Packaging Container

Abstract

To provide a packaging container which has a good appearance at the time of display, a good recyclability at the time of producing the container, and can reduce the cost of a gas replacement and extend a quality retention period of a filled food.SOLUTION: The present invention is a packaging container in which a food is filled, sealed and packaged. The packaging container comprises a multilayer structure having a gas barrier layer, the maximum height roughness (Rz) of the container surface measured according to JIS-B 0601 (2001) is 1 μm or more and 30 μm or less, the oxygen permeability per unit volume under conditions of 20°C, 65%RH is between 0.00001 cc / cmday atm and 0.001 cc / cmday atm inclusive, an oxygen concentration O (10) of a gas inside, 10 days after the sealed packaging is between 0% and 5% by volume inclusive.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a packaging container. [Background technology]

[0002] In general, food deteriorates due to oxidation caused by oxygen in the air, and aerobic bacteria contained in food grow in the presence of oxygen. In order to prevent deterioration of quality due to oxygen and the growth of aerobic bacteria and to extend the quality retention period (best-before date) of food, food may be packaged to remove oxygen from the packaging container. One such packaging method is gas replacement filling packaging (packaging that replaces the gas in the container with nitrogen or carbon dioxide).

[0003] As an example of the use of gas replacement filling packaging, Patent Document 1 describes a method in which a food is sealed together with an oxygen scavenger in an inner container with gas barrier properties, gas replacement filling packaging is performed, and this inner container is then gas replacement filling packaginged in an outer container with gas barrier properties and sealed. It describes that such gas replacement filling packaging is suitable for packaging flavorful foods such as bonito flakes, dried sardines, flavor seasonings, furikake rice seasonings, seaweed, tea, herbs, delicacies, nuts, sweets, and bread.

[0004] Patent Document 2 describes a method for packaging frozen foods in which pre-frozen food is filled into a container or bag made of a laminated sheet / film having at least an oxygen gas barrier resin layer and a heat-sealable thermoplastic resin layer, and then the inside of the container or bag is replaced with an inert gas and heat-sealed, and it is described that this packaging method enables frozen foods to be stored for long periods of time with good quality. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2002-308342 A [Patent Document 2] JP 2001-048235 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, when a product is displayed at an angle to improve its appearance, in packaging containers to which the above-mentioned conventional gas replacement filling packaging can be applied, it has been found that the food tends to slip inside the container depending on the angle at which it is displayed, deteriorating the appearance of the product. On the other hand, it has been found that if the surface of the inside of the container is made uneven in order to prevent food from slipping inside the container, fine powder is generated when trims (cut-out parts) generated during container manufacturing or defective products are collected and reused (recycled), which can cause problems in the extrusion process.

[0007] In addition, the oxygen concentration in the gas-exchanged filled package can be adjusted by changing the gas exchange conditions, but completely replacing the air in the package with the exchange gas tends to be costly. On the other hand, if the gas exchange rate is lowered to reduce costs, the food quality retention period tends to be shortened due to oxidation deterioration of the food and the proliferation of aerobic bacteria.

[0008] The present invention has been made based on the above circumstances, and its object is to provide a packaging container that maintains a good appearance when displayed while having good recyclability when manufactured, and that can extend the quality retention period of the food filled therein while reducing gas replacement costs. [Means for solving the problem]

[0009] That is, the present invention provides [1] A packaging container in which food is filled and sealed, the packaging container having a multilayer structure with a gas barrier layer, the maximum height roughness (Rz) of the container surface measured in accordance with JIS-B0601 (2001) being 1 μm or more and 30 μm or less, and the oxygen permeability of the packaging container under conditions of 20°C and 65% RH is 0.00001 cc / cm 3 ·day · atm or more 0.001cc / cm 3·day·atm or less, and the oxygen concentration O(10) of the gas inside the packaging container on the 10th day after sealing and packaging is between 0% and 5% by volume; [2] A packaging container according to [1], the arithmetic mean roughness (Ra) of the container surface measured in accordance with JIS-B0613 (2001) is 0.1 μm or more and 2.5 μ or less; [3] A packaging container according to [1] or [2] in which the oxygen concentration O(0) of the gas inside immediately after sealing is between 0.1% and 5% by volume; [4] A packaging container according to any one of [1] to [3], in which the ratio O(10) / O(0) of the oxygen concentration O(10) to the oxygen concentration O(0) of the gas inside the container immediately after the container is sealed is greater than or equal to 0 and less than 1; [5] The packaging container according to any one of [1] to [4], wherein the gas contains at least one selected from nitrogen and carbon dioxide; [6] A packaging container according to [5], in which the carbon dioxide concentration of the gas is 0.5% by volume or more and 40% by volume or less; [7] The packaging container according to any one of [1] to [6], wherein the gas barrier layer contains, as a main component, an ethylene-vinyl alcohol copolymer, a composite structure containing phosphorus and a polyvalent metal element, or modified starch; This is achieved by providing: Effect of the Invention

[0010] The packaging container of the present invention maintains a good appearance when displayed and has good recyclability during container production. It also reduces gas replacement costs and can extend the quality retention period of the packed food. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing an example of a co-extrusion device for producing a multilayer structure provided in a packaging container of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view of a tray-shaped container showing an example of how the packaging container of the present invention can be used. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The packaging container of the present invention is a packaging container in which food is filled and sealed, the packaging container having a multilayer structure with a gas barrier layer, the maximum height roughness (Rz) of the container surface measured in accordance with JIS-B0601 (2001) is 1 μm or more and 30 μm or less, and the oxygen transmission rate of the packaging container under conditions of 20° C. and 65% RH is 0.00001 cc / cm 3 ·day · atm or more 0.001cc / cm 3 The oxygen concentration O(10) of the gas inside the container 10 days after sealing and packaging is 0% by volume or more and 5% by volume or less. In this application, the surface of the packaging container means both the inner and outer surfaces of the packaging container.

[0013] The packaging container of the present invention may be composed of only the multilayer structure or may be composed of a combination of the multilayer structure and other materials. From the viewpoint of more effectively solving the problem to be solved by the present invention, it is preferable that the packaging container of the present invention is composed of only the multilayer structure.

[0014] Foods to be filled in the packaging container of the present invention include foods that can be sealed and packaged with low possibility of generating gases such as ethylene, and are preferably processed foods. Examples of processed foods include cooked foods such as instant curry, cooked curry, instant stew, cooked stew, sauce mix, Chinese food base, mixed rice base, cooked rice products, and microwave-only foods; home-made ingredients such as premixes, honey, starch syrup, syrup, dough / skin, and dessert base; noodles such as dried noodles, raw noodles / boiled noodles, spaghetti, and macaroni; grains such as rice and packaged rice cakes; processed meats such as livestock ham, livestock sausage, fish ham, fish sausage, roast pork, and bacon; paste products such as kamaboko, hanpen, and chikuwa; water-based foods such as tofu, konjac, and fried tofu; side dishes such as salads, boiled beans, Japanese side dishes, Chinese side dishes, and Western side dishes; foods for infants; health foods; and food gifts. Among these, solid foods are preferred, and prepared foods are more preferred.

[0015] The maximum height roughness (Rz) of the packaging container surface is 1 μm or more, preferably 2 μm or more. The maximum height roughness (Rz) of the packaging container surface is 30 μm or less, preferably 20 μm or less, more preferably 15 μm or less. If the maximum height roughness (Rz) is less than 1 μm, the food in the container tends to become uneven when displayed at an angle, which impairs the appearance. If the maximum height roughness (Rz) exceeds 30 μm or more, fine powder is generated when trimmings (cut-out parts) generated during container manufacturing or defective products are collected and reused (recycled), which tends to cause problems in the extrusion process.

[0016] The arithmetic mean roughness (Ra) of the packaging container surface is preferably 0.1 μm or more, more preferably 0.2 μm or more. The arithmetic mean roughness (Ra) of the packaging container surface is preferably 2.5 μm or less, more preferably 2.0 μm or less. If the arithmetic mean roughness (Ra) is less than 0.1 μm, the food in the container tends to become uneven when displayed at an angle, which impairs the appearance. If the arithmetic mean roughness (Ra) exceeds 2.5 μm, fine powder is generated when trims (cut-out parts) generated during container manufacturing or defective products are collected and reused (recycled), which tends to cause problems in the extrusion process.

[0017] The surface roughness (maximum height roughness (Rz) and arithmetic mean roughness (Ra)) of the packaging container surface in the present invention means the average value of values ​​measured in a non-contact manner with a cutoff value (λc) of 2.5 mm in accordance with JIS-B0601 (2001) by arbitrarily selecting 10 points in an evaluation range of a maximum width of 1414 μm and a height of 1060 μm from the packaging container surface. Note that steps larger than the average thickness of the multilayer structure are excluded from the evaluation value of the surface roughness, and a range that does not include such steps is selected within the arbitrarily selected observation range.

[0018] The maximum height roughness (Rz) and arithmetic mean roughness (Ra) of the packaging container surface of the present invention can be adjusted, for example, by controlling the surface roughness of the inner surface of the die in the coextrusion device or injection molding, particularly the inner surface of the outlet portion (die). This is believed to be because the surface shape of the inner surface of the die outlet portion is transferred to the multilayer structure to be extruded. Therefore, by increasing the smoothness of the inner surface of the die, the surface roughness of the resulting multilayer structure and packaging container can be reduced. In addition, the surface roughness can also be adjusted by the air slit of the coextrusion device described later.

[0019] The ten-point average roughness (Rz JIS94 ) is preferably 15 μm or less, more preferably 5 μm or less, further preferably 3 μm or less, and particularly preferably 1 μm or less. JIS94 ) may be 0.1 μm or more, or 0.3 μm or more. The arithmetic mean roughness (Ra) of the die inner surface is preferably 1.2 μm or less, more preferably 1 μm or less, and even more preferably 0.5 μm or less. On the other hand, the arithmetic mean roughness (Ra) may be 0.01 μm or more, or 0.03 μm or more. When the surface roughness of the die inner surface is within the above range, there is a tendency that the surface roughness of the obtained multilayer structure and packaging container can be adjusted to the preferred range of the present invention.

[0020] Here, the ten-point average roughness (Rz JIS94 The arithmetic mean roughness (Ra) and the arithmetic mean roughness (Rz) are the average values ​​of measurements taken at 10 randomly selected points. JIS94 The measured values ​​of the roughness average roughness (Ra) are in accordance with JIS-B0601 (1994), with a cut-off value (λc) of 2.5 mm, an evaluation length (1) of 7.5 mm, and a contact method.

[0021] The oxygen concentration O(0) of the gas inside the packaging container of the present invention immediately after the packaging container is sealed is preferably as close to 0 as possible from the viewpoint of suppressing oxidation deterioration of food and the proliferation of aerobic bacteria, but the closer O(0) is to 0, the higher the gas replacement cost tends to be. The inventors have found through their studies that since the oxygen concentration inside the container decreases due to oxygen consumption by the contents after the packaging container is sealed, if O(0) is within the range of 5% by volume or less in the case of the packaging container of the present invention, the deterioration of food caused by oxygen in the packaging container and the proliferation of aerobic bacteria can be suppressed and the food quality retention period can be sufficiently extended. From the viewpoint of extending the food quality retention period while suppressing the cost of gas replacement, the oxygen concentration O(0) of the gas inside the packaging container of the present invention immediately after the packaging container is sealed is preferably 0.1% by volume or more, more preferably 0.3% or more. In addition, O(0) is preferably 5% by volume or less, more preferably 4% or less, and even more preferably 3% or less.

[0022] The oxygen concentration O(10) of the gas inside the packaging container of the present invention on the 10th day after the packaging is sealed is 0% by volume or more. In addition, O(10) is 5% by volume or less, preferably 4% or less, and more preferably 3% or less. If O(10) exceeds 5% by volume, the food quality storage period will be significantly reduced due to deterioration of the food caused by oxygen and proliferation of aerobic bacteria, which is not preferable.

[0023] In the packaging container of the present invention, the ratio O(10) / O(0) of the oxygen concentration O(10) to the oxygen concentration O(0) of the gas inside immediately after the sealed packaging is preferably 0 or more. In addition, O(10) / O(0) is preferably less than 1, more preferably 0.9 or less, even more preferably 0.8 or less, and particularly preferably 0.7 or less. When O(10) / O(0) is within the above range, the oxygen concentration inside the packaging container can be kept low at all times, so that the freshness and flavor of the food can be better maintained. Methods for adjusting O(10) / O(0) to the above range include a method of using a multilayer structure with high gas barrier properties and a method of increasing the volume percentage of food in the packaging container.

[0024] The gas other than oxygen inside the packaging container of the present invention preferably contains at least one gas selected from nitrogen and carbon dioxide. When nitrogen is contained inside the packaging container, oxidative deterioration of food tends to be suppressed. Also, when carbon dioxide is contained inside the packaging container, the proliferation of aerobic bacteria tends to be suppressed.

[0025] When nitrogen is contained inside the packaging container of the present invention, the nitrogen content in the gas inside the container other than oxygen and carbon dioxide is preferably 95% by volume or more, more preferably 98% by volume or more, even more preferably 99% by volume or more, and may be 100% by volume.

[0026] When carbon dioxide is contained inside the packaging container of the present invention, the carbon dioxide content in the gas inside the container is preferably 30% by volume or less, more preferably 25% by volume or less. The carbon dioxide content in the gas inside the container is preferably 0.5% by volume or more, more preferably 1% by volume or more. By setting the carbon dioxide content within the above range, the proliferation of aerobic bacteria can be effectively suppressed.

[0027] The volume ratio (volume %) of the food to the volume of the storage section of the packaging container of the present invention is preferably 15 volume % or more and 80 volume % or less. If the volume ratio of the food is 15 volume % or more, it tends to be easier to prevent the food from being unevenly distributed when displayed at an angle. Also, if the volume ratio of the food is 80 volume % or less, gas replacement tends to be relatively easy.

[0028] The oxygen permeability of the packaging container of the present invention under conditions of 20°C and 65% RH is 0.00001 cc / (cm 3 ·day·atm) or more, and is 0.00005cc / (cm 3 The packaging container of the present invention may have an oxygen permeability of 0.001 cc / (cm 2 ·day ·atm) or more under conditions of 20°C and 65% RH. 3 ·day·atm) or less, and 0.0005cc / (cm 3 ·day·atm) or less is preferable, and 0.0003cc / (cm 3The oxygen permeability of the packaging container of the present invention is preferably 0.001 cc / cm 3 If the oxygen concentration is above 0.00001cc / (cm 3 The oxygen permeability of a container is the amount of oxygen that passes through it in one day under 1 atmosphere of oxygen per cm 3 This means that a hit is 0.00001cc.

[0029] [Gas barrier layer] The gas barrier layer in the multilayer structure of the packaging container of the present invention is a layer having a function of preventing gas permeation. Specifically, the oxygen permeability measured in accordance with JIS-K7126-2 (2006) Part 2 (constant pressure method) under conditions of 20°C and 65% RH is 100cc·20μm / (m 2 The oxygen permeability of the gas barrier layer used in the present invention is 50cc·20μm / (m 2 ·day·atm) or less is preferable, and 10cc·20μm / (m 2 ·day·atm) or less is more preferable. 2 The oxygen permeability of "1 m2 of 20 μm barrier material" is 2 This means that the daily oxygen transmission rate under 1 atmosphere of oxygen is 100cc.

[0030] Examples of the gas barrier material contained in the gas barrier layer include ethylene-vinyl alcohol copolymer (hereinafter also referred to as "EVOH"), a composite structure containing phosphorus and a polyvalent metal element, modified starch, polyamide, polyester, polyvinylidene chloride, acrylonitrile copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, polyvinyl alcohol, etc. Among them, EVOH, a composite structure containing phosphorus and a polyvalent metal element, or modified starch are preferred from the viewpoint of gas barrier properties, and EVOH is more preferred from the viewpoint of melt moldability.

[0031] (EVOH) EVOH can usually be obtained by saponifying an ethylene-vinyl ester copolymer. The production and saponification of the ethylene-vinyl ester copolymer can be carried out by a known method. A representative vinyl ester is vinyl acetate, but other fatty acid vinyl esters such as vinyl formate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl pivalate, and vinyl versatate may also be used.

[0032] The ethylene unit content of the EVOH is preferably 20 mol% or more, more preferably 22 mol% or more, and even more preferably 24 mol% or more. The ethylene unit content of the EVOH is preferably 60 mol% or less, more preferably 55 mol% or less, and even more preferably 50 mol% or less. When the ethylene unit content is 20 mol% or more, the melt moldability and gas barrier properties under high humidity tend to be good. On the other hand, when the ethylene unit content is 60 mol% or less, the gas barrier properties tend to be improved. The ethylene unit content of the EVOH can be determined by a nuclear magnetic resonance (NMR) method.

[0033] The saponification degree of the vinyl ester component of EVOH is preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 99 mol% or more. By making the saponification degree 90 mol% or more, it is possible to improve the gas barrier properties of the molded article. The saponification degree of EVOH may be 100 mol% or less, or 99.99 mol% or less. The saponification degree of EVOH is 1 The degree of saponification of EVOH is in the above range, and the gas barrier property tends to be good.

[0034] In addition, EVOH may have units derived from other monomers other than ethylene, vinyl esters, and saponified products thereof, within the scope of the present invention. When EVOH has the other monomer units, the content of the other monomer units relative to the total structural units of EVOH is preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 10 mol% or less, and particularly preferably 5 mol% or less. In addition, when EVOH has units derived from the other monomers, the lower limit may be 0.05 mol% or 0.10 mol%. Examples of the other monomers include alkenes such as propylene, butylene, pentene, and hexene; 3-acyloxy-1-propene, 3-acyloxy-1-butene, 4-acyloxy-1-butene, 3,4-diacyloxy-1-butene, 3-acyloxy-4-methyl-1-butene, 4-acyloxy-2-methyl-1-butene, and 4-acyloxy-3-methyl. -1-butene, 3,4-diacyloxy-2-methyl-1-butene, 4-acyloxy-1-pentene, 5-acyloxy-1-pentene, 4,5-diacyloxy-1-pentene, 4-acyloxy-1-hexene, 5-acyloxy-1-hexene, 6-acyloxy-1-hexene, 5,6-diacyloxy-1-hexene, 1,3-diacetoxy-2-methyl alkenes having an ester group such as dimethylpropane or saponified products thereof; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, or the like, or their anhydrides, salts, or mono- or dialkyl esters; nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methacrylamide; olefin sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, methallylsulfonic acid, or the like, or their salts; vinyl silane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxy-ethoxy)silane, γ-methacryloxypropylmethoxysilane; alkyl vinyl ethers, vinyl ketones, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, and the like.

[0035] The EVOH may be EVOH that has been modified by a method such as urethanization, acetalization, cyanoethylation, oxyalkylenation, etc. Such modified EVOH tends to have good melt moldability.

[0036] As the EVOH, two or more kinds of EVOH differing in ethylene unit content, degree of saponification, copolymer component, presence or absence of modification or type of modification, etc. may be mixed and used.

[0037] EVOH can be polymerized by known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Bulk polymerization or solution polymerization, in which polymerization is allowed to proceed without a solvent or in a solution such as alcohol, is usually used.

[0038] The solvent used in the solution polymerization method is not particularly limited, but an alcohol is preferably used, and for example, a lower alcohol such as methanol, ethanol, propanol, etc. The amount of the solvent used in the polymerization reaction solution may be selected in consideration of the viscosity average polymerization degree of the target EVOH and chain transfer of the solvent, and the weight ratio of the solvent to the total monomers (solvent / total monomers) contained in the reaction solution is preferably 0.01 to 10, more preferably 0.05 to 3.

[0039] Examples of the catalyst used in the polymerization include azo initiators such as 2,2-azobisisobutyronitrile, 2,2-azobis-(2,4-dimethylvaleronitrile), 2,2-azobis-(4-methoxy-2,4-dimethylvaleronitrile), and 2,2-azobis-(2-cyclopropylpropionitrile); and organic peroxide initiators such as isobutyryl peroxide, cumyl peroxy neodecanoate, diisopropyl peroxycarbonate, di-n-propyl peroxy dicarbonate, t-butyl peroxy neodecanoate, lauroyl peroxide, benzoyl peroxide, and t-butyl hydroperoxide.

[0040] The polymerization temperature is preferably 20 to 90°C, more preferably 40 to 70°C. The polymerization time is preferably 2 to 15 hours, more preferably 3 to 11 hours. The polymerization rate is preferably 10 to 90% based on the charged vinyl ester, more preferably 30 to 80%. The resin content in the solution after polymerization is preferably 5 to 85%, more preferably 20 to 70%.

[0041] After a predetermined period of polymerization or after a predetermined polymerization rate has been reached, a polymerization inhibitor is added as necessary, unreacted ethylene gas is removed by evaporation, and then unreacted vinyl ester is removed.

[0042] Next, an alkali catalyst is added to the copolymer solution to saponify the copolymer. The saponification method can be either continuous or batchwise. As the alkali catalyst, for example, sodium hydroxide, potassium hydroxide, alkali metal alcoholate, etc. can be used.

[0043] Since the EVOH after the saponification reaction contains an alkali catalyst, by-product salts such as sodium acetate and potassium acetate, and other impurities, it is preferable to remove these by neutralization and washing as necessary. Here, when the EVOH after the saponification reaction is washed with water such as ion-exchanged water that contains almost no metal ions, chloride ions, etc., some of the sodium acetate, potassium acetate, etc. may remain.

[0044] EVOH may contain other components such as other thermoplastic resins, metal salts, acids, boron compounds, plasticizers, fillers, antiblocking agents, lubricants, stabilizers, surfactants, colorants, UV absorbers, antistatic agents, drying agents, crosslinking agents, fillers, reinforcing materials such as various fibers, etc. Among these, it is preferable that EVOH contains metal salts and acids from the viewpoints of thermal stability and adhesion to other resins.

[0045] The metal salt is preferably an alkali metal salt from the viewpoint of further increasing interlayer adhesion, and is preferably an alkaline earth metal salt from the viewpoint of thermal stability. When EVOH contains a metal salt, the content is preferably 1 ppm or more, more preferably 5 ppm or more, even more preferably 10 ppm or more, and particularly preferably 20 ppm or more, calculated as the metal atom of the metal salt relative to EVOH. The content of the metal salt is preferably 10,000 ppm or less, more preferably 5,000 ppm or less, even more preferably 1,000 ppm or less, and particularly preferably 500 ppm or less, calculated as the metal atom of the metal salt relative to EVOH. When the content of the metal salt is within the above range, the thermal stability during recycling tends to be good while maintaining good interlayer adhesion.

[0046] As the acid, a carboxylic acid compound or a phosphoric acid compound is preferable from the viewpoint of increasing the thermal stability during EVOH melt molding. When EVOH contains a carboxylic acid compound, the content of the carboxylic acid (the content of the carboxylic acid in the dry composition of the gas barrier layer containing EVOH) is preferably 1 ppm or more, more preferably 10 ppm or more, and even more preferably 50 ppm or more. In addition, the content of the carboxylic acid is preferably 10000 ppm or less, more preferably 1000 ppm or less, and even more preferably 500 ppm or less. When EVOH contains a phosphoric acid compound, the content of the phosphoric acid compound (the content of the phosphoric acid compound in the gas barrier layer containing EVOH in terms of phosphate radical) is preferably 1 ppm or more, more preferably 10 ppm or more, and even more preferably 30 ppm or more. On the other hand, the content of the phosphoric acid compound is preferably 10000 ppm or less, more preferably 1000 ppm or less, and even more preferably 300 ppm or less. When EVOH contains a carboxylic acid compound or a phosphoric acid compound within the above range, the thermal stability during melt molding tends to be improved.

[0047] When EVOH contains the boron compound, its content (the boron-equivalent content of the boron compound in the dry composition of the gas barrier layer containing EVOH) is preferably 1 ppm or more, more preferably 10 ppm or more, and even more preferably 50 ppm or more. The content of the boron compound is preferably 2000 ppm or more, more preferably 1000 ppm or more, and even more preferably 500 ppm or more. When the content of the boron compound is within the above range, the thermal stability during melt molding tends to be good.

[0048] The method of incorporating the phosphoric acid compound, carboxylic acid or boron compound into the gas barrier layer containing EVOH is not particularly limited, and for example, a method of adding the compound to the composition and kneading it when preparing pellets of the composition containing EVOH is preferably adopted. The method of adding the compound to the composition is also not particularly limited, and examples thereof include a method of adding the compound as a dry powder, a method of adding the compound in a paste form impregnated with a solvent, a method of adding the compound in a suspended state in a liquid, a method of adding the compound as a solution by dissolving the compound in a solvent, and a method of immersing the compound in a solution. Among these, from the viewpoint of uniform dispersion, the method of adding the compound as a solution by dissolving the compound in a solvent or the method of immersing the compound in a solution is preferred. The solvent is not particularly limited, but water is preferably used from the viewpoints of the solubility of the additive, cost, ease of handling, safety of the working environment, and the like.

[0049] When the gas barrier layer in the multilayer structure contains EVOH as a main component, the proportion of EVOH is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and may be 100% by mass. Here, the "main component" means the component that has the largest mass percentage among the components constituting the gas barrier layer.

[0050] When the gas barrier layer in the multilayer structure contains EVOH as a main component, the average thickness of the single gas barrier layer is preferably 3 μm or more, more preferably 5 μm or more, and more preferably 10 μm or more. The average thickness of the single gas barrier layer containing EVOH as a main component is preferably 100 μm or less, and more preferably 50 μm or less. The average thickness of the single gas barrier layer containing EVOH as a main component refers to the total thickness of the entire gas barrier layer containing EVOH as a main component in the multilayer structure divided by the number of layers of the gas barrier layer. When the average thickness of the gas barrier layer is within the above range, the durability, flexibility, and appearance properties of the packaging container of the present invention tend to be good.

[0051] (Composite structure containing phosphorus and polyvalent metal elements) The composite structure containing phosphorus and a polyvalent metal element has a barrier layer formed by the reaction of a phosphorus compound with a polyvalent metal compound. A solution containing a phosphorus compound and a solution or dispersion containing a polyvalent metal compound are mixed to form a coating agent, and the coating agent is applied to a substrate to react the polyvalent metal compound with the phosphorus compound. When the polyvalent metal atom is represented by M, a bond represented by MOP is generated between the polyvalent metal atom M and the phosphorus atom. The MOP bond has a characteristic absorption band in the infrared absorption spectrum of 1080 to 1130 cm. -1 In the infrared absorption spectrum of the composite structure, the absorption peak is in the range of 800 to 1400 cm -1 The maximum absorption wavenumber in the region is 1080-1130 cm -1 When the maximum absorption wave number of the composite structure is within the above range, excellent gas barrier properties tend to be obtained.

[0052] The substrate to which the coating agent is applied is not particularly limited, and examples thereof include resins such as thermoplastic resins and thermosetting resins; fiber assemblies such as cloth and paper; wood; glass, etc. Among them, thermoplastic resins and fiber assemblies are preferred, and thermoplastic resins are more preferred. The form of the substrate is not particularly limited, and may be a layer such as a film or sheet. The substrate is preferably one containing at least one selected from the group consisting of thermoplastic resin films and paper, more preferably one containing a thermoplastic resin film, and even more preferably a thermoplastic resin film. The thermoplastic resin film is preferably polyester, and more preferably polyethylene terephthalate from the viewpoint of the mechanical strength of the composite structure.

[0053] As the polyvalent metal element, any element can be used as long as it is a polyvalent metal element that can react with two or more molecules of a phosphorus compound. It may be a semi-polyvalent metal element. For example, elements such as magnesium, calcium, zinc, aluminum, silicon, titanium, and zirconium are used. Among them, aluminum is preferable.

[0054] As the compound of the polyvalent metal element, any compound can be used as long as it can react with the phosphorus compound to form a composite structure. The polyvalent metal compound can be used as a solution dissolved in a solvent, or as a dispersion liquid in which fine particles of the polyvalent metal compound are dispersed in a solvent. For example, aluminum nitrate can be used as the polyvalent metal compound and as an aqueous solution thereof.

[0055] Also, the fine particles of polyvalent metal oxide can be dispersed in water or an aqueous solvent and used as a dispersion liquid, and a dispersion liquid of aluminum oxide fine particles is preferred. Generally, the fine particles of polyvalent metal oxide have hydroxyl groups on their surface, and react with the phosphorus compound due to the presence of the hydroxyl groups to form the above bond. The fine particles of polyvalent metal oxide can be synthesized, for example, by hydrolyzing a compound in which a hydrolyzable characteristic group is bonded to a metal atom as a raw material, and condensing the hydrolysis product. Examples of raw materials include aluminum chloride, aluminum triethoxide, and aluminum isopropoxide. Examples of methods for condensing the above hydrolysis products include liquid phase synthesis methods such as the sol-gel method. The shape of the fine particles of polyvalent metal oxide is preferably, for example, spherical, flat, polyhedral, fibrous, and acicular, and from the viewpoint of improving gas barrier properties, fibrous or acicular is more preferred. In addition, the average particle size of the fine particles of polyvalent metal oxide is preferably 1 nm or more and 100 nm or less in order to improve gas barrier properties and transparency.

[0056] Any phosphorus compound can be used as long as it can react with a polyvalent metal compound to form the above bond. Examples of phosphorus compounds include phosphoric acid compounds and their derivatives, specifically phosphoric acid, polyphosphoric acid, phosphorous acid, and phosphonic acid. Examples of the polyphosphoric acid that can be used include pyrophosphoric acid, triphosphoric acid, or polyphosphoric acid in which four or more phosphoric acids are condensed. Derivatives of phosphoric acid compounds may be phosphates, esters (e.g., trimethyl phosphate), or halides, or dehydrates (e.g., phosphorus pentoxide) and halides can be used.

[0057] The phosphorus compound can be used in the form of a solution, for example, an aqueous solution using water as a solvent, or a solution in a hydrophilic organic solvent such as a solution in a lower alcohol.

[0058] A coating agent can be prepared by mixing a solution or dispersion of a polyvalent metal compound with a solution of a phosphorus compound. Other components may be added to the coating agent, such as polymer compounds, metal complexes, clay compounds, crosslinking agents, plasticizers, antioxidants, ultraviolet absorbers, and flame retardants. Examples of the polymer compounds include polyvinyl alcohol, partially saponified polyvinyl acetate, polyhydroxyethyl (meth)acrylate, polysaccharides (such as starch), acrylic polymers (such as polyacrylic acid, polymethacrylic acid, acrylic acid-methacrylic acid copolymers, and salts thereof, ethylene-vinyl alcohol copolymers, ethylene-maleic anhydride copolymers, styrene-maleic anhydride copolymers, isobutylene-maleic anhydride alternating copolymers, ethylene-acrylic acid copolymers, and saponified ethylene-ethyl acrylate copolymers.

[0059] The coating agent is applied, the solvent is removed, and the coating film obtained by drying is then subjected to, for example, heat treatment, whereby the polyvalent metal compound and the phosphorus compound react to generate the above bonds, thereby forming a composite structure containing phosphorus and a polyvalent metal element. The heat treatment temperature is preferably 110°C or higher, more preferably 120°C or higher, even more preferably 140°C or higher, and particularly preferably 170°C or higher. If the heat treatment temperature is low, the time required to generate sufficient bonds increases, and productivity decreases. The upper limit of the heat treatment temperature varies depending on the type of base film, and is preferably 240°C or lower, more preferably 220°C or lower. The lower limit of the heat treatment time is preferably 0.1 seconds, more preferably 1 second, and even more preferably 5 seconds. The upper limit of the heat treatment time is preferably 1 hour, more preferably 15 minutes, and even more preferably 5 minutes. The heat treatment can be performed in any of an air atmosphere, a nitrogen atmosphere, and an argon atmosphere.

[0060] <Modified starch> The starch used as the raw material for the modified starch is not particularly limited, and examples thereof include those derived from wheat, corn, tapioca, potato, rice, oats, arrowroot and pea raw materials. As the starch, high amylose starch is preferred, and high amylose corn starch and high amylose tapioca starch are more preferred.

[0061] The modified starch is preferably chemically modified so that the hydroxyl groups are replaced with functional groups which are ethers, esters or combinations thereof. The modified starch is preferably modified to contain hydroxyalkyl groups having 2 to 6 carbon atoms or modified by reaction with a carboxylic anhydride. When the modified starch is modified to contain hydroxyalkyl groups having 2 to 6 carbon atoms, the substituent of the modified starch preferably has a functional group having 2 to 4 carbon atoms, for example a hydroxyethyl group or a hydroxybutyl group for generating a hydroxyether substituent. When the modified starch is modified by reaction with a carboxylic anhydride, the functional group is preferably a butanoic acid ester or a lower homologue, more preferably an acetate ester. Dicarboxylic anhydrides such as maleic, phthalic or octenylsuccinic anhydride can also be used to prepare the ester derivatives.

[0062] As the modified starch, hydroxypropylated amylose starch containing hydroxypropyl groups is preferred, and hydroxypropylated high amylose starch is more preferred.

[0063] The degree of substitution of the modified starch is expressed as the average number of substituents per anhydrous glucose unit, and usually has a maximum value of 3. The degree of substitution of the modified starch is preferably 0.05 or more and less than 1.5.

[0064] The modified starch may also include other starches, such as mixtures of high and low amylose starches.

[0065] The modified starch may contain water, which can function as a plasticizer. The upper limit of the water content is preferably 20% by mass, more preferably 12% by mass. The moisture content of the gas barrier layer mainly composed of modified starch is generally the equilibrium moisture content at the relative humidity in the usage environment.

[0066] The modified starch may contain one or more water-soluble polymers. The water-soluble polymer is not particularly limited, but may be, for example, polyvinyl acetate, polyvinyl alcohol, or a combination thereof. Among them, polyvinyl alcohol is preferred. The upper limit of the content of one or more water-soluble polymers is preferably 1% by mass, more preferably 4% by mass. The lower limit of the content is preferably 20% by mass, more preferably 12% by mass.

[0067] The modified starch may contain one or more plasticizers. The plasticizer is not particularly limited, but is preferably a polyol, more preferably sorbitol, glycerol, maltitol, xylitol or a combination thereof. The upper limit of the content of one or more plasticizers is preferably 20% by weight, more preferably 12% by weight.

[0068] The processed starch may contain a lubricant. The lubricant is preferably a fatty acid having 12 to 22 carbon atoms, a fatty acid salt having 12 to 22 carbon atoms, or a combination thereof, and the content of the lubricant is preferably 5 mass % or less.

[0069] The lower limit of the average thickness of the single gas barrier layer containing modified starch as a main component is preferably 10 μm, more preferably 100 μm. On the other hand, the upper limit of the average thickness of the single gas barrier layer is preferably 1000 μm, more preferably 800 μm. The average thickness of the single gas barrier layer containing modified starch as a main component refers to the total thickness of the entire gas barrier layer containing modified starch as a main component in the multilayer structure divided by the number of layers of the gas barrier layer. If the average thickness of the single gas barrier layer is smaller than the lower limit, it becomes difficult to mold the layer with a uniform thickness, and the durability of the multilayer structure may decrease. On the other hand, if the average thickness of the single gas barrier layer exceeds the upper limit, the flexibility, stretchability, thermoformability, etc. of the multilayer structure may decrease.

[0070] [Multilayer structure] The multilayer structure of the packaging container of the present invention has at least one gas barrier layer, and the layer configuration of the multilayer structure can be appropriately set depending on the application, etc. When multiple gas barrier layers and thermoplastic resin layers are used, the materials constituting each layer may be the same or different.

[0071] The number of gas barrier layers in the multilayer structure is preferably 1 or more from the viewpoint of further improving gas barrier properties, and the number of thermoplastic resin layers is preferably 1 or more, more preferably 2 or more, from the viewpoint of improving impact resistance.

[0072] [Thermoplastic resin layer] The thermoplastic resin layer is a layer mainly composed of a resin composition containing a thermoplastic resin. The thermoplastic resin layer may be mainly composed of a single thermoplastic resin or may be mainly composed of a plurality of thermoplastic resins. The multilayer structure of the present invention can improve stretchability and thermoformability by laminating a thermoplastic resin layer mainly composed of a resin composition containing a thermoplastic resin.

[0073] The average thickness of the single thermoplastic resin layer is preferably 100 μm or more, more preferably 200 μm or more. The average thickness of the single thermoplastic resin layer is preferably 1000 μm or less, more preferably 500 μm or less, more preferably 400 μm or less. When the average thickness of the single thermoplastic resin layer is 100 μm or more, the thickness can be easily adjusted, and the durability of the multilayer structure of the present invention can be further improved. When the average thickness of the single thermoplastic resin layer is 500 μm or less, the thermoformability tends to be good.

[0074] The thermoplastic resin is not particularly limited as long as it is a resin that softens and exhibits plasticity when heated to a glass transition temperature or melting point, and examples thereof include polyolefin resins (polyethylene resins, polypropylene resins, etc.), grafted polyolefin resins graft-modified with unsaturated carboxylic acids or their esters, halogenated polyolefin resins, ethylene-vinyl acetate copolymer resins, ethylene-acrylic acid copolymer resins, ethylene-acrylic acid ester copolymer resins, polyester resins, polyamide resins, polyvinyl chloride resins, polyvinylidene chloride resins, acrylic resins, polystyrene resins, vinyl ester resins, ionomers, polyester elastomers, polyurethane elastomers, aromatic or aliphatic polyketones, etc. Among these, polyolefin resins are preferred in terms of mechanical strength and moldability, and polyethylene resins and polypropylene resins are more preferred.

[0075] Additives The thermoplastic resin layer may contain additives within a range that does not impair the object of the present invention. Examples of additives include resins other than the above-mentioned thermoplastic resins, heat stabilizers, ultraviolet absorbers, antioxidants, colorants, fillers, etc. When the thermoplastic resin layer contains additives, the content of the additives is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, based on the total amount of the thermoplastic resin layer.

[0076] [Adhesive layer] In the present invention, the multilayer structure may have an adhesive layer (hereinafter, may be abbreviated as "Ad") to increase the relative adhesive strength. Known adhesive resins can be used as the adhesive layer, and can be appropriately selected according to the manufacturing method of the multilayer structure.

[0077] When the multilayer structure of the packaging container of the present invention is manufactured by a lamination method or the like, the adhesive layer is preferably a two-liquid reactive polyurethane adhesive in which a polyisocyanate component and a polyol component are mixed and reacted. In addition, the adhesive layer may have a further increased adhesiveness by adding a small amount of additives such as a known silane coupling agent to the adhesive layer.

[0078] When the multilayer structure of the packaging container of the present invention is manufactured by the co-extrusion molding method, the adhesive layer is not particularly limited as long as it has adhesiveness with the gas barrier layer and the thermoplastic resin layer, but an adhesive resin containing a carboxylic acid-modified polyolefin is preferred. As the carboxylic acid-modified polyolefin, a modified olefin polymer containing a carboxyl group obtained by chemically bonding (for example, addition reaction, graft reaction, etc.) an ethylenically unsaturated carboxylic acid, its ester, or its anhydride to an olefin polymer can be preferably used. Here, the olefin polymer means polyolefins such as polyethylene (low pressure, medium pressure, high pressure), linear low-density polyethylene, polypropylene, and polybutene, and copolymers of olefins and other monomers (vinyl esters, unsaturated carboxylic acid esters, etc.) (for example, ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers, etc.). Among them, linear low-density polyethylene, ethylene-vinyl acetate copolymers (vinyl acetate content 5 to 55% by mass), and ethylene-ethyl acrylate copolymers (ethyl acrylate content 8 to 35% by mass) are preferred, and linear low-density polyethylene and ethylene-vinyl acetate copolymers are particularly preferred. Examples of the ethylenically unsaturated carboxylic acid, its ester or its anhydride include an ethylenically unsaturated monocarboxylic acid or its ester, an ethylenically unsaturated dicarboxylic acid or its mono- or diester or its anhydride, among which an ethylenically unsaturated dicarboxylic acid anhydride is preferred.Specific examples include maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, maleic acid monomethyl ester, maleic acid monoethyl ester, maleic acid diethyl ester, fumaric acid monomethyl ester, etc., and maleic anhydride is particularly preferred.

[0079] The amount of addition or grafting (modification degree) of the ethylenically unsaturated carboxylic acid or its anhydride to the olefin polymer is 0.0001 to 15% by mass, preferably 0.001 to 10% by mass, based on the olefin polymer. The addition reaction or grafting reaction of the ethylenically unsaturated carboxylic acid or its anhydride to the olefin polymer can be carried out, for example, by radical polymerization in the presence of a solvent (such as xylene) and a catalyst (such as peroxide). The melt flow rate (MFR) of the carboxylic acid modified polyolefin thus obtained, measured at 210°C, is preferably 0.2 to 30 g / 10 min, more preferably 0.5 to 10 g / 10 min. These adhesive resins may be used alone or in combination of two or more.

[0080] The average thickness of the multilayer structure is preferably 100 μm or more, more preferably 200 μm or more. The average thickness of the multilayer structure of the present invention is preferably 2000 μm or less, more preferably 1000 μm or less, and even more preferably 800 μm or less. When the average thickness of the multilayer structure is 100 μm or more, the impact resistance tends to be excellent. When the average thickness of the multilayer structure is 2000 μm or less, the manufacturing cost tends to be reduced and good thermoformability tends to be obtained.

[0081] The layer structure of the multilayer structure of the present invention is not particularly limited, and examples thereof include structures such as T / E / T, E / Ad / T, and T / Ad / E / Ad / T, where E is a gas barrier layer, Ad is an adhesive layer, and T is a layer obtained from a thermoplastic resin. In the case where a recovery layer is provided, examples thereof include structures such as T / Reg / Ad / E / Ad / Reg / T, T / Reg / Ad / E / Ad / T, and T / Ad / E / Ad / Reg / T, where Reg / Ad / E / Ad / T are each a single layer or a multilayer. From the viewpoint of improving impact resistance, the multilayer structure of the present invention preferably has a layer structure having a thermoplastic resin layer as the outermost layer.

[0082] The multilayer structure can be produced by a known method such as coextrusion molding, coinjection molding, extrusion lamination, dry lamination, etc. Examples of the coextrusion molding method include coextrusion lamination, coextrusion sheet molding, coextrusion inflation molding, and coextrusion blow molding.

[0083] An example of manufacturing a multilayer structure by a co-extrusion device will be described with reference to FIG. 1. The co-extrusion device shown in FIG. 1 includes an extrusion die 70 for extruding polymers (polymer 60 / polymer 50 / polymer 60), a first conveying roll 80 and a second conveying roll 90 for conveying a multilayer structure 100 extruded from the extrusion die 70, and an air slit 110 disposed on the opposite side of the multilayer structure 100 from the first conveying roll 80. By this co-extrusion device, the polymer 60 forming the thermoplastic resin layer and the polymer 50 forming the gas barrier layer are co-extruded from the extrusion die 70, and the multilayer structure 100 made of the polymers extruded from the extrusion die 70 is wound up while being conveyed by the first conveying roll 80 and the second conveying roll 90, etc., to obtain a multilayer structure film. In FIG. 1, hatching showing the cross-sectional structure is omitted for the extrusion die 70, the first conveying roll 80, the second conveying roll 90, and the air slit 110.

[0084] The pressure of the air A introduced into the air slit 110 is preferably 0.01 MPa or more, and more preferably 0.05 MPa or more. The pressure of the air A is preferably 0.4 MPa or less, and more preferably 0.3 MPa or less. By setting the pressure of the air A introduced into the air slit 110 within the above range, the smoothness of the multilayer structure can be controlled, and the roughness of the surface of the resulting packaging container can be reduced.

[0085] [Packaging container] The type of packaging container having the multilayer structure of the present invention is not particularly limited, and examples thereof include tray-shaped containers, cup-shaped containers, bag-shaped containers, bottle-shaped containers, pouch-shaped containers, etc. Among these, tray-shaped containers and pouch-shaped containers are preferred from the viewpoint of display in retail stores.

[0086] Examples of the other layers include a thermosetting resin layer, a fiber assembly layer such as fabric or paper, a wood layer, and a glass layer.

[0087] In the packaging container of the present invention, after the food is filled in the storage section, the food is sealed and packaged in a state in which the oxygen concentration inside the packaging container is replaced with a predetermined gas concentration.

[0088] (Tray-shaped container) A packaging container according to one embodiment of the present invention will be specifically described using a tray-shaped container shown in Fig. 2. However, the tray-shaped container is merely one example of a packaging container, and the following description of the tray-shaped container does not limit the scope of the present invention.

[0089] The tray-shaped container 1 in Fig. 2 comprises a tray body 2 and a lid 5, which serve as the container. This tray-shaped container 1 is used by filling the tray body 2 with food 10, which is the content, and then sealing the lid 5 to the flange 3 of the tray body 2 so as to close the opening of the tray body 2 while replacing the atmosphere inside the tray-shaped container 4 with gas so that the oxygen concentration is 5% or less. The tray body 2 and the lid 5 can be obtained by thermoforming a multilayer structure, for example, in the form of a film or sheet.

[0090] The multilayer structure of the tray body 2 is made up of three layers, and the layer structure is such that a thermoplastic resin layer 2a containing polypropylene as a main component, which is a thermoplastic resin, is laminated on both sides of a gas barrier layer 2b containing EVOH as a main component, which is a gas barrier material. Meanwhile, the multilayer structure of the lid 5 is also made up of three layers, and the layer structure is such that a gas barrier layer 5b containing EVOH as a main component, which is a gas barrier material, is laminated on the upper surface side of a first thermoplastic resin layer 5c containing polypropylene as a main component, which is a thermoplastic resin. Then, a second thermoplastic resin layer 5a containing nylon as a main component, which is a thermoplastic resin, is laminated on the upper surface side of this gas barrier layer 5b, and the second thermoplastic resin layer 5a constitutes the outermost layer.

[0091] When the multilayer structure of the present invention is used for a tray-shaped container, the gas barrier material used for the tray body is preferably EVOH or modified starch, and the gas barrier material used for the tray lid is preferably EVOH or a composite structure containing phosphorus and a polyvalent metal element.

[0092] The packaging container of the present invention can be formed by a method in which a multilayer structure such as a film or sheet is heated and softened, and then molded to fit the shape of a mold (thermoforming), or by a method in which the structure is injected into the desired mold (injection molding).

[0093] Examples of thermoforming methods include a method of forming into a mold shape using vacuum or compressed air, and if necessary, a plug (straight method, drape method, air slip method, snapback method, plug assist method, etc.), and a press molding method. Various molding conditions such as molding temperature, degree of vacuum, compressed air pressure, and molding speed are appropriately set depending on the plug shape, mold shape, properties of the raw material film or sheet, etc. The molding temperature is not particularly limited as long as it is a temperature at which the resin can be softened sufficiently for molding, and the suitable temperature range varies depending on the configuration of the multilayer structure such as a film or sheet.

[0094] When thermoforming a film, it is preferable not to heat the film to a temperature so high that the film melts or the unevenness of the metal surface of the heater plate is transferred to the film, but not to a temperature so low that the shaping is insufficient. Specifically, the film temperature is preferably 50° C. or higher, more preferably 60° C. or higher. The film temperature is preferably 120° C. or lower, more preferably 110° C. or lower.

[0095] On the other hand, when a sheet is thermoformed, it may be possible to form the sheet at a higher temperature than in the case of a film. In this case, the sheet temperature is preferably, for example, 130°C or higher and 180°C or lower.

[0096] [Food sealing packaging method] An example of a method for hermetically packaging food according to the present invention is a method in which food is filled into a molded tray body, a lid is heat-sealed to the flange of the tray body under gas-purged conditions so that the oxygen concentration inside the tray-shaped container is 5% or less, and the tray-shaped container is hermetically packaged.

[0097] The gas replacement method for the packaging container of the present invention can be a known method, and examples thereof include a nozzle type, a chamber type, and a gas flush type. The nozzle type is a method in which a nozzle is inserted into the mouth of the packaging container, the packaging container is degassed, and then the bag is filled with gas. The chamber type is a method in which a packaging container is set in a chamber, the entire chamber is degassed, and then the chamber is filled with gas. The gas flush type is a method in which gas is sprayed while the contents are being filled, and the air in the container is expelled and the gas is replaced.

[0098] [Sterilization method] Sterilization methods include low-temperature sterilization (hot pack, boiling sterilization), high-temperature sterilization (retort sterilization), moist heat sterilization, dry heat sterilization, high-frequency heating, infrared heating, electrical resistance heating, etc. Sterilization may be performed before or after the food is packed into the packaging material, but sterilization after filling the packaging material is preferred from the viewpoint of suppressing the introduction of bacteria.

[0099] [Other embodiments] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is not limited to the configurations of the above-described embodiments, but is indicated by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0100] In the above embodiment, the multilayer structure of the packaging container has one or more gas barrier layers and one or more thermoplastic resin layers, but the multilayer structure may include layers other than the gas barrier layer and the thermoplastic resin layer. The type of resin composition constituting the other layers is not particularly limited, but it is preferable that the resin composition has high adhesion to the gas barrier layer, the thermoplastic resin layer, or between these layers. EXAMPLES

[0101] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples in any way.

[0102] <Materials used in the examples> "EVAL(trademark) J171B": Manufactured by Kuraray Co., Ltd., EVOH, ethylene unit content 32mol% "EVAL (trademark) E105B": Manufactured by Kuraray Co., Ltd., EVOH, ethylene unit content 44 mol% "EVAL (trademark) G156B": Manufactured by Kuraray Co., Ltd., EVOH, ethylene unit content 48 mol% "Eval (trademark) Film EF-XL": Kuraray Co., Ltd., biaxially oriented EVOH film, thickness 12 μm "Novatec (trademark) PP EA7AD": Polypropylene (hereinafter sometimes abbreviated as "PP"), manufactured by Japan Polypropylene Corporation. "Admer (trademark) QF500": Adhesive polyolefin manufactured by Mitsui Chemicals "OP U-1": Mitsui Chemicals Tocello Co., Ltd., biaxially oriented polypropylene film, thickness 20 μm (hereinafter, may be abbreviated as "OPP") "Takelac (trademark) A-385": Two-component adhesive manufactured by Takeda Pharmaceutical Co., Ltd. "Takenate (trademark) A-10": Two-component adhesive manufactured by Takeda Pharmaceutical Co., Ltd. "EMBLEM (trademark) ONBC-15": Manufactured by Unitika Ltd., oriented nylon film, thickness 15μm (hereinafter may be abbreviated as "ONY")

[0103] <Evaluation method> (1) Die surface roughness Using a small surface roughness measuring instrument, Surf Test SJ-400 (contact type, manufactured by Mitutoyo Corporation), the ten-point average roughness (Rz JIS94) and arithmetic mean roughness (Ra), and the average value at 10 arbitrarily selected points was taken as the measured value. (2) Surface roughness of packaging containers Using a shape measuring laser microscope "VK-X200" (non-contact type, manufactured by Keyence Corporation), the maximum height roughness (Rz) and arithmetic mean roughness (Ra) of the container were measured in an evaluation area of ​​1414 μm wide and 1060 μm high with a cutoff value (λc) of 2.5 mm in accordance with JIS-B0601 (2001), and the average value in 10 arbitrarily selected evaluation areas was taken as the measured value. Note that steps larger than the average thickness of the multilayer structure were excluded from the evaluation value of the surface roughness, and a range that did not include such steps was selected within the arbitrarily selected observation range. (3) Uneven thickness during collection The mixture was passed through nip rolls heated to 80°C and crushed in a film / sheet crusher (manufactured by HORAI Co., Ltd.) with the screen opening diameter adjusted to 15 mm to obtain laminated flake-shaped chips. Five L-shaped pipes were installed every 10 m along a 50 m pipe with an inner diameter of 100 mm. 1 ton of flake-shaped chips was air-transported through this L-shaped pipe by an air-transporting device equipped with a hopper with a cyclone, and using the flake-shaped chips after transporting 1 ton, a monolayer film was formed using a 20 mm extruder "D2020" (D (mm) = 20, L / D = 20, compression ratio = 2.0, screw: full flight) manufactured by Toyo Seiki Seisakusho Co., Ltd. under the following conditions to obtain a monolayer film. Extrusion temperature: Feeding section / Compression section / Metering section / Die =180 / 220 / 220 / 220℃ Screw rotation speed: 60 rpm Discharge amount: 1.3kg / hr Take-up roll temperature: 80℃ Take-off roll speed: 1.1m / min. Film thickness: 90μm In the continuous film production, samples were taken in the MD direction 1 hour after the start of film production, and the thickness was measured over a 2m length range using a continuous thickness meter. Points were taken at 25mm intervals, and the standard deviation (μm) was calculated to evaluate the thickness unevenness according to the following criteria. A: 5.0μm or less B: More than 5.0μm and less than 7.5μm C: More than 7.5μm and less than 10μm D: More than 10μm and less than 15μm E: More than 15μm (4) Measurement of slipperiness of drip sheets inside containers To evaluate the slipperiness of the drip sheet in the container, a traymate (Unicharm) was attached to the thread of a friction tester (Toyo Seiki Seisakusho) and the multilayer sheet prepared above was placed on the slip plate. The plate was tilted at 2.9 degrees / sec, and the tilt was stopped as soon as the thread tilted, and the angle of tilt was measured and judged as follows. A: Starts sliding at 15 degrees or more B: Starts sliding at an angle less than 15 degrees (5) Measurement of oxygen permeability of containers The oxygen permeability of the multi-layer container and the multi-layer film was measured in accordance with Part 2 (isobaric method) of JIS-K7126-2 (2006) under conditions of 15°C and 50% RH using an oxygen permeability measuring device OX-TRAN2 / 20 (detection limit 0.0005 cc / pck day atm) manufactured by MOCON INC. The size of the multi-layer container was measured and the volume was calculated. The total oxygen permeability of the multi-layer container and the multi-layer film was divided by the volume to obtain the oxygen permeability per unit (cc / cm 3 The oxygen permeability of 0.0005cc / (pck·day·atm) means that the oxygen permeability per day under 1 atmosphere of oxygen is 0.0005cc per container (pck). (6) Measurement of gas composition in the vessel The oxygen concentration inside the container was measured using CheckPoint3 manufactured by MOCON Europe. (7) General bacterial count (aerobic bacterial count) After storing at 15℃ and 50% RH for 10 days, measurements were performed using the standard agar medium method (35℃±1℃, 48±3 hours) in accordance with the Food Sanitation Inspection Guidelines: Microorganisms (2015). In all examples and comparative examples, the general bacteria count was 10 CFU / g or less immediately after sealing. (8) Food color The coloration of the food products after storage for 10 days at 15°C and 50% RH was visually inspected and judged as follows: A: Almost the same as before storage B: Slightly faded C: Slightly faded (9) Food odor The odor of the food was checked after storage for 10 days at 15°C and 50% RH and judged as follows: A: Almost the same as before storage B: The smell has slightly disappeared. C: Almost no smell left (10) Food taste The taste of the food was checked after storage for 10 days at 15°C and 50% RH and judged as follows: A: Almost the same as before storage B: Slightly less flavorful C: The flavor has become weaker

[0104] <Example 1> (Preparation of multi-layer structure (for tray body)) Using EVOH "EVAL (trademark) J171B" as the gas barrier layer, polypropylene "Novatec (trademark) PP EA7AD" (PP) as the thermoplastic resin layer, and adhesive polyolefin "Admer (trademark) QF500" (Ad) as the adhesive layer, a 3-type 5-layer multilayer structure (PP / Ad / EVOH / Ad / PP = 270 μm / 15 μm / 30 μm / 15 μm / 270 μm) was obtained by the following method / conditions. The film-forming equipment had a temperature-controllable take-up roll after the extruder with a film-forming die, and the obtained multilayer structure was wound up by a winding machine. EVOH extruder: 20mmφ extruder, lab machine ME type CO-EXT (manufactured by Toyo Seiki Co., Ltd.) Ad extruder: 25mmφ extruder P25-18AC (Osaka Seiki Co., Ltd.) PP extruder: 32mmφ extruder GF-32-A (manufactured by Plastics Engineering Research Institute) EVOH extrusion temperature Feeding section / Compression section / Metering section / Die =175 / 210 / 220 / 220℃ Ad Extrusion temperature Feeding section / Compression section / Metering section / Die =100 / 160 / 220 / 220℃ PP extrusion temperature Feeding section / Compression section / Metering section / Die =150 / 200 / 210 / 220℃ Die: 300mm wide coat hanger die (manufactured by Plastics Engineering Research Institute) Take-up roll temperature: 80℃ (Forming the tray body) The obtained multilayer structure (for the tray body) was thermoformed (compressed air: 5 kg / cm) into a container shape (length 12 cm × width 9 cm × height 3 cm) at a sheet temperature of 150°C using a thermoforming machine (manufactured by Asano Seisakusho). 2 , plug temperature: 150°C, mold temperature: 70°C) was used to obtain a thermoformed container (tray body). (Preparation of multi-layer structure (for tray lid)) A two-component adhesive (Takelac (trademark) A-385 / Takenate A-10) was applied to one side of the biaxially oriented polypropylene film "OP U-1" (OPP) at a solid content of 2.5 g / m 2 After coating with a basis weight of 1000g, a biaxially oriented EVOH film "EVAL (trademark) EF-XL" used as a gas barrier layer was laminated by dry lamination. Next, a stretched nylon film "EMBLEM (trademark) ONBC-15" was laminated in the same manner to produce a multilayer structure (thickness 47μm) with a structure of OPP / EF-XL / ONY. (Production of packaging containers) Using a semi-automatic tray sealer M manufactured by Sealpac GmbH, 80 g of fried chicken was filled into the prepared tray body, and the prepared multilayer structure (for the tray lid) was used as a lid material to carry out gas replacement airtight packaging to produce a packaged container filled with food. Nitrogen gas was used as the gas.

[0105] The obtained packaging container was evaluated for the surface roughness of the die, the surface roughness of the packaging container, thickness unevenness during collection, and the slipperiness of the drip sheet inside the container according to the above-mentioned evaluation methods (1) to (4). The evaluation results are shown in Table 1. In addition, according to the above-mentioned evaluation methods (5) to (10), the oxygen permeability of the packaging container, the gas composition inside the packaging container, the general bacterial count, the color of the food, the smell of the food, and the taste of the food were evaluated. The evaluation results are shown in Table 2.

[0106] <Examples 2 to 9 and Comparative Examples 1 to 4> Except for changing the type of barrier layer and the type of food as shown in Table 1 and appropriately changing the screw rotation speed of the EVOH extruder, packaging containers were produced and evaluated in the same manner as in Example 1. The evaluation results are shown in Tables 1 and 2. <Example 10> A packaging container was produced and evaluated in the same manner as in Example 1, except that an air slit with a gap of 0.3 mm for the air outlet was provided at a position 3 cm above the casting roll, and air was blown through the air slit at 0.1 MPa simultaneously with extrusion from the die onto the take-up roll. The evaluation results are shown in Tables 1 and 2. <Comparative Example 5> A packaging container was produced and evaluated in the same manner as in Example 1, except that an air slit with a gap of 0.3 mm for the air outlet was provided at a position 3 cm above the casting roll, and air was blown through the air slit at 0.3 MPa simultaneously with extrusion from the die onto the take-up roll. The evaluation results are shown in Tables 1 and 2.

[0107] [Table 1]

[0108] [Table 2]

[0109] In Example 1, the oxygen permeability and initial oxygen concentration of the packaging container, the maximum height roughness (Rz) of the container surface, and the arithmetic mean roughness (Ra) were adjusted to a suitable range, and the recyclability during container manufacturing was good while maintaining a good appearance during display, and the quality retention period of the filled food could be extended. In Examples 2 to 5, the oxygen permeability or initial oxygen concentration of the packaging container was adjusted to be higher than that of Example 1, and although the food quality evaluation was somewhat inferior to that of Example 1, it was confirmed that the food quality evaluation showed a good value because the oxygen concentration O(10) of the gas inside the packaging container on the 10th day after sealing and packaging was 5 volume% or less. In Examples 6 and 7, the same effect as in Example 1 could be confirmed even for processed foods with a low possibility of generating gases such as ethylene. In Examples 8 to 10, the maximum height roughness (Rz) and arithmetic mean roughness (Ra) of the container surface were adjusted to be high by adjusting the surface roughness of the inner surface of the mold, especially the inner surface of the outlet part (die) and the air slit installed in the extrusion device, and it was confirmed that although the recyclability was somewhat inferior to that of Example 1, it could be recycled well. In Comparative Examples 1 to 3, although the initial oxygen concentration was kept low, the oxygen permeability of the packaging container under conditions of 20°C and 65% RH was 0.001 cc / cm 3 ·day·atm, the quality of the filled food could not be maintained. In Comparative Examples 1, 3, 4, and 5, the maximum height roughness (Rz) and arithmetic mean roughness (Ra) of the container surface were outside the preferable ranges, and it was confirmed that the appearance during display and the recyclability during container manufacturing were deteriorated. [Industrial Applicability]

[0110] The packaging container of the present invention can be used as a packaging container with excellent recyclability while maintaining a good appearance when displayed. Furthermore, the packaging container of the present invention can extend the quality retention period even if the amount of gas used during gas replacement is reduced, and a gas replacement filling packaging container can be provided at low cost. [Explanation of symbols]

[0111] 1 Tray-shaped container 2 Tray body 2a Thermoplastic resin layer 2b Gas barrier layer 3 Flange 4 Inside the container 5 Lid 5a Second thermoplastic resin layer 5b Gas barrier layer 5c 1st thermoplastic resin layer 10 Food 50 Polymer (gas barrier layer) 60 Polymer (thermoplastic resin layer) 70 Extrusion Die 80 First transport roll 90 Second transport roll 100 multilayer structure 110 Air slit

Claims

1. A packaging container in which food is filled and sealed, the packaging container has a multilayer structure composed of a gas barrier layer and a thermoplastic resin layer other than the gas barrier layer, and the maximum height roughness (Rz) of the container surface measured in accordance with JIS-B0601 (2001) is 10.5 μm or more and 30 μm or less, The oxygen permeability of the packaging container under conditions of 20° C. and 65% RH is 0.00001 cc / cm ３ ・day・atm or more 0.001cc / cm ３ ・Day・atm or less, The oxygen concentration O(10) of the gas inside the packaging container 10 days after the packaging is sealed is 0% by volume or more and 5% by volume or less; The container surface is both an inner surface and an outer surface, the gas barrier layer contains an ethylene-vinyl alcohol copolymer as a main component, The packaging container, wherein the thermoplastic resin layer contains a polyolefin resin or a carboxylic acid-modified polyolefin as a main component.

2. 2. The packaging container according to claim 1, wherein the arithmetic mean roughness (Ra) of the container surface measured in accordance with JIS-B0601 (2001) is 0.1 μm or more and 2.5 μm or less.

3. 3. The packaging container according to claim 1, wherein the oxygen concentration O(0) of the gas inside the container immediately after the container is sealed and packaged is 0.1% by volume or more and 5% by volume or less.

4. The packaging container according to any one of claims 1 to 3, wherein the ratio O(10) / O(0) of the oxygen concentration O(10) to the oxygen concentration O(0) of the gas inside immediately after the sealing packaging is 0 or more and less than 1.

5. The packaging container according to any one of claims 1 to 4, wherein the gas comprises at least one selected from nitrogen and carbon dioxide.

6. 6. The packaging container according to claim 5, wherein the gas has a carbon dioxide concentration of 0.5% by volume or more and 40% by volume or less.

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