KR20180055758A - Copolyester polyester and metal primer coating using the same - Google Patents

Abstract

To provide a copolymer polyester effective as a binder component of a metal primer coating for coil coating. Also disclosed is a coating composition using the copolymer polyester, which provides a metal primer coating excellent in surface hardness, flexibility, corrosion resistance and chemical resistance. A copolymerized polyester comprising a polycarboxylic acid component and a polyhydric alcohol component as copolymer components, wherein the content of the aromatic dicarboxylic acid component is 95 to 100 mol%, the content of the aliphatic dicarboxylic acid component Wherein the content of the glycol component having a specific structure is 1 to 30 mol% and the glass transition temperature is in the range of 25 to 50 DEG C, when the content of the acid component is 0 to 5 mol% and the content of the total polyhydric alcohol component is 100 mol% Copolymer polyester (A).

Description

Copolyester polyester and metal primer coating using the same

The present invention relates to a copolymer polyester and a metal primer coating using the same. More specifically, the present invention relates to a resin and a coating composition excellent in corrosion resistance and processability.

The copolymerized polyester is widely used as a raw material for a resin composition used for a coating agent, an ink and an adhesive, and is generally composed of a polyvalent carboxylic acid and a polyhydric alcohol. Flexibility and selectivity of polyvalent carboxylic acids and polyhydric alcohols can be freely controlled and the molecular weights can be freely controlled. Thus, they are widely used for various uses including coatings and adhesives.

Among them, in the case of a precoated metal formed by coating a metal foil with a paint containing a resin component, a paint using a high molecular weight copolymer polyester excellent in flexibility of a coating film is widely used (for example, Patent Document 1). However, a polyol having a bisphenol A skeleton, which is concerned with health effects, is used as an essential component, and when the solid content concentration of the high molecular weight polyester is made high when the coating material is made into a coating, the solution viscosity becomes very high and handling becomes difficult. On the other hand, lowering the solid content concentration makes it difficult to increase the thickness of the coating film, and it is necessary to use a large amount of solvent, which is problematic in terms of economy and environment.

Patent Document 1: JP-A-5-295239

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art. That is, an object of the present invention is to provide a copolymerized polyester which is effective as a binder component to be blended in a metal primer coating (metal undercoat paint), and to provide a copolymerized polyester having high molecular weight polyester To provide a coating composition capable of forming a coating film having an equivalent high flexural strength and excellent in hardness, corrosion resistance and chemical resistance.

As a result of intensive studies, the inventors of the present invention have found that the above problems can be solved by means described below, and the present invention has been reached.

That is, the present invention has the following configuration.

A copolymerized polyester comprising a polycarboxylic acid component and a polyhydric alcohol component as copolymer components, wherein the content of the aromatic dicarboxylic acid component is 95 to 100 mol%, the content of the aliphatic dicarboxylic acid component (1) is from 1 to 30 mol%, and the glass transition temperature is from 25 to 50 캜, when the content of the glycol component is 0 to 5 mol% and the total polyhydric alcohol component is 100 mol% (A). ≪ / RTI >

In the general formula (1), n is an integer of 3 or more.

The number-average molecular weight of the copolymer polyester (A) is preferably in the range of 4,000 to 9,000. In addition, it is preferable that no aliphatic dicarboxylic acid component is contained.

The above general formula (1) is preferably triethylene glycol.

A metal primer coating composition comprising the copolymerizable polyester (A), the crosslinking agent (B), the pigment (C), the additive (D) and the organic solvent (E) according to any one of the above.

And a metal primer layer as a primer layer.

The metal primer coating material using the copolymer polyester of the present invention exhibits a high solids content, low solution viscosity, and exhibits high hardness, high bending property, high corrosion resistance and excellent chemical resistance. Therefore, it is suitable for a primer layer of coil coating for home appliances and building materials.

Hereinafter, the present invention will be described in detail.

≪ Copolymerized polyester (A) >

The metal primer coating material using the copolymer polyester (A) of the present invention exhibits excellent flexibility, hardness, corrosion resistance and chemical resistance. For this reason, it is suitable for undercoating on a metal steel sheet which requires deformation processing after coating, and a product produced by using the copolymer polyester (A) of the present invention has a coating film having high hardness, high porosity and high corrosion resistance.

The copolymer polyester (A) of the present invention has a chemical structure obtainable by a polycondensation product of a polycarboxylic acid component and a polyhydric alcohol component, and the polycarboxylic acid component and the polyhydric alcohol component are respectively one or more And a selected component.

In the copolymer polyester (A) of the present invention, the polyvalent carboxylic acid component is preferably a dicarboxylic acid, more preferably an aromatic dicarboxylic acid. The copolymerization amount of the aromatic dicarboxylic acid with respect to the total dicarboxylic acid component is required to be 95 mol% to 100 mol%. , Preferably 98 mol% or more, and more preferably 100 mol%. If the dicarboxylic acid component other than the aromatic dicarboxylic acid component as a copolymerization component is contained in an amount exceeding 5 mol%, the chemical resistance of the coating film may be lowered.

Examples of the aromatic dicarboxylic acid constituting the copolymer polyester (A) of the present invention include, but are not limited to, terephthalic acid, isophthalic acid, orthophthalic acid, naphthalene dicarboxylic acid, 4,4'-dicarboxybiphenyl, 5- Sodium sulfoisophthalic acid, and the like. Among them, terephthalic acid and isophthalic acid are preferable.

The aliphatic dicarboxylic acid constituting the copolymer polyester (A) of the present invention is not particularly limited, but succinic acid, adipic acid, azelaic acid, sebacic acid, cyclohexanedicarboxylic acid, tetrahydrophthalic acid and the like can be used have. Among them, sebacic acid is preferable. The copolymerization amount of the aliphatic dicarboxylic acid with respect to the total dicarboxylic acid is preferably 5 mol% or less, more preferably 2 mol% or less, still more preferably 0 mol%. If it exceeds 5 mol%, the chemical resistance of the coating film may be deteriorated.

In the copolymer polyester (A) of the present invention, it is necessary that the glycol component represented by the general formula (1) is copolymerized with 1 to 30 mol% with respect to the total polyhydric alcohol component.

In the general formula (1), n is an integer of 3 or more. Preferably an integer of 23 or less, more preferably an integer of 15 or less, still more preferably an integer of 5 or less, particularly preferably an integer of 4 or less, and most preferably 3. When n is less than 3, the flexibility of the coating film tends to decrease. On the other hand, if n is too large, the corrosion resistance may decrease.

Examples of the glycol component represented by the general formula (1) include triethylene glycol, tetraethylene glycol, pentaethylene glycol, polyethylene glycol (number average molecular weight 650), polyethylene glycol (number average molecular weight 1000) have. Of these, triethylene glycol is preferable because it has a good balance between the amount of ester bonding and the amount of ether bonding that contribute to adhesion to the coated steel sheet.

The copolymerization amount of the glycol component represented by the general formula (1) is preferably not less than 3 mol%, more preferably not less than 5 mol%, based on 100 mol% of the total polyhydric alcohol component. The content is preferably 28 mol% or less, more preferably 25 mol% or less, still more preferably 20 mol% or less. If it is excessively small, the glass transition temperature of the copolymer polyester (A) becomes high, and the flexibility (workability) may be lowered. On the other hand, when the amount is too large, the glass transition temperature of the copolymerizable polyester (A) is excessively low, resulting in a decrease in hardness and corrosion resistance.

The polyhydric alcohol constituting the copolymer polyester (A) of the present invention is preferably a glycol component other than the glycol component represented by the general formula (1). The glycol component other than the general formula (1) is not particularly limited, and examples thereof include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, Propanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1-methyl- Aliphatic glycol components such as octanediol, 2,2-diethyl-1,3-propanediol and 2-ethyl-2-butyl-1,3-propanediol can be used. Of these, Or more can be used. Further, alicyclic glycol components such as 1,4-cyclohexane dimethanol and tricyclodecane dimethanol, and polyalkylene ether glycol components such as polytetramethylene glycol and polypropylene glycol can also be used. Preferred are ethylene glycol, 1,2-propanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, Butyl-1,3-propanediol, and 1,4-cyclohexanedimethanol.

The copolymerization amount of the aliphatic glycol component, alicyclic glycol component and polyalkylene ether glycol component other than the general formula (1) is preferably 70 to 99 mol% when the total polyhydric alcohol component is taken as 100 mol%. When the amount is too small, the glass transition temperature of the copolymer polyester (A) is excessively low, and the hardness and corrosion resistance may be lowered. On the other hand, when the amount is too large, the glass transition temperature of the copolymer polyester (A) increases and the flexibility (workability) may decrease.

Further, it is preferable to reduce the glycol component having a bisphenol skeleton such as bisphenol A or bisphenol F because there is a risk of endocrine disruptor. The copolymerization amount of the glycol component having a bisphenol skeleton is preferably 5 mol% or less, more preferably 1 mol% or less, and even more preferably 0 mol%, based on 100 mol% of the total polyhydric alcohol component.

The glass transition temperature of the copolymer polyester (A) of the present invention is required to be in the range of 25 to 50 占 폚. When the glass transition temperature is in the range of 25 to 50 占 폚, the corrosion resistance and the bendability can be made compatible. Preferably 30 to 48 占 폚, and more preferably 35 to 45 占 폚. If the glass transition temperature is lower than 25 占 폚, the corrosion resistance may be lowered. When the glass transition temperature exceeds 50 캜, the flexibility of the coating film tends to be lowered, which is not preferable.

To the copolymer polyester (A) of the present invention, a trivalent or more polyvalent carboxylic acid component and / or trivalent or more polyvalent alcohol component may be copolymerized. Examples of the trivalent or higher polyvalent carboxylic acid component include aromatic carboxylic acids such as trimellitic acid, pyromellitic acid, benzophenonetetracarboxylic acid, and trimesic acid, 1,2,3,4-butanetetracarboxylic acid and the like Of an aliphatic carboxylic acid and the like. Examples of polyvalent alcohol components having a trivalent or higher valence include glycerin, trimethylol propane, trimethylol ethane, pentaerythritol, alpha -methyl glucose, mannitol, sorbitol, and one or more of them can be used. The copolymerization amount of the polyvalent carboxylic acid component having a trivalent or more valence is preferably 5% by mole or less, more preferably 2% by mole or less, more preferably 1% by mole or less, based on 100% by mole of the total polyvalent carboxylic acid component , And it may be 0 mol%. The copolymerization amount of the polyvalent alcohol component having a trivalent or higher valence is preferably 2 mol% or less, more preferably 1 mol% or less, and still more preferably 0 mol%, based on 100 mol% of the total polyvalent alcohol component. If it is excessively large, gelation may occur during polymerization of the copolymer polyester (A).

The number average molecular weight of the copolymer polyester (A) of the present invention is preferably 2000 or more, more preferably 4000 or more. Further, it is preferably 9000 or less, more preferably 8000 or less, and further preferably 7400 or less. If the number average molecular weight is less than 2000, the flexibility of the coating film may be lowered, which is not preferable. On the other hand, if it is more than 9000, the viscosity becomes high when the coating material is used, which makes handling difficult, which is not preferable.

The reduced viscosity of the copolymer polyester (A) of the present invention is preferably 0.15 dl / g or more, more preferably 0.18 dl / g or more. Further, it is preferably 0.35 dl / g or less, more preferably 0.32 dl / g or less. If the reduced viscosity is too small, the bending property of the coating film may be deteriorated. If it is excessively large, the viscosity when dissolved in an organic solvent becomes excessively high, which may make handling difficult.

Examples of the polymerization condensation reaction for producing the copolymer polyester (A) of the present invention include: 1) heating a polyvalent carboxylic acid and a polyhydric alcohol in the presence of an arbitrary catalyst to obtain a dehydrated alcohol, And 2) a method in which an alcohol ester polycondensate of a polycarboxylic acid and a polyhydric alcohol are heated in the presence of an arbitrary catalyst to carry out an ester exchange reaction to carry out a polycondensation reaction with a polyhydric alcohol. In the above methods 1) and 2), part or all of the acid component may be replaced with an acid anhydride.

In producing the copolymer polyester (A) of the present invention, conventionally known polymerization catalysts such as titanium compounds such as tetra-n-butyl titanate, tetraisopropyl titanate, and titanium oxyacetylacetonate, antimony trioxide, tri Germanium oxide, germanium compounds such as tetra-n-butoxy germanium and the like, and acetate salts such as magnesium, iron, zinc, manganese, cobalt and aluminum. These catalysts may be used alone or in combination of two or more.

In the production of the copolymer polyester (A) of the present invention, the resin acid value of the copolymer polyester (A) may be increased in order to improve the substrate adhesion property and the crosslinking property. The resin acid value is preferably 1 eq / 10 ⁶ g or more, more preferably 3 eq / 10 ⁶ g or more, and still more preferably 5 eq / 10 ⁶ g or more. In addition, 200 eq / 10 ⁶ g or less is preferred, and, 100 eq / 10 ⁶ g more preferably not more than, and, 50 eq / 10 ⁶ g is more preferred less and, 40 eq / 10 ⁶ g is particularly preferred, and 30 or less eq / 10 < ⁶ > g or less. These effects can be expected by setting the resin acid value within the above range. If the acid value of the resin is too small, the improvement of the adhesion of the substrate and the improvement of the crosslinkability may be difficult to obtain. If the acid value is too large, the adhesion to the substrate and the crosslinkability are improved. However, the chemical resistance may be lowered.

As the method for raising the acid value of the copolymer polyester (A) of the present invention, for example, (1) a polycarboxylic acid and / or an anhydride polycarboxylic acid is added and reacted after completion of the polycondensation reaction, (2) There is a method in which heat, oxygen, water or the like is caused to act on the resin during delamination to effect deliberate resin alteration. These methods can be arbitrarily performed.

The copolymer polyester (A) of the present invention can be used in a state dissolved in a known organic solvent. Examples of known organic solvents that can be used include aromatic hydrocarbons such as toluene, xylene and sorbesol (registered trademark), esters such as ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate and dibasic acid ester, Ketones such as methyl isobutyl ketone, cyclohexanone and isophorone, ethers such as n-butyl cellosolve and t-butyl cellosolve, and the like. In consideration of solubility and evaporation rate (dryness) It is arbitrarily selected and compounded. Among them, a mixed solvent of aromatic hydrocarbons and ketones is preferable, and a mixed solvent of sorbese and cyclohexanone is preferable.

The polyester (A) of the present invention is preferably dissolved in the organic solvent at a concentration of 40 mass% or more at 25 캜, more preferably at a concentration of 50 mass% or more, and more preferably at a concentration of 60 mass% More preferable. By virtue of the above solubility, the solid content concentration as the metal primer coating can be increased, and handling is facilitated.

≪ Crosslinking agent (B) >

The copolymerizable polyester (A) of the present invention can be used together with the crosslinking agent (B). As the crosslinking agent (B), known crosslinking agents may be used. The crosslinking agent (B) is not particularly limited as long as it causes a crosslinking reaction to the copolymer polyester (A), and preferred examples thereof include an isocyanate compound, an epoxy resin, an amino resin (general name of an alkyl etherified formaldehyde resin) And one kind or two kinds or more of them can be arbitrarily selected and used.

The isocyanate compound is not particularly limited, but may be an aromatic, alicyclic or aliphatic polyisocyanate compound, and may be either a low molecular weight type or a high molecular weight type. Examples of the isocyanate compound include tetramethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, And the activity of the isocyanate compound and the ethylene glycol, trimethylol propane, propylene glycol, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine, polyester polyols, polyether polyols and polyamides And a terminal isocyanate compound obtained by reacting with a hydrogen compound. These may be used alone or in combination of two or more.

Further, when the blocked isocyanate compound is used as the isocyanate compound, the pot life of the metal primer coating can be prolonged. Examples of the blocking agent of the blocked isocyanate compound include phenols such as phenol, thiophenol, methylthiophenol, cresol, xylenol, resorcinol, nitrophenol and chlorophenol, acetoxime, methylethylketooxime, cyclohexanone oxime Oximes such as oximes, alcohols such as methanol, ethanol, propanol, butanol, t-butanol and t-pentanol, lactams such as ε-caprolactam, other aromatic amines, imides, acetylacetone, acetoacetic acid ester, Active methylene compounds such as ethyl lactate and ethyl lactate, mercaptans, imines, ureas, and the like. The blocked isocyanate compound is obtained by reacting the isocyanate compound and the blocking agent according to a conventionally known method and can be used alone or in combination of two or more.

Examples of the epoxy resin include glycidyl ether of bisphenol-A and its oligomer, diglycidyl orthophthalate, diglycidyl isophthalate, diglycidyl terephthalate, diglycidyl p-hydroxybenzoate , Tetrahydrophthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, succinic acid diglycidyl ester, adipic acid diglycidyl ester, sebacic acid diglycidyl ester, ethylene glycol diglycidyl ester, Propylene glycol diglycidyl ester, 1,4-butanediol diglycidyl ester, 1,6-hexanediol diglycidyl ester and polyalkylene glycol diglycidyl esters, trimellitic acid triglycidyl ester, Triglycidyl isocyanurate, 1,4-glycidyloxybenzene, diglycidyl propylene urea, glycerol triglycidyl ether, trimethylol ethane glycidyl Trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, triglycidyl ether of glycerol alkylene oxide adduct, and the like. These may be used alone or in combination of two or more.

Examples of the amino resin include, but are not limited to, amino compounds such as melamine, urea, benzoguanamine, acetoguanamine, stigoguanamine, spiroguanamine, dicyandiamide, and formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde Of an amino resin obtained by reaction with an aldehyde component. The amino resin in which the methylol group of the methylol amino resin is etherified with an alcohol having 1 to 6 carbon atoms is also included in the amino resin. These may be used alone or in combination of two or more.

As the phenol resin, a resol-type phenol resin can be used. Examples of the resol-type phenol resin include phenol resins such as phenol, m-cresol, m-methylphenol, 3,5-xylenol, m-methoxyphenol, o-cresol, p-cresol, p- Phenol, 2,3-xylenol, 2,5-xylenol bisphenol-A, and bisphenol-F. These phenol resins can be used alone or in combination of two or more.

The crosslinking agent (B) is preferably at least 1 part by mass, more preferably at least 5 parts by mass, and further preferably at least 10 parts by mass with respect to 100 parts by mass of the copolymer polyester (A). It is more preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and further preferably 30 parts by mass or less. If it is too small, crosslinking of the coating film obtained from the metal primer coating becomes insufficient, and the hardness, firmness and adhesion strength of the coating film required may not be obtained in some cases. If it is excessively large, the bending property of the coating film required may be lowered.

In the present invention, a catalyst that contributes to a crosslinking reaction between the copolymerizable polyester (A) and the crosslinking agent (B) can be further used. As the acid catalyst, for example, organic sulfonic acid compounds such as p-toluenesulfonic acid, dodecylbenzenesulfonic acid and camphorsulfonic acid, phosphoric acid compounds and amine neutralized products thereof may be used. As the base catalyst, an amine compound can be used. As the metal catalyst, organic acid salts, halogenated salts, nitrate salts, sulfate salts and organic ligand compounds of various metals can be used. These catalysts may be used alone or in combination of two or more thereof in accordance with the curing behavior of the crosslinking agent (B).

≪ Pigment (C) >

The copolymer polyester (A) of the present invention can be used together with the pigment (C). Specific examples of the pigment (C) include, but are not limited to, titanium oxide, zinc oxide, zirconium oxide, calcium carbonate, barium sulfate, aluminum oxide, chromium oxide, chromate, kaolin gray, carbon black, iron oxide, talc, Inorganic pigments such as iron phosphate, aluminum phosphate, zinc phosphite, aluminum tripolyphosphate, calcium molybdate, aluminum molybdate, barium molybdate, vanadium oxide, strontium chromate, zinc chromate, calcium silicate, water-dispersed silica and fumed silica, phthalocyanine Blue, phthalocyanine green, carbazole dioxazine violet, anthrapyrimidine yellow, isoindolinone yellow, and indanthrene blue. By adding one or more of these, it is possible to expect effects such as improvement in coloring, system and durability.

The pigment (C) is preferably 5 parts by mass or more, more preferably 50 parts by mass or more, and further preferably 100 parts by mass or more, per 100 parts by mass of the copolymer polyester (A). Further, it is preferably 300 parts by mass or less, more preferably 250 parts by mass or less, and even more preferably 200 parts by mass or less. If the amount of the pigment (C) is excessively small, the desired effect such as coloring and the method may not be obtained. If too much, the bending property of the coating film may be lowered.

≪ Additive (D) >

The additive (D) of the copolymer polyester (A) of the present invention can be used if necessary. Specific examples of the additive (D) include, but not particularly limited to, acid catalysts such as p-toluenesulfonic acid, dodecylbenzenesulfonic acid, camphorsulfonic acid and phosphoric acid compounds, base catalysts such as amine compounds, antifoaming agents, leveling agents, , A viscosity adjusting agent, and a wax. One or more of these may be used. The additive (D) can be freely compounded so long as it does not affect the physical properties of the coating film. Preferably, it is 0.1 part by mass or more and 5 parts by mass or less based on 100 parts by mass of the copolymerizable polyester (A).

≪ Organic solvent (E) >

The organic solvent (E) used in the present invention is not particularly limited as long as it dissolves the copolymer polyester (A). Specific examples of the solvent include aromatic hydrocarbons such as toluene, xylene and Solvesso (registered trademark), esters such as ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate and dibasic acid ester, methyl ethyl ketone, methyl isobutyl ketone , Ketones such as cyclohexanone and isophorone, ethers such as n-butyl cellosolve and t-butyl cellosolve and the like can be arbitrarily selected and compounded in consideration of solubility and evaporation rate (dryness) do. Among them, a mixed solvent of aromatic hydrocarbons and ketones is preferable, and a mixed solvent of sorbese and cyclohexanone is preferable.

The amount of the organic solvent (E) is preferably 50 parts by mass or more, more preferably 100 parts by mass or more, and even more preferably 150 parts by mass or more, based on 100 parts by mass of the copolymer polyester (A). It is preferably 500 parts by mass or less, more preferably 400 parts by mass or less, and further preferably 300 parts by mass or less. If the amount is too small, the storage stability may be deteriorated. If the amount is excessively large, the cost may be impaired, which may be impractical.

<Metal primer coating>

The metal primer coating material of the present invention is a coating material containing a copolymerizable polyester (A), a crosslinking agent (B), a pigment (C), an additive (D) and an organic solvent (E).

<Metal stamp plate>

The metal coated board of the present invention has a metal primer coating of the present invention as a primer layer on at least one side of a metal sheet. The coating method is not particularly limited, but it can take a roll coater coating, a curtain flow coater coating, an air spray coating, an electrostatic spray coating, a screen printing, and the like.

The metal plate is not particularly limited, and examples of the metal plate include a heat-stretched steel plate, an electrogalvanized steel plate, an alloy-plated steel plate, an aluminum zinc alloy plated steel plate, an aluminum plate, a tin-plated steel plate, a stainless steel plate, a copper plate, Nickel-plated steel sheet, ultra-thin tin-plated steel sheet, chrome-treated steel sheet and the like are preferable.

Example

Hereinafter, the present invention will be described in detail with reference to Examples. In the present Examples and Comparative Examples, parts denote parts by mass.

(1) Measurement of Composition of Copolymer Polyester (A)

The molar ratio of the polyvalent carboxylic acid component and the polyhydric alcohol component constituting the copolymer polyester (A) was determined using a ¹ H-NMR spectrometer (hereinafter abbreviated as NMR in some cases) of 400 MHz . Chloroform was used as the solvent. When the acid value of the copolyester was increased by acid backbone, the molar ratio of each component was calculated assuming that the total amount of acid components other than the acid component used in the acid backbone was 100 mol%.

(2) Measurement of number average molecular weight of copolymerized polyester (A)

4 mg of the sample (copolymerizable polyester (A)) was dissolved in 4 mL of tetrahydrofuran and then filtered through a membrane filter made of polysulfide ethylene having a pore diameter of 0.2 μm. This was used as a sample solution and analyzed by gel permeation chromatography (GPC). The device was measured using a TOSOH HLC-8220, a detector using a differential refractive index detector, and a mobile phase using tetrahydrofuran at a flow rate of 1 mL / min and a column temperature of 40 ° C. Columns KF-802, 804L and 806L manufactured by Showa Denko KK were used. As the molecular weight standard, monodisperse polystyrene was used, and the number average molecular weight was taken as a standard polystyrene conversion value, and a portion corresponding to a molecular weight of less than 1000 was discarded and calculated.

(3) Measurement of glass transition temperature

The measurement was carried out using a differential scanning calorimeter (SII, DSC-200). 5 mg of the sample (copolymer polyester (A)) was placed in an aluminum push-cover type container, sealed, and cooled to -50 ° C using liquid nitrogen. Then, the temperature was raised to 150 ° C. at a rate of 20 ° C./min. In the endothermic curve obtained during the temperature raising process, an extension line of the baseline before the endothermic peak (below the glass transition temperature) (Tangent line indicating the maximum inclination between the beginning of the peak and the peak of the peak), and the glass transition temperature (Tg, unit: 占 폚).

(4) Measurement of acid value

0.2 g of the sample (copolymer polyester (A)) was crystallized and dissolved in 40 ml of chloroform. Subsequently, titration was performed with an ethanol solution of 0.01 N potassium hydroxide. Phenolphthalein was used as an indicator. With respect to the sample, to obtain potassium hydroxide equivalent, the measurement sample 10 ⁶ g in terms of per equivalent, and the unit was the equivalent / 10 ⁶ g.

(5) Measurement of reduced viscosity [? Sp / c (dl / g)]

0.10 g of a sample (copolymerizable polyester (A)) was dissolved in 25 cc of a mixed solvent of phenol / tetrachloroethane (weight ratio 6/4) and measured at 30 캜 using a Ubbelohde viscometer.

Production examples of the copolyester (A) of the present invention and the copolyester as a comparative example are shown below.

Production Example of Copolymerized Polyester (a1)

809 parts of dimethyl terephthalate, 793 parts of dimethyl isophthalate, 19 parts of trimellitic acid anhydride, 407 parts of ethylene glycol, 540 parts of neopentyl glycol, 287 parts of triethylene glycol, and 0.45 parts of orthotitanic acid as a catalyst were added to a reaction vessel equipped with a stirrer, a condenser and a thermometer Tetrabutyl was fed in an amount of 0.03 mol% based on the total amount of the acid components, and the transesterification reaction was carried out while the temperature was elevated from 160 DEG C to 220 DEG C over 4 hours and a demethanizer step. Next, in the polycondensation reaction step, the system was depressurized to 5 mmHg over 20 minutes, and the temperature was further raised to 250 ° C. Subsequently, the pressure was reduced to 0.3 mmHg or less, and a polycondensation reaction was conducted for 60 minutes, and this was taken out. As a result of the compositional analysis by NMR, the obtained copolymer polyester (a1) was found to have a molar ratio of terephthalic acid / isophthalic acid / trimellitic acid / ethylene glycol / neopentyl glycol / triethylene glycol = 50/49/1/40/40/20 Mole ratio]. The number average molecular weight was 7000, the glass transition temperature was 40 占 폚, and the acid value was 20 eq / 10 ⁶ g. The results are shown in Table 1.

Production Example of Copolymerized Polyesters (a2) to (a10)

The copolyesters (a2) to (a11) of the present invention were prepared by changing the kind and blending ratio of the raw materials in accordance with the production example of the copolyester (a1). The results are shown in Table 1.

Example 1

Preparation of metal primer coating (A1)

80 parts of the copolymer polyester (a1) was dissolved in a mixed solvent of 100 parts of cyclohexanone and 100 parts of Solvesso 150. 50 parts of calcium silicate, 13 parts of aluminum tripolyphosphate and 37 parts of titanium oxide were added thereto and dispersed for 6 hours using a shaker. As a crosslinking agent, 20 parts of Cymel 303 (a melamine curing agent, manufactured by Ornex Company) and 0.2 parts of dodecylbenzenesulfonic acid as a curing catalyst were added to obtain the metal primer coating material (A1) of the present invention.

Examples 2 to 10 and Comparative Examples 1 to 3

Preparation of metal primer coatings (A2) to (K1)

Metal primer coatings (A2) to (K1), which are examples or comparative examples of the present invention, were obtained in the same manner as the metal primer coating (A1). The compounding ratios are shown in Table 2.

Evaluation of metal coating plates

Specimen Creation

A hot-dip galvanized steel sheet having a thickness of 0.5 mm was prepared, and the metal primer coating described in the above-mentioned examples was coated so as to have a film thickness after drying of 5 탆 and dried at 210 캜 for 45 seconds. Further, 16 parts by mass of copolymerized polyester resin having a number average molecular weight of 15000 and a glass transition temperature of 38 占 폚 so as to have a film thickness after drying of 15 占 퐉, 4 parts by mass of melamine resin, 20 parts by mass of titanium oxide and 60 parts by mass of cyclohexanone , And dried at 250 DEG C for 60 seconds to obtain a test piece of a metal coating plate.

(Film hardness)

A pencil core was slid at an angle of 45 degrees with respect to the coating surface of the metal coating plate test piece, and slid forward in a load of 1 kg. The hardness of the core of the pencil was determined by hardness, and the maximum hardness without scratching was evaluated by using H, F, HB, B, and 2B. The higher the hardness, the higher the hardness of the coating and the less likely it is to scratch.

Evaluation standard

○: H or more

?: F to B

×: 2B or less

(Flexibility)

The above-mentioned metal-coated plate test piece was subjected to a bending test at 180 占 폚 at 25 占 폚, and cracks of the coated film were visually observed. 2T means that the coating film does not crack when the metal plate having the same thickness as the test metal plate is bent between two sheets. The smaller the number, the better the bendability.

O: 0 to 2T

?: 3 to 4 T

×: 5 T or more

(Corrosion resistance)

The ends of the above-mentioned metal-coated plate test piece were protected with a tape and cross-cut with a cutter knife to the surface was carried out and then subjected to a neutral salt spray test for 500 hours by the method described in JIS Z2371-2015. The magnitude of the expansion from the crosscut portion of the coated plate after the test was measured. The smaller the magnitude of expansion, the better the corrosion resistance.

Evaluation standard

?: Diameter of 3 mm or less

?: Diameter exceeding 3 mm and less than 7 mm

X: diameter of 7 mm or more

(High solids suitability (solution viscosity))

The obtained copolymer polyester (A) was dissolved in a mixed solution of cyclohexanone and Solvesso 150 in the same weight ratio as a solid solution concentration of 60% by weight, and a B type rotational viscometer (EM type, manufactured by Tokyo Keiki Co., , 12 rpm) was used to measure the solution viscosity at 25 ° C. If the solution viscosity exceeds 200 poise, handling during the production of the coating becomes difficult.

Evaluation standard

○: Less than 130 poise

DELTA: 130 poise or more and 200 poise or less

×: exceeding 200 poise

(Chemical resistance)

The end portion of the metal coated plate test piece was protected with a tape, immersed in an aqueous solution of 5% by weight of sodium hydroxide for 48 hours in an atmosphere of 25 占 폚, and then the appearance was visually evaluated. The smaller the swelling, the better the chemical resistance.

○: no swelling ~ slight swelling less than 1 mm in diameter

Δ: Large swelling of 1 mm or more in diameter

X: Peeling of the coating film

The copolymer polyester and coating composition of the present invention are excellent in workability, corrosion resistance and chemical resistance and are useful as a resin for a primer coating of a metal plate. And is particularly useful as a component used in coil coating for household appliances.

Claims (6)

A copolymerized polyester comprising a polycarboxylic acid component and a polyhydric alcohol component as copolymer components, wherein the content of the aromatic dicarboxylic acid component is 95 to 100 mol%, the content of the aliphatic dicarboxylic acid component (1) is from 1 to 30 mol%, and the glass transition temperature is from 25 to 50 캜, when the content of the glycol component is 0 to 5 mol% and the total polyhydric alcohol component is 100 mol% (A). &Lt; / RTI &gt;

In the general formula (1), n is an integer of 3 or more. The copolyester (A) according to claim 1, wherein the number average molecular weight is in the range of 4000 to 9000. The copolyester (A) according to any one of claims 1 to 3, which does not contain an aliphatic dicarboxylic acid component. 4. The copolyester (A) according to any one of claims 1 to 3, wherein the general formula (1) is triethylene glycol. A metal primer coating composition comprising the copolymerizable polyester (A), the crosslinking agent (B), the pigment (C), the additive (D) and the organic solvent (E) according to any one of claims 1 to 4. A metal coated board having the primer layer of the metal primer coating according to claim 5.