (crack resistance) Each test plate obtained in the examples and comparative examples was cut to 5cm x 3cm and pre-bent using a seam-folding machine (manufactured by Ueshima Seisakusho Co., Ltd.) so that the coated surface was facing outwards. Five steel plates of the same thickness (0.35mm) were placed between the test pieces and bent using a press machine (manufactured by Kyōritsu Kogyo Co., Ltd.). The condition of the coated film (cracks) in the processed area was observed with a 15x magnifying glass, and the processability was evaluated according to the following criteria. A score of 4 or higher was considered a pass. The test conditions were a temperature of 23°C and a humidity of 60RH%. 5: No cracks were observed in the processed area. 4. Cracks are observed in less than 20% of the processed area (more than 0%). 3: Cracks are observed in 20% to less than 50% of the processed area. 2: Cracks are observed in 50% to less than 80% of the processed area. 1: Cracks are observed in more than 80% of the processed area.

[0120] 8) Corrosion resistance (salt spray test) Each test plate obtained in the examples and comparative examples was cut with a utility knife to reach the substrate, with a length of 70 mm. A salt spray test (SST) was then performed for 1,000 hours using a salt spray tester ST-11L (manufactured by Suga Test Instruments Co., Ltd.) according to the neutral salt spray resistance test method described in JIS K 5600-7-1 (JIS Z 2371). The corrosion state of the cross-cut area was visually observed, and the average value of the blister width (sum of both sides) on the exposed substrate with a cut width of 0.5 mm was evaluated according to the following criteria. A score of ○ or higher was considered acceptable. ◎: The blister width of the cross-cut section is less than 5 mm. ○: The width of the bulge in the cross-cut section is 5 mm or more and less than 10 mm. △: The width of the bulge in the cross-cut section is 10 mm or more but less than 15 mm. ×: The bulge width of the cross-cut section is 15 mm or more.

[0121] 9) Weather resistance Each test panel obtained in the examples and comparative examples was subjected to a 2,000-hour accelerated weathering test using a Sunshine Weather Meter S80 (manufactured by Suga Test Instruments Co., Ltd.), a sunshine carbon arc lamp type accelerated weathering tester. The operating conditions were as follows. Irradiance: 255W / m 2 Black panel temperature: 63℃ Water injection time: 18 minutes out of 120 minutes The weather resistance was evaluated by visually observing the difference in the appearance of the coating on each test panel after the accelerated weathering test compared to the initial test panel (a test panel that had not been tested). The evaluation criteria were as follows: A score of △ or higher was considered a pass. ○: There is almost no change in appearance. △: Minimal change in appearance (slight discoloration, chalking, and / or cracking may occur). ×: Significant changes in appearance (discoloration, chalking, and / or cracking occur).

[0122] [Table 4]

[0123] [Table 5]

[0124] [Table 6]

[0125] [Table 7]

[0126] Examples 1 to 30 are embodiments of the present invention, and the resulting coating compositions exhibit good stability, high hardness and processability, and excellent durability and moisture resistance.

[0127] Comparative Examples 1 to 3 are examples in which isosorbide was not used as the polyol (a2), which is one of the components of the polyester resin (A1). It was confirmed that the resulting coating film had poor alkali resistance, boiling water resistance, processability, corrosion resistance, and weather resistance. Comparative Example 4 is an example in which hydroxycarboxylic acid (a3), one of the components of the polyester resin (A1), is not used, and it was not possible to adjust the viscosity to an appropriate level for a paint composition. [Industrial applicability]

[0128] The paint composition disclosed herein is a paint composition using biomass raw materials, has an appropriate viscosity, and the resulting coating film has good hardness and processability in PCM applications. For this reason, the paint composition disclosed herein is preferably used in PCM applications, for example, for coating metal substrates such as cold-rolled steel sheets and plated steel sheets, in particular for building components such as steel furniture, shutters, storm shutters, doors, roofs and siding, exterior materials for electrical equipment such as air conditioner outdoor units, and interior materials.

Claims

1. It comprises a coating-forming resin (A) and a crosslinking agent (B), The aforementioned coating-forming resin (A) includes a polyester resin (A1), The polyester resin (A1) comprises a reaction product of a polycarboxylic acid (a1), a polyol (a2), and hydroxycarboxylic acids (a3). The polyol (a2) is a paint composition containing isosorbide.

2. The paint composition according to claim 1, wherein the polycarboxylic acid (a1) comprises an aliphatic dicarboxylic acid having 4 to 10 carbon atoms.

3. The paint composition according to claim 1, wherein the amount of the polycarboxylic acid (a1) is 30 mol% or more and 50 mol% or less of the total amount of polycarboxylic acid (a1), polyol (a2), and hydroxycarboxylic acids (a3) ​​in 100 mol%.

4. The coating composition according to claim 1, wherein the polyol (a2) further comprises a divalent polyol other than isosorbide and a trivalent or higher polyol.

5. The paint composition according to claim 1, wherein the amount of isosorbide is 3 mol% or more and 90 mol% or less of the total amount of polyol (a2) in 100 mol%.

6. The paint composition according to claim 1, wherein the amount of divalent polyol other than isosorbide is 3 mol% or more and 80 mol% or less of the total amount of polyol (a2) in 100 mol%.

7. The paint composition according to claim 1, wherein the amount of the trivalent polyol is 0 mol% or more and 20 mol% or less of the total amount of the polyol (a2) in 100 mol%.

8. The paint composition according to claim 1, wherein the hydroxycarboxylic acids (a3) ​​include hydroxycarboxylic acids having 3 to 7 carbon atoms.

9. The paint composition according to claim 1, wherein the amount of the hydroxycarboxylic acid (a3) ​​is greater than 0 mol% and 45 mol% or less of the total amount of polycarboxylic acid (a1), polyol (a2), and hydroxycarboxylic acid (a3) ​​in 100 mol%.

10. The coating composition according to claim 1, wherein the hydroxyl value of the polyester resin (A1) is 5 mg KOH / g or more and 200 mg KOH / g or less.

11. The paint composition according to claim 1, wherein the acid value of the polyester resin (A1) is 1 mg KOH / g or more and 50 mg KOH / g or less.

12. The paint composition according to claim 1, wherein the crystallization temperature of the polyester resin (A1) is -70°C or higher and 5°C or lower.

13. The paint composition according to claim 1, wherein the weight-average molecular weight of the polyester resin (A1) is 3,000 or more and 35,000 or less.

14. The paint composition according to claim 1, wherein the crosslinking agent (B) comprises one or more selected from the group consisting of amino resins and blocked isocyanate compounds.

15. The paint composition according to claim 1, wherein the content of the crosslinking agent (B) is 1 part by mass or more and 150 parts by mass or less per 100 parts by mass of the coating film forming resin (A).

16. A painting step of applying the paint composition according to any one of claims 1 to 15 to an object to be painted to obtain a paint film, and A method for manufacturing a coating film, comprising a curing step of curing the aforementioned coating film at a temperature of 150°C to 270°C to obtain a coating film.

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