Oxygen-absorbing film

Abstract

The present application provides an oxygen-absorbing film (1) suitable as a packaging material for inhibiting oxidation, excellent in non-adsorption of aroma components, and excellent in tearability, according to at least sequentially laminating, from the outer layer side, a surface base material layer (2) having oxygen barrier properties, an oxygen-absorbing resin layer (3), and an inner face base material layer (4) including a stretched PET base material and capable of heat sealing.

Description

TECHNICAL FIELD

[0001] The present application relates to an oxygen-absorbing film. BACKGROUND

[0002] In the past, in order to prevent deterioration of contents and the like, a so-called gas-substitution packaging in which a packaging body is substituted with an inert gas such as nitrogen gas while filling and sealing the contents has been known. At the time of gas substitution, air is sucked and exhausted from the packaging body at the time of filling the contents, or the air in the packaging body is forcibly substituted with the inert gas, but even with the gas-substitution packaging, it is difficult to completely remove oxygen in the packaging body. Therefore, the present applicant has proposed a packaging film having an oxygen-absorbing function, for example, in Patent Document 1.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT DOCUMENTS

[0005] Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 2001-039475

[0006] Patent Document 2: Japanese Patent Application Laid-Open (JP-A) No. 11-302405

[0007] Patent Document 3: Japanese Patent Application Laid-Open (JP-A) No. 2001-329077

[0008] Patent Document 4: Japanese Patent Application Laid-Open (JP-A) No. 6-220220

[0009] Patent Document 5: Japanese Patent Application Laid-Open (JP-A) No. 2004-196951 SUMMARY

[0010] PROBLEMS TO BE SOLVED BY THE INVENTION

[0011] With such a packaging film having an oxygen-absorbing function, it is possible to remove the oxygen remaining in the packaging body after filling, and thereby prevent deterioration and the like caused by oxidation of the packaging object, and long-term preservation is possible.

[0012] However, for example, in the case where a favorite such as coffee or the like that also acts on the sense of smell is used as the packaging object, it is important not only to suppress deterioration caused by oxidation, but also to maintain the aroma components, and a packaging film that can prevent the aroma components from being adsorbed to the packaging body itself is required.

[0013] Further, although the film for packaging is used as a packaging bag in various forms, tearability at the time of opening is also required. For example, generally, a polyester film is used as a part of a multilayered packaging body for food, pharmaceutical products. In view of the technical problem of improving the tearability of such a packaging body, a biaxially stretched polyester film made by mixing modified polybutylene terephthalate (PBT) in polyethylene terephthalate, a biaxially stretched polyester film made by mixing polycarbonate (PC) in polyethylene terephthalate, a biaxially stretched polyester film made by mixing acrylonitrile-styrene copolymer in polybutylene terephthalate, and the like are proposed (see Patent Documents 2, 3, 4, 5). Although improvement in tearability can be expected in all of them, in order to perform non-compatible blending of different kinds of thermoplastic resins, there are technical problems such as, for example, the haze of the film itself is high and the visual confirmation of the contents is reduced, or film breakage is easily caused when a single layer film is subjected to a stretching process, and the like.

[0014] The present inventors have completed the present application in view of the above circumstances, and an object thereof is to provide an oxygen absorbing film which is excellent in oxygen inhibition, non-adsorption of aroma components, and tearability, and is suitable as a packaging material for a packaging object.

[0015] Technical Solution

[0016] The oxygen absorbing film of the present application is configured to have, in order from the outer layer side, a surface base material layer having oxygen barrier properties, an oxygen absorbing resin layer, and an inner face base material layer including a stretched PET base material and capable of heat sealing.

[0017] Effects of the Invention

[0018] According to the present application, an oxygen absorbing film which is excellent in oxygen inhibition, non-adsorption of aroma components, and tearability, and is suitable as a packaging material for a packaging object can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a view for explaining one example of the oxygen absorbing film of the embodiment of the present application. DETAILED DESCRIPTION

[0020] Hereinafter, with respect to the oxygen absorbing film of the present application, an embodiment thereof is shown and explained.

[0021] The oxygen-absorbing film 1 in the present embodiment is at least sequentially stacked from the outer layer side with a surface base material layer 2 having oxygen barrier properties, an oxygen-absorbing resin layer 3, and an inner face base material layer 4 including a stretched PET base material and capable of heat sealing, in a manner such that the surface base material layer 2 is on the outer layer side and the inner face base material layer 4 is on the inner face side, and is suitable for use as a packaging material capable of long-term storage of a packaging object, for example, in a desired form such as a gusset pouch, a gusseted pouch, a flat pouch, a pillow form, and the like, in accordance with the packaging object.

[0022] [Surface base material layer]

[0023] In the surface base material layer 2, from the viewpoints of scratch resistance, chemical resistance, and the like, for example, a biaxially stretched film composed of a polyester-based resin such as polyethylene terephthalate, a polyamide-based resin such as nylon, or the like is preferably used as a base film; a laminated film including a coating layer containing an oxygen barrier resin such as a polyvinyl alcohol-based resin, an ethylene-vinyl alcohol copolymer, a polyacrylic acid-based resin, a vinylidene chloride-based resin, or the like as a main agent, a metal oxide such as silicon dioxide, aluminum oxide, or the like, or a vapor-deposited film of a metal, or the like is used as a surface base material, but is not limited thereto. In the surface base material layer 2, various base materials having oxygen barrier properties having an oxygen permeability of less than 50 cc / (m 2 ·day·atm), more preferably less than 25 cc / (m 2 ·day·atm) in an environment of 25°C-90% RH can be used as a surface base material.

[0024] [Oxygen-absorbing resin layer]

[0025] As the oxygen-absorbing resin used in the oxygen-absorbing resin layer 3, an oxygen-absorbing polyester-based resin including a functional group or a bonding group having reactivity with oxygen in the structure is preferably used. As the functional group or the bonding group having reactivity with oxygen, for example, a carbon-carbon double bond group, an aldehyde group, a phenolic hydroxyl group, or the like can be listed. An unsaturated polyester-based resin having a carbon-carbon double bond group is particularly preferable, and a polyester-based resin having an unsaturated alicyclic structure is more preferable. In the case of the polyester-based resin having an unsaturated alicyclic structure, the amount of production of low-molecular-weight decomposition components, which are by-products in the autoxidation reaction of the resin, is inhibited, and thus is advantageous.

[0026] As the polyester-based resin having an unsaturated alicyclic structure, for example, a polyester obtained by polymerization of a diol component with tetrahydrophthalic acid or a derivative thereof or tetrahydrophthalic anhydride or a derivative thereof as an acid component can be listed. In the case of tetrahydrophthalic acid or a derivative thereof or tetrahydrophthalic anhydride or a derivative thereof as the acid component, they can also be esterified as a methyl ester or the like.

[0027] As tetrahydrophthalic acid or its derivatives, or tetrahydrophthalic anhydride or its derivatives, 4-methyl-Δ is particularly preferred. 3 -Tetrahydrophthalic acid or 4-methyl-Δ 3 -Tetrahydrophthalic anhydride, cis-3-methyl-Δ 4 -Tetrahydrophthalic acid or cis-3-methyl-Δ 4 -Tetrahydrophthalic anhydride. These tetrahydrophthalic acids or their derivatives, or tetrahydrophthalic anhydrides or their derivatives, are highly reactive with oxygen, and therefore suitable for use as acid components.

[0028] It should be noted that these tetrahydrophthalic acids or their derivatives, or tetrahydrophthalic anhydrides or their derivatives, can be produced by making the 4-methyl-Δ 4 The 4-methyl-Δ-di(t-) is obtained and industrially manufactured by structural isomerization of a mixture of tetrahydrophthalic anhydride isomers. 4 -Tetrahydrophthalic anhydride is obtained by reacting the C5 fraction of naphtha, which is mainly composed of isoprene and trans-isoprene, with maleic anhydride.

[0029] Examples of diols include: ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, neopentanediol, 1,4-cyclohexanediol, 2-phenylpropanediol, 2-(4-hydroxyphenyl)ethanol, α,α-dihydroxy-1,3-diisopropylbenzene, o-xylenediol, m-xylenediol, p-xylenediol, α,α-dihydroxy-1,4-diisopropylbenzene, hydroquinone, 4,4-dihydroxybiphenyl, naphthol, or their derivatives. Aliphatic diols are preferred, such as diethylene glycol, triethylene glycol, and 1,4-butanediol, with 1,4-butanediol being more preferred. Using 1,4-butanediol yields oxygen-absorbing polyester resins with high oxygen absorption performance and low amounts of decomposition products generated during oxidation. These diol components can be used alone or in combination of two or more.

[0030] Oxygen-absorbing polyester resins, in addition to tetrahydrophthalic acid or its derivatives or tetrahydrophthalic anhydride or its derivatives, can also be substances that copolymerize aromatic dicarboxylic acids, aliphatic dicarboxylic acids, aliphatic hydroxycarboxylic acids, and other acid components or their derivatives contained in the raw material monomers.

[0031] As the aromatic dicarboxylic acid and its derivatives, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, and the like can be exemplified. Among them, phthalic acid, phthalic anhydride, isophthalic acid, and terephthalic acid are preferable.

[0032] As the aliphatic dicarboxylic acid and its derivatives, oxalic acid, malonic acid, succinic acid, succinic anhydride, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, 3,3-dimethylglutaric acid, and the like can be exemplified. Among them, succinic acid, succinic anhydride, adipic acid, and sebacic acid are preferable, and succinic acid is particularly preferable. Hexahydrophthalic acid, dimer acid, and their derivatives having an alicyclic structure can also be exemplified.

[0033] As the aliphatic hydroxycarboxylic acid and its derivatives, glycolic acid, lactic acid, hydroxypivalic acid, hydroxycaproic acid, and the like can be exemplified.

[0034] These other acid components can be esterified, for example, as dimethyl terephthalate, bis-2-hydroxydiethyl terephthalate, or can be anhydrides, for example, phthalic anhydride, succinic anhydride. These other acid components can be used alone or in combination of two or more.

[0035] By copolymerizing the other acid components, the glass transition temperature of the obtained oxygen-absorbing polyester-based resin can be easily controlled, and the oxygen-absorbing property can be improved. Furthermore, by controlling the crystallinity of the oxygen-absorbing polyester-based resin, the solubility in an organic solvent can also be improved.

[0036] In addition, tetrahydrophthalic acid or its derivatives or tetrahydrophthalic anhydride or its derivatives easily undergo a radical crosslinking reaction due to heat during polymerization, and thus by incorporating the other acid components, the composition ratio of tetrahydrophthalic acid or its derivatives or tetrahydrophthalic anhydride or its derivatives contained in the raw material monomers is reduced, and the gelation during polymerization can be suppressed, and a high-molecular-weight oxygen-absorbing polyester-based resin can be stably obtained.

[0037] The oxygen-absorbing polyester-based resin can further include a structural unit derived from a polyol, a polycarboxylic acid, or their derivatives, and the like. By introducing a polyol and a polycarboxylic acid and controlling the branched chain structure, the melt viscosity characteristics, the solution viscosity characteristics of the polyester dissolved in a solvent can be adjusted.

[0038] As the polyhydric alcohol and derivatives thereof, 1,2,3-propanetriol, sorbitol, 1,3,5-pentanetriol, 1,5,8-heptanetriol, trimethylolpropane, pentaerythritol, 3,5-dihydroxybenzyl alcohol, glycerol, or derivatives thereof can be exemplified.

[0039] As the polycarboxylic acid and derivatives thereof, 1,2,3-propanetricarboxylic acid, meso-butane-1,2,3,4-tetracarboxylic acid, citric acid, hemimellitic acid, pyromellitic acid, or derivatives thereof can be exemplified.

[0040] Further, in the case of copolymerizing a component having a functional group of three or more functions such as a polyhydric alcohol, a polycarboxylic acid, or the like, it is preferable to set it to 5 mol% or less with respect to the total acid component.

[0041] In the present embodiment, as the oxygen-absorbing resin, it is preferable to use an oxygen-absorbing polyester-based resin obtained by copolymerizing tetrahydrophthalic acid or a derivative thereof or tetrahydrophthalic anhydride or a derivative thereof as an acid component, 1,4-butanediol as a diol component, and succinic acid or succinic anhydride as another acid component.

[0042] In this case, the proportion of the structural unit derived from tetrahydrophthalic acid or a derivative thereof or tetrahydrophthalic anhydride or a derivative thereof in the oxygen-absorbing polyester-based resin with respect to the total acid component is preferably 70 mol% to 95 mol%, more preferably 75 mol% to 95 mol%, and further preferably 80 mol% to 95 mol%.

[0043] Further, the proportion of the structural unit derived from succinic acid or succinic anhydride with respect to the total acid component is preferably 0 mol% to 15 mol%, more preferably 0 mol% to 12.5 mol%, and further preferably 0 mol% to 10 mol%.

[0044] By setting the composition ratio as such, an oxygen-absorbing resin excellent in oxygen-absorbing properties and adhesiveness and excellent in solubility in an organic solvent can be obtained.

[0045] The oxygen-absorbing polyester-based resin can be synthesized, for example, by interfacial polycondensation, solution polycondensation, melt polycondensation, or solid-phase polycondensation, or the like. At this time, although a polymerization catalyst is not necessarily required, a general polyester polymerization catalyst such as a titanium-based, germanium-based, antimony-based, tin-based, aluminum-based, or the like can be used. A known polymerization catalyst such as a nitrogen-containing basic compound, a boric acid and a boric acid ester, an organic sulfonic acid-based compound, or the like can also be used. Furthermore, various additives such as an anti-coloring agent, an antioxidant, or the like can also be added at the time of polymerization. By adding an antioxidant, oxygen absorption during polymerization and after polymerization in processing can be suppressed, and thus a decrease in properties and gelation of the oxygen-absorbing resin can be suppressed.

[0046] Further, at the time of polymerization, it is preferable to appropriately adjust the composition ratio of the raw material monomers, the molecular weight, and the like polymerization conditions in such a manner that the melt viscosity at a shear rate of 100 s"1at a temperature of 220°C is less than 90 Pa-s, preferably less than 60 Pa-s, more preferably less than 30 Pa-s. By suppressing the melt viscosity to be low, good coatability can be exerted, and further, by incorporating a curing agent, an arbitrary material strength can be made, and thus it can be suitably used as a solvent-soluble dry lamination adhesive.

[0047] The number average molecular weight of the oxygen-absorbing polyester-based resin is preferably 500 to 100,000, more preferably 2,000 to 10,000. Further, the weight average molecular weight is preferably 5,000 to 200,000, more preferably 10,000 to 100,000, further preferably 20,000 to 70,000. In the case where the molecular weight is lower than the above range, the cohesion of the resin, that is, the creep resistance decreases, and in the case where the molecular weight is higher than the above range, a decrease in coatability caused by a decrease in solubility in an organic solvent and an increase in solution viscosity occurs, and thus it is not preferable.

[0048] The glass transition temperature of the oxygen-absorbing polyester-based resin is preferably -20°C to 10°C, more preferably -15°C to 6°C, further preferably -12°C to 2°C. By setting the glass transition temperature to such a range, sufficient oxygen-absorbing properties can be obtained.

[0049] In order to obtain sufficient oxygen-absorbing properties, the acid value of the oxygen-absorbing polyester-based resin is preferably 5 mgKOH / g or less, more preferably 1 mgKOH / g or less. In the case where the acid value exceeds 5 mgKOH / g, a rapid autoxidation reaction can be sometimes hindered, and stable oxygen-absorbing properties cannot be obtained.

[0050] Note that the method for measuring the acid value of the oxygen-absorbing polyester-based resin is based on JIS K 0070.

[0051] Further, when the oxygen-absorbing polyester-based resin is used as a solvent-soluble dry lamination adhesive, the lamination strength can sometimes decrease due to internal stress generated along with an oxygen-absorbing reaction (oxidative curing reaction). In order to suppress such a case, a component having a low glass transition temperature, in which a saturated polyester resin is a main component, can be incorporated. Such a component can alleviate the internal stress generated along with the oxidative curing reaction using its softness.

[0052] The saturated polyester resin is a polyester resin substantially free of carbon-carbon double bond groups, and can be obtained, for example, by polycondensation of a dicarboxylic acid component and a diol component, a hydroxycarboxylic acid component. The saturated polyester resin is preferably a polyester having an iodine value of 3 g / 100 g or less, and particularly preferably a polyester having an iodine value of 1 g / 100 g or less. In the case where the iodine value of the saturated polyester resin exceeds 3 g / 100 g, low-molecular-weight decomposition components are easily produced along with the oxygen absorption reaction of the oxygen-absorbing resin, and thus are not preferred.

[0053] Note that the method for measuring the iodine value is based on JIS K 0070.

[0054] As the dicarboxylic acid component, the aromatic dicarboxylic acids, aliphatic dicarboxylic acids, hexahydrophthalic acid, dimer acid, or derivatives thereof, and the like exemplified as the component of the oxygen-absorbing polyester-based resin can be exemplified. They can be used alone or in combination of two or more.

[0055] As the diol component, the diols exemplified as the component of the oxygen-absorbing polyester-based resin can be exemplified. They can be used alone or in combination of two or more.

[0056] As the hydroxycarboxylic acid component, the aliphatic hydroxycarboxylic acids exemplified as the component of the oxygen-absorbing polyester-based resin can be exemplified.

[0057] The glass transition temperature of the saturated polyester resin is preferably -10°C or lower, more preferably -70°C to -15°C, and further preferably -60°C to -20°C. By setting the glass transition temperature to such a range, the internal stress produced by the oxidative curing reaction due to oxygen absorption can be effectively mitigated.

[0058] The ratio A / B of the oxygen-absorbing polyester-based resin (A) to the saturated polyester resin (B) is preferably 0.6 to 9, more preferably 1 to 9, and further preferably 2 to 9. By setting the ratio A / B to such a range, excellent oxygen-absorbing properties can be exhibited, and a strong lamination strength is maintained before and after oxygen absorption.

[0059] In the oxygen-absorbing resin layer 3 formed using the oxygen-absorbing resin as described above, a transition metal catalyst can also be added in order to promote the oxygen-absorbing reaction. As the transition metal catalyst, mention can be made of transition metals such as manganese, iron, cobalt, nickel, copper, silver, tin, titanium, zirconium, vanadium, and chromium, and in particular, inorganic salts, organic salts, or complex salts of transition metals such as manganese, iron, cobalt, nickel, and copper are preferred. More specifically, as the transition metal catalyst, mention can be made of transition metal salts composed of a transition metal selected from the group consisting of manganese, iron, cobalt, nickel, and copper and an organic acid. In particular, from the viewpoint of promoting the oxygen-absorbing reaction of the oxygen-absorbing resin and improving the oxygen-absorbing property, the transition metal catalyst is preferably an organic acid salt of manganese, iron, or cobalt, and in particular, an organic acid salt of cobalt is preferred. The content of the transition metal catalyst in the oxygen-absorbing resin layer 3 is preferably 1 ppm to 1000 ppm, more preferably 10 ppm to 500 ppm, and further preferably 20 ppm to 300 ppm, in terms of the amount of metal.

[0060] Further, in forming the oxygen-absorbing resin layer 3, the oxygen-absorbing resin is preferably prepared in a manner that it can be dissolved in an organic solvent and used as a dry-type laminating adhesive. As the organic solvent, mention can be made of ethyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, isopropyl alcohol, and the like. In particular, ethyl acetate is less likely to cause malodor trouble due to residual solvent, and thus is generally used as a solvent for dry-type laminating adhesives for soft packaging, and when industrial application is considered, the use of ethyl acetate alone without toluene, xylene, or the like is preferred.

[0061] In the case of using an oxygen-absorbing polyester-based resin, an isocyanate-based curing agent can be incorporated to be used as a two-liquid curing type adhesive. In the case where an isocyanate-based curing agent is incorporated, the adhesive strength and cohesion are increased, and further, curing can be performed at a low temperature near room temperature.

[0062] As the isocyanate-based curing agent, mention can be made of, for example, aliphatic isocyanate-based curing agents such as xylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), lysine diisocyanate, lysine methyl ester diisocyanate, trimethyl hexamethylene diisocyanate, n-pentane-1, 4-diisocyanate, and the like; and alicyclic isocyanate-based curing agents such as isophorone diisocyanate (IPDI), cyclohexane-1, 4-diisocyanate, methylcyclohexyl diisocyanate, dicyclohexylmethane-4, 4'-diisocyanate, and the like. Among these, as the aliphatic isocyanate-based curing agent, XDI and HDI are preferred, and as the alicyclic isocyanate-based curing agent, IPDI is preferred. XDI is particularly preferred. By using XDI, the most excellent oxygen-absorbing performance is exerted.

[0063] These aliphatic and / or alicyclic isocyanate-based curing agents are preferably used as polyisocyanate compounds having a large molecular weight such as adducts, isocyanurates, biuret bodies, and the like.

[0064] In addition, these aliphatic and / or cycloaliphatic isocyanate-based curing agents can be used alone or in combination with two or more.

[0065] The isocyanate-based curing agent is preferably added in an amount of 3 to 30 parts by weight, more preferably 3 to 20 parts by weight, and further preferably 3 to 15 parts by weight, based on the solid content, relative to the oxygen-absorbing polyester-based resin as the main agent. When the amount added is too small, the adhesion and cohesion become insufficient, and when the amount added is too large, the amount of the oxygen-absorbing component contained in the unit weight of the resin composition becomes small, and the oxygen-absorbing performance becomes insufficient. In addition, in the case where the mobility of the resin is significantly reduced due to curing, the oxygen-absorbing reaction does not easily proceed, and the oxygen-absorbing performance is reduced.

[0066] [Inner surface substrate layer]

[0067] In order to make the tearability and non-adsorption of aroma components excellent, the inner surface substrate layer 4 is preferably formed using, as a surface substrate, a material that can be heat-sealed by laminating a heat-sealable polyester-based resin layer on the inner surface side of a stretched PET substrate, or a material that can be heat-sealed by making the entire thickness direction of the stretched PET substrate amorphous or low-crystalline in at least a heat-sealable region of the stretched PET substrate. For example, a general heat-sealant using a polyolefin-based resin as the main raw material can be single-sidedly coated on a film to be heat-sealable on a stretched PET substrate, but the non-adsorption is poor, and thus is insufficient.

[0068] Note that the inner surface side of the stretched PET substrate refers to the side opposite to the side of the oxygen-absorbing resin layer 3, and the heat-sealable region refers to a portion that is heat-sealed when a bag is made in the desired form as described above.

[0069] For such an inner surface substrate layer 4, first, a description will be given of a scheme including a stretched PET substrate and a heat-sealable polyester-based resin layer laminated on the inner surface side of the stretched PET substrate.

[0070] As the stretched PET substrate, a polyethylene terephthalate film after stretching and orientation is preferably used, and a biaxially stretched polyethylene terephthalate film is particularly preferably used. The stretched PET substrate is composed of a polyethylene terephthalate resin, but from the viewpoint of controlling the film moldability, crystallinity, and the like, it is preferably composed of a polyethylene terephthalate resin in which 0.1 to 3 mol% of terephthalic acid, which is an acid component, is modified with isophthalic acid. The thickness of the stretched PET substrate is not particularly limited as long as it has a desired oxygen permeability so as not to hinder the oxygen absorbing function of the oxygen absorbing resin layer 3, but in order to maintain the handleability and improve the oxygen permeability, the thickness of the stretched PET substrate is preferably 6 to 20 μm, more preferably 6 to 16 μm, and further preferably 7 to 14 μm.

[0071] From the viewpoint of non-adsorption of the aroma component, the heat-sealable polyester resin layer is preferably formed using a copolymer polyester that can be heat-sealed. It is particularly preferable to form using a copolymer polyester that is copolymerized with at least one acid component selected from the group consisting of terephthalic acid, isophthalic acid, and adipic acid, and at least one diol component selected from the group consisting of ethylene glycol, diethylene glycol, neopentyl glycol, propylene glycol, butanediol, and 1,4-cyclohexane dimethanol. In this case, in the polyester in which isophthalic acid is copolymerized with terephthalic acid as the acid component, the glass transition temperature is high, and thus the non-adsorption of the aroma component is also excellent, and furthermore, by copolymerization, the crystallinity of the resin can be controlled to be low, and thus the resin becomes amorphous, and thus the heat-sealability is also good, and is particularly preferable.

[0072] As the copolymer polyester that can be heat-sealed, for example, a copolymer polyester composed of terephthalic acid, ethylene glycol, and neopentyl glycol; a copolymer polyester composed of terephthalic acid, isophthalic acid, and ethylene glycol; a copolymer polyester composed of terephthalic acid, isophthalic acid, and propylene glycol; a copolymer polyester composed of terephthalic acid, ethylene glycol, and 1,4-cyclohexane dimethanol; a copolymer polyester composed of terephthalic acid, isophthalic acid, ethylene glycol, and neopentyl glycol; and a copolymer polyester composed of terephthalic acid, isophthalic acid, ethylene glycol, and diethylene glycol can be exemplified, but the present application is not particularly limited thereto.

[0073] Such a copolymer polyester has non-adsorption of the aroma component, heat-sealability, and moderate oxygen permeability, and thus does not hinder the oxygen absorbing function of the oxygen absorbing resin layer 3, and furthermore, has high adhesion to the stretched PET substrate, and thus the adhesive layer between the stretched PET substrate and the heat-sealable polyester resin layer can be omitted, and thus is suitable as the resin for forming the heat-sealable polyester resin layer in the present application.

[0074] The thickness of the heat-sealable polyester resin layer is preferably 0.1 μm to 5.0 μm, more preferably 0.5 μm to 4.0 μm, and further preferably 0.5 μm to 3 μm. In this case, although it is expected that the thicker the heat-sealable polyester resin layer, the higher the heat-seal strength, in the case where the heat-sealable polyester resin layer is made thinner than the thickness of the stretched PET substrate, both the tearability and the non-adsorption of aroma components are excellent, and thus this is particularly preferable.

[0075] As a method of laminating the heat-sealable polyester resin layer on the inner side of the stretched PET substrate, a known method can be used. For example, it can be produced by a method in which a coating agent in which the above resin is dissolved is applied to one side of the stretched PET substrate and dried, or after a double-layer film composed of a PET resin and the above copolyester resin is produced by a T-die method, uniaxial stretching or biaxial stretching treatment or the like is appropriately performed to the extent that the heat-sealability derived from the copolyester resin is not impaired, but it is not particularly limited thereto.

[0076] Next, a scheme in which the inner substrate layer 4 includes a stretched PET substrate, and in at least the heat-seal region of the stretched PET substrate, the entire thickness direction of the stretched PET substrate is amorphized or low-crystallized is described.

[0077] As the stretched PET substrate, the same material as in the above scheme can be used, and thus repeated description is omitted. The polyethylene terephthalate film after the stretching orientation is highly crystalline due to the orientation crystallization, and does not have heat-sealability, but by preheating the film surface as needed, and then scanning and irradiating the film surface with an ultraviolet laser beam or an infrared laser beam, and immediately quenching after the scanning is completed, it is possible to selectively amorphize or low-crystallize only a part of the film to impart heat-sealability, and thus it can be used as an inner substrate for forming the inner substrate layer 4 including a stretched PET substrate and capable of heat-sealing. This scheme is particularly preferable in view of the non-adsorption characteristics inherent to the polyethylene terephthalate resin itself.

[0078] The crystallinity of the untreated stretched PET region and the amorphized or low-crystallized PET region can be measured by a known method. For example, in addition to the usual density method (density based on a density gradient tube method), there is a method of measuring the density distribution using a laser Raman method and calculating the crystallinity from a conversion formula, which is described in Japanese Patent No. 7-80502.

[0079] In the present embodiment, in a case where at least the heat seal region of the stretched and oriented polyethylene terephthalate film is amorphized or low-crystallized, only the portion required for heat sealing is treated, and thus the treatment time can be shortened. In addition, the untreated portion other than this is excellent in non-adsorptivity derived from the stretched PET substrate, and is also high in crystallinity and excellent in tearability, and thus is preferable. In order to amorphize or low-crystallize at least the heat seal region of the stretched and oriented polyethylene terephthalate film, for example, the treatment method recited in Japanese Patent Application Publication No. 2016-000796, Japanese Patent Application Publication No. 2020-189892 can be applied.

[0080] In addition, in a case where at least the heat seal region of the stretched PET substrate is amorphized or low-crystallized by applying these treatment methods, the stretched PET substrate can also be laminated with other layers as needed, and the stretched PET substrate can be subjected to treatment.

[0081] As such, the inner substrate layer 4 in the present embodiment can be provided in any one of a scheme including a stretched PET substrate and a heat sealable polyester-based resin layer laminated on the inner surface side of the stretched PET substrate, or a scheme including a stretched PET substrate, and in at least the heat seal region of the stretched PET substrate, the entire thickness direction of the stretched PET substrate is amorphized or low-crystallized. Also, in any one of the schemes, in order not to hinder the oxygen absorbing function of the oxygen absorbing resin layer 3, the oxygen permeability of the inner substrate layer 4 is preferably 50 cc / (m 2 ·day·atm) or more, more preferably 80 cc / (m 2 ·day·atm) or more, and further preferably 100 cc / (m 2 ·day·atm) or more.

[0082] In the present embodiment, using the dry lamination adhesive containing the oxygen absorbing resin prepared as described above, the inner substrate forming the inner substrate layer 4 is dry-laminated on the surface substrate forming the surface substrate layer 2, and thus the oxygen absorbing film 1 can be manufactured. At this time, a publicly known dry lamination machine can be used, and for example, by a series of lamination processes of applying the dry lamination adhesive containing the oxygen absorbing resin to the surface substrate, volatilizing the organic solvent by a drying oven, and adhering the inner substrate to the surface substrate using a nip roll heated to 50°C to 120°C, the oxygen absorbing resin layer 3 composed of the oxygen absorbing adhesive resin contained in the dry lamination adhesive is formed between the surface substrate and the inner substrate. Thus, the oxygen absorbing film 1 in which the surface substrate layer 2 having oxygen barrier properties, the oxygen absorbing resin layer 3, and the inner substrate layer 4 are sequentially laminated can be manufactured.

[0083] In manufacturing the oxygen-absorbing film 1 like this, the coating amount of the dry-type laminating adhesive containing the oxygen-absorbing resin is preferably 0.1 g / m2or more, more preferably 1 g / m2or more, and even more preferably 2 g / m2or more, and is preferably 30 g / m2or less, more preferably 15 g / m2or less, and even more preferably 10 g / m2or less, in terms of solid content. 2 ~ 30 g / m2 2 , more preferably 1 g / m2 2 ~ 15 g / m2 2 , even more preferably 2 g / m2 2 ~ 10 g / m2 2 .

[0084] As the heat-seal strength of the oxygen-absorbing film 1, there is no particular limitation as long as the heat-seal interface is sufficiently sealed by being melted, and, for example, it is preferably 2 N / 15 mm or more as a lower limit value, and more preferably 9 N / 15 mm or more. At this time, the higher the heat-seal strength is, the more preferable it is in general, but as a packaging target, it can be appropriate to use for cases of relatively light foodstuffs, pharmaceuticals, and the like.

[0085] Further, if the heat-seal strength is too high, it is difficult to disassemble, and therefore the heat-seal strength is preferably 12 N / 15 mm or less as an upper limit value, more preferably 9 N / 15 mm or less, and particularly preferably 7 N / 15 mm or less.

[0086] According to the present embodiment as described above, it is possible to provide an oxygen-absorbing film 1 that is suitable as a packaging target, is excellent in non-adsorption of oxidation inhibitors and aroma components, and is also excellent in tearability.

[0087] Further, as described above, when the oxygen-absorbing polyester-based resin is used as the oxygen-absorbing resin and is prepared as a dry-type laminating adhesive for use, the laminating strength is sometimes reduced due to internal stress generated along with the oxygen-absorbing reaction. If the laminating strength is reduced and delamination occurs at the time of tearing, it can be difficult to tear the film, but by the inner face substrate layer 4 containing the stretched PET substrate, such a disadvantage can be effectively avoided.

[0088] Example

[0089] Hereinafter, specific examples will be given to describe the present application in more detail.

[0090] [Example 1]

[0091] A reaction vessel was charged with methyltetrahydrophthalic anhydride isomer mixture (manufactured by Hitachi Chemical Co., Ltd.; HN-2200) as an acid component at a molar ratio of 0.9, succinic anhydride as another acid component at a molar ratio of 0.1, 1,4-butanediol as a diol component at a molar ratio of 1.3, and tetraisopropyl titanate as a polymerization catalyst at 300 ppm in terms of composition ratio, and the mixture was allowed to react at 150°C to 200°C under a nitrogen atmosphere while removing water produced, for about 6 hours. Subsequently, the polymerization was performed at 200°C to 220°C under reduced pressure of 0.1 kPa for about 3 hours to obtain an oxygen-absorbing polyester resin (A). The number average molecular weight (Mn) of the oxygen-absorbing polyester resin (A) was 3400, the weight average molecular weight (Mw) was 52600, and the glass transition point (Tg) was -5.0°C.

[0092] A saturated polyester resin (B) having a Tg of 26°C (manufactured by DIC Co., Ltd.; POLYCIZER W4010 / Mn: 3600, Mw: 9500) was mixed into the obtained oxygen-absorbing polyester resin (A) at a solid component weight ratio A / B of 4.0, and HDI / IPDI-based curing agent (manufactured by DIC Graphic Co., Ltd.; KL-75) was mixed into the mixture at 7 parts per hundred resin (phr) in terms of solid component, as an isocyanate-based curing agent. Further, cobalt neodecanoate was added at 80 ppm in terms of metal content with respect to the total solid component, as a catalyst, and dissolved in ethyl acetate to prepare a dry lamination adhesive containing the oxygen-absorbing resin at a solid component concentration of 32 wt%.

[0093] Subsequently, a surface base material obtained by dry-laminating an aluminum foil having a thickness of 7 μm with a urethane-based adhesive, and an inner surface base material (oxygen permeability: 130 cc / (m2dayatm) at 25°C-60% RH) obtained by laminating a heat-sealable polyester-based resin layer composed of a copolyester having terephthalic acid and isophthalic acid as acid components, and ethylene glycol and neopentyl glycol as diol components (copolymerization ratio: terephthalic acid 29 mol%, isophthalic acid 21 mol%, ethylene glycol 28 mol%, neopentyl glycol 22 mol%) at a thickness of 1 μm on one side of a biaxially-stretched PET film (stretched PET base material) having a thickness of 12 μm were prepared, and they were placed in a dry lamination machine. 2 ·day·atm)) were prepared, and they were placed in a dry lamination machine.

[0094] Then, on the aluminum foil side of the surface base material, a pressure-sensitive adhesive layer was formed by coating a pressure-sensitive adhesive (manufactured by Nitto Co., Ltd.; OP-930) at a coating amount of 5 g / m 2The above dry lamination adhesive was coated and dry-laminated to the stretched PET side of the inner surface substrate, and further, stored for five days under a nitrogen atmosphere at 35°C, whereby an oxygen-absorbing film 1 composed of layers of a surface substrate layer (biaxially stretched PET film / amino acid ester adhesive / aluminum foil) 2 / oxygen-absorbing resin layer 3 / inner surface substrate layer (biaxially stretched PET film / heat-sealable polyester resin layer) 4 was obtained.

[0095] Note that the oxygen permeability of the inner surface substrate was determined as follows: The inner surface substrate was cut to a size of 50.2 cm 2 in length, 30.2 cm in width, and 0.02 cm in thickness, and mounted in a mixed gas permeation device (GTR TEC Co., Ltd.; flow type / water vapor permeability measuring device GTR-20XFTSK) to measure the oxygen permeability under the conditions of a temperature of 25°C, a humidity of 60% RH, an oxygen test gas flow rate of 40 ml / min, and a helium flow gas flow rate of 5 ml / min.

[0096] The obtained oxygen-absorbing film 1 was evaluated for (a) oxygen-absorbing performance, (b) tear strength, and (c) non-adsorption as described below. The results are shown in Table 1.

[0097] (a) Oxygen-absorbing performance

[0098] A test piece was cut from the oxygen-absorbing film 1 to a size of 2 cm in length and 15 cm in width, and loaded into an oxygen-impermeable steel foil laminated cup having an internal volume of 85 cm 3 with a humidity control solution composed of a glycerin aqueous solution, and heat-sealed with an aluminum foil laminated film cap, and stored under a 25°C atmosphere. The humidity inside the cup was controlled to 60% RH by the humidity control solution, and the oxygen concentration inside the cup after 28 days of storage was measured using a micro gas chromatograph device (INFICON Co., Ltd.; 3000 MICRO GC), and the oxygen-absorbing amount per 1 cm 2 of film was calculated. An oxygen-absorbing amount of 0.030 ml / cm 2 or more after 28 days of storage was set as good (O), and less than 0.030 ml / cm 2 was set as poor.

[0099] (b) Tear strength

[0100] A test piece was cut out from the oxygen-absorbing film 1 in a size of 150 mm x 50 mm, and a slit was cut in the long dimension of the test piece to form a pant-shaped test piece. The long leg of the pant-shaped test piece was attached to a tensile tester (Autograph AG-IS, manufactured by Shimadzu Corporation) under a temperature of 23°C and a humidity of 50% RH, and the tear strength (unit: N) was measured at a tearing speed of 200 mm / min in accordance with JIS K 7128-1. The tear strength was set to the average strength of 50 mm excluding 20 mm at the start of tearing and 5 mm at the end of tearing. The tear strength in the MD (flow direction) and TD (perpendicular direction) of less than 0.2 N was set to be good (O), and 0.2 N or more was set to be poor (X).

[0101] (c) Non-adsorbing

[0102] A test piece was cut out from the oxygen-absorbing film 1 in a size of 5 cm x 4 cm, and the heat-sealed layer 5 side was brought into contact with Salonpas Ae (manufactured by Dailichi Pharmaceutical Co., Ltd.). After the test piece was returned to the original product individual packaging bag and heat-sealed, it was left to stand for two weeks in an environment at a temperature of 22°C. Then, only the test piece was taken out, sealed in a glass vial, and warmed at 80°C for 30 minutes. The amount of adsorbed components volatilized was quantitatively measured using a gas chromatograph device (6890 Series GC System, manufactured by Agilent Technologies, Inc.; detector: FID) with a headspace sampler. The measurement target was set to three components of dl-camphor, 1-methanol, and methyl salicylate, and the adsorption amount in each sample was calculated as a relative value when the adsorption amount of a commercially available 12-μm stretched PET film was set to 1. The total of the relative values of the adsorption amounts of the three components was set to be less than 10 to be good (O), and 10 or more was set to be poor (X).

[0103] (d) Heat-sealing strength

[0104] A heat-sealing tester (manufactured by Tester Sangyo Co., Ltd.) was used, and the sealing time was fixed at 1 second and the sealing pressure was fixed at 2 kgf / cm 2 The sealing temperature range was set to 110°C to 190°C, and a test piece for measurement was prepared while measuring the temperature at the sealing interface. The heat-sealing strength was measured using a precision universal tester Autograph AG-IS (manufactured by Shimadzu Corporation) in an environment at a temperature of 23°C and a humidity of 50% RH in accordance with JIS-Z1707. The maximum test force (N / 15 mm width) was measured as the heat-sealing strength at a stretching speed of 300 mm / min in the flow direction (MD) of the film. In addition, the maximum value of the sealing strength in the above sealing temperature range was set to be the heat-sealing strength.

[0105] [Table 1]

[0106]

[0107] [Example 2]

[0108] As the inner face substrate, an inner face substrate (oxygen permeability: 140 cc / (m2dayatm) at 25°C-60% RH) in which a heat-sealable polyester-based resin layer composed of a copolyester (copolymerization ratio: terephthalic acid 41 mol%, isophthalic acid 9 mol%, ethylene glycol 48 mol%, diethylene glycol 2 mol%) in which the acid component was terephthalic acid and isophthalic acid and the diol component was ethylene glycol and diethylene glycol was layered at a thickness of 3 μm on one side of a biaxially stretched PET film (stretched PET substrate) having a thickness of 9 μm was used, and otherwise, the oxygen-absorbing film 1 was obtained in the same manner as in Example 1. For the obtained oxygen-absorbing film 1, (a) oxygen-absorbing performance, (b) tear strength, and (c) non-adsorptivity were evaluated. The results thereof are shown together in Table 1. 2 • day • atm) at 25°C-60% RH was used, and otherwise, the oxygen-absorbing film 1 was obtained in the same manner as in Example 1. For the obtained oxygen-absorbing film 1, (a) oxygen-absorbing performance, (b) tear strength, and (c) non-adsorptivity were evaluated. The results thereof are shown together in Table 1.

[0109] [Example 3]

[0110] For the stretched PET substrate having a thickness of 12 μm, a carbon dioxide gas laser oscillation device (wavelength 10.6 μm) was used, the output power was 35 W, the light spot diameter on the irradiation surface was about 2.7 mm, and the scanning line interval was 1 100 μm, and an inner face substrate in which only the heat-seal region of the stretched PET substrate and the entire thickness direction were amorphized was used at a scanning speed of 540 mm / sec, and otherwise, the oxygen-absorbing film 1 was obtained in the same manner as in Example 1. For the obtained oxygen-absorbing film, (a) oxygen-absorbing performance, (b) tear strength, and (c) non-adsorptivity were evaluated. The results thereof are shown together in Table 1.

[0111] Note that, at the time of evaluation, the test piece was cut out from outside the heat-seal region.

[0112] [Example 4]

[0113] In the oxygen-absorbing polyester resin (A), an HDI / IPDI-based curing agent (DIC Graphic Co., Ltd.; KL-75) was mixed as an isocyanate-based curing agent at 10 phr in terms of solid content, and a dry-type laminating adhesive containing the oxygen-absorbing resin was prepared, and otherwise, the oxygen-absorbing film 1 was obtained in the same manner as in Example 1. For the obtained oxygen-absorbing film 1, (a) oxygen-absorbing performance, (b) tear strength, and (c) non-adsorptivity were evaluated. The results thereof are shown together in Table 1.

[0114] [Example 5]

[0115] An oxygen-absorbing film 1 was obtained in the same manner as in Example 2, except that the dry-type laminating adhesive containing the oxygen-absorbing resin prepared in Example 4 was used. The obtained oxygen-absorbing film 1 was evaluated for (a) oxygen-absorbing property, (b) tear strength, and (c) non-adsorptivity. The results are shown in Table 1.

[0116] [Example 6]

[0117] An oxygen-absorbing film 1 was obtained in the same manner as in Example 3, except that the dry-type laminating adhesive containing the oxygen-absorbing resin prepared in Example 4 was used. The obtained oxygen-absorbing film 1 was evaluated for (a) oxygen-absorbing property, (b) tear strength, and (c) non-adsorptivity. The results are shown in Table 1.

[0118] [Comparative Example 1]

[0119] An oxygen-absorbing film 1 was obtained in the same manner as in Example 1, except that a non-stretched isophthalic acid-modified PET film (Toyo Rika Co., Ltd.; Fine Cast Film) having a thickness of 17 μm was used as the inner base material. The obtained oxygen-absorbing film 1 was evaluated for (a) oxygen-absorbing property, (b) tear strength, and (c) non-adsorptivity. The results are shown in Table 1.

[0120] [Comparative Example 2]

[0121] An oxygen-absorbing film 1 was obtained in the same manner as in Example 1, except that an amorphous PET film (Tama Poly Co., Ltd.; Hitoron PG) composed of a cyclohexane dimethanol-modified polyethylene terephthalate resin having a thickness of 30 μm was used as the inner base material. The obtained oxygen-absorbing film 1 was evaluated for (a) oxygen-absorbing property and (c) non-adsorptivity. The results are shown in Table 1.

[0122] The present application has been described above based on the preferred embodiments, but the present application is not limited to the above-described embodiments, and it is needless to say that various modifications can be made within the scope of the present application.

[0123] Explanation of Reference Numerals

[0124] 1 Oxygen-absorbing film

[0125] 2 Surface base material layer

[0126] 3 Oxygen-absorbing resin layer

[0127] 4 Inner base material layer

Claims

1. An oxygen-absorbing film characterized by, the oxygen-absorbing film has, from the outer layer side, a surface base material layer having oxygen barrier properties, an oxygen-absorbing resin layer, and an inner face base material layer including a biaxially-stretched PET base material after stretching whose thickness is 6 µm to 16 µm and which does not have heat sealability, stacked in this order, the inner face base material layer includes the biaxially-stretched PET base material and a heat sealable polyester-based resin layer whose thickness is 0.1 µm to 5.0 µm stacked on the inner face side of the biaxially-stretched PET base material, the heat sealable polyester-based resin layer is formed using a copolyester composed of terephthalic acid, ethylene glycol, and neopentyl glycol as three components, a copolyester composed of terephthalic acid, isophthalic acid, ethylene glycol, and neopentyl glycol as four components, or a copolyester composed of terephthalic acid, isophthalic acid, ethylene glycol, and diethylene glycol as four components.

2. The oxygen-absorbing film according to claim 1, wherein, The oxygen permeability of the inner substrate layer is 50 cc / (m 2 ·day·atm) or more at 25°C - 60% RH.

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