Oxygen-absorbing resin composition, molded article, and deoxidation method

Abstract

This oxygen-absorbing resin composition contains an easily oxidizable thermoplastic resin and a metal catalyst, and exhibits oxygen-absorbing ability when being irradiated with energy rays. The metal catalyst is a fatty acid salt of manganese.

Description

Oxygen-absorbing resin composition, molded product, and deoxidation method

[0001] The present invention relates to an oxygen-absorbing resin composition, a molded article thereof, and a method for removing oxygen using the resin composition.

[0002] Oxygen absorbers that remove oxygen have been used for the purpose of preventing oxidation of various products that are susceptible to deterioration due to the influence of oxygen, such as foods, pharmaceuticals, metal products, and electronic products. The form of these oxygen absorbers that was first developed and is still widely used today is a granular or powdered oxygen absorber composition packed in a small bag.

[0003] In recent years, resin materials that exhibit oxygen absorbing properties have been proposed as oxygen absorbers that are easier to handle, have a high degree of freedom in shape, and have a wide range of applications (Patent Document 1). In order to maintain its oxygen absorbing properties, oxygen absorbers using oxygen-absorbing resins desirably do not absorb oxygen during molding, storage, or packaging of the resin material in a product. On the other hand, desirably, oxygen absorbers that require a trigger to initiate oxygen absorption desirably exhibit their oxygen absorbing properties quickly upon use. Patent Document 1 proposes a method in which irradiation with ultraviolet light is used as a trigger to initiate oxygen absorption.

[0004] Patent No. 4978884

[0005] However, oxygen absorbers using such oxygen-absorbing resins begin absorbing oxygen immediately after irradiation with a triggering energy ray. Therefore, depending on the exposure time in the atmosphere, there are problems such as the oxygen absorber being inactivated before being sealed with the preserved object, and the oxygen absorption cannot be maintained for a long period of time after being sealed with the preserved object. In particular, in industrial product applications requiring long assembly work, it may take a long time to seal the oxygen absorber with the industrial product, making the above problems more pronounced. Therefore, there has been a demand for an oxygen-absorbing resin material that exhibits sufficient oxygen absorption performance even after being kept in the atmosphere for a certain period of time after being irradiated with energy rays.

[0006] That is, the gist of the present invention is as follows. [1] An oxygen-absorbing resin composition containing an easily oxidizable thermoplastic resin and a metal catalyst, which exhibits oxygen absorption ability when irradiated with energy rays, wherein the metal catalyst is a fatty acid salt of manganese. [2] The oxygen-absorbing resin composition according to [1] above, wherein the content of the fatty acid salt of manganese is 0.001 to 5 parts by mass, in terms of manganese (Mn), relative to 100 parts by mass of the easily oxidizable thermoplastic resin. [3] The oxygen-absorbing resin composition according to [1] or [2] above, wherein the content of the fatty acid salt of manganese is 0.001 to 10 parts by mass, in terms of manganese (Mn), relative to 100 parts by mass of the oxygen-absorbing resin composition. [4] The oxygen-absorbing resin composition according to any one of [1] to [3] above, wherein the fatty acid constituting the fatty acid salt of manganese has 4 to 22 carbon atoms. [5] The oxygen-absorbing resin composition according to any one of the above [1] to [4], wherein the fatty acid constituting the manganese fatty acid salt is at least one selected from the group consisting of octylic acid, octanoic acid, stearic acid, oleic acid, and linoleic acid. [6] The oxygen-absorbing resin composition according to any one of the above [1] to [5], wherein the easily oxidizable thermoplastic resin contains at least one selected from the group consisting of polybutadiene (X1), polyisoprene (X2), and a resin (Y) having a carbon-carbon double bond and a structural unit represented by the following general formula (1): (In the formula, R １ ~R ７ is -H, -CH ３ , -CH ２ R, -CHR ２ , -CR ３ , -OR, -COOR, -SiR ３ , —O—SiR ３, —COCl, or a halogen atom, which may be the same or different, and R represents a linear or cyclic alkyl group, alkenyl group, halogenated alkyl group, halogenated alkenyl group, or allyl group.) [7] The oxygen-absorbing resin composition according to the above [6], wherein the easily oxidizable thermoplastic resin contains the polybutadiene (X1) and the resin (Y). [8] The oxygen-absorbing resin composition according to the above [6] or [7], wherein the polybutadiene (X1) is 1,2-polybutadiene. [9] The oxygen-absorbing resin composition according to any one of the above [6] to [8], wherein the resin (Y) is one or more selected from the group consisting of a styrene-isoprene-styrene block copolymer and a styrene-butadiene-styrene block copolymer.

[10] A molded article made of the oxygen-absorbing resin composition according to any one of the above [1] to [9].

[11] A method for absorbing oxygen, comprising the steps of: (1) irradiating the oxygen-absorbing resin composition according to any one of the above items [1] to [9] with energy rays to obtain an oxygen scavenger; and (2) sealing the oxygen scavenger together with an object to be preserved in a storage container, wherein the time period during which the oxygen scavenger is kept in the atmosphere after the step (1) and before the sealing in the step (2) is from 1 hour to 3 days.

[0007] According to the present invention, it is possible to provide an oxygen-absorbing resin composition that exhibits sufficient oxygen absorption performance even after being kept in the atmosphere for a certain period of time after being irradiated with energy rays, a molded product thereof, and a deoxidation method using the resin composition.

[0008] Embodiments of the oxygen-absorbing resin composition, molded article, and deoxidation method according to the present invention are described in detail below. In this specification, the term "A to B" used to describe numerical values ​​means "A or more and B or less" (when A<B) or "A or less and B or more" (when A>B). In addition, in the present invention, a combination of preferred embodiments is a more preferred embodiment.

[0009] [Oxygen-absorbing resin composition] The oxygen-absorbing resin composition of the present invention contains an easily oxidizable thermoplastic resin and a metal catalyst, and exhibits oxygen absorption ability when irradiated with energy rays, the metal catalyst being a fatty acid salt of manganese. Because of the above-mentioned configuration, the oxygen-absorbing resin composition of the present invention exhibits sufficient oxygen absorption performance even after being kept in the atmosphere for a certain period of time after being irradiated with energy rays.

[0010] In this specification, "an oxygen-absorbing resin composition that exhibits oxygen absorbing ability when irradiated with energy rays" means both (1) an oxygen-absorbing resin composition that is capable of exhibiting oxygen absorbing ability when irradiated with energy rays before irradiation with energy rays, and (2) an oxygen-absorbing resin composition that is exhibiting or is in a state where it can exhibit oxygen absorbing ability when irradiated with energy rays after irradiation with energy rays. Here, the above (2) "in a state where it can exhibit oxygen absorbing ability when irradiated with energy rays" means a state in which, after irradiation with energy rays, the resin composition is stored in an oxygen-barrier bag or the like with low oxygen permeability and kept in an oxygen-free environment, and exhibits oxygen absorbing ability when placed in an oxygen-containing environment.

[0011] The reason why the oxygen-absorbing resin composition of the present invention exhibits the above-mentioned effects is unclear, but one possible reason is as follows. Conventional oxygen-absorbing resin compositions containing an easily oxidizable thermoplastic resin and a metal catalyst have the problem of beginning to absorb oxygen immediately after irradiation with energy rays and subsequently becoming deactivated when kept in the atmosphere for a certain period of time. One possible cause of this problem is thought to be that conventional oxygen-absorbing resin compositions absorb a large amount of oxygen in the early stages of the oxygen-absorbing reaction. Therefore, it is presumed that the composition absorbs a large amount of oxygen in the early stages of the oxygen-absorbing reaction and is almost completely deactivated in the middle to late stages, resulting in a significant decrease in the amount of oxygen absorbed. After extensive research, the present inventors discovered that by selecting the type of metal catalyst, the amount of oxygen absorbed in the early stages of the oxygen-absorbing reaction after irradiation with energy rays can be controlled, leading to the completion of the present invention. Specifically, the oxygen-absorbing resin composition of the present invention is characterized in that it contains a manganese fatty acid salt as the metal catalyst. It is believed that the inclusion of the specific metal catalyst can suppress the amount of oxygen absorbed in the early stages of the oxygen-absorbing reaction after irradiation with energy rays, and subsequently maintain or even increase the amount of oxygen absorbed compared to the early stages over a long period of time. As a result, it is believed that the oxygen absorbing resin composition after irradiation with energy rays will still exhibit sufficient oxygen absorbing performance even after being kept in the atmosphere for a certain period of time.

[0012] Each component will be described below. (Easily Oxidizable Thermoplastic Resin) The oxygen-absorbing resin composition of the present invention contains an easily oxidizable thermoplastic resin. The easily oxidizable thermoplastic resin in the oxygen-absorbing resin composition of the present invention is a main component when the oxygen-absorbing resin composition exhibits oxygen absorption ability upon irradiation with energy rays. The easily oxidizable thermoplastic resin is a resin that undergoes an oxidation reaction upon irradiation with energy rays and has a moiety in which carbon atoms are bonded together via a double bond, an allylic carbon (a carbon adjacent to a carbon-carbon double bond), a structural unit of the following general formula (1), a hydroxy group, an ether group, an aldehyde group, a ketone group, a hydrogen atom bonded to a tertiary carbon atom, etc.

[0013] Examples of easily oxidizable thermoplastic resins include organic polymer compounds having a portion where carbon atoms are bonded by a double bond, organic polymer compounds having an allylic carbon (a carbon adjacent to a carbon-carbon double bond), organic polymer compounds having a structural unit represented by the following general formula (1), organic polymer compounds having a hydroxyl group, organic polymer compounds having an ether group, organic polymer compounds having an aldehyde group, organic polymer compounds having a ketone group, and organic polymer compounds having a hydrogen atom bonded to a tertiary carbon atom. These may be used alone or in combination of two or more. In organic polymer compounds having a portion where carbon atoms are bonded by a double bond or organic polymer compounds having an allylic carbon, the carbon-carbon double bond or allylic carbon may be in the main chain or in a side chain of the polymer. Among these, preferred is one or more selected from the group consisting of organic polymer compounds having a moiety where carbon atoms are bonded together via a double bond, organic polymer compounds having a structural unit of the following general formula (1), organic polymer compounds having a hydroxy group, organic polymer compounds having an ether group, organic polymer compounds having an aldehyde group, organic polymer compounds having a ketone group, and organic polymer compounds having a hydrogen atom bonded to a tertiary carbon atom, and more preferred is one or more selected from organic polymer compounds having a moiety where carbon atoms are bonded together via a double bond, organic polymer compounds having a structural unit of the following general formula (1), and organic polymer compounds having a hydrogen atom bonded to a tertiary carbon atom. Note that the organic polymer compounds having a moiety where carbon atoms are bonded together via a double bond also include organic polymer compounds having an allylic carbon. The easily oxidizable thermoplastic resin preferably contains one or more resins selected from the group consisting of polybutadiene (X1), polyisoprene (X2), and resin (Y) having a carbon-carbon double bond and a structural unit represented by the following general formula (1), more preferably contains polybutadiene (X1) and / or polyisoprene (X2) and the above resin (Y), and even more preferably contains polybutadiene (X1) and the above resin (Y).Furthermore, the easily oxidizable thermoplastic resin is more preferably at least one selected from the group consisting of polybutadiene (X1), polyisoprene (X2), and resin (Y) having a carbon-carbon double bond and a structural unit represented by the following general formula (1), even more preferably consisting of polybutadiene (X1) and / or polyisoprene (X2) and the above resin (Y), and even more preferably consisting of polybutadiene (X1) and the above resin (Y).

[0014] (In the formula, R １ ~R ７ is -H, -CH ３ , -CH ２ R, -CHR ２ , -CR ３ , -OR, -COOR, -SiR ３ , —O—SiR ３ , —COCl, or a halogen atom, which may be the same or different, and R represents a linear or cyclic alkyl group, alkenyl group, halogenated alkyl group, halogenated alkenyl group, or allyl group.

[0015] The polybutadiene (X1) is not particularly limited, but examples thereof include 1,4-polybutadiene, 1,2-polybutadiene, etc. Among these, 1,2-polybutadiene is preferred from the viewpoint of oxygen absorption performance.

[0016] The polyisoprene (X2) is not particularly limited, but examples thereof include cis-1,4-polyisoprene, trans-1,4-polyisoprene, 1,2-polyisoprene, and 3,4-polyisoprene. Among these, cis-1,4-polyisoprene and 3,4-polyisoprene are preferred from the viewpoints of oxygen absorption performance and easy availability.

[0017] The resin (Y) has a carbon-carbon double bond and a structural unit of the general formula (1). The carbon-carbon double bond may be in the main chain or in a side chain of the resin. The resin (Y) is not particularly limited, but examples thereof include a styrene-isoprene-styrene block copolymer, a styrene-butadiene-styrene block copolymer, a styrene-butadiene rubber, and a styrene-isoprene rubber. Among these, one or more types selected from the group consisting of a styrene-isoprene-styrene block copolymer and a styrene-butadiene-styrene block copolymer are preferred, and a styrene-isoprene-styrene block copolymer is more preferred.

[0018] In the above general formula (1), R １ ~R ７ are each independently —H, —CH ３ , -CH ２ R, -CHR ２ , -CR ３ , -OR, -COOR, -SiR ３ , —O—SiR ３ , —COCl or a halogen atom. １ ~R ７ In the formula, R each independently represents a linear or cyclic alkyl group, an alkenyl group, a halogenated alkyl group, a halogenated alkenyl group, or an allyl group. １ ~R ７ It is particularly preferred that is —H.

[0019] Other easily oxidizable thermoplastic resins include organic polymer compounds having a carbon-carbon double bond other than those mentioned above, such as ethylene-methyl acrylate-cyclohexenyl methyl acrylate copolymer. Also, examples of organic polymer compounds having a structural unit of the general formula (1) include hydrogenated styrene-butadiene rubber and hydrogenated styrene-isoprene rubber. Examples of organic polymer compounds having a hydrogen atom bonded to a tertiary carbon atom include polypropylene and polymethylpentene.

[0020] The easily oxidizable thermoplastic resin is preferably one or more selected from polybutadiene (X1), polyisoprene (X2), and the above-mentioned resin (Y), more preferably polybutadiene (X1) and the above-mentioned resin (Y), and even more preferably 1,2-polybutadiene and a styrene-isoprene-styrene block copolymer. Note that each of the above-mentioned components may be used alone or in combination of two or more.

[0021] When the easily oxidizable thermoplastic resin contains polybutadiene (X1) and / or polyisoprene (X2) and the resin (Y), the content of the resin (Y) is not particularly limited, but is preferably 3 parts by mass or more and 1,000 parts by mass or less, more preferably 5 parts by mass or more and 500 parts by mass or less, even more preferably 10 parts by mass or more and 200 parts by mass or less, and still more preferably 20 parts by mass or more and 100 parts by mass or less, relative to 100 parts by mass of the polybutadiene (X1) and / or polyisoprene (X2). By setting the content within the above range, good oxygen absorption performance is exhibited.

[0022] Furthermore, the content of the easily oxidizable thermoplastic resin in the oxygen-absorbing resin composition is not particularly limited, but is preferably 10% by mass or more and 99% by mass or less, more preferably 10% by mass or more and 75% by mass or less, even more preferably 20% by mass or more and 50% by mass or less, and even more preferably 25% by mass or more and 40% by mass or less.

[0023] (Metal catalyst) The oxygen absorbing resin composition of the present invention contains a metal catalyst. The metal catalyst in the oxygen absorbing resin composition of the present invention is a fatty acid salt of manganese. By using a fatty acid salt of manganese as the metal catalyst, the amount of oxygen absorbed in the oxygen absorbing resin composition after irradiation with energy rays can be suppressed at the initial stage of the oxygen absorption reaction, and thereafter, the oxygen absorption amount can be sufficiently maintained for a long period of time, or even increased compared to the initial stage.

[0024] The manganese fatty acid salt is not particularly limited and can be appropriately selected from known salts. From the viewpoint of oxygen absorption performance, however, the number of carbon atoms in the fatty acid constituting the manganese fatty acid salt is preferably 4 or more and 22 or less, more preferably 6 or more and 18 or less, even more preferably 6 or more and 12 or less, and still more preferably 8 or more and 12 or less.

[0025] More specifically, the fatty acid constituting the manganese fatty acid salt is preferably one or more selected from the group consisting of octylic acid, octanoic acid, stearic acid, oleic acid, and linoleic acid, more preferably one or more selected from the group consisting of octylic acid, octanoic acid, oleic acid, and linoleic acid, even more preferably one or more selected from the group consisting of octanoic acid, oleic acid, and linoleic acid, and even more preferably one or more selected from the group consisting of octanoic acid and tall oil fatty acid (a mixture of oleic acid and linoleic acid).

[0026] The form of the manganese fatty acid salt is not particularly limited, and may be a solid (powder) or liquid at room temperature and normal pressure, or may be a solution dissolved or dispersed in a solvent. Among these, the form of the manganese fatty acid salt is preferably a solid, and more preferably a powder. When the manganese fatty acid salt is in the form of a liquid or solution, it is preferably supported on or impregnated with a carrier material described below.

[0027] The content of the manganese fatty acid salt in the easily oxidizable thermoplastic resin is not particularly limited, but is preferably 0.001 to 10 parts by mass, more preferably 0.001 to 5 parts by mass, even more preferably 0.01 to 3 parts by mass, even more preferably 0.01 to 1.5 parts by mass, even more preferably 0.01 to 1 part by mass, and still more preferably 0.05 to 0.5 parts by mass, relative to 100 parts by mass of the easily oxidizable thermoplastic resin, in terms of manganese (Mn). The content of the manganese fatty acid salt in the oxygen-absorbing resin composition is preferably 0.001 to 10 parts by mass, more preferably 0.001 to 5 parts by mass, even more preferably 0.01 to 1 part by mass, and still more preferably 0.05 to 0.5 parts by mass, relative to 100 parts by mass of the oxygen-absorbing resin composition, in terms of manganese (Mn).

[0028] (Other Components) The oxygen-absorbing resin composition of the present invention may contain other components than those described above, provided that the effects of the present invention are not impaired. Examples of other components include thermoplastic resins other than easily oxidizable thermoplastic resins, carrier materials for supporting metal catalysts, and other known additives.

[0029] <Thermoplastic resin other than easily oxidizable thermoplastic resin> The oxygen-absorbing resin composition may further contain a thermoplastic resin other than the easily oxidizable thermoplastic resin (hereinafter, also simply referred to as "thermoplastic resin") from the viewpoint of improving the dispersibility of the blended components, improving the oxygen absorption performance, and improving the moldability.

[0030] The thermoplastic resin is preferably one that is highly compatible with easily oxidizable thermoplastic resins or has high oxygen permeability. Specific examples include polyolefin resins, ethylene-based copolymers, soft polyvinyl chloride, polystyrene, polymethylpentene, silicone resins, and copolymers of polysiloxane with other resins. Preferably, the resin is one or more selected from the group consisting of polyolefin resins, ethylene-based copolymers, soft polyvinyl chloride, polystyrene, and polymethylpentene. More preferably, the resin is one or more selected from the group consisting of polyolefin resins, ethylene-based copolymers, polystyrene, and polymethylpentene. Even more preferably, the resin is one or more selected from the group consisting of polyolefin resins and ethylene-based copolymers. Polyolefin resins include polyethylene, ethylene-α-olefin copolymers, polypropylene, propylene-ethylene random copolymers, propylene-ethylene block copolymers, and ethylene-cyclic olefin copolymers. Of these, polyethylene is preferred, and linear low-density polyethylene is more preferred. Examples of ethylene copolymers include ethylene-(meth)acrylic acid copolymers, ethylene-methyl (meth)acrylate, various ion-crosslinked products of ethylene-(meth)acrylic acid copolymers, ethylene-vinyl acetate copolymers, etc. These thermoplastic resins other than easily oxidizable thermoplastic resins can be used alone or in combination of two or more.

[0031] When the oxygen-absorbing resin composition contains a thermoplastic resin, the content of the thermoplastic resin is preferably 1 part by mass or more and 1,000 parts by mass or less, more preferably 10 parts by mass or more and 500 parts by mass or less, even more preferably 100 parts by mass or more and 500 parts by mass or less, and still more preferably 100 parts by mass or more and 300 parts by mass or less, relative to 100 parts by mass of the easily oxidizable thermoplastic resin.

[0032] <Carrier material supporting metal catalyst> The oxygen-absorbing resin composition may further contain a carrier material, if necessary. Furthermore, when the metal catalyst is in the form of a liquid or solution, the metal catalyst can be supported or impregnated on a carrier material to form a support (hereinafter also referred to as a "metal catalyst supporter") in which the metal catalyst is supported or impregnated on a carrier material. By supporting or impregnating the metal catalyst on a carrier material, the contact area with oxygen can be increased, and the oxygen absorption rate or oxygen absorption amount can be increased. Furthermore, the metal catalyst can be made into a powder form, making it easier to handle.

[0033] The support material is not particularly limited, but examples include silicon dioxide, zeolite, diatomaceous earth, calcium silicates, etc. As the support material, agglomerates having a size of 0.1 to 200 μm during and after catalyst preparation are preferred because they are easy to handle. Furthermore, a support material that disaggregates to a size of 1 to 100 nm when dispersed in a resin is preferred because it gives a transparent resin composition when blended with the resin. Silicon dioxide is an example of such a support material. The support material is preferably one or more selected from the group consisting of silicon dioxide and calcium silicate, and more preferably silicon dioxide.

[0034] When the oxygen-absorbing resin composition contains a carrier material, the content of the carrier material is preferably 20 parts by mass or more and 1,000 parts by mass or less, more preferably 50 parts by mass or more and 500 parts by mass or less, and even more preferably 50 parts by mass or more and 200 parts by mass or less, relative to 100 parts by mass of the liquid or solution of the metal catalyst.

[0035] <Additives> The oxygen-absorbing resin composition may contain various additives as needed. The additives are not particularly limited, and known additives that are usually used in oxygen-absorbing resin compositions may be used, including, for example, a photoinitiator, an antifoaming agent such as calcium oxide, a lubricant such as zinc stearate or calcium stearate, a phenolic or phosphorus-based antioxidant, a colorant such as an organic or inorganic dye or pigment such as titanium oxide, a silane or titanate-based dispersant, a polyacrylic acid-based water absorbent, a filler such as silica or clay, a gas adsorbent such as zeolite or activated carbon, a desiccant, and an antibacterial agent.

[0036] In particular, from the viewpoint of further enhancing oxygen absorption performance or reducing the dose of energy rays, a photoinitiator may be further contained. Known photoinitiators include hydrogen abstraction initiators and intramolecular cleavage initiators. In hydrogen abstraction initiators, excited initiator molecules abstract hydrogen from the resin to generate active radicals, thereby initiating an oxidation reaction. In intramolecular cleavage initiators, excited initiator molecules undergo α-cleavage to generate radicals, which then add to the double bond of the resin to generate new radicals. These radicals further abstract hydrogen from the resin to generate active radicals, thereby progressing the oxidation reaction. Examples of hydrogen abstraction initiators include, but are not limited to, benzophenones, thiazines, metal porphyrins, anthraquinones, xanthones, thioxanthones, fluorenones, and benzoquinones. Among these, fluorenones, thioxanthones, and anthraquinones are preferred. On the other hand, examples of intramolecular cleavage initiators include α-hydroxyketones (Irgacure 127, Irgacure 184, Irgacure 2959, etc.), benzil ketals (Irgacure 651, etc.), acylphosphine oxides (Darocur TPO, Irgacure 819, etc.), and oxime esters (Irgacure OXE01, Irgacure OXE02, etc.), but are not particularly limited to these. Among these, α-hydroxyketones and acylphosphine oxides are preferred. When the oxygen-absorbing resin composition contains a photoinitiator, the content of the photoinitiator in the oxygen-absorbing resin composition is preferably 0.1 to 1 mass% from the viewpoint of further improving the oxygen absorption performance or reducing the irradiation dose of energy rays. Note that, from the viewpoint of suppressing external migration of the photoinitiator from the oxygen-absorbing resin composition and improving the transparency and aesthetics of the resulting molded product (e.g., sheet or film), it is preferable that the oxygen-absorbing resin composition is substantially free of a photoinitiator. Here, "substantially free of photoinitiator" means that the content of the photoinitiator in the oxygen-absorbing resin composition is 0% by mass or more and less than 0.1% by mass, preferably 0% by mass or more and less than 0.01% by mass, more preferably 0% by mass or more and less than 0.001% by mass, and even more preferably 0% by mass.In particular, it is preferable that the oxygen absorbing resin composition does not contain a benzophenone-based photoinitiator as the photoinitiator.

[0037] (Energy Rays to be Irradiated) The energy rays to be irradiated to the oxygen absorbing resin composition to initiate oxygen absorption are not particularly limited, and examples include ultraviolet rays, electron beams, α-rays, β-rays, γ-rays, and X-rays. Irradiation with these energy rays cleaves carbon-hydrogen bonds or carbon-carbon bonds in the easily oxidizable thermoplastic resin to generate radicals, thereby initiating an oxidation reaction. Oxygen absorption can also be initiated by applying energy such as heat, high frequency, or ultrasonic waves. Among these, the energy rays to be irradiated are preferably one or more types selected from ultraviolet rays, electron beams, and γ-rays, and more preferably ultraviolet rays.

[0038] Ultraviolet (UV) rays can be generated from an ultraviolet irradiation device equipped with, for example, a high-pressure mercury lamp, a low-pressure mercury lamp, a metal halide lamp, an electrodeless lamp, or the like, and more preferably a low-pressure mercury lamp. The wavelength of the ultraviolet rays generated from the ultraviolet irradiation device can be appropriately adjusted depending on the composition of the oxygen-absorbing resin composition, the processing amount, etc., and is not particularly limited, but is, for example, 100 nm or more and 400 nm or less, preferably 200 nm or more and 380 nm or less, and more preferably 250 nm or more and 370 nm or less. The integrated light amount of the ultraviolet rays can be appropriately adjusted depending on the composition of the oxygen-absorbing resin composition, the processing amount, etc., and is not particularly limited, but is, for example, 1 mJ / cm ２ More than 20000mJ / cm ２ Preferably 100 mJ / cm or less ２ More than 10000mJ / cm ２ or less, more preferably 500 mJ / cm ２ More than 5000mJ / cm ２ The following is the result.

[0039] (Production Method) The method for producing the oxygen absorbing resin composition of the present invention is not particularly limited, but the following preferred examples can be mentioned.

[0040] The oxygen-absorbing resin composition can be obtained by kneading an easily oxidizable thermoplastic resin and a metal catalyst at a temperature equal to or higher than the melting temperature of the resin, and further mixing and kneading a thermoplastic resin other than the easily oxidizable thermoplastic resin and additives as necessary, to uniformly disperse the easily oxidizable thermoplastic resin and the metal catalyst.

[0041] The metal catalyst may be prepared by first preparing a metal catalyst-containing resin composition (master batch) containing a powdered metal catalyst or a metal catalyst carrier at a high concentration, and then kneading the metal catalyst-containing resin composition with an easily oxidizable thermoplastic resin at a temperature equal to or higher than the melting point of the resin. The same applies to the addition of additives.

[0042] The amount of each component can be appropriately adjusted depending on the content of each component constituting the above-mentioned oxygen-absorbing resin composition. In particular, before irradiation with energy rays, the composition of the oxygen-absorbing resin composition is substantially the same as the blended composition, and the amount of each component is the same as the content of each component constituting the above-mentioned oxygen-absorbing resin composition.

[0043] The oxygen-absorbing resin composition prepared in this manner exhibits oxygen absorbing ability when irradiated with energy rays. After irradiation with energy rays, the oxygen absorption reaction proceeds in an environment where oxygen is present, so it is preferably stored in an oxygen-barrier bag or the like with low oxygen permeability and kept in an oxygen-free environment until it is used as an oxygen scavenger. From the viewpoint of such ease of handling and the viewpoint of maintaining good oxygen absorbing performance, the oxygen-absorbing resin composition is preferably an oxygen-absorbing resin composition that can exhibit oxygen absorbing ability when irradiated with energy rays before being irradiated with energy rays.

[0044] [Molded Article] The molded article of the present invention is made of the oxygen-absorbing resin composition of the present invention. Such a molded article exhibits sufficient oxygen absorption performance even after being irradiated with energy rays and then kept in the atmosphere for a certain period of time.

[0045] The size and shape of the molded product are not particularly limited, and a desired molded product can be obtained using a known molding device used for press molding, injection molding, extrusion molding, etc. The oxygen-absorbing resin composition has a high degree of freedom in shape design, so it can be molded into a desired shape for use. Specifically, the molded product can be used in various forms, such as a film, a sheet, a small piece, or a block.

[0046] The molded article can be produced by a known method. Specifically, when the molded article is a film or sheet, (1) the oxygen-absorbing resin composition may be melt-kneaded in an extruder, then extruded through a strand die, cooled, pelletized with a pelletizer, and the pellets made of the oxygen-absorbing resin composition are pressed to obtain a film or sheet, or (2) the oxygen-absorbing resin composition may be melt-kneaded in an extruder, then formed into a film using a T-die to obtain a film or sheet. Furthermore, when the molded article is in the form of small pieces or blocks, the oxygen-absorbing resin composition may be melt-kneaded in an extruder, then extruded through a strand die, cooled, pelletized with a pelletizer, and molded by injection molding, blow molding, extrusion molding, vacuum molding, pressure molding, or the like to obtain a small piece-shaped molded article or a block-shaped molded article.

[0047] [Oxygen scavenging method] The oxygen-absorbing resin composition of the present invention can be suitably used in the following oxygen scavenging method. That is, a preferred oxygen scavenging method of the present invention comprises a step (1) of irradiating the oxygen-absorbing resin composition with energy rays to obtain an oxygen scavenger, and a step (2) of sealing the oxygen scavenger together with a preserved object in a storage container, and the time period for which the oxygen scavenger is kept in the atmosphere after the step (1) and before being sealed in the step (2) is from 1 hour to 3 days.

[0048] The oxygen-absorbing resin composition of the present invention exhibits sufficient oxygen-absorbing performance even after being kept in the atmosphere for a certain period of time after being irradiated with energy rays, and therefore can exhibit sufficient oxygen-absorbing performance even when the oxygen scavenger is used in a manner in which it is kept in the atmosphere for, for example, 24 hours or more and 3 days or less.

[0049] <Step (1)> Step (1) is a step of irradiating the oxygen-absorbing resin composition with energy rays to obtain an oxygen scavenger. The oxygen-absorbing resin composition and the irradiation of energy rays are as described above. After irradiation with energy rays, the oxygen-absorbing resin composition exhibits oxygen absorbing ability and can function as an oxygen scavenger. In other words, the "oxygen scavenger" in this oxygen scavenging method is "an oxygen-absorbing resin composition that has been irradiated with energy rays and is in a state where it exhibits or can exhibit oxygen absorbing ability due to the irradiation with energy rays" or a molded product of the oxygen-absorbing resin composition. In such an oxygen scavenger, the oxygen absorption reaction proceeds gradually in an oxygen-present environment. Therefore, if a long time is required until the oxygen scavenger is used as an oxygen scavenger, i.e., until it is sealed in a storage container together with the preserved material in step (2) described below, the oxygen scavenger is preferably stored in an oxygen-free environment, such as an oxygen barrier bag with low oxygen permeability, in order to maintain good oxygen scavenging performance. At this time, in order to quickly create a low-oxygen atmosphere inside the oxygen barrier bag, another oxygen absorber that exhibits oxygen absorption performance may be present in the oxygen barrier bag in addition to the oxygen absorber used in the oxygen removal method of the present invention.

[0050] <Step (2)> Step (2) is a step of sealing the oxygen absorber obtained in step (1) together with the object to be preserved in a storage container. The object to be preserved is not particularly limited, but examples include various products that are easily affected by oxygen and are susceptible to deterioration, such as food, pharmaceuticals, metal products, and electronic products. In particular, the oxygen absorbing method of the present invention is suitable for use in industrial products that require long assembly times, and the object to be preserved is preferably an industrial product that requires a long time to seal, such as a metal product or an electronic product.

[0051] There are no particular restrictions on the storage container, and the size and shape may be selected appropriately in relation to the item to be stored. However, from the viewpoint of using the oxygen absorber to quickly create an oxygen-free state inside the container and maintaining that state, the material is preferably one with gas barrier properties (particularly oxygen barrier properties), and more preferably an aluminum barrier bag with light-blocking and gas barrier properties.

[0052] Furthermore, the method for sealing the storage container is not particularly limited, and a simple seal that allows slight breathability may be used, but a sealed seal is preferred from the viewpoint of creating a low-oxygen state inside the container in a short period of time using an oxygen scavenger and maintaining that state.

[0053] <From step (1) until sealing in step (2)> The time for which the oxygen scavenger is kept in the atmosphere after step (1) until sealing in step (2) is from 1 hour to 3 days. As described above, the oxygen absorption reaction of the oxygen scavenger proceeds gradually in an environment where oxygen is present, so after the oxygen-absorbing resin composition is irradiated with energy rays, the shorter the time for which it is kept in the atmosphere, the better. However, the oxygen scavenger made of the oxygen-absorbing resin composition of the present invention exhibits sufficient oxygen-absorbing performance even after being kept in the atmosphere for up to 3 days.

[0054] Here, "the oxygen scavenger is maintained in the atmosphere" refers to a state in which the oxygen scavenger is present in the atmosphere after the oxygen-absorbing resin composition is irradiated with energy rays until it is sealed in a storage container, regardless of whether it is in a stationary state. Note that when the oxygen scavenger is stored in an oxygen-free state in a gas barrier bag and is present in the atmosphere, this does not fall under the category of "the oxygen scavenger is maintained in the atmosphere."

[0055] The time for which the oxygen scavenger is kept in the atmosphere may be from 1 hour to 3 days, but from the viewpoint of maintaining good oxygen absorption performance, it is preferably 2 days or less, more preferably 1 day or less. Furthermore, since the oxygen-absorbing resin composition of the present invention maintains sufficient oxygen absorption performance even after being kept in the atmosphere for a certain period of time after irradiation with energy rays, it is more suitable when the oxygen scavenger is kept in the atmosphere for preferably 1 hour or more, more preferably 5 hours or more, even more preferably 10 hours or more, and even more preferably 20 hours or more. The oxygen-absorbing resin composition of the present invention can maintain sufficient oxygen absorption performance as long as the time for which the oxygen scavenger is kept in the atmosphere is 1 day or more but not more than 3 days, and can be suitably used in industrial product applications requiring particularly long assembly times, etc. That is, conventional oxygen-absorbing resin compositions have the problem that oxygen absorption begins immediately after irradiation with energy rays and the oxygen scavenger is subsequently deactivated when kept in the atmosphere for a certain period of time. However, the oxygen scavenger of the present invention maintains sufficient oxygen absorption performance even after being kept in the atmosphere for a certain period of time, and therefore exhibits particularly remarkable effects when kept in the atmosphere for a long period of time, making it more suitable for use.

[0056] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, but includes all aspects encompassed by the concept of the present invention and the scope of the claims, and can be modified in various ways within the scope of the present invention.

[0057] The present embodiment will be described in detail below using examples and comparative examples, but the present embodiment can be modified as appropriate as long as the effects of the present invention are achieved.

[0058] <Materials> The materials used in the examples and comparative examples are listed below. Manganese octylate support: Prepared in Preparation Example 1 below. (Preparation Example 1) Manganese octylate solution (manufactured by Toei Chemical Co., Ltd., manganese content: 8% by mass) and silicon dioxide powder (manufactured by Tosoh Corporation, average particle size: 6 μm) were mixed in a mass ratio of 4:5 to obtain a powdered manganese octylate support. Manganese octanoate powder: manufactured by Mitsuwa Chemical Co., Ltd., average particle size: 156 μm Manganese stearate powder: manufactured by Mitsuwa Chemical Co., Ltd., powdered, average particle size: 201 μm Tall oil fatty acid manganese support: Prepared in Preparation Example 2 below. (Preparation Example 2) A tall oil fatty acid manganese support was prepared in the same manner as in Preparation Example 1, except that a tall oil fatty acid manganese solution (manufactured by Toei Chemical Co., Ltd., manganese content: 8% by mass) was used instead of the manganese octylate solution. Cobalt octylate support: Prepared in Preparation Example 3 below. (Preparation Example 3) A powdery cobalt octylate support was obtained in the same manner as in Preparation Example 1, except that a cobalt octylate solution (manufactured by Toei Kako Co., Ltd., cobalt content: 8% by mass) was used instead of the manganese octylate solution. Syndiotactic 1,2-polybutadiene: manufactured by ENEOS Material Trading Co., Ltd., hereinafter referred to as "RB". Styrene-isoprene-styrene block copolymer: manufactured by ENEOS Material Trading Co., Ltd., hereinafter referred to as "SIS". Linear low-density polyethylene: manufactured by Dow Chemical Co., Ltd., hereinafter referred to as "LLDPE". Commercially available oxygen scavenger: GE-100 manufactured by Mitsubishi Gas Chemical Co., Inc.

[0059] (Example 1) [1] Preparation of oxygen-absorbing resin composition A manganese octylate carrier as a metal catalyst and RB, SIS, and LLDPE as resins were compounded in the composition ratios shown in Table 1 and dry-blended. The mixture was then kneaded and extruded at 150°C or higher and 170°C or lower using a small twin-screw segment extruder ("2D15W" manufactured by Toyo Seiki Seisaku-sho, Ltd.), extruded through a strand die, cooled, and cut with a pelletizer to obtain pellets (oxygen-absorbing resin composition).

[0060]

[0061] [2] Preparation of molded body The oxygen-absorbing resin composition obtained in [1] above was press-molded into a sheet having a thickness of 0.1 mm to obtain a molded body (150 mm x 150 mm) made of the oxygen-absorbing resin composition.

[0062] [3] UV irradiation The molded body obtained in [2] above was irradiated with ultraviolet light (UV) under the following conditions: [UV irradiation conditions] Light source: Mercury lamp (manufactured by iGraphics Co., Ltd.) UV wavelength: mainly 365 nm Accumulated irradiation dose: 2000 mJ / cm ２ (Illuminance 500mW / cm ２ , irradiation time 4 seconds)

[0063] [4] Storage The molded body after UV irradiation obtained in [3] above was stored in a 35 cm ２ The resulting mixture was cut into small pieces (5 cm x 7 cm). The time required for this process was approximately 1 minute. One of the resulting small pieces was sealed in an aluminum barrier bag (manufactured by Mitsubishi Gas Chemical Co., Inc.) together with the commercially available oxygen absorber (GE-100). The barrier bag was then stored at 25°C and 60% RH for 5 days.

[0064] (Example 2) Steps [1] to [4] were carried out in the same manner as in Example 1, except that manganese octanoate powder was used as the metal catalyst in step [1] of Example 1. In the composition ratios shown in Table 1, the amount of manganese octanoate powder was blended so that it was 0.3 parts by mass, calculated as a metal atom, per 100 parts by mass of the oxygen-absorbing resin composition and 1.0 part by mass, calculated as a metal atom, per 100 parts by mass of the easily oxidizable thermoplastic resin, and the amount of LLDPE was the remainder.

[0065] (Example 3) Operations [1] to [4] were carried out in the same manner as in Example 1, except that manganese stearate powder was used as the metal catalyst in [1] of Example 1. In the composition ratios shown in Table 1, the amount of manganese stearate powder was blended so that it was 0.3 part by mass, calculated as a metal atom, per 100 parts by mass of the oxygen-absorbing resin composition and 1.0 part by mass, calculated as a metal atom, per 100 parts by mass of the easily oxidizable thermoplastic resin, and the amount of LLDPE was the remainder.

[0066] (Example 4) The steps [1] to [4] were carried out in the same manner as in Example 1, except that in [1] of Example 1, a tall oil fatty acid manganese carrier was used as the metal catalyst. The ingredients were blended to obtain the composition ratio shown in Table 1.

[0067] Comparative Example 1 [1] to [4] were carried out in the same manner as in Example 1, except that in [1] of Example 1, a cobalt octylate carrier was used as the metal catalyst. The components were mixed to obtain the composition ratio shown in Table 1.

[0068] <Evaluation> The following evaluations were performed using the UV-irradiated molded articles stored for 5 days in [4] of Examples 1 to 4 and Comparative Example 1. The results are shown in Table 2. (Oxygen Absorption Amount) The oxygen absorption amount was measured using the following method. [4] In the storage step, a small piece of the UV-irradiated molded article stored for 5 days was removed from the gas barrier bag, and one small piece of the molded article and 300 ml of air at 25°C were placed in an aluminum foil-laminated plastic film bag (manufactured by Mitsubishi Gas Chemical Company, Inc., size 180 mm x 250 mm, hereinafter referred to as the "aluminum barrier bag"), and the opening was heat-sealed to seal it. Furthermore, the oxygen concentration (initial oxygen concentration) inside the aluminum barrier bag at this time was measured. The aluminum barrier bag was then immediately placed in a thermostatic chamber at 25°C and 60% RH and maintained there for 7 days. During this period, the oxygen concentration in the aluminum barrier bag (oxygen concentration after storage) was measured at each of the following times: 1 day (1 d), 3 days (3 d), and 7 days (7 d). The amount of oxygen absorbed at each time point (initial oxygen concentration - oxygen concentration after storage) was calculated. Furthermore, the area (35 cm) of the small piece of the molded product was measured. ２ ) to obtain the oxygen absorption amount per unit area of ​​the molded body (ml / cm ２) was calculated. The oxygen concentration was measured using a gas analyzer (MOCON's "Check Mate 3"). The measurement was performed by inserting a hollow needle at the tip of a sampling silicone tube attached to the gas analyzer into the inside of the bag through a sampling rubber sheet that had been previously attached to the aluminum barrier bag, and measuring the oxygen concentration inside the aluminum barrier bag. The above measurement was performed three times for each Example and Comparative Example, and the average value for each was calculated. The results are shown in Table 2. A larger amount of oxygen absorption means higher oxygen absorption performance.

[0069] (Oxygen absorption rate after storage) To evaluate the oxygen absorption performance after storage in the atmosphere for a certain period of time, the oxygen absorption rate after storage in the atmosphere was calculated as follows. From the oxygen absorption rates at 3 and 7 days, the oxygen absorption rate from 3 days to 7 days (7d - 3d) out of the total oxygen absorption rate over 7 days (7d) was calculated as the "oxygen absorption rate after storage" [100 × (7d - 3d) / 7d] (%). In this example, an oxygen absorption rate after storage from 3 days to 7 days [100 × (7d - 3d) / 7d] (%) of 30% or more was evaluated as good, and an oxygen absorption rate of 60% or more was evaluated as even better. A higher oxygen absorption rate after storage from 3 days to 7 days means that higher oxygen absorption performance can be exhibited and maintained after storage in the atmosphere for 3 days.

[0070]

[0071] As shown in Table 2, in an oxygen-absorbing resin composition containing an easily oxidizable thermoplastic resin and a metal catalyst, which exhibits oxygen absorption capacity when irradiated with energy rays, when the metal catalyst is a fatty acid salt of manganese, the amount of oxygen absorbed up to the third day was small, and even after three days, a sufficient amount of oxygen was observed, and it was confirmed that sufficient oxygen absorption performance was exhibited even when kept in the atmosphere for a certain period of time (for example, three days) (Examples 1 to 4). This shows that the oxygen-absorbing resin composition of the present invention can suppress the amount of oxygen absorbed in the early stage of the oxygen absorption reaction, and thereafter can sufficiently maintain the amount of oxygen absorbed over a long period of time, and can even increase the amount of oxygen absorbed compared to the initial stage.

[0072] On the other hand, when the metal catalyst was not a fatty acid salt of manganese, a large amount of oxygen was absorbed by the third day, and the improvement in the amount of oxygen absorbed after three days was small, with the amount of oxygen absorbed decreasing early, confirming that the catalyst was unable to exhibit sufficient oxygen absorption performance over the long term (Comparative Example 1).

Claims

1. An oxygen-absorbing resin composition comprising an easily oxidizable thermoplastic resin and a metal catalyst, the composition exhibiting oxygen absorption ability upon irradiation with energy rays, The oxygen-absorbing resin composition, wherein the metal catalyst is a fatty acid salt of manganese.

2. 2. The oxygen-absorbing resin composition according to claim 1, wherein the content of the fatty acid salt of manganese is, in terms of manganese (Mn), 0.001 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the easily oxidizable thermoplastic resin.

3. 3. The oxygen-absorbing resin composition according to claim 1, wherein the content of the fatty acid salt of manganese is, in terms of manganese (Mn), 0.001 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the oxygen-absorbing resin composition.

4. 3. The oxygen-absorbing resin composition according to claim 1, wherein the fatty acid constituting the manganese fatty acid salt has 4 or more and 22 or less carbon atoms.

5. 5. The oxygen-absorbing resin composition according to claim 4, wherein the fatty acid constituting the manganese fatty acid salt is at least one selected from the group consisting of octylic acid, octanoic acid, stearic acid, oleic acid, and linoleic acid.

6. The oxygen-absorbing resin composition according to claim 1 or 2, wherein the easily oxidizable thermoplastic resin contains at least one resin selected from the group consisting of polybutadiene (X1), polyisoprene (X2), and a resin (Y) having a carbon-carbon double bond and a structural unit represented by the following general formula (1): 【Chemistry 1】 (In the formula, R １ ~R ７ is -H, -CH ３ , -CH ２ R, -CHR ２ , -CR ３ , -OR, -COOR, -SiR ３ , —O—SiR ３ , —COCl, or a halogen atom, which may be the same or different, and R represents a linear or cyclic alkyl group, alkenyl group, halogenated alkyl group, halogenated alkenyl group, or allyl group.

7. 7. The oxygen-absorbing resin composition according to claim 6, wherein the easily oxidizable thermoplastic resin contains the polybutadiene (X1) and the resin (Y).

8. The oxygen-absorbing resin composition according to claim 6, wherein the polybutadiene (X1) is 1,2-polybutadiene.

9. The oxygen-absorbing resin composition according to claim 6, wherein the resin (Y) is at least one selected from the group consisting of a styrene-isoprene-styrene block copolymer and a styrene-butadiene-styrene block copolymer.

10. A molded article comprising the oxygen-absorbing resin composition according to claim 1 or 2.

11. A step (1) of irradiating the oxygen absorbing resin composition according to claim 1 or 2 with energy rays to obtain an oxygen scavenger; and (2) sealing the oxygen absorber together with the object to be preserved in a storage container, The oxygen absorbing method, wherein the time period during which the oxygen absorbing agent is kept in the atmosphere after the step (1) and before the sealing in the step (2) is from 1 hour to 3 days.

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