JP2010179643A - Method of manufacturing oxygen absorptive resin composition and oxygen absorptive resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an oxygen absorptive resin composition which has superior oxygen absorption function (high oxygen absorption and high oxygen absorption rate), without generating an unpleasant odor due to oxygen absorption, and shows superior workability. <P>SOLUTION: The method of manufacturing an oxygen absorptive resin composition using a biaxial extruder includes a process to melt and knead a resin raw material inside the extruder. The resin raw material contains a thermoplastic resin (A) with a carbon-carbon double bond and at least, one kind of gas barrier resin (D) selected from the group consisting of a polyvinyl chloride-based resin, a polyacrylonitrile-based resin and a polyvinyl alcohol-based resin. The extruder is equipped with two or more feed openings and a vent port located downstream from the feed opening. The resin raw material is supplied from a first feed opening located at the extreme end of the upstream side of the extruder, and water is supplied from a second feed opening downstream from the first feed opening and removed from the vent port. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for producing an oxygen-absorbing resin composition and an oxygen-absorbing resin composition obtained by the method.

  A gas barrier resin, for example, an ethylene-vinyl alcohol copolymer (hereinafter sometimes referred to as EVOH) is a material excellent in oxygen gas barrier property and carbon dioxide gas barrier property. Since such a resin can be melt-molded, it is laminated with a layer of thermoplastic resin (polyolefin, polyester, etc.) excellent in moisture resistance, mechanical properties, etc., and is suitably used as a multilayer plastic packaging material.

  However, the gas permeability of these gas barrier resins is not completely zero and permeates a non-negligible amount of gas. In order to reduce such gas permeation, in particular oxygen permeation, which greatly affects the quality of the contents, and to remove oxygen already present inside the package at the time of packaging of the contents, It is known to use oxygen absorbers.

  For example, as an improved oxygen absorbent, a composition containing a transition metal catalyst and an ethylenically unsaturated compound and an oxygen absorbent resin composition containing the above EVOH and an oxygen absorbent have been proposed (Patent Document 1). And 2). In particular, since the oxygen-absorbing resin composition containing EVOH can be melt-molded similarly to EVOH, it can be suitably used as various packaging materials.

  However, when the oxygen absorbent or the oxygen-absorbing resin composition as described above is used as a packaging material, the oxygen absorbent may be decomposed as oxygen absorption proceeds to generate an unpleasant odor. Therefore, further improvements are desired in applications where fragrance is important, such as for preservation of foods sensitive to odor.

  For example, as an oxygen-absorbing resin composition that does not generate an unpleasant odor, some of the present inventors have reported that an oxygen containing a thermoplastic resin having a carbon-carbon double bond only in the main chain and a transition metal salt. An absorbent resin composition is proposed (see Patent Document 3).

  However, even in the oxygen-absorbing resin composition described in Patent Document 3, due to impurities and oligomer components contained in the resin constituting the composition, or by decomposition of the resin component by a transition metal catalyst, Some odor is still unavoidable. Therefore, oxygen-absorbing resin compositions used for storing foods that are particularly sensitive to odors are required to generate less unpleasant odors due to oxygen absorption.

  On the other hand, as a countermeasure against the odor of the oxygen absorbent, a multilayer structure having an odor barrier layer containing a deodorant or an odor absorbent on the outside and inside of the oxygen absorbent layer has been proposed (see Patent Document 4). However, since it has an odor barrier layer in addition to the base material and the oxygen absorbing layer, the layer structure becomes complicated, and it is often difficult to manufacture with existing facilities, and there is a problem that it lacks versatility.

  Further, when the odor barrier layer is present inside the oxygen absorbing layer, there is a problem in that the efficiency of removing oxygen present inside the package is reduced.

Japanese Patent Laid-Open No. 5-115776 International Publication No. 02/18496 Japanese Patent Laying-Open No. 2005-187808 JP 2005-1371 A

  An object of the present invention is to provide an oxygen-absorbing resin composition having an excellent oxygen absorption function (high oxygen absorption amount and high oxygen absorption rate), no unpleasant odor due to oxygen absorption, and excellent workability. And an oxygen-absorbing resin composition having the above-described excellent properties.

  The present invention is a method for producing an oxygen-absorbing resin composition using a twin screw extruder, the method comprising a step of melt-kneading a resin raw material in the extruder, the resin raw material comprising carbon-carbon At least selected from the group consisting of a thermoplastic resin (A) having a double bond (hereinafter simply referred to as a thermoplastic resin (A)), a polyvinyl chloride resin, a polyacrylonitrile resin, and a polyvinyl alcohol resin. 1 type of gas barrier resin (D) (hereinafter simply referred to as gas barrier resin (D)), and the extruder includes two or more supply ports and a vent port downstream of the supply ports. The resin raw material is supplied from the first supply port upstream of the extruder, and water is supplied from the second supply port downstream of the first supply port and removed from the vent port.

  In one embodiment, when the said resin raw material is 100 mass%, the said water is supplied in the quantity of 1-50 mass%.

  In another embodiment, nitrogen gas is further supplied from the first supply port or a third supply port between the first supply port and the second supply port.

  In still another embodiment, the resin temperature in the extruder is 250 ° C. or lower.

  In still another embodiment, the moisture content of the oxygen-absorbing resin composition is 0.6% by mass or less.

  In still another embodiment, the thermoplastic resin (A) has a carbon-carbon double bond substantially only in the main chain.

  In one embodiment, the thermoplastic resin (A) is polyoctenylene.

  In still another embodiment, the gas barrier resin (D) is an ethylene-vinyl alcohol copolymer having an ethylene content of 5 to 60 mol% and a saponification degree of 90% or more.

  In still another embodiment, the resin raw material further contains a transition metal salt (C).

  In one embodiment, the transition metal salt (C) is at least one metal salt selected from the group consisting of iron salt, nickel salt, copper salt, manganese salt and cobalt salt.

  Furthermore, the present invention is an oxygen-absorbing resin composition produced by the above method.

  According to the present invention, an oxygen-absorbing resin composition having an excellent oxygen absorption function (high oxygen absorption amount and high oxygen absorption rate), no unpleasant odor due to oxygen absorption, and excellent workability And an oxygen-absorbing resin composition having the excellent properties described above.

  Hereinafter, embodiments of the present invention will be described.

  The method for producing an oxygen-absorbing resin composition using a twin-screw extruder according to the present invention includes a step of melt-kneading a resin raw material in the extruder, the resin raw material comprising a thermoplastic resin (A), A gas barrier resin (D), and the extruder includes two or more supply ports and a vent port downstream of the supply port, and the resin raw material is a first supply port upstream of the extruder. And water is supplied from a second supply port downstream of the first supply port and removed from the vent port. By producing an oxygen-absorbing resin composition by such a method, the oxygen-absorbing resin composition has an excellent oxygen-absorbing function, does not generate an unpleasant odor due to oxygen absorption, and has excellent processability. Is obtained.

(I) Resin raw material In the method of the present invention, the thermoplastic resin (A) and the gas barrier resin (D), and the transition metal salt (C), compatibilizer (E) and other additives added as necessary. An additive is used as a resin raw material.

(1) Thermoplastic resin (A)
The thermoplastic resin (A) used in the method of the present invention has a carbon-carbon double bond in the molecule, and preferably has a carbon-carbon double bond substantially only in the main chain. “Substantially only having a carbon-carbon double bond in the main chain” means that the carbon-carbon double bonds existing in the main chain of the thermoplastic resin (A) are all carbon-carbon double bonds in the molecule. 90% or more, and the carbon-carbon double bond existing in the side chain is 10% or less of the total carbon-carbon double bond in the molecule. The proportion of carbon-carbon double bonds present in the side chain is preferably 7% or less, more preferably 5% or less.

  Examples of such thermoplastic resins (A) include polydienes (polybutadiene, polyisoprene, polychloroprene, poly (2-ethylbutadiene), poly (2-butylbutadiene), etc.); cycloolefin ring-opening metathesis polymers (Polyoctenylene, polypentenylene, polynorbornene, etc.). Among these, a 1,4-position polymer of polydiene and polyoctenylene are preferable, and 1,4-polybutadiene and polyoctenylene are more preferable.

Generally, the carbon-carbon double bond existing in the main chain of the thermoplastic resin molecule has a lower oxygen absorption rate and a slower oxygen absorption rate than the carbon-carbon double bond present in the side chain. There are many. However, in the main chain, the adjacent carbon - having repeating units present methylene chain is more than three between carbon double bond _{(i.e., -C = C- (CH 2)} n ≧ 3 -C = C-) a It was found that the thermoplastic resin has an amount of oxygen absorbed per carbon-carbon double bond larger than expected. Therefore, in the production method of the present invention, the adjacent carbon-carbon double bond is preferably used as the thermoplastic resin (A) from the viewpoint that odor is hardly generated and an excellent oxygen absorption function can be obtained with a small addition amount. A thermoplastic resin having a repeating unit in which three or more methylene chains are present is used. Examples of such thermoplastic resins include polyoctenylene and polypentenylene, and polyoctenylene is particularly preferable.

  The amount of carbon-carbon double bonds contained in the thermoplastic resin (A) is preferably 0.001 eq / g (equivalent / g) or more, more preferably 0.005 eq / g or more, and 0.01 eq / g. g or more is more preferable. When the content of carbon-carbon double bonds is less than 0.001 eq / g, the obtained oxygen-absorbing resin composition tends not to have a sufficient oxygen-absorbing function.

  The weight average molecular weight of the thermoplastic resin (A) is preferably 1,000 to 500,000, more preferably 10,000 to 250,000, and further preferably 40,000 to 200,000. When the weight average molecular weight is less than 1000 or exceeds 500,000, the resulting oxygen-absorbing resin composition may have poor molding processability and handling properties, or a machine such as strength and elongation when formed into a molded body. Tend to decrease the physical properties. In addition, when used by mixing with a matrix resin, the dispersibility of the resin is lowered, and thus the oxygen absorbing function of the obtained oxygen-absorbing resin composition tends to be lowered.

  When the thermoplastic resin (A) is a ring-opening metathesis polymer of a cyclic olefin, it is unavoidable that a certain amount of oligomers are inevitably mixed due to the mechanism of the ring-opening metathesis polymerization. Under normal use conditions, problems such as odor are unlikely to occur if the monomer is removed. However, when the package obtained by molding is stored under high temperature and high humidity, if these oligomers are present, odor may be felt in the contents of the package. On the other hand, the amount of oligomer is preferably as low as possible from the viewpoint of odor and the like, but if it is attempted to be lower than necessary, the production process becomes complicated. Therefore, in consideration of storage at high temperature and high humidity, the oligomer having a molecular weight of 1000 or less present in the ring-opening metathesis polymer is preferably 6% by mass or less, more preferably 4% by mass or less, and further preferably 2%. It is below mass%.

  Examples of the method for removing the oligomer from the ring-opening metathesis polymer include a method for removing by washing with an organic solvent such as acetone.

  The thermoplastic resin (A) may contain an antioxidant. Examples of the antioxidant include 2,5-di-tert-butylhydroquinone, 2,6-di-tert-butyl-p-cresol, 4,4′-thiobis (6-tert-butylphenol), 2,2 '-Methylene-bis (4-methyl-6-tert-butylphenol), octadecyl-3- (3', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate, 4,4'-thiobis (6 -Tert-butylphenol), 2-tert-butyl-6- (3-tert-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, pentaerythritol tetrakis (3-laurylthiopropionate), 2,6-di- (tert-butyl) -4-methylphenol, 2,2-methylenebis (6-te t- butyl -p- cresol), triphenyl phosphite, tris (nonylphenyl) phosphite, and the like dilauryl thiodipropionate.

  When the thermoplastic resin (A) contains an antioxidant, the amount thereof takes into consideration the type and content of the resin raw material contained in the oxygen-absorbing resin composition, the intended use of the resulting molded product, storage conditions, and the like. When the total mass of the thermoplastic resin (A) and the antioxidant is 100% by mass, it is preferably 0.01-1% by mass, more preferably 0.02-0.5% by mass. It is. If the content of the antioxidant exceeds 1% by mass, the reaction between the thermoplastic resin (A) and oxygen tends to be hindered. On the other hand, when the content of the antioxidant is less than 0.01% by mass, the reaction with oxygen proceeds when the thermoplastic resin (A) is stored or melt kneaded, and the actual oxygen-absorbing resin composition thus obtained is obtained. Before use, the oxygen absorption function may be reduced.

(2) Gas barrier resin (D)
The gas barrier resin (D) used in the method of the present invention functions as a support for diluting or dispersing the thermoplastic resin (A) and has a gas barrier property in the oxygen-absorbing resin composition of the present invention. It has a function to grant. When an oxygen-absorbing resin composition containing a gas barrier resin as a matrix resin is used as a predetermined molded body such as a container, the odorous component generated after the thermoplastic resin (A) absorbs oxygen is diffused outside the molded body. Can be suppressed.

The gas barrier resin (D) preferably has a gas barrier property with an oxygen transmission rate of 500 ml · 20 μm / m ² · day · atm (20 ° C., 65% RH (relative humidity)) or less. This oxygen transmission rate is the volume of oxygen that permeates a film of 1 m ² area and 20 μm thickness per day in the presence of an oxygen differential pressure of 1 atm when measured in an environment of 20 ° C. and 65% RH. Means 500 ml or less. When the oxygen permeation rate exceeds 500 ml · 20 μm / m ² · day · atm, the resulting oxygen-absorbing resin composition is less effective in suppressing the outward diffusion of odors generated after absorbing oxygen. The oxygen permeation rate of the gas barrier resin (D) is more preferably 100 ml · 20 μm / m ² · day · atm or less, further preferably 20 ml · 20 μm / m ² · day · atm or less, and most preferably 5 ml. -It is below 20micrometer / m < ² > * day * atm. By containing such a gas barrier resin (D) and the thermoplastic resin (A), an oxygen absorbing effect is exhibited in addition to the gas barrier effect, and as a result, an oxygen absorbing resin composition having extremely high gas barrier properties. Can be obtained.

  Examples of such a gas barrier resin (D) include polyvinyl alcohol resins, polyvinyl chloride resins, polyacrylonitrile resins, and the like.

  As the gas barrier resin (D), one of these resins may be used, or a mixture of two or more may be used. In particular, a polyvinyl alcohol-based resin is preferable, and the ethylene content An ethylene-vinyl alcohol copolymer (EVOH) having 5 to 60 mol% and a saponification degree of 90% or more is more preferable.

  Among the gas barrier resins (D), the polyvinyl alcohol resin is a vinyl ester homopolymer or a copolymer of vinyl ester and another monomer (particularly a copolymer of vinyl ester and ethylene), Obtained by saponification using an alkali catalyst or the like. As the vinyl ester, vinyl acetate is a typical compound, but other fatty acid vinyl esters (vinyl propionate, vinyl pivalate, etc.) can also be used.

  The saponification degree of the vinyl ester component of the polyvinyl alcohol resin is preferably 90% or more, more preferably 95% or more, and further preferably 98% or more. When the saponification degree is less than 90 mol%, the gas barrier property under high humidity is lowered.

  Among the polyvinyl alcohol-based resins, EVOH is particularly preferable because it can be melt-molded and has good gas barrier properties under high humidity.

  Among the polyvinyl alcohol-based resins, EVOH preferably has an ethylene content of 5 to 60 mol% and a saponification degree of 90% or more. The ethylene content of EVOH is preferably 10 mol% or more, more preferably 15 mol% or more, and even more preferably 20 mol% or more. When the ethylene content of EVOH is less than 5 mol%, the gas barrier property under high humidity tends to decrease. On the other hand, the ethylene content of EVOH is preferably 55 mol% or less, more preferably 50 mol% or less. When the ethylene content of EVOH exceeds 60 mol%, gas barrier properties tend to decrease. The saponification degree of EVOH is preferably 95% or more, more preferably 98% or more. When the saponification degree of EVOH is less than 90%, the thermal stability of the obtained oxygen-absorbing resin composition becomes insufficient, and gels and blisters are likely to occur in the molded article. The ethylene content and saponification degree of EVOH can be determined by a nuclear magnetic resonance (NMR) method.

  Among the gas barrier resins (D), examples of the polyvinyl chloride resin include, in addition to vinyl chloride or vinylidene chloride homopolymers, copolymers with vinyl acetate, maleic acid derivatives, higher alkyl vinyl ethers, and the like. .

  Among the gas barrier resins (D), examples of the polyacrylonitrile-based resin include acrylonitrile homopolymers and copolymers with acrylic acid esters and the like.

  When the total mass of the resin raw materials is 100% by mass, the thermoplastic resin (A) is preferably contained in a proportion of 30 to 1% by mass and the gas barrier resin (D) in a proportion of 70 to 99% by mass. For example, when the content of the gas barrier resin (D) is less than 70% by mass, the gas barrier property against oxygen gas, carbon dioxide gas and the like of the obtained oxygen-absorbing resin composition tends to be lowered. On the other hand, when the content of the gas barrier resin (D) exceeds 99% by mass, the oxygen-absorbing function of the obtained oxygen-absorbing resin composition tends to be lowered. The thermoplastic resin (A) is more preferably contained in a proportion of 20 to 2% by mass, more preferably 15 to 3% by mass, and the gas barrier resin (D) is more preferably 80 to 98% by mass, and further preferably. Is contained at a ratio of 85 to 97% by mass.

(3) Transition metal salt (C)
The transition metal salt (C) has an effect of improving the oxygen absorption function of the oxygen-absorbing resin composition by promoting the oxidation reaction of the thermoplastic resin (A).

  Examples of the transition metal contained in the transition metal salt (C) include, but are not limited to, iron, nickel, copper, manganese, cobalt, rhodium, titanium, chromium, vanadium, and ruthenium. Among these, iron, nickel, copper, manganese, and cobalt are preferable, manganese or cobalt is more preferable, and cobalt is most preferable.

  Examples of the counter ion of the transition metal contained in the transition metal salt (C) include an anion derived from an organic acid or chloride, and an anion derived from an organic acid is preferable. Examples of the organic acid include acetic acid, stearic acid, dimethyldithiocarbamic acid, palmitic acid, 2-ethylhexanoic acid, neodecanoic acid, linoleic acid, toluic acid, oleic acid, capric acid, and naphthenic acid. It is not limited to. As the transition metal salt (C), cobalt 2-ethylhexanoate, cobalt neodecanoate, and cobalt stearate are particularly preferable.

  The transition metal salt (C) is preferably blended in the range of 1 to 50000 ppm, more preferably 5 to 10000 ppm, and still more preferably 10 to 5000 ppm in terms of transition metal, assuming that the total mass of the resin raw materials is 100 mass%. When the blending amount of the transition metal salt (C) exceeds 50000 ppm, the thermal stability of the obtained oxygen-absorbing resin composition is lowered, and the formation of gels and blisters in the molded product may be remarkable. On the other hand, when the blending amount of the transition metal salt (C) is less than 1 ppm, the oxygen-absorbing function of the obtained oxygen-absorbing resin composition may be insufficient.

(4) Compatibilizer (E)
For the purpose of improving the compatibility between the thermoplastic resin (A) and the gas barrier resin (D) contained in the oxygen-absorbing resin composition and giving the oxygen-absorbing resin composition a stable morphology, as necessary. A compatibilizer (E) can be added. The type of the compatibilizer (E) is not particularly limited, and can be appropriately selected depending on the combination of the thermoplastic resin (A) and the gas barrier resin (D) used.

  For example, since the gas barrier resin (D) is a highly polar resin, the compatibilizer (E) is preferably a hydrocarbon polymer containing a polar group. In the case where the compatibilizer (E) is a hydrocarbon polymer containing a polar group, the compatibilizer (E) and the thermoplastic resin (A) are separated by a hydrocarbon polymer portion serving as a base of the polymer. Affinity is good. Furthermore, the affinity between the compatibilizer (E) and the gas barrier resin (D) is improved by the polar group of the compatibilizer (E). As a result, a stable morphology can be formed in the obtained oxygen-absorbing resin composition. Specific examples of the compatibilizer (E) having such a polar group are disclosed in detail in, for example, Patent Document 3.

  When the total mass of the resin raw materials is 100% by mass, preferably 29.9 to 1% by mass of the thermoplastic resin (A), 70 to 98.9% by mass of the gas barrier resin (D), and a compatibilizer ( E) is included in a proportion of 29 to 0.1% by mass. When the content of the gas barrier resin (D) is less than 70% by mass, the gas barrier property against oxygen gas, carbon dioxide gas and the like of the obtained oxygen-absorbing resin composition tends to be lowered. On the other hand, when the content of the gas barrier resin (D) exceeds 98.9% by mass, the oxygen-absorbing function of the obtained oxygen-absorbing resin composition tends to be lowered, and the morphology of the oxygen-absorbing resin composition is further reduced. The stability tends to be impaired. The thermoplastic resin (A) is more preferably contained in a proportion of 19.5 to 2% by mass, more preferably 14 to 3% by mass. The gas barrier resin (D) is more preferably contained in an amount of 80 to 97.5% by mass, and more preferably 85 to 96% by mass. The compatibilizer (E) is more preferably contained in a proportion of 18 to 0.5% by mass, and more preferably 12 to 1% by mass.

(5) Other additives The resin raw material may contain various additives as long as the effects of the present invention are not inhibited. Additives include plasticizers, heat stabilizers (melting stabilizers), photoinitiators, deodorants, UV absorbers, antistatic agents, lubricants, colorants, drying agents, fillers, processing aids, flame retardants, Antifogging agents, other polymer compounds and the like can be mentioned.

(II) Twin Screw Extruder The twin screw extruder used in the method of the present invention includes two or more supply ports and a vent port downstream of the supply ports. The resin raw material is supplied into the twin-screw extruder from the first upstream supply port of the twin-screw extruder. That is, the first supply port functions as a resin raw material supply port. Further, water is supplied into the twin screw extruder from the second supply port downstream of the first supply port. That is, the second supply port functions as a water supply port. The twin-screw extruder used in the method of the present invention may include a third supply port between the first supply port and the second supply port, and the nitrogen gas may be supplied from the first supply port or the third supply port. It is supplied into the twin screw extruder from the supply port. The vent port is used for removing water out of the twin screw extruder and, if necessary, for removing gas in the twin screw extruder. In addition, the twin-screw extruder used for the method of this invention is naturally equipped with the discharge port of the oxygen absorptive resin composition manufactured by melt-kneading. As a commercially available twin screw extruder, for example, “TEX” (trade name) manufactured by Nippon Steel Works, “ZSK” (trade name) manufactured by Werner & Pfleiderer, “TEM” (trade name) manufactured by Toshiba Machine Co., Ltd. “PCM” (trade name) manufactured by Ikegai Iron Works Co., Ltd.

(III) Melt kneading step In the method of the present invention, the resin raw material is supplied into the twin screw extruder from the resin raw material supply port, melt kneading is started, and water is added to the part where the resin raw material is melt kneaded. Therefore, water is supplied into the twin screw extruder from the water supply port. Next, water from the portion where the resin raw material is melt-kneaded is removed from the vent port to the outside of the twin-screw extruder. In this series of steps, the addition of water suppresses an increase in the resin temperature due to melt kneading, and suppresses the generation of odor components due to the thermal decomposition of the resin. In particular, when a transition metal salt (C) is present in the resin raw material, deterioration of the gas barrier resin (D) proceeds and low-molecular odor components are likely to be generated. It is effective in suppressing The water added to the resin is originally contained in the resin raw material or takes in impurities such as odor components generated during melt kneading, and the impurities are removed together with the water from the portion where the resin raw material is melt kneaded. Estimated. Thus, the odor of the oxygen-absorbing resin composition obtained by the method of the present invention can be reduced.

  The method for supplying the resin raw material into the twin screw extruder is not particularly limited. For example, when the thermoplastic resin (A), the gas barrier resin (D), and the transition metal salt (C) are mixed, they are supplied from separate resin raw material supply ports (quantitative supply ports) connected to the first supply port. Alternatively, a material obtained by dry blending each raw material in advance may be supplied from the first supply port. In addition to supplying the resin raw material from the first supply port, a part of the resin raw material may be supplied from another supply port.

  From the viewpoint of suppressing the generation of odor components, it is necessary to suppress the decomposition of the resin raw material during melt-kneading. Therefore, when the transition metal salt (C) is used as the resin raw material, the transition metal salt (C) and the thermoplastic resin It is preferable to shorten the contact time with (A) and the gas barrier resin (D).

  As a method of shortening the contact time between the transition metal salt (C), the thermoplastic resin (A) and the gas barrier resin (D), first, the thermoplastic resin (A) and the gas barrier resin (D) are melt-kneaded. A method in which the transition metal salt (C) is supplied from another supply port after being supplied into the twin-screw extruder is preferable. In this case, the transition metal salt (C) may be supplied alone or may be supplied by dry blending with a part of the thermoplastic resin (A) or the gas barrier resin (D).

  The method for supplying water into the twin screw extruder is not particularly limited, but it is preferable to supply water continuously during melt kneading. The position of the second supply port for supplying water into the twin-screw extruder is a portion where the resin raw material is melt-kneaded from the viewpoint of suppressing an increase in the resin temperature during melt-kneading and enhancing the effect of removing odor components. In order to add water, it is appropriately set between the first supply port and the vent port.

  The amount of water to be supplied is preferably 1% by mass to 50% by mass, more preferably 3% by mass to 30% by mass, and further preferably 5% by mass to 20% by mass, assuming that the total mass of the resin raw materials is 100% by mass. It is. When the amount of water to be supplied is less than 1% by mass, the increase in the resin temperature during melt-kneading is suppressed, and the effect of removing odor components is reduced. On the other hand, when the amount of water supplied exceeds 50% by mass, the moisture cannot be sufficiently removed from the resin raw material, and the moisture may remain in the obtained oxygen-absorbing resin composition.

  The method of removing water outside the twin-screw extruder is not particularly limited, but water can be removed efficiently by reducing the pressure at the vent port using a vacuum pump. Is preferably removed. When there are two or more vent ports, all the vent ports may be decompressed, or a vent port opened at normal pressure and a vent port depressurized may be combined. The position of the vent port for removing water outside the twin-screw extruder enhances the effect of removing odor components, and from the viewpoint of controlling the moisture content of the obtained oxygen-absorbing resin composition, it is downstream of the second supply port. Is set as appropriate. Further, the residence time of water in the portion where the resin raw material is melt-kneaded is preferably 5 to 300 seconds, and more preferably 10 to 60 seconds.

  The moisture content in the obtained oxygen-absorbing resin composition is preferably 0.6% by mass or less, more preferably 0.5% by mass or less, and still more preferably 0.4% by mass or less. When the moisture content exceeds 0.6% by mass, foaming may occur in the molded body when the oxygen-absorbing resin composition is used to form a film, sheet, bottle, tube or the like.

  In order to suppress oxidative deterioration of the resin raw material during melt-kneading, it is effective to remove oxygen gas from the twin screw extruder. Therefore, it is preferable that nitrogen gas is supplied into the twin screw extruder during melt kneading. The method of supplying nitrogen gas into the twin screw extruder is not particularly limited, but it is preferable to supply nitrogen gas continuously during melt kneading. The position of the third supply port for supplying nitrogen gas into the twin-screw extruder is appropriately set between the first supply port and the second supply port, but nitrogen gas is supplied from the first supply port. Also good. The method for removing oxygen gas and nitrogen gas in the twin screw extruder to the outside of the twin screw extruder is not particularly limited, but these gases can be efficiently removed by reducing the vent port using a vacuum pump. It is preferable to remove these gases continuously during melt-kneading.

  In order to suppress decomposition of the resin raw material during melt kneading, it is also effective to lower the resin temperature during melt kneading. Therefore, the resin temperature in the twin screw extruder is preferably 250 ° C. or lower, more preferably 245 ° C. or lower. When the temperature is 250 ° C. or higher, the thermoplastic resin (A) and the gas barrier resin (D) are likely to be decomposed. Although the minimum of resin temperature is not specifically limited, It needs to be higher than melting | fusing point of a resin raw material. Further, in order to finely and uniformly disperse each resin raw material, it is necessary to set the screw rotation speed to a certain level, and as a result, the resin temperature rises. Therefore, the practical resin temperature is 200 ° C. or higher.

(IV) Oxygen-absorbing resin composition produced by the method of the present invention The oxygen-absorbing resin composition obtained by the method of the present invention has a carbon number of 4 to 8, which is a typical odor component generated after oxygen absorption. It is preferable that the sum of the order units (the concentration of each component / the odor threshold value of each component) of the aliphatic linear saturated fatty acid and the aliphatic linear saturated aldehyde having 6 to 9 carbon atoms is 15000 or less. The larger the order unit, the greater the odor intensity. Even if the concentration of the generated odor component is low, the order unit becomes large and the odor intensity increases if the odor threshold value of the component is small. Conversely, even if the concentration of the generated odor component is high, if the odor threshold value of the component is large, the order unit is small and the odor intensity is also small. That is, when the contents of the acid and aldehyde order units, which are the main causes of odor, are set to 15000 or less, foods, beverages, pet foods, pharmaceuticals, cosmetics, and the like that are particularly important for flavor are packaged. It is possible to prevent the odor content from being transferred. The order unit is more preferably 13000 or less, and still more preferably 10,000 or less. Note that the order unit is calculated by a method described in an example described later.

  The oxygen-absorbing resin composition obtained by the method of the present invention can be molded into various molded bodies, for example, films, sheets, containers and other packaging bodies by appropriately adopting a molding method. At this time, the oxygen-absorbing resin composition may be once formed into pellets and then subjected to molding, or the oxygen-absorbing resin composition obtained by melt-kneading may be directly subjected to molding.

  Examples of the molding method and the molded body include hollow containers such as bottles molded by the hollow molding method, such as films and sheets molded by the melt extrusion molding method, containers molded by the injection molding method, and the like. The hollow molding method includes an extrusion hollow molding method (a method in which a parison is molded by an extrusion molding method and blown to form), and an injection hollow molding method (a preform is molded by the injection molding method and then blown). And the like).

  The molded body may be a single layer, but is preferably a multilayer structure laminated with other layers from the viewpoint of imparting properties such as mechanical properties, water vapor barrier properties, and further gas barrier properties.

  The oxygen-absorbing resin composition of the present invention has an excellent oxygen-absorbing function (high oxygen absorption amount and high oxygen absorption rate) and does not generate an unpleasant odor due to oxygen absorption. It is suitably used as a packaging material for easy contents (for example, foods, beverages, pharmaceuticals, cosmetics, etc.). In particular, it is suitable as a packaging material for foods, beverages, processed meats sensitive to quality changes, pet foods, etc. that emphasize flavor.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated concretely, this invention is not limited to these Examples.

  Analysis and evaluation in Examples and Comparative Examples were performed as follows.

(1) Molecular structure of the thermoplastic resin (A) The molecular structure of the thermoplastic resin (A) was measured by ¹ H-NMR (nuclear magnetic resonance) measurement using deuterated chloroform as a solvent (“JNM-GX-” manufactured by JEOL Ltd.). From the obtained spectrum.

(2) Weight average molecular weight of thermoplastic resin (A) The weight average molecular weight of the thermoplastic resin (A) was measured by gel permeation chromatography (GPC) and indicated as a polystyrene equivalent value. The detailed conditions of measurement are as follows.

<Analysis conditions>
Apparatus: Shodex gel permeation chromatography (GPC) SYSTEM-11
Column: Shodex KF-806L
Column temperature: 40 ° C
Mobile phase: tetrahydrofuran, flow rate 1.0 ml / min Run: 15 minutes Detector: RI
Concentration: 0.1%
Injection volume: 100 μl

(3) Odor component order unit <Odor component collection>
The oxygen-absorbing resin composition pellets obtained in the examples and comparative examples were pulverized into powder. 5.0 g of the obtained powder was sealed in a 20 ml headspace vial in an atmosphere of 23 ° C. and 50% RH (relative humidity) and allowed to stand at 60 ° C. for 7 days. Next, a solid phase microextraction (SPME) fiber (SPELCO, 65 μm PDMS-DVB) was inserted into the headspace of the headspace vial. The vial was placed in an oven at 60 ° C. and heated for 2 hours to collect volatile components in SPME fibers.

<Identification of odor components>
The volatile component collected in the fiber is introduced into the GC column, and the component separated by the column is a mass detector (MS) and an olfactory detection port (ODP2 manufactured by GERSTEL) using a distributor (CROSPICE GRAPHPACK 3D / 2 manufactured by GERSTEL). ) And led. By this method, it is possible to specify a component that is actually felt as an odor. In Examples and Comparative Examples, aliphatic linear saturated fatty acids having 4 to 8 carbon atoms and aliphatic linear saturated aldehydes having 6 to 9 carbon atoms were detected as odor components.

<Analysis conditions>
GC: GasChromatograph HP6890 manufactured by Hewlett-Packard
MS: Mass Sensitive Detector 5973 from Hewlett-Packard
Column: DB-5 made by J & W (length 60m, inner diameter 0.25mm)
Column temperature: 40 ° C. × 13 minutes → temperature rise (6 ° C./min)→250° C. × 10 minutes Mobile phase: helium, flow rate: 1.8 ml / min

<Odor component order unit>
Prepare each standard solution of 50, 100 and 200 μg / ml by diluting each component of C4-8 aliphatic linear saturated fatty acid and C6-9 aliphatic linear saturated aldehyde with n-hexane. Then, a calibration curve was prepared for each component from the above analysis results of the standard solution. Using this calibration curve, the concentration of each odor component in Examples and Comparative Examples was determined, and the order unit was calculated. The order unit of each odor component is a value obtained by dividing the concentration of each component by the odor threshold value of each component.

Here, the odor threshold value of each component is as follows.
n-butanoic acid: 0.19 ppb
n-Pentanoic acid: 0.037 ppb
n-Hexanoic acid: 0.6 ppb
n-Heptanoic acid: 0.21 ppb
n-octanoic acid: 5 ppb
n-hexanal: 0.28 ppb
n-heptanal: 0.18 ppb
n-octanal: 0.01 ppb
n-nonanal: 0.34 ppb

(4) Sensory test 0.1 g of the oxygen-absorbing resin composition films obtained in the examples and comparative examples were precisely weighed and wound into a roll after 5 hours of molding, at 23 ° C., 50% RH, volume ratio. It was placed in a standard bottle with a capacity of 85 ml filled with air containing 21:79 oxygen and nitrogen. Next, 15 ml of pure water was put into this standard bottle, and a part of the film was immersed in water. The standard bottle was covered and allowed to stand at 30 ° C. for 1 week. Next, five panelists evaluated the taste of water in the standard bottle according to the following criteria.
A: Compared to pure water, no change in the taste of water is felt.
○: Compared with pure water, a slight change in the taste of water is felt.

(Synthesis Example 1: Synthesis of polyoctenylene (a-1))
(polymerization)
The inside of the three-necked flask equipped with a stirrer and a thermometer was replaced with dry nitrogen gas. To a three-necked flask, 624 parts by mass of heptane in which 110 parts by mass of cis-cyclooctene and 0.187 parts by mass of cis-4-octene were dissolved was added.

  Next, 0.0424 parts by mass of [1,3-bis (2,4,6-trimethylphenyl) -2-imidazolidinylidene] dichloro (phenylmethylene) (tricyclohexylphosphine) ruthenium was dissolved in 3 parts by mass of toluene. A catalyst solution was prepared. This catalyst solution was quickly added to a three-necked flask, and ring-opening metathesis polymerization was performed at 55 ° C. After 1 hour, the reaction solution was analyzed by gas chromatography (manufactured by Shimadzu Corporation, GC-14B; column: manufactured by Chemical Inspection Association, G-100) to confirm the disappearance of cis-cyclooctene. Next, 1.08 parts by mass of ethyl vinyl ether was added to the three-necked flask, and the mixture was further stirred for 10 minutes.

  200 mass parts of water was added to the obtained reaction liquid, and it stirred at 40 degreeC for 30 minutes. Subsequently, it left still at 40 degreeC for 1 hour, and after liquid separation, the water layer was removed. Again, 100 parts by mass of water was added to the reaction solution, and the mixture was stirred at 45 ° C. for 30 minutes. Subsequently, it left still at 40 degreeC for 1 hour, and after liquid separation, the water layer was removed. Heptane was distilled off from the reaction solution under reduced pressure, and further, dried using a vacuum dryer at 1 Pa and 100 ° C. for 6 hours. The weight average molecular weight (Mw) was 142000 and the ratio of oligomers having a molecular weight of 1000 or less was 9.2. 102.1 parts by mass (yield 92%) of a polymer by mass was obtained. The ratio of the carbon-carbon double bond in the side chain of this polymer (polyoctenylene) to the total carbon-carbon double bond was 0%.

(Acetone washing)
The obtained polymer was crushed to about 1 mm square and added to a separable flask equipped with a stirrer, a reflux tube, and a thermometer. Next, 300 parts by mass of acetone was added to the separable flask and stirred at 40 ° C. for 3 hours. Acetone was removed by decantation. Again, 300 parts by mass of acetone was added to the separable flask and stirred at 40 ° C. for 3 hours. Acetone was removed by decantation. Residual acetone was distilled off under reduced pressure, and further dried at 1 Pa and 100 ° C. for 6 hours using a vacuum dryer. 99.0 parts by mass of a polymer (polyoctenylene (a-1)) with a proportion of 3.1% was obtained.

Example 1
(Preparation of oxygen-absorbing resin composition)
A screw and three vent ports are installed in a twin-screw extruder (TEX30α, 30 mmφ, L / D = 45.5 manufactured by Nippon Steel Co., Ltd.), and one water supply is provided between the resin supply port and the vent port. Mouth set up. This twin-screw extruder was operated under conditions of a barrel temperature of 190 ° C., a discharge rate of 15 kg / hr, and a screw rotation speed of 150 rpm, while cooling the resin supply port.

As gas barrier resin (D), ethylene content 32 mol%; saponification degree 99.5 mol%; MFR 1.6 g / 10 min (190 ° C., 2160 g load); melting point 183 ° C .; and 20 ° C., 65% RH Obtained in Synthesis Example 1 as 92 parts by mass of EVOH (hereinafter referred to as EVOH (d-1)) having an oxygen permeation rate of 0.4 ml · 20 μm / (m ² · day · atm) and a thermoplastic resin (A) 8 parts by mass of polyoctenylene (a-1) and 0.4242 parts by mass of cobalt stearate (II) (0.04 parts by mass as cobalt atoms) were dry blended to prepare a mixture.

  Next, this mixture was supplied from the resin supply port into the twin screw extruder, and melt kneaded while continuously supplying nitrogen gas into the twin screw extruder. During melt-kneading, 20 parts by mass of pure water was continuously supplied from the water supply port into the twin screw extruder, and water and gas were continuously removed from the three vent ports to the outside of the twin screw extruder. As a result, an oxygen-absorbing resin composition (P) comprising EVOH (d-1), polyoctenylene (a-1), and cobalt stearate (II) (hereinafter referred to as oxygen-absorbing resin composition (p-1)) (To be described).

  The resin temperature during melt kneading was 230 ° C. Further, the moisture content of the oxygen-absorbing resin composition (p-1) immediately after being discharged from the die hole of the twin-screw extruder was measured using a halogen moisture meter HR73 manufactured by METTLER TOLEDO Co., Ltd. It was mass%.

(Preparation and evaluation of film)
The pellets of the oxygen-absorbing resin composition (p-1) were melt-extruded from a coat hanger die at 210 ° C. using a 20 mmφ single screw extruder to obtain a film having a thickness of 20 μm.

  When the cut surface of the film was observed with a scanning electron microscope (SEM), polyoctenylene (a-1) having a particle diameter of 1 μm or less was dispersed in a matrix composed of EVOH (d-1).

  0.2 g of the obtained film was put in a standard bottle with an internal volume of 260 ml filled with air of 23 ° C. and 50% RH. The air in the standard bottle contained 21:79 oxygen and nitrogen in a volume ratio. The mouth of the standard bottle was sealed with an epoxy resin using a multilayer sheet containing an aluminum layer, and then left at 23 ° C.

  Then, 14 days after standing, the air inside the standard bottle was sampled with a syringe, and the oxygen concentration of this air was measured using gas chromatography. The amount of decrease in oxygen was calculated from the volume ratio of oxygen and nitrogen obtained by the measurement, and the oxygen absorption rate was calculated from the following formula (I). As a result, it was 2.0 (ml / (g · day)). there were.

F = G / (H × I × 2) (I)
here,
F: Oxygen absorption rate (ml / (g · day))
G: Reduction amount of oxygen (ml)
H: Storage days (days) = 14 (days)
I: Surface area of the film sample (m ² )

Moreover, the surface area of the film sample was calculated | required from the following formula | equation (II).
I = J / (K × L) (II)
here,
J: Weight of film sample (g)
K: Sample thickness (μm)
L: Density of film sample (g / cm ³ )

  On the other hand, 0.1 g of the film obtained above is precisely weighed, wound up in a roll shape 5 hours after molding, and filled with air containing oxygen and nitrogen at 23 ° C., 50% RH, and a volume ratio of 21:79. In a standard bottle with a volume of 85 ml. In order to set the internal relative humidity to 100% RH, a filter paper soaked with water was put together. The mouth of the standard bottle was sealed with an epoxy resin using a multilayer sheet containing an aluminum layer and allowed to stand at 60 ° C. Next, the internal air was sampled with a syringe over time, and the oxygen concentration was measured by gas chromatography. The holes generated in the multilayer sheet at the time of sampling were sealed every time using an epoxy resin. The amount of oxygen decrease was calculated from the volume ratio of oxygen and nitrogen obtained by the measurement, and the amount of oxygen absorbed in the film at 60 ° C. and 100% RH was determined. The amount of oxygen absorbed (integrated amount) 30 days after the encapsulation was 59.2 ml / g.

  About the oxygen-absorbing resin composition (p-1), when the order unit of the odor component was evaluated, an aliphatic linear saturated fatty acid having 4 to 8 carbon atoms and an aliphatic linear saturated aldehyde having 6 to 9 carbon atoms. The total order unit was 12288. The results are shown in Table 1.

  When the sensory test was done about the film obtained above, the change in the taste of water was not felt.

(Example 2)
Except that the amount of cobalt stearate (II) was 0.2121 parts by mass (0.02 parts by mass as cobalt atoms), an oxygen-absorbing resin composition pellet was obtained in the same procedure as in Example 1, and was carried out. Films were prepared and evaluated in the same procedure as in Example 1. The results are shown in Table 1.

(Example 3)
Except that the amount of cobalt stearate (II) was 0.1061 parts by mass (0.01 parts by mass as cobalt atoms), an oxygen-absorbing resin composition pellet was obtained in the same procedure as in Example 1, and was carried out. Films were prepared and evaluated in the same procedure as in Example 1. The results are shown in Table 1.

(Comparative Example 1)
(Preparation of oxygen-absorbing resin composition)
The same procedure as in Example 1 except that 20 parts by mass of pure water was not supplied from the water supply port into the twin-screw extruder and water was not removed from the vent port to the outside of the twin-screw extruder during melt kneading. Thus, pellets of an oxygen-absorbing resin composition (hereinafter referred to as oxygen-absorbing resin composition (p-2)) composed of EVOH (d-1), polyoctenylene (a-1), and cobalt stearate were obtained. .

  The resin temperature during melt kneading was 258 ° C. Further, when the moisture content of the oxygen-absorbing resin composition (p-2) immediately after being discharged from the die hole of the twin-screw extruder was measured using a halogen moisture meter HR73 manufactured by METTLER TOLEDO Co., Ltd., 0.17 It was mass%.

(Preparation and evaluation of film)
The pellets of the oxygen-absorbing resin composition (p-2) were melt-extruded from a coat hanger die at 210 ° C. using a 20 mmφ single screw extruder to obtain a film having a thickness of 20 μm.

  When the cut surface of the film was observed by SEM, polyoctenylene (a-1) having a particle diameter of 1 μm or less was dispersed in a matrix composed of EVOH (d-1).

  0.2 g of the obtained film was precisely weighed, and the oxygen absorption rate and the oxygen absorption amount were determined in the same procedure as in Example 1. The results are shown in Table 1.

  About the oxygen-absorbing resin composition (p-2), when the order unit of the odor component was evaluated, an aliphatic linear saturated fatty acid having 4 to 8 carbon atoms and an aliphatic linear saturated aldehyde having 6 to 9 carbon atoms. The total order unit was 16720. The results are shown in Table 1.

  When the sensory test was performed on the film obtained above, a slight change in the taste of water was felt.

(Comparative Example 2)
Except that the screw rotation speed of the twin screw extruder was 130 rpm, an oxygen-absorbing resin composition pellet was obtained in the same procedure as in Comparative Example 1, and a film was prepared and evaluated in the same procedure as in Example 1. Went. The results are shown in Table 1.

  According to the present invention, an oxygen-absorbing resin composition having an excellent oxygen absorption function (high oxygen absorption amount and high oxygen absorption rate), no unpleasant odor due to oxygen absorption, and excellent workability And an oxygen-absorbing resin composition having the excellent properties described above. Therefore, the oxygen-absorbing resin composition obtained by the method of the present invention is useful as a packaging material for contents (for example, foods, beverages, pharmaceuticals, cosmetics, etc.) that are easily deteriorated by the influence of oxygen.

Claims (11)

A method for producing an oxygen-absorbing resin composition using a twin screw extruder,
Including a step of melt-kneading a resin raw material in the extruder,
The resin raw material is at least one gas barrier resin selected from the group consisting of a thermoplastic resin (A) having a carbon-carbon double bond, a polyvinyl chloride resin, a polyacrylonitrile resin, and a polyvinyl alcohol resin. (D) and
The extruder includes two or more supply ports, and a vent port downstream of the supply ports,
The resin raw material is supplied from a first supply port that is most upstream of the extruder, and water is supplied from a second supply port that is downstream of the first supply port, and is removed from the vent port.
Method.   The method according to claim 1, wherein the water is supplied in an amount of 1 to 50 mass% when the resin raw material is 100 mass%.   The method according to claim 1 or 2, wherein nitrogen gas is further supplied from the first supply port or a third supply port between the first supply port and the second supply port.   The method according to any one of claims 1 to 3, wherein a resin temperature in the extruder is 250 ° C or lower.   The method according to any one of claims 1 to 4, wherein a moisture content of the oxygen-absorbing resin composition is 0.6% by mass or less.   The method according to any one of claims 1 to 5, wherein the thermoplastic resin (A) has a carbon-carbon double bond substantially only in the main chain.   The method according to claim 6, wherein the thermoplastic resin (A) is polyoctenylene.   The method according to any one of claims 1 to 7, wherein the gas barrier resin (D) is an ethylene-vinyl alcohol copolymer having an ethylene content of 5 to 60 mol% and a saponification degree of 90% or more.   The method according to any one of claims 1 to 8, wherein the resin raw material further contains a transition metal salt (C).   The method according to claim 9, wherein the transition metal salt (C) is at least one metal salt selected from the group consisting of an iron salt, a nickel salt, a copper salt, a manganese salt, and a cobalt salt.   An oxygen-absorbing resin composition produced by the method according to any one of claims 1 to 10.