Oxygen-absorbing nanofiber aggregate

Abstract

Provided is an oxygen-absorbing nanofiber aggregate comprising an easily-oxidizable thermoplastic resin and a radical generator. The oxygen-absorbing nanofiber aggregate either contains no transition metal catalyst or contains not more than 10 mass ppm of a transition metal catalyst, in terms of transition metal. The specific surface area is 1.0-100.0 m2 / g<sp / >. Also provided is a method for producing an oxygen-absorbing nanofiber aggregate, said method comprising: a step 1 for dissolving an easily-oxidizable thermoplastic resin and a radical generator in a solvent to obtain a solution; and a step 2 for obtaining an oxygen-absorbing nanofiber aggregate by performing electrospinning with respect to the solution.

Description

Oxygen-absorbing nanofiber aggregate

[0001] The present invention relates to an oxygen-absorbing nanofiber aggregate.

[0002] For the purpose of preventing oxidation of various products that are easily degraded by the influence of oxygen, typified by foods, pharmaceuticals, metal products, and electronic products, oxygen scavengers that remove oxygen have been conventionally used. The form that was initially developed as this oxygen scavenger and is still widely used today is that of a granular or powdery oxygen scavenger composition packaged in a small sachet.

[0003] In recent years, resin materials exhibiting oxygen absorption performance have been proposed as oxygen scavengers that are easier to handle, have a higher degree of freedom in shape, and have a wider range of applications. For example, Patent Document 1 discloses an oxygen-absorbing resin composition characterized in that a compound containing a transition metal and a photosensitizer are blended into a resin composition containing a thermoplastic resin, an alicyclic unsaturated compound or a derivative thereof. Further, Patent Document 2 discloses an oxygen-absorbing resin that has a carbon atom bonded to a carbon-carbon double bond group and bonded to one hydrogen atom, said carbon atom is included in an alicyclic structure, and has been subjected to radiation irradiation treatment.

[0004] Japanese Unexamined Patent Application Publication No. 2003-253131 International Publication No. WO 2005 / 105887

[0005] The oxygen-absorbing resin as described above absorbs oxygen when the oxidation sites contained in its skeleton react with oxygen, but there is a problem that by-product gas is generated due to side reactions accompanying oxidation. The by-product gases are mainly aldehydes, carboxylic acids, and the like, which cause odor. In Patent Document 2, attempts have been made to solve the above problem with a resin that absorbs oxygen in the absence of a transition metal catalyst such as a Co salt, but recently, higher oxygen absorption performance is also required for oxygen-absorbing resins. Therefore, from the viewpoint of achieving both by-product gas suppression and oxygen absorption performance, conventional resins such as those disclosed in Patent Document 2 cannot be said to be sufficient. For this reason, there has been a demand for a resin material having excellent oxygen-absorbing properties that sufficiently suppresses the generation of by-product gas and odor while having excellent oxygen-absorbing properties. Therefore, the problem to be solved by the present invention is to provide an oxygen-absorbing nanofiber aggregate that suppresses by-product gas and has high oxygen-absorbing performance.

[0006] The gist and configuration of the present invention is as follows. [1] An oxygen-absorbing nanofiber aggregate that contains an easily oxidizable thermoplastic resin and a radical generator, does not contain a transition metal catalyst or contains a transition metal catalyst in an amount of 10 mass ppm or less in terms of transition metal, and has a specific surface area of 1.0 m 2 / g or more and 100.0 m 2 / g or less. [2] The easily oxidizable thermoplastic resin is an organic polymer compound having a moiety where carbon and carbon are bonded by a double bond, an organic polymer compound having an allylic carbon, an organic polymer compound having a structural unit of the following formula (1), an organic polymer compound having a hydroxy group, an organic polymer compound having an ether group, an organic polymer compound having an aldehyde group, an organic polymer compound having a ketone group, and an organic polymer compound having a hydrogen atom bonded to a tertiary carbon atom. The oxygen-absorbing nanofiber aggregate according to [1] above, which is at least one selected from the group consisting of the above. (In the formula, R １ to R ７ represent -H, -CH ３ , -CH ２ R, -CHR ２ , -CR ３ , -OR, -COOR, -SiR ３ , -O-SiR ３ , -COCl or a halogen atom, each of 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. ) [3] The oxygen-absorbing nanofiber aggregate according to [1] or [2] above, 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 of the general formula (1). [4] The oxygen-absorbing nanofiber aggregate according to any one of [1] to [3] above, wherein the easily oxidizable thermoplastic resin contains at least one selected from the group consisting of styrene-isoprene-styrene block copolymers and styrene-butadiene-styrene block copolymers. [5] The cross-sectional area of the fibers constituting the oxygen-absorbing nanofiber aggregate is 10 -16 m 2 or more and 10 -11 m2 The oxygen-absorbing nanofiber aggregate according to any one of [1] to [4] above, which is as follows: [6] The oxygen-absorbing nanofiber aggregate according to any one of [1] to [5] above, wherein the radical generator is at least one selected from the group consisting of a benzophenone-based radical generator, a thioxanthone-based radical generator, and an acetophenone-based radical generator. [7] The oxygen-absorbing nanofiber aggregate according to any one of [1] to [6] above, wherein the content of the radical generator is 0.01% by mass or more and 1% by mass or less. [8] A method for producing the oxygen-absorbing nanofiber aggregate according to any one of [1] to [7] above, comprising the following steps 1 and 2: Step 1: A step of dissolving an easily oxidizable thermoplastic resin and a radical generator in a solvent to obtain a solution. Step 2: A step of spinning the solution by electrospinning to obtain an oxygen-absorbing nanofiber aggregate.

[0007] According to the present invention, it is possible to provide an oxygen-absorbing nanofiber aggregate that suppresses by-product gases during oxygen absorption and has high oxygen absorption performance. Because the oxygen-absorbing nanofiber aggregate of the present invention has the above-mentioned excellent properties, it can be suitably used as a film-type oxygen absorber in various applications. In particular, because it has high oxygen absorption performance and suppresses by-product gases, it can be used in applications where safety and odor are sensitive.

[0008] Embodiments of oxygen-absorbing nanofiber aggregates and methods for producing the same according to the present invention will be described in detail below. In this specification, the terms "A to B" in relation to numerical values ​​mean "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 preferred combination of embodiments is a more preferred embodiment.

[0009] [Oxygen-absorbing nanofiber aggregate] The oxygen-absorbing nanofiber aggregate of the present invention contains an easily oxidizable thermoplastic resin and a radical generator, and does not contain a transition metal catalyst, or contains a transition metal catalyst at a rate of 10 ppm by mass or less in terms of transition metal, and has a specific surface area of ​​1.0 m². 2 / g or more 100.0m 2The amount is less than or equal to / g. The oxygen-absorbing nanofiber aggregate of the present invention, having the above configuration, suppresses by-product gases and has high oxygen absorption performance.

[0010] The reason why the oxygen-absorbing nanofiber aggregates of the present invention exhibit the above effects is not entirely clear, but one possible reason is as follows: Easily oxidizable thermoplastic resins absorb oxygen by generating hydroperoxides at their oxidation sites. Although the nanofiber aggregates of the present invention do not substantially contain the transition metal catalysts usually required to promote the decomposition of hydroperoxides, their form, which consists of aggregated nanofibers, allows for a large specific surface area, increasing the number of reaction sites per unit weight, and suppressing side reactions, even while maintaining a film-like or other shape. As a result, the oxygen-absorbing nanofiber aggregates of the present invention are thought to suppress by-product gases during oxygen absorption and possess high oxygen absorption performance. The components and other details will be described below.

[0011] <Easily Oxidizable Thermoplastic Resin> The oxygen-absorbing nanofiber aggregate of the present invention contains an easily oxidizable thermoplastic resin. The easily oxidizable thermoplastic resin in the oxygen-absorbing nanofiber aggregate of the present invention is the main component when the oxygen-absorbing nanofiber aggregate exhibits oxygen absorption capacity through the generation of radicals. The easily oxidizable thermoplastic resin is a thermoplastic resin that undergoes an oxidation reaction due to radicals generated from a radical generator. The easily oxidizable thermoplastic resin is preferably a resin having a carbon-carbon double bond, an allyl carbon (carbon adjacent to the carbon-carbon double bond), a constituent unit of the following general formula (1), a hydroxyl group, an ether group, an aldehyde group, a ketone group, a hydrogen atom bonded to a tertiary carbon atom, etc.

[0012] The easily oxidizable thermoplastic resin is more preferably at least one selected from the group consisting of an organic polymer compound having a carbon-carbon double bond, an organic polymer compound having an allyl carbon (carbon adjacent to the carbon-carbon double bond), an organic polymer compound having the constituent unit of the following formula (1), an organic polymer compound having a hydroxyl group, an organic polymer compound having an ether group, an organic polymer compound having an aldehyde group, an organic polymer compound having a ketone group, and an organic polymer compound having a hydrogen atom bonded to a tertiary carbon atom. The organic polymer compound having a carbon-carbon double bond includes an organic polymer compound having an allyl carbon. Furthermore, in the case of an organic polymer compound having a carbon-carbon double bond or an organic polymer compound having an allyl carbon, the carbon-carbon double bond or the allyl carbon may be in the main chain of the polymer or in the side chain.

[0013] (In the formula, R １ ~R ７ is -H, -CH ３ ien-CH ２ R_CHR ２ , -CR ３ , -OR, -COOR, -SiR ３ , -O-SiR ３ , -COCl, or 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.

[0014] Furthermore, organic polymer compounds having two characteristic parts in a single molecule are also included in the above-mentioned easily oxidizable thermoplastic resins. For example, organic polymer compounds having a part in which carbon and carbon are bonded by a double bond, and having the constituent unit of formula (1), are also included in the above-mentioned easily oxidizable thermoplastic resins. In the present invention, organic polymer compounds having two characteristic parts in a single molecule are conveniently classified as follows: Organic polymer compounds having a part in which carbon and carbon are bonded by a double bond are classified as organic polymer compounds having a part in which carbon and carbon are bonded by a double bond. Organic polymer compounds other than organic polymer compounds having a part in which carbon and carbon are bonded by a double bond, and having the constituent unit of formula (1), are classified as organic polymer compounds having the constituent unit of formula (1). Organic polymer compounds other than organic polymer compounds having a part in which carbon and carbon are bonded by a double bond and organic polymer compounds having the constituent unit of formula (1), and having a hydrogen atom bonded to a tertiary carbon atom, are classified as organic polymer compounds having a hydrogen atom bonded to a tertiary carbon atom. Organic polymer compounds other than the above three types of organic polymer compounds and having a hydroxyl group are classified as organic polymer compounds having a hydroxyl group. Organic polymer compounds having an ether group, other than the four types of organic polymer compounds mentioned above, are classified as organic polymer compounds having an ether group. Organic polymer compounds having an aldehyde group, other than the five types of organic polymer compounds mentioned above, are classified as organic polymer compounds having an aldehyde group. Organic polymer compounds having a ketone group, other than the six types of organic polymer compounds mentioned above, are classified as organic polymer compounds having a ketone group.

[0015] In the above general formula (1), R １ ~R ７ These are, independently, -H and -CH. ３ ien-CH ２ R_CHR ２ , -CR ３ , -OR, -COOR, -SiR ３ , -O-SiR ３ , represents -COCl or a halogen atom. Also, R １ ~R ７Each R in the given expression independently represents a linear or cyclic alkyl group, alkenyl group, halogenated alkyl group, halogenated alkenyl group, or allyl group. １ ~R ７ Preferably, it is -H.

[0016] The easily oxidizable thermoplastic resin is more preferably at least one selected from the group consisting of organic polymer compounds having a portion in which carbon and carbon are bonded by a double bond, organic polymer compounds having the constituent unit of formula (1), and organic polymer compounds having a hydrogen atom bonded to a tertiary carbon atom; even more preferably at least one selected from the group consisting of organic polymer compounds having a portion in which carbon and carbon are bonded by a double bond, and organic polymer compounds having the constituent unit of formula (1); even more preferably, an organic polymer compound having a portion in which carbon and carbon are bonded by a double bond, and even more preferably, an organic polymer compound having a portion in which carbon and carbon are bonded by a double bond and having the constituent unit of formula (1). The easily oxidizable thermoplastic resin may be used alone or in combination of two or more types.

[0017] The easily oxidizable thermoplastic resin more preferably contains at least one selected from the group consisting of polybutadiene (X1), polyisoprene (X2), and resin (Y) having a carbon-carbon double bond and the constituent unit of general formula (1), even more preferably contains at least one selected from the group consisting of polybutadiene (X1) and resin (Y), and even more preferably contains resin (Y). Each of the above components may be used individually or in combination of two or more. In "resin (Y) having a carbon-carbon double bond and the constituent unit of general formula (1)," the "carbon-carbon double bond" refers to a carbon-carbon double bond present in parts other than the "constituent unit of formula (1)," and refers to the benzene ring and R of formula (1). １ ~R ７ It does not contain carbon-carbon double bonds.

[0018] Polybutadiene (X1) is not particularly limited, but examples include 1,4-polybutadiene and 1,2-polybutadiene. Among these, 1,2-polybutadiene is preferred from the viewpoint of oxygen absorption performance.

[0019] The polyisoprene (X2) is not particularly limited, but examples 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 viewpoint of oxygen absorption performance and availability.

[0020] The above resin (Y) has a carbon-carbon double bond and the constituent unit of the above general formula (1). The carbon-carbon double bond may be in the main chain or the side chain of the resin. The above resin (Y) is not particularly limited, but examples include styrene-isoprene-styrene block copolymer, styrene-butadiene-styrene block copolymer, styrene-butadiene rubber, styrene-isoprene rubber, etc. Among these, at least one selected from the group consisting of styrene-isoprene-styrene block copolymer and styrene-butadiene-styrene block copolymer is preferred, and styrene-isoprene-styrene block copolymer is more preferred. Therefore, the easily oxidizable thermoplastic resin more preferably contains at least one selected from the group consisting of styrene-isoprene-styrene block copolymer and styrene-butadiene-styrene block copolymer, and even more preferably contains styrene-isoprene-styrene block copolymer.

[0021] Therefore, the easily oxidizable thermoplastic resin more preferably contains at least one selected from the group consisting of 1,2-polybutadiene, cis-1,4-polyisoprene, 3,4-polyisoprene, and styrene-isoprene-styrene block copolymer, and even more preferably contains at least one selected from the group consisting of 1,2-polybutadiene and styrene-isoprene-styrene block copolymer, and even more preferably contains styrene-isoprene-styrene block copolymer. Each of the above components may be used individually or in combination of two or more.

[0022] Other easily oxidizable thermoplastic resins include organic polymer compounds having carbon-carbon double bonded portions other than those mentioned above, such as ethylene-methyl acrylate-cyclohexenylmethyl acrylate copolymer. Furthermore, organic polymer compounds having the constituent unit of general formula (1) other than those mentioned above include hydrogenated styrene-butadiene rubber and hydrogenated styrene-isoprene rubber. Organic polymer compounds having hydrogen atoms bonded to tertiary carbon atoms include polypropylene and polymethylpentene. Note that each of the above components may be used individually or in combination of two or more.

[0023] The content of the easily oxidizable thermoplastic resin in the oxygen-absorbing nanofiber aggregate is preferably 30% by mass or more and 99.99% by mass or less, more preferably 50% by mass or more and 99.9% by mass or less, even more preferably 80% by mass or more and 99.8% by mass or less, even more preferably 90% by mass or more and 99.7% by mass or less, and even more preferably 95% by mass or more and 99.6% by mass or less. By having the content of the easily oxidizable thermoplastic resin within the above range, oxygen absorption of the oxygen-absorbing nanofiber aggregate can be promoted, the oxygen absorption performance can be enhanced, and by-product gases during oxygen absorption can be suppressed.

[0024] <Transition Metal Catalyst> The oxygen-absorbing nanofiber aggregate of the present invention either does not contain a transition metal catalyst or contains a transition metal catalyst at a rate of 10 ppm by mass or less in terms of transition metal. That is, the content of the transition metal catalyst in the oxygen-absorbing nanofiber aggregate of the present invention is 0 to 10 ppm by mass in terms of transition metal. In other words, the oxygen-absorbing nanofiber aggregate of the present invention is substantially free of transition metal catalysts. Transition metal catalysts substantially not contained in the oxygen-absorbing nanofiber aggregate of the present invention are particularly manganese catalysts, cobalt catalysts, copper catalysts, iron catalysts, nickel catalysts, or chromium catalysts. Among these, it is preferable that the material not contain a manganese catalyst, and more preferably that it not contain a fatty acid salt of manganese.

[0025] The content of the transition metal catalyst in the oxygen-absorbing nanofiber aggregate is 10 ppm by mass or less, preferably 8 ppm by mass or less, more preferably 5 ppm by mass or less, even more preferably 2 ppm by mass or less, even more preferably 1 ppm by mass or less, even more preferably 0.5 ppm by mass or less, even more preferably 0.1 ppm by mass or less, and even more preferably 0 ppm by mass, and it is even more preferable that it is not contained. By substantially not containing the transition metal catalyst in the oxygen-absorbing nanofiber aggregate, it is possible to effectively suppress the generation of by-product gases while exhibiting high oxygen absorption performance.

[0026] <Radical Generator> The oxygen-absorbing nanofiber aggregate of the present invention contains a radical generator. A radical generator is a substance that can generate radicals in response to relatively weak external stimuli such as heat or light, and compounds known as radical polymerization initiators, which are generally used in the synthesis of polymers, are preferred. Furthermore, compounds containing transition metals are excluded from the radical generator in the present invention.

[0027] The radical generator in the present invention is not particularly limited as long as it does not contain transition metals and is capable of generating radicals, but a photoradical generator capable of generating radicals by irradiation with energy rays is preferred, and compounds known as photoradical polymerization initiators are preferred. Among these, the photoradical generator is preferably at least one selected from the group consisting of benzophenone-based radical generators, thioxanthone-based radical generators, and acetophenone-based radical generators, and more preferably an acetophenone-based radical generator. Examples of benzophenone-based radical generators include benzophenone, benzyl, and methyl orthobenzoyl benzoate. Examples of thioxanthone-based radical generators include 2-methylthioxanthone and 2-isopropylthioxanthone. The acetophenone-based radical generator is preferably at least one selected from the group consisting of 2,2-dimethoxy-2-phenylacetophenone (BDK), 2,2-diethoxyacetophenone, 2-hydroxy-2-methylpropiophenone, 4-isopropyl-2-hydroxy-2-methylpropiophenone, and 1,1-dichloroacetophenone, and more preferably 2,2-dimethoxy-2-phenylacetophenone (BDK).

[0028] The content of the radical generator in the oxygen-absorbing nanofiber aggregate is preferably 0.01% by mass or more and 1% by mass or less, more preferably 0.02% by mass or more and 0.9% by mass or less, and even more preferably 0.03% by mass or more and 0.8% by mass or less, relative to the total amount of the oxygen-absorbing nanofiber aggregate. From the viewpoint of suppressing chain reactions, it is even more preferably 0.1% by mass or more and 0.5% by mass or less, and even more preferably 0.12% by mass or more and 0.3% by mass or less. By having the radical generator content within the above range, oxygen absorption of the oxygen-absorbing nanofiber aggregate can be promoted, the oxygen absorption performance can be improved, and by-product gases during oxygen absorption can be suppressed.

[0029] <Composition and properties of oxygen-absorbing nanofiber aggregates> The oxygen-absorbing nanofiber aggregate of the present invention has a specific surface area of ​​1.0 m². 2 / g or more 100.0m 2It is less than or equal to / g, preferably 3.0m 2 / g or more 50.0m 2 It is less than or equal to / g, and more preferably 5.0m 2 / g or more 40.0m 2 It is less than or equal to / g, and more preferably 6.0m 2 / g or more 30.0m 2 It is less than or equal to / g, and more preferably 6.5m 2 / g or more 20.0m 2 It is less than or equal to / g, and more preferably 7.0m 2 / g or more 10.0m 2 The specific surface area of ​​the oxygen-absorbing nanofiber aggregate is within the above range, which is why the oxygen-absorbing nanofiber aggregate has high oxygen absorption performance.

[0030] The cross-sectional area of ​​the fibers constituting the oxygen-absorbing nanofiber aggregate of the present invention is preferably 10 -16 I understand 2 The above 10 -11 I understand 2 The following, more preferably 10 -15 I understand 2 The above 10 -11 I understand 2 The following, and more preferably 10 -14 I understand 2 The above 10 -11 I understand 2 The following, and more preferably 10 -13 I understand 2 The above 10 -11 I understand 2 The following, and more preferably 10 -13 I understand 2 The above 10 -12 I understand 2 The following is true: By having the cross-sectional area of ​​the fibers constituting the oxygen-absorbing nanofiber aggregates within the above range, the oxygen-absorbing nanofiber aggregates have high oxygen absorption performance.

[0031] (Other Components) The oxygen-absorbing nanofiber aggregates of the present invention may contain components other than those listed above, to the extent that they do not impede the effects of the present invention. Examples of components other than those listed above include thermoplastic resins other than easily oxidizable thermoplastic resins, and other known additives.

[0032] The oxygen-absorbing nanofiber aggregate may further contain thermoplastic resins other than the above-mentioned easily oxidizable thermoplastic resin (hereinafter also simply referred to as "thermoplastic resin") for purposes such as improving the dispersibility of the blended components.

[0033] The thermoplastic resin is preferably one that has high compatibility with easily oxidizable thermoplastic resins and high oxygen permeability. Specifically, examples include polyolefin resins, ethylene copolymers, flexible polyvinyl chloride, polystyrene, polymethylpentene, silicone resins, and copolymers of polysiloxane and other resins. Preferably, it is one or more selected from the group consisting of polyolefin resins, ethylene copolymers, flexible polyvinyl chloride, polystyrene, and polymethylpentene. More preferably, it is one or more selected from the group consisting of polyolefin resins, ethylene copolymers, polystyrene, and polymethylpentene. Even more preferably, it is one or more selected from the group consisting of polyolefin resins and ethylene copolymers, and even more preferably, it is a polyolefin resin. Examples of polyolefin resins include polyethylene, ethylene-α-olefin copolymer, polypropylene, propylene-ethylene random copolymer, propylene-ethylene block copolymer, and ethylene-cyclic olefin copolymer. Among these, polyethylene is preferred, and linear low-density polyethylene is more preferred. Examples of ethylene-based copolymers include ethylene-(meth)acrylic acid copolymers, ethylene-(meth)acrylic acid methyl copolymers, various ionic crosslinked products of ethylene-(meth)acrylic acid copolymers, and ethylene-vinyl acetate copolymers. These thermoplastic resins other than easily oxidizable thermoplastic resins can be used individually or in combination of two or more.

[0034] The oxygen-absorbing nanofiber aggregate may contain various additives as needed. The additives are not particularly limited, and known additives commonly used in oxygen absorbers (oxygen-absorbing resins) can be used. Examples include defoaming agents such as calcium oxide, lubricants such as zinc stearate and calcium stearate, antioxidants such as phenolic or phosphorus-based agents, colorants such as organic or inorganic dyes or pigments such as titanium dioxide, dispersants such as silane or titanate-based agents, water absorbents such as polyacrylic acid, fillers such as silica or clay, gas adsorbents such as zeolite or activated carbon, desiccants, and antibacterial agents.

[0035] (Deoxygenation Method) The oxygen-absorbing nanofiber aggregate of the present invention can preferably absorb oxygen and deoxygenate the product as follows. It is preferable to use a photoradical polymerization initiator as the radical generator. When a photoradical polymerization initiator is used as the radical generator, the oxygen-absorbing nanofiber aggregate and the product to be stored are placed in a storage container and sealed, and then irradiated with energy rays to generate radicals and start oxygen absorption. If the storage container is made of a material that does not easily transmit light, the oxygen-absorbing nanofiber aggregate may be irradiated with energy rays, and then quickly placed in a storage container with the product to be stored and sealed to start oxygen absorption. The product to be stored is not particularly limited, but examples include various products that are easily altered by the effects of oxygen, such as food, pharmaceuticals, metal products, and electronic products.

[0036] The aforementioned energy rays are not particularly limited, but include ultraviolet rays, electron beams, alpha rays, beta rays, gamma rays, X-rays, etc. Irradiation with these energy rays can initiate an oxidation reaction by breaking carbon-hydrogen bonds and carbon-carbon bonds in the easily oxidizable thermoplastic resin, thereby generating radicals. Oxygen absorption can also be initiated by applying energy such as heat, high frequency, or ultrasound. In particular, the energy rays to be irradiated are preferably one or more selected from ultraviolet rays, electron beams, and gamma rays, and more preferably ultraviolet rays.

[0037] Ultraviolet (UV) light can be generated from an UV irradiation device equipped with, for example, a high-pressure mercury lamp, a low-pressure mercury lamp, a metal halide lamp, or an electrodeless lamp, with low-pressure mercury lamps being more preferable. The wavelength of UV light generated from the UV irradiation device can be appropriately adjusted according to the composition of the oxygen-absorbing nanofiber aggregates and the processing amount, and is not particularly limited, but is for example 100 nm to 400 nm, preferably 200 nm to 380 nm, and more preferably 250 nm to 370 nm. The integrated amount of UV light can be appropriately adjusted according to the composition of the oxygen-absorbing nanofiber aggregates and the processing amount, and is not particularly limited, but is for example 1 mJ / cm². ２ More than 20000mJ / cm ２ Preferably, the following is 100 mJ / cm ２ More than 10000mJ / cm ２ More preferably, 500 mJ / cm ２ More than 5000mJ / cm ２ The following applies:

[0038] [Method for producing oxygen-absorbing nanofiber aggregates] The method for producing the oxygen-absorbing nanofiber aggregates is not particularly limited, but is preferably the following. Therefore, the method for producing oxygen-absorbing nanofiber aggregates of the present invention preferably comprises the following steps 1 and 2. Step 1: A step of dissolving an easily oxidizable thermoplastic resin and a radical generator in a solvent to obtain a solution. Step 2: A step of spinning the solution by electrospinning to obtain oxygen-absorbing nanofiber aggregates.

[0039] <Step 1> Step 1 is the process of dissolving an easily oxidizable thermoplastic resin and a radical generator in a solvent to obtain a solution.

[0040] The solvent used in step 1 may be any solvent that dissolves the easily oxidizable thermoplastic resin and the radical generator, and various solvents can be used depending on the type of easily oxidizable thermoplastic resin and radical generator. Preferably, the solvent is at least one selected from the group consisting of water and organic solvents, and more preferably an organic solvent. The type of organic solvent may also be any solvent that dissolves the easily oxidizable thermoplastic resin and the radical generator, but a solvent with high solubility for the easily oxidizable thermoplastic resin is preferred. Furthermore, since the obtained solution is sprayed from a syringe or the like by electrospinning, a solvent with low viscosity is preferred. Preferably, the organic solvent is a halogen-based solvent, an amide-based solvent, or a hydrocarbon solvent, more preferably a halogen-based solvent and an amide-based solvent, and even more preferably a halogen-based solvent. In step 1, one type of solvent may be used, or two or more types may be used, but it is preferable to use two or more types in order to optimize solubility and viscosity. Preferred combinations of two or more organic solvents include a combination of a halogen-based solvent and an amide-based solvent, and a combination of a halogen-based solvent and a hydrocarbon solvent, with the combination of a halogen-based solvent and an amide-based solvent being preferred.

[0041] The halogenated solvents specifically include, preferably, chlorobenzene, chloroform, hexafluoro-2-propanol, and tetrafluoroethylene, and more preferably at least one selected from the group consisting of chlorobenzene, chloroform, hexafluoro-2-propanol, and tetrafluoroethylene, more preferably at least one selected from the group consisting of chlorobenzene and chloroform, and even more preferably chlorobenzene.

[0042] For amide solvents, dimethylacetamide is preferred. For hydrocarbon solvents, decahydronaphthalene is preferred.

[0043] Therefore, among the above solvents, at least one selected from the group consisting of chlorobenzene and dimethylacetamide is more preferably, and even more preferably a mixed solvent of chlorobenzene and dimethylacetamide. By using the above solvent, the spinning process in the next step can be carried out well, and nanofibers of the desired shape and aggregates thereof can be obtained.

[0044] The total concentration of the easily oxidizable thermoplastic resin and radical generator (resin composition) in the solution obtained by dissolving the easily oxidizable thermoplastic resin and radical generator in a solvent can be adjusted as appropriate, taking into account the viscosity of the solution, but is preferably 5 to 35% by mass, more preferably 10 to 30% by mass, even more preferably 10 to 25% by mass, and even more preferably 15 to 23% by mass. By using the above resin composition concentration, the spinning process in the next step can be carried out smoothly, and nanofibers of the desired shape and aggregates thereof can be obtained.

[0045] <Step 2> Step 2 is a step of obtaining oxygen-absorbing nanofiber aggregates by spinning the solution by electrospinning. Known methods can be used for the electrospinning method. Specifically, a resin solution is placed in a container such as a syringe having a spinning nozzle, a high voltage is applied at the spinning nozzle, and a large potential difference is generated between the spinning nozzle and the target, causing a jet of charged resin solution to be ejected from the spinning nozzle. The solvent in the jet volatilizes and becomes resin nanofibers when it reaches the target, and nanofiber aggregates are obtained by depositing these nanofibers.

[0046] The oxygen-absorbing nanofiber aggregates of the present invention have high oxygen absorption performance and suppress by-product gases, making them suitable for applications where safety and odor are sensitive. Therefore, the target material can be selected according to the application. For example, the inner wall of a packaging container is one such example. To increase the contact area with oxygen and to maximize the performance of the oxygen-absorbing nanofiber aggregates of the present invention, it is preferable to laminate the nanofiber aggregates onto a permeable film, paper, or nonwoven fabric. Next, the preferred spinning conditions for the electrospinning method in step 2 of the manufacturing method of the present invention are shown below. By spinning under the following conditions, nanofibers with excellent oxygen absorption can be obtained.

[0047] The applied voltage varies depending on the distance to the target, but is preferably 5 to 30 kV, more preferably 10 to 25 kV, even more preferably 15 to 25 kV, and even more preferably 16 to 22 kV.

[0048] The injection distance (distance between the spinneret and the target) is preferably 50 to 300 mm, more preferably 100 to 300 mm, even more preferably 100 to 200 mm, and even more preferably 130 to 180 mm.

[0049] For the spinneret, a metal needle (capillary) can be suitably used, for example. The inner diameter of the spinneret is preferably 0.1 to 0.5 mm, more preferably 0.1 to 0.4 mm, even more preferably 0.1 to 0.3 mm, and even more preferably 0.15 to 0.25 mm.

[0050] The discharge rate varies depending on the viscosity of the solution, the properties of the resin, etc., but is preferably 0.1 to 10.0 mL / hour, preferably 0.2 to 8.0 mL / hour, more preferably 0.3 to 5.0 mL / hour, even more preferably 0.4 to 3.0 mL / hour, and even more preferably 0.5 to 2.0 mL / hour.

[0051] According to the above manufacturing method, an oxygen-absorbing nanofiber aggregate can be obtained that has high oxygen absorption performance and can suppress by-product gases during oxygen absorption.

[0052] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and includes all aspects included in the concept and claims of the present invention, and can be modified in various ways within the scope of the present invention.

[0053] The embodiment will be described in detail below using examples and comparative examples, but this embodiment can be modified as appropriate insofar as it achieves the effects and advantages of the present invention.

[0054] [Materials] The materials used in the examples and comparative examples, along with their abbreviations, are shown below. SIS resin: Styrene-isoprene-styrene block copolymer (manufactured by ENEOS Material Trading Co., Ltd.) BDK: 2,2-dimethoxy-2-phenylacetophenone RB resin: Syndiotactic 1,2-polybutadiene (manufactured by ENEOS Material Trading Co., Ltd.)

[0055] [Measurement of Specific Surface Area] The specific surface area of ​​the nanofiber aggregates and films of the examples and comparative examples was measured as follows. For the nanofiber aggregates, the fiber diameter and fiber length were measured using a microscope while they were coated on paper, and the surface area was calculated. SIS resin density: 0.92 g / cm³ 3 The mass of the fibers was calculated, and the specific surface area was calculated from these values. For the film, the diameter of a circular film was measured, and it was assumed that the film surface had no irregularities. The sides of the film (thickness direction) were not considered, and the surface area was calculated. In addition, the mass of the film itself was measured using an electronic balance, and the specific surface area was calculated from these values.

[0056] [Evaluation of Oxygen Absorption Performance] The oxygen absorption performance of the nanofiber aggregates and films of the examples and comparative examples was evaluated as follows. The nanofiber aggregates or films coated on paper were each placed in an NK bag (multilayer transparent gas barrier bag, resin type and thickness (μm) of each layer: OPP / PE / NY / PE / LLDPE = 20 / 20 / 15 / 20 / 30, size 250 mm x 400 mm), and 300 mL of a mixed gas of oxygen and nitrogen (oxygen to nitrogen concentration ratio 5 / 95 (volume)) was added and sealed. Then, UV light (wavelength 254 nm intensity: 16 mW / cm) was used with a metal halide lamp. 2The NK bag was irradiated with the light for 3 minutes (cumulative light intensity: 522 mJ / cm²). ２ The amount of oxygen absorbed was calculated from the change in oxygen concentration inside the bag before and after irradiation. The results are shown in Tables 1 and 2. The higher the value of oxygen absorbed, the higher and superior the oxygen absorption performance. In particular, a high value of oxygen absorbed per gram is preferable because a large amount of oxygen can be absorbed with a small amount of resin.

[0057] [Evaluation of By-product Gas Suppression Effect 1] The by-product gas suppression effect during oxygen absorption was evaluated for the nanofiber aggregates and films obtained by the manufacturing methods of Example 1 and Comparative Example 1 as follows. The nanofiber aggregates or films coated on paper were each placed in an NK bag (multilayer transparent gas barrier bag, resin type and thickness (μm) of each layer: OPP / PE / NY / PE / LLDPE = 20 / 20 / 15 / 20 / 30, size 250 mm × 400 mm), 300 mL of a mixed gas of oxygen and nitrogen (oxygen to nitrogen concentration ratio 5 / 95 (volume)) was added, and the bags were sealed. Then, UV irradiation was performed under the following conditions. After UV irradiation, the bags were left to stand while shielded from light, and after one week, the amount of aldehyde gas and carboxylic acid gas generated was measured using a detector tube. The amount of gas generated per 0.1 g of nanofiber aggregate or film was then calculated. The results are shown in Table 1. In this evaluation, aldehyde gas refers to a gas having an aldehyde structure with a carbonyl group, and carboxylic acid gas refers to a gas having a carboxylic acid structure with a carboxyl group. The smaller the values ​​of aldehyde gas and carboxylic acid gas generation, the better the performance in suppressing by-product gases during oxygen absorption. (UV irradiation conditions) A UV irradiation device manufactured by iGraphics Co., Ltd. was used. The light source was an EYE CUBE LIGHT, and irradiation was performed four times at 1.5 kW for 1 minute each, so that the irradiation time was 4 minutes (integrated light intensity: 696 mJ / cm²). ２ ).

[0058] [Production of Oxygen-Absorbing Nanofiber Aggregates and Oxygen-Absorbing Films] Example 1 (Production of Oxygen-Absorbing Nanofiber Aggregates) 100 g of SIS resin and 0.16 g of BDK were dissolved in a mixed solvent of chlorobenzene and dimethylacetamide (chlorobenzene / dimethylacetamide mass ratio = 76 / 24) so ​​that the total concentration of SIS resin and BDK was 21% by mass to obtain a resin composition solution. Nanofiber aggregates were obtained using the above resin composition solution by electrospinning under the following conditions. The evaluation results are shown in Table 1. For the spinning conditions, a nanofiber electrospinning apparatus (NANON-04, manufactured by MEC Corporation) was used, and the setting parameters were a voltage of 20 kV, a distance of 150 mm, a nozzle of 27 G, and a discharge rate of 1.0 mL / hour, and spinning was performed for 24 minutes, resulting in a fiber diameter of 580 nm (fiber cross-sectional area 2.6 × 10⁻⁶). -13 I understand 2 Approximately 0.1 g of nanofibers of ) are used in paper (basis weight 40 g / m²). 2 The material was applied to Japanese paper ("Neolon MP," manufactured by MOLZA Corporation) to obtain nanofiber aggregates.

[0059] Comparative Example 1 (Production of Oxygen-Absorbing Film) 100 parts by mass of RB resin, 0.13 parts by mass of cobalt octoate (0.022 parts by mass in terms of transition metals), and 0.21 parts by mass of phenylbenzophenone were placed in a kneading and extrusion apparatus (Laboplastmill 2D15W, Toyo Seiki Seisakusho Co., Ltd.) and melt-kneaded under the conditions of an extrusion temperature of 170°C and a screw rotation speed of 60 rpm to obtain a resin composition. The resin composition was molded in a hot press under the conditions of 160°C and 50 kN to obtain a film. The evaluation results are shown in Table 1.

[0060]

[0061] As shown in Table 1, the oxygen-absorbing nanofiber aggregates of the examples have a higher oxygen absorption value compared to the oxygen-absorbing film of the comparative example. Furthermore, the oxygen-absorbing nanofiber aggregates of the examples produce significantly less aldehyde gas and carboxylic acid gas during oxygen absorption compared to the oxygen-absorbing film of the comparative example. From this, it can be seen that the oxygen-absorbing nanofiber aggregates of the examples can absorb a large amount of oxygen, have excellent oxygen absorption performance, and have excellent performance in suppressing by-product gases during oxygen absorption. From the above, it can be seen that the oxygen-absorbing nanofiber aggregates of the present invention suppress by-product gases and have high oxygen absorption performance. Due to these excellent properties, they can be suitably used as film-type oxygen absorbers in various applications. In particular, because they have high oxygen absorption performance and suppress by-product gases, they can be used in applications where safety and odor are sensitive.

[0062] [Comparison with oxygen-absorbing film without transition metal catalyst] Example 2 (Production of oxygen-absorbing nanofiber aggregates) 100 g of SIS resin and 0.80 g of BDK were dissolved in a mixed solvent of chlorobenzene and dimethylacetamide (chlorobenzene / dimethylacetamide mass ratio = 76 / 24) so ​​that the total concentration of SIS resin and BDK was 21% by mass to obtain a resin composition solution. Nanofiber aggregates were obtained using the above resin composition solution by electrospinning under the following conditions. The evaluation results of oxygen absorption performance are shown in Table 2. For the spinning conditions, a nanofiber electrospinning apparatus (NANON-04) was used, and the setting parameters were a voltage of 20 kV, a distance of 150 mm, a nozzle of 27 G, and a discharge rate of 1.0 mL / hour, and spinning was performed for 24 minutes, resulting in a fiber diameter of 580 nm (fiber cross-sectional area 2.6 × 10⁻⁶). -13 I understand 2 Approximately 0.1 g of nanofibers of ) are used in paper (basis weight 40 g / m²). 2 The material was applied to Japanese paper ("Neolon MP," manufactured by MOLZA Corporation) to obtain nanofiber aggregates. The results of the oxygen absorption performance evaluation are shown in Table 2.

[0063] Comparative Example 2 (Production of Oxygen-Absorbing Film) 100 g of SIS resin and 0.80 g of BDK were melt-kneaded using a kneading and extrusion apparatus (Laboplastmill 2D15W, Toyo Seiki Seisakusho Co., Ltd.) under the conditions of an extrusion temperature of 180°C and a screw rotation speed of 60 rpm to obtain a resin composition. The resin composition was molded in a hot press machine under the conditions of 160°C and 50 kN to obtain a film. The evaluation results of the oxygen absorption performance are shown in Table 2.

[0064]

[0065] As shown in Table 2, the oxygen-absorbing nanofiber aggregates of the examples exhibit significantly higher oxygen absorption values ​​compared to the oxygen-absorbing film of the comparative example. Thus, the oxygen-absorbing nanofiber aggregates of the examples can absorb a large amount of oxygen even without containing a transition metal catalyst, demonstrating excellent oxygen absorption performance.

[0066] [Investigation of Transition Metal Catalyst Amount] Example 3 (Production of Oxygen-Absorbing Nanofiber Aggregates Containing Transition Metal Catalyst) A resin composition solution was obtained in the same manner as in Example 1, except that when obtaining the resin composition solution, 0.0106 g of cobalt stearate (transition metal catalyst) (0.0010 g in terms of transition metal) was dissolved in the mixed solvent in addition to 100 g of SIS resin and 0.16 g of BDK. The resin composition solution was then spun and coated onto paper in the same manner as in Example 1 to obtain nanofiber aggregates.

[0067] Comparative Example 3 (Production of oxygen-absorbing nanofiber aggregates containing a transition metal catalyst) A resin composition solution was obtained in the same manner as in Example 1, except that when obtaining the resin composition solution, 0.4248 g of cobalt stearate (transition metal catalyst) (0.0400 g in terms of transition metal) was dissolved in the mixed solvent in addition to 100 g of SIS resin and 0.16 g of BDK. Nanofiber aggregates were obtained by spinning and coating onto paper in the same manner as in Example 1.

[0068] <Evaluation of By-product Gas Suppression Effect 2> The by-product gas suppression effect during oxygen absorption was evaluated for the nanofiber aggregates obtained by the manufacturing methods of Examples 1 and 3 and Comparative Example 3 as follows. The nanofiber aggregates coated on paper were each placed in an NK bag (multilayer transparent gas barrier bag, resin type and thickness (μm) of each layer: OPP / PE / NY / PE / LLDPE = 20 / 20 / 15 / 20 / 30, size 250 mm x 400 mm), 300 mL of a mixed gas of oxygen and nitrogen (oxygen to nitrogen concentration ratio 5 / 95 (volume)) was added, and the bags were sealed. After that, UV irradiation was performed under the following conditions. After UV irradiation, the amount of aldehyde gas and carboxylic acid gas generated was measured using a detector tube (amount generated immediately after). Next, each identical nanofiber aggregate was placed in a newly prepared aluminum foil laminate bag (manufactured by Fujimori Sangyo Co., Ltd., size 250 mm x 400 mm), and 300 mL of a mixed gas of oxygen and nitrogen (oxygen to nitrogen concentration ratio 5 / 95 (volume)) was added and sealed. The bags were left to stand in the dark, and after one week, the amount of aldehyde gas and carboxylic acid gas generated was measured using a detector tube (amount generated after one week). The amount of gas generated per 0.1 g of nanofiber aggregate was then calculated from the sum of the amounts generated immediately after and after one week. The results are shown in Table 3. In this evaluation, aldehyde gas refers to a gas having an aldehyde structure with a carbonyl group, and carboxylic acid gas refers to a gas having a carboxylic acid structure with a carboxyl group. The smaller the values ​​of aldehyde gas and carboxylic acid gas generation, the better the performance in suppressing by-product gases during oxygen absorption. (UV irradiation conditions) A UV irradiation device manufactured by I-Graphics Co., Ltd. was used. The light source used was an EYE CUBE LIGHT, with four 1.5 kW, 1-minute irradiation sessions, resulting in a total irradiation time of 4 minutes (cumulative light intensity: 696 mJ / cm²). ２ In Table 3, ">20" means "more than 20 volumes ppm".

[0069]

[0070] As shown in Table 3, the oxygen-absorbing nanofiber aggregates of the examples exhibit superior performance in suppressing by-product gases during oxygen absorption, as evidenced by the smaller amounts of aldehyde gas and carboxylic acid gas generated during oxygen absorption compared to the oxygen-absorbing nanofiber aggregates of the comparative examples. Thus, the oxygen-absorbing nanofiber aggregates of the present invention, which either do not contain a transition metal catalyst or contain a transition metal catalyst at a rate of 10 ppm by mass or less in terms of transition metal, can suppress by-product gases.

Claims

1. Contains an easily oxidizable thermoplastic resin and a radical generator, does not contain a transition metal catalyst, or contains a transition metal catalyst at a rate of 10 ppm by mass or less in terms of transition metal, and has a specific surface area of ​​1.0 m². 2 / g or more 100.0m 2 An oxygen-absorbing nanofiber aggregate with a concentration of less than / g.

2. The oxygen-absorbing nanofiber aggregate according to claim 1, wherein the easily oxidizable thermoplastic resin is at least one selected from the group consisting of organic polymer compounds having a carbon-carbon double bond moiety, organic polymer compounds having allyl carbon, organic polymer compounds having a structural unit of the following 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. (wherein R １ to R ７ represent -H, -CH ３ , -CH ２ R, -CHR ２ , -CR ３ , -OR, -COOR, -SiR ３ , -O-SiR ３ , -COCl or a halogen atom, each of 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.) 3. The oxygen-absorbing nanofiber aggregate according to claim 1 or 2, wherein the easily oxidizable thermoplastic resin contains at least one selected from the group consisting of polybutadiene (X1), polyisoprene (X2), and resin (Y) having a carbon-carbon double bond and the constituent unit of the general formula (1).

4. The oxygen-absorbing nanofiber aggregate according to any one of claims 1 to 3, wherein the easily oxidizable thermoplastic resin contains at least one selected from the group consisting of styrene-isoprene-styrene block copolymer and styrene-butadiene-styrene block copolymer.

5. The cross-sectional area of ​​the fibers constituting the oxygen-absorbing nanofiber aggregate is 10 -16 I understand 2 The above 10 -11 I understand 2 The oxygen-absorbing nanofiber aggregate according to any one of claims 1 to 4, which is as follows:

6. The oxygen-absorbing nanofiber aggregate according to any one of claims 1 to 5, wherein the radical generating agent is at least one selected from the group consisting of benzophenone-based radical generating agents, thioxanthone-based radical generating agents, and acetophenone-based radical generating agents.

7. The oxygen-absorbing nanofiber aggregate according to any one of claims 1 to 6, wherein the content of the radical generating agent is 0.01% by mass or more and 1% by mass or less.

8. A method for producing an oxygen-absorbing nanofiber aggregate according to any one of claims 1 to 7, comprising the following steps 1 and 2. Step 1: Dissolve an easily oxidizable thermoplastic resin and a radical generator in a solvent to obtain a solution. Step 2: Spin the solution by electrospinning to obtain an oxygen-absorbing nanofiber aggregate.

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