JP2012201412A - Multi-layered container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-layered container having a gas barrier property and transparency favorable as a food packaging material to be sterilized by boiling and stored at a high temperature.SOLUTION: In the multi-layered container having a layer structure of three or more layers constituted of a layer (X) containing polypropylene as a main component, an adhesion layer (Y) made of an adhesive thermoplastic resin, and a gas barrier layer (Z) made of a polyamide resin (A), the polyamide resin (A) is a polyamide resin consisting of a diamine unit containing a methaxylylene diamine unit of at least 70 mol%, and a dicarboxylic acid unit containing an adipic acid unit of 85-95 mol% and an isophthalic acid unit of 5-15 mol%, and is subjected to hydrothermal treatment at a temperature of not less than 80°C and not more than 100°C.

Description

  The present invention relates to a multilayer container mainly composed of polypropylene, and more particularly to a multilayer container excellent in transparency and gas barrier properties even after a hot water immersion treatment at 80 ° C. or higher and 100 ° C. or lower.

  Conventionally, as food containers that require heat sterilization treatment, canned foods have been used to prevent deterioration, discoloration, and discoloration of food during heat sterilization treatment and storage. However, in the case of using canned foods, high effects are exhibited for various gas barrier properties such as oxygen and water vapor, but the contents cannot be visually confirmed before opening, and heat treatment using a microwave oven cannot be performed. There is a problem that it is difficult to take out food when placing the filled food on a plate or the like, it cannot be stacked after disposal, and the canned food is bulky and lacks suitability for disposal.

  An alternative food storage container is a thermoformed container made of a thermoplastic resin, and is widely used. In particular, a container made of polypropylene (hereinafter sometimes abbreviated as “PP”) requires a heat sterilization treatment because its melting point is higher than a heat sterilization treatment temperature such as a boil sterilization treatment or a retort sterilization treatment. It is also widely used as a food storage container. However, although PP is excellent in moisture resistance, it has a property of easily permeating oxygen that causes deterioration, discoloration, and discoloration of food, so that performance is insufficient as a container for storing food for a long period of time. .

  As a method for enabling long-term storage of food in a container made of PP, a method using a multilayer container in which a thermoplastic resin having an oxygen barrier property is present as an intermediate layer is known. As a resin constituting the gas barrier layer, an ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as “EVOH”) is known. EVOH is a resin with excellent oxygen barrier properties and is widely used in containers for long-term storage of various foods. However, since the barrier resin has a hydroxyl group in the molecular structure, the oxygen barrier properties depend on humidity. It has a high defect. In particular, when storing and storing foods that require heat sterilization at 100 ° C or higher, multilayer containers using EVOH as a gas barrier layer are heated because they are exposed to hot water or steam for a certain period of time during heat sterilization. Oxygen barrier properties are greatly reduced by sterilization treatment. In addition, EVOH remains greatly reduced in oxygen barrier properties even after heat sterilization treatment, and although it recovers to the original oxygen barrier performance over time, it takes a long time for complete recovery. A large amount of oxygen permeation is allowed, and a problem remains in the storage stability of the heat-sterilized food.

  In addition to EVOH, as a thermoplastic resin excellent in oxygen barrier properties, polymetaxylylene adipamide (hereinafter sometimes abbreviated as “N-MXD6”) is known, and a multilayer container combined with polyolefin is known. It is disclosed (for example, see Patent Document 1). Polymetaxylylene adipamide is a polyamide resin obtained by polycondensation of metaxylylenediamine and adipic acid, and since it does not have a hydroxyl group in the molecular structure of the resin, it is less dependent on humidity than EVOH, Even during the heat sterilization treatment with hot water or steam, the oxygen barrier property is not significantly lowered, so that the amount of oxygen permeated into the container can be kept low, and the preservability of the heat sterilized food can be enhanced. However, since N-MXD6 crystallizes very rapidly at a thermoforming temperature of PP of 150 to 180 ° C., a multilayer container using N-MXD6 as a gas barrier layer is not capable of cutting the N-MXD6 layer during molding. Thickness unevenness and whitening are observed, and there are drawbacks in that performance such as gas barrier properties and transparency is deteriorated or deformed.

  In order to obtain a PP multi-layer container having N-MXD6 as an intermediate layer, it is necessary to reduce the crystallization speed of N-MXD6, and a method of copolymerizing N-MXD6 with isophthalic acid as a dicarboxylic acid component (for example, Patent Document 2). For example). It is described that the moldability of a multilayer container with PP is improved by copolymerizing N-MXD6 with isophthalic acid to slow the crystallization rate, and the multilayer container under retort treatment (steam treatment) conditions. It has been described that the whitening of the resin is suppressed. However, there is no description about the whitening suppression of the multilayer container in other heat sterilization treatment methods (for example, boil treatment).

As a means for suppressing whitening of N-MXD6, a method of adding a specific fatty acid metal salt (for example, see Patent Document 3) and a method of adding a specific diamide compound or a diester compound (for example, see Patent Document 4). It is disclosed. Inhibition of whitening by these additives, such as PET / N-MXD6 / PET multilayer stretched bottles using a single layer film directly exposed to water or polyethylene terephthalate (hereinafter sometimes abbreviated as “PET”). It is disclosed that there is an effect in applications where the film is stretched (see, for example, Patent Document 5). However, these whitening suppression prescriptions are prescriptions under temperature conditions close to room temperature of about 30 ° C. to 60 ° C., and the whitening suppression effect after heat sterilization treatment by hot water immersion at 80 ° C. or higher is not satisfactory.
Further, it is disclosed that a method of combining a specific diamide compound or diester compound and a crystallization nucleating agent of talc or benzylidene sorbitol (for example, Patent Document 6) has a further effect on whitening suppression. However, in the multilayer container combining MXD6 to which the above compound is added and PP having a high moisture permeability, the whitening suppression effect after the heat sterilization treatment by the retort treatment is not satisfactory. In addition, these additives have little effect unless 0.1% or more is added, and when 0.1% or more is added, N-MXD6 becomes powdery and when formed into a multilayer container, N-MXD6 and others There was a problem that the adhesiveness with the resin layer was lowered.

JP 02-125733 A JP 2004-160987 A JP 11-315207 A JP 2000-248176 A JP 2001-199024 A JP 2011-26417 A

  An object of the present invention is a multilayer having gas barrier properties and transparency suitable as packaging materials for foods that require boiling sterilization treatment (hereinafter referred to as hot water treatment) by hot water treatment at 80 ° C. or higher and 100 ° C. or lower or high temperature storage. Is to provide a container.

  As a result of intensive research on multilayer containers having gas barrier properties and transparency after hot water treatment and high-temperature storage, the present inventors have used a specific polyamide resin for the gas barrier layer, thereby enabling boil sterilization by hot water treatment. It has been found that the gas barrier property and transparency are excellent even after the treatment, and the present invention has been completed.

  That is, in the present invention, a layer (X) mainly composed of polypropylene, an adhesive layer (Y) made of an adhesive thermoplastic resin, and a gas barrier layer (Z) made of a polyamide resin (A) are laminated in this order from the inner layer to the outer layer. A multilayer container having a layer structure of three or more layers, wherein the polyamide resin (A) comprises 85 to 95 mol% of a diamine unit and adipic acid unit containing 70 mol% or more of metaxylylenediamine units, and isophthalic acid Multilayer container which is a polyamide resin composed of dicarboxylic acid units containing 5 to 15 mol% of units

  The multilayer container of the present invention has gas barrier properties and transparency suitable as a packaging material for foods that require boil sterilization treatment (hereinafter referred to as hot water treatment) by hot water immersion at 80 ° C. or higher and 100 ° C. or lower or high temperature storage. . Therefore, food can be stored for a long period of time, and the contents can be visually confirmed even after applying a heat history such as hot water treatment or high-temperature storage, so that the convenience of customers can be improved. be able to.

The multilayer container of the present invention comprises a layer containing polypropylene as a main component (hereinafter sometimes abbreviated as “PP layer”) (X), an adhesive layer (Y) made of an adhesive thermoplastic resin, and a gas barrier layer ( At least three layers Z) are laminated in this order from the inner layer to the outer layer.
A layer made of another thermoplastic resin such as an adhesive layer, a PP layer, or polyamide 6 may be further laminated outside the three layers. For example, in order to give a characteristic to a multilayer container, a thermoplastic resin layer made of polycarbonate or various easy peel resins can be laminated inside the PP layer. Not limited to these, various thermoplastic resin layers can be laminated according to the purpose. The multilayer container of the present invention preferably has a four-layer structure of PP layer / adhesive layer / gas barrier layer / polyamide from the inner layer side to the outer side and a five-layer structure of PP layer / adhesive layer / gas barrier layer / adhesive layer / PP layer. .
Moreover, the said 3 layer should just be laminated | stacked in that order, and the intermediate | middle layer may be laminated | stacked between the layers. For example, the trimming waste generated by trimming at the time of manufacturing the multilayer sheet and the multilayer container is pulverized, and the pulverized product alone or mixed with PP or other thermoplastic resin as a recycled resin layer, the PP layer and the adhesive layer It can be laminated as an intermediate layer.

The PP layer (X) constituting the multilayer container of the present invention is a layer mainly composed of polypropylene, and has a role of isolating the gas barrier layer from food and a sealant for adhering to the top film after the food is stored in the container. As a role. A well-known thing can be used for a polypropylene. Specific examples thereof include homopolypropylene, propylene-ethylene random copolymer, and propylene-ethylene block copolymer.
In the present invention, “mainly composed of polypropylene” means containing 50% by mass or more of polypropylene, and preferably 70% by mass or more. In the PP layer, antioxidants, matting agents, weathering stabilizers, UV absorbers, crystallization nucleating agents, plasticizers, flame retardants, electrification to prevent oxidative degradation of polypropylene within the range not impairing the effects of the present invention. Additives such as inhibitors can be added. In some cases, a thermoplastic resin such as polyethylene or ethylene-α-olefin copolymer may be added to modify the physical properties of polypropylene.
Although the thickness of PP layer (X) is not specifically limited, From a viewpoint of intensity | strength and cost, 20-2000 micrometers is preferable and 50-1000 micrometers is more preferable.

The adhesive layer (Y) constituting the multilayer container of the present invention has a role of adhering the PP layer and the gas barrier layer with sufficient strength. Examples of the adhesive thermoplastic resin used in the adhesive layer include acid-modified polyolefins obtained by modifying an olefin resin with an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, maleic acid, and maleic anhydride. Among these, an acid-modified thermoplastic resin mainly composed of polypropylene is particularly preferably used from the viewpoint of adhesiveness with the PP layer.
Although the thickness of an adhesion layer (Y) is not specifically limited, From a viewpoint of adhesiveness and cost, 1-200 micrometers is preferable and 5-100 micrometers is more preferable.

The gas barrier layer (Z) constituting the multilayer container of the present invention has a role of blocking oxygen entering from the outside of the container and preventing oxidative deterioration of food. From the viewpoint of good gas barrier properties, the polyamide resin (A) constituting the gas barrier layer (Z) has an oxygen permeability coefficient of 0.09 ml · mm / m ² · day · atm or less in an environment of 23 ° C. and 60% RH. It is preferably 0.05 to 0.09 ml · mm / m ² · day · atm. The oxygen permeability coefficient can be measured according to ASTM D3985, and can be measured using, for example, OX-TRAN 2/21 (trade name, manufactured by Mocon).
Although the thickness of a gas barrier layer (Z) is not specifically limited, 1-400 micrometers is preferable from a viewpoint of gas barrier property, transparency, and cost, and 5-150 micrometers is more preferable. In addition, the thickness of the gas barrier layer (Z) in the multilayer container of the present invention is preferably in the range of 2 to 20%, more preferably from the total thickness of the multilayer container, from the viewpoints of gas barrier properties, transparency and cost. Is 3 to 18%, more preferably 5 to 15%.

The gas barrier layer (Z) constituting the multilayer container of the present invention comprises a polyamide resin (A), and the polyamide resin (A) contains 85 diamine units and adipic acid units containing 70 mol% or more of metaxylylenediamine units. To 95 mol% and dicarboxylic acid units containing 5 to 15 mol% of isophthalic acid units.
The diamine unit in the polyamide resin (A) preferably contains a metaxylylenediamine unit in an amount of 70 mol% or more, more preferably 80 mol% or more and 100 mol% or less, particularly from the viewpoint of developing excellent gas barrier properties. Is 90 mol% or more and 100 mol% or less. Compounds that can constitute diamine units other than metaxylylenediamine units include diamines containing aromatic rings such as paraxylylenediamine, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane. Linear aliphatic diamines such as alicyclic diamine such as tetramethylene diamine, hexamethylene diamine, nonamethylene diamine and 2-methyl-1,5-pentane diamine, etc., are not limited thereto. .

The dicarboxylic acid unit in the polyamide resin (A) contains 85 to 95 mol% adipic acid units and 15 to 5 mol% isophthalic acid units. More preferably, the dicarboxylic acid unit in the polyamide resin (A) preferably contains 88 to 93 mol% adipic acid units and 12 to 7 mol% isophthalic acid units, and 90 to 95 mol% adipic acid units and isophthalic acid units. More preferably, the unit contains 10 to 5 mol%.
By including 85 mol% or more of adipic acid units among dicarboxylic acid units, it is possible to avoid a decrease in gas barrier properties and an excessive decrease in crystallinity. In addition, when the isophthalic acid unit is contained in an amount of 5 mol% or more, the non-crystalline property of the polyamide resin (A) is increased and the crystallization speed is decreased. It is possible to suppress boil sterilization by hot water immersion treatment at ˜100 ° C. and whitening during high temperature storage.
If the isophthalic acid unit content exceeds 15 mol%, the polyamide resin (A) does not reach the melt viscosity required for molding the multilayer container, making it difficult to produce the multilayer container. ) Hardly shows crystallinity, and PP multi-layer containers using the polyamide resin (A) as a gas barrier layer are preferable because they increase boil sterilization treatment by hot water immersion treatment at 80 ° C. to 100 ° C. and whitening during high-temperature storage. Absent.

In the present invention, the polyamide resin (A) is crystalline, and the half crystallization time (ST (P)) by crystallization at 160 ° C. in the depolarization photometric method is preferably 80 seconds or more and 700 seconds or less. The polyamide resin is more preferably in the range of 80 seconds to 650 seconds. By making the polyamide resin appropriate crystallinity, even if the multilayer container is subjected to hot water treatment at 80 ° C. or higher and 100 ° C. or lower, extreme whitening can be suppressed and transparency can be maintained. In addition, by controlling the half crystallization time to 80 seconds or more, whitening and molding defects due to crystallization can be suppressed during secondary processing such as deep drawing of a multilayer structure. If the half crystallization time is 700 seconds or less, it is possible to prevent the crystallinity from being excessively lowered while maintaining the secondary workability, and further, the polyamide layer is softened during the hot water treatment to thereby provide a multilayer structure. And can prevent deformation of multilayer molded products

In the polyamide resin (A) in the present invention, the increase in crystallinity obtained by DSC before and after dry heat treatment at 100 ° C. for 1 hour is preferably 1% or less, and more preferably 0.5% or less. If the increase in crystallinity obtained by DSC before and after dry heat treatment exceeds 1%, whitening due to crystallization occurs during hydrothermal treatment, which is not preferable.
The dry heat treatment in the present invention refers to a dry heat treatment using a hot air dryer or the like, and is not necessarily in a nitrogen atmosphere.

The polyamide resin (A) can be obtained by polycondensing a diamine component containing 70 mol% or more of metaxylylenediamine and a dicarboxylic acid component containing 85 to 95 mol% adipic acid and 15 to 5 mol% isophthalic acid. it can. A small amount of monoamine or monocarboxylic acid may be added as a molecular weight modifier during polycondensation.
The polyamide resin (A) is preferably produced by polycondensation by a melt polymerization method and further solid phase polymerization. Examples of the melt polycondensation method include a method in which a nylon salt composed of a diamine component and a dicarboxylic acid component is heated in pressure in the presence of water and polymerized in a molten state while removing the added water and condensed water. It is done. Moreover, the method of adding a diamine component directly to the dicarboxylic acid component of a molten state, and performing polycondensation can also be mentioned. In this case, in order to keep the reaction system in a uniform liquid state, the diamine component is continuously added to the dicarboxylic acid component, and during this time, the reaction system is raised so that the reaction temperature does not fall below the melting point of the generated oligoamide and polyamide resins. The polycondensation proceeds while warming.

  The solid phase polymerization is preferably performed after once taking out the polymer obtained by melt polycondensation. The heating device used in the solid-phase polymerization is preferably a batch heating device that is superior in airtightness and highly capable of cutting off the contact between oxygen and the polyamide resin, and more particularly a tumble dryer or conical. A rotary drum-type heating device called a dryer or a rotary dryer and a conical heating device called a Nauta mixer with a rotating blade inside can be preferably used, but are not limited thereto.

  The solid phase polymerization step of the polyamide resin is, for example, a first step of increasing the degree of crystallinity of the polyamide resin so that the polyamide resin pellets are not fused to each other and the polyamide resin pellets are not attached to the inner wall of the apparatus. It is preferable to proceed by the second step of increasing the molecular weight, and the third step of cooling the polyamide resin after proceeding the solid phase polymerization to the desired molecular weight. The first step is preferably performed at a temperature lower than the glass transition temperature of the polyamide resin. The second step is preferably performed at a temperature lower than the melting point of the polyamide resin under reduced pressure, but is not limited thereto.

Polyamide resin (A) is a lubricant, matting agent, heat stabilizer, weather stabilizer, UV absorber, crystallization nucleator, plasticizer, flame retardant, antistatic agent, as long as the effects of the present invention are not impaired. You may contain arbitrary additives, such as a coloring inhibitor and an antigelling agent.

  If necessary, the amorphous polyamide resin (B) can be melt-mixed with the polyamide resin (A) for use. A specific amorphous polyamide resin (B) is polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer (hereinafter referred to as 6T / 6I), which is a polycondensation of terephthalic acid, isophthalic acid, and hexamethylenediamine. It is a copolymer obtained by doing this. In the polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer, the blending ratio of 6T / 6I is 50/50 to 10/90 (mol%), preferably 45/55 to 15/85 (% mol), more preferably Is 40/60 to 20/80 (mol%). N-6T / 6I may be a block copolymer or a random copolymer. As N-6T / 6I, a commercially available product can be used. For example, Novamid X21 (trade name, manufactured by Mitsubishi Engineering Plastics) or SEALA PA3426 (manufactured by Mitsui DuPont Polychemical) may be used.

The content of the polyamide resin (B) when the amorphous polyamide resin (B) is melt-mixed with the polyamide resin (A) is (A) :( B) is 80 to 100% by mass: 20 to 0% by mass. Yes, preferably 85 to 100% by mass: 15 to 0% by mass. When the crystallization rate of the polyamide resin (A) is slow due to the introduction of isophthalic acid units, it is not necessary to contain the polyamide (B).
Further, when the content of the amorphous polyamide resin (B) in the polyamide resin (A) is 20% by mass or less, a container having good gas barrier properties and suppressing whitening after the heat sterilization treatment can be obtained. .

  The amorphous polyamide (B) is basically a conventionally known polyamide obtained by a melt polycondensation method in the presence of water or a melt polycondensation method in the absence of water, or these melt polycondensation methods. Can be produced by a method of further solid-phase polymerization. The melt polycondensation reaction may be performed in one stage or may be performed in multiple stages. These may be comprised from a batch-type reaction apparatus, and may be comprised from the continuous-type reaction apparatus. The melt polycondensation step and the solid phase polymerization step may be operated continuously or may be operated separately.

  The polyamide resin (A) and the amorphous polyamide resin (B) can be prepared by applying any mixing method and / or kneading method. As a mixing method, for example, polyamide resin pellets may be charged and mixed in a rotating hollow container, or a predetermined amount may be charged into a hopper using a quantitative feeder. Examples of the kneading method include melt kneading. The polyamide resin (A) and the amorphous polyamide resin (B) may be mixed and / or kneaded. In particular, it is particularly preferable to prepare by dry blending and pouring the mixture into a hopper.

  In addition, the polyamide resin (A) is a fatty acid metal salt having 18 to 50 carbon atoms, a fatty acid having 8 to 30 carbon atoms and 2 to 10 carbon atoms from the viewpoint of further whitening suppression and bleed-out after sterilization treatment by hot water treatment. It may contain at least one selected from the group consisting of a diamide compound obtained from the diamine and a diester compound obtained from a fatty acid having 8 to 30 carbon atoms and a diol having 2 to 10 carbon atoms. Moreover, the compounding quantity becomes like this. Preferably it is 0.01-1.0 mass part with respect to 100 mass parts of polyamide resins (A), More preferably, it is 0.02-0.8 mass part, More preferably, it is 0.02-. You may contain 0.5 mass part. The said fatty acid metal salt, diamide compound, and diester compound may contain only 1 type, and may contain it in combination of 2 or more type.

The fatty acid metal salt that can be used in the present invention has 18 to 50 carbon atoms, preferably 18 carbon atoms, from the viewpoint of whitening suppression effect after sterilization treatment by hot water treatment and uniform dispersibility in the polyamide resin (A). ~ 34 fatty acid metal salts are preferred.
Fatty acids may have side chains or double bonds, but stearic acid (18 carbon atoms), eicoic acid (20 carbon atoms), behenic acid (22 carbon atoms), montanic acid (28 carbon atoms), triacontanoic acid Straight chain saturated fatty acids such as (C30) are preferred. The metal that forms a salt with the fatty acid is not particularly limited, and examples thereof include alkali metals such as sodium, potassium and lithium, alkaline earth metals such as calcium, barium, magnesium and strontium, and aluminum and zinc. Among these, sodium, potassium, lithium, calcium, aluminum, or zinc is particularly preferable.
Specific examples of the fatty acid metal salt include sodium stearate, calcium stearate, sodium montanate, calcium montanate and the like. Among these, calcium stearate and calcium montanate are preferable from the viewpoint of whitening suppression effect. The said fatty acid metal salt may contain only 1 type and may contain it in combination of 2 or more type.

As the diamide compound that can be used in the present invention, fatty acid having 8 to 30 carbon atoms and 2 to 2 carbon atoms from the viewpoint of whitening suppression effect after sterilization treatment by hot water treatment and uniform dispersibility in the polyamide resin (A). Diamide compounds obtained from 10 diamines are preferred.
As the fatty acid component of the diamide compound, there may be a side chain or a double bond, but a straight chain fatty acid is preferable, stearic acid (carbon number 18), eicoic acid (carbon number 20), behenic acid (carbon number 22), Examples include montanic acid (carbon number 28), triacontanoic acid (carbon number 30), and the like. One type of fatty acid component may be used alone, or two or more types may be combined.
Examples of the diamine component of the diamide compound include ethylenediamine, butylenediamine, hexanediamine, xylylenediamine, and bis (aminomethyl) cyclohexane. A diamine component may be used individually by 1 type, and may combine two or more types.
The diamide compound is preferably a diamide compound obtained from a fatty acid having 8 to 30 carbon atoms and ethylenediamine, or a diamide compound obtained from montanic acid and a diamine having 2 to 10 carbon atoms, and a diamide obtained from stearic acid and ethylenediamine. Compounds are particularly preferred. A diamide compound may contain only 1 type and may contain it in combination of 2 or more type.

The diester compound that can be used in the present invention is a fatty acid having 8 to 30 carbon atoms and a diol having 2 to 10 carbon atoms from the viewpoint of whitening suppression effect after hydrothermal treatment and uniform dispersibility in the polyamide resin (A). Diester compounds obtained from are preferred.
The fatty acid component of the diester compound is the same as the fatty acid component of the diamide compound. Examples of the diol component of the diester compound include ethylene glycol, propanediol, butanediol, hexanediol, xylylene glycol, and cyclohexanedimethanol. A diol component may be used individually by 1 type, and may combine two or more types.
The diester compound is preferably a diester compound obtained from a fatty acid having 8 to 30 carbon atoms and a diol composed of ethylene glycol and / or 1,3-butanediol, and mainly montanic acid and ethylene glycol and / or 1,3-butane. Diester compounds obtained from diols consisting of diols are particularly preferred. A diester compound may contain only 1 type and may contain it in combination of 2 or more type.

In the multilayer container of the present invention, the haze value (h (a)) of the multilayer container after hydrothermal treatment at 80 ° C. or more and 100 ° C. or less is the haze value (h (b)) of the multilayer container before hydrothermal treatment. The value of the divided value H (H = h (a) / h (b)) is preferably 1.0 or more and 1.4 or less, and more preferably 1.0 or more and 1.2 or less.
If the increase in the haze value after the hot water treatment of the multilayer container is in the above range, the contents can be visually recognized, and thus the transparency of the multilayer container after the heat treatment is in a practical range.

  The multilayer container of the present invention can be produced by any method such as extrusion molding, extrusion / blow molding. For example, using a multilayer sheet manufacturing apparatus equipped with three extruders, a feed block, a T-die, a cooling roll, a winder, etc., PP is adhesive from the first extruder and adhesiveness from the second extruder. The polyamide resin (A) constituting the gas barrier layer (Z) is extruded from a third extruder, respectively, and the PP layer / adhesive layer / gas barrier layer / adhesive layer / PP layer 3 types 5 through the feed block After producing a multilayer sheet with a layer structure and heat-softening it, the sheet is brought into close contact with the mold by vacuum, compressed air, or a thermoforming method using a combination of vacuum and compressed air, and formed into a container shape, and then trimmed The method of obtaining a container is mentioned. Here, the sheet surface temperature during thermoforming is preferably in the range of 130 to 200 ° C and more preferably in the range of 150 to 180 ° C from the viewpoint of formability. The multilayer sheet manufacturing apparatus and the container forming method are not limited to these, and any method can be applied.

  The shape of the multilayer container of the present invention is not particularly limited, and may be, for example, a molded container such as a bottle, a cup, a tube, a tray, or tupperware, or a bag shape such as a pouch, a standing pouch, or a zipper-type storage bag. It may be a container. Moreover, when a multilayer container has a flange part, you may give the special process for providing an easy peel function to the flange part.

  The multilayer container of the present invention can store and store various articles whose contents are to be visualized in order to increase the customer's willingness to purchase. For example, processed marine products, processed livestock products, rice, and liquid food. For example, tuna, bonito, salmon, trout, mackerel, sardine, saury, herring, eel, crab, scallop, red shellfish, clams, oysters, mussel, northern shellfish, top shell, squid, laver, hijiki, agar, sardine, kelp, etc. Seafood products such as boiled, oiled, smoked oiled, smoked, tomato pickled, corned beef, beef, sausage, ham, pork, chicken, chicken egg, quail egg, salted, oiled, boiled, seasoned Processed products, curry, stew, hashed beef, pasta sauce, sauces for cooking, liquid foods such as soups such as Western soup, Chinese soup, Japanese soup, mandarin, peach, pineapple, cherry, apricot, chestnut , Grapes, processed agricultural products such as tomatoes, corn, bamboo shoots and mushrooms, and pet food ingredients for dogs and cats.

Examples of the method for sterilizing the multilayer container of the present invention by hot water treatment include a wet heat method in which the multilayer container is immersed in a hot water tank at a constant temperature in a basket and then taken in a cold water tank, but is limited to this method. is not. The sterilization temperature is preferably in the range of 80 ° C to 100 ° C, and the sterilization time is preferably 10 to 120 minutes.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In this example, various measurements were performed by the following methods.
(1) Semi-crystallization time It measured by the depolarization photometric method. Specifically, a polymer crystallization rate measuring device (manufactured by Kotaki Seisakusho, model: MK701) was used, and measurement was performed under the following conditions.
Sample melting temperature: 270 ° C
Sample melting time: 3 minutes Crystallization oil bath temperature: 160 ° C

(2) Crystallinity by DSC (%)
Using a differential scanning calorimeter (DSC-60, manufactured by Shimadzu Corporation), the polyamide resin (A) and the untreated polyamide resin (A) subjected to a dry heat treatment at 100 ° C. for 1 hour in a hot air dryer are used. DSC measurement was performed in a nitrogen stream at a heating rate of 10 ° C./min. Peak temperature (crystallization peak temperature) due to crystallization during the measurement, exothermic peak (calorie (1)) and peak temperature due to melting The crystallinity was determined from the (melting point) and endothermic peak (calorie (2)) using the following formula (1). The heat of crystal melting (calorie (3)) is 151 J / g, and the calories A and B are indicated by absolute values.
Crystallinity = ((calorie (2)) − (calorie (1))) / (calorie (3)) × 100 (%) (1)

(3) Gas barrier properties Measured according to ASTM D3985. Specifically, using an oxygen permeability measuring device (OX-TRAN 2 / 21A, trade name, manufactured by Mocon), oxygen permeability in a 23 ° C., 60% RH environment of a gas barrier film made of polyamide resin (A). The coefficient (ml · mm / m ² · day · atm) was measured.

(4) Haze
A single layer film, a multilayer container and a multilayer pouch were immersed in hot water at 90 ° C. for 30 minutes using an autoclave (SR-240, trade name, manufactured by Tommy Seiko Co., Ltd.). Haze was measured according to K-7105. The retort processing time does not include heating and cooling time. As the measuring device, a color / turbidity measuring device (trade name: COH-300A, manufactured by Nippon Denshoku Industries Co., Ltd.) was used. The thickness at the haze measurement location was measured and taken as a value converted to a thickness of 100 μm. It shows that transparency is so high that a haze value is small.

(5) Formability evaluation of mature molding Using a compressed air vacuum forming machine (manufactured by Asano Laboratories) equipped with plug assist, after heating the sheet surface temperature to 170 ° C at a ceramic heater temperature: 480 ° C, compressed air vacuum forming Went. The bottom and side surfaces of the obtained thermoformed container were observed and evaluated according to the following criteria.
○: Good molded product without stretch unevenness ×: Appearance defect due to stretch unevenness

Example 1
In a reactor equipped with a jacket equipped with a stirrer, a partial condenser, a cooler, a thermometer, a dropping tank and a nitrogen gas introduction tube, 95 mol% of adipic acid (AdA) (manufactured by Asahi Kasei) and isophthalic acid (IPA) ) (Manufactured by AI International Co., Ltd.) was added so as to be 5 mol%, sufficiently substituted with nitrogen, further heated to 170 ° C. under a nitrogen stream to make the dicarboxylic acid fluid, and then metaxylylenediamine ( MXDA) (manufactured by Mitsubishi Gas Chemical) was added dropwise with stirring. During this time, the internal temperature was continuously raised to 245 ° C., and the water distilled with the addition of metaxylylenediamine was removed out of the system through a condenser and a cooler. After the completion of the dropwise addition of metaxylylenediamine, the internal temperature was continuously raised to 255 ° C., and the reaction was continued for 15 minutes. Thereafter, the internal pressure of the reaction system was continuously reduced to 600 mmHg over 10 minutes, and then the reaction was continued for 40 minutes. During this time, the reaction temperature was continuously raised to 260 ° C. After completion of the reaction, the inside of the reaction vessel was pressurized with nitrogen gas at a pressure of 0.2 MPa, the polymer was taken out as a strand from the nozzle at the bottom of the polymerization tank, and was cut after water cooling to obtain a pellet-shaped polymer.

Next, this pellet was charged into a stainless steel drum-type heating device and rotated at 5 rpm. The atmosphere in the reaction system was raised from room temperature to 140 ° C. under a small nitrogen flow. When the reaction system temperature reached 140 ° C., the pressure was reduced to 1 torr or less, and the system temperature was further increased to 180 ° C. in 110 minutes. From the time when the system temperature reached 190 ° C., the solid state polymerization reaction was continued for 190 minutes at the same temperature. After completion of the reaction, the decompression was terminated, the system temperature was lowered under a nitrogen stream, and when the temperature reached 60 ° C., the pellets were taken out, so that metaxylylenediamine units, 95 mol% adipic acid units, and 5 mol isophthalic acid units were obtained. % Polymetaxylylene adipamide / polymetaxylylene isophthalamide copolymer (hereinafter sometimes abbreviated as “N-MXD6 / MXDI”) (polyamide resin (A1)).

  Next, the polyamide resin (A1) was extruded with a single screw extruder to produce a gas barrier film having a thickness of 50 μm. The semi-crystallization time at 160 ° C., the crystallinity, and the oxygen permeability coefficient in a 23 ° C./60% RH environment of the gas barrier film made of the polyamide resin (A1) were measured. The results are shown in Table 1.

Using a multilayer sheet manufacturing apparatus equipped with three extruders, feed block, T die, cooling roll, winder, etc., polypropylene (from Nippon Polypro Co., Ltd., trade name: Novatec PP, grade) from the first extruder Name: FY6, melt index: 2.5) at 260 ° C. Adhesive resin (manufactured by Mitsui Chemicals, trade name: Admer, grade: QB515) from the second extruder at 230 ° C. Polyamide resin (A1) is extruded from the extruder at 260 ° C., and PP layer (X layer) / adhesive layer (Y layer) / gas barrier layer (Z layer) / adhesive layer (Y layer) / PP layer through the feed block A multilayer sheet having a three-kind five-layer structure (layer X) was produced. The thickness of each layer was 425/25/100/25/425 (μm).
Next, using a compressed air vacuum forming machine equipped with plug assist, when the sheet surface temperature reaches 170 ° C., thermoforming is performed, and the opening 79 mm square × bottom 63 mm × depth 25 mm, surface area 110 cm ² , volume 100 ml. A container was prepared. The obtained cup-shaped container was immersed in hot water at 90 ° C. for 30 minutes, and the container side surface haze before and after the hot water treatment was measured. The results are shown in Table 1.
In addition, using a multilayer sheet manufacturing apparatus equipped with four extruders, a feed block, a T die, a cooling roll, a winder, etc., polypropylene (from Nippon Polypro Co., Ltd., trade name: Novatec PP) , Grade name: FY6, melt index: 2.5) at 260 ° C., adhesive resin (Mitsui Chemicals, trade name: Admer, grade: QB515) from the second extruder at 230 ° C., 3 units The polyamide resin (A1) is extruded from the eye extruder at 260 ° C., and the polyamide 6 resin (product name: UBE nylon 6, grade: 1024B manufactured by Ube Industries, Ltd.) is extruded from the fourth extruder at 240 ° C. and fed. A multilayer sheet having 4 types and 4 layers of PP layer (X layer) / adhesive layer (Y layer) / gas barrier layer (Z layer) / polyamide 6 layer was produced through the block. The thickness of each layer was 120/10/30/120/20 (μm).
Next, using a heat sealing machine, create a four-way sealed PP multilayer pouch (vertical 200 mm, horizontal 100 mm), put 10 cc of water, heat seal, and then autoclave (SR-240 manufactured by Tommy Seiko). Hot water immersion treatment was performed at 90 ° C. for 30 minutes, and the haze of the pouch film before and after the hot water treatment was measured. The results are shown in Table 1.

Example 2
A prototype film was produced in the same manner as in Example 1 except that N-MXD6 / MXDI (polyamide resin (A2)) composed of metaxylylenediamine units, 94 mol% of adipic acid units and 6 mol% of isophthalic acid units was used. The measurement was carried out to measure the half crystallization time at 160 ° C., the degree of crystallinity, and the oxygen transmission coefficient in an environment of 23 ° C. and 60% RH. The results are shown in Table 1. In addition, a PP multilayer cup was molded, immersed in hot water at 90 ° C. for 30 minutes, and the haze of the container side surface and the pouch film before and after the hot water treatment was measured. The results are shown in Table 1.

Example 3
A film prototype was prepared in the same manner as in Example 1 except that N-MXD6 / MXDI (polyamide resin (A3)) composed of a metaxylylenediamine unit, 90 mol% adipic acid units and 10 mol% isophthalic acid units was used. The measurement was carried out to measure the half crystallization time at 160 ° C., the degree of crystallinity, and the oxygen transmission coefficient in an environment of 23 ° C. and 60% RH. The results are shown in Table 1. In addition, a PP multilayer cup and a pouch were molded, boiled at 90 ° C. for 30 minutes, and the haze of the container side surface and the pouch film before and after the boil treatment was measured. The results are shown in Table 1.

Example 4
A film prototype was prepared in the same manner as in Example 1 except that N-MXD6 / MXDI (polyamide resin (A4)) composed of metaxylylenediamine units, 85 mol% adipic acid units and 15 mol% isophthalic acid units was used. The measurement was carried out, and the semi-crystallization time at 160 ° C., the crystallinity, and the oxygen transmission coefficient in an environment of 23 ° C. and 60% RH were measured. The results are shown in Table 1. In addition, a PP multilayer cup and a pouch were molded, boiled at 90 ° C. for 30 minutes, and the haze of the container side surface and the pouch film before and after the boil treatment was measured. The results are shown in Table 1.

Reference example 1
To 100 parts by mass of N-MXD6 / MXDI (polyamide resin (A2)) comprising metaxylylenediamine units, 94 mol% of adipic acid units and 6 mol% of isophthalic acid units, ethylene bisstearylamide (EBS) (trade name: Alflow H-50T (manufactured by NOF Corporation) extruded 0.2 parts by mass of a resin in a strand form using a 37 mmφ twin screw extruder at an extrusion temperature of 260 ° C. to 270 ° C. and a screw speed of 100 rpm. After cooling with water, it was pelletized to prepare a polyamide resin composition. Except that this polyamide resin composition was used, a film trial was made in the same manner as in Example 1, and the half crystallization time at 160 ° C., the degree of crystallinity, and the oxygen permeation coefficient at 23 ° C. and 60% RH were measured. The results are shown in Table 1. Moreover, PP multilayer cup and pouch were shape | molded, 90 degreeC 30 minute hot water immersion process, and the haze of the container side part before and behind a hot water process and a pouch film were measured. The results are shown in Table 1.

Comparative Example 1
A polyamide resin (A5) was obtained in the same manner as in Example 1 except that the composition ratio of the polyamide resin (A) was changed to 100 mol% of adipic acid in terms of molar ratio. Film prototyping was carried out in the same manner as in Example 1, and the semi-crystallization time at 160 ° C., the degree of crystallinity, and the oxygen permeability coefficient at 23 ° C. and 60% RH were measured. The results are shown in Table 1. Moreover, PP multilayer cup and pouch were shape | molded, and the hot water immersion process was performed at 90 degreeC for 30 minutes, and the haze of the container side part before and behind a hot water process and a pouch film was measured. The results are shown in Table 1.

Comparative Example 2
A film prototype was produced in the same manner as in Example 1 except that N-MXD6 / MXDI (polyamide resin (A6)) composed of a metaxylylenediamine unit, 96 mol% of adipic acid units and 4 mol% of isophthalic acid units was used. The measurement was carried out, and the semi-crystallization time at 160 ° C., the crystallinity, and the oxygen transmission coefficient in an environment of 23 ° C. and 60% RH were measured. The results are shown in Table 1. Moreover, PP multilayer cup and pouch were shape | molded, 90 degreeC 30 minute hot water immersion process, and the haze of the container side part before and behind a hot water process and a pouch film were measured. The results are shown in Table 1.

Comparative Example 3
As in Example 1, except that the metaxylylenediamine unit and the diamine unit were N-MXD6 / MXDI (polyamide resin (A7)) composed of 80 mol% adipic acid units and 20 mol% isophthalic acid units. A prototype film was prepared, and the half crystallization time at 160 ° C., the crystallinity, and the oxygen permeability coefficient at 23 ° C. and 60% RH were measured. The results are shown in Table 1. Moreover, PP multilayer cup and pouch were shape | molded, and the hot water immersion process was performed at 90 degreeC for 30 minutes, and the haze of the container side part before and behind a hot water process and a pouch film was measured. The results are shown in Table 1.

Comparative Example 4
The film, PP multilayer cup, and pouch produced in Example 2 were retorted at 121 ° C. for 30 minutes in an autoclave (Tomy Seiko SR-240), and the haze of the container side surface and the pouch film after retorting was measured. . The results are shown in Table 2.

Comparative Example 5
The film, PP multilayer cup, and pouch produced in Example 4 were retorted at 121 ° C. for 30 minutes in an autoclave (Tomy Seiko SR-240), and the haze of the container side surface and the pouch film after retorting was measured. . The results are shown in Table 2.

ＡｄＡ：アジピン酸
ＩＰＡ：イソフタル酸
ＭＸＤＡ：メタキシレンジアミン
ＥＢＳ：エチレンビスステアリルアミド
Ｎ．Ｄ．：ＰＰ多層容器成形できないためデータ無し
１）フィルムの厚さ：５０μｍ厚
２）PP多層容器＝PP（425μｍ）/接着層（25μｍ）／ガスバリア層（１００μｍ）／接着層（25μｍ）／PP（４２５μｍ）のカップ状容器。容器側面についてhazeを測定した。
３）90℃、30分熱水浸漬処理
４） Haze比＝（ｈ（ａ））/（ｈ（ｂ））
５）ＰＰ多層パウチ＝ＰＰ（120μｍ）/接着層（10μｍ）/ガスバリア層（30μｍ）/ポリアミド６層（１２０μｍ）

AdA: adipic acid IPA: isophthalic acid MXDA: metaxylenediamine EBS: ethylenebisstearylamide D. : No data because PP multilayer container cannot be molded 1) Film thickness: 50 μm thickness 2) PP multilayer container = PP (425 μm) / adhesive layer (25 μm) / gas barrier layer (100 μm) / adhesive layer (25 μm) / PP (425 μm) ) Cup-shaped container. The haze was measured on the side of the container.
3) Hot water immersion treatment at 90 ° C. for 30 minutes 4) Haze ratio = (h (a)) / (h (b))
5) PP multilayer pouch = PP (120 μm) / adhesive layer (10 μm) / gas barrier layer (30 μm) / polyamide 6 layer (120 μm)

１）フィルムの厚さ：５０μｍ厚
２）PP多層容器＝PP（425μｍ）/接着層（25μｍ）／ガスバリア層（１００μｍ）／接着層（25μｍ）／PP（４２５μｍ）容器の側面についてhazeを測定した。
３）１２1℃、30分加圧熱水処理
４） Haze比＝（ｈ（ａ））/（ｈ（ｂ））
５）ＰＰ多層パウチ＝ＰＰ（120μｍ）/接着層（10μｍ）/ガスバリア層（30μｍ）/ポリアミド６層（１２０μｍ）

1) Film thickness: 50 μm thickness 2) PP multilayer container = PP (425 μm) / adhesive layer (25 μm) / gas barrier layer (100 μm) / adhesive layer (25 μm) / PP (425 μm) The haze was measured on the side of the container. .
3) Pressurized hot water treatment at 121 ° C for 30 minutes 4) Haze ratio = (h (a)) / (h (b))
5) PP multilayer pouch = PP (120 μm) / adhesive layer (10 μm) / gas barrier layer (30 μm) / polyamide 6 layer (120 μm)

In Comparative Example 1 using the polyamide resin (A5) not containing an isophthalic acid unit, the haze of the single layer film before the hot water treatment was 2%, but the film after the hot water treatment had a transparency of 79%. It got worse. Moreover, since the polyamide resin (A5) has a short half-crystallization time, it could not be molded into a PP multilayer container. In Comparative Example 2 using the polyamide resin (A6) having an isophthalic acid unit of 4 mol%, the haze of the single layer film was greatly deteriorated although the half crystallization time was increased. Further, whitening suppression in PP multilayer containers and PP multilayer pouches has not been sufficiently improved to a practical level.
Further, in Comparative Example 3 of the polyamide resin (A7) having an isophthalic acid unit of 20 mol%, the haze after the boil treatment of the single layer film is hardly changed and the transparency is good. Since the gas barrier layer made of (A7) could not be stably formed, the multilayer container and the multilayer pouch could not be formed. On the other hand, in Examples 1 to 4 using a polyamide resin (A1 to A4) having 5 to 15 mol% of isophthalic acid units according to the present invention, the half crystallization time is 80 seconds to 700 seconds, Since the change in crystallinity after the water treatment was small, the haze of the film after the hot water treatment did not increase greatly, and the transparency could be maintained. Thus, since the haze change in the single layer film was also small, the haze change before and after the hot water treatment of the multilayer container and the multilayer pouch was small, and whitening could be sufficiently suppressed. Further, the value of the oxygen permeation coefficient at 23 ° C. and 60% RH was also good compared to the polyamide (A5) containing no isophthalic acid in Comparative Example 1.
Moreover, the haze deteriorated in the film, PP multilayer container / PP multilayer pouch in which the polyamide resin (A1 to A4) having 5 to 15 mol% of isophthalic acid unit according to the present invention was subjected to pressurized hot water treatment at 121 ° C. for 30 minutes.
On the other hand, when the polyamide resin (A1 to A4) having 5 to 15 mol% of the sophthalic acid unit of the present invention is subjected to hot water immersion treatment at 80 to 100 ° C. which is the hydrothermal treatment condition of the present application, a whitening inhibitor Even when no whitening agent was added, the same level of transparency as in the case of adding a whitening inhibitor (Reference Example 1) or higher (Reference Example 1).

  The multi-layer container of the present invention is excellent in gas barrier properties and transparency even after sterilization by hot water treatment at 80 ° C. or higher and 100 ° C. or lower, and can be stored and visually confirmed. Furthermore, by using a specific resin for the gas barrier layer of the present invention, it is possible to maintain the transparency without using a whitening inhibitor, and thus it is possible to reduce costs. As a result, its industrial value is high as a packaging material for foods that require customer convenience.

Claims (8)

  Three or more layers in which a layer (X) mainly composed of polypropylene, an adhesive layer (Y) made of an adhesive thermoplastic resin, and a gas barrier layer (Z) made of a polyamide resin (A) are laminated in this order from the inner layer to the outer layer. The polyamide resin (A) comprises a diamine unit containing at least 70 mol% of metaxylylenediamine units, 85 to 95 mol% of adipic acid units, and 5 to 15 of isophthalic acid units. A multilayer container which is a polyamide resin composed of a dicarboxylic acid unit containing mol%. 2. The multilayer container according to claim 1, wherein the polyamide resin (A) has a semi-crystallization time (ST (P)) in crystallization at 160 ° C. by depolarization photometry of 80 seconds or more and 700 seconds or less. The multilayer container according to claim 1 or 2, wherein an increase in crystallinity of the polyamide resin (A) obtained by DSC before and after dry heat treatment at 100 ° C for 1 hour is 1% or less. The multilayer container according to any one of claims 1 to 3, wherein the polyamide resin (A) has an oxygen permeability coefficient of 0.09 ml · mm / m ² · day · atm or less in an environment of 23 ° C and 60% RH.   A ratio H (= h (a) / of haze value (h (a)) when the multilayer container is hydrothermally treated at 80 ° C. or higher and 100 ° C. or lower and haze value (h (b)) before hydrothermal treatment. The multilayer container according to any one of claims 1 to 4, wherein h (b)) is 1.0 to 1.40.   The multilayer container according to any one of claims 1 to 5, wherein a thickness of the gas barrier layer (Z) is 2 to 20% with respect to a total thickness of the multilayer container.   The multilayer container according to any one of 1 to 6, wherein another polyamide is laminated outside the gas barrier layer (Z). The adhesive layer (Y) made of an adhesive thermoplastic resin on the outer layer side of the gas barrier layer (Z), and the layer (X) mainly composed of polypropylene are laminated in this order from the inner layer to the outer layer. The multilayer container as described.