JP2011037199A - Multilayer container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer container having a gas barrier property and transparency suitable as a packaging material of food which requires heat sterilization. <P>SOLUTION: The multilayer container has a layer structure of ≥3 layers of a layer (X) consisting essentially of polypropylene, an adhesive layer (Y) comprising an adhesive thermoplastic resin and a gas barrier layer (Z) comprising a polyamide resin composition (P), laminated in this order from the inner layer to the outer layer. The polyamide resin composition (P) contains 80-99.9 mass% polyamide resin (A) comprising a diamine unit containing ≥70 mol% methaxylene diamine unit, a dicarboxylic acid unit containing 80-97 mol% α,ω-linear aliphatic dicarboxylic acid unit and 20-3 mol% aromatic dicarboxylic acid unit and 20-0.1 mass% aliphatic polyamide resin (B). <P>COPYRIGHT: (C)2011,JPO&INPIT

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 has excellent moisture proofing properties, it has a property that allows oxygen to easily permeate the food, causing deterioration, discoloration, and discoloration. Therefore, PP has insufficient performance 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. The suppression 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 research 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 a diamine unit containing at least 70 mol% of a metaxylylenediamine unit and an α, ω-linear fatty acid Polyamide resin (A) comprising 80 to 99.9% by mass of an aliphatic dicarboxylic acid unit and 80 to 99.9% by mass of a dicarboxylic acid unit containing 20 to 3 mol% of an aromatic dicarboxylic acid unit, and an aliphatic polyamide resin (B) 20 The present invention relates to a multilayer container characterized by containing 0.1 to 0.1% by mass.

  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, a thermoplastic resin layer made of polycarbonate or various easy-peeling resins can be laminated on the front side of the PP layer in order to give characteristics to the multilayer container. 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 oxygen permeability coefficient of the gas barrier layer (Z) in an environment of 23 ° C. and 60% RH is preferably 1.0 ml · mm / m ² · day · atm or less, 0.05 to More preferably, it is 0.5 ml · 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 containing at least 70 mol% of a metaxylylenediamine unit and α , Ω-linear aliphatic dicarboxylic acid units 80 to 97 mol% and a dicarboxylic acid unit comprising aromatic dicarboxylic acid units 20 to 3 mol% (A) 80 to 99.9% by mass, Group polyamide resin (B) 20 to 0.1 mass%.

The polyamide resin (A) comprises a diamine unit containing at least 70 mol% of a metaxylylenediamine unit, an α, ω-linear aliphatic dicarboxylic acid unit of 80 to 97 mol%, and an aromatic dicarboxylic acid unit of 20 to 3 mol%. Containing dicarboxylic acid units.
The diamine unit in the polyamide resin (A) contains 70 mol% or more of metaxylylenediamine units, preferably 80 mol% or more and 100 mol% or less, more preferably 90 mol%, from the viewpoint of developing excellent gas barrier properties. More than 100 mol%. Compounds that can constitute diamine units other than metaxylylenediamine units include paraxylylenediamine, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, tetramethylenediamine, and hexamethylene. Examples include diamine, nonamethylenediamine, 2-methyl-1,5-pentanediamine, but are not limited thereto.

  The dicarboxylic acid unit in the polyamide resin (A) contains 80 to 97 mol% of α, ω-linear aliphatic dicarboxylic acid units and 20 to 3 mol% of aromatic dicarboxylic acid units. By containing 80 mol% or more of α, ω-linear aliphatic dicarboxylic acid units among the dicarboxylic acid units, it is possible to avoid a decrease in gas barrier properties and an excessive decrease in crystallinity. In addition, when the aromatic dicarboxylic acid unit is contained in an amount of 3 mol% or more, the amorphous property of the polyamide resin (A) is increased and the crystallization rate is decreased, so that the thermoformability at the time of container molding is improved. On the other hand, if the content of the aromatic dicarboxylic acid unit exceeds 20 mol%, it is difficult to produce a multilayer container because it cannot be polymerized to the melt viscosity necessary for forming the multilayer container, and the polyamide resin ( Since A) hardly shows crystallinity, the PP multilayer container using the polyamide resin (A) as a gas barrier layer has a large whitening after the heat sterilization treatment. The dicarboxylic acid units in the polyamide resin (A) preferably contain 85 to 96 mol% of α, ω-linear aliphatic dicarboxylic acid units and 15 to 4 mol% of aromatic dicarboxylic acid units, and α, ω- More preferably, it contains 90 to 95 mol% of linear aliphatic dicarboxylic acid units and 10 to 5 mol% of aromatic dicarboxylic acid units.

  As the compound that can constitute the α, ω-linear aliphatic dicarboxylic acid unit, one or more of α, ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms are preferable, and adipic acid is particularly preferable. . Examples of the compound that can constitute the aromatic dicarboxylic acid unit include terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid, and isophthalic acid is particularly preferable.

The polyamide resin (A) is a dicarboxylic acid containing a diamine component containing at least 70 mol% of metaxylylenediamine, 80 to 97 mol% of an α, ω-linear aliphatic dicarboxylic acid, and 20 to 3 mol% of an aromatic dicarboxylic acid. It can be obtained by polycondensation with components. 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-type heating device that is superior in air tightness and capable of cutting off contact between oxygen and the polyamide resin at a higher level than a continuous heating device, and is particularly a tumble dryer or a conical dryer. A rotary drum type heating device called a rotary dryer or the like and a conical type heating device equipped with rotary blades inside called a Nauta mixer 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 aliphatic polyamide resin (B) is a crystalline polyamide resin, and acts as a crystallization nucleating agent for the polyamide resin (A) during the heat sterilization treatment, thereby reducing the spherulite size of the polyamide resin (A). Thereby, whitening at the time of heat-processing the multilayer container of this invention can be suppressed.
Specific examples of the aliphatic polyamide resin (B) include nylon 6, nylon 66, nylon 6,66, nylon 4,6 and the like. Nylon 6 is preferable from the viewpoint of melting point and crystallization speed at the time of melt processing. preferable.

  The content of the polyamide resin (A) and the aliphatic polyamide resin (B) in the polyamide resin composition (P) is (A) :( B) of 80 to 99.9% by mass: 20 to 0.1% by mass. Yes, preferably 82-99.5 mass%: 18-0.5 mass%, more preferably 85-99.0 mass%: 15-1.0 mass%. When the content of the aliphatic polyamide resin (B) is less than 0.1% by mass, the action of the polyamide resin (A) as a crystallization nucleating agent is insufficient, and whitening occurs after the heat sterilization treatment. If the content of the aliphatic polyamide resin (B) exceeds 20% by mass, the crystallization speed is increased by the aliphatic polyamide resin (B). This is not preferable because it lowers and further deforms after heat treatment.

  The polyamide resin composition (P) is a lubricant, matting agent, heat stabilizer, weather stabilizer, ultraviolet absorber, crystallization nucleating agent, plasticizer, flame retardant, antistatic, as long as the effects of the present invention are not impaired. You may contain arbitrary additives, such as an agent, a coloring prevention agent, and a gelling prevention agent.

In the present invention, the polyamide resin composition (P) has a half crystallization time (ST (P)) of 30 seconds to 300 seconds in crystallization at 160 ° C. by a depolarization photometric method, and the polyamide resin The ratio of the half crystallization time (ST (A) / ST (B)) in crystallization at 120 ° C. by depolarizing photometry of (A) and aliphatic polyamide resin (B) is not less than 10 seconds and not more than 1000 seconds. Preferably there is.
The semi-crystallization time (ST (P)) of the polyamide resin composition (P) by crystallization at 160 ° C. by depolarization photometry is an index of the crystallization speed when the multilayer container of the present invention is thermoformed. In view of thermoformability, 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 ratio of the half crystallization time (ST (A) / ST (B)) in the crystallization of the polyamide resin (A) and the aliphatic polyamide resin (B) at 120 ° C. by the depolarization photometric method is the multilayer of the present invention. It is an index of the crystallization rate when the container is subjected to heat sterilization treatment, and is preferably in the range of 10 seconds to 1000 seconds, more preferably in the range of 20 seconds to 900 seconds, from the viewpoint of gas barrier properties and whitening suppression effect, 50 A range of from second to 800 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. It is particularly preferable to prepare a polyamide resin composition (P) by dry blending a predetermined amount of the polyamide resin (A) and the polyamide resin (B), and charging the mixture into a hopper at once.

  In addition, the polyamide resin composition (P) has a carbon content of 100 parts by mass in total of the polyamide resin (A) and the aliphatic polyamide resin (B) from the viewpoint of whitening suppression effect after heat sterilization treatment and bleeding out. Preferably, at least one selected from the group consisting of a diamide compound or a diester compound obtained from a fatty acid metal salt having 18 to 50 carbon atoms and a fatty acid having 8 to 30 carbon atoms and a diamine or diol having 2 to 10 carbon atoms, preferably 0 0.01-1.0 mass part, More preferably, it may contain 0.02-0.8 mass part, More preferably, you may contain 0.02-0.5 mass part. A fatty acid metal salt, a diamide compound, and a 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.
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. There is no particular limitation on the metal that forms a salt with a fatty acid, but sodium, potassium, lithium, calcium, barium, magnesium, strontium, aluminum, zinc, etc. can be exemplified, and among these, sodium, potassium, and lithium, calcium, aluminum, And zinc are particularly preferred.
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.

The diamide 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). 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. Examples of the diamine component of the diamide compound include ethylenediamine, butylenediamine, hexanediamine, xylylenediamine, and bis (aminomethyl) cyclohexane.
The diamide compound is preferably a diamide compound obtained from a fatty acid having 8 to 30 carbon atoms and a diamine mainly composed of ethylenediamine, or a diamide compound obtained from a fatty acid mainly comprising montanic acid and a diamine having 2 to 10 carbon atoms. A diamide compound obtained from a fatty acid composed of stearic acid and a diamine composed mainly of ethylenediamine is 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.
As the diester compound, a diester compound obtained from a fatty acid having 8 to 30 carbon atoms and a diol mainly composed of ethylene glycol and / or 1,3-butanediol is preferable, and a fatty acid mainly composed of montanic acid and mainly ethylene glycol and / or A diester compound obtained from a diol composed of 1,3-butanediol is 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. A gas barrier resin is extruded from a third extruder, and a multi-layer sheet of three types and five layers of PP layer / adhesive layer / gas barrier layer / adhesive layer / PP layer is produced through a feed block. There is a method in which after heat softening, a sheet is brought into close contact with a mold by vacuum, compressed air, or a thermoforming method using a combination of vacuum and compressed air to form a container and trimmed to obtain 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 eggs, quail eggs, 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: 120 ° C or 160 ° C
(2) Gas barrier properties Measured according to ASTM D3985. Specifically, an oxygen permeability measurement device (OX-TRAN 10 / 50A, trade name, manufactured by Modern Controls) was used, and the oxygen permeability coefficient (ml · mm / mm) of the gas barrier film in a 23 ° C. 60% RH environment. m ² · day · atm) was measured.
(3) Haze Using a retort food autoclave (SR-240, trade name, manufactured by Tommy Seiko Co., Ltd.), the multilayer container was retorted at 121 ° C. for 30 minutes, and the container side surface before and after the retort treatment was cut out, and JIS K- The haze was measured according to 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 300 μm.

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 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)). The half crystallization time ST (A1) in crystallization of the polyamide resin (A1) at 120 ° C. was 1950 seconds.
Next, the polyamide resin (A1) and nylon 6 (manufactured by Ube Industries, trade name: UBE nylon, grade name: 1015B) (polyamide resin (B1)) are charged into a single screw extruder and kneaded and pelletized. Thus, a polyamide resin composition (P1) composed of 99% by mass of the polyamide resin (A1) and 1% by mass of the polyamide resin (B1) was prepared. The half crystallization time ST (B1) in crystallization of the polyamide resin (B1) at 120 ° C. was 6 seconds. Moreover, the half crystallization time ST (P1) in the crystallization at 160 ° C. of the polyamide resin composition (P1) was 129 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 composed of the polyamide resin composition (P1) in an environment of 23 ° C. and 60% RH was 0.07 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: FY6C, Melt Index: 2.5) at 240 ° C. Adhesive resin (Mitsui Chemicals, trade name: Admer, grade: QB515) from the second extruder at 230 ° C. The polyamide resin composition (P1) is extruded from the extruder at 250 ° 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, when a sheet surface temperature reaches 165 ° C. using a pressure forming machine equipped with a plug assist, thermoforming is performed, and a cup having a diameter of 90 mm × bottom diameter of 80 mm × depth of 63 mm, a surface area of 221 cm ² and a volume of 250 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. Moreover, the container after the retort process was visually observed. The results are shown in Table 1.

Example 2
A polyamide resin composition in the same manner as in Example 1 except that the content ratio of the polyamide resin (A1) and the polyamide resin (B1) was changed to 95% by mass of the polyamide resin (A1) and 5% by mass of the polyamide resin (B1). (P2) was prepared. The half crystallization time ST (P2) in crystallization at 160 ° C. of the polyamide resin composition (P2) was 102 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 permeability coefficient of the gas barrier film made of the polyamide resin composition (P2) in an environment of 23 ° C. and 60% RH was 0.08 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. Moreover, the container after the retort process was visually observed. The results are shown in Table 1.

Example 3
A polyamide resin composition in the same manner as in Example 1 except that the content ratio of the polyamide resin (A1) and the polyamide resin (B1) was changed to 90% by mass of the polyamide resin (A1) and 10% by mass of the polyamide resin (B1). (P3) was prepared. The half crystallization time ST (P3) in crystallization of the polyamide resin composition (P3) at 160 ° C. was 89 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 permeability coefficient of the gas barrier film made of the polyamide resin composition (P3) in an environment of 23 ° C. and 60% RH was 0.09 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. Moreover, the container after the retort process was visually observed. The results are shown in Table 1.

Example 4
N-MXD6 / MXDI (polyamide resin (A2) composed of metaxylylenediamine units, 85 mol% adipic acid units and 15 mol% isophthalic acid units by changing the input amounts of metaxylylenediamine, adipic acid and isophthalic acid )). The half crystallization time ST (A2) in crystallization of the polyamide resin (A2) at 120 ° C. was 3600 seconds.
Next, the polyamide resin (A2) and the polyamide resin (B1) are charged into a single-screw extruder, kneaded and pelletized to obtain 95% by mass of the polyamide resin (A2) and 5% by mass of the polyamide resin (B1). A polyamide resin composition (P4) comprising: Moreover, the half crystallization time ST (P4) in the crystallization at 160 ° C. of the polyamide resin composition (P4) was 192 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 0.08 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. Moreover, the container after the retort process was visually observed. The results are shown in Table 1.

Example 5
A polyamide resin composition (P5) was prepared in the same manner as in Example 2 except that 0.5 parts by mass of calcium stearate was added to 100 parts by mass of the polyamide resin (A1) and the polyamide resin (B1). . The half crystallization time ST (P5) in the crystallization of the polyamide resin composition (P5) at 160 ° C. was 36 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 (P5). The oxygen barrier coefficient of the gas barrier film made of the polyamide resin composition (P5) in an environment of 23 ° C. and 60% RH was 0.08 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. Moreover, the container after the retort process was visually observed. The results are shown in Table 1.

Example 6
Example except that 0.02 part by mass of modified ethylenebisstearylamide (trade name: WH-255, manufactured by Kyoeisha Chemical Co., Ltd.) was added to 100 parts by mass of the polyamide resin (A1) and the polyamide resin (B1). In the same manner as in 2, a polyamide resin composition (P6) was prepared. The half crystallization time ST (P6) in the crystallization of the polyamide resin composition (P6) at 160 ° C. was 37 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 (P6). The oxygen barrier coefficient of the gas barrier film composed of the polyamide resin composition (P6) in an environment of 23 ° C. and 60% RH was 0.08 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. Moreover, the container after the retort process was visually observed. The results are shown in Table 1.

Example 7
A polyamide resin composition (P7) was prepared in the same manner as in Example 6 except that the amount of the modified ethylenebisstearylamide added was changed to 0.5 parts by mass. The half crystallization time ST (P7) in crystallization of the polyamide resin composition (P7) at 160 ° C. was 36 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 (P7). The oxygen barrier coefficient of the gas barrier film made of the polyamide resin composition (P7) in an environment of 23 ° C. and 60% RH was 0.08 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. Moreover, the container after the retort process was visually observed. The results are shown in Table 1.

Comparative Example 1
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 0.07 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. Moreover, the container after the retort process was visually observed. The results are shown in Table 2.

Comparative Example 2
N-MXD6 / MXDI (polyamide resin (A3) composed of metaxylylenediamine units, 75 mol% adipic acid units and 25 mol% isophthalic acid units by changing the input amounts of metaxylylenediamine, adipic acid and isophthalic acid. )). The half crystallization time ST (A3) in crystallization of the polyamide resin (A3) at 120 ° C. was 6250 seconds.
Next, the polyamide resin (A3) and the polyamide resin (B1) are put into a single-screw extruder, kneaded and pelletized to obtain 95% by mass of the polyamide resin (A3) and 5% by mass of the polyamide resin (B1). A polyamide resin composition (P8) comprising: Moreover, the half crystallization time ST (P8) in the crystallization at 160 ° C. of the polyamide resin composition (P8) was 405 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 (P8). The oxygen barrier coefficient of the gas barrier film made of the polyamide resin composition (P8) in an environment of 23 ° C. and 60% RH was 0.09 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. Moreover, the container after the retort process was visually observed. The results are shown in Table 2.

Comparative Example 3
A polyamide resin composition in the same manner as in Example 1 except that the content ratio of the polyamide resin (A1) and the polyamide resin (B1) was changed to 75% by mass of the polyamide resin (A1) and 25% by mass of the polyamide resin (B1). (P9) was prepared. The half crystallization time ST (P9) in crystallization of the polyamide resin composition (P9) at 160 ° C. was 44 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 (P9). The oxygen barrier coefficient of the gas barrier film comprising the polyamide resin composition (P9) in an environment of 23 ° C. and 60% RH was 0.14 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. Moreover, the container after the retort process was visually observed. The results are shown in Table 2.

Comparative Example 4
Polyamide resin composition in the same manner as Comparative Example 1 except that 0.5 parts by mass of modified ethylenebisstearylamide (trade name: WH-255, manufactured by Kyoeisha Chemical Co., Ltd.) was added to 100 parts by mass of the polyamide resin (A1). A product (P10) was prepared. The half crystallization time ST (P10) in the crystallization of the polyamide resin composition (P10) at 160 ° C. was 130 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 (P10). The oxygen barrier coefficient of the gas barrier film comprising the polyamide resin composition (P10) in an environment of 23 ° C. and 60% RH was 0.07 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. Moreover, the container after the retort process was visually observed. The results are shown in Table 2.

Comparative Example 5
Example except that 1.1 parts by mass of modified ethylene bisstearylamide (trade name: WH-255, manufactured by Kyoeisha Chemical Co., Ltd.) was added to 100 parts by mass of the polyamide resin (A1) and the polyamide resin (B1). In the same manner as in 2, a polyamide resin composition (P11) was prepared. The half crystallization time ST (P11) in crystallization of the polyamide resin composition (P11) at 160 ° C. was 34 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 (P11). The oxygen barrier coefficient of the gas barrier film composed of the polyamide resin composition (P11) in an environment of 23 ° C. and 60% RH was 0.08 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. Moreover, the container after the retort process was visually observed. The results are shown in Table 2.

In Comparative Example 1 using only the polyamide resin (A1) made of N-MXD6 / MXDI, the container was whitened by retort treatment and was inferior in transparency. This is presumably because the spherulites of N-MXD6 grew greatly due to the crystallization of N-MXD6 slowly during the heat sterilization treatment at 121 ° C. In Comparative Example 2 using the polyamide resin composition (P8) containing the polyamide resin (A3) containing a large amount of isophthalic acid units, it became difficult to crystallize and the degree of whitening due to the retort treatment increased. In Comparative Example 3 using the polyamide resin (P9) containing a large amount of nylon 6, the container was deformed by the retort treatment. Moreover, in the comparative example 4 using the polyamide resin composition (P10) which added the diamide compound to the polyamide resin (A1) as a whitening inhibitor, the container was whitened by the retort treatment and inferior in transparency. The diamide compound is known to be effective in suppressing whitening in a single layer film or a PET multilayer stretch blow bottle, but was found to be insufficient for suppressing whitening after retorting in a PP multilayer container. Further, in Comparative Example 5 containing a large amount of the diamide compound, white foreign matters resulting from the uneven distribution of the diamide compound were produced, and the appearance was poor. In addition, bleed-out was caused by the retort treatment, and whitening was caused after the retort treatment.
On the other hand, the multilayer containers of Examples 1 to 7 can be obtained by thermoforming, and it has been found that they have excellent gas barrier properties and transparency even after retorting. In particular, in Examples 5 to 7 using the polyamide resin compositions (P5) to (P7) containing a fatty acid metal salt or an amide compound, the degree of whitening after the retort treatment is small and the transparency is higher. It was.

  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 (6)

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) were laminated in this order from the inner layer to the outer layer 3 A multi-layer container having a layer structure of more than one layer,
The polyamide resin composition (P) is composed of a diamine unit containing at least 70 mol% of a metaxylylenediamine unit, 80 to 97 mol% of an α, ω-linear aliphatic dicarboxylic acid unit and 20 to 3 of an aromatic dicarboxylic acid unit. A multilayer container comprising 80 to 99.9% by mass of a polyamide resin (A) composed of a dicarboxylic acid unit containing mol% and 20 to 0.1% by mass of an aliphatic polyamide resin (B).   The polyamide resin composition (P) has a half crystallization time (ST (P)) in crystallization at 160 ° C. by depolarization photometry of 30 seconds to 300 seconds, and the polyamide resin (A) And the ratio of the half crystallization time (ST (A) / ST (B)) in the crystallization of the aliphatic polyamide resin (B) at 120 ° C. by depolarization photometry is not less than 10 seconds and not more than 1000 seconds. The multilayer container according to claim 1.   The polyamide resin composition (P) is a fatty acid metal salt having 18 to 50 carbon atoms and 8 to 8 carbon atoms with respect to a total of 100 parts by mass of the polyamide resin (A) and the aliphatic polyamide resin (B). It contains 0.01-1.0 mass part at least 1 sort (s) chosen from the group which consists of a diamide compound or a diester compound obtained from a 30 fatty acid and a C2-C10 diamine or diol. The multilayer container according to 2. The multilayer container according to any one of claims 1 to 3, wherein the gas barrier layer (Z) has an oxygen permeability coefficient of not more than 1.0 ml · mm / m ² · day · atm in a 23 ° C, 60% RH environment.   The multilayer container according to any one of claims 1 to 4, wherein the aliphatic polyamide resin (B) is nylon 6.   The multilayer container in any one of Claims 1-5 whose thickness of the said gas barrier layer (Z) is 2-20% with respect to the total thickness of a multilayer container.