Polyester resin with little foreign matter and coating composition or adhesive composition using the same

Abstract

[Problem] To provide a polyester resin of good productivity and good color tones, the polyester resin containing fewer foreign substances, the polyester resin further having good adhesiveness to a metal substrate and a good curing capability. [Solution] A polyester resin containing titanium in an amount of 2-10 mass ppm in terms of metal, and zinc in an amount of 50-100 mass ppm in terms of metal, 5 g of the polyester resin containing at most 15 foreign substances.

Description

[Technical Field]

[0001] The present invention relates to a polyester resin having a low content of foreign matter and a coating composition or adhesive composition using the same. More specifically, the present invention relates to a polyester resin suitable for dry laminating adhesives for metal substrates, coatings for precoating metals, and can coatings. [Background technology]

[0002] Titanium compounds and zinc compounds have been used as catalysts in the industrial production of polyester resins from dicarboxylic acids or their ester-forming derivatives and diol components (see, for example, Patent Documents 1 and 2). However, these conventional techniques have had problems in that increasing the amount of catalyst added to increase polymerization activity can cause gelation during polymerization and deterioration in thermal stability, storage stability, and color tone.

[0003] Patent Document 3 discloses a technology in which gelation can be suppressed in the reaction process by limiting the amounts of titanium and zinc catalysts added, polycondensation can be carried out efficiently without scattering of low molecular weight substances during polycondensation, and polyester with excellent thermal stability (suppression of black foreign matter and gelation) can be produced. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-268087 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-159872 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-1656 Summary of the Invention Problems to be Solved by the Invention

[0005] However, Patent Document 3 does not take into consideration the zinc salts produced as foreign matter by reaction with the carboxylic acid raw material, and there is a problem in that when the polyester resin is dissolved in a solvent or dispersed in water, zinc-derived foreign matter precipitates as insoluble matter. More specifically, when foreign matter precipitates, defects due to the foreign matter occur during varnish application, such as poor appearance of the coating film in pre-coated metal or can paint applications, and poor adhesion to the substrate in dry lamination adhesives for metal substrates.

[0006] The present invention has been made in view of the problems of the prior art. That is, an object of the present invention is to provide a polyester resin that is easy to produce, has good color tone, contains little foreign matter, and has good adhesion to metal substrates and good curability.

[0007] The present inventors have conducted extensive research to solve the above problems and have completed the present invention, which comprises the following features.

[0008] Titanium is 2 to 10 mass ppm in metal equivalent and zinc is 50 to 90 It is a polyester resin containing ppm by mass, The content of antimony converted to metal is 1 mass ppm or less, And the content of foreign matter in 5 g of the polyester resin is 12 Polyester resin having a molecular weight of 100 or less.

[0009] The foreign matter preferably contains a zinc salt of a polycarboxylic acid.

[0010] The polyester resin preferably has a reduced viscosity of 0.10 dl / g or more, an acid value of 50 eq / t or more, and a trimellitic anhydride content of 1000 mass ppm or less.

[0011] a polyester resin composition containing the polyester resin and an isocyanate curing agent or a phenolic curing agent; a coating composition or adhesive composition containing the polyester resin composition;

[0012] The method for producing the polyester resin comprises producing a prepolymer in the presence of a titanium catalyst but in the absence of a zinc catalyst, and then polycondensing the prepolymer in the presence of a titanium catalyst and a zinc catalyst. [Effects of the Invention]

[0013] The present invention makes it possible to provide a polyester resin that is excellent in productivity, color tone, contains little foreign matter, and has excellent metal adhesion and curability. [Brief explanation of the drawings]

[0014] [Figure 1] Figure 1 is a scanning electron microscope (SEM) photograph of foreign matter contained in polyester resin. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention will be described in detail below.

[0016] <Polyester resin> The polyester resin of the present invention must contain titanium in an amount of 2 ppm by mass or more and 10 ppm by mass or less, calculated as the metal. In order to increase productivity, facilitate the production of a high-molecular-weight polyester resin, and improve solid storage stability and metal adhesion, the titanium content is preferably 3 ppm by mass or more, more preferably 4 ppm by mass or more, and even more preferably 5 ppm by mass or more. Furthermore, in order to improve the color tone of the polyester resin, the titanium content is preferably 9 ppm by mass or less, more preferably 8 ppm by mass or less, and even more preferably 7 ppm by mass or less.

[0017] The polyester resin of the present invention must contain zinc in an amount of 50 ppm by mass or more and 100 ppm by mass or less, calculated as the metal. The zinc content is preferably 55 ppm by mass or more, and more preferably 60 ppm by mass or more, because this improves the curability of the polyester resin, particularly the curability (reactivity) with an isocyanate curing agent. Furthermore, the zinc content is preferably 95 ppm by mass or less, and more preferably 90 ppm by mass or less, because this reduces the generation of zinc-derived foreign matter, improves the color tone of the polyester resin, improves dissolution stability, and reduces the amount of foreign matter.

[0018] The polyester resin of the present invention preferably has an antimony content of 10 ppm by mass or less in terms of metal. The lower the content, the better, as this suppresses the generation of foreign matter containing antimony metal, and the lower the content, preferably 5 ppm by mass or less, more preferably 1 ppm by mass or less, and even more preferably 0 ppm.

[0019] In the present invention, the titanium content and zinc content in the polyester resin are values ​​analyzed by the dry ashing / acid decomposition method, and the antimony content is a value analyzed by the yttrium nitrate method (nitrate ashing method).

[0020] The titanium and zinc contained in the polyester resin may be contained as simple metals or as compounds. In either case, it is sufficient that they are contained in a predetermined amount converted to metals. It is preferable that they are contained in the same composition as the catalyst used in polymerizing the polyester resin.

[0021] Examples of titanium compounds include titanium halide compounds such as titanium tetrafluoride, titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, and hexafluorotitanic acid; titanic acid compounds such as α-titanic acid, β-titanic acid, ammonium titanate, sodium titanate, peroxotitanic acid complexes, and anatase; inorganic acid titanium salt compounds such as titanium sulfate, titanium nitrate, titanium phosphate, and titanium silicate; titanium organometallic compounds such as tetramethyltitanium, tetraethyltitanium, tetrabenzyltitanium, tetraphenyltitanium, and bis(cyclopentadienyl)titanium dichloride; aryloxytitanium compounds such as tetraphenoxytitanium; and siloxytitanium compounds such as tetrakis(trimethylsiloxy)titanium and tetrakis(triphenylsiloxy)titanium. Titanium acetate, titanium propionate, titanium lactate, titanium citrate, titanium tartrate, potassium titanyl oxalate, organic titanium sulfonates, organic titanium phosphonates and other organic acid titanium salt compounds, titanium amide compounds such as tetrakis(diethylamino)titanium and titanium tetrapyrrolide, titanium tetraalkoxides such as titanium tetramethoxide, titanium tetraethoxide, titanium tetra-n-propoxide, titanium tetraisopropoxide, titanium tetra-n-butoxide, and titanium tetra-2-ethylhexoxide, poly(dibutyl titanate), Ti7O4(OC2H5) 20 , Ti 16 O 16 (OC2H5) 32condensed titanium alkoxides such as titanium chlorotriisopropoxide and titanium dichlorodiethoxide, halogen-substituted titanium alkoxides such as titanium acetate triisopropoxide and titanium methacrylate triisopropoxide, carboxylic acid-substituted titanium alkoxides such as titanium acetate triisopropoxide and titanium methacrylate triisopropoxide, phosphonic acid-substituted titanium alkoxides such as titanium tris(dioctylpyrophosphate) isopropoxide and titanium (monoethylphosphate) triisopropoxide, sulfonic acid-substituted titanium alkoxides such as titanium tris(dodecylbenzenesulfonate) isopropoxide, ammonium hexaethoxy titanate, sodium hexaethoxy titanate, Examples of suitable titanium alkoxides include alkoxy titanates such as hexaethoxytitanate, potassium hexaethoxytitanate, and sodium hexa-n-propoxytitanate, β-diketonate-substituted titanium alkoxides such as titanium bis(2,4-pentanedionato)diisopropoxide and titanium bis(ethylacetoacetate)diisopropoxide, α-hydroxycarboxylic acid-substituted titanium alkoxides such as titanium bis(ammonium lactate)diisopropoxide, and aminoalcohol-substituted titanium alkoxides such as titanium bis(triethanolamine)diisopropoxide and 2-aminoethoxytitanium triisopropoxide. Among these, tetra-n-butyl titanate is preferred.

[0022] Examples of zinc compounds include zinc powder and other simple substances, zinc salts of organic acids such as zinc acetate and zinc acetylacetonate, zinc salts of inorganic acids such as zinc carbonate, zinc chloride, zinc nitrate, zinc phosphate, zinc sulfate, zinc borate and zinc aluminate, other organic zinc compounds such as dimethyl zinc and diethyl zinc, and other inorganic zinc compounds such as zinc oxide, zinc sulfide and zinc chloride. Of these, zinc acetate dihydrate is preferred.

[0023] The foreign matter in the present invention is a matter containing at least a zinc salt of a polycarboxylic acid. Specifically, it is a zinc salt of a polycarboxylic acid, which is a raw material for polyester resin, such as a zinc salt of terephthalic acid, a zinc salt of isophthalic acid, a zinc salt of orthophthalic acid, or a zinc salt of trimellitic acid. Among these, the zinc salt of terephthalic acid, a zinc salt of isophthalic acid, or a zinc salt of trimellitic acid is included as the main component. The zinc salt of a polycarboxylic acid contained in the foreign matter is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass.

[0024] The polyester resin of the present invention has a content of the above-mentioned foreign matter of 15 or less per 5 g of the polyester resin (hereinafter also referred to as "15 / 5 g"). The lower the content of foreign matter, the better, and it is preferably 14 or less (14 / 5 g), more preferably 12 or less (12 / 5 g), even more preferably 10 or less (10 / 5 g), still more preferably 9 or less (9 / 5 g), and particularly preferably 8 or less (8 / 5 g). There is no particular lower limit, and industrially it is sufficient as long as it is 1 or more (1 / 5 g), and it is also acceptable to have 2 or more (2 / 5 g).

[0025] Foreign matter is counted by dissolving 5 g of polyester resin in 100 mL of a mixed solvent of phenol / tetrachloroethane (60 / 40 (mass ratio)), filtering through a membrane filter with a pore size of 0.5 μm, and observing (visually) the filtered material with an SEM. Figure 1 is an SEM photograph of the filtered material, and the areas marked with a circle are foreign matter.

[0026] In the present invention, the foreign matter analysis means preferably uses SEM-EDX (Scanning Electron Microscope-Energy Dispersive X-ray Spectroscopy), which can effectively distinguish between impurities derived from organic substances such as gels or metals other than zinc and foreign matter containing zinc salts of polycarboxylic acids.

[0027] The major axis of the foreign matter is preferably 5 μm or more, more preferably 8 μm or more, and even more preferably 10 μm or more. It is also preferably 80 μm or less, more preferably 70 μm or less, and even more preferably 60 μm or less. The polyester resin of the present invention can reduce the number of foreign matters within the above range to 15 or less per 5 g.

[0028] Since the polyester resin of the present invention contains no more than a predetermined amount of foreign matter, defects due to foreign matter do not occur when the varnish (polyester resin composition) is applied. For example, when used in pre-coated metals and can coatings, the appearance of the coating film does not deteriorate, and when used as a dry lamination adhesive for metal substrates, poor adhesion to the substrate does not occur.

[0029] The polyester resin of the present invention is preferably a polyester having a polycarboxylic acid component and a polyhydric alcohol component as copolymerization components.

[0030] Dicarboxylic acid components include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, unsaturated aliphatic dicarboxylic acids, and alicyclic dicarboxylic acids. Examples include terephthalic acid, isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, 5-lithium sulfoisophthalic acid, 2-sodium sulfoterephthalic acid, 4,4'-diphenylmethanedicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and 4,4'-stilbenedicarboxylic acid. These can be used alone or in combination. Aliphatic dicarboxylic acids include, but are not limited to, pimelic acid, suberic acid, adipic acid, azelaic acid, sebacic acid, dodecanoic diacid, and dimer acid. These can be used alone or in combination. Unsaturated aliphatic dicarboxylic acids include fumaric acid, maleic acid, itaconic acid, hexahydrophthalic acid, and tetrahydrophthalic acid. Alicyclic dicarboxylic acids such as 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid can also be used. Among these, aromatic dicarboxylic acids or aliphatic dicarboxylic acids are preferred. As aromatic dicarboxylic acids, terephthalic acid or isophthalic acid is more preferred, and as aliphatic dicarboxylic acids, sebacic acid is more preferred.

[0031] When the total polycarboxylic acid components in the polyester resin are taken as 100 mol%, the aromatic dicarboxylic acid preferably accounts for 50 mol% or more, more preferably 60 mol% or more, and even more preferably 70 mol% or more. Here, if an acid anhydride or the like is added (acid addition) after polyester polymerization to impart an acid value, the total amount of the polycarboxylic acid components and the polyhydric alcohol components may exceed 200 mol%. In this case, the total amount of the composition excluding the components to which the acid anhydride or the like has been added (post-added) is calculated as 200 mol%.

[0032] Trivalent or higher polycarboxylic acids can also be used. Examples of trivalent or higher polycarboxylic acid components include polycarboxylic acids such as trimellitic acid, pyromellitic acid, benzophenonetetracarboxylic acid, biphenylsulfonetetracarboxylic acid, and biphenyltetracarboxylic acid, as well as their anhydrides. These trivalent or higher polycarboxylic acid components may be used alone or in combination of two or more. Among these, trimellitic acid or trimellitic anhydride is preferred.

[0033] Examples of the glycol component include aliphatic glycols, alicyclic glycols, aromatic glycols, and polyalkylene glycols. Specific examples include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, neopentyl glycol (NPG), 3-methyl-1,5-pentanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, and dimethyl glycol. Examples of suitable glycol components include aliphatic glycols such as methyltricyclodecane, diethylene glycol, triethylene glycol, dipropylene glycol, and tripropylene glycol; alicyclic glycols such as 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol; aromatic glycols such as bisphenol A, bisphenol S, bisphenol C, bisphenol Z, bisphenol AP, and 4,4'-biphenol, and their ethylene oxide adducts or propylene oxide adducts; and polyalkylene glycols such as polyethylene glycol and polypropylene glycol. These glycol components can be used alone or in combination. Among these, aliphatic glycols and alicyclic glycols are preferred. Ethylene glycol and neopentyl glycol are preferred as aliphatic glycols, and 1,4-cyclohexanedimethanol is preferred as a alicyclic glycol.

[0034] Trihydric or higher polyhydric alcohols can also be used. Examples of trihydric or higher polyhydric alcohol components include glycerin, trimethylolethane, trimethylolpropane, mannitol, sorbitol, pentaerythritol, and α-methyl glucoside. These trihydric or higher polyhydric alcohol components can be used alone or in combination of two or more.

[0035] When the total polyhydric alcohol components in the polyester resin is taken as 100 mol %, the aliphatic glycol preferably accounts for 50 mol % or more, more preferably 60 mol % or more, and even more preferably 65 mol % or more.

[0036] Furthermore, biomass-derived glycols can also be used as the glycol component. Examples of biomass-derived glycol components include, but are not limited to, ethylene glycol and neopentyl glycol. For example, biomass-derived ethylene glycol is obtained from ethanol (biomass ethanol) produced from biomass as a raw material. For example, biomass-derived ethylene glycol can be obtained by converting biomass ethanol into ethylene oxide using a conventionally known method to produce ethylene glycol. Alternatively, commercially available biomass ethylene glycols may be used; for example, biomass ethylene glycols commercially available from India Glycoal Limited and biomass neopentyl glycols (Neeture series, N20, N40, N100) commercially available from Perstorp Limited can be suitably used.

[0037] In a method for producing a polyester resin, an esterification reaction (hereinafter also referred to as an esterification step) is preferably followed by a polycondensation reaction (hereinafter also referred to as a polycondensation step). That is, in the esterification step, the dicarboxylic acid and diol components are esterified at preferably 150 to 250°C. In the esterification step, a low-molecular-weight prepolymer (oligomer) or the like is produced. The reaction temperature in the esterification step is more preferably 160 to 245°C, and even more preferably 180 to 240°C. The reaction time can be appropriately set depending on the reaction temperature, and is preferably 1 to 10 hours, and more preferably 2 to 8 hours. Next, in the polycondensation step, a polycondensation reaction is carried out preferably at 230 to 300°C while reducing the pressure in the system. The reaction temperature in the polycondensation step is more preferably 240 to 290°C, and even more preferably 250 to 280°C. The reaction time can be appropriately set depending on the reaction temperature, and is preferably 0.5 to 5 hours, and more preferably 1 to 3 hours. The degree of vacuum is preferably 10 mmHg or less, more preferably 5 mmHg or less, even more preferably 1 mmHg or less, and particularly preferably 0.5 mmHg or less. There is no particular lower limit, and from an industrial perspective, the pressure should be 0.01 mmHg or more, and even 0.05 mmHg or more is acceptable. The target polyester resin can be obtained by the above production method.

[0038] The titanium catalyst may be present in a predetermined amount during the polycondensation step. That is, it may be added during the esterification step, after the esterification step is completed, before the polycondensation step, or after the start of the polycondensation step. It is preferably added during the esterification step. The amount of titanium catalyst added is proportional to the titanium content in the polyester resin to be produced. Therefore, the amount is preferably 2 ppm by mass or more, more preferably 3 ppm by mass or more, even more preferably 4 ppm by mass or more, and particularly preferably 5 ppm by mass, calculated as titanium metal, relative to the polyester resin. Furthermore, it is preferably 10 ppm by mass or less, more preferably 9 ppm by mass or less, even more preferably 8 ppm by mass or less, and particularly preferably 7 ppm by mass or less.

[0039] It is preferable to add a predetermined amount of zinc catalyst during the polycondensation step (after the esterification step). If the zinc catalyst is present during the esterification step, the zinc catalyst is more likely to form a salt with unreacted polycarboxylic acid, which makes it easier to produce foreign matter containing a zinc salt of the polycarboxylic acid. In other words, adding a predetermined amount during the polycondensation step can prevent the production of foreign matter. The amount of zinc catalyst added is proportional to the zinc content in the polyester resin to be produced. Therefore, the amount is preferably 50 ppm by mass or more, more preferably 55 ppm by mass or more, and even more preferably 60 ppm by mass or more, calculated as zinc metal, relative to the polyester resin. Furthermore, it is preferably 100 ppm by mass or less, more preferably 95 ppm by mass or less, and even more preferably 90 ppm by mass or less.

[0040] In order to impart metal adhesion to the polyester resin of the present invention and improve reactivity with a curing agent, the acid value of the polyester resin is preferably 40 eq / t or more, more preferably 50 eq / t or more, even more preferably 60 eq / t or more, even more preferably 70 eq / t or more, and particularly preferably 100 eq / t or more. By setting the acid value within the above range, metal adhesion and curability (curing speed) are improved. There is no particular upper limit for the acid value, but it is preferably 400 eq / t or less, more preferably 300 eq / t or less, and even more preferably 200 eq / t or less. By setting the acid value within the above range, the solid storage stability (reduced viscosity retention) of the polyester resin is improved.

[0041] The polyester resin of the present invention may be imparted with an acid value by any method. By imparting an acid value, effects such as improved curability with a curing agent and improved adhesion to metal materials may be obtained. Methods for imparting an acid value include a depolymerization method in which a polycarboxylic acid anhydride is added in the later stage of the polycondensation process, and a method in which a polycarboxylic acid is added to the prepolymer (oligomer) stage in the esterification process to increase the acid value, followed by a polycondensation reaction. The latter method of increasing the acid value in the esterification process is preferred because it can reduce the amount of unreacted trimellitic anhydride and trimellitic acid contained (remaining) in the polyester resin.

[0042] Another method for imparting an acid value is to adjust the molar ratio (diol component / dicarboxylic acid component) of the dicarboxylic acid component and the diol component (glycol component) charged in the esterification step. The molar ratio (diol component / dicarboxylic acid component) is preferably greater than 1.0 and not greater than 1.1, more preferably 1.01 or greater and 1.08 or less. By adjusting the ratio to be equal to or greater than the lower limit, the polyester resin can be made to have a high molecular weight without polymerization failure. Furthermore, by adjusting the ratio to be equal to or less than the upper limit, a prepolymer with a high acid value can be obtained, and an acid value can be imparted to the polyester resin. Furthermore, metal adhesion and curability are improved.

[0043] The amount of trimellitic anhydride component contained (residual) in the polyester resin of the present invention is preferably 1,000 ppm by mass or less. Because this improves the solution stability of the polyester resin, it is more preferably 500 ppm by mass or less, even more preferably 100 ppm by mass or less, even more preferably 50 ppm by mass or less, and particularly preferably 20 ppm by mass or less. By keeping the amount 1,000 ppm by mass or less, acid-induced hydrolysis of the polyester resin is suppressed, resulting in good dissolution stability of the polyester resin. Since a lower amount of trimellitic anhydride component contained in the polyester resin is preferable, the lower limit is not particularly limited, but industrially, it may be 1 ppm by mass or more, or even 2 ppm by mass or more. Here, the trimellitic anhydride component contained in the polyester resin mainly refers to trimellitic anhydride component that did not react (unreacted) in the esterification step or polycondensation step, and includes, for example, trimellitic anhydride that has simply reacted with water to open the ring. That is, the trimellitic anhydride component is the total amount of trimellitic anhydride and trimellitic acid.

[0044] In the present invention, the content of the trimellitic anhydride component contained in the polyester resin can be measured by HPLC.

[0045] The reduced viscosity (symbol: ηsp / c, unit: dl / g) of the polyester resin of the present invention is not particularly limited, but is preferably 0.10 dl / g or more, more preferably 0.40 dl / g or more. If it is 0.10 dl / g or more, the strength of the coating film and metal adhesion of the adhesive composition containing the polyester resin are improved. In addition, handling during application and storage stability are improved. The reduced viscosity in the present invention is a value determined by the method described in the Examples. There is no particular upper limit to the reduced viscosity, but it is preferably 2.00 dl / g or less, more preferably 1.00 dl / g or less. By keeping it below the upper limit, the solvent solubility of the polyester resin is improved and the dissolution stability is improved.

[0046] <Curing agent> The curing agent is preferably one that reacts with the polyester resin of the present invention to form a crosslinked structure, and examples thereof include phenol curing agents and isocyanate curing agents.

[0047] The phenolic curing agent is preferably a resol-type phenolic resin synthesized from a phenolic compound. Examples of trifunctional or higher phenolic compounds include phenol, m-cresol, m-ethylphenol, 3,5-xylenol, m-methoxyphenol, bisphenol-A, and bisphenol-F. Examples of bifunctional phenolic compounds include o-cresol, p-cresol, p-tert-butylphenol, p-ethylphenol, 2,3-xylenol, and 2,5-xylenol. These compounds have two or more methylolable functional groups per molecule of the phenolic compound and can be synthesized by methylolation with formaldehyde or the like. These compounds can be used alone or in combination.

[0048] The blending ratio of these trifunctional or higher phenolic compounds to bifunctional phenolic compounds is arbitrarily blended depending on the required coating film (cured film), but is preferably 1 / 99 to 100 / 0 (parts by mass). For example, if the coating film requires hardness and acid resistance, it is preferable to use more than 30 parts by mass of trifunctional or higher phenolic compounds, and if the coating film requires flexibility and low residual stress after processing, it is preferable to use less than 50 parts by mass of trifunctional or higher phenolic compounds.

[0049] The formaldehydes used to convert these phenolic compounds into phenolic resins include formaldehyde, paraformaldehyde and trioxane, and these can be used alone or in combination of two or more.

[0050] The alcohol used to alkyl-etherify a portion of the methylol groups of the methylolated phenolic resin may be a monohydric alcohol having 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms, such as methanol, ethanol, n-propanol, n-butanol, isopropanol, isobutanol, and tert-butanol. From the viewpoints of compatibility with the polyester resin (A) and reaction curability, n-butanol is preferred.

[0051] The phenolic resin has an average of 0.3 or more alkoxymethyl groups per phenolic nucleus, preferably 0.5 to 3, in terms of reactivity and compatibility with polyester resins. If the number is less than 0.3, the curing with the polyester resin may be poor, resulting in reduced strength of the cured coating film. There is no particular upper limit, but if the upper limit is exceeded, stability when blended with a curing agent may be impaired.

[0052] As a method for obtaining a phenolic resin containing a mixture of these trifunctional or higher phenolic compounds and bifunctional phenolic compounds, the compounds may be mixed in any desired ratio before being converted into a phenolic resin with formaldehyde, or the trifunctional or higher phenolic compounds and bifunctional phenolic compounds may be separately converted into phenolic resins, and then these may be mixed in any desired ratio.

[0053] Examples of the isocyanate curing agent include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylene-1,4-diisocyanate, xylene-1,3-diisocyanate, tetramethylxylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylether diisocyanate, and 2-nitrodiphenyl 4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4 diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl- Examples of suitable diisocyanates include aromatic diisocyanates such as 4,4'-diisocyanate, aromatic polyisocyanates such as polymethylene polyisocyanate and crude tolylene diisocyanate, aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), decamethylene diisocyanate and lysine diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate (IPDI), hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate and hydrogenated diphenylmethane diisocyanate, and biuret, uretdione-modified, carbodiimide-modified, isocyanurate-modified, uretonimine-modified, adducts with polyols, and mixed modified products thereof. One or more of these can be selected and used. Furthermore, it may also be used in the form of a urethane precursor such as a prepolymer, modified product, derivative, or mixture, which is made of an isocyanate compound and an active hydrogen-containing compound such as a polyol or polyamine.

[0054] As the isocyanate curing agent, a blocked isocyanate curing agent obtained by blocking the terminal NCO group of an isocyanate compound may be used. Examples of blocking agents include phenolic compounds such as phenol, cresol, ethylphenol, and butylphenol, alcoholic compounds such as 2-hydroxypyridine, butyl cellosolve, propylene glycol monomethyl ether, benzyl alcohol, methanol, ethanol, n-butanol, isobutanol, and 2-ethylhexanol, active methylene compounds such as dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, and acetylaceton, mercaptan compounds such as butyl mercaptan and dodecyl mercaptan, and acetanilide. Examples of suitable amine compounds include acid amide compounds such as amide and acetic acid amide, lactam compounds such as ε-caprolactam, δ-valerolactam, and γ-butyrolactam, imidazole compounds such as imidazole and 2-methylimidazole, urea compounds such as urea, thiourea, and ethyleneurea, oxime compounds such as formamide oxime, acetaldoxime, acetone oxime, methyl ethyl ketoxime, methyl isobutyl ketoxime, and cyclohexanone oxime, and amine compounds such as diphenylaniline, aniline, carbazole, ethyleneimine, and polyethyleneimine. These compounds can be used alone or in combination of two or more.

[0055] The reaction between such a blocking agent and an isocyanate compound can be carried out, for example, at 20 to 200° C., using a known inert solvent or catalyst, if necessary. The blocking agent is preferably used in an amount of 0.7 to 1.5 times by mole relative to the terminal isocyanate group.

[0056] The blending ratio of the polyester resin to the curing agent in the polyester resin composition of the present invention is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, of the curing agent per 100 parts by mass of the polyester resin to improve the solvent resistance of the cured coating film. Furthermore, to avoid a decrease in the strength of the cured coating film due to remaining unreacted curing agent components, the blending ratio of the curing agent is preferably 30 parts by mass or less, more preferably 20 parts by mass or less.

[0057] A curing catalyst may be further added to the polyester resin composition. The inclusion of a catalyst can improve the performance of the cured film. When the curing agent is a phenolic resin, examples of the catalyst include sulfuric acid, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, naphthalenesulfonic acid, dinonylnaphthalenesulfonic acid, dinonylnaphthalenedisulfonic acid, camphorsulfonic acid, phosphoric acid, and amine-blocked versions of these (partially neutralized by adding an amine). One or more of these can be used in combination. From the standpoints of compatibility with polyester resins and hygiene, dodecylbenzenesulfonic acid and its neutralized products are preferred. When the curing agent is an isocyanate curing agent, examples include organotin compounds such as stannous octoate and dibutyltin dilaurate, and triethylamine. One or more of these can be used in combination.

[0058] The polyester resin composition of the present invention is preferably a solvent-based composition, and the solids concentration is preferably 20 to 60% by mass, more preferably 30 to 50% by mass. The solvent is used after the production of the polyester resin or during the production of the resin composition, and is further used as a diluent during coating. Usable solvents are not particularly limited, but examples include esters such as ethyl acetate, butyl acetate, and cellosolve acetate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ethers such as tetrahydrofuran and dioxane; and aromatic hydrocarbons such as toluene and xylene. Among these, ethyl acetate and methyl ethyl ketone are typically preferred in terms of cost, productivity, and safety.

[0059] The polyester resin and polyester resin composition of the present invention have excellent metal adhesion, curability, and storage stability, and can be suitably used in coating compositions and adhesive compositions. Examples of coatings include those for metal substrates, specifically pre-coated metal (PCM) coatings and can coatings. Examples of adhesives include dry lamination adhesives for bonding metal substrates such as aluminum foil to plastic films. [Example]

[0060] Examples will be given below to explain the present invention more specifically, but the present invention is not limited to these examples. The measured values ​​described in the examples were measured by the following methods. In the examples and comparative examples, "parts" simply refers to "parts by mass" and "%" refers to "% by mass".

[0061] (1) Measurement of resin composition The polyester resin was dissolved in deuterated chloroform and analyzed using a VARIAN 400-MR NMR instrument. 1 H-NMR analysis was carried out, and the molar ratio was determined from the ratio of the integral values.

[0062] (2) Quantitative determination of metal elements <Dry ashing and acid decomposition method (quantitative determination of titanium and zinc elements)> 0.5 g of sample (polyester resin) was weighed into a platinum crucible and pre-carbonized on a hot plate at 400 °C. Subsequently, ashing was performed for 8 hours at 550 °C using a Yamato Scientific FO610 electric furnace. After ashing, 3 mL of 6.0 N hydrochloric acid was added, and acid decomposition was performed on a hot plate at 100 °C, followed by heat treatment until the hydrochloric acid was completely evaporated. After acid decomposition, the solution was adjusted to a constant volume with 20 mL of 1.2 N hydrochloric acid. The treated solution was then measured using a high-frequency inductively coupled plasma optical emission spectrometer (SPECTROBLUE, Hitachi High-Tech Science Corporation). A blank test was separately conducted, and the amount of metal elements in the sample was quantified using a calibration curve prepared using standard solutions of the target elements. The amount of metal elements in the sample was calculated using the following formula. The content of an element in 0.5 g of sample can be calculated as follows. A = (BC) x 20 / 0.5 Element content in sample: A (mass ppm) Element concentration in pretreatment solution: B (mg / L) Element concentration in blank test solution (measurement blank): C (mg / L)

[0063] <Yttrium nitrate method (nitrate ashing method) (quantitative determination of antimony element)> 0.5 g of sample (polyester resin) was weighed into a platinum crucible, 5 mL of a 5% yttrium nitrate ethanol solution was added, and the mixture was pre-carbonized on a hot plate to 400 °C. The mixture was then ashed for 8 hours at 550 °C using a Yamato Scientific FO610 electric furnace. After ashing, 20 mL of 1.2 N hydrochloric acid was added to dissolve the nitrate, resulting in a measurement solution. Measurements were performed using a high-frequency inductively coupled plasma optical emission spectrometer (SPECTROBLUE, Hitachi High-Tech Science Corporation). A blank test was separately conducted, and the amount of metal elements in the sample was quantified using a calibration curve prepared with a standard solution of the target element. The amount of metal elements in the sample was calculated using the following formula. The content of an element in 0.5 g of sample can be calculated as follows: A = (BC) x 20 / 0.5 Element content in sample: A (mass ppm) Element concentration in pretreatment solution: B (mg / L) Element concentration in blank test solution (measurement blank): C (mg / L) The detection limit of this method is 1 mass ppm, and measurement results below the detection limit are expressed as <1 (mass ppm).

[0064] (3) Productivity evaluation In the present invention, the polymerization time is defined as the time required for the polycondensation step to reach a predetermined reduced viscosity (ηsp / c>0.50 dL / g) after the temperature reached 260°C and the vacuum level reached 0.3 mmHg or less. The polycondensation step was terminated when the polymerization time exceeded 100 minutes, and the polyester resin was removed. (judgement) ○: Polymerization time ≦ 100 min ×: Polymerization time > 100 minutes

[0065] (4) Measurement of color tone (color b value, Co-b) A polyester resin solution with a solid content of 30% by mass was prepared by dissolving the polyester resin in methyl ethyl ketone / toluene = 1 / 1 (mass ratio) at 25 ° C. The color b value of the polyester resin solution was measured using a petroleum product color tester (manufactured by Nippon Denshoku Industries Co., Ltd., OME-2000).

[0066] (5) Measurement of the number of foreign objects Five grams of polyester resin was added to 80 mL of a phenol / tetrachloroethane (6 / 4 (mass ratio)) mixed solvent and dissolved by stirring at 135°C for 2 hours. The solution was then filtered through a 0.5 μm pore size polytetrafluoroethylene (PTFE) filter, and the residue was observed (visually) and counted using a SEM-EDX (JEOL Ltd., JSM-6510A) (magnification: 100x, signal: SEI (secondary electron image), focal length: 10 mm, applied voltage: 15 kV, vacuum mode: 0.1 mPa). When a large amount of foreign matter was found on the entire surface of the filter and it was difficult to count, the filter was evaluated as "X".

[0067] (6) Measurement of reduced viscosity (ηsp / c, unit: dl / g) (initial value) A 0.1g ± 0.005g sample of polyester resin is dissolved in a phenol / tetrachloroethane (6 / 4 (mass ratio)) mixed solvent at approximately 50°C, and the solution is made up to 25mL in a measuring flask to prepare a sample solution. The sample solution is then placed in a viscosity tube and placed in a 30°C water bath for 15-20 minutes so that the sample solution reaches 30°C. Once the specified temperature is reached, the drop time is measured while checking the marked line on the viscosity tube, and the reduced viscosity (unit: dl / g) is calculated from the difference in the drop time for the blank solvent. The calculation formula is shown in Equation 1. Formula 1: {(Drop time of sample solution) - (Drop time of blank)} / (Drop time of blank) / (Mass of polyester resin x 100 / 25)

[0068] (7) Measurement of acid value (AV, unit: eq / t) 0.2 g of a polyester resin sample was dissolved in 40 ml of chloroform and titrated with 0.01 N potassium hydroxide ethanol solution to obtain 10% of the polyester resin. 6 The equivalent weight per gram (eq / t) was calculated. Phenolphthalein was used as an indicator.

[0069] (8) Solid storage stability (reduced viscosity retention rate) The polyester resin was stored in a polyethylene bag at a temperature of 40°C and a humidity of 50% for three months, and the presence or absence of a decrease in molecular weight was checked. The decrease in molecular weight was evaluated by the reduced viscosity retention rate. Reduced viscosity retention rate (%) = (reduced viscosity of polyester resin after 3 months of storage) / (initial reduced viscosity of polyester resin) × 100 The reduced viscosity at the start of storage is taken as the initial value.

[0070] (9)Dissolution stability A polyester resin was dissolved in ethyl acetate to a solid content of 30% by mass to prepare a resin solution. The resin solution was stored in a static state at a temperature of 40°C and a humidity of 50% for 3 months, and the presence or absence of haze was checked. (judgement) ○: No haze occurs in the resin solution. ×: The resin solution is hazy.

[0071] (10) Metal adhesion <Laminate creation> A three-layer laminate of polyethylene terephthalate film (PET: Toyobo E5107, 25 μm) / polyester resin layer (5 μm thick) / aluminum foil (9 μm thick) was prepared using the method described below. First, polyester resin was dissolved in methyl ethyl ketone to obtain a polyester resin solution with a solids concentration of 30% by mass. Next, the polyester resin solution was applied to the corona-treated surface of the PET film using an applicator at room temperature so that the polyester resin solution coating thickness after drying would be 5 μm. The solvent was then evaporated in a hot air dryer at 120°C for 30 seconds. The coated surface was then overlapped with aluminum foil, and the laminate was bonded by dry lamination at a roll temperature of 120°C, a roll load of 0.3 MPa, and a pressure-bonded material speed of 1 m / min to prepare a three-layer laminate, which was then cut to a width of 25 mm.

[0072] <Adhesive strength> The adhesive strength between the aluminum foil and PET film of the three-layer laminate film was measured using a tensile tester. The ambient temperature during measurement was set to 25°C, the peeling speed was set to 100 mm / min, and the tensile strength when peeled at a 90° angle was taken as the adhesive strength, and the adhesive strength was expressed in units of N / 25 mm. The results are shown in Table 1. (judgement) ○:5N / 25mm or more △: 3N / 25mm or more and less than 5N / 25mm ×: Less than 3N / 25mm

[0073] (11) Phenol curing <Test piece preparation> A polyester resin solution with a solids content of 40% by weight was prepared by dissolving the polyester resin in a 1:1 mixture of cyclohexanone and Solvesso-150. Next, 42.5 parts of the polyester resin solution were mixed with 5 parts of a resol-type phenolic resin (PR-521, manufactured by Allnex, solids content 60% by weight) as a curing agent and 2 parts of dodecylbenzenesulfonic acid (Nacure® 5076, manufactured by King Industries, solids content 1% by weight) as a catalyst. The mixture was then diluted with a 1:1 mixture of cyclohexanone and Solvesso-150 to a viscosity suitable for application, resulting in a phenolic curing agent formulation. A phenolic hardener compound was applied to one side of a tinplate (JIS G 3303 (2008) SPTE, 70 mm x 150 mm x 0.3 mm) using a bar coater so that the film thickness after drying would be 10 ± 2 μm, and the coating was cured and baked under baking conditions of 240°C (PMT: maximum temperature reached by the substrate) for 1 minute to prepare a test specimen (hereinafter referred to as the test specimen).

[0074] <Curing evaluation> A gauze felt soaked in methyl ethyl ketone was placed 1 cm on the cured film surface of the test piece. 2 The test piece was pressed against the substrate so as to come into contact with the substrate, and a rubbing test was carried out with a load of 500 g applied. The number of times the test piece was rubbed until the cured film peeled off (one reciprocation counted as one rub) was evaluated according to the following criteria. (judgement) ◯: The coating film did not peel off even after 50 or more times, and no changes were observed in the coating film. △: The coating peeled off after 20 to 49 times, exposing the tin plate. ×: The coating peeled off after 19 times or less, exposing the tin plate.

[0075] (12) Isocyanate (NCO) curing <Preparing test samples> A polyester resin was dissolved in methyl ethyl ketone to prepare a polyester resin solution with a solid content of 30% by mass. Next, 10 parts of the polyester resin solution and 1 part of an isocyanurate of hexamethylene diisocyanate (DESMODUR® N3300, manufactured by Covestro, solid content 30% by mass) as a curing agent were blended to obtain an isocyanate curing agent blend. The isocyanate curing agent mixture was applied to a polyethylene terephthalate film (PET film) so that the thickness after drying was 30 μm, and after hot air drying at 100°C for 90 seconds, it was kept at 40°C for 3 days (aging) to prepare a sample for curing test.

[0076] <Curing evaluation> The curability test sample was immersed in a solution of methyl ethyl ketone / toluene = 1 / 1 (mass ratio) at room temperature for 1 hour so that the sample was completely immersed, and then the gel fraction was calculated from the remaining amount that did not dissolve using the following formula. Gel fraction (%) = (mass of curing test sample after immersion - mass of PET film) / (mass of curing test sample before immersion - mass of PET film) x 100 (judgement) ○: 80% or more △: 20% or more but less than 80% ×: Less than 20%

[0077] (13) Trimellitic anhydride component (unreacted TMA) <Sample preparation> 1. Dissolve 100 mg of polyester resin in 2 ml of chloroform. 2. Add 18 ml of acetonitrile to the solution to reprecipitate, then centrifuge. 3. Centrifuge 2 ml of the supernatant, dry it (completely distill off the solvent), and then dissolve it in 250 μl of DMF (N,N-dimethylformamide) to prepare the sample. 4. Measure using a high performance liquid chromatograph (HPLC) under the following conditions. <HPLC measurement conditions> Apparatus: ACQUITY UPLC (manufactured by Waters) Column: BEH-C18 2.1×1mm (manufactured by Waters) Mobile phase: Eluent A: 0.1% formic acid aqueous solution (v / v) Eluent B: Acetonitrile Gradient B%: 5→98→98% (0→25→35 minutes) Flow rate: 0.2 ml / min Column temperature: 40°C Detector: UV-258 nm <Quantification method> Under the above HPLC analysis conditions, measure each unreacted acid component, confirm the elution time, and measure the peak area value of each component. Then, measure the sample under the above HPLC analysis conditions, and calculate the amount of the unreacted acid component (absolute calibration curve method) based on the ratio of the peak area value of the obtained chromatogram to the peak area value of the standard.

[0078] <Example 1> A reactor equipped with a stirrer, a condenser, and a thermometer was charged with 233.0 parts of terephthalic acid, 532.1 parts of isophthalic acid, 13.5 parts of trimellitic anhydride, 155.3 parts of ethylene glycol, 260.5 parts of neopentyl glycol, and 0.0023 mol% of tetra-n-butyl titanate (hereinafter sometimes abbreviated as TBT) as a catalyst relative to the total acid components. The esterification reaction (esterification step) was carried out while raising the temperature from 180 ° C. to 240 ° C. over 4 hours (total polyhydric alcohol components / total polycarboxylic acid components = 1.07 (molar ratio)). Then, 0.023 mol% of zinc acetate dihydrate was charged relative to the total acid components, and the pressure in the system was gradually reduced to 5 mmHg over 20 minutes. The system was then further reduced to 0.3 mmHg or less under vacuum at 260 ° C. for 80 minutes. The polycondensation reaction (polycondensation step) was carried out. Composition analysis of the obtained polyester resin (1) by NMR revealed that the molar ratio of the polycarboxylic acid components was terephthalic acid / isophthalic acid / trimellitic acid = 30.0 / 68.5 / 1.5 (mol%), and the molar ratio of the polyhydric alcohol components was ethylene glycol / neopentyl glycol = 50.0 / 50.0. The reduced viscosity was 0.63 (dl / g), the acid value was 55 (eq / t), and the metal content was titanium 5 (ppm by mass) and zinc 71 (ppm by mass). The performance evaluation results are shown in Table 1.

[0079] Example 2 、3、 5, 8, 9, Comparative Examples 2 to 4 、8 > Polyol components and polycarboxylic acid components were added to produce polyester resins in the same manner as in Example 1. However, the blending ratio of the metal catalyst was changed so that the specified amount was used for the resulting polyester resin. The resin composition, resin properties, and evaluation results are shown in Table 1.

[0080] <Examples 6 and 7> A polyester resin was produced in the same manner as in Example 1, except that the amounts of ethylene glycol and neopentyl glycol were changed so that the charging ratio of all polyhydric alcohol components to all polycarboxylic acid components (total polyhydric alcohol components / total polyhydric alcohol components (molar ratio)) was 1.02 and 1.10, respectively. The resin composition, resin properties, and evaluation results are shown in Table 1.

[0081] Example 10 A reactor equipped with a stirrer, condenser, and thermometer was charged with 196.5 parts of terephthalic acid, 474.2 parts of isophthalic acid, 7.8 parts of trimellitic anhydride, 27.1 parts of ethylene glycol, 263.6 parts of neopentyl glycol, 201.4 parts of 1,4-cyclohexanedimethanol, and 0.0051 mol% of TBT as a catalyst relative to the total acid components, and the temperature was raised from 180 ° C. to 240 ° C. over 4 hours to carry out an esterification reaction (esterification step). Next, 0.019 mol% of zinc acetate dihydrate relative to the total acid components was charged, and the pressure in the system was gradually reduced to 5 mmHg over 20 minutes. A polycondensation reaction (polycondensation step) was carried out at 260 ° C. for 80 minutes under a vacuum of 0.3 mmHg or less. The pressure was then removed, the mixture was cooled to 220°C under a nitrogen stream, 7.8 parts of trimellitic anhydride was added, and the mixture was stirred at 220°C for 2 hours to carry out carboxyl group modification (post-addition), yielding a polyester resin. The resin composition, resin properties, and evaluation results are shown in Table 1.

[0082] <Comparative Example 1> A polyester resin was produced in accordance with the production example of Example 1, except that the amount of TBT charged was changed to 0.00024 mol% based on the total acid components, and the amount of zinc acetate dihydrate charged was changed to 0.017 mol% based on the total acid components. The polycondensation reaction was stopped after 100 minutes. The resin composition, resin properties, and evaluation results are shown in Table 1.

[0083] <Comparative Example 5> A polyester resin was produced in the same manner as in Example 7, except that the amount of zinc acetate dihydrate added was changed to 0.00326 mol % based on the total acid components. The resin composition, resin properties, and evaluation results are shown in Table 1.

[0084] <Comparative Example 6> A polyester resin was produced in accordance with the production example of Example 1, except that the procedure was changed and zinc acetate dihydrate was added before the esterification reaction (esterification step). The resin composition, resin properties, and evaluation results are shown in Table 1.

[0085] <Comparative Example 7> A polyester resin was produced in the same manner as in Example 1, except that the amount of TBT charged was changed to 0.056 mol % based on the total acid components and zinc acetate dihydrate was not used. The resin composition, resin properties, and evaluation results are shown in Table 1.

[0086] JPEG0007825157000001.jpg196166

[0087] In Table 1, the copolymerization components of the resin are represented by the following abbreviations. TPA: Terephthalic acid IPA: Isophthalic acid SA: Sebacic acid TMA: Trimellitic anhydride EG: Ethylene glycol NPG: Neopentyl glycol CHDM: 1,4-cyclohexanedimethanol Biomass EG: Biomass ethylene glycol (manufactured by India Glycol) Biomass NPG: Biomass neopentyl glycol (Perstorp, Neeture N40) [Industrial Applicability]

[0088] The present invention provides a polyester resin that is highly productive, has good color tone, contains little foreign matter, and has excellent metal adhesion and curability. Because this resin has excellent metal adhesion, curability, and storage stability, it is suitable for use as an adhesive for dry lamination, particularly for bonding metal substrates such as aluminum foil to plastic films, and for coating applications, particularly as PCM (precoated metal) paints for metal plate painting and can paints.

Claims

1. A polyester resin composition containing a polyester resin and an isocyanate curing agent or a phenol curing agent, wherein the polyester resin contains 2 to 10 mass ppm of titanium in metal equivalent and 50 to 90 mass ppm of zinc in metal equivalent, and the antimony content in metal equivalent is 1 mass ppm or less, and the polyester resin composition is obtained by dissolving 5 g of the polyester resin in 100 mL of a mixed solvent of phenol / tetrachloroethane (60 / 40 (mass ratio)), filtering the filtered material through a membrane filter with a pore size of 0.5 μm, visually observing the filtered material with an SEM, and counting the number of foreign matter particles with a major axis of 5 μm or more, which is 12 or less.

2. 2. The polyester resin composition according to claim 1, wherein the foreign matter comprises a zinc salt of a polycarboxylic acid.

3. A polyester resin composition according to claim 1 or 2, wherein the reduced viscosity of the polyester resin is 0.10 dl / g or more and the acid value is 50 eq / t or more.

4. A polyester resin composition described in any one of claims 1 to 3, characterized in that the content of trimellitic anhydride in the polyester resin is 1000 mass ppm or less.

5. A coating composition comprising the polyester resin composition according to claim 1.

6. An adhesive composition comprising the polyester resin composition according to claim 1.

7. A method for producing a polyester resin composition described in any of claims 1 to 4, wherein the polyester resin is obtained by producing a prepolymer in the presence of a titanium catalyst but in the absence of a zinc catalyst, and then polycondensing the prepolymer in the presence of a titanium catalyst and a zinc catalyst.

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