Multilayer container and method for manufacturing the same

Abstract

To provide a multilayer container which has high transparency after boil treatment and retort treatment, is also excellent in oxygen barrier property after retort treatment, and is excellent in moldability, and a method for manufacturing the same.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, 30-60 mol% of the dicarboxylic acid-derived structural unit is derived from an α,ω-straight-chain aliphatic dicarboxylic acid having 4 to 20 carbon atoms, and 70-40 mol% thereof is derived from an isophthalic acid, an MFR of the acid-unmodified polyolefin is 20 g / 10 min or more, and an MFR of the acid-modified polyolefin is larger than the MFR of the acid-unmodified polyolefin.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. As a method for enabling the long-term storage of foods and medicines in a PP container, a method using a multilayer container having an oxygen-barrier thermoplastic resin layer as an intermediate layer is known. Specifically, the multilayer structure is a coinjection-molded multilayer structure having a barrier layer and outer layers laminated on both sides of the barrier layer, the barrier layer being made of a resin composition containing an ethylene-vinyl alcohol copolymer (A) and an alkali metal salt (B) of a higher fatty acid having a melting point of 250°C or less, the ethylene content of the ethylene-vinyl alcohol copolymer (A) being 20 to 60 mol%, the degree of saponification being 90% or more, and the melt flow rate (MFR) at 190°C and 2160 g being 3 to 20 g / 10 min, A coinjection-molded multilayer structure is known, in which the content of alkali metal salt (B) in the barrier layer is 50 to 1500 ppm in terms of metal atoms, and the outer layer is made of a resin composition containing unmodified polypropylene (E) and maleic anhydride-modified polypropylene (F) having a lower melt viscosity than unmodified polypropylene (E), and the mass ratio of the maleic anhydride-modified polypropylene (F) to the total of the unmodified polypropylene (E) and the maleic anhydride-modified polypropylene (F), [F / (E+F)], is 0.025 to 0.2 (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 074445 Summary of the Invention [Problem to be solved by the invention]

[0005] However, it has been found that the transparency of the above-mentioned multilayer containers deteriorates after boiling or retorting. Furthermore, the multilayer containers are also required to have oxygen barrier properties after retorting. It has also been found that the moldability (appearance) of the multilayer containers may be poor. The present invention aims to solve these problems and to provide a multilayer container that has high transparency after boiling treatment or retort treatment, excellent oxygen barrier properties after retort treatment, and excellent formability, as well as a method for manufacturing the same. [Means for solving the problem]

[0006] In light of the above-mentioned problems, the present inventors have conducted studies and have found that the above-mentioned problems can be solved by using a predetermined polyamide resin as a barrier resin and blending an acid-modified polyolefin having a predetermined MFR with an acid-unmodified polyolefin in the polyolefin layer. Specifically, the above problems were solved by the following means. <1> a polyamide resin layer in contact with the polyolefin layer and containing a polyamide resin, the polyamide resin containing 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, 30 to 60 mol % of the dicarboxylic acid-derived structural units are derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms, and 70 to 40 mol % of the dicarboxylic acid-derived structural units are derived from isophthalic acid; and the acid-unmodified polyolefin is heated to a temperature X PO The melt flow rate measured under the conditions of temperature X and 2.16 kgf is 20 g / 10 min or more, PO is a multi-layer container having a melting point of acid-unmodified polyolefin of +65°C. <2> According to JIS K7210-1:2014, the temperature X mPO the melt flow rate measured at the temperature X°C and 2.16 kgf is greater than the melt flow rate of the unmodified polyolefin; mPO is the melting point of the acid-modified polyolefin + 55°C. <1> The multilayer container according to claim 1. <3> 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> or <2> The multilayer container according to claim 1. <4> The acid-modified polyolefin includes acid-modified polypropylene. <1> ~ <3> 10. The multilayer container according to claim 9, wherein the multilayer container is a multilayer container. <5> The melt flow rate of the acid-modified polyolefin is more than 20 g / 10 min and not more than 500 g / 10 min. <1> ~ <4> 10. The multilayer container according to claim 9, wherein the multilayer container is a multilayer container. <6> The acid-unmodified polyolefin comprises polypropylene. <1> ~ <5> 10. The multilayer container according to claim 9, wherein the multilayer container is a multilayer container. <7> The melt flow rate of the acid-unmodified polyolefin is 20 to 50 g / 10 min. <1> ~ <6> 10. The multilayer container according to claim 9, wherein the multilayer container is a multilayer container. <8> The polyamide resin has a terminal amino group concentration of 10 to 70 μeq / g. <1> ~ <7> 10. The multilayer container according to claim 9, wherein the multilayer container is a multilayer container. <9> The multilayer container is a multilayer injection molded container. <1> ~ <8> 10. The multilayer container according to claim 9, wherein the multilayer container is a multilayer container. <10> The haze of the multilayer container measured in accordance with JIS K-7105 is 10% or less. <1> ~ <9> 10. The multilayer container according to claim 9, wherein the multilayer container is a multilayer container. <11> The haze measured in accordance with JIS K-7105 after boiling at 85°C for 30 minutes is not more than twice the haze before the boiling treatment. <1> ~ <10> 10. The multilayer container according to claim 9, wherein the multilayer container is a multilayer container. <12> The polyamide resin (a) is an amorphous resin. <1> ~ <11> 10. The multilayer container according to claim 9, wherein the multilayer container is a multilayer container. <13> The acid-modified polyolefin and the acid-unmodified polyolefin are contained, and the acid-unmodified polyolefin is subjected to a temperature X POThe method includes injection molding a polyolefin layer formed from the polyolefin layer-forming composition and a polyamide resin layer-forming composition having a melt flow rate of 20 g / 10 min or more measured under conditions of 1000 °C and 2.16 kgf, and a polyamide resin layer-forming composition containing 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, 30 to 60 mol % of the dicarboxylic acid-derived structural units are derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms, and 70 to 40 mol % are derived from isophthalic acid, 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, PO is a method for manufacturing a multilayer container in which the melting point of the acid-unmodified polyolefin is +65°C. <14> According to JIS K7210-1:2014, the temperature X mPO the melt flow rate measured at the temperature X°C and 2.16 kgf is greater than the melt flow rate of the unmodified polyolefin; mPO is the melting point of the acid-modified polyolefin + 55°C. <13> A method for producing a multilayer container according to claim 1. <15> The multilayer container is <1> ~ <12> The multilayer container according to any one of the above items. <13> or <14> 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 high transparency after boiling or retort treatment, excellent oxygen barrier properties after retort treatment, and excellent moldability, as well as a method for producing the same. [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, 2022, 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 diamine-derived structural units and dicarboxylic acid-derived structural units, 70 mol % or more of the diamine-derived structural units being derived from metaxylylenediamine, 30 to 60 mol % of the dicarboxylic acid-derived structural units being derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms, and 70 to 40 mol % being derived from isophthalic acid, and the acid-unmodified polyolefin is heated to a temperature of 1000°C or higher in accordance with JIS K7210-1:2014. PO The melt flow rate measured under the conditions of temperature X and 2.16 kgf is 20 g / 10 min or more, PO is characterized by a melting point of the acid-unmodified polyolefin of 65°C. By adopting such a configuration, a multilayer container (transparent multilayer container) can be obtained that has high transparency after boiling treatment or retort treatment and also has excellent oxygen barrier properties after retort treatment. Furthermore, a multilayer container that can be molded by injection molding can be obtained, and in particular, a multilayer container that is almost free of weld lines and streaks can be obtained. It is also possible to produce a multilayer container having excellent adhesion between the polyolefin layer and the polyamide resin layer. The details of this embodiment will be described below.

[0011] <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, thereby improving the appearance even when the acid-unmodified polyolefin is injection molded.

[0012] <<Unmodified acid polyolefin>> The acid-unmodified polyolefin used in this embodiment is a polyolefin having a temperature of X PO The melt flow rate measured under the conditions of 20 g / 10 min or more at temperature X ° C. and 2.16 kgf. PO is the melting point of the acid-unmodified polyolefin + 65°C, and the melting point is a value measured by DSC, specifically by the method described in the Examples below. 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, and even more preferably 30 g / 10 min or more. Furthermore, the MFR of the acid-unmodified polyolefin is preferably 50 g / 10 min or less, and more preferably 48 g / 10 min or less. Setting the MFR within this range tends to improve thin-wall moldability.

[0013] 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.

[0014] 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.

[0015] 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 170°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 in the Examples below.

[0016] The content of 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. 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.

[0017] <<Acid-modified polyolefin>> The acid-modified polyolefin used in this embodiment is not particularly limited in type, etc., but is preferably denatured at a temperature of X mPO It is preferable that the MFR measured under the conditions of °C and 2.16 kgf is larger than the MFR of the acid-unmodified polyolefin. It is presumed that such a configuration makes the acid-modified polyolefin more compatible with the acid-unmodified polyolefin. As a result, it is presumed that the number of contact points between the acid-modified polyolefin and the polyamide resin layer in the polyolefin layer increases, the proportion of covalent bonds between the acid groups of the acid-modified polyolefin and the amino groups of the polyamide resin (a) increases, and the adhesiveness is further improved. mPO is the melting point of the acid-modified polyolefin + 55°C, and the melting point is a value measured according to DSC, specifically by the method described in the Examples below. According to JIS K7210-1:2014, the temperature X mPO The MFR measured under conditions of ° C. and 2.16 kgf is preferably more than 20 g / 10 min, more preferably 30 g / 10 min or more, even more preferably 50 g / 10 min or more, even more preferably 100 g / 10 min or more, even more preferably 200 g / 10 min or more, even more preferably 300 g / 10 min or more, and particularly preferably 400 g / 10 min or more. By setting the MFR at or above the lower limit, compatibility with acid-unmodified polyolefins tends to be further improved. Furthermore, the MFR of the acid-modified polyolefin is preferably 500 g / 10 min or less. By setting the MFR at or below the upper limit, the overall fluidity does not become too high, and moldability tends to be good.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] The melting point of the acid-modified polyolefin is preferably 150°C or higher, more preferably 60°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-modified polyolefin is preferably 180°C or lower, more preferably 170°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-modified polyolefins, the melting point is the melting point of the acid-unmodified polyolefin that is contained in the greatest amount. The melting point is measured as described in the Examples below.

[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>> Next, the relationship between acid-modified polyolefins and acid-unmodified polyolefins will be described. In this embodiment, the difference in MFR between the a-fins (MFR of acid-modified polyolefin - MFR of acid-unmodified polyolefin) is preferably 1 g / 10 min or more, more preferably 10 g / 10 min or more, even more preferably 50 g / 10 min or more, even more preferably 100 g / 10 min or more, and even more preferably 200 g / 10 min or more. By making the difference equal to or greater than the lower limit, the acid-modified polyolefin becomes more compatible with the acid-unmodified polyolefin, and the adhesion between the polyolefin layer and the polyamide resin layer tends to be improved. Furthermore, the difference in MFR between the acid-modified polyolefin and the acid-unmodified polyolefin in the polyolefin layer is preferably, for example, 450 g / 10 min or less.

[0024] Furthermore, the ratio of the MFR of the acid-modified polyolefin to the MFR of the acid-unmodified polyolefin in the polyolefin layer (ratio of MFR of acid-modified polyolefin / MFR of acid-unmodified polyolefin) is preferably greater than 1, more preferably 2 or more, even more preferably 5 or more, still more preferably 7 or more, and even more preferably 9 or more. By making the ratio equal to or greater than the lower limit, adhesion tends to be further improved. Furthermore, the ratio of MFR of the acid-modified polyolefin / MFR of the acid-unmodified polyolefin is preferably 50 or less, more preferably 20 or less, even more preferably 18 or less, still more preferably 15 or less, and even more preferably 13 or less. By making the ratio equal to or less than the upper limit, moldability tends to be improved.

[0025] 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.

[0026] 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.

[0027] <<Other Ingredients>> The polyolefin layer in this embodiment may contain components other than the acid-modified polyolefin and the acid-unmodified polyolefin, without departing from the spirit 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.

[0028] <Polyamide resin layer> The polyamide resin layer in this embodiment is in contact with the polyolefin layer and contains a polyamide resin (a). In this embodiment, by using the above-mentioned polyolefin layer, unlike conventional multilayer containers having a polyolefin layer and a polyamide resin layer, 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, and further, high transparency can be maintained even after boiling treatment and retort treatment.

[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, 30 to 60 mol % of the dicarboxylic acid-derived structural units are derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms, and 70 to 40 mol % are derived from isophthalic acid. 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. In addition, such polyamide resin (a) has high transparency. In particular, since it has excellent transparency after heat treatment, it can be preferably used for containers that are retorted or boiled. Furthermore, although polyamide resin (a) is significantly different from polyolefin in structure, etc., it can maintain high adhesion with 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 to 60 mol % of the dicarboxylic acid-derived structural units in the polyamide resin (a) are derived from α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms, and 70 to 40 mol % are derived from isophthalic acid.

[0033] Of all the dicarboxylic acids constituting the dicarboxylic acid-derived structural units in the polyamide resin (a), the lower limit for 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) is 30 mol% or more, preferably 33 mol% or more, more preferably 35 mol% or more, even more preferably 38 mol% or more, still more preferably 40 mol% or more, and may even be 45 mol% or more. The upper limit for the proportion of the α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms is 60 mol% or less, preferably 55 mol% or less. By setting the proportion 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 polyamide resins 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 it ensures that the melting point of the polyamide resin falls within a range suitable for molding and processing. Of all dicarboxylic acids constituting the dicarboxylic acid-derived structural units in polyamide resin (a), the lower limit of the proportion of isophthalic acid is 40 mol% or more, preferably 45 mol% or more. The upper limit of the proportion of isophthalic acid is 70 mol% or less, 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 55 mol% or less. By setting the proportion within this range, the oxygen barrier properties of the multilayer container of this embodiment tend to be further improved.

[0035] 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.

[0036] Examples of dicarboxylic acids other than isophthalic acid and α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms 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. 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.

[0037] 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.

[0038] 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.

[0039] The polyamide resin (a) used in this embodiment is preferably an amorphous resin. By using an amorphous resin, the polyamide resin (a) is less likely to whiten even when subjected to boiling treatment or retort treatment, and high transparency can be maintained. The amorphous resin refers to a resin that does not have a clear melting point. The melting point is the melting point measured according to the description in paragraph 0036 of WO 2017 / 090556.

[0040] 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.

[0041] <<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.

[0042] 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.

[0043] 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.

[0044] <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 preferred that each of the two polyolefin layers contains an acid-modified polyolefin and an acid-unmodified polyolefin, and that the MFR of the unmodified polyolefin is 20 g / 10 min or more.Furthermore, it is preferred that each of the two polyolefin layers contains an acid-modified polyolefin and an acid-unmodified polyolefin, and that the MFR of the acid-modified polyolefin is 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.

[0045] 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.

[0046] The multilayer container of this embodiment preferably has high transparency even after boiling. Specifically, the haze measured according to JIS K-7105 after boiling at 85°C for 30 minutes is preferably no more than twice the haze before boiling, more preferably no more than 1.5 times, and even more preferably no more than 1.2 times. The ideal lower limit is 1.0 times, but in cases where the transparency after boiling is superior (e.g., 0.8 times or more), it is also preferably used. Furthermore, the initial haze of the multilayer container of this embodiment (haze after molding without boiling or retort treatment), measured in accordance with JIS K-7105, is preferably 10% or less, more preferably 5% or less, and even more preferably 3% or less. Ideally, the lower limit of the haze is 0%, but even if it is 0.1% or more, the performance requirements are sufficiently met.

[0047] <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 the step of: subjecting an acid-modified polyolefin and an acid-unmodified polyolefin to a temperature of X PO The method includes injection molding a polyolefin layer formed from the polyolefin layer-forming composition and a polyamide resin layer-forming composition having a melt flow rate of 20 g / 10 min or more measured under conditions of 1000 °C and 2.16 kgf, and a polyamide resin layer-forming composition containing 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, 30 to 60 mol % of the dicarboxylic acid-derived structural units are derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms, and 70 to 40 mol % are derived from isophthalic acid, 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, PO is preferably the melting point of the acid-unmodified polyolefin + 65° C. In particular, it is preferable to inject the resin so that the portion in contact with the mold becomes a polyolefin layer (for example, a polyolefin layer / polyamide resin layer / polyolefin layer). The multilayer container is preferably the multilayer container of the present embodiment described above. That is, the multilayer container is a container that has been subjected to a temperature X mPO the melt flow rate measured at the temperature X°C and 2.16 kgf is greater than the melt flow rate of the unmodified polyolefin; mPOis preferably the melting point of the acid-modified polyolefin + 55°C. Furthermore, 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.

[0048] 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.

[0049] 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.

[0050] 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, 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.

[0051] <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. In particular, the transparent container is preferably used as a container for retort foods or foods to be boiled. [Example]

[0052] 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.

[0053] 1. Raw materials MXD6I: Amorphous polyamide resin synthesized from metaxylylenediamine, adipic acid, and isophthalic acid. The proportion of isophthalic acid in the dicarboxylic acid is 50 mol%. The terminal amino group concentration is in the range of 10-70 μeq / g. EVOH: Soarnol DC3212B, ethylene-vinyl alcohol copolymer, manufactured by Mitsubishi Chemical Corporation. Crystalline resin.

[0054] PP1: Acid-unmodified polypropylene, temperature X according to JIS K7210-1:2014 PO MFR 45g / 10min measured under the conditions of °C = melting point + 65°C, 2.16kgf, Novatec BX05FS manufactured by Japan Polypropylene Corporation

[0055] PP2: Acid-unmodified polypropylene, temperature X according to JIS K7210-1:2014 PO MFR 10g / 10min measured under conditions of °C = melting point + 65°C, 2.16kgf, Novatec MA3H, manufactured by Japan Polypropylene Corporation

[0056] Mah-PP1: Maleic anhydride modified polypropylene, temperature X according to JIS K7210-1:2014 mPOMeasured at a temperature of ℃ = melting point + 55℃ and a load of 2.16 kgf, MFR is 450 g / 10 min, manufactured by DuPont, Bynel 50E803

[0057] Mah-PP2: Maleic anhydride modified polypropylene, manufactured by Mitsui Chemicals, Inc., Admer QF551 In accordance with JIS K7210-1:2014, at temperature X mPO At a temperature of ℃ = melting point + 55℃, the MVR was too low to be measured. In accordance with JIS K7210-1:2014, at temperature X mPO Measured at a temperature of ℃ = melting point + 95℃ and a load of 2.16 kgf, MFR was 5.7 g / 10 min.

[0058] <Melting point and glass transition temperature> The melting point and glass transition temperature of the resin were measured according to the DSC (Differential Scanning Calorimetry) method. Specifically, the melting point is the temperature at the peak top of the endothermic peak observed during the heating process by the DSC (Differential Scanning Calorimetry) method. The glass transition temperature refers to the glass transition temperature measured after heating and melting the sample once to eliminate the influence of the heat history on crystallinity and then heating it again. For the measurement, differential scanning calorimetry was used. The sample amount was about 5 mg. As the ambient gas, nitrogen was flowed at 30 ml / min. The melting point was determined from the temperature at the peak top of the endothermic peak observed when heating from room temperature to a temperature above the expected melting point at a heating rate of 10℃ / min until melting. Then, the melted resin was quenched with dry ice and heated again to a temperature above the melting point at a rate of 10℃ / min to determine the glass transition temperature. For differential scanning calorimetry, "DSC-60" manufactured by SHIMADZU CORPORATION was used.

[0059] <Synthesis example of MXD6I> A 50-L jacketed reactor equipped with a stirrer, partial condenser, condenser, thermometer, dropping tank, and nitrogen gas inlet tube was charged with 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. The reactor was thoroughly purged with nitrogen and heated to 180°C under a small nitrogen stream until the adipic acid and isophthalic acid were homogeneously melted. Then, 13.9 kg of meta-xylylenediamine was added dropwise over 170 minutes while stirring. During this time, the internal temperature was continuously raised to 265°C. Water produced by polycondensation was removed from the system via the partial condenser and condenser. After the dropwise addition of meta-xylylenediamine, the internal temperature was further raised to 270°C. The reaction was continued for 10 minutes, after which the polymer was removed as strands from a nozzle at the bottom of the reactor, cooled with water, and pelletized to obtain the polymer. The polymer obtained by the above procedure was then placed in a 250 L rotary tumbler equipped with a heating jacket, a nitrogen gas inlet tube, and a vacuum line. The system was then reduced in pressure while rotating, and then returned to normal pressure with nitrogen of 99% or higher by volume. This procedure was repeated three times. The system was then heated to 115°C under a nitrogen flow. The system was then reduced in pressure and held at 115°C for 24 hours. Nitrogen was then introduced to return the system to normal pressure, and the system was then cooled to obtain polyamide resin (MXD6I). No alkali metal salt of a higher fatty acid was blended. Furthermore, when an attempt was made to measure the melting point according to the description in paragraph 0036 of WO 2017 / 090556, it was found that the resin did not have a clear melting point and was an amorphous resin.

[0060] 2. Examples 1 and 2, Comparative Examples 1 to 4 <Preparation of Polyolefin Layer-Forming Composition> Pellets of the acid-modified polyolefin (Mah-PP) and pellets of the acid-unmodified polyolefin (PP) shown in Table 1 were dry blended at a mass ratio of 5:95.

[0061] <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 Resin composition for forming polyolefin layer (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 Resin composition for forming polyolefin layer: 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).

[0062] <HAZE(ヘイズ)> The polyamide resin layer was separated from the obtained multilayer injection-molded container (immediately after molding), and the haze was measured. The haze was measured in accordance with JIS K-7105. The smaller the haze value (unit: %), the higher the transparency. The measurement device used was a color / turbidity measuring instrument (product name: COH-400A, manufactured by Nippon Denshoku Industries Co., Ltd.). Furthermore, the haze of the multilayer containers subjected to the boiling treatment described below and the multilayer containers subjected to the retort treatment described below was measured in the same manner as above. <<Boiling process>> Processing equipment: Tomy Seiko SR-240 Processing temperature: 85°C Processing time: 30 minutes (heating and cooling times are not included in the processing time) <<Retort processing>> Processing equipment: SR-240 manufactured by Tommy Seiko Processing temperature: 121°C Processing time: 30 minutes (heating and cooling times are not included in the processing time)

[0063] <OTR (Cumulative oxygen transmission rate)> Measured in accordance with ASTM D3985. The oxygen transmission rate (cc / 0.21atm·day·package) of the multilayer container after the above retort processing was measured in an atmosphere of 23°C, 100% relative humidity inside the container, and 50% relative humidity outside. The cumulative oxygen transmission amount (cc / 0.21atm·package) permeated into the container was calculated from the measured oxygen transmission rate. During the measurement, OX-TRAN 2 / 61 manufactured by Modern Controls was used.

[0064] <Adhesive strength> The obtained multilayer container filled with water and heat-sealed with aluminum was dropped 10 times from a height of 1 m so that the same side was the falling surface, and the cup was visually observed and evaluated according to the following criteria. 3: No delamination was observed. 2: Some delamination was observed. 1: Significant delamination was observed.

[0065] <Formability (Appearance)> Regarding the obtained multilayer container, taking Comparative Example 1 as 2 as the standard, the amount of welds and streaks was compared with it. Five experts evaluated and a majority vote was taken. 3: No welds or streaks, or almost none 2: Welds and / or streaks are slightly visible 1: Welds and / or streaks are visible

[0066]

Table 1

[0067] As is clear from the above results, the multilayer containers of the present invention had low haze and excellent transparency even after boiling and retorting (Examples 1 and 2). Furthermore, the multilayer containers of the present invention had few welds in the polyolefin layer and were excellent in moldability (appearance). Furthermore, unlike when EVOH is used as the barrier resin, there was concern that the adhesion between the barrier resin layer (polyamide resin layer) and the polyolefin layer would be poor, but they were sufficiently bonded. Furthermore, the multilayer containers of the present invention also had excellent oxygen barrier properties after retorting. In contrast, Comparative Examples 1 to 3, which used ethylene-vinyl alcohol copolymer (EVOH) as the barrier resin, showed significantly poorer haze after boiling and also poorer oxygen barrier properties after retort treatment. Furthermore, when the MFR of the acid-unmodified polyolefin was outside the range of the present invention (Comparative Examples 2 and 4), the resulting multilayer containers had welds in the polyolefin layers and were poor in moldability (appearance). Furthermore, by making the MFR of the acid-modified polyolefin larger than the MFR of the acid-unmodified polyolefin, the adhesive strength between the polyamide resin layer and the polyolefin layer could be further improved (comparison between Example 1 and Example 2). [Explanation of symbols]

[0068] 1 polyolefin layer 2 Polyamide resin layer 3 Polyolefin Layer

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) 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, 30 to 60 mol % of the dicarboxylic acid-derived structural units are derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms, and 70 to 40 mol % are derived from isophthalic acid; The acid-unmodified polyolefin was subjected to the temperature X ＰＯ The melt flow rate measured under the conditions of ° C. and 2.16 kgf is 20 g / 10 min or more, The temperature X ＰＯ is the melting point of the unmodified polyolefin + 65°C. Multilayer container.

2. The acid-modified polyolefin was subjected to the temperature X ｍＰＯ The melt flow rate measured under the conditions of ° C. and 2.16 kgf is greater than the melt flow rate of the unmodified polyolefin, The temperature X ｍＰＯ is the melting point of the acid-modified polyolefin + 55°C, The multilayer container according to claim 1.

3. 3. 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.

4. The multilayer container according to any one of claims 1 to 3, wherein the acid-modified polyolefin comprises acid-modified polypropylene.

5. The multilayer container according to any one of claims 1 to 4, wherein the acid-modified polyolefin has a melt flow rate of more than 20 g / 10 min and not more than 500 g / 10 min.

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

7. 7. The multilayer container according to claim 1, wherein the acid-unmodified polyolefin has a melt flow rate of 20 to 50 g / 10 min.

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

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

10. The multilayer container according to any one of claims 1 to 9, wherein the multilayer container has a haze of 10% or less as measured in accordance with JIS K-7105.

11. The multilayer container according to any one of claims 1 to 10, wherein the haze measured in accordance with JIS K-7105 after boiling treatment at 85°C for 30 minutes is not more than twice the haze before the boiling treatment.

12. The multilayer container according to any one of claims 1 to 11, wherein the polyamide resin (a) is an amorphous resin.

13. The acid-modified polyolefin and the acid-unmodified polyolefin are contained, and the acid-unmodified polyolefin is subjected to a temperature X ＰＯ a polyolefin layer-forming composition having a melt flow rate of 20 g / 10 min or more measured under conditions of ° C. and 2.16 kgf; 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, 30 to 60 mol % of the dicarboxylic acid-derived structural units are derived from an α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms, and 70 to 40 mol % are derived from isophthalic acid; 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 temperature X ＰＯ is the melting point of the unmodified polyolefin + 65°C. Method for manufacturing multilayer containers.

14. The acid-modified polyolefin was subjected to the temperature X ｍＰＯ The melt flow rate measured under the conditions of ° C. and 2.16 kgf is greater than the melt flow rate of the unmodified polyolefin, The temperature X ｍＰＯ is the melting point of the acid-modified polyolefin + 55°C, The method for producing the multilayer container according to claim 13.

15. The method for producing a multilayer container according to claim 13 or 14, wherein the multilayer container is the multilayer container according to any one of claims 1 to 12.

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