Composition for aqueous coating material using polyester resin

Abstract

Provided are: a composition for an aqueous coating material that comprises a polyester resin and inorganic particles, the composition having excellent adhesiveness and easy peelability with respect to a polyester base film, antifogging properties, and blocking resistance; a laminate; and a packaging material. The composition for an aqueous coating material contains a polyester resin (A) satisfying the following conditions and inorganic particles (B): (i) among the polycarboxylic acid components constituting (A), aromatic polyvalent carboxylic acid components having no sulfonic acid groups constitute 60-88 mol% of said polycarboxylic acid components, aromatic polyvalent carboxylic acid components having a sulfonic acid group constitute 8-20 mol% of said polycarboxylic acid components, and aliphatic polyvalent carboxylic acid components and / or alicyclic dicarboxylic acids constitute 5-20 mol% of said polycarboxylic acid components; (ii) among the polyhydric alcohol components constituting (A), glycols containing an ether group constitute more than 50 mol% of said polyhydric alcohol components; and (iii) the glass transition temperature of (A) is less than 20° C.

Description

Water-based paint composition using polyester resin

[0001] The present invention relates to an aqueous coating composition using a polyester resin with excellent water dispersibility. More specifically, the aqueous coating composition contains a polyester resin with extremely high hydrophilicity and water dispersibility as its main component, and when formed into a coating film, it has high adhesion, easy peelability, and anti-fogging properties.

[0002] Polyester resins are widely used as raw materials for resin compositions used in paints, coatings, adhesives, etc. Polyester resins are generally composed of polycarboxylic acids and polyhydric alcohols. By selecting and combining the polycarboxylic acids and polyhydric alcohols, the molecular weight can be freely controlled, and the resulting polyester resins are used in a variety of applications, including paints and adhesives.

[0003] In the molecular design of polyester resins, the selection of copolymerization components is important. Polycarboxylic acid components and polyhydric alcohol components can be broadly classified into aromatic, aliphatic, and alicyclic groups. The glass transition temperature (Tg), which indicates the flexibility of the polyester resin, can be determined by selecting these components. Generally, polyester resins are used as organic solvent solutions or aqueous dispersions, which are applied to substrates. However, in recent years, environmental concerns have led to a demand for aqueous dispersions. Among these, aqueous dispersions that do not use cosolvents or surfactants are most highly sought after from the perspectives of environmental concerns and recyclability.

[0004] Furthermore, in response to the recent trend toward mono-materials, lid materials for PET (amorphous polyethylene terephthalate) packaging containers have been used in which a polyester film is coated with a heat-sealable polyester adhesive composition and bonded to the film. There is a demand for polyester coating compositions that can be used for food applications and that combine excellent adhesion, easy peelability, anti-fogging properties, and blocking resistance.

[0005] For example, Patent Document 1 proposes a composition in which an anti-fog additive and an anti-blocking agent are added to a blend of a semi-crystalline polyester resin having a Tg of −30 to 0° C. and an amorphous polyester resin having a Tg of 45 to 110° C. Furthermore, Patent Document 2 proposes an anti-fog coating agent comprising a polyester resin, a metal compound, and a surfactant.

[0006] Patent No. 7280826 JP 2023-51805

[0007] However, in Patent Document 1, although the resin composition has anti-fogging properties and high adhesive strength, it is necessary to add an anti-fogging additive other than polyester to impart anti-fogging properties, which poses a problem in recyclability when applied to a PET substrate. Also, in Patent Document 2, it is necessary to add a surfactant in addition to the resin to impart water dispersibility and anti-fogging properties to the resin composition, which also poses a problem in recyclability when applied to a PET substrate.

[0008] The present invention has been made in view of the above-mentioned problems of the prior art, and its object is to provide an aqueous coating composition, a laminate and a packaging material comprising a polyester resin and inorganic particles, which have excellent adhesion, easy peelability, anti-fogging properties and anti-blocking properties, particularly for polyester substrates.

[0009] As a result of extensive research to achieve the above object, the present inventors have found that by combining a polyester resin of a specific composition with inorganic particles, it is possible to obtain an aqueous coating composition that can be used in food packaging applications, exhibits excellent adhesion to A-PET containers, and furthermore, does not require co-solvents, surfactants, or anti-fogging agents because the resin itself has excellent water dispersibility and anti-fogging properties, thereby completing the present invention.

[0010] That is, the present invention comprises the following (1) to (9).

[0011] (1) An aqueous coating composition containing a polyester resin (A) and inorganic particles (B), characterized in that the polyester resin (A) satisfies the following conditions (i) to (iii): (i) among the polycarboxylic acid components constituting the polyester resin (A), it contains 60 to 88 mol % of an aromatic polycarboxylic acid component not having a sulfonic acid group, 8 to 20 mol % of an aromatic polycarboxylic acid component having a sulfonic acid group, and 5 to 20 mol % of an aliphatic polycarboxylic acid component and / or an alicyclic dicarboxylic acid; (ii) among the polyhydric alcohol components constituting the polyester resin (A), it contains more than 50 mol % of a glycol containing an ether group; (iii) the glass transition temperature of the polyester resin (A) is less than 20°C. (2) The aqueous coating composition according to (1), wherein the reduced viscosity of the polyester resin (A) is 0.2 to 0.7 dl / g. (3) The aqueous coating composition according to (1), wherein the inorganic particles (B) have a particle size of 1 to 30 μm and a pore volume of 2 ml / g or less. (4) The aqueous coating composition according to (1), characterized in that it does not contain a curing agent. (5) A laminate film, characterized in that the aqueous coating composition according to any one of (1) to (4) is applied to at least one surface of a thermoplastic resin film. (6) The laminate film according to (5), wherein the thermoplastic resin film is a PET film. (7) A packaging material having the laminate film according to (6) as a constituent element. (8) A lid material for a food packaging container having the packaging material according to (7) as a constituent element. (9) A food packaging container having the lid material according to (8) as a constituent element.

[0012] The aqueous coating composition of the present invention has anti-fogging properties and also has high adhesion to PET and easy peelability, making it suitable for use as a heat seal layer in recyclable food packaging containers.

[0013] Hereinafter, embodiments of the present invention will be described in detail.

[0014] The aqueous coating composition of the present invention contains a polyester resin (A) that meets specific requirements and inorganic particles (B).

[0015] <Polyester Resin (A)> The polyester resin (A) has a chemical structure that can be obtained by polycondensation of a polycarboxylic acid component and a polyhydric alcohol component, and the polycarboxylic acid component and the polyhydric alcohol component each consist of one or more selected components.

[0016] The polycarboxylic acid component constituting the polyester resin (A) may be an aromatic carboxylic acid, an alicyclic polycarboxylic acid, and / or an aliphatic polycarboxylic acid, with aromatic dicarboxylic acids and aliphatic dicarboxylic acids being preferred.

[0017] The polycarboxylic acid component contains 60 to 88 mol %, preferably 65 to 85 mol %, and more preferably 70 to 80 mol % of an aromatic polycarboxylic acid component having no sulfonic acid group. If the amount of the aromatic polycarboxylic acid component having no sulfonic acid group is less than the above range, the adhesive strength of the coating film decreases, and if the amount is more than the above range, the substrate may be destroyed during peeling.

[0018] Examples of the aromatic polycarboxylic acid component not having a sulfonic acid group include aromatic polycarboxylic acid components such as terephthalic acid, isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, phenylenedicarboxylic acid, trimellitic acid, pyromellitic acid, benzophenonetetracarboxylic acid, and alkali metal salts thereof. While these may be used alone or in combination, isophthalic acid is preferred from the viewpoint of water dispersibility. Furthermore, in order to suppress gelation during synthesis, the content of trifunctional or higher aromatic polycarboxylic acid components is preferably 3 mol % or less.

[0019] The polycarboxylic acid component contains 8 to 20 mol %, preferably 10 to 15 mol %, of an aromatic polycarboxylic acid component having a sulfonic acid group. If the amount of the aromatic polycarboxylic acid component having a sulfonic acid group is less than the above range, the water dispersibility of the resin may decrease, and if the amount is more than the above range, the water resistance of the resin may decrease.

[0020] Examples of the aromatic polycarboxylic acid component having a sulfonic acid group include 5-sulfoisophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, 5-[4-sulfophenoxy]isophthalic acid, and alkali metal salts thereof. These can be used alone or in combination of two or more.

[0021] The polycarboxylic acid component contains 5 to 20 mol %, preferably 6 to 18 mol %, and more preferably 10 to 15 mol % of an aliphatic polycarboxylic acid component and / or an alicyclic polycarboxylic acid component. If the content of the aliphatic polycarboxylic acid component and / or the alicyclic polycarboxylic acid component is less than the above range, the water dispersibility of the resin may decrease, and if it is more than the above range, the moisture resistance of the resin may decrease. The aliphatic polycarboxylic acid component and / or the alicyclic polycarboxylic acid component preferably does not have a sulfonic acid group.

[0022] Examples of the aliphatic polycarboxylic acid component include succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, dimer acid, fumaric acid, maleic acid, itaconic acid, and citraconic acid, and examples of the alicyclic polycarboxylic acid include 1,4-cyclohexanedicarboxylic acid, tetrahydrophthalic acid, hexahydroisophthalic acid, 1,2-cyclohexenedicarboxylic acid, and 2,5-norbornanedicarboxylic acid. These may be used alone or in combination of two or more.

[0023] Among the polyhydric alcohol components, it is preferable to contain more than 50 mol% of an ether group-containing glycol, such as diethylene glycol. This is preferably 55 mol% or more, more preferably 60 mol% or more, even more preferably 70 mol% or more, and even more preferably 80 mol% or more, and even 100 mol% is acceptable. When the ether group-containing glycol is contained in an amount of more than 50 mol%, the resin has good water dispersibility, which is preferable. It is preferable in terms of moisture resistance to incorporate components other than the ether group-containing glycol in an amount of 50 mol% or less. Among the ether group-containing glycols, diethylene glycol is particularly preferable from the viewpoint of not distributing the hydrophilic portion of the resin skeleton unevenly and improving moisture resistance due to hydrolysis.

[0024] Among the polyhydric alcohol components, examples other than diethylene glycol include aliphatic glycols such as ethylene glycol, 1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1,4-butanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 2-methyl-1,8-octanediol, 3-methyl-1,6-hexanediol, 4-methyl-1,7-heptanediol, 4-methyl-1,8-octanediol, and 1,9-nonanediol; alicyclic glycols such as 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tricyclodecane glycols, and hydrogenated bisphenols; and polyether glycols such as triethylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. These may be used alone or in combination of two or more.

[0025] In addition, in order to impart an acid value, acid anhydrides such as trimellitic anhydride and pyromellitic anhydride may be added (post-added) after the polymerization of the polyester resin (A). Specific examples of acid anhydrides for imparting an acid value include trimellitic anhydride, pyromellitic anhydride, and ethylene glycol bisanhydrotrimellitate, and one or more of these can be used. When added (post-added), the total amount of the polycarboxylic acid component and the polyhydric alcohol component may exceed 200 mol%. In this case, the total amount of the composition excluding the component to which the acid anhydride or the like is added (post-added) is calculated as 200 mol%.

[0026] When producing the polyester resin (A), examples of polymerization catalysts that can be used include titanium compounds such as tetra-n-butyl titanate, tetraisopropyl titanate, and titanium oxyacetylcetonate, antimony compounds such as antimony trioxide and tributoxyantimony, germanium compounds such as germanium oxide and tetra-n-butoxygermanium, and acetates of magnesium, iron, zinc, manganese, cobalt, and aluminum. These catalysts can be used alone or in combination of two or more.

[0027] The method for producing polyester resin (A) is not particularly limited, and examples thereof include 1) a method in which a polycarboxylic acid and a polyhydric alcohol are heated in the presence of an arbitrary catalyst, followed by a dehydration esterification step, followed by a polyhydric alcohol removal / polycondensation reaction, and 2) a method in which an alcohol ester of a polycarboxylic acid and a polyhydric alcohol are heated in the presence of an arbitrary catalyst, followed by a transesterification reaction, followed by a polyhydric alcohol removal / polycondensation reaction, etc. In the methods 1) and 2), part or all of the acid component may be substituted with an acid anhydride.

[0028] The glass transition temperature (Tg) of the polyester resin (A) is less than 20°C, preferably −15°C or higher and lower than 20°C, and more preferably −10°C or higher and lower than 20°C. A Tg of less than 20°C is preferable because it improves the ease of opening when the coating composition according to the present invention is used as a lid material for a container. A Tg of −15°C or higher is preferable because it prevents blocking from occurring during preparation of the coating composition.

[0029] The reduced viscosity (ηsp / c) of the polyester resin (A) is preferably 0.2 to 0.7 dl / g, more preferably 0.3 to 0.6 dl / g. By setting it to be equal to or greater than the lower limit, the resin cohesive force is improved, and excellent adhesive properties can be exhibited. Furthermore, by setting it to be equal to or less than the upper limit, water dispersibility is improved. The reduced viscosity can be adjusted as desired by changing the polymerization time, temperature, and degree of reduced pressure during polymerization (in the case of reduced pressure polymerization) of the polyester resin.

[0030] The polyester resin (A) is preferably 95% by mass or more relative to 100% by mass of the solids content of the aqueous coating composition. By adjusting the amount to be equal to or more than the lower limit, excellent anti-fogging properties and adhesiveness can be achieved by the aromatic polycarboxylic acid component having sulfonic acid groups and the glycol having ether groups, which are the hydrophilic parts of the polyester resin (A), without blending an anti-fogging agent.

[0031] <Inorganic particles (B)> Inorganic particles (B) are not particularly limited, but include inorganic particles containing oxides, hydroxides, sulfates, carbonates, or silicates of metals such as magnesium, calcium, barium, zinc, zirconium, molybdenum, silicon, antimony, or titanium.Among these inorganic particles, silica particles are particularly preferred.The shape of the particles may be any shape, such as powder, granules, granules, platelets, or needles, and is not particularly limited.

[0032] The inorganic particles (B) preferably have an average particle size of 1 to 30 μm, more preferably 1 to 20 μm, and even more preferably 1 to 12 μm. If the average particle size is less than the above range, the anti-blocking effect may not be exhibited. If the average particle size is greater than the above range, the adhesive strength of the coating film may decrease.

[0033] The pore volume of the inorganic particles (B) is preferably 2 ml / g or less, more preferably 1 ml / g or less. If the pore volume is greater than 2 ml / g, the particles may be destroyed during preparation of the coating composition, and a sufficient anti-blocking effect may not be exhibited. In addition, the pore volume of the inorganic particles (B) is preferably 0.1 ml / g or more from the viewpoint of exhibiting the anti-blocking effect.

[0034] The inorganic particles (B) are preferably less than 5% by mass relative to 100% by mass of the solid content of the aqueous coating composition. By setting the content below the upper limit, anti-blocking properties can be exhibited without reducing adhesiveness. In addition, from the viewpoint of exhibiting the anti-blocking effect, the inorganic particles (B) are preferably 0.5% by mass or more relative to 100% by mass of the solid content of the aqueous coating composition.

[0035] The aqueous coating composition of the present invention can form a coating film without adding a curing agent. Therefore, it is preferable that the coating composition of the present invention does not substantially contain a curing agent, that is, the curing agent content is preferably less than 1 part by mass (solid content equivalent) per 100 parts by mass (solid content equivalent) of the polyester resin (A). By not adding a curing agent, recycling of the coating film becomes easier.

[0036] In the aqueous coating composition of the present invention, the content of the curing agent is preferably less than 1 part by mass, more preferably less than 0.5 parts by mass, and even more preferably less than 0.1 parts by mass, per 100 parts by mass of the polyester resin (A) (solid content), and most preferably no curing agent is contained.

[0037] Here, the curing agent refers to a known curing agent that reacts with a polyester resin to form a crosslinked structure, and the form of the crosslinked structure can be, for example, a reaction in which unsaturated double bonds in the polyester resin are reacted by a radical addition reaction, a cation addition reaction, an anion addition reaction, etc. to form an intermolecular carbon-carbon bond, or the formation of an intermolecular bond by a condensation reaction with a polycarboxylic acid group or a polyhydric alcohol group in the polyester resin, a polyaddition reaction, an ester exchange reaction, etc. Examples of the curing agent include phenolic resins, amino resins, isocyanate compounds, epoxy compounds, β-hydroxylamide compounds, unsaturated bond-containing resins, etc.

[0038] In the aqueous coating composition of the present invention, the content of the antifogging agent is preferably less than 1 part by mass, more preferably less than 0.5 parts by mass, even more preferably less than 0.1 parts by mass, per 100 parts by mass of the polyester resin (A) (solid content), and most preferably no antifogging agent is contained.

[0039] Examples of the anti-fogging agent include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants.

[0040] <Laminate film> The laminate film of the present invention is formed by applying the aqueous coating composition described above to at least one surface of a thermoplastic resin film. In particular, the laminate film of the present invention is obtained by applying the aqueous coating composition described above to a thermoplastic resin film as a substrate, followed by a drying treatment.

[0041] Examples of thermoplastic resin films include polyester-based resin films, polypropylene-based resin films, polyamide-based resin films, polyvinyl alcohol-based resin films, and polyvinylidene chloride-based resin films. Among these, polyester-based resin films, particularly PET films, are preferred because they are suitable as lid materials for food packaging containers.

[0042] The laminated film of the present invention has excellent adhesiveness and anti-fogging properties, making it suitable as a component of packaging materials and blister packs for pharmaceuticals, etc. It is particularly suitable as a lid material for food packaging containers for fresh foods, processed foods such as yogurt, etc. When used as a lid material for a food packaging container, the contents can be sealed by heat-sealing the coated surface of the laminated film to the food packaging container, and the lid material can also have anti-fogging properties. The food packaging container is not particularly limited, but a polyester-based resin is preferred.

[0043] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to these examples. In the examples and comparative examples, parts simply refer to parts by mass. (Methods for measuring physical properties)

[0044] Measurement of polyester resin composition: Using a 400 MHz 1H-nuclear magnetic resonance spectrometer (1H-NMR), the molar ratios of the polycarboxylic acid components and polyhydric alcohol components constituting the polyester resin were determined. Deuterated chloroform was used as the solvent.

[0045] Measurement of Glass Transition Temperature (Tg) Using a differential scanning calorimeter (DSC) DSC-220 manufactured by Seiko Instruments Inc., 5 mg of a sample (heat-sealable polyester resin) was sealed in an aluminum lid-type container, and measurement was carried out from −100° C. to 250° C. at a temperature increase rate of 20° C. / min. Glass transition temperature (Tg) was determined as the temperature at the intersection of an extension of the baseline below the glass transition temperature and a tangent line showing the maximum slope between the rising part of the peak and the apex of the peak.

[0046] Measurement of reduced viscosity (unit: dl / g) The polyester resin was dissolved in a measurement solvent of phenol / tetrachloroethane (mass ratio 6 / 4) at a sample concentration of 0.1 g / 25 ml, and the viscosity was measured at a measurement temperature of 30° C. using an Ubbelohde viscometer.

[0047] Evaluation of Water Dispersibility 210 parts by mass of polyester resin and 490 parts by mass of water were mixed and stirred and dissolved at 80°C, and the state of dispersion was evaluated according to the following evaluation criteria. <Evaluation criteria> ⊚: Dispersed in water within 1 hour of stirring without leaving any unemulsified matter. The unemulsified matter referred to here refers to components that settle when the aqueous dispersion is left standing at 25°C for 1 day after preparation. ◯: Dispersed in water within 1 to 3 hours of stirring without leaving any unemulsified matter. ×: Not dispersed in water or unemulsified matter remains even after stirring for more than 3 hours

[0048] Evaluation of Moisture Resistance Polyester resin was stored (left to stand) for 2 weeks at 40°C and 80% RH, and its reduced viscosity retention rate (before storage / after storage) was confirmed. <Evaluation criteria> ○: retention rate of 90% or more ×: retention rate of less than 90%

[0049] <Average particle size of inorganic particles> Measurement was performed using a HORIBA LA-750 Particle Size Analyzer. The particle size corresponding to 50 mass percent was read and this value was taken as the average particle size.

[0050] <Pore Volume of Inorganic Particles> The pore volume was determined by measuring the BET nitrogen adsorption isotherm using AS-1 manufactured by Quantachrome Co., Ltd. Specifically, the pore volume was determined when the relative pressure P / P0 was 0.98.

[0051] The aqueous coating compositions obtained in the Examples and Comparative Examples were applied to a 25 μm thick biaxially stretched PET film (Toyobo Ester E5102, manufactured by Toyobo Co., Ltd.) to a thickness of 3 to 4 μm. The film was then dried at 100° C. for 60 seconds to obtain a laminate film.

[0052] Blocking evaluation The laminated film for evaluation was cut into a 10 cm square, and the coated surface was heat-pressed against a 10 cm square untreated surface of a 25 μm thick A-PET film at a temperature of 45° C. and a pressure of 1.5 MPa for 30 seconds. Blocking was then evaluated by peeling it off by hand. <Evaluation criteria> ○: Able to be peeled off by hand without breaking the material ×: Cannot be peeled off by hand without breaking the material

[0053] Anti-fogging evaluation 100 ml of water at 50°C was poured into a 200 ml mayonnaise bottle, and the laminated film for evaluation was attached to the opening of the bottle with the coating surface facing inward. After that, the film was left to stand at 5°C for 1 hour so that water would not come into direct contact with the coating film, and then the appearance of the film was visually inspected. <Evaluation criteria> ○: No condensation occurred on the film ×: Condensation occurred on the film

[0054] Peel strength (adhesion) The coated surface of the laminated film for evaluation was heat-sealed to a 25 μm thick A-PET film at a temperature of 130°C and a pressure of 0.2 MPa for 1 second. Then, a 15 mm wide test piece was cut out and subjected to a 180° peel test at a tensile speed of 200 mm / min using an Autograph AG-Xplus manufactured by Shimadzu Corporation at 25°C to measure the peel strength. <Evaluation criteria> ◎: 7 N / 15 mm or more ○: 5 N / 15 mm or more but less than 7 N / 15 mm △: Less than 5 N / 15 mm ×: Material failure

[0055] Synthesis of Polyester Resin (A-1) In a reactor equipped with a stirrer, thermometer, heater, cooling device, and distillation condenser, 373 parts by mass of dimethyl isophthalate, 71 parts by mass of 5-dimethyl sulfoisophthalate, 458 parts by mass of diethylene glycol, and 0.2 parts by mass of tetrabutyl titanate were charged, and the temperature was raised to 220 ° C. while carrying out a transesterification reaction over 3 hours. Thereafter, the temperature was lowered once to 150 ° C., 49 parts by mass of sebacic acid was added, and the temperature was again raised to 220 ° C. while carrying out an esterification reaction over 4 hours. After completion of the esterification reaction, the pressure inside the system was raised to 270 ° C. while reducing the pressure to 10 torr over 60 minutes, and further reduced to a vacuum of 1 torr or less, and a polycondensation reaction was carried out at 270 ° C. until the predetermined viscosity was reached. After completion of the reaction, the polyester resin was removed and cooled to obtain polyester resin (A-1).

[0056] Synthesis of Polyester Resins (A-2) to (A-10) and (B-1) to (B-9) As in the synthesis example of polyester resin (A-1), polyester resins (A-2) to (A-10) and (B-1) to (B-9) were obtained by changing the types and blending ratios of raw materials as shown in Table 1.

[0057] Example 1: Preparation of aqueous coating composition (A-1) Polyester resin (A-1) was dispersed in water according to the following procedure. 206 parts by mass of polyester resin (A-1), 4 parts by mass of silica particles (powder, particle size 3 μm, pore volume 0.6 ml / g), and 490 parts by mass of water were charged into a reaction vessel equipped with a stirrer, condenser, and thermometer, and the mixture was stirred at 80°C for 1 to 3 hours. After cooling to room temperature, the mixture was removed from the reaction vessel to obtain aqueous coating composition (A-1).

[0058] Examples 2 to 10, Comparative Examples 1 to 9 In the same manner as in Example 1, polyester resins (A-2) to (A-10) and (B-1) to (B-9) were used to obtain aqueous coating compositions (A-2) to (A-10) and (B-1) to (B-9), respectively.

[0059] The polyester resin compositions, physical properties, and evaluation results of various characteristics of Examples 1 to 10 and Comparative Examples 1 to 9 are shown in Table 1.

[0060]

[0061] As is clear from Table 1, the aqueous coating compositions of Examples 1 to 10 all achieved satisfactory water dispersibility, moisture resistance, anti-blocking properties, anti-fogging properties, and adhesive strength. On the other hand, the aqueous coating composition of Comparative Example 1 lacked anti-blocking properties due to the absence of inorganic particles. Furthermore, the aqueous coating compositions of Comparative Examples 2 to 9 were deficient in one or more of the physical properties due to differences in the composition ratio of the polyester resin or differences in glass transition temperature.

[0062] A laminate film coated with the aqueous coating composition of the present invention exhibits excellent water dispersibility, moisture resistance, anti-blocking properties, anti-fogging properties, and adhesive strength when heat-sealed as a lid material for a packaging container. Furthermore, since no anti-fogging agent is used, the coating is highly recyclable when applied to a thermoplastic resin film. Therefore, the aqueous coating composition of the present invention is extremely useful in the food packaging container industry.

Claims

1. An aqueous coating composition containing a polyester resin (A) and inorganic particles (B), characterized in that the polyester resin (A) satisfies the following conditions (i) to (iii): (i) among the polycarboxylic acid components constituting the polyester resin (A), it contains 60 to 88 mol % of an aromatic polycarboxylic acid component not having a sulfonic acid group, 8 to 20 mol % of an aromatic polycarboxylic acid component having a sulfonic acid group, and 5 to 20 mol % of an aliphatic polycarboxylic acid component and / or an alicyclic dicarboxylic acid; (ii) among the polyhydric alcohol components constituting the polyester resin (A), it contains more than 50 mol % of a glycol containing an ether group; (iii) the glass transition temperature of the polyester resin (A) is less than 20°C.

2. The aqueous coating composition according to claim 1, wherein the polyester resin (A) has a reduced viscosity of 0.2 to 0.7 dl / g.

3. The aqueous coating composition according to claim 1, wherein the inorganic particles (B) have a particle size of 1 to 30 μm and a pore volume of 2 ml / g or less.

4. The aqueous coating composition according to claim 1, which does not contain a curing agent.

5. A laminated film comprising a thermoplastic resin film and a water-based coating composition according to any one of claims 1 to 4 applied to at least one surface of the film.

6. The laminated film according to claim 5, wherein the thermoplastic resin film is a PET film.

7. A packaging material having the laminated film according to claim 6 as a component.

8. A lid material for a food packaging container, comprising the packaging material according to claim 7 as a component.

9. A food packaging container having the lid material according to claim 8 as a component.

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