Multilayer container and method for manufacturing the same

Abstract

To provide a multilayer container which is adhesion between a polyolefin layer and a polyamide resin layer, and is excellent in moldability, and a method for manufacturing a multilayer container.SOLUTION: A multilayer container has a polyolefin layer containing acid-modified polyolefin and acid-unmodified polyolefin, and a polyamide resin layer which comes in contact with the polyolefin layer and contains a polyamide resin, wherein the polyamide resin contains a polyamide resin (a) containing a diamine-derived structural unit and a dicarboxylic acid-derived structural unit in which 70 mol% or more of the diamine-derived structural unit is derived from metaxylylenediamine, and 30 mol% or more of the dicarboxylic acid-derived structural unit is derived from an α,ω-straight-chain aliphatic dicarboxylic acid having 4 to 20 carbon atoms, a melt flow rate of the acid-unmodified polyolefin is 20 g / 10 min or more, a melt flow rate of the polyamide resin contained in the polyamide resin layer is 5 g / 10 min or more, and a difference between the melt flow rate of the polyolefin layer and the melt flow rate of the polyamide resin layer is within a range of 10-53 g / 10 min.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a multilayer container and a method for manufacturing the same, and more particularly to a multilayer container having a barrier layer made of a polyamide resin. [Background technology]

[0002] Conventionally, canned or bottled foods have been used as a method for preserving foods and pharmaceuticals because it is necessary to prevent deterioration, discoloration, and fading of the foods. However, although canned or bottled foods exhibit high barrier properties against various gases such as oxygen and water vapor, they have problems such as inability to be heated using a microwave oven, difficulty in removing the filled food when serving it on a plate, and the inability to stack cans after use makes the discarded cans bulky and inappropriate for disposal.

[0003] Thermoformed containers made of thermoplastic resins are widely used as alternative storage containers. In particular, containers made of polyolefins, especially polypropylene (hereinafter sometimes abbreviated as "PP"), have a melting point higher than the retort sterilization temperature, and are therefore widely used as storage containers for foods that require retort processing. However, although PP has excellent moisture-proof properties, it is easily permeable to oxygen, which causes deterioration, discoloration, and fading of food and chemicals, making it insufficient for use as a container for long-term storage of food and chemicals. A known method for enabling long-term storage of food or medicine in a PP container is to use a multilayer container with an oxygen-barrier thermoplastic resin layer as an intermediate layer. Specifically, a multilayer container consisting of a PP layer, an adhesive resin layer, a polyamide resin layer as a gas barrier layer, an adhesive resin layer, and a PP layer has been disclosed (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-65923 Summary of the Invention [Problem to be solved by the invention]

[0005] Although the multilayer container described in Patent Document 1 is excellent, it is difficult to provide an adhesive resin layer when molding the container by injection molding, for example. However, without an adhesive resin layer, the adhesion between the PP layer and the gas barrier layer (polyamide resin layer) becomes an issue. It has also been found that when a multilayer container made of PP is manufactured by injection molding, the appearance may be affected. Furthermore, moldability problems may arise, such as the gas barrier layer (polyamide resin layer) not being able to be sufficiently filled into the mold or variations in thickness. The present invention aims to solve these problems and to provide a multilayer container having a polyolefin layer such as a PP layer and a polyamide resin layer that can serve as a gas barrier layer, which has excellent adhesion between the polyolefin layer and the polyamide resin layer and excellent moldability (appearance of the polyolefin layer side), as well as a method for manufacturing the multilayer container. [Means for solving the problem]

[0006] In light of the above-mentioned problems, the present inventors have conducted research and have found that the above-mentioned problems can be solved by blending an acid-modified polyolefin having a predetermined MFR and an acid-unmodified polyolefin in the polyolefin layer, and by setting the difference in MFR between the polyolefin layer and the polyamide resin layer within a predetermined range. Specifically, the above problems were solved by the following means. <1> A film comprising a polyolefin layer containing an acid-modified polyolefin and an acid-unmodified polyolefin, and a polyamide resin layer in contact with the polyolefin layer and containing a polyamide resin, wherein the polyamide resin contains a polyamide resin (a) containing diamine-derived structural units and dicarboxylic acid-derived structural units, 70 mol % or more of the diamine-derived structural units being derived from metaxylylenediamine, and 30 mol % or more of the dicarboxylic acid-derived structural units being derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms, the acid-unmodified polyolefin having a melt flow rate of 20 g / 10 min or more measured at 230°C and 2.16 kgf in accordance with JIS K7210-1:2014, and the polyamide resin contained in the polyamide resin layer has a melt flow rate of 20 g / 10 min or more measured at 230°C and 2.16 kgf in accordance with JIS K7210-1:2014. A multilayer container having a melt flow rate of 5 g / 10 min or more as measured in accordance with JIS K7210-1:2014 at 250°C and 2.16 kgf, and a difference between the melt flow rate of the mixture of acid-unmodified polyolefin and acid-modified polyolefin contained in the polyolefin layer as measured in accordance with JIS K7210-1:2014 at 230°C and 2.16 kgf and the melt flow rate of the polyamide resin contained in the polyamide resin layer is in the range of 10 to 53 g / 10 min. <2> the content of the alkali metal salt of a higher fatty acid contained in the polyamide resin layer is less than 50 ppm by mass in terms of alkali metal atoms; <1> The multilayer container according to claim 1. <3> The acid-modified polyolefin includes acid-modified polypropylene. <1> or <2> The multilayer container according to claim 1. <4> a mass ratio of the acid-modified polyolefin to the acid-unmodified polyolefin in the polyolefin layer is 1 to 10 parts by mass of the acid-unmodified polyolefin relative to 100 parts by mass of the acid-modified polyolefin; <1> ~ <3> 10. The multilayer container according to claim 9, wherein the multilayer container is a multilayer container. <5> The acid-unmodified polyolefin comprises polypropylene. <1> ~ <4> 10. The multilayer container according to claim 9, wherein the multilayer container is a multilayer container. <6> a difference between a melt flow rate of the mixture of acid-unmodified polyolefin and acid-modified polyolefin contained in the polyolefin layer, measured in accordance with JIS K7210-1:2014 under conditions of 230°C and 2.16 kgf, and a melt flow rate of the polyamide resin contained in the polyamide resin layer, is in the range of 40 to 50 g / 10 min; <1> ~ <5> 10. The multilayer container according to claim 9, wherein the multilayer container is a multilayer container. <7> The polyamide resin has a terminal amino group concentration of 10 to 70 μeq / g. <1> ~ <6> 10. The multilayer container according to claim 9, wherein the multilayer container is a multilayer container. <8> The multilayer container is a multilayer injection molded container. <1> ~ <7> 10. The multilayer container according to claim 9, wherein the multilayer container is a multilayer container. <9> The method includes injection molding by injecting a polyolefin layer-forming composition containing an acid-modified polyolefin and an acid-unmodified polyolefin, and a polyamide resin layer-forming composition containing a polyamide resin (a) that contains diamine-derived structural units and dicarboxylic acid-derived structural units, wherein 70 mol % or more of the diamine-derived structural units are derived from metaxylylenediamine and 30 mol % or more of the dicarboxylic acid-derived structural units are derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms, into a mold so that a polyolefin layer formed from the polyolefin layer-forming composition and a polyamide resin layer formed from the polyamide resin layer-forming composition are in contact with each other, wherein the acid-unmodified polyolefin has a melt flow rate of 20 g / 10 min or more measured under conditions of 230°C and 2.16 kgf in accordance with JIS K7210-1:2014, and the polyamide resin contained in the polyamide resin layer-forming composition meets the JIS A method for producing a multilayer container, wherein the melt flow rate measured in accordance with JIS K7210-1:2014 at 250°C and 2.16 kgf is 5 g / 10 min or more, and the difference between the melt flow rate of the mixture of acid-unmodified polyolefin and acid-modified polyolefin contained in the polyolefin layer, measured in accordance with JIS K7210-1:2014 at 230°C and 2.16 kgf, and the melt flow rate of the polyamide resin contained in the polyamide resin layer is in the range of 10 to 53 g / 10 min. <10> The multilayer container is <1> ~ <8> The multilayer container according to any one of the above items. <9> A method for producing a multilayer container according to claim 1. [Effects of the Invention]

[0007] The present invention makes it possible to provide a multilayer container that has excellent adhesion between a polyolefin layer such as a PP layer and a polyamide resin layer that can serve as a gas barrier layer, and that also has excellent moldability (appearance of the polyolefin layer side), as well as a method for manufacturing the multilayer container. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is an example of a cross-sectional schematic diagram of the body of the multilayer container of this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. Note that the present embodiment is an example for explaining the present invention, and the present invention is not limited to only this embodiment. In this specification, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit. In this specification, various physical properties and characteristic values ​​are those at 23°C unless otherwise specified. If the standards shown in this specification differ depending on the year and the measurement method, etc., they will be based on the standards as of January 1, 2021, unless otherwise stated.

[0010] The multilayer container of the present embodiment comprises a polyolefin layer containing an acid-modified polyolefin and an acid-unmodified polyolefin, and a polyamide resin layer in contact with the polyolefin layer and containing a polyamide resin, wherein the polyamide resin contains a polyamide resin (a) containing diamine-derived structural units and dicarboxylic acid-derived structural units, in which 70 mol % or more of the diamine-derived structural units are derived from metaxylylenediamine and 30 mol % or more of the dicarboxylic acid-derived structural units are derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms, the acid-unmodified polyolefin having a melt flow rate of 20 g / 10 min or more measured at 230°C and 2.16 kgf in accordance with JIS K7210-1:2014, and the polyamide resin contained in the polyamide resin layer has a melt flow rate of 20 g / 10 min or more measured at 230°C and 2.16 kgf in accordance with JIS K7210-1:2014. The polyamide resin layer is characterized in that the melt flow rate measured in accordance with JIS K7210-1:2014 at 250°C and 2.16 kgf is 5 g / 10 min or more, and the difference between the melt flow rate of the mixture of acid-unmodified and acid-modified polyolefins contained in the polyolefin layer, measured in accordance with JIS K7210-1:2014 at 230°C and 2.16 kgf, and the melt flow rate of the polyamide resin contained in the polyamide resin layer is in the range of 10 to 53 g / 10 min. This configuration makes it possible to provide a multilayer container that has excellent adhesion between the polyolefin layer and the polyamide resin layer and excellent moldability (appearance of the polyolefin layer side). Furthermore, the multilayer container also has excellent compatibility between the acid-modified polyolefin and the acid-unmodified polyolefin contained in the polyolefin layer.

[0011] That is, by blending an acid-modified polyolefin with an unmodified polyolefin having an MFR of 20 g / 10 min or more in the polyolefin resin layer and adjusting the melt flow rate (MFR) of the polyolefin (mixture) contained in the polyolefin resin layer to a predetermined value, it is presumed that the acid-modified polyolefin is sufficiently dispersed in the unmodified polyolefin, making it easier for acid groups to be scattered throughout the polyolefin layer. It is presumed that the acid groups scattered throughout the polyolefin layer are then covalently bonded to the amino groups of the polyamide resin contained in the polyamide resin layer. Therefore, it is presumed that excellent adhesion between the polyolefin layer and the polyamide resin layer can be achieved without the need for an adhesive resin layer, as in the past. Furthermore, it is presumed that by sufficiently increasing the MFR of the unmodified polyolefin, sufficient fluidity is maintained even in the injection molding mold, resulting in a multilayer container with excellent appearance. Furthermore, when molding the multilayer container of this embodiment, if there is a difference in melt flow rate (MFR) between the polyolefin (blend) contained in the polyolefin layer and the polyamide resin contained in the polyamide resin layer, the polyamide resin layer in the multilayer container will be relatively thin, which may result in insufficient filling of the polyamide resin layer into the mold and poor appearance of the resulting molded product. In this embodiment, it is presumed that this problem can be solved by reducing the difference in MFR between the two. Furthermore, while polyamide resins with a fast crystallization rate are prone to variations in the thickness of the polyamide resin layer, this embodiment makes it possible to achieve an appropriate thickness even for polyamide resins with a fast crystallization rate. The details of this embodiment will be described below.

[0012] <Polyolefin layer> The polyolefin layer of this embodiment contains an acid-modified polyolefin and an acid-unmodified polyolefin. It is presumed that the acid-modified polyolefin enhances adhesion to the polyamide resin layer, and that even when the acid-unmodified polyolefin is injection molded, a molded product with excellent appearance can be obtained.

[0013] <<Unmodified acid polyolefin>> The acid-unmodified polyolefin used in this embodiment has a melt flow rate of 20 g / 10 min or more, measured in accordance with JIS K7210-1:2014 under conditions of 230°C and 2.16 kgf. Conventional multilayer containers manufactured by extrusion molding use polyolefins with an MFR of approximately 2 to 3 g / 10 min. In this embodiment, by setting the MFR of the polyolefin to 20 g / 10 min or more, the appearance of the resulting multilayer container can be improved even when molded by injection molding. The MFR of the acid-unmodified polyolefin is preferably 20 g / 10 min or more, more preferably 25 g / 10 min or more, even more preferably 30 g / 10 min or more, and even more preferably 35 g / 10 min or more. Furthermore, the MFR of the acid-unmodified polyolefin is preferably 50 g / 10 min or less, more preferably 48 g / 10 min or less. By setting the MFR within this range, thin-wall moldability tends to be improved.

[0014] In the present embodiment, the acid-unmodified polyolefin refers to a polyolefin having a sufficiently smaller number of acid groups than the acid-modified polyolefin, and specifically, the amount of acid groups is 15 mol % or less of the acid groups contained in the acid-modified polyolefin, preferably 10 mol % or less, more preferably 5 mol % or less, even more preferably 3 mol % or less, even more preferably 1 mol % or less, and even more preferably contains no acid groups. The acid-unmodified polyolefin in this embodiment preferably does not contain any polar groups other than acid groups.

[0015] The acid-unmodified polyolefin in this embodiment preferably contains polypropylene. The polypropylene in this embodiment includes a propylene homopolymer and a copolymer copolymerized with 5% by mass or less (preferably 3% by mass or less) of another olefin such as ethylene, and is preferably a propylene homopolymer.

[0016] The melting point of the acid-unmodified polyolefin is preferably 150°C or higher, more preferably 155°C or higher. By setting the melting point at or above the lower limit, moldability tends to be improved. Furthermore, the melting point of the acid-unmodified polyolefin is preferably 180°C or lower, more preferably 175°C or lower. By setting the melting point at or below the upper limit, moldability tends to be improved. In the present embodiment, when the polyolefin layer contains two or more kinds of acid-unmodified polyolefins, the melting point is the melting point of the acid-unmodified polyolefin with the largest content. The melting point is measured as described below.

[0017] The content of the acid-unmodified polyolefin (preferably acid-unmodified polypropylene) in the polyolefin layer is preferably 90% by mass or more, more preferably 93% by mass or more, and even more preferably 94% by mass or more, and the content of the acid-unmodified polyolefin in the polyolefin layer is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 96% by mass or less. The polyolefin layer may contain only one kind of acid-unmodified polyolefin, or may contain two or more kinds. When two or more kinds are contained, the total amount is preferably in the above range.

[0018] <<Acid-modified polyolefin>> The polyolefin resin layer in this embodiment contains an acid-modified polyolefin as well as an acid-unmodified polyolefin. It is believed that this configuration makes the acid-modified polyolefin more compatible with the acid-unmodified polyolefin. As a result, it is believed that the number of contact points between the acid-modified polyolefin and the polyamide resin layer in the polyolefin layer increases, increasing the proportion of covalent bonds between the acid groups of the acid-modified polyolefin and the amino groups of the polyamide resin (a), thereby improving adhesion.

[0019] The polyolefin constituting the acid-modified polyolefin in this embodiment preferably contains polypropylene. The polypropylene in this embodiment includes a propylene homopolymer and a copolymer copolymerized with 5% by mass or less (preferably 3% by mass or less) of another olefin such as ethylene, and is preferably a propylene homopolymer.

[0020] Examples of compounds capable of acid-modifying polyolefins include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, methyl maleic acid, methyl fumaric acid, mesaconic acid, citraconic acid, glutaconic acid, cis-4-cyclohexene-1,2-dicarboxylic acid, endobicyclo[2.2.1]-5-heptene-2,3-dicarboxylic acid, and metal salts of these carboxylic acids, monomethyl maleate, monomethyl itaconate, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, hydroxyethyl acrylate, and methyl methacrylate. Preferred examples include methyl methacrylate, 2-ethylhexyl methacrylate, hydroxyethyl methacrylate, aminoethyl methacrylate, dimethyl maleate, dimethyl itaconate, maleic anhydride, itaconic anhydride, citraconic anhydride, endobicyclo-[2.2.1]-5-heptene-2,3-dicarboxylic anhydride, maleimide, N-ethylmaleimide, N-butylmaleimide, N-phenylmaleimide, acrylamide, methacrylamide, glycidyl acrylate, glycidyl methacrylate, glycidyl ethacrylate, glycidyl itaconate, and glycidyl citraconate. These can be used alone or in combination of two or more. Among these, maleic anhydride is preferred.

[0021] In the present embodiment, the acid-modified polyolefin that is particularly preferably used is acid-modified polypropylene, and maleic anhydride-modified polypropylene is more preferred.

[0022] The content of acid-modified polyolefin (preferably acid-modified polypropylene, more preferably maleic anhydride-modified polypropylene) in the polyolefin layer is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 4% by mass or more, in the polyolefin layer. By making the content equal to or greater than the lower limit, adhesion to the barrier layer tends to be further improved. Furthermore, the content of acid-modified polyolefin in the polyolefin layer is preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 6% by mass or less, in the polyolefin layer. By making the content equal to or less than the upper limit, the barrier layer tends to separate more easily during recycling. The polyolefin layer may contain only one kind of acid-modified polyolefin, or may contain two or more kinds. When two or more kinds are contained, the total amount is preferably in the above range.

[0023] <<Acid-modified polyolefin and acid-unmodified polyolefin>> In this embodiment, the melt flow rate of the polyolefin (mixture) contained in the polyolefin layer is preferably 12 g / 10 min or more, more preferably 15 g / 10 min or more, even more preferably 20 g / 10 min or more, and even more preferably 30 g / 10 min or more. It may be more than 40 g / 10 min, or even 45 g / 10 min or more, and particularly 50 g / 10 min or more. By setting it to the above lower limit or above, moldability (appearance) tends to be further improved. The melt flow rate of the polyolefin contained in the polyolefin layer is also preferably 600 g / 10 min or less, more preferably 500 g / 10 min or less, and may further be 400 g / 10 min or less, 300 g / 10 min or less, 200 g / 10 min or less, 100 g / 10 min or less, 80 g / 10 min or less, or 60 g / 10 min or less. By setting it to the above upper limit or below, moldability (appearance) tends to be further improved. The "polyolefin contained in the polyolefin layer" means both acid-modified polyolefin and acid-unmodified polyolefin, and the melt flow rate of the polyolefin contained in the polyolefin layer is the melt flow rate of the polyolefin mixture.

[0024] The mass ratio of the acid-modified polyolefin to the acid-unmodified polyolefin in the polyolefin layer is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the acid-modified polyolefin. By setting the mass ratio at or above the lower limit, adhesion tends to be further improved. Furthermore, the mass ratio of the acid-modified polyolefin to the acid-unmodified polyolefin in the polyolefin layer is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, per 100 parts by mass of the acid-modified polyolefin. By setting the mass ratio at or below the upper limit, separation of the barrier material tends to be facilitated during recycling.

[0025] In this embodiment, the polyolefin content in the polyolefin layer (total content of acid-modified polyolefin and acid-unmodified polyolefin) is preferably 85% by mass or more of the entire polyolefin layer, more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 99% by mass or more. The upper limit of the polyolefin content in the polyolefin layer (total content of acid-modified polyolefin and acid-unmodified polyolefin) is 100% by mass or less.

[0026] <<Other Ingredients>> The polyolefin layer in this embodiment may contain components other than the acid-modified polyolefin and the acid-unmodified polyolefin, within the scope of the present invention. Examples of other components include thermoplastic resins other than polyolefins, plasticizers, antioxidants, heat stabilizers, UV absorbers, light stabilizers, lubricants, inorganic fillers, antistatic agents, flame retardants, crystallization accelerators, etc. The total content of these other components is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, and may be 1% by mass or less.

[0027] <Polyamide resin layer> The polyamide resin layer in this embodiment is in contact with the polyolefin layer and contains a polyamide resin (a), and further, the polyamide resin contained in the polyamide resin layer has a melt flow rate of 5 g / 10 min or more measured under conditions of 250°C and 2.16 kgf in accordance with JIS K7210-1:2014. In this embodiment, by using the above-mentioned polyolefin layer, unlike conventional multilayer containers having a polyolefin layer and a polyamide resin layer, the adhesion between the polyolefin layer and the polyamide resin layer can be ensured without providing an adhesive resin layer between the polyolefin layer and the polyamide resin layer. In addition, when the polyamide resin layer in this embodiment also contains polyamide resins other than polyamide resin (a), the MFR of the polyamide resin contained in the polyamide resin layer refers to the MFR of a mixture of polyamide resins also containing polyamide resins other than polyamide resin (a).

[0028] The MFR of the polyamide resin is preferably 6 g / 10 min or more, more preferably 7 g / 10 min or more, and even more preferably 8 g / 10 min or more. By setting it to the lower limit or more, moldability tends to be further improved. The MFR of the polyamide resin is preferably 50 g / 10 min or less, more preferably 40 g / 10 min or less, even more preferably 30 g / 10 min or less, and may even be 20 g / 10 min or less, or 15 g / 10 min or less. By setting it to the upper limit or less, moldability tends to be further improved.

[0029] <<Polyamide resin (a)>> The polyamide resin layer in this embodiment contains a polyamide resin (a) that contains diamine-derived structural units and dicarboxylic acid-derived structural units, in which 70 mol % or more of the diamine-derived structural units are derived from metaxylylenediamine and 30 mol % or more of the dicarboxylic acid-derived structural units are derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms. Such polyamide resin (a) has high oxygen barrier properties. Therefore, the polyamide resin layer functions as an oxygen barrier layer in the multilayer container of this embodiment. Furthermore, despite being significantly different in structure from polyolefin, polyamide resin (a) can maintain high adhesion to the polyolefin layer.

[0030] In the polyamide resin (a), 70 mol % or more, preferably 80 mol % or more, more preferably 90 mol % or more, even more preferably 95 mol % or more, and even more preferably 99 mol % or more of the diamine-derived structural units are derived from xylylenediamine. Preferred xylylenediamines are metaxylylenediamine and paraxylylenediamine, and more preferably metaxylylenediamine. An example of a preferred embodiment of the polyamide resin (a) in this embodiment is a polyamide resin in which 70 mol% or more (preferably 80 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more, and even more preferably 99 mol% or more) of the diamine-derived structural units are derived from metaxylylenediamine.

[0031] Examples of diamines other than xylylenediamine include aromatic diamines such as paraphenylenediamine, and aliphatic diamines such as 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, octamethylenediamine, nonamethylenediamine, etc. These other diamines may be used alone or in combination of two or more. When a diamine other than xylylenediamine is used as the diamine component, it is used in a proportion of 30 mol % or less, more preferably 1 to 25 mol %, and particularly preferably 5 to 20 mol % of the diamine-derived structural units.

[0032] In this embodiment, as described above, 30 mol % or more of the dicarboxylic acid-derived constitutional units in the polyamide resin (a) are derived from α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms.

[0033] The lower limit of the proportion of α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms (preferably α,ω-linear aliphatic dicarboxylic acids having 4 to 8 carbon atoms, more preferably adipic acid) among all dicarboxylic acids constituting the dicarboxylic acid-derived structural units in polyamide resin (a) is 30 mol% or more, preferably 33 mol% or more, more preferably 35 mol% or more, even more preferably 38 mol% or more, even more preferably 40 mol% or more, and may be 42 mol% or more, and may even be 50 mol% or more, 51 mol% or more, more than 55 mol%, more than 60 mol%, 70 mol% or more, 80 mol% or more, 90 mol% or more, 94 mol% or more, 98 mol% or more, or 99 mol% or more, depending on the application. The upper limit of the proportion of the α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms is 100 mol% or less, and may be 99 mol% or less, 80 mol% or less, 60 mol% or less, or 59 mol% or less, depending on the application. By setting the content within this range, the oxygen barrier properties of the multilayer container of this embodiment are further improved, and the transparency of the resulting multilayer container also tends to be further improved.

[0034] As described above, the α,ω-straight chain aliphatic dicarboxylic acid having 4 to 20 carbon atoms is preferably an α,ω-straight chain aliphatic dicarboxylic acid having 4 to 8 carbon atoms. Examples of α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms that are suitable for use as the raw dicarboxylic acid component of the polyamide resin include succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, adipic acid, sebacic acid, undecanedioic acid, and dodecanedioic acid. These can be used alone or in combination of two or more. Among these, adipic acid is preferred because the melting point of the polyamide resin (a) falls within a range suitable for molding and processing.

[0035] The polyamide resin (a) may also contain structural units derived from isophthalic acid in a proportion of 70 mol% or less of the structural units derived from dicarboxylic acids. When the polyamide resin (a) contains structural units derived from isophthalic acid, the proportion of the structural units derived from isophthalic acid is preferably 1 mol% or more, more preferably 5 mol% or more, even more preferably 20 mol% or more, even more preferably 40 mol% or more, and even more preferably 41 mol% or more, based on the total dicarboxylic acids constituting the structural units derived from dicarboxylic acids. The upper limit of the proportion of isophthalic acid is preferably 67 mol% or less, more preferably 65 mol% or less, even more preferably 62 mol% or less, even more preferably 60 mol% or less, and may be 58 mol% or less, or, depending on the application, 50 mol% or less, 49 mol% or less, 45 mol% or less, 40 mol% or less, less than 40 mol%, 30 mol% or less, 20 mol% or less, 10 mol% or less, 6 mol% or less, 2 mol% or less, or 1 mol% or less. By setting the content within this range, the oxygen barrier properties of the multilayer container of this embodiment tend to be further improved.

[0036] In the polyamide resin (a), among the dicarboxylic acid-derived structural units, the total proportion of isophthalic acid-derived structural units and structural units derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms is preferably 90 mol% or more, more preferably 95 mol% or more, even more preferably 98 mol% or more, and even more preferably 99 mol% or more. The upper limit of the total proportion of isophthalic acid-derived structural units and structural units derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms does not exceed 100 mol%. By setting the proportion in this range, the transparency of the multilayer body of this embodiment tends to be further improved.

[0037] Examples of dicarboxylic acids other than α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms and isophthalic acid include phthalic acid compounds such as terephthalic acid and orthophthalic acid, and naphthalenedicarboxylic acids such as 1,2-naphthalenedicarboxylic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 1,7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid, and these can be used alone or in combination of two or more. It is preferable that the polyamide resin (a) is substantially free of structural units derived from terephthalic acid. "Substantially free" means that the molar amount of isophthalic acid contained in the polyamide resin (a) is 5 mol % or less, preferably 3 mol % or less, more preferably 1 mol % or less, and even more preferably 0 mol %. By adopting such a constitution, appropriate molding processability is maintained, and the gas barrier property is less susceptible to changes due to humidity.

[0038] The polyamide resin (a) preferably has a terminal amino group concentration of 10 to 70 μeq / g. By adjusting the concentration to be equal to or greater than the lower limit, adhesion to acid-modified polyolefins can be further improved. The terminal amino group concentration is determined by adding 0.3 g of polyamide resin (a) to a mixed solvent of phenol / ethanol = 4 / 1 (volume ratio), stirring at 20 to 30°C until completely dissolved, rinsing the inner wall of the container with 5 mL of methanol while stirring, and neutralizing titrating with 0.01 mol / L aqueous hydrochloric acid solution to determine the terminal amino group concentration [NH2]. Furthermore, it is preferable that the terminal amino group concentration of the polyamide resin contained in the polyamide resin layer in this embodiment, that is, the mixture of polyamide resin (a) and other polyamide resins, satisfies the above range.

[0039] The polyamide resin (a) used in this embodiment contains dicarboxylic acid-derived structural units and diamine-derived structural units as its main components, but may also contain structural units other than the dicarboxylic acid-derived structural units and diamine-derived structural units, as well as other moieties such as terminal groups. Examples of other structural units include, but are not limited to, lactams such as ε-caprolactam, valerolactam, laurolactam, and undecalactam, and structural units derived from aminocarboxylic acids such as 11-aminoundecanoic acid and 12-aminododecanoic acid. Furthermore, the polyamide resin (a) used in this embodiment contains trace components such as additives used in the synthesis. The polyamide resin (a) used in this embodiment typically contains 95% by mass or more, preferably 98% by mass or more, of dicarboxylic acid-derived structural units or diamine-derived structural units.

[0040] The polyamide resin (a) used in this embodiment may be a crystalline resin or an amorphous resin. One embodiment of the polyamide resin (a) is a crystalline resin. Another embodiment of the polyamide resin (a) is an amorphous resin.

[0041] When the polyamide resin (a) is a crystalline resin, the melting point of the polyamide resin (a) is preferably 150°C or higher, more preferably 180°C or higher. By setting the melting point at or above the lower limit, moldability tends to be further improved. Furthermore, the melting point of the polyamide resin (a) is preferably 300°C or lower, more preferably 260°C or lower. By setting the melting point at or below the upper limit, moldability tends to be improved. In the present embodiment, when the polyamide resin layer contains two or more types of polyamide resin (a), the melting point is the melting point of the polyamide resin (a) that is contained in the largest amount. The melting point is measured as described below.

[0042] When the polyamide resin (a) is an amorphous resin, the glass transition temperature of the polyamide resin (a) is preferably 100° C. or higher, and more preferably 110° C. or higher. The glass transition temperature of the polyamide resin (a) is preferably 200° C. or lower, and more preferably 180° C. or lower. In the present embodiment, when the polyamide resin layer contains two or more types of polyamide resin (a), the glass transition temperature is the glass transition temperature of the polyamide resin (a) that is contained in the largest amount. The glass transition temperature is measured as described below.

[0043] In the polyamide resin layer of this embodiment, the content of polyamide resin (a) is preferably 85% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, still more preferably 98% by mass or more, and even more preferably 99% by mass or more, of the entire polyamide resin layer. The upper limit of the content of polyamide resin (a) in the polyamide resin layer is 100% by mass or less. The polyamide resin layer may contain only one type of polyamide resin (a), or may contain two or more types. When two or more types are contained, the total amount is preferably within the above range.

[0044] <<Other Ingredients>> The polyamide resin layer in this embodiment may contain components other than the polyamide resin (a) within the scope of the present invention. Other components may include thermoplastic resins other than polyamide resin (a), inorganic fillers such as glass fiber and carbon fiber; plate-like inorganic fillers such as glass flakes, talc, kaolin, mica, montmorillonite, and organic clay; impact modifiers such as various elastomers; crystal nucleating agents; lubricants such as fatty acid amides and fatty acid amide compounds; antioxidants such as copper compounds, organic or inorganic halogen compounds, hindered phenols, hindered amines, hydrazines, sulfur compounds, and phosphorus compounds; color inhibitors; ultraviolet absorbers such as benzotriazoles; additives such as release agents, plasticizers, colorants, and flame retardants; and additives such as oxidation reaction accelerators, recycling aids, and compounds containing benzoquinones, anthraquinones, and naphthoquinones. The total content of these other components is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and may even be 1% by mass or less. For the oxidation reaction accelerator, please refer to paragraphs 0034 to 0036 of WO 2019 / 058986, the contents of which are incorporated herein by reference.

[0045] The polyamide resin other than the polyamide resin (a) may be an aliphatic polyamide resin or a semi-aromatic polyamide resin, with an aliphatic polyamide resin being preferred. Examples of aliphatic polyamide resins include polyamide 6, polyamide 66, polyamide 10, polyamide 11, polyamide 12, polyamide 46, polyamide 610, polyamide 612, and polyamide 666, with polyamide 6 being preferred, and polyamide 6 being more preferred. Examples of semi-aromatic polyamide resins include 6T, 6T / 6I, 9T, and 9N (polycondensates of nonanediamine and naphthalenedicarboxylic acid). These polyamide resins other than the polyamide resin (a) may be used alone or in combination of two or more.

[0046] In this embodiment, the polyamide resin layer may or may not contain an alkali metal salt of a higher fatty acid. In this embodiment, the content of the alkali metal salt of a higher fatty acid contained in the polyamide resin layer is preferably less than 50 ppm by mass, more preferably less than 40 ppm by mass, and even more preferably less than 30 ppm by mass, calculated as alkali metal atoms. Reducing the alkali metal salt of a higher fatty acid in the polyamide resin layer has advantages such as improving the appearance of the resulting multilayer container. The alkali metal salt of a higher fatty acid is preferably a salt of a fatty acid having 12 to 30 carbon atoms. Fatty acids that form salts include saturated fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, and behenic acid. The alkali metal is preferably potassium or sodium.

[0047] <Difference between MFR of polyolefin contained in polyolefin layer and MFR of polyamide resin contained in polyamide resin layer> In this embodiment, the difference between the melt flow rate of the mixture of acid-unmodified polyolefin and acid-modified polyolefin contained in the polyolefin layer, measured in accordance with JIS K7210-1:2014 under conditions of 230°C and 2.16 kgf, and the melt flow rate of the polyamide resin contained in the polyamide resin layer, is in the range of 10 to 53 g / 10 min. By setting the melt flow rate at or above the lower limit, the thickness of the polyamide resin layer tends to become more uniform. The difference between the melt flow rate of the polyolefin contained in the polyolefin layer and the melt flow rate of the polyamide resin contained in the polyamide resin layer is preferably 20 g / 10 min or more, more preferably 30 g / 10 min or more, even more preferably 40 g / 10 min or more, and preferably 50 g / 10 min or less.

[0048] <Layer structure of multi-layer container> The multilayer container of this embodiment has a polyolefin layer and a polyamide resin layer in contact with the polyolefin layer. Typically, the polyolefin layer is on the outside. Furthermore, the multilayer container of this embodiment preferably has a three-layer structure of polyolefin layer / polyamide resin layer / polyolefin layer. Specifically, as illustrated in FIG. 1 , the cross section of the body of the multilayer container is, from outside, composed of polyolefin layer 1, polyamide resin layer 2, and polyolefin layer 3. Polyolefin layer 1 and polyamide resin layer 2 are in contact with each other in a plane perpendicular to the cross section of the body, and polyamide resin layer 2 and polyolefin layer 3 are also in contact with each other in a plane perpendicular to the cross section of the body. The thickness in FIG. 1 is not necessarily proportional to the actual thickness. It is preferable that the multilayer container of this embodiment also has a three-layer structure of polyolefin layer / polyamide resin layer / polyolefin layer in parts other than the body, such as the bottom, but this is not necessarily limited to this. In this case, the two polyolefin layers may be polyolefin layers of the same composition, or may be polyolefin layers of different compositions. However, it is preferable that each of the two polyolefin layers contains an acid-modified polyolefin and an acid-unmodified polyolefin, the unmodified polyolefin having an MFR of 20 g / 10 min or more, and the acid-modified polyolefin having an MFR greater than the MFR of the acid-unmodified polyolefin. Furthermore, the multilayer container of this embodiment may have a five-layer structure such as a polyolefin layer / polyamide resin layer / polyolefin layer / polyamide resin layer / polyolefin layer. In this case, it is sufficient that at least one polyamide resin layer is in contact with at least one adjacent polyolefin layer, but it is preferable that all polyamide resin layers are in contact with adjacent polyolefin layers. Furthermore, the multilayer container of this embodiment may have other layers as long as it has a polyolefin layer and a polyamide resin layer in contact with the polyolefin layer.

[0049] The thickness ratio of the polyolefin layer to the polyamide resin layer in the multilayer container of this embodiment is not particularly limited, but when the thickness of one polyolefin layer is taken as 100, the thickness of one polyamide resin layer is preferably 0.5 to 40, and more preferably 1 to 30. Furthermore, when the multilayer container of this embodiment has a layer structure of polyolefin layer / polyamide resin layer / polyolefin layer, the thickness of the polyamide resin layer is preferably 1 to 20, and more preferably 2 to 15, when the total thickness of the polyolefin layers is taken as 100. The thickness of each polyamide resin layer is preferably 10 μm or more, more preferably 20 μm or more, and is preferably 150 μm or less, more preferably 100 μm or less, and even more preferably 90 μm. The thickness of each polyolefin layer is preferably 0.2 mm or more, more preferably 0.3 mm or more, and is preferably 1.4 mm or less, more preferably 1.0 mm or less. The thickness of the multilayer container is preferably 0.4 mm or more, more preferably 0.7 mm or more, and is preferably 3 mm or less, more preferably 2 mm or less.

[0050] <Manufacturing method for multilayer containers> The multilayer container of this embodiment is preferably formed by injection molding. That is, the multilayer container of this embodiment is preferably a multilayer injection-molded container. Therefore, although welds originating from the mold are formed in the multilayer container of this embodiment, by using a desired polyolefin layer (polyolefin layer-forming composition) in this embodiment, the welds can be made smaller. More specifically, the method for producing a multilayer container of the present embodiment includes injecting a polyolefin layer-forming composition containing an acid-modified polyolefin and an acid-unmodified polyolefin, and a polyamide resin layer-forming composition containing a polyamide resin (a) that contains diamine-derived structural units and dicarboxylic acid-derived structural units, in which 70 mol % or more of the diamine-derived structural units are derived from meta-xylylenediamine and 30 mol % or more of the dicarboxylic acid-derived structural units are derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms, into a mold so that a polyolefin layer formed from the polyolefin layer-forming composition and a polyamide resin layer formed from the polyamide resin layer-forming composition are in contact with each other, thereby performing injection molding; and the acid-unmodified polyolefin has a melt flow rate of 20 g / 10 min or more measured at 230° C. and 2.16 kgf in accordance with JIS K7210-1:2014, and the polyamide resin contained in the polyamide resin layer-forming composition .... The melt flow rate measured in accordance with JIS K7210-1:2014 at 250°C and 2.16 kgf is 5 g / 10 min or more, and the difference between the melt flow rate of the mixture of acid-unmodified polyolefin and acid-modified polyolefin contained in the polyolefin layer measured in accordance with JIS K7210-1:2014 at 230°C and 2.16 kgf and the melt flow rate of the polyamide resin contained in the polyamide resin layer is in the range of 10 to 53 g / 10 min. In particular, it is preferable to perform injection so that the portion in contact with the mold is a polyolefin layer (for example, polyolefin layer / polyamide resin layer / polyolefin layer). The multilayer container is preferably the multilayer container of the present embodiment described above. Therefore, the preferred materials constituting the polyolefin layer-forming composition and their contents are the same as those described above for the polyolefin layer. Furthermore, the preferred materials constituting the polyamide resin layer-forming composition and their contents are the same as those described above for the polyamide resin layer.

[0051] Injection molding in the manufacturing method of this embodiment is, for example, a molding method in which a melt of a polyolefin layer-forming composition and a melt of a polyamide resin layer-forming composition are each injected and filled into a pre-closed mold, and solidified to form a multilayer container. Therefore, it is desirable that the melts of the polyolefin layer-forming composition and the polyamide resin layer-forming composition (particularly the melt of the polyolefin layer-forming composition) in the mold have high fluidity. In this embodiment, since a polyolefin with a high MFR is used as the polyolefin, molding is possible by injection molding (preferably co-injection molding). That is, excellent multilayer containers can be molded by injecting and filling the polyolefin layer-forming composition and the polyamide resin layer-forming composition into the mold almost simultaneously, rather than by two-color molding. Furthermore, unlike the biaxially stretched blow molding described below, the shape of the mold into which the melts of the polyolefin layer-forming composition and the polyamide resin layer-forming composition are initially filled directly determines the shape of the final product, so the fluidity of the melts is important. That is, the injection molding in this embodiment does not include biaxially stretched blow molding. Furthermore, the multilayer container of this embodiment is usually formed by injection molding, and therefore has welds. In contrast, in extrusion blow molding, in which the molding material is heated and melted and extruded into a cylindrical shape, sandwiched between molds, and air is blown into the interior to form a hollow article, the fluidity of the material is not as much of an issue as in injection molding. Furthermore, in biaxial stretch blow molding, in which only the body wall of a preform (semi-finished product) obtained by injection molding is reheated, a stretch rod is inserted into the interior of a blow mold, and high-pressure air is blown into the preform to form a hollow article, the fluidity of the material is also not as much of an issue as in injection molding. The multilayer container of this embodiment is suitable for production by injection molding, but this does not exclude multilayer containers formed by other molding methods including blow molding and biaxial stretch molding.

[0052] In addition, when performing co-injection molding, the polyamide resin layer-forming composition and the polyolefin layer-forming composition are co-injected, and preferably, the polyamide resin layer-forming composition is used as an intermediate layer, and the polyolefin layer-forming composition is molded so that it contacts both sides of the polyamide resin layer-forming composition (for example, polyolefin layer / polyamide resin layer / polyolefin layer). It is also possible to form an additional layer further outside the polyolefin layer. It is also possible to form an innermost layer separately.

[0053] The injection timing of the polyolefin layer-forming composition and the polyamide resin layer-forming composition can be adjusted appropriately depending on the shape of the desired multilayer container. For example, by first starting the injection of the polyolefin layer-forming composition, which is the outer layer, and then starting the injection of the polyamide resin layer-forming composition immediately thereafter (e.g., 0.1 to 0.5 seconds later), it is possible to prevent the polyamide resin layer from being exposed at the tip. The temperature during injection molding can be adjusted taking into account the melting point and softening point of the resin used. In this embodiment, the injection molding temperature can be, for example, 220 to 290°C.

[0054] <Application> The multilayer container of this embodiment can be preferably used as a container lid, a bottle, a cup, a tray, a tube, and the like. The multilayer container of this embodiment is preferably used for packaging and preserving medicines, foods (processed seafood products, processed livestock products, rice dishes, liquid foods), etc. For details thereof, please refer to paragraphs 0033 to 0035 of JP 2011-37199 A, the contents of which are incorporated herein by reference.

[0055] <Melting point and glass transition temperature> In this embodiment, the melting point and glass transition temperature of the resin are measured according to a DSC (differential scanning calorimetry) method. Specifically, the melting point is the temperature at the top of the endothermic peak observed during heating by DSC (differential scanning calorimetry).The glass transition temperature is the glass transition temperature measured by heating a sample once to melt it and eliminate the influence of its thermal history on crystallinity, and then heating it again. The measurement is performed using differential scanning calorimetry, with a sample weight of approximately 5 mg, nitrogen gas flowing at 50 mL / min, and a heating rate of 10°C / min. The melting point is determined from the temperature at the top of the endothermic peak observed when the sample is heated from room temperature to a temperature above the expected melting point. The molten resin is then rapidly cooled with dry ice and heated again at a rate of 10°C / min to a temperature above the melting point, and the glass transition temperature is determined. For differential scanning calorimetry, a "DSC-60" manufactured by SHIMADZU CORPORATION can be used. [Example]

[0056] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. If the measuring instruments used in the examples are difficult to obtain due to discontinuation or the like, measurements can be made using other instruments with equivalent performance. When measuring the MFR (melt flow rate), a melt indexer manufactured by Toyo Seiki Seisakusho, Ltd. was used.

[0057] 1.Raw materials PA1: Polyamide resin (MXD6) synthesized from metaxylylenediamine and adipic acid, manufactured by Mitsubishi Gas Chemical Company, Inc., product number: S6007. Terminal amino group concentration is within the range of 10-70 μeq / g. It does not contain alkali metal salts of higher fatty acids. It is a crystalline resin. The melt flow rate measured at 250°C and 2.16 kgf in accordance with JIS K7210-1:2014 is 10 g / 10 min.

[0058] PA2: This polyamide resin is synthesized from metaxylylenediamine, adipic acid, and isophthalic acid. The proportion of isophthalic acid in the dicarboxylic acid is 7 mol% (MXD6I(7)). The terminal amino group concentration is within the range of 10-70 μeq / g. It does not contain alkali metal salts of higher fatty acids. It is a crystalline resin. The melt flow rate measured in accordance with JIS K7210-1:2014 at 250 and 2.16 kgf is 8 g / 10 min.

[0059] PA3: This polyamide resin is synthesized from metaxylylenediamine, adipic acid, and isophthalic acid. The ratio of isophthalic acid to the dicarboxylic acid is 50 mol% (MXD6I(50)). The terminal amino group concentration is within the range of 10-70 μeq / g. It does not contain alkali metal salts of higher fatty acids. It is an amorphous resin. The melt flow rate measured in accordance with JIS K7210-1:2014 at 250 and 2.16 kgf is 9 g / 10 min.

[0060] PA4: Polyamide resin (MXD6) synthesized from metaxylylenediamine and adipic acid, manufactured by Mitsubishi Gas Chemical Company, Inc., S6121. Terminal amino group concentration is within the range of 10-70 μeq / g. It does not contain alkali metal salts of higher fatty acids. It is a crystalline resin. The melt flow rate measured in accordance with JIS K7210-1:2014 at 250°C and 2.16 kgf is 3 g / 10 min.

[0061] PP1: Acid-unmodified polypropylene, MFR 45g / 10min measured at 230℃ and 2.16kgf in accordance with JIS K7210-1:2014, manufactured by Japan Polypropylene Corporation, Novatec BX05FS

[0062] PP2: Acid-unmodified polypropylene, MFR 10g / 10min measured at 230℃ and 2.16kgf in accordance with JIS K7210-1:2014, manufactured by Japan Polypropylene Corporation, Novatec MA3H

[0063] Mah-PP1: Maleic anhydride-modified polypropylene, manufactured by DuPont, Bynel 50E803, could not be measured for MFR under the conditions of 230 °C and 2.16 kgf in accordance with JIS K7210-1:2014. The MFR measured under the conditions of 190 °C and 2.16 kgf in accordance with JIS K7210-1:2014 was 450 g / 10 min.

[0064] Mah-PP2: Maleic anhydride-modified polypropylene, MFR 5.7 g / 10 min measured under the conditions of 230 °C and 2.16 kgf in accordance with JIS K7210-1:2014, manufactured by Mitsui Chemicals, Inc., Admer QF551

[0065] <Synthesis example of PA2((MXD6I(7)))> Into a 50 L jacketed reactor equipped with a stirrer, a partial condenser, a cooler, a thermometer, a dropping funnel, and a nitrogen gas inlet tube, 14.8 kg of adipic acid, 1.3 kg of isophthalic acid, 13.9 g of sodium hypophosphite monohydrate, and 7.2 g of sodium acetate were charged, and after sufficient nitrogen replacement, the temperature was raised to 180 °C under a small amount of nitrogen flow, and after adipic acid was uniformly melted, while stirring the system, 14.9 kg of metaxylylenediamine was dropped therein over 110 minutes. During this period, the internal temperature was continuously raised to 245 °C. The water generated by polycondensation was removed out of the system through the partial condenser and the cooler. After the dropping of metaxylylenediamine was completed, the internal temperature was further raised to 260 °C, and after the reaction was continued for 1 hour, the polymer was taken out as a strand from the nozzle at the bottom of the reactor, and after water cooling, it was pelletized to obtain the polymer. Next, the polymer obtained by the above operation was put into a 250 L rotary tumbler equipped with a heating jacket, a nitrogen gas inlet tube, and a vacuum line, and while rotating, the pressure inside the system was reduced, and then the operation of returning to normal pressure with nitrogen having a purity of 99% by volume or more was performed three times. Thereafter, the temperature inside the system was raised to 140 °C under nitrogen flow. Next, the pressure inside the system was reduced, and the temperature was continuously raised to 200 °C, and after holding at 200 °C for 30 minutes, nitrogen was introduced to return the pressure inside the system to normal pressure, and then it was cooled to obtain a polyamide resin (MXD6I(7)). No alkali metal salt of higher fatty acid is formulated. Also, when an attempt was made to measure the melting point, it had a clear melting point and was a crystalline resin.

[0066] <Synthesis Example of PA3((MXD6I(50)))> Into a 50 L jacketed reaction vessel equipped with a stirrer, a partial condenser, a cooler, a thermometer, a dropping tank, and a nitrogen gas inlet pipe, 7.5 kg of adipic acid, 8.5 kg of isophthalic acid, 9.3 g of sodium hypophosphite monohydrate, and 4.8 g of sodium acetate were charged, thoroughly purged with nitrogen, and further heated to 180 °C under a small amount of nitrogen flow to uniformly melt the adipic acid and isophthalic acid. Then, while stirring the system, 13.9 kg of metaxylylenediamine was dropped therein over 170 minutes. During this time, the internal temperature was continuously raised to 265 °C. The water generated by polycondensation was removed outside the system through the partial condenser and the cooler. After the dropping of metaxylylenediamine was completed, the internal temperature was further raised to 270 °C, and after continuing the reaction for 10 minutes, the polymer was taken out as a strand from the nozzle at the bottom of the reaction vessel, water-cooled, and pelletized to obtain the polymer. Next, the polymer obtained by the above operation was put into a 250 L rotary tumbler equipped with a heating jacket, a nitrogen gas inlet pipe, and a vacuum line. While rotating, the pressure inside the system was reduced, and then the operation of returning to normal pressure with nitrogen having a purity of 99% by volume or more was performed three times. Then, the temperature inside the system was raised to 115 °C under nitrogen flow. Next, the pressure inside the system was reduced and held at 115 °C for 24 hours, then nitrogen was introduced to return the pressure inside the system to normal pressure, and then it was cooled to obtain a polyamide resin (MXD6I(50)). No alkali metal salt of higher fatty acid is formulated. Also, when an attempt was made to measure the melting point, it had no clear melting point and was an amorphous resin.

[0067] 2. Examples 1 to 3, Comparative Examples 1 to 5 <Preparation of Composition for Forming Polyolefin Layer> Pellets of acid-modified polyolefin (Mah-PP) and pellets of acid-unmodified polyolefin (PP) shown in Table 1 were dry-blended at a mass ratio of 5:95. After dry blending, the MFR of the mixture of the acid-unmodified polyolefin and the acid-modified polyolefin was measured under conditions of 230°C and 2.16 kgf in accordance with JIS K7210-1:2014.

[0068] <Manufacturing of multi-layer injection molded containers> The resin compositions (pellets) were co-injected almost simultaneously to form three layers, such that the inner layer was made of the polyamide resin composition (pellets) obtained above, and the two outer layers were made of the polyolefin layer-forming composition (pellets) obtained above (polyolefin resin layer / polyamide resin layer / polyolefin resin layer), to obtain an injection-molded multilayer structure. The detailed conditions were as follows: Equipment: Injection molding machine, Sumitomo Heavy Industries Machinery Co., Ltd., SE130DU-CI Screw diameter Polyamide resin composition: diameter 16 mm PP resin composition (resin composition containing unmodified PP and modified PP): diameter 32 mm Hot runner: Kortec ·Temperature conditions Polyamide resin composition: Zone 1 = 230°C to 250°C, Zones 2 to 4 = 240°C to 280°C, Zone 5 = 250°C to 280°C PP resin composition: Zone 1 = 230°C, Zones 2 to 4 = 240°C to 250°C, Zone 5 = 250°C Hot runner temperature: 240℃~270℃ Mold temperature: 15℃ The obtained multilayer injection-molded container had a polyamide resin layer thickness of 80 μm and a total thickness of the polyolefin layers of 800 μm (each polyolefin layer thickness was 400 μm).

[0069] <Adhesive strength> The resulting multilayer container was filled with water and heat-sealed with aluminum, and then dropped 10 times from a height of 1 m with the same side facing downwards. The cup was then visually inspected and evaluated according to the following criteria. 3: No delamination was observed. 2: Some delamination was observed. 1: Significant delamination was observed.

[0070] <Compatibilization> The center of the side of the obtained multilayer container was cut into 4-5 cm squares, embedded in epoxy resin, and left overnight. The cross section of the resin-embedded multilayer container was trimmed with a glass knife, and then ultrathin sections of 100 nm were prepared using an ultramicrotome (Leica Microsystems) and a diamond knife. STEM transmission electron images of the obtained ultrathin cross sections of the multilayer container were observed under the following measurement conditions to confirm the presence or absence of compatibilization. Equipment: Carl Zeiss Gemini 500 Accelerating voltage: 30 kV, aperture: 20 mm WD: approx. 2.2 mm, detection signal: transmission electron image 2: In unmodified polypropylene and acid-modified polypropylene, no sea-island structure was observed by STEM transmission electron image observation. 1: The sea-island structure was observed in unmodified polypropylene and acid-modified polypropylene by STEM transmission electron image observation.

[0071] <Moldability (appearance)> The amount of welds and streaks in the obtained multilayer containers was compared with that of Comparative Example 4, which was set as 1. Evaluation was carried out by five experts and a majority vote was used. 3: No or almost no welds or streaks 2: Slight welds and / or streaks are visible 1: Welds and / or streaks are visible

[0072] [Table 1]

[0073] In Table 1 above, the unit of melt flow rate (MFR) is g / 10 min. In Table 1 above, ΔMFR[PP-PA] is the difference in MFR between the mixed polyolefin contained in the polyolefin layer and the polyamide resin contained in the polyamide resin layer. As is clear from the above results, the multilayer containers of the present invention had high adhesive strength between the polyamide resin layer and the polyolefin layer and also had excellent appearance (Examples 1 to 3). On the other hand, when the thickness was outside the range of the present invention (Comparative Examples 1 to 5), the resulting multilayer containers had poor moldability. In particular, when ΔMFR[PP-PA] was 40 g / 10 min or more, a significantly excellent effect was achieved. [Explanation of symbols]

[0074] 1 polyolefin layer 2 Polyamide resin layer 3 polyolefin layers

Claims

1. a polyolefin layer containing an acid-modified polyolefin and an acid-unmodified polyolefin; a polyamide resin layer that is in contact with the polyolefin layer and contains a polyamide resin, the polyamide resin comprises a polyamide resin (a) containing diamine-derived structural units and dicarboxylic acid-derived structural units, in which 70 mol % or more of the diamine-derived structural units are derived from metaxylylenediamine, and 30 mol % or more of the dicarboxylic acid-derived structural units are derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms; The acid-unmodified polyolefin has a melt flow rate of 20 g / 10 min or more, as measured in accordance with JIS K7210-1:2014 under conditions of 230°C and 2.16 kgf; The polyamide resin contained in the polyamide resin layer has a melt flow rate of 5 g / 10 min or more, measured in accordance with JIS K7210-1:2014 under conditions of 250 ° C. and 2.16 kgf, and a difference between a melt flow rate of the mixture of acid-unmodified polyolefin and acid-modified polyolefin contained in the polyolefin layer, measured in accordance with JIS K7210-1:2014 under conditions of 230°C and 2.16 kgf, and a melt flow rate of the polyamide resin contained in the polyamide resin layer, is in the range of 10 to 53 g / 10 min; Multilayer container.

2. 2. The multilayer container according to claim 1, wherein the content of the alkali metal salt of a higher fatty acid contained in the polyamide resin layer is less than 50 ppm by mass in terms of alkali metal atoms.

3. The multilayer container according to claim 1 or 2, wherein the acid-modified polyolefin comprises acid-modified polypropylene.

4. The multilayer container according to any one of claims 1 to 3, wherein the mass ratio of the acid-modified polyolefin to the acid-unmodified polyolefin in the polyolefin layer is 1 to 10 parts by mass of the acid-unmodified polyolefin per 100 parts by mass of the acid-modified polyolefin.

5. The multilayer container according to any one of claims 1 to 4, wherein the acid-unmodified polyolefin comprises polypropylene.

6. The multilayer container according to any one of claims 1 to 5, wherein the difference between the melt flow rate of the mixture of acid-unmodified polyolefin and acid-modified polyolefin contained in the polyolefin layer, measured in accordance with JIS K7210-1:2014 under conditions of 230°C and 2.16 kgf, and the melt flow rate of the polyamide resin contained in the polyamide resin layer, is in the range of 40 to 50 g / 10 min.

7. 7. The multilayer container according to claim 1, wherein the polyamide resin has a terminal amino group concentration of 10 to 70 μeq / g.

8. The multilayer container according to any one of claims 1 to 7, which is a multilayer injection-molded container.

9. a polyolefin layer-forming composition containing an acid-modified polyolefin and an acid-unmodified polyolefin; a polyamide resin layer-forming composition containing a polyamide resin (a) that contains diamine-derived structural units and dicarboxylic acid-derived structural units, wherein 70 mol % or more of the diamine-derived structural units are derived from metaxylylenediamine and 30 mol % or more of the dicarboxylic acid-derived structural units are derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms; and injecting the composition into a mold so that a polyolefin layer formed from the polyolefin layer-forming composition and a polyamide resin layer formed from the polyamide resin layer-forming composition are in contact with each other, thereby performing injection molding. The acid-unmodified polyolefin has a melt flow rate of 20 g / 10 min or more, as measured in accordance with JIS K7210-1:2014 under conditions of 230°C and 2.16 kgf; The polyamide resin contained in the composition for forming a polyamide resin layer has a melt flow rate of 5 g / 10 min or more, measured under conditions of 250 ° C. and 2.16 kgf in accordance with JIS K7210-1:2014, and a difference between a melt flow rate of the mixture of acid-unmodified polyolefin and acid-modified polyolefin contained in the polyolefin layer, measured in accordance with JIS K7210-1:2014 under conditions of 230°C and 2.16 kgf, and a melt flow rate of the polyamide resin contained in the polyamide resin layer, is in the range of 10 to 53 g / 10 min; Method for manufacturing multilayer containers.

10. The method for producing a multilayer container according to claim 9, wherein the multilayer container is the multilayer container according to any one of claims 1 to 8.

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