JP5672826B2 - Multi-layer container - Google Patents

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 heat sterilization treatment.

  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”) has a melting point higher than the retort sterilization temperature, and is therefore widely used as a storage container for foods that require retort treatment. . However, although PP is excellent in moisture resistance, it has a property of easily permeating oxygen that causes deterioration, discoloration, and discoloration of food, and therefore, 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 having an excellent oxygen barrier property and is widely used in containers for long-term storage of various foods, but has a hydroxyl group in the barrier resin composition, so the oxygen barrier property is highly dependent on humidity. Has drawbacks. 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 during sterilization. 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. Since it does not have a hydroxyl group in the resin composition, it is less dependent on humidity than EVOH and is heat sterilized. Since it has the characteristic that oxygen barrier property fall is small also at the time of a process, the oxygen permeation amount inside a container can be restrained low and the preservability of heat-sterilized foodstuff can be improved. 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 isophthalic acid as a third component with N-MXD6 (for example, Patent Document 2). For example). However, it is possible to obtain a multilayer container by suppressing the crystallization at the time of thermoforming by making it difficult to crystallize, but the obtained multilayer container is whitened when subjected to heat sterilization treatment, and thus is inferior in transparency.

  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 a single-layer film directly exposed to water, or a PET / N-MXD6 / PET multilayer stretched bottle using polyethylene terephthalate (hereinafter sometimes abbreviated as “PET”). Although it is disclosed that the stretched application (see, for example, Patent Document 5) is effective, the whitening suppression effect after heat sterilization treatment is not satisfactory in a PP multilayer container combined with PP having low moisture permeability. Absent.

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

  The objective of this invention is providing the multilayer container which has gas barrier property and transparency suitable as a packaging material of the foodstuff which needs a heat sterilization process.

  As a result of intensive studies on a multilayer container having both gas barrier properties and transparency after heat sterilization treatment, the present inventors have used a specific polyamide resin composition for the gas barrier layer, thereby heat sterilization treatment at 80 ° C. or higher. Later, it was found that the gas barrier property and transparency were excellent, and the present invention was 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 composition (P) are transferred from the inner layer to the outer layer. A multilayer container having a layer structure of three or more layers laminated in order, wherein the polyamide resin composition (P) comprises 80 to 97 moles of diamine units and adipic acid units containing 70 mole% or more of metaxylylenediamine units. % And a dicarboxylic acid unit containing 3 to 20 mol% of isophthalic acid unit (A) 80 to 100% by mass, and a polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer (hereinafter referred to as “N-6T / 6I ")) (B) Polyamide resin composition (M) consisting of 20 to 0% by mass, 100% by mass If, it relates to a multilayer container having an average particle size characterized in that it comprises a 0.01 to 5μm in a crystallization accelerator (C) 0.01 to 2 parts by weight.

  The multilayer container of the present invention has gas barrier properties and transparency suitable as packaging materials for foods that require heat sterilization. Therefore, the food can be stored for a long time, and the contents can be visually recognized even after the heat sterilization process such as the retort process, and the convenience of the customer can be improved by the canned substitute.

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.
An adhesive layer, a PP layer, or a layer made of another resin 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 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 composition (P) constituting the gas barrier layer (Z) has an oxygen permeability coefficient of 1.0 ml · mm / m ² · day · atm or less in an environment of 23 ° C. and 60% RH. It is preferable that it is 0.05-0.5ml * mm / m < ² > * day * atm. The oxygen transmission coefficient can be measured according to ASTM D3985, and can be measured using, for example, OX-TRAN 10 / 50A (trade name, manufactured by Modern Controls).
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 composition (P), and the polyamide resin composition (P) comprises a diamine unit and adipine containing 70 mol% or more of metaxylylenediamine units. Polyamide resin (A) 80 to 100% by mass comprising 80 to 97 mol% of acid units and 3 to 20 mol% of isophthalic acid units, and polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer ( Hereinafter, it may be abbreviated as “N-6T / 6I.” (B) 100 parts by mass of a polyamide resin composition (M) comprising 20 to 0% by mass and an average particle size of 0.01 to 5 μm. Crystallization accelerator (C) 0.01 to 2 parts by mass.

First, the polyamide resin composition (M) will be described. The polyamide resin composition (M) comprises a polyamide resin (A) and a polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer (B) (hereinafter also referred to as polyamide resin (B)).
The polyamide resin (A) is obtained by polycondensing a diamine unit containing 70 mol% or more of metaxylylenediamine units with a dicarboxylic acid unit containing 80 to 97 mol% of adipic acid units and 3 to 20 mol% of isophthalic acid units. Become.
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 80 to 97 mol% adipic acid units and 20 to 3 mol% isophthalic acid units. More preferably, the dicarboxylic acid unit in the polyamide resin (A) preferably contains 85 to 96 mol% adipic acid units and 15 to 4 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 80 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. Moreover, by including 3 mol% or more of isophthalic acid units, the amorphous property of the polyamide resin (A) is increased and the crystallization speed is decreased, so that the thermoformability at the time of container molding is improved.
If the isophthalic acid unit content exceeds 20 mol%, the polymerization of the polyamide resin (A) does not reach the melt viscosity necessary for forming the multilayer container, making it difficult to produce the multilayer container. ) Hardly shows crystallinity, and the PP multilayer container using the polyamide resin (A) as a gas barrier layer is not preferable because whitening after the heat sterilization treatment is increased.

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 80 to 97 mol% adipic acid and 20 to 3 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.

  The polyamide resin (B) is a polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer, which is a copolymer obtained by polycondensation of terephthalic acid, isophthalic acid, and hexamethylenediamine. 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%). By setting the amount within this range, the polyamide resin (B) becomes an amorphous polyamide resin. In the polyamide resin composition (M), the crystallization speed of the polyamide resin (A) is reduced, and thermoforming (molding a container from the multilayer sheet) ( Improves formability during secondary processing. 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 Co., Ltd.), SEALA PA3426 (manufactured by Mitsui DuPont Polychemical Co., Ltd.) may be used.

The content of the polyamide resin (A) and the polyamide resin (B) in the polyamide resin composition (M) is such that (A) :( B) is 80-100% by mass: 20-0% by mass, preferably 85-85%. 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).
Moreover, if content of the polyamide resin (B) in a polyamide resin composition (M) is 20 mass% or less, the gas barrier property is favorable and the container by which the whitening after heat sterilization treatment was suppressed can be obtained.

  The polyamide resin composition (P) includes a polyamide resin composition (M) and a crystallization accelerator (C). The polyamide resin composition (P) is a lubricant, matting agent, heat stabilizer, weather stabilizer, ultraviolet absorber, crystallization nucleator, plasticizer, flame retardant, and the like within a range not impairing the effects of the present invention. You may contain arbitrary additives, such as an antistatic agent, a coloring prevention agent, and an antigelling agent.

In the present invention, the crystallization accelerator (C) is used as the crystallization nucleating agent for the polyamide resin.
Examples of inorganic crystallization accelerators used in the present invention include glass fillers (glass fibers, ground glass fibers (milled fibers), glass flakes, glass beads, etc.), calcium silicate fillers (wollastonite, etc.), Examples include mica, talc, kaolin, potassium titanate whisker, boron nitride, and lamellar silicate clays, nanofillers, and carbon fibers. The average particle size of the inorganic crystallization accelerator is preferably 0.01 to 5 μm. In particular, powder talc having an average particle diameter of 3.0 μm or less is preferable, powder talc having an average particle diameter of about 1.5 to 3.0 μm is more preferable, and powder talc having an average particle diameter of 2.0 μm or less is particularly preferable. preferable. However, powdered talc has a low bulk density, which may cause deterioration of the working environment due to dust and poor dispersion due to aggregation. Therefore, as the crystallization accelerator (C), granular talc in which powdered talc is bound with rosin resin is preferable because it is well dispersed in the polyamide resin. In addition, in this application, an average particle diameter represents the volume average particle diameter (or accumulation 50% particle diameter) of the particle | grains which comprise a crystallization nucleating agent.
As the rosin resin, a rosin ester can be applied. For example, various rosin esters such as tall oil rosin, gum rosin, wood rosin, and purified rosin can be used. In addition, α, β-unsaturated monocarboxylic acid and / or ester of addition reaction product of α, β-unsaturated dicarboxylic acid and rosin can also be used.
Organic crystallization accelerators may be those used in ordinary thermoplastic resins, such as capsules composed of bimolecular films in which a nucleating agent component or the like is added in a micro-level to nano-level size capsule, benzylidene sorbitol And phosphine-based crystallizing nucleating agents, rosinamide-based gelling agents, and the like, and bis (benzylidene) sorbitol-based crystallization nucleating agents are particularly preferable. Two or more of these crystallization accelerators can be used in combination.

  The content of the polyamide resin composition (M) and the crystallization accelerator (C) in the polyamide resin composition (P) is 0.01 to 2 parts by mass with respect to 100 parts by mass of the polyamide resin composition (M). is there. When 0.01 parts by mass or more of the crystallization accelerator (C) is contained, the action as a crystallization nucleating agent is sufficient, and whitening after the heat sterilization treatment can be suppressed. If the content of the crystallization accelerator (C) is 2% by mass or less, the crystallization speed by the crystallization accelerator (C) becomes an appropriate speed, and defects such as elongation unevenness due to crystallization in thermoforming, gas barrier properties. In addition, it is possible to obtain a container having a good appearance and without deformation after heat treatment.

  In the present invention, the semi-crystallization time (ST (P)) in crystallization of the polyamide resin composition (P) at 160 ° C. by the depolarization photometric method is the crystal at the time of thermoforming the multilayer container of the present invention. From the viewpoint of thermoforming properties, gas barrier properties and whitening suppression effect, a range of 30 seconds to 300 seconds is preferable, and a range of 35 seconds to 200 seconds is more preferable.

  The polyamide resin composition (P) 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. Further, after the polyamide resin (A) and the polyamide resin (B) are mixed and / or kneaded to prepare the polyamide resin composition (M), the obtained polyamide resin composition (M) and the crystallization accelerator ( C) may be prepared by mixing and / or kneading, and a predetermined amount of the three components of polyamide resin (A), polyamide resin (B) and crystallization accelerator (C) may be simultaneously mixed and / or kneaded. May be prepared. A polyamide resin composition (P) is prepared by dry blending a predetermined amount of the three components of polyamide resin (A), polyamide resin (B) and crystallization accelerator (C), and pouring the mixture into a hopper. Is particularly preferred.

  Moreover, a polyamide resin composition (P) is a C18-C50 fatty acid metal salt, a C8-C30 fatty acid, and C2-C10 from a viewpoint of the whitening suppression effect after a heat sterilization process, and a bleed-out. You may contain at least 1 sort (s) chosen from the group which consists of the diamide compound obtained from a diamine, and the diester compound obtained from a C8-C30 fatty acid and a C2-C10 diol. Moreover, the compounding quantity becomes like this. Preferably it is 0.01-1.0 mass part with respect to 100 mass parts of polyamide resin compositions (M), More preferably, it is 0.02-0.8 mass part, More preferably, it is 0.00. You may contain 02-0.5 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 to carbon atoms, from the viewpoint of whitening suppression effect after heat sterilization treatment and uniform dispersibility in the polyamide resin composition (P). 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 a diamide compound that can be used in the present invention, a fatty acid having 8 to 30 carbon atoms and 2 to 10 carbon atoms from the viewpoint of whitening suppression effect after heat sterilization treatment and uniform dispersibility in the polyamide resin composition (P). Diamide compounds obtained from 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. One diamine component may be used alone, or two or more diamine components may be combined.
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 fatty acid having 2 to 10 carbon atoms from the viewpoint of whitening suppression effect after heat sterilization treatment and uniform dispersibility in the polyamide resin composition (P). Diester compounds obtained from diols 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. One diol component may be used alone, or two or more diol components may be combined.
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.

  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 composition (P) constituting the gas barrier layer (Z) is extruded from the third extruder, and the PP layer / adhesive layer / gas barrier layer / adhesive layer / PP layer 3 is fed through the feed block. After producing a multi-layered sheet of seed 5-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 both vacuum and compressed air, and is then trimmed. And a method for obtaining a container. 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. In particular, the heat sterilization temperature is as high as 100 ° C. or higher, and it is suitable for storing tuna such as tuna and bonito, which are easily affected by oxygen.

  Examples of the method for heat sterilizing the multilayer container of the present invention include a steam type, a hot water storage type, a shower type and the like. The sterilization temperature is preferably in the range of 80 ° C to 140 ° 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) Gas barrier properties Measured according to ASTM D3985. Specifically, using an oxygen permeability measuring device (OX-TRAN 2 / 20A, trade name, manufactured by Modern Controls), a gas barrier film made of a polyamide resin composition (P) at 23 ° C. and 60% RH environment. The lower oxygen permeability coefficient (ml · mm / m ² · day · atm) was measured.
(3) Haze
Using a retort food autoclave (SR-240, trade name, manufactured by Tommy Seiko Co., Ltd.), the multi-layer container was subjected to steam retort treatment at 120 ° C. for 30 minutes, and the container side part before and after the retort treatment was cut out. JIS K-7105 The haze was measured according to the above. 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 300 μm. It shows that transparency is so high that a haze value is small.
(4) Using a compressed air vacuum forming machine (manufactured by Asano Laboratories) equipped with a mature molding plug assist, the sheet surface temperature was heated to 170 ° C. at a ceramic heater temperature: 480 ° C., and then compressed air vacuum forming was performed. 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
Into a jacketed reactor equipped with a stirrer, a condenser, a cooler, a thermometer, a dripping tank, and a nitrogen gas introduction tube, a molar ratio of 94 mol% of adipic acid and 6 mol% of isophthalic acid is added. Then, after sufficiently purging with nitrogen, the temperature was further raised to 170 ° C. under a nitrogen stream to bring the dicarboxylic acid into a fluid state, and then 100 mol% of metaxylylenediamine 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 to obtain a metaxylylenediamine unit, 94 mol% adipic acid unit and 6 mol isophthalic acid unit. % Polymetaxylylene adipamide / polymetaxylylene isophthalamide copolymer (hereinafter sometimes abbreviated as “N-MXD6 / MXDI”) (polyamide resin (A1)).

Next, the polyamide resin (A1) and N-6T / 6I (Mitsubishi Engineering Plastics, trade name: Novamid X21) (polyamide resin (B1)) are charged into a single screw extruder, kneaded and pelletized. Thus, a polyamide resin composition (M1) composed of 90% by mass of the polyamide resin (A1) and 10% by mass of the polyamide resin (B1) was prepared.
Next, crystallization accelerator (C) (granular talc granulated by using a rosin derivative: HT-7000 manufactured by Harima Chemicals, talc average particle diameter: 100 parts by mass of the polyamide resin composition (M1): The polyamide resin composition (1.8 μm, granule diameter: 0.2 to 3.0 mm) obtained by dry blending 0.1 part by mass into a twin-screw extruder, kneaded, and pelletized to obtain a polyamide resin composition ( P1) was prepared. The half crystallization time ST (P1) in crystallization of the polyamide resin composition (P1) at 160 ° C. was 97 seconds.
The obtained polyamide resin composition (P1) was extruded with a single screw extruder to produce a gas barrier film having a thickness of 50 μm. The oxygen barrier coefficient of the gas barrier film made of the polyamide resin composition (P1) in an environment of 23 ° C. and 60% RH was 0.11 ml · mm / m ² · day · atm.

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. The polyamide resin composition (P1) is extruded from an extruder at 260 ° C., and PP layer (X layer) / adhesive layer (Y layer) / gas barrier layer (Z layer) / adhesive layer (Y layer) / A multilayer sheet having a three-kind five-layer structure of PP layer (X layer) 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 retort-processed and the container side surface haze before and after the retort process was measured. The results are shown in Table 1.

Example 2
The content ratio of the polyamide resin composition (M1) and the crystallization accelerator (C) (granular talc: HT-7000 manufactured by Harima Chemicals) is set to 100 parts by mass of the polyamide resin composition (M1). C) (Granular talc: HT-7000 manufactured by Harima Chemicals Co., Ltd.) A polyamide resin composition (P2) was prepared in the same manner as in Example 1 except that 1.0 part by mass was used. The half crystallization time ST (P2) in crystallization at 160 ° C. of the polyamide resin composition (P2) was 58 seconds.
Further, a gas barrier film, a multilayer sheet and a cup-shaped container were produced in the same manner as in Example 1 except that the polyamide resin composition (P1) was changed to the polyamide resin composition (P2). The oxygen barrier coefficient of the gas barrier film made of the polyamide resin composition (P2) in an environment of 23 ° C. and 60% RH was 0.10 ml · mm / m ² · day · atm.
The obtained cup-shaped container was retort-processed and the container side surface haze before and after the retort process was measured. The results are shown in Table 1.

Example 3
A polyamide resin (A2) was obtained in the same manner as in Example 1 except that the composition ratio of the polyamide resin (A) was 90 mol% adipic acid and 10 mol% isophthalic acid.
Next, a biaxial polyamide resin composition obtained by dry blending 1.0 part by mass of the crystallization accelerator (C) (granular talc: HT-7000 manufactured by Harima Chemicals) with respect to 100 parts by mass of the polyamide resin (A2) The polyamide resin composition (P3) was prepared by putting into an extruder and kneading and pelletizing. The half crystallization time ST (P3) in crystallization at 160 ° C. of the polyamide resin composition (P3) was 48 seconds.
Further, a gas barrier film, a multilayer sheet and a cup-shaped container were produced in the same manner as in Example 1 except that the polyamide resin composition (P1) was changed to the polyamide resin composition (P3). The oxygen barrier coefficient of the gas barrier film comprising the polyamide resin composition (P3) in an environment of 23 ° C. and 60% RH was 0.10 ml · mm / m ² · day · atm.
The obtained cup-shaped container was retort-processed and the container side surface haze before and after the retort process was measured. The results are shown in Table 1.

Example 4
A polyamide resin (A4) was obtained in the same manner as in Example 1 except that the composition ratio of the polyamide resin (A) was 85 mol% for adipic acid and 15 mol% for isophthalic acid.
Next, a biaxial polyamide resin composition obtained by dry blending 1.8 parts by mass of the crystallization accelerator (C) (granular talc: HT-7000 manufactured by Harima Chemicals) with respect to 100 parts by mass of the polyamide resin (A4) The polyamide resin composition (P4) was prepared by putting into an extruder and kneading and pelletizing. The half crystallization time ST (P4) in crystallization at 160 ° C. of the polyamide resin composition (P4) was 95 seconds.
Further, a gas barrier film, a multilayer sheet and a cup-shaped container were produced in the same manner as in Example 1 except that the polyamide resin composition (P1) was changed to the polyamide resin composition (P4). The oxygen barrier coefficient of the gas barrier film made of the polyamide resin composition (P4) in an environment of 23 ° C. and 60% RH was 0.10 ml · mm / m ² · day · atm.
The obtained cup-shaped container was retort-processed and the container side surface haze before and after the retort process was measured. The results are shown in Table 1.

Comparative Example 1
A polyamide resin (A4) 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.
The polyamide resin (A4) was extruded with a single screw extruder to produce a film with a thickness of 50 μm. The half crystallization time for crystallization of the polyamide resin (A4) at 160 ° C. was 25 seconds. The film made of polyamide resin (A4) had an oxygen permeability coefficient of 0.09 ml · mm / m ² · day · atm in a 23 ° C. and 60% RH environment.
A multilayer sheet and a cup-shaped container were prepared in the same manner as in Example 1 except that the polyamide resin composition (P1) was changed to the polyamide resin (A4). Could not be produced.

Comparative Example 2
Polyamide resin in the same manner as in Example 1 except that the crystallization accelerator (C) (granular talc: HT-7000 manufactured by Harima Chemicals) is changed to 0.5% by mass with respect to 100% by mass of the polyamide resin (A4). A composition (P5) was prepared. The half crystallization time ST (P5) in crystallization of the polyamide resin composition (P5) at 160 ° C. was 14 seconds. The film of the polyamide resin composition (P5) had an oxygen permeability coefficient of 0.08 ml · mm / m ² · day · atm in a 23 ° C. 60% RH environment.
Further, except that the polyamide resin composition (P1) was changed to the polyamide resin composition (P5), an attempt was made to produce a multilayer sheet and a cup-shaped container in the same manner as in Example 1, but the elongation unevenness was observed during thermoforming. As a result, the container could not be produced.

Comparative Example 3
The polyamide resin (A1) was extruded with a single screw extruder to produce a gas barrier film having a thickness of 50 μm. The half crystallization time for crystallization of the polyamide resin (A1) at 160 ° C. was 132 seconds. The oxygen permeability coefficient of the gas barrier film made of the polyamide resin (A1) in an environment of 23 ° C. and 60% RH was 0.09 ml · mm / m ² · day · atm.
Further, a multilayer sheet and a cup-shaped container were produced in the same manner as in Example 1 except that the polyamide resin composition (P1) was changed to the polyamide resin (A1).
The obtained cup-shaped container was retort-processed and the container side surface haze before and after the retort process was measured. The results are shown in Table 1.

Comparative Example 4
The composition ratio of the polyamide resin (A1) and N-6T / 6I (Mitsubishi Engineering Plastics, trade name: Novamid X21) (polyamide resin (B1)) is 70% by mass of polyamide resin (A1) and polyamide resin ( B1) A polyamide resin composition (M2) was prepared in the same manner as in Example 1 except that the content was 30% by mass.
Next, the crystallization accelerator was used in such a manner that the content ratio of the polyamide resin composition (M2) and the crystallization accelerator (C) (granular talc: HT-7000 manufactured by Harima Kasei) was 100% by mass with respect to 100% by mass of the polyamide resin composition (M2). (C) A polyamide resin composition (P6) was prepared in the same manner as in Example 1 except that the content was changed to 1.0% by mass. The half crystallization time ST (P6) in crystallization of the polyamide resin composition (P6) at 160 ° C. was 152 seconds. The film made of the polyamide resin composition (P6) had an oxygen permeability coefficient of 0.16 ml · mm / m ² · day · atm in a 23 ° C. and 60% RH environment.
A multilayer sheet and a cup-shaped container were produced in the same manner as in Example 1 except that the polyamide resin composition (P1) was changed to the polyamide resin composition (P6).
The obtained cup-shaped container was retort-processed and the container side surface haze before and after the retort process was measured. The results are shown in Table 1.

Comparative Example 5
Example except that the polyamide resin composition (P1) was changed to 3.0% by mass of the crystallization accelerator (C) (granular talc: HT-7000 manufactured by Harima Chemicals) with respect to 100 parts by weight of the polyamide resin (A1). In the same manner as in Example 1, a polyamide resin composition (P6) was prepared. The half crystallization time ST (P6) in the crystallization at 160 ° C. of the polyamide resin composition (P6) was 8 seconds. Further, the oxygen transmission coefficient of the film made of the polyamide resin composition (P6) in an environment of 23 ° C. and 60% RH was 0.09 ml · mm / m ² · day · atm.
Further, except that the polyamide resin composition (P1) was changed to the polyamide resin composition (P6), an attempt was made to produce a multilayer sheet and a cup-shaped container in the same manner as in Example 1, but the elongation unevenness was observed during thermoforming. As a result, the container could not be produced.

Comparative Example 6
Example 1 except that the crystallization accelerator (C) (fine talc: Nippon Talc K-1, average particle diameter 8 μm) was changed to 1.0% by mass with respect to 100% by mass of the polyamide resin (A2). Thus, a polyamide resin composition (P8) was prepared. The half crystallization time ST (P8) in crystallization of the polyamide resin composition (P8) at 160 ° C. was 35 seconds. Further, the oxygen transmission coefficient of the film made of the polyamide resin composition (P8) in an environment of 23 ° C. and 60% RH was 0.08 ml · mm / m ² · day · atm. However, the obtained monolayer film has a lumped aggregated talc, resulting in poor appearance of the film.
Further, except that the polyamide resin composition (P1) was changed to the polyamide resin composition (P8), an attempt was made to produce a multilayer sheet and a cup-shaped container in the same manner as in Example 1, but thermoforming with aggregated talc. Due to the unevenness of elongation at the time, the container could not be produced.

ＡＡ：アジピン酸
ＩＰＡ：イソフタル酸
ＭＸＤＡ：メタキシレンジアミン
Ｎ−６Ｔ／６Ｉ：ポリヘキサメチレンテレフタルアミド／ポリヘキサメチレンイソフタルアミドコポリマー
ＨＴ−７０００：ハリマ化成(株)製 顆粒状タルク
Ｋ-1：日本タルク(株)製 微粉タルク

AA: Adipic acid IPA: Isophthalic acid MXDA: Metaxylenediamine N-6T / 6I: Polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer HT-7000: Harima Kasei Co., Ltd. Granular talc K-1: Nippon Talc Co., Ltd. Fine talc

In Comparative Example 1 using only the polyamide resin (A4) not containing an isophthalic acid unit and in Comparative Example 2 containing a crystallization accelerator (C) in a polyamide (A4) containing no isophthalic acid unit, the polyamide resin composition was crystallized. The container was not able to be produced because of uneven elongation during thermoforming. In Comparative Example 3 using only the polyamide resin (A1) and Comparative Example 4 using the polyamide resin composition (M2) in which the composition ratio of the polyamide resin (A1) and N-6T / 6I is out of the range, container molding However, the haze of the molded product (before the retort treatment) was high, the haze was further increased by the retort treatment, and the transparency was poor. This is because the spherulites of the polyamide resin (A) grew greatly due to the crystallization of the polyamide resin composition proceeding slowly during the thermoforming and the heat sterilization treatment at 120 ° C. In Comparative Example 5 using the polyamide resin composition (P7) containing a large amount of the crystallization accelerator (C), crystallization of the polyamide resin (A1) proceeds in the preheating step during thermoforming due to the crystallization promotion effect, Elongation unevenness occurred during thermoforming. In Comparative Example 6 using the crystallization accelerator (C) not bound with the rosin-based resin (fine powder talc: Nippon Talc K1, average particle size 8 μm), the appearance of the thermoformed container was poor due to aggregation of talc. .
On the other hand, the multilayer containers of Examples 1 to 4 can be obtained by thermoforming, and are excellent in transparency as compared with Comparative Examples 3 and 4 before the retort treatment, and the degree of whitening after retort is small. It had high transparency.

  The multilayer container of the present invention is excellent in gas barrier properties and transparency even after heat sterilization treatment such as retort treatment, so that food can be stored and visually confirmed. Very expensive.

Claims (4)

A layer mainly composed of polypropylene (X), an adhesive layer (Y) made of an adhesive thermoplastic resin,
And a gas barrier layer (Z) composed of the polyamide resin composition (P) is a multilayer container having a layer structure of three or more layers laminated in this order from the inner layer to the outer layer, wherein the polyamide resin composition (P) Polyamide resin (A) comprising 80 to 100% by mass of a diamine unit containing 70 mol% or more of xylylenediamine units, a dicarboxylic acid unit containing 80 to 97 mol% of adipic acid units and 3 to 20 mol% of isophthalic acid units, In addition, 100 parts by mass of a polyamide resin composition (M) comprising 20 to 0% by mass of a polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer (B), and a powdery talc having a rosin resin as a binder and an average particle size Characterized by containing 0.01 to 2 parts by mass of a crystallization accelerator (C) having a molecular weight of 0.01 to 5 μm. Multilayer container that. The multilayer container according to claim 1, wherein the polyamide resin composition (P) has a semi-crystallization time (ST (P)) of 30 seconds to 300 seconds in crystallization at 160 ° C by a depolarization photometric method. . 3. The multilayer according to claim 1, wherein the polyamide resin composition (P) has an oxygen permeability coefficient of 1.0 ml · mm / m ² · day · atm or less in an environment of 23 ° C. and 60% RH. container.   The multilayer container in any one of Claims 1-3 whose thickness of the said gas barrier layer (Z) is 2-20% with respect to the total thickness of a multilayer container.