Multilayer container and method for manufacturing a multilayer container

Abstract

Provided is a multilayer container having high transparency after boiling treatment, excellent oxygen barrier properties after retort treatment, and excellent moldability, and a method for producing the same. A multilayer container having: 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, the polyamide resin containing a polyamide resin (a) in which 70 mol% or more of structural units derived from a diamine are derived from m-xylylenediamine, and 30 to 60 mol% of structural units derived from a dicarboxylic acid are derived from an α,ω-linear aliphatic dicarboxylic acid having a carbon number of 4 to 20 and 70 to 40 mol% are derived from isophthalic acid, and the acid-unmodified polyolefin has a melt flow rate of 20 g / 10 min or more, and a temperature X PO is a melting point of the acid-unmodified polyolefin + 65°C.

Description

Technical Field

[0001] This invention relates to multilayer containers and methods for manufacturing multilayer containers. In particular, it relates to multilayer containers using polyamide resin as a barrier layer. Background Technology

[0002] In the past, canning and bottling were used to preserve food and medicine in order to prevent food from deteriorating, discoloring, and fading. However, while canning and bottling offer excellent barrier properties against various gases such as oxygen and water vapor, they also present the following problems: they cannot be used for heating in a microwave oven; it is difficult to remove food from plates or other containers; and discarded cans are bulky and cannot be stacked, leading to a lack of proper disposal methods.

[0003] As alternative storage containers, thermoformed containers made of thermoplastic resins are widely used. Containers made of polyolefins, especially polypropylene (hereinafter sometimes abbreviated as "PP"), have melting points higher than the temperature required for sterilization, and are therefore widely used as storage containers for foods requiring sterilization. However, while PP has excellent moisture resistance, it is easily permeable to oxygen, which can cause deterioration, discoloration, and fading of food and pharmaceuticals. Therefore, it is not adequately suited as a container for long-term storage of food and pharmaceuticals.

[0004] As a method for long-term preservation of food and medicine using containers formed of PP, a known method is to use a multilayer container with an oxygen-barrier thermoplastic resin layer as an intermediate layer. Specifically, a co-injection molded multilayer structure is known, which is a co-injection molded multilayer structure having a barrier layer and outer layers stacked on both sides thereof. The barrier layer is formed of a resin composition comprising an ethylene-vinyl alcohol copolymer (A) and an alkali metal salt (B) of a higher fatty acid with a melting point below 250°C. The ethylene content of the ethylene-vinyl alcohol copolymer (A) is 20-60 mol%, the degree of saponification is 90% or more, and the melt flow rate (MF) at 190°C and 2160g is [not specified]. R) is 3 to 20 g / 10 minutes, the content of alkali metal salt (B) in the aforementioned barrier layer is 50 to 1500 ppm in terms of metal atoms, and the aforementioned outer layer is formed of a resin composition comprising unmodified polypropylene (E) and maleic anhydride-modified polypropylene (F) with a melt viscosity lower than that, and the mass ratio of maleic anhydride-modified polypropylene (F) to the total mass of unmodified polypropylene (E) and maleic anhydride-modified polypropylene (F) [F / (E+F)] is 0.025 to 0.2 (Patent Document 1).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: International Publication No. 2018 / 074445 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] However, it is known that the transparency of the aforementioned multi-layer containers will be poor after boiling or steaming treatment. Furthermore, oxygen barrier properties are also required for multi-layer containers after steaming treatment. Additionally, it is known that there are time differences in the formability (appearance) of multi-layer containers.

[0010] The purpose of this invention is to solve the above-mentioned problems and to provide a multi-layer container with high transparency after boiling treatment and cooking treatment, excellent oxygen barrier properties after cooking treatment, and excellent formability, as well as a method for manufacturing the same.

[0011] Solution for solving the problem

[0012] Based on the above-mentioned problems, the inventors conducted research and found that by using a specified polyamide resin as the barrier resin and by mixing acid-modified polyolefin and acid-unmodified polyolefin with a specified MFR in the polyolefin layer, the above-mentioned problems were solved.

[0013] Specifically, the above-mentioned problems were solved according to the following solution.

[0014] <1> A multi-layer container having:

[0015] A polyolefin layer comprising acid-modified polyolefin and acid-unmodified polyolefin; and,

[0016] A polyamide resin layer in contact with the aforementioned polyolefin layer and comprising polyamide resin.

[0017] The aforementioned polyamide resin comprises polyamide resin (a), wherein the polyamide resin (a) comprises structural units derived from diamines and structural units derived from dicarboxylic acids, wherein more than 70 mol% of the aforementioned diamine-derived structural units are derived from m-phenylenediamine, and 30 to 60 mol% of the aforementioned dicarboxylic acid-derived structural units 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.

[0018] The aforementioned acid-unmodified polyolefins are based on JIS K7210-1:2014, at temperature X PO The melt flow rate, measured at ℃ and 2.16 kgf, was over 20 g / 10 min.

[0019] The aforementioned temperature X PO The melting point of acid-unmodified polyolefins is +65℃.

[0020] <2> according to <1> The aforementioned multilayer container, wherein the acid-modified polyolefin is formulated according to JIS K7210-1:2014, at temperature X mPO The melt flow rate measured at ℃ and 2.16 kgf is greater than that of the aforementioned acid-unmodified polyolefin.

[0021] The aforementioned temperature X mPO The melting point of acid-modified polyolefins is +55℃.

[0022] <3> according to <1> or <2> In the multilayer container, the content of alkali metal salts of higher fatty acids contained in the aforementioned polyamide resin layer is less than 50 ppm by mass, calculated in terms of alkali metal atoms.

[0023] <4> according to <1> ~ <3> The multilayer container according to any one of the following, wherein the aforementioned acid-modified polyolefin comprises acid-modified polypropylene.

[0024] <5> according to <1> ~ <4> The multilayer container according to any one of the following methods, wherein the melt flow rate of the aforementioned acid-modified polyolefin is more than 20 g / 10 min and less than 500 g / 10 min.

[0025] <6> according to <1> ~ <5> The multilayer container according to any one of the following, wherein the aforementioned acid-unmodified polyolefin comprises polypropylene.

[0026] <7> according to <1> ~ <6> The multilayer container according to any one of the following methods, wherein the melt flow rate of the aforementioned acid-unmodified polyolefin is 20-50 g / 10 min.

[0027] <8> according to <1> ~ <7> The multilayer container according to any one of the above-mentioned polyamide resins, wherein the terminal amino concentration is 10 to 70 μeq / g.

[0028] <9> according to <1> ~ <8> The multi-layer container as described in any one of the following descriptions, wherein the aforementioned multi-layer container is a multi-layer injection-molded container.

[0029] <10> according to <1> ~ <9> The multi-layer container according to any one of the following methods, wherein the haze of the aforementioned multi-layer container, as measured according to JIS K-7105, is less than 10%.

[0030] <11> according to <1> ~ <10> In any one of the multi-layer containers, the haze measured according to JIS K-7105 after boiling treatment at 85°C for 30 minutes is less than twice the haze before the boiling treatment.

[0031] <12> according to <1> ~ <11> The multilayer container according to any one of the following methods, wherein the aforementioned polyamide resin (a) is an amorphous resin.

[0032] <13> A method for manufacturing a multi-layer container, the method comprising the following steps:

[0033] The polyolefin layer forming composition and the polyamide resin layer forming composition are injected into a mold in such a manner that the polyolefin layer formed by the polyolefin layer forming composition and the polyamide resin layer formed by the polyamide resin layer forming composition are in contact, and injection molding is performed.

[0034] The composition for forming the polyolefin layer comprises an acid-modified polyolefin and an acid-unmodified polyolefin, wherein the aforementioned acid-unmodified polyolefin is formulated according to JIS K7210-1:2014 at a temperature X. PO The melt flow rate, measured at ℃ and 2.16 kgf, was over 20 g / 10 min.

[0035] The composition for forming the polyamide resin layer comprises a polyamide resin (a), wherein the polyamide resin (a) comprises structural units derived from diamines and structural units derived from dicarboxylic acids, wherein more than 70 mol% of the aforementioned diamine-derived structural units are derived from m-phenylenediamine, and 30 to 60 mol% of the aforementioned dicarboxylic acid-derived structural units 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.

[0036] The aforementioned temperature X PO The melting point of acid-unmodified polyolefins is +65℃.

[0037] <14> according to <13> The method for manufacturing the multilayer container, wherein the aforementioned acid-modified polyolefin is manufactured according to JIS K 7210-1:2014 at a temperature X mPO The melt flow rate measured at ℃ and 2.16 kgf is greater than that of the aforementioned acid-unmodified polyolefin.

[0038] The aforementioned temperature X mPO The melting point of acid-modified polyolefins is +55℃.

[0039] <15> according to <13> or <14> The method for manufacturing a multi-layer container, wherein the aforementioned multi-layer container is... <1> ~ <12> The multi-layer container as described in any one of the above.

[0040] The effects of the invention

[0041] According to the present invention, a multilayer container with high transparency after boiling treatment and cooking treatment, excellent oxygen barrier properties after cooking treatment, and excellent formability, and a method thereof can be provided. Attached Figure Description

[0042] Figure 1 This is an example of a cross-sectional schematic diagram of the main body of the multi-layer container in this embodiment. Detailed Implementation

[0043] Hereinafter, a method for implementing the present invention (hereinafter referred to as "this embodiment") will be described in detail. It should be noted that the following embodiment is an example for illustrating the present invention, and the present invention is not limited to this embodiment.

[0044] It should be noted that in this specification, “~” is used to include the values ​​recorded before and after it as the lower limit and upper limit values.

[0045] In this manual, all physical properties and characteristic values ​​are assumed to be those obtained at 23°C unless otherwise specified.

[0046] Unless otherwise specified, the standards shown in this manual are based on the standards as of January 1, 2022, and the measurement methods may vary depending on the year.

[0047] The multilayer container of this embodiment is characterized by having: a polyolefin layer comprising an acid-modified polyolefin and an acid-unmodified polyolefin; and a polyamide resin layer in contact with the aforementioned polyolefin layer and comprising a polyamide resin, wherein the aforementioned polyamide resin comprises polyamide resin (a), the polyamide resin (a) comprising structural units derived from diamines and structural units derived from dicarboxylic acids, wherein more than 70 mol% of the aforementioned diamine-derived structural units are derived from m-phenylenediamine, and 30 to 60 mol% of the aforementioned dicarboxylic acid-derived structural units 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, and the aforementioned acid-unmodified polyolefin is formulated according to JIS K7210-1:2014, at a temperature X PO The melt flow rate measured at ℃ and 2.16 kgf was greater than 20 g / 10 min. The aforementioned temperature X PO The melting point of acid-unmodified polyolefins is +65℃.

[0048] By forming this structure, a multi-layer container (transparent multi-layer container) with high transparency after boiling treatment and cooking treatment, and excellent oxygen barrier properties after cooking treatment is obtained.

[0049] Furthermore, multi-layer containers that can be injection molded are obtained. In particular, multi-layer containers with almost no weld lines or streaks are obtained.

[0050] Alternatively, it can also form multilayer containers with excellent adhesion between the polyolefin layer and the polyamide resin layer.

[0051] The following is a detailed description of this embodiment.

[0052] <Polyolefin layer>

[0053] The polyolefin layer in this embodiment comprises acid-modified polyolefin and acid-unmodified polyolefin. It is presumed that the acid-modified polyolefin improves adhesion to the polyamide resin layer, while the acid-unmodified polyolefin, formed by injection molding, also improves the appearance.

[0054] <<Acid-Unmodified Polyolefins>>

[0055] The acid-unmodified polyolefin used in this embodiment is based on JIS K7210-1:2014, at temperature X PO The melt flow rate, measured at ℃ and 2.16 kgf, was greater than 20 g / 10 min. Here, temperature X... PO The melting point of the acid-unmodified polyolefin is +65°C. The melting point is a value determined by DSC, specifically by the method described in the examples below. In multilayer containers manufactured by conventional extrusion molding, the MFR of the polyolefin used is approximately 2 to 3 g / 10 minutes. In this embodiment, by making the MFR of the polyolefin 20 g / 10 minutes or more, the appearance of the resulting multilayer container can be improved by injection molding. The aforementioned MFR of the acid-unmodified polyolefin is preferably 20 g / 10 minutes or more, more preferably 25 g / 10 minutes or more, and even more preferably 30 g / 10 minutes or more. In addition, the aforementioned MFR of the acid-unmodified polyolefin is preferably 50 g / 10 minutes or less, more preferably 48 g / 10 minutes or less. By setting it to the aforementioned range, there is a tendency to improve thin-wall formability.

[0056] In this embodiment, unmodified polyolefin refers to a polyolefin in which the number of acid groups is sufficiently less than that of acid-modified polyolefin. 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, and even more preferably 1 mol% or less, and even more preferably no acid groups.

[0057] In this embodiment, the acid-unmodified polyolefin preferably also does not contain polar groups other than acid groups.

[0058] In this embodiment, the acid-unmodified polyolefin preferably includes polypropylene. Examples of polypropylene in this embodiment include homopolymers of propylene and copolymers of other olefins such as ethylene with 5% or less by mass (preferably 3% or less by mass) of propylene, with homopolymers of propylene being preferred.

[0059] The melting point of the acid-unmodified polyolefin is preferably 150°C or higher, more preferably 155°C or higher. By setting it to the aforementioned lower limit or higher, there is a tendency for improved moldability. Furthermore, the melting point of the acid-unmodified polyolefin is preferably 180°C or lower, more preferably 170°C or lower. By setting it to the aforementioned upper limit or lower, there is a tendency for improved moldability.

[0060] In this embodiment, when the polyolefin layer contains two or more acid-unmodified polyolefins, the aforementioned melting point is recorded as the melting point of the acid-unmodified polyolefin with the highest content.

[0061] The aforementioned melting point was determined according to the description of the embodiments described later.

[0062] 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.

[0063] In addition, the content of 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.

[0064] The polyolefin layer may contain only one type or two or more acid-unmodified polyolefins. When two or more types are included, the total amount is preferably within the range described above.

[0065] <<Acid-Modified Polyolefins>>

[0066] The type of acid-modified polyolefin used in this embodiment is not particularly limited, but it is preferably based on JIS K 7210-1:2014, at temperature X. mPO The MFR measured at ℃ and 2.16 kgf was greater than that of the acid-unmodified polyolefin. It is speculated that this configuration makes the acid-modified polyolefin more miscible with the acid-unmodified polyolefin. The results suggest that the increased number of interfaces between the acid-modified polyolefin and the polyamide resin layer in the polyolefin layer, and the increased ratio of covalent bonds between the acid groups of the acid-modified polyolefin and the amino groups of the polyamide resin (a), further improve adhesion. The aforementioned temperature X... mPO The melting point is +55°C of the acid-modified polyolefin. The melting point is a value determined by DSC, specifically by the method described in the examples below.

[0067] The aforementioned acid-modified polyolefins are based on JIS K7210-1:2014, at temperature X. mPO The MFR measured at ℃ and 2.16 kgf is preferably greater than 20 g / 10 min, more preferably greater than 30 g / 10 min, even more preferably greater than 50 g / 10 min, even more preferably greater than 100 g / 10 min, even more preferably greater than 200 g / 10 min, even more preferably greater than 300 g / 10 min, and particularly preferably greater than 400 g / 10 min. By setting it to the aforementioned lower limit or above, there is a tendency to further improve the compatibility with acid-unmodified polyolefins. In addition, the MFR of the aforementioned acid-modified polyolefin is preferably less than 500 g / 10 min. By setting it to the aforementioned upper limit or below, there is a tendency to avoid excessively increasing the overall fluidity and improve the moldability.

[0068] The polyolefin constituting the acid-modified polyolefin in this embodiment preferably includes polypropylene. Examples of polypropylene in this embodiment include homopolymers of propylene and copolymers of other olefins such as ethylene with 5% by mass or less (preferably 3% by mass or less) of propylene, with homopolymers of propylene being preferred.

[0069] Preferred compounds for acid modification of polyolefins include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, butenoic acid, methylmaleic acid, methylfumaric acid, nicotinic acid, citraconic acid, pentenoic acid, cis-4-cyclohexene-1,2-dicarboxylic acid, intracyclo[2.2.1]-5-heptene-2,3-dicarboxylic acid and metal salts of these carboxylic acids, monomethyl maleate, monomethyl itaconic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, hydroxyethyl acrylate, methyl methacrylate, and so on. 2-Ethylhexyl acrylate, hydroxyethyl methacrylate, aminoethyl methacrylate, dimethyl maleate, dimethyl itaconic acid, maleic anhydride, itaconic anhydride, citraconic anhydride, intracyclic bicyclic-[2.2.1]-5-heptene-2,3-dicarboxylic anhydride, maleimide, N-ethylmaleimide, N-butylmaleimide, N-phenylmaleimide, acrylamide, methacrylamide, glycidyl acrylate, glycidyl methacrylate, ethyl glycidyl acrylate, itaconic acid glycidyl acrylate, citraconic acid glycidyl acrylate, etc. These can be used in one or in combination of two or more. Among these, maleic anhydride is preferred.

[0070] In this embodiment, acid-modified polyolefin is particularly suitable for use, and more preferably maleic anhydride-modified polyolefin.

[0071] The melting point of acid-modified polyolefins is preferably 150°C or higher, more preferably 60°C or higher. By setting it to the aforementioned lower limit or higher, there is a tendency for improved moldability. Furthermore, the melting point of acid-modified polyolefins is preferably 180°C or lower, more preferably 170°C or lower. By setting it to the aforementioned upper limit or lower, there is a tendency for improved moldability.

[0072] In this embodiment, when the polyolefin layer contains two or more acid-modified polyolefins, the aforementioned melting point is recorded as the melting point of the most abundant acid-unmodified polyolefin.

[0073] The aforementioned melting point was determined according to the description of the embodiments described later.

[0074] 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. By setting it to the aforementioned lower limit or above, there is a tendency for further improvement in adhesion to the barrier layer. 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. By setting it to the aforementioned upper limit or below, there is a tendency for the barrier layer to easily separate during reuse.

[0075] The polyolefin layer may contain only one type or two or more acid-modified polyolefins. When two or more types are included, the total amount is preferably within the range described above.

[0076] <<Acid-Modified Polyolefins and Unmodified Polyolefins>>

[0077] Next, the relationship between acid-modified polyolefins and acid-unmodified polyolefins will be explained.

[0078] In this embodiment, the difference in MFR between the olefins (MFR of the acid-modified polyolefin - MFR of the acid-unmodified polyolefin) is preferably 1 g / 10 min or more, more preferably 10 g / 10 min or more, further 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 setting this to the aforementioned lower limit or above, the acid-modified polyolefin tends to be more miscible in the acid-unmodified polyolefin, and the adhesion between the polyolefin layer and the polyamide resin layer is improved. In addition, the difference between the MFR of the acid-modified polyolefin and the MFR of the acid-unmodified polyolefin in the aforementioned polyolefin layer is preferably, for example, 450 g / 10 min or less.

[0079] Furthermore, the ratio of the MFR of the acid-modified polyolefin to the MFR of the unmodified polyolefin in the polyolefin layer (the ratio of MFR of acid-modified polyolefin to MFR of unmodified polyolefin) is preferably greater than 1, more preferably greater than 2, further preferably greater than 5, even more preferably greater than 7, and even more preferably greater than 9. By setting it to the aforementioned lower limit value or above, there is a tendency for further improvement in adhesion. Additionally, the aforementioned ratio of MFR of acid-modified polyolefin to MFR of unmodified polyolefin is preferably 50 or less, more preferably less than 20, further preferably less than 18, even more preferably less than 15, and even more preferably less than 13. By setting it to the aforementioned upper limit value or below, there is a tendency for improved moldability.

[0080] The mass ratio of acid-modified polyolefin to acid-unmodified polyolefin in the polyolefin layer, relative to 100 parts by mass of acid-modified polyolefin, is preferably 1 part by mass or more, more preferably 2 parts by mass or more, further preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more. By setting this to the aforementioned lower limit or above, there is a tendency for further improvement in adhesion. Furthermore, the mass ratio of acid-modified polyolefin to acid-unmodified polyolefin in the polyolefin layer, relative to 100 parts by mass of acid-modified polyolefin, is preferably 10 parts by mass or less, more preferably 7 parts by mass or less. By setting this to the aforementioned upper limit or below, there is a tendency for the barrier material to become easier to separate during reuse.

[0081] In this embodiment, the content of polyolefin in the polyolefin layer (the total content of acid-modified polyolefin and acid-unmodified polyolefin) is preferably 85% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, further preferably 98% by mass or more, and even more preferably 99% by mass or more. The upper limit of the aforementioned content of polyolefin in the polyolefin layer (the total content of acid-modified polyolefin and acid-unmodified polyolefin) is 100% by mass or less.

[0082] <<Other Ingredients>>

[0083] In this embodiment, the polyolefin layer may also contain other components besides acid-modified polyolefin and acid-unmodified polyolefin without departing from the spirit of the invention.

[0084] Other components may include thermoplastic resins other than polyolefins, plasticizers, antioxidants, heat stabilizers, ultraviolet absorbers, light stabilizers, lubricants, inorganic fillers, antistatic agents, flame retardants, crystallization promoters, 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.

[0085] <Polyamide resin layer>

[0086] In this embodiment, the polyamide resin layer is bonded to the polyolefin layer and contains polyamide resin (a). In this embodiment, by using the above-mentioned polyolefin layer, unlike existing multilayer containers with polyolefin and polyamide resin layers, the adhesion between the polyolefin layer and the polyamide resin layer can be ensured even if no adhesive resin layer is provided between the polyolefin layer and the polyamide resin layer, and thus, high transparency can be maintained after boiling treatment and cooking treatment.

[0087] <<Polyamide Resin (a)>>

[0088] The polyamide resin layer in this embodiment comprises polyamide resin (a), which comprises structural units derived from diamine and structural units derived from dicarboxylic acid. More than 70 mol% of the aforementioned structural units derived from diamine are derived from m-phenylenediamine, and 30 to 60 mol% of the aforementioned structural units derived from dicarboxylic acid are derived from α,ω-linear aliphatic dicarboxylic acids with 4 to 20 carbon atoms, and 70 to 40 mol% are derived from isophthalic acid.

[0089] This 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, this polyamide resin (a) has high transparency. In particular, its transparency is excellent after heat treatment, making it ideal for use in containers for cooking or boiling. Moreover, although the structure of the polyamide resin (a) differs significantly from that of polyolefins, it can still maintain a high degree of adhesion to the polyolefin layer.

[0090] The polyamide resin (a) comprises 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more, further preferably 95 mol% or more, and even more preferably 99 mol% or more of diamine-derived structural units derived from phenylenediamine. Phenylenediamine is preferably m-phenylenediamine and p-phenylenediamine, more preferably m-phenylenediamine.

[0091] In this embodiment, a preferred embodiment of the polyamide resin (a) is a polyamide resin in which 70 mol% or more (preferably 80 mol% or more, more preferably 90 mol% or more, further preferably 95 mol% or more, and even more preferably 99 mol% or more) of the structural unit derived from diamine is derived from m-phenylenediamine.

[0092] Examples of diamines other than phenylenediamine include aromatic diamines such as p-phenylenediamine, and aliphatic diamines such as 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, octamethylenediamine, and nonamethylenediamine. These other diamines may be one or more.

[0093] When using a diamine other than phenylenediamine as the diamine component, it is used at a ratio of 30 mol% or less, more preferably 1 to 25 mol%, and particularly preferably 5 to 20 mol% of the structural units derived from the diamine.

[0094] 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 with 4 to 20 carbon atoms, and 70 to 40 mol% are derived from isophthalic acid.

[0095] The lower limit of the proportion of α,ω-linear aliphatic dicarboxylic acids (preferably α,ω-linear aliphatic dicarboxylic acids with 4 to 20 carbon atoms, more preferably adipic acid) in all dicarboxylic acids constituting the dicarboxylic acid structural units of the polyamide resin (a) is 30 mol% or more, preferably 33 mol% or more, more preferably 35 mol% or more, further preferably 38 mol% or more, and even more preferably 40 mol% or more, and can be 45 mol% or more. The upper limit of the aforementioned proportion of α,ω-linear aliphatic dicarboxylic acids with 4 to 20 carbon atoms is 60 mol% or less, preferably 55 mol% or less. By setting it within this range, there is a tendency to further improve the oxygen barrier properties of the multilayer container of this embodiment, and also to further improve the transparency of the obtained multilayer container.

[0096] α,ω-linear aliphatic dicarboxylic acids with 4 to 20 carbon atoms, preferably α,ω-linear aliphatic dicarboxylic acids with 4 to 8 carbon atoms, as described above.

[0097] As preferred raw materials for polyamide resins, α,ω-linear aliphatic dicarboxylic acids with 4 to 20 carbon atoms are preferred dicarboxylic acid components. Examples of aliphatic dicarboxylic acids include succinic acid, glutaric acid, pimelic acid, octanoic acid, azelaic acid, adipic acid, sebacic acid, undecanoic acid, and dodecanoic acid. One or more of these can be used. Among these, adipic acid is preferred from the perspective of making the melting point of the polyamide resin suitable for molding and processing.

[0098] The lower limit of the proportion of isophthalic acid in all dicarboxylic acids constituting the dicarboxylic acid structural units in the polyamide resin (a) is 40 mol% or more, preferably 45 mol% or more. The upper limit of the aforementioned proportion of isophthalic acid is 70 mol% or less, preferably 67 mol% or less, more preferably 65 mol% or less, further preferably 62 mol% or less, and even more preferably 60 mol% or less, and can be 55 mol% or less. By setting it within this range, there is a tendency to further improve the oxygen barrier properties of the multilayer container of this embodiment.

[0099] In the polyamide resin (a), the total proportion of structural units derived from dicarboxylic acids, specifically those derived from isophthalic acid, to structural units derived from α,ω-linear aliphatic dicarboxylic acids 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 still more preferably 99 mol% or more. The upper limit of the aforementioned proportion of structural units derived from isophthalic acid to the total proportion of structural units derived from α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms is no more than 100 mol%. By setting this proportion, there is a tendency to further improve the transparency of the multilayer of this embodiment.

[0100] As dicarboxylic acids other than isophthalic acid and α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms, examples include phthalic acid compounds such as terephthalic acid and phthalic 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. One or a mixture of two or more can be used.

[0101] The polyamide resin (a) preferably contains substantially no structural units derived from terephthalic acid. "Substantially no" 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 this configuration, moderate molding processability is maintained, and gas barrier properties become less susceptible to variation depending on humidity.

[0102] The terminal amino group concentration of polyamide resin (a) is preferably 10–70 μeq / g. By setting it to a value above the aforementioned lower limit, the adhesion to acid-modified polyolefins can be further improved. The aforementioned terminal amino group concentration is set as follows: 0.3 g of polyamide resin (a) is added to a mixed solvent of phenol / ethanol = 4 / 1 (volume ratio), stirred at 20–30°C until completely dissolved, and while stirring, the inner wall of the container is rinsed with 5 mL of methanol. The solution is then neutralized and titrated with 0.01 mol / L hydrochloric acid aqueous solution to determine the terminal amino group concentration [NH2].

[0103] In addition, it is preferable that the concentration of the terminal amino groups in the polyamide resin contained in the polyamide resin layer of this embodiment, i.e., the mixture of polyamide resin (a) and other polyamide resins, meets the above-mentioned range.

[0104] It should be noted that the polyamide resin (a) used in this embodiment contains structural units derived from dicarboxylic acids and structural units derived from diamines as main components, but may also contain structural units other than those derived from dicarboxylic acids and diamines, terminal groups, and other sites. Examples of other structural units include those derived from lactams such as ε-caprolactam, valproic acid, laurolactam, and undecanoic acid, as well as aminocarboxylic acids such as 11-aminoundecanoic acid and 12-aminododecanoic acid, but it is not limited to these. Furthermore, the polyamide resin (a) used in this embodiment contains trace amounts of additives used in the synthesis. The polyamide resin (a) used in this embodiment typically contains 95% or more, preferably 98% or more, structural units derived from dicarboxylic acids or diamines.

[0105] The polyamide resin (a) used in this embodiment is preferably an amorphous resin. By using an amorphous resin, the polyamide resin (a) is less prone to whitening even after boiling or boiling treatment, and can maintain high transparency.

[0106] Amorphous resins are resins that do not have a definite melting point. The melting point is recorded in accordance with paragraph 0036 of International Publication No. 2017 / 090556.

[0107] In this embodiment, the content of polyamide resin (a) in the polyamide resin layer is preferably 85% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 98% by mass or more, and even more preferably 99% by mass or more. The upper limit of the content of polyamide resin (a) in the polyamide resin layer is 100% by mass or less.

[0108] The polyamide resin layer may contain only one type or two or more types of polyamide resin (a). When two or more types are contained, the total amount is preferably within the range described above.

[0109] <<Other Ingredients>>

[0110] The polyamide resin layer in this embodiment may also contain other components besides polyamide resin (a) without departing from the spirit of the invention.

[0111] 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-resistant modifiers such as various elastomers; 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; anti-coloring agents; ultraviolet absorbers such as benzotriazoles; additives such as release agents, plasticizers, colorants, and flame retardants; oxidation reaction promoters, recycling aids, and additives such as 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, and even more preferably 3% by mass or less, and can be 1% by mass or less.

[0112] The description of oxidation reaction promoters can be found in paragraphs 0034 to 0036 of International Publication No. 2019 / 058986, the contents of which are incorporated into this specification.

[0113] The polyamide resin other than polyamide resin (a) can be an aliphatic polyamide resin or a semi-aromatic polyamide resin, with aliphatic polyamide resins 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, polyamide 66, and polyamide 666 being preferred, and polyamide 6 being even more preferred. Examples of semi-aromatic polyamide resins include 6T, 6T / 6I, 9T, and 9N (a condensation polymer of nonanediamine and naphthalene dicarboxylic acid). Only one or more of these polyamide resins other than polyamide resin (a) can be used.

[0114] In this embodiment, the polyamide resin layer may contain alkali metal salts of higher fatty acids, or it may not contain alkali metal salts of higher fatty acids.

[0115] In this embodiment, the content of alkali metal salts of higher fatty acids 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 in terms of alkali metal atoms. By reducing the alkali metal salts of higher fatty acids in the polyamide resin layer, advantages such as improved appearance of the resulting multilayer container are achieved.

[0116] Alkali metal salts of higher fatty acids are preferably salts of fatty acids with 12 to 30 carbon atoms. Examples of suitable salt-forming fatty acids include saturated fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, and benzolic acid. Potassium and sodium are preferred alkali metals.

[0117] <Layer Composition of Multi-Layer Containers>

[0118] The multilayer container of this embodiment has a polyolefin layer and a polyamide resin layer bonded to the aforementioned polyolefin layer. Typically, the polyolefin layer is on the outer side. Furthermore, the multilayer container of this embodiment preferably has a three-layer structure of polyolefin layer / polyamide resin layer / polyolefin layer. Specifically, as... Figure 1 The example illustrates that the cross-section of the main body of the multi-layer container, from the outside, consists of a polyolefin layer 1, a polyamide resin layer 2, and a polyolefin layer 3. Polyolefin layer 1 and polyamide resin layer 2 are joined in a plane perpendicular to the cross-section of the main body, and polyamide resin layer 2 and polyolefin layer 3 are also joined in a plane perpendicular to the cross-section of the main body. It should be noted that... Figure 1The thickness in the text may not be proportional to the actual thickness. The multilayer container of this embodiment, excluding the main body such as the bottom, preferably also has the aforementioned three-layer structure of polyolefin layer / polyamide resin layer / polyolefin layer, but is not limited to this. Furthermore, in this case, the two polyolefin layers can be polyolefin layers composed of the same composition or polyolefin layers composed of different compositions. However, both polyolefin layers preferably contain acid-modified polyolefin and acid-unmodified polyolefin, with the unmodified polyolefin having an MFR of 20 g / 10 minutes or more. Further, both polyolefin layers preferably have an MFR of acid-modified polyolefin greater than the MFR of acid-unmodified polyolefin.

[0119] Furthermore, the multilayer container of this embodiment can also be a 5-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, and preferably all polyamide resin layers are in contact with adjacent polyolefin layers. In addition, the multilayer container of this embodiment only needs to have a polyolefin layer and a polyamide resin layer in contact with the aforementioned polyolefin layer, but it may also have other layers.

[0120] In this embodiment, the thickness ratio of the polyolefin layer to the polyamide resin layer in the multilayer container is not particularly limited. When the thickness of the polyolefin layer 1 is set to 100, the thickness of the polyamide resin layer 1 is preferably 0.5 to 40, 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, when the total thickness of the polyolefin layer is set to 100, the thickness of the polyamide resin layer is preferably 1 to 20, more preferably 2 to 15.

[0121] The thickness of each polyamide resin layer is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 150 μm or less, more preferably 100 μm or less, and even more preferably 90 μm.

[0122] The thickness of each polyolefin layer is preferably 0.2 mm or more, more preferably 0.3 mm or more, and preferably 1.4 mm or less, more preferably 1.0 mm or less.

[0123] In addition, the thickness of the multi-layer container is preferably 0.4 mm or more, more preferably 0.7 mm or more, and preferably 3 mm or less, more preferably 2 mm or less.

[0124] The multi-layer container of this embodiment preferably exhibits high transparency even after boiling treatment. Specifically, the haze measured according to JIS K-7105 after boiling treatment at 85°C for 30 minutes is preferably less than 2 times, more preferably less than 1.5 times, and even more preferably less than 1.2 times, the haze before boiling treatment. Regarding the lower limit, 1.0 times is ideal, but boiling treatment is also preferred when excellent transparency is achieved (e.g., more than 0.8 times).

[0125] Furthermore, the initial haze (haze after molding without boiling or cooking treatment) of the multi-layer container in this embodiment, measured according to 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 aforementioned haze is 0%, but even 0.1% or more is sufficient to meet the performance requirements.

[0126] <Manufacturing Method of Multi-Layer Containers>

[0127] The multi-layer container of this embodiment is preferably formed by injection molding. That is, the multi-layer container of this embodiment is preferably a multi-layer injection molded container. Therefore, a welded portion originating from the mold will be formed in the multi-layer container of this embodiment, but in this embodiment, by using a desired polyolefin layer (polyolefin layer forming composition), the welded portion can be further reduced.

[0128] More specifically, the manufacturing method of the multilayer container of this embodiment includes the following steps: injecting a polyolefin layer forming composition and a polyamide resin layer forming composition into a mold in such a way that the polyolefin layer formed by the polyolefin layer forming composition is in contact with the polyamide resin layer formed by the polyamide resin layer forming composition, and performing injection molding. The polyolefin layer forming composition comprises acid-modified polyolefin and acid-unmodified polyolefin, and the aforementioned acid-unmodified polyolefin is formulated according to JIS K7210-1:2014 at a temperature X. PO The melt flow rate measured at ℃ and 2.16 kgf is 20 g / 10 min or more. The polyamide resin layer forming composition comprises a polyamide resin (a), wherein the polyamide resin (a) comprises structural units derived from diamines and structural units derived from dicarboxylic acids. At least 70 mol% of the aforementioned diamine-derived structural units are derived from m-phenylenediamine, and 30-60 mol% of the aforementioned dicarboxylic acid-derived structural units are derived from α,ω-linear aliphatic dicarboxylic acids having 4-20 carbon atoms, and 70-40 mol% are derived from isophthalic acid. The aforementioned temperature X... PO The melting point of the acid-unmodified polyolefin is +65°C. It is particularly preferred that the injection molding be performed in such a way that the part in contact with the mold is a polyolefin layer (e.g., a polyolefin layer / polyamide resin layer / polyolefin layer).

[0129] The aforementioned multilayer container is preferably the multilayer container of this embodiment described above. That is, the aforementioned multilayer container is preferably made of the aforementioned acid-modified polyolefin according to JIS K7210-1:2014, at temperature X. mPO The melt flow rate measured at ℃ and 2.16 kgf is greater than the melt flow rate of the aforementioned acid-unmodified polyolefin, and the aforementioned temperature X mPO The melting point of the acid-modified polyolefin is +55°C. Furthermore, the preferred materials constituting the composition for forming the polyolefin layer and their contents have the same meaning as those described above for the polyolefin layer. Additionally, the preferred materials constituting the composition for forming the polyamide resin layer and their contents also have the same meaning as those described above for the polyamide resin layer.

[0130] Injection molding in the manufacturing method of this embodiment refers to, 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 pre-injected into a closed mold and then cured to form a multilayer container. Therefore, it is desirable that the melts of the polyolefin layer-forming composition and the melt of the polyamide resin layer-forming composition (especially the melt of the polyolefin layer-forming composition) within the mold have high flowability. In this embodiment, a polyolefin with a high MFR is used as the polyolefin, therefore, molding can be performed by injection molding (preferably co-injection molding). That is, an excellent multilayer container can be formed by injecting the polyolefin layer-forming composition and the polyamide resin layer-forming composition into the mold almost simultaneously without two-color molding. Furthermore, unlike biaxial stretch blow molding described later, the shape of the mold initially filled with the melts of the polyolefin layer-forming composition and the polyamide resin layer-forming composition directly becomes the shape of the final product; therefore, the flowability of the aforementioned melts becomes important. In other words, biaxial stretch blow molding is not included in the injection molding method of this embodiment. In addition, the multi-layer container in this embodiment is usually formed by injection molding, and therefore has welded parts.

[0131] In contrast, in extrusion blow molding, where the molding material is heated and melted, extruded into a cylindrical shape, clamped in a mold, and air is blown into it to form a hollow product, material flowability is not an issue as prevalent as in injection molding. Furthermore, in biaxial stretch blow molding, where only the main wall of the preform (semi-finished product) obtained by injection molding is reheated, a stretching rod is extended inward within a blow molding mold, and high-pressure air is blown in to form a hollow product, material flowability is also not an issue as prevalent as in injection molding.

[0132] It should be noted that the multi-layer container of this embodiment is suitable for manufacturing by injection molding, but multi-layer containers formed by other molding methods including blow molding and biaxial stretch molding are not excluded.

[0133] Furthermore, during co-injection molding, the polyamide resin layer forming composition and the polyolefin layer forming composition are co-injected together. Preferably, the polyamide resin layer forming composition is used as an intermediate layer, and the polyolefin layer forming composition and the polyamide resin layer forming composition are joined on both sides (e.g., forming a polyolefin layer / polyamide resin layer / polyolefin layer). An additional layer may also be formed further outside the polyolefin layer. Additionally, an innermost layer may be formed separately.

[0134] The injection timing of the polyolefin layer forming composition and the polyamide resin layer forming composition can be appropriately adjusted according to the shape of the target multilayer container. For example, injection of the polyolefin layer forming composition as the two outer layers can be started first, followed by injection of the polyamide resin layer forming composition, thereby preventing the polyamide resin layer from being exposed at the front end. The injection molding temperature can be adjusted taking into account the melting point and softening point of the resin to be used. In this embodiment, the injection molding temperature can be set to, for example, 220–290°C.

[0135] <Uses>

[0136] The multi-layer container of this embodiment can preferably be used for container lids, bottles, cups, trays, tubes, etc.

[0137] The multi-layer container of this embodiment is preferably used for packaging and preserving pharmaceuticals, food (processed aquatic products, processed livestock products, rice, liquid foods), etc. Details of these containers can be found in paragraphs 0033 to 0035 of Japanese Patent Application Publication No. 2011-37199, and these contents are incorporated herein by reference.

[0138] In particular, containers that are transparent and used for steaming or boiling foods are preferred.

[0139] Example

[0140] The following examples illustrate the present invention in further detail. The materials, amounts, proportions, processing contents, and processing steps shown in the following examples can be appropriately modified without departing from the spirit of the invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

[0141] If the measuring equipment used in the examples is difficult to obtain due to production stoppages or other reasons, other equipment with equivalent performance can be used for measurement.

[0142] When measuring MFR (melt flow rate), a product manufactured by Toyo Seiki Co., Ltd. is used as a melt indexer.

[0143] 1. Raw materials

[0144] MXD6I:

[0145] The polyamide resin is synthesized from m-phenylenediamine, adipic acid, and isophthalic acid, with isophthalic acid comprising 50 mol% of the dicarboxylic acid. It is an amorphous resin. The concentration of terminal amino groups is in the range of 10–70 μeq / g.

[0146] EVOH:

[0147] Soarnol DC3212B, manufactured by Mitsubishi Chemical Corporation, is an ethylene-vinyl alcohol copolymer. It is a crystalline resin.

[0148] PP1:

[0149] Acid-unmodified polypropylene, according to JIS K7210-1:2014, at temperature X PO MFR 45g / 10min, measured at ℃ = melting point + 65℃ and 2.16kgf, manufactured by Japan Polypropylene Corporation, Novatec BX05FS

[0150] PP2:

[0151] Acid-unmodified polypropylene, according to JIS K7210-1:2014, at temperature X PO MFR 10g / 10min, measured at ℃ = melting point + 65℃ and 2.16kgf, manufactured by Japan Polypropylene Corporation, Novatec MA3H.

[0152] Mah-PP1:

[0153] Maleic anhydride modified polypropylene, according to JIS K7210-1:2014, at temperature X mPO MFR 450g / 10min, measured at ℃ = melting point + 55℃ and 2.16kgf, manufactured by DuPont, Bynel 50E803.

[0154] Mah-PP2:

[0155] Maleic anhydride modified polypropylene, manufactured by Mitsui Chemicals, Inc., Admer QF551

[0156] According to JIS K7210-1:2014, at temperature X mPO At ℃ = melting point + 55℃, the MVR cannot be measured due to its excessively low value. It should be noted that, according to JIS K7210-1:2014, at temperature X... mPO The MFR measured at ℃ = melting point + 95℃ and 2.16 kgf was 5.7 g / 10 minutes.

[0157] <Melting point and glass transition temperature>

[0158] The melting point and glass transition temperature of the resin were determined using DSC (differential scanning calorimetry).

[0159] Specifically, melting point refers to the peak temperature of the endothermic peak observed by DSC (differential scanning calorimetry) during heating. Glass transition temperature, on the other hand, is the temperature measured after the sample has been heated to melt once to eliminate the influence of thermal history on crystallinity, and then heated again.

[0160] Differential scanning calorimetry (DSC) was used in the determination. The sample amount was set to approximately 5 mg, and nitrogen gas was used as the atmosphere gas, flowing at a rate of 30 ml / min. The melting point was determined by the peak temperature of the endothermic peak observed when the resin melted at a heating rate of 10 °C / min from room temperature to a temperature above the expected melting point. Next, the molten resin was quenched in dry ice and then reheated at a rate of 10 °C / min to a temperature above the melting point to determine the glass transition temperature.

[0161] Differential scanning calorimetry was performed using a "DSC-60" manufactured by Shimadzu Corporation.

[0162] <Example of MXD6I Synthesis>

[0163] In a jacketed 50L reactor equipped with a stirrer, condenser, condenser, thermometer, dropping tank, and nitrogen 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 added. The reactor was thoroughly purged with nitrogen, and then heated to 180°C under a small nitrogen flow to ensure uniform melting of the adipic acid and isophthalic acid. While stirring the system, 13.9 kg of m-phenylenediamine was added dropwise over 170 minutes. During this period, the internal temperature was continuously raised to 265°C. It should be noted that the water generated during the polycondensation was discharged outside the system through the condenser and condenser. After the addition of m-phenylenediamine was completed, the internal temperature was further raised to 270°C, and the reaction was continued for 10 minutes. The polymer was then extracted as a thread from a nozzle at the bottom of the reactor, water-cooled, and granulated to obtain the final polymer.

[0164] Next, the polymer obtained from the above operation was placed in a 250L rotary drum equipped with a heating jacket, a nitrogen inlet pipe, and a vacuum line. While rotating, the system was depressurized, and then the process was repeated three times under nitrogen gas with a purity of 99% or higher to achieve atmospheric pressure. Afterward, the system was heated to 115°C with nitrogen flowing through it. Then, the system was depressurized and maintained at 115°C for 24 hours. Nitrogen gas was then introduced to restore the system to atmospheric pressure, followed by cooling to obtain polyamide resin (MXD6I).

[0165] Alkali metal salts without added higher fatty acids. Furthermore, an attempt was made to determine the melting point according to paragraph 0036 of International Publication No. 2017 / 090556, but no definite melting point was found, indicating it is an amorphous resin.

[0166] 2. Examples 1 and 2, Comparative Examples 1 to 4

[0167] <Preparation of Compositions for Polyolefin Layer Formation>

[0168] The acid-modified polyolefin (Mah-PP) granules shown in Table 1 were dry-mixed with the acid-unmodified polyolefin (PP) granules at a mass ratio of 5:95.

[0169] <Manufacturing of Multi-Layer Injection Molded Containers>

[0170] A multilayer injection molding compound is obtained by injecting three layers of each resin composition (granules) almost simultaneously, using an inner layer formed from the polyamide resin composition (granules) obtained above and two outer layers formed from the polyolefin layer composition (granules) obtained above (polyolefin resin layer / polyamide resin layer / polyolefin resin layer). Detailed conditions are described below.

[0171] Equipment: Injection molding machine, Sumitomo Heavy Industries, Ltd., SE130DU-CI

[0172] Screw diameter

[0173] Polyamide resin composition: 16mm in diameter

[0174] Resin composition for polyolefin layer formation (resin composition comprising unmodified PP and modified PP): 32mm in diameter

[0175] Hot runner: Kortec

[0176] Temperature conditions

[0177] Polyamide resin composition: Region 1 = 230℃~250℃, Regions 2~4 = 240℃~280℃, Region 5 = 250℃~280℃

[0178] Resin composition for polyolefin layer formation: Zone 1 = 230℃, Zones 2-4 = 240℃-250℃, Zone 5 = 250℃

[0179] Hot runner temperature: 240℃~270℃

[0180] • Mold temperature: 15℃

[0181] The polyamide resin layer of the resulting multilayer injection molded container has a thickness of 80 μm, and the total thickness of the polyolefin layer is 800 μm (each polyolefin layer has a thickness of 400 μm).

[0182] <HAZE>

[0183] Separate the polyamide resin layers from the resulting multilayer injection-molded container (the freshly molded latter) and measure the haze. The haze was measured according to JIS K-7105. A lower haze value (in %) indicates higher transparency.

[0184] The measuring device used is a color / turbidity meter (trade name: COH-400A, manufactured by Nippon Denshoku Kogyo Co., Ltd.).

[0185] In addition, the fog level was measured in the same manner as above for multi-layer containers that have undergone the following boiling treatment and multi-layer containers that have undergone the following cooking treatment.

[0186] <<Boiling Treatment>>

[0187] Processing unit: TOMY SEIKO CO.,LTD. SR-240

[0188] Processing temperature: 85℃

[0189] Processing time: 30 minutes (excluding heating and cooling time)

[0190] <<Steaming and cooking treatment>>

[0191] Processing unit: TOMY SEIKO CO.,LTD. SR-240

[0192] Processing temperature: 121℃

[0193] Processing time: 30 minutes (excluding heating and cooling time)

[0194] <OTR (Cumulative Oxygen Permeability)>

[0195] Measured according to ASTM D3985.

[0196] The oxygen permeability (cc / 0.21atm·day·package) of the multi-layer container after the above-mentioned cooking treatment was measured under an atmosphere of 23°C, 100% relative humidity inside the container, and 50% relative humidity outside. The cumulative oxygen permeation (cc / 0.21atm·package) was calculated from the measured oxygen permeability.

[0197] For the measurement, MODERN CONTROLS, INC., OX-TRAN 2 / 61 was used.

[0198] <Adhesion strength>

[0199] The resulting multi-layered container, filled with water and heat-sealed from aluminum, was dropped 10 times from a height of 1m with the same side facing down. The resulting container was then visually observed and evaluated according to the following criteria.

[0200] 3: No interlayer delamination (delamination) was observed.

[0201] 2: The layers have been confirmed.

[0202] 1: Clear stratification has been identified.

[0203] <Formability (Appearance)>

[0204] For the obtained multi-layered containers, Comparative Example 1 was used as a benchmark to compare the quantities of weld points and striations relative to it. Evaluations were conducted by a majority vote of five professional evaluators.

[0205] 3: No or almost no weld points and streaks

[0206] 2: Slightly visible weld points and / or streaks

[0207] 1: Visible weld points and / or streaks [Table 1]

[0208]

[0209] The above results demonstrate that the multilayer container of the present invention exhibits low haze and excellent transparency after boiling and cooking (Examples 1 and 2). Furthermore, the multilayer container of the present invention has fewer weld points in the polyolefin layer, resulting in excellent formability (appearance). Moreover, unlike cases where EVOH is used as the barrier resin, where there are concerns about poor adhesion between the barrier resin layer (polyamide resin layer) and the polyolefin layer, the present invention achieves excellent adhesion. Additionally, the multilayer container of the present invention also exhibits excellent oxygen barrier properties after cooking.

[0210] In contrast, the haze of Comparative Examples 1-3, which used ethylene-vinyl alcohol copolymer (EVOH) as the barrier resin, was exceptionally poor after boiling. Furthermore, their oxygen barrier properties after cooking were also poor.

[0211] In addition, when the MFR of acid-unmodified polyolefin is not within the scope of the present invention (Comparative Examples 2 and 4), the resulting multilayer containers have visible weld points in the polyolefin layer, resulting in poor formability (appearance).

[0212] Furthermore, by making the MFR of the acid-modified polyolefin greater than that of the acid-unmodified polyolefin, the bonding strength between the polyamide resin layer and the polyolefin layer can be further improved (comparison between Example 1 and Example 2).

[0213] Explanation of reference numerals in the attached figures

[0214] 1. Polyolefin layer

[0215] 2 Polyamide resin layer

[0216] 3. Polyolefin layer.

Claims

1. A multi-layered container, comprising: A polyolefin layer comprising acid-modified polyolefin and acid-unmodified polyolefin; and, A polyamide resin layer in contact with the polyolefin layer and comprising polyamide resin. The polyamide resin comprises polyamide resin (a), wherein the polyamide resin (a) comprises structural units derived from diamines and structural units derived from dicarboxylic acids, wherein more than 70 mol% of the structural units derived from diamines are derived from m-phenylenediamine, and 30-60 mol% of the structural units derived from dicarboxylic acids are derived from α,ω-linear aliphatic dicarboxylic acids having 4-20 carbon atoms, and 70-40 mol% are derived from isophthalic acid. The acid-unmodified polyolefin is based on JIS K7210-1:2014, at temperature X PO The melt flow rate, measured at ℃ and 2.16 kgf, was over 20 g / 10 min. The temperature X PO The melting point of acid-unmodified polyolefins is +65℃.

2. The multi-layer container according to claim 1, wherein, The acid-modified polyolefin is based on JIS K7210-1:2014, at temperature X mPO The melt flow rate measured at ℃ and 2.16 kgf is greater than that of the acid-unmodified polyolefin. The temperature X mPO The melting point of acid-modified polyolefins is +55℃.

3. The multi-layer container according to claim 1 or 2, wherein, The content of alkali metal salts of higher fatty acids contained in the polyamide resin layer is less than 50 ppm by mass, calculated in alkali metal atomic form.

4. The multi-layer container according to claim 1 or 2, wherein, The acid-modified polyolefin includes acid-modified polypropylene.

5. The multi-layer container according to claim 1 or 2, wherein, The melt flow rate of the acid-modified polyolefin exceeds 20 g / 10 min and is less than 500 g / 10 min.

6. The multi-layer container according to claim 1 or 2, wherein, The acid-unmodified polyolefin comprises polypropylene.

7. The multi-layer container according to claim 1 or 2, wherein, The melt flow rate of the acid-unmodified polyolefin is 20~50 g / 10 min.

8. The multi-layer container according to claim 1 or 2, wherein, The concentration of terminal amino groups in the polyamide resin is 10~70 μeq / g.

9. The multi-layer container according to claim 1 or 2, wherein, The multi-layer container is a multi-layer injection molded container.

10. The multi-layer container according to claim 1 or 2, wherein, The haze of the multi-layer container, as measured according to JIS K-7105, is less than 10%.

11. The multi-layer container according to claim 1 or 2, wherein, The haze measured according to JIS K-7105 after boiling treatment at 85°C for 30 minutes is less than twice the haze before boiling treatment.

12. The multi-layer container according to claim 1 or 2, wherein, The polyamide resin (a) is an amorphous resin.

13. A method for manufacturing a multi-layer container, the method comprising the following steps: The polyolefin layer forming composition and the polyamide resin layer forming composition are injected into a mold in such a manner that the polyolefin layer formed by the polyolefin layer forming composition and the polyamide resin layer formed by the polyamide resin layer forming composition are in contact, and injection molding is performed. The composition for forming the polyolefin layer comprises an acid-modified polyolefin and an acid-unmodified polyolefin, and the acid-unmodified polyolefin is formulated according to JIS K7210-1:2014 at a temperature X. PO The melt flow rate, measured at ℃ and 2.16 kgf, was over 20 g / 10 min. The composition for forming the polyamide resin layer comprises a polyamide resin (a), wherein the polyamide resin (a) comprises structural units derived from diamines and structural units derived from dicarboxylic acids, wherein more than 70 mol% of the structural units derived from diamines are derived from m-phenylenediamine, and 30-60 mol% of the structural units derived from dicarboxylic acids are derived from α,ω-linear aliphatic dicarboxylic acids having 4-20 carbon atoms, and 70-40 mol% are derived from isophthalic acid. The temperature X PO The melting point of acid-unmodified polyolefins is +65℃.

14. The method for manufacturing a multi-layer container according to claim 13, wherein, The acid-modified polyolefin is based on JIS K7210-1:2014, at temperature X mPO The melt flow rate measured at ℃ and 2.16 kgf is greater than that of the acid-unmodified polyolefin. The temperature X mPO The melting point of acid-modified polyolefins is +55℃.

15. The method for manufacturing a multi-layer container according to claim 13 or 14, wherein, The multi-layer container is the multi-layer container according to any one of claims 1 to 12.

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