Polyester resins with minimal foreign matter and coating or adhesive compositions using this resin

Abstract

The objective of this invention is to provide a polyester resin that is productive, has good color tone, contains few foreign matter, and exhibits good adhesion and curing properties to metal substrates. The solution of this invention is a polyester resin containing 2-10 ppm titanium (based on metal conversion) and 50-100 ppm zinc (based on metal conversion), wherein the content of foreign matter in 5g of the polyester resin is 15 or less.

Description

Polyester resins with minimal foreign matter and coating or adhesive compositions using this resin This invention relates to polyester resins with minimal foreign matter and coating or adhesive compositions using the same resin. More specifically, it relates to polyester resins suitable for dry-layer adhesives for metal substrates, pre-coated metal coatings, and can coatings. Previously, titanium compounds and zinc compounds were used as catalysts in the industrial manufacture of polyester resins from dicarboxylic acids or their ester-forming derivatives and diol components (e.g., Patent Documents 1 and 2). However, this prior art has problems such as gelation, thermal stability, storage stability, and color deterioration if the amount of catalyst added is increased in order to improve polymerization activity. Patent Document 3 discloses a technique that, by limiting the amount of titanium and zinc catalysts added, gelation in the reaction step can be suppressed, allowing low molecular weight compounds in the polymerization condensation to polymerize effectively without dispersion, and enabling the manufacture of polyesters with excellent thermal stability (black foreign matter, suppression of gelation). [Previous Art Documents] [Patent Documents] [Patent Document 1] Japanese Patent Application Publication No. 2003-268087 [Patent Document 2] Japanese Patent Application Publication No. 2000-159872 [Patent Document 3] Japanese Patent Application Publication No. 2009-1656 [The problem that the invention aims to solve] However, Patent Document 3 does not consider the problem that zinc salts, which are foreign substances generated by the reaction with the carboxylic acid of the raw materials, may precipitate as insoluble foreign matter when the polyester resin is dissolved in a solvent or dispersed in water. More specifically, the precipitation of foreign matter can cause defects in varnish coating, such as poor coating appearance when used in pre-coated metal or can coating applications, and poor adhesion to the substrate when using dry lamination adhesives on metal substrates. This invention is based on the subject matter of this prior art. That is, the object of this invention is to provide a polyester resin that is productive, has good color, few foreign matter, and good adhesion and curing properties to metal substrates. The inventors of this case completed this invention as a result of their diligent research in order to solve the aforementioned problems. That is, this invention is composed of the following components. A polyester resin contains 2 to 10 ppm of titanium by mass and 50 to 100 ppm of zinc by mass, and the content of foreign matter in 5g of the polyester resin is less than 15. Ideally, the foreign substance should contain zinc salts of polycarboxylic acids. Ideally, the polyester resin should have a reduced viscosity of 0.10 dl / g or higher and an acid value of 50 eq / t or higher. Furthermore, an ideal content of trimellitic anhydride in the polyester resin should be below 1000 ppm by mass. A polyester resin composition comprising the polyester resin and an isocyanate curing agent or a phenol curing agent. A coating composition or an adhesive composition comprising the polyester resin composition. A method for manufacturing the polyester resin involves manufacturing a prepolymer in the presence of a titanium catalyst and in the absence of a zinc catalyst, followed by polycondensation in the presence of both a titanium catalyst and a zinc catalyst. [Effects of the Invention] This invention provides a polyester resin that is productive, has good color and few foreign matter, and has excellent metal adhesion and curing properties. The present invention will now be described in detail. <Polyester Resin> The polyester resin of this invention must contain titanium at a concentration of 2 ppm by mass and 10 ppm by mass, calculated on a metal-to-residue basis. Considering the need for improved productivity, ease of obtaining high molecular weight polyester resins, and good solid storage stability and metal adhesion, a concentration of 3 ppm by mass or more is preferable, 4 ppm by mass or more is even more preferable, and 5 ppm by mass or more is even more preferable. Furthermore, considering the need for good color tone in the polyester resin, a concentration of 9 ppm by mass or less is preferable, 8 ppm by mass or less is even more preferable, and 7 ppm by mass or less is even more preferable. The polyester resin of this invention must contain zinc at a concentration of 50 ppm to 100 ppm by mass (based on metal conversion). Considering the need for good curing properties of the polyester resin, especially its curing properties (reactivity) with isocyanate curing agents, a concentration of 55 ppm by mass or higher is preferable, and 60 ppm by mass or higher is even more desirable. Furthermore, considering the need to suppress foreign matter from zinc, resulting in good color tone of the polyester resin, good solubility stability, and reduced foreign matter content, a concentration of 95 ppm by mass or lower is preferable, and 90 ppm by mass or lower is even more desirable. The polyester resin of this invention ideally contains antimony at a content of 10 ppm or less by mass (based on metal conversion). Considering the need to suppress the formation of foreign matter containing antimony metal, a lower content is preferable, 5 ppm or less is preferable, 1 ppm or less is more preferable, and 0 ppm is even more preferable. In this invention, the titanium and zinc contents in the polyester resin are obtained by analysis using dry ashing and acid decomposition methods, and the antimony content is obtained by analysis using the yttrium nitrate method (nitrate ashing method). The presence of titanium and zinc in polyester resin is acceptable, whether as metallic monomers or in compound form. The key is to ensure they are present in a predetermined amount calculated based on metal conversion. Ideally, they should be contained in a composition identical to the catalyst used in the polymerization of the polyester resin. Regarding titanium compounds, examples include titanium halide compounds such as titanium tetrafluoride, titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, and hexafluorotitanic acid; titanium acid compounds such as α-titanic acid, β-titanic acid, ammonium titanate, sodium titanate, peroxytitanic acid complexes, and anatase; inorganic acid titanium salt compounds such as titanium sulfate, titanium nitrate, titanium phosphate, and titanium silicate; organometallic titanium compounds such as tetramethyltitanium, tetraethyltitanium, tetrabenzyltitanium, tetraphenyltitanium, and bis(cyclopentadienyl)dichloride; and aryloxytitanium compounds such as tetraphenoxytitanium. Tetra(trimethylsiloxy)titanium, tetra(triphenylsiloxy)titanium, and other silica-based titanium compounds; titanium acetate, titanium propionate, titanium lactate, titanium citrate, titanium tartrate, potassium oxalate titanium oxide, organic sulfonate titanium, organic phosphonate titanium, and other organic acid titanium salts; tetra(diethylamino)titanium, tetrapyrrole titanium, and other titanium amine compounds; tetramethoxytitanium, tetraethoxytitanium, tetra-n-propoxytitanium, tetraisopropoxytitanium, tetra-n-butoxytitanium, tetra-2-ethylhexyloxytitanium, and other tetraalkyl titanium oxides; poly(dibutyl titanate), Ti 7 O 4 (OC 2 H 5) 20 Ti 16 O 16 (OC 2 H 5) 32 Condensed alkane titanium oxides; halogen-substituted alkane titanium oxides such as triisopropoxy titanium chloride and diethoxy titanium dichloride; carboxylic acid-substituted alkane titanium oxides such as triisopropoxy acetate and triisopropoxy methacrylate; phosphonic acid-substituted alkane titanium oxides such as isopropoxy-3-(dioctyl pyrophosphate) titanium and triisopropoxy-3-(monoethyl phosphate) titanium; sulfonic acid-substituted alkane titanium oxides such as isopropoxy-3-(dodecylbenzene sulfonic acid) titanium; alkoxy titanates such as ammonium hexaethoxytitanate, ammonium hexaethoxytitanate, potassium hexaethoxytitanate, and sodium hexa-n-propoxytitanate; β-diketone-substituted alkane titanium oxides such as diisopropoxybis(acetyl acetone) titanium and diisopropoxybis(acetyl ethyl acetate) titanium; α-hydroxycarboxylic acid-substituted alkane titanium oxides such as diisopropoxybis(ammonium lactate) titanium; and amino alcohol-substituted alkane titanium oxides such as diisopropoxybis(triethanolamine) titanium and triisopropoxy-2-aminoethoxytitanate titanium. Among these, tetrabutyl titanate is the most ideal. Regarding zinc compounds, examples include zinc monomers such as zinc powder; organic zinc acid salts such as zinc acetate and zinc acetone; inorganic zinc acid salts such as zinc carbonate, zinc chloride, zinc nitrate, zinc phosphate, zinc sulfate, zinc borate, and zinc aluminate; other organozinc compounds such as dimethyl zinc and diethyl zinc; and other inorganic zinc compounds such as zinc oxide, zinc sulfide, and zinc chloride. Among these, zinc acetate dihydrate is considered the most ideal. The term "foreign substance" in this invention refers to a substance containing at least a zinc salt of a polycarboxylic acid. Specifically, it refers to a zinc salt of a polycarboxylic acid from the raw material of polyester resin, such as zinc salts of terephthalic acid, isophthalic acid, phthalic acid, and trimellitic acid. The main component is a zinc salt of terephthalic acid, isophthalic acid, or trimellitic acid. Ideally, the zinc salt of the polycarboxylic acid contained in the foreign substance should be 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass. The polyester resin of this invention contains 15 or fewer foreign matter per 5g (also referred to as "15 per 5g"). The lower the content of foreign matter, the better; 14 or fewer (14 per 5g) is ideal, 12 or fewer (12 per 5g) is more ideal, 10 or fewer (10 per 5g) is even more ideal, 9 or fewer (9 per 5g) is still more ideal, and 8 or fewer (8 per 5g) is particularly ideal. The lower limit is not particularly limited; industrially, 1 or more (1 per 5g) is acceptable, and even 2 or more (2 per 5g) is not a problem. Foreign matter was identified by dissolving 5g of polyester resin in 100mL of a mixed solvent of phenol / tetrachloroethane (60 / 40 mass ratio), filtering the solution through a 0.5μm membrane filter, and then visually observing and counting the filtered material using SEM. Figure 1 shows an SEM image of the filtered material; the areas marked with '0' indicate foreign matter. Regarding the foreign matter analysis method of this invention, SEM-EDX (Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy) is more ideal. By using the above-mentioned analytical method, it is possible to ideally identify organic matter such as gels, impurities or metal species other than zinc, and foreign matter containing zinc salts of polycarboxylic acids. Ideally, the major diameter of the foreign matter should be 5 μm or more, more ideally 8 μm or more, and even more ideally 10 μm or more. Furthermore, a diameter of 80 μm or less is ideal, 70 μm or less is more ideal, and 60 μm or less is even more ideal. The polyester resin of this invention can reduce the number of foreign matter within the above range to less than 15 per 5g. Because the amount of foreign matter in the polyester resin of this invention is less than a predetermined amount, no defects caused by foreign matter will occur when coating with varnish (polyester resin composition). For example, no poor appearance of the coating film will occur when it is used for pre-coating metal and can coatings, and no poor adhesion to the substrate will occur when it is used as a dry lamination adhesive for metal substrates. The polyester resin of the present invention is preferably a polyester in which polycarboxylic acid components and polyol components are used as copolymerization components. Regarding dicarboxylic acids, examples include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, unsaturated aliphatic dicarboxylic acids, and alicyclic dicarboxylic acids. Examples include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, sodium isophthalate-5-sulfonate, lithium isophthalate-5-sulfonate, sodium terephthalate-2-sulfonate, 4,4'-diphenylmethanedicarboxylic acid, 4,4'-diphenyl etherdicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and 4,4'-stilbenedicarboxylic acid. These can be used alone or in combination of two or more. Regarding aliphatic dicarboxylic acids, there are no particular limitations; examples include pimelic acid, octanoic acid, adipic acid, azelaic acid, sebacic acid, dodecanoic acid, and dimer acids. These can be used alone or in combination of two or more. Examples of unsaturated aliphatic dicarboxylic acids include fumaric acid, maleic acid, itaconic acid, hexahydrophthalic acid, and tetrahydrophthalic acid. Examples of alicyclic dicarboxylic acids include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid. Among these, aromatic or aliphatic dicarboxylic acids are preferred. For aromatic dicarboxylic acids, terephthalic acid or isophthalic acid are more ideal; for aliphatic dicarboxylic acids, sebacic acid is more ideal. When all polycarboxylic acid components in the polyester resin are considered as 100 mol%, it is ideal for aromatic dicarboxylic acids to be 50 mol% or more, more ideal to be 60 mol% or more, and even more ideal to be 70 mol% or more. However, if anhydrides or other components are added post-polymerized (acid addition) to impart an acid value, the total amount of polycarboxylic acid components and polyol components may exceed 200 mol%. In this case, the total amount of components other than the post-added (post-attached) anhydrides is calculated as 200 mol%. Alternatively, polycarboxylic acids with a valence of 3 or higher can be used. Examples of polycarboxylic acids with a valence of 3 or higher include trimellitic acid, pyrocyanic acid, benzophenone tetracarboxylic acid, diphenyl tannic acid, biphenyl tetracarboxylic acid, and their anhydrides. These polycarboxylic acids with a valence of 3 or higher can be used alone or in combination of two or more. Among these, trimellitic acid or trimellitic anhydride is preferred. Regarding diols, examples include aliphatic diols, alicyclic diols, aromatic diols, and polyalkylene diols. Specifically, 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-heptahydratediol, and so on. - Aliphatic diols such as octanediol, 1,9-nonanediol, 1,10-decanediol, dimethyloltricyclodecane, diethylene glycol, triethylene glycol, dipropylene glycol, and tripropylene glycol; alicyclic diols such as 1,2-cyclohexanediethanol, 1,3-cyclohexanediethanol, and 1,4-cyclohexanediethanol; aromatic diols such as bisphenol A, bisphenol S, bisphenol C, bisphenol Z, bisphenol AP, 4,4'-biphenol, and their ethylene oxide adducts or propylene oxide adducts; and polyalkylene glycols such as polyethylene glycol and polypropylene glycol. These diols can be used alone or in combination. Aliphatic or alicyclic diols are preferred. For aliphatic diols, ethylene glycol and neopentyl glycol are preferred, while for alicyclic diols, 1,4-cyclohexanediethanol is preferred. Alternatively, polyols with a oxidation state of 3 or higher can also be used. Examples of polyols with a oxidation state of 3 or higher include glycerol, trimethylolethane, trimethylolpropane, mannitol, sorbitol, neopentyl tertrol, and α-methylglucoside. These polyols with a oxidation state of 3 or higher can be used alone or in combination of two or more. When all polyol components in polyester resin are considered as 100 mol%, it is ideal for aliphatic diols to be 50 mol or more, even more ideal for 60 mol or more, and even more ideal for 65 mol or more. Regarding the glycol component, bio-derived glycols can also be used. There are no particular limitations on the bio-derived glycol component; ethylene glycol and neopentyl glycol can be used. For example, bio-derived ethylene glycol is produced from ethanol (bioethanol) manufactured using biomass as a raw material. For instance, bio-derived ethylene glycol can be obtained by using conventionally known methods, such as the production of ethylene glycol from ethylene oxide. Furthermore, commercially available bio-ethylene glycol can also be used; ideally, bio-ethylene glycol sold by India Glycols Ltd. or bio-neopentyl glycol (Neeture series, N20, N40, N100) sold by Perstorp can be used. Regarding the manufacturing method of polyester resin, it is ideal to perform a polycondensation reaction (hereinafter, also referred to as the polycondensation step) after an esterification reaction. That is, in the esterification step, it is ideal to perform the esterification reaction of the aforementioned dicarboxylic acid and diol components at 150-250°C. The esterification step generates low molecular weight prepolymers (oligopolymers), etc. The reaction temperature of the esterification step is more ideal at 160-245°C, and even more ideal at 180-240°C. Furthermore, the reaction time can be appropriately set according to the reaction temperature, with 1-10 hours being more ideal, and 2-8 hours being even more ideal. Then, in the polycondensation step, it is ideal to perform the polycondensation reaction at 230-300°C while the system is under reduced pressure. The reaction temperature of the polycondensation step is more ideal at 240-290°C, and even more ideal at 250-280°C. Furthermore, the reaction time can be appropriately set according to the reaction temperature, with 0.5 to 5 hours being ideal, and 1 to 3 hours being even more ideal. A pressure reduction of less than 10 mmHg is ideal, less than 5 mmHg is even more ideal, less than 1 mmHg is even better, and less than 0.5 mmHg is particularly ideal. The lower limit is not particularly limited; industrially, anything above 0.01 mmHg is acceptable, even 0.05 mmHg is not a problem. According to the above manufacturing method, the target polyester resin can be obtained. The aforementioned titanium catalyst only needs to be present in a predetermined amount during the polycondensation step. That is, it can be added during the esterification step, or after the start of the polycondensation step. Adding it during the esterification step is more ideal. The amount of titanium catalyst added is proportional to the titanium content in the resulting polyester resin. Therefore, in terms of titanium metal, 2 ppm by mass or more relative to the polyester resin is more ideal, 3 ppm by mass or more is even more ideal, 4 ppm by mass or more is even better, and 5 ppm by mass is particularly ideal. Furthermore, 10 ppm by mass or less is more ideal, 9 ppm by mass or less is even more ideal, 8 ppm by mass or less is even better, and 7 ppm by mass or less is particularly ideal. It is ideal to add a predetermined amount of zinc catalyst during the polycondensation step (after the esterification step is completed). If zinc catalyst is present during the esterification step, it will readily form salts with unreacted polycarboxylic acids, easily generating foreign substances containing zinc salts of polycarboxylic acids. In other words, by adding a predetermined amount during the polycondensation step, the formation of foreign substances can be suppressed. The amount of zinc catalyst added is proportional to the zinc content in the resulting polyester resin. Therefore, in terms of zinc metal content, 50 ppm by mass or more relative to the polyester resin is ideal, 55 ppm by mass or more is even more ideal, and 60 ppm by mass or more is even better. Furthermore, 100 ppm by mass or less is ideal, 95 ppm by mass or less is even more ideal, and 90 ppm by mass or less is even better. To impart metallic adhesion to the polyester resin of this invention and improve its reactivity with the curing agent, an acid value of 40 eq / t or higher is ideal, 50 eq / t or higher is more ideal, 60 eq / t or higher is even more ideal, 70 eq / t or higher is still more ideal, and 100 eq / t or higher is particularly ideal. If the acid value falls within the above range, both metallic adhesion and curing properties (curing speed) will be improved. The upper limit of the acid value is not particularly limited, but 400 eq / t or lower is ideal, 300 eq / t or lower is more ideal, and 200 eq / t or lower is even more ideal. Falling within the above range will result in better solid storage stability (reduced viscosity retention) of the polyester resin. An acid value can be imparted to the polyester resin of this invention by any method. By imparting an acid value, effects such as improved curing properties with curing agents and improved adhesion to metallic materials can sometimes be obtained. Regarding methods for imparting an acid value, there are methods such as adding depolymerization of polycarboxylic anhydrides in the later stages of the polycondensation step, and methods such as adding polycarboxylic acids to the prepolymer (oligopolymer) stage in the esterification step to increase the acid value before carrying out the polycondensation reaction. The latter method of increasing the acid value in the esterification step is more ideal because it reduces the amount of unreacted trimellitic anhydride and trimellitic acid present in the polyester resin. Regarding other methods of imparting an acid value, one example is adjusting the feed molar ratio (diol / dicarboxylic acid) of the dicarboxylic acid component and the diol component (glycol component) during the esterification step. A molar ratio (diol / dicarboxylic acid) of more than 1.0 and less than 1.1 is ideal, and more than 1.01 and less than 1.08 is even more ideal. If the value is above the lower limit mentioned above, the polyester resin can be polymerized to a higher molecular weight without poor polymerization. Conversely, if the value is below the upper limit mentioned above, a prepolymer with a high acid value can be obtained, and an acid value can be imparted to the polyester resin. Furthermore, this results in good metal adhesion and curing properties. Ideally, the amount of trimellitic anhydride (residual) in the polyester resin of this invention should be below 1,000 ppm by mass. Considering the improvement of solution stability of the polyester resin, below 500 ppm by mass is more ideal, below 100 ppm by mass is even more ideal, below 50 ppm by mass is still more ideal, and below 20 ppm by mass is particularly ideal. Below 1,000 ppm by mass, hydrolysis of the polyester resin caused by acid is suppressed, resulting in good solubility stability. Since a lower amount of trimellitic anhydride in the polyester resin is more ideal, the lower limit is not particularly limited; industrially, 1 ppm by mass or more is acceptable, even 2 ppm by mass or more is fine. Here, the trimellitic anhydride in the polyester resin mainly refers to unreacted trimellitic anhydride that has not reacted in the esterification and polycondensation steps, including, for example, trimellitic acid formed by the reaction of trimellitic anhydride with water, resulting only in ring opening. In other words, trimellitic anhydride is the sum of trimellitic anhydride and trimellitic acid. In this invention, the content of trimellitic anhydride in the polyester resin can be determined by HPLC. The reduced viscosity (denoted as ηsp / c, unit: dl / g) of the polyester resin of this invention is not particularly limited, but 0.10 dl / g or higher is preferable, and 0.40 dl / g or higher is even more desirable. If it is 0.10 dl / g or higher, the strength and metal adhesion of the coating film containing the polyester resin adhesive composition will be improved. Furthermore, the handling and storage stability during coating will be improved. In addition, the reduced viscosity in this invention is a value determined using the method described in the examples. The upper limit of the reduced viscosity is not particularly limited, but 2.00 dl / g or lower is preferable, and 1.00 dl / g or lower is even more desirable. If it is below the above upper limit, the solvent solubility of the polyester resin will be improved, and the solubility stability will be better. <Curing Agent> The curing agent is preferably one that reacts with the polyester resin of the present invention to form a cross-linked structure, such as phenol curing agents or isocyanate curing agents. Regarding phenol curing agents, methyl phenolic resins synthesized from phenol compounds are more ideal. Examples of phenol compounds with three or more functionalities include phenol, m-cresol, m-ethylphenol, 3,5-xylenol, m-methoxyphenol, bisphenol-A, and bisphenol-F. Examples of difunctional phenol compounds include o-cresol, p-cresol, p-tert-butylphenol, p-ethylphenol, 2,3-xylenol, and 2,5-xylenol. These are phenol compounds with two or more functional groups capable of hydroxymethylation per molecule, and can be synthesized using the hydroxymethylation of formaldehyde, etc. One type or a mixture of two or more can be used. The blending ratio of these trifunctional or higher phenolic compounds to difunctional phenolic compounds is arbitrary and depends on the desired coating (hardened film), but a ratio of 1 / 99 to 100 / 0 (parts by mass) is ideal. For example, when the coating requires hardness and acid resistance, it is ideal to have more than 30 parts by mass of trifunctional or higher phenolic compounds; when the coating requires flexibility and low residual stress after processing is desired, it is ideal to have less than 50 parts by mass of trifunctional or higher phenolic compounds. Regarding the formaldehydes used to make these phenolic compounds into phenolic resins, examples include formaldehyde, trioxymethylene, or trioxymethylene, and one or more of them may be used. Regarding the alcohol used to alkylate a portion of the hydroxymethyl group in the hydroxymethylated phenolic resin, monovalent alcohols with 1 to 8 carbon atoms, ideally 1 to 4, can be used, such as methanol, ethanol, n-propanol, n-butanol, isopropanol, isobutanol, tributanol, etc. Considering the compatibility and reaction curing properties with polyester resin (A), n-butanol is more ideal. For the aforementioned phenolic resins, considering their reactivity and compatibility with polyester resins, the average number of alkoxymethyl groups per phenolic core should be 0.3 or more, with 0.5 to 3 being more ideal. If the number is less than 0.3, the curing properties with the polyester resin may be insufficient, and the strength of the cured coating film may decrease. There is no specific upper limit, but exceeding this range may sometimes worsen the stability when incorporated with a curing agent. Regarding the method for obtaining a phenolic resin composed of a mixture of phenolic compounds with three or more functions and phenolic compounds with two functions, a method can be used to premix the phenolic compounds in any proportion before phenolic resinification using formaldehyde, or a method can be used to phenolic resinify the phenolic compounds with three or more functions and the phenolic compounds with two functions separately and then mix them in any mixing proportion. Examples of isocyanate curing agents include 2,4-toluene diisocyanate, 2,6-methylenephenyl diisocyanate, xylene-1,4-diisocyanate, xylene-1,3-diisocyanate, tetramethylxylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, isophenylene diisocyanate, terephthalene diisocyanate, naphthalene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, and 3,3'-dimethoxy Aromatic diisocyanates such as diphenyl-4,4'-diisocyanate; aromatic polyisocyanates such as polymethylene polyisocyanate and crude toluene diisocyanate; aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), decamethylene diisocyanate, and lysine diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate (IPDI), hydrogenated toluene diisocyanate, hydrogenated xylene diisocyanate, and hydrogenated diphenylmethane diisocyanate; and diisocyanates such as biuret, urea diketone modified, carbodiimide modified, isocyanurate modified, urea ketone imide modified, adducts with polyols, and mixed modified forms thereof, may be selected from one or more of these. Furthermore, it can also be used in the form of carbamate precursors, such as prepolymers, modifiers, derivatives, and mixtures composed of isocyanate compounds and polyols, polyamines, and other compounds containing active hydrogen. Regarding the aforementioned isocyanate curing agents, end-capped isocyanate curing agents obtained by capping the terminal NCO groups of the isocyanate compound can also be used. Examples of end-capping agents include phenolic compounds such as phenol, cresol, ethylphenol, and butylphenol; alcoholic compounds such as 2-hydroxypyridine, butylceroxox, propylene glycol monomethyl ether, benzyl alcohol, methanol, ethanol, n-butanol, isobutanol, and 2-ethylhexanol; active methylene compounds such as dimethyl malonate, diethyl malonate, methyl acetate, ethyl acetate, and acetone; and thiol compounds such as butanethiol and dodecyl mercaptan. Acetanilide, acetylamine, and other acetylamine compounds; ε-caprolactam, δ-valerolactam, γ-butyrolactam, and other lactam compounds; imidazole, 2-methylimidazol, and other imidazole compounds; urea, thiourea, ethylene urea, and other urea compounds; oxime compounds such as methylamine oxime, acetaldehyde oxime, acetone oxime, methyl ethyl ketone oxime, methyl isobutyl ketone oxime, and cyclohexanone oxime; and amine compounds such as triphenylamine, aniline, carbazole, ethyleneimine, and polyethyleneimine. One or more of these compounds may be used in combination. The reaction of this capping agent with isocyanate compounds can be carried out, for example, at 20–200°C using known inert solvents or catalysts as needed. It is ideal to use a capping agent in an amount of 0.7–1.5 moles relative to the terminal isocyanate group. Regarding the blending ratio of polyester resin to hardener in the polyester resin composition of the present invention, in order to improve the solvent resistance of the cured coating, it is more ideal for the hardener to be 5 parts by mass or more than 10 parts by mass of polyester resin, and even more ideal for the hardener to be 10 parts by mass or more. Furthermore, to avoid the residue of unreacted hardener components and to avoid a decrease in the strength of the cured coating, it is more ideal for the hardener to be blended in a ratio of 30 parts by mass or less, and even more ideal for a ratio of 20 parts by mass or less. Curing catalysts can also be added to polyester resin compositions. The presence of a catalyst can improve the performance of the cured film. Regarding catalysts, when the curing agent is a phenolic resin, examples include sulfuric acid, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, naphthalenesulfonic acid, dinonylnaphthalenesulfonic acid, dinonylnaphthalenedisulfonic acid, camphorsulfonic acid, phosphoric acid, and those prepared by amine protection (adding amines to neutralize a portion). One or more of these can be used in combination. Considering compatibility and hygiene with polyester resins, dodecylbenzenesulfonic acid and its neutralization products are more ideal. 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. The polyester resin composition of this invention is preferably solvent-based, with a solid content concentration of 20-60% by mass being ideal, and 30-50% by mass being even more ideal. The solvent is used after the manufacture of the polyester resin, during the manufacture of the resin composition, and also as a diluent during coating. The solvents that can be used are not particularly limited, but examples include esters such as ethyl acetate, butyl acetate, and ceroxythionate acetate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ethers such as tetrahydrofuran and dimethyl ether; and aromatic hydrocarbons such as toluene and xylene. Among these, considering price, productivity, and safety, ethyl acetate and methyl ethyl ketone are generally preferred. The polyester resin and polyester resin composition of this invention are ideally suited for use in coating compositions and adhesive compositions due to their excellent metal adhesion, curing properties, and storage stability. In the case of coatings, applications on metal substrates include, specifically, pre-coated metal (PCM) coatings and can coatings. In the case of adhesives, examples include dry lamination adhesives for bonding metal substrates such as aluminum foil to plastic films. [Examples] Hereinafter, embodiments are illustrated to illustrate the present invention in more detail, but the present invention is not limited by these embodiments. Furthermore, the measured values ​​described in the embodiments were determined by the following methods. Also, in the embodiments and comparative examples, "parts" refers to "parts by mass," and "%" represents "% by mass." (1) Determination of resin composition: Polyester resin was dissolved in deuterated chloroform and analyzed using a VARIAN 400-MR NMR apparatus. 1 H-NMR analysis was performed, and the molar ratio was obtained from the ratio of its integral values. (2) Quantitative Analysis of Metal Elements <Dry Ashing and Acid Decomposition Method (Quantitative Analysis of Titanium and Zinc)> 0.5 g of the sample (polyester resin) was weighed into a platinum crucible and pre-carbonized on a hot plate to 400°C. Then, an ashing treatment was performed at 550°C for 8 hours 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 until the hydrochloric acid completely evaporated. After the acid decomposition was completed, 20 mL of 1.2 N hydrochloric acid was used to make up the volume. The treated solution was then measured using a high-frequency inductively coupled plasmaluminescence analyzer (Hitachi High-Tech Science, SPECTROBLUE). Additionally, a blank test was performed to quantify the amount of metal elements in the sample 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 elemental content in 0.5g of sample can be determined as follows: A = (BC) × 20 / 0.5 Elemental content in sample: A (mass ppm) Elemental concentration in pretreatment solution: B (mg / L) Elemental concentration in blank test solution (background value determination): C (mg / L) <Yttrium Nitrate Method (Nitrate Ashing Method) (Quantification of Antimony)> 0.5 g of the sample (polyester resin) was weighed into a platinum crucible, and 5 mL of 5% yttrium nitrate ethanol solution was added. Preliminary carbonization was performed on a hot plate up to 400°C. Then, ashing was carried out at 550°C for 8 hours using a YAMATO SCIENTIFIC FO610 electric furnace. After ashing, 20 mL of 1.2N hydrochloric acid was added, and the resulting solution after dissolving the nitrate was used as the assay solution. The determination was performed using a high-frequency inductively coupled plasmaluminescence analyzer (Hitachi High-Tech Science, SPECTROBLUE). A blank test was also performed to quantify the amount of metal element in the sample using a calibration curve prepared with a standard solution of the target element. The amount of metal element in the sample was calculated using the following formula. The element content in 0.5 g of the sample can be obtained using the following method. A = (BC) × 20 / 0.5 Element content in sample: A (mass ppm) Element concentration in pretreatment solution: B (mg / L) Element concentration in blank test solution (background value determination): C (mg / L) In addition, the detection limit of this method is 1 mass ppm, and the result of the determination that does not reach the detection limit is recorded as <1 (mass ppm). (3) Productivity Evaluation In this invention, the polymerization time refers to the time taken during the polycondensation step from reaching a temperature of 260°C and a vacuum level of 0.3 mmHg or less until the predetermined reduced viscosity (ηsp / c > 0.50 dl / g) is achieved. The polycondensation step is terminated when the polymerization time exceeds 100 minutes, and the polyester resin is removed. (Judgment) 〇: Polymerization time ≤ 100 minutes ×: Polymerization time > 100 minutes (4) Determination of Hue (color b value, Co-b): Polyester resin was dissolved in methyl ethyl ketone / toluene = 1 / 1 (mass ratio) at 25°C to prepare a polyester resin solution with a solid content of 30% by mass. The color b value of the polyester resin solution was determined using a petroleum product colorimeter (manufactured by Nippon Denshoku Kogyo Co., Ltd., OME-2000). (5) Determination of Foreign Matter Quantity: 5g of polyester resin was added to 80mL of a mixed solvent of phenol / tetrachloroethane (6 / 4 (mass ratio)) and stirred at 135°C for 2 hours to dissolve it. The solution was then filtered through a 0.5μm PTFE filter medium. The resulting filter media was observed (visually) using a SEM-EDX (JEOL Ltd., JSM-6510A) (magnification: 100x, signal: SEI (secondary electron imaging), focal distance: 10mm, applied voltage: 15kV, vacuum mode: 0.1mPa) and the foreign matter was counted. Cases where the filter medium had a large number of foreign matter on its surface that were difficult to count were rated as "×". (6) Determination of Reduced Viscosity (ηsp / c, unit: dl / g) (Initial Value) 0.1 g ± 0.005 g of polyester resin sample was dissolved in a phenol / tetrachloroethane (6 / 4 (mass ratio)) mixed solvent at approximately 50°C, and diluted in a 25 mL volumetric flask to prepare a sample solution. The sample solution was then placed in a viscosity tube and immersed in a 30°C water bath for 15-20 minutes to bring the sample solution to 30°C. After reaching the predetermined temperature, the falling time was measured while checking the mark on the viscosity tube. The reduced viscosity (unit: dl / g) was calculated based on the difference between the falling time of the sample solution and that of the blank solvent. The formula is shown in Equation 1. Equation 1: {(falling time of sample solution) - (falling time of blank solvent)} / (falling time of blank solvent) / (mass of polyester resin × 100 / 25) (7) Determination of acid value (AV, unit: eq / t): Dissolve 0.2 g of polyester resin sample in 40 ml of chloroform, and titrate with 0.01 N potassium hydroxide ethanol solution to determine the acid value per 10 liters of polyester resin. 6 The equivalent in g (eq / t). Phenolphthalein was used as an indicator. (8) Solid Storage Stability (Reduction Viscosity Retention Rate) Polyester resin was stored in a polyethylene bag at 40°C and 50% humidity for 3 months to check for any decrease in molecular weight. The reduction in molecular weight was evaluated using the reduction viscosity retention rate. Reduction viscosity retention rate (%) = (Reduction viscosity of polyester resin after 3 months of storage) / (Initial reduction viscosity of polyester resin) × 100 Additionally, the reduction viscosity at the beginning of storage was used as the initial value. (9) Solubility stability: The polyester resin was dissolved in ethyl acetate to prepare a resin solution with a solid content of 30% by mass. The resin solution was stored in a static state at 40°C and 50% humidity for 3 months, and the presence or absence of turbidity was checked. (Judgment) 〇: No turbidity was generated in the resin solution. ×: Turbidity was generated in the resin solution. (10) Metallic Adhesion <Fabrication of the Laminate> A three-layer laminate consisting of polyethylene terephthalate film (PET: Toyobo E5107, 25μm) / polyester resin layer (thickness 5μm) / aluminum foil (thickness 9μm) was fabricated according to the method described below. First, polyester resin was dissolved in methyl ethyl ketone to obtain a polyester resin solution with a solid content concentration of 30% by mass. Then, at room temperature, the polyester resin solution was coated onto the corona-treated surface of the PET film with a coating tool to a thickness of 5μm after drying. The solvent was evaporated using a hot air dryer at 120°C for 30 seconds. Afterward, the coated surface was overlapped with the aluminum foil, and the three-layer laminate was fabricated by dry lamination under conditions of roller temperature 120°C, roller load 0.3MPa, and substrate speed 1m / min. The laminate was then cut to a width of 25mm. <Adhesion Strength> The adhesion strength between aluminum foil and PET film in a three-layer laminated film was determined using a tensile testing machine. The ambient temperature was set to 25°C and the peel speed to 100 mm / min. The tensile strength obtained by peeling using a 90° peel method was taken as the adhesion strength, and the unit of adhesion strength was set to N / 25 mm. The results are shown in Table 1. (Judgment) 〇: 5 N / 25 mm or more △: 3 N / 25 mm or more but less than 5 N / 25 mm ×: Less than 3 N / 25 mm (11) Phenol curing properties <Preparation of test pieces> Polyester resin was dissolved in cyclohexanone / Solvesso 150 = 1 / 1 (mass ratio) to prepare a polyester resin solution with a solid content of 40% by mass. Then, 42.5 parts of the polyester resin solution, 5 parts of methyl phenolic resin (Allnex, PR-521, 60% by mass, solid content) as a curing agent, and 2 parts of dodecylbenzenesulfonic acid (King Industries, Nacurre 5076, 1% by mass, solid content) as a catalyst were mixed and diluted with cyclohexanone / Solvesso 150 = 1 / 1 (mass ratio) to a viscosity suitable for coating to obtain a phenol curing agent blend. The phenol curing agent mixture was applied to one side of a tinplate (JIS G 3303(2008) SPTE, 70mm×150mm×0.3mm) with a smearing stick to achieve a film thickness of 10±2μm after drying. The curing was carried out under the condition of 240℃ (PMT: the highest temperature reached by the substrate)×1 minute, and the resulting sample was used as a test piece (hereinafter referred to as the test piece). <Evaluation of Hardening Properties> Apply a gauze pad soaked in methyl ethyl ketone to a depth of 1 cm. 2The coating is applied to the hardened film surface of the test piece and subjected to a 500g load for a friction test. The number of times the hardened film peels off is evaluated according to the following criteria (one round trip is counted as one test). (Judgment) 〇: Even after more than 50 tests, the coating does not peel off, and no change in the coating is visible. △: After 20-49 tests, the coating peels off, exposing the tinplate. ×: After less than 19 tests, the coating peels off, exposing the tinplate. (12) Curing Properties of Isocyanate (NCO) <Preparation of Test Specimens> Polyester resin was dissolved in methyl ethyl ketone to prepare a polyester resin solution with a solid content of 30% by mass. Then, 10 parts of the polyester resin solution and 1 part of the isocyanurate body of hexamethylene diisocyanate (DESMODUR (registered trademark) N3300: manufactured by Covestro, with a solid content of 30% by mass) as a curing agent were mixed to obtain an isocyanate curing agent blend. The above isocyanate curing agent blend was coated on a polyethylene terephthalate film (PET film) to achieve a thickness of 30 μm after drying. After hot air drying at 100°C for 90 seconds, the film was kept at 40°C for 3 days (aging) to prepare a specimen for curing property testing. <Cureability Evaluation> After immersing the entire specimen for the curability test in a 1 / 1 (mass ratio) solution of methyl ethyl ketone (MEK) and toluene for 1 hour at room temperature, the gel fraction is calculated from the undissolved residue using the following formula: Gel Fraction (%) = (Mass of the specimen after immersion - Mass of the PET film) / (Mass of the specimen before immersion - Mass of the PET film) × 100 (Judgment) 〇: 80% or more △: 20% or more but less than 80% ×: Less than 20% (13) Triphenyltricarboxylic anhydride (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 for reprecipitation and centrifuge. 3. Dry 2 ml of the supernatant after centrifugation (completely distill off the solvent) and then dissolve it in 250 μl of DMF (N,N-dimethylformamide) to prepare the sample. 4. Analyze the sample using high-performance liquid chromatography (HPLC) under the following conditions. <HPLC Determination Conditions> Apparatus: ACQUITY UPLC (Waters) Column: BEH-C18 2.1×150mm (Waters) Mobile Phase: Isolation Solution A: 0.1% formic acid aqueous solution (v / v) Isolation Solution B: Acetonitrile gradient B%: 5→98→98% (0→25→35 min) Flow Rate: 0.2 ml / min Column Temperature: 40℃ Detector: UV-258nm <Quantitative Method> Under the above HPLC analytical conditions, the unreacted acid components were determined, the dissolution time was confirmed, and the peak area of ​​each component was measured. Then, under the above HPLC analytical conditions, the sample was analyzed, and the amount of unreacted acid components was calculated from the ratio of the peak area of ​​the obtained chromatogram to the peak area of ​​the standard (absolute calibration method). <Example 1> 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 tetrabutyl titanate (hereinafter sometimes abbreviated as TBT) as a catalyst at 0.0023 moles relative to all acid components were fed into a reaction vessel equipped with a stirrer, condenser, and thermometer. An esterification reaction (esterification step) was carried out while the temperature was increased from 180°C to 240°C over 4 hours (total polyol content / total polycarboxylic acid content = 1.07 (moles ratio)). Then, zinc acetate dihydrate at 0.023 moles relative to all acid components was fed, and the system was slowly depressurized over 20 minutes until the depressurization reached 5 mmHg. A polycondensation reaction (polycondensation step) was then carried out under a vacuum of less than 0.3 mmHg at 260°C for 80 minutes. The obtained polyester resin (1) was analyzed by NMR. The polycarboxylic acid content, in molar ratio, was 30.0 / 68.5 / 1.5 (molar%) for terephthalic acid / isophthalic acid / trimethoxylic acid, and the polyol content, in molar ratio, was 50.0 / 50.0 for ethylene glycol / neopentyl glycol. The reduced viscosity was 0.63 (dl / g), the acid value was 55 (eq / t), the titanium content was 5 (ppm by mass), and the zinc content was 71 (ppm by mass). The performance evaluation results are recorded in Table 1. <Examples 2-5, 8, 9, Comparative Examples 2-4> Following the manufacturing example of Example 1, a polyester resin was manufactured by feeding in a polyol component and a polycarboxylic acid component. However, the blending ratio of the metal catalyst was changed so that the amount relative to the obtained polyester resin was a predetermined amount. The resin composition, resin properties, and evaluation results are recorded in Table 1. <Examples 6 and 7> The amounts of ethylene glycol and neopentyl glycol were varied so that the feed ratios of all polyols and all polycarboxylic acids (all polyols / all polycarboxylic acids (molar ratio)) were 1.02 and 1.10, respectively. Otherwise, polyester resins were manufactured in the same manner as in Example 1. The resin composition, resin properties, and evaluation results are recorded in Table 1. <Example 10> 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-cyclohexanediol, and TBT as a catalyst (at 0.0051 moles relative to all acids) were fed into a reaction vessel equipped with a stirrer, condenser, and thermometer. An esterification reaction (esterification step) was carried out while the temperature was increased from 180°C to 240°C over 4 hours. Then, zinc acetate dihydrate (at 0.019 moles relative to all acids) was fed into the system, and the pressure was slowly reduced to 5 mmHg over 20 minutes. A polycondensation reaction (polycondensation step) was then carried out under a vacuum of less than 0.3 mmHg at 260°C for 80 minutes. Afterwards, the pressure was stopped, and the mixture was cooled to 220°C under nitrogen circulation. Then, 7.8 parts of trimellitic anhydride were added, and the mixture was stirred at 220°C for 2 hours to perform carboxyl modification (added later) to obtain the polyester resin. The resin composition, resin properties, and evaluation results are shown in Table 1. <Comparative Example 1> The feed amount of TBT was changed to 0.00024 mol% relative to all acid components, and the feed amount of zinc acetate dihydrate was changed to 0.017 mol% relative to all acid components. Otherwise, the polyester resin was manufactured according to the manufacturing example of Example 1. In addition, the reaction was terminated when the polycondensation reaction time reached 100 minutes. The resin composition, resin properties and evaluation results are recorded in Table 1. <Comparative Example 5> The feed amount of zinc acetate dihydrate was changed to 0.00326 mol% relative to all acid components, and the polyester resin was manufactured in the same manner as in Example 7. The resin composition, resin properties and evaluation results are recorded in Table 1. <Comparative Example 6> Following the manufacturing example of Example 1, but with a change in procedure, zinc acetate dihydrate was added before the esterification reaction (esterification step) to manufacture the polyester resin. The resin composition, resin properties, and evaluation results are recorded in Table 1. <Comparative Example 7> The feed rate of TBT was changed to 0.056 moles relative to all acid components, and zinc acetate dihydrate was not used. Otherwise, the polyester resin was manufactured in the same manner as in Example 1. The resin composition, resin properties, and evaluation results are recorded in Table 1. [Table 1] In Table 1, the copolymer components of the resins are represented by the following abbreviations: TPA: Terephthalic acid; IPA: Isophthalic acid; SA: Sebacic acid; TMA: Triterpenoid anhydride; EG: Ethylene glycol; NPG: Neopentyl glycol; CHDM: 1,4-Cyclohexanediethanol; Biopolymer EG: Biopolymer ethylene glycol (manufactured by India Glycols Ltd.); Biopolymer NPG: Biopolymer neopentyl glycol (manufactured by Perstorp, Neeture N40). [Industrial Applicability] According to the present invention, a polyester resin with good productivity, good color tone, low foreign matter content, and excellent metal adhesion and curing properties can be provided. Because of its excellent metal adhesion, curing properties, and storage stability, this resin is suitable for dry lamination adhesives, especially for bonding metal substrates such as aluminum foil to plastic films, and for coating applications, particularly for PCM (pre-coated metal) coatings and can coatings for metal sheets. [Figure 1] Figure 1 is a scanning electron microscope (SEM) image of foreign matter contained in polyester resin.

Claims

1. A polyester resin containing 2 to 10 ppm titanium by mass conversion and 50 to 90 ppm zinc by mass conversion, with antimony content of less than 1 ppm by mass conversion, wherein 5 g of the polyester resin is dissolved in 100 mL of a mixed solvent of phenol / tetrachloroethane (60 / 40 (mass ratio)), and the filtered material after filtration through a membrane filter with a pore size of 0.5 μm is visually observed by SEM to contain less than 12 foreign objects with a major diameter of 5 μm or larger, wherein the foreign objects include zinc salts of polycarboxylic acids.

2. The polyester resin as claimed in claim 1, wherein, The foreign substance is a zinc salt of a polycarboxylic acid.

3. The polyester resin as requested in item 1 or 2, wherein, The reduced viscosity is above 0.10 dl / g, and the acid value is above 50 eq / t.

4. The polyester resin as claimed in item 1 or 2, wherein, The content of trimellitic anhydride is less than 1000 ppm by mass.

5. A polyester resin composition comprising a polyester resin as claimed in any one of claims 1 to 4, and an isocyanate curing agent or a phenol curing agent.

6. A coating composition comprising the polyester resin composition of claim 5.

7. An adhesive composition comprising the polyester resin composition of claim 5.

8. A method for manufacturing a polyester resin as claimed in any one of claims 1 to 4, comprising manufacturing a prepolymer in the presence of a titanium catalyst and in the absence of a zinc catalyst, followed by polycondensation in the presence of both a titanium catalyst and a zinc catalyst.

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