WO2018084065A1 - Polyester polyol resin and coating - Google Patents

Abstract

Provided are a polyester polyol resin having an exceptional balance of hardness and flexibility in a cured coating film and having high solubility in weak solvents, a curable resin composition in which the polyester polyol resin is used, a coating, and a coated steel plate. A polyester polyol resin having a weight-average molecular weight (Mw) within the range of 3,000-120,000, wherein the polyester polyol resin is characterized by having the following (A), (B), and (C1) or (C2) as essential reaction raw materials. (A) A diol compound having an ether bond site in the molecular structure; (B) an aliphatic diol compound having a branched structure in the molecular structure; (C1) a trifunctional or higher polyol compound; (C2) a trifunctional or higher polycarboxylic acid compound or a derivative thereof.

Description

Polyester polyol resin and paint

The present invention relates to a polyester polyol resin having high solubility in a weak solvent and excellent balance between hardness and flexibility in a cured coating film, a curable resin composition using the same, a paint, and a coated steel sheet.

As a coating method for various metal parts or metal molded products such as home appliances, automobile parts, building materials, and can manufacturing applications, a pre-coating method in which a steel plate is pre-coated and a post-coating method in which the steel plate is formed and then coated are known. The steel plate used for the pre-coating method is generally called pre-coated metal (hereinafter may be abbreviated as “PCM”), and is used by cutting a pre-coated steel plate according to the application and forming it into various shapes. PCM paints are required to have very high flexibility and steel sheet adhesion, in addition to the hardness and gloss of the coating surface. In addition, from the viewpoint of improving the coating work environment, high solubility in a solvent having a low environmental load generally called a weak solvent, storage stability of the weak solvent solution, and the like are also important performances. Various types of paint such as two-component curing type, ultraviolet curing type, and volatile drying type are used for PCM paint, and there are various types of resin such as polyester resin, fluorine resin, acrylic resin, etc. In particular, a two-component curable coating mainly comprising a polyester resin is widely used.

Examples of two-component curable PCM paints based on polyester resins include, for example, number average molecular weights using terephthalic acid, isophthalic acid, 2-methyl-1,3-propanediol, and 1,6-hexanediol as reaction raw materials ( Although a coating mainly composed of a polyester resin having a Mn of 11,000 is known (see Patent Document 1), the polyester resin described in Patent Document 1 has low solubility in a weak solvent and surface hardness in a cured coating film. The balance between performance and flexibility was not sufficient.

Japanese Patent Laid-Open No. 9-12969

Therefore, the problem to be solved by the present invention is a polyester polyol resin having high solubility in a weak solvent and excellent balance between hardness and flexibility in a cured coating film, a curable resin composition using the same, a coating material, and a coating material. It is to provide a coated steel sheet.

As a result of intensive studies to solve the above problems, the present inventors have found that a diol compound having an ether bond site in the molecular structure, an aliphatic diol compound having a branched structure in the molecular structure, and a trifunctional or higher functional polyol compound. Alternatively, a polyester polyol resin using a polycarboxylic acid compound having three or more functionals as an essential reaction raw material has been found to have a high solubility in a weak solvent and an excellent balance between hardness and flexibility in a cured coating film. It came to complete.

That is, the present invention is a polyester polyol resin having a weight average molecular weight (Mw) in the range of 3,000 to 120,000, comprising the following (A) and (B) and (C1) or (C2): The present invention relates to a polyester polyol resin characterized by being an essential reaction raw material.
Diol compound having an ether bond site in the molecular structure (A)
Aliphatic diol compound (B) having a branched structure in the molecular structure
Trifunctional or higher polyol compound (C1)
Trifunctional or higher polycarboxylic acid compound or derivative (C2)

The present invention further relates to a curable resin composition comprising a main component containing the polyester polyol resin and a curing agent.

The present invention further relates to a paint comprising the curable resin composition.

The present invention further relates to a coated steel sheet having a coating film made of the paint.

According to the present invention, a polyester polyol resin having high solubility in a weak solvent and excellent balance between hardness and flexibility in a cured coating film, a curable resin composition using the same, a paint, and a coated steel sheet are provided. Can do.

The polyester polyol resin of the present invention has a weight average molecular weight (Mw) in the range of 3,000 to 120,000, and the following (A) and (B) and (C1) or (C2) are essential reaction raw materials. It is characterized by.
Diol compound having an ether bond site in the molecular structure (A)
Aliphatic diol compound (B) having a branched structure in the molecular structure
Trifunctional or higher polyol compound (C1)
Trifunctional or higher polycarboxylic acid compound or derivative (C2)

The diol compound (A) having an ether bond site in the molecular structure is not particularly limited as long as it is a diol compound having one or more ether bond sites in the molecular structure, and various compounds can be used. . Specific examples of the diol compound (B) having an ether bond site in the molecular structure include, for example, the following structural formula (1)

（式中Ｒはそれぞれ独立して炭素原子数１～６の脂肪族炭化水素基であり、ｎは１以上の整数である。）
で表される分子構造を有するものが挙げられる。

(In the formula, each R is independently an aliphatic hydrocarbon group having 1 to 6 carbon atoms, and n is an integer of 1 or more.)
The thing which has the molecular structure represented by these is mentioned.

In the structural formula (1), R is an aliphatic hydrocarbon group having 1 to 6 carbon atoms, and may be linear or branched. Specifically, methylene group, ethylene group, 1,2-propylene group, 1,3-propylene group, tetramethylene group, 2-methyl-1,3-propylene group, pentamethylene group, 2,2-dimethyl- Examples include 1,3-propylene group, hexamethylene group, 3-methyl-1,5-pentylene group and the like. Among these, an aliphatic hydrocarbon group having 2 to 4 carbon atoms is preferable because of excellent balance between hardness and flexibility in a cured coating film and excellent solvent resistance. N in the structural formula (1) is an integer of 1 or more. Among these, an integer of 1 to 4 is preferable because a balance between hardness and flexibility in a cured coating film is excellent, and it is particularly preferable to use a compound in which n is 1 as an essential component.

As long as the aliphatic diol compound (B) having a branched structure in the molecular structure is an aliphatic hydrocarbon diol compound having a branched chain, the number and molecular weight of the branched chain are not particularly limited. May be. Specifically, 2-methyl-1,3-propanediol, neopentyl glycol, 2-ethyl-1,3-propanediol, 2-methyl-1,4-butanediol, 2-ethyl-2-methyl- 1,3-propanediol, 2-ethylbutane-14-butanediol, 2,3-dimethyl-1,4-butanediol, 3-methyl-1,5-pentanediol, 2,4-dimethyl-1,5- Pentanediol, 3,3-dimethylpentane-1,5-diol, 2,2-diethyl-1,3-propanediol, 3-propylpentane-1,5-diol, 2,2-diethyl-1,4- Butanediol, 2,4-diethyl-1,5-pentanediol, 2,2-dipropyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanedio Le, 2,5-diethyl-1,6-hexanediol, and the like. The aliphatic diol compound (B) having a branched structure in the molecular structure may be used alone or in combination of two or more. Among them, a compound having 4 to 6 carbon atoms is preferable, and 2-methyl-1,3-propanediol is more preferable from the viewpoint of excellent balance between hardness and flexibility in a cured coating film.

In addition to the diol compound (A) having an ether bond site in the molecular structure and the aliphatic diol compound (B) having a branched structure in the molecular structure, the polyester polyol resin of the present invention uses other diol compounds as reaction raw materials. You may use as a part of. Other diol compounds include, for example, linear aliphatic diol compounds, alicyclic structure-containing diol compounds such as cyclohexane diol and cyclohexane dialcohol, aromatic ring-containing diol compounds such as biphenol and bisphenol, polyether diol, polycarbonate diol, and the like. Can be mentioned.

The polyester polyol resin of the present invention is excellent in the balance between hardness and flexibility in the cured coating film, and sufficiently exhibits the effect of high solubility in a weak solvent. The total mass of the diol compound (A) having an ether bond site in the molecular structure and the aliphatic diol compound (B) having a branched structure in the molecular structure is preferably 60% by mass or more, and 90% by mass or more. It is more preferable that Further, the ratio of the diol compound (A) having an ether bond site in the molecular structure to the total mass of the diol raw material is preferably in the range of 30 to 98% by mass, and in the range of 40 to 95% by mass. preferable. The ratio of the aliphatic diol compound (B) having a branched structure in the molecular structure to the total mass of the diol raw material is preferably in the range of 1 to 70% by mass, and preferably in the range of 5 to 55% by mass. . Furthermore, the mass ratio [(A) / (B)] of the diol compound (A) having an ether bond site in the molecular structure and the aliphatic diol compound (B) having a branched structure in the molecular structure is 40 / The range of 60 to 95/5 is preferable.

The tri- or higher functional polyol compound (C1) is not particularly limited as long as it is a compound having three or more hydroxyl groups in one molecule, and a wide variety of compounds can be used. Specific examples of the tri- or higher functional polyol compound (C1) include, for example, aliphatic polyol compounds such as trimethylolethane, trimethylolpropane, glycerin, hexanetriol, and pentaerythritol; aromatic polyol compounds such as trihydroxybenzene; Obtained by ring-opening polymerization of the aliphatic polyol compound or aromatic polyol compound and a cyclic ether compound such as ethylene oxide, propylene oxide, tetrahydrofuran, ethyl glycidyl ether, propyl glycidyl ether, butyl glycidyl ether, phenyl glycidyl ether, and allyl glycidyl ether. And polyether-modified polyol compounds. The trifunctional or higher functional polyol compound (C1) may be used alone or in combination of two or more. Especially, it is preferable to use an aliphatic polyol compound and it is more preferable to use a trifunctional aliphatic polyol compound at the point which is excellent in the balance of the hardness and the softness | flexibility in a cured coating film.

The tri- or higher functional polycarboxylic acid compound or derivative thereof (C2) is not particularly limited as long as it is a compound having three or more carboxy groups in one molecule, and various compounds are used. Can do. Specific examples of the trifunctional or higher functional polycarboxylic acid compound or derivative (C2) include aliphatic polycarboxylic acid compounds such as 1,2,5-hexanetricarboxylic acid and 1,2,4-cyclohexanetricarboxylic acid. And acid anhydrides and acid halides thereof; aromatic polycarboxylic acid compounds such as trimellitic acid, trimellitic anhydride, 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, and the like An acid anhydride, an acid halide, etc. are mentioned. These may be used alone or in combination of two or more.

In the polyester polyol resin of the present invention, the trifunctional or higher functional polyol compound (C1) and the trifunctional or higher functional polycarboxylic acid compound or its derivative (C2) are components used for introducing a branched structure into the resin structure. Both can be used equally. The polyester polyol resin of the present invention is excellent in the balance between hardness and flexibility in a cured coating film, and sufficiently exhibits the effect of high solubility in a weak solvent. The trifunctional or higher functional polyol compound (C1) or the trifunctional or higher functional polycarboxylic acid compound or its derivative (C2) is preferably used in the range of 0.05 to 15% by mass, preferably in the range of 0.1 to 10% by mass. It is more preferable to use in.

The polyester polyol resin of the present invention preferably uses a dicarboxylic acid compound or a derivative thereof as a reaction raw material in addition to the component (A), the component (B), the component (C1) or the component (C2). Examples of the dicarboxylic acid compound or derivative thereof include, for example, an aliphatic dicarboxylic acid compound or derivative thereof (D1), an aromatic dicarboxylic acid compound or derivative thereof (D2), an alicyclic dicarboxylic acid compound or derivative thereof (D3), and the like. Is mentioned.

Examples of the aliphatic dicarboxylic acid compound or derivative (D1) thereof include oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and These acid anhydrides and acid halides can be mentioned. Examples of the aromatic dicarboxylic acid compound or derivative (D2) include phthalic acid, isophthalic acid, terephthalic acid, and acid anhydrides and acid halides thereof. Examples of the alicyclic dicarboxylic acid compound or derivative (D3) thereof include hexahydrophthalic acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, and acid anhydrides and acid halides thereof. These may be used alone or in combination of two or more. Among them, the aliphatic dicarboxylic acid compound or a derivative thereof (D1) is preferably used from the viewpoint of excellent flexibility in a cured coating film, and a linear saturated aliphatic dicarboxylic acid compound having 4 to 8 carbon atoms or a derivative thereof. It is more preferable to use Moreover, it is preferable to use the said aromatic dicarboxylic acid compound or its derivative (D2) in the point which is excellent in the hardness in a cured coating film.

The polyester polyol resin of the present invention is excellent in the balance between hardness and flexibility in the cured coating film, and since the effect of high solubility in a weak solvent is sufficiently exerted, relative to the total mass of the dicarboxylic acid raw material, The aliphatic dicarboxylic acid compound or derivative thereof (D1) is preferably used in an amount of 1% by mass or more, more preferably 1-30% by mass. The aromatic dicarboxylic acid compound or derivative thereof (D2) is preferably used in an amount of 70% by mass or more, more preferably 75 to 99% by mass, based on the total mass of the dicarboxylic acid raw material. Furthermore, the total mass of the aliphatic dicarboxylic acid compound or derivative (D1) and the aromatic dicarboxylic acid compound or derivative (D2) is preferably 60% by mass or more based on the total mass of the dicarboxylic acid raw material. 90% by mass or more is more preferable. Further, the mass ratio [(D1) / (D2)] of the aliphatic dicarboxylic acid compound or derivative (D1) and the aromatic dicarboxylic acid compound or derivative (D2) is in the range of 1/97 to 30/70. It is preferable that

The production method of the polyester polyol resin of the present invention is not particularly limited, and may be produced by any method. Specifically, all of the reaction raw materials may be reacted at once, or may be produced by a method of adding a part of the reaction raw materials in a divided manner. The reaction temperature is preferably about 180 to 300 ° C., similar to the reaction temperature of general polyester resins, and a known and usual esterification catalyst may be used if necessary.

The polyester polyol resin of the present invention may be reacted in an organic solvent as necessary, or the viscosity or the like may be adjusted by adding an organic solvent after completion of the reaction. The organic solvent is not particularly limited as long as it can dissolve the polyester polyol resin, and known and conventional solvents can be used. In particular, the polyester polyol resin of the present invention has high solubility in an organic solvent of a kind generally called a weak solvent. Examples of organic solvents generally called weak solvents include “Naphtha No. 6” manufactured by Yamaichi Chemical Co., Ltd., “Mineral Spirit” manufactured by JX Nippon Oil & Energy Corporation, “A Solvent manufactured by JX Nippon Mining & Energy Corporation” "Solvesso 100", "Solvesso 150" manufactured by ExxonMobil Co., Ltd., and the like. These may be used alone or in combination of two or more.

In addition, examples of the organic solvent having high solubility of the polyester polyol resin of the present invention include alkylene glycols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, and propylene glycol monomethyl ether. Monoalkyl ethers; Dialkylene glycol dialkyl ethers such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol dibutyl ether; ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, etc. Alkylene glycol alkyl ether acetate: toluene, aromatic hydrocarbons such as xylene. These may be used alone or in combination of two or more.

The dilution rate with these organic solvents is appropriately adjusted depending on the application, etc. For example, when the polyester polyol resin is used for coating, it is preferable to dilute the non-volatile content to 40 to 80% by mass. . Moreover, it is preferable to use 70 mass% or more of weak solvents among the organic solvents to be used, and it is more preferable to use 90 mass% or more.

The weight average molecular weight (Mw) of the polyester polyol resin of the present invention is preferably in the range of 3,000 to 120,000, in terms of excellent balance between hardness and flexibility in the cured coating film. More preferably, it is in the range of 100,000. The number average molecular weight (Mn) is preferably in the range of 2,000 to 10,000. The molecular weight distribution (Mw) / (Mn) is preferably in the range of 2-20. In the present invention, the molecular weight of the polyester polyol resin is a value measured by gel permeation chromatography (GPC) under the following conditions.

Measuring device: HLC-8320GPC manufactured by Tosoh Corporation
Column: Tosoh Corporation TSKgel 4000HXL, TSKgel 3000HXL, TSKgel 2000HXL, TSKgel 1000HXL
Detector: RI (differential refractometer)
Data processing; Multi-station GPC-8020 model II manufactured by Tosoh Corporation Measurement conditions; Column temperature 40 ° C
Solvent Tetrahydrofuran Flow rate 0.35 ml / min Standard; Monodisperse polystyrene Sample; Filtered 0.2% tetrahydrofuran solution in terms of resin solids with a microfilter (100 μl)

The hydroxyl value of the polyester polyol resin of the present invention is preferably in the range of 2 to 100 mgKOH / g, more preferably 5 to 50 mgKOH / g, since it becomes a resin having excellent curability. Moreover, it is preferable that the acid value of the polyester polyol resin of this invention is 10 mgKOH / g or less.

The curable resin composition of the present invention comprises a main agent containing the polyester polyol resin and a curing agent.

The main agent may contain other resins other than the polyester polyol resin of the present invention. Examples of other resins include other polyol resins other than the polyester polyol resin of the present invention. When these other resins are used, the main agent is contained because the effect of excellent balance between hardness and flexibility in the cured coating film produced by the present invention and high solubility in weak solvents is exhibited. The polyester polyol resin of the present invention is preferably used in an amount of 50% by mass or more, more preferably 80% by mass or more based on the total mass of the resin component to be processed.

The curing agent only needs to contain a component capable of causing a curing reaction with the polyester polyol resin of the present invention. Examples of such a component include an amino resin, a polyisocyanate resin, a resole resin, and an epoxy resin. Can be mentioned. These may be used alone or in combination of two or more. The components of the curing agent are appropriately selected according to the use and use environment of the curable resin composition, desired cured product properties, etc., as long as the polyester polyol resin of the present invention is used as the main agent, any curing agent was used. Even if it is a case, the effect which is excellent in the balance of the hardness and the softness | flexibility in the cured coating film which this invention show | plays is fully exhibited.

Specific examples of the amino resin include, for example, a methylolated amino resin synthesized from at least one of melamine, urea, and benzoguanamine and formaldehyde; methanol or a part or all of the methylol group of the methylolated amino resin; Examples include alkyl etherified compounds with lower monohydric alcohols such as ethanol, propanol, isopropanol, butanol, and isobutanol.

Examples of such amino resin products include, for example, “Cymel 303” (methylated melamine resin) manufactured by Allnex, “Cymel 350” (methylated melamine resin), “Uban 520” manufactured by Mitsui Chemicals, Inc. ( n-Butylated Modified Melamine Resin), “Uban 20-SE-60” (n-Butylated Modified Melamine Resin), “Uban 2021” (n-Butylated Modified Melamine Resin), “Uban 220” (n-Butylated) Modified melamine resin), “Uban 22R” (n-butylated modified melamine resin), “Uban 2028” (n-butylated modified melamine resin), “Uban 165” (isobutylated modified melamine resin), “Uban 114” ( Isobutylated modified melamine resin), “Uban 62” (isobutylated modified melamine resin), “you Emissions 60R "(isobutyl-modified melamine resin). When these amino resins are used, an acid compound such as a phosphate ester may be added as a curing accelerator.

Specific examples of the polyisocyanate resin include aliphatic diisocyanate compounds such as butane diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate; norbornane diisocyanate, Cycloaliphatic diisocyanate compounds such as isophorone diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate; aromatic diisocyanate compounds such as tolylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate A polymethylene polymer having a repeating structure represented by the following structural formula (2) Polyphenyl isocyanate; these isocyanurate modified product, a biuret modified product, an allophanate modified product, and a blocked polyisocyanate resin or the like.

［式中、Ｒ^１はそれぞれ独立に水素原子、炭素原子数１～６の炭化水素基の何れかである。Ｒ^２はそれぞれ独立に炭素原子数１～４のアルキル基、又は構造式（２）で表される構造部位と＊印が付されたメチレン基を介して連結する結合点の何れかである。ｍは０又は１～３の整数であり、ｌは１以上の整数である。］

[Wherein, R ¹ is independently a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms. R ² is each independently an alkyl group having 1 to 4 carbon atoms or a bonding point linked to a structural moiety represented by the structural formula (2) via a methylene group marked with *. m is 0 or an integer of 1 to 3, and l is an integer of 1 or more. ]

Specific examples of the epoxy resin include a polyglycidyl ether of a polyol compound, a polyglycidyl ester of a polycarboxylic acid compound, a bisphenol type epoxy resin, a novolac type epoxy resin, and the like.

The curable resin composition of the present invention includes a curing catalyst, a curing accelerator, a pigment, a pigment dispersant, a matting agent, a leveling agent, a drying inhibitor, an ultraviolet absorber, an antifoaming agent, a thickener, an antisettling agent, An organic solvent or the like may be added. The blending ratio of these components and the kind of the blend are appropriately adjusted depending on the use and desired performance of the curable resin composition. The curable resin composition of the present invention may be a one-pack type or a two-pack type. When the curable resin composition of the present invention is a two-pack type, the various additives can be added to either or both of the main agent and the curing agent.

Although the use of the curable resin composition of the present invention is not particularly limited, it can be preferably used for paints and adhesives because of its excellent balance between hardness and flexibility in a cured coating, and is particularly suitable as a paint for coated steel sheets. Can be used. The coated steel sheet of the present invention can be used, for example, for various metal parts such as home appliances, automobile parts, building materials, pre-coated metal for metal molded products, can manufacturing applications, and the like.

When the paint of the present invention is used for a coated steel sheet, the paint may be applied directly to the steel sheet, or after forming a primer layer on the steel sheet, the paint of the present invention may be applied thereon. The primer layer can be formed using, for example, a primer coating mainly composed of polyester resin, urethane resin, epoxy resin, or the like. The thickness of the primer layer is preferably about 0.5 to 30 μm. Any known and commonly used method can be used for applying the paint, and examples thereof include spray coating, dip coating, spin coating, flow coating, and roller coating. The film thickness when applying the paint is preferably about 1 to 60 μm. The curing conditions of the coating are appropriately adjusted depending on the selection of the curing agent, the film thickness, and the like, but a method of heat curing for about several seconds to several minutes in a temperature range of about 120 to 350 ° C. is preferable.

Hereinafter, the present invention will be described in more detail with reference to specific synthesis examples and examples. Hereinafter, “parts” and “%” are based on mass unless otherwise specified.

In the examples of the present application, the number average molecular weight (Mn), the weight average molecular weight (Mw), and the molecular weight distribution (Mw / Mn) were measured by gel permeation chromatography (GPC) under the following conditions.

Measuring device: HLC-8320GPC manufactured by Tosoh Corporation
Column: Tosoh Corporation TSKgel 4000HXL, TSKgel 3000HXL, TSKgel 2000HXL, TSKgel 1000HXL
Detector: RI (differential refractometer)
Data processing; Multi-station GPC-8020 model II manufactured by Tosoh Corporation Measurement conditions; Column temperature 40 ° C
Solvent Tetrahydrofuran Flow rate 0.35 ml / min Standard; Monodisperse polystyrene Sample; Filtered 0.2% tetrahydrofuran solution in terms of resin solids with a microfilter (100 μl)

Example 1 Production of Polyester Polyol Resin (1) Solution In a reaction vessel equipped with a stirrer, a condenser and a thermometer, 528.4 parts by mass of 2-methyl-1,3-propanediol, 650 parts by mass of diethylene glycol, 172 of trimethylolpropane Part by mass, 1549 parts by mass of terephthalic acid, 100 parts by mass of adipic acid, 450 parts by mass of isophthalic acid, and 1.72 parts by mass of a titanium phosphate catalyst (“Orgatechs TA-21” manufactured by Matsumoto Fine Chemical Co., Ltd.) were added. The mixture was reacted for 10 hours at 200 to 250 ° C. with stirring under a nitrogen stream, and had a number average molecular weight (Mn) of 4000, a weight average molecular weight (Mw) of 60,900, an acid value of 7.4 mgKOH / g, and a hydroxyl value of 41 mgKOH / g. A polyester polyol resin (1) was obtained. The obtained polyester polyol resin (1) was dissolved in a mixed solvent of 1452 parts by mass of “Solvesso 100” manufactured by ExxonMobil Co., Ltd. and 622 parts by mass of propylene glycol monomethyl ether acetate, and the non-volatile content was 56.9% by mass and the Gardner viscosity. A polyester polyol resin (1) solution of Z3 ² -Z4 was obtained.

Example 2 Production of Polyester Polyol Resin (2) Solution In a reaction vessel equipped with a stirrer, a condenser and a thermometer, 146.3 parts by mass of 2-methyl-1,3-propanediol, 1200 parts by mass of diethylene glycol, 1700 parts by mass of terephthalic acid Parts, 200 parts by mass of adipic acid, 100 parts by mass of trimellitic anhydride, and 1.67 parts by mass of a titanium phosphate catalyst (“Orgatechs TA-21” manufactured by Matsumoto Fine Chemical Co., Ltd.). The reaction was carried out at 200 to 250 ° C. for 18 hours with stirring under a nitrogen stream, and the number average molecular weight (Mn) 4,800, the weight average molecular weight (Mw) 27,600, the acid value 9.4 mgKOH / g, the hydroxyl value 15 mgKOH / g of polyester polyol resin (2) was obtained. The obtained polyester polyol resin (2) is dissolved in a mixed solvent of 1233 parts by mass of “Solvesso 100” manufactured by ExxonMobil Co., Ltd. and 528 parts by mass of propylene glycol monomethyl ether acetate, and has a nonvolatile content of 59.7% by mass and a Gardner viscosity. A polyester polyol resin (2) solution of Z2 ² -Z3 was obtained.

Comparative Example 1 Production of Polyester Polyol Resin (1 ′) Solution In a reaction vessel equipped with a stirrer, condenser and thermometer, 453.2 parts by mass of neopentyl glycol, 440.0 parts by mass of 1,6-hexanediol, trimethylolpropane 190.0 parts by mass, 464.4 parts by mass of phthalic anhydride, 1215.3 parts by mass of isophthalic acid, and 464.4 parts by mass of neodecanoic acid glycidyl ester were added. The polyester polyol resin (1 ′) having a weight average molecular weight (Mw) of 12,000, an acid value of 8.5 mgKOH / g, and a hydroxyl value of 52 mgKOH / g was reacted by stirring for 13 hours at 180 to 250 ° C. with stirring in a nitrogen stream. Obtained. The obtained polyester polyol resin (1 ′) was dissolved in a mixed solvent of 1364.4 parts by mass of “Solvesso 100” manufactured by ExxonMobil Co., Ltd. and 151.8 parts by mass of propylene glycol monomethyl ether acetate to give a nonvolatile content of 65.0. A mass% polyester polyol resin (1 ′) solution was obtained. The Gardner viscosity of the polyester polyol resin (1 ′) solution was ZZ1.

Solubility test in weak solvent The polyester polyol resin solutions obtained in Examples 1 and 2 and Comparative Example 1 were stored at room temperature of 25 ° C., and the state after one month was visually evaluated.
Polyester polyol resin (1) solution: No cloudiness was observed and fluidity was good.
Polyester polyol resin (2) solution: No cloudiness was observed and fluidity was good.
Polyester polyol resin (1 ′) had no cloudiness and fluidity was good.

Example 3 Production of Top Coat Paint (1) 82.9 parts by mass of polyester polyol resin (1) solution, 94.5 parts by mass of titanium oxide, 0.9 part by mass of silica, 16 parts by mass of mixed solvent (1) Dispersion was performed with a paint shaker until the particle size of titanium oxide became 10 μm or less. Next, 82.9 parts by mass of the polyester polyol resin (1) solution, 16.7 parts by mass of the amino resin, 0.9 parts by mass of the curing accelerator, 0.9 parts by mass of the matting agent, and 1.5 parts by mass of the leveling agent are mixed. 2.8 parts by mass of the solvent (1) was added and mixed, and further the Ford Cup # 4 viscosity at 25 ° C. was adjusted with the mixed solvent to be about 100 seconds to obtain a topcoat paint (1).

Example 4 Production of Top Coat Paint (2) 78.8 parts by mass of polyester polyol resin (2) solution, 94.5 parts by mass of titanium oxide, 0.9 part by mass of silica, 23 parts by mass of mixed solvent (1) Dispersion was performed with a paint shaker until the particle size of titanium oxide became 10 μm or less. Next, 78.8 parts by mass of polyester polyol resin (2) solution, 16.7 parts by mass of amino resin, 0.9 parts by mass of curing accelerator, 0.9 parts by mass of matting agent, 1.5 parts by mass of leveling agent, and mixing 4.1 parts by weight of solvent (1) was added and mixed, and the viscosity was adjusted with a mixed solvent so that the Ford Cup # 4 viscosity at 25 ° C. was about 100 seconds to obtain a topcoat paint (2).

Comparative Example 2 Production of Top Coat Paint (1 ′) 72.7 parts by mass of the previously obtained polyester polyol resin (1 ′) solution, 94.5 parts by mass of titanium oxide, 0.9 part by mass of silica, mixed solvent (1 33.3 parts by mass were mixed and dispersed with a paint shaker until the particle size of titanium oxide was 10 μm or less. Next, 72.7 parts by mass of the polyester polyol resin (1) solution, 16.7 parts by mass of the amino resin, 0.9 parts by mass of the curing accelerator, 0.9 parts by mass of the matting agent, and 1.5 parts by mass of the leveling agent are mixed. 6.2 parts by mass of solvent (1) was added and mixed, and the viscosity was adjusted with a mixed solvent so that the Ford Cup # 4 viscosity at 25 ° C. was about 100 seconds to obtain a topcoat paint (1 ′).

Production Example 1 Production of Primer Paint In a reaction vessel equipped with a stirrer, a condenser and a thermometer, 946 parts by mass of neopentyl glycol, 178 parts by mass of trimethylolpropane, 371 parts by mass of 1,6-hexanediol, 1881 parts by mass of isophthalic acid, 176 parts by mass of adipic acid was added. The mixture was reacted at 200 to 250 ° C. for 12 hours with stirring under a nitrogen stream to obtain a polyester polyol resin having a weight average molecular weight (Mw) of 4,500, an acid value of 10.8 mgKOH / g, and a hydroxyl value of 55 mgKOH / g. The obtained polyester polyol resin was dissolved in a mixed solvent of 1151.3 parts by mass of “Solvesso 100” manufactured by ExxonMobil Co., Ltd. and 127.9 parts by mass of butyl cellosolve, and a polyester having a nonvolatile content of 70% by mass and a Gardner viscosity of Z2-Z3 A polyol resin solution was obtained.
67.5 parts by mass of the polyester polyol resin solution obtained above, 23.9 parts by mass of calcium phosphate, 70.6 parts by mass of titanium oxide, 0.9 part by mass of silica, and 43.4 parts by mass of the mixed solvent (2) were mixed. The dispersion was performed with a paint shaker until the particle size of the titanium oxide was 10 μm or less. Next, 67.5 parts by mass of a polyester polyol resin solution, 16.7 parts by mass of an amino resin, 0.9 part by mass of a curing accelerator, 0.9 part by mass of a matting agent, and 7.7 parts by mass of a mixed solvent (2) were added. The mixture was further mixed and adjusted with a mixed solvent so that the viscosity of Ford Cup # 4 at 25 ° C. was about 100 seconds to obtain a primer paint.

Details of each compounding component used in the production of the paint and primer paint are as follows: Titanium oxide: “Ti-PureR960” manufactured by Dupont
Silica: “Aerosil R972” manufactured by Evonik Industries
Mixed solvent (1): “Solvesso 100” manufactured by ExxonMobil Co., Ltd. and propylene glycol monomethyl ether acetate mixed at a mass ratio of 7: 3 Mixed solvent (2): “Solvesso 100” manufactured by ExxonMobil Co., Ltd. and butyl cellosolve Amino resin: "Cymel 303" manufactured by Allnex
Curing accelerator: “Cycat 4040” manufactured by Allnex: sulfonic acid-based catalyst matting agent: “Syloid ED3” manufactured by Allnex: Leveling agent of silica-based matting agent: “Modaflow 2100” manufactured by Allnex:
Calcium phosphate: “Halox 430” manufactured by ICL / Advanced additive

Examples 5 and 6 and Comparative Example 3 Production and Evaluation of Painted Steel Sheet Coated steel sheets were produced in the following manner and various evaluations were performed. The results are shown in Table 1.

Manufacture of coated steel sheet Primer paint is applied to a 0.5mm thick hot dip galvanized chromate-treated steel sheet with a bar coater and heat-dried in an oven at 250 ° C for 20 seconds (metal peak temperature is 199 to 204 ° C) to form a dry film A primer layer having a thickness of 5 μm was formed. Next, a top coat paint is applied onto the primer layer with a bar coater, and heated and dried in an oven at 250 ° C. for 40 seconds (metal peak temperature is 232 to 241 ° C.), and a coated steel sheet having a top coat layer with a dry film thickness of 15 μm. Got.

Measurement of gloss The 60 ° reflectance of the coated surface of the coated steel sheet obtained above was measured according to EN 13523-2 and evaluated as follows.
A: 90% or more B: Less than 90%

Measurement of pencil hardness The pencil hardness of the coated surface of the coated steel plate obtained earlier was measured according to EN 13523-4.

Evaluation of flexibility (1) Crack-free test The flexibility of the coating film was evaluated by a T-bend bending test. In accordance with EN 13523-7, the coated steel plate obtained above was bent 180 °, and cracks generated in the bent portion were observed with a 10-fold magnifier. 0T when the coated steel plate is bent 180 ° without any bending at the bent part, and (X / 2) T when the bent part is bent with X sheets of the same thickness as the coated steel plate as the bent part. Evaluation was made at the minimum value at which no cracks occurred.

Evaluation of flexibility (2) Tape test The flexibility of the coating film was evaluated by a T-bend bending test. In accordance with EN 13523-7, the coated steel sheet was bent 180 °, “cello tape” manufactured by Nichiban Co., Ltd. was applied to the bent part, and the presence or absence of peeling of the coating film was evaluated. When the coated steel plate is folded 180 ° without any bending at the bent part, it is 0T. When the bent part is bent with X sheets of the same thickness as the coated steel sheet, it is (X / 2) T. Evaluation was made with the minimum value that did not occur.

Claims (8)

A polyester polyol resin having a weight average molecular weight (Mw) in the range of 3,000 to 120,000, wherein the following (A) and (B) and (C1) or (C2) are essential reaction raw materials A polyester polyol resin characterized by that.
Diol compound having an ether bond site in the molecular structure (A)
Aliphatic diol compound (B) having a branched structure in the molecular structure
Trifunctional or higher polyol compound (C1)
Trifunctional or higher polycarboxylic acid compound or derivative (C2) The diol compound (A) having an ether bond site in the molecular structure is represented by the following structural formula (1)

(In the formula, each R is independently an aliphatic hydrocarbon group having 1 to 6 carbon atoms, and n is an integer of 1 or more.)
The polyester polyol resin according to claim 1, which is a compound having a molecular structure represented by: The polyester polyol resin according to claim 1, wherein the aliphatic diol compound (B) having a branched structure in the molecular structure is 2-methyl-1,3-propanediol. 2. The polyester polyol resin according to claim 1, wherein an aliphatic dicarboxylic acid compound having 4 to 8 carbon atoms or a derivative thereof is an essential reaction raw material. The polyester polyol resin according to claim 1, wherein the hydroxyl value is in the range of 2 to 100 mgKOH / g. A curable resin composition comprising a main agent containing the polyester polyol resin according to any one of claims 1 to 5 and a curing agent. A paint comprising the curable resin composition according to claim 6. A coated steel sheet having a coating film comprising the paint according to claim 7.