Pellets, methods for manufacturing the same, and multilayer structures using the same

Abstract

To provide a resin composition which has high gas barrier properties and humidity resistance under high temperature and high humidity, and is excellent in moldability.SOLUTION: A resin composition contains an ethylene-vinyl alcohol copolymer (A) and a drying agent (B), in which a content of the ethylene-vinyl alcohol copolymer (A) is 70-99 mass%, a content of the drying agent (B) is 1-30 mass%, the drying agent (B) is a metal salt capable of forming a hydrate, an average particle diameter of the drying agent (B) is 10-300 nm, an average length of crystals of the ethylene-vinyl alcohol copolymer (A) is 10-65 nm, and a ratio (ΔH1 / ΔH0) of a crystal melting enthalpy ΔH1(J / g) of the resin composition when the resin composition has been melted and quenched, and then the temperature has been raised to a crystal melting enthalpy ΔH0(J / g) of a reference resin obtained by removing the drying agent (B) from the resin composition when the reference resin has been melted and quenched, and then the temperature has been raised is 0.95 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition containing an ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as "EVOH") and a desiccant, and to a method for producing the same. It also relates to a multilayer structure having a layer made of the resin composition, and in particular to a packaging container. [Background technology]

[0002] Glass, metal, and metal foil still hold a dominant position as materials for containers used in the retort processing of foods such as vegetables and seafood. However, recently, rigid or semi-rigid plastic containers have become commonly used for the retort processing of other foods such as soups and pet food. EVOH is being adopted as a barrier resin for such plastic containers due to its good processability and excellent gas barrier properties.

[0003] Due to its chemical structure, EVOH is known to have a tendency to lose its gas barrier properties in environments with relative humidity exceeding 85%. This is thought to be because water acts as a plasticizer for EVOH, weakening the hydrogen bonds in the amorphous regions of EVOH and increasing its free volume, thereby increasing gas diffusion within the polymer matrix. Consequently, when packaging is subjected to typical steam retort processing at 110-132°C for 15-80 minutes, the oxygen permeation rate of EVOH increases dramatically, leading to oxidative degradation of the food, resulting in reduced flavor and a shorter shelf life.

[0004] As a countermeasure against such a decrease in gas barrier properties, a method is known in which a desiccant consisting of a salt capable of forming a hydrate is incorporated into EVOH. When a container using a resin composition obtained by such a method as a barrier layer is retorted, the decrease in the gas barrier properties of the resin composition is suppressed because the incorporated desiccant absorbs water. Patent Document 1 describes a composition in which desiccant particles such as a salt capable of forming a hydrate are dispersed in an EVOH matrix, and the average surface area diameter of the desiccant particles with a major diameter of 10 μm or more is 30 μm or less, and a method for producing the composition by melt-kneading EVOH and desiccant particles.

[0005] Patent Document 2 describes a resin composition containing EVOH and an inorganic compound such as kaolinite, with a crystallinity of 36% or more, and a method for producing the resin composition, which involves adding an aqueous dispersion of the inorganic compound to molten EVOH in an extruder equipped with a screw-type side feeder and then melt-kneading it. Patent Document 2 states that by increasing the crystallinity, the dispersibility of the inorganic compound is improved and the gas barrier properties are improved, and its examples show that aggregates of 200 μm or larger are reduced. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 63-113062 [Patent Document 2] WO2016 / 88862 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the resin compositions described in Patent Documents 1 and 2 had problems because they contained metal salts or inorganic compounds capable of forming hydrates, which worsened their melt moldability.

[0008] The present invention was made to solve the above problems, and aims to provide a resin composition that has high gas barrier properties, high moisture resistance under high temperature and high humidity conditions, and excellent moldability. [Means for solving the problem]

[0009] The above problems are solved by providing a resin composition comprising EVOH(A) and a desiccant (B), wherein the EVOH(A) content is 70 to 99% by mass, the desiccant (B) content is 1 to 30% by mass, the desiccant (B) is a metal salt capable of forming a hydrate, the average particle size of the desiccant (B) is 10 to 300 nm, and the ratio (ΔH1 / ΔH0) of the crystalline enthalpy of melting of the resin composition obtained by melting the resin composition, rapidly cooling it, and then heating it, to the crystalline enthalpy of melting of the standard resin obtained by melting the resin composition, rapidly cooling it, and then heating it, is 0.95 or less.

[0010] It is preferable that the metal salt is at least one selected from the group consisting of phosphates, sulfates, phosphonates, phosphinates, sulfonates, sulfinates, and carboxylates. It is preferable that the average length of the crystals of the ethylene-vinyl alcohol copolymer (A) is 10 to 65 nm.

[0011] The above problems can also be solved by providing a method for producing the resin composition, which includes a step of mixing molten or dissolved EVOH(A) with dissolved desiccant(B). The above problems can also be solved by providing a method for producing the resin composition, which includes a step of precipitating EVOH(A) and desiccant(B) from a solution in which EVOH(A) and desiccant(B) are dissolved. Furthermore, the above problems can also be solved by providing a method for producing the resin composition, which includes a step of adding an aqueous solution containing desiccant(B) to a molten product containing EVOH(A) and water, and a step of melting and kneading the molten product to which the aqueous solution has been added.

[0012] A multilayer structure having a layer made of the resin composition is a preferred embodiment of the present invention, and a packaging container made of the multilayer structure is a more preferred embodiment. It is preferable that the multilayer structure further has a layer made of a recovered composition obtained by melt-kneading a multilayer structure having a layer containing at least one thermoplastic resin selected from the group consisting of polyolefin, polystyrene, polyester, polyamide, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, and polyacrylonitrile. A package obtained by filling the packaging container with a content is a preferred embodiment of the packaging container. A method of sterilizing the package with steam or hot water at 70°C or higher and 140°C or lower is a preferred embodiment of the package.

Effects of the Invention

[0013] The resin composition of the present invention has high gas barrier properties and moisture resistance under high temperature and high humidity, and is also excellent in molding processability. Therefore, a multilayer structure using the resin composition is produced with good productivity and has high gas barrier properties even after being treated with steam or hot water.

Brief Description of the Drawings

[0014] [Figure 1] It is a transmission electron microscope image of the cross section of the resin composition pellet in Example 1. [Figure 2] It is a transmission electron microscope image of the cross section of the resin composition pellet in Comparative Example 1. [Figure 3] It is a scanning electron microscope image of the cross section of the resin composition pellet in Example 1. [Figure 4] It is a scanning electron microscope image of the cross section of the resin composition pellet in Comparative Example 1.

Modes for Carrying Out the Invention

[0015] The resin composition of the present invention contains EVOH(A) and a desiccant (B), wherein the EVOH(A) content is 70 to 99% by mass, the desiccant (B) content is 1 to 30% by mass, the desiccant (B) is a metal salt capable of forming a hydrate, the average particle size of the desiccant (B) is 10 to 300 nm, and the ratio (ΔH1 / ΔH0) of the crystalline fusion enthalpy ΔH1 (J / g) of the resin composition when it is melted, rapidly cooled and heated, to the crystalline fusion enthalpy ΔH0 (J / g) of the standard resin obtained by melting the resin composition, rapidly cooling and heating, is 0.95 or less.

[0016] [EVOH(A)] The ethylene unit content of EVOH(A) contained in the resin composition of the present invention is preferably 15 to 65 mol%. When the ethylene unit content is 15 mol% or more, the moisture resistance of the resin composition is further improved. The ethylene unit content is more preferably 20 mol% or more, and even more preferably 25 mol% or more. On the other hand, when the ethylene unit content is 65 mol% or less, the gas barrier properties of the resin composition are further improved. The ethylene unit content is more preferably 50 mol% or less, and even more preferably 40 mol% or less. The ethylene unit content and degree of saponification of EVOH(A) can be determined by nuclear magnetic resonance (NMR) spectroscopy.

[0017] The degree of saponification of EVOH(A) (i.e., the ratio of moles of vinyl alcohol units to the total number of moles of vinyl alcohol units and vinyl ester units in EVOH(A)) is preferably 95 mol% or higher. When the degree of saponification is 95 mol% or higher, the gas barrier properties are further improved, as is the thermal stability during melt molding. A degree of saponification of 98 mol% or higher is more preferable, and 99 mol% or higher is even more preferable.

[0018] The melt flow rate of EVOH(A) (at 210°C under a 2160g load) is preferably 0.1 to 50 g / 10 min. If the melt flow rate is less than 0.1 g / 10 min, melt molding may become difficult. The melt flow rate is more preferably 0.5 g / 10 min or more, and even more preferably 1 g / 10 min or more. On the other hand, if the melt flow rate exceeds 50 g / 10 min, extrusion molding of the resin composition becomes difficult, and the strength of the resulting layer made of the resin composition may decrease. The melt flow rate is more preferably 20 g / 10 min or less, and even more preferably 10 g / 10 min or less.

[0019] EVOH(A) may contain other monomer units other than ethylene monomer units, vinyl ester monomer units, and vinyl alcohol monomer units, to the extent that the effects of the present invention are not inhibited. If EVOH(A) contains other monomer units, the content is preferably 0.05 mol% or more, more preferably 0.1 mol% or more, even more preferably 0.5 mol% or more, and particularly preferably 1 mol% or more. On the other hand, the content of other monomer units is preferably 30 mol% or less, more preferably 15 mol% or less, even more preferably 10 mol% or less, particularly preferably 5 mol% or less, and most preferably 3 mol% or less. Examples of other monomer units include units derived from vinylsilane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxy-ethoxy)silane, and γ-methacryloxypropylmethoxysilane.

[0020] EVOH(A) may contain, to the extent that the effects of the present invention are not hindered, at least one selected from the structural units represented by the following formulas (I), (II), or (III) as the other monomer units. Having such structural units in EVOH(A) improves the flexibility and processing properties of the resin composition, thereby enhancing the thermoformability of the resulting multilayer structure.

[0021] [ka]

[0022] In formula (I), R 1 ~R 3 each independently represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or a hydroxyl group. The aliphatic hydrocarbon group may be an acyclic aliphatic hydrocarbon group having 1 to 10 carbon atoms, or may be an alicyclic hydrocarbon group having 3 to 10 carbon atoms. One pair of R 1 ~R 3 may combine to form a ring. Also, some or all of the hydrogen atoms in the aliphatic hydrocarbon group or the aromatic hydrocarbon group may be substituted with a hydroxyl group, a carboxyl group, or a halogen atom.

[0023] In formula (II), R 4 ~R 7 each independently represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or a hydroxyl group. The aliphatic hydrocarbon group may be an acyclic aliphatic hydrocarbon group having 1 to 10 carbon atoms, or may be an alicyclic hydrocarbon group having 3 to 10 carbon atoms. R 4 and R 5 , or R 6 and R 7 may each combine to form a ring. Also, some or all of the hydrogen atoms in the aliphatic hydrocarbon group or the aromatic hydrocarbon group may be substituted with a hydroxyl group, an alkoxy group, a carboxyl group, or a halogen atom.

[0024] In formula (III), R 8 ~R 11 each independently represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or a hydroxyl group. The aliphatic hydrocarbon group may be an acyclic aliphatic hydrocarbon group having 1 to 10 carbon atoms, or may be an alicyclic hydrocarbon group having 3 to 10 carbon atoms. Some or all of the hydrogen atoms in the aliphatic hydrocarbon group and the aromatic hydrocarbon group may be substituted with a hydroxyl group, an alkoxy group, a carboxyl group, or a halogen atom. R 12 and R 13 each independently represents a hydrogen atom, a formyl group, or an alkanoyl group having 2 to 10 carbon atoms.

[0025] In formulas (I) to (III), R 1 ~R 11 Examples of acyclic aliphatic hydrocarbon groups used as such include alkyl groups and alkenyl groups, examples of alicyclic hydrocarbon groups include cycloalkyl groups and cycloalkenyl groups, and examples of aromatic hydrocarbon groups include phenyl groups.

[0026] In formula (I), R 1 ~R 3 However, each is preferably independently a hydrogen atom, a methyl group, an ethyl group, a hydroxyl group, a hydroxymethyl group, or a hydroxyethyl group, and more preferably independently a hydrogen atom, a methyl group, a hydroxyl group, or a hydroxymethyl group.

[0027] In formula (II), R 4 and R 5 It is preferable that R is a hydrogen atom. 6 and R 7 It is also preferable that one of them is the aliphatic hydrocarbon group and the other is a hydrogen atom. In this case, alkyl groups and alkenyl groups are preferred as the aliphatic hydrocarbon group. When the gas barrier properties of the resulting multilayer structure are important, R 6 and R 7 The aliphatic hydrocarbon group used as is more preferably a methyl group or an ethyl group, (CH2) h It is also more preferable that the substituent is represented by OH (where h is an integer from 1 to 8). h is preferably an integer from 1 to 4, more preferably 1 or 2, and particularly preferably 1.

[0028] In structural unit (III), R 8 ~R 11 However, each is preferably independently a hydrogen atom or an aliphatic hydrocarbon group having 1 to 5 carbon atoms. Preferred aliphatic hydrocarbon groups are methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, and n-pentyl groups.

[0029] EVOH(A) can be used alone or in combination of two or more types.

[0030] [Desiccant (B)] The resin composition of the present invention contains a metal salt capable of forming a hydrate as a desiccant (B). When treated with steam or hot water, the desiccant (B) absorbs the infiltrating moisture, thereby maintaining high gas barrier properties even after the treatment.

[0031] The metal salt used as the desiccant (B) is not particularly limited as long as it is capable of forming a hydrate, but it is preferable that the metal salt is at least one selected from the group consisting of phosphates, sulfates, phosphonates, phosphinates, sulfonates, sulfinates, and carboxylates. The metal salt may be a metal salt of an organic acid or a metal salt of an inorganic acid. The number of carbon atoms in the metal salt of the organic acid is preferably 1 to 10. Furthermore, the metal salt may be a hydrate, an anhydride, or a mixture thereof.

[0032] The metal cation constituting the metal salt is preferably a cation of a metal belonging to Group 1 or 2 of the periodic table, and more preferably a cation of a metal belonging to Group 1 of the periodic table. Specifically, the metal ions that form the metal salt include cations of metals belonging to Group 1 of the periodic table, such as sodium ions, potassium ions, and lithium ions; and cations of metals belonging to Group 2 of the periodic table, such as calcium ions and magnesium ions, with sodium ions and potassium ions being preferred among them.

[0033] It is more preferable that the metal salt is at least one selected from the group consisting of phosphates, sulfates, phosphonates, phosphinic acids, and carboxylates, and even more preferable that it is at least one selected from the group consisting of phosphates, sulfates, and carboxylates, and among these, it is particularly preferable that it is a phosphate. The phosphate forms a hydrate containing multiple water molecules as crystal water, and therefore can absorb a large amount of water per unit mass. Furthermore, as the humidity increases, the number of water molecules that can be incorporated as crystal water increases stepwise, so the phosphate can gradually absorb moisture as the humidity increases.

[0034] Specific examples of organic phosphates used as the desiccant (B) include phosphate ester salts such as disodium phenyl phosphate, disodium 4-nitrophenyl phosphate, disodium ethyl phosphate, monosodium 1-naphthyl phosphate, disodium 1-naphthyl phosphate, disodium α-glycerophosphate, disodium β-glycerophosphate, phenylcalcium phosphate, and phenylmagnesium phosphate. From the viewpoint of further improving the moldability of the resin composition, organic phosphates are preferred as the phosphate, and phosphate ester salts are more preferred. The phosphate ester salt may be either a phosphate monoester salt or a phosphate diester salt, but a phosphate monoester salt is preferred, and phenyl disodium phosphate is more preferred.

[0035] Examples of inorganic phosphates used as desiccants (B) include sodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium polyphosphate, lithium phosphate, dilithium hydrogen phosphate, lithium dihydrogen phosphate, lithium polyphosphate, potassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, potassium polyphosphate, calcium phosphate, calcium hydrogen phosphate, calcium dihydrogen phosphate, and calcium polyphosphate. Here, polyphosphates include diphosphates (pyrophosphates), triphosphates (tripolyphosphates), etc. From a safety standpoint, inorganic phosphates are preferred as the phosphates.

[0036] Examples of the aforementioned sulfates include magnesium sulfate and sodium sulfate.

[0037] Examples of the phosphonate mentioned above include sodium phosphonate and disodium phenylphosphonate.

[0038] Examples of the phosphinate include sodium phosphinate.

[0039] Examples of the aforementioned sulfonates include sodium benzenesulfonate, sodium p-toluenesulfonate, and calcium bis(2,5-dihydroxybenzenesulfonate).

[0040] Examples of the aforementioned sulfinate salts include sodium p-toluenesulfinate.

[0041] Examples of the aforementioned carboxylate salts include disodium succinate, sodium tartrate, and trisodium citrate.

[0042] [Resin composition] The EVOH(A) content in the resin composition of the present invention is 70 to 99% by mass. When the content is 70% by mass or more, a matrix of EVOH(A), which is the main component, is formed, and the high gas barrier properties of the resin composition are maintained. The content is preferably 75% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more. On the other hand, when the EVOH(A) content is 99% by mass or less, the moisture resistance of the resin composition, especially moisture resistance under high temperature and high humidity, is improved, as is the moldability. The content is preferably 98% by mass or less, more preferably 97% by mass or less, even more preferably 96% by mass or less, particularly preferably 94% by mass or less, and most preferably 93% by mass or less.

[0043] The content of the desiccant (B) in the resin composition is 1 to 30% by mass. When the content is 1% by mass or more, the moisture resistance of the resin composition, especially its moisture resistance under high temperature and high humidity, is improved, as is its moldability. The content of the desiccant (B) is preferably 2% by mass or more, more preferably 3% by mass or more, even more preferably 4% by mass or more, particularly preferably 5% by mass or more, and most preferably 7% by mass or more. On the other hand, when the content of the desiccant (B) is 30% by mass or less, the high gas barrier properties of the resin composition are maintained. The content of the desiccant (B) is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less. Note that if the desiccant (B) in the resin composition forms a hydrate, the content of the desiccant (B) refers to the content converted to an anhydrous form. That is, the content of the desiccant (B) means the content of the metal salt excluding the water of hydration.

[0044] The average particle size of the desiccant (B) in the resin composition must be 10 to 300 nm. Surprisingly, the extremely small average particle size of the desiccant (B) in the resin composition improves both the moldability and gas barrier properties of the resin composition. Normally, adding metal salts or inorganic compounds to EVOH reduces moldability. In contrast, in the resin composition of the present invention, the dispersion of the desiccant (B) with an extremely small average particle size in EVOH (A) is thought to inhibit the crystallization of EVOH (A). This inhibition of crystallization shortens the average length of the crystals, and as will be described later, the amount of energy required for molding the resin composition is reduced, improving moldability. The average particle size is preferably 250 nm or less, more preferably 200 nm or less, even more preferably 180 nm or less, and particularly preferably 130 nm or less. On the other hand, the average particle size is preferably 30 nm or more.

[0045] It is preferable that the average length of the EVOH(A) crystals in the resin composition is 10 to 65 nm. A relatively short average length of EVOH(A) crystals reduces the enthalpy of fusion ΔH1 (J / g) of the resin composition. This reduction in enthalpy of fusion ΔH1 (J / g) reduces the amount of energy required for molding the resin composition, improving its moldability. Furthermore, a relatively short average length of EVOH(A) crystals also tends to lower the melting point Tm1 (°C) of the resin composition. This reduction in melting point Tm1 (°C) improves the melt moldability of the resin composition, further enhancing its moldability. The average length is more preferably 55 nm or less, even more preferably 45 nm or less, and particularly preferably 35 nm or less. On the other hand, an average length of 20 nm or more is more preferable. The average length of the EVOH(A) crystals is the arithmetic mean of the lengths (longest lengths) of crystalline domains in the cross-sectional map image of the resin composition obtained using a transmission electron microscope, and is measured by the method described in the examples.

[0046] It is preferable that the crystalline melting enthalpy ΔH1 of the resin composition of the present invention, after being melted, rapidly cooled, and then heated, is 65 (J / g) or less. When ΔH1 is 65 (J / g) or less, the amount of energy required for molding the resin composition is reduced, further improving moldability. A ΔH1 of 60 (J / g) or less is more preferable. On the other hand, ΔH1 is usually 40 (J / g) or more. The crystalline melting enthalpy of the resin composition of the present invention and the reference resin described later are measured by the method described in the examples.

[0047] The ratio (ΔH1 / ΔH0) of the enthalpy of crystalline melting of the resin composition of the present invention, obtained by melting the resin composition of the present invention, rapidly cooling it, and then heating it, to the enthalpy of crystalline melting of the standard resin obtained by melting the standard resin obtained by removing the desiccant (B) from the resin composition of the present invention, and then rapidly cooling and then heating the standard resin, must be 0.95 or less. A ratio (ΔH1 / ΔH0) of 0.95 or less means that the enthalpy of crystalline melting of the resin composition of the present invention decreases by adding the desiccant (B). By decreasing the enthalpy of crystalline melting of ΔH1 (J / g), the amount of energy required for molding is reduced, and the moldability of the resin composition of the present invention is improved. The ratio (ΔH1 / ΔH0) is preferably 0.94 or less, more preferably 0.925 or less, even more preferably 0.91 or less, and particularly preferably 0.9 or less. On the other hand, the ratio (ΔH1 / ΔH0) is usually 0.5 or higher. The standard resin is obtained by removing the desiccant (B) from the resin composition containing EVOH(A) and the desiccant (B). The method for removing the desiccant (B) from the resin composition is not particularly limited, and can be determined according to the type of desiccant (B), etc. For example, one method is to dissolve the resin composition containing EVOH(A) and the desiccant (B) described in the examples in a solvent, and then add the solution containing the dissolved EVOH(A) and the desiccant (B) to a solvent in which the solubility of EVOH(A) is low and the solubility of the desiccant (B) is high, thereby precipitating EVOH(A).

[0048] The melting point Tm1 of the resin composition of the present invention is preferably 185°C or lower. A Tm1 of 185°C or lower improves the melt-moldability of the resin composition, further enhancing its moldability. A Tm1 of 183°C or lower is more preferable. On the other hand, Tm1 is usually 175°C or higher. The melting points of the resin composition of the present invention and the reference resin described later are measured by the method described in the examples.

[0049] It is preferable that the difference (T0-T1) between the melting point Tm0 (°C) of a reference resin obtained by removing the desiccant (B) from the resin composition of the present invention and the melting point Tm1 (°C) of the resin composition of the present invention is 1.5°C or more. A difference in melting points (Tm0-Tm1) of 1.5°C or more means that the melting point T1 (°C) of the resin composition of the present invention decreases when the desiccant (B) is added. By decreasing the melting point Tm1 (°C), the melt moldability of the resin composition is improved, and the moldability is further improved. A difference in melting points (Tm0-Tm1) of 2.0°C or more is more preferable, 2.6°C or more is even more preferable, 3°C or more is particularly preferable, and 4°C or more is most preferable. On the other hand, the difference in melting points (Tm0-Tm1) is usually 10°C or less.

[0050] The resin composition of the present invention may contain other additives besides EVOH(A) and the desiccant (B), as long as they do not impair the effects of the present invention. Examples of other additives include other resins besides EVOH(A), dispersants, plasticizers, stabilizers, surfactants, colorants, ultraviolet absorbers, antistatic agents, crosslinking agents, metal salts, fillers, and reinforcing agents for various fibers. The content of other additives in the resin composition of the present invention is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0051] Other resins include polyethylene (ultra-low density, low density, medium density, high density), ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, polypropylene, ethylene-propylene copolymer, ionomer and other polyolefins; semi-aromatic polyesters such as polyethylene terephthalate and polybutylene terephthalate; aliphatic polyesters such as polyvalerolactone, polycaprolactone, polyethylene succinate and polybutylene succinate; and polyethers such as polyethylene glycol and polyphenylene ether.

[0052] Other resins mentioned above include polyamides, specifically polycapramid (nylon 6), poly-ω-aminoheptanoic acid (nylon 7), poly-ω-aminononanoic acid (nylon 9), polyundecaneamide (nylon 11), polylauryl lactam (nylon 12), polyethylenediamine adipamide (nylon 26), polytetramethylene adipamide (nylon 46), polyhexamethylene adipamide (nylon 66), polyhexamethylene sebaamide (nylon 610), and polyhexamethylene dodecane. Camide (Nylon 612), Polyoctamethylene adipamide (Nylon 86), Polydecamethylene adipamide (Nylon 106), Caprolactam / Lauryl Lactam Copolymer (Nylon 6 / 12), Caprolactam / ω-Aminonanoic Acid Copolymer (Nylon 6 / 9), Caprolactam / Hexamethylenediammonium Adipate Copolymer (Nylon 6 / 66), Lauryl Lactam / Hexamethylenediammonium Adipate Copolymer (Nylon 12 / 66), Ethylenediammonium Adipate / Hexa Methylenediammonium adipate copolymer (Nylon 26 / 66), caprolactam / hexamethylenediammonium adipate / hexamethylenediammonium sebacate copolymer (Nylon 6 / 66 / 610), ethylenediammonium adipate / hexamethylenediammonium adipate / hexamethylenediammonium sebacate copolymer (Nylon 26 / 66 / 610), polyhexamethylene isophthalamide (Nylon 6I), polyhexamethylene terephthalamide (Nylon 6T), Examples include xamethylene isophthalamide / hexamethylene terephthalamide copolymer (nylon 6I / 6T), 11-aminoundecaneamide / hexamethylene terephthalamide copolymer, polynonameethylene terephthalamide (nylon 9T), polydecamethylene terephthalamide (nylon 10T), polyhexamethylene cyclohexylamide, polynonameethylene cyclohexylamide, or these polyamides modified with aromatic amines such as methylenebenzylamine and metaxylenediamine. Metaxylylenediammonium adipate is also an example.

[0053] The method for producing the resin composition of the present invention is not particularly limited, but a method including a step of mixing molten or dissolved EVOH(A) and dissolved desiccant (B) (hereinafter, this step may be abbreviated as the mixing step) is preferred because it makes it easier to reduce the average particle size of the desiccant (B). At this time, it is sufficient that the EVOH(A) is molten or dissolved and the desiccant (B) is dissolved by the time the mixing step is completed. Therefore, the EVOH(A) used for mixing may be molten or dissolved beforehand, or it may be neither molten nor dissolved. Similarly, the desiccant (B) used for mixing may be dissolved or it may be undissolved.

[0054] In the mixing process, the specific method for mixing EVOH (A) and the desiccant (B) is as follows: (1) A method of mixing pre-dissolved EVOH (A) with pre-dissolved desiccant (B), (2) A method of dissolving EVOH(A) by mixing undissolved EVOH(A) with a pre-dissolved desiccant (B), (3) A method of dissolving the desiccant (B) by mixing pre-dissolved EVOH (A) with an undissolved desiccant (B), (4) A method of dissolving EVOH(A) and desiccant(B) by mixing undissolved EVOH(A), undissolved desiccant(B), and solvent. (5) A method of mixing molten EVOH (A) with a pre-dissolved desiccant (B) is one example. In addition, as a method of mixing EVOH (A) and desiccant (B), (6) A method of mixing undissolved EVOH (A) with a pre-dissolved desiccant (B), (7) Another method involves mixing undissolved EVOH (A) with undissolved desiccant (B).

[0055] In the mixing step, the solvent used to dissolve EVOH(A) is not particularly limited as long as it can dissolve EVOH(A), but water or an alcohol is preferred. The alcohol is preferably an alcohol having 1 to 5 carbon atoms, more preferably methanol, ethanol, propanol, isopropanol, and butanol, and even more preferably methanol.

[0056] In the mixing process, the solvents described above can be used to dissolve the drying agent (B) and the solvents to dissolve EVOH (A).

[0057] In order to make it easier to reduce the average particle size of the desiccant (B), it is preferable to use a molten product containing EVOH(A) and water as the molten EVOH(A) used in the method of (5) above. In the method of (5) above, it is also preferable to use an aqueous solution containing the desiccant (B) as the dissolved desiccant (B). Furthermore, in the method of (5) above, it is also preferable to mix the molten EVOH(A) and the dissolved desiccant (B) and then melt-knead the resulting mixture. In order to make it easier to reduce the average particle size of the desiccant (B), it is also preferable as a method for producing the resin composition of the present invention to include the steps of adding an aqueous solution containing the desiccant (B) to a molten product containing EVOH(A) and water, and melt-kneading the molten product to which the aqueous solution has been added. The water content in the molten product containing EVOH(A) and water before adding the aqueous solution containing the desiccant (B) is preferably 0.1 to 30 parts by mass per 100 parts by mass of EVOH(A).

[0058] The apparatus used for mixing EVOH (A) and the desiccant (B) is not particularly limited, and known mixing or kneading apparatus such as a kneader-ruder, extruder, mixing roll, or Banbury mixer may be used.

[0059] When melt-mixing a mixture of molten EVOH (A) and dissolved desiccant (B) in an extruder, general equipment used for melt-mixing resins can be employed. Continuous mixing equipment such as a single-screw extruder or twin-screw extruder may be used, or batch-type mixing equipment such as a Banbury mixer may be used.

[0060] The temperature during melt-mixing in the extruder is not particularly limited as long as it is a temperature at which EVOH(A) can melt, but 180 to 250°C is preferred. If the melt-mixing temperature is below 180°C, the melting of EVOH(A) may be insufficient. A melt-mixing temperature of 190°C or higher is more preferred. If the melt-mixing temperature exceeds 250°C, EVOH(A) or the desiccant (B) may decompose. A melt-mixing temperature of 240°C or lower is more preferred.

[0061] In the method described in (6) above, it is preferable to mix undissolved EVOH(A) with a pre-dissolved desiccant (B) and remove the solvent from the resulting mixture. At this time, from the viewpoint of how easily the desiccant (B) can be incorporated into EVOH(A), it is more preferable to mix the pre-dissolved desiccant (B) with an aqueous mixture containing the undissolved EVOH(A) and water. The water content in the aqueous mixture is preferably 30 to 200 parts by mass per 100 parts by mass of EVOH(A). Specific methods of the method described in (6) above include immersing EVOH(A) pellets in a solution in which the desiccant (B) is dissolved, and then drying the pellets. It is preferable that the pellets are aqueous pellets containing undissolved EVOH(A) and water.

[0062] In the method described in (7) above, it is preferable to mix the undissolved EVOH (A) and the undissolved drying agent (B), and then melt-knead the resulting mixture. The method described above as the method used in (5) above is used for melt-kneading the mixture.

[0063] From the standpoint of easily reducing the average particle size of the desiccant (B), a method for producing the resin composition of the present invention that includes a step of precipitating EVOH(A) and desiccant (B) from a solution in which EVOH(A) and desiccant (B) are dissolved is also preferred. The solution in which EVOH(A) and desiccant (B) are dissolved is obtained by the mixing method of EVOH(A) and desiccant (B) described in (1) to (4) above. The total content of EVOH(A) and desiccant (B) in the solution is preferably 10 to 50% by mass. As a solvent in the solution, the solvents described above for dissolving EVOH(A) are listed, and a solvent containing the alcohol is preferred. The solvent containing the alcohol may further contain water, in which case the mass ratio of the alcohol to water (alcohol / water) is preferably 30 / 70 to 70 / 10. The temperature when dissolving EVOH(A) in the solvent is preferably 75 to 95°C.

[0064] A method for precipitating EVOH(A) and desiccant(B) from a solution in which EVOH(A) and desiccant(B) are dissolved is: (1) A method of extruding the solution into a poor solvent of EVOH(A), (2) A method of removing the solvent from the solution by distillation is one example, and (1) is preferred.

[0065] The poor solvent used in (1) above is preferably one that contains water. The water-containing poor solvent may further contain alcohol, in which case the mass ratio of alcohol to water (alcohol / water) can be appropriately adjusted according to the type of alcohol, the composition of the solution in which EVOH(A) and the drying agent (B) are dissolved, the temperature of the poor solvent, etc. The alcohol can be the one described above as a solvent for dissolving EVOH(A). The resin composition of the present invention can be obtained by pelletizing and drying the precipitate of EVOH(A) and the drying agent (B) obtained.

[0066] The resin composition of the present invention exhibits minimal reduction in gas barrier properties even after processing under high-temperature and high-humidity conditions such as retort processing. Furthermore, it is expected that similar effects can be obtained not only in conventional retort processing, which involves heating to over 100°C and pressurizing in an autoclave, but also in steam retort processing, water cascade retort processing, microwave retort processing, hot filling, sterilization processing, boiling processing, and other similar processes.

[0067] The resin composition of the present invention can be molded into various molded products such as films, sheets, containers, pipes, and fibers by melt molding. Possible melt molding methods include extrusion molding, inflation extrusion, blow molding, melt spinning, and injection molding. The melt molding temperature varies depending on the melting point of EVOH(A), but is preferably around 150 to 270°C.

[0068] [Multilayer structure] A multilayer structure having a layer made of the resin composition of the present invention (hereinafter sometimes abbreviated as the resin composition layer) is a preferred embodiment of the present invention.

[0069] It is preferable that the multilayer structure of the present invention has a layer made of the resin composition and a layer containing a thermoplastic resin (hereinafter sometimes abbreviated as the thermoplastic resin layer). It is preferable that the thermoplastic resin layer contains a thermoplastic resin other than EVOH(A). Specifically, it is preferable that the thermoplastic resin layer contains at least one selected from the group consisting of polyolefin, polystyrene, polyester, polyamide, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate and polyacrylonitrile, more preferably at least one selected from the group consisting of polyolefin, polystyrene and polyester, and even more preferably polyolefin. The total content of the thermoplastic resin other than EVOH(A) in the thermoplastic resin layer is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0070] Examples of polyolefins contained in the thermoplastic resin layer include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, polypropylene, polybutene, polymethylpentene, and ionomer.

[0071] In the multilayer structure of the present invention, it is preferable to have the thermoplastic resin layer on both sides of the layer made of the resin composition of the present invention. This configuration further improves the moisture resistance of the multilayer structure of the present invention. It is also preferable that the multilayer structure of the present invention has the thermoplastic resin layer via a layer containing an adhesive resin (hereinafter sometimes abbreviated as an adhesive resin layer) on at least one side of the resin composition layer.

[0072] The adhesive resin is not particularly limited as long as it can bond the resin composition layer and the thermoplastic resin layer, but carboxylic acid-modified polyolefins are preferred. Carboxylic acid-modified polyolefins are modified olefin polymers containing carboxyl groups obtained by chemically (for example, by addition reaction, graft reaction) bonding an ethylenically unsaturated carboxylic acid or its anhydride to an olefin polymer. Furthermore, olefin polymers refer to polyolefins such as polyethylene (low pressure, medium pressure, high pressure), linear low-density polyethylene, polypropylene, and polybutene; and copolymers of olefins and comonomers (vinyl esters, unsaturated carboxylic acid esters, etc.) copolymerizable with the olefin, such as ethylene-vinyl acetate copolymers and ethylene-ethyl acrylate copolymers. Examples of ethylenically unsaturated carboxylic acids or their anhydrides include ethylenically unsaturated monocarboxylic acids, their esters, ethylenically unsaturated dicarboxylic acids, their mono or diesters, or their anhydrides, with ethylenically unsaturated dicarboxylic acid anhydrides being preferred. Specifically, examples include maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, monomethyl maleic acid, monoethyl maleic acid, diethyl maleic acid, monomethyl fumaric acid, etc., with maleic anhydride being particularly preferred.

[0073] The amount of ethylenically unsaturated carboxylic acid or its anhydride added to or grafted onto an olefin polymer (degree of modification) is typically 0.01 to 15% by mass relative to the olefin polymer.

[0074] Various additives can be incorporated into each layer of the multilayer structure of the present invention. Examples of such additives include antioxidants, plasticizers, heat stabilizers, ultraviolet absorbers, antistatic agents, lubricants, colorants, and fillers. Specifically, those mentioned above are examples of additives that can be added to the resin composition of the present invention.

[0075] Examples of the layer configuration of the multilayer structure include X / Y, X / Y / X, X / Z / Y, X / Z / Y / Z / X, X / Y / X / Y / X, X / Z / Y / Z / X / Z / Y / Z / X, etc., where X / Y / Y / Z / X / Z / Y / Z / X / Z / Y / Z / X.

[0076] From an economic standpoint, a preferred embodiment of the present invention is to recover and reuse scrap such as trim and defective products generated during the molding of multilayer structures. Therefore, it is preferable that the multilayer structure further comprises a layer (hereinafter sometimes abbreviated as the recovered composition layer) made of a recovered composition obtained by melting and kneading the recovered materials of such a multilayer structure. In this case, possible layer configurations include those in the example of the layer configuration of the multilayer structure described above, in which the thermoplastic resin layer X is replaced with the recovered composition layer, or in which the recovered composition layer is added to a position adjacent to the thermoplastic resin layer X. The recovered multilayer structure preferably contains the thermoplastic resin layer, and may be the multilayer structure of the present invention as described above.

[0077] The recovered composition may be obtained by melt-kneading the recovered material of the multilayer structure with unused resin. Examples of unused resin include thermoplastic resins used in the layers containing the thermoplastic resin in the multilayer structure of the present invention. The EVOH(A) content in the recovered composition is usually 20% by mass or less.

[0078] The thickness of each layer in the multilayer structure of the present invention is not particularly limited, but from the viewpoint of moldability and cost, the ratio of the total thickness of the layers Y made of the resin composition of the present invention to the thickness of the multilayer structure is preferably 2 to 20%.

[0079] The method for manufacturing the multilayer structure is not particularly limited, but examples include molding methods commonly used in the field of polyolefins, such as extrusion molding, blow molding, injection molding, and thermoforming. Among these, co-extrusion molding and co-injection molding are preferred, with co-extrusion molding being more preferred.

[0080] Various molded products (films, sheets, tubes, bottles, etc.) can be obtained by secondary processing of co-extruded or co-injection multilayer structures obtained from the resin composition of the present invention. For example, the following can be cited. (1) A multilayer co-stretched sheet or film obtained by stretching a multilayer structure (sheet or film, etc.) in a uniaxial or biaxial direction and heat-treating it as necessary. (2) Multilayer rolled sheet or film obtained by rolling a multilayer structure (sheet or film, etc.) (3) Multilayer tray cup-shaped container obtained by thermoforming a multilayer structure (sheet or film, etc.) by vacuum forming, pressure forming, vacuum pressure forming, etc. (4) Bottles and cup-shaped containers obtained by stretch blow molding from multilayer structures (pipes, etc.) (5) Bottle-shaped containers obtained by biaxial stretch blow molding or the like from multilayer structures (parisons, etc.)

[0081] The applications of the resin composition and multilayer structure of the present invention are not particularly limited, and they are suitably used as materials for packaging containers, packaging films, deep-drawn containers, cup-shaped containers, bottles, and the like. A packaging container made of the multilayer structure is a preferred embodiment of the present invention. The multilayer structure of the present invention is particularly suitable as a packaging container for retort processing because it has excellent gas barrier properties even under high temperature and high humidity conditions. In addition to conventional retort processing, which involves heating to 100°C or higher and pressurizing, steam retort processing, water cascade retort processing, microwave retort processing, etc., can also be used as retort processing. Furthermore, it is not limited to retort processing, but is also suitable as a container for hot filling, sterilization processing, and boiling processing.

[0082] A packaged body, formed by filling the packaging container of the present invention with contents, is a preferred embodiment of the packaging container. The contents to be filled into the container are not particularly limited, but examples include food, beverages, pharmaceuticals, etc.

[0083] A preferred embodiment of the packaging is a method of sterilizing the packaging with steam or hot water at a temperature of 70°C to 140°C. Specifically, the sterilization treatment can be retort treatment or boiling treatment. The temperature for retort treatment is preferably 105°C to 140°C, and the treatment time is preferably 5 to 120 minutes. The retort treatment may also be performed under a pressure of 0.15 to 0.3 MPa. Retort treatment devices include steam type using heated steam and hot water immersion type using pressurized superheated water, and are used appropriately depending on the sterilization conditions of the contents of the food, etc. Boiling treatment is a method of sterilizing the contents of food, etc. with hot water to preserve them, and although it depends on the contents, usually the packaging container filled with contents is sterilized at atmospheric pressure at 70 to 100°C for 10 to 120 minutes. Boiling is typically performed using a hot water bath. There are two main methods: a batch method, where the food is immersed in a hot water bath at a constant temperature and then removed after a certain period of time; and a continuous method, where the food is sterilized by passing it through a tunnel-like structure in the hot water bath.

[0084] Even after such sterilization treatment, the packaging container retains excellent gas barrier properties, thus suppressing the deterioration of the quality of its contents, such as food and pharmaceuticals, for an extended period. [Examples]

[0085] The present invention will be described in more detail below using examples, but the present invention is not limited in any way by these examples.

[0086] (1) Measurement of Tm1, Tm0, ΔH1 and ΔH0 For the resin composition pellets obtained in each example and comparative example, Tm1, Tm0, ΔH1, and ΔH0 were determined in accordance with JIS K7121 using a differential scanning calorimeter "Q2000" manufactured by TA Instrument Co., Ltd. Indium was used for temperature calibration. The preparation method and measurement procedure for the samples used in each measurement are as follows.

[0087] (1-1) Measurement of Tm1 and ΔH1 5 mg of the resin composition pellets obtained in each example and comparative example was sealed in an aluminum pan (manufactured by TA Instrument Co., Ltd.), heated from 30°C to 241°C at a rate of 10°C / min, rapidly cooled to 92°C at a rate of 10°C / min, and then heated again from 92°C to 241°C at a rate of 10°C / min to perform DSC measurements. The melting point Tm1 (°C) was determined from the peak temperature of the temperature range from the start to the end of melting during the second heating in the obtained DSC curve, and the crystalline melting enthalpy ΔH1 (J / g) was determined from the peak area.

[0088] (1-2) Measurement of Tm0 and ΔH0 A mixed solvent was prepared by adding 900 g of pure water and 900 g of methanol to a 5 L separable flask. 200 g of the resin composition pellets obtained in each example and comparative example were added to the resulting mixed solvent and dissolved while stirring at 90°C. The resulting solution was a paste-like liquid. The obtained solution was continuously extruded into a poor solvent containing water and methanol at 0°C (mass ratio (water / methanol) = 90 / 10) to precipitate the hydrated EVOH resin in strand form while removing the desiccant (B). The resulting strands were then cut to obtain hydrated EVOH resin chips (100 parts by mass of EVOH resin, 150 parts by mass of water). The desiccant (B) removal operation was repeated two more times in the same manner as above, except that the obtained hydrated EVOH resin chips were used instead of the resin composition pellets, to remove the desiccant (B) from the EVOH resin. After washing, the water-containing EVOH resin chips were placed in a steam dryer and dried at 80°C for 3 hours, then placed in a hot air dryer and dried at 80°C for 3 hours, and finally dried at 120°C for 15 hours to obtain EVOH(A) resin chips (reference resin).

[0089] DSC measurements were performed on the obtained resin chips (reference resin) in the same manner as in (1-1). The melting point (Tm0) of the resin chips (reference resin) was determined from the peak temperature of the temperature range from the start to the end of melting during the second heating in the obtained DSC curve, and the crystalline enthalpy of melting (ΔH0) of the resin chips (reference resin) was determined from the peak area.

[0090] (2) Oxygen permeability rate after retort processing (OTR, multilayer sheet) Multilayer sheets were prepared using the resin composition pellets obtained in each example and comparative example as follows. Using a 3-type, 5-layer co-extruder, multilayer sheets with a 5-layer structure consisting of a polypropylene (PP) layer (210 μm) / adhesive resin layer (20 μm) / resin composition layer (40 μm) / adhesive resin layer (20 μm) / PP layer (210 μm) were prepared. Novatec EG7FTB manufactured by Nippon Polypropylene Co., Ltd. was used for the PP, and Admer QF500 manufactured by Mitsui Chemicals, Inc. was used for the adhesive resin. The co-extrusion conditions were as follows: melting temperature of PP 230°C, melting temperature of adhesive resin 220°C, melting temperature of resin composition pellet 220°C, and die temperature 230°C. The extruder and T-die used in this test are as follows. For adhesive resin layers and resin composition layers: 20φ extruder laboratory machine ME type CO-EXT (manufactured by Toyo Seiki) For PP layers: 32φ extruder GF-32-A (manufactured by Plastics Engineering Laboratory) T-die: 300mm wide coat hanger die (manufactured by Plastics Engineering Laboratory)

[0091] The obtained multilayer sheets were retorted using the "RCS-60" retort processing device manufactured by Hisaka Works, Ltd., by immersing them in hot water at 120°C for 30 minutes. Immediately after removal from the device, the multilayer sheets were conditioned for 24 hours at 20°C, 65%RH (outside) / 100%RH (inside). Under the same conditions, the oxygen permeability rate (cc·20μm / m²) was measured using the "OX-TORANMODEL2 / 21" oxygen permeability measuring device manufactured by Mocon. 2 We measured (day·atm).

[0092] (3) Thickness of the resin composition layer at the corner of the cup A multilayer sheet was prepared in the same manner as in (2), except that the thickness of each layer was changed as follows. Specifically, a multilayer sheet with a five-layer structure consisting of a polypropylene (PP) layer (320 μm) / adhesive resin layer (40 μm) / resin composition layer (80 μm) / adhesive resin layer (40 μm) / PP layer (320 μm) was prepared using a three-type five-layer co-extruder. The obtained multilayer sheet was molded using a vacuum pressure molding machine (manufactured by Asano Research Institute Co., Ltd.) under conditions of a sheet surface temperature of 170°C, a pressure of 0.3 MPa, and a drawing ratio of 0.5, resulting in a base area of ​​33 cm².2 The lateral surface area is 79 cm². 2 A multilayer thermoformed cup having a circular base was fabricated.

[0093] The resulting thermoformed cup was cut perpendicular to its bottom surface to obtain a cross-section. The thickness of the resin composition layer at the corners, which consist of the bottom and sides of the cup, was measured using an optical microscope (average value for n=5). The corners of the cup are particularly prone to thinning during thermoforming, and a thicker resin composition layer at the corners indicates better thermoformability.

[0094] (4) Oxygen permeation rate after retort processing (OTR, thermoformed container) The thermoformed containers obtained in the same manner as in (3) were retorted using the "RCS-60" retort processing device manufactured by Hisaka Works, Ltd., by immersing them in hot water at 120°C for 30 minutes. Immediately after removal from the device, the thermoformed containers were conditioned for 14 days at 20°C, 65%RH (outside) / 100%RH (inside), and then the oxygen permeability rate was measured under the same conditions using the "OX-TORANMODEL2 / 21" oxygen permeability measuring device manufactured by Mocon. The unit of oxygen permeability rate is per thermoformed cup (base area 33 cm²). 2 , side area 79cm 2 The oxygen permeability rate (cc / pkg·day·atm) was defined as the oxygen permeability rate (cc / pkg·day·atm).

[0095] (5) Average crystal length of EVOH(A) Pretreatment / Dyeing The resin composition pellets obtained in each example and comparative example were embedded in epoxy resin and cured. The resulting embedded resin was stained by exposure to water vapor of a 4% osmium tetroxide solution for 7 days and drying. After that, ultrathin sections for transmission electron microscopy (TEM) observation were prepared by cutting using a Leica ultramicrotome (model: Ultracut S / FC-S). The cutting conditions were as follows. Sample: -100℃ Knife: -100℃ Cutting speed: 0.4~1.0mm / s Cutting thickness setting: 170~200nm Thickness: 170-200nm The obtained ultrathin sections were collected on a copper mesh (1000 mesh).

[0096] Morphological observation Morphological observations of the resin composition were performed under the following conditions, and the crystal length of EVOH(A) was measured. A Hitachi High-Technologies transmission electron microscope (TEM) "HT7700" was used for morphological observations. Acceleration voltage: 100KV LaB6 electron beam irradiation amount: 10μA Electron beam spot size: 1 μm Condenser aperture hole diameter: 0.1mm (No.2) 3D objective movable aperture hole diameter: 0.16mm (No.3) CCD camera for recording: AMT bottom-mount camera (Model: XR81B, 8-megapixel camera) Observation magnification: 30,000x

[0097] Calculation of the average length of a crystal The average crystal length of EVOH(A) was determined from a map image of the cross-section of the resin composition pellet, based on the method described in Japanese Patent Application Publication No. 2009-013357. Figures 1 and 2 show transmission electron microscope images of the cross-section of the resin composition pellet obtained in Example 1 and Comparative Example 1. Figures 1 and 2 are transmission electron microscope images at 30,000x magnification. As shown in these microscope images, bright crystalline plate-like domains (lamellar crystals, enclosed by white lines in Figures 1 and 2) are present throughout the field of view. Relatively narrow, dark regions exist between these domains. The relatively bright areas in the map image were considered to be the crystalline portions (plate-like domains) of EVOH(A), and the longest length of these crystalline portions was taken as the crystal length. Twenty bright crystalline plate-like domains were arbitrarily selected from the observation field, and the crystal length of each was measured. The arithmetic mean of the obtained values ​​was taken as the average crystal length. The results are shown in Table 1.

[0098] (6) Average particle size of the desiccant (B) The resin composition pellets obtained in each example and comparative example were embedded in epoxy resin and cured. The obtained resin composition pellets were cut using a Leica ultramicrotome (model: Ultracut S / FC-S). Platinum-palladium was deposited onto the obtained pellet cross-section under reduced pressure. The cross-section with deposited platinum-palladium was observed using a scanning electron microscope (SEM, Hitachi High-Tech Corporation "SU8000"). The observation conditions were as follows. From the obtained scanning electron microscope images, the average particle size of the desiccant (B) in the resin composition pellets obtained in the examples and comparative examples was determined as follows. Acceleration voltage: 3KV Observation magnification: 5000x

[0099] Calculation of average particle diameter Figures 3 and 4 show scanning electron microscope images of the cross-sections of the resin composition pellets obtained in Example 1 and Comparative Example 1. Figures 3 and 4 are scanning electron microscope images at 5000x magnification. As shown in these microscope images, granular parts (areas enclosed by white lines in Figures 3 and 4) are observed in the EVOH(A) phase. The granular parts in the map image were considered as desiccant (B) particles, and the longest length of these granular parts was taken as the particle diameter of desiccant (B). Twenty granular parts were arbitrarily selected from the observation field, and the particle diameter of each was measured. The arithmetic mean of the obtained values ​​was taken as the average particle diameter of desiccant (B). The results are shown in Table 1.

[0100] Example 1 A mixed solvent was prepared by adding 930 g of pure water and 930 g of methanol to a 5 L separable flask. 140 g of phenyl disodium phosphate dihydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to the resulting mixed solvent and dissolved. 1100 g of EVOH resin (ethylene unit content 27 mol%, degree of saponification 99.9 mol%, MFR (210°C, 2160 g load) 4.0 g / min) was added to the resulting solution and dissolved while stirring at 90°C. The resulting solution was a paste-like, highly viscous liquid. The resulting solution was continuously extruded into a poor solvent containing water and methanol at 0°C (mass ratio (water / methanol) = 90 / 10) to precipitate in strand form. The resulting strands were then cut to obtain water-containing resin composition chips (water content 145 mass%).

[0101] The obtained water-containing resin composition chips were placed in a steam dryer and dried at 80°C for 3 hours, then in a hot air dryer at 80°C for 3 hours, and finally dried at 120°C for 15 hours. After drying, EVOH resin composition pellets were obtained using the EVOH resin composition chips and a 20mm extruder "D2020" manufactured by Toyo Seiki Seisakusho Co., Ltd. (D(mm)=20, L / D=20, compression ratio=3.0, screw: full flight) under the following conditions. Various physical properties of the obtained EVOH resin composition pellets were evaluated as described above. The results are shown in Table 1. Cylinder temperature: Feed section 180°C, Compression section 220°C, Metering section 220°C Die temperature: 220℃ Screw rotation speed: 120 rpm Discharge amount: 2.1kg / hour

[0102] Example 2, Comparative Examples 3 and 4 Resin composition pellets were prepared and evaluated in the same manner as in Example 1, except that the content of the desiccant (B) was changed as shown in Table 1. The results are shown in Table 1.

[0103] Example 3 A mixed solvent was prepared by adding 930 g of pure water and 930 g of methanol to a 5 L separable flask. 1100 g of EVOH resin (ethylene unit content 27 mol%, degree of saponification 99.9 mol%, MFR (210°C, 2160 g load) 4.0 g / min) was added to the resulting mixed solvent and dissolved while stirring at 90°C. The resulting solution was continuously extruded into a poor solvent containing water and methanol at 0°C (mass ratio (water / methanol) = 90 / 10) to precipitate in strand form, and the resulting strands were cut. Subsequently, the obtained water-containing tips were washed with a large amount of water three times to obtain water-containing EVOH resin tips (100 parts by mass of EVOH resin, 143 parts by mass of water). The same operation was repeated nine more times to obtain a total of 11000 g of water-containing EVOH resin tips (100 parts by mass of EVOH resin, 143 parts by mass of water). The obtained water-containing EVOH resin chips were placed in a hot air dryer and dried at 80°C for 4 hours to obtain water-containing EVOH resin chips containing 100 parts by mass of EVOH resin and 5 parts by mass of water.

[0104] Next, using the above-mentioned water-containing EVOH resin chip (100 parts by mass of EVOH resin, 5 parts by mass of water), resin composition pellets were obtained using a Toshiba Machine Co., Ltd. twin-screw extruder "TEM-35BS" (37 mmφ, L / D=52.5) ​​under the following conditions. A 25% by mass aqueous solution of disodium phenyl phosphate was added from the compression section of the extruder, and the water was removed from the vent. Various physical properties of the obtained resin composition pellets were evaluated as described above. The results are shown in Table 1. Cylinder temperature: Feed section 110°C, Compression section 200°C, Metering section 200°C Die temperature: 200℃ Screw rotation speed: 200 rpm Discharge amount: 10.0kg / hour

[0105] Comparative Example 1 A mixed solvent was prepared by adding 930 g of pure water and 930 g of methanol to a 5 L separable flask. 1100 g of EVOH resin (ethylene unit content 27 mol%, degree of saponification 99.9 mol%, MFR (210°C, 2160 g load) 4.0 g / min) was added to the resulting mixed solvent and dissolved while stirring at 90°C. The resulting solution was continuously extruded into a poor solvent containing water and methanol at 0°C (mass ratio (water / methanol) = 90 / 10) to precipitate in strand form, and the resulting strands were cut. The resulting water-containing tips were washed with a large amount of water three times to obtain water-containing EVOH resin tips containing 100 parts by mass of EVOH resin and 137 parts by mass of water.

[0106] Next, an aqueous solution was prepared by adding 6500g of pure water and 420g of phenyl disodium phosphate dihydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) to a 10L plastic bucket. 1800g of the above-mentioned hydrated EVOH resin chips (100 parts by mass of EVOH resin, 137 parts by mass of water) were added to the resulting aqueous solution and stirred at 20°C for 4 hours. Afterward, the hydrated resin composition chips were removed from the aqueous solution and dried in a hot air dryer at 80°C for 3 hours, followed by drying at 120°C for 15 hours. After drying, resin composition pellets were obtained using the resin composition chips with a 20mm extruder "D2020" (D(mm)=20, L / D=20, compression ratio=3.0, screw: full flight) manufactured by Toyo Seiki Seisakusho Co., Ltd., under the following conditions. Various physical properties of the obtained resin composition pellets were evaluated as described above. The results are shown in Table 1. Cylinder temperature: Feed section 180°C, Compression section 220°C, Metering section 220°C Die temperature: 220℃ Screw rotation speed: 120 rpm Discharge amount: 2.0kg / hour

[0107] Comparative Example 2 Phenylenidus disodium phosphate dihydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was ground while being heated and dried in a 120°C convection oven for 12 hours using a fluidized bed jet mill (Hosokawa AFG-400, manufactured by Alpine and Hosokawa Micron Powder Systems) to obtain powder of anhydrous phenyl disodium phosphate. The obtained powder of anhydrous phenyl disodium phosphate and EVOH resin (Eval L171, manufactured by Kuraray Co., Ltd.) were melt-kneaded so that the phenyl disodium phosphate content in the resulting resin composition was 5% by mass. Melt-kneading was performed using a 25mm extruder "D2020" (D(mm)=25, L / D=25, compression ratio=3.0, screw: fully meshed in the same direction) manufactured by Toyo Seiki Seisakusho Co., Ltd., and resin composition pellets were obtained under the following conditions. Various physical properties of the obtained resin composition pellets were evaluated as described above. The results are shown in Table 1. Cylinder temperature: Feed section 180°C, Compression section 230°C, Metering section 230°C Die temperature: 230℃ Feeder rotation speed: 170 rpm Screw rotation speed: 100 rpm Discharge amount: 6.0kg / hour

[0108] Comparative Example 5 Resin composition pellets were prepared in the same manner as in Example 1, except that the temperature at which EVOH(A) was dissolved in a phenyl disodium phosphate solution was changed to 70°C. However, the melting of EVOH(A) was insufficient. The results of the evaluation are shown in Table 1.

[0109] [Table 1]

Claims

1. A pellet comprising a resin composition containing an ethylene-vinyl alcohol copolymer (A) and a desiccant (B), The content of ethylene-vinyl alcohol copolymer (A) is 70 to 99% by mass. Average length of crystals of ethylene-vinyl alcohol copolymer (A) (Pellet cross-section) The analysis of the transmission electron microscope image is 10-65 nm. The content of the desiccant (B) is 1 to 30% by mass. The desiccant (B) is a metal salt capable of forming a hydrate, The average particle size of the desiccant (B) (analysis of scanning electron microscope images of the pellet cross-section) is 10 to 300 nm, and The crystalline fusion enthalpy ΔH of the reference resin obtained by removing the desiccant (B) from the resin composition is melted, rapidly cooled, and then heated. ０ The crystalline enthalpy ΔH of the resin composition when the resin composition is melted, rapidly cooled, and then heated, relative to (J / g). １ (J / g) ratio (ΔH １ / ΔH ０ Pellets in which the ratio is 0.95 or less.

2. The pellet according to claim 1, wherein the metal salt is at least one selected from the group consisting of phosphates, sulfates, phosphonates, phosphinates, sulfonates, sulfinates, and carboxylates.

3. A method for producing pellets according to claim 1 or 2, comprising the step of mixing a molten or dissolved ethylene-vinyl alcohol copolymer (A) with a dissolved desiccant (B).

4. A method for producing pellets according to claim 1 or 2, comprising the step of precipitating the ethylene-vinyl alcohol copolymer (A) and the desiccant (B) from a solution in which the ethylene-vinyl alcohol copolymer (A) and the desiccant (B) are dissolved.

5. A method for producing pellets according to claim 1 or 2, comprising the steps of adding an aqueous solution containing a desiccant (B) to a molten material containing an ethylene-vinyl alcohol copolymer (A) and water, and melt-kneading the molten material to which the aqueous solution has been added.

6. A multilayer structure having a layer formed by extruding the pellets described in claim 1 or 2.

7. The multilayer structure according to claim 6, further comprising a layer made of a recovered composition obtained by melt-kneading a multilayer structure having a layer containing at least one thermoplastic resin selected from the group consisting of polyolefin, polystyrene, polyester, polyamide, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, and polyacrylonitrile.

8. A packaging container comprising a multilayer structure according to claim 6 or 7.

9. A packaged body comprising a packaging container according to claim 8 filled with contents.

10. A method for sterilizing the package described in claim 9 with steam or hot water at a temperature of 70°C to 140°C.

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