JP7127257B2 - Oxygen-absorbing resin composition, method for producing the same, and container - Google Patents

Description

TECHNICAL FIELD The present invention relates to an oxygen-absorbing resin composition, a method for producing the same, and a container.

BACKGROUND ART In recent years, various plastic containers have been used as packaging containers because of their advantages such as light weight, transparency, and easy moldability. Since plastic containers are inferior in oxygen barrier property to metal containers and glass containers, deterioration and deterioration of flavor of the contents filled in the container pose problems.

In order to prevent these problems, for example, the container wall of a plastic container has a multi-layered structure and is provided with a layer containing a resin having excellent oxygen barrier properties, such as an ethylene-vinyl alcohol copolymer. In addition, an oxygen absorbing layer is provided to remove oxygen remaining inside the container and oxygen entering from the outside of the container. Examples of materials for the oxygen absorbing layer include polyolefin resin (A) obtained by polymerizing an olefin having 2 to 8 carbon atoms, and a resin other than resin (A), which does not oxidize resin (A). Contains a trigger resin (B) and a transition metal catalyst (C), the resin (B) is dispersed in the matrix of the resin (A), and the matrix resin (A) is oxidized when it comes into contact with oxygen. An oxygen-absorbing resin composition is disclosed which is characterized in that the reaction progresses and oxygen is absorbed.

WO2004/018556

When an oxygen-absorbing layer is formed using the oxygen-absorbing resin composition described in Patent Document 1, the oxygen-absorbing layer exhibits high oxygen-absorbing capacity, but from the viewpoint of sufficiently removing oxygen inside the container, the It is desirable to have an oxygen absorption capacity.

An object of the present invention is to provide an oxygen-absorbing resin composition that can absorb a large amount of oxygen while suppressing an increase in material cost, a method for producing the same, and a container.

The oxygen-absorbing resin composition according to the present invention comprises a resin (A) which is an olefin polymer having 2 to 8 carbon atoms and a trigger for oxidation of the resin (A) other than the resin (A). An oxygen-absorbing resin composition containing a resin (B) and a transition metal catalyst (C),
It is characterized in that the content of the resin (B) in the oxygen-absorbing resin composition is less than 1.0% by mass.

The method for producing an oxygen-absorbing resin composition according to the present invention comprises a resin (A1) that is an olefin polymer having 2 to 8 carbon atoms, and a resin (A1) other than the resin (A1) that is oxidized a step of melt-kneading the trigger resin (B) and the transition metal catalyst (C) to prepare an oxygen-absorbing resin composition precursor;
a step of mixing the oxygen-absorbing resin composition precursor with a resin (A2) that is an olefin polymer having 2 to 8 carbon atoms;
A method for producing an oxygen-absorbing resin composition having
It is characterized in that the content of the resin (B) in the oxygen-absorbing resin composition is less than 1.0% by mass.

The oxygen-absorbing resin composition according to the present invention is produced by the method for producing an oxygen-absorbing resin composition according to the present invention.

A container according to the present invention is characterized by having a layer comprising the oxygen-absorbing resin composition according to the present invention.

Advantageous Effects of Invention According to the present invention, it is possible to provide an oxygen-absorbing resin composition having a large oxygen absorption amount while suppressing an increase in material cost, a method for producing the same, and a container.

[Oxygen-absorbing resin composition]
The oxygen-absorbing resin composition according to the present invention comprises a resin (A) which is an olefin polymer having 2 to 8 carbon atoms and a trigger for oxidation of the resin (A) other than the resin (A). It contains a resin (B) and a transition metal catalyst (C). Here, the content of the resin (B) in the oxygen-absorbing resin composition is less than 1.0% by mass.

In the oxygen-absorbing resin composition according to the present invention, the resin (B) serves as a trigger for oxidation of the resin (A), and the resin (A) itself functions as an oxygen absorber. Here, in the present invention, since the content of the resin (B) in the oxygen-absorbing resin composition is less than 1.0% by mass, the material cost can be suppressed, and the oxygen-absorbing resin composition can be A larger amount of the resin (A) functioning as an oxygen absorber can be contained. Therefore, the oxygen-absorbing resin composition according to the present invention can have a large oxygen absorption capacity. Moreover, the oxygen-absorbing resin composition can further contain an adsorbent (D). In this case, low-molecular-weight odorous components such as aldehydes, ketones and furans generated by oxidative decomposition of the resin can be sufficiently captured. The details of the present invention will be described below.

(Resin (A))
Resin (A) is an olefin polymer having 2 to 8 carbon atoms. Examples of the resin (A) include low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), linear very low density polyethylene (LVLDPE), isotactic tic or syndiotactic polypropylene, ethylene-propylene copolymer, polybutene-1, ethylene-butene-1 copolymer, propylene-butene-1 copolymer, ethylene-propylene-butene-1 copolymer, ethylene-acetic acid Examples include vinyl copolymers, ionically crosslinked olefin copolymers (ionomers), and mixtures thereof. Acid-modified olefin resins obtained by using these resins as base polymers and graft-modified with unsaturated carboxylic acids or derivatives thereof can also be used. The resin (A) is preferably a polyolefin resin having an ethylene structure. Specifically, low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), linear low density polyethylene ( LLDPE), linear very low density polyethylene (LVLDPE), ethylene-propylene copolymers, ethylene-butene-1 copolymers, etc. are preferred. The resin (A) preferably contains low density polyethylene (LDPE) or linear low density polyethylene (LLDPE) from the viewpoint of exhibiting a higher oxygen absorption capacity. These resins may be used alone or in combination of two or more.

The content of the resin (A) in the oxygen-absorbing resin composition is preferably 90% by mass or more, more preferably 92% by mass or more, from the viewpoint of exhibiting a larger oxygen absorption amount. More preferably, it is 94% by mass or more. Although the upper limit of the content range is not particularly limited, it can be, for example, 99.5% by mass or less.

(Resin (B))
The resin (B) is a resin other than the resin (A) and serves as a trigger for oxidation of the resin (A). The working mechanism of the presumed trigger function of the resin (B) will be described later. As the resin (B), for example, a resin having an aliphatic carbon-carbon double bond in the main chain or side chain, a resin having an alicyclic carbon-carbon double bond in the main chain or side chain, a main chain Examples include resins containing tertiary carbon atoms in and resins having active methylene groups in the main chain. These resins may be used alone or in combination of two or more.

As the resin having an aliphatic carbon-carbon double bond in the main chain or side chain, or the resin having an alicyclic carbon-carbon double bond in the main chain or side chain, a linear or cyclic conjugated or Included are resins comprising units derived from non-conjugated polyenes. Examples of monomers for such resins include conjugated dienes such as butadiene and isoprene; Chain non-conjugated dienes such as 1,4-hexadiene, 4,5-dimethyl-1,4-hexadiene, 7-methyl-1,6-octadiene; methyltetrahydroindene, 5-ethylidene-2-norbornene, 5-methylene -cyclic non-conjugated dienes such as 2-norbornene, 5-isopropylidene-2-norbornene, 5-vinylidene-2-norbornene, 6-chloromethyl-5-isopropenyl-2-norbornene, dicyclopentadiene; Examples thereof include trienes such as diisopropylidene-5-norbornene, 2-ethylidene-3-isopropylidene-5-norbornene, 2-propenyl-2,2-norbornadiene, and the like. Specific polymers include poly-1,2-butadiene, poly-1,4-butadiene, poly-1,2-isoprene, poly-1,4-isoprene, styrene-butadiene copolymer, styrene-isoprene Examples thereof include copolymers, ethylene-propylene-diene copolymers, and polyesters containing methyltetrahydrophthalic anhydride as an acid component.

The resin containing a tertiary carbon atom in the main chain is a polymer or copolymer containing a unit derived from an α-olefin having 3 to 20 carbon atoms, or a monomer weight having a benzene ring in a side chain. Coalesces or copolymers may be mentioned. Specific examples of the α-olefin include propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-nonadecene, 1-eicosene, 9-methyl-1-decene, 11-methyl-1-dodecene, 12- and ethyl-1-tetradecene. Specific polymers include polypropylene, poly-1-butene, poly-1-hexene, poly-1-octene, ethylene-propylene copolymer, ethylene-butene-1 copolymer, ethylene-propylene-1- butene copolymers, and the like. Examples of the monomer having a benzene ring in the side chain include alkenylbenzenes such as styrene, 3-phenylpropene and 2-phenyl-2-butene. Specific polymers include polystyrene and styrene copolymers.

Examples of resins having an active methylene group in the main chain include resins having an electron-withdrawing group, particularly a carbonyl group and a methylene group adjacent thereto, in the main chain. Specific examples include copolymers of carbon monoxide and olefins, particularly carbon monoxide-ethylene copolymers.

In particular, polystyrene or a styrene copolymer is preferable as the resin (B) from the viewpoint of more easily functioning as a trigger for oxidation of the resin (A). The content of the styrene moiety in the styrene copolymer is preferably 10% by mass or more, more preferably 15 to 50% by mass, from the viewpoint of radical generation efficiency. Moreover, it is preferable that the styrene copolymer is a block copolymer from the viewpoint of excellent compatibility and dispersibility with respect to the resin (A). Moreover, the styrene copolymer is preferably a block copolymer having a polystyrene block at the molecular terminal portion from the viewpoint of the mechanical properties of the oxygen-absorbing resin composition. Moreover, from the viewpoint of the trigger effect on the resin (A), it is preferably a block copolymer containing a butadiene unit. That is, the resin (B) is preferably a styrene copolymer such as a styrene-butadiene copolymer. preferable. Moreover, the styrene copolymer may be hydrogenated.

The resin (B) is a resin having an aliphatic carbon-carbon double bond in the main chain or side chain, a resin containing a tertiary carbon atom in the main chain, or a resin having an active methylene group in the main chain. In some cases, the amount of carbon-carbon double bonds other than benzene rings in the resin (B) is 0.018 eq/g from the viewpoint of the thermal stability during molding and the function as a trigger for oxidation of the resin (A). The following is preferable, and 0.0001 to 0.015 eq/g is more preferable. Furthermore, from the viewpoint of promoting oxidation of the resin (A), the amount of carbon-carbon double bonds other than benzene rings in the oxygen-absorbing resin composition according to the present invention is preferably 0.001 eq/g or less. 00001 to 0.0007 eq/g is more preferred.

The molecular weight of the resin (B) is not particularly limited, but from the viewpoint of dispersibility in the resin (A), the number average molecular weight of the resin (B) is preferably 1,000 to 500,000, preferably 10,000 to 250,000. is more preferred.

In the present invention, the content of the resin (B) in the oxygen-absorbing resin composition is less than 1.0% by mass. When the content is less than 1.0% by mass, an oxygen-absorbing resin composition having a large oxygen absorption capacity can be obtained. The content of the resin (B) is preferably 0.1 to 0.9% by mass, more preferably 0.2 to 0.8% by mass, and 0.3 to 0.7% by mass. It is even more preferable to have

In addition, in the oxygen-absorbing resin composition according to the present invention, it is preferable that the resin (B) exists in a dispersed state in the matrix of the resin (A). The resin (B) is preferably dispersed in the form of particles having an average particle size of 10 µm or less, and more preferably dispersed in the form of particles having an average particle size of 5 µm or less. By uniformly dispersing the resin (B) in the matrix of the resin (A), the trigger action of the resin (B) is further improved, and the resin (A) can function more effectively as an oxygen absorber. The presence of the resin (B) in a dispersed state in the matrix of the resin (A) can be confirmed using an electron microscope. For example, it can be confirmed by observing a cross section of a container having a layer of the oxygen-absorbing resin composition with a scanning electron microscope (trade name: JSM-6300F, manufactured by JEOL Ltd.).

(Transition metal catalyst (C))
Examples of transition metals contained in the transition metal catalyst (C) include periodic table Group VIII metals such as iron, cobalt and nickel; Group I metals such as copper and silver; Group IV metals such as tin, titanium and zirconium; , V group metals such as vanadium, VI group metals such as chromium, and VII group metals such as manganese. Among these, metals of Group VIII of the periodic table such as iron, cobalt and nickel are preferable, and cobalt is more preferable because of its high oxygen absorption rate.

The transition metal catalyst (C) can be a low valence inorganic acid salt, an organic acid salt or a complex of the transition metal. Examples of inorganic acid salts include halides such as chlorides, oxoacid salts of sulfur such as sulfates, oxoacid salts of nitrogen such as nitrates, oxoacid salts of phosphorus such as phosphates, and silicates.

Organic acid salts include carboxylates, sulfonates, phosphonates, and the like. Carboxylate is preferable among these. Specific examples of carboxylates include acetic acid, propionic acid, isopropionic acid, butanoic acid, isobutanoic acid, pentanoic acid, isopentanoic acid, hexanoic acid, heptanoic acid, isoheptanoic acid, octanoic acid, 2-ethylhexanoic acid, and nonanoic acid. , 3,5,5-trimethylhexanoic acid, decanoic acid, neodecanoic acid, undecanoic acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, arachidic acid, Lindelic acid, tuzunic acid, petroselinic acid, oleic acid , linoleic acid, linolenic acid, arachidonic acid, formic acid, oxalic acid, sulfamic acid, naphthenic acid and the like.

Complexes of transition metals include complexes with β-diketones or β-keto acid esters. β-diketones or β-keto acid esters include, for example, acetylacetone, ethyl acetoacetate, 1,3-cyclohexadione, methylenebis-1,3-cyclohexadione, 2-benzyl-1,3-cyclohexadione, Acetyltetralone, palmitoyltetralone, stearoyltetralone, benzoyltetralone, 2-acetylcyclohexanone, 2-benzoylcyclohexanone, 2-acetyl-1,3-cyclohexanedione, benzoyl-p-chlorobenzoylmethane, bis(4-methyl benzoyl)methane, bis(2-hydroxybenzoyl)methane, benzoylacetone, tribenzoylmethane, diacetylbenzoylmethane, stearoylbenzoylmethane, palmitoylbenzoylmethane, lauroylbenzoylmethane, dibenzoylmethane, bis(4-chlorobenzoyl)methane, bis (methylene-3,4-dioxybenzoyl)methane, benzoylacetylphenylmethane, stearoyl(4-methoxybenzoyl)methane, butanoylacetone, distearoylmethane, acetylacetone, stearoylacetone, bis(cyclohexanoyl)-methane, di and pivaloylmethane. The transition metal catalyst (C) may be used alone or in combination of two or more.

The content of the transition metal catalyst (C) in the oxygen-absorbing resin composition can reduce the cost, suppress the deterioration of moldability due to deterioration of flow characteristics, and low molecular weight decomposition products that cause offensive odors. From the viewpoint of suppressing by-products, the metal conversion amount based on the oxygen-absorbing resin composition is preferably 500 mass ppm or less, more preferably 300 mass ppm or less, and further preferably 100 mass ppm or less. preferable. Although the lower limit of the content range is not particularly limited, it can be, for example, 1 ppm by mass or more.

(Adsorbent (D))
The oxygen-absorbing resin composition according to the present invention preferably further contains an adsorbent (D). As the adsorbent (D), an oxidation by-product scavenger that captures oxidation by-products such as aldehydes, ketones, and furans generated by oxidative decomposition of the resin, and corrosive gases from contents other than the oxidation by-products. and corrosive gas/volatile sulfur compound scavengers that capture volatile sulfur compounds by reaction.

Oxidation by-product scavengers include, for example, natural zeolite, synthetic zeolite, silica gel, activated carbon, impregnated activated carbon, activated clay, activated aluminum oxide, clay, diatomaceous earth, kaolin, talc, bentonite, sepiolite, atavulgite, magnesium oxide, iron oxide, Examples include aluminum hydroxide, magnesium hydroxide, iron hydroxide, magnesium silicate, aluminum silicate, synthetic hydrotalcite, amine-supported porous silica, and the like. When zeolite is used as the oxidation by-product scavenger, the zeolite preferably has an average particle size of 0.5 to 10 μm.

Examples of corrosive gas/volatile sulfur compound scavengers include metal compounds such as Zn, Sn, and Mn, such as inorganic acid salts or organic acid salts of these metals. Examples of inorganic acid salts include halides such as oxides and chlorides, sulfur oxoacids such as sulfates, nitrogen oxoacids such as nitrates, phosphorus oxoacids such as phosphates, and silicates. mentioned. Organic acid salts include carboxylates, sulfonates, phosphonates, and the like. Further, as zinc compounds, specifically, zinc silicate, zinc oxide, zinc sulfate, zinc chloride, zinc phosphate, zinc nitrate, zinc carbonate, zinc acetate, zinc oxalate, zinc citrate, zinc fumarate, and zinc formate. From the viewpoint of improving the transparency of the container containing the oxygen-absorbing resin composition according to the present invention, organic acid salts are preferable, and higher fatty acid metal salts such as stearic acid metal salts are more preferable.

When the oxygen-absorbing resin composition contains the adsorbent, the content of the adsorbent in the oxygen-absorbing resin composition is preferably 0.1 to 10% by mass, more preferably 0.5 to 9% by mass. More preferably, 1 to 8% by mass is more preferable, and 3 to 7% by mass is particularly preferable. When the content is 0.1% by mass or more, oxidation by-products and the like can be sufficiently captured. Moreover, when the content is 10% by mass or less, a large oxygen absorption amount can be obtained.

(Other additives)
The oxygen-absorbing resin composition according to the present invention can optionally contain other additives such as radical initiators and photosensitizers. Examples of radical initiators and photosensitizers include benzoin and its alkyl ethers such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether; acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2 -diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 1-hydroxycyclohexylphenylketone, 2-hydroxycyclohexylphenylketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propane- Acetophenones such as 1-one; Anthraquinones such as 2-methylanthraquinone and 2-amylanthraquinone; Thioxanthones such as 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone and 2,4-diisopropylthioxanthone ketals such as acetophenone dimethyl ketal and benzyl dimethyl ketal; benzophenones such as benzophenone; and photoinitiators such as xanthones. These photoinitiators can be used in combination with one or more of known photopolymerization accelerators such as benzoic acid-based or tertiary amine-based photoinitiators.

Other additives other than radical initiators and photosensitizers include fillers, colorants, heat stabilizers, weather stabilizers, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, and antistatic agents. , lubricants such as metal soaps and waxes, modifying resins, rubbers, and the like. For example, by blending a lubricant, the biting of the resin into the screw during kneading is improved. Lubricants include metal soaps such as magnesium stearate and calcium stearate, hydrocarbon lubricants such as fluid, natural or synthetic paraffin, microwax, polyethylene wax, and chlorinated polyethylene wax, and fatty acid lubricants such as stearic acid and lauric acid. Lubricants, stearic acid amide, palmitic acid amide, oleic acid amide, esylic acid amide, methylenebisstearamide, ethylenebisstearamide and other fatty acid monoamide or bisamide type lubricants, butyl stearate, hydrogenated castor oil, ethylene glycol and ester lubricants such as monostearate, and mixtures thereof.

(Action mechanism of trigger function of resin (B))
Although not all of the mechanism of action of the trigger function of the resin (B) that triggers the oxidation of the resin (A) in the oxygen-absorbing resin composition according to the present invention has been elucidated, one of them is The following mechanism is inferred from the study of the present inventors. Note that the action mechanism of the trigger function is not limited to this.

In the oxygen-absorbing resin composition according to the present invention, hydrogen is first extracted from the resin (B) by the transition metal catalyst (C) to generate radicals. Subsequently, hydrogen is abstracted from the resin (A) by the attack by the radicals and the transition metal catalyst (C), and radicals are also generated in the resin (A). It is believed that in the presence of radicals thus generated, initial oxidation of resin (A) occurs when oxygen comes into contact with resin (A). It is believed that the oxidation reaction of the resin (A) thereafter proceeds in a chain reaction according to the theory of autoxidation due to the action of the transition metal catalyst (C), and the resin (A) itself functions as an oxygen absorber.

As described above, in the presumed mechanism of action, it is essential that the transition metal catalyst (C) first generates radicals of the resin (B). Therefore, the resin (B) preferably has a carbon-hydrogen bond that facilitates hydrogen abstraction from a methylene chain. With such a resin (B), radicals can be efficiently supplied, and an excellent trigger function can be exhibited. An example of an index of the likelihood of hydrogen abstraction is C—H bond dissociation energy. The C—H bond dissociation energy is the energy required to cleave a specific C—H bond within a molecule (radical). When a molecule (radical) is represented by RH, the bond dissociation energy of the C--H bond is given as the enthalpy change of the following reaction, and its value can be obtained by molecular orbital calculation or the like. Typical values are shown in Table 1 (Kagaku Binran Basic Edition, Second Revised Edition, The Chemical Society of Japan, Maruzen Co., Ltd., pp.976-978).

RH(g) → R(g)+H(g)

[Method for producing oxygen-absorbing resin composition]
The method for producing an oxygen-absorbing resin composition according to the present invention comprises a resin (A1) that is an olefin polymer having 2 to 8 carbon atoms, and a resin (A1) other than the resin (A1) that is oxidized A step of melt-kneading the trigger resin (B) and the transition metal catalyst (C) to prepare an oxygen-absorbing resin composition precursor (hereinafter also referred to as a precursor preparation step), and the oxygen-absorbing resin. A step of mixing a composition precursor with a resin (A2) that is an olefin polymer having 2 to 8 carbon atoms (hereinafter also referred to as a resin composition preparation step). Here, the content of the resin (B) in the oxygen-absorbing resin composition is less than 1.0% by mass.

In the method according to the present invention, first, the resin (A1), the resin (B), and the transition metal catalyst (C) are melt-kneaded to prepare an oxygen-absorbing resin composition precursor. At this time, it is considered that part of the resin (A1) absorbs oxygen due to the action mechanism of the aforementioned trigger function of the resin (B) due to the melt-kneading. After that, the oxygen-absorbing resin composition precursor and the resin (A2) are mixed. ) and the resin (A2) are more likely to absorb oxygen. That is, by causing oxygen absorption to occur in stages, a small amount of the resin (A1) that has already absorbed oxygen in the oxygen-absorbing resin composition promotes radical generation and oxidation reaction, so that the oxygen-absorbing resin composition Even if the content of the resin (B) in the product is less than 1.0% by mass, and even if the content of the transition metal catalyst (C) in the final oxygen-absorbing resin composition is small, It is presumed that the resin (A1) and the resin (A2) in the oxygen-absorbing resin composition can sufficiently function as oxygen absorbers. Therefore, since the content of the resin (B) in the oxygen-absorbing resin composition can be less than 1.0% by mass, the oxygen-absorbing resin composition contains the resin (A) functioning as an oxygen absorber. It can be contained in a larger amount, and the oxygen absorption amount of the oxygen-absorbing resin composition can be improved at low cost. In addition, the oxygen-absorbing resin composition may further contain an adsorbent (D), in which case it is possible to sufficiently capture low-molecular-weight odorous components such as aldehydes, ketones, and furans produced by oxidative decomposition of the resin. . The resin (A1) and the resin (A2) correspond to the resin (A) in the oxygen-absorbing resin composition according to the invention. Details of each step will be described below.

(Precursor preparation step)
In this step, a resin (A1) that is an olefin polymer having 2 to 8 carbon atoms, a resin (B) other than the resin (A1) that serves as a trigger for oxidation of the resin (A1), and a transition metal The catalyst (C) is melt-kneaded to prepare an oxygen-absorbing resin composition precursor.

The resin (A) can be used as the resin (A1). However, the resin (A1) preferably contains low-density polyethylene (LDPE) or linear low-density polyethylene (LLDPE) from the viewpoint that a part of it easily absorbs oxygen when heated. The resin (A1) preferably contains 80% by mass or more of low-density polyethylene (LDPE) or linear low-density polyethylene (LLDPE), more preferably 90% by mass or more, and even more preferably 95% by mass or more. , low density polyethylene (LDPE) or linear low density polyethylene (LLDPE). As the resin (B) and the transition metal catalyst (C), the above resin (B) and transition metal catalyst (C) can be used, respectively. The contents of the resin (A1), the resin (B) and the transition metal catalyst (C) in the oxygen-absorbing resin composition precursor are the resin (A) and the resin The contents of (B) and the transition metal catalyst (C) can be appropriately selected so as to fall within the ranges described above.

As a method for mixing the resin (A1), the resin (B) and the transition metal catalyst (C), each component may be mixed separately, or two of these three components may be mixed in advance to obtain The resulting mixture may be mixed with the remaining ingredients. For example, a method of premixing the resin (A1) and the resin (B) and mixing the resulting mixture with the transition metal catalyst (C), a method of premixing the resin (A1) and the transition metal catalyst (C), and a method of premixing the resin (B) and the transition metal catalyst (C) and then mixing the resulting mixture with the resin (A1).

The method of mixing the transition metal catalyst (C) with the resin (A1) and/or the resin (B) includes a method of dry mixing the transition metal catalyst (C) with the resin, and a method of mixing the transition metal catalyst (C) with an organic solvent. A method of dissolving, mixing this solution with a powder or granular resin, and drying this mixture under an inert atmosphere if necessary. Examples of organic solvents for dissolving the transition metal catalyst (C) include alcohol solvents such as methanol, ethanol and butanol; ether solvents such as dimethyl ether, diethyl ether, methyl ethyl ether, tetrahydrofuran and dioxane; and ketone solvents such as methyl ethyl ketone and cyclohexanone. Solvents include hydrocarbon solvents such as n-hexane and cyclohexane. The concentration of the transition metal catalyst (C) in the solution is preferably 5-90 mass %.

Melt-kneading of the resin (A1), the resin (B) and the transition metal catalyst (C) can be performed using a twin-screw extruder or the like. A part of the resin (A1) can absorb oxygen by performing the melt-kneading. The heating temperature during melt-kneading depends on the type of the resin (A1), but from the viewpoint that a part of the resin (A1) can easily absorb oxygen, it is preferably 50 to 400 ° C. It is more preferably 100 to 300°C, even more preferably 150 to 250°C. The obtained oxygen-absorbing resin composition precursor may be formed into pellets having a cylindrical shape or the like.

(Resin composition preparation step)
In this step, the oxygen-absorbing resin composition precursor obtained in the precursor preparation step is mixed with resin (A2), which is an olefin polymer having 2 to 8 carbon atoms. Thereby, the oxygen-absorbing resin composition according to the present invention is obtained. The resin (A) can be used as the resin (A2).

The amounts of the oxygen-absorbing resin composition precursor and the resin (A2) to be added are determined according to the amount of the resin (A), the resin (B), and the transition metal catalyst (C) in the finally obtained oxygen-absorbing resin composition. It can be appropriately selected so that the content is within the range described above. The amount of the oxygen-absorbing resin composition precursor added to 100% by mass of the obtained oxygen-absorbing resin composition can be, for example, 1 to 20% by mass, preferably 5 to 15% by mass. The amount of the resin (A2) added to 100% by mass of the resulting oxygen-absorbing resin composition can be, for example, 20 to 50% by mass, preferably 30 to 40% by mass.

In addition to the oxygen-absorbing resin composition precursor and the resin (A2), an adsorbent (D) is preferably mixed in this step. The type and content of the adsorbent (D) described above can be applied.

Further, in this step, in addition to the oxygen-absorbing resin composition precursor and the resin (A2), it is preferable to further mix a scrap resin containing an olefin polymer having 2 to 8 carbon atoms. Here, the "scrap resin" is the resin discharged at the start of molding and the resin obtained by pulverizing parts other than the container, such as burrs. can be lowered. The scrap resin contains an olefin polymer having 2 to 8 carbon atoms corresponding to the resin (A), and is, for example, a scrap resin generated in the production of a container having a layer made of the oxygen-absorbing resin composition according to the present invention. be able to. The amount of the scrap resin added to 100% by mass of the obtained oxygen-absorbing resin composition can be, for example, 30 to 70% by mass, preferably 40 to 60% by mass. The content of the olefin polymer having 2 to 8 carbon atoms in the scrap resin is not particularly limited, but can be, for example, 90% by mass or more.

In the oxygen-absorbing resin composition produced by the method according to the present invention, the content of the resin (B) can be less than 1.0% by mass while suppressing the material cost as described above. It can contain a larger amount of the resin (A) functioning as the oxygen absorption amount.

[container]
A container according to the present invention has a layer (hereinafter also referred to as a main layer) made of the oxygen-absorbing resin composition according to the present invention. Since the container according to the present invention has the main layer according to the present invention, it has a large oxygen absorption capacity. The container according to the present invention is not particularly limited as long as it is a sealable container having the main layer according to the present invention. It may be a container consisting of two or more layers having a layer of Layers other than the main layer include an outer layer, an inner layer, an adhesive layer, a gas barrier layer, and the like. For example, the container may have a three-layer structure of outer layer/main layer/inner layer in order from the outside. Further, the container may have a six-layer structure of outer layer/adhesive layer/gas barrier layer/adhesive layer/main layer/inner layer in order from the outside. Types of containers include direct blow bottles, biaxially stretched blow bottles, cups, pouches, and the like.

(main layer)
The main layer is a layer made of the oxygen-absorbing resin composition according to the present invention, and functions as an oxygen-absorbing layer. When the oxygen-absorbing resin composition contains the adsorbent (D), the main layer also functions as an odor trapping layer. Moreover, when the oxygen-absorbing resin composition contains a scrap resin, the main layer also functions as a scrap layer. That is, the main layer according to the present invention can function not only as an oxygen absorbing layer, but also as an odor trapping layer and a scrap layer which have been separately provided in the conventional art, so that the layer structure can be simplified. Therefore, the manufacturing equipment can be simplified, and the space required for the manufacturing equipment can be reduced. In addition, the resin (A) contained in the scrap layer, which conventionally does not function as an oxygen absorber, can also function as an oxygen absorber. can be reduced.

The ratio of the thickness of the main layer to the thickness of the wall of the container is preferably 50% or more, more preferably 55 to 90%, more preferably 60 to 60%, from the viewpoint of having a larger oxygen absorption capacity of the container. More preferably 80%. When the container has a layer other than the main layer, the position of the main layer is not particularly limited, but the main layer may be placed in contact with the inner layer to more efficiently absorb oxygen inside the container. It is preferable because it can

(outer layer, inner layer)
The outer layer and the inner layer are layers respectively located on the surface in contact with the outside air and the surface in contact with the contents of the container. Olefin resins and polyester resins are preferably used as materials for the outer layer and the inner layer.

Examples of olefinic resins include polyethylenes such as low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), and linear very low density polyethylene (LVLDPE). , polypropylene, ethylene-propylene copolymer, polybutene-1, ethylene-butene-1 copolymer, propylene-butene-1 copolymer, ethylene-propylene-butene-1 copolymer, ethylene-vinyl acetate copolymer Coalescing, ionically crosslinked olefin copolymers (ionomers), and the like can be mentioned. Amorphous to low-crystalline copolymers (COC) of acyclic olefins and cyclic olefins can also be used.

Examples of polyester resins include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), amorphous polyester resins in which a small amount of copolyester units are introduced into ethylene terephthalate units, and the like. be able to. These materials can be used singly or in combination of two or more.

In addition, the outer layer and the inner layer may contain lubricants, ultraviolet absorbers, pigments, dyes, various fillers, etc., in amounts that do not impair the basic properties of the container, depending on the application.

(adhesive layer)
The adhesive layer is a layer capable of bonding a layer in contact with one surface and a layer in contact with the other surface. Acid-modified polyethylene, for example, can be used as the material of the adhesive layer. Examples of acid-modified polyethylene include those obtained by graft-modifying polyethylene with carboxylic acids such as maleic acid, itaconic acid and fumaric acid, and their anhydrides, amides and esters. Among these, polyethylene graft-modified with maleic acid or maleic anhydride is preferable as the acid-modified polyethylene. Modified polyethylene is not particularly limited, but examples thereof include low density polyethylene (LDPE) and linear low density polyethylene (LLDPE).

(Gas barrier layer)
The gas barrier layer is a layer that can inhibit permeation of oxygen, and by providing the gas barrier layer, it is possible to effectively suppress oxidative deterioration of the contents due to permeation of oxygen from the outside. The gas barrier layer has, for example, an oxygen permeability coefficient (PO2) of preferably 5.5×10 ⁻¹² cc·cm/cm ² sec·cmHg or less, more preferably 4.5×10 ⁻¹² cc·cm/cm ² sec. • It can be a layer of cmHg or less.

Examples of materials for the gas barrier layer include ethylene-vinyl alcohol copolymers (ethylene-vinyl acetate copolymer saponified products), aromatic polyamides such as poly-meta-xylylene adipamide (MXD6), and the like. Among these, ethylene-vinyl alcohol copolymers are preferred from the viewpoint of having high oxygen barrier properties.

The ethylene content of the ethylene-vinyl alcohol copolymer is preferably 20 to 60 mol%, more preferably 25 to 50 mol%. As the ethylene-vinyl alcohol copolymer, for example, an ethylene-vinyl acetate copolymer having the above ethylene content is saponified to a degree of saponification of preferably 96 mol% or more, more preferably 99 mol% or more. The obtained copolymer saponified product can be used.

The gas barrier layer may contain materials other than the above materials within a range that does not significantly impair the oxygen barrier properties. Examples of the other materials include resins that impart adhesiveness to other layers, such as polyolefins and ionomers. The gas barrier layer can contain, for example, 30% by mass or less of the other material.

Although the ratio of the thickness of the gas barrier layer to the thickness of the container wall is not particularly limited, it can be, for example, 0.5 to 10%, preferably 1 to 5%. Regarding the arrangement position of the gas barrier layer, if it is provided outside the main layer, it is possible to more effectively block oxygen permeation from the outside, and the main layer efficiently captures oxygen from the inside of the container. It is preferable because it can

(Container manufacturing method)
The container according to the present invention can be manufactured, for example, by co-extrusion of the materials of each layer to form a tubular parison and direct blow molding using a two-part mold to form a bottle shape. Furthermore, it is also possible to produce a cylindrical preform with a bottom by co-injection molding the materials of each layer, and then biaxially stretch blow mold this preform into a bottle shape. Further, the container according to the present invention can be manufactured by, for example, forming a flat plate-shaped preform having a predetermined layer structure by extrusion molding, injection molding, or the like, and then plug-assist molding the preform into a cup shape. can also

(Use of container)
Since the container according to the present invention has a large amount of oxygen absorption, contents that tend to deteriorate in the presence of oxygen, such as beverages such as beer, wine, fruit juice, and carbonated soft drinks, and foods such as fruits, nuts, vegetables, and meat products. , baby food, coffee, jam, mayonnaise, ketchup, edible oil, dressing, sauces, foods boiled in soy, dairy products, etc., and other containers such as medicines, cosmetics, gasoline, etc.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. The container obtained in each example was evaluated by the following methods.

[Evaluation of oxygen absorption]
The body of the container was cut into strips, and a piece weighed 5 g was placed in an oxygen-impermeable container with an internal volume of 84 cc (trade name: Hi-Retflex: HR78-84, manufactured by Toyo Seikan Co., Ltd., polypropylene / steel It was placed in a foil/polypropylene cup-shaped laminated container) and heat-sealed with a lid material of polypropylene (inner layer)/aluminum foil/polyester (outer layer). A small amount of distilled water was put into the oxygen-impermeable container so that the humidity was 100% RH, but the distilled water did not come into direct contact with the pieces of the container so as not to interfere with oxygen absorption. This was stored in a constant temperature storage at 30°C, and the oxygen concentration (%) in the container immediately after filling, after storage for 1 week, and after storage for 2 weeks was measured by gas chromatography for 5 tubes at each level. The amount of oxygen absorbed per 1 g of the main layer was calculated from the obtained measured values, the charged amount, the thickness of the main layer of the container, and the amount of head space. Table 2 shows the oxygen absorption per container (cc/bottle). Based on the oxygen absorption amount, evaluation was made according to the following criteria.
A: The oxygen absorption amount is 5.0 cc/bottle or more.
○: The oxygen absorption amount is 2.5 cc/bottle or more and less than 5.0 cc/bottle.
Δ: The oxygen absorption amount is 1.0 cc/bottle or more and less than 2.5 cc/bottle.
x: The oxygen absorption amount is less than 1.0 cc/bottle.

[Water flavor property evaluation]
The resulting container was filled with 180 ml of distilled water for HPLC manufactured by Wako Pure Chemical Industries, Ltd. heated to 80° C., sealed with a cap, and stored at 30° C.-80% RH for 1 week. After that, the sample was adjusted to room temperature, and the taste (flavor) of the content liquid was sensory evaluated according to the following ratings (1 point = tasteless, 2 points = slight taste, 3 points = tasteful, 4 points = quite tasty). The average score of 6 panelists was used to evaluate water flavor properties according to the following criteria. Table 2 shows the results.
A: The average score is less than 2.0.
○: The average score is 2.0 or more and less than 2.5.
Δ: The average score is 2.5 or more and less than 3.0.
x: The average score is 3.0 or more.

[Example 1]
(Preparation of oxygen-absorbing resin composition precursor)
As the resin (A1), Ziegler-Natta catalyst linear low-density polyethylene LLDPE (trade name: Neozex 20201J, manufactured by Mitsui Chemicals, Inc.) (LLDPE-A) 23.71 parts by mass and single-site catalyst linear low-density polyethylene LLDPE ( Product name: Evolue SP0511, manufactured by Mitsui Chemicals, Inc. (LLDPE-B) 71.01 parts by mass, and a hydrogenated styrene-butadiene-styrene copolymer (trade name: Tuftec P2000, Asahi Chemicals) as the resin (B) Co., Ltd.) and 2.51 parts by mass of a hydrogenated styrene-butadiene-styrene copolymer (trade name: Dynaron 8601P, manufactured by JSR Corporation), and a tablet as a transition metal catalyst (C). 0.26 parts by mass of cobalt stearate (manufactured by DIC Corporation) (250 ppm by mass in terms of metal) was dry-blended in a tumbler and charged into the hopper of a twin-screw extruder manufactured by Toshiba Machine Co., Ltd. .

At a resin temperature of 200°C and a discharge rate of 100 kg/h, nitrogen was continuously purged from the bottom of the hopper to prevent oxidative and thermal deterioration during kneading, and a vacuum vent was further pulled to melt and knead, and extruded from a die into strands. . After cooling this strand in a water tank controlled at a water temperature of 30 to 40° C. so that the surface temperature becomes 70° C., it is cut with a pelletizer to obtain an outer diameter of φ2.0 to 3.0 mm and a length of 3.0 to 4.0 mm. A cylindrical pellet of The obtained pellets are continuously charged into a surge tank (maximum charge of 250 kg) from the upper inlet, and after 132 minutes, 20 kg of pellets are taken out from the outlet at the bottom of the surge tank every 12 minutes. It was packed in a bag to obtain pellets of the oxygen-absorbing resin composition precursor. The surface temperature of the pellets when taken out was 50°C.

(Preparation of oxygen-absorbing resin composition)
10 parts by weight of pellets made of the precursor of the oxygen-absorbing resin composition, and 50 parts by weight of scrap resin mainly containing low-density polyethylene (LDPE), which is obtained by pulverizing parts other than the container such as resin and burrs discharged at the start of molding. part, 35 parts by mass of low-density polyethylene (LDPE) (trade name: Novatec ZE-41K, manufactured by Japan Polyethylene Co., Ltd., density: 0.921 g/cm ³ ) as resin (A2), and adsorbent (D) was mixed with 5 parts by mass of high silica zeolite (trade name: Silton, manufactured by Mizusawa Chemical Industry Co., Ltd.) to prepare an oxygen-absorbing resin composition. The content of resin (A) in the oxygen-absorbing resin composition is 94.5% by mass, the content of resin (B) is 0.5% by mass, and the content of transition metal catalyst (C) is 25 ppm by mass. (In terms of metal), the content of the adsorbent (D) was 5% by mass.

(Production of container)
Using four extruders, the following 4 types and 6 layers of multilayer parisons are molded, and by direct blow molding using the multilayer parisons, the following 4 types and 6 layers of containers (plastic bottles, internal volume: 610 ml, 25 g) are produced. made.
Outer layer (200 μm)/Adhesive layer (30 μm)/Gas barrier layer (20 μm)/Adhesive layer (30 μm)/Main layer (650 μm)/Inner layer (100 μm) (The numbers in parentheses indicate the thickness of each layer of the container. Ratio of main layer thickness to wall thickness: 63%)
Materials for each layer are as follows.

Outer layer: Low-density polyethylene (LDPE) (trade name: Novatec ZE-41K, manufactured by Japan Polyethylene Co., Ltd., density: 0.921 g/cm ³ )
Adhesive layer (common to 2 layers): acid-modified polyethylene (trade name: Modic L522, manufactured by Mitsubishi Chemical Corporation)
Gas barrier layer: ethylene-vinyl alcohol copolymer (trade name: EVAL F101B, manufactured by Kuraray Co., Ltd.)
Main layer: the oxygen-absorbing resin composition Inner layer: low-density polyethylene (LDPE) (trade name: Novatec ZE-41K, manufactured by Japan Polyethylene Co., Ltd., density: 0.921 g/cm ³ )
The resulting container was evaluated for oxygen absorption and water flavor by the methods described above. Table 2 shows the results.

[Example 2]
In the preparation of the oxygen-absorbing resin composition, low-density polyethylene (LDPE) (trade name: Novatec ZE-41K, manufactured by Japan Polyethylene Co., Ltd., density: 0.921 g/cm ³ ) was used instead of 50 parts by mass of scrap resin. An oxygen-absorbing resin composition was prepared in the same manner as in Example 1 except that 50 parts by mass was used, and a container was produced and evaluated. Table 2 shows the results.

[Example 3]
In the preparation of the oxygen-absorbing resin composition, the procedure was the same as in Example 1, except that 5 parts by mass of high silica zeolite (trade name: Silton, manufactured by Mizusawa Chemical Industry Co., Ltd.) as an adsorbent (D) was not mixed. Similarly, an oxygen-absorbing resin composition was prepared, and a container was produced and evaluated. Table 2 shows the results.

Claims (4)

A resin (A1) that is an olefin polymer having 2 to 8 carbon atoms, a resin (B) other than the resin (A1) that serves as a trigger for oxidation of the resin (A1), and a transition metal catalyst (C). and melt-kneading to prepare an oxygen-absorbing resin composition precursor;
a step of mixing the oxygen-absorbing resin composition precursor with a resin (A2) that is an olefin polymer having 2 to 8 carbon atoms;
A method for producing an oxygen-absorbing resin composition having
The resin (B) is an optionally hydrogenated styrene-butadiene copolymer,
A method for producing an oxygen-absorbing resin composition, wherein the content of the resin (B) in the oxygen-absorbing resin composition is 0.1% by mass or more and less than 1.0% by mass. 2. The method for producing an oxygen-absorbing resin composition according to claim 1, wherein the resin (B) is an optionally hydrogenated styrene-butadiene block copolymer. 2. The method for producing an oxygen-absorbing resin composition according to claim 1, wherein the resin (B) is an optionally hydrogenated styrene-butadiene-styrene triblock copolymer. 4. The oxygen-absorbing resin composition according to any one of claims 1 to 3, wherein an adsorbent (D) is further mixed in the step of mixing the oxygen-absorbing resin composition precursor and the resin (A2). A method of making things.