JP2011136766A - Preservation method of cooked rice - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a preservation method which enables sterile cooked rice to be well preserved for a long time without degradation in taste. <P>SOLUTION: The preservation method of cooked rice is for storing the cooked rice in an oxygen-absorbing container employing, in the entire container or a part of the container, an oxygen-absorbing multilayer material comprising at least three layers including a sealant layer made of polyolefin resin, an oxygen-absorbing layer containing polyolefin resin, a transition metal catalyst and polyamide resin, and a gas barrier layer made of a gas barrier material which are laminated from the inward in the order named. The polyamide resin has a terminal amino group concentration obtained by polycondensing aromatic diamine with dicarboxylic acid of 30 μeq/g or less, and the sum of the contents of the transition metal catalyst and the polyamide resin in the oxygen-absorbing layer is 15-60 wt.% relative to the total amount of the oxygen-absorbing layer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention shows an excellent oxygen absorption performance, does not cause a decrease in strength due to oxidative degradation of the resin, is excellent in resin processability, has good transparency, and has no odor generation. It relates to a method for preserving cooked rice used throughout.

  Conventionally, containers such as metal cans, glass bottles, and various plastic packages have been known as packaging containers, but quality deterioration due to oxygen in the packaging containers has been a problem. For this reason, in recent years, as one of the deoxygenation packaging technologies, a container is constituted by a multilayer material in which an oxygen absorption layer composed of an oxygen absorption resin composition in which an iron-based oxygen absorber is blended with a thermoplastic resin is provided. Development of packaging containers in which the gas barrier property is improved and the container itself is provided with an oxygen absorbing function has been performed. For example, an oxygen-absorbing multilayer film is a thermoplastic in which an oxygen absorbent is dispersed between a conventional gas-barrier multilayer film in which a heat seal layer and a gas barrier layer are laminated, and optionally through an intermediate layer made of a thermoplastic resin. It is used as a resin layer with an oxygen absorption layer added to the outside to prevent oxygen permeation, and to absorb oxygen in the container. It is manufactured using a method (see Patent Document 1).

  On the other hand, retort cooked rice was the mainstream as a method for storing commercially processed cooked cooked rice. However, in this manufacturing method, since heat sterilization is performed under conditions different from normal rice cooking conditions, there is a problem that the taste is poor. Therefore, aseptic rice has been commercialized by processing rice using a normal rice cooking method in an aseptic environment. In recent years, a technique for packaging this sterile cooked rice with a multilayer body having an oxygen absorption function has been disclosed (see Patent Document 2). Furthermore, the manufacturing method of the rice cooking rice which fills rice and water in a deoxidization multilayer container, is sealed after replacing oxygen in a container, and cooks by heating is disclosed (refer patent document 3).

  However, those using an oxygen absorber such as iron powder are detected by metal detectors used to detect foreign substances such as food, and when used as a lid material, iron powder adheres to the flange part when opened, workability However, since it was inferior to transparency, it had the subject that there was no content visibility.

  On the other hand, in a composition composed of a polymer and having an oxygen scavenging property, a resin composition comprising a polyamide, particularly a xylylene group-containing polyamide and a transition metal, is known as an oxidizable organic component, and a resin composition having an oxygen scavenging function or There are also examples of oxygen absorbers obtained by molding the resin composition, packaging materials, and multilayer laminated films for packaging (see Patent Documents 4 to 8).

  However, a resin composition containing a transition metal catalyst and oxidizing a polyamide resin or the like to develop an oxygen absorbing function oxidizes the xylylene group-containing polyamide resin, resulting in a decrease in strength due to oxidative degradation of the resin, and the packaging container itself There is a problem that the strength of the glass is reduced.

  Furthermore, there is an example of MXD6, which is a polyamide obtained by polycondensation of metaxylylenediamine and adipic acid, which shows an oxidation reaction with a polyamide resin and a transition metal catalyst, but a system in which transition metal is mixed with MXD6 Then, in order to preserve | save an object to be preserve | saved favorably using it as an oxygen absorption resin composition, there existed a case where oxygen absorption capability was low. In addition, a system in which transition metal is mixed with MXD6 usually uses a blend of a polyester resin such as polyethylene terephthalate (hereinafter referred to as PET) or a resin having a relatively high melting point such as nylon 6.

Japanese Patent Laid-Open No. 9-234832 JP-A-8-133345 JP-A-7-39329 Japanese Patent Laid-Open No. 5-140555 JP 2001-252560 A JP 2003-341747 A JP 2005-119893 A JP 2001-179090 A

  The object of the present invention is to improve the flavor of cooked rice by using an oxygen-absorbing multilayer body excellent in oxygen absorption performance, resin strength, resin processability and transparency, which solves the above-mentioned problems, in a part or the whole of a container. It is to provide a method for preserving cooked rice.

  The present inventors blend specific polyamides, transition metals and polyolefin resins in specific proportions, so that they have excellent oxygen absorption performance, retain resin strength after storage, and are excellent in workability and transparency. It was found that the flavor of cooked rice was preserved well over a long period of time by storing the cooked rice using the oxygen-absorbing multilayer body in a part or the whole of the container.

  That is, the present invention comprises at least three layers of cooked rice in order from the inside: a sealant layer made of a polyolefin resin, an oxygen absorbing layer containing a polyolefin resin, a transition metal catalyst, and a polyamide resin, and a gas barrier layer made of a gas barrier material. A method for storing cooked rice which is stored in an oxygen-absorbing container using all or part of a laminated oxygen-absorbing multilayer body, wherein the polyamide resin is obtained by polycondensation of an aromatic diamine and a dicarboxylic acid Cooked rice having a terminal amino group concentration of 30 μeq / g or less and a total content of the transition metal catalyst and the polyamide resin in the oxygen absorption layer of 15 to 60% by weight based on the total amount of the oxygen absorption layer This is a storage method.

  According to the present invention, the oxygen-absorbing multilayer body having high oxygen absorption performance and almost no deterioration in strength due to oxidation of the polyamide resin is used for all or part of the rice storage container, and the flavor of the cooked rice is good for a long period of time. A method for storing cooked rice can be provided.

  In the present invention, the cooked rice is sealed and stored in an oxygen-absorbing container using part or all of the oxygen-absorbing multilayer body.

  Examples of the cooked rice in the present invention include sterile cooked rice cooked in an aseptic environment, or cooked rice cooked in a pressure heating kettle after filling and sealing the rice and water in an oxygen-absorbing container. In order to maintain the flavor, cooked rice cooked at a heating temperature of 110 ° C. or less is filled in the oxygen-absorbing container of the present invention and sealed, but the inside of the container is replaced with an inert gas such as nitrogen gas or carbon dioxide during filling. The oxygen concentration may be reduced.

  The oxygen-absorbing multilayer body of the present invention comprises a polyamide resin obtained by laminating at least three layers of a sealant layer, an oxygen-absorbing layer and a gas barrier layer in this order, and the oxygen-absorbing layer is obtained by polycondensation of an aromatic diamine and a dicarboxylic acid. An oxygen-absorbing resin composition comprising a polyamide resin having a terminal amino group concentration of 30 μeq / g or less (hereinafter, the polyamide resin is particularly referred to as “polyamide resin A”), a transition metal catalyst, and a polyolefin resin. This is an oxygen-absorbing multilayer body made of a material. Details of each layer and each composition will be described.

  Polyolefin resins used in the sealant layer of the present invention include high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, various polyethylenes such as polyethylene using a metallocene catalyst, polystyrene, polymethyl Polypropylenes such as pentene, propylene homopolymer, propylene-ethylene block copolymer and propylene-ethylene random copolymer can be used alone or in combination. These polyolefin resins include ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, if necessary. A polymer, an ethylene-methyl methacrylate copolymer, or a thermoplastic elastomer may be added. The melt flow rate (hereinafter referred to as MFR) of the thermoplastic resin is 1 to 35 g / 10 min at 200 ° C. and 2 to 45 g / 10 min at 240 ° C., considering the processability of the multilayer body. Preferably used. In addition, MFR as used in this specification is MFR of the said resin measured on the conditions of the load of 2160g in specific temperature using the apparatus based on JISK7210, unless there is particular notice, "g / 10. Expressed with the measured temperature in units of minutes.

  The polyolefin resin used in the sealant layer of the present invention is filled with coloring pigments such as titanium oxide, additives such as antioxidants, slip agents, antistatic agents, stabilizers, calcium carbonate, clay, mica, silica, etc. An agent, deodorant, etc. may be added. In particular, it is preferable to add an antioxidant in order to recycle and reprocess offcuts generated during production.

  The oxygen absorption performance of the oxygen absorbing layer is considered to be better when there are more polyamide resins having oxygen absorbing ability, but surprisingly, when the polyamide resin A, transition metal and polyolefin resin are blended at a certain ratio, It has been found that it exhibits a high oxygen absorption capacity.

  The polyamide resin A in the present invention is obtained by polycondensation of an aromatic diamine and a dicarboxylic acid. The polycondensation of the aromatic diamine and the dicarboxylic acid can proceed by melt polymerization for melting the aromatic diamine and dicarboxylic acid, solid phase polymerization for heating the polyamide resin pellets, or the like under reduced pressure.

  Examples of the aromatic diamine in obtaining the polyamide resin A include orthoxylylenediamine, paraxylylenediamine, and metaxylylenediamine, but paraxylylenediamine, metaxylylenediamine, or these from the viewpoint of oxygen absorption performance. A mixture is preferably used, and metaxylylenediamine is particularly preferably used. In addition, various aliphatic diamines and aromatic diamines may be incorporated as copolymerization components as long as the performance is not affected.

  Examples of the dicarboxylic acid for obtaining the polyamide resin A include adipic acid, azelaic acid, sebacic acid, dodecanoic acid, isophthalic acid, terephthalic acid, and malonic acid. Among these, from the viewpoint of oxygen absorption performance, adipic acid, sebacic acid, isophthalic acid or a mixture thereof is preferable, and a mixture of adipic acid and sebacic acid or a mixture of adipic acid and isophthalic acid is particularly preferable. The molar ratio in the case of using a mixture of adipic acid and sebacic acid is preferably sebacic acid: adipic acid = 0.3-0.7: 0.7-0.3, and 0.4-0.6: 0.6 -0.4 is particularly preferred. Further, when using a mixture of adipic acid and isophthalic acid, adipic acid: isophthalic acid is preferably 0.7 to 0.97: 0.3 to 0.03, and 0.8 to 0.95: 0.2 to 0 .05 is particularly preferred. In addition, various aliphatic dicarboxylic acids and aromatic dicarboxylic acids may be incorporated as copolymerization components as long as the performance is not affected.

  The polyamide resin A in the present invention is a polyamide resin having a terminal amino group concentration of 30 μeq / g or less obtained by polycondensation of at least an aromatic diamine and a dicarboxylic acid, but has a terminal amino group concentration of 25 μeq / g or less. And oxygen absorption performance are improved, and it is more preferably 20 μeq / g or less because oxygen absorption performance is further improved. Thus, the oxygen absorption performance tends to improve as the terminal amino group concentration decreases, and it is preferable to reduce the concentration as much as possible. However, in consideration of economic rationality, the lower limit is 5 μeq / g or more. It is preferable to do. If the terminal amino group concentration is higher than 30 μeq / g, good oxygen absorption performance cannot be obtained.

In order to reduce the terminal amino group concentration of the polyamide resin to 30 μeq / g or less,
1) Method for carrying out polycondensation by adjusting the molar ratio of aromatic diamine and dicarboxylic acid 2) Method for reacting polyamide resin with carboxylic acid to seal the terminal amino group 3) Method for solid-phase polymerization of polyamide resin These methods are preferably carried out, and these methods can be carried out alone or in combination. In particular, it is preferable to combine the methods 1), 3), 2) and 3) because a polyamide resin having better oxygen absorption performance and moldability during film production can be obtained. Hereinafter, these methods will be described.

  1) In the method of carrying out polycondensation by adjusting the molar ratio of aromatic diamine and dicarboxylic acid, dicarboxylic acid is used excessively with respect to aromatic diamine. Specifically, aromatic diamine and dicarboxylic acid are used. The molar ratio (aromatic diamine / dicarboxylic acid) is preferably 0.985 to 0.997, particularly preferably 0.988 to 0.995. When the molar ratio is less than 0.985, it is difficult to increase the degree of polymerization of the polyamide resin.

  2) In the method of reacting the polyamide resin with carboxylic acid to seal the terminal amino group, the terminal amino group concentration of the polyamide resin is reacted with the carboxylic acid to adjust the terminal amino group concentration. The carboxylic acid to be used is not particularly limited, but a carboxylic anhydride is preferable, and specifically, phthalic anhydride, maleic anhydride, benzoic anhydride, glutaric anhydride, itaconic anhydride, citraconic anhydride, acetic anhydride, anhydrous Examples include butyric acid, isobutyric anhydride, trimellitic anhydride, pyromellitic anhydride, and the like. The polyamide resin and the carboxylic acid can be reacted by, for example, a method of adding at the time of melt polymerization or a method of adding a carboxylic acid to the polyamide resin obtained by melt polymerization and then melt-kneading the polyamide resin. In order to increase the degree of polymerization, melt kneading is preferred.

  3) In the method of solid-phase polymerization of polyamide resin, the terminal amino group concentration is adjusted by further subjecting the polyamide resin obtained by melt polymerization to a solid-phase polymerization reaction. Solid phase polymerization proceeds by heating polyamide resin pellets under reduced pressure. The pressure during the solid phase polymerization is preferably 100 torr or less, and more preferably 30 torr or less. Further, the temperature at the time of solid phase polymerization needs to be 130 ° C. or higher, more preferably 150 ° C. or higher, and preferably 10 ° C. or higher, more preferably 15 ° C. or lower than the melting point of the polyamide resin. The solid state polymerization time is preferably 3 hours or more. By performing solid phase polymerization, the terminal amino group concentration of the polyamide resin is decreased, the molecular weight is increased, and the viscosity can be adjusted.

  As the polyamide resin A of the present invention, those having low crystallinity are preferably used. Specifically, those having a low crystallinity with a half-crystallization time of 150 seconds or more, or those having no melting point peak when the melting point is measured by DSC are preferable. When the half crystallization time of the polyamide resin A is 150 seconds or more, higher oxygen absorption performance can be obtained.

  Further, the polyamide resin A preferably has a low melting point and glass transition temperature (hereinafter referred to as Tg) in consideration of processability and oxygen absorption performance with a polyolefin resin. The melting point of the polyamide resin A is preferably 200 ° C. or lower, more preferably 190 ° C. or lower or a resin having no melting point. Tg is preferably 90 ° C. or lower, and particularly preferably 80 ° C. or lower.

The oxygen permeability coefficient of the polyamide resin A is preferably 0.2 to 1.5 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH), and 0.3 to 1.0 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH) is more preferable. When the oxygen permeability coefficient is 0.2 to 1.5 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH), when the polyamide resin A and the polyolefin resin are blended, higher oxygen absorption performance is obtained. can get.

  When the polyamide resin A and the polyolefin resin are mixed, considering the processability, the melt flow rate (hereinafter referred to as MFR) of the polyamide resin A is 200 ° C., 3 to 20 g / 10 minutes, 240 ° C., 4 Those having ˜25 g / 10 min are preferably used. In this case, when the resin is processed at a temperature where the difference between the MFR of the polyolefin resin and the MFR of the polyamide resin A is ± 20 g / 10 minutes, preferably ± 10 g / 10 minutes, the kneaded state becomes good, and a film or sheet is obtained. In this case, a processed product having no problem in appearance can be obtained. The MFR of the polyamide resin A can be adjusted by adjusting the molecular weight, for example. Examples of a method for adjusting the molecular weight include a method of adding a phosphorus compound as a polymerization accelerator and a method of solid-phase polymerization after melt polymerization of the polyamide resin A.

  The polyamide resin A obtained by polycondensation of an aromatic diamine and a dicarboxylic acid is preferably synthesized by a method that undergoes two steps of solid phase polymerization after melt polymerization. The number average molecular weight of the polyamide resin A is preferably 18000 to 27000, particularly preferably 20000 to 26000.

  You may add a stabilizer etc. to the polyamide resin A obtained by this invention suitably. In particular, phosphorus compounds are preferably used as stabilizers, and specifically, diphosphites are preferable. The phosphorus compound is preferably not more than 200 ppm, particularly preferably not more than 100 ppm because the polyamide resin A is stable and affects the oxygen absorption performance.

The polyolefin resin used for the oxygen absorbing layer in the present invention is a high density polyethylene, a medium density polyethylene, a low density polyethylene, a linear low density polyethylene, an ultra low density polyethylene, various polyethylenes such as a metallocene catalyst polyethylene, polystyrene, etc. Polypropylenes such as polymethylpentene, propylene homopolymer, propylene-ethylene block copolymer, propylene-ethylene random copolymer can be used alone or in combination. Among these polyolefin resins, from the viewpoint of oxygen absorption performance, the oxygen permeability coefficient is preferably 80 to 200 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH). When the polyolefin resin is used, good oxygen absorption performance can be obtained. Due to oxygen absorption performance and film processability, polyolefin resins include high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, various polyethylenes such as polyethylene using a metallocene catalyst, and propylene-ethylene block copolymers. Various polypropylenes such as propylene-ethylene random copolymer are particularly preferably used. These polyolefin resins include ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, if necessary. A polymer, an ethylene-methyl methacrylate copolymer, or a thermoplastic elastomer may be added.

  In consideration of the miscibility with the polyamide resin A, it is particularly preferable to add a maleic anhydride-modified polyolefin resin or an epoxy group-containing polyolefin resin. The addition amount of the maleic anhydride-modified polyolefin resin or the epoxy group-containing polyolefin resin is preferably from 1 to 30 wt%, particularly preferably from 3 to 15 wt%, based on the polyolefin resin.

  Further, the polyolefin resin of the present invention includes coloring pigments such as titanium oxide, additives such as antioxidants, slip agents, antistatic agents, stabilizers, fillers such as calcium carbonate, clay, mica, silica, and deodorants. An agent or the like may be added. In particular, it is preferable to add an antioxidant in order to recycle and reprocess offcuts generated during production.

  Examples of the transition metal catalyst used in the present invention include compounds of a first transition element such as Fe, Mn, Co, and Cu. Further, transition metal organic acid salts, chlorides, phosphates, phosphites, hypophosphites, nitrates and the like alone or a mixture thereof can be cited as examples of transition metal catalysts. Examples of the organic acid include salts of C2-C22 aliphatic alkyl acids such as acetic acid, propionic acid, octanoic acid, lauric acid, stearic acid, or malonic acid, succinic acid, adipic acid, sebacic acid, hexahydrophthalic acid A salt of a dibasic acid, a salt of butanetetracarboxylic acid, benzoic acid, toluic acid, o-phthalic acid, isophthalic acid, terephthalic acid, trimesic acid alone or a mixture thereof. Among the transition metal catalysts, an organic acid salt of Co is preferable from the viewpoint of oxygen absorption, and Co stearate is particularly preferable from the viewpoint of safety and workability.

  The transition metal catalyst is preferably added to the polyamide resin A and then mixed with the polyolefin resin. The transition metal catalyst is preferably added so that the concentration of all transition metals in the catalyst with respect to the polyamide resin A is 10 ppm to 5000 ppm, preferably 50 ppm to 3000 ppm. In this case, compared with the case where the addition amount is out of the above range, the oxygen absorption performance of the polyamide resin A can be improved, and the deterioration of the resin processability due to the decrease in the viscosity can be prevented.

Another method for producing the oxygen-absorbing resin composition of the present invention is preferably a method for producing an oxygen-absorbing resin composition in which a masterbatch containing a polyolefin resin and a transition metal catalyst and a polyamide resin are melt-kneaded.
The transition metal catalyst is kneaded with the polyolefin resin to produce a master batch, and then melt mixed with the polyamide resin A to obtain an oxygen-absorbing resin composition. The transition metal catalyst is added so that the concentration of all transition metals in the catalyst with respect to the polyolefin resin is preferably 200 ppm to 5000 ppm, more preferably 300 ppm to 3000 ppm. In this case, the oxygen absorption performance of the polyamide resin A can be enhanced as compared with the case where the addition amount is out of the above range. Moreover, when it exceeds 5000 ppm, it may become difficult to manufacture a masterbatch, and it may become impossible to manufacture what has a uniform property. If a transition metal catalyst is added to the polyamide resin A, the resin processability is deteriorated due to a decrease in the viscosity of the polyamide resin A.

  The total content of the transition metal catalyst and the polyamide resin A in the oxygen absorbing layer is 15 to 60% by weight, preferably 17 to 60% by weight, more preferably 20 to 60% by weight, and particularly preferably 25 to 50% by weight. preferable. When the content of the polyamide resin A containing the transition metal catalyst in the oxygen-absorbing resin composition is less than 15% by weight or exceeds 60% by weight, the oxygen-absorbing ability is lowered. On the other hand, if it exceeds 60% by weight, resin degradation due to oxidation of the polyamide resin A occurs, causing problems such as strength reduction.

  Examples of the gas barrier material used for the gas barrier layer in the oxygen absorbing multilayer body constituting the oxygen absorbing container of the present invention include various deposited films such as silica, alumina, and aluminum, ethylene-vinyl alcohol copolymer, MXD6, and polyvinylidene chloride. A known gas barrier material such as a gas barrier resin such as an amine-epoxy curing agent or a metal foil such as an aluminum foil is used.

  As the gas barrier resin, the thickness when the thermoplastic resin is used for the gas barrier layer is preferably 5 to 200 μm, particularly preferably 10 to 100 μm. Further, when a thermosetting resin such as an amine-epoxy curing agent is used for the gas barrier adhesive layer as the gas barrier resin, 0.1 to 100 μm is preferable, and 0.5 to 20 μm is particularly preferable. When the thickness is within the above range, the gas barrier property can be further improved and the workability and economy can be prevented from being impaired as compared with the case where the thickness is not within the above range.

  Although there is no restriction | limiting in particular in the thickness of an oxygen absorption layer, 5-100 micrometers is preferable and 10-50 micrometers is especially preferable. In this case, as compared with the case where the thickness is out of the above range, it is possible to further improve the performance of the oxygen absorbing layer to absorb oxygen and to prevent the workability and economy from being impaired. Further, the thickness of the sealant layer is preferably less because the sealant layer becomes an isolation layer from the oxygen absorbing layer, but is particularly preferably 2 to 50 μm, and particularly preferably 5 to 30 μm. In this case, compared with the case where the thickness is out of the above range, it is possible to increase the rate of absorbing oxygen in the oxygen absorbing layer and to prevent the workability from being impaired. When processing into a film or sheet, considering the workability, the thickness ratio of the sealant layer and the oxygen absorbing layer is preferably 1: 0.5 to 1: 3, and 1: 1 to 1: 2.5. Particularly preferred.

  In consideration of the workability of the oxygen-absorbing container, an intermediate layer containing a polyolefin resin is preferably interposed between the gas barrier layer containing the gas barrier substance and the oxygen-absorbing layer. The thickness of the intermediate layer is preferably substantially the same as the thickness of the sealant layer from the viewpoint of workability. In this case, considering variations due to processing, the thickness is the same if the thickness ratio is within ± 10%.

  The oxygen-absorbing container in the present invention may be a container composed entirely of an oxygen-absorbing multilayer body, but at least a gas barrier molded container or gas barrier film composed of a thermoplastic resin inner layer, a gas barrier layer, and a thermoplastic resin outer layer, and an oxygen-absorbing multilayer body. And may be used in combination.

  A thermoplastic resin is used for the outer thermoplastic resin layer and the inner thermoplastic resin layer constituting the gas barrier molded container or the gas barrier film. The thermoplastic resins used include high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, various polyethylenes such as polyethylene using a metallocene catalyst, polystyrene, and ethylene-vinyl acetate copolymer. Polymer, ionomer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, polymethylpentene , Propylene homopolymer, propylene-ethylene block copolymer, propylene-ethylene random copolymer, various polypropylenes such as polypropylene by metallocene catalyst, thermoplastic elastomer, polyethylene terephthalate, nylon, etc. It can be used alone or in combination.

  A gas barrier material is used for the gas barrier layer constituting the gas barrier molded container or the gas barrier film. Examples of the gas barrier substance include ethylene-vinyl alcohol copolymer, nylon MXD6, polyvinylidene chloride, and aluminum. Nylon MXD6 is particularly preferably used for heat treatment at 80 ° C. or higher such as retort or boil sterilization. A nylon MXD6 resin composition in which amorphous nylon is mixed with nylon MXD6 may be used.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In the examples and comparative examples, various physical property values were measured by the following measuring methods and measuring apparatuses.

(Measurement method of Tg)
Tg was measured according to JIS K7122. The measuring apparatus used was “DSC-60” manufactured by Shimadzu Corporation.

(Measuring method of melting point)
The melting point was determined by measuring the DSC melting peak temperature according to ISO11357. The measuring apparatus used was “DSC-60” manufactured by Shimadzu Corporation.

(Measurement method of number average molecular weight)
The number average molecular weight was measured by GPC-LALLS. As a measuring apparatus, “Shodex GPC-2001” manufactured by Showa Denko KK was used.

(Measurement method of MFR)
The MFR of each resin is measured under a load of 2160 g at a specific temperature using an apparatus in accordance with JIS K7210 (“Melt Indexer” manufactured by Toyo Seiki Seisakusho Co., Ltd.), and the value is described together with the temperature. (Unit: “g / 10 min”). In addition, when MFR was measured based on JISK7210, it was described that much.

(Measurement method of oxygen permeability coefficient)
The oxygen transmission coefficient was measured using “OX-TRAN-2 / 21” manufactured by MOCON under the conditions of 23 ° C., 60% RH and a cell area of 50 cm ² .

(Method for measuring terminal amino group concentration)
0.5 g of sample was dissolved in 30 mL of phenol / ethanol = 4/1 (volume ratio), 5 mL of methanol was added, and an automatic titrator with 0.01 N hydrochloric acid as a titrant (“COM-2000” manufactured by Hiranuma Seisakusho) Titration with The same operation titrated without adding a sample was used as a blank, and the terminal amino group concentration was calculated from the following formula.
Terminal amino group concentration (μeq / g) = (A−B) × f × 10 / C
(A: titer (mL), B: blank titer (mL), f: factor of normal solution, C: sample amount (g)).

(Measurement method of terminal carboxyl group concentration)
0.5 g of a sample was dissolved in 30 mL of benzyl alcohol, 10 mL of methanol was added, and titrated with an automatic titration apparatus (“COM-2000” manufactured by Hiranuma Seisakusho) with 0.01 N sodium hydroxide solution as a titrant. The same operation titrated without adding a sample was used as a blank, and the terminal carboxyl group concentration was calculated from the following formula.
Terminal carboxyl group concentration (μeq / g) = (A−B) × f × 10 / C
(A: titer (mL), B: blank titer (mL), f: factor of normal solution, C: sample amount (g)).

(Measurement method of semi-crystallization time)
When the pellet is melted at each temperature and the resin is crystallized at each temperature, the time for all to crystallize is called the crystallization time, and the time for reaching 50% crystallization is called the semi-crystallization time. The half crystallization time was measured by the depolarized intensity method. That is, when the sample pellets are irradiated with light and the sample pellets are crystallized, the amount of light transmission decreases and becomes stable when the amount of light transmission is stabilized. The time is defined as the crystallization time, and the amount of light transmission is 50%. The time to reach was defined as the half crystallization time. Although the crystallization time and the half crystallization time differ depending on the measurement temperature, in the following description, among the half crystallization times at each temperature, the one with the shortest half crystallization time is referred to as “half crystallization time”. Described. In addition, a “polymer crystallization rate measuring apparatus MK-701 type” manufactured by Kotaki was used to measure the crystallization time and the semi-crystallization time.

(Synthesis conditions by melt polymerization of polyamide resin)
After heating and melting the dicarboxylic acid in a reaction can at 170 ° C., the aromatic diamine is gradually and continuously added so that the molar ratio of the dicarboxylic acid to the dicarboxylic acid is about 1: 1 while stirring the contents. And the temperature was raised to 240 ° C. After completion of dropping, the temperature was raised to 260 ° C. and the reaction was continued. After completion of the reaction, the inside of the reaction can was slightly pressurized with nitrogen, the strand was extruded from a die head having holes, and pelletized with a pelletizer.

(Synthesis conditions by solid phase polymerization of polyamide resin)
The pellets obtained by melt polymerization by the above method were charged into a rotary tumbler equipped with a heating device, the pressure inside the tumbler was reduced to 1 torr or less while rotating, and the operation of bringing the pressure to normal pressure with nitrogen was performed three times. Thereafter, the inside of the apparatus was heated while rotating the tumbler to 30 torr or less, the inside of the apparatus was adjusted to 150 ° C. or more, and the reaction was performed at that temperature for a predetermined time. Then, it cooled to 60 degreeC and obtained the polyamide resin.

(Example 1)
Polyamide resin was synthesized by performing melt polymerization and solid phase polymerization under the above synthesis conditions using metaxylylenediamine: sebacic acid: adipic acid in a molar ratio of 0.994: 0.5: 0.5. (Hereinafter, the polyamide resin is referred to as polyamide 1). The dropping time was 2 hours, the reaction time for melt polymerization was 1 hour, the pressure in the apparatus during solid phase polymerization was 1 torr or less, the polymerization temperature was 160 ° C., and the polymerization time was 4 hours. Polyamide 1 has a Tg of 71 ° C., a melting point of 176 ° C., a semicrystallization time of 2000 seconds or more, a terminal amino group concentration of 18.9 μeq / g, a terminal carboxyl group concentration of 83.3 μeq / g, a number average molecular weight of 23500, and an MFR of 240 ° C. It was 10.7 g / 10 minutes. Moreover, when the unstretched film was produced with the obtained polyamide 1 alone and the oxygen transmission coefficient was determined, it was 0.35 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH). . These results are shown in Table 1.

  Cobalt stearate was added to polyamide 1 as a transition metal catalyst by a side feed to molten polyamide 1 with a twin screw extruder so as to have a cobalt concentration of 400 ppm. Furthermore, an ethylene-propylene random copolymer (product name: Sun Allomer Co., Ltd. “PC540R”) was used as a polyolefin resin in a mixture of the obtained polyamide and cobalt stearate (hereinafter referred to as cobalt stearate-containing polyamide 1). , 230 ° C. MFR 5.0 g / 10 min (measured according to JIS K7210), hereinafter referred to as PP1), melted at 240 ° C. in a weight ratio of cobalt stearate-containing polyamide 1: PP1 = 30: 70 It knead | mixed and the pellet which consists of oxygen absorption resin composition A was obtained.

  The obtained oxygen-absorbing resin composition A was used as an oxygen-absorbing layer, PP1 was used as a sealant layer, and a two-layer two-layer film 1 (thickness; oxygen-absorbing layer 25 μm / sealant layer 25 μm) having a width of 800 mm and 100 m / min Then, the oxygen absorbing layer surface was subjected to corona discharge treatment to produce a film roll. The film roll had no uneven thickness such as bumps, the appearance of the obtained film was good, and the HAZE was 72%. Nylon film A (product name; manufactured by Toyobo Co., Ltd.) using urethane-type dry laminate adhesive (product name: “AD817 / CAT-RT86L-60” manufactured by Toyo Morton Co., Ltd.) on the corona-treated surface side. N1202 ”) and alumina vapor-deposited PET (product name:“ GL-AEH ”manufactured by Toppan Printing Co., Ltd.), and alumina vapor-deposited PET (12) / adhesive (3) / nylon film A (15) / adhesive ( 3) An oxygen-absorbing multilayer film comprising an oxygen-absorbing multilayer body of oxygen absorbing resin (25) / PP1 (25) was obtained. The numbers in parentheses mean the thickness of each layer (unit: μm).

  Next, using a three-kind five-layer multi-layer sheet forming apparatus consisting of a first to third extruder, a feed block, a T die, a cooling roll, and a sheet take-up machine, each extruder was used to make a first extruder; Polymer (product name: “NOVATEC PP EG7F” manufactured by Nippon Polypro Co., Ltd., MFR 1.3 g / 10 min (measured according to JIS K7210), 240 ° C. MFR 8.2 g / 10 min, 250 ° C. MFR 9.8 g / 10 minutes, hereinafter referred to as PP2), second extruder; nylon MXD6 (product name; “MX nylon S7007” manufactured by Mitsubishi Gas Chemical Co., Ltd.) and third extruder; maleic anhydride-modified polypropylene (product name; (Modic AP P604, manufactured by Mitsubishi Chemical Corporation) was extruded to obtain a gas barrier multilayer sheet. The composition of the gas barrier multilayer sheet is PP2 (130) / maleic anhydride modified polypropylene (product name: same as above, 15) / nylon MXD6 (product name: same as above, 40) / maleic anhydride modified polypropylene (product name: same as above). 15) / PP2 (300). Further, the multilayer sheet obtained by coextrusion was a multilayer sheet having a good appearance without thickness unevenness.

Next, the obtained gas barrier multilayer sheet was thermoformed into a tray-like container (internal volume 400 cc, surface area 200 cm ² ) using a vacuum forming machine (hereinafter referred to as gas barrier molded container 1). . The obtained gas barrier molded container 1 had good appearance with no thickness unevenness. In this container, 110 g of washed rice and 90 g of sterilized water were placed, and oxygen in the container was replaced with nitrogen gas to make the oxygen concentration 10%. Next, the oxygen-absorbing multilayer film was used as a cover material with the alumina-deposited PET side as the outer surface, and the container was sealed by heat sealing. This container was put into a pressure heating kettle and cooked by heating at 105 ° C. for 40 minutes, and after cooling, stored under conditions of 23 ° C. and 50% RH. After cooling, the oxygen concentration was measured, opened 3 months after the start of storage, and the flavor of cooked rice and the strength of the oxygen absorbing container were confirmed. These results are shown in Table 2.

(Example 2)
An oxygen-absorbing multilayer film was obtained in the same manner as in Example 1 except that the weight ratio at the time of melt kneading was changed to cobalt stearate-containing polyamide 1: PP1 = 20: 80. The same storage test as in Example 1 was performed. These results are shown in Table 2.

(Example 3)
An oxygen-absorbing multilayer film was obtained in the same manner as in Example 1 except that the weight ratio at the time of melt kneading was changed to cobalt stearate-containing polyamide 1: PP1 = 55: 45. The same storage test as in Example 1 was performed. These results are shown in Table 2.

Example 4
An oxygen-absorbing multilayer film was obtained in the same manner as in Example 1 except that the weight ratio at the time of melt kneading was changed to cobalt stearate-containing polyamide 1: PP1 = 16: 84. The same storage test as in Example 1 was performed. These results are shown in Table 2.

(Example 5)
Cobalt stearate was added to PP1 by a side feed to melted PP1 with a twin screw extruder so that the cobalt concentration was 600 ppm. Further, polyamide 1 was melt kneaded at 240 ° C. in a weight ratio of polyamide 1: cobalt stearate-containing PP = 30: 70 to the obtained PP1 and cobalt stearate mixture, and oxygen was added in the same manner as in Example 1. After obtaining the absorption multilayer film, the same storage test as in Example 1 was performed using the gas barrier molded container 1 as a lid. These results are shown in Table 2.

(Example 6)
Polyamide resin was synthesized by performing melt polymerization and solid phase polymerization under the above synthesis conditions using metaxylylenediamine: sebacic acid: adipic acid in a molar ratio of 0.991: 0.4: 0.6. (Hereinafter, the polyamide resin is referred to as polyamide 2). The dropping time was 2 hours, the reaction time for melt polymerization was 1 hour, the pressure in the apparatus during solid phase polymerization was 1 torr or less, the polymerization temperature was 160 ° C., and the polymerization time was 4 hours. Polyamide 2 has a Tg of 75 ° C., a melting point of 183 ° C., a semi-crystallization time of 2000 seconds or more, a terminal amino group concentration of 19.4 μeq / g, a terminal carboxyl group concentration of 91.6 μeq / g, a number average molecular weight of 21,500, and an MFR of 240 ° C. Was 10.8 g / 10 min. Moreover, when an unstretched film was prepared with the obtained polyamide 2 alone and its oxygen permeability coefficient was determined, it was 0.40 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH). . These results are shown in Table 1.

  Thereafter, in the same manner as in Example 1, cobalt stearate was added to a cobalt concentration of 400 ppm, and PP1 was added to the obtained polyamide 2 and cobalt stearate mixture (hereinafter referred to as cobalt stearate-containing polyamide 2). Was melt-kneaded at 240 ° C. in a weight ratio of cobalt stearate-containing polyamide 2: PP1 = 30: 70 to obtain oxygen-absorbing resin pellets. Further, after obtaining an oxygen-absorbing multilayer film in the same manner as in Example 1, the same storage test as in Example 1 was performed using it as a cover material of the gas barrier molded container 1. These results are shown in Table 2.

(Example 7)
Polyamide resin was synthesized by performing melt polymerization and solid phase polymerization under the above-mentioned synthesis conditions using metaxylylenediamine: sebacic acid: adipic acid in a molar ratio of 0.996: 0.3: 0.7. (Hereinafter, the polyamide resin is referred to as polyamide 3). The dropping time was 2 hours, the reaction time for melt polymerization was 1 hour, the pressure in the apparatus during solid phase polymerization was 1 torr or less, the polymerization temperature was 160 ° C., and the polymerization time was 4 hours. Polyamide 3 has a Tg of 77 ° C., a melting point of 190 ° C., a crystallization time of 2000 seconds or more, a terminal amino group concentration of 22.4 μeq / g, a terminal carboxyl group concentration of 82.1 μeq / g, a number average molecular weight of 22000, and an MFR of 240 ° C. It was 11.1 g / 10 minutes. Moreover, when an unstretched film was prepared from the obtained polyamide 3 alone and its oxygen permeability coefficient was determined, it was 0.37 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH). . These results are shown in Table 1.

  Thereafter, in the same manner as in Example 1, cobalt stearate was added so as to have a cobalt concentration of 400 ppm, and PP1 was added to the obtained mixture of polyamide 3 and cobalt stearate (hereinafter referred to as cobalt stearate-containing polyamide 3). Was melt-kneaded at 240 ° C. in a weight ratio of cobalt stearate-containing polyamide 3: PP1 = 30: 70 to obtain oxygen-absorbing resin pellets. Further, after obtaining an oxygen-absorbing multilayer film in the same manner as in Example 1, the same storage test as in Example 1 was performed using it as a cover material of the gas barrier molded container 1. These results are shown in Table 2.

(Example 8)
After using metaxylylenediamine: sebacic acid: adipic acid in a molar ratio of 0.991: 0.9: 0.1 and synthesizing a polyamide resin only by melt polymerization under the above synthesis conditions, anhydrous 0.2 wt% of phthalic acid was added and melt kneaded at 270 ° C. with a twin screw extruder to seal the terminal amino group (hereinafter, the polyamide resin is referred to as polyamide 4). However, the dropping time was 2 hours, the polymerization temperature after completion of dropping of metaxylylenediamine in melt polymerization was 270 ° C., and the reaction time was 30 minutes. This polyamide 4 had a Tg of 83 ° C., a melting point of 227 ° C., a half crystallization time of 375 seconds, a terminal amino group concentration of 23.9 μeq / g, a terminal carboxyl group concentration of 89.3 μeq / g, and a number average molecular weight of 18,500. Moreover, since it was near melting | fusing point in 240 degreeC, MFR was not measurable, MFR of 250 degreeC was measured, and MFR in 250 degreeC was 33.4 g / 10min. An unstretched film was prepared from the obtained polyamide 4 alone, and the oxygen permeability coefficient was determined. The oxygen permeability coefficient was 0.25 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH). there were. These results are shown in Table 1.

  Thereafter, the addition of cobalt stearate to polyamide 4 and melt-kneading with PP1 were carried out in the same manner as in Example 1 except that the temperature at the time of melt-kneading was 250 ° C. After obtaining the absorption multilayer film, the same storage test as in Example 1 was performed using the gas barrier molded container 1 as a lid. These results are shown in Table 2.

Example 9
A polyamide resin was synthesized by performing melt polymerization and solid phase polymerization using metaxylylenediamine: adipic acid: isophthalic acid in a molar ratio of 0.994: 0.95: 0.05 (hereinafter referred to as the polyamide). The resin is denoted as polyamide 5.) The dropping time was 2 hours, the reaction time for melt polymerization was 1 hour, the pressure in the apparatus during solid phase polymerization was 1 torr or less, the polymerization temperature was 205 ° C., and the polymerization time was 10 hours. This polyamide 5 has a Tg of 82 ° C., a melting point of 231 ° C., a semicrystallization time of 295 seconds, a terminal amino group concentration of 16.8 μeq / g, a terminal carboxyl group concentration of 80.5 μeq / g, a number average molecular weight of 25000, and at 240 ° C. Since it was near the melting point, the MFR could not be measured, the MFR at 250 ° C. was measured, and the MFR at 250 ° C. was 12.3 g / 10 minutes. An unstretched film was prepared from the obtained polyamide 5 alone, and the oxygen permeability coefficient was determined. The oxygen permeability coefficient was 0.66 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH). there were. These results are shown in Table 1.

  Thereafter, except that the melt kneading temperature was 250 ° C., the addition of cobalt stearate to the polyamide 5 and the melt kneading with PP1 were carried out in the same manner as in Example 1, and the oxygen absorption was carried out in the same manner as in Example 1. After obtaining the multilayer film, the same storage test as in Example 1 was carried out using it as a cover material of the gas barrier molded container 1. These results are shown in Table 2.

(Example 10)
Polyamide resin was synthesized by performing melt polymerization and solid phase polymerization under the above-described synthesis conditions using metaxylylenediamine: sebacic acid in a molar ratio of 0.989: 1 (hereinafter, the polyamide resin was referred to as polyamide 6). ). The dropping time was 2 hours, the reaction time for melt polymerization was 1 hour, the pressure in the apparatus during solid phase polymerization was 1 torr or less, the polymerization temperature was 160 ° C., and the polymerization time was 4 hours. This polyamide 6 had a Tg of 69 ° C., a melting point of 187 ° C., a half crystallization time of 230 seconds, a terminal amino group of 25.2 μeq / g, a terminal carboxyl group concentration of 88.3 μeq / g, and a number average molecular weight of 23,000. The MFR at 240 ° C. was 20.8 g / 10 minutes. An unstretched film was prepared from the obtained polyamide 4 alone, and the oxygen permeability coefficient was determined. The oxygen permeability coefficient was 1.05 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH). there were. These results are shown in Table 1.

  Thereafter, the addition of cobalt stearate to polyamide 6 and melt-kneading with PP1 were carried out in the same manner as in Example 1, and after obtaining an oxygen-absorbing multilayer film in the same manner as in Example 1, gas barrier molded container 1 The same storage test as in Example 1 was performed. These results are shown in Table 2.

(Comparative Example 1)
A film was produced in the same manner as in Example 1 except that the weight ratio at the time of melt-kneading was changed to cobalt stearate-containing polyamide 1: PP1 = 75: 25, and then used as a lid material for the gas barrier molded container 1 as in Example 1. A storage test was conducted. These results are shown in Table 2.

(Comparative Example 2)
A film was produced in the same manner as in Example 1 except that the weight ratio at the time of melt kneading was changed to cobalt stearate-containing polyamide 1: PP1 = 10: 90, and then used as a lid material for the gas barrier molded container 1 and the same as in Example 1. A storage test was conducted. These results are shown in Table 2.

(Comparative Example 3)
A film was produced in the same manner as in Example 1 except that it was not melt-kneaded with PP1 and the cobalt-containing stearate-containing polyamide 1 was used only as the oxygen absorbing layer, and then used as a lid material for the gas barrier molded container 1 as in Example 1. A storage test was conducted. These results are shown in Table 2.

(Comparative Example 4)
Example 1 except that metaxylylenediamine: adipic acid: isophthalic acid was used in a molar ratio of 1.0: 0.95: 0.05 and the solid phase polymerization time was 1 hour. Then, a polyamide resin was synthesized (hereinafter, the polyamide resin is referred to as polyamide 7). This polyamide 7 had a Tg of 77 ° C., a melting point of 230 ° C., a half crystallization time of 430 seconds, a terminal amino group concentration of 38.7 μeq / g, a terminal carboxyl group concentration of 72.1 μeq / g, and a number average molecular weight of 19000. Moreover, since it was near melting | fusing point at 240 degreeC, MFR was not able to be measured, MFR of 250 degreeC was measured, and MFR in 250 degreeC was 52.1 g / 10min. Moreover, when the unstretched film was produced with the obtained polyamide 7 alone and the oxygen permeability coefficient was determined, it was 0.44 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH). . These results are shown in Table 1.

  Thereafter, except that the temperature at the time of melt kneading was set to 250 ° C., a film was produced in the same manner as in Example 1 by adding cobalt stearate to polyamide 7 and melt kneading with PP1. After that, the same storage test as in Example 1 was performed by using the gas barrier molded container 1 as a lid. These results are shown in Table 2.

(Comparative Example 5)
A polyamide resin was synthesized in the same manner as in Example 1 except that metaxylylenediamine and adipic acid were used in a molar ratio of 0.997: 1, and solid phase polymerization was not performed (hereinafter, the polyamide resin). The resin is denoted as polyamide 8). Polyamide 8 had a Tg of 89 ° C., a melting point of 238 ° C., a half crystallization time of 110 seconds, a terminal amino group concentration of 40.2 μeq / g, a terminal carboxyl group concentration of 73.8 μeq / g, and a number average molecular weight of 17,500. Moreover, since it was near melting | fusing point at 240 degreeC, MFR was not measurable, MFR of 250 degreeC was measured, and MFR in 250 degreeC was 64.8 g / 10min. An unstretched film was prepared from the obtained polyamide 8 alone, and the oxygen permeability coefficient was determined. The oxygen permeability coefficient was 0.09 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH). there were. These results are shown in Table 1.

  Thereafter, except that the temperature at the time of melt kneading was set to 250 ° C., addition of cobalt stearate to polyamide 8 and melt kneading with PP1 were carried out in the same manner as in Example 1 to obtain oxygen-absorbing resin pellets. Further, after obtaining an oxygen-absorbing multilayer film in the same manner as in Example 1, it was used as a cover material for the gas barrier molded container 1 and the same storage test as in Example 1 was performed. These results are shown in Table 2.

(Example 11)
Example except that PP2 is used as the polyolefin resin instead of PP1, and cobalt stearate is added so that the cobalt concentration is 200 ppm, and the weight ratio of cobalt stearate-containing polyamide 1: PP2 = 40: 60 is used. The pellet which consists of oxygen absorption resin composition B similarly to 1 was obtained.

  Next, using a four-kind 6-layer multi-layer sheet forming apparatus comprising a first to a fourth extruder, a feed block, a T die, a cooling roll, and a sheet take-up machine, the first extruder; PP2, the second extrusion Oxygen-absorbing resin composition B, third extruder; ethylene-vinyl alcohol copolymer (product name; “Eval E105B” manufactured by Kuraray), and fourth extruder; polypropylene adhesive resin (product name; (product) Name: “Admer QF500” manufactured by Mitsui Chemicals Co., Ltd.) was extruded to obtain an oxygen-absorbing multilayer sheet composed of PP2 (70) / oxygen-absorbing resin composition B (90) / adhesion from the inner layer. Layer (15) / ethylene-vinyl alcohol copolymer (30) / adhesive layer (15) / PP2 (300) The multilayer sheet produced by coextrusion is a multilayer sheet having a good appearance with no unevenness in thickness. It was.

The resulting multilayer sheet was then thermoformed into a tray-like container (inner volume 400 cc, surface area 200 cm ² ) using a vacuum forming machine to obtain an oxygen-absorbing multilayer container. Next, nylon film B (product name: “Super Neal SP” manufactured by Mitsubishi Plastics, Inc.) was used by using an urethane dry laminate adhesive (product name: “AD817 / CAT-RT86L-60” manufactured by Toyo Morton Co., Ltd.). -R "), PET film A (product name:" E5102 "manufactured by Toyobo Co., Ltd.) and unstretched polypropylene film (product name:" Allomer UT21 "manufactured by Okamoto Co., Ltd.), and barrier film 1 (PET Film A (12) / adhesive (3) / nylon film B (25) / adhesive (3) / unstretched polypropylene film (60)) was obtained. Next, the oxygen-absorbing multilayer container was sterilized by ultraviolet sterilization, and 250 g of aseptic cooked rice immediately after cooking was placed in the container, and oxygen in the container was replaced with nitrogen gas to adjust the oxygen concentration to 0.5%. Next, the barrier film 1 was used as a top film and sterilized with ultraviolet rays in the same manner as the container, and then the container was sealed and stored at 23 ° C. and 50% RH. When opened three months after the start of storage, the color tone and flavor of the cooked rice were well maintained. In addition, the strength of the oxygen-absorbing multilayer container was well maintained.

(Comparative Example 6)
150 kg of iron powder with an average particle size of 20 μm is put into a vacuum dryer equipped with a heating jacket, mixed with 150 kg at a reduced pressure of 10 mmHg at 150 ° C., sprayed with 70 kg of a 45% by weight aqueous solution of calcium chloride, dried, sieved and coarsened The iron-based oxygen absorbent 1 having an average particle diameter of 20 μm was obtained by removing the grains. Next, while extruding PP2 using a vented twin screw extruder, iron-based oxygen absorbent and calcium oxide are supplied by side feed, and PP2: iron-based oxygen absorbent 1: calcium oxide is 58:40: 2 to obtain a pellet made of the oxygen-absorbing resin composition C.

An oxygen-absorbing multilayer sheet was produced in the same manner as in Example 11 except that the oxygen-absorbing resin composition C was used instead of the oxygen-absorbing resin composition B. The obtained oxygen-absorbing multilayer sheet was subjected to thermoforming on a tray-like container (with an internal volume of 400 cc and a surface area of 200 cm ² ) using a vacuum forming machine in the same manner as in Example 11, but was drawn down. The processability was poor and thermoforming was difficult. However, since a container having an outer appearance was obtained, the barrier film 1 was used as a top film, and a storage test for aseptic cooked rice was performed in the same manner as in Example 11. When opened three months after the start of storage, the color tone and flavor of cooked rice and the strength of the oxygen-absorbing multilayer container were well maintained, but the container is not transparent, so check the color without opening. I couldn't.

(Example 12)
Instead of PP1, linear low density polyethylene (product name: “Umerit 4040F” manufactured by Ube Maruzen Polyethylene Co., Ltd.), MFR 4.0 g / 10 min (measured according to JIS K7210), MFR 7.9 g / 240 ° C. 10 minutes, MFR 8.7 g / 10 minutes at 250 ° C., hereinafter referred to as LLDPE1), and the same as in Example 1 except that the weight ratio of cobalt stearate-containing polyamide 1: LLDPE1 = 30: 70 was used. The pellet which consists of oxygen absorption resin composition D was obtained.

  The obtained oxygen-absorbing resin composition D was used as an oxygen-absorbing layer, and linear low-density polyethylene (product name: “Novatech LL UF943” manufactured by Nippon Polyethylene Co., Ltd.), MFR 2.1 g / 10 min (according to JIS K7210) Measurement), 2 types 2 layer film 2 (thickness; oxygen absorption layer 30 μm / sealant layer 30 μm) having MFR 5.5 g / 10 min at 250 ° C., hereinafter referred to as LLDPE2) as a sealant layer, with a width of 800 mm, The surface of the oxygen absorbing layer was subjected to corona discharge treatment at 100 m / min to produce a film roll. The film roll had no uneven thickness such as bumps, the appearance of the obtained film was good, and the HAZE was 14%. Next, a nylon film B and a PET film B (product name: “T4102” manufactured by Toyobo Co., Ltd.) are laminated using a two-layer two-layer film 2, and a PET film B (12) / adhesive (3) An oxygen-absorbing multilayer film comprising an oxygen-absorbing multilayer body of / nylon film B (25) / adhesive (3) / oxygen-absorbing resin (30) / LLDPE2 (30) was obtained. Next, using the multilayer film, a L × PE2 layer side is used as an inner surface to produce a 16 × 22 cm four-side sealed bag, this container is sterilized by ultraviolet sterilization, and then filled with 250 g of red rice cooked in an aseptic environment, The oxygen in the container was replaced with nitrogen gas to make the oxygen concentration 0.5%, and the container was sealed. When the appearance of the produced four-side seal bag was confirmed, the bag had good transparency and the contents could be visually confirmed. Next, the four-side sealed bag filled with red rice was stored under conditions of 23 ° C. and 50% RH. When the flavor of the contents three months after the start of storage was confirmed, the color and flavor of red rice were well maintained. In addition, the transparency and strength of the oxygen-absorbing multilayer film were well maintained, and the color tone of the contents could be confirmed with the four-side sealed bag unopened.

(Comparative Example 7)
An oxygen-absorbing resin composition was used in the same manner as in Comparative Example 6 except that LLDPE1 was used in place of PP2 and LLDPE1: iron-based oxygen absorbent 1: calcium oxide was kneaded to a weight ratio of 68: 30: 2. A pellet consisting of E was obtained.

  Using the oxygen-absorbing resin composition E in place of the oxygen-absorbing resin composition D, an attempt was made to produce a two-layer two-layer film using LLDPE2 as a sealant in the same manner as in Example 12. Unevenness occurred, the processability was poor, and no film was obtained. Therefore, when oxygen absorbing resin composition E is extruded and laminated at a thickness of 30 μm as an oxygen absorbing layer on LLDPE2 having a thickness of 30 μm, a two-kind two-layer film (hereinafter referred to as a two-kind two-layer film 3) can be produced. Met. An oxygen-absorbing multilayer film was obtained in the same manner as in Example 12 using the two-type two-layer film 3. The configuration of the multilayer film was PET film B (12) / adhesive (3) / nylon film B (25) / adhesive (3) / oxygen absorbing resin (30) / LLDPE2 (30). Next, a 16 × 22 cm four-side sealed bag was produced from the multilayer film in the same manner as in Example 12 with the LLDPE2 layer side as the inner surface, and the prepared four-side sealed bag was filled with red rice in the same manner as in Example 12. Sealed. When the appearance of the produced four-side seal bag was confirmed, the bag was not transparent and the contents could not be visually confirmed. Next, the four-side sealed bag filled with red rice was stored under conditions of 23 ° C. and 50% RH. When the flavor of the contents after 3 months from the start of storage was confirmed, the flavor and color tone of red rice were well maintained, but the four-sided seal bag is not transparent, so the contents can be seen without opening. I couldn't.

  The present invention relates to a method for preserving cooked rice in which the oxygen-absorbing multilayer body excellent in oxygen absorption performance, resin strength, resin processability and transparency is used for a part or the whole of a container and the flavor of cooked rice is well preserved. Met.

Claims (6)

  Oxygen absorption in which cooked rice is laminated in order from the inside, at least three layers: a sealant layer made of polyolefin resin, an oxygen absorption layer containing polyolefin resin, a transition metal catalyst, and a polyamide resin, and a gas barrier layer made of a gas barrier material A method for preserving cooked rice which is stored in an oxygen-absorbing container using all or part of a multilayer body, wherein the polyamide resin has a terminal amino group concentration of 30 μeq obtained by polycondensation of an aromatic diamine and a dicarboxylic acid. / G or less of the polyamide resin and the total content of the transition metal catalyst and the polyamide resin in the oxygen absorbing layer is 15 to 60% by weight based on the total amount of the oxygen absorbing layer.   The storage method according to claim 1, wherein adipic acid, sebacic acid, isophthalic acid or a mixture thereof is used as the dicarboxylic acid.   3. The preservation method according to claim 1, wherein paraxylylenediamine, metaxylylenediamine, or a mixture thereof is used as the aromatic diamine.   The storage method according to any one of claims 1 to 3, wherein the transition metal catalyst is cobalt stearate.   The molar ratio when obtaining the polyamide resin is aromatic diamine: sebacic acid: adipic acid = 0.985-0.997: 0.3-0.7: 0.7-0.3, The storage method according to any one of claims 2 to 4.   The molar ratio for obtaining the polyamide resin is aromatic diamine: adipic acid: isophthalic acid = 0.985-0.997: 0.7-0.97: 0.3-0.03 The storage method according to any one of claims 2 to 4.