Oxygen-absorbing resin composition and oxygen-absorbing film containing the same

Abstract

To provide an oxygen absorbent resin composition capable of being stably used even under ambient air by suppressing inactivation during handling, and capable of easily controlling oxygen absorption reactions, and an oxygen absorbent film containing the same.SOLUTION: The invention relates to an oxygen absorbent resin composition containing an oxygen absorbent resin, a transition metal catalyst, and an acid compound having 2 or more functional groups selected from a carboxyl group and a hydroxyl group in the same molecule, preferably an oxygen absorbent resin composition in which at least one of acid dissociation constant (pKa) of a diluted solution of the acid compound at 25°C is smaller than 3.7.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an oxygen-absorbing resin composition whose oxygen-absorbing reaction can be controlled by controlling temperature, humidity, etc., and an oxygen-absorbing film containing the same. [Background technology]

[0002] Various oxygen-absorbing resin materials have been proposed for use as packaging materials for beverages, foods, and pharmaceuticals (for example, Patent Document 1). Furthermore, an oxygen-absorbing adhesive resin composition using such an oxygen-absorbing resin material has been proposed (Patent Document 2). However, when oxygen-absorbing packaging materials using such oxygen-absorbing resins are exposed to the atmosphere, they immediately start an oxidation reaction, which makes them difficult to handle during film production and bag-making processes, and the film can become inactivated depending on the exposure time. For example, when oxygen-absorbing packaging materials using oxygen-absorbing resins are stored for a long period of time, they may not be able to exhibit the desired oxygen absorption capacity when used. For example, in Patent Document 3, the incorporation of an antioxidant into an oxygen-absorbing resin layer was considered in order to prevent deactivation during handling and improve oxygen absorption capacity, and an appropriate amount of antioxidant was found to increase the amount of oxygen absorbed by the packaging material and prevent discoloration of the packaging material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4978884 [Patent Document 2] Patent No. 5671802 [Patent Document 3] Patent No. 5862988 [Patent Document 4] Patent No. 4863042 Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, methods of controlling the oxygen absorption reaction itself have been investigated, focusing on the oxygen absorption capacity of oxygen-absorbing resins. For example, Patent Document 4 considers a method of inducing an oxygen absorption reaction by irradiating a laminate containing an oxygen-absorbing resin with ultraviolet light in a specific wavelength range. However, this method requires special processes such as irradiation equipment, which results in problems such as high manufacturing costs and poor productivity. The present invention aims to provide an oxygen-absorbing resin composition that can be stably used even in the atmosphere by suppressing deactivation during handling, and that can easily control the oxygen absorption reaction, and an oxygen-absorbing film containing the same. [Means for solving the problem]

[0005] The present inventors focused on developing an oxygen-absorbing resin having an oxygen absorption trigger, which prevents the oxygen absorption reaction from starting until the oxygen absorption capacity is required, and an oxygen-absorbing film containing the same, and which can easily start the oxygen absorption reaction at any timing. As a result of intensive research, the present inventors discovered that by adding a transition metal catalyst and an acid compound such as a specific organic acid or inorganic acid to the oxygen-absorbing resin, the oxygen absorption capacity of the oxygen-absorbing resin can be controlled in conjunction with control of external environmental conditions such as humidity, and thus completed the present invention. That is, the present invention is configured as follows: [1] to [7]. [1] An oxygen-absorbing resin composition comprising an oxygen-absorbing resin, a transition metal catalyst, and an acid compound having two or more functional groups selected from a carboxyl group and a hydroxyl group in the same molecule. [2] The oxygen-absorbing resin composition according to [1] above, wherein at least one of the acid dissociation constants (pKa) of the acid compound in a diluted aqueous solution at 25°C is lower than 3.7. [3] The oxygen-absorbing resin composition according to [1] or [2], wherein the acid compound is one or more selected from the group consisting of oxalic acid, citric acid, glycolic acid, and phosphoric acid. [4] The oxygen absorbing resin is 4-methyl-△ 3-Tetrahydrophthalic acid, 4-methyl-△ 3 -Tetrahydrophthalic anhydride, cis-3-methyl-△ 4 -Tetrahydrophthalic acid, cis-3-methyl-△ 4 The oxygen-absorbing resin composition according to any one of [1] to [3] above, which contains an oxygen-absorbing polyester resin having a structural unit derived from tetrahydrophthalic anhydride or a derivative thereof. [5] The oxygen-absorbing resin composition according to any one of the above [1] to [4], wherein the transition metal catalyst is a transition metal salt composed of a transition metal selected from manganese, iron, cobalt, nickel, and copper and an organic acid. [6] An oxygen-absorbing adhesive comprising an isocyanate-based curing agent and the oxygen-absorbing resin composition according to any one of [1] to [5] above. [7] An oxygen-absorbing film having a laminated structure including a film substrate and an oxygen-absorbing layer, An oxygen-absorbing film, wherein the oxygen-absorbing layer comprises the oxygen-absorbing resin composition according to any one of [1] to [5] above or the oxygen-absorbing adhesive according to [6] above. [Effects of the Invention]

[0006] The present invention can provide an oxygen-absorbing resin having an oxygen absorption trigger function that can control the oxygen absorption reaction in a simple manner and at low production costs, and an oxygen-absorbing film containing the same. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a graph showing the oxygen absorption trigger obtained from the oxygen-absorbing resin composition of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] <Oxygen-absorbing resin composition> The oxygen-absorbing resin composition of the present invention contains at least an oxygen-absorbing resin, a transition metal catalyst, and an acid compound having two or more functional groups selected from carboxyl and hydroxyl groups in the same molecule. In the oxygen-absorbing film of the present invention, the incorporation of both the transition metal catalyst and a specific acid compound makes it possible to control the activity of the transition metal catalyst and the oxygen-absorbing capacity of the oxygen-absorbing resin itself, thereby imparting a humidity-dependent oxygen absorption reaction. When the inherent oxygen-absorbing capacity of the oxygen-absorbing resin composition is taken as 100%, and the time at which the oxygen-absorbing capacity reaches 100% is taken as day 0, the oxygen-absorbing resin composition of the present invention is characterized by its ability to maintain at least 75%, more preferably 80%, and even more preferably 90% of its oxygen-absorbing capacity without absorbing oxygen for at least about 1 day, more preferably 3 days, and even more preferably 7 days, when placed in an environment at an ambient temperature (22°C) and a relative humidity (RH) of 75% RH or less, more preferably 60% RH or less, and even more preferably 50% RH or less. The oxygen absorption trigger function in this specification refers to the ability of the oxygen-absorbing resin composition to exhibit at least 40%, preferably at least 50%, and even more preferably at least 60% of its oxygen absorption capacity within three days, preferably within one day, only when the composition is placed in an environment with an ambient temperature (22°C) and a relative humidity (RH) of 80% or higher, more preferably at least 85%, and even more preferably at least 90%. Herein, the oxygen absorption capacity of the oxygen-absorbing resin composition is defined as the amount of oxygen absorbed when a resin composition containing only the corresponding oxygen-absorbing resin and a transition metal catalyst (referred to as a standard composition) is placed in an environment with an ambient temperature (22°C) and a humidity of 90% for seven days. This oxygen absorption capacity can be measured, for example, by the method described in the Examples below.

[0009] It is believed that the oxygen-absorbing resin composition of the present invention, by containing the specific acid compound, can suppress the catalytic activity of the transition metal catalyst and / or the autoxidation reaction of the oxygen-absorbing resin composition in an environment of 40°C or less and a relative humidity of 75% RH or less. Therefore, for example, when the acid compound is not contained, oxygen absorption begins immediately regardless of the ambient temperature or humidity. Furthermore, it is believed that as the humidity of the ambient environment increases, the activity of the transition metal catalyst is no longer suppressed and the autoxidation reaction of the oxygen-absorbing resin composition also becomes more active. Therefore, as the humidity of the ambient environment increases, the oxygen absorption rate increases, and as the temperature of the ambient environment increases, the oxygen absorption rate also increases. By combining the oxygen absorption reaction described above, the autoxidation reaction can be controlled. As shown in Figure 1, the oxygen absorption reaction can be initiated quickly by first managing the material under low humidity and then shifting to a high humidity environment at any time.

[0010] Furthermore, when the oxygen-absorbing resin composition of the present invention contains the above-mentioned acid compound, it is possible to irradiate ultraviolet rays having a wavelength in the ultraviolet wavelength region of 200 to 400 nm at an ultraviolet irradiation dose of at least 300 mJ / cm. 2 When irradiated under the above conditions, the oxygen absorption reaction rate increases, and even in an environment where the ambient temperature is 22°C and the relative humidity is 75%RH or less, the oxygen absorption capacity can be exhibited to 40% or more, more preferably 50% or more, and even more preferably 60% or more of the oxygen absorption capacity within 3 days, more preferably within 1 day. That is, the oxygen absorption trigger function in this specification means, in addition to the above definition, a function of irradiating the oxygen-absorbing resin composition with ultraviolet light having a wavelength in the ultraviolet light wavelength range of 200 to 400 nm at an ultraviolet light irradiation dose of at least 300 mJ / cm even when the oxygen-absorbing resin composition is placed in an environment where the ambient temperature is 22°C and the relative humidity (RH) is 75%RH or less. 2 When irradiated under the above conditions, the oxygen absorption reaction rate increases, and the oxygen absorption capacity is increased to 40% or more, more preferably 50% or more, and even more preferably 60% or more of the oxygen absorption capacity within 3 days, more preferably within 1 day. The oxygen-absorbing resin composition of the present invention can be used as an adhesive by further containing a curing agent as described below, but it can also be used as a paint in addition to adhesive applications, and can be applied as a coating film for various films and the like. Each component will be described in detail below.

[0011] ≪Transition metal catalyst≫ The oxygen-absorbing resin composition of the present invention contains a transition metal catalyst whose main purpose is to promote the oxygen absorption reaction. Examples of such transition metal catalysts include inorganic salts, organic salts, or complex salts of transition metals such as iron, cobalt, nickel, copper, silver, tin, titanium, zirconium, vanadium, chromium, and manganese, and particularly preferably manganese, iron, cobalt, nickel, and copper. More specifically, the transition metal catalyst includes a transition metal salt composed of a transition metal selected from manganese, iron, cobalt, nickel, and copper and an organic acid. In particular, from the viewpoint of promoting the oxygen absorption reaction of the oxygen-absorbing resin and improving the oxygen absorption ability, the transition metal catalyst is preferably an organic acid salt of manganese, iron, or cobalt, and particularly preferably an organic acid salt of cobalt. The content of the transition metal catalyst in the oxygen-absorbing resin composition is 1 ppm to 1000 ppm, preferably 10 ppm to 500 ppm, and more preferably 20 ppm to 300 ppm, in terms of metal. If the transition metal catalyst is not blended into the oxygen-absorbing resin composition, the oxygen absorption trigger function cannot be imparted. Therefore, the transition metal catalyst must be contained in an amount of at least 1 ppm in terms of metal. Furthermore, if the content of the transition metal catalyst in the oxygen-absorbing resin composition is greater than 1000 ppm, a correspondingly larger amount of acid compound must also be added, which may result in insufficient oxygen absorption trigger effect.

[0012] ≪Acid compound≫ The oxygen-absorbing resin composition of the present invention contains an acid compound having two or more functional groups selected from carboxyl and hydroxyl groups in the same molecule, with the primary purpose of inhibiting the oxygen absorption reaction in a low-humidity environment. Preferably, at least one of the acid dissociation constants (pKa) of the acid compound in a diluted aqueous solution at 25°C is lower than 3.7, more preferably lower than 3.0, and even more preferably lower than 2.0. If the acid dissociation constant is 3.7 or higher, the effect of inhibiting the catalytic activity of the transition metal catalyst is weakened, and the desired inhibition of the oxygen absorption reaction may not be achieved. Furthermore, examples of the acid compound of the present invention include organic acids such as polycarboxylic acids (e.g., oxalic acid, citric acid, and phthalic acid) and glycolic acid, and inorganic acids such as phosphoric acid. However, oxalic acid is particularly preferred due to its low acid dissociation constant and strong interaction with the transition metal catalyst. For example, when comparing acid dissociation constants, an organic acid having an ionic strength of 0.10 mol / dm OH at 25°C may be used. -3 In the case of inorganic acids such as phosphoric acid, the acid dissociation constant measured in a dilute aqueous solution of 0.20 mol / dm HCl at 25°C using potassium chloride as the supporting electrolyte can be used. -3 The acid dissociation constants measured in diluted aqueous solutions of 100 mg / kg of acetic acid can be used for comparison.

[0013] The content of the acid compound in the oxygen-absorbing resin composition is, in terms of volume concentration, 10 ppm to 20,000 ppm, more preferably 20 ppm to 1,000 ppm, and even more preferably 50 ppm to 1,000 ppm. If the amount of the acid compound added is insufficient relative to the amount of the transition metal catalyst, the acid compound may not function sufficiently as an oxygen absorption trigger, and if added in excess, the oxygen absorption reaction may simply be inhibited and the trigger effect may not be obtained.

[0014] <Oxygen absorbing resin> The oxygen-absorbing resin of the present invention preferably contains an oxygen-absorbing polyester resin (A) mainly composed of an unsaturated polyester resin. The oxygen-absorbing polyester resin (A) may also contain a saturated polyester resin (B) to the extent that the oxygen-absorbing reaction is not inhibited.

[0015] The oxygen-absorbing polyester resin (A) is a polyester resin containing a functional group or a bonded group reactive with oxygen in its structure. Examples of the functional group or bonded group reactive with oxygen include a carbon-carbon double bond group, an aldehyde group, and a phenolic hydroxyl group. In particular, a polyester resin having a carbon-carbon double bond group is preferred, and a polyester resin having an unsaturated alicyclic structure is more preferred. The reaction between the unsaturated alicyclic structure and oxygen is preferred because it suppresses the generation of low-molecular-weight decomposition components, which are by-products in the autoxidation reaction of the resin. Examples of polyester resins having an unsaturated alicyclic structure include polyesters made from tetrahydrophthalic acid or its derivatives, or tetrahydrophthalic anhydride or its derivatives. Particularly preferred as tetrahydrophthalic acid or a derivative thereof or tetrahydrophthalic anhydride or a derivative thereof is 4-methyl-△ 3 -Tetrahydrophthalic acid or 4-methyl-△ 3 -Tetrahydrophthalic anhydride, cis-3-methyl-△ 4 -Tetrahydrophthalic acid or cis-3-methyl-△ 4 The tetrahydrophthalic acid or its derivatives or tetrahydrophthalic anhydride or its derivatives are highly reactive with oxygen and therefore can be suitably used as raw materials for oxygen absorbing resins. In addition, these tetrahydrophthalic acids or their derivatives or tetrahydrophthalic anhydrides or their derivatives are obtained by reacting a C5 fraction of naphtha, which is mainly composed of isoprene and trans-piperylene, with maleic anhydride to produce 4-methyl-△ 4 It can be obtained by structural isomerization of an isomer mixture containing 1-tetrahydrophthalic anhydride, and is produced industrially. When tetrahydrophthalic acid or a derivative thereof, or tetrahydrophthalic anhydride or a derivative thereof is used as a raw material to polymerize the oxygen-absorbing polyester resin (A), the dicarboxylic acid and dicarboxylic anhydride may be esterified to a methyl ester or the like.

[0016] The oxygen-absorbing polyester resin (A) can be produced by reacting tetrahydrophthalic acid or a derivative thereof, or tetrahydrophthalic anhydride or a derivative thereof with a diol component. Examples of diol components 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, neopentyl glycol, 1,4-cyclohexanedimethanol, 2-phenylpropanediol, 2-(4-hydroxyphenyl)ethyl alcohol, α,α-dihydroxy-1,3-diisopropylbenzene, o-xylene glycol, m-xylene glycol, p-xylene glycol, α,α-dihydroxy-1,4-diisopropylbenzene, hydroquinone, 4,4-dihydroxydiphenyl, naphthalenediol, and derivatives thereof. Preferably, an aliphatic diol such as diethylene glycol, triethylene glycol, or 1,4-butanediol is used, and more preferably, 1,4-butanediol. When 1,4-butanediol is used, the oxygen absorption performance of the resin is high, and further, the amount of decomposition products generated during the oxidation process is small. These may be used alone or in combination of two or more.

[0017] The oxygen-absorbing polyester resin (A) may contain, in addition to tetrahydrophthalic acid or a derivative thereof or tetrahydrophthalic anhydride or a derivative thereof, other acid components and their derivatives as raw materials, such as aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and aliphatic hydroxycarboxylic acids. Examples of aromatic dicarboxylic acids and derivatives thereof include phthalic acid, phthalic anhydride, benzene dicarboxylic acids such as isophthalic acid and terephthalic acid, naphthalenedicarboxylic acids such as 2,6-naphthalenedicarboxylic acid, anthracene dicarboxylic acid, sulfoisophthalic acid, sodium sulfoisophthalate, and derivatives thereof. Among these, phthalic acid, phthalic anhydride, isophthalic acid, and terephthalic acid are preferred. Examples of aliphatic dicarboxylic acids and derivatives thereof include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, 3,3-dimethylpentanedioic acid, and derivatives thereof. Among these, adipic acid and succinic acid are preferred, with succinic acid being particularly preferred. Other examples include hexahydrophthalic acid and dimer acid having an alicyclic structure, and derivatives thereof. Examples of the aliphatic hydroxycarboxylic acid and its derivatives include glycolic acid, lactic acid, hydroxypivalic acid, hydroxycaproic acid, hydroxyhexanoic acid, and derivatives thereof. These acid components may be esterified, for example, as in dimethyl terephthalate or bis-2-hydroxydiethyl terephthalate. They may also be acid anhydrides, such as phthalic anhydride or succinic anhydride. These may be used alone or in combination of two or more. By copolymerizing the other acid components, the glass transition temperature of the resulting polyester can be easily controlled, improving its oxygen absorption performance. Furthermore, controlling the crystallinity of the polyester resin can improve its solubility in organic solvents. Furthermore, since tetrahydrophthalic acid or a derivative thereof, or tetrahydrophthalic anhydride or a derivative thereof is prone to undergo a radical crosslinking reaction due to heat during polymerization, when the composition ratio of tetrahydrophthalic acid or a derivative thereof, or tetrahydrophthalic anhydride or a derivative thereof contained in the polyester is reduced by the other acid component, gelation during polymerization is suppressed, and a high molecular weight resin can be stably obtained.

[0018] The oxygen-absorbing polyester resin (A) may further contain structural units derived from polyhydric alcohols, polycarboxylic acids, or derivatives thereof. By introducing polyhydric alcohols and polycarboxylic acids to control the branched structure, it is possible to adjust the melt viscosity characteristics and the solution viscosity characteristics of the polyester dissolved in a solvent. Examples of polyhydric alcohols and derivatives thereof include 1,2,3-propanetriol, sorbitol, 1,3,5-pentanetriol, 1,5,8-heptanetriol, trimethylolpropane, pentaerythritol, 3,5-dihydroxybenzyl alcohol, glycerin, and derivatives thereof. Examples of polycarboxylic acids and derivatives thereof include 1,2,3-propanetricarboxylic acid, meso-butane-1,2,3,4-tetracarboxylic acid, citric acid, trimellitic acid, pyromellitic acid, and derivatives thereof. When a component having three or more functional groups, such as a polyhydric alcohol or a polycarboxylic acid, is copolymerized, the amount is preferably 5 mol % or less of the total acid components.

[0019] Polyesters obtainable by copolymerizing a tetrahydrophthalic acid derivative or a tetrahydrophthalic anhydride derivative, 1,4-butanediol, and, as an optional component, succinic acid or succinic anhydride, are preferred as the oxygen-absorbing polyester resin (A). In this case, the structural units derived from tetrahydrophthalic acid or a derivative thereof or tetrahydrophthalic anhydride or a derivative thereof contained in the oxygen-absorbing polyester resin (A) account for 70 to 95 mol %, preferably 75 to 95 mol %, and more preferably 80 to 95 mol %, of the total acid components. Furthermore, the structural units derived from succinic acid or succinic anhydride account for 0 to 15 mol %, preferably 0 to 12.5 mol %, and more preferably 0 to 10 mol %, of the total acid components. By achieving such a composition ratio, an oxygen-absorbing resin having excellent oxygen-absorbing performance and adhesiveness, as well as excellent solubility in organic solvents, can be obtained.

[0020] The glass transition temperature of the oxygen-absorbing polyester resin (A) is −20° C. to 10° C., preferably −15° C. to 6° C., and more preferably −12° C. to 2° C. By setting the glass transition temperature within this range, sufficient oxygen absorption performance can be obtained. In order to obtain sufficient oxygen absorption performance, the acid value of the oxygen-absorbing polyester resin (A) is preferably 5 mg KOH / g or less, more preferably 1 mg KOH / g or less. If the acid value of the polyester exceeds 5 mg KOH / g, a rapid autoxidation reaction may be hindered, and stable oxygen absorption performance may not be obtained. The acid value of the oxygen-absorbing polyester resin (A) is measured according to JIS K 0070. The oxygen-absorbing polyester resin (A) may be used alone or in combination of two or more kinds.

[0021] The saturated polyester resin (B) is a polyester resin that does not substantially contain carbon-carbon double bond groups, and can be obtained, for example, by polycondensation of a dicarboxylic acid component, a diol component, and a hydroxycarboxylic acid component. The saturated polyester resin (B) is preferably a polyester having an iodine value of 3 g / 100 g or less, particularly 1 g / 100 g or less. The iodine value is measured in accordance with JIS K 0070. If the iodine value of the saturated polyester resin (B) exceeds 3 g / 100 g, it is undesirable because low-molecular-weight decomposition components are likely to be generated during the oxygen absorption reaction of the oxygen-absorbing resin composition. Examples of the dicarboxylic acid component include the aliphatic dicarboxylic acids and aromatic dicarboxylic acids described above as components of the oxygen-absorbing polyester resin (A), hexahydrophthalic acid, dimer acid, and derivatives thereof, which can be used alone or in combination of two or more. Examples of the diol component include the diols described above as components of the oxygen-absorbing polyester resin (A), which can be used alone or in combination of two or more. Examples of the hydroxycarboxylic acid component include the aliphatic hydroxycarboxylic acids described as components of the oxygen-absorbing polyester resin (A). When the terminal functional group of the saturated polyester resin (B) is a hydroxyl group, curing proceeds together with the oxygen-absorbing polyester resin (A) by a curing agent such as an isocyanate curing agent, and cohesive strength increases when used as an adhesive as described below, which is preferable. It is also preferable to modify the saturated polyester resin (B) with alkyl groups at its terminals using monoalcohols such as n-butanol and 2-ethylhexanol, fatty acids, etc. The glass transition temperature of the saturated polyester resin (B) is −10° C. or lower, preferably −70° C. to −15° C., and more preferably −60° C. to −20° C. By setting the glass transition temperature within this range, it is possible to effectively alleviate the internal stress generated by the oxidative curing reaction accompanying oxygen absorption.

[0022] A suitable embodiment of the oxygen-absorbing resin composition is a composition containing an oxygen-absorbing polyester resin (A) having a glass transition temperature of -20°C to 10°C and a saturated polyester resin (B) having a glass transition temperature of -10°C or lower. The oxygen-absorbing polyester resin (A) and saturated polyester resin (B) used in the present invention can be obtained by any polyester polycondensation method known to those skilled in the art, such as interfacial polycondensation, solution polycondensation, melt polycondensation, and solid-state polycondensation. When synthesizing the oxygen-absorbing polyester resin (A) and saturated polyester resin (B) used in the present invention, a polymerization catalyst is not necessarily required, but a typical polyester polymerization catalyst such as a titanium-based, germanium-based, antimony-based, tin-based, aluminum-based, etc. Also, known polymerization catalysts such as nitrogen-containing basic compounds, boric acid and boric acid esters, and organic sulfonic acid compounds can be used. Furthermore, various additives such as a coloring inhibitor such as a phosphorus compound and an antioxidant can be added during polymerization. By adding an antioxidant, oxygen absorption during polymerization and subsequent processing can be suppressed, and therefore performance degradation and gelation of the oxygen-absorbing resin can be suppressed. The number-average molecular weight of the oxygen-absorbing polyester resin (A) used in the present invention is preferably 500 to 100,000, more preferably 2,000 to 10,000. The weight-average molecular weight is preferably 5,000 to 200,000, more preferably 10,000 to 100,000, and even more preferably 20,000 to 70,000. If the molecular weight is lower than the above range, the cohesive strength, i.e., creep resistance, of the resin decreases, while if it is higher, it is undesirable because it reduces solubility in organic solvents and increases solution viscosity, resulting in reduced coatability. The number-average molecular weight of the saturated polyester resin (B) is preferably 500 to 100,000, more preferably 500 to 10,000. The weight-average molecular weight is preferably 1,000 to 100,000, more preferably 1,000 to 70,000, and even more preferably 1,000 to 50,000. A molecular weight lower than the above range results in a significant decrease in cohesive strength, while a molecular weight higher than the above range results in a decrease in compatibility with the oxygen-absorbing polyester resin (A) and an increase in solution viscosity, resulting in a decrease in coatability, which is undesirable. When the molecular weights of the oxygen-absorbing polyester resin (A) and the saturated polyester resin (B) are each within the above ranges, an oxygen-absorbing adhesive can be obtained that exhibits excellent cohesive strength, adhesive properties, and solubility in organic solvents, and that has viscosity characteristics suitable for an adhesive solution, as described below.

[0023] <Oxygen-absorbing adhesive> The oxygen-absorbing resin of the present invention can be used as an oxygen-absorbing adhesive by further containing a curing agent. Examples of adhesives include acrylic adhesives, urethane adhesives, epoxy adhesives, ethylene-vinyl acetate adhesives, vinyl chloride adhesives, silicone adhesives, rubber adhesives, etc., to which oxygen-absorbing functionality has been added. In particular, when used as an adhesive for dry lamination, urethane adhesives are preferred, and two-component curing urethane adhesives that combine an oxygen-absorbing polyester base agent with an isocyanate curing agent are more preferred.

[0024] The ratio A / B of the oxygen-absorbing polyester resin (A) to the saturated polyester resin (B) in the oxygen-absorbing adhesive or in the oxygen-absorbing adhesive layer of the oxygen-absorbing film described below is preferably 0.6 to 9, more preferably 1 to 9, and even more preferably 2 to 9. By setting the ratio A / B in this range, it is possible to achieve excellent oxygen-absorbing performance while maintaining high laminate strength before and after oxygen absorption.

[0025] The oxygen-absorbing adhesive is preferably cured by blending with an isocyanate-based curing agent, such as an aliphatic and / or alicyclic isocyanate-based curing agent. The oxygen-absorbing adhesive layer of the oxygen-absorbing film of the present invention, described below, preferably contains an oxygen-absorbing adhesive obtained by blending an isocyanate-based curing agent, such as an aliphatic and / or alicyclic isocyanate-based curing agent, with a base resin consisting of an oxygen-absorbing polyester-based resin (A) and a saturated polyester resin (B). The incorporation of an isocyanate-based curing agent increases adhesive strength and cohesive strength, and enables curing at low temperatures, such as around room temperature. Examples of aliphatic isocyanate-based curing agents include xylylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), lysine diisocyanate, lysine methyl ester diisocyanate, trimethylhexamethylene diisocyanate, and n-pentane-1,4-diisocyanate. Examples of alicyclic isocyanate curing agents include isophorone diisocyanate (IPDI), cyclohexane-1,4-diisocyanate, methylcyclohexyl diisocyanate, and dicyclohexylmethane-4,4'-diisocyanate. Among these, XDI and HDI are preferred as aliphatic isocyanate curing agents, and IPDI is preferred as an alicyclic isocyanate curing agent. XDI is particularly preferred. By using XDI, the oxygen-absorbing adhesive of the present invention or the oxygen-absorbing adhesive layer of the oxygen-absorbing film described below exhibits the most excellent oxygen-absorbing performance. It is also preferred to use a combination of IPDI and XDI, or IPDI and HDI. Aromatic isocyanate curing agents can also be used, but although aromatic isocyanate curing agents improve the adhesiveness and cohesive strength of the resin, they are not preferred because they may reduce oxygen-absorbing performance. The reason for this is thought to be that the aromatic urethane moiety formed when the aromatic isocyanate curing agent reacts with the hydroxyl group at the end of the polyester base, which acts in the same way as aromatic amines, which act as antioxidants, deactivating and stabilizing radicals.

[0026] These isocyanate-based curing agents are preferably used as polyisocyanate compounds with increased molecular weight, such as adducts, isocyanurates, and biuret forms. These isocyanate curing agents may be used alone or in combination of two or more. The isocyanate-based curing agent component is preferably added in an amount of 3 to 30 phr, more preferably 3 to 20 phr, and even more preferably 3 to 15 phr, based on the solids weight of the oxygen-absorbing resin as the main component. If the amount added is too small, the adhesiveness and cohesive strength will be insufficient, while if the amount added is too large, the amount of oxygen-absorbing component contained in the resin composition per unit weight will be small, resulting in insufficient oxygen-absorbing performance. Furthermore, if the mobility of the resin is significantly reduced by curing, the oxygen-absorbing reaction will be less likely to proceed, and the oxygen-absorbing performance will be reduced.

[0027] One embodiment of the oxygen-absorbing adhesive of the present invention has a single glass transition temperature of -2°C or lower. In this case, it is possible to effectively relieve internal stress caused by the oxidative curing reaction accompanying oxygen absorption and ensure sufficient transparency. The single glass transition temperature is more preferably -50°C to -2°C, and even more preferably -20°C to -2°C.

[0028] The oxygen-absorbing adhesive preferably contains a solvent such as an organic solvent. Examples of the solvent include ethyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, isopropanol, etc. Ethyl acetate, in particular, is generally used as a solvent for adhesives used in dry lamination of flexible packaging because it is relatively free of odor problems caused by residual solvents. In consideration of industrial applications, it is preferable to use a single solvent of ethyl acetate that does not contain toluene, xylene, etc. as the solvent of the present invention. Various additives such as silane coupling agents, antioxidants, ultraviolet absorbers, hydrolysis inhibitors, anti-mold agents, curing catalysts, thickeners, plasticizers, pigments, fillers, polyester resins, and epoxy resins may be added to the oxygen-absorbing adhesive of the present invention or the oxygen-absorbing adhesive layer of the oxygen-absorbing film described below, as needed, within the scope of not impairing the object of the present invention.

[0029] <Oxygen absorbing film> The oxygen-absorbing film of the present invention is an oxygen-absorbing film having a laminated structure including a film substrate and an oxygen-absorbing layer, and the oxygen-absorbing layer includes the oxygen-absorbing resin composition or oxygen-absorbing adhesive described above. The oxygen-absorbing adhesive of the present invention can be used, for example, as an oxygen-absorbing adhesive layer constituting the oxygen-absorbing layer of an oxygen-absorbing film, for the purpose of laminating multiple film substrates in the same manner as with ordinary dry lamination adhesives. It is particularly suitable for laminating a film substrate having oxygen barrier properties with a sealant film having heat-sealing properties and oxygen gas permeability. In this case, the laminate structure is oxygen barrier substrate layer / oxygen-absorbing adhesive layer / sealant layer from the outer layer side, and the oxygen barrier substrate blocks oxygen permeating in from the outside, thereby suppressing a decrease in oxygen absorption performance due to oxygen outside the container and allowing the oxygen-absorbing adhesive to quickly absorb oxygen inside the container via the oxygen-permeable sealant film, which is preferable. The oxygen-barrier film substrate and the sealant film may each be a single layer or a laminate. Suitable oxygen-barrier film substrates include biaxially oriented PET films, biaxially oriented polyamide films, and biaxially oriented polypropylene films, each of which has a barrier coating layer primarily composed of a vapor-deposited thin film of a metal oxide or metal, such as silica or alumina, or a gas-barrier organic material, such as a polyvinyl alcohol resin, an ethylene-vinyl alcohol copolymer, a polyacrylic acid resin, or a vinylidene chloride resin. Ethylene-vinyl alcohol copolymer films, polymetaxylylene adipamide films, polyvinylidene chloride films, and metal foils, such as aluminum foil, are also preferred. These oxygen-barrier film substrates can be used by laminating the same type of substrate or two or more different types of substrates. It is also preferred to use a laminate of biaxially oriented PET films, biaxially oriented polyamide films, biaxially oriented polypropylene films, cellophane, paper, or the like.

[0030] Suitable sealant film materials include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, linear very-low-density polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, cyclic olefin polymers, cyclic olefin copolymers, polyolefins such as random or block copolymers of α-olefins such as ethylene, propylene, 1-butene, and 4-methyl-1-pentene, ethylene-vinyl acetate copolymers, ethylene-(meth)acrylic acid copolymers and their ionically crosslinked products (ionomers), and ethylene-vinyl compound copolymers such as ethylene-methyl methacrylate copolymers, heat-sealable polyesters such as PET, A-PET, PETG, and PBT, and amorphous nylon. Two or more of these materials can be blended, or the same or different materials can be laminated.

[0031] When laminating multiple film substrates using the oxygen-absorbing adhesive of the present invention, a known dry laminator can be used. The dry laminator can carry out a series of lamination steps, including coating the oxygen-absorbing adhesive onto the barrier film substrate, volatilizing the solvent in a drying oven, and bonding to the sealant film using nip rolls heated to 50 to 120°C. The amount of oxygen-absorbing adhesive applied is 0.1 to 30 g / m2 in solids. 2 , preferably 1 to 15 g / m 2 and more preferably 2 to 10 g / m 2 It is also preferable to age (cure) the oxygen-absorbing laminate film laminated with the oxygen-absorbing adhesive to promote the curing reaction at a temperature near room temperature, for example, 10 to 60°C. Curing is mainly due to a crosslinking reaction caused by an isocyanate-based curing agent, which is preferable because curing improves adhesive strength and cohesive force. It is preferable to perform the aging in the absence of oxygen or while blocking oxygen, for example by sealing the oxygen-absorbing laminate film in an oxygen-impermeable bag. This makes it possible to suppress the deterioration of oxygen absorption performance due to oxygen in the air during aging. The oxygen-absorbing resin composition of the present invention can also be used as a solvent-free adhesive without dissolving it in a solvent, in which case an oxygen-absorbing laminated film can be obtained using a known non-solvent laminator.

[0032] The oxygen-absorbing film and the oxygen-absorbing resin composition of the present invention can be subjected to a light irradiation treatment, if necessary. A commonly used ultraviolet ray irradiation device or an electron beam irradiation device can be used as the light irradiation device. Examples of the form of light irradiation include a laminate film, a bag-shaped container, a lid, and a packaging bag filled with contents.

[0033] The oxygen-absorbing film of the present invention can be suitably used as a lid material for various types of bag-like containers and cup / tray containers, such as flat pouches sealed on three or four sides, pouches with gussets, standing pouches, and pillow packaging bags. An oxygen-absorbing container that uses an oxygen-absorbing film in at least a portion thereof effectively blocks oxygen that permeates from the outside of the container and absorbs oxygen remaining inside the container, making it useful as a container that can maintain a low oxygen concentration inside the container for a long period of time, prevent oxygen-related quality deterioration of the contents, and extend shelf life. In particular, contents that are susceptible to deterioration in the presence of oxygen include, but are not limited to, food products such as coffee beans, tea leaves, snacks, rice crackers, fresh and semi-fresh confectioneries, fruits, nuts, vegetables, fish and meat products, paste products, dried fish, smoked foods, foods boiled in soy sauce, raw rice, cooked rice, infant foods, jams, mayonnaise, ketchup, cooking oils, dressings, sauces, and dairy products; beverages such as beer, wine, fruit juice, green tea, and coffee; and other products such as pharmaceuticals, cosmetics, and electronic components. [Example]

[0034] The present invention will be described in more detail below with reference to examples. Each value was measured by the following method. (1) Number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution index (Mw / Mn) Measurement was performed using gel permeation chromatography (GPC, manufactured by Tosoh Corporation; HLC-8320 type GPC) in terms of polystyrene. Chloroform was used as the solvent. (2) Oxygen absorption A laminated film test piece cut to 2 cm x 15 cm was placed in a container with an internal volume of 85 cm 3 The contents were placed in an oxygen-impermeable steel foil laminated cup, heat-sealed with an aluminum foil laminated film lid, and stored in an atmosphere at 22°C. After storage for the number of days shown in Table 1, the oxygen concentration in the cup was measured using a micro gas chromatograph (Shimadzu Corporation; GC-2014AT). 2 The amount of oxygen absorbed per unit was calculated. Regarding the humidity dependency of the oxygen absorption reaction, the oxygen absorption amount (0.038 cc / cm) after storage for 7 days at 22°C-90% RH (relative humidity) in Comparative Example 1 was 2) was used as a control. In Examples 1 to 6, samples in which the oxygen absorption amount of the sample after storage for the number of days listed in Table 1 was 50% or more of the control at 22°C-90% RH and 50% or less of the control at 22°C-50% RH were evaluated as having good humidity dependency (◯). In Comparative Examples 1 to 3, samples in which the oxygen absorption amount after storage for 7 days at 22°C-50% RH exceeded 50% of the oxygen absorption amount after storage for 7 days at 22°C-90% RH in the respective Comparative Examples were evaluated as not having humidity dependency (×). Regarding the trigger function of the oxygen absorption reaction, the amount of oxygen absorbed 3 days after the humidity change was 0.038 cc / cm after storage for 7 days at 22°C and 90% RH in Comparative Example 1. 2 ) was judged to have a good trigger function (◯), and that less than 50% was judged to have no trigger function (×).

[0035] Example 1 The acid component was a methyl tetrahydrophthalic anhydride isomer mixture (Hitachi Chemical; HN-2200) in a molar ratio of 0.9, the other acid component was succinic anhydride in a molar ratio of 0.1, the diol component was 1,4-butanediol in a molar ratio of 1.3, and 300 ppm of isopropyl titanate was used as a polymerization catalyst. The mixture was reacted in a nitrogen atmosphere at 150-200°C for approximately 6 hours while removing the water generated. Polymerization was then continued under a reduced pressure of 0.1 kPa at 200-220°C for approximately 3 hours, yielding oxygen-absorbing polyester resin (A). The Mn was 4800, the Mw was 57200, and the Tg was -5.0°C. The resulting oxygen-absorbing polyester resin (A) was mixed with saturated polyester resin (B1) (Polysizer W4010, manufactured by DIC Corporation, Mn: 3600, Mw: 9500) with a Tg of -26°C so that the solids weight ratio A / B1 was 2.3. An HDI / IPDI curing agent (KL-75, manufactured by DIC Graphics) was added as an isocyanate curing agent to the solids of the mixture so that the solids weight ratio was 7 phr (parts per hundred resin). Cobalt neodecanoate was further added as a catalyst so that the metal content relative to the solids was 80 ppm, and 240 ppm of oxalic acid was added as an acid compound. The mixture was dissolved in ethyl acetate, and the resulting oxygen-absorbing adhesive (a) solution with a solids concentration of 20 wt% was applied to the barrier coating surface of a transparent vapor-deposited PET film (GL-AE, manufactured by Toppan Printing Co., Ltd., film thickness 13 μm) using a #15 bar coater. After volatilizing the solvent with hot air from a hair dryer, the adhesive-coated surface of the laminated film and the 40 μm LDPE film were subjected to corona treatment (discharge rate 25 W·min / m 2 The film was passed through a heated roll at 50°C with the two 2) surfaces facing each other to obtain an oxygen-absorbing laminated film consisting of a transparent vapor-deposited PET film (film thickness 13 μm) / oxygen-absorbing adhesive (a) (film thickness 4 μm) / LDPE (film thickness 40 μm). The obtained oxygen-absorbing laminated film was cured at 35° C. in a nitrogen atmosphere for 5 days, and then the amount of oxygen absorbed was evaluated.

[0036] Example 2 Evaluation was carried out in the same manner as in Example 1, except that the acid compound in Example 1 was changed to citric acid. The results are shown in Table 1.

[0037] Example 3 Evaluation was carried out in the same manner as in Example 1, except that the acid compound was changed to citric acid, the concentration was changed to 960 ppm, and the time period was changed to 9 days. The results are shown in Table 1.

[0038] Example 4 Evaluation was carried out in the same manner as in Example 1, except that the acid compound was changed to glycolic acid and the time period was changed to 1 day. The results are shown in Table 1.

[0039] Example 5 Evaluation was carried out in the same manner as in Example 1, except that the acid compound was changed to phosphoric acid and the elapsed time was changed to 8 days. The results are shown in Table 1.

[0040] Example 6 Evaluation was carried out in the same manner as in Example 1, except that the catalyst was changed to iron heptanoate and the aging period was changed to 14 days. The results are shown in Table 1.

[0041] (Comparative Example 1) The evaluation was carried out in the same manner as in Example 1, except that no acid compound was added. The results are shown in Table 1.

[0042] (Comparative Example 2) Evaluation was carried out in the same manner as in Example 1, except that acetic acid was used as the acid compound. The results are shown in Table 1.

[0043] (Comparative Example 3) Evaluation was carried out in the same manner as in Example 1, except that dodecylbenzenesulfonic acid was used as the acid compound. The results are shown in Table 1.

[0044] [Table 1]

[0045] The results in Table 1 show that the inclusion of an acid compound in the present invention causes the amount of oxygen absorption to change depending on humidity.

[0046] Example 7 The oxygen-absorbing laminate film obtained in Example 1 was left to stand at 22°C and 50% RH (in the atmosphere) for 1 day, and then stored at 22°C and 90% RH for 3 days, after which the amount of oxygen absorbed was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0047] Example 8 The oxygen-absorbing laminate film obtained in Example 1 was left to stand for 4 days at 22°C and 50% RH (in the atmosphere), and then stored for 3 days at 22°C and 90% RH, after which the amount of oxygen absorbed was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0048] Example 9 The oxygen-absorbing laminate film obtained in Example 1 was left to stand for 7 days at 22°C and 50% RH (in the atmosphere), and then stored for 3 days at 22°C and 90% RH, after which the amount of oxygen absorbed was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0049] [Table 2]

[0050] From the results in Table 1, the oxygen absorption capacity of the oxygen-absorbing adhesive of Example 1 when left for 7 days at 22°C and 50% RH (in the atmosphere) was 0.004 cc / cm 2 In light of this, the results in Table 2 demonstrate that the oxygen absorbing adhesive of the present invention can change the amount of oxygen absorbed in response to changes in humidity.

[0051] Example 10 The LDPE surface of the oxygen-absorbing laminate film obtained in Example 1 was irradiated with ultraviolet light (metal halide light source ultraviolet irradiation device (peak wavelength 370 nm)) at an irradiation dose of 300 mJ / cm 2 After irradiation, the sample was evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0052] Example 11 The LDPE surface of the oxygen-absorbing laminate film obtained in Example 1 was irradiated with ultraviolet light at a dose of 600 mJ / cm. 2 After irradiation, the sample was evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0053] [Table 3] From the results in Table 3, it was found that the oxygen absorbing laminate film of the present invention can control (improve) its oxygen absorbing ability by ultraviolet irradiation, even when it is left for 7 days in an environment of 22°C and 50% RH. (From the results in Table 1, it was found that the oxygen absorbing laminate film of the present invention, without ultraviolet irradiation, had an oxygen absorption amount of 0.004 cc / cm.) 2 The effect of ultraviolet light irradiation is clear, as the effect was only about 100%.

[0054] Example 12 Using a film similar to the sample used in Example 1 in Table 1, the change in oxygen absorption capacity over time was measured when the temperature was changed from low humidity conditions (22°C-0%RH) to high humidity conditions (22°C-90%RH). The results showed a humidity-dependent oxygen absorption reaction, as shown in Figure 1. The results in Figure 1 clearly demonstrate that the oxygen-absorbing resin composition of the present invention exhibits an oxygen absorption trigger.

Claims

1. Oxygen absorbing resin, A method for controlling the oxygen absorption reaction of the oxygen absorbing resin by adding a transition metal catalyst and an acid compound, controlling the oxygen absorption reaction includes making the oxygen absorbing resin composition containing the oxygen absorbing resin, the transition metal catalyst, and the acid compound have an oxygen absorption trigger function when placed in an environment at 22°C and a relative humidity of 80% RH or more, The oxygen absorption trigger function is a function of absorbing oxygen by exerting 50% or more of the oxygen absorption capacity within 3 days, The oxygen absorption capacity is the amount of oxygen absorbed when a resin composition containing only the oxygen-absorbing resin and the transition metal catalyst is left in an environment of 22°C and 90% RH for 7 days, The method, wherein the acid compound is one or more selected from the group consisting of oxalic acid, citric acid, and glycolic acid.

2. The method described in claim 1, wherein the oxygen-absorbing resin has a carbon-carbon double bond.

3. A method according to claim 1 or 2, wherein the oxygen-absorbing resin is contained in an oxygen-absorbing adhesive containing an isocyanate-based curing agent.

4. A method according to any one of claims 1 to 3, wherein the oxygen-absorbing resin or the oxygen-absorbing adhesive is contained in the oxygen-absorbing layer of an oxygen-absorbing film having a laminated structure comprising a film substrate and an oxygen-absorbing layer.

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