Container for heat sterilization

Abstract

To provide a container for heat sterilization allowing oxygen barrier performance to be secured as well as a used amount of ethylene-vinyl alcohol copolymer to be reduced and recyclability to be improved when undergoing heat sterilization such as retort sterilization.SOLUTION: A container for heat sterilization is provided at least with a substrate layer having olefin resin, a barrier layer 3 having ethylene-vinyl alcohol copolymer, and an oxygen absorbing layer 4 including an oxygen absorbent including reduced iron, wherein a thickness of a container body is 240 μm or more, a thickness of the barrier layer is 12 to 40 μm, a thickness of the oxygen absorbing layer is 18 to 50 μm, and the oxygen absorbent is contained in an amount of 26 pts.mass or more based on 100 pts.mass of the ethylene-vinyl alcohol.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a container that can be subjected to heat sterilization such as retort sterilization, and more specifically to a container for heat sterilization that is provided with an ethylene-vinyl alcohol copolymer-containing barrier layer and an oxygen-absorbing layer containing an iron-based oxygen absorber, and that exhibits excellent preservation properties for the contents even when subjected to heat sterilization such as retort sterilization. [Background technology]

[0002] Olefin resins such as polyethylene and polypropylene have excellent properties such as moldability, transparency, mechanical strength, and chemical resistance, and are particularly suitable for use as packaging materials for cups, trays, bottles, and the like. In the field of packaging materials, blocking oxygen is required to prevent oxidation and deterioration of the contents. However, plastic packaging materials have poorer oxygen barrier properties than glass or metal, so their oxygen barrier properties are generally improved by using a multilayer structure with an intermediate layer of an oxygen-barrier resin.

[0003] In the above-described multilayer structure, a typical example of the oxygen barrier resin is an ethylene vinyl alcohol copolymer (hereinafter sometimes referred to as "EVOH"). However, such an oxygen barrier resin layer physically suppresses oxygen permeation, and its oxygen barrier performance is lower than that of glass, etc., so it has conventionally been used in combination with an oxygen absorber that actively absorbs permeating oxygen or residual oxygen within the container. For example, Patent Document 1 listed below describes a multi-layer plastic packaging material having inner and outer layers made of polypropylene, a first intermediate layer (barrier layer) made of EVOH located on the outer layer side, and a second intermediate layer (oxygen absorbing layer) made of a resin composition containing an oxygen scavenger located on the inner layer side.This plastic packaging material has excellent storage stability and flavor retention for the contents, as the barrier layer blocks permeating oxygen and the oxygen absorber can absorb permeating oxygen and residual oxygen in the container. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3630706 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a plastic packaging material having the above-described layer structure is subjected to sterilization under high-temperature, high-humidity conditions, such as retort sterilization, the barrier properties of the barrier layer made of EVOH tend to be reduced by water vapor. In addition, since the iron-based oxygen absorber has a high oxygen absorption capacity under high-temperature, high-humidity conditions, the oxygen absorption performance of the oxygen absorber is used up during retort sterilization, and there is a risk that the oxygen absorber will be inactivated, making it difficult to ensure the shelf life of the contents over a long period of time. Furthermore, to improve the oxygen barrier properties of packaging materials, a barrier layer of a certain thickness is necessary, but in response to recent demands for recycling of plastic products, it is necessary to reduce the content of barrier resins that are different from the olefin-based resin that forms the base material of the packaging material, such as the inner and outer layers. Ethylene-vinyl alcohol copolymers in particular are susceptible to thermal decomposition, and may become discolored or generate low-molecular-weight components when heated, which may hinder the recyclability of the packaging material.

[0006] Therefore, an object of the present invention is to provide a container for heat sterilization which ensures oxygen barrier properties even when subjected to heat sterilization such as retort sterilization, reduces the amount of ethylene-vinyl alcohol copolymer used, and improves recyclability. [Means for solving the problem]

[0007] According to the present invention, there is provided a container for heat sterilization comprising at least a base layer having an olefin resin, a barrier layer having an ethylene-vinyl alcohol copolymer, and an oxygen absorbing layer containing an oxygen absorber containing reduced iron, wherein the thickness of the container is 240 μm or more, the thickness of the barrier layer is 12 to 40 μm, the thickness of the oxygen absorbing layer is 18 to 50 μm, and the oxygen absorber is used in an amount of 26 parts by mass or more per 100 parts by mass of the ethylene-vinyl alcohol copolymer.

[0008] In the container for heat sterilization of the present invention, (1) The thickness of the oxygen absorbing layer is greater than the thickness of the barrier layer; (2) The oxygen absorbing layer contains 1 to 40 parts by mass of an oxygen absorbent relative to 100 parts by mass of the base resin of the oxygen absorbing layer. (3) The container contains an ethylene vinyl alcohol copolymer in an amount of less than 10 parts by mass per 100 parts by mass of the container. (4) The olefin-based resin is polypropylene. (5) The container has an inner layer and an outer layer, each of which is made of an olefin-based resin, and the oxygen absorbing layer is located on the inner layer side of the barrier layer. (6) A repro layer is provided between the barrier layer and the outer layer. is preferred. [Effects of the Invention]

[0009] In the container for heat sterilization of the present invention, by providing an oxygen absorbing layer containing a specific amount of oxygen absorber relative to the EVOH content, the functionality of the oxygen absorber is not completely lost even when placed under high-temperature, high-humidity conditions such as retort sterilization, and excellent oxygen barrier properties can be maintained even when the barrier properties of the barrier layer made of EVOH are reduced, making it possible to create a container that has excellent storage properties for the contents for a long period of time even after heat sterilization. The container for heat sterilization of the present invention has a reduced amount of EVOH, and therefore the recyclability of the olefin resin is improved. The container of the present invention can be used for conventional heat sterilization, and is particularly suitable for sterilization treatments such as retort sterilization and boiling sterilization, which are performed under high temperature and high humidity conditions. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view showing an example of the layer structure of a container for heat sterilization of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] The container for heat sterilization of the present invention comprises at least a substrate layer containing an olefin-based resin, a barrier layer containing an ethylene-vinyl alcohol copolymer, and an oxygen-absorbing layer containing an oxygen absorber containing reduced iron. Fig. 1 is a cross-sectional view showing an example of the layer structure of a container of the present invention, which comprises an outer layer 1, an adhesive layer 2a, a barrier layer 3, an adhesive layer 2b, an oxygen absorbing layer 4, and an inner layer 5. The outer layer 1 and the inner layer 5 each correspond to a base layer and are made of an olefin resin. The barrier layer 3 is made of EVOH, and the oxygen absorbing layer 4 is made of an oxygen absorbing layer containing an oxygen absorber including reduced iron. A first important feature of the present invention is that the thickness of the container is 240 μm or more, the thickness of the barrier layer 3 made of EVOH is 12 to 40 μm, and the thickness of the oxygen absorbing layer is 18 to 50 μm, and a second important feature is that the oxygen absorbing layer 4 contains an oxygen absorber containing reduced iron, and the oxygen absorber is used in an amount of 26 parts by mass or more per 100 parts by weight of the EVOH used in the barrier layer. That is, even if the container of the present invention is subjected to heat sterilization under high-temperature and high-humidity conditions such as retort sterilization, and the function of the barrier layer made of EVOH is deteriorated, the oxygen absorbing layer containing a specific amount of oxygen absorber captures permeated oxygen or oxygen inside the container, so that the oxygen barrier property is not deteriorated and the shelf life of the contents is guaranteed for a long period of time even after retort sterilization. In this specification, the thickness of each layer of a container refers to the thickness of each layer of the constituent film or sheet when the container is in the form of a packaging bag such as a pouch, and refers to the thickness of each layer at the center of the bottom, which has the least amount of processing, when the container is a cup, tray, bottle, etc.

[0012] (barrier layer) In the container of the present invention, the barrier layer is made of an ethylene-vinyl alcohol copolymer (saponified ethylene-vinyl acetate copolymer), and as mentioned above, it is important that the thickness is 12 to 40 μm, and from the viewpoint of recyclability, it is particularly preferable that the thickness is in the range of 15 to 36 μm, 15 to 30 μm, or 15 to 25 μm. The mass of the barrier layer is preferably in the range of 5 to 10 parts by mass, particularly 5 to 7 parts by mass, relative to 100 parts by mass of the container. Any known ethylene-vinyl alcohol copolymer can be used for the barrier layer without any restrictions. However, from the viewpoint of barrier properties and recyclability in particular, a saponified copolymer obtained by saponifying an ethylene-vinyl acetate copolymer having an ethylene content of 20 to 50 mol % to a degree of saponification of 96 mol % or more, particularly 99 mol % or more, can be preferably used. In the present invention, as described above, it is preferable to use ethylene vinyl alcohol copolymer (EVOH) as the barrier layer. In this case, it is preferable that the EVOH is contained in an amount of less than 11 parts by mass, particularly 5 to 10 parts by mass, per 100 parts by mass of the container, and it is also preferable that the thickness of the oxygen absorbing layer is at least 0.8 times, 1.5 to 10 times, particularly 1.5 to 3 times the thickness of the EVOH barrier layer.

[0013] (oxygen absorbing layer) In the container of the present invention, the oxygen absorbing layer is made of an oxygen absorbing resin composition containing an oxygen absorber including reduced iron in a base resin, and as mentioned above, it is important that the thickness is 18 to 50 μm, and it is particularly preferable that it is in the range of 21 to 48 μm. As described above, the oxygen absorbing layer contains an oxygen absorber containing reduced iron. It is important that the oxygen absorber is used in an amount of 26 parts by mass or more per 100 parts by mass of EVOH used in the barrier layer, and it is particularly preferable that the oxygen absorber be contained in an amount in the range of 26 to 70 parts by mass. The oxygen absorbent preferably contains reduced iron and a metal halide. By containing a metal halide, it is possible to improve the oxygen absorption performance. Rotary reduced iron powder is preferably used as the reduced iron, which has high purity and a large specific surface area, and therefore has excellent oxygen absorption performance. The content of reduced iron in the oxygen absorbent is preferably 1 to 40 parts by mass, and more preferably 10 to 40 parts by mass.

[0014] Examples of metal halides include halides of alkali metals, alkaline earth metals, copper, zinc, iron, etc. Specific examples include sodium chloride, sodium bromide, sodium iodide, potassium chloride, potassium bromide, potassium iodide, calcium chloride, magnesium chloride, barium chloride, etc. Among these, sodium chloride is preferred. These metal halides may be used alone or in combination of two or more. The metal halide is preferably blended in an amount of 0.1 to 10 parts by mass, particularly 1 to 5 parts by mass, per 100 parts by mass of reduced iron, which is the main component of the oxygen absorber.

[0015] The oxygen absorbent may further contain an alkaline substance in addition to reduced iron and a metal halide. By including an alkaline substance, the amount of hydrogen generated by the reaction between iron and water can be reduced. Examples of alkaline substances include magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, magnesium carbonate, calcium carbonate, strontium carbonate, and barium carbonate. Among these, calcium hydroxide and calcium oxide, which is a dehydrated product of calcium hydroxide, are preferred. These alkaline substances may be used alone or in combination of two or more. When the oxygen absorber contains an alkaline substance, the alkaline substance is preferably blended in an amount of 0.5 to 2 parts by mass, particularly 1 to 2 parts by mass, per 100 parts by mass of reduced iron.

[0016] The oxygen absorber can be prepared by a conventionally known method. For example, reduced iron is coarsely pulverized, and then a metal halide and, if necessary, an alkaline substance are added thereto and the resulting mixture is finely pulverized while being mixed. The finely pulverized product is then classified to remove coarse particles, and then heat-treated. After the heat treatment, the product is further classified, if necessary, to remove coarse particles, thereby obtaining the oxygen absorber.

[0017] The base resin of the oxygen absorbing layer may be a conventionally known thermoplastic resin, but from the viewpoints of adhesion to other layers and recyclability, it is preferable to use an olefin-based resin similar to that used in the inner and outer layers. The olefin-based resin will be described later. As mentioned above, it is important to determine the content of the oxygen absorber based on the EVOH standard for the barrier layer, but it is also preferable that the oxygen absorber be used in the oxygen absorbing layer in an amount of 1 to 30 parts by mass, particularly 10 to 30 parts by mass, per 100 parts by mass of the base resin. If the amount of oxygen absorber is less than the above range, there is a risk that sufficient oxygen absorption performance will not be exhibited compared to when it is within the above range. On the other hand, if the amount of oxygen absorber is more than the above range, not only will it be less economical but it may also hinder the moldability of the container. The oxygen-absorbing resin composition can be prepared by a conventionally known method. When a small amount of oxygen absorbent is blended, it is preferable to prepare and use a masterbatch. The thickness of the oxygen absorbing layer is particularly preferably in the range of 18 to 50 μm, 20 to 50 μm, 21 to 48 μm, or 30 to 50 μm. In this case, the oxygen absorbing layer is preferably formed in an amount of 7 to 25 parts by mass relative to 100 parts by mass of the container.

[0018] (base material layer) In the container of the present invention, the inner and outer layers serving as base layers are made of an olefin-based resin, and examples of such an olefin-based resin include low-, medium-, or high-density polyethylene, polypropylene, polybutene-1, poly4-methyl-1-pentene, or polyolefins such as random or block copolymers of α-olefins such as ethylene, propylene, 1-butene, and 4-methyl-1-pentene, and cyclic olefin copolymers, but polypropylene is particularly preferred from the viewpoint of heat resistance. The materials of the inner and outer layers may be the same or different. In particular, polypropylene is suitable from the viewpoint of heat resistance. The materials of the inner layer and the outer layer may be the same or different.

[0019] Furthermore, the raw materials or part of the raw materials of the olefin resin are not limited to petroleum-derived materials, but may be chemically recycled materials from waste plastics by monomerization techniques such as gasification or liquefaction, or olefin resins produced from biomass materials such as plant-derived materials. The biomass content can be measured by measuring the radioactive carbon concentration, etc. Furthermore, when manufacturing olefin resins, from the perspective of reducing environmental impact, SVHC substances (listed under the European Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) regulations) such as phthalate ester compounds are not used in the polymerization stage from raw materials. S ubstance of V ery H igh C It is desirable to produce it using a catalyst system that does not use an oxidizer. Recycled materials can also be used, which are made by collecting, sorting, and cleaning multi-layer packaging materials and processed plastic materials that have been used once, then melting them down and turning them into pellets.

[0020] The inner layer and / or outer layer preferably contains a white pigment such as titanium oxide to conceal the black color of the oxygen absorbing layer derived from the iron powder. The amount of such a white pigment is preferably 1 to 30 parts by mass per 100 parts by mass of the olefin resin constituting the inner layer and / or outer layer. The thickness of the inner or outer layer is not particularly limited, but is preferably in the range of 60 to 240 μm, and is preferably 10 to 60% of the total thickness of the container.

[0021] (Other layers) In addition to the barrier layer, oxygen absorbing layer, and base layer described above, the container of the present invention may also be provided with an adhesive layer, a layer made of a reproduction resin (hereinafter referred to as the "reproduction layer"), an easily peelable layer, a deodorizing layer, etc. The adhesive layer may be made of a conventionally known adhesive resin, including, but not limited to, ethylene-acrylic acid copolymer, ion-crosslinked olefin copolymer, maleic anhydride grafted polyethylene, maleic anhydride grafted polypropylene, acrylic acid grafted polyolefin, ethylene-vinyl acetate copolymer, etc. The thickness of the adhesive layer is not particularly limited, but is preferably in the range of 1 to 30 μm.

[0022] The reproduced resin is a resin obtained by pulverizing and reducing resins and films discharged during the process of producing the container of the present invention, and is a resin whose main component is an olefin-based resin such as polypropylene. Alternatively, due to growing environmental awareness, recycled material, chemical recycled material, or biomass material may be blended. In particular, with recycled material, it is preferable to use less EVOH and nylon-based resins in terms of deterioration of physical properties and compatibility with olefins. The reproduced resin may also contain virgin olefin-based resins. The thickness of the recycled layer is preferably in the range of 3 to 300 μm.

[0023] Furthermore, the easily peelable layer may be made of a conventionally known blend capable of cohesive failure, including, but not limited to, a blend of polypropylene and polyethylene, or a blend of the above blends optionally containing a rubber-based compatibilizer such as ethylene-propylene copolymer (EPR).The thickness of the easily peelable layer is not particularly limited, but is preferably in the range of 1 to 100 μm. Furthermore, a layer containing a deodorizer can be formed to prevent flavor degradation due to the oxygen absorber in the oxygen absorbing layer, and is composed of a resin composition in which an adsorbent component such as activated carbon or diatomaceous earth is blended with a base resin.

[0024] (Layer composition) The container of the present invention is not limited to the layer structure shown in FIG. 1, and various layer structures can be adopted depending on the application and structure. For example, examples include outer layer / adhesive layer / barrier layer / adhesive layer / oxygen absorbing layer / inner layer / easy-peel layer, outer layer / recycling layer / adhesive layer / barrier layer / adhesive layer / oxygen absorbing layer / inner layer / easy-peel layer, outer layer / recycling layer / adhesive layer / barrier layer / adhesive layer / oxygen absorbing layer / recycling layer / inner layer, outer layer / recycling layer / adhesive layer / barrier layer / adhesive layer / oxygen absorbing layer / recycling layer / inner layer / easy-peel layer, outer layer / recycling layer / adhesive layer / barrier layer / adhesive layer / oxygen absorbing layer / inner layer / recycling ...deodorizing layer / inner layer, etc. Furthermore, a plurality of repro layers, barrier layers, or oxygen absorbing layers may be provided as long as the constitution of the present invention is satisfied, and in that case, the total thickness of the respective layers is taken as the thickness.

[0025] (Manufacturing method) The container of the present invention can be produced by a method known per se, except for the layer structure described above. In multilayer coextrusion, the resin layers are melt-mixed in extruders corresponding to the respective resin layers and then extruded into a desired shape through a multilayer die such as a T-die or circular die. Alternatively, the resin layers are melt-mixed in injectors corresponding to the respective resin layers and then co-injected or sequentially into an injection mold to produce a multilayer container or a preform for a container. Other lamination methods, such as dry lamination, sandwich lamination, and extrusion coating, can also be used.

[0026] The container may be in the form of a film, a sheet, a parison or pipe for forming a bottle or tube, a preform for forming a bottle or tube, etc. A bottle can be formed from the parison, pipe, or preform by pinching off the extrudate with a pair of split dies and blowing a fluid into the interior. Alternatively, a stretch-blown bottle or the like can be obtained by cooling the pipe or preform, heating it to a stretching temperature, stretching it axially, and blowing it circumferentially with fluid pressure.

[0027] Furthermore, the film or sheet can be subjected to vacuum forming, pressure forming, bulging forming, plug assist forming or the like to obtain a container in the shape of a cup, tray or the like. Furthermore, the multilayer film can be laminated or folded into a bag-like shape and the periphery heat-sealed to form a bag-like container. [Example]

[0028] (Resin used and layer structure) Starting from the inner layer, the base layer was made of block polypropylene with added titanium white pigment; the oxygen-absorbing layer was made of a polypropylene oxygen-absorbing resin composition (shown as "OXY" in the table) prepared by blending an oxygen absorber (containing 2 parts by mass of sodium chloride per 100 parts by mass of reduced iron) with a base resin made of random polypropylene; the adhesive layer (5 μm thick) was made of maleic anhydride; the barrier layer was made of ethylene-vinyl alcohol copolymer (ethylene content 32 mol%, shown as "EVOH" in the table), the adhesive layer (5 μm thick) was made of maleic anhydride; and the base layer was made of random polypropylene with added titanium white pigment.

[0029] (Evaluation of the shelf life of contents after retort sterilization) 5 cc of water was placed in the container, and the container was heat-sealed with a gas-impermeable metal foil laminated film in an atmosphere with an oxygen concentration of 1%. At this time, the internal volume of the container was 105 ml. The container was retort sterilized at 121°C for 30 minutes, and then stored at 30°C and 80% RH for 100 days. The oxygen concentration inside the container was measured using a gas chromatograph (product name: CP4900, manufactured by Agilent). The shelf life of the contents was evaluated based on the oxygen concentration inside the container after storage according to the following criteria. ◎: The oxygen concentration inside the container after storage is less than 0.5%. ○: The oxygen concentration inside the container after storage is 0.5% or more and less than 1.0%. ×: The oxygen concentration in the container after storage is 1.0% or more.

[0030] (Measurement of hydrogen concentration inside the container) Water was used as the container contents, and the headspace was replaced with 80% carbon dioxide and 20% nitrogen. After sealing and retort sterilization, the sealed container was left for two weeks. The hydrogen concentration inside the container was measured using a micro gas chromatograph (GC-323, manufactured by GL Sciences).

[0031] (Measurement of maximum lid displacement fluctuation and evaluation of inspection suitability) Water was used as the container contents, and the headspace was replaced with 80% carbon dioxide and 20% nitrogen. The headspace was sealed, and the distance from the flange near the center of the lid (lid H0) was measured 24 hours after retort sterilization, and the distance from the flange near the center of the lid (lid H1) was measured after the lid was left to cool at room temperature for two weeks after retort sterilization. Note that upward movement from the flange in the axial direction of the container was considered positive (+), and downward movement from the flange in the axial direction of the container was considered negative (-), and lid H0 - lid H1 was defined as the lid displacement fluctuation. After filling the contents, the lid displacement fluctuation can be used to determine whether the container is sealed and whether bacteria are growing inside. If the maximum displacement fluctuation of the lid material is greater than 0.10 mm, it is determined that the reduced pressure state cannot be maintained inside the container and is marked as fail (×); if the maximum displacement fluctuation is 0.10 mm or less, it is determined that the reduced pressure state can be maintained inside the container and is marked as pass (〇); and if the maximum displacement fluctuation is -0.00 mm or less, it is determined that the reduced pressure state can be maintained inside the container more strictly and is marked as pass (◎), and the suitability for testing was evaluated.

[0032] (Examples 1 to 10, Comparative Examples 1 and 2) A multilayer sheet was produced by coextrusion lamination using the above-mentioned resin and an oxygen-absorbing resin composition with an adjusted oxygen absorber content. This multilayer sheet was then used to form a multilayer container with an opening diameter of 84 x 84 mm, a height of 32 mm, and a capacity of 105 ml using a vacuum / compressed air molding machine. The cross section of the container is shown in Figure 1. The center of the bottom of the manufactured container was cut out, and the thickness of each layer was measured using an optical microscope. The results are shown in Table 1. The thickness of the multilayer sheet was 10 / 3 times the thickness of the container, and the thickness of each layer generally showed a similar tendency. Furthermore, in Examples 5 to 9, the storage stability was particularly good, and the maximum lid displacement fluctuation was -0.00 mm or less, making it possible to use a leak test to determine whether or not there was a leak due to the degree of reduced pressure. This is presumably because the thin EVOH layer allowed hydrogen generated during oxygen absorption to quickly permeate out of the container, thereby lowering the hydrogen concentration inside the container.

[0033] [Table 1] [Industrial Applicability]

[0034] The container for heat sterilization of the present invention is a container mainly made of an olefin-based resin and provided with a barrier layer made of an ethylene-vinyl alcohol copolymer, and even when subjected to heat sterilization under high-temperature and high-humidity conditions such as retort sterilization, it maintains its oxygen barrier properties and can exhibit excellent shelf life for the contents over a long period of time. Therefore, it can be suitably used as a food container where shelf life for the contents over a long period of time is required. [Explanation of symbols]

[0035] 1 outer layer, 2a, 2b adhesive layers, 3 barrier layer, 4 oxygen absorbing layer, 5 inner layer.

Claims

1. A container for heat sterilization comprising at least a substrate layer having an olefin-based resin, a barrier layer having an ethylene-vinyl alcohol copolymer, and an oxygen absorbing layer containing an oxygen absorber including reduced iron, The thickness of the container is 240 μm or more, The thickness of the barrier layer is 12 to 40 μm, The oxygen absorbing layer has a thickness of 18 to 50 μm, A container for heat sterilization, characterized in that the oxygen absorber is contained in an amount of 26 parts by mass or more per 100 parts by mass of ethylene-vinyl alcohol copolymer.

2. 2. The container for heat sterilization according to claim 1, wherein the oxygen absorbing layer is thicker than the barrier layer.

3. 3. The container for heat sterilization according to claim 1, wherein the oxygen absorbing layer contains 1 to 40 parts by mass of an oxygen absorber per 100 parts by mass of the base resin of the oxygen absorbing layer.

4. 3. The container for heat sterilization according to claim 1, wherein the ethylene-vinyl alcohol copolymer is contained in an amount of less than 10 parts by mass per 100 parts by mass of the container.

5. 3. The container for heat sterilization according to claim 1, wherein the olefin-based resin is polypropylene.

6. 3. The container for heat sterilization according to claim 1, wherein the base layer containing the olefin-based resin is an inner layer and an outer layer, and the oxygen absorbing layer is located on the inner layer side of the barrier layer.

7. 3. The container for heat sterilization according to claim 1, further comprising a repro layer between the barrier layer and the outer layer.

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